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Manipulation/199bb55b-1c98-451b-b065-6d0fccbafb25_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..81c3ff756068ea685993e6c0d80c60a7d304aa7c --- /dev/null +++ b/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/199bb55b-1c98-451b-b065-6d0fccbafb25_content_list.json @@ -0,0 +1,1649 @@ +[ + { + "type": "text", + "text": "Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation", + "text_level": 1, + "bbox": [ + 86, + 128, + 880, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Tianshui Chen", + "bbox": [ + 200, + 204, + 320, + 220 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "tianshuichen@gmail.com", + "bbox": [ + 161, + 224, + 359, + 238 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Jianman Lin", + "bbox": [ + 460, + 204, + 560, + 220 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "linjianmancjx@gmail.com", + "bbox": [ + 408, + 224, + 614, + 238 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Zhijing Yang*", + "bbox": [ + 679, + 204, + 792, + 222 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "yzhj@gdut.edu.cn", + "bbox": [ + 661, + 224, + 805, + 238 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Chunmei Qing", + "bbox": [ + 308, + 247, + 429, + 263 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "qchem@scut.edu.cn", + "bbox": [ + 297, + 268, + 442, + 281 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Liang Lin", + "bbox": [ + 550, + 247, + 633, + 263 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "linliang@ieee.org", + "bbox": [ + 514, + 267, + 666, + 281 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 316, + 313, + 332 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Speech-preserving facial expression manipulation (SPFEM) aims to modify facial emotions while meticulously maintaining the mouth animation associated with spoken content. Current works depend on inaccessible paired training samples for the person, where two aligned frames exhibit the same speech content yet differ in emotional expression, limiting the SPFEM applications in real-world scenarios. In this work, we discover that speakers who convey the same content with different emotions exhibit highly correlated local facial animations, providing valuable supervision for SPFEM. To capitalize on this insight, we propose a novel adaptive spatial coherent correlation learning (ASCCL) algorithm, which models the aforementioned correlation as an explicit metric and integrates the metric to supervise manipulating facial expression and meanwhile better preserving the facial animation of spoken contents. To this end, it first learns a spatial coherent correlation metric, ensuring the visual disparities of adjacent local regions of the image belonging to one emotion are similar to those of the corresponding counterpart of the image belonging to another emotion. Recognizing that visual disparities are not uniform across all regions, we have also crafted a disparity-aware adaptive strategy that prioritizes regions that present greater challenges. During SPFEM model training, we construct the adaptive spatial coherent correlation metric between corresponding local regions of the input and output images as addition loss to supervise the generation", + "bbox": [ + 75, + 348, + 472, + 772 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "*Zhijing Yang is the corresponding author. Tianshui Chen, Jianman Lin, and Zhijing Yang are with Guangdong University of Technology. Chunmei Qing is with South China University of Technology. Liang Lin is with Sun Yat-Sen University. This work was supported in part by National Natural Science Foundation of China (NSFC) under Grant No. 62206060, in Part by Natural Science Foundation of Guangdong Province (2022A1515011555, 2023A1515012568, 2023A1515012561), Guangdong Provincial Key Laboratory of Human Digital Twin (2022B1212010004), and in part by Guangzhou Basic and Applied Basic Research Foundation under Grant No. SL2022A04J01626.", + "bbox": [ + 75, + 779, + 468, + 900 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/6b0e354072400563f18108657bd541a8a864b9721d2e4bed4fa3fef9b457a5a0.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 516, + 315, + 602, + 385 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c187ee25cdee843d1d2774091926625fe525f9231db0cf37dfe1615beace3232.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 604, + 316, + 692, + 385 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c33067396d0828d8874adfccbf049efacbb9f14802019e8e3fdf8c845df3b1ff.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 316, + 781, + 385 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/f5d26f30ce57d709891c6c743694456fac9c4ece3848358256da114121dac0c9.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 782, + 316, + 870, + 385 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/221bb87971eb216d18aa00d1346890382ebf39e35cbd74fde87fe02db22d3867.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 516, + 386, + 602, + 454 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/919ade3a423de243bda8832a60722e8eb47ef3680d4bdaa934ff8bb43e65f409.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 604, + 386, + 692, + 454 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/6ad9332ffcf2b620ff05b2a0045ff003af55d2ff0f8966df9042f115bf9acadb.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 386, + 781, + 454 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/44685ee7bae0c6ccf9bc8cb97d96cdc40d1f866a8e50fc3468ee353f910c59c5.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 782, + 386, + 870, + 454 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e5359e6cf7e2b8ef940cc728db38a18a3677807bdb92837747b22dfc8992bf38.jpg", + "image_caption": [ + "Reference" + ], + "image_footnote": [ + "Figure 1. Several examples are generated by the current advanced NED with and without the proposed ASCCL algorithm. Incorporating the ASCCL can better manipulate the expressions and meanwhile preserve mouth shapes." + ], + "bbox": [ + 516, + 454, + 602, + 522 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/311f9eaea3c1f25d89a97f185c0484ae96c3861f20b2048a3641427d1ccb1aa2.jpg", + "image_caption": [ + "Source" + ], + "image_footnote": [], + "bbox": [ + 604, + 454, + 692, + 522 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/462339c19202073d974cd03df916240046ebaab09c5177d91e52ddbf9da18b20.jpg", + "image_caption": [ + "NED" + ], + "image_footnote": [], + "bbox": [ + 694, + 454, + 781, + 522 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e383473bd08bc307742835f93f35de629d6479c73d5c4af30adeea86a051760e.jpg", + "image_caption": [ + "ASCCL" + ], + "image_footnote": [], + "bbox": [ + 782, + 454, + 870, + 522 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "process. We conduct extensive experiments on variant datasets, and the results demonstrate the effectiveness of the proposed ASCCL algorithm. Code is publicly available at https://github.com/jianmanlincjx/ASCCL", + "bbox": [ + 496, + 604, + 893, + 664 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 500, + 683, + 632, + 698 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Speech-preserving facial expression manipulation (SPFEM), which aims to manipulate facial emotions while preserving the mouth animations in static images or dynamic videos, can enhance human expressiveness and thus benefit variant applications including virtual avatars and film & television production. For example, it requires lots of effects and repeated remakes to capture an expected actor's emotions in a movie & shooting. In contrast, a robust SPFEM system can easily modify the facial emotions to achieve comparable performance in the post-production stage and thus is urgently expected.", + "bbox": [ + 496, + 703, + 890, + 869 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Current SPFEM literature either predominantly previous face reenactment algorithms [10, 28] or harnesses decou", + "bbox": [ + 498, + 869, + 890, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "7267", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "pled semantic representations equipped by cyclic consistency [23, 36]. The former category of works [10, 28] typically manipulates facial expressions through the exchange of latent codes [17] or facial action units [13], and employs the reference images as surrogate labels to construct frame-by-frame construction supervision. However, these surrogate images are not perfect representations of the desired outcomes and the reliance on them may lead to generating sub-optimal results. The latter approach [23] posits a one-to-one correspondence between images exhibiting varied emotional expressions and employs cyclic consistency for paired supervision. Despite achieving better performance, the global cyclical consistency constraint makes it difficult to capture alterations in fine-grained facial information under different emotions. Consequently, these methods either fail to accurately translate the intended emotions (as illustrated in the first and third examples in Figure 1) or do not maintain the original mouth animation tied to the spoken content (as evidenced in the first and second examples in Figure 1).", + "bbox": [ + 80, + 90, + 467, + 392 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To establish accurate information for additional supervisory guidance, we investigate a plausible and reasonable assumption: a single speaker articulating identical content across varied emotional states exhibits a high degree of correlation in local facial animations. Within the realm of the SPFEM task, we posit that there exists a strong correlation between adjacent local regions of the input images and their corresponding counterparts in the output images. For a more detailed analysis, we delve into the examination of similarities and correlation coefficients between corresponding local regions of the input and output images, and those between non-corresponding local regions of the input and output images. As depicted in Figure 2, there is a notable presence of high similarities and correlation coefficients for corresponding local regions. Conversely, the noncorresponding local regions demonstrate values approaching zero. These observations provide robust empirical support for the previously stated assumption and underscore the merit of modeling these correlations to facilitate SPFEM performance.", + "bbox": [ + 80, + 397, + 467, + 698 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this work, we design a novel adaptive spatial coherent correlation learning (ASCCL) algorithm, which discerns the correlations between adjacent local regions within images that display varying emotional states and incorporates these correlations as additional guidance to supervise the manipulation of expressions in a manner that is attuned to difficulty. Formally, we leverage visual disparities as a means to characterize the interactions between adjacent local regions, given that local motion disparities are critical to the realism of facial animations. Then, we formulate a spatial coherent correlation metric ensuring the visual disparities of adjacent local regions of the image belonging to one emotion are similar to those of the correspond", + "bbox": [ + 80, + 704, + 467, + 898 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "ing counterpart of the image belonging to another emotion. Recognizing the variable complexity across different facial regions, we introduce a disparity-aware adaptive strategy, which preferentially weights more challenging regions with higher values while proportionally reducing the weight for less complex areas. During SPFEM model training, we establish a network of dense correlations between local regions of the input and output images, employing this adaptive spatially coherent correlation metric as an auxiliary supervision. ASCCL is trained using a set of paired data and can be used to construct supervision for any other persons to facilitate generating high-quality results in a plug-and-play manner.", + "bbox": [ + 503, + 90, + 888, + 285 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The contributions can be summarized into three folds. Firstly, we introduce an adaptive spatial coherent correlation learning (ASCCL) algorithm, which learns the consistent correlations between input and generated images in terms of the visual disparities of adjacent local regions. It can be seamlessly integrated into current SPFEM methods to improve their performance in a plug-and-play manner. Secondly, we introduce a difficult-aware adaptive strategy that weights more challenging regions with higher constraints while proportionally reducing the weight for less complex areas. Lastly, we conduct extensive experiments that integrate the ASCCL algorithms into current advanced methods, demonstrating the effectiveness of the proposed ASCCL algorithm.", + "bbox": [ + 503, + 287, + 888, + 498 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 503, + 512, + 645, + 527 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Video-based face manipulation. To modify talking/moving faces, video-based face manipulation algorithms frequently employ conditionally Generative Adversarial Networks (GANs) [14, 19, 29, 31, 33] or 3DMM [2, 9, 11, 12, 27]. For example, GANimation [25] leverages adversarial learning conditioning on action unit [13] annotations to describe facial movements in a continuous manifold. [29] apply StyleGAN [18] to learn low-frequency information to accomplish temporal coherency. DSM [26] learns disentangled representation and controls facial expressions via semantic representation. SPFEM is more difficult than simple face manipulation since it requires not only modifying facial expressions but also retaining the facial motion of original speech contents.", + "bbox": [ + 503, + 537, + 888, + 748 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Face reenactment. Facial reenactment, in which a specific actor imitates speech and expressions from a reference video [4, 8, 10, 28, 34] and other [35]. For example, ICface [28] controls the pose and expression with interpretable control signals such as head pose angles and action units. To create temporally consistent videos, Head2Head++ [10] employs a sequential generator and a customized dynamics discriminator. StyleHEAT [34] extends the latent code of StyleGAN [17] to aid in motion and expression generation and animation. SPFEM is similar to this task in expression", + "bbox": [ + 503, + 750, + 888, + 898 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "7268", + "bbox": [ + 483, + 946, + 513, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/42431e3cfb51c347aae1284abf6f45d96ade88ed9e79ebb2e882800bf6371af0.jpg", + "image_caption": [ + "Figure 2. (a) Average similarities and (b) Average Pearson correlation coefficients of the positive and negative samples." + ], + "image_footnote": [], + "bbox": [ + 89, + 103, + 267, + 323 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/b28a6e552bfa3e6164b8207a90af3c7d5dd6cdf695e9ced53ee8b6572bb17714.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 279, + 102, + 464, + 324 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "manipulation, but it also requires preserving mouth movement of original speech contents, making SPFEM a more difficult task.", + "bbox": [ + 75, + 371, + 468, + 415 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Speech-preserving facial expression manipulation. SPFEM seeks to alter the given source video to the desired emotion while keeping the voice content's facial animation. Previous research has adapted facial reenactment algorithms such as ICface [28] to this job. However, facial reenactment can keep both the expression and the mouth form, but not the speech substance. To accomplish this challenge, [23] propose combining the 3DMM parameters of source identification and target emotion. Despite making significant progress, these works lack paired supervision, resulting in sub-optimal performance in emotion manipulation and speech preservation. Different from the above-mentioned works, we present in-depth analyses about the spatial coherent correlations across images belonging to different emotions and find there exist strong correlations between adjacent local regions of the input image of one emotion and their corresponding counterparts in the output image of another emotion. We propose to learn adaptive spatial coherent correlations to construct additional supervision for SPFEM.", + "bbox": [ + 75, + 417, + 472, + 720 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Motivation", + "text_level": 1, + "bbox": [ + 76, + 736, + 194, + 752 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As discussed above, we make a plausible and reasonable assumption that a single speaker articulating identical content across varied emotional states exhibits a high degree of correlation in local facial animations. To present a more in-depth and direct analysis, we further conduct statistical experiments to validate this assumption.", + "bbox": [ + 75, + 763, + 468, + 854 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Formally, given two images of the same speaker expressing the same content with two different emotions, denoted as $x$ and $y$ , we use the output of the last convolution layer", + "bbox": [ + 75, + 854, + 470, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "of pre-trained network [7] to compute their feature $x^{f}$ and $y^{f}$ . Here, we use visual disparity to denote the relationship of regions at locations $i$ and $j$ , and the similarity between visual disparities of corresponding and non-corresponding adjacent local regions, formulated as:", + "bbox": [ + 496, + 90, + 893, + 167 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\ns _ {i \\rightarrow j} ^ {p} = \\varphi \\left(x _ {i \\rightarrow j} ^ {f}, y _ {i \\rightarrow j} ^ {f}\\right) \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 602, + 172, + 890, + 200 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {s} _ {i \\rightarrow k} ^ {n} = \\varphi (x _ {i \\rightarrow j} ^ {f}, y _ {i \\rightarrow k, k \\neq j} ^ {f})\n$$\n", + "text_format": "latex", + "bbox": [ + 602, + 195, + 787, + 219 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "$x_{i\\rightarrow j}^{f}$ and $y_{i\\rightarrow j}^{f}$ denote visual disparities of regions $i$ and $j$ of the images $x$ and $y$ . $\\varphi$ represents the cosine similarity function. For each emotion pair, we retrieve thousands of corresponding and non-corresponding adjacent local regions and compute their average similarities. As shown in Figure 2 (a), we present the average similarities of corresponding and non-corresponding adjacent local regions according to the emotion pairs of neural to other six emotions. We find the average similarities of the non-corresponding adjacent local regions approach 0, and that of the corresponding adjacent local regions range from 0.43 to 0.49. Moreover, we further compute Pearson correlation coefficients [6] between visual disparities of visual disparities of corresponding and non-corresponding adjacent local regions. Similarly, we use thousands of corresponding and non-corresponding adjacent local regions and compute their average Pearson correlation coefficients. As presented in Figure 2 (b), a similar phenomenon is observed. These results suggest there exist strong correlations between the corresponding adjacent local regions between two images expressing the same content while differing in emotions. Thus, it is worth investigating to learn the correlations and integrate the correlations to facilitate the SPFEM performance.", + "bbox": [ + 496, + 224, + 893, + 575 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Method", + "text_level": 1, + "bbox": [ + 498, + 587, + 591, + 602 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "It first learns the spatially coherent correlation metric, ensuring the alignment between the visual disparity of adjacent local regions of the source input image and that of the corresponding counterpart of the output generated image. Then, it designs a disparity-aware adaptive strategy to weigh more challenging regions with higher values while reducing the weight for less complex regions. The ASCCL algorithm can be used to supervise generating visual contents, including intermediate results (e.g., 3DMM [1]) and final rendered images in a plug-and-play manner. An overall pipeline for incorporating ASCCL into the two-stage NED [23] method is illustrated in Figure 3.", + "bbox": [ + 496, + 612, + 893, + 794 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. Spatial Coherent Correlation Metric Learning", + "text_level": 1, + "bbox": [ + 498, + 801, + 890, + 816 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As suggested in Section 3, there inherently exist strong correlations between adjacent regions of two images that one speaker expresses the same content while differing in different emotions. Indeed, we can further strengthen the correlations by learning the spatial coherent correlation (SCC)", + "bbox": [ + 496, + 825, + 893, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "7269", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/829fc1f243459bd1f27ebb34763134787971bbcbf9666fcde42c384f36e756f5.jpg", + "image_caption": [ + "Figure 3. An overall pipeline of incorporating the proposed ASCCL algorithm to the current advanced NED [23] method to supervise generating the intermediate 3DMM meshes and final rendered images. It computes visual disparities of corresponding and non-corresponding local regions between the source and generated images, followed by the disparity-aware adaptive strategy to obtain the final loss to supervise final image generation. An identical process is performed on the source and generated 3DMM meshes to supervise the intermediate 3DMM mesh generation." + ], + "image_footnote": [], + "bbox": [ + 158, + 88, + 816, + 316 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/e90aa919c89124e169d48b9fee978780ee9c2fefc580e8c353437939049e0ac6.jpg", + "image_caption": [ + "Figure 4. An illustration of spatial coherent correlation metric learning. It retrieves the corresponding adjacent local regions of the input and output images as positive samples and the noncorresponding counterparts as negative samples. The process is performed in the feature maps to construct dense positive and negative samples to train the metric." + ], + "image_footnote": [], + "bbox": [ + 78, + 393, + 473, + 468 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "metric using paired data, which can assign a higher value to the correlation between corresponding adjacent regions and assign a smaller value to the correlation between noncorresponding counterparts. In this way, it can provide better-synchronized signals to supervise the generation process. Here, we introduce the SCC metric learning in detail.", + "bbox": [ + 75, + 575, + 468, + 667 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Formally, given two images of the same speaker expressing the same content with two different emotions, we need to extract corresponding regions $i$ and $j$ of both two images. However, pose bias typically exists between these two images, potentially compromising the calculation accuracy. To address this issue, we first introduce a pose alignment module that extracts landmark coordinates using a pre-trained model in the OpenCV library for both two images and utilizes these coordinates to compute an affine transformation matrix. This matrix is subsequently applied to align the pose information between the two images and obtain two images $x$ and $y$ that ensure geometric correspondence.", + "bbox": [ + 75, + 670, + 470, + 852 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Figure 4 exhibits the detailed computation process of the SCC metric. Owing to the locality and translation invariance characteristics of convolutional neural networks", + "bbox": [ + 76, + 854, + 470, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "[7, 15], the mapping of pixels in the feature space back to the original image is approximately equivalent to a local region, and as the depth of the network increases, the receptive field also expands. Leveraging these characteristics, we employ the output of multiple convolutional layers to obtain the multi-scale features. Formally, we can extract the feature of layer $l$ as:", + "bbox": [ + 496, + 393, + 893, + 501 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nx ^ {f, l} = \\phi^ {l} (x) \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 650, + 506, + 890, + 532 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ny ^ {f, l} = \\phi^ {l} (y)\n$$\n", + "text_format": "latex", + "bbox": [ + 653, + 529, + 738, + 546 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Here, $\\phi^l (\\cdot)$ is feature extractor for layer $l$ . We adopt the Arcface network [7], and use the output of four convolutional layers with dimension decline and thus $l\\in [1,2,3,4]$ . Given two regions $i$ and $j$ , we compute the visual disparity using a mapping of the feature difference, denoted as:", + "bbox": [ + 496, + 554, + 890, + 631 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nx _ {i \\rightarrow j} ^ {f, l} = f \\left(x _ {i} ^ {f, l} - x _ {j} ^ {f, l}\\right) \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 617, + 637, + 890, + 665 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ny _ {i \\rightarrow j} ^ {f, l} = f (y _ {i} ^ {f, l} - y _ {j} ^ {f, l})\n$$\n", + "text_format": "latex", + "bbox": [ + 622, + 660, + 769, + 681 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $f(\\cdot)$ denotes a mapping function and it is implemented using two stacked fully-connected layers cooperated with the rectified linear unit non-linear function. Inspired by the recent progress in previous works [3, 16, 22, 32], we define an identical contrastive loss, formulated as:", + "bbox": [ + 496, + 688, + 890, + 763 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\ell_ {x y} ^ {l, i \\rightarrow j} = \\frac {\\exp \\left(\\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow j} ^ {f , l}}{\\tau}\\right)}{\\exp \\left(\\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow j} ^ {f , l}}{\\tau}\\right) + \\exp \\left(\\sum_ {k = 1 , k! = j} ^ {m} \\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow k} ^ {f , l}}{\\tau}\\right)} \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 509, + 781, + 890, + 847 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\tau$ stands for a temperature hyper-parameter set to 0.07 by default. The final loss can be defined as the summation of all image pairs, corresponding region pairs, and four", + "bbox": [ + 496, + 854, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "7270", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "layers, formulated as:", + "bbox": [ + 76, + 90, + 223, + 104 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {s c c l} = \\sum_ {l = 1} \\sum_ {i, j} \\sum_ {x, y} \\ell_ {x y} ^ {l, i \\rightarrow j} \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 183, + 114, + 468, + 148 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "By minimizing losses through backpropagation, we can align the visual disparities of $y$ to $x$ with different emotions, and thus provide visual consistency correlations to supervise SPFEM model training.", + "bbox": [ + 75, + 159, + 468, + 219 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Disparity-Aware Adaptive Strategy", + "text_level": 1, + "bbox": [ + 76, + 228, + 382, + 244 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Once the SCCL metric is learned, we can use to $\\mathcal{L}_{sccl}$ loss between the input source (source 3DMM) and output generated (generated 3DMM) images as additional supervision. Here, we observe a notable phenomenon that the complexity varies across different facial regions. For example, it is more complex and challenging for the mouth regions as it change dramatically when the speaker is talking. In contrast, when the regions are positioned at the cheek area, the visual disparity is reduced, promoting a faster convergence. This underscores the region-specific sensitivity of visual disparity. Consequently, by enabling the SCC metric to independently discern and dynamically modulate learning strategies for specific regions, we can enhance the extraction of spatially coherent correlation information in an adaptive manner.", + "bbox": [ + 75, + 251, + 468, + 476 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Inspired by the idea of [20], DAAS is engineered to enable the SCC metric to discern this variability and tailor its learning strategies based on the characteristics of the regions, prioritizing those with higher learning complexity. Specifically, when the visual disparity $x_{i\\rightarrow j}^{f,l}$ is larger, this region is deemed a challenging region, to which we assign a larger weight value. Conversely, when $x_{i\\rightarrow j}^{f,l}$ is small, it is considered a simple region that can achieve rapid convergence, we reduce the weight for those simple regions. To this end, we propose to assign different weights according to the visual disparity, formulated as:", + "bbox": [ + 75, + 478, + 468, + 643 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nw _ {i j} ^ {l} = \\lambda \\cdot \\operatorname {s i g m o i d} \\left(x _ {i \\rightarrow j} ^ {f, l}\\right) ^ {r} \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 183, + 652, + 468, + 674 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $w_{ij}^{l}$ represents the weight value of adjacent regions $i \\rightarrow j$ for images $x$ and $y$ at the feature map layer $l$ . $\\lambda$ and $r$ are hyper-parameters, both of which are set to 2 to ensure a reasonable weight. The final loss function can be defined as:", + "bbox": [ + 75, + 683, + 468, + 758 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {a s c c l} = \\sum_ {l = 1} \\sum_ {i, j} \\sum_ {x, y} w _ {i j} ^ {l} \\cdot \\ell_ {x y} ^ {l, i \\rightarrow j} \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 161, + 767, + 468, + 801 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Current SPFEM algorithms can be divided into two types. The first involves a two-stage generation: initially creating 3DMM parameters and then using them to render final images [23]. The second method directly produces rendered images [28]. Visual information here refers to either the 3DMM parameters or the final images. $\\mathcal{L}_{asccl}$ can be used", + "bbox": [ + 75, + 809, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "for both these two types of algorithms as shown in Figure 3. Due to page limit, we present more implementation details, including network architectures, integration to current NED and ICface method, and training details.", + "bbox": [ + 496, + 90, + 890, + 151 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 167, + 630, + 184 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.1. Dataset", + "text_level": 1, + "bbox": [ + 500, + 191, + 594, + 207 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We performed experiments on the MEAD dataset [30], which contains 60 speakers, and each speaker records 30 videos in each emotional state (i.e., neutral, happy, angry, surprised, fear, sad, and disgusted). Here, we selected videos of 36 speakers that have 7,560 videos to train the ASCCL algorithm. To evaluate the SPFEM model's performance, we select 6 non-overlapped speakers (M003, M009, W029, M012, M030, and W015) that have 1,260 videos. We randomly selected $90\\%$ as the training set and the rest $10\\%$ as the test set similar to previous works [23]. We additionally employ the ASCCL algorithm on the well-established RAVDESS dataset [21] without the need for retraining. Specifically, we focus on 6 speakers (actors 1-6) encompassing 168 videos. Similarly, $90\\%$ of the videos are randomly chosen for the training set, while the remaining $10\\%$ constitute the test set.", + "bbox": [ + 496, + 215, + 890, + 457 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.2. Evaluation Protocol", + "text_level": 1, + "bbox": [ + 500, + 469, + 689, + 483 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this work, we use these metrics for evaluation: 1) Frechet Arcface Distance (FAD) gauges video realism by comparing feature vectors of generated and real videos using advanced face recognition technology [7]. Lower FAD values indicate better realism. 2) Cosine Similarity (CSIM) assesses emotional similarity between generated and target emotional videos using a state-of-the-art expression recognition network, with higher CSIM values denoting greater similarity. 3) Lip Sync Error Distance (LSE-D) [24] evaluates lip-audio accuracy using a pre-trained model [5] to measure the disparities between lip and audio representations, with smaller LSE-D indicates a higher lip-audio accuracy. We present the results of two settings: inter-identification, where emotion reference and source video share the same speaker, and cross-identification, involving different speakers.", + "bbox": [ + 496, + 492, + 890, + 734 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.3. Comparison with Baseline Methods", + "text_level": 1, + "bbox": [ + 500, + 746, + 807, + 762 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.3.1 Quantitative Comparisons", + "text_level": 1, + "bbox": [ + 500, + 768, + 736, + 785 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We first present the performance comparisons on MEAD in Table 1. When ASCCL is integrated into NED, the resulting image sequences are greatly improved in FAD, LSE-D, and CSIM. In the Cross-ID setting, compared with NED itself, FAD, LSE-D, and CSIM have all improved to a certain extent, with FAD reduced from 4.448 to 4.264, LSE-D from 9.906 to 9.238, and CSIM from 0.773 to 0.791. Among", + "bbox": [ + 496, + 794, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "7271", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/e6b025f9b1ba8e14ee0b778e6704ed46d45d74856ee050616bfdfc2157d50940.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
SettingsEmotionsICfaceOurs (ICface)NEDOurs (NED)
FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑
Inter-IDNeutral7.1149.7600.7797.1589.3820.7810.9069.2640.8830.8919.1130.911
Angry6.42010.4830.7416.1959.7660.8032.1779.5790.8021.1959.5500.896
Disgusted7.38310.4330.8056.2659.2660.8093.8389.1280.7721.6799.4160.854
Fear6.5679.8550.7546.6989.4810.8001.65910.1720.8481.33010.0390.900
Happy6.21310.1800.7756.1919.5560.8371.9399.1370.8391.3268.9750.930
Sad7.30110.0170.7556.7279.2930.7792.5389.0740.8121.1628.9060.906
Surprised6.5679.8510.8177.4709.2710.7951.7009.8210.8641.0569.3820.902
Avg.6.79510.0830.7756.6729.4310.8012.1089.4540.8311.2349.3400.900
Cross-IDNeutral10.56011.2260.7059.74510.6040.6712.0229.8120.8411.8659.1340.852
Angry9.47011.0730.6489.27110.4560.6934.8519.9040.7174.8539.2390.748
Disgusted9.23011.1840.6379.32310.3380.7645.09410.1210.7914.8409.3470.814
Fear9.12211.2040.7279.27310.2210.7294.9839.7410.7504.8209.2390.761
Happy8.49311.3220.7179.50510.4210.7933.9199.9360.8423.3839.1780.866
Sad10.36411.5260.6649.71010.3140.6645.66510.1790.6915.4759.4270.720
Surprised9.54111.1330.7219.53410.2730.7664.6009.6460.7804.6159.1050.779
Avg.9.54011.2380.6889.48010.3750.7264.4489.9060.7734.2649.2380.791
", + "bbox": [ + 93, + 89, + 875, + 279 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Comparison results of FAD, CSIM, and LSE-D of NED, ICFACE with and without our ASCCL on the inter-Identification and cross-IDentification settings on the MEAD dataset.", + "bbox": [ + 75, + 279, + 890, + 306 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "them, the LSE-D has seen significant improvements, and these notable advancements in the LSE-D metric can be attributed to ASCCL's pivotal role in supervising the training of the SPFEM model. This supervision accentuates the intrinsic visual correlations between the SPFEM model's input and output, ensuring the visual disparity of the input and output align closely thereby enhancing consistency in mouth shape modifications related to emotion. Additionally, the betterment in FAD and CSIM further attests that ASCCL not only maintains but can also elevate the model's training quality, steering it towards superior optimization. In the inter-ID setting, these three indicators are also improved to a certain extent, indicating that the proposed ASCCL algorithm has strong generalization and can adapt to the emotional migration of inter-ID and cross-ID. When incorporating the ASCCL into the single-stage method ICface can also obtain significant performance improvement. In the Inter-ID setting, compared with ICface itself, FAD, LSE-D, and CSIM have all improved to a certain extent, with FAD reduced from 6.795 to 6.672, LSE-D from 10.083 to 9.431, and CSIM from 0.775 to 0.801. Cross-ID is a more general and practical setting, and incorporating the ASCCL also achieves evident improvement on FAD, LSE-D, and CSIM of different expression manipulation as well as the average FAD, LSE-D, and CSIM as shown in Table 1", + "bbox": [ + 75, + 321, + 472, + 699 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To demonstrate the generalization ability of the trained ASCCL, we also present the performance comparisons on the RAVDESS [21] dataset without retraining ASCCL. As shown in Table 2, incorporating ASCCL can also obtain obvious improvement for different expression manipulation in both settings. when using the ICface baseline in the interID setting, it decreases the average FAD, LSE-D by 1.142, 0.436, and increases the average CSIM by 0.01. In the Cross-ID setting, it decreases the average FAD, LSE-D by 0.521, 1.226, and the average CSIM remains the same. Similar performance improvement is obtained when using the NED baseline. The experiment corroborates ASCCL's robustness across different methods and data domains.", + "bbox": [ + 75, + 703, + 472, + 900 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/8638923617c3cd2f8ebd6eb731c85ee1c73580f6949e179ca7def8f71704298c.jpg", + "image_caption": [ + "Figure 5. Qualitative comparisons of NED with and without the proposed ASCCL algorithm. The samples are selected from the MEAD dataset." + ], + "image_footnote": [], + "bbox": [ + 511, + 315, + 883, + 681 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.3.2 Qualitative Comparisons", + "text_level": 1, + "bbox": [ + 498, + 747, + 728, + 762 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In this section, we exhibit some visualization results of the baseline NED methodology, both with and without the ASCCL algorithm, as illustrated in Figure 5. Analogous to the quantitative metrics, we also dissect the qualitative comparisons from three dimensions. 1) Realism: The eye region tends to be more closed as a consequence of the NED [23] application, as exemplified in the third column of the second and fifth rows. Furthermore, the mouth region is distorted due to the imprecise prediction of the mouth shape as", + "bbox": [ + 496, + 763, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "7272", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/4e5e0ab32762417dcd85049e2e4fc2d89c885bd3505d5cbff85a8642dd3a7aab.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
SettingsEmotionsICfaceOurs (ICface)NEDOurs (NED)
FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑
Inter-IDNeutral9.8168.2090.7498.3027.2390.7622.0417.3760.8472.8107.5670.853
Angry7.0479.5040.7036.1829.4530.7113.2887.7570.8053.7227.6010.799
Disgusted8.6898.2950.7757.0668.6490.7834.1447.8220.7863.1948.1000.836
Fear8.4138.5230.7227.4068.6250.7412.6357.4520.8422.5887.8210.831
Happy8.4138.9020.7977.4037.9240.7973.7147.7420.7933.0256.6780.826
Sad8.0868.3460.7667.3377.0180.7812.5957.5600.8552.5257.0860.842
Surprised8.6367.5780.7727.4117.4020.7812.9807.2260.8483.4107.2990.824
Avg.8.4438.4800.7557.3018.0440.7653.0577.5620.8253.0397.4500.830
Cross-IDNeutral10.47810.7360.67710.3439.3020.6823.5587.8560.8203.1607.4580.813
Angry8.70412.4150.6468.24210.5220.7065.5468.0850.7664.8518.5130.739
Disgusted9.26011.8600.7178.94810.2340.6527.3888.1070.7417.4437.8480.689
Fear9.10611.2790.6499.06210.3820.7535.0088.1510.7494.1607.8420.799
Happy9.06111.1500.7389.0639.7060.6765.6488.0730.8044.9107.9510.796
Sad9.63911.3050.6669.0439.9160.6345.5888.0060.7264.8477.5450.741
Surprised9.71812.0280.6448.90310.3130.6775.1457.9620.7134.2847.5810.748
Avg.9.42411.5390.6778.90310.3130.6775.4128.0340.7604.8087.8200.761
", + "bbox": [ + 91, + 89, + 875, + 279 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "shown in the third column for the first rows. The ASCCL ameliorates this NED shortcoming by aligning the visual consistency between inputs and outputs, as demonstrated in the fourth column. 2) Emotional Similarity: Existing works fall short in manipulating facial expressions to communicate the emotions of the reference subject; they generally favor direct replication of facial components into the source, as depicted in the third column in the second, and fifth rows. The ASCCL, by maximizing the alignment of visual disparities between input and output, directs the model to prioritize the extraction of emotional information rather than merely duplicating facial components from the reference into the source, as demonstrated in the fourth column. By incorporating the ASCCL, the NED methodology is more proficient in preserving the source's contours while accomplishing emotional transference. 3) Lip-Audio Preserving Accuracy: The proposed DAAS is designed to focus on regions around with mouth area, which exhibits considerable changes in the input and output of the SFPEM model. Thus, the ASCCL can achieve consistency of the mouth shape by constraining the maximum consistency of the visual disparities for this particular region in the positive samples, as depicted in Figure 5. The results presented in the fourth column demonstrate a superior ability to retain the source's mouth shape compared to those in the third column. We will represent more visualization results of NED and ICface with and without ASCCL algorithm on the MEAD and RAVDESS dataset in the Supplementary materials. We also present some video comparisons for more direct comparison in the Supplementary materials", + "bbox": [ + 73, + 321, + 472, + 775 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3.3 User study", + "text_level": 1, + "bbox": [ + 76, + 789, + 207, + 806 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We conducted web-based user studies to compare the performance of NED with and without the ASCCL algorithm. The study comprises three segments corresponding to the previously mentioned metrics: realism, emotion similarity with the reference emotion, and mouth shape similarity with the source video, covering seven basic emotions.", + "bbox": [ + 75, + 809, + 468, + 901 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/3aca0c2ed52cf94a7f11624f8f16335546bfad5ae3b765bdd489024380b09eb7.jpg", + "table_caption": [ + "Table 2. Comparison results of FAD, CSIM, and LSE-D of NED, ICFACE with and without our ASCCL on the inter-Identification and cross-IDentification settings on the RAVDESS dataset." + ], + "table_footnote": [], + "table_body": "
EmotionRealismEmotion similarityMouth shape similarity
NEDASCCLNEDASCCLNEDASCCL
Neutral28%72%24%76%31%69%
Angry28%72%36%64%30%70%
Disgusted35%65%34%66%26%74%
Fear28%72%35%65%29%71%
Happy28%72%33%67%28%72%
Sad35%65%28%72%25%75%
Surprised30%70%27%73%24%76%
Avg.30%70%31%69%27%73%
", + "bbox": [ + 539, + 319, + 851, + 439 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 3. Realism, emotion similarity, and mouth shape similarity ratings of the user study on NED and our ASCCL.", + "bbox": [ + 500, + 439, + 890, + 465 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "For each emotion, we carefully selected 10 videos for both inter-identification and cross-identification settings, totaling 70 videos. Involving 25 participants, each participant was tasked with assessing the three aspects of each video. As detailed in Table 3, the inclusion of the ASCCL algorithm consistently outshines the baseline NED method across all seven emotions in all three metrics. On average, the integration of the ASCCL algorithm demonstrates significant improvement, achieving a $40\\%$ higher rating in realism, a $38\\%$ higher rating in emotion similarity, and an impressive $46\\%$ higher rating in mouth shape similarity compared to the NED baseline. Supplementary materials include user studies utilizing the ICface baseline on MEAD and employing both NED and ICface baselines on RAVDESS.", + "bbox": [ + 496, + 479, + 893, + 691 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.4. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 700, + 653, + 717 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In the ablation experiment section, we first investigate the effect of pre-training ASCCL with paired data on the final result. Following that, the pre-trained ASCCL is integrated into the NED, with an analysis of supervision on different results(3DMM or render image) and an examination of the impact of DAAS.", + "bbox": [ + 496, + 723, + 893, + 814 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.4.1 Analyses of ASCCL metric learning", + "text_level": 1, + "bbox": [ + 500, + 820, + 805, + 835 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our statistical analysis demonstrates an inherent spatially coherent correlation between the input and output of the SPFEM model. Even untrained, the ASCCL can approximate this correlation, as depicted in Figure 2. By pre", + "bbox": [ + 496, + 839, + 893, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "7273", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "training ASCCL with paired data, we enhance the ASCCL's ability to discern inherent visual consistency. As shown in Figure 6, there is a notable improvement in the similarity and correlation coefficients for positive samples. Fur", + "bbox": [ + 75, + 90, + 470, + 151 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d083bd48d1964216cda113f1e0c4eee88e1547e499409efd06946f202eac9a75.jpg", + "image_caption": [ + "(a)", + "Figure 6. (a) Average similarities and (b) Average Pearson correlation coefficients of the positive and negative samples after training the SCCL metric" + ], + "image_footnote": [], + "bbox": [ + 102, + 172, + 267, + 356 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c24500cebe7786f216d9e6eeba2d09184072b095d31e78308392d7e37553c214.jpg", + "image_caption": [ + "(b)" + ], + "image_footnote": [], + "bbox": [ + 282, + 172, + 454, + 356 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "thermore, we employ both trained and untrained ASCCL to guide the SPFEM model's training, as depicted in Table 4. Irrespective of whether the ASCCL has been pretrained, it can serve as a guide when integrated into the SFPEM model. The pre-trained ASCCL demonstrated superior performance to the untrained ASCCL on measures including FAD, LSE-D, and CSIM. This indicates that by utilizing paired data to train the ASCCL, we can more effectively capture the spatial coherent correlations between the SFPEM's input and output, thereby enhancing the model's guidance.", + "bbox": [ + 75, + 431, + 468, + 599 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/be612114a5e5868df50a93e5827ff21ba9e6188039f1b1b2e3db6603872594d2.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours untrained1.5099.4340.861
Ours trained1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours untrained4.3069.4580.784
Ours trained4.2649.2380.791
", + "bbox": [ + 114, + 614, + 429, + 694 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4.2 Analysis of supervision on different outputs", + "text_level": 1, + "bbox": [ + 76, + 731, + 433, + 746 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ASCCL can supervise either the intermediate 3DMM parameters or the final rendered images. In this section, we present two additional baselines that solely utilize the objective on the 3DMM parameters (Ours 3DMM) or final rendered images (Ours Image). As depicted in Table 5, incorporating the objective solely to either 3DMM parameters or images results in significant improvements across various metrics. Moreover, introducing the objective to both the 3DMM parameters and rendered images yields even greater improvement.", + "bbox": [ + 75, + 753, + 468, + 904 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/1b2f0aea38b44c4093496f0d0912fab59f45ae6f7be2cf376b7bc7826e7263f5.jpg", + "table_caption": [ + "Table 4. The performance of ASSCL with and without training." + ], + "table_footnote": [], + "table_body": "
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours 3DMM1.3329.3880.887
Ours image1.3139.3940.889
Ours1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours 3DMM4.3099.3110.787
Ours image4.2769.3210.785
Ours4.2649.2380.791
", + "bbox": [ + 542, + 88, + 849, + 189 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4.3 Analysis of Disparity-Aware Adaptive Strategy", + "text_level": 1, + "bbox": [ + 500, + 258, + 879, + 273 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/da5e85d91a75e6df22ead0b3f8956e1e3e2d6b24a2403890e0cf05c6ae2ae205.jpg", + "table_caption": [ + "Table 5. Comparison results of average FAD, CSIM, and LSE-D of NED, with supervision on different outputs." + ], + "table_footnote": [], + "table_body": "
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours w/o DAAS1.3429.4020.885
Ours DAAS1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours w/o DAAS4.3189.3300.786
Ours DAAS4.2649.2380.791
", + "bbox": [ + 534, + 297, + 857, + 378 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 6. Comparison results of average FAD, CSIM, and LSE-D of NED, with or w/o DAAS", + "bbox": [ + 498, + 390, + 890, + 417 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Through empirical analysis, we observed that visual disparities are sensitive to regions. We employed DAAS to direct the ASCCL's attention toward those challenging regions, thereby enhancing the consistency of mouth movements between input and output. In this section, We examined the influence of incorporating DAAS into the outcome. As depicted in Table 6, in the absence of DAAS, our approach outperforms NED across all metrics. Moreover, when DAAS is integrated into our method, ASCCL achieves even more optimal results by dynamically adapting the learning strategy to different regions.", + "bbox": [ + 496, + 426, + 890, + 592 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 606, + 617, + 619 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we propose an adaptive spatial coherent correlation learning (ASCCL) algorithm to investigate the inherent visual correlations between the SPFEM model's input and output to construct paired supervision to improve facial expression manipulation and meanwhile better preserve the facial animation of speech content. It first characterizes the visual disparities, and then constrains the visual disparities in adjacent local regions of the input image to align with those in corresponding adjacent regions of the output image from the SPFEM model, together with a disparity-aware adaptive strategy to adaptively learn based on the visual disparity of each adjacent region. ASCCL is implemented by a plug-and-play loss that can be seamlessly integrated into any advanced methods to facilitate SPFEM performance. We conduct extensive experiments that integrate ASCCL to two advanced SPFEM models and carry out variant quantitative and qualitative comparisons as well as user studies to demonstrate the effectiveness.", + "bbox": [ + 496, + 628, + 890, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "7274", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 106 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Volker Blanz and Thomas Vetter. A morphable model for the synthesis of 3d faces. In Proceedings of the 26th annual conference on Computer graphics and interactive techniques, pages 187-194, 1999.", + "[2] Volker Blanz and Thomas Vetter. A morphable model for the synthesis of 3d faces. 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Springer, 2022.", + "[35] Bingyuan Zhang, Xulong Zhang, Ning Cheng, Jun Yu, Jing Xiao, and Jianzong Wang. Emotalker: Emotionally editable talking face generation via diffusion model. In 2024 IEEE International Conference on Acoustics, Speech, and Signal Processing, 2024.", + "[36] Jun-Yan Zhu, Taesung Park, Phillip Isola, and Alexei A Efros. Unpaired image-to-image translation using cycle-consistent adversarial networks. In Proceedings of the IEEE international conference on computer vision, pages 2223-2232, 2017." + ], + "bbox": [ + 503, + 92, + 890, + 367 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "7276", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/199bb55b-1c98-451b-b065-6d0fccbafb25_model.json b/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/199bb55b-1c98-451b-b065-6d0fccbafb25_model.json new file mode 100644 index 0000000000000000000000000000000000000000..ff80961ab1333202289bc4180e2d30a45fe4db60 --- /dev/null +++ b/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/199bb55b-1c98-451b-b065-6d0fccbafb25_model.json @@ -0,0 +1,2090 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.088, + 0.13, + 0.882, + 0.177 + ], + "angle": 0, + "content": "Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation" + }, + { + "type": "text", + "bbox": [ + 0.202, + 0.205, + 0.321, + 0.221 + ], + "angle": 0, + "content": "Tianshui Chen" + }, + { + "type": "text", + "bbox": [ + 0.163, + 0.226, + 0.361, + 0.239 + ], + "angle": 0, + "content": "tianshuichen@gmail.com" + }, + { + "type": "text", + "bbox": [ + 0.461, + 0.205, + 0.562, + 0.221 + ], + "angle": 0, + "content": "Jianman Lin" + }, + { + "type": "text", + "bbox": [ + 0.41, + 0.226, + 0.615, + 0.239 + ], + "angle": 0, + "content": "linjianmancjx@gmail.com" + }, + { + "type": "text", + "bbox": [ + 0.68, + 0.205, + 0.794, + 0.223 + ], + "angle": 0, + "content": "Zhijing Yang*" + }, + { + "type": "text", + "bbox": [ + 0.663, + 0.226, + 0.807, + 0.239 + ], + "angle": 0, + "content": "yzhj@gdut.edu.cn" + }, + { + "type": "text", + "bbox": [ + 0.31, + 0.248, + 0.431, + 0.265 + ], + "angle": 0, + "content": "Chunmei Qing" + }, + { + "type": "text", + "bbox": [ + 0.299, + 0.269, + 0.443, + 0.282 + ], + "angle": 0, + "content": "qchem@scut.edu.cn" + }, + { + "type": "text", + "bbox": [ + 0.552, + 0.248, + 0.634, + 0.265 + ], + "angle": 0, + "content": "Liang Lin" + }, + { + "type": "text", + "bbox": [ + 0.515, + 0.268, + 0.667, + 0.282 + ], + "angle": 0, + "content": "linliang@ieee.org" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.317, + 0.314, + 0.333 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.349, + 0.473, + 0.773 + ], + "angle": 0, + "content": "Speech-preserving facial expression manipulation (SPFEM) aims to modify facial emotions while meticulously maintaining the mouth animation associated with spoken content. Current works depend on inaccessible paired training samples for the person, where two aligned frames exhibit the same speech content yet differ in emotional expression, limiting the SPFEM applications in real-world scenarios. In this work, we discover that speakers who convey the same content with different emotions exhibit highly correlated local facial animations, providing valuable supervision for SPFEM. To capitalize on this insight, we propose a novel adaptive spatial coherent correlation learning (ASCCL) algorithm, which models the aforementioned correlation as an explicit metric and integrates the metric to supervise manipulating facial expression and meanwhile better preserving the facial animation of spoken contents. To this end, it first learns a spatial coherent correlation metric, ensuring the visual disparities of adjacent local regions of the image belonging to one emotion are similar to those of the corresponding counterpart of the image belonging to another emotion. Recognizing that visual disparities are not uniform across all regions, we have also crafted a disparity-aware adaptive strategy that prioritizes regions that present greater challenges. During SPFEM model training, we construct the adaptive spatial coherent correlation metric between corresponding local regions of the input and output images as addition loss to supervise the generation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.47, + 0.901 + ], + "angle": 0, + "content": "*Zhijing Yang is the corresponding author. Tianshui Chen, Jianman Lin, and Zhijing Yang are with Guangdong University of Technology. Chunmei Qing is with South China University of Technology. Liang Lin is with Sun Yat-Sen University. This work was supported in part by National Natural Science Foundation of China (NSFC) under Grant No. 62206060, in Part by Natural Science Foundation of Guangdong Province (2022A1515011555, 2023A1515012568, 2023A1515012561), Guangdong Provincial Key Laboratory of Human Digital Twin (2022B1212010004), and in part by Guangzhou Basic and Applied Basic Research Foundation under Grant No. SL2022A04J01626." + }, + { + "type": "image", + "bbox": [ + 0.517, + 0.316, + 0.604, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.605, + 0.317, + 0.693, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.317, + 0.782, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.783, + 0.317, + 0.871, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.517, + 0.387, + 0.604, + 0.455 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.605, + 0.387, + 0.693, + 0.455 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.387, + 0.782, + 0.455 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.783, + 0.387, + 0.871, + 0.455 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.517, + 0.455, + 0.604, + 0.523 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.605, + 0.455, + 0.693, + 0.523 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.455, + 0.782, + 0.523 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.783, + 0.455, + 0.871, + 0.523 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.536, + 0.525, + 0.586, + 0.535 + ], + "angle": 0, + "content": "Reference" + }, + { + "type": "image_caption", + "bbox": [ + 0.631, + 0.525, + 0.666, + 0.535 + ], + "angle": 0, + "content": "Source" + }, + { + "type": "image_caption", + "bbox": [ + 0.724, + 0.525, + 0.75, + 0.535 + ], + "angle": 0, + "content": "NED" + }, + { + "type": "image_caption", + "bbox": [ + 0.807, + 0.525, + 0.845, + 0.534 + ], + "angle": 0, + "content": "ASCCL" + }, + { + "type": "image_footnote", + "bbox": [ + 0.5, + 0.534, + 0.892, + 0.588 + ], + "angle": 0, + "content": "Figure 1. Several examples are generated by the current advanced NED with and without the proposed ASCCL algorithm. Incorporating the ASCCL can better manipulate the expressions and meanwhile preserve mouth shapes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.605, + 0.895, + 0.665 + ], + "angle": 0, + "content": "process. We conduct extensive experiments on variant datasets, and the results demonstrate the effectiveness of the proposed ASCCL algorithm. Code is publicly available at https://github.com/jianmanlincjx/ASCCL" + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.684, + 0.633, + 0.699 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.704, + 0.892, + 0.87 + ], + "angle": 0, + "content": "Speech-preserving facial expression manipulation (SPFEM), which aims to manipulate facial emotions while preserving the mouth animations in static images or dynamic videos, can enhance human expressiveness and thus benefit variant applications including virtual avatars and film & television production. For example, it requires lots of effects and repeated remakes to capture an expected actor's emotions in a movie & shooting. In contrast, a robust SPFEM system can easily modify the facial emotions to achieve comparable performance in the post-production stage and thus is urgently expected." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Current SPFEM literature either predominantly previous face reenactment algorithms [10, 28] or harnesses decou" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7267" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.081, + 0.092, + 0.468, + 0.393 + ], + "angle": 0, + "content": "pled semantic representations equipped by cyclic consistency [23, 36]. The former category of works [10, 28] typically manipulates facial expressions through the exchange of latent codes [17] or facial action units [13], and employs the reference images as surrogate labels to construct frame-by-frame construction supervision. However, these surrogate images are not perfect representations of the desired outcomes and the reliance on them may lead to generating sub-optimal results. The latter approach [23] posits a one-to-one correspondence between images exhibiting varied emotional expressions and employs cyclic consistency for paired supervision. Despite achieving better performance, the global cyclical consistency constraint makes it difficult to capture alterations in fine-grained facial information under different emotions. Consequently, these methods either fail to accurately translate the intended emotions (as illustrated in the first and third examples in Figure 1) or do not maintain the original mouth animation tied to the spoken content (as evidenced in the first and second examples in Figure 1)." + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.398, + 0.468, + 0.699 + ], + "angle": 0, + "content": "To establish accurate information for additional supervisory guidance, we investigate a plausible and reasonable assumption: a single speaker articulating identical content across varied emotional states exhibits a high degree of correlation in local facial animations. Within the realm of the SPFEM task, we posit that there exists a strong correlation between adjacent local regions of the input images and their corresponding counterparts in the output images. For a more detailed analysis, we delve into the examination of similarities and correlation coefficients between corresponding local regions of the input and output images, and those between non-corresponding local regions of the input and output images. As depicted in Figure 2, there is a notable presence of high similarities and correlation coefficients for corresponding local regions. Conversely, the noncorresponding local regions demonstrate values approaching zero. These observations provide robust empirical support for the previously stated assumption and underscore the merit of modeling these correlations to facilitate SPFEM performance." + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.705, + 0.468, + 0.9 + ], + "angle": 0, + "content": "In this work, we design a novel adaptive spatial coherent correlation learning (ASCCL) algorithm, which discerns the correlations between adjacent local regions within images that display varying emotional states and incorporates these correlations as additional guidance to supervise the manipulation of expressions in a manner that is attuned to difficulty. Formally, we leverage visual disparities as a means to characterize the interactions between adjacent local regions, given that local motion disparities are critical to the realism of facial animations. Then, we formulate a spatial coherent correlation metric ensuring the visual disparities of adjacent local regions of the image belonging to one emotion are similar to those of the correspond" + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.092, + 0.89, + 0.286 + ], + "angle": 0, + "content": "ing counterpart of the image belonging to another emotion. Recognizing the variable complexity across different facial regions, we introduce a disparity-aware adaptive strategy, which preferentially weights more challenging regions with higher values while proportionally reducing the weight for less complex areas. During SPFEM model training, we establish a network of dense correlations between local regions of the input and output images, employing this adaptive spatially coherent correlation metric as an auxiliary supervision. ASCCL is trained using a set of paired data and can be used to construct supervision for any other persons to facilitate generating high-quality results in a plug-and-play manner." + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.288, + 0.89, + 0.499 + ], + "angle": 0, + "content": "The contributions can be summarized into three folds. Firstly, we introduce an adaptive spatial coherent correlation learning (ASCCL) algorithm, which learns the consistent correlations between input and generated images in terms of the visual disparities of adjacent local regions. It can be seamlessly integrated into current SPFEM methods to improve their performance in a plug-and-play manner. Secondly, we introduce a difficult-aware adaptive strategy that weights more challenging regions with higher constraints while proportionally reducing the weight for less complex areas. Lastly, we conduct extensive experiments that integrate the ASCCL algorithms into current advanced methods, demonstrating the effectiveness of the proposed ASCCL algorithm." + }, + { + "type": "title", + "bbox": [ + 0.504, + 0.513, + 0.647, + 0.529 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.538, + 0.89, + 0.749 + ], + "angle": 0, + "content": "Video-based face manipulation. To modify talking/moving faces, video-based face manipulation algorithms frequently employ conditionally Generative Adversarial Networks (GANs) [14, 19, 29, 31, 33] or 3DMM [2, 9, 11, 12, 27]. For example, GANimation [25] leverages adversarial learning conditioning on action unit [13] annotations to describe facial movements in a continuous manifold. [29] apply StyleGAN [18] to learn low-frequency information to accomplish temporal coherency. DSM [26] learns disentangled representation and controls facial expressions via semantic representation. SPFEM is more difficult than simple face manipulation since it requires not only modifying facial expressions but also retaining the facial motion of original speech contents." + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.75, + 0.89, + 0.9 + ], + "angle": 0, + "content": "Face reenactment. Facial reenactment, in which a specific actor imitates speech and expressions from a reference video [4, 8, 10, 28, 34] and other [35]. For example, ICface [28] controls the pose and expression with interpretable control signals such as head pose angles and action units. To create temporally consistent videos, Head2Head++ [10] employs a sequential generator and a customized dynamics discriminator. StyleHEAT [34] extends the latent code of StyleGAN [17] to aid in motion and expression generation and animation. SPFEM is similar to this task in expression" + }, + { + "type": "page_number", + "bbox": [ + 0.485, + 0.947, + 0.514, + 0.957 + ], + "angle": 0, + "content": "7268" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.09, + 0.104, + 0.268, + 0.324 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.281, + 0.103, + 0.465, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.327, + 0.47, + 0.356 + ], + "angle": 0, + "content": "Figure 2. (a) Average similarities and (b) Average Pearson correlation coefficients of the positive and negative samples." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.372, + 0.47, + 0.416 + ], + "angle": 0, + "content": "manipulation, but it also requires preserving mouth movement of original speech contents, making SPFEM a more difficult task." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.418, + 0.473, + 0.721 + ], + "angle": 0, + "content": "Speech-preserving facial expression manipulation. SPFEM seeks to alter the given source video to the desired emotion while keeping the voice content's facial animation. Previous research has adapted facial reenactment algorithms such as ICface [28] to this job. However, facial reenactment can keep both the expression and the mouth form, but not the speech substance. To accomplish this challenge, [23] propose combining the 3DMM parameters of source identification and target emotion. Despite making significant progress, these works lack paired supervision, resulting in sub-optimal performance in emotion manipulation and speech preservation. Different from the above-mentioned works, we present in-depth analyses about the spatial coherent correlations across images belonging to different emotions and find there exist strong correlations between adjacent local regions of the input image of one emotion and their corresponding counterparts in the output image of another emotion. We propose to learn adaptive spatial coherent correlations to construct additional supervision for SPFEM." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.737, + 0.195, + 0.753 + ], + "angle": 0, + "content": "3. Motivation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.764, + 0.47, + 0.856 + ], + "angle": 0, + "content": "As discussed above, we make a plausible and reasonable assumption that a single speaker articulating identical content across varied emotional states exhibits a high degree of correlation in local facial animations. To present a more in-depth and direct analysis, we further conduct statistical experiments to validate this assumption." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Formally, given two images of the same speaker expressing the same content with two different emotions, denoted as \\( x \\) and \\( y \\), we use the output of the last convolution layer" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.091, + 0.895, + 0.168 + ], + "angle": 0, + "content": "of pre-trained network [7] to compute their feature \\( x^{f} \\) and \\( y^{f} \\). Here, we use visual disparity to denote the relationship of regions at locations \\( i \\) and \\( j \\), and the similarity between visual disparities of corresponding and non-corresponding adjacent local regions, formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.603, + 0.174, + 0.892, + 0.202 + ], + "angle": 0, + "content": "\\[\ns _ {i \\rightarrow j} ^ {p} = \\varphi \\left(x _ {i \\rightarrow j} ^ {f}, y _ {i \\rightarrow j} ^ {f}\\right) \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.603, + 0.196, + 0.789, + 0.22 + ], + "angle": 0, + "content": "\\[\n\\mathbf {s} _ {i \\rightarrow k} ^ {n} = \\varphi (x _ {i \\rightarrow j} ^ {f}, y _ {i \\rightarrow k, k \\neq j} ^ {f})\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.226, + 0.895, + 0.576 + ], + "angle": 0, + "content": "\\(x_{i\\rightarrow j}^{f}\\) and \\(y_{i\\rightarrow j}^{f}\\) denote visual disparities of regions \\(i\\) and \\(j\\) of the images \\(x\\) and \\(y\\). \\(\\varphi\\) represents the cosine similarity function. For each emotion pair, we retrieve thousands of corresponding and non-corresponding adjacent local regions and compute their average similarities. As shown in Figure 2 (a), we present the average similarities of corresponding and non-corresponding adjacent local regions according to the emotion pairs of neural to other six emotions. We find the average similarities of the non-corresponding adjacent local regions approach 0, and that of the corresponding adjacent local regions range from 0.43 to 0.49. Moreover, we further compute Pearson correlation coefficients [6] between visual disparities of visual disparities of corresponding and non-corresponding adjacent local regions. Similarly, we use thousands of corresponding and non-corresponding adjacent local regions and compute their average Pearson correlation coefficients. As presented in Figure 2 (b), a similar phenomenon is observed. These results suggest there exist strong correlations between the corresponding adjacent local regions between two images expressing the same content while differing in emotions. Thus, it is worth investigating to learn the correlations and integrate the correlations to facilitate the SPFEM performance." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.588, + 0.593, + 0.603 + ], + "angle": 0, + "content": "4. Method" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.613, + 0.894, + 0.795 + ], + "angle": 0, + "content": "It first learns the spatially coherent correlation metric, ensuring the alignment between the visual disparity of adjacent local regions of the source input image and that of the corresponding counterpart of the output generated image. Then, it designs a disparity-aware adaptive strategy to weigh more challenging regions with higher values while reducing the weight for less complex regions. The ASCCL algorithm can be used to supervise generating visual contents, including intermediate results (e.g., 3DMM [1]) and final rendered images in a plug-and-play manner. An overall pipeline for incorporating ASCCL into the two-stage NED [23] method is illustrated in Figure 3." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.802, + 0.892, + 0.818 + ], + "angle": 0, + "content": "4.1. Spatial Coherent Correlation Metric Learning" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.894, + 0.901 + ], + "angle": 0, + "content": "As suggested in Section 3, there inherently exist strong correlations between adjacent regions of two images that one speaker expresses the same content while differing in different emotions. Indeed, we can further strengthen the correlations by learning the spatial coherent correlation (SCC)" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7269" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.159, + 0.089, + 0.817, + 0.317 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.318, + 0.895, + 0.388 + ], + "angle": 0, + "content": "Figure 3. An overall pipeline of incorporating the proposed ASCCL algorithm to the current advanced NED [23] method to supervise generating the intermediate 3DMM meshes and final rendered images. It computes visual disparities of corresponding and non-corresponding local regions between the source and generated images, followed by the disparity-aware adaptive strategy to obtain the final loss to supervise final image generation. An identical process is performed on the source and generated 3DMM meshes to supervise the intermediate 3DMM mesh generation." + }, + { + "type": "image", + "bbox": [ + 0.079, + 0.395, + 0.475, + 0.469 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.472, + 0.471, + 0.555 + ], + "angle": 0, + "content": "Figure 4. An illustration of spatial coherent correlation metric learning. It retrieves the corresponding adjacent local regions of the input and output images as positive samples and the noncorresponding counterparts as negative samples. The process is performed in the feature maps to construct dense positive and negative samples to train the metric." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.576, + 0.47, + 0.669 + ], + "angle": 0, + "content": "metric using paired data, which can assign a higher value to the correlation between corresponding adjacent regions and assign a smaller value to the correlation between noncorresponding counterparts. In this way, it can provide better-synchronized signals to supervise the generation process. Here, we introduce the SCC metric learning in detail." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.671, + 0.471, + 0.853 + ], + "angle": 0, + "content": "Formally, given two images of the same speaker expressing the same content with two different emotions, we need to extract corresponding regions \\(i\\) and \\(j\\) of both two images. However, pose bias typically exists between these two images, potentially compromising the calculation accuracy. To address this issue, we first introduce a pose alignment module that extracts landmark coordinates using a pre-trained model in the OpenCV library for both two images and utilizes these coordinates to compute an affine transformation matrix. This matrix is subsequently applied to align the pose information between the two images and obtain two images \\(x\\) and \\(y\\) that ensure geometric correspondence." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Figure 4 exhibits the detailed computation process of the SCC metric. Owing to the locality and translation invariance characteristics of convolutional neural networks" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.395, + 0.895, + 0.502 + ], + "angle": 0, + "content": "[7, 15], the mapping of pixels in the feature space back to the original image is approximately equivalent to a local region, and as the depth of the network increases, the receptive field also expands. Leveraging these characteristics, we employ the output of multiple convolutional layers to obtain the multi-scale features. Formally, we can extract the feature of layer \\(l\\) as:" + }, + { + "type": "equation", + "bbox": [ + 0.651, + 0.507, + 0.891, + 0.534 + ], + "angle": 0, + "content": "\\[\nx ^ {f, l} = \\phi^ {l} (x) \\tag {2}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.655, + 0.53, + 0.739, + 0.547 + ], + "angle": 0, + "content": "\\[\ny ^ {f, l} = \\phi^ {l} (y)\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.555, + 0.892, + 0.632 + ], + "angle": 0, + "content": "Here, \\(\\phi^l (\\cdot)\\) is feature extractor for layer \\(l\\). We adopt the Arcface network [7], and use the output of four convolutional layers with dimension decline and thus \\(l\\in [1,2,3,4]\\). Given two regions \\(i\\) and \\(j\\), we compute the visual disparity using a mapping of the feature difference, denoted as:" + }, + { + "type": "equation", + "bbox": [ + 0.618, + 0.638, + 0.891, + 0.666 + ], + "angle": 0, + "content": "\\[\nx _ {i \\rightarrow j} ^ {f, l} = f \\left(x _ {i} ^ {f, l} - x _ {j} ^ {f, l}\\right) \\tag {3}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.623, + 0.661, + 0.771, + 0.682 + ], + "angle": 0, + "content": "\\[\ny _ {i \\rightarrow j} ^ {f, l} = f (y _ {i} ^ {f, l} - y _ {j} ^ {f, l})\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.892, + 0.765 + ], + "angle": 0, + "content": "where \\( f(\\cdot) \\) denotes a mapping function and it is implemented using two stacked fully-connected layers cooperated with the rectified linear unit non-linear function. Inspired by the recent progress in previous works [3, 16, 22, 32], we define an identical contrastive loss, formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.51, + 0.782, + 0.892, + 0.848 + ], + "angle": 0, + "content": "\\[\n\\ell_ {x y} ^ {l, i \\rightarrow j} = \\frac {\\exp \\left(\\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow j} ^ {f , l}}{\\tau}\\right)}{\\exp \\left(\\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow j} ^ {f , l}}{\\tau}\\right) + \\exp \\left(\\sum_ {k = 1 , k! = j} ^ {m} \\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow k} ^ {f , l}}{\\tau}\\right)} \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.895, + 0.903 + ], + "angle": 0, + "content": "where \\(\\tau\\) stands for a temperature hyper-parameter set to 0.07 by default. The final loss can be defined as the summation of all image pairs, corresponding region pairs, and four" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7270" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.224, + 0.106 + ], + "angle": 0, + "content": "layers, formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.184, + 0.116, + 0.47, + 0.15 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {s c c l} = \\sum_ {l = 1} \\sum_ {i, j} \\sum_ {x, y} \\ell_ {x y} ^ {l, i \\rightarrow j} \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.16, + 0.47, + 0.22 + ], + "angle": 0, + "content": "By minimizing losses through backpropagation, we can align the visual disparities of \\( y \\) to \\( x \\) with different emotions, and thus provide visual consistency correlations to supervise SPFEM model training." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.229, + 0.383, + 0.245 + ], + "angle": 0, + "content": "4.2. Disparity-Aware Adaptive Strategy" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.252, + 0.47, + 0.477 + ], + "angle": 0, + "content": "Once the SCCL metric is learned, we can use to \\(\\mathcal{L}_{sccl}\\) loss between the input source (source 3DMM) and output generated (generated 3DMM) images as additional supervision. Here, we observe a notable phenomenon that the complexity varies across different facial regions. For example, it is more complex and challenging for the mouth regions as it change dramatically when the speaker is talking. In contrast, when the regions are positioned at the cheek area, the visual disparity is reduced, promoting a faster convergence. This underscores the region-specific sensitivity of visual disparity. Consequently, by enabling the SCC metric to independently discern and dynamically modulate learning strategies for specific regions, we can enhance the extraction of spatially coherent correlation information in an adaptive manner." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.479, + 0.47, + 0.645 + ], + "angle": 0, + "content": "Inspired by the idea of [20], DAAS is engineered to enable the SCC metric to discern this variability and tailor its learning strategies based on the characteristics of the regions, prioritizing those with higher learning complexity. Specifically, when the visual disparity \\( x_{i\\rightarrow j}^{f,l} \\) is larger, this region is deemed a challenging region, to which we assign a larger weight value. Conversely, when \\( x_{i\\rightarrow j}^{f,l} \\) is small, it is considered a simple region that can achieve rapid convergence, we reduce the weight for those simple regions. To this end, we propose to assign different weights according to the visual disparity, formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.184, + 0.653, + 0.469, + 0.675 + ], + "angle": 0, + "content": "\\[\nw _ {i j} ^ {l} = \\lambda \\cdot \\operatorname {s i g m o i d} \\left(x _ {i \\rightarrow j} ^ {f, l}\\right) ^ {r} \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.684, + 0.469, + 0.759 + ], + "angle": 0, + "content": "where \\( w_{ij}^{l} \\) represents the weight value of adjacent regions \\( i \\rightarrow j \\) for images \\( x \\) and \\( y \\) at the feature map layer \\( l \\). \\( \\lambda \\) and \\( r \\) are hyper-parameters, both of which are set to 2 to ensure a reasonable weight. The final loss function can be defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.163, + 0.768, + 0.469, + 0.802 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {a s c c l} = \\sum_ {l = 1} \\sum_ {i, j} \\sum_ {x, y} w _ {i j} ^ {l} \\cdot \\ell_ {x y} ^ {l, i \\rightarrow j} \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.469, + 0.902 + ], + "angle": 0, + "content": "Current SPFEM algorithms can be divided into two types. The first involves a two-stage generation: initially creating 3DMM parameters and then using them to render final images [23]. The second method directly produces rendered images [28]. Visual information here refers to either the 3DMM parameters or the final images. \\(\\mathcal{L}_{asccl}\\) can be used" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.152 + ], + "angle": 0, + "content": "for both these two types of algorithms as shown in Figure 3. Due to page limit, we present more implementation details, including network architectures, integration to current NED and ICface method, and training details." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.168, + 0.632, + 0.185 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.193, + 0.596, + 0.208 + ], + "angle": 0, + "content": "5.1. Dataset" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.217, + 0.892, + 0.458 + ], + "angle": 0, + "content": "We performed experiments on the MEAD dataset [30], which contains 60 speakers, and each speaker records 30 videos in each emotional state (i.e., neutral, happy, angry, surprised, fear, sad, and disgusted). Here, we selected videos of 36 speakers that have 7,560 videos to train the ASCCL algorithm. To evaluate the SPFEM model's performance, we select 6 non-overlapped speakers (M003, M009, W029, M012, M030, and W015) that have 1,260 videos. We randomly selected \\(90\\%\\) as the training set and the rest \\(10\\%\\) as the test set similar to previous works [23]. We additionally employ the ASCCL algorithm on the well-established RAVDESS dataset [21] without the need for retraining. Specifically, we focus on 6 speakers (actors 1-6) encompassing 168 videos. Similarly, \\(90\\%\\) of the videos are randomly chosen for the training set, while the remaining \\(10\\%\\) constitute the test set." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.47, + 0.691, + 0.484 + ], + "angle": 0, + "content": "5.2. Evaluation Protocol" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.493, + 0.892, + 0.735 + ], + "angle": 0, + "content": "In this work, we use these metrics for evaluation: 1) Frechet Arcface Distance (FAD) gauges video realism by comparing feature vectors of generated and real videos using advanced face recognition technology [7]. Lower FAD values indicate better realism. 2) Cosine Similarity (CSIM) assesses emotional similarity between generated and target emotional videos using a state-of-the-art expression recognition network, with higher CSIM values denoting greater similarity. 3) Lip Sync Error Distance (LSE-D) [24] evaluates lip-audio accuracy using a pre-trained model [5] to measure the disparities between lip and audio representations, with smaller LSE-D indicates a higher lip-audio accuracy. We present the results of two settings: inter-identification, where emotion reference and source video share the same speaker, and cross-identification, involving different speakers." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.747, + 0.808, + 0.763 + ], + "angle": 0, + "content": "5.3. Comparison with Baseline Methods" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.77, + 0.738, + 0.786 + ], + "angle": 0, + "content": "5.3.1 Quantitative Comparisons" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We first present the performance comparisons on MEAD in Table 1. When ASCCL is integrated into NED, the resulting image sequences are greatly improved in FAD, LSE-D, and CSIM. In the Cross-ID setting, compared with NED itself, FAD, LSE-D, and CSIM have all improved to a certain extent, with FAD reduced from 4.448 to 4.264, LSE-D from 9.906 to 9.238, and CSIM from 0.773 to 0.791. Among" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.514, + 0.957 + ], + "angle": 0, + "content": "7271" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.094, + 0.09, + 0.877, + 0.28 + ], + "angle": 0, + "content": "
SettingsEmotionsICfaceOurs (ICface)NEDOurs (NED)
FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑
Inter-IDNeutral7.1149.7600.7797.1589.3820.7810.9069.2640.8830.8919.1130.911
Angry6.42010.4830.7416.1959.7660.8032.1779.5790.8021.1959.5500.896
Disgusted7.38310.4330.8056.2659.2660.8093.8389.1280.7721.6799.4160.854
Fear6.5679.8550.7546.6989.4810.8001.65910.1720.8481.33010.0390.900
Happy6.21310.1800.7756.1919.5560.8371.9399.1370.8391.3268.9750.930
Sad7.30110.0170.7556.7279.2930.7792.5389.0740.8121.1628.9060.906
Surprised6.5679.8510.8177.4709.2710.7951.7009.8210.8641.0569.3820.902
Avg.6.79510.0830.7756.6729.4310.8012.1089.4540.8311.2349.3400.900
Cross-IDNeutral10.56011.2260.7059.74510.6040.6712.0229.8120.8411.8659.1340.852
Angry9.47011.0730.6489.27110.4560.6934.8519.9040.7174.8539.2390.748
Disgusted9.23011.1840.6379.32310.3380.7645.09410.1210.7914.8409.3470.814
Fear9.12211.2040.7279.27310.2210.7294.9839.7410.7504.8209.2390.761
Happy8.49311.3220.7179.50510.4210.7933.9199.9360.8423.3839.1780.866
Sad10.36411.5260.6649.71010.3140.6645.66510.1790.6915.4759.4270.720
Surprised9.54111.1330.7219.53410.2730.7664.6009.6460.7804.6159.1050.779
Avg.9.54011.2380.6889.48010.3750.7264.4489.9060.7734.2649.2380.791
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.28, + 0.892, + 0.308 + ], + "angle": 0, + "content": "Table 1. Comparison results of FAD, CSIM, and LSE-D of NED, ICFACE with and without our ASCCL on the inter-Identification and cross-IDentification settings on the MEAD dataset." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.322, + 0.473, + 0.7 + ], + "angle": 0, + "content": "them, the LSE-D has seen significant improvements, and these notable advancements in the LSE-D metric can be attributed to ASCCL's pivotal role in supervising the training of the SPFEM model. This supervision accentuates the intrinsic visual correlations between the SPFEM model's input and output, ensuring the visual disparity of the input and output align closely thereby enhancing consistency in mouth shape modifications related to emotion. Additionally, the betterment in FAD and CSIM further attests that ASCCL not only maintains but can also elevate the model's training quality, steering it towards superior optimization. In the inter-ID setting, these three indicators are also improved to a certain extent, indicating that the proposed ASCCL algorithm has strong generalization and can adapt to the emotional migration of inter-ID and cross-ID. When incorporating the ASCCL into the single-stage method ICface can also obtain significant performance improvement. In the Inter-ID setting, compared with ICface itself, FAD, LSE-D, and CSIM have all improved to a certain extent, with FAD reduced from 6.795 to 6.672, LSE-D from 10.083 to 9.431, and CSIM from 0.775 to 0.801. Cross-ID is a more general and practical setting, and incorporating the ASCCL also achieves evident improvement on FAD, LSE-D, and CSIM of different expression manipulation as well as the average FAD, LSE-D, and CSIM as shown in Table 1" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.704, + 0.473, + 0.901 + ], + "angle": 0, + "content": "To demonstrate the generalization ability of the trained ASCCL, we also present the performance comparisons on the RAVDESS [21] dataset without retraining ASCCL. As shown in Table 2, incorporating ASCCL can also obtain obvious improvement for different expression manipulation in both settings. when using the ICface baseline in the interID setting, it decreases the average FAD, LSE-D by 1.142, 0.436, and increases the average CSIM by 0.01. In the Cross-ID setting, it decreases the average FAD, LSE-D by 0.521, 1.226, and the average CSIM remains the same. Similar performance improvement is obtained when using the NED baseline. The experiment corroborates ASCCL's robustness across different methods and data domains." + }, + { + "type": "image", + "bbox": [ + 0.513, + 0.316, + 0.885, + 0.683 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.691, + 0.892, + 0.731 + ], + "angle": 0, + "content": "Figure 5. Qualitative comparisons of NED with and without the proposed ASCCL algorithm. The samples are selected from the MEAD dataset." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.748, + 0.729, + 0.763 + ], + "angle": 0, + "content": "5.3.2 Qualitative Comparisons" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In this section, we exhibit some visualization results of the baseline NED methodology, both with and without the ASCCL algorithm, as illustrated in Figure 5. Analogous to the quantitative metrics, we also dissect the qualitative comparisons from three dimensions. 1) Realism: The eye region tends to be more closed as a consequence of the NED [23] application, as exemplified in the third column of the second and fifth rows. Furthermore, the mouth region is distorted due to the imprecise prediction of the mouth shape as" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7272" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.093, + 0.09, + 0.877, + 0.28 + ], + "angle": 0, + "content": "
SettingsEmotionsICfaceOurs (ICface)NEDOurs (NED)
FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑
Inter-IDNeutral9.8168.2090.7498.3027.2390.7622.0417.3760.8472.8107.5670.853
Angry7.0479.5040.7036.1829.4530.7113.2887.7570.8053.7227.6010.799
Disgusted8.6898.2950.7757.0668.6490.7834.1447.8220.7863.1948.1000.836
Fear8.4138.5230.7227.4068.6250.7412.6357.4520.8422.5887.8210.831
Happy8.4138.9020.7977.4037.9240.7973.7147.7420.7933.0256.6780.826
Sad8.0868.3460.7667.3377.0180.7812.5957.5600.8552.5257.0860.842
Surprised8.6367.5780.7727.4117.4020.7812.9807.2260.8483.4107.2990.824
Avg.8.4438.4800.7557.3018.0440.7653.0577.5620.8253.0397.4500.830
Cross-IDNeutral10.47810.7360.67710.3439.3020.6823.5587.8560.8203.1607.4580.813
Angry8.70412.4150.6468.24210.5220.7065.5468.0850.7664.8518.5130.739
Disgusted9.26011.8600.7178.94810.2340.6527.3888.1070.7417.4437.8480.689
Fear9.10611.2790.6499.06210.3820.7535.0088.1510.7494.1607.8420.799
Happy9.06111.1500.7389.0639.7060.6765.6488.0730.8044.9107.9510.796
Sad9.63911.3050.6669.0439.9160.6345.5888.0060.7264.8477.5450.741
Surprised9.71812.0280.6448.90310.3130.6775.1457.9620.7134.2847.5810.748
Avg.9.42411.5390.6778.90310.3130.6775.4128.0340.7604.8087.8200.761
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.28, + 0.892, + 0.308 + ], + "angle": 0, + "content": "Table 2. Comparison results of FAD, CSIM, and LSE-D of NED, ICFACE with and without our ASCCL on the inter-Identification and cross-IDentification settings on the RAVDESS dataset." + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.322, + 0.473, + 0.776 + ], + "angle": 0, + "content": "shown in the third column for the first rows. The ASCCL ameliorates this NED shortcoming by aligning the visual consistency between inputs and outputs, as demonstrated in the fourth column. 2) Emotional Similarity: Existing works fall short in manipulating facial expressions to communicate the emotions of the reference subject; they generally favor direct replication of facial components into the source, as depicted in the third column in the second, and fifth rows. The ASCCL, by maximizing the alignment of visual disparities between input and output, directs the model to prioritize the extraction of emotional information rather than merely duplicating facial components from the reference into the source, as demonstrated in the fourth column. By incorporating the ASCCL, the NED methodology is more proficient in preserving the source's contours while accomplishing emotional transference. 3) Lip-Audio Preserving Accuracy: The proposed DAAS is designed to focus on regions around with mouth area, which exhibits considerable changes in the input and output of the SFPEM model. Thus, the ASCCL can achieve consistency of the mouth shape by constraining the maximum consistency of the visual disparities for this particular region in the positive samples, as depicted in Figure 5. The results presented in the fourth column demonstrate a superior ability to retain the source's mouth shape compared to those in the third column. We will represent more visualization results of NED and ICface with and without ASCCL algorithm on the MEAD and RAVDESS dataset in the Supplementary materials. We also present some video comparisons for more direct comparison in the Supplementary materials" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.79, + 0.208, + 0.807 + ], + "angle": 0, + "content": "5.3.3 User study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.47, + 0.902 + ], + "angle": 0, + "content": "We conducted web-based user studies to compare the performance of NED with and without the ASCCL algorithm. The study comprises three segments corresponding to the previously mentioned metrics: realism, emotion similarity with the reference emotion, and mouth shape similarity with the source video, covering seven basic emotions." + }, + { + "type": "table", + "bbox": [ + 0.54, + 0.32, + 0.852, + 0.44 + ], + "angle": 0, + "content": "
EmotionRealismEmotion similarityMouth shape similarity
NEDASCCLNEDASCCLNEDASCCL
Neutral28%72%24%76%31%69%
Angry28%72%36%64%30%70%
Disgusted35%65%34%66%26%74%
Fear28%72%35%65%29%71%
Happy28%72%33%67%28%72%
Sad35%65%28%72%25%75%
Surprised30%70%27%73%24%76%
Avg.30%70%31%69%27%73%
" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.44, + 0.892, + 0.467 + ], + "angle": 0, + "content": "Table 3. Realism, emotion similarity, and mouth shape similarity ratings of the user study on NED and our ASCCL." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.481, + 0.895, + 0.693 + ], + "angle": 0, + "content": "For each emotion, we carefully selected 10 videos for both inter-identification and cross-identification settings, totaling 70 videos. Involving 25 participants, each participant was tasked with assessing the three aspects of each video. As detailed in Table 3, the inclusion of the ASCCL algorithm consistently outshines the baseline NED method across all seven emotions in all three metrics. On average, the integration of the ASCCL algorithm demonstrates significant improvement, achieving a \\(40\\%\\) higher rating in realism, a \\(38\\%\\) higher rating in emotion similarity, and an impressive \\(46\\%\\) higher rating in mouth shape similarity compared to the NED baseline. Supplementary materials include user studies utilizing the ICface baseline on MEAD and employing both NED and ICface baselines on RAVDESS." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.701, + 0.655, + 0.718 + ], + "angle": 0, + "content": "5.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.724, + 0.894, + 0.815 + ], + "angle": 0, + "content": "In the ablation experiment section, we first investigate the effect of pre-training ASCCL with paired data on the final result. Following that, the pre-trained ASCCL is integrated into the NED, with an analysis of supervision on different results(3DMM or render image) and an examination of the impact of DAAS." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.821, + 0.807, + 0.837 + ], + "angle": 0, + "content": "5.4.1 Analyses of ASCCL metric learning" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Our statistical analysis demonstrates an inherent spatially coherent correlation between the input and output of the SPFEM model. Even untrained, the ASCCL can approximate this correlation, as depicted in Figure 2. By pre" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7273" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.152 + ], + "angle": 0, + "content": "training ASCCL with paired data, we enhance the ASCCL's ability to discern inherent visual consistency. As shown in Figure 6, there is a notable improvement in the similarity and correlation coefficients for positive samples. Fur" + }, + { + "type": "image", + "bbox": [ + 0.103, + 0.174, + 0.268, + 0.357 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.165, + 0.357, + 0.185, + 0.368 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.173, + 0.455, + 0.357 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.355, + 0.357, + 0.374, + 0.368 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.379, + 0.47, + 0.419 + ], + "angle": 0, + "content": "Figure 6. (a) Average similarities and (b) Average Pearson correlation coefficients of the positive and negative samples after training the SCCL metric" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.433, + 0.47, + 0.601 + ], + "angle": 0, + "content": "thermore, we employ both trained and untrained ASCCL to guide the SPFEM model's training, as depicted in Table 4. Irrespective of whether the ASCCL has been pretrained, it can serve as a guide when integrated into the SFPEM model. The pre-trained ASCCL demonstrated superior performance to the untrained ASCCL on measures including FAD, LSE-D, and CSIM. This indicates that by utilizing paired data to train the ASCCL, we can more effectively capture the spatial coherent correlations between the SFPEM's input and output, thereby enhancing the model's guidance." + }, + { + "type": "table", + "bbox": [ + 0.115, + 0.615, + 0.43, + 0.695 + ], + "angle": 0, + "content": "
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours untrained1.5099.4340.861
Ours trained1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours untrained4.3069.4580.784
Ours trained4.2649.2380.791
" + }, + { + "type": "table_caption", + "bbox": [ + 0.085, + 0.695, + 0.461, + 0.709 + ], + "angle": 0, + "content": "Table 4. The performance of ASSCL with and without training." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.732, + 0.434, + 0.747 + ], + "angle": 0, + "content": "5.4.2 Analysis of supervision on different outputs" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.754, + 0.47, + 0.905 + ], + "angle": 0, + "content": "ASCCL can supervise either the intermediate 3DMM parameters or the final rendered images. In this section, we present two additional baselines that solely utilize the objective on the 3DMM parameters (Ours 3DMM) or final rendered images (Ours Image). As depicted in Table 5, incorporating the objective solely to either 3DMM parameters or images results in significant improvements across various metrics. Moreover, introducing the objective to both the 3DMM parameters and rendered images yields even greater improvement." + }, + { + "type": "table", + "bbox": [ + 0.544, + 0.089, + 0.851, + 0.19 + ], + "angle": 0, + "content": "
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours 3DMM1.3329.3880.887
Ours image1.3139.3940.889
Ours1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours 3DMM4.3099.3110.787
Ours image4.2769.3210.785
Ours4.2649.2380.791
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.201, + 0.892, + 0.23 + ], + "angle": 0, + "content": "Table 5. Comparison results of average FAD, CSIM, and LSE-D of NED, with supervision on different outputs." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.259, + 0.88, + 0.275 + ], + "angle": 0, + "content": "5.4.3 Analysis of Disparity-Aware Adaptive Strategy" + }, + { + "type": "table", + "bbox": [ + 0.535, + 0.299, + 0.859, + 0.38 + ], + "angle": 0, + "content": "
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours w/o DAAS1.3429.4020.885
Ours DAAS1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours w/o DAAS4.3189.3300.786
Ours DAAS4.2649.2380.791
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.391, + 0.892, + 0.418 + ], + "angle": 0, + "content": "Table 6. Comparison results of average FAD, CSIM, and LSE-D of NED, with or w/o DAAS" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.427, + 0.892, + 0.593 + ], + "angle": 0, + "content": "Through empirical analysis, we observed that visual disparities are sensitive to regions. We employed DAAS to direct the ASCCL's attention toward those challenging regions, thereby enhancing the consistency of mouth movements between input and output. In this section, We examined the influence of incorporating DAAS into the outcome. As depicted in Table 6, in the absence of DAAS, our approach outperforms NED across all metrics. Moreover, when DAAS is integrated into our method, ASCCL achieves even more optimal results by dynamically adapting the learning strategy to different regions." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.607, + 0.619, + 0.621 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.892, + 0.9 + ], + "angle": 0, + "content": "In this work, we propose an adaptive spatial coherent correlation learning (ASCCL) algorithm to investigate the inherent visual correlations between the SPFEM model's input and output to construct paired supervision to improve facial expression manipulation and meanwhile better preserve the facial animation of speech content. It first characterizes the visual disparities, and then constrains the visual disparities in adjacent local regions of the input image to align with those in corresponding adjacent regions of the output image from the SPFEM model, together with a disparity-aware adaptive strategy to adaptively learn based on the visual disparity of each adjacent region. ASCCL is implemented by a plug-and-play loss that can be seamlessly integrated into any advanced methods to facilitate SPFEM performance. We conduct extensive experiments that integrate ASCCL to two advanced SPFEM models and carry out variant quantitative and qualitative comparisons as well as user studies to demonstrate the effectiveness." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7274" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.176, + 0.107 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.088, + 0.116, + 0.47, + 0.176 + ], + "angle": 0, + "content": "[1] Volker Blanz and Thomas Vetter. A morphable model for the synthesis of 3d faces. In Proceedings of the 26th annual conference on Computer graphics and interactive techniques, pages 187-194, 1999." + }, + { + "type": "ref_text", + "bbox": [ + 0.088, + 0.178, + 0.472, + 0.237 + ], + "angle": 0, + "content": "[2] Volker Blanz and Thomas Vetter. A morphable model for the synthesis of 3d faces. 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In Proceedings of the IEEE international conference on computer vision, pages 2223-2232, 2017." + }, + { + "type": "list", + "bbox": [ + 0.504, + 0.093, + 0.892, + 0.368 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.516, + 0.956 + ], + "angle": 0, + "content": "7276" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/199bb55b-1c98-451b-b065-6d0fccbafb25_origin.pdf b/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/199bb55b-1c98-451b-b065-6d0fccbafb25_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..4a131e6b1fd11014ff28e6dc9ef4b91ef3b7f240 --- /dev/null +++ b/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/199bb55b-1c98-451b-b065-6d0fccbafb25_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:b56e40ba5b59ffa5b019b79d2efd9ae5c824608519ebc5d741aaadfc1a2baf11 +size 770267 diff --git a/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/full.md b/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/full.md new file mode 100644 index 0000000000000000000000000000000000000000..5aacb671a4b18ab74b6d4a41f21f1b982057d7f8 --- /dev/null +++ b/2024/Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation/full.md @@ -0,0 +1,317 @@ +# Learning Adaptive Spatial Coherent Correlations for Speech-Preserving Facial Expression Manipulation + +Tianshui Chen + +tianshuichen@gmail.com + +Jianman Lin + +linjianmancjx@gmail.com + +Zhijing Yang* + +yzhj@gdut.edu.cn + +Chunmei Qing + +qchem@scut.edu.cn + +Liang Lin + +linliang@ieee.org + +# Abstract + +Speech-preserving facial expression manipulation (SPFEM) aims to modify facial emotions while meticulously maintaining the mouth animation associated with spoken content. Current works depend on inaccessible paired training samples for the person, where two aligned frames exhibit the same speech content yet differ in emotional expression, limiting the SPFEM applications in real-world scenarios. In this work, we discover that speakers who convey the same content with different emotions exhibit highly correlated local facial animations, providing valuable supervision for SPFEM. To capitalize on this insight, we propose a novel adaptive spatial coherent correlation learning (ASCCL) algorithm, which models the aforementioned correlation as an explicit metric and integrates the metric to supervise manipulating facial expression and meanwhile better preserving the facial animation of spoken contents. To this end, it first learns a spatial coherent correlation metric, ensuring the visual disparities of adjacent local regions of the image belonging to one emotion are similar to those of the corresponding counterpart of the image belonging to another emotion. Recognizing that visual disparities are not uniform across all regions, we have also crafted a disparity-aware adaptive strategy that prioritizes regions that present greater challenges. During SPFEM model training, we construct the adaptive spatial coherent correlation metric between corresponding local regions of the input and output images as addition loss to supervise the generation + +*Zhijing Yang is the corresponding author. Tianshui Chen, Jianman Lin, and Zhijing Yang are with Guangdong University of Technology. Chunmei Qing is with South China University of Technology. Liang Lin is with Sun Yat-Sen University. This work was supported in part by National Natural Science Foundation of China (NSFC) under Grant No. 62206060, in Part by Natural Science Foundation of Guangdong Province (2022A1515011555, 2023A1515012568, 2023A1515012561), Guangdong Provincial Key Laboratory of Human Digital Twin (2022B1212010004), and in part by Guangzhou Basic and Applied Basic Research Foundation under Grant No. SL2022A04J01626. + +![](images/6b0e354072400563f18108657bd541a8a864b9721d2e4bed4fa3fef9b457a5a0.jpg) + +![](images/c187ee25cdee843d1d2774091926625fe525f9231db0cf37dfe1615beace3232.jpg) + +![](images/c33067396d0828d8874adfccbf049efacbb9f14802019e8e3fdf8c845df3b1ff.jpg) + +![](images/f5d26f30ce57d709891c6c743694456fac9c4ece3848358256da114121dac0c9.jpg) + +![](images/221bb87971eb216d18aa00d1346890382ebf39e35cbd74fde87fe02db22d3867.jpg) + +![](images/919ade3a423de243bda8832a60722e8eb47ef3680d4bdaa934ff8bb43e65f409.jpg) + +![](images/6ad9332ffcf2b620ff05b2a0045ff003af55d2ff0f8966df9042f115bf9acadb.jpg) + +![](images/44685ee7bae0c6ccf9bc8cb97d96cdc40d1f866a8e50fc3468ee353f910c59c5.jpg) + +Reference +![](images/e5359e6cf7e2b8ef940cc728db38a18a3677807bdb92837747b22dfc8992bf38.jpg) +Figure 1. Several examples are generated by the current advanced NED with and without the proposed ASCCL algorithm. Incorporating the ASCCL can better manipulate the expressions and meanwhile preserve mouth shapes. + +![](images/311f9eaea3c1f25d89a97f185c0484ae96c3861f20b2048a3641427d1ccb1aa2.jpg) +Source + +![](images/462339c19202073d974cd03df916240046ebaab09c5177d91e52ddbf9da18b20.jpg) +NED + +![](images/e383473bd08bc307742835f93f35de629d6479c73d5c4af30adeea86a051760e.jpg) +ASCCL + +process. We conduct extensive experiments on variant datasets, and the results demonstrate the effectiveness of the proposed ASCCL algorithm. Code is publicly available at https://github.com/jianmanlincjx/ASCCL + +# 1. Introduction + +Speech-preserving facial expression manipulation (SPFEM), which aims to manipulate facial emotions while preserving the mouth animations in static images or dynamic videos, can enhance human expressiveness and thus benefit variant applications including virtual avatars and film & television production. For example, it requires lots of effects and repeated remakes to capture an expected actor's emotions in a movie & shooting. In contrast, a robust SPFEM system can easily modify the facial emotions to achieve comparable performance in the post-production stage and thus is urgently expected. + +Current SPFEM literature either predominantly previous face reenactment algorithms [10, 28] or harnesses decou + +pled semantic representations equipped by cyclic consistency [23, 36]. The former category of works [10, 28] typically manipulates facial expressions through the exchange of latent codes [17] or facial action units [13], and employs the reference images as surrogate labels to construct frame-by-frame construction supervision. However, these surrogate images are not perfect representations of the desired outcomes and the reliance on them may lead to generating sub-optimal results. The latter approach [23] posits a one-to-one correspondence between images exhibiting varied emotional expressions and employs cyclic consistency for paired supervision. Despite achieving better performance, the global cyclical consistency constraint makes it difficult to capture alterations in fine-grained facial information under different emotions. Consequently, these methods either fail to accurately translate the intended emotions (as illustrated in the first and third examples in Figure 1) or do not maintain the original mouth animation tied to the spoken content (as evidenced in the first and second examples in Figure 1). + +To establish accurate information for additional supervisory guidance, we investigate a plausible and reasonable assumption: a single speaker articulating identical content across varied emotional states exhibits a high degree of correlation in local facial animations. Within the realm of the SPFEM task, we posit that there exists a strong correlation between adjacent local regions of the input images and their corresponding counterparts in the output images. For a more detailed analysis, we delve into the examination of similarities and correlation coefficients between corresponding local regions of the input and output images, and those between non-corresponding local regions of the input and output images. As depicted in Figure 2, there is a notable presence of high similarities and correlation coefficients for corresponding local regions. Conversely, the noncorresponding local regions demonstrate values approaching zero. These observations provide robust empirical support for the previously stated assumption and underscore the merit of modeling these correlations to facilitate SPFEM performance. + +In this work, we design a novel adaptive spatial coherent correlation learning (ASCCL) algorithm, which discerns the correlations between adjacent local regions within images that display varying emotional states and incorporates these correlations as additional guidance to supervise the manipulation of expressions in a manner that is attuned to difficulty. Formally, we leverage visual disparities as a means to characterize the interactions between adjacent local regions, given that local motion disparities are critical to the realism of facial animations. Then, we formulate a spatial coherent correlation metric ensuring the visual disparities of adjacent local regions of the image belonging to one emotion are similar to those of the correspond + +ing counterpart of the image belonging to another emotion. Recognizing the variable complexity across different facial regions, we introduce a disparity-aware adaptive strategy, which preferentially weights more challenging regions with higher values while proportionally reducing the weight for less complex areas. During SPFEM model training, we establish a network of dense correlations between local regions of the input and output images, employing this adaptive spatially coherent correlation metric as an auxiliary supervision. ASCCL is trained using a set of paired data and can be used to construct supervision for any other persons to facilitate generating high-quality results in a plug-and-play manner. + +The contributions can be summarized into three folds. Firstly, we introduce an adaptive spatial coherent correlation learning (ASCCL) algorithm, which learns the consistent correlations between input and generated images in terms of the visual disparities of adjacent local regions. It can be seamlessly integrated into current SPFEM methods to improve their performance in a plug-and-play manner. Secondly, we introduce a difficult-aware adaptive strategy that weights more challenging regions with higher constraints while proportionally reducing the weight for less complex areas. Lastly, we conduct extensive experiments that integrate the ASCCL algorithms into current advanced methods, demonstrating the effectiveness of the proposed ASCCL algorithm. + +# 2. Related Works + +Video-based face manipulation. To modify talking/moving faces, video-based face manipulation algorithms frequently employ conditionally Generative Adversarial Networks (GANs) [14, 19, 29, 31, 33] or 3DMM [2, 9, 11, 12, 27]. For example, GANimation [25] leverages adversarial learning conditioning on action unit [13] annotations to describe facial movements in a continuous manifold. [29] apply StyleGAN [18] to learn low-frequency information to accomplish temporal coherency. DSM [26] learns disentangled representation and controls facial expressions via semantic representation. SPFEM is more difficult than simple face manipulation since it requires not only modifying facial expressions but also retaining the facial motion of original speech contents. + +Face reenactment. Facial reenactment, in which a specific actor imitates speech and expressions from a reference video [4, 8, 10, 28, 34] and other [35]. For example, ICface [28] controls the pose and expression with interpretable control signals such as head pose angles and action units. To create temporally consistent videos, Head2Head++ [10] employs a sequential generator and a customized dynamics discriminator. StyleHEAT [34] extends the latent code of StyleGAN [17] to aid in motion and expression generation and animation. SPFEM is similar to this task in expression + +![](images/42431e3cfb51c347aae1284abf6f45d96ade88ed9e79ebb2e882800bf6371af0.jpg) +Figure 2. (a) Average similarities and (b) Average Pearson correlation coefficients of the positive and negative samples. + +![](images/b28a6e552bfa3e6164b8207a90af3c7d5dd6cdf695e9ced53ee8b6572bb17714.jpg) + +manipulation, but it also requires preserving mouth movement of original speech contents, making SPFEM a more difficult task. + +Speech-preserving facial expression manipulation. SPFEM seeks to alter the given source video to the desired emotion while keeping the voice content's facial animation. Previous research has adapted facial reenactment algorithms such as ICface [28] to this job. However, facial reenactment can keep both the expression and the mouth form, but not the speech substance. To accomplish this challenge, [23] propose combining the 3DMM parameters of source identification and target emotion. Despite making significant progress, these works lack paired supervision, resulting in sub-optimal performance in emotion manipulation and speech preservation. Different from the above-mentioned works, we present in-depth analyses about the spatial coherent correlations across images belonging to different emotions and find there exist strong correlations between adjacent local regions of the input image of one emotion and their corresponding counterparts in the output image of another emotion. We propose to learn adaptive spatial coherent correlations to construct additional supervision for SPFEM. + +# 3. Motivation + +As discussed above, we make a plausible and reasonable assumption that a single speaker articulating identical content across varied emotional states exhibits a high degree of correlation in local facial animations. To present a more in-depth and direct analysis, we further conduct statistical experiments to validate this assumption. + +Formally, given two images of the same speaker expressing the same content with two different emotions, denoted as $x$ and $y$ , we use the output of the last convolution layer + +of pre-trained network [7] to compute their feature $x^{f}$ and $y^{f}$ . Here, we use visual disparity to denote the relationship of regions at locations $i$ and $j$ , and the similarity between visual disparities of corresponding and non-corresponding adjacent local regions, formulated as: + +$$ +s _ {i \rightarrow j} ^ {p} = \varphi \left(x _ {i \rightarrow j} ^ {f}, y _ {i \rightarrow j} ^ {f}\right) \tag {1} +$$ + +$$ +\mathbf {s} _ {i \rightarrow k} ^ {n} = \varphi (x _ {i \rightarrow j} ^ {f}, y _ {i \rightarrow k, k \neq j} ^ {f}) +$$ + +$x_{i\rightarrow j}^{f}$ and $y_{i\rightarrow j}^{f}$ denote visual disparities of regions $i$ and $j$ of the images $x$ and $y$ . $\varphi$ represents the cosine similarity function. For each emotion pair, we retrieve thousands of corresponding and non-corresponding adjacent local regions and compute their average similarities. As shown in Figure 2 (a), we present the average similarities of corresponding and non-corresponding adjacent local regions according to the emotion pairs of neural to other six emotions. We find the average similarities of the non-corresponding adjacent local regions approach 0, and that of the corresponding adjacent local regions range from 0.43 to 0.49. Moreover, we further compute Pearson correlation coefficients [6] between visual disparities of visual disparities of corresponding and non-corresponding adjacent local regions. Similarly, we use thousands of corresponding and non-corresponding adjacent local regions and compute their average Pearson correlation coefficients. As presented in Figure 2 (b), a similar phenomenon is observed. These results suggest there exist strong correlations between the corresponding adjacent local regions between two images expressing the same content while differing in emotions. Thus, it is worth investigating to learn the correlations and integrate the correlations to facilitate the SPFEM performance. + +# 4. Method + +It first learns the spatially coherent correlation metric, ensuring the alignment between the visual disparity of adjacent local regions of the source input image and that of the corresponding counterpart of the output generated image. Then, it designs a disparity-aware adaptive strategy to weigh more challenging regions with higher values while reducing the weight for less complex regions. The ASCCL algorithm can be used to supervise generating visual contents, including intermediate results (e.g., 3DMM [1]) and final rendered images in a plug-and-play manner. An overall pipeline for incorporating ASCCL into the two-stage NED [23] method is illustrated in Figure 3. + +# 4.1. Spatial Coherent Correlation Metric Learning + +As suggested in Section 3, there inherently exist strong correlations between adjacent regions of two images that one speaker expresses the same content while differing in different emotions. Indeed, we can further strengthen the correlations by learning the spatial coherent correlation (SCC) + +![](images/829fc1f243459bd1f27ebb34763134787971bbcbf9666fcde42c384f36e756f5.jpg) +Figure 3. An overall pipeline of incorporating the proposed ASCCL algorithm to the current advanced NED [23] method to supervise generating the intermediate 3DMM meshes and final rendered images. It computes visual disparities of corresponding and non-corresponding local regions between the source and generated images, followed by the disparity-aware adaptive strategy to obtain the final loss to supervise final image generation. An identical process is performed on the source and generated 3DMM meshes to supervise the intermediate 3DMM mesh generation. + +![](images/e90aa919c89124e169d48b9fee978780ee9c2fefc580e8c353437939049e0ac6.jpg) +Figure 4. An illustration of spatial coherent correlation metric learning. It retrieves the corresponding adjacent local regions of the input and output images as positive samples and the noncorresponding counterparts as negative samples. The process is performed in the feature maps to construct dense positive and negative samples to train the metric. + +metric using paired data, which can assign a higher value to the correlation between corresponding adjacent regions and assign a smaller value to the correlation between noncorresponding counterparts. In this way, it can provide better-synchronized signals to supervise the generation process. Here, we introduce the SCC metric learning in detail. + +Formally, given two images of the same speaker expressing the same content with two different emotions, we need to extract corresponding regions $i$ and $j$ of both two images. However, pose bias typically exists between these two images, potentially compromising the calculation accuracy. To address this issue, we first introduce a pose alignment module that extracts landmark coordinates using a pre-trained model in the OpenCV library for both two images and utilizes these coordinates to compute an affine transformation matrix. This matrix is subsequently applied to align the pose information between the two images and obtain two images $x$ and $y$ that ensure geometric correspondence. + +Figure 4 exhibits the detailed computation process of the SCC metric. Owing to the locality and translation invariance characteristics of convolutional neural networks + +[7, 15], the mapping of pixels in the feature space back to the original image is approximately equivalent to a local region, and as the depth of the network increases, the receptive field also expands. Leveraging these characteristics, we employ the output of multiple convolutional layers to obtain the multi-scale features. Formally, we can extract the feature of layer $l$ as: + +$$ +x ^ {f, l} = \phi^ {l} (x) \tag {2} +$$ + +$$ +y ^ {f, l} = \phi^ {l} (y) +$$ + +Here, $\phi^l (\cdot)$ is feature extractor for layer $l$ . We adopt the Arcface network [7], and use the output of four convolutional layers with dimension decline and thus $l\in [1,2,3,4]$ . Given two regions $i$ and $j$ , we compute the visual disparity using a mapping of the feature difference, denoted as: + +$$ +x _ {i \rightarrow j} ^ {f, l} = f \left(x _ {i} ^ {f, l} - x _ {j} ^ {f, l}\right) \tag {3} +$$ + +$$ +y _ {i \rightarrow j} ^ {f, l} = f (y _ {i} ^ {f, l} - y _ {j} ^ {f, l}) +$$ + +where $f(\cdot)$ denotes a mapping function and it is implemented using two stacked fully-connected layers cooperated with the rectified linear unit non-linear function. Inspired by the recent progress in previous works [3, 16, 22, 32], we define an identical contrastive loss, formulated as: + +$$ +\ell_ {x y} ^ {l, i \rightarrow j} = \frac {\exp \left(\frac {x _ {i \rightarrow j} ^ {f , l} \cdot y _ {i \rightarrow j} ^ {f , l}}{\tau}\right)}{\exp \left(\frac {x _ {i \rightarrow j} ^ {f , l} \cdot y _ {i \rightarrow j} ^ {f , l}}{\tau}\right) + \exp \left(\sum_ {k = 1 , k! = j} ^ {m} \frac {x _ {i \rightarrow j} ^ {f , l} \cdot y _ {i \rightarrow k} ^ {f , l}}{\tau}\right)} \tag {4} +$$ + +where $\tau$ stands for a temperature hyper-parameter set to 0.07 by default. The final loss can be defined as the summation of all image pairs, corresponding region pairs, and four + +layers, formulated as: + +$$ +\mathcal {L} _ {s c c l} = \sum_ {l = 1} \sum_ {i, j} \sum_ {x, y} \ell_ {x y} ^ {l, i \rightarrow j} \tag {5} +$$ + +By minimizing losses through backpropagation, we can align the visual disparities of $y$ to $x$ with different emotions, and thus provide visual consistency correlations to supervise SPFEM model training. + +# 4.2. Disparity-Aware Adaptive Strategy + +Once the SCCL metric is learned, we can use to $\mathcal{L}_{sccl}$ loss between the input source (source 3DMM) and output generated (generated 3DMM) images as additional supervision. Here, we observe a notable phenomenon that the complexity varies across different facial regions. For example, it is more complex and challenging for the mouth regions as it change dramatically when the speaker is talking. In contrast, when the regions are positioned at the cheek area, the visual disparity is reduced, promoting a faster convergence. This underscores the region-specific sensitivity of visual disparity. Consequently, by enabling the SCC metric to independently discern and dynamically modulate learning strategies for specific regions, we can enhance the extraction of spatially coherent correlation information in an adaptive manner. + +Inspired by the idea of [20], DAAS is engineered to enable the SCC metric to discern this variability and tailor its learning strategies based on the characteristics of the regions, prioritizing those with higher learning complexity. Specifically, when the visual disparity $x_{i\rightarrow j}^{f,l}$ is larger, this region is deemed a challenging region, to which we assign a larger weight value. Conversely, when $x_{i\rightarrow j}^{f,l}$ is small, it is considered a simple region that can achieve rapid convergence, we reduce the weight for those simple regions. To this end, we propose to assign different weights according to the visual disparity, formulated as: + +$$ +w _ {i j} ^ {l} = \lambda \cdot \operatorname {s i g m o i d} \left(x _ {i \rightarrow j} ^ {f, l}\right) ^ {r} \tag {6} +$$ + +where $w_{ij}^{l}$ represents the weight value of adjacent regions $i \rightarrow j$ for images $x$ and $y$ at the feature map layer $l$ . $\lambda$ and $r$ are hyper-parameters, both of which are set to 2 to ensure a reasonable weight. The final loss function can be defined as: + +$$ +\mathcal {L} _ {a s c c l} = \sum_ {l = 1} \sum_ {i, j} \sum_ {x, y} w _ {i j} ^ {l} \cdot \ell_ {x y} ^ {l, i \rightarrow j} \tag {7} +$$ + +Current SPFEM algorithms can be divided into two types. The first involves a two-stage generation: initially creating 3DMM parameters and then using them to render final images [23]. The second method directly produces rendered images [28]. Visual information here refers to either the 3DMM parameters or the final images. $\mathcal{L}_{asccl}$ can be used + +for both these two types of algorithms as shown in Figure 3. Due to page limit, we present more implementation details, including network architectures, integration to current NED and ICface method, and training details. + +# 5. Experiments + +# 5.1. Dataset + +We performed experiments on the MEAD dataset [30], which contains 60 speakers, and each speaker records 30 videos in each emotional state (i.e., neutral, happy, angry, surprised, fear, sad, and disgusted). Here, we selected videos of 36 speakers that have 7,560 videos to train the ASCCL algorithm. To evaluate the SPFEM model's performance, we select 6 non-overlapped speakers (M003, M009, W029, M012, M030, and W015) that have 1,260 videos. We randomly selected $90\%$ as the training set and the rest $10\%$ as the test set similar to previous works [23]. We additionally employ the ASCCL algorithm on the well-established RAVDESS dataset [21] without the need for retraining. Specifically, we focus on 6 speakers (actors 1-6) encompassing 168 videos. Similarly, $90\%$ of the videos are randomly chosen for the training set, while the remaining $10\%$ constitute the test set. + +# 5.2. Evaluation Protocol + +In this work, we use these metrics for evaluation: 1) Frechet Arcface Distance (FAD) gauges video realism by comparing feature vectors of generated and real videos using advanced face recognition technology [7]. Lower FAD values indicate better realism. 2) Cosine Similarity (CSIM) assesses emotional similarity between generated and target emotional videos using a state-of-the-art expression recognition network, with higher CSIM values denoting greater similarity. 3) Lip Sync Error Distance (LSE-D) [24] evaluates lip-audio accuracy using a pre-trained model [5] to measure the disparities between lip and audio representations, with smaller LSE-D indicates a higher lip-audio accuracy. We present the results of two settings: inter-identification, where emotion reference and source video share the same speaker, and cross-identification, involving different speakers. + +# 5.3. Comparison with Baseline Methods + +# 5.3.1 Quantitative Comparisons + +We first present the performance comparisons on MEAD in Table 1. When ASCCL is integrated into NED, the resulting image sequences are greatly improved in FAD, LSE-D, and CSIM. In the Cross-ID setting, compared with NED itself, FAD, LSE-D, and CSIM have all improved to a certain extent, with FAD reduced from 4.448 to 4.264, LSE-D from 9.906 to 9.238, and CSIM from 0.773 to 0.791. Among + +
SettingsEmotionsICfaceOurs (ICface)NEDOurs (NED)
FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑
Inter-IDNeutral7.1149.7600.7797.1589.3820.7810.9069.2640.8830.8919.1130.911
Angry6.42010.4830.7416.1959.7660.8032.1779.5790.8021.1959.5500.896
Disgusted7.38310.4330.8056.2659.2660.8093.8389.1280.7721.6799.4160.854
Fear6.5679.8550.7546.6989.4810.8001.65910.1720.8481.33010.0390.900
Happy6.21310.1800.7756.1919.5560.8371.9399.1370.8391.3268.9750.930
Sad7.30110.0170.7556.7279.2930.7792.5389.0740.8121.1628.9060.906
Surprised6.5679.8510.8177.4709.2710.7951.7009.8210.8641.0569.3820.902
Avg.6.79510.0830.7756.6729.4310.8012.1089.4540.8311.2349.3400.900
Cross-IDNeutral10.56011.2260.7059.74510.6040.6712.0229.8120.8411.8659.1340.852
Angry9.47011.0730.6489.27110.4560.6934.8519.9040.7174.8539.2390.748
Disgusted9.23011.1840.6379.32310.3380.7645.09410.1210.7914.8409.3470.814
Fear9.12211.2040.7279.27310.2210.7294.9839.7410.7504.8209.2390.761
Happy8.49311.3220.7179.50510.4210.7933.9199.9360.8423.3839.1780.866
Sad10.36411.5260.6649.71010.3140.6645.66510.1790.6915.4759.4270.720
Surprised9.54111.1330.7219.53410.2730.7664.6009.6460.7804.6159.1050.779
Avg.9.54011.2380.6889.48010.3750.7264.4489.9060.7734.2649.2380.791
+ +Table 1. Comparison results of FAD, CSIM, and LSE-D of NED, ICFACE with and without our ASCCL on the inter-Identification and cross-IDentification settings on the MEAD dataset. + +them, the LSE-D has seen significant improvements, and these notable advancements in the LSE-D metric can be attributed to ASCCL's pivotal role in supervising the training of the SPFEM model. This supervision accentuates the intrinsic visual correlations between the SPFEM model's input and output, ensuring the visual disparity of the input and output align closely thereby enhancing consistency in mouth shape modifications related to emotion. Additionally, the betterment in FAD and CSIM further attests that ASCCL not only maintains but can also elevate the model's training quality, steering it towards superior optimization. In the inter-ID setting, these three indicators are also improved to a certain extent, indicating that the proposed ASCCL algorithm has strong generalization and can adapt to the emotional migration of inter-ID and cross-ID. When incorporating the ASCCL into the single-stage method ICface can also obtain significant performance improvement. In the Inter-ID setting, compared with ICface itself, FAD, LSE-D, and CSIM have all improved to a certain extent, with FAD reduced from 6.795 to 6.672, LSE-D from 10.083 to 9.431, and CSIM from 0.775 to 0.801. Cross-ID is a more general and practical setting, and incorporating the ASCCL also achieves evident improvement on FAD, LSE-D, and CSIM of different expression manipulation as well as the average FAD, LSE-D, and CSIM as shown in Table 1 + +To demonstrate the generalization ability of the trained ASCCL, we also present the performance comparisons on the RAVDESS [21] dataset without retraining ASCCL. As shown in Table 2, incorporating ASCCL can also obtain obvious improvement for different expression manipulation in both settings. when using the ICface baseline in the interID setting, it decreases the average FAD, LSE-D by 1.142, 0.436, and increases the average CSIM by 0.01. In the Cross-ID setting, it decreases the average FAD, LSE-D by 0.521, 1.226, and the average CSIM remains the same. Similar performance improvement is obtained when using the NED baseline. The experiment corroborates ASCCL's robustness across different methods and data domains. + +![](images/8638923617c3cd2f8ebd6eb731c85ee1c73580f6949e179ca7def8f71704298c.jpg) +Figure 5. Qualitative comparisons of NED with and without the proposed ASCCL algorithm. The samples are selected from the MEAD dataset. + +# 5.3.2 Qualitative Comparisons + +In this section, we exhibit some visualization results of the baseline NED methodology, both with and without the ASCCL algorithm, as illustrated in Figure 5. Analogous to the quantitative metrics, we also dissect the qualitative comparisons from three dimensions. 1) Realism: The eye region tends to be more closed as a consequence of the NED [23] application, as exemplified in the third column of the second and fifth rows. Furthermore, the mouth region is distorted due to the imprecise prediction of the mouth shape as + +
SettingsEmotionsICfaceOurs (ICface)NEDOurs (NED)
FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑
Inter-IDNeutral9.8168.2090.7498.3027.2390.7622.0417.3760.8472.8107.5670.853
Angry7.0479.5040.7036.1829.4530.7113.2887.7570.8053.7227.6010.799
Disgusted8.6898.2950.7757.0668.6490.7834.1447.8220.7863.1948.1000.836
Fear8.4138.5230.7227.4068.6250.7412.6357.4520.8422.5887.8210.831
Happy8.4138.9020.7977.4037.9240.7973.7147.7420.7933.0256.6780.826
Sad8.0868.3460.7667.3377.0180.7812.5957.5600.8552.5257.0860.842
Surprised8.6367.5780.7727.4117.4020.7812.9807.2260.8483.4107.2990.824
Avg.8.4438.4800.7557.3018.0440.7653.0577.5620.8253.0397.4500.830
Cross-IDNeutral10.47810.7360.67710.3439.3020.6823.5587.8560.8203.1607.4580.813
Angry8.70412.4150.6468.24210.5220.7065.5468.0850.7664.8518.5130.739
Disgusted9.26011.8600.7178.94810.2340.6527.3888.1070.7417.4437.8480.689
Fear9.10611.2790.6499.06210.3820.7535.0088.1510.7494.1607.8420.799
Happy9.06111.1500.7389.0639.7060.6765.6488.0730.8044.9107.9510.796
Sad9.63911.3050.6669.0439.9160.6345.5888.0060.7264.8477.5450.741
Surprised9.71812.0280.6448.90310.3130.6775.1457.9620.7134.2847.5810.748
Avg.9.42411.5390.6778.90310.3130.6775.4128.0340.7604.8087.8200.761
+ +shown in the third column for the first rows. The ASCCL ameliorates this NED shortcoming by aligning the visual consistency between inputs and outputs, as demonstrated in the fourth column. 2) Emotional Similarity: Existing works fall short in manipulating facial expressions to communicate the emotions of the reference subject; they generally favor direct replication of facial components into the source, as depicted in the third column in the second, and fifth rows. The ASCCL, by maximizing the alignment of visual disparities between input and output, directs the model to prioritize the extraction of emotional information rather than merely duplicating facial components from the reference into the source, as demonstrated in the fourth column. By incorporating the ASCCL, the NED methodology is more proficient in preserving the source's contours while accomplishing emotional transference. 3) Lip-Audio Preserving Accuracy: The proposed DAAS is designed to focus on regions around with mouth area, which exhibits considerable changes in the input and output of the SFPEM model. Thus, the ASCCL can achieve consistency of the mouth shape by constraining the maximum consistency of the visual disparities for this particular region in the positive samples, as depicted in Figure 5. The results presented in the fourth column demonstrate a superior ability to retain the source's mouth shape compared to those in the third column. We will represent more visualization results of NED and ICface with and without ASCCL algorithm on the MEAD and RAVDESS dataset in the Supplementary materials. We also present some video comparisons for more direct comparison in the Supplementary materials + +# 5.3.3 User study + +We conducted web-based user studies to compare the performance of NED with and without the ASCCL algorithm. The study comprises three segments corresponding to the previously mentioned metrics: realism, emotion similarity with the reference emotion, and mouth shape similarity with the source video, covering seven basic emotions. + +Table 2. Comparison results of FAD, CSIM, and LSE-D of NED, ICFACE with and without our ASCCL on the inter-Identification and cross-IDentification settings on the RAVDESS dataset. + +
EmotionRealismEmotion similarityMouth shape similarity
NEDASCCLNEDASCCLNEDASCCL
Neutral28%72%24%76%31%69%
Angry28%72%36%64%30%70%
Disgusted35%65%34%66%26%74%
Fear28%72%35%65%29%71%
Happy28%72%33%67%28%72%
Sad35%65%28%72%25%75%
Surprised30%70%27%73%24%76%
Avg.30%70%31%69%27%73%
+ +Table 3. Realism, emotion similarity, and mouth shape similarity ratings of the user study on NED and our ASCCL. + +For each emotion, we carefully selected 10 videos for both inter-identification and cross-identification settings, totaling 70 videos. Involving 25 participants, each participant was tasked with assessing the three aspects of each video. As detailed in Table 3, the inclusion of the ASCCL algorithm consistently outshines the baseline NED method across all seven emotions in all three metrics. On average, the integration of the ASCCL algorithm demonstrates significant improvement, achieving a $40\%$ higher rating in realism, a $38\%$ higher rating in emotion similarity, and an impressive $46\%$ higher rating in mouth shape similarity compared to the NED baseline. Supplementary materials include user studies utilizing the ICface baseline on MEAD and employing both NED and ICface baselines on RAVDESS. + +# 5.4. Ablation Study + +In the ablation experiment section, we first investigate the effect of pre-training ASCCL with paired data on the final result. Following that, the pre-trained ASCCL is integrated into the NED, with an analysis of supervision on different results(3DMM or render image) and an examination of the impact of DAAS. + +# 5.4.1 Analyses of ASCCL metric learning + +Our statistical analysis demonstrates an inherent spatially coherent correlation between the input and output of the SPFEM model. Even untrained, the ASCCL can approximate this correlation, as depicted in Figure 2. By pre + +training ASCCL with paired data, we enhance the ASCCL's ability to discern inherent visual consistency. As shown in Figure 6, there is a notable improvement in the similarity and correlation coefficients for positive samples. Fur + +![](images/d083bd48d1964216cda113f1e0c4eee88e1547e499409efd06946f202eac9a75.jpg) +(a) +Figure 6. (a) Average similarities and (b) Average Pearson correlation coefficients of the positive and negative samples after training the SCCL metric + +![](images/c24500cebe7786f216d9e6eeba2d09184072b095d31e78308392d7e37553c214.jpg) +(b) + +thermore, we employ both trained and untrained ASCCL to guide the SPFEM model's training, as depicted in Table 4. Irrespective of whether the ASCCL has been pretrained, it can serve as a guide when integrated into the SFPEM model. The pre-trained ASCCL demonstrated superior performance to the untrained ASCCL on measures including FAD, LSE-D, and CSIM. This indicates that by utilizing paired data to train the ASCCL, we can more effectively capture the spatial coherent correlations between the SFPEM's input and output, thereby enhancing the model's guidance. + +
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours untrained1.5099.4340.861
Ours trained1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours untrained4.3069.4580.784
Ours trained4.2649.2380.791
+ +# 5.4.2 Analysis of supervision on different outputs + +ASCCL can supervise either the intermediate 3DMM parameters or the final rendered images. In this section, we present two additional baselines that solely utilize the objective on the 3DMM parameters (Ours 3DMM) or final rendered images (Ours Image). As depicted in Table 5, incorporating the objective solely to either 3DMM parameters or images results in significant improvements across various metrics. Moreover, introducing the objective to both the 3DMM parameters and rendered images yields even greater improvement. + +Table 4. The performance of ASSCL with and without training. + +
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours 3DMM1.3329.3880.887
Ours image1.3139.3940.889
Ours1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours 3DMM4.3099.3110.787
Ours image4.2769.3210.785
Ours4.2649.2380.791
+ +# 5.4.3 Analysis of Disparity-Aware Adaptive Strategy + +Table 5. Comparison results of average FAD, CSIM, and LSE-D of NED, with supervision on different outputs. + +
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours w/o DAAS1.3429.4020.885
Ours DAAS1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours w/o DAAS4.3189.3300.786
Ours DAAS4.2649.2380.791
+ +Table 6. Comparison results of average FAD, CSIM, and LSE-D of NED, with or w/o DAAS + +Through empirical analysis, we observed that visual disparities are sensitive to regions. We employed DAAS to direct the ASCCL's attention toward those challenging regions, thereby enhancing the consistency of mouth movements between input and output. In this section, We examined the influence of incorporating DAAS into the outcome. As depicted in Table 6, in the absence of DAAS, our approach outperforms NED across all metrics. Moreover, when DAAS is integrated into our method, ASCCL achieves even more optimal results by dynamically adapting the learning strategy to different regions. + +# 6. Conclusion + +In this work, we propose an adaptive spatial coherent correlation learning (ASCCL) algorithm to investigate the inherent visual correlations between the SPFEM model's input and output to construct paired supervision to improve facial expression manipulation and meanwhile better preserve the facial animation of speech content. It first characterizes the visual disparities, and then constrains the visual disparities in adjacent local regions of the input image to align with those in corresponding adjacent regions of the output image from the SPFEM model, together with a disparity-aware adaptive strategy to adaptively learn based on the visual disparity of each adjacent region. ASCCL is implemented by a plug-and-play loss that can be seamlessly integrated into any advanced methods to facilitate SPFEM performance. 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[ + { + "bbox": [ + 46, + 276, + 289, + 612 + ], + "type": "text", + "content": "Speech-preserving facial expression manipulation (SPFEM) aims to modify facial emotions while meticulously maintaining the mouth animation associated with spoken content. Current works depend on inaccessible paired training samples for the person, where two aligned frames exhibit the same speech content yet differ in emotional expression, limiting the SPFEM applications in real-world scenarios. In this work, we discover that speakers who convey the same content with different emotions exhibit highly correlated local facial animations, providing valuable supervision for SPFEM. To capitalize on this insight, we propose a novel adaptive spatial coherent correlation learning (ASCCL) algorithm, which models the aforementioned correlation as an explicit metric and integrates the metric to supervise manipulating facial expression and meanwhile better preserving the facial animation of spoken contents. To this end, it first learns a spatial coherent correlation metric, ensuring the visual disparities of adjacent local regions of the image belonging to one emotion are similar to those of the corresponding counterpart of the image belonging to another emotion. Recognizing that visual disparities are not uniform across all regions, we have also crafted a disparity-aware adaptive strategy that prioritizes regions that present greater challenges. During SPFEM model training, we construct the adaptive spatial coherent correlation metric between corresponding local regions of the input and output images as addition loss to supervise the generation" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "content": "*Zhijing Yang is the corresponding author. Tianshui Chen, Jianman Lin, and Zhijing Yang are with Guangdong University of Technology. Chunmei Qing is with South China University of Technology. Liang Lin is with Sun Yat-Sen University. This work was supported in part by National Natural Science Foundation of China (NSFC) under Grant No. 62206060, in Part by Natural Science Foundation of Guangdong Province (2022A1515011555, 2023A1515012568, 2023A1515012561), Guangdong Provincial Key Laboratory of Human Digital Twin (2022B1212010004), and in part by Guangzhou Basic and Applied Basic Research Foundation under Grant No. SL2022A04J01626." + } + ] + } + ], + "index": 15 + }, + { + "type": "image", + "bbox": [ + 316, + 250, + 369, + 305 + ], + "blocks": [ + { + "bbox": [ + 316, + 250, + 369, + 305 + ], + "lines": [ + { + "bbox": [ + 316, + 250, + 369, + 305 + ], + "spans": [ + { + "bbox": [ + 316, + 250, + 369, + 305 + ], + "type": "image", + "image_path": "6b0e354072400563f18108657bd541a8a864b9721d2e4bed4fa3fef9b457a5a0.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + } + ], + "index": 16 + }, + { + "type": "image", + "bbox": [ + 370, + 251, + 424, + 305 + ], + "blocks": [ + { + "bbox": [ + 370, 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Several examples are generated by the current advanced NED with and without the proposed ASCCL algorithm. Incorporating the ASCCL can better manipulate the expressions and meanwhile preserve mouth shapes." + } + ] + } + ], + "index": 32, + "angle": 0, + "type": "image_footnote" + } + ], + "index": 24 + }, + { + "type": "image", + "bbox": [ + 370, + 360, + 424, + 414 + ], + "blocks": [ + { + "bbox": [ + 370, + 360, + 424, + 414 + ], + "lines": [ + { + "bbox": [ + 370, + 360, + 424, + 414 + ], + "spans": [ + { + "bbox": [ + 370, + 360, + 424, + 414 + ], + "type": "image", + "image_path": "311f9eaea3c1f25d89a97f185c0484ae96c3861f20b2048a3641427d1ccb1aa2.jpg" + } + ] + } + ], + "index": 25, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 386, + 415, + 407, + 423 + ], + "lines": [ + { + "bbox": [ + 386, + 415, + 407, + 423 + ], + "spans": [ + { + "bbox": [ + 386, + 415, + 407, + 423 + ], + "type": "text", + "content": "Source" + } + ] + } + ], + "index": 29, + "angle": 0, + "type": "image_caption" + } + ], + "index": 25 + }, + { + "type": "image", + "bbox": [ + 425, + 360, + 478, + 414 + ], + "blocks": [ + { + "bbox": [ + 425, + 360, + 478, + 414 + ], + "lines": [ + { + "bbox": [ + 425, + 360, + 478, + 414 + ], + "spans": [ + { + "bbox": [ + 425, + 360, + 478, + 414 + ], + "type": "image", + "image_path": "462339c19202073d974cd03df916240046ebaab09c5177d91e52ddbf9da18b20.jpg" + } + ] + } + ], + "index": 26, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 443, + 415, + 459, + 423 + ], + "lines": [ + { + "bbox": [ + 443, + 415, + 459, + 423 + ], + "spans": [ + { + "bbox": [ + 443, + 415, + 459, + 423 + ], + "type": "text", + "content": "NED" + } + ] + } + ], + "index": 30, + "angle": 0, + "type": "image_caption" + } + ], + "index": 26 + }, + { + "type": "image", + "bbox": [ + 479, + 360, + 533, + 414 + ], + "blocks": [ + { + "bbox": [ + 479, + 360, + 533, + 414 + ], + "lines": [ + { + "bbox": [ + 479, + 360, + 533, + 414 + ], + "spans": [ + { + "bbox": [ + 479, + 360, + 533, + 414 + ], + "type": "image", + "image_path": "e383473bd08bc307742835f93f35de629d6479c73d5c4af30adeea86a051760e.jpg" + } + ] + } + ], + "index": 27, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 493, + 415, + 517, + 422 + ], + "lines": [ + { + "bbox": [ + 493, + 415, + 517, + 422 + ], + "spans": [ + { + "bbox": [ + 493, + 415, + 517, + 422 + ], + "type": "text", + "content": "ASCCL" + } + ] + } + ], + "index": 31, + "angle": 0, + "type": "image_caption" + } + ], + "index": 27 + }, + { + "bbox": [ + 304, + 479, + 547, + 526 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 479, + 547, + 526 + ], + "spans": [ + { + "bbox": [ + 304, + 479, + 547, + 526 + ], + "type": "text", + "content": "process. We conduct extensive experiments on variant datasets, and the results demonstrate the effectiveness of the proposed ASCCL algorithm. Code is publicly available at https://github.com/jianmanlincjx/ASCCL" + } + ] + } + ], + "index": 33 + }, + { + "bbox": [ + 306, + 541, + 387, + 553 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 541, + 387, + 553 + ], + "spans": [ + { + "bbox": [ + 306, + 541, + 387, + 553 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 34 + }, + { + "bbox": [ + 304, + 557, + 545, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 557, + 545, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 557, + 545, + 689 + ], + "type": "text", + "content": "Speech-preserving facial expression manipulation (SPFEM), which aims to manipulate facial emotions while preserving the mouth animations in static images or dynamic videos, can enhance human expressiveness and thus benefit variant applications including virtual avatars and film & television production. For example, it requires lots of effects and repeated remakes to capture an expected actor's emotions in a movie & shooting. In contrast, a robust SPFEM system can easily modify the facial emotions to achieve comparable performance in the post-production stage and thus is urgently expected." + } + ] + } + ], + "index": 35 + }, + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "content": "Current SPFEM literature either predominantly previous face reenactment algorithms [10, 28] or harnesses decou" + } + ] + } + ], + "index": 36 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7267" + } + ] + } + ], + "index": 37 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 49, + 72, + 286, + 311 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 72, + 286, + 311 + ], + "spans": [ + { + "bbox": [ + 49, + 72, + 286, + 311 + ], + "type": "text", + "content": "pled semantic representations equipped by cyclic consistency [23, 36]. The former category of works [10, 28] typically manipulates facial expressions through the exchange of latent codes [17] or facial action units [13], and employs the reference images as surrogate labels to construct frame-by-frame construction supervision. However, these surrogate images are not perfect representations of the desired outcomes and the reliance on them may lead to generating sub-optimal results. The latter approach [23] posits a one-to-one correspondence between images exhibiting varied emotional expressions and employs cyclic consistency for paired supervision. Despite achieving better performance, the global cyclical consistency constraint makes it difficult to capture alterations in fine-grained facial information under different emotions. Consequently, these methods either fail to accurately translate the intended emotions (as illustrated in the first and third examples in Figure 1) or do not maintain the original mouth animation tied to the spoken content (as evidenced in the first and second examples in Figure 1)." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 49, + 315, + 286, + 553 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 315, + 286, + 553 + ], + "spans": [ + { + "bbox": [ + 49, + 315, + 286, + 553 + ], + "type": "text", + "content": "To establish accurate information for additional supervisory guidance, we investigate a plausible and reasonable assumption: a single speaker articulating identical content across varied emotional states exhibits a high degree of correlation in local facial animations. Within the realm of the SPFEM task, we posit that there exists a strong correlation between adjacent local regions of the input images and their corresponding counterparts in the output images. For a more detailed analysis, we delve into the examination of similarities and correlation coefficients between corresponding local regions of the input and output images, and those between non-corresponding local regions of the input and output images. As depicted in Figure 2, there is a notable presence of high similarities and correlation coefficients for corresponding local regions. Conversely, the noncorresponding local regions demonstrate values approaching zero. These observations provide robust empirical support for the previously stated assumption and underscore the merit of modeling these correlations to facilitate SPFEM performance." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 49, + 558, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 558, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 49, + 558, + 286, + 712 + ], + "type": "text", + "content": "In this work, we design a novel adaptive spatial coherent correlation learning (ASCCL) algorithm, which discerns the correlations between adjacent local regions within images that display varying emotional states and incorporates these correlations as additional guidance to supervise the manipulation of expressions in a manner that is attuned to difficulty. Formally, we leverage visual disparities as a means to characterize the interactions between adjacent local regions, given that local motion disparities are critical to the realism of facial animations. Then, we formulate a spatial coherent correlation metric ensuring the visual disparities of adjacent local regions of the image belonging to one emotion are similar to those of the correspond" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 308, + 72, + 544, + 226 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 72, + 544, + 226 + ], + "spans": [ + { + "bbox": [ + 308, + 72, + 544, + 226 + ], + "type": "text", + "content": "ing counterpart of the image belonging to another emotion. Recognizing the variable complexity across different facial regions, we introduce a disparity-aware adaptive strategy, which preferentially weights more challenging regions with higher values while proportionally reducing the weight for less complex areas. During SPFEM model training, we establish a network of dense correlations between local regions of the input and output images, employing this adaptive spatially coherent correlation metric as an auxiliary supervision. ASCCL is trained using a set of paired data and can be used to construct supervision for any other persons to facilitate generating high-quality results in a plug-and-play manner." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 308, + 228, + 544, + 395 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 228, + 544, + 395 + ], + "spans": [ + { + "bbox": [ + 308, + 228, + 544, + 395 + ], + "type": "text", + "content": "The contributions can be summarized into three folds. Firstly, we introduce an adaptive spatial coherent correlation learning (ASCCL) algorithm, which learns the consistent correlations between input and generated images in terms of the visual disparities of adjacent local regions. It can be seamlessly integrated into current SPFEM methods to improve their performance in a plug-and-play manner. Secondly, we introduce a difficult-aware adaptive strategy that weights more challenging regions with higher constraints while proportionally reducing the weight for less complex areas. Lastly, we conduct extensive experiments that integrate the ASCCL algorithms into current advanced methods, demonstrating the effectiveness of the proposed ASCCL algorithm." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 308, + 406, + 395, + 418 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 406, + 395, + 418 + ], + "spans": [ + { + "bbox": [ + 308, + 406, + 395, + 418 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 308, + 426, + 544, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 426, + 544, + 593 + ], + "spans": [ + { + "bbox": [ + 308, + 426, + 544, + 593 + ], + "type": "text", + "content": "Video-based face manipulation. To modify talking/moving faces, video-based face manipulation algorithms frequently employ conditionally Generative Adversarial Networks (GANs) [14, 19, 29, 31, 33] or 3DMM [2, 9, 11, 12, 27]. For example, GANimation [25] leverages adversarial learning conditioning on action unit [13] annotations to describe facial movements in a continuous manifold. [29] apply StyleGAN [18] to learn low-frequency information to accomplish temporal coherency. DSM [26] learns disentangled representation and controls facial expressions via semantic representation. SPFEM is more difficult than simple face manipulation since it requires not only modifying facial expressions but also retaining the facial motion of original speech contents." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 308, + 594, + 544, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 594, + 544, + 712 + ], + "spans": [ + { + "bbox": [ + 308, + 594, + 544, + 712 + ], + "type": "text", + "content": "Face reenactment. Facial reenactment, in which a specific actor imitates speech and expressions from a reference video [4, 8, 10, 28, 34] and other [35]. For example, ICface [28] controls the pose and expression with interpretable control signals such as head pose angles and action units. To create temporally consistent videos, Head2Head++ [10] employs a sequential generator and a customized dynamics discriminator. StyleHEAT [34] extends the latent code of StyleGAN [17] to aid in motion and expression generation and animation. SPFEM is similar to this task in expression" + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 296, + 750, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 296, + 750, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 296, + 750, + 314, + 757 + ], + "type": "text", + "content": "7268" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 55, + 82, + 164, + 256 + ], + "blocks": [ + { + "bbox": [ + 55, + 82, + 164, + 256 + ], + "lines": [ + { + "bbox": [ + 55, + 82, + 164, + 256 + ], + "spans": [ + { + "bbox": [ + 55, + 82, + 164, + 256 + ], + "type": "image", + "image_path": "42431e3cfb51c347aae1284abf6f45d96ade88ed9e79ebb2e882800bf6371af0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 258, + 287, + 281 + ], + "lines": [ + { + "bbox": [ + 47, + 258, + 287, + 281 + ], + "spans": [ + { + "bbox": [ + 47, + 258, + 287, + 281 + ], + "type": "text", + "content": "Figure 2. (a) Average similarities and (b) Average Pearson correlation coefficients of the positive and negative samples." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 171, + 81, + 284, + 257 + ], + "blocks": [ + { + "bbox": [ + 171, + 81, + 284, + 257 + ], + "lines": [ + { + "bbox": [ + 171, + 81, + 284, + 257 + ], + "spans": [ + { + "bbox": [ + 171, + 81, + 284, + 257 + ], + "type": "image", + "image_path": "b28a6e552bfa3e6164b8207a90af3c7d5dd6cdf695e9ced53ee8b6572bb17714.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 294, + 287, + 329 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 294, + 287, + 329 + ], + "spans": [ + { + "bbox": [ + 46, + 294, + 287, + 329 + ], + "type": "text", + "content": "manipulation, but it also requires preserving mouth movement of original speech contents, making SPFEM a more difficult task." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 331, + 289, + 571 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 331, + 289, + 571 + ], + "spans": [ + { + "bbox": [ + 46, + 331, + 289, + 571 + ], + "type": "text", + "content": "Speech-preserving facial expression manipulation. SPFEM seeks to alter the given source video to the desired emotion while keeping the voice content's facial animation. Previous research has adapted facial reenactment algorithms such as ICface [28] to this job. However, facial reenactment can keep both the expression and the mouth form, but not the speech substance. To accomplish this challenge, [23] propose combining the 3DMM parameters of source identification and target emotion. Despite making significant progress, these works lack paired supervision, resulting in sub-optimal performance in emotion manipulation and speech preservation. Different from the above-mentioned works, we present in-depth analyses about the spatial coherent correlations across images belonging to different emotions and find there exist strong correlations between adjacent local regions of the input image of one emotion and their corresponding counterparts in the output image of another emotion. We propose to learn adaptive spatial coherent correlations to construct additional supervision for SPFEM." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 583, + 119, + 596 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 583, + 119, + 596 + ], + "spans": [ + { + "bbox": [ + 47, + 583, + 119, + 596 + ], + "type": "text", + "content": "3. Motivation" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 605, + 287, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 677 + ], + "type": "text", + "content": "As discussed above, we make a plausible and reasonable assumption that a single speaker articulating identical content across varied emotional states exhibits a high degree of correlation in local facial animations. To present a more in-depth and direct analysis, we further conduct statistical experiments to validate this assumption." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "type": "text", + "content": "Formally, given two images of the same speaker expressing the same content with two different emotions, denoted as " + }, + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "type": "text", + "content": ", we use the output of the last convolution layer" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "text", + "content": "of pre-trained network [7] to compute their feature " + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "inline_equation", + "content": "x^{f}" + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "inline_equation", + "content": "y^{f}" + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "text", + "content": ". Here, we use visual disparity to denote the relationship of regions at locations " + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "text", + "content": ", and the similarity between visual disparities of corresponding and non-corresponding adjacent local regions, formulated as:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 369, + 137, + 545, + 159 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 369, + 137, + 545, + 159 + ], + "spans": [ + { + "bbox": [ + 369, + 137, + 545, + 159 + ], + "type": "interline_equation", + "content": "s _ {i \\rightarrow j} ^ {p} = \\varphi \\left(x _ {i \\rightarrow j} ^ {f}, y _ {i \\rightarrow j} ^ {f}\\right) \\tag {1}", + "image_path": "5428db1dd6b03f78d739a3a017a454affedc2f7159e61701b94f332681a477a2.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 369, + 155, + 482, + 174 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 369, + 155, + 482, + 174 + ], + "spans": [ + { + "bbox": [ + 369, + 155, + 482, + 174 + ], + "type": "interline_equation", + "content": "\\mathbf {s} _ {i \\rightarrow k} ^ {n} = \\varphi (x _ {i \\rightarrow j} ^ {f}, y _ {i \\rightarrow k, k \\neq j} ^ {f})", + "image_path": "27d3577822299cbe126c4eb5335dad0f6c86d6646b2e922244d6c7a6fd4d533a.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "spans": [ + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "inline_equation", + "content": "x_{i\\rightarrow j}^{f}" + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "inline_equation", + "content": "y_{i\\rightarrow j}^{f}" + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "text", + "content": " denote visual disparities of regions " + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "text", + "content": " of the images " + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "inline_equation", + "content": "\\varphi" + }, + { + "bbox": [ + 304, + 178, + 547, + 456 + ], + "type": "text", + "content": " represents the cosine similarity function. For each emotion pair, we retrieve thousands of corresponding and non-corresponding adjacent local regions and compute their average similarities. As shown in Figure 2 (a), we present the average similarities of corresponding and non-corresponding adjacent local regions according to the emotion pairs of neural to other six emotions. We find the average similarities of the non-corresponding adjacent local regions approach 0, and that of the corresponding adjacent local regions range from 0.43 to 0.49. Moreover, we further compute Pearson correlation coefficients [6] between visual disparities of visual disparities of corresponding and non-corresponding adjacent local regions. Similarly, we use thousands of corresponding and non-corresponding adjacent local regions and compute their average Pearson correlation coefficients. As presented in Figure 2 (b), a similar phenomenon is observed. These results suggest there exist strong correlations between the corresponding adjacent local regions between two images expressing the same content while differing in emotions. Thus, it is worth investigating to learn the correlations and integrate the correlations to facilitate the SPFEM performance." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 465, + 362, + 477 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 465, + 362, + 477 + ], + "spans": [ + { + "bbox": [ + 305, + 465, + 362, + 477 + ], + "type": "text", + "content": "4. Method" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 485, + 547, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 485, + 547, + 629 + ], + "spans": [ + { + "bbox": [ + 304, + 485, + 547, + 629 + ], + "type": "text", + "content": "It first learns the spatially coherent correlation metric, ensuring the alignment between the visual disparity of adjacent local regions of the source input image and that of the corresponding counterpart of the output generated image. Then, it designs a disparity-aware adaptive strategy to weigh more challenging regions with higher values while reducing the weight for less complex regions. The ASCCL algorithm can be used to supervise generating visual contents, including intermediate results (e.g., 3DMM [1]) and final rendered images in a plug-and-play manner. An overall pipeline for incorporating ASCCL into the two-stage NED [23] method is illustrated in Figure 3." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 635, + 545, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 635, + 545, + 647 + ], + "spans": [ + { + "bbox": [ + 305, + 635, + 545, + 647 + ], + "type": "text", + "content": "4.1. Spatial Coherent Correlation Metric Learning" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": "As suggested in Section 3, there inherently exist strong correlations between adjacent regions of two images that one speaker expresses the same content while differing in different emotions. Indeed, we can further strengthen the correlations by learning the spatial coherent correlation (SCC)" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7269" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 97, + 70, + 500, + 251 + ], + "blocks": [ + { + "bbox": [ + 97, + 70, + 500, + 251 + ], + "lines": [ + { + "bbox": [ + 97, + 70, + 500, + 251 + ], + "spans": [ + { + "bbox": [ + 97, + 70, + 500, + 251 + ], + "type": "image", + "image_path": "829fc1f243459bd1f27ebb34763134787971bbcbf9666fcde42c384f36e756f5.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 251, + 547, + 307 + ], + "lines": [ + { + "bbox": [ + 46, + 251, + 547, + 307 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 547, + 307 + ], + "type": "text", + "content": "Figure 3. An overall pipeline of incorporating the proposed ASCCL algorithm to the current advanced NED [23] method to supervise generating the intermediate 3DMM meshes and final rendered images. It computes visual disparities of corresponding and non-corresponding local regions between the source and generated images, followed by the disparity-aware adaptive strategy to obtain the final loss to supervise final image generation. An identical process is performed on the source and generated 3DMM meshes to supervise the intermediate 3DMM mesh generation." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 48, + 312, + 290, + 371 + ], + "blocks": [ + { + "bbox": [ + 48, + 312, + 290, + 371 + ], + "lines": [ + { + "bbox": [ + 48, + 312, + 290, + 371 + ], + "spans": [ + { + "bbox": [ + 48, + 312, + 290, + 371 + ], + "type": "image", + "image_path": "e90aa919c89124e169d48b9fee978780ee9c2fefc580e8c353437939049e0ac6.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 373, + 288, + 439 + ], + "lines": [ + { + "bbox": [ + 46, + 373, + 288, + 439 + ], + "spans": [ + { + "bbox": [ + 46, + 373, + 288, + 439 + ], + "type": "text", + "content": "Figure 4. An illustration of spatial coherent correlation metric learning. It retrieves the corresponding adjacent local regions of the input and output images as positive samples and the noncorresponding counterparts as negative samples. The process is performed in the feature maps to construct dense positive and negative samples to train the metric." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 456, + 287, + 529 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 456, + 287, + 529 + ], + "spans": [ + { + "bbox": [ + 46, + 456, + 287, + 529 + ], + "type": "text", + "content": "metric using paired data, which can assign a higher value to the correlation between corresponding adjacent regions and assign a smaller value to the correlation between noncorresponding counterparts. In this way, it can provide better-synchronized signals to supervise the generation process. Here, we introduce the SCC metric learning in detail." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "spans": [ + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "text", + "content": "Formally, given two images of the same speaker expressing the same content with two different emotions, we need to extract corresponding regions " + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "text", + "content": " of both two images. However, pose bias typically exists between these two images, potentially compromising the calculation accuracy. To address this issue, we first introduce a pose alignment module that extracts landmark coordinates using a pre-trained model in the OpenCV library for both two images and utilizes these coordinates to compute an affine transformation matrix. This matrix is subsequently applied to align the pose information between the two images and obtain two images " + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 531, + 288, + 675 + ], + "type": "text", + "content": " that ensure geometric correspondence." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "type": "text", + "content": "Figure 4 exhibits the detailed computation process of the SCC metric. Owing to the locality and translation invariance characteristics of convolutional neural networks" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 312, + 547, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 312, + 547, + 397 + ], + "spans": [ + { + "bbox": [ + 304, + 312, + 547, + 397 + ], + "type": "text", + "content": "[7, 15], the mapping of pixels in the feature space back to the original image is approximately equivalent to a local region, and as the depth of the network increases, the receptive field also expands. Leveraging these characteristics, we employ the output of multiple convolutional layers to obtain the multi-scale features. Formally, we can extract the feature of layer " + }, + { + "bbox": [ + 304, + 312, + 547, + 397 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 304, + 312, + 547, + 397 + ], + "type": "text", + "content": " as:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 398, + 401, + 545, + 422 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 398, + 401, + 545, + 422 + ], + "spans": [ + { + "bbox": [ + 398, + 401, + 545, + 422 + ], + "type": "interline_equation", + "content": "x ^ {f, l} = \\phi^ {l} (x) \\tag {2}", + "image_path": "6845500c56fc37ee89b5ba656fd0b3c7f02ddb5dcc5cfcdcb850a14bc9f6fa0f.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 400, + 419, + 452, + 433 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 400, + 419, + 452, + 433 + ], + "spans": [ + { + "bbox": [ + 400, + 419, + 452, + 433 + ], + "type": "interline_equation", + "content": "y ^ {f, l} = \\phi^ {l} (y)", + "image_path": "ede14ac1a437a3fa571e76bede7dcaa211fd79d497e068335f5b9c2c7b19e247.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "spans": [ + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "text", + "content": "Here, " + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "inline_equation", + "content": "\\phi^l (\\cdot)" + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "text", + "content": " is feature extractor for layer " + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "text", + "content": ". We adopt the Arcface network [7], and use the output of four convolutional layers with dimension decline and thus " + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "inline_equation", + "content": "l\\in [1,2,3,4]" + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "text", + "content": ". Given two regions " + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 439, + 545, + 500 + ], + "type": "text", + "content": ", we compute the visual disparity using a mapping of the feature difference, denoted as:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 378, + 505, + 545, + 527 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 378, + 505, + 545, + 527 + ], + "spans": [ + { + "bbox": [ + 378, + 505, + 545, + 527 + ], + "type": "interline_equation", + "content": "x _ {i \\rightarrow j} ^ {f, l} = f \\left(x _ {i} ^ {f, l} - x _ {j} ^ {f, l}\\right) \\tag {3}", + "image_path": "4095881466d025154935cb6349ddc670039b771204e6867b530864ac7debdef2.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 381, + 523, + 471, + 540 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 381, + 523, + 471, + 540 + ], + "spans": [ + { + "bbox": [ + 381, + 523, + 471, + 540 + ], + "type": "interline_equation", + "content": "y _ {i \\rightarrow j} ^ {f, l} = f (y _ {i} ^ {f, l} - y _ {j} ^ {f, l})", + "image_path": "31e6cdfcd4ce29a5322309be6cdd16233de212018ca18f3ebb0cc7c4e188af0b.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 545, + 545, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 545, + 605 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 545, + 605 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 545, + 545, + 605 + ], + "type": "inline_equation", + "content": "f(\\cdot)" + }, + { + "bbox": [ + 304, + 545, + 545, + 605 + ], + "type": "text", + "content": " denotes a mapping function and it is implemented using two stacked fully-connected layers cooperated with the rectified linear unit non-linear function. Inspired by the recent progress in previous works [3, 16, 22, 32], we define an identical contrastive loss, formulated as:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 312, + 619, + 545, + 671 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 619, + 545, + 671 + ], + "spans": [ + { + "bbox": [ + 312, + 619, + 545, + 671 + ], + "type": "interline_equation", + "content": "\\ell_ {x y} ^ {l, i \\rightarrow j} = \\frac {\\exp \\left(\\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow j} ^ {f , l}}{\\tau}\\right)}{\\exp \\left(\\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow j} ^ {f , l}}{\\tau}\\right) + \\exp \\left(\\sum_ {k = 1 , k! = j} ^ {m} \\frac {x _ {i \\rightarrow j} ^ {f , l} \\cdot y _ {i \\rightarrow k} ^ {f , l}}{\\tau}\\right)} \\tag {4}", + "image_path": "7c83b260aeebc2b15a2f9b6ddac46aa6b47b2ab6c3b6f8339c533ede5b37d2a4.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": " stands for a temperature hyper-parameter set to 0.07 by default. The final loss can be defined as the summation of all image pairs, corresponding region pairs, and four" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7270" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 137, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 137, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 137, + 83 + ], + "type": "text", + "content": "layers, formulated as:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 112, + 91, + 287, + 118 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 112, + 91, + 287, + 118 + ], + "spans": [ + { + "bbox": [ + 112, + 91, + 287, + 118 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {s c c l} = \\sum_ {l = 1} \\sum_ {i, j} \\sum_ {x, y} \\ell_ {x y} ^ {l, i \\rightarrow j} \\tag {5}", + "image_path": "b304e8999ce111d6d14e2f07206a7768093c50dc0b1ee3779a35ee932fc7eb8f.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 126, + 287, + 174 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 126, + 287, + 174 + ], + "spans": [ + { + "bbox": [ + 46, + 126, + 287, + 174 + ], + "type": "text", + "content": "By minimizing losses through backpropagation, we can align the visual disparities of " + }, + { + "bbox": [ + 46, + 126, + 287, + 174 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 126, + 287, + 174 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 126, + 287, + 174 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 126, + 287, + 174 + ], + "type": "text", + "content": " with different emotions, and thus provide visual consistency correlations to supervise SPFEM model training." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 181, + 234, + 194 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 181, + 234, + 194 + ], + "spans": [ + { + "bbox": [ + 47, + 181, + 234, + 194 + ], + "type": "text", + "content": "4.2. Disparity-Aware Adaptive Strategy" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 199, + 287, + 377 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 199, + 287, + 377 + ], + "spans": [ + { + "bbox": [ + 46, + 199, + 287, + 377 + ], + "type": "text", + "content": "Once the SCCL metric is learned, we can use to " + }, + { + "bbox": [ + 46, + 199, + 287, + 377 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{sccl}" + }, + { + "bbox": [ + 46, + 199, + 287, + 377 + ], + "type": "text", + "content": " loss between the input source (source 3DMM) and output generated (generated 3DMM) images as additional supervision. Here, we observe a notable phenomenon that the complexity varies across different facial regions. For example, it is more complex and challenging for the mouth regions as it change dramatically when the speaker is talking. In contrast, when the regions are positioned at the cheek area, the visual disparity is reduced, promoting a faster convergence. This underscores the region-specific sensitivity of visual disparity. Consequently, by enabling the SCC metric to independently discern and dynamically modulate learning strategies for specific regions, we can enhance the extraction of spatially coherent correlation information in an adaptive manner." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 379, + 287, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 379, + 287, + 510 + ], + "spans": [ + { + "bbox": [ + 46, + 379, + 287, + 510 + ], + "type": "text", + "content": "Inspired by the idea of [20], DAAS is engineered to enable the SCC metric to discern this variability and tailor its learning strategies based on the characteristics of the regions, prioritizing those with higher learning complexity. Specifically, when the visual disparity " + }, + { + "bbox": [ + 46, + 379, + 287, + 510 + ], + "type": "inline_equation", + "content": "x_{i\\rightarrow j}^{f,l}" + }, + { + "bbox": [ + 46, + 379, + 287, + 510 + ], + "type": "text", + "content": " is larger, this region is deemed a challenging region, to which we assign a larger weight value. Conversely, when " + }, + { + "bbox": [ + 46, + 379, + 287, + 510 + ], + "type": "inline_equation", + "content": "x_{i\\rightarrow j}^{f,l}" + }, + { + "bbox": [ + 46, + 379, + 287, + 510 + ], + "type": "text", + "content": " is small, it is considered a simple region that can achieve rapid convergence, we reduce the weight for those simple regions. To this end, we propose to assign different weights according to the visual disparity, formulated as:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 112, + 517, + 287, + 534 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 112, + 517, + 287, + 534 + ], + "spans": [ + { + "bbox": [ + 112, + 517, + 287, + 534 + ], + "type": "interline_equation", + "content": "w _ {i j} ^ {l} = \\lambda \\cdot \\operatorname {s i g m o i d} \\left(x _ {i \\rightarrow j} ^ {f, l}\\right) ^ {r} \\tag {6}", + "image_path": "e5eb0d230da1f665bdcaf44e169db23b31cc65367776d7f8322faf89c3cda2df.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "spans": [ + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "inline_equation", + "content": "w_{ij}^{l}" + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "content": " represents the weight value of adjacent regions " + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "inline_equation", + "content": "i \\rightarrow j" + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "content": " for images " + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "content": " at the feature map layer " + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "inline_equation", + "content": "r" + }, + { + "bbox": [ + 46, + 541, + 287, + 601 + ], + "type": "text", + "content": " are hyper-parameters, both of which are set to 2 to ensure a reasonable weight. The final loss function can be defined as:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 99, + 608, + 287, + 635 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 99, + 608, + 287, + 635 + ], + "spans": [ + { + "bbox": [ + 99, + 608, + 287, + 635 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {a s c c l} = \\sum_ {l = 1} \\sum_ {i, j} \\sum_ {x, y} w _ {i j} ^ {l} \\cdot \\ell_ {x y} ^ {l, i \\rightarrow j} \\tag {7}", + "image_path": "5c43225cbfcf6065988c94d616422c69edb6ba62ea0c067764d09f34adf68693.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": "Current SPFEM algorithms can be divided into two types. The first involves a two-stage generation: initially creating 3DMM parameters and then using them to render final images [23]. The second method directly produces rendered images [28]. Visual information here refers to either the 3DMM parameters or the final images. " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{asccl}" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": " can be used" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "content": "for both these two types of algorithms as shown in Figure 3. Due to page limit, we present more implementation details, including network architectures, integration to current NED and ICface method, and training details." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 133, + 386, + 146 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 133, + 386, + 146 + ], + "spans": [ + { + "bbox": [ + 306, + 133, + 386, + 146 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 152, + 364, + 164 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 152, + 364, + 164 + ], + "spans": [ + { + "bbox": [ + 306, + 152, + 364, + 164 + ], + "type": "text", + "content": "5.1. Dataset" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "spans": [ + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "text", + "content": "We performed experiments on the MEAD dataset [30], which contains 60 speakers, and each speaker records 30 videos in each emotional state (i.e., neutral, happy, angry, surprised, fear, sad, and disgusted). Here, we selected videos of 36 speakers that have 7,560 videos to train the ASCCL algorithm. To evaluate the SPFEM model's performance, we select 6 non-overlapped speakers (M003, M009, W029, M012, M030, and W015) that have 1,260 videos. We randomly selected " + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "text", + "content": " as the training set and the rest " + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "text", + "content": " as the test set similar to previous works [23]. We additionally employ the ASCCL algorithm on the well-established RAVDESS dataset [21] without the need for retraining. Specifically, we focus on 6 speakers (actors 1-6) encompassing 168 videos. Similarly, " + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "text", + "content": " of the videos are randomly chosen for the training set, while the remaining " + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 304, + 171, + 545, + 362 + ], + "type": "text", + "content": " constitute the test set." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 372, + 422, + 383 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 372, + 422, + 383 + ], + "spans": [ + { + "bbox": [ + 306, + 372, + 422, + 383 + ], + "type": "text", + "content": "5.2. Evaluation Protocol" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 390, + 545, + 582 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 390, + 545, + 582 + ], + "spans": [ + { + "bbox": [ + 304, + 390, + 545, + 582 + ], + "type": "text", + "content": "In this work, we use these metrics for evaluation: 1) Frechet Arcface Distance (FAD) gauges video realism by comparing feature vectors of generated and real videos using advanced face recognition technology [7]. Lower FAD values indicate better realism. 2) Cosine Similarity (CSIM) assesses emotional similarity between generated and target emotional videos using a state-of-the-art expression recognition network, with higher CSIM values denoting greater similarity. 3) Lip Sync Error Distance (LSE-D) [24] evaluates lip-audio accuracy using a pre-trained model [5] to measure the disparities between lip and audio representations, with smaller LSE-D indicates a higher lip-audio accuracy. We present the results of two settings: inter-identification, where emotion reference and source video share the same speaker, and cross-identification, involving different speakers." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 591, + 494, + 604 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 591, + 494, + 604 + ], + "spans": [ + { + "bbox": [ + 306, + 591, + 494, + 604 + ], + "type": "text", + "content": "5.3. Comparison with Baseline Methods" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 609, + 451, + 622 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 609, + 451, + 622 + ], + "spans": [ + { + "bbox": [ + 306, + 609, + 451, + 622 + ], + "type": "text", + "content": "5.3.1 Quantitative Comparisons" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": "We first present the performance comparisons on MEAD in Table 1. When ASCCL is integrated into NED, the resulting image sequences are greatly improved in FAD, LSE-D, and CSIM. In the Cross-ID setting, compared with NED itself, FAD, LSE-D, and CSIM have all improved to a certain extent, with FAD reduced from 4.448 to 4.264, LSE-D from 9.906 to 9.238, and CSIM from 0.773 to 0.791. Among" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "text", + "content": "7271" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 57, + 71, + 536, + 221 + ], + "blocks": [ + { + "bbox": [ + 57, + 71, + 536, + 221 + ], + "lines": [ + { + "bbox": [ + 57, + 71, + 536, + 221 + ], + "spans": [ + { + "bbox": [ + 57, + 71, + 536, + 221 + ], + "type": "table", + "html": "
SettingsEmotionsICfaceOurs (ICface)NEDOurs (NED)
FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑
Inter-IDNeutral7.1149.7600.7797.1589.3820.7810.9069.2640.8830.8919.1130.911
Angry6.42010.4830.7416.1959.7660.8032.1779.5790.8021.1959.5500.896
Disgusted7.38310.4330.8056.2659.2660.8093.8389.1280.7721.6799.4160.854
Fear6.5679.8550.7546.6989.4810.8001.65910.1720.8481.33010.0390.900
Happy6.21310.1800.7756.1919.5560.8371.9399.1370.8391.3268.9750.930
Sad7.30110.0170.7556.7279.2930.7792.5389.0740.8121.1628.9060.906
Surprised6.5679.8510.8177.4709.2710.7951.7009.8210.8641.0569.3820.902
Avg.6.79510.0830.7756.6729.4310.8012.1089.4540.8311.2349.3400.900
Cross-IDNeutral10.56011.2260.7059.74510.6040.6712.0229.8120.8411.8659.1340.852
Angry9.47011.0730.6489.27110.4560.6934.8519.9040.7174.8539.2390.748
Disgusted9.23011.1840.6379.32310.3380.7645.09410.1210.7914.8409.3470.814
Fear9.12211.2040.7279.27310.2210.7294.9839.7410.7504.8209.2390.761
Happy8.49311.3220.7179.50510.4210.7933.9199.9360.8423.3839.1780.866
Sad10.36411.5260.6649.71010.3140.6645.66510.1790.6915.4759.4270.720
Surprised9.54111.1330.7219.53410.2730.7664.6009.6460.7804.6159.1050.779
Avg.9.54011.2380.6889.48010.3750.7264.4489.9060.7734.2649.2380.791
", + "image_path": "e6b025f9b1ba8e14ee0b778e6704ed46d45d74856ee050616bfdfc2157d50940.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 221, + 545, + 243 + ], + "lines": [ + { + "bbox": [ + 46, + 221, + 545, + 243 + ], + "spans": [ + { + "bbox": [ + 46, + 221, + 545, + 243 + ], + "type": "text", + "content": "Table 1. Comparison results of FAD, CSIM, and LSE-D of NED, ICFACE with and without our ASCCL on the inter-Identification and cross-IDentification settings on the MEAD dataset." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 255, + 289, + 554 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 255, + 289, + 554 + ], + "spans": [ + { + "bbox": [ + 46, + 255, + 289, + 554 + ], + "type": "text", + "content": "them, the LSE-D has seen significant improvements, and these notable advancements in the LSE-D metric can be attributed to ASCCL's pivotal role in supervising the training of the SPFEM model. This supervision accentuates the intrinsic visual correlations between the SPFEM model's input and output, ensuring the visual disparity of the input and output align closely thereby enhancing consistency in mouth shape modifications related to emotion. Additionally, the betterment in FAD and CSIM further attests that ASCCL not only maintains but can also elevate the model's training quality, steering it towards superior optimization. In the inter-ID setting, these three indicators are also improved to a certain extent, indicating that the proposed ASCCL algorithm has strong generalization and can adapt to the emotional migration of inter-ID and cross-ID. When incorporating the ASCCL into the single-stage method ICface can also obtain significant performance improvement. In the Inter-ID setting, compared with ICface itself, FAD, LSE-D, and CSIM have all improved to a certain extent, with FAD reduced from 6.795 to 6.672, LSE-D from 10.083 to 9.431, and CSIM from 0.775 to 0.801. Cross-ID is a more general and practical setting, and incorporating the ASCCL also achieves evident improvement on FAD, LSE-D, and CSIM of different expression manipulation as well as the average FAD, LSE-D, and CSIM as shown in Table 1" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": "To demonstrate the generalization ability of the trained ASCCL, we also present the performance comparisons on the RAVDESS [21] dataset without retraining ASCCL. As shown in Table 2, incorporating ASCCL can also obtain obvious improvement for different expression manipulation in both settings. when using the ICface baseline in the interID setting, it decreases the average FAD, LSE-D by 1.142, 0.436, and increases the average CSIM by 0.01. In the Cross-ID setting, it decreases the average FAD, LSE-D by 0.521, 1.226, and the average CSIM remains the same. Similar performance improvement is obtained when using the NED baseline. The experiment corroborates ASCCL's robustness across different methods and data domains." + } + ] + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 313, + 250, + 541, + 540 + ], + "blocks": [ + { + "bbox": [ + 313, + 250, + 541, + 540 + ], + "lines": [ + { + "bbox": [ + 313, + 250, + 541, + 540 + ], + "spans": [ + { + "bbox": [ + 313, + 250, + 541, + 540 + ], + "type": "image", + "image_path": "8638923617c3cd2f8ebd6eb731c85ee1c73580f6949e179ca7def8f71704298c.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 547, + 545, + 578 + ], + "lines": [ + { + "bbox": [ + 304, + 547, + 545, + 578 + ], + "spans": [ + { + "bbox": [ + 304, + 547, + 545, + 578 + ], + "type": "text", + "content": "Figure 5. Qualitative comparisons of NED with and without the proposed ASCCL algorithm. The samples are selected from the MEAD dataset." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 305, + 592, + 446, + 604 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 592, + 446, + 604 + ], + "spans": [ + { + "bbox": [ + 305, + 592, + 446, + 604 + ], + "type": "text", + "content": "5.3.2 Qualitative Comparisons" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": "In this section, we exhibit some visualization results of the baseline NED methodology, both with and without the ASCCL algorithm, as illustrated in Figure 5. Analogous to the quantitative metrics, we also dissect the qualitative comparisons from three dimensions. 1) Realism: The eye region tends to be more closed as a consequence of the NED [23] application, as exemplified in the third column of the second and fifth rows. Furthermore, the mouth region is distorted due to the imprecise prediction of the mouth shape as" + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "7272" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 56, + 71, + 536, + 221 + ], + "blocks": [ + { + "bbox": [ + 56, + 71, + 536, + 221 + ], + "lines": [ + { + "bbox": [ + 56, + 71, + 536, + 221 + ], + "spans": [ + { + "bbox": [ + 56, + 71, + 536, + 221 + ], + "type": "table", + "html": "
SettingsEmotionsICfaceOurs (ICface)NEDOurs (NED)
FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑FAD↓LSE-D↓CSIM↑
Inter-IDNeutral9.8168.2090.7498.3027.2390.7622.0417.3760.8472.8107.5670.853
Angry7.0479.5040.7036.1829.4530.7113.2887.7570.8053.7227.6010.799
Disgusted8.6898.2950.7757.0668.6490.7834.1447.8220.7863.1948.1000.836
Fear8.4138.5230.7227.4068.6250.7412.6357.4520.8422.5887.8210.831
Happy8.4138.9020.7977.4037.9240.7973.7147.7420.7933.0256.6780.826
Sad8.0868.3460.7667.3377.0180.7812.5957.5600.8552.5257.0860.842
Surprised8.6367.5780.7727.4117.4020.7812.9807.2260.8483.4107.2990.824
Avg.8.4438.4800.7557.3018.0440.7653.0577.5620.8253.0397.4500.830
Cross-IDNeutral10.47810.7360.67710.3439.3020.6823.5587.8560.8203.1607.4580.813
Angry8.70412.4150.6468.24210.5220.7065.5468.0850.7664.8518.5130.739
Disgusted9.26011.8600.7178.94810.2340.6527.3888.1070.7417.4437.8480.689
Fear9.10611.2790.6499.06210.3820.7535.0088.1510.7494.1607.8420.799
Happy9.06111.1500.7389.0639.7060.6765.6488.0730.8044.9107.9510.796
Sad9.63911.3050.6669.0439.9160.6345.5888.0060.7264.8477.5450.741
Surprised9.71812.0280.6448.90310.3130.6775.1457.9620.7134.2847.5810.748
Avg.9.42411.5390.6778.90310.3130.6775.4128.0340.7604.8087.8200.761
", + "image_path": "4e5e0ab32762417dcd85049e2e4fc2d89c885bd3505d5cbff85a8642dd3a7aab.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 45, + 255, + 289, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 255, + 289, + 614 + ], + "spans": [ + { + "bbox": [ + 45, + 255, + 289, + 614 + ], + "type": "text", + "content": "shown in the third column for the first rows. The ASCCL ameliorates this NED shortcoming by aligning the visual consistency between inputs and outputs, as demonstrated in the fourth column. 2) Emotional Similarity: Existing works fall short in manipulating facial expressions to communicate the emotions of the reference subject; they generally favor direct replication of facial components into the source, as depicted in the third column in the second, and fifth rows. The ASCCL, by maximizing the alignment of visual disparities between input and output, directs the model to prioritize the extraction of emotional information rather than merely duplicating facial components from the reference into the source, as demonstrated in the fourth column. By incorporating the ASCCL, the NED methodology is more proficient in preserving the source's contours while accomplishing emotional transference. 3) Lip-Audio Preserving Accuracy: The proposed DAAS is designed to focus on regions around with mouth area, which exhibits considerable changes in the input and output of the SFPEM model. Thus, the ASCCL can achieve consistency of the mouth shape by constraining the maximum consistency of the visual disparities for this particular region in the positive samples, as depicted in Figure 5. The results presented in the fourth column demonstrate a superior ability to retain the source's mouth shape compared to those in the third column. We will represent more visualization results of NED and ICface with and without ASCCL algorithm on the MEAD and RAVDESS dataset in the Supplementary materials. We also present some video comparisons for more direct comparison in the Supplementary materials" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 625, + 127, + 639 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 625, + 127, + 639 + ], + "spans": [ + { + "bbox": [ + 47, + 625, + 127, + 639 + ], + "type": "text", + "content": "5.3.3 User study" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": "We conducted web-based user studies to compare the performance of NED with and without the ASCCL algorithm. The study comprises three segments corresponding to the previously mentioned metrics: realism, emotion similarity with the reference emotion, and mouth shape similarity with the source video, covering seven basic emotions." + } + ] + } + ], + "index": 4 + }, + { + "type": "table", + "bbox": [ + 330, + 253, + 521, + 348 + ], + "blocks": [ + { + "bbox": [ + 46, + 221, + 545, + 243 + ], + "lines": [ + { + "bbox": [ + 46, + 221, + 545, + 243 + ], + "spans": [ + { + "bbox": [ + 46, + 221, + 545, + 243 + ], + "type": "text", + "content": "Table 2. Comparison results of FAD, CSIM, and LSE-D of NED, ICFACE with and without our ASCCL on the inter-Identification and cross-IDentification settings on the RAVDESS dataset." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 330, + 253, + 521, + 348 + ], + "lines": [ + { + "bbox": [ + 330, + 253, + 521, + 348 + ], + "spans": [ + { + "bbox": [ + 330, + 253, + 521, + 348 + ], + "type": "table", + "html": "
EmotionRealismEmotion similarityMouth shape similarity
NEDASCCLNEDASCCLNEDASCCL
Neutral28%72%24%76%31%69%
Angry28%72%36%64%30%70%
Disgusted35%65%34%66%26%74%
Fear28%72%35%65%29%71%
Happy28%72%33%67%28%72%
Sad35%65%28%72%25%75%
Surprised30%70%27%73%24%76%
Avg.30%70%31%69%27%73%
", + "image_path": "3aca0c2ed52cf94a7f11624f8f16335546bfad5ae3b765bdd489024380b09eb7.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_body" + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 348, + 545, + 369 + ], + "lines": [ + { + "bbox": [ + 306, + 348, + 545, + 369 + ], + "spans": [ + { + "bbox": [ + 306, + 348, + 545, + 369 + ], + "type": "text", + "content": "Table 3. Realism, emotion similarity, and mouth shape similarity ratings of the user study on NED and our ASCCL." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "spans": [ + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "type": "text", + "content": "For each emotion, we carefully selected 10 videos for both inter-identification and cross-identification settings, totaling 70 videos. Involving 25 participants, each participant was tasked with assessing the three aspects of each video. As detailed in Table 3, the inclusion of the ASCCL algorithm consistently outshines the baseline NED method across all seven emotions in all three metrics. On average, the integration of the ASCCL algorithm demonstrates significant improvement, achieving a " + }, + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "type": "inline_equation", + "content": "40\\%" + }, + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "type": "text", + "content": " higher rating in realism, a " + }, + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "type": "inline_equation", + "content": "38\\%" + }, + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "type": "text", + "content": " higher rating in emotion similarity, and an impressive " + }, + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "type": "inline_equation", + "content": "46\\%" + }, + { + "bbox": [ + 304, + 380, + 547, + 548 + ], + "type": "text", + "content": " higher rating in mouth shape similarity compared to the NED baseline. Supplementary materials include user studies utilizing the ICface baseline on MEAD and employing both NED and ICface baselines on RAVDESS." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 555, + 400, + 568 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 555, + 400, + 568 + ], + "spans": [ + { + "bbox": [ + 306, + 555, + 400, + 568 + ], + "type": "text", + "content": "5.4. Ablation Study" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 573, + 547, + 645 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 573, + 547, + 645 + ], + "spans": [ + { + "bbox": [ + 304, + 573, + 547, + 645 + ], + "type": "text", + "content": "In the ablation experiment section, we first investigate the effect of pre-training ASCCL with paired data on the final result. Following that, the pre-trained ASCCL is integrated into the NED, with an analysis of supervision on different results(3DMM or render image) and an examination of the impact of DAAS." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 650, + 493, + 662 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 650, + 493, + 662 + ], + "spans": [ + { + "bbox": [ + 306, + 650, + 493, + 662 + ], + "type": "text", + "content": "5.4.1 Analyses of ASCCL metric learning" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": "Our statistical analysis demonstrates an inherent spatially coherent correlation between the input and output of the SPFEM model. Even untrained, the ASCCL can approximate this correlation, as depicted in Figure 2. By pre" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7273" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 120 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 120 + ], + "type": "text", + "content": "training ASCCL with paired data, we enhance the ASCCL's ability to discern inherent visual consistency. As shown in Figure 6, there is a notable improvement in the similarity and correlation coefficients for positive samples. Fur" + } + ] + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 63, + 137, + 164, + 282 + ], + "blocks": [ + { + "bbox": [ + 63, + 137, + 164, + 282 + ], + "lines": [ + { + "bbox": [ + 63, + 137, + 164, + 282 + ], + "spans": [ + { + "bbox": [ + 63, + 137, + 164, + 282 + ], + "type": "image", + "image_path": "d083bd48d1964216cda113f1e0c4eee88e1547e499409efd06946f202eac9a75.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 100, + 282, + 113, + 291 + ], + "lines": [ + { + "bbox": [ + 100, + 282, + 113, + 291 + ], + "spans": [ + { + "bbox": [ + 100, + 282, + 113, + 291 + ], + "type": "text", + "content": "(a)" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 300, + 287, + 331 + ], + "lines": [ + { + "bbox": [ + 46, + 300, + 287, + 331 + ], + "spans": [ + { + "bbox": [ + 46, + 300, + 287, + 331 + ], + "type": "text", + "content": "Figure 6. (a) Average similarities and (b) Average Pearson correlation coefficients of the positive and negative samples after training the SCCL metric" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 173, + 137, + 278, + 282 + ], + "blocks": [ + { + "bbox": [ + 173, + 137, + 278, + 282 + ], + "lines": [ + { + "bbox": [ + 173, + 137, + 278, + 282 + ], + "spans": [ + { + "bbox": [ + 173, + 137, + 278, + 282 + ], + "type": "image", + "image_path": "c24500cebe7786f216d9e6eeba2d09184072b095d31e78308392d7e37553c214.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 217, + 282, + 228, + 291 + ], + "lines": [ + { + "bbox": [ + 217, + 282, + 228, + 291 + ], + "spans": [ + { + "bbox": [ + 217, + 282, + 228, + 291 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 342, + 287, + 475 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 342, + 287, + 475 + ], + "spans": [ + { + "bbox": [ + 46, + 342, + 287, + 475 + ], + "type": "text", + "content": "thermore, we employ both trained and untrained ASCCL to guide the SPFEM model's training, as depicted in Table 4. Irrespective of whether the ASCCL has been pretrained, it can serve as a guide when integrated into the SFPEM model. The pre-trained ASCCL demonstrated superior performance to the untrained ASCCL on measures including FAD, LSE-D, and CSIM. This indicates that by utilizing paired data to train the ASCCL, we can more effectively capture the spatial coherent correlations between the SFPEM's input and output, thereby enhancing the model's guidance." + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 70, + 487, + 263, + 550 + ], + "blocks": [ + { + "bbox": [ + 70, + 487, + 263, + 550 + ], + "lines": [ + { + "bbox": [ + 70, + 487, + 263, + 550 + ], + "spans": [ + { + "bbox": [ + 70, + 487, + 263, + 550 + ], + "type": "table", + "html": "
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours untrained1.5099.4340.861
Ours trained1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours untrained4.3069.4580.784
Ours trained4.2649.2380.791
", + "image_path": "be612114a5e5868df50a93e5827ff21ba9e6188039f1b1b2e3db6603872594d2.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 579, + 265, + 591 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 579, + 265, + 591 + ], + "spans": [ + { + "bbox": [ + 47, + 579, + 265, + 591 + ], + "type": "text", + "content": "5.4.2 Analysis of supervision on different outputs" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 597, + 287, + 716 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 597, + 287, + 716 + ], + "spans": [ + { + "bbox": [ + 46, + 597, + 287, + 716 + ], + "type": "text", + "content": "ASCCL can supervise either the intermediate 3DMM parameters or the final rendered images. In this section, we present two additional baselines that solely utilize the objective on the 3DMM parameters (Ours 3DMM) or final rendered images (Ours Image). As depicted in Table 5, incorporating the objective solely to either 3DMM parameters or images results in significant improvements across various metrics. Moreover, introducing the objective to both the 3DMM parameters and rendered images yields even greater improvement." + } + ] + } + ], + "index": 10 + }, + { + "type": "table", + "bbox": [ + 332, + 70, + 520, + 150 + ], + "blocks": [ + { + "bbox": [ + 52, + 550, + 282, + 561 + ], + "lines": [ + { + "bbox": [ + 52, + 550, + 282, + 561 + ], + "spans": [ + { + "bbox": [ + 52, + 550, + 282, + 561 + ], + "type": "text", + "content": "Table 4. The performance of ASSCL with and without training." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 332, + 70, + 520, + 150 + ], + "lines": [ + { + "bbox": [ + 332, + 70, + 520, + 150 + ], + "spans": [ + { + "bbox": [ + 332, + 70, + 520, + 150 + ], + "type": "table", + "html": "
SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours 3DMM1.3329.3880.887
Ours image1.3139.3940.889
Ours1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours 3DMM4.3099.3110.787
Ours image4.2769.3210.785
Ours4.2649.2380.791
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SettingsMethodsFAD↓LSE-D↓CSIM↑
Inter-IDNED2.1089.4540.831
Ours w/o DAAS1.3429.4020.885
Ours DAAS1.2349.3400.900
Cross-IDNED4.4489.9060.773
Ours w/o DAAS4.3189.3300.786
Ours DAAS4.2649.2380.791
", + "image_path": "da5e85d91a75e6df22ead0b3f8956e1e3e2d6b24a2403890e0cf05c6ae2ae205.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "table_body" + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 309, + 545, + 331 + ], + "lines": [ + { + "bbox": [ + 305, + 309, + 545, + 331 + ], + "spans": [ + { + "bbox": [ + 305, + 309, + 545, + 331 + ], + "type": "text", + "content": "Table 6. Comparison results of average FAD, CSIM, and LSE-D of NED, with or w/o DAAS" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 338, + 545, + 469 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 338, + 545, + 469 + ], + "spans": [ + { + "bbox": [ + 304, + 338, + 545, + 469 + ], + "type": "text", + "content": "Through empirical analysis, we observed that visual disparities are sensitive to regions. We employed DAAS to direct the ASCCL's attention toward those challenging regions, thereby enhancing the consistency of mouth movements between input and output. In this section, We examined the influence of incorporating DAAS into the outcome. As depicted in Table 6, in the absence of DAAS, our approach outperforms NED across all metrics. Moreover, when DAAS is integrated into our method, ASCCL achieves even more optimal results by dynamically adapting the learning strategy to different regions." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 480, + 378, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 480, + 378, + 491 + ], + "spans": [ + { + "bbox": [ + 306, + 480, + 378, + 491 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 498, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 545, + 712 + ], + "type": "text", + "content": "In this work, we propose an adaptive spatial coherent correlation learning (ASCCL) algorithm to investigate the inherent visual correlations between the SPFEM model's input and output to construct paired supervision to improve facial expression manipulation and meanwhile better preserve the facial animation of speech content. It first characterizes the visual disparities, and then constrains the visual disparities in adjacent local regions of the input image to align with those in corresponding adjacent regions of the output image from the SPFEM model, together with a disparity-aware adaptive strategy to adaptively learn based on the visual disparity of each adjacent region. ASCCL is implemented by a plug-and-play loss that can be seamlessly integrated into any advanced methods to facilitate SPFEM performance. We conduct extensive experiments that integrate ASCCL to two advanced SPFEM models and carry out variant quantitative and qualitative comparisons as well as user studies to demonstrate the effectiveness." + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7274" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 12, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 139 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 139 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 139 + ], + "type": "text", + "content": "[1] Volker Blanz and Thomas Vetter. 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Unpaired image-to-image translation using cycle-consistent adversarial networks. In Proceedings of the IEEE international conference on computer vision, pages 2223-2232, 2017." + } + ] + } + ], + "index": 15 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "7276" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Background Prompts to Discover Implicit Knowledge for Open Vocabulary Object Detection/57bc7ecd-3bfc-4e56-9aff-1de8b9713c30_content_list.json b/2024/Learning Background Prompts to Discover Implicit Knowledge for Open Vocabulary Object Detection/57bc7ecd-3bfc-4e56-9aff-1de8b9713c30_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..1f09ff706f1543ad37ba989a913a6e09a4c6ab87 --- /dev/null +++ b/2024/Learning Background Prompts to Discover Implicit Knowledge for Open Vocabulary Object Detection/57bc7ecd-3bfc-4e56-9aff-1de8b9713c30_content_list.json @@ -0,0 +1,1695 @@ +[ + { + "type": "text", + "text": "Learning Background Prompts to Discover Implicit Knowledge for Open Vocabulary Object Detection", + "text_level": 1, + "bbox": [ + 148, + 161, + 821, + 204 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Jiaming Li $^{1}$ Jiacheng Zhang $^{1}$ Jichang Li $^{1,2}$ Ge Li $^{3}$ Si Liu $^{4}$ Liang Lin $^{1}$ Guanbin Li $^{1,5,6*}$", + "bbox": [ + 245, + 227, + 723, + 260 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{1}$ School of Computer Science and Engineering, Sun Yat-sen University, Guangzhou, China", + "bbox": [ + 158, + 260, + 813, + 277 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ Department of Computer Science, The University of Hong Kong, Hong Kong", + "bbox": [ + 202, + 277, + 769, + 294 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{3}$ SECE, Shenzhen Graduate School, Peking University, Shenzhen, China", + "bbox": [ + 223, + 294, + 748, + 309 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{4}$ Institute of Artificial Intelligence, Beihang University, China", + "bbox": [ + 263, + 310, + 709, + 325 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "5GuangDong Province Key Laboratory of Information Security Technology", + "bbox": [ + 212, + 325, + 756, + 340 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{6}$ Research Institute, Sun Yat-sen University, Shenzhen, China", + "bbox": [ + 263, + 342, + 707, + 357 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{lijm48,zhangjch58}@mail2.sysu.edu.cn,{liguanbin,linlng}@mail.sysu.edu.cn", + "bbox": [ + 189, + 359, + 782, + 375 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "csjcli=connect.hku.hk, lige@pku.edu.cn, liusi@buaa.edu.cn", + "bbox": [ + 251, + 377, + 714, + 388 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 256, + 421, + 328, + 436 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Open vocabulary object detection (OVD) aims at seeking an optimal object detector capable of recognizing objects from both base and novel categories. Recent advances leverage knowledge distillation to transfer insightful knowledge from pre-trained large-scale vision-language models to the task of object detection, significantly generalizing the powerful capabilities of the detector to identify more unknown object categories. However, these methods face significant challenges in background interpretation and model overfitting and thus often result in the loss of crucial background knowledge, giving rise to sub-optimal inference performance of the detector. To mitigate these issues, we present a novel OVD framework termed LBP to propose learning background prompts to harness explored implicit background knowledge, thus enhancing the detection performance w.r.t. base and novel categories. Specifically, we devise three modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification, to empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. Evaluation on two benchmark datasets, OV-COCO and OV-LVIS, demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks.", + "bbox": [ + 109, + 518, + 473, + 851 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/43bef6be581de375cf2e35f8e7aa0303771555752ea9a7ed376f09897d35b472.jpg", + "image_caption": [ + "Conventional designs" + ], + "image_footnote": [], + "bbox": [ + 516, + 420, + 619, + 500 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c3bc295216c78fc7280a9025d101cdd810db3508cbde6aa0ad2e5e8c3c21afc1.jpg", + "image_caption": [ + "DetPro" + ], + "image_footnote": [], + "bbox": [ + 627, + 420, + 730, + 500 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/7c6e4898177e4d4d20b19f27dd598c37c8639672ec4773ceb2bfc55195e43e63.jpg", + "image_caption": [ + "LBP(ours)" + ], + "image_footnote": [], + "bbox": [ + 740, + 420, + 844, + 500 + ], + "page_idx": 0 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "★ Visual embedding encoded by CLIP $\\bullet$ Background class embedding", + "$\\bigcirc$ Base class contextual embedding RoI embeddings encoded by detector", + "Distillation loss Background classification loss", + "Uniform distribution boundary Background underlying class embedding" + ], + "bbox": [ + 516, + 512, + 834, + 547 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Figure 1. An example to illustrate previous and our designs in background interpretation. Conventional designs use a single background embedding to push the RoI embedding away from the CLIP embedding. DetPro [4] proposes to uniformly push the RoI embedding away when the CLIP embedding nears a base class embedding, leading to a loss of class relation. Our LBP, on the other hand, learns multiple background underlying class embeddings, effectively preserving class relations and alleviating loss conflict. \"Distillation loss\" uses knowledge distillation to align visual features encoded by the decoder with CLIP embeddings, while \"Background classification loss\" refers to the classification loss for background proposals.", + "bbox": [ + 496, + 558, + 859, + 712 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 500, + 729, + 619, + 744 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Compared to conventional vision tasks [11, 12, 18-22, 39], object detection has witnessed significant success in research, such as [26, 30, 32, 41], however, solely detecting and classifying objects within known categories (base classes) during inference significantly diminishes its generalization capacity in real-world applications. Open Vo", + "bbox": [ + 496, + 755, + 857, + 839 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 138, + 45, + 207, + 80 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 258, + 42, + 782, + 84 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author.", + "bbox": [ + 514, + 853, + 633, + 864 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "16678", + "bbox": [ + 480, + 890, + 517, + 901 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "cabulary Object Detection (OVD) emerges as a prospective means to overcome this restriction, endowed with the capability to detect unseen categories (novel classes), without the explicit need for annotations.", + "bbox": [ + 111, + 126, + 470, + 180 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Leveraging large-scale pre-trained Vision and Language Models (PVLMs), exemplified by CLIP [29] and ALIGN [13], recent advances in OVD, e.g. [4, 7, 35], employ knowledge distillation to transfer insightful knowledge of PVLMs to the task of object detection, generalizing its powerful capabilities to detect more unknown object categories. However, these methods face a critical limitation in background interpretation. Specifically, these approaches tend to represent background proposals with a single \"background class\", encompassing all categories beyond foreground base classes. With solely a singular learnable embedding to interpret this background class, the trained model may fail to capture the diverse implicit knowledge within background proposals. This leads to the loss of essential background information, resulting in incomplete and ambiguous representations of unseen categories by the model. Consequently, the model is incapable of distinguishing objects from those unknown categories using their representations.", + "bbox": [ + 111, + 183, + 473, + 445 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To tackle this problem, researchers experimented with various strategies like binary cross-entropy loss [2] or soft background loss [4] for background interpretation. However, their basic assumption that background proposals are uniformly dissimilar to any foreground category overlooks the nuanced class relations between foreground and background classes, as illustrated in Figure 1. Additionally, these methods struggle with model overfitting during training due to an abundance of fully supervised data from base classes, which makes detectors biased toward those categories. Recent advances like [2, 5, 6, 40] propose mining implicit objects of novel categories from background proposals and employing pseudo-labeling to enhance their interpretation. Yet, these methods often rely on additional prior knowledge, such as the names of novel categories, leaving substantial unexplored knowledge.", + "bbox": [ + 111, + 449, + 473, + 671 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this paper, we present LBP, a novel framework for open-vocabulary object detection. Without any prior knowledge, LBP proposes learning background prompts to harness explored implicit background knowledge, thus enhancing the detection performance w.r.t. base and novel categories. Specifically, the LBP framework initially introduces a Background Category-specific Prompt module. It discovers and represents background underlying categories estimated from background proposals by leveraging learnable category-specific contexts, consequently resulting in improved background interpretation. Then, an online module, namely Background Object Discovery, is introduced to further explore and exploit implicit object knowledge correlated with those estimated underlying categories from", + "bbox": [ + 111, + 672, + 473, + 867 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "background proposals, significantly contributing to mitigating model overfitting. Moreover, an Inference Probability Rectification module is presented to address conceptual overlaps between estimated background categories and novel categories provided during inference. This rectification enables the model to accurately compute probabilities for novel categories, thereby significantly enhancing the detector performance. The contributions are summarized as follows.", + "bbox": [ + 496, + 126, + 857, + 248 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose a novel framework, termed LBP, for open-vocabulary object detection, where learning background prompts is presented to harness explored implicit background knowledge, thereby enhancing detection of both base and novel categories during inference.", + "- We devise three modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification, to empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals.", + "- Evaluation on two benchmark datasets, OV-COCO [25] and OV-LVIS [9], demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks." + ], + "bbox": [ + 500, + 250, + 857, + 443 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 455, + 629, + 470 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Open vocabulary object detection (OVD). OVR-CNN [38] pioneered open vocabulary object detection, by expanding object detection capabilities through image-caption datasets. Subsequently, prevailing approaches to tackle OVD have primarily relied on fine-tuning PVLMs [16, 17, 23, 24, 28, 42]. However, retraining PVLMs with large-scale learnable model weights is resource-intensive. Consequently, more recent approaches rooted in knowledge distillation [27, 34, 36] to address OVD by leveraging knowledge distilled from CLIP [29] into the detector, predominantly adopting source-free strategies. For example, ViLD [7] aligns detector-encoded features with CLIP embeddings, while BARON [35] generates region ensembles using random masking within grid spaces to distill visual concept co-occurrence within a scene. Despite partially transferring knowledge of novel categories from PVLMs, detectors exhibit bias towards base classes due to disparities between vision-language alignment and detection tasks. To mitigate this bias, researchers explore pseudo labeling techniques utilizing prior knowledge of novel category names [40] or weakly-supervised annotations to the detection dataset [2, 6, 46]. However, integrating additional knowledge poses limitations in real-world scenarios.", + "bbox": [ + 496, + 479, + 857, + 809 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our proposed method extracts background implicit knowledge about classes beyond known/base categories from the provided detection dataset without requiring prior information about novel categories during inference. This", + "bbox": [ + 496, + 811, + 857, + 867 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "16679", + "bbox": [ + 480, + 890, + 517, + 901 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/38ffbef51f90408addcce8c51f17e36bd985dd2eaa3ff216597e6d4fe9695c24.jpg", + "image_caption": [ + "Figure 2. An overview of the proposed LBP approach, consisting of three modules: Background Category-specific Prompt (BCP), Background Object Discovery (BOD), and Inference Probability Rectification (IPR). During training, BCP is first proposed to discover and represent background underlying categories, estimated from background proposals, with learnable background category-specific contexts. Then, BOD is presented to employ $k$ -means clustering on background proposals across all images to harness implicit objects explored from background underlying knowledge. During inference, IPR is introduced to rectify probability scores of novel categories provided, by loosening their conceptual overlaps with background underlying categories estimated from background proposals." + ], + "image_footnote": [], + "bbox": [ + 127, + 123, + 848, + 421 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "utilization of implicit knowledge enables the detector to identify objects from unknown categories, enhancing its applicability across diverse scenarios.", + "bbox": [ + 109, + 530, + 472, + 571 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Prompt tuning for OVD: Prompt tuning, stemming from natural language processing, has evolved with PVLM advancements to enhance their efficacy in specific downstream tasks [15]. CoOp, proposed in [44], introduces learnable contexts for 2D vision-language classification. CoCoOp, an extension proposed by [43], further enhances CoOp by generating input-conditioned tokens for each image. Various visual prompting approaches advocate integrating prompts into the image encoder of PVLMs, including works such as [1, 3, 8, 14].", + "bbox": [ + 109, + 574, + 470, + 712 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In the realm of OVD, DetPro [29] pioneered prompt engineering by implementing a soft background loss, significantly improving the detector's ability to represent specific categories. Similarly, proposals for pre-training prompts on large-scale datasets [5, 31] aim to generate more universally applicable prompts. In contrast to DetPro [29], our approach has no reliance on uniform distribution assumption. Instead, by prompting underlying background categories estimated from proposals, our method enhances the learning of unknown category representations, leading to significant performance gains in detection.", + "bbox": [ + 109, + 714, + 472, + 866 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Approach", + "text_level": 1, + "bbox": [ + 500, + 529, + 598, + 545 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Preliminaries", + "text_level": 1, + "bbox": [ + 500, + 551, + 627, + 566 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Problem formulation. Open vocabulary object detection (OVD) aims at seeking an optimal object detector capable of recognizing objects from both base and novel (previously unseen) categories, denoted by $\\mathcal{C}_b = \\{c_i\\}_{i=1}^{n_b}$ and $\\mathcal{C}_u = \\{c_i\\}_{i=1}^{n_u}$ , respectively, in the inference dataset $\\mathcal{D}_I$ . This detector is achieved through optimization on the training dataset $\\mathcal{D}_T$ , annotated exclusively with instances from the base classes within $\\mathcal{C}_b$ . Here, $\\mathcal{C}_b \\cap \\mathcal{C}_u = \\emptyset$ , while $n_b$ and $n_u$ represent the cardinality of the respective category sets.", + "bbox": [ + 496, + 574, + 857, + 699 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Built upon Faster R-CNN [30], given an input image, it is initially encoded by Faster R-CNN into global image features and generates a set of proposals through a region proposal network (RPN). In general, these region proposals are categorized into foreground proposals and background proposals [4], designated as $\\mathcal{P}$ and $\\mathcal{N}$ , respectively. The foreground proposals in $\\mathcal{P}$ encompass all base categories within $\\mathcal{C}_b$ , while all background proposals from $\\mathcal{N}$ are collectively classified as a singular super-class (denoted as $c_{bg}$ here), representing any category outside of $\\mathcal{C}_b$ .", + "bbox": [ + 496, + 699, + 857, + 838 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Knowledge distillation. Leveraging large-scale pre-trained large-scale Vision and Language Models (PVLMs), specif", + "bbox": [ + 500, + 839, + 857, + 866 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "16680", + "bbox": [ + 480, + 890, + 517, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ically CLIP [44], knowledge distillation empowers Faster R-CNN to effectively detect objects from arbitrary vocabularies by transferring insightful knowledge from CLIP. This process involves aligning the proposal features generated by the detector (actually output by the RoI Head of the detector, denoted by $w(\\cdot)$ ) with those extracted by the image encoder of CLIP (denoted by $\\mathcal{I}(\\cdot)$ ), effectively simulating coherence between the feature spaces of the detector and CLIP. Consequently, this process implicitly projects the visual embedding space of the detector into the textual embedding space of CLIP (output by the text encoder of CLIP, denoted by $\\mathcal{T}(\\cdot)$ ). In this way, the original classifier of Faster R-CNN is replaced.", + "bbox": [ + 109, + 125, + 472, + 305 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Foreground/background interpretation. Given class $c$ from $\\mathcal{C}_b$ , its contextual prompt is defined as 'a photo of {category} in the scene', noted as $V_{c}$ . Here, '\\{category\\}' denotes the contextual word for class $c$ . Then its contextual embedding is obtained by feeding $V_{c}$ into the CLIP text encoder $\\mathcal{T}(\\cdot)$ , as follows,", + "bbox": [ + 112, + 305, + 472, + 388 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {t} _ {c} = \\mathcal {T} (\\boldsymbol {V} _ {c}). \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 250, + 398, + 470, + 414 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "However, it is challenging to determine the contextual word for the \"background\" class $c_{bg}$ . ViLD [7] or BARON [35] represents it with a learnable contextual embedding, without encoding it via CLIP's text encoder $\\mathcal{T}(\\cdot)$ , thus defining it as $t_{bg}$ .", + "bbox": [ + 109, + 422, + 472, + 491 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Probability calculation. Having obtained $\\{t_c|c\\in \\mathcal{C}_b\\} \\cup$ $\\{\\pmb {t}_{bg}\\}$ , let $\\pmb {w}(\\cdot)$ denote the visual embedding of a proposal generated by the RoI Head of the object detector. Consider $\\mathcal{C}_b^{bg} = \\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\}$ . For any proposal $x\\in \\mathcal{P}\\cup \\mathcal{N}$ from $\\mathcal{D}_T$ with its visual embedding $\\pmb {w}(\\pmb {x})$ , the probability of categorizing this proposal under the category $c\\in \\mathcal{C}_b^{bg}$ is defined as follows:", + "bbox": [ + 112, + 491, + 472, + 589 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\np (c | x; \\mathcal {C} _ {b} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c}) / \\tau)}{\\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {b} ^ {b g}} \\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau)}, \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 148, + 595, + 472, + 630 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\exp (\\cdot)$ and $\\cos (\\cdot)$ represent the exponential function and cosine similarity, respectively, while $\\tau$ is the temperature parameter used for rescaling the values.", + "bbox": [ + 109, + 638, + 472, + 680 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "During inference, once the novel classes from $\\mathcal{C}_u$ are introduced, the probability of a proposal from $\\mathcal{D}_I$ being classified as class $c$ of $\\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\} \\cup \\mathcal{C}_u$ during detection can be computed simply by replacing $\\mathcal{C}_b^{bg}$ in Eq. (2) with $\\mathcal{C}_{b,u}^{bg} = \\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\} \\cup \\mathcal{C}_u$", + "bbox": [ + 109, + 680, + 472, + 755 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. The Proposed Method", + "text_level": 1, + "bbox": [ + 112, + 762, + 302, + 777 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this paper, we introduce LBP, a novel framework designed for open-vocabulary object detection. The key idea of LBP is that without any prior knowledge, learning background prompts is proposed to harness explored implicit background knowledge. This ensures the model attains improved background interpretation and decreased model", + "bbox": [ + 109, + 782, + 472, + 866 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "overfitting, thus empowering the detector capable of better recognizing both base and novel categories. Specifically, the LBP framework initially introduces a Background Category-specific Prompt (BCP) module, discovering underlying categories from background proposals, and representing those using learnable context-specific prompts. Moreover, we introduce an online Background Object Discovery (BOD) to further exploit implicit object knowledge w.r.t. those estimated underlying categories, consequently alleviating model bias towards base categories, and present an Inference Probability Rectification (IPR) module to resolve conceptual overlaps between estimated background categories and novel categories during inference, leading to precisely computed probability scores for novel categories. Our primary focus lies in exploring background interpretation, distinct from prevailing OVD approaches rooted in knowledge distillation. This enables seamless integration of our method into existing OVD frameworks [35] and ViLD [7], etc. An overview of the proposed approach is illustrated in Figure 2.", + "bbox": [ + 496, + 125, + 859, + 404 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2.1 Background Category-specific Prompt", + "text_level": 1, + "bbox": [ + 498, + 419, + 795, + 431 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this section, we model the underlying categories for background proposals in OVD and learn the corresponding category-specific prompts. However, the absence of prior knowledge of those categories necessitates the estimation of their optimal number in background proposals.", + "bbox": [ + 496, + 440, + 857, + 508 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Towards this end, we first produce background proposals for all training images using a class-agnostic RPN trained on $\\mathcal{D}_T$ with only base classes, adopting a similar technique as in VL-PLM [40]. Those proposals are subsequently filtered based on RPN scores (with a threshold $\\theta$ ), and Non-Maximum Suppression (NMS). Then, we obtain features for these filtered proposals generated from the image encoder of CLIP, and we refer to [10, 41] to estimate the optimal number of the underlying categories in background proposals via K-mean clustering [33], denoted by $n_o$ , in the obtained proposal features. During this procedure, potential ambiguity in data partitioning during estimation may arise due to feature overlap, leading to the underestimation of $n_o$ . Consequently, we expand the count of background underlying categories to $n_o + n_a$ , where $n_a$ serves as a pre-defined hyper-parameter. Here, let $\\mathcal{C}_O = \\{c_i\\}_{i=1}^{n_o + n_a}$ denote those estimated background categories, for simplicity.", + "bbox": [ + 496, + 508, + 857, + 744 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "However, due to the absence of prior knowledge of $\\mathcal{C}_O$ , identifying their contextual words is a non-trivial task. To address this issue, we propose to learn category-specific context vectors. In this case, the contextual words of those background underlying categories can be described with the learned continuous vectors. Specifically, we adopt the prompt form for a given class $c \\in \\mathcal{C}_O$ as follows:", + "bbox": [ + 496, + 744, + 857, + 840 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\bar {V} _ {c} = ^ {\\prime} a \\text {p h o t o o f} \\left\\{v _ {c} \\right\\} \\text {i n t h e s c e n e} ^ {\\prime}, \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 516, + 851, + 857, + 867 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "16681", + "bbox": [ + 480, + 890, + 514, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the context vectors $\\{v_{c}|c\\in \\mathcal{C}_{O}\\}$ are learnable. Following Eq. (1), the corresponding contextual embeddings can be acquired as $\\bar{\\iota}_c = \\mathcal{T}(\\overline{\\mathbf{V}}_c)$ .", + "bbox": [ + 111, + 125, + 470, + 167 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Additionally, we present a specific sub-class category, $\\overline{c}_{bg}$ , designed to represent the \"background\" within background proposals, distinct from the super-class \"background\" $c_{bg}$ . Specifically, $\\overline{c}_{bg}$ covers unexplored categories not estimated in $\\mathcal{C}_O$ and includes any untargeted object within background proposals. Similar to $t_{bg}$ , we define a learnable contextual embedding, $\\overline{t}_{bg}$ , for this category $\\overline{c}_{bg}$ .", + "bbox": [ + 111, + 167, + 470, + 263 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Once we obtain $\\{\\pmb{t}_c|c\\in \\mathcal{C}_b\\} \\cup \\{\\bar{\\pmb{t}}_c|c\\in \\mathcal{C}_O\\} \\cup \\{\\bar{\\pmb{t}}_{bg}\\}$ , the corresponding set of categories can be defined as $\\mathcal{C}_{b,o}^{bg} = \\mathcal{C}_b\\cup \\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}$ . With reference to Eq. (2), for any proposal $x\\in \\mathcal{P}\\cup \\mathcal{N}$ , its probability of being classified as class $c\\in \\mathcal{C}_{b,o}^{bg}$ can be defined as $p(c|x;\\mathcal{C}_{b,o}^{bg})$ . At this point, the model optimization in the BCP for the proposals in $\\mathcal{P}$ and $\\mathcal{N}$ can be achieved using the following cross-entropy losses:", + "bbox": [ + 111, + 263, + 470, + 362 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {c l s} = \\frac {1}{| \\mathcal {P} |} \\sum_ {x \\in \\mathcal {P}} - \\log p (c = \\boldsymbol {C} (x) | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 161, + 366, + 470, + 398 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {b c p} = \\frac {1}{| \\mathcal {N} |} \\sum_ {x \\in \\mathcal {N}} - \\log \\sum_ {c \\in \\mathcal {C} _ {O} \\cup \\{\\bar {\\mathfrak {c}} _ {b g} \\}} p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 148, + 404, + 470, + 440 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $C(x)$ represents the true label class of the given proposal $x$ . $\\mathcal{L}_{bcp}$ enhances the sum of probabilities of all background underlying categories estimated and $\\overline{c}_{bg}$ within each background proposal, enabling the detector to softly learn the probabilities scores assigned for those categories.", + "bbox": [ + 111, + 443, + 470, + 513 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "However, contextual embeddings of $\\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}$ might not be sufficient to represent all background proposals with diverse scenes. When a background proposal belongs to $\\overline{c}_{bg}$ and cannot be adequately represented by its contextual embedding, the visual embeddings of that proposal will be distant from any contextual embeddings of the estimated categories from $\\mathcal{C}_O$ . Consequently, the sum of probabilities of those categories, i.e., $\\sum_{c\\in \\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}}p(c|x;\\mathcal{C}_{b,o}^{bg})$ in Eq. (5), denoted as $p_o^{bg}$ , for simplicity, would become very small.", + "bbox": [ + 111, + 512, + 470, + 638 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this situation, we should uniformly push the visual embeddings of that proposal towards the estimated background underlying categories and $\\bar{c}_{bg}$ , given that the proposal is distinct from those categories. When $p_{o}^{bg} < \\gamma$ , we introduce an additional softer background loss component to relax $\\mathcal{L}_{bcp}$ for all background proposals in $\\mathcal{N}$ as follows,", + "bbox": [ + 111, + 638, + 470, + 722 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {r l x} = \\frac {1}{| \\mathcal {N} |} \\sum_ {x \\in \\mathcal {N}} \\frac {1}{n _ {o a}} \\sum_ {c \\in \\mathcal {C} _ {O} \\cup \\{\\bar {e} _ {b g} \\}} - \\log p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 127, + 726, + 470, + 762 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $n_{oa} = n_o + n_a + 1$ represents the size of $\\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}$ while $\\gamma$ is a threshold with a small value. Therefore, the final version of the loss component in this BCP for background proposals to optimize the model is formulated as,", + "bbox": [ + 111, + 767, + 470, + 823 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {b c p} ^ {\\prime} = \\left\\{ \\begin{array}{l l} \\mathcal {L} _ {b c p}, & \\text {i f} \\boldsymbol {p} _ {o} ^ {b g} \\geq \\gamma , \\\\ \\mathcal {L} _ {r l x}, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 202, + 832, + 470, + 869 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Note that $\\mathcal{L}_{bcp}^{\\prime}$ enriches the discrimination capability of the detector by incorporating diverse contextual embeddings of estimated background categories, diverging from the soft background loss in DetPro [4]. This enables the model to exploit implicit object knowledge w.r.t. those estimated underlying categories, while also reconciling training conflicts between the losses utilized for classification and distillation, as highlighted in prior works [35].", + "bbox": [ + 496, + 125, + 857, + 237 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.2.2 Background Object Discovery", + "text_level": 1, + "bbox": [ + 498, + 253, + 741, + 267 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To enhance model training, we introduce an online Background Object Discovery (BOD) module to effectively discover and exploit unseen objects. This aims to extract implicit objects w.r.t. the underlying categories estimated from background proposals. To simplify, we here decompose $\\mathcal{C}_O$ into $\\mathcal{C}_O' = \\{c_i\\}_{i=1}^{n_o}$ and $\\mathcal{C}_a = \\{c_i\\}_{i=1}^{n_a}$ in this section.", + "bbox": [ + 496, + 273, + 857, + 358 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "During initial training, with a given $n_o$ , we conduct $k$ means clustering (where $k$ is set to $n_o$ ) on the set of visual embeddings $\\{\\mathcal{I}(x)|x\\in \\mathcal{N}\\}$ generated by the image encoder of CLIP for background proposals as in Sec. 3.2.1. Then, we subsequently obtain the embeddings of the cluster centers, denoted as $\\{\\tilde{w}_c|c\\in \\mathcal{C}_O^{\\prime}\\}$ . These cluster centers function as the embedding centers for the estimated background categories within $\\mathcal{C}_O^\\prime$ , allowing for online generation of pseudo labels from background proposals in each training batch. Throughout the training process, motivated by VL-PLM proposed in [40], background proposals of each training batch undergo being filtered based on RPN scores using a threshold of $\\theta$ , with an additional step to filter out proposals overlapping with ground-truth boxes. Subsequently, CLIP is employed to generate pseudo labels, preventing the detector from being biased towards estimated background categories.", + "bbox": [ + 496, + 358, + 857, + 592 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Then, for a proposal $x\\in \\mathcal{N}$ , its probability score of being classified as $c\\in \\mathcal{C}_O^{\\prime}$ is calculated as follows,", + "bbox": [ + 498, + 592, + 857, + 619 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {p} (c | x; \\mathcal {C} _ {O} ^ {\\prime}) = \\frac {\\exp (\\cos (\\mathcal {I} (x) , \\tilde {\\boldsymbol {w}} _ {c}) / \\tau)}{\\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O} ^ {\\prime}} \\exp (\\cos (\\mathcal {I} (x) . \\tilde {\\boldsymbol {w}} _ {c ^ {\\prime}}) / \\tau)}. \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 535, + 628, + 857, + 664 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Once such background proposal has probability scores corresponding to all categories in $\\mathcal{C}_O^{\\prime}$ , we choose the predicted class label with the highest score as its pseudo label,", + "bbox": [ + 496, + 672, + 857, + 714 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {Y} ^ {o} (x) = \\underset {c} {\\operatorname {a r g m a x}} \\left\\{\\tilde {p} \\left(c | x; \\mathcal {C} _ {O} ^ {\\prime}\\right) | c \\in \\mathcal {C} _ {O} ^ {\\prime} \\right\\}. \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 560, + 723, + 857, + 746 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To eliminate unconfident pseudo labels generated above, we will filter proposals based on probability scores of pseudo labels using a threshold $\\theta$ . Referring to VL-PLM [40], we also apply per-class NMS and use RoI Head to refine their box predictions, generating final pseudo labels. Afterward, those final pseudo labels are used to assign class labels of $\\mathcal{C}_O^\\prime$ for all background proposals $\\mathcal{N}^B\\subseteq \\mathcal{N}$ in each training batch. Let $\\mathcal{N}_p^B$ denote the set of positive", + "bbox": [ + 496, + 755, + 857, + 867 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "16682", + "bbox": [ + 480, + 890, + 517, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "background proposals assigned class labels from $\\mathcal{C}_O^{\\prime}$ , while the remaining proposals are all collected as $\\mathcal{N}_n^B$ .", + "bbox": [ + 111, + 125, + 470, + 152 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Therefore, the loss component proposed by this BOD module to optimize the model is formulated as follows,", + "bbox": [ + 112, + 154, + 470, + 181 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {b o d} = \\frac {1}{| \\mathcal {N} _ {p} ^ {B} |} \\sum_ {x \\in \\mathcal {N} _ {p} ^ {B}} - \\log p (c = y ^ {o} (x) | x; \\mathcal {C} _ {b, o} ^ {b g}) \\\\ + \\lambda_ {b g} \\frac {1}{\\left| \\mathcal {N} _ {n} ^ {B} \\right|} \\sum_ {x \\in \\mathcal {N} _ {n} ^ {B}} - \\log \\sum_ {c \\in \\mathcal {C} _ {a} \\cup \\{\\bar {\\epsilon} _ {b g} \\}} p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {10} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 130, + 190, + 470, + 279 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $\\lambda_{bg}$ is a loss weight with a small value used for background proposals. This loss component emphasizes aligning visual embeddings of background proposals with their contextual embeddings related to estimated background categories from $C_O$ . It is especially critical for majority classes within $C_O$ , which are more prone to knowledge loss. Additionally, it empowers BOD to leverage insights from implicit objects within background proposals.", + "bbox": [ + 111, + 289, + 470, + 400 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Training Objective. The final training objective for model optimization is a combination of the loss components formulated by Eq. (4), Eq. (7), and Eq. (10), respectively:", + "bbox": [ + 111, + 400, + 470, + 441 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {f i n a l}} = \\mathcal {L} _ {\\text {c l s}} + \\mathcal {L} _ {\\text {b c p}} ^ {\\prime} + \\mathcal {L} _ {\\text {b o d}}. \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 197, + 455, + 470, + 470 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "It's worth noting that, the text encoder and image encoder of CLIP should be frozen during model training.", + "bbox": [ + 111, + 476, + 470, + 503 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "3.2.3 Inference Probability Rectification", + "text_level": 1, + "bbox": [ + 112, + 521, + 382, + 534 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Once performed BCP and BOD, the detector capability of recognizing previously unseen classes has been significantly enhanced. However, a new challenge arises during inference. The background underlying categories $\\mathcal{C}_O$ , estimated from background proposals during training, might share semantics similarities with the novel classes $\\mathcal{C}_u$ of the detector aiming to classify during inference, vividly symbolized by $\\mathcal{C}_O \\cap \\mathcal{C}_u \\neq \\emptyset$ . In such cases, there exist conceptual overlaps of contextual embeddings between those two types of categories during inference. This overlap could hinder the accurate computation of probability scores for novel classes, leading to detection ambiguity during inference. To overcome this, an Inference Probability Rectification (IPR) is presented to enable the detector to precisely predict the probabilities of novel classes during inference.", + "bbox": [ + 111, + 542, + 470, + 750 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To be specific, let $\\mathcal{C}_{b,u,o}^{bg} = \\mathcal{C}_b\\cup \\mathcal{C}_u\\cup \\mathcal{C}_O\\cup \\{\\overline{\\mathbf{c}}_{bg}\\}$ . Then, with reference to Eq. (2), the probability of a proposal $x\\in$ $\\mathcal{D}_I$ being classified as class $c\\in \\mathcal{C}_b\\cup \\mathcal{C}_u$ during inference can be computed as follows,", + "bbox": [ + 112, + 750, + 470, + 805 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\np (c | x; \\mathcal {C} _ {b, u, o} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c}) / \\tau)}{\\boldsymbol {\\Sigma} ^ {b , u} + \\boldsymbol {\\Sigma} ^ {o} + \\boldsymbol {\\Sigma} ^ {b g}}, \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 171, + 814, + 470, + 843 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where", + "bbox": [ + 112, + 852, + 153, + 864 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\boldsymbol {\\Sigma} ^ {b, u} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {b} \\cup \\mathcal {C} _ {u}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau), \\\\ \\boldsymbol {\\Sigma} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau), \\\\ \\boldsymbol {\\Sigma} ^ {b g} = \\sum_ {c ^ {\\prime} \\in \\{\\overline {{\\boldsymbol {t}}} _ {b g} \\}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau). \\tag {13} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 555, + 145, + 856, + 242 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Assuming that a proposal $x$ carries its true class label $c \\in \\mathcal{C}_u$ simultaneously sharing conceptual overlap with categories in $\\mathcal{C}_O$ , then the probability computation of for this category, namely $p(c|x; \\mathcal{C}_{b,u,o}^{bg})$ , tends to underestimate its value. This underestimation occurs due to the presence of $c$ simultaneously contributing in both $\\Sigma^{b,u}$ and $\\Sigma^o$ in the denominator of Eq. (12). In essence, $p(c|x; \\mathcal{C}_{b,u,o}^{bg})$ becomes smaller than its true probability value, denoted as $P(c|x)$ , which is a theoretical but unknown value, being discussed later. To address this issue, our goal is to resolve the conceptual overlaps between novel categories in $\\mathcal{C}_u$ and estimated background underlying categories within $\\mathcal{C}_O$ . This aims to reduce the influence of $c$ contributing $\\Sigma^o$ , leading to a re-estimation of $\\Sigma^o$ and thus resulting in $\\hat{\\Sigma}^o$ .", + "bbox": [ + 496, + 248, + 857, + 441 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Here, we simplify the function $s(\\cdot ,\\cdot) = \\exp (\\cos (\\cdot ,\\cdot) / \\tau)$ in Eqs. (12) to (13) and term its resulting value as the cosine exponential score. As per the definitions of the softmax function, individual probabilities for each category are computed by normalizing the cosine exponential scores, dividing each by the total sum of cosine exponential scores corresponding to all categories. We hypothesize that the cosine exponential score proportionally reflects its true probability. Hence, $\\tilde{\\Sigma}^o$ can be represented as:", + "bbox": [ + 496, + 441, + 857, + 566 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {\\boldsymbol {\\Sigma}} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} s (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) \\cdot \\left(1 - \\frac {\\sum_ {c ^ {\\prime \\prime} \\in \\mathcal {C} _ {u}} P \\left(c ^ {\\prime} , c ^ {\\prime \\prime} \\mid x\\right)}{P \\left(c ^ {\\prime} \\mid x\\right)}\\right). \\tag {14}\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 571, + 857, + 609 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "According to the Multiplication Rule of Joint Probabilities, the joint probability $P(c', c''|x)$ for any $c' \\in \\mathcal{C}_O$ and $c'' \\in \\mathcal{C}_u$ can be estimated as follows:", + "bbox": [ + 496, + 614, + 857, + 656 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nP \\left(c ^ {\\prime}, c ^ {\\prime \\prime} | x\\right) = P \\left(c ^ {\\prime} | x\\right) P \\left(c ^ {\\prime \\prime} | x, c ^ {\\prime}\\right). \\tag {15}\n$$\n", + "text_format": "latex", + "bbox": [ + 573, + 662, + 856, + 680 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "With Eq. (15), Eq. (14) can be reformulated as follows:", + "bbox": [ + 516, + 686, + 852, + 700 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {\\boldsymbol {\\Sigma}} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} s (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) \\cdot \\left(1 - \\sum_ {c ^ {\\prime \\prime} \\in \\mathcal {C} _ {u}} P \\left(c ^ {\\prime \\prime} | x, c ^ {\\prime}\\right)\\right). \\tag {16}\n$$\n", + "text_format": "latex", + "bbox": [ + 513, + 707, + 857, + 738 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "However, estimating $P(c''|x,c')$ poses challenges. Hence, we assume $P(c''|x,c')$ to be sample-agnostic, resulting in $P(c''|c')$ . Given that the embedding space serves as a metric space for probability calculation, $P(c''|c')$ can be estimated by leveraging the cosine similarity between the contextual embeddings of these two categories as follows,", + "bbox": [ + 496, + 744, + 857, + 828 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nP \\left(c ^ {\\prime \\prime} \\mid x, c ^ {\\prime}\\right) = P \\left(c ^ {\\prime \\prime} \\mid c ^ {\\prime}\\right) = \\frac {s \\left(\\boldsymbol {t} _ {c ^ {\\prime}} , \\boldsymbol {t} _ {c ^ {\\prime \\prime}}\\right)}{\\sum_ {c \\in \\mathcal {C} _ {b , u , o} ^ {b g} \\setminus \\{c ^ {\\prime} \\}} s \\left(\\boldsymbol {t} _ {c ^ {\\prime}} , \\boldsymbol {t} _ {c}\\right)}. \\tag {17}\n$$\n", + "text_format": "latex", + "bbox": [ + 509, + 835, + 857, + 869 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "16683", + "bbox": [ + 480, + 890, + 517, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Considering Eq. (16) and Eq. (17) into Eq. (12), the probability of a proposal $x \\in \\mathcal{D}_I$ being classified as class $c \\in \\mathcal{C}_b \\cup \\mathcal{C}_u$ during inference can be reformulated as follows,", + "bbox": [ + 112, + 125, + 470, + 167 + ], + "page_idx": 6 + }, + { + "type": "equation", + "text": "\n$$\np (c | x; \\mathcal {C} _ {b, u, o} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , t _ {c}) / \\tau)}{\\boldsymbol {\\Sigma} ^ {b , u} + \\tilde {\\boldsymbol {\\Sigma}} ^ {o} + \\boldsymbol {\\Sigma} ^ {b g}}. \\tag {18}\n$$\n", + "text_format": "latex", + "bbox": [ + 171, + 179, + 470, + 209 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 112, + 220, + 233, + 234 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.1. Experimental Setups", + "text_level": 1, + "bbox": [ + 112, + 243, + 292, + 258 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Datasets. To assess the effectiveness of the proposed LBP framework in handling the OVD task, we conducted experiments on two established object detection benchmark datasets: MS-COCO [25] and LVIS [9]. These experiments were conducted in traditional open vocabulary settings [7, 34, 35], referred to as OV-COCO and OV-LVIS, respectively. As outlined in prior works [34, 35], we divided 48 categories as base classes and 17 categories as novel classes in the OV-COCO task. The primary metric used to evaluate the detection performance is the mean average precision at IoU with a threshold of 0.50 (denoted as $\\mathrm{AP}_{50}$ ). Specifically, we represent $\\mathrm{AP}_{50}$ for base and novel categories as $\\mathrm{AP}_{50}^{n}$ and $\\mathrm{AP}_{50}^{b}$ , respectively. For OV-LVIS, following [34, 35], we classified 337 rare categories as novel classes, while considering the remaining common and frequent categories as base classes (resulting in a total of 866 categories). Here, the detector's performance is evaluated using the mean average precision averaged across IoUs from 0.50 to 0.95 (denoted as AP). We report AP values for rare categories $(\\mathrm{AP}_r)$ , common categories $(\\mathrm{AP}_c)$ , frequent categories $(\\mathrm{AP}_f)$ , and all classes. Furthermore, we include experimental results for instance segmentation on LVIS. The metrics $\\mathrm{AP}_{50}^{n}$ and $\\mathrm{AP}_r$ are used as the primary measures to assess the detector's performance on OV-COCO and OV-LVIS, respectively.", + "bbox": [ + 111, + 265, + 473, + 609 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Baselines. We compare LBP with the following state-of-the-art (SOTA) algorithms to handle the OVD task on OV-COCO: Detric [46], Object-centric-OVD [2], OVDETR [37], RegionCLIP [42], ViLD [7], OADP [34] and BARON [35]. Besides, we perform our comparison on OV-LVIS with previous methods, including ViLD [7], DetPro [4] and BARON [35].", + "bbox": [ + 111, + 611, + 470, + 708 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Comparisons with State-of-the-Arts", + "text_level": 1, + "bbox": [ + 112, + 719, + 397, + 733 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results on OV-COCO and OV-LVIS are reported in Table 1 and Table 2, respectively. As shown, our LBP method outperforms previous state-of-the-art (SOTA) algorithms for the OVD task in all cases, validating its effectiveness.", + "bbox": [ + 111, + 739, + 470, + 796 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results on OV-COCO. Similar to OADP [34], we categorize the comparison baselines into four OVD benchmark settings: Vanilla OVD (V-OVD), Caption-based OVD (C-OVD), Generalized OVD (G-OVD), and Weakly Supervised OVD (WS-OVD). The emphasis of our proposed ap", + "bbox": [ + 111, + 797, + 470, + 866 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/e1ef554240d4335b9848e8a0d37d49e25f4e3fef82a0c9a0cf3897bde9bc0d84.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodBenchmarkDetectorAPn50APb50AP50
Detic [46]WS-OVDCenterNet2[45]' 27.847.145.0
Object-centric-OVD [2]WS-OVDFaster R-CNN36.654.049.4
VL-PLMG-OVDFaster R-CNN32.354.048.3
OV-DETR [37]G-OVDDeformableDETR[47]29.461.052.7
RegionCLIP [42]C-OVDCLIP26.854.847.5
ViLD [7]V-OVDFaster R-CNN27.659.551.3
OADP [34]V-OVDFaster R-CNN30.053.347.2
BARON [35]V-OVDFaster R-CNN34.060.453.5
BARON†V-OVDFaster R-CNN35.858.252.3
LBP (ours)V-OVDFaster R-CNN35.960.854.3
LBP† (ours)V-OVDFaster R-CNN37.858.753.2
", + "bbox": [ + 503, + 123, + 856, + 243 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/628987137dc0867d587212ed3f11d20ce8959f531e09721ca3c84b760f838c77.jpg", + "table_caption": [ + "Table 1. Comparison results of LBP and existing SOTA methods on OV-COCO. $\\dagger$ indicates model optimization using a batch size of 16, used for mitigating model overfitting towards base classes." + ], + "table_footnote": [], + "table_body": "
MethodObject detectionInstance segmentation
APrAPcAPfAPAPrAPcAPfAP
ViLD [7]16.726.534.227.816.624.630.325.5
DetPro [4]20.827.832.428.419.825.628.925.9
BARON [35]20.128.432.228.419.226.829.426.5
BARON‡23.229.332.529.522.627.629.827.6
LBP (ours)22.228.832.429.122.127.029.727.2
LBP‡ (ours)24.129.532.829.923.727.730.128.0
", + "bbox": [ + 503, + 300, + 856, + 392 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Comparison results of LBP and existing SOTA methods on OV-LVIS. $\\ddagger$ indicates the model trained using learnable prompt templates, proposed by DetPro [4].", + "bbox": [ + 498, + 401, + 857, + 439 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "proach lies in V-OVD, but we also present performance results across other settings. Table 1 demonstrates that in this dataset, our LBP approach excels across various benchmark settings, particularly in V-OVD, surpassing existing methods by a notable margin. For instance, compared to $\\mathrm{BARON}^{\\dagger}$ , our method demonstrates a $2.0\\%$ improvement in $\\mathrm{AP}_{50}^{n}$ and $0.5\\%$ in $\\mathrm{AP}_{50}^{b}$ in the V-OVD setting, showcasing its efficacy in detecting both base and novel classes during inference. Moreover, it outperforms previous approaches in other settings, affirming its generality and superiority.", + "bbox": [ + 496, + 463, + 857, + 601 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results on OV-LVIS. Compared to OV-COCO, OV-LVIS poses greater challenges due to increased categories and fewer implicit instances for novel classes. The outcomes in Table 2 showcase the exceptional performance of our approach. For the task of object detection, our method enhances BARON's performance by $2.1\\%$ on $\\mathrm{AP}_r$ without learnable prompts and by $0.9\\%$ with them. Additionally, our approach consistently boosts the performance of BARON by $2.9\\%$ on $\\mathrm{AP}_r$ in the task of instance segmentation. These comparisons underline the applicability of the proposed method in more complex tasks including object detection and instance segmentation with a larger number of categories, thereby corroborating its effectiveness.", + "bbox": [ + 496, + 601, + 857, + 781 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Ablation Analysis", + "text_level": 1, + "bbox": [ + 500, + 789, + 658, + 804 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Impact of individual proposed modules. We conducted an ablation study to assess the effectiveness of each individual module within our method, namely Background Category Prompts (BCP), Background Object Discovery", + "bbox": [ + 498, + 811, + 857, + 867 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "16684", + "bbox": [ + 480, + 890, + 517, + 901 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/533dee749bf5bc8ec726fc9d486645ceb05e32a469c9d7575392d7ae6cc55cee.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
BCPBODIPRAP50nAP50bAP50
---35.858.252.3
✓--34.359.052.5
-✓-35.258.552.4
✓✓-35.658.752.7
✓-✓36.859.053.2
-✓✓36.958.753.0
✓✓✓37.858.753.2
", + "bbox": [ + 163, + 123, + 421, + 224 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/acc884f5fdc17acb324186c1130595a261f8cecffe229e201631fbe4e22e902c.jpg", + "table_caption": [ + "Table 3. Ablation study results in individual proposed modules of LBP on OV-COCO." + ], + "table_footnote": [], + "table_body": "
MethodAP50nAP50bAP50
Single embedding35.858.252.3
Soft background loss36.458.452.6
Lbcp37.358.853.1
Lrlx36.958.452.8
LBP (ours)37.858.753.2
", + "bbox": [ + 163, + 277, + 419, + 358 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4. Additional ablation study results of BCP on OV-COCO.", + "bbox": [ + 114, + 368, + 467, + 381 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "(BOD), and Inference Probability Rectification (IPR). By incrementally integrating these modules into the full model, we sought to understand their individual impact. Table 3 illustrates the outcomes. We observed that employing only BCP notably improves the baseline's performance w.r.t. base classes but results in a decline in performance for novel classes. This observation highlights the inherent conceptual overlap generated between the estimated background underlying classes and novel classes when exclusively relying on BCP. However, combining BCP with IPR demonstrates a $2.5\\%$ performance improvement of novel classes, showcasing the effect of IPR. Building upon the above variant model, the addition of BOD further enhances the model, resulting in a $1.0\\%$ mAP50 performance improvement on novel classes. This validates its increased role in identifying objects within the estimated underlying categories from background proposals.", + "bbox": [ + 111, + 407, + 472, + 643 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Further analysis of BCP. To further validate BCP's efficacy, we explore various conventional designs for background interpretation in Table 4. We refer \"Single embedding\" as the design with only a learnable \"background\" embedding $t_{bg}$ , akin to prior schemes [7, 35], while \"Soft background loss\" pertains to the soft background loss outlined in DetPro [4]. Subsequently, $\\mathcal{L}_{bcp}$ and $\\mathcal{L}_{rlx}$ indicate our substitution of $\\mathcal{L}_{bcp}'$ in Eq. (7) with only $\\mathcal{L}_{bcp}$ and $\\mathcal{L}_{rlx}$ , respectively. The results considerably highlight the superiority of our proposed design for background interpretation. Specifically, our design significantly outperforms \"Soft background loss\" proposed by DetPro [4], showcasing its effectiveness in preserving class relations. Moreover, the comparison using only $\\mathcal{L}_{bcp}$ and $\\mathcal{L}_{rlx}$ emphasizes the individual importance of each loss component proposed by BCP used for background interpretation.", + "bbox": [ + 111, + 645, + 472, + 866 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/64d4e480bd2c048e9c76c1cfd0acd54a438bc34764a203d4598100af54a2e728.jpg", + "image_caption": [ + "(a)" + ], + "image_footnote": [], + "bbox": [ + 506, + 125, + 669, + 218 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d8d7e12c1061675eba81408162908ca073f159c093430cddd2242ecd7e3d59f9.jpg", + "image_caption": [ + "(b)", + "Figure 3. Visualizations of feature distributions for novel category proposals. Note that proposals are selected for those that exhibit significant IoU overlap with the ground truth boxes of novel categories. Different colors denote distinct categories. (a) and (b) showcase the feature distributions generated by BARON [35] and our LBP, respectively. Compared to BARON, our LBP algorithm leads to more compact distributions for the same novel category representations." + ], + "image_footnote": [], + "bbox": [ + 687, + 125, + 852, + 218 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Furthermore, we use t-SNE to visualize the feature distribution of novel category proposals, further highlighting the efficacy of our designed schemes in background interpretation. As displayed in Figure 3(a) and Figure 3 (b), compared our approach LBP with BARON [35], the findings illustrate that the proposed LBP approach enables the detector to learn more discriminative features for the proposals associated with novel categories.", + "bbox": [ + 496, + 359, + 857, + 470 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusions", + "text_level": 1, + "bbox": [ + 500, + 489, + 614, + 503 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we have introduced LBP, a novel framework addressing the challenges of open-vocabulary object detection. In this approach, learning background prompts is proposed to harness explored implicit background knowledge. This can enhance the capacity of the detector to recognize both base and novel categories during inference. To achieve this, we have devised three essential modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification. These modules collectively empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. Our proposed approach has been rigorously evaluated through extensive experiments and thorough ablation studies, confirming its superior performance.", + "bbox": [ + 496, + 515, + 857, + 710 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments", + "text_level": 1, + "bbox": [ + 500, + 729, + 643, + 744 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported in part by the National Natural Science Foundation of China (NO. 62322608), in part by the CAAI-MindSpore Open Fund, developed on OpenI Community, in part by the Shenzhen Science and Technology Program (NO. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 3961-3970, 2022. 1, 4", + "[42] Yiwu Zhong, Jianwei Yang, Pengchuan Zhang, Chunyuan Li, Noel Codella, Liunian Harold Li, Luowei Zhou, Xiyang Dai, Lu Yuan, Yin Li, et al. Regionclip: Region-based language-image pretraining. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 16793-16803, 2022. 2, 7", + "[43] Kaiyang Zhou, Jingkang Yang, Chen Change Loy, and Ziwei Liu. Conditional prompt learning for vision-language models. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 16816-16825, 2022. 3", + "[44] Kaiyang Zhou, Jingkang Yang, Chen Change Loy, and Ziwei Liu. Learning to prompt for vision-language models. International Journal of Computer Vision, 130(9):2337-2348, 2022. 3, 4", + "[45] Xingyi Zhou, Vladlen Koltun, and Philipp Krähenbühl. Probabilistic two-stage detection. arXiv preprint arXiv:2103.07461, 2021. 7", + "[46] Xingyi Zhou, Rohit Girdhar, Armand Joulin, Philipp Krahenbihl, and Ishan Misra. Detecting twenty-thousand classes using image-level supervision. In European Conference on Computer Vision, pages 350-368. Springer, 2022. 2, 7", + "[47] Xizhou Zhu, Weijie Su, Lewei Lu, Bin Li, Xiaogang Wang, and Jifeng Dai. Deformable detr: Deformable transformers for end-to-end object detection. arXiv preprint arXiv:2010.04159, 2020. 7" + ], + "bbox": [ + 501, + 126, + 856, + 782 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "16687", + "bbox": [ + 480, + 890, + 517, + 901 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Background Prompts to Discover Implicit Knowledge for Open Vocabulary Object Detection/57bc7ecd-3bfc-4e56-9aff-1de8b9713c30_model.json b/2024/Learning Background Prompts to Discover Implicit Knowledge for Open Vocabulary Object Detection/57bc7ecd-3bfc-4e56-9aff-1de8b9713c30_model.json new file mode 100644 index 0000000000000000000000000000000000000000..60983b5867a5643cd9ea2c3ddeb9fe6dd26cbb6f --- /dev/null +++ b/2024/Learning Background Prompts to Discover Implicit Knowledge for Open Vocabulary Object Detection/57bc7ecd-3bfc-4e56-9aff-1de8b9713c30_model.json @@ -0,0 +1,2266 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.14, + 0.046, + 0.209, + 0.082 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.259, + 0.044, + 0.784, + 0.085 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.15, + 0.162, + 0.823, + 0.205 + ], + "angle": 0, + "content": "Learning Background Prompts to Discover Implicit Knowledge for Open Vocabulary Object Detection" + }, + { + "type": "text", + "bbox": [ + 0.246, + 0.228, + 0.725, + 0.261 + ], + "angle": 0, + "content": "Jiaming Li\\(^{1}\\) Jiacheng Zhang\\(^{1}\\) Jichang Li\\(^{1,2}\\) Ge Li\\(^{3}\\) Si Liu\\(^{4}\\) Liang Lin\\(^{1}\\) Guanbin Li\\(^{1,5,6*}\\)" + }, + { + "type": "text", + "bbox": [ + 0.16, + 0.261, + 0.815, + 0.278 + ], + "angle": 0, + "content": "\\(^{1}\\)School of Computer Science and Engineering, Sun Yat-sen University, Guangzhou, China" + }, + { + "type": "text", + "bbox": [ + 0.203, + 0.278, + 0.77, + 0.295 + ], + "angle": 0, + "content": "\\(^{2}\\)Department of Computer Science, The University of Hong Kong, Hong Kong" + }, + { + "type": "text", + "bbox": [ + 0.224, + 0.295, + 0.749, + 0.31 + ], + "angle": 0, + "content": "\\(^{3}\\)SECE, Shenzhen Graduate School, Peking University, Shenzhen, China" + }, + { + "type": "text", + "bbox": [ + 0.264, + 0.311, + 0.71, + 0.326 + ], + "angle": 0, + "content": "\\(^{4}\\)Institute of Artificial Intelligence, Beihang University, China" + }, + { + "type": "text", + "bbox": [ + 0.214, + 0.326, + 0.758, + 0.342 + ], + "angle": 0, + "content": "5GuangDong Province Key Laboratory of Information Security Technology" + }, + { + "type": "text", + "bbox": [ + 0.264, + 0.343, + 0.708, + 0.358 + ], + "angle": 0, + "content": "\\(^{6}\\)Research Institute, Sun Yat-sen University, Shenzhen, China" + }, + { + "type": "text", + "bbox": [ + 0.19, + 0.361, + 0.783, + 0.375 + ], + "angle": 0, + "content": "{lijm48,zhangjch58}@mail2.sysu.edu.cn,{liguanbin,linlng}@mail.sysu.edu.cn" + }, + { + "type": "text", + "bbox": [ + 0.253, + 0.378, + 0.715, + 0.39 + ], + "angle": 0, + "content": "csjcli=connect.hku.hk, lige@pku.edu.cn, liusi@buaa.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.257, + 0.422, + 0.33, + 0.437 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.519, + 0.475, + 0.852 + ], + "angle": 0, + "content": "Open vocabulary object detection (OVD) aims at seeking an optimal object detector capable of recognizing objects from both base and novel categories. Recent advances leverage knowledge distillation to transfer insightful knowledge from pre-trained large-scale vision-language models to the task of object detection, significantly generalizing the powerful capabilities of the detector to identify more unknown object categories. However, these methods face significant challenges in background interpretation and model overfitting and thus often result in the loss of crucial background knowledge, giving rise to sub-optimal inference performance of the detector. To mitigate these issues, we present a novel OVD framework termed LBP to propose learning background prompts to harness explored implicit background knowledge, thus enhancing the detection performance w.r.t. base and novel categories. Specifically, we devise three modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification, to empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. Evaluation on two benchmark datasets, OV-COCO and OV-LVIS, demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks." + }, + { + "type": "image", + "bbox": [ + 0.517, + 0.421, + 0.62, + 0.5 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.52, + 0.502, + 0.617, + 0.511 + ], + "angle": 0, + "content": "Conventional designs" + }, + { + "type": "image", + "bbox": [ + 0.629, + 0.421, + 0.732, + 0.5 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.666, + 0.502, + 0.698, + 0.511 + ], + "angle": 0, + "content": "DetPro" + }, + { + "type": "image", + "bbox": [ + 0.741, + 0.421, + 0.845, + 0.5 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.773, + 0.502, + 0.819, + 0.511 + ], + "angle": 0, + "content": "LBP(ours)" + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.513, + 0.795, + 0.523 + ], + "angle": 0, + "content": "★ Visual embedding encoded by CLIP \\(\\bullet\\) Background class embedding" + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.523, + 0.822, + 0.531 + ], + "angle": 0, + "content": "\\(\\bigcirc\\) Base class contextual embedding RoI embeddings encoded by detector" + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.532, + 0.799, + 0.54 + ], + "angle": 0, + "content": "Distillation loss Background classification loss" + }, + { + "type": "text", + "bbox": [ + 0.517, + 0.54, + 0.836, + 0.549 + ], + "angle": 0, + "content": "Uniform distribution boundary Background underlying class embedding" + }, + { + "type": "list", + "bbox": [ + 0.517, + 0.513, + 0.836, + 0.549 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.559, + 0.86, + 0.713 + ], + "angle": 0, + "content": "Figure 1. An example to illustrate previous and our designs in background interpretation. Conventional designs use a single background embedding to push the RoI embedding away from the CLIP embedding. DetPro [4] proposes to uniformly push the RoI embedding away when the CLIP embedding nears a base class embedding, leading to a loss of class relation. Our LBP, on the other hand, learns multiple background underlying class embeddings, effectively preserving class relations and alleviating loss conflict. \"Distillation loss\" uses knowledge distillation to align visual features encoded by the decoder with CLIP embeddings, while \"Background classification loss\" refers to the classification loss for background proposals." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.731, + 0.62, + 0.745 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.756, + 0.859, + 0.84 + ], + "angle": 0, + "content": "Compared to conventional vision tasks [11, 12, 18-22, 39], object detection has witnessed significant success in research, such as [26, 30, 32, 41], however, solely detecting and classifying objects within known categories (base classes) during inference significantly diminishes its generalization capacity in real-world applications. Open Vo" + }, + { + "type": "page_footnote", + "bbox": [ + 0.516, + 0.854, + 0.634, + 0.866 + ], + "angle": 0, + "content": "*Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.891, + 0.518, + 0.902 + ], + "angle": 0, + "content": "16678" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.112, + 0.127, + 0.471, + 0.181 + ], + "angle": 0, + "content": "cabulary Object Detection (OVD) emerges as a prospective means to overcome this restriction, endowed with the capability to detect unseen categories (novel classes), without the explicit need for annotations." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.184, + 0.474, + 0.446 + ], + "angle": 0, + "content": "Leveraging large-scale pre-trained Vision and Language Models (PVLMs), exemplified by CLIP [29] and ALIGN [13], recent advances in OVD, e.g. [4, 7, 35], employ knowledge distillation to transfer insightful knowledge of PVLMs to the task of object detection, generalizing its powerful capabilities to detect more unknown object categories. However, these methods face a critical limitation in background interpretation. Specifically, these approaches tend to represent background proposals with a single \"background class\", encompassing all categories beyond foreground base classes. With solely a singular learnable embedding to interpret this background class, the trained model may fail to capture the diverse implicit knowledge within background proposals. This leads to the loss of essential background information, resulting in incomplete and ambiguous representations of unseen categories by the model. Consequently, the model is incapable of distinguishing objects from those unknown categories using their representations." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.45, + 0.474, + 0.672 + ], + "angle": 0, + "content": "To tackle this problem, researchers experimented with various strategies like binary cross-entropy loss [2] or soft background loss [4] for background interpretation. However, their basic assumption that background proposals are uniformly dissimilar to any foreground category overlooks the nuanced class relations between foreground and background classes, as illustrated in Figure 1. Additionally, these methods struggle with model overfitting during training due to an abundance of fully supervised data from base classes, which makes detectors biased toward those categories. Recent advances like [2, 5, 6, 40] propose mining implicit objects of novel categories from background proposals and employing pseudo-labeling to enhance their interpretation. Yet, these methods often rely on additional prior knowledge, such as the names of novel categories, leaving substantial unexplored knowledge." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.673, + 0.474, + 0.868 + ], + "angle": 0, + "content": "In this paper, we present LBP, a novel framework for open-vocabulary object detection. Without any prior knowledge, LBP proposes learning background prompts to harness explored implicit background knowledge, thus enhancing the detection performance w.r.t. base and novel categories. Specifically, the LBP framework initially introduces a Background Category-specific Prompt module. It discovers and represents background underlying categories estimated from background proposals by leveraging learnable category-specific contexts, consequently resulting in improved background interpretation. Then, an online module, namely Background Object Discovery, is introduced to further explore and exploit implicit object knowledge correlated with those estimated underlying categories from" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.127, + 0.858, + 0.249 + ], + "angle": 0, + "content": "background proposals, significantly contributing to mitigating model overfitting. Moreover, an Inference Probability Rectification module is presented to address conceptual overlaps between estimated background categories and novel categories provided during inference. This rectification enables the model to accurately compute probabilities for novel categories, thereby significantly enhancing the detector performance. The contributions are summarized as follows." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.251, + 0.858, + 0.319 + ], + "angle": 0, + "content": "- We propose a novel framework, termed LBP, for open-vocabulary object detection, where learning background prompts is presented to harness explored implicit background knowledge, thereby enhancing detection of both base and novel categories during inference." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.32, + 0.858, + 0.388 + ], + "angle": 0, + "content": "- We devise three modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification, to empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.389, + 0.858, + 0.444 + ], + "angle": 0, + "content": "- Evaluation on two benchmark datasets, OV-COCO [25] and OV-LVIS [9], demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.251, + 0.858, + 0.444 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.457, + 0.63, + 0.471 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.48, + 0.859, + 0.81 + ], + "angle": 0, + "content": "Open vocabulary object detection (OVD). OVR-CNN [38] pioneered open vocabulary object detection, by expanding object detection capabilities through image-caption datasets. Subsequently, prevailing approaches to tackle OVD have primarily relied on fine-tuning PVLMs [16, 17, 23, 24, 28, 42]. However, retraining PVLMs with large-scale learnable model weights is resource-intensive. Consequently, more recent approaches rooted in knowledge distillation [27, 34, 36] to address OVD by leveraging knowledge distilled from CLIP [29] into the detector, predominantly adopting source-free strategies. For example, ViLD [7] aligns detector-encoded features with CLIP embeddings, while BARON [35] generates region ensembles using random masking within grid spaces to distill visual concept co-occurrence within a scene. Despite partially transferring knowledge of novel categories from PVLMs, detectors exhibit bias towards base classes due to disparities between vision-language alignment and detection tasks. To mitigate this bias, researchers explore pseudo labeling techniques utilizing prior knowledge of novel category names [40] or weakly-supervised annotations to the detection dataset [2, 6, 46]. However, integrating additional knowledge poses limitations in real-world scenarios." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.812, + 0.859, + 0.868 + ], + "angle": 0, + "content": "Our proposed method extracts background implicit knowledge about classes beyond known/base categories from the provided detection dataset without requiring prior information about novel categories during inference. This" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.891, + 0.518, + 0.902 + ], + "angle": 0, + "content": "16679" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.129, + 0.124, + 0.849, + 0.422 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.111, + 0.431, + 0.862, + 0.508 + ], + "angle": 0, + "content": "Figure 2. An overview of the proposed LBP approach, consisting of three modules: Background Category-specific Prompt (BCP), Background Object Discovery (BOD), and Inference Probability Rectification (IPR). During training, BCP is first proposed to discover and represent background underlying categories, estimated from background proposals, with learnable background category-specific contexts. Then, BOD is presented to employ \\( k \\)-means clustering on background proposals across all images to harness implicit objects explored from background underlying knowledge. During inference, IPR is introduced to rectify probability scores of novel categories provided, by loosening their conceptual overlaps with background underlying categories estimated from background proposals." + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.531, + 0.473, + 0.573 + ], + "angle": 0, + "content": "utilization of implicit knowledge enables the detector to identify objects from unknown categories, enhancing its applicability across diverse scenarios." + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.575, + 0.472, + 0.713 + ], + "angle": 0, + "content": "Prompt tuning for OVD: Prompt tuning, stemming from natural language processing, has evolved with PVLM advancements to enhance their efficacy in specific downstream tasks [15]. CoOp, proposed in [44], introduces learnable contexts for 2D vision-language classification. CoCoOp, an extension proposed by [43], further enhances CoOp by generating input-conditioned tokens for each image. Various visual prompting approaches advocate integrating prompts into the image encoder of PVLMs, including works such as [1, 3, 8, 14]." + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.715, + 0.473, + 0.867 + ], + "angle": 0, + "content": "In the realm of OVD, DetPro [29] pioneered prompt engineering by implementing a soft background loss, significantly improving the detector's ability to represent specific categories. Similarly, proposals for pre-training prompts on large-scale datasets [5, 31] aim to generate more universally applicable prompts. In contrast to DetPro [29], our approach has no reliance on uniform distribution assumption. Instead, by prompting underlying background categories estimated from proposals, our method enhances the learning of unknown category representations, leading to significant performance gains in detection." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.53, + 0.599, + 0.546 + ], + "angle": 0, + "content": "3. Approach" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.553, + 0.629, + 0.567 + ], + "angle": 0, + "content": "3.1. Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.575, + 0.859, + 0.7 + ], + "angle": 0, + "content": "Problem formulation. Open vocabulary object detection (OVD) aims at seeking an optimal object detector capable of recognizing objects from both base and novel (previously unseen) categories, denoted by \\(\\mathcal{C}_b = \\{c_i\\}_{i=1}^{n_b}\\) and \\(\\mathcal{C}_u = \\{c_i\\}_{i=1}^{n_u}\\), respectively, in the inference dataset \\(\\mathcal{D}_I\\). This detector is achieved through optimization on the training dataset \\(\\mathcal{D}_T\\), annotated exclusively with instances from the base classes within \\(\\mathcal{C}_b\\). Here, \\(\\mathcal{C}_b \\cap \\mathcal{C}_u = \\emptyset\\), while \\(n_b\\) and \\(n_u\\) represent the cardinality of the respective category sets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.7, + 0.859, + 0.839 + ], + "angle": 0, + "content": "Built upon Faster R-CNN [30], given an input image, it is initially encoded by Faster R-CNN into global image features and generates a set of proposals through a region proposal network (RPN). In general, these region proposals are categorized into foreground proposals and background proposals [4], designated as \\(\\mathcal{P}\\) and \\(\\mathcal{N}\\), respectively. The foreground proposals in \\(\\mathcal{P}\\) encompass all base categories within \\(\\mathcal{C}_b\\), while all background proposals from \\(\\mathcal{N}\\) are collectively classified as a singular super-class (denoted as \\(c_{bg}\\) here), representing any category outside of \\(\\mathcal{C}_b\\)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.84, + 0.858, + 0.867 + ], + "angle": 0, + "content": "Knowledge distillation. Leveraging large-scale pre-trained large-scale Vision and Language Models (PVLMs), specif" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.891, + 0.518, + 0.902 + ], + "angle": 0, + "content": "16680" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.111, + 0.126, + 0.473, + 0.306 + ], + "angle": 0, + "content": "ically CLIP [44], knowledge distillation empowers Faster R-CNN to effectively detect objects from arbitrary vocabularies by transferring insightful knowledge from CLIP. This process involves aligning the proposal features generated by the detector (actually output by the RoI Head of the detector, denoted by \\( w(\\cdot) \\)) with those extracted by the image encoder of CLIP (denoted by \\( \\mathcal{I}(\\cdot) \\)), effectively simulating coherence between the feature spaces of the detector and CLIP. Consequently, this process implicitly projects the visual embedding space of the detector into the textual embedding space of CLIP (output by the text encoder of CLIP, denoted by \\( \\mathcal{T}(\\cdot) \\)). In this way, the original classifier of Faster R-CNN is replaced." + }, + { + "type": "text", + "bbox": [ + 0.113, + 0.306, + 0.473, + 0.389 + ], + "angle": 0, + "content": "Foreground/background interpretation. Given class \\(c\\) from \\(\\mathcal{C}_b\\), its contextual prompt is defined as 'a photo of {category} in the scene', noted as \\(V_{c}\\). Here, '\\{category\\}' denotes the contextual word for class \\(c\\). Then its contextual embedding is obtained by feeding \\(V_{c}\\) into the CLIP text encoder \\(\\mathcal{T}(\\cdot)\\), as follows," + }, + { + "type": "equation", + "bbox": [ + 0.251, + 0.399, + 0.472, + 0.415 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {t} _ {c} = \\mathcal {T} (\\boldsymbol {V} _ {c}). \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.424, + 0.473, + 0.492 + ], + "angle": 0, + "content": "However, it is challenging to determine the contextual word for the \"background\" class \\( c_{bg} \\). ViLD [7] or BARON [35] represents it with a learnable contextual embedding, without encoding it via CLIP's text encoder \\( \\mathcal{T}(\\cdot) \\), thus defining it as \\( t_{bg} \\)." + }, + { + "type": "text", + "bbox": [ + 0.113, + 0.492, + 0.473, + 0.59 + ], + "angle": 0, + "content": "Probability calculation. Having obtained \\(\\{t_c|c\\in \\mathcal{C}_b\\} \\cup\\) \\(\\{\\pmb {t}_{bg}\\}\\) , let \\(\\pmb {w}(\\cdot)\\) denote the visual embedding of a proposal generated by the RoI Head of the object detector. Consider \\(\\mathcal{C}_b^{bg} = \\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\}\\) . For any proposal \\(x\\in \\mathcal{P}\\cup \\mathcal{N}\\) from \\(\\mathcal{D}_T\\) with its visual embedding \\(\\pmb {w}(\\pmb {x})\\) , the probability of categorizing this proposal under the category \\(c\\in \\mathcal{C}_b^{bg}\\) is defined as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.149, + 0.597, + 0.473, + 0.631 + ], + "angle": 0, + "content": "\\[\np (c | x; \\mathcal {C} _ {b} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c}) / \\tau)}{\\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {b} ^ {b g}} \\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau)}, \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.64, + 0.473, + 0.681 + ], + "angle": 0, + "content": "where \\(\\exp (\\cdot)\\) and \\(\\cos (\\cdot)\\) represent the exponential function and cosine similarity, respectively, while \\(\\tau\\) is the temperature parameter used for rescaling the values." + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.681, + 0.473, + 0.756 + ], + "angle": 0, + "content": "During inference, once the novel classes from \\(\\mathcal{C}_u\\) are introduced, the probability of a proposal from \\(\\mathcal{D}_I\\) being classified as class \\(c\\) of \\(\\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\} \\cup \\mathcal{C}_u\\) during detection can be computed simply by replacing \\(\\mathcal{C}_b^{bg}\\) in Eq. (2) with \\(\\mathcal{C}_{b,u}^{bg} = \\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\} \\cup \\mathcal{C}_u\\)" + }, + { + "type": "title", + "bbox": [ + 0.113, + 0.763, + 0.303, + 0.778 + ], + "angle": 0, + "content": "3.2. The Proposed Method" + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.784, + 0.473, + 0.867 + ], + "angle": 0, + "content": "In this paper, we introduce LBP, a novel framework designed for open-vocabulary object detection. The key idea of LBP is that without any prior knowledge, learning background prompts is proposed to harness explored implicit background knowledge. This ensures the model attains improved background interpretation and decreased model" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.126, + 0.86, + 0.405 + ], + "angle": 0, + "content": "overfitting, thus empowering the detector capable of better recognizing both base and novel categories. Specifically, the LBP framework initially introduces a Background Category-specific Prompt (BCP) module, discovering underlying categories from background proposals, and representing those using learnable context-specific prompts. Moreover, we introduce an online Background Object Discovery (BOD) to further exploit implicit object knowledge w.r.t. those estimated underlying categories, consequently alleviating model bias towards base categories, and present an Inference Probability Rectification (IPR) module to resolve conceptual overlaps between estimated background categories and novel categories during inference, leading to precisely computed probability scores for novel categories. Our primary focus lies in exploring background interpretation, distinct from prevailing OVD approaches rooted in knowledge distillation. This enables seamless integration of our method into existing OVD frameworks [35] and ViLD [7], etc. An overview of the proposed approach is illustrated in Figure 2." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.42, + 0.796, + 0.433 + ], + "angle": 0, + "content": "3.2.1 Background Category-specific Prompt" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.441, + 0.859, + 0.51 + ], + "angle": 0, + "content": "In this section, we model the underlying categories for background proposals in OVD and learn the corresponding category-specific prompts. However, the absence of prior knowledge of those categories necessitates the estimation of their optimal number in background proposals." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.51, + 0.859, + 0.745 + ], + "angle": 0, + "content": "Towards this end, we first produce background proposals for all training images using a class-agnostic RPN trained on \\(\\mathcal{D}_T\\) with only base classes, adopting a similar technique as in VL-PLM [40]. Those proposals are subsequently filtered based on RPN scores (with a threshold \\(\\theta\\)), and Non-Maximum Suppression (NMS). Then, we obtain features for these filtered proposals generated from the image encoder of CLIP, and we refer to [10, 41] to estimate the optimal number of the underlying categories in background proposals via K-mean clustering [33], denoted by \\(n_o\\), in the obtained proposal features. During this procedure, potential ambiguity in data partitioning during estimation may arise due to feature overlap, leading to the underestimation of \\(n_o\\). Consequently, we expand the count of background underlying categories to \\(n_o + n_a\\), where \\(n_a\\) serves as a pre-defined hyper-parameter. Here, let \\(\\mathcal{C}_O = \\{c_i\\}_{i=1}^{n_o + n_a}\\) denote those estimated background categories, for simplicity." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.745, + 0.859, + 0.842 + ], + "angle": 0, + "content": "However, due to the absence of prior knowledge of \\( \\mathcal{C}_O \\), identifying their contextual words is a non-trivial task. To address this issue, we propose to learn category-specific context vectors. In this case, the contextual words of those background underlying categories can be described with the learned continuous vectors. Specifically, we adopt the prompt form for a given class \\( c \\in \\mathcal{C}_O \\) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.517, + 0.852, + 0.858, + 0.868 + ], + "angle": 0, + "content": "\\[\n\\bar {V} _ {c} = ^ {\\prime} a \\text {p h o t o o f} \\left\\{v _ {c} \\right\\} \\text {i n t h e s c e n e} ^ {\\prime}, \\tag {3}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.891, + 0.516, + 0.902 + ], + "angle": 0, + "content": "16681" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.112, + 0.126, + 0.471, + 0.168 + ], + "angle": 0, + "content": "where the context vectors \\(\\{v_{c}|c\\in \\mathcal{C}_{O}\\}\\) are learnable. Following Eq. (1), the corresponding contextual embeddings can be acquired as \\(\\bar{\\iota}_c = \\mathcal{T}(\\overline{\\mathbf{V}}_c)\\)." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.168, + 0.472, + 0.265 + ], + "angle": 0, + "content": "Additionally, we present a specific sub-class category, \\(\\overline{c}_{bg}\\), designed to represent the \"background\" within background proposals, distinct from the super-class \"background\" \\(c_{bg}\\). Specifically, \\(\\overline{c}_{bg}\\) covers unexplored categories not estimated in \\(\\mathcal{C}_O\\) and includes any untargeted object within background proposals. Similar to \\(t_{bg}\\), we define a learnable contextual embedding, \\(\\overline{t}_{bg}\\), for this category \\(\\overline{c}_{bg}\\)." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.265, + 0.472, + 0.363 + ], + "angle": 0, + "content": "Once we obtain \\(\\{\\pmb{t}_c|c\\in \\mathcal{C}_b\\} \\cup \\{\\bar{\\pmb{t}}_c|c\\in \\mathcal{C}_O\\} \\cup \\{\\bar{\\pmb{t}}_{bg}\\}\\), the corresponding set of categories can be defined as \\(\\mathcal{C}_{b,o}^{bg} = \\mathcal{C}_b\\cup \\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}\\). With reference to Eq. (2), for any proposal \\(x\\in \\mathcal{P}\\cup \\mathcal{N}\\), its probability of being classified as class \\(c\\in \\mathcal{C}_{b,o}^{bg}\\) can be defined as \\(p(c|x;\\mathcal{C}_{b,o}^{bg})\\). At this point, the model optimization in the BCP for the proposals in \\(\\mathcal{P}\\) and \\(\\mathcal{N}\\) can be achieved using the following cross-entropy losses:" + }, + { + "type": "equation", + "bbox": [ + 0.162, + 0.367, + 0.472, + 0.4 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {c l s} = \\frac {1}{| \\mathcal {P} |} \\sum_ {x \\in \\mathcal {P}} - \\log p (c = \\boldsymbol {C} (x) | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {4}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.15, + 0.405, + 0.472, + 0.441 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {b c p} = \\frac {1}{| \\mathcal {N} |} \\sum_ {x \\in \\mathcal {N}} - \\log \\sum_ {c \\in \\mathcal {C} _ {O} \\cup \\{\\bar {\\mathfrak {c}} _ {b g} \\}} p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.444, + 0.472, + 0.514 + ], + "angle": 0, + "content": "where \\( C(x) \\) represents the true label class of the given proposal \\( x \\). \\( \\mathcal{L}_{bcp} \\) enhances the sum of probabilities of all background underlying categories estimated and \\( \\overline{c}_{bg} \\) within each background proposal, enabling the detector to softly learn the probabilities scores assigned for those categories." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.513, + 0.472, + 0.64 + ], + "angle": 0, + "content": "However, contextual embeddings of \\(\\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}\\) might not be sufficient to represent all background proposals with diverse scenes. When a background proposal belongs to \\(\\overline{c}_{bg}\\) and cannot be adequately represented by its contextual embedding, the visual embeddings of that proposal will be distant from any contextual embeddings of the estimated categories from \\(\\mathcal{C}_O\\). Consequently, the sum of probabilities of those categories, i.e., \\(\\sum_{c\\in \\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}}p(c|x;\\mathcal{C}_{b,o}^{bg})\\) in Eq. (5), denoted as \\(p_o^{bg}\\), for simplicity, would become very small." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.64, + 0.472, + 0.723 + ], + "angle": 0, + "content": "In this situation, we should uniformly push the visual embeddings of that proposal towards the estimated background underlying categories and \\(\\bar{c}_{bg}\\), given that the proposal is distinct from those categories. When \\(p_{o}^{bg} < \\gamma\\), we introduce an additional softer background loss component to relax \\(\\mathcal{L}_{bcp}\\) for all background proposals in \\(\\mathcal{N}\\) as follows," + }, + { + "type": "equation", + "bbox": [ + 0.128, + 0.727, + 0.472, + 0.763 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {r l x} = \\frac {1}{| \\mathcal {N} |} \\sum_ {x \\in \\mathcal {N}} \\frac {1}{n _ {o a}} \\sum_ {c \\in \\mathcal {C} _ {O} \\cup \\{\\bar {e} _ {b g} \\}} - \\log p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.768, + 0.472, + 0.824 + ], + "angle": 0, + "content": "where \\(n_{oa} = n_o + n_a + 1\\) represents the size of \\(\\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}\\) while \\(\\gamma\\) is a threshold with a small value. Therefore, the final version of the loss component in this BCP for background proposals to optimize the model is formulated as," + }, + { + "type": "equation", + "bbox": [ + 0.203, + 0.833, + 0.472, + 0.87 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {b c p} ^ {\\prime} = \\left\\{ \\begin{array}{l l} \\mathcal {L} _ {b c p}, & \\text {i f} \\boldsymbol {p} _ {o} ^ {b g} \\geq \\gamma , \\\\ \\mathcal {L} _ {r l x}, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.126, + 0.858, + 0.238 + ], + "angle": 0, + "content": "Note that \\(\\mathcal{L}_{bcp}^{\\prime}\\) enriches the discrimination capability of the detector by incorporating diverse contextual embeddings of estimated background categories, diverging from the soft background loss in DetPro [4]. This enables the model to exploit implicit object knowledge w.r.t. those estimated underlying categories, while also reconciling training conflicts between the losses utilized for classification and distillation, as highlighted in prior works [35]." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.254, + 0.742, + 0.268 + ], + "angle": 0, + "content": "3.2.2 Background Object Discovery" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.275, + 0.858, + 0.359 + ], + "angle": 0, + "content": "To enhance model training, we introduce an online Background Object Discovery (BOD) module to effectively discover and exploit unseen objects. This aims to extract implicit objects w.r.t. the underlying categories estimated from background proposals. To simplify, we here decompose \\(\\mathcal{C}_O\\) into \\(\\mathcal{C}_O' = \\{c_i\\}_{i=1}^{n_o}\\) and \\(\\mathcal{C}_a = \\{c_i\\}_{i=1}^{n_a}\\) in this section." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.359, + 0.858, + 0.593 + ], + "angle": 0, + "content": "During initial training, with a given \\(n_o\\), we conduct \\(k\\) means clustering (where \\(k\\) is set to \\(n_o\\)) on the set of visual embeddings \\(\\{\\mathcal{I}(x)|x\\in \\mathcal{N}\\}\\) generated by the image encoder of CLIP for background proposals as in Sec. 3.2.1. Then, we subsequently obtain the embeddings of the cluster centers, denoted as \\(\\{\\tilde{w}_c|c\\in \\mathcal{C}_O^{\\prime}\\}\\). These cluster centers function as the embedding centers for the estimated background categories within \\(\\mathcal{C}_O^\\prime\\), allowing for online generation of pseudo labels from background proposals in each training batch. Throughout the training process, motivated by VL-PLM proposed in [40], background proposals of each training batch undergo being filtered based on RPN scores using a threshold of \\(\\theta\\), with an additional step to filter out proposals overlapping with ground-truth boxes. Subsequently, CLIP is employed to generate pseudo labels, preventing the detector from being biased towards estimated background categories." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.593, + 0.858, + 0.621 + ], + "angle": 0, + "content": "Then, for a proposal \\(x\\in \\mathcal{N}\\), its probability score of being classified as \\(c\\in \\mathcal{C}_O^{\\prime}\\) is calculated as follows," + }, + { + "type": "equation", + "bbox": [ + 0.537, + 0.63, + 0.858, + 0.665 + ], + "angle": 0, + "content": "\\[\n\\tilde {p} (c | x; \\mathcal {C} _ {O} ^ {\\prime}) = \\frac {\\exp (\\cos (\\mathcal {I} (x) , \\tilde {\\boldsymbol {w}} _ {c}) / \\tau)}{\\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O} ^ {\\prime}} \\exp (\\cos (\\mathcal {I} (x) . \\tilde {\\boldsymbol {w}} _ {c ^ {\\prime}}) / \\tau)}. \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.673, + 0.858, + 0.715 + ], + "angle": 0, + "content": "Once such background proposal has probability scores corresponding to all categories in \\(\\mathcal{C}_O^{\\prime}\\), we choose the predicted class label with the highest score as its pseudo label," + }, + { + "type": "equation", + "bbox": [ + 0.561, + 0.724, + 0.858, + 0.747 + ], + "angle": 0, + "content": "\\[\n\\mathcal {Y} ^ {o} (x) = \\underset {c} {\\operatorname {a r g m a x}} \\left\\{\\tilde {p} \\left(c | x; \\mathcal {C} _ {O} ^ {\\prime}\\right) | c \\in \\mathcal {C} _ {O} ^ {\\prime} \\right\\}. \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.756, + 0.859, + 0.868 + ], + "angle": 0, + "content": "To eliminate unconfident pseudo labels generated above, we will filter proposals based on probability scores of pseudo labels using a threshold \\(\\theta\\). Referring to VL-PLM [40], we also apply per-class NMS and use RoI Head to refine their box predictions, generating final pseudo labels. Afterward, those final pseudo labels are used to assign class labels of \\(\\mathcal{C}_O^\\prime\\) for all background proposals \\(\\mathcal{N}^B\\subseteq \\mathcal{N}\\) in each training batch. Let \\(\\mathcal{N}_p^B\\) denote the set of positive" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.891, + 0.518, + 0.902 + ], + "angle": 0, + "content": "16682" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.112, + 0.126, + 0.471, + 0.154 + ], + "angle": 0, + "content": "background proposals assigned class labels from \\(\\mathcal{C}_O^{\\prime}\\), while the remaining proposals are all collected as \\(\\mathcal{N}_n^B\\)." + }, + { + "type": "text", + "bbox": [ + 0.113, + 0.155, + 0.472, + 0.182 + ], + "angle": 0, + "content": "Therefore, the loss component proposed by this BOD module to optimize the model is formulated as follows," + }, + { + "type": "equation", + "bbox": [ + 0.131, + 0.191, + 0.472, + 0.28 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {b o d} = \\frac {1}{| \\mathcal {N} _ {p} ^ {B} |} \\sum_ {x \\in \\mathcal {N} _ {p} ^ {B}} - \\log p (c = y ^ {o} (x) | x; \\mathcal {C} _ {b, o} ^ {b g}) \\\\ + \\lambda_ {b g} \\frac {1}{\\left| \\mathcal {N} _ {n} ^ {B} \\right|} \\sum_ {x \\in \\mathcal {N} _ {n} ^ {B}} - \\log \\sum_ {c \\in \\mathcal {C} _ {a} \\cup \\{\\bar {\\epsilon} _ {b g} \\}} p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {10} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.29, + 0.472, + 0.401 + ], + "angle": 0, + "content": "where \\(\\lambda_{bg}\\) is a loss weight with a small value used for background proposals. This loss component emphasizes aligning visual embeddings of background proposals with their contextual embeddings related to estimated background categories from \\(C_O\\). It is especially critical for majority classes within \\(C_O\\), which are more prone to knowledge loss. Additionally, it empowers BOD to leverage insights from implicit objects within background proposals." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.401, + 0.472, + 0.443 + ], + "angle": 0, + "content": "Training Objective. The final training objective for model optimization is a combination of the loss components formulated by Eq. (4), Eq. (7), and Eq. (10), respectively:" + }, + { + "type": "equation", + "bbox": [ + 0.199, + 0.456, + 0.472, + 0.472 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {f i n a l}} = \\mathcal {L} _ {\\text {c l s}} + \\mathcal {L} _ {\\text {b c p}} ^ {\\prime} + \\mathcal {L} _ {\\text {b o d}}. \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.477, + 0.472, + 0.505 + ], + "angle": 0, + "content": "It's worth noting that, the text encoder and image encoder of CLIP should be frozen during model training." + }, + { + "type": "title", + "bbox": [ + 0.114, + 0.522, + 0.383, + 0.535 + ], + "angle": 0, + "content": "3.2.3 Inference Probability Rectification" + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.543, + 0.472, + 0.75 + ], + "angle": 0, + "content": "Once performed BCP and BOD, the detector capability of recognizing previously unseen classes has been significantly enhanced. However, a new challenge arises during inference. The background underlying categories \\(\\mathcal{C}_O\\), estimated from background proposals during training, might share semantics similarities with the novel classes \\(\\mathcal{C}_u\\) of the detector aiming to classify during inference, vividly symbolized by \\(\\mathcal{C}_O \\cap \\mathcal{C}_u \\neq \\emptyset\\). In such cases, there exist conceptual overlaps of contextual embeddings between those two types of categories during inference. This overlap could hinder the accurate computation of probability scores for novel classes, leading to detection ambiguity during inference. To overcome this, an Inference Probability Rectification (IPR) is presented to enable the detector to precisely predict the probabilities of novel classes during inference." + }, + { + "type": "text", + "bbox": [ + 0.113, + 0.75, + 0.472, + 0.806 + ], + "angle": 0, + "content": "To be specific, let \\(\\mathcal{C}_{b,u,o}^{bg} = \\mathcal{C}_b\\cup \\mathcal{C}_u\\cup \\mathcal{C}_O\\cup \\{\\overline{\\mathbf{c}}_{bg}\\}\\). Then, with reference to Eq. (2), the probability of a proposal \\(x\\in\\) \\(\\mathcal{D}_I\\) being classified as class \\(c\\in \\mathcal{C}_b\\cup \\mathcal{C}_u\\) during inference can be computed as follows," + }, + { + "type": "equation", + "bbox": [ + 0.172, + 0.815, + 0.472, + 0.844 + ], + "angle": 0, + "content": "\\[\np (c | x; \\mathcal {C} _ {b, u, o} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c}) / \\tau)}{\\boldsymbol {\\Sigma} ^ {b , u} + \\boldsymbol {\\Sigma} ^ {o} + \\boldsymbol {\\Sigma} ^ {b g}}, \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.113, + 0.853, + 0.155, + 0.865 + ], + "angle": 0, + "content": "where" + }, + { + "type": "equation", + "bbox": [ + 0.557, + 0.146, + 0.857, + 0.243 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\boldsymbol {\\Sigma} ^ {b, u} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {b} \\cup \\mathcal {C} _ {u}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau), \\\\ \\boldsymbol {\\Sigma} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau), \\\\ \\boldsymbol {\\Sigma} ^ {b g} = \\sum_ {c ^ {\\prime} \\in \\{\\overline {{\\boldsymbol {t}}} _ {b g} \\}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau). \\tag {13} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.249, + 0.859, + 0.442 + ], + "angle": 0, + "content": "Assuming that a proposal \\(x\\) carries its true class label \\(c \\in \\mathcal{C}_u\\) simultaneously sharing conceptual overlap with categories in \\(\\mathcal{C}_O\\), then the probability computation of for this category, namely \\(p(c|x; \\mathcal{C}_{b,u,o}^{bg})\\), tends to underestimate its value. This underestimation occurs due to the presence of \\(c\\) simultaneously contributing in both \\(\\Sigma^{b,u}\\) and \\(\\Sigma^o\\) in the denominator of Eq. (12). In essence, \\(p(c|x; \\mathcal{C}_{b,u,o}^{bg})\\) becomes smaller than its true probability value, denoted as \\(P(c|x)\\), which is a theoretical but unknown value, being discussed later. To address this issue, our goal is to resolve the conceptual overlaps between novel categories in \\(\\mathcal{C}_u\\) and estimated background underlying categories within \\(\\mathcal{C}_O\\). This aims to reduce the influence of \\(c\\) contributing \\(\\Sigma^o\\), leading to a re-estimation of \\(\\Sigma^o\\) and thus resulting in \\(\\hat{\\Sigma}^o\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.442, + 0.858, + 0.567 + ], + "angle": 0, + "content": "Here, we simplify the function \\( s(\\cdot ,\\cdot) = \\exp (\\cos (\\cdot ,\\cdot) / \\tau) \\) in Eqs. (12) to (13) and term its resulting value as the cosine exponential score. As per the definitions of the softmax function, individual probabilities for each category are computed by normalizing the cosine exponential scores, dividing each by the total sum of cosine exponential scores corresponding to all categories. We hypothesize that the cosine exponential score proportionally reflects its true probability. Hence, \\( \\tilde{\\Sigma}^o \\) can be represented as:" + }, + { + "type": "equation", + "bbox": [ + 0.507, + 0.572, + 0.858, + 0.61 + ], + "angle": 0, + "content": "\\[\n\\tilde {\\boldsymbol {\\Sigma}} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} s (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) \\cdot \\left(1 - \\frac {\\sum_ {c ^ {\\prime \\prime} \\in \\mathcal {C} _ {u}} P \\left(c ^ {\\prime} , c ^ {\\prime \\prime} \\mid x\\right)}{P \\left(c ^ {\\prime} \\mid x\\right)}\\right). \\tag {14}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.615, + 0.859, + 0.657 + ], + "angle": 0, + "content": "According to the Multiplication Rule of Joint Probabilities, the joint probability \\( P(c', c''|x) \\) for any \\( c' \\in \\mathcal{C}_O \\) and \\( c'' \\in \\mathcal{C}_u \\) can be estimated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.574, + 0.664, + 0.857, + 0.681 + ], + "angle": 0, + "content": "\\[\nP \\left(c ^ {\\prime}, c ^ {\\prime \\prime} | x\\right) = P \\left(c ^ {\\prime} | x\\right) P \\left(c ^ {\\prime \\prime} | x, c ^ {\\prime}\\right). \\tag {15}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.517, + 0.687, + 0.854, + 0.702 + ], + "angle": 0, + "content": "With Eq. (15), Eq. (14) can be reformulated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.514, + 0.708, + 0.858, + 0.739 + ], + "angle": 0, + "content": "\\[\n\\tilde {\\boldsymbol {\\Sigma}} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} s (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) \\cdot \\left(1 - \\sum_ {c ^ {\\prime \\prime} \\in \\mathcal {C} _ {u}} P \\left(c ^ {\\prime \\prime} | x, c ^ {\\prime}\\right)\\right). \\tag {16}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.745, + 0.859, + 0.829 + ], + "angle": 0, + "content": "However, estimating \\( P(c''|x,c') \\) poses challenges. Hence, we assume \\( P(c''|x,c') \\) to be sample-agnostic, resulting in \\( P(c''|c') \\). Given that the embedding space serves as a metric space for probability calculation, \\( P(c''|c') \\) can be estimated by leveraging the cosine similarity between the contextual embeddings of these two categories as follows," + }, + { + "type": "equation", + "bbox": [ + 0.51, + 0.836, + 0.858, + 0.871 + ], + "angle": 0, + "content": "\\[\nP \\left(c ^ {\\prime \\prime} \\mid x, c ^ {\\prime}\\right) = P \\left(c ^ {\\prime \\prime} \\mid c ^ {\\prime}\\right) = \\frac {s \\left(\\boldsymbol {t} _ {c ^ {\\prime}} , \\boldsymbol {t} _ {c ^ {\\prime \\prime}}\\right)}{\\sum_ {c \\in \\mathcal {C} _ {b , u , o} ^ {b g} \\setminus \\{c ^ {\\prime} \\}} s \\left(\\boldsymbol {t} _ {c ^ {\\prime}} , \\boldsymbol {t} _ {c}\\right)}. \\tag {17}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.891, + 0.518, + 0.902 + ], + "angle": 0, + "content": "16683" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.113, + 0.126, + 0.471, + 0.168 + ], + "angle": 0, + "content": "Considering Eq. (16) and Eq. (17) into Eq. (12), the probability of a proposal \\(x \\in \\mathcal{D}_I\\) being classified as class \\(c \\in \\mathcal{C}_b \\cup \\mathcal{C}_u\\) during inference can be reformulated as follows," + }, + { + "type": "equation", + "bbox": [ + 0.172, + 0.18, + 0.472, + 0.21 + ], + "angle": 0, + "content": "\\[\np (c | x; \\mathcal {C} _ {b, u, o} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , t _ {c}) / \\tau)}{\\boldsymbol {\\Sigma} ^ {b , u} + \\tilde {\\boldsymbol {\\Sigma}} ^ {o} + \\boldsymbol {\\Sigma} ^ {b g}}. \\tag {18}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.113, + 0.221, + 0.234, + 0.236 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.113, + 0.244, + 0.293, + 0.259 + ], + "angle": 0, + "content": "4.1. Experimental Setups" + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.266, + 0.474, + 0.61 + ], + "angle": 0, + "content": "Datasets. To assess the effectiveness of the proposed LBP framework in handling the OVD task, we conducted experiments on two established object detection benchmark datasets: MS-COCO [25] and LVIS [9]. These experiments were conducted in traditional open vocabulary settings [7, 34, 35], referred to as OV-COCO and OV-LVIS, respectively. As outlined in prior works [34, 35], we divided 48 categories as base classes and 17 categories as novel classes in the OV-COCO task. The primary metric used to evaluate the detection performance is the mean average precision at IoU with a threshold of 0.50 (denoted as \\(\\mathrm{AP}_{50}\\)). Specifically, we represent \\(\\mathrm{AP}_{50}\\) for base and novel categories as \\(\\mathrm{AP}_{50}^{n}\\) and \\(\\mathrm{AP}_{50}^{b}\\), respectively. For OV-LVIS, following [34, 35], we classified 337 rare categories as novel classes, while considering the remaining common and frequent categories as base classes (resulting in a total of 866 categories). Here, the detector's performance is evaluated using the mean average precision averaged across IoUs from 0.50 to 0.95 (denoted as AP). We report AP values for rare categories \\((\\mathrm{AP}_r)\\), common categories \\((\\mathrm{AP}_c)\\), frequent categories \\((\\mathrm{AP}_f)\\), and all classes. Furthermore, we include experimental results for instance segmentation on LVIS. The metrics \\(\\mathrm{AP}_{50}^{n}\\) and \\(\\mathrm{AP}_r\\) are used as the primary measures to assess the detector's performance on OV-COCO and OV-LVIS, respectively." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.612, + 0.472, + 0.709 + ], + "angle": 0, + "content": "Baselines. We compare LBP with the following state-of-the-art (SOTA) algorithms to handle the OVD task on OV-COCO: Detric [46], Object-centric-OVD [2], OVDETR [37], RegionCLIP [42], ViLD [7], OADP [34] and BARON [35]. Besides, we perform our comparison on OV-LVIS with previous methods, including ViLD [7], DetPro [4] and BARON [35]." + }, + { + "type": "title", + "bbox": [ + 0.113, + 0.72, + 0.398, + 0.734 + ], + "angle": 0, + "content": "4.2. Comparisons with State-of-the-Arts" + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.741, + 0.472, + 0.797 + ], + "angle": 0, + "content": "Results on OV-COCO and OV-LVIS are reported in Table 1 and Table 2, respectively. As shown, our LBP method outperforms previous state-of-the-art (SOTA) algorithms for the OVD task in all cases, validating its effectiveness." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.798, + 0.472, + 0.867 + ], + "angle": 0, + "content": "Results on OV-COCO. Similar to OADP [34], we categorize the comparison baselines into four OVD benchmark settings: Vanilla OVD (V-OVD), Caption-based OVD (C-OVD), Generalized OVD (G-OVD), and Weakly Supervised OVD (WS-OVD). The emphasis of our proposed ap" + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.124, + 0.857, + 0.244 + ], + "angle": 0, + "content": "
MethodBenchmarkDetectorAPn50APb50AP50
Detic [46]WS-OVDCenterNet2[45]' 27.847.145.0
Object-centric-OVD [2]WS-OVDFaster R-CNN36.654.049.4
VL-PLMG-OVDFaster R-CNN32.354.048.3
OV-DETR [37]G-OVDDeformableDETR[47]29.461.052.7
RegionCLIP [42]C-OVDCLIP26.854.847.5
ViLD [7]V-OVDFaster R-CNN27.659.551.3
OADP [34]V-OVDFaster R-CNN30.053.347.2
BARON [35]V-OVDFaster R-CNN34.060.453.5
BARON†V-OVDFaster R-CNN35.858.252.3
LBP (ours)V-OVDFaster R-CNN35.960.854.3
LBP† (ours)V-OVDFaster R-CNN37.858.753.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.253, + 0.858, + 0.292 + ], + "angle": 0, + "content": "Table 1. Comparison results of LBP and existing SOTA methods on OV-COCO. \\(\\dagger\\) indicates model optimization using a batch size of 16, used for mitigating model overfitting towards base classes." + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.301, + 0.857, + 0.393 + ], + "angle": 0, + "content": "
MethodObject detectionInstance segmentation
APrAPcAPfAPAPrAPcAPfAP
ViLD [7]16.726.534.227.816.624.630.325.5
DetPro [4]20.827.832.428.419.825.628.925.9
BARON [35]20.128.432.228.419.226.829.426.5
BARON‡23.229.332.529.522.627.629.827.6
LBP (ours)22.228.832.429.122.127.029.727.2
LBP‡ (ours)24.129.532.829.923.727.730.128.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.402, + 0.859, + 0.44 + ], + "angle": 0, + "content": "Table 2. Comparison results of LBP and existing SOTA methods on OV-LVIS. \\(\\ddagger\\) indicates the model trained using learnable prompt templates, proposed by DetPro [4]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.464, + 0.859, + 0.602 + ], + "angle": 0, + "content": "proach lies in V-OVD, but we also present performance results across other settings. Table 1 demonstrates that in this dataset, our LBP approach excels across various benchmark settings, particularly in V-OVD, surpassing existing methods by a notable margin. For instance, compared to \\(\\mathrm{BARON}^{\\dagger}\\), our method demonstrates a \\(2.0\\%\\) improvement in \\(\\mathrm{AP}_{50}^{n}\\) and \\(0.5\\%\\) in \\(\\mathrm{AP}_{50}^{b}\\) in the V-OVD setting, showcasing its efficacy in detecting both base and novel classes during inference. Moreover, it outperforms previous approaches in other settings, affirming its generality and superiority." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.602, + 0.859, + 0.782 + ], + "angle": 0, + "content": "Results on OV-LVIS. Compared to OV-COCO, OV-LVIS poses greater challenges due to increased categories and fewer implicit instances for novel classes. The outcomes in Table 2 showcase the exceptional performance of our approach. For the task of object detection, our method enhances BARON's performance by \\(2.1\\%\\) on \\(\\mathrm{AP}_r\\) without learnable prompts and by \\(0.9\\%\\) with them. Additionally, our approach consistently boosts the performance of BARON by \\(2.9\\%\\) on \\(\\mathrm{AP}_r\\) in the task of instance segmentation. These comparisons underline the applicability of the proposed method in more complex tasks including object detection and instance segmentation with a larger number of categories, thereby corroborating its effectiveness." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.79, + 0.659, + 0.805 + ], + "angle": 0, + "content": "4.3. Ablation Analysis" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.812, + 0.859, + 0.868 + ], + "angle": 0, + "content": "Impact of individual proposed modules. We conducted an ablation study to assess the effectiveness of each individual module within our method, namely Background Category Prompts (BCP), Background Object Discovery" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.891, + 0.518, + 0.902 + ], + "angle": 0, + "content": "16684" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.165, + 0.124, + 0.422, + 0.226 + ], + "angle": 0, + "content": "
BCPBODIPRAP50nAP50bAP50
---35.858.252.3
✓--34.359.052.5
-✓-35.258.552.4
✓✓-35.658.752.7
✓-✓36.859.053.2
-✓✓36.958.753.0
✓✓✓37.858.753.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.113, + 0.236, + 0.473, + 0.261 + ], + "angle": 0, + "content": "Table 3. Ablation study results in individual proposed modules of LBP on OV-COCO." + }, + { + "type": "table", + "bbox": [ + 0.165, + 0.278, + 0.421, + 0.359 + ], + "angle": 0, + "content": "
MethodAP50nAP50bAP50
Single embedding35.858.252.3
Soft background loss36.458.452.6
Lbcp37.358.853.1
Lrlx36.958.452.8
LBP (ours)37.858.753.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.116, + 0.369, + 0.468, + 0.382 + ], + "angle": 0, + "content": "Table 4. Additional ablation study results of BCP on OV-COCO." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.409, + 0.473, + 0.644 + ], + "angle": 0, + "content": "(BOD), and Inference Probability Rectification (IPR). By incrementally integrating these modules into the full model, we sought to understand their individual impact. Table 3 illustrates the outcomes. We observed that employing only BCP notably improves the baseline's performance w.r.t. base classes but results in a decline in performance for novel classes. This observation highlights the inherent conceptual overlap generated between the estimated background underlying classes and novel classes when exclusively relying on BCP. However, combining BCP with IPR demonstrates a \\(2.5\\%\\) performance improvement of novel classes, showcasing the effect of IPR. Building upon the above variant model, the addition of BOD further enhances the model, resulting in a \\(1.0\\%\\) mAP50 performance improvement on novel classes. This validates its increased role in identifying objects within the estimated underlying categories from background proposals." + }, + { + "type": "text", + "bbox": [ + 0.112, + 0.646, + 0.473, + 0.867 + ], + "angle": 0, + "content": "Further analysis of BCP. To further validate BCP's efficacy, we explore various conventional designs for background interpretation in Table 4. We refer \"Single embedding\" as the design with only a learnable \"background\" embedding \\( t_{bg} \\), akin to prior schemes [7, 35], while \"Soft background loss\" pertains to the soft background loss outlined in DetPro [4]. Subsequently, \\( \\mathcal{L}_{bcp} \\) and \\( \\mathcal{L}_{rlx} \\) indicate our substitution of \\( \\mathcal{L}_{bcp}' \\) in Eq. (7) with only \\( \\mathcal{L}_{bcp} \\) and \\( \\mathcal{L}_{rlx} \\), respectively. The results considerably highlight the superiority of our proposed design for background interpretation. Specifically, our design significantly outperforms \"Soft background loss\" proposed by DetPro [4], showcasing its effectiveness in preserving class relations. Moreover, the comparison using only \\( \\mathcal{L}_{bcp} \\) and \\( \\mathcal{L}_{rlx} \\) emphasizes the individual importance of each loss component proposed by BCP used for background interpretation." + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.125, + 0.67, + 0.219 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.581, + 0.224, + 0.597, + 0.234 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.688, + 0.125, + 0.853, + 0.219 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.763, + 0.224, + 0.779, + 0.234 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.237, + 0.858, + 0.338 + ], + "angle": 0, + "content": "Figure 3. Visualizations of feature distributions for novel category proposals. Note that proposals are selected for those that exhibit significant IoU overlap with the ground truth boxes of novel categories. Different colors denote distinct categories. (a) and (b) showcase the feature distributions generated by BARON [35] and our LBP, respectively. Compared to BARON, our LBP algorithm leads to more compact distributions for the same novel category representations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.36, + 0.858, + 0.471 + ], + "angle": 0, + "content": "Furthermore, we use t-SNE to visualize the feature distribution of novel category proposals, further highlighting the efficacy of our designed schemes in background interpretation. As displayed in Figure 3(a) and Figure 3 (b), compared our approach LBP with BARON [35], the findings illustrate that the proposed LBP approach enables the detector to learn more discriminative features for the proposals associated with novel categories." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.491, + 0.615, + 0.505 + ], + "angle": 0, + "content": "5. Conclusions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.516, + 0.859, + 0.711 + ], + "angle": 0, + "content": "In this paper, we have introduced LBP, a novel framework addressing the challenges of open-vocabulary object detection. In this approach, learning background prompts is proposed to harness explored implicit background knowledge. This can enhance the capacity of the detector to recognize both base and novel categories during inference. To achieve this, we have devised three essential modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification. These modules collectively empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. Our proposed approach has been rigorously evaluated through extensive experiments and thorough ablation studies, confirming its superior performance." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.731, + 0.645, + 0.746 + ], + "angle": 0, + "content": "Acknowledgments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.756, + 0.859, + 0.867 + ], + "angle": 0, + "content": "This work was supported in part by the National Natural Science Foundation of China (NO. 62322608), in part by the CAAI-MindSpore Open Fund, developed on OpenI Community, in part by the Shenzhen Science and Technology Program (NO. JCYJ20220530141211024), in part by the Open Project Program of State Key Laboratory of Virtual Reality Technology and Systems, Beihang University (No.VRLAB2023A01)." + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.891, + 0.518, + 0.902 + ], + "angle": 0, + "content": "16685" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.115, + 0.125, + 0.201, + 0.139 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.122, + 0.148, + 0.473, + 0.198 + ], + "angle": 0, + "content": "[1] Hyojin Bahng, Ali Jahanian, Swami Sankaranarayanan, and Phillip Isola. Visual prompting: Modifying pixel space to adapt pre-trained models. arXiv preprint arXiv:2203.17274, 3:11-12, 2022. 3" + }, + { + "type": "ref_text", + "bbox": [ + 0.122, + 0.2, + 0.472, + 0.263 + ], + "angle": 0, + "content": "[2] Hanoona Bangalath, Muhammad Maaz, Muhammad Uzair Khattak, Salman H Khan, and Fahad Shahbaz Khan. 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Recent advances leverage knowledge distillation to transfer insightful knowledge from pre-trained large-scale vision-language models to the task of object detection, significantly generalizing the powerful capabilities of the detector to identify more unknown object categories. However, these methods face significant challenges in background interpretation and model overfitting and thus often result in the loss of crucial background knowledge, giving rise to sub-optimal inference performance of the detector. To mitigate these issues, we present a novel OVD framework termed LBP to propose learning background prompts to harness explored implicit background knowledge, thus enhancing the detection performance w.r.t. base and novel categories. Specifically, we devise three modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification, to empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. Evaluation on two benchmark datasets, OV-COCO and OV-LVIS, demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks. + +![](images/43bef6be581de375cf2e35f8e7aa0303771555752ea9a7ed376f09897d35b472.jpg) +Conventional designs + +![](images/c3bc295216c78fc7280a9025d101cdd810db3508cbde6aa0ad2e5e8c3c21afc1.jpg) +DetPro + +![](images/7c6e4898177e4d4d20b19f27dd598c37c8639672ec4773ceb2bfc55195e43e63.jpg) +LBP(ours) + +★ Visual embedding encoded by CLIP $\bullet$ Background class embedding +$\bigcirc$ Base class contextual embedding RoI embeddings encoded by detector +Distillation loss Background classification loss +Uniform distribution boundary Background underlying class embedding + +Figure 1. An example to illustrate previous and our designs in background interpretation. Conventional designs use a single background embedding to push the RoI embedding away from the CLIP embedding. DetPro [4] proposes to uniformly push the RoI embedding away when the CLIP embedding nears a base class embedding, leading to a loss of class relation. Our LBP, on the other hand, learns multiple background underlying class embeddings, effectively preserving class relations and alleviating loss conflict. "Distillation loss" uses knowledge distillation to align visual features encoded by the decoder with CLIP embeddings, while "Background classification loss" refers to the classification loss for background proposals. + +# 1. Introduction + +Compared to conventional vision tasks [11, 12, 18-22, 39], object detection has witnessed significant success in research, such as [26, 30, 32, 41], however, solely detecting and classifying objects within known categories (base classes) during inference significantly diminishes its generalization capacity in real-world applications. Open Vo + +cabulary Object Detection (OVD) emerges as a prospective means to overcome this restriction, endowed with the capability to detect unseen categories (novel classes), without the explicit need for annotations. + +Leveraging large-scale pre-trained Vision and Language Models (PVLMs), exemplified by CLIP [29] and ALIGN [13], recent advances in OVD, e.g. [4, 7, 35], employ knowledge distillation to transfer insightful knowledge of PVLMs to the task of object detection, generalizing its powerful capabilities to detect more unknown object categories. However, these methods face a critical limitation in background interpretation. Specifically, these approaches tend to represent background proposals with a single "background class", encompassing all categories beyond foreground base classes. With solely a singular learnable embedding to interpret this background class, the trained model may fail to capture the diverse implicit knowledge within background proposals. This leads to the loss of essential background information, resulting in incomplete and ambiguous representations of unseen categories by the model. Consequently, the model is incapable of distinguishing objects from those unknown categories using their representations. + +To tackle this problem, researchers experimented with various strategies like binary cross-entropy loss [2] or soft background loss [4] for background interpretation. However, their basic assumption that background proposals are uniformly dissimilar to any foreground category overlooks the nuanced class relations between foreground and background classes, as illustrated in Figure 1. Additionally, these methods struggle with model overfitting during training due to an abundance of fully supervised data from base classes, which makes detectors biased toward those categories. Recent advances like [2, 5, 6, 40] propose mining implicit objects of novel categories from background proposals and employing pseudo-labeling to enhance their interpretation. Yet, these methods often rely on additional prior knowledge, such as the names of novel categories, leaving substantial unexplored knowledge. + +In this paper, we present LBP, a novel framework for open-vocabulary object detection. Without any prior knowledge, LBP proposes learning background prompts to harness explored implicit background knowledge, thus enhancing the detection performance w.r.t. base and novel categories. Specifically, the LBP framework initially introduces a Background Category-specific Prompt module. It discovers and represents background underlying categories estimated from background proposals by leveraging learnable category-specific contexts, consequently resulting in improved background interpretation. Then, an online module, namely Background Object Discovery, is introduced to further explore and exploit implicit object knowledge correlated with those estimated underlying categories from + +background proposals, significantly contributing to mitigating model overfitting. Moreover, an Inference Probability Rectification module is presented to address conceptual overlaps between estimated background categories and novel categories provided during inference. This rectification enables the model to accurately compute probabilities for novel categories, thereby significantly enhancing the detector performance. The contributions are summarized as follows. + +- We propose a novel framework, termed LBP, for open-vocabulary object detection, where learning background prompts is presented to harness explored implicit background knowledge, thereby enhancing detection of both base and novel categories during inference. +- We devise three modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification, to empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. +- Evaluation on two benchmark datasets, OV-COCO [25] and OV-LVIS [9], demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks. + +# 2. Related Work + +Open vocabulary object detection (OVD). OVR-CNN [38] pioneered open vocabulary object detection, by expanding object detection capabilities through image-caption datasets. Subsequently, prevailing approaches to tackle OVD have primarily relied on fine-tuning PVLMs [16, 17, 23, 24, 28, 42]. However, retraining PVLMs with large-scale learnable model weights is resource-intensive. Consequently, more recent approaches rooted in knowledge distillation [27, 34, 36] to address OVD by leveraging knowledge distilled from CLIP [29] into the detector, predominantly adopting source-free strategies. For example, ViLD [7] aligns detector-encoded features with CLIP embeddings, while BARON [35] generates region ensembles using random masking within grid spaces to distill visual concept co-occurrence within a scene. Despite partially transferring knowledge of novel categories from PVLMs, detectors exhibit bias towards base classes due to disparities between vision-language alignment and detection tasks. To mitigate this bias, researchers explore pseudo labeling techniques utilizing prior knowledge of novel category names [40] or weakly-supervised annotations to the detection dataset [2, 6, 46]. However, integrating additional knowledge poses limitations in real-world scenarios. + +Our proposed method extracts background implicit knowledge about classes beyond known/base categories from the provided detection dataset without requiring prior information about novel categories during inference. This + +![](images/38ffbef51f90408addcce8c51f17e36bd985dd2eaa3ff216597e6d4fe9695c24.jpg) +Figure 2. An overview of the proposed LBP approach, consisting of three modules: Background Category-specific Prompt (BCP), Background Object Discovery (BOD), and Inference Probability Rectification (IPR). During training, BCP is first proposed to discover and represent background underlying categories, estimated from background proposals, with learnable background category-specific contexts. Then, BOD is presented to employ $k$ -means clustering on background proposals across all images to harness implicit objects explored from background underlying knowledge. During inference, IPR is introduced to rectify probability scores of novel categories provided, by loosening their conceptual overlaps with background underlying categories estimated from background proposals. + +utilization of implicit knowledge enables the detector to identify objects from unknown categories, enhancing its applicability across diverse scenarios. + +Prompt tuning for OVD: Prompt tuning, stemming from natural language processing, has evolved with PVLM advancements to enhance their efficacy in specific downstream tasks [15]. CoOp, proposed in [44], introduces learnable contexts for 2D vision-language classification. CoCoOp, an extension proposed by [43], further enhances CoOp by generating input-conditioned tokens for each image. Various visual prompting approaches advocate integrating prompts into the image encoder of PVLMs, including works such as [1, 3, 8, 14]. + +In the realm of OVD, DetPro [29] pioneered prompt engineering by implementing a soft background loss, significantly improving the detector's ability to represent specific categories. Similarly, proposals for pre-training prompts on large-scale datasets [5, 31] aim to generate more universally applicable prompts. In contrast to DetPro [29], our approach has no reliance on uniform distribution assumption. Instead, by prompting underlying background categories estimated from proposals, our method enhances the learning of unknown category representations, leading to significant performance gains in detection. + +# 3. Approach + +# 3.1. Preliminaries + +Problem formulation. Open vocabulary object detection (OVD) aims at seeking an optimal object detector capable of recognizing objects from both base and novel (previously unseen) categories, denoted by $\mathcal{C}_b = \{c_i\}_{i=1}^{n_b}$ and $\mathcal{C}_u = \{c_i\}_{i=1}^{n_u}$ , respectively, in the inference dataset $\mathcal{D}_I$ . This detector is achieved through optimization on the training dataset $\mathcal{D}_T$ , annotated exclusively with instances from the base classes within $\mathcal{C}_b$ . Here, $\mathcal{C}_b \cap \mathcal{C}_u = \emptyset$ , while $n_b$ and $n_u$ represent the cardinality of the respective category sets. + +Built upon Faster R-CNN [30], given an input image, it is initially encoded by Faster R-CNN into global image features and generates a set of proposals through a region proposal network (RPN). In general, these region proposals are categorized into foreground proposals and background proposals [4], designated as $\mathcal{P}$ and $\mathcal{N}$ , respectively. The foreground proposals in $\mathcal{P}$ encompass all base categories within $\mathcal{C}_b$ , while all background proposals from $\mathcal{N}$ are collectively classified as a singular super-class (denoted as $c_{bg}$ here), representing any category outside of $\mathcal{C}_b$ . + +Knowledge distillation. Leveraging large-scale pre-trained large-scale Vision and Language Models (PVLMs), specif + +ically CLIP [44], knowledge distillation empowers Faster R-CNN to effectively detect objects from arbitrary vocabularies by transferring insightful knowledge from CLIP. This process involves aligning the proposal features generated by the detector (actually output by the RoI Head of the detector, denoted by $w(\cdot)$ ) with those extracted by the image encoder of CLIP (denoted by $\mathcal{I}(\cdot)$ ), effectively simulating coherence between the feature spaces of the detector and CLIP. Consequently, this process implicitly projects the visual embedding space of the detector into the textual embedding space of CLIP (output by the text encoder of CLIP, denoted by $\mathcal{T}(\cdot)$ ). In this way, the original classifier of Faster R-CNN is replaced. + +Foreground/background interpretation. Given class $c$ from $\mathcal{C}_b$ , its contextual prompt is defined as 'a photo of {category} in the scene', noted as $V_{c}$ . Here, '\{category\}' denotes the contextual word for class $c$ . Then its contextual embedding is obtained by feeding $V_{c}$ into the CLIP text encoder $\mathcal{T}(\cdot)$ , as follows, + +$$ +\boldsymbol {t} _ {c} = \mathcal {T} (\boldsymbol {V} _ {c}). \tag {1} +$$ + +However, it is challenging to determine the contextual word for the "background" class $c_{bg}$ . ViLD [7] or BARON [35] represents it with a learnable contextual embedding, without encoding it via CLIP's text encoder $\mathcal{T}(\cdot)$ , thus defining it as $t_{bg}$ . + +Probability calculation. Having obtained $\{t_c|c\in \mathcal{C}_b\} \cup$ $\{\pmb {t}_{bg}\}$ , let $\pmb {w}(\cdot)$ denote the visual embedding of a proposal generated by the RoI Head of the object detector. Consider $\mathcal{C}_b^{bg} = \mathcal{C}_b\cup \{\pmb {c}_{bg}\}$ . For any proposal $x\in \mathcal{P}\cup \mathcal{N}$ from $\mathcal{D}_T$ with its visual embedding $\pmb {w}(\pmb {x})$ , the probability of categorizing this proposal under the category $c\in \mathcal{C}_b^{bg}$ is defined as follows: + +$$ +p (c | x; \mathcal {C} _ {b} ^ {b g}) = \frac {\exp (\cos (\boldsymbol {w} (x) , \boldsymbol {t} _ {c}) / \tau)}{\sum_ {c ^ {\prime} \in \mathcal {C} _ {b} ^ {b g}} \exp (\cos (\boldsymbol {w} (x) , \boldsymbol {t} _ {c ^ {\prime}}) / \tau)}, \tag {2} +$$ + +where $\exp (\cdot)$ and $\cos (\cdot)$ represent the exponential function and cosine similarity, respectively, while $\tau$ is the temperature parameter used for rescaling the values. + +During inference, once the novel classes from $\mathcal{C}_u$ are introduced, the probability of a proposal from $\mathcal{D}_I$ being classified as class $c$ of $\mathcal{C}_b\cup \{\pmb {c}_{bg}\} \cup \mathcal{C}_u$ during detection can be computed simply by replacing $\mathcal{C}_b^{bg}$ in Eq. (2) with $\mathcal{C}_{b,u}^{bg} = \mathcal{C}_b\cup \{\pmb {c}_{bg}\} \cup \mathcal{C}_u$ + +# 3.2. The Proposed Method + +In this paper, we introduce LBP, a novel framework designed for open-vocabulary object detection. The key idea of LBP is that without any prior knowledge, learning background prompts is proposed to harness explored implicit background knowledge. This ensures the model attains improved background interpretation and decreased model + +overfitting, thus empowering the detector capable of better recognizing both base and novel categories. Specifically, the LBP framework initially introduces a Background Category-specific Prompt (BCP) module, discovering underlying categories from background proposals, and representing those using learnable context-specific prompts. Moreover, we introduce an online Background Object Discovery (BOD) to further exploit implicit object knowledge w.r.t. those estimated underlying categories, consequently alleviating model bias towards base categories, and present an Inference Probability Rectification (IPR) module to resolve conceptual overlaps between estimated background categories and novel categories during inference, leading to precisely computed probability scores for novel categories. Our primary focus lies in exploring background interpretation, distinct from prevailing OVD approaches rooted in knowledge distillation. This enables seamless integration of our method into existing OVD frameworks [35] and ViLD [7], etc. An overview of the proposed approach is illustrated in Figure 2. + +# 3.2.1 Background Category-specific Prompt + +In this section, we model the underlying categories for background proposals in OVD and learn the corresponding category-specific prompts. However, the absence of prior knowledge of those categories necessitates the estimation of their optimal number in background proposals. + +Towards this end, we first produce background proposals for all training images using a class-agnostic RPN trained on $\mathcal{D}_T$ with only base classes, adopting a similar technique as in VL-PLM [40]. Those proposals are subsequently filtered based on RPN scores (with a threshold $\theta$ ), and Non-Maximum Suppression (NMS). Then, we obtain features for these filtered proposals generated from the image encoder of CLIP, and we refer to [10, 41] to estimate the optimal number of the underlying categories in background proposals via K-mean clustering [33], denoted by $n_o$ , in the obtained proposal features. During this procedure, potential ambiguity in data partitioning during estimation may arise due to feature overlap, leading to the underestimation of $n_o$ . Consequently, we expand the count of background underlying categories to $n_o + n_a$ , where $n_a$ serves as a pre-defined hyper-parameter. Here, let $\mathcal{C}_O = \{c_i\}_{i=1}^{n_o + n_a}$ denote those estimated background categories, for simplicity. + +However, due to the absence of prior knowledge of $\mathcal{C}_O$ , identifying their contextual words is a non-trivial task. To address this issue, we propose to learn category-specific context vectors. In this case, the contextual words of those background underlying categories can be described with the learned continuous vectors. Specifically, we adopt the prompt form for a given class $c \in \mathcal{C}_O$ as follows: + +$$ +\bar {V} _ {c} = ^ {\prime} a \text {p h o t o o f} \left\{v _ {c} \right\} \text {i n t h e s c e n e} ^ {\prime}, \tag {3} +$$ + +where the context vectors $\{v_{c}|c\in \mathcal{C}_{O}\}$ are learnable. Following Eq. (1), the corresponding contextual embeddings can be acquired as $\bar{\iota}_c = \mathcal{T}(\overline{\mathbf{V}}_c)$ . + +Additionally, we present a specific sub-class category, $\overline{c}_{bg}$ , designed to represent the "background" within background proposals, distinct from the super-class "background" $c_{bg}$ . Specifically, $\overline{c}_{bg}$ covers unexplored categories not estimated in $\mathcal{C}_O$ and includes any untargeted object within background proposals. Similar to $t_{bg}$ , we define a learnable contextual embedding, $\overline{t}_{bg}$ , for this category $\overline{c}_{bg}$ . + +Once we obtain $\{\pmb{t}_c|c\in \mathcal{C}_b\} \cup \{\bar{\pmb{t}}_c|c\in \mathcal{C}_O\} \cup \{\bar{\pmb{t}}_{bg}\}$ , the corresponding set of categories can be defined as $\mathcal{C}_{b,o}^{bg} = \mathcal{C}_b\cup \mathcal{C}_O\cup \{\overline{c}_{bg}\}$ . With reference to Eq. (2), for any proposal $x\in \mathcal{P}\cup \mathcal{N}$ , its probability of being classified as class $c\in \mathcal{C}_{b,o}^{bg}$ can be defined as $p(c|x;\mathcal{C}_{b,o}^{bg})$ . At this point, the model optimization in the BCP for the proposals in $\mathcal{P}$ and $\mathcal{N}$ can be achieved using the following cross-entropy losses: + +$$ +\mathcal {L} _ {c l s} = \frac {1}{| \mathcal {P} |} \sum_ {x \in \mathcal {P}} - \log p (c = \boldsymbol {C} (x) | x; \mathcal {C} _ {b, o} ^ {b g}), \tag {4} +$$ + +$$ +\mathcal {L} _ {b c p} = \frac {1}{| \mathcal {N} |} \sum_ {x \in \mathcal {N}} - \log \sum_ {c \in \mathcal {C} _ {O} \cup \{\bar {\mathfrak {c}} _ {b g} \}} p (c | x; \mathcal {C} _ {b, o} ^ {b g}), \tag {5} +$$ + +where $C(x)$ represents the true label class of the given proposal $x$ . $\mathcal{L}_{bcp}$ enhances the sum of probabilities of all background underlying categories estimated and $\overline{c}_{bg}$ within each background proposal, enabling the detector to softly learn the probabilities scores assigned for those categories. + +However, contextual embeddings of $\mathcal{C}_O\cup \{\overline{c}_{bg}\}$ might not be sufficient to represent all background proposals with diverse scenes. When a background proposal belongs to $\overline{c}_{bg}$ and cannot be adequately represented by its contextual embedding, the visual embeddings of that proposal will be distant from any contextual embeddings of the estimated categories from $\mathcal{C}_O$ . Consequently, the sum of probabilities of those categories, i.e., $\sum_{c\in \mathcal{C}_O\cup \{\overline{c}_{bg}\}}p(c|x;\mathcal{C}_{b,o}^{bg})$ in Eq. (5), denoted as $p_o^{bg}$ , for simplicity, would become very small. + +In this situation, we should uniformly push the visual embeddings of that proposal towards the estimated background underlying categories and $\bar{c}_{bg}$ , given that the proposal is distinct from those categories. When $p_{o}^{bg} < \gamma$ , we introduce an additional softer background loss component to relax $\mathcal{L}_{bcp}$ for all background proposals in $\mathcal{N}$ as follows, + +$$ +\mathcal {L} _ {r l x} = \frac {1}{| \mathcal {N} |} \sum_ {x \in \mathcal {N}} \frac {1}{n _ {o a}} \sum_ {c \in \mathcal {C} _ {O} \cup \{\bar {e} _ {b g} \}} - \log p (c | x; \mathcal {C} _ {b, o} ^ {b g}), \tag {6} +$$ + +where $n_{oa} = n_o + n_a + 1$ represents the size of $\mathcal{C}_O\cup \{\overline{c}_{bg}\}$ while $\gamma$ is a threshold with a small value. Therefore, the final version of the loss component in this BCP for background proposals to optimize the model is formulated as, + +$$ +\mathcal {L} _ {b c p} ^ {\prime} = \left\{ \begin{array}{l l} \mathcal {L} _ {b c p}, & \text {i f} \boldsymbol {p} _ {o} ^ {b g} \geq \gamma , \\ \mathcal {L} _ {r l x}, & \text {o t h e r w i s e .} \end{array} \right. \tag {7} +$$ + +Note that $\mathcal{L}_{bcp}^{\prime}$ enriches the discrimination capability of the detector by incorporating diverse contextual embeddings of estimated background categories, diverging from the soft background loss in DetPro [4]. This enables the model to exploit implicit object knowledge w.r.t. those estimated underlying categories, while also reconciling training conflicts between the losses utilized for classification and distillation, as highlighted in prior works [35]. + +# 3.2.2 Background Object Discovery + +To enhance model training, we introduce an online Background Object Discovery (BOD) module to effectively discover and exploit unseen objects. This aims to extract implicit objects w.r.t. the underlying categories estimated from background proposals. To simplify, we here decompose $\mathcal{C}_O$ into $\mathcal{C}_O' = \{c_i\}_{i=1}^{n_o}$ and $\mathcal{C}_a = \{c_i\}_{i=1}^{n_a}$ in this section. + +During initial training, with a given $n_o$ , we conduct $k$ means clustering (where $k$ is set to $n_o$ ) on the set of visual embeddings $\{\mathcal{I}(x)|x\in \mathcal{N}\}$ generated by the image encoder of CLIP for background proposals as in Sec. 3.2.1. Then, we subsequently obtain the embeddings of the cluster centers, denoted as $\{\tilde{w}_c|c\in \mathcal{C}_O^{\prime}\}$ . These cluster centers function as the embedding centers for the estimated background categories within $\mathcal{C}_O^\prime$ , allowing for online generation of pseudo labels from background proposals in each training batch. Throughout the training process, motivated by VL-PLM proposed in [40], background proposals of each training batch undergo being filtered based on RPN scores using a threshold of $\theta$ , with an additional step to filter out proposals overlapping with ground-truth boxes. Subsequently, CLIP is employed to generate pseudo labels, preventing the detector from being biased towards estimated background categories. + +Then, for a proposal $x\in \mathcal{N}$ , its probability score of being classified as $c\in \mathcal{C}_O^{\prime}$ is calculated as follows, + +$$ +\tilde {p} (c | x; \mathcal {C} _ {O} ^ {\prime}) = \frac {\exp (\cos (\mathcal {I} (x) , \tilde {\boldsymbol {w}} _ {c}) / \tau)}{\sum_ {c ^ {\prime} \in \mathcal {C} _ {O} ^ {\prime}} \exp (\cos (\mathcal {I} (x) . \tilde {\boldsymbol {w}} _ {c ^ {\prime}}) / \tau)}. \tag {8} +$$ + +Once such background proposal has probability scores corresponding to all categories in $\mathcal{C}_O^{\prime}$ , we choose the predicted class label with the highest score as its pseudo label, + +$$ +\mathcal {Y} ^ {o} (x) = \underset {c} {\operatorname {a r g m a x}} \left\{\tilde {p} \left(c | x; \mathcal {C} _ {O} ^ {\prime}\right) | c \in \mathcal {C} _ {O} ^ {\prime} \right\}. \tag {9} +$$ + +To eliminate unconfident pseudo labels generated above, we will filter proposals based on probability scores of pseudo labels using a threshold $\theta$ . Referring to VL-PLM [40], we also apply per-class NMS and use RoI Head to refine their box predictions, generating final pseudo labels. Afterward, those final pseudo labels are used to assign class labels of $\mathcal{C}_O^\prime$ for all background proposals $\mathcal{N}^B\subseteq \mathcal{N}$ in each training batch. Let $\mathcal{N}_p^B$ denote the set of positive + +background proposals assigned class labels from $\mathcal{C}_O^{\prime}$ , while the remaining proposals are all collected as $\mathcal{N}_n^B$ . + +Therefore, the loss component proposed by this BOD module to optimize the model is formulated as follows, + +$$ +\begin{array}{l} \mathcal {L} _ {b o d} = \frac {1}{| \mathcal {N} _ {p} ^ {B} |} \sum_ {x \in \mathcal {N} _ {p} ^ {B}} - \log p (c = y ^ {o} (x) | x; \mathcal {C} _ {b, o} ^ {b g}) \\ + \lambda_ {b g} \frac {1}{\left| \mathcal {N} _ {n} ^ {B} \right|} \sum_ {x \in \mathcal {N} _ {n} ^ {B}} - \log \sum_ {c \in \mathcal {C} _ {a} \cup \{\bar {\epsilon} _ {b g} \}} p (c | x; \mathcal {C} _ {b, o} ^ {b g}), \tag {10} \\ \end{array} +$$ + +where $\lambda_{bg}$ is a loss weight with a small value used for background proposals. This loss component emphasizes aligning visual embeddings of background proposals with their contextual embeddings related to estimated background categories from $C_O$ . It is especially critical for majority classes within $C_O$ , which are more prone to knowledge loss. Additionally, it empowers BOD to leverage insights from implicit objects within background proposals. + +Training Objective. The final training objective for model optimization is a combination of the loss components formulated by Eq. (4), Eq. (7), and Eq. (10), respectively: + +$$ +\mathcal {L} _ {\text {f i n a l}} = \mathcal {L} _ {\text {c l s}} + \mathcal {L} _ {\text {b c p}} ^ {\prime} + \mathcal {L} _ {\text {b o d}}. \tag {11} +$$ + +It's worth noting that, the text encoder and image encoder of CLIP should be frozen during model training. + +# 3.2.3 Inference Probability Rectification + +Once performed BCP and BOD, the detector capability of recognizing previously unseen classes has been significantly enhanced. However, a new challenge arises during inference. The background underlying categories $\mathcal{C}_O$ , estimated from background proposals during training, might share semantics similarities with the novel classes $\mathcal{C}_u$ of the detector aiming to classify during inference, vividly symbolized by $\mathcal{C}_O \cap \mathcal{C}_u \neq \emptyset$ . In such cases, there exist conceptual overlaps of contextual embeddings between those two types of categories during inference. This overlap could hinder the accurate computation of probability scores for novel classes, leading to detection ambiguity during inference. To overcome this, an Inference Probability Rectification (IPR) is presented to enable the detector to precisely predict the probabilities of novel classes during inference. + +To be specific, let $\mathcal{C}_{b,u,o}^{bg} = \mathcal{C}_b\cup \mathcal{C}_u\cup \mathcal{C}_O\cup \{\overline{\mathbf{c}}_{bg}\}$ . Then, with reference to Eq. (2), the probability of a proposal $x\in$ $\mathcal{D}_I$ being classified as class $c\in \mathcal{C}_b\cup \mathcal{C}_u$ during inference can be computed as follows, + +$$ +p (c | x; \mathcal {C} _ {b, u, o} ^ {b g}) = \frac {\exp (\cos (\boldsymbol {w} (x) , \boldsymbol {t} _ {c}) / \tau)}{\boldsymbol {\Sigma} ^ {b , u} + \boldsymbol {\Sigma} ^ {o} + \boldsymbol {\Sigma} ^ {b g}}, \tag {12} +$$ + +where + +$$ +\begin{array}{l} \boldsymbol {\Sigma} ^ {b, u} = \sum_ {c ^ {\prime} \in \mathcal {C} _ {b} \cup \mathcal {C} _ {u}} \exp (\cos (\boldsymbol {w} (x), \boldsymbol {t} _ {c ^ {\prime}}) / \tau), \\ \boldsymbol {\Sigma} ^ {o} = \sum_ {c ^ {\prime} \in \mathcal {C} _ {O}} \exp (\cos (\boldsymbol {w} (x), \boldsymbol {t} _ {c ^ {\prime}}) / \tau), \\ \boldsymbol {\Sigma} ^ {b g} = \sum_ {c ^ {\prime} \in \{\overline {{\boldsymbol {t}}} _ {b g} \}} \exp (\cos (\boldsymbol {w} (x), \boldsymbol {t} _ {c ^ {\prime}}) / \tau). \tag {13} \\ \end{array} +$$ + +Assuming that a proposal $x$ carries its true class label $c \in \mathcal{C}_u$ simultaneously sharing conceptual overlap with categories in $\mathcal{C}_O$ , then the probability computation of for this category, namely $p(c|x; \mathcal{C}_{b,u,o}^{bg})$ , tends to underestimate its value. This underestimation occurs due to the presence of $c$ simultaneously contributing in both $\Sigma^{b,u}$ and $\Sigma^o$ in the denominator of Eq. (12). In essence, $p(c|x; \mathcal{C}_{b,u,o}^{bg})$ becomes smaller than its true probability value, denoted as $P(c|x)$ , which is a theoretical but unknown value, being discussed later. To address this issue, our goal is to resolve the conceptual overlaps between novel categories in $\mathcal{C}_u$ and estimated background underlying categories within $\mathcal{C}_O$ . This aims to reduce the influence of $c$ contributing $\Sigma^o$ , leading to a re-estimation of $\Sigma^o$ and thus resulting in $\hat{\Sigma}^o$ . + +Here, we simplify the function $s(\cdot ,\cdot) = \exp (\cos (\cdot ,\cdot) / \tau)$ in Eqs. (12) to (13) and term its resulting value as the cosine exponential score. As per the definitions of the softmax function, individual probabilities for each category are computed by normalizing the cosine exponential scores, dividing each by the total sum of cosine exponential scores corresponding to all categories. We hypothesize that the cosine exponential score proportionally reflects its true probability. Hence, $\tilde{\Sigma}^o$ can be represented as: + +$$ +\tilde {\boldsymbol {\Sigma}} ^ {o} = \sum_ {c ^ {\prime} \in \mathcal {C} _ {O}} s (\boldsymbol {w} (x), \boldsymbol {t} _ {c ^ {\prime}}) \cdot \left(1 - \frac {\sum_ {c ^ {\prime \prime} \in \mathcal {C} _ {u}} P \left(c ^ {\prime} , c ^ {\prime \prime} \mid x\right)}{P \left(c ^ {\prime} \mid x\right)}\right). \tag {14} +$$ + +According to the Multiplication Rule of Joint Probabilities, the joint probability $P(c', c''|x)$ for any $c' \in \mathcal{C}_O$ and $c'' \in \mathcal{C}_u$ can be estimated as follows: + +$$ +P \left(c ^ {\prime}, c ^ {\prime \prime} | x\right) = P \left(c ^ {\prime} | x\right) P \left(c ^ {\prime \prime} | x, c ^ {\prime}\right). \tag {15} +$$ + +With Eq. (15), Eq. (14) can be reformulated as follows: + +$$ +\tilde {\boldsymbol {\Sigma}} ^ {o} = \sum_ {c ^ {\prime} \in \mathcal {C} _ {O}} s (\boldsymbol {w} (x), \boldsymbol {t} _ {c ^ {\prime}}) \cdot \left(1 - \sum_ {c ^ {\prime \prime} \in \mathcal {C} _ {u}} P \left(c ^ {\prime \prime} | x, c ^ {\prime}\right)\right). \tag {16} +$$ + +However, estimating $P(c''|x,c')$ poses challenges. Hence, we assume $P(c''|x,c')$ to be sample-agnostic, resulting in $P(c''|c')$ . Given that the embedding space serves as a metric space for probability calculation, $P(c''|c')$ can be estimated by leveraging the cosine similarity between the contextual embeddings of these two categories as follows, + +$$ +P \left(c ^ {\prime \prime} \mid x, c ^ {\prime}\right) = P \left(c ^ {\prime \prime} \mid c ^ {\prime}\right) = \frac {s \left(\boldsymbol {t} _ {c ^ {\prime}} , \boldsymbol {t} _ {c ^ {\prime \prime}}\right)}{\sum_ {c \in \mathcal {C} _ {b , u , o} ^ {b g} \setminus \{c ^ {\prime} \}} s \left(\boldsymbol {t} _ {c ^ {\prime}} , \boldsymbol {t} _ {c}\right)}. \tag {17} +$$ + +Considering Eq. (16) and Eq. (17) into Eq. (12), the probability of a proposal $x \in \mathcal{D}_I$ being classified as class $c \in \mathcal{C}_b \cup \mathcal{C}_u$ during inference can be reformulated as follows, + +$$ +p (c | x; \mathcal {C} _ {b, u, o} ^ {b g}) = \frac {\exp (\cos (\boldsymbol {w} (x) , t _ {c}) / \tau)}{\boldsymbol {\Sigma} ^ {b , u} + \tilde {\boldsymbol {\Sigma}} ^ {o} + \boldsymbol {\Sigma} ^ {b g}}. \tag {18} +$$ + +# 4. Experiments + +# 4.1. Experimental Setups + +Datasets. To assess the effectiveness of the proposed LBP framework in handling the OVD task, we conducted experiments on two established object detection benchmark datasets: MS-COCO [25] and LVIS [9]. These experiments were conducted in traditional open vocabulary settings [7, 34, 35], referred to as OV-COCO and OV-LVIS, respectively. As outlined in prior works [34, 35], we divided 48 categories as base classes and 17 categories as novel classes in the OV-COCO task. The primary metric used to evaluate the detection performance is the mean average precision at IoU with a threshold of 0.50 (denoted as $\mathrm{AP}_{50}$ ). Specifically, we represent $\mathrm{AP}_{50}$ for base and novel categories as $\mathrm{AP}_{50}^{n}$ and $\mathrm{AP}_{50}^{b}$ , respectively. For OV-LVIS, following [34, 35], we classified 337 rare categories as novel classes, while considering the remaining common and frequent categories as base classes (resulting in a total of 866 categories). Here, the detector's performance is evaluated using the mean average precision averaged across IoUs from 0.50 to 0.95 (denoted as AP). We report AP values for rare categories $(\mathrm{AP}_r)$ , common categories $(\mathrm{AP}_c)$ , frequent categories $(\mathrm{AP}_f)$ , and all classes. Furthermore, we include experimental results for instance segmentation on LVIS. The metrics $\mathrm{AP}_{50}^{n}$ and $\mathrm{AP}_r$ are used as the primary measures to assess the detector's performance on OV-COCO and OV-LVIS, respectively. + +Baselines. We compare LBP with the following state-of-the-art (SOTA) algorithms to handle the OVD task on OV-COCO: Detric [46], Object-centric-OVD [2], OVDETR [37], RegionCLIP [42], ViLD [7], OADP [34] and BARON [35]. Besides, we perform our comparison on OV-LVIS with previous methods, including ViLD [7], DetPro [4] and BARON [35]. + +# 4.2. Comparisons with State-of-the-Arts + +Results on OV-COCO and OV-LVIS are reported in Table 1 and Table 2, respectively. As shown, our LBP method outperforms previous state-of-the-art (SOTA) algorithms for the OVD task in all cases, validating its effectiveness. + +Results on OV-COCO. Similar to OADP [34], we categorize the comparison baselines into four OVD benchmark settings: Vanilla OVD (V-OVD), Caption-based OVD (C-OVD), Generalized OVD (G-OVD), and Weakly Supervised OVD (WS-OVD). The emphasis of our proposed ap + +
MethodBenchmarkDetectorAPn50APb50AP50
Detic [46]WS-OVDCenterNet2[45]' 27.847.145.0
Object-centric-OVD [2]WS-OVDFaster R-CNN36.654.049.4
VL-PLMG-OVDFaster R-CNN32.354.048.3
OV-DETR [37]G-OVDDeformableDETR[47]29.461.052.7
RegionCLIP [42]C-OVDCLIP26.854.847.5
ViLD [7]V-OVDFaster R-CNN27.659.551.3
OADP [34]V-OVDFaster R-CNN30.053.347.2
BARON [35]V-OVDFaster R-CNN34.060.453.5
BARON†V-OVDFaster R-CNN35.858.252.3
LBP (ours)V-OVDFaster R-CNN35.960.854.3
LBP† (ours)V-OVDFaster R-CNN37.858.753.2
+ +Table 1. Comparison results of LBP and existing SOTA methods on OV-COCO. $\dagger$ indicates model optimization using a batch size of 16, used for mitigating model overfitting towards base classes. + +
MethodObject detectionInstance segmentation
APrAPcAPfAPAPrAPcAPfAP
ViLD [7]16.726.534.227.816.624.630.325.5
DetPro [4]20.827.832.428.419.825.628.925.9
BARON [35]20.128.432.228.419.226.829.426.5
BARON‡23.229.332.529.522.627.629.827.6
LBP (ours)22.228.832.429.122.127.029.727.2
LBP‡ (ours)24.129.532.829.923.727.730.128.0
+ +Table 2. Comparison results of LBP and existing SOTA methods on OV-LVIS. $\ddagger$ indicates the model trained using learnable prompt templates, proposed by DetPro [4]. + +proach lies in V-OVD, but we also present performance results across other settings. Table 1 demonstrates that in this dataset, our LBP approach excels across various benchmark settings, particularly in V-OVD, surpassing existing methods by a notable margin. For instance, compared to $\mathrm{BARON}^{\dagger}$ , our method demonstrates a $2.0\%$ improvement in $\mathrm{AP}_{50}^{n}$ and $0.5\%$ in $\mathrm{AP}_{50}^{b}$ in the V-OVD setting, showcasing its efficacy in detecting both base and novel classes during inference. Moreover, it outperforms previous approaches in other settings, affirming its generality and superiority. + +Results on OV-LVIS. Compared to OV-COCO, OV-LVIS poses greater challenges due to increased categories and fewer implicit instances for novel classes. The outcomes in Table 2 showcase the exceptional performance of our approach. For the task of object detection, our method enhances BARON's performance by $2.1\%$ on $\mathrm{AP}_r$ without learnable prompts and by $0.9\%$ with them. Additionally, our approach consistently boosts the performance of BARON by $2.9\%$ on $\mathrm{AP}_r$ in the task of instance segmentation. These comparisons underline the applicability of the proposed method in more complex tasks including object detection and instance segmentation with a larger number of categories, thereby corroborating its effectiveness. + +# 4.3. Ablation Analysis + +Impact of individual proposed modules. We conducted an ablation study to assess the effectiveness of each individual module within our method, namely Background Category Prompts (BCP), Background Object Discovery + +
BCPBODIPRAP50nAP50bAP50
---35.858.252.3
✓--34.359.052.5
-✓-35.258.552.4
✓✓-35.658.752.7
✓-✓36.859.053.2
-✓✓36.958.753.0
✓✓✓37.858.753.2
+ +Table 3. Ablation study results in individual proposed modules of LBP on OV-COCO. + +
MethodAP50nAP50bAP50
Single embedding35.858.252.3
Soft background loss36.458.452.6
Lbcp37.358.853.1
Lrlx36.958.452.8
LBP (ours)37.858.753.2
+ +Table 4. Additional ablation study results of BCP on OV-COCO. + +(BOD), and Inference Probability Rectification (IPR). By incrementally integrating these modules into the full model, we sought to understand their individual impact. Table 3 illustrates the outcomes. We observed that employing only BCP notably improves the baseline's performance w.r.t. base classes but results in a decline in performance for novel classes. This observation highlights the inherent conceptual overlap generated between the estimated background underlying classes and novel classes when exclusively relying on BCP. However, combining BCP with IPR demonstrates a $2.5\%$ performance improvement of novel classes, showcasing the effect of IPR. Building upon the above variant model, the addition of BOD further enhances the model, resulting in a $1.0\%$ mAP50 performance improvement on novel classes. This validates its increased role in identifying objects within the estimated underlying categories from background proposals. + +Further analysis of BCP. To further validate BCP's efficacy, we explore various conventional designs for background interpretation in Table 4. We refer "Single embedding" as the design with only a learnable "background" embedding $t_{bg}$ , akin to prior schemes [7, 35], while "Soft background loss" pertains to the soft background loss outlined in DetPro [4]. Subsequently, $\mathcal{L}_{bcp}$ and $\mathcal{L}_{rlx}$ indicate our substitution of $\mathcal{L}_{bcp}'$ in Eq. (7) with only $\mathcal{L}_{bcp}$ and $\mathcal{L}_{rlx}$ , respectively. The results considerably highlight the superiority of our proposed design for background interpretation. Specifically, our design significantly outperforms "Soft background loss" proposed by DetPro [4], showcasing its effectiveness in preserving class relations. Moreover, the comparison using only $\mathcal{L}_{bcp}$ and $\mathcal{L}_{rlx}$ emphasizes the individual importance of each loss component proposed by BCP used for background interpretation. + +![](images/64d4e480bd2c048e9c76c1cfd0acd54a438bc34764a203d4598100af54a2e728.jpg) +(a) + +![](images/d8d7e12c1061675eba81408162908ca073f159c093430cddd2242ecd7e3d59f9.jpg) +(b) +Figure 3. Visualizations of feature distributions for novel category proposals. Note that proposals are selected for those that exhibit significant IoU overlap with the ground truth boxes of novel categories. Different colors denote distinct categories. (a) and (b) showcase the feature distributions generated by BARON [35] and our LBP, respectively. Compared to BARON, our LBP algorithm leads to more compact distributions for the same novel category representations. + +Furthermore, we use t-SNE to visualize the feature distribution of novel category proposals, further highlighting the efficacy of our designed schemes in background interpretation. As displayed in Figure 3(a) and Figure 3 (b), compared our approach LBP with BARON [35], the findings illustrate that the proposed LBP approach enables the detector to learn more discriminative features for the proposals associated with novel categories. + +# 5. Conclusions + +In this paper, we have introduced LBP, a novel framework addressing the challenges of open-vocabulary object detection. In this approach, learning background prompts is proposed to harness explored implicit background knowledge. This can enhance the capacity of the detector to recognize both base and novel categories during inference. To achieve this, we have devised three essential modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification. These modules collectively empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. Our proposed approach has been rigorously evaluated through extensive experiments and thorough ablation studies, confirming its superior performance. + +# Acknowledgments + +This work was supported in part by the National Natural Science Foundation of China (NO. 62322608), in part by the CAAI-MindSpore Open Fund, developed on OpenI Community, in part by the Shenzhen Science and Technology Program (NO. JCYJ20220530141211024), in part by the Open Project Program of State Key Laboratory of Virtual Reality Technology and Systems, Beihang University (No.VRLAB2023A01). + +# References + +[1] Hyojin Bahng, Ali Jahanian, Swami Sankaranarayanan, and Phillip Isola. 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"type": "text", + "content": "Open vocabulary object detection (OVD) aims at seeking an optimal object detector capable of recognizing objects from both base and novel categories. Recent advances leverage knowledge distillation to transfer insightful knowledge from pre-trained large-scale vision-language models to the task of object detection, significantly generalizing the powerful capabilities of the detector to identify more unknown object categories. However, these methods face significant challenges in background interpretation and model overfitting and thus often result in the loss of crucial background knowledge, giving rise to sub-optimal inference performance of the detector. To mitigate these issues, we present a novel OVD framework termed LBP to propose learning background prompts to harness explored implicit background knowledge, thus enhancing the detection performance w.r.t. base and novel categories. Specifically, we devise three modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification, to empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. Evaluation on two benchmark datasets, OV-COCO and OV-LVIS, demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks." + } + ] + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 316, + 333, + 379, + 396 + ], + "blocks": [ + { + "bbox": [ + 316, + 333, + 379, + 396 + ], + "lines": [ + { + "bbox": [ + 316, + 333, + 379, + 396 + ], + "spans": [ + { + "bbox": [ + 316, + 333, + 379, + 396 + ], + "type": "image", + "image_path": "43bef6be581de375cf2e35f8e7aa0303771555752ea9a7ed376f09897d35b472.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 318, + 397, + 377, + 404 + ], + "lines": [ + { + "bbox": [ + 318, + 397, + 377, + 404 + ], + "spans": [ + { + "bbox": [ + 318, + 397, + 377, + 404 + ], + "type": "text", + "content": "Conventional designs" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 384, + 333, + 447, + 396 + ], + "blocks": [ + { + "bbox": [ + 384, + 333, + 447, + 396 + ], + "lines": [ + { + "bbox": [ + 384, + 333, + 447, + 396 + ], + "spans": [ + { + "bbox": [ + 384, + 333, + 447, + 396 + ], + "type": "image", + "image_path": "c3bc295216c78fc7280a9025d101cdd810db3508cbde6aa0ad2e5e8c3c21afc1.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 407, + 397, + 427, + 404 + ], + "lines": [ + { + "bbox": [ + 407, + 397, + 427, + 404 + ], + "spans": [ + { + "bbox": [ + 407, + 397, + 427, + 404 + ], + "type": "text", + "content": "DetPro" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 16 + }, + { + "type": "image", + "bbox": [ + 453, + 333, + 517, + 396 + ], + "blocks": [ + { + "bbox": [ + 453, + 333, + 517, + 396 + ], + "lines": [ + { + "bbox": [ + 453, + 333, + 517, + 396 + ], + "spans": [ + { + "bbox": [ + 453, + 333, + 517, + 396 + ], + "type": "image", + "image_path": "7c6e4898177e4d4d20b19f27dd598c37c8639672ec4773ceb2bfc55195e43e63.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 473, + 397, + 501, + 404 + ], + "lines": [ + { + "bbox": [ + 473, + 397, + 501, + 404 + ], + "spans": [ + { + "bbox": [ + 473, + 397, + 501, + 404 + ], + "type": "text", + "content": "LBP(ours)" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "bbox": [ + 316, + 406, + 511, + 434 + ], + "type": "list", + "angle": 0, + "index": 24, + "blocks": [ + { + "bbox": [ + 317, + 406, + 486, + 414 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 406, + 486, + 414 + ], + "spans": [ + { + "bbox": [ + 317, + 406, + 486, + 414 + ], + "type": "text", + "content": "★ Visual embedding encoded by CLIP " + }, + { + "bbox": [ + 317, + 406, + 486, + 414 + ], + "type": "inline_equation", + "content": "\\bullet" + }, + { + "bbox": [ + 317, + 406, + 486, + 414 + ], + "type": "text", + "content": " Background class embedding" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 317, + 414, + 503, + 420 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 414, + 503, + 420 + ], + "spans": [ + { + "bbox": [ + 317, + 414, + 503, + 420 + ], + "type": "inline_equation", + "content": "\\bigcirc" + }, + { + "bbox": [ + 317, + 414, + 503, + 420 + ], + "type": "text", + "content": " Base class contextual embedding RoI embeddings encoded by detector" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 317, + 421, + 488, + 427 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 421, + 488, + 427 + ], + "spans": [ + { + "bbox": [ + 317, + 421, + 488, + 427 + ], + "type": "text", + "content": "Distillation loss Background classification loss" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 316, + 427, + 511, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 316, + 427, + 511, + 434 + ], + "spans": [ + { + "bbox": [ + 316, + 427, + 511, + 434 + ], + "type": "text", + "content": "Uniform distribution boundary Background underlying class embedding" + } + ] + } + ], + "index": 23 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 304, + 442, + 526, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 442, + 526, + 564 + ], + "spans": [ + { + "bbox": [ + 304, + 442, + 526, + 564 + ], + "type": "text", + "content": "Figure 1. An example to illustrate previous and our designs in background interpretation. Conventional designs use a single background embedding to push the RoI embedding away from the CLIP embedding. DetPro [4] proposes to uniformly push the RoI embedding away when the CLIP embedding nears a base class embedding, leading to a loss of class relation. Our LBP, on the other hand, learns multiple background underlying class embeddings, effectively preserving class relations and alleviating loss conflict. \"Distillation loss\" uses knowledge distillation to align visual features encoded by the decoder with CLIP embeddings, while \"Background classification loss\" refers to the classification loss for background proposals." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 306, + 578, + 379, + 590 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 578, + 379, + 590 + ], + "spans": [ + { + "bbox": [ + 306, + 578, + 379, + 590 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 304, + 598, + 525, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 598, + 525, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 598, + 525, + 665 + ], + "type": "text", + "content": "Compared to conventional vision tasks [11, 12, 18-22, 39], object detection has witnessed significant success in research, such as [26, 30, 32, 41], however, solely detecting and classifying objects within known categories (base classes) during inference significantly diminishes its generalization capacity in real-world applications. Open Vo" + } + ] + } + ], + "index": 27 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 85, + 36, + 127, + 64 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 85, + 36, + 127, + 64 + ], + "spans": [ + { + "bbox": [ + 85, + 36, + 127, + 64 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 158, + 34, + 479, + 67 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 158, + 34, + 479, + 67 + ], + "spans": [ + { + "bbox": [ + 158, + 34, + 479, + 67 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 315, + 676, + 388, + 685 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 676, + 388, + 685 + ], + "spans": [ + { + "bbox": [ + 315, + 676, + 388, + 685 + ], + "type": "text", + "content": "*Corresponding author." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "text", + "content": "16678" + } + ] + } + ], + "index": 29 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 68, + 100, + 288, + 143 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 100, + 288, + 143 + ], + "spans": [ + { + "bbox": [ + 68, + 100, + 288, + 143 + ], + "type": "text", + "content": "cabulary Object Detection (OVD) emerges as a prospective means to overcome this restriction, endowed with the capability to detect unseen categories (novel classes), without the explicit need for annotations." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 68, + 145, + 290, + 353 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 145, + 290, + 353 + ], + "spans": [ + { + "bbox": [ + 68, + 145, + 290, + 353 + ], + "type": "text", + "content": "Leveraging large-scale pre-trained Vision and Language Models (PVLMs), exemplified by CLIP [29] and ALIGN [13], recent advances in OVD, e.g. [4, 7, 35], employ knowledge distillation to transfer insightful knowledge of PVLMs to the task of object detection, generalizing its powerful capabilities to detect more unknown object categories. However, these methods face a critical limitation in background interpretation. Specifically, these approaches tend to represent background proposals with a single \"background class\", encompassing all categories beyond foreground base classes. With solely a singular learnable embedding to interpret this background class, the trained model may fail to capture the diverse implicit knowledge within background proposals. This leads to the loss of essential background information, resulting in incomplete and ambiguous representations of unseen categories by the model. Consequently, the model is incapable of distinguishing objects from those unknown categories using their representations." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 68, + 356, + 290, + 532 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 356, + 290, + 532 + ], + "spans": [ + { + "bbox": [ + 68, + 356, + 290, + 532 + ], + "type": "text", + "content": "To tackle this problem, researchers experimented with various strategies like binary cross-entropy loss [2] or soft background loss [4] for background interpretation. However, their basic assumption that background proposals are uniformly dissimilar to any foreground category overlooks the nuanced class relations between foreground and background classes, as illustrated in Figure 1. Additionally, these methods struggle with model overfitting during training due to an abundance of fully supervised data from base classes, which makes detectors biased toward those categories. Recent advances like [2, 5, 6, 40] propose mining implicit objects of novel categories from background proposals and employing pseudo-labeling to enhance their interpretation. Yet, these methods often rely on additional prior knowledge, such as the names of novel categories, leaving substantial unexplored knowledge." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 68, + 533, + 290, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 533, + 290, + 687 + ], + "spans": [ + { + "bbox": [ + 68, + 533, + 290, + 687 + ], + "type": "text", + "content": "In this paper, we present LBP, a novel framework for open-vocabulary object detection. Without any prior knowledge, LBP proposes learning background prompts to harness explored implicit background knowledge, thus enhancing the detection performance w.r.t. base and novel categories. Specifically, the LBP framework initially introduces a Background Category-specific Prompt module. It discovers and represents background underlying categories estimated from background proposals by leveraging learnable category-specific contexts, consequently resulting in improved background interpretation. Then, an online module, namely Background Object Discovery, is introduced to further explore and exploit implicit object knowledge correlated with those estimated underlying categories from" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 100, + 525, + 197 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 100, + 525, + 197 + ], + "spans": [ + { + "bbox": [ + 304, + 100, + 525, + 197 + ], + "type": "text", + "content": "background proposals, significantly contributing to mitigating model overfitting. Moreover, an Inference Probability Rectification module is presented to address conceptual overlaps between estimated background categories and novel categories provided during inference. This rectification enables the model to accurately compute probabilities for novel categories, thereby significantly enhancing the detector performance. The contributions are summarized as follows." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 198, + 525, + 351 + ], + "type": "list", + "angle": 0, + "index": 8, + "blocks": [ + { + "bbox": [ + 306, + 198, + 525, + 252 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 198, + 525, + 252 + ], + "spans": [ + { + "bbox": [ + 306, + 198, + 525, + 252 + ], + "type": "text", + "content": "- We propose a novel framework, termed LBP, for open-vocabulary object detection, where learning background prompts is presented to harness explored implicit background knowledge, thereby enhancing detection of both base and novel categories during inference." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 253, + 525, + 307 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 253, + 525, + 307 + ], + "spans": [ + { + "bbox": [ + 306, + 253, + 525, + 307 + ], + "type": "text", + "content": "- We devise three modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification, to empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 308, + 525, + 351 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 308, + 525, + 351 + ], + "spans": [ + { + "bbox": [ + 306, + 308, + 525, + 351 + ], + "type": "text", + "content": "- Evaluation on two benchmark datasets, OV-COCO [25] and OV-LVIS [9], demonstrates the superiority of our proposed method over existing state-of-the-art approaches in handling the OVD tasks." + } + ] + } + ], + "index": 7 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 361, + 385, + 373 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 361, + 385, + 373 + ], + "spans": [ + { + "bbox": [ + 306, + 361, + 385, + 373 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 380, + 525, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 380, + 525, + 641 + ], + "spans": [ + { + "bbox": [ + 304, + 380, + 525, + 641 + ], + "type": "text", + "content": "Open vocabulary object detection (OVD). OVR-CNN [38] pioneered open vocabulary object detection, by expanding object detection capabilities through image-caption datasets. Subsequently, prevailing approaches to tackle OVD have primarily relied on fine-tuning PVLMs [16, 17, 23, 24, 28, 42]. However, retraining PVLMs with large-scale learnable model weights is resource-intensive. Consequently, more recent approaches rooted in knowledge distillation [27, 34, 36] to address OVD by leveraging knowledge distilled from CLIP [29] into the detector, predominantly adopting source-free strategies. For example, ViLD [7] aligns detector-encoded features with CLIP embeddings, while BARON [35] generates region ensembles using random masking within grid spaces to distill visual concept co-occurrence within a scene. Despite partially transferring knowledge of novel categories from PVLMs, detectors exhibit bias towards base classes due to disparities between vision-language alignment and detection tasks. To mitigate this bias, researchers explore pseudo labeling techniques utilizing prior knowledge of novel category names [40] or weakly-supervised annotations to the detection dataset [2, 6, 46]. However, integrating additional knowledge poses limitations in real-world scenarios." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 643, + 525, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 643, + 525, + 687 + ], + "spans": [ + { + "bbox": [ + 304, + 643, + 525, + 687 + ], + "type": "text", + "content": "Our proposed method extracts background implicit knowledge about classes beyond known/base categories from the provided detection dataset without requiring prior information about novel categories during inference. This" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "text", + "content": "16679" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 78, + 98, + 519, + 334 + ], + "blocks": [ + { + "bbox": [ + 78, + 98, + 519, + 334 + ], + "lines": [ + { + "bbox": [ + 78, + 98, + 519, + 334 + ], + "spans": [ + { + "bbox": [ + 78, + 98, + 519, + 334 + ], + "type": "image", + "image_path": "38ffbef51f90408addcce8c51f17e36bd985dd2eaa3ff216597e6d4fe9695c24.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 67, + 341, + 527, + 402 + ], + "lines": [ + { + "bbox": [ + 67, + 341, + 527, + 402 + ], + "spans": [ + { + "bbox": [ + 67, + 341, + 527, + 402 + ], + "type": "text", + "content": "Figure 2. An overview of the proposed LBP approach, consisting of three modules: Background Category-specific Prompt (BCP), Background Object Discovery (BOD), and Inference Probability Rectification (IPR). During training, BCP is first proposed to discover and represent background underlying categories, estimated from background proposals, with learnable background category-specific contexts. Then, BOD is presented to employ " + }, + { + "bbox": [ + 67, + 341, + 527, + 402 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 67, + 341, + 527, + 402 + ], + "type": "text", + "content": "-means clustering on background proposals across all images to harness implicit objects explored from background underlying knowledge. During inference, IPR is introduced to rectify probability scores of novel categories provided, by loosening their conceptual overlaps with background underlying categories estimated from background proposals." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 67, + 420, + 289, + 453 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 420, + 289, + 453 + ], + "spans": [ + { + "bbox": [ + 67, + 420, + 289, + 453 + ], + "type": "text", + "content": "utilization of implicit knowledge enables the detector to identify objects from unknown categories, enhancing its applicability across diverse scenarios." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 67, + 455, + 288, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 455, + 288, + 564 + ], + "spans": [ + { + "bbox": [ + 67, + 455, + 288, + 564 + ], + "type": "text", + "content": "Prompt tuning for OVD: Prompt tuning, stemming from natural language processing, has evolved with PVLM advancements to enhance their efficacy in specific downstream tasks [15]. CoOp, proposed in [44], introduces learnable contexts for 2D vision-language classification. CoCoOp, an extension proposed by [43], further enhances CoOp by generating input-conditioned tokens for each image. Various visual prompting approaches advocate integrating prompts into the image encoder of PVLMs, including works such as [1, 3, 8, 14]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 67, + 566, + 289, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 566, + 289, + 686 + ], + "spans": [ + { + "bbox": [ + 67, + 566, + 289, + 686 + ], + "type": "text", + "content": "In the realm of OVD, DetPro [29] pioneered prompt engineering by implementing a soft background loss, significantly improving the detector's ability to represent specific categories. Similarly, proposals for pre-training prompts on large-scale datasets [5, 31] aim to generate more universally applicable prompts. In contrast to DetPro [29], our approach has no reliance on uniform distribution assumption. Instead, by prompting underlying background categories estimated from proposals, our method enhances the learning of unknown category representations, leading to significant performance gains in detection." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 419, + 366, + 432 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 419, + 366, + 432 + ], + "spans": [ + { + "bbox": [ + 306, + 419, + 366, + 432 + ], + "type": "text", + "content": "3. Approach" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 437, + 384, + 449 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 437, + 384, + 449 + ], + "spans": [ + { + "bbox": [ + 306, + 437, + 384, + 449 + ], + "type": "text", + "content": "3.1. Preliminaries" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "spans": [ + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": "Problem formulation. Open vocabulary object detection (OVD) aims at seeking an optimal object detector capable of recognizing objects from both base and novel (previously unseen) categories, denoted by " + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b = \\{c_i\\}_{i=1}^{n_b}" + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_u = \\{c_i\\}_{i=1}^{n_u}" + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": ", respectively, in the inference dataset " + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_I" + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": ". This detector is achieved through optimization on the training dataset " + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_T" + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": ", annotated exclusively with instances from the base classes within " + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b" + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": ". Here, " + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b \\cap \\mathcal{C}_u = \\emptyset" + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": ", while " + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "inline_equation", + "content": "n_b" + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "inline_equation", + "content": "n_u" + }, + { + "bbox": [ + 304, + 455, + 525, + 554 + ], + "type": "text", + "content": " represent the cardinality of the respective category sets." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "spans": [ + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "content": "Built upon Faster R-CNN [30], given an input image, it is initially encoded by Faster R-CNN into global image features and generates a set of proposals through a region proposal network (RPN). In general, these region proposals are categorized into foreground proposals and background proposals [4], designated as " + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "inline_equation", + "content": "\\mathcal{N}" + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "content": ", respectively. The foreground proposals in " + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "content": " encompass all base categories within " + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b" + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "content": ", while all background proposals from " + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "inline_equation", + "content": "\\mathcal{N}" + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "content": " are collectively classified as a singular super-class (denoted as " + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "inline_equation", + "content": "c_{bg}" + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "content": " here), representing any category outside of " + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b" + }, + { + "bbox": [ + 304, + 554, + 525, + 664 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 665, + 525, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 665, + 525, + 686 + ], + "spans": [ + { + "bbox": [ + 306, + 665, + 525, + 686 + ], + "type": "text", + "content": "Knowledge distillation. Leveraging large-scale pre-trained large-scale Vision and Language Models (PVLMs), specif" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "text", + "content": "16680" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "spans": [ + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "type": "text", + "content": "ically CLIP [44], knowledge distillation empowers Faster R-CNN to effectively detect objects from arbitrary vocabularies by transferring insightful knowledge from CLIP. This process involves aligning the proposal features generated by the detector (actually output by the RoI Head of the detector, denoted by " + }, + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "type": "inline_equation", + "content": "w(\\cdot)" + }, + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "type": "text", + "content": ") with those extracted by the image encoder of CLIP (denoted by " + }, + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "type": "inline_equation", + "content": "\\mathcal{I}(\\cdot)" + }, + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "type": "text", + "content": "), effectively simulating coherence between the feature spaces of the detector and CLIP. Consequently, this process implicitly projects the visual embedding space of the detector into the textual embedding space of CLIP (output by the text encoder of CLIP, denoted by " + }, + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "type": "inline_equation", + "content": "\\mathcal{T}(\\cdot)" + }, + { + "bbox": [ + 67, + 99, + 289, + 242 + ], + "type": "text", + "content": "). In this way, the original classifier of Faster R-CNN is replaced." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "spans": [ + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "text", + "content": "Foreground/background interpretation. Given class " + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b" + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "text", + "content": ", its contextual prompt is defined as 'a photo of {category} in the scene', noted as " + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "inline_equation", + "content": "V_{c}" + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "text", + "content": ". Here, '\\{category\\}' denotes the contextual word for class " + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "text", + "content": ". Then its contextual embedding is obtained by feeding " + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "inline_equation", + "content": "V_{c}" + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "text", + "content": " into the CLIP text encoder " + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "inline_equation", + "content": "\\mathcal{T}(\\cdot)" + }, + { + "bbox": [ + 69, + 242, + 289, + 308 + ], + "type": "text", + "content": ", as follows," + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 153, + 316, + 288, + 328 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 153, + 316, + 288, + 328 + ], + "spans": [ + { + "bbox": [ + 153, + 316, + 288, + 328 + ], + "type": "interline_equation", + "content": "\\boldsymbol {t} _ {c} = \\mathcal {T} (\\boldsymbol {V} _ {c}). \\tag {1}", + "image_path": "b61dfd17659f26129816a07597bd2d986134b22e7ea71f20307131099f8d6b35.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "spans": [ + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "type": "text", + "content": "However, it is challenging to determine the contextual word for the \"background\" class " + }, + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "type": "inline_equation", + "content": "c_{bg}" + }, + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "type": "text", + "content": ". ViLD [7] or BARON [35] represents it with a learnable contextual embedding, without encoding it via CLIP's text encoder " + }, + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "type": "inline_equation", + "content": "\\mathcal{T}(\\cdot)" + }, + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "type": "text", + "content": ", thus defining it as " + }, + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "type": "inline_equation", + "content": "t_{bg}" + }, + { + "bbox": [ + 67, + 335, + 289, + 389 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "spans": [ + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "content": "Probability calculation. Having obtained " + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "inline_equation", + "content": "\\{t_c|c\\in \\mathcal{C}_b\\} \\cup" + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "inline_equation", + "content": "\\{\\pmb {t}_{bg}\\}" + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "content": " , let " + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "inline_equation", + "content": "\\pmb {w}(\\cdot)" + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "content": " denote the visual embedding of a proposal generated by the RoI Head of the object detector. Consider " + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b^{bg} = \\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\}" + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "content": " . For any proposal " + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "inline_equation", + "content": "x\\in \\mathcal{P}\\cup \\mathcal{N}" + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_T" + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "content": " with its visual embedding " + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "inline_equation", + "content": "\\pmb {w}(\\pmb {x})" + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "content": " , the probability of categorizing this proposal under the category " + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "inline_equation", + "content": "c\\in \\mathcal{C}_b^{bg}" + }, + { + "bbox": [ + 69, + 389, + 289, + 467 + ], + "type": "text", + "content": " is defined as follows:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 91, + 472, + 289, + 499 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 91, + 472, + 289, + 499 + ], + "spans": [ + { + "bbox": [ + 91, + 472, + 289, + 499 + ], + "type": "interline_equation", + "content": "p (c | x; \\mathcal {C} _ {b} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c}) / \\tau)}{\\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {b} ^ {b g}} \\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau)}, \\tag {2}", + "image_path": "4549932a5115eed0852497276f8883d65c85d916b2b29e5cd73a6ba1065b7933.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "spans": [ + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "type": "inline_equation", + "content": "\\exp (\\cdot)" + }, + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "type": "inline_equation", + "content": "\\cos (\\cdot)" + }, + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "type": "text", + "content": " represent the exponential function and cosine similarity, respectively, while " + }, + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 67, + 506, + 289, + 539 + ], + "type": "text", + "content": " is the temperature parameter used for rescaling the values." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "spans": [ + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "text", + "content": "During inference, once the novel classes from " + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_u" + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "text", + "content": " are introduced, the probability of a proposal from " + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_I" + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "text", + "content": " being classified as class " + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\} \\cup \\mathcal{C}_u" + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "text", + "content": " during detection can be computed simply by replacing " + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_b^{bg}" + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "text", + "content": " in Eq. (2) with " + }, + { + "bbox": [ + 67, + 539, + 289, + 598 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_{b,u}^{bg} = \\mathcal{C}_b\\cup \\{\\pmb {c}_{bg}\\} \\cup \\mathcal{C}_u" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 69, + 604, + 185, + 616 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 604, + 185, + 616 + ], + "spans": [ + { + "bbox": [ + 69, + 604, + 185, + 616 + ], + "type": "text", + "content": "3.2. The Proposed Method" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 67, + 620, + 289, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 620, + 289, + 686 + ], + "spans": [ + { + "bbox": [ + 67, + 620, + 289, + 686 + ], + "type": "text", + "content": "In this paper, we introduce LBP, a novel framework designed for open-vocabulary object detection. The key idea of LBP is that without any prior knowledge, learning background prompts is proposed to harness explored implicit background knowledge. This ensures the model attains improved background interpretation and decreased model" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 99, + 526, + 320 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 99, + 526, + 320 + ], + "spans": [ + { + "bbox": [ + 304, + 99, + 526, + 320 + ], + "type": "text", + "content": "overfitting, thus empowering the detector capable of better recognizing both base and novel categories. Specifically, the LBP framework initially introduces a Background Category-specific Prompt (BCP) module, discovering underlying categories from background proposals, and representing those using learnable context-specific prompts. Moreover, we introduce an online Background Object Discovery (BOD) to further exploit implicit object knowledge w.r.t. those estimated underlying categories, consequently alleviating model bias towards base categories, and present an Inference Probability Rectification (IPR) module to resolve conceptual overlaps between estimated background categories and novel categories during inference, leading to precisely computed probability scores for novel categories. Our primary focus lies in exploring background interpretation, distinct from prevailing OVD approaches rooted in knowledge distillation. This enables seamless integration of our method into existing OVD frameworks [35] and ViLD [7], etc. An overview of the proposed approach is illustrated in Figure 2." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 332, + 487, + 342 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 332, + 487, + 342 + ], + "spans": [ + { + "bbox": [ + 305, + 332, + 487, + 342 + ], + "type": "text", + "content": "3.2.1 Background Category-specific Prompt" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 349, + 525, + 403 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 349, + 525, + 403 + ], + "spans": [ + { + "bbox": [ + 304, + 349, + 525, + 403 + ], + "type": "text", + "content": "In this section, we model the underlying categories for background proposals in OVD and learn the corresponding category-specific prompts. However, the absence of prior knowledge of those categories necessitates the estimation of their optimal number in background proposals." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "content": "Towards this end, we first produce background proposals for all training images using a class-agnostic RPN trained on " + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_T" + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "content": " with only base classes, adopting a similar technique as in VL-PLM [40]. Those proposals are subsequently filtered based on RPN scores (with a threshold " + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "content": "), and Non-Maximum Suppression (NMS). Then, we obtain features for these filtered proposals generated from the image encoder of CLIP, and we refer to [10, 41] to estimate the optimal number of the underlying categories in background proposals via K-mean clustering [33], denoted by " + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "inline_equation", + "content": "n_o" + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "content": ", in the obtained proposal features. During this procedure, potential ambiguity in data partitioning during estimation may arise due to feature overlap, leading to the underestimation of " + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "inline_equation", + "content": "n_o" + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "content": ". Consequently, we expand the count of background underlying categories to " + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "inline_equation", + "content": "n_o + n_a" + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "inline_equation", + "content": "n_a" + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "content": " serves as a pre-defined hyper-parameter. Here, let " + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O = \\{c_i\\}_{i=1}^{n_o + n_a}" + }, + { + "bbox": [ + 304, + 403, + 525, + 590 + ], + "type": "text", + "content": " denote those estimated background categories, for simplicity." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 590, + 525, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 590, + 525, + 666 + ], + "spans": [ + { + "bbox": [ + 304, + 590, + 525, + 666 + ], + "type": "text", + "content": "However, due to the absence of prior knowledge of " + }, + { + "bbox": [ + 304, + 590, + 525, + 666 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O" + }, + { + "bbox": [ + 304, + 590, + 525, + 666 + ], + "type": "text", + "content": ", identifying their contextual words is a non-trivial task. To address this issue, we propose to learn category-specific context vectors. In this case, the contextual words of those background underlying categories can be described with the learned continuous vectors. Specifically, we adopt the prompt form for a given class " + }, + { + "bbox": [ + 304, + 590, + 525, + 666 + ], + "type": "inline_equation", + "content": "c \\in \\mathcal{C}_O" + }, + { + "bbox": [ + 304, + 590, + 525, + 666 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 316, + 674, + 525, + 687 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 316, + 674, + 525, + 687 + ], + "spans": [ + { + "bbox": [ + 316, + 674, + 525, + 687 + ], + "type": "interline_equation", + "content": "\\bar {V} _ {c} = ^ {\\prime} a \\text {p h o t o o f} \\left\\{v _ {c} \\right\\} \\text {i n t h e s c e n e} ^ {\\prime}, \\tag {3}", + "image_path": "ea2af76cd8b7e7d025d98e1ca7ec3199ae636272ef696437eb72cd50ec319131.jpg" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 705, + 315, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 315, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 315, + 714 + ], + "type": "text", + "content": "16681" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 68, + 99, + 288, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 99, + 288, + 133 + ], + "spans": [ + { + "bbox": [ + 68, + 99, + 288, + 133 + ], + "type": "text", + "content": "where the context vectors " + }, + { + "bbox": [ + 68, + 99, + 288, + 133 + ], + "type": "inline_equation", + "content": "\\{v_{c}|c\\in \\mathcal{C}_{O}\\}" + }, + { + "bbox": [ + 68, + 99, + 288, + 133 + ], + "type": "text", + "content": " are learnable. Following Eq. (1), the corresponding contextual embeddings can be acquired as " + }, + { + "bbox": [ + 68, + 99, + 288, + 133 + ], + "type": "inline_equation", + "content": "\\bar{\\iota}_c = \\mathcal{T}(\\overline{\\mathbf{V}}_c)" + }, + { + "bbox": [ + 68, + 99, + 288, + 133 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "spans": [ + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "content": "Additionally, we present a specific sub-class category, " + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "inline_equation", + "content": "\\overline{c}_{bg}" + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "content": ", designed to represent the \"background\" within background proposals, distinct from the super-class \"background\" " + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "inline_equation", + "content": "c_{bg}" + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "content": ". Specifically, " + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "inline_equation", + "content": "\\overline{c}_{bg}" + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "content": " covers unexplored categories not estimated in " + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O" + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "content": " and includes any untargeted object within background proposals. Similar to " + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "inline_equation", + "content": "t_{bg}" + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "content": ", we define a learnable contextual embedding, " + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "inline_equation", + "content": "\\overline{t}_{bg}" + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "content": ", for this category " + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "inline_equation", + "content": "\\overline{c}_{bg}" + }, + { + "bbox": [ + 68, + 133, + 288, + 209 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "spans": [ + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "content": "Once we obtain " + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "inline_equation", + "content": "\\{\\pmb{t}_c|c\\in \\mathcal{C}_b\\} \\cup \\{\\bar{\\pmb{t}}_c|c\\in \\mathcal{C}_O\\} \\cup \\{\\bar{\\pmb{t}}_{bg}\\}" + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "content": ", the corresponding set of categories can be defined as " + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_{b,o}^{bg} = \\mathcal{C}_b\\cup \\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}" + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "content": ". With reference to Eq. (2), for any proposal " + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "inline_equation", + "content": "x\\in \\mathcal{P}\\cup \\mathcal{N}" + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "content": ", its probability of being classified as class " + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "inline_equation", + "content": "c\\in \\mathcal{C}_{b,o}^{bg}" + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "content": " can be defined as " + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "inline_equation", + "content": "p(c|x;\\mathcal{C}_{b,o}^{bg})" + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "content": ". At this point, the model optimization in the BCP for the proposals in " + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "inline_equation", + "content": "\\mathcal{N}" + }, + { + "bbox": [ + 68, + 209, + 288, + 287 + ], + "type": "text", + "content": " can be achieved using the following cross-entropy losses:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 99, + 290, + 288, + 316 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 99, + 290, + 288, + 316 + ], + "spans": [ + { + "bbox": [ + 99, + 290, + 288, + 316 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {c l s} = \\frac {1}{| \\mathcal {P} |} \\sum_ {x \\in \\mathcal {P}} - \\log p (c = \\boldsymbol {C} (x) | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {4}", + "image_path": "474df62b9fef5da82cbba9465afdacefa177f384f0f6d0504a35cf104e50f38e.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 91, + 320, + 288, + 349 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 91, + 320, + 288, + 349 + ], + "spans": [ + { + "bbox": [ + 91, + 320, + 288, + 349 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {b c p} = \\frac {1}{| \\mathcal {N} |} \\sum_ {x \\in \\mathcal {N}} - \\log \\sum_ {c \\in \\mathcal {C} _ {O} \\cup \\{\\bar {\\mathfrak {c}} _ {b g} \\}} p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {5}", + "image_path": "dffbd7d68e47ee9756b99a8646927af1df45da0d1293eea2f8230f0bba6cbac3.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "spans": [ + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "inline_equation", + "content": "C(x)" + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "text", + "content": " represents the true label class of the given proposal " + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{bcp}" + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "text", + "content": " enhances the sum of probabilities of all background underlying categories estimated and " + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "inline_equation", + "content": "\\overline{c}_{bg}" + }, + { + "bbox": [ + 68, + 351, + 288, + 407 + ], + "type": "text", + "content": " within each background proposal, enabling the detector to softly learn the probabilities scores assigned for those categories." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "spans": [ + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "text", + "content": "However, contextual embeddings of " + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}" + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "text", + "content": " might not be sufficient to represent all background proposals with diverse scenes. When a background proposal belongs to " + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "inline_equation", + "content": "\\overline{c}_{bg}" + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "text", + "content": " and cannot be adequately represented by its contextual embedding, the visual embeddings of that proposal will be distant from any contextual embeddings of the estimated categories from " + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O" + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "text", + "content": ". Consequently, the sum of probabilities of those categories, i.e., " + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "inline_equation", + "content": "\\sum_{c\\in \\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}}p(c|x;\\mathcal{C}_{b,o}^{bg})" + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "text", + "content": " in Eq. (5), denoted as " + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "inline_equation", + "content": "p_o^{bg}" + }, + { + "bbox": [ + 68, + 406, + 288, + 506 + ], + "type": "text", + "content": ", for simplicity, would become very small." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "spans": [ + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "text", + "content": "In this situation, we should uniformly push the visual embeddings of that proposal towards the estimated background underlying categories and " + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "inline_equation", + "content": "\\bar{c}_{bg}" + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "text", + "content": ", given that the proposal is distinct from those categories. When " + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "inline_equation", + "content": "p_{o}^{bg} < \\gamma" + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "text", + "content": ", we introduce an additional softer background loss component to relax " + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{bcp}" + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "text", + "content": " for all background proposals in " + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "inline_equation", + "content": "\\mathcal{N}" + }, + { + "bbox": [ + 68, + 506, + 288, + 572 + ], + "type": "text", + "content": " as follows," + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 78, + 575, + 288, + 604 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 78, + 575, + 288, + 604 + ], + "spans": [ + { + "bbox": [ + 78, + 575, + 288, + 604 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {r l x} = \\frac {1}{| \\mathcal {N} |} \\sum_ {x \\in \\mathcal {N}} \\frac {1}{n _ {o a}} \\sum_ {c \\in \\mathcal {C} _ {O} \\cup \\{\\bar {e} _ {b g} \\}} - \\log p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {6}", + "image_path": "44dbd78f55b7518ab2d89a45d6ff53fdb8c0c2f20253c6fb68078c2911d39aaa.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "spans": [ + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "type": "inline_equation", + "content": "n_{oa} = n_o + n_a + 1" + }, + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "type": "text", + "content": " represents the size of " + }, + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O\\cup \\{\\overline{c}_{bg}\\}" + }, + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "type": "text", + "content": " while " + }, + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 68, + 608, + 288, + 652 + ], + "type": "text", + "content": " is a threshold with a small value. Therefore, the final version of the loss component in this BCP for background proposals to optimize the model is formulated as," + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 124, + 659, + 288, + 689 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 124, + 659, + 288, + 689 + ], + "spans": [ + { + "bbox": [ + 124, + 659, + 288, + 689 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {b c p} ^ {\\prime} = \\left\\{ \\begin{array}{l l} \\mathcal {L} _ {b c p}, & \\text {i f} \\boldsymbol {p} _ {o} ^ {b g} \\geq \\gamma , \\\\ \\mathcal {L} _ {r l x}, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {7}", + "image_path": "1c7d9ae394aef0f0105f569da792c8a8a705bdf87fc9862620b96ff72357b7e2.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 99, + 525, + 188 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 99, + 525, + 188 + ], + "spans": [ + { + "bbox": [ + 304, + 99, + 525, + 188 + ], + "type": "text", + "content": "Note that " + }, + { + "bbox": [ + 304, + 99, + 525, + 188 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{bcp}^{\\prime}" + }, + { + "bbox": [ + 304, + 99, + 525, + 188 + ], + "type": "text", + "content": " enriches the discrimination capability of the detector by incorporating diverse contextual embeddings of estimated background categories, diverging from the soft background loss in DetPro [4]. This enables the model to exploit implicit object knowledge w.r.t. those estimated underlying categories, while also reconciling training conflicts between the losses utilized for classification and distillation, as highlighted in prior works [35]." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 201, + 454, + 212 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 201, + 454, + 212 + ], + "spans": [ + { + "bbox": [ + 305, + 201, + 454, + 212 + ], + "type": "text", + "content": "3.2.2 Background Object Discovery" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "spans": [ + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "type": "text", + "content": "To enhance model training, we introduce an online Background Object Discovery (BOD) module to effectively discover and exploit unseen objects. This aims to extract implicit objects w.r.t. the underlying categories estimated from background proposals. To simplify, we here decompose " + }, + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O" + }, + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "type": "text", + "content": " into " + }, + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O' = \\{c_i\\}_{i=1}^{n_o}" + }, + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_a = \\{c_i\\}_{i=1}^{n_a}" + }, + { + "bbox": [ + 304, + 217, + 525, + 284 + ], + "type": "text", + "content": " in this section." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "spans": [ + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": "During initial training, with a given " + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "inline_equation", + "content": "n_o" + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": ", we conduct " + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": " means clustering (where " + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": " is set to " + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "inline_equation", + "content": "n_o" + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": ") on the set of visual embeddings " + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{I}(x)|x\\in \\mathcal{N}\\}" + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": " generated by the image encoder of CLIP for background proposals as in Sec. 3.2.1. Then, we subsequently obtain the embeddings of the cluster centers, denoted as " + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "inline_equation", + "content": "\\{\\tilde{w}_c|c\\in \\mathcal{C}_O^{\\prime}\\}" + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": ". These cluster centers function as the embedding centers for the estimated background categories within " + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O^\\prime" + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": ", allowing for online generation of pseudo labels from background proposals in each training batch. Throughout the training process, motivated by VL-PLM proposed in [40], background proposals of each training batch undergo being filtered based on RPN scores using a threshold of " + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 304, + 284, + 525, + 469 + ], + "type": "text", + "content": ", with an additional step to filter out proposals overlapping with ground-truth boxes. Subsequently, CLIP is employed to generate pseudo labels, preventing the detector from being biased towards estimated background categories." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 469, + 525, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 469, + 525, + 491 + ], + "spans": [ + { + "bbox": [ + 305, + 469, + 525, + 491 + ], + "type": "text", + "content": "Then, for a proposal " + }, + { + "bbox": [ + 305, + 469, + 525, + 491 + ], + "type": "inline_equation", + "content": "x\\in \\mathcal{N}" + }, + { + "bbox": [ + 305, + 469, + 525, + 491 + ], + "type": "text", + "content": ", its probability score of being classified as " + }, + { + "bbox": [ + 305, + 469, + 525, + 491 + ], + "type": "inline_equation", + "content": "c\\in \\mathcal{C}_O^{\\prime}" + }, + { + "bbox": [ + 305, + 469, + 525, + 491 + ], + "type": "text", + "content": " is calculated as follows," + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 328, + 498, + 525, + 526 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 328, + 498, + 525, + 526 + ], + "spans": [ + { + "bbox": [ + 328, + 498, + 525, + 526 + ], + "type": "interline_equation", + "content": "\\tilde {p} (c | x; \\mathcal {C} _ {O} ^ {\\prime}) = \\frac {\\exp (\\cos (\\mathcal {I} (x) , \\tilde {\\boldsymbol {w}} _ {c}) / \\tau)}{\\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O} ^ {\\prime}} \\exp (\\cos (\\mathcal {I} (x) . \\tilde {\\boldsymbol {w}} _ {c ^ {\\prime}}) / \\tau)}. \\tag {8}", + "image_path": "ba595c0ce493ccc520ffbcb897814729cd238c71072107382dcc5c2cd385d790.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 533, + 525, + 566 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 525, + 566 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 525, + 566 + ], + "type": "text", + "content": "Once such background proposal has probability scores corresponding to all categories in " + }, + { + "bbox": [ + 304, + 533, + 525, + 566 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O^{\\prime}" + }, + { + "bbox": [ + 304, + 533, + 525, + 566 + ], + "type": "text", + "content": ", we choose the predicted class label with the highest score as its pseudo label," + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 343, + 573, + 525, + 591 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 343, + 573, + 525, + 591 + ], + "spans": [ + { + "bbox": [ + 343, + 573, + 525, + 591 + ], + "type": "interline_equation", + "content": "\\mathcal {Y} ^ {o} (x) = \\underset {c} {\\operatorname {a r g m a x}} \\left\\{\\tilde {p} \\left(c | x; \\mathcal {C} _ {O} ^ {\\prime}\\right) | c \\in \\mathcal {C} _ {O} ^ {\\prime} \\right\\}. \\tag {9}", + "image_path": "76c7c77151a944586644d66972dfaac4d947745d096730f838e52b1936268e51.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "spans": [ + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "text", + "content": "To eliminate unconfident pseudo labels generated above, we will filter proposals based on probability scores of pseudo labels using a threshold " + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "text", + "content": ". Referring to VL-PLM [40], we also apply per-class NMS and use RoI Head to refine their box predictions, generating final pseudo labels. Afterward, those final pseudo labels are used to assign class labels of " + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O^\\prime" + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "text", + "content": " for all background proposals " + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "inline_equation", + "content": "\\mathcal{N}^B\\subseteq \\mathcal{N}" + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "text", + "content": " in each training batch. Let " + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_p^B" + }, + { + "bbox": [ + 304, + 598, + 525, + 687 + ], + "type": "text", + "content": " denote the set of positive" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "text", + "content": "16682" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 68, + 99, + 288, + 121 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 99, + 288, + 121 + ], + "spans": [ + { + "bbox": [ + 68, + 99, + 288, + 121 + ], + "type": "text", + "content": "background proposals assigned class labels from " + }, + { + "bbox": [ + 68, + 99, + 288, + 121 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O^{\\prime}" + }, + { + "bbox": [ + 68, + 99, + 288, + 121 + ], + "type": "text", + "content": ", while the remaining proposals are all collected as " + }, + { + "bbox": [ + 68, + 99, + 288, + 121 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_n^B" + }, + { + "bbox": [ + 68, + 99, + 288, + 121 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 69, + 122, + 288, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 122, + 288, + 144 + ], + "spans": [ + { + "bbox": [ + 69, + 122, + 288, + 144 + ], + "type": "text", + "content": "Therefore, the loss component proposed by this BOD module to optimize the model is formulated as follows," + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 80, + 151, + 288, + 221 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 80, + 151, + 288, + 221 + ], + "spans": [ + { + "bbox": [ + 80, + 151, + 288, + 221 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {b o d} = \\frac {1}{| \\mathcal {N} _ {p} ^ {B} |} \\sum_ {x \\in \\mathcal {N} _ {p} ^ {B}} - \\log p (c = y ^ {o} (x) | x; \\mathcal {C} _ {b, o} ^ {b g}) \\\\ + \\lambda_ {b g} \\frac {1}{\\left| \\mathcal {N} _ {n} ^ {B} \\right|} \\sum_ {x \\in \\mathcal {N} _ {n} ^ {B}} - \\log \\sum_ {c \\in \\mathcal {C} _ {a} \\cup \\{\\bar {\\epsilon} _ {b g} \\}} p (c | x; \\mathcal {C} _ {b, o} ^ {b g}), \\tag {10} \\\\ \\end{array}", + "image_path": "f4d925708c1afa612b74a2dd653816313b94c09058ab11eaa99c266791eaf659.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "spans": [ + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "type": "inline_equation", + "content": "\\lambda_{bg}" + }, + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "type": "text", + "content": " is a loss weight with a small value used for background proposals. This loss component emphasizes aligning visual embeddings of background proposals with their contextual embeddings related to estimated background categories from " + }, + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "type": "inline_equation", + "content": "C_O" + }, + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "type": "text", + "content": ". It is especially critical for majority classes within " + }, + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "type": "inline_equation", + "content": "C_O" + }, + { + "bbox": [ + 68, + 229, + 288, + 317 + ], + "type": "text", + "content": ", which are more prone to knowledge loss. Additionally, it empowers BOD to leverage insights from implicit objects within background proposals." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 68, + 317, + 288, + 350 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 317, + 288, + 350 + ], + "spans": [ + { + "bbox": [ + 68, + 317, + 288, + 350 + ], + "type": "text", + "content": "Training Objective. The final training objective for model optimization is a combination of the loss components formulated by Eq. (4), Eq. (7), and Eq. (10), respectively:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 121, + 361, + 288, + 373 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 121, + 361, + 288, + 373 + ], + "spans": [ + { + "bbox": [ + 121, + 361, + 288, + 373 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {f i n a l}} = \\mathcal {L} _ {\\text {c l s}} + \\mathcal {L} _ {\\text {b c p}} ^ {\\prime} + \\mathcal {L} _ {\\text {b o d}}. \\tag {11}", + "image_path": "7418d05d77210a75bf7754c51d56123f7d53dabde6bc911287836394534f1fe7.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 68, + 377, + 288, + 399 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 377, + 288, + 399 + ], + "spans": [ + { + "bbox": [ + 68, + 377, + 288, + 399 + ], + "type": "text", + "content": "It's worth noting that, the text encoder and image encoder of CLIP should be frozen during model training." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 69, + 413, + 234, + 423 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 413, + 234, + 423 + ], + "spans": [ + { + "bbox": [ + 69, + 413, + 234, + 423 + ], + "type": "text", + "content": "3.2.3 Inference Probability Rectification" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "spans": [ + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "type": "text", + "content": "Once performed BCP and BOD, the detector capability of recognizing previously unseen classes has been significantly enhanced. However, a new challenge arises during inference. The background underlying categories " + }, + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O" + }, + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "type": "text", + "content": ", estimated from background proposals during training, might share semantics similarities with the novel classes " + }, + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_u" + }, + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "type": "text", + "content": " of the detector aiming to classify during inference, vividly symbolized by " + }, + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O \\cap \\mathcal{C}_u \\neq \\emptyset" + }, + { + "bbox": [ + 68, + 430, + 288, + 594 + ], + "type": "text", + "content": ". In such cases, there exist conceptual overlaps of contextual embeddings between those two types of categories during inference. This overlap could hinder the accurate computation of probability scores for novel classes, leading to detection ambiguity during inference. To overcome this, an Inference Probability Rectification (IPR) is presented to enable the detector to precisely predict the probabilities of novel classes during inference." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "spans": [ + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "text", + "content": "To be specific, let " + }, + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_{b,u,o}^{bg} = \\mathcal{C}_b\\cup \\mathcal{C}_u\\cup \\mathcal{C}_O\\cup \\{\\overline{\\mathbf{c}}_{bg}\\}" + }, + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "text", + "content": ". Then, with reference to Eq. (2), the probability of a proposal " + }, + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "inline_equation", + "content": "x\\in" + }, + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_I" + }, + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "text", + "content": " being classified as class " + }, + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "inline_equation", + "content": "c\\in \\mathcal{C}_b\\cup \\mathcal{C}_u" + }, + { + "bbox": [ + 69, + 594, + 288, + 638 + ], + "type": "text", + "content": " during inference can be computed as follows," + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 105, + 645, + 288, + 668 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 105, + 645, + 288, + 668 + ], + "spans": [ + { + "bbox": [ + 105, + 645, + 288, + 668 + ], + "type": "interline_equation", + "content": "p (c | x; \\mathcal {C} _ {b, u, o} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , \\boldsymbol {t} _ {c}) / \\tau)}{\\boldsymbol {\\Sigma} ^ {b , u} + \\boldsymbol {\\Sigma} ^ {o} + \\boldsymbol {\\Sigma} ^ {b g}}, \\tag {12}", + "image_path": "d575ec441bffc3c28dfdeae5687cbc9166d4b0facb6c617938585c42168b2f15.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 69, + 675, + 94, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 675, + 94, + 685 + ], + "spans": [ + { + "bbox": [ + 69, + 675, + 94, + 685 + ], + "type": "text", + "content": "where" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 340, + 115, + 524, + 192 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 340, + 115, + 524, + 192 + ], + "spans": [ + { + "bbox": [ + 340, + 115, + 524, + 192 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\boldsymbol {\\Sigma} ^ {b, u} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {b} \\cup \\mathcal {C} _ {u}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau), \\\\ \\boldsymbol {\\Sigma} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau), \\\\ \\boldsymbol {\\Sigma} ^ {b g} = \\sum_ {c ^ {\\prime} \\in \\{\\overline {{\\boldsymbol {t}}} _ {b g} \\}} \\exp (\\cos (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) / \\tau). \\tag {13} \\\\ \\end{array}", + "image_path": "14606533ede9c2c68aaf1b79be967d7419152a101a05ce545d9ee80652278861.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "spans": [ + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": "Assuming that a proposal " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " carries its true class label " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "c \\in \\mathcal{C}_u" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " simultaneously sharing conceptual overlap with categories in " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": ", then the probability computation of for this category, namely " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "p(c|x; \\mathcal{C}_{b,u,o}^{bg})" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": ", tends to underestimate its value. This underestimation occurs due to the presence of " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " simultaneously contributing in both " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "\\Sigma^{b,u}" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "\\Sigma^o" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " in the denominator of Eq. (12). In essence, " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "p(c|x; \\mathcal{C}_{b,u,o}^{bg})" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " becomes smaller than its true probability value, denoted as " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "P(c|x)" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": ", which is a theoretical but unknown value, being discussed later. To address this issue, our goal is to resolve the conceptual overlaps between novel categories in " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_u" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " and estimated background underlying categories within " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_O" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": ". This aims to reduce the influence of " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " contributing " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "\\Sigma^o" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": ", leading to a re-estimation of " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "\\Sigma^o" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": " and thus resulting in " + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "inline_equation", + "content": "\\hat{\\Sigma}^o" + }, + { + "bbox": [ + 304, + 197, + 525, + 350 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 350, + 525, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 350, + 525, + 449 + ], + "spans": [ + { + "bbox": [ + 304, + 350, + 525, + 449 + ], + "type": "text", + "content": "Here, we simplify the function " + }, + { + "bbox": [ + 304, + 350, + 525, + 449 + ], + "type": "inline_equation", + "content": "s(\\cdot ,\\cdot) = \\exp (\\cos (\\cdot ,\\cdot) / \\tau)" + }, + { + "bbox": [ + 304, + 350, + 525, + 449 + ], + "type": "text", + "content": " in Eqs. (12) to (13) and term its resulting value as the cosine exponential score. As per the definitions of the softmax function, individual probabilities for each category are computed by normalizing the cosine exponential scores, dividing each by the total sum of cosine exponential scores corresponding to all categories. We hypothesize that the cosine exponential score proportionally reflects its true probability. Hence, " + }, + { + "bbox": [ + 304, + 350, + 525, + 449 + ], + "type": "inline_equation", + "content": "\\tilde{\\Sigma}^o" + }, + { + "bbox": [ + 304, + 350, + 525, + 449 + ], + "type": "text", + "content": " can be represented as:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 310, + 453, + 525, + 483 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 453, + 525, + 483 + ], + "spans": [ + { + "bbox": [ + 310, + 453, + 525, + 483 + ], + "type": "interline_equation", + "content": "\\tilde {\\boldsymbol {\\Sigma}} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} s (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) \\cdot \\left(1 - \\frac {\\sum_ {c ^ {\\prime \\prime} \\in \\mathcal {C} _ {u}} P \\left(c ^ {\\prime} , c ^ {\\prime \\prime} \\mid x\\right)}{P \\left(c ^ {\\prime} \\mid x\\right)}\\right). \\tag {14}", + "image_path": "9034b8d11811d890ed45cda4a9ff428bdbf1c762a6d7311c51fe161829982aa4.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "spans": [ + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "type": "text", + "content": "According to the Multiplication Rule of Joint Probabilities, the joint probability " + }, + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "type": "inline_equation", + "content": "P(c', c''|x)" + }, + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "type": "text", + "content": " for any " + }, + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "type": "inline_equation", + "content": "c' \\in \\mathcal{C}_O" + }, + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "type": "inline_equation", + "content": "c'' \\in \\mathcal{C}_u" + }, + { + "bbox": [ + 304, + 487, + 525, + 520 + ], + "type": "text", + "content": " can be estimated as follows:" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 351, + 525, + 524, + 539 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 351, + 525, + 524, + 539 + ], + "spans": [ + { + "bbox": [ + 351, + 525, + 524, + 539 + ], + "type": "interline_equation", + "content": "P \\left(c ^ {\\prime}, c ^ {\\prime \\prime} | x\\right) = P \\left(c ^ {\\prime} | x\\right) P \\left(c ^ {\\prime \\prime} | x, c ^ {\\prime}\\right). \\tag {15}", + "image_path": "8e47235b7e336ac8f48f84c5cea965b6f5a6df508c48b3a777606aab1b0cbaaa.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 316, + 544, + 522, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 316, + 544, + 522, + 555 + ], + "spans": [ + { + "bbox": [ + 316, + 544, + 522, + 555 + ], + "type": "text", + "content": "With Eq. (15), Eq. (14) can be reformulated as follows:" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 314, + 560, + 525, + 585 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 314, + 560, + 525, + 585 + ], + "spans": [ + { + "bbox": [ + 314, + 560, + 525, + 585 + ], + "type": "interline_equation", + "content": "\\tilde {\\boldsymbol {\\Sigma}} ^ {o} = \\sum_ {c ^ {\\prime} \\in \\mathcal {C} _ {O}} s (\\boldsymbol {w} (x), \\boldsymbol {t} _ {c ^ {\\prime}}) \\cdot \\left(1 - \\sum_ {c ^ {\\prime \\prime} \\in \\mathcal {C} _ {u}} P \\left(c ^ {\\prime \\prime} | x, c ^ {\\prime}\\right)\\right). \\tag {16}", + "image_path": "e986eb73581695ddd112bc74f1b46d0f2551ffb69d1ae8f4286eee6299ffb409.jpg" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "spans": [ + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "text", + "content": "However, estimating " + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "inline_equation", + "content": "P(c''|x,c')" + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "text", + "content": " poses challenges. Hence, we assume " + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "inline_equation", + "content": "P(c''|x,c')" + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "text", + "content": " to be sample-agnostic, resulting in " + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "inline_equation", + "content": "P(c''|c')" + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "text", + "content": ". Given that the embedding space serves as a metric space for probability calculation, " + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "inline_equation", + "content": "P(c''|c')" + }, + { + "bbox": [ + 304, + 590, + 525, + 656 + ], + "type": "text", + "content": " can be estimated by leveraging the cosine similarity between the contextual embeddings of these two categories as follows," + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 312, + 662, + 525, + 689 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 662, + 525, + 689 + ], + "spans": [ + { + "bbox": [ + 312, + 662, + 525, + 689 + ], + "type": "interline_equation", + "content": "P \\left(c ^ {\\prime \\prime} \\mid x, c ^ {\\prime}\\right) = P \\left(c ^ {\\prime \\prime} \\mid c ^ {\\prime}\\right) = \\frac {s \\left(\\boldsymbol {t} _ {c ^ {\\prime}} , \\boldsymbol {t} _ {c ^ {\\prime \\prime}}\\right)}{\\sum_ {c \\in \\mathcal {C} _ {b , u , o} ^ {b g} \\setminus \\{c ^ {\\prime} \\}} s \\left(\\boldsymbol {t} _ {c ^ {\\prime}} , \\boldsymbol {t} _ {c}\\right)}. \\tag {17}", + "image_path": "20afc0c99e6a7dc42b9cd8c32f3b3011ca946b6c965f0d265b8fa96ad047bd12.jpg" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "text", + "content": "16683" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "bbox": [ + 69, + 99, + 288, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 99, + 288, + 133 + ], + "spans": [ + { + "bbox": [ + 69, + 99, + 288, + 133 + ], + "type": "text", + "content": "Considering Eq. (16) and Eq. (17) into Eq. (12), the probability of a proposal " + }, + { + "bbox": [ + 69, + 99, + 288, + 133 + ], + "type": "inline_equation", + "content": "x \\in \\mathcal{D}_I" + }, + { + "bbox": [ + 69, + 99, + 288, + 133 + ], + "type": "text", + "content": " being classified as class " + }, + { + "bbox": [ + 69, + 99, + 288, + 133 + ], + "type": "inline_equation", + "content": "c \\in \\mathcal{C}_b \\cup \\mathcal{C}_u" + }, + { + "bbox": [ + 69, + 99, + 288, + 133 + ], + "type": "text", + "content": " during inference can be reformulated as follows," + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 105, + 142, + 288, + 166 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 105, + 142, + 288, + 166 + ], + "spans": [ + { + "bbox": [ + 105, + 142, + 288, + 166 + ], + "type": "interline_equation", + "content": "p (c | x; \\mathcal {C} _ {b, u, o} ^ {b g}) = \\frac {\\exp (\\cos (\\boldsymbol {w} (x) , t _ {c}) / \\tau)}{\\boldsymbol {\\Sigma} ^ {b , u} + \\tilde {\\boldsymbol {\\Sigma}} ^ {o} + \\boldsymbol {\\Sigma} ^ {b g}}. \\tag {18}", + "image_path": "94a03216170d1166006207a9d998f703170ebd30cb2864a7fed8f5e2e555307f.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 69, + 175, + 143, + 186 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 175, + 143, + 186 + ], + "spans": [ + { + "bbox": [ + 69, + 175, + 143, + 186 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 69, + 193, + 179, + 205 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 193, + 179, + 205 + ], + "spans": [ + { + "bbox": [ + 69, + 193, + 179, + 205 + ], + "type": "text", + "content": "4.1. Experimental Setups" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "spans": [ + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": "Datasets. To assess the effectiveness of the proposed LBP framework in handling the OVD task, we conducted experiments on two established object detection benchmark datasets: MS-COCO [25] and LVIS [9]. These experiments were conducted in traditional open vocabulary settings [7, 34, 35], referred to as OV-COCO and OV-LVIS, respectively. As outlined in prior works [34, 35], we divided 48 categories as base classes and 17 categories as novel classes in the OV-COCO task. The primary metric used to evaluate the detection performance is the mean average precision at IoU with a threshold of 0.50 (denoted as " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{50}" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": "). Specifically, we represent " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{50}" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": " for base and novel categories as " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{50}^{n}" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{50}^{b}" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": ", respectively. For OV-LVIS, following [34, 35], we classified 337 rare categories as novel classes, while considering the remaining common and frequent categories as base classes (resulting in a total of 866 categories). Here, the detector's performance is evaluated using the mean average precision averaged across IoUs from 0.50 to 0.95 (denoted as AP). We report AP values for rare categories " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "(\\mathrm{AP}_r)" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": ", common categories " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "(\\mathrm{AP}_c)" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": ", frequent categories " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "(\\mathrm{AP}_f)" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": ", and all classes. Furthermore, we include experimental results for instance segmentation on LVIS. The metrics " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{50}^{n}" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_r" + }, + { + "bbox": [ + 68, + 210, + 290, + 483 + ], + "type": "text", + "content": " are used as the primary measures to assess the detector's performance on OV-COCO and OV-LVIS, respectively." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 68, + 484, + 288, + 561 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 484, + 288, + 561 + ], + "spans": [ + { + "bbox": [ + 68, + 484, + 288, + 561 + ], + "type": "text", + "content": "Baselines. We compare LBP with the following state-of-the-art (SOTA) algorithms to handle the OVD task on OV-COCO: Detric [46], Object-centric-OVD [2], OVDETR [37], RegionCLIP [42], ViLD [7], OADP [34] and BARON [35]. Besides, we perform our comparison on OV-LVIS with previous methods, including ViLD [7], DetPro [4] and BARON [35]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 69, + 570, + 243, + 581 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 570, + 243, + 581 + ], + "spans": [ + { + "bbox": [ + 69, + 570, + 243, + 581 + ], + "type": "text", + "content": "4.2. Comparisons with State-of-the-Arts" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 68, + 586, + 288, + 631 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 586, + 288, + 631 + ], + "spans": [ + { + "bbox": [ + 68, + 586, + 288, + 631 + ], + "type": "text", + "content": "Results on OV-COCO and OV-LVIS are reported in Table 1 and Table 2, respectively. As shown, our LBP method outperforms previous state-of-the-art (SOTA) algorithms for the OVD task in all cases, validating its effectiveness." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 68, + 632, + 288, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 632, + 288, + 686 + ], + "spans": [ + { + "bbox": [ + 68, + 632, + 288, + 686 + ], + "type": "text", + "content": "Results on OV-COCO. Similar to OADP [34], we categorize the comparison baselines into four OVD benchmark settings: Vanilla OVD (V-OVD), Caption-based OVD (C-OVD), Generalized OVD (G-OVD), and Weakly Supervised OVD (WS-OVD). The emphasis of our proposed ap" + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 308, + 98, + 524, + 193 + ], + "blocks": [ + { + "bbox": [ + 308, + 98, + 524, + 193 + ], + "lines": [ + { + "bbox": [ + 308, + 98, + 524, + 193 + ], + "spans": [ + { + "bbox": [ + 308, + 98, + 524, + 193 + ], + "type": "table", + "html": "
MethodBenchmarkDetectorAPn50APb50AP50
Detic [46]WS-OVDCenterNet2[45]' 27.847.145.0
Object-centric-OVD [2]WS-OVDFaster R-CNN36.654.049.4
VL-PLMG-OVDFaster R-CNN32.354.048.3
OV-DETR [37]G-OVDDeformableDETR[47]29.461.052.7
RegionCLIP [42]C-OVDCLIP26.854.847.5
ViLD [7]V-OVDFaster R-CNN27.659.551.3
OADP [34]V-OVDFaster R-CNN30.053.347.2
BARON [35]V-OVDFaster R-CNN34.060.453.5
BARON†V-OVDFaster R-CNN35.858.252.3
LBP (ours)V-OVDFaster R-CNN35.960.854.3
LBP† (ours)V-OVDFaster R-CNN37.858.753.2
", + "image_path": "e1ef554240d4335b9848e8a0d37d49e25f4e3fef82a0c9a0cf3897bde9bc0d84.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 308, + 238, + 524, + 311 + ], + "blocks": [ + { + "bbox": [ + 305, + 200, + 525, + 231 + ], + "lines": [ + { + "bbox": [ + 305, + 200, + 525, + 231 + ], + "spans": [ + { + "bbox": [ + 305, + 200, + 525, + 231 + ], + "type": "text", + "content": "Table 1. Comparison results of LBP and existing SOTA methods on OV-COCO. " + }, + { + "bbox": [ + 305, + 200, + 525, + 231 + ], + "type": "inline_equation", + "content": "\\dagger" + }, + { + "bbox": [ + 305, + 200, + 525, + 231 + ], + "type": "text", + "content": " indicates model optimization using a batch size of 16, used for mitigating model overfitting towards base classes." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 308, + 238, + 524, + 311 + ], + "lines": [ + { + "bbox": [ + 308, + 238, + 524, + 311 + ], + "spans": [ + { + "bbox": [ + 308, + 238, + 524, + 311 + ], + "type": "table", + "html": "
MethodObject detectionInstance segmentation
APrAPcAPfAPAPrAPcAPfAP
ViLD [7]16.726.534.227.816.624.630.325.5
DetPro [4]20.827.832.428.419.825.628.925.9
BARON [35]20.128.432.228.419.226.829.426.5
BARON‡23.229.332.529.522.627.629.827.6
LBP (ours)22.228.832.429.122.127.029.727.2
LBP‡ (ours)24.129.532.829.923.727.730.128.0
", + "image_path": "628987137dc0867d587212ed3f11d20ce8959f531e09721ca3c84b760f838c77.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 318, + 525, + 348 + ], + "lines": [ + { + "bbox": [ + 305, + 318, + 525, + 348 + ], + "spans": [ + { + "bbox": [ + 305, + 318, + 525, + 348 + ], + "type": "text", + "content": "Table 2. Comparison results of LBP and existing SOTA methods on OV-LVIS. " + }, + { + "bbox": [ + 305, + 318, + 525, + 348 + ], + "type": "inline_equation", + "content": "\\ddagger" + }, + { + "bbox": [ + 305, + 318, + 525, + 348 + ], + "type": "text", + "content": " indicates the model trained using learnable prompt templates, proposed by DetPro [4]." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "spans": [ + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "text", + "content": "proach lies in V-OVD, but we also present performance results across other settings. Table 1 demonstrates that in this dataset, our LBP approach excels across various benchmark settings, particularly in V-OVD, surpassing existing methods by a notable margin. For instance, compared to " + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "inline_equation", + "content": "\\mathrm{BARON}^{\\dagger}" + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "text", + "content": ", our method demonstrates a " + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "inline_equation", + "content": "2.0\\%" + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "text", + "content": " improvement in " + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{50}^{n}" + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "inline_equation", + "content": "0.5\\%" + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{50}^{b}" + }, + { + "bbox": [ + 304, + 367, + 525, + 476 + ], + "type": "text", + "content": " in the V-OVD setting, showcasing its efficacy in detecting both base and novel classes during inference. Moreover, it outperforms previous approaches in other settings, affirming its generality and superiority." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "spans": [ + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "text", + "content": "Results on OV-LVIS. Compared to OV-COCO, OV-LVIS poses greater challenges due to increased categories and fewer implicit instances for novel classes. The outcomes in Table 2 showcase the exceptional performance of our approach. For the task of object detection, our method enhances BARON's performance by " + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "inline_equation", + "content": "2.1\\%" + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "text", + "content": " on " + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_r" + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "text", + "content": " without learnable prompts and by " + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "inline_equation", + "content": "0.9\\%" + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "text", + "content": " with them. Additionally, our approach consistently boosts the performance of BARON by " + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "inline_equation", + "content": "2.9\\%" + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "text", + "content": " on " + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_r" + }, + { + "bbox": [ + 304, + 476, + 525, + 619 + ], + "type": "text", + "content": " in the task of instance segmentation. These comparisons underline the applicability of the proposed method in more complex tasks including object detection and instance segmentation with a larger number of categories, thereby corroborating its effectiveness." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 625, + 403, + 637 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 625, + 403, + 637 + ], + "spans": [ + { + "bbox": [ + 306, + 625, + 403, + 637 + ], + "type": "text", + "content": "4.3. Ablation Analysis" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 643, + 525, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 643, + 525, + 687 + ], + "spans": [ + { + "bbox": [ + 305, + 643, + 525, + 687 + ], + "type": "text", + "content": "Impact of individual proposed modules. We conducted an ablation study to assess the effectiveness of each individual module within our method, namely Background Category Prompts (BCP), Background Object Discovery" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "text", + "content": "16684" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 100, + 98, + 258, + 178 + ], + "blocks": [ + { + "bbox": [ + 100, + 98, + 258, + 178 + ], + "lines": [ + { + "bbox": [ + 100, + 98, + 258, + 178 + ], + "spans": [ + { + "bbox": [ + 100, + 98, + 258, + 178 + ], + "type": "table", + "html": "
BCPBODIPRAP50nAP50bAP50
---35.858.252.3
✓--34.359.052.5
-✓-35.258.552.4
✓✓-35.658.752.7
✓-✓36.859.053.2
-✓✓36.958.753.0
✓✓✓37.858.753.2
", + "image_path": "533dee749bf5bc8ec726fc9d486645ceb05e32a469c9d7575392d7ae6cc55cee.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 100, + 220, + 257, + 284 + ], + "blocks": [ + { + "bbox": [ + 69, + 186, + 289, + 206 + ], + "lines": [ + { + "bbox": [ + 69, + 186, + 289, + 206 + ], + "spans": [ + { + "bbox": [ + 69, + 186, + 289, + 206 + ], + "type": "text", + "content": "Table 3. Ablation study results in individual proposed modules of LBP on OV-COCO." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 100, + 220, + 257, + 284 + ], + "lines": [ + { + "bbox": [ + 100, + 220, + 257, + 284 + ], + "spans": [ + { + "bbox": [ + 100, + 220, + 257, + 284 + ], + "type": "table", + "html": "
MethodAP50nAP50bAP50
Single embedding35.858.252.3
Soft background loss36.458.452.6
Lbcp37.358.853.1
Lrlx36.958.452.8
LBP (ours)37.858.753.2
", + "image_path": "acc884f5fdc17acb324186c1130595a261f8cecffe229e201631fbe4e22e902c.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 70, + 292, + 286, + 302 + ], + "lines": [ + { + "bbox": [ + 70, + 292, + 286, + 302 + ], + "spans": [ + { + "bbox": [ + 70, + 292, + 286, + 302 + ], + "type": "text", + "content": "Table 4. Additional ablation study results of BCP on OV-COCO." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 68, + 323, + 289, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 323, + 289, + 510 + ], + "spans": [ + { + "bbox": [ + 68, + 323, + 289, + 510 + ], + "type": "text", + "content": "(BOD), and Inference Probability Rectification (IPR). By incrementally integrating these modules into the full model, we sought to understand their individual impact. Table 3 illustrates the outcomes. We observed that employing only BCP notably improves the baseline's performance w.r.t. base classes but results in a decline in performance for novel classes. This observation highlights the inherent conceptual overlap generated between the estimated background underlying classes and novel classes when exclusively relying on BCP. However, combining BCP with IPR demonstrates a " + }, + { + "bbox": [ + 68, + 323, + 289, + 510 + ], + "type": "inline_equation", + "content": "2.5\\%" + }, + { + "bbox": [ + 68, + 323, + 289, + 510 + ], + "type": "text", + "content": " performance improvement of novel classes, showcasing the effect of IPR. Building upon the above variant model, the addition of BOD further enhances the model, resulting in a " + }, + { + "bbox": [ + 68, + 323, + 289, + 510 + ], + "type": "inline_equation", + "content": "1.0\\%" + }, + { + "bbox": [ + 68, + 323, + 289, + 510 + ], + "type": "text", + "content": " mAP50 performance improvement on novel classes. This validates its increased role in identifying objects within the estimated underlying categories from background proposals." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "spans": [ + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": "Further analysis of BCP. To further validate BCP's efficacy, we explore various conventional designs for background interpretation in Table 4. We refer \"Single embedding\" as the design with only a learnable \"background\" embedding " + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "inline_equation", + "content": "t_{bg}" + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": ", akin to prior schemes [7, 35], while \"Soft background loss\" pertains to the soft background loss outlined in DetPro [4]. Subsequently, " + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{bcp}" + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{rlx}" + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": " indicate our substitution of " + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{bcp}'" + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": " in Eq. (7) with only " + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{bcp}" + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{rlx}" + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": ", respectively. The results considerably highlight the superiority of our proposed design for background interpretation. Specifically, our design significantly outperforms \"Soft background loss\" proposed by DetPro [4], showcasing its effectiveness in preserving class relations. Moreover, the comparison using only " + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{bcp}" + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{rlx}" + }, + { + "bbox": [ + 68, + 511, + 289, + 686 + ], + "type": "text", + "content": " emphasizes the individual importance of each loss component proposed by BCP used for background interpretation." + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 310, + 99, + 410, + 173 + ], + "blocks": [ + { + "bbox": [ + 310, + 99, + 410, + 173 + ], + "lines": [ + { + "bbox": [ + 310, + 99, + 410, + 173 + ], + "spans": [ + { + "bbox": [ + 310, + 99, + 410, + 173 + ], + "type": "image", + "image_path": "64d4e480bd2c048e9c76c1cfd0acd54a438bc34764a203d4598100af54a2e728.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 355, + 177, + 365, + 185 + ], + "lines": [ + { + "bbox": [ + 355, + 177, + 365, + 185 + ], + "spans": [ + { + "bbox": [ + 355, + 177, + 365, + 185 + ], + "type": "text", + "content": "(a)" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 421, + 99, + 522, + 173 + ], + "blocks": [ + { + "bbox": [ + 421, + 99, + 522, + 173 + ], + "lines": [ + { + "bbox": [ + 421, + 99, + 522, + 173 + ], + "spans": [ + { + "bbox": [ + 421, + 99, + 522, + 173 + ], + "type": "image", + "image_path": "d8d7e12c1061675eba81408162908ca073f159c093430cddd2242ecd7e3d59f9.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 466, + 177, + 476, + 185 + ], + "lines": [ + { + "bbox": [ + 466, + 177, + 476, + 185 + ], + "spans": [ + { + "bbox": [ + 466, + 177, + 476, + 185 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 187, + 525, + 267 + ], + "lines": [ + { + "bbox": [ + 304, + 187, + 525, + 267 + ], + "spans": [ + { + "bbox": [ + 304, + 187, + 525, + 267 + ], + "type": "text", + "content": "Figure 3. Visualizations of feature distributions for novel category proposals. Note that proposals are selected for those that exhibit significant IoU overlap with the ground truth boxes of novel categories. Different colors denote distinct categories. (a) and (b) showcase the feature distributions generated by BARON [35] and our LBP, respectively. Compared to BARON, our LBP algorithm leads to more compact distributions for the same novel category representations." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 285, + 525, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 285, + 525, + 373 + ], + "spans": [ + { + "bbox": [ + 304, + 285, + 525, + 373 + ], + "type": "text", + "content": "Furthermore, we use t-SNE to visualize the feature distribution of novel category proposals, further highlighting the efficacy of our designed schemes in background interpretation. As displayed in Figure 3(a) and Figure 3 (b), compared our approach LBP with BARON [35], the findings illustrate that the proposed LBP approach enables the detector to learn more discriminative features for the proposals associated with novel categories." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 388, + 376, + 399 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 388, + 376, + 399 + ], + "spans": [ + { + "bbox": [ + 306, + 388, + 376, + 399 + ], + "type": "text", + "content": "5. Conclusions" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 408, + 525, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 408, + 525, + 563 + ], + "spans": [ + { + "bbox": [ + 304, + 408, + 525, + 563 + ], + "type": "text", + "content": "In this paper, we have introduced LBP, a novel framework addressing the challenges of open-vocabulary object detection. In this approach, learning background prompts is proposed to harness explored implicit background knowledge. This can enhance the capacity of the detector to recognize both base and novel categories during inference. To achieve this, we have devised three essential modules: Background Category-specific Prompt, Background Object Discovery, and Inference Probability Rectification. These modules collectively empower the detector to discover, represent, and leverage implicit object knowledge explored from background proposals. Our proposed approach has been rigorously evaluated through extensive experiments and thorough ablation studies, confirming its superior performance." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 578, + 394, + 590 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 578, + 394, + 590 + ], + "spans": [ + { + "bbox": [ + 306, + 578, + 394, + 590 + ], + "type": "text", + "content": "Acknowledgments" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 598, + 525, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 598, + 525, + 686 + ], + "spans": [ + { + "bbox": [ + 304, + 598, + 525, + 686 + ], + "type": "text", + "content": "This work was supported in part by the National Natural Science Foundation of China (NO. 62322608), in part by the CAAI-MindSpore Open Fund, developed on OpenI Community, in part by the Shenzhen Science and Technology Program (NO. JCYJ20220530141211024), in part by the Open Project Program of State Key Laboratory of Virtual Reality Technology and Systems, Beihang University (No.VRLAB2023A01)." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "text", + "content": "16685" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 70, + 99, + 123, + 110 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 70, + 99, + 123, + 110 + ], + "spans": [ + { + "bbox": [ + 70, + 99, + 123, + 110 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 70, + 117, + 289, + 685 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 74, + 117, + 289, + 156 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 74, + 117, + 289, + 156 + ], + "spans": [ + { + "bbox": [ + 74, + 117, + 289, + 156 + ], + "type": "text", + "content": "[1] Hyojin Bahng, Ali Jahanian, Swami Sankaranarayanan, and Phillip Isola. 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Deformable detr: Deformable transformers for end-to-end object detection. arXiv preprint arXiv:2010.04159, 2020. 7" + } + ] + } + ], + "index": 22 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "spans": [ + { + "bbox": [ + 294, + 705, + 317, + 714 + ], + "type": "text", + "content": "16687" + } + ] + } + ], + "index": 24 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning CNN on ViT_ A Hybrid Model to Explicitly Class-specific Boundaries for Domain Adaptation/f88da0d8-496d-49e1-8c98-717f50be5563_content_list.json b/2024/Learning CNN on ViT_ A Hybrid Model to Explicitly Class-specific Boundaries for Domain Adaptation/f88da0d8-496d-49e1-8c98-717f50be5563_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..07ff9e404e9a6a82fbf01e8d87bfc36169f1ebd5 --- /dev/null +++ b/2024/Learning CNN on ViT_ A Hybrid Model to Explicitly Class-specific Boundaries for Domain Adaptation/f88da0d8-496d-49e1-8c98-717f50be5563_content_list.json @@ -0,0 +1,1437 @@ +[ + { + "type": "text", + "text": "Learning CNN on ViT: A Hybrid Model to Explicitly Class-specific Boundaries for Domain Adaptation", + "text_level": 1, + "bbox": [ + 78, + 128, + 890, + 175 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Ba Hung Ngo $^{1,\\ast}$ , Nhat-Tuong Do-Tran $^{2,\\ast}$ , Tuan-Ngoc Nguyen $^{3}$ , Hae-Gon Jeon $^{4}$ , Tae Jong Choi $^{1,\\dagger}$", + "bbox": [ + 122, + 202, + 890, + 220 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1Graduate School of Data Science, Chonnam National University, South Korea", + "bbox": [ + 192, + 222, + 818, + 238 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ Department of Computer Science, National Yang Ming Chiao Tung University, Taiwan", + "bbox": [ + 158, + 239, + 852, + 256 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{3}$ Digital Transformation Center, FPT Telecom, VietNam, $^{4}$ AI Graduate School, GIST, South Korea", + "bbox": [ + 117, + 256, + 893, + 273 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ngohung@chonnam.ac.kr tuongdotn.cs11@nycu.edu.tw tuannn55@fpt.com haegonj@gist.ac.kr ctj17@jnu.ac.kr", + "bbox": [ + 86, + 277, + 919, + 291 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 325, + 313, + 342 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Most domain adaptation (DA) methods are based on either a convolutional neural networks (CNNs) or a vision transformers (ViTs). They align the distribution differences between domains as encoders without considering their unique characteristics. For instance, ViT excels in accuracy due to its superior ability to capture global representations, while CNN has an advantage in capturing local representations. This fact has led us to design a hybrid method to fully take advantage of both ViT and CNN, called Explicitly Class-specific Boundaries (ECB). ECB learns CNN on ViT to combine their distinct strengths. In particular, we leverage ViT's properties to explicitly find class-specific decision boundaries by maximizing the discrepancy between the outputs of the two classifiers to detect target samples far from the source support. In contrast, the CNN encoder clusters target features based on the previously defined class-specific boundaries by minimizing the discrepancy between the probabilities of the two classifiers. Finally, ViT and CNN mutually exchange knowledge to improve the quality of pseudo labels and reduce the knowledge discrepancies of these models. Compared to conventional DA methods, our ECB achieves superior performance, which verifies its effectiveness in this hybrid model. The project website can be found here.", + "bbox": [ + 75, + 358, + 473, + 705 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 719, + 209, + 734 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Over the past few years, convolutional neural networks (CNNs) [13] have been the cornerstone of deep learning techniques in computer vision tasks. This progress is mainly attributed to a convolution layer, which efficiently captures local spatial hierarchies for robust image representations. This local feature extraction capability has enabled CNNs to achieve State-of-the-Art (SOTA) performance in a variety of vision tasks, from image classification to object detection. In spite of its powerful local feature extraction, CNNs are some-", + "bbox": [ + 75, + 744, + 470, + 880 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e7c22c892a4dd5072e13738cbf0fe032e201816fba1dafcad8d477e6b3f8564c.jpg", + "image_caption": [ + "Figure 1. Illustration of the proposed hybrid network architecture that leverages the strengths of ViT and CNN models." + ], + "image_footnote": [], + "bbox": [ + 511, + 325, + 879, + 599 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "what limited in capturing more global and comprehensive visual context. To overcome this limitation, vision transformer (ViT) [7] was introduced. ViT starts by dividing an image into patches, which are transformed into a sequence of tokens. Positional embeddings are incorporated into the tokens to retain the order of these patches. The model then uses transformer blocks to extract these tokens into features as image representations. Thanks to self-attention mechanisms in ViT, it is able to weigh the importance of different regions in an image irrespective of their spatial proximity, leading to comprehensive global representations with impressive accuracy. The advancements in ViT have led to a growing inclination in the machine learning realm over CNN-based approaches for a range of tasks.", + "bbox": [ + 496, + 654, + 893, + 866 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Instead of focusing solely on replacing CNN with ViT, our approach diverges from this trend. We believe that both", + "bbox": [ + 498, + 869, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "\\*Co-first author. \\*Corresponding author.", + "bbox": [ + 94, + 886, + 339, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "28545", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ViT and CNN architectures have their own strengths that can be harnessed when combined well. For instance, ViT has shown the capability to capture global representations and demonstrates robustness when trained on large datasets. Yet, because it is composed of multilayer perceptron (MLP) layers, ViT can overfit if the dataset is limited. On the other hand, CNNs perform well with relatively small datasets thanks to their spatial invariance and robustness in capturing local representations. Motivated by this, we propose a novel method that capitalizes on the distinct strengths of both architectures. As shown in Fig. 1, we exploit the superior accuracy of ViT in identifying more general class-specific boundaries by maximizing the discrepancy between the outputs of the two classifiers, enabling us to estimate the worst-case hyperspaces. Once these class-specific boundaries are defined, CNN minimizes the discrepancy by clustering target features closer to the source domain, aiming to minimize errors within the identified hyperspaces. However, the knowledge discrepancies between ViT and CNN still exist, so we applied additional co-training to bridge this gap while improving the quality of the pseudo labels. In the field of unsupervised domain adaptation (UDA), MCD [30] emphasizes the importance of maximizing the discrepancy between classifier outputs for target samples, which are far from the source domain's support, and then minimizing this discrepancy through a feature generator to align the target features closer to the source's support.", + "bbox": [ + 76, + 90, + 472, + 500 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Although UDA has made significant advancements in domain adaptation (DA) tasks, the semi-supervised domain adaptation (SSDA) scenarios, as discussed in [11, 14-16, 28, 31, 34-36], are extensively employed to yield remarkable classification accuracy compared to the UDA setting [2, 4, 5, 19, 37]. This is because a model trained under UDA is only accessed to labeled source data, while a model trained with the SSDA setting benefits from the extra target information with a few labeled target samples besides labeled source data. However, the previous DA methods only take full advantage of the unique benefits of CNN as a feature extractor. Specifically, works in [12, 15, 21, 31] use a combination of a CNN encoder followed by an MLP classifier, but the decision boundary towards the source domain leads to data bias in DA. To address this bias, some previous works [27, 28, 37] introduce a multi-model by adding one more MLP classifier, which consists of a single CNN encoder and two MLP classifiers. Furthermore, the first DA approaches in [22, 34] use two CNN encoders and two MLP classifiers to boost the classification accuracy by leveraging a co-training strategy that ensures the consistency of unlabeled target data through knowledge exchange. However, these methodologies still follow the same rule, where the CNN model is selected as the encoder, and MLP is assigned as the classifier. Therefore, the capabilities of ViT in capturing global information remain unexploited. Inspired by the ideal,", + "bbox": [ + 76, + 508, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "we make use of this multi-model architecture to build a new hybrid framework that leverages the advantages of ViT and CNN for DA settings. However, the proposed method does not require any additional complexity compared to previous works in the test phase. We summarize the contributions of this paper as follows:", + "bbox": [ + 496, + 90, + 893, + 181 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We introduce a hybrid model that can take advantage of ViT. Beyond simply replacing CNN with ViT, we can drive the feature space of ViT to CNN.", + "- Our approach demonstrates the successful integration of ViT and CNN, making a synergy with these two powerful frameworks.", + "- The proposed method outperforms the prior works to achieve SOTA performances on DA benchmark datasets." + ], + "bbox": [ + 500, + 181, + 890, + 301 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 500, + 316, + 650, + 333 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Co-training. In the realm of semi-supervised learning (SSL), co-training is a scheme to improve the robustness, first proposed by [1], and harnesses data from dual views, enabling two models to iteratively 'teach' each other. During this process, each model alternately makes predictions on unlabeled data, with the most confident predictions used to augment the training set of the other model. This mutual teaching strategy can significantly improve the performance of both models, particularly when labeled data is scarce. In the DA context, FixBi [22], DECOTA [34], and MVCL [23] offer innovative co-training strategies. Notably, FixBi and DECOTA utilize two distinct branches, each including a feature extractor and a classifier. They utilize MIXUP augmentation to reduce the gap in multiple intermediate domains between the source and target domain during co-training. However, they miss the potential benefits of strong augmentation. In contrast, while MVCL employs both weak and strong augmentation to bolster its co-training approach, it relies on a single CNN-based encoder and two classifiers to produce two views. This limits the representation of unlabeled target data, depriving its comprehensive global information. To address these limitations, we employ the ViT in conjunction with a CNN-based encoder. This combination generates two representational views that encapsulate both local and global information. Additionally, we integrate both weak and strong augmentations for unlabeled target samples, which enhances the interactivity and effectiveness of our co-training strategy.", + "bbox": [ + 496, + 340, + 893, + 750 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Domain Adaptation Framework. In the realm of DA, various frameworks have been presented. Early methods such as MME [31], APE [15], and SENTRY [26] adopt the conventional approach of constructing deep learning frameworks that have a feature extractor coupled with a classifier. However, source and target domains share the same decision boundary, which leads to data bias toward the source domain. To alleviate data bias, MDD [37] and UODA [27] introduce two distinct classifiers. They demonstrate that using a dual-classifier setup can improve the performance", + "bbox": [ + 496, + 750, + 895, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "28546", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/98e617a6b54508ffd327993b1c332ae7c6144f4512afc623de5ffca6204ae759.jpg", + "image_caption": [ + "Figure 2. Illustration of a hybrid network with the proposed Finding to Conquering strategy. We use ViT to build $E_{1}$ that drives two classifiers $F_{1}$ and $F_{2}$ to expand class-specific boundaries comprehensively. Besides, we select CNN for the second encoder $E_{2}$ to cluster target features based on the boundaries identified by ViT. These encoders all use two classifiers $F_{1}, F_{2}$ ." + ], + "image_footnote": [], + "bbox": [ + 76, + 85, + 893, + 304 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "of classification tasks. These methods use a single feature extractor to train on both labeled source and target datasets. However, the source domain is more reliable than the target domain thanks to labeled source samples, which can lead the feature extractor to overly focus on source data representations. This results in a learning bias toward the source domain, accumulating errors during the training process. To solve this problem, DECOTA [34] proposes a novel architecture by decomposing two distinct branches, UDA and SSL, each consisting of a feature extractor and a single classifier. Specifically, the UDA branch is trained on labeled source data and unlabeled target data, while the SSL branch is trained on labeled and unlabeled target data. Thanks to the SSL branch, focusing solely on the target domain facilitates the alleviation of learning bias. In addition, the UDA branch is capable of mitigating learning bias by leveraging extra information from the SSL branch via the co-training strategy. Despite the notable advancements in the field, DECOTA still follows the framework of using CNN as the feature extractor. Therefore, it is impossible to completely improve the quality of pseudo labels for unlabeled target samples and exploit learning space based on the properties of ViT. As a result, the capabilities of ViT in capturing global information still need to be explored. Instead of solely replacing CNN with ViT, we propose a hybrid model that combines their strengths of both architectures.", + "bbox": [ + 75, + 376, + 473, + 767 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Methodology", + "text_level": 1, + "bbox": [ + 76, + 780, + 210, + 797 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In DA scenarios, we deal with the following data setting:", + "bbox": [ + 76, + 805, + 452, + 820 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Labeled source domain: Denoted as $\\mathcal{D}_S = \\{(x_i^{\\mathcal{S}},y_i^{\\mathcal{S}})\\}_{i = 1}^{\\mathcal{N}_S}$ includes $\\mathcal{N}_S$ richly labeled samples.", + "- Labeled target domain: Denoted as $\\mathcal{D}_{\\mathcal{T}_l} = \\{(x_i^{\\mathcal{T}_l},y_i^{\\mathcal{T}_l})\\}_{i = 1}^{\\mathcal{N}_{\\mathcal{T}_l}}$ includes $\\mathcal{N}_{\\mathcal{T}_l}$ limited labeled target samples. Notably, $\\mathcal{D}_{\\mathcal{T}_l}$ is empty in UDA." + ], + "bbox": [ + 76, + 821, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "- Unlabeled target domain: Denoted as $\\mathcal{D}_{\\mathcal{T}_u} = \\{(x_i^{\\mathcal{T}_u},y_i^{\\mathcal{T}_u})\\}_{i = 1}^{\\mathcal{N}_{\\mathcal{T}_u}}$ includes $\\mathcal{N}_{\\mathcal{T}_u}$ target samples that do not have corresponding labels during the training phase.", + "bbox": [ + 500, + 376, + 890, + 426 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this setup, the sample $x_{i}^{S}$ and $x_{i}^{\\mathcal{T}_{l}}$ from the source domain and the labeled target domain are associated with corresponding ground-truth labels $y_{i}^{S}$ and $y_{i}^{\\mathcal{T}_{l}}$ , respectively. There is an assumption that the label $y^{S}, y^{\\mathcal{T}_{l}}$ , and $y^{\\mathcal{T}_{u}}$ all belong to the same label space with $K$ classes. Notably, $y^{\\mathcal{T}_{u}}$ , which denotes labels for the unlabeled target data, are only used during the testing phase. Furthermore, the number of labeled target samples $\\mathcal{N}_{\\mathcal{T}_l}$ is much smaller than both $\\mathcal{N}_S$ and $\\mathcal{N}_{\\mathcal{T}_u}$ . Moreover, we implement two varied stochastic data transformations: $Aug_{w}(\\cdot)$ and $Aug_{str}(\\cdot)$ . The function $Aug_{w}(\\cdot)$ is a weak augmentation method employing light perturbations such as random horizontal flipping and random cropping, whereas $Aug_{str}(\\cdot)$ stands as a strong augmentation method, using RandAugment [3], which involves 14 transformation techniques. Specifically, both $Aug_{w}(\\cdot)$ and $Aug_{str}(\\cdot)$ are applied to the unlabeled set $\\mathcal{D}_{\\mathcal{T}_u}$ , transforming a sample $x_{i}^{\\mathcal{T}_{u}}$ to two versions $x_{i,w}^{\\mathcal{T}_u}$ and $x_{i,str}^{\\mathcal{T}_u}$ , respectively. Subsequently, we train the model on the labeled set $D_{l} = D_{S}\\cup D_{\\mathcal{T}_{l}}$ and the unlabeled set $\\mathcal{D}_{\\mathcal{T}_u}$ , and evaluate the trained model on $\\mathcal{D}_{\\mathcal{T}_u}$ .", + "bbox": [ + 496, + 426, + 893, + 715 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To improve the performance on $\\mathcal{D}_{\\mathcal{T}_u}$ , we propose a hybrid model consisting of ViT and CNN branches. The ViT branch is made up of a ViT encoder $E_1(\\cdot;\\pmb{\\theta}_{E_1})$ and a classifier $F_1(\\cdot;\\pmb{\\theta}_{F_1})$ , while the CNN branch includes a CNN encoder $E_2(\\cdot;\\pmb{\\theta}_{E_2})$ and a classifier $F_2(\\cdot;\\pmb{\\theta}_{F_2})$ . Our strategy training proceeds in three steps:", + "bbox": [ + 498, + 717, + 890, + 808 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. Supervised Training: We train both ViT and CNN branches on $\\mathcal{D}_l$ whose knowledge is adapted to the $\\mathcal{D}_{\\mathcal{T}_u}$ as illustrated in Fig. 2.", + "2. Finding to Conquering: In Fig. 2, we find class-specific boundaries based on fixed $E_{1}$ by maximizing discrepancy between $F_{1}$ and $F_{2}$ . Subsequently, the $E_{2}$ clusters the" + ], + "bbox": [ + 500, + 809, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "28547", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "target features based on those class-specific boundaries by minimizing discrepancy.", + "bbox": [ + 96, + 90, + 468, + 119 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3. Co-training: To exchange effectively knowledge between two branches on $\\mathcal{D}_{\\mathcal{T}_u}$ , the ViT branch generates a pseudo label for weakly version $x_{i,w}^{\\mathcal{T}_u}$ to teach the CNN branch with strongly version $x_{i,str}^{\\mathcal{T}_u}$ . Then, the reverse process is also applied as depicted in Fig. 3.", + "bbox": [ + 76, + 121, + 468, + 200 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.1. Supervised Training", + "text_level": 1, + "bbox": [ + 76, + 208, + 269, + 224 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this phase, we employ the standard cross-entropy loss to train a model's two branches: ViT branch and CNN branch. In the ViT branch, we aim to minimize the empirical loss of labeled data, which is defined as follows:", + "bbox": [ + 76, + 229, + 470, + 291 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {v i t} ^ {s u p} \\left(\\boldsymbol {\\theta} _ {E _ {1}}, \\boldsymbol {\\theta} _ {F _ {1}}\\right) = \\frac {1}{\\mathcal {N} _ {l}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {l}} H \\left(y _ {i} ^ {l}, p _ {1} ^ {l} \\left(x _ {i} ^ {l}\\right)\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 133, + 297, + 468, + 339 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $H(\\cdot)$ denotes the standard cross-entropy loss. When $p_1^l (x_i^l) = \\sigma (F_1(E_1(x_i^l)))$ , $\\sigma$ represents the softmax function, which transforms the logits into probabilities across $K$ categories. Initially, ViT encoder $E_{1}$ maps the labeled sample $x_{i}^{l}$ into a $d$ -dimensional feature space. The classifier $F_{1}$ then categorizes the input feature space $E_{1}(x_{i}^{l})$ into the logits. Finally, we minimize the cross-entropy loss between the predicted labeled probability by $p_1^l (x_i^l)$ and the provided ground-truth label $y_{i}^{l}$ , ensuring accurate predictions on labeled data.", + "bbox": [ + 76, + 347, + 470, + 496 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Similarly, the CNN branch is also trained using labeled data to minimize the empirical loss as follows:", + "bbox": [ + 76, + 497, + 468, + 527 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {c n n} ^ {s u p} \\left(\\boldsymbol {\\theta} _ {E _ {2}}, \\boldsymbol {\\theta} _ {F _ {2}}\\right) = \\frac {1}{\\mathcal {N} _ {l}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {l}} H \\left(y _ {i} ^ {l}, p _ {2} ^ {l} \\left(x _ {i} ^ {l}\\right)\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 133, + 536, + 468, + 578 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $p_2^l (x_i^l) = \\sigma (F_2(E_2(x_i^l)))$ is obtained by extracting features from the labeled sample $x_{i}^{l}$ using the CNN encoder $E_{2}$ . These features are then mapped to logits through the classifier $F_{2}$ . Finally, the softmax function $\\sigma$ transforms these logits into probabilities across $K$ categories. The main goal of this process is to minimize the cross-entropy loss to ensure a close alignment between the predicted probabilities $p_2^l (x_i^l)$ and the ground-truth labels $y_{i}^{l}$ .", + "bbox": [ + 76, + 585, + 468, + 708 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Finding to Conquering", + "text_level": 1, + "bbox": [ + 76, + 715, + 289, + 732 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Discrepancy Loss Definition. In this work, we use the absolute difference between the probabilistic outputs $\\mathbf{a}$ and $\\mathbf{b}$ from two distinct classifiers $F_{1}$ and $F_{2}$ , respectively, for each class to guarantee that the discrepancy loss is always non-negative as follows:", + "bbox": [ + 76, + 738, + 468, + 813 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nd (\\mathbf {a}, \\mathbf {b}) = \\frac {1}{K} \\sum_ {k = 1} ^ {K} | a _ {k} - b _ {k} |, \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 179, + 821, + 468, + 863 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $a_{k}$ and $b_{k}$ correspond to the probability outputs of the two classifiers for the $k$ -th class. Normalizing with the", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "total number of categories assures that the discrepancy loss is scale-invariant and bounded between 0 and 1. The discrepancy loss serves as a measure of divergence between the probabilistic outputs of two classifiers, $\\mathbf{a}$ and $\\mathbf{b}$ . A discrepancy loss of zero indicates the perfect agreement between them across all classes. On the other hand, a higher discrepancy loss points to a more significant divergence in the two classifiers's predictions. This loss is beneficial in scenarios where we want to expand class-specific boundaries.", + "bbox": [ + 496, + 90, + 893, + 226 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Finding Stage. In this stage, we aim to expand the class-specific boundaries of the classifiers $(F_{1}, F_{2})$ in relation to the fixed ViT encoder $E_{1}$ by maximizing the discrepancy loss between their outputs. This means we have a possibility to estimate worst-case hyperspaces, which identifies target samples that fall outside the broader source distribution's support, rather than using CNN encoder $E_{2}$ . To avoid this issue, we add a supervised loss on the labeled samples as follows:", + "bbox": [ + 496, + 227, + 893, + 362 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {\\text {f i n d}} \\left(\\boldsymbol {\\theta} _ {F _ {1}}, \\boldsymbol {\\theta} _ {F _ {2}}\\right) = \\mathcal {L} _ {v i t} ^ {\\sup } + \\mathcal {L} _ {c n n} ^ {\\sup } \\\\ - \\frac {1}{\\mathcal {N} _ {\\mathcal {T} _ {u}}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {\\mathcal {T} _ {u}}} d \\left(p _ {1} ^ {f i n d} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right), p _ {2} ^ {f i n d} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {4} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 563, + 372, + 890, + 441 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $p_1^{find}(x_i^{\\mathcal{T}_u}) = \\sigma (F_1(E_1(x_i^{\\mathcal{T}_u})))$ and $p_2^{find}(x_i^{\\mathcal{T}_u}) = \\sigma (F_2(E_1(x_i^{\\mathcal{T}_u})))$ denote the probability outputs of $F_{1}$ and $F_{2}$ with ViT encoder $E_{1}$ on the unlabeled target data $x_{i}^{\\mathcal{T}_{u}}$ , respectively. By integrating the supervised loss on the labeled samples, we ensure that the classifiers not only distinguish different classes, but also push to deviate as far as possible from the currently learned class-specific boundaries while all labeled samples are correctly distinguished. In essence, the Finding Stage is a delicate balance between maximizing the discrepancy to explore the class-specific boundaries and minimizing the supervised loss to maintain classification accuracy.", + "bbox": [ + 496, + 448, + 893, + 635 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Conquering Stage. In this stage, we leverage the class-specific boundaries established by the ViT encoder $E_{1}$ as a reference to guide the optimization of the CNN encoder $E_{2}$ , while keeping the classifiers $F_{1}$ and $F_{2}$ fixed. The primary is to minimize the discrepancy between the outputs of two classifiers, $F_{1}$ and $F_{2}$ , allowing the features extracted by CNN encoder $E_{2}$ to be accurately classified. The objective function is formulated as follows:", + "bbox": [ + 496, + 636, + 893, + 755 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {c o n q}} \\left(\\boldsymbol {\\theta} _ {E _ {2}}\\right) = \\frac {1}{\\mathcal {N} \\tau_ {u}} \\sum_ {i = 1} ^ {\\mathcal {N} \\tau_ {u}} d \\left(p _ {1} ^ {\\text {c o n q}} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right), p _ {2} ^ {\\text {c o n q}} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 509, + 766, + 890, + 808 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $p_1^{conq}(x_i^{\\mathcal{T}_u}) = \\sigma (F_1(E_2(x_i^{\\mathcal{T}_u})))$ and $p_2^{conq}(x_i^{\\mathcal{T}_u}) = \\sigma (F_2(E_2(x_i^{\\mathcal{T}_u})))$ denote the probability outputs of $F_{1}$ and $F_{2}$ with CNN encoder $E_{2}$ on the unlabeled target data, $x_{i}^{\\mathcal{T}_{u}}$ . By focusing on minimizing the discrepancy loss, the features extracted by the CNN encoder $E_{2}$ are clustered on the", + "bbox": [ + 496, + 819, + 893, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "28548", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/bebe0027db065a274d31abf4c7dadd9872c4e54a60bfd95af0b44a805c5052ca.jpg", + "image_caption": [ + "Figure 3. Illustration of co-training strategy." + ], + "image_footnote": [], + "bbox": [ + 81, + 87, + 467, + 220 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "class-specific boundaries of the ViT encoder $E_{1}$ , even when estimating the worst-case hyperspaces. This alignment is crucial as it guarantees that the unlabeled samples are not only correctly classified but also robust to variations in the class-specific boundaries.", + "bbox": [ + 75, + 258, + 470, + 335 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Co-training", + "text_level": 1, + "bbox": [ + 76, + 345, + 205, + 362 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Following the Finding-to-Conquering (FTC) strategy, we recognize a significant gap in the knowledge discrepancy between the ViT and CNN branches that needs to be minimized for the optimal performance. To resolve this, we have adopted a co-training strategy with dual objectives as illustrated in Fig. 3. The first objective focuses on reducing the gap between the two branches by enabling mutual enhancement and leveraging each branch's strength to improve the quality of pseudo labels. The second objective is to specifically improve the performance of the CNN branch, thanks to the potential to capture complex patterns and relationships in the data of the ViT branch.", + "bbox": [ + 75, + 369, + 472, + 549 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Initially, we employ pseudo labels generated by the ViT branch to teach the learning process of the CNN branch. This is achieved by setting a fixed threshold, denoted as $\\tau_{vit}$ , and applying it as follows:", + "bbox": [ + 75, + 551, + 470, + 613 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {v i t \\rightarrow c n n} ^ {u n l} (\\boldsymbol {\\theta} _ {E _ {2}}, \\boldsymbol {\\theta} _ {F _ {2}}) =\n$$\n", + "text_format": "latex", + "bbox": [ + 192, + 623, + 351, + 643 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\frac {1}{\\mathcal {N} \\tau_ {u}} \\sum_ {i = 1} ^ {\\mathcal {N} \\tau_ {u}} \\mathbb {1} \\left[ \\max \\left(\\mathbf {q} _ {i} ^ {v}\\right) \\geq \\tau_ {v i t} \\right] H \\left(\\hat {q} _ {i} ^ {v}, p ^ {c} \\left(x _ {i, s t r} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 114, + 652, + 468, + 696 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathbb{1}[\\cdot ]$ is the binary indicator, returning 1 if the condition inside $[\\cdot ]$ is satisfied, and 0 otherwise. In this context, $\\mathbf{q}_i^v = \\sigma (F_1(E_1(x_{i,w}^{T_u})))$ indicates the ViT branch's prediction for a weakly augmented version of an unlabeled target sample. Then, the highest prediction, exceeding the fixed threshold $\\tau_{vit}$ , is converted into pseudo label $\\hat{q}_i^v = \\mathrm{argmax}(\\mathbf{q}_i^v)$ . Finally, the output prediction $p^c (x_{i,str}^{T_u}) = \\sigma (F_2(E_2(x_{i,str}^{T_u})))$ of the CNN branch on the strongly augmented target sample is adjusted to closely align with the pseudo label $\\hat{q}_i^v$ using the cross-entropy loss. This process ensures that the CNN branch effectively learns from the ViT branch's predictions, making the consistency and alignment between the two branches better.", + "bbox": [ + 75, + 703, + 472, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Similarly, we also leverage the pseudo labels from the CNN branch to guide the learning process of the ViT branch. This is achieved by setting another fixed threshold, denoted as $\\tau_{cnn}$ , and using it as follows:", + "bbox": [ + 496, + 90, + 893, + 151 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {c n n \\rightarrow v i t} ^ {u n l} \\left(\\boldsymbol {\\theta} _ {E _ {1}}, \\boldsymbol {\\theta} _ {F _ {1}}\\right) =\n$$\n", + "text_format": "latex", + "bbox": [ + 617, + 161, + 772, + 181 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\frac {1}{\\mathcal {N} _ {\\tau_ {u}}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {\\tau_ {u}}} \\mathbb {1} \\left[ \\max \\left(\\mathbf {q} _ {i} ^ {c}\\right) \\geq \\tau_ {c n n} \\right] H \\left(\\hat {q} _ {i} ^ {c}, p ^ {v} \\left(x _ {i, s t r} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 535, + 190, + 892, + 233 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathbf{q}_i^c = \\sigma (F_2(E_2(x_{i,w}^{\\mathcal{T}_u})))$ is the CNN branch's prediction for a weakly augmented target sample. The pseudo label $\\hat{q}_i^c$ is generated from the highest predictions of the CNN branch that is higher than the threshold $\\tau_{\\text{conn}}$ . Meanwhile, $p^v (x_{i,\\text{str}}^{\\mathcal{T}_u}) = \\sigma (F_1(E_1(x_{i,\\text{str}}^{\\mathcal{T}_u})))$ indicates the output prediction of the ViT branch on the strongly augmented target sample and is adjusted to closely align with the pseudo label $\\hat{q}_i^c$ , using the cross-entropy loss. Through the co-training process, we enhance the model's ability to generalize and perform accurately on unlabeled target data.", + "bbox": [ + 496, + 242, + 893, + 395 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Testing Phase", + "text_level": 1, + "bbox": [ + 498, + 405, + 640, + 421 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For a fair comparison with the previous DA methods [12, 16, 26, 31, 36], we select the CNN encoder $E_{2}$ associated with its classifier $F_{2}$ in the testing phase as illustrated in Fig. 2 as follows:", + "bbox": [ + 496, + 429, + 893, + 488 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {y} _ {i} ^ {\\mathcal {T} _ {u}} = \\operatorname {a r g m a x} \\left(F _ {2} \\left(E _ {2} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right)\\right), \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 586, + 500, + 892, + 520 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\hat{y}_i^{\\mathcal{T}_u}$ is the predicted class of unlabeled target sample.", + "bbox": [ + 498, + 532, + 885, + 550 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 498, + 564, + 633, + 580 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Experiment Setup", + "text_level": 1, + "bbox": [ + 498, + 589, + 674, + 606 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We conduct extensive evaluations on standard DA benchmark datasets: Office-Home [29] and DomainNet [25]. On Office-Home dataset, we perform experiments on all possible combinations of these 4 domains: Real $(R)$ , Clipart $(C)$ , Art $(A)$ , and Product $(P)$ with 65 categories. Consistent with prior SSDA methods [11, 16, 17, 31, 36], we conduct an evaluation on a subset of DomainNet that includes 126 categories in 4 domains: Real (rel), Clipart (clp), Painting (pnt), and Sketch (skt) using 7 different mixtures of these domains.", + "bbox": [ + 496, + 612, + 893, + 762 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Implementation Details. We use the ViT/B-16 [7] for the ViT encoder $E_{1}$ , while the ResNet [10] is adopted for the CNN encoder $E_{2}$ . For UDA, we used ResNet-50 as the backbone network following previous works [2, 12, 30, 37]. Similarly, we follow the evaluation protocol of previous SSDA methods [9, 17, 28, 31], ResNet-34 is applied for this scenario on the DomainNet dataset. Each model is initially pre-trained on the ImageNet-1K [6]. Given the disparate nature of the backbone architectures, we will have", + "bbox": [ + 496, + 763, + 893, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "28549", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/6ad271db001d9393b995119ba197cda77dc7f5cf757afbccb3d093d65fbeb430.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodA→CA→PA→RC→AC→PC→RP→AP→CP→RR→AR→CR→PMean
DANN [8]45.659.370.147.058.560.946.143.768.563.251.876.857.6
MCD [30]48.968.374.661.367.668.857.047.175.169.152.279.664.1
BNM [4]52.373.980.063.372.974.961.749.579.770.553.682.267.9
MDD [37]54.973.777.860.071.471.861.253.678.172.560.282.368.1
MCC [12]55.175.279.563.373.275.866.152.176.973.858.483.669.4
GVB [5]57.074.779.864.674.174.665.255.181.074.659.784.370.4
DCAN [18]54.575.781.267.474.076.367.452.780.674.159.183.570.5
DALN [2]57.879.982.066.376.277.266.755.581.373.560.485.371.8
FixBi [22]58.177.380.467.779.578.165.857.981.776.462.986.772.7
DCAN+SCDA [19]60.776.482.869.877.578.468.959.082.774.961.884.573.1
ATDOC [20]60.277.882.268.578.677.968.458.483.174.861.587.273.2
EIDCo [38]63.880.882.671.580.180.972.161.384.578.665.887.175.8
ECB (CNN)68.585.488.379.286.889.079.366.488.581.071.190.481.2
", + "bbox": [ + 78, + 88, + 890, + 284 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/bb0591ceff40de3ea7314d8af54db79e55d8066b0c24f2c2a43937cc83022609.jpg", + "table_caption": [ + "Table 1. Accuracy (%) on Office-Home of UDA methods across different domain shifts. ECB (CNN) represents the performance of our method when applied to ResNet-50. The top and second-best accuracy results are highlighted in bold and underline for easy identification." + ], + "table_footnote": [], + "table_body": "
Methodrel→clprel→pntpnt→clpclp→sktskt→pntrel→sktpnt→relMean
1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot
ENT [9]65.271.065.969.265.471.154.660.059.762.152.161.175.078.662.667.6
MME [31]70.072.267.769.769.071.756.361.864.866.861.061.976.178.566.468.9
S3D [35]73.375.968.972.173.475.160.864.468.270.065.166.779.580.369.972.1
ATDOC [20]74.976.971.372.572.874.265.666.768.770.865.264.681.281.271.472.4
MAP-F [24]75.377.074.075.074.377.065.869.573.073.367.569.281.783.373.174.9
DECOTA [34]79.180.474.975.276.978.765.168.672.072.769.771.979.681.573.975.6
CDAC [16]77.479.674.275.175.579.367.669.971.073.469.272.580.481.973.676.0
ASDA [28]77.079.475.476.775.578.366.570.272.174.270.972.179.782.373.976.2
CDAC+SLA [36]79.881.675.676.077.480.368.171.371.773.571.773.580.482.575.076.9
ProML [11]78.580.275.476.577.878.970.272.074.175.472.473.584.084.876.177.4
MVCL [23]78.879.876.077.478.080.370.873.075.176.772.474.482.485.176.278.1
G-ABC [17]80.782.176.876.779.381.672.073.775.076.373.274.383.483.977.278.4
ECB (CNN)83.887.485.485.686.487.379.780.683.485.679.581.788.790.383.885.5
", + "bbox": [ + 80, + 328, + 890, + 547 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Accuracy (%) on DomainNet of SSDA methods in both 1-shot and 3-shot settings using ResNet-34.", + "bbox": [ + 156, + 551, + 810, + 566 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "two different classifiers, $F_{1}$ and $F_{2}$ , consisting of two fully-connected layers followed by the softmax function. We optimize our models using stochastic gradient descent with a 0.9 momentum and 0.0005 weight decay. Considering the different architectures of the ViT and the CNN branches, we set the initial learning rates for ViT and CNN at $1e - 4$ and $1e - 3$ , respectively. The size of the mini-batch is set to 32 for both $\\mathcal{D}_l$ and $\\mathcal{D}_{\\tau_u}$ . The confidence threshold values for pseudo-label selection are set to $\\tau_{vit} = 0.6$ and $\\tau_{cnn} = 0.9$ . The warmup phase for both branches on $\\mathcal{D}_l$ is finetuned for 100,000 iterations. Then, we update the learning rate scheduler and proceed with 50,000 iterations of training for our method.", + "bbox": [ + 75, + 573, + 472, + 770 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Comparison Results", + "text_level": 1, + "bbox": [ + 76, + 784, + 269, + 801 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We evaluate our ECB method and the previous SOTA methods on Office-Home and DomainNet under UDA and SSDA settings, respectively. For a fair comparison with other DA methods, we rely on classification outcomes from the CNN branch, employing ResNet-50 as the backbone for UDA and ResNet-34 for SSDA. As a result, our method does not", + "bbox": [ + 75, + 809, + 470, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "add any testing complexity compared to previous DA approaches. Besides, we have included further details about the experimental results in Supplementary Materials.", + "bbox": [ + 496, + 573, + 893, + 619 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Results on Office-Home under UDA setting. The implementation of our ECB method has significantly boosted classification efficiency in all domain shift tasks, consistently outperforming the comparison methods, as detailed in Tab. 1. Remarkably, our approach has recorded accuracy enhancements of $+7.7\\%$ , $+8.1\\%$ , and $+7.2\\%$ for the $C \\rightarrow A$ , $C \\rightarrow R$ , and $P \\rightarrow A$ tasks, respectively, surpassing the results of the second-best. In addition, our method has achieved an impressive average classification accuracy of $81.2\\%$ , showing a remarkable margin of $+5.4\\%$ over the nearest-competitor EIDCo [38].", + "bbox": [ + 496, + 623, + 895, + 789 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Results on DomainNet under SSDA setting. The results on the DomainNet dataset are presented for both 1-shot and 3-shot settings in Tab. 2, where the CNN branch of our ECB method outperforms all prior methods. In comparison to the nearest-competitor method, G-ABC [17], the ECB (CNN) achieves an impressive maximum performance increase of $+9.3\\%$ in the $skt \\rightarrow pnt$ task for 3-shot learning. Even in the", + "bbox": [ + 496, + 794, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "28550", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/98be8bd78d48a33e43ae512d8c4539935510be09b552906995f420a117aacc4f.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Methodrel→clprel→pntpnt→clpclp→sktskt→pntrel→sktpnt→relMean
ViTCNNViTCNNViTCNNViTCNNViTCNNViTCNNViTCNNViTCNN
vit→cnn73.379.078.881.075.179.271.674.778.680.867.272.088.188.876.179.4
cnn→vit74.261.976.866.876.167.469.557.274.964.667.454.886.076.175.064.1
co-training87.487.485.885.687.387.380.780.685.885.681.781.790.990.385.785.5
", + "bbox": [ + 78, + 89, + 890, + 196 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 3. Ablation study on DomainNet between co-training and one-direction teaching under 3-shot settings.", + "bbox": [ + 156, + 205, + 810, + 220 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/dbe488371fa09397e48f84bcbedae63ff69e31b6716fd692fee73f92a3fd4e2f.jpg", + "image_caption": [ + "(a)" + ], + "image_footnote": [], + "bbox": [ + 80, + 234, + 269, + 344 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/8e9b1244c90e4a85035fceeaadd8588edab0240787eb178c71dd63a758b227a2.jpg", + "image_caption": [ + "(b)", + "Figure 4. (a) The quality and quantity of the pseudo labels are generated by the CNN branch on DomainNet under the 3-shot setting of the $rel \\rightarrow clp$ task using ResNet-34. (b) Comparison between backbone settings on DomainNet under the 3-shot setting. Displayed is the mean accuracy across all domain shift tasks." + ], + "image_footnote": [], + "bbox": [ + 274, + 234, + 460, + 344 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "more restrictive 1-shot learning, the ECB method demonstrates robust performance, showing a minimum increase of $+3.1\\%$ in the $rel \\rightarrow clp$ task. On average, the ECB method validates a performance improvement of $+6.6\\%$ in the 1-shot setting and $+7.1\\%$ in the 3-shot setting.", + "bbox": [ + 73, + 439, + 470, + 515 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5. Analyses", + "text_level": 1, + "bbox": [ + 75, + 527, + 176, + 544 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Ablation studies. A single classifier is concurrently trained with both labeled source and target data. It is thus easily dominated by the labeled source data. This imbalance prevents the classifier from using the extra-labeled target data effectively, resulting in a misalignment between the learned and true class-specific boundaries. This misalignment is called data bias. Therefore, we perform an ablation study to evaluate the effectiveness of each stage in the proposed method. The emphasis is on addressing the data bias issue within the ViT branch, leveraging the CNN branch's capability to generate high-quality pseudo labels during the rel $\\rightarrow$ clp task on DomainNet under, as illustrated in Fig. 4a. Initially, during the Supervised Training phase, we are only able to generate around 8,000 total pseudo labels. Following the integration of the FTC strategy, the total pseudo labels smoothly increase up to 14,000 with steady maintenance of 10,000 correct pseudo labels. This plays a crucial role in substantially mitigating data bias by generating numerous pseudo-labels, which improves the diversity and representativeness of the unlabeled target dataset. The final experiment is implemented to highlight that co-training is necessary for reducing the remaining gap following the FTC stage, which yields a total of 18,000 pseudo labels and 16,000 correct", + "bbox": [ + 73, + 551, + 472, + 902 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/f220ef5d845e4e37316072f9a933416a52eeda881814153bfeff23ab489b85c0.jpg", + "image_caption": [ + "Table 4. Visualize the feature maps for the 'Cannon' and 'Bird' examples to investigate the learning behaviors of CNN and ViT with and without using the proposed method ECB." + ], + "image_footnote": [], + "bbox": [ + 501, + 233, + 890, + 373 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "pseudo labels.", + "bbox": [ + 500, + 444, + 596, + 458 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effectiveness of co-training. We further investigate a variant of ECB termed one-direction teaching on the DomainNet under the 3-shot setting. In this approach, we employ either $\\mathcal{L}_{vit\\rightarrow cnn}^{unl}$ or $\\mathcal{L}_{cnn\\rightarrow vit}^{unl}$ to generate pseudo labels for the remaining branch, while maintaining the standard configurations through the use of Supervised Training followed by FTC strategy. As depicted in Tab. 3, there is a performance drop when using one-direction teaching. Specifically, in the $vit\\rightarrow cnn$ scenario, the ViT branch generates pseudo labels for the unlabeled target data to teach the CNN branch through minimizing $\\mathcal{L}_{vit\\rightarrow cnn}^{unl}$ . It is crucial to highlight that the ViT branch does not receive pseudo labels from the CNN branch, resulting in the CNN branch outperforming the ViT branch by $+3.3\\%$ . In contrast, in the $cnn\\rightarrow vit$ scenario, where $\\mathcal{L}_{cnn\\rightarrow vit}^{unl}$ is minimized, the average performance on the ViT branch is $+10.9\\%$ more outstanding than the CNN branch. However, it is worth mentioning that the performance on the ViT branch suffers from $-1.1\\%$ reduction over the $vit\\rightarrow cnn$ scenario. This performance drop is attributed to the introduction of noise by the CNN branch during the learning process of the ViT branch. On the other hand, when employing $\\mathcal{L}_{vit\\rightarrow cnn}^{unl}$ , the CNN branch provides a significant boost in the average performance by $+15.3\\%$ , highlighting the superior generalization capabilities of the ViT branch compared to the CNN branch. These scenarios try to leverage the unique strengths of CNN and ViT through the co-training strategy, showcasing the mutual exchange of knowledge between two branches and its potential for generalizing to unlabeled target data. As a result of co-training,", + "bbox": [ + 496, + 462, + 895, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "28551", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/f9915791bf1d75165082d6613f986ff7dd559b68e909a56bba743b1331ec18d0.jpg", + "image_caption": [ + "(a)" + ], + "image_footnote": [], + "bbox": [ + 86, + 88, + 271, + 229 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/fa3af9115c5bfcf0cbfa8d93fa6cdde09b46189d5a658f5b8a44dce9b921b456.jpg", + "image_caption": [ + "(b)", + "Figure 5. We visualize feature spaces for the $rel \\to skt$ task on DomainNet in the 3-shot scenario using t-SNE [33]. Figures (a) and (b) illustrate the features obtained by CNN and ViT branches before adaptation, respectively. Figures (c) and (d) showcase the distribution changes of the CNN branch depending on the presence of the FTC strategy when implementing our ECB method." + ], + "image_footnote": [], + "bbox": [ + 282, + 88, + 468, + 229 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9775fccb92ce6112b76147e0d77ffdcc2f37f70a6ad6abe18931e6d0dbf82767.jpg", + "image_caption": [ + "(c)" + ], + "image_footnote": [], + "bbox": [ + 480, + 88, + 666, + 229 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/6f7d15e2a42a06e324c913b2f063bd27bdc7c232c0e9cebb36e3160fc34d313a.jpg", + "image_caption": [ + "(d)" + ], + "image_footnote": [], + "bbox": [ + 681, + 88, + 866, + 229 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "the average performance on the target domain of the ViT and CNN branches reaches the optimal results of $85.7\\%$ and $85.5\\%$ , respectively.", + "bbox": [ + 75, + 301, + 470, + 347 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Architecture analysis. We examine the effectiveness of the unique strengths of ViT and CNN over variations of architectures such as \"CNN + CNN\" and \"ViT + ViT\" on DomainNet under 3-shot settings using ResNet-34 for CNN and ViT/B-16 for ViT as shown in Fig. 4b. On average, the results show that \"CNN + CNN\" only achieves around $77.0\\%$ due to the lack of global information when just using CNN. In addition, the introduction of ViT with the primary goal of improving performance drives the \"ViT + ViT\" architecture to achieve a significant increase of $+7.0\\%$ compared to the \"CNN + CNN\" architecture. This architecture makes it possible to establish more general class-specific boundaries, yet is unfair when compared with the previous SSDA methods [20, 30, 31, 34, 36] using ResNet-34 as the backbone, and the lack of local representation is extremely important. As a result, the evidence shows that combining \"CNN + ViT\" with the bridge of co-training achieves the highest accuracy of about $85.5\\%$ for both branches.", + "bbox": [ + 75, + 349, + 472, + 622 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Attention map visualization analysis. To demonstrate the effectiveness of our designing framework methodology, we provide the attention map visualization results by using GradCAM [32], as visualized in Tab. 4. CNN supports ViT: Before applying ECB, ViT was background-sensitive in the \"Cannon\" class, whereas CNN still captures the correct object. However, after applying ECB, ViT can explicitly recognize the target object and back to enhance the robustness of CNN. ViT supports CNN: In the \"Bird\" class before applying ECB, CNN only obtains the part of the target, while ViT can cover the whole input object. Then, CNN is complemented to focus on the object accurately by ViT using ECB. Consequently, these findings validate that both branches offer distinct expertise and enhance each other rather than one overshadowing the other.", + "bbox": [ + 75, + 626, + 470, + 852 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Feature Visualization. We present a detailed visualization of the feature space for the DomainNet dataset within the $rel \\rightarrow skt$ task under the 3-shot setting. This visualization", + "bbox": [ + 76, + 854, + 470, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "distinctly highlights the source domain (blue-colored) and the target domain (red-colored). Figs. 5a and 5b show the domain alignment of both the CNN and ViT branches before adaptation. In particular, Fig. 5a visualizes the feature space extracted by the CNN branch before applying ECB, reflecting a scatter that indicates weak classifier performance. In contrast, Fig. 5b displays the well-defined clusters in the ViT branch for the same unlabeled target data, which emphasizes the robustness of ViT in identifying more general class-specific boundaries compared to the CNN branch. Figs. 5c and 5d show the distribution changes of the CNN branch depending on the presence of the FTC strategy when implementing ECB. Initially, Fig. 5c indicates that the target representations overlap (highlighted with green box) when implementing ECB without the FTC strategy. On the other hand, Fig. 5d shows the well-aligned source and target domain representations with clusters to distinct separation when applying the FTC strategy, which demonstrates the effectiveness of our proposed method.", + "bbox": [ + 496, + 301, + 893, + 590 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 611, + 619, + 626 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we have developed a novel method for learning CNN on ViT with ECB strategy, taking advantage of ViT and CNN. This innovative approach focuses on reducing data bias and significantly improves the precision of pseudo labels generated, which aligns between source and target domains. Our method is also fair when evaluated on the CNN branch and outperforms the previous SOTA methods on various DA benchmark datasets.", + "bbox": [ + 496, + 638, + 893, + 758 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "**Discussions.** We found that identifying an optimal threshold pair $\\{\\tau_{vit}$ and $\\tau_{cnn}\\}$ was quite time-consuming. Therefore, we leave an open task for future research that uses a dynamic threshold algorithm for domain adaptation instead of the fixed threshold.", + "bbox": [ + 496, + 762, + 893, + 835 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIT) (No. RS-2023-00214326 and No. RS-2023-00242528).", + "bbox": [ + 496, + 839, + 893, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "28552", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Avrim Blum and Tom Mitchell. Combining labeled and unlabeled data with co-training. 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Vis., pages 11388-11399, 2023. 6" + ], + "bbox": [ + 78, + 90, + 470, + 686 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "28554", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning CNN on ViT_ A Hybrid Model to Explicitly Class-specific Boundaries for Domain Adaptation/f88da0d8-496d-49e1-8c98-717f50be5563_model.json b/2024/Learning CNN on ViT_ A Hybrid Model to Explicitly Class-specific Boundaries for Domain Adaptation/f88da0d8-496d-49e1-8c98-717f50be5563_model.json new file mode 100644 index 0000000000000000000000000000000000000000..2b46f5a9e78c514d6ccb954ebd3f58711c91068e --- /dev/null +++ b/2024/Learning CNN on ViT_ A Hybrid Model to Explicitly Class-specific Boundaries for Domain Adaptation/f88da0d8-496d-49e1-8c98-717f50be5563_model.json @@ -0,0 +1,1980 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.079, + 0.13, + 0.892, + 0.176 + ], + "angle": 0, + "content": "Learning CNN on ViT: A Hybrid Model to Explicitly Class-specific Boundaries for Domain Adaptation" + }, + { + "type": "text", + "bbox": [ + 0.124, + 0.203, + 0.892, + 0.222 + ], + "angle": 0, + "content": "Ba Hung Ngo\\(^{1,\\ast}\\), Nhat-Tuong Do-Tran\\(^{2,\\ast}\\), Tuan-Ngoc Nguyen\\(^{3}\\), Hae-Gon Jeon\\(^{4}\\), Tae Jong Choi\\(^{1,\\dagger}\\)" + }, + { + "type": "text", + "bbox": [ + 0.194, + 0.223, + 0.819, + 0.239 + ], + "angle": 0, + "content": "1Graduate School of Data Science, Chonnam National University, South Korea" + }, + { + "type": "text", + "bbox": [ + 0.159, + 0.24, + 0.853, + 0.257 + ], + "angle": 0, + "content": "\\(^{2}\\)Department of Computer Science, National Yang Ming Chiao Tung University, Taiwan" + }, + { + "type": "text", + "bbox": [ + 0.119, + 0.257, + 0.895, + 0.275 + ], + "angle": 0, + "content": "\\(^{3}\\)Digital Transformation Center, FPT Telecom, VietNam, \\(^{4}\\)AI Graduate School, GIST, South Korea" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.279, + 0.92, + 0.292 + ], + "angle": 0, + "content": "ngohung@chonnam.ac.kr tuongdotn.cs11@nycu.edu.tw tuannn55@fpt.com haegonj@gist.ac.kr ctj17@jnu.ac.kr" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.327, + 0.314, + 0.343 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.359, + 0.474, + 0.707 + ], + "angle": 0, + "content": "Most domain adaptation (DA) methods are based on either a convolutional neural networks (CNNs) or a vision transformers (ViTs). They align the distribution differences between domains as encoders without considering their unique characteristics. For instance, ViT excels in accuracy due to its superior ability to capture global representations, while CNN has an advantage in capturing local representations. This fact has led us to design a hybrid method to fully take advantage of both ViT and CNN, called Explicitly Class-specific Boundaries (ECB). ECB learns CNN on ViT to combine their distinct strengths. In particular, we leverage ViT's properties to explicitly find class-specific decision boundaries by maximizing the discrepancy between the outputs of the two classifiers to detect target samples far from the source support. In contrast, the CNN encoder clusters target features based on the previously defined class-specific boundaries by minimizing the discrepancy between the probabilities of the two classifiers. Finally, ViT and CNN mutually exchange knowledge to improve the quality of pseudo labels and reduce the knowledge discrepancies of these models. Compared to conventional DA methods, our ECB achieves superior performance, which verifies its effectiveness in this hybrid model. The project website can be found here." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.72, + 0.21, + 0.735 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.745, + 0.471, + 0.881 + ], + "angle": 0, + "content": "Over the past few years, convolutional neural networks (CNNs) [13] have been the cornerstone of deep learning techniques in computer vision tasks. This progress is mainly attributed to a convolution layer, which efficiently captures local spatial hierarchies for robust image representations. This local feature extraction capability has enabled CNNs to achieve State-of-the-Art (SOTA) performance in a variety of vision tasks, from image classification to object detection. In spite of its powerful local feature extraction, CNNs are some-" + }, + { + "type": "image", + "bbox": [ + 0.513, + 0.326, + 0.88, + 0.601 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.61, + 0.892, + 0.639 + ], + "angle": 0, + "content": "Figure 1. Illustration of the proposed hybrid network architecture that leverages the strengths of ViT and CNN models." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.655, + 0.895, + 0.867 + ], + "angle": 0, + "content": "what limited in capturing more global and comprehensive visual context. To overcome this limitation, vision transformer (ViT) [7] was introduced. ViT starts by dividing an image into patches, which are transformed into a sequence of tokens. Positional embeddings are incorporated into the tokens to retain the order of these patches. The model then uses transformer blocks to extract these tokens into features as image representations. Thanks to self-attention mechanisms in ViT, it is able to weigh the importance of different regions in an image irrespective of their spatial proximity, leading to comprehensive global representations with impressive accuracy. The advancements in ViT have led to a growing inclination in the machine learning realm over CNN-based approaches for a range of tasks." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Instead of focusing solely on replacing CNN with ViT, our approach diverges from this trend. We believe that both" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.341, + 0.9 + ], + "angle": 0, + "content": "\\*Co-first author. \\*Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28545" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.501 + ], + "angle": 0, + "content": "ViT and CNN architectures have their own strengths that can be harnessed when combined well. For instance, ViT has shown the capability to capture global representations and demonstrates robustness when trained on large datasets. Yet, because it is composed of multilayer perceptron (MLP) layers, ViT can overfit if the dataset is limited. On the other hand, CNNs perform well with relatively small datasets thanks to their spatial invariance and robustness in capturing local representations. Motivated by this, we propose a novel method that capitalizes on the distinct strengths of both architectures. As shown in Fig. 1, we exploit the superior accuracy of ViT in identifying more general class-specific boundaries by maximizing the discrepancy between the outputs of the two classifiers, enabling us to estimate the worst-case hyperspaces. Once these class-specific boundaries are defined, CNN minimizes the discrepancy by clustering target features closer to the source domain, aiming to minimize errors within the identified hyperspaces. However, the knowledge discrepancies between ViT and CNN still exist, so we applied additional co-training to bridge this gap while improving the quality of the pseudo labels. In the field of unsupervised domain adaptation (UDA), MCD [30] emphasizes the importance of maximizing the discrepancy between classifier outputs for target samples, which are far from the source domain's support, and then minimizing this discrepancy through a feature generator to align the target features closer to the source's support." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.509, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Although UDA has made significant advancements in domain adaptation (DA) tasks, the semi-supervised domain adaptation (SSDA) scenarios, as discussed in [11, 14-16, 28, 31, 34-36], are extensively employed to yield remarkable classification accuracy compared to the UDA setting [2, 4, 5, 19, 37]. This is because a model trained under UDA is only accessed to labeled source data, while a model trained with the SSDA setting benefits from the extra target information with a few labeled target samples besides labeled source data. However, the previous DA methods only take full advantage of the unique benefits of CNN as a feature extractor. Specifically, works in [12, 15, 21, 31] use a combination of a CNN encoder followed by an MLP classifier, but the decision boundary towards the source domain leads to data bias in DA. To address this bias, some previous works [27, 28, 37] introduce a multi-model by adding one more MLP classifier, which consists of a single CNN encoder and two MLP classifiers. Furthermore, the first DA approaches in [22, 34] use two CNN encoders and two MLP classifiers to boost the classification accuracy by leveraging a co-training strategy that ensures the consistency of unlabeled target data through knowledge exchange. However, these methodologies still follow the same rule, where the CNN model is selected as the encoder, and MLP is assigned as the classifier. Therefore, the capabilities of ViT in capturing global information remain unexploited. Inspired by the ideal," + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.182 + ], + "angle": 0, + "content": "we make use of this multi-model architecture to build a new hybrid framework that leverages the advantages of ViT and CNN for DA settings. However, the proposed method does not require any additional complexity compared to previous works in the test phase. We summarize the contributions of this paper as follows:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.183, + 0.892, + 0.227 + ], + "angle": 0, + "content": "- We introduce a hybrid model that can take advantage of ViT. Beyond simply replacing CNN with ViT, we can drive the feature space of ViT to CNN." + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.228, + 0.892, + 0.271 + ], + "angle": 0, + "content": "- Our approach demonstrates the successful integration of ViT and CNN, making a synergy with these two powerful frameworks." + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.273, + 0.892, + 0.303 + ], + "angle": 0, + "content": "- The proposed method outperforms the prior works to achieve SOTA performances on DA benchmark datasets." + }, + { + "type": "list", + "bbox": [ + 0.501, + 0.183, + 0.892, + 0.303 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.317, + 0.651, + 0.334 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.342, + 0.895, + 0.75 + ], + "angle": 0, + "content": "Co-training. In the realm of semi-supervised learning (SSL), co-training is a scheme to improve the robustness, first proposed by [1], and harnesses data from dual views, enabling two models to iteratively 'teach' each other. During this process, each model alternately makes predictions on unlabeled data, with the most confident predictions used to augment the training set of the other model. This mutual teaching strategy can significantly improve the performance of both models, particularly when labeled data is scarce. In the DA context, FixBi [22], DECOTA [34], and MVCL [23] offer innovative co-training strategies. Notably, FixBi and DECOTA utilize two distinct branches, each including a feature extractor and a classifier. They utilize MIXUP augmentation to reduce the gap in multiple intermediate domains between the source and target domain during co-training. However, they miss the potential benefits of strong augmentation. In contrast, while MVCL employs both weak and strong augmentation to bolster its co-training approach, it relies on a single CNN-based encoder and two classifiers to produce two views. This limits the representation of unlabeled target data, depriving its comprehensive global information. To address these limitations, we employ the ViT in conjunction with a CNN-based encoder. This combination generates two representational views that encapsulate both local and global information. Additionally, we integrate both weak and strong augmentations for unlabeled target samples, which enhances the interactivity and effectiveness of our co-training strategy." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.751, + 0.897, + 0.902 + ], + "angle": 0, + "content": "Domain Adaptation Framework. In the realm of DA, various frameworks have been presented. Early methods such as MME [31], APE [15], and SENTRY [26] adopt the conventional approach of constructing deep learning frameworks that have a feature extractor coupled with a classifier. However, source and target domains share the same decision boundary, which leads to data bias toward the source domain. To alleviate data bias, MDD [37] and UODA [27] introduce two distinct classifiers. They demonstrate that using a dual-classifier setup can improve the performance" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.521, + 0.957 + ], + "angle": 0, + "content": "28546" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.086, + 0.895, + 0.305 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.315, + 0.895, + 0.358 + ], + "angle": 0, + "content": "Figure 2. Illustration of a hybrid network with the proposed Finding to Conquering strategy. We use ViT to build \\( E_{1} \\) that drives two classifiers \\( F_{1} \\) and \\( F_{2} \\) to expand class-specific boundaries comprehensively. Besides, we select CNN for the second encoder \\( E_{2} \\) to cluster target features based on the boundaries identified by ViT. These encoders all use two classifiers \\( F_{1}, F_{2} \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.377, + 0.474, + 0.768 + ], + "angle": 0, + "content": "of classification tasks. These methods use a single feature extractor to train on both labeled source and target datasets. However, the source domain is more reliable than the target domain thanks to labeled source samples, which can lead the feature extractor to overly focus on source data representations. This results in a learning bias toward the source domain, accumulating errors during the training process. To solve this problem, DECOTA [34] proposes a novel architecture by decomposing two distinct branches, UDA and SSL, each consisting of a feature extractor and a single classifier. Specifically, the UDA branch is trained on labeled source data and unlabeled target data, while the SSL branch is trained on labeled and unlabeled target data. Thanks to the SSL branch, focusing solely on the target domain facilitates the alleviation of learning bias. In addition, the UDA branch is capable of mitigating learning bias by leveraging extra information from the SSL branch via the co-training strategy. Despite the notable advancements in the field, DECOTA still follows the framework of using CNN as the feature extractor. Therefore, it is impossible to completely improve the quality of pseudo labels for unlabeled target samples and exploit learning space based on the properties of ViT. As a result, the capabilities of ViT in capturing global information still need to be explored. Instead of solely replacing CNN with ViT, we propose a hybrid model that combines their strengths of both architectures." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.781, + 0.212, + 0.799 + ], + "angle": 0, + "content": "3. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.806, + 0.454, + 0.821 + ], + "angle": 0, + "content": "In DA scenarios, we deal with the following data setting:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.822, + 0.469, + 0.853 + ], + "angle": 0, + "content": "- Labeled source domain: Denoted as \\(\\mathcal{D}_S = \\{(x_i^{\\mathcal{S}},y_i^{\\mathcal{S}})\\}_{i = 1}^{\\mathcal{N}_S}\\) includes \\(\\mathcal{N}_S\\) richly labeled samples." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.853, + 0.47, + 0.902 + ], + "angle": 0, + "content": "- Labeled target domain: Denoted as \\(\\mathcal{D}_{\\mathcal{T}_l} = \\{(x_i^{\\mathcal{T}_l},y_i^{\\mathcal{T}_l})\\}_{i = 1}^{\\mathcal{N}_{\\mathcal{T}_l}}\\) includes \\(\\mathcal{N}_{\\mathcal{T}_l}\\) limited labeled target samples. Notably, \\(\\mathcal{D}_{\\mathcal{T}_l}\\) is empty in UDA." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.822, + 0.47, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.377, + 0.892, + 0.427 + ], + "angle": 0, + "content": "- Unlabeled target domain: Denoted as \\(\\mathcal{D}_{\\mathcal{T}_u} = \\{(x_i^{\\mathcal{T}_u},y_i^{\\mathcal{T}_u})\\}_{i = 1}^{\\mathcal{N}_{\\mathcal{T}_u}}\\) includes \\(\\mathcal{N}_{\\mathcal{T}_u}\\) target samples that do not have corresponding labels during the training phase." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.428, + 0.895, + 0.717 + ], + "angle": 0, + "content": "In this setup, the sample \\( x_{i}^{S} \\) and \\( x_{i}^{\\mathcal{T}_{l}} \\) from the source domain and the labeled target domain are associated with corresponding ground-truth labels \\( y_{i}^{S} \\) and \\( y_{i}^{\\mathcal{T}_{l}} \\), respectively. There is an assumption that the label \\( y^{S}, y^{\\mathcal{T}_{l}} \\), and \\( y^{\\mathcal{T}_{u}} \\) all belong to the same label space with \\( K \\) classes. Notably, \\( y^{\\mathcal{T}_{u}} \\), which denotes labels for the unlabeled target data, are only used during the testing phase. Furthermore, the number of labeled target samples \\( \\mathcal{N}_{\\mathcal{T}_l} \\) is much smaller than both \\( \\mathcal{N}_S \\) and \\( \\mathcal{N}_{\\mathcal{T}_u} \\). Moreover, we implement two varied stochastic data transformations: \\( Aug_{w}(\\cdot) \\) and \\( Aug_{str}(\\cdot) \\). The function \\( Aug_{w}(\\cdot) \\) is a weak augmentation method employing light perturbations such as random horizontal flipping and random cropping, whereas \\( Aug_{str}(\\cdot) \\) stands as a strong augmentation method, using RandAugment [3], which involves 14 transformation techniques. Specifically, both \\( Aug_{w}(\\cdot) \\) and \\( Aug_{str}(\\cdot) \\) are applied to the unlabeled set \\( \\mathcal{D}_{\\mathcal{T}_u} \\), transforming a sample \\( x_{i}^{\\mathcal{T}_{u}} \\) to two versions \\( x_{i,w}^{\\mathcal{T}_u} \\) and \\( x_{i,str}^{\\mathcal{T}_u} \\), respectively. Subsequently, we train the model on the labeled set \\( D_{l} = D_{S}\\cup D_{\\mathcal{T}_{l}} \\) and the unlabeled set \\( \\mathcal{D}_{\\mathcal{T}_u} \\), and evaluate the trained model on \\( \\mathcal{D}_{\\mathcal{T}_u} \\)." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.718, + 0.892, + 0.809 + ], + "angle": 0, + "content": "To improve the performance on \\(\\mathcal{D}_{\\mathcal{T}_u}\\), we propose a hybrid model consisting of ViT and CNN branches. The ViT branch is made up of a ViT encoder \\(E_1(\\cdot;\\pmb{\\theta}_{E_1})\\) and a classifier \\(F_1(\\cdot;\\pmb{\\theta}_{F_1})\\), while the CNN branch includes a CNN encoder \\(E_2(\\cdot;\\pmb{\\theta}_{E_2})\\) and a classifier \\(F_2(\\cdot;\\pmb{\\theta}_{F_2})\\). Our strategy training proceeds in three steps:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.81, + 0.892, + 0.856 + ], + "angle": 0, + "content": "1. Supervised Training: We train both ViT and CNN branches on \\(\\mathcal{D}_l\\) whose knowledge is adapted to the \\(\\mathcal{D}_{\\mathcal{T}_u}\\) as illustrated in Fig. 2." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "2. Finding to Conquering: In Fig. 2, we find class-specific boundaries based on fixed \\( E_{1} \\) by maximizing discrepancy between \\( F_{1} \\) and \\( F_{2} \\). Subsequently, the \\( E_{2} \\) clusters the" + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.81, + 0.892, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28547" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.097, + 0.092, + 0.469, + 0.121 + ], + "angle": 0, + "content": "target features based on those class-specific boundaries by minimizing discrepancy." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.122, + 0.47, + 0.201 + ], + "angle": 0, + "content": "3. Co-training: To exchange effectively knowledge between two branches on \\(\\mathcal{D}_{\\mathcal{T}_u}\\), the ViT branch generates a pseudo label for weakly version \\(x_{i,w}^{\\mathcal{T}_u}\\) to teach the CNN branch with strongly version \\(x_{i,str}^{\\mathcal{T}_u}\\). Then, the reverse process is also applied as depicted in Fig. 3." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.209, + 0.27, + 0.225 + ], + "angle": 0, + "content": "3.1. Supervised Training" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.231, + 0.471, + 0.292 + ], + "angle": 0, + "content": "In this phase, we employ the standard cross-entropy loss to train a model's two branches: ViT branch and CNN branch. In the ViT branch, we aim to minimize the empirical loss of labeled data, which is defined as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.135, + 0.299, + 0.47, + 0.34 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {v i t} ^ {s u p} \\left(\\boldsymbol {\\theta} _ {E _ {1}}, \\boldsymbol {\\theta} _ {F _ {1}}\\right) = \\frac {1}{\\mathcal {N} _ {l}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {l}} H \\left(y _ {i} ^ {l}, p _ {1} ^ {l} \\left(x _ {i} ^ {l}\\right)\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.348, + 0.471, + 0.497 + ], + "angle": 0, + "content": "where \\( H(\\cdot) \\) denotes the standard cross-entropy loss. When \\( p_1^l (x_i^l) = \\sigma (F_1(E_1(x_i^l))) \\), \\( \\sigma \\) represents the softmax function, which transforms the logits into probabilities across \\( K \\) categories. Initially, ViT encoder \\( E_{1} \\) maps the labeled sample \\( x_{i}^{l} \\) into a \\( d \\)-dimensional feature space. The classifier \\( F_{1} \\) then categorizes the input feature space \\( E_{1}(x_{i}^{l}) \\) into the logits. Finally, we minimize the cross-entropy loss between the predicted labeled probability by \\( p_1^l (x_i^l) \\) and the provided ground-truth label \\( y_{i}^{l} \\), ensuring accurate predictions on labeled data." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.498, + 0.469, + 0.529 + ], + "angle": 0, + "content": "Similarly, the CNN branch is also trained using labeled data to minimize the empirical loss as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.134, + 0.537, + 0.47, + 0.579 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {c n n} ^ {s u p} \\left(\\boldsymbol {\\theta} _ {E _ {2}}, \\boldsymbol {\\theta} _ {F _ {2}}\\right) = \\frac {1}{\\mathcal {N} _ {l}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {l}} H \\left(y _ {i} ^ {l}, p _ {2} ^ {l} \\left(x _ {i} ^ {l}\\right)\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.586, + 0.469, + 0.709 + ], + "angle": 0, + "content": "where \\( p_2^l (x_i^l) = \\sigma (F_2(E_2(x_i^l))) \\) is obtained by extracting features from the labeled sample \\( x_{i}^{l} \\) using the CNN encoder \\( E_{2} \\). These features are then mapped to logits through the classifier \\( F_{2} \\). Finally, the softmax function \\( \\sigma \\) transforms these logits into probabilities across \\( K \\) categories. The main goal of this process is to minimize the cross-entropy loss to ensure a close alignment between the predicted probabilities \\( p_2^l (x_i^l) \\) and the ground-truth labels \\( y_{i}^{l} \\)." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.716, + 0.29, + 0.733 + ], + "angle": 0, + "content": "3.2. Finding to Conquering" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.739, + 0.469, + 0.814 + ], + "angle": 0, + "content": "Discrepancy Loss Definition. In this work, we use the absolute difference between the probabilistic outputs \\(\\mathbf{a}\\) and \\(\\mathbf{b}\\) from two distinct classifiers \\(F_{1}\\) and \\(F_{2}\\), respectively, for each class to guarantee that the discrepancy loss is always non-negative as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.18, + 0.822, + 0.47, + 0.864 + ], + "angle": 0, + "content": "\\[\nd (\\mathbf {a}, \\mathbf {b}) = \\frac {1}{K} \\sum_ {k = 1} ^ {K} | a _ {k} - b _ {k} |, \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.901 + ], + "angle": 0, + "content": "where \\(a_{k}\\) and \\(b_{k}\\) correspond to the probability outputs of the two classifiers for the \\(k\\)-th class. Normalizing with the" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.894, + 0.227 + ], + "angle": 0, + "content": "total number of categories assures that the discrepancy loss is scale-invariant and bounded between 0 and 1. The discrepancy loss serves as a measure of divergence between the probabilistic outputs of two classifiers, \\(\\mathbf{a}\\) and \\(\\mathbf{b}\\). A discrepancy loss of zero indicates the perfect agreement between them across all classes. On the other hand, a higher discrepancy loss points to a more significant divergence in the two classifiers's predictions. This loss is beneficial in scenarios where we want to expand class-specific boundaries." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.228, + 0.894, + 0.363 + ], + "angle": 0, + "content": "Finding Stage. In this stage, we aim to expand the class-specific boundaries of the classifiers \\((F_{1}, F_{2})\\) in relation to the fixed ViT encoder \\(E_{1}\\) by maximizing the discrepancy loss between their outputs. This means we have a possibility to estimate worst-case hyperspaces, which identifies target samples that fall outside the broader source distribution's support, rather than using CNN encoder \\(E_{2}\\). To avoid this issue, we add a supervised loss on the labeled samples as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.564, + 0.373, + 0.892, + 0.443 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {\\text {f i n d}} \\left(\\boldsymbol {\\theta} _ {F _ {1}}, \\boldsymbol {\\theta} _ {F _ {2}}\\right) = \\mathcal {L} _ {v i t} ^ {\\sup } + \\mathcal {L} _ {c n n} ^ {\\sup } \\\\ - \\frac {1}{\\mathcal {N} _ {\\mathcal {T} _ {u}}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {\\mathcal {T} _ {u}}} d \\left(p _ {1} ^ {f i n d} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right), p _ {2} ^ {f i n d} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {4} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.449, + 0.894, + 0.636 + ], + "angle": 0, + "content": "where \\( p_1^{find}(x_i^{\\mathcal{T}_u}) = \\sigma (F_1(E_1(x_i^{\\mathcal{T}_u}))) \\) and \\( p_2^{find}(x_i^{\\mathcal{T}_u}) = \\sigma (F_2(E_1(x_i^{\\mathcal{T}_u}))) \\) denote the probability outputs of \\( F_{1} \\) and \\( F_{2} \\) with ViT encoder \\( E_{1} \\) on the unlabeled target data \\( x_{i}^{\\mathcal{T}_{u}} \\), respectively. By integrating the supervised loss on the labeled samples, we ensure that the classifiers not only distinguish different classes, but also push to deviate as far as possible from the currently learned class-specific boundaries while all labeled samples are correctly distinguished. In essence, the Finding Stage is a delicate balance between maximizing the discrepancy to explore the class-specific boundaries and minimizing the supervised loss to maintain classification accuracy." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.637, + 0.894, + 0.756 + ], + "angle": 0, + "content": "Conquering Stage. In this stage, we leverage the class-specific boundaries established by the ViT encoder \\( E_{1} \\) as a reference to guide the optimization of the CNN encoder \\( E_{2} \\), while keeping the classifiers \\( F_{1} \\) and \\( F_{2} \\) fixed. The primary is to minimize the discrepancy between the outputs of two classifiers, \\( F_{1} \\) and \\( F_{2} \\), allowing the features extracted by CNN encoder \\( E_{2} \\) to be accurately classified. The objective function is formulated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.511, + 0.767, + 0.892, + 0.809 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {c o n q}} \\left(\\boldsymbol {\\theta} _ {E _ {2}}\\right) = \\frac {1}{\\mathcal {N} \\tau_ {u}} \\sum_ {i = 1} ^ {\\mathcal {N} \\tau_ {u}} d \\left(p _ {1} ^ {\\text {c o n q}} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right), p _ {2} ^ {\\text {c o n q}} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.82, + 0.894, + 0.901 + ], + "angle": 0, + "content": "where \\(p_1^{conq}(x_i^{\\mathcal{T}_u}) = \\sigma (F_1(E_2(x_i^{\\mathcal{T}_u})))\\) and \\(p_2^{conq}(x_i^{\\mathcal{T}_u}) = \\sigma (F_2(E_2(x_i^{\\mathcal{T}_u})))\\) denote the probability outputs of \\(F_{1}\\) and \\(F_{2}\\) with CNN encoder \\(E_{2}\\) on the unlabeled target data, \\(x_{i}^{\\mathcal{T}_{u}}\\). By focusing on minimizing the discrepancy loss, the features extracted by the CNN encoder \\(E_{2}\\) are clustered on the" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28548" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.088, + 0.468, + 0.222 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.141, + 0.23, + 0.405, + 0.246 + ], + "angle": 0, + "content": "Figure 3. Illustration of co-training strategy." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.26, + 0.471, + 0.336 + ], + "angle": 0, + "content": "class-specific boundaries of the ViT encoder \\( E_{1} \\), even when estimating the worst-case hyperspaces. This alignment is crucial as it guarantees that the unlabeled samples are not only correctly classified but also robust to variations in the class-specific boundaries." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.347, + 0.206, + 0.363 + ], + "angle": 0, + "content": "3.3. Co-training" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.371, + 0.473, + 0.55 + ], + "angle": 0, + "content": "Following the Finding-to-Conquering (FTC) strategy, we recognize a significant gap in the knowledge discrepancy between the ViT and CNN branches that needs to be minimized for the optimal performance. To resolve this, we have adopted a co-training strategy with dual objectives as illustrated in Fig. 3. The first objective focuses on reducing the gap between the two branches by enabling mutual enhancement and leveraging each branch's strength to improve the quality of pseudo labels. The second objective is to specifically improve the performance of the CNN branch, thanks to the potential to capture complex patterns and relationships in the data of the ViT branch." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.553, + 0.472, + 0.614 + ], + "angle": 0, + "content": "Initially, we employ pseudo labels generated by the ViT branch to teach the learning process of the CNN branch. This is achieved by setting a fixed threshold, denoted as \\(\\tau_{vit}\\), and applying it as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.194, + 0.624, + 0.352, + 0.644 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {v i t \\rightarrow c n n} ^ {u n l} (\\boldsymbol {\\theta} _ {E _ {2}}, \\boldsymbol {\\theta} _ {F _ {2}}) =\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.116, + 0.654, + 0.47, + 0.697 + ], + "angle": 0, + "content": "\\[\n\\frac {1}{\\mathcal {N} \\tau_ {u}} \\sum_ {i = 1} ^ {\\mathcal {N} \\tau_ {u}} \\mathbb {1} \\left[ \\max \\left(\\mathbf {q} _ {i} ^ {v}\\right) \\geq \\tau_ {v i t} \\right] H \\left(\\hat {q} _ {i} ^ {v}, p ^ {c} \\left(x _ {i, s t r} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.704, + 0.473, + 0.901 + ], + "angle": 0, + "content": "where \\(\\mathbb{1}[\\cdot ]\\) is the binary indicator, returning 1 if the condition inside \\([\\cdot ]\\) is satisfied, and 0 otherwise. In this context, \\(\\mathbf{q}_i^v = \\sigma (F_1(E_1(x_{i,w}^{T_u})))\\) indicates the ViT branch's prediction for a weakly augmented version of an unlabeled target sample. Then, the highest prediction, exceeding the fixed threshold \\(\\tau_{vit}\\), is converted into pseudo label \\(\\hat{q}_i^v = \\mathrm{argmax}(\\mathbf{q}_i^v)\\). Finally, the output prediction \\(p^c (x_{i,str}^{T_u}) = \\sigma (F_2(E_2(x_{i,str}^{T_u})))\\) of the CNN branch on the strongly augmented target sample is adjusted to closely align with the pseudo label \\(\\hat{q}_i^v\\) using the cross-entropy loss. This process ensures that the CNN branch effectively learns from the ViT branch's predictions, making the consistency and alignment between the two branches better." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.894, + 0.152 + ], + "angle": 0, + "content": "Similarly, we also leverage the pseudo labels from the CNN branch to guide the learning process of the ViT branch. This is achieved by setting another fixed threshold, denoted as \\(\\tau_{cnn}\\), and using it as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.618, + 0.162, + 0.774, + 0.182 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {c n n \\rightarrow v i t} ^ {u n l} \\left(\\boldsymbol {\\theta} _ {E _ {1}}, \\boldsymbol {\\theta} _ {F _ {1}}\\right) =\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.536, + 0.191, + 0.893, + 0.234 + ], + "angle": 0, + "content": "\\[\n\\frac {1}{\\mathcal {N} _ {\\tau_ {u}}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {\\tau_ {u}}} \\mathbb {1} \\left[ \\max \\left(\\mathbf {q} _ {i} ^ {c}\\right) \\geq \\tau_ {c n n} \\right] H \\left(\\hat {q} _ {i} ^ {c}, p ^ {v} \\left(x _ {i, s t r} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.243, + 0.895, + 0.396 + ], + "angle": 0, + "content": "where \\(\\mathbf{q}_i^c = \\sigma (F_2(E_2(x_{i,w}^{\\mathcal{T}_u})))\\) is the CNN branch's prediction for a weakly augmented target sample. The pseudo label \\(\\hat{q}_i^c\\) is generated from the highest predictions of the CNN branch that is higher than the threshold \\(\\tau_{\\text{conn}}\\). Meanwhile, \\(p^v (x_{i,\\text{str}}^{\\mathcal{T}_u}) = \\sigma (F_1(E_1(x_{i,\\text{str}}^{\\mathcal{T}_u})))\\) indicates the output prediction of the ViT branch on the strongly augmented target sample and is adjusted to closely align with the pseudo label \\(\\hat{q}_i^c\\), using the cross-entropy loss. Through the co-training process, we enhance the model's ability to generalize and perform accurately on unlabeled target data." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.406, + 0.642, + 0.422 + ], + "angle": 0, + "content": "3.4. Testing Phase" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.43, + 0.894, + 0.489 + ], + "angle": 0, + "content": "For a fair comparison with the previous DA methods [12, 16, 26, 31, 36], we select the CNN encoder \\( E_{2} \\) associated with its classifier \\( F_{2} \\) in the testing phase as illustrated in Fig. 2 as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.588, + 0.501, + 0.893, + 0.521 + ], + "angle": 0, + "content": "\\[\n\\hat {y} _ {i} ^ {\\mathcal {T} _ {u}} = \\operatorname {a r g m a x} \\left(F _ {2} \\left(E _ {2} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right)\\right), \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.533, + 0.886, + 0.551 + ], + "angle": 0, + "content": "where \\(\\hat{y}_i^{\\mathcal{T}_u}\\) is the predicted class of unlabeled target sample." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.565, + 0.634, + 0.582 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.59, + 0.676, + 0.607 + ], + "angle": 0, + "content": "4.1. Experiment Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.613, + 0.894, + 0.763 + ], + "angle": 0, + "content": "Datasets. We conduct extensive evaluations on standard DA benchmark datasets: Office-Home [29] and DomainNet [25]. On Office-Home dataset, we perform experiments on all possible combinations of these 4 domains: Real \\((R)\\), Clipart \\((C)\\), Art \\((A)\\), and Product \\((P)\\) with 65 categories. Consistent with prior SSDA methods [11, 16, 17, 31, 36], we conduct an evaluation on a subset of DomainNet that includes 126 categories in 4 domains: Real (rel), Clipart (clp), Painting (pnt), and Sketch (skt) using 7 different mixtures of these domains." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Implementation Details. We use the ViT/B-16 [7] for the ViT encoder \\( E_{1} \\), while the ResNet [10] is adopted for the CNN encoder \\( E_{2} \\). For UDA, we used ResNet-50 as the backbone network following previous works [2, 12, 30, 37]. Similarly, we follow the evaluation protocol of previous SSDA methods [9, 17, 28, 31], ResNet-34 is applied for this scenario on the DomainNet dataset. Each model is initially pre-trained on the ImageNet-1K [6]. Given the disparate nature of the backbone architectures, we will have" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "28549" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.08, + 0.089, + 0.891, + 0.285 + ], + "angle": 0, + "content": "
MethodA→CA→PA→RC→AC→PC→RP→AP→CP→RR→AR→CR→PMean
DANN [8]45.659.370.147.058.560.946.143.768.563.251.876.857.6
MCD [30]48.968.374.661.367.668.857.047.175.169.152.279.664.1
BNM [4]52.373.980.063.372.974.961.749.579.770.553.682.267.9
MDD [37]54.973.777.860.071.471.861.253.678.172.560.282.368.1
MCC [12]55.175.279.563.373.275.866.152.176.973.858.483.669.4
GVB [5]57.074.779.864.674.174.665.255.181.074.659.784.370.4
DCAN [18]54.575.781.267.474.076.367.452.780.674.159.183.570.5
DALN [2]57.879.982.066.376.277.266.755.581.373.560.485.371.8
FixBi [22]58.177.380.467.779.578.165.857.981.776.462.986.772.7
DCAN+SCDA [19]60.776.482.869.877.578.468.959.082.774.961.884.573.1
ATDOC [20]60.277.882.268.578.677.968.458.483.174.861.587.273.2
EIDCo [38]63.880.882.671.580.180.972.161.384.578.665.887.175.8
ECB (CNN)68.585.488.379.286.889.079.366.488.581.071.190.481.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.291, + 0.893, + 0.32 + ], + "angle": 0, + "content": "Table 1. Accuracy (%) on Office-Home of UDA methods across different domain shifts. ECB (CNN) represents the performance of our method when applied to ResNet-50. The top and second-best accuracy results are highlighted in bold and underline for easy identification." + }, + { + "type": "table", + "bbox": [ + 0.081, + 0.329, + 0.891, + 0.548 + ], + "angle": 0, + "content": "
Methodrel→clprel→pntpnt→clpclp→sktskt→pntrel→sktpnt→relMean
1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot
ENT [9]65.271.065.969.265.471.154.660.059.762.152.161.175.078.662.667.6
MME [31]70.072.267.769.769.071.756.361.864.866.861.061.976.178.566.468.9
S3D [35]73.375.968.972.173.475.160.864.468.270.065.166.779.580.369.972.1
ATDOC [20]74.976.971.372.572.874.265.666.768.770.865.264.681.281.271.472.4
MAP-F [24]75.377.074.075.074.377.065.869.573.073.367.569.281.783.373.174.9
DECOTA [34]79.180.474.975.276.978.765.168.672.072.769.771.979.681.573.975.6
CDAC [16]77.479.674.275.175.579.367.669.971.073.469.272.580.481.973.676.0
ASDA [28]77.079.475.476.775.578.366.570.272.174.270.972.179.782.373.976.2
CDAC+SLA [36]79.881.675.676.077.480.368.171.371.773.571.773.580.482.575.076.9
ProML [11]78.580.275.476.577.878.970.272.074.175.472.473.584.084.876.177.4
MVCL [23]78.879.876.077.478.080.370.873.075.176.772.474.482.485.176.278.1
G-ABC [17]80.782.176.876.779.381.672.073.775.076.373.274.383.483.977.278.4
ECB (CNN)83.887.485.485.686.487.379.780.683.485.679.581.788.790.383.885.5
" + }, + { + "type": "table_caption", + "bbox": [ + 0.157, + 0.552, + 0.812, + 0.567 + ], + "angle": 0, + "content": "Table 2. Accuracy (%) on DomainNet of SSDA methods in both 1-shot and 3-shot settings using ResNet-34." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.574, + 0.473, + 0.771 + ], + "angle": 0, + "content": "two different classifiers, \\( F_{1} \\) and \\( F_{2} \\), consisting of two fully-connected layers followed by the softmax function. We optimize our models using stochastic gradient descent with a 0.9 momentum and 0.0005 weight decay. Considering the different architectures of the ViT and the CNN branches, we set the initial learning rates for ViT and CNN at \\( 1e - 4 \\) and \\( 1e - 3 \\), respectively. The size of the mini-batch is set to 32 for both \\( \\mathcal{D}_l \\) and \\( \\mathcal{D}_{\\tau_u} \\). The confidence threshold values for pseudo-label selection are set to \\( \\tau_{vit} = 0.6 \\) and \\( \\tau_{cnn} = 0.9 \\). The warmup phase for both branches on \\( \\mathcal{D}_l \\) is finetuned for 100,000 iterations. Then, we update the learning rate scheduler and proceed with 50,000 iterations of training for our method." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.785, + 0.27, + 0.802 + ], + "angle": 0, + "content": "4.2. Comparison Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.472, + 0.901 + ], + "angle": 0, + "content": "We evaluate our ECB method and the previous SOTA methods on Office-Home and DomainNet under UDA and SSDA settings, respectively. For a fair comparison with other DA methods, we rely on classification outcomes from the CNN branch, employing ResNet-50 as the backbone for UDA and ResNet-34 for SSDA. As a result, our method does not" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.574, + 0.895, + 0.621 + ], + "angle": 0, + "content": "add any testing complexity compared to previous DA approaches. Besides, we have included further details about the experimental results in Supplementary Materials." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.624, + 0.897, + 0.79 + ], + "angle": 0, + "content": "Results on Office-Home under UDA setting. The implementation of our ECB method has significantly boosted classification efficiency in all domain shift tasks, consistently outperforming the comparison methods, as detailed in Tab. 1. Remarkably, our approach has recorded accuracy enhancements of \\(+7.7\\%\\), \\(+8.1\\%\\), and \\(+7.2\\%\\) for the \\(C \\rightarrow A\\), \\(C \\rightarrow R\\), and \\(P \\rightarrow A\\) tasks, respectively, surpassing the results of the second-best. In addition, our method has achieved an impressive average classification accuracy of \\(81.2\\%\\), showing a remarkable margin of \\(+5.4\\%\\) over the nearest-competitor EIDCo [38]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Results on DomainNet under SSDA setting. The results on the DomainNet dataset are presented for both 1-shot and 3-shot settings in Tab. 2, where the CNN branch of our ECB method outperforms all prior methods. In comparison to the nearest-competitor method, G-ABC [17], the ECB (CNN) achieves an impressive maximum performance increase of \\(+9.3\\%\\) in the \\(skt \\rightarrow pnt\\) task for 3-shot learning. Even in the" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "28550" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.08, + 0.09, + 0.891, + 0.198 + ], + "angle": 0, + "content": "
Methodrel→clprel→pntpnt→clpclp→sktskt→pntrel→sktpnt→relMean
ViTCNNViTCNNViTCNNViTCNNViTCNNViTCNNViTCNNViTCNN
vit→cnn73.379.078.881.075.179.271.674.778.680.867.272.088.188.876.179.4
cnn→vit74.261.976.866.876.167.469.557.274.964.667.454.886.076.175.064.1
co-training87.487.485.885.687.387.380.780.685.885.681.781.790.990.385.785.5
" + }, + { + "type": "table_caption", + "bbox": [ + 0.157, + 0.206, + 0.812, + 0.221 + ], + "angle": 0, + "content": "Table 3. Ablation study on DomainNet between co-training and one-direction teaching under 3-shot settings." + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.235, + 0.27, + 0.345 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.167, + 0.347, + 0.184, + 0.359 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.276, + 0.235, + 0.462, + 0.345 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.36, + 0.347, + 0.377, + 0.359 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.365, + 0.471, + 0.435 + ], + "angle": 0, + "content": "Figure 4. (a) The quality and quantity of the pseudo labels are generated by the CNN branch on DomainNet under the 3-shot setting of the \\(rel \\rightarrow clp\\) task using ResNet-34. (b) Comparison between backbone settings on DomainNet under the 3-shot setting. Displayed is the mean accuracy across all domain shift tasks." + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.44, + 0.471, + 0.516 + ], + "angle": 0, + "content": "more restrictive 1-shot learning, the ECB method demonstrates robust performance, showing a minimum increase of \\(+3.1\\%\\) in the \\(rel \\rightarrow clp\\) task. On average, the ECB method validates a performance improvement of \\(+6.6\\%\\) in the 1-shot setting and \\(+7.1\\%\\) in the 3-shot setting." + }, + { + "type": "title", + "bbox": [ + 0.076, + 0.529, + 0.178, + 0.545 + ], + "angle": 0, + "content": "5. Analyses" + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.553, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Ablation studies. A single classifier is concurrently trained with both labeled source and target data. It is thus easily dominated by the labeled source data. This imbalance prevents the classifier from using the extra-labeled target data effectively, resulting in a misalignment between the learned and true class-specific boundaries. This misalignment is called data bias. Therefore, we perform an ablation study to evaluate the effectiveness of each stage in the proposed method. The emphasis is on addressing the data bias issue within the ViT branch, leveraging the CNN branch's capability to generate high-quality pseudo labels during the rel \\(\\rightarrow\\) clp task on DomainNet under, as illustrated in Fig. 4a. Initially, during the Supervised Training phase, we are only able to generate around 8,000 total pseudo labels. Following the integration of the FTC strategy, the total pseudo labels smoothly increase up to 14,000 with steady maintenance of 10,000 correct pseudo labels. This plays a crucial role in substantially mitigating data bias by generating numerous pseudo-labels, which improves the diversity and representativeness of the unlabeled target dataset. The final experiment is implemented to highlight that co-training is necessary for reducing the remaining gap following the FTC stage, which yields a total of 18,000 pseudo labels and 16,000 correct" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.234, + 0.891, + 0.374 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.384, + 0.894, + 0.427 + ], + "angle": 0, + "content": "Table 4. Visualize the feature maps for the 'Cannon' and 'Bird' examples to investigate the learning behaviors of CNN and ViT with and without using the proposed method ECB." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.445, + 0.598, + 0.459 + ], + "angle": 0, + "content": "pseudo labels." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.463, + 0.896, + 0.903 + ], + "angle": 0, + "content": "Effectiveness of co-training. We further investigate a variant of ECB termed one-direction teaching on the DomainNet under the 3-shot setting. In this approach, we employ either \\(\\mathcal{L}_{vit\\rightarrow cnn}^{unl}\\) or \\(\\mathcal{L}_{cnn\\rightarrow vit}^{unl}\\) to generate pseudo labels for the remaining branch, while maintaining the standard configurations through the use of Supervised Training followed by FTC strategy. As depicted in Tab. 3, there is a performance drop when using one-direction teaching. Specifically, in the \\(vit\\rightarrow cnn\\) scenario, the ViT branch generates pseudo labels for the unlabeled target data to teach the CNN branch through minimizing \\(\\mathcal{L}_{vit\\rightarrow cnn}^{unl}\\). It is crucial to highlight that the ViT branch does not receive pseudo labels from the CNN branch, resulting in the CNN branch outperforming the ViT branch by \\(+3.3\\%\\). In contrast, in the \\(cnn\\rightarrow vit\\) scenario, where \\(\\mathcal{L}_{cnn\\rightarrow vit}^{unl}\\) is minimized, the average performance on the ViT branch is \\(+10.9\\%\\) more outstanding than the CNN branch. However, it is worth mentioning that the performance on the ViT branch suffers from \\(-1.1\\%\\) reduction over the \\(vit\\rightarrow cnn\\) scenario. This performance drop is attributed to the introduction of noise by the CNN branch during the learning process of the ViT branch. On the other hand, when employing \\(\\mathcal{L}_{vit\\rightarrow cnn}^{unl}\\), the CNN branch provides a significant boost in the average performance by \\(+15.3\\%\\), highlighting the superior generalization capabilities of the ViT branch compared to the CNN branch. These scenarios try to leverage the unique strengths of CNN and ViT through the co-training strategy, showcasing the mutual exchange of knowledge between two branches and its potential for generalizing to unlabeled target data. As a result of co-training," + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "28551" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.087, + 0.089, + 0.272, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.178, + 0.233, + 0.195, + 0.244 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.089, + 0.47, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.375, + 0.232, + 0.393, + 0.244 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image", + "bbox": [ + 0.482, + 0.089, + 0.667, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.574, + 0.232, + 0.591, + 0.244 + ], + "angle": 0, + "content": "(c)" + }, + { + "type": "image", + "bbox": [ + 0.682, + 0.089, + 0.867, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.771, + 0.232, + 0.79, + 0.244 + ], + "angle": 0, + "content": "(d)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.247, + 0.895, + 0.29 + ], + "angle": 0, + "content": "Figure 5. We visualize feature spaces for the \\(rel \\to skt\\) task on DomainNet in the 3-shot scenario using t-SNE [33]. Figures (a) and (b) illustrate the features obtained by CNN and ViT branches before adaptation, respectively. Figures (c) and (d) showcase the distribution changes of the CNN branch depending on the presence of the FTC strategy when implementing our ECB method." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.303, + 0.471, + 0.348 + ], + "angle": 0, + "content": "the average performance on the target domain of the ViT and CNN branches reaches the optimal results of \\(85.7\\%\\) and \\(85.5\\%\\), respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.351, + 0.473, + 0.623 + ], + "angle": 0, + "content": "Architecture analysis. We examine the effectiveness of the unique strengths of ViT and CNN over variations of architectures such as \"CNN + CNN\" and \"ViT + ViT\" on DomainNet under 3-shot settings using ResNet-34 for CNN and ViT/B-16 for ViT as shown in Fig. 4b. On average, the results show that \"CNN + CNN\" only achieves around \\(77.0\\%\\) due to the lack of global information when just using CNN. In addition, the introduction of ViT with the primary goal of improving performance drives the \"ViT + ViT\" architecture to achieve a significant increase of \\(+7.0\\%\\) compared to the \"CNN + CNN\" architecture. This architecture makes it possible to establish more general class-specific boundaries, yet is unfair when compared with the previous SSDA methods [20, 30, 31, 34, 36] using ResNet-34 as the backbone, and the lack of local representation is extremely important. As a result, the evidence shows that combining \"CNN + ViT\" with the bridge of co-training achieves the highest accuracy of about \\(85.5\\%\\) for both branches." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.627, + 0.472, + 0.853 + ], + "angle": 0, + "content": "Attention map visualization analysis. To demonstrate the effectiveness of our designing framework methodology, we provide the attention map visualization results by using GradCAM [32], as visualized in Tab. 4. CNN supports ViT: Before applying ECB, ViT was background-sensitive in the \"Cannon\" class, whereas CNN still captures the correct object. However, after applying ECB, ViT can explicitly recognize the target object and back to enhance the robustness of CNN. ViT supports CNN: In the \"Bird\" class before applying ECB, CNN only obtains the part of the target, while ViT can cover the whole input object. Then, CNN is complemented to focus on the object accurately by ViT using ECB. Consequently, these findings validate that both branches offer distinct expertise and enhance each other rather than one overshadowing the other." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Feature Visualization. We present a detailed visualization of the feature space for the DomainNet dataset within the \\(rel \\rightarrow skt\\) task under the 3-shot setting. This visualization" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.303, + 0.895, + 0.591 + ], + "angle": 0, + "content": "distinctly highlights the source domain (blue-colored) and the target domain (red-colored). Figs. 5a and 5b show the domain alignment of both the CNN and ViT branches before adaptation. In particular, Fig. 5a visualizes the feature space extracted by the CNN branch before applying ECB, reflecting a scatter that indicates weak classifier performance. In contrast, Fig. 5b displays the well-defined clusters in the ViT branch for the same unlabeled target data, which emphasizes the robustness of ViT in identifying more general class-specific boundaries compared to the CNN branch. Figs. 5c and 5d show the distribution changes of the CNN branch depending on the presence of the FTC strategy when implementing ECB. Initially, Fig. 5c indicates that the target representations overlap (highlighted with green box) when implementing ECB without the FTC strategy. On the other hand, Fig. 5d shows the well-aligned source and target domain representations with clusters to distinct separation when applying the FTC strategy, which demonstrates the effectiveness of our proposed method." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.612, + 0.62, + 0.627 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.639, + 0.894, + 0.759 + ], + "angle": 0, + "content": "In this work, we have developed a novel method for learning CNN on ViT with ECB strategy, taking advantage of ViT and CNN. This innovative approach focuses on reducing data bias and significantly improves the precision of pseudo labels generated, which aligns between source and target domains. Our method is also fair when evaluated on the CNN branch and outperforms the previous SOTA methods on various DA benchmark datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.763, + 0.895, + 0.837 + ], + "angle": 0, + "content": "**Discussions.** We found that identifying an optimal threshold pair \\(\\{\\tau_{vit}\\) and \\(\\tau_{cnn}\\}\\) was quite time-consuming. Therefore, we leave an open task for future research that uses a dynamic threshold algorithm for domain adaptation instead of the fixed threshold." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.9 + ], + "angle": 0, + "content": "Acknowledgement. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIT) (No. RS-2023-00214326 and No. RS-2023-00242528)." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "28552" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.169 + ], + "angle": 0, + "content": "[1] Avrim Blum and Tom Mitchell. Combining labeled and unlabeled data with co-training. 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They align the distribution differences between domains as encoders without considering their unique characteristics. For instance, ViT excels in accuracy due to its superior ability to capture global representations, while CNN has an advantage in capturing local representations. This fact has led us to design a hybrid method to fully take advantage of both ViT and CNN, called Explicitly Class-specific Boundaries (ECB). ECB learns CNN on ViT to combine their distinct strengths. In particular, we leverage ViT's properties to explicitly find class-specific decision boundaries by maximizing the discrepancy between the outputs of the two classifiers to detect target samples far from the source support. In contrast, the CNN encoder clusters target features based on the previously defined class-specific boundaries by minimizing the discrepancy between the probabilities of the two classifiers. Finally, ViT and CNN mutually exchange knowledge to improve the quality of pseudo labels and reduce the knowledge discrepancies of these models. Compared to conventional DA methods, our ECB achieves superior performance, which verifies its effectiveness in this hybrid model. The project website can be found here. + +# 1. Introduction + +Over the past few years, convolutional neural networks (CNNs) [13] have been the cornerstone of deep learning techniques in computer vision tasks. This progress is mainly attributed to a convolution layer, which efficiently captures local spatial hierarchies for robust image representations. This local feature extraction capability has enabled CNNs to achieve State-of-the-Art (SOTA) performance in a variety of vision tasks, from image classification to object detection. In spite of its powerful local feature extraction, CNNs are some- + +![](images/e7c22c892a4dd5072e13738cbf0fe032e201816fba1dafcad8d477e6b3f8564c.jpg) +Figure 1. Illustration of the proposed hybrid network architecture that leverages the strengths of ViT and CNN models. + +what limited in capturing more global and comprehensive visual context. To overcome this limitation, vision transformer (ViT) [7] was introduced. ViT starts by dividing an image into patches, which are transformed into a sequence of tokens. Positional embeddings are incorporated into the tokens to retain the order of these patches. The model then uses transformer blocks to extract these tokens into features as image representations. Thanks to self-attention mechanisms in ViT, it is able to weigh the importance of different regions in an image irrespective of their spatial proximity, leading to comprehensive global representations with impressive accuracy. The advancements in ViT have led to a growing inclination in the machine learning realm over CNN-based approaches for a range of tasks. + +Instead of focusing solely on replacing CNN with ViT, our approach diverges from this trend. We believe that both + +ViT and CNN architectures have their own strengths that can be harnessed when combined well. For instance, ViT has shown the capability to capture global representations and demonstrates robustness when trained on large datasets. Yet, because it is composed of multilayer perceptron (MLP) layers, ViT can overfit if the dataset is limited. On the other hand, CNNs perform well with relatively small datasets thanks to their spatial invariance and robustness in capturing local representations. Motivated by this, we propose a novel method that capitalizes on the distinct strengths of both architectures. As shown in Fig. 1, we exploit the superior accuracy of ViT in identifying more general class-specific boundaries by maximizing the discrepancy between the outputs of the two classifiers, enabling us to estimate the worst-case hyperspaces. Once these class-specific boundaries are defined, CNN minimizes the discrepancy by clustering target features closer to the source domain, aiming to minimize errors within the identified hyperspaces. However, the knowledge discrepancies between ViT and CNN still exist, so we applied additional co-training to bridge this gap while improving the quality of the pseudo labels. In the field of unsupervised domain adaptation (UDA), MCD [30] emphasizes the importance of maximizing the discrepancy between classifier outputs for target samples, which are far from the source domain's support, and then minimizing this discrepancy through a feature generator to align the target features closer to the source's support. + +Although UDA has made significant advancements in domain adaptation (DA) tasks, the semi-supervised domain adaptation (SSDA) scenarios, as discussed in [11, 14-16, 28, 31, 34-36], are extensively employed to yield remarkable classification accuracy compared to the UDA setting [2, 4, 5, 19, 37]. This is because a model trained under UDA is only accessed to labeled source data, while a model trained with the SSDA setting benefits from the extra target information with a few labeled target samples besides labeled source data. However, the previous DA methods only take full advantage of the unique benefits of CNN as a feature extractor. Specifically, works in [12, 15, 21, 31] use a combination of a CNN encoder followed by an MLP classifier, but the decision boundary towards the source domain leads to data bias in DA. To address this bias, some previous works [27, 28, 37] introduce a multi-model by adding one more MLP classifier, which consists of a single CNN encoder and two MLP classifiers. Furthermore, the first DA approaches in [22, 34] use two CNN encoders and two MLP classifiers to boost the classification accuracy by leveraging a co-training strategy that ensures the consistency of unlabeled target data through knowledge exchange. However, these methodologies still follow the same rule, where the CNN model is selected as the encoder, and MLP is assigned as the classifier. Therefore, the capabilities of ViT in capturing global information remain unexploited. Inspired by the ideal, + +we make use of this multi-model architecture to build a new hybrid framework that leverages the advantages of ViT and CNN for DA settings. However, the proposed method does not require any additional complexity compared to previous works in the test phase. We summarize the contributions of this paper as follows: + +- We introduce a hybrid model that can take advantage of ViT. Beyond simply replacing CNN with ViT, we can drive the feature space of ViT to CNN. +- Our approach demonstrates the successful integration of ViT and CNN, making a synergy with these two powerful frameworks. +- The proposed method outperforms the prior works to achieve SOTA performances on DA benchmark datasets. + +# 2. Related Works + +Co-training. In the realm of semi-supervised learning (SSL), co-training is a scheme to improve the robustness, first proposed by [1], and harnesses data from dual views, enabling two models to iteratively 'teach' each other. During this process, each model alternately makes predictions on unlabeled data, with the most confident predictions used to augment the training set of the other model. This mutual teaching strategy can significantly improve the performance of both models, particularly when labeled data is scarce. In the DA context, FixBi [22], DECOTA [34], and MVCL [23] offer innovative co-training strategies. Notably, FixBi and DECOTA utilize two distinct branches, each including a feature extractor and a classifier. They utilize MIXUP augmentation to reduce the gap in multiple intermediate domains between the source and target domain during co-training. However, they miss the potential benefits of strong augmentation. In contrast, while MVCL employs both weak and strong augmentation to bolster its co-training approach, it relies on a single CNN-based encoder and two classifiers to produce two views. This limits the representation of unlabeled target data, depriving its comprehensive global information. To address these limitations, we employ the ViT in conjunction with a CNN-based encoder. This combination generates two representational views that encapsulate both local and global information. Additionally, we integrate both weak and strong augmentations for unlabeled target samples, which enhances the interactivity and effectiveness of our co-training strategy. + +Domain Adaptation Framework. In the realm of DA, various frameworks have been presented. Early methods such as MME [31], APE [15], and SENTRY [26] adopt the conventional approach of constructing deep learning frameworks that have a feature extractor coupled with a classifier. However, source and target domains share the same decision boundary, which leads to data bias toward the source domain. To alleviate data bias, MDD [37] and UODA [27] introduce two distinct classifiers. They demonstrate that using a dual-classifier setup can improve the performance + +![](images/98e617a6b54508ffd327993b1c332ae7c6144f4512afc623de5ffca6204ae759.jpg) +Figure 2. Illustration of a hybrid network with the proposed Finding to Conquering strategy. We use ViT to build $E_{1}$ that drives two classifiers $F_{1}$ and $F_{2}$ to expand class-specific boundaries comprehensively. Besides, we select CNN for the second encoder $E_{2}$ to cluster target features based on the boundaries identified by ViT. These encoders all use two classifiers $F_{1}, F_{2}$ . + +of classification tasks. These methods use a single feature extractor to train on both labeled source and target datasets. However, the source domain is more reliable than the target domain thanks to labeled source samples, which can lead the feature extractor to overly focus on source data representations. This results in a learning bias toward the source domain, accumulating errors during the training process. To solve this problem, DECOTA [34] proposes a novel architecture by decomposing two distinct branches, UDA and SSL, each consisting of a feature extractor and a single classifier. Specifically, the UDA branch is trained on labeled source data and unlabeled target data, while the SSL branch is trained on labeled and unlabeled target data. Thanks to the SSL branch, focusing solely on the target domain facilitates the alleviation of learning bias. In addition, the UDA branch is capable of mitigating learning bias by leveraging extra information from the SSL branch via the co-training strategy. Despite the notable advancements in the field, DECOTA still follows the framework of using CNN as the feature extractor. Therefore, it is impossible to completely improve the quality of pseudo labels for unlabeled target samples and exploit learning space based on the properties of ViT. As a result, the capabilities of ViT in capturing global information still need to be explored. Instead of solely replacing CNN with ViT, we propose a hybrid model that combines their strengths of both architectures. + +# 3. Methodology + +In DA scenarios, we deal with the following data setting: + +- Labeled source domain: Denoted as $\mathcal{D}_S = \{(x_i^{\mathcal{S}},y_i^{\mathcal{S}})\}_{i = 1}^{\mathcal{N}_S}$ includes $\mathcal{N}_S$ richly labeled samples. +- Labeled target domain: Denoted as $\mathcal{D}_{\mathcal{T}_l} = \{(x_i^{\mathcal{T}_l},y_i^{\mathcal{T}_l})\}_{i = 1}^{\mathcal{N}_{\mathcal{T}_l}}$ includes $\mathcal{N}_{\mathcal{T}_l}$ limited labeled target samples. Notably, $\mathcal{D}_{\mathcal{T}_l}$ is empty in UDA. + +- Unlabeled target domain: Denoted as $\mathcal{D}_{\mathcal{T}_u} = \{(x_i^{\mathcal{T}_u},y_i^{\mathcal{T}_u})\}_{i = 1}^{\mathcal{N}_{\mathcal{T}_u}}$ includes $\mathcal{N}_{\mathcal{T}_u}$ target samples that do not have corresponding labels during the training phase. + +In this setup, the sample $x_{i}^{S}$ and $x_{i}^{\mathcal{T}_{l}}$ from the source domain and the labeled target domain are associated with corresponding ground-truth labels $y_{i}^{S}$ and $y_{i}^{\mathcal{T}_{l}}$ , respectively. There is an assumption that the label $y^{S}, y^{\mathcal{T}_{l}}$ , and $y^{\mathcal{T}_{u}}$ all belong to the same label space with $K$ classes. Notably, $y^{\mathcal{T}_{u}}$ , which denotes labels for the unlabeled target data, are only used during the testing phase. Furthermore, the number of labeled target samples $\mathcal{N}_{\mathcal{T}_l}$ is much smaller than both $\mathcal{N}_S$ and $\mathcal{N}_{\mathcal{T}_u}$ . Moreover, we implement two varied stochastic data transformations: $Aug_{w}(\cdot)$ and $Aug_{str}(\cdot)$ . The function $Aug_{w}(\cdot)$ is a weak augmentation method employing light perturbations such as random horizontal flipping and random cropping, whereas $Aug_{str}(\cdot)$ stands as a strong augmentation method, using RandAugment [3], which involves 14 transformation techniques. Specifically, both $Aug_{w}(\cdot)$ and $Aug_{str}(\cdot)$ are applied to the unlabeled set $\mathcal{D}_{\mathcal{T}_u}$ , transforming a sample $x_{i}^{\mathcal{T}_{u}}$ to two versions $x_{i,w}^{\mathcal{T}_u}$ and $x_{i,str}^{\mathcal{T}_u}$ , respectively. Subsequently, we train the model on the labeled set $D_{l} = D_{S}\cup D_{\mathcal{T}_{l}}$ and the unlabeled set $\mathcal{D}_{\mathcal{T}_u}$ , and evaluate the trained model on $\mathcal{D}_{\mathcal{T}_u}$ . + +To improve the performance on $\mathcal{D}_{\mathcal{T}_u}$ , we propose a hybrid model consisting of ViT and CNN branches. The ViT branch is made up of a ViT encoder $E_1(\cdot;\pmb{\theta}_{E_1})$ and a classifier $F_1(\cdot;\pmb{\theta}_{F_1})$ , while the CNN branch includes a CNN encoder $E_2(\cdot;\pmb{\theta}_{E_2})$ and a classifier $F_2(\cdot;\pmb{\theta}_{F_2})$ . Our strategy training proceeds in three steps: + +1. Supervised Training: We train both ViT and CNN branches on $\mathcal{D}_l$ whose knowledge is adapted to the $\mathcal{D}_{\mathcal{T}_u}$ as illustrated in Fig. 2. +2. Finding to Conquering: In Fig. 2, we find class-specific boundaries based on fixed $E_{1}$ by maximizing discrepancy between $F_{1}$ and $F_{2}$ . Subsequently, the $E_{2}$ clusters the + +target features based on those class-specific boundaries by minimizing discrepancy. + +3. Co-training: To exchange effectively knowledge between two branches on $\mathcal{D}_{\mathcal{T}_u}$ , the ViT branch generates a pseudo label for weakly version $x_{i,w}^{\mathcal{T}_u}$ to teach the CNN branch with strongly version $x_{i,str}^{\mathcal{T}_u}$ . Then, the reverse process is also applied as depicted in Fig. 3. + +# 3.1. Supervised Training + +In this phase, we employ the standard cross-entropy loss to train a model's two branches: ViT branch and CNN branch. In the ViT branch, we aim to minimize the empirical loss of labeled data, which is defined as follows: + +$$ +\mathcal {L} _ {v i t} ^ {s u p} \left(\boldsymbol {\theta} _ {E _ {1}}, \boldsymbol {\theta} _ {F _ {1}}\right) = \frac {1}{\mathcal {N} _ {l}} \sum_ {i = 1} ^ {\mathcal {N} _ {l}} H \left(y _ {i} ^ {l}, p _ {1} ^ {l} \left(x _ {i} ^ {l}\right)\right), \tag {1} +$$ + +where $H(\cdot)$ denotes the standard cross-entropy loss. When $p_1^l (x_i^l) = \sigma (F_1(E_1(x_i^l)))$ , $\sigma$ represents the softmax function, which transforms the logits into probabilities across $K$ categories. Initially, ViT encoder $E_{1}$ maps the labeled sample $x_{i}^{l}$ into a $d$ -dimensional feature space. The classifier $F_{1}$ then categorizes the input feature space $E_{1}(x_{i}^{l})$ into the logits. Finally, we minimize the cross-entropy loss between the predicted labeled probability by $p_1^l (x_i^l)$ and the provided ground-truth label $y_{i}^{l}$ , ensuring accurate predictions on labeled data. + +Similarly, the CNN branch is also trained using labeled data to minimize the empirical loss as follows: + +$$ +\mathcal {L} _ {c n n} ^ {s u p} \left(\boldsymbol {\theta} _ {E _ {2}}, \boldsymbol {\theta} _ {F _ {2}}\right) = \frac {1}{\mathcal {N} _ {l}} \sum_ {i = 1} ^ {\mathcal {N} _ {l}} H \left(y _ {i} ^ {l}, p _ {2} ^ {l} \left(x _ {i} ^ {l}\right)\right), \tag {2} +$$ + +where $p_2^l (x_i^l) = \sigma (F_2(E_2(x_i^l)))$ is obtained by extracting features from the labeled sample $x_{i}^{l}$ using the CNN encoder $E_{2}$ . These features are then mapped to logits through the classifier $F_{2}$ . Finally, the softmax function $\sigma$ transforms these logits into probabilities across $K$ categories. The main goal of this process is to minimize the cross-entropy loss to ensure a close alignment between the predicted probabilities $p_2^l (x_i^l)$ and the ground-truth labels $y_{i}^{l}$ . + +# 3.2. Finding to Conquering + +Discrepancy Loss Definition. In this work, we use the absolute difference between the probabilistic outputs $\mathbf{a}$ and $\mathbf{b}$ from two distinct classifiers $F_{1}$ and $F_{2}$ , respectively, for each class to guarantee that the discrepancy loss is always non-negative as follows: + +$$ +d (\mathbf {a}, \mathbf {b}) = \frac {1}{K} \sum_ {k = 1} ^ {K} | a _ {k} - b _ {k} |, \tag {3} +$$ + +where $a_{k}$ and $b_{k}$ correspond to the probability outputs of the two classifiers for the $k$ -th class. Normalizing with the + +total number of categories assures that the discrepancy loss is scale-invariant and bounded between 0 and 1. The discrepancy loss serves as a measure of divergence between the probabilistic outputs of two classifiers, $\mathbf{a}$ and $\mathbf{b}$ . A discrepancy loss of zero indicates the perfect agreement between them across all classes. On the other hand, a higher discrepancy loss points to a more significant divergence in the two classifiers's predictions. This loss is beneficial in scenarios where we want to expand class-specific boundaries. + +Finding Stage. In this stage, we aim to expand the class-specific boundaries of the classifiers $(F_{1}, F_{2})$ in relation to the fixed ViT encoder $E_{1}$ by maximizing the discrepancy loss between their outputs. This means we have a possibility to estimate worst-case hyperspaces, which identifies target samples that fall outside the broader source distribution's support, rather than using CNN encoder $E_{2}$ . To avoid this issue, we add a supervised loss on the labeled samples as follows: + +$$ +\begin{array}{l} \mathcal {L} _ {\text {f i n d}} \left(\boldsymbol {\theta} _ {F _ {1}}, \boldsymbol {\theta} _ {F _ {2}}\right) = \mathcal {L} _ {v i t} ^ {\sup } + \mathcal {L} _ {c n n} ^ {\sup } \\ - \frac {1}{\mathcal {N} _ {\mathcal {T} _ {u}}} \sum_ {i = 1} ^ {\mathcal {N} _ {\mathcal {T} _ {u}}} d \left(p _ {1} ^ {f i n d} \left(x _ {i} ^ {\mathcal {T} _ {u}}\right), p _ {2} ^ {f i n d} \left(x _ {i} ^ {\mathcal {T} _ {u}}\right)\right), \tag {4} \\ \end{array} +$$ + +where $p_1^{find}(x_i^{\mathcal{T}_u}) = \sigma (F_1(E_1(x_i^{\mathcal{T}_u})))$ and $p_2^{find}(x_i^{\mathcal{T}_u}) = \sigma (F_2(E_1(x_i^{\mathcal{T}_u})))$ denote the probability outputs of $F_{1}$ and $F_{2}$ with ViT encoder $E_{1}$ on the unlabeled target data $x_{i}^{\mathcal{T}_{u}}$ , respectively. By integrating the supervised loss on the labeled samples, we ensure that the classifiers not only distinguish different classes, but also push to deviate as far as possible from the currently learned class-specific boundaries while all labeled samples are correctly distinguished. In essence, the Finding Stage is a delicate balance between maximizing the discrepancy to explore the class-specific boundaries and minimizing the supervised loss to maintain classification accuracy. + +Conquering Stage. In this stage, we leverage the class-specific boundaries established by the ViT encoder $E_{1}$ as a reference to guide the optimization of the CNN encoder $E_{2}$ , while keeping the classifiers $F_{1}$ and $F_{2}$ fixed. The primary is to minimize the discrepancy between the outputs of two classifiers, $F_{1}$ and $F_{2}$ , allowing the features extracted by CNN encoder $E_{2}$ to be accurately classified. The objective function is formulated as follows: + +$$ +\mathcal {L} _ {\text {c o n q}} \left(\boldsymbol {\theta} _ {E _ {2}}\right) = \frac {1}{\mathcal {N} \tau_ {u}} \sum_ {i = 1} ^ {\mathcal {N} \tau_ {u}} d \left(p _ {1} ^ {\text {c o n q}} \left(x _ {i} ^ {\mathcal {T} _ {u}}\right), p _ {2} ^ {\text {c o n q}} \left(x _ {i} ^ {\mathcal {T} _ {u}}\right)\right), \tag {5} +$$ + +where $p_1^{conq}(x_i^{\mathcal{T}_u}) = \sigma (F_1(E_2(x_i^{\mathcal{T}_u})))$ and $p_2^{conq}(x_i^{\mathcal{T}_u}) = \sigma (F_2(E_2(x_i^{\mathcal{T}_u})))$ denote the probability outputs of $F_{1}$ and $F_{2}$ with CNN encoder $E_{2}$ on the unlabeled target data, $x_{i}^{\mathcal{T}_{u}}$ . By focusing on minimizing the discrepancy loss, the features extracted by the CNN encoder $E_{2}$ are clustered on the + +![](images/bebe0027db065a274d31abf4c7dadd9872c4e54a60bfd95af0b44a805c5052ca.jpg) +Figure 3. Illustration of co-training strategy. + +class-specific boundaries of the ViT encoder $E_{1}$ , even when estimating the worst-case hyperspaces. This alignment is crucial as it guarantees that the unlabeled samples are not only correctly classified but also robust to variations in the class-specific boundaries. + +# 3.3. Co-training + +Following the Finding-to-Conquering (FTC) strategy, we recognize a significant gap in the knowledge discrepancy between the ViT and CNN branches that needs to be minimized for the optimal performance. To resolve this, we have adopted a co-training strategy with dual objectives as illustrated in Fig. 3. The first objective focuses on reducing the gap between the two branches by enabling mutual enhancement and leveraging each branch's strength to improve the quality of pseudo labels. The second objective is to specifically improve the performance of the CNN branch, thanks to the potential to capture complex patterns and relationships in the data of the ViT branch. + +Initially, we employ pseudo labels generated by the ViT branch to teach the learning process of the CNN branch. This is achieved by setting a fixed threshold, denoted as $\tau_{vit}$ , and applying it as follows: + +$$ +\mathcal {L} _ {v i t \rightarrow c n n} ^ {u n l} (\boldsymbol {\theta} _ {E _ {2}}, \boldsymbol {\theta} _ {F _ {2}}) = +$$ + +$$ +\frac {1}{\mathcal {N} \tau_ {u}} \sum_ {i = 1} ^ {\mathcal {N} \tau_ {u}} \mathbb {1} \left[ \max \left(\mathbf {q} _ {i} ^ {v}\right) \geq \tau_ {v i t} \right] H \left(\hat {q} _ {i} ^ {v}, p ^ {c} \left(x _ {i, s t r} ^ {\mathcal {T} _ {u}}\right)\right), \tag {6} +$$ + +where $\mathbb{1}[\cdot ]$ is the binary indicator, returning 1 if the condition inside $[\cdot ]$ is satisfied, and 0 otherwise. In this context, $\mathbf{q}_i^v = \sigma (F_1(E_1(x_{i,w}^{T_u})))$ indicates the ViT branch's prediction for a weakly augmented version of an unlabeled target sample. Then, the highest prediction, exceeding the fixed threshold $\tau_{vit}$ , is converted into pseudo label $\hat{q}_i^v = \mathrm{argmax}(\mathbf{q}_i^v)$ . Finally, the output prediction $p^c (x_{i,str}^{T_u}) = \sigma (F_2(E_2(x_{i,str}^{T_u})))$ of the CNN branch on the strongly augmented target sample is adjusted to closely align with the pseudo label $\hat{q}_i^v$ using the cross-entropy loss. This process ensures that the CNN branch effectively learns from the ViT branch's predictions, making the consistency and alignment between the two branches better. + +Similarly, we also leverage the pseudo labels from the CNN branch to guide the learning process of the ViT branch. This is achieved by setting another fixed threshold, denoted as $\tau_{cnn}$ , and using it as follows: + +$$ +\mathcal {L} _ {c n n \rightarrow v i t} ^ {u n l} \left(\boldsymbol {\theta} _ {E _ {1}}, \boldsymbol {\theta} _ {F _ {1}}\right) = +$$ + +$$ +\frac {1}{\mathcal {N} _ {\tau_ {u}}} \sum_ {i = 1} ^ {\mathcal {N} _ {\tau_ {u}}} \mathbb {1} \left[ \max \left(\mathbf {q} _ {i} ^ {c}\right) \geq \tau_ {c n n} \right] H \left(\hat {q} _ {i} ^ {c}, p ^ {v} \left(x _ {i, s t r} ^ {\mathcal {T} _ {u}}\right)\right), \tag {7} +$$ + +where $\mathbf{q}_i^c = \sigma (F_2(E_2(x_{i,w}^{\mathcal{T}_u})))$ is the CNN branch's prediction for a weakly augmented target sample. The pseudo label $\hat{q}_i^c$ is generated from the highest predictions of the CNN branch that is higher than the threshold $\tau_{\text{conn}}$ . Meanwhile, $p^v (x_{i,\text{str}}^{\mathcal{T}_u}) = \sigma (F_1(E_1(x_{i,\text{str}}^{\mathcal{T}_u})))$ indicates the output prediction of the ViT branch on the strongly augmented target sample and is adjusted to closely align with the pseudo label $\hat{q}_i^c$ , using the cross-entropy loss. Through the co-training process, we enhance the model's ability to generalize and perform accurately on unlabeled target data. + +# 3.4. Testing Phase + +For a fair comparison with the previous DA methods [12, 16, 26, 31, 36], we select the CNN encoder $E_{2}$ associated with its classifier $F_{2}$ in the testing phase as illustrated in Fig. 2 as follows: + +$$ +\hat {y} _ {i} ^ {\mathcal {T} _ {u}} = \operatorname {a r g m a x} \left(F _ {2} \left(E _ {2} \left(x _ {i} ^ {\mathcal {T} _ {u}}\right)\right)\right), \tag {8} +$$ + +where $\hat{y}_i^{\mathcal{T}_u}$ is the predicted class of unlabeled target sample. + +# 4. Experiments + +# 4.1. Experiment Setup + +Datasets. We conduct extensive evaluations on standard DA benchmark datasets: Office-Home [29] and DomainNet [25]. On Office-Home dataset, we perform experiments on all possible combinations of these 4 domains: Real $(R)$ , Clipart $(C)$ , Art $(A)$ , and Product $(P)$ with 65 categories. Consistent with prior SSDA methods [11, 16, 17, 31, 36], we conduct an evaluation on a subset of DomainNet that includes 126 categories in 4 domains: Real (rel), Clipart (clp), Painting (pnt), and Sketch (skt) using 7 different mixtures of these domains. + +Implementation Details. We use the ViT/B-16 [7] for the ViT encoder $E_{1}$ , while the ResNet [10] is adopted for the CNN encoder $E_{2}$ . For UDA, we used ResNet-50 as the backbone network following previous works [2, 12, 30, 37]. Similarly, we follow the evaluation protocol of previous SSDA methods [9, 17, 28, 31], ResNet-34 is applied for this scenario on the DomainNet dataset. Each model is initially pre-trained on the ImageNet-1K [6]. Given the disparate nature of the backbone architectures, we will have + +
MethodA→CA→PA→RC→AC→PC→RP→AP→CP→RR→AR→CR→PMean
DANN [8]45.659.370.147.058.560.946.143.768.563.251.876.857.6
MCD [30]48.968.374.661.367.668.857.047.175.169.152.279.664.1
BNM [4]52.373.980.063.372.974.961.749.579.770.553.682.267.9
MDD [37]54.973.777.860.071.471.861.253.678.172.560.282.368.1
MCC [12]55.175.279.563.373.275.866.152.176.973.858.483.669.4
GVB [5]57.074.779.864.674.174.665.255.181.074.659.784.370.4
DCAN [18]54.575.781.267.474.076.367.452.780.674.159.183.570.5
DALN [2]57.879.982.066.376.277.266.755.581.373.560.485.371.8
FixBi [22]58.177.380.467.779.578.165.857.981.776.462.986.772.7
DCAN+SCDA [19]60.776.482.869.877.578.468.959.082.774.961.884.573.1
ATDOC [20]60.277.882.268.578.677.968.458.483.174.861.587.273.2
EIDCo [38]63.880.882.671.580.180.972.161.384.578.665.887.175.8
ECB (CNN)68.585.488.379.286.889.079.366.488.581.071.190.481.2
+ +Table 1. Accuracy (%) on Office-Home of UDA methods across different domain shifts. ECB (CNN) represents the performance of our method when applied to ResNet-50. The top and second-best accuracy results are highlighted in bold and underline for easy identification. + +
Methodrel→clprel→pntpnt→clpclp→sktskt→pntrel→sktpnt→relMean
1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot
ENT [9]65.271.065.969.265.471.154.660.059.762.152.161.175.078.662.667.6
MME [31]70.072.267.769.769.071.756.361.864.866.861.061.976.178.566.468.9
S3D [35]73.375.968.972.173.475.160.864.468.270.065.166.779.580.369.972.1
ATDOC [20]74.976.971.372.572.874.265.666.768.770.865.264.681.281.271.472.4
MAP-F [24]75.377.074.075.074.377.065.869.573.073.367.569.281.783.373.174.9
DECOTA [34]79.180.474.975.276.978.765.168.672.072.769.771.979.681.573.975.6
CDAC [16]77.479.674.275.175.579.367.669.971.073.469.272.580.481.973.676.0
ASDA [28]77.079.475.476.775.578.366.570.272.174.270.972.179.782.373.976.2
CDAC+SLA [36]79.881.675.676.077.480.368.171.371.773.571.773.580.482.575.076.9
ProML [11]78.580.275.476.577.878.970.272.074.175.472.473.584.084.876.177.4
MVCL [23]78.879.876.077.478.080.370.873.075.176.772.474.482.485.176.278.1
G-ABC [17]80.782.176.876.779.381.672.073.775.076.373.274.383.483.977.278.4
ECB (CNN)83.887.485.485.686.487.379.780.683.485.679.581.788.790.383.885.5
+ +Table 2. Accuracy (%) on DomainNet of SSDA methods in both 1-shot and 3-shot settings using ResNet-34. + +two different classifiers, $F_{1}$ and $F_{2}$ , consisting of two fully-connected layers followed by the softmax function. We optimize our models using stochastic gradient descent with a 0.9 momentum and 0.0005 weight decay. Considering the different architectures of the ViT and the CNN branches, we set the initial learning rates for ViT and CNN at $1e - 4$ and $1e - 3$ , respectively. The size of the mini-batch is set to 32 for both $\mathcal{D}_l$ and $\mathcal{D}_{\tau_u}$ . The confidence threshold values for pseudo-label selection are set to $\tau_{vit} = 0.6$ and $\tau_{cnn} = 0.9$ . The warmup phase for both branches on $\mathcal{D}_l$ is finetuned for 100,000 iterations. Then, we update the learning rate scheduler and proceed with 50,000 iterations of training for our method. + +# 4.2. Comparison Results + +We evaluate our ECB method and the previous SOTA methods on Office-Home and DomainNet under UDA and SSDA settings, respectively. For a fair comparison with other DA methods, we rely on classification outcomes from the CNN branch, employing ResNet-50 as the backbone for UDA and ResNet-34 for SSDA. As a result, our method does not + +add any testing complexity compared to previous DA approaches. Besides, we have included further details about the experimental results in Supplementary Materials. + +Results on Office-Home under UDA setting. The implementation of our ECB method has significantly boosted classification efficiency in all domain shift tasks, consistently outperforming the comparison methods, as detailed in Tab. 1. Remarkably, our approach has recorded accuracy enhancements of $+7.7\%$ , $+8.1\%$ , and $+7.2\%$ for the $C \rightarrow A$ , $C \rightarrow R$ , and $P \rightarrow A$ tasks, respectively, surpassing the results of the second-best. In addition, our method has achieved an impressive average classification accuracy of $81.2\%$ , showing a remarkable margin of $+5.4\%$ over the nearest-competitor EIDCo [38]. + +Results on DomainNet under SSDA setting. The results on the DomainNet dataset are presented for both 1-shot and 3-shot settings in Tab. 2, where the CNN branch of our ECB method outperforms all prior methods. In comparison to the nearest-competitor method, G-ABC [17], the ECB (CNN) achieves an impressive maximum performance increase of $+9.3\%$ in the $skt \rightarrow pnt$ task for 3-shot learning. Even in the + +
Methodrel→clprel→pntpnt→clpclp→sktskt→pntrel→sktpnt→relMean
ViTCNNViTCNNViTCNNViTCNNViTCNNViTCNNViTCNNViTCNN
vit→cnn73.379.078.881.075.179.271.674.778.680.867.272.088.188.876.179.4
cnn→vit74.261.976.866.876.167.469.557.274.964.667.454.886.076.175.064.1
co-training87.487.485.885.687.387.380.780.685.885.681.781.790.990.385.785.5
+ +Table 3. Ablation study on DomainNet between co-training and one-direction teaching under 3-shot settings. + +![](images/dbe488371fa09397e48f84bcbedae63ff69e31b6716fd692fee73f92a3fd4e2f.jpg) +(a) + +![](images/8e9b1244c90e4a85035fceeaadd8588edab0240787eb178c71dd63a758b227a2.jpg) +(b) +Figure 4. (a) The quality and quantity of the pseudo labels are generated by the CNN branch on DomainNet under the 3-shot setting of the $rel \rightarrow clp$ task using ResNet-34. (b) Comparison between backbone settings on DomainNet under the 3-shot setting. Displayed is the mean accuracy across all domain shift tasks. + +more restrictive 1-shot learning, the ECB method demonstrates robust performance, showing a minimum increase of $+3.1\%$ in the $rel \rightarrow clp$ task. On average, the ECB method validates a performance improvement of $+6.6\%$ in the 1-shot setting and $+7.1\%$ in the 3-shot setting. + +# 5. Analyses + +Ablation studies. A single classifier is concurrently trained with both labeled source and target data. It is thus easily dominated by the labeled source data. This imbalance prevents the classifier from using the extra-labeled target data effectively, resulting in a misalignment between the learned and true class-specific boundaries. This misalignment is called data bias. Therefore, we perform an ablation study to evaluate the effectiveness of each stage in the proposed method. The emphasis is on addressing the data bias issue within the ViT branch, leveraging the CNN branch's capability to generate high-quality pseudo labels during the rel $\rightarrow$ clp task on DomainNet under, as illustrated in Fig. 4a. Initially, during the Supervised Training phase, we are only able to generate around 8,000 total pseudo labels. Following the integration of the FTC strategy, the total pseudo labels smoothly increase up to 14,000 with steady maintenance of 10,000 correct pseudo labels. This plays a crucial role in substantially mitigating data bias by generating numerous pseudo-labels, which improves the diversity and representativeness of the unlabeled target dataset. The final experiment is implemented to highlight that co-training is necessary for reducing the remaining gap following the FTC stage, which yields a total of 18,000 pseudo labels and 16,000 correct + +![](images/f220ef5d845e4e37316072f9a933416a52eeda881814153bfeff23ab489b85c0.jpg) +Table 4. Visualize the feature maps for the 'Cannon' and 'Bird' examples to investigate the learning behaviors of CNN and ViT with and without using the proposed method ECB. + +pseudo labels. + +Effectiveness of co-training. We further investigate a variant of ECB termed one-direction teaching on the DomainNet under the 3-shot setting. In this approach, we employ either $\mathcal{L}_{vit\rightarrow cnn}^{unl}$ or $\mathcal{L}_{cnn\rightarrow vit}^{unl}$ to generate pseudo labels for the remaining branch, while maintaining the standard configurations through the use of Supervised Training followed by FTC strategy. As depicted in Tab. 3, there is a performance drop when using one-direction teaching. Specifically, in the $vit\rightarrow cnn$ scenario, the ViT branch generates pseudo labels for the unlabeled target data to teach the CNN branch through minimizing $\mathcal{L}_{vit\rightarrow cnn}^{unl}$ . It is crucial to highlight that the ViT branch does not receive pseudo labels from the CNN branch, resulting in the CNN branch outperforming the ViT branch by $+3.3\%$ . In contrast, in the $cnn\rightarrow vit$ scenario, where $\mathcal{L}_{cnn\rightarrow vit}^{unl}$ is minimized, the average performance on the ViT branch is $+10.9\%$ more outstanding than the CNN branch. However, it is worth mentioning that the performance on the ViT branch suffers from $-1.1\%$ reduction over the $vit\rightarrow cnn$ scenario. This performance drop is attributed to the introduction of noise by the CNN branch during the learning process of the ViT branch. On the other hand, when employing $\mathcal{L}_{vit\rightarrow cnn}^{unl}$ , the CNN branch provides a significant boost in the average performance by $+15.3\%$ , highlighting the superior generalization capabilities of the ViT branch compared to the CNN branch. These scenarios try to leverage the unique strengths of CNN and ViT through the co-training strategy, showcasing the mutual exchange of knowledge between two branches and its potential for generalizing to unlabeled target data. As a result of co-training, + +![](images/f9915791bf1d75165082d6613f986ff7dd559b68e909a56bba743b1331ec18d0.jpg) +(a) + +![](images/fa3af9115c5bfcf0cbfa8d93fa6cdde09b46189d5a658f5b8a44dce9b921b456.jpg) +(b) +Figure 5. We visualize feature spaces for the $rel \to skt$ task on DomainNet in the 3-shot scenario using t-SNE [33]. Figures (a) and (b) illustrate the features obtained by CNN and ViT branches before adaptation, respectively. Figures (c) and (d) showcase the distribution changes of the CNN branch depending on the presence of the FTC strategy when implementing our ECB method. + +![](images/9775fccb92ce6112b76147e0d77ffdcc2f37f70a6ad6abe18931e6d0dbf82767.jpg) +(c) + +![](images/6f7d15e2a42a06e324c913b2f063bd27bdc7c232c0e9cebb36e3160fc34d313a.jpg) +(d) + +the average performance on the target domain of the ViT and CNN branches reaches the optimal results of $85.7\%$ and $85.5\%$ , respectively. + +Architecture analysis. We examine the effectiveness of the unique strengths of ViT and CNN over variations of architectures such as "CNN + CNN" and "ViT + ViT" on DomainNet under 3-shot settings using ResNet-34 for CNN and ViT/B-16 for ViT as shown in Fig. 4b. On average, the results show that "CNN + CNN" only achieves around $77.0\%$ due to the lack of global information when just using CNN. In addition, the introduction of ViT with the primary goal of improving performance drives the "ViT + ViT" architecture to achieve a significant increase of $+7.0\%$ compared to the "CNN + CNN" architecture. This architecture makes it possible to establish more general class-specific boundaries, yet is unfair when compared with the previous SSDA methods [20, 30, 31, 34, 36] using ResNet-34 as the backbone, and the lack of local representation is extremely important. As a result, the evidence shows that combining "CNN + ViT" with the bridge of co-training achieves the highest accuracy of about $85.5\%$ for both branches. + +Attention map visualization analysis. To demonstrate the effectiveness of our designing framework methodology, we provide the attention map visualization results by using GradCAM [32], as visualized in Tab. 4. CNN supports ViT: Before applying ECB, ViT was background-sensitive in the "Cannon" class, whereas CNN still captures the correct object. However, after applying ECB, ViT can explicitly recognize the target object and back to enhance the robustness of CNN. ViT supports CNN: In the "Bird" class before applying ECB, CNN only obtains the part of the target, while ViT can cover the whole input object. Then, CNN is complemented to focus on the object accurately by ViT using ECB. Consequently, these findings validate that both branches offer distinct expertise and enhance each other rather than one overshadowing the other. + +Feature Visualization. We present a detailed visualization of the feature space for the DomainNet dataset within the $rel \rightarrow skt$ task under the 3-shot setting. This visualization + +distinctly highlights the source domain (blue-colored) and the target domain (red-colored). Figs. 5a and 5b show the domain alignment of both the CNN and ViT branches before adaptation. In particular, Fig. 5a visualizes the feature space extracted by the CNN branch before applying ECB, reflecting a scatter that indicates weak classifier performance. In contrast, Fig. 5b displays the well-defined clusters in the ViT branch for the same unlabeled target data, which emphasizes the robustness of ViT in identifying more general class-specific boundaries compared to the CNN branch. Figs. 5c and 5d show the distribution changes of the CNN branch depending on the presence of the FTC strategy when implementing ECB. Initially, Fig. 5c indicates that the target representations overlap (highlighted with green box) when implementing ECB without the FTC strategy. On the other hand, Fig. 5d shows the well-aligned source and target domain representations with clusters to distinct separation when applying the FTC strategy, which demonstrates the effectiveness of our proposed method. + +# 6. Conclusion + +In this work, we have developed a novel method for learning CNN on ViT with ECB strategy, taking advantage of ViT and CNN. This innovative approach focuses on reducing data bias and significantly improves the precision of pseudo labels generated, which aligns between source and target domains. Our method is also fair when evaluated on the CNN branch and outperforms the previous SOTA methods on various DA benchmark datasets. + +**Discussions.** We found that identifying an optimal threshold pair $\{\tau_{vit}$ and $\tau_{cnn}\}$ was quite time-consuming. Therefore, we leave an open task for future research that uses a dynamic threshold algorithm for domain adaptation instead of the fixed threshold. + +Acknowledgement. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIT) (No. RS-2023-00214326 and No. RS-2023-00242528). + +# References + +[1] Avrim Blum and Tom Mitchell. 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+ "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 284, + 290, + 559 + ], + "spans": [ + { + "bbox": [ + 46, + 284, + 290, + 559 + ], + "type": "text", + "content": "Most domain adaptation (DA) methods are based on either a convolutional neural networks (CNNs) or a vision transformers (ViTs). They align the distribution differences between domains as encoders without considering their unique characteristics. For instance, ViT excels in accuracy due to its superior ability to capture global representations, while CNN has an advantage in capturing local representations. This fact has led us to design a hybrid method to fully take advantage of both ViT and CNN, called Explicitly Class-specific Boundaries (ECB). ECB learns CNN on ViT to combine their distinct strengths. In particular, we leverage ViT's properties to explicitly find class-specific decision boundaries by maximizing the discrepancy between the outputs of the two classifiers to detect target samples far from the source support. In contrast, the CNN encoder clusters target features based on the previously defined class-specific boundaries by minimizing the discrepancy between the probabilities of the two classifiers. Finally, ViT and CNN mutually exchange knowledge to improve the quality of pseudo labels and reduce the knowledge discrepancies of these models. Compared to conventional DA methods, our ECB achieves superior performance, which verifies its effectiveness in this hybrid model. The project website can be found here." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 570, + 128, + 582 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 570, + 128, + 582 + ], + "spans": [ + { + "bbox": [ + 47, + 570, + 128, + 582 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 590, + 288, + 697 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 590, + 288, + 697 + ], + "spans": [ + { + "bbox": [ + 46, + 590, + 288, + 697 + ], + "type": "text", + "content": "Over the past few years, convolutional neural networks (CNNs) [13] have been the cornerstone of deep learning techniques in computer vision tasks. This progress is mainly attributed to a convolution layer, which efficiently captures local spatial hierarchies for robust image representations. This local feature extraction capability has enabled CNNs to achieve State-of-the-Art (SOTA) performance in a variety of vision tasks, from image classification to object detection. 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Illustration of the proposed hybrid network architecture that leverages the strengths of ViT and CNN models." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 518, + 547, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 518, + 547, + 686 + ], + "spans": [ + { + "bbox": [ + 304, + 518, + 547, + 686 + ], + "type": "text", + "content": "what limited in capturing more global and comprehensive visual context. To overcome this limitation, vision transformer (ViT) [7] was introduced. ViT starts by dividing an image into patches, which are transformed into a sequence of tokens. Positional embeddings are incorporated into the tokens to retain the order of these patches. The model then uses transformer blocks to extract these tokens into features as image representations. Thanks to self-attention mechanisms in ViT, it is able to weigh the importance of different regions in an image irrespective of their spatial proximity, leading to comprehensive global representations with impressive accuracy. The advancements in ViT have led to a growing inclination in the machine learning realm over CNN-based approaches for a range of tasks." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 689, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 547, + 713 + ], + "type": "text", + "content": "Instead of focusing solely on replacing CNN with ViT, our approach diverges from this trend. We believe that both" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 208, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 208, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 208, + 712 + ], + "type": "text", + "content": "\\*Co-first author. \\*Corresponding author." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28545" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 396 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 396 + ], + "type": "text", + "content": "ViT and CNN architectures have their own strengths that can be harnessed when combined well. For instance, ViT has shown the capability to capture global representations and demonstrates robustness when trained on large datasets. Yet, because it is composed of multilayer perceptron (MLP) layers, ViT can overfit if the dataset is limited. On the other hand, CNNs perform well with relatively small datasets thanks to their spatial invariance and robustness in capturing local representations. Motivated by this, we propose a novel method that capitalizes on the distinct strengths of both architectures. As shown in Fig. 1, we exploit the superior accuracy of ViT in identifying more general class-specific boundaries by maximizing the discrepancy between the outputs of the two classifiers, enabling us to estimate the worst-case hyperspaces. Once these class-specific boundaries are defined, CNN minimizes the discrepancy by clustering target features closer to the source domain, aiming to minimize errors within the identified hyperspaces. However, the knowledge discrepancies between ViT and CNN still exist, so we applied additional co-training to bridge this gap while improving the quality of the pseudo labels. In the field of unsupervised domain adaptation (UDA), MCD [30] emphasizes the importance of maximizing the discrepancy between classifier outputs for target samples, which are far from the source domain's support, and then minimizing this discrepancy through a feature generator to align the target features closer to the source's support." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 403, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 403, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 403, + 289, + 715 + ], + "type": "text", + "content": "Although UDA has made significant advancements in domain adaptation (DA) tasks, the semi-supervised domain adaptation (SSDA) scenarios, as discussed in [11, 14-16, 28, 31, 34-36], are extensively employed to yield remarkable classification accuracy compared to the UDA setting [2, 4, 5, 19, 37]. This is because a model trained under UDA is only accessed to labeled source data, while a model trained with the SSDA setting benefits from the extra target information with a few labeled target samples besides labeled source data. However, the previous DA methods only take full advantage of the unique benefits of CNN as a feature extractor. Specifically, works in [12, 15, 21, 31] use a combination of a CNN encoder followed by an MLP classifier, but the decision boundary towards the source domain leads to data bias in DA. To address this bias, some previous works [27, 28, 37] introduce a multi-model by adding one more MLP classifier, which consists of a single CNN encoder and two MLP classifiers. Furthermore, the first DA approaches in [22, 34] use two CNN encoders and two MLP classifiers to boost the classification accuracy by leveraging a co-training strategy that ensures the consistency of unlabeled target data through knowledge exchange. However, these methodologies still follow the same rule, where the CNN model is selected as the encoder, and MLP is assigned as the classifier. Therefore, the capabilities of ViT in capturing global information remain unexploited. Inspired by the ideal," + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 304, + 72, + 547, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 144 + ], + "type": "text", + "content": "we make use of this multi-model architecture to build a new hybrid framework that leverages the advantages of ViT and CNN for DA settings. However, the proposed method does not require any additional complexity compared to previous works in the test phase. We summarize the contributions of this paper as follows:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 306, + 144, + 545, + 239 + ], + "type": "list", + "angle": 0, + "index": 6, + "blocks": [ + { + "bbox": [ + 306, + 144, + 545, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 144, + 545, + 179 + ], + "spans": [ + { + "bbox": [ + 306, + 144, + 545, + 179 + ], + "type": "text", + "content": "- We introduce a hybrid model that can take advantage of ViT. Beyond simply replacing CNN with ViT, we can drive the feature space of ViT to CNN." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 306, + 180, + 545, + 214 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 180, + 545, + 214 + ], + "spans": [ + { + "bbox": [ + 306, + 180, + 545, + 214 + ], + "type": "text", + "content": "- Our approach demonstrates the successful integration of ViT and CNN, making a synergy with these two powerful frameworks." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 216, + 545, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 216, + 545, + 239 + ], + "spans": [ + { + "bbox": [ + 306, + 216, + 545, + 239 + ], + "type": "text", + "content": "- The proposed method outperforms the prior works to achieve SOTA performances on DA benchmark datasets." + } + ] + } + ], + "index": 5 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 251, + 398, + 264 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 251, + 398, + 264 + ], + "spans": [ + { + "bbox": [ + 306, + 251, + 398, + 264 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 270, + 547, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 270, + 547, + 594 + ], + "spans": [ + { + "bbox": [ + 304, + 270, + 547, + 594 + ], + "type": "text", + "content": "Co-training. In the realm of semi-supervised learning (SSL), co-training is a scheme to improve the robustness, first proposed by [1], and harnesses data from dual views, enabling two models to iteratively 'teach' each other. During this process, each model alternately makes predictions on unlabeled data, with the most confident predictions used to augment the training set of the other model. This mutual teaching strategy can significantly improve the performance of both models, particularly when labeled data is scarce. In the DA context, FixBi [22], DECOTA [34], and MVCL [23] offer innovative co-training strategies. Notably, FixBi and DECOTA utilize two distinct branches, each including a feature extractor and a classifier. They utilize MIXUP augmentation to reduce the gap in multiple intermediate domains between the source and target domain during co-training. However, they miss the potential benefits of strong augmentation. In contrast, while MVCL employs both weak and strong augmentation to bolster its co-training approach, it relies on a single CNN-based encoder and two classifiers to produce two views. This limits the representation of unlabeled target data, depriving its comprehensive global information. To address these limitations, we employ the ViT in conjunction with a CNN-based encoder. This combination generates two representational views that encapsulate both local and global information. Additionally, we integrate both weak and strong augmentations for unlabeled target samples, which enhances the interactivity and effectiveness of our co-training strategy." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 594, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 548, + 714 + ], + "type": "text", + "content": "Domain Adaptation Framework. In the realm of DA, various frameworks have been presented. Early methods such as MME [31], APE [15], and SENTRY [26] adopt the conventional approach of constructing deep learning frameworks that have a feature extractor coupled with a classifier. However, source and target domains share the same decision boundary, which leads to data bias toward the source domain. To alleviate data bias, MDD [37] and UODA [27] introduce two distinct classifiers. They demonstrate that using a dual-classifier setup can improve the performance" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "text", + "content": "28546" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 68, + 547, + 241 + ], + "blocks": [ + { + "bbox": [ + 47, + 68, + 547, + 241 + ], + "lines": [ + { + "bbox": [ + 47, + 68, + 547, + 241 + ], + "spans": [ + { + "bbox": [ + 47, + 68, + 547, + 241 + ], + "type": "image", + "image_path": "98e617a6b54508ffd327993b1c332ae7c6144f4512afc623de5ffca6204ae759.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "lines": [ + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "spans": [ + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "text", + "content": "Figure 2. Illustration of a hybrid network with the proposed Finding to Conquering strategy. We use ViT to build " + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "inline_equation", + "content": "E_{1}" + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "text", + "content": " that drives two classifiers " + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "text", + "content": " to expand class-specific boundaries comprehensively. Besides, we select CNN for the second encoder " + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "text", + "content": " to cluster target features based on the boundaries identified by ViT. These encoders all use two classifiers " + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "inline_equation", + "content": "F_{1}, F_{2}" + }, + { + "bbox": [ + 46, + 249, + 547, + 283 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 298, + 290, + 608 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 298, + 290, + 608 + ], + "spans": [ + { + "bbox": [ + 46, + 298, + 290, + 608 + ], + "type": "text", + "content": "of classification tasks. These methods use a single feature extractor to train on both labeled source and target datasets. However, the source domain is more reliable than the target domain thanks to labeled source samples, which can lead the feature extractor to overly focus on source data representations. This results in a learning bias toward the source domain, accumulating errors during the training process. To solve this problem, DECOTA [34] proposes a novel architecture by decomposing two distinct branches, UDA and SSL, each consisting of a feature extractor and a single classifier. Specifically, the UDA branch is trained on labeled source data and unlabeled target data, while the SSL branch is trained on labeled and unlabeled target data. Thanks to the SSL branch, focusing solely on the target domain facilitates the alleviation of learning bias. In addition, the UDA branch is capable of mitigating learning bias by leveraging extra information from the SSL branch via the co-training strategy. Despite the notable advancements in the field, DECOTA still follows the framework of using CNN as the feature extractor. Therefore, it is impossible to completely improve the quality of pseudo labels for unlabeled target samples and exploit learning space based on the properties of ViT. As a result, the capabilities of ViT in capturing global information still need to be explored. Instead of solely replacing CNN with ViT, we propose a hybrid model that combines their strengths of both architectures." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 618, + 129, + 632 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 618, + 129, + 632 + ], + "spans": [ + { + "bbox": [ + 47, + 618, + 129, + 632 + ], + "type": "text", + "content": "3. Methodology" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 638, + 277, + 650 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 638, + 277, + 650 + ], + "spans": [ + { + "bbox": [ + 47, + 638, + 277, + 650 + ], + "type": "text", + "content": "In DA scenarios, we deal with the following data setting:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 651, + 287, + 714 + ], + "type": "list", + "angle": 0, + "index": 7, + "blocks": [ + { + "bbox": [ + 47, + 651, + 287, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 651, + 287, + 675 + ], + "spans": [ + { + "bbox": [ + 47, + 651, + 287, + 675 + ], + "type": "text", + "content": "- Labeled source domain: Denoted as " + }, + { + "bbox": [ + 47, + 651, + 287, + 675 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_S = \\{(x_i^{\\mathcal{S}},y_i^{\\mathcal{S}})\\}_{i = 1}^{\\mathcal{N}_S}" + }, + { + "bbox": [ + 47, + 651, + 287, + 675 + ], + "type": "text", + "content": " includes " + }, + { + "bbox": [ + 47, + 651, + 287, + 675 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_S" + }, + { + "bbox": [ + 47, + 651, + 287, + 675 + ], + "type": "text", + "content": " richly labeled samples." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "type": "text", + "content": "- Labeled target domain: Denoted as " + }, + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_l} = \\{(x_i^{\\mathcal{T}_l},y_i^{\\mathcal{T}_l})\\}_{i = 1}^{\\mathcal{N}_{\\mathcal{T}_l}}" + }, + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "type": "text", + "content": " includes " + }, + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_{\\mathcal{T}_l}" + }, + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "type": "text", + "content": " limited labeled target samples. Notably, " + }, + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_l}" + }, + { + "bbox": [ + 47, + 675, + 287, + 714 + ], + "type": "text", + "content": " is empty in UDA." + } + ] + } + ], + "index": 6 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 298, + 545, + 338 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 298, + 545, + 338 + ], + "spans": [ + { + "bbox": [ + 306, + 298, + 545, + 338 + ], + "type": "text", + "content": "- Unlabeled target domain: Denoted as " + }, + { + "bbox": [ + 306, + 298, + 545, + 338 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_u} = \\{(x_i^{\\mathcal{T}_u},y_i^{\\mathcal{T}_u})\\}_{i = 1}^{\\mathcal{N}_{\\mathcal{T}_u}}" + }, + { + "bbox": [ + 306, + 298, + 545, + 338 + ], + "type": "text", + "content": " includes " + }, + { + "bbox": [ + 306, + 298, + 545, + 338 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_{\\mathcal{T}_u}" + }, + { + "bbox": [ + 306, + 298, + 545, + 338 + ], + "type": "text", + "content": " target samples that do not have corresponding labels during the training phase." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "spans": [ + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": "In this setup, the sample " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "x_{i}^{S}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "x_{i}^{\\mathcal{T}_{l}}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " from the source domain and the labeled target domain are associated with corresponding ground-truth labels " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "y_{i}^{S}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "y_{i}^{\\mathcal{T}_{l}}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": ", respectively. There is an assumption that the label " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "y^{S}, y^{\\mathcal{T}_{l}}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "y^{\\mathcal{T}_{u}}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " all belong to the same label space with " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " classes. Notably, " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "y^{\\mathcal{T}_{u}}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": ", which denotes labels for the unlabeled target data, are only used during the testing phase. Furthermore, the number of labeled target samples " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_{\\mathcal{T}_l}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " is much smaller than both " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_S" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_{\\mathcal{T}_u}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": ". Moreover, we implement two varied stochastic data transformations: " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "Aug_{w}(\\cdot)" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "Aug_{str}(\\cdot)" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": ". The function " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "Aug_{w}(\\cdot)" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " is a weak augmentation method employing light perturbations such as random horizontal flipping and random cropping, whereas " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "Aug_{str}(\\cdot)" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " stands as a strong augmentation method, using RandAugment [3], which involves 14 transformation techniques. Specifically, both " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "Aug_{w}(\\cdot)" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "Aug_{str}(\\cdot)" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " are applied to the unlabeled set " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_u}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": ", transforming a sample " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "x_{i}^{\\mathcal{T}_{u}}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " to two versions " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "x_{i,w}^{\\mathcal{T}_u}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "x_{i,str}^{\\mathcal{T}_u}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": ", respectively. Subsequently, we train the model on the labeled set " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "D_{l} = D_{S}\\cup D_{\\mathcal{T}_{l}}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": " and the unlabeled set " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_u}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": ", and evaluate the trained model on " + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_u}" + }, + { + "bbox": [ + 304, + 338, + 547, + 567 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "spans": [ + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "text", + "content": "To improve the performance on " + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_u}" + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "text", + "content": ", we propose a hybrid model consisting of ViT and CNN branches. The ViT branch is made up of a ViT encoder " + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "inline_equation", + "content": "E_1(\\cdot;\\pmb{\\theta}_{E_1})" + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "text", + "content": " and a classifier " + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "inline_equation", + "content": "F_1(\\cdot;\\pmb{\\theta}_{F_1})" + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "text", + "content": ", while the CNN branch includes a CNN encoder " + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "inline_equation", + "content": "E_2(\\cdot;\\pmb{\\theta}_{E_2})" + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "text", + "content": " and a classifier " + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "inline_equation", + "content": "F_2(\\cdot;\\pmb{\\theta}_{F_2})" + }, + { + "bbox": [ + 305, + 568, + 545, + 640 + ], + "type": "text", + "content": ". Our strategy training proceeds in three steps:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 641, + 545, + 713 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 306, + 641, + 545, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 641, + 545, + 677 + ], + "spans": [ + { + "bbox": [ + 306, + 641, + 545, + 677 + ], + "type": "text", + "content": "1. Supervised Training: We train both ViT and CNN branches on " + }, + { + "bbox": [ + 306, + 641, + 545, + 677 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_l" + }, + { + "bbox": [ + 306, + 641, + 545, + 677 + ], + "type": "text", + "content": " whose knowledge is adapted to the " + }, + { + "bbox": [ + 306, + 641, + 545, + 677 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_u}" + }, + { + "bbox": [ + 306, + 641, + 545, + 677 + ], + "type": "text", + "content": " as illustrated in Fig. 2." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "content": "2. Finding to Conquering: In Fig. 2, we find class-specific boundaries based on fixed " + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "inline_equation", + "content": "E_{1}" + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "content": " by maximizing discrepancy between " + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "content": ". Subsequently, the " + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "content": " clusters the" + } + ] + } + ], + "index": 12 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28547" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 59, + 72, + 287, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 72, + 287, + 95 + ], + "spans": [ + { + "bbox": [ + 59, + 72, + 287, + 95 + ], + "type": "text", + "content": "target features based on those class-specific boundaries by minimizing discrepancy." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "spans": [ + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "type": "text", + "content": "3. Co-training: To exchange effectively knowledge between two branches on " + }, + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathcal{T}_u}" + }, + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "type": "text", + "content": ", the ViT branch generates a pseudo label for weakly version " + }, + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "type": "inline_equation", + "content": "x_{i,w}^{\\mathcal{T}_u}" + }, + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "type": "text", + "content": " to teach the CNN branch with strongly version " + }, + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "type": "inline_equation", + "content": "x_{i,str}^{\\mathcal{T}_u}" + }, + { + "bbox": [ + 47, + 96, + 287, + 159 + ], + "type": "text", + "content": ". Then, the reverse process is also applied as depicted in Fig. 3." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 165, + 165, + 178 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 165, + 165, + 178 + ], + "spans": [ + { + "bbox": [ + 47, + 165, + 165, + 178 + ], + "type": "text", + "content": "3.1. Supervised Training" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 182, + 288, + 231 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 182, + 288, + 231 + ], + "spans": [ + { + "bbox": [ + 47, + 182, + 288, + 231 + ], + "type": "text", + "content": "In this phase, we employ the standard cross-entropy loss to train a model's two branches: ViT branch and CNN branch. In the ViT branch, we aim to minimize the empirical loss of labeled data, which is defined as follows:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 82, + 236, + 287, + 269 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 82, + 236, + 287, + 269 + ], + "spans": [ + { + "bbox": [ + 82, + 236, + 287, + 269 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {v i t} ^ {s u p} \\left(\\boldsymbol {\\theta} _ {E _ {1}}, \\boldsymbol {\\theta} _ {F _ {1}}\\right) = \\frac {1}{\\mathcal {N} _ {l}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {l}} H \\left(y _ {i} ^ {l}, p _ {1} ^ {l} \\left(x _ {i} ^ {l}\\right)\\right), \\tag {1}", + "image_path": "1c90572e4aa25229488beb74e8a46da520f58f61c36bb576ca8b826ce4552969.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "spans": [ + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "H(\\cdot)" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": " denotes the standard cross-entropy loss. When " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "p_1^l (x_i^l) = \\sigma (F_1(E_1(x_i^l)))" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": " represents the softmax function, which transforms the logits into probabilities across " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": " categories. Initially, ViT encoder " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "E_{1}" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": " maps the labeled sample " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "x_{i}^{l}" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": " into a " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": "-dimensional feature space. The classifier " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": " then categorizes the input feature space " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "E_{1}(x_{i}^{l})" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": " into the logits. Finally, we minimize the cross-entropy loss between the predicted labeled probability by " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "p_1^l (x_i^l)" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": " and the provided ground-truth label " + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "inline_equation", + "content": "y_{i}^{l}" + }, + { + "bbox": [ + 47, + 275, + 288, + 393 + ], + "type": "text", + "content": ", ensuring accurate predictions on labeled data." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 394, + 287, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 394, + 287, + 418 + ], + "spans": [ + { + "bbox": [ + 47, + 394, + 287, + 418 + ], + "type": "text", + "content": "Similarly, the CNN branch is also trained using labeled data to minimize the empirical loss as follows:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 82, + 425, + 287, + 458 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 82, + 425, + 287, + 458 + ], + "spans": [ + { + "bbox": [ + 82, + 425, + 287, + 458 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {c n n} ^ {s u p} \\left(\\boldsymbol {\\theta} _ {E _ {2}}, \\boldsymbol {\\theta} _ {F _ {2}}\\right) = \\frac {1}{\\mathcal {N} _ {l}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {l}} H \\left(y _ {i} ^ {l}, p _ {2} ^ {l} \\left(x _ {i} ^ {l}\\right)\\right), \\tag {2}", + "image_path": "5edc9cb20011411136c74464db8809eb2f29558d69deed7745c086645a67df9b.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "spans": [ + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "inline_equation", + "content": "p_2^l (x_i^l) = \\sigma (F_2(E_2(x_i^l)))" + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": " is obtained by extracting features from the labeled sample " + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "inline_equation", + "content": "x_{i}^{l}" + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": " using the CNN encoder " + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": ". These features are then mapped to logits through the classifier " + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": ". Finally, the softmax function " + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": " transforms these logits into probabilities across " + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": " categories. The main goal of this process is to minimize the cross-entropy loss to ensure a close alignment between the predicted probabilities " + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "inline_equation", + "content": "p_2^l (x_i^l)" + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": " and the ground-truth labels " + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "inline_equation", + "content": "y_{i}^{l}" + }, + { + "bbox": [ + 47, + 464, + 287, + 561 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 567, + 177, + 580 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 567, + 177, + 580 + ], + "spans": [ + { + "bbox": [ + 47, + 567, + 177, + 580 + ], + "type": "text", + "content": "3.2. Finding to Conquering" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "spans": [ + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "text", + "content": "Discrepancy Loss Definition. In this work, we use the absolute difference between the probabilistic outputs " + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "inline_equation", + "content": "\\mathbf{a}" + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "inline_equation", + "content": "\\mathbf{b}" + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "text", + "content": " from two distinct classifiers " + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 47, + 585, + 287, + 644 + ], + "type": "text", + "content": ", respectively, for each class to guarantee that the discrepancy loss is always non-negative as follows:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 110, + 651, + 287, + 684 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 110, + 651, + 287, + 684 + ], + "spans": [ + { + "bbox": [ + 110, + 651, + 287, + 684 + ], + "type": "interline_equation", + "content": "d (\\mathbf {a}, \\mathbf {b}) = \\frac {1}{K} \\sum_ {k = 1} ^ {K} | a _ {k} - b _ {k} |, \\tag {3}", + "image_path": "4ae730215590e48e13eae51d777c0ab48d3d3119a027ce4be28cfd0800298dfe.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "inline_equation", + "content": "a_{k}" + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "inline_equation", + "content": "b_{k}" + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": " correspond to the probability outputs of the two classifiers for the " + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "-th class. Normalizing with the" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 72, + 547, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 179 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 179 + ], + "type": "text", + "content": "total number of categories assures that the discrepancy loss is scale-invariant and bounded between 0 and 1. The discrepancy loss serves as a measure of divergence between the probabilistic outputs of two classifiers, " + }, + { + "bbox": [ + 304, + 72, + 547, + 179 + ], + "type": "inline_equation", + "content": "\\mathbf{a}" + }, + { + "bbox": [ + 304, + 72, + 547, + 179 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 179 + ], + "type": "inline_equation", + "content": "\\mathbf{b}" + }, + { + "bbox": [ + 304, + 72, + 547, + 179 + ], + "type": "text", + "content": ". A discrepancy loss of zero indicates the perfect agreement between them across all classes. On the other hand, a higher discrepancy loss points to a more significant divergence in the two classifiers's predictions. This loss is beneficial in scenarios where we want to expand class-specific boundaries." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "spans": [ + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "type": "text", + "content": "Finding Stage. In this stage, we aim to expand the class-specific boundaries of the classifiers " + }, + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "type": "inline_equation", + "content": "(F_{1}, F_{2})" + }, + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "type": "text", + "content": " in relation to the fixed ViT encoder " + }, + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "type": "inline_equation", + "content": "E_{1}" + }, + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "type": "text", + "content": " by maximizing the discrepancy loss between their outputs. This means we have a possibility to estimate worst-case hyperspaces, which identifies target samples that fall outside the broader source distribution's support, rather than using CNN encoder " + }, + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 304, + 180, + 547, + 287 + ], + "type": "text", + "content": ". To avoid this issue, we add a supervised loss on the labeled samples as follows:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 345, + 295, + 545, + 350 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 345, + 295, + 545, + 350 + ], + "spans": [ + { + "bbox": [ + 345, + 295, + 545, + 350 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {\\text {f i n d}} \\left(\\boldsymbol {\\theta} _ {F _ {1}}, \\boldsymbol {\\theta} _ {F _ {2}}\\right) = \\mathcal {L} _ {v i t} ^ {\\sup } + \\mathcal {L} _ {c n n} ^ {\\sup } \\\\ - \\frac {1}{\\mathcal {N} _ {\\mathcal {T} _ {u}}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {\\mathcal {T} _ {u}}} d \\left(p _ {1} ^ {f i n d} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right), p _ {2} ^ {f i n d} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {4} \\\\ \\end{array}", + "image_path": "c5fbfbb534f30d8bf5b14daff297b6fb0d413c5bb1c7d2dfb79515b02b647d6d.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "spans": [ + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "inline_equation", + "content": "p_1^{find}(x_i^{\\mathcal{T}_u}) = \\sigma (F_1(E_1(x_i^{\\mathcal{T}_u})))" + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "inline_equation", + "content": "p_2^{find}(x_i^{\\mathcal{T}_u}) = \\sigma (F_2(E_1(x_i^{\\mathcal{T}_u})))" + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "text", + "content": " denote the probability outputs of " + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "text", + "content": " with ViT encoder " + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "inline_equation", + "content": "E_{1}" + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "text", + "content": " on the unlabeled target data " + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "inline_equation", + "content": "x_{i}^{\\mathcal{T}_{u}}" + }, + { + "bbox": [ + 304, + 355, + 547, + 503 + ], + "type": "text", + "content": ", respectively. By integrating the supervised loss on the labeled samples, we ensure that the classifiers not only distinguish different classes, but also push to deviate as far as possible from the currently learned class-specific boundaries while all labeled samples are correctly distinguished. In essence, the Finding Stage is a delicate balance between maximizing the discrepancy to explore the class-specific boundaries and minimizing the supervised loss to maintain classification accuracy." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "spans": [ + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "content": "Conquering Stage. In this stage, we leverage the class-specific boundaries established by the ViT encoder " + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "inline_equation", + "content": "E_{1}" + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "content": " as a reference to guide the optimization of the CNN encoder " + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "content": ", while keeping the classifiers " + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "content": " fixed. The primary is to minimize the discrepancy between the outputs of two classifiers, " + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "content": ", allowing the features extracted by CNN encoder " + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 304, + 504, + 547, + 598 + ], + "type": "text", + "content": " to be accurately classified. The objective function is formulated as follows:" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 312, + 607, + 545, + 640 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 607, + 545, + 640 + ], + "spans": [ + { + "bbox": [ + 312, + 607, + 545, + 640 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {c o n q}} \\left(\\boldsymbol {\\theta} _ {E _ {2}}\\right) = \\frac {1}{\\mathcal {N} \\tau_ {u}} \\sum_ {i = 1} ^ {\\mathcal {N} \\tau_ {u}} d \\left(p _ {1} ^ {\\text {c o n q}} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right), p _ {2} ^ {\\text {c o n q}} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {5}", + "image_path": "a74b84db8ec4edc69591147e759c2af287ec74d0bf934bc1e4c60671a3a8d6e0.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "inline_equation", + "content": "p_1^{conq}(x_i^{\\mathcal{T}_u}) = \\sigma (F_1(E_2(x_i^{\\mathcal{T}_u})))" + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "inline_equation", + "content": "p_2^{conq}(x_i^{\\mathcal{T}_u}) = \\sigma (F_2(E_2(x_i^{\\mathcal{T}_u})))" + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "content": " denote the probability outputs of " + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "content": " with CNN encoder " + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "content": " on the unlabeled target data, " + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "inline_equation", + "content": "x_{i}^{\\mathcal{T}_{u}}" + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "content": ". By focusing on minimizing the discrepancy loss, the features extracted by the CNN encoder " + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 304, + 649, + 547, + 713 + ], + "type": "text", + "content": " are clustered on the" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28548" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 69, + 286, + 175 + ], + "blocks": [ + { + "bbox": [ + 50, + 69, + 286, + 175 + ], + "lines": [ + { + "bbox": [ + 50, + 69, + 286, + 175 + ], + "spans": [ + { + "bbox": [ + 50, + 69, + 286, + 175 + ], + "type": "image", + "image_path": "bebe0027db065a274d31abf4c7dadd9872c4e54a60bfd95af0b44a805c5052ca.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 86, + 182, + 247, + 194 + ], + "lines": [ + { + "bbox": [ + 86, + 182, + 247, + 194 + ], + "spans": [ + { + "bbox": [ + 86, + 182, + 247, + 194 + ], + "type": "text", + "content": "Figure 3. Illustration of co-training strategy." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 205, + 288, + 266 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 205, + 288, + 266 + ], + "spans": [ + { + "bbox": [ + 46, + 205, + 288, + 266 + ], + "type": "text", + "content": "class-specific boundaries of the ViT encoder " + }, + { + "bbox": [ + 46, + 205, + 288, + 266 + ], + "type": "inline_equation", + "content": "E_{1}" + }, + { + "bbox": [ + 46, + 205, + 288, + 266 + ], + "type": "text", + "content": ", even when estimating the worst-case hyperspaces. This alignment is crucial as it guarantees that the unlabeled samples are not only correctly classified but also robust to variations in the class-specific boundaries." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 274, + 126, + 287 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 274, + 126, + 287 + ], + "spans": [ + { + "bbox": [ + 47, + 274, + 126, + 287 + ], + "type": "text", + "content": "3.3. Co-training" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 293, + 289, + 435 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 293, + 289, + 435 + ], + "spans": [ + { + "bbox": [ + 46, + 293, + 289, + 435 + ], + "type": "text", + "content": "Following the Finding-to-Conquering (FTC) strategy, we recognize a significant gap in the knowledge discrepancy between the ViT and CNN branches that needs to be minimized for the optimal performance. To resolve this, we have adopted a co-training strategy with dual objectives as illustrated in Fig. 3. The first objective focuses on reducing the gap between the two branches by enabling mutual enhancement and leveraging each branch's strength to improve the quality of pseudo labels. The second objective is to specifically improve the performance of the CNN branch, thanks to the potential to capture complex patterns and relationships in the data of the ViT branch." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 437, + 288, + 486 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 288, + 486 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 288, + 486 + ], + "type": "text", + "content": "Initially, we employ pseudo labels generated by the ViT branch to teach the learning process of the CNN branch. This is achieved by setting a fixed threshold, denoted as " + }, + { + "bbox": [ + 46, + 437, + 288, + 486 + ], + "type": "inline_equation", + "content": "\\tau_{vit}" + }, + { + "bbox": [ + 46, + 437, + 288, + 486 + ], + "type": "text", + "content": ", and applying it as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 118, + 494, + 215, + 510 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 118, + 494, + 215, + 510 + ], + "spans": [ + { + "bbox": [ + 118, + 494, + 215, + 510 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {v i t \\rightarrow c n n} ^ {u n l} (\\boldsymbol {\\theta} _ {E _ {2}}, \\boldsymbol {\\theta} _ {F _ {2}}) =", + "image_path": "bcdb3d0edcbb8a2e787cdcf6d54eaeeb6209763c46915e9090a7718218afaf83.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 70, + 517, + 287, + 552 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 70, + 517, + 287, + 552 + ], + "spans": [ + { + "bbox": [ + 70, + 517, + 287, + 552 + ], + "type": "interline_equation", + "content": "\\frac {1}{\\mathcal {N} \\tau_ {u}} \\sum_ {i = 1} ^ {\\mathcal {N} \\tau_ {u}} \\mathbb {1} \\left[ \\max \\left(\\mathbf {q} _ {i} ^ {v}\\right) \\geq \\tau_ {v i t} \\right] H \\left(\\hat {q} _ {i} ^ {v}, p ^ {c} \\left(x _ {i, s t r} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {6}", + "image_path": "975f7a3b784c70e4a19040555d566e0ebc3d132b06cb3903371373738d4d5224.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\mathbb{1}[\\cdot ]" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " is the binary indicator, returning 1 if the condition inside " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "[\\cdot ]" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " is satisfied, and 0 otherwise. In this context, " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{q}_i^v = \\sigma (F_1(E_1(x_{i,w}^{T_u})))" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " indicates the ViT branch's prediction for a weakly augmented version of an unlabeled target sample. Then, the highest prediction, exceeding the fixed threshold " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\tau_{vit}" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": ", is converted into pseudo label " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\hat{q}_i^v = \\mathrm{argmax}(\\mathbf{q}_i^v)" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": ". Finally, the output prediction " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "p^c (x_{i,str}^{T_u}) = \\sigma (F_2(E_2(x_{i,str}^{T_u})))" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " of the CNN branch on the strongly augmented target sample is adjusted to closely align with the pseudo label " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\hat{q}_i^v" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " using the cross-entropy loss. This process ensures that the CNN branch effectively learns from the ViT branch's predictions, making the consistency and alignment between the two branches better." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 547, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 120 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 120 + ], + "type": "text", + "content": "Similarly, we also leverage the pseudo labels from the CNN branch to guide the learning process of the ViT branch. This is achieved by setting another fixed threshold, denoted as " + }, + { + "bbox": [ + 304, + 72, + 547, + 120 + ], + "type": "inline_equation", + "content": "\\tau_{cnn}" + }, + { + "bbox": [ + 304, + 72, + 547, + 120 + ], + "type": "text", + "content": ", and using it as follows:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 378, + 128, + 473, + 144 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 378, + 128, + 473, + 144 + ], + "spans": [ + { + "bbox": [ + 378, + 128, + 473, + 144 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {c n n \\rightarrow v i t} ^ {u n l} \\left(\\boldsymbol {\\theta} _ {E _ {1}}, \\boldsymbol {\\theta} _ {F _ {1}}\\right) =", + "image_path": "72a773b5c6ae08bb6931928bc17ac360baf23cffe4accb49e799ffe39e6f248f.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 328, + 151, + 546, + 185 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 328, + 151, + 546, + 185 + ], + "spans": [ + { + "bbox": [ + 328, + 151, + 546, + 185 + ], + "type": "interline_equation", + "content": "\\frac {1}{\\mathcal {N} _ {\\tau_ {u}}} \\sum_ {i = 1} ^ {\\mathcal {N} _ {\\tau_ {u}}} \\mathbb {1} \\left[ \\max \\left(\\mathbf {q} _ {i} ^ {c}\\right) \\geq \\tau_ {c n n} \\right] H \\left(\\hat {q} _ {i} ^ {c}, p ^ {v} \\left(x _ {i, s t r} ^ {\\mathcal {T} _ {u}}\\right)\\right), \\tag {7}", + "image_path": "e3f55edfbc334264de04218a50ccda4df3b40d401f729239e89c42378a8f4a13.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "spans": [ + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "inline_equation", + "content": "\\mathbf{q}_i^c = \\sigma (F_2(E_2(x_{i,w}^{\\mathcal{T}_u})))" + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "text", + "content": " is the CNN branch's prediction for a weakly augmented target sample. The pseudo label " + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "inline_equation", + "content": "\\hat{q}_i^c" + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "text", + "content": " is generated from the highest predictions of the CNN branch that is higher than the threshold " + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "inline_equation", + "content": "\\tau_{\\text{conn}}" + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "text", + "content": ". Meanwhile, " + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "inline_equation", + "content": "p^v (x_{i,\\text{str}}^{\\mathcal{T}_u}) = \\sigma (F_1(E_1(x_{i,\\text{str}}^{\\mathcal{T}_u})))" + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "text", + "content": " indicates the output prediction of the ViT branch on the strongly augmented target sample and is adjusted to closely align with the pseudo label " + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "inline_equation", + "content": "\\hat{q}_i^c" + }, + { + "bbox": [ + 304, + 192, + 547, + 313 + ], + "type": "text", + "content": ", using the cross-entropy loss. Through the co-training process, we enhance the model's ability to generalize and perform accurately on unlabeled target data." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 321, + 392, + 334 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 321, + 392, + 334 + ], + "spans": [ + { + "bbox": [ + 305, + 321, + 392, + 334 + ], + "type": "text", + "content": "3.4. Testing Phase" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 340, + 547, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 340, + 547, + 387 + ], + "spans": [ + { + "bbox": [ + 304, + 340, + 547, + 387 + ], + "type": "text", + "content": "For a fair comparison with the previous DA methods [12, 16, 26, 31, 36], we select the CNN encoder " + }, + { + "bbox": [ + 304, + 340, + 547, + 387 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 304, + 340, + 547, + 387 + ], + "type": "text", + "content": " associated with its classifier " + }, + { + "bbox": [ + 304, + 340, + 547, + 387 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 304, + 340, + 547, + 387 + ], + "type": "text", + "content": " in the testing phase as illustrated in Fig. 2 as follows:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 359, + 396, + 546, + 412 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 359, + 396, + 546, + 412 + ], + "spans": [ + { + "bbox": [ + 359, + 396, + 546, + 412 + ], + "type": "interline_equation", + "content": "\\hat {y} _ {i} ^ {\\mathcal {T} _ {u}} = \\operatorname {a r g m a x} \\left(F _ {2} \\left(E _ {2} \\left(x _ {i} ^ {\\mathcal {T} _ {u}}\\right)\\right)\\right), \\tag {8}", + "image_path": "34ff243b0ae5e3cfd8c0bf8776b750514eeb15a8a228da58d28c3accb7102baa.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 422, + 542, + 436 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 422, + 542, + 436 + ], + "spans": [ + { + "bbox": [ + 305, + 422, + 542, + 436 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 422, + 542, + 436 + ], + "type": "inline_equation", + "content": "\\hat{y}_i^{\\mathcal{T}_u}" + }, + { + "bbox": [ + 305, + 422, + 542, + 436 + ], + "type": "text", + "content": " is the predicted class of unlabeled target sample." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 447, + 388, + 460 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 447, + 388, + 460 + ], + "spans": [ + { + "bbox": [ + 305, + 447, + 388, + 460 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 467, + 413, + 480 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 467, + 413, + 480 + ], + "spans": [ + { + "bbox": [ + 305, + 467, + 413, + 480 + ], + "type": "text", + "content": "4.1. Experiment Setup" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "spans": [ + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "text", + "content": "Datasets. We conduct extensive evaluations on standard DA benchmark datasets: Office-Home [29] and DomainNet [25]. On Office-Home dataset, we perform experiments on all possible combinations of these 4 domains: Real " + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "inline_equation", + "content": "(R)" + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "text", + "content": ", Clipart " + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "inline_equation", + "content": "(C)" + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "text", + "content": ", Art " + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "inline_equation", + "content": "(A)" + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "text", + "content": ", and Product " + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "inline_equation", + "content": "(P)" + }, + { + "bbox": [ + 304, + 485, + 547, + 604 + ], + "type": "text", + "content": " with 65 categories. Consistent with prior SSDA methods [11, 16, 17, 31, 36], we conduct an evaluation on a subset of DomainNet that includes 126 categories in 4 domains: Real (rel), Clipart (clp), Painting (pnt), and Sketch (skt) using 7 different mixtures of these domains." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "content": "Implementation Details. We use the ViT/B-16 [7] for the ViT encoder " + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "inline_equation", + "content": "E_{1}" + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "content": ", while the ResNet [10] is adopted for the CNN encoder " + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "inline_equation", + "content": "E_{2}" + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "content": ". For UDA, we used ResNet-50 as the backbone network following previous works [2, 12, 30, 37]. Similarly, we follow the evaluation protocol of previous SSDA methods [9, 17, 28, 31], ResNet-34 is applied for this scenario on the DomainNet dataset. Each model is initially pre-trained on the ImageNet-1K [6]. Given the disparate nature of the backbone architectures, we will have" + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "28549" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 70, + 545, + 225 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 545, + 225 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 545, + 225 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 545, + 225 + ], + "type": "table", + "html": "
MethodA→CA→PA→RC→AC→PC→RP→AP→CP→RR→AR→CR→PMean
DANN [8]45.659.370.147.058.560.946.143.768.563.251.876.857.6
MCD [30]48.968.374.661.367.668.857.047.175.169.152.279.664.1
BNM [4]52.373.980.063.372.974.961.749.579.770.553.682.267.9
MDD [37]54.973.777.860.071.471.861.253.678.172.560.282.368.1
MCC [12]55.175.279.563.373.275.866.152.176.973.858.483.669.4
GVB [5]57.074.779.864.674.174.665.255.181.074.659.784.370.4
DCAN [18]54.575.781.267.474.076.367.452.780.674.159.183.570.5
DALN [2]57.879.982.066.376.277.266.755.581.373.560.485.371.8
FixBi [22]58.177.380.467.779.578.165.857.981.776.462.986.772.7
DCAN+SCDA [19]60.776.482.869.877.578.468.959.082.774.961.884.573.1
ATDOC [20]60.277.882.268.578.677.968.458.483.174.861.587.273.2
EIDCo [38]63.880.882.671.580.180.972.161.384.578.665.887.175.8
ECB (CNN)68.585.488.379.286.889.079.366.488.581.071.190.481.2
", + "image_path": "6ad271db001d9393b995119ba197cda77dc7f5cf757afbccb3d093d65fbeb430.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 49, + 260, + 545, + 434 + ], + "blocks": [ + { + "bbox": [ + 47, + 230, + 546, + 253 + ], + "lines": [ + { + "bbox": [ + 47, + 230, + 546, + 253 + ], + "spans": [ + { + "bbox": [ + 47, + 230, + 546, + 253 + ], + "type": "text", + "content": "Table 1. Accuracy (%) on Office-Home of UDA methods across different domain shifts. ECB (CNN) represents the performance of our method when applied to ResNet-50. The top and second-best accuracy results are highlighted in bold and underline for easy identification." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 49, + 260, + 545, + 434 + ], + "lines": [ + { + "bbox": [ + 49, + 260, + 545, + 434 + ], + "spans": [ + { + "bbox": [ + 49, + 260, + 545, + 434 + ], + "type": "table", + "html": "
Methodrel→clprel→pntpnt→clpclp→sktskt→pntrel→sktpnt→relMean
1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot1-shot3-shot
ENT [9]65.271.065.969.265.471.154.660.059.762.152.161.175.078.662.667.6
MME [31]70.072.267.769.769.071.756.361.864.866.861.061.976.178.566.468.9
S3D [35]73.375.968.972.173.475.160.864.468.270.065.166.779.580.369.972.1
ATDOC [20]74.976.971.372.572.874.265.666.768.770.865.264.681.281.271.472.4
MAP-F [24]75.377.074.075.074.377.065.869.573.073.367.569.281.783.373.174.9
DECOTA [34]79.180.474.975.276.978.765.168.672.072.769.771.979.681.573.975.6
CDAC [16]77.479.674.275.175.579.367.669.971.073.469.272.580.481.973.676.0
ASDA [28]77.079.475.476.775.578.366.570.272.174.270.972.179.782.373.976.2
CDAC+SLA [36]79.881.675.676.077.480.368.171.371.773.571.773.580.482.575.076.9
ProML [11]78.580.275.476.577.878.970.272.074.175.472.473.584.084.876.177.4
MVCL [23]78.879.876.077.478.080.370.873.075.176.772.474.482.485.176.278.1
G-ABC [17]80.782.176.876.779.381.672.073.775.076.373.274.383.483.977.278.4
ECB (CNN)83.887.485.485.686.487.379.780.683.485.679.581.788.790.383.885.5
", + "image_path": "bb0591ceff40de3ea7314d8af54db79e55d8066b0c24f2c2a43937cc83022609.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 96, + 437, + 496, + 449 + ], + "lines": [ + { + "bbox": [ + 96, + 437, + 496, + 449 + ], + "spans": [ + { + "bbox": [ + 96, + 437, + 496, + 449 + ], + "type": "text", + "content": "Table 2. Accuracy (%) on DomainNet of SSDA methods in both 1-shot and 3-shot settings using ResNet-34." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "spans": [ + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": "two different classifiers, " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "F_{2}" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": ", consisting of two fully-connected layers followed by the softmax function. We optimize our models using stochastic gradient descent with a 0.9 momentum and 0.0005 weight decay. Considering the different architectures of the ViT and the CNN branches, we set the initial learning rates for ViT and CNN at " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "1e - 4" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "1e - 3" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": ", respectively. The size of the mini-batch is set to 32 for both " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_l" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\tau_u}" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": ". The confidence threshold values for pseudo-label selection are set to " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "\\tau_{vit} = 0.6" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "\\tau_{cnn} = 0.9" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": ". The warmup phase for both branches on " + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_l" + }, + { + "bbox": [ + 46, + 454, + 289, + 610 + ], + "type": "text", + "content": " is finetuned for 100,000 iterations. Then, we update the learning rate scheduler and proceed with 50,000 iterations of training for our method." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 621, + 165, + 635 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 621, + 165, + 635 + ], + "spans": [ + { + "bbox": [ + 47, + 621, + 165, + 635 + ], + "type": "text", + "content": "4.2. Comparison Results" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 641, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 288, + 713 + ], + "type": "text", + "content": "We evaluate our ECB method and the previous SOTA methods on Office-Home and DomainNet under UDA and SSDA settings, respectively. For a fair comparison with other DA methods, we rely on classification outcomes from the CNN branch, employing ResNet-50 as the backbone for UDA and ResNet-34 for SSDA. As a result, our method does not" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 454, + 547, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 454, + 547, + 491 + ], + "spans": [ + { + "bbox": [ + 304, + 454, + 547, + 491 + ], + "type": "text", + "content": "add any testing complexity compared to previous DA approaches. Besides, we have included further details about the experimental results in Supplementary Materials." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "spans": [ + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": "Results on Office-Home under UDA setting. The implementation of our ECB method has significantly boosted classification efficiency in all domain shift tasks, consistently outperforming the comparison methods, as detailed in Tab. 1. Remarkably, our approach has recorded accuracy enhancements of " + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "inline_equation", + "content": "+7.7\\%" + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "inline_equation", + "content": "+8.1\\%" + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "inline_equation", + "content": "+7.2\\%" + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": " for the " + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "inline_equation", + "content": "C \\rightarrow A" + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "inline_equation", + "content": "C \\rightarrow R" + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "inline_equation", + "content": "P \\rightarrow A" + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": " tasks, respectively, surpassing the results of the second-best. In addition, our method has achieved an impressive average classification accuracy of " + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "inline_equation", + "content": "81.2\\%" + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": ", showing a remarkable margin of " + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "inline_equation", + "content": "+5.4\\%" + }, + { + "bbox": [ + 304, + 494, + 548, + 625 + ], + "type": "text", + "content": " over the nearest-competitor EIDCo [38]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": "Results on DomainNet under SSDA setting. The results on the DomainNet dataset are presented for both 1-shot and 3-shot settings in Tab. 2, where the CNN branch of our ECB method outperforms all prior methods. In comparison to the nearest-competitor method, G-ABC [17], the ECB (CNN) achieves an impressive maximum performance increase of " + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "inline_equation", + "content": "+9.3\\%" + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": " in the " + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "inline_equation", + "content": "skt \\rightarrow pnt" + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": " task for 3-shot learning. Even in the" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "28550" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 71, + 545, + 156 + ], + "blocks": [ + { + "bbox": [ + 48, + 71, + 545, + 156 + ], + "lines": [ + { + "bbox": [ + 48, + 71, + 545, + 156 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 545, + 156 + ], + "type": "table", + "html": "
Methodrel→clprel→pntpnt→clpclp→sktskt→pntrel→sktpnt→relMean
ViTCNNViTCNNViTCNNViTCNNViTCNNViTCNNViTCNNViTCNN
vit→cnn73.379.078.881.075.179.271.674.778.680.867.272.088.188.876.179.4
cnn→vit74.261.976.866.876.167.469.557.274.964.667.454.886.076.175.064.1
co-training87.487.485.885.687.387.380.780.685.885.681.781.790.990.385.785.5
", + "image_path": "98be8bd78d48a33e43ae512d8c4539935510be09b552906995f420a117aacc4f.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 96, + 163, + 496, + 175 + ], + "lines": [ + { + "bbox": [ + 96, + 163, + 496, + 175 + ], + "spans": [ + { + "bbox": [ + 96, + 163, + 496, + 175 + ], + "type": "text", + "content": "Table 3. Ablation study on DomainNet between co-training and one-direction teaching under 3-shot settings." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 49, + 186, + 165, + 273 + ], + "blocks": [ + { + "bbox": [ + 49, + 186, + 165, + 273 + ], + "lines": [ + { + "bbox": [ + 49, + 186, + 165, + 273 + ], + "spans": [ + { + "bbox": [ + 49, + 186, + 165, + 273 + ], + "type": "image", + "image_path": "dbe488371fa09397e48f84bcbedae63ff69e31b6716fd692fee73f92a3fd4e2f.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 102, + 274, + 112, + 284 + ], + "lines": [ + { + "bbox": [ + 102, + 274, + 112, + 284 + ], + "spans": [ + { + "bbox": [ + 102, + 274, + 112, + 284 + ], + "type": "text", + "content": "(a)" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 168, + 186, + 282, + 273 + ], + "blocks": [ + { + "bbox": [ + 168, + 186, + 282, + 273 + ], + "lines": [ + { + "bbox": [ + 168, + 186, + 282, + 273 + ], + "spans": [ + { + "bbox": [ + 168, + 186, + 282, + 273 + ], + "type": "image", + "image_path": "8e9b1244c90e4a85035fceeaadd8588edab0240787eb178c71dd63a758b227a2.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 220, + 274, + 230, + 284 + ], + "lines": [ + { + "bbox": [ + 220, + 274, + 230, + 284 + ], + "spans": [ + { + "bbox": [ + 220, + 274, + 230, + 284 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 289, + 288, + 344 + ], + "lines": [ + { + "bbox": [ + 46, + 289, + 288, + 344 + ], + "spans": [ + { + "bbox": [ + 46, + 289, + 288, + 344 + ], + "type": "text", + "content": "Figure 4. (a) The quality and quantity of the pseudo labels are generated by the CNN branch on DomainNet under the 3-shot setting of the " + }, + { + "bbox": [ + 46, + 289, + 288, + 344 + ], + "type": "inline_equation", + "content": "rel \\rightarrow clp" + }, + { + "bbox": [ + 46, + 289, + 288, + 344 + ], + "type": "text", + "content": " task using ResNet-34. (b) Comparison between backbone settings on DomainNet under the 3-shot setting. Displayed is the mean accuracy across all domain shift tasks." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "spans": [ + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "text", + "content": "more restrictive 1-shot learning, the ECB method demonstrates robust performance, showing a minimum increase of " + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "inline_equation", + "content": "+3.1\\%" + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "text", + "content": " in the " + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "inline_equation", + "content": "rel \\rightarrow clp" + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "text", + "content": " task. On average, the ECB method validates a performance improvement of " + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "inline_equation", + "content": "+6.6\\%" + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "text", + "content": " in the 1-shot setting and " + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "inline_equation", + "content": "+7.1\\%" + }, + { + "bbox": [ + 45, + 348, + 288, + 408 + ], + "type": "text", + "content": " in the 3-shot setting." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 418, + 108, + 431 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 418, + 108, + 431 + ], + "spans": [ + { + "bbox": [ + 46, + 418, + 108, + 431 + ], + "type": "text", + "content": "5. Analyses" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 45, + 437, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 437, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 45, + 437, + 289, + 715 + ], + "type": "text", + "content": "Ablation studies. A single classifier is concurrently trained with both labeled source and target data. It is thus easily dominated by the labeled source data. This imbalance prevents the classifier from using the extra-labeled target data effectively, resulting in a misalignment between the learned and true class-specific boundaries. This misalignment is called data bias. Therefore, we perform an ablation study to evaluate the effectiveness of each stage in the proposed method. The emphasis is on addressing the data bias issue within the ViT branch, leveraging the CNN branch's capability to generate high-quality pseudo labels during the rel " + }, + { + "bbox": [ + 45, + 437, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 45, + 437, + 289, + 715 + ], + "type": "text", + "content": " clp task on DomainNet under, as illustrated in Fig. 4a. Initially, during the Supervised Training phase, we are only able to generate around 8,000 total pseudo labels. Following the integration of the FTC strategy, the total pseudo labels smoothly increase up to 14,000 with steady maintenance of 10,000 correct pseudo labels. This plays a crucial role in substantially mitigating data bias by generating numerous pseudo-labels, which improves the diversity and representativeness of the unlabeled target dataset. The final experiment is implemented to highlight that co-training is necessary for reducing the remaining gap following the FTC stage, which yields a total of 18,000 pseudo labels and 16,000 correct" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 307, + 185, + 545, + 296 + ], + "blocks": [ + { + "bbox": [ + 307, + 185, + 545, + 296 + ], + "lines": [ + { + "bbox": [ + 307, + 185, + 545, + 296 + ], + "spans": [ + { + "bbox": [ + 307, + 185, + 545, + 296 + ], + "type": "image", + "image_path": "f220ef5d845e4e37316072f9a933416a52eeda881814153bfeff23ab489b85c0.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 304, + 547, + 338 + ], + "lines": [ + { + "bbox": [ + 305, + 304, + 547, + 338 + ], + "spans": [ + { + "bbox": [ + 305, + 304, + 547, + 338 + ], + "type": "text", + "content": "Table 4. Visualize the feature maps for the 'Cannon' and 'Bird' examples to investigate the learning behaviors of CNN and ViT with and without using the proposed method ECB." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 352, + 365, + 363 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 352, + 365, + 363 + ], + "spans": [ + { + "bbox": [ + 306, + 352, + 365, + 363 + ], + "type": "text", + "content": "pseudo labels." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": "Effectiveness of co-training. We further investigate a variant of ECB termed one-direction teaching on the DomainNet under the 3-shot setting. In this approach, we employ either " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{vit\\rightarrow cnn}^{unl}" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": " or " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{cnn\\rightarrow vit}^{unl}" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": " to generate pseudo labels for the remaining branch, while maintaining the standard configurations through the use of Supervised Training followed by FTC strategy. As depicted in Tab. 3, there is a performance drop when using one-direction teaching. Specifically, in the " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "vit\\rightarrow cnn" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": " scenario, the ViT branch generates pseudo labels for the unlabeled target data to teach the CNN branch through minimizing " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{vit\\rightarrow cnn}^{unl}" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": ". It is crucial to highlight that the ViT branch does not receive pseudo labels from the CNN branch, resulting in the CNN branch outperforming the ViT branch by " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "+3.3\\%" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": ". In contrast, in the " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "cnn\\rightarrow vit" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": " scenario, where " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{cnn\\rightarrow vit}^{unl}" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": " is minimized, the average performance on the ViT branch is " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "+10.9\\%" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": " more outstanding than the CNN branch. However, it is worth mentioning that the performance on the ViT branch suffers from " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "-1.1\\%" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": " reduction over the " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "vit\\rightarrow cnn" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": " scenario. This performance drop is attributed to the introduction of noise by the CNN branch during the learning process of the ViT branch. On the other hand, when employing " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{vit\\rightarrow cnn}^{unl}" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": ", the CNN branch provides a significant boost in the average performance by " + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "inline_equation", + "content": "+15.3\\%" + }, + { + "bbox": [ + 304, + 366, + 548, + 715 + ], + "type": "text", + "content": ", highlighting the superior generalization capabilities of the ViT branch compared to the CNN branch. These scenarios try to leverage the unique strengths of CNN and ViT through the co-training strategy, showcasing the mutual exchange of knowledge between two branches and its potential for generalizing to unlabeled target data. As a result of co-training," + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28551" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 70, + 166, + 182 + ], + "blocks": [ + { + "bbox": [ + 53, + 70, + 166, + 182 + ], + "lines": [ + { + "bbox": [ + 53, + 70, + 166, + 182 + ], + "spans": [ + { + "bbox": [ + 53, + 70, + 166, + 182 + ], + "type": "image", + "image_path": "f9915791bf1d75165082d6613f986ff7dd559b68e909a56bba743b1331ec18d0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 108, + 184, + 119, + 193 + ], + "lines": [ + { + "bbox": [ + 108, + 184, + 119, + 193 + ], + "spans": [ + { + "bbox": [ + 108, + 184, + 119, + 193 + ], + "type": "text", + "content": "(a)" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 173, + 70, + 287, + 182 + ], + "blocks": [ + { + "bbox": [ + 173, + 70, + 287, + 182 + ], + "lines": [ + { + "bbox": [ + 173, + 70, + 287, + 182 + ], + "spans": [ + { + "bbox": [ + 173, + 70, + 287, + 182 + ], + "type": "image", + "image_path": "fa3af9115c5bfcf0cbfa8d93fa6cdde09b46189d5a658f5b8a44dce9b921b456.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 229, + 183, + 240, + 193 + ], + "lines": [ + { + "bbox": [ + 229, + 183, + 240, + 193 + ], + "spans": [ + { + "bbox": [ + 229, + 183, + 240, + 193 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 195, + 547, + 229 + ], + "lines": [ + { + "bbox": [ + 46, + 195, + 547, + 229 + ], + "spans": [ + { + "bbox": [ + 46, + 195, + 547, + 229 + ], + "type": "text", + "content": "Figure 5. We visualize feature spaces for the " + }, + { + "bbox": [ + 46, + 195, + 547, + 229 + ], + "type": "inline_equation", + "content": "rel \\to skt" + }, + { + "bbox": [ + 46, + 195, + 547, + 229 + ], + "type": "text", + "content": " task on DomainNet in the 3-shot scenario using t-SNE [33]. Figures (a) and (b) illustrate the features obtained by CNN and ViT branches before adaptation, respectively. Figures (c) and (d) showcase the distribution changes of the CNN branch depending on the presence of the FTC strategy when implementing our ECB method." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 294, + 70, + 408, + 182 + ], + "blocks": [ + { + "bbox": [ + 294, + 70, + 408, + 182 + ], + "lines": [ + { + "bbox": [ + 294, + 70, + 408, + 182 + ], + "spans": [ + { + "bbox": [ + 294, + 70, + 408, + 182 + ], + "type": "image", + "image_path": "9775fccb92ce6112b76147e0d77ffdcc2f37f70a6ad6abe18931e6d0dbf82767.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 351, + 183, + 361, + 193 + ], + "lines": [ + { + "bbox": [ + 351, + 183, + 361, + 193 + ], + "spans": [ + { + "bbox": [ + 351, + 183, + 361, + 193 + ], + "type": "text", + "content": "(c)" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 417, + 70, + 530, + 182 + ], + "blocks": [ + { + "bbox": [ + 417, + 70, + 530, + 182 + ], + "lines": [ + { + "bbox": [ + 417, + 70, + 530, + 182 + ], + "spans": [ + { + "bbox": [ + 417, + 70, + 530, + 182 + ], + "type": "image", + "image_path": "6f7d15e2a42a06e324c913b2f063bd27bdc7c232c0e9cebb36e3160fc34d313a.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 471, + 183, + 483, + 193 + ], + "lines": [ + { + "bbox": [ + 471, + 183, + 483, + 193 + ], + "spans": [ + { + "bbox": [ + 471, + 183, + 483, + 193 + ], + "type": "text", + "content": "(d)" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 239, + 288, + 275 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 239, + 288, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 239, + 288, + 275 + ], + "type": "text", + "content": "the average performance on the target domain of the ViT and CNN branches reaches the optimal results of " + }, + { + "bbox": [ + 46, + 239, + 288, + 275 + ], + "type": "inline_equation", + "content": "85.7\\%" + }, + { + "bbox": [ + 46, + 239, + 288, + 275 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 239, + 288, + 275 + ], + "type": "inline_equation", + "content": "85.5\\%" + }, + { + "bbox": [ + 46, + 239, + 288, + 275 + ], + "type": "text", + "content": ", respectively." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "spans": [ + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "type": "text", + "content": "Architecture analysis. We examine the effectiveness of the unique strengths of ViT and CNN over variations of architectures such as \"CNN + CNN\" and \"ViT + ViT\" on DomainNet under 3-shot settings using ResNet-34 for CNN and ViT/B-16 for ViT as shown in Fig. 4b. On average, the results show that \"CNN + CNN\" only achieves around " + }, + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "type": "inline_equation", + "content": "77.0\\%" + }, + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "type": "text", + "content": " due to the lack of global information when just using CNN. In addition, the introduction of ViT with the primary goal of improving performance drives the \"ViT + ViT\" architecture to achieve a significant increase of " + }, + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "type": "inline_equation", + "content": "+7.0\\%" + }, + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "type": "text", + "content": " compared to the \"CNN + CNN\" architecture. This architecture makes it possible to establish more general class-specific boundaries, yet is unfair when compared with the previous SSDA methods [20, 30, 31, 34, 36] using ResNet-34 as the backbone, and the lack of local representation is extremely important. As a result, the evidence shows that combining \"CNN + ViT\" with the bridge of co-training achieves the highest accuracy of about " + }, + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "type": "inline_equation", + "content": "85.5\\%" + }, + { + "bbox": [ + 46, + 277, + 289, + 493 + ], + "type": "text", + "content": " for both branches." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 496, + 288, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 496, + 288, + 675 + ], + "spans": [ + { + "bbox": [ + 46, + 496, + 288, + 675 + ], + "type": "text", + "content": "Attention map visualization analysis. To demonstrate the effectiveness of our designing framework methodology, we provide the attention map visualization results by using GradCAM [32], as visualized in Tab. 4. CNN supports ViT: Before applying ECB, ViT was background-sensitive in the \"Cannon\" class, whereas CNN still captures the correct object. However, after applying ECB, ViT can explicitly recognize the target object and back to enhance the robustness of CNN. ViT supports CNN: In the \"Bird\" class before applying ECB, CNN only obtains the part of the target, while ViT can cover the whole input object. Then, CNN is complemented to focus on the object accurately by ViT using ECB. Consequently, these findings validate that both branches offer distinct expertise and enhance each other rather than one overshadowing the other." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "type": "text", + "content": "Feature Visualization. We present a detailed visualization of the feature space for the DomainNet dataset within the " + }, + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "type": "inline_equation", + "content": "rel \\rightarrow skt" + }, + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "type": "text", + "content": " task under the 3-shot setting. This visualization" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 239, + 547, + 468 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 239, + 547, + 468 + ], + "spans": [ + { + "bbox": [ + 304, + 239, + 547, + 468 + ], + "type": "text", + "content": "distinctly highlights the source domain (blue-colored) and the target domain (red-colored). Figs. 5a and 5b show the domain alignment of both the CNN and ViT branches before adaptation. In particular, Fig. 5a visualizes the feature space extracted by the CNN branch before applying ECB, reflecting a scatter that indicates weak classifier performance. In contrast, Fig. 5b displays the well-defined clusters in the ViT branch for the same unlabeled target data, which emphasizes the robustness of ViT in identifying more general class-specific boundaries compared to the CNN branch. Figs. 5c and 5d show the distribution changes of the CNN branch depending on the presence of the FTC strategy when implementing ECB. Initially, Fig. 5c indicates that the target representations overlap (highlighted with green box) when implementing ECB without the FTC strategy. On the other hand, Fig. 5d shows the well-aligned source and target domain representations with clusters to distinct separation when applying the FTC strategy, which demonstrates the effectiveness of our proposed method." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 484, + 379, + 496 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 484, + 379, + 496 + ], + "spans": [ + { + "bbox": [ + 306, + 484, + 379, + 496 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 506, + 547, + 601 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 506, + 547, + 601 + ], + "spans": [ + { + "bbox": [ + 304, + 506, + 547, + 601 + ], + "type": "text", + "content": "In this work, we have developed a novel method for learning CNN on ViT with ECB strategy, taking advantage of ViT and CNN. This innovative approach focuses on reducing data bias and significantly improves the precision of pseudo labels generated, which aligns between source and target domains. Our method is also fair when evaluated on the CNN branch and outperforms the previous SOTA methods on various DA benchmark datasets." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 604, + 547, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 604, + 547, + 662 + ], + "spans": [ + { + "bbox": [ + 304, + 604, + 547, + 662 + ], + "type": "text", + "content": "**Discussions.** We found that identifying an optimal threshold pair " + }, + { + "bbox": [ + 304, + 604, + 547, + 662 + ], + "type": "inline_equation", + "content": "\\{\\tau_{vit}" + }, + { + "bbox": [ + 304, + 604, + 547, + 662 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 604, + 547, + 662 + ], + "type": "inline_equation", + "content": "\\tau_{cnn}\\}" + }, + { + "bbox": [ + 304, + 604, + 547, + 662 + ], + "type": "text", + "content": " was quite time-consuming. Therefore, we leave an open task for future research that uses a dynamic threshold algorithm for domain adaptation instead of the fixed threshold." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 665, + 547, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 712 + ], + "type": "text", + "content": "Acknowledgement. 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Pattern Recog., 2023. 2, 5, 6, 8" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 48, + 455, + 288, + 498 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 455, + 288, + 498 + ], + "spans": [ + { + "bbox": [ + 48, + 455, + 288, + 498 + ], + "type": "text", + "content": "[37] Yuchen Zhang, Tianle Liu, Mingsheng Long, and Michael Jordan. Bridging theory and algorithm for domain adaptation. In International Conference on Machine Learning, pages 7404-7413. PMLR, 2019. 2, 5, 6" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 48, + 500, + 288, + 544 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 500, + 288, + 544 + ], + "spans": [ + { + "bbox": [ + 48, + 500, + 288, + 544 + ], + "type": "text", + "content": "[38] Yixin Zhang, Zilei Wang, Junjie Li, Jiafan Zhuang, and Zihan Lin. Towards effective instance discrimination contrastive loss for unsupervised domain adaptation. In Int. Conf. Comput. Vis., pages 11388-11399, 2023. 6" + } + ] + } + ], + "index": 10 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "28554" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_content_list.json b/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..ed23d04f3c1fa269b002a362b98df73ecd2f1ed6 --- /dev/null +++ b/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_content_list.json @@ -0,0 +1,1739 @@ +[ + { + "type": "text", + "text": "Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification", + "text_level": 1, + "bbox": [ + 209, + 130, + 759, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Zhenyu Cui $^{1}$ , Jiahuan Zhou $^{1}$ , Xun Wang $^{2}$ , Manyu Zhu $^{2}$ , Yuxin Peng $^{1*}$ $^{1}$ Wangxuan Institute of Computer Technology, Peking University $^{2}$ ByteDance Inc", + "bbox": [ + 186, + 202, + 833, + 239 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "cuizhenyu@stu.pku.edu.cn, {jiahuanzhou,pengyuxin}@pku.edu.cn, {wangxun.2,zhumanyu}@bytedance.com", + "bbox": [ + 86, + 241, + 933, + 257 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 291, + 313, + 306 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Lifelong Person Re-identification (L-ReID) aims to learn from sequentially collected data to match a person across different scenes. Once an L-ReID model is updated using new data, all historical images in the gallery are required to be re-calculated to obtain new features for testing, known as \"re-indexing\". However, it is infeasible when raw images in the gallery are unavailable due to data privacy concerns, resulting in incompatible retrieval between the query and the gallery features calculated by different models, which causes significant performance degradation. In this paper, we focus on a new task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which requires achieving effective L-ReID without re-indexing raw images in the gallery. To this end, we propose a Continual Compatible Representation $(C^2 R)$ method, which facilitates the query feature calculated by the continuously updated model to effectively retrieve the gallery feature calculated by the old model in a compatible manner. Specifically, we design a Continual Compatible Transfer (CCT) network to continuously transfer and consolidate the old gallery feature into the new feature space. Besides, a Balanced Compatible Distillation module is introduced to achieve compatibility by aligning the transferred feature space with the new feature space. Finally, a Balanced Anti-forgetting Distillation module is proposed to eliminate the accumulated forgetting of old knowledge during the continual compatible transfer. Extensive experiments on several benchmark L-ReID datasets demonstrate the effectiveness of our method against state-of-the-art methods for both RFL-ReID and L-ReID tasks. The source code of this paper is available at https://github.com/PKU-ICST-MIPL/C2R_CVPR2024.", + "bbox": [ + 76, + 321, + 473, + 792 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 820, + 209, + 835 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Person re-identification (ReID) aims to identify the same person across different areas at different times [42]. Exist", + "bbox": [ + 76, + 845, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/31e7454ba4523e21e92fc12b7ad34760216ce9b67260102ed66e121f13f3abef.jpg", + "image_caption": [ + "(a) Traditional Lifelong ReID" + ], + "image_footnote": [], + "bbox": [ + 511, + 290, + 882, + 459 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/77ab8203d07cdf1dc555afb29bf56c428c1ef8596d98b59f68a3f474663afa99.jpg", + "image_caption": [ + "(b) Re-indexing Free Lifelong ReID", + "Figure 1. Comparison between (a) the traditional Lifelong Person Re-identification (L-ReID) task and (b) the Re-indexing Free Lifelong Person Re-identification (RFL-ReID) task." + ], + "image_footnote": [], + "bbox": [ + 511, + 476, + 880, + 616 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ing methods [26, 32, 44] have made remarkable progress based on deep learning methods [37] and large-scale datasets [34, 41, 43]. However, their performance is often limited when training data are continuously collected from a series of different scenarios due to the well-known catastrophic forgetting challenge [3].", + "bbox": [ + 496, + 702, + 890, + 794 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Recently, Lifelong person ReID (L-ReID) has aroused great concerns involving acquiring knowledge from streaming data and performing well across all data [5, 18, 19, 38]. Its challenge is to balance the anti-forgetting of old knowledge with the acquisition of new knowledge. To this end, existing L-ReID methods usually adopt the exemplar replay [38] and the knowledge distillation [27] to preserve", + "bbox": [ + 496, + 795, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author.", + "bbox": [ + 94, + 886, + 223, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "16614", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/0d4017b48f613c8a0f9c711419f06cb7c736505594f06c2d4fe572d1c08a702a.jpg", + "image_caption": [ + "Figure 2. Performance Comparison between the traditional Lifelong Person Re-identification (L-ReID) task and the Re-indexing Free Lifelong Person Re-identification (RFL-ReID) task." + ], + "image_footnote": [], + "bbox": [ + 78, + 88, + 459, + 224 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "old knowledge when updating the model. The updated new model will be sequentially deployed by \"re-indexing\" [24] features of old data in the gallery. As shown in Fig. 1 (a), the old gallery features are replaced by the re-indexed gallery features to be compatible with the new model. However, massive incremental images in the gallery bring unbearable computational costs and prevent the re-indexing process [21, 39]. Besides, in the context of data privacy concerns [25], re-indexing is legally forbidden due to the impracticality of storing and re-indexing unauthorized raw images within privacy-sensitive scenarios [1, 4, 14], also known as Re-indexing Free Lifelong ReID (RFL-ReID), as shown in Fig. 1 (b). In this case, the domain gap between different datasets leads to the incompatibility between features calculated by the old and the new models. Consequently, as shown in Fig. 2, the performance of existing methods [11, 18, 27] often degrades significantly.", + "bbox": [ + 75, + 294, + 467, + 551 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which entails deploying L-ReID models continuously without re-indexing raw images in the gallery. It is extremely challenging when considering not only balancing the acquisition of old and new knowledge but also achieving the compatibility between the old and the new feature space. To this end, Compatible Training (CT) [16, 21, 23] becomes a feasible solution which promotes the compatibility. Unfortunately, most existing CT methods only focus on compatibility within the same dataset. However, the large domain gap [5, 19] between different ReID datasets typically leads to the forgetting of old knowledge, causing the feature shift problem, which seriously degrades the performance of existing CT methods.", + "bbox": [ + 75, + 551, + 467, + 777 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Inspired by the above observation, we propose a Continua! ReID. The core idea of $\\mathrm{C}^2\\mathrm{R}$ is to continuously update old features in the gallery to make it compatible with new query features. To tackle the domain shift problem, a Continua! ReID Transfer (CCT) network is proposed to update old gallery features continuously, which transfers the old feature into the new feature space by adaptively cap", + "bbox": [ + 75, + 780, + 467, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "turing the knowledge from different domains. Correspondingly, to achieve the compatibility between the transferred features and the new ones, a Balanced Compatible Distillation (BCD) module is designed to preserve the relationship between the old and the transferred features in a unified feature space. Finally, to eliminate the accumulated forgetting of old knowledge during the continuous transfer, a Balanced Anti-forgetting Distillation (BAD) module is introduced to balance the old and the new discriminative information. Overall, the main contributions of this paper can be summarized as follows:", + "bbox": [ + 496, + 90, + 890, + 256 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1) This paper proposes a Continual Compatible Representation scheme to solve the challenging Re-indexing Free Lifelong Person Re-identification task, which prevents reindexing to raw images in the old gallery.", + "2) A continual compatible transfer network is designed to adaptively capture the old and the new knowledge, which promotes the updating of old gallery features.", + "3) To achieve compatibility of the old and the new data, a balanced compatible distillation module is designed to balance the relationship between the old and the new features in a unified feature space.", + "4) A balanced anti-forgetting distillation module is introduced to balance the acquisition of the old and the new knowledge without rehearsing the old data." + ], + "bbox": [ + 496, + 257, + 890, + 472 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 488, + 640, + 503 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Lifelong Person Re-identification", + "text_level": 1, + "bbox": [ + 500, + 513, + 790, + 529 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Lifelong Person Re-identification (L-ReID) aims to use streaming data from different domains to train a ReID model to continuously match the same person across all domains [18]. It requires continuously accumulating knowledge from new data and preventing catastrophic forgetting of knowledge learned in old data. To this end, rehearsal-based methods rehearsed old data for the anti-forgetting of old knowledge [5, 35, 38]. Yu et al. [38] proposed a knowledge refreshing and consolidation framework to achieve both positive forward and backward transfers, which simultaneously promotes person matching in both old and new domains. However, limited by data privacy concerns, the old data is usually difficult to rehearse for L-ReID. Therefore, some methods focus on developing rehearsal-free methods [18, 19, 27, 33]. Sun et al. [27] proposed a patch-based knowledge distillation method, which can mitigate catastrophic forgetting problems by preserving patch-level knowledge within individual patch features and mutual relations. Despite achieving some progress, existing methods require re-indexing old data in the gallery after training on new data to adapt to the updated model. In this paper, we focus on a new and challenging task called RFL-ReID, which prohibits re-indexing the old data in the gallery due to data privacy issues.", + "bbox": [ + 496, + 537, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "16615", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/e0f8d7db28a16bcae7851051bf91271f5b757bbc35f815860bec2766bf00ab22.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 83, + 90, + 875, + 277 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/b802098599ed5f5c907536492d4a21334137c1398a987c220740854119e7448d.jpg", + "image_caption": [ + "Figure 3. The architecture of our proposed Continual Compatible Representation $(\\mathbf{C}^2\\mathbf{R})$ method. Our $\\mathrm{C}^2\\mathrm{R}$ consists of a Continual Compatible Transfer (CCT) network, a Balanced Compatible Distillation (BCD) module, and a Balanced Anti-forgetting Distillation (BAD) module. In the training phase, all the above components will be trained, and the CCT network will be used to update the old feature set, thereby achieving re-indexing free lifelong person re-identification." + ], + "image_footnote": [], + "bbox": [ + 86, + 286, + 872, + 373 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Compatible Training", + "text_level": 1, + "bbox": [ + 76, + 460, + 274, + 477 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Compatible Training (CT) aims to achieve the compatibility between the old model and the new model without reindexing, which encourages the feature calculated by the new model to be closer to the same object feature calculated by the old model. Existing CT methods can be categorized into two branches: backward CT [16, 24, 39] and forward CT methods [21, 30, 45]. Pan et al. [16] proposed an adversarial learning-based backward CT method, which optimized the distribution discrepancy and improved the backward compatibility of the updated model. Ramanujan et al. [21] proposed a flexible forward CT method by employing side-information to facilitate the updating of the new model. However, most existing CT methods only achieve compatibility between the old and the new models updated using the same dataset, ignoring the requirement to be compatible with multiple different datasets continuously. To this end, Wan et al. [30] proposed a long-term visual search framework to realize CT in the continual learning scenario, which allows new classes to occur in the new data. However, it relies heavily on old data and old features to achieve the compatibility, which is infeasible for the privacy-sensitive scenario.", + "bbox": [ + 75, + 488, + 472, + 820 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Different from these methods, we propose a continual compatible representation scheme called $\\mathrm{C}^2\\mathrm{R}$ , which achieves leading L-ReID performance when old data in the gallery cannot be re-indexed in the practical privacy-sensitive scenario.", + "bbox": [ + 75, + 825, + 468, + 898 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 500, + 459, + 589, + 474 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Problem Formulation", + "text_level": 1, + "bbox": [ + 500, + 486, + 700, + 500 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID). Formally, given the sequentially collected datasets $\\mathcal{D} = \\{\\mathcal{D}^1,\\mathcal{D}^2,\\dots ,\\mathcal{D}^S\\}$ , where $S$ denotes the total number. The $s^{th}$ dataset $\\mathcal{D}^s = \\{\\mathcal{T}^s,\\mathcal{G}^s\\}$ contains a training set $\\mathcal{T}^s$ and the corresponding gallery set $\\mathcal{G}^s$ without overlapping person identities. Each $\\mathcal{T}^s = \\{x_i^s,y_i^s\\}_{i = 1}^{N^s}$ contains $N^s$ training images $x_{i}^{s}$ and the corresponding identity labels $y_{i}^{s}$ . Our goal is to train a feature extraction model $\\phi^S (\\cdot):x_i\\to z_i$ to extract the feature $z_{i}$ for each input image $x_{i}$ . $\\phi^S (\\cdot)$ is expected to maximize the similarity between the images belonging to the same person, thereby performing well on the overall retrieval performance of all $S$ tasks. Particularly, when training on the $s^{th}$ dataset $\\mathcal{D}^s$ , the previous $s - 1$ datasets $\\{\\mathcal{D}^1,\\dots ,\\mathcal{D}^{s - 1}\\}$ are absolutely unavailable due to data privacy concerns, including the training sets $\\{\\mathcal{T}^j\\}_{j = 1}^{s - 1}$ and the gallery sets $\\{\\mathcal{G}^j\\}_{j = 1}^{s - 1}$ . Therefore, each image in $\\mathcal{G}^j$ can only be extracted once based on the model $\\phi^j (\\cdot)$ within the $j^{th}$ training stage.", + "bbox": [ + 496, + 511, + 890, + 800 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Overview", + "text_level": 1, + "bbox": [ + 500, + 815, + 609, + 829 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As shown in Fig. 3, our proposed Continual Compatible Representation $(\\mathrm{C}^2\\mathrm{R})$ method consists of a Continual Compatible Transfer (CCT) network, a Balanced Compatible Distillation (BCD) module, and a Balanced Anti-forgetting", + "bbox": [ + 496, + 839, + 892, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "16616", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Distillation (BAD) module. At the beginning of the $s^{th}$ training stage $(s\\geq 2)$ , a copy of the model $\\phi^o$ and the classifier $\\psi^o$ are frozen to serve as the old knowledge. Then, we train the model with the CCT network based on the BCD and the BAD modules, as shown in Fig. 3 (a). After the training of the $s^{th}$ stage, we reform a new gallery feature set $\\mathcal{F}^s$ by updating the transferred features in the old gallery feature set $\\mathcal{F}^{s - 1}$ using our proposed CCT network, and extracting the features of the current gallery set $\\mathcal{G}^s$ using $\\phi^s$ (Fig. 3 (b)). When testing at the $s^{th}$ stage, we rank each feature in $\\mathcal{F}^s$ with the query feature calculated by $\\phi^s$ (Fig. 3 (c)) to validate the ReID performance on all $s$ datasets.", + "bbox": [ + 75, + 90, + 472, + 272 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Lifelong Person Re-identification Baseline", + "text_level": 1, + "bbox": [ + 76, + 281, + 434, + 296 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this section, we start by presenting a lifelong person re-identification baseline. The baseline model consists of a feature extraction model $\\phi (\\cdot)$ and a classifier head $\\psi (\\cdot)$ , where $\\phi (\\cdot)$ extracts a feature $z_{i}$ for each input image $x_{i}$ , and $\\psi (\\cdot)$ predicts the probability $p_i$ of each person's identity.", + "bbox": [ + 75, + 304, + 468, + 380 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Considering that the RFL-ReID task aims to continuously match the same person across the sequentially given datasets, we employ a cross-entropy loss $\\mathcal{L}_{ce}$ [13] and a triplet loss $\\mathcal{L}_{trip}$ [8] to learn a discriminative representation for each person in the current dataset $\\mathcal{D}^s$ . However, despite certain performance improvements in $\\mathcal{D}^s$ , it has been verified to cause the catastrophic forgetting problem on the previous $(s - 1)$ datasets [3]. To balance the acquisition of new knowledge and the anti-forgetting of old knowledge, we introduce an anti-forgetting loss $\\mathcal{L}_{pkd}$ [27] based on image patch knowledge distillation to build a basic L-ReID model. Therefore, the overall loss function for our baseline model is formulated as:", + "bbox": [ + 75, + 380, + 470, + 575 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {b a s e}} = \\mathcal {L} _ {c e} + \\mathcal {L} _ {\\text {t r i p}} + \\mathcal {L} _ {\\text {p k d}}. \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 171, + 585, + 468, + 603 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The above baseline method achieves a performance trade-off between new and old datasets by re-indexing data in old galleries using the new model. However, when the old data is unavailable to the new model due to data privacy concerns, the performance will be significantly degraded due to the incompatibility of the features output by the old model and the new model. To tackle the above issue, we will detail present each component of our $\\mathrm{C^2R}$ scheme in the following sections.", + "bbox": [ + 75, + 612, + 468, + 748 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.4. Continual Compatible Transfer Network", + "text_level": 1, + "bbox": [ + 76, + 756, + 426, + 772 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To tackle the domain shift problem, we design a Continual Compatible Transfer (CCT) network to transfer the old feature into the new feature space continuously. To this end, our CCT is designed as a two-stream network to capture transfer-related knowledge from different domains.", + "bbox": [ + 75, + 780, + 468, + 854 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Specifically, we first design a Knowledge Capturing Module (KCM) module to capture knowledge from new domains. Let $z^o \\in \\mathbb{R}^C$ be the feature output by the old model", + "bbox": [ + 75, + 854, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "$\\phi^o (\\cdot)$ based on the sample $x^{s}$ , $\\pmb{v}_{p} \\in \\mathbb{R}^{P \\times C}$ be a learnable new knowledge prototype set with length $P$ . In order to enable $\\pmb{z}^o$ to capture new knowledge for compatibility, we first calculate a capturing probability $\\pmb{k}^o \\in \\mathbb{R}^P$ for each new knowledge prototype:", + "bbox": [ + 496, + 90, + 890, + 167 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {k} ^ {o} = \\delta \\left(g _ {c} \\left(\\tilde {\\boldsymbol {z}} ^ {o}\\right)\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 638, + 178, + 890, + 195 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $g_{c}(\\cdot)$ denotes a three-layer fully connected network, $\\delta (\\cdot)$ denotes the softmax function, and $(\\widetilde{\\cdot})$ denotes the 12-normalized function. Then, we combine the captured new knowledge with a weighted summation of the prototypes:", + "bbox": [ + 496, + 207, + 890, + 267 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {z} ^ {t} = \\sum_ {p = 1} ^ {P} \\boldsymbol {k} _ {i} ^ {o} \\cdot \\boldsymbol {v} _ {p}. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 635, + 277, + 890, + 321 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Sequentially, a parallel Forward Mapping Module (FMM) is designed to directly map the old feature to the new one, thereby preserving the old knowledge from old domains. The designed mapping network consists of sequential fully connected layers, Batch Normalization [9] layers, and PReLU [6] layers. The first fully connected layer reduces the channel number to $C_0$ , while the last layer recovers it back to the original number, which keeps the representation capability while saving redundant operations:", + "bbox": [ + 496, + 332, + 890, + 468 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nz ^ {m} = g _ {s} \\left(\\widetilde {z} ^ {o}\\right). \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 645, + 479, + 890, + 496 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Finally, CCT takes the input $\\widetilde{z}^o$ to generate a factor $a^m$ to adaptively balance the above two features ( $z^t$ and $z^m$ ) obtained by the KCM module and FMM module. Meanwhile, the original features are added by the residual skipconnection to alleviate the gradient vanishing issue [31]. The transferred result $z^w$ of CCT network can be formulated as follows:", + "bbox": [ + 496, + 508, + 890, + 613 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {z} ^ {w} = \\left(1 - a ^ {m}\\right) \\cdot \\boldsymbol {z} ^ {t} + a ^ {m} \\cdot \\boldsymbol {z} ^ {m} + \\widetilde {\\boldsymbol {z}} ^ {o}. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 625, + 890, + 642 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Following [14], we leverage 4 cascaded CCT networks to build up a strong transfer network, which sequentially transfers features from previous stages to the current stage.", + "bbox": [ + 496, + 654, + 890, + 700 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.5. Balanced Compatible Distillation", + "text_level": 1, + "bbox": [ + 500, + 709, + 790, + 724 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To make the transferred features compatible with the new one, we design a Balanced Compatible Distillation (BCD) module to simultaneously preserve the relationships of the old and the transferred features in the new feature space.", + "bbox": [ + 496, + 732, + 890, + 792 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given a mini-batch of training samples $\\{x_i^s, y_i^s\\}_{i=1}^B$ , where $B$ is the batch size, and a new feature $z_i^n$ calculated by the new model $\\phi(\\cdot)^n$ . We start by directly aligning the above features with 12-loss:", + "bbox": [ + 496, + 792, + 890, + 852 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {c a} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\left| \\left| \\tilde {z} _ {i} ^ {n} - \\tilde {z} _ {i} ^ {w} \\right| \\right| _ {2}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 589, + 862, + 890, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "16617", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The above alignment loss promotes compatibility of new features in the new feature space, while ignoring the relationship between the old features, thus limiting the ReID performance on old data. Therefore, we propose a relationship distillation loss to overcome the above issue.", + "bbox": [ + 76, + 90, + 467, + 165 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Firstly, we construct an old similarity matrix $\\mathcal{M}^o\\in$ $\\mathbb{R}^{B\\times B}$ , which is calculated by the affinity between each two features in $\\{\\widetilde{z}_i^o\\}_{i = 1}^B$ to represent the relationship between the corresponding images in the old feature space:", + "bbox": [ + 76, + 166, + 467, + 226 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {M} _ {i, j} ^ {o} = \\frac {e ^ {\\langle \\widetilde {z} _ {i} ^ {o} , \\widetilde {z} _ {j} ^ {o} \\rangle}}{\\sum_ {k = 1} ^ {B} e ^ {\\langle \\widetilde {z} _ {i} ^ {o} , \\widetilde {z} _ {k} ^ {o} \\rangle}}, (i, j \\in [ 1, B ]), \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 138, + 234, + 467, + 275 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\langle \\cdot ,\\cdot \\rangle$ denotes the cosine similarity. Similarly, a transferred similarity matrix $\\mathcal{M}^w$ is also constructed to represent the relationship between the transferred features $\\{\\widetilde{z}_i^w\\}_{i = 1}^B$ . Apparently, the alignment in Eq. (6) will promote higher similarity between samples with the same identity in $\\mathcal{M}^w$ , which will conflict with the corresponding similarity in $\\mathcal{M}^o$ . Therefore, we remove the similarities between samples belonging to the same identity to avoid the above conflicts for relationship distillation:", + "bbox": [ + 76, + 284, + 467, + 419 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {M} _ {i, j} ^ {x} = \\left\\{ \\begin{array}{l l} \\mathcal {M} _ {i, j} ^ {x}, I D (i) \\neq I D (j) \\\\ 0, \\quad I D (i) = I D (j), \\end{array} \\right. \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 148, + 431, + 467, + 470 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $ID(\\cdot)$ denotes the identity of the given sample, and $x \\in o, w$ . Next, a widely-used knowledge distillation loss $\\mathcal{L}_{cr}$ based on Kullback-Leibler (KL) divergence is imposed to distil the relationship between old features as follows:", + "bbox": [ + 76, + 479, + 467, + 540 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {c r} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\sigma \\left(M _ {i,:} ^ {o}\\right) \\log \\left(\\frac {\\sigma \\left(M _ {i,:} ^ {o}\\right)}{\\sigma \\left(M _ {i,:} ^ {w}\\right)}\\right), \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 143, + 551, + 467, + 590 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\sigma (\\cdot)$ denotes the row-wise 11-normalized function.", + "bbox": [ + 76, + 603, + 450, + 617 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In all, the loss function for the BCD module can be calculated as follows:", + "bbox": [ + 76, + 618, + 467, + 646 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {b c d} = \\mu_ {1} \\mathcal {L} _ {c a} + \\mu_ {2} \\mathcal {L} _ {c r}, \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 189, + 660, + 467, + 675 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mu_{1}$ and $\\mu_{2}$ denote two hyper-parameters to balance our proposed balanced compatible distillation.", + "bbox": [ + 76, + 686, + 467, + 715 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.6. Balanced Anti-forgetting Distillation", + "text_level": 1, + "bbox": [ + 76, + 726, + 392, + 741 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Although the proposed BCD module achieves the compatibility by selectively distilling the relationship, it ignores the accumulated forgetting of old knowledge during the continual compatible transfer, thereby reducing the inter-class discrimination of old data. Therefore, we propose a Balanced Anti-forgetting Distillation (BAD) module to preserve the discriminative information within the old and new features in the new feature space.", + "bbox": [ + 76, + 750, + 467, + 868 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To this end, we employ the old classifier head $\\psi^o (\\cdot)$ to extract and distil the discriminative information. Therefore,", + "bbox": [ + 76, + 869, + 467, + 898 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "we extract old identity logits $\\pmb{q}^{o}$ of the old feature $z^{o}$ as the theoretical distribution of the discriminative information:", + "bbox": [ + 500, + 90, + 888, + 119 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {q} ^ {o} = \\delta \\left(\\psi^ {o} \\left(\\boldsymbol {z} ^ {o}\\right)\\right). \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 637, + 133, + 888, + 148 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Considering that the transferred feature $z^w$ and $z^o$ come from different datasets, it is challenging to extract consistent discriminative information directly using $\\psi^o(\\cdot)$ . To tackle the above problem, we perform an inverse 12-normalization on $z^w$ so that it can be extracted as the real distribution of the transferred discriminative information:", + "bbox": [ + 498, + 160, + 890, + 250 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {q} ^ {w} = \\delta \\left(\\psi^ {o} \\left(\\widetilde {\\boldsymbol {z}} ^ {w} \\cdot \\left\\| \\boldsymbol {z} ^ {o} \\right\\| _ {2}\\right)\\right). \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 606, + 262, + 888, + 277 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Sequentially, we use an anti-forgetting loss $\\mathcal{L}_{ad}$ to preserve the old discriminative knowledge, which can be calculated as follows:", + "bbox": [ + 498, + 291, + 888, + 334 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {a d} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\boldsymbol {q} _ {i} ^ {o} \\log \\left(\\frac {\\boldsymbol {q} _ {i} ^ {o}}{\\boldsymbol {q} _ {i} ^ {w}}\\right). \\tag {13}\n$$\n", + "text_format": "latex", + "bbox": [ + 599, + 344, + 888, + 383 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Despite achieving the anti-forgetting, the distillation in Eq. (13) will also limit the discrimination of the transferred feature in the new feature space. Therefore, we introduce a discriminative consistency-based loss $\\mathcal{L}_{dc}$ to balance the discrimination for both transferred and new features:", + "bbox": [ + 498, + 395, + 888, + 468 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {d c} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} (1 - \\cos \\left\\langle \\frac {\\widetilde {z} _ {i} ^ {w} - \\widetilde {z} _ {i} ^ {o}}{\\left| \\left| \\widetilde {z} _ {i} ^ {w} - \\widetilde {z} _ {i} ^ {o} \\right| \\right| _ {2}}, \\frac {\\widetilde {z} _ {i} ^ {n} - \\widetilde {z} _ {i} ^ {o}}{\\left| \\left| \\widetilde {z} _ {i} ^ {n} - \\widetilde {z} _ {i} ^ {o} \\right| \\right| _ {2}} \\right\\rangle). \\tag {14}\n$$\n", + "text_format": "latex", + "bbox": [ + 501, + 479, + 888, + 532 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The overall loss function for the BAD module can be calculated as follows:", + "bbox": [ + 498, + 534, + 888, + 561 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {b a d} = \\mu_ {3} \\mathcal {L} _ {a d} + \\mu_ {4} \\mathcal {L} _ {d c}, \\tag {15}\n$$\n", + "text_format": "latex", + "bbox": [ + 611, + 575, + 888, + 590 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mu_{3}$ and $\\mu_{4}$ denote two hyper-parameters when training the model.", + "bbox": [ + 498, + 603, + 888, + 632 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.7. Objective Function", + "text_level": 1, + "bbox": [ + 500, + 642, + 681, + 657 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Finally, the total loss $\\mathcal{L}$ of $\\mathrm{C}^2\\mathrm{R}$ is calculated as follows:", + "bbox": [ + 500, + 665, + 862, + 680 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {\\text {b a s e}} + \\mathcal {L} _ {\\text {b c d}} + \\mathcal {L} _ {\\text {b a d}}. \\tag {16}\n$$\n", + "text_format": "latex", + "bbox": [ + 604, + 696, + 888, + 710 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Through the joint optimizing of $\\mathcal{L}$ , our $\\mathrm{C}^2\\mathrm{R}$ achieves the compatibility between the old and the new models and prevents re-indexing to raw images in the old gallery.", + "bbox": [ + 498, + 717, + 888, + 763 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 777, + 630, + 792 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Datasets and Evaluation Metrics", + "text_level": 1, + "bbox": [ + 500, + 801, + 784, + 815 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. To verify the effectiveness of our method, we conduct extensive experiments on five benchmark lifelong person ReID datasets, including Market-1501 [41], CUHK-SYSU [36], DukeMTMC-ReID [43], MSMT17-V2 [34] and CUHK03 [12]. For CUHK-SYSU, we follow the", + "bbox": [ + 498, + 824, + 888, + 898 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "16618", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/4bf416d060f3031c6a1908b36827f86a4259c5a5eadb97c4358c6e7496ccd9ee.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
TaskMethodMarket-1501CUHK-SYSUDukeMTMC-ReIDMSMT17-V2CUHK03Average
mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1
L-ReIDJointTrain68.185.281.483.860.475.724.648.942.743.655.467.5
SPD [28]35.661.261.764.027.547.15.215.542.244.334.446.4
LwF [11]56.377.172.975.129.646.56.016.636.137.540.250.6
CRL [40]58.078.272.575.128.345.26.015.837.439.840.550.8
AKA [18]58.177.472.574.828.745.26.116.238.740.440.850.8
MEGE [20]39.061.673.376.616.930.34.613.436.437.134.043.8
PatchKD [27]68.585.775.678.633.850.46.517.034.136.843.753.7
Ours69.086.876.779.533.248.66.617.435.636.244.253.7
RFL-ReIDLwF* [11]39.158.040.040.77.815.32.67.123.323.922.629.0
AKA* [18]36.152.238.637.67.613.83.18.326.526.522.427.7
CVS* [30]38.855.649.049.719.330.04.611.524.724.727.334.3
PatchKD* [27]61.478.457.859.020.834.45.112.836.037.636.244.4
Ours62.779.764.466.326.741.76.815.737.237.639.548.2
", + "bbox": [ + 119, + 88, + 846, + 310 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/e3893674e092a0928a77ce16a9696d644038532d56d2d977bf31f8bb44412910.jpg", + "table_caption": [ + "Table 1. Performance on training Order-1: Market-1501→CUHK-SYSU→DukeMTMC-ReID→MSMT17-V2→CUHK03." + ], + "table_footnote": [], + "table_body": "
TaskMethodDukeMTMC-ReIDMSMT17-V2Market-1501CUHK-SYSUCUHK03Average
mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1
L-ReIDJointTrain60.475.724.648.968.185.281.483.842.743.655.467.5
SPD [28]28.548.53.711.532.357.462.165.043.045.233.945.5
LwF [11]42.761.75.114.334.458.669.973.034.134.137.248.4
CRL [40]43.563.14.813.735.059.870.072.834.536.837.649.2
AKA [18]42.260.15.415.137.259.871.273.936.937.938.649.4
MEGE [20]21.635.53.09.325.049.869.973.134.735.130.840.6
PatchKD [27]58.374.16.417.443.267.474.576.933.734.843.254.1
Ours59.775.07.319.242.466.576.077.837.839.344.755.6
RFL-ReIDLwF* [11]15.022.91.23.29.519.438.837.520.219.616.920.5
AKA* [18]11.115.11.33.213.427.335.934.725.225.617.421.2
CVS* [30]29.041.93.59.430.749.660.061.228.529.930.338.4
PatchKD* [27]46.560.94.010.431.150.563.064.035.836.636.144.5
Ours48.463.66.214.937.055.667.468.439.239.539.748.4
", + "bbox": [ + 119, + 337, + 846, + 560 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Performance on training Order-2: DukeMTMC-ReID $\\rightarrow$ MSMT17-V2 $\\rightarrow$ Market-1501 $\\rightarrow$ CUHK-SYSU $\\rightarrow$ CUHK03.", + "bbox": [ + 117, + 564, + 849, + 578 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "same pre-processing and evaluation of GwFReLU [35], which crops the person images with the ground-truth person bounding box annotation and re-organized as a ReID dataset with corresponding identities. To simulate the lifelong person ReID process in the real scenarios, we evaluate our method by employing two training orders used in [18], including Order-1: Market-1501 $\\rightarrow$ CUHK-SYSU $\\rightarrow$ DukeMTMC-ReID $\\rightarrow$ MSMT17-V2 $\\rightarrow$ CUHK03 and Order-2: DukeMTMC-ReID $\\rightarrow$ MSMT17-V2 $\\rightarrow$ Market-1501 $\\rightarrow$ CUHK-SYSU $\\rightarrow$ CUHK03.", + "bbox": [ + 75, + 599, + 470, + 750 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation Metrics. We employ mean Average Precision (mAP) [41] and Rank@1 accuracy (R@1) [15] to evaluate our method on each datasets. The above metrics of our method are reported after sequentially training all datasets. Besides, the corresponding mean accuracy is also reported to evaluate the overall performance on all tasks. Besides, the Average Forgetting (AF) [2] on the above metrics are reported to evaluate the anti-forgetting performance of our method, which averages the difference between the highest", + "bbox": [ + 75, + 763, + 470, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "accuracy and the final accuracy on each dataset throughout the lifelong learning process.", + "bbox": [ + 498, + 599, + 890, + 630 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Implementation Details", + "text_level": 1, + "bbox": [ + 498, + 647, + 718, + 664 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Our proposed $\\mathrm{C^2R}$ is implemented with PyTorch [17] on NVIDIA A40 GPUs. We adopt a ResNet-50 [7] network pre-trained on ImageNet [22] as our backbone network. In each training stage, we train the model for 50 epochs with 150 iterations. We use Adam [10] optimizer for training. The learning rate is set to $3.5\\times 10^{-4}$ initially, which decayed by 0.1 at the $25^{th}$ and the $35^{th}$ epochs. We set the hyper-parameters $\\mu_{1},\\mu_{2},\\mu_{3}$ , and $\\mu_{4}$ as 50, 1, 0.01 and 0.05, respectively. The prototype length $P$ and the channel number $C_0$ are empirically set to 16 and 32. Input images are resized to $256\\times 128$ . The batch size is set to 128, with 4 images for each identity. Following [27], each dataset is randomly sampled with 500 identities to alleviate the problem of unbalanced class numbers among different datasets for fairness comparison.", + "bbox": [ + 496, + 672, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "16619", + "bbox": [ + 480, + 945, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/8b23d3088e480e20b863f03197ed2fd640b0d8b37d11ea64547a9f203e9adfcf.jpg", + "table_caption": [], + "table_footnote": [ + "Table 3. AF performance of ${\\mathrm{C}}^{2}\\mathrm{R}$ compared with existing methods. (The lower the AF is, the less the model forgets.)" + ], + "table_body": "
MethodLwFAKACVSPatchKDOurs
AF(mAP)24.826.421.016.513.9
AF(R@1)30.835.025.718.514.5
", + "bbox": [ + 93, + 88, + 450, + 135 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Comparison with State-of-the-arts Methods", + "text_level": 1, + "bbox": [ + 76, + 186, + 447, + 203 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In this section, we compared our $\\mathrm{C}^2\\mathrm{R}$ with several state-of-the-art methods on both RFL-ReID and traditional L-ReID tasks, including SPD [28], LwF [11], CRL [40], AKA [18], MEGE [20], PatchKD [27], and CVS [30], where CSV is a continual compatible training method and the others are L-ReID methods. The best results are bolded, and the second-best results are underlined.", + "bbox": [ + 75, + 214, + 467, + 320 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparison on the RFL-ReID task. Tab. 1 and Tab. 2 summarize the results of our method compared to existing methods, which are reproduced by the released code and denoted as $*$ . Compared with these methods, our $\\mathrm{C}^2\\mathrm{R}$ achieves the highest average mAP and R@1 accuracy by $39.5\\% /48.2\\%$ on Order-1 and $39.7\\% /48.4\\%$ on Order-2, leading PatchKD by $3.3\\% /3.8\\%$ and $3.6\\% /3.9\\%$ , respectively. This is because our $\\mathrm{C}^2\\mathrm{R}$ method can achieve compatible transfer for old gallery features by balancing the anti-forgetting of old knowledge with the compatibility to the new model, thereby updating old features without reindexing old data effectively.", + "bbox": [ + 75, + 325, + 467, + 507 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In addition, Tab. 3 reports the AF performance of mAP and R@1 on Order-1. It can be seen that our $\\mathrm{C}^2\\mathrm{R}$ achieves the lowest AF on both mAP and R@1 accuracy, which is lower than PatchKD by $2.6\\%$ and $4.0\\%$ , respectively. Notably, compared to CVS, our C2R does not introduce additional old data while achieving the best RFL-ReID accuracy and the best AF performance. Specifically, as shown in Fig. 4, our proposed $\\mathrm{C}^2\\mathrm{R}$ achieves the best average performance on the seen datasets in each stage. The above results intuitively demonstrate that our proposed $\\mathrm{C}^2\\mathrm{R}$ outperforms SOTA methods on average R@1 and mAP at each stage.", + "bbox": [ + 75, + 512, + 467, + 679 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The above results imply that our $\\mathrm{C^2R}$ can adaptively map old features and capture new knowledge, thus balancing compatibility with new feature spaces by preserving old discriminative knowledge.", + "bbox": [ + 75, + 683, + 467, + 744 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparison on the traditional L-ReID task. We further evaluate our method on the traditional L-ReID task. As shown in Tab. 1 and Tab. 2, our proposed $\\mathrm{C}^2\\mathrm{R}$ also achieves state-of-the-art performance on both two training orders, which leads PatchKD on mAP accuracy by $0.5\\%$ and $1.5\\%$ on Order-1 and Order-2, respectively. The above results imply that our method achieves the best RFL-ReID performance without compromising the performance of traditional L-ReID. Therefore, our $\\mathrm{C}^2\\mathrm{R}$ has better generalization in both general and privacy-sensitive scenarios.", + "bbox": [ + 75, + 750, + 467, + 900 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/02a65ad41234195c104ccb631acd1b00cb748314ac3dbfb816b2b092316d99f8.jpg", + "image_caption": [ + "Figure 4. Lifelong learning performance comparison in RFL-ReID task on mAP and $\\mathbb{R}@\\mathbb{1}$ accuracy." + ], + "image_footnote": [], + "bbox": [ + 501, + 90, + 697, + 242 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/48d670bf3fc1955b64e03956db569ec2b4b05b0cbaed703d37cb821ba11132bf.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 90, + 893, + 241 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/cdc957ff6111a16fa0edd27e16d990ba2de27d27666175447e1f588946d5e9db.jpg", + "table_caption": [], + "table_footnote": [ + "Table 4. Ablation study on different balancing factors in continual compatible transfer network." + ], + "table_body": "
am0.00.20.40.60.81.0Ours
mAP38.238.739.038.438.938.739.5
R@146.346.947.647.547.847.748.2
", + "bbox": [ + 503, + 291, + 885, + 339 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Ablation Studies", + "text_level": 1, + "bbox": [ + 500, + 387, + 663, + 402 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In this section, we conduct ablation studies on Order-1 to evaluate the effectiveness of each component in our $\\mathrm{C}^2\\mathrm{R}$ . Our Base method is the baseline introduced in Sec. 3.3.", + "bbox": [ + 498, + 412, + 890, + 455 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effectiveness of CCT network. We compared the adaptively balancing strategy in our continual compatible transfer network with a fixed balancing strategy, which introduces fixed values for $a^m$ in Eq. (5). As shown in Tab. 4, our method achieves the best mAP and R@1 accuracy among the fixed balancing strategies. It indicates that by adaptively generating the most appropriate fusion factor through different old features, our CCT network balances the forward mapping of old knowledge and the knowledge capturing of new knowledge, verifying its superior effectiveness.", + "bbox": [ + 498, + 459, + 890, + 609 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effectiveness of BCD module. As shown in Tab. 5, we evaluate the two important loss functions $\\mathcal{L}_{ca}$ (Eq. (6)) and $\\mathcal{L}_{cr}$ (Eq. (9)) in the balanced compatible distillation module. It can be seen that compared with the Base method, $\\mathcal{L}_{ca}$ improves the average mAP/R@1 by $1.7\\%$ and $1.2\\%$ , and the full version of the BCD module improves by $1.9\\%$ and $2.3\\%$ . The above results indicate that the alignment in $\\mathcal{L}_{ca}$ and the relationship distillation in $\\mathcal{L}_{cr}$ are both important for RFL-ReID. The former ensures that old features can continue to be compatible with the new ones, while the latter preserves the relationship within the old feature space. Finally, the BCD module achieves promising improvement by modelling the above functions in a balanced manner.", + "bbox": [ + 498, + 612, + 890, + 808 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effectiveness of BAD module. We further evaluate two main components $\\mathcal{L}_{ad}$ (Eq. (13)) and $\\mathcal{L}_{dc}$ (Eq. (14)) in the balanced anti-forgetting module. As shown in Tab. 5, $\\mathcal{L}_{ad}$ brings an improvement by $1.1\\%$ on average mAP accuracy. When combined with $\\mathcal{L}_{dc}$ , the accuracy further improved by $0.3\\%$ . It indicates that by distilling the discriminative", + "bbox": [ + 498, + 809, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "16620", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/e0471a24581f73ffcb9a3942b4d7b29a272eac9128dba128fd5a8c6b114bd874.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
BaseCCTBCDBADmAPR@1
LcaLcrLadLdc
✓-----36.244.4
✓✓✓---37.945.6
✓✓✓✓--38.146.7
✓✓✓✓✓-39.247.1
✓✓✓✓✓✓39.548.2
", + "bbox": [ + 83, + 88, + 460, + 195 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 5. Ablation studies of each component in ${\\mathrm{C}}^{2}\\mathrm{R}$ on Order-1.", + "bbox": [ + 80, + 196, + 465, + 209 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "information within the old feature, BAD balances the antiforgetting of the old discrimination knowledge with the acquisition of the new knowledge and thus plays an important role in our $\\mathrm{C}^2\\mathrm{R}$ method.", + "bbox": [ + 75, + 222, + 468, + 281 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Hyper-parameter Study. There are 4 hyper-parameters for the training of our $\\mathrm{C^2R}$ method, i.e. $\\mu_1$ , $\\mu_2$ , $\\mu_3$ , and $\\mu_4$ . Therefore, we evaluate the effect of the above parameters respectively, as shown in Fig. 6. It can be seen that a slight or excessive $\\mu_1$ will eliminate the alignment of the old feature to the new feature. In addition, as $\\mu_2$ increases, the relationship between old features will prevent the model from learning new knowledge. Therefore, the moderate $\\mu_1(=50)$ and $\\mu_2(=1)$ are chosen in the BCD module to balance the relationship between the old and new features. Similarly, we set a moderate $\\mu_3(=0.01)$ and $\\mu_4(=0.05)$ to balance the discriminative information in the old and new features.", + "bbox": [ + 75, + 284, + 470, + 464 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.5. Visualization", + "text_level": 1, + "bbox": [ + 76, + 476, + 215, + 491 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To intuitively verify the effectiveness of our $\\mathrm{C^2R}$ , we use t-SNE [29] to visualize and compare the gallery feature and query feature calculated by our method with the Base method. The features are randomly selected from the five benchmark datasets. As shown in Fig. 5, the features calculated by our $\\mathrm{C^2R}$ achieve tighter intra-class representation while retaining more inter-class discriminability. The above results indicate that our $\\mathrm{C^2R}$ can preserve more discriminative information after transferring old gallery features, which can be further aligned by new query features to achieve RFL-ReID.", + "bbox": [ + 75, + 500, + 468, + 666 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9694da0a586a66655a27e078c631b2c8688698141a7852380dd22413edf89d49.jpg", + "image_caption": [ + "(a) Base", + "Figure 5. TSNE results of our $C^2 R$ compared with Base method. Different colours represent different identities, while the circles and the triangles represent gallery and query features, respectively." + ], + "image_footnote": [], + "bbox": [ + 81, + 676, + 272, + 823 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7bec8af77eb3df7ec9f2d212405d15f615675f0df444594e273eee45e8212305.jpg", + "image_caption": [ + "(b) our $\\mathrm{C}^2\\mathrm{R}$" + ], + "image_footnote": [], + "bbox": [ + 277, + 676, + 467, + 823 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9de7e20172300eb503e9cf0c9d470e0db2c1e18c901af2c6336138d1c0e3eedb.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 509, + 89, + 696, + 232 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c0ee8effc310116df7c5cf3c2f4e636e3b9ba97055c03468eb3ef327a3812899.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 696, + 89, + 883, + 233 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/61312fb8dd085e436752a0849abfe2b010c8c90279e93567f4aefa28a69a1c85.jpg", + "image_caption": [ + "Figure 6. The influence of hyper-parameters in our $C^2 R$ ." + ], + "image_footnote": [], + "bbox": [ + 508, + 234, + 696, + 378 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/06e38eff4ae95eed22171268027c1de148ae0466de6f80f170fc7dfcbce5e10d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 696, + 234, + 883, + 378 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.6. Limitation and Future Work", + "text_level": 1, + "bbox": [ + 500, + 409, + 756, + 422 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Our $\\mathrm{C}^2\\mathrm{R}$ can support L-ReID without re-indexing old data in the gallery. However, it is difficult to capture enough new knowledge to facilitate feature transfer and updating when the amount of new data is limited. Therefore, it is worthy of future research on efficient transfer under a few-shot scenario. In addition, when there is noise in new data, how to utilize old knowledge to eliminate such noise to achieve selective transfer should be studied in the future.", + "bbox": [ + 496, + 431, + 890, + 553 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 571, + 617, + 587 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which prohibits the re-indexing of raw images in the gallery due to data privacy concerns. To this end, we propose a Continual Compatible Representation $(\\mathrm{C}^2\\mathrm{R})$ method, which introduces a Continual Compatible Transfer (CCT) network to continuously transfer old gallery features to the new feature space. Besides, a Balanced Compatible Distillation module and a Balanced Anti-forgetting Distillation module are proposed to balance the anti-forgetting of old knowledge with the compatibility to the new model. Extensive experiments on five widely-used benchmark L-ReID datasets verify the effectiveness of our method on the RFL-ReID task while maintaining the state-of-the-art performance on the general L-ReID scenario.", + "bbox": [ + 496, + 599, + 890, + 825 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements", + "text_level": 1, + "bbox": [ + 500, + 844, + 656, + 859 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by the National Natural Science Foundation of China (61925201, 62132001, 62376011).", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "16621", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Shafiq Ahmad, Gianluca Scarpellini, Pietro Morerio, and Alessio Del Bue. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 9046–9056, 2022. 3" + ], + "bbox": [ + 501, + 90, + 890, + 612 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "16623", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_model.json b/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_model.json new file mode 100644 index 0000000000000000000000000000000000000000..62fff370a8e1d41a5fce8e550ecf961601df50fa --- /dev/null +++ b/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_model.json @@ -0,0 +1,2277 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.044 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.21, + 0.131, + 0.761, + 0.177 + ], + "angle": 0, + "content": "Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification" + }, + { + "type": "text", + "bbox": [ + 0.187, + 0.203, + 0.834, + 0.24 + ], + "angle": 0, + "content": "Zhenyu Cui\\(^{1}\\), Jiahuan Zhou\\(^{1}\\), Xun Wang\\(^{2}\\), Manyu Zhu\\(^{2}\\), Yuxin Peng\\(^{1*}\\) \n\\(^{1}\\)Wangxuan Institute of Computer Technology, Peking University \\(^{2}\\)ByteDance Inc" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.242, + 0.934, + 0.258 + ], + "angle": 0, + "content": "cuizhenyu@stu.pku.edu.cn, {jiahuanzhou,pengyuxin}@pku.edu.cn, {wangxun.2,zhumanyu}@bytedance.com" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.292, + 0.314, + 0.308 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.323, + 0.474, + 0.794 + ], + "angle": 0, + "content": "Lifelong Person Re-identification (L-ReID) aims to learn from sequentially collected data to match a person across different scenes. Once an L-ReID model is updated using new data, all historical images in the gallery are required to be re-calculated to obtain new features for testing, known as \"re-indexing\". However, it is infeasible when raw images in the gallery are unavailable due to data privacy concerns, resulting in incompatible retrieval between the query and the gallery features calculated by different models, which causes significant performance degradation. In this paper, we focus on a new task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which requires achieving effective L-ReID without re-indexing raw images in the gallery. To this end, we propose a Continual Compatible Representation \\((C^2 R)\\) method, which facilitates the query feature calculated by the continuously updated model to effectively retrieve the gallery feature calculated by the old model in a compatible manner. Specifically, we design a Continual Compatible Transfer (CCT) network to continuously transfer and consolidate the old gallery feature into the new feature space. Besides, a Balanced Compatible Distillation module is introduced to achieve compatibility by aligning the transferred feature space with the new feature space. Finally, a Balanced Anti-forgetting Distillation module is proposed to eliminate the accumulated forgetting of old knowledge during the continual compatible transfer. Extensive experiments on several benchmark L-ReID datasets demonstrate the effectiveness of our method against state-of-the-art methods for both RFL-ReID and L-ReID tasks. The source code of this paper is available at https://github.com/PKU-ICST-MIPL/C2R_CVPR2024." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.821, + 0.21, + 0.837 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.847, + 0.47, + 0.879 + ], + "angle": 0, + "content": "Person re-identification (ReID) aims to identify the same person across different areas at different times [42]. Exist" + }, + { + "type": "image", + "bbox": [ + 0.513, + 0.291, + 0.883, + 0.46 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.612, + 0.462, + 0.782, + 0.474 + ], + "angle": 0, + "content": "(a) Traditional Lifelong ReID" + }, + { + "type": "image", + "bbox": [ + 0.513, + 0.477, + 0.882, + 0.617 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.597, + 0.618, + 0.799, + 0.631 + ], + "angle": 0, + "content": "(b) Re-indexing Free Lifelong ReID" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.646, + 0.895, + 0.688 + ], + "angle": 0, + "content": "Figure 1. Comparison between (a) the traditional Lifelong Person Re-identification (L-ReID) task and (b) the Re-indexing Free Lifelong Person Re-identification (RFL-ReID) task." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.703, + 0.892, + 0.795 + ], + "angle": 0, + "content": "ing methods [26, 32, 44] have made remarkable progress based on deep learning methods [37] and large-scale datasets [34, 41, 43]. However, their performance is often limited when training data are continuously collected from a series of different scenarios due to the well-known catastrophic forgetting challenge [3]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Recently, Lifelong person ReID (L-ReID) has aroused great concerns involving acquiring knowledge from streaming data and performing well across all data [5, 18, 19, 38]. Its challenge is to balance the anti-forgetting of old knowledge with the acquisition of new knowledge. To this end, existing L-ReID methods usually adopt the exemplar replay [38] and the knowledge distillation [27] to preserve" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.224, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "16614" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.079, + 0.089, + 0.46, + 0.226 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.238, + 0.47, + 0.28 + ], + "angle": 0, + "content": "Figure 2. Performance Comparison between the traditional Lifelong Person Re-identification (L-ReID) task and the Re-indexing Free Lifelong Person Re-identification (RFL-ReID) task." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.295, + 0.468, + 0.552 + ], + "angle": 0, + "content": "old knowledge when updating the model. The updated new model will be sequentially deployed by \"re-indexing\" [24] features of old data in the gallery. As shown in Fig. 1 (a), the old gallery features are replaced by the re-indexed gallery features to be compatible with the new model. However, massive incremental images in the gallery bring unbearable computational costs and prevent the re-indexing process [21, 39]. Besides, in the context of data privacy concerns [25], re-indexing is legally forbidden due to the impracticality of storing and re-indexing unauthorized raw images within privacy-sensitive scenarios [1, 4, 14], also known as Re-indexing Free Lifelong ReID (RFL-ReID), as shown in Fig. 1 (b). In this case, the domain gap between different datasets leads to the incompatibility between features calculated by the old and the new models. Consequently, as shown in Fig. 2, the performance of existing methods [11, 18, 27] often degrades significantly." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.553, + 0.468, + 0.779 + ], + "angle": 0, + "content": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which entails deploying L-ReID models continuously without re-indexing raw images in the gallery. It is extremely challenging when considering not only balancing the acquisition of old and new knowledge but also achieving the compatibility between the old and the new feature space. To this end, Compatible Training (CT) [16, 21, 23] becomes a feasible solution which promotes the compatibility. Unfortunately, most existing CT methods only focus on compatibility within the same dataset. However, the large domain gap [5, 19] between different ReID datasets typically leads to the forgetting of old knowledge, causing the feature shift problem, which seriously degrades the performance of existing CT methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.468, + 0.902 + ], + "angle": 0, + "content": "Inspired by the above observation, we propose a Continua! ReID. The core idea of \\(\\mathrm{C}^2\\mathrm{R}\\) is to continuously update old features in the gallery to make it compatible with new query features. To tackle the domain shift problem, a Continua! ReID Transfer (CCT) network is proposed to update old gallery features continuously, which transfers the old feature into the new feature space by adaptively cap" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.257 + ], + "angle": 0, + "content": "turing the knowledge from different domains. Correspondingly, to achieve the compatibility between the transferred features and the new ones, a Balanced Compatible Distillation (BCD) module is designed to preserve the relationship between the old and the transferred features in a unified feature space. Finally, to eliminate the accumulated forgetting of old knowledge during the continuous transfer, a Balanced Anti-forgetting Distillation (BAD) module is introduced to balance the old and the new discriminative information. Overall, the main contributions of this paper can be summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.258, + 0.892, + 0.319 + ], + "angle": 0, + "content": "1) This paper proposes a Continual Compatible Representation scheme to solve the challenging Re-indexing Free Lifelong Person Re-identification task, which prevents reindexing to raw images in the old gallery." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.32, + 0.892, + 0.365 + ], + "angle": 0, + "content": "2) A continual compatible transfer network is designed to adaptively capture the old and the new knowledge, which promotes the updating of old gallery features." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.366, + 0.892, + 0.426 + ], + "angle": 0, + "content": "3) To achieve compatibility of the old and the new data, a balanced compatible distillation module is designed to balance the relationship between the old and the new features in a unified feature space." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.427, + 0.892, + 0.473 + ], + "angle": 0, + "content": "4) A balanced anti-forgetting distillation module is introduced to balance the acquisition of the old and the new knowledge without rehearsing the old data." + }, + { + "type": "list", + "bbox": [ + 0.498, + 0.258, + 0.892, + 0.473 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.489, + 0.642, + 0.505 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.515, + 0.792, + 0.53 + ], + "angle": 0, + "content": "2.1. Lifelong Person Re-identification" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.539, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Lifelong Person Re-identification (L-ReID) aims to use streaming data from different domains to train a ReID model to continuously match the same person across all domains [18]. It requires continuously accumulating knowledge from new data and preventing catastrophic forgetting of knowledge learned in old data. To this end, rehearsal-based methods rehearsed old data for the anti-forgetting of old knowledge [5, 35, 38]. Yu et al. [38] proposed a knowledge refreshing and consolidation framework to achieve both positive forward and backward transfers, which simultaneously promotes person matching in both old and new domains. However, limited by data privacy concerns, the old data is usually difficult to rehearse for L-ReID. Therefore, some methods focus on developing rehearsal-free methods [18, 19, 27, 33]. Sun et al. [27] proposed a patch-based knowledge distillation method, which can mitigate catastrophic forgetting problems by preserving patch-level knowledge within individual patch features and mutual relations. Despite achieving some progress, existing methods require re-indexing old data in the gallery after training on new data to adapt to the updated model. In this paper, we focus on a new and challenging task called RFL-ReID, which prohibits re-indexing the old data in the gallery due to data privacy issues." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "16615" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.092, + 0.877, + 0.278 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.088, + 0.287, + 0.874, + 0.374 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.391, + 0.893, + 0.448 + ], + "angle": 0, + "content": "Figure 3. The architecture of our proposed Continual Compatible Representation \\((\\mathbf{C}^2\\mathbf{R})\\) method. Our \\(\\mathrm{C}^2\\mathrm{R}\\) consists of a Continual Compatible Transfer (CCT) network, a Balanced Compatible Distillation (BCD) module, and a Balanced Anti-forgetting Distillation (BAD) module. In the training phase, all the above components will be trained, and the CCT network will be used to update the old feature set, thereby achieving re-indexing free lifelong person re-identification." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.461, + 0.276, + 0.478 + ], + "angle": 0, + "content": "2.2. Compatible Training" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.489, + 0.473, + 0.821 + ], + "angle": 0, + "content": "Compatible Training (CT) aims to achieve the compatibility between the old model and the new model without reindexing, which encourages the feature calculated by the new model to be closer to the same object feature calculated by the old model. Existing CT methods can be categorized into two branches: backward CT [16, 24, 39] and forward CT methods [21, 30, 45]. Pan et al. [16] proposed an adversarial learning-based backward CT method, which optimized the distribution discrepancy and improved the backward compatibility of the updated model. Ramanujan et al. [21] proposed a flexible forward CT method by employing side-information to facilitate the updating of the new model. However, most existing CT methods only achieve compatibility between the old and the new models updated using the same dataset, ignoring the requirement to be compatible with multiple different datasets continuously. To this end, Wan et al. [30] proposed a long-term visual search framework to realize CT in the continual learning scenario, which allows new classes to occur in the new data. However, it relies heavily on old data and old features to achieve the compatibility, which is infeasible for the privacy-sensitive scenario." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.826, + 0.47, + 0.9 + ], + "angle": 0, + "content": "Different from these methods, we propose a continual compatible representation scheme called \\(\\mathrm{C}^2\\mathrm{R}\\), which achieves leading L-ReID performance when old data in the gallery cannot be re-indexed in the practical privacy-sensitive scenario." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.46, + 0.591, + 0.476 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.487, + 0.702, + 0.501 + ], + "angle": 0, + "content": "3.1. Problem Formulation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.512, + 0.892, + 0.801 + ], + "angle": 0, + "content": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID). Formally, given the sequentially collected datasets \\(\\mathcal{D} = \\{\\mathcal{D}^1,\\mathcal{D}^2,\\dots ,\\mathcal{D}^S\\}\\), where \\(S\\) denotes the total number. The \\(s^{th}\\) dataset \\(\\mathcal{D}^s = \\{\\mathcal{T}^s,\\mathcal{G}^s\\}\\) contains a training set \\(\\mathcal{T}^s\\) and the corresponding gallery set \\(\\mathcal{G}^s\\) without overlapping person identities. Each \\(\\mathcal{T}^s = \\{x_i^s,y_i^s\\}_{i = 1}^{N^s}\\) contains \\(N^s\\) training images \\(x_{i}^{s}\\) and the corresponding identity labels \\(y_{i}^{s}\\). Our goal is to train a feature extraction model \\(\\phi^S (\\cdot):x_i\\to z_i\\) to extract the feature \\(z_{i}\\) for each input image \\(x_{i}\\). \\(\\phi^S (\\cdot)\\) is expected to maximize the similarity between the images belonging to the same person, thereby performing well on the overall retrieval performance of all \\(S\\) tasks. Particularly, when training on the \\(s^{th}\\) dataset \\(\\mathcal{D}^s\\), the previous \\(s - 1\\) datasets \\(\\{\\mathcal{D}^1,\\dots ,\\mathcal{D}^{s - 1}\\}\\) are absolutely unavailable due to data privacy concerns, including the training sets \\(\\{\\mathcal{T}^j\\}_{j = 1}^{s - 1}\\) and the gallery sets \\(\\{\\mathcal{G}^j\\}_{j = 1}^{s - 1}\\). Therefore, each image in \\(\\mathcal{G}^j\\) can only be extracted once based on the model \\(\\phi^j (\\cdot)\\) within the \\(j^{th}\\) training stage." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.816, + 0.61, + 0.83 + ], + "angle": 0, + "content": "3.2. Overview" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.893, + 0.903 + ], + "angle": 0, + "content": "As shown in Fig. 3, our proposed Continual Compatible Representation \\((\\mathrm{C}^2\\mathrm{R})\\) method consists of a Continual Compatible Transfer (CCT) network, a Balanced Compatible Distillation (BCD) module, and a Balanced Anti-forgetting" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "16616" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.091, + 0.473, + 0.273 + ], + "angle": 0, + "content": "Distillation (BAD) module. At the beginning of the \\(s^{th}\\) training stage \\((s\\geq 2)\\), a copy of the model \\(\\phi^o\\) and the classifier \\(\\psi^o\\) are frozen to serve as the old knowledge. Then, we train the model with the CCT network based on the BCD and the BAD modules, as shown in Fig. 3 (a). After the training of the \\(s^{th}\\) stage, we reform a new gallery feature set \\(\\mathcal{F}^s\\) by updating the transferred features in the old gallery feature set \\(\\mathcal{F}^{s - 1}\\) using our proposed CCT network, and extracting the features of the current gallery set \\(\\mathcal{G}^s\\) using \\(\\phi^s\\) (Fig. 3 (b)). When testing at the \\(s^{th}\\) stage, we rank each feature in \\(\\mathcal{F}^s\\) with the query feature calculated by \\(\\phi^s\\) (Fig. 3 (c)) to validate the ReID performance on all \\(s\\) datasets." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.282, + 0.436, + 0.297 + ], + "angle": 0, + "content": "3.3. Lifelong Person Re-identification Baseline" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.305, + 0.47, + 0.381 + ], + "angle": 0, + "content": "In this section, we start by presenting a lifelong person re-identification baseline. The baseline model consists of a feature extraction model \\(\\phi (\\cdot)\\) and a classifier head \\(\\psi (\\cdot)\\), where \\(\\phi (\\cdot)\\) extracts a feature \\(z_{i}\\) for each input image \\(x_{i}\\), and \\(\\psi (\\cdot)\\) predicts the probability \\(p_i\\) of each person's identity." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.381, + 0.471, + 0.576 + ], + "angle": 0, + "content": "Considering that the RFL-ReID task aims to continuously match the same person across the sequentially given datasets, we employ a cross-entropy loss \\(\\mathcal{L}_{ce}\\) [13] and a triplet loss \\(\\mathcal{L}_{trip}\\) [8] to learn a discriminative representation for each person in the current dataset \\(\\mathcal{D}^s\\). However, despite certain performance improvements in \\(\\mathcal{D}^s\\), it has been verified to cause the catastrophic forgetting problem on the previous \\((s - 1)\\) datasets [3]. To balance the acquisition of new knowledge and the anti-forgetting of old knowledge, we introduce an anti-forgetting loss \\(\\mathcal{L}_{pkd}\\) [27] based on image patch knowledge distillation to build a basic L-ReID model. Therefore, the overall loss function for our baseline model is formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.173, + 0.587, + 0.47, + 0.604 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {b a s e}} = \\mathcal {L} _ {c e} + \\mathcal {L} _ {\\text {t r i p}} + \\mathcal {L} _ {\\text {p k d}}. \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.613, + 0.47, + 0.749 + ], + "angle": 0, + "content": "The above baseline method achieves a performance trade-off between new and old datasets by re-indexing data in old galleries using the new model. However, when the old data is unavailable to the new model due to data privacy concerns, the performance will be significantly degraded due to the incompatibility of the features output by the old model and the new model. To tackle the above issue, we will detail present each component of our \\(\\mathrm{C^2R}\\) scheme in the following sections." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.757, + 0.427, + 0.773 + ], + "angle": 0, + "content": "3.4. Continual Compatible Transfer Network" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.469, + 0.856 + ], + "angle": 0, + "content": "To tackle the domain shift problem, we design a Continual Compatible Transfer (CCT) network to transfer the old feature into the new feature space continuously. To this end, our CCT is designed as a two-stream network to capture transfer-related knowledge from different domains." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Specifically, we first design a Knowledge Capturing Module (KCM) module to capture knowledge from new domains. Let \\( z^o \\in \\mathbb{R}^C \\) be the feature output by the old model" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.091, + 0.892, + 0.168 + ], + "angle": 0, + "content": "\\(\\phi^o (\\cdot)\\) based on the sample \\(x^{s}\\), \\(\\pmb{v}_{p} \\in \\mathbb{R}^{P \\times C}\\) be a learnable new knowledge prototype set with length \\(P\\). In order to enable \\(\\pmb{z}^o\\) to capture new knowledge for compatibility, we first calculate a capturing probability \\(\\pmb{k}^o \\in \\mathbb{R}^P\\) for each new knowledge prototype:" + }, + { + "type": "equation", + "bbox": [ + 0.639, + 0.179, + 0.892, + 0.196 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {k} ^ {o} = \\delta \\left(g _ {c} \\left(\\tilde {\\boldsymbol {z}} ^ {o}\\right)\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.208, + 0.892, + 0.268 + ], + "angle": 0, + "content": "where \\(g_{c}(\\cdot)\\) denotes a three-layer fully connected network, \\(\\delta (\\cdot)\\) denotes the softmax function, and \\((\\widetilde{\\cdot})\\) denotes the 12-normalized function. Then, we combine the captured new knowledge with a weighted summation of the prototypes:" + }, + { + "type": "equation", + "bbox": [ + 0.636, + 0.279, + 0.892, + 0.322 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {z} ^ {t} = \\sum_ {p = 1} ^ {P} \\boldsymbol {k} _ {i} ^ {o} \\cdot \\boldsymbol {v} _ {p}. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.333, + 0.892, + 0.469 + ], + "angle": 0, + "content": "Sequentially, a parallel Forward Mapping Module (FMM) is designed to directly map the old feature to the new one, thereby preserving the old knowledge from old domains. The designed mapping network consists of sequential fully connected layers, Batch Normalization [9] layers, and PReLU [6] layers. The first fully connected layer reduces the channel number to \\( C_0 \\), while the last layer recovers it back to the original number, which keeps the representation capability while saving redundant operations:" + }, + { + "type": "equation", + "bbox": [ + 0.647, + 0.48, + 0.892, + 0.497 + ], + "angle": 0, + "content": "\\[\nz ^ {m} = g _ {s} \\left(\\widetilde {z} ^ {o}\\right). \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.509, + 0.892, + 0.614 + ], + "angle": 0, + "content": "Finally, CCT takes the input \\(\\widetilde{z}^o\\) to generate a factor \\(a^m\\) to adaptively balance the above two features (\\(z^t\\) and \\(z^m\\)) obtained by the KCM module and FMM module. Meanwhile, the original features are added by the residual skipconnection to alleviate the gradient vanishing issue [31]. The transferred result \\(z^w\\) of CCT network can be formulated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.57, + 0.626, + 0.892, + 0.643 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {z} ^ {w} = \\left(1 - a ^ {m}\\right) \\cdot \\boldsymbol {z} ^ {t} + a ^ {m} \\cdot \\boldsymbol {z} ^ {m} + \\widetilde {\\boldsymbol {z}} ^ {o}. \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.655, + 0.892, + 0.701 + ], + "angle": 0, + "content": "Following [14], we leverage 4 cascaded CCT networks to build up a strong transfer network, which sequentially transfers features from previous stages to the current stage." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.71, + 0.792, + 0.726 + ], + "angle": 0, + "content": "3.5. Balanced Compatible Distillation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.733, + 0.892, + 0.793 + ], + "angle": 0, + "content": "To make the transferred features compatible with the new one, we design a Balanced Compatible Distillation (BCD) module to simultaneously preserve the relationships of the old and the transferred features in the new feature space." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.794, + 0.892, + 0.853 + ], + "angle": 0, + "content": "Given a mini-batch of training samples \\(\\{x_i^s, y_i^s\\}_{i=1}^B\\), where \\(B\\) is the batch size, and a new feature \\(z_i^n\\) calculated by the new model \\(\\phi(\\cdot)^n\\). We start by directly aligning the above features with 12-loss:" + }, + { + "type": "equation", + "bbox": [ + 0.591, + 0.863, + 0.892, + 0.904 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {c a} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\left| \\left| \\tilde {z} _ {i} ^ {n} - \\tilde {z} _ {i} ^ {w} \\right| \\right| _ {2}. \\tag {6}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "16617" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.468, + 0.166 + ], + "angle": 0, + "content": "The above alignment loss promotes compatibility of new features in the new feature space, while ignoring the relationship between the old features, thus limiting the ReID performance on old data. Therefore, we propose a relationship distillation loss to overcome the above issue." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.167, + 0.468, + 0.227 + ], + "angle": 0, + "content": "Firstly, we construct an old similarity matrix \\(\\mathcal{M}^o\\in\\) \\(\\mathbb{R}^{B\\times B}\\) , which is calculated by the affinity between each two features in \\(\\{\\widetilde{z}_i^o\\}_{i = 1}^B\\) to represent the relationship between the corresponding images in the old feature space:" + }, + { + "type": "equation", + "bbox": [ + 0.14, + 0.236, + 0.468, + 0.276 + ], + "angle": 0, + "content": "\\[\n\\mathcal {M} _ {i, j} ^ {o} = \\frac {e ^ {\\langle \\widetilde {z} _ {i} ^ {o} , \\widetilde {z} _ {j} ^ {o} \\rangle}}{\\sum_ {k = 1} ^ {B} e ^ {\\langle \\widetilde {z} _ {i} ^ {o} , \\widetilde {z} _ {k} ^ {o} \\rangle}}, (i, j \\in [ 1, B ]), \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.285, + 0.468, + 0.42 + ], + "angle": 0, + "content": "where \\(\\langle \\cdot ,\\cdot \\rangle\\) denotes the cosine similarity. Similarly, a transferred similarity matrix \\(\\mathcal{M}^w\\) is also constructed to represent the relationship between the transferred features \\(\\{\\widetilde{z}_i^w\\}_{i = 1}^B\\). Apparently, the alignment in Eq. (6) will promote higher similarity between samples with the same identity in \\(\\mathcal{M}^w\\), which will conflict with the corresponding similarity in \\(\\mathcal{M}^o\\). Therefore, we remove the similarities between samples belonging to the same identity to avoid the above conflicts for relationship distillation:" + }, + { + "type": "equation", + "bbox": [ + 0.15, + 0.432, + 0.468, + 0.471 + ], + "angle": 0, + "content": "\\[\n\\mathcal {M} _ {i, j} ^ {x} = \\left\\{ \\begin{array}{l l} \\mathcal {M} _ {i, j} ^ {x}, I D (i) \\neq I D (j) \\\\ 0, \\quad I D (i) = I D (j), \\end{array} \\right. \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.481, + 0.468, + 0.541 + ], + "angle": 0, + "content": "where \\(ID(\\cdot)\\) denotes the identity of the given sample, and \\(x \\in o, w\\). Next, a widely-used knowledge distillation loss \\(\\mathcal{L}_{cr}\\) based on Kullback-Leibler (KL) divergence is imposed to distil the relationship between old features as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.145, + 0.553, + 0.468, + 0.592 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {c r} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\sigma \\left(M _ {i,:} ^ {o}\\right) \\log \\left(\\frac {\\sigma \\left(M _ {i,:} ^ {o}\\right)}{\\sigma \\left(M _ {i,:} ^ {w}\\right)}\\right), \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.604, + 0.452, + 0.618 + ], + "angle": 0, + "content": "where \\(\\sigma (\\cdot)\\) denotes the row-wise 11-normalized function." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.619, + 0.468, + 0.647 + ], + "angle": 0, + "content": "In all, the loss function for the BCD module can be calculated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.191, + 0.661, + 0.468, + 0.676 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {b c d} = \\mu_ {1} \\mathcal {L} _ {c a} + \\mu_ {2} \\mathcal {L} _ {c r}, \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.688, + 0.468, + 0.717 + ], + "angle": 0, + "content": "where \\(\\mu_{1}\\) and \\(\\mu_{2}\\) denote two hyper-parameters to balance our proposed balanced compatible distillation." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.727, + 0.393, + 0.742 + ], + "angle": 0, + "content": "3.6. Balanced Anti-forgetting Distillation" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.75, + 0.468, + 0.869 + ], + "angle": 0, + "content": "Although the proposed BCD module achieves the compatibility by selectively distilling the relationship, it ignores the accumulated forgetting of old knowledge during the continual compatible transfer, thereby reducing the inter-class discrimination of old data. Therefore, we propose a Balanced Anti-forgetting Distillation (BAD) module to preserve the discriminative information within the old and new features in the new feature space." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.468, + 0.899 + ], + "angle": 0, + "content": "To this end, we employ the old classifier head \\(\\psi^o (\\cdot)\\) to extract and distil the discriminative information. Therefore," + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.89, + 0.12 + ], + "angle": 0, + "content": "we extract old identity logits \\( \\pmb{q}^{o} \\) of the old feature \\( z^{o} \\) as the theoretical distribution of the discriminative information:" + }, + { + "type": "equation", + "bbox": [ + 0.638, + 0.134, + 0.89, + 0.149 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {q} ^ {o} = \\delta \\left(\\psi^ {o} \\left(\\boldsymbol {z} ^ {o}\\right)\\right). \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.161, + 0.892, + 0.25 + ], + "angle": 0, + "content": "Considering that the transferred feature \\( z^w \\) and \\( z^o \\) come from different datasets, it is challenging to extract consistent discriminative information directly using \\( \\psi^o(\\cdot) \\). To tackle the above problem, we perform an inverse 12-normalization on \\( z^w \\) so that it can be extracted as the real distribution of the transferred discriminative information:" + }, + { + "type": "equation", + "bbox": [ + 0.607, + 0.263, + 0.89, + 0.279 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {q} ^ {w} = \\delta \\left(\\psi^ {o} \\left(\\widetilde {\\boldsymbol {z}} ^ {w} \\cdot \\left\\| \\boldsymbol {z} ^ {o} \\right\\| _ {2}\\right)\\right). \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.292, + 0.89, + 0.335 + ], + "angle": 0, + "content": "Sequentially, we use an anti-forgetting loss \\(\\mathcal{L}_{ad}\\) to preserve the old discriminative knowledge, which can be calculated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.6, + 0.345, + 0.89, + 0.385 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {a d} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\boldsymbol {q} _ {i} ^ {o} \\log \\left(\\frac {\\boldsymbol {q} _ {i} ^ {o}}{\\boldsymbol {q} _ {i} ^ {w}}\\right). \\tag {13}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.396, + 0.89, + 0.469 + ], + "angle": 0, + "content": "Despite achieving the anti-forgetting, the distillation in Eq. (13) will also limit the discrimination of the transferred feature in the new feature space. Therefore, we introduce a discriminative consistency-based loss \\(\\mathcal{L}_{dc}\\) to balance the discrimination for both transferred and new features:" + }, + { + "type": "equation", + "bbox": [ + 0.503, + 0.48, + 0.89, + 0.533 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {d c} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} (1 - \\cos \\left\\langle \\frac {\\widetilde {z} _ {i} ^ {w} - \\widetilde {z} _ {i} ^ {o}}{\\left| \\left| \\widetilde {z} _ {i} ^ {w} - \\widetilde {z} _ {i} ^ {o} \\right| \\right| _ {2}}, \\frac {\\widetilde {z} _ {i} ^ {n} - \\widetilde {z} _ {i} ^ {o}}{\\left| \\left| \\widetilde {z} _ {i} ^ {n} - \\widetilde {z} _ {i} ^ {o} \\right| \\right| _ {2}} \\right\\rangle). \\tag {14}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.535, + 0.89, + 0.562 + ], + "angle": 0, + "content": "The overall loss function for the BAD module can be calculated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.612, + 0.577, + 0.89, + 0.592 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {b a d} = \\mu_ {3} \\mathcal {L} _ {a d} + \\mu_ {4} \\mathcal {L} _ {d c}, \\tag {15}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.604, + 0.89, + 0.633 + ], + "angle": 0, + "content": "where \\(\\mu_{3}\\) and \\(\\mu_{4}\\) denote two hyper-parameters when training the model." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.643, + 0.683, + 0.658 + ], + "angle": 0, + "content": "3.7. Objective Function" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.666, + 0.864, + 0.681 + ], + "angle": 0, + "content": "Finally, the total loss \\(\\mathcal{L}\\) of \\(\\mathrm{C}^2\\mathrm{R}\\) is calculated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.605, + 0.697, + 0.89, + 0.711 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {\\text {b a s e}} + \\mathcal {L} _ {\\text {b c d}} + \\mathcal {L} _ {\\text {b a d}}. \\tag {16}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.718, + 0.89, + 0.764 + ], + "angle": 0, + "content": "Through the joint optimizing of \\(\\mathcal{L}\\), our \\(\\mathrm{C}^2\\mathrm{R}\\) achieves the compatibility between the old and the new models and prevents re-indexing to raw images in the old gallery." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.778, + 0.631, + 0.794 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.802, + 0.785, + 0.816 + ], + "angle": 0, + "content": "4.1. Datasets and Evaluation Metrics" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.825, + 0.89, + 0.899 + ], + "angle": 0, + "content": "Datasets. To verify the effectiveness of our method, we conduct extensive experiments on five benchmark lifelong person ReID datasets, including Market-1501 [41], CUHK-SYSU [36], DukeMTMC-ReID [43], MSMT17-V2 [34] and CUHK03 [12]. For CUHK-SYSU, we follow the" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.956 + ], + "angle": 0, + "content": "16618" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.12, + 0.089, + 0.847, + 0.311 + ], + "angle": 0, + "content": "
TaskMethodMarket-1501CUHK-SYSUDukeMTMC-ReIDMSMT17-V2CUHK03Average
mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1
L-ReIDJointTrain68.185.281.483.860.475.724.648.942.743.655.467.5
SPD [28]35.661.261.764.027.547.15.215.542.244.334.446.4
LwF [11]56.377.172.975.129.646.56.016.636.137.540.250.6
CRL [40]58.078.272.575.128.345.26.015.837.439.840.550.8
AKA [18]58.177.472.574.828.745.26.116.238.740.440.850.8
MEGE [20]39.061.673.376.616.930.34.613.436.437.134.043.8
PatchKD [27]68.585.775.678.633.850.46.517.034.136.843.753.7
Ours69.086.876.779.533.248.66.617.435.636.244.253.7
RFL-ReIDLwF* [11]39.158.040.040.77.815.32.67.123.323.922.629.0
AKA* [18]36.152.238.637.67.613.83.18.326.526.522.427.7
CVS* [30]38.855.649.049.719.330.04.611.524.724.727.334.3
PatchKD* [27]61.478.457.859.020.834.45.112.836.037.636.244.4
Ours62.779.764.466.326.741.76.815.737.237.639.548.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.12, + 0.316, + 0.85, + 0.33 + ], + "angle": 0, + "content": "Table 1. Performance on training Order-1: Market-1501→CUHK-SYSU→DukeMTMC-ReID→MSMT17-V2→CUHK03." + }, + { + "type": "table", + "bbox": [ + 0.12, + 0.338, + 0.847, + 0.561 + ], + "angle": 0, + "content": "
TaskMethodDukeMTMC-ReIDMSMT17-V2Market-1501CUHK-SYSUCUHK03Average
mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1
L-ReIDJointTrain60.475.724.648.968.185.281.483.842.743.655.467.5
SPD [28]28.548.53.711.532.357.462.165.043.045.233.945.5
LwF [11]42.761.75.114.334.458.669.973.034.134.137.248.4
CRL [40]43.563.14.813.735.059.870.072.834.536.837.649.2
AKA [18]42.260.15.415.137.259.871.273.936.937.938.649.4
MEGE [20]21.635.53.09.325.049.869.973.134.735.130.840.6
PatchKD [27]58.374.16.417.443.267.474.576.933.734.843.254.1
Ours59.775.07.319.242.466.576.077.837.839.344.755.6
RFL-ReIDLwF* [11]15.022.91.23.29.519.438.837.520.219.616.920.5
AKA* [18]11.115.11.33.213.427.335.934.725.225.617.421.2
CVS* [30]29.041.93.59.430.749.660.061.228.529.930.338.4
PatchKD* [27]46.560.94.010.431.150.563.064.035.836.636.144.5
Ours48.463.66.214.937.055.667.468.439.239.539.748.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.119, + 0.565, + 0.851, + 0.579 + ], + "angle": 0, + "content": "Table 2. Performance on training Order-2: DukeMTMC-ReID \\( \\rightarrow \\) MSMT17-V2 \\( \\rightarrow \\) Market-1501 \\( \\rightarrow \\) CUHK-SYSU \\( \\rightarrow \\) CUHK03." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.6, + 0.471, + 0.751 + ], + "angle": 0, + "content": "same pre-processing and evaluation of GwFReLU [35], which crops the person images with the ground-truth person bounding box annotation and re-organized as a ReID dataset with corresponding identities. To simulate the lifelong person ReID process in the real scenarios, we evaluate our method by employing two training orders used in [18], including Order-1: Market-1501 \\(\\rightarrow\\) CUHK-SYSU \\(\\rightarrow\\) DukeMTMC-ReID \\(\\rightarrow\\) MSMT17-V2 \\(\\rightarrow\\) CUHK03 and Order-2: DukeMTMC-ReID \\(\\rightarrow\\) MSMT17-V2 \\(\\rightarrow\\) Market-1501 \\(\\rightarrow\\) CUHK-SYSU \\(\\rightarrow\\) CUHK03." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Evaluation Metrics. We employ mean Average Precision (mAP) [41] and Rank@1 accuracy (R@1) [15] to evaluate our method on each datasets. The above metrics of our method are reported after sequentially training all datasets. Besides, the corresponding mean accuracy is also reported to evaluate the overall performance on all tasks. Besides, the Average Forgetting (AF) [2] on the above metrics are reported to evaluate the anti-forgetting performance of our method, which averages the difference between the highest" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.6, + 0.892, + 0.631 + ], + "angle": 0, + "content": "accuracy and the final accuracy on each dataset throughout the lifelong learning process." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.648, + 0.719, + 0.665 + ], + "angle": 0, + "content": "4.2. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.674, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Our proposed \\(\\mathrm{C^2R}\\) is implemented with PyTorch [17] on NVIDIA A40 GPUs. We adopt a ResNet-50 [7] network pre-trained on ImageNet [22] as our backbone network. In each training stage, we train the model for 50 epochs with 150 iterations. We use Adam [10] optimizer for training. The learning rate is set to \\(3.5\\times 10^{-4}\\) initially, which decayed by 0.1 at the \\(25^{th}\\) and the \\(35^{th}\\) epochs. We set the hyper-parameters \\(\\mu_{1},\\mu_{2},\\mu_{3}\\), and \\(\\mu_{4}\\) as 50, 1, 0.01 and 0.05, respectively. The prototype length \\(P\\) and the channel number \\(C_0\\) are empirically set to 16 and 32. Input images are resized to \\(256\\times 128\\). The batch size is set to 128, with 4 images for each identity. Following [27], each dataset is randomly sampled with 500 identities to alleviate the problem of unbalanced class numbers among different datasets for fairness comparison." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.946, + 0.52, + 0.957 + ], + "angle": 0, + "content": "16619" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.094, + 0.089, + 0.451, + 0.136 + ], + "angle": 0, + "content": "
MethodLwFAKACVSPatchKDOurs
AF(mAP)24.826.421.016.513.9
AF(R@1)30.835.025.718.514.5
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.077, + 0.138, + 0.468, + 0.166 + ], + "angle": 0, + "content": "Table 3. AF performance of \\( {\\mathrm{C}}^{2}\\mathrm{R} \\) compared with existing methods. (The lower the AF is, the less the model forgets.)" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.187, + 0.449, + 0.204 + ], + "angle": 0, + "content": "4.3. Comparison with State-of-the-arts Methods" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.215, + 0.468, + 0.321 + ], + "angle": 0, + "content": "In this section, we compared our \\(\\mathrm{C}^2\\mathrm{R}\\) with several state-of-the-art methods on both RFL-ReID and traditional L-ReID tasks, including SPD [28], LwF [11], CRL [40], AKA [18], MEGE [20], PatchKD [27], and CVS [30], where CSV is a continual compatible training method and the others are L-ReID methods. The best results are bolded, and the second-best results are underlined." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.327, + 0.468, + 0.508 + ], + "angle": 0, + "content": "Comparison on the RFL-ReID task. Tab. 1 and Tab. 2 summarize the results of our method compared to existing methods, which are reproduced by the released code and denoted as \\(*\\). Compared with these methods, our \\(\\mathrm{C}^2\\mathrm{R}\\) achieves the highest average mAP and R@1 accuracy by \\(39.5\\% /48.2\\%\\) on Order-1 and \\(39.7\\% /48.4\\%\\) on Order-2, leading PatchKD by \\(3.3\\% /3.8\\%\\) and \\(3.6\\% /3.9\\%\\), respectively. This is because our \\(\\mathrm{C}^2\\mathrm{R}\\) method can achieve compatible transfer for old gallery features by balancing the anti-forgetting of old knowledge with the compatibility to the new model, thereby updating old features without reindexing old data effectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.513, + 0.468, + 0.68 + ], + "angle": 0, + "content": "In addition, Tab. 3 reports the AF performance of mAP and R@1 on Order-1. It can be seen that our \\(\\mathrm{C}^2\\mathrm{R}\\) achieves the lowest AF on both mAP and R@1 accuracy, which is lower than PatchKD by \\(2.6\\%\\) and \\(4.0\\%\\), respectively. Notably, compared to CVS, our C2R does not introduce additional old data while achieving the best RFL-ReID accuracy and the best AF performance. Specifically, as shown in Fig. 4, our proposed \\(\\mathrm{C}^2\\mathrm{R}\\) achieves the best average performance on the seen datasets in each stage. The above results intuitively demonstrate that our proposed \\(\\mathrm{C}^2\\mathrm{R}\\) outperforms SOTA methods on average R@1 and mAP at each stage." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.684, + 0.468, + 0.745 + ], + "angle": 0, + "content": "The above results imply that our \\(\\mathrm{C^2R}\\) can adaptively map old features and capture new knowledge, thus balancing compatibility with new feature spaces by preserving old discriminative knowledge." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Comparison on the traditional L-ReID task. We further evaluate our method on the traditional L-ReID task. As shown in Tab. 1 and Tab. 2, our proposed \\(\\mathrm{C}^2\\mathrm{R}\\) also achieves state-of-the-art performance on both two training orders, which leads PatchKD on mAP accuracy by \\(0.5\\%\\) and \\(1.5\\%\\) on Order-1 and Order-2, respectively. The above results imply that our method achieves the best RFL-ReID performance without compromising the performance of traditional L-ReID. Therefore, our \\(\\mathrm{C}^2\\mathrm{R}\\) has better generalization in both general and privacy-sensitive scenarios." + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.091, + 0.698, + 0.243 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.699, + 0.092, + 0.894, + 0.242 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.247, + 0.892, + 0.275 + ], + "angle": 0, + "content": "Figure 4. Lifelong learning performance comparison in RFL-ReID task on mAP and \\(\\mathbb{R}@\\mathbb{1}\\) accuracy." + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.292, + 0.887, + 0.34 + ], + "angle": 0, + "content": "
am0.00.20.40.60.81.0Ours
mAP38.238.739.038.438.938.739.5
R@146.346.947.647.547.847.748.2
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.5, + 0.342, + 0.892, + 0.369 + ], + "angle": 0, + "content": "Table 4. Ablation study on different balancing factors in continual compatible transfer network." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.388, + 0.664, + 0.403 + ], + "angle": 0, + "content": "4.4. Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.413, + 0.892, + 0.457 + ], + "angle": 0, + "content": "In this section, we conduct ablation studies on Order-1 to evaluate the effectiveness of each component in our \\(\\mathrm{C}^2\\mathrm{R}\\). Our Base method is the baseline introduced in Sec. 3.3." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.46, + 0.892, + 0.611 + ], + "angle": 0, + "content": "Effectiveness of CCT network. We compared the adaptively balancing strategy in our continual compatible transfer network with a fixed balancing strategy, which introduces fixed values for \\(a^m\\) in Eq. (5). As shown in Tab. 4, our method achieves the best mAP and R@1 accuracy among the fixed balancing strategies. It indicates that by adaptively generating the most appropriate fusion factor through different old features, our CCT network balances the forward mapping of old knowledge and the knowledge capturing of new knowledge, verifying its superior effectiveness." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.613, + 0.892, + 0.809 + ], + "angle": 0, + "content": "Effectiveness of BCD module. As shown in Tab. 5, we evaluate the two important loss functions \\(\\mathcal{L}_{ca}\\) (Eq. (6)) and \\(\\mathcal{L}_{cr}\\) (Eq. (9)) in the balanced compatible distillation module. It can be seen that compared with the Base method, \\(\\mathcal{L}_{ca}\\) improves the average mAP/R@1 by \\(1.7\\%\\) and \\(1.2\\%\\), and the full version of the BCD module improves by \\(1.9\\%\\) and \\(2.3\\%\\). The above results indicate that the alignment in \\(\\mathcal{L}_{ca}\\) and the relationship distillation in \\(\\mathcal{L}_{cr}\\) are both important for RFL-ReID. The former ensures that old features can continue to be compatible with the new ones, while the latter preserves the relationship within the old feature space. Finally, the BCD module achieves promising improvement by modelling the above functions in a balanced manner." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.81, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Effectiveness of BAD module. We further evaluate two main components \\(\\mathcal{L}_{ad}\\) (Eq. (13)) and \\(\\mathcal{L}_{dc}\\) (Eq. (14)) in the balanced anti-forgetting module. As shown in Tab. 5, \\(\\mathcal{L}_{ad}\\) brings an improvement by \\(1.1\\%\\) on average mAP accuracy. When combined with \\(\\mathcal{L}_{dc}\\), the accuracy further improved by \\(0.3\\%\\). It indicates that by distilling the discriminative" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "16620" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.084, + 0.089, + 0.462, + 0.196 + ], + "angle": 0, + "content": "
BaseCCTBCDBADmAPR@1
LcaLcrLadLdc
✓-----36.244.4
✓✓✓---37.945.6
✓✓✓✓--38.146.7
✓✓✓✓✓-39.247.1
✓✓✓✓✓✓39.548.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.081, + 0.197, + 0.466, + 0.21 + ], + "angle": 0, + "content": "Table 5. Ablation studies of each component in \\( {\\mathrm{C}}^{2}\\mathrm{R} \\) on Order-1." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.223, + 0.469, + 0.282 + ], + "angle": 0, + "content": "information within the old feature, BAD balances the antiforgetting of the old discrimination knowledge with the acquisition of the new knowledge and thus plays an important role in our \\(\\mathrm{C}^2\\mathrm{R}\\) method." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.285, + 0.471, + 0.465 + ], + "angle": 0, + "content": "Hyper-parameter Study. There are 4 hyper-parameters for the training of our \\(\\mathrm{C^2R}\\) method, i.e. \\(\\mu_1\\), \\(\\mu_2\\), \\(\\mu_3\\), and \\(\\mu_4\\). Therefore, we evaluate the effect of the above parameters respectively, as shown in Fig. 6. It can be seen that a slight or excessive \\(\\mu_1\\) will eliminate the alignment of the old feature to the new feature. In addition, as \\(\\mu_2\\) increases, the relationship between old features will prevent the model from learning new knowledge. Therefore, the moderate \\(\\mu_1(=50)\\) and \\(\\mu_2(=1)\\) are chosen in the BCD module to balance the relationship between the old and new features. Similarly, we set a moderate \\(\\mu_3(=0.01)\\) and \\(\\mu_4(=0.05)\\) to balance the discriminative information in the old and new features." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.477, + 0.216, + 0.492 + ], + "angle": 0, + "content": "4.5. Visualization" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.5, + 0.47, + 0.667 + ], + "angle": 0, + "content": "To intuitively verify the effectiveness of our \\(\\mathrm{C^2R}\\), we use t-SNE [29] to visualize and compare the gallery feature and query feature calculated by our method with the Base method. The features are randomly selected from the five benchmark datasets. As shown in Fig. 5, the features calculated by our \\(\\mathrm{C^2R}\\) achieve tighter intra-class representation while retaining more inter-class discriminability. The above results indicate that our \\(\\mathrm{C^2R}\\) can preserve more discriminative information after transferring old gallery features, which can be further aligned by new query features to achieve RFL-ReID." + }, + { + "type": "image", + "bbox": [ + 0.083, + 0.678, + 0.273, + 0.824 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.155, + 0.827, + 0.2, + 0.839 + ], + "angle": 0, + "content": "(a) Base" + }, + { + "type": "image", + "bbox": [ + 0.278, + 0.678, + 0.468, + 0.824 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.339, + 0.827, + 0.404, + 0.839 + ], + "angle": 0, + "content": "(b) our \\(\\mathrm{C}^2\\mathrm{R}\\)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.845, + 0.47, + 0.888 + ], + "angle": 0, + "content": "Figure 5. TSNE results of our \\(C^2 R\\) compared with Base method. Different colours represent different identities, while the circles and the triangles represent gallery and query features, respectively." + }, + { + "type": "image", + "bbox": [ + 0.51, + 0.09, + 0.697, + 0.233 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.697, + 0.09, + 0.885, + 0.234 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.509, + 0.235, + 0.697, + 0.379 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.697, + 0.235, + 0.885, + 0.379 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.528, + 0.385, + 0.863, + 0.4 + ], + "angle": 0, + "content": "Figure 6. The influence of hyper-parameters in our \\(C^2 R\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.41, + 0.757, + 0.424 + ], + "angle": 0, + "content": "4.6. Limitation and Future Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.433, + 0.892, + 0.554 + ], + "angle": 0, + "content": "Our \\(\\mathrm{C}^2\\mathrm{R}\\) can support L-ReID without re-indexing old data in the gallery. However, it is difficult to capture enough new knowledge to facilitate feature transfer and updating when the amount of new data is limited. Therefore, it is worthy of future research on efficient transfer under a few-shot scenario. In addition, when there is noise in new data, how to utilize old knowledge to eliminate such noise to achieve selective transfer should be studied in the future." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.573, + 0.619, + 0.588 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.6, + 0.892, + 0.826 + ], + "angle": 0, + "content": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which prohibits the re-indexing of raw images in the gallery due to data privacy concerns. To this end, we propose a Continual Compatible Representation \\((\\mathrm{C}^2\\mathrm{R})\\) method, which introduces a Continual Compatible Transfer (CCT) network to continuously transfer old gallery features to the new feature space. Besides, a Balanced Compatible Distillation module and a Balanced Anti-forgetting Distillation module are proposed to balance the anti-forgetting of old knowledge with the compatibility to the new model. Extensive experiments on five widely-used benchmark L-ReID datasets verify the effectiveness of our method on the RFL-ReID task while maintaining the state-of-the-art performance on the general L-ReID scenario." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.845, + 0.657, + 0.861 + ], + "angle": 0, + "content": "Acknowledgements" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This work was supported by the National Natural Science Foundation of China (61925201, 62132001, 62376011)." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "16621" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.185 + ], + "angle": 0, + "content": "[1] Shafiq Ahmad, Gianluca Scarpellini, Pietro Morerio, and Alessio Del Bue. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 9046–9056, 2022. 3" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.092, + 0.892, + 0.613 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "16623" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_origin.pdf b/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..f4fe8b4a999b885408f679d7793b145851b4fc1c --- /dev/null +++ b/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/68315fca-b218-4982-8c8a-e271e8d926b8_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:d966d0751497a1fc519a8c130080d0ef4b48c8d6c69d09346626521542f2a28a +size 591823 diff --git a/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/full.md b/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/full.md new file mode 100644 index 0000000000000000000000000000000000000000..b207fe198b20f0bd2b6fe456531601f93022ea79 --- /dev/null +++ b/2024/Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification/full.md @@ -0,0 +1,351 @@ +# Learning Continual Compatible Representation for Re-indexing Free Lifelong Person Re-identification + +Zhenyu Cui $^{1}$ , Jiahuan Zhou $^{1}$ , Xun Wang $^{2}$ , Manyu Zhu $^{2}$ , Yuxin Peng $^{1*}$ $^{1}$ Wangxuan Institute of Computer Technology, Peking University $^{2}$ ByteDance Inc + +cuizhenyu@stu.pku.edu.cn, {jiahuanzhou,pengyuxin}@pku.edu.cn, {wangxun.2,zhumanyu}@bytedance.com + +# Abstract + +Lifelong Person Re-identification (L-ReID) aims to learn from sequentially collected data to match a person across different scenes. Once an L-ReID model is updated using new data, all historical images in the gallery are required to be re-calculated to obtain new features for testing, known as "re-indexing". However, it is infeasible when raw images in the gallery are unavailable due to data privacy concerns, resulting in incompatible retrieval between the query and the gallery features calculated by different models, which causes significant performance degradation. In this paper, we focus on a new task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which requires achieving effective L-ReID without re-indexing raw images in the gallery. To this end, we propose a Continual Compatible Representation $(C^2 R)$ method, which facilitates the query feature calculated by the continuously updated model to effectively retrieve the gallery feature calculated by the old model in a compatible manner. Specifically, we design a Continual Compatible Transfer (CCT) network to continuously transfer and consolidate the old gallery feature into the new feature space. Besides, a Balanced Compatible Distillation module is introduced to achieve compatibility by aligning the transferred feature space with the new feature space. Finally, a Balanced Anti-forgetting Distillation module is proposed to eliminate the accumulated forgetting of old knowledge during the continual compatible transfer. Extensive experiments on several benchmark L-ReID datasets demonstrate the effectiveness of our method against state-of-the-art methods for both RFL-ReID and L-ReID tasks. The source code of this paper is available at https://github.com/PKU-ICST-MIPL/C2R_CVPR2024. + +# 1. Introduction + +Person re-identification (ReID) aims to identify the same person across different areas at different times [42]. Exist + +![](images/31e7454ba4523e21e92fc12b7ad34760216ce9b67260102ed66e121f13f3abef.jpg) +(a) Traditional Lifelong ReID + +![](images/77ab8203d07cdf1dc555afb29bf56c428c1ef8596d98b59f68a3f474663afa99.jpg) +(b) Re-indexing Free Lifelong ReID +Figure 1. Comparison between (a) the traditional Lifelong Person Re-identification (L-ReID) task and (b) the Re-indexing Free Lifelong Person Re-identification (RFL-ReID) task. + +ing methods [26, 32, 44] have made remarkable progress based on deep learning methods [37] and large-scale datasets [34, 41, 43]. However, their performance is often limited when training data are continuously collected from a series of different scenarios due to the well-known catastrophic forgetting challenge [3]. + +Recently, Lifelong person ReID (L-ReID) has aroused great concerns involving acquiring knowledge from streaming data and performing well across all data [5, 18, 19, 38]. Its challenge is to balance the anti-forgetting of old knowledge with the acquisition of new knowledge. To this end, existing L-ReID methods usually adopt the exemplar replay [38] and the knowledge distillation [27] to preserve + +![](images/0d4017b48f613c8a0f9c711419f06cb7c736505594f06c2d4fe572d1c08a702a.jpg) +Figure 2. Performance Comparison between the traditional Lifelong Person Re-identification (L-ReID) task and the Re-indexing Free Lifelong Person Re-identification (RFL-ReID) task. + +old knowledge when updating the model. The updated new model will be sequentially deployed by "re-indexing" [24] features of old data in the gallery. As shown in Fig. 1 (a), the old gallery features are replaced by the re-indexed gallery features to be compatible with the new model. However, massive incremental images in the gallery bring unbearable computational costs and prevent the re-indexing process [21, 39]. Besides, in the context of data privacy concerns [25], re-indexing is legally forbidden due to the impracticality of storing and re-indexing unauthorized raw images within privacy-sensitive scenarios [1, 4, 14], also known as Re-indexing Free Lifelong ReID (RFL-ReID), as shown in Fig. 1 (b). In this case, the domain gap between different datasets leads to the incompatibility between features calculated by the old and the new models. Consequently, as shown in Fig. 2, the performance of existing methods [11, 18, 27] often degrades significantly. + +In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which entails deploying L-ReID models continuously without re-indexing raw images in the gallery. It is extremely challenging when considering not only balancing the acquisition of old and new knowledge but also achieving the compatibility between the old and the new feature space. To this end, Compatible Training (CT) [16, 21, 23] becomes a feasible solution which promotes the compatibility. Unfortunately, most existing CT methods only focus on compatibility within the same dataset. However, the large domain gap [5, 19] between different ReID datasets typically leads to the forgetting of old knowledge, causing the feature shift problem, which seriously degrades the performance of existing CT methods. + +Inspired by the above observation, we propose a Continua! ReID. The core idea of $\mathrm{C}^2\mathrm{R}$ is to continuously update old features in the gallery to make it compatible with new query features. To tackle the domain shift problem, a Continua! ReID Transfer (CCT) network is proposed to update old gallery features continuously, which transfers the old feature into the new feature space by adaptively cap + +turing the knowledge from different domains. Correspondingly, to achieve the compatibility between the transferred features and the new ones, a Balanced Compatible Distillation (BCD) module is designed to preserve the relationship between the old and the transferred features in a unified feature space. Finally, to eliminate the accumulated forgetting of old knowledge during the continuous transfer, a Balanced Anti-forgetting Distillation (BAD) module is introduced to balance the old and the new discriminative information. Overall, the main contributions of this paper can be summarized as follows: + +1) This paper proposes a Continual Compatible Representation scheme to solve the challenging Re-indexing Free Lifelong Person Re-identification task, which prevents reindexing to raw images in the old gallery. +2) A continual compatible transfer network is designed to adaptively capture the old and the new knowledge, which promotes the updating of old gallery features. +3) To achieve compatibility of the old and the new data, a balanced compatible distillation module is designed to balance the relationship between the old and the new features in a unified feature space. +4) A balanced anti-forgetting distillation module is introduced to balance the acquisition of the old and the new knowledge without rehearsing the old data. + +# 2. Related Work + +# 2.1. Lifelong Person Re-identification + +Lifelong Person Re-identification (L-ReID) aims to use streaming data from different domains to train a ReID model to continuously match the same person across all domains [18]. It requires continuously accumulating knowledge from new data and preventing catastrophic forgetting of knowledge learned in old data. To this end, rehearsal-based methods rehearsed old data for the anti-forgetting of old knowledge [5, 35, 38]. Yu et al. [38] proposed a knowledge refreshing and consolidation framework to achieve both positive forward and backward transfers, which simultaneously promotes person matching in both old and new domains. However, limited by data privacy concerns, the old data is usually difficult to rehearse for L-ReID. Therefore, some methods focus on developing rehearsal-free methods [18, 19, 27, 33]. Sun et al. [27] proposed a patch-based knowledge distillation method, which can mitigate catastrophic forgetting problems by preserving patch-level knowledge within individual patch features and mutual relations. Despite achieving some progress, existing methods require re-indexing old data in the gallery after training on new data to adapt to the updated model. In this paper, we focus on a new and challenging task called RFL-ReID, which prohibits re-indexing the old data in the gallery due to data privacy issues. + +![](images/e0f8d7db28a16bcae7851051bf91271f5b757bbc35f815860bec2766bf00ab22.jpg) + +![](images/b802098599ed5f5c907536492d4a21334137c1398a987c220740854119e7448d.jpg) +Figure 3. The architecture of our proposed Continual Compatible Representation $(\mathbf{C}^2\mathbf{R})$ method. Our $\mathrm{C}^2\mathrm{R}$ consists of a Continual Compatible Transfer (CCT) network, a Balanced Compatible Distillation (BCD) module, and a Balanced Anti-forgetting Distillation (BAD) module. In the training phase, all the above components will be trained, and the CCT network will be used to update the old feature set, thereby achieving re-indexing free lifelong person re-identification. + +# 2.2. Compatible Training + +Compatible Training (CT) aims to achieve the compatibility between the old model and the new model without reindexing, which encourages the feature calculated by the new model to be closer to the same object feature calculated by the old model. Existing CT methods can be categorized into two branches: backward CT [16, 24, 39] and forward CT methods [21, 30, 45]. Pan et al. [16] proposed an adversarial learning-based backward CT method, which optimized the distribution discrepancy and improved the backward compatibility of the updated model. Ramanujan et al. [21] proposed a flexible forward CT method by employing side-information to facilitate the updating of the new model. However, most existing CT methods only achieve compatibility between the old and the new models updated using the same dataset, ignoring the requirement to be compatible with multiple different datasets continuously. To this end, Wan et al. [30] proposed a long-term visual search framework to realize CT in the continual learning scenario, which allows new classes to occur in the new data. However, it relies heavily on old data and old features to achieve the compatibility, which is infeasible for the privacy-sensitive scenario. + +Different from these methods, we propose a continual compatible representation scheme called $\mathrm{C}^2\mathrm{R}$ , which achieves leading L-ReID performance when old data in the gallery cannot be re-indexed in the practical privacy-sensitive scenario. + +# 3. Method + +# 3.1. Problem Formulation + +In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID). Formally, given the sequentially collected datasets $\mathcal{D} = \{\mathcal{D}^1,\mathcal{D}^2,\dots ,\mathcal{D}^S\}$ , where $S$ denotes the total number. The $s^{th}$ dataset $\mathcal{D}^s = \{\mathcal{T}^s,\mathcal{G}^s\}$ contains a training set $\mathcal{T}^s$ and the corresponding gallery set $\mathcal{G}^s$ without overlapping person identities. Each $\mathcal{T}^s = \{x_i^s,y_i^s\}_{i = 1}^{N^s}$ contains $N^s$ training images $x_{i}^{s}$ and the corresponding identity labels $y_{i}^{s}$ . Our goal is to train a feature extraction model $\phi^S (\cdot):x_i\to z_i$ to extract the feature $z_{i}$ for each input image $x_{i}$ . $\phi^S (\cdot)$ is expected to maximize the similarity between the images belonging to the same person, thereby performing well on the overall retrieval performance of all $S$ tasks. Particularly, when training on the $s^{th}$ dataset $\mathcal{D}^s$ , the previous $s - 1$ datasets $\{\mathcal{D}^1,\dots ,\mathcal{D}^{s - 1}\}$ are absolutely unavailable due to data privacy concerns, including the training sets $\{\mathcal{T}^j\}_{j = 1}^{s - 1}$ and the gallery sets $\{\mathcal{G}^j\}_{j = 1}^{s - 1}$ . Therefore, each image in $\mathcal{G}^j$ can only be extracted once based on the model $\phi^j (\cdot)$ within the $j^{th}$ training stage. + +# 3.2. Overview + +As shown in Fig. 3, our proposed Continual Compatible Representation $(\mathrm{C}^2\mathrm{R})$ method consists of a Continual Compatible Transfer (CCT) network, a Balanced Compatible Distillation (BCD) module, and a Balanced Anti-forgetting + +Distillation (BAD) module. At the beginning of the $s^{th}$ training stage $(s\geq 2)$ , a copy of the model $\phi^o$ and the classifier $\psi^o$ are frozen to serve as the old knowledge. Then, we train the model with the CCT network based on the BCD and the BAD modules, as shown in Fig. 3 (a). After the training of the $s^{th}$ stage, we reform a new gallery feature set $\mathcal{F}^s$ by updating the transferred features in the old gallery feature set $\mathcal{F}^{s - 1}$ using our proposed CCT network, and extracting the features of the current gallery set $\mathcal{G}^s$ using $\phi^s$ (Fig. 3 (b)). When testing at the $s^{th}$ stage, we rank each feature in $\mathcal{F}^s$ with the query feature calculated by $\phi^s$ (Fig. 3 (c)) to validate the ReID performance on all $s$ datasets. + +# 3.3. Lifelong Person Re-identification Baseline + +In this section, we start by presenting a lifelong person re-identification baseline. The baseline model consists of a feature extraction model $\phi (\cdot)$ and a classifier head $\psi (\cdot)$ , where $\phi (\cdot)$ extracts a feature $z_{i}$ for each input image $x_{i}$ , and $\psi (\cdot)$ predicts the probability $p_i$ of each person's identity. + +Considering that the RFL-ReID task aims to continuously match the same person across the sequentially given datasets, we employ a cross-entropy loss $\mathcal{L}_{ce}$ [13] and a triplet loss $\mathcal{L}_{trip}$ [8] to learn a discriminative representation for each person in the current dataset $\mathcal{D}^s$ . However, despite certain performance improvements in $\mathcal{D}^s$ , it has been verified to cause the catastrophic forgetting problem on the previous $(s - 1)$ datasets [3]. To balance the acquisition of new knowledge and the anti-forgetting of old knowledge, we introduce an anti-forgetting loss $\mathcal{L}_{pkd}$ [27] based on image patch knowledge distillation to build a basic L-ReID model. Therefore, the overall loss function for our baseline model is formulated as: + +$$ +\mathcal {L} _ {\text {b a s e}} = \mathcal {L} _ {c e} + \mathcal {L} _ {\text {t r i p}} + \mathcal {L} _ {\text {p k d}}. \tag {1} +$$ + +The above baseline method achieves a performance trade-off between new and old datasets by re-indexing data in old galleries using the new model. However, when the old data is unavailable to the new model due to data privacy concerns, the performance will be significantly degraded due to the incompatibility of the features output by the old model and the new model. To tackle the above issue, we will detail present each component of our $\mathrm{C^2R}$ scheme in the following sections. + +# 3.4. Continual Compatible Transfer Network + +To tackle the domain shift problem, we design a Continual Compatible Transfer (CCT) network to transfer the old feature into the new feature space continuously. To this end, our CCT is designed as a two-stream network to capture transfer-related knowledge from different domains. + +Specifically, we first design a Knowledge Capturing Module (KCM) module to capture knowledge from new domains. Let $z^o \in \mathbb{R}^C$ be the feature output by the old model + +$\phi^o (\cdot)$ based on the sample $x^{s}$ , $\pmb{v}_{p} \in \mathbb{R}^{P \times C}$ be a learnable new knowledge prototype set with length $P$ . In order to enable $\pmb{z}^o$ to capture new knowledge for compatibility, we first calculate a capturing probability $\pmb{k}^o \in \mathbb{R}^P$ for each new knowledge prototype: + +$$ +\boldsymbol {k} ^ {o} = \delta \left(g _ {c} \left(\tilde {\boldsymbol {z}} ^ {o}\right)\right), \tag {2} +$$ + +where $g_{c}(\cdot)$ denotes a three-layer fully connected network, $\delta (\cdot)$ denotes the softmax function, and $(\widetilde{\cdot})$ denotes the 12-normalized function. Then, we combine the captured new knowledge with a weighted summation of the prototypes: + +$$ +\boldsymbol {z} ^ {t} = \sum_ {p = 1} ^ {P} \boldsymbol {k} _ {i} ^ {o} \cdot \boldsymbol {v} _ {p}. \tag {3} +$$ + +Sequentially, a parallel Forward Mapping Module (FMM) is designed to directly map the old feature to the new one, thereby preserving the old knowledge from old domains. The designed mapping network consists of sequential fully connected layers, Batch Normalization [9] layers, and PReLU [6] layers. The first fully connected layer reduces the channel number to $C_0$ , while the last layer recovers it back to the original number, which keeps the representation capability while saving redundant operations: + +$$ +z ^ {m} = g _ {s} \left(\widetilde {z} ^ {o}\right). \tag {4} +$$ + +Finally, CCT takes the input $\widetilde{z}^o$ to generate a factor $a^m$ to adaptively balance the above two features ( $z^t$ and $z^m$ ) obtained by the KCM module and FMM module. Meanwhile, the original features are added by the residual skipconnection to alleviate the gradient vanishing issue [31]. The transferred result $z^w$ of CCT network can be formulated as follows: + +$$ +\boldsymbol {z} ^ {w} = \left(1 - a ^ {m}\right) \cdot \boldsymbol {z} ^ {t} + a ^ {m} \cdot \boldsymbol {z} ^ {m} + \widetilde {\boldsymbol {z}} ^ {o}. \tag {5} +$$ + +Following [14], we leverage 4 cascaded CCT networks to build up a strong transfer network, which sequentially transfers features from previous stages to the current stage. + +# 3.5. Balanced Compatible Distillation + +To make the transferred features compatible with the new one, we design a Balanced Compatible Distillation (BCD) module to simultaneously preserve the relationships of the old and the transferred features in the new feature space. + +Given a mini-batch of training samples $\{x_i^s, y_i^s\}_{i=1}^B$ , where $B$ is the batch size, and a new feature $z_i^n$ calculated by the new model $\phi(\cdot)^n$ . We start by directly aligning the above features with 12-loss: + +$$ +\mathcal {L} _ {c a} = - \frac {1}{B} \sum_ {i = 1} ^ {B} \left| \left| \tilde {z} _ {i} ^ {n} - \tilde {z} _ {i} ^ {w} \right| \right| _ {2}. \tag {6} +$$ + +The above alignment loss promotes compatibility of new features in the new feature space, while ignoring the relationship between the old features, thus limiting the ReID performance on old data. Therefore, we propose a relationship distillation loss to overcome the above issue. + +Firstly, we construct an old similarity matrix $\mathcal{M}^o\in$ $\mathbb{R}^{B\times B}$ , which is calculated by the affinity between each two features in $\{\widetilde{z}_i^o\}_{i = 1}^B$ to represent the relationship between the corresponding images in the old feature space: + +$$ +\mathcal {M} _ {i, j} ^ {o} = \frac {e ^ {\langle \widetilde {z} _ {i} ^ {o} , \widetilde {z} _ {j} ^ {o} \rangle}}{\sum_ {k = 1} ^ {B} e ^ {\langle \widetilde {z} _ {i} ^ {o} , \widetilde {z} _ {k} ^ {o} \rangle}}, (i, j \in [ 1, B ]), \tag {7} +$$ + +where $\langle \cdot ,\cdot \rangle$ denotes the cosine similarity. Similarly, a transferred similarity matrix $\mathcal{M}^w$ is also constructed to represent the relationship between the transferred features $\{\widetilde{z}_i^w\}_{i = 1}^B$ . Apparently, the alignment in Eq. (6) will promote higher similarity between samples with the same identity in $\mathcal{M}^w$ , which will conflict with the corresponding similarity in $\mathcal{M}^o$ . Therefore, we remove the similarities between samples belonging to the same identity to avoid the above conflicts for relationship distillation: + +$$ +\mathcal {M} _ {i, j} ^ {x} = \left\{ \begin{array}{l l} \mathcal {M} _ {i, j} ^ {x}, I D (i) \neq I D (j) \\ 0, \quad I D (i) = I D (j), \end{array} \right. \tag {8} +$$ + +where $ID(\cdot)$ denotes the identity of the given sample, and $x \in o, w$ . Next, a widely-used knowledge distillation loss $\mathcal{L}_{cr}$ based on Kullback-Leibler (KL) divergence is imposed to distil the relationship between old features as follows: + +$$ +\mathcal {L} _ {c r} = - \frac {1}{B} \sum_ {i = 1} ^ {B} \sigma \left(M _ {i,:} ^ {o}\right) \log \left(\frac {\sigma \left(M _ {i,:} ^ {o}\right)}{\sigma \left(M _ {i,:} ^ {w}\right)}\right), \tag {9} +$$ + +where $\sigma (\cdot)$ denotes the row-wise 11-normalized function. + +In all, the loss function for the BCD module can be calculated as follows: + +$$ +\mathcal {L} _ {b c d} = \mu_ {1} \mathcal {L} _ {c a} + \mu_ {2} \mathcal {L} _ {c r}, \tag {10} +$$ + +where $\mu_{1}$ and $\mu_{2}$ denote two hyper-parameters to balance our proposed balanced compatible distillation. + +# 3.6. Balanced Anti-forgetting Distillation + +Although the proposed BCD module achieves the compatibility by selectively distilling the relationship, it ignores the accumulated forgetting of old knowledge during the continual compatible transfer, thereby reducing the inter-class discrimination of old data. Therefore, we propose a Balanced Anti-forgetting Distillation (BAD) module to preserve the discriminative information within the old and new features in the new feature space. + +To this end, we employ the old classifier head $\psi^o (\cdot)$ to extract and distil the discriminative information. Therefore, + +we extract old identity logits $\pmb{q}^{o}$ of the old feature $z^{o}$ as the theoretical distribution of the discriminative information: + +$$ +\boldsymbol {q} ^ {o} = \delta \left(\psi^ {o} \left(\boldsymbol {z} ^ {o}\right)\right). \tag {11} +$$ + +Considering that the transferred feature $z^w$ and $z^o$ come from different datasets, it is challenging to extract consistent discriminative information directly using $\psi^o(\cdot)$ . To tackle the above problem, we perform an inverse 12-normalization on $z^w$ so that it can be extracted as the real distribution of the transferred discriminative information: + +$$ +\boldsymbol {q} ^ {w} = \delta \left(\psi^ {o} \left(\widetilde {\boldsymbol {z}} ^ {w} \cdot \left\| \boldsymbol {z} ^ {o} \right\| _ {2}\right)\right). \tag {12} +$$ + +Sequentially, we use an anti-forgetting loss $\mathcal{L}_{ad}$ to preserve the old discriminative knowledge, which can be calculated as follows: + +$$ +\mathcal {L} _ {a d} = - \frac {1}{B} \sum_ {i = 1} ^ {B} \boldsymbol {q} _ {i} ^ {o} \log \left(\frac {\boldsymbol {q} _ {i} ^ {o}}{\boldsymbol {q} _ {i} ^ {w}}\right). \tag {13} +$$ + +Despite achieving the anti-forgetting, the distillation in Eq. (13) will also limit the discrimination of the transferred feature in the new feature space. Therefore, we introduce a discriminative consistency-based loss $\mathcal{L}_{dc}$ to balance the discrimination for both transferred and new features: + +$$ +\mathcal {L} _ {d c} = - \frac {1}{B} \sum_ {i = 1} ^ {B} (1 - \cos \left\langle \frac {\widetilde {z} _ {i} ^ {w} - \widetilde {z} _ {i} ^ {o}}{\left| \left| \widetilde {z} _ {i} ^ {w} - \widetilde {z} _ {i} ^ {o} \right| \right| _ {2}}, \frac {\widetilde {z} _ {i} ^ {n} - \widetilde {z} _ {i} ^ {o}}{\left| \left| \widetilde {z} _ {i} ^ {n} - \widetilde {z} _ {i} ^ {o} \right| \right| _ {2}} \right\rangle). \tag {14} +$$ + +The overall loss function for the BAD module can be calculated as follows: + +$$ +\mathcal {L} _ {b a d} = \mu_ {3} \mathcal {L} _ {a d} + \mu_ {4} \mathcal {L} _ {d c}, \tag {15} +$$ + +where $\mu_{3}$ and $\mu_{4}$ denote two hyper-parameters when training the model. + +# 3.7. Objective Function + +Finally, the total loss $\mathcal{L}$ of $\mathrm{C}^2\mathrm{R}$ is calculated as follows: + +$$ +\mathcal {L} = \mathcal {L} _ {\text {b a s e}} + \mathcal {L} _ {\text {b c d}} + \mathcal {L} _ {\text {b a d}}. \tag {16} +$$ + +Through the joint optimizing of $\mathcal{L}$ , our $\mathrm{C}^2\mathrm{R}$ achieves the compatibility between the old and the new models and prevents re-indexing to raw images in the old gallery. + +# 4. Experiments + +# 4.1. Datasets and Evaluation Metrics + +Datasets. To verify the effectiveness of our method, we conduct extensive experiments on five benchmark lifelong person ReID datasets, including Market-1501 [41], CUHK-SYSU [36], DukeMTMC-ReID [43], MSMT17-V2 [34] and CUHK03 [12]. For CUHK-SYSU, we follow the + +
TaskMethodMarket-1501CUHK-SYSUDukeMTMC-ReIDMSMT17-V2CUHK03Average
mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1
L-ReIDJointTrain68.185.281.483.860.475.724.648.942.743.655.467.5
SPD [28]35.661.261.764.027.547.15.215.542.244.334.446.4
LwF [11]56.377.172.975.129.646.56.016.636.137.540.250.6
CRL [40]58.078.272.575.128.345.26.015.837.439.840.550.8
AKA [18]58.177.472.574.828.745.26.116.238.740.440.850.8
MEGE [20]39.061.673.376.616.930.34.613.436.437.134.043.8
PatchKD [27]68.585.775.678.633.850.46.517.034.136.843.753.7
Ours69.086.876.779.533.248.66.617.435.636.244.253.7
RFL-ReIDLwF* [11]39.158.040.040.77.815.32.67.123.323.922.629.0
AKA* [18]36.152.238.637.67.613.83.18.326.526.522.427.7
CVS* [30]38.855.649.049.719.330.04.611.524.724.727.334.3
PatchKD* [27]61.478.457.859.020.834.45.112.836.037.636.244.4
Ours62.779.764.466.326.741.76.815.737.237.639.548.2
+ +Table 1. Performance on training Order-1: Market-1501→CUHK-SYSU→DukeMTMC-ReID→MSMT17-V2→CUHK03. + +
TaskMethodDukeMTMC-ReIDMSMT17-V2Market-1501CUHK-SYSUCUHK03Average
mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1
L-ReIDJointTrain60.475.724.648.968.185.281.483.842.743.655.467.5
SPD [28]28.548.53.711.532.357.462.165.043.045.233.945.5
LwF [11]42.761.75.114.334.458.669.973.034.134.137.248.4
CRL [40]43.563.14.813.735.059.870.072.834.536.837.649.2
AKA [18]42.260.15.415.137.259.871.273.936.937.938.649.4
MEGE [20]21.635.53.09.325.049.869.973.134.735.130.840.6
PatchKD [27]58.374.16.417.443.267.474.576.933.734.843.254.1
Ours59.775.07.319.242.466.576.077.837.839.344.755.6
RFL-ReIDLwF* [11]15.022.91.23.29.519.438.837.520.219.616.920.5
AKA* [18]11.115.11.33.213.427.335.934.725.225.617.421.2
CVS* [30]29.041.93.59.430.749.660.061.228.529.930.338.4
PatchKD* [27]46.560.94.010.431.150.563.064.035.836.636.144.5
Ours48.463.66.214.937.055.667.468.439.239.539.748.4
+ +Table 2. Performance on training Order-2: DukeMTMC-ReID $\rightarrow$ MSMT17-V2 $\rightarrow$ Market-1501 $\rightarrow$ CUHK-SYSU $\rightarrow$ CUHK03. + +same pre-processing and evaluation of GwFReLU [35], which crops the person images with the ground-truth person bounding box annotation and re-organized as a ReID dataset with corresponding identities. To simulate the lifelong person ReID process in the real scenarios, we evaluate our method by employing two training orders used in [18], including Order-1: Market-1501 $\rightarrow$ CUHK-SYSU $\rightarrow$ DukeMTMC-ReID $\rightarrow$ MSMT17-V2 $\rightarrow$ CUHK03 and Order-2: DukeMTMC-ReID $\rightarrow$ MSMT17-V2 $\rightarrow$ Market-1501 $\rightarrow$ CUHK-SYSU $\rightarrow$ CUHK03. + +Evaluation Metrics. We employ mean Average Precision (mAP) [41] and Rank@1 accuracy (R@1) [15] to evaluate our method on each datasets. The above metrics of our method are reported after sequentially training all datasets. Besides, the corresponding mean accuracy is also reported to evaluate the overall performance on all tasks. Besides, the Average Forgetting (AF) [2] on the above metrics are reported to evaluate the anti-forgetting performance of our method, which averages the difference between the highest + +accuracy and the final accuracy on each dataset throughout the lifelong learning process. + +# 4.2. Implementation Details + +Our proposed $\mathrm{C^2R}$ is implemented with PyTorch [17] on NVIDIA A40 GPUs. We adopt a ResNet-50 [7] network pre-trained on ImageNet [22] as our backbone network. In each training stage, we train the model for 50 epochs with 150 iterations. We use Adam [10] optimizer for training. The learning rate is set to $3.5\times 10^{-4}$ initially, which decayed by 0.1 at the $25^{th}$ and the $35^{th}$ epochs. We set the hyper-parameters $\mu_{1},\mu_{2},\mu_{3}$ , and $\mu_{4}$ as 50, 1, 0.01 and 0.05, respectively. The prototype length $P$ and the channel number $C_0$ are empirically set to 16 and 32. Input images are resized to $256\times 128$ . The batch size is set to 128, with 4 images for each identity. Following [27], each dataset is randomly sampled with 500 identities to alleviate the problem of unbalanced class numbers among different datasets for fairness comparison. + +
MethodLwFAKACVSPatchKDOurs
AF(mAP)24.826.421.016.513.9
AF(R@1)30.835.025.718.514.5
+ +Table 3. AF performance of ${\mathrm{C}}^{2}\mathrm{R}$ compared with existing methods. (The lower the AF is, the less the model forgets.) + +# 4.3. Comparison with State-of-the-arts Methods + +In this section, we compared our $\mathrm{C}^2\mathrm{R}$ with several state-of-the-art methods on both RFL-ReID and traditional L-ReID tasks, including SPD [28], LwF [11], CRL [40], AKA [18], MEGE [20], PatchKD [27], and CVS [30], where CSV is a continual compatible training method and the others are L-ReID methods. The best results are bolded, and the second-best results are underlined. + +Comparison on the RFL-ReID task. Tab. 1 and Tab. 2 summarize the results of our method compared to existing methods, which are reproduced by the released code and denoted as $*$ . Compared with these methods, our $\mathrm{C}^2\mathrm{R}$ achieves the highest average mAP and R@1 accuracy by $39.5\% /48.2\%$ on Order-1 and $39.7\% /48.4\%$ on Order-2, leading PatchKD by $3.3\% /3.8\%$ and $3.6\% /3.9\%$ , respectively. This is because our $\mathrm{C}^2\mathrm{R}$ method can achieve compatible transfer for old gallery features by balancing the anti-forgetting of old knowledge with the compatibility to the new model, thereby updating old features without reindexing old data effectively. + +In addition, Tab. 3 reports the AF performance of mAP and R@1 on Order-1. It can be seen that our $\mathrm{C}^2\mathrm{R}$ achieves the lowest AF on both mAP and R@1 accuracy, which is lower than PatchKD by $2.6\%$ and $4.0\%$ , respectively. Notably, compared to CVS, our C2R does not introduce additional old data while achieving the best RFL-ReID accuracy and the best AF performance. Specifically, as shown in Fig. 4, our proposed $\mathrm{C}^2\mathrm{R}$ achieves the best average performance on the seen datasets in each stage. The above results intuitively demonstrate that our proposed $\mathrm{C}^2\mathrm{R}$ outperforms SOTA methods on average R@1 and mAP at each stage. + +The above results imply that our $\mathrm{C^2R}$ can adaptively map old features and capture new knowledge, thus balancing compatibility with new feature spaces by preserving old discriminative knowledge. + +Comparison on the traditional L-ReID task. We further evaluate our method on the traditional L-ReID task. As shown in Tab. 1 and Tab. 2, our proposed $\mathrm{C}^2\mathrm{R}$ also achieves state-of-the-art performance on both two training orders, which leads PatchKD on mAP accuracy by $0.5\%$ and $1.5\%$ on Order-1 and Order-2, respectively. The above results imply that our method achieves the best RFL-ReID performance without compromising the performance of traditional L-ReID. Therefore, our $\mathrm{C}^2\mathrm{R}$ has better generalization in both general and privacy-sensitive scenarios. + +![](images/02a65ad41234195c104ccb631acd1b00cb748314ac3dbfb816b2b092316d99f8.jpg) +Figure 4. Lifelong learning performance comparison in RFL-ReID task on mAP and $\mathbb{R}@\mathbb{1}$ accuracy. + +![](images/48d670bf3fc1955b64e03956db569ec2b4b05b0cbaed703d37cb821ba11132bf.jpg) + +
am0.00.20.40.60.81.0Ours
mAP38.238.739.038.438.938.739.5
R@146.346.947.647.547.847.748.2
+ +Table 4. Ablation study on different balancing factors in continual compatible transfer network. + +# 4.4. Ablation Studies + +In this section, we conduct ablation studies on Order-1 to evaluate the effectiveness of each component in our $\mathrm{C}^2\mathrm{R}$ . Our Base method is the baseline introduced in Sec. 3.3. + +Effectiveness of CCT network. We compared the adaptively balancing strategy in our continual compatible transfer network with a fixed balancing strategy, which introduces fixed values for $a^m$ in Eq. (5). As shown in Tab. 4, our method achieves the best mAP and R@1 accuracy among the fixed balancing strategies. It indicates that by adaptively generating the most appropriate fusion factor through different old features, our CCT network balances the forward mapping of old knowledge and the knowledge capturing of new knowledge, verifying its superior effectiveness. + +Effectiveness of BCD module. As shown in Tab. 5, we evaluate the two important loss functions $\mathcal{L}_{ca}$ (Eq. (6)) and $\mathcal{L}_{cr}$ (Eq. (9)) in the balanced compatible distillation module. It can be seen that compared with the Base method, $\mathcal{L}_{ca}$ improves the average mAP/R@1 by $1.7\%$ and $1.2\%$ , and the full version of the BCD module improves by $1.9\%$ and $2.3\%$ . The above results indicate that the alignment in $\mathcal{L}_{ca}$ and the relationship distillation in $\mathcal{L}_{cr}$ are both important for RFL-ReID. The former ensures that old features can continue to be compatible with the new ones, while the latter preserves the relationship within the old feature space. Finally, the BCD module achieves promising improvement by modelling the above functions in a balanced manner. + +Effectiveness of BAD module. We further evaluate two main components $\mathcal{L}_{ad}$ (Eq. (13)) and $\mathcal{L}_{dc}$ (Eq. (14)) in the balanced anti-forgetting module. As shown in Tab. 5, $\mathcal{L}_{ad}$ brings an improvement by $1.1\%$ on average mAP accuracy. When combined with $\mathcal{L}_{dc}$ , the accuracy further improved by $0.3\%$ . It indicates that by distilling the discriminative + +
BaseCCTBCDBADmAPR@1
LcaLcrLadLdc
✓-----36.244.4
✓✓✓---37.945.6
✓✓✓✓--38.146.7
✓✓✓✓✓-39.247.1
✓✓✓✓✓✓39.548.2
+ +Table 5. Ablation studies of each component in ${\mathrm{C}}^{2}\mathrm{R}$ on Order-1. + +information within the old feature, BAD balances the antiforgetting of the old discrimination knowledge with the acquisition of the new knowledge and thus plays an important role in our $\mathrm{C}^2\mathrm{R}$ method. + +Hyper-parameter Study. There are 4 hyper-parameters for the training of our $\mathrm{C^2R}$ method, i.e. $\mu_1$ , $\mu_2$ , $\mu_3$ , and $\mu_4$ . Therefore, we evaluate the effect of the above parameters respectively, as shown in Fig. 6. It can be seen that a slight or excessive $\mu_1$ will eliminate the alignment of the old feature to the new feature. In addition, as $\mu_2$ increases, the relationship between old features will prevent the model from learning new knowledge. Therefore, the moderate $\mu_1(=50)$ and $\mu_2(=1)$ are chosen in the BCD module to balance the relationship between the old and new features. Similarly, we set a moderate $\mu_3(=0.01)$ and $\mu_4(=0.05)$ to balance the discriminative information in the old and new features. + +# 4.5. Visualization + +To intuitively verify the effectiveness of our $\mathrm{C^2R}$ , we use t-SNE [29] to visualize and compare the gallery feature and query feature calculated by our method with the Base method. The features are randomly selected from the five benchmark datasets. As shown in Fig. 5, the features calculated by our $\mathrm{C^2R}$ achieve tighter intra-class representation while retaining more inter-class discriminability. The above results indicate that our $\mathrm{C^2R}$ can preserve more discriminative information after transferring old gallery features, which can be further aligned by new query features to achieve RFL-ReID. + +![](images/9694da0a586a66655a27e078c631b2c8688698141a7852380dd22413edf89d49.jpg) +(a) Base +Figure 5. TSNE results of our $C^2 R$ compared with Base method. Different colours represent different identities, while the circles and the triangles represent gallery and query features, respectively. + +![](images/7bec8af77eb3df7ec9f2d212405d15f615675f0df444594e273eee45e8212305.jpg) +(b) our $\mathrm{C}^2\mathrm{R}$ + +![](images/9de7e20172300eb503e9cf0c9d470e0db2c1e18c901af2c6336138d1c0e3eedb.jpg) + +![](images/c0ee8effc310116df7c5cf3c2f4e636e3b9ba97055c03468eb3ef327a3812899.jpg) + +![](images/61312fb8dd085e436752a0849abfe2b010c8c90279e93567f4aefa28a69a1c85.jpg) +Figure 6. The influence of hyper-parameters in our $C^2 R$ . + +![](images/06e38eff4ae95eed22171268027c1de148ae0466de6f80f170fc7dfcbce5e10d.jpg) + +# 4.6. Limitation and Future Work + +Our $\mathrm{C}^2\mathrm{R}$ can support L-ReID without re-indexing old data in the gallery. However, it is difficult to capture enough new knowledge to facilitate feature transfer and updating when the amount of new data is limited. Therefore, it is worthy of future research on efficient transfer under a few-shot scenario. In addition, when there is noise in new data, how to utilize old knowledge to eliminate such noise to achieve selective transfer should be studied in the future. + +# 5. Conclusion + +In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which prohibits the re-indexing of raw images in the gallery due to data privacy concerns. To this end, we propose a Continual Compatible Representation $(\mathrm{C}^2\mathrm{R})$ method, which introduces a Continual Compatible Transfer (CCT) network to continuously transfer old gallery features to the new feature space. Besides, a Balanced Compatible Distillation module and a Balanced Anti-forgetting Distillation module are proposed to balance the anti-forgetting of old knowledge with the compatibility to the new model. Extensive experiments on five widely-used benchmark L-ReID datasets verify the effectiveness of our method on the RFL-ReID task while maintaining the state-of-the-art performance on the general L-ReID scenario. + +# Acknowledgements + +This work was supported by the National Natural Science Foundation of China (61925201, 62132001, 62376011). + +# References + +[1] Shafiq Ahmad, Gianluca Scarpellini, Pietro Morerio, and Alessio Del Bue. Event-driven re-id: A new benchmark and method towards privacy-preserving person re-identification. In Proceedings of the IEEE/CVF Winter Conference on Applications of Computer Vision, pages 459–468, 2022. 2 +[2] Arslan Chaudhry, Puneet K Dokania, Thalaiyasingam Ajthan, and Philip HS Torr. Riemannian walk for incremental learning: Understanding forgetting and intransigence. 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Once an L-ReID model is updated using new data, all historical images in the gallery are required to be re-calculated to obtain new features for testing, known as \"re-indexing\". However, it is infeasible when raw images in the gallery are unavailable due to data privacy concerns, resulting in incompatible retrieval between the query and the gallery features calculated by different models, which causes significant performance degradation. In this paper, we focus on a new task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which requires achieving effective L-ReID without re-indexing raw images in the gallery. To this end, we propose a Continual Compatible Representation " + }, + { + "bbox": [ + 47, + 255, + 290, + 628 + ], + "type": "inline_equation", + "content": "(C^2 R)" + }, + { + "bbox": [ + 47, + 255, + 290, + 628 + ], + "type": "text", + "content": " method, which facilitates the query feature calculated by the continuously updated model to effectively retrieve the gallery feature calculated by the old model in a compatible manner. Specifically, we design a Continual Compatible Transfer (CCT) network to continuously transfer and consolidate the old gallery feature into the new feature space. Besides, a Balanced Compatible Distillation module is introduced to achieve compatibility by aligning the transferred feature space with the new feature space. Finally, a Balanced Anti-forgetting Distillation module is proposed to eliminate the accumulated forgetting of old knowledge during the continual compatible transfer. Extensive experiments on several benchmark L-ReID datasets demonstrate the effectiveness of our method against state-of-the-art methods for both RFL-ReID and L-ReID tasks. The source code of this paper is available at https://github.com/PKU-ICST-MIPL/C2R_CVPR2024." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 650, + 128, + 662 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 650, + 128, + 662 + ], + "spans": [ + { + "bbox": [ + 47, + 650, + 128, + 662 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 670, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 287, + 696 + ], + "type": "text", + "content": "Person re-identification (ReID) aims to identify the same person across different areas at different times [42]. Exist" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 313, + 230, + 540, + 364 + ], + "blocks": [ + { + "bbox": [ + 313, + 230, + 540, + 364 + ], + "lines": [ + { + "bbox": [ + 313, + 230, + 540, + 364 + ], + "spans": [ + { + "bbox": [ + 313, + 230, + 540, + 364 + ], + "type": "image", + "image_path": "31e7454ba4523e21e92fc12b7ad34760216ce9b67260102ed66e121f13f3abef.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 374, + 365, + 478, + 375 + ], + "lines": [ + { + "bbox": [ + 374, + 365, + 478, + 375 + ], + "spans": [ + { + "bbox": [ + 374, + 365, + 478, + 375 + ], + "type": "text", + "content": "(a) Traditional Lifelong ReID" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 313, + 377, + 539, + 488 + ], + "blocks": [ + { + "bbox": [ + 313, + 377, + 539, + 488 + ], + "lines": [ + { + "bbox": [ + 313, + 377, + 539, + 488 + ], + "spans": [ + { + "bbox": [ + 313, + 377, + 539, + 488 + ], + "type": "image", + "image_path": "77ab8203d07cdf1dc555afb29bf56c428c1ef8596d98b59f68a3f474663afa99.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 365, + 489, + 488, + 499 + ], + "lines": [ + { + "bbox": [ + 365, + 489, + 488, + 499 + ], + "spans": [ + { + "bbox": [ + 365, + 489, + 488, + 499 + ], + "type": "text", + "content": "(b) Re-indexing Free Lifelong ReID" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 305, + 511, + 547, + 544 + ], + "lines": [ + { + "bbox": [ + 305, + 511, + 547, + 544 + ], + "spans": [ + { + "bbox": [ + 305, + 511, + 547, + 544 + ], + "type": "text", + "content": "Figure 1. Comparison between (a) the traditional Lifelong Person Re-identification (L-ReID) task and (b) the Re-indexing Free Lifelong Person Re-identification (RFL-ReID) task." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 556, + 545, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 556, + 545, + 629 + ], + "spans": [ + { + "bbox": [ + 304, + 556, + 545, + 629 + ], + "type": "text", + "content": "ing methods [26, 32, 44] have made remarkable progress based on deep learning methods [37] and large-scale datasets [34, 41, 43]. However, their performance is often limited when training data are continuously collected from a series of different scenarios due to the well-known catastrophic forgetting challenge [3]." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "content": "Recently, Lifelong person ReID (L-ReID) has aroused great concerns involving acquiring knowledge from streaming data and performing well across all data [5, 18, 19, 38]. Its challenge is to balance the anti-forgetting of old knowledge with the acquisition of new knowledge. To this end, existing L-ReID methods usually adopt the exemplar replay [38] and the knowledge distillation [27] to preserve" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 137, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 137, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 137, + 712 + ], + "type": "text", + "content": "*Corresponding author." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "16614" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 70, + 281, + 178 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 281, + 178 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 281, + 178 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 281, + 178 + ], + "type": "image", + "image_path": "0d4017b48f613c8a0f9c711419f06cb7c736505594f06c2d4fe572d1c08a702a.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 188, + 287, + 221 + ], + "lines": [ + { + "bbox": [ + 46, + 188, + 287, + 221 + ], + "spans": [ + { + "bbox": [ + 46, + 188, + 287, + 221 + ], + "type": "text", + "content": "Figure 2. Performance Comparison between the traditional Lifelong Person Re-identification (L-ReID) task and the Re-indexing Free Lifelong Person Re-identification (RFL-ReID) task." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 233, + 286, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 233, + 286, + 437 + ], + "spans": [ + { + "bbox": [ + 46, + 233, + 286, + 437 + ], + "type": "text", + "content": "old knowledge when updating the model. The updated new model will be sequentially deployed by \"re-indexing\" [24] features of old data in the gallery. As shown in Fig. 1 (a), the old gallery features are replaced by the re-indexed gallery features to be compatible with the new model. However, massive incremental images in the gallery bring unbearable computational costs and prevent the re-indexing process [21, 39]. Besides, in the context of data privacy concerns [25], re-indexing is legally forbidden due to the impracticality of storing and re-indexing unauthorized raw images within privacy-sensitive scenarios [1, 4, 14], also known as Re-indexing Free Lifelong ReID (RFL-ReID), as shown in Fig. 1 (b). In this case, the domain gap between different datasets leads to the incompatibility between features calculated by the old and the new models. Consequently, as shown in Fig. 2, the performance of existing methods [11, 18, 27] often degrades significantly." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 437, + 286, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 286, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 286, + 616 + ], + "type": "text", + "content": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which entails deploying L-ReID models continuously without re-indexing raw images in the gallery. It is extremely challenging when considering not only balancing the acquisition of old and new knowledge but also achieving the compatibility between the old and the new feature space. To this end, Compatible Training (CT) [16, 21, 23] becomes a feasible solution which promotes the compatibility. Unfortunately, most existing CT methods only focus on compatibility within the same dataset. However, the large domain gap [5, 19] between different ReID datasets typically leads to the forgetting of old knowledge, causing the feature shift problem, which seriously degrades the performance of existing CT methods." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 618, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 286, + 714 + ], + "type": "text", + "content": "Inspired by the above observation, we propose a Continua! ReID. The core idea of " + }, + { + "bbox": [ + 46, + 618, + 286, + 714 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 618, + 286, + 714 + ], + "type": "text", + "content": " is to continuously update old features in the gallery to make it compatible with new query features. To tackle the domain shift problem, a Continua! ReID Transfer (CCT) network is proposed to update old gallery features continuously, which transfers the old feature into the new feature space by adaptively cap" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 545, + 203 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 203 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 203 + ], + "type": "text", + "content": "turing the knowledge from different domains. Correspondingly, to achieve the compatibility between the transferred features and the new ones, a Balanced Compatible Distillation (BCD) module is designed to preserve the relationship between the old and the transferred features in a unified feature space. Finally, to eliminate the accumulated forgetting of old knowledge during the continuous transfer, a Balanced Anti-forgetting Distillation (BAD) module is introduced to balance the old and the new discriminative information. Overall, the main contributions of this paper can be summarized as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 204, + 545, + 374 + ], + "type": "list", + "angle": 0, + "index": 10, + "blocks": [ + { + "bbox": [ + 304, + 204, + 545, + 252 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 204, + 545, + 252 + ], + "spans": [ + { + "bbox": [ + 304, + 204, + 545, + 252 + ], + "type": "text", + "content": "1) This paper proposes a Continual Compatible Representation scheme to solve the challenging Re-indexing Free Lifelong Person Re-identification task, which prevents reindexing to raw images in the old gallery." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "spans": [ + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "type": "text", + "content": "2) A continual compatible transfer network is designed to adaptively capture the old and the new knowledge, which promotes the updating of old gallery features." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 289, + 545, + 337 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 289, + 545, + 337 + ], + "spans": [ + { + "bbox": [ + 304, + 289, + 545, + 337 + ], + "type": "text", + "content": "3) To achieve compatibility of the old and the new data, a balanced compatible distillation module is designed to balance the relationship between the old and the new features in a unified feature space." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 338, + 545, + 374 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 338, + 545, + 374 + ], + "spans": [ + { + "bbox": [ + 304, + 338, + 545, + 374 + ], + "type": "text", + "content": "4) A balanced anti-forgetting distillation module is introduced to balance the acquisition of the old and the new knowledge without rehearsing the old data." + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 387, + 392, + 399 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 387, + 392, + 399 + ], + "spans": [ + { + "bbox": [ + 306, + 387, + 392, + 399 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 407, + 484, + 419 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 407, + 484, + 419 + ], + "spans": [ + { + "bbox": [ + 306, + 407, + 484, + 419 + ], + "type": "text", + "content": "2.1. Lifelong Person Re-identification" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 426, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 545, + 713 + ], + "type": "text", + "content": "Lifelong Person Re-identification (L-ReID) aims to use streaming data from different domains to train a ReID model to continuously match the same person across all domains [18]. It requires continuously accumulating knowledge from new data and preventing catastrophic forgetting of knowledge learned in old data. To this end, rehearsal-based methods rehearsed old data for the anti-forgetting of old knowledge [5, 35, 38]. Yu et al. [38] proposed a knowledge refreshing and consolidation framework to achieve both positive forward and backward transfers, which simultaneously promotes person matching in both old and new domains. However, limited by data privacy concerns, the old data is usually difficult to rehearse for L-ReID. Therefore, some methods focus on developing rehearsal-free methods [18, 19, 27, 33]. Sun et al. [27] proposed a patch-based knowledge distillation method, which can mitigate catastrophic forgetting problems by preserving patch-level knowledge within individual patch features and mutual relations. Despite achieving some progress, existing methods require re-indexing old data in the gallery after training on new data to adapt to the updated model. In this paper, we focus on a new and challenging task called RFL-ReID, which prohibits re-indexing the old data in the gallery due to data privacy issues." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "16615" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 72, + 536, + 220 + ], + "blocks": [ + { + "bbox": [ + 51, + 72, + 536, + 220 + ], + "lines": [ + { + "bbox": [ + 51, + 72, + 536, + 220 + ], + "spans": [ + { + "bbox": [ + 51, + 72, + 536, + 220 + ], + "type": "image", + "image_path": "e0f8d7db28a16bcae7851051bf91271f5b757bbc35f815860bec2766bf00ab22.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 53, + 227, + 534, + 296 + ], + "blocks": [ + { + "bbox": [ + 53, + 227, + 534, + 296 + ], + "lines": [ + { + "bbox": [ + 53, + 227, + 534, + 296 + ], + "spans": [ + { + "bbox": [ + 53, + 227, + 534, + 296 + ], + "type": "image", + "image_path": "b802098599ed5f5c907536492d4a21334137c1398a987c220740854119e7448d.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 309, + 546, + 354 + ], + "lines": [ + { + "bbox": [ + 46, + 309, + 546, + 354 + ], + "spans": [ + { + "bbox": [ + 46, + 309, + 546, + 354 + ], + "type": "text", + "content": "Figure 3. The architecture of our proposed Continual Compatible Representation " + }, + { + "bbox": [ + 46, + 309, + 546, + 354 + ], + "type": "inline_equation", + "content": "(\\mathbf{C}^2\\mathbf{R})" + }, + { + "bbox": [ + 46, + 309, + 546, + 354 + ], + "type": "text", + "content": " method. Our " + }, + { + "bbox": [ + 46, + 309, + 546, + 354 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 309, + 546, + 354 + ], + "type": "text", + "content": " consists of a Continual Compatible Transfer (CCT) network, a Balanced Compatible Distillation (BCD) module, and a Balanced Anti-forgetting Distillation (BAD) module. In the training phase, all the above components will be trained, and the CCT network will be used to update the old feature set, thereby achieving re-indexing free lifelong person re-identification." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 365, + 168, + 378 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 365, + 168, + 378 + ], + "spans": [ + { + "bbox": [ + 47, + 365, + 168, + 378 + ], + "type": "text", + "content": "2.2. Compatible Training" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 387, + 289, + 650 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 387, + 289, + 650 + ], + "spans": [ + { + "bbox": [ + 46, + 387, + 289, + 650 + ], + "type": "text", + "content": "Compatible Training (CT) aims to achieve the compatibility between the old model and the new model without reindexing, which encourages the feature calculated by the new model to be closer to the same object feature calculated by the old model. Existing CT methods can be categorized into two branches: backward CT [16, 24, 39] and forward CT methods [21, 30, 45]. Pan et al. [16] proposed an adversarial learning-based backward CT method, which optimized the distribution discrepancy and improved the backward compatibility of the updated model. Ramanujan et al. [21] proposed a flexible forward CT method by employing side-information to facilitate the updating of the new model. However, most existing CT methods only achieve compatibility between the old and the new models updated using the same dataset, ignoring the requirement to be compatible with multiple different datasets continuously. To this end, Wan et al. [30] proposed a long-term visual search framework to realize CT in the continual learning scenario, which allows new classes to occur in the new data. However, it relies heavily on old data and old features to achieve the compatibility, which is infeasible for the privacy-sensitive scenario." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "text", + "content": "Different from these methods, we propose a continual compatible representation scheme called " + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "text", + "content": ", which achieves leading L-ReID performance when old data in the gallery cannot be re-indexed in the practical privacy-sensitive scenario." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 364, + 361, + 376 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 364, + 361, + 376 + ], + "spans": [ + { + "bbox": [ + 306, + 364, + 361, + 376 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 385, + 429, + 396 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 385, + 429, + 396 + ], + "spans": [ + { + "bbox": [ + 306, + 385, + 429, + 396 + ], + "type": "text", + "content": "3.1. Problem Formulation" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "spans": [ + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID). Formally, given the sequentially collected datasets " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\mathcal{D} = \\{\\mathcal{D}^1,\\mathcal{D}^2,\\dots ,\\mathcal{D}^S\\}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " denotes the total number. The " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "s^{th}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " dataset " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\mathcal{D}^s = \\{\\mathcal{T}^s,\\mathcal{G}^s\\}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " contains a training set " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\mathcal{T}^s" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " and the corresponding gallery set " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\mathcal{G}^s" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " without overlapping person identities. Each " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\mathcal{T}^s = \\{x_i^s,y_i^s\\}_{i = 1}^{N^s}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " contains " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "N^s" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " training images " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "x_{i}^{s}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " and the corresponding identity labels " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "y_{i}^{s}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": ". Our goal is to train a feature extraction model " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\phi^S (\\cdot):x_i\\to z_i" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " to extract the feature " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "z_{i}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " for each input image " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "x_{i}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\phi^S (\\cdot)" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " is expected to maximize the similarity between the images belonging to the same person, thereby performing well on the overall retrieval performance of all " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " tasks. Particularly, when training on the " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "s^{th}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " dataset " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\mathcal{D}^s" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": ", the previous " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "s - 1" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " datasets " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{D}^1,\\dots ,\\mathcal{D}^{s - 1}\\}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " are absolutely unavailable due to data privacy concerns, including the training sets " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{T}^j\\}_{j = 1}^{s - 1}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " and the gallery sets " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{G}^j\\}_{j = 1}^{s - 1}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": ". Therefore, each image in " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\mathcal{G}^j" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " can only be extracted once based on the model " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "\\phi^j (\\cdot)" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " within the " + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "inline_equation", + "content": "j^{th}" + }, + { + "bbox": [ + 304, + 405, + 545, + 634 + ], + "type": "text", + "content": " training stage." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 646, + 373, + 657 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 646, + 373, + 657 + ], + "spans": [ + { + "bbox": [ + 306, + 646, + 373, + 657 + ], + "type": "text", + "content": "3.2. Overview" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 665, + 546, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 546, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 546, + 715 + ], + "type": "text", + "content": "As shown in Fig. 3, our proposed Continual Compatible Representation " + }, + { + "bbox": [ + 304, + 665, + 546, + 715 + ], + "type": "inline_equation", + "content": "(\\mathrm{C}^2\\mathrm{R})" + }, + { + "bbox": [ + 304, + 665, + 546, + 715 + ], + "type": "text", + "content": " method consists of a Continual Compatible Transfer (CCT) network, a Balanced Compatible Distillation (BCD) module, and a Balanced Anti-forgetting" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "16616" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": "Distillation (BAD) module. At the beginning of the " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "s^{th}" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " training stage " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "(s\\geq 2)" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": ", a copy of the model " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "\\phi^o" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " and the classifier " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "\\psi^o" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " are frozen to serve as the old knowledge. Then, we train the model with the CCT network based on the BCD and the BAD modules, as shown in Fig. 3 (a). After the training of the " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "s^{th}" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " stage, we reform a new gallery feature set " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "\\mathcal{F}^s" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " by updating the transferred features in the old gallery feature set " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "\\mathcal{F}^{s - 1}" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " using our proposed CCT network, and extracting the features of the current gallery set " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "\\mathcal{G}^s" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " using " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "\\phi^s" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " (Fig. 3 (b)). When testing at the " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "s^{th}" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " stage, we rank each feature in " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "\\mathcal{F}^s" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " with the query feature calculated by " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "\\phi^s" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " (Fig. 3 (c)) to validate the ReID performance on all " + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": " datasets." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 223, + 266, + 235 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 223, + 266, + 235 + ], + "spans": [ + { + "bbox": [ + 47, + 223, + 266, + 235 + ], + "type": "text", + "content": "3.3. Lifelong Person Re-identification Baseline" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "spans": [ + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": "In this section, we start by presenting a lifelong person re-identification baseline. The baseline model consists of a feature extraction model " + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "inline_equation", + "content": "\\phi (\\cdot)" + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": " and a classifier head " + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "inline_equation", + "content": "\\psi (\\cdot)" + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "inline_equation", + "content": "\\phi (\\cdot)" + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": " extracts a feature " + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "inline_equation", + "content": "z_{i}" + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": " for each input image " + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "inline_equation", + "content": "x_{i}" + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "inline_equation", + "content": "\\psi (\\cdot)" + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": " predicts the probability " + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "inline_equation", + "content": "p_i" + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": " of each person's identity." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "spans": [ + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "text", + "content": "Considering that the RFL-ReID task aims to continuously match the same person across the sequentially given datasets, we employ a cross-entropy loss " + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ce}" + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "text", + "content": " [13] and a triplet loss " + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{trip}" + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "text", + "content": " [8] to learn a discriminative representation for each person in the current dataset " + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "inline_equation", + "content": "\\mathcal{D}^s" + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "text", + "content": ". However, despite certain performance improvements in " + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "inline_equation", + "content": "\\mathcal{D}^s" + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "text", + "content": ", it has been verified to cause the catastrophic forgetting problem on the previous " + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "inline_equation", + "content": "(s - 1)" + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "text", + "content": " datasets [3]. To balance the acquisition of new knowledge and the anti-forgetting of old knowledge, we introduce an anti-forgetting loss " + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{pkd}" + }, + { + "bbox": [ + 46, + 301, + 288, + 456 + ], + "type": "text", + "content": " [27] based on image patch knowledge distillation to build a basic L-ReID model. Therefore, the overall loss function for our baseline model is formulated as:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 105, + 464, + 287, + 478 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 105, + 464, + 287, + 478 + ], + "spans": [ + { + "bbox": [ + 105, + 464, + 287, + 478 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {b a s e}} = \\mathcal {L} _ {c e} + \\mathcal {L} _ {\\text {t r i p}} + \\mathcal {L} _ {\\text {p k d}}. \\tag {1}", + "image_path": "8cf327cf298c823bf06fa90d61061f7287dbc096685be4157e9fa3a68735bb63.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 485, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 485, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 485, + 287, + 593 + ], + "type": "text", + "content": "The above baseline method achieves a performance trade-off between new and old datasets by re-indexing data in old galleries using the new model. However, when the old data is unavailable to the new model due to data privacy concerns, the performance will be significantly degraded due to the incompatibility of the features output by the old model and the new model. To tackle the above issue, we will detail present each component of our " + }, + { + "bbox": [ + 46, + 485, + 287, + 593 + ], + "type": "inline_equation", + "content": "\\mathrm{C^2R}" + }, + { + "bbox": [ + 46, + 485, + 287, + 593 + ], + "type": "text", + "content": " scheme in the following sections." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 599, + 261, + 612 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 599, + 261, + 612 + ], + "spans": [ + { + "bbox": [ + 47, + 599, + 261, + 612 + ], + "type": "text", + "content": "3.4. Continual Compatible Transfer Network" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 618, + 287, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 287, + 677 + ], + "type": "text", + "content": "To tackle the domain shift problem, we design a Continual Compatible Transfer (CCT) network to transfer the old feature into the new feature space continuously. To this end, our CCT is designed as a two-stream network to capture transfer-related knowledge from different domains." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": "Specifically, we first design a Knowledge Capturing Module (KCM) module to capture knowledge from new domains. Let " + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "inline_equation", + "content": "z^o \\in \\mathbb{R}^C" + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": " be the feature output by the old model" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "inline_equation", + "content": "\\phi^o (\\cdot)" + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": " based on the sample " + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "inline_equation", + "content": "x^{s}" + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "inline_equation", + "content": "\\pmb{v}_{p} \\in \\mathbb{R}^{P \\times C}" + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": " be a learnable new knowledge prototype set with length " + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": ". In order to enable " + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "inline_equation", + "content": "\\pmb{z}^o" + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": " to capture new knowledge for compatibility, we first calculate a capturing probability " + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "inline_equation", + "content": "\\pmb{k}^o \\in \\mathbb{R}^P" + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": " for each new knowledge prototype:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 391, + 141, + 545, + 155 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 391, + 141, + 545, + 155 + ], + "spans": [ + { + "bbox": [ + 391, + 141, + 545, + 155 + ], + "type": "interline_equation", + "content": "\\boldsymbol {k} ^ {o} = \\delta \\left(g _ {c} \\left(\\tilde {\\boldsymbol {z}} ^ {o}\\right)\\right), \\tag {2}", + "image_path": "d0abd75634f3ec3dee4d65af31a06c667d7ed5fbf30c24d823d2e653ceb2b455.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "spans": [ + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "type": "inline_equation", + "content": "g_{c}(\\cdot)" + }, + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "type": "text", + "content": " denotes a three-layer fully connected network, " + }, + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "type": "inline_equation", + "content": "\\delta (\\cdot)" + }, + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "type": "text", + "content": " denotes the softmax function, and " + }, + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "type": "inline_equation", + "content": "(\\widetilde{\\cdot})" + }, + { + "bbox": [ + 304, + 164, + 545, + 212 + ], + "type": "text", + "content": " denotes the 12-normalized function. Then, we combine the captured new knowledge with a weighted summation of the prototypes:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 389, + 220, + 545, + 255 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 389, + 220, + 545, + 255 + ], + "spans": [ + { + "bbox": [ + 389, + 220, + 545, + 255 + ], + "type": "interline_equation", + "content": "\\boldsymbol {z} ^ {t} = \\sum_ {p = 1} ^ {P} \\boldsymbol {k} _ {i} ^ {o} \\cdot \\boldsymbol {v} _ {p}. \\tag {3}", + "image_path": "3f43b50e64199459edba1edeb6b7ef32bd33846de45356c419f69f471cce2ca8.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 263, + 545, + 371 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 263, + 545, + 371 + ], + "spans": [ + { + "bbox": [ + 304, + 263, + 545, + 371 + ], + "type": "text", + "content": "Sequentially, a parallel Forward Mapping Module (FMM) is designed to directly map the old feature to the new one, thereby preserving the old knowledge from old domains. The designed mapping network consists of sequential fully connected layers, Batch Normalization [9] layers, and PReLU [6] layers. The first fully connected layer reduces the channel number to " + }, + { + "bbox": [ + 304, + 263, + 545, + 371 + ], + "type": "inline_equation", + "content": "C_0" + }, + { + "bbox": [ + 304, + 263, + 545, + 371 + ], + "type": "text", + "content": ", while the last layer recovers it back to the original number, which keeps the representation capability while saving redundant operations:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 395, + 380, + 545, + 393 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 395, + 380, + 545, + 393 + ], + "spans": [ + { + "bbox": [ + 395, + 380, + 545, + 393 + ], + "type": "interline_equation", + "content": "z ^ {m} = g _ {s} \\left(\\widetilde {z} ^ {o}\\right). \\tag {4}", + "image_path": "d3278af6ebafbf91c1ad83fc60dbfbe79f1632da18491fb465f00d2a652498f7.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "text", + "content": "Finally, CCT takes the input " + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "inline_equation", + "content": "\\widetilde{z}^o" + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "text", + "content": " to generate a factor " + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "inline_equation", + "content": "a^m" + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "text", + "content": " to adaptively balance the above two features (" + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "inline_equation", + "content": "z^t" + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "inline_equation", + "content": "z^m" + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "text", + "content": ") obtained by the KCM module and FMM module. Meanwhile, the original features are added by the residual skipconnection to alleviate the gradient vanishing issue [31]. The transferred result " + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "inline_equation", + "content": "z^w" + }, + { + "bbox": [ + 304, + 403, + 545, + 486 + ], + "type": "text", + "content": " of CCT network can be formulated as follows:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 348, + 495, + 545, + 509 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 495, + 545, + 509 + ], + "spans": [ + { + "bbox": [ + 348, + 495, + 545, + 509 + ], + "type": "interline_equation", + "content": "\\boldsymbol {z} ^ {w} = \\left(1 - a ^ {m}\\right) \\cdot \\boldsymbol {z} ^ {t} + a ^ {m} \\cdot \\boldsymbol {z} ^ {m} + \\widetilde {\\boldsymbol {z}} ^ {o}. \\tag {5}", + "image_path": "b0ae381977b4105c6dc56841b33731083efe3e6cc8390eda26b1dec2c799910a.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 518, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 518, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 518, + 545, + 555 + ], + "type": "text", + "content": "Following [14], we leverage 4 cascaded CCT networks to build up a strong transfer network, which sequentially transfers features from previous stages to the current stage." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 562, + 484, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 562, + 484, + 574 + ], + "spans": [ + { + "bbox": [ + 306, + 562, + 484, + 574 + ], + "type": "text", + "content": "3.5. Balanced Compatible Distillation" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 580, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 580, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 580, + 545, + 628 + ], + "type": "text", + "content": "To make the transferred features compatible with the new one, we design a Balanced Compatible Distillation (BCD) module to simultaneously preserve the relationships of the old and the transferred features in the new feature space." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "spans": [ + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "text", + "content": "Given a mini-batch of training samples " + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "inline_equation", + "content": "\\{x_i^s, y_i^s\\}_{i=1}^B" + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "inline_equation", + "content": "B" + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "text", + "content": " is the batch size, and a new feature " + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "inline_equation", + "content": "z_i^n" + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "text", + "content": " calculated by the new model " + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "inline_equation", + "content": "\\phi(\\cdot)^n" + }, + { + "bbox": [ + 304, + 628, + 545, + 675 + ], + "type": "text", + "content": ". We start by directly aligning the above features with 12-loss:" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 361, + 683, + 545, + 715 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 361, + 683, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 361, + 683, + 545, + 715 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {c a} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\left| \\left| \\tilde {z} _ {i} ^ {n} - \\tilde {z} _ {i} ^ {w} \\right| \\right| _ {2}. \\tag {6}", + "image_path": "3493faeb0c806dfec0840ebdb6e4545704e2a95bd52234751d01c3ebf12dea9e.jpg" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "16617" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 286, + 131 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 286, + 131 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 286, + 131 + ], + "type": "text", + "content": "The above alignment loss promotes compatibility of new features in the new feature space, while ignoring the relationship between the old features, thus limiting the ReID performance on old data. Therefore, we propose a relationship distillation loss to overcome the above issue." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 132, + 286, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 132, + 286, + 179 + ], + "spans": [ + { + "bbox": [ + 47, + 132, + 286, + 179 + ], + "type": "text", + "content": "Firstly, we construct an old similarity matrix " + }, + { + "bbox": [ + 47, + 132, + 286, + 179 + ], + "type": "inline_equation", + "content": "\\mathcal{M}^o\\in" + }, + { + "bbox": [ + 47, + 132, + 286, + 179 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{B\\times B}" + }, + { + "bbox": [ + 47, + 132, + 286, + 179 + ], + "type": "text", + "content": " , which is calculated by the affinity between each two features in " + }, + { + "bbox": [ + 47, + 132, + 286, + 179 + ], + "type": "inline_equation", + "content": "\\{\\widetilde{z}_i^o\\}_{i = 1}^B" + }, + { + "bbox": [ + 47, + 132, + 286, + 179 + ], + "type": "text", + "content": " to represent the relationship between the corresponding images in the old feature space:" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 85, + 186, + 286, + 218 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 85, + 186, + 286, + 218 + ], + "spans": [ + { + "bbox": [ + 85, + 186, + 286, + 218 + ], + "type": "interline_equation", + "content": "\\mathcal {M} _ {i, j} ^ {o} = \\frac {e ^ {\\langle \\widetilde {z} _ {i} ^ {o} , \\widetilde {z} _ {j} ^ {o} \\rangle}}{\\sum_ {k = 1} ^ {B} e ^ {\\langle \\widetilde {z} _ {i} ^ {o} , \\widetilde {z} _ {k} ^ {o} \\rangle}}, (i, j \\in [ 1, B ]), \\tag {7}", + "image_path": "1a7ef92055a20538aecf8d322d79e494a0e07a7621b314092bceb7b305d450cd.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "spans": [ + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "inline_equation", + "content": "\\langle \\cdot ,\\cdot \\rangle" + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "text", + "content": " denotes the cosine similarity. Similarly, a transferred similarity matrix " + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "inline_equation", + "content": "\\mathcal{M}^w" + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "text", + "content": " is also constructed to represent the relationship between the transferred features " + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "inline_equation", + "content": "\\{\\widetilde{z}_i^w\\}_{i = 1}^B" + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "text", + "content": ". Apparently, the alignment in Eq. (6) will promote higher similarity between samples with the same identity in " + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "inline_equation", + "content": "\\mathcal{M}^w" + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "text", + "content": ", which will conflict with the corresponding similarity in " + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "inline_equation", + "content": "\\mathcal{M}^o" + }, + { + "bbox": [ + 47, + 225, + 286, + 332 + ], + "type": "text", + "content": ". Therefore, we remove the similarities between samples belonging to the same identity to avoid the above conflicts for relationship distillation:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 91, + 342, + 286, + 373 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 91, + 342, + 286, + 373 + ], + "spans": [ + { + "bbox": [ + 91, + 342, + 286, + 373 + ], + "type": "interline_equation", + "content": "\\mathcal {M} _ {i, j} ^ {x} = \\left\\{ \\begin{array}{l l} \\mathcal {M} _ {i, j} ^ {x}, I D (i) \\neq I D (j) \\\\ 0, \\quad I D (i) = I D (j), \\end{array} \\right. \\tag {8}", + "image_path": "934c799ed4e70df30c1f9f4d1e8717283ef4e56179bb7b686fa91606a47e332c.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "spans": [ + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "type": "inline_equation", + "content": "ID(\\cdot)" + }, + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "type": "text", + "content": " denotes the identity of the given sample, and " + }, + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "type": "inline_equation", + "content": "x \\in o, w" + }, + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "type": "text", + "content": ". Next, a widely-used knowledge distillation loss " + }, + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{cr}" + }, + { + "bbox": [ + 47, + 380, + 286, + 428 + ], + "type": "text", + "content": " based on Kullback-Leibler (KL) divergence is imposed to distil the relationship between old features as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 88, + 437, + 286, + 468 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 88, + 437, + 286, + 468 + ], + "spans": [ + { + "bbox": [ + 88, + 437, + 286, + 468 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {c r} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\sigma \\left(M _ {i,:} ^ {o}\\right) \\log \\left(\\frac {\\sigma \\left(M _ {i,:} ^ {o}\\right)}{\\sigma \\left(M _ {i,:} ^ {w}\\right)}\\right), \\tag {9}", + "image_path": "3f5f87f8a7dffee1b527e1a92a97b734a14d9295b140252d59a5911774006881.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 478, + 276, + 489 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 478, + 276, + 489 + ], + "spans": [ + { + "bbox": [ + 47, + 478, + 276, + 489 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 478, + 276, + 489 + ], + "type": "inline_equation", + "content": "\\sigma (\\cdot)" + }, + { + "bbox": [ + 47, + 478, + 276, + 489 + ], + "type": "text", + "content": " denotes the row-wise 11-normalized function." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 490, + 286, + 512 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 490, + 286, + 512 + ], + "spans": [ + { + "bbox": [ + 47, + 490, + 286, + 512 + ], + "type": "text", + "content": "In all, the loss function for the BCD module can be calculated as follows:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 116, + 523, + 286, + 535 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 116, + 523, + 286, + 535 + ], + "spans": [ + { + "bbox": [ + 116, + 523, + 286, + 535 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {b c d} = \\mu_ {1} \\mathcal {L} _ {c a} + \\mu_ {2} \\mathcal {L} _ {c r}, \\tag {10}", + "image_path": "bc23aa72a7c0b91b4b0029082075177e8132fab5acfdb9cc3e102111da7d7cd0.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 544, + 286, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 544, + 286, + 567 + ], + "spans": [ + { + "bbox": [ + 47, + 544, + 286, + 567 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 544, + 286, + 567 + ], + "type": "inline_equation", + "content": "\\mu_{1}" + }, + { + "bbox": [ + 47, + 544, + 286, + 567 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 544, + 286, + 567 + ], + "type": "inline_equation", + "content": "\\mu_{2}" + }, + { + "bbox": [ + 47, + 544, + 286, + 567 + ], + "type": "text", + "content": " denote two hyper-parameters to balance our proposed balanced compatible distillation." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 575, + 240, + 587 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 575, + 240, + 587 + ], + "spans": [ + { + "bbox": [ + 47, + 575, + 240, + 587 + ], + "type": "text", + "content": "3.6. Balanced Anti-forgetting Distillation" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 594, + 286, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 594, + 286, + 688 + ], + "spans": [ + { + "bbox": [ + 47, + 594, + 286, + 688 + ], + "type": "text", + "content": "Although the proposed BCD module achieves the compatibility by selectively distilling the relationship, it ignores the accumulated forgetting of old knowledge during the continual compatible transfer, thereby reducing the inter-class discrimination of old data. Therefore, we propose a Balanced Anti-forgetting Distillation (BAD) module to preserve the discriminative information within the old and new features in the new feature space." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 47, + 689, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 286, + 712 + ], + "type": "text", + "content": "To this end, we employ the old classifier head " + }, + { + "bbox": [ + 47, + 689, + 286, + 712 + ], + "type": "inline_equation", + "content": "\\psi^o (\\cdot)" + }, + { + "bbox": [ + 47, + 689, + 286, + 712 + ], + "type": "text", + "content": " to extract and distil the discriminative information. Therefore," + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 72, + 544, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 544, + 95 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 544, + 95 + ], + "type": "text", + "content": "we extract old identity logits " + }, + { + "bbox": [ + 306, + 72, + 544, + 95 + ], + "type": "inline_equation", + "content": "\\pmb{q}^{o}" + }, + { + "bbox": [ + 306, + 72, + 544, + 95 + ], + "type": "text", + "content": " of the old feature " + }, + { + "bbox": [ + 306, + 72, + 544, + 95 + ], + "type": "inline_equation", + "content": "z^{o}" + }, + { + "bbox": [ + 306, + 72, + 544, + 95 + ], + "type": "text", + "content": " as the theoretical distribution of the discriminative information:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 390, + 106, + 544, + 118 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 390, + 106, + 544, + 118 + ], + "spans": [ + { + "bbox": [ + 390, + 106, + 544, + 118 + ], + "type": "interline_equation", + "content": "\\boldsymbol {q} ^ {o} = \\delta \\left(\\psi^ {o} \\left(\\boldsymbol {z} ^ {o}\\right)\\right). \\tag {11}", + "image_path": "900d66d10dd6afc88ae93a0071244a02517675b7f6ebfcecd5b1c41cc5a20c32.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "spans": [ + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "text", + "content": "Considering that the transferred feature " + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "inline_equation", + "content": "z^w" + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "inline_equation", + "content": "z^o" + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "text", + "content": " come from different datasets, it is challenging to extract consistent discriminative information directly using " + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "inline_equation", + "content": "\\psi^o(\\cdot)" + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "text", + "content": ". To tackle the above problem, we perform an inverse 12-normalization on " + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "inline_equation", + "content": "z^w" + }, + { + "bbox": [ + 305, + 127, + 545, + 198 + ], + "type": "text", + "content": " so that it can be extracted as the real distribution of the transferred discriminative information:" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 371, + 208, + 544, + 220 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 371, + 208, + 544, + 220 + ], + "spans": [ + { + "bbox": [ + 371, + 208, + 544, + 220 + ], + "type": "interline_equation", + "content": "\\boldsymbol {q} ^ {w} = \\delta \\left(\\psi^ {o} \\left(\\widetilde {\\boldsymbol {z}} ^ {w} \\cdot \\left\\| \\boldsymbol {z} ^ {o} \\right\\| _ {2}\\right)\\right). \\tag {12}", + "image_path": "9bb2d83b6481fd83bcb86bd451a44ea3209230417f601a6ab7c9528a986bb2b9.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 231, + 544, + 265 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 231, + 544, + 265 + ], + "spans": [ + { + "bbox": [ + 305, + 231, + 544, + 265 + ], + "type": "text", + "content": "Sequentially, we use an anti-forgetting loss " + }, + { + "bbox": [ + 305, + 231, + 544, + 265 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ad}" + }, + { + "bbox": [ + 305, + 231, + 544, + 265 + ], + "type": "text", + "content": " to preserve the old discriminative knowledge, which can be calculated as follows:" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 367, + 273, + 544, + 304 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 367, + 273, + 544, + 304 + ], + "spans": [ + { + "bbox": [ + 367, + 273, + 544, + 304 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {a d} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} \\boldsymbol {q} _ {i} ^ {o} \\log \\left(\\frac {\\boldsymbol {q} _ {i} ^ {o}}{\\boldsymbol {q} _ {i} ^ {w}}\\right). \\tag {13}", + "image_path": "fe049f473774126bf21f9c3948a86a8a0aca418c4cdd56f08881be0a8b922f03.jpg" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 313, + 544, + 371 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 313, + 544, + 371 + ], + "spans": [ + { + "bbox": [ + 305, + 313, + 544, + 371 + ], + "type": "text", + "content": "Despite achieving the anti-forgetting, the distillation in Eq. (13) will also limit the discrimination of the transferred feature in the new feature space. Therefore, we introduce a discriminative consistency-based loss " + }, + { + "bbox": [ + 305, + 313, + 544, + 371 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{dc}" + }, + { + "bbox": [ + 305, + 313, + 544, + 371 + ], + "type": "text", + "content": " to balance the discrimination for both transferred and new features:" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 307, + 380, + 544, + 422 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 307, + 380, + 544, + 422 + ], + "spans": [ + { + "bbox": [ + 307, + 380, + 544, + 422 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {d c} = - \\frac {1}{B} \\sum_ {i = 1} ^ {B} (1 - \\cos \\left\\langle \\frac {\\widetilde {z} _ {i} ^ {w} - \\widetilde {z} _ {i} ^ {o}}{\\left| \\left| \\widetilde {z} _ {i} ^ {w} - \\widetilde {z} _ {i} ^ {o} \\right| \\right| _ {2}}, \\frac {\\widetilde {z} _ {i} ^ {n} - \\widetilde {z} _ {i} ^ {o}}{\\left| \\left| \\widetilde {z} _ {i} ^ {n} - \\widetilde {z} _ {i} ^ {o} \\right| \\right| _ {2}} \\right\\rangle). \\tag {14}", + "image_path": "ebc079be6dab0cb8b2f9e9e163ad636a1b60308408f5bcba43bc987eb0ab2dbb.jpg" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 305, + 423, + 544, + 445 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 423, + 544, + 445 + ], + "spans": [ + { + "bbox": [ + 305, + 423, + 544, + 445 + ], + "type": "text", + "content": "The overall loss function for the BAD module can be calculated as follows:" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 374, + 456, + 544, + 468 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 374, + 456, + 544, + 468 + ], + "spans": [ + { + "bbox": [ + 374, + 456, + 544, + 468 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {b a d} = \\mu_ {3} \\mathcal {L} _ {a d} + \\mu_ {4} \\mathcal {L} _ {d c}, \\tag {15}", + "image_path": "406e9910f9b673d1e46a9731af52e8b769476c41707013e5d447be4012fc2144.jpg" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 305, + 478, + 544, + 501 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 478, + 544, + 501 + ], + "spans": [ + { + "bbox": [ + 305, + 478, + 544, + 501 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 478, + 544, + 501 + ], + "type": "inline_equation", + "content": "\\mu_{3}" + }, + { + "bbox": [ + 305, + 478, + 544, + 501 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 478, + 544, + 501 + ], + "type": "inline_equation", + "content": "\\mu_{4}" + }, + { + "bbox": [ + 305, + 478, + 544, + 501 + ], + "type": "text", + "content": " denote two hyper-parameters when training the model." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 306, + 509, + 417, + 521 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 509, + 417, + 521 + ], + "spans": [ + { + "bbox": [ + 306, + 509, + 417, + 521 + ], + "type": "text", + "content": "3.7. Objective Function" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 306, + 527, + 528, + 539 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 527, + 528, + 539 + ], + "spans": [ + { + "bbox": [ + 306, + 527, + 528, + 539 + ], + "type": "text", + "content": "Finally, the total loss " + }, + { + "bbox": [ + 306, + 527, + 528, + 539 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 306, + 527, + 528, + 539 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 306, + 527, + 528, + 539 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 306, + 527, + 528, + 539 + ], + "type": "text", + "content": " is calculated as follows:" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 370, + 552, + 544, + 563 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 370, + 552, + 544, + 563 + ], + "spans": [ + { + "bbox": [ + 370, + 552, + 544, + 563 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {\\text {b a s e}} + \\mathcal {L} _ {\\text {b c d}} + \\mathcal {L} _ {\\text {b a d}}. \\tag {16}", + "image_path": "0bc41b460d5f471451ecc6349d4f8e741f9c797048a1326853e00c5a1484f915.jpg" + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 305, + 568, + 544, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 568, + 544, + 605 + ], + "spans": [ + { + "bbox": [ + 305, + 568, + 544, + 605 + ], + "type": "text", + "content": "Through the joint optimizing of " + }, + { + "bbox": [ + 305, + 568, + 544, + 605 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 305, + 568, + 544, + 605 + ], + "type": "text", + "content": ", our " + }, + { + "bbox": [ + 305, + 568, + 544, + 605 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 305, + 568, + 544, + 605 + ], + "type": "text", + "content": " achieves the compatibility between the old and the new models and prevents re-indexing to raw images in the old gallery." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 306, + 616, + 386, + 628 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 616, + 386, + 628 + ], + "spans": [ + { + "bbox": [ + 306, + 616, + 386, + 628 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 306, + 635, + 480, + 646 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 635, + 480, + 646 + ], + "spans": [ + { + "bbox": [ + 306, + 635, + 480, + 646 + ], + "type": "text", + "content": "4.1. Datasets and Evaluation Metrics" + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 305, + 653, + 544, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 653, + 544, + 712 + ], + "spans": [ + { + "bbox": [ + 305, + 653, + 544, + 712 + ], + "type": "text", + "content": "Datasets. To verify the effectiveness of our method, we conduct extensive experiments on five benchmark lifelong person ReID datasets, including Market-1501 [41], CUHK-SYSU [36], DukeMTMC-ReID [43], MSMT17-V2 [34] and CUHK03 [12]. For CUHK-SYSU, we follow the" + } + ] + } + ], + "index": 31 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "16618" + } + ] + } + ], + "index": 32 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 73, + 70, + 518, + 246 + ], + "blocks": [ + { + "bbox": [ + 73, + 70, + 518, + 246 + ], + "lines": [ + { + "bbox": [ + 73, + 70, + 518, + 246 + ], + "spans": [ + { + "bbox": [ + 73, + 70, + 518, + 246 + ], + "type": "table", + "html": "
TaskMethodMarket-1501CUHK-SYSUDukeMTMC-ReIDMSMT17-V2CUHK03Average
mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1
L-ReIDJointTrain68.185.281.483.860.475.724.648.942.743.655.467.5
SPD [28]35.661.261.764.027.547.15.215.542.244.334.446.4
LwF [11]56.377.172.975.129.646.56.016.636.137.540.250.6
CRL [40]58.078.272.575.128.345.26.015.837.439.840.550.8
AKA [18]58.177.472.574.828.745.26.116.238.740.440.850.8
MEGE [20]39.061.673.376.616.930.34.613.436.437.134.043.8
PatchKD [27]68.585.775.678.633.850.46.517.034.136.843.753.7
Ours69.086.876.779.533.248.66.617.435.636.244.253.7
RFL-ReIDLwF* [11]39.158.040.040.77.815.32.67.123.323.922.629.0
AKA* [18]36.152.238.637.67.613.83.18.326.526.522.427.7
CVS* [30]38.855.649.049.719.330.04.611.524.724.727.334.3
PatchKD* [27]61.478.457.859.020.834.45.112.836.037.636.244.4
Ours62.779.764.466.326.741.76.815.737.237.639.548.2
", + "image_path": "4bf416d060f3031c6a1908b36827f86a4259c5a5eadb97c4358c6e7496ccd9ee.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 73, + 267, + 518, + 444 + ], + "blocks": [ + { + "bbox": [ + 73, + 250, + 520, + 261 + ], + "lines": [ + { + "bbox": [ + 73, + 250, + 520, + 261 + ], + "spans": [ + { + "bbox": [ + 73, + 250, + 520, + 261 + ], + "type": "text", + "content": "Table 1. Performance on training Order-1: Market-1501→CUHK-SYSU→DukeMTMC-ReID→MSMT17-V2→CUHK03." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 73, + 267, + 518, + 444 + ], + "lines": [ + { + "bbox": [ + 73, + 267, + 518, + 444 + ], + "spans": [ + { + "bbox": [ + 73, + 267, + 518, + 444 + ], + "type": "table", + "html": "
TaskMethodDukeMTMC-ReIDMSMT17-V2Market-1501CUHK-SYSUCUHK03Average
mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1mAPR@1
L-ReIDJointTrain60.475.724.648.968.185.281.483.842.743.655.467.5
SPD [28]28.548.53.711.532.357.462.165.043.045.233.945.5
LwF [11]42.761.75.114.334.458.669.973.034.134.137.248.4
CRL [40]43.563.14.813.735.059.870.072.834.536.837.649.2
AKA [18]42.260.15.415.137.259.871.273.936.937.938.649.4
MEGE [20]21.635.53.09.325.049.869.973.134.735.130.840.6
PatchKD [27]58.374.16.417.443.267.474.576.933.734.843.254.1
Ours59.775.07.319.242.466.576.077.837.839.344.755.6
RFL-ReIDLwF* [11]15.022.91.23.29.519.438.837.520.219.616.920.5
AKA* [18]11.115.11.33.213.427.335.934.725.225.617.421.2
CVS* [30]29.041.93.59.430.749.660.061.228.529.930.338.4
PatchKD* [27]46.560.94.010.431.150.563.064.035.836.636.144.5
Ours48.463.66.214.937.055.667.468.439.239.539.748.4
", + "image_path": "e3893674e092a0928a77ce16a9696d644038532d56d2d977bf31f8bb44412910.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "lines": [ + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "spans": [ + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "text", + "content": "Table 2. Performance on training Order-2: DukeMTMC-ReID " + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "text", + "content": " MSMT17-V2 " + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "text", + "content": " Market-1501 " + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "text", + "content": " CUHK-SYSU " + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 72, + 447, + 520, + 458 + ], + "type": "text", + "content": " CUHK03." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "spans": [ + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": "same pre-processing and evaluation of GwFReLU [35], which crops the person images with the ground-truth person bounding box annotation and re-organized as a ReID dataset with corresponding identities. To simulate the lifelong person ReID process in the real scenarios, we evaluate our method by employing two training orders used in [18], including Order-1: Market-1501 " + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": " CUHK-SYSU " + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": " DukeMTMC-ReID " + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": " MSMT17-V2 " + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": " CUHK03 and Order-2: DukeMTMC-ReID " + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": " MSMT17-V2 " + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": " Market-1501 " + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": " CUHK-SYSU " + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 475, + 288, + 594 + ], + "type": "text", + "content": " CUHK03." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": "Evaluation Metrics. We employ mean Average Precision (mAP) [41] and Rank@1 accuracy (R@1) [15] to evaluate our method on each datasets. The above metrics of our method are reported after sequentially training all datasets. Besides, the corresponding mean accuracy is also reported to evaluate the overall performance on all tasks. Besides, the Average Forgetting (AF) [2] on the above metrics are reported to evaluate the anti-forgetting performance of our method, which averages the difference between the highest" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 475, + 545, + 499 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 475, + 545, + 499 + ], + "spans": [ + { + "bbox": [ + 305, + 475, + 545, + 499 + ], + "type": "text", + "content": "accuracy and the final accuracy on each dataset throughout the lifelong learning process." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 513, + 440, + 526 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 513, + 440, + 526 + ], + "spans": [ + { + "bbox": [ + 305, + 513, + 440, + 526 + ], + "type": "text", + "content": "4.2. Implementation Details" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": "Our proposed " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{C^2R}" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": " is implemented with PyTorch [17] on NVIDIA A40 GPUs. We adopt a ResNet-50 [7] network pre-trained on ImageNet [22] as our backbone network. In each training stage, we train the model for 50 epochs with 150 iterations. We use Adam [10] optimizer for training. The learning rate is set to " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "3.5\\times 10^{-4}" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": " initially, which decayed by 0.1 at the " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "25^{th}" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": " and the " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "35^{th}" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": " epochs. We set the hyper-parameters " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mu_{1},\\mu_{2},\\mu_{3}" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mu_{4}" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": " as 50, 1, 0.01 and 0.05, respectively. The prototype length " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": " and the channel number " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "C_0" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": " are empirically set to 16 and 32. Input images are resized to " + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "inline_equation", + "content": "256\\times 128" + }, + { + "bbox": [ + 304, + 533, + 545, + 713 + ], + "type": "text", + "content": ". The batch size is set to 128, with 4 images for each identity. Following [27], each dataset is randomly sampled with 500 identities to alleviate the problem of unbalanced class numbers among different datasets for fairness comparison." + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 749, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 749, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 749, + 318, + 757 + ], + "type": "text", + "content": "16619" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 57, + 70, + 276, + 107 + ], + "blocks": [ + { + "bbox": [ + 57, + 70, + 276, + 107 + ], + "lines": [ + { + "bbox": [ + 57, + 70, + 276, + 107 + ], + "spans": [ + { + "bbox": [ + 57, + 70, + 276, + 107 + ], + "type": "table", + "html": "
MethodLwFAKACVSPatchKDOurs
AF(mAP)24.826.421.016.513.9
AF(R@1)30.835.025.718.514.5
", + "image_path": "8b23d3088e480e20b863f03197ed2fd640b0d8b37d11ea64547a9f203e9adfcf.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 47, + 109, + 286, + 131 + ], + "lines": [ + { + "bbox": [ + 47, + 109, + 286, + 131 + ], + "spans": [ + { + "bbox": [ + 47, + 109, + 286, + 131 + ], + "type": "text", + "content": "Table 3. AF performance of " + }, + { + "bbox": [ + 47, + 109, + 286, + 131 + ], + "type": "inline_equation", + "content": "{\\mathrm{C}}^{2}\\mathrm{R}" + }, + { + "bbox": [ + 47, + 109, + 286, + 131 + ], + "type": "text", + "content": " compared with existing methods. (The lower the AF is, the less the model forgets.)" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 148, + 274, + 161 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 148, + 274, + 161 + ], + "spans": [ + { + "bbox": [ + 47, + 148, + 274, + 161 + ], + "type": "text", + "content": "4.3. Comparison with State-of-the-arts Methods" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 170, + 286, + 254 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 170, + 286, + 254 + ], + "spans": [ + { + "bbox": [ + 46, + 170, + 286, + 254 + ], + "type": "text", + "content": "In this section, we compared our " + }, + { + "bbox": [ + 46, + 170, + 286, + 254 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 170, + 286, + 254 + ], + "type": "text", + "content": " with several state-of-the-art methods on both RFL-ReID and traditional L-ReID tasks, including SPD [28], LwF [11], CRL [40], AKA [18], MEGE [20], PatchKD [27], and CVS [30], where CSV is a continual compatible training method and the others are L-ReID methods. The best results are bolded, and the second-best results are underlined." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "spans": [ + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "content": "Comparison on the RFL-ReID task. Tab. 1 and Tab. 2 summarize the results of our method compared to existing methods, which are reproduced by the released code and denoted as " + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "inline_equation", + "content": "*" + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "content": ". Compared with these methods, our " + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "content": " achieves the highest average mAP and R@1 accuracy by " + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "inline_equation", + "content": "39.5\\% /48.2\\%" + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "content": " on Order-1 and " + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "inline_equation", + "content": "39.7\\% /48.4\\%" + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "content": " on Order-2, leading PatchKD by " + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "inline_equation", + "content": "3.3\\% /3.8\\%" + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "inline_equation", + "content": "3.6\\% /3.9\\%" + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "content": ", respectively. This is because our " + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 258, + 286, + 402 + ], + "type": "text", + "content": " method can achieve compatible transfer for old gallery features by balancing the anti-forgetting of old knowledge with the compatibility to the new model, thereby updating old features without reindexing old data effectively." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "spans": [ + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "text", + "content": "In addition, Tab. 3 reports the AF performance of mAP and R@1 on Order-1. It can be seen that our " + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "text", + "content": " achieves the lowest AF on both mAP and R@1 accuracy, which is lower than PatchKD by " + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "inline_equation", + "content": "2.6\\%" + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "inline_equation", + "content": "4.0\\%" + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "text", + "content": ", respectively. Notably, compared to CVS, our C2R does not introduce additional old data while achieving the best RFL-ReID accuracy and the best AF performance. Specifically, as shown in Fig. 4, our proposed " + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "text", + "content": " achieves the best average performance on the seen datasets in each stage. The above results intuitively demonstrate that our proposed " + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 406, + 286, + 538 + ], + "type": "text", + "content": " outperforms SOTA methods on average R@1 and mAP at each stage." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 541, + 286, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 541, + 286, + 590 + ], + "spans": [ + { + "bbox": [ + 46, + 541, + 286, + 590 + ], + "type": "text", + "content": "The above results imply that our " + }, + { + "bbox": [ + 46, + 541, + 286, + 590 + ], + "type": "inline_equation", + "content": "\\mathrm{C^2R}" + }, + { + "bbox": [ + 46, + 541, + 286, + 590 + ], + "type": "text", + "content": " can adaptively map old features and capture new knowledge, thus balancing compatibility with new feature spaces by preserving old discriminative knowledge." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "text", + "content": "Comparison on the traditional L-ReID task. We further evaluate our method on the traditional L-ReID task. As shown in Tab. 1 and Tab. 2, our proposed " + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "text", + "content": " also achieves state-of-the-art performance on both two training orders, which leads PatchKD on mAP accuracy by " + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "inline_equation", + "content": "0.5\\%" + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "inline_equation", + "content": "1.5\\%" + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "text", + "content": " on Order-1 and Order-2, respectively. The above results imply that our method achieves the best RFL-ReID performance without compromising the performance of traditional L-ReID. Therefore, our " + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "text", + "content": " has better generalization in both general and privacy-sensitive scenarios." + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 307, + 72, + 427, + 192 + ], + "blocks": [ + { + "bbox": [ + 307, + 72, + 427, + 192 + ], + "lines": [ + { + "bbox": [ + 307, + 72, + 427, + 192 + ], + "spans": [ + { + "bbox": [ + 307, + 72, + 427, + 192 + ], + "type": "image", + "image_path": "02a65ad41234195c104ccb631acd1b00cb748314ac3dbfb816b2b092316d99f8.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 195, + 545, + 217 + ], + "lines": [ + { + "bbox": [ + 305, + 195, + 545, + 217 + ], + "spans": [ + { + "bbox": [ + 305, + 195, + 545, + 217 + ], + "type": "text", + "content": "Figure 4. Lifelong learning performance comparison in RFL-ReID task on mAP and " + }, + { + "bbox": [ + 305, + 195, + 545, + 217 + ], + "type": "inline_equation", + "content": "\\mathbb{R}@\\mathbb{1}" + }, + { + "bbox": [ + 305, + 195, + 545, + 217 + ], + "type": "text", + "content": " accuracy." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 427, + 72, + 547, + 191 + ], + "blocks": [ + { + "bbox": [ + 427, + 72, + 547, + 191 + ], + "lines": [ + { + "bbox": [ + 427, + 72, + 547, + 191 + ], + "spans": [ + { + "bbox": [ + 427, + 72, + 547, + 191 + ], + "type": "image", + "image_path": "48d670bf3fc1955b64e03956db569ec2b4b05b0cbaed703d37cb821ba11132bf.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 308, + 231, + 542, + 269 + ], + "blocks": [ + { + "bbox": [ + 308, + 231, + 542, + 269 + ], + "lines": [ + { + "bbox": [ + 308, + 231, + 542, + 269 + ], + "spans": [ + { + "bbox": [ + 308, + 231, + 542, + 269 + ], + "type": "table", + "html": "
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", + "image_path": "cdc957ff6111a16fa0edd27e16d990ba2de27d27666175447e1f588946d5e9db.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 306, + 270, + 545, + 292 + ], + "lines": [ + { + "bbox": [ + 306, + 270, + 545, + 292 + ], + "spans": [ + { + "bbox": [ + 306, + 270, + 545, + 292 + ], + "type": "text", + "content": "Table 4. Ablation study on different balancing factors in continual compatible transfer network." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 307, + 406, + 319 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 307, + 406, + 319 + ], + "spans": [ + { + "bbox": [ + 306, + 307, + 406, + 319 + ], + "type": "text", + "content": "4.4. Ablation Studies" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 327, + 545, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 327, + 545, + 361 + ], + "spans": [ + { + "bbox": [ + 305, + 327, + 545, + 361 + ], + "type": "text", + "content": "In this section, we conduct ablation studies on Order-1 to evaluate the effectiveness of each component in our " + }, + { + "bbox": [ + 305, + 327, + 545, + 361 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 305, + 327, + 545, + 361 + ], + "type": "text", + "content": ". Our Base method is the baseline introduced in Sec. 3.3." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 364, + 545, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 364, + 545, + 483 + ], + "spans": [ + { + "bbox": [ + 305, + 364, + 545, + 483 + ], + "type": "text", + "content": "Effectiveness of CCT network. We compared the adaptively balancing strategy in our continual compatible transfer network with a fixed balancing strategy, which introduces fixed values for " + }, + { + "bbox": [ + 305, + 364, + 545, + 483 + ], + "type": "inline_equation", + "content": "a^m" + }, + { + "bbox": [ + 305, + 364, + 545, + 483 + ], + "type": "text", + "content": " in Eq. (5). As shown in Tab. 4, our method achieves the best mAP and R@1 accuracy among the fixed balancing strategies. It indicates that by adaptively generating the most appropriate fusion factor through different old features, our CCT network balances the forward mapping of old knowledge and the knowledge capturing of new knowledge, verifying its superior effectiveness." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "spans": [ + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": "Effectiveness of BCD module. As shown in Tab. 5, we evaluate the two important loss functions " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ca}" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": " (Eq. (6)) and " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{cr}" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": " (Eq. (9)) in the balanced compatible distillation module. It can be seen that compared with the Base method, " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ca}" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": " improves the average mAP/R@1 by " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "1.7\\%" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "1.2\\%" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": ", and the full version of the BCD module improves by " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "1.9\\%" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "2.3\\%" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": ". The above results indicate that the alignment in " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ca}" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": " and the relationship distillation in " + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{cr}" + }, + { + "bbox": [ + 305, + 485, + 545, + 640 + ], + "type": "text", + "content": " are both important for RFL-ReID. The former ensures that old features can continue to be compatible with the new ones, while the latter preserves the relationship within the old feature space. Finally, the BCD module achieves promising improvement by modelling the above functions in a balanced manner." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "text", + "content": "Effectiveness of BAD module. We further evaluate two main components " + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ad}" + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "text", + "content": " (Eq. (13)) and " + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{dc}" + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "text", + "content": " (Eq. (14)) in the balanced anti-forgetting module. As shown in Tab. 5, " + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ad}" + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "text", + "content": " brings an improvement by " + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "1.1\\%" + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "text", + "content": " on average mAP accuracy. When combined with " + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{dc}" + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "text", + "content": ", the accuracy further improved by " + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "0.3\\%" + }, + { + "bbox": [ + 305, + 641, + 545, + 713 + ], + "type": "text", + "content": ". It indicates that by distilling the discriminative" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "16620" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 70, + 282, + 155 + ], + "blocks": [ + { + "bbox": [ + 51, + 70, + 282, + 155 + ], + "lines": [ + { + "bbox": [ + 51, + 70, + 282, + 155 + ], + "spans": [ + { + "bbox": [ + 51, + 70, + 282, + 155 + ], + "type": "table", + "html": "
BaseCCTBCDBADmAPR@1
LcaLcrLadLdc
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✓✓✓---37.945.6
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", + "image_path": "e0471a24581f73ffcb9a3942b4d7b29a272eac9128dba128fd5a8c6b114bd874.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 49, + 156, + 285, + 166 + ], + "lines": [ + { + "bbox": [ + 49, + 156, + 285, + 166 + ], + "spans": [ + { + "bbox": [ + 49, + 156, + 285, + 166 + ], + "type": "text", + "content": "Table 5. Ablation studies of each component in " + }, + { + "bbox": [ + 49, + 156, + 285, + 166 + ], + "type": "inline_equation", + "content": "{\\mathrm{C}}^{2}\\mathrm{R}" + }, + { + "bbox": [ + 49, + 156, + 285, + 166 + ], + "type": "text", + "content": " on Order-1." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 176, + 287, + 223 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 176, + 287, + 223 + ], + "spans": [ + { + "bbox": [ + 46, + 176, + 287, + 223 + ], + "type": "text", + "content": "information within the old feature, BAD balances the antiforgetting of the old discrimination knowledge with the acquisition of the new knowledge and thus plays an important role in our " + }, + { + "bbox": [ + 46, + 176, + 287, + 223 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 46, + 176, + 287, + 223 + ], + "type": "text", + "content": " method." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "spans": [ + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": "Hyper-parameter Study. There are 4 hyper-parameters for the training of our " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mathrm{C^2R}" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": " method, i.e. " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_1" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_2" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_3" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_4" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": ". Therefore, we evaluate the effect of the above parameters respectively, as shown in Fig. 6. It can be seen that a slight or excessive " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_1" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": " will eliminate the alignment of the old feature to the new feature. In addition, as " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_2" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": " increases, the relationship between old features will prevent the model from learning new knowledge. Therefore, the moderate " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_1(=50)" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_2(=1)" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": " are chosen in the BCD module to balance the relationship between the old and new features. Similarly, we set a moderate " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_3(=0.01)" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "inline_equation", + "content": "\\mu_4(=0.05)" + }, + { + "bbox": [ + 46, + 225, + 288, + 368 + ], + "type": "text", + "content": " to balance the discriminative information in the old and new features." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 377, + 132, + 389 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 377, + 132, + 389 + ], + "spans": [ + { + "bbox": [ + 47, + 377, + 132, + 389 + ], + "type": "text", + "content": "4.5. Visualization" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "spans": [ + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "type": "text", + "content": "To intuitively verify the effectiveness of our " + }, + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "type": "inline_equation", + "content": "\\mathrm{C^2R}" + }, + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "type": "text", + "content": ", we use t-SNE [29] to visualize and compare the gallery feature and query feature calculated by our method with the Base method. The features are randomly selected from the five benchmark datasets. As shown in Fig. 5, the features calculated by our " + }, + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "type": "inline_equation", + "content": "\\mathrm{C^2R}" + }, + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "type": "text", + "content": " achieve tighter intra-class representation while retaining more inter-class discriminability. The above results indicate that our " + }, + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "type": "inline_equation", + "content": "\\mathrm{C^2R}" + }, + { + "bbox": [ + 46, + 396, + 287, + 528 + ], + "type": "text", + "content": " can preserve more discriminative information after transferring old gallery features, which can be further aligned by new query features to achieve RFL-ReID." + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 50, + 536, + 167, + 652 + ], + "blocks": [ + { + "bbox": [ + 50, + 536, + 167, + 652 + ], + "lines": [ + { + "bbox": [ + 50, + 536, + 167, + 652 + ], + "spans": [ + { + "bbox": [ + 50, + 536, + 167, + 652 + ], + "type": "image", + "image_path": "9694da0a586a66655a27e078c631b2c8688698141a7852380dd22413edf89d49.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 94, + 654, + 122, + 664 + ], + "lines": [ + { + "bbox": [ + 94, + 654, + 122, + 664 + ], + "spans": [ + { + "bbox": [ + 94, + 654, + 122, + 664 + ], + "type": "text", + "content": "(a) Base" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 669, + 287, + 703 + ], + "lines": [ + { + "bbox": [ + 46, + 669, + 287, + 703 + ], + "spans": [ + { + "bbox": [ + 46, + 669, + 287, + 703 + ], + "type": "text", + "content": "Figure 5. TSNE results of our " + }, + { + "bbox": [ + 46, + 669, + 287, + 703 + ], + "type": "inline_equation", + "content": "C^2 R" + }, + { + "bbox": [ + 46, + 669, + 287, + 703 + ], + "type": "text", + "content": " compared with Base method. Different colours represent different identities, while the circles and the triangles represent gallery and query features, respectively." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 170, + 536, + 286, + 652 + ], + "blocks": [ + { + "bbox": [ + 170, + 536, + 286, + 652 + ], + "lines": [ + { + "bbox": [ + 170, + 536, + 286, + 652 + ], + "spans": [ + { + "bbox": [ + 170, + 536, + 286, + 652 + ], + "type": "image", + "image_path": "7bec8af77eb3df7ec9f2d212405d15f615675f0df444594e273eee45e8212305.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 207, + 654, + 247, + 664 + ], + "lines": [ + { + "bbox": [ + 207, + 654, + 247, + 664 + ], + "spans": [ + { + "bbox": [ + 207, + 654, + 247, + 664 + ], + "type": "text", + "content": "(b) our " + }, + { + "bbox": [ + 207, + 654, + 247, + 664 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 312, + 71, + 426, + 184 + ], + "blocks": [ + { + "bbox": [ + 312, + 71, + 426, + 184 + ], + "lines": [ + { + "bbox": [ + 312, + 71, + 426, + 184 + ], + "spans": [ + { + "bbox": [ + 312, + 71, + 426, + 184 + ], + "type": "image", + "image_path": "9de7e20172300eb503e9cf0c9d470e0db2c1e18c901af2c6336138d1c0e3eedb.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 426, + 71, + 541, + 185 + ], + "blocks": [ + { + "bbox": [ + 426, + 71, + 541, + 185 + ], + "lines": [ + { + "bbox": [ + 426, + 71, + 541, + 185 + ], + "spans": [ + { + "bbox": [ + 426, + 71, + 541, + 185 + ], + "type": "image", + "image_path": "c0ee8effc310116df7c5cf3c2f4e636e3b9ba97055c03468eb3ef327a3812899.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 311, + 186, + 426, + 300 + ], + "blocks": [ + { + "bbox": [ + 311, + 186, + 426, + 300 + ], + "lines": [ + { + "bbox": [ + 311, + 186, + 426, + 300 + ], + "spans": [ + { + "bbox": [ + 311, + 186, + 426, + 300 + ], + "type": "image", + "image_path": "61312fb8dd085e436752a0849abfe2b010c8c90279e93567f4aefa28a69a1c85.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 323, + 304, + 528, + 316 + ], + "lines": [ + { + "bbox": [ + 323, + 304, + 528, + 316 + ], + "spans": [ + { + "bbox": [ + 323, + 304, + 528, + 316 + ], + "type": "text", + "content": "Figure 6. The influence of hyper-parameters in our " + }, + { + "bbox": [ + 323, + 304, + 528, + 316 + ], + "type": "inline_equation", + "content": "C^2 R" + }, + { + "bbox": [ + 323, + 304, + 528, + 316 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 426, + 186, + 541, + 300 + ], + "blocks": [ + { + "bbox": [ + 426, + 186, + 541, + 300 + ], + "lines": [ + { + "bbox": [ + 426, + 186, + 541, + 300 + ], + "spans": [ + { + "bbox": [ + 426, + 186, + 541, + 300 + ], + "type": "image", + "image_path": "06e38eff4ae95eed22171268027c1de148ae0466de6f80f170fc7dfcbce5e10d.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 324, + 463, + 335 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 324, + 463, + 335 + ], + "spans": [ + { + "bbox": [ + 306, + 324, + 463, + 335 + ], + "type": "text", + "content": "4.6. Limitation and Future Work" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 342, + 545, + 438 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 342, + 545, + 438 + ], + "spans": [ + { + "bbox": [ + 304, + 342, + 545, + 438 + ], + "type": "text", + "content": "Our " + }, + { + "bbox": [ + 304, + 342, + 545, + 438 + ], + "type": "inline_equation", + "content": "\\mathrm{C}^2\\mathrm{R}" + }, + { + "bbox": [ + 304, + 342, + 545, + 438 + ], + "type": "text", + "content": " can support L-ReID without re-indexing old data in the gallery. However, it is difficult to capture enough new knowledge to facilitate feature transfer and updating when the amount of new data is limited. Therefore, it is worthy of future research on efficient transfer under a few-shot scenario. In addition, when there is noise in new data, how to utilize old knowledge to eliminate such noise to achieve selective transfer should be studied in the future." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 453, + 378, + 465 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 453, + 378, + 465 + ], + "spans": [ + { + "bbox": [ + 306, + 453, + 378, + 465 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 475, + 545, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 475, + 545, + 654 + ], + "spans": [ + { + "bbox": [ + 304, + 475, + 545, + 654 + ], + "type": "text", + "content": "In this paper, we focus on a practical and challenging task called Re-indexing Free Lifelong Person Re-identification (RFL-ReID), which prohibits the re-indexing of raw images in the gallery due to data privacy concerns. To this end, we propose a Continual Compatible Representation " + }, + { + "bbox": [ + 304, + 475, + 545, + 654 + ], + "type": "inline_equation", + "content": "(\\mathrm{C}^2\\mathrm{R})" + }, + { + "bbox": [ + 304, + 475, + 545, + 654 + ], + "type": "text", + "content": " method, which introduces a Continual Compatible Transfer (CCT) network to continuously transfer old gallery features to the new feature space. Besides, a Balanced Compatible Distillation module and a Balanced Anti-forgetting Distillation module are proposed to balance the anti-forgetting of old knowledge with the compatibility to the new model. Extensive experiments on five widely-used benchmark L-ReID datasets verify the effectiveness of our method on the RFL-ReID task while maintaining the state-of-the-art performance on the general L-ReID scenario." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 669, + 402, + 681 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 669, + 402, + 681 + ], + "spans": [ + { + "bbox": [ + 306, + 669, + 402, + 681 + ], + "type": "text", + "content": "Acknowledgements" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "This work was supported by the National Natural Science Foundation of China (61925201, 62132001, 62376011)." + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "16621" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 146 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 146 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 146 + ], + "type": "text", + "content": "[1] Shafiq Ahmad, Gianluca Scarpellini, Pietro Morerio, and Alessio Del Bue. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 9046–9056, 2022. 3" + } + ] + } + ], + "index": 21 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "text", + "content": "16623" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_content_list.json b/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..d1916afaff9cab070ec87781b2b41515bdd2955d --- /dev/null +++ b/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_content_list.json @@ -0,0 +1,1230 @@ +[ + { + "type": "text", + "text": "Learning Continuous 3D Words for Text-to-Image Generation", + "text_level": 1, + "bbox": [ + 171, + 130, + 799, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Ta-Ying Cheng $^{1*}$ Matheus Gadelha $^{2}$ Thibault Groueix $^{2}$ Matthew Fisher $^{2}$ Radomír Měch $^{2}$ Andrew Markham $^{1}$ Niki Trigoni $^{1}$", + "bbox": [ + 186, + 188, + 782, + 232 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1University of Oxford 2Adobe Research", + "bbox": [ + 318, + 242, + 648, + 261 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/4ea8e0c5b72d074ace34a7cde2aed386fa93c1dfe3ae78fb94bba68e9518eb17.jpg", + "image_caption": [ + "Figure 1. We introduce Continuous 3D Words - special tokens in text-to-image models that allow users to have fine-grained control over several attributes like illumination [ ] (a and c), non-rigid shape change [ ] (d), orientation [ ] (c and d), and camera parameters [ ] (b). Our approach can be trained using a single 3D mesh and a rendering engine while incurring into negligible runtime and memory costs." + ], + "image_footnote": [], + "bbox": [ + 81, + 303, + 472, + 628 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/a8a555aa2a5bbb803f2ec86f602ed437ac16d562037bacd0d0db205b22e91737.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 495, + 305, + 890, + 627 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 700, + 313, + 718 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Current controls over diffusion models (e.g., through text or ControlNet) for image generation fall short in recognizing abstract, continuous attributes like illumination direction or non-rigid shape change. In this paper, we present an approach for allowing users of text-to-image models to have fine-grained control of several attributes in an image. We do this by engineering special sets of input tokens that can be transformed in a continuous manner - we call them Continuous 3D Words. These attributes can, for example, be represented as sliders and applied jointly with text prompts for fine-grained control over image", + "bbox": [ + 73, + 734, + 473, + 902 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "generation. Given only a single mesh and a rendering engine, we show that our approach can be adopted to provide continuous user control over several 3D-aware attributes, including time-of-day illumination, bird wing orientation, dollyzoom effect, and object poses. Our method is capable of conditioning image creation with multiple Continuous 3D Words and text descriptions simultaneously while adding no overhead to the generative process. Project Page: https://ttchengab.github.io/continuous_3d_words", + "bbox": [ + 496, + 703, + 895, + 839 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Work was done during internship at Adobe Research.", + "bbox": [ + 526, + 886, + 812, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "6753", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 80, + 90, + 207, + 104 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Photography is fascinating because it enables very detailed control over the composition and aesthetics of the final image. On the one hand, this is simply the result of application of physical laws to achieve image acquisition. On the other, the slightest changes in the moment captured, illumination, object orientation, or camera parameters bring a completely different feeling to the viewer. While the giant leap of modern text-to-image diffusion can bring generated 2-D images to close proximity with real photos, text prompts are inherently limited to high-level descriptions, far removed from the detailed controls one has over actual photography. This is mainly due to the scarcity of such descriptions in the training dataset — very few would describe a photo based on exact object movements and camera parameters like the wing pose of a bird or the rotation of a person's head in degrees. On the other hand, 3D rendering engines allow us to mimic many of these 3D controls that photographers enjoy. We can render images of objects with predefined camera, illumination and pose changes at a very fine-grained scale. However, creating detailed 3D worlds is incredibly laborious, which limits the diversity of the scenes that can be generated by non-specialized practitioners. In that regard, using text-to-image diffusion to create images is a much more accessible technology, whereas precise 3D scene control remains firmly in the domain of experts.", + "bbox": [ + 80, + 114, + 468, + 491 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this work, we aim to bring together the best of two worlds by expanding the vocabulary of text-to-image diffusion models with very few samples generated from rendering engines. Specifically, we render meshes based on the attribute we aim to control, creating images with color and other useful information to generate a small set of data samples. The goal is to disentangle these abstract attributes from the original object and encode them into the textual space in a controllable manner – we term these attributes Continuous 3D Words. They allow users to create custom sliders that enable fine-grained control during image generation and can be seamlessly used along text prompts.", + "bbox": [ + 80, + 493, + 468, + 672 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "At the heart of our approach is an algorithm to learn a continuous vocabulary. The benefits of continuity are twofold: $i)$ the association between different values of the same attribute makes it much easier to learn, rather than having to learn hundreds of discrete tokens as an approximation and $ii)$ we learn an MLP that would allow interpolation during inference to generate an actual continuous control. On top of this, we also propose two training strategies to prevent degenerate solutions and enable generalization on new objects beyond the training category. First, we apply a two-stage training strategy: we first apply the Dreambooth [25] approach to learn the object identity of the underlying mesh used for rendering, then sequentially learn the various attribute values disentangled from the object identity. This prevents the model from falling into a degenerate solution of encoding", + "bbox": [ + 80, + 675, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "each value of an attribute as a new object, which would prevent us from generalizing the attribute to new objects. Second, we apply ControlNet [30] with various conditioned images to generate a set of additional images with varying backgrounds and object textures. This prevents the model from overfitting to the artificial backgrounds of rendered images. The entire training was done in a light-weight Lower Rank Adaptation (LoRA) [14] manner, making it fast and accessible with single GPUs.", + "bbox": [ + 501, + 90, + 890, + 226 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We implement our continuous vocabulary and training method, across various sets of single (e.g., dollyzoom extracted from chairs) and multiple (e.g., object pose and illumination extracted from a dog mesh) attributes, and show through quantitative user studies and qualitative comparisons that our method can properly reflect various attributes while maintaining the aesthetics of the image — significantly outperforming competitive baselines.", + "bbox": [ + 503, + 227, + 890, + 347 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In summary, we present 1) Continuous 3D Words, a new method of gaining 3D-aware, continuous attribute controls over text-to-image generation that can be easily tailored to a plethora of new conditions, 2) a series of training strategies to disentangle the attributes from object identity to enhance the improvements in image generation and 3) extensive qualitative and quantitative studies to showcase our approach in various interesting applications.", + "bbox": [ + 503, + 348, + 890, + 468 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 503, + 483, + 638, + 497 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Conditional Diffusion Models. Ever since diffusion models [13, 27] pushed the quality and generalizability of image generation beyond GANs [10], the vision community has introduced a diverse range of modalities that can be used as conditions to control the image generation process. The most common condition is currently text. Works such as DALLE [2, 22, 23] and Imagen [26] used large scale text-image datasets and strong language understandings from pretrained LLMs [4, 8, 21] to guide the generation process. Stable Diffusion further popularized this class of methods by employing memory efficient models through latent-space diffusion [24]. Other works built on top of these models by adding other forms of conditioning [19, 30]. Highly relevant to our work is ControlNet [30], which proposes a general pipeline with zero-convolutions for conditioning on text and image data (e.g., depth maps, canny maps, sketches). Despite their impressive image quality, it is not clear how to use these models to control other attributes of images like illumination or object orientation.", + "bbox": [ + 503, + 507, + 890, + 792 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Other set of works explored how to perform image edits using textual instructions. Given a text-generated image, they demonstrate how the user can edit the image by amending the prompt, yet still preserve some aspects of the original image [3, 12, 20]. While convenient, these approaches do not allow fine-grained control over image elements since they are ultimately restricted by the user's ability to describe", + "bbox": [ + 503, + 795, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "6754", + "bbox": [ + 483, + 946, + 513, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/87676faa54a52997856d3f4221b7e6a469938b12c460eb3bc2281579c44fcddc.jpg", + "image_caption": [ + "Figure 2. Method Overview. Finetuning: Our finetuning is divided into two stages. In the first stage, we render a series of images using different attribute values (e.g., illumination and pose). We feed them into the text-to-image diffusion model to learn token embedding [Obj] representing the single mesh used for training. In the second stage, we add the tokens representing individual attributes into the prompt embedding. The two stage training allows us to better disentangle the individual attributes against [Obj]. Inference: Attributes can be applied to different objects for text-to-image generation." + ], + "image_footnote": [], + "bbox": [ + 81, + 89, + 890, + 392 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/ed1d9efbc15f1d2d99234496c9ec0e49c6c66cc0c726f4a6f0cc0dad38791bd8.jpg", + "image_caption": [ + "Figure 3. ControlNet Augmentations. Depth ControlNet is used for attributes creating direct shape changes. Lineart ControlNet is applied for more subtle changes that cannot be reflected by depths (e.g., illumination)." + ], + "image_footnote": [], + "bbox": [ + 78, + 496, + 472, + 652 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "visual content through text – e.g., it would be very difficult to change the illumination direction by a precise angle such as $11^{\\circ}$ .", + "bbox": [ + 75, + 748, + 468, + 792 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Recently, as the amount of 3D data available significantly increased, Liu et al. [16] introduced Zero-1-to-3, a diffusion model trained on various viewpoints of 3D rendering that enables viewpoint editing given an image of a single object. Similarly, works like DreamSparse [29] also employ diffusion models to synthesize novel views on open-set categories. Differently from our approach, these techniques are", + "bbox": [ + 75, + 795, + 470, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "focused only on object orientation and rely on vast 3D shape datasets. On the other hand, we investigate how to learn several continuous concepts (e.g. illumination [ ] , wing pose [ $\\mathcal{V}$ ], dolly zoom [ $\\text{公} _ { \\text{公} } ^ { \\text{公} }$ ]) that can be directly used in text-to-image scenarios; i.e. we don't generate an image to then change the orientation or illumination later, but instead we use Continuous Words directly on text prompts.", + "bbox": [ + 496, + 501, + 893, + 609 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Learning new concepts on diffusion models. With diffusion models being trained on unforeseen quantities in images and texts, a stream of work focused on adding specific concepts with very few data samples. For example, given a small set of images representing one particular object instance, textual inversion learns a new word embedding to describe the object, such that the word can be applied with new text prompts for image generation [9]. NETI [1] extended the word embedding to a time-space conditioned neural mapper for better generation while preserving quality. Similarly, Dreambooth [25] aims to achieve the same goal, but by using a repurposed token rarely used in text and finetuning the entire diffusion model with an additional constraint to prevent generative loss. There are numerous subsequent works showing improvements on finetuning different layers/weights and by improving the training strategy [11, 15, 17].", + "bbox": [ + 496, + 628, + 895, + 883 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Despite the advances in adding new personalized entities", + "bbox": [ + 517, + 885, + 890, + 901 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "6755", + "bbox": [ + 482, + 944, + 514, + 957 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "to existing models, few works focus on learning general concepts that can be applied to a variety of scenarios. A concurrent work, ViewNETI [5], is the first to learn viewpoints as a concept, but we hypothesise that the 3D awareness of large text-to-image diffusion models goes far beyond merely viewpoints, allowing us to associate and even create interactions with multiple 3D-aware concepts like illumination, pose and camera parameters at the same time. Our method, despite being trained only using a single mesh, shows superior generalization properties – while trained to learn illumination and orientation from renderings of a single dog, we are capable of employing the learned concepts to generate cars, horses (Figure 4), polar bears (Figure 8), lions (Figure 1) and so on.", + "bbox": [ + 75, + 90, + 472, + 287 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 304, + 168, + 319 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.1. Preliminaries", + "text_level": 1, + "bbox": [ + 76, + 330, + 217, + 344 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We define an image $I$ that captures object $O$ from category $C$ as a function of several attributes $I = f(a_{1},a_{2},a_{3},\\dots,a_{n})$ , where $a_{i}$ belongs to a vast set of image attributes $\\mathcal{A}$ : shape, material reflectivity, rotation/translation, camera parameters, shape deformations, etc. Some of these components can be translated to other categories while others cannot, so for simplicity we assume they only work for a single category. In the experimental section of this study, we will demonstrate that the definition of category for some attributes is rather loose and the user is capable of generating images with continuous words depicting objects very different from the ones seen during training. Notice that images annotated with the attributes we are interested are very rare, so the models do not have a very precise knowledge of them, except for what is already described in text-image pairs.", + "bbox": [ + 75, + 354, + 472, + 580 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given an image set $I^O$ with images capturing an object $O$ , previous methods like Dreambooth [25], Custom Diffusion [15], or Textual-Inversion [9] aim to minimize the following objective:", + "bbox": [ + 75, + 580, + 470, + 642 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbb {E} _ {\\hat {I} _ {\\epsilon , i}, T _ {O}, I _ {i} \\in I ^ {O}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , i}, P (T _ {O})\\right) - I _ {i} \\right\\| _ {2} ^ {2} \\right], \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 127, + 655, + 472, + 689 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $S_{\\theta}$ is a Text-to-Image diffusion model [24], $\\hat{I}_{\\epsilon,i}$ is a noised image $\\alpha_t I_i + \\sigma_t \\epsilon$ with noise $\\epsilon$ and noise schedulers $\\alpha_t, \\sigma_t$ . $P(T_O)$ is the prompt condition which contains a token embedding $T_O$ used as an identifier of object $O$ . In practise $P(\\cdot)$ is the text encoder from CLIP. The finetuned network $S_{\\theta}$ can then generate new images containing $O$ when given a new prompt condition $P'(T_O)$ and some Gaussian noise. Unlike previous methods, our goal is not to add concepts representing specific objects, but rather have them describe some attributes $a_i \\in \\mathcal{A}$ , by learning to disentangle them using as few objects as possible within $C$ - most of the time just one object suffices. Our model can also be easily extended to controlling multiple attributes at the same time.", + "bbox": [ + 75, + 703, + 472, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Continuous Control", + "text_level": 1, + "bbox": [ + 500, + 90, + 689, + 104 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "A naive way to control an attribute $a$ is to use some realistic rendering engine to generate images of the available objects that have the same value $a = x$ , and then apply similar approaches to previous works by assigning a token $T_{x}$ to identify images with this particular value. This is not ideal, however, since $a$ is often continuous and have infinitely many values – we would require an unfeasible number of tokens to gain fine-grained control over these attributes.", + "bbox": [ + 496, + 113, + 893, + 233 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Therefore, we propose to instead learn a continuous function $g_{\\phi}(\\mathbf{a}) : \\mathcal{D} \\to \\mathcal{T}$ that maps a set of attributes from some continuous domain $\\mathcal{D}$ to the token embedding domain $\\mathcal{T}$ . We use positional encoding to first cast each attribute $a \\in \\mathbf{a}$ to a higher frequency space before feeding into the function, which is represented by a very simple 2-layer MLP. The output of this network is named Continuous 3D Word and will allow users to easily control continuous attributes from text prompts augmented by these tokens. Finally, our training objective can then be formulated as:", + "bbox": [ + 496, + 234, + 893, + 385 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\arg \\min _ {\\theta , \\phi} \\mathbb {E} _ {\\hat {I} _ {\\epsilon , \\mathbf {a}}, \\mathbf {a}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , \\mathbf {a}}, P \\left(g _ {\\phi} (\\mathbf {a})\\right)\\right) - I _ {\\mathbf {a}} \\right\\| _ {2} ^ {2} \\right]. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 534, + 393, + 892, + 429 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Disentangling Object Identity and Attributes", + "text_level": 1, + "bbox": [ + 498, + 436, + 879, + 454 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In practice, when we only utilize a single object to learn attributes, a degenerate solution occurs when directly optimizing (2), where $S_{\\theta}$ treats the same object with different values for $a$ as different objects. This hinders the generalization capability of changing the attribute when given an image of a new object. To this end, we propose two strategies, one during training and one during inference, to disentangle the object identity and individual attributes.", + "bbox": [ + 496, + 460, + 893, + 580 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Training: Learning identity and attributes. We provide a simple regularization by explicitly forcing the model to use the same identifier for images representing the same object. The objective can thus be formulated as:", + "bbox": [ + 496, + 585, + 893, + 647 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\arg \\min _ {\\theta , \\phi} \\mathbb {E} _ {\\hat {I} _ {\\epsilon , \\mathbf {a}}, \\mathbf {a}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , \\mathbf {a}}, P \\left(T _ {O}, g _ {\\phi} (\\mathbf {a})\\right)\\right) - I _ {\\mathbf {a}} \\right\\| _ {2} ^ {2} \\right]. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 511, + 656, + 892, + 689 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Optimizing both $T_{O}$ and $g_{\\phi}(\\mathbf{a})$ concurrently proved to be difficult from our experiments (see Section 5). We propose a two-stage training strategy as depicted in Figure 2. For every available image in $I^{O}$ with varying $\\mathbf{a}$ , we first use the same prompt condition $P(T_{O})$ to associate them to the same object, then learn the diffusion model parameters $\\theta$ and our Continuous 3D Words MLP $g_{\\phi}$ by using the prompt condition $P(T_{O},g_{\\phi}(\\mathbf{a}))$ .", + "bbox": [ + 496, + 699, + 893, + 820 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Inference: Negatively prompting object identifier. To further the disentanglement of attributes against object identities. We propose a simple trick during inference by adding the object identity as a negative prompt. Specifically, for each sampling step, we swap the null-text embedding used", + "bbox": [ + 496, + 825, + 893, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "6756", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/ad36a39bc9a31be19c09bfa53cf400a69381bff6a67724871cb774165296d29c.jpg", + "image_caption": [ + "Figure 4. Qualitative Comparisons. We compare our Continuous 3D Words trained under three settings against ControlNet of various strengths. Note that the dollyzoom setup was trained with trained with multiple chair meshes, so we give additional ControlNet by manually picking the chair rendering that best follows the prompt (i.e., \"comfortable\" and in \"the office\")." + ], + "image_footnote": [], + "bbox": [ + 76, + 88, + 893, + 568 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/eaa5b8038232620981dbb92faaf41d23f3d168bbe4a9c2b5a0bacd8809fb2811.jpg", + "image_caption": [ + "Figure 5. Disentangling Multiple Attributes. We show four examples of controlling multiple Continuous 3D words in addition to text descriptions. Left: trained with a single golden retriever mesh. Right: trained with a single animated dove." + ], + "image_footnote": [], + "bbox": [ + 94, + 643, + 457, + 785 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "by classifier-free guidance with $T_{O}$ . Intuitively, since our training happened mostly using $O$ , we want to disincentivize the model to generate images containing such object.", + "bbox": [ + 75, + 854, + 470, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. ControlNet Augmentation", + "text_level": 1, + "bbox": [ + 500, + 646, + 736, + 662 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To prevent the fine-tuning process from overfitting to a simple white backgrounds and pre-defined object textures, we augment the backgrounds and textures in the rendering process. However, directly doing this in simulation engines is time consuming specially if one is targeting realistic scenes. Thus, we propose an automated solution by utilizing pretrained ControlNets.", + "bbox": [ + 496, + 671, + 893, + 775 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Figure 3 shows two types of ControlNet augmentations we used in our framework. For attributes that can be directly reflected on shape changes (e.g., wing pose), we directly render the ground-truth depth maps to use as the condition for ControlNet. On the other hand, for attributes that cannot be reflected directly from depths (e.g., illumination), we first render the images without textures, then use a linear extractor to obtain a \"sketch\" of the image. This captures", + "bbox": [ + 496, + 779, + 893, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "6757", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "subtle changes such as shades and shadows in the pixel space, which can then be used as the condition for Lineart ControlNet.", + "bbox": [ + 75, + 90, + 468, + 133 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We add additional prompts describing the object appearance and background during the ControlNet generation. It is important to note that prompts deviating away too much from the original mesh category would lead to degenerate images, so our prompts are in general very simple and straightforward (details in supplemental material). We include the ControlNet generated images as a small set of data augmentation, and we use the same prompt which we use to guide ControlNet generation to guide our Stage 2 fine-tuning.", + "bbox": [ + 75, + 136, + 470, + 272 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 285, + 207, + 301 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We use off-the-shelf Stable Diffusion v2.1 [24] as the backbone of our method. We resort to the recent Low-Rank Adaptation (LoRA) [14] for the fine-tuning of the denoising U-Net and text encoder, allowing us to train on a single A10 GPU occupying roughly 16GB of memory. Thanks to the low-rank optimization, our models have a very small size (approximately 6MB). Training time varies by the complexity of the single/multiple attributes to learn, but falls within 15k to 20k steps, which generally takes around 3-4 hours in a single GPU. For ControlNet augmentation, we use the official implementation of ControlNet v1.1 [30].", + "bbox": [ + 75, + 310, + 470, + 474 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We implement our Continuous 3D words under five different attribute settings. For single attributes we implement 1) illumination [ ] using a single dog mesh, 2) wing pose [ ] using a single animated dove mesh, and 3) Dolly zoom [ ] with five Pix3D chairs [28]. For multi-concepts, we train 4) illumination and object orientation [ ] + [ ] using a single dog mesh and 5) wing pose and orientation [ ] + [ ] using a single animated dove mesh. Settings 1) and 4) use linear images [6] while the others use depth map to compute the ControlNet background augmentation (see Section 3.4).", + "bbox": [ + 75, + 476, + 470, + 642 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.1. Comparison with Baselines", + "text_level": 1, + "bbox": [ + 76, + 650, + 321, + 666 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baseline Design. We design a very competitive baseline that enables fine-grained attribute control in image generation by combining the mesh training data we used in our experiments, a rendering engine and ControlNet [30]. Specifically, we take a novel text prompt for a training object, and grab a corresponding condition map in the training set rendered with the intended attributes. For example, if the prompt is a $[\\varpi]$ eagle flying in a forest, we select the frame of the dove mesh that corresponds to the user-prescribed wing pose $[\\varpi]$ , render its depth map using a rendering engine and pass it through ControlNet with the same prompt but removing the continuous $3D$ word. The strength of the ControlNet guidance is a critical hyperparameter — increase in strength could increase the accuracy of reflecting the attribute but decrease the robustness to general-", + "bbox": [ + 75, + 674, + 470, + 900 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/4adf4c0f9cf858aee4cc5be71a90a01606b97bbe1a0e2af6bd3b95d675f75176.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodUser Preference (%) ↑
[✓][?][✓] / [?][?] / [?]Avg.
ControlNet (1.0)28.3%16.2%35.0%15.0%23.6%
ControlNet (0.5)10.0%28.8%12.5%32.5%21.0%
Ours61.7%55.0%52.5%52.5%55.4%
Average User Ranking ↑
Method[✓][?][✓] / [?][?] / [?]Avg.
ControlNet (1.0)2.07 ± 0.701.49 ± 0.762.20 ± 0.681.60 ± 0.741.84 ± 0.72
ControlNet (0.5)1.38 ± 0.662.11 ± 0.671.38 ± 0.702.06 ± 0.761.73 ± 0.70
Ours2.55 ± 0.622.40 ± 0.732.43 ± 0.672.33 ± 0.772.43 ± 0.70
", + "bbox": [ + 504, + 89, + 890, + 234 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. User study results. We asked users to rank three images according to their preference and how well they followed the given conditions – text prompt and one or two continuous controls. The controls were described by representative images (i.e. arrows for orientation, shaded sphere for illumination, etc.). See supplemental material for more details. We evaluate four different control types: wing pose \\([\\sim]\\), illumination \\([\\diamond]\\), wing pose \\([\\sim] + orientation \\([\\triangle]\\), and illumination \\([\\diamond] + orientation \\([\\triangle]\\). Cells colored as red and yellow represent the best and second best method, respectively. Our method was selected as the favorite for the majority of users in all evaluated setups.", + "bbox": [ + 496, + 244, + 893, + 398 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "ize to the text-prompt intended object. Therefore, we present the ControlNet baseline with both full and half strength in terms of guidance. We also explored an interpolation of null-text embedding [18] baseline, but the results failed to capture even the simplest attributes, so they were omitted from our analysis.", + "bbox": [ + 496, + 419, + 892, + 510 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Quantitative Results. Due to the complexity and abstract nature of the attributes we are analyzing, automatically measuring whether a generated image reflects a set of values is a considerable challenge. Thus, following previous papers [12, 25, 30], we create a user study to evaluate the quality of the generated images while controlling several attributes. For each setting 1, 2, 4, and 5, we randomly sample a set of 3D conditions and prompts, generating over 60 questions per setting. Similarly to the user studies above, we then invite 20 participants, showing them all the given constraints we want the image to pertain (prompts and attributes), and ask them to rank each image from best to worst.", + "bbox": [ + 496, + 518, + 893, + 699 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1 shows the results in both the percentage of user preference (image chose as the best one) and the overall ranking. Best results are highlighted as red. Our Continuous 3D Words won the majority of votes (over $50\\%$ ) in all analyzed scenarios. Interestingly, the second best (as highlighted in yellow) alternates between the two guidance strengths of ControlNet. For wing-pose based controls, having a weaker control diminishes the strong prior offered by the depth map, resulting in inaccurate poses. Conversely, strong guidance for illumination forces ControlNet to generate objects around the shadow outline (further shown in Figure 4). Differently from the baselines, our training strategy is one-size-fits-all without any hyperparameter required.", + "bbox": [ + 496, + 704, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "6758", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Qualitative Analyses We present a detailed comparison of", + "text_level": 1, + "bbox": [ + 76, + 90, + 468, + 104 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/beda9bee85ed0815ec80ab61ff9ce6ef8e8ff08ff30f522c083d6c16de3b184e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 76, + 104, + 491, + 324 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Multi-Concep", + "text_level": 1, + "bbox": [ + 76, + 335, + 218, + 352 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1e26b9cdc3995b87b251225d79cf98976e933019a944240cec42a3a6b34a6955.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 218, + 327, + 491, + 381 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Just like sentences with but each disentangled from one another when controlling the image generation, our Continuous 3D Words can do the same. We show four examples in Figure 5, two from [ ] and [ ], and two [ ] and [ ], where we can keep one attribute fixed but change the other without sabotaging the quality of image generations. They can be jointly used with complex prompts describing the background and object texture. Moreover, while all these words are learned from a single mesh, we can easily transfer the attribute to objects with fairly close semantics (e.g., a Labrador mesh to a polar bear, or a dove mesh to a parrot).", + "bbox": [ + 75, + 364, + 468, + 544 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Real World Image Editing", + "text_level": 1, + "bbox": [ + 76, + 563, + 313, + 579 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our Continuous 3D Words can be directly applied to real world images to perform editing. To do so, we simply have to encode a real world image to a rare token via Dreambooth [25]. Then, we only have to use that token in conjunction with our Continuous 3D Words to generate the edited image. We show 4 examples in Figure 6, changing $[\\bullet]$ , $[\\neg]$ , $[\\uparrow]$ . As we can see, the Dreambooth token preserves most of the image appearance, while our Continuous Words understand and brings edits to the main subject.", + "bbox": [ + 75, + 590, + 468, + 726 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparing with Zero-1-to-3 While our approach is focused on enhancing text-to-image, given the capabilities of real-world image editing, we can use the same setup to provide a comparison with only with object orientation changes (Figure 6). Notice that Zero1-to-3 [16] operates in foreground-only images so we also had to segment the object [7], inpaint the background [24], and place the novel orientation back to the image. Each step contains errors that, when compounded, hurt the quality of the final result. More importantly, our method allows controls beyond orientation changes without relying on massive 3D datasets.", + "bbox": [ + 75, + 734, + 470, + 900 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a836c4c49ec1b7690c17b91762088001ac43687519f2737d862913d9e57500e8.jpg", + "image_caption": [ + "Figure 6. Real World results & Comparison w/ Zero1-to-3. We learn tokens representing single images and use along with Continuous 3D Words for image editing. The learned image token encodes most of the image appearance, while the Continuous 3D Word modifies its relevant aspects. Zero123, on the other hand, tends to yield images where the modified object is deformed or not properly harmonized." + ], + "image_footnote": [], + "bbox": [ + 514, + 90, + 877, + 385 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/b0ceddadd32708a752082b8c1a60ffbf24d49e39a75c999ec04ec75ead275a63.jpg", + "image_caption": [ + "Figure 7. Interpolating continuous 3D words. We present two results of interpolation, one with discrete tokens and one with our Continuous 3D Words. Our method preserves the attributes better and enables interpolation between two values." + ], + "image_footnote": [], + "bbox": [ + 501, + 518, + 890, + 642 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5. Discussion and Limitations", + "text_level": 1, + "bbox": [ + 500, + 737, + 750, + 753 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Why Not Discrete Tokens? The benefits of fitting a single MLP instead of multiple tokens on an attribute with different values are twofold. First, the MLP learns a continuous function, allowing us to interpolate between two training data samples whereas fitting multiple tokens leads to two datapoints as two discrete mappings. Second, finetuning a model to learn multiple custom tokens simultaneously is very hard. These benefits are illustrated in Figure 7. We show a comparison of learning a single Continuous 3D Word $[\\nu^{\\prime}]$", + "bbox": [ + 496, + 763, + 893, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "6759", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/313b5b9bafcb9996731113ce513b628a30c5ea1f4594825d980f426938cdb2ef.jpg", + "image_caption": [ + "Figure 8. Ablation Study. We present our ablations for: w/o two-stage training, w/o ControlNet augmentation, w/o [obj] as negative prompt, and our full pipeline. Notice that, when the prompt deviates a lot from the training data (truck in prompt, mesh of a dog for training), the ablated version fails to follow the prompt. Without two-stage training, it ignores the prompt and creates a dog; without the other parts it yields deformed shadows and dog-shaped trucks." + ], + "image_footnote": [], + "bbox": [ + 81, + 88, + 472, + 248 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "and 18 discrete tokens for different values of a wing pose. Both were learned with the same training method (2-stage with ControlNet augmentation). We present the generated results of three attribute values that are present in the training set, as well as the results when you interpolate the value in between. Interpolation is straightforward for our case where we just input the intermediate value into our Continuous 3D Words MLP. For discrete tokens, we interpolate between two nearest discrete bins. Notice that the discrete tokens have difficulty not only in interpolating results but also in learning the concept simultaneously. The eagle wings in the second row of Figure 7 do not follow the training data and sometimes generate a completely different pose (third column, second row). On the other hand, our images closely follow the pose prescribed by the user (top row) while yielding appealing images even when the values were not seen during training (columns 2, 4 and 6; second row).", + "bbox": [ + 75, + 371, + 472, + 628 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Ablation study. Figure 8 shows an ablation of our training strategy. We remove each component of our training strategy (w/o two-stage training, w/o ControlNet augmentation, w/o [obj] as negative prompt) and compare it with our full pipeline. Two examples are presented: one where the prompt is similar to the training and another one where it is significantly different. Without the two-stage training, the model fails to disentangle object identity with our attributes, hindering the generalization capability to new objects. This is particularly noticeable for the bottom row when the text prompt is a truck but a dog similar to the training mesh is generated when the two-stage training is removed. Without ControlNet, the finetuning process often overfits to the background training renderings, resulting in an inability to generate realistic backgrounds. Finally, adding [obj] as the negative prompt serves as a minor improvement in further disentangling both the backgrounds and object shape seen during training, resulting in a more aesthetic image.", + "bbox": [ + 75, + 628, + 473, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9fef82724241552dea150b7e7b53b0aa3774ebc2cca2349ebace37664efdd43e.jpg", + "image_caption": [ + "a)" + ], + "image_footnote": [], + "bbox": [ + 501, + 90, + 694, + 191 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/cb70a70993e0c41c5ce8c9180fde570b75dfd68f8af9a5aa5632bbdbb4d19180.jpg", + "image_caption": [ + "b)", + "Figure 9. Condition v.s. Accuracy in User Study. a) shows two images generated by the prompt “a $[v^{-}]$ photo of a white bird on sand”. b) shows two images generated by the prompt “a $[v^{-}]$ photo of a colorful bird”. Left is ours, right is ControlNet (1.0). Users preferred right over left for both." + ], + "image_footnote": [], + "bbox": [ + 697, + 90, + 890, + 190 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ff2677fc474c4dadcb5c1dd3d90511afbef3c3129ce94b2f96d2323fc7e91f97.jpg", + "image_caption": [ + "a)", + "Figure 10. Failure cases. a) shows images generated with prompt \"a [ ] [ Monet Painting of ....\". b) shows images generated with \"a [ ] [ photo of a T-Rex\"." + ], + "image_footnote": [], + "bbox": [ + 501, + 292, + 694, + 392 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d875225246450d141f0a913c9c072888216f2a9cc19fc59350f4dcaf7007d2ac.jpg", + "image_caption": [ + "b)" + ], + "image_footnote": [], + "bbox": [ + 697, + 292, + 890, + 391 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Condition v.s. Generated Accuracy in User Study. During our user study, we realize that occasionally users select the image which more strictly follows the exact conditions over the more physically probable image. For example, in Figure 9 a) and b), the head of the bird is generated poorly, but users preferred them as they are \"whiter\" and \"more colorful\".", + "bbox": [ + 496, + 453, + 890, + 542 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Failure Cases. We present in Figure 10 two examples of typical failure cases in our results. First, our model currently fails on more difficult scenarios where the style is given by the text prompt. In a), the image cannot fully reflect the \"Monet painting\" style imposed by our prompt. Second, the generated object may sometimes still overfit to the training set. In b), the T-Rex had four feet on the ground instead of standing with two claws in air – an attribute that is similar to the training dog mesh used to learn illumination.", + "bbox": [ + 496, + 544, + 893, + 679 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 694, + 617, + 709 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We presented Continuous 3D Words, a framework that allows us to learn 3D-aware attributes reflected in renderings of meshes as special words, which can then be injected into the text prompts for fine-grained text-to-image generation. Extensive study on learning both single and multiple continuous words shows that we can control challenging attributes. With the lightweight design and promising results, we hope that this work opens up interesting applications in the vision community to create their own 3D words with a single mesh and an accessible rendering engine.", + "bbox": [ + 496, + 719, + 893, + 869 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements. This work is supported in part by the EPSRC ACE-OPS grant EP/S030832/1.", + "bbox": [ + 498, + 869, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "6760", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Yuval Alaluf, Elad Richardson, Gal Metzer, and Daniel Cohen-Or. 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In IEEE International Conference on Computer Vision (ICCV), 2023. 2, 6" + ], + "bbox": [ + 78, + 90, + 468, + 246 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "6762", + "bbox": [ + 482, + 945, + 516, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_model.json b/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_model.json new file mode 100644 index 0000000000000000000000000000000000000000..bbf064d248b2df849fb01f7dc8b533528a785c9d --- /dev/null +++ b/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_model.json @@ -0,0 +1,1639 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.044 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.172, + 0.131, + 0.8, + 0.154 + ], + "angle": 0, + "content": "Learning Continuous 3D Words for Text-to-Image Generation" + }, + { + "type": "text", + "bbox": [ + 0.187, + 0.189, + 0.784, + 0.233 + ], + "angle": 0, + "content": "Ta-Ying Cheng\\(^{1*}\\) Matheus Gadelha\\(^{2}\\) Thibault Groueix\\(^{2}\\) Matthew Fisher\\(^{2}\\) Radomír Měch\\(^{2}\\) Andrew Markham\\(^{1}\\) Niki Trigoni\\(^{1}\\)" + }, + { + "type": "text", + "bbox": [ + 0.319, + 0.243, + 0.649, + 0.262 + ], + "angle": 0, + "content": "1University of Oxford 2Adobe Research" + }, + { + "type": "image", + "bbox": [ + 0.083, + 0.304, + 0.473, + 0.63 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.496, + 0.306, + 0.891, + 0.628 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.075, + 0.647, + 0.895, + 0.691 + ], + "angle": 0, + "content": "Figure 1. We introduce Continuous 3D Words - special tokens in text-to-image models that allow users to have fine-grained control over several attributes like illumination [ ] (a and c), non-rigid shape change [ ] (d), orientation [ ] (c and d), and camera parameters [ ] (b). Our approach can be trained using a single 3D mesh and a rendering engine while incurring into negligible runtime and memory costs." + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.702, + 0.314, + 0.719 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.735, + 0.474, + 0.903 + ], + "angle": 0, + "content": "Current controls over diffusion models (e.g., through text or ControlNet) for image generation fall short in recognizing abstract, continuous attributes like illumination direction or non-rigid shape change. In this paper, we present an approach for allowing users of text-to-image models to have fine-grained control of several attributes in an image. We do this by engineering special sets of input tokens that can be transformed in a continuous manner - we call them Continuous 3D Words. These attributes can, for example, be represented as sliders and applied jointly with text prompts for fine-grained control over image" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.704, + 0.897, + 0.84 + ], + "angle": 0, + "content": "generation. Given only a single mesh and a rendering engine, we show that our approach can be adopted to provide continuous user control over several 3D-aware attributes, including time-of-day illumination, bird wing orientation, dollyzoom effect, and object poses. Our method is capable of conditioning image creation with multiple Continuous 3D Words and text descriptions simultaneously while adding no overhead to the generative process. Project Page: https://ttchengab.github.io/continuous_3d_words" + }, + { + "type": "page_footnote", + "bbox": [ + 0.527, + 0.887, + 0.813, + 0.901 + ], + "angle": 0, + "content": "*Work was done during internship at Adobe Research." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "6753" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.081, + 0.091, + 0.208, + 0.106 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.116, + 0.47, + 0.492 + ], + "angle": 0, + "content": "Photography is fascinating because it enables very detailed control over the composition and aesthetics of the final image. On the one hand, this is simply the result of application of physical laws to achieve image acquisition. On the other, the slightest changes in the moment captured, illumination, object orientation, or camera parameters bring a completely different feeling to the viewer. While the giant leap of modern text-to-image diffusion can bring generated 2-D images to close proximity with real photos, text prompts are inherently limited to high-level descriptions, far removed from the detailed controls one has over actual photography. This is mainly due to the scarcity of such descriptions in the training dataset — very few would describe a photo based on exact object movements and camera parameters like the wing pose of a bird or the rotation of a person's head in degrees. On the other hand, 3D rendering engines allow us to mimic many of these 3D controls that photographers enjoy. We can render images of objects with predefined camera, illumination and pose changes at a very fine-grained scale. However, creating detailed 3D worlds is incredibly laborious, which limits the diversity of the scenes that can be generated by non-specialized practitioners. In that regard, using text-to-image diffusion to create images is a much more accessible technology, whereas precise 3D scene control remains firmly in the domain of experts." + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.494, + 0.47, + 0.674 + ], + "angle": 0, + "content": "In this work, we aim to bring together the best of two worlds by expanding the vocabulary of text-to-image diffusion models with very few samples generated from rendering engines. Specifically, we render meshes based on the attribute we aim to control, creating images with color and other useful information to generate a small set of data samples. The goal is to disentangle these abstract attributes from the original object and encode them into the textual space in a controllable manner – we term these attributes Continuous 3D Words. They allow users to create custom sliders that enable fine-grained control during image generation and can be seamlessly used along text prompts." + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.676, + 0.47, + 0.901 + ], + "angle": 0, + "content": "At the heart of our approach is an algorithm to learn a continuous vocabulary. The benefits of continuity are twofold: \\( i) \\) the association between different values of the same attribute makes it much easier to learn, rather than having to learn hundreds of discrete tokens as an approximation and \\( ii) \\) we learn an MLP that would allow interpolation during inference to generate an actual continuous control. On top of this, we also propose two training strategies to prevent degenerate solutions and enable generalization on new objects beyond the training category. First, we apply a two-stage training strategy: we first apply the Dreambooth [25] approach to learn the object identity of the underlying mesh used for rendering, then sequentially learn the various attribute values disentangled from the object identity. This prevents the model from falling into a degenerate solution of encoding" + }, + { + "type": "text", + "bbox": [ + 0.503, + 0.092, + 0.892, + 0.227 + ], + "angle": 0, + "content": "each value of an attribute as a new object, which would prevent us from generalizing the attribute to new objects. Second, we apply ControlNet [30] with various conditioned images to generate a set of additional images with varying backgrounds and object textures. This prevents the model from overfitting to the artificial backgrounds of rendered images. The entire training was done in a light-weight Lower Rank Adaptation (LoRA) [14] manner, making it fast and accessible with single GPUs." + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.228, + 0.892, + 0.348 + ], + "angle": 0, + "content": "We implement our continuous vocabulary and training method, across various sets of single (e.g., dollyzoom extracted from chairs) and multiple (e.g., object pose and illumination extracted from a dog mesh) attributes, and show through quantitative user studies and qualitative comparisons that our method can properly reflect various attributes while maintaining the aesthetics of the image — significantly outperforming competitive baselines." + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.349, + 0.892, + 0.469 + ], + "angle": 0, + "content": "In summary, we present 1) Continuous 3D Words, a new method of gaining 3D-aware, continuous attribute controls over text-to-image generation that can be easily tailored to a plethora of new conditions, 2) a series of training strategies to disentangle the attributes from object identity to enhance the improvements in image generation and 3) extensive qualitative and quantitative studies to showcase our approach in various interesting applications." + }, + { + "type": "title", + "bbox": [ + 0.504, + 0.484, + 0.64, + 0.498 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.508, + 0.892, + 0.794 + ], + "angle": 0, + "content": "Conditional Diffusion Models. Ever since diffusion models [13, 27] pushed the quality and generalizability of image generation beyond GANs [10], the vision community has introduced a diverse range of modalities that can be used as conditions to control the image generation process. The most common condition is currently text. Works such as DALLE [2, 22, 23] and Imagen [26] used large scale text-image datasets and strong language understandings from pretrained LLMs [4, 8, 21] to guide the generation process. Stable Diffusion further popularized this class of methods by employing memory efficient models through latent-space diffusion [24]. Other works built on top of these models by adding other forms of conditioning [19, 30]. Highly relevant to our work is ControlNet [30], which proposes a general pipeline with zero-convolutions for conditioning on text and image data (e.g., depth maps, canny maps, sketches). Despite their impressive image quality, it is not clear how to use these models to control other attributes of images like illumination or object orientation." + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.796, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Other set of works explored how to perform image edits using textual instructions. Given a text-generated image, they demonstrate how the user can edit the image by amending the prompt, yet still preserve some aspects of the original image [3, 12, 20]. While convenient, these approaches do not allow fine-grained control over image elements since they are ultimately restricted by the user's ability to describe" + }, + { + "type": "page_number", + "bbox": [ + 0.485, + 0.947, + 0.514, + 0.957 + ], + "angle": 0, + "content": "6754" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.09, + 0.891, + 0.393 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.406, + 0.896, + 0.477 + ], + "angle": 0, + "content": "Figure 2. Method Overview. Finetuning: Our finetuning is divided into two stages. In the first stage, we render a series of images using different attribute values (e.g., illumination and pose). We feed them into the text-to-image diffusion model to learn token embedding [Obj] representing the single mesh used for training. In the second stage, we add the tokens representing individual attributes into the prompt embedding. The two stage training allows us to better disentangle the individual attributes against [Obj]. Inference: Attributes can be applied to different objects for text-to-image generation." + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.497, + 0.473, + 0.653 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.663, + 0.47, + 0.72 + ], + "angle": 0, + "content": "Figure 3. ControlNet Augmentations. Depth ControlNet is used for attributes creating direct shape changes. Lineart ControlNet is applied for more subtle changes that cannot be reflected by depths (e.g., illumination)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.749, + 0.47, + 0.793 + ], + "angle": 0, + "content": "visual content through text – e.g., it would be very difficult to change the illumination direction by a precise angle such as \\(11^{\\circ}\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Recently, as the amount of 3D data available significantly increased, Liu et al. [16] introduced Zero-1-to-3, a diffusion model trained on various viewpoints of 3D rendering that enables viewpoint editing given an image of a single object. Similarly, works like DreamSparse [29] also employ diffusion models to synthesize novel views on open-set categories. Differently from our approach, these techniques are" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.502, + 0.895, + 0.61 + ], + "angle": 0, + "content": "focused only on object orientation and rely on vast 3D shape datasets. On the other hand, we investigate how to learn several continuous concepts (e.g. illumination [ ] , wing pose [ \\(\\mathcal{V}\\) ], dolly zoom [ \\(\\text{公} _ { \\text{公} } ^ { \\text{公} }\\) ]) that can be directly used in text-to-image scenarios; i.e. we don't generate an image to then change the orientation or illumination later, but instead we use Continuous Words directly on text prompts." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.897, + 0.885 + ], + "angle": 0, + "content": "Learning new concepts on diffusion models. With diffusion models being trained on unforeseen quantities in images and texts, a stream of work focused on adding specific concepts with very few data samples. For example, given a small set of images representing one particular object instance, textual inversion learns a new word embedding to describe the object, such that the word can be applied with new text prompts for image generation [9]. NETI [1] extended the word embedding to a time-space conditioned neural mapper for better generation while preserving quality. Similarly, Dreambooth [25] aims to achieve the same goal, but by using a repurposed token rarely used in text and finetuning the entire diffusion model with an additional constraint to prevent generative loss. There are numerous subsequent works showing improvements on finetuning different layers/weights and by improving the training strategy [11, 15, 17]." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.886, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Despite the advances in adding new personalized entities" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.958 + ], + "angle": 0, + "content": "6755" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.289 + ], + "angle": 0, + "content": "to existing models, few works focus on learning general concepts that can be applied to a variety of scenarios. A concurrent work, ViewNETI [5], is the first to learn viewpoints as a concept, but we hypothesise that the 3D awareness of large text-to-image diffusion models goes far beyond merely viewpoints, allowing us to associate and even create interactions with multiple 3D-aware concepts like illumination, pose and camera parameters at the same time. Our method, despite being trained only using a single mesh, shows superior generalization properties – while trained to learn illumination and orientation from renderings of a single dog, we are capable of employing the learned concepts to generate cars, horses (Figure 4), polar bears (Figure 8), lions (Figure 1) and so on." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.305, + 0.169, + 0.32 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.331, + 0.218, + 0.345 + ], + "angle": 0, + "content": "3.1. Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.355, + 0.473, + 0.581 + ], + "angle": 0, + "content": "We define an image \\(I\\) that captures object \\(O\\) from category \\(C\\) as a function of several attributes \\(I = f(a_{1},a_{2},a_{3},\\dots,a_{n})\\), where \\(a_{i}\\) belongs to a vast set of image attributes \\(\\mathcal{A}\\): shape, material reflectivity, rotation/translation, camera parameters, shape deformations, etc. Some of these components can be translated to other categories while others cannot, so for simplicity we assume they only work for a single category. In the experimental section of this study, we will demonstrate that the definition of category for some attributes is rather loose and the user is capable of generating images with continuous words depicting objects very different from the ones seen during training. Notice that images annotated with the attributes we are interested are very rare, so the models do not have a very precise knowledge of them, except for what is already described in text-image pairs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.582, + 0.472, + 0.643 + ], + "angle": 0, + "content": "Given an image set \\( I^O \\) with images capturing an object \\( O \\), previous methods like Dreambooth [25], Custom Diffusion [15], or Textual-Inversion [9] aim to minimize the following objective:" + }, + { + "type": "equation", + "bbox": [ + 0.128, + 0.656, + 0.473, + 0.69 + ], + "angle": 0, + "content": "\\[\n\\mathbb {E} _ {\\hat {I} _ {\\epsilon , i}, T _ {O}, I _ {i} \\in I ^ {O}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , i}, P (T _ {O})\\right) - I _ {i} \\right\\| _ {2} ^ {2} \\right], \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.704, + 0.473, + 0.901 + ], + "angle": 0, + "content": "where \\( S_{\\theta} \\) is a Text-to-Image diffusion model [24], \\( \\hat{I}_{\\epsilon,i} \\) is a noised image \\( \\alpha_t I_i + \\sigma_t \\epsilon \\) with noise \\( \\epsilon \\) and noise schedulers \\( \\alpha_t, \\sigma_t \\). \\( P(T_O) \\) is the prompt condition which contains a token embedding \\( T_O \\) used as an identifier of object \\( O \\). In practise \\( P(\\cdot) \\) is the text encoder from CLIP. The finetuned network \\( S_{\\theta} \\) can then generate new images containing \\( O \\) when given a new prompt condition \\( P'(T_O) \\) and some Gaussian noise. Unlike previous methods, our goal is not to add concepts representing specific objects, but rather have them describe some attributes \\( a_i \\in \\mathcal{A} \\), by learning to disentangle them using as few objects as possible within \\( C \\) - most of the time just one object suffices. Our model can also be easily extended to controlling multiple attributes at the same time." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.091, + 0.691, + 0.105 + ], + "angle": 0, + "content": "3.2. Continuous Control" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.114, + 0.894, + 0.234 + ], + "angle": 0, + "content": "A naive way to control an attribute \\( a \\) is to use some realistic rendering engine to generate images of the available objects that have the same value \\( a = x \\), and then apply similar approaches to previous works by assigning a token \\( T_{x} \\) to identify images with this particular value. This is not ideal, however, since \\( a \\) is often continuous and have infinitely many values – we would require an unfeasible number of tokens to gain fine-grained control over these attributes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.236, + 0.895, + 0.386 + ], + "angle": 0, + "content": "Therefore, we propose to instead learn a continuous function \\( g_{\\phi}(\\mathbf{a}) : \\mathcal{D} \\to \\mathcal{T} \\) that maps a set of attributes from some continuous domain \\( \\mathcal{D} \\) to the token embedding domain \\( \\mathcal{T} \\). We use positional encoding to first cast each attribute \\( a \\in \\mathbf{a} \\) to a higher frequency space before feeding into the function, which is represented by a very simple 2-layer MLP. The output of this network is named Continuous 3D Word and will allow users to easily control continuous attributes from text prompts augmented by these tokens. Finally, our training objective can then be formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.535, + 0.395, + 0.893, + 0.43 + ], + "angle": 0, + "content": "\\[\n\\arg \\min _ {\\theta , \\phi} \\mathbb {E} _ {\\hat {I} _ {\\epsilon , \\mathbf {a}}, \\mathbf {a}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , \\mathbf {a}}, P \\left(g _ {\\phi} (\\mathbf {a})\\right)\\right) - I _ {\\mathbf {a}} \\right\\| _ {2} ^ {2} \\right]. \\tag {2}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.438, + 0.88, + 0.455 + ], + "angle": 0, + "content": "3.3. Disentangling Object Identity and Attributes" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.461, + 0.894, + 0.582 + ], + "angle": 0, + "content": "In practice, when we only utilize a single object to learn attributes, a degenerate solution occurs when directly optimizing (2), where \\( S_{\\theta} \\) treats the same object with different values for \\( a \\) as different objects. This hinders the generalization capability of changing the attribute when given an image of a new object. To this end, we propose two strategies, one during training and one during inference, to disentangle the object identity and individual attributes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.587, + 0.894, + 0.648 + ], + "angle": 0, + "content": "Training: Learning identity and attributes. We provide a simple regularization by explicitly forcing the model to use the same identifier for images representing the same object. The objective can thus be formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.512, + 0.657, + 0.893, + 0.69 + ], + "angle": 0, + "content": "\\[\n\\arg \\min _ {\\theta , \\phi} \\mathbb {E} _ {\\hat {I} _ {\\epsilon , \\mathbf {a}}, \\mathbf {a}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , \\mathbf {a}}, P \\left(T _ {O}, g _ {\\phi} (\\mathbf {a})\\right)\\right) - I _ {\\mathbf {a}} \\right\\| _ {2} ^ {2} \\right]. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.7, + 0.894, + 0.821 + ], + "angle": 0, + "content": "Optimizing both \\( T_{O} \\) and \\( g_{\\phi}(\\mathbf{a}) \\) concurrently proved to be difficult from our experiments (see Section 5). We propose a two-stage training strategy as depicted in Figure 2. For every available image in \\( I^{O} \\) with varying \\( \\mathbf{a} \\), we first use the same prompt condition \\( P(T_{O}) \\) to associate them to the same object, then learn the diffusion model parameters \\( \\theta \\) and our Continuous 3D Words MLP \\( g_{\\phi} \\) by using the prompt condition \\( P(T_{O},g_{\\phi}(\\mathbf{a})) \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Inference: Negatively prompting object identifier. To further the disentanglement of attributes against object identities. We propose a simple trick during inference by adding the object identity as a negative prompt. Specifically, for each sampling step, we swap the null-text embedding used" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.516, + 0.957 + ], + "angle": 0, + "content": "6756" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.089, + 0.895, + 0.569 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.579, + 0.895, + 0.622 + ], + "angle": 0, + "content": "Figure 4. Qualitative Comparisons. We compare our Continuous 3D Words trained under three settings against ControlNet of various strengths. Note that the dollyzoom setup was trained with trained with multiple chair meshes, so we give additional ControlNet by manually picking the chair rendering that best follows the prompt (i.e., \"comfortable\" and in \"the office\")." + }, + { + "type": "image", + "bbox": [ + 0.095, + 0.644, + 0.459, + 0.786 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.798, + 0.471, + 0.854 + ], + "angle": 0, + "content": "Figure 5. Disentangling Multiple Attributes. We show four examples of controlling multiple Continuous 3D words in addition to text descriptions. Left: trained with a single golden retriever mesh. Right: trained with a single animated dove." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.471, + 0.903 + ], + "angle": 0, + "content": "by classifier-free guidance with \\( T_{O} \\). Intuitively, since our training happened mostly using \\( O \\), we want to disincentivize the model to generate images containing such object." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.647, + 0.738, + 0.664 + ], + "angle": 0, + "content": "3.4. ControlNet Augmentation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.672, + 0.895, + 0.776 + ], + "angle": 0, + "content": "To prevent the fine-tuning process from overfitting to a simple white backgrounds and pre-defined object textures, we augment the backgrounds and textures in the rendering process. However, directly doing this in simulation engines is time consuming specially if one is targeting realistic scenes. Thus, we propose an automated solution by utilizing pretrained ControlNets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Figure 3 shows two types of ControlNet augmentations we used in our framework. For attributes that can be directly reflected on shape changes (e.g., wing pose), we directly render the ground-truth depth maps to use as the condition for ControlNet. On the other hand, for attributes that cannot be reflected directly from depths (e.g., illumination), we first render the images without textures, then use a linear extractor to obtain a \"sketch\" of the image. This captures" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "6757" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.135 + ], + "angle": 0, + "content": "subtle changes such as shades and shadows in the pixel space, which can then be used as the condition for Lineart ControlNet." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.137, + 0.471, + 0.273 + ], + "angle": 0, + "content": "We add additional prompts describing the object appearance and background during the ControlNet generation. It is important to note that prompts deviating away too much from the original mesh category would lead to degenerate images, so our prompts are in general very simple and straightforward (details in supplemental material). We include the ControlNet generated images as a small set of data augmentation, and we use the same prompt which we use to guide ControlNet generation to guide our Stage 2 fine-tuning." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.286, + 0.208, + 0.303 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.311, + 0.471, + 0.476 + ], + "angle": 0, + "content": "We use off-the-shelf Stable Diffusion v2.1 [24] as the backbone of our method. We resort to the recent Low-Rank Adaptation (LoRA) [14] for the fine-tuning of the denoising U-Net and text encoder, allowing us to train on a single A10 GPU occupying roughly 16GB of memory. Thanks to the low-rank optimization, our models have a very small size (approximately 6MB). Training time varies by the complexity of the single/multiple attributes to learn, but falls within 15k to 20k steps, which generally takes around 3-4 hours in a single GPU. For ControlNet augmentation, we use the official implementation of ControlNet v1.1 [30]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.477, + 0.471, + 0.643 + ], + "angle": 0, + "content": "We implement our Continuous 3D words under five different attribute settings. For single attributes we implement 1) illumination [ ] using a single dog mesh, 2) wing pose [ ] using a single animated dove mesh, and 3) Dolly zoom [ ] with five Pix3D chairs [28]. For multi-concepts, we train 4) illumination and object orientation [ ] + [ ] using a single dog mesh and 5) wing pose and orientation [ ] + [ ] using a single animated dove mesh. Settings 1) and 4) use linear images [6] while the others use depth map to compute the ControlNet background augmentation (see Section 3.4)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.651, + 0.322, + 0.667 + ], + "angle": 0, + "content": "4.1. Comparison with Baselines" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.675, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Baseline Design. We design a very competitive baseline that enables fine-grained attribute control in image generation by combining the mesh training data we used in our experiments, a rendering engine and ControlNet [30]. Specifically, we take a novel text prompt for a training object, and grab a corresponding condition map in the training set rendered with the intended attributes. For example, if the prompt is a \\([\\varpi]\\) eagle flying in a forest, we select the frame of the dove mesh that corresponds to the user-prescribed wing pose \\([\\varpi]\\), render its depth map using a rendering engine and pass it through ControlNet with the same prompt but removing the continuous \\(3D\\) word. The strength of the ControlNet guidance is a critical hyperparameter — increase in strength could increase the accuracy of reflecting the attribute but decrease the robustness to general-" + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.09, + 0.891, + 0.236 + ], + "angle": 0, + "content": "
MethodUser Preference (%) ↑
[✓][?][✓] / [?][?] / [?]Avg.
ControlNet (1.0)28.3%16.2%35.0%15.0%23.6%
ControlNet (0.5)10.0%28.8%12.5%32.5%21.0%
Ours61.7%55.0%52.5%52.5%55.4%
Average User Ranking ↑
Method[✓][?][✓] / [?][?] / [?]Avg.
ControlNet (1.0)2.07 ± 0.701.49 ± 0.762.20 ± 0.681.60 ± 0.741.84 ± 0.72
ControlNet (0.5)1.38 ± 0.662.11 ± 0.671.38 ± 0.702.06 ± 0.761.73 ± 0.70
Ours2.55 ± 0.622.40 ± 0.732.43 ± 0.672.33 ± 0.772.43 ± 0.70
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.246, + 0.894, + 0.4 + ], + "angle": 0, + "content": "Table 1. User study results. We asked users to rank three images according to their preference and how well they followed the given conditions – text prompt and one or two continuous controls. The controls were described by representative images (i.e. arrows for orientation, shaded sphere for illumination, etc.). See supplemental material for more details. We evaluate four different control types: wing pose \\([\\sim]\\), illumination \\([\\diamond]\\), wing pose \\([\\sim] + orientation \\([\\triangle]\\), and illumination \\([\\diamond] + orientation \\([\\triangle]\\). Cells colored as red and yellow represent the best and second best method, respectively. Our method was selected as the favorite for the majority of users in all evaluated setups." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.42, + 0.893, + 0.511 + ], + "angle": 0, + "content": "ize to the text-prompt intended object. Therefore, we present the ControlNet baseline with both full and half strength in terms of guidance. We also explored an interpolation of null-text embedding [18] baseline, but the results failed to capture even the simplest attributes, so they were omitted from our analysis." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.52, + 0.894, + 0.7 + ], + "angle": 0, + "content": "Quantitative Results. Due to the complexity and abstract nature of the attributes we are analyzing, automatically measuring whether a generated image reflects a set of values is a considerable challenge. Thus, following previous papers [12, 25, 30], we create a user study to evaluate the quality of the generated images while controlling several attributes. For each setting 1, 2, 4, and 5, we randomly sample a set of 3D conditions and prompts, generating over 60 questions per setting. Similarly to the user studies above, we then invite 20 participants, showing them all the given constraints we want the image to pertain (prompts and attributes), and ask them to rank each image from best to worst." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Table 1 shows the results in both the percentage of user preference (image chose as the best one) and the overall ranking. Best results are highlighted as red. Our Continuous 3D Words won the majority of votes (over \\(50\\%\\)) in all analyzed scenarios. Interestingly, the second best (as highlighted in yellow) alternates between the two guidance strengths of ControlNet. For wing-pose based controls, having a weaker control diminishes the strong prior offered by the depth map, resulting in inaccurate poses. Conversely, strong guidance for illumination forces ControlNet to generate objects around the shadow outline (further shown in Figure 4). Differently from the baselines, our training strategy is one-size-fits-all without any hyperparameter required." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "6758" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.078, + 0.092, + 0.47, + 0.105 + ], + "angle": 0, + "content": "Qualitative Analyses We present a detailed comparison of" + }, + { + "type": "image", + "bbox": [ + 0.078, + 0.106, + 0.493, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.337, + 0.219, + 0.353 + ], + "angle": 0, + "content": "4.2. Multi-Concep" + }, + { + "type": "image", + "bbox": [ + 0.219, + 0.328, + 0.493, + 0.382 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.365, + 0.47, + 0.545 + ], + "angle": 0, + "content": "Just like sentences with but each disentangled from one another when controlling the image generation, our Continuous 3D Words can do the same. We show four examples in Figure 5, two from [ ] and [ ], and two [ ] and [ ], where we can keep one attribute fixed but change the other without sabotaging the quality of image generations. They can be jointly used with complex prompts describing the background and object texture. Moreover, while all these words are learned from a single mesh, we can easily transfer the attribute to objects with fairly close semantics (e.g., a Labrador mesh to a polar bear, or a dove mesh to a parrot)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.564, + 0.315, + 0.58 + ], + "angle": 0, + "content": "4.3. Real World Image Editing" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.591, + 0.47, + 0.727 + ], + "angle": 0, + "content": "Our Continuous 3D Words can be directly applied to real world images to perform editing. To do so, we simply have to encode a real world image to a rare token via Dreambooth [25]. Then, we only have to use that token in conjunction with our Continuous 3D Words to generate the edited image. We show 4 examples in Figure 6, changing \\([\\bullet]\\), \\([\\neg]\\), \\([\\uparrow]\\). As we can see, the Dreambooth token preserves most of the image appearance, while our Continuous Words understand and brings edits to the main subject." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Comparing with Zero-1-to-3 While our approach is focused on enhancing text-to-image, given the capabilities of real-world image editing, we can use the same setup to provide a comparison with only with object orientation changes (Figure 6). Notice that Zero1-to-3 [16] operates in foreground-only images so we also had to segment the object [7], inpaint the background [24], and place the novel orientation back to the image. Each step contains errors that, when compounded, hurt the quality of the final result. More importantly, our method allows controls beyond orientation changes without relying on massive 3D datasets." + }, + { + "type": "image", + "bbox": [ + 0.515, + 0.092, + 0.878, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.4, + 0.895, + 0.497 + ], + "angle": 0, + "content": "Figure 6. Real World results & Comparison w/ Zero1-to-3. We learn tokens representing single images and use along with Continuous 3D Words for image editing. The learned image token encodes most of the image appearance, while the Continuous 3D Word modifies its relevant aspects. Zero123, on the other hand, tends to yield images where the modified object is deformed or not properly harmonized." + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.519, + 0.892, + 0.643 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.654, + 0.892, + 0.709 + ], + "angle": 0, + "content": "Figure 7. Interpolating continuous 3D words. We present two results of interpolation, one with discrete tokens and one with our Continuous 3D Words. Our method preserves the attributes better and enables interpolation between two values." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.738, + 0.75, + 0.754 + ], + "angle": 0, + "content": "5. Discussion and Limitations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Why Not Discrete Tokens? The benefits of fitting a single MLP instead of multiple tokens on an attribute with different values are twofold. First, the MLP learns a continuous function, allowing us to interpolate between two training data samples whereas fitting multiple tokens leads to two datapoints as two discrete mappings. Second, finetuning a model to learn multiple custom tokens simultaneously is very hard. These benefits are illustrated in Figure 7. We show a comparison of learning a single Continuous 3D Word \\([\\nu^{\\prime}]\\)" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.516, + 0.957 + ], + "angle": 0, + "content": "6759" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.089, + 0.473, + 0.249 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.26, + 0.473, + 0.359 + ], + "angle": 0, + "content": "Figure 8. Ablation Study. We present our ablations for: w/o two-stage training, w/o ControlNet augmentation, w/o [obj] as negative prompt, and our full pipeline. Notice that, when the prompt deviates a lot from the training data (truck in prompt, mesh of a dog for training), the ablated version fails to follow the prompt. Without two-stage training, it ignores the prompt and creates a dog; without the other parts it yields deformed shadows and dog-shaped trucks." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.372, + 0.473, + 0.629 + ], + "angle": 0, + "content": "and 18 discrete tokens for different values of a wing pose. Both were learned with the same training method (2-stage with ControlNet augmentation). We present the generated results of three attribute values that are present in the training set, as well as the results when you interpolate the value in between. Interpolation is straightforward for our case where we just input the intermediate value into our Continuous 3D Words MLP. For discrete tokens, we interpolate between two nearest discrete bins. Notice that the discrete tokens have difficulty not only in interpolating results but also in learning the concept simultaneously. The eagle wings in the second row of Figure 7 do not follow the training data and sometimes generate a completely different pose (third column, second row). On the other hand, our images closely follow the pose prescribed by the user (top row) while yielding appealing images even when the values were not seen during training (columns 2, 4 and 6; second row)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.63, + 0.474, + 0.902 + ], + "angle": 0, + "content": "Ablation study. Figure 8 shows an ablation of our training strategy. We remove each component of our training strategy (w/o two-stage training, w/o ControlNet augmentation, w/o [obj] as negative prompt) and compare it with our full pipeline. Two examples are presented: one where the prompt is similar to the training and another one where it is significantly different. Without the two-stage training, the model fails to disentangle object identity with our attributes, hindering the generalization capability to new objects. This is particularly noticeable for the bottom row when the text prompt is a truck but a dog similar to the training mesh is generated when the two-stage training is removed. Without ControlNet, the finetuning process often overfits to the background training renderings, resulting in an inability to generate realistic backgrounds. Finally, adding [obj] as the negative prompt serves as a minor improvement in further disentangling both the backgrounds and object shape seen during training, resulting in a more aesthetic image." + }, + { + "type": "image_caption", + "bbox": [ + 0.503, + 0.08, + 0.519, + 0.09 + ], + "angle": 0, + "content": "a)" + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.091, + 0.695, + 0.192 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.699, + 0.08, + 0.715, + 0.09 + ], + "angle": 0, + "content": "b)" + }, + { + "type": "image", + "bbox": [ + 0.698, + 0.091, + 0.892, + 0.191 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.204, + 0.895, + 0.274 + ], + "angle": 0, + "content": "Figure 9. Condition v.s. Accuracy in User Study. a) shows two images generated by the prompt “a \\([v^{-}]\\) photo of a white bird on sand”. b) shows two images generated by the prompt “a \\([v^{-}]\\) photo of a colorful bird”. Left is ours, right is ControlNet (1.0). Users preferred right over left for both." + }, + { + "type": "image_caption", + "bbox": [ + 0.504, + 0.283, + 0.518, + 0.293 + ], + "angle": 0, + "content": "a)" + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.293, + 0.695, + 0.393 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.699, + 0.282, + 0.716, + 0.293 + ], + "angle": 0, + "content": "b)" + }, + { + "type": "image", + "bbox": [ + 0.698, + 0.293, + 0.892, + 0.392 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.4, + 0.894, + 0.442 + ], + "angle": 0, + "content": "Figure 10. Failure cases. a) shows images generated with prompt \"a [ ] [ Monet Painting of ....\". b) shows images generated with \"a [ ] [ photo of a T-Rex\"." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.454, + 0.892, + 0.544 + ], + "angle": 0, + "content": "Condition v.s. Generated Accuracy in User Study. During our user study, we realize that occasionally users select the image which more strictly follows the exact conditions over the more physically probable image. For example, in Figure 9 a) and b), the head of the bird is generated poorly, but users preferred them as they are \"whiter\" and \"more colorful\"." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.545, + 0.894, + 0.68 + ], + "angle": 0, + "content": "Failure Cases. We present in Figure 10 two examples of typical failure cases in our results. First, our model currently fails on more difficult scenarios where the style is given by the text prompt. In a), the image cannot fully reflect the \"Monet painting\" style imposed by our prompt. Second, the generated object may sometimes still overfit to the training set. In b), the T-Rex had four feet on the ground instead of standing with two claws in air – an attribute that is similar to the training dog mesh used to learn illumination." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.695, + 0.619, + 0.71 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.87 + ], + "angle": 0, + "content": "We presented Continuous 3D Words, a framework that allows us to learn 3D-aware attributes reflected in renderings of meshes as special words, which can then be injected into the text prompts for fine-grained text-to-image generation. Extensive study on learning both single and multiple continuous words shows that we can control challenging attributes. With the lightweight design and promising results, we hope that this work opens up interesting applications in the vision community to create their own 3D words with a single mesh and an accessible rendering engine." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Acknowledgements. This work is supported in part by the EPSRC ACE-OPS grant EP/S030832/1." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "6760" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.472, + 0.169 + ], + "angle": 0, + "content": "[1] Yuval Alaluf, Elad Richardson, Gal Metzer, and Daniel Cohen-Or. 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In IEEE International Conference on Computer Vision (ICCV), 2023. 2, 6" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.47, + 0.247 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.517, + 0.956 + ], + "angle": 0, + "content": "6762" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_origin.pdf b/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..322cfdb75a7ae69d0f7cd3404e5c811206f0f106 --- /dev/null +++ b/2024/Learning Continuous 3D Words for Text-to-Image Generation/276644cc-5935-4e67-b150-37736c673436_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:108095087f745f63c2d4a389d3a124fd8f94ee445c7e8a598d4b9099d44d28b9 +size 5108282 diff --git a/2024/Learning Continuous 3D Words for Text-to-Image Generation/full.md b/2024/Learning Continuous 3D Words for Text-to-Image Generation/full.md new file mode 100644 index 0000000000000000000000000000000000000000..9a77dd3350f12b1823bddbb756f5e25b333d7a16 --- /dev/null +++ b/2024/Learning Continuous 3D Words for Text-to-Image Generation/full.md @@ -0,0 +1,224 @@ +# Learning Continuous 3D Words for Text-to-Image Generation + +Ta-Ying Cheng $^{1*}$ Matheus Gadelha $^{2}$ Thibault Groueix $^{2}$ Matthew Fisher $^{2}$ Radomír Měch $^{2}$ Andrew Markham $^{1}$ Niki Trigoni $^{1}$ + +1University of Oxford 2Adobe Research + +![](images/4ea8e0c5b72d074ace34a7cde2aed386fa93c1dfe3ae78fb94bba68e9518eb17.jpg) +Figure 1. We introduce Continuous 3D Words - special tokens in text-to-image models that allow users to have fine-grained control over several attributes like illumination [ ] (a and c), non-rigid shape change [ ] (d), orientation [ ] (c and d), and camera parameters [ ] (b). Our approach can be trained using a single 3D mesh and a rendering engine while incurring into negligible runtime and memory costs. + +![](images/a8a555aa2a5bbb803f2ec86f602ed437ac16d562037bacd0d0db205b22e91737.jpg) + +# Abstract + +Current controls over diffusion models (e.g., through text or ControlNet) for image generation fall short in recognizing abstract, continuous attributes like illumination direction or non-rigid shape change. In this paper, we present an approach for allowing users of text-to-image models to have fine-grained control of several attributes in an image. We do this by engineering special sets of input tokens that can be transformed in a continuous manner - we call them Continuous 3D Words. These attributes can, for example, be represented as sliders and applied jointly with text prompts for fine-grained control over image + +generation. Given only a single mesh and a rendering engine, we show that our approach can be adopted to provide continuous user control over several 3D-aware attributes, including time-of-day illumination, bird wing orientation, dollyzoom effect, and object poses. Our method is capable of conditioning image creation with multiple Continuous 3D Words and text descriptions simultaneously while adding no overhead to the generative process. Project Page: https://ttchengab.github.io/continuous_3d_words + +# 1. Introduction + +Photography is fascinating because it enables very detailed control over the composition and aesthetics of the final image. On the one hand, this is simply the result of application of physical laws to achieve image acquisition. On the other, the slightest changes in the moment captured, illumination, object orientation, or camera parameters bring a completely different feeling to the viewer. While the giant leap of modern text-to-image diffusion can bring generated 2-D images to close proximity with real photos, text prompts are inherently limited to high-level descriptions, far removed from the detailed controls one has over actual photography. This is mainly due to the scarcity of such descriptions in the training dataset — very few would describe a photo based on exact object movements and camera parameters like the wing pose of a bird or the rotation of a person's head in degrees. On the other hand, 3D rendering engines allow us to mimic many of these 3D controls that photographers enjoy. We can render images of objects with predefined camera, illumination and pose changes at a very fine-grained scale. However, creating detailed 3D worlds is incredibly laborious, which limits the diversity of the scenes that can be generated by non-specialized practitioners. In that regard, using text-to-image diffusion to create images is a much more accessible technology, whereas precise 3D scene control remains firmly in the domain of experts. + +In this work, we aim to bring together the best of two worlds by expanding the vocabulary of text-to-image diffusion models with very few samples generated from rendering engines. Specifically, we render meshes based on the attribute we aim to control, creating images with color and other useful information to generate a small set of data samples. The goal is to disentangle these abstract attributes from the original object and encode them into the textual space in a controllable manner – we term these attributes Continuous 3D Words. They allow users to create custom sliders that enable fine-grained control during image generation and can be seamlessly used along text prompts. + +At the heart of our approach is an algorithm to learn a continuous vocabulary. The benefits of continuity are twofold: $i)$ the association between different values of the same attribute makes it much easier to learn, rather than having to learn hundreds of discrete tokens as an approximation and $ii)$ we learn an MLP that would allow interpolation during inference to generate an actual continuous control. On top of this, we also propose two training strategies to prevent degenerate solutions and enable generalization on new objects beyond the training category. First, we apply a two-stage training strategy: we first apply the Dreambooth [25] approach to learn the object identity of the underlying mesh used for rendering, then sequentially learn the various attribute values disentangled from the object identity. This prevents the model from falling into a degenerate solution of encoding + +each value of an attribute as a new object, which would prevent us from generalizing the attribute to new objects. Second, we apply ControlNet [30] with various conditioned images to generate a set of additional images with varying backgrounds and object textures. This prevents the model from overfitting to the artificial backgrounds of rendered images. The entire training was done in a light-weight Lower Rank Adaptation (LoRA) [14] manner, making it fast and accessible with single GPUs. + +We implement our continuous vocabulary and training method, across various sets of single (e.g., dollyzoom extracted from chairs) and multiple (e.g., object pose and illumination extracted from a dog mesh) attributes, and show through quantitative user studies and qualitative comparisons that our method can properly reflect various attributes while maintaining the aesthetics of the image — significantly outperforming competitive baselines. + +In summary, we present 1) Continuous 3D Words, a new method of gaining 3D-aware, continuous attribute controls over text-to-image generation that can be easily tailored to a plethora of new conditions, 2) a series of training strategies to disentangle the attributes from object identity to enhance the improvements in image generation and 3) extensive qualitative and quantitative studies to showcase our approach in various interesting applications. + +# 2. Related Work + +Conditional Diffusion Models. Ever since diffusion models [13, 27] pushed the quality and generalizability of image generation beyond GANs [10], the vision community has introduced a diverse range of modalities that can be used as conditions to control the image generation process. The most common condition is currently text. Works such as DALLE [2, 22, 23] and Imagen [26] used large scale text-image datasets and strong language understandings from pretrained LLMs [4, 8, 21] to guide the generation process. Stable Diffusion further popularized this class of methods by employing memory efficient models through latent-space diffusion [24]. Other works built on top of these models by adding other forms of conditioning [19, 30]. Highly relevant to our work is ControlNet [30], which proposes a general pipeline with zero-convolutions for conditioning on text and image data (e.g., depth maps, canny maps, sketches). Despite their impressive image quality, it is not clear how to use these models to control other attributes of images like illumination or object orientation. + +Other set of works explored how to perform image edits using textual instructions. Given a text-generated image, they demonstrate how the user can edit the image by amending the prompt, yet still preserve some aspects of the original image [3, 12, 20]. While convenient, these approaches do not allow fine-grained control over image elements since they are ultimately restricted by the user's ability to describe + +![](images/87676faa54a52997856d3f4221b7e6a469938b12c460eb3bc2281579c44fcddc.jpg) +Figure 2. Method Overview. Finetuning: Our finetuning is divided into two stages. In the first stage, we render a series of images using different attribute values (e.g., illumination and pose). We feed them into the text-to-image diffusion model to learn token embedding [Obj] representing the single mesh used for training. In the second stage, we add the tokens representing individual attributes into the prompt embedding. The two stage training allows us to better disentangle the individual attributes against [Obj]. Inference: Attributes can be applied to different objects for text-to-image generation. + +![](images/ed1d9efbc15f1d2d99234496c9ec0e49c6c66cc0c726f4a6f0cc0dad38791bd8.jpg) +Figure 3. ControlNet Augmentations. Depth ControlNet is used for attributes creating direct shape changes. Lineart ControlNet is applied for more subtle changes that cannot be reflected by depths (e.g., illumination). + +visual content through text – e.g., it would be very difficult to change the illumination direction by a precise angle such as $11^{\circ}$ . + +Recently, as the amount of 3D data available significantly increased, Liu et al. [16] introduced Zero-1-to-3, a diffusion model trained on various viewpoints of 3D rendering that enables viewpoint editing given an image of a single object. Similarly, works like DreamSparse [29] also employ diffusion models to synthesize novel views on open-set categories. Differently from our approach, these techniques are + +focused only on object orientation and rely on vast 3D shape datasets. On the other hand, we investigate how to learn several continuous concepts (e.g. illumination [ ] , wing pose [ $\mathcal{V}$ ], dolly zoom [ $\text{公} _ { \text{公} } ^ { \text{公} }$ ]) that can be directly used in text-to-image scenarios; i.e. we don't generate an image to then change the orientation or illumination later, but instead we use Continuous Words directly on text prompts. + +Learning new concepts on diffusion models. With diffusion models being trained on unforeseen quantities in images and texts, a stream of work focused on adding specific concepts with very few data samples. For example, given a small set of images representing one particular object instance, textual inversion learns a new word embedding to describe the object, such that the word can be applied with new text prompts for image generation [9]. NETI [1] extended the word embedding to a time-space conditioned neural mapper for better generation while preserving quality. Similarly, Dreambooth [25] aims to achieve the same goal, but by using a repurposed token rarely used in text and finetuning the entire diffusion model with an additional constraint to prevent generative loss. There are numerous subsequent works showing improvements on finetuning different layers/weights and by improving the training strategy [11, 15, 17]. + +Despite the advances in adding new personalized entities + +to existing models, few works focus on learning general concepts that can be applied to a variety of scenarios. A concurrent work, ViewNETI [5], is the first to learn viewpoints as a concept, but we hypothesise that the 3D awareness of large text-to-image diffusion models goes far beyond merely viewpoints, allowing us to associate and even create interactions with multiple 3D-aware concepts like illumination, pose and camera parameters at the same time. Our method, despite being trained only using a single mesh, shows superior generalization properties – while trained to learn illumination and orientation from renderings of a single dog, we are capable of employing the learned concepts to generate cars, horses (Figure 4), polar bears (Figure 8), lions (Figure 1) and so on. + +# 3. Method + +# 3.1. Preliminaries + +We define an image $I$ that captures object $O$ from category $C$ as a function of several attributes $I = f(a_{1},a_{2},a_{3},\dots,a_{n})$ , where $a_{i}$ belongs to a vast set of image attributes $\mathcal{A}$ : shape, material reflectivity, rotation/translation, camera parameters, shape deformations, etc. Some of these components can be translated to other categories while others cannot, so for simplicity we assume they only work for a single category. In the experimental section of this study, we will demonstrate that the definition of category for some attributes is rather loose and the user is capable of generating images with continuous words depicting objects very different from the ones seen during training. Notice that images annotated with the attributes we are interested are very rare, so the models do not have a very precise knowledge of them, except for what is already described in text-image pairs. + +Given an image set $I^O$ with images capturing an object $O$ , previous methods like Dreambooth [25], Custom Diffusion [15], or Textual-Inversion [9] aim to minimize the following objective: + +$$ +\mathbb {E} _ {\hat {I} _ {\epsilon , i}, T _ {O}, I _ {i} \in I ^ {O}} \left[ \left\| S _ {\theta} \left(\hat {I} _ {\epsilon , i}, P (T _ {O})\right) - I _ {i} \right\| _ {2} ^ {2} \right], \tag {1} +$$ + +where $S_{\theta}$ is a Text-to-Image diffusion model [24], $\hat{I}_{\epsilon,i}$ is a noised image $\alpha_t I_i + \sigma_t \epsilon$ with noise $\epsilon$ and noise schedulers $\alpha_t, \sigma_t$ . $P(T_O)$ is the prompt condition which contains a token embedding $T_O$ used as an identifier of object $O$ . In practise $P(\cdot)$ is the text encoder from CLIP. The finetuned network $S_{\theta}$ can then generate new images containing $O$ when given a new prompt condition $P'(T_O)$ and some Gaussian noise. Unlike previous methods, our goal is not to add concepts representing specific objects, but rather have them describe some attributes $a_i \in \mathcal{A}$ , by learning to disentangle them using as few objects as possible within $C$ - most of the time just one object suffices. Our model can also be easily extended to controlling multiple attributes at the same time. + +# 3.2. Continuous Control + +A naive way to control an attribute $a$ is to use some realistic rendering engine to generate images of the available objects that have the same value $a = x$ , and then apply similar approaches to previous works by assigning a token $T_{x}$ to identify images with this particular value. This is not ideal, however, since $a$ is often continuous and have infinitely many values – we would require an unfeasible number of tokens to gain fine-grained control over these attributes. + +Therefore, we propose to instead learn a continuous function $g_{\phi}(\mathbf{a}) : \mathcal{D} \to \mathcal{T}$ that maps a set of attributes from some continuous domain $\mathcal{D}$ to the token embedding domain $\mathcal{T}$ . We use positional encoding to first cast each attribute $a \in \mathbf{a}$ to a higher frequency space before feeding into the function, which is represented by a very simple 2-layer MLP. The output of this network is named Continuous 3D Word and will allow users to easily control continuous attributes from text prompts augmented by these tokens. Finally, our training objective can then be formulated as: + +$$ +\arg \min _ {\theta , \phi} \mathbb {E} _ {\hat {I} _ {\epsilon , \mathbf {a}}, \mathbf {a}} \left[ \left\| S _ {\theta} \left(\hat {I} _ {\epsilon , \mathbf {a}}, P \left(g _ {\phi} (\mathbf {a})\right)\right) - I _ {\mathbf {a}} \right\| _ {2} ^ {2} \right]. \tag {2} +$$ + +# 3.3. Disentangling Object Identity and Attributes + +In practice, when we only utilize a single object to learn attributes, a degenerate solution occurs when directly optimizing (2), where $S_{\theta}$ treats the same object with different values for $a$ as different objects. This hinders the generalization capability of changing the attribute when given an image of a new object. To this end, we propose two strategies, one during training and one during inference, to disentangle the object identity and individual attributes. + +Training: Learning identity and attributes. We provide a simple regularization by explicitly forcing the model to use the same identifier for images representing the same object. The objective can thus be formulated as: + +$$ +\arg \min _ {\theta , \phi} \mathbb {E} _ {\hat {I} _ {\epsilon , \mathbf {a}}, \mathbf {a}} \left[ \left\| S _ {\theta} \left(\hat {I} _ {\epsilon , \mathbf {a}}, P \left(T _ {O}, g _ {\phi} (\mathbf {a})\right)\right) - I _ {\mathbf {a}} \right\| _ {2} ^ {2} \right]. \tag {3} +$$ + +Optimizing both $T_{O}$ and $g_{\phi}(\mathbf{a})$ concurrently proved to be difficult from our experiments (see Section 5). We propose a two-stage training strategy as depicted in Figure 2. For every available image in $I^{O}$ with varying $\mathbf{a}$ , we first use the same prompt condition $P(T_{O})$ to associate them to the same object, then learn the diffusion model parameters $\theta$ and our Continuous 3D Words MLP $g_{\phi}$ by using the prompt condition $P(T_{O},g_{\phi}(\mathbf{a}))$ . + +Inference: Negatively prompting object identifier. To further the disentanglement of attributes against object identities. We propose a simple trick during inference by adding the object identity as a negative prompt. Specifically, for each sampling step, we swap the null-text embedding used + +![](images/ad36a39bc9a31be19c09bfa53cf400a69381bff6a67724871cb774165296d29c.jpg) +Figure 4. Qualitative Comparisons. We compare our Continuous 3D Words trained under three settings against ControlNet of various strengths. Note that the dollyzoom setup was trained with trained with multiple chair meshes, so we give additional ControlNet by manually picking the chair rendering that best follows the prompt (i.e., "comfortable" and in "the office"). + +![](images/eaa5b8038232620981dbb92faaf41d23f3d168bbe4a9c2b5a0bacd8809fb2811.jpg) +Figure 5. Disentangling Multiple Attributes. We show four examples of controlling multiple Continuous 3D words in addition to text descriptions. Left: trained with a single golden retriever mesh. Right: trained with a single animated dove. + +by classifier-free guidance with $T_{O}$ . Intuitively, since our training happened mostly using $O$ , we want to disincentivize the model to generate images containing such object. + +# 3.4. ControlNet Augmentation + +To prevent the fine-tuning process from overfitting to a simple white backgrounds and pre-defined object textures, we augment the backgrounds and textures in the rendering process. However, directly doing this in simulation engines is time consuming specially if one is targeting realistic scenes. Thus, we propose an automated solution by utilizing pretrained ControlNets. + +Figure 3 shows two types of ControlNet augmentations we used in our framework. For attributes that can be directly reflected on shape changes (e.g., wing pose), we directly render the ground-truth depth maps to use as the condition for ControlNet. On the other hand, for attributes that cannot be reflected directly from depths (e.g., illumination), we first render the images without textures, then use a linear extractor to obtain a "sketch" of the image. This captures + +subtle changes such as shades and shadows in the pixel space, which can then be used as the condition for Lineart ControlNet. + +We add additional prompts describing the object appearance and background during the ControlNet generation. It is important to note that prompts deviating away too much from the original mesh category would lead to degenerate images, so our prompts are in general very simple and straightforward (details in supplemental material). We include the ControlNet generated images as a small set of data augmentation, and we use the same prompt which we use to guide ControlNet generation to guide our Stage 2 fine-tuning. + +# 4. Experiments + +We use off-the-shelf Stable Diffusion v2.1 [24] as the backbone of our method. We resort to the recent Low-Rank Adaptation (LoRA) [14] for the fine-tuning of the denoising U-Net and text encoder, allowing us to train on a single A10 GPU occupying roughly 16GB of memory. Thanks to the low-rank optimization, our models have a very small size (approximately 6MB). Training time varies by the complexity of the single/multiple attributes to learn, but falls within 15k to 20k steps, which generally takes around 3-4 hours in a single GPU. For ControlNet augmentation, we use the official implementation of ControlNet v1.1 [30]. + +We implement our Continuous 3D words under five different attribute settings. For single attributes we implement 1) illumination [ ] using a single dog mesh, 2) wing pose [ ] using a single animated dove mesh, and 3) Dolly zoom [ ] with five Pix3D chairs [28]. For multi-concepts, we train 4) illumination and object orientation [ ] + [ ] using a single dog mesh and 5) wing pose and orientation [ ] + [ ] using a single animated dove mesh. Settings 1) and 4) use linear images [6] while the others use depth map to compute the ControlNet background augmentation (see Section 3.4). + +# 4.1. Comparison with Baselines + +Baseline Design. We design a very competitive baseline that enables fine-grained attribute control in image generation by combining the mesh training data we used in our experiments, a rendering engine and ControlNet [30]. Specifically, we take a novel text prompt for a training object, and grab a corresponding condition map in the training set rendered with the intended attributes. For example, if the prompt is a $[\varpi]$ eagle flying in a forest, we select the frame of the dove mesh that corresponds to the user-prescribed wing pose $[\varpi]$ , render its depth map using a rendering engine and pass it through ControlNet with the same prompt but removing the continuous $3D$ word. The strength of the ControlNet guidance is a critical hyperparameter — increase in strength could increase the accuracy of reflecting the attribute but decrease the robustness to general- + +
MethodUser Preference (%) ↑
[✓][?][✓] / [?][?] / [?]Avg.
ControlNet (1.0)28.3%16.2%35.0%15.0%23.6%
ControlNet (0.5)10.0%28.8%12.5%32.5%21.0%
Ours61.7%55.0%52.5%52.5%55.4%
Average User Ranking ↑
Method[✓][?][✓] / [?][?] / [?]Avg.
ControlNet (1.0)2.07 ± 0.701.49 ± 0.762.20 ± 0.681.60 ± 0.741.84 ± 0.72
ControlNet (0.5)1.38 ± 0.662.11 ± 0.671.38 ± 0.702.06 ± 0.761.73 ± 0.70
Ours2.55 ± 0.622.40 ± 0.732.43 ± 0.672.33 ± 0.772.43 ± 0.70
+ +Table 1. User study results. We asked users to rank three images according to their preference and how well they followed the given conditions – text prompt and one or two continuous controls. The controls were described by representative images (i.e. arrows for orientation, shaded sphere for illumination, etc.). See supplemental material for more details. We evaluate four different control types: wing pose \([\sim]\), illumination \([\diamond]\), wing pose \([\sim] + orientation \([\triangle]\), and illumination \([\diamond] + orientation \([\triangle]\). Cells colored as red and yellow represent the best and second best method, respectively. Our method was selected as the favorite for the majority of users in all evaluated setups. + +ize to the text-prompt intended object. Therefore, we present the ControlNet baseline with both full and half strength in terms of guidance. We also explored an interpolation of null-text embedding [18] baseline, but the results failed to capture even the simplest attributes, so they were omitted from our analysis. + +Quantitative Results. Due to the complexity and abstract nature of the attributes we are analyzing, automatically measuring whether a generated image reflects a set of values is a considerable challenge. Thus, following previous papers [12, 25, 30], we create a user study to evaluate the quality of the generated images while controlling several attributes. For each setting 1, 2, 4, and 5, we randomly sample a set of 3D conditions and prompts, generating over 60 questions per setting. Similarly to the user studies above, we then invite 20 participants, showing them all the given constraints we want the image to pertain (prompts and attributes), and ask them to rank each image from best to worst. + +Table 1 shows the results in both the percentage of user preference (image chose as the best one) and the overall ranking. Best results are highlighted as red. Our Continuous 3D Words won the majority of votes (over $50\%$ ) in all analyzed scenarios. Interestingly, the second best (as highlighted in yellow) alternates between the two guidance strengths of ControlNet. For wing-pose based controls, having a weaker control diminishes the strong prior offered by the depth map, resulting in inaccurate poses. Conversely, strong guidance for illumination forces ControlNet to generate objects around the shadow outline (further shown in Figure 4). Differently from the baselines, our training strategy is one-size-fits-all without any hyperparameter required. + +# Qualitative Analyses We present a detailed comparison of + +![](images/beda9bee85ed0815ec80ab61ff9ce6ef8e8ff08ff30f522c083d6c16de3b184e.jpg) + +# 4.2. Multi-Concep + +![](images/1e26b9cdc3995b87b251225d79cf98976e933019a944240cec42a3a6b34a6955.jpg) + +Just like sentences with but each disentangled from one another when controlling the image generation, our Continuous 3D Words can do the same. We show four examples in Figure 5, two from [ ] and [ ], and two [ ] and [ ], where we can keep one attribute fixed but change the other without sabotaging the quality of image generations. They can be jointly used with complex prompts describing the background and object texture. Moreover, while all these words are learned from a single mesh, we can easily transfer the attribute to objects with fairly close semantics (e.g., a Labrador mesh to a polar bear, or a dove mesh to a parrot). + +# 4.3. Real World Image Editing + +Our Continuous 3D Words can be directly applied to real world images to perform editing. To do so, we simply have to encode a real world image to a rare token via Dreambooth [25]. Then, we only have to use that token in conjunction with our Continuous 3D Words to generate the edited image. We show 4 examples in Figure 6, changing $[\bullet]$ , $[\neg]$ , $[\uparrow]$ . As we can see, the Dreambooth token preserves most of the image appearance, while our Continuous Words understand and brings edits to the main subject. + +Comparing with Zero-1-to-3 While our approach is focused on enhancing text-to-image, given the capabilities of real-world image editing, we can use the same setup to provide a comparison with only with object orientation changes (Figure 6). Notice that Zero1-to-3 [16] operates in foreground-only images so we also had to segment the object [7], inpaint the background [24], and place the novel orientation back to the image. Each step contains errors that, when compounded, hurt the quality of the final result. More importantly, our method allows controls beyond orientation changes without relying on massive 3D datasets. + +![](images/a836c4c49ec1b7690c17b91762088001ac43687519f2737d862913d9e57500e8.jpg) +Figure 6. Real World results & Comparison w/ Zero1-to-3. We learn tokens representing single images and use along with Continuous 3D Words for image editing. The learned image token encodes most of the image appearance, while the Continuous 3D Word modifies its relevant aspects. Zero123, on the other hand, tends to yield images where the modified object is deformed or not properly harmonized. + +![](images/b0ceddadd32708a752082b8c1a60ffbf24d49e39a75c999ec04ec75ead275a63.jpg) +Figure 7. Interpolating continuous 3D words. We present two results of interpolation, one with discrete tokens and one with our Continuous 3D Words. Our method preserves the attributes better and enables interpolation between two values. + +# 5. Discussion and Limitations + +Why Not Discrete Tokens? The benefits of fitting a single MLP instead of multiple tokens on an attribute with different values are twofold. First, the MLP learns a continuous function, allowing us to interpolate between two training data samples whereas fitting multiple tokens leads to two datapoints as two discrete mappings. Second, finetuning a model to learn multiple custom tokens simultaneously is very hard. These benefits are illustrated in Figure 7. We show a comparison of learning a single Continuous 3D Word $[\nu^{\prime}]$ + +![](images/313b5b9bafcb9996731113ce513b628a30c5ea1f4594825d980f426938cdb2ef.jpg) +Figure 8. Ablation Study. We present our ablations for: w/o two-stage training, w/o ControlNet augmentation, w/o [obj] as negative prompt, and our full pipeline. Notice that, when the prompt deviates a lot from the training data (truck in prompt, mesh of a dog for training), the ablated version fails to follow the prompt. Without two-stage training, it ignores the prompt and creates a dog; without the other parts it yields deformed shadows and dog-shaped trucks. + +and 18 discrete tokens for different values of a wing pose. Both were learned with the same training method (2-stage with ControlNet augmentation). We present the generated results of three attribute values that are present in the training set, as well as the results when you interpolate the value in between. Interpolation is straightforward for our case where we just input the intermediate value into our Continuous 3D Words MLP. For discrete tokens, we interpolate between two nearest discrete bins. Notice that the discrete tokens have difficulty not only in interpolating results but also in learning the concept simultaneously. The eagle wings in the second row of Figure 7 do not follow the training data and sometimes generate a completely different pose (third column, second row). On the other hand, our images closely follow the pose prescribed by the user (top row) while yielding appealing images even when the values were not seen during training (columns 2, 4 and 6; second row). + +Ablation study. Figure 8 shows an ablation of our training strategy. We remove each component of our training strategy (w/o two-stage training, w/o ControlNet augmentation, w/o [obj] as negative prompt) and compare it with our full pipeline. Two examples are presented: one where the prompt is similar to the training and another one where it is significantly different. Without the two-stage training, the model fails to disentangle object identity with our attributes, hindering the generalization capability to new objects. This is particularly noticeable for the bottom row when the text prompt is a truck but a dog similar to the training mesh is generated when the two-stage training is removed. Without ControlNet, the finetuning process often overfits to the background training renderings, resulting in an inability to generate realistic backgrounds. Finally, adding [obj] as the negative prompt serves as a minor improvement in further disentangling both the backgrounds and object shape seen during training, resulting in a more aesthetic image. + +![](images/9fef82724241552dea150b7e7b53b0aa3774ebc2cca2349ebace37664efdd43e.jpg) +a) + +![](images/cb70a70993e0c41c5ce8c9180fde570b75dfd68f8af9a5aa5632bbdbb4d19180.jpg) +b) +Figure 9. Condition v.s. Accuracy in User Study. a) shows two images generated by the prompt “a $[v^{-}]$ photo of a white bird on sand”. b) shows two images generated by the prompt “a $[v^{-}]$ photo of a colorful bird”. Left is ours, right is ControlNet (1.0). Users preferred right over left for both. + +![](images/ff2677fc474c4dadcb5c1dd3d90511afbef3c3129ce94b2f96d2323fc7e91f97.jpg) +a) +Figure 10. Failure cases. a) shows images generated with prompt "a [ ] [ Monet Painting of ....". b) shows images generated with "a [ ] [ photo of a T-Rex". + +![](images/d875225246450d141f0a913c9c072888216f2a9cc19fc59350f4dcaf7007d2ac.jpg) +b) + +Condition v.s. Generated Accuracy in User Study. During our user study, we realize that occasionally users select the image which more strictly follows the exact conditions over the more physically probable image. For example, in Figure 9 a) and b), the head of the bird is generated poorly, but users preferred them as they are "whiter" and "more colorful". + +Failure Cases. We present in Figure 10 two examples of typical failure cases in our results. First, our model currently fails on more difficult scenarios where the style is given by the text prompt. In a), the image cannot fully reflect the "Monet painting" style imposed by our prompt. Second, the generated object may sometimes still overfit to the training set. In b), the T-Rex had four feet on the ground instead of standing with two claws in air – an attribute that is similar to the training dog mesh used to learn illumination. + +# 6. Conclusion + +We presented Continuous 3D Words, a framework that allows us to learn 3D-aware attributes reflected in renderings of meshes as special words, which can then be injected into the text prompts for fine-grained text-to-image generation. Extensive study on learning both single and multiple continuous words shows that we can control challenging attributes. With the lightweight design and promising results, we hope that this work opens up interesting applications in the vision community to create their own 3D words with a single mesh and an accessible rendering engine. + +Acknowledgements. This work is supported in part by the EPSRC ACE-OPS grant EP/S030832/1. + +# References + +[1] Yuval Alaluf, Elad Richardson, Gal Metzer, and Daniel Cohen-Or. A neural space-time representation for text-to-image personalization. arXiv preprint arXiv:2305.15391, 2023. 3 +[2] James Betker, Gabriel Goh, Li Jing, † TimBrooks, Jianfeng Wang, Linjie Li, † LongOuyang, † JuntangZhuang, † JoyceLee, † YufeiGuo, † WesamManassra, † PrafullaDhariwal, † CaseyChu, † YunxinJiao, and Aditya Ramesh. Improving image generation with better captions, 2023. 2 +[3] Tim Brooks, Aleksander Holynski, and Alexei A. Efros. Instructpix2pix: Learning to follow image editing instructions. In CVPR, 2023. 2 +[4] Tom Brown, Benjamin Mann, Nick Ryder, Melanie Subbiah, Jared D Kaplan, Prafulla Dhariwal, Arvind Neelakantan, Pranav Shyam, Girish Sastry, Amanda Askell, et al. Language models are few-shot learners. Advances in neural information processing systems, 33:1877-1901, 2020. 2 +[5] James Burgess, Kuan-Chieh Wang, and Serena Yeung. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), 2023. 3, 4 +[16] Ruoshi Liu, Rundi Wu, Basile Van Hoorick, Pavel Tokmakov, Sergey Zakharov, and Carl Vondrick. Zero-1-to-3: Zero-shot one image to 3d object, 2023. 3, 7 +[17] Zhiheng Liu, Yifei Zhang, Yujun Shen, Kecheng Zheng, Kai Zhu, Ruili Feng, Yu Liu, Deli Zhao, Jingren Zhou, and Yang Cao. Cones 2: Customizable image synthesis with multiple subjects. arXiv preprint arXiv:2305.19327, 2023. 3 +[18] Ron Mokady, Amir Hertz, Kfir Aberman, Yael Pritch, and Daniel Cohen-Or. Null-text inversion for editing real images using guided diffusion models. arXiv preprint arXiv:2211.09794, 2022. 6 +[19] Chong Mou, Xintao Wang, Liangbin Xie, Jian Zhang, Zhonggang Qi, Ying Shan, and Xiaohu Qie. T2i-adapter: Learning adapters to dig out more controllable ability for text-to-image diffusion models. arXiv preprint arXiv:2302.08453, 2023. 2 +[20] Gaurav Parmar, Krishna Kumar Singh, Richard Zhang, Yijun Li, Jingwan Lu, and Jun-Yan Zhu. Zero-shot image-to-image translation. In ACM SIGGRAPH 2023 Conference Proceedings, pages 1-11, 2023. 2 +[21] Colin Raffel, Noam Shazeer, Adam Roberts, Katherine Lee, Sharan Narang, Michael Matena, Yanqi Zhou, Wei Li, and Peter J Liu. Exploring the limits of transfer learning with a unified text-to-text transformer. The Journal of Machine Learning Research, 21(1):5485-5551, 2020. 2 +[22] Aditya Ramesh, Mikhail Pavlov, Gabriel Goh, Scott Gray, Chelsea Voss, Alec Radford, Mark Chen, and Ilya Sutskever. Zero-shot text-to-image generation. In International Conference on Machine Learning, pages 8821-8831. PMLR, 2021. 2 +[23] Aditya Ramesh, Prafulla Dhariwal, Alex Nichol, Casey Chu, and Mark Chen. Hierarchical text-conditional image generation with clip latents. In arXiv preprint arXiv:2204.06125, page 3, 2022. 2 +[24] Robin Rombach, Andreas Blattmann, Dominik Lorenz, Patrick Esser, and Björn Ommer. High-resolution image synthesis with latent diffusion models, 2021. 2, 4, 6, 7 +[25] Nataniel Ruiz, Yuanzhen Li, Varun Jampani, Yael Pritch, Michael Rubinstein, and Kfir Aberman. Dreambooth: Fine tuning text-to-image diffusion models for subject-driven generation. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 22500-22510, 2023. 2, 3, 4, 6, 7 +[26] Chitwan Sahara, William Chan, Saurabh Saxena, Lala Li, Jay Whang, Emily L Denton, Kamyar Ghasemipour, Raphael Gontijo Lopes, Burcu Karagol Ayan, Tim Salimans, et al. Photorealistic text-to-image diffusion models with deep language understanding. Advances in Neural Information Processing Systems, 35:36479-36494, 2022. 2 +[27] Jiaming Song, Chenlin Meng, and Stefano Ermon. Denoising diffusion implicit models. In International Conference on Learning Representations, 2020. 2 +[28] Xingyuan Sun, Jiajun Wu, Xiuming Zhang, Zhoutong Zhang, Chengkai Zhang, Tianfan Xue, Joshua B Tenenbaum, and William T Freeman. Pix3d: Dataset and methods for single- + +image 3d shape modeling. In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 2974-2983, 2018. 6 +[29] Paul Yoo, Jiaxian Guo, Yutaka Matsuo, and Shixiang Shane Gu. Dreamsparse: Escaping from Plato's cave with 2d diffusion model given sparse views. arXiv preprint arXiv:2306.03414, 2023. 3 +[30] Lvmin Zhang, Anyi Rao, and Maneesh Agrawala. Adding conditional control to text-to-image diffusion models. 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We introduce Continuous 3D Words - special tokens in text-to-image models that allow users to have fine-grained control over several attributes like illumination [ ] (a and c), non-rigid shape change [ ] (d), orientation [ ] (c and d), and camera parameters [ ] (b). Our approach can be trained using a single 3D mesh and a rendering engine while incurring into negligible runtime and memory costs." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 303, + 242, + 545, + 497 + ], + "blocks": [ + { + "bbox": [ + 303, + 242, + 545, + 497 + ], + "lines": [ + { + "bbox": [ + 303, + 242, + 545, + 497 + ], + "spans": [ + { + "bbox": [ + 303, + 242, + 545, + 497 + ], + "type": "image", + "image_path": "a8a555aa2a5bbb803f2ec86f602ed437ac16d562037bacd0d0db205b22e91737.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "bbox": [ + 143, + 555, + 192, + 569 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 555, + 192, + 569 + ], + "spans": [ + { + "bbox": [ + 143, + 555, + 192, + 569 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 45, + 582, + 290, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 582, + 290, + 715 + ], + "spans": [ + { + "bbox": [ + 45, + 582, + 290, + 715 + ], + "type": "text", + "content": "Current controls over diffusion models (e.g., through text or ControlNet) for image generation fall short in recognizing abstract, continuous attributes like illumination direction or non-rigid shape change. In this paper, we present an approach for allowing users of text-to-image models to have fine-grained control of several attributes in an image. We do this by engineering special sets of input tokens that can be transformed in a continuous manner - we call them Continuous 3D Words. These attributes can, for example, be represented as sliders and applied jointly with text prompts for fine-grained control over image" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 557, + 548, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 557, + 548, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 557, + 548, + 665 + ], + "type": "text", + "content": "generation. Given only a single mesh and a rendering engine, we show that our approach can be adopted to provide continuous user control over several 3D-aware attributes, including time-of-day illumination, bird wing orientation, dollyzoom effect, and object poses. 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Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 322, + 702, + 497, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 322, + 702, + 497, + 713 + ], + "spans": [ + { + "bbox": [ + 322, + 702, + 497, + 713 + ], + "type": "text", + "content": "*Work was done during internship at Adobe Research." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "6753" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 49, + 72, + 127, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 72, + 127, + 83 + ], + "spans": [ + { + "bbox": [ + 49, + 72, + 127, + 83 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 49, + 91, + 287, + 389 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 91, + 287, + 389 + ], + "spans": [ + { + "bbox": [ + 49, + 91, + 287, + 389 + ], + "type": "text", + "content": "Photography is fascinating because it enables very detailed control over the composition and aesthetics of the final image. On the one hand, this is simply the result of application of physical laws to achieve image acquisition. On the other, the slightest changes in the moment captured, illumination, object orientation, or camera parameters bring a completely different feeling to the viewer. While the giant leap of modern text-to-image diffusion can bring generated 2-D images to close proximity with real photos, text prompts are inherently limited to high-level descriptions, far removed from the detailed controls one has over actual photography. This is mainly due to the scarcity of such descriptions in the training dataset — very few would describe a photo based on exact object movements and camera parameters like the wing pose of a bird or the rotation of a person's head in degrees. On the other hand, 3D rendering engines allow us to mimic many of these 3D controls that photographers enjoy. We can render images of objects with predefined camera, illumination and pose changes at a very fine-grained scale. However, creating detailed 3D worlds is incredibly laborious, which limits the diversity of the scenes that can be generated by non-specialized practitioners. In that regard, using text-to-image diffusion to create images is a much more accessible technology, whereas precise 3D scene control remains firmly in the domain of experts." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 49, + 391, + 287, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 391, + 287, + 533 + ], + "spans": [ + { + "bbox": [ + 49, + 391, + 287, + 533 + ], + "type": "text", + "content": "In this work, we aim to bring together the best of two worlds by expanding the vocabulary of text-to-image diffusion models with very few samples generated from rendering engines. Specifically, we render meshes based on the attribute we aim to control, creating images with color and other useful information to generate a small set of data samples. The goal is to disentangle these abstract attributes from the original object and encode them into the textual space in a controllable manner – we term these attributes Continuous 3D Words. They allow users to create custom sliders that enable fine-grained control during image generation and can be seamlessly used along text prompts." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 49, + 535, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 535, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 49, + 535, + 287, + 713 + ], + "type": "text", + "content": "At the heart of our approach is an algorithm to learn a continuous vocabulary. The benefits of continuity are twofold: " + }, + { + "bbox": [ + 49, + 535, + 287, + 713 + ], + "type": "inline_equation", + "content": "i)" + }, + { + "bbox": [ + 49, + 535, + 287, + 713 + ], + "type": "text", + "content": " the association between different values of the same attribute makes it much easier to learn, rather than having to learn hundreds of discrete tokens as an approximation and " + }, + { + "bbox": [ + 49, + 535, + 287, + 713 + ], + "type": "inline_equation", + "content": "ii)" + }, + { + "bbox": [ + 49, + 535, + 287, + 713 + ], + "type": "text", + "content": " we learn an MLP that would allow interpolation during inference to generate an actual continuous control. On top of this, we also propose two training strategies to prevent degenerate solutions and enable generalization on new objects beyond the training category. First, we apply a two-stage training strategy: we first apply the Dreambooth [25] approach to learn the object identity of the underlying mesh used for rendering, then sequentially learn the various attribute values disentangled from the object identity. This prevents the model from falling into a degenerate solution of encoding" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 307, + 72, + 545, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 307, + 72, + 545, + 179 + ], + "spans": [ + { + "bbox": [ + 307, + 72, + 545, + 179 + ], + "type": "text", + "content": "each value of an attribute as a new object, which would prevent us from generalizing the attribute to new objects. Second, we apply ControlNet [30] with various conditioned images to generate a set of additional images with varying backgrounds and object textures. This prevents the model from overfitting to the artificial backgrounds of rendered images. The entire training was done in a light-weight Lower Rank Adaptation (LoRA) [14] manner, making it fast and accessible with single GPUs." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 308, + 180, + 545, + 275 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 180, + 545, + 275 + ], + "spans": [ + { + "bbox": [ + 308, + 180, + 545, + 275 + ], + "type": "text", + "content": "We implement our continuous vocabulary and training method, across various sets of single (e.g., dollyzoom extracted from chairs) and multiple (e.g., object pose and illumination extracted from a dog mesh) attributes, and show through quantitative user studies and qualitative comparisons that our method can properly reflect various attributes while maintaining the aesthetics of the image — significantly outperforming competitive baselines." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 308, + 276, + 545, + 371 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 276, + 545, + 371 + ], + "spans": [ + { + "bbox": [ + 308, + 276, + 545, + 371 + ], + "type": "text", + "content": "In summary, we present 1) Continuous 3D Words, a new method of gaining 3D-aware, continuous attribute controls over text-to-image generation that can be easily tailored to a plethora of new conditions, 2) a series of training strategies to disentangle the attributes from object identity to enhance the improvements in image generation and 3) extensive qualitative and quantitative studies to showcase our approach in various interesting applications." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 308, + 383, + 391, + 394 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 383, + 391, + 394 + ], + "spans": [ + { + "bbox": [ + 308, + 383, + 391, + 394 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 308, + 402, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 402, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 308, + 402, + 545, + 628 + ], + "type": "text", + "content": "Conditional Diffusion Models. Ever since diffusion models [13, 27] pushed the quality and generalizability of image generation beyond GANs [10], the vision community has introduced a diverse range of modalities that can be used as conditions to control the image generation process. The most common condition is currently text. Works such as DALLE [2, 22, 23] and Imagen [26] used large scale text-image datasets and strong language understandings from pretrained LLMs [4, 8, 21] to guide the generation process. Stable Diffusion further popularized this class of methods by employing memory efficient models through latent-space diffusion [24]. Other works built on top of these models by adding other forms of conditioning [19, 30]. Highly relevant to our work is ControlNet [30], which proposes a general pipeline with zero-convolutions for conditioning on text and image data (e.g., depth maps, canny maps, sketches). Despite their impressive image quality, it is not clear how to use these models to control other attributes of images like illumination or object orientation." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 308, + 630, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 630, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 308, + 630, + 545, + 713 + ], + "type": "text", + "content": "Other set of works explored how to perform image edits using textual instructions. Given a text-generated image, they demonstrate how the user can edit the image by amending the prompt, yet still preserve some aspects of the original image [3, 12, 20]. While convenient, these approaches do not allow fine-grained control over image elements since they are ultimately restricted by the user's ability to describe" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 296, + 750, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 296, + 750, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 296, + 750, + 314, + 757 + ], + "type": "text", + "content": "6754" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 71, + 545, + 311 + ], + "blocks": [ + { + "bbox": [ + 50, + 71, + 545, + 311 + ], + "lines": [ + { + "bbox": [ + 50, + 71, + 545, + 311 + ], + "spans": [ + { + "bbox": [ + 50, + 71, + 545, + 311 + ], + "type": "image", + "image_path": "87676faa54a52997856d3f4221b7e6a469938b12c460eb3bc2281579c44fcddc.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 321, + 548, + 377 + ], + "lines": [ + { + "bbox": [ + 46, + 321, + 548, + 377 + ], + "spans": [ + { + "bbox": [ + 46, + 321, + 548, + 377 + ], + "type": "text", + "content": "Figure 2. Method Overview. Finetuning: Our finetuning is divided into two stages. In the first stage, we render a series of images using different attribute values (e.g., illumination and pose). We feed them into the text-to-image diffusion model to learn token embedding [Obj] representing the single mesh used for training. In the second stage, we add the tokens representing individual attributes into the prompt embedding. The two stage training allows us to better disentangle the individual attributes against [Obj]. Inference: Attributes can be applied to different objects for text-to-image generation." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 48, + 393, + 289, + 517 + ], + "blocks": [ + { + "bbox": [ + 48, + 393, + 289, + 517 + ], + "lines": [ + { + "bbox": [ + 48, + 393, + 289, + 517 + ], + "spans": [ + { + "bbox": [ + 48, + 393, + 289, + 517 + ], + "type": "image", + "image_path": "ed1d9efbc15f1d2d99234496c9ec0e49c6c66cc0c726f4a6f0cc0dad38791bd8.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 525, + 287, + 570 + ], + "lines": [ + { + "bbox": [ + 46, + 525, + 287, + 570 + ], + "spans": [ + { + "bbox": [ + 46, + 525, + 287, + 570 + ], + "type": "text", + "content": "Figure 3. ControlNet Augmentations. Depth ControlNet is used for attributes creating direct shape changes. Lineart ControlNet is applied for more subtle changes that cannot be reflected by depths (e.g., illumination)." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 593, + 287, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 593, + 287, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 593, + 287, + 628 + ], + "type": "text", + "content": "visual content through text – e.g., it would be very difficult to change the illumination direction by a precise angle such as " + }, + { + "bbox": [ + 46, + 593, + 287, + 628 + ], + "type": "inline_equation", + "content": "11^{\\circ}" + }, + { + "bbox": [ + 46, + 593, + 287, + 628 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "content": "Recently, as the amount of 3D data available significantly increased, Liu et al. [16] introduced Zero-1-to-3, a diffusion model trained on various viewpoints of 3D rendering that enables viewpoint editing given an image of a single object. Similarly, works like DreamSparse [29] also employ diffusion models to synthesize novel views on open-set categories. Differently from our approach, these techniques are" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 397, + 547, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 397, + 547, + 483 + ], + "spans": [ + { + "bbox": [ + 304, + 397, + 547, + 483 + ], + "type": "text", + "content": "focused only on object orientation and rely on vast 3D shape datasets. On the other hand, we investigate how to learn several continuous concepts (e.g. illumination [ ] , wing pose [ " + }, + { + "bbox": [ + 304, + 397, + 547, + 483 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 304, + 397, + 547, + 483 + ], + "type": "text", + "content": " ], dolly zoom [ " + }, + { + "bbox": [ + 304, + 397, + 547, + 483 + ], + "type": "inline_equation", + "content": "\\text{公} _ { \\text{公} } ^ { \\text{公} }" + }, + { + "bbox": [ + 304, + 397, + 547, + 483 + ], + "type": "text", + "content": " ]) that can be directly used in text-to-image scenarios; i.e. we don't generate an image to then change the orientation or illumination later, but instead we use Continuous Words directly on text prompts." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 498, + 548, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 548, + 700 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 548, + 700 + ], + "type": "text", + "content": "Learning new concepts on diffusion models. With diffusion models being trained on unforeseen quantities in images and texts, a stream of work focused on adding specific concepts with very few data samples. For example, given a small set of images representing one particular object instance, textual inversion learns a new word embedding to describe the object, such that the word can be applied with new text prompts for image generation [9]. NETI [1] extended the word embedding to a time-space conditioned neural mapper for better generation while preserving quality. Similarly, Dreambooth [25] aims to achieve the same goal, but by using a repurposed token rarely used in text and finetuning the entire diffusion model with an additional constraint to prevent generative loss. There are numerous subsequent works showing improvements on finetuning different layers/weights and by improving the training strategy [11, 15, 17]." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "type": "text", + "content": "Despite the advances in adding new personalized entities" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 758 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 758 + ], + "type": "text", + "content": "6755" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": "to existing models, few works focus on learning general concepts that can be applied to a variety of scenarios. A concurrent work, ViewNETI [5], is the first to learn viewpoints as a concept, but we hypothesise that the 3D awareness of large text-to-image diffusion models goes far beyond merely viewpoints, allowing us to associate and even create interactions with multiple 3D-aware concepts like illumination, pose and camera parameters at the same time. Our method, despite being trained only using a single mesh, shows superior generalization properties – while trained to learn illumination and orientation from renderings of a single dog, we are capable of employing the learned concepts to generate cars, horses (Figure 4), polar bears (Figure 8), lions (Figure 1) and so on." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 241, + 103, + 253 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 241, + 103, + 253 + ], + "spans": [ + { + "bbox": [ + 47, + 241, + 103, + 253 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 262, + 133, + 273 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 262, + 133, + 273 + ], + "spans": [ + { + "bbox": [ + 47, + 262, + 133, + 273 + ], + "type": "text", + "content": "3.1. Preliminaries" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "spans": [ + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "text", + "content": "We define an image " + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "text", + "content": " that captures object " + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "inline_equation", + "content": "O" + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "text", + "content": " from category " + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "text", + "content": " as a function of several attributes " + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "inline_equation", + "content": "I = f(a_{1},a_{2},a_{3},\\dots,a_{n})" + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "inline_equation", + "content": "a_{i}" + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "text", + "content": " belongs to a vast set of image attributes " + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 46, + 281, + 289, + 460 + ], + "type": "text", + "content": ": shape, material reflectivity, rotation/translation, camera parameters, shape deformations, etc. Some of these components can be translated to other categories while others cannot, so for simplicity we assume they only work for a single category. In the experimental section of this study, we will demonstrate that the definition of category for some attributes is rather loose and the user is capable of generating images with continuous words depicting objects very different from the ones seen during training. Notice that images annotated with the attributes we are interested are very rare, so the models do not have a very precise knowledge of them, except for what is already described in text-image pairs." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 460, + 288, + 509 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 460, + 288, + 509 + ], + "spans": [ + { + "bbox": [ + 46, + 460, + 288, + 509 + ], + "type": "text", + "content": "Given an image set " + }, + { + "bbox": [ + 46, + 460, + 288, + 509 + ], + "type": "inline_equation", + "content": "I^O" + }, + { + "bbox": [ + 46, + 460, + 288, + 509 + ], + "type": "text", + "content": " with images capturing an object " + }, + { + "bbox": [ + 46, + 460, + 288, + 509 + ], + "type": "inline_equation", + "content": "O" + }, + { + "bbox": [ + 46, + 460, + 288, + 509 + ], + "type": "text", + "content": ", previous methods like Dreambooth [25], Custom Diffusion [15], or Textual-Inversion [9] aim to minimize the following objective:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 78, + 519, + 289, + 546 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 78, + 519, + 289, + 546 + ], + "spans": [ + { + "bbox": [ + 78, + 519, + 289, + 546 + ], + "type": "interline_equation", + "content": "\\mathbb {E} _ {\\hat {I} _ {\\epsilon , i}, T _ {O}, I _ {i} \\in I ^ {O}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , i}, P (T _ {O})\\right) - I _ {i} \\right\\| _ {2} ^ {2} \\right], \\tag {1}", + "image_path": "f68a2a4fef1940c21e1d40bf8d1e6948467f2ad71c708f763be2c104beaf670e.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "S_{\\theta}" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " is a Text-to-Image diffusion model [24], " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\hat{I}_{\\epsilon,i}" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " is a noised image " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\alpha_t I_i + \\sigma_t \\epsilon" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " with noise " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " and noise schedulers " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\alpha_t, \\sigma_t" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "P(T_O)" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " is the prompt condition which contains a token embedding " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "T_O" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " used as an identifier of object " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "O" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": ". In practise " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "P(\\cdot)" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " is the text encoder from CLIP. The finetuned network " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "S_{\\theta}" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " can then generate new images containing " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "O" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " when given a new prompt condition " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "P'(T_O)" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " and some Gaussian noise. Unlike previous methods, our goal is not to add concepts representing specific objects, but rather have them describe some attributes " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "a_i \\in \\mathcal{A}" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": ", by learning to disentangle them using as few objects as possible within " + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 557, + 289, + 713 + ], + "type": "text", + "content": " - most of the time just one object suffices. Our model can also be easily extended to controlling multiple attributes at the same time." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 72, + 422, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 422, + 83 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 422, + 83 + ], + "type": "text", + "content": "3.2. Continuous Control" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "spans": [ + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "text", + "content": "A naive way to control an attribute " + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "text", + "content": " is to use some realistic rendering engine to generate images of the available objects that have the same value " + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "inline_equation", + "content": "a = x" + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "text", + "content": ", and then apply similar approaches to previous works by assigning a token " + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "inline_equation", + "content": "T_{x}" + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "text", + "content": " to identify images with this particular value. This is not ideal, however, since " + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 304, + 90, + 547, + 185 + ], + "type": "text", + "content": " is often continuous and have infinitely many values – we would require an unfeasible number of tokens to gain fine-grained control over these attributes." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "spans": [ + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "text", + "content": "Therefore, we propose to instead learn a continuous function " + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "inline_equation", + "content": "g_{\\phi}(\\mathbf{a}) : \\mathcal{D} \\to \\mathcal{T}" + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "text", + "content": " that maps a set of attributes from some continuous domain " + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "text", + "content": " to the token embedding domain " + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "text", + "content": ". We use positional encoding to first cast each attribute " + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "inline_equation", + "content": "a \\in \\mathbf{a}" + }, + { + "bbox": [ + 304, + 186, + 547, + 305 + ], + "type": "text", + "content": " to a higher frequency space before feeding into the function, which is represented by a very simple 2-layer MLP. The output of this network is named Continuous 3D Word and will allow users to easily control continuous attributes from text prompts augmented by these tokens. Finally, our training objective can then be formulated as:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 327, + 312, + 546, + 340 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 327, + 312, + 546, + 340 + ], + "spans": [ + { + "bbox": [ + 327, + 312, + 546, + 340 + ], + "type": "interline_equation", + "content": "\\arg \\min _ {\\theta , \\phi} \\mathbb {E} _ {\\hat {I} _ {\\epsilon , \\mathbf {a}}, \\mathbf {a}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , \\mathbf {a}}, P \\left(g _ {\\phi} (\\mathbf {a})\\right)\\right) - I _ {\\mathbf {a}} \\right\\| _ {2} ^ {2} \\right]. \\tag {2}", + "image_path": "5814045a5ae4e0349794968998f6efd6ca72e6cbdcfc6c7450898fc4ae45143d.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 346, + 538, + 360 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 346, + 538, + 360 + ], + "spans": [ + { + "bbox": [ + 305, + 346, + 538, + 360 + ], + "type": "text", + "content": "3.3. Disentangling Object Identity and Attributes" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 365, + 547, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 365, + 547, + 460 + ], + "spans": [ + { + "bbox": [ + 304, + 365, + 547, + 460 + ], + "type": "text", + "content": "In practice, when we only utilize a single object to learn attributes, a degenerate solution occurs when directly optimizing (2), where " + }, + { + "bbox": [ + 304, + 365, + 547, + 460 + ], + "type": "inline_equation", + "content": "S_{\\theta}" + }, + { + "bbox": [ + 304, + 365, + 547, + 460 + ], + "type": "text", + "content": " treats the same object with different values for " + }, + { + "bbox": [ + 304, + 365, + 547, + 460 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 304, + 365, + 547, + 460 + ], + "type": "text", + "content": " as different objects. This hinders the generalization capability of changing the attribute when given an image of a new object. To this end, we propose two strategies, one during training and one during inference, to disentangle the object identity and individual attributes." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 464, + 547, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 464, + 547, + 513 + ], + "spans": [ + { + "bbox": [ + 304, + 464, + 547, + 513 + ], + "type": "text", + "content": "Training: Learning identity and attributes. We provide a simple regularization by explicitly forcing the model to use the same identifier for images representing the same object. The objective can thus be formulated as:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 313, + 520, + 546, + 546 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 520, + 546, + 546 + ], + "spans": [ + { + "bbox": [ + 313, + 520, + 546, + 546 + ], + "type": "interline_equation", + "content": "\\arg \\min _ {\\theta , \\phi} \\mathbb {E} _ {\\hat {I} _ {\\epsilon , \\mathbf {a}}, \\mathbf {a}} \\left[ \\left\\| S _ {\\theta} \\left(\\hat {I} _ {\\epsilon , \\mathbf {a}}, P \\left(T _ {O}, g _ {\\phi} (\\mathbf {a})\\right)\\right) - I _ {\\mathbf {a}} \\right\\| _ {2} ^ {2} \\right]. \\tag {3}", + "image_path": "fce6f4137ab954eee550ed7571051ab3b307c7bf891b47b2ca43f689c4aa9635.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "spans": [ + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": "Optimizing both " + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "inline_equation", + "content": "T_{O}" + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "inline_equation", + "content": "g_{\\phi}(\\mathbf{a})" + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": " concurrently proved to be difficult from our experiments (see Section 5). We propose a two-stage training strategy as depicted in Figure 2. For every available image in " + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "inline_equation", + "content": "I^{O}" + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": " with varying " + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "inline_equation", + "content": "\\mathbf{a}" + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": ", we first use the same prompt condition " + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "inline_equation", + "content": "P(T_{O})" + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": " to associate them to the same object, then learn the diffusion model parameters " + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": " and our Continuous 3D Words MLP " + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "inline_equation", + "content": "g_{\\phi}" + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": " by using the prompt condition " + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "inline_equation", + "content": "P(T_{O},g_{\\phi}(\\mathbf{a}))" + }, + { + "bbox": [ + 304, + 554, + 547, + 650 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": "Inference: Negatively prompting object identifier. To further the disentanglement of attributes against object identities. We propose a simple trick during inference by adding the object identity as a negative prompt. Specifically, for each sampling step, we swap the null-text embedding used" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "6756" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 70, + 547, + 450 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 547, + 450 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 547, + 450 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 547, + 450 + ], + "type": "image", + "image_path": "ad36a39bc9a31be19c09bfa53cf400a69381bff6a67724871cb774165296d29c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 458, + 547, + 492 + ], + "lines": [ + { + "bbox": [ + 46, + 458, + 547, + 492 + ], + "spans": [ + { + "bbox": [ + 46, + 458, + 547, + 492 + ], + "type": "text", + "content": "Figure 4. Qualitative Comparisons. We compare our Continuous 3D Words trained under three settings against ControlNet of various strengths. Note that the dollyzoom setup was trained with trained with multiple chair meshes, so we give additional ControlNet by manually picking the chair rendering that best follows the prompt (i.e., \"comfortable\" and in \"the office\")." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 58, + 510, + 280, + 622 + ], + "blocks": [ + { + "bbox": [ + 58, + 510, + 280, + 622 + ], + "lines": [ + { + "bbox": [ + 58, + 510, + 280, + 622 + ], + "spans": [ + { + "bbox": [ + 58, + 510, + 280, + 622 + ], + "type": "image", + "image_path": "eaa5b8038232620981dbb92faaf41d23f3d168bbe4a9c2b5a0bacd8809fb2811.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 632, + 288, + 676 + ], + "lines": [ + { + "bbox": [ + 46, + 632, + 288, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 632, + 288, + 676 + ], + "type": "text", + "content": "Figure 5. Disentangling Multiple Attributes. We show four examples of controlling multiple Continuous 3D words in addition to text descriptions. Left: trained with a single golden retriever mesh. Right: trained with a single animated dove." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "text", + "content": "by classifier-free guidance with " + }, + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "inline_equation", + "content": "T_{O}" + }, + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "text", + "content": ". Intuitively, since our training happened mostly using " + }, + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "inline_equation", + "content": "O" + }, + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "text", + "content": ", we want to disincentivize the model to generate images containing such object." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 512, + 451, + 525 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 512, + 451, + 525 + ], + "spans": [ + { + "bbox": [ + 306, + 512, + 451, + 525 + ], + "type": "text", + "content": "3.4. ControlNet Augmentation" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 532, + 547, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 532, + 547, + 614 + ], + "spans": [ + { + "bbox": [ + 304, + 532, + 547, + 614 + ], + "type": "text", + "content": "To prevent the fine-tuning process from overfitting to a simple white backgrounds and pre-defined object textures, we augment the backgrounds and textures in the rendering process. However, directly doing this in simulation engines is time consuming specially if one is targeting realistic scenes. Thus, we propose an automated solution by utilizing pretrained ControlNets." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": "Figure 3 shows two types of ControlNet augmentations we used in our framework. For attributes that can be directly reflected on shape changes (e.g., wing pose), we directly render the ground-truth depth maps to use as the condition for ControlNet. On the other hand, for attributes that cannot be reflected directly from depths (e.g., illumination), we first render the images without textures, then use a linear extractor to obtain a \"sketch\" of the image. This captures" + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "6757" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 106 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 106 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 106 + ], + "type": "text", + "content": "subtle changes such as shades and shadows in the pixel space, which can then be used as the condition for Lineart ControlNet." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 108, + 288, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 108, + 288, + 216 + ], + "spans": [ + { + "bbox": [ + 46, + 108, + 288, + 216 + ], + "type": "text", + "content": "We add additional prompts describing the object appearance and background during the ControlNet generation. It is important to note that prompts deviating away too much from the original mesh category would lead to degenerate images, so our prompts are in general very simple and straightforward (details in supplemental material). We include the ControlNet generated images as a small set of data augmentation, and we use the same prompt which we use to guide ControlNet generation to guide our Stage 2 fine-tuning." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 226, + 127, + 239 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 226, + 127, + 239 + ], + "spans": [ + { + "bbox": [ + 47, + 226, + 127, + 239 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 246, + 288, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 246, + 288, + 376 + ], + "spans": [ + { + "bbox": [ + 46, + 246, + 288, + 376 + ], + "type": "text", + "content": "We use off-the-shelf Stable Diffusion v2.1 [24] as the backbone of our method. We resort to the recent Low-Rank Adaptation (LoRA) [14] for the fine-tuning of the denoising U-Net and text encoder, allowing us to train on a single A10 GPU occupying roughly 16GB of memory. Thanks to the low-rank optimization, our models have a very small size (approximately 6MB). Training time varies by the complexity of the single/multiple attributes to learn, but falls within 15k to 20k steps, which generally takes around 3-4 hours in a single GPU. For ControlNet augmentation, we use the official implementation of ControlNet v1.1 [30]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 377, + 288, + 509 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 377, + 288, + 509 + ], + "spans": [ + { + "bbox": [ + 46, + 377, + 288, + 509 + ], + "type": "text", + "content": "We implement our Continuous 3D words under five different attribute settings. For single attributes we implement 1) illumination [ ] using a single dog mesh, 2) wing pose [ ] using a single animated dove mesh, and 3) Dolly zoom [ ] with five Pix3D chairs [28]. For multi-concepts, we train 4) illumination and object orientation [ ] + [ ] using a single dog mesh and 5) wing pose and orientation [ ] + [ ] using a single animated dove mesh. Settings 1) and 4) use linear images [6] while the others use depth map to compute the ControlNet background augmentation (see Section 3.4)." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 515, + 197, + 528 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 515, + 197, + 528 + ], + "spans": [ + { + "bbox": [ + 47, + 515, + 197, + 528 + ], + "type": "text", + "content": "4.1. Comparison with Baselines" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "type": "text", + "content": "Baseline Design. We design a very competitive baseline that enables fine-grained attribute control in image generation by combining the mesh training data we used in our experiments, a rendering engine and ControlNet [30]. Specifically, we take a novel text prompt for a training object, and grab a corresponding condition map in the training set rendered with the intended attributes. For example, if the prompt is a " + }, + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "type": "inline_equation", + "content": "[\\varpi]" + }, + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "type": "text", + "content": " eagle flying in a forest, we select the frame of the dove mesh that corresponds to the user-prescribed wing pose " + }, + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "type": "inline_equation", + "content": "[\\varpi]" + }, + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "type": "text", + "content": ", render its depth map using a rendering engine and pass it through ControlNet with the same prompt but removing the continuous " + }, + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "type": "inline_equation", + "content": "3D" + }, + { + "bbox": [ + 46, + 534, + 288, + 713 + ], + "type": "text", + "content": " word. The strength of the ControlNet guidance is a critical hyperparameter — increase in strength could increase the accuracy of reflecting the attribute but decrease the robustness to general-" + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 309, + 71, + 545, + 186 + ], + "blocks": [ + { + "bbox": [ + 309, + 71, + 545, + 186 + ], + "lines": [ + { + "bbox": [ + 309, + 71, + 545, + 186 + ], + "spans": [ + { + "bbox": [ + 309, + 71, + 545, + 186 + ], + "type": "table", + "html": "
MethodUser Preference (%) ↑
[✓][?][✓] / [?][?] / [?]Avg.
ControlNet (1.0)28.3%16.2%35.0%15.0%23.6%
ControlNet (0.5)10.0%28.8%12.5%32.5%21.0%
Ours61.7%55.0%52.5%52.5%55.4%
Average User Ranking ↑
Method[✓][?][✓] / [?][?] / [?]Avg.
ControlNet (1.0)2.07 ± 0.701.49 ± 0.762.20 ± 0.681.60 ± 0.741.84 ± 0.72
ControlNet (0.5)1.38 ± 0.662.11 ± 0.671.38 ± 0.702.06 ± 0.761.73 ± 0.70
Ours2.55 ± 0.622.40 ± 0.732.43 ± 0.672.33 ± 0.772.43 ± 0.70
", + "image_path": "4adf4c0f9cf858aee4cc5be71a90a01606b97bbe1a0e2af6bd3b95d675f75176.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 194, + 547, + 316 + ], + "lines": [ + { + "bbox": [ + 304, + 194, + 547, + 316 + ], + "spans": [ + { + "bbox": [ + 304, + 194, + 547, + 316 + ], + "type": "text", + "content": "Table 1. User study results. We asked users to rank three images according to their preference and how well they followed the given conditions – text prompt and one or two continuous controls. The controls were described by representative images (i.e. arrows for orientation, shaded sphere for illumination, etc.). See supplemental material for more details. We evaluate four different control types: wing pose \\([\\sim]\\), illumination \\([\\diamond]\\), wing pose \\([\\sim] + orientation \\([\\triangle]\\), and illumination \\([\\diamond] + orientation \\([\\triangle]\\). Cells colored as red and yellow represent the best and second best method, respectively. Our method was selected as the favorite for the majority of users in all evaluated setups." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 332, + 546, + 404 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 332, + 546, + 404 + ], + "spans": [ + { + "bbox": [ + 304, + 332, + 546, + 404 + ], + "type": "text", + "content": "ize to the text-prompt intended object. Therefore, we present the ControlNet baseline with both full and half strength in terms of guidance. We also explored an interpolation of null-text embedding [18] baseline, but the results failed to capture even the simplest attributes, so they were omitted from our analysis." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 411, + 547, + 554 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 411, + 547, + 554 + ], + "spans": [ + { + "bbox": [ + 304, + 411, + 547, + 554 + ], + "type": "text", + "content": "Quantitative Results. Due to the complexity and abstract nature of the attributes we are analyzing, automatically measuring whether a generated image reflects a set of values is a considerable challenge. Thus, following previous papers [12, 25, 30], we create a user study to evaluate the quality of the generated images while controlling several attributes. For each setting 1, 2, 4, and 5, we randomly sample a set of 3D conditions and prompts, generating over 60 questions per setting. Similarly to the user studies above, we then invite 20 participants, showing them all the given constraints we want the image to pertain (prompts and attributes), and ask them to rank each image from best to worst." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 558, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 547, + 713 + ], + "type": "text", + "content": "Table 1 shows the results in both the percentage of user preference (image chose as the best one) and the overall ranking. Best results are highlighted as red. Our Continuous 3D Words won the majority of votes (over " + }, + { + "bbox": [ + 304, + 558, + 547, + 713 + ], + "type": "inline_equation", + "content": "50\\%" + }, + { + "bbox": [ + 304, + 558, + 547, + 713 + ], + "type": "text", + "content": ") in all analyzed scenarios. Interestingly, the second best (as highlighted in yellow) alternates between the two guidance strengths of ControlNet. For wing-pose based controls, having a weaker control diminishes the strong prior offered by the depth map, resulting in inaccurate poses. Conversely, strong guidance for illumination forces ControlNet to generate objects around the shadow outline (further shown in Figure 4). Differently from the baselines, our training strategy is one-size-fits-all without any hyperparameter required." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "6758" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 83 + ], + "type": "text", + "content": "Qualitative Analyses We present a detailed comparison of" + } + ] + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 47, + 83, + 301, + 257 + ], + "blocks": [ + { + "bbox": [ + 47, + 83, + 301, + 257 + ], + "lines": [ + { + "bbox": [ + 47, + 83, + 301, + 257 + ], + "spans": [ + { + "bbox": [ + 47, + 83, + 301, + 257 + ], + "type": "image", + "image_path": "beda9bee85ed0815ec80ab61ff9ce6ef8e8ff08ff30f522c083d6c16de3b184e.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 266, + 134, + 279 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 266, + 134, + 279 + ], + "spans": [ + { + "bbox": [ + 47, + 266, + 134, + 279 + ], + "type": "text", + "content": "4.2. Multi-Concep" + } + ] + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 134, + 259, + 301, + 302 + ], + "blocks": [ + { + "bbox": [ + 134, + 259, + 301, + 302 + ], + "lines": [ + { + "bbox": [ + 134, + 259, + 301, + 302 + ], + "spans": [ + { + "bbox": [ + 134, + 259, + 301, + 302 + ], + "type": "image", + "image_path": "1e26b9cdc3995b87b251225d79cf98976e933019a944240cec42a3a6b34a6955.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 289, + 287, + 431 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 289, + 287, + 431 + ], + "spans": [ + { + "bbox": [ + 46, + 289, + 287, + 431 + ], + "type": "text", + "content": "Just like sentences with but each disentangled from one another when controlling the image generation, our Continuous 3D Words can do the same. We show four examples in Figure 5, two from [ ] and [ ], and two [ ] and [ ], where we can keep one attribute fixed but change the other without sabotaging the quality of image generations. They can be jointly used with complex prompts describing the background and object texture. Moreover, while all these words are learned from a single mesh, we can easily transfer the attribute to objects with fairly close semantics (e.g., a Labrador mesh to a polar bear, or a dove mesh to a parrot)." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 446, + 192, + 459 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 446, + 192, + 459 + ], + "spans": [ + { + "bbox": [ + 47, + 446, + 192, + 459 + ], + "type": "text", + "content": "4.3. Real World Image Editing" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "spans": [ + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "type": "text", + "content": "Our Continuous 3D Words can be directly applied to real world images to perform editing. To do so, we simply have to encode a real world image to a rare token via Dreambooth [25]. Then, we only have to use that token in conjunction with our Continuous 3D Words to generate the edited image. We show 4 examples in Figure 6, changing " + }, + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "type": "inline_equation", + "content": "[\\bullet]" + }, + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "type": "inline_equation", + "content": "[\\neg]" + }, + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "type": "inline_equation", + "content": "[\\uparrow]" + }, + { + "bbox": [ + 46, + 468, + 287, + 575 + ], + "type": "text", + "content": ". As we can see, the Dreambooth token preserves most of the image appearance, while our Continuous Words understand and brings edits to the main subject." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "type": "text", + "content": "Comparing with Zero-1-to-3 While our approach is focused on enhancing text-to-image, given the capabilities of real-world image editing, we can use the same setup to provide a comparison with only with object orientation changes (Figure 6). Notice that Zero1-to-3 [16] operates in foreground-only images so we also had to segment the object [7], inpaint the background [24], and place the novel orientation back to the image. Each step contains errors that, when compounded, hurt the quality of the final result. More importantly, our method allows controls beyond orientation changes without relying on massive 3D datasets." + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 315, + 72, + 537, + 305 + ], + "blocks": [ + { + "bbox": [ + 315, + 72, + 537, + 305 + ], + "lines": [ + { + "bbox": [ + 315, + 72, + 537, + 305 + ], + "spans": [ + { + "bbox": [ + 315, + 72, + 537, + 305 + ], + "type": "image", + "image_path": "a836c4c49ec1b7690c17b91762088001ac43687519f2737d862913d9e57500e8.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 316, + 547, + 393 + ], + "lines": [ + { + "bbox": [ + 305, + 316, + 547, + 393 + ], + "spans": [ + { + "bbox": [ + 305, + 316, + 547, + 393 + ], + "type": "text", + "content": "Figure 6. Real World results & Comparison w/ Zero1-to-3. We learn tokens representing single images and use along with Continuous 3D Words for image editing. The learned image token encodes most of the image appearance, while the Continuous 3D Word modifies its relevant aspects. Zero123, on the other hand, tends to yield images where the modified object is deformed or not properly harmonized." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 307, + 411, + 545, + 509 + ], + "blocks": [ + { + "bbox": [ + 307, + 411, + 545, + 509 + ], + "lines": [ + { + "bbox": [ + 307, + 411, + 545, + 509 + ], + "spans": [ + { + "bbox": [ + 307, + 411, + 545, + 509 + ], + "type": "image", + "image_path": "b0ceddadd32708a752082b8c1a60ffbf24d49e39a75c999ec04ec75ead275a63.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 517, + 545, + 561 + ], + "lines": [ + { + "bbox": [ + 305, + 517, + 545, + 561 + ], + "spans": [ + { + "bbox": [ + 305, + 517, + 545, + 561 + ], + "type": "text", + "content": "Figure 7. Interpolating continuous 3D words. We present two results of interpolation, one with discrete tokens and one with our Continuous 3D Words. Our method preserves the attributes better and enables interpolation between two values." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 584, + 459, + 597 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 584, + 459, + 597 + ], + "spans": [ + { + "bbox": [ + 306, + 584, + 459, + 597 + ], + "type": "text", + "content": "5. Discussion and Limitations" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "content": "Why Not Discrete Tokens? The benefits of fitting a single MLP instead of multiple tokens on an attribute with different values are twofold. First, the MLP learns a continuous function, allowing us to interpolate between two training data samples whereas fitting multiple tokens leads to two datapoints as two discrete mappings. Second, finetuning a model to learn multiple custom tokens simultaneously is very hard. These benefits are illustrated in Figure 7. We show a comparison of learning a single Continuous 3D Word " + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "inline_equation", + "content": "[\\nu^{\\prime}]" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "6759" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 70, + 289, + 197 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 289, + 197 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 289, + 197 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 289, + 197 + ], + "type": "image", + "image_path": "313b5b9bafcb9996731113ce513b628a30c5ea1f4594825d980f426938cdb2ef.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 205, + 289, + 284 + ], + "lines": [ + { + "bbox": [ + 46, + 205, + 289, + 284 + ], + "spans": [ + { + "bbox": [ + 46, + 205, + 289, + 284 + ], + "type": "text", + "content": "Figure 8. Ablation Study. We present our ablations for: w/o two-stage training, w/o ControlNet augmentation, w/o [obj] as negative prompt, and our full pipeline. Notice that, when the prompt deviates a lot from the training data (truck in prompt, mesh of a dog for training), the ablated version fails to follow the prompt. Without two-stage training, it ignores the prompt and creates a dog; without the other parts it yields deformed shadows and dog-shaped trucks." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 294, + 289, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 294, + 289, + 498 + ], + "spans": [ + { + "bbox": [ + 46, + 294, + 289, + 498 + ], + "type": "text", + "content": "and 18 discrete tokens for different values of a wing pose. Both were learned with the same training method (2-stage with ControlNet augmentation). We present the generated results of three attribute values that are present in the training set, as well as the results when you interpolate the value in between. Interpolation is straightforward for our case where we just input the intermediate value into our Continuous 3D Words MLP. For discrete tokens, we interpolate between two nearest discrete bins. Notice that the discrete tokens have difficulty not only in interpolating results but also in learning the concept simultaneously. The eagle wings in the second row of Figure 7 do not follow the training data and sometimes generate a completely different pose (third column, second row). On the other hand, our images closely follow the pose prescribed by the user (top row) while yielding appealing images even when the values were not seen during training (columns 2, 4 and 6; second row)." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 498, + 290, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 290, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 290, + 714 + ], + "type": "text", + "content": "Ablation study. Figure 8 shows an ablation of our training strategy. We remove each component of our training strategy (w/o two-stage training, w/o ControlNet augmentation, w/o [obj] as negative prompt) and compare it with our full pipeline. Two examples are presented: one where the prompt is similar to the training and another one where it is significantly different. Without the two-stage training, the model fails to disentangle object identity with our attributes, hindering the generalization capability to new objects. This is particularly noticeable for the bottom row when the text prompt is a truck but a dog similar to the training mesh is generated when the two-stage training is removed. Without ControlNet, the finetuning process often overfits to the background training renderings, resulting in an inability to generate realistic backgrounds. Finally, adding [obj] as the negative prompt serves as a minor improvement in further disentangling both the backgrounds and object shape seen during training, resulting in a more aesthetic image." + } + ] + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 307, + 72, + 425, + 152 + ], + "blocks": [ + { + "bbox": [ + 307, + 63, + 317, + 71 + ], + "lines": [ + { + "bbox": [ + 307, + 63, + 317, + 71 + ], + "spans": [ + { + "bbox": [ + 307, + 63, + 317, + 71 + ], + "type": "text", + "content": "a)" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 307, + 72, + 425, + 152 + ], + "lines": [ + { + "bbox": [ + 307, + 72, + 425, + 152 + ], + "spans": [ + { + "bbox": [ + 307, + 72, + 425, + 152 + ], + "type": "image", + "image_path": "9fef82724241552dea150b7e7b53b0aa3774ebc2cca2349ebace37664efdd43e.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 427, + 72, + 545, + 151 + ], + "blocks": [ + { + "bbox": [ + 427, + 63, + 437, + 71 + ], + "lines": [ + { + "bbox": [ + 427, + 63, + 437, + 71 + ], + "spans": [ + { + "bbox": [ + 427, + 63, + 437, + 71 + ], + "type": "text", + "content": "b)" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 427, + 72, + 545, + 151 + ], + "lines": [ + { + "bbox": [ + 427, + 72, + 545, + 151 + ], + "spans": [ + { + "bbox": [ + 427, + 72, + 545, + 151 + ], + "type": "image", + "image_path": "cb70a70993e0c41c5ce8c9180fde570b75dfd68f8af9a5aa5632bbdbb4d19180.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 161, + 547, + 217 + ], + "lines": [ + { + "bbox": [ + 304, + 161, + 547, + 217 + ], + "spans": [ + { + "bbox": [ + 304, + 161, + 547, + 217 + ], + "type": "text", + "content": "Figure 9. Condition v.s. Accuracy in User Study. a) shows two images generated by the prompt “a " + }, + { + "bbox": [ + 304, + 161, + 547, + 217 + ], + "type": "inline_equation", + "content": "[v^{-}]" + }, + { + "bbox": [ + 304, + 161, + 547, + 217 + ], + "type": "text", + "content": " photo of a white bird on sand”. b) shows two images generated by the prompt “a " + }, + { + "bbox": [ + 304, + 161, + 547, + 217 + ], + "type": "inline_equation", + "content": "[v^{-}]" + }, + { + "bbox": [ + 304, + 161, + 547, + 217 + ], + "type": "text", + "content": " photo of a colorful bird”. Left is ours, right is ControlNet (1.0). Users preferred right over left for both." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 307, + 232, + 425, + 311 + ], + "blocks": [ + { + "bbox": [ + 308, + 224, + 317, + 232 + ], + "lines": [ + { + "bbox": [ + 308, + 224, + 317, + 232 + ], + "spans": [ + { + "bbox": [ + 308, + 224, + 317, + 232 + ], + "type": "text", + "content": "a)" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 307, + 232, + 425, + 311 + ], + "lines": [ + { + "bbox": [ + 307, + 232, + 425, + 311 + ], + "spans": [ + { + "bbox": [ + 307, + 232, + 425, + 311 + ], + "type": "image", + "image_path": "ff2677fc474c4dadcb5c1dd3d90511afbef3c3129ce94b2f96d2323fc7e91f97.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 316, + 547, + 350 + ], + "lines": [ + { + "bbox": [ + 304, + 316, + 547, + 350 + ], + "spans": [ + { + "bbox": [ + 304, + 316, + 547, + 350 + ], + "type": "text", + "content": "Figure 10. Failure cases. a) shows images generated with prompt \"a [ ] [ Monet Painting of ....\". b) shows images generated with \"a [ ] [ photo of a T-Rex\"." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 427, + 232, + 545, + 310 + ], + "blocks": [ + { + "bbox": [ + 427, + 223, + 438, + 232 + ], + "lines": [ + { + "bbox": [ + 427, + 223, + 438, + 232 + ], + "spans": [ + { + "bbox": [ + 427, + 223, + 438, + 232 + ], + "type": "text", + "content": "b)" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 427, + 232, + 545, + 310 + ], + "lines": [ + { + "bbox": [ + 427, + 232, + 545, + 310 + ], + "spans": [ + { + "bbox": [ + 427, + 232, + 545, + 310 + ], + "type": "image", + "image_path": "d875225246450d141f0a913c9c072888216f2a9cc19fc59350f4dcaf7007d2ac.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 359, + 545, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 359, + 545, + 430 + ], + "spans": [ + { + "bbox": [ + 304, + 359, + 545, + 430 + ], + "type": "text", + "content": "Condition v.s. Generated Accuracy in User Study. During our user study, we realize that occasionally users select the image which more strictly follows the exact conditions over the more physically probable image. For example, in Figure 9 a) and b), the head of the bird is generated poorly, but users preferred them as they are \"whiter\" and \"more colorful\"." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 431, + 547, + 538 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 431, + 547, + 538 + ], + "spans": [ + { + "bbox": [ + 304, + 431, + 547, + 538 + ], + "type": "text", + "content": "Failure Cases. We present in Figure 10 two examples of typical failure cases in our results. First, our model currently fails on more difficult scenarios where the style is given by the text prompt. In a), the image cannot fully reflect the \"Monet painting\" style imposed by our prompt. Second, the generated object may sometimes still overfit to the training set. In b), the T-Rex had four feet on the ground instead of standing with two claws in air – an attribute that is similar to the training dog mesh used to learn illumination." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 550, + 378, + 562 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 550, + 378, + 562 + ], + "spans": [ + { + "bbox": [ + 306, + 550, + 378, + 562 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 570, + 547, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 689 + ], + "type": "text", + "content": "We presented Continuous 3D Words, a framework that allows us to learn 3D-aware attributes reflected in renderings of meshes as special words, which can then be injected into the text prompts for fine-grained text-to-image generation. Extensive study on learning both single and multiple continuous words shows that we can control challenging attributes. With the lightweight design and promising results, we hope that this work opens up interesting applications in the vision community to create their own 3D words with a single mesh and an accessible rendering engine." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "content": "Acknowledgements. This work is supported in part by the EPSRC ACE-OPS grant EP/S030832/1." + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "6760" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 288, + 133 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 288, + 133 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 288, + 133 + ], + "type": "text", + "content": "[1] Yuval Alaluf, Elad Richardson, Gal Metzer, and Daniel Cohen-Or. 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In IEEE International Conference on Computer Vision (ICCV), 2023. 2, 6" + } + ] + } + ], + "index": 2 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 316, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 316, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 316, + 757 + ], + "type": "text", + "content": "6762" + } + ] + } + ], + "index": 4 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Correlation Structures for Vision Transformers/3e02995b-1bff-4a49-8649-a6ad79f7017d_content_list.json b/2024/Learning Correlation Structures for Vision Transformers/3e02995b-1bff-4a49-8649-a6ad79f7017d_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..2e0b4db18572e6908676a12274d35911df326e41 --- /dev/null +++ b/2024/Learning Correlation Structures for Vision Transformers/3e02995b-1bff-4a49-8649-a6ad79f7017d_content_list.json @@ -0,0 +1,1868 @@ +[ + { + "type": "text", + "text": "Learning Correlation Structures for Vision Transformers", + "text_level": 1, + "bbox": [ + 194, + 130, + 774, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Manjin Kim1", + "bbox": [ + 194, + 179, + 303, + 199 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Paul Hongsuck $\\mathrm{Seo}^{2*}$", + "bbox": [ + 323, + 180, + 493, + 198 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Cordelia Schmid3", + "bbox": [ + 506, + 180, + 650, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Minsu Cho $^{1*}$", + "bbox": [ + 669, + 180, + 774, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{1}$ POSTECH", + "bbox": [ + 202, + 202, + 302, + 220 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ Korea University", + "bbox": [ + 388, + 202, + 535, + 222 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "3Google Research", + "bbox": [ + 616, + 202, + 761, + 222 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "http://cvlab.postech.ac.kr/research/StructViT/", + "bbox": [ + 207, + 227, + 751, + 244 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 279, + 313, + 295 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We introduce a new attention mechanism, dubbed structural self-attention (StructSA), that leverages rich correlation patterns naturally emerging in key-query interactions of attention. StructSA generates attention maps by recognizing space-time structures of key-query correlations via convolution and uses them to dynamically aggregate local contexts of value features. This effectively leverages rich structural patterns in images and videos such as scene layouts, object motion, and inter-object relations. Using StructSA as a main building block, we develop the structural vision transformer (StructViT) and evaluate its effectiveness on both image and video classification tasks, achieving state-of-the-art results on ImageNet-1K, Kinetics-400, Something-Something V1 & V2, Diving-48, and FineGym.", + "bbox": [ + 75, + 311, + 473, + 522 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 550, + 209, + 566 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "How visual elements interact with each other in space and time is a crucial cue for visual understanding, e.g., recognizing actions in a video or analyzing scene layout patterns in an image. In computer vision, such relational patterns are effectively captured by the structure of correlations or similarities across visual elements in different positions [3, 57]; a correlation structure of an image reveals spatial layouts of similar patterns [30, 33] and that of a video provides bidirectional motion likelihoods [32, 36]. The ability to recognize those structural patterns may allow to better perform visual reasoning and generalize against challenging appearance variations and domain shifts [21, 65].", + "bbox": [ + 75, + 575, + 468, + 756 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In this work, we introduce a novel self-attention mechanism, named structural self-attention (StructSA), that effectively leverages diverse structural patterns for visual representation learning. While the standard self-attention mechanism uses raw query-key correlations individually and ignores their geometric structures, the proposed StructSA recognizes diverse structural patterns from the correlations between the query and local chunks of keys via convolu", + "bbox": [ + 75, + 757, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/5777cb2dbd004a634c140f935354a1c0cc2bfab64f48b175cbf5e27f32cfc166.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 504, + 279, + 575, + 335 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/d37c80eea780989de2fd998082a33196170e1677f5bc5c9e3a852547f8926a3f.jpg", + "image_caption": [ + "(a) Input video" + ], + "image_footnote": [], + "bbox": [ + 576, + 280, + 647, + 334 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/372dd048039d55491b0875978ad2ff995ae4818f3377aab702fc0841b48154ff.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 651, + 280, + 720, + 334 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/b59a677dc96456af73cfd481ed0e2959a6b6bc21024689726fb0af062a05b5e2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 723, + 280, + 792, + 334 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/b09a227551a1f00417550fce772d91eb50dd0b2332c3a90e87c5ea21892cead6.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 797, + 280, + 867, + 334 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/80f0691ab275d4ef2d1a0070e1645f814c35977e275fed5a4adb75c4c9167a95.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 504, + 354, + 573, + 411 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/1fff8d1bb2d2a758a2176d23c8129f4b24519c7a47e458721ff39370b0dbcbe5.jpg", + "image_caption": [ + "(b) Query-key correlation map" + ], + "image_footnote": [], + "bbox": [ + 576, + 354, + 647, + 411 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/6bb8fec36114aded9caf559a64104439a1c074defa582df805b975c20bd6cdb9.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 651, + 354, + 720, + 411 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/24798d14a8e5571a1c8bd33538939b655077b30eb721d52d5aa7d9daf1f761cf.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 723, + 354, + 794, + 411 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/d48eee41befa1acdb73b9e35ce155594c7005c049d6cc7ab2a72549580ee2ce4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 797, + 354, + 867, + 411 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/1a1b245e42a24c536fe41c0ddb9e71c9c31989b7278a0695011c88d1b5fcc464.jpg", + "image_caption": [ + "(c) Structural self-attention (StructSA)", + "Figure 1. Structural Self-Attention. Given an input video and a query indicated by the red box in (a), the query-key correlation maps in (b) clearly reveal the structures of spatial layout and motion with respect to the query. The proposed attention mechanism in (c) is designed to leverage these rich structural patterns for computing attention scores in the self-attention process." + ], + "image_footnote": [], + "bbox": [ + 501, + 431, + 888, + 555 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "tion and uses them to dynamically aggregate local contexts of value features, effectively capturing rich structural patterns such as scene layouts, object motion, and interobject relations in images and video. As illustrated in Fig. 1 and detailed in Sec. 3, this is mainly achieved by empowering the standard self-attention mechanism with long-range convolutional interactions and dynamic contextual feature aggregation. To investigate the effect of StructSA, we also provide an in-depth analysis on the relationship to recent self-attention variants with convolutional projection [18, 41, 42, 70, 72], showing their potential and limitation in leveraging structural patterns.", + "bbox": [ + 496, + 684, + 892, + 866 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To validate the effect of StructSA, we develop the structural vision transformer that adopts it as a main building", + "bbox": [ + 500, + 869, + 892, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Co-corresponding authors.", + "bbox": [ + 94, + 886, + 243, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "18941", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "block, and perform an extensive set of experiments on both image and video classification tasks, showing the effectiveness of learning structural patterns for visual representations. Our main contributions are as follows:", + "bbox": [ + 75, + 90, + 468, + 150 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We introduce structural self-attention (StructSA) that learns correlation structures for visual representations with the vision transformer.", + "- We provide an in-depth analysis on the relationship between StructSA and self-attention variants with convolutional projections.", + "- Our new transformer network achieves state-of-the-art results on ImageNet-1K, Kinetics-400, Something-Something V1&V2, Diving-48, and FineGym." + ], + "bbox": [ + 76, + 151, + 468, + 287 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 297, + 217, + 314 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Transformer Networks in Vision. Since transformer networks [66] showed remarkable success in natural language processing [5, 14], they have widely been adopted in various computer vision tasks as an alternative to CNNs [1, 7, 17, 58, 59]. Despite of their success, the pure transformer networks require a large amount of training data compared to CNNs where convolution operations introduce desirable inductive biases such as locality and translation invariance allowing more efficient training [17, 53]. This incentivized several methods to inherit the convolutional inductive biases via knowledge distillation [63], local self-attention [27, 45, 54], and architectural fusion [9, 12, 23, 38, 70, 72]. While recent methods using a convolutional projection [18, 41, 70, 72] achieve remarkable improvements, we show that self-attention with a convolutional projection can be derived as a special form of our proposed method.", + "bbox": [ + 75, + 323, + 468, + 566 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Correlation Structure Modeling. Geometric structure of correlations between visual features, i.e., patterns of how they are similar to each other, allows us to understand relational patterns in visual data for various computer vision tasks. Spatial self-correlation in images is used for suppressing photometric variations and revealing geometric layout of objects in the image [30, 33, 57]. Spatial cross-correlation between different images is often used for establishing semantic correspondences capturing structural similarities [24, 50, 55]. In the video domain, several methods exploit the structure of spatial cross-correlations between consecutive frames to estimate optical flow [16, 74] or to learn motion features for action recognition [35, 67]. Kwon et al. [36] propose spatio-temporal self-correlations for learning bi-directional motion features and Kim et al. [32] introduce relational self-attention that generates attention weights dynamically from the structure of the spatio-temporal self-correlations. However, these two methods use self-correlations between the query and its local spatio-temporal neighborhoods only, thus, are limited in learning global relational patterns between distant features. Inspired by this, we introduce structural self", + "bbox": [ + 75, + 568, + 470, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "attention that capturing not only the spatio-temporal local self-correlation but also cross-correlations between features in the distance, utilizing both motion and global spatiotemporal inter-feature relations for learning motion-centric video representations.", + "bbox": [ + 496, + 90, + 890, + 167 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. Our Approach", + "text_level": 1, + "bbox": [ + 498, + 179, + 648, + 196 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We propose a novel self-attention mechanism, named structural self-attention (StructSA), that is designed to leverage rich correlation structures naturally emerging in key-query interactions of attention. We start by revisiting the vanilla self-attention and its limitation and then describe the details of StructSA. We also provide an in-depth analysis of recent self-attention variants with convolutional projections from the perspective of learning structural patterns.", + "bbox": [ + 496, + 204, + 890, + 325 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3.1. Background: Self-Attention", + "text_level": 1, + "bbox": [ + 498, + 333, + 751, + 349 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Self-attention (SA) [66] is a primitive operation for modern transformer networks [1, 17, 63]. Given $N$ input features $\\mathbf{X} = [\\pmb{x}_1,\\dots ,\\pmb{x}_N]\\in \\mathbb{R}^{N\\times C}$ , SA first projects the input $\\mathbf{X}$ linearly into queries, keys, and values, and transforms each $C$ -dimensional input feature $\\pmb{x}_i$ into a contextualized output feature $\\pmb{y}_i$ by", + "bbox": [ + 496, + 356, + 890, + 446 + ], + "page_idx": 1 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sigma \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} ^ {\\top}\\right) \\boldsymbol {V} = \\sum_ {j} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {k} _ {j} ^ {\\top}\\right) \\boldsymbol {v} _ {j} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {1} \\\\ \\boldsymbol {q} _ {i} = \\boldsymbol {x} _ {i} \\boldsymbol {W} ^ {\\mathrm {Q}}, \\quad \\boldsymbol {K} = \\boldsymbol {X} \\boldsymbol {W} ^ {\\mathrm {K}}, \\quad \\boldsymbol {V} = \\boldsymbol {X} \\boldsymbol {W} ^ {\\mathrm {V}} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 516, + 450, + 890, + 515 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "where $\\sigma$ is a softmax function and $W^{Q}, W^{K}, W^{V} \\in \\mathbb{R}^{C \\times C}$ are projection matrices for query $q_{i} \\in \\mathbb{R}^{1 \\times C}$ , keys $K \\in \\mathbb{R}^{N \\times C}$ , and values $V \\in \\mathbb{R}^{N \\times C}$ , respectively. Here we use a 1-dimensional sequence of input features for notational simplicity, and the operation can be extended to a larger dimensionality. After computing a correlation map $q_{i} K^{\\top}$ , the vanilla SA uses individual correlation values independently, i.e., $q_{i} k_{j}^{\\top}$ , for value aggregation while ignoring the structure of the map, which leads to the same output regardless of the order of features. This permutation invariance prevents SA from capturing spatial layouts [27, 57] or motions [32, 36, 44] of objects in images or videos. Positional encoding for SA helps spatial awareness, but the structures of correlations are still not recognized in value aggregation [10, 11, 32].", + "bbox": [ + 496, + 523, + 890, + 750 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3.2. Structural Self-Attention", + "text_level": 1, + "bbox": [ + 500, + 756, + 728, + 771 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We introduce a novel self-attention mechanism, named structural self-attention (StructSA), that effectively incorporates rich structural patterns of query-key correlation into contextual feature aggregation. The StructSA mechanism consists of two steps: (i) structural query-key attention and (ii) contextual value aggregation. Unlike the vanilla query-key attention where individual correlation values themselves are used as attention scores, the structural query-key", + "bbox": [ + 496, + 779, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "18942", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "attention takes the correlation map as a whole and detect structural patterns from it in attention scoring. The subsequent contextual value aggregation then combines the attention scores together to compute diverse sets of kernel weights that are used for dynamically collecting local contexts of value features.", + "bbox": [ + 75, + 90, + 468, + 181 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Structural Query-Key Attention. To transform the vanilla query-key attention into structure-aware one, the structural query-key attention (SQKA) deploy convolutions on top of query-key correlation $\\mathbf{q}_i\\mathbf{K}^\\top$ :", + "bbox": [ + 75, + 184, + 470, + 246 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {A} _ {i} = \\sigma \\left(\\operatorname {c o n v} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K}, \\boldsymbol {U} ^ {\\mathrm {K}}\\right)\\right) \\in \\mathbb {R} ^ {N \\times D}, \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 138, + 253, + 468, + 272 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathbf{U}^{\\mathrm{K}} \\in \\mathbb{R}^{M \\times D}$ is $D$ convolutional kernels with size $M$ . Note that $\\sigma$ is a softmax function taken over all $ND$ entries in the input matrix; we observe that it is empirically more stable compared to $D$ individual softmax operations over $N$ entries. Each element of $A_{i}$ is computed as", + "bbox": [ + 76, + 280, + 468, + 357 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {a} _ {i, j} = \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\in \\mathbb {R} ^ {1 \\times D}, \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 163, + 364, + 468, + 383 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {K} _ {j} = \\boldsymbol {X} _ {(j)} \\boldsymbol {W} ^ {\\mathrm {K}} \\in \\mathbb {R} ^ {M \\times C},\n$$\n", + "text_format": "latex", + "bbox": [ + 168, + 385, + 351, + 405 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\sigma_{j}$ returns a $D$ -dimensional softmax-ed output for $j$ th location and $\\mathbf{X}_{(j)} \\in \\mathbb{R}^{M \\times C}$ is local context features whose context window is centered at $j$ .", + "bbox": [ + 75, + 412, + 468, + 458 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Unlike the vanilla query-key attention, which is agnostic to its neighborhood structure, SQKA is empowered by convolution to recognize a local correlation structure of $\\pmb{q}_i\\pmb{K}_j^{\\top} \\in \\mathbb{R}^{1\\times M}$ and transform it into a $D$ -dimensional vector; the convolution kernels $U^{\\mathrm{K}}$ act as correlation pattern detectors. In particular, when $i = j$ , the correlation map reduces to local self-similarity [57] that is known to be effective for capturing spatial layout patterns [57] or spatiotemporal motion [32, 36], meaning that SQKA recognizes diverse correlation patterns including self-similarity [57] via long-range interaction between query $i$ and context $j$ .", + "bbox": [ + 75, + 459, + 468, + 626 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Contextual Value Aggregation. Given SQKA recognizing structural patterns of correlation, StructSA combines SQKA entries into a weight $\\kappa_{i,j}^{\\mathrm{struct}}$ to aggregate value $\\pmb{v}_j$ :", + "bbox": [ + 75, + 628, + 468, + 676 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {v} _ {j} = \\sum_ {j = 1} ^ {N} \\kappa_ {i, j} ^ {\\text {s t r u c t}} \\boldsymbol {v} _ {j}, \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 96, + 696, + 468, + 739 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathbf{u}^{\\mathrm{V}}\\in \\mathbb{R}^{1\\times D}$ is a vector that linearly combines $D$ pattern scores to the final attention weight.", + "bbox": [ + 75, + 748, + 468, + 777 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We further extend Eq. (4) to generate a spatial kernel not a single scalar for each position $j$ . We call this method contextual aggregation and it has a following form:", + "bbox": [ + 75, + 779, + 468, + 825 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\boldsymbol {U} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {j} = \\sum_ {j = 1} ^ {N} \\kappa_ {i, j} ^ {\\text {s t r u c t}} \\boldsymbol {V} _ {j}, \\tag {5} \\\\ \\boldsymbol {V} _ {j} = \\boldsymbol {X} _ {(j)} \\boldsymbol {W} ^ {\\mathrm {V}} \\in \\mathbb {R} ^ {M \\times C}. \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 91, + 834, + 468, + 897 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Compared to $\\pmb{u}^{\\mathrm{V}}$ that produces a scalar weighting a single element $v_{j}$ , $\\pmb{U}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times D}$ generates spatial kernel dynamically aggregating a local context of value $\\pmb{V}_{j}$ for every position $j$ ; each column of $\\pmb{U}^{\\mathrm{V}}$ , i.e., $\\pmb{U}_{i,d}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times 1}$ , plays a role as a context aggregator that performs a weighted pooling of local context $\\pmb{V}_{j}$ and thus different combinations of these context aggregators result in diverse dynamic kernels $\\kappa_{i,j}^{\\mathrm{struct}}$ for different locations $j$ .", + "bbox": [ + 496, + 90, + 890, + 213 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.3. Relationship to Convolutional Self-Attention", + "text_level": 1, + "bbox": [ + 498, + 223, + 877, + 239 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Recent vision transformers [18, 23, 41, 70, 72] often adopt convolutional inductive biases in the form of self-attention with convolutional projections (ConvSA). In this section, we analyze ConvSA with a lens of StructSA and show its potential and limitation for learning structures from query-key correlations. Different from SA, ConvSA computes project keys and values $K^{\\mathrm{conv}}$ , $V^{\\mathrm{conv}} \\in \\mathbb{R}^{N \\times C}$ using a convolution operation over the input feature map $X$ :", + "bbox": [ + 496, + 247, + 890, + 368 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {K} ^ {\\text {c o n v}} = \\left[ \\boldsymbol {k} _ {1} ^ {\\text {c o n v}}, \\dots , \\boldsymbol {k} _ {N} ^ {\\text {c o n v}} \\right] = \\operatorname {c o n v} (\\boldsymbol {X}, \\boldsymbol {W} ^ {\\mathrm {K}}), \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 524, + 380, + 890, + 398 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {V} ^ {\\text {c o n v}} = \\left[ \\boldsymbol {v} _ {1} ^ {\\text {c o n v}}, \\dots , \\boldsymbol {v} _ {N} ^ {\\text {c o n v}} \\right] = \\operatorname {c o n v} \\left(\\boldsymbol {X}, \\boldsymbol {W} ^ {\\mathrm {V}}\\right), \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 527, + 401, + 890, + 420 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where conv is a convolution operation, and $\\mathbf{W}^{\\mathrm{K}},\\mathbf{W}^{\\mathrm{V}}\\in$ $\\mathbb{R}^{M\\times C\\times C}$ are kernel weights with a kernel size $M$ for key and value projections, respectively.", + "bbox": [ + 496, + 434, + 890, + 481 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In most previous methods, ConvSA is implemented with a channel-wise separable convolution [26], which consists of two factorized convolution operations, i.e., point-wise and channel-wise convolutions [18, 23, 41, 70, 72]. In this case, each key $\\pmb{k}_i^{\\mathrm{conv}}$ and value $\\pmb{v}_i^{\\mathrm{conv}}$ is computed from a local context $X_i$ by", + "bbox": [ + 496, + 481, + 890, + 571 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {k} _ {i} ^ {\\text {c o n v}} = \\boldsymbol {u} ^ {\\mathrm {K} ^ {\\mathsf {T}}} \\boldsymbol {X} _ {i} \\boldsymbol {W} ^ {\\mathrm {K}} = \\boldsymbol {u} ^ {\\mathrm {K} ^ {\\mathsf {T}}} \\boldsymbol {K} _ {i} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 550, + 585, + 890, + 606 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {v} _ {i} ^ {\\text {c o n v}} = \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {X} _ {i} \\boldsymbol {W} ^ {\\mathrm {V}} = \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {i} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 553, + 608, + 890, + 628 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\pmb{W}^{\\mathrm{K}},\\pmb{W}^{\\mathrm{V}}\\in \\mathbb{R}^{C\\times C}$ are weights for the linear projection that are equivalent to point-wise convolution, and $\\pmb{u}^{\\mathrm{K}},\\pmb{u}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times 1}$ are channel-wise convolution weights that are used to spatially aggregate linearly projected context $\\pmb{K}_i$ and $\\pmb{V}_i$ , respectively. Note that here we assume the channel-wise convolution weights are shared across channels for simplicity without loss of generality and the full derivation is available in our supplementary material A.", + "bbox": [ + 496, + 642, + 890, + 763 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "From Eq. (1) combined with Eq. (8) and (9), a transformed output $\\pmb{y}_i$ in ConvSA is obtained by", + "bbox": [ + 496, + 765, + 890, + 796 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {k} _ {j} ^ {\\text {c o n v} ^ {\\mathsf {T}}}\\right) \\boldsymbol {v} _ {j} ^ {\\text {c o n v}} \\\\ = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {u} ^ {\\mathrm {K}}\\right) \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {j} = \\sum_ {j = 1} ^ {N} \\boldsymbol {\\kappa} _ {i, j} ^ {\\text {c o n v}} \\boldsymbol {V} _ {j}, \\tag {10} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 517, + 808, + 890, + 897 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "18943", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/ab91793394a81af57e0df3bd0aeac68ed72687683e1485412ba0781d66a8b8c3.jpg", + "image_caption": [ + "Figure 2. Visualization of ConvSA and StructSA on ImageNet-1K. The query location $i$ is set to the center of the image and the kernel size $M = 3 \\times 3$ . Given the left input image, we compare ConvSA ( $D = 1$ ) and StructSA ( $D = 8$ ) in terms of (a) $D$ attention maps $\\sigma_{jD}(\\pmb{q}_i \\pmb{K}_j^\\top \\pmb{U}^{\\mathrm{KT}})$ , (b) local feature aggregation patterns learned in $\\pmb{U}^V$ , and (c) the combinations of (a) and (b). Note that in (c), each location $j$ has an aggregation map of the kernel size $M = 3 \\times 3$ and thus we also show enlarged images for four different sample locations $j$ ." + ], + "image_footnote": [], + "bbox": [ + 140, + 88, + 834, + 234 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\sigma_{j}$ is $j$ th entry of the softmax over $N$ tokens. This reveals that an attention score $\\sigma_{j}(\\pmb{q}_{i}\\pmb{k}_{j}^{\\mathrm{conv}^{\\top}})$ is computed by projecting a local correlation map $\\pmb{q}_{i}\\pmb{K}_{j}^{\\top} \\in \\mathbb{R}^{1 \\times M}$ by $\\pmb{u}^{\\mathrm{K}}$ , and a dynamic kernel $\\kappa_{i,j}^{\\mathrm{conv}}$ for the final feature aggregation of $\\pmb{V}_{j}$ is obtained by weighting the aggregation pattern presented in $\\pmb{u}^{\\mathrm{V}}$ using the computed attention map. Given that correlation map $\\pmb{q}_{i}\\pmb{K}_{j}^{\\top}$ represents a structural pattern, we can interpret that $\\pmb{u}^{\\mathrm{K}}$ acts as a pattern detector that extracts a specific correlation pattern from $\\pmb{q}_{i}\\pmb{K}_{j}^{\\top}$ , whereas $\\pmb{u}^{\\mathrm{V}}$ plays a role as a context aggregator that performs a weighted pooling of local context $\\pmb{V}_{j}$ . Due to the presence of this pattern detector $\\pmb{u}^{\\mathrm{K}}$ and its corresponding context aggregator $\\pmb{u}^{\\mathrm{V}}$ , ConvSA can leverage a structural pattern of input for context aggregation.", + "bbox": [ + 75, + 316, + 472, + 534 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Limitation. Although ConvSA can learn, unlike SA, a structural pattern over correlation maps by $\\pmb{u}^{\\mathrm{K}}$ , it only learns a single pattern and encodes various shapes in correlation maps into a scalar value representing the similarity against the learned pattern; as the result, the final dynamic kernel $\\kappa_{i,j}^{\\mathrm{conv}}$ for every $j$ reduces to the identical pattern of $\\pmb{u}^{\\mathrm{V}}$ with different weighting only. This lack of expressiveness in $\\pmb{u}^{\\mathrm{K}}$ and $\\pmb{u}^{\\mathrm{V}}$ prevents ConvSA from capturing diverse structural patterns and generating diverse dynamic kernels. In constraint, StructSA learns $D$ different pattern extractors in $\\pmb{U}^{\\mathrm{K}}$ and represents various local correlation shapes by a set of $D$ similarity scores. These scores are then combined with the $D$ context aggregators in $\\pmb{U}^{\\mathrm{V}}$ ; different combinations of these context aggregators result in diverse dynamic kernels $\\kappa_{i,j}^{\\mathrm{struct}}$ for different locations $j$ .", + "bbox": [ + 75, + 542, + 472, + 773 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Visualization. The aforementioned difference between ConvSA and StructSA, as well as their effects, can be better understood by visualizing the kernel computation process. Figure 2 provides such a visual comparison of how structural patterns are used in ConvSA and StructSA given an example image from ImageNet-1K [13]. From a query-key correlation map, ConvSA generates a single attention map (Fig. 2a, top). These scores are then combined with the", + "bbox": [ + 75, + 779, + 472, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "context aggregator $\\boldsymbol{u}^{\\mathrm{V}}$ (Fig. 2b, top), which conveys only a single aggregation pattern. This causes local features to be aggregated with the identical pattern in $\\boldsymbol{u}^{\\mathrm{V}}$ for all locations, and the only difference remains in their scales (Fig. 2c, top). In contrast, StructSA generates diverse attention maps using $D$ pattern detectors, each capturing different structures in the query-key correlation maps (Fig. 2a, bottom), and combines them with different context aggregators (Fig. 2b, bottom) resulting in rich aggregation patterns for different locations $j$ (Fig. 2c, bottom). For more in-depth comparison, please refer to our supplementary material D.", + "bbox": [ + 496, + 316, + 893, + 484 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 494, + 633, + 512 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To validate the effectiveness of the proposed method on visual representation learning, we conduct extensive experiments on image and video classification benchmarks.", + "bbox": [ + 496, + 520, + 892, + 566 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 500, + 573, + 689, + 589 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Datasets. ImageNet-1K [13] is a large-scale dataset with 1.2M images labeled by 1000 object classes. Kinetics-400 [31] is one of the most popular large-scale video datasets with 400 action classes. We use 241k action clips available online. Something-Something-V1 & V2 [22, 49] are both large-scale action recognition benchmarks, including 108k and 220k action clips, respectively. Both datasets share the same motion-centric action classes, e.g., 'pushing something from left to right,' so thus capturing fine-grained motion is crucial to achieving the better performance. Diving-48 [39] is a fine-grained action benchmark that is heavily dependent on temporal modeling [3], containing 18k videos with 48 diving classes. FineGym [56] is a motion-centric benchmark that includes gymnastics action classes with severe deformations.", + "bbox": [ + 496, + 595, + 893, + 821 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Training & Testing Protocols. For image classification, we follow the training strategy of DeiT [63] adopting random clipping, random horizontal flipping, mixup [80], cutmix [78], random erasing [81] and label-smoothing [51] to", + "bbox": [ + 496, + 839, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "18944", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "augment the input images for training. We train all models from scratch for 300 epochs using AdamW optimizer [48] with a cosine learning rate schedule including 5 warm-up epochs. The batch size, learning rate, and weight decay are set to 1024, 1e-3, and 0.05, respectively. For comparison on stronger experiment setup [29, 38, 41, 77], we also train our models using Token Labeling [29] and larger resolution images, i.e., $384 \\times 384$ , following the protocols in [38].", + "bbox": [ + 75, + 90, + 468, + 210 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For video classification, we follow training protocols and data augmentation recipes in MViT [18]. For Kinetics-400, we sample 16 or 32 frames using the dense sampling strategy [71]. We temporally inflate the model weights pretrained on ImageNet-1K and finetune it for 110 epochs including 10 warm-up epochs. We use AdamW [48] optimizer with the cosine learning rate schedule. We set the batch size, learning rate, weight decay, and stochastic depth rate to 64, 2e-4, 0.05, and 0.1, respectively. For Something-Something, Diving-48, and FineGym, we utilize the segment-based sampling strategy [68] and do not use the random horizontal flip for data augmentation. We initialize the model with the weights pretrained on Kinetics-400 and finetune the model for 60 epochs including 5 warm-up epochs. Other training hyperparameters are the same as those for Kinetics-400. For testing, we sample multiple clips at different temporal indices for each clip or cropping different spatial regions and then obtain the final score by computing an average over the scores for each clip. We train all models once using 8 to 16 NVIDIA A100 GPUs.", + "bbox": [ + 75, + 210, + 470, + 513 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Metrics. We measure top-1 and top-5 accuracy as performance metrics, except for FineGym, we compute averaged per-class top-1 accuracy. As efficiency metrics, we measure the number of parameters and FLOPs.", + "bbox": [ + 76, + 517, + 468, + 578 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Analysis of StructSA", + "text_level": 1, + "bbox": [ + 76, + 587, + 272, + 602 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "StructSA can be readily integrated into any existing ViTs to enhance visual representations by capturing correlation structures. In this subsection, we experimentally validate and analyze the impact of StructSA. Here, for a direct comparison with SA, we choose to use DeiT-S [63] as the baseline backbone; DeiT is a pure SA-based vision transformer and thus adequate for validating the effect of StructSA, avoiding any intervention of additional components. In this analysis, we replace all the SA layers in DeiT with StructSA layers. The evaluations are done on ImageNet-1K [13] and Something-Something-V1 [22] benchmarks while varying the structure dimension $D$ , the kernel size $M$ , and context aggregation methods. We follow the training and testing protocols in Sec. 4.1, except that we directly finetune the ImageNet-1K-pretrained model on Something-Something-V1 using random cropping only for data augmentation.", + "bbox": [ + 75, + 609, + 468, + 851 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Structure Dimension $D$ . Table 1a shows the effect of the structure dimension $D$ . Compared to the baseline with the vanilla SA $(D = 0)$ , applying ConvSA $(D = 1)$ improves", + "bbox": [ + 75, + 854, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/88739604cca06744d127917e56266c6d5a9dede86ea84abf4aecd80a2bac104c.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DImageNet-1KSomething V1
top-1top-5top-1top-5
080.595.048.376.6
180.895.249.777.6
280.995.250.178.0
481.195.450.478.2
881.395.550.678.5
", + "bbox": [ + 506, + 88, + 887, + 188 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/e70cdd99388ac7ca9848dbaccef98bcf6d061afc24c88a28ae70c97beb6e7a3f.jpg", + "table_caption": [ + "(a) Structure dimension $D$" + ], + "table_footnote": [], + "table_body": "
MImageNet-1KSomething V1
top-1top-5top-1top-5
-80.595.048.376.6
1 × 1 (×1)80.695.048.576.9
3 × 3 (×3)81.195.450.478.2
5 × 5 (×5)81.195.450.578.2
7 × 7 (×7)81.095.250.578.1
", + "bbox": [ + 506, + 208, + 887, + 308 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/f3af4afcee8cd911d8ca7427c0bde9443787c85a5846bebdd1a7150f66d12353.jpg", + "table_caption": [ + "(b) Kernel size $M$" + ], + "table_footnote": [], + "table_body": "
aggregationImageNet-1KSomething V1
top-1top-5top-1top-5
-80.595.048.376.6
element80.995.249.677.5
context81.195.450.478.2
", + "bbox": [ + 506, + 328, + 887, + 402 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "(c) Context aggregation method.", + "bbox": [ + 604, + 404, + 787, + 416 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Table 1. Ablation studies on ImageNet-1K and Something-Something V1. Top-1 and top-5 accuracies $(\\%)$ are shown. Otherwise specified, we use 16 frames as input and set $D = 4$ $M = 3\\times 3\\times 3$ , and patch-wise context aggregation as default.", + "bbox": [ + 498, + 425, + 890, + 481 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "the performance as shown in [9, 72]. As we increase $D$ from 1 to 8, we obtain gradual improvements up to $0.5\\% \\mathrm{p}$ and $0.9\\% \\mathrm{p}$ at top-1 accuracy on ImageNet-1K and Something-Something-V1. This confirms the limitation of ConvSA and the effectiveness of StructSA.", + "bbox": [ + 498, + 501, + 890, + 575 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Kernel Size $M$ . In Table 1b, we also investigate different kernel sizes $M$ . Compared to the baseline, the model with the kernel size $M = 1 \\times 1 \\times 1$ performs similar accuracies on both datasets whereas that with $M = 3 \\times 3 \\times 3$ improves the performance dramatically; it validates the effectiveness of learning geometric structures. The performance saturates as the kernel size gets larger than $5 \\times 5 \\times 5$ .", + "bbox": [ + 496, + 580, + 890, + 686 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Context Aggregation Method. In Table 1c, we also compare different context aggregation method. As a result, patch-wise aggregation performs $0.2\\% \\mathrm{p}$ and $0.7\\% \\mathrm{p}$ at top-1 accuracy on ImageNet-1K and Something-Something-V1. For more ablation experiments, please refer to our supplementary material B.", + "bbox": [ + 496, + 691, + 890, + 781 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3. Comparison to State of the Art", + "text_level": 1, + "bbox": [ + 500, + 792, + 772, + 808 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3.1 Structural Vision Transformer (StructViT)", + "text_level": 1, + "bbox": [ + 500, + 815, + 851, + 830 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To build an advanced vision transformer considering the recent development of multiscale representation learning [18, 38, 41, 70, 76], we integrate StructSA into UniFormer [38]. The transformer network, dubbed the Structural Vision", + "bbox": [ + 498, + 839, + 890, + 898 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "18945", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/3695f38f04d1ff8215235b62708bddf0e3f45204dcb36bc7640e4c3025a9e177.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
modeltype# blocks# channels (# heads)
StructViT-S[C,C,S,S][3,4,8,3][64,128,320(5),512(8)]
StructViT-B[C,C,S,S][5,8,20,7][64,128,320(5),512(8)]
StructViT-L[C,C,S,S][5,10,24,7][128,192,448(7),640(10)]
", + "bbox": [ + 80, + 74, + 470, + 132 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Transformer (StructViT) is constructed by replacing all vanilla self-attention in UniFormer with StructSA as a main building block. It takes as input either a video clip or an image $\\tilde{\\pmb{X}}\\in \\mathbb{R}^{T\\times H\\times W\\times 3}$ , where $T$ , $H$ , and $W$ denotes the temporal length, height, and width of the input, respectively. For images as input, we set the temporal length $T = 1$ . Before being fed into our networks, the input video is tokenized into overlapping 3D tablets of size $3\\times 4\\times 4\\times 3$ with a stride of $2\\times 4\\times 4$ while the input image is into nonoverlapping 2D patches of size $4\\times 4\\times 3$ .", + "bbox": [ + 75, + 179, + 468, + 329 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Our networks comprise four stages, each of which has multiple neural blocks, and leverage a hierarchical design with decreasing resolutions and increasing number of channels from early to late stages following [38]. For the first two stages, each block consists of a conditional positional encoding layer [9], a convolutional layer, and an MLP, whereas the convolutional layer is replaced by a StructSA layer in the blocks in the last two stages. Note that when we employ StructSA, we use multi-head configurations and do not share weights across channels for channel-wise convolutions. We build three different StructViT architectures as shown in Table 2. Our models are comparable to UniFormers [38] in the same sizes as our model configurations are based on UniFormer's; adding the structure dimension $D$ in StructSA introduces only few additional parameters.", + "bbox": [ + 75, + 330, + 468, + 556 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In practice, StructSA introduces additional FLOPs for processing instances compared to the vanilla SA. One way of building an efficient StructSA is to adopt a larger stride in the key/value projections, which effectively reduces the number of keys and values [18, 41]. We test a few variants with a larger stride to see the performances of StructViT with matching FLOPs with their corresponding UniFormer architectures. We denote each model with StructViT- $X$ - $D-S$ where $X$ , $D$ , and $S$ represent the architecture size, the structure dimension, and the stride, respectively. For training, we use stochastic depth [28] with the probability of $0.1/0.3/0.4$ for StructViT-S/B/L, respectively. We use random cropping only for StructViT-B on Something-Something, Diving-48, and FineGym. We use 8 NVIDIA A100 GPUs for training StructViT-S/B and 16 GPUs for StructViT-L. We follow the protocols in Sec. 4.1 for the rest.", + "bbox": [ + 75, + 556, + 470, + 800 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3.2 Image Classification", + "text_level": 1, + "bbox": [ + 76, + 816, + 272, + 830 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In Table 3, we compare StructViT with other state-of-the-art CNNs, ViTs, and their hybrid models. The results show that StructViT outperforms other methods in all sizes. Compared to EfficientNets [61, 62] that are obtained by exten", + "bbox": [ + 75, + 839, + 468, + 902 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/dd22e93b74987593cd89936071fddffe2ba1c02e3f702c2681af71fa07d6ddf0.jpg", + "table_caption": [ + "Table 2. Configurations of StructViT variants. \"C\" and \"S\" denote a convolution and StructSA block, respectively." + ], + "table_footnote": [], + "table_body": "
method#params (M)FLOPs (G)IN1K top-1
EfficientNet-B5 [61]309.983.6
ConvNext-T [46]294.583.1
DeiT-S [63]224.679.9
PVT-S [70]253.879.8
Swin-T [45]294.581.3
Focal-T [75]294.982.2
CSwin-T [15]234.382.7
CvT-13 [72]204.581.6
CoAtNet-0 [12]254.281.6
LV-ViT-S [29]266.683.3
UniFormer-S [38]223.682.9
UniFormer-S*↑384 [38]2211.984.6
MViTv2-S [41]244.782.3
StructViT-S-4-2233.682.9
StructViT-S-4-1234.383.2
StructViT-S-8-1245.483.3
StructViT-S-4-1*234.384.0
StructViT-S-4-1*↑3842317.385.2
EfficientNet-B7 [61]6639.284.3
ConvNext-B [46]8915.483.8
ConvNext-B ↑384 [46]8945.085.1
PVT-L [70]619.881.7
Swin-S [45]508.783.0
Focal-S [75]519.183.5
CSwin-S [15]356.983.6
CvT-21 [72]327.182.5
CoAtNet-1 [12]428.483.3
LV-ViT-M [29]5616.084.1
UniFormer-B [38]508.383.8
UniFormer-B*↑384 [38]5027.286.0
MViTv2-S [41]357.083.6
MViTv2-B [41]5210.284.4
MViTv2-B ↑384 [41]5236.785.2
StructViT-B-4-2518.384.0
StructViT-B-4-1519.984.2
StructViT-B-8-15212.084.3
StructViT-B-4-1*519.985.4
StructViT-B-4-1*↑3845140.786.5
EfficientNetV2-L [62]1215285.7
ConvNext-L [46]19834.484.3
ConvNext-L ↑384 [46]198101.085.5
Swin-B [45]8815.483.3
Focal-B [75]9016.083.8
CSwin-B [15]7815.084.2
CoAtNet-3 [12]16834.784.5
LV-ViT-L ↑288 [29]15059.085.3
UniFormer-L* [38]10012.685.6
UniFormer-L*↑384 [38]10039.286.0
MViTv2-L [41]21842.185.3
MViTv2-L ↑384 [41]218140.286.0
StructViT-L-4-1*10315.486.0
StructViT-L-4-1*↑38410385.286.7
", + "bbox": [ + 504, + 73, + 890, + 818 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 3. Comparisons to the state-of-the-art methods on ImageNet-1K. *Trained with Token Labeling [29].", + "bbox": [ + 500, + 819, + 890, + 847 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "sive architecture search, our models show comparable or even better performances in both base and large configura", + "bbox": [ + 498, + 869, + 890, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "18946", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "tions, requiring much less amount of computational cost. Compared to our baseline, UniFormers, StructViTs consistently improve top-1 accuracy regardless of their sizes, demonstrating the benefits of learning geometric structures in image understanding. We further evaluate our models on stronger setup using Token Labeling [29] and $384 \\times 384$ images, and observe consistent improvements over the baselines. While StructSA introduces some additional FLOPs, we also test variants whose stride for key/value convolutions is set to 2 (S-4-2 and B-4-2) matching its FLOPs to that of the baseline; we still observe some gain with the base model (B-4-2) without additional FLOPs while the small model (S-4-2) shows comparable results. For more comprehensive analysis, we provide experimental results on dense prediction tasks, i.e., object detection, semantic segmentation, and instance segmentation. Please refer to our supplementary material C for the detail.", + "bbox": [ + 75, + 90, + 472, + 349 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3.3 Video Classification", + "text_level": 1, + "bbox": [ + 76, + 372, + 269, + 386 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Kinetics-400. Table 4 compares our method with previous state-of-the-art methods on Kinetics-400. Each block in the table groups methods based on their network structures: CNNs, ViTs, and hybrid methods. We first observe that our best model (B-4-1) achieves state-of-the-art performance. Our method outperforms CNN-based approaches even with less computational cost (S-4-2) in most cases. Compared to MoViNets [34] which are the most advanced CNNs obtained by an extensive NAS, our method shows comparable scores with fewer FLOPs (S-4-1).", + "bbox": [ + 75, + 398, + 468, + 547 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "When we compare our model to the ViT-based ones, our model outperforms them by large margins while using significantly fewer compute. For instance, StructViT-B-4-1 with single crop (second last row in Table 4) shows top-1 accuracy gain by $1.6\\%$ while using only $55\\%$ of computes compared to MTV-B, the best performing ViT-based model. Note also that our model is pretrained on ImageNet-1K, which is much smaller than ImageNet-21K on which the ViT-based models are pretrained.", + "bbox": [ + 75, + 550, + 468, + 686 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Finally, our best models (S-8-1 & B-4-1) show $0.5\\%$ p to $0.8\\%$ p accuracy gains over the baseline UniFormer models in different size configurations. When we use larger strides (S-4-2 and B-4-2) to match the FLOPs of the baselines, we still observe accuracy gains ranging from $0.2\\%$ p to $0.3\\%$ p.", + "bbox": [ + 75, + 686, + 468, + 762 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Something-Something, Diving-48 and FineGym. Table 5a summarizes the results on Something-Something-V1&V2. We observe the same trends as on Kinetics-400. StructViT-S-4-2 outperforms UniFormer-S on Something-Something-V2 by $0.6\\%$ p in top-1 accuracy, and StructViTS-8-1 enlarges the gap to $1.3\\%$ p, leveraging correlation structures more effectively. StructViT-B-4-1 achieves new state-of-the-art performances on both V1 and V2 without the strong data augmentation methods used in [38, 41].", + "bbox": [ + 75, + 763, + 468, + 901 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/736948275a44206204c4969467a9cf75ac8ce7ee23b1c85db110ff579e397811.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
methodpretrainframe× crop×clipFLOPs (G)K400 top-1top-5
SlowFast+NL [20]-16×3×10702079.893.9
ip-CSN [64]Sports1M32×3×10327079.293.8
X3D-XL [19]-16×3×10145279.193.9
MoViNet-A5 [34]-120×1×128180.994.9
MoViNet-A6 [34]-120×1×138681.595.3
TimeSformer-HR [4]IN-21K16×3×1510979.794.4
TimeSformer-L [4]IN-21K96×3×1714080.794.7
X-ViT [6]IN-21K16×3×185080.294.7
Mformer-HR [52]IN-21K16×3×102876481.195.2
ViViT-L [1]IN-21K16×3×41735280.694.7
Swin-B [47]IN-1K32×3×4338480.694.6
Swin-B [47]IN-21K32×3×4338482.795.5
MTV-B [73]IN-21K32×3×4479081.895.0
MViT-B,16×4 [18]-16×1×535378.493.5
MViT-B,32×3 [18]-32×1×585080.294.4
Dualformer-S [42]IN-1K32×1×463680.694.9
Dualformer-B [42]IN-1K32×1×4107281.195.0
UniFormer-S [38]IN-1K16×1×416780.894.7
UniFormer-B [38]IN-1K32×1×4103682.995.4
MViTv2-B,32×3 [41]-32×1×5112582.995.7
StructViT-S-4-2IN-1K16×1×416981.195.5
StructViT-S-4-1IN-1K16×1×432781.495.7
StructViT-S-8-1IN-1K16×1×454181.695.8
StructViT-B-4-2IN-1K32×1×4104583.195.5
StructViT-B-4-1IN-1K32×1×4265883.395.6
StructViT-B-4-1IN-1K32×3×4797483.495.8
", + "bbox": [ + 504, + 89, + 890, + 474 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 4. Comparisons to the state-of-the-art methods on Kinetics-400.", + "bbox": [ + 500, + 478, + 890, + 503 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 5b and Table 5c show the results on Diving-48 [39] and FineGym [56]. Our models outperform the baseline, UniFormer-B, obtaining significant accuracy gains by $0.9\\% \\mathrm{p}$ and $0.7\\% \\mathrm{p}$ on Diving-48 and FineGym, respectively. This indicates that learning spatio-temporal correlation structures play a crucial role in capturing fine-grained motion patterns. Our model sets new state-of-the-art performances with large margins (4.1% p on Diving-48; 3.3% p and 3.1% p on FineGym) over the previous methods without additional box annotations on both datasets. Note that ORViT [25] uses additional object bounding box annotations to train an object detector.", + "bbox": [ + 496, + 527, + 890, + 709 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Visualizations of StructSA", + "text_level": 1, + "bbox": [ + 500, + 736, + 736, + 750 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Figure 3 visualizes example dynamic kernels $\\kappa_{i,j}^{\\mathrm{struct}}$ computed from self-similarity map ( $i = j$ ) on Something-Something-V1 to illustrate how StructSA encodes motion features from the spatiotemporal correlation structure. We observe that StructSA builds kernels for spatiotemporal gradient filters similar to those that are already known to be effective for capturing different types of motions [60], e.g., Sobel filters (first) or Laplacian filters (second and third), over local contexts similarly to [32].", + "bbox": [ + 496, + 763, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "18947", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/5065ec2e8c1a8b74176a631a9127c774cfa9eb8390bb50d4eaa628b248d4f8c1.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
methodpretrainframe× crop×clipFLOPs (G)Something V1 top-1top-5Something V2 top-1top-5
TEA [40]IN-1K16×1×17051.980.3--
MSNet [35]IN-1K16×1×110152.182.364.789.4
CT-Net [37]IN-1K16×1×17552.580.964.589.3
TDN [69]IN-1K16×1×17253.982.165.389.5
SELFYNet [36]IN-1K16×1×17754.382.965.789.8
RSANet [32]IN-1K16×1×17254.081.166.089.9
TimeSformer-HR [4]IN-21K16×3×15109--62.5-
TimeSformer-L [4]IN-21K96×3×17140--62.3-
ViViT-L [1]K40016×3×411892--65.489.8
X-ViT [6]IN-21K32×3×11270--65.490.7
Mformer-HR [52]K40016×3×12876--67.190.6
Mformer-L [52]K40032×3×13555--68.191.2
Swin-B [47]K40032×3×1963--69.692.7
MViT-B,64×3 [18]K40064×1×31365--67.790.9
MViT-B-24,32×3 [18]K60032×1×3708--68.791.5
UniFormer-S [38]K40016×3×112557.284.967.791.4
UniFormer-B [38]K40032×3×177760.987.371.292.8
MViTv2-B [41]K40032×3×1675--70.592.7
StructViT-S-4-2K40016×3×112657.685.368.391.3
StructViT-S-4-1K40016×3×124658.085.568.891.9
StructViT-S-8-1K40016×3×140558.085.769.092.1
StructViT-B-4-2K40032×3×178461.187.771.192.7
StructViT-B-4-1K40032×3×1196361.387.871.593.1
", + "bbox": [ + 81, + 80, + 609, + 428 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/ff01851c0b239d11d66c42eb51def91af901bb44bafac9604e36367480208b5c.jpg", + "table_caption": [ + "(a) Something-Something V1 & V2" + ], + "table_footnote": [], + "table_body": "
modeltop-1
SlowFast-R101 [20]77.6
TimeSformer [4]75.0
TimeSformer-HR [4]78.0
SViT-DD [2]79.8
TimeSformer-L [4]81.0
TQN [79]81.8
RSANet-R50 [32]84.2
UniFormer-B* [38]87.4
ORViT† [25]88.0
StructViT-B-4-287.8
StructViT-B-4-188.3
", + "bbox": [ + 625, + 80, + 879, + 250 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/1a982e090d726e0b1fd75c3e9da2a785af670c1e35d33d68b492c0fa48da5055.jpg", + "table_caption": [ + "(b) Diving-48" + ], + "table_footnote": [], + "table_body": "
modelGym288Gym99
TRN [82]33.168.7
I3D [8]27.963.2
TSM [43]34.870.6
\\(\\mathsf{TSM}_{\\text{Two-stream}}\\) [43]46.581.2
RSANet-R50 [32]50.986.4
UniFormer-B* [38]53.588.9
StructViT-B-4-253.889.3
StructViT-B-4-154.289.5
", + "bbox": [ + 624, + 300, + 879, + 428 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "(c) FineGym", + "bbox": [ + 715, + 429, + 787, + 441 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 5. Comparisons to the state-of-the-art methods on three motion-centric video classification benchmarks. Our StructViT achieves new state-of-the-art on all the benchmarks. For FineGym, we measure averaged per-class accuracy while top- $k$ accuracy is measured for Something-Something and Diving-48. *Reproduced by our experimental setup. †Trained with additionalbbox annotations.", + "bbox": [ + 75, + 446, + 892, + 489 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7625cce2a7f4375b45d1b51a45b274f3a79a0a4db17213043d10df2843ac46b9.jpg", + "image_caption": [ + "input video" + ], + "image_footnote": [], + "bbox": [ + 292, + 503, + 810, + 585 + ], + "page_idx": 7 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {\\kappa} _ {i, j} ^ {\\mathrm {s t r u c t}} = \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K} ^ {\\top}}\\right) \\boldsymbol {U} ^ {\\mathrm {V}}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 619, + 279, + 643 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/07ee50b9ed555248ce4bea9fc5c9ba633f4acc168a7081ecbaff8ab446315d67.jpg", + "image_caption": [ + "Figure 3. Visualization of dynamic kernels $\\kappa_{i,j}^{\\mathrm{struct}}$ in StructSA on Something-V1. The top row shows the input frames that contain the input spatiotemporal local context (indicated by green boxes) used in the dynamic kernel computation. The bottom row presents the resulting dynamic kernels $\\kappa_{i,j}^{\\mathrm{struct}}$ for a StructSA head when $i = j$ . Note that the computed dynamic kernels are computed with self-similarity map $(i = j)$ to illustrate its effectiveness in capturing motions in videos. We use StructViT-S-4-1 with $M = 5 \\times 5 \\times 5$ ." + ], + "image_footnote": [], + "bbox": [ + 297, + 593, + 388, + 660 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/b355afc4d5fad76f45c8b3acc795d22c211f073d0bc45f8b3b214df1abf9f63d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 401, + 594, + 491, + 660 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/8f0897e41f1a0838d1d69fd6fd609aea68af6459ad27bc8ebef4c931a25ffdc1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 506, + 594, + 594, + 660 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7852b71cb59cdca57a65394c362561cd2693c647071eeb462c9c2d31d5526c2c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 612, + 595, + 700, + 660 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a5314ee2556c02f276468696ab520bf32c76714974f695db5306447c10c58665.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 717, + 595, + 805, + 660 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 76, + 739, + 194, + 753 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We have introduced a novel self-attention mechanism, StructSA, that exploits rich structural patterns of querykey correlation for visual representation learning. StructSA leverages spatial (and temporal) structures of local correlations and aggregates chunks of local features globally across entire locations. Structural Vision Transformer (StructViT) using StructSA as the main attention module achieves state-of-the-art results on both image and video classification benchmarks. We believe leveraging structural", + "bbox": [ + 75, + 763, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "patterns of correlation in attention will also benefit other tasks in computer vision and natural language processing. We leave this for future work.", + "bbox": [ + 496, + 739, + 890, + 785 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements This work was supported by the IITP grants (No. 2022-0-00290: Visual Intelligence for space-time understanding and generation $(45\\%)$ , No. 2022-0-00264: Comprehensive video understanding and generation with knowledge-based deep logic $(50\\%)$ , No. 2019-0-01906: AI graduate school program at POSTECH $(5\\%))$ funded by Ministry of Science and ICT, Korea.", + "bbox": [ + 496, + 794, + 892, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "18948", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Anurag Arnab, Mostafa Dehghani, Georg Heigold, Chen Sun, Mario Lučić, and Cordelia Schmid. 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In ECCV, 2018. 8" + ], + "bbox": [ + 501, + 90, + 892, + 273 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "18951", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Correlation Structures for Vision Transformers/3e02995b-1bff-4a49-8649-a6ad79f7017d_model.json b/2024/Learning Correlation Structures for Vision Transformers/3e02995b-1bff-4a49-8649-a6ad79f7017d_model.json new file mode 100644 index 0000000000000000000000000000000000000000..8a877ac8e57d3c4a00620b8db6614d57bf4b8ad8 --- /dev/null +++ b/2024/Learning Correlation Structures for Vision Transformers/3e02995b-1bff-4a49-8649-a6ad79f7017d_model.json @@ -0,0 +1,2752 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.044 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.196, + 0.131, + 0.776, + 0.154 + ], + "angle": 0, + "content": "Learning Correlation Structures for Vision Transformers" + }, + { + "type": "text", + "bbox": [ + 0.195, + 0.18, + 0.304, + 0.2 + ], + "angle": 0, + "content": "Manjin Kim1" + }, + { + "type": "text", + "bbox": [ + 0.324, + 0.181, + 0.495, + 0.199 + ], + "angle": 0, + "content": "Paul Hongsuck \\(\\mathrm{Seo}^{2*}\\)" + }, + { + "type": "text", + "bbox": [ + 0.508, + 0.181, + 0.651, + 0.198 + ], + "angle": 0, + "content": "Cordelia Schmid3" + }, + { + "type": "text", + "bbox": [ + 0.671, + 0.181, + 0.776, + 0.198 + ], + "angle": 0, + "content": "Minsu Cho\\(^{1*}\\)" + }, + { + "type": "text", + "bbox": [ + 0.203, + 0.203, + 0.303, + 0.221 + ], + "angle": 0, + "content": "\\(^{1}\\)POSTECH" + }, + { + "type": "text", + "bbox": [ + 0.39, + 0.203, + 0.536, + 0.223 + ], + "angle": 0, + "content": "\\(^{2}\\)Korea University" + }, + { + "type": "text", + "bbox": [ + 0.617, + 0.203, + 0.762, + 0.223 + ], + "angle": 0, + "content": "3Google Research" + }, + { + "type": "text", + "bbox": [ + 0.209, + 0.228, + 0.753, + 0.245 + ], + "angle": 0, + "content": "http://cvlab.postech.ac.kr/research/StructViT/" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.28, + 0.314, + 0.296 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.312, + 0.474, + 0.523 + ], + "angle": 0, + "content": "We introduce a new attention mechanism, dubbed structural self-attention (StructSA), that leverages rich correlation patterns naturally emerging in key-query interactions of attention. StructSA generates attention maps by recognizing space-time structures of key-query correlations via convolution and uses them to dynamically aggregate local contexts of value features. This effectively leverages rich structural patterns in images and videos such as scene layouts, object motion, and inter-object relations. Using StructSA as a main building block, we develop the structural vision transformer (StructViT) and evaluate its effectiveness on both image and video classification tasks, achieving state-of-the-art results on ImageNet-1K, Kinetics-400, Something-Something V1 & V2, Diving-48, and FineGym." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.551, + 0.21, + 0.567 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.577, + 0.47, + 0.757 + ], + "angle": 0, + "content": "How visual elements interact with each other in space and time is a crucial cue for visual understanding, e.g., recognizing actions in a video or analyzing scene layout patterns in an image. In computer vision, such relational patterns are effectively captured by the structure of correlations or similarities across visual elements in different positions [3, 57]; a correlation structure of an image reveals spatial layouts of similar patterns [30, 33] and that of a video provides bidirectional motion likelihoods [32, 36]. The ability to recognize those structural patterns may allow to better perform visual reasoning and generalize against challenging appearance variations and domain shifts [21, 65]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.758, + 0.47, + 0.879 + ], + "angle": 0, + "content": "In this work, we introduce a novel self-attention mechanism, named structural self-attention (StructSA), that effectively leverages diverse structural patterns for visual representation learning. While the standard self-attention mechanism uses raw query-key correlations individually and ignores their geometric structures, the proposed StructSA recognizes diverse structural patterns from the correlations between the query and local chunks of keys via convolu" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.28, + 0.576, + 0.336 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.578, + 0.281, + 0.648, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.652, + 0.281, + 0.722, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.725, + 0.281, + 0.794, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.798, + 0.281, + 0.869, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.645, + 0.337, + 0.729, + 0.351 + ], + "angle": 0, + "content": "(a) Input video" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.356, + 0.575, + 0.412 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.578, + 0.356, + 0.648, + 0.412 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.652, + 0.356, + 0.722, + 0.412 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.725, + 0.356, + 0.795, + 0.412 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.798, + 0.356, + 0.869, + 0.412 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.601, + 0.414, + 0.773, + 0.428 + ], + "angle": 0, + "content": "(b) Query-key correlation map" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.432, + 0.889, + 0.556 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.578, + 0.56, + 0.795, + 0.574 + ], + "angle": 0, + "content": "(c) Structural self-attention (StructSA)" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.58, + 0.895, + 0.665 + ], + "angle": 0, + "content": "Figure 1. Structural Self-Attention. Given an input video and a query indicated by the red box in (a), the query-key correlation maps in (b) clearly reveal the structures of spatial layout and motion with respect to the query. The proposed attention mechanism in (c) is designed to leverage these rich structural patterns for computing attention scores in the self-attention process." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.685, + 0.893, + 0.867 + ], + "angle": 0, + "content": "tion and uses them to dynamically aggregate local contexts of value features, effectively capturing rich structural patterns such as scene layouts, object motion, and interobject relations in images and video. As illustrated in Fig. 1 and detailed in Sec. 3, this is mainly achieved by empowering the standard self-attention mechanism with long-range convolutional interactions and dynamic contextual feature aggregation. To investigate the effect of StructSA, we also provide an in-depth analysis on the relationship to recent self-attention variants with convolutional projection [18, 41, 42, 70, 72], showing their potential and limitation in leveraging structural patterns." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.893, + 0.902 + ], + "angle": 0, + "content": "To validate the effect of StructSA, we develop the structural vision transformer that adopts it as a main building" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.245, + 0.9 + ], + "angle": 0, + "content": "*Co-corresponding authors." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "18941" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.151 + ], + "angle": 0, + "content": "block, and perform an extensive set of experiments on both image and video classification tasks, showing the effectiveness of learning structural patterns for visual representations. Our main contributions are as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.152, + 0.47, + 0.196 + ], + "angle": 0, + "content": "- We introduce structural self-attention (StructSA) that learns correlation structures for visual representations with the vision transformer." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.197, + 0.469, + 0.243 + ], + "angle": 0, + "content": "- We provide an in-depth analysis on the relationship between StructSA and self-attention variants with convolutional projections." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.243, + 0.469, + 0.288 + ], + "angle": 0, + "content": "- Our new transformer network achieves state-of-the-art results on ImageNet-1K, Kinetics-400, Something-Something V1&V2, Diving-48, and FineGym." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.152, + 0.47, + 0.288 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.299, + 0.218, + 0.315 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.324, + 0.47, + 0.567 + ], + "angle": 0, + "content": "Transformer Networks in Vision. Since transformer networks [66] showed remarkable success in natural language processing [5, 14], they have widely been adopted in various computer vision tasks as an alternative to CNNs [1, 7, 17, 58, 59]. Despite of their success, the pure transformer networks require a large amount of training data compared to CNNs where convolution operations introduce desirable inductive biases such as locality and translation invariance allowing more efficient training [17, 53]. This incentivized several methods to inherit the convolutional inductive biases via knowledge distillation [63], local self-attention [27, 45, 54], and architectural fusion [9, 12, 23, 38, 70, 72]. While recent methods using a convolutional projection [18, 41, 70, 72] achieve remarkable improvements, we show that self-attention with a convolutional projection can be derived as a special form of our proposed method." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.569, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Correlation Structure Modeling. Geometric structure of correlations between visual features, i.e., patterns of how they are similar to each other, allows us to understand relational patterns in visual data for various computer vision tasks. Spatial self-correlation in images is used for suppressing photometric variations and revealing geometric layout of objects in the image [30, 33, 57]. Spatial cross-correlation between different images is often used for establishing semantic correspondences capturing structural similarities [24, 50, 55]. In the video domain, several methods exploit the structure of spatial cross-correlations between consecutive frames to estimate optical flow [16, 74] or to learn motion features for action recognition [35, 67]. Kwon et al. [36] propose spatio-temporal self-correlations for learning bi-directional motion features and Kim et al. [32] introduce relational self-attention that generates attention weights dynamically from the structure of the spatio-temporal self-correlations. However, these two methods use self-correlations between the query and its local spatio-temporal neighborhoods only, thus, are limited in learning global relational patterns between distant features. Inspired by this, we introduce structural self" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.168 + ], + "angle": 0, + "content": "attention that capturing not only the spatio-temporal local self-correlation but also cross-correlations between features in the distance, utilizing both motion and global spatiotemporal inter-feature relations for learning motion-centric video representations." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.18, + 0.649, + 0.197 + ], + "angle": 0, + "content": "3. Our Approach" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.205, + 0.892, + 0.326 + ], + "angle": 0, + "content": "We propose a novel self-attention mechanism, named structural self-attention (StructSA), that is designed to leverage rich correlation structures naturally emerging in key-query interactions of attention. We start by revisiting the vanilla self-attention and its limitation and then describe the details of StructSA. We also provide an in-depth analysis of recent self-attention variants with convolutional projections from the perspective of learning structural patterns." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.334, + 0.753, + 0.35 + ], + "angle": 0, + "content": "3.1. Background: Self-Attention" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.357, + 0.892, + 0.448 + ], + "angle": 0, + "content": "Self-attention (SA) [66] is a primitive operation for modern transformer networks [1, 17, 63]. Given \\(N\\) input features \\(\\mathbf{X} = [\\pmb{x}_1,\\dots ,\\pmb{x}_N]\\in \\mathbb{R}^{N\\times C}\\), SA first projects the input \\(\\mathbf{X}\\) linearly into queries, keys, and values, and transforms each \\(C\\)-dimensional input feature \\(\\pmb{x}_i\\) into a contextualized output feature \\(\\pmb{y}_i\\) by" + }, + { + "type": "equation", + "bbox": [ + 0.517, + 0.452, + 0.892, + 0.516 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sigma \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} ^ {\\top}\\right) \\boldsymbol {V} = \\sum_ {j} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {k} _ {j} ^ {\\top}\\right) \\boldsymbol {v} _ {j} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {1} \\\\ \\boldsymbol {q} _ {i} = \\boldsymbol {x} _ {i} \\boldsymbol {W} ^ {\\mathrm {Q}}, \\quad \\boldsymbol {K} = \\boldsymbol {X} \\boldsymbol {W} ^ {\\mathrm {K}}, \\quad \\boldsymbol {V} = \\boldsymbol {X} \\boldsymbol {W} ^ {\\mathrm {V}} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.525, + 0.892, + 0.75 + ], + "angle": 0, + "content": "where \\(\\sigma\\) is a softmax function and \\(W^{Q}, W^{K}, W^{V} \\in \\mathbb{R}^{C \\times C}\\) are projection matrices for query \\(q_{i} \\in \\mathbb{R}^{1 \\times C}\\), keys \\(K \\in \\mathbb{R}^{N \\times C}\\), and values \\(V \\in \\mathbb{R}^{N \\times C}\\), respectively. Here we use a 1-dimensional sequence of input features for notational simplicity, and the operation can be extended to a larger dimensionality. After computing a correlation map \\(q_{i} K^{\\top}\\), the vanilla SA uses individual correlation values independently, i.e., \\(q_{i} k_{j}^{\\top}\\), for value aggregation while ignoring the structure of the map, which leads to the same output regardless of the order of features. This permutation invariance prevents SA from capturing spatial layouts [27, 57] or motions [32, 36, 44] of objects in images or videos. Positional encoding for SA helps spatial awareness, but the structures of correlations are still not recognized in value aggregation [10, 11, 32]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.757, + 0.729, + 0.772 + ], + "angle": 0, + "content": "3.2. Structural Self-Attention" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We introduce a novel self-attention mechanism, named structural self-attention (StructSA), that effectively incorporates rich structural patterns of query-key correlation into contextual feature aggregation. The StructSA mechanism consists of two steps: (i) structural query-key attention and (ii) contextual value aggregation. Unlike the vanilla query-key attention where individual correlation values themselves are used as attention scores, the structural query-key" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18942" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.182 + ], + "angle": 0, + "content": "attention takes the correlation map as a whole and detect structural patterns from it in attention scoring. The subsequent contextual value aggregation then combines the attention scores together to compute diverse sets of kernel weights that are used for dynamically collecting local contexts of value features." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.185, + 0.471, + 0.247 + ], + "angle": 0, + "content": "Structural Query-Key Attention. To transform the vanilla query-key attention into structure-aware one, the structural query-key attention (SQKA) deploy convolutions on top of query-key correlation \\( \\mathbf{q}_i\\mathbf{K}^\\top \\):" + }, + { + "type": "equation", + "bbox": [ + 0.14, + 0.254, + 0.469, + 0.273 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {A} _ {i} = \\sigma \\left(\\operatorname {c o n v} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K}, \\boldsymbol {U} ^ {\\mathrm {K}}\\right)\\right) \\in \\mathbb {R} ^ {N \\times D}, \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.281, + 0.469, + 0.358 + ], + "angle": 0, + "content": "where \\( \\mathbf{U}^{\\mathrm{K}} \\in \\mathbb{R}^{M \\times D} \\) is \\( D \\) convolutional kernels with size \\( M \\). Note that \\( \\sigma \\) is a softmax function taken over all \\( ND \\) entries in the input matrix; we observe that it is empirically more stable compared to \\( D \\) individual softmax operations over \\( N \\) entries. Each element of \\( A_{i} \\) is computed as" + }, + { + "type": "equation", + "bbox": [ + 0.164, + 0.365, + 0.469, + 0.385 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {a} _ {i, j} = \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\in \\mathbb {R} ^ {1 \\times D}, \\tag {3}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.169, + 0.386, + 0.352, + 0.406 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {K} _ {j} = \\boldsymbol {X} _ {(j)} \\boldsymbol {W} ^ {\\mathrm {K}} \\in \\mathbb {R} ^ {M \\times C},\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.414, + 0.469, + 0.459 + ], + "angle": 0, + "content": "where \\(\\sigma_{j}\\) returns a \\(D\\)-dimensional softmax-ed output for \\(j\\)th location and \\(\\mathbf{X}_{(j)} \\in \\mathbb{R}^{M \\times C}\\) is local context features whose context window is centered at \\(j\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.46, + 0.469, + 0.627 + ], + "angle": 0, + "content": "Unlike the vanilla query-key attention, which is agnostic to its neighborhood structure, SQKA is empowered by convolution to recognize a local correlation structure of \\( \\pmb{q}_i\\pmb{K}_j^{\\top} \\in \\mathbb{R}^{1\\times M} \\) and transform it into a \\( D \\)-dimensional vector; the convolution kernels \\( U^{\\mathrm{K}} \\) act as correlation pattern detectors. In particular, when \\( i = j \\), the correlation map reduces to local self-similarity [57] that is known to be effective for capturing spatial layout patterns [57] or spatiotemporal motion [32, 36], meaning that SQKA recognizes diverse correlation patterns including self-similarity [57] via long-range interaction between query \\( i \\) and context \\( j \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.63, + 0.469, + 0.678 + ], + "angle": 0, + "content": "Contextual Value Aggregation. Given SQKA recognizing structural patterns of correlation, StructSA combines SQKA entries into a weight \\(\\kappa_{i,j}^{\\mathrm{struct}}\\) to aggregate value \\(\\pmb{v}_j\\):" + }, + { + "type": "equation", + "bbox": [ + 0.098, + 0.697, + 0.469, + 0.74 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {v} _ {j} = \\sum_ {j = 1} ^ {N} \\kappa_ {i, j} ^ {\\text {s t r u c t}} \\boldsymbol {v} _ {j}, \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.749, + 0.469, + 0.779 + ], + "angle": 0, + "content": "where \\(\\mathbf{u}^{\\mathrm{V}}\\in \\mathbb{R}^{1\\times D}\\) is a vector that linearly combines \\(D\\) pattern scores to the final attention weight." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.469, + 0.826 + ], + "angle": 0, + "content": "We further extend Eq. (4) to generate a spatial kernel not a single scalar for each position \\(j\\). We call this method contextual aggregation and it has a following form:" + }, + { + "type": "equation", + "bbox": [ + 0.093, + 0.835, + 0.469, + 0.898 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\boldsymbol {U} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {j} = \\sum_ {j = 1} ^ {N} \\kappa_ {i, j} ^ {\\text {s t r u c t}} \\boldsymbol {V} _ {j}, \\tag {5} \\\\ \\boldsymbol {V} _ {j} = \\boldsymbol {X} _ {(j)} \\boldsymbol {W} ^ {\\mathrm {V}} \\in \\mathbb {R} ^ {M \\times C}. \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.214 + ], + "angle": 0, + "content": "Compared to \\(\\pmb{u}^{\\mathrm{V}}\\) that produces a scalar weighting a single element \\(v_{j}\\), \\(\\pmb{U}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times D}\\) generates spatial kernel dynamically aggregating a local context of value \\(\\pmb{V}_{j}\\) for every position \\(j\\); each column of \\(\\pmb{U}^{\\mathrm{V}}\\), i.e., \\(\\pmb{U}_{i,d}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times 1}\\), plays a role as a context aggregator that performs a weighted pooling of local context \\(\\pmb{V}_{j}\\) and thus different combinations of these context aggregators result in diverse dynamic kernels \\(\\kappa_{i,j}^{\\mathrm{struct}}\\) for different locations \\(j\\)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.224, + 0.878, + 0.24 + ], + "angle": 0, + "content": "3.3. Relationship to Convolutional Self-Attention" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.248, + 0.892, + 0.369 + ], + "angle": 0, + "content": "Recent vision transformers [18, 23, 41, 70, 72] often adopt convolutional inductive biases in the form of self-attention with convolutional projections (ConvSA). In this section, we analyze ConvSA with a lens of StructSA and show its potential and limitation for learning structures from query-key correlations. Different from SA, ConvSA computes project keys and values \\( K^{\\mathrm{conv}} \\), \\( V^{\\mathrm{conv}} \\in \\mathbb{R}^{N \\times C} \\) using a convolution operation over the input feature map \\( X \\):" + }, + { + "type": "equation", + "bbox": [ + 0.526, + 0.381, + 0.891, + 0.4 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {K} ^ {\\text {c o n v}} = \\left[ \\boldsymbol {k} _ {1} ^ {\\text {c o n v}}, \\dots , \\boldsymbol {k} _ {N} ^ {\\text {c o n v}} \\right] = \\operatorname {c o n v} (\\boldsymbol {X}, \\boldsymbol {W} ^ {\\mathrm {K}}), \\tag {6}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.529, + 0.402, + 0.891, + 0.421 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {V} ^ {\\text {c o n v}} = \\left[ \\boldsymbol {v} _ {1} ^ {\\text {c o n v}}, \\dots , \\boldsymbol {v} _ {N} ^ {\\text {c o n v}} \\right] = \\operatorname {c o n v} \\left(\\boldsymbol {X}, \\boldsymbol {W} ^ {\\mathrm {V}}\\right), \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.435, + 0.891, + 0.482 + ], + "angle": 0, + "content": "where conv is a convolution operation, and \\(\\mathbf{W}^{\\mathrm{K}},\\mathbf{W}^{\\mathrm{V}}\\in\\) \\(\\mathbb{R}^{M\\times C\\times C}\\) are kernel weights with a kernel size \\(M\\) for key and value projections, respectively." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.482, + 0.892, + 0.573 + ], + "angle": 0, + "content": "In most previous methods, ConvSA is implemented with a channel-wise separable convolution [26], which consists of two factorized convolution operations, i.e., point-wise and channel-wise convolutions [18, 23, 41, 70, 72]. In this case, each key \\( \\pmb{k}_i^{\\mathrm{conv}} \\) and value \\( \\pmb{v}_i^{\\mathrm{conv}} \\) is computed from a local context \\( X_i \\) by" + }, + { + "type": "equation", + "bbox": [ + 0.552, + 0.586, + 0.891, + 0.607 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {k} _ {i} ^ {\\text {c o n v}} = \\boldsymbol {u} ^ {\\mathrm {K} ^ {\\mathsf {T}}} \\boldsymbol {X} _ {i} \\boldsymbol {W} ^ {\\mathrm {K}} = \\boldsymbol {u} ^ {\\mathrm {K} ^ {\\mathsf {T}}} \\boldsymbol {K} _ {i} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {8}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.555, + 0.609, + 0.891, + 0.63 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {v} _ {i} ^ {\\text {c o n v}} = \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {X} _ {i} \\boldsymbol {W} ^ {\\mathrm {V}} = \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {i} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.892, + 0.765 + ], + "angle": 0, + "content": "where \\(\\pmb{W}^{\\mathrm{K}},\\pmb{W}^{\\mathrm{V}}\\in \\mathbb{R}^{C\\times C}\\) are weights for the linear projection that are equivalent to point-wise convolution, and \\(\\pmb{u}^{\\mathrm{K}},\\pmb{u}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times 1}\\) are channel-wise convolution weights that are used to spatially aggregate linearly projected context \\(\\pmb{K}_i\\) and \\(\\pmb{V}_i\\), respectively. Note that here we assume the channel-wise convolution weights are shared across channels for simplicity without loss of generality and the full derivation is available in our supplementary material A." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.766, + 0.891, + 0.797 + ], + "angle": 0, + "content": "From Eq. (1) combined with Eq. (8) and (9), a transformed output \\( \\pmb{y}_i \\) in ConvSA is obtained by" + }, + { + "type": "equation", + "bbox": [ + 0.519, + 0.809, + 0.891, + 0.898 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {k} _ {j} ^ {\\text {c o n v} ^ {\\mathsf {T}}}\\right) \\boldsymbol {v} _ {j} ^ {\\text {c o n v}} \\\\ = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {u} ^ {\\mathrm {K}}\\right) \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {j} = \\sum_ {j = 1} ^ {N} \\boldsymbol {\\kappa} _ {i, j} ^ {\\text {c o n v}} \\boldsymbol {V} _ {j}, \\tag {10} \\\\ \\end{array}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18943" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.142, + 0.089, + 0.835, + 0.236 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.241, + 0.895, + 0.3 + ], + "angle": 0, + "content": "Figure 2. Visualization of ConvSA and StructSA on ImageNet-1K. The query location \\(i\\) is set to the center of the image and the kernel size \\(M = 3 \\times 3\\). Given the left input image, we compare ConvSA (\\(D = 1\\)) and StructSA (\\(D = 8\\)) in terms of (a) \\(D\\) attention maps \\(\\sigma_{jD}(\\pmb{q}_i \\pmb{K}_j^\\top \\pmb{U}^{\\mathrm{KT}})\\), (b) local feature aggregation patterns learned in \\(\\pmb{U}^V\\), and (c) the combinations of (a) and (b). Note that in (c), each location \\(j\\) has an aggregation map of the kernel size \\(M = 3 \\times 3\\) and thus we also show enlarged images for four different sample locations \\(j\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.318, + 0.473, + 0.535 + ], + "angle": 0, + "content": "where \\(\\sigma_{j}\\) is \\(j\\)th entry of the softmax over \\(N\\) tokens. This reveals that an attention score \\(\\sigma_{j}(\\pmb{q}_{i}\\pmb{k}_{j}^{\\mathrm{conv}^{\\top}})\\) is computed by projecting a local correlation map \\(\\pmb{q}_{i}\\pmb{K}_{j}^{\\top} \\in \\mathbb{R}^{1 \\times M}\\) by \\(\\pmb{u}^{\\mathrm{K}}\\), and a dynamic kernel \\(\\kappa_{i,j}^{\\mathrm{conv}}\\) for the final feature aggregation of \\(\\pmb{V}_{j}\\) is obtained by weighting the aggregation pattern presented in \\(\\pmb{u}^{\\mathrm{V}}\\) using the computed attention map. Given that correlation map \\(\\pmb{q}_{i}\\pmb{K}_{j}^{\\top}\\) represents a structural pattern, we can interpret that \\(\\pmb{u}^{\\mathrm{K}}\\) acts as a pattern detector that extracts a specific correlation pattern from \\(\\pmb{q}_{i}\\pmb{K}_{j}^{\\top}\\), whereas \\(\\pmb{u}^{\\mathrm{V}}\\) plays a role as a context aggregator that performs a weighted pooling of local context \\(\\pmb{V}_{j}\\). Due to the presence of this pattern detector \\(\\pmb{u}^{\\mathrm{K}}\\) and its corresponding context aggregator \\(\\pmb{u}^{\\mathrm{V}}\\), ConvSA can leverage a structural pattern of input for context aggregation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.543, + 0.473, + 0.775 + ], + "angle": 0, + "content": "Limitation. Although ConvSA can learn, unlike SA, a structural pattern over correlation maps by \\(\\pmb{u}^{\\mathrm{K}}\\), it only learns a single pattern and encodes various shapes in correlation maps into a scalar value representing the similarity against the learned pattern; as the result, the final dynamic kernel \\(\\kappa_{i,j}^{\\mathrm{conv}}\\) for every \\(j\\) reduces to the identical pattern of \\(\\pmb{u}^{\\mathrm{V}}\\) with different weighting only. This lack of expressiveness in \\(\\pmb{u}^{\\mathrm{K}}\\) and \\(\\pmb{u}^{\\mathrm{V}}\\) prevents ConvSA from capturing diverse structural patterns and generating diverse dynamic kernels. In constraint, StructSA learns \\(D\\) different pattern extractors in \\(\\pmb{U}^{\\mathrm{K}}\\) and represents various local correlation shapes by a set of \\(D\\) similarity scores. These scores are then combined with the \\(D\\) context aggregators in \\(\\pmb{U}^{\\mathrm{V}}\\); different combinations of these context aggregators result in diverse dynamic kernels \\(\\kappa_{i,j}^{\\mathrm{struct}}\\) for different locations \\(j\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Visualization. The aforementioned difference between ConvSA and StructSA, as well as their effects, can be better understood by visualizing the kernel computation process. Figure 2 provides such a visual comparison of how structural patterns are used in ConvSA and StructSA given an example image from ImageNet-1K [13]. From a query-key correlation map, ConvSA generates a single attention map (Fig. 2a, top). These scores are then combined with the" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.318, + 0.895, + 0.486 + ], + "angle": 0, + "content": "context aggregator \\( \\boldsymbol{u}^{\\mathrm{V}} \\) (Fig. 2b, top), which conveys only a single aggregation pattern. This causes local features to be aggregated with the identical pattern in \\( \\boldsymbol{u}^{\\mathrm{V}} \\) for all locations, and the only difference remains in their scales (Fig. 2c, top). In contrast, StructSA generates diverse attention maps using \\( D \\) pattern detectors, each capturing different structures in the query-key correlation maps (Fig. 2a, bottom), and combines them with different context aggregators (Fig. 2b, bottom) resulting in rich aggregation patterns for different locations \\( j \\) (Fig. 2c, bottom). For more in-depth comparison, please refer to our supplementary material D." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.496, + 0.634, + 0.513 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.521, + 0.893, + 0.567 + ], + "angle": 0, + "content": "To validate the effectiveness of the proposed method on visual representation learning, we conduct extensive experiments on image and video classification benchmarks." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.574, + 0.691, + 0.59 + ], + "angle": 0, + "content": "4.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.597, + 0.895, + 0.823 + ], + "angle": 0, + "content": "Datasets. ImageNet-1K [13] is a large-scale dataset with 1.2M images labeled by 1000 object classes. Kinetics-400 [31] is one of the most popular large-scale video datasets with 400 action classes. We use 241k action clips available online. Something-Something-V1 & V2 [22, 49] are both large-scale action recognition benchmarks, including 108k and 220k action clips, respectively. Both datasets share the same motion-centric action classes, e.g., 'pushing something from left to right,' so thus capturing fine-grained motion is crucial to achieving the better performance. Diving-48 [39] is a fine-grained action benchmark that is heavily dependent on temporal modeling [3], containing 18k videos with 48 diving classes. FineGym [56] is a motion-centric benchmark that includes gymnastics action classes with severe deformations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Training & Testing Protocols. For image classification, we follow the training strategy of DeiT [63] adopting random clipping, random horizontal flipping, mixup [80], cutmix [78], random erasing [81] and label-smoothing [51] to" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "18944" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.212 + ], + "angle": 0, + "content": "augment the input images for training. We train all models from scratch for 300 epochs using AdamW optimizer [48] with a cosine learning rate schedule including 5 warm-up epochs. The batch size, learning rate, and weight decay are set to 1024, 1e-3, and 0.05, respectively. For comparison on stronger experiment setup [29, 38, 41, 77], we also train our models using Token Labeling [29] and larger resolution images, i.e., \\(384 \\times 384\\), following the protocols in [38]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.212, + 0.471, + 0.514 + ], + "angle": 0, + "content": "For video classification, we follow training protocols and data augmentation recipes in MViT [18]. For Kinetics-400, we sample 16 or 32 frames using the dense sampling strategy [71]. We temporally inflate the model weights pretrained on ImageNet-1K and finetune it for 110 epochs including 10 warm-up epochs. We use AdamW [48] optimizer with the cosine learning rate schedule. We set the batch size, learning rate, weight decay, and stochastic depth rate to 64, 2e-4, 0.05, and 0.1, respectively. For Something-Something, Diving-48, and FineGym, we utilize the segment-based sampling strategy [68] and do not use the random horizontal flip for data augmentation. We initialize the model with the weights pretrained on Kinetics-400 and finetune the model for 60 epochs including 5 warm-up epochs. Other training hyperparameters are the same as those for Kinetics-400. For testing, we sample multiple clips at different temporal indices for each clip or cropping different spatial regions and then obtain the final score by computing an average over the scores for each clip. We train all models once using 8 to 16 NVIDIA A100 GPUs." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.518, + 0.47, + 0.579 + ], + "angle": 0, + "content": "Metrics. We measure top-1 and top-5 accuracy as performance metrics, except for FineGym, we compute averaged per-class top-1 accuracy. As efficiency metrics, we measure the number of parameters and FLOPs." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.588, + 0.273, + 0.603 + ], + "angle": 0, + "content": "4.2. Analysis of StructSA" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.61, + 0.47, + 0.852 + ], + "angle": 0, + "content": "StructSA can be readily integrated into any existing ViTs to enhance visual representations by capturing correlation structures. In this subsection, we experimentally validate and analyze the impact of StructSA. Here, for a direct comparison with SA, we choose to use DeiT-S [63] as the baseline backbone; DeiT is a pure SA-based vision transformer and thus adequate for validating the effect of StructSA, avoiding any intervention of additional components. In this analysis, we replace all the SA layers in DeiT with StructSA layers. The evaluations are done on ImageNet-1K [13] and Something-Something-V1 [22] benchmarks while varying the structure dimension \\( D \\), the kernel size \\( M \\), and context aggregation methods. We follow the training and testing protocols in Sec. 4.1, except that we directly finetune the ImageNet-1K-pretrained model on Something-Something-V1 using random cropping only for data augmentation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Structure Dimension \\(D\\). Table 1a shows the effect of the structure dimension \\(D\\). Compared to the baseline with the vanilla SA \\((D = 0)\\), applying ConvSA \\((D = 1)\\) improves" + }, + { + "type": "table", + "bbox": [ + 0.507, + 0.089, + 0.888, + 0.189 + ], + "angle": 0, + "content": "
DImageNet-1KSomething V1
top-1top-5top-1top-5
080.595.048.376.6
180.895.249.777.6
280.995.250.178.0
481.195.450.478.2
881.395.550.678.5
" + }, + { + "type": "table_caption", + "bbox": [ + 0.62, + 0.191, + 0.773, + 0.203 + ], + "angle": 0, + "content": "(a) Structure dimension \\(D\\)" + }, + { + "type": "table", + "bbox": [ + 0.507, + 0.209, + 0.888, + 0.309 + ], + "angle": 0, + "content": "
MImageNet-1KSomething V1
top-1top-5top-1top-5
-80.595.048.376.6
1 × 1 (×1)80.695.048.576.9
3 × 3 (×3)81.195.450.478.2
5 × 5 (×5)81.195.450.578.2
7 × 7 (×7)81.095.250.578.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.645, + 0.312, + 0.748, + 0.323 + ], + "angle": 0, + "content": "(b) Kernel size \\(M\\)" + }, + { + "type": "table", + "bbox": [ + 0.507, + 0.329, + 0.888, + 0.403 + ], + "angle": 0, + "content": "
aggregationImageNet-1KSomething V1
top-1top-5top-1top-5
-80.595.048.376.6
element80.995.249.677.5
context81.195.450.478.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.605, + 0.405, + 0.788, + 0.417 + ], + "angle": 0, + "content": "(c) Context aggregation method." + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.426, + 0.892, + 0.482 + ], + "angle": 0, + "content": "Table 1. Ablation studies on ImageNet-1K and Something-Something V1. Top-1 and top-5 accuracies \\((\\%)\\) are shown. Otherwise specified, we use 16 frames as input and set \\(D = 4\\) \\(M = 3\\times 3\\times 3\\) , and patch-wise context aggregation as default." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.502, + 0.892, + 0.576 + ], + "angle": 0, + "content": "the performance as shown in [9, 72]. As we increase \\(D\\) from 1 to 8, we obtain gradual improvements up to \\(0.5\\% \\mathrm{p}\\) and \\(0.9\\% \\mathrm{p}\\) at top-1 accuracy on ImageNet-1K and Something-Something-V1. This confirms the limitation of ConvSA and the effectiveness of StructSA." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.582, + 0.892, + 0.687 + ], + "angle": 0, + "content": "Kernel Size \\( M \\). In Table 1b, we also investigate different kernel sizes \\( M \\). Compared to the baseline, the model with the kernel size \\( M = 1 \\times 1 \\times 1 \\) performs similar accuracies on both datasets whereas that with \\( M = 3 \\times 3 \\times 3 \\) improves the performance dramatically; it validates the effectiveness of learning geometric structures. The performance saturates as the kernel size gets larger than \\( 5 \\times 5 \\times 5 \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.692, + 0.892, + 0.782 + ], + "angle": 0, + "content": "Context Aggregation Method. In Table 1c, we also compare different context aggregation method. As a result, patch-wise aggregation performs \\(0.2\\% \\mathrm{p}\\) and \\(0.7\\% \\mathrm{p}\\) at top-1 accuracy on ImageNet-1K and Something-Something-V1. For more ablation experiments, please refer to our supplementary material B." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.793, + 0.774, + 0.809 + ], + "angle": 0, + "content": "4.3. Comparison to State of the Art" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.816, + 0.852, + 0.831 + ], + "angle": 0, + "content": "4.3.1 Structural Vision Transformer (StructViT)" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.84, + 0.892, + 0.9 + ], + "angle": 0, + "content": "To build an advanced vision transformer considering the recent development of multiscale representation learning [18, 38, 41, 70, 76], we integrate StructSA into UniFormer [38]. The transformer network, dubbed the Structural Vision" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18945" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.081, + 0.075, + 0.472, + 0.133 + ], + "angle": 0, + "content": "
modeltype# blocks# channels (# heads)
StructViT-S[C,C,S,S][3,4,8,3][64,128,320(5),512(8)]
StructViT-B[C,C,S,S][5,8,20,7][64,128,320(5),512(8)]
StructViT-L[C,C,S,S][5,10,24,7][128,192,448(7),640(10)]
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.136, + 0.471, + 0.164 + ], + "angle": 0, + "content": "Table 2. Configurations of StructViT variants. \"C\" and \"S\" denote a convolution and StructSA block, respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.18, + 0.47, + 0.33 + ], + "angle": 0, + "content": "Transformer (StructViT) is constructed by replacing all vanilla self-attention in UniFormer with StructSA as a main building block. It takes as input either a video clip or an image \\(\\tilde{\\pmb{X}}\\in \\mathbb{R}^{T\\times H\\times W\\times 3}\\), where \\(T\\), \\(H\\), and \\(W\\) denotes the temporal length, height, and width of the input, respectively. For images as input, we set the temporal length \\(T = 1\\). Before being fed into our networks, the input video is tokenized into overlapping 3D tablets of size \\(3\\times 4\\times 4\\times 3\\) with a stride of \\(2\\times 4\\times 4\\) while the input image is into nonoverlapping 2D patches of size \\(4\\times 4\\times 3\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.331, + 0.47, + 0.557 + ], + "angle": 0, + "content": "Our networks comprise four stages, each of which has multiple neural blocks, and leverage a hierarchical design with decreasing resolutions and increasing number of channels from early to late stages following [38]. For the first two stages, each block consists of a conditional positional encoding layer [9], a convolutional layer, and an MLP, whereas the convolutional layer is replaced by a StructSA layer in the blocks in the last two stages. Note that when we employ StructSA, we use multi-head configurations and do not share weights across channels for channel-wise convolutions. We build three different StructViT architectures as shown in Table 2. Our models are comparable to UniFormers [38] in the same sizes as our model configurations are based on UniFormer's; adding the structure dimension \\(D\\) in StructSA introduces only few additional parameters." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.558, + 0.471, + 0.801 + ], + "angle": 0, + "content": "In practice, StructSA introduces additional FLOPs for processing instances compared to the vanilla SA. One way of building an efficient StructSA is to adopt a larger stride in the key/value projections, which effectively reduces the number of keys and values [18, 41]. We test a few variants with a larger stride to see the performances of StructViT with matching FLOPs with their corresponding UniFormer architectures. We denote each model with StructViT-\\(X\\)-\\(D-S\\) where \\(X\\), \\(D\\), and \\(S\\) represent the architecture size, the structure dimension, and the stride, respectively. For training, we use stochastic depth [28] with the probability of \\(0.1/0.3/0.4\\) for StructViT-S/B/L, respectively. We use random cropping only for StructViT-B on Something-Something, Diving-48, and FineGym. We use 8 NVIDIA A100 GPUs for training StructViT-S/B and 16 GPUs for StructViT-L. We follow the protocols in Sec. 4.1 for the rest." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.817, + 0.273, + 0.832 + ], + "angle": 0, + "content": "4.3.2 Image Classification" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.47, + 0.903 + ], + "angle": 0, + "content": "In Table 3, we compare StructViT with other state-of-the-art CNNs, ViTs, and their hybrid models. The results show that StructViT outperforms other methods in all sizes. Compared to EfficientNets [61, 62] that are obtained by exten" + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.074, + 0.891, + 0.819 + ], + "angle": 0, + "content": "
method#params (M)FLOPs (G)IN1K top-1
EfficientNet-B5 [61]309.983.6
ConvNext-T [46]294.583.1
DeiT-S [63]224.679.9
PVT-S [70]253.879.8
Swin-T [45]294.581.3
Focal-T [75]294.982.2
CSwin-T [15]234.382.7
CvT-13 [72]204.581.6
CoAtNet-0 [12]254.281.6
LV-ViT-S [29]266.683.3
UniFormer-S [38]223.682.9
UniFormer-S*↑384 [38]2211.984.6
MViTv2-S [41]244.782.3
StructViT-S-4-2233.682.9
StructViT-S-4-1234.383.2
StructViT-S-8-1245.483.3
StructViT-S-4-1*234.384.0
StructViT-S-4-1*↑3842317.385.2
EfficientNet-B7 [61]6639.284.3
ConvNext-B [46]8915.483.8
ConvNext-B ↑384 [46]8945.085.1
PVT-L [70]619.881.7
Swin-S [45]508.783.0
Focal-S [75]519.183.5
CSwin-S [15]356.983.6
CvT-21 [72]327.182.5
CoAtNet-1 [12]428.483.3
LV-ViT-M [29]5616.084.1
UniFormer-B [38]508.383.8
UniFormer-B*↑384 [38]5027.286.0
MViTv2-S [41]357.083.6
MViTv2-B [41]5210.284.4
MViTv2-B ↑384 [41]5236.785.2
StructViT-B-4-2518.384.0
StructViT-B-4-1519.984.2
StructViT-B-8-15212.084.3
StructViT-B-4-1*519.985.4
StructViT-B-4-1*↑3845140.786.5
EfficientNetV2-L [62]1215285.7
ConvNext-L [46]19834.484.3
ConvNext-L ↑384 [46]198101.085.5
Swin-B [45]8815.483.3
Focal-B [75]9016.083.8
CSwin-B [15]7815.084.2
CoAtNet-3 [12]16834.784.5
LV-ViT-L ↑288 [29]15059.085.3
UniFormer-L* [38]10012.685.6
UniFormer-L*↑384 [38]10039.286.0
MViTv2-L [41]21842.185.3
MViTv2-L ↑384 [41]218140.286.0
StructViT-L-4-1*10315.486.0
StructViT-L-4-1*↑38410385.286.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.82, + 0.892, + 0.848 + ], + "angle": 0, + "content": "Table 3. Comparisons to the state-of-the-art methods on ImageNet-1K. *Trained with Token Labeling [29]." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.892, + 0.903 + ], + "angle": 0, + "content": "sive architecture search, our models show comparable or even better performances in both base and large configura" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "18946" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.351 + ], + "angle": 0, + "content": "tions, requiring much less amount of computational cost. Compared to our baseline, UniFormers, StructViTs consistently improve top-1 accuracy regardless of their sizes, demonstrating the benefits of learning geometric structures in image understanding. We further evaluate our models on stronger setup using Token Labeling [29] and \\(384 \\times 384\\) images, and observe consistent improvements over the baselines. While StructSA introduces some additional FLOPs, we also test variants whose stride for key/value convolutions is set to 2 (S-4-2 and B-4-2) matching its FLOPs to that of the baseline; we still observe some gain with the base model (B-4-2) without additional FLOPs while the small model (S-4-2) shows comparable results. For more comprehensive analysis, we provide experimental results on dense prediction tasks, i.e., object detection, semantic segmentation, and instance segmentation. Please refer to our supplementary material C for the detail." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.373, + 0.27, + 0.387 + ], + "angle": 0, + "content": "4.3.3 Video Classification" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.399, + 0.47, + 0.549 + ], + "angle": 0, + "content": "Kinetics-400. Table 4 compares our method with previous state-of-the-art methods on Kinetics-400. Each block in the table groups methods based on their network structures: CNNs, ViTs, and hybrid methods. We first observe that our best model (B-4-1) achieves state-of-the-art performance. Our method outperforms CNN-based approaches even with less computational cost (S-4-2) in most cases. Compared to MoViNets [34] which are the most advanced CNNs obtained by an extensive NAS, our method shows comparable scores with fewer FLOPs (S-4-1)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.551, + 0.47, + 0.687 + ], + "angle": 0, + "content": "When we compare our model to the ViT-based ones, our model outperforms them by large margins while using significantly fewer compute. For instance, StructViT-B-4-1 with single crop (second last row in Table 4) shows top-1 accuracy gain by \\(1.6\\%\\) while using only \\(55\\%\\) of computes compared to MTV-B, the best performing ViT-based model. Note also that our model is pretrained on ImageNet-1K, which is much smaller than ImageNet-21K on which the ViT-based models are pretrained." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.688, + 0.47, + 0.763 + ], + "angle": 0, + "content": "Finally, our best models (S-8-1 & B-4-1) show \\(0.5\\%\\) p to \\(0.8\\%\\) p accuracy gains over the baseline UniFormer models in different size configurations. When we use larger strides (S-4-2 and B-4-2) to match the FLOPs of the baselines, we still observe accuracy gains ranging from \\(0.2\\%\\) p to \\(0.3\\%\\) p." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Something-Something, Diving-48 and FineGym. Table 5a summarizes the results on Something-Something-V1&V2. We observe the same trends as on Kinetics-400. StructViT-S-4-2 outperforms UniFormer-S on Something-Something-V2 by \\(0.6\\%\\) p in top-1 accuracy, and StructViTS-8-1 enlarges the gap to \\(1.3\\%\\) p, leveraging correlation structures more effectively. StructViT-B-4-1 achieves new state-of-the-art performances on both V1 and V2 without the strong data augmentation methods used in [38, 41]." + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.09, + 0.892, + 0.476 + ], + "angle": 0, + "content": "
methodpretrainframe× crop×clipFLOPs (G)K400 top-1top-5
SlowFast+NL [20]-16×3×10702079.893.9
ip-CSN [64]Sports1M32×3×10327079.293.8
X3D-XL [19]-16×3×10145279.193.9
MoViNet-A5 [34]-120×1×128180.994.9
MoViNet-A6 [34]-120×1×138681.595.3
TimeSformer-HR [4]IN-21K16×3×1510979.794.4
TimeSformer-L [4]IN-21K96×3×1714080.794.7
X-ViT [6]IN-21K16×3×185080.294.7
Mformer-HR [52]IN-21K16×3×102876481.195.2
ViViT-L [1]IN-21K16×3×41735280.694.7
Swin-B [47]IN-1K32×3×4338480.694.6
Swin-B [47]IN-21K32×3×4338482.795.5
MTV-B [73]IN-21K32×3×4479081.895.0
MViT-B,16×4 [18]-16×1×535378.493.5
MViT-B,32×3 [18]-32×1×585080.294.4
Dualformer-S [42]IN-1K32×1×463680.694.9
Dualformer-B [42]IN-1K32×1×4107281.195.0
UniFormer-S [38]IN-1K16×1×416780.894.7
UniFormer-B [38]IN-1K32×1×4103682.995.4
MViTv2-B,32×3 [41]-32×1×5112582.995.7
StructViT-S-4-2IN-1K16×1×416981.195.5
StructViT-S-4-1IN-1K16×1×432781.495.7
StructViT-S-8-1IN-1K16×1×454181.695.8
StructViT-B-4-2IN-1K32×1×4104583.195.5
StructViT-B-4-1IN-1K32×1×4265883.395.6
StructViT-B-4-1IN-1K32×3×4797483.495.8
" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.479, + 0.892, + 0.505 + ], + "angle": 0, + "content": "Table 4. Comparisons to the state-of-the-art methods on Kinetics-400." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.529, + 0.892, + 0.71 + ], + "angle": 0, + "content": "Table 5b and Table 5c show the results on Diving-48 [39] and FineGym [56]. Our models outperform the baseline, UniFormer-B, obtaining significant accuracy gains by \\(0.9\\% \\mathrm{p}\\) and \\(0.7\\% \\mathrm{p}\\) on Diving-48 and FineGym, respectively. This indicates that learning spatio-temporal correlation structures play a crucial role in capturing fine-grained motion patterns. Our model sets new state-of-the-art performances with large margins (4.1% p on Diving-48; 3.3% p and 3.1% p on FineGym) over the previous methods without additional box annotations on both datasets. Note that ORViT [25] uses additional object bounding box annotations to train an object detector." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.737, + 0.738, + 0.751 + ], + "angle": 0, + "content": "4.4. Visualizations of StructSA" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Figure 3 visualizes example dynamic kernels \\(\\kappa_{i,j}^{\\mathrm{struct}}\\) computed from self-similarity map (\\(i = j\\)) on Something-Something-V1 to illustrate how StructSA encodes motion features from the spatiotemporal correlation structure. We observe that StructSA builds kernels for spatiotemporal gradient filters similar to those that are already known to be effective for capturing different types of motions [60], e.g., Sobel filters (first) or Laplacian filters (second and third), over local contexts similarly to [32]." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.956 + ], + "angle": 0, + "content": "18947" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.082, + 0.082, + 0.611, + 0.429 + ], + "angle": 0, + "content": "
methodpretrainframe× crop×clipFLOPs (G)Something V1 top-1top-5Something V2 top-1top-5
TEA [40]IN-1K16×1×17051.980.3--
MSNet [35]IN-1K16×1×110152.182.364.789.4
CT-Net [37]IN-1K16×1×17552.580.964.589.3
TDN [69]IN-1K16×1×17253.982.165.389.5
SELFYNet [36]IN-1K16×1×17754.382.965.789.8
RSANet [32]IN-1K16×1×17254.081.166.089.9
TimeSformer-HR [4]IN-21K16×3×15109--62.5-
TimeSformer-L [4]IN-21K96×3×17140--62.3-
ViViT-L [1]K40016×3×411892--65.489.8
X-ViT [6]IN-21K32×3×11270--65.490.7
Mformer-HR [52]K40016×3×12876--67.190.6
Mformer-L [52]K40032×3×13555--68.191.2
Swin-B [47]K40032×3×1963--69.692.7
MViT-B,64×3 [18]K40064×1×31365--67.790.9
MViT-B-24,32×3 [18]K60032×1×3708--68.791.5
UniFormer-S [38]K40016×3×112557.284.967.791.4
UniFormer-B [38]K40032×3×177760.987.371.292.8
MViTv2-B [41]K40032×3×1675--70.592.7
StructViT-S-4-2K40016×3×112657.685.368.391.3
StructViT-S-4-1K40016×3×124658.085.568.891.9
StructViT-S-8-1K40016×3×140558.085.769.092.1
StructViT-B-4-2K40032×3×178461.187.771.192.7
StructViT-B-4-1K40032×3×1196361.387.871.593.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.25, + 0.431, + 0.447, + 0.443 + ], + "angle": 0, + "content": "(a) Something-Something V1 & V2" + }, + { + "type": "table", + "bbox": [ + 0.626, + 0.082, + 0.88, + 0.25 + ], + "angle": 0, + "content": "
modeltop-1
SlowFast-R101 [20]77.6
TimeSformer [4]75.0
TimeSformer-HR [4]78.0
SViT-DD [2]79.8
TimeSformer-L [4]81.0
TQN [79]81.8
RSANet-R50 [32]84.2
UniFormer-B* [38]87.4
ORViT† [25]88.0
StructViT-B-4-287.8
StructViT-B-4-188.3
" + }, + { + "type": "table_caption", + "bbox": [ + 0.715, + 0.252, + 0.792, + 0.265 + ], + "angle": 0, + "content": "(b) Diving-48" + }, + { + "type": "table", + "bbox": [ + 0.625, + 0.301, + 0.88, + 0.429 + ], + "angle": 0, + "content": "
modelGym288Gym99
TRN [82]33.168.7
I3D [8]27.963.2
TSM [43]34.870.6
\\(\\mathsf{TSM}_{\\text{Two-stream}}\\) [43]46.581.2
RSANet-R50 [32]50.986.4
UniFormer-B* [38]53.588.9
StructViT-B-4-253.889.3
StructViT-B-4-154.289.5
" + }, + { + "type": "table_caption", + "bbox": [ + 0.716, + 0.43, + 0.789, + 0.443 + ], + "angle": 0, + "content": "(c) FineGym" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.448, + 0.893, + 0.491 + ], + "angle": 0, + "content": "Table 5. Comparisons to the state-of-the-art methods on three motion-centric video classification benchmarks. Our StructViT achieves new state-of-the-art on all the benchmarks. For FineGym, we measure averaged per-class accuracy while top- \\(k\\) accuracy is measured for Something-Something and Diving-48. *Reproduced by our experimental setup. †Trained with additionalbbox annotations." + }, + { + "type": "image_caption", + "bbox": [ + 0.181, + 0.532, + 0.277, + 0.552 + ], + "angle": 0, + "content": "input video" + }, + { + "type": "image", + "bbox": [ + 0.293, + 0.504, + 0.812, + 0.586 + ], + "angle": 0, + "content": null + }, + { + "type": "equation", + "bbox": [ + 0.09, + 0.62, + 0.281, + 0.644 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {\\kappa} _ {i, j} ^ {\\mathrm {s t r u c t}} = \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K} ^ {\\top}}\\right) \\boldsymbol {U} ^ {\\mathrm {V}}\n\\]" + }, + { + "type": "image", + "bbox": [ + 0.299, + 0.594, + 0.389, + 0.661 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.403, + 0.595, + 0.493, + 0.661 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.595, + 0.596, + 0.661 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.614, + 0.596, + 0.702, + 0.661 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.718, + 0.597, + 0.807, + 0.661 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.666, + 0.893, + 0.723 + ], + "angle": 0, + "content": "Figure 3. Visualization of dynamic kernels \\(\\kappa_{i,j}^{\\mathrm{struct}}\\) in StructSA on Something-V1. The top row shows the input frames that contain the input spatiotemporal local context (indicated by green boxes) used in the dynamic kernel computation. The bottom row presents the resulting dynamic kernels \\(\\kappa_{i,j}^{\\mathrm{struct}}\\) for a StructSA head when \\(i = j\\). Note that the computed dynamic kernels are computed with self-similarity map \\((i = j)\\) to illustrate its effectiveness in capturing motions in videos. We use StructViT-S-4-1 with \\(M = 5 \\times 5 \\times 5\\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.74, + 0.196, + 0.755 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.47, + 0.901 + ], + "angle": 0, + "content": "We have introduced a novel self-attention mechanism, StructSA, that exploits rich structural patterns of querykey correlation for visual representation learning. StructSA leverages spatial (and temporal) structures of local correlations and aggregates chunks of local features globally across entire locations. Structural Vision Transformer (StructViT) using StructSA as the main attention module achieves state-of-the-art results on both image and video classification benchmarks. We believe leveraging structural" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.741, + 0.892, + 0.786 + ], + "angle": 0, + "content": "patterns of correlation in attention will also benefit other tasks in computer vision and natural language processing. We leave this for future work." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Acknowledgements This work was supported by the IITP grants (No. 2022-0-00290: Visual Intelligence for space-time understanding and generation \\((45\\%)\\), No. 2022-0-00264: Comprehensive video understanding and generation with knowledge-based deep logic \\((50\\%)\\), No. 2019-0-01906: AI graduate school program at POSTECH \\((5\\%))\\) funded by Ministry of Science and ICT, Korea." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18948" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.169 + ], + "angle": 0, + "content": "[1] Anurag Arnab, Mostafa Dehghani, Georg Heigold, Chen Sun, Mario Lučić, and Cordelia Schmid. 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StructSA generates attention maps by recognizing space-time structures of key-query correlations via convolution and uses them to dynamically aggregate local contexts of value features. This effectively leverages rich structural patterns in images and videos such as scene layouts, object motion, and inter-object relations. Using StructSA as a main building block, we develop the structural vision transformer (StructViT) and evaluate its effectiveness on both image and video classification tasks, achieving state-of-the-art results on ImageNet-1K, Kinetics-400, Something-Something V1 & V2, Diving-48, and FineGym. + +# 1. Introduction + +How visual elements interact with each other in space and time is a crucial cue for visual understanding, e.g., recognizing actions in a video or analyzing scene layout patterns in an image. In computer vision, such relational patterns are effectively captured by the structure of correlations or similarities across visual elements in different positions [3, 57]; a correlation structure of an image reveals spatial layouts of similar patterns [30, 33] and that of a video provides bidirectional motion likelihoods [32, 36]. The ability to recognize those structural patterns may allow to better perform visual reasoning and generalize against challenging appearance variations and domain shifts [21, 65]. + +In this work, we introduce a novel self-attention mechanism, named structural self-attention (StructSA), that effectively leverages diverse structural patterns for visual representation learning. While the standard self-attention mechanism uses raw query-key correlations individually and ignores their geometric structures, the proposed StructSA recognizes diverse structural patterns from the correlations between the query and local chunks of keys via convolu + +![](images/5777cb2dbd004a634c140f935354a1c0cc2bfab64f48b175cbf5e27f32cfc166.jpg) + +![](images/d37c80eea780989de2fd998082a33196170e1677f5bc5c9e3a852547f8926a3f.jpg) +(a) Input video + +![](images/372dd048039d55491b0875978ad2ff995ae4818f3377aab702fc0841b48154ff.jpg) + +![](images/b59a677dc96456af73cfd481ed0e2959a6b6bc21024689726fb0af062a05b5e2.jpg) + +![](images/b09a227551a1f00417550fce772d91eb50dd0b2332c3a90e87c5ea21892cead6.jpg) + +![](images/80f0691ab275d4ef2d1a0070e1645f814c35977e275fed5a4adb75c4c9167a95.jpg) + +![](images/1fff8d1bb2d2a758a2176d23c8129f4b24519c7a47e458721ff39370b0dbcbe5.jpg) +(b) Query-key correlation map + +![](images/6bb8fec36114aded9caf559a64104439a1c074defa582df805b975c20bd6cdb9.jpg) + +![](images/24798d14a8e5571a1c8bd33538939b655077b30eb721d52d5aa7d9daf1f761cf.jpg) + +![](images/d48eee41befa1acdb73b9e35ce155594c7005c049d6cc7ab2a72549580ee2ce4.jpg) + +![](images/1a1b245e42a24c536fe41c0ddb9e71c9c31989b7278a0695011c88d1b5fcc464.jpg) +(c) Structural self-attention (StructSA) +Figure 1. Structural Self-Attention. Given an input video and a query indicated by the red box in (a), the query-key correlation maps in (b) clearly reveal the structures of spatial layout and motion with respect to the query. The proposed attention mechanism in (c) is designed to leverage these rich structural patterns for computing attention scores in the self-attention process. + +tion and uses them to dynamically aggregate local contexts of value features, effectively capturing rich structural patterns such as scene layouts, object motion, and interobject relations in images and video. As illustrated in Fig. 1 and detailed in Sec. 3, this is mainly achieved by empowering the standard self-attention mechanism with long-range convolutional interactions and dynamic contextual feature aggregation. To investigate the effect of StructSA, we also provide an in-depth analysis on the relationship to recent self-attention variants with convolutional projection [18, 41, 42, 70, 72], showing their potential and limitation in leveraging structural patterns. + +To validate the effect of StructSA, we develop the structural vision transformer that adopts it as a main building + +block, and perform an extensive set of experiments on both image and video classification tasks, showing the effectiveness of learning structural patterns for visual representations. Our main contributions are as follows: + +- We introduce structural self-attention (StructSA) that learns correlation structures for visual representations with the vision transformer. +- We provide an in-depth analysis on the relationship between StructSA and self-attention variants with convolutional projections. +- Our new transformer network achieves state-of-the-art results on ImageNet-1K, Kinetics-400, Something-Something V1&V2, Diving-48, and FineGym. + +# 2. Related Work + +Transformer Networks in Vision. Since transformer networks [66] showed remarkable success in natural language processing [5, 14], they have widely been adopted in various computer vision tasks as an alternative to CNNs [1, 7, 17, 58, 59]. Despite of their success, the pure transformer networks require a large amount of training data compared to CNNs where convolution operations introduce desirable inductive biases such as locality and translation invariance allowing more efficient training [17, 53]. This incentivized several methods to inherit the convolutional inductive biases via knowledge distillation [63], local self-attention [27, 45, 54], and architectural fusion [9, 12, 23, 38, 70, 72]. While recent methods using a convolutional projection [18, 41, 70, 72] achieve remarkable improvements, we show that self-attention with a convolutional projection can be derived as a special form of our proposed method. + +Correlation Structure Modeling. Geometric structure of correlations between visual features, i.e., patterns of how they are similar to each other, allows us to understand relational patterns in visual data for various computer vision tasks. Spatial self-correlation in images is used for suppressing photometric variations and revealing geometric layout of objects in the image [30, 33, 57]. Spatial cross-correlation between different images is often used for establishing semantic correspondences capturing structural similarities [24, 50, 55]. In the video domain, several methods exploit the structure of spatial cross-correlations between consecutive frames to estimate optical flow [16, 74] or to learn motion features for action recognition [35, 67]. Kwon et al. [36] propose spatio-temporal self-correlations for learning bi-directional motion features and Kim et al. [32] introduce relational self-attention that generates attention weights dynamically from the structure of the spatio-temporal self-correlations. However, these two methods use self-correlations between the query and its local spatio-temporal neighborhoods only, thus, are limited in learning global relational patterns between distant features. Inspired by this, we introduce structural self + +attention that capturing not only the spatio-temporal local self-correlation but also cross-correlations between features in the distance, utilizing both motion and global spatiotemporal inter-feature relations for learning motion-centric video representations. + +# 3. Our Approach + +We propose a novel self-attention mechanism, named structural self-attention (StructSA), that is designed to leverage rich correlation structures naturally emerging in key-query interactions of attention. We start by revisiting the vanilla self-attention and its limitation and then describe the details of StructSA. We also provide an in-depth analysis of recent self-attention variants with convolutional projections from the perspective of learning structural patterns. + +# 3.1. Background: Self-Attention + +Self-attention (SA) [66] is a primitive operation for modern transformer networks [1, 17, 63]. Given $N$ input features $\mathbf{X} = [\pmb{x}_1,\dots ,\pmb{x}_N]\in \mathbb{R}^{N\times C}$ , SA first projects the input $\mathbf{X}$ linearly into queries, keys, and values, and transforms each $C$ -dimensional input feature $\pmb{x}_i$ into a contextualized output feature $\pmb{y}_i$ by + +$$ +\begin{array}{l} \boldsymbol {y} _ {i} = \sigma \left(\boldsymbol {q} _ {i} \boldsymbol {K} ^ {\top}\right) \boldsymbol {V} = \sum_ {j} ^ {N} \sigma_ {j} \left(\boldsymbol {q} _ {i} \boldsymbol {k} _ {j} ^ {\top}\right) \boldsymbol {v} _ {j} \in \mathbb {R} ^ {1 \times C}, \tag {1} \\ \boldsymbol {q} _ {i} = \boldsymbol {x} _ {i} \boldsymbol {W} ^ {\mathrm {Q}}, \quad \boldsymbol {K} = \boldsymbol {X} \boldsymbol {W} ^ {\mathrm {K}}, \quad \boldsymbol {V} = \boldsymbol {X} \boldsymbol {W} ^ {\mathrm {V}} \\ \end{array} +$$ + +where $\sigma$ is a softmax function and $W^{Q}, W^{K}, W^{V} \in \mathbb{R}^{C \times C}$ are projection matrices for query $q_{i} \in \mathbb{R}^{1 \times C}$ , keys $K \in \mathbb{R}^{N \times C}$ , and values $V \in \mathbb{R}^{N \times C}$ , respectively. Here we use a 1-dimensional sequence of input features for notational simplicity, and the operation can be extended to a larger dimensionality. After computing a correlation map $q_{i} K^{\top}$ , the vanilla SA uses individual correlation values independently, i.e., $q_{i} k_{j}^{\top}$ , for value aggregation while ignoring the structure of the map, which leads to the same output regardless of the order of features. This permutation invariance prevents SA from capturing spatial layouts [27, 57] or motions [32, 36, 44] of objects in images or videos. Positional encoding for SA helps spatial awareness, but the structures of correlations are still not recognized in value aggregation [10, 11, 32]. + +# 3.2. Structural Self-Attention + +We introduce a novel self-attention mechanism, named structural self-attention (StructSA), that effectively incorporates rich structural patterns of query-key correlation into contextual feature aggregation. The StructSA mechanism consists of two steps: (i) structural query-key attention and (ii) contextual value aggregation. Unlike the vanilla query-key attention where individual correlation values themselves are used as attention scores, the structural query-key + +attention takes the correlation map as a whole and detect structural patterns from it in attention scoring. The subsequent contextual value aggregation then combines the attention scores together to compute diverse sets of kernel weights that are used for dynamically collecting local contexts of value features. + +Structural Query-Key Attention. To transform the vanilla query-key attention into structure-aware one, the structural query-key attention (SQKA) deploy convolutions on top of query-key correlation $\mathbf{q}_i\mathbf{K}^\top$ : + +$$ +\boldsymbol {A} _ {i} = \sigma \left(\operatorname {c o n v} \left(\boldsymbol {q} _ {i} \boldsymbol {K}, \boldsymbol {U} ^ {\mathrm {K}}\right)\right) \in \mathbb {R} ^ {N \times D}, \tag {2} +$$ + +where $\mathbf{U}^{\mathrm{K}} \in \mathbb{R}^{M \times D}$ is $D$ convolutional kernels with size $M$ . Note that $\sigma$ is a softmax function taken over all $ND$ entries in the input matrix; we observe that it is empirically more stable compared to $D$ individual softmax operations over $N$ entries. Each element of $A_{i}$ is computed as + +$$ +\boldsymbol {a} _ {i, j} = \sigma_ {j} \left(\boldsymbol {q} _ {i} \boldsymbol {K} _ {j} ^ {\top} \boldsymbol {U} ^ {\mathrm {K}}\right) \in \mathbb {R} ^ {1 \times D}, \tag {3} +$$ + +$$ +\boldsymbol {K} _ {j} = \boldsymbol {X} _ {(j)} \boldsymbol {W} ^ {\mathrm {K}} \in \mathbb {R} ^ {M \times C}, +$$ + +where $\sigma_{j}$ returns a $D$ -dimensional softmax-ed output for $j$ th location and $\mathbf{X}_{(j)} \in \mathbb{R}^{M \times C}$ is local context features whose context window is centered at $j$ . + +Unlike the vanilla query-key attention, which is agnostic to its neighborhood structure, SQKA is empowered by convolution to recognize a local correlation structure of $\pmb{q}_i\pmb{K}_j^{\top} \in \mathbb{R}^{1\times M}$ and transform it into a $D$ -dimensional vector; the convolution kernels $U^{\mathrm{K}}$ act as correlation pattern detectors. In particular, when $i = j$ , the correlation map reduces to local self-similarity [57] that is known to be effective for capturing spatial layout patterns [57] or spatiotemporal motion [32, 36], meaning that SQKA recognizes diverse correlation patterns including self-similarity [57] via long-range interaction between query $i$ and context $j$ . + +Contextual Value Aggregation. Given SQKA recognizing structural patterns of correlation, StructSA combines SQKA entries into a weight $\kappa_{i,j}^{\mathrm{struct}}$ to aggregate value $\pmb{v}_j$ : + +$$ +\boldsymbol {y} _ {i} = \sum_ {j = 1} ^ {N} \sigma_ {j} \left(\boldsymbol {q} _ {i} \boldsymbol {K} _ {j} ^ {\top} \boldsymbol {U} ^ {\mathrm {K}}\right) \boldsymbol {u} ^ {\mathrm {V} ^ {\top}} \boldsymbol {v} _ {j} = \sum_ {j = 1} ^ {N} \kappa_ {i, j} ^ {\text {s t r u c t}} \boldsymbol {v} _ {j}, \tag {4} +$$ + +where $\mathbf{u}^{\mathrm{V}}\in \mathbb{R}^{1\times D}$ is a vector that linearly combines $D$ pattern scores to the final attention weight. + +We further extend Eq. (4) to generate a spatial kernel not a single scalar for each position $j$ . We call this method contextual aggregation and it has a following form: + +$$ +\begin{array}{l} \boldsymbol {y} _ {i} = \sum_ {j = 1} ^ {N} \sigma_ {j} \left(\boldsymbol {q} _ {i} \boldsymbol {K} _ {j} ^ {\top} \boldsymbol {U} ^ {\mathrm {K}}\right) \boldsymbol {U} ^ {\mathrm {V} ^ {\top}} \boldsymbol {V} _ {j} = \sum_ {j = 1} ^ {N} \kappa_ {i, j} ^ {\text {s t r u c t}} \boldsymbol {V} _ {j}, \tag {5} \\ \boldsymbol {V} _ {j} = \boldsymbol {X} _ {(j)} \boldsymbol {W} ^ {\mathrm {V}} \in \mathbb {R} ^ {M \times C}. \\ \end{array} +$$ + +Compared to $\pmb{u}^{\mathrm{V}}$ that produces a scalar weighting a single element $v_{j}$ , $\pmb{U}^{\mathrm{V}}\in \mathbb{R}^{M\times D}$ generates spatial kernel dynamically aggregating a local context of value $\pmb{V}_{j}$ for every position $j$ ; each column of $\pmb{U}^{\mathrm{V}}$ , i.e., $\pmb{U}_{i,d}^{\mathrm{V}}\in \mathbb{R}^{M\times 1}$ , plays a role as a context aggregator that performs a weighted pooling of local context $\pmb{V}_{j}$ and thus different combinations of these context aggregators result in diverse dynamic kernels $\kappa_{i,j}^{\mathrm{struct}}$ for different locations $j$ . + +# 3.3. Relationship to Convolutional Self-Attention + +Recent vision transformers [18, 23, 41, 70, 72] often adopt convolutional inductive biases in the form of self-attention with convolutional projections (ConvSA). In this section, we analyze ConvSA with a lens of StructSA and show its potential and limitation for learning structures from query-key correlations. Different from SA, ConvSA computes project keys and values $K^{\mathrm{conv}}$ , $V^{\mathrm{conv}} \in \mathbb{R}^{N \times C}$ using a convolution operation over the input feature map $X$ : + +$$ +\boldsymbol {K} ^ {\text {c o n v}} = \left[ \boldsymbol {k} _ {1} ^ {\text {c o n v}}, \dots , \boldsymbol {k} _ {N} ^ {\text {c o n v}} \right] = \operatorname {c o n v} (\boldsymbol {X}, \boldsymbol {W} ^ {\mathrm {K}}), \tag {6} +$$ + +$$ +\boldsymbol {V} ^ {\text {c o n v}} = \left[ \boldsymbol {v} _ {1} ^ {\text {c o n v}}, \dots , \boldsymbol {v} _ {N} ^ {\text {c o n v}} \right] = \operatorname {c o n v} \left(\boldsymbol {X}, \boldsymbol {W} ^ {\mathrm {V}}\right), \tag {7} +$$ + +where conv is a convolution operation, and $\mathbf{W}^{\mathrm{K}},\mathbf{W}^{\mathrm{V}}\in$ $\mathbb{R}^{M\times C\times C}$ are kernel weights with a kernel size $M$ for key and value projections, respectively. + +In most previous methods, ConvSA is implemented with a channel-wise separable convolution [26], which consists of two factorized convolution operations, i.e., point-wise and channel-wise convolutions [18, 23, 41, 70, 72]. In this case, each key $\pmb{k}_i^{\mathrm{conv}}$ and value $\pmb{v}_i^{\mathrm{conv}}$ is computed from a local context $X_i$ by + +$$ +\boldsymbol {k} _ {i} ^ {\text {c o n v}} = \boldsymbol {u} ^ {\mathrm {K} ^ {\mathsf {T}}} \boldsymbol {X} _ {i} \boldsymbol {W} ^ {\mathrm {K}} = \boldsymbol {u} ^ {\mathrm {K} ^ {\mathsf {T}}} \boldsymbol {K} _ {i} \in \mathbb {R} ^ {1 \times C}, \tag {8} +$$ + +$$ +\boldsymbol {v} _ {i} ^ {\text {c o n v}} = \boldsymbol {u} ^ {\mathrm {V} ^ {\top}} \boldsymbol {X} _ {i} \boldsymbol {W} ^ {\mathrm {V}} = \boldsymbol {u} ^ {\mathrm {V} ^ {\top}} \boldsymbol {V} _ {i} \in \mathbb {R} ^ {1 \times C}, \tag {9} +$$ + +where $\pmb{W}^{\mathrm{K}},\pmb{W}^{\mathrm{V}}\in \mathbb{R}^{C\times C}$ are weights for the linear projection that are equivalent to point-wise convolution, and $\pmb{u}^{\mathrm{K}},\pmb{u}^{\mathrm{V}}\in \mathbb{R}^{M\times 1}$ are channel-wise convolution weights that are used to spatially aggregate linearly projected context $\pmb{K}_i$ and $\pmb{V}_i$ , respectively. Note that here we assume the channel-wise convolution weights are shared across channels for simplicity without loss of generality and the full derivation is available in our supplementary material A. + +From Eq. (1) combined with Eq. (8) and (9), a transformed output $\pmb{y}_i$ in ConvSA is obtained by + +$$ +\begin{array}{l} \boldsymbol {y} _ {i} = \sum_ {j = 1} ^ {N} \sigma_ {j} \left(\boldsymbol {q} _ {i} \boldsymbol {k} _ {j} ^ {\text {c o n v} ^ {\mathsf {T}}}\right) \boldsymbol {v} _ {j} ^ {\text {c o n v}} \\ = \sum_ {j = 1} ^ {N} \sigma_ {j} \left(\boldsymbol {q} _ {i} \boldsymbol {K} _ {j} ^ {\top} \boldsymbol {u} ^ {\mathrm {K}}\right) \boldsymbol {u} ^ {\mathrm {V} ^ {\top}} \boldsymbol {V} _ {j} = \sum_ {j = 1} ^ {N} \boldsymbol {\kappa} _ {i, j} ^ {\text {c o n v}} \boldsymbol {V} _ {j}, \tag {10} \\ \end{array} +$$ + +![](images/ab91793394a81af57e0df3bd0aeac68ed72687683e1485412ba0781d66a8b8c3.jpg) +Figure 2. Visualization of ConvSA and StructSA on ImageNet-1K. The query location $i$ is set to the center of the image and the kernel size $M = 3 \times 3$ . Given the left input image, we compare ConvSA ( $D = 1$ ) and StructSA ( $D = 8$ ) in terms of (a) $D$ attention maps $\sigma_{jD}(\pmb{q}_i \pmb{K}_j^\top \pmb{U}^{\mathrm{KT}})$ , (b) local feature aggregation patterns learned in $\pmb{U}^V$ , and (c) the combinations of (a) and (b). Note that in (c), each location $j$ has an aggregation map of the kernel size $M = 3 \times 3$ and thus we also show enlarged images for four different sample locations $j$ . + +where $\sigma_{j}$ is $j$ th entry of the softmax over $N$ tokens. This reveals that an attention score $\sigma_{j}(\pmb{q}_{i}\pmb{k}_{j}^{\mathrm{conv}^{\top}})$ is computed by projecting a local correlation map $\pmb{q}_{i}\pmb{K}_{j}^{\top} \in \mathbb{R}^{1 \times M}$ by $\pmb{u}^{\mathrm{K}}$ , and a dynamic kernel $\kappa_{i,j}^{\mathrm{conv}}$ for the final feature aggregation of $\pmb{V}_{j}$ is obtained by weighting the aggregation pattern presented in $\pmb{u}^{\mathrm{V}}$ using the computed attention map. Given that correlation map $\pmb{q}_{i}\pmb{K}_{j}^{\top}$ represents a structural pattern, we can interpret that $\pmb{u}^{\mathrm{K}}$ acts as a pattern detector that extracts a specific correlation pattern from $\pmb{q}_{i}\pmb{K}_{j}^{\top}$ , whereas $\pmb{u}^{\mathrm{V}}$ plays a role as a context aggregator that performs a weighted pooling of local context $\pmb{V}_{j}$ . Due to the presence of this pattern detector $\pmb{u}^{\mathrm{K}}$ and its corresponding context aggregator $\pmb{u}^{\mathrm{V}}$ , ConvSA can leverage a structural pattern of input for context aggregation. + +Limitation. Although ConvSA can learn, unlike SA, a structural pattern over correlation maps by $\pmb{u}^{\mathrm{K}}$ , it only learns a single pattern and encodes various shapes in correlation maps into a scalar value representing the similarity against the learned pattern; as the result, the final dynamic kernel $\kappa_{i,j}^{\mathrm{conv}}$ for every $j$ reduces to the identical pattern of $\pmb{u}^{\mathrm{V}}$ with different weighting only. This lack of expressiveness in $\pmb{u}^{\mathrm{K}}$ and $\pmb{u}^{\mathrm{V}}$ prevents ConvSA from capturing diverse structural patterns and generating diverse dynamic kernels. In constraint, StructSA learns $D$ different pattern extractors in $\pmb{U}^{\mathrm{K}}$ and represents various local correlation shapes by a set of $D$ similarity scores. These scores are then combined with the $D$ context aggregators in $\pmb{U}^{\mathrm{V}}$ ; different combinations of these context aggregators result in diverse dynamic kernels $\kappa_{i,j}^{\mathrm{struct}}$ for different locations $j$ . + +Visualization. The aforementioned difference between ConvSA and StructSA, as well as their effects, can be better understood by visualizing the kernel computation process. Figure 2 provides such a visual comparison of how structural patterns are used in ConvSA and StructSA given an example image from ImageNet-1K [13]. From a query-key correlation map, ConvSA generates a single attention map (Fig. 2a, top). These scores are then combined with the + +context aggregator $\boldsymbol{u}^{\mathrm{V}}$ (Fig. 2b, top), which conveys only a single aggregation pattern. This causes local features to be aggregated with the identical pattern in $\boldsymbol{u}^{\mathrm{V}}$ for all locations, and the only difference remains in their scales (Fig. 2c, top). In contrast, StructSA generates diverse attention maps using $D$ pattern detectors, each capturing different structures in the query-key correlation maps (Fig. 2a, bottom), and combines them with different context aggregators (Fig. 2b, bottom) resulting in rich aggregation patterns for different locations $j$ (Fig. 2c, bottom). For more in-depth comparison, please refer to our supplementary material D. + +# 4. Experiments + +To validate the effectiveness of the proposed method on visual representation learning, we conduct extensive experiments on image and video classification benchmarks. + +# 4.1. Experimental Setup + +Datasets. ImageNet-1K [13] is a large-scale dataset with 1.2M images labeled by 1000 object classes. Kinetics-400 [31] is one of the most popular large-scale video datasets with 400 action classes. We use 241k action clips available online. Something-Something-V1 & V2 [22, 49] are both large-scale action recognition benchmarks, including 108k and 220k action clips, respectively. Both datasets share the same motion-centric action classes, e.g., 'pushing something from left to right,' so thus capturing fine-grained motion is crucial to achieving the better performance. Diving-48 [39] is a fine-grained action benchmark that is heavily dependent on temporal modeling [3], containing 18k videos with 48 diving classes. FineGym [56] is a motion-centric benchmark that includes gymnastics action classes with severe deformations. + +Training & Testing Protocols. For image classification, we follow the training strategy of DeiT [63] adopting random clipping, random horizontal flipping, mixup [80], cutmix [78], random erasing [81] and label-smoothing [51] to + +augment the input images for training. We train all models from scratch for 300 epochs using AdamW optimizer [48] with a cosine learning rate schedule including 5 warm-up epochs. The batch size, learning rate, and weight decay are set to 1024, 1e-3, and 0.05, respectively. For comparison on stronger experiment setup [29, 38, 41, 77], we also train our models using Token Labeling [29] and larger resolution images, i.e., $384 \times 384$ , following the protocols in [38]. + +For video classification, we follow training protocols and data augmentation recipes in MViT [18]. For Kinetics-400, we sample 16 or 32 frames using the dense sampling strategy [71]. We temporally inflate the model weights pretrained on ImageNet-1K and finetune it for 110 epochs including 10 warm-up epochs. We use AdamW [48] optimizer with the cosine learning rate schedule. We set the batch size, learning rate, weight decay, and stochastic depth rate to 64, 2e-4, 0.05, and 0.1, respectively. For Something-Something, Diving-48, and FineGym, we utilize the segment-based sampling strategy [68] and do not use the random horizontal flip for data augmentation. We initialize the model with the weights pretrained on Kinetics-400 and finetune the model for 60 epochs including 5 warm-up epochs. Other training hyperparameters are the same as those for Kinetics-400. For testing, we sample multiple clips at different temporal indices for each clip or cropping different spatial regions and then obtain the final score by computing an average over the scores for each clip. We train all models once using 8 to 16 NVIDIA A100 GPUs. + +Metrics. We measure top-1 and top-5 accuracy as performance metrics, except for FineGym, we compute averaged per-class top-1 accuracy. As efficiency metrics, we measure the number of parameters and FLOPs. + +# 4.2. Analysis of StructSA + +StructSA can be readily integrated into any existing ViTs to enhance visual representations by capturing correlation structures. In this subsection, we experimentally validate and analyze the impact of StructSA. Here, for a direct comparison with SA, we choose to use DeiT-S [63] as the baseline backbone; DeiT is a pure SA-based vision transformer and thus adequate for validating the effect of StructSA, avoiding any intervention of additional components. In this analysis, we replace all the SA layers in DeiT with StructSA layers. The evaluations are done on ImageNet-1K [13] and Something-Something-V1 [22] benchmarks while varying the structure dimension $D$ , the kernel size $M$ , and context aggregation methods. We follow the training and testing protocols in Sec. 4.1, except that we directly finetune the ImageNet-1K-pretrained model on Something-Something-V1 using random cropping only for data augmentation. + +Structure Dimension $D$ . Table 1a shows the effect of the structure dimension $D$ . Compared to the baseline with the vanilla SA $(D = 0)$ , applying ConvSA $(D = 1)$ improves + +
DImageNet-1KSomething V1
top-1top-5top-1top-5
080.595.048.376.6
180.895.249.777.6
280.995.250.178.0
481.195.450.478.2
881.395.550.678.5
+ +(a) Structure dimension $D$ + +
MImageNet-1KSomething V1
top-1top-5top-1top-5
-80.595.048.376.6
1 × 1 (×1)80.695.048.576.9
3 × 3 (×3)81.195.450.478.2
5 × 5 (×5)81.195.450.578.2
7 × 7 (×7)81.095.250.578.1
+ +(b) Kernel size $M$ + +
aggregationImageNet-1KSomething V1
top-1top-5top-1top-5
-80.595.048.376.6
element80.995.249.677.5
context81.195.450.478.2
+ +(c) Context aggregation method. + +Table 1. Ablation studies on ImageNet-1K and Something-Something V1. Top-1 and top-5 accuracies $(\%)$ are shown. Otherwise specified, we use 16 frames as input and set $D = 4$ $M = 3\times 3\times 3$ , and patch-wise context aggregation as default. + +the performance as shown in [9, 72]. As we increase $D$ from 1 to 8, we obtain gradual improvements up to $0.5\% \mathrm{p}$ and $0.9\% \mathrm{p}$ at top-1 accuracy on ImageNet-1K and Something-Something-V1. This confirms the limitation of ConvSA and the effectiveness of StructSA. + +Kernel Size $M$ . In Table 1b, we also investigate different kernel sizes $M$ . Compared to the baseline, the model with the kernel size $M = 1 \times 1 \times 1$ performs similar accuracies on both datasets whereas that with $M = 3 \times 3 \times 3$ improves the performance dramatically; it validates the effectiveness of learning geometric structures. The performance saturates as the kernel size gets larger than $5 \times 5 \times 5$ . + +Context Aggregation Method. In Table 1c, we also compare different context aggregation method. As a result, patch-wise aggregation performs $0.2\% \mathrm{p}$ and $0.7\% \mathrm{p}$ at top-1 accuracy on ImageNet-1K and Something-Something-V1. For more ablation experiments, please refer to our supplementary material B. + +# 4.3. Comparison to State of the Art + +# 4.3.1 Structural Vision Transformer (StructViT) + +To build an advanced vision transformer considering the recent development of multiscale representation learning [18, 38, 41, 70, 76], we integrate StructSA into UniFormer [38]. The transformer network, dubbed the Structural Vision + +
modeltype# blocks# channels (# heads)
StructViT-S[C,C,S,S][3,4,8,3][64,128,320(5),512(8)]
StructViT-B[C,C,S,S][5,8,20,7][64,128,320(5),512(8)]
StructViT-L[C,C,S,S][5,10,24,7][128,192,448(7),640(10)]
+ +Transformer (StructViT) is constructed by replacing all vanilla self-attention in UniFormer with StructSA as a main building block. It takes as input either a video clip or an image $\tilde{\pmb{X}}\in \mathbb{R}^{T\times H\times W\times 3}$ , where $T$ , $H$ , and $W$ denotes the temporal length, height, and width of the input, respectively. For images as input, we set the temporal length $T = 1$ . Before being fed into our networks, the input video is tokenized into overlapping 3D tablets of size $3\times 4\times 4\times 3$ with a stride of $2\times 4\times 4$ while the input image is into nonoverlapping 2D patches of size $4\times 4\times 3$ . + +Our networks comprise four stages, each of which has multiple neural blocks, and leverage a hierarchical design with decreasing resolutions and increasing number of channels from early to late stages following [38]. For the first two stages, each block consists of a conditional positional encoding layer [9], a convolutional layer, and an MLP, whereas the convolutional layer is replaced by a StructSA layer in the blocks in the last two stages. Note that when we employ StructSA, we use multi-head configurations and do not share weights across channels for channel-wise convolutions. We build three different StructViT architectures as shown in Table 2. Our models are comparable to UniFormers [38] in the same sizes as our model configurations are based on UniFormer's; adding the structure dimension $D$ in StructSA introduces only few additional parameters. + +In practice, StructSA introduces additional FLOPs for processing instances compared to the vanilla SA. One way of building an efficient StructSA is to adopt a larger stride in the key/value projections, which effectively reduces the number of keys and values [18, 41]. We test a few variants with a larger stride to see the performances of StructViT with matching FLOPs with their corresponding UniFormer architectures. We denote each model with StructViT- $X$ - $D-S$ where $X$ , $D$ , and $S$ represent the architecture size, the structure dimension, and the stride, respectively. For training, we use stochastic depth [28] with the probability of $0.1/0.3/0.4$ for StructViT-S/B/L, respectively. We use random cropping only for StructViT-B on Something-Something, Diving-48, and FineGym. We use 8 NVIDIA A100 GPUs for training StructViT-S/B and 16 GPUs for StructViT-L. We follow the protocols in Sec. 4.1 for the rest. + +# 4.3.2 Image Classification + +In Table 3, we compare StructViT with other state-of-the-art CNNs, ViTs, and their hybrid models. The results show that StructViT outperforms other methods in all sizes. Compared to EfficientNets [61, 62] that are obtained by exten + +Table 2. Configurations of StructViT variants. "C" and "S" denote a convolution and StructSA block, respectively. + +
method#params (M)FLOPs (G)IN1K top-1
EfficientNet-B5 [61]309.983.6
ConvNext-T [46]294.583.1
DeiT-S [63]224.679.9
PVT-S [70]253.879.8
Swin-T [45]294.581.3
Focal-T [75]294.982.2
CSwin-T [15]234.382.7
CvT-13 [72]204.581.6
CoAtNet-0 [12]254.281.6
LV-ViT-S [29]266.683.3
UniFormer-S [38]223.682.9
UniFormer-S*↑384 [38]2211.984.6
MViTv2-S [41]244.782.3
StructViT-S-4-2233.682.9
StructViT-S-4-1234.383.2
StructViT-S-8-1245.483.3
StructViT-S-4-1*234.384.0
StructViT-S-4-1*↑3842317.385.2
EfficientNet-B7 [61]6639.284.3
ConvNext-B [46]8915.483.8
ConvNext-B ↑384 [46]8945.085.1
PVT-L [70]619.881.7
Swin-S [45]508.783.0
Focal-S [75]519.183.5
CSwin-S [15]356.983.6
CvT-21 [72]327.182.5
CoAtNet-1 [12]428.483.3
LV-ViT-M [29]5616.084.1
UniFormer-B [38]508.383.8
UniFormer-B*↑384 [38]5027.286.0
MViTv2-S [41]357.083.6
MViTv2-B [41]5210.284.4
MViTv2-B ↑384 [41]5236.785.2
StructViT-B-4-2518.384.0
StructViT-B-4-1519.984.2
StructViT-B-8-15212.084.3
StructViT-B-4-1*519.985.4
StructViT-B-4-1*↑3845140.786.5
EfficientNetV2-L [62]1215285.7
ConvNext-L [46]19834.484.3
ConvNext-L ↑384 [46]198101.085.5
Swin-B [45]8815.483.3
Focal-B [75]9016.083.8
CSwin-B [15]7815.084.2
CoAtNet-3 [12]16834.784.5
LV-ViT-L ↑288 [29]15059.085.3
UniFormer-L* [38]10012.685.6
UniFormer-L*↑384 [38]10039.286.0
MViTv2-L [41]21842.185.3
MViTv2-L ↑384 [41]218140.286.0
StructViT-L-4-1*10315.486.0
StructViT-L-4-1*↑38410385.286.7
+ +Table 3. Comparisons to the state-of-the-art methods on ImageNet-1K. *Trained with Token Labeling [29]. + +sive architecture search, our models show comparable or even better performances in both base and large configura + +tions, requiring much less amount of computational cost. Compared to our baseline, UniFormers, StructViTs consistently improve top-1 accuracy regardless of their sizes, demonstrating the benefits of learning geometric structures in image understanding. We further evaluate our models on stronger setup using Token Labeling [29] and $384 \times 384$ images, and observe consistent improvements over the baselines. While StructSA introduces some additional FLOPs, we also test variants whose stride for key/value convolutions is set to 2 (S-4-2 and B-4-2) matching its FLOPs to that of the baseline; we still observe some gain with the base model (B-4-2) without additional FLOPs while the small model (S-4-2) shows comparable results. For more comprehensive analysis, we provide experimental results on dense prediction tasks, i.e., object detection, semantic segmentation, and instance segmentation. Please refer to our supplementary material C for the detail. + +# 4.3.3 Video Classification + +Kinetics-400. Table 4 compares our method with previous state-of-the-art methods on Kinetics-400. Each block in the table groups methods based on their network structures: CNNs, ViTs, and hybrid methods. We first observe that our best model (B-4-1) achieves state-of-the-art performance. Our method outperforms CNN-based approaches even with less computational cost (S-4-2) in most cases. Compared to MoViNets [34] which are the most advanced CNNs obtained by an extensive NAS, our method shows comparable scores with fewer FLOPs (S-4-1). + +When we compare our model to the ViT-based ones, our model outperforms them by large margins while using significantly fewer compute. For instance, StructViT-B-4-1 with single crop (second last row in Table 4) shows top-1 accuracy gain by $1.6\%$ while using only $55\%$ of computes compared to MTV-B, the best performing ViT-based model. Note also that our model is pretrained on ImageNet-1K, which is much smaller than ImageNet-21K on which the ViT-based models are pretrained. + +Finally, our best models (S-8-1 & B-4-1) show $0.5\%$ p to $0.8\%$ p accuracy gains over the baseline UniFormer models in different size configurations. When we use larger strides (S-4-2 and B-4-2) to match the FLOPs of the baselines, we still observe accuracy gains ranging from $0.2\%$ p to $0.3\%$ p. + +Something-Something, Diving-48 and FineGym. Table 5a summarizes the results on Something-Something-V1&V2. We observe the same trends as on Kinetics-400. StructViT-S-4-2 outperforms UniFormer-S on Something-Something-V2 by $0.6\%$ p in top-1 accuracy, and StructViTS-8-1 enlarges the gap to $1.3\%$ p, leveraging correlation structures more effectively. StructViT-B-4-1 achieves new state-of-the-art performances on both V1 and V2 without the strong data augmentation methods used in [38, 41]. + +
methodpretrainframe× crop×clipFLOPs (G)K400 top-1top-5
SlowFast+NL [20]-16×3×10702079.893.9
ip-CSN [64]Sports1M32×3×10327079.293.8
X3D-XL [19]-16×3×10145279.193.9
MoViNet-A5 [34]-120×1×128180.994.9
MoViNet-A6 [34]-120×1×138681.595.3
TimeSformer-HR [4]IN-21K16×3×1510979.794.4
TimeSformer-L [4]IN-21K96×3×1714080.794.7
X-ViT [6]IN-21K16×3×185080.294.7
Mformer-HR [52]IN-21K16×3×102876481.195.2
ViViT-L [1]IN-21K16×3×41735280.694.7
Swin-B [47]IN-1K32×3×4338480.694.6
Swin-B [47]IN-21K32×3×4338482.795.5
MTV-B [73]IN-21K32×3×4479081.895.0
MViT-B,16×4 [18]-16×1×535378.493.5
MViT-B,32×3 [18]-32×1×585080.294.4
Dualformer-S [42]IN-1K32×1×463680.694.9
Dualformer-B [42]IN-1K32×1×4107281.195.0
UniFormer-S [38]IN-1K16×1×416780.894.7
UniFormer-B [38]IN-1K32×1×4103682.995.4
MViTv2-B,32×3 [41]-32×1×5112582.995.7
StructViT-S-4-2IN-1K16×1×416981.195.5
StructViT-S-4-1IN-1K16×1×432781.495.7
StructViT-S-8-1IN-1K16×1×454181.695.8
StructViT-B-4-2IN-1K32×1×4104583.195.5
StructViT-B-4-1IN-1K32×1×4265883.395.6
StructViT-B-4-1IN-1K32×3×4797483.495.8
+ +Table 4. Comparisons to the state-of-the-art methods on Kinetics-400. + +Table 5b and Table 5c show the results on Diving-48 [39] and FineGym [56]. Our models outperform the baseline, UniFormer-B, obtaining significant accuracy gains by $0.9\% \mathrm{p}$ and $0.7\% \mathrm{p}$ on Diving-48 and FineGym, respectively. This indicates that learning spatio-temporal correlation structures play a crucial role in capturing fine-grained motion patterns. Our model sets new state-of-the-art performances with large margins (4.1% p on Diving-48; 3.3% p and 3.1% p on FineGym) over the previous methods without additional box annotations on both datasets. Note that ORViT [25] uses additional object bounding box annotations to train an object detector. + +# 4.4. Visualizations of StructSA + +Figure 3 visualizes example dynamic kernels $\kappa_{i,j}^{\mathrm{struct}}$ computed from self-similarity map ( $i = j$ ) on Something-Something-V1 to illustrate how StructSA encodes motion features from the spatiotemporal correlation structure. We observe that StructSA builds kernels for spatiotemporal gradient filters similar to those that are already known to be effective for capturing different types of motions [60], e.g., Sobel filters (first) or Laplacian filters (second and third), over local contexts similarly to [32]. + +
methodpretrainframe× crop×clipFLOPs (G)Something V1 top-1top-5Something V2 top-1top-5
TEA [40]IN-1K16×1×17051.980.3--
MSNet [35]IN-1K16×1×110152.182.364.789.4
CT-Net [37]IN-1K16×1×17552.580.964.589.3
TDN [69]IN-1K16×1×17253.982.165.389.5
SELFYNet [36]IN-1K16×1×17754.382.965.789.8
RSANet [32]IN-1K16×1×17254.081.166.089.9
TimeSformer-HR [4]IN-21K16×3×15109--62.5-
TimeSformer-L [4]IN-21K96×3×17140--62.3-
ViViT-L [1]K40016×3×411892--65.489.8
X-ViT [6]IN-21K32×3×11270--65.490.7
Mformer-HR [52]K40016×3×12876--67.190.6
Mformer-L [52]K40032×3×13555--68.191.2
Swin-B [47]K40032×3×1963--69.692.7
MViT-B,64×3 [18]K40064×1×31365--67.790.9
MViT-B-24,32×3 [18]K60032×1×3708--68.791.5
UniFormer-S [38]K40016×3×112557.284.967.791.4
UniFormer-B [38]K40032×3×177760.987.371.292.8
MViTv2-B [41]K40032×3×1675--70.592.7
StructViT-S-4-2K40016×3×112657.685.368.391.3
StructViT-S-4-1K40016×3×124658.085.568.891.9
StructViT-S-8-1K40016×3×140558.085.769.092.1
StructViT-B-4-2K40032×3×178461.187.771.192.7
StructViT-B-4-1K40032×3×1196361.387.871.593.1
+ +(a) Something-Something V1 & V2 + +
modeltop-1
SlowFast-R101 [20]77.6
TimeSformer [4]75.0
TimeSformer-HR [4]78.0
SViT-DD [2]79.8
TimeSformer-L [4]81.0
TQN [79]81.8
RSANet-R50 [32]84.2
UniFormer-B* [38]87.4
ORViT† [25]88.0
StructViT-B-4-287.8
StructViT-B-4-188.3
+ +(b) Diving-48 + +
modelGym288Gym99
TRN [82]33.168.7
I3D [8]27.963.2
TSM [43]34.870.6
\(\mathsf{TSM}_{\text{Two-stream}}\) [43]46.581.2
RSANet-R50 [32]50.986.4
UniFormer-B* [38]53.588.9
StructViT-B-4-253.889.3
StructViT-B-4-154.289.5
+ +(c) FineGym + +Table 5. Comparisons to the state-of-the-art methods on three motion-centric video classification benchmarks. Our StructViT achieves new state-of-the-art on all the benchmarks. For FineGym, we measure averaged per-class accuracy while top- $k$ accuracy is measured for Something-Something and Diving-48. *Reproduced by our experimental setup. †Trained with additionalbbox annotations. + +![](images/7625cce2a7f4375b45d1b51a45b274f3a79a0a4db17213043d10df2843ac46b9.jpg) +input video + +$$ +\boldsymbol {\kappa} _ {i, j} ^ {\mathrm {s t r u c t}} = \sigma_ {j} \left(\boldsymbol {q} _ {i} \boldsymbol {K} _ {j} ^ {\top} \boldsymbol {U} ^ {\mathrm {K} ^ {\top}}\right) \boldsymbol {U} ^ {\mathrm {V}} +$$ + +![](images/07ee50b9ed555248ce4bea9fc5c9ba633f4acc168a7081ecbaff8ab446315d67.jpg) +Figure 3. Visualization of dynamic kernels $\kappa_{i,j}^{\mathrm{struct}}$ in StructSA on Something-V1. The top row shows the input frames that contain the input spatiotemporal local context (indicated by green boxes) used in the dynamic kernel computation. The bottom row presents the resulting dynamic kernels $\kappa_{i,j}^{\mathrm{struct}}$ for a StructSA head when $i = j$ . Note that the computed dynamic kernels are computed with self-similarity map $(i = j)$ to illustrate its effectiveness in capturing motions in videos. We use StructViT-S-4-1 with $M = 5 \times 5 \times 5$ . + +![](images/b355afc4d5fad76f45c8b3acc795d22c211f073d0bc45f8b3b214df1abf9f63d.jpg) + +![](images/8f0897e41f1a0838d1d69fd6fd609aea68af6459ad27bc8ebef4c931a25ffdc1.jpg) + +![](images/7852b71cb59cdca57a65394c362561cd2693c647071eeb462c9c2d31d5526c2c.jpg) + +![](images/a5314ee2556c02f276468696ab520bf32c76714974f695db5306447c10c58665.jpg) + +# 5. Conclusion + +We have introduced a novel self-attention mechanism, StructSA, that exploits rich structural patterns of querykey correlation for visual representation learning. StructSA leverages spatial (and temporal) structures of local correlations and aggregates chunks of local features globally across entire locations. Structural Vision Transformer (StructViT) using StructSA as the main attention module achieves state-of-the-art results on both image and video classification benchmarks. We believe leveraging structural + +patterns of correlation in attention will also benefit other tasks in computer vision and natural language processing. We leave this for future work. + +Acknowledgements This work was supported by the IITP grants (No. 2022-0-00290: Visual Intelligence for space-time understanding and generation $(45\%)$ , No. 2022-0-00264: Comprehensive video understanding and generation with knowledge-based deep logic $(50\%)$ , No. 2019-0-01906: AI graduate school program at POSTECH $(5\%))$ funded by Ministry of Science and ICT, Korea. + +# References + +[1] Anurag Arnab, Mostafa Dehghani, Georg Heigold, Chen Sun, Mario Lučić, and Cordelia Schmid. Vivit: A video vision transformer. arXiv preprint arXiv:2103.15691, 2021. 2, 7, 8 +[2] Elad Ben-Avraham, Roei Herzig, Karttikeya Mangalam, Amir Bar, Anna Rohrbach, Leonid Karlinsky, Trevor Darrell, and Amir Globerson. Bringing image scene structure to video via frame-clip consistency of object tokens. arXiv preprint arXiv:2206.06346, 2022. 8 +[3] Chiraz BenAbdelkader, Ross G Cutler, and Larry S Davis. Gait recognition using image self-similarity. 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Introduction" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 456, + 287, + 599 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 456, + 287, + 599 + ], + "spans": [ + { + "bbox": [ + 46, + 456, + 287, + 599 + ], + "type": "text", + "content": "How visual elements interact with each other in space and time is a crucial cue for visual understanding, e.g., recognizing actions in a video or analyzing scene layout patterns in an image. In computer vision, such relational patterns are effectively captured by the structure of correlations or similarities across visual elements in different positions [3, 57]; a correlation structure of an image reveals spatial layouts of similar patterns [30, 33] and that of a video provides bidirectional motion likelihoods [32, 36]. 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[ + { + "bbox": [ + 353, + 443, + 486, + 454 + ], + "type": "text", + "content": "(c) Structural self-attention (StructSA)" + } + ] + } + ], + "index": 29, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 459, + 547, + 526 + ], + "lines": [ + { + "bbox": [ + 304, + 459, + 547, + 526 + ], + "spans": [ + { + "bbox": [ + 304, + 459, + 547, + 526 + ], + "type": "text", + "content": "Figure 1. Structural Self-Attention. Given an input video and a query indicated by the red box in (a), the query-key correlation maps in (b) clearly reveal the structures of spatial layout and motion with respect to the query. The proposed attention mechanism in (c) is designed to leverage these rich structural patterns for computing attention scores in the self-attention process." + } + ] + } + ], + "index": 30, + "angle": 0, + "type": "image_caption" + } + ], + "index": 28 + }, + { + "bbox": [ + 304, + 542, + 546, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 542, + 546, + 686 + ], + "spans": [ + { + "bbox": [ + 304, + 542, + 546, + 686 + ], + "type": "text", + "content": "tion and uses them to dynamically aggregate local contexts of value features, effectively capturing rich structural patterns such as scene layouts, object motion, and interobject relations in images and video. As illustrated in Fig. 1 and detailed in Sec. 3, this is mainly achieved by empowering the standard self-attention mechanism with long-range convolutional interactions and dynamic contextual feature aggregation. To investigate the effect of StructSA, we also provide an in-depth analysis on the relationship to recent self-attention variants with convolutional projection [18, 41, 42, 70, 72], showing their potential and limitation in leveraging structural patterns." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 306, + 689, + 546, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 546, + 714 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 546, + 714 + ], + "type": "text", + "content": "To validate the effect of StructSA, we develop the structural vision transformer that adopts it as a main building" + } + ] + } + ], + "index": 32 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 149, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 149, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 149, + 712 + ], + "type": "text", + "content": "*Co-corresponding authors." + } + ] + } + ], + "index": 33 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18941" + } + ] + } + ], + "index": 34 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "content": "block, and perform an extensive set of experiments on both image and video classification tasks, showing the effectiveness of learning structural patterns for visual representations. Our main contributions are as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 120, + 287, + 228 + ], + "type": "list", + "angle": 0, + "index": 4, + "blocks": [ + { + "bbox": [ + 47, + 120, + 287, + 155 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 120, + 287, + 155 + ], + "spans": [ + { + "bbox": [ + 47, + 120, + 287, + 155 + ], + "type": "text", + "content": "- We introduce structural self-attention (StructSA) that learns correlation structures for visual representations with the vision transformer." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 156, + 287, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 156, + 287, + 192 + ], + "spans": [ + { + "bbox": [ + 47, + 156, + 287, + 192 + ], + "type": "text", + "content": "- We provide an in-depth analysis on the relationship between StructSA and self-attention variants with convolutional projections." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 192, + 287, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 192, + 287, + 228 + ], + "spans": [ + { + "bbox": [ + 47, + 192, + 287, + 228 + ], + "type": "text", + "content": "- Our new transformer network achieves state-of-the-art results on ImageNet-1K, Kinetics-400, Something-Something V1&V2, Diving-48, and FineGym." + } + ] + } + ], + "index": 3 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 236, + 133, + 249 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 236, + 133, + 249 + ], + "spans": [ + { + "bbox": [ + 47, + 236, + 133, + 249 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 256, + 287, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 256, + 287, + 449 + ], + "spans": [ + { + "bbox": [ + 46, + 256, + 287, + 449 + ], + "type": "text", + "content": "Transformer Networks in Vision. Since transformer networks [66] showed remarkable success in natural language processing [5, 14], they have widely been adopted in various computer vision tasks as an alternative to CNNs [1, 7, 17, 58, 59]. Despite of their success, the pure transformer networks require a large amount of training data compared to CNNs where convolution operations introduce desirable inductive biases such as locality and translation invariance allowing more efficient training [17, 53]. This incentivized several methods to inherit the convolutional inductive biases via knowledge distillation [63], local self-attention [27, 45, 54], and architectural fusion [9, 12, 23, 38, 70, 72]. While recent methods using a convolutional projection [18, 41, 70, 72] achieve remarkable improvements, we show that self-attention with a convolutional projection can be derived as a special form of our proposed method." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 450, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 450, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 450, + 288, + 713 + ], + "type": "text", + "content": "Correlation Structure Modeling. Geometric structure of correlations between visual features, i.e., patterns of how they are similar to each other, allows us to understand relational patterns in visual data for various computer vision tasks. Spatial self-correlation in images is used for suppressing photometric variations and revealing geometric layout of objects in the image [30, 33, 57]. Spatial cross-correlation between different images is often used for establishing semantic correspondences capturing structural similarities [24, 50, 55]. In the video domain, several methods exploit the structure of spatial cross-correlations between consecutive frames to estimate optical flow [16, 74] or to learn motion features for action recognition [35, 67]. Kwon et al. [36] propose spatio-temporal self-correlations for learning bi-directional motion features and Kim et al. [32] introduce relational self-attention that generates attention weights dynamically from the structure of the spatio-temporal self-correlations. However, these two methods use self-correlations between the query and its local spatio-temporal neighborhoods only, thus, are limited in learning global relational patterns between distant features. Inspired by this, we introduce structural self" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": "attention that capturing not only the spatio-temporal local self-correlation but also cross-correlations between features in the distance, utilizing both motion and global spatiotemporal inter-feature relations for learning motion-centric video representations." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 142, + 397, + 156 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 142, + 397, + 156 + ], + "spans": [ + { + "bbox": [ + 305, + 142, + 397, + 156 + ], + "type": "text", + "content": "3. Our Approach" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 162, + 545, + 258 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 162, + 545, + 258 + ], + "spans": [ + { + "bbox": [ + 304, + 162, + 545, + 258 + ], + "type": "text", + "content": "We propose a novel self-attention mechanism, named structural self-attention (StructSA), that is designed to leverage rich correlation structures naturally emerging in key-query interactions of attention. We start by revisiting the vanilla self-attention and its limitation and then describe the details of StructSA. We also provide an in-depth analysis of recent self-attention variants with convolutional projections from the perspective of learning structural patterns." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 264, + 460, + 277 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 264, + 460, + 277 + ], + "spans": [ + { + "bbox": [ + 305, + 264, + 460, + 277 + ], + "type": "text", + "content": "3.1. Background: Self-Attention" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "spans": [ + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "text", + "content": "Self-attention (SA) [66] is a primitive operation for modern transformer networks [1, 17, 63]. Given " + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "text", + "content": " input features " + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\mathbf{X} = [\\pmb{x}_1,\\dots ,\\pmb{x}_N]\\in \\mathbb{R}^{N\\times C}" + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "text", + "content": ", SA first projects the input " + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\mathbf{X}" + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "text", + "content": " linearly into queries, keys, and values, and transforms each " + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "text", + "content": "-dimensional input feature " + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\pmb{x}_i" + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "text", + "content": " into a contextualized output feature " + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\pmb{y}_i" + }, + { + "bbox": [ + 304, + 282, + 545, + 354 + ], + "type": "text", + "content": " by" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 316, + 357, + 545, + 408 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 316, + 357, + 545, + 408 + ], + "spans": [ + { + "bbox": [ + 316, + 357, + 545, + 408 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sigma \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} ^ {\\top}\\right) \\boldsymbol {V} = \\sum_ {j} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {k} _ {j} ^ {\\top}\\right) \\boldsymbol {v} _ {j} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {1} \\\\ \\boldsymbol {q} _ {i} = \\boldsymbol {x} _ {i} \\boldsymbol {W} ^ {\\mathrm {Q}}, \\quad \\boldsymbol {K} = \\boldsymbol {X} \\boldsymbol {W} ^ {\\mathrm {K}}, \\quad \\boldsymbol {V} = \\boldsymbol {X} \\boldsymbol {W} ^ {\\mathrm {V}} \\\\ \\end{array}", + "image_path": "01ffd4ffb2bd1ff2aceb25e8e2def154bc04edc79d062fc7acabc39b8995a547.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "spans": [ + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "content": " is a softmax function and " + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "inline_equation", + "content": "W^{Q}, W^{K}, W^{V} \\in \\mathbb{R}^{C \\times C}" + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "content": " are projection matrices for query " + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "inline_equation", + "content": "q_{i} \\in \\mathbb{R}^{1 \\times C}" + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "content": ", keys " + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "inline_equation", + "content": "K \\in \\mathbb{R}^{N \\times C}" + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "content": ", and values " + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "inline_equation", + "content": "V \\in \\mathbb{R}^{N \\times C}" + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "content": ", respectively. Here we use a 1-dimensional sequence of input features for notational simplicity, and the operation can be extended to a larger dimensionality. After computing a correlation map " + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "inline_equation", + "content": "q_{i} K^{\\top}" + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "content": ", the vanilla SA uses individual correlation values independently, i.e., " + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "inline_equation", + "content": "q_{i} k_{j}^{\\top}" + }, + { + "bbox": [ + 304, + 415, + 545, + 594 + ], + "type": "text", + "content": ", for value aggregation while ignoring the structure of the map, which leads to the same output regardless of the order of features. This permutation invariance prevents SA from capturing spatial layouts [27, 57] or motions [32, 36, 44] of objects in images or videos. Positional encoding for SA helps spatial awareness, but the structures of correlations are still not recognized in value aggregation [10, 11, 32]." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 599, + 446, + 611 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 599, + 446, + 611 + ], + "spans": [ + { + "bbox": [ + 306, + 599, + 446, + 611 + ], + "type": "text", + "content": "3.2. Structural Self-Attention" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "content": "We introduce a novel self-attention mechanism, named structural self-attention (StructSA), that effectively incorporates rich structural patterns of query-key correlation into contextual feature aggregation. The StructSA mechanism consists of two steps: (i) structural query-key attention and (ii) contextual value aggregation. Unlike the vanilla query-key attention where individual correlation values themselves are used as attention scores, the structural query-key" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18942" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "content": "attention takes the correlation map as a whole and detect structural patterns from it in attention scoring. The subsequent contextual value aggregation then combines the attention scores together to compute diverse sets of kernel weights that are used for dynamically collecting local contexts of value features." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 146, + 288, + 195 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 146, + 288, + 195 + ], + "spans": [ + { + "bbox": [ + 46, + 146, + 288, + 195 + ], + "type": "text", + "content": "Structural Query-Key Attention. To transform the vanilla query-key attention into structure-aware one, the structural query-key attention (SQKA) deploy convolutions on top of query-key correlation " + }, + { + "bbox": [ + 46, + 146, + 288, + 195 + ], + "type": "inline_equation", + "content": "\\mathbf{q}_i\\mathbf{K}^\\top" + }, + { + "bbox": [ + 46, + 146, + 288, + 195 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 85, + 201, + 287, + 216 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 85, + 201, + 287, + 216 + ], + "spans": [ + { + "bbox": [ + 85, + 201, + 287, + 216 + ], + "type": "interline_equation", + "content": "\\boldsymbol {A} _ {i} = \\sigma \\left(\\operatorname {c o n v} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K}, \\boldsymbol {U} ^ {\\mathrm {K}}\\right)\\right) \\in \\mathbb {R} ^ {N \\times D}, \\tag {2}", + "image_path": "f78896e8b15dd9d984a83413cbf999a99e885aec7553e59db8f8db245123de06.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "spans": [ + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "inline_equation", + "content": "\\mathbf{U}^{\\mathrm{K}} \\in \\mathbb{R}^{M \\times D}" + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": " is " + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": " convolutional kernels with size " + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": ". Note that " + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": " is a softmax function taken over all " + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "inline_equation", + "content": "ND" + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": " entries in the input matrix; we observe that it is empirically more stable compared to " + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": " individual softmax operations over " + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": " entries. Each element of " + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "inline_equation", + "content": "A_{i}" + }, + { + "bbox": [ + 47, + 222, + 287, + 283 + ], + "type": "text", + "content": " is computed as" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 100, + 289, + 287, + 304 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 100, + 289, + 287, + 304 + ], + "spans": [ + { + "bbox": [ + 100, + 289, + 287, + 304 + ], + "type": "interline_equation", + "content": "\\boldsymbol {a} _ {i, j} = \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\in \\mathbb {R} ^ {1 \\times D}, \\tag {3}", + "image_path": "a13e3863beadef14a05b53d9b1c3be54f422c7c0adb9a83b3461d4941271a6ac.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 103, + 305, + 215, + 321 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 103, + 305, + 215, + 321 + ], + "spans": [ + { + "bbox": [ + 103, + 305, + 215, + 321 + ], + "type": "interline_equation", + "content": "\\boldsymbol {K} _ {j} = \\boldsymbol {X} _ {(j)} \\boldsymbol {W} ^ {\\mathrm {K}} \\in \\mathbb {R} ^ {M \\times C},", + "image_path": "672c602766c68c6ad0d72a51d8312d3f03459e2645e290171077bec8c69d46bd.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "spans": [ + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "inline_equation", + "content": "\\sigma_{j}" + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "text", + "content": " returns a " + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "text", + "content": "-dimensional softmax-ed output for " + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "text", + "content": "th location and " + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "inline_equation", + "content": "\\mathbf{X}_{(j)} \\in \\mathbb{R}^{M \\times C}" + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "text", + "content": " is local context features whose context window is centered at " + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 327, + 287, + 363 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "spans": [ + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "text", + "content": "Unlike the vanilla query-key attention, which is agnostic to its neighborhood structure, SQKA is empowered by convolution to recognize a local correlation structure of " + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "inline_equation", + "content": "\\pmb{q}_i\\pmb{K}_j^{\\top} \\in \\mathbb{R}^{1\\times M}" + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "text", + "content": " and transform it into a " + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "text", + "content": "-dimensional vector; the convolution kernels " + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "inline_equation", + "content": "U^{\\mathrm{K}}" + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "text", + "content": " act as correlation pattern detectors. In particular, when " + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "inline_equation", + "content": "i = j" + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "text", + "content": ", the correlation map reduces to local self-similarity [57] that is known to be effective for capturing spatial layout patterns [57] or spatiotemporal motion [32, 36], meaning that SQKA recognizes diverse correlation patterns including self-similarity [57] via long-range interaction between query " + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "text", + "content": " and context " + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 364, + 287, + 496 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 498, + 287, + 536 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 287, + 536 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 287, + 536 + ], + "type": "text", + "content": "Contextual Value Aggregation. Given SQKA recognizing structural patterns of correlation, StructSA combines SQKA entries into a weight " + }, + { + "bbox": [ + 46, + 498, + 287, + 536 + ], + "type": "inline_equation", + "content": "\\kappa_{i,j}^{\\mathrm{struct}}" + }, + { + "bbox": [ + 46, + 498, + 287, + 536 + ], + "type": "text", + "content": " to aggregate value " + }, + { + "bbox": [ + 46, + 498, + 287, + 536 + ], + "type": "inline_equation", + "content": "\\pmb{v}_j" + }, + { + "bbox": [ + 46, + 498, + 287, + 536 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 59, + 552, + 287, + 586 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 552, + 287, + 586 + ], + "spans": [ + { + "bbox": [ + 59, + 552, + 287, + 586 + ], + "type": "interline_equation", + "content": "\\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {v} _ {j} = \\sum_ {j = 1} ^ {N} \\kappa_ {i, j} ^ {\\text {s t r u c t}} \\boldsymbol {v} _ {j}, \\tag {4}", + "image_path": "d3f321bd41edba4c2366fc6d3ce12a5fb51ae8106941d5b18afb7443f3bf333e.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 593, + 287, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 593, + 287, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 593, + 287, + 616 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 593, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\mathbf{u}^{\\mathrm{V}}\\in \\mathbb{R}^{1\\times D}" + }, + { + "bbox": [ + 46, + 593, + 287, + 616 + ], + "type": "text", + "content": " is a vector that linearly combines " + }, + { + "bbox": [ + 46, + 593, + 287, + 616 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 593, + 287, + 616 + ], + "type": "text", + "content": " pattern scores to the final attention weight." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 617, + 287, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 287, + 654 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 287, + 654 + ], + "type": "text", + "content": "We further extend Eq. (4) to generate a spatial kernel not a single scalar for each position " + }, + { + "bbox": [ + 46, + 617, + 287, + 654 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 617, + 287, + 654 + ], + "type": "text", + "content": ". We call this method contextual aggregation and it has a following form:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 56, + 661, + 287, + 711 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 56, + 661, + 287, + 711 + ], + "spans": [ + { + "bbox": [ + 56, + 661, + 287, + 711 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K}}\\right) \\boldsymbol {U} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {j} = \\sum_ {j = 1} ^ {N} \\kappa_ {i, j} ^ {\\text {s t r u c t}} \\boldsymbol {V} _ {j}, \\tag {5} \\\\ \\boldsymbol {V} _ {j} = \\boldsymbol {X} _ {(j)} \\boldsymbol {W} ^ {\\mathrm {V}} \\in \\mathbb {R} ^ {M \\times C}. \\\\ \\end{array}", + "image_path": "9bf7c81c854333c7c35668274ce80c9207dc8494a3cdb8fdd448d70d82f48638.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": "Compared to " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{V}}" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": " that produces a scalar weighting a single element " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "v_{j}" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "\\pmb{U}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times D}" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": " generates spatial kernel dynamically aggregating a local context of value " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "\\pmb{V}_{j}" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": " for every position " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": "; each column of " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "\\pmb{U}^{\\mathrm{V}}" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": ", i.e., " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "\\pmb{U}_{i,d}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times 1}" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": ", plays a role as a context aggregator that performs a weighted pooling of local context " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "\\pmb{V}_{j}" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": " and thus different combinations of these context aggregators result in diverse dynamic kernels " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "\\kappa_{i,j}^{\\mathrm{struct}}" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": " for different locations " + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 72, + 545, + 169 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 177, + 537, + 190 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 177, + 537, + 190 + ], + "spans": [ + { + "bbox": [ + 305, + 177, + 537, + 190 + ], + "type": "text", + "content": "3.3. Relationship to Convolutional Self-Attention" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "spans": [ + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "type": "text", + "content": "Recent vision transformers [18, 23, 41, 70, 72] often adopt convolutional inductive biases in the form of self-attention with convolutional projections (ConvSA). In this section, we analyze ConvSA with a lens of StructSA and show its potential and limitation for learning structures from query-key correlations. Different from SA, ConvSA computes project keys and values " + }, + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "type": "inline_equation", + "content": "K^{\\mathrm{conv}}" + }, + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "type": "inline_equation", + "content": "V^{\\mathrm{conv}} \\in \\mathbb{R}^{N \\times C}" + }, + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "type": "text", + "content": " using a convolution operation over the input feature map " + }, + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "type": "inline_equation", + "content": "X" + }, + { + "bbox": [ + 304, + 196, + 545, + 292 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 321, + 301, + 545, + 316 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 321, + 301, + 545, + 316 + ], + "spans": [ + { + "bbox": [ + 321, + 301, + 545, + 316 + ], + "type": "interline_equation", + "content": "\\boldsymbol {K} ^ {\\text {c o n v}} = \\left[ \\boldsymbol {k} _ {1} ^ {\\text {c o n v}}, \\dots , \\boldsymbol {k} _ {N} ^ {\\text {c o n v}} \\right] = \\operatorname {c o n v} (\\boldsymbol {X}, \\boldsymbol {W} ^ {\\mathrm {K}}), \\tag {6}", + "image_path": "1bd9ef88d058d032e188947a0961da20dee0ea46f75382b1ae2a551ee6ec6b9e.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 323, + 318, + 545, + 333 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 323, + 318, + 545, + 333 + ], + "spans": [ + { + "bbox": [ + 323, + 318, + 545, + 333 + ], + "type": "interline_equation", + "content": "\\boldsymbol {V} ^ {\\text {c o n v}} = \\left[ \\boldsymbol {v} _ {1} ^ {\\text {c o n v}}, \\dots , \\boldsymbol {v} _ {N} ^ {\\text {c o n v}} \\right] = \\operatorname {c o n v} \\left(\\boldsymbol {X}, \\boldsymbol {W} ^ {\\mathrm {V}}\\right), \\tag {7}", + "image_path": "ae77a45dd77291162cc64595dd07749a3f9ed21ea112b7b149492d72584c16d0.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 344, + 545, + 381 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 344, + 545, + 381 + ], + "spans": [ + { + "bbox": [ + 304, + 344, + 545, + 381 + ], + "type": "text", + "content": "where conv is a convolution operation, and " + }, + { + "bbox": [ + 304, + 344, + 545, + 381 + ], + "type": "inline_equation", + "content": "\\mathbf{W}^{\\mathrm{K}},\\mathbf{W}^{\\mathrm{V}}\\in" + }, + { + "bbox": [ + 304, + 344, + 545, + 381 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{M\\times C\\times C}" + }, + { + "bbox": [ + 304, + 344, + 545, + 381 + ], + "type": "text", + "content": " are kernel weights with a kernel size " + }, + { + "bbox": [ + 304, + 344, + 545, + 381 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 344, + 545, + 381 + ], + "type": "text", + "content": " for key and value projections, respectively." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "spans": [ + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "type": "text", + "content": "In most previous methods, ConvSA is implemented with a channel-wise separable convolution [26], which consists of two factorized convolution operations, i.e., point-wise and channel-wise convolutions [18, 23, 41, 70, 72]. In this case, each key " + }, + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "type": "inline_equation", + "content": "\\pmb{k}_i^{\\mathrm{conv}}" + }, + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "type": "text", + "content": " and value " + }, + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "type": "inline_equation", + "content": "\\pmb{v}_i^{\\mathrm{conv}}" + }, + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "type": "text", + "content": " is computed from a local context " + }, + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "type": "inline_equation", + "content": "X_i" + }, + { + "bbox": [ + 304, + 381, + 545, + 453 + ], + "type": "text", + "content": " by" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 337, + 464, + 545, + 480 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 337, + 464, + 545, + 480 + ], + "spans": [ + { + "bbox": [ + 337, + 464, + 545, + 480 + ], + "type": "interline_equation", + "content": "\\boldsymbol {k} _ {i} ^ {\\text {c o n v}} = \\boldsymbol {u} ^ {\\mathrm {K} ^ {\\mathsf {T}}} \\boldsymbol {X} _ {i} \\boldsymbol {W} ^ {\\mathrm {K}} = \\boldsymbol {u} ^ {\\mathrm {K} ^ {\\mathsf {T}}} \\boldsymbol {K} _ {i} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {8}", + "image_path": "ad2d220f5686b2a789658ad54bbf59076dcfe430eb58d7a5ad2bc123483bdf28.jpg" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 339, + 482, + 545, + 498 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 339, + 482, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 339, + 482, + 545, + 498 + ], + "type": "interline_equation", + "content": "\\boldsymbol {v} _ {i} ^ {\\text {c o n v}} = \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {X} _ {i} \\boldsymbol {W} ^ {\\mathrm {V}} = \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {i} \\in \\mathbb {R} ^ {1 \\times C}, \\tag {9}", + "image_path": "ec278f4399a7300df62cee8e6a5081892f2a1ac82bb850b8215253ba8e030a93.jpg" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "inline_equation", + "content": "\\pmb{W}^{\\mathrm{K}},\\pmb{W}^{\\mathrm{V}}\\in \\mathbb{R}^{C\\times C}" + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "text", + "content": " are weights for the linear projection that are equivalent to point-wise convolution, and " + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{K}},\\pmb{u}^{\\mathrm{V}}\\in \\mathbb{R}^{M\\times 1}" + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "text", + "content": " are channel-wise convolution weights that are used to spatially aggregate linearly projected context " + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "inline_equation", + "content": "\\pmb{K}_i" + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "inline_equation", + "content": "\\pmb{V}_i" + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "text", + "content": ", respectively. Note that here we assume the channel-wise convolution weights are shared across channels for simplicity without loss of generality and the full derivation is available in our supplementary material A." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 606, + 545, + 631 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 606, + 545, + 631 + ], + "spans": [ + { + "bbox": [ + 304, + 606, + 545, + 631 + ], + "type": "text", + "content": "From Eq. (1) combined with Eq. (8) and (9), a transformed output " + }, + { + "bbox": [ + 304, + 606, + 545, + 631 + ], + "type": "inline_equation", + "content": "\\pmb{y}_i" + }, + { + "bbox": [ + 304, + 606, + 545, + 631 + ], + "type": "text", + "content": " in ConvSA is obtained by" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 317, + 640, + 545, + 711 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 640, + 545, + 711 + ], + "spans": [ + { + "bbox": [ + 317, + 640, + 545, + 711 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\boldsymbol {y} _ {i} = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {k} _ {j} ^ {\\text {c o n v} ^ {\\mathsf {T}}}\\right) \\boldsymbol {v} _ {j} ^ {\\text {c o n v}} \\\\ = \\sum_ {j = 1} ^ {N} \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {u} ^ {\\mathrm {K}}\\right) \\boldsymbol {u} ^ {\\mathrm {V} ^ {\\top}} \\boldsymbol {V} _ {j} = \\sum_ {j = 1} ^ {N} \\boldsymbol {\\kappa} _ {i, j} ^ {\\text {c o n v}} \\boldsymbol {V} _ {j}, \\tag {10} \\\\ \\end{array}", + "image_path": "e2cc7d583fa0acb81d594fd34a84296b5b8997d9338a5e94bfdda486e9eb9822.jpg" + } + ] + } + ], + "index": 24 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18943" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 86, + 70, + 511, + 186 + ], + "blocks": [ + { + "bbox": [ + 86, + 70, + 511, + 186 + ], + "lines": [ + { + "bbox": [ + 86, + 70, + 511, + 186 + ], + "spans": [ + { + "bbox": [ + 86, + 70, + 511, + 186 + ], + "type": "image", + "image_path": "ab91793394a81af57e0df3bd0aeac68ed72687683e1485412ba0781d66a8b8c3.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "lines": [ + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "spans": [ + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": "Figure 2. Visualization of ConvSA and StructSA on ImageNet-1K. The query location " + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": " is set to the center of the image and the kernel size " + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "M = 3 \\times 3" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": ". Given the left input image, we compare ConvSA (" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "D = 1" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": ") and StructSA (" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "D = 8" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": ") in terms of (a) " + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": " attention maps " + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "\\sigma_{jD}(\\pmb{q}_i \\pmb{K}_j^\\top \\pmb{U}^{\\mathrm{KT}})" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": ", (b) local feature aggregation patterns learned in " + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "\\pmb{U}^V" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": ", and (c) the combinations of (a) and (b). Note that in (c), each location " + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": " has an aggregation map of the kernel size " + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "M = 3 \\times 3" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": " and thus we also show enlarged images for four different sample locations " + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 190, + 547, + 237 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\sigma_{j}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " is " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": "th entry of the softmax over " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " tokens. This reveals that an attention score " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\sigma_{j}(\\pmb{q}_{i}\\pmb{k}_{j}^{\\mathrm{conv}^{\\top}})" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " is computed by projecting a local correlation map " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{q}_{i}\\pmb{K}_{j}^{\\top} \\in \\mathbb{R}^{1 \\times M}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " by " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{K}}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": ", and a dynamic kernel " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\kappa_{i,j}^{\\mathrm{conv}}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " for the final feature aggregation of " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{V}_{j}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " is obtained by weighting the aggregation pattern presented in " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{V}}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " using the computed attention map. Given that correlation map " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{q}_{i}\\pmb{K}_{j}^{\\top}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " represents a structural pattern, we can interpret that " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{K}}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " acts as a pattern detector that extracts a specific correlation pattern from " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{q}_{i}\\pmb{K}_{j}^{\\top}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": ", whereas " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{V}}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " plays a role as a context aggregator that performs a weighted pooling of local context " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{V}_{j}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": ". Due to the presence of this pattern detector " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{K}}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": " and its corresponding context aggregator " + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{V}}" + }, + { + "bbox": [ + 46, + 251, + 289, + 423 + ], + "type": "text", + "content": ", ConvSA can leverage a structural pattern of input for context aggregation." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": "Limitation. Although ConvSA can learn, unlike SA, a structural pattern over correlation maps by " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{K}}" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": ", it only learns a single pattern and encodes various shapes in correlation maps into a scalar value representing the similarity against the learned pattern; as the result, the final dynamic kernel " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "\\kappa_{i,j}^{\\mathrm{conv}}" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " for every " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " reduces to the identical pattern of " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{V}}" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " with different weighting only. This lack of expressiveness in " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{K}}" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "\\pmb{u}^{\\mathrm{V}}" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " prevents ConvSA from capturing diverse structural patterns and generating diverse dynamic kernels. In constraint, StructSA learns " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " different pattern extractors in " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "\\pmb{U}^{\\mathrm{K}}" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " and represents various local correlation shapes by a set of " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " similarity scores. These scores are then combined with the " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " context aggregators in " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "\\pmb{U}^{\\mathrm{V}}" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": "; different combinations of these context aggregators result in diverse dynamic kernels " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "\\kappa_{i,j}^{\\mathrm{struct}}" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": " for different locations " + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 430, + 289, + 613 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "content": "Visualization. The aforementioned difference between ConvSA and StructSA, as well as their effects, can be better understood by visualizing the kernel computation process. Figure 2 provides such a visual comparison of how structural patterns are used in ConvSA and StructSA given an example image from ImageNet-1K [13]. From a query-key correlation map, ConvSA generates a single attention map (Fig. 2a, top). These scores are then combined with the" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "spans": [ + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "text", + "content": "context aggregator " + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "inline_equation", + "content": "\\boldsymbol{u}^{\\mathrm{V}}" + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "text", + "content": " (Fig. 2b, top), which conveys only a single aggregation pattern. This causes local features to be aggregated with the identical pattern in " + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "inline_equation", + "content": "\\boldsymbol{u}^{\\mathrm{V}}" + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "text", + "content": " for all locations, and the only difference remains in their scales (Fig. 2c, top). In contrast, StructSA generates diverse attention maps using " + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "text", + "content": " pattern detectors, each capturing different structures in the query-key correlation maps (Fig. 2a, bottom), and combines them with different context aggregators (Fig. 2b, bottom) resulting in rich aggregation patterns for different locations " + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 251, + 547, + 384 + ], + "type": "text", + "content": " (Fig. 2c, bottom). For more in-depth comparison, please refer to our supplementary material D." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 392, + 388, + 406 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 392, + 388, + 406 + ], + "spans": [ + { + "bbox": [ + 306, + 392, + 388, + 406 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 412, + 546, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 412, + 546, + 449 + ], + "spans": [ + { + "bbox": [ + 304, + 412, + 546, + 449 + ], + "type": "text", + "content": "To validate the effectiveness of the proposed method on visual representation learning, we conduct extensive experiments on image and video classification benchmarks." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 454, + 422, + 467 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 454, + 422, + 467 + ], + "spans": [ + { + "bbox": [ + 306, + 454, + 422, + 467 + ], + "type": "text", + "content": "4.1. Experimental Setup" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "spans": [ + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "type": "text", + "content": "Datasets. ImageNet-1K [13] is a large-scale dataset with 1.2M images labeled by 1000 object classes. Kinetics-400 [31] is one of the most popular large-scale video datasets with 400 action classes. We use 241k action clips available online. Something-Something-V1 & V2 [22, 49] are both large-scale action recognition benchmarks, including 108k and 220k action clips, respectively. Both datasets share the same motion-centric action classes, e.g., 'pushing something from left to right,' so thus capturing fine-grained motion is crucial to achieving the better performance. Diving-48 [39] is a fine-grained action benchmark that is heavily dependent on temporal modeling [3], containing 18k videos with 48 diving classes. FineGym [56] is a motion-centric benchmark that includes gymnastics action classes with severe deformations." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": "Training & Testing Protocols. For image classification, we follow the training strategy of DeiT [63] adopting random clipping, random horizontal flipping, mixup [80], cutmix [78], random erasing [81] and label-smoothing [51] to" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "18944" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 167 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 167 + ], + "type": "text", + "content": "augment the input images for training. We train all models from scratch for 300 epochs using AdamW optimizer [48] with a cosine learning rate schedule including 5 warm-up epochs. The batch size, learning rate, and weight decay are set to 1024, 1e-3, and 0.05, respectively. For comparison on stronger experiment setup [29, 38, 41, 77], we also train our models using Token Labeling [29] and larger resolution images, i.e., " + }, + { + "bbox": [ + 46, + 72, + 287, + 167 + ], + "type": "inline_equation", + "content": "384 \\times 384" + }, + { + "bbox": [ + 46, + 72, + 287, + 167 + ], + "type": "text", + "content": ", following the protocols in [38]." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 167, + 288, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 167, + 288, + 407 + ], + "spans": [ + { + "bbox": [ + 46, + 167, + 288, + 407 + ], + "type": "text", + "content": "For video classification, we follow training protocols and data augmentation recipes in MViT [18]. For Kinetics-400, we sample 16 or 32 frames using the dense sampling strategy [71]. We temporally inflate the model weights pretrained on ImageNet-1K and finetune it for 110 epochs including 10 warm-up epochs. We use AdamW [48] optimizer with the cosine learning rate schedule. We set the batch size, learning rate, weight decay, and stochastic depth rate to 64, 2e-4, 0.05, and 0.1, respectively. For Something-Something, Diving-48, and FineGym, we utilize the segment-based sampling strategy [68] and do not use the random horizontal flip for data augmentation. We initialize the model with the weights pretrained on Kinetics-400 and finetune the model for 60 epochs including 5 warm-up epochs. Other training hyperparameters are the same as those for Kinetics-400. For testing, we sample multiple clips at different temporal indices for each clip or cropping different spatial regions and then obtain the final score by computing an average over the scores for each clip. We train all models once using 8 to 16 NVIDIA A100 GPUs." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 410, + 287, + 458 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 410, + 287, + 458 + ], + "spans": [ + { + "bbox": [ + 47, + 410, + 287, + 458 + ], + "type": "text", + "content": "Metrics. We measure top-1 and top-5 accuracy as performance metrics, except for FineGym, we compute averaged per-class top-1 accuracy. As efficiency metrics, we measure the number of parameters and FLOPs." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 465, + 167, + 477 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 465, + 167, + 477 + ], + "spans": [ + { + "bbox": [ + 47, + 465, + 167, + 477 + ], + "type": "text", + "content": "4.2. Analysis of StructSA" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 483, + 287, + 674 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 483, + 287, + 674 + ], + "spans": [ + { + "bbox": [ + 46, + 483, + 287, + 674 + ], + "type": "text", + "content": "StructSA can be readily integrated into any existing ViTs to enhance visual representations by capturing correlation structures. In this subsection, we experimentally validate and analyze the impact of StructSA. Here, for a direct comparison with SA, we choose to use DeiT-S [63] as the baseline backbone; DeiT is a pure SA-based vision transformer and thus adequate for validating the effect of StructSA, avoiding any intervention of additional components. In this analysis, we replace all the SA layers in DeiT with StructSA layers. The evaluations are done on ImageNet-1K [13] and Something-Something-V1 [22] benchmarks while varying the structure dimension " + }, + { + "bbox": [ + 46, + 483, + 287, + 674 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 483, + 287, + 674 + ], + "type": "text", + "content": ", the kernel size " + }, + { + "bbox": [ + 46, + 483, + 287, + 674 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 46, + 483, + 287, + 674 + ], + "type": "text", + "content": ", and context aggregation methods. We follow the training and testing protocols in Sec. 4.1, except that we directly finetune the ImageNet-1K-pretrained model on Something-Something-V1 using random cropping only for data augmentation." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": "Structure Dimension " + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": ". Table 1a shows the effect of the structure dimension " + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": ". 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aggregationImageNet-1KSomething V1
top-1top-5top-1top-5
-80.595.048.376.6
element80.995.249.677.5
context81.195.450.478.2
", + "image_path": "f3af4afcee8cd911d8ca7427c0bde9443787c85a5846bebdd1a7150f66d12353.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 370, + 320, + 482, + 330 + ], + "lines": [ + { + "bbox": [ + 370, + 320, + 482, + 330 + ], + "spans": [ + { + "bbox": [ + 370, + 320, + 482, + 330 + ], + "type": "text", + "content": "(c) Context aggregation method." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 305, + 337, + 545, + 381 + ], + "lines": [ + { + "bbox": [ + 305, + 337, + 545, + 381 + ], + "spans": [ + { + "bbox": [ + 305, + 337, + 545, + 381 + ], + "type": "text", + "content": "Table 1. Ablation studies on ImageNet-1K and Something-Something V1. Top-1 and top-5 accuracies " + }, + { + "bbox": [ + 305, + 337, + 545, + 381 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 305, + 337, + 545, + 381 + ], + "type": "text", + "content": " are shown. Otherwise specified, we use 16 frames as input and set " + }, + { + "bbox": [ + 305, + 337, + 545, + 381 + ], + "type": "inline_equation", + "content": "D = 4" + }, + { + "bbox": [ + 305, + 337, + 545, + 381 + ], + "type": "inline_equation", + "content": "M = 3\\times 3\\times 3" + }, + { + "bbox": [ + 305, + 337, + 545, + 381 + ], + "type": "text", + "content": " , and patch-wise context aggregation as default." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "type": "text", + "content": "the performance as shown in [9, 72]. As we increase " + }, + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "type": "text", + "content": " from 1 to 8, we obtain gradual improvements up to " + }, + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "type": "inline_equation", + "content": "0.5\\% \\mathrm{p}" + }, + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "type": "inline_equation", + "content": "0.9\\% \\mathrm{p}" + }, + { + "bbox": [ + 305, + 397, + 545, + 456 + ], + "type": "text", + "content": " at top-1 accuracy on ImageNet-1K and Something-Something-V1. This confirms the limitation of ConvSA and the effectiveness of StructSA." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "text", + "content": "Kernel Size " + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "text", + "content": ". In Table 1b, we also investigate different kernel sizes " + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "text", + "content": ". Compared to the baseline, the model with the kernel size " + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "inline_equation", + "content": "M = 1 \\times 1 \\times 1" + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "text", + "content": " performs similar accuracies on both datasets whereas that with " + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "inline_equation", + "content": "M = 3 \\times 3 \\times 3" + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "text", + "content": " improves the performance dramatically; it validates the effectiveness of learning geometric structures. The performance saturates as the kernel size gets larger than " + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "inline_equation", + "content": "5 \\times 5 \\times 5" + }, + { + "bbox": [ + 304, + 460, + 545, + 544 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 548, + 545, + 619 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 548, + 545, + 619 + ], + "spans": [ + { + "bbox": [ + 304, + 548, + 545, + 619 + ], + "type": "text", + "content": "Context Aggregation Method. In Table 1c, we also compare different context aggregation method. As a result, patch-wise aggregation performs " + }, + { + "bbox": [ + 304, + 548, + 545, + 619 + ], + "type": "inline_equation", + "content": "0.2\\% \\mathrm{p}" + }, + { + "bbox": [ + 304, + 548, + 545, + 619 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 548, + 545, + 619 + ], + "type": "inline_equation", + "content": "0.7\\% \\mathrm{p}" + }, + { + "bbox": [ + 304, + 548, + 545, + 619 + ], + "type": "text", + "content": " at top-1 accuracy on ImageNet-1K and Something-Something-V1. For more ablation experiments, please refer to our supplementary material B." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 628, + 473, + 640 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 628, + 473, + 640 + ], + "spans": [ + { + "bbox": [ + 306, + 628, + 473, + 640 + ], + "type": "text", + "content": "4.3. Comparison to State of the Art" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 646, + 521, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 646, + 521, + 658 + ], + "spans": [ + { + "bbox": [ + 306, + 646, + 521, + 658 + ], + "type": "text", + "content": "4.3.1 Structural Vision Transformer (StructViT)" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 665, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 665, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 305, + 665, + 545, + 712 + ], + "type": "text", + "content": "To build an advanced vision transformer considering the recent development of multiscale representation learning [18, 38, 41, 70, 76], we integrate StructSA into UniFormer [38]. The transformer network, dubbed the Structural Vision" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18945" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 49, + 59, + 288, + 105 + ], + "blocks": [ + { + "bbox": [ + 49, + 59, + 288, + 105 + ], + "lines": [ + { + "bbox": [ + 49, + 59, + 288, + 105 + ], + "spans": [ + { + "bbox": [ + 49, + 59, + 288, + 105 + ], + "type": "table", + "html": "
modeltype# blocks# channels (# heads)
StructViT-S[C,C,S,S][3,4,8,3][64,128,320(5),512(8)]
StructViT-B[C,C,S,S][5,8,20,7][64,128,320(5),512(8)]
StructViT-L[C,C,S,S][5,10,24,7][128,192,448(7),640(10)]
", + "image_path": "3695f38f04d1ff8215235b62708bddf0e3f45204dcb36bc7640e4c3025a9e177.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "spans": [ + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": "Transformer (StructViT) is constructed by replacing all vanilla self-attention in UniFormer with StructSA as a main building block. It takes as input either a video clip or an image " + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "inline_equation", + "content": "\\tilde{\\pmb{X}}\\in \\mathbb{R}^{T\\times H\\times W\\times 3}" + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "inline_equation", + "content": "H" + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "inline_equation", + "content": "W" + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": " denotes the temporal length, height, and width of the input, respectively. For images as input, we set the temporal length " + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "inline_equation", + "content": "T = 1" + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": ". Before being fed into our networks, the input video is tokenized into overlapping 3D tablets of size " + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "inline_equation", + "content": "3\\times 4\\times 4\\times 3" + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": " with a stride of " + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "inline_equation", + "content": "2\\times 4\\times 4" + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": " while the input image is into nonoverlapping 2D patches of size " + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "inline_equation", + "content": "4\\times 4\\times 3" + }, + { + "bbox": [ + 46, + 142, + 287, + 261 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 262, + 287, + 441 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 262, + 287, + 441 + ], + "spans": [ + { + "bbox": [ + 46, + 262, + 287, + 441 + ], + "type": "text", + "content": "Our networks comprise four stages, each of which has multiple neural blocks, and leverage a hierarchical design with decreasing resolutions and increasing number of channels from early to late stages following [38]. For the first two stages, each block consists of a conditional positional encoding layer [9], a convolutional layer, and an MLP, whereas the convolutional layer is replaced by a StructSA layer in the blocks in the last two stages. Note that when we employ StructSA, we use multi-head configurations and do not share weights across channels for channel-wise convolutions. We build three different StructViT architectures as shown in Table 2. Our models are comparable to UniFormers [38] in the same sizes as our model configurations are based on UniFormer's; adding the structure dimension " + }, + { + "bbox": [ + 46, + 262, + 287, + 441 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 262, + 287, + 441 + ], + "type": "text", + "content": " in StructSA introduces only few additional parameters." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "spans": [ + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "text", + "content": "In practice, StructSA introduces additional FLOPs for processing instances compared to the vanilla SA. One way of building an efficient StructSA is to adopt a larger stride in the key/value projections, which effectively reduces the number of keys and values [18, 41]. We test a few variants with a larger stride to see the performances of StructViT with matching FLOPs with their corresponding UniFormer architectures. We denote each model with StructViT-" + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "inline_equation", + "content": "X" + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "text", + "content": "-" + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "inline_equation", + "content": "D-S" + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "inline_equation", + "content": "X" + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "text", + "content": " represent the architecture size, the structure dimension, and the stride, respectively. For training, we use stochastic depth [28] with the probability of " + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "inline_equation", + "content": "0.1/0.3/0.4" + }, + { + "bbox": [ + 46, + 441, + 288, + 634 + ], + "type": "text", + "content": " for StructViT-S/B/L, respectively. We use random cropping only for StructViT-B on Something-Something, Diving-48, and FineGym. We use 8 NVIDIA A100 GPUs for training StructViT-S/B and 16 GPUs for StructViT-L. We follow the protocols in Sec. 4.1 for the rest." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 647, + 167, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 647, + 167, + 658 + ], + "spans": [ + { + "bbox": [ + 47, + 647, + 167, + 658 + ], + "type": "text", + "content": "4.3.2 Image Classification" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "type": "text", + "content": "In Table 3, we compare StructViT with other state-of-the-art CNNs, ViTs, and their hybrid models. The results show that StructViT outperforms other methods in all sizes. Compared to EfficientNets [61, 62] that are obtained by exten" + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 309, + 58, + 545, + 648 + ], + "blocks": [ + { + "bbox": [ + 47, + 107, + 288, + 129 + ], + "lines": [ + { + "bbox": [ + 47, + 107, + 288, + 129 + ], + "spans": [ + { + "bbox": [ + 47, + 107, + 288, + 129 + ], + "type": "text", + "content": "Table 2. Configurations of StructViT variants. \"C\" and \"S\" denote a convolution and StructSA block, respectively." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 58, + 545, + 648 + ], + "lines": [ + { + "bbox": [ + 309, + 58, + 545, + 648 + ], + "spans": [ + { + "bbox": [ + 309, + 58, + 545, + 648 + ], + "type": "table", + "html": "
method#params (M)FLOPs (G)IN1K top-1
EfficientNet-B5 [61]309.983.6
ConvNext-T [46]294.583.1
DeiT-S [63]224.679.9
PVT-S [70]253.879.8
Swin-T [45]294.581.3
Focal-T [75]294.982.2
CSwin-T [15]234.382.7
CvT-13 [72]204.581.6
CoAtNet-0 [12]254.281.6
LV-ViT-S [29]266.683.3
UniFormer-S [38]223.682.9
UniFormer-S*↑384 [38]2211.984.6
MViTv2-S [41]244.782.3
StructViT-S-4-2233.682.9
StructViT-S-4-1234.383.2
StructViT-S-8-1245.483.3
StructViT-S-4-1*234.384.0
StructViT-S-4-1*↑3842317.385.2
EfficientNet-B7 [61]6639.284.3
ConvNext-B [46]8915.483.8
ConvNext-B ↑384 [46]8945.085.1
PVT-L [70]619.881.7
Swin-S [45]508.783.0
Focal-S [75]519.183.5
CSwin-S [15]356.983.6
CvT-21 [72]327.182.5
CoAtNet-1 [12]428.483.3
LV-ViT-M [29]5616.084.1
UniFormer-B [38]508.383.8
UniFormer-B*↑384 [38]5027.286.0
MViTv2-S [41]357.083.6
MViTv2-B [41]5210.284.4
MViTv2-B ↑384 [41]5236.785.2
StructViT-B-4-2518.384.0
StructViT-B-4-1519.984.2
StructViT-B-8-15212.084.3
StructViT-B-4-1*519.985.4
StructViT-B-4-1*↑3845140.786.5
EfficientNetV2-L [62]1215285.7
ConvNext-L [46]19834.484.3
ConvNext-L ↑384 [46]198101.085.5
Swin-B [45]8815.483.3
Focal-B [75]9016.083.8
CSwin-B [15]7815.084.2
CoAtNet-3 [12]16834.784.5
LV-ViT-L ↑288 [29]15059.085.3
UniFormer-L* [38]10012.685.6
UniFormer-L*↑384 [38]10039.286.0
MViTv2-L [41]21842.185.3
MViTv2-L ↑384 [41]218140.286.0
StructViT-L-4-1*10315.486.0
StructViT-L-4-1*↑38410385.286.7
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Comparisons to the state-of-the-art methods on ImageNet-1K. *Trained with Token Labeling [29]." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 305, + 689, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 715 + ], + "type": "text", + "content": "sive architecture search, our models show comparable or even better performances in both base and large configura" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "18946" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 277 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 277 + ], + "type": "text", + "content": "tions, requiring much less amount of computational cost. Compared to our baseline, UniFormers, StructViTs consistently improve top-1 accuracy regardless of their sizes, demonstrating the benefits of learning geometric structures in image understanding. We further evaluate our models on stronger setup using Token Labeling [29] and " + }, + { + "bbox": [ + 46, + 72, + 289, + 277 + ], + "type": "inline_equation", + "content": "384 \\times 384" + }, + { + "bbox": [ + 46, + 72, + 289, + 277 + ], + "type": "text", + "content": " images, and observe consistent improvements over the baselines. While StructSA introduces some additional FLOPs, we also test variants whose stride for key/value convolutions is set to 2 (S-4-2 and B-4-2) matching its FLOPs to that of the baseline; we still observe some gain with the base model (B-4-2) without additional FLOPs while the small model (S-4-2) shows comparable results. For more comprehensive analysis, we provide experimental results on dense prediction tasks, i.e., object detection, semantic segmentation, and instance segmentation. Please refer to our supplementary material C for the detail." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 295, + 165, + 306 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 295, + 165, + 306 + ], + "spans": [ + { + "bbox": [ + 47, + 295, + 165, + 306 + ], + "type": "text", + "content": "4.3.3 Video Classification" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 316, + 287, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 316, + 287, + 434 + ], + "spans": [ + { + "bbox": [ + 46, + 316, + 287, + 434 + ], + "type": "text", + "content": "Kinetics-400. Table 4 compares our method with previous state-of-the-art methods on Kinetics-400. Each block in the table groups methods based on their network structures: CNNs, ViTs, and hybrid methods. We first observe that our best model (B-4-1) achieves state-of-the-art performance. Our method outperforms CNN-based approaches even with less computational cost (S-4-2) in most cases. Compared to MoViNets [34] which are the most advanced CNNs obtained by an extensive NAS, our method shows comparable scores with fewer FLOPs (S-4-1)." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "content": "When we compare our model to the ViT-based ones, our model outperforms them by large margins while using significantly fewer compute. For instance, StructViT-B-4-1 with single crop (second last row in Table 4) shows top-1 accuracy gain by " + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "inline_equation", + "content": "1.6\\%" + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "content": " while using only " + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "inline_equation", + "content": "55\\%" + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "content": " of computes compared to MTV-B, the best performing ViT-based model. Note also that our model is pretrained on ImageNet-1K, which is much smaller than ImageNet-21K on which the ViT-based models are pretrained." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "text", + "content": "Finally, our best models (S-8-1 & B-4-1) show " + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "inline_equation", + "content": "0.5\\%" + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "text", + "content": " p to " + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "inline_equation", + "content": "0.8\\%" + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "text", + "content": " p accuracy gains over the baseline UniFormer models in different size configurations. When we use larger strides (S-4-2 and B-4-2) to match the FLOPs of the baselines, we still observe accuracy gains ranging from " + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "inline_equation", + "content": "0.2\\%" + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "text", + "content": " p to " + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "inline_equation", + "content": "0.3\\%" + }, + { + "bbox": [ + 46, + 544, + 287, + 604 + ], + "type": "text", + "content": " p." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 605, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 714 + ], + "type": "text", + "content": "Something-Something, Diving-48 and FineGym. Table 5a summarizes the results on Something-Something-V1&V2. We observe the same trends as on Kinetics-400. StructViT-S-4-2 outperforms UniFormer-S on Something-Something-V2 by " + }, + { + "bbox": [ + 46, + 605, + 287, + 714 + ], + "type": "inline_equation", + "content": "0.6\\%" + }, + { + "bbox": [ + 46, + 605, + 287, + 714 + ], + "type": "text", + "content": " p in top-1 accuracy, and StructViTS-8-1 enlarges the gap to " + }, + { + "bbox": [ + 46, + 605, + 287, + 714 + ], + "type": "inline_equation", + "content": "1.3\\%" + }, + { + "bbox": [ + 46, + 605, + 287, + 714 + ], + "type": "text", + "content": " p, leveraging correlation structures more effectively. StructViT-B-4-1 achieves new state-of-the-art performances on both V1 and V2 without the strong data augmentation methods used in [38, 41]." + } + ] + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 309, + 71, + 545, + 376 + ], + "blocks": [ + { + "bbox": [ + 309, + 71, + 545, + 376 + ], + "lines": [ + { + "bbox": [ + 309, + 71, + 545, + 376 + ], + "spans": [ + { + "bbox": [ + 309, + 71, + 545, + 376 + ], + "type": "table", + "html": "
methodpretrainframe× crop×clipFLOPs (G)K400 top-1top-5
SlowFast+NL [20]-16×3×10702079.893.9
ip-CSN [64]Sports1M32×3×10327079.293.8
X3D-XL [19]-16×3×10145279.193.9
MoViNet-A5 [34]-120×1×128180.994.9
MoViNet-A6 [34]-120×1×138681.595.3
TimeSformer-HR [4]IN-21K16×3×1510979.794.4
TimeSformer-L [4]IN-21K96×3×1714080.794.7
X-ViT [6]IN-21K16×3×185080.294.7
Mformer-HR [52]IN-21K16×3×102876481.195.2
ViViT-L [1]IN-21K16×3×41735280.694.7
Swin-B [47]IN-1K32×3×4338480.694.6
Swin-B [47]IN-21K32×3×4338482.795.5
MTV-B [73]IN-21K32×3×4479081.895.0
MViT-B,16×4 [18]-16×1×535378.493.5
MViT-B,32×3 [18]-32×1×585080.294.4
Dualformer-S [42]IN-1K32×1×463680.694.9
Dualformer-B [42]IN-1K32×1×4107281.195.0
UniFormer-S [38]IN-1K16×1×416780.894.7
UniFormer-B [38]IN-1K32×1×4103682.995.4
MViTv2-B,32×3 [41]-32×1×5112582.995.7
StructViT-S-4-2IN-1K16×1×416981.195.5
StructViT-S-4-1IN-1K16×1×432781.495.7
StructViT-S-8-1IN-1K16×1×454181.695.8
StructViT-B-4-2IN-1K32×1×4104583.195.5
StructViT-B-4-1IN-1K32×1×4265883.395.6
StructViT-B-4-1IN-1K32×3×4797483.495.8
", + "image_path": "736948275a44206204c4969467a9cf75ac8ce7ee23b1c85db110ff579e397811.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_body" + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 379, + 545, + 399 + ], + "lines": [ + { + "bbox": [ + 306, + 379, + 545, + 399 + ], + "spans": [ + { + "bbox": [ + 306, + 379, + 545, + 399 + ], + "type": "text", + "content": "Table 4. Comparisons to the state-of-the-art methods on Kinetics-400." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 418, + 545, + 562 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 418, + 545, + 562 + ], + "spans": [ + { + "bbox": [ + 304, + 418, + 545, + 562 + ], + "type": "text", + "content": "Table 5b and Table 5c show the results on Diving-48 [39] and FineGym [56]. Our models outperform the baseline, UniFormer-B, obtaining significant accuracy gains by " + }, + { + "bbox": [ + 304, + 418, + 545, + 562 + ], + "type": "inline_equation", + "content": "0.9\\% \\mathrm{p}" + }, + { + "bbox": [ + 304, + 418, + 545, + 562 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 418, + 545, + 562 + ], + "type": "inline_equation", + "content": "0.7\\% \\mathrm{p}" + }, + { + "bbox": [ + 304, + 418, + 545, + 562 + ], + "type": "text", + "content": " on Diving-48 and FineGym, respectively. This indicates that learning spatio-temporal correlation structures play a crucial role in capturing fine-grained motion patterns. Our model sets new state-of-the-art performances with large margins (4.1% p on Diving-48; 3.3% p and 3.1% p on FineGym) over the previous methods without additional box annotations on both datasets. Note that ORViT [25] uses additional object bounding box annotations to train an object detector." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 583, + 451, + 594 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 583, + 451, + 594 + ], + "spans": [ + { + "bbox": [ + 306, + 583, + 451, + 594 + ], + "type": "text", + "content": "4.4. Visualizations of StructSA" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": "Figure 3 visualizes example dynamic kernels " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\kappa_{i,j}^{\\mathrm{struct}}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": " computed from self-similarity map (" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "i = j" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": ") on Something-Something-V1 to illustrate how StructSA encodes motion features from the spatiotemporal correlation structure. We observe that StructSA builds kernels for spatiotemporal gradient filters similar to those that are already known to be effective for capturing different types of motions [60], e.g., Sobel filters (first) or Laplacian filters (second and third), over local contexts similarly to [32]." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18947" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 64, + 373, + 339 + ], + "blocks": [ + { + "bbox": [ + 50, + 64, + 373, + 339 + ], + "lines": [ + { + "bbox": [ + 50, + 64, + 373, + 339 + ], + "spans": [ + { + "bbox": [ + 50, + 64, + 373, + 339 + ], + "type": "table", + "html": "
methodpretrainframe× crop×clipFLOPs (G)Something V1 top-1top-5Something V2 top-1top-5
TEA [40]IN-1K16×1×17051.980.3--
MSNet [35]IN-1K16×1×110152.182.364.789.4
CT-Net [37]IN-1K16×1×17552.580.964.589.3
TDN [69]IN-1K16×1×17253.982.165.389.5
SELFYNet [36]IN-1K16×1×17754.382.965.789.8
RSANet [32]IN-1K16×1×17254.081.166.089.9
TimeSformer-HR [4]IN-21K16×3×15109--62.5-
TimeSformer-L [4]IN-21K96×3×17140--62.3-
ViViT-L [1]K40016×3×411892--65.489.8
X-ViT [6]IN-21K32×3×11270--65.490.7
Mformer-HR [52]K40016×3×12876--67.190.6
Mformer-L [52]K40032×3×13555--68.191.2
Swin-B [47]K40032×3×1963--69.692.7
MViT-B,64×3 [18]K40064×1×31365--67.790.9
MViT-B-24,32×3 [18]K60032×1×3708--68.791.5
UniFormer-S [38]K40016×3×112557.284.967.791.4
UniFormer-B [38]K40032×3×177760.987.371.292.8
MViTv2-B [41]K40032×3×1675--70.592.7
StructViT-S-4-2K40016×3×112657.685.368.391.3
StructViT-S-4-1K40016×3×124658.085.568.891.9
StructViT-S-8-1K40016×3×140558.085.769.092.1
StructViT-B-4-2K40032×3×178461.187.771.192.7
StructViT-B-4-1K40032×3×1196361.387.871.593.1
", + "image_path": "5065ec2e8c1a8b74176a631a9127c774cfa9eb8390bb50d4eaa628b248d4f8c1.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 383, + 64, + 538, + 198 + ], + "blocks": [ + { + "bbox": [ + 153, + 341, + 273, + 350 + ], + "lines": [ + { + "bbox": [ + 153, + 341, + 273, + 350 + ], + "spans": [ + { + "bbox": [ + 153, + 341, + 273, + 350 + ], + "type": "text", + "content": "(a) Something-Something V1 & V2" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 383, + 64, + 538, + 198 + ], + "lines": [ + { + "bbox": [ + 383, + 64, + 538, + 198 + ], + "spans": [ + { + "bbox": [ + 383, + 64, + 538, + 198 + ], + "type": "table", + "html": "
modeltop-1
SlowFast-R101 [20]77.6
TimeSformer [4]75.0
TimeSformer-HR [4]78.0
SViT-DD [2]79.8
TimeSformer-L [4]81.0
TQN [79]81.8
RSANet-R50 [32]84.2
UniFormer-B* [38]87.4
ORViT† [25]88.0
StructViT-B-4-287.8
StructViT-B-4-188.3
", + "image_path": "ff01851c0b239d11d66c42eb51def91af901bb44bafac9604e36367480208b5c.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 382, + 238, + 538, + 339 + ], + "blocks": [ + { + "bbox": [ + 437, + 199, + 484, + 209 + ], + "lines": [ + { + "bbox": [ + 437, + 199, + 484, + 209 + ], + "spans": [ + { + "bbox": [ + 437, + 199, + 484, + 209 + ], + "type": "text", + "content": "(b) Diving-48" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 382, + 238, + 538, + 339 + ], + "lines": [ + { + "bbox": [ + 382, + 238, + 538, + 339 + ], + "spans": [ + { + "bbox": [ + 382, + 238, + 538, + 339 + ], + "type": "table", + "html": "
modelGym288Gym99
TRN [82]33.168.7
I3D [8]27.963.2
TSM [43]34.870.6
\\(\\mathsf{TSM}_{\\text{Two-stream}}\\) [43]46.581.2
RSANet-R50 [32]50.986.4
UniFormer-B* [38]53.588.9
StructViT-B-4-253.889.3
StructViT-B-4-154.289.5
", + "image_path": "1a982e090d726e0b1fd75c3e9da2a785af670c1e35d33d68b492c0fa48da5055.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 438, + 340, + 482, + 350 + ], + "lines": [ + { + "bbox": [ + 438, + 340, + 482, + 350 + ], + "spans": [ + { + "bbox": [ + 438, + 340, + 482, + 350 + ], + "type": "text", + "content": "(c) FineGym" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 354, + 546, + 388 + ], + "lines": [ + { + "bbox": [ + 46, + 354, + 546, + 388 + ], + "spans": [ + { + "bbox": [ + 46, + 354, + 546, + 388 + ], + "type": "text", + "content": "Table 5. Comparisons to the state-of-the-art methods on three motion-centric video classification benchmarks. Our StructViT achieves new state-of-the-art on all the benchmarks. For FineGym, we measure averaged per-class accuracy while top- " + }, + { + "bbox": [ + 46, + 354, + 546, + 388 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 354, + 546, + 388 + ], + "type": "text", + "content": " accuracy is measured for Something-Something and Diving-48. *Reproduced by our experimental setup. †Trained with additionalbbox annotations." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 179, + 399, + 496, + 464 + ], + "blocks": [ + { + "bbox": [ + 110, + 421, + 169, + 437 + ], + "lines": [ + { + "bbox": [ + 110, + 421, + 169, + 437 + ], + "spans": [ + { + "bbox": [ + 110, + 421, + 169, + 437 + ], + "type": "text", + "content": "input video" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 179, + 399, + 496, + 464 + ], + "lines": [ + { + "bbox": [ + 179, + 399, + 496, + 464 + ], + "spans": [ + { + "bbox": [ + 179, + 399, + 496, + 464 + ], + "type": "image", + "image_path": "7625cce2a7f4375b45d1b51a45b274f3a79a0a4db17213043d10df2843ac46b9.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 55, + 491, + 171, + 510 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 491, + 171, + 510 + ], + "spans": [ + { + "bbox": [ + 55, + 491, + 171, + 510 + ], + "type": "interline_equation", + "content": "\\boldsymbol {\\kappa} _ {i, j} ^ {\\mathrm {s t r u c t}} = \\sigma_ {j} \\left(\\boldsymbol {q} _ {i} \\boldsymbol {K} _ {j} ^ {\\top} \\boldsymbol {U} ^ {\\mathrm {K} ^ {\\top}}\\right) \\boldsymbol {U} ^ {\\mathrm {V}}", + "image_path": "bd77890ca361007eb83d18c1e4a6b83215c0a1ce56a9684b4a1d69d69328bf58.jpg" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 182, + 470, + 238, + 523 + ], + "blocks": [ + { + "bbox": [ + 182, + 470, + 238, + 523 + ], + "lines": [ + { + "bbox": [ + 182, + 470, + 238, + 523 + ], + "spans": [ + { + "bbox": [ + 182, + 470, + 238, + 523 + ], + "type": "image", + "image_path": "07ee50b9ed555248ce4bea9fc5c9ba633f4acc168a7081ecbaff8ab446315d67.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "lines": [ + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "spans": [ + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "text", + "content": "Figure 3. Visualization of dynamic kernels " + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "inline_equation", + "content": "\\kappa_{i,j}^{\\mathrm{struct}}" + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "text", + "content": " in StructSA on Something-V1. The top row shows the input frames that contain the input spatiotemporal local context (indicated by green boxes) used in the dynamic kernel computation. The bottom row presents the resulting dynamic kernels " + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "inline_equation", + "content": "\\kappa_{i,j}^{\\mathrm{struct}}" + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "text", + "content": " for a StructSA head when " + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "inline_equation", + "content": "i = j" + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "text", + "content": ". Note that the computed dynamic kernels are computed with self-similarity map " + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "inline_equation", + "content": "(i = j)" + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "text", + "content": " to illustrate its effectiveness in capturing motions in videos. We use StructViT-S-4-1 with " + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "inline_equation", + "content": "M = 5 \\times 5 \\times 5" + }, + { + "bbox": [ + 46, + 527, + 546, + 572 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 246, + 471, + 301, + 523 + ], + "blocks": [ + { + "bbox": [ + 246, + 471, + 301, + 523 + ], + "lines": [ + { + "bbox": [ + 246, + 471, + 301, + 523 + ], + "spans": [ + { + "bbox": [ + 246, + 471, + 301, + 523 + ], + "type": "image", + "image_path": "b355afc4d5fad76f45c8b3acc795d22c211f073d0bc45f8b3b214df1abf9f63d.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 310, + 471, + 364, + 523 + ], + "blocks": [ + { + "bbox": [ + 310, + 471, + 364, + 523 + ], + "lines": [ + { + "bbox": [ + 310, + 471, + 364, + 523 + ], + "spans": [ + { + "bbox": [ + 310, + 471, + 364, + 523 + ], + "type": "image", + "image_path": "8f0897e41f1a0838d1d69fd6fd609aea68af6459ad27bc8ebef4c931a25ffdc1.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 375, + 472, + 429, + 523 + ], + "blocks": [ + { + "bbox": [ + 375, + 472, + 429, + 523 + ], + "lines": [ + { + "bbox": [ + 375, + 472, + 429, + 523 + ], + "spans": [ + { + "bbox": [ + 375, + 472, + 429, + 523 + ], + "type": "image", + "image_path": "7852b71cb59cdca57a65394c362561cd2693c647071eeb462c9c2d31d5526c2c.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 439, + 472, + 493, + 523 + ], + "blocks": [ + { + "bbox": [ + 439, + 472, + 493, + 523 + ], + "lines": [ + { + "bbox": [ + 439, + 472, + 493, + 523 + ], + "spans": [ + { + "bbox": [ + 439, + 472, + 493, + 523 + ], + "type": "image", + "image_path": "a5314ee2556c02f276468696ab520bf32c76714974f695db5306447c10c58665.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + } + ], + "index": 14 + }, + { + "bbox": [ + 47, + 586, + 119, + 597 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 586, + 119, + 597 + ], + "spans": [ + { + "bbox": [ + 47, + 586, + 119, + 597 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "content": "We have introduced a novel self-attention mechanism, StructSA, that exploits rich structural patterns of querykey correlation for visual representation learning. StructSA leverages spatial (and temporal) structures of local correlations and aggregates chunks of local features globally across entire locations. Structural Vision Transformer (StructViT) using StructSA as the main attention module achieves state-of-the-art results on both image and video classification benchmarks. We believe leveraging structural" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 586, + 545, + 622 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 586, + 545, + 622 + ], + "spans": [ + { + "bbox": [ + 304, + 586, + 545, + 622 + ], + "type": "text", + "content": "patterns of correlation in attention will also benefit other tasks in computer vision and natural language processing. We leave this for future work." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "type": "text", + "content": "Acknowledgements This work was supported by the IITP grants (No. 2022-0-00290: Visual Intelligence for space-time understanding and generation " + }, + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "type": "inline_equation", + "content": "(45\\%)" + }, + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "type": "text", + "content": ", No. 2022-0-00264: Comprehensive video understanding and generation with knowledge-based deep logic " + }, + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "type": "inline_equation", + "content": "(50\\%)" + }, + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "type": "text", + "content": ", No. 2019-0-01906: AI graduate school program at POSTECH " + }, + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "type": "inline_equation", + "content": "(5\\%))" + }, + { + "bbox": [ + 304, + 629, + 546, + 713 + ], + "type": "text", + "content": " funded by Ministry of Science and ICT, Korea." + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18948" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 713 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 133 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 133 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 133 + ], + "type": "text", + "content": "[1] Anurag Arnab, Mostafa Dehghani, Georg Heigold, Chen Sun, Mario Lučić, and Cordelia Schmid. 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To conduct training on real-world unpaired data, current methods focus on synthesizing pseudo LR images to associate unpaired images. However, the realness and diversity of pseudo LR images are vulnerable due to the large image space. In this paper, we circumvent the difficulty of image generation and propose an alternative to build the connection between unpaired images in a compact proxy space. Specifically, we first construct coupled HR and LR dictionaries, and then encode HR and LR images into a common latent code space using these dictionaries. In addition, we develop an autoencoder-based framework to couple these dictionaries during optimization by reconstructing input HR and LR images. The coupled dictionaries enable our method to employ a shallow network architecture with only 18 layers to achieve efficient image SR. Extensive experiments show that our method (DictSR) can effectively model the LR-to-HR mapping in coupled dictionaries and produces state-of-the-art performance on benchmark datasets.", + "bbox": [ + 75, + 300, + 473, + 633 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 662, + 209, + 679 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Image super-resolution (SR) aims at reconstructing a high-resolution (HR) image from low-resolution (LR) observations. To this end, most existing learning-based methods [1-4] rely on paired training data to build an LR-to-HR mapping. Since paired data is difficult to acquire in the real world, manually designed degradations are commonly employed to synthesize paired data for training [5, 6]. Nevertheless, as pre-defined degradations are empirical, synthetic images cannot meet the diversity of real-world images and limit the performance of previous methods in real scenarios [7, 8].", + "bbox": [ + 75, + 688, + 468, + 853 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To remedy this problem, numerous efforts have been made to directly conduct training on unpaired data [7-9]. To enable the learning of LR-to-HR mapping, existing meth", + "bbox": [ + 75, + 854, + 468, + 900 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/70ccbe9eb4a0e5e5f99ba2e904fa64cb843ca29bf7312967549a948d83d45c3b.jpg", + "image_caption": [ + "(a) Previous Approaches" + ], + "image_footnote": [], + "bbox": [ + 514, + 268, + 883, + 353 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/908af80b98b71c23c1ce0a975309839aaa338c8811e4d510f6cd0c15f95e8bb6.jpg", + "image_caption": [ + "(b) Our Approach", + "Figure 1. Comparison between previous approaches and our approach. Instead of synthesizing pseudo LR images and minimizing the gap in the image space (a), we encode HR and LR images into a common latent code space using coupled dictionaries to associate unpaired HR and LR images (b)." + ], + "image_footnote": [], + "bbox": [ + 511, + 383, + 883, + 464 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ods focus on synthesizing pseudo paired data for training. Given HR images $x \\sim p_x$ (target domain) and LR images $y \\sim p_y$ (source domain), pseudo LR images are generated by learning an HR-to-LR mapping. Then, HR images and the resultant pseudo LR images are adopted to learn the LR-to-HR mapping. Early methods [7, 9] commonly use generative adversarial networks (GANs) with cycle-consistency or adversarial loss to synthesize pseudo LR images. However, these GAN-based methods usually suffer mode collapse and require elaborate fine-tuning. Recently, more powerful diffusion model [10] is introduced for pseudo LR image synthesis. The large latent space in the diffusion model improves the diversity of synthesized images at the cost of lower content fidelity, which hinders further performance improvements.", + "bbox": [ + 496, + 595, + 893, + 821 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Due to the low rank characteristic of natural images, an image can be represented as a spare code on an overcomplete dictionary [11, 12]. On top of this perspective, we seek to associate unpaired LR and HR images in a compact space without relying on synthesizing pseudo LR im", + "bbox": [ + 496, + 825, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 808, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "25712", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ages high in diversity and realness (Fig. 1). By representing images using spatial codes over a dictionary, the description length is significantly reduced, which allows us to efficiently minimize the gap between HR and LR image domains. To this end, we use autoencoders to learn LR and HR dictionaries rich of context information from LR and HR images. To fit the large space of real-world LR patches, our LR dictionary explicitly models the content and degradation variations in a hierarchical manner (Fig. 2). During training, by coupling HR and LR dictionaries, an LR-to-HR mapping can be learned in the dictionaries. During inference, an LR image is first decomposed over the LR dictionary and then using the HR dictionary for reconstruction to produce the SR result. The contributions of this paper can be summarized as follows:", + "bbox": [ + 75, + 90, + 472, + 316 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We associate unpaired images using coupled HR and LR dictionaries instead of synthesizing pseudo LR images. By decomposing unpaired images over the dictionary to obtain compact proxy codes, an LR-to-HR mapping can be efficiently learned in the code space.", + "- We formulate the LR dictionary as a combination of an LR content dictionary and a degradation dictionary to model LR images in a hierarchical manner.", + "- We develop an autoencoder-based framework to optimize coupled dictionaries together with the network parameters in an end-to-end manner.", + "- Extensive experiments show that our coupled dictionaries can effectively learn the LR-to-HR mapping and our method (DictSR) achieves state-of-the-art performance on benchmark datasets." + ], + "bbox": [ + 76, + 316, + 468, + 542 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 76, + 556, + 225, + 571 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this section, we first review recent advances of paired and unpaired image SR methods. Then, we discuss dictionary learning approach that is related to our work.", + "bbox": [ + 76, + 582, + 468, + 628 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Paired Image SR", + "text_level": 1, + "bbox": [ + 76, + 635, + 243, + 651 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Most previous learning-based image SR methods rely on paired data with aligned contents for training. Early methods [1-3, 13-15] commonly employ bicubic downsampling to synthesize HR-LR image pairs as the training data. Despite promising results on synthetic data, these methods suffer severe performance drop on real-world images since their degradations differ from the bicubic one. Later, several methods adopt more complicated degradations including blur, compression, and noise to generate HR-LR image pairs [5, 16-19]. Although the handcrafted degradations span a large space, the gap between real-world degradations still remains and limits the accuracy in real scenarios. Recently, a number of real-world paired datasets are developed to capture real degradations [20, 21]. However, the high labor cost limits the scales of these datasets, thereby hindering further performance improvement.", + "bbox": [ + 75, + 659, + 472, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.2. Unpaired Image SR", + "text_level": 1, + "bbox": [ + 500, + 90, + 689, + 107 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To circumvents the difficulty of acquiring real-world paired data, a number of methods directly conduct training on unpaired images. Early approaches assume real-world LR images follow a specific distribution and employ GANs to synthesize pseudo LR image in this distribution. Specifically, Bulat et al. [22] and Lugmayr et al. [23] first trained a degradation network to synthesize pseudo LR images from HR images and then use these paired images to learn the LR-to-HR mapping. Yuan et al. [9] and Maeda et al. [7] developed unified frameworks to simultaneously learn a degradation network and an SR network, which produce superior accuracy. Liu et al. [24] and Yang et al. [25] introduced physical properties to LR image synthesis as regularizations for higher realness. Despite improved performance against paired approaches, these GAN-based methods usually suffer mode collapse and cannot generate LR images as diverse as real ones.", + "bbox": [ + 496, + 112, + 890, + 369 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To address the aforementioned problem of GAN-based methods, Wolf et al. [26] developed a flow-based model to synthesize LR images. Although the diversity of synthesized LR images is improved, this method has a high computational cost due to the limited expressive power of flow-based models [27, 28]. Recently, Yang et al. [10] introduced the powerful diffusion model for pseudo LR image synthesis. The large latent space in the diffusion model improves the diversity but decreases the content fidelity, which also results in limited performance.", + "bbox": [ + 496, + 369, + 890, + 521 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.3. Dictionary Learning", + "text_level": 1, + "bbox": [ + 500, + 530, + 692, + 546 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Dictionary learning aims at finding a sparse representation of the input data in the form of a linear combination of basic elements as well as those basic elements themselves. The idea of dictionary learning can be dated back to several decades ago [29, 30]. Before the era of deep learning, dictionary learning is widely used to model the LR-to-HR mapping for image SR. Specifically, Yang et al. [12] proposed coupled dictionaries to associate LR and HR image patches via sparse coding. Zhang et al. [11] developed a multi-scale dictionary to simultaneously model local and non-local priors in the images. Lu et al. [31] took the geometrical structure of the dictionary into consideration and proposed a geometry constrained sparse coding method for image SR.", + "bbox": [ + 496, + 553, + 890, + 763 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Since the huge success of neural networks, learning-based methods have dominated a wide range of tasks. Recently, the idea of dictionary learning has been introduced to learning-based frameworks and produces superior performance. Specifically, Van et al. [32] proposed a vector quantized variational autoencoder (VQ-VAE) to learn discrete representations of an image over a codebook. Then, a CNN is trained to model their distribution for image synthesis. Then, Razavi et al. [33] extended this approach to a", + "bbox": [ + 496, + 765, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "25713", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/b04f27404eb7d265265f4607e01631942daf85ecf24aa6fcc036b676381090e2.jpg", + "image_caption": [ + "Figure 2. An illustration of our framework during training phase (a) and test phase (b). Entries with different colors correspond to various contents while entries with different shades refer to the same content but diverse degradations." + ], + "image_footnote": [], + "bbox": [ + 86, + 90, + 883, + 554 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "hierarchical one to learn discrete representation at different scale, which achieves superior performance. Later, Esser et al. [34] further developed VQ-GAN by leveraging the powerful transformer to model the composition of images. Recently, Maeda et al. [35] introduced dictionary learning for image SR by plugging a learnable dictionary into a CNN framework. However, this method relies on paired data to learn the LR-to-HR mapping and cannot be extended to unpaired SR.", + "bbox": [ + 75, + 627, + 470, + 762 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Methodology", + "text_level": 1, + "bbox": [ + 76, + 782, + 210, + 800 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Ideally, a pair of LR and HR images can be decomposed to a common latent code over coupled LR-HR dictionaries. From this point of view, we seek to learn coupled dictionaries from unpaired data for image SR. To this end, we formulate the coupled dictionaries as a combination of an HR content dictionary $\\mathbf{D}^{HR}$ , an LR content dictionary $\\mathbf{D}^{LR}$ , and a", + "bbox": [ + 75, + 809, + 470, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "degradation dictionary $\\mathbf{D}_{deg}$ . These three dictionaries are tightly coupled and jointly optimized in three branches, as illustrated in Fig. 2. During the training phase, the pipeline for each branch consists of three stages, including encoding, discretization, and decoding. Specifically, input images are first encoded into embeddings. Then, these embeddings are discretized in the embedding space to the entries in corresponding dictionaries. Finally, the discretized embeddings are fed to the decoders to reconstruct the input image. During the test phase, the input LR image is first encoded to an indicex map using $\\mathbf{D}^{LR}$ and $\\mathbf{D}_{deg}$ . Then, the corresponding entries in $\\mathbf{D}^{HR}$ is retrieved to reconstruct the SR result.", + "bbox": [ + 496, + 627, + 890, + 808 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Encoding Stage", + "text_level": 1, + "bbox": [ + 500, + 816, + 656, + 833 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given an HR image $\\mathbf{I}^{HR} \\in \\mathbb{R}^{H \\times W \\times 3}$ and a unpaired LR image $\\mathbf{I}^{LR} \\in \\mathbb{R}^{h \\times w \\times 3}$ , $\\mathbf{I}^{HR}$ is first downscaled to obtain $\\mathbf{I}^{HR\\downarrow} \\in \\mathbb{R}^{\\frac{H}{s} \\times \\frac{W}{s} \\times 3}$ . Here, $s$ is the scale factor and set to 4 as we focus on $\\times 4$ SR in this paper. Then, $\\mathbf{I}^{HR}$ is fed", + "bbox": [ + 496, + 838, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "25714", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "to the HR image encoder to produce $\\mathbf{F}^{HR} \\in \\mathbb{R}^{\\frac{H}{8} \\times \\frac{W}{8} \\times 512}$ , with each embedding corresponding to a $8 \\times 8$ patch in the input HR image. Meanwhile, $\\mathbf{I}^{LR}$ and $\\mathbf{I}^{HR\\downarrow}$ are passed to the LR image encoder to obtain $\\mathbf{F}^{LR} \\in \\mathbb{R}^{\\frac{h}{2} \\times \\frac{w}{2} \\times 128}$ and $\\mathbf{F}^{HR\\downarrow} \\in \\mathbb{R}^{\\frac{H}{8} \\times \\frac{W}{8} \\times 128}$ , respectively. Each embedding in the resultant feature maps corresponds to a $2 \\times 2$ patch in the input LR image.", + "bbox": [ + 75, + 88, + 468, + 196 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The HR image encoder employs a fully convolutional structure and consists of four residual blocks at four resolution levels (i.e., $H \\times W$ , $\\frac{H}{2} \\times \\frac{W}{2}$ , $\\frac{H}{4} \\times \\frac{W}{4}$ , and $\\frac{H}{8} \\times \\frac{W}{8}$ ). Meanwhile, the LR image encoder consists of two residual blocks at $h \\times w$ and $\\frac{h}{2} \\times \\frac{w}{2}$ resolution levels.", + "bbox": [ + 75, + 196, + 468, + 275 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Discretization Stage", + "text_level": 1, + "bbox": [ + 76, + 282, + 266, + 300 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "After the encoding stage, the resultant embedding at each location of the feature map is discretized to its closest dictionary entry in the embedding space, resulting in $\\mathbf{F}_q^{HR}$ , $\\mathbf{F}_q^{HR\\downarrow}$ , and $\\mathbf{F}_q^{LR}$ . Motivated by [36], we introduce a linear projection to map the output feature maps to a low-dimensional latent space (4-dim in our experiments) for code index lookup. Then, the discretized embedding is projected back to the embedding space through another projection layer. During backpropagation, straight-through estimator (STE) is employed for end-to-end optimization.", + "bbox": [ + 75, + 306, + 468, + 460 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To associate HR and LR images, HR and LR dictionaries should be coupled at this stage. However, there exists two major challenges: (1) Misaligned Content. Under paired settings, corresponding patches in HR and LR images share the same content, which can be employed as a cue to couple HR and LR dictionaries for joint optimization. However, this cue does not hold for unpaired images, which imposes great challenges to learning coupled dictionaries. (2) **Diverse Degradations**. Since an HR image corresponds to infinite LR images under various degradations, modeling such a one-to-many correlation using coupled dictionaries is quite difficult. To address the above challenges, we formulate the coupled dictionaries as a combination of an HR content dictionary, an LR content dictionary, and a degradation dictionary. The LR content dictionary couples with the HR content dictionary to build connections between LR and HR image contents. Meanwhile, the degradation dictionary captures the degradation variations for different image contents.", + "bbox": [ + 75, + 460, + 468, + 748 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2.1 HR and LR Content Dictionary", + "text_level": 1, + "bbox": [ + 76, + 768, + 351, + 786 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "First, we construct an HR content dictionary $\\mathbf{D}^{HR} \\in \\mathbb{R}^{N \\times 4}$ and an LR content dictionary $\\mathbf{D}^{LR} \\in \\mathbb{R}^{N \\times 4}$ to model the content variation in the embedding space, where $N$ is the number of entries. To handle the first challenge, we introduce downscaled version of HR images as a bridge to associate HR and LR content dictionaries to enable joint training. For embeddings $f^{HR} \\in \\mathbf{F}^{HR}$ (branch 1) and", + "bbox": [ + 75, + 792, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "$f^{HR\\downarrow} \\in \\mathbf{F}^{HR\\downarrow}$ (branch 2), the discretized embeddings $f_{q}^{HR}$ and $f_{q}^{HR\\downarrow}$ are obtained as:", + "bbox": [ + 498, + 88, + 890, + 125 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ni = \\underset {i} {\\arg \\min } | | f ^ {H R \\downarrow} - \\mathbf {D} ^ {L R} (i) | |, \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 586, + 133, + 890, + 161 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{ \\begin{array}{l} f _ {q} ^ {H R \\downarrow} = \\mathbf {D} ^ {L R} (i) \\\\ f _ {q} ^ {H R} = \\mathbf {D} ^ {H R} (i) \\end{array} , \\right. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 625, + 175, + 890, + 217 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $i$ is the index of the closest entry in $\\mathbf{D}^{LR}$ to the embedding $f^{HR\\downarrow}$ . By employing the same spatial codes (i.e., $i$ ) to represent both $f^{HR}$ and $f^{HR\\downarrow}$ , HR and LR content dictionaries are coupled. Inspired by [34], the discretization losses for branches 1 and 2 are defined as:", + "bbox": [ + 498, + 223, + 890, + 299 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{ \\begin{array}{l} \\mathcal {L} _ {d i s} ^ {1} = | | \\mathbf {F} ^ {H R} - \\mathbf {F} _ {q} ^ {H R} | | _ {2} ^ {2} \\\\ \\mathcal {L} _ {d i s} ^ {2} = | | \\mathbf {F} ^ {H R \\downarrow} - \\mathbf {F} _ {q} ^ {H R \\downarrow} | | _ {2} ^ {2}. \\end{array} \\right. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 596, + 306, + 890, + 349 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2.2 Degradation Dictionary", + "text_level": 1, + "bbox": [ + 500, + 364, + 718, + 380 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Second, we construct a degradation dictionary $\\mathbf{D}_{deg} \\in \\mathbb{R}^{N \\times K \\times 4}$ on top of $\\mathbf{D}^{LR}$ to model the degradation variations. Specifically, each group of entries (e.g., $\\mathbf{D}_{deg}(i) \\in \\mathbb{R}^{K \\times 4}$ ) is used to capture the degradation variation around the corresponding entry in the content dictionary (i.e., $\\mathbf{D}^{LR}(i)$ ). During discretization, a hierarchical approach is employed to obtain the discretized embedding $f_{q}^{LR}$ :", + "bbox": [ + 498, + 388, + 890, + 496 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{ \\begin{array}{l} j = \\underset {j} {\\arg \\min } | | f ^ {L R} - \\mathbf {D} ^ {L R} (j) | | \\\\ k = \\underset {k} {\\arg \\min } | | f ^ {L R} - \\left(\\mathbf {D} ^ {L R} (j) + \\mathbf {D} _ {d e g} (j, k)\\right) | | \\end{array} . \\right. \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 506, + 890, + 563 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For each embedding $f^{LR}$ in $\\mathbf{F}^{LR}$ (branch 3), the closest entry in $\\mathbf{D}^{LR}$ is first selected. $\\mathbf{D}^{LR}(j)$ depicts the clean image content in $f^{LR}$ but ignores the degradation. Then, the degradation is taken into consideration by retrieving the closest entry in $\\mathbf{D}^{LR}(j) + \\mathbf{D}_{deg}(j)$ , resulting in $f_{q}^{LR}$ . Similarly, a discretization loss is defined as:", + "bbox": [ + 498, + 574, + 890, + 666 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {d i s} ^ {3} = \\left\\| \\mathbf {F} ^ {L R} - \\mathbf {F} _ {q} ^ {L R} \\right\\| _ {2} ^ {2}. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 612, + 676, + 890, + 696 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Decoding Stage", + "text_level": 1, + "bbox": [ + 500, + 705, + 653, + 722 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "After the discretization stage, the feature map produced by the encoders are represented using the dictionaries. Then, $\\mathbf{F}_q^{HR}$ is fed to the HR image decoder to reconstruct the HR image $\\hat{\\mathbf{I}}^{HR}$ . Meanwhile, $\\mathbf{F}_q^{HR\\downarrow}$ and $\\mathbf{F}_q^{LR}$ are passed to the LR image decoder to produce $\\hat{\\mathbf{I}}^{HR\\downarrow}$ and $\\hat{\\mathbf{I}}^{LR}$ , respectively. The reconstruction loss is defined as the L1 loss between the reconstructed results and the input images:", + "bbox": [ + 498, + 729, + 890, + 847 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {r e c} = \\left| \\left| \\hat {\\mathbf {I}} ^ {H R} - \\mathbf {I} ^ {H R} \\right| \\right| + \\left| \\left| \\phi \\left(\\hat {\\mathbf {I}} ^ {H R}\\right) - \\phi (\\mathbf {I} ^ {H R}) \\right| \\right| + \\tag {6} \\\\ \\left| \\left| \\hat {\\mathbf {I}} ^ {H R \\downarrow} - \\mathbf {I} ^ {H R \\downarrow} \\right| \\right| + \\left| \\left| \\hat {\\mathbf {I}} ^ {L R} - \\mathbf {I} ^ {L R} \\right| \\right|, \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 524, + 856, + 890, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "25715", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\phi (\\mathbf{I}^{HR})$ refers to the feature maps extracted by a pretrained VGG model [37].", + "bbox": [ + 76, + 89, + 468, + 119 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Similar with the encoders, the HR image decoder is composed of four residual blocks at different resolution levels and a tail convolutional layer to regress the reconstructed images. Meanwhile, the LR image decoder comprises of two residual blocks and a tail convolutional layer.", + "bbox": [ + 76, + 121, + 468, + 196 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Loss Function", + "text_level": 1, + "bbox": [ + 76, + 205, + 222, + 219 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The overall loss function used for training is defined as follows:", + "bbox": [ + 76, + 229, + 467, + 257 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {r e c} + \\lambda_ {1} \\times \\left(\\mathcal {L} _ {d i s} ^ {1} + \\mathcal {L} _ {d i s} ^ {2} + \\mathcal {L} _ {d i s} ^ {3}\\right) \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 133, + 268, + 468, + 286 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\lambda_{1}$ is empirically set to 10 in our experiments.", + "bbox": [ + 76, + 296, + 423, + 311 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 325, + 207, + 340 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this section, we first introduce the experimental setup. Then, we compare our method with previous paired and unpaired image SR methods on benchmark datasets. Finally, we conduct experiments to investigate the effectiveness of our major designs.", + "bbox": [ + 76, + 349, + 468, + 425 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 76, + 434, + 264, + 450 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1.1 Datasets and Metrics", + "text_level": 1, + "bbox": [ + 76, + 457, + 277, + 470 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We conduct experiments on two widely applied unpaired SR datasets, including AIM-RWSR [38] and NTIRE-RWSR [39]. Note that, we focus on $\\times 4$ SR in this paper and our method can be extended to SR tasks with different scale factors.", + "bbox": [ + 76, + 481, + 468, + 555 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "AIM-RWSR. The AIM-RWSR dataset is a synthetic dataset and uses handcrafted degradations to synthesize 2650 noisy and compressed LR images. Meanwhile, 800 images in the DIV2K dataset are employed as HR images.", + "bbox": [ + 76, + 556, + 468, + 616 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "NTIRE-RWSR. The NTIRE-RWSR dataset follows the same setting as the AIM-RWSR dataset to produce unpaired HR and LR images. Different from AIM-RWSR, NTIRE-RWSR features a more complicated degradation type that consists of highly related high-frequency noises.", + "bbox": [ + 76, + 617, + 468, + 691 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For evaluation on the AIM-RWSR and NTIRE-RWSR datasets, we use peak signal-to-noise ratio (PSNR), structural similarity (SSIM) and learned perceptual image patch similarity (LPIPS) as metrics.", + "bbox": [ + 76, + 691, + 468, + 752 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1.2 Training Details", + "text_level": 1, + "bbox": [ + 76, + 771, + 243, + 786 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "During the training phase, 24 LR patches of size $64 \\times 64$ and 24 HR patches of size $256 \\times 256$ were randomly cropped from LR and HR images, respectively. Random rotation and random flipping were employed for data augmentation. The Adam method [40] with $\\beta_{1} = 0.9$ and $\\beta_{2} = 0.999$ was used for optimization. The learning rate was initialized as $2 \\times 10^{-4}$ and halved after every 25 epochs. The training was", + "bbox": [ + 76, + 794, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/a435cd8c155f5934b97814c0a81bf174e7d40b87eba5525f9a6d143bdfe69d59.jpg", + "table_caption": [ + "Table 1. Results achieved on AIM-RWSR for $\\times 4\\mathrm{{SR}}$ . Best and second best results are highlighted and underlined." + ], + "table_footnote": [], + "table_body": "
Method#LayersMACsLPIPSPSNRSSIM
PairedBicubic--0.53722.350.617
RCAN [3]400260G0.47222.320.604
ZSSR [41]8-0.63922.210.603
IKC [5]18880G0.47922.250.600
DAN [42]171315G0.47122.410.609
BSRGAN [17]350291G0.29922.470.623
Real-ESRGAN [16]350291G0.23822.080.622
UnpairedCycleGAN [38]350291G0.47621.190.530
CinCGAN [9]37823G0.46121.600.613
Lugmayr et al. [23]350291G0.47221.590.550
FSSR [43]350291G0.39020.820.510
DASR [8]350291G0.33621.600.564
DeFlow [26]350291G0.34922.250.620
PCR-ESRGAN [46]350291G0.32121.590.610
DictSR (Ours)18129G0.25922.460.629
", + "bbox": [ + 501, + 121, + 890, + 356 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "stopped after 100 epochs. In our experiments, the numbers of entries in the dictionaries (i.e., $N$ and $K$ ) were set to 4096 and 32, respectively.", + "bbox": [ + 498, + 383, + 890, + 430 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Performance Evaluation", + "text_level": 1, + "bbox": [ + 500, + 439, + 723, + 454 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For performance evaluation, six representative paired SR methods (RCAN [3], ZSSR [41], IKC [5], DAN [42], BSRGAN [17] and Real-ESRGAN [16]) and eight state-of-the-art unpaired image SR methods (CinCGAN [9], Lugmayr et al. [23], FSSR [43], Impressionism [44], DASR [8], DeFlow [26], DAP [45], and PCR-ESRGAN [46]) are included for comparison. Quantitative results are presented in Tables 1 and 2 while visual results are provided in Fig. 3. Note that, Lugmayr et al., FSSR, DASR, DeFlow, Impressionism, and DAP employ ESRGAN as the SR model. For our DictSR, the LR image encoder and the HR image decoder are included to calculate the numbers of layers since only these modules are employed during inference. For other methods, the numbers of layers in the SR networks are presented. MACs (multiply-accumulate operations) is calculated based on $128 \\times 128$ input LR images. The MACs of ZSSR is not reported since this method conducts training during the inference time and requires considerable computational cost.", + "bbox": [ + 496, + 462, + 890, + 747 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Quantitative Results. For the AIM-RWSR dataset, it can be observed from Table 1 that our DictSR achieves the best performance in terms of all metrics among all unpaired SR methods. Moreover, our DictSR also produces competitive results as compared to paired SR methods. Previous unpaired SR methods synthesize pseudo LR images to associate unpaired LR and HR images. However, the large image space poses great challenges to these methods to balance the realness and diversity. In contrast, by building the connection between unpaired images in a compact", + "bbox": [ + 496, + 750, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "25716", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/ef36e2bb3c7ae81b45964181fb595d63ec86ddd0eda9f5b26e0e5636b153c66d.jpg", + "image_caption": [ + "LR" + ], + "image_footnote": [], + "bbox": [ + 81, + 138, + 272, + 277 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/69a4c84903363aeef582a8bb3d1899af88ff4fb15e7e44a6698a6dc158a69675.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 279, + 90, + 478, + 213 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/75f49cbca94195e84b45dc0dd1b60a53692b7d9ed626f9b9a2b1425fa965d297.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 483, + 90, + 684, + 213 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/9f4a1e4a4bdbf61f352b42ce72e98d63bde195e9f7ad1b3606ab3d188d173da8.jpg", + "image_caption": [ + "DASR" + ], + "image_footnote": [], + "bbox": [ + 687, + 90, + 885, + 213 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/8751491d33da5be5e606a9caca7980d6a301354491d2e8990f9b4f63908c231a.jpg", + "image_caption": [ + "Bicubic", + "DeFlow" + ], + "image_footnote": [], + "bbox": [ + 281, + 226, + 478, + 347 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/d3c9fec1366401f0b51c50b00c653351ceaf96fb9ab5f5971739e66fccfb0e08.jpg", + "image_caption": [ + "FSSR", + "DictSR (Ours)" + ], + "image_footnote": [], + "bbox": [ + 485, + 226, + 683, + 347 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/bbd0153462403c28dbc59f9c73996f1885862027f1cb0cd6457ded1b71d12f33.jpg", + "image_caption": [ + "GT" + ], + "image_footnote": [], + "bbox": [ + 687, + 226, + 885, + 347 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/dec942ae75c6c83cefcc69ab1eda6e639009843ef250f37d02bfc8c30957eb72.jpg", + "image_caption": [ + "LR" + ], + "image_footnote": [], + "bbox": [ + 83, + 417, + 272, + 554 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/04dd3c935f3bcb121a61d10492b250c7c82e9da8c66af08d71f58ccefbd2388b.jpg", + "image_caption": [ + "Bicubic" + ], + "image_footnote": [], + "bbox": [ + 281, + 364, + 478, + 484 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/b87e1e37998690dda8ed5f05f666f6269eeeec2f7e2f30b17c232dc7cbdbb0d5.jpg", + "image_caption": [ + "FSSR" + ], + "image_footnote": [], + "bbox": [ + 485, + 364, + 683, + 484 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/27d5908a6fa74086fd5b5baedaf33c1ea54629e50d7c4f87be1851a209494276.jpg", + "image_caption": [ + "DASR" + ], + "image_footnote": [], + "bbox": [ + 687, + 364, + 885, + 484 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/bd23a77ec1e03a7d3f4f411275c96cec8cf499d23ec1f31ceaadb24bf8bc1077.jpg", + "image_caption": [ + "DeFlow", + "Figure 3. Visualization results produced by different methods." + ], + "image_footnote": [], + "bbox": [ + 281, + 500, + 478, + 619 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/bd4a2c4509c7249a890956f3e59350cdc4c6c67852726f0fbe7d2c2e4451d2d1.jpg", + "image_caption": [ + "DictSR (Ours)" + ], + "image_footnote": [], + "bbox": [ + 485, + 500, + 683, + 619 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/ffaad2778f88851e642aa8c1eaffc307bb93cf751ee7f5c7f236b67a9a02bb64.jpg", + "image_caption": [ + "GT" + ], + "image_footnote": [], + "bbox": [ + 687, + 500, + 885, + 619 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "proxy space using dictionaries, our DictSR produces superior quantitative results. In addition, our DictSR employs a shallow and efficient network structure with much lower computational complexity. Specifically, our method gradually reduces the spatial resolution of feature maps to $\\frac{1}{4}$ size while previous methods maintain full-resolution feature maps. As compared to previous methods, our 18-layer network produces superior performance with only half MACs, which further demonstrates the effectiveness of our method.", + "bbox": [ + 75, + 688, + 468, + 837 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For the NTIRE-RWSR dataset, we can observe from Table 2 that our DictSR also produces competitive results. As compared to DeFlow, although the improvements in terms of PSNR and SSIM are marginal, our method produces no", + "bbox": [ + 75, + 839, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "table gains on LPIPS (0.204 vs. 0.218). This demonstrates the superior perceptual quality of our results. In addition, our DictSR also surpasses most previous paired methods with much a shallower network. This further shows the great potential of our learned coupled dictionaries.", + "bbox": [ + 496, + 688, + 890, + 763 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Qualitative Results. Figure 3 compares the visual results produced by different unpaired image SR methods. It can be observed that our method produces higher perceptual quality with fewer artifacts. For example, in the second scene, FSSR and DeFlow produces results with unpleasant ringing artifacts while DASR suffer notable blurring artifacts. In contrast, the results of our DisctSR can better recover the text details. This further demonstrates the superiority of our method.", + "bbox": [ + 496, + 763, + 892, + 898 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "25717", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/70afbbc07f2ffc43c6ef1ae749443ecbf5dc76bedad58bcfcf31ad1e0efbd0f7.jpg", + "table_caption": [ + "Table 2. Results achieved on NTIRE-RWSR for $\\times 4\\mathrm{{SR}}$ . Best and second best results are highlighted and underlined." + ], + "table_footnote": [], + "table_body": "
Method#LayersMACsLPIPSPSNRSSIM
PairedBicubic--0.63225.520.671
RCAN [3]400260G0.57625.310.640
ZSSR [41]8-0.62024.930.642
IKC [5]18880G0.38426.500.748
DAN [42]171315G0.55425.150.671
BSRGAN [17]350291G0.26524.560.669
Real-ESRGAN [16]350291G0.25124.680.687
UnpairedCycleGAN [38]350291G0.41724.750.700
CinCGAN [9]37823G-24.190.683
Impressionism [44]350291G0.23224.670.683
FSSR [43]350291G0.33223.040.590
DeFlow [26]350291G0.21825.870.710
DAP [45]350291G0.25225.400.707
PCR-ESRGAN [46]350291G0.22324.970.682
DictSR (Ours)18129G0.20425.900.711
", + "bbox": [ + 78, + 121, + 468, + 356 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/47da1b4baba16e2aa291c35935519c8b4ca9d8a7fca2598d11ddf17677b7ae31.jpg", + "image_caption": [ + "Figure 4. Visualization of the embedding space. Blue circles represent the embeddings of LR patches while other 100 stars correspond to 100 entries in the LR content dictionary $\\mathbf{D}^{LR}$ ." + ], + "image_footnote": [], + "bbox": [ + 145, + 381, + 398, + 575 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Model Analyses", + "text_level": 1, + "bbox": [ + 76, + 651, + 235, + 667 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In this subsection, we conduct experiments to study our method from three aspects. First, we study our dictionaries. Then, we demonstrate the effectiveness of our learning framework. Finally, we investigate the effect of different encoder and decoder architectures. All experiments are conducted on the AIM-RWSR dataset.", + "bbox": [ + 75, + 675, + 468, + 765 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3.1 Dictionaries", + "text_level": 1, + "bbox": [ + 76, + 786, + 215, + 800 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "(1) Hierarchical Structure", + "text_level": 1, + "bbox": [ + 76, + 809, + 264, + 823 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "To cover diverse degradations in LR images while associating HR and LR image contents, a combination of an LR content dictionary $\\mathbf{D}^{LR}$ and a degradation dictionary $\\mathbf{D}_{deg}$ is employed. To demonstrate the effectiveness of such a hierarchical structure, we remove $\\mathbf{D}_{deg}$ and directly use $\\mathbf{D}^{LR}$", + "bbox": [ + 75, + 824, + 468, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "to discretize feature maps extracted from LR images (i.e., A1 in Table 3). It can be observed that model A1 suffers an accuracy drop as compared to the full model (Ours in Table 3). Without the hierarchical structure, the LR content dictionary $\\mathbf{D}^{LR}$ cannot well cover the large degradation space, thereby producing limited performance. In contrast, the hierarchical structure facilitates our method to achieve notable gains.", + "bbox": [ + 496, + 90, + 890, + 210 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "(2) Dictionary Size", + "text_level": 1, + "bbox": [ + 500, + 213, + 635, + 227 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Intuitively, larger dictionaries contribute to larger model capacity and ultimately result in higher performance. Consequently, we conduct experiments to study the effect of dictionary size from the following three aspects.", + "bbox": [ + 496, + 228, + 890, + 289 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Entry. We first conduct experiments to investigate dictionaries with different numbers of entries. Specifically, we develop two network variants (B1/B2 in Table 3) by employing dictionaries with more/fewer entries. Using dictionaries with fewer entries (2048 entries), the performance of model B1 is slightly lower than our full model. However, further including more entries (8192 entries) cannot introduce consistent gains on all metrics. Consequently, we employ 4096 entries as the default setting.", + "bbox": [ + 496, + 289, + 890, + 426 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Dimension. During the discretization stage, a linear projection is employed to map the feature maps to a low-dimensional latent space for code index lookup. Here, we conduct experiments to study the dimension of the latent space. As the dimension of the latent codes is reduced from 64 to 4, the number of activated entries is increased from 105 to 4050. This indicates that the dictionary can better cover the embeddings in the low-dimensional latent space to activate more entries. As a result, the LPIPS/PSNR/SSIM scores are improved from 0.268/21.99/0.616 to 0.259/22.46/0.629. In our experiments, the dimension of 4 is adopted as the default setting.", + "bbox": [ + 496, + 426, + 890, + 608 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "(3) Visualization of Dictionaries", + "text_level": 1, + "bbox": [ + 500, + 609, + 725, + 622 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "To further study the embedding space of LR feature maps, we visualize the entries of the LR content dictionary $\\mathbf{D}^{LR}$ and the embeddings of $\\mathbf{F}^{LR}$ in Fig. 4. As we can see, the entries in $\\mathbf{D}^{LR}$ span the space of embeddings extracted from LR patches. This validates that $\\mathbf{D}^{LR}$ can well cover the content variation in the LR embedding space.", + "bbox": [ + 496, + 625, + 890, + 715 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3.2 Learning Framework", + "text_level": 1, + "bbox": [ + 500, + 738, + 702, + 753 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "(1) Encoder", + "text_level": 1, + "bbox": [ + 500, + 763, + 588, + 777 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Each entry in our LR/HR dictionaries corresponds a $2 \\times 2 / 8 \\times 8$ patch in the LR/HR image. We further conduct experiments to investigate the effect of the patch size. Specifically, we deepen the LR/HR encoders to encode larger patches into embeddings for discretization. Small patch size cannot well distinguish the degradations and image contents in the LR image. As a result, the degradations will also be reconstructed in the SR results with inferior perfor", + "bbox": [ + 496, + 779, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "25718", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/81c86fdd01a3df9aabef490a7bd559eda5b4890dc723ef2dc87e276944949398.jpg", + "table_caption": [ + "Table 3. Results achieved by our method with different settings." + ], + "table_footnote": [], + "table_body": "
DictionaryFrameworkActivated Entries (DLR)LPIPS (↓)PSNR (↑)SSIM (↑)
HierarchicalEntriesDimPatch (LR/HR)Coupling
A1X409642×2/8×8✓35600.28122.400.619
B1✓204842×2/8×8✓20270.27822.410.621
B2✓819242×2/8×8✓80500.26922.440.626
C1✓4096162×2/8×8✓5680.26222.250.625
C2✓4096642×2/8×8✓1050.26821.990.616
D1✓409641×1/4×4✓15220.27122.410.623
D2✓409644×4/16×16✓38100.31321.430.588
E1✓409642×2/8×8X40960.5338.280.050
Ours✓409642×2/8×8✓40500.25922.460.629
", + "bbox": [ + 89, + 107, + 877, + 281 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/0a1a27e25b1c33ec0e09a96affcce866f89a599166f57a8a68c1b5fe049f61a3.jpg", + "table_caption": [ + "Table 4. Results achieved by our method with different network architectures. $\\mathrm{E}_{\\mathrm{HR}}$ , $\\mathrm{D}_{\\mathrm{HR}}$ , $\\mathrm{E}_{\\mathrm{LR}}$ and $\\mathrm{D}_{\\mathrm{LR}}$ represent HR image encoder, HR image decoder, LR image encoder, and LR image decoder, respectively." + ], + "table_footnote": [], + "table_body": "
EHRDHRELRDLRLPIPS (↓)PSNR (↑)SSIM (↑)
F120-layer12-layer6-layer6-layer0.27122.460.625
F212-layer20-layer6-layer6-layer0.25622.490.631
F312-layer12-layer14-layer6-layer0.26322.480.629
F412-layer12-layer6-layer14-layer0.26122.480.630
Ours12-layer12-layer6-layer6-layer0.25922.460.629
", + "bbox": [ + 173, + 321, + 797, + 419 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "mance. Although large patch size can identify structured image contents from degradations, the reconstructed SR results are usually of high quality but low fidelity [47]. In summary, a reasonable patch size is critical to the performance. Compared to model D1 and D2, our model produces superior accuracy in terms of all metrics. Consequently, patch sizes of $2 \\times 2$ and $8 \\times 8$ are adopted as the default setting.", + "bbox": [ + 75, + 446, + 470, + 568 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "(2) Coupling Operation", + "text_level": 1, + "bbox": [ + 76, + 569, + 246, + 584 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "By employing the same spatial codes over HR content dictionary $\\mathbf{D}^{HR}$ and LR content dictionary $\\mathbf{D}^{LR}$ to represent paired HR and LR images, these dictionaries are tightly coupled. To investigate its effectiveness, we introduce a network variant (E1 in Table 3) by removing this coupling operation. Specifically, HR and LR feature maps are represented using separate spatial codes during the discretization stage. From Table 3 we can see that model E1 produces extremely low quantitative scores. Without the coupling operation, the HR and LR content dictionaries are not associated such that the reconstructed SR result does not share the same content with the LR input. In contrast, the coupling operation enables our model to produce SR results faithful to the LR image.", + "bbox": [ + 75, + 584, + 468, + 795 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3.3 Network Architecture", + "text_level": 1, + "bbox": [ + 76, + 816, + 284, + 830 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Our network consists of four modules, including HR image encoder, HR image decoder, LR image encoder, and LR image decoder. We conduct experiments to study the effect of the model capacity for these four modules. Specif", + "bbox": [ + 75, + 839, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ically, we first develop four network variants (F1-F4 in Table 4) by deepening these four modules. As we can see, our method does not obtain consistent performance gains as the HR encoder, LR encoder and LR decoder are deepened. Meanwhile, with larger HR decoder, model F2 produces slight improvements on all metrics. This indicates that our method relies more on the design of dictionaries (Table 3) rather than the designs of the network architecture. Despite the marginal improvements brought by larger HR decoder, a 12-layer decoder is employed to achieve the accuracy-efficiency balance.", + "bbox": [ + 496, + 446, + 893, + 613 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 631, + 619, + 646 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we propose to associate unpaired LR and HR images using coupled dictionaries rather than synthesizing pseudo LR images. Specifically, we construct an HR content dictionary, an LR content dictionary, and a degradation dictionary to model unpaired HR and LR images. To couple these dictionaries, we develop an autoencoder-based framework for optimization. By representing images using compact proxy codes, an LR-to-HR mapping can be effectively learned by our dictionaries. Experiments on several benchmarks show that our method produces superior performance against previous state-of-the-art approaches.", + "bbox": [ + 496, + 657, + 893, + 824 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments: This work was partially supported by the National Natural Science Foundation of China (No. 62301601, 62301306, and 62306331), the Shenzhen Science and Technology Program (No. RCYX20200714114641140), the Guangdong Basic and Applied Basic Research Foundation (2022B1515020103), and the Young Elite Scientists Sponsorship Program by CAST (No. 2023QNRC001).", + "bbox": [ + 496, + 827, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "25719", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Chao Dong, Chen Change Loy, Kaiming He, and Xiaou Tang. 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Springer, 2022. 8" + ], + "bbox": [ + 78, + 90, + 467, + 828 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "25721", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/14c29cf4-a5f6-481c-be92-86ff4e2cfb38_model.json b/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/14c29cf4-a5f6-481c-be92-86ff4e2cfb38_model.json new file mode 100644 index 0000000000000000000000000000000000000000..87480ecfa4059023ec1ed2ad79f3aa3f1b34f13d --- /dev/null +++ b/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/14c29cf4-a5f6-481c-be92-86ff4e2cfb38_model.json @@ -0,0 +1,2310 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.809, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.082, + 0.131, + 0.89, + 0.153 + ], + "angle": 0, + "content": "Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution" + }, + { + "type": "text", + "bbox": [ + 0.165, + 0.18, + 0.804, + 0.235 + ], + "angle": 0, + "content": "Longguang Wang\\(^{1}\\), Juncheng Li\\(^{2}\\), Yingqian Wang\\(^{3}\\), Qingyong Hu\\(^{4}\\), Yulan Guo\\(^{3*}\\) \n\\(^{1}\\)Aviation University of Air Force \\(^{2}\\)Shanghai University \n\\(^{3}\\)National University of Defense Technology \\(^{4}\\)Independent Researcher" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.301, + 0.474, + 0.635 + ], + "angle": 0, + "content": "The difficulty of acquiring high-resolution (HR) and low-resolution (LR) image pairs in real scenarios limits the performance of existing learning-based image super-resolution (SR) methods in the real world. To conduct training on real-world unpaired data, current methods focus on synthesizing pseudo LR images to associate unpaired images. However, the realness and diversity of pseudo LR images are vulnerable due to the large image space. In this paper, we circumvent the difficulty of image generation and propose an alternative to build the connection between unpaired images in a compact proxy space. Specifically, we first construct coupled HR and LR dictionaries, and then encode HR and LR images into a common latent code space using these dictionaries. In addition, we develop an autoencoder-based framework to couple these dictionaries during optimization by reconstructing input HR and LR images. The coupled dictionaries enable our method to employ a shallow network architecture with only 18 layers to achieve efficient image SR. Extensive experiments show that our method (DictSR) can effectively model the LR-to-HR mapping in coupled dictionaries and produces state-of-the-art performance on benchmark datasets." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.664, + 0.21, + 0.68 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.47, + 0.854 + ], + "angle": 0, + "content": "Image super-resolution (SR) aims at reconstructing a high-resolution (HR) image from low-resolution (LR) observations. To this end, most existing learning-based methods [1-4] rely on paired training data to build an LR-to-HR mapping. Since paired data is difficult to acquire in the real world, manually designed degradations are commonly employed to synthesize paired data for training [5, 6]. Nevertheless, as pre-defined degradations are empirical, synthetic images cannot meet the diversity of real-world images and limit the performance of previous methods in real scenarios [7, 8]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "To remedy this problem, numerous efforts have been made to directly conduct training on unpaired data [7-9]. To enable the learning of LR-to-HR mapping, existing meth" + }, + { + "type": "image", + "bbox": [ + 0.515, + 0.269, + 0.885, + 0.354 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.609, + 0.358, + 0.783, + 0.373 + ], + "angle": 0, + "content": "(a) Previous Approaches" + }, + { + "type": "image", + "bbox": [ + 0.513, + 0.385, + 0.884, + 0.465 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.634, + 0.468, + 0.76, + 0.484 + ], + "angle": 0, + "content": "(b) Our Approach" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.496, + 0.895, + 0.567 + ], + "angle": 0, + "content": "Figure 1. Comparison between previous approaches and our approach. Instead of synthesizing pseudo LR images and minimizing the gap in the image space (a), we encode HR and LR images into a common latent code space using coupled dictionaries to associate unpaired HR and LR images (b)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.597, + 0.895, + 0.822 + ], + "angle": 0, + "content": "ods focus on synthesizing pseudo paired data for training. Given HR images \\( x \\sim p_x \\) (target domain) and LR images \\( y \\sim p_y \\) (source domain), pseudo LR images are generated by learning an HR-to-LR mapping. Then, HR images and the resultant pseudo LR images are adopted to learn the LR-to-HR mapping. Early methods [7, 9] commonly use generative adversarial networks (GANs) with cycle-consistency or adversarial loss to synthesize pseudo LR images. However, these GAN-based methods usually suffer mode collapse and require elaborate fine-tuning. Recently, more powerful diffusion model [10] is introduced for pseudo LR image synthesis. The large latent space in the diffusion model improves the diversity of synthesized images at the cost of lower content fidelity, which hinders further performance improvements." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.894, + 0.903 + ], + "angle": 0, + "content": "Due to the low rank characteristic of natural images, an image can be represented as a spare code on an overcomplete dictionary [11, 12]. On top of this perspective, we seek to associate unpaired LR and HR images in a compact space without relying on synthesizing pseudo LR im" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25712" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.317 + ], + "angle": 0, + "content": "ages high in diversity and realness (Fig. 1). By representing images using spatial codes over a dictionary, the description length is significantly reduced, which allows us to efficiently minimize the gap between HR and LR image domains. To this end, we use autoencoders to learn LR and HR dictionaries rich of context information from LR and HR images. To fit the large space of real-world LR patches, our LR dictionary explicitly models the content and degradation variations in a hierarchical manner (Fig. 2). During training, by coupling HR and LR dictionaries, an LR-to-HR mapping can be learned in the dictionaries. During inference, an LR image is first decomposed over the LR dictionary and then using the HR dictionary for reconstruction to produce the SR result. The contributions of this paper can be summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.318, + 0.47, + 0.393 + ], + "angle": 0, + "content": "- We associate unpaired images using coupled HR and LR dictionaries instead of synthesizing pseudo LR images. By decomposing unpaired images over the dictionary to obtain compact proxy codes, an LR-to-HR mapping can be efficiently learned in the code space." + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.394, + 0.469, + 0.438 + ], + "angle": 0, + "content": "- We formulate the LR dictionary as a combination of an LR content dictionary and a degradation dictionary to model LR images in a hierarchical manner." + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.439, + 0.469, + 0.483 + ], + "angle": 0, + "content": "- We develop an autoencoder-based framework to optimize coupled dictionaries together with the network parameters in an end-to-end manner." + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.484, + 0.469, + 0.543 + ], + "angle": 0, + "content": "- Extensive experiments show that our coupled dictionaries can effectively learn the LR-to-HR mapping and our method (DictSR) achieves state-of-the-art performance on benchmark datasets." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.318, + 0.47, + 0.543 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.558, + 0.227, + 0.572 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.583, + 0.469, + 0.629 + ], + "angle": 0, + "content": "In this section, we first review recent advances of paired and unpaired image SR methods. Then, we discuss dictionary learning approach that is related to our work." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.636, + 0.245, + 0.652 + ], + "angle": 0, + "content": "2.1. Paired Image SR" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.66, + 0.473, + 0.902 + ], + "angle": 0, + "content": "Most previous learning-based image SR methods rely on paired data with aligned contents for training. Early methods [1-3, 13-15] commonly employ bicubic downsampling to synthesize HR-LR image pairs as the training data. Despite promising results on synthetic data, these methods suffer severe performance drop on real-world images since their degradations differ from the bicubic one. Later, several methods adopt more complicated degradations including blur, compression, and noise to generate HR-LR image pairs [5, 16-19]. Although the handcrafted degradations span a large space, the gap between real-world degradations still remains and limits the accuracy in real scenarios. Recently, a number of real-world paired datasets are developed to capture real degradations [20, 21]. However, the high labor cost limits the scales of these datasets, thereby hindering further performance improvement." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.091, + 0.691, + 0.108 + ], + "angle": 0, + "content": "2.2. Unpaired Image SR" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.113, + 0.892, + 0.37 + ], + "angle": 0, + "content": "To circumvents the difficulty of acquiring real-world paired data, a number of methods directly conduct training on unpaired images. Early approaches assume real-world LR images follow a specific distribution and employ GANs to synthesize pseudo LR image in this distribution. Specifically, Bulat et al. [22] and Lugmayr et al. [23] first trained a degradation network to synthesize pseudo LR images from HR images and then use these paired images to learn the LR-to-HR mapping. Yuan et al. [9] and Maeda et al. [7] developed unified frameworks to simultaneously learn a degradation network and an SR network, which produce superior accuracy. Liu et al. [24] and Yang et al. [25] introduced physical properties to LR image synthesis as regularizations for higher realness. Despite improved performance against paired approaches, these GAN-based methods usually suffer mode collapse and cannot generate LR images as diverse as real ones." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.371, + 0.892, + 0.522 + ], + "angle": 0, + "content": "To address the aforementioned problem of GAN-based methods, Wolf et al. [26] developed a flow-based model to synthesize LR images. Although the diversity of synthesized LR images is improved, this method has a high computational cost due to the limited expressive power of flow-based models [27, 28]. Recently, Yang et al. [10] introduced the powerful diffusion model for pseudo LR image synthesis. The large latent space in the diffusion model improves the diversity but decreases the content fidelity, which also results in limited performance." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.531, + 0.694, + 0.547 + ], + "angle": 0, + "content": "2.3. Dictionary Learning" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.554, + 0.892, + 0.765 + ], + "angle": 0, + "content": "Dictionary learning aims at finding a sparse representation of the input data in the form of a linear combination of basic elements as well as those basic elements themselves. The idea of dictionary learning can be dated back to several decades ago [29, 30]. Before the era of deep learning, dictionary learning is widely used to model the LR-to-HR mapping for image SR. Specifically, Yang et al. [12] proposed coupled dictionaries to associate LR and HR image patches via sparse coding. Zhang et al. [11] developed a multi-scale dictionary to simultaneously model local and non-local priors in the images. Lu et al. [31] took the geometrical structure of the dictionary into consideration and proposed a geometry constrained sparse coding method for image SR." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.766, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Since the huge success of neural networks, learning-based methods have dominated a wide range of tasks. Recently, the idea of dictionary learning has been introduced to learning-based frameworks and produces superior performance. Specifically, Van et al. [32] proposed a vector quantized variational autoencoder (VQ-VAE) to learn discrete representations of an image over a codebook. Then, a CNN is trained to model their distribution for image synthesis. Then, Razavi et al. [33] extended this approach to a" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25713" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.088, + 0.092, + 0.885, + 0.555 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.572, + 0.893, + 0.603 + ], + "angle": 0, + "content": "Figure 2. An illustration of our framework during training phase (a) and test phase (b). Entries with different colors correspond to various contents while entries with different shades refer to the same content but diverse degradations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.628, + 0.471, + 0.763 + ], + "angle": 0, + "content": "hierarchical one to learn discrete representation at different scale, which achieves superior performance. Later, Esser et al. [34] further developed VQ-GAN by leveraging the powerful transformer to model the composition of images. Recently, Maeda et al. [35] introduced dictionary learning for image SR by plugging a learnable dictionary into a CNN framework. However, this method relies on paired data to learn the LR-to-HR mapping and cannot be extended to unpaired SR." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.783, + 0.212, + 0.801 + ], + "angle": 0, + "content": "3. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Ideally, a pair of LR and HR images can be decomposed to a common latent code over coupled LR-HR dictionaries. From this point of view, we seek to learn coupled dictionaries from unpaired data for image SR. To this end, we formulate the coupled dictionaries as a combination of an HR content dictionary \\(\\mathbf{D}^{HR}\\), an LR content dictionary \\(\\mathbf{D}^{LR}\\), and a" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.628, + 0.892, + 0.809 + ], + "angle": 0, + "content": "degradation dictionary \\(\\mathbf{D}_{deg}\\). These three dictionaries are tightly coupled and jointly optimized in three branches, as illustrated in Fig. 2. During the training phase, the pipeline for each branch consists of three stages, including encoding, discretization, and decoding. Specifically, input images are first encoded into embeddings. Then, these embeddings are discretized in the embedding space to the entries in corresponding dictionaries. Finally, the discretized embeddings are fed to the decoders to reconstruct the input image. During the test phase, the input LR image is first encoded to an indicex map using \\(\\mathbf{D}^{LR}\\) and \\(\\mathbf{D}_{deg}\\). Then, the corresponding entries in \\(\\mathbf{D}^{HR}\\) is retrieved to reconstruct the SR result." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.818, + 0.658, + 0.834 + ], + "angle": 0, + "content": "3.1. Encoding Stage" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.839, + 0.894, + 0.903 + ], + "angle": 0, + "content": "Given an HR image \\(\\mathbf{I}^{HR} \\in \\mathbb{R}^{H \\times W \\times 3}\\) and a unpaired LR image \\(\\mathbf{I}^{LR} \\in \\mathbb{R}^{h \\times w \\times 3}\\), \\(\\mathbf{I}^{HR}\\) is first downscaled to obtain \\(\\mathbf{I}^{HR\\downarrow} \\in \\mathbb{R}^{\\frac{H}{s} \\times \\frac{W}{s} \\times 3}\\). Here, \\(s\\) is the scale factor and set to 4 as we focus on \\(\\times 4\\) SR in this paper. Then, \\(\\mathbf{I}^{HR}\\) is fed" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25714" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.089, + 0.47, + 0.198 + ], + "angle": 0, + "content": "to the HR image encoder to produce \\(\\mathbf{F}^{HR} \\in \\mathbb{R}^{\\frac{H}{8} \\times \\frac{W}{8} \\times 512}\\), with each embedding corresponding to a \\(8 \\times 8\\) patch in the input HR image. Meanwhile, \\(\\mathbf{I}^{LR}\\) and \\(\\mathbf{I}^{HR\\downarrow}\\) are passed to the LR image encoder to obtain \\(\\mathbf{F}^{LR} \\in \\mathbb{R}^{\\frac{h}{2} \\times \\frac{w}{2} \\times 128}\\) and \\(\\mathbf{F}^{HR\\downarrow} \\in \\mathbb{R}^{\\frac{H}{8} \\times \\frac{W}{8} \\times 128}\\), respectively. Each embedding in the resultant feature maps corresponds to a \\(2 \\times 2\\) patch in the input LR image." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.198, + 0.47, + 0.276 + ], + "angle": 0, + "content": "The HR image encoder employs a fully convolutional structure and consists of four residual blocks at four resolution levels (i.e., \\( H \\times W \\), \\( \\frac{H}{2} \\times \\frac{W}{2} \\), \\( \\frac{H}{4} \\times \\frac{W}{4} \\), and \\( \\frac{H}{8} \\times \\frac{W}{8} \\)). Meanwhile, the LR image encoder consists of two residual blocks at \\( h \\times w \\) and \\( \\frac{h}{2} \\times \\frac{w}{2} \\) resolution levels." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.284, + 0.267, + 0.301 + ], + "angle": 0, + "content": "3.2. Discretization Stage" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.308, + 0.469, + 0.462 + ], + "angle": 0, + "content": "After the encoding stage, the resultant embedding at each location of the feature map is discretized to its closest dictionary entry in the embedding space, resulting in \\(\\mathbf{F}_q^{HR}\\), \\(\\mathbf{F}_q^{HR\\downarrow}\\), and \\(\\mathbf{F}_q^{LR}\\). Motivated by [36], we introduce a linear projection to map the output feature maps to a low-dimensional latent space (4-dim in our experiments) for code index lookup. Then, the discretized embedding is projected back to the embedding space through another projection layer. During backpropagation, straight-through estimator (STE) is employed for end-to-end optimization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.462, + 0.47, + 0.749 + ], + "angle": 0, + "content": "To associate HR and LR images, HR and LR dictionaries should be coupled at this stage. However, there exists two major challenges: (1) Misaligned Content. Under paired settings, corresponding patches in HR and LR images share the same content, which can be employed as a cue to couple HR and LR dictionaries for joint optimization. However, this cue does not hold for unpaired images, which imposes great challenges to learning coupled dictionaries. (2) **Diverse Degradations**. Since an HR image corresponds to infinite LR images under various degradations, modeling such a one-to-many correlation using coupled dictionaries is quite difficult. To address the above challenges, we formulate the coupled dictionaries as a combination of an HR content dictionary, an LR content dictionary, and a degradation dictionary. The LR content dictionary couples with the HR content dictionary to build connections between LR and HR image contents. Meanwhile, the degradation dictionary captures the degradation variations for different image contents." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.77, + 0.352, + 0.787 + ], + "angle": 0, + "content": "3.2.1 HR and LR Content Dictionary" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.793, + 0.469, + 0.901 + ], + "angle": 0, + "content": "First, we construct an HR content dictionary \\(\\mathbf{D}^{HR} \\in \\mathbb{R}^{N \\times 4}\\) and an LR content dictionary \\(\\mathbf{D}^{LR} \\in \\mathbb{R}^{N \\times 4}\\) to model the content variation in the embedding space, where \\(N\\) is the number of entries. To handle the first challenge, we introduce downscaled version of HR images as a bridge to associate HR and LR content dictionaries to enable joint training. For embeddings \\(f^{HR} \\in \\mathbf{F}^{HR}\\) (branch 1) and" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.089, + 0.892, + 0.126 + ], + "angle": 0, + "content": "\\(f^{HR\\downarrow} \\in \\mathbf{F}^{HR\\downarrow}\\) (branch 2), the discretized embeddings \\(f_{q}^{HR}\\) and \\(f_{q}^{HR\\downarrow}\\) are obtained as:" + }, + { + "type": "equation", + "bbox": [ + 0.587, + 0.135, + 0.892, + 0.162 + ], + "angle": 0, + "content": "\\[\ni = \\underset {i} {\\arg \\min } | | f ^ {H R \\downarrow} - \\mathbf {D} ^ {L R} (i) | |, \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.627, + 0.176, + 0.892, + 0.218 + ], + "angle": 0, + "content": "\\[\n\\left\\{ \\begin{array}{l} f _ {q} ^ {H R \\downarrow} = \\mathbf {D} ^ {L R} (i) \\\\ f _ {q} ^ {H R} = \\mathbf {D} ^ {H R} (i) \\end{array} , \\right. \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.224, + 0.892, + 0.3 + ], + "angle": 0, + "content": "where \\(i\\) is the index of the closest entry in \\(\\mathbf{D}^{LR}\\) to the embedding \\(f^{HR\\downarrow}\\). By employing the same spatial codes (i.e., \\(i\\)) to represent both \\(f^{HR}\\) and \\(f^{HR\\downarrow}\\), HR and LR content dictionaries are coupled. Inspired by [34], the discretization losses for branches 1 and 2 are defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.597, + 0.308, + 0.892, + 0.351 + ], + "angle": 0, + "content": "\\[\n\\left\\{ \\begin{array}{l} \\mathcal {L} _ {d i s} ^ {1} = | | \\mathbf {F} ^ {H R} - \\mathbf {F} _ {q} ^ {H R} | | _ {2} ^ {2} \\\\ \\mathcal {L} _ {d i s} ^ {2} = | | \\mathbf {F} ^ {H R \\downarrow} - \\mathbf {F} _ {q} ^ {H R \\downarrow} | | _ {2} ^ {2}. \\end{array} \\right. \\tag {3}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.365, + 0.72, + 0.381 + ], + "angle": 0, + "content": "3.2.2 Degradation Dictionary" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.389, + 0.892, + 0.497 + ], + "angle": 0, + "content": "Second, we construct a degradation dictionary \\(\\mathbf{D}_{deg} \\in \\mathbb{R}^{N \\times K \\times 4}\\) on top of \\(\\mathbf{D}^{LR}\\) to model the degradation variations. Specifically, each group of entries (e.g., \\(\\mathbf{D}_{deg}(i) \\in \\mathbb{R}^{K \\times 4}\\)) is used to capture the degradation variation around the corresponding entry in the content dictionary (i.e., \\(\\mathbf{D}^{LR}(i)\\)). During discretization, a hierarchical approach is employed to obtain the discretized embedding \\(f_{q}^{LR}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.52, + 0.507, + 0.892, + 0.564 + ], + "angle": 0, + "content": "\\[\n\\left\\{ \\begin{array}{l} j = \\underset {j} {\\arg \\min } | | f ^ {L R} - \\mathbf {D} ^ {L R} (j) | | \\\\ k = \\underset {k} {\\arg \\min } | | f ^ {L R} - \\left(\\mathbf {D} ^ {L R} (j) + \\mathbf {D} _ {d e g} (j, k)\\right) | | \\end{array} . \\right. \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.575, + 0.892, + 0.667 + ], + "angle": 0, + "content": "For each embedding \\( f^{LR} \\) in \\( \\mathbf{F}^{LR} \\) (branch 3), the closest entry in \\( \\mathbf{D}^{LR} \\) is first selected. \\( \\mathbf{D}^{LR}(j) \\) depicts the clean image content in \\( f^{LR} \\) but ignores the degradation. Then, the degradation is taken into consideration by retrieving the closest entry in \\( \\mathbf{D}^{LR}(j) + \\mathbf{D}_{deg}(j) \\), resulting in \\( f_{q}^{LR} \\). Similarly, a discretization loss is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.614, + 0.677, + 0.891, + 0.698 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {d i s} ^ {3} = \\left\\| \\mathbf {F} ^ {L R} - \\mathbf {F} _ {q} ^ {L R} \\right\\| _ {2} ^ {2}. \\tag {5}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.707, + 0.655, + 0.723 + ], + "angle": 0, + "content": "3.3. Decoding Stage" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.73, + 0.892, + 0.848 + ], + "angle": 0, + "content": "After the discretization stage, the feature map produced by the encoders are represented using the dictionaries. Then, \\(\\mathbf{F}_q^{HR}\\) is fed to the HR image decoder to reconstruct the HR image \\(\\hat{\\mathbf{I}}^{HR}\\). Meanwhile, \\(\\mathbf{F}_q^{HR\\downarrow}\\) and \\(\\mathbf{F}_q^{LR}\\) are passed to the LR image decoder to produce \\(\\hat{\\mathbf{I}}^{HR\\downarrow}\\) and \\(\\hat{\\mathbf{I}}^{LR}\\), respectively. The reconstruction loss is defined as the L1 loss between the reconstructed results and the input images:" + }, + { + "type": "equation", + "bbox": [ + 0.525, + 0.857, + 0.892, + 0.904 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {r e c} = \\left| \\left| \\hat {\\mathbf {I}} ^ {H R} - \\mathbf {I} ^ {H R} \\right| \\right| + \\left| \\left| \\phi \\left(\\hat {\\mathbf {I}} ^ {H R}\\right) - \\phi (\\mathbf {I} ^ {H R}) \\right| \\right| + \\tag {6} \\\\ \\left| \\left| \\hat {\\mathbf {I}} ^ {H R \\downarrow} - \\mathbf {I} ^ {H R \\downarrow} \\right| \\right| + \\left| \\left| \\hat {\\mathbf {I}} ^ {L R} - \\mathbf {I} ^ {L R} \\right| \\right|, \\\\ \\end{array}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25715" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.09, + 0.469, + 0.121 + ], + "angle": 0, + "content": "where \\(\\phi (\\mathbf{I}^{HR})\\) refers to the feature maps extracted by a pretrained VGG model [37]." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.122, + 0.469, + 0.197 + ], + "angle": 0, + "content": "Similar with the encoders, the HR image decoder is composed of four residual blocks at different resolution levels and a tail convolutional layer to regress the reconstructed images. Meanwhile, the LR image decoder comprises of two residual blocks and a tail convolutional layer." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.207, + 0.223, + 0.22 + ], + "angle": 0, + "content": "3.4. Loss Function" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.23, + 0.468, + 0.258 + ], + "angle": 0, + "content": "The overall loss function used for training is defined as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.135, + 0.269, + 0.469, + 0.287 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {r e c} + \\lambda_ {1} \\times \\left(\\mathcal {L} _ {d i s} ^ {1} + \\mathcal {L} _ {d i s} ^ {2} + \\mathcal {L} _ {d i s} ^ {3}\\right) \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.297, + 0.424, + 0.313 + ], + "angle": 0, + "content": "where \\(\\lambda_{1}\\) is empirically set to 10 in our experiments." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.326, + 0.208, + 0.342 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.351, + 0.469, + 0.426 + ], + "angle": 0, + "content": "In this section, we first introduce the experimental setup. Then, we compare our method with previous paired and unpaired image SR methods on benchmark datasets. Finally, we conduct experiments to investigate the effectiveness of our major designs." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.435, + 0.266, + 0.451 + ], + "angle": 0, + "content": "4.1. Experimental Setup" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.458, + 0.278, + 0.472 + ], + "angle": 0, + "content": "4.1.1 Datasets and Metrics" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.482, + 0.469, + 0.556 + ], + "angle": 0, + "content": "We conduct experiments on two widely applied unpaired SR datasets, including AIM-RWSR [38] and NTIRE-RWSR [39]. Note that, we focus on \\(\\times 4\\) SR in this paper and our method can be extended to SR tasks with different scale factors." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.557, + 0.469, + 0.617 + ], + "angle": 0, + "content": "AIM-RWSR. The AIM-RWSR dataset is a synthetic dataset and uses handcrafted degradations to synthesize 2650 noisy and compressed LR images. Meanwhile, 800 images in the DIV2K dataset are employed as HR images." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.618, + 0.469, + 0.692 + ], + "angle": 0, + "content": "NTIRE-RWSR. The NTIRE-RWSR dataset follows the same setting as the AIM-RWSR dataset to produce unpaired HR and LR images. Different from AIM-RWSR, NTIRE-RWSR features a more complicated degradation type that consists of highly related high-frequency noises." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.693, + 0.469, + 0.753 + ], + "angle": 0, + "content": "For evaluation on the AIM-RWSR and NTIRE-RWSR datasets, we use peak signal-to-noise ratio (PSNR), structural similarity (SSIM) and learned perceptual image patch similarity (LPIPS) as metrics." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.772, + 0.244, + 0.787 + ], + "angle": 0, + "content": "4.1.2 Training Details" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.795, + 0.469, + 0.901 + ], + "angle": 0, + "content": "During the training phase, 24 LR patches of size \\(64 \\times 64\\) and 24 HR patches of size \\(256 \\times 256\\) were randomly cropped from LR and HR images, respectively. Random rotation and random flipping were employed for data augmentation. The Adam method [40] with \\(\\beta_{1} = 0.9\\) and \\(\\beta_{2} = 0.999\\) was used for optimization. The learning rate was initialized as \\(2 \\times 10^{-4}\\) and halved after every 25 epochs. The training was" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.09, + 0.892, + 0.118 + ], + "angle": 0, + "content": "Table 1. Results achieved on AIM-RWSR for \\( \\times 4\\mathrm{{SR}} \\) . Best and second best results are highlighted and underlined." + }, + { + "type": "table", + "bbox": [ + 0.502, + 0.122, + 0.892, + 0.357 + ], + "angle": 0, + "content": "
Method#LayersMACsLPIPSPSNRSSIM
PairedBicubic--0.53722.350.617
RCAN [3]400260G0.47222.320.604
ZSSR [41]8-0.63922.210.603
IKC [5]18880G0.47922.250.600
DAN [42]171315G0.47122.410.609
BSRGAN [17]350291G0.29922.470.623
Real-ESRGAN [16]350291G0.23822.080.622
UnpairedCycleGAN [38]350291G0.47621.190.530
CinCGAN [9]37823G0.46121.600.613
Lugmayr et al. [23]350291G0.47221.590.550
FSSR [43]350291G0.39020.820.510
DASR [8]350291G0.33621.600.564
DeFlow [26]350291G0.34922.250.620
PCR-ESRGAN [46]350291G0.32121.590.610
DictSR (Ours)18129G0.25922.460.629
" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.385, + 0.892, + 0.431 + ], + "angle": 0, + "content": "stopped after 100 epochs. In our experiments, the numbers of entries in the dictionaries (i.e., \\(N\\) and \\(K\\)) were set to 4096 and 32, respectively." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.44, + 0.724, + 0.455 + ], + "angle": 0, + "content": "4.2. Performance Evaluation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.463, + 0.892, + 0.748 + ], + "angle": 0, + "content": "For performance evaluation, six representative paired SR methods (RCAN [3], ZSSR [41], IKC [5], DAN [42], BSRGAN [17] and Real-ESRGAN [16]) and eight state-of-the-art unpaired image SR methods (CinCGAN [9], Lugmayr et al. [23], FSSR [43], Impressionism [44], DASR [8], DeFlow [26], DAP [45], and PCR-ESRGAN [46]) are included for comparison. Quantitative results are presented in Tables 1 and 2 while visual results are provided in Fig. 3. Note that, Lugmayr et al., FSSR, DASR, DeFlow, Impressionism, and DAP employ ESRGAN as the SR model. For our DictSR, the LR image encoder and the HR image decoder are included to calculate the numbers of layers since only these modules are employed during inference. For other methods, the numbers of layers in the SR networks are presented. MACs (multiply-accumulate operations) is calculated based on \\(128 \\times 128\\) input LR images. The MACs of ZSSR is not reported since this method conducts training during the inference time and requires considerable computational cost." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Quantitative Results. For the AIM-RWSR dataset, it can be observed from Table 1 that our DictSR achieves the best performance in terms of all metrics among all unpaired SR methods. Moreover, our DictSR also produces competitive results as compared to paired SR methods. Previous unpaired SR methods synthesize pseudo LR images to associate unpaired LR and HR images. However, the large image space poses great challenges to these methods to balance the realness and diversity. In contrast, by building the connection between unpaired images in a compact" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "25716" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.083, + 0.139, + 0.273, + 0.278 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.169, + 0.281, + 0.19, + 0.294 + ], + "angle": 0, + "content": "LR" + }, + { + "type": "image", + "bbox": [ + 0.281, + 0.092, + 0.48, + 0.214 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.355, + 0.215, + 0.406, + 0.227 + ], + "angle": 0, + "content": "Bicubic" + }, + { + "type": "image", + "bbox": [ + 0.485, + 0.092, + 0.685, + 0.214 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.569, + 0.215, + 0.603, + 0.227 + ], + "angle": 0, + "content": "FSSR" + }, + { + "type": "image", + "bbox": [ + 0.689, + 0.092, + 0.887, + 0.214 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.769, + 0.215, + 0.807, + 0.226 + ], + "angle": 0, + "content": "DASR" + }, + { + "type": "image", + "bbox": [ + 0.282, + 0.227, + 0.48, + 0.348 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.354, + 0.349, + 0.407, + 0.361 + ], + "angle": 0, + "content": "DeFlow" + }, + { + "type": "image", + "bbox": [ + 0.486, + 0.227, + 0.684, + 0.348 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.541, + 0.348, + 0.631, + 0.362 + ], + "angle": 0, + "content": "DictSR (Ours)" + }, + { + "type": "image", + "bbox": [ + 0.688, + 0.227, + 0.887, + 0.348 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.777, + 0.349, + 0.799, + 0.36 + ], + "angle": 0, + "content": "GT" + }, + { + "type": "image", + "bbox": [ + 0.084, + 0.419, + 0.273, + 0.555 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.169, + 0.558, + 0.189, + 0.57 + ], + "angle": 0, + "content": "LR" + }, + { + "type": "image", + "bbox": [ + 0.282, + 0.365, + 0.48, + 0.486 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.355, + 0.487, + 0.406, + 0.499 + ], + "angle": 0, + "content": "Bicubic" + }, + { + "type": "image", + "bbox": [ + 0.486, + 0.365, + 0.684, + 0.486 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.569, + 0.487, + 0.603, + 0.499 + ], + "angle": 0, + "content": "FSSR" + }, + { + "type": "image", + "bbox": [ + 0.689, + 0.365, + 0.887, + 0.486 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.769, + 0.487, + 0.807, + 0.498 + ], + "angle": 0, + "content": "DASR" + }, + { + "type": "image", + "bbox": [ + 0.282, + 0.5, + 0.48, + 0.62 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.354, + 0.622, + 0.407, + 0.634 + ], + "angle": 0, + "content": "DeFlow" + }, + { + "type": "image", + "bbox": [ + 0.486, + 0.5, + 0.684, + 0.62 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.54, + 0.621, + 0.631, + 0.635 + ], + "angle": 0, + "content": "DictSR (Ours)" + }, + { + "type": "image", + "bbox": [ + 0.689, + 0.5, + 0.887, + 0.62 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.777, + 0.622, + 0.799, + 0.634 + ], + "angle": 0, + "content": "GT" + }, + { + "type": "image_caption", + "bbox": [ + 0.3, + 0.648, + 0.669, + 0.662 + ], + "angle": 0, + "content": "Figure 3. Visualization results produced by different methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.47, + 0.838 + ], + "angle": 0, + "content": "proxy space using dictionaries, our DictSR produces superior quantitative results. In addition, our DictSR employs a shallow and efficient network structure with much lower computational complexity. Specifically, our method gradually reduces the spatial resolution of feature maps to \\(\\frac{1}{4}\\) size while previous methods maintain full-resolution feature maps. As compared to previous methods, our 18-layer network produces superior performance with only half MACs, which further demonstrates the effectiveness of our method." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.471, + 0.902 + ], + "angle": 0, + "content": "For the NTIRE-RWSR dataset, we can observe from Table 2 that our DictSR also produces competitive results. As compared to DeFlow, although the improvements in terms of PSNR and SSIM are marginal, our method produces no" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.892, + 0.764 + ], + "angle": 0, + "content": "table gains on LPIPS (0.204 vs. 0.218). This demonstrates the superior perceptual quality of our results. In addition, our DictSR also surpasses most previous paired methods with much a shallower network. This further shows the great potential of our learned coupled dictionaries." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.893, + 0.9 + ], + "angle": 0, + "content": "Qualitative Results. Figure 3 compares the visual results produced by different unpaired image SR methods. It can be observed that our method produces higher perceptual quality with fewer artifacts. For example, in the second scene, FSSR and DeFlow produces results with unpleasant ringing artifacts while DASR suffer notable blurring artifacts. In contrast, the results of our DisctSR can better recover the text details. This further demonstrates the superiority of our method." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "25717" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.09, + 0.47, + 0.118 + ], + "angle": 0, + "content": "Table 2. Results achieved on NTIRE-RWSR for \\( \\times 4\\mathrm{{SR}} \\) . Best and second best results are highlighted and underlined." + }, + { + "type": "table", + "bbox": [ + 0.079, + 0.122, + 0.47, + 0.357 + ], + "angle": 0, + "content": "
Method#LayersMACsLPIPSPSNRSSIM
PairedBicubic--0.63225.520.671
RCAN [3]400260G0.57625.310.640
ZSSR [41]8-0.62024.930.642
IKC [5]18880G0.38426.500.748
DAN [42]171315G0.55425.150.671
BSRGAN [17]350291G0.26524.560.669
Real-ESRGAN [16]350291G0.25124.680.687
UnpairedCycleGAN [38]350291G0.41724.750.700
CinCGAN [9]37823G-24.190.683
Impressionism [44]350291G0.23224.670.683
FSSR [43]350291G0.33223.040.590
DeFlow [26]350291G0.21825.870.710
DAP [45]350291G0.25225.400.707
PCR-ESRGAN [46]350291G0.22324.970.682
DictSR (Ours)18129G0.20425.900.711
" + }, + { + "type": "image", + "bbox": [ + 0.147, + 0.382, + 0.4, + 0.576 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.584, + 0.47, + 0.626 + ], + "angle": 0, + "content": "Figure 4. Visualization of the embedding space. Blue circles represent the embeddings of LR patches while other 100 stars correspond to 100 entries in the LR content dictionary \\(\\mathbf{D}^{LR}\\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.652, + 0.236, + 0.669 + ], + "angle": 0, + "content": "4.3. Model Analyses" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.676, + 0.469, + 0.766 + ], + "angle": 0, + "content": "In this subsection, we conduct experiments to study our method from three aspects. First, we study our dictionaries. Then, we demonstrate the effectiveness of our learning framework. Finally, we investigate the effect of different encoder and decoder architectures. All experiments are conducted on the AIM-RWSR dataset." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.787, + 0.216, + 0.801 + ], + "angle": 0, + "content": "4.3.1 Dictionaries" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.81, + 0.265, + 0.824 + ], + "angle": 0, + "content": "(1) Hierarchical Structure" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.469, + 0.903 + ], + "angle": 0, + "content": "To cover diverse degradations in LR images while associating HR and LR image contents, a combination of an LR content dictionary \\(\\mathbf{D}^{LR}\\) and a degradation dictionary \\(\\mathbf{D}_{deg}\\) is employed. To demonstrate the effectiveness of such a hierarchical structure, we remove \\(\\mathbf{D}_{deg}\\) and directly use \\(\\mathbf{D}^{LR}\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.212 + ], + "angle": 0, + "content": "to discretize feature maps extracted from LR images (i.e., A1 in Table 3). It can be observed that model A1 suffers an accuracy drop as compared to the full model (Ours in Table 3). Without the hierarchical structure, the LR content dictionary \\(\\mathbf{D}^{LR}\\) cannot well cover the large degradation space, thereby producing limited performance. In contrast, the hierarchical structure facilitates our method to achieve notable gains." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.214, + 0.636, + 0.228 + ], + "angle": 0, + "content": "(2) Dictionary Size" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.229, + 0.892, + 0.29 + ], + "angle": 0, + "content": "Intuitively, larger dictionaries contribute to larger model capacity and ultimately result in higher performance. Consequently, we conduct experiments to study the effect of dictionary size from the following three aspects." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.29, + 0.892, + 0.427 + ], + "angle": 0, + "content": "Entry. We first conduct experiments to investigate dictionaries with different numbers of entries. Specifically, we develop two network variants (B1/B2 in Table 3) by employing dictionaries with more/fewer entries. Using dictionaries with fewer entries (2048 entries), the performance of model B1 is slightly lower than our full model. However, further including more entries (8192 entries) cannot introduce consistent gains on all metrics. Consequently, we employ 4096 entries as the default setting." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.428, + 0.892, + 0.609 + ], + "angle": 0, + "content": "Dimension. During the discretization stage, a linear projection is employed to map the feature maps to a low-dimensional latent space for code index lookup. Here, we conduct experiments to study the dimension of the latent space. As the dimension of the latent codes is reduced from 64 to 4, the number of activated entries is increased from 105 to 4050. This indicates that the dictionary can better cover the embeddings in the low-dimensional latent space to activate more entries. As a result, the LPIPS/PSNR/SSIM scores are improved from 0.268/21.99/0.616 to 0.259/22.46/0.629. In our experiments, the dimension of 4 is adopted as the default setting." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.61, + 0.726, + 0.623 + ], + "angle": 0, + "content": "(3) Visualization of Dictionaries" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.625, + 0.892, + 0.716 + ], + "angle": 0, + "content": "To further study the embedding space of LR feature maps, we visualize the entries of the LR content dictionary \\(\\mathbf{D}^{LR}\\) and the embeddings of \\(\\mathbf{F}^{LR}\\) in Fig. 4. As we can see, the entries in \\(\\mathbf{D}^{LR}\\) span the space of embeddings extracted from LR patches. This validates that \\(\\mathbf{D}^{LR}\\) can well cover the content variation in the LR embedding space." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.739, + 0.704, + 0.754 + ], + "angle": 0, + "content": "4.3.2 Learning Framework" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.764, + 0.589, + 0.778 + ], + "angle": 0, + "content": "(1) Encoder" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Each entry in our LR/HR dictionaries corresponds a \\(2 \\times 2 / 8 \\times 8\\) patch in the LR/HR image. We further conduct experiments to investigate the effect of the patch size. Specifically, we deepen the LR/HR encoders to encode larger patches into embeddings for discretization. Small patch size cannot well distinguish the degradations and image contents in the LR image. As a result, the degradations will also be reconstructed in the SR results with inferior perfor" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25718" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.295, + 0.089, + 0.674, + 0.104 + ], + "angle": 0, + "content": "Table 3. Results achieved by our method with different settings." + }, + { + "type": "table", + "bbox": [ + 0.09, + 0.108, + 0.878, + 0.282 + ], + "angle": 0, + "content": "
DictionaryFrameworkActivated Entries (DLR)LPIPS (↓)PSNR (↑)SSIM (↑)
HierarchicalEntriesDimPatch (LR/HR)Coupling
A1X409642×2/8×8✓35600.28122.400.619
B1✓204842×2/8×8✓20270.27822.410.621
B2✓819242×2/8×8✓80500.26922.440.626
C1✓4096162×2/8×8✓5680.26222.250.625
C2✓4096642×2/8×8✓1050.26821.990.616
D1✓409641×1/4×4✓15220.27122.410.623
D2✓409644×4/16×16✓38100.31321.430.588
E1✓409642×2/8×8X40960.5338.280.050
Ours✓409642×2/8×8✓40500.25922.460.629
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.291, + 0.893, + 0.32 + ], + "angle": 0, + "content": "Table 4. Results achieved by our method with different network architectures. \\( \\mathrm{E}_{\\mathrm{HR}} \\), \\( \\mathrm{D}_{\\mathrm{HR}} \\), \\( \\mathrm{E}_{\\mathrm{LR}} \\) and \\( \\mathrm{D}_{\\mathrm{LR}} \\) represent HR image encoder, HR image decoder, LR image encoder, and LR image decoder, respectively." + }, + { + "type": "table", + "bbox": [ + 0.174, + 0.323, + 0.798, + 0.42 + ], + "angle": 0, + "content": "
EHRDHRELRDLRLPIPS (↓)PSNR (↑)SSIM (↑)
F120-layer12-layer6-layer6-layer0.27122.460.625
F212-layer20-layer6-layer6-layer0.25622.490.631
F312-layer12-layer14-layer6-layer0.26322.480.629
F412-layer12-layer6-layer14-layer0.26122.480.630
Ours12-layer12-layer6-layer6-layer0.25922.460.629
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.448, + 0.471, + 0.569 + ], + "angle": 0, + "content": "mance. Although large patch size can identify structured image contents from degradations, the reconstructed SR results are usually of high quality but low fidelity [47]. In summary, a reasonable patch size is critical to the performance. Compared to model D1 and D2, our model produces superior accuracy in terms of all metrics. Consequently, patch sizes of \\( 2 \\times 2 \\) and \\( 8 \\times 8 \\) are adopted as the default setting." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.57, + 0.248, + 0.585 + ], + "angle": 0, + "content": "(2) Coupling Operation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.585, + 0.47, + 0.796 + ], + "angle": 0, + "content": "By employing the same spatial codes over HR content dictionary \\(\\mathbf{D}^{HR}\\) and LR content dictionary \\(\\mathbf{D}^{LR}\\) to represent paired HR and LR images, these dictionaries are tightly coupled. To investigate its effectiveness, we introduce a network variant (E1 in Table 3) by removing this coupling operation. Specifically, HR and LR feature maps are represented using separate spatial codes during the discretization stage. From Table 3 we can see that model E1 produces extremely low quantitative scores. Without the coupling operation, the HR and LR content dictionaries are not associated such that the reconstructed SR result does not share the same content with the LR input. In contrast, the coupling operation enables our model to produce SR results faithful to the LR image." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.817, + 0.285, + 0.831 + ], + "angle": 0, + "content": "4.3.3 Network Architecture" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Our network consists of four modules, including HR image encoder, HR image decoder, LR image encoder, and LR image decoder. We conduct experiments to study the effect of the model capacity for these four modules. Specif" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.448, + 0.895, + 0.614 + ], + "angle": 0, + "content": "ically, we first develop four network variants (F1-F4 in Table 4) by deepening these four modules. As we can see, our method does not obtain consistent performance gains as the HR encoder, LR encoder and LR decoder are deepened. Meanwhile, with larger HR decoder, model F2 produces slight improvements on all metrics. This indicates that our method relies more on the design of dictionaries (Table 3) rather than the designs of the network architecture. Despite the marginal improvements brought by larger HR decoder, a 12-layer decoder is employed to achieve the accuracy-efficiency balance." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.632, + 0.62, + 0.647 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.658, + 0.894, + 0.825 + ], + "angle": 0, + "content": "In this paper, we propose to associate unpaired LR and HR images using coupled dictionaries rather than synthesizing pseudo LR images. Specifically, we construct an HR content dictionary, an LR content dictionary, and a degradation dictionary to model unpaired HR and LR images. To couple these dictionaries, we develop an autoencoder-based framework for optimization. By representing images using compact proxy codes, an LR-to-HR mapping can be effectively learned by our dictionaries. Experiments on several benchmarks show that our method produces superior performance against previous state-of-the-art approaches." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.828, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Acknowledgments: This work was partially supported by the National Natural Science Foundation of China (No. 62301601, 62301306, and 62306331), the Shenzhen Science and Technology Program (No. RCYX20200714114641140), the Guangdong Basic and Applied Basic Research Foundation (2022B1515020103), and the Young Elite Scientists Sponsorship Program by CAST (No. 2023QNRC001)." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25719" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.469, + 0.156 + ], + "angle": 0, + "content": "[1] Chao Dong, Chen Change Loy, Kaiming He, and Xiaou Tang. 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Springer, 2022. 8" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.468, + 0.829 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.518, + 0.957 + ], + "angle": 0, + "content": "25721" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/14c29cf4-a5f6-481c-be92-86ff4e2cfb38_origin.pdf b/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/14c29cf4-a5f6-481c-be92-86ff4e2cfb38_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..ccd9821793a4943ba5ec24abdb92b43a6ff36fde --- /dev/null +++ b/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/14c29cf4-a5f6-481c-be92-86ff4e2cfb38_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:3fdbf2af273c4863b103c4803e390c35d4a84860ae6843f1472ee175e7cd5c22 +size 3810223 diff --git a/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/full.md b/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/full.md new file mode 100644 index 0000000000000000000000000000000000000000..50d19771adc350d5e1df7694384c2691705e6521 --- /dev/null +++ b/2024/Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution/full.md @@ -0,0 +1,331 @@ +# Learning Coupled Dictionaries from Unpaired Data for Image Super-Resolution + +Longguang Wang $^{1}$ , Juncheng Li $^{2}$ , Yingqian Wang $^{3}$ , Qingyong Hu $^{4}$ , Yulan Guo $^{3*}$ $^{1}$ Aviation University of Air Force $^{2}$ Shanghai University + $^{3}$ National University of Defense Technology $^{4}$ Independent Researcher + +# Abstract + +The difficulty of acquiring high-resolution (HR) and low-resolution (LR) image pairs in real scenarios limits the performance of existing learning-based image super-resolution (SR) methods in the real world. To conduct training on real-world unpaired data, current methods focus on synthesizing pseudo LR images to associate unpaired images. However, the realness and diversity of pseudo LR images are vulnerable due to the large image space. In this paper, we circumvent the difficulty of image generation and propose an alternative to build the connection between unpaired images in a compact proxy space. Specifically, we first construct coupled HR and LR dictionaries, and then encode HR and LR images into a common latent code space using these dictionaries. In addition, we develop an autoencoder-based framework to couple these dictionaries during optimization by reconstructing input HR and LR images. The coupled dictionaries enable our method to employ a shallow network architecture with only 18 layers to achieve efficient image SR. Extensive experiments show that our method (DictSR) can effectively model the LR-to-HR mapping in coupled dictionaries and produces state-of-the-art performance on benchmark datasets. + +# 1. Introduction + +Image super-resolution (SR) aims at reconstructing a high-resolution (HR) image from low-resolution (LR) observations. To this end, most existing learning-based methods [1-4] rely on paired training data to build an LR-to-HR mapping. Since paired data is difficult to acquire in the real world, manually designed degradations are commonly employed to synthesize paired data for training [5, 6]. Nevertheless, as pre-defined degradations are empirical, synthetic images cannot meet the diversity of real-world images and limit the performance of previous methods in real scenarios [7, 8]. + +To remedy this problem, numerous efforts have been made to directly conduct training on unpaired data [7-9]. To enable the learning of LR-to-HR mapping, existing meth + +![](images/70ccbe9eb4a0e5e5f99ba2e904fa64cb843ca29bf7312967549a948d83d45c3b.jpg) +(a) Previous Approaches + +![](images/908af80b98b71c23c1ce0a975309839aaa338c8811e4d510f6cd0c15f95e8bb6.jpg) +(b) Our Approach +Figure 1. Comparison between previous approaches and our approach. Instead of synthesizing pseudo LR images and minimizing the gap in the image space (a), we encode HR and LR images into a common latent code space using coupled dictionaries to associate unpaired HR and LR images (b). + +ods focus on synthesizing pseudo paired data for training. Given HR images $x \sim p_x$ (target domain) and LR images $y \sim p_y$ (source domain), pseudo LR images are generated by learning an HR-to-LR mapping. Then, HR images and the resultant pseudo LR images are adopted to learn the LR-to-HR mapping. Early methods [7, 9] commonly use generative adversarial networks (GANs) with cycle-consistency or adversarial loss to synthesize pseudo LR images. However, these GAN-based methods usually suffer mode collapse and require elaborate fine-tuning. Recently, more powerful diffusion model [10] is introduced for pseudo LR image synthesis. The large latent space in the diffusion model improves the diversity of synthesized images at the cost of lower content fidelity, which hinders further performance improvements. + +Due to the low rank characteristic of natural images, an image can be represented as a spare code on an overcomplete dictionary [11, 12]. On top of this perspective, we seek to associate unpaired LR and HR images in a compact space without relying on synthesizing pseudo LR im + +ages high in diversity and realness (Fig. 1). By representing images using spatial codes over a dictionary, the description length is significantly reduced, which allows us to efficiently minimize the gap between HR and LR image domains. To this end, we use autoencoders to learn LR and HR dictionaries rich of context information from LR and HR images. To fit the large space of real-world LR patches, our LR dictionary explicitly models the content and degradation variations in a hierarchical manner (Fig. 2). During training, by coupling HR and LR dictionaries, an LR-to-HR mapping can be learned in the dictionaries. During inference, an LR image is first decomposed over the LR dictionary and then using the HR dictionary for reconstruction to produce the SR result. The contributions of this paper can be summarized as follows: + +- We associate unpaired images using coupled HR and LR dictionaries instead of synthesizing pseudo LR images. By decomposing unpaired images over the dictionary to obtain compact proxy codes, an LR-to-HR mapping can be efficiently learned in the code space. +- We formulate the LR dictionary as a combination of an LR content dictionary and a degradation dictionary to model LR images in a hierarchical manner. +- We develop an autoencoder-based framework to optimize coupled dictionaries together with the network parameters in an end-to-end manner. +- Extensive experiments show that our coupled dictionaries can effectively learn the LR-to-HR mapping and our method (DictSR) achieves state-of-the-art performance on benchmark datasets. + +# 2. Related Works + +In this section, we first review recent advances of paired and unpaired image SR methods. Then, we discuss dictionary learning approach that is related to our work. + +# 2.1. Paired Image SR + +Most previous learning-based image SR methods rely on paired data with aligned contents for training. Early methods [1-3, 13-15] commonly employ bicubic downsampling to synthesize HR-LR image pairs as the training data. Despite promising results on synthetic data, these methods suffer severe performance drop on real-world images since their degradations differ from the bicubic one. Later, several methods adopt more complicated degradations including blur, compression, and noise to generate HR-LR image pairs [5, 16-19]. Although the handcrafted degradations span a large space, the gap between real-world degradations still remains and limits the accuracy in real scenarios. Recently, a number of real-world paired datasets are developed to capture real degradations [20, 21]. However, the high labor cost limits the scales of these datasets, thereby hindering further performance improvement. + +# 2.2. Unpaired Image SR + +To circumvents the difficulty of acquiring real-world paired data, a number of methods directly conduct training on unpaired images. Early approaches assume real-world LR images follow a specific distribution and employ GANs to synthesize pseudo LR image in this distribution. Specifically, Bulat et al. [22] and Lugmayr et al. [23] first trained a degradation network to synthesize pseudo LR images from HR images and then use these paired images to learn the LR-to-HR mapping. Yuan et al. [9] and Maeda et al. [7] developed unified frameworks to simultaneously learn a degradation network and an SR network, which produce superior accuracy. Liu et al. [24] and Yang et al. [25] introduced physical properties to LR image synthesis as regularizations for higher realness. Despite improved performance against paired approaches, these GAN-based methods usually suffer mode collapse and cannot generate LR images as diverse as real ones. + +To address the aforementioned problem of GAN-based methods, Wolf et al. [26] developed a flow-based model to synthesize LR images. Although the diversity of synthesized LR images is improved, this method has a high computational cost due to the limited expressive power of flow-based models [27, 28]. Recently, Yang et al. [10] introduced the powerful diffusion model for pseudo LR image synthesis. The large latent space in the diffusion model improves the diversity but decreases the content fidelity, which also results in limited performance. + +# 2.3. Dictionary Learning + +Dictionary learning aims at finding a sparse representation of the input data in the form of a linear combination of basic elements as well as those basic elements themselves. The idea of dictionary learning can be dated back to several decades ago [29, 30]. Before the era of deep learning, dictionary learning is widely used to model the LR-to-HR mapping for image SR. Specifically, Yang et al. [12] proposed coupled dictionaries to associate LR and HR image patches via sparse coding. Zhang et al. [11] developed a multi-scale dictionary to simultaneously model local and non-local priors in the images. Lu et al. [31] took the geometrical structure of the dictionary into consideration and proposed a geometry constrained sparse coding method for image SR. + +Since the huge success of neural networks, learning-based methods have dominated a wide range of tasks. Recently, the idea of dictionary learning has been introduced to learning-based frameworks and produces superior performance. Specifically, Van et al. [32] proposed a vector quantized variational autoencoder (VQ-VAE) to learn discrete representations of an image over a codebook. Then, a CNN is trained to model their distribution for image synthesis. Then, Razavi et al. [33] extended this approach to a + +![](images/b04f27404eb7d265265f4607e01631942daf85ecf24aa6fcc036b676381090e2.jpg) +Figure 2. An illustration of our framework during training phase (a) and test phase (b). Entries with different colors correspond to various contents while entries with different shades refer to the same content but diverse degradations. + +hierarchical one to learn discrete representation at different scale, which achieves superior performance. Later, Esser et al. [34] further developed VQ-GAN by leveraging the powerful transformer to model the composition of images. Recently, Maeda et al. [35] introduced dictionary learning for image SR by plugging a learnable dictionary into a CNN framework. However, this method relies on paired data to learn the LR-to-HR mapping and cannot be extended to unpaired SR. + +# 3. Methodology + +Ideally, a pair of LR and HR images can be decomposed to a common latent code over coupled LR-HR dictionaries. From this point of view, we seek to learn coupled dictionaries from unpaired data for image SR. To this end, we formulate the coupled dictionaries as a combination of an HR content dictionary $\mathbf{D}^{HR}$ , an LR content dictionary $\mathbf{D}^{LR}$ , and a + +degradation dictionary $\mathbf{D}_{deg}$ . These three dictionaries are tightly coupled and jointly optimized in three branches, as illustrated in Fig. 2. During the training phase, the pipeline for each branch consists of three stages, including encoding, discretization, and decoding. Specifically, input images are first encoded into embeddings. Then, these embeddings are discretized in the embedding space to the entries in corresponding dictionaries. Finally, the discretized embeddings are fed to the decoders to reconstruct the input image. During the test phase, the input LR image is first encoded to an indicex map using $\mathbf{D}^{LR}$ and $\mathbf{D}_{deg}$ . Then, the corresponding entries in $\mathbf{D}^{HR}$ is retrieved to reconstruct the SR result. + +# 3.1. Encoding Stage + +Given an HR image $\mathbf{I}^{HR} \in \mathbb{R}^{H \times W \times 3}$ and a unpaired LR image $\mathbf{I}^{LR} \in \mathbb{R}^{h \times w \times 3}$ , $\mathbf{I}^{HR}$ is first downscaled to obtain $\mathbf{I}^{HR\downarrow} \in \mathbb{R}^{\frac{H}{s} \times \frac{W}{s} \times 3}$ . Here, $s$ is the scale factor and set to 4 as we focus on $\times 4$ SR in this paper. Then, $\mathbf{I}^{HR}$ is fed + +to the HR image encoder to produce $\mathbf{F}^{HR} \in \mathbb{R}^{\frac{H}{8} \times \frac{W}{8} \times 512}$ , with each embedding corresponding to a $8 \times 8$ patch in the input HR image. Meanwhile, $\mathbf{I}^{LR}$ and $\mathbf{I}^{HR\downarrow}$ are passed to the LR image encoder to obtain $\mathbf{F}^{LR} \in \mathbb{R}^{\frac{h}{2} \times \frac{w}{2} \times 128}$ and $\mathbf{F}^{HR\downarrow} \in \mathbb{R}^{\frac{H}{8} \times \frac{W}{8} \times 128}$ , respectively. Each embedding in the resultant feature maps corresponds to a $2 \times 2$ patch in the input LR image. + +The HR image encoder employs a fully convolutional structure and consists of four residual blocks at four resolution levels (i.e., $H \times W$ , $\frac{H}{2} \times \frac{W}{2}$ , $\frac{H}{4} \times \frac{W}{4}$ , and $\frac{H}{8} \times \frac{W}{8}$ ). Meanwhile, the LR image encoder consists of two residual blocks at $h \times w$ and $\frac{h}{2} \times \frac{w}{2}$ resolution levels. + +# 3.2. Discretization Stage + +After the encoding stage, the resultant embedding at each location of the feature map is discretized to its closest dictionary entry in the embedding space, resulting in $\mathbf{F}_q^{HR}$ , $\mathbf{F}_q^{HR\downarrow}$ , and $\mathbf{F}_q^{LR}$ . Motivated by [36], we introduce a linear projection to map the output feature maps to a low-dimensional latent space (4-dim in our experiments) for code index lookup. Then, the discretized embedding is projected back to the embedding space through another projection layer. During backpropagation, straight-through estimator (STE) is employed for end-to-end optimization. + +To associate HR and LR images, HR and LR dictionaries should be coupled at this stage. However, there exists two major challenges: (1) Misaligned Content. Under paired settings, corresponding patches in HR and LR images share the same content, which can be employed as a cue to couple HR and LR dictionaries for joint optimization. However, this cue does not hold for unpaired images, which imposes great challenges to learning coupled dictionaries. (2) **Diverse Degradations**. Since an HR image corresponds to infinite LR images under various degradations, modeling such a one-to-many correlation using coupled dictionaries is quite difficult. To address the above challenges, we formulate the coupled dictionaries as a combination of an HR content dictionary, an LR content dictionary, and a degradation dictionary. The LR content dictionary couples with the HR content dictionary to build connections between LR and HR image contents. Meanwhile, the degradation dictionary captures the degradation variations for different image contents. + +# 3.2.1 HR and LR Content Dictionary + +First, we construct an HR content dictionary $\mathbf{D}^{HR} \in \mathbb{R}^{N \times 4}$ and an LR content dictionary $\mathbf{D}^{LR} \in \mathbb{R}^{N \times 4}$ to model the content variation in the embedding space, where $N$ is the number of entries. To handle the first challenge, we introduce downscaled version of HR images as a bridge to associate HR and LR content dictionaries to enable joint training. For embeddings $f^{HR} \in \mathbf{F}^{HR}$ (branch 1) and + +$f^{HR\downarrow} \in \mathbf{F}^{HR\downarrow}$ (branch 2), the discretized embeddings $f_{q}^{HR}$ and $f_{q}^{HR\downarrow}$ are obtained as: + +$$ +i = \underset {i} {\arg \min } | | f ^ {H R \downarrow} - \mathbf {D} ^ {L R} (i) | |, \tag {1} +$$ + +$$ +\left\{ \begin{array}{l} f _ {q} ^ {H R \downarrow} = \mathbf {D} ^ {L R} (i) \\ f _ {q} ^ {H R} = \mathbf {D} ^ {H R} (i) \end{array} , \right. \tag {2} +$$ + +where $i$ is the index of the closest entry in $\mathbf{D}^{LR}$ to the embedding $f^{HR\downarrow}$ . By employing the same spatial codes (i.e., $i$ ) to represent both $f^{HR}$ and $f^{HR\downarrow}$ , HR and LR content dictionaries are coupled. Inspired by [34], the discretization losses for branches 1 and 2 are defined as: + +$$ +\left\{ \begin{array}{l} \mathcal {L} _ {d i s} ^ {1} = | | \mathbf {F} ^ {H R} - \mathbf {F} _ {q} ^ {H R} | | _ {2} ^ {2} \\ \mathcal {L} _ {d i s} ^ {2} = | | \mathbf {F} ^ {H R \downarrow} - \mathbf {F} _ {q} ^ {H R \downarrow} | | _ {2} ^ {2}. \end{array} \right. \tag {3} +$$ + +# 3.2.2 Degradation Dictionary + +Second, we construct a degradation dictionary $\mathbf{D}_{deg} \in \mathbb{R}^{N \times K \times 4}$ on top of $\mathbf{D}^{LR}$ to model the degradation variations. Specifically, each group of entries (e.g., $\mathbf{D}_{deg}(i) \in \mathbb{R}^{K \times 4}$ ) is used to capture the degradation variation around the corresponding entry in the content dictionary (i.e., $\mathbf{D}^{LR}(i)$ ). During discretization, a hierarchical approach is employed to obtain the discretized embedding $f_{q}^{LR}$ : + +$$ +\left\{ \begin{array}{l} j = \underset {j} {\arg \min } | | f ^ {L R} - \mathbf {D} ^ {L R} (j) | | \\ k = \underset {k} {\arg \min } | | f ^ {L R} - \left(\mathbf {D} ^ {L R} (j) + \mathbf {D} _ {d e g} (j, k)\right) | | \end{array} . \right. \tag {4} +$$ + +For each embedding $f^{LR}$ in $\mathbf{F}^{LR}$ (branch 3), the closest entry in $\mathbf{D}^{LR}$ is first selected. $\mathbf{D}^{LR}(j)$ depicts the clean image content in $f^{LR}$ but ignores the degradation. Then, the degradation is taken into consideration by retrieving the closest entry in $\mathbf{D}^{LR}(j) + \mathbf{D}_{deg}(j)$ , resulting in $f_{q}^{LR}$ . Similarly, a discretization loss is defined as: + +$$ +\mathcal {L} _ {d i s} ^ {3} = \left\| \mathbf {F} ^ {L R} - \mathbf {F} _ {q} ^ {L R} \right\| _ {2} ^ {2}. \tag {5} +$$ + +# 3.3. Decoding Stage + +After the discretization stage, the feature map produced by the encoders are represented using the dictionaries. Then, $\mathbf{F}_q^{HR}$ is fed to the HR image decoder to reconstruct the HR image $\hat{\mathbf{I}}^{HR}$ . Meanwhile, $\mathbf{F}_q^{HR\downarrow}$ and $\mathbf{F}_q^{LR}$ are passed to the LR image decoder to produce $\hat{\mathbf{I}}^{HR\downarrow}$ and $\hat{\mathbf{I}}^{LR}$ , respectively. The reconstruction loss is defined as the L1 loss between the reconstructed results and the input images: + +$$ +\begin{array}{l} \mathcal {L} _ {r e c} = \left| \left| \hat {\mathbf {I}} ^ {H R} - \mathbf {I} ^ {H R} \right| \right| + \left| \left| \phi \left(\hat {\mathbf {I}} ^ {H R}\right) - \phi (\mathbf {I} ^ {H R}) \right| \right| + \tag {6} \\ \left| \left| \hat {\mathbf {I}} ^ {H R \downarrow} - \mathbf {I} ^ {H R \downarrow} \right| \right| + \left| \left| \hat {\mathbf {I}} ^ {L R} - \mathbf {I} ^ {L R} \right| \right|, \\ \end{array} +$$ + +where $\phi (\mathbf{I}^{HR})$ refers to the feature maps extracted by a pretrained VGG model [37]. + +Similar with the encoders, the HR image decoder is composed of four residual blocks at different resolution levels and a tail convolutional layer to regress the reconstructed images. Meanwhile, the LR image decoder comprises of two residual blocks and a tail convolutional layer. + +# 3.4. Loss Function + +The overall loss function used for training is defined as follows: + +$$ +\mathcal {L} = \mathcal {L} _ {r e c} + \lambda_ {1} \times \left(\mathcal {L} _ {d i s} ^ {1} + \mathcal {L} _ {d i s} ^ {2} + \mathcal {L} _ {d i s} ^ {3}\right) \tag {7} +$$ + +where $\lambda_{1}$ is empirically set to 10 in our experiments. + +# 4. Experiments + +In this section, we first introduce the experimental setup. Then, we compare our method with previous paired and unpaired image SR methods on benchmark datasets. Finally, we conduct experiments to investigate the effectiveness of our major designs. + +# 4.1. Experimental Setup + +# 4.1.1 Datasets and Metrics + +We conduct experiments on two widely applied unpaired SR datasets, including AIM-RWSR [38] and NTIRE-RWSR [39]. Note that, we focus on $\times 4$ SR in this paper and our method can be extended to SR tasks with different scale factors. + +AIM-RWSR. The AIM-RWSR dataset is a synthetic dataset and uses handcrafted degradations to synthesize 2650 noisy and compressed LR images. Meanwhile, 800 images in the DIV2K dataset are employed as HR images. + +NTIRE-RWSR. The NTIRE-RWSR dataset follows the same setting as the AIM-RWSR dataset to produce unpaired HR and LR images. Different from AIM-RWSR, NTIRE-RWSR features a more complicated degradation type that consists of highly related high-frequency noises. + +For evaluation on the AIM-RWSR and NTIRE-RWSR datasets, we use peak signal-to-noise ratio (PSNR), structural similarity (SSIM) and learned perceptual image patch similarity (LPIPS) as metrics. + +# 4.1.2 Training Details + +During the training phase, 24 LR patches of size $64 \times 64$ and 24 HR patches of size $256 \times 256$ were randomly cropped from LR and HR images, respectively. Random rotation and random flipping were employed for data augmentation. The Adam method [40] with $\beta_{1} = 0.9$ and $\beta_{2} = 0.999$ was used for optimization. The learning rate was initialized as $2 \times 10^{-4}$ and halved after every 25 epochs. The training was + +Table 1. Results achieved on AIM-RWSR for $\times 4\mathrm{{SR}}$ . Best and second best results are highlighted and underlined. + +
Method#LayersMACsLPIPSPSNRSSIM
PairedBicubic--0.53722.350.617
RCAN [3]400260G0.47222.320.604
ZSSR [41]8-0.63922.210.603
IKC [5]18880G0.47922.250.600
DAN [42]171315G0.47122.410.609
BSRGAN [17]350291G0.29922.470.623
Real-ESRGAN [16]350291G0.23822.080.622
UnpairedCycleGAN [38]350291G0.47621.190.530
CinCGAN [9]37823G0.46121.600.613
Lugmayr et al. [23]350291G0.47221.590.550
FSSR [43]350291G0.39020.820.510
DASR [8]350291G0.33621.600.564
DeFlow [26]350291G0.34922.250.620
PCR-ESRGAN [46]350291G0.32121.590.610
DictSR (Ours)18129G0.25922.460.629
+ +stopped after 100 epochs. In our experiments, the numbers of entries in the dictionaries (i.e., $N$ and $K$ ) were set to 4096 and 32, respectively. + +# 4.2. Performance Evaluation + +For performance evaluation, six representative paired SR methods (RCAN [3], ZSSR [41], IKC [5], DAN [42], BSRGAN [17] and Real-ESRGAN [16]) and eight state-of-the-art unpaired image SR methods (CinCGAN [9], Lugmayr et al. [23], FSSR [43], Impressionism [44], DASR [8], DeFlow [26], DAP [45], and PCR-ESRGAN [46]) are included for comparison. Quantitative results are presented in Tables 1 and 2 while visual results are provided in Fig. 3. Note that, Lugmayr et al., FSSR, DASR, DeFlow, Impressionism, and DAP employ ESRGAN as the SR model. For our DictSR, the LR image encoder and the HR image decoder are included to calculate the numbers of layers since only these modules are employed during inference. For other methods, the numbers of layers in the SR networks are presented. MACs (multiply-accumulate operations) is calculated based on $128 \times 128$ input LR images. The MACs of ZSSR is not reported since this method conducts training during the inference time and requires considerable computational cost. + +Quantitative Results. For the AIM-RWSR dataset, it can be observed from Table 1 that our DictSR achieves the best performance in terms of all metrics among all unpaired SR methods. Moreover, our DictSR also produces competitive results as compared to paired SR methods. Previous unpaired SR methods synthesize pseudo LR images to associate unpaired LR and HR images. However, the large image space poses great challenges to these methods to balance the realness and diversity. In contrast, by building the connection between unpaired images in a compact + +![](images/ef36e2bb3c7ae81b45964181fb595d63ec86ddd0eda9f5b26e0e5636b153c66d.jpg) +LR + +![](images/69a4c84903363aeef582a8bb3d1899af88ff4fb15e7e44a6698a6dc158a69675.jpg) + +![](images/75f49cbca94195e84b45dc0dd1b60a53692b7d9ed626f9b9a2b1425fa965d297.jpg) + +![](images/9f4a1e4a4bdbf61f352b42ce72e98d63bde195e9f7ad1b3606ab3d188d173da8.jpg) +DASR + +![](images/8751491d33da5be5e606a9caca7980d6a301354491d2e8990f9b4f63908c231a.jpg) +Bicubic +DeFlow + +![](images/d3c9fec1366401f0b51c50b00c653351ceaf96fb9ab5f5971739e66fccfb0e08.jpg) +FSSR +DictSR (Ours) + +![](images/bbd0153462403c28dbc59f9c73996f1885862027f1cb0cd6457ded1b71d12f33.jpg) +GT + +![](images/dec942ae75c6c83cefcc69ab1eda6e639009843ef250f37d02bfc8c30957eb72.jpg) +LR + +![](images/04dd3c935f3bcb121a61d10492b250c7c82e9da8c66af08d71f58ccefbd2388b.jpg) +Bicubic + +![](images/b87e1e37998690dda8ed5f05f666f6269eeeec2f7e2f30b17c232dc7cbdbb0d5.jpg) +FSSR + +![](images/27d5908a6fa74086fd5b5baedaf33c1ea54629e50d7c4f87be1851a209494276.jpg) +DASR + +![](images/bd23a77ec1e03a7d3f4f411275c96cec8cf499d23ec1f31ceaadb24bf8bc1077.jpg) +DeFlow +Figure 3. Visualization results produced by different methods. + +![](images/bd4a2c4509c7249a890956f3e59350cdc4c6c67852726f0fbe7d2c2e4451d2d1.jpg) +DictSR (Ours) + +![](images/ffaad2778f88851e642aa8c1eaffc307bb93cf751ee7f5c7f236b67a9a02bb64.jpg) +GT + +proxy space using dictionaries, our DictSR produces superior quantitative results. In addition, our DictSR employs a shallow and efficient network structure with much lower computational complexity. Specifically, our method gradually reduces the spatial resolution of feature maps to $\frac{1}{4}$ size while previous methods maintain full-resolution feature maps. As compared to previous methods, our 18-layer network produces superior performance with only half MACs, which further demonstrates the effectiveness of our method. + +For the NTIRE-RWSR dataset, we can observe from Table 2 that our DictSR also produces competitive results. As compared to DeFlow, although the improvements in terms of PSNR and SSIM are marginal, our method produces no + +table gains on LPIPS (0.204 vs. 0.218). This demonstrates the superior perceptual quality of our results. In addition, our DictSR also surpasses most previous paired methods with much a shallower network. This further shows the great potential of our learned coupled dictionaries. + +Qualitative Results. Figure 3 compares the visual results produced by different unpaired image SR methods. It can be observed that our method produces higher perceptual quality with fewer artifacts. For example, in the second scene, FSSR and DeFlow produces results with unpleasant ringing artifacts while DASR suffer notable blurring artifacts. In contrast, the results of our DisctSR can better recover the text details. This further demonstrates the superiority of our method. + +Table 2. Results achieved on NTIRE-RWSR for $\times 4\mathrm{{SR}}$ . Best and second best results are highlighted and underlined. + +
Method#LayersMACsLPIPSPSNRSSIM
PairedBicubic--0.63225.520.671
RCAN [3]400260G0.57625.310.640
ZSSR [41]8-0.62024.930.642
IKC [5]18880G0.38426.500.748
DAN [42]171315G0.55425.150.671
BSRGAN [17]350291G0.26524.560.669
Real-ESRGAN [16]350291G0.25124.680.687
UnpairedCycleGAN [38]350291G0.41724.750.700
CinCGAN [9]37823G-24.190.683
Impressionism [44]350291G0.23224.670.683
FSSR [43]350291G0.33223.040.590
DeFlow [26]350291G0.21825.870.710
DAP [45]350291G0.25225.400.707
PCR-ESRGAN [46]350291G0.22324.970.682
DictSR (Ours)18129G0.20425.900.711
+ +![](images/47da1b4baba16e2aa291c35935519c8b4ca9d8a7fca2598d11ddf17677b7ae31.jpg) +Figure 4. Visualization of the embedding space. Blue circles represent the embeddings of LR patches while other 100 stars correspond to 100 entries in the LR content dictionary $\mathbf{D}^{LR}$ . + +# 4.3. Model Analyses + +In this subsection, we conduct experiments to study our method from three aspects. First, we study our dictionaries. Then, we demonstrate the effectiveness of our learning framework. Finally, we investigate the effect of different encoder and decoder architectures. All experiments are conducted on the AIM-RWSR dataset. + +# 4.3.1 Dictionaries + +# (1) Hierarchical Structure + +To cover diverse degradations in LR images while associating HR and LR image contents, a combination of an LR content dictionary $\mathbf{D}^{LR}$ and a degradation dictionary $\mathbf{D}_{deg}$ is employed. To demonstrate the effectiveness of such a hierarchical structure, we remove $\mathbf{D}_{deg}$ and directly use $\mathbf{D}^{LR}$ + +to discretize feature maps extracted from LR images (i.e., A1 in Table 3). It can be observed that model A1 suffers an accuracy drop as compared to the full model (Ours in Table 3). Without the hierarchical structure, the LR content dictionary $\mathbf{D}^{LR}$ cannot well cover the large degradation space, thereby producing limited performance. In contrast, the hierarchical structure facilitates our method to achieve notable gains. + +# (2) Dictionary Size + +Intuitively, larger dictionaries contribute to larger model capacity and ultimately result in higher performance. Consequently, we conduct experiments to study the effect of dictionary size from the following three aspects. + +Entry. We first conduct experiments to investigate dictionaries with different numbers of entries. Specifically, we develop two network variants (B1/B2 in Table 3) by employing dictionaries with more/fewer entries. Using dictionaries with fewer entries (2048 entries), the performance of model B1 is slightly lower than our full model. However, further including more entries (8192 entries) cannot introduce consistent gains on all metrics. Consequently, we employ 4096 entries as the default setting. + +Dimension. During the discretization stage, a linear projection is employed to map the feature maps to a low-dimensional latent space for code index lookup. Here, we conduct experiments to study the dimension of the latent space. As the dimension of the latent codes is reduced from 64 to 4, the number of activated entries is increased from 105 to 4050. This indicates that the dictionary can better cover the embeddings in the low-dimensional latent space to activate more entries. As a result, the LPIPS/PSNR/SSIM scores are improved from 0.268/21.99/0.616 to 0.259/22.46/0.629. In our experiments, the dimension of 4 is adopted as the default setting. + +# (3) Visualization of Dictionaries + +To further study the embedding space of LR feature maps, we visualize the entries of the LR content dictionary $\mathbf{D}^{LR}$ and the embeddings of $\mathbf{F}^{LR}$ in Fig. 4. As we can see, the entries in $\mathbf{D}^{LR}$ span the space of embeddings extracted from LR patches. This validates that $\mathbf{D}^{LR}$ can well cover the content variation in the LR embedding space. + +# 4.3.2 Learning Framework + +# (1) Encoder + +Each entry in our LR/HR dictionaries corresponds a $2 \times 2 / 8 \times 8$ patch in the LR/HR image. We further conduct experiments to investigate the effect of the patch size. Specifically, we deepen the LR/HR encoders to encode larger patches into embeddings for discretization. Small patch size cannot well distinguish the degradations and image contents in the LR image. As a result, the degradations will also be reconstructed in the SR results with inferior perfor + +Table 3. Results achieved by our method with different settings. + +
DictionaryFrameworkActivated Entries (DLR)LPIPS (↓)PSNR (↑)SSIM (↑)
HierarchicalEntriesDimPatch (LR/HR)Coupling
A1X409642×2/8×8✓35600.28122.400.619
B1✓204842×2/8×8✓20270.27822.410.621
B2✓819242×2/8×8✓80500.26922.440.626
C1✓4096162×2/8×8✓5680.26222.250.625
C2✓4096642×2/8×8✓1050.26821.990.616
D1✓409641×1/4×4✓15220.27122.410.623
D2✓409644×4/16×16✓38100.31321.430.588
E1✓409642×2/8×8X40960.5338.280.050
Ours✓409642×2/8×8✓40500.25922.460.629
+ +Table 4. Results achieved by our method with different network architectures. $\mathrm{E}_{\mathrm{HR}}$ , $\mathrm{D}_{\mathrm{HR}}$ , $\mathrm{E}_{\mathrm{LR}}$ and $\mathrm{D}_{\mathrm{LR}}$ represent HR image encoder, HR image decoder, LR image encoder, and LR image decoder, respectively. + +
EHRDHRELRDLRLPIPS (↓)PSNR (↑)SSIM (↑)
F120-layer12-layer6-layer6-layer0.27122.460.625
F212-layer20-layer6-layer6-layer0.25622.490.631
F312-layer12-layer14-layer6-layer0.26322.480.629
F412-layer12-layer6-layer14-layer0.26122.480.630
Ours12-layer12-layer6-layer6-layer0.25922.460.629
+ +mance. Although large patch size can identify structured image contents from degradations, the reconstructed SR results are usually of high quality but low fidelity [47]. In summary, a reasonable patch size is critical to the performance. Compared to model D1 and D2, our model produces superior accuracy in terms of all metrics. Consequently, patch sizes of $2 \times 2$ and $8 \times 8$ are adopted as the default setting. + +# (2) Coupling Operation + +By employing the same spatial codes over HR content dictionary $\mathbf{D}^{HR}$ and LR content dictionary $\mathbf{D}^{LR}$ to represent paired HR and LR images, these dictionaries are tightly coupled. To investigate its effectiveness, we introduce a network variant (E1 in Table 3) by removing this coupling operation. Specifically, HR and LR feature maps are represented using separate spatial codes during the discretization stage. From Table 3 we can see that model E1 produces extremely low quantitative scores. Without the coupling operation, the HR and LR content dictionaries are not associated such that the reconstructed SR result does not share the same content with the LR input. In contrast, the coupling operation enables our model to produce SR results faithful to the LR image. + +# 4.3.3 Network Architecture + +Our network consists of four modules, including HR image encoder, HR image decoder, LR image encoder, and LR image decoder. We conduct experiments to study the effect of the model capacity for these four modules. Specif + +ically, we first develop four network variants (F1-F4 in Table 4) by deepening these four modules. As we can see, our method does not obtain consistent performance gains as the HR encoder, LR encoder and LR decoder are deepened. Meanwhile, with larger HR decoder, model F2 produces slight improvements on all metrics. This indicates that our method relies more on the design of dictionaries (Table 3) rather than the designs of the network architecture. Despite the marginal improvements brought by larger HR decoder, a 12-layer decoder is employed to achieve the accuracy-efficiency balance. + +# 5. Conclusion + +In this paper, we propose to associate unpaired LR and HR images using coupled dictionaries rather than synthesizing pseudo LR images. Specifically, we construct an HR content dictionary, an LR content dictionary, and a degradation dictionary to model unpaired HR and LR images. To couple these dictionaries, we develop an autoencoder-based framework for optimization. By representing images using compact proxy codes, an LR-to-HR mapping can be effectively learned by our dictionaries. Experiments on several benchmarks show that our method produces superior performance against previous state-of-the-art approaches. + +Acknowledgments: This work was partially supported by the National Natural Science Foundation of China (No. 62301601, 62301306, and 62306331), the Shenzhen Science and Technology Program (No. RCYX20200714114641140), the Guangdong Basic and Applied Basic Research Foundation (2022B1515020103), and the Young Elite Scientists Sponsorship Program by CAST (No. 2023QNRC001). + +# References + +[1] Chao Dong, Chen Change Loy, Kaiming He, and Xiaou Tang. Learning a deep convolutional network for image super-resolution. In ECCV, pages 184-199, 2014. 1, 2 +[2] Bee Lim, Sanghyun Son, Heewon Kim, Seungjun Nah, and Young Mu Lee. Enhanced deep residual networks for single image super-resolution. In CVPRW, pages 136-144, 2017. +[3] Yulun Zhang, Kunpeng Li, Kai Li, Lichen Wang, Bineng Zhong, and Yun Fu. 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To conduct training on real-world unpaired data, current methods focus on synthesizing pseudo LR images to associate unpaired images. However, the realness and diversity of pseudo LR images are vulnerable due to the large image space. In this paper, we circumvent the difficulty of image generation and propose an alternative to build the connection between unpaired images in a compact proxy space. Specifically, we first construct coupled HR and LR dictionaries, and then encode HR and LR images into a common latent code space using these dictionaries. In addition, we develop an autoencoder-based framework to couple these dictionaries during optimization by reconstructing input HR and LR images. The coupled dictionaries enable our method to employ a shallow network architecture with only 18 layers to achieve efficient image SR. Extensive experiments show that our method (DictSR) can effectively model the LR-to-HR mapping in coupled dictionaries and produces state-of-the-art performance on benchmark datasets." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 525, + 128, + 538 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 525, + 128, + 538 + ], + "spans": [ + { + "bbox": [ + 47, + 525, + 128, + 538 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 545, + 287, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 287, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 287, + 676 + ], + "type": "text", + "content": "Image super-resolution (SR) aims at reconstructing a high-resolution (HR) image from low-resolution (LR) observations. To this end, most existing learning-based methods [1-4] rely on paired training data to build an LR-to-HR mapping. Since paired data is difficult to acquire in the real world, manually designed degradations are commonly employed to synthesize paired data for training [5, 6]. Nevertheless, as pre-defined degradations are empirical, synthetic images cannot meet the diversity of real-world images and limit the performance of previous methods in real scenarios [7, 8]." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": "To remedy this problem, numerous efforts have been made to directly conduct training on unpaired data [7-9]. To enable the learning of LR-to-HR mapping, existing meth" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 315, + 213, + 541, + 280 + ], + "blocks": [ + { + "bbox": [ + 315, + 213, + 541, + 280 + ], + "lines": [ + { + "bbox": [ + 315, + 213, + 541, + 280 + ], + "spans": [ + { + "bbox": [ + 315, + 213, + 541, + 280 + ], + "type": "image", + "image_path": "70ccbe9eb4a0e5e5f99ba2e904fa64cb843ca29bf7312967549a948d83d45c3b.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 372, + 283, + 479, + 295 + ], + "lines": [ + { + "bbox": [ + 372, + 283, + 479, + 295 + ], + "spans": [ + { + "bbox": [ + 372, + 283, + 479, + 295 + ], + "type": "text", + "content": "(a) Previous Approaches" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 313, + 304, + 541, + 368 + ], + "blocks": [ + { + "bbox": [ + 313, + 304, + 541, + 368 + ], + "lines": [ + { + "bbox": [ + 313, + 304, + 541, + 368 + ], + "spans": [ + { + "bbox": [ + 313, + 304, + 541, + 368 + ], + "type": "image", + "image_path": "908af80b98b71c23c1ce0a975309839aaa338c8811e4d510f6cd0c15f95e8bb6.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 388, + 370, + 465, + 383 + ], + "lines": [ + { + "bbox": [ + 388, + 370, + 465, + 383 + ], + "spans": [ + { + "bbox": [ + 388, + 370, + 465, + 383 + ], + "type": "text", + "content": "(b) Our Approach" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 392, + 547, + 449 + ], + "lines": [ + { + "bbox": [ + 304, + 392, + 547, + 449 + ], + "spans": [ + { + "bbox": [ + 304, + 392, + 547, + 449 + ], + "type": "text", + "content": "Figure 1. Comparison between previous approaches and our approach. Instead of synthesizing pseudo LR images and minimizing the gap in the image space (a), we encode HR and LR images into a common latent code space using coupled dictionaries to associate unpaired HR and LR images (b)." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "spans": [ + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "type": "text", + "content": "ods focus on synthesizing pseudo paired data for training. Given HR images " + }, + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "type": "inline_equation", + "content": "x \\sim p_x" + }, + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "type": "text", + "content": " (target domain) and LR images " + }, + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "type": "inline_equation", + "content": "y \\sim p_y" + }, + { + "bbox": [ + 304, + 472, + 547, + 651 + ], + "type": "text", + "content": " (source domain), pseudo LR images are generated by learning an HR-to-LR mapping. Then, HR images and the resultant pseudo LR images are adopted to learn the LR-to-HR mapping. Early methods [7, 9] commonly use generative adversarial networks (GANs) with cycle-consistency or adversarial loss to synthesize pseudo LR images. However, these GAN-based methods usually suffer mode collapse and require elaborate fine-tuning. Recently, more powerful diffusion model [10] is introduced for pseudo LR image synthesis. The large latent space in the diffusion model improves the diversity of synthesized images at the cost of lower content fidelity, which hinders further performance improvements." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "type": "text", + "content": "Due to the low rank characteristic of natural images, an image can be represented as a spare code on an overcomplete dictionary [11, 12]. On top of this perspective, we seek to associate unpaired LR and HR images in a compact space without relying on synthesizing pseudo LR im" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 495, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 495, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 495, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25712" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 251 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 251 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 251 + ], + "type": "text", + "content": "ages high in diversity and realness (Fig. 1). By representing images using spatial codes over a dictionary, the description length is significantly reduced, which allows us to efficiently minimize the gap between HR and LR image domains. To this end, we use autoencoders to learn LR and HR dictionaries rich of context information from LR and HR images. To fit the large space of real-world LR patches, our LR dictionary explicitly models the content and degradation variations in a hierarchical manner (Fig. 2). During training, by coupling HR and LR dictionaries, an LR-to-HR mapping can be learned in the dictionaries. During inference, an LR image is first decomposed over the LR dictionary and then using the HR dictionary for reconstruction to produce the SR result. The contributions of this paper can be summarized as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 251, + 287, + 430 + ], + "type": "list", + "angle": 0, + "index": 5, + "blocks": [ + { + "bbox": [ + 47, + 251, + 287, + 311 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 251, + 287, + 311 + ], + "spans": [ + { + "bbox": [ + 47, + 251, + 287, + 311 + ], + "type": "text", + "content": "- We associate unpaired images using coupled HR and LR dictionaries instead of synthesizing pseudo LR images. By decomposing unpaired images over the dictionary to obtain compact proxy codes, an LR-to-HR mapping can be efficiently learned in the code space." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 48, + 312, + 287, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 312, + 287, + 346 + ], + "spans": [ + { + "bbox": [ + 48, + 312, + 287, + 346 + ], + "type": "text", + "content": "- We formulate the LR dictionary as a combination of an LR content dictionary and a degradation dictionary to model LR images in a hierarchical manner." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 48, + 347, + 287, + 382 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 347, + 287, + 382 + ], + "spans": [ + { + "bbox": [ + 48, + 347, + 287, + 382 + ], + "type": "text", + "content": "- We develop an autoencoder-based framework to optimize coupled dictionaries together with the network parameters in an end-to-end manner." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 48, + 383, + 287, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 383, + 287, + 430 + ], + "spans": [ + { + "bbox": [ + 48, + 383, + 287, + 430 + ], + "type": "text", + "content": "- Extensive experiments show that our coupled dictionaries can effectively learn the LR-to-HR mapping and our method (DictSR) achieves state-of-the-art performance on benchmark datasets." + } + ] + } + ], + "index": 4 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 441, + 138, + 453 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 441, + 138, + 453 + ], + "spans": [ + { + "bbox": [ + 47, + 441, + 138, + 453 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 461, + 287, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 461, + 287, + 498 + ], + "spans": [ + { + "bbox": [ + 47, + 461, + 287, + 498 + ], + "type": "text", + "content": "In this section, we first review recent advances of paired and unpaired image SR methods. Then, we discuss dictionary learning approach that is related to our work." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 503, + 149, + 516 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 503, + 149, + 516 + ], + "spans": [ + { + "bbox": [ + 47, + 503, + 149, + 516 + ], + "type": "text", + "content": "2.1. Paired Image SR" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 522, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 522, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 522, + 289, + 714 + ], + "type": "text", + "content": "Most previous learning-based image SR methods rely on paired data with aligned contents for training. Early methods [1-3, 13-15] commonly employ bicubic downsampling to synthesize HR-LR image pairs as the training data. Despite promising results on synthetic data, these methods suffer severe performance drop on real-world images since their degradations differ from the bicubic one. Later, several methods adopt more complicated degradations including blur, compression, and noise to generate HR-LR image pairs [5, 16-19]. Although the handcrafted degradations span a large space, the gap between real-world degradations still remains and limits the accuracy in real scenarios. Recently, a number of real-world paired datasets are developed to capture real degradations [20, 21]. However, the high labor cost limits the scales of these datasets, thereby hindering further performance improvement." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 72, + 422, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 422, + 85 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 422, + 85 + ], + "type": "text", + "content": "2.2. Unpaired Image SR" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 89, + 545, + 293 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 89, + 545, + 293 + ], + "spans": [ + { + "bbox": [ + 304, + 89, + 545, + 293 + ], + "type": "text", + "content": "To circumvents the difficulty of acquiring real-world paired data, a number of methods directly conduct training on unpaired images. Early approaches assume real-world LR images follow a specific distribution and employ GANs to synthesize pseudo LR image in this distribution. Specifically, Bulat et al. [22] and Lugmayr et al. [23] first trained a degradation network to synthesize pseudo LR images from HR images and then use these paired images to learn the LR-to-HR mapping. Yuan et al. [9] and Maeda et al. [7] developed unified frameworks to simultaneously learn a degradation network and an SR network, which produce superior accuracy. Liu et al. [24] and Yang et al. [25] introduced physical properties to LR image synthesis as regularizations for higher realness. Despite improved performance against paired approaches, these GAN-based methods usually suffer mode collapse and cannot generate LR images as diverse as real ones." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 293, + 545, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 293, + 545, + 413 + ], + "spans": [ + { + "bbox": [ + 304, + 293, + 545, + 413 + ], + "type": "text", + "content": "To address the aforementioned problem of GAN-based methods, Wolf et al. [26] developed a flow-based model to synthesize LR images. Although the diversity of synthesized LR images is improved, this method has a high computational cost due to the limited expressive power of flow-based models [27, 28]. Recently, Yang et al. [10] introduced the powerful diffusion model for pseudo LR image synthesis. The large latent space in the diffusion model improves the diversity but decreases the content fidelity, which also results in limited performance." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 420, + 424, + 433 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 420, + 424, + 433 + ], + "spans": [ + { + "bbox": [ + 306, + 420, + 424, + 433 + ], + "type": "text", + "content": "2.3. Dictionary Learning" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 438, + 545, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 438, + 545, + 605 + ], + "spans": [ + { + "bbox": [ + 304, + 438, + 545, + 605 + ], + "type": "text", + "content": "Dictionary learning aims at finding a sparse representation of the input data in the form of a linear combination of basic elements as well as those basic elements themselves. The idea of dictionary learning can be dated back to several decades ago [29, 30]. Before the era of deep learning, dictionary learning is widely used to model the LR-to-HR mapping for image SR. Specifically, Yang et al. [12] proposed coupled dictionaries to associate LR and HR image patches via sparse coding. Zhang et al. [11] developed a multi-scale dictionary to simultaneously model local and non-local priors in the images. Lu et al. [31] took the geometrical structure of the dictionary into consideration and proposed a geometry constrained sparse coding method for image SR." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 606, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 606, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 606, + 545, + 713 + ], + "type": "text", + "content": "Since the huge success of neural networks, learning-based methods have dominated a wide range of tasks. Recently, the idea of dictionary learning has been introduced to learning-based frameworks and produces superior performance. Specifically, Van et al. [32] proposed a vector quantized variational autoencoder (VQ-VAE) to learn discrete representations of an image over a codebook. Then, a CNN is trained to model their distribution for image synthesis. Then, Razavi et al. [33] extended this approach to a" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25713" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 72, + 541, + 439 + ], + "blocks": [ + { + "bbox": [ + 53, + 72, + 541, + 439 + ], + "lines": [ + { + "bbox": [ + 53, + 72, + 541, + 439 + ], + "spans": [ + { + "bbox": [ + 53, + 72, + 541, + 439 + ], + "type": "image", + "image_path": "b04f27404eb7d265265f4607e01631942daf85ecf24aa6fcc036b676381090e2.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 453, + 546, + 477 + ], + "lines": [ + { + "bbox": [ + 46, + 453, + 546, + 477 + ], + "spans": [ + { + "bbox": [ + 46, + 453, + 546, + 477 + ], + "type": "text", + "content": "Figure 2. An illustration of our framework during training phase (a) and test phase (b). Entries with different colors correspond to various contents while entries with different shades refer to the same content but diverse degradations." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 497, + 288, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 497, + 288, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 497, + 288, + 604 + ], + "type": "text", + "content": "hierarchical one to learn discrete representation at different scale, which achieves superior performance. Later, Esser et al. [34] further developed VQ-GAN by leveraging the powerful transformer to model the composition of images. Recently, Maeda et al. [35] introduced dictionary learning for image SR by plugging a learnable dictionary into a CNN framework. However, this method relies on paired data to learn the LR-to-HR mapping and cannot be extended to unpaired SR." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 620, + 129, + 634 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 620, + 129, + 634 + ], + "spans": [ + { + "bbox": [ + 47, + 620, + 129, + 634 + ], + "type": "text", + "content": "3. Methodology" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "type": "text", + "content": "Ideally, a pair of LR and HR images can be decomposed to a common latent code over coupled LR-HR dictionaries. From this point of view, we seek to learn coupled dictionaries from unpaired data for image SR. To this end, we formulate the coupled dictionaries as a combination of an HR content dictionary " + }, + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{HR}" + }, + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "type": "text", + "content": ", an LR content dictionary " + }, + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "type": "text", + "content": ", and a" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "spans": [ + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "text", + "content": "degradation dictionary " + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathbf{D}_{deg}" + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "text", + "content": ". These three dictionaries are tightly coupled and jointly optimized in three branches, as illustrated in Fig. 2. During the training phase, the pipeline for each branch consists of three stages, including encoding, discretization, and decoding. Specifically, input images are first encoded into embeddings. Then, these embeddings are discretized in the embedding space to the entries in corresponding dictionaries. Finally, the discretized embeddings are fed to the decoders to reconstruct the input image. During the test phase, the input LR image is first encoded to an indicex map using " + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathbf{D}_{deg}" + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "text", + "content": ". Then, the corresponding entries in " + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{HR}" + }, + { + "bbox": [ + 304, + 497, + 545, + 640 + ], + "type": "text", + "content": " is retrieved to reconstruct the SR result." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 647, + 402, + 660 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 647, + 402, + 660 + ], + "spans": [ + { + "bbox": [ + 306, + 647, + 402, + 660 + ], + "type": "text", + "content": "3.1. Encoding Stage" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": "Given an HR image " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{I}^{HR} \\in \\mathbb{R}^{H \\times W \\times 3}" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " and a unpaired LR image " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{I}^{LR} \\in \\mathbb{R}^{h \\times w \\times 3}" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{I}^{HR}" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " is first downscaled to obtain " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{I}^{HR\\downarrow} \\in \\mathbb{R}^{\\frac{H}{s} \\times \\frac{W}{s} \\times 3}" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": ". Here, " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " is the scale factor and set to 4 as we focus on " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\times 4" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " SR in this paper. Then, " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{I}^{HR}" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " is fed" + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25714" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "content": "to the HR image encoder to produce " + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "inline_equation", + "content": "\\mathbf{F}^{HR} \\in \\mathbb{R}^{\\frac{H}{8} \\times \\frac{W}{8} \\times 512}" + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "content": ", with each embedding corresponding to a " + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "inline_equation", + "content": "8 \\times 8" + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "content": " patch in the input HR image. Meanwhile, " + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "inline_equation", + "content": "\\mathbf{I}^{LR}" + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "inline_equation", + "content": "\\mathbf{I}^{HR\\downarrow}" + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "content": " are passed to the LR image encoder to obtain " + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "inline_equation", + "content": "\\mathbf{F}^{LR} \\in \\mathbb{R}^{\\frac{h}{2} \\times \\frac{w}{2} \\times 128}" + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "inline_equation", + "content": "\\mathbf{F}^{HR\\downarrow} \\in \\mathbb{R}^{\\frac{H}{8} \\times \\frac{W}{8} \\times 128}" + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "content": ", respectively. Each embedding in the resultant feature maps corresponds to a " + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "inline_equation", + "content": "2 \\times 2" + }, + { + "bbox": [ + 46, + 70, + 287, + 156 + ], + "type": "text", + "content": " patch in the input LR image." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "spans": [ + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "text", + "content": "The HR image encoder employs a fully convolutional structure and consists of four residual blocks at four resolution levels (i.e., " + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "inline_equation", + "content": "H \\times W" + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "inline_equation", + "content": "\\frac{H}{2} \\times \\frac{W}{2}" + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "inline_equation", + "content": "\\frac{H}{4} \\times \\frac{W}{4}" + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "inline_equation", + "content": "\\frac{H}{8} \\times \\frac{W}{8}" + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "text", + "content": "). Meanwhile, the LR image encoder consists of two residual blocks at " + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "inline_equation", + "content": "h \\times w" + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "inline_equation", + "content": "\\frac{h}{2} \\times \\frac{w}{2}" + }, + { + "bbox": [ + 46, + 156, + 287, + 218 + ], + "type": "text", + "content": " resolution levels." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 224, + 163, + 238 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 224, + 163, + 238 + ], + "spans": [ + { + "bbox": [ + 47, + 224, + 163, + 238 + ], + "type": "text", + "content": "3.2. Discretization Stage" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "spans": [ + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "type": "text", + "content": "After the encoding stage, the resultant embedding at each location of the feature map is discretized to its closest dictionary entry in the embedding space, resulting in " + }, + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_q^{HR}" + }, + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_q^{HR\\downarrow}" + }, + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_q^{LR}" + }, + { + "bbox": [ + 46, + 243, + 287, + 365 + ], + "type": "text", + "content": ". Motivated by [36], we introduce a linear projection to map the output feature maps to a low-dimensional latent space (4-dim in our experiments) for code index lookup. Then, the discretized embedding is projected back to the embedding space through another projection layer. During backpropagation, straight-through estimator (STE) is employed for end-to-end optimization." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 365, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 365, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 365, + 287, + 593 + ], + "type": "text", + "content": "To associate HR and LR images, HR and LR dictionaries should be coupled at this stage. However, there exists two major challenges: (1) Misaligned Content. Under paired settings, corresponding patches in HR and LR images share the same content, which can be employed as a cue to couple HR and LR dictionaries for joint optimization. However, this cue does not hold for unpaired images, which imposes great challenges to learning coupled dictionaries. (2) **Diverse Degradations**. Since an HR image corresponds to infinite LR images under various degradations, modeling such a one-to-many correlation using coupled dictionaries is quite difficult. To address the above challenges, we formulate the coupled dictionaries as a combination of an HR content dictionary, an LR content dictionary, and a degradation dictionary. The LR content dictionary couples with the HR content dictionary to build connections between LR and HR image contents. Meanwhile, the degradation dictionary captures the degradation variations for different image contents." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 609, + 215, + 623 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 609, + 215, + 623 + ], + "spans": [ + { + "bbox": [ + 47, + 609, + 215, + 623 + ], + "type": "text", + "content": "3.2.1 HR and LR Content Dictionary" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "text", + "content": "First, we construct an HR content dictionary " + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{HR} \\in \\mathbb{R}^{N \\times 4}" + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "text", + "content": " and an LR content dictionary " + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR} \\in \\mathbb{R}^{N \\times 4}" + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "text", + "content": " to model the content variation in the embedding space, where " + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "text", + "content": " is the number of entries. To handle the first challenge, we introduce downscaled version of HR images as a bridge to associate HR and LR content dictionaries to enable joint training. For embeddings " + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "inline_equation", + "content": "f^{HR} \\in \\mathbf{F}^{HR}" + }, + { + "bbox": [ + 46, + 628, + 287, + 713 + ], + "type": "text", + "content": " (branch 1) and" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 70, + 545, + 99 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 70, + 545, + 99 + ], + "spans": [ + { + "bbox": [ + 305, + 70, + 545, + 99 + ], + "type": "inline_equation", + "content": "f^{HR\\downarrow} \\in \\mathbf{F}^{HR\\downarrow}" + }, + { + "bbox": [ + 305, + 70, + 545, + 99 + ], + "type": "text", + "content": " (branch 2), the discretized embeddings " + }, + { + "bbox": [ + 305, + 70, + 545, + 99 + ], + "type": "inline_equation", + "content": "f_{q}^{HR}" + }, + { + "bbox": [ + 305, + 70, + 545, + 99 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 70, + 545, + 99 + ], + "type": "inline_equation", + "content": "f_{q}^{HR\\downarrow}" + }, + { + "bbox": [ + 305, + 70, + 545, + 99 + ], + "type": "text", + "content": " are obtained as:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 359, + 106, + 545, + 128 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 359, + 106, + 545, + 128 + ], + "spans": [ + { + "bbox": [ + 359, + 106, + 545, + 128 + ], + "type": "interline_equation", + "content": "i = \\underset {i} {\\arg \\min } | | f ^ {H R \\downarrow} - \\mathbf {D} ^ {L R} (i) | |, \\tag {1}", + "image_path": "0ec80a5cb2d205cb0f47b5716115f033d2b880a35585784d086f8e4a8b1b19c5.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 383, + 139, + 545, + 172 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 383, + 139, + 545, + 172 + ], + "spans": [ + { + "bbox": [ + 383, + 139, + 545, + 172 + ], + "type": "interline_equation", + "content": "\\left\\{ \\begin{array}{l} f _ {q} ^ {H R \\downarrow} = \\mathbf {D} ^ {L R} (i) \\\\ f _ {q} ^ {H R} = \\mathbf {D} ^ {H R} (i) \\end{array} , \\right. \\tag {2}", + "image_path": "03ed0f16a2bda4f73233db5a970db5c4e80c85debe1edeffc6a4464d75ce90da.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "spans": [ + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "text", + "content": " is the index of the closest entry in " + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "text", + "content": " to the embedding " + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "inline_equation", + "content": "f^{HR\\downarrow}" + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "text", + "content": ". By employing the same spatial codes (i.e., " + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "text", + "content": ") to represent both " + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "inline_equation", + "content": "f^{HR}" + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "inline_equation", + "content": "f^{HR\\downarrow}" + }, + { + "bbox": [ + 305, + 177, + 545, + 237 + ], + "type": "text", + "content": ", HR and LR content dictionaries are coupled. Inspired by [34], the discretization losses for branches 1 and 2 are defined as:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 365, + 243, + 545, + 277 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 365, + 243, + 545, + 277 + ], + "spans": [ + { + "bbox": [ + 365, + 243, + 545, + 277 + ], + "type": "interline_equation", + "content": "\\left\\{ \\begin{array}{l} \\mathcal {L} _ {d i s} ^ {1} = | | \\mathbf {F} ^ {H R} - \\mathbf {F} _ {q} ^ {H R} | | _ {2} ^ {2} \\\\ \\mathcal {L} _ {d i s} ^ {2} = | | \\mathbf {F} ^ {H R \\downarrow} - \\mathbf {F} _ {q} ^ {H R \\downarrow} | | _ {2} ^ {2}. \\end{array} \\right. \\tag {3}", + "image_path": "b3b3d8521b7a61e68acb715f41c3b4f14ec3edf67b883189465e9c5a14d35f8e.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 289, + 440, + 301 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 289, + 440, + 301 + ], + "spans": [ + { + "bbox": [ + 306, + 289, + 440, + 301 + ], + "type": "text", + "content": "3.2.2 Degradation Dictionary" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "spans": [ + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "text", + "content": "Second, we construct a degradation dictionary " + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "inline_equation", + "content": "\\mathbf{D}_{deg} \\in \\mathbb{R}^{N \\times K \\times 4}" + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "text", + "content": " on top of " + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "text", + "content": " to model the degradation variations. Specifically, each group of entries (e.g., " + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "inline_equation", + "content": "\\mathbf{D}_{deg}(i) \\in \\mathbb{R}^{K \\times 4}" + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "text", + "content": ") is used to capture the degradation variation around the corresponding entry in the content dictionary (i.e., " + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}(i)" + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "text", + "content": "). During discretization, a hierarchical approach is employed to obtain the discretized embedding " + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "inline_equation", + "content": "f_{q}^{LR}" + }, + { + "bbox": [ + 305, + 308, + 545, + 393 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 318, + 401, + 545, + 446 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 401, + 545, + 446 + ], + "spans": [ + { + "bbox": [ + 318, + 401, + 545, + 446 + ], + "type": "interline_equation", + "content": "\\left\\{ \\begin{array}{l} j = \\underset {j} {\\arg \\min } | | f ^ {L R} - \\mathbf {D} ^ {L R} (j) | | \\\\ k = \\underset {k} {\\arg \\min } | | f ^ {L R} - \\left(\\mathbf {D} ^ {L R} (j) + \\mathbf {D} _ {d e g} (j, k)\\right) | | \\end{array} . \\right. \\tag {4}", + "image_path": "050bf05a7dfae664131472a9f3f38f679b15548808f27f571cc7cf64c306acee.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "spans": [ + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "content": "For each embedding " + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "inline_equation", + "content": "f^{LR}" + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "inline_equation", + "content": "\\mathbf{F}^{LR}" + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "content": " (branch 3), the closest entry in " + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "content": " is first selected. " + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}(j)" + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "content": " depicts the clean image content in " + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "inline_equation", + "content": "f^{LR}" + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "content": " but ignores the degradation. Then, the degradation is taken into consideration by retrieving the closest entry in " + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}(j) + \\mathbf{D}_{deg}(j)" + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "content": ", resulting in " + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "inline_equation", + "content": "f_{q}^{LR}" + }, + { + "bbox": [ + 305, + 455, + 545, + 528 + ], + "type": "text", + "content": ". Similarly, a discretization loss is defined as:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 375, + 536, + 545, + 552 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 375, + 536, + 545, + 552 + ], + "spans": [ + { + "bbox": [ + 375, + 536, + 545, + 552 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {d i s} ^ {3} = \\left\\| \\mathbf {F} ^ {L R} - \\mathbf {F} _ {q} ^ {L R} \\right\\| _ {2} ^ {2}. \\tag {5}", + "image_path": "660f4e6af30d67d1af5ae1e59ce583603f1e96a1be872b6a094c3a17d77e4c83.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 559, + 400, + 572 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 559, + 400, + 572 + ], + "spans": [ + { + "bbox": [ + 306, + 559, + 400, + 572 + ], + "type": "text", + "content": "3.3. Decoding Stage" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "spans": [ + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "text", + "content": "After the discretization stage, the feature map produced by the encoders are represented using the dictionaries. Then, " + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_q^{HR}" + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "text", + "content": " is fed to the HR image decoder to reconstruct the HR image " + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}^{HR}" + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "text", + "content": ". Meanwhile, " + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_q^{HR\\downarrow}" + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_q^{LR}" + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "text", + "content": " are passed to the LR image decoder to produce " + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}^{HR\\downarrow}" + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}^{LR}" + }, + { + "bbox": [ + 305, + 578, + 545, + 671 + ], + "type": "text", + "content": ", respectively. The reconstruction loss is defined as the L1 loss between the reconstructed results and the input images:" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 321, + 678, + 545, + 715 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 321, + 678, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 321, + 678, + 545, + 715 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {r e c} = \\left| \\left| \\hat {\\mathbf {I}} ^ {H R} - \\mathbf {I} ^ {H R} \\right| \\right| + \\left| \\left| \\phi \\left(\\hat {\\mathbf {I}} ^ {H R}\\right) - \\phi (\\mathbf {I} ^ {H R}) \\right| \\right| + \\tag {6} \\\\ \\left| \\left| \\hat {\\mathbf {I}} ^ {H R \\downarrow} - \\mathbf {I} ^ {H R \\downarrow} \\right| \\right| + \\left| \\left| \\hat {\\mathbf {I}} ^ {L R} - \\mathbf {I} ^ {L R} \\right| \\right|, \\\\ \\end{array}", + "image_path": "5c65a7f2a79d3b68e7dec66db0acc4a3ae32e890d86c6b5a869f5c3c5f8b9382.jpg" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25715" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 71, + 287, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 71, + 287, + 95 + ], + "spans": [ + { + "bbox": [ + 47, + 71, + 287, + 95 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 71, + 287, + 95 + ], + "type": "inline_equation", + "content": "\\phi (\\mathbf{I}^{HR})" + }, + { + "bbox": [ + 47, + 71, + 287, + 95 + ], + "type": "text", + "content": " refers to the feature maps extracted by a pretrained VGG model [37]." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 96, + 287, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 96, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 47, + 96, + 287, + 156 + ], + "type": "text", + "content": "Similar with the encoders, the HR image decoder is composed of four residual blocks at different resolution levels and a tail convolutional layer to regress the reconstructed images. Meanwhile, the LR image decoder comprises of two residual blocks and a tail convolutional layer." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 163, + 136, + 174 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 163, + 136, + 174 + ], + "spans": [ + { + "bbox": [ + 47, + 163, + 136, + 174 + ], + "type": "text", + "content": "3.4. Loss Function" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 182, + 286, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 182, + 286, + 204 + ], + "spans": [ + { + "bbox": [ + 47, + 182, + 286, + 204 + ], + "type": "text", + "content": "The overall loss function used for training is defined as follows:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 82, + 213, + 287, + 227 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 82, + 213, + 287, + 227 + ], + "spans": [ + { + "bbox": [ + 82, + 213, + 287, + 227 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {r e c} + \\lambda_ {1} \\times \\left(\\mathcal {L} _ {d i s} ^ {1} + \\mathcal {L} _ {d i s} ^ {2} + \\mathcal {L} _ {d i s} ^ {3}\\right) \\tag {7}", + "image_path": "dc23de36ece55f375452cbfccbfb154e75779faae088d74ec748b4e238c9529b.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 235, + 259, + 247 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 235, + 259, + 247 + ], + "spans": [ + { + "bbox": [ + 47, + 235, + 259, + 247 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 235, + 259, + 247 + ], + "type": "inline_equation", + "content": "\\lambda_{1}" + }, + { + "bbox": [ + 47, + 235, + 259, + 247 + ], + "type": "text", + "content": " is empirically set to 10 in our experiments." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 258, + 127, + 270 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 258, + 127, + 270 + ], + "spans": [ + { + "bbox": [ + 47, + 258, + 127, + 270 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 277, + 287, + 337 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 277, + 287, + 337 + ], + "spans": [ + { + "bbox": [ + 47, + 277, + 287, + 337 + ], + "type": "text", + "content": "In this section, we first introduce the experimental setup. Then, we compare our method with previous paired and unpaired image SR methods on benchmark datasets. Finally, we conduct experiments to investigate the effectiveness of our major designs." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 344, + 162, + 357 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 344, + 162, + 357 + ], + "spans": [ + { + "bbox": [ + 47, + 344, + 162, + 357 + ], + "type": "text", + "content": "4.1. Experimental Setup" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 362, + 170, + 373 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 362, + 170, + 373 + ], + "spans": [ + { + "bbox": [ + 47, + 362, + 170, + 373 + ], + "type": "text", + "content": "4.1.1 Datasets and Metrics" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 381, + 287, + 440 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 381, + 287, + 440 + ], + "spans": [ + { + "bbox": [ + 47, + 381, + 287, + 440 + ], + "type": "text", + "content": "We conduct experiments on two widely applied unpaired SR datasets, including AIM-RWSR [38] and NTIRE-RWSR [39]. Note that, we focus on " + }, + { + "bbox": [ + 47, + 381, + 287, + 440 + ], + "type": "inline_equation", + "content": "\\times 4" + }, + { + "bbox": [ + 47, + 381, + 287, + 440 + ], + "type": "text", + "content": " SR in this paper and our method can be extended to SR tasks with different scale factors." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 441, + 287, + 488 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 441, + 287, + 488 + ], + "spans": [ + { + "bbox": [ + 47, + 441, + 287, + 488 + ], + "type": "text", + "content": "AIM-RWSR. The AIM-RWSR dataset is a synthetic dataset and uses handcrafted degradations to synthesize 2650 noisy and compressed LR images. Meanwhile, 800 images in the DIV2K dataset are employed as HR images." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 489, + 287, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 489, + 287, + 548 + ], + "spans": [ + { + "bbox": [ + 47, + 489, + 287, + 548 + ], + "type": "text", + "content": "NTIRE-RWSR. The NTIRE-RWSR dataset follows the same setting as the AIM-RWSR dataset to produce unpaired HR and LR images. Different from AIM-RWSR, NTIRE-RWSR features a more complicated degradation type that consists of highly related high-frequency noises." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 47, + 548, + 287, + 596 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 548, + 287, + 596 + ], + "spans": [ + { + "bbox": [ + 47, + 548, + 287, + 596 + ], + "type": "text", + "content": "For evaluation on the AIM-RWSR and NTIRE-RWSR datasets, we use peak signal-to-noise ratio (PSNR), structural similarity (SSIM) and learned perceptual image patch similarity (LPIPS) as metrics." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 611, + 149, + 623 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 611, + 149, + 623 + ], + "spans": [ + { + "bbox": [ + 47, + 611, + 149, + 623 + ], + "type": "text", + "content": "4.1.2 Training Details" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "text", + "content": "During the training phase, 24 LR patches of size " + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "64 \\times 64" + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "text", + "content": " and 24 HR patches of size " + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "256 \\times 256" + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "text", + "content": " were randomly cropped from LR and HR images, respectively. Random rotation and random flipping were employed for data augmentation. The Adam method [40] with " + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\beta_{1} = 0.9" + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\beta_{2} = 0.999" + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "text", + "content": " was used for optimization. The learning rate was initialized as " + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "2 \\times 10^{-4}" + }, + { + "bbox": [ + 47, + 629, + 287, + 713 + ], + "type": "text", + "content": " and halved after every 25 epochs. The training was" + } + ] + } + ], + "index": 15 + }, + { + "type": "table", + "bbox": [ + 307, + 96, + 545, + 282 + ], + "blocks": [ + { + "bbox": [ + 306, + 71, + 545, + 93 + ], + "lines": [ + { + "bbox": [ + 306, + 71, + 545, + 93 + ], + "spans": [ + { + "bbox": [ + 306, + 71, + 545, + 93 + ], + "type": "text", + "content": "Table 1. Results achieved on AIM-RWSR for " + }, + { + "bbox": [ + 306, + 71, + 545, + 93 + ], + "type": "inline_equation", + "content": "\\times 4\\mathrm{{SR}}" + }, + { + "bbox": [ + 306, + 71, + 545, + 93 + ], + "type": "text", + "content": " . Best and second best results are highlighted and underlined." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 307, + 96, + 545, + 282 + ], + "lines": [ + { + "bbox": [ + 307, + 96, + 545, + 282 + ], + "spans": [ + { + "bbox": [ + 307, + 96, + 545, + 282 + ], + "type": "table", + "html": "
Method#LayersMACsLPIPSPSNRSSIM
PairedBicubic--0.53722.350.617
RCAN [3]400260G0.47222.320.604
ZSSR [41]8-0.63922.210.603
IKC [5]18880G0.47922.250.600
DAN [42]171315G0.47122.410.609
BSRGAN [17]350291G0.29922.470.623
Real-ESRGAN [16]350291G0.23822.080.622
UnpairedCycleGAN [38]350291G0.47621.190.530
CinCGAN [9]37823G0.46121.600.613
Lugmayr et al. [23]350291G0.47221.590.550
FSSR [43]350291G0.39020.820.510
DASR [8]350291G0.33621.600.564
DeFlow [26]350291G0.34922.250.620
PCR-ESRGAN [46]350291G0.32121.590.610
DictSR (Ours)18129G0.25922.460.629
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In our experiments, the numbers of entries in the dictionaries (i.e., " + }, + { + "bbox": [ + 305, + 304, + 545, + 341 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 305, + 304, + 545, + 341 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 304, + 545, + 341 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 305, + 304, + 545, + 341 + ], + "type": "text", + "content": ") were set to 4096 and 32, respectively." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 348, + 443, + 360 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 348, + 443, + 360 + ], + "spans": [ + { + "bbox": [ + 306, + 348, + 443, + 360 + ], + "type": "text", + "content": "4.2. Performance Evaluation" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 366, + 545, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 366, + 545, + 592 + ], + "spans": [ + { + "bbox": [ + 304, + 366, + 545, + 592 + ], + "type": "text", + "content": "For performance evaluation, six representative paired SR methods (RCAN [3], ZSSR [41], IKC [5], DAN [42], BSRGAN [17] and Real-ESRGAN [16]) and eight state-of-the-art unpaired image SR methods (CinCGAN [9], Lugmayr et al. [23], FSSR [43], Impressionism [44], DASR [8], DeFlow [26], DAP [45], and PCR-ESRGAN [46]) are included for comparison. Quantitative results are presented in Tables 1 and 2 while visual results are provided in Fig. 3. Note that, Lugmayr et al., FSSR, DASR, DeFlow, Impressionism, and DAP employ ESRGAN as the SR model. 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In addition, our DictSR employs a shallow and efficient network structure with much lower computational complexity. Specifically, our method gradually reduces the spatial resolution of feature maps to " + }, + { + "bbox": [ + 46, + 545, + 287, + 663 + ], + "type": "inline_equation", + "content": "\\frac{1}{4}" + }, + { + "bbox": [ + 46, + 545, + 287, + 663 + ], + "type": "text", + "content": " size while previous methods maintain full-resolution feature maps. As compared to previous methods, our 18-layer network produces superior performance with only half MACs, which further demonstrates the effectiveness of our method." + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "content": "For the NTIRE-RWSR dataset, we can observe from Table 2 that our DictSR also produces competitive results. As compared to DeFlow, although the improvements in terms of PSNR and SSIM are marginal, our method produces no" + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 304, + 545, + 545, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 545, + 605 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 545, + 605 + ], + "type": "text", + "content": "table gains on LPIPS (0.204 vs. 0.218). This demonstrates the superior perceptual quality of our results. In addition, our DictSR also surpasses most previous paired methods with much a shallower network. This further shows the great potential of our learned coupled dictionaries." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 304, + 605, + 546, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 546, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 546, + 712 + ], + "type": "text", + "content": "Qualitative Results. Figure 3 compares the visual results produced by different unpaired image SR methods. It can be observed that our method produces higher perceptual quality with fewer artifacts. For example, in the second scene, FSSR and DeFlow produces results with unpleasant ringing artifacts while DASR suffer notable blurring artifacts. In contrast, the results of our DisctSR can better recover the text details. This further demonstrates the superiority of our method." + } + ] + } + ], + "index": 32 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "25717" + } + ] + } + ], + "index": 33 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 96, + 287, + 282 + ], + "blocks": [ + { + "bbox": [ + 47, + 71, + 287, + 93 + ], + "lines": [ + { + "bbox": [ + 47, + 71, + 287, + 93 + ], + "spans": [ + { + "bbox": [ + 47, + 71, + 287, + 93 + ], + "type": "text", + "content": "Table 2. Results achieved on NTIRE-RWSR for " + }, + { + "bbox": [ + 47, + 71, + 287, + 93 + ], + "type": "inline_equation", + "content": "\\times 4\\mathrm{{SR}}" + }, + { + "bbox": [ + 47, + 71, + 287, + 93 + ], + "type": "text", + "content": " . Best and second best results are highlighted and underlined." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 96, + 287, + 282 + ], + "lines": [ + { + "bbox": [ + 48, + 96, + 287, + 282 + ], + "spans": [ + { + "bbox": [ + 48, + 96, + 287, + 282 + ], + "type": "table", + "html": "
Method#LayersMACsLPIPSPSNRSSIM
PairedBicubic--0.63225.520.671
RCAN [3]400260G0.57625.310.640
ZSSR [41]8-0.62024.930.642
IKC [5]18880G0.38426.500.748
DAN [42]171315G0.55425.150.671
BSRGAN [17]350291G0.26524.560.669
Real-ESRGAN [16]350291G0.25124.680.687
UnpairedCycleGAN [38]350291G0.41724.750.700
CinCGAN [9]37823G-24.190.683
Impressionism [44]350291G0.23224.670.683
FSSR [43]350291G0.33223.040.590
DeFlow [26]350291G0.21825.870.710
DAP [45]350291G0.25225.400.707
PCR-ESRGAN [46]350291G0.22324.970.682
DictSR (Ours)18129G0.20425.900.711
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Blue circles represent the embeddings of LR patches while other 100 stars correspond to 100 entries in the LR content dictionary " + }, + { + "bbox": [ + 46, + 462, + 287, + 495 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 46, + 462, + 287, + 495 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 516, + 144, + 529 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 516, + 144, + 529 + ], + "spans": [ + { + "bbox": [ + 47, + 516, + 144, + 529 + ], + "type": "text", + "content": "4.3. Model Analyses" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 535, + 287, + 606 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 535, + 287, + 606 + ], + "spans": [ + { + "bbox": [ + 46, + 535, + 287, + 606 + ], + "type": "text", + "content": "In this subsection, we conduct experiments to study our method from three aspects. First, we study our dictionaries. Then, we demonstrate the effectiveness of our learning framework. Finally, we investigate the effect of different encoder and decoder architectures. All experiments are conducted on the AIM-RWSR dataset." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 623, + 132, + 634 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 623, + 132, + 634 + ], + "spans": [ + { + "bbox": [ + 47, + 623, + 132, + 634 + ], + "type": "text", + "content": "4.3.1 Dictionaries" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 641, + 162, + 652 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 641, + 162, + 652 + ], + "spans": [ + { + "bbox": [ + 47, + 641, + 162, + 652 + ], + "type": "text", + "content": "(1) Hierarchical Structure" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "content": "To cover diverse degradations in LR images while associating HR and LR image contents, a combination of an LR content dictionary " + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "content": " and a degradation dictionary " + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{D}_{deg}" + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "content": " is employed. To demonstrate the effectiveness of such a hierarchical structure, we remove " + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{D}_{deg}" + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "content": " and directly use " + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "type": "text", + "content": "to discretize feature maps extracted from LR images (i.e., A1 in Table 3). It can be observed that model A1 suffers an accuracy drop as compared to the full model (Ours in Table 3). Without the hierarchical structure, the LR content dictionary " + }, + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "type": "text", + "content": " cannot well cover the large degradation space, thereby producing limited performance. In contrast, the hierarchical structure facilitates our method to achieve notable gains." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 169, + 389, + 180 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 169, + 389, + 180 + ], + "spans": [ + { + "bbox": [ + 306, + 169, + 389, + 180 + ], + "type": "text", + "content": "(2) Dictionary Size" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 181, + 545, + 229 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 181, + 545, + 229 + ], + "spans": [ + { + "bbox": [ + 304, + 181, + 545, + 229 + ], + "type": "text", + "content": "Intuitively, larger dictionaries contribute to larger model capacity and ultimately result in higher performance. Consequently, we conduct experiments to study the effect of dictionary size from the following three aspects." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 229, + 545, + 338 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 229, + 545, + 338 + ], + "spans": [ + { + "bbox": [ + 304, + 229, + 545, + 338 + ], + "type": "text", + "content": "Entry. We first conduct experiments to investigate dictionaries with different numbers of entries. Specifically, we develop two network variants (B1/B2 in Table 3) by employing dictionaries with more/fewer entries. Using dictionaries with fewer entries (2048 entries), the performance of model B1 is slightly lower than our full model. However, further including more entries (8192 entries) cannot introduce consistent gains on all metrics. Consequently, we employ 4096 entries as the default setting." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 338, + 545, + 482 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 338, + 545, + 482 + ], + "spans": [ + { + "bbox": [ + 304, + 338, + 545, + 482 + ], + "type": "text", + "content": "Dimension. During the discretization stage, a linear projection is employed to map the feature maps to a low-dimensional latent space for code index lookup. Here, we conduct experiments to study the dimension of the latent space. As the dimension of the latent codes is reduced from 64 to 4, the number of activated entries is increased from 105 to 4050. This indicates that the dictionary can better cover the embeddings in the low-dimensional latent space to activate more entries. As a result, the LPIPS/PSNR/SSIM scores are improved from 0.268/21.99/0.616 to 0.259/22.46/0.629. In our experiments, the dimension of 4 is adopted as the default setting." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 483, + 444, + 493 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 483, + 444, + 493 + ], + "spans": [ + { + "bbox": [ + 306, + 483, + 444, + 493 + ], + "type": "text", + "content": "(3) Visualization of Dictionaries" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "spans": [ + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "text", + "content": "To further study the embedding space of LR feature maps, we visualize the entries of the LR content dictionary " + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "text", + "content": " and the embeddings of " + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "inline_equation", + "content": "\\mathbf{F}^{LR}" + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "text", + "content": " in Fig. 4. As we can see, the entries in " + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "text", + "content": " span the space of embeddings extracted from LR patches. This validates that " + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 304, + 495, + 545, + 567 + ], + "type": "text", + "content": " can well cover the content variation in the LR embedding space." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 585, + 430, + 597 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 585, + 430, + 597 + ], + "spans": [ + { + "bbox": [ + 306, + 585, + 430, + 597 + ], + "type": "text", + "content": "4.3.2 Learning Framework" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 605, + 360, + 616 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 605, + 360, + 616 + ], + "spans": [ + { + "bbox": [ + 306, + 605, + 360, + 616 + ], + "type": "text", + "content": "(1) Encoder" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "content": "Each entry in our LR/HR dictionaries corresponds a " + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "inline_equation", + "content": "2 \\times 2 / 8 \\times 8" + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "content": " patch in the LR/HR image. We further conduct experiments to investigate the effect of the patch size. Specifically, we deepen the LR/HR encoders to encode larger patches into embeddings for discretization. Small patch size cannot well distinguish the degradations and image contents in the LR image. As a result, the degradations will also be reconstructed in the SR results with inferior perfor" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25718" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 55, + 85, + 537, + 223 + ], + "blocks": [ + { + "bbox": [ + 180, + 70, + 412, + 82 + ], + "lines": [ + { + "bbox": [ + 180, + 70, + 412, + 82 + ], + "spans": [ + { + "bbox": [ + 180, + 70, + 412, + 82 + ], + "type": "text", + "content": "Table 3. Results achieved by our method with different settings." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 55, + 85, + 537, + 223 + ], + "lines": [ + { + "bbox": [ + 55, + 85, + 537, + 223 + ], + "spans": [ + { + "bbox": [ + 55, + 85, + 537, + 223 + ], + "type": "table", + "html": "
DictionaryFrameworkActivated Entries (DLR)LPIPS (↓)PSNR (↑)SSIM (↑)
HierarchicalEntriesDimPatch (LR/HR)Coupling
A1X409642×2/8×8✓35600.28122.400.619
B1✓204842×2/8×8✓20270.27822.410.621
B2✓819242×2/8×8✓80500.26922.440.626
C1✓4096162×2/8×8✓5680.26222.250.625
C2✓4096642×2/8×8✓1050.26821.990.616
D1✓409641×1/4×4✓15220.27122.410.623
D2✓409644×4/16×16✓38100.31321.430.588
E1✓409642×2/8×8X40960.5338.280.050
Ours✓409642×2/8×8✓40500.25922.460.629
", + "image_path": "81c86fdd01a3df9aabef490a7bd559eda5b4890dc723ef2dc87e276944949398.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 106, + 255, + 488, + 332 + ], + "blocks": [ + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "lines": [ + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "spans": [ + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "text", + "content": "Table 4. Results achieved by our method with different network architectures. " + }, + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "inline_equation", + "content": "\\mathrm{E}_{\\mathrm{HR}}" + }, + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "inline_equation", + "content": "\\mathrm{D}_{\\mathrm{HR}}" + }, + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "inline_equation", + "content": "\\mathrm{E}_{\\mathrm{LR}}" + }, + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "inline_equation", + "content": "\\mathrm{D}_{\\mathrm{LR}}" + }, + { + "bbox": [ + 46, + 230, + 546, + 253 + ], + "type": "text", + "content": " represent HR image encoder, HR image decoder, LR image encoder, and LR image decoder, respectively." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 106, + 255, + 488, + 332 + ], + "lines": [ + { + "bbox": [ + 106, + 255, + 488, + 332 + ], + "spans": [ + { + "bbox": [ + 106, + 255, + 488, + 332 + ], + "type": "table", + "html": "
EHRDHRELRDLRLPIPS (↓)PSNR (↑)SSIM (↑)
F120-layer12-layer6-layer6-layer0.27122.460.625
F212-layer20-layer6-layer6-layer0.25622.490.631
F312-layer12-layer14-layer6-layer0.26322.480.629
F412-layer12-layer6-layer14-layer0.26122.480.630
Ours12-layer12-layer6-layer6-layer0.25922.460.629
", + "image_path": "0a1a27e25b1c33ec0e09a96affcce866f89a599166f57a8a68c1b5fe049f61a3.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 354, + 288, + 450 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 354, + 288, + 450 + ], + "spans": [ + { + "bbox": [ + 46, + 354, + 288, + 450 + ], + "type": "text", + "content": "mance. Although large patch size can identify structured image contents from degradations, the reconstructed SR results are usually of high quality but low fidelity [47]. In summary, a reasonable patch size is critical to the performance. Compared to model D1 and D2, our model produces superior accuracy in terms of all metrics. Consequently, patch sizes of " + }, + { + "bbox": [ + 46, + 354, + 288, + 450 + ], + "type": "inline_equation", + "content": "2 \\times 2" + }, + { + "bbox": [ + 46, + 354, + 288, + 450 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 354, + 288, + 450 + ], + "type": "inline_equation", + "content": "8 \\times 8" + }, + { + "bbox": [ + 46, + 354, + 288, + 450 + ], + "type": "text", + "content": " are adopted as the default setting." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 451, + 151, + 463 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 451, + 151, + 463 + ], + "spans": [ + { + "bbox": [ + 47, + 451, + 151, + 463 + ], + "type": "text", + "content": "(2) Coupling Operation" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 463, + 287, + 630 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 463, + 287, + 630 + ], + "spans": [ + { + "bbox": [ + 46, + 463, + 287, + 630 + ], + "type": "text", + "content": "By employing the same spatial codes over HR content dictionary " + }, + { + "bbox": [ + 46, + 463, + 287, + 630 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{HR}" + }, + { + "bbox": [ + 46, + 463, + 287, + 630 + ], + "type": "text", + "content": " and LR content dictionary " + }, + { + "bbox": [ + 46, + 463, + 287, + 630 + ], + "type": "inline_equation", + "content": "\\mathbf{D}^{LR}" + }, + { + "bbox": [ + 46, + 463, + 287, + 630 + ], + "type": "text", + "content": " to represent paired HR and LR images, these dictionaries are tightly coupled. To investigate its effectiveness, we introduce a network variant (E1 in Table 3) by removing this coupling operation. Specifically, HR and LR feature maps are represented using separate spatial codes during the discretization stage. From Table 3 we can see that model E1 produces extremely low quantitative scores. Without the coupling operation, the HR and LR content dictionaries are not associated such that the reconstructed SR result does not share the same content with the LR input. In contrast, the coupling operation enables our model to produce SR results faithful to the LR image." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 647, + 174, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 647, + 174, + 658 + ], + "spans": [ + { + "bbox": [ + 47, + 647, + 174, + 658 + ], + "type": "text", + "content": "4.3.3 Network Architecture" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 665, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 715 + ], + "type": "text", + "content": "Our network consists of four modules, including HR image encoder, HR image decoder, LR image encoder, and LR image decoder. We conduct experiments to study the effect of the model capacity for these four modules. Specif" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 354, + 547, + 486 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 354, + 547, + 486 + ], + "spans": [ + { + "bbox": [ + 304, + 354, + 547, + 486 + ], + "type": "text", + "content": "ically, we first develop four network variants (F1-F4 in Table 4) by deepening these four modules. As we can see, our method does not obtain consistent performance gains as the HR encoder, LR encoder and LR decoder are deepened. Meanwhile, with larger HR decoder, model F2 produces slight improvements on all metrics. This indicates that our method relies more on the design of dictionaries (Table 3) rather than the designs of the network architecture. Despite the marginal improvements brought by larger HR decoder, a 12-layer decoder is employed to achieve the accuracy-efficiency balance." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 500, + 379, + 512 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 500, + 379, + 512 + ], + "spans": [ + { + "bbox": [ + 306, + 500, + 379, + 512 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 521, + 547, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 547, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 547, + 653 + ], + "type": "text", + "content": "In this paper, we propose to associate unpaired LR and HR images using coupled dictionaries rather than synthesizing pseudo LR images. Specifically, we construct an HR content dictionary, an LR content dictionary, and a degradation dictionary to model unpaired HR and LR images. To couple these dictionaries, we develop an autoencoder-based framework for optimization. By representing images using compact proxy codes, an LR-to-HR mapping can be effectively learned by our dictionaries. Experiments on several benchmarks show that our method produces superior performance against previous state-of-the-art approaches." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 655, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 655, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 655, + 547, + 713 + ], + "type": "text", + "content": "Acknowledgments: This work was partially supported by the National Natural Science Foundation of China (No. 62301601, 62301306, and 62306331), the Shenzhen Science and Technology Program (No. RCYX20200714114641140), the Guangdong Basic and Applied Basic Research Foundation (2022B1515020103), and the Young Elite Scientists Sponsorship Program by CAST (No. 2023QNRC001)." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25719" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 712 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "type": "text", + "content": "[1] Chao Dong, Chen Change Loy, Kaiming He, and Xiaou Tang. 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Springer, 2022. 8" + } + ] + } + ], + "index": 14 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "25721" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_content_list.json b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..f50e3b3b35721850b916834ca9215ad1f10832a7 --- /dev/null +++ b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_content_list.json @@ -0,0 +1,1518 @@ +[ + { + "type": "text", + "text": "Learning Degradation-Independent Representations for Camera ISP Pipelines", + "text_level": 1, + "bbox": [ + 91, + 130, + 879, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yanhui Guo* \nMcMaster University, Canada \nguoy143@mcmaster.ca", + "bbox": [ + 91, + 180, + 330, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Fangzhou Luo* \nMcMaster University, Canada \nluof1@mcmaster.ca", + "bbox": [ + 364, + 181, + 604, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Xiaolin Wu† \nMcMaster University, Canada \nxwu@mcmaster.ca", + "bbox": [ + 638, + 180, + 877, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 268, + 313, + 284 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Image signal processing (ISP) pipeline plays a fundamental role in digital cameras, which converts raw Bayer sensor data to RGB images. However, ISP-generated images usually suffer from imperfections due to the compounded degradations that stem from sensor noises, demosaicing noises, compression artifacts, and possibly adverse effects of erroneous ISP hyperparameter settings such as ISO and gamma values. In a general sense, these ISP imperfections can be considered as degradations. The highly complex mechanisms of ISP degradations, some of which are even unknown, pose great challenges to the generalization capability of deep neural networks (DNN) for image restoration and to their adaptability to downstream tasks. To tackle the issues, we propose a novel DNN approach to learn degradation-independent representations (DiR) through the refinement of a self-supervised learned baseline representation. The proposed DiR learning technique has remarkable domain generalization capability and consequently, it outperforms state-of-the-art methods across various downstream tasks, including blind image restoration, object detection, and instance segmentation, as verified in our experiments.", + "bbox": [ + 76, + 300, + 473, + 618 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 645, + 209, + 660 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In our information era, digital cameras have become ubiquitous and indispensable in all walks of socioeconomic life. They are arguably the most common type of sensory device for both humans and their intelligent agents to sense the environment. The applications of digital imaging fall into two categories depending on their end purposes: human vision oriented and machine vision oriented. Examples of the first category include smartphones, social media, internet videos, etc., while robotics, automation, and medical imaging are examples of the second category.", + "bbox": [ + 75, + 670, + 470, + 820 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "For human vision oriented applications, the image quality metrics should correspond to human visual perception, because the images are primarily intended to please our", + "bbox": [ + 75, + 821, + 470, + 867 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "eyes. On the other hand, for machine vision oriented applications [18, 19, 40, 49], the image quality requirements may not completely align with those of human perception. In the latter case, what matters most is the preservation of semantically critical image features that are needed to solve computer vision problems of recognition and classification.", + "bbox": [ + 500, + 268, + 893, + 361 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "For either human viewing or downstream computer vision tasks, the image acquisition process of digital cameras is the same. All images are generated by a hardware image signal processing (ISP) pipeline that transforms raw Bayer sensor data into RGB images. The ISP pipeline consists of a set of cascaded steps, including denoising, color demosaicking, and compression. Each of the ISP steps can cause a level of degradation in image quality. At the beginning of the ISP pipeline, there are sensor noises, particularly in dark environments with a low signal-to-noise ratio. The noisy RAW data are then demosaiced to produce the corresponding RGB images. This demosaicking process introduces interpolation noises of its own. Finally, the RGB image is compressed for bandwidth efficiency, which adds extra compression noises on top of sensor noises and demosaicking noises. The resulting compound effects of these cascaded noises are very difficult to model precisely [11]. The underlying complex image quality degradation mechanism prevents the synthesis of clean and degraded image pairs for supervised learning.", + "bbox": [ + 496, + 366, + 893, + 654 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yet, there is another type of ISP degradation that exerts adverse effects on the applications of ISP-generated images in downstream tasks. The camera ISP involves a number of adjustable hyperparameters such as gamma correction, ISO, gain control, and white balance. Their optimal settings may vary from application to application, i.e., there exists no one-fits-all solution. Most cameras have a default hyperparameter setting that is tailored to perceptual quality rather than optimized for a specific computer vision task. We consider the deviations of ISP hyperparameters from their optimal settings, in a general sense, to be degradations as well. This second type of ISP degradation can lead to underperformances or even outright failures of downstream computer vision algorithms [32, 38]. Like the first type of signal-level degradations, the second type of semantic-level degradations is extremely difficult, if not impossible,", + "bbox": [ + 496, + 657, + 895, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "* Equal contribution.", + "bbox": [ + 94, + 875, + 207, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "† Corresponding author.", + "bbox": [ + 96, + 887, + 225, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "25774", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "to model and synthesize, not only because the space of ISP hyperparameters is of very high dimensions but also because the two types of ISP degradations are intertwined.", + "bbox": [ + 75, + 90, + 468, + 137 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/e456d7c2f496f03a50796fe28ecd3173fc1232a3d34a1b20d5befd2e2e2335d2.jpg", + "image_caption": [ + "Canonical", + "Figure 1. Comparison of the canonical learning paradigm and our DiR learning technique." + ], + "image_footnote": [], + "bbox": [ + 112, + 151, + 269, + 282 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/e377d5ec4af4ba88fe20daf50ceb9fc741a559400f9faa20bbbff07cf079ac00.jpg", + "image_caption": [ + "Ours" + ], + "image_footnote": [], + "bbox": [ + 272, + 151, + 437, + 282 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "As discussed above, it is either intractable or highly expensive to obtain the ISP-degraded and the corresponding latent degradation-free (ground truth) image pairs. Moreover, exhausting all ISP degradation variants in a brute force way is impossible, many of which are not even known or understood [27, 28]. To meet these challenges, we introduce a notion of degradation-independent latent representation (DiR) that is robust against camera-captured non-ideal real-world images and propose a new deep neural network approach to learn the DiR. Fig. 1 illustrates the difference between our DiR learning paradigm and the canonical learning paradigm. Within the framework of our DiR learning, the learned DiR representations contain intrinsic information of the original degradation-free image and hence it is more general and robust with respect to unseen degradation types and severity when used in downstream computer vision and image processing tasks. The DiR learning, carried out by a deep neural network called DiRNet, is self-supervised, and the DiRNet is trained with two learning objectives: any two degraded images are mapped to the same DiR, and all DiRs are sampled from a normal distribution, which is learning a variational auto-encoder (VAE) by the multi-view mutual information (MMI) maximization[7, 15, 43].", + "bbox": [ + 75, + 340, + 472, + 686 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Moreover, we take advantage of known priors of the ISP workflow to synthesize original and degraded pairs, so that the above baseline DiR can be reinforced by an auxiliary self-supervised learning branch. This auxiliary branch learns the reference representation $\\mathbf{r}^*$ of the degradation-free images, using high-quality images (surrogate ground truth). The baseline DiR result $\\mathbf{r}^{(0)}$ is statistically aligned with the result $\\mathbf{r}^*$ of the auxiliary branch by an alignment network module. This alignment module is trained using the aforementioned synthesized pairs and learns to align the baseline DiR $\\mathbf{r}^{(0)}$ to the degradation-free representation reference (DfR) $\\mathbf{r}^*$ , yielding a refined DiR $\\mathbf{r}^+$ ; finally, the refined DiR $\\mathbf{r}^+$ is ready for being used in downstream tasks. Overall, the refined DiR benefits from the best of both self-supervised and supervised", + "bbox": [ + 75, + 688, + 472, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "learning, and strikes a good balance between the model's robustness and precision for applications.", + "bbox": [ + 498, + 90, + 890, + 121 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our main contributions and key results can be summarized as follows:", + "bbox": [ + 498, + 122, + 893, + 151 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- A novel method is proposed for self-supervised learning of the DiR representation by multivariate mutual information maximization, which requires only degraded training images.", + "- A joint learning approach is employed to refine the DiR representation for optimal performance in the targeted end-task network.", + "- The versatility of the proposed methods across a wide range of tasks, including image restoration, object detection, and instance segmentation, is supported by ample empirical evidence." + ], + "bbox": [ + 500, + 152, + 893, + 318 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 325, + 640, + 340 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Degradation blind image restoration network There is a long history of research on image restoration tasks that are blind to degradation parameters, such as blind image deconvolution algorithms [23]. Accompanying the proliferation of deep learning based image restoration methods, recent years have seen a number of papers [9, 10, 12, 24, 26, 28, 36, 47] on the topic of improving the generalization ability of image restoration networks. Wang et al. [47] used a high-order degradation model to mimic real-world degradations. Luo et al. [28] proposed a novel adversarial neural degradation model to simulate degraded training data. Li et al. [24] introduced a distortion invariant representation learning paradigm from the causality perspective, to improve the generalization ability of restoration networks for unknown degradations.", + "bbox": [ + 496, + 352, + 893, + 564 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "End-to-end neural network solutions for ISP pipelines A more holistic design of neural networks [34, 41, 51] for image restoration is to replace the cascaded stages of the hardware ISP pipeline with a single end-to-end mapping from raw Bayer sensor data to the intended ideal RGB images, instead of postprocessing the output images of the camera ISP. For instance, Chen et al. [2] proposed a CNN method, called SID (see in the dark), which directly converts a low lighting noisy Bayer image to a corresponding properly exposed RGB image, without generating the underexposed ineligible RGB image first and then restoring it. Tseng et al. [44] leveraged a convolutional neural network to parameterize a differentiable mapping between the ISP configuration space and evaluation metrics of downstream tasks and validated their method on the tasks of object detection, and extreme low-light imaging. Yu et al. [52] replaced the conventional ISP with a trainable ISP framework that improves the quality of ISP-generated results by using a differential neural architecture search algorithm to search for the optimal ISP architecture and hyperparameters.", + "bbox": [ + 496, + 566, + 893, + 868 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Image enhancement for high-level tasks In general practice, image restoration networks tend to be optimized for", + "bbox": [ + 498, + 869, + 893, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "25775", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/2669202ed069507a51e3d8c39267519c4d07a7bf0680f26b2540b89f5c05f809.jpg", + "image_caption": [ + "Figure 2. Self-supervised MMI maximization for DiRNet." + ], + "image_footnote": [], + "bbox": [ + 80, + 88, + 472, + 327 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "human visual perception rather than for computer vision tasks. However, the human vision-centric neural network may not provide optimal results on high-level computer vision tasks. This motivates the development of a family of image restoration networks that are tuned in line with the subsequent computer vision tasks, such as recognition, detection, and classification [4, 39, 52]. For example, Cui et al. [4] proposed a multitask auto-encoding transformation model to learn the intrinsic visual structure by considering the physical sensor noise model in ISP, demonstrating effectiveness for dark object detection. Mosleh et al. [32] investigated a so-called \"hardware-in-the-loop\" strategy to directly optimize the hyperparameters of hardware ISP pipelines, by solving a nonlinear multi-objective optimization problem with a 0th-order stochastic solver. Qin et al. [39] designed a sequential CNN model to recurrently adjust the ISP hyperparameters for downstream tasks and demonstrate the advantages of the model.", + "bbox": [ + 75, + 359, + 472, + 632 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Approach", + "text_level": 1, + "bbox": [ + 76, + 646, + 184, + 662 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we first detail the DiRNet mentioned in the introduction to learn the baseline $\\mathrm{DiR}\\mathbf{r}^{(0)}$ of multiple degraded images. The DiRNet training is driven by the MMI maximization. Then, we discuss how to learn the degradation-free latent representation $\\mathbf{r}^*$ using a variant of DiRNet. The two latent representations $\\mathbf{r}^{(0)}$ and $\\mathbf{r}^*$ are prepared to train an alignment network to produce a refined DiR $\\mathbf{r}^{+}$ . Finally, we elaborate on the process to jointly optimize the alignment network and an auxiliary network for a downstream task.", + "bbox": [ + 75, + 671, + 470, + 806 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Optimizing DiRNet by MMI Maximization", + "text_level": 1, + "bbox": [ + 76, + 816, + 449, + 832 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Mutual information maximization To begin, we pave the way for computing the multi-view mutual information (MMI) maximization by introducing a mutual information estimator. For estimating mutual information", + "bbox": [ + 75, + 839, + 470, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "$I(\\mathbf{x};\\mathbf{y})$ of two random variables $\\mathbf{x}$ and $\\mathbf{y}$ , it is equivalent to computing the Kullback-Leibler (KL) divergence $\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{x},\\mathbf{y})||p(\\mathbf{x})p(\\mathbf{y}))$ . However, the KL divergence has no theoretical upper bound. Maximizing it cannot guarantee the convergence of the optimization process. Following previous works [35, 45], we exploit a non-KL divergence named Jensen-Shannon divergence (JSD) to devise the lower bound of mutual information, which satisfies the below proposition. Proposition 1 Let $\\mathbf{x}$ and $\\mathbf{y}$ represent two random variables, the $\\mathbf{J} = p(\\mathbf{x},\\mathbf{y})$ and $\\mathbf{M} = p(\\mathbf{x})p(\\mathbf{y})$ are the joint and the product of marginals of the two variables, respectively. The mutual information between the variables satisfies1", + "bbox": [ + 496, + 90, + 893, + 272 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} I (\\mathbf {x}; \\mathbf {y}) := \\mathcal {D} _ {\\mathrm {J S D}} (\\mathbf {J}; \\mathbf {M}) \\\\ \\geq \\mathbb {E} _ {z \\sim \\mathbf {J}} [ - \\sigma (- \\mathcal {F} _ {\\omega} (z)) ] - \\mathbb {E} _ {z ^ {\\prime} \\sim \\mathbf {M}} [ \\sigma (\\mathcal {F} _ {\\omega} (z ^ {\\prime})) ], \\tag {1} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 513, + 280, + 892, + 316 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\sigma(t) = \\log(1 + e^t)$ , and the discriminator function $\\mathcal{F}_{\\omega}$ [35] is modeled by a neural network with parameters $\\omega$ . Multi-view mutual information maximization The baseline DiR $\\mathbf{r}^{(0)}$ is a degradation-independent representation shared among all degraded images that originate from an ideal degradation-free image. From the perspective of information theory, the DiR representation should satisfy the criterion of shared information maximization between it and multiple degraded observations. This shared information maximization is so-called multi-view mutual information (MMI) maximization[7] a.k.a interaction information maximization [43] for the three variables. We state its definition as follows: Given two degraded images $\\mathbf{x}_1$ and $\\mathbf{x}_2$ , their shared latent DiR $\\mathbf{r}^{(0)}$ can be found by maximizing their MMI $I(\\mathbf{r}^{(0)}; \\mathbf{x}_1; \\mathbf{x}_2)$ that is defined as", + "bbox": [ + 496, + 321, + 893, + 547 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1}; \\mathbf {x} _ {2}\\right) = I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1}\\right) - \\underbrace {I \\left(\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {1} \\mid \\mathbf {x} _ {2}\\right)} _ {\\text {R e d u n d a n c y}} (2) \\\\ = I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {2}\\right) - I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {2} \\mid \\mathbf {x} _ {1}\\right), (3) \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 540, + 554, + 890, + 613 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where Eq. (3) holds due to symmetry. The conditional mutual information $I(\\mathbf{r}^{(0)};\\mathbf{x}_1|\\mathbf{x}_2)$ represents the incremental mutual information between $\\mathbf{r}^{(0)}$ and the degraded observation $\\mathbf{x}_1$ when given another degraded observation $\\mathbf{x}_2$ . This incremental information denotes the information not shared by the observations $\\mathbf{x}_1$ and $\\mathbf{x}_2$ , due to the differences in various degradation sources, which should be minimized. Maximizing $I(\\mathbf{r}^{(0)};\\mathbf{x}_1;\\mathbf{x}_2)$ encourages $\\mathbf{r}^{(0)}$ to encode the degradation-independent information shared by the given multiple degraded images.", + "bbox": [ + 496, + 622, + 893, + 772 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The network DiRNet for learning the baseline DiR is of VAE type [14]. The DiRNet takes the ISP-generated images (i.e. camera captured) as inputs and maps them into a canonical representation space i.e. the DiR latent space, by removing the degradation-specific information. Fig. 2 shows the training process for the DiRNet. To continue the development, we introduce the following proposition [15]:", + "bbox": [ + 496, + 773, + 893, + 878 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "1The derivation is in Sec.B and Sec.C of the supplementary material.", + "bbox": [ + 517, + 886, + 880, + 898 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "25776", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Proposition 2 Given two degraded images $\\mathbf{x}_1$ and $\\mathbf{x}_2$ , and the baseline DiR representation $\\mathbf{r}^{(0)}$ , the conditional mutual information $I(\\mathbf{r}^{(0)};\\mathbf{x}_1|\\mathbf{x}_2)$ satisfies:", + "bbox": [ + 76, + 90, + 470, + 137 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nI \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1} \\mid \\mathbf {x} _ {2}\\right) \\leq \\mathbb {E} _ {p \\left(\\mathbf {x} _ {1}, \\mathbf {x} _ {2}\\right)} \\left[ \\right. \\mathcal {D} _ {\\mathrm {K L}} \\left( \\right.p \\left(\\mathbf {r} ^ {(0)} \\mid \\mathbf {x} _ {1}, \\mathbf {x} _ {2}\\right)\\left. \\right\\lvert | p _ {\\varphi} \\left(\\mathbf {r} ^ {(0)} \\mid \\mathbf {x} _ {2}\\right)\\left. \\right)\\left. \\right]. \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 78, + 148, + 468, + 179 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To maximize $I(\\mathbf{r}^{(0)};\\mathbf{x}_1;\\mathbf{x}_2)$ , the overall training objective of DiRNet is defined by the average of Eq. (2) and Eq. (3):", + "bbox": [ + 76, + 181, + 470, + 214 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {0} = - \\frac {I (\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {1}) + I (\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {2})}{2} \\\\ + \\lambda \\mathbb {E} _ {p (\\mathbf {x} _ {1}, \\mathbf {x} _ {2})} [ \\mathcal {D} _ {\\mathrm {A K L}} ] \\\\ + \\beta \\mathcal {D} _ {\\mathrm {K L}} \\left[ p \\left(\\mathbf {r} ^ {(0)}\\right) | | \\mathcal {N} (0, \\mathbf {I}) \\right], \\tag {5} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 151, + 237, + 468, + 316 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "in which we can maximize the upper bound of the conditional mutual information according to Proposition 2. In Eq.(5), $\\lambda$ and $\\beta$ are the trade-off hyperparameters. The DiR representation is regularized by the Gaussian prior $\\mathcal{N}(0,\\mathbf{I})$ as in VAE [14]. $\\mathcal{D}_{\\mathrm{AKL}}$ stands for the average of $\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{r}^{(0)}|\\mathbf{x}_1,\\mathbf{x}_2)\\parallel p_\\varphi (\\mathbf{r}^{(0)}|\\mathbf{x}_1))$ and $\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{r}^{(0)}|\\mathbf{x}_1,\\mathbf{x}_2)\\parallel p_\\varphi (\\mathbf{r}^{(0)}|\\mathbf{x}_2))$ . The trainable network is the DiRNet $p_{\\varphi}$ that produces the baseline DiR and an auxiliary network to estimate the upper bound [15].", + "bbox": [ + 76, + 328, + 470, + 465 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Degradation-Free Representation Reference", + "text_level": 1, + "bbox": [ + 76, + 474, + 450, + 491 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Although the baseline DiR $\\mathbf{r}^{(0)}$ aims to distill the degradation-invariant intrinsic elements and structures, it may have biases toward the degraded data because the learning process of $\\mathbf{r}^{(0)}$ has not observed degradation-free samples. To compensate for this insufficiency, we collect a large set of high-quality RGB images and assume them to be free of degradation. As these images are captured by real non-idealistic cameras the degradation-free assumption is not strictly true, but it is acceptable for practical purposes. These degradation-free images are used to learn the degradation-free latent representation (DfR) $\\mathbf{r}^*$ ; the above two latent representations $\\mathbf{r}^{(0)}$ and $\\mathbf{r}^*$ will be aligned to produce a refined DiR $\\mathbf{r}^+$ by a so-called alignment network, whose construction and rationale will be discussed in Sec. 3.3.", + "bbox": [ + 75, + 500, + 470, + 710 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Similar to training DiRNet for the baseline $\\mathrm{DiR}\\mathbf{r}^{(0)}$ , we propose the DfRNet to learn the DfR $\\mathbf{r}^*$ from a degradation-free image (surrogate ground truth). Since this DfR learning is with respect to a single image, the MMI training for $\\mathbf{r}^*$ is simplified to the mutual information maximization i.e. maximizing $I(\\mathbf{r}^*;\\mathbf{y}^*)$ , which can be solved by maximizing the lower bound derived by Proposition 1. Moreover, following VAE [14], we train the decoder $D_{*}$ that forces the learned DfR to be able to reconstruct the degradation-free image. The objective of the above DfR learning is to minimize $\\mathcal{L}_{*}$", + "bbox": [ + 75, + 710, + 470, + 863 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "defined as follows", + "bbox": [ + 500, + 90, + 624, + 104 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {*} = - I \\left(\\mathbf {r} ^ {*}; \\mathbf {y} ^ {*}\\right) + \\mathbb {E} \\left[ \\left\\| D _ {*} \\left(\\mathbf {r} ^ {*}\\right) - \\mathbf {y} ^ {*} \\right\\| _ {1} \\right] \\\\ + \\beta^ {*} \\mathcal {D} _ {\\mathrm {K L}} [ p (\\mathbf {r} ^ {*}) | | \\mathcal {N} (0, \\mathbf {I}) ], \\tag {6} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 557, + 113, + 890, + 148 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\beta^{*}$ is the trade-off hyperparameter. The defined training objective in Eq. (6) is the same as the InfoVAE [54].", + "bbox": [ + 498, + 156, + 893, + 186 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Alignment Network for Refined DiR", + "text_level": 1, + "bbox": [ + 500, + 194, + 820, + 210 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Alignment network As mentioned in the introduction, we can neutralize, to a certain extent, possible biases in the baseline DiR $\\mathbf{r}^{(0)}$ by aligning $\\mathbf{r}^{(0)}$ with the above DfR $\\mathbf{r}^*$ in distribution. This is accomplished by a so-called alignment network $\\mathcal{A}$ . To guide the statistical alignment of $\\mathbf{r}^{(0)}$ and $\\mathbf{r}^*$ , we also feed the degraded training image $\\mathbf{x}$ to network DfR-Net and use the resulting latent representation $\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x})$ , called the pilot representation. This guided alignment process is a mapping function", + "bbox": [ + 498, + 218, + 893, + 354 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {A} \\left(\\mathbf {r} ^ {(0)}, \\vec {\\mathbf {r}}\\right): \\mathbf {r} ^ {(0)} \\xrightarrow [ \\vec {\\mathbf {r}} = \\mathrm {D f R} (\\mathbf {x}) ]{\\text {G u i d e d b y} \\vec {\\mathbf {r}}} \\mathbf {r} ^ {+}. \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 570, + 364, + 890, + 401 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Next, we describe the architecture of the alignment network $\\mathcal{A}$ and discuss the role of the pilot representation $\\vec{\\mathbf{r}}$ .", + "bbox": [ + 498, + 409, + 893, + 440 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/595af94a3f5e8c8a7fdd9e98aef9b739895eff59cf3cde2fb1c21cc06ddbc702.jpg", + "image_caption": [ + "Figure 3. Illustration of the alignment network." + ], + "image_footnote": [], + "bbox": [ + 501, + 445, + 890, + 633 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Network structure Fig. 3 shows the network structure of the alignment network $\\mathcal{A}$ . It consists of three cascaded modules $\\mathcal{A}_1, \\mathcal{A}_2$ and $\\mathcal{A}_3$ . The front module $\\mathcal{A}_1$ of $m_1$ convolution layers is used to extract the features from the input image. The middle module $\\mathcal{A}_2$ of $m_2$ layers is designed to modulate the latent features with the guidance of the pilot DfR $\\vec{\\mathbf{r}}$ . The end module $\\mathcal{A}_3$ of $m_3$ convolution layers is used to produce the final refined DiR $\\mathbf{r}^+$ .", + "bbox": [ + 496, + 652, + 893, + 775 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In the guidance module $\\mathcal{A}_2$ , $\\vec{\\mathbf{r}}$ is fed to convolution layers with $3\\times 3$ kernels, followed by the average pooling layer to obtain the modulation feature tensors. These modulation tensors are then reshaped to form $k$ adaptive convolution kernels. We use a so-called G-Conv module formed by these adaptive convolution kernels to convolve with the input features to produce the guided features $f_{k}$ which are embedded with the information of the pilot DfR $\\vec{\\mathbf{r}}$ . In addition,", + "bbox": [ + 496, + 777, + 893, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_footnote", + "text": "2The full derivation of $\\mathcal{L}_0$ can be found in Sec.B of the supplementary material.", + "bbox": [ + 76, + 875, + 467, + 898 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "25777", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "we exploit a spatial attention branch to assist the guidance information extraction. This attention branch predicts the attention maps to strengthen the feature units that have a high correlation to pilot DfR $\\vec{\\mathbf{r}}$ , yielding the attention-weighted intermediate features $f_{a}$ . Finally, the guided features $f_{k}$ and the attention-weighted features $f_{a}$ are fused by an addition layer to produce the refined DiR $\\mathbf{r}^{+}$ , which is ready for use in downstream tasks. In our experiments, we jointly train this alignment network $\\mathcal{A}$ and a task-aligned auxiliary network $\\mathcal{T}$ , which will be introduced in Sec. 3.4.", + "bbox": [ + 75, + 90, + 472, + 243 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/caf2b32cea7b9b7239d6af5a72a656477d74571572bab7777f19d1c6c50bb2e8.jpg", + "image_caption": [ + "Figure 4. Visualization of the pilot DfR representations $\\vec{\\mathbf{r}}$ and the expected DfR representations $\\mathbf{r}^*$ . The information provided by the pilot DfR can guide the alignment to find the optimal DfR." + ], + "image_footnote": [], + "bbox": [ + 137, + 244, + 406, + 460 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Discussion on the pilot DfR $\\vec{\\mathbf{r}}$ To explain the rationale behind the guidance design of the alignment network, we conduct experiments for visualization. More specifically, we choose four different degradation-free images to extract their corresponding DfRs $\\mathbf{r}^*$ . We then use the ISP pipeline as in [39] by adding noise to generate 200 various degraded copies of each degradation-free image. These degraded samples, which share the same image content but have different ISP degradations, are fed into the network DfR to produce the pilot DfRs $\\mathbf{r}^*$ . Fig. 4 shows the visualized results by using t-SNE [46], where the red stars denote the expected ground truth DfRs $\\mathbf{r}^*$ for the alignment network training, and the green stars stand for the pilot DfRs $\\vec{\\mathbf{r}}$ . We can observe that the green points are projected near the red points, suggesting that the pilot DfRs have a strong correlation with the ground truth DfRs. This is because the pilot DfRs and the ground truth DfRs share the same degradation-free content. Inspired by this phenomenon, the alignment network is designed to take into account the assistant information provided by $\\vec{\\mathbf{r}}$ to guide the refinement of the baseline DiR.", + "bbox": [ + 75, + 513, + 472, + 823 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Joint Task-Aligned Refinement Learning", + "text_level": 1, + "bbox": [ + 76, + 832, + 431, + 849 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For training the alignment network, we simulate the Bayer RAW data from the degradation-free images $\\mathbf{y}^*$ (surrogate ground truth) by using the inverse ISP [21]. These RAW data", + "bbox": [ + 75, + 854, + 470, + 901 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/407725b575d4357fbb2ec31c383faa3ae9b94fed108c4aa781da979c85f4a4a4.jpg", + "image_caption": [ + "Figure 5. Illustration of the joint task-aligned refinement learning." + ], + "image_footnote": [], + "bbox": [ + 501, + 88, + 893, + 242 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "are used to generate the degraded RGB images $\\mathbf{x}$ with the ISP software tool [39]. Fig. 5 illustrates the joint task-aligned refinement learning process. The DiRNet and DfRNet are frozen to extract the paired representations $(\\mathbf{r}^{(0)},\\mathbf{r}^{*})$ from the paired degraded and degradation-free images $(\\mathbf{x},\\mathbf{y}^{*})$ . The alignment network is driven by the pairs $(\\mathbf{r}^{(0)},\\mathbf{r}^{*})$ to learn the mapping function $\\mathcal{A}:\\mathbf{r}^{(0)}\\to \\mathbf{r}^{+}$ , where the final refined DiR $\\mathbf{r}^{+}$ lies in the degradation-free latent representation space determined by the DfRNet.", + "bbox": [ + 496, + 268, + 893, + 404 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The paired images $(\\mathbf{x},\\mathbf{y}^{*})$ and the associated labels $\\tilde{\\mathbf{y}}$ w.r.t. the downstream task are used to supervise the joint training of the alignment network $\\mathcal{A}$ and the task-related auxiliary network $\\mathcal{T}$ . As the auxiliary network for the downstream task usually takes an RGB image as input, we adopt the decoder $D_{*}$ trained for the DfRNet to reconstruct the RGB images from the refined DiRs $\\mathbf{r}^{+}$ . The joint training loss in the alignment phase is to minimize $\\mathcal{L}_{+}$ defined as", + "bbox": [ + 496, + 404, + 893, + 526 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {+} = \\mathbb {E} \\left[ \\| \\mathbf {r} ^ {+} - \\mathbf {r} ^ {*} \\| _ {1} \\right] + \\gamma_ {1} \\mathcal {L} _ {\\text {t a s k}} \\left(\\mathcal {T} \\left(D _ {*} (\\mathbf {r} ^ {+})\\right), \\tilde {\\mathbf {y}}\\right) \\\\ + \\gamma_ {2} \\mathbb {E} \\left[ \\| D _ {*} \\left(\\mathbf {r} ^ {+}\\right) - \\mathbf {y} ^ {*} \\| _ {1} \\right], \\tag {8} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 532, + 532, + 890, + 573 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\gamma_{1}$ and $\\gamma_{2}$ are the trade-off parameters, the DfR $\\mathbf{r}^{*} = \\mathrm{DfR}(\\mathbf{y}^{*})$ , and the refined DiR representation $\\mathbf{r}^{+} = \\mathcal{A}(\\mathbf{r}^{(0)},\\vec{\\mathbf{r}})$ , where $\\mathbf{r}^{(0)} = \\mathrm{DiR}(\\mathbf{x})$ and $\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x})$ . The alignment network $\\mathcal{A}$ and the auxiliary network $\\mathcal{T}$ are jointly optimized, whereas the pretrained networks DiRNet and DfRNet as well as the decoder $D_{*}$ are frozen. The second term $\\mathcal{L}_{\\mathrm{task}}$ is a task-related loss for a downstream task, such as the cross-entropy for image segmentation. The third term is an image reconstruction loss that forces the refined DiR to inherit the complete information from the degradation-free image through the pixel-wise reconstruction restriction. We summarize the DiR learning process in Algorithm 1.", + "bbox": [ + 496, + 580, + 890, + 765 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 777, + 633, + 794 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Implementation Details", + "text_level": 1, + "bbox": [ + 500, + 801, + 717, + 816 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets and evaluation As previously introduced, DiR learning comprises two stages: Stage I, dedicated to training the DiRNet and DfRNet, and Stage II, where the alignment network $\\mathcal{A}$ and the task-related auxiliary network $\\mathcal{T}$ are jointly trained. For the training dataset, we adopt the", + "bbox": [ + 496, + 824, + 893, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "25778", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Algorithm 1 DiR Learning and Task-Aligned Refinement", + "text_level": 1, + "bbox": [ + 78, + 90, + 460, + 106 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Input: Degradation-free RAW image $\\mathbf{y}$ and corresponding degradation-free RGB image $\\mathbf{y}^*$ , task-related label $\\tilde{\\mathbf{y}}$ \nStage I:", + "bbox": [ + 78, + 109, + 468, + 143 + ], + "page_idx": 5 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1: repeat", + "2: Generate two images $\\mathbf{x}_1$ and $\\mathbf{x}_2$ from a degradation-free image $\\mathbf{y}$ using two randomly sampled ISP degradations.", + "3: Train DiRNet using $(\\mathbf{x}_1,\\mathbf{x}_2)$ (min $\\mathcal{L}_0$ in Eq.5", + "4: Train DfRNet using $\\mathbf{y}^*$ (min $\\mathcal{L}_*$ in Eq. (6))", + "5: until reaching the maximum number of epochs \nStage II:", + "6:re", + "7: Generate an image $\\mathbf{x}$ from a degradation-free image $\\mathbf{y}$ using randomly sampled ISP degradations.", + "8: $\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x}),\\mathbf{r}^{*} = \\mathrm{DfR}(\\mathbf{y}^{*})$", + "9: $\\mathbf{r}^{+} = \\mathcal{A}(\\mathbf{r}^{(0)},\\vec{\\mathbf{r}})$", + "10: Train the alignment network $\\mathcal{A}$ using the paired $(\\mathbf{x},\\mathbf{r}^{*})$ with the guidance of the pilot DfR $\\vec{\\mathbf{r}}$ , and jointly train the auxiliary $\\mathcal{T}$ using the pairs of $(D_{*}(\\mathbf{r}^{+}),\\tilde{\\mathbf{y}})$ (min $\\mathcal{L}_{+}$ in Eq. (8))", + "11: until reaching the maximum number of epochs" + ], + "bbox": [ + 78, + 143, + 468, + 335 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "DIV2K dataset [1] and degrade the images by synthetic ISP degradations. To simulate ISP degradations, we begin by converting RGB images into RAW data by applying the reversed ISP model [21]. Subsequently, we employ a synthetic ISP pipeline [32, 39] with random parameters to generate degraded ISP-generated images from the simulated RAW data3. In Stage II, we employ the identical simulation process used in Stage I to synthesize ISP-degraded images and use the MS COCO dataset [25] for experiments.", + "bbox": [ + 75, + 364, + 470, + 501 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For evaluation, we test the proposed method on three downstream tasks, including 1) the image restoration experiments on real-world datasets including the PolyU-Real [50], NC12 [22], Nam [33], and DND $^4$ [37] datasets, where the test images involve real complex ISP degradations, 2) the object detection experiments on the MS COCO [25] dataset, and 3) the image segmentation experiments on the MS COCO dataset and the ADE20k dataset [55].", + "bbox": [ + 75, + 501, + 468, + 622 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Training settings At Stage I, we randomly select the contrastive degraded pairs to enable the MMI maximization for the training of the DiRNet. For training the DfRNet, we follow the same setting as in [54], by setting the parameter $\\beta^{*} = 1$ in Eq. (6). We adopt the encoder network of [17] as the architectures of the DiRNet and the DfRNet. During training, the learning rate is initially set to $10^{-4}$ and reduced to $10^{-6}$ after 200 epochs. At Stage II, we randomly form pairs of degraded and degradation-free RGB images for training the alignment network. The learning rate is initially set to $10^{-3}$ and reduced to $10^{-6}$ after 300 epochs. For the image restoration task, we set $\\gamma_{1} = 0$ , $\\gamma_{2} = 1$ , because the decoder $D_{*}$ can serve as the auxiliary network for the RGB image reconstruction using the refined DiR $\\mathbf{r}^{+}$ . For the object detection and image segmentation tasks, the trade-off parameters are set to $\\gamma_{1} = 2$ , $\\gamma_{2} = 1$ and $\\gamma_{1} = 5$ , $\\gamma_{2} = 1$ ,", + "bbox": [ + 75, + 625, + 470, + 866 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "respectively. The hyperparameters $m_{1}, m_{2}$ , and $m_{3}$ in the alignment network are separately set to 4, 2, and 4.", + "bbox": [ + 500, + 90, + 890, + 121 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Results on ISP-Degraded Image Restoration", + "text_level": 1, + "bbox": [ + 500, + 125, + 874, + 140 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "First, we present the experimental results of the proposed method and compare them with those of eight competing methods [5, 6, 8, 24, 36, 48, 53], on the restoration of ISP-degraded images. The task is to remove ISP artifacts caused by complex coupling of multiple degradation sources, including sensor noises, demosaicing noises, compression noises, and possibly adverse effects of incorrect settings of ISO and gamma correction. Here, like in all other image restoration methods for human viewers, our goal is to pursue the highest possible perceptual image quality.", + "bbox": [ + 496, + 147, + 893, + 297 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In Fig. 6 the reader can compare the visual quality of the DiR learning based restoration method against those of SOTA image restoration methods [6, 8, 24, 26, 36, 48, 53], on restoring real-world ISP-degraded images taken by four different cameras, whose true degradation models are unknown. We can observe that the proposed method succeeds in achieving its design goal of blind restoration, as it removes most of the ISP artifacts caused by unknown degradation sources. On the contrary, the competing methods fail to remove complex artifacts while preserving the sharpness and clarity of edges and textures. Table 1 reports the quantitative performance evaluation results. Since there is no ideal degradation-free ground truth, we adopt the non-reference image quality assessment methods, including NIQE [31], NRQM [29], and BIQA [42]. In agreement with the visual comparisons in Fig. 6, the proposed DiR method also outperforms the competitors in terms of all three metrics. Both subjective and objective evaluations demonstrate superior robustness of the proposed method when being applied to data unseen in the training, indicating that the DiR learning approach can distill degradation-free representations from ISP-degraded images, regardless of whether observed or not.", + "bbox": [ + 496, + 299, + 893, + 630 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/03de2cfe0e302dcbc3d1ebfd22272ed059038867c6149547e132ecaa4d9a9087.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodNIQE ↓ / NRQM ↑ / BIQA ↑
PolyU-RealNC12NamDND
BM3D [5]9.72/2.60/40.512.78/3.75/30.812.58/2.56/41.212.89/1.84/40.1
CBDNet [8]7.32/3.78/44.110.67/6.88/33.110.26/3.62/42.19.74/2.96/41.1
LIR [6]8.37/4.52/48.111.41/7.19/33.710.69/4.25/49.811.86/3.19/44.3
MPRNet [53]6.12/4.23/38.711.21/6.30/32.97.25/3.94/33.99.53/2.77/45.2
Uformer [48]6.25/3.96/37.410.54/6.05/31.27.92/3.62/34.69.58/2.72/45.1
SCPGab [26]8.71/3.25/41.111.75/3.93/31.910.60/3.25/40.79.80/2.53/42.0
DIL [24]7.28/4.10/41.810.88/6.52/30.89.11/3.59/40.87.86/3.72/44.7
SDAP [36]9.62/3.00/46.111.34/3.88/32.512.38/2.95/45.710.74/2.33/45.8
Ours6.57/4.91/51.99.06/7.41/34.48.96/4.64/53.68.62/3.59/46.9
", + "bbox": [ + 503, + 643, + 890, + 790 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Quantitative results on real-world ISP-degraded images.", + "bbox": [ + 501, + 795, + 887, + 810 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Results on Object Detection", + "text_level": 1, + "bbox": [ + 500, + 816, + 750, + 832 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Following [39], we utilize the MS COCO dataset [25] to evaluate our proposed method's performance on object detection. We compare our method with the SOTA neural ISP solvers [38, 39], which replace the conventional ISP pipeline", + "bbox": [ + 496, + 839, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_footnote", + "text": "3Additional details can be found in the supplementary material", + "bbox": [ + 93, + 873, + 426, + 886 + ], + "page_idx": 5 + }, + { + "type": "page_footnote", + "text": "4We randomly select 500 images for the experiments", + "bbox": [ + 96, + 887, + 375, + 898 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "25779", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/a96d526630d17eed62096f3e869b611ed54f6ed198e543bd101d29559d655f7f.jpg", + "image_caption": [ + "Figure 6. Qualitative comparison on real-world ISP-degraded images. The degraded images, from top to bottom, are from the real-world datasets PolyU-Real [50], NC12 [22], Nam [33], and DND [37]. Please zoom in for better visualization." + ], + "image_footnote": [], + "bbox": [ + 80, + 90, + 890, + 388 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "with end-to-end trained neural networks while considering the downstream task as their optimization objectives. Following the approach in [32, 39], we choose the ISP pipeline with default parameters as the baseline. Our method utilizes these ISP-generated results with default settings as inputs. For comparison, we adopt the pre-trained object detection model [40] for performance benchmarking, and we assess the results using the mean accuracy score (mAP) as the evaluation metric. The quantitative results are reported in Table 2. Our method demonstrates a significant improvement compared to the baseline and outperforms the SOTA solutions [38, 39]. The left side of Fig 7 illustrates the qualitative results. As a reference, we include the results produced by the expert-tuned ISP for visual comparison. We can observe that while the expert-tuned ISP can produce more visually appealing results aligned with human perception preferences, it is inferior to our method on the task of object detection.", + "bbox": [ + 75, + 429, + 473, + 686 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Results on Image Segmentation", + "text_level": 1, + "bbox": [ + 76, + 707, + 354, + 724 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Similar to the object detection experiments, we adopt the MS COCO dataset [25] to evaluate the performance of image segmentation. We benchmark the performance using a pre-trained segmentation model [13] and report the results in Table 3. As shown, our method outperforms the SOTA method Attention-aware [38] by about $3.9\\%$ on the $\\mathrm{mAP}@0.5$ . Quantitative results are shown on the right side of Fig 7. These results are in line with the observations in the object detection experiments. Our method consistently outperforms the expert-tuned ISP in achieving better segmentation results.", + "bbox": [ + 75, + 734, + 470, + 900 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/af54bbac2b1d513e8e561a4f35c35c76c4911a100f9486226da18a0cd7a8ef5d.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodsISP ModelmAP↑
0.50.750.5:0.95
Default ParamsISP [32]15.--
Blockwise-tuned [34]20.--
Hardware-tuned [32]39.--
Default ParamsISP [39]34.122.421.4
Attention-aware [38]61.044.141.0
Sequential-tuned [39]62.845.242.3
Ours63.946.443.3
", + "bbox": [ + 522, + 428, + 866, + 544 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/b1cc200dc3125b8beebb2d27e7965ef11ac7d15068432058e983c803a81296e1.jpg", + "table_caption": [ + "Table 2. Quantitative results on object detection." + ], + "table_footnote": [], + "table_body": "
MethodsISP ModelmAP↑
0.50.750.5:0.95
Default ParamsISP [32]12.--
Hardware-tuned [32]32.--
Default ParamsISP [39]22.713.212.0
Attention-aware [38]52.333.431.5
Sequential-tuned [39]54.235.132.6
Ours56.337.134.8
", + "bbox": [ + 522, + 561, + 866, + 669 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 3. Quantitative results on image segmentation.", + "bbox": [ + 537, + 670, + 849, + 684 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Additionally, we conduct experiments to evaluate the performance of the proposed method in low signal-to-noise ratio situations, such as dark environments where the noise level is very high. To mimic the degradations, we increase the noise level in the aforementioned synthetic ISP pipeline by adding Gaussian noise with the standard deviation $\\sigma$ randomly sampled between the range of [0.15, 0.35] and the Poisson noise with the magnitude $\\lambda$ randomly sampled between the range of [0.02, 0.04]. We compare the proposed DiR learning based method with the SOTA methods [16, 20] for ISP degradation removal and present the results in Table 4. To evaluate performance, we use two pretrained segmentation models, including DeeplabV3 [3] and SegFormer [49]. We observe that our method outperforms all", + "bbox": [ + 496, + 689, + 893, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "25780", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/47cb120df4bb44c38397adeb17b30e1b21bc8bff5b84a08d75261d1100e48b44.jpg", + "image_caption": [ + "Figure 7. We evaluate different ISP-generated images for the tasks of object detection (left) and instance segmentation (right) on the COCO dataset. From top to bottom, we show the results from the images generated by default ISP hyperparameters, expert-tuned ISP hyperparameters, and the refined DiR with the proposed method. The proposed method achieves better performance for downstream tasks." + ], + "image_footnote": [], + "bbox": [ + 96, + 88, + 477, + 406 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ecd2d514145d85621e5b060ba30102552b06c3b53be353a5973a0827feb2e1ce.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 480, + 88, + 867, + 406 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/6eb56882a86f6ccee04e669845bacad092fe053367fff5f2ac006e3f58e9a0a4.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodsDeeplabV3 [3]SegFormer [49]
aAcc↑mIoU↑mAcc↑aAcc↑mIoU↑mAcc↑
Default ISP64.822.628.974.836.945.1
PyNET [16]67.725.131.574.337.445.8
DNF [20]71.429.636.975.437.846.2
Ours75.534.644.579.742.452.9
", + "bbox": [ + 81, + 460, + 464, + 536 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "the competitors. For example, compared to the DNF [20], our method increases the mAcc by $7.6\\%$ and $6.7\\%$ when using the DeeplabV3 and SegFormer models, respectively.", + "bbox": [ + 75, + 559, + 470, + 604 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.5. Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 617, + 230, + 633 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Ablation studies are conducted to assess the effectiveness of the proposed components: the baseline $\\mathrm{DiR}\\mathbf{r}^{(0)}$ , the alignment network $\\mathcal{A}$ , and the pilot DfR $\\vec{\\mathbf{r}}$ . For experiments, we apply the synthetic ISP process as described in [39] to generate ISP-degraded test images using the Set14 and BSD100 [30] datasets. To simulate degradation, we introduce noise into the synthetic ISP process. The added noise includes random Gaussian noise with a standard deviation ranging from 0.05 to 0.1 and JPEG compression noise with a quality factor randomly chosen in the range [10, 30]. As a reference, we train an auto-encoder model, labeled as \"Auto-Encoder\". This model adopts the same encoder architecture as DiR-Net and the same decoder architecture as $D_{*}$ . The training process of this auto-encoder model follows the canonical paradigm, i.e., it learns a direct mapping from degraded images to their degradation-free counterparts. Table 5 shows comparisons: when excluding the pilot DfR (2nd row) from", + "bbox": [ + 75, + 641, + 472, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "the complete DiR learning technique (3rd row), we observe a decrease in PSNR by 0.2 dB and 0.4 dB for the Set14 and BSD100 datasets. In comparison to using only the baseline DiR, the inclusion of the alignment network $\\mathcal{A}$ leads to a PSNR improvement from 22.4 dB to 23.9 dB and 23.8 dB to 24.6 dB on the two datasets. This enhancement is attributed to the alignment network's ability to refine the baseline DiR by aligning it with the degradation-free representation.", + "bbox": [ + 496, + 462, + 890, + 583 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/8e753a28cba95ec4c20f29a1a1a846488f67871a372304a1ee2a1fdefd97aea8.jpg", + "table_caption": [ + "Table 4. Results of image segmentation on the ADE20k [55]." + ], + "table_footnote": [], + "table_body": "
MethodSet14BSD100
r(0)A→rPSNR ↑LPIPS ↓PSNR ↑LPIPS ↓
✓XX22.40.35923.80.379
✓✓X23.90.24324.60.313
✓✓✓24.10.22825.00.288
Auto-Encoder21.60.37823.10.408
", + "bbox": [ + 521, + 585, + 867, + 674 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 5. Ablation studies on each module in DiR learning.", + "bbox": [ + 521, + 676, + 867, + 691 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 694, + 617, + 709 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This paper presents a novel method of learning degradation-independent representations for ISP-degraded images. In the proposed method, we devise a DiRNet to learn baseline DiR representations from diverse ISP-degraded observations in a self-supervised learning manner, ensuring adaptability to various degradation scenarios. Furthermore, we employ a guided alignment network to refine the baseline DiRs by aligning them with latent degradation-free representations. Our proposed approach demonstrates superior performance and scalability, as validated by extensive empirical results from synthetic and real-world datasets across various downstream applications.", + "bbox": [ + 496, + 719, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "25781", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Eirikur Agustsson and Radu Timofte. Ntire 2017 challenge on single image super-resolution: Dataset and study. In The IEEE Conference on Computer Vision and Pattern Recognition (CVPR) Workshops, July 2017. 6", + "[2] Chen Chen, Qifeng Chen, Jia Xu, and Vladlen Koltun. Learning to see in the dark. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 5122-5130, 2017. 6, 8" + ], + "bbox": [ + 503, + 92, + 893, + 890 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "25783", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_model.json b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_model.json new file mode 100644 index 0000000000000000000000000000000000000000..88a1bc2f3996d3a0d6ddae792f01b5098b363316 --- /dev/null +++ b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_model.json @@ -0,0 +1,2310 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.092, + 0.131, + 0.88, + 0.154 + ], + "angle": 0, + "content": "Learning Degradation-Independent Representations for Camera ISP Pipelines" + }, + { + "type": "text", + "bbox": [ + 0.092, + 0.181, + 0.331, + 0.234 + ], + "angle": 0, + "content": "Yanhui Guo* \nMcMaster University, Canada \nguoy143@mcmaster.ca" + }, + { + "type": "text", + "bbox": [ + 0.366, + 0.182, + 0.605, + 0.234 + ], + "angle": 0, + "content": "Fangzhou Luo* \nMcMaster University, Canada \nluof1@mcmaster.ca" + }, + { + "type": "text", + "bbox": [ + 0.64, + 0.181, + 0.879, + 0.234 + ], + "angle": 0, + "content": "Xiaolin Wu† \nMcMaster University, Canada \nxwu@mcmaster.ca" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.301, + 0.474, + 0.619 + ], + "angle": 0, + "content": "Image signal processing (ISP) pipeline plays a fundamental role in digital cameras, which converts raw Bayer sensor data to RGB images. However, ISP-generated images usually suffer from imperfections due to the compounded degradations that stem from sensor noises, demosaicing noises, compression artifacts, and possibly adverse effects of erroneous ISP hyperparameter settings such as ISO and gamma values. In a general sense, these ISP imperfections can be considered as degradations. The highly complex mechanisms of ISP degradations, some of which are even unknown, pose great challenges to the generalization capability of deep neural networks (DNN) for image restoration and to their adaptability to downstream tasks. To tackle the issues, we propose a novel DNN approach to learn degradation-independent representations (DiR) through the refinement of a self-supervised learned baseline representation. The proposed DiR learning technique has remarkable domain generalization capability and consequently, it outperforms state-of-the-art methods across various downstream tasks, including blind image restoration, object detection, and instance segmentation, as verified in our experiments." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.646, + 0.21, + 0.661 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.671, + 0.471, + 0.821 + ], + "angle": 0, + "content": "In our information era, digital cameras have become ubiquitous and indispensable in all walks of socioeconomic life. They are arguably the most common type of sensory device for both humans and their intelligent agents to sense the environment. The applications of digital imaging fall into two categories depending on their end purposes: human vision oriented and machine vision oriented. Examples of the first category include smartphones, social media, internet videos, etc., while robotics, automation, and medical imaging are examples of the second category." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.822, + 0.471, + 0.868 + ], + "angle": 0, + "content": "For human vision oriented applications, the image quality metrics should correspond to human visual perception, because the images are primarily intended to please our" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.27, + 0.895, + 0.362 + ], + "angle": 0, + "content": "eyes. On the other hand, for machine vision oriented applications [18, 19, 40, 49], the image quality requirements may not completely align with those of human perception. In the latter case, what matters most is the preservation of semantically critical image features that are needed to solve computer vision problems of recognition and classification." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.367, + 0.895, + 0.655 + ], + "angle": 0, + "content": "For either human viewing or downstream computer vision tasks, the image acquisition process of digital cameras is the same. All images are generated by a hardware image signal processing (ISP) pipeline that transforms raw Bayer sensor data into RGB images. The ISP pipeline consists of a set of cascaded steps, including denoising, color demosaicking, and compression. Each of the ISP steps can cause a level of degradation in image quality. At the beginning of the ISP pipeline, there are sensor noises, particularly in dark environments with a low signal-to-noise ratio. The noisy RAW data are then demosaiced to produce the corresponding RGB images. This demosaicking process introduces interpolation noises of its own. Finally, the RGB image is compressed for bandwidth efficiency, which adds extra compression noises on top of sensor noises and demosaicking noises. The resulting compound effects of these cascaded noises are very difficult to model precisely [11]. The underlying complex image quality degradation mechanism prevents the synthesis of clean and degraded image pairs for supervised learning." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.897, + 0.902 + ], + "angle": 0, + "content": "Yet, there is another type of ISP degradation that exerts adverse effects on the applications of ISP-generated images in downstream tasks. The camera ISP involves a number of adjustable hyperparameters such as gamma correction, ISO, gain control, and white balance. Their optimal settings may vary from application to application, i.e., there exists no one-fits-all solution. Most cameras have a default hyperparameter setting that is tailored to perceptual quality rather than optimized for a specific computer vision task. We consider the deviations of ISP hyperparameters from their optimal settings, in a general sense, to be degradations as well. This second type of ISP degradation can lead to underperformances or even outright failures of downstream computer vision algorithms [32, 38]. Like the first type of signal-level degradations, the second type of semantic-level degradations is extremely difficult, if not impossible," + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.875, + 0.208, + 0.888 + ], + "angle": 0, + "content": "* Equal contribution." + }, + { + "type": "page_footnote", + "bbox": [ + 0.097, + 0.888, + 0.226, + 0.9 + ], + "angle": 0, + "content": "† Corresponding author." + }, + { + "type": "list", + "bbox": [ + 0.096, + 0.875, + 0.226, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25774" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.138 + ], + "angle": 0, + "content": "to model and synthesize, not only because the space of ISP hyperparameters is of very high dimensions but also because the two types of ISP degradations are intertwined." + }, + { + "type": "image", + "bbox": [ + 0.113, + 0.152, + 0.271, + 0.283 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.17, + 0.284, + 0.227, + 0.295 + ], + "angle": 0, + "content": "Canonical" + }, + { + "type": "image", + "bbox": [ + 0.274, + 0.152, + 0.438, + 0.284 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.337, + 0.285, + 0.367, + 0.295 + ], + "angle": 0, + "content": "Ours" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.306, + 0.47, + 0.334 + ], + "angle": 0, + "content": "Figure 1. Comparison of the canonical learning paradigm and our DiR learning technique." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.341, + 0.473, + 0.688 + ], + "angle": 0, + "content": "As discussed above, it is either intractable or highly expensive to obtain the ISP-degraded and the corresponding latent degradation-free (ground truth) image pairs. Moreover, exhausting all ISP degradation variants in a brute force way is impossible, many of which are not even known or understood [27, 28]. To meet these challenges, we introduce a notion of degradation-independent latent representation (DiR) that is robust against camera-captured non-ideal real-world images and propose a new deep neural network approach to learn the DiR. Fig. 1 illustrates the difference between our DiR learning paradigm and the canonical learning paradigm. Within the framework of our DiR learning, the learned DiR representations contain intrinsic information of the original degradation-free image and hence it is more general and robust with respect to unseen degradation types and severity when used in downstream computer vision and image processing tasks. The DiR learning, carried out by a deep neural network called DiRNet, is self-supervised, and the DiRNet is trained with two learning objectives: any two degraded images are mapped to the same DiR, and all DiRs are sampled from a normal distribution, which is learning a variational auto-encoder (VAE) by the multi-view mutual information (MMI) maximization[7, 15, 43]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.473, + 0.902 + ], + "angle": 0, + "content": "Moreover, we take advantage of known priors of the ISP workflow to synthesize original and degraded pairs, so that the above baseline DiR can be reinforced by an auxiliary self-supervised learning branch. This auxiliary branch learns the reference representation \\(\\mathbf{r}^*\\) of the degradation-free images, using high-quality images (surrogate ground truth). The baseline DiR result \\(\\mathbf{r}^{(0)}\\) is statistically aligned with the result \\(\\mathbf{r}^*\\) of the auxiliary branch by an alignment network module. This alignment module is trained using the aforementioned synthesized pairs and learns to align the baseline DiR \\(\\mathbf{r}^{(0)}\\) to the degradation-free representation reference (DfR) \\(\\mathbf{r}^*\\), yielding a refined DiR \\(\\mathbf{r}^+\\); finally, the refined DiR \\(\\mathbf{r}^+\\) is ready for being used in downstream tasks. Overall, the refined DiR benefits from the best of both self-supervised and supervised" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.892, + 0.122 + ], + "angle": 0, + "content": "learning, and strikes a good balance between the model's robustness and precision for applications." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.123, + 0.894, + 0.152 + ], + "angle": 0, + "content": "Our main contributions and key results can be summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.153, + 0.894, + 0.213 + ], + "angle": 0, + "content": "- A novel method is proposed for self-supervised learning of the DiR representation by multivariate mutual information maximization, which requires only degraded training images." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.214, + 0.892, + 0.258 + ], + "angle": 0, + "content": "- A joint learning approach is employed to refine the DiR representation for optimal performance in the targeted end-task network." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.259, + 0.894, + 0.319 + ], + "angle": 0, + "content": "- The versatility of the proposed methods across a wide range of tasks, including image restoration, object detection, and instance segmentation, is supported by ample empirical evidence." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.153, + 0.894, + 0.319 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.327, + 0.642, + 0.342 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.353, + 0.895, + 0.565 + ], + "angle": 0, + "content": "Degradation blind image restoration network There is a long history of research on image restoration tasks that are blind to degradation parameters, such as blind image deconvolution algorithms [23]. Accompanying the proliferation of deep learning based image restoration methods, recent years have seen a number of papers [9, 10, 12, 24, 26, 28, 36, 47] on the topic of improving the generalization ability of image restoration networks. Wang et al. [47] used a high-order degradation model to mimic real-world degradations. Luo et al. [28] proposed a novel adversarial neural degradation model to simulate degraded training data. Li et al. [24] introduced a distortion invariant representation learning paradigm from the causality perspective, to improve the generalization ability of restoration networks for unknown degradations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.567, + 0.895, + 0.869 + ], + "angle": 0, + "content": "End-to-end neural network solutions for ISP pipelines A more holistic design of neural networks [34, 41, 51] for image restoration is to replace the cascaded stages of the hardware ISP pipeline with a single end-to-end mapping from raw Bayer sensor data to the intended ideal RGB images, instead of postprocessing the output images of the camera ISP. For instance, Chen et al. [2] proposed a CNN method, called SID (see in the dark), which directly converts a low lighting noisy Bayer image to a corresponding properly exposed RGB image, without generating the underexposed ineligible RGB image first and then restoring it. Tseng et al. [44] leveraged a convolutional neural network to parameterize a differentiable mapping between the ISP configuration space and evaluation metrics of downstream tasks and validated their method on the tasks of object detection, and extreme low-light imaging. Yu et al. [52] replaced the conventional ISP with a trainable ISP framework that improves the quality of ISP-generated results by using a differential neural architecture search algorithm to search for the optimal ISP architecture and hyperparameters." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Image enhancement for high-level tasks In general practice, image restoration networks tend to be optimized for" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25775" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.473, + 0.328 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.1, + 0.339, + 0.446, + 0.354 + ], + "angle": 0, + "content": "Figure 2. Self-supervised MMI maximization for DiRNet." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.361, + 0.473, + 0.633 + ], + "angle": 0, + "content": "human visual perception rather than for computer vision tasks. However, the human vision-centric neural network may not provide optimal results on high-level computer vision tasks. This motivates the development of a family of image restoration networks that are tuned in line with the subsequent computer vision tasks, such as recognition, detection, and classification [4, 39, 52]. For example, Cui et al. [4] proposed a multitask auto-encoding transformation model to learn the intrinsic visual structure by considering the physical sensor noise model in ISP, demonstrating effectiveness for dark object detection. Mosleh et al. [32] investigated a so-called \"hardware-in-the-loop\" strategy to directly optimize the hyperparameters of hardware ISP pipelines, by solving a nonlinear multi-objective optimization problem with a 0th-order stochastic solver. Qin et al. [39] designed a sequential CNN model to recurrently adjust the ISP hyperparameters for downstream tasks and demonstrate the advantages of the model." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.647, + 0.185, + 0.664 + ], + "angle": 0, + "content": "3. Approach" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.672, + 0.471, + 0.807 + ], + "angle": 0, + "content": "In this section, we first detail the DiRNet mentioned in the introduction to learn the baseline \\(\\mathrm{DiR}\\mathbf{r}^{(0)}\\) of multiple degraded images. The DiRNet training is driven by the MMI maximization. Then, we discuss how to learn the degradation-free latent representation \\(\\mathbf{r}^*\\) using a variant of DiRNet. The two latent representations \\(\\mathbf{r}^{(0)}\\) and \\(\\mathbf{r}^*\\) are prepared to train an alignment network to produce a refined DiR \\(\\mathbf{r}^{+}\\). Finally, we elaborate on the process to jointly optimize the alignment network and an auxiliary network for a downstream task." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.817, + 0.45, + 0.833 + ], + "angle": 0, + "content": "3.1. Optimizing DiRNet by MMI Maximization" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.472, + 0.901 + ], + "angle": 0, + "content": "Mutual information maximization To begin, we pave the way for computing the multi-view mutual information (MMI) maximization by introducing a mutual information estimator. For estimating mutual information" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.273 + ], + "angle": 0, + "content": "\\(I(\\mathbf{x};\\mathbf{y})\\) of two random variables \\(\\mathbf{x}\\) and \\(\\mathbf{y}\\), it is equivalent to computing the Kullback-Leibler (KL) divergence \\(\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{x},\\mathbf{y})||p(\\mathbf{x})p(\\mathbf{y}))\\). However, the KL divergence has no theoretical upper bound. Maximizing it cannot guarantee the convergence of the optimization process. Following previous works [35, 45], we exploit a non-KL divergence named Jensen-Shannon divergence (JSD) to devise the lower bound of mutual information, which satisfies the below proposition. Proposition 1 Let \\(\\mathbf{x}\\) and \\(\\mathbf{y}\\) represent two random variables, the \\(\\mathbf{J} = p(\\mathbf{x},\\mathbf{y})\\) and \\(\\mathbf{M} = p(\\mathbf{x})p(\\mathbf{y})\\) are the joint and the product of marginals of the two variables, respectively. The mutual information between the variables satisfies1" + }, + { + "type": "equation", + "bbox": [ + 0.514, + 0.281, + 0.893, + 0.317 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} I (\\mathbf {x}; \\mathbf {y}) := \\mathcal {D} _ {\\mathrm {J S D}} (\\mathbf {J}; \\mathbf {M}) \\\\ \\geq \\mathbb {E} _ {z \\sim \\mathbf {J}} [ - \\sigma (- \\mathcal {F} _ {\\omega} (z)) ] - \\mathbb {E} _ {z ^ {\\prime} \\sim \\mathbf {M}} [ \\sigma (\\mathcal {F} _ {\\omega} (z ^ {\\prime})) ], \\tag {1} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.323, + 0.895, + 0.549 + ], + "angle": 0, + "content": "where \\(\\sigma(t) = \\log(1 + e^t)\\), and the discriminator function \\(\\mathcal{F}_{\\omega}\\) [35] is modeled by a neural network with parameters \\(\\omega\\). Multi-view mutual information maximization The baseline DiR \\(\\mathbf{r}^{(0)}\\) is a degradation-independent representation shared among all degraded images that originate from an ideal degradation-free image. From the perspective of information theory, the DiR representation should satisfy the criterion of shared information maximization between it and multiple degraded observations. This shared information maximization is so-called multi-view mutual information (MMI) maximization[7] a.k.a interaction information maximization [43] for the three variables. We state its definition as follows: Given two degraded images \\(\\mathbf{x}_1\\) and \\(\\mathbf{x}_2\\), their shared latent DiR \\(\\mathbf{r}^{(0)}\\) can be found by maximizing their MMI \\(I(\\mathbf{r}^{(0)}; \\mathbf{x}_1; \\mathbf{x}_2)\\) that is defined as" + }, + { + "type": "equation", + "bbox": [ + 0.541, + 0.555, + 0.892, + 0.614 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1}; \\mathbf {x} _ {2}\\right) = I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1}\\right) - \\underbrace {I \\left(\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {1} \\mid \\mathbf {x} _ {2}\\right)} _ {\\text {R e d u n d a n c y}} (2) \\\\ = I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {2}\\right) - I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {2} \\mid \\mathbf {x} _ {1}\\right), (3) \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.623, + 0.895, + 0.773 + ], + "angle": 0, + "content": "where Eq. (3) holds due to symmetry. The conditional mutual information \\( I(\\mathbf{r}^{(0)};\\mathbf{x}_1|\\mathbf{x}_2) \\) represents the incremental mutual information between \\( \\mathbf{r}^{(0)} \\) and the degraded observation \\( \\mathbf{x}_1 \\) when given another degraded observation \\( \\mathbf{x}_2 \\). This incremental information denotes the information not shared by the observations \\( \\mathbf{x}_1 \\) and \\( \\mathbf{x}_2 \\), due to the differences in various degradation sources, which should be minimized. Maximizing \\( I(\\mathbf{r}^{(0)};\\mathbf{x}_1;\\mathbf{x}_2) \\) encourages \\( \\mathbf{r}^{(0)} \\) to encode the degradation-independent information shared by the given multiple degraded images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.774, + 0.894, + 0.88 + ], + "angle": 0, + "content": "The network DiRNet for learning the baseline DiR is of VAE type [14]. The DiRNet takes the ISP-generated images (i.e. camera captured) as inputs and maps them into a canonical representation space i.e. the DiR latent space, by removing the degradation-specific information. Fig. 2 shows the training process for the DiRNet. To continue the development, we introduce the following proposition [15]:" + }, + { + "type": "page_footnote", + "bbox": [ + 0.518, + 0.887, + 0.882, + 0.9 + ], + "angle": 0, + "content": "1The derivation is in Sec.B and Sec.C of the supplementary material." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "25776" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.471, + 0.138 + ], + "angle": 0, + "content": "Proposition 2 Given two degraded images \\(\\mathbf{x}_1\\) and \\(\\mathbf{x}_2\\), and the baseline DiR representation \\(\\mathbf{r}^{(0)}\\), the conditional mutual information \\(I(\\mathbf{r}^{(0)};\\mathbf{x}_1|\\mathbf{x}_2)\\) satisfies:" + }, + { + "type": "equation", + "bbox": [ + 0.08, + 0.15, + 0.47, + 0.18 + ], + "angle": 0, + "content": "\\[\nI \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1} \\mid \\mathbf {x} _ {2}\\right) \\leq \\mathbb {E} _ {p \\left(\\mathbf {x} _ {1}, \\mathbf {x} _ {2}\\right)} \\left[ \\right. \\mathcal {D} _ {\\mathrm {K L}} \\left( \\right.p \\left(\\mathbf {r} ^ {(0)} \\mid \\mathbf {x} _ {1}, \\mathbf {x} _ {2}\\right)\\left. \\right\\lvert | p _ {\\varphi} \\left(\\mathbf {r} ^ {(0)} \\mid \\mathbf {x} _ {2}\\right)\\left. \\right)\\left. \\right]. \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.183, + 0.471, + 0.215 + ], + "angle": 0, + "content": "To maximize \\( I(\\mathbf{r}^{(0)};\\mathbf{x}_1;\\mathbf{x}_2) \\), the overall training objective of DiRNet is defined by the average of Eq. (2) and Eq. (3):" + }, + { + "type": "equation", + "bbox": [ + 0.152, + 0.238, + 0.47, + 0.318 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {0} = - \\frac {I (\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {1}) + I (\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {2})}{2} \\\\ + \\lambda \\mathbb {E} _ {p (\\mathbf {x} _ {1}, \\mathbf {x} _ {2})} [ \\mathcal {D} _ {\\mathrm {A K L}} ] \\\\ + \\beta \\mathcal {D} _ {\\mathrm {K L}} \\left[ p \\left(\\mathbf {r} ^ {(0)}\\right) | | \\mathcal {N} (0, \\mathbf {I}) \\right], \\tag {5} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.329, + 0.471, + 0.466 + ], + "angle": 0, + "content": "in which we can maximize the upper bound of the conditional mutual information according to Proposition 2. In Eq.(5), \\(\\lambda\\) and \\(\\beta\\) are the trade-off hyperparameters. The DiR representation is regularized by the Gaussian prior \\(\\mathcal{N}(0,\\mathbf{I})\\) as in VAE [14]. \\(\\mathcal{D}_{\\mathrm{AKL}}\\) stands for the average of \\(\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{r}^{(0)}|\\mathbf{x}_1,\\mathbf{x}_2)\\parallel p_\\varphi (\\mathbf{r}^{(0)}|\\mathbf{x}_1))\\) and \\(\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{r}^{(0)}|\\mathbf{x}_1,\\mathbf{x}_2)\\parallel p_\\varphi (\\mathbf{r}^{(0)}|\\mathbf{x}_2))\\). The trainable network is the DiRNet \\(p_{\\varphi}\\) that produces the baseline DiR and an auxiliary network to estimate the upper bound [15]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.476, + 0.452, + 0.492 + ], + "angle": 0, + "content": "3.2. Degradation-Free Representation Reference" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.5, + 0.471, + 0.711 + ], + "angle": 0, + "content": "Although the baseline DiR \\(\\mathbf{r}^{(0)}\\) aims to distill the degradation-invariant intrinsic elements and structures, it may have biases toward the degraded data because the learning process of \\(\\mathbf{r}^{(0)}\\) has not observed degradation-free samples. To compensate for this insufficiency, we collect a large set of high-quality RGB images and assume them to be free of degradation. As these images are captured by real non-idealistic cameras the degradation-free assumption is not strictly true, but it is acceptable for practical purposes. These degradation-free images are used to learn the degradation-free latent representation (DfR) \\(\\mathbf{r}^*\\); the above two latent representations \\(\\mathbf{r}^{(0)}\\) and \\(\\mathbf{r}^*\\) will be aligned to produce a refined DiR \\(\\mathbf{r}^+\\) by a so-called alignment network, whose construction and rationale will be discussed in Sec. 3.3." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.712, + 0.471, + 0.864 + ], + "angle": 0, + "content": "Similar to training DiRNet for the baseline \\(\\mathrm{DiR}\\mathbf{r}^{(0)}\\), we propose the DfRNet to learn the DfR \\(\\mathbf{r}^*\\) from a degradation-free image (surrogate ground truth). Since this DfR learning is with respect to a single image, the MMI training for \\(\\mathbf{r}^*\\) is simplified to the mutual information maximization i.e. maximizing \\(I(\\mathbf{r}^*;\\mathbf{y}^*)\\), which can be solved by maximizing the lower bound derived by Proposition 1. Moreover, following VAE [14], we train the decoder \\(D_{*}\\) that forces the learned DfR to be able to reconstruct the degradation-free image. The objective of the above DfR learning is to minimize \\(\\mathcal{L}_{*}\\)" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.625, + 0.105 + ], + "angle": 0, + "content": "defined as follows" + }, + { + "type": "equation", + "bbox": [ + 0.558, + 0.114, + 0.892, + 0.15 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {*} = - I \\left(\\mathbf {r} ^ {*}; \\mathbf {y} ^ {*}\\right) + \\mathbb {E} \\left[ \\left\\| D _ {*} \\left(\\mathbf {r} ^ {*}\\right) - \\mathbf {y} ^ {*} \\right\\| _ {1} \\right] \\\\ + \\beta^ {*} \\mathcal {D} _ {\\mathrm {K L}} [ p (\\mathbf {r} ^ {*}) | | \\mathcal {N} (0, \\mathbf {I}) ], \\tag {6} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.157, + 0.894, + 0.188 + ], + "angle": 0, + "content": "where \\(\\beta^{*}\\) is the trade-off hyperparameter. The defined training objective in Eq. (6) is the same as the InfoVAE [54]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.195, + 0.821, + 0.211 + ], + "angle": 0, + "content": "3.3. Alignment Network for Refined DiR" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.219, + 0.894, + 0.356 + ], + "angle": 0, + "content": "Alignment network As mentioned in the introduction, we can neutralize, to a certain extent, possible biases in the baseline DiR \\(\\mathbf{r}^{(0)}\\) by aligning \\(\\mathbf{r}^{(0)}\\) with the above DfR \\(\\mathbf{r}^*\\) in distribution. This is accomplished by a so-called alignment network \\(\\mathcal{A}\\). To guide the statistical alignment of \\(\\mathbf{r}^{(0)}\\) and \\(\\mathbf{r}^*\\), we also feed the degraded training image \\(\\mathbf{x}\\) to network DfR-Net and use the resulting latent representation \\(\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x})\\), called the pilot representation. This guided alignment process is a mapping function" + }, + { + "type": "equation", + "bbox": [ + 0.571, + 0.365, + 0.892, + 0.402 + ], + "angle": 0, + "content": "\\[\n\\mathcal {A} \\left(\\mathbf {r} ^ {(0)}, \\vec {\\mathbf {r}}\\right): \\mathbf {r} ^ {(0)} \\xrightarrow [ \\vec {\\mathbf {r}} = \\mathrm {D f R} (\\mathbf {x}) ]{\\text {G u i d e d b y} \\vec {\\mathbf {r}}} \\mathbf {r} ^ {+}. \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.41, + 0.894, + 0.441 + ], + "angle": 0, + "content": "Next, we describe the architecture of the alignment network \\(\\mathcal{A}\\) and discuss the role of the pilot representation \\(\\vec{\\mathbf{r}}\\)." + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.446, + 0.892, + 0.634 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.554, + 0.637, + 0.836, + 0.651 + ], + "angle": 0, + "content": "Figure 3. Illustration of the alignment network." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.654, + 0.894, + 0.776 + ], + "angle": 0, + "content": "Network structure Fig. 3 shows the network structure of the alignment network \\(\\mathcal{A}\\). It consists of three cascaded modules \\(\\mathcal{A}_1, \\mathcal{A}_2\\) and \\(\\mathcal{A}_3\\). The front module \\(\\mathcal{A}_1\\) of \\(m_1\\) convolution layers is used to extract the features from the input image. The middle module \\(\\mathcal{A}_2\\) of \\(m_2\\) layers is designed to modulate the latent features with the guidance of the pilot DfR \\(\\vec{\\mathbf{r}}\\). The end module \\(\\mathcal{A}_3\\) of \\(m_3\\) convolution layers is used to produce the final refined DiR \\(\\mathbf{r}^+\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.778, + 0.894, + 0.901 + ], + "angle": 0, + "content": "In the guidance module \\(\\mathcal{A}_2\\), \\(\\vec{\\mathbf{r}}\\) is fed to convolution layers with \\(3\\times 3\\) kernels, followed by the average pooling layer to obtain the modulation feature tensors. These modulation tensors are then reshaped to form \\(k\\) adaptive convolution kernels. We use a so-called G-Conv module formed by these adaptive convolution kernels to convolve with the input features to produce the guided features \\(f_{k}\\) which are embedded with the information of the pilot DfR \\(\\vec{\\mathbf{r}}\\). In addition," + }, + { + "type": "page_footnote", + "bbox": [ + 0.077, + 0.875, + 0.468, + 0.9 + ], + "angle": 0, + "content": "2The full derivation of \\(\\mathcal{L}_0\\) can be found in Sec.B of the supplementary material." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "25777" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.244 + ], + "angle": 0, + "content": "we exploit a spatial attention branch to assist the guidance information extraction. This attention branch predicts the attention maps to strengthen the feature units that have a high correlation to pilot DfR \\(\\vec{\\mathbf{r}}\\), yielding the attention-weighted intermediate features \\(f_{a}\\). Finally, the guided features \\(f_{k}\\) and the attention-weighted features \\(f_{a}\\) are fused by an addition layer to produce the refined DiR \\(\\mathbf{r}^{+}\\), which is ready for use in downstream tasks. In our experiments, we jointly train this alignment network \\(\\mathcal{A}\\) and a task-aligned auxiliary network \\(\\mathcal{T}\\), which will be introduced in Sec. 3.4." + }, + { + "type": "image", + "bbox": [ + 0.138, + 0.246, + 0.408, + 0.462 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.464, + 0.472, + 0.507 + ], + "angle": 0, + "content": "Figure 4. Visualization of the pilot DfR representations \\(\\vec{\\mathbf{r}}\\) and the expected DfR representations \\(\\mathbf{r}^*\\). The information provided by the pilot DfR can guide the alignment to find the optimal DfR." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.515, + 0.473, + 0.824 + ], + "angle": 0, + "content": "Discussion on the pilot DfR \\(\\vec{\\mathbf{r}}\\) To explain the rationale behind the guidance design of the alignment network, we conduct experiments for visualization. More specifically, we choose four different degradation-free images to extract their corresponding DfRs \\(\\mathbf{r}^*\\). We then use the ISP pipeline as in [39] by adding noise to generate 200 various degraded copies of each degradation-free image. These degraded samples, which share the same image content but have different ISP degradations, are fed into the network DfR to produce the pilot DfRs \\(\\mathbf{r}^*\\). Fig. 4 shows the visualized results by using t-SNE [46], where the red stars denote the expected ground truth DfRs \\(\\mathbf{r}^*\\) for the alignment network training, and the green stars stand for the pilot DfRs \\(\\vec{\\mathbf{r}}\\). We can observe that the green points are projected near the red points, suggesting that the pilot DfRs have a strong correlation with the ground truth DfRs. This is because the pilot DfRs and the ground truth DfRs share the same degradation-free content. Inspired by this phenomenon, the alignment network is designed to take into account the assistant information provided by \\(\\vec{\\mathbf{r}}\\) to guide the refinement of the baseline DiR." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.833, + 0.433, + 0.85 + ], + "angle": 0, + "content": "3.4. Joint Task-Aligned Refinement Learning" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.471, + 0.902 + ], + "angle": 0, + "content": "For training the alignment network, we simulate the Bayer RAW data from the degradation-free images \\(\\mathbf{y}^*\\) (surrogate ground truth) by using the inverse ISP [21]. These RAW data" + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.089, + 0.895, + 0.243 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.248, + 0.892, + 0.263 + ], + "angle": 0, + "content": "Figure 5. Illustration of the joint task-aligned refinement learning." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.269, + 0.895, + 0.405 + ], + "angle": 0, + "content": "are used to generate the degraded RGB images \\(\\mathbf{x}\\) with the ISP software tool [39]. Fig. 5 illustrates the joint task-aligned refinement learning process. The DiRNet and DfRNet are frozen to extract the paired representations \\((\\mathbf{r}^{(0)},\\mathbf{r}^{*})\\) from the paired degraded and degradation-free images \\((\\mathbf{x},\\mathbf{y}^{*})\\). The alignment network is driven by the pairs \\((\\mathbf{r}^{(0)},\\mathbf{r}^{*})\\) to learn the mapping function \\(\\mathcal{A}:\\mathbf{r}^{(0)}\\to \\mathbf{r}^{+}\\), where the final refined DiR \\(\\mathbf{r}^{+}\\) lies in the degradation-free latent representation space determined by the DfRNet." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.405, + 0.895, + 0.527 + ], + "angle": 0, + "content": "The paired images \\((\\mathbf{x},\\mathbf{y}^{*})\\) and the associated labels \\(\\tilde{\\mathbf{y}}\\) w.r.t. the downstream task are used to supervise the joint training of the alignment network \\(\\mathcal{A}\\) and the task-related auxiliary network \\(\\mathcal{T}\\). As the auxiliary network for the downstream task usually takes an RGB image as input, we adopt the decoder \\(D_{*}\\) trained for the DfRNet to reconstruct the RGB images from the refined DiRs \\(\\mathbf{r}^{+}\\). The joint training loss in the alignment phase is to minimize \\(\\mathcal{L}_{+}\\) defined as" + }, + { + "type": "equation", + "bbox": [ + 0.533, + 0.534, + 0.892, + 0.574 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {+} = \\mathbb {E} \\left[ \\| \\mathbf {r} ^ {+} - \\mathbf {r} ^ {*} \\| _ {1} \\right] + \\gamma_ {1} \\mathcal {L} _ {\\text {t a s k}} \\left(\\mathcal {T} \\left(D _ {*} (\\mathbf {r} ^ {+})\\right), \\tilde {\\mathbf {y}}\\right) \\\\ + \\gamma_ {2} \\mathbb {E} \\left[ \\| D _ {*} \\left(\\mathbf {r} ^ {+}\\right) - \\mathbf {y} ^ {*} \\| _ {1} \\right], \\tag {8} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.581, + 0.892, + 0.766 + ], + "angle": 0, + "content": "where \\(\\gamma_{1}\\) and \\(\\gamma_{2}\\) are the trade-off parameters, the DfR \\(\\mathbf{r}^{*} = \\mathrm{DfR}(\\mathbf{y}^{*})\\), and the refined DiR representation \\(\\mathbf{r}^{+} = \\mathcal{A}(\\mathbf{r}^{(0)},\\vec{\\mathbf{r}})\\), where \\(\\mathbf{r}^{(0)} = \\mathrm{DiR}(\\mathbf{x})\\) and \\(\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x})\\). The alignment network \\(\\mathcal{A}\\) and the auxiliary network \\(\\mathcal{T}\\) are jointly optimized, whereas the pretrained networks DiRNet and DfRNet as well as the decoder \\(D_{*}\\) are frozen. The second term \\(\\mathcal{L}_{\\mathrm{task}}\\) is a task-related loss for a downstream task, such as the cross-entropy for image segmentation. The third term is an image reconstruction loss that forces the refined DiR to inherit the complete information from the degradation-free image through the pixel-wise reconstruction restriction. We summarize the DiR learning process in Algorithm 1." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.778, + 0.634, + 0.795 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.802, + 0.718, + 0.818 + ], + "angle": 0, + "content": "4.1. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.895, + 0.902 + ], + "angle": 0, + "content": "Datasets and evaluation As previously introduced, DiR learning comprises two stages: Stage I, dedicated to training the DiRNet and DfRNet, and Stage II, where the alignment network \\(\\mathcal{A}\\) and the task-related auxiliary network \\(\\mathcal{T}\\) are jointly trained. For the training dataset, we adopt the" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25778" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.092, + 0.462, + 0.107 + ], + "angle": 0, + "content": "Algorithm 1 DiR Learning and Task-Aligned Refinement" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.111, + 0.47, + 0.145 + ], + "angle": 0, + "content": "Input: Degradation-free RAW image \\(\\mathbf{y}\\) and corresponding degradation-free RGB image \\(\\mathbf{y}^*\\), task-related label \\(\\tilde{\\mathbf{y}}\\) \nStage I:" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.145, + 0.141, + 0.156 + ], + "angle": 0, + "content": "1: repeat" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.157, + 0.469, + 0.179 + ], + "angle": 0, + "content": "2: Generate two images \\(\\mathbf{x}_1\\) and \\(\\mathbf{x}_2\\) from a degradation-free image \\(\\mathbf{y}\\) using two randomly sampled ISP degradations." + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.179, + 0.384, + 0.191 + ], + "angle": 0, + "content": "3: Train DiRNet using \\((\\mathbf{x}_1,\\mathbf{x}_2)\\) (min \\(\\mathcal{L}_0\\) in Eq.5" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.191, + 0.353, + 0.202 + ], + "angle": 0, + "content": "4: Train DfRNet using \\(\\mathbf{y}^*\\) (min \\(\\mathcal{L}_*\\) in Eq. (6))" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.203, + 0.351, + 0.224 + ], + "angle": 0, + "content": "5: until reaching the maximum number of epochs \nStage II:" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.225, + 0.114, + 0.235 + ], + "angle": 0, + "content": "6:re" + }, + { + "type": "text", + "bbox": [ + 0.084, + 0.236, + 0.47, + 0.258 + ], + "angle": 0, + "content": "7: Generate an image \\(\\mathbf{x}\\) from a degradation-free image \\(\\mathbf{y}\\) using randomly sampled ISP degradations." + }, + { + "type": "text", + "bbox": [ + 0.084, + 0.259, + 0.285, + 0.274 + ], + "angle": 0, + "content": "8: \\(\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x}),\\mathbf{r}^{*} = \\mathrm{DfR}(\\mathbf{y}^{*})\\)" + }, + { + "type": "text", + "bbox": [ + 0.084, + 0.274, + 0.221, + 0.288 + ], + "angle": 0, + "content": "9: \\(\\mathbf{r}^{+} = \\mathcal{A}(\\mathbf{r}^{(0)},\\vec{\\mathbf{r}})\\)" + }, + { + "type": "text", + "bbox": [ + 0.08, + 0.288, + 0.469, + 0.326 + ], + "angle": 0, + "content": "10: Train the alignment network \\(\\mathcal{A}\\) using the paired \\((\\mathbf{x},\\mathbf{r}^{*})\\) with the guidance of the pilot DfR \\(\\vec{\\mathbf{r}}\\), and jointly train the auxiliary \\(\\mathcal{T}\\) using the pairs of \\((D_{*}(\\mathbf{r}^{+}),\\tilde{\\mathbf{y}})\\) (min \\(\\mathcal{L}_{+}\\) in Eq. (8))" + }, + { + "type": "text", + "bbox": [ + 0.08, + 0.326, + 0.352, + 0.337 + ], + "angle": 0, + "content": "11: until reaching the maximum number of epochs" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.145, + 0.47, + 0.337 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.366, + 0.471, + 0.502 + ], + "angle": 0, + "content": "DIV2K dataset [1] and degrade the images by synthetic ISP degradations. To simulate ISP degradations, we begin by converting RGB images into RAW data by applying the reversed ISP model [21]. Subsequently, we employ a synthetic ISP pipeline [32, 39] with random parameters to generate degraded ISP-generated images from the simulated RAW data3. In Stage II, we employ the identical simulation process used in Stage I to synthesize ISP-degraded images and use the MS COCO dataset [25] for experiments." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.502, + 0.47, + 0.623 + ], + "angle": 0, + "content": "For evaluation, we test the proposed method on three downstream tasks, including 1) the image restoration experiments on real-world datasets including the PolyU-Real [50], NC12 [22], Nam [33], and DND\\(^4\\) [37] datasets, where the test images involve real complex ISP degradations, 2) the object detection experiments on the MS COCO [25] dataset, and 3) the image segmentation experiments on the MS COCO dataset and the ADE20k dataset [55]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.625, + 0.471, + 0.867 + ], + "angle": 0, + "content": "Training settings At Stage I, we randomly select the contrastive degraded pairs to enable the MMI maximization for the training of the DiRNet. For training the DfRNet, we follow the same setting as in [54], by setting the parameter \\(\\beta^{*} = 1\\) in Eq. (6). We adopt the encoder network of [17] as the architectures of the DiRNet and the DfRNet. During training, the learning rate is initially set to \\(10^{-4}\\) and reduced to \\(10^{-6}\\) after 200 epochs. At Stage II, we randomly form pairs of degraded and degradation-free RGB images for training the alignment network. The learning rate is initially set to \\(10^{-3}\\) and reduced to \\(10^{-6}\\) after 300 epochs. For the image restoration task, we set \\(\\gamma_{1} = 0\\), \\(\\gamma_{2} = 1\\), because the decoder \\(D_{*}\\) can serve as the auxiliary network for the RGB image reconstruction using the refined DiR \\(\\mathbf{r}^{+}\\). For the object detection and image segmentation tasks, the trade-off parameters are set to \\(\\gamma_{1} = 2\\), \\(\\gamma_{2} = 1\\) and \\(\\gamma_{1} = 5\\), \\(\\gamma_{2} = 1\\)," + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.122 + ], + "angle": 0, + "content": "respectively. The hyperparameters \\(m_{1}, m_{2}\\), and \\(m_{3}\\) in the alignment network are separately set to 4, 2, and 4." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.125, + 0.875, + 0.141 + ], + "angle": 0, + "content": "4.2. Results on ISP-Degraded Image Restoration" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.148, + 0.894, + 0.299 + ], + "angle": 0, + "content": "First, we present the experimental results of the proposed method and compare them with those of eight competing methods [5, 6, 8, 24, 36, 48, 53], on the restoration of ISP-degraded images. The task is to remove ISP artifacts caused by complex coupling of multiple degradation sources, including sensor noises, demosaicing noises, compression noises, and possibly adverse effects of incorrect settings of ISO and gamma correction. Here, like in all other image restoration methods for human viewers, our goal is to pursue the highest possible perceptual image quality." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.3, + 0.895, + 0.631 + ], + "angle": 0, + "content": "In Fig. 6 the reader can compare the visual quality of the DiR learning based restoration method against those of SOTA image restoration methods [6, 8, 24, 26, 36, 48, 53], on restoring real-world ISP-degraded images taken by four different cameras, whose true degradation models are unknown. We can observe that the proposed method succeeds in achieving its design goal of blind restoration, as it removes most of the ISP artifacts caused by unknown degradation sources. On the contrary, the competing methods fail to remove complex artifacts while preserving the sharpness and clarity of edges and textures. Table 1 reports the quantitative performance evaluation results. Since there is no ideal degradation-free ground truth, we adopt the non-reference image quality assessment methods, including NIQE [31], NRQM [29], and BIQA [42]. In agreement with the visual comparisons in Fig. 6, the proposed DiR method also outperforms the competitors in terms of all three metrics. Both subjective and objective evaluations demonstrate superior robustness of the proposed method when being applied to data unseen in the training, indicating that the DiR learning approach can distill degradation-free representations from ISP-degraded images, regardless of whether observed or not." + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.644, + 0.892, + 0.791 + ], + "angle": 0, + "content": "
MethodNIQE ↓ / NRQM ↑ / BIQA ↑
PolyU-RealNC12NamDND
BM3D [5]9.72/2.60/40.512.78/3.75/30.812.58/2.56/41.212.89/1.84/40.1
CBDNet [8]7.32/3.78/44.110.67/6.88/33.110.26/3.62/42.19.74/2.96/41.1
LIR [6]8.37/4.52/48.111.41/7.19/33.710.69/4.25/49.811.86/3.19/44.3
MPRNet [53]6.12/4.23/38.711.21/6.30/32.97.25/3.94/33.99.53/2.77/45.2
Uformer [48]6.25/3.96/37.410.54/6.05/31.27.92/3.62/34.69.58/2.72/45.1
SCPGab [26]8.71/3.25/41.111.75/3.93/31.910.60/3.25/40.79.80/2.53/42.0
DIL [24]7.28/4.10/41.810.88/6.52/30.89.11/3.59/40.87.86/3.72/44.7
SDAP [36]9.62/3.00/46.111.34/3.88/32.512.38/2.95/45.710.74/2.33/45.8
Ours6.57/4.91/51.99.06/7.41/34.48.96/4.64/53.68.62/3.59/46.9
" + }, + { + "type": "table_caption", + "bbox": [ + 0.502, + 0.796, + 0.888, + 0.811 + ], + "angle": 0, + "content": "Table 1. Quantitative results on real-world ISP-degraded images." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.818, + 0.75, + 0.833 + ], + "angle": 0, + "content": "4.3. Results on Object Detection" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Following [39], we utilize the MS COCO dataset [25] to evaluate our proposed method's performance on object detection. We compare our method with the SOTA neural ISP solvers [38, 39], which replace the conventional ISP pipeline" + }, + { + "type": "page_footnote", + "bbox": [ + 0.094, + 0.874, + 0.428, + 0.887 + ], + "angle": 0, + "content": "3Additional details can be found in the supplementary material" + }, + { + "type": "page_footnote", + "bbox": [ + 0.097, + 0.888, + 0.376, + 0.9 + ], + "angle": 0, + "content": "4We randomly select 500 images for the experiments" + }, + { + "type": "list", + "bbox": [ + 0.094, + 0.874, + 0.428, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25779" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.091, + 0.891, + 0.389 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.393, + 0.893, + 0.421 + ], + "angle": 0, + "content": "Figure 6. Qualitative comparison on real-world ISP-degraded images. The degraded images, from top to bottom, are from the real-world datasets PolyU-Real [50], NC12 [22], Nam [33], and DND [37]. Please zoom in for better visualization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.43, + 0.474, + 0.688 + ], + "angle": 0, + "content": "with end-to-end trained neural networks while considering the downstream task as their optimization objectives. Following the approach in [32, 39], we choose the ISP pipeline with default parameters as the baseline. Our method utilizes these ISP-generated results with default settings as inputs. For comparison, we adopt the pre-trained object detection model [40] for performance benchmarking, and we assess the results using the mean accuracy score (mAP) as the evaluation metric. The quantitative results are reported in Table 2. Our method demonstrates a significant improvement compared to the baseline and outperforms the SOTA solutions [38, 39]. The left side of Fig 7 illustrates the qualitative results. As a reference, we include the results produced by the expert-tuned ISP for visual comparison. We can observe that while the expert-tuned ISP can produce more visually appealing results aligned with human perception preferences, it is inferior to our method on the task of object detection." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.708, + 0.355, + 0.725 + ], + "angle": 0, + "content": "4.4. Results on Image Segmentation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.472, + 0.901 + ], + "angle": 0, + "content": "Similar to the object detection experiments, we adopt the MS COCO dataset [25] to evaluate the performance of image segmentation. We benchmark the performance using a pre-trained segmentation model [13] and report the results in Table 3. As shown, our method outperforms the SOTA method Attention-aware [38] by about \\(3.9\\%\\) on the \\(\\mathrm{mAP}@0.5\\). Quantitative results are shown on the right side of Fig 7. These results are in line with the observations in the object detection experiments. Our method consistently outperforms the expert-tuned ISP in achieving better segmentation results." + }, + { + "type": "table", + "bbox": [ + 0.524, + 0.429, + 0.867, + 0.545 + ], + "angle": 0, + "content": "
MethodsISP ModelmAP↑
0.50.750.5:0.95
Default ParamsISP [32]15.--
Blockwise-tuned [34]20.--
Hardware-tuned [32]39.--
Default ParamsISP [39]34.122.421.4
Attention-aware [38]61.044.141.0
Sequential-tuned [39]62.845.242.3
Ours63.946.443.3
" + }, + { + "type": "table_caption", + "bbox": [ + 0.55, + 0.548, + 0.84, + 0.561 + ], + "angle": 0, + "content": "Table 2. Quantitative results on object detection." + }, + { + "type": "table", + "bbox": [ + 0.524, + 0.563, + 0.867, + 0.67 + ], + "angle": 0, + "content": "
MethodsISP ModelmAP↑
0.50.750.5:0.95
Default ParamsISP [32]12.--
Hardware-tuned [32]32.--
Default ParamsISP [39]22.713.212.0
Attention-aware [38]52.333.431.5
Sequential-tuned [39]54.235.132.6
Ours56.337.134.8
" + }, + { + "type": "table_caption", + "bbox": [ + 0.538, + 0.671, + 0.851, + 0.685 + ], + "angle": 0, + "content": "Table 3. Quantitative results on image segmentation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.69, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Additionally, we conduct experiments to evaluate the performance of the proposed method in low signal-to-noise ratio situations, such as dark environments where the noise level is very high. To mimic the degradations, we increase the noise level in the aforementioned synthetic ISP pipeline by adding Gaussian noise with the standard deviation \\(\\sigma\\) randomly sampled between the range of [0.15, 0.35] and the Poisson noise with the magnitude \\(\\lambda\\) randomly sampled between the range of [0.02, 0.04]. We compare the proposed DiR learning based method with the SOTA methods [16, 20] for ISP degradation removal and present the results in Table 4. To evaluate performance, we use two pretrained segmentation models, including DeeplabV3 [3] and SegFormer [49]. We observe that our method outperforms all" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25780" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.098, + 0.089, + 0.478, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.481, + 0.089, + 0.868, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.411, + 0.895, + 0.455 + ], + "angle": 0, + "content": "Figure 7. We evaluate different ISP-generated images for the tasks of object detection (left) and instance segmentation (right) on the COCO dataset. From top to bottom, we show the results from the images generated by default ISP hyperparameters, expert-tuned ISP hyperparameters, and the refined DiR with the proposed method. The proposed method achieves better performance for downstream tasks." + }, + { + "type": "table", + "bbox": [ + 0.083, + 0.461, + 0.465, + 0.537 + ], + "angle": 0, + "content": "
MethodsDeeplabV3 [3]SegFormer [49]
aAcc↑mIoU↑mAcc↑aAcc↑mIoU↑mAcc↑
Default ISP64.822.628.974.836.945.1
PyNET [16]67.725.131.574.337.445.8
DNF [20]71.429.636.975.437.846.2
Ours75.534.644.579.742.452.9
" + }, + { + "type": "table_caption", + "bbox": [ + 0.09, + 0.54, + 0.455, + 0.555 + ], + "angle": 0, + "content": "Table 4. Results of image segmentation on the ADE20k [55]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.56, + 0.472, + 0.606 + ], + "angle": 0, + "content": "the competitors. For example, compared to the DNF [20], our method increases the mAcc by \\(7.6\\%\\) and \\(6.7\\%\\) when using the DeeplabV3 and SegFormer models, respectively." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.618, + 0.231, + 0.635 + ], + "angle": 0, + "content": "4.5. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.642, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Ablation studies are conducted to assess the effectiveness of the proposed components: the baseline \\(\\mathrm{DiR}\\mathbf{r}^{(0)}\\), the alignment network \\(\\mathcal{A}\\), and the pilot DfR \\(\\vec{\\mathbf{r}}\\). For experiments, we apply the synthetic ISP process as described in [39] to generate ISP-degraded test images using the Set14 and BSD100 [30] datasets. To simulate degradation, we introduce noise into the synthetic ISP process. The added noise includes random Gaussian noise with a standard deviation ranging from 0.05 to 0.1 and JPEG compression noise with a quality factor randomly chosen in the range [10, 30]. As a reference, we train an auto-encoder model, labeled as \"Auto-Encoder\". This model adopts the same encoder architecture as DiR-Net and the same decoder architecture as \\(D_{*}\\). The training process of this auto-encoder model follows the canonical paradigm, i.e., it learns a direct mapping from degraded images to their degradation-free counterparts. Table 5 shows comparisons: when excluding the pilot DfR (2nd row) from" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.463, + 0.892, + 0.584 + ], + "angle": 0, + "content": "the complete DiR learning technique (3rd row), we observe a decrease in PSNR by 0.2 dB and 0.4 dB for the Set14 and BSD100 datasets. In comparison to using only the baseline DiR, the inclusion of the alignment network \\(\\mathcal{A}\\) leads to a PSNR improvement from 22.4 dB to 23.9 dB and 23.8 dB to 24.6 dB on the two datasets. This enhancement is attributed to the alignment network's ability to refine the baseline DiR by aligning it with the degradation-free representation." + }, + { + "type": "table", + "bbox": [ + 0.522, + 0.587, + 0.868, + 0.675 + ], + "angle": 0, + "content": "
MethodSet14BSD100
r(0)A→rPSNR ↑LPIPS ↓PSNR ↑LPIPS ↓
✓XX22.40.35923.80.379
✓✓X23.90.24324.60.313
✓✓✓24.10.22825.00.288
Auto-Encoder21.60.37823.10.408
" + }, + { + "type": "table_caption", + "bbox": [ + 0.522, + 0.678, + 0.868, + 0.692 + ], + "angle": 0, + "content": "Table 5. Ablation studies on each module in DiR learning." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.695, + 0.619, + 0.71 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.901 + ], + "angle": 0, + "content": "This paper presents a novel method of learning degradation-independent representations for ISP-degraded images. In the proposed method, we devise a DiRNet to learn baseline DiR representations from diverse ISP-degraded observations in a self-supervised learning manner, ensuring adaptability to various degradation scenarios. Furthermore, we employ a guided alignment network to refine the baseline DiRs by aligning them with latent degradation-free representations. Our proposed approach demonstrates superior performance and scalability, as validated by extensive empirical results from synthetic and real-world datasets across various downstream applications." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.946, + 0.518, + 0.957 + ], + "angle": 0, + "content": "25781" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.17 + ], + "angle": 0, + "content": "[1] Eirikur Agustsson and Radu Timofte. Ntire 2017 challenge on single image super-resolution: Dataset and study. In The IEEE Conference on Computer Vision and Pattern Recognition (CVPR) Workshops, July 2017. 6" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.17, + 0.472, + 0.224 + ], + "angle": 0, + "content": "[2] Chen Chen, Qifeng Chen, Jia Xu, and Vladlen Koltun. Learning to see in the dark. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 5122-5130, 2017. 6, 8" + }, + { + "type": "list", + "bbox": [ + 0.504, + 0.093, + 0.894, + 0.891 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25783" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_origin.pdf b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..e59938d1e6d279c09534911470ef1de77fe24cec --- /dev/null +++ b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/9184b776-09c8-4040-9313-78bc29f34068_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:7e0f65be3a50608f3cf8d27d8ab0fd368a96bb075b5bc1a4c8f67aa790a73a6c +size 7939600 diff --git a/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/full.md b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/full.md new file mode 100644 index 0000000000000000000000000000000000000000..c9d8e2a07d242d07ffeb81e3143bd8a6ae494564 --- /dev/null +++ b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/full.md @@ -0,0 +1,310 @@ +# Learning Degradation-Independent Representations for Camera ISP Pipelines + +Yanhui Guo* +McMaster University, Canada +guoy143@mcmaster.ca + +Fangzhou Luo* +McMaster University, Canada +luof1@mcmaster.ca + +Xiaolin Wu† +McMaster University, Canada +xwu@mcmaster.ca + +# Abstract + +Image signal processing (ISP) pipeline plays a fundamental role in digital cameras, which converts raw Bayer sensor data to RGB images. However, ISP-generated images usually suffer from imperfections due to the compounded degradations that stem from sensor noises, demosaicing noises, compression artifacts, and possibly adverse effects of erroneous ISP hyperparameter settings such as ISO and gamma values. In a general sense, these ISP imperfections can be considered as degradations. The highly complex mechanisms of ISP degradations, some of which are even unknown, pose great challenges to the generalization capability of deep neural networks (DNN) for image restoration and to their adaptability to downstream tasks. To tackle the issues, we propose a novel DNN approach to learn degradation-independent representations (DiR) through the refinement of a self-supervised learned baseline representation. The proposed DiR learning technique has remarkable domain generalization capability and consequently, it outperforms state-of-the-art methods across various downstream tasks, including blind image restoration, object detection, and instance segmentation, as verified in our experiments. + +# 1. Introduction + +In our information era, digital cameras have become ubiquitous and indispensable in all walks of socioeconomic life. They are arguably the most common type of sensory device for both humans and their intelligent agents to sense the environment. The applications of digital imaging fall into two categories depending on their end purposes: human vision oriented and machine vision oriented. Examples of the first category include smartphones, social media, internet videos, etc., while robotics, automation, and medical imaging are examples of the second category. + +For human vision oriented applications, the image quality metrics should correspond to human visual perception, because the images are primarily intended to please our + +eyes. On the other hand, for machine vision oriented applications [18, 19, 40, 49], the image quality requirements may not completely align with those of human perception. In the latter case, what matters most is the preservation of semantically critical image features that are needed to solve computer vision problems of recognition and classification. + +For either human viewing or downstream computer vision tasks, the image acquisition process of digital cameras is the same. All images are generated by a hardware image signal processing (ISP) pipeline that transforms raw Bayer sensor data into RGB images. The ISP pipeline consists of a set of cascaded steps, including denoising, color demosaicking, and compression. Each of the ISP steps can cause a level of degradation in image quality. At the beginning of the ISP pipeline, there are sensor noises, particularly in dark environments with a low signal-to-noise ratio. The noisy RAW data are then demosaiced to produce the corresponding RGB images. This demosaicking process introduces interpolation noises of its own. Finally, the RGB image is compressed for bandwidth efficiency, which adds extra compression noises on top of sensor noises and demosaicking noises. The resulting compound effects of these cascaded noises are very difficult to model precisely [11]. The underlying complex image quality degradation mechanism prevents the synthesis of clean and degraded image pairs for supervised learning. + +Yet, there is another type of ISP degradation that exerts adverse effects on the applications of ISP-generated images in downstream tasks. The camera ISP involves a number of adjustable hyperparameters such as gamma correction, ISO, gain control, and white balance. Their optimal settings may vary from application to application, i.e., there exists no one-fits-all solution. Most cameras have a default hyperparameter setting that is tailored to perceptual quality rather than optimized for a specific computer vision task. We consider the deviations of ISP hyperparameters from their optimal settings, in a general sense, to be degradations as well. This second type of ISP degradation can lead to underperformances or even outright failures of downstream computer vision algorithms [32, 38]. Like the first type of signal-level degradations, the second type of semantic-level degradations is extremely difficult, if not impossible, + +to model and synthesize, not only because the space of ISP hyperparameters is of very high dimensions but also because the two types of ISP degradations are intertwined. + +![](images/e456d7c2f496f03a50796fe28ecd3173fc1232a3d34a1b20d5befd2e2e2335d2.jpg) +Canonical +Figure 1. Comparison of the canonical learning paradigm and our DiR learning technique. + +![](images/e377d5ec4af4ba88fe20daf50ceb9fc741a559400f9faa20bbbff07cf079ac00.jpg) +Ours + +As discussed above, it is either intractable or highly expensive to obtain the ISP-degraded and the corresponding latent degradation-free (ground truth) image pairs. Moreover, exhausting all ISP degradation variants in a brute force way is impossible, many of which are not even known or understood [27, 28]. To meet these challenges, we introduce a notion of degradation-independent latent representation (DiR) that is robust against camera-captured non-ideal real-world images and propose a new deep neural network approach to learn the DiR. Fig. 1 illustrates the difference between our DiR learning paradigm and the canonical learning paradigm. Within the framework of our DiR learning, the learned DiR representations contain intrinsic information of the original degradation-free image and hence it is more general and robust with respect to unseen degradation types and severity when used in downstream computer vision and image processing tasks. The DiR learning, carried out by a deep neural network called DiRNet, is self-supervised, and the DiRNet is trained with two learning objectives: any two degraded images are mapped to the same DiR, and all DiRs are sampled from a normal distribution, which is learning a variational auto-encoder (VAE) by the multi-view mutual information (MMI) maximization[7, 15, 43]. + +Moreover, we take advantage of known priors of the ISP workflow to synthesize original and degraded pairs, so that the above baseline DiR can be reinforced by an auxiliary self-supervised learning branch. This auxiliary branch learns the reference representation $\mathbf{r}^*$ of the degradation-free images, using high-quality images (surrogate ground truth). The baseline DiR result $\mathbf{r}^{(0)}$ is statistically aligned with the result $\mathbf{r}^*$ of the auxiliary branch by an alignment network module. This alignment module is trained using the aforementioned synthesized pairs and learns to align the baseline DiR $\mathbf{r}^{(0)}$ to the degradation-free representation reference (DfR) $\mathbf{r}^*$ , yielding a refined DiR $\mathbf{r}^+$ ; finally, the refined DiR $\mathbf{r}^+$ is ready for being used in downstream tasks. Overall, the refined DiR benefits from the best of both self-supervised and supervised + +learning, and strikes a good balance between the model's robustness and precision for applications. + +Our main contributions and key results can be summarized as follows: + +- A novel method is proposed for self-supervised learning of the DiR representation by multivariate mutual information maximization, which requires only degraded training images. +- A joint learning approach is employed to refine the DiR representation for optimal performance in the targeted end-task network. +- The versatility of the proposed methods across a wide range of tasks, including image restoration, object detection, and instance segmentation, is supported by ample empirical evidence. + +# 2. Related Work + +Degradation blind image restoration network There is a long history of research on image restoration tasks that are blind to degradation parameters, such as blind image deconvolution algorithms [23]. Accompanying the proliferation of deep learning based image restoration methods, recent years have seen a number of papers [9, 10, 12, 24, 26, 28, 36, 47] on the topic of improving the generalization ability of image restoration networks. Wang et al. [47] used a high-order degradation model to mimic real-world degradations. Luo et al. [28] proposed a novel adversarial neural degradation model to simulate degraded training data. Li et al. [24] introduced a distortion invariant representation learning paradigm from the causality perspective, to improve the generalization ability of restoration networks for unknown degradations. + +End-to-end neural network solutions for ISP pipelines A more holistic design of neural networks [34, 41, 51] for image restoration is to replace the cascaded stages of the hardware ISP pipeline with a single end-to-end mapping from raw Bayer sensor data to the intended ideal RGB images, instead of postprocessing the output images of the camera ISP. For instance, Chen et al. [2] proposed a CNN method, called SID (see in the dark), which directly converts a low lighting noisy Bayer image to a corresponding properly exposed RGB image, without generating the underexposed ineligible RGB image first and then restoring it. Tseng et al. [44] leveraged a convolutional neural network to parameterize a differentiable mapping between the ISP configuration space and evaluation metrics of downstream tasks and validated their method on the tasks of object detection, and extreme low-light imaging. Yu et al. [52] replaced the conventional ISP with a trainable ISP framework that improves the quality of ISP-generated results by using a differential neural architecture search algorithm to search for the optimal ISP architecture and hyperparameters. + +Image enhancement for high-level tasks In general practice, image restoration networks tend to be optimized for + +![](images/2669202ed069507a51e3d8c39267519c4d07a7bf0680f26b2540b89f5c05f809.jpg) +Figure 2. Self-supervised MMI maximization for DiRNet. + +human visual perception rather than for computer vision tasks. However, the human vision-centric neural network may not provide optimal results on high-level computer vision tasks. This motivates the development of a family of image restoration networks that are tuned in line with the subsequent computer vision tasks, such as recognition, detection, and classification [4, 39, 52]. For example, Cui et al. [4] proposed a multitask auto-encoding transformation model to learn the intrinsic visual structure by considering the physical sensor noise model in ISP, demonstrating effectiveness for dark object detection. Mosleh et al. [32] investigated a so-called "hardware-in-the-loop" strategy to directly optimize the hyperparameters of hardware ISP pipelines, by solving a nonlinear multi-objective optimization problem with a 0th-order stochastic solver. Qin et al. [39] designed a sequential CNN model to recurrently adjust the ISP hyperparameters for downstream tasks and demonstrate the advantages of the model. + +# 3. Approach + +In this section, we first detail the DiRNet mentioned in the introduction to learn the baseline $\mathrm{DiR}\mathbf{r}^{(0)}$ of multiple degraded images. The DiRNet training is driven by the MMI maximization. Then, we discuss how to learn the degradation-free latent representation $\mathbf{r}^*$ using a variant of DiRNet. The two latent representations $\mathbf{r}^{(0)}$ and $\mathbf{r}^*$ are prepared to train an alignment network to produce a refined DiR $\mathbf{r}^{+}$ . Finally, we elaborate on the process to jointly optimize the alignment network and an auxiliary network for a downstream task. + +# 3.1. Optimizing DiRNet by MMI Maximization + +Mutual information maximization To begin, we pave the way for computing the multi-view mutual information (MMI) maximization by introducing a mutual information estimator. For estimating mutual information + +$I(\mathbf{x};\mathbf{y})$ of two random variables $\mathbf{x}$ and $\mathbf{y}$ , it is equivalent to computing the Kullback-Leibler (KL) divergence $\mathcal{D}_{\mathrm{KL}}(p(\mathbf{x},\mathbf{y})||p(\mathbf{x})p(\mathbf{y}))$ . However, the KL divergence has no theoretical upper bound. Maximizing it cannot guarantee the convergence of the optimization process. Following previous works [35, 45], we exploit a non-KL divergence named Jensen-Shannon divergence (JSD) to devise the lower bound of mutual information, which satisfies the below proposition. Proposition 1 Let $\mathbf{x}$ and $\mathbf{y}$ represent two random variables, the $\mathbf{J} = p(\mathbf{x},\mathbf{y})$ and $\mathbf{M} = p(\mathbf{x})p(\mathbf{y})$ are the joint and the product of marginals of the two variables, respectively. The mutual information between the variables satisfies1 + +$$ +\begin{array}{l} I (\mathbf {x}; \mathbf {y}) := \mathcal {D} _ {\mathrm {J S D}} (\mathbf {J}; \mathbf {M}) \\ \geq \mathbb {E} _ {z \sim \mathbf {J}} [ - \sigma (- \mathcal {F} _ {\omega} (z)) ] - \mathbb {E} _ {z ^ {\prime} \sim \mathbf {M}} [ \sigma (\mathcal {F} _ {\omega} (z ^ {\prime})) ], \tag {1} \\ \end{array} +$$ + +where $\sigma(t) = \log(1 + e^t)$ , and the discriminator function $\mathcal{F}_{\omega}$ [35] is modeled by a neural network with parameters $\omega$ . Multi-view mutual information maximization The baseline DiR $\mathbf{r}^{(0)}$ is a degradation-independent representation shared among all degraded images that originate from an ideal degradation-free image. From the perspective of information theory, the DiR representation should satisfy the criterion of shared information maximization between it and multiple degraded observations. This shared information maximization is so-called multi-view mutual information (MMI) maximization[7] a.k.a interaction information maximization [43] for the three variables. We state its definition as follows: Given two degraded images $\mathbf{x}_1$ and $\mathbf{x}_2$ , their shared latent DiR $\mathbf{r}^{(0)}$ can be found by maximizing their MMI $I(\mathbf{r}^{(0)}; \mathbf{x}_1; \mathbf{x}_2)$ that is defined as + +$$ +\begin{array}{l} I \left(\mathbf {r} ^ {(0)}; \mathbf {x} _ {1}; \mathbf {x} _ {2}\right) = I \left(\mathbf {r} ^ {(0)}; \mathbf {x} _ {1}\right) - \underbrace {I \left(\mathbf {r} ^ {(0)} ; \mathbf {x} _ {1} \mid \mathbf {x} _ {2}\right)} _ {\text {R e d u n d a n c y}} (2) \\ = I \left(\mathbf {r} ^ {(0)}; \mathbf {x} _ {2}\right) - I \left(\mathbf {r} ^ {(0)}; \mathbf {x} _ {2} \mid \mathbf {x} _ {1}\right), (3) \\ \end{array} +$$ + +where Eq. (3) holds due to symmetry. The conditional mutual information $I(\mathbf{r}^{(0)};\mathbf{x}_1|\mathbf{x}_2)$ represents the incremental mutual information between $\mathbf{r}^{(0)}$ and the degraded observation $\mathbf{x}_1$ when given another degraded observation $\mathbf{x}_2$ . This incremental information denotes the information not shared by the observations $\mathbf{x}_1$ and $\mathbf{x}_2$ , due to the differences in various degradation sources, which should be minimized. Maximizing $I(\mathbf{r}^{(0)};\mathbf{x}_1;\mathbf{x}_2)$ encourages $\mathbf{r}^{(0)}$ to encode the degradation-independent information shared by the given multiple degraded images. + +The network DiRNet for learning the baseline DiR is of VAE type [14]. The DiRNet takes the ISP-generated images (i.e. camera captured) as inputs and maps them into a canonical representation space i.e. the DiR latent space, by removing the degradation-specific information. Fig. 2 shows the training process for the DiRNet. To continue the development, we introduce the following proposition [15]: + +Proposition 2 Given two degraded images $\mathbf{x}_1$ and $\mathbf{x}_2$ , and the baseline DiR representation $\mathbf{r}^{(0)}$ , the conditional mutual information $I(\mathbf{r}^{(0)};\mathbf{x}_1|\mathbf{x}_2)$ satisfies: + +$$ +I \left(\mathbf {r} ^ {(0)}; \mathbf {x} _ {1} \mid \mathbf {x} _ {2}\right) \leq \mathbb {E} _ {p \left(\mathbf {x} _ {1}, \mathbf {x} _ {2}\right)} \left[ \right. \mathcal {D} _ {\mathrm {K L}} \left( \right.p \left(\mathbf {r} ^ {(0)} \mid \mathbf {x} _ {1}, \mathbf {x} _ {2}\right)\left. \right\lvert | p _ {\varphi} \left(\mathbf {r} ^ {(0)} \mid \mathbf {x} _ {2}\right)\left. \right)\left. \right]. \tag {4} +$$ + +To maximize $I(\mathbf{r}^{(0)};\mathbf{x}_1;\mathbf{x}_2)$ , the overall training objective of DiRNet is defined by the average of Eq. (2) and Eq. (3): + +$$ +\begin{array}{l} \mathcal {L} _ {0} = - \frac {I (\mathbf {r} ^ {(0)} ; \mathbf {x} _ {1}) + I (\mathbf {r} ^ {(0)} ; \mathbf {x} _ {2})}{2} \\ + \lambda \mathbb {E} _ {p (\mathbf {x} _ {1}, \mathbf {x} _ {2})} [ \mathcal {D} _ {\mathrm {A K L}} ] \\ + \beta \mathcal {D} _ {\mathrm {K L}} \left[ p \left(\mathbf {r} ^ {(0)}\right) | | \mathcal {N} (0, \mathbf {I}) \right], \tag {5} \\ \end{array} +$$ + +in which we can maximize the upper bound of the conditional mutual information according to Proposition 2. In Eq.(5), $\lambda$ and $\beta$ are the trade-off hyperparameters. The DiR representation is regularized by the Gaussian prior $\mathcal{N}(0,\mathbf{I})$ as in VAE [14]. $\mathcal{D}_{\mathrm{AKL}}$ stands for the average of $\mathcal{D}_{\mathrm{KL}}(p(\mathbf{r}^{(0)}|\mathbf{x}_1,\mathbf{x}_2)\parallel p_\varphi (\mathbf{r}^{(0)}|\mathbf{x}_1))$ and $\mathcal{D}_{\mathrm{KL}}(p(\mathbf{r}^{(0)}|\mathbf{x}_1,\mathbf{x}_2)\parallel p_\varphi (\mathbf{r}^{(0)}|\mathbf{x}_2))$ . The trainable network is the DiRNet $p_{\varphi}$ that produces the baseline DiR and an auxiliary network to estimate the upper bound [15]. + +# 3.2. Degradation-Free Representation Reference + +Although the baseline DiR $\mathbf{r}^{(0)}$ aims to distill the degradation-invariant intrinsic elements and structures, it may have biases toward the degraded data because the learning process of $\mathbf{r}^{(0)}$ has not observed degradation-free samples. To compensate for this insufficiency, we collect a large set of high-quality RGB images and assume them to be free of degradation. As these images are captured by real non-idealistic cameras the degradation-free assumption is not strictly true, but it is acceptable for practical purposes. These degradation-free images are used to learn the degradation-free latent representation (DfR) $\mathbf{r}^*$ ; the above two latent representations $\mathbf{r}^{(0)}$ and $\mathbf{r}^*$ will be aligned to produce a refined DiR $\mathbf{r}^+$ by a so-called alignment network, whose construction and rationale will be discussed in Sec. 3.3. + +Similar to training DiRNet for the baseline $\mathrm{DiR}\mathbf{r}^{(0)}$ , we propose the DfRNet to learn the DfR $\mathbf{r}^*$ from a degradation-free image (surrogate ground truth). Since this DfR learning is with respect to a single image, the MMI training for $\mathbf{r}^*$ is simplified to the mutual information maximization i.e. maximizing $I(\mathbf{r}^*;\mathbf{y}^*)$ , which can be solved by maximizing the lower bound derived by Proposition 1. Moreover, following VAE [14], we train the decoder $D_{*}$ that forces the learned DfR to be able to reconstruct the degradation-free image. The objective of the above DfR learning is to minimize $\mathcal{L}_{*}$ + +defined as follows + +$$ +\begin{array}{l} \mathcal {L} _ {*} = - I \left(\mathbf {r} ^ {*}; \mathbf {y} ^ {*}\right) + \mathbb {E} \left[ \left\| D _ {*} \left(\mathbf {r} ^ {*}\right) - \mathbf {y} ^ {*} \right\| _ {1} \right] \\ + \beta^ {*} \mathcal {D} _ {\mathrm {K L}} [ p (\mathbf {r} ^ {*}) | | \mathcal {N} (0, \mathbf {I}) ], \tag {6} \\ \end{array} +$$ + +where $\beta^{*}$ is the trade-off hyperparameter. The defined training objective in Eq. (6) is the same as the InfoVAE [54]. + +# 3.3. Alignment Network for Refined DiR + +Alignment network As mentioned in the introduction, we can neutralize, to a certain extent, possible biases in the baseline DiR $\mathbf{r}^{(0)}$ by aligning $\mathbf{r}^{(0)}$ with the above DfR $\mathbf{r}^*$ in distribution. This is accomplished by a so-called alignment network $\mathcal{A}$ . To guide the statistical alignment of $\mathbf{r}^{(0)}$ and $\mathbf{r}^*$ , we also feed the degraded training image $\mathbf{x}$ to network DfR-Net and use the resulting latent representation $\vec{\mathbf{r}} = \mathrm{DfR}(\mathbf{x})$ , called the pilot representation. This guided alignment process is a mapping function + +$$ +\mathcal {A} \left(\mathbf {r} ^ {(0)}, \vec {\mathbf {r}}\right): \mathbf {r} ^ {(0)} \xrightarrow [ \vec {\mathbf {r}} = \mathrm {D f R} (\mathbf {x}) ]{\text {G u i d e d b y} \vec {\mathbf {r}}} \mathbf {r} ^ {+}. \tag {7} +$$ + +Next, we describe the architecture of the alignment network $\mathcal{A}$ and discuss the role of the pilot representation $\vec{\mathbf{r}}$ . + +![](images/595af94a3f5e8c8a7fdd9e98aef9b739895eff59cf3cde2fb1c21cc06ddbc702.jpg) +Figure 3. Illustration of the alignment network. + +Network structure Fig. 3 shows the network structure of the alignment network $\mathcal{A}$ . It consists of three cascaded modules $\mathcal{A}_1, \mathcal{A}_2$ and $\mathcal{A}_3$ . The front module $\mathcal{A}_1$ of $m_1$ convolution layers is used to extract the features from the input image. The middle module $\mathcal{A}_2$ of $m_2$ layers is designed to modulate the latent features with the guidance of the pilot DfR $\vec{\mathbf{r}}$ . The end module $\mathcal{A}_3$ of $m_3$ convolution layers is used to produce the final refined DiR $\mathbf{r}^+$ . + +In the guidance module $\mathcal{A}_2$ , $\vec{\mathbf{r}}$ is fed to convolution layers with $3\times 3$ kernels, followed by the average pooling layer to obtain the modulation feature tensors. These modulation tensors are then reshaped to form $k$ adaptive convolution kernels. We use a so-called G-Conv module formed by these adaptive convolution kernels to convolve with the input features to produce the guided features $f_{k}$ which are embedded with the information of the pilot DfR $\vec{\mathbf{r}}$ . In addition, + +we exploit a spatial attention branch to assist the guidance information extraction. This attention branch predicts the attention maps to strengthen the feature units that have a high correlation to pilot DfR $\vec{\mathbf{r}}$ , yielding the attention-weighted intermediate features $f_{a}$ . Finally, the guided features $f_{k}$ and the attention-weighted features $f_{a}$ are fused by an addition layer to produce the refined DiR $\mathbf{r}^{+}$ , which is ready for use in downstream tasks. In our experiments, we jointly train this alignment network $\mathcal{A}$ and a task-aligned auxiliary network $\mathcal{T}$ , which will be introduced in Sec. 3.4. + +![](images/caf2b32cea7b9b7239d6af5a72a656477d74571572bab7777f19d1c6c50bb2e8.jpg) +Figure 4. Visualization of the pilot DfR representations $\vec{\mathbf{r}}$ and the expected DfR representations $\mathbf{r}^*$ . The information provided by the pilot DfR can guide the alignment to find the optimal DfR. + +Discussion on the pilot DfR $\vec{\mathbf{r}}$ To explain the rationale behind the guidance design of the alignment network, we conduct experiments for visualization. More specifically, we choose four different degradation-free images to extract their corresponding DfRs $\mathbf{r}^*$ . We then use the ISP pipeline as in [39] by adding noise to generate 200 various degraded copies of each degradation-free image. These degraded samples, which share the same image content but have different ISP degradations, are fed into the network DfR to produce the pilot DfRs $\mathbf{r}^*$ . Fig. 4 shows the visualized results by using t-SNE [46], where the red stars denote the expected ground truth DfRs $\mathbf{r}^*$ for the alignment network training, and the green stars stand for the pilot DfRs $\vec{\mathbf{r}}$ . We can observe that the green points are projected near the red points, suggesting that the pilot DfRs have a strong correlation with the ground truth DfRs. This is because the pilot DfRs and the ground truth DfRs share the same degradation-free content. Inspired by this phenomenon, the alignment network is designed to take into account the assistant information provided by $\vec{\mathbf{r}}$ to guide the refinement of the baseline DiR. + +# 3.4. Joint Task-Aligned Refinement Learning + +For training the alignment network, we simulate the Bayer RAW data from the degradation-free images $\mathbf{y}^*$ (surrogate ground truth) by using the inverse ISP [21]. These RAW data + +![](images/407725b575d4357fbb2ec31c383faa3ae9b94fed108c4aa781da979c85f4a4a4.jpg) +Figure 5. Illustration of the joint task-aligned refinement learning. + +are used to generate the degraded RGB images $\mathbf{x}$ with the ISP software tool [39]. Fig. 5 illustrates the joint task-aligned refinement learning process. The DiRNet and DfRNet are frozen to extract the paired representations $(\mathbf{r}^{(0)},\mathbf{r}^{*})$ from the paired degraded and degradation-free images $(\mathbf{x},\mathbf{y}^{*})$ . The alignment network is driven by the pairs $(\mathbf{r}^{(0)},\mathbf{r}^{*})$ to learn the mapping function $\mathcal{A}:\mathbf{r}^{(0)}\to \mathbf{r}^{+}$ , where the final refined DiR $\mathbf{r}^{+}$ lies in the degradation-free latent representation space determined by the DfRNet. + +The paired images $(\mathbf{x},\mathbf{y}^{*})$ and the associated labels $\tilde{\mathbf{y}}$ w.r.t. the downstream task are used to supervise the joint training of the alignment network $\mathcal{A}$ and the task-related auxiliary network $\mathcal{T}$ . As the auxiliary network for the downstream task usually takes an RGB image as input, we adopt the decoder $D_{*}$ trained for the DfRNet to reconstruct the RGB images from the refined DiRs $\mathbf{r}^{+}$ . The joint training loss in the alignment phase is to minimize $\mathcal{L}_{+}$ defined as + +$$ +\begin{array}{l} \mathcal {L} _ {+} = \mathbb {E} \left[ \| \mathbf {r} ^ {+} - \mathbf {r} ^ {*} \| _ {1} \right] + \gamma_ {1} \mathcal {L} _ {\text {t a s k}} \left(\mathcal {T} \left(D _ {*} (\mathbf {r} ^ {+})\right), \tilde {\mathbf {y}}\right) \\ + \gamma_ {2} \mathbb {E} \left[ \| D _ {*} \left(\mathbf {r} ^ {+}\right) - \mathbf {y} ^ {*} \| _ {1} \right], \tag {8} \\ \end{array} +$$ + +where $\gamma_{1}$ and $\gamma_{2}$ are the trade-off parameters, the DfR $\mathbf{r}^{*} = \mathrm{DfR}(\mathbf{y}^{*})$ , and the refined DiR representation $\mathbf{r}^{+} = \mathcal{A}(\mathbf{r}^{(0)},\vec{\mathbf{r}})$ , where $\mathbf{r}^{(0)} = \mathrm{DiR}(\mathbf{x})$ and $\vec{\mathbf{r}} = \mathrm{DfR}(\mathbf{x})$ . The alignment network $\mathcal{A}$ and the auxiliary network $\mathcal{T}$ are jointly optimized, whereas the pretrained networks DiRNet and DfRNet as well as the decoder $D_{*}$ are frozen. The second term $\mathcal{L}_{\mathrm{task}}$ is a task-related loss for a downstream task, such as the cross-entropy for image segmentation. The third term is an image reconstruction loss that forces the refined DiR to inherit the complete information from the degradation-free image through the pixel-wise reconstruction restriction. We summarize the DiR learning process in Algorithm 1. + +# 4. Experiments + +# 4.1. Implementation Details + +Datasets and evaluation As previously introduced, DiR learning comprises two stages: Stage I, dedicated to training the DiRNet and DfRNet, and Stage II, where the alignment network $\mathcal{A}$ and the task-related auxiliary network $\mathcal{T}$ are jointly trained. For the training dataset, we adopt the + +# Algorithm 1 DiR Learning and Task-Aligned Refinement + +Input: Degradation-free RAW image $\mathbf{y}$ and corresponding degradation-free RGB image $\mathbf{y}^*$ , task-related label $\tilde{\mathbf{y}}$ +Stage I: + +1: repeat +2: Generate two images $\mathbf{x}_1$ and $\mathbf{x}_2$ from a degradation-free image $\mathbf{y}$ using two randomly sampled ISP degradations. +3: Train DiRNet using $(\mathbf{x}_1,\mathbf{x}_2)$ (min $\mathcal{L}_0$ in Eq.5 +4: Train DfRNet using $\mathbf{y}^*$ (min $\mathcal{L}_*$ in Eq. (6)) +5: until reaching the maximum number of epochs +Stage II: +6:re +7: Generate an image $\mathbf{x}$ from a degradation-free image $\mathbf{y}$ using randomly sampled ISP degradations. +8: $\vec{\mathbf{r}} = \mathrm{DfR}(\mathbf{x}),\mathbf{r}^{*} = \mathrm{DfR}(\mathbf{y}^{*})$ +9: $\mathbf{r}^{+} = \mathcal{A}(\mathbf{r}^{(0)},\vec{\mathbf{r}})$ +10: Train the alignment network $\mathcal{A}$ using the paired $(\mathbf{x},\mathbf{r}^{*})$ with the guidance of the pilot DfR $\vec{\mathbf{r}}$ , and jointly train the auxiliary $\mathcal{T}$ using the pairs of $(D_{*}(\mathbf{r}^{+}),\tilde{\mathbf{y}})$ (min $\mathcal{L}_{+}$ in Eq. (8)) +11: until reaching the maximum number of epochs + +DIV2K dataset [1] and degrade the images by synthetic ISP degradations. To simulate ISP degradations, we begin by converting RGB images into RAW data by applying the reversed ISP model [21]. Subsequently, we employ a synthetic ISP pipeline [32, 39] with random parameters to generate degraded ISP-generated images from the simulated RAW data3. In Stage II, we employ the identical simulation process used in Stage I to synthesize ISP-degraded images and use the MS COCO dataset [25] for experiments. + +For evaluation, we test the proposed method on three downstream tasks, including 1) the image restoration experiments on real-world datasets including the PolyU-Real [50], NC12 [22], Nam [33], and DND $^4$ [37] datasets, where the test images involve real complex ISP degradations, 2) the object detection experiments on the MS COCO [25] dataset, and 3) the image segmentation experiments on the MS COCO dataset and the ADE20k dataset [55]. + +Training settings At Stage I, we randomly select the contrastive degraded pairs to enable the MMI maximization for the training of the DiRNet. For training the DfRNet, we follow the same setting as in [54], by setting the parameter $\beta^{*} = 1$ in Eq. (6). We adopt the encoder network of [17] as the architectures of the DiRNet and the DfRNet. During training, the learning rate is initially set to $10^{-4}$ and reduced to $10^{-6}$ after 200 epochs. At Stage II, we randomly form pairs of degraded and degradation-free RGB images for training the alignment network. The learning rate is initially set to $10^{-3}$ and reduced to $10^{-6}$ after 300 epochs. For the image restoration task, we set $\gamma_{1} = 0$ , $\gamma_{2} = 1$ , because the decoder $D_{*}$ can serve as the auxiliary network for the RGB image reconstruction using the refined DiR $\mathbf{r}^{+}$ . For the object detection and image segmentation tasks, the trade-off parameters are set to $\gamma_{1} = 2$ , $\gamma_{2} = 1$ and $\gamma_{1} = 5$ , $\gamma_{2} = 1$ , + +respectively. The hyperparameters $m_{1}, m_{2}$ , and $m_{3}$ in the alignment network are separately set to 4, 2, and 4. + +# 4.2. Results on ISP-Degraded Image Restoration + +First, we present the experimental results of the proposed method and compare them with those of eight competing methods [5, 6, 8, 24, 36, 48, 53], on the restoration of ISP-degraded images. The task is to remove ISP artifacts caused by complex coupling of multiple degradation sources, including sensor noises, demosaicing noises, compression noises, and possibly adverse effects of incorrect settings of ISO and gamma correction. Here, like in all other image restoration methods for human viewers, our goal is to pursue the highest possible perceptual image quality. + +In Fig. 6 the reader can compare the visual quality of the DiR learning based restoration method against those of SOTA image restoration methods [6, 8, 24, 26, 36, 48, 53], on restoring real-world ISP-degraded images taken by four different cameras, whose true degradation models are unknown. We can observe that the proposed method succeeds in achieving its design goal of blind restoration, as it removes most of the ISP artifacts caused by unknown degradation sources. On the contrary, the competing methods fail to remove complex artifacts while preserving the sharpness and clarity of edges and textures. Table 1 reports the quantitative performance evaluation results. Since there is no ideal degradation-free ground truth, we adopt the non-reference image quality assessment methods, including NIQE [31], NRQM [29], and BIQA [42]. In agreement with the visual comparisons in Fig. 6, the proposed DiR method also outperforms the competitors in terms of all three metrics. Both subjective and objective evaluations demonstrate superior robustness of the proposed method when being applied to data unseen in the training, indicating that the DiR learning approach can distill degradation-free representations from ISP-degraded images, regardless of whether observed or not. + +
MethodNIQE ↓ / NRQM ↑ / BIQA ↑
PolyU-RealNC12NamDND
BM3D [5]9.72/2.60/40.512.78/3.75/30.812.58/2.56/41.212.89/1.84/40.1
CBDNet [8]7.32/3.78/44.110.67/6.88/33.110.26/3.62/42.19.74/2.96/41.1
LIR [6]8.37/4.52/48.111.41/7.19/33.710.69/4.25/49.811.86/3.19/44.3
MPRNet [53]6.12/4.23/38.711.21/6.30/32.97.25/3.94/33.99.53/2.77/45.2
Uformer [48]6.25/3.96/37.410.54/6.05/31.27.92/3.62/34.69.58/2.72/45.1
SCPGab [26]8.71/3.25/41.111.75/3.93/31.910.60/3.25/40.79.80/2.53/42.0
DIL [24]7.28/4.10/41.810.88/6.52/30.89.11/3.59/40.87.86/3.72/44.7
SDAP [36]9.62/3.00/46.111.34/3.88/32.512.38/2.95/45.710.74/2.33/45.8
Ours6.57/4.91/51.99.06/7.41/34.48.96/4.64/53.68.62/3.59/46.9
+ +Table 1. Quantitative results on real-world ISP-degraded images. + +# 4.3. Results on Object Detection + +Following [39], we utilize the MS COCO dataset [25] to evaluate our proposed method's performance on object detection. We compare our method with the SOTA neural ISP solvers [38, 39], which replace the conventional ISP pipeline + +![](images/a96d526630d17eed62096f3e869b611ed54f6ed198e543bd101d29559d655f7f.jpg) +Figure 6. Qualitative comparison on real-world ISP-degraded images. The degraded images, from top to bottom, are from the real-world datasets PolyU-Real [50], NC12 [22], Nam [33], and DND [37]. Please zoom in for better visualization. + +with end-to-end trained neural networks while considering the downstream task as their optimization objectives. Following the approach in [32, 39], we choose the ISP pipeline with default parameters as the baseline. Our method utilizes these ISP-generated results with default settings as inputs. For comparison, we adopt the pre-trained object detection model [40] for performance benchmarking, and we assess the results using the mean accuracy score (mAP) as the evaluation metric. The quantitative results are reported in Table 2. Our method demonstrates a significant improvement compared to the baseline and outperforms the SOTA solutions [38, 39]. The left side of Fig 7 illustrates the qualitative results. As a reference, we include the results produced by the expert-tuned ISP for visual comparison. We can observe that while the expert-tuned ISP can produce more visually appealing results aligned with human perception preferences, it is inferior to our method on the task of object detection. + +# 4.4. Results on Image Segmentation + +Similar to the object detection experiments, we adopt the MS COCO dataset [25] to evaluate the performance of image segmentation. We benchmark the performance using a pre-trained segmentation model [13] and report the results in Table 3. As shown, our method outperforms the SOTA method Attention-aware [38] by about $3.9\%$ on the $\mathrm{mAP}@0.5$ . Quantitative results are shown on the right side of Fig 7. These results are in line with the observations in the object detection experiments. Our method consistently outperforms the expert-tuned ISP in achieving better segmentation results. + +
MethodsISP ModelmAP↑
0.50.750.5:0.95
Default ParamsISP [32]15.--
Blockwise-tuned [34]20.--
Hardware-tuned [32]39.--
Default ParamsISP [39]34.122.421.4
Attention-aware [38]61.044.141.0
Sequential-tuned [39]62.845.242.3
Ours63.946.443.3
+ +Table 2. Quantitative results on object detection. + +
MethodsISP ModelmAP↑
0.50.750.5:0.95
Default ParamsISP [32]12.--
Hardware-tuned [32]32.--
Default ParamsISP [39]22.713.212.0
Attention-aware [38]52.333.431.5
Sequential-tuned [39]54.235.132.6
Ours56.337.134.8
+ +Table 3. Quantitative results on image segmentation. + +Additionally, we conduct experiments to evaluate the performance of the proposed method in low signal-to-noise ratio situations, such as dark environments where the noise level is very high. To mimic the degradations, we increase the noise level in the aforementioned synthetic ISP pipeline by adding Gaussian noise with the standard deviation $\sigma$ randomly sampled between the range of [0.15, 0.35] and the Poisson noise with the magnitude $\lambda$ randomly sampled between the range of [0.02, 0.04]. We compare the proposed DiR learning based method with the SOTA methods [16, 20] for ISP degradation removal and present the results in Table 4. To evaluate performance, we use two pretrained segmentation models, including DeeplabV3 [3] and SegFormer [49]. We observe that our method outperforms all + +![](images/47cb120df4bb44c38397adeb17b30e1b21bc8bff5b84a08d75261d1100e48b44.jpg) +Figure 7. We evaluate different ISP-generated images for the tasks of object detection (left) and instance segmentation (right) on the COCO dataset. From top to bottom, we show the results from the images generated by default ISP hyperparameters, expert-tuned ISP hyperparameters, and the refined DiR with the proposed method. The proposed method achieves better performance for downstream tasks. + +![](images/ecd2d514145d85621e5b060ba30102552b06c3b53be353a5973a0827feb2e1ce.jpg) + +
MethodsDeeplabV3 [3]SegFormer [49]
aAcc↑mIoU↑mAcc↑aAcc↑mIoU↑mAcc↑
Default ISP64.822.628.974.836.945.1
PyNET [16]67.725.131.574.337.445.8
DNF [20]71.429.636.975.437.846.2
Ours75.534.644.579.742.452.9
+ +the competitors. For example, compared to the DNF [20], our method increases the mAcc by $7.6\%$ and $6.7\%$ when using the DeeplabV3 and SegFormer models, respectively. + +# 4.5. Ablation Study + +Ablation studies are conducted to assess the effectiveness of the proposed components: the baseline $\mathrm{DiR}\mathbf{r}^{(0)}$ , the alignment network $\mathcal{A}$ , and the pilot DfR $\vec{\mathbf{r}}$ . For experiments, we apply the synthetic ISP process as described in [39] to generate ISP-degraded test images using the Set14 and BSD100 [30] datasets. To simulate degradation, we introduce noise into the synthetic ISP process. The added noise includes random Gaussian noise with a standard deviation ranging from 0.05 to 0.1 and JPEG compression noise with a quality factor randomly chosen in the range [10, 30]. As a reference, we train an auto-encoder model, labeled as "Auto-Encoder". This model adopts the same encoder architecture as DiR-Net and the same decoder architecture as $D_{*}$ . The training process of this auto-encoder model follows the canonical paradigm, i.e., it learns a direct mapping from degraded images to their degradation-free counterparts. Table 5 shows comparisons: when excluding the pilot DfR (2nd row) from + +the complete DiR learning technique (3rd row), we observe a decrease in PSNR by 0.2 dB and 0.4 dB for the Set14 and BSD100 datasets. In comparison to using only the baseline DiR, the inclusion of the alignment network $\mathcal{A}$ leads to a PSNR improvement from 22.4 dB to 23.9 dB and 23.8 dB to 24.6 dB on the two datasets. This enhancement is attributed to the alignment network's ability to refine the baseline DiR by aligning it with the degradation-free representation. + +Table 4. Results of image segmentation on the ADE20k [55]. + +
MethodSet14BSD100
r(0)A→rPSNR ↑LPIPS ↓PSNR ↑LPIPS ↓
✓XX22.40.35923.80.379
✓✓X23.90.24324.60.313
✓✓✓24.10.22825.00.288
Auto-Encoder21.60.37823.10.408
+ +Table 5. Ablation studies on each module in DiR learning. + +# 5. Conclusion + +This paper presents a novel method of learning degradation-independent representations for ISP-degraded images. In the proposed method, we devise a DiRNet to learn baseline DiR representations from diverse ISP-degraded observations in a self-supervised learning manner, ensuring adaptability to various degradation scenarios. Furthermore, we employ a guided alignment network to refine the baseline DiRs by aligning them with latent degradation-free representations. Our proposed approach demonstrates superior performance and scalability, as validated by extensive empirical results from synthetic and real-world datasets across various downstream applications. + +# References + +[1] Eirikur Agustsson and Radu Timofte. Ntire 2017 challenge on single image super-resolution: Dataset and study. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 5122-5130, 2017. 6, 8 \ No newline at end of file diff --git a/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/images.zip b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..a31e34d2db0dc55d2393ecbf9d5eacc907012f63 --- /dev/null +++ b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:f22fe90ad5fe9df66c61014c564e60245c870c2693ab03ca3186a32db3ca776e +size 757491 diff --git a/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/layout.json b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..6580a12fb8b5bd89a3322f67364c2e5e83d40e16 --- /dev/null +++ b/2024/Learning Degradation-Independent Representations for Camera ISP Pipelines/layout.json @@ -0,0 +1,10480 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 56, + 103, + 538, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 56, + 103, + 538, + 121 + ], + "spans": [ + { + "bbox": [ + 56, + 103, + 538, + 121 + ], + "type": "text", + "content": "Learning Degradation-Independent Representations for Camera ISP Pipelines" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 56, + 143, + 202, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 56, + 143, + 202, + 185 + ], + "spans": [ + { + "bbox": [ + 56, + 143, + 202, + 185 + ], + "type": "text", + "content": "Yanhui Guo* \nMcMaster University, Canada \nguoy143@mcmaster.ca" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 223, + 144, + 370, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 223, + 144, + 370, + 185 + ], + "spans": [ + { + "bbox": [ + 223, + 144, + 370, + 185 + ], + "type": "text", + "content": "Fangzhou Luo* \nMcMaster University, Canada \nluof1@mcmaster.ca" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 391, + 143, + 537, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 391, + 143, + 537, + 185 + ], + "spans": [ + { + "bbox": [ + 391, + 143, + 537, + 185 + ], + "type": "text", + "content": "Xiaolin Wu† \nMcMaster University, Canada \nxwu@mcmaster.ca" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "spans": [ + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 238, + 290, + 490 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 238, + 290, + 490 + ], + "spans": [ + { + "bbox": [ + 47, + 238, + 290, + 490 + ], + "type": "text", + "content": "Image signal processing (ISP) pipeline plays a fundamental role in digital cameras, which converts raw Bayer sensor data to RGB images. However, ISP-generated images usually suffer from imperfections due to the compounded degradations that stem from sensor noises, demosaicing noises, compression artifacts, and possibly adverse effects of erroneous ISP hyperparameter settings such as ISO and gamma values. In a general sense, these ISP imperfections can be considered as degradations. The highly complex mechanisms of ISP degradations, some of which are even unknown, pose great challenges to the generalization capability of deep neural networks (DNN) for image restoration and to their adaptability to downstream tasks. To tackle the issues, we propose a novel DNN approach to learn degradation-independent representations (DiR) through the refinement of a self-supervised learned baseline representation. The proposed DiR learning technique has remarkable domain generalization capability and consequently, it outperforms state-of-the-art methods across various downstream tasks, including blind image restoration, object detection, and instance segmentation, as verified in our experiments." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 511, + 128, + 523 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 511, + 128, + 523 + ], + "spans": [ + { + "bbox": [ + 47, + 511, + 128, + 523 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 531, + 288, + 650 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 531, + 288, + 650 + ], + "spans": [ + { + "bbox": [ + 46, + 531, + 288, + 650 + ], + "type": "text", + "content": "In our information era, digital cameras have become ubiquitous and indispensable in all walks of socioeconomic life. They are arguably the most common type of sensory device for both humans and their intelligent agents to sense the environment. The applications of digital imaging fall into two categories depending on their end purposes: human vision oriented and machine vision oriented. Examples of the first category include smartphones, social media, internet videos, etc., while robotics, automation, and medical imaging are examples of the second category." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 651, + 288, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 651, + 288, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 651, + 288, + 687 + ], + "type": "text", + "content": "For human vision oriented applications, the image quality metrics should correspond to human visual perception, because the images are primarily intended to please our" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 213, + 547, + 286 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 213, + 547, + 286 + ], + "spans": [ + { + "bbox": [ + 306, + 213, + 547, + 286 + ], + "type": "text", + "content": "eyes. On the other hand, for machine vision oriented applications [18, 19, 40, 49], the image quality requirements may not completely align with those of human perception. In the latter case, what matters most is the preservation of semantically critical image features that are needed to solve computer vision problems of recognition and classification." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 290, + 547, + 518 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 290, + 547, + 518 + ], + "spans": [ + { + "bbox": [ + 304, + 290, + 547, + 518 + ], + "type": "text", + "content": "For either human viewing or downstream computer vision tasks, the image acquisition process of digital cameras is the same. All images are generated by a hardware image signal processing (ISP) pipeline that transforms raw Bayer sensor data into RGB images. The ISP pipeline consists of a set of cascaded steps, including denoising, color demosaicking, and compression. Each of the ISP steps can cause a level of degradation in image quality. At the beginning of the ISP pipeline, there are sensor noises, particularly in dark environments with a low signal-to-noise ratio. The noisy RAW data are then demosaiced to produce the corresponding RGB images. This demosaicking process introduces interpolation noises of its own. Finally, the RGB image is compressed for bandwidth efficiency, which adds extra compression noises on top of sensor noises and demosaicking noises. The resulting compound effects of these cascaded noises are very difficult to model precisely [11]. The underlying complex image quality degradation mechanism prevents the synthesis of clean and degraded image pairs for supervised learning." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 521, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 548, + 714 + ], + "type": "text", + "content": "Yet, there is another type of ISP degradation that exerts adverse effects on the applications of ISP-generated images in downstream tasks. The camera ISP involves a number of adjustable hyperparameters such as gamma correction, ISO, gain control, and white balance. Their optimal settings may vary from application to application, i.e., there exists no one-fits-all solution. Most cameras have a default hyperparameter setting that is tailored to perceptual quality rather than optimized for a specific computer vision task. We consider the deviations of ISP hyperparameters from their optimal settings, in a general sense, to be degradations as well. This second type of ISP degradation can lead to underperformances or even outright failures of downstream computer vision algorithms [32, 38]. Like the first type of signal-level degradations, the second type of semantic-level degradations is extremely difficult, if not impossible," + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 693, + 127, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 693, + 127, + 703 + ], + "spans": [ + { + "bbox": [ + 58, + 693, + 127, + 703 + ], + "type": "text", + "content": "* Equal contribution." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 59, + 703, + 138, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 138, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 138, + 712 + ], + "type": "text", + "content": "† Corresponding author." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25774" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "text", + "content": "to model and synthesize, not only because the space of ISP hyperparameters is of very high dimensions but also because the two types of ISP degradations are intertwined." + } + ] + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 69, + 120, + 165, + 224 + ], + "blocks": [ + { + "bbox": [ + 69, + 120, + 165, + 224 + ], + "lines": [ + { + "bbox": [ + 69, + 120, + 165, + 224 + ], + "spans": [ + { + "bbox": [ + 69, + 120, + 165, + 224 + ], + "type": "image", + "image_path": "e456d7c2f496f03a50796fe28ecd3173fc1232a3d34a1b20d5befd2e2e2335d2.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 104, + 224, + 138, + 233 + ], + "lines": [ + { + "bbox": [ + 104, + 224, + 138, + 233 + ], + "spans": [ + { + "bbox": [ + 104, + 224, + 138, + 233 + ], + "type": "text", + "content": "Canonical" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 242, + 287, + 264 + ], + "lines": [ + { + "bbox": [ + 46, + 242, + 287, + 264 + ], + "spans": [ + { + "bbox": [ + 46, + 242, + 287, + 264 + ], + "type": "text", + "content": "Figure 1. Comparison of the canonical learning paradigm and our DiR learning technique." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 167, + 120, + 268, + 224 + ], + "blocks": [ + { + "bbox": [ + 167, + 120, + 268, + 224 + ], + "lines": [ + { + "bbox": [ + 167, + 120, + 268, + 224 + ], + "spans": [ + { + "bbox": [ + 167, + 120, + 268, + 224 + ], + "type": "image", + "image_path": "e377d5ec4af4ba88fe20daf50ceb9fc741a559400f9faa20bbbff07cf079ac00.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 206, + 225, + 224, + 233 + ], + "lines": [ + { + "bbox": [ + 206, + 225, + 224, + 233 + ], + "spans": [ + { + "bbox": [ + 206, + 225, + 224, + 233 + ], + "type": "text", + "content": "Ours" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 270, + 289, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 270, + 289, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 270, + 289, + 544 + ], + "type": "text", + "content": "As discussed above, it is either intractable or highly expensive to obtain the ISP-degraded and the corresponding latent degradation-free (ground truth) image pairs. Moreover, exhausting all ISP degradation variants in a brute force way is impossible, many of which are not even known or understood [27, 28]. To meet these challenges, we introduce a notion of degradation-independent latent representation (DiR) that is robust against camera-captured non-ideal real-world images and propose a new deep neural network approach to learn the DiR. Fig. 1 illustrates the difference between our DiR learning paradigm and the canonical learning paradigm. Within the framework of our DiR learning, the learned DiR representations contain intrinsic information of the original degradation-free image and hence it is more general and robust with respect to unseen degradation types and severity when used in downstream computer vision and image processing tasks. The DiR learning, carried out by a deep neural network called DiRNet, is self-supervised, and the DiRNet is trained with two learning objectives: any two degraded images are mapped to the same DiR, and all DiRs are sampled from a normal distribution, which is learning a variational auto-encoder (VAE) by the multi-view mutual information (MMI) maximization[7, 15, 43]." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": "Moreover, we take advantage of known priors of the ISP workflow to synthesize original and degraded pairs, so that the above baseline DiR can be reinforced by an auxiliary self-supervised learning branch. This auxiliary branch learns the reference representation " + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": " of the degradation-free images, using high-quality images (surrogate ground truth). The baseline DiR result " + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": " is statistically aligned with the result " + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": " of the auxiliary branch by an alignment network module. This alignment module is trained using the aforementioned synthesized pairs and learns to align the baseline DiR " + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": " to the degradation-free representation reference (DfR) " + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": ", yielding a refined DiR " + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^+" + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": "; finally, the refined DiR " + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^+" + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": " is ready for being used in downstream tasks. Overall, the refined DiR benefits from the best of both self-supervised and supervised" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "text", + "content": "learning, and strikes a good balance between the model's robustness and precision for applications." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 97, + 547, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 97, + 547, + 120 + ], + "spans": [ + { + "bbox": [ + 305, + 97, + 547, + 120 + ], + "type": "text", + "content": "Our main contributions and key results can be summarized as follows:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 121, + 547, + 252 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 306, + 121, + 547, + 168 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 121, + 547, + 168 + ], + "spans": [ + { + "bbox": [ + 306, + 121, + 547, + 168 + ], + "type": "text", + "content": "- A novel method is proposed for self-supervised learning of the DiR representation by multivariate mutual information maximization, which requires only degraded training images." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 169, + 545, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 169, + 545, + 204 + ], + "spans": [ + { + "bbox": [ + 306, + 169, + 545, + 204 + ], + "type": "text", + "content": "- A joint learning approach is employed to refine the DiR representation for optimal performance in the targeted end-task network." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 205, + 547, + 252 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 205, + 547, + 252 + ], + "spans": [ + { + "bbox": [ + 306, + 205, + 547, + 252 + ], + "type": "text", + "content": "- The versatility of the proposed methods across a wide range of tasks, including image restoration, object detection, and instance segmentation, is supported by ample empirical evidence." + } + ] + } + ], + "index": 12 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 258, + 392, + 270 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 258, + 392, + 270 + ], + "spans": [ + { + "bbox": [ + 306, + 258, + 392, + 270 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 279, + 547, + 447 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 279, + 547, + 447 + ], + "spans": [ + { + "bbox": [ + 304, + 279, + 547, + 447 + ], + "type": "text", + "content": "Degradation blind image restoration network There is a long history of research on image restoration tasks that are blind to degradation parameters, such as blind image deconvolution algorithms [23]. Accompanying the proliferation of deep learning based image restoration methods, recent years have seen a number of papers [9, 10, 12, 24, 26, 28, 36, 47] on the topic of improving the generalization ability of image restoration networks. Wang et al. [47] used a high-order degradation model to mimic real-world degradations. Luo et al. [28] proposed a novel adversarial neural degradation model to simulate degraded training data. Li et al. [24] introduced a distortion invariant representation learning paradigm from the causality perspective, to improve the generalization ability of restoration networks for unknown degradations." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 449, + 547, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 449, + 547, + 688 + ], + "spans": [ + { + "bbox": [ + 304, + 449, + 547, + 688 + ], + "type": "text", + "content": "End-to-end neural network solutions for ISP pipelines A more holistic design of neural networks [34, 41, 51] for image restoration is to replace the cascaded stages of the hardware ISP pipeline with a single end-to-end mapping from raw Bayer sensor data to the intended ideal RGB images, instead of postprocessing the output images of the camera ISP. For instance, Chen et al. [2] proposed a CNN method, called SID (see in the dark), which directly converts a low lighting noisy Bayer image to a corresponding properly exposed RGB image, without generating the underexposed ineligible RGB image first and then restoring it. Tseng et al. [44] leveraged a convolutional neural network to parameterize a differentiable mapping between the ISP configuration space and evaluation metrics of downstream tasks and validated their method on the tasks of object detection, and extreme low-light imaging. Yu et al. [52] replaced the conventional ISP with a trainable ISP framework that improves the quality of ISP-generated results by using a differential neural architecture search algorithm to search for the optimal ISP architecture and hyperparameters." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 689, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 547, + 713 + ], + "type": "text", + "content": "Image enhancement for high-level tasks In general practice, image restoration networks tend to be optimized for" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25775" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 70, + 289, + 259 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 289, + 259 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 289, + 259 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 289, + 259 + ], + "type": "image", + "image_path": "2669202ed069507a51e3d8c39267519c4d07a7bf0680f26b2540b89f5c05f809.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 61, + 268, + 272, + 280 + ], + "lines": [ + { + "bbox": [ + 61, + 268, + 272, + 280 + ], + "spans": [ + { + "bbox": [ + 61, + 268, + 272, + 280 + ], + "type": "text", + "content": "Figure 2. Self-supervised MMI maximization for DiRNet." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 285, + 289, + 501 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 285, + 289, + 501 + ], + "spans": [ + { + "bbox": [ + 46, + 285, + 289, + 501 + ], + "type": "text", + "content": "human visual perception rather than for computer vision tasks. However, the human vision-centric neural network may not provide optimal results on high-level computer vision tasks. This motivates the development of a family of image restoration networks that are tuned in line with the subsequent computer vision tasks, such as recognition, detection, and classification [4, 39, 52]. For example, Cui et al. [4] proposed a multitask auto-encoding transformation model to learn the intrinsic visual structure by considering the physical sensor noise model in ISP, demonstrating effectiveness for dark object detection. Mosleh et al. [32] investigated a so-called \"hardware-in-the-loop\" strategy to directly optimize the hyperparameters of hardware ISP pipelines, by solving a nonlinear multi-objective optimization problem with a 0th-order stochastic solver. Qin et al. [39] designed a sequential CNN model to recurrently adjust the ISP hyperparameters for downstream tasks and demonstrate the advantages of the model." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 512, + 113, + 525 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 512, + 113, + 525 + ], + "spans": [ + { + "bbox": [ + 47, + 512, + 113, + 525 + ], + "type": "text", + "content": "3. Approach" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "spans": [ + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "text", + "content": "In this section, we first detail the DiRNet mentioned in the introduction to learn the baseline " + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "inline_equation", + "content": "\\mathrm{DiR}\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "text", + "content": " of multiple degraded images. The DiRNet training is driven by the MMI maximization. Then, we discuss how to learn the degradation-free latent representation " + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "text", + "content": " using a variant of DiRNet. The two latent representations " + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "text", + "content": " are prepared to train an alignment network to produce a refined DiR " + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{+}" + }, + { + "bbox": [ + 46, + 532, + 288, + 639 + ], + "type": "text", + "content": ". Finally, we elaborate on the process to jointly optimize the alignment network and an auxiliary network for a downstream task." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 647, + 275, + 659 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 647, + 275, + 659 + ], + "spans": [ + { + "bbox": [ + 47, + 647, + 275, + 659 + ], + "type": "text", + "content": "3.1. Optimizing DiRNet by MMI Maximization" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 665, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 713 + ], + "type": "text", + "content": "Mutual information maximization To begin, we pave the way for computing the multi-view mutual information (MMI) maximization by introducing a mutual information estimator. For estimating mutual information" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "I(\\mathbf{x};\\mathbf{y})" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " of two random variables " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": ", it is equivalent to computing the Kullback-Leibler (KL) divergence " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{x},\\mathbf{y})||p(\\mathbf{x})p(\\mathbf{y}))" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": ". However, the KL divergence has no theoretical upper bound. Maximizing it cannot guarantee the convergence of the optimization process. Following previous works [35, 45], we exploit a non-KL divergence named Jensen-Shannon divergence (JSD) to devise the lower bound of mutual information, which satisfies the below proposition. Proposition 1 Let " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " represent two random variables, the " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{J} = p(\\mathbf{x},\\mathbf{y})" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{M} = p(\\mathbf{x})p(\\mathbf{y})" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " are the joint and the product of marginals of the two variables, respectively. The mutual information between the variables satisfies1" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 314, + 222, + 546, + 251 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 314, + 222, + 546, + 251 + ], + "spans": [ + { + "bbox": [ + 314, + 222, + 546, + 251 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} I (\\mathbf {x}; \\mathbf {y}) := \\mathcal {D} _ {\\mathrm {J S D}} (\\mathbf {J}; \\mathbf {M}) \\\\ \\geq \\mathbb {E} _ {z \\sim \\mathbf {J}} [ - \\sigma (- \\mathcal {F} _ {\\omega} (z)) ] - \\mathbb {E} _ {z ^ {\\prime} \\sim \\mathbf {M}} [ \\sigma (\\mathcal {F} _ {\\omega} (z ^ {\\prime})) ], \\tag {1} \\\\ \\end{array}", + "image_path": "358e8fe37e9c1cb90cde7e833a3bcf9589234f747e7cb3999cdcef914f7c8b7b.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "spans": [ + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "inline_equation", + "content": "\\sigma(t) = \\log(1 + e^t)" + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": ", and the discriminator function " + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\omega}" + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": " [35] is modeled by a neural network with parameters " + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "inline_equation", + "content": "\\omega" + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": ". Multi-view mutual information maximization The baseline DiR " + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": " is a degradation-independent representation shared among all degraded images that originate from an ideal degradation-free image. From the perspective of information theory, the DiR representation should satisfy the criterion of shared information maximization between it and multiple degraded observations. This shared information maximization is so-called multi-view mutual information (MMI) maximization[7] a.k.a interaction information maximization [43] for the three variables. We state its definition as follows: Given two degraded images " + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_1" + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_2" + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": ", their shared latent DiR " + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": " can be found by maximizing their MMI " + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "inline_equation", + "content": "I(\\mathbf{r}^{(0)}; \\mathbf{x}_1; \\mathbf{x}_2)" + }, + { + "bbox": [ + 304, + 255, + 547, + 434 + ], + "type": "text", + "content": " that is defined as" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 331, + 439, + 545, + 486 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 331, + 439, + 545, + 486 + ], + "spans": [ + { + "bbox": [ + 331, + 439, + 545, + 486 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1}; \\mathbf {x} _ {2}\\right) = I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1}\\right) - \\underbrace {I \\left(\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {1} \\mid \\mathbf {x} _ {2}\\right)} _ {\\text {R e d u n d a n c y}} (2) \\\\ = I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {2}\\right) - I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {2} \\mid \\mathbf {x} _ {1}\\right), (3) \\\\ \\end{array}", + "image_path": "def21f809aab3b182c1d4f4d029d8983d47faf36506fc9840eb5cc9354add85d.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "spans": [ + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": "where Eq. (3) holds due to symmetry. The conditional mutual information " + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "inline_equation", + "content": "I(\\mathbf{r}^{(0)};\\mathbf{x}_1|\\mathbf{x}_2)" + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": " represents the incremental mutual information between " + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": " and the degraded observation " + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_1" + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": " when given another degraded observation " + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_2" + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": ". This incremental information denotes the information not shared by the observations " + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_1" + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_2" + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": ", due to the differences in various degradation sources, which should be minimized. Maximizing " + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "inline_equation", + "content": "I(\\mathbf{r}^{(0)};\\mathbf{x}_1;\\mathbf{x}_2)" + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": " encourages " + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 304, + 493, + 547, + 612 + ], + "type": "text", + "content": " to encode the degradation-independent information shared by the given multiple degraded images." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 613, + 547, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 613, + 547, + 696 + ], + "spans": [ + { + "bbox": [ + 304, + 613, + 547, + 696 + ], + "type": "text", + "content": "The network DiRNet for learning the baseline DiR is of VAE type [14]. The DiRNet takes the ISP-generated images (i.e. camera captured) as inputs and maps them into a canonical representation space i.e. the DiR latent space, by removing the degradation-specific information. Fig. 2 shows the training process for the DiRNet. To continue the development, we introduce the following proposition [15]:" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 317, + 702, + 539, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 702, + 539, + 712 + ], + "spans": [ + { + "bbox": [ + 317, + 702, + 539, + 712 + ], + "type": "text", + "content": "1The derivation is in Sec.B and Sec.C of the supplementary material." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "25776" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "text", + "content": "Proposition 2 Given two degraded images " + }, + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_1" + }, + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_2" + }, + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "text", + "content": ", and the baseline DiR representation " + }, + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "text", + "content": ", the conditional mutual information " + }, + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "inline_equation", + "content": "I(\\mathbf{r}^{(0)};\\mathbf{x}_1|\\mathbf{x}_2)" + }, + { + "bbox": [ + 47, + 72, + 288, + 109 + ], + "type": "text", + "content": " satisfies:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 118, + 287, + 142 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 118, + 287, + 142 + ], + "spans": [ + { + "bbox": [ + 48, + 118, + 287, + 142 + ], + "type": "interline_equation", + "content": "I \\left(\\mathbf {r} ^ {(0)}; \\mathbf {x} _ {1} \\mid \\mathbf {x} _ {2}\\right) \\leq \\mathbb {E} _ {p \\left(\\mathbf {x} _ {1}, \\mathbf {x} _ {2}\\right)} \\left[ \\right. \\mathcal {D} _ {\\mathrm {K L}} \\left( \\right.p \\left(\\mathbf {r} ^ {(0)} \\mid \\mathbf {x} _ {1}, \\mathbf {x} _ {2}\\right)\\left. \\right\\lvert | p _ {\\varphi} \\left(\\mathbf {r} ^ {(0)} \\mid \\mathbf {x} _ {2}\\right)\\left. \\right)\\left. \\right]. \\tag {4}", + "image_path": "b5fbc3538eedc66b4f2caecc96a77e1cbc7abb124dc3235613356be414812aff.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 144, + 288, + 170 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 144, + 288, + 170 + ], + "spans": [ + { + "bbox": [ + 47, + 144, + 288, + 170 + ], + "type": "text", + "content": "To maximize " + }, + { + "bbox": [ + 47, + 144, + 288, + 170 + ], + "type": "inline_equation", + "content": "I(\\mathbf{r}^{(0)};\\mathbf{x}_1;\\mathbf{x}_2)" + }, + { + "bbox": [ + 47, + 144, + 288, + 170 + ], + "type": "text", + "content": ", the overall training objective of DiRNet is defined by the average of Eq. (2) and Eq. (3):" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 93, + 188, + 287, + 251 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 93, + 188, + 287, + 251 + ], + "spans": [ + { + "bbox": [ + 93, + 188, + 287, + 251 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {0} = - \\frac {I (\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {1}) + I (\\mathbf {r} ^ {(0)} ; \\mathbf {x} _ {2})}{2} \\\\ + \\lambda \\mathbb {E} _ {p (\\mathbf {x} _ {1}, \\mathbf {x} _ {2})} [ \\mathcal {D} _ {\\mathrm {A K L}} ] \\\\ + \\beta \\mathcal {D} _ {\\mathrm {K L}} \\left[ p \\left(\\mathbf {r} ^ {(0)}\\right) | | \\mathcal {N} (0, \\mathbf {I}) \\right], \\tag {5} \\\\ \\end{array}", + "image_path": "05977a67ded8520218baaaccb79720bdee04443919253e3f58abad6f0aed31ee.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "spans": [ + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "content": "in which we can maximize the upper bound of the conditional mutual information according to Proposition 2. In Eq.(5), " + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "content": " are the trade-off hyperparameters. The DiR representation is regularized by the Gaussian prior " + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "inline_equation", + "content": "\\mathcal{N}(0,\\mathbf{I})" + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "content": " as in VAE [14]. " + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathrm{AKL}}" + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "content": " stands for the average of " + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{r}^{(0)}|\\mathbf{x}_1,\\mathbf{x}_2)\\parallel p_\\varphi (\\mathbf{r}^{(0)}|\\mathbf{x}_1))" + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathrm{KL}}(p(\\mathbf{r}^{(0)}|\\mathbf{x}_1,\\mathbf{x}_2)\\parallel p_\\varphi (\\mathbf{r}^{(0)}|\\mathbf{x}_2))" + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "content": ". The trainable network is the DiRNet " + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "inline_equation", + "content": "p_{\\varphi}" + }, + { + "bbox": [ + 47, + 260, + 288, + 369 + ], + "type": "text", + "content": " that produces the baseline DiR and an auxiliary network to estimate the upper bound [15]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 376, + 276, + 389 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 376, + 276, + 389 + ], + "spans": [ + { + "bbox": [ + 47, + 376, + 276, + 389 + ], + "type": "text", + "content": "3.2. Degradation-Free Representation Reference" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "spans": [ + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "text", + "content": "Although the baseline DiR " + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "text", + "content": " aims to distill the degradation-invariant intrinsic elements and structures, it may have biases toward the degraded data because the learning process of " + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "text", + "content": " has not observed degradation-free samples. To compensate for this insufficiency, we collect a large set of high-quality RGB images and assume them to be free of degradation. As these images are captured by real non-idealistic cameras the degradation-free assumption is not strictly true, but it is acceptable for practical purposes. These degradation-free images are used to learn the degradation-free latent representation (DfR) " + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "text", + "content": "; the above two latent representations " + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "text", + "content": " will be aligned to produce a refined DiR " + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^+" + }, + { + "bbox": [ + 46, + 396, + 288, + 563 + ], + "type": "text", + "content": " by a so-called alignment network, whose construction and rationale will be discussed in Sec. 3.3." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "spans": [ + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "text", + "content": "Similar to training DiRNet for the baseline " + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "inline_equation", + "content": "\\mathrm{DiR}\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "text", + "content": ", we propose the DfRNet to learn the DfR " + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "text", + "content": " from a degradation-free image (surrogate ground truth). Since this DfR learning is with respect to a single image, the MMI training for " + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "text", + "content": " is simplified to the mutual information maximization i.e. maximizing " + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "inline_equation", + "content": "I(\\mathbf{r}^*;\\mathbf{y}^*)" + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "text", + "content": ", which can be solved by maximizing the lower bound derived by Proposition 1. Moreover, following VAE [14], we train the decoder " + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "inline_equation", + "content": "D_{*}" + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "text", + "content": " that forces the learned DfR to be able to reconstruct the degradation-free image. The objective of the above DfR learning is to minimize " + }, + { + "bbox": [ + 46, + 563, + 288, + 684 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{*}" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 72, + 382, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 382, + 83 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 382, + 83 + ], + "type": "text", + "content": "defined as follows" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 341, + 90, + 545, + 118 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 341, + 90, + 545, + 118 + ], + "spans": [ + { + "bbox": [ + 341, + 90, + 545, + 118 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {*} = - I \\left(\\mathbf {r} ^ {*}; \\mathbf {y} ^ {*}\\right) + \\mathbb {E} \\left[ \\left\\| D _ {*} \\left(\\mathbf {r} ^ {*}\\right) - \\mathbf {y} ^ {*} \\right\\| _ {1} \\right] \\\\ + \\beta^ {*} \\mathcal {D} _ {\\mathrm {K L}} [ p (\\mathbf {r} ^ {*}) | | \\mathcal {N} (0, \\mathbf {I}) ], \\tag {6} \\\\ \\end{array}", + "image_path": "fec237cbd563c4e3fe145d1ba109e1933b27af5d224267308ffb2c7f29d908fe.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 124, + 547, + 148 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 124, + 547, + 148 + ], + "spans": [ + { + "bbox": [ + 305, + 124, + 547, + 148 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 124, + 547, + 148 + ], + "type": "inline_equation", + "content": "\\beta^{*}" + }, + { + "bbox": [ + 305, + 124, + 547, + 148 + ], + "type": "text", + "content": " is the trade-off hyperparameter. The defined training objective in Eq. (6) is the same as the InfoVAE [54]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 154, + 502, + 167 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 154, + 502, + 167 + ], + "spans": [ + { + "bbox": [ + 306, + 154, + 502, + 167 + ], + "type": "text", + "content": "3.3. Alignment Network for Refined DiR" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "spans": [ + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": "Alignment network As mentioned in the introduction, we can neutralize, to a certain extent, possible biases in the baseline DiR " + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": " by aligning " + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": " with the above DfR " + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": " in distribution. This is accomplished by a so-called alignment network " + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": ". To guide the statistical alignment of " + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": ", we also feed the degraded training image " + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": " to network DfR-Net and use the resulting latent representation " + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x})" + }, + { + "bbox": [ + 305, + 173, + 547, + 281 + ], + "type": "text", + "content": ", called the pilot representation. This guided alignment process is a mapping function" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 349, + 289, + 545, + 318 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 349, + 289, + 545, + 318 + ], + "spans": [ + { + "bbox": [ + 349, + 289, + 545, + 318 + ], + "type": "interline_equation", + "content": "\\mathcal {A} \\left(\\mathbf {r} ^ {(0)}, \\vec {\\mathbf {r}}\\right): \\mathbf {r} ^ {(0)} \\xrightarrow [ \\vec {\\mathbf {r}} = \\mathrm {D f R} (\\mathbf {x}) ]{\\text {G u i d e d b y} \\vec {\\mathbf {r}}} \\mathbf {r} ^ {+}. \\tag {7}", + "image_path": "4a9686271efdfc3df30bc7ea2e2fb3018e0be2203956e426a992f2ff9308d610.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 324, + 547, + 349 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 324, + 547, + 349 + ], + "spans": [ + { + "bbox": [ + 305, + 324, + 547, + 349 + ], + "type": "text", + "content": "Next, we describe the architecture of the alignment network " + }, + { + "bbox": [ + 305, + 324, + 547, + 349 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 305, + 324, + 547, + 349 + ], + "type": "text", + "content": " and discuss the role of the pilot representation " + }, + { + "bbox": [ + 305, + 324, + 547, + 349 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 305, + 324, + 547, + 349 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 307, + 353, + 545, + 502 + ], + "blocks": [ + { + "bbox": [ + 307, + 353, + 545, + 502 + ], + "lines": [ + { + "bbox": [ + 307, + 353, + 545, + 502 + ], + "spans": [ + { + "bbox": [ + 307, + 353, + 545, + 502 + ], + "type": "image", + "image_path": "595af94a3f5e8c8a7fdd9e98aef9b739895eff59cf3cde2fb1c21cc06ddbc702.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 339, + 504, + 511, + 515 + ], + "lines": [ + { + "bbox": [ + 339, + 504, + 511, + 515 + ], + "spans": [ + { + "bbox": [ + 339, + 504, + 511, + 515 + ], + "type": "text", + "content": "Figure 3. Illustration of the alignment network." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "spans": [ + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": "Network structure Fig. 3 shows the network structure of the alignment network " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": ". It consists of three cascaded modules " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "\\mathcal{A}_1, \\mathcal{A}_2" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "\\mathcal{A}_3" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": ". The front module " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "\\mathcal{A}_1" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "m_1" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": " convolution layers is used to extract the features from the input image. The middle module " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "\\mathcal{A}_2" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "m_2" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": " layers is designed to modulate the latent features with the guidance of the pilot DfR " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": ". The end module " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "\\mathcal{A}_3" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "m_3" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": " convolution layers is used to produce the final refined DiR " + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^+" + }, + { + "bbox": [ + 304, + 517, + 547, + 614 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "text", + "content": "In the guidance module " + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{A}_2" + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "text", + "content": " is fed to convolution layers with " + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "inline_equation", + "content": "3\\times 3" + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "text", + "content": " kernels, followed by the average pooling layer to obtain the modulation feature tensors. These modulation tensors are then reshaped to form " + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "text", + "content": " adaptive convolution kernels. We use a so-called G-Conv module formed by these adaptive convolution kernels to convolve with the input features to produce the guided features " + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "inline_equation", + "content": "f_{k}" + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "text", + "content": " which are embedded with the information of the pilot DfR " + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 304, + 616, + 547, + 713 + ], + "type": "text", + "content": ". In addition," + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 47, + 693, + 286, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 286, + 712 + ], + "type": "text", + "content": "2The full derivation of " + }, + { + "bbox": [ + 47, + 693, + 286, + 712 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_0" + }, + { + "bbox": [ + 47, + 693, + 286, + 712 + ], + "type": "text", + "content": " can be found in Sec.B of the supplementary material." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25777" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": "we exploit a spatial attention branch to assist the guidance information extraction. This attention branch predicts the attention maps to strengthen the feature units that have a high correlation to pilot DfR " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": ", yielding the attention-weighted intermediate features " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "f_{a}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": ". Finally, the guided features " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "f_{k}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": " and the attention-weighted features " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "f_{a}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": " are fused by an addition layer to produce the refined DiR " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{+}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": ", which is ready for use in downstream tasks. In our experiments, we jointly train this alignment network " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": " and a task-aligned auxiliary network " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": ", which will be introduced in Sec. 3.4." + } + ] + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 84, + 194, + 249, + 365 + ], + "blocks": [ + { + "bbox": [ + 84, + 194, + 249, + 365 + ], + "lines": [ + { + "bbox": [ + 84, + 194, + 249, + 365 + ], + "spans": [ + { + "bbox": [ + 84, + 194, + 249, + 365 + ], + "type": "image", + "image_path": "caf2b32cea7b9b7239d6af5a72a656477d74571572bab7777f19d1c6c50bb2e8.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 367, + 288, + 401 + ], + "lines": [ + { + "bbox": [ + 46, + 367, + 288, + 401 + ], + "spans": [ + { + "bbox": [ + 46, + 367, + 288, + 401 + ], + "type": "text", + "content": "Figure 4. Visualization of the pilot DfR representations " + }, + { + "bbox": [ + 46, + 367, + 288, + 401 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 46, + 367, + 288, + 401 + ], + "type": "text", + "content": " and the expected DfR representations " + }, + { + "bbox": [ + 46, + 367, + 288, + 401 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 367, + 288, + 401 + ], + "type": "text", + "content": ". The information provided by the pilot DfR can guide the alignment to find the optimal DfR." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "spans": [ + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "text", + "content": "Discussion on the pilot DfR " + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "text", + "content": " To explain the rationale behind the guidance design of the alignment network, we conduct experiments for visualization. More specifically, we choose four different degradation-free images to extract their corresponding DfRs " + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "text", + "content": ". We then use the ISP pipeline as in [39] by adding noise to generate 200 various degraded copies of each degradation-free image. These degraded samples, which share the same image content but have different ISP degradations, are fed into the network DfR to produce the pilot DfRs " + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "text", + "content": ". Fig. 4 shows the visualized results by using t-SNE [46], where the red stars denote the expected ground truth DfRs " + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^*" + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "text", + "content": " for the alignment network training, and the green stars stand for the pilot DfRs " + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "text", + "content": ". We can observe that the green points are projected near the red points, suggesting that the pilot DfRs have a strong correlation with the ground truth DfRs. This is because the pilot DfRs and the ground truth DfRs share the same degradation-free content. Inspired by this phenomenon, the alignment network is designed to take into account the assistant information provided by " + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 46, + 407, + 289, + 652 + ], + "type": "text", + "content": " to guide the refinement of the baseline DiR." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 659, + 264, + 673 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 659, + 264, + 673 + ], + "spans": [ + { + "bbox": [ + 47, + 659, + 264, + 673 + ], + "type": "text", + "content": "3.4. Joint Task-Aligned Refinement Learning" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 677, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 288, + 714 + ], + "type": "text", + "content": "For training the alignment network, we simulate the Bayer RAW data from the degradation-free images " + }, + { + "bbox": [ + 46, + 677, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{y}^*" + }, + { + "bbox": [ + 46, + 677, + 288, + 714 + ], + "type": "text", + "content": " (surrogate ground truth) by using the inverse ISP [21]. These RAW data" + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 307, + 70, + 547, + 192 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 547, + 192 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 547, + 192 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 547, + 192 + ], + "type": "image", + "image_path": "407725b575d4357fbb2ec31c383faa3ae9b94fed108c4aa781da979c85f4a4a4.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 196, + 545, + 208 + ], + "lines": [ + { + "bbox": [ + 305, + 196, + 545, + 208 + ], + "spans": [ + { + "bbox": [ + 305, + 196, + 545, + 208 + ], + "type": "text", + "content": "Figure 5. Illustration of the joint task-aligned refinement learning." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "spans": [ + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "text", + "content": "are used to generate the degraded RGB images " + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "text", + "content": " with the ISP software tool [39]. Fig. 5 illustrates the joint task-aligned refinement learning process. The DiRNet and DfRNet are frozen to extract the paired representations " + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "inline_equation", + "content": "(\\mathbf{r}^{(0)},\\mathbf{r}^{*})" + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "text", + "content": " from the paired degraded and degradation-free images " + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "inline_equation", + "content": "(\\mathbf{x},\\mathbf{y}^{*})" + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "text", + "content": ". The alignment network is driven by the pairs " + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "inline_equation", + "content": "(\\mathbf{r}^{(0)},\\mathbf{r}^{*})" + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "text", + "content": " to learn the mapping function " + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "inline_equation", + "content": "\\mathcal{A}:\\mathbf{r}^{(0)}\\to \\mathbf{r}^{+}" + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "text", + "content": ", where the final refined DiR " + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{+}" + }, + { + "bbox": [ + 304, + 213, + 547, + 320 + ], + "type": "text", + "content": " lies in the degradation-free latent representation space determined by the DfRNet." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "spans": [ + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "content": "The paired images " + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "inline_equation", + "content": "(\\mathbf{x},\\mathbf{y}^{*})" + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "content": " and the associated labels " + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "inline_equation", + "content": "\\tilde{\\mathbf{y}}" + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "content": " w.r.t. the downstream task are used to supervise the joint training of the alignment network " + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "content": " and the task-related auxiliary network " + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "content": ". As the auxiliary network for the downstream task usually takes an RGB image as input, we adopt the decoder " + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "inline_equation", + "content": "D_{*}" + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "content": " trained for the DfRNet to reconstruct the RGB images from the refined DiRs " + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{+}" + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "content": ". The joint training loss in the alignment phase is to minimize " + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{+}" + }, + { + "bbox": [ + 304, + 320, + 547, + 417 + ], + "type": "text", + "content": " defined as" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 326, + 422, + 545, + 454 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 326, + 422, + 545, + 454 + ], + "spans": [ + { + "bbox": [ + 326, + 422, + 545, + 454 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {+} = \\mathbb {E} \\left[ \\| \\mathbf {r} ^ {+} - \\mathbf {r} ^ {*} \\| _ {1} \\right] + \\gamma_ {1} \\mathcal {L} _ {\\text {t a s k}} \\left(\\mathcal {T} \\left(D _ {*} (\\mathbf {r} ^ {+})\\right), \\tilde {\\mathbf {y}}\\right) \\\\ + \\gamma_ {2} \\mathbb {E} \\left[ \\| D _ {*} \\left(\\mathbf {r} ^ {+}\\right) - \\mathbf {y} ^ {*} \\| _ {1} \\right], \\tag {8} \\\\ \\end{array}", + "image_path": "35fd368d58bb678042b3719c99d3514ec91ebfebc067f021308475d469ee74d5.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\gamma_{1}" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\gamma_{2}" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": " are the trade-off parameters, the DfR " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{*} = \\mathrm{DfR}(\\mathbf{y}^{*})" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": ", and the refined DiR representation " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{+} = \\mathcal{A}(\\mathbf{r}^{(0)},\\vec{\\mathbf{r}})" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{(0)} = \\mathrm{DiR}(\\mathbf{x})" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x})" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": ". The alignment network " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": " and the auxiliary network " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": " are jointly optimized, whereas the pretrained networks DiRNet and DfRNet as well as the decoder " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "D_{*}" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": " are frozen. The second term " + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{task}}" + }, + { + "bbox": [ + 304, + 460, + 545, + 606 + ], + "type": "text", + "content": " is a task-related loss for a downstream task, such as the cross-entropy for image segmentation. The third term is an image reconstruction loss that forces the refined DiR to inherit the complete information from the degradation-free image through the pixel-wise reconstruction restriction. We summarize the DiR learning process in Algorithm 1." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 616, + 388, + 629 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 616, + 388, + 629 + ], + "spans": [ + { + "bbox": [ + 306, + 616, + 388, + 629 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 635, + 439, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 635, + 439, + 647 + ], + "spans": [ + { + "bbox": [ + 306, + 635, + 439, + 647 + ], + "type": "text", + "content": "4.1. Implementation Details" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 653, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 714 + ], + "type": "text", + "content": "Datasets and evaluation As previously introduced, DiR learning comprises two stages: Stage I, dedicated to training the DiRNet and DfRNet, and Stage II, where the alignment network " + }, + { + "bbox": [ + 304, + 653, + 547, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 304, + 653, + 547, + 714 + ], + "type": "text", + "content": " and the task-related auxiliary network " + }, + { + "bbox": [ + 304, + 653, + 547, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 304, + 653, + 547, + 714 + ], + "type": "text", + "content": " are jointly trained. For the training dataset, we adopt the" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25778" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 72, + 282, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 72, + 282, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 72, + 282, + 84 + ], + "type": "text", + "content": "Algorithm 1 DiR Learning and Task-Aligned Refinement" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "spans": [ + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "type": "text", + "content": "Input: Degradation-free RAW image " + }, + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "type": "text", + "content": " and corresponding degradation-free RGB image " + }, + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "type": "inline_equation", + "content": "\\mathbf{y}^*" + }, + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "type": "text", + "content": ", task-related label " + }, + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "type": "inline_equation", + "content": "\\tilde{\\mathbf{y}}" + }, + { + "bbox": [ + 48, + 87, + 287, + 114 + ], + "type": "text", + "content": " \nStage I:" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 48, + 114, + 287, + 266 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 52, + 114, + 86, + 123 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 114, + 86, + 123 + ], + "spans": [ + { + "bbox": [ + 52, + 114, + 86, + 123 + ], + "type": "text", + "content": "1: repeat" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "spans": [ + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "type": "text", + "content": "2: Generate two images " + }, + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_1" + }, + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_2" + }, + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "type": "text", + "content": " from a degradation-free image " + }, + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 52, + 124, + 287, + 141 + ], + "type": "text", + "content": " using two randomly sampled ISP degradations." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 52, + 141, + 235, + 151 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 141, + 235, + 151 + ], + "spans": [ + { + "bbox": [ + 52, + 141, + 235, + 151 + ], + "type": "text", + "content": "3: Train DiRNet using " + }, + { + "bbox": [ + 52, + 141, + 235, + 151 + ], + "type": "inline_equation", + "content": "(\\mathbf{x}_1,\\mathbf{x}_2)" + }, + { + "bbox": [ + 52, + 141, + 235, + 151 + ], + "type": "text", + "content": " (min " + }, + { + "bbox": [ + 52, + 141, + 235, + 151 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_0" + }, + { + "bbox": [ + 52, + 141, + 235, + 151 + ], + "type": "text", + "content": " in Eq.5" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 52, + 151, + 216, + 159 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 151, + 216, + 159 + ], + "spans": [ + { + "bbox": [ + 52, + 151, + 216, + 159 + ], + "type": "text", + "content": "4: Train DfRNet using " + }, + { + "bbox": [ + 52, + 151, + 216, + 159 + ], + "type": "inline_equation", + "content": "\\mathbf{y}^*" + }, + { + "bbox": [ + 52, + 151, + 216, + 159 + ], + "type": "text", + "content": " (min " + }, + { + "bbox": [ + 52, + 151, + 216, + 159 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_*" + }, + { + "bbox": [ + 52, + 151, + 216, + 159 + ], + "type": "text", + "content": " in Eq. (6))" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 52, + 160, + 214, + 177 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 160, + 214, + 177 + ], + "spans": [ + { + "bbox": [ + 52, + 160, + 214, + 177 + ], + "type": "text", + "content": "5: until reaching the maximum number of epochs \nStage II:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 52, + 178, + 69, + 186 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 178, + 69, + 186 + ], + "spans": [ + { + "bbox": [ + 52, + 178, + 69, + 186 + ], + "type": "text", + "content": "6:re" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 51, + 186, + 287, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 51, + 186, + 287, + 204 + ], + "spans": [ + { + "bbox": [ + 51, + 186, + 287, + 204 + ], + "type": "text", + "content": "7: Generate an image " + }, + { + "bbox": [ + 51, + 186, + 287, + 204 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 51, + 186, + 287, + 204 + ], + "type": "text", + "content": " from a degradation-free image " + }, + { + "bbox": [ + 51, + 186, + 287, + 204 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 51, + 186, + 287, + 204 + ], + "type": "text", + "content": " using randomly sampled ISP degradations." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 51, + 205, + 174, + 217 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 51, + 205, + 174, + 217 + ], + "spans": [ + { + "bbox": [ + 51, + 205, + 174, + 217 + ], + "type": "text", + "content": "8: " + }, + { + "bbox": [ + 51, + 205, + 174, + 217 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}} = \\mathrm{DfR}(\\mathbf{x}),\\mathbf{r}^{*} = \\mathrm{DfR}(\\mathbf{y}^{*})" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 51, + 217, + 135, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 51, + 217, + 135, + 228 + ], + "spans": [ + { + "bbox": [ + 51, + 217, + 135, + 228 + ], + "type": "text", + "content": "9: " + }, + { + "bbox": [ + 51, + 217, + 135, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{+} = \\mathcal{A}(\\mathbf{r}^{(0)},\\vec{\\mathbf{r}})" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "spans": [ + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "text", + "content": "10: Train the alignment network " + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "text", + "content": " using the paired " + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "inline_equation", + "content": "(\\mathbf{x},\\mathbf{r}^{*})" + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "text", + "content": " with the guidance of the pilot DfR " + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "text", + "content": ", and jointly train the auxiliary " + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "text", + "content": " using the pairs of " + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "inline_equation", + "content": "(D_{*}(\\mathbf{r}^{+}),\\tilde{\\mathbf{y}})" + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "text", + "content": " (min " + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{+}" + }, + { + "bbox": [ + 48, + 228, + 287, + 258 + ], + "type": "text", + "content": " in Eq. (8))" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 48, + 258, + 215, + 266 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 258, + 215, + 266 + ], + "spans": [ + { + "bbox": [ + 48, + 258, + 215, + 266 + ], + "type": "text", + "content": "11: until reaching the maximum number of epochs" + } + ] + } + ], + "index": 12 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 46, + 289, + 288, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 289, + 288, + 397 + ], + "spans": [ + { + "bbox": [ + 46, + 289, + 288, + 397 + ], + "type": "text", + "content": "DIV2K dataset [1] and degrade the images by synthetic ISP degradations. To simulate ISP degradations, we begin by converting RGB images into RAW data by applying the reversed ISP model [21]. Subsequently, we employ a synthetic ISP pipeline [32, 39] with random parameters to generate degraded ISP-generated images from the simulated RAW data3. In Stage II, we employ the identical simulation process used in Stage I to synthesize ISP-degraded images and use the MS COCO dataset [25] for experiments." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 397, + 287, + 493 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 397, + 287, + 493 + ], + "spans": [ + { + "bbox": [ + 46, + 397, + 287, + 493 + ], + "type": "text", + "content": "For evaluation, we test the proposed method on three downstream tasks, including 1) the image restoration experiments on real-world datasets including the PolyU-Real [50], NC12 [22], Nam [33], and DND" + }, + { + "bbox": [ + 46, + 397, + 287, + 493 + ], + "type": "inline_equation", + "content": "^4" + }, + { + "bbox": [ + 46, + 397, + 287, + 493 + ], + "type": "text", + "content": " [37] datasets, where the test images involve real complex ISP degradations, 2) the object detection experiments on the MS COCO [25] dataset, and 3) the image segmentation experiments on the MS COCO dataset and the ADE20k dataset [55]." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "spans": [ + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": "Training settings At Stage I, we randomly select the contrastive degraded pairs to enable the MMI maximization for the training of the DiRNet. For training the DfRNet, we follow the same setting as in [54], by setting the parameter " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "\\beta^{*} = 1" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": " in Eq. (6). We adopt the encoder network of [17] as the architectures of the DiRNet and the DfRNet. During training, the learning rate is initially set to " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "10^{-4}" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": " and reduced to " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "10^{-6}" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": " after 200 epochs. At Stage II, we randomly form pairs of degraded and degradation-free RGB images for training the alignment network. The learning rate is initially set to " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "10^{-3}" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": " and reduced to " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "10^{-6}" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": " after 300 epochs. For the image restoration task, we set " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "\\gamma_{1} = 0" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "\\gamma_{2} = 1" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": ", because the decoder " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "D_{*}" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": " can serve as the auxiliary network for the RGB image reconstruction using the refined DiR " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "\\mathbf{r}^{+}" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": ". For the object detection and image segmentation tasks, the trade-off parameters are set to " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "\\gamma_{1} = 2" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "\\gamma_{2} = 1" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "\\gamma_{1} = 5" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "inline_equation", + "content": "\\gamma_{2} = 1" + }, + { + "bbox": [ + 46, + 495, + 288, + 686 + ], + "type": "text", + "content": "," + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "type": "text", + "content": "respectively. The hyperparameters " + }, + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "type": "inline_equation", + "content": "m_{1}, m_{2}" + }, + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "type": "inline_equation", + "content": "m_{3}" + }, + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "type": "text", + "content": " in the alignment network are separately set to 4, 2, and 4." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 99, + 535, + 111 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 99, + 535, + 111 + ], + "spans": [ + { + "bbox": [ + 306, + 99, + 535, + 111 + ], + "type": "text", + "content": "4.2. Results on ISP-Degraded Image Restoration" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 117, + 547, + 236 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 117, + 547, + 236 + ], + "spans": [ + { + "bbox": [ + 304, + 117, + 547, + 236 + ], + "type": "text", + "content": "First, we present the experimental results of the proposed method and compare them with those of eight competing methods [5, 6, 8, 24, 36, 48, 53], on the restoration of ISP-degraded images. The task is to remove ISP artifacts caused by complex coupling of multiple degradation sources, including sensor noises, demosaicing noises, compression noises, and possibly adverse effects of incorrect settings of ISO and gamma correction. Here, like in all other image restoration methods for human viewers, our goal is to pursue the highest possible perceptual image quality." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 237, + 547, + 499 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 237, + 547, + 499 + ], + "spans": [ + { + "bbox": [ + 304, + 237, + 547, + 499 + ], + "type": "text", + "content": "In Fig. 6 the reader can compare the visual quality of the DiR learning based restoration method against those of SOTA image restoration methods [6, 8, 24, 26, 36, 48, 53], on restoring real-world ISP-degraded images taken by four different cameras, whose true degradation models are unknown. We can observe that the proposed method succeeds in achieving its design goal of blind restoration, as it removes most of the ISP artifacts caused by unknown degradation sources. On the contrary, the competing methods fail to remove complex artifacts while preserving the sharpness and clarity of edges and textures. Table 1 reports the quantitative performance evaluation results. Since there is no ideal degradation-free ground truth, we adopt the non-reference image quality assessment methods, including NIQE [31], NRQM [29], and BIQA [42]. In agreement with the visual comparisons in Fig. 6, the proposed DiR method also outperforms the competitors in terms of all three metrics. Both subjective and objective evaluations demonstrate superior robustness of the proposed method when being applied to data unseen in the training, indicating that the DiR learning approach can distill degradation-free representations from ISP-degraded images, regardless of whether observed or not." + } + ] + } + ], + "index": 20 + }, + { + "type": "table", + "bbox": [ + 308, + 510, + 545, + 626 + ], + "blocks": [ + { + "bbox": [ + 308, + 510, + 545, + 626 + ], + "lines": [ + { + "bbox": [ + 308, + 510, + 545, + 626 + ], + "spans": [ + { + "bbox": [ + 308, + 510, + 545, + 626 + ], + "type": "table", + "html": "
MethodNIQE ↓ / NRQM ↑ / BIQA ↑
PolyU-RealNC12NamDND
BM3D [5]9.72/2.60/40.512.78/3.75/30.812.58/2.56/41.212.89/1.84/40.1
CBDNet [8]7.32/3.78/44.110.67/6.88/33.110.26/3.62/42.19.74/2.96/41.1
LIR [6]8.37/4.52/48.111.41/7.19/33.710.69/4.25/49.811.86/3.19/44.3
MPRNet [53]6.12/4.23/38.711.21/6.30/32.97.25/3.94/33.99.53/2.77/45.2
Uformer [48]6.25/3.96/37.410.54/6.05/31.27.92/3.62/34.69.58/2.72/45.1
SCPGab [26]8.71/3.25/41.111.75/3.93/31.910.60/3.25/40.79.80/2.53/42.0
DIL [24]7.28/4.10/41.810.88/6.52/30.89.11/3.59/40.87.86/3.72/44.7
SDAP [36]9.62/3.00/46.111.34/3.88/32.512.38/2.95/45.710.74/2.33/45.8
Ours6.57/4.91/51.99.06/7.41/34.48.96/4.64/53.68.62/3.59/46.9
", + "image_path": "03de2cfe0e302dcbc3d1ebfd22272ed059038867c6149547e132ecaa4d9a9087.jpg" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "table_body" + } + ], + "index": 21 + }, + { + "bbox": [ + 307, + 630, + 543, + 642 + ], + "lines": [ + { + "bbox": [ + 307, + 630, + 543, + 642 + ], + "spans": [ + { + "bbox": [ + 307, + 630, + 543, + 642 + ], + "type": "text", + "content": "Table 1. Quantitative results on real-world ISP-degraded images." + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 306, + 647, + 459, + 659 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 647, + 459, + 659 + ], + "spans": [ + { + "bbox": [ + 306, + 647, + 459, + 659 + ], + "type": "text", + "content": "4.3. Results on Object Detection" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": "Following [39], we utilize the MS COCO dataset [25] to evaluate our proposed method's performance on object detection. We compare our method with the SOTA neural ISP solvers [38, 39], which replace the conventional ISP pipeline" + } + ] + } + ], + "index": 24 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 57, + 692, + 261, + 702 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 692, + 261, + 702 + ], + "spans": [ + { + "bbox": [ + 57, + 692, + 261, + 702 + ], + "type": "text", + "content": "3Additional details can be found in the supplementary material" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 59, + 703, + 230, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 230, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 230, + 712 + ], + "type": "text", + "content": "4We randomly select 500 images for the experiments" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25779" + } + ] + } + ], + "index": 28 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 72, + 545, + 308 + ], + "blocks": [ + { + "bbox": [ + 49, + 72, + 545, + 308 + ], + "lines": [ + { + "bbox": [ + 49, + 72, + 545, + 308 + ], + "spans": [ + { + "bbox": [ + 49, + 72, + 545, + 308 + ], + "type": "image", + "image_path": "a96d526630d17eed62096f3e869b611ed54f6ed198e543bd101d29559d655f7f.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 311, + 546, + 333 + ], + "lines": [ + { + "bbox": [ + 46, + 311, + 546, + 333 + ], + "spans": [ + { + "bbox": [ + 46, + 311, + 546, + 333 + ], + "type": "text", + "content": "Figure 6. Qualitative comparison on real-world ISP-degraded images. The degraded images, from top to bottom, are from the real-world datasets PolyU-Real [50], NC12 [22], Nam [33], and DND [37]. Please zoom in for better visualization." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 340, + 290, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 340, + 290, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 340, + 290, + 544 + ], + "type": "text", + "content": "with end-to-end trained neural networks while considering the downstream task as their optimization objectives. Following the approach in [32, 39], we choose the ISP pipeline with default parameters as the baseline. Our method utilizes these ISP-generated results with default settings as inputs. For comparison, we adopt the pre-trained object detection model [40] for performance benchmarking, and we assess the results using the mean accuracy score (mAP) as the evaluation metric. The quantitative results are reported in Table 2. Our method demonstrates a significant improvement compared to the baseline and outperforms the SOTA solutions [38, 39]. The left side of Fig 7 illustrates the qualitative results. As a reference, we include the results produced by the expert-tuned ISP for visual comparison. We can observe that while the expert-tuned ISP can produce more visually appealing results aligned with human perception preferences, it is inferior to our method on the task of object detection." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 560, + 217, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 560, + 217, + 574 + ], + "spans": [ + { + "bbox": [ + 47, + 560, + 217, + 574 + ], + "type": "text", + "content": "4.4. Results on Image Segmentation" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "type": "text", + "content": "Similar to the object detection experiments, we adopt the MS COCO dataset [25] to evaluate the performance of image segmentation. We benchmark the performance using a pre-trained segmentation model [13] and report the results in Table 3. As shown, our method outperforms the SOTA method Attention-aware [38] by about " + }, + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "type": "inline_equation", + "content": "3.9\\%" + }, + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "type": "text", + "content": " on the " + }, + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{mAP}@0.5" + }, + { + "bbox": [ + 46, + 582, + 288, + 713 + ], + "type": "text", + "content": ". Quantitative results are shown on the right side of Fig 7. These results are in line with the observations in the object detection experiments. Our method consistently outperforms the expert-tuned ISP in achieving better segmentation results." + } + ] + } + ], + "index": 4 + }, + { + "type": "table", + "bbox": [ + 320, + 339, + 530, + 431 + ], + "blocks": [ + { + "bbox": [ + 320, + 339, + 530, + 431 + ], + "lines": [ + { + "bbox": [ + 320, + 339, + 530, + 431 + ], + "spans": [ + { + "bbox": [ + 320, + 339, + 530, + 431 + ], + "type": "table", + "html": "
MethodsISP ModelmAP↑
0.50.750.5:0.95
Default ParamsISP [32]15.--
Blockwise-tuned [34]20.--
Hardware-tuned [32]39.--
Default ParamsISP [39]34.122.421.4
Attention-aware [38]61.044.141.0
Sequential-tuned [39]62.845.242.3
Ours63.946.443.3
", + "image_path": "af54bbac2b1d513e8e561a4f35c35c76c4911a100f9486226da18a0cd7a8ef5d.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_body" + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 320, + 445, + 530, + 530 + ], + "blocks": [ + { + "bbox": [ + 336, + 434, + 514, + 444 + ], + "lines": [ + { + "bbox": [ + 336, + 434, + 514, + 444 + ], + "spans": [ + { + "bbox": [ + 336, + 434, + 514, + 444 + ], + "type": "text", + "content": "Table 2. Quantitative results on object detection." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 320, + 445, + 530, + 530 + ], + "lines": [ + { + "bbox": [ + 320, + 445, + 530, + 530 + ], + "spans": [ + { + "bbox": [ + 320, + 445, + 530, + 530 + ], + "type": "table", + "html": "
MethodsISP ModelmAP↑
0.50.750.5:0.95
Default ParamsISP [32]12.--
Hardware-tuned [32]32.--
Default ParamsISP [39]22.713.212.0
Attention-aware [38]52.333.431.5
Sequential-tuned [39]54.235.132.6
Ours56.337.134.8
", + "image_path": "b1cc200dc3125b8beebb2d27e7965ef11ac7d15068432058e983c803a81296e1.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 329, + 531, + 520, + 542 + ], + "lines": [ + { + "bbox": [ + 329, + 531, + 520, + 542 + ], + "spans": [ + { + "bbox": [ + 329, + 531, + 520, + 542 + ], + "type": "text", + "content": "Table 3. Quantitative results on image segmentation." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "type": "text", + "content": "Additionally, we conduct experiments to evaluate the performance of the proposed method in low signal-to-noise ratio situations, such as dark environments where the noise level is very high. To mimic the degradations, we increase the noise level in the aforementioned synthetic ISP pipeline by adding Gaussian noise with the standard deviation " + }, + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "type": "text", + "content": " randomly sampled between the range of [0.15, 0.35] and the Poisson noise with the magnitude " + }, + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "type": "text", + "content": " randomly sampled between the range of [0.02, 0.04]. We compare the proposed DiR learning based method with the SOTA methods [16, 20] for ISP degradation removal and present the results in Table 4. To evaluate performance, we use two pretrained segmentation models, including DeeplabV3 [3] and SegFormer [49]. We observe that our method outperforms all" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25780" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 59, + 70, + 292, + 322 + ], + "blocks": [ + { + "bbox": [ + 59, + 70, + 292, + 322 + ], + "lines": [ + { + "bbox": [ + 59, + 70, + 292, + 322 + ], + "spans": [ + { + "bbox": [ + 59, + 70, + 292, + 322 + ], + "type": "image", + "image_path": "47cb120df4bb44c38397adeb17b30e1b21bc8bff5b84a08d75261d1100e48b44.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 325, + 547, + 360 + ], + "lines": [ + { + "bbox": [ + 46, + 325, + 547, + 360 + ], + "spans": [ + { + "bbox": [ + 46, + 325, + 547, + 360 + ], + "type": "text", + "content": "Figure 7. We evaluate different ISP-generated images for the tasks of object detection (left) and instance segmentation (right) on the COCO dataset. From top to bottom, we show the results from the images generated by default ISP hyperparameters, expert-tuned ISP hyperparameters, and the refined DiR with the proposed method. The proposed method achieves better performance for downstream tasks." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 294, + 70, + 531, + 322 + ], + "blocks": [ + { + "bbox": [ + 294, + 70, + 531, + 322 + ], + "lines": [ + { + "bbox": [ + 294, + 70, + 531, + 322 + ], + "spans": [ + { + "bbox": [ + 294, + 70, + 531, + 322 + ], + "type": "image", + "image_path": "ecd2d514145d85621e5b060ba30102552b06c3b53be353a5973a0827feb2e1ce.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 50, + 365, + 284, + 425 + ], + "blocks": [ + { + "bbox": [ + 50, + 365, + 284, + 425 + ], + "lines": [ + { + "bbox": [ + 50, + 365, + 284, + 425 + ], + "spans": [ + { + "bbox": [ + 50, + 365, + 284, + 425 + ], + "type": "table", + "html": "
MethodsDeeplabV3 [3]SegFormer [49]
aAcc↑mIoU↑mAcc↑aAcc↑mIoU↑mAcc↑
Default ISP64.822.628.974.836.945.1
PyNET [16]67.725.131.574.337.445.8
DNF [20]71.429.636.975.437.846.2
Ours75.534.644.579.742.452.9
", + "image_path": "6eb56882a86f6ccee04e669845bacad092fe053367fff5f2ac006e3f58e9a0a4.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 443, + 288, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 443, + 288, + 479 + ], + "spans": [ + { + "bbox": [ + 46, + 443, + 288, + 479 + ], + "type": "text", + "content": "the competitors. For example, compared to the DNF [20], our method increases the mAcc by " + }, + { + "bbox": [ + 46, + 443, + 288, + 479 + ], + "type": "inline_equation", + "content": "7.6\\%" + }, + { + "bbox": [ + 46, + 443, + 288, + 479 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 443, + 288, + 479 + ], + "type": "inline_equation", + "content": "6.7\\%" + }, + { + "bbox": [ + 46, + 443, + 288, + 479 + ], + "type": "text", + "content": " when using the DeeplabV3 and SegFormer models, respectively." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 489, + 141, + 502 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 489, + 141, + 502 + ], + "spans": [ + { + "bbox": [ + 47, + 489, + 141, + 502 + ], + "type": "text", + "content": "4.5. Ablation Study" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "text", + "content": "Ablation studies are conducted to assess the effectiveness of the proposed components: the baseline " + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{DiR}\\mathbf{r}^{(0)}" + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "text", + "content": ", the alignment network " + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "text", + "content": ", and the pilot DfR " + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\vec{\\mathbf{r}}" + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "text", + "content": ". For experiments, we apply the synthetic ISP process as described in [39] to generate ISP-degraded test images using the Set14 and BSD100 [30] datasets. To simulate degradation, we introduce noise into the synthetic ISP process. The added noise includes random Gaussian noise with a standard deviation ranging from 0.05 to 0.1 and JPEG compression noise with a quality factor randomly chosen in the range [10, 30]. As a reference, we train an auto-encoder model, labeled as \"Auto-Encoder\". This model adopts the same encoder architecture as DiR-Net and the same decoder architecture as " + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "inline_equation", + "content": "D_{*}" + }, + { + "bbox": [ + 46, + 508, + 289, + 713 + ], + "type": "text", + "content": ". The training process of this auto-encoder model follows the canonical paradigm, i.e., it learns a direct mapping from degraded images to their degradation-free counterparts. Table 5 shows comparisons: when excluding the pilot DfR (2nd row) from" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 366, + 545, + 462 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 366, + 545, + 462 + ], + "spans": [ + { + "bbox": [ + 304, + 366, + 545, + 462 + ], + "type": "text", + "content": "the complete DiR learning technique (3rd row), we observe a decrease in PSNR by 0.2 dB and 0.4 dB for the Set14 and BSD100 datasets. In comparison to using only the baseline DiR, the inclusion of the alignment network " + }, + { + "bbox": [ + 304, + 366, + 545, + 462 + ], + "type": "inline_equation", + "content": "\\mathcal{A}" + }, + { + "bbox": [ + 304, + 366, + 545, + 462 + ], + "type": "text", + "content": " leads to a PSNR improvement from 22.4 dB to 23.9 dB and 23.8 dB to 24.6 dB on the two datasets. This enhancement is attributed to the alignment network's ability to refine the baseline DiR by aligning it with the degradation-free representation." + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 319, + 464, + 531, + 534 + ], + "blocks": [ + { + "bbox": [ + 55, + 427, + 278, + 439 + ], + "lines": [ + { + "bbox": [ + 55, + 427, + 278, + 439 + ], + "spans": [ + { + "bbox": [ + 55, + 427, + 278, + 439 + ], + "type": "text", + "content": "Table 4. Results of image segmentation on the ADE20k [55]." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 319, + 464, + 531, + 534 + ], + "lines": [ + { + "bbox": [ + 319, + 464, + 531, + 534 + ], + "spans": [ + { + "bbox": [ + 319, + 464, + 531, + 534 + ], + "type": "table", + "html": "
MethodSet14BSD100
r(0)A→rPSNR ↑LPIPS ↓PSNR ↑LPIPS ↓
✓XX22.40.35923.80.379
✓✓X23.90.24324.60.313
✓✓✓24.10.22825.00.288
Auto-Encoder21.60.37823.10.408
", + "image_path": "8e753a28cba95ec4c20f29a1a1a846488f67871a372304a1ee2a1fdefd97aea8.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 319, + 536, + 531, + 548 + ], + "lines": [ + { + "bbox": [ + 319, + 536, + 531, + 548 + ], + "spans": [ + { + "bbox": [ + 319, + 536, + 531, + 548 + ], + "type": "text", + "content": "Table 5. Ablation studies on each module in DiR learning." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 306, + 550, + 378, + 562 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 550, + 378, + 562 + ], + "spans": [ + { + "bbox": [ + 306, + 550, + 378, + 562 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": "This paper presents a novel method of learning degradation-independent representations for ISP-degraded images. In the proposed method, we devise a DiRNet to learn baseline DiR representations from diverse ISP-degraded observations in a self-supervised learning manner, ensuring adaptability to various degradation scenarios. Furthermore, we employ a guided alignment network to refine the baseline DiRs by aligning them with latent degradation-free representations. Our proposed approach demonstrates superior performance and scalability, as validated by extensive empirical results from synthetic and real-world datasets across various downstream applications." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "25781" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "text", + "content": "[1] Eirikur Agustsson and Radu Timofte. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 5122-5130, 2017. 6, 8" + } + ] + } + ], + "index": 29 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "25783" + } + ] + } + ], + "index": 31 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_content_list.json b/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..7e19c8485b0babc266f21b31df7edd6b866d0921 --- /dev/null +++ b/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_content_list.json @@ -0,0 +1,1696 @@ +[ + { + "type": "text", + "text": "Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration", + "text_level": 1, + "bbox": [ + 122, + 130, + 849, + 174 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Lianxin Xie $^{1}$ , Csbingbing Zheng $^{1}$ , Wen Xue $^{1}$ , Le Jiang $^{1}$ , Cheng Liu $^{4}$ , Si Wu $^{1,2,3*}$ , Hau San Wong $^{5*}$ $^{1}$ School of Computer Science and Engineering, South China University of Technology", + "bbox": [ + 96, + 200, + 870, + 239 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ Peng Cheng Laboratory", + "bbox": [ + 387, + 239, + 583, + 257 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{3}$ PAZHOU LAB", + "bbox": [ + 418, + 256, + 550, + 272 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{4}$ Departent of Computer Science, Shantou University", + "bbox": [ + 274, + 273, + 694, + 292 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{5}$ Department of Computer Science, City University of Hong Kong", + "bbox": [ + 223, + 292, + 745, + 310 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{cslianxin.xie, 202321044369, csxuewen, 202220143385}@mail.scut.edu.cn", + "bbox": [ + 176, + 311, + 792, + 325 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "cliu@stu.edu.cn, cswusi@scut.edu.cn, cshswong@cityu.edu.hk", + "bbox": [ + 227, + 330, + 741, + 344 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 378, + 312, + 395 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Blind face restoration focuses on restoring high-fidelity details from images subjected to complex and unknown degradations, while preserving identity information. In this paper, we present a Prior-based Latent Transformation approach (PLTrans), which is specifically designed to learn a degradation-unaware representation, thereby allowing the restoration network to effectively generalize to real-world degradation. Toward this end, PLTrans learns a degradation-unaware query via a latent diffusion-based regularization module. Furthermore, conditioned on the features of a degraded face image, a latent dictionary that captures the priors of HQ face images is leveraged to refine the features by mapping the top-d nearest elements. The refined version will be used to build key and value for the cross-attention computation, which is tailored to each degraded image and exhibits reduced sensitivity to different degradation factors. Conditioned on the resulting representation, we train a decoding network that synthesizes face images with authentic details and identity preservation. Through extensive experiments, we verify the effectiveness of the design elements and demonstrate the generalization ability of our proposed approach for both synthetic and unknown degradations. We finally demonstrate the applicability of PLTrans in other vision tasks.", + "bbox": [ + 75, + 411, + 473, + 773 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 800, + 209, + 815 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Blind Face Restoration (BFR) aims to restore facial details while preserving the identity in degraded images that have been subjected to varying and unidentified degradations. Many CNN-based and Transformer-based BFR frameworks have been previously designed to enhance", + "bbox": [ + 75, + 824, + 468, + 902 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/81087be5a85622a5a4659b4b08705c87a16946caf199a73e2bc134628984f508.jpg", + "image_caption": [ + "Figure 1. An example to illustrate that a better query empowers a generic model to generate HQ images, and vice versa. Enhancing the quality of key and value yields relatively slight effect. The restored image quality can be sorted as: $(\\mathrm{b}) > (\\mathrm{c}) > (\\mathrm{d}) > (\\mathrm{a})$" + ], + "image_footnote": [], + "bbox": [ + 517, + 378, + 874, + 513 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "restoration performance, leading to significant advancements in the field. However, it is impractical to gather sufficient pairs of degraded-clean training data in real-world situations. In the pursuit of synthesizing clear and realistic face images from degraded ones, recent BFR methods have incorporated various face priors, including high-quality(HQ) exemplars with the same identity or geometric information. These methods often rely on capturing the correlation between degraded and clean images, making them susceptible to significant performance drops when handling unseen degradations. Additionally, there have been attempts to apply generative priors to BFR. Generative Adversarial Networks (GAN) [12] that are well-trained on face images represent strong priors due to their ability to generate high-fidelity samples, while GAN-based models are typically trained on specific datasets, thus limiting their generalization performance.", + "bbox": [ + 496, + 594, + 892, + 851 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The generic transformer-based model takes a high/low-quality (HQ/LQ) image as input and generates a set of corresponding HQ/LQ query, key and value in each block. The", + "bbox": [ + 498, + 854, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "footer", + "text": "\\*Co-corresponding author.", + "bbox": [ + 76, + 936, + 256, + 954 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "9120", + "bbox": [ + 480, + 970, + 514, + 983 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "result shown in Figure 1 suggests that improving query and key-value leads to varying improvements for face restoration. Inspired by this observation, we propose a Prior-based Latent Transformation approach for BFR, which we refer to as PLTrans. The core idea behind PLTrans is to transform the preliminary features of degraded images to become degradation-unaware query, while at the same time to refine the preliminary feature to build key and value which are used in cross-attention computation. To achieve this, we incorporate a latent diffusion module to remove degradation from the features, in which various types of degradations become indistinguishable as Gaussian noise is added. In order to maintain the semantic similarity of the restored image to the degraded one, the features at each transition step is also combined with the input's low-frequency information obtained through a 2D discrete wavelet transform [49] during the reverse diffusion process. The resulting features are subsequently decoded into a query. Additionally, by incorporating a latent dictionary encoding rich details from the features of HQ face images via vector quantization [36], We learns a global mapping over the retrieved priors based on the top- $d$ elements that are nearest neighbors of the input features to build key and value. The cross-attention computation is performed over the obtained query, key and value for restoring the features of clean face. Extensive experiments are performed to demonstrate the effectiveness of the design elements and the improvement in generalization performance on real-world images with unknown degradation. We summarize the main contributions of this work as follows:", + "bbox": [ + 76, + 90, + 472, + 542 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We address BFR from a new perspective of performing prior-based transformations on query, key and value for the attention computation in a latent transformer.", + "- By incorporating the wavelet-based low-frequency components of the degraded features as supplementary information into the intermediate stages, we can effectively guide the reverse diffusion process to synthesize the degradation-unaware features, while preserving essential semantics from the input.", + "- To restore the features of clean face, we further leverage a latent dictionary to refine the features of the degraded image, based on which we learn key and value to perform cross-attention computation with the degradation-unaware features as query." + ], + "bbox": [ + 96, + 555, + 468, + 791 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 806, + 218, + 821 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Blind Face Restoration", + "text_level": 1, + "bbox": [ + 76, + 830, + 290, + 845 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Significant progress has been achieved in face image restoration recent years [8, 18, 20, 26]. A typical strategy is to regard the restoration as a domain translation task", + "bbox": [ + 76, + 854, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "[10, 34, 45]. Considering facial structures, there have been many attempts to incorporate a variety of priors in the generation process. In [4, 16, 29], landmark estimation were used to recover clear face images from low-resolution ones based on facial geometry priors in the form of facial parsing maps. Given a HQ reference image of the same identity, a warping network was learnt to correct pose and expression for better recovery of fine details [7, 24, 25]. However, the reference-guided methods were only applicable in limited scenes. To effectively obtain the priors associated with the degraded images, a dictionary of semantic facial components was learnt in the feature space of a pretrained VGG [22], which was designed for face recognition. In addition, 3D morphable models explicitly modeled face attributes and can thus be applied to regularize the facial structures and identity information [15, 51].", + "bbox": [ + 496, + 90, + 890, + 332 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Another research line is to exploit the priors encapsulated in the pre-trained generative models. The generative prior-based methods typically projected the degraded image back to the latent space of StyleGAN [19], and the resulting latent codes are transformed and decoded into a HQ face image [30]. To improve the efficiency of GAN inversion, a dedicated encoder was trained for latent code prediction, conditioned on the input image [31]. However, the restoration performance was limited by low dimensionality and poor spatial expression capability of the latent space. To address this issue, facial structural information was utilized by injecting the external features extracted from the degraded image into the generator of GFP-GAN [41], GPEN [48] and GLEAN [2]. Another effective approach is to perform progressive latent space extension across multiple intermediate layers of StyleGAN [32]. Based on a pre-trained Denoising Diffusion Probabilistic Model (DDPM) [14], different attempts were made to control the generation process. Choi et al. [5] proposed an Iterative Latent Variable Refinement (ILVR) method to condition the generative process on a given reference image. Further, Wang et al. [44] applied ILVR to BFR, and the proposed model is referred to as DR2, in which a degraded image was corrupted by Gaussian noise, and the corresponding HQ image could be recovered from its noisy version via an iterative denoising process.", + "bbox": [ + 496, + 338, + 890, + 731 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "There are fundamental differences between the proposed PLTrans and the above methods. DDPM was designed for generic image synthesis, which differs from our restoration task. DR2 [44] utilized a pre-trained DDPM to perform sampling in the data space, while we learn a task-specific latent diffusion module to generate a degradation-unaware representation. Although RestoreFormer [43] captures clear face priors in the form of a latent dictionary, our model uses a dictionary to quantize the features of degraded images. We further learn a global mapping over the top- $d$ nearest elements to enhance the expressiveness of the resulting fea", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "9121", + "bbox": [ + 480, + 970, + 513, + 983 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "tures.", + "bbox": [ + 76, + 92, + 117, + 104 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Vision Transformer", + "text_level": 1, + "bbox": [ + 76, + 116, + 264, + 131 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Transformers have emerged as powerful deep learning architectures for natural language processing [6,38]. Due to their excellent capability in capturing long-range dependencies between elements, the transformer-based models have been applied in a variety of vision tasks, including image classification [9], semantic segmentation [40], object detection [1, 52], and so on. Vision Transformers (ViTs) typically learnt to represent an image as a sequence of patches and estimate their underlying relationships [9, 35]. To deal with high-resolution images and visual objects with large variations in scale, SwinTransformer [27] adopted a shifted window strategy to enhance the modeling power of ViT and yield a hierarchical representation. By performing vector quantization in the latent space, a transformer was applied to high-resolution image generation by predicting the sequence of codebook indices [11]. In [50], a computationally efficient transformer was designed to perform multi-scale local-global representation learning for image restoration. On the other hand, a large-scale pre-trained transformer was also applied for multiple image processing tasks [3]. In this work, we apply a transformer architecture to BFR by modifying the intermediate feature as the query through a denoising diffusion process and learning the prior-based key and value for cross attention computation.", + "bbox": [ + 76, + 140, + 472, + 503 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Proposed Method", + "text_level": 1, + "bbox": [ + 76, + 516, + 250, + 532 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Overview", + "text_level": 1, + "bbox": [ + 76, + 541, + 187, + 556 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Our proposed PLTrans is built on an encoder-transformer-decoder architecture. As depicted in Figure 2, an encoder $E$ processes a degraded face image $x$ to extract preliminary features $q = E(x)$ . A Latent Diffusion-based Feature Regularization Module takes $q$ as input and returns the degradation-irrelevant feature $\\hat{q}$ which is encouraged to be as consistent as possible with the corresponding ground truth. To recover rich face details, we utilize a pre-trained latent dictionary $\\mathcal{V}$ , learned from HQ face images, to quantize $z$ . The resulting features $q$ are further refined and used to build the key and value vectors. A cross-attention-based transformer block takes the obtained query, key and value as input and returns the features to be decoded into a clear face image, which is encouraged to be as consistent as possible with the corresponding ground truth.", + "bbox": [ + 76, + 565, + 472, + 792 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Latent Diffusion-based Feature Regularization", + "text_level": 1, + "bbox": [ + 76, + 801, + 468, + 816 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The structural information of an image with heavy degradation is typically disordered, and thus the preliminary features extracted by a generic encoder are potentially inadequate for capturing accurate semantics. Naively decoding the preliminary features may result in artifacts within the", + "bbox": [ + 76, + 824, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The purpose of this section is to present a new method for the synthesis of the original content. To address this issue, we propose to regularize the preliminary features via a latent diffusion module. Specifically, a mapping network $E_{Q}$ is adopted to take the feature $q$ as input and produces a latent variable $u^{lq}$ or $u^{hq}$ . Our objective is to construct a Markov Chain that incrementally approximates the HQ data distribution starting from a Gaussian prior. The regularization process attempts to restore the features from its noisy version while simultaneously preserving the low-frequency content inherent in the preliminary features. To attain this objective, we perform n-step perturbations to obtain probability $p_{\\pi}(u_{n}^{lq}|u^{lq})$ , subsequently compute the transition probability $p_{\\theta}(u_{t - 1}^{hq}|u_t^{hq})$ , and finally obtain $p_{\\theta}(u_s^{hq}|u_n^{lq})$ , where $u_{n}^{lq}\\approx u_{n}^{hq}$ and $s < t\\leq n$ . Finally, we can get $\\hat{u}_0^{hq}$ by computing probability $p_{\\theta}(\\hat{u}_0^{hq}|u_s^{hq})$ directly. On the other hand, auxiliary information in the form of the low-frequency signals from $u_{t}^{lq}$ are injected at multiple intermediate stages of the reverse diffusion process. We combine the multi-scale high-frequency signals from $u_{t}^{hq}$ and the low-frequency signals from $u_{t}^{lq}$ using Discrete Wavelet Transform (DWT) as follows:", + "bbox": [ + 496, + 90, + 893, + 430 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nu _ {t} ^ {h q} \\leftarrow \\phi^ {\\prime} \\left(\\phi^ {l f} \\left(u _ {t} ^ {l q}\\right), \\phi^ {h f} \\left(u _ {t} ^ {h q}\\right)\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 588, + 438, + 890, + 458 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\phi^{lf / hf}(\\cdot)$ represents the DWT function that extracts the low/high-frequency information, and $\\phi^{\\prime}(\\cdot)$ denotes the Inverse Discrete Wavelet Transform (IDWT). As will be demonstrated in the experiments, $\\hat{u}_0^{hq}$ is less sensitive to degradation and can retain the primary semantics from $u^{lq}$ . Conditioned on the regularized variable, a mapping network $D_{Q}$ is responsible for yielding degradation-irrelevant features $\\hat{q}$ in the same space of $q$ . Considering that a latent space with excessively high variance could affect the training stability and the quality of sample generation in both the diffusion and reverse processes, we impose a Kullback-Leibler (KL) divergence-based penalty on the latent variable $u$ to promote adherence to a standard normal distribution as follows:", + "bbox": [ + 496, + 465, + 893, + 678 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {K L} = K L \\left(p _ {u} \\| p _ {g}\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 622, + 689, + 890, + 707 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $p_u$ and $p_g$ denote a $u$ 's distribution and a Gaussian distribution. Conditioned on $u$ , $D_Q$ is trained to recover $q$ as accurately as possible for reconstruction, and the consistency loss is defined as follows:", + "bbox": [ + 496, + 715, + 893, + 776 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {c o n s}} ^ {q} = \\mathbf {E} _ {q} [ | \\hat {q} - q | _ {1} ], \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 617, + 786, + 890, + 805 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\hat{q} = D_Q(u)$ denotes the prediction. Given the training data in the form of HQ face image features $u^{hq}$ , our latent diffusion module is optimized by a standard mean-squared error loss as follows:", + "bbox": [ + 496, + 813, + 893, + 873 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {d i f} = \\mathbf {E} _ {\\epsilon} \\left[ | \\epsilon - \\epsilon_ {\\theta} \\left(\\sqrt {\\bar {a} _ {t}} u _ {t} ^ {h q} + \\sqrt {1 - \\bar {a} _ {t}} \\epsilon , t\\right) | _ {2} ^ {2} \\right], \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 539, + 883, + 890, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "9122", + "bbox": [ + 480, + 970, + 514, + 983 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/86081e24704685b2755fae42c06267b0855d59e4a58dc2937f345d2d39901a82.jpg", + "image_caption": [ + "Figure 2. Overview of the proposed PLTrans framework. An encoder $E$ extracts the preliminary feature $q$ from a degraded face image $x$ . A latent diffusion-based regularization module is applied to $q$ to obtain its degradation-irrelevant version $\\hat{q}$ as query. On the other hand, a prior-based key-value module quantizes and transforms $q$ to learn key $k$ and value $v$ . We perform cross-attention computation over $\\hat{q}, k$ and $v$ in each transformer block, and feed the resulting feature into a generator $G$ to synthesize a HQ face image." + ], + "image_footnote": [], + "bbox": [ + 83, + 78, + 630, + 329 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/24cedb48b5e9459fed255abea070798648a86f7612bc24c4ce2c9f2ca8d5feaf.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 635, + 80, + 890, + 328 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\epsilon_{\\theta}(u_t^{hq},t)$ is a U-net model used to predict the noise from $u_{t}^{hq}$ at step $t,\\epsilon \\sim \\mathcal{N}(\\mathbf{0},\\mathbf{I})$ and $\\bar{\\alpha}_{t} = \\prod_{m = 1}^{t}(1 - \\beta_{m})$ in which $\\{\\beta_1,\\beta_2,\\dots,\\beta_t\\}$ is the variance schedule used to control the degree of noise addition.", + "bbox": [ + 75, + 406, + 470, + 470 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Prior-based Key-Value", + "text_level": 1, + "bbox": [ + 76, + 479, + 289, + 494 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In addition to regularizing the preliminary features as query, we also learn key and value within our transformation by integrating HQ face priors via a latent dictionary $\\mathcal{V}$ . The elements in $\\mathcal{V}$ are expected to offer a wealth of clear face details. Initially, we utilize the preliminary feature $q$ to compute $z$ through convolution and self-attention operations. Then, $z$ is quantized by retrieving the $d$ nearest elements from $\\mathcal{V}$ , which serve as the respective priors, as follows:", + "bbox": [ + 75, + 503, + 468, + 637 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{e ^ {(1)}, \\dots , e ^ {(d)} \\right\\} _ {(i, j)} = \\arg \\min _ {e \\in \\mathcal {V}} \\| e - z _ {(i, j)} \\| _ {2} ^ {2}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 122, + 648, + 468, + 674 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $z_{(i,j)}$ denotes the feature vector at the spatial location $(i,j)$ . Rather than replacing $z$ with the most similar element, the retrieved top- $d$ priors contain more richer information. Note that $\\mathcal{V}$ may not generalize well to the reconstruction of degraded data. A global mapping over the top- $d$ priors is performed as follows:", + "bbox": [ + 75, + 684, + 468, + 775 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\widetilde {z} _ {(i, j)} = \\sum_ {l = 1} ^ {d} r _ {l} e ^ {(l)}, \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 209, + 787, + 468, + 829 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathbf{r} = [r_1, \\ldots, r_d]$ denotes a learnable combination coefficient vector $e^{(l)} \\in \\{e^{(1)}, \\ldots, e^{(d)}\\}_{(i,j)}$ . Different from generic dictionary-based representation for data reconstruction, the global mapping is optimized for our restoration", + "bbox": [ + 75, + 839, + 470, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "task and thus its expressiveness of the retrieved elements can be enhanced. Building upon the priors $\\widetilde{z}$ , we learn $k, v$ by utilizing a lightweight transformer module which can be formulated as:", + "bbox": [ + 498, + 407, + 892, + 467 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\{k, v \\} = \\Phi (\\widetilde {z}, z) + \\widetilde {z}, \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 620, + 479, + 890, + 496 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\Phi (\\cdot)$ denotes the standard transformer operations. We compute the estimated features of the corresponding clear face image by performing cross-attention between $\\hat{q}$ and $k,v$ to promote adherence as follows:", + "bbox": [ + 498, + 506, + 892, + 566 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\widehat {z} = \\operatorname {C o n v} \\left(\\operatorname {s o f t m a x} \\left(\\frac {Q K ^ {T}}{\\sqrt {N}}\\right) V\\right) + k, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 555, + 577, + 890, + 619 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where Conv represents the convolutional operation, $N$ denotes the number of feature channels, and", + "bbox": [ + 498, + 627, + 890, + 657 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nQ = \\hat {q} W _ {Q} + b _ {Q},\n$$\n", + "text_format": "latex", + "bbox": [ + 633, + 667, + 750, + 684 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nK = k W _ {K} + b _ {K}, \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 635, + 686, + 890, + 703 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nV = v W _ {V} + b _ {V},\n$$\n", + "text_format": "latex", + "bbox": [ + 635, + 705, + 751, + 720 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "and $W_{Q / K / V}$ and $b_{Q / K / V}$ are learnable parameters. We then restore the clear face image $\\widehat{y}$ by feeding $\\widehat{z}$ into a decoder $G$ .", + "bbox": [ + 498, + 731, + 890, + 776 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.4. Model Training", + "text_level": 1, + "bbox": [ + 500, + 786, + 656, + 801 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Let $\\widehat{y}$ denote the restored clear face image from a degraded input $x$ . We first adopt the widely used pixel-level loss to assess the consistency to the ground truth, and the corresponding function is defined as follows:", + "bbox": [ + 498, + 809, + 890, + 869 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {c o n s}} = \\mathbf {E} _ {(x, y)} \\left[ | \\widehat {y} - y | _ {1} + \\| \\varphi (\\widehat {y}) - \\varphi (y) \\| _ {2} ^ {2} \\right], \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 527, + 881, + 890, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "9123", + "bbox": [ + 480, + 970, + 514, + 983 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $y$ denotes the ground-truth clear image with respect to $x$ , and $\\varphi(\\cdot)$ represents the feature maps extracted by a pre-trained VGG [33]. We also adopt an adversarial training strategy to improve the visual quality of restored images, and the loss function is defined as follows:", + "bbox": [ + 75, + 90, + 472, + 167 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {a d v} ^ {\\text {r e a l}} = \\mathbf {E} _ {y} [ \\log D (y) ], \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 169, + 178, + 468, + 202 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {a d v} ^ {s y n c} = \\mathbf {E} _ {x} \\big [ \\log (1 - D (\\widehat {y})) \\big ],\n$$\n", + "text_format": "latex", + "bbox": [ + 171, + 199, + 375, + 218 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $D(\\cdot)$ denotes the predicted probability of an input face image being real. By integrating the above training losses, we formulate the optimization problem of our restoration model as follows:", + "bbox": [ + 75, + 231, + 470, + 292 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\min _ {R} \\mathcal {L} _ {c o n s} ^ {q} + \\lambda \\mathcal {L} _ {K L} + \\mathcal {L} _ {d i f},\n$$\n", + "text_format": "latex", + "bbox": [ + 179, + 305, + 374, + 327 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\min _ {E, P, G} \\mathcal {L} _ {\\text {c o n s}} + \\mathcal {L} _ {\\text {a d v}} ^ {\\text {s y n c}}, \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 173, + 329, + 468, + 352 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\max _ {D} \\mathcal {L} _ {a d v} ^ {r e a l} + \\mathcal {L} _ {a d v} ^ {s y n c},\n$$\n", + "text_format": "latex", + "bbox": [ + 178, + 356, + 316, + 378 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\lambda$ denotes a weighting factor that controls the relative importance of the KL Divergence-based regularization term. Note that the latent dictionary $\\mathcal{V}$ is learnt by performing vector quantization [36] in a clear face image reconstruction process.", + "bbox": [ + 75, + 393, + 468, + 469 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 487, + 209, + 505 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this section, extensive experiments are performed to evaluate the proposed PLTrans on a variety of face restoration tasks. We first introduce the experimental settings including the training and test datasets, implementation details and evaluation protocol. Next, we show how the latent transformations benefit face restoration, followed by quantitative and qualitative comparison with state-of-the-art methods. Finally, we demonstrate the applicability of PLTrans to multiple vision tasks.", + "bbox": [ + 75, + 515, + 468, + 650 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Experimental Settings", + "text_level": 1, + "bbox": [ + 76, + 665, + 284, + 681 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1.1 Training Data", + "text_level": 1, + "bbox": [ + 76, + 690, + 230, + 705 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "PLTrans was trained on FFHQ [19], which contains 70,000 HQ face images. To construct LQ training images, we follow [48] to degrade the FFHQ images as follows:", + "bbox": [ + 75, + 715, + 468, + 763 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nI _ {L Q} = \\left(\\left(I _ {H Q} \\otimes \\mathcal {K} _ {\\rho}\\right) _ {\\downarrow b} + n _ {\\sigma}\\right) _ {J P E G _ {w}}. \\tag {13}\n$$\n", + "text_format": "latex", + "bbox": [ + 145, + 777, + 468, + 795 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Each HQ image is first convoluted with the Gaussian blur kernel which has a standard deviation $\\rho \\in \\{0:0.1:5\\}$ . Afterwards, it is downsampled $b \\in \\{0.8:32\\}$ times, and is corrupted by Gaussian noise with intensity parameter $\\sigma \\in \\{0:10\\}$ . Furthermore, the JPEG compression with quality factor $w \\in \\{50:100\\}$ is then applied to the resulting image.", + "bbox": [ + 76, + 809, + 470, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1.2 Test Data", + "text_level": 1, + "bbox": [ + 500, + 90, + 620, + 104 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We assess the restoration performance of the proposed PLTrans and the competing methods on a well-known benchmark dataset: CelebA-HQ [28], and multiple in-the-wild datasets: WIDER FACE [47], LFW-Test [17] and WebPhoto-Test [41]. Specifically, we randomly sample 2,000 CelebA-HQ images and apply the degeneration operation defined in Eq.(13) to construct degraded images, and the resulting test dataset is referred to as CelebA-Test. WIDER-Hard/Medium are derived from the WIDER FACE dataset, and there are 13,890/3407 face images with heavy/medium degradations. In addition, LFW-Test and WebPhoto-Test contain 1,711 and 407 mildly degraded face images, respectively.", + "bbox": [ + 496, + 114, + 893, + 311 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1.3 Implementation Details", + "text_level": 1, + "bbox": [ + 498, + 330, + 718, + 345 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We adopt an encoder-transformer-decoder architecture together with a generic discriminator for the proposed PLTrans. We implement PLTrans using PyTorch with two NVIDIA GeForce RTX 3090s. For the optimizer, we adopt Adam [21] with a learning rate of $5 \\times 10^{-5}$ . There are a total of 30 training epochs with a batch size of 4. For the hyperparameters, we set the number of fetched elements $d$ and the weighting factor $\\lambda$ in Eq.(12) are set to 8 and $5 \\times 10^{-5}$ , respectively.", + "bbox": [ + 496, + 354, + 892, + 491 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1.4 Evaluation Protocol", + "text_level": 1, + "bbox": [ + 500, + 510, + 692, + 523 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We implement all the competing methods based on the open source codes, and both training and test images are resized to $512 \\times 512$ for a fair comparison. The widely used metrics: Peak Signal-to-Noise Ratio (PSNR) and the Learned Perceptual Image Patch Similarity (LPIPS) are used to quantitatively evaluate the consistency between the restored face images and the corresponding ground truth. Considering that identity preservation is critical for BFR, we further report the IDentity Similarity (IDS) to the ground truth after restoration in the feature space of a well-trained face recognition model: CosFace [39]. In addition, we assess the diversity and the degree of realism of the synthesized data in terms of Fréchet Inception Distances (FID) [13].", + "bbox": [ + 496, + 534, + 890, + 731 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Degradation-unaware Representation", + "text_level": 1, + "bbox": [ + 500, + 741, + 823, + 757 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We begin by verifying the effectiveness of our latent diffusion module in producing degradation-irrelevant features. There are 500 HQ images and the corresponding 500 LQ images randomly sampled from CelebA-Test. For each HQ image and its degraded counterpart, we extract and denote their encoder features as $q_{hq}$ and $q_{lq}$ . We apply the latent diffusion-based regularization on $q_{lq}$ , and denote the regularized version as $\\hat{q}_{lq}$ . In Figure 3, we visualize the feature distributions by using t-SNE [37], and can observe that the", + "bbox": [ + 496, + 763, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "9124", + "bbox": [ + 480, + 970, + 514, + 982 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/e51848852e6dc174fd2166bb88b843b06d9b71d769242e219b0ec20861f044eb.jpg", + "image_caption": [ + "Figure 3. Distributions of HQ image features $q_{hq}$ , LQ image features $q_{lq}$ , and the regularized LQ image features $\\hat{q}_{lq}$" + ], + "image_footnote": [], + "bbox": [ + 109, + 78, + 433, + 223 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/83cec7c15c3a87fa0a68b2765f012dacec8ddea594d89e52a2928df0108d6378.jpg", + "image_caption": [ + "Figure 4. The average distances between the regularized LQ image features and the HQ counterparts in the training process." + ], + "image_footnote": [], + "bbox": [ + 86, + 253, + 455, + 398 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "clusters of $q_{hq}$ and $q_{lq}$ are separable, while the data points of $\\hat{q}_{lq}$ mix with those of $q_{hq}$ . This indicates that our regularization module is useful for mitigating degradations to a certain extent.", + "bbox": [ + 75, + 452, + 468, + 513 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Impact of the Number of Diffusion Steps", + "text_level": 1, + "bbox": [ + 76, + 527, + 424, + 545 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To obtain the degradation-unaware features, we regularize the preliminary features by performing $n$ -step perturbations followed by a reverse diffusion process. It is nontrivial to determine the optimal number of diffusion steps for BFR. For a given image with heavy degradation, it typically takes more perturbation and denoising steps to restore it, and vice versa. To illustrate this point, we perform an experiment on the face images with four levels of degradations ( $\\times 8/16/32/64$ downsampling). In Figure 4, we plot the average distances between the regularized features of LQ CelebA-Test images and the preliminary features of the HQ counterparts in the training process, and the shaded regions around these lines illustrate their variance. One can observe that the average distance to the HQ data quickly achieves the minimum value for the cases where the degree of degradation is low. This confirms that more diffusion steps are needed to restore the clean face image from a heavily degraded one. After the minima are attained, increasing the steps leads to a performance drop, since the relationship between the preliminary features and the corrupted features fades. In Figure 5, we visualize the restored face images at $\\times 32$ downsampling scale, showcasing the effects of using varying numbers of diffusion steps.", + "bbox": [ + 75, + 553, + 470, + 902 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/fe404441ff446860a7c6c5b9596ca2701c2786287d8c69ea3f5d0ebc703a1115.jpg", + "image_caption": [ + "Figure 5. The restoration results of PLTrans with different numbers of diffusion steps." + ], + "image_footnote": [], + "bbox": [ + 531, + 90, + 857, + 152 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/d359acca2edb317be770bb48de34c753c965169e9a24eb2c24992051203bd8d3.jpg", + "table_caption": [ + "Table 1. Results of PLTrans and ablative models on CelebA-Test." + ], + "table_footnote": [], + "table_body": "
MethodsFID↓LPIPS↓PSNR↑IDS↑
PLTrans w/o V90.120.480818.810.2866
PLTrans w/o DIFF44.960.430418.890.4820
PLTrans w/o LT42.120.430119.110.5201
PLTrans w/o DWT41.570.448717.990.4672
PLTrans39.580.426019.360.5264
", + "bbox": [ + 527, + 219, + 859, + 303 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.4. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 325, + 653, + 340 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We consider that the superior restoration performance of our PLTrans is mainly due to the latent diffusion-based regularization, HQ face prior, DWT-based low-frequency information injection and the prior-based key-value. To highlight the effectiveness of the four factors in BFR, we perform a number of ablative experiments. Specifically, we build four variants by disabling the diffusion module (DIFF), DWT, dictionary and Lightweight Transformer (LT) in the Prior-based Key-Value Module, and the resulting models are referred to as 'PLTrans w/o DIFF', 'PLTrans w/o DWT', 'PLTrans w/o V' and 'PLTrans w/o LT' respectively. The experiments are performed on CelebA-Test, and we summarize the results of the models in terms of FID, PSNR, LPIPS and IDS in Table 1. We can make the following observations: PLTrans outperforms its variants, yielding superior quantitative results across all the metrics. Without the latent diffusion-based regularization, it is difficult to restore the disordered structural information of degraded images, and the restoration performance reduces 5.38 in terms of FID. A number of artifacts in the resulting synthesized images are also observed as shown in Figure 6. When compared with 'PLTrans w/o V', the inclusion of the latent dictionary leads to 0.0548 improved performance in terms of LPIPS. This demonstrates that the HQ face prior is useful for synthesizing texture details. When disabling the lightweight transformer module, 'PLTrans w/o LT' learns the key and value vectors directly from the dictionary features, and we can observe a performance drop of 0.25 in terms of PSNR. We conclude that this module can infer a reasonable transformation to leverage the prior knowledge, which is useful for plausible synthesis. What's more, when disabling the DWT-based information injection module, 'PLTrans w/o DWT' leads to a significant performance drop of 0.0592 in terms of IDS. This suggests the information injection module is beneficial for preserving the semantics of the input image.", + "bbox": [ + 496, + 357, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "9125", + "bbox": [ + 482, + 970, + 514, + 983 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/b4116cbe3d270c612e3f1c203f3388c28d0ee30867b3e3a30c391e66d42f246e.jpg", + "image_caption": [ + "Input" + ], + "image_footnote": [], + "bbox": [ + 117, + 78, + 236, + 172 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/03f50d58217954f5755426d76595e57eb6edc6e6e8bfcbaa1bc3466fd5e2bf7b.jpg", + "image_caption": [ + "PLTrans w/o $\\mathcal{V}$" + ], + "image_footnote": [], + "bbox": [ + 238, + 78, + 359, + 172 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ada034fd33533eaeeb81bf795cd8205a9260be88258e1554031b07662cbccac5.jpg", + "image_caption": [ + "PLTrans w/o DIFF", + "Figure 6. Visual comparison between PLTrans and ablative models on an in-the-wild image." + ], + "image_footnote": [], + "bbox": [ + 362, + 78, + 482, + 172 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a02add26539532025428a810b580ec7eae4ad031487c853b07b60bd18b33af5a.jpg", + "image_caption": [ + "PLTrans w/o LT" + ], + "image_footnote": [], + "bbox": [ + 483, + 78, + 604, + 172 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/7ac751655b9254fce6baaa4f289827d29bd7d64a9e230b225857b8f159dbaa7b.jpg", + "image_caption": [ + "PLTrans w/o DWT" + ], + "image_footnote": [], + "bbox": [ + 604, + 78, + 725, + 172 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/265e491bd06f3c5cf13c3234255c0858a53eecce0bd206b3324ded1da8d75dbc.jpg", + "image_caption": [ + "PLTrans" + ], + "image_footnote": [], + "bbox": [ + 727, + 78, + 846, + 172 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.5. Comparison to State-of-the-arts", + "text_level": 1, + "bbox": [ + 76, + 213, + 357, + 229 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "To demonstrate the superiority of the proposed PLTrans, we perform quantitative and qualitative comparisons with state-of-the-arts, including generic image enhancement methods: Restormer [50] and DIL [23], BFR methods: GFP-GAN [41], GPEN [48], RestoreFormer [43] and Panini [42], and two diffusion-based methods: ILVR [5] and DR2 [44].", + "bbox": [ + 75, + 237, + 467, + 342 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.5.1 Results on CelebA-Test", + "text_level": 1, + "bbox": [ + 76, + 364, + 292, + 378 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We adopt the same setting as [43] to perform the experiments, where PLTrans and the competing methods are used to restore the degraded face images across a spectrum of downsampling ratios $(\\times 16, \\times 32, \\times 64)$ . The results of the methods are summarized in Table 2. GPEN, DR2 and RestoreFormer achieve lower FID/LPIPS and higher IDS scores than the other competing methods, which indicates that they perform better in terms of the precision and realism of the restored face images. On the other hand, PLTrans surpasses the competing methods in terms of all the metrics. In particular, for the most difficult case of downsampling $\\times 64$ , PLTrans is able to achieve the FID and PSNR scores of 39.58 and 19.36, which are lower and higher than the second best methods (GPEN: FID 45.12; DIL: PSNR 19.25) by 5.54 and 0.11, respectively.", + "bbox": [ + 75, + 388, + 468, + 616 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Both ILVR and DR2 are diffusion-based methods, and DR2 outperforms ILVR in the above comparison. Different from DR2 which relies on a pre-trained DDPM model, PLTrans learns a latent diffusion module to regularize the preliminary features of degraded images. We perform an additional experiment to further highlight the advantage of PLTrans over DR2. We apply the methods to handle four types of degradation: Gaussian Noise, Blur, Downsample, and JPEG. Figure 7 shows the PLTrans is able to significantly outperform DR2. This suggests that the proposed latent diffusion strategy is more effective for our task.", + "bbox": [ + 75, + 616, + 468, + 782 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1aa2f7047b97914df1dd7fe3784af129616e7d9d68759c929ce53af8bd167768.jpg", + "image_caption": [ + "Figure 7. Comparison between PLTrans and DR2 over different types of degradations." + ], + "image_footnote": [], + "bbox": [ + 107, + 789, + 267, + 881 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1aaa3fa1a325004e267c477bfc70f71be36ea789a274af6a872a51d6f5356f00.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 269, + 789, + 433, + 881 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.5.2 User Study on In-the-wild Data", + "text_level": 1, + "bbox": [ + 500, + 214, + 772, + 228 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We further evaluate PLTrans and the competing methods on WIDER-Hard/Medium, LFW-Test and WebPhoto-Test. Please note that all the models are trained on FFHQ only. In Figure 8, we also present a number of representative restoration results to demonstrate the advantages of PLTrans in reducing artifacts, restoring realistic details, and preserving identity. A user study is performed to assess the restoration quality. We randomly sample 50 degraded face images from the four datasets, and there are 80 workers who are required to score the restoration results of the methods, ranging from 0 to 10. The maximum attainable score is 10 points. The high-score results should represent delightful content with realistic details, while at the same time properly preserving the basic information of the degraded ones. To ensure an unbiased evaluation, the results of the models are presented in a random order. Figure 9 shows the average scores of the models. Our PLTrans achieves the best performance in terms of the highest average scores with a small variance.", + "bbox": [ + 496, + 237, + 890, + 508 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.6. Extended Applications", + "text_level": 1, + "bbox": [ + 500, + 520, + 709, + 536 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Due to the inclusion of the latent diffusion module, the proposed PLTrans is capable of performing various image synthesis and editing tasks. We impose Gaussian regularization on the latent variable $u$ in Eq.(2), and is thus able to synthesize diverse face images by sampling $u$ from the prior distribution. In addition, we apply linear interpolation to construct a path between two latent variables: $u_{1}$ and $u_{2}$ , and decode the interpolated vectors. We find that PLTrans can produce continuously changing images along the path. By feeding out-of-domain images, such as cartoon, incomplete image, human scribble and segmentation map, the synthesized face images are realistic while at the same time preserving semantic consistency with the input to a certain extent. We can also edit face components by replacing the $u$ 's subvector associated with the customized region with the counterparts of the reference. As shown in Figure 10, PLTrans produces realistic face images in different tasks. This demonstrates the greater capability of PLTrans in face image enhancement.", + "bbox": [ + 496, + 542, + 890, + 830 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 844, + 617, + 859 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "This paper presents a prior-based latent transformation approach for blind face restoration. We facilitate this task", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "9126", + "bbox": [ + 480, + 970, + 514, + 982 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/c15a6811eeed02655b0ddb8f205b69595bc3431da4ddb71113fa58fa97248899.jpg", + "table_caption": [ + "Table 2. Quantitative Comparison between PLTrans and competing methods on CelebA-Test." + ], + "table_footnote": [], + "table_body": "
Methods× 16× 32× 64
FID↓LPIPS↓PSNR↑IDS↑FID↓LPIPS↓PSNR↑IDS↑FID↓LPIPS↓PSNR↑IDS↑
GFPGAN [46]40.830.358321.000.6446107.650.433418.910.2523159.240.459018.410.1679
GPEN [48]25.820.378120.280.712636.220.433918.620.569845.120.451218.200.5011
ILVR [5]103.080.570821.080.576897.960.544619.760.5173107.830.573419.210.4627
Panini [42]47.140.393521.900.675444.230.483819.010.485752.370.486419.060.4272
Restormer [50]148.560.598122.120.3346185.250.630219.790.1771197.320.645919.240.1332
RestoreFormer [43]24.320.359221.990.737839.390.439719.410.537946.280.459719.110.4778
DIL [23]207.880.637521.910.3626406.170.683519.810.1697463.760.691819.250.1230
DR2 [44]35.180.411521.090.596543.410.427619.620.527349.640.456019.140.4721
PLTrans19.640.320722.130.741232.360.397819.910.596339.580.427019.360.5264
", + "bbox": [ + 109, + 93, + 857, + 224 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/0e092d063e80102937f318e8198b5592ad3d5f7579b028a1833fe5cb210e232b.jpg", + "image_caption": [ + "Figure 8. Visual comparison between PLTrans and competing methods on representative in-the-wild images." + ], + "image_footnote": [], + "bbox": [ + 117, + 227, + 848, + 378 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/564b189c5fd09ddcad263bbda523f8294983989a48f237c31e8e0f2e8617a4bc.jpg", + "image_caption": [ + "Figure 9. The scoring result of user study on in-the-wild data." + ], + "image_footnote": [], + "bbox": [ + 114, + 407, + 424, + 571 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "by improving the attention computation in a restoration transformer, which represents an effective attempt to transform query, key and value vectors to synthesize the clear face images from degraded ones. Toward this end, we incorporate a latent diffusion module to regularize the preliminary features, such that the regularized version becomes less sensitive to degradations. This is essential for enhancing the generalization performance over unknown degradations. We further incorporate a HQ face prior in the form of a latent dictionary to learn key and value, followed by cross-attention computation with the regularized features as query. Extensive experiments validate the effectiveness of our proposed framework PLTrans in restoring faithful details and preserving identity information.", + "bbox": [ + 75, + 601, + 468, + 813 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Acknowledgments", + "text_level": 1, + "bbox": [ + 76, + 829, + 254, + 845 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported in part by the National Natural Science Foundation of China (Project No. 62072189, 62106136), in part by the Research Grants Coun", + "bbox": [ + 75, + 854, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/551f5913e21724ff884b0336cb81aa00f569817624383cfa525bb9b9fc532a06.jpg", + "image_caption": [ + "Figure 10. Representative results of PLTrans on different vision tasks." + ], + "image_footnote": [], + "bbox": [ + 521, + 405, + 869, + 753 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "cil of the Hong Kong Special Administration Region (Project No. CityU 11206622), in part by the Guang-Dong Basic and Applied Basic Research Foundation (Project No. 2020A1515010484, 2022A1515011160, 2022A1515010434), and in part by TCL Science and Technology Innovation Fund (Project No. 20231752).", + "bbox": [ + 496, + 808, + 890, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "9127", + "bbox": [ + 480, + 970, + 514, + 982 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 106 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Nicolas Carion, Francisco Massa, Gabriel Synnaeve, Nicolas Usunier, Alexander Kirillov, and Sergey Zagoruyko. 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In International Conference on Learning Representations, 2021. 3" + ], + "bbox": [ + 501, + 92, + 890, + 882 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "9129", + "bbox": [ + 482, + 970, + 514, + 982 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_model.json b/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_model.json new file mode 100644 index 0000000000000000000000000000000000000000..965375cce717c4686664f87978f9f6702dc94900 --- /dev/null +++ b/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_model.json @@ -0,0 +1,2354 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.123, + 0.131, + 0.85, + 0.175 + ], + "angle": 0, + "content": "Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration" + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.202, + 0.871, + 0.24 + ], + "angle": 0, + "content": "Lianxin Xie\\(^{1}\\), Csbingbing Zheng\\(^{1}\\), Wen Xue\\(^{1}\\), Le Jiang\\(^{1}\\), Cheng Liu\\(^{4}\\), Si Wu\\(^{1,2,3*}\\), Hau San Wong\\(^{5*}\\) \n\\(^{1}\\)School of Computer Science and Engineering, South China University of Technology" + }, + { + "type": "text", + "bbox": [ + 0.388, + 0.24, + 0.584, + 0.258 + ], + "angle": 0, + "content": "\\(^{2}\\)Peng Cheng Laboratory" + }, + { + "type": "text", + "bbox": [ + 0.419, + 0.257, + 0.551, + 0.273 + ], + "angle": 0, + "content": "\\(^{3}\\)PAZHOU LAB" + }, + { + "type": "text", + "bbox": [ + 0.276, + 0.275, + 0.696, + 0.293 + ], + "angle": 0, + "content": "\\(^{4}\\)Departent of Computer Science, Shantou University" + }, + { + "type": "text", + "bbox": [ + 0.225, + 0.293, + 0.746, + 0.311 + ], + "angle": 0, + "content": "\\(^{5}\\)Department of Computer Science, City University of Hong Kong" + }, + { + "type": "text", + "bbox": [ + 0.178, + 0.313, + 0.793, + 0.327 + ], + "angle": 0, + "content": "{cslianxin.xie, 202321044369, csxuewen, 202220143385}@mail.scut.edu.cn" + }, + { + "type": "text", + "bbox": [ + 0.228, + 0.331, + 0.742, + 0.345 + ], + "angle": 0, + "content": "cliu@stu.edu.cn, cswusi@scut.edu.cn, cshswong@cityu.edu.hk" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.38, + 0.313, + 0.396 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.412, + 0.474, + 0.775 + ], + "angle": 0, + "content": "Blind face restoration focuses on restoring high-fidelity details from images subjected to complex and unknown degradations, while preserving identity information. In this paper, we present a Prior-based Latent Transformation approach (PLTrans), which is specifically designed to learn a degradation-unaware representation, thereby allowing the restoration network to effectively generalize to real-world degradation. Toward this end, PLTrans learns a degradation-unaware query via a latent diffusion-based regularization module. Furthermore, conditioned on the features of a degraded face image, a latent dictionary that captures the priors of HQ face images is leveraged to refine the features by mapping the top-d nearest elements. The refined version will be used to build key and value for the cross-attention computation, which is tailored to each degraded image and exhibits reduced sensitivity to different degradation factors. Conditioned on the resulting representation, we train a decoding network that synthesizes face images with authentic details and identity preservation. Through extensive experiments, we verify the effectiveness of the design elements and demonstrate the generalization ability of our proposed approach for both synthetic and unknown degradations. We finally demonstrate the applicability of PLTrans in other vision tasks." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.801, + 0.21, + 0.816 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Blind Face Restoration (BFR) aims to restore facial details while preserving the identity in degraded images that have been subjected to varying and unidentified degradations. Many CNN-based and Transformer-based BFR frameworks have been previously designed to enhance" + }, + { + "type": "image", + "bbox": [ + 0.518, + 0.379, + 0.875, + 0.514 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.519, + 0.895, + 0.575 + ], + "angle": 0, + "content": "Figure 1. An example to illustrate that a better query empowers a generic model to generate HQ images, and vice versa. Enhancing the quality of key and value yields relatively slight effect. The restored image quality can be sorted as: \\((\\mathrm{b}) > (\\mathrm{c}) > (\\mathrm{d}) > (\\mathrm{a})\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.595, + 0.893, + 0.852 + ], + "angle": 0, + "content": "restoration performance, leading to significant advancements in the field. However, it is impractical to gather sufficient pairs of degraded-clean training data in real-world situations. In the pursuit of synthesizing clear and realistic face images from degraded ones, recent BFR methods have incorporated various face priors, including high-quality(HQ) exemplars with the same identity or geometric information. These methods often rely on capturing the correlation between degraded and clean images, making them susceptible to significant performance drops when handling unseen degradations. Additionally, there have been attempts to apply generative priors to BFR. Generative Adversarial Networks (GAN) [12] that are well-trained on face images represent strong priors due to their ability to generate high-fidelity samples, while GAN-based models are typically trained on specific datasets, thus limiting their generalization performance." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.856, + 0.894, + 0.903 + ], + "angle": 0, + "content": "The generic transformer-based model takes a high/low-quality (HQ/LQ) image as input and generates a set of corresponding HQ/LQ query, key and value in each block. The" + }, + { + "type": "footer", + "bbox": [ + 0.078, + 0.938, + 0.258, + 0.955 + ], + "angle": 0, + "content": "\\*Co-corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.972, + 0.516, + 0.984 + ], + "angle": 0, + "content": "9120" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.543 + ], + "angle": 0, + "content": "result shown in Figure 1 suggests that improving query and key-value leads to varying improvements for face restoration. Inspired by this observation, we propose a Prior-based Latent Transformation approach for BFR, which we refer to as PLTrans. The core idea behind PLTrans is to transform the preliminary features of degraded images to become degradation-unaware query, while at the same time to refine the preliminary feature to build key and value which are used in cross-attention computation. To achieve this, we incorporate a latent diffusion module to remove degradation from the features, in which various types of degradations become indistinguishable as Gaussian noise is added. In order to maintain the semantic similarity of the restored image to the degraded one, the features at each transition step is also combined with the input's low-frequency information obtained through a 2D discrete wavelet transform [49] during the reverse diffusion process. The resulting features are subsequently decoded into a query. Additionally, by incorporating a latent dictionary encoding rich details from the features of HQ face images via vector quantization [36], We learns a global mapping over the retrieved priors based on the top-\\(d\\) elements that are nearest neighbors of the input features to build key and value. The cross-attention computation is performed over the obtained query, key and value for restoring the features of clean face. Extensive experiments are performed to demonstrate the effectiveness of the design elements and the improvement in generalization performance on real-world images with unknown degradation. We summarize the main contributions of this work as follows:" + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.556, + 0.47, + 0.603 + ], + "angle": 0, + "content": "- We address BFR from a new perspective of performing prior-based transformations on query, key and value for the attention computation in a latent transformer." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.614, + 0.47, + 0.705 + ], + "angle": 0, + "content": "- By incorporating the wavelet-based low-frequency components of the degraded features as supplementary information into the intermediate stages, we can effectively guide the reverse diffusion process to synthesize the degradation-unaware features, while preserving essential semantics from the input." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.716, + 0.47, + 0.792 + ], + "angle": 0, + "content": "- To restore the features of clean face, we further leverage a latent dictionary to refine the features of the degraded image, based on which we learn key and value to perform cross-attention computation with the degradation-unaware features as query." + }, + { + "type": "list", + "bbox": [ + 0.097, + 0.556, + 0.47, + 0.792 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.807, + 0.22, + 0.822 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.832, + 0.291, + 0.847 + ], + "angle": 0, + "content": "2.1. Blind Face Restoration" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Significant progress has been achieved in face image restoration recent years [8, 18, 20, 26]. A typical strategy is to regard the restoration as a domain translation task" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.333 + ], + "angle": 0, + "content": "[10, 34, 45]. Considering facial structures, there have been many attempts to incorporate a variety of priors in the generation process. In [4, 16, 29], landmark estimation were used to recover clear face images from low-resolution ones based on facial geometry priors in the form of facial parsing maps. Given a HQ reference image of the same identity, a warping network was learnt to correct pose and expression for better recovery of fine details [7, 24, 25]. However, the reference-guided methods were only applicable in limited scenes. To effectively obtain the priors associated with the degraded images, a dictionary of semantic facial components was learnt in the feature space of a pretrained VGG [22], which was designed for face recognition. In addition, 3D morphable models explicitly modeled face attributes and can thus be applied to regularize the facial structures and identity information [15, 51]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.339, + 0.892, + 0.732 + ], + "angle": 0, + "content": "Another research line is to exploit the priors encapsulated in the pre-trained generative models. The generative prior-based methods typically projected the degraded image back to the latent space of StyleGAN [19], and the resulting latent codes are transformed and decoded into a HQ face image [30]. To improve the efficiency of GAN inversion, a dedicated encoder was trained for latent code prediction, conditioned on the input image [31]. However, the restoration performance was limited by low dimensionality and poor spatial expression capability of the latent space. To address this issue, facial structural information was utilized by injecting the external features extracted from the degraded image into the generator of GFP-GAN [41], GPEN [48] and GLEAN [2]. Another effective approach is to perform progressive latent space extension across multiple intermediate layers of StyleGAN [32]. Based on a pre-trained Denoising Diffusion Probabilistic Model (DDPM) [14], different attempts were made to control the generation process. Choi et al. [5] proposed an Iterative Latent Variable Refinement (ILVR) method to condition the generative process on a given reference image. Further, Wang et al. [44] applied ILVR to BFR, and the proposed model is referred to as DR2, in which a degraded image was corrupted by Gaussian noise, and the corresponding HQ image could be recovered from its noisy version via an iterative denoising process." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "There are fundamental differences between the proposed PLTrans and the above methods. DDPM was designed for generic image synthesis, which differs from our restoration task. DR2 [44] utilized a pre-trained DDPM to perform sampling in the data space, while we learn a task-specific latent diffusion module to generate a degradation-unaware representation. Although RestoreFormer [43] captures clear face priors in the form of a latent dictionary, our model uses a dictionary to quantize the features of degraded images. We further learn a global mapping over the top- \\(d\\) nearest elements to enhance the expressiveness of the resulting fea" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.972, + 0.514, + 0.984 + ], + "angle": 0, + "content": "9121" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.078, + 0.093, + 0.118, + 0.105 + ], + "angle": 0, + "content": "tures." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.117, + 0.266, + 0.132 + ], + "angle": 0, + "content": "2.2. Vision Transformer" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.141, + 0.473, + 0.504 + ], + "angle": 0, + "content": "Transformers have emerged as powerful deep learning architectures for natural language processing [6,38]. Due to their excellent capability in capturing long-range dependencies between elements, the transformer-based models have been applied in a variety of vision tasks, including image classification [9], semantic segmentation [40], object detection [1, 52], and so on. Vision Transformers (ViTs) typically learnt to represent an image as a sequence of patches and estimate their underlying relationships [9, 35]. To deal with high-resolution images and visual objects with large variations in scale, SwinTransformer [27] adopted a shifted window strategy to enhance the modeling power of ViT and yield a hierarchical representation. By performing vector quantization in the latent space, a transformer was applied to high-resolution image generation by predicting the sequence of codebook indices [11]. In [50], a computationally efficient transformer was designed to perform multi-scale local-global representation learning for image restoration. On the other hand, a large-scale pre-trained transformer was also applied for multiple image processing tasks [3]. In this work, we apply a transformer architecture to BFR by modifying the intermediate feature as the query through a denoising diffusion process and learning the prior-based key and value for cross attention computation." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.517, + 0.251, + 0.534 + ], + "angle": 0, + "content": "3. Proposed Method" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.542, + 0.188, + 0.557 + ], + "angle": 0, + "content": "3.1. Overview" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.566, + 0.473, + 0.793 + ], + "angle": 0, + "content": "Our proposed PLTrans is built on an encoder-transformer-decoder architecture. As depicted in Figure 2, an encoder \\( E \\) processes a degraded face image \\( x \\) to extract preliminary features \\( q = E(x) \\). A Latent Diffusion-based Feature Regularization Module takes \\( q \\) as input and returns the degradation-irrelevant feature \\( \\hat{q} \\) which is encouraged to be as consistent as possible with the corresponding ground truth. To recover rich face details, we utilize a pre-trained latent dictionary \\( \\mathcal{V} \\), learned from HQ face images, to quantize \\( z \\). The resulting features \\( q \\) are further refined and used to build the key and value vectors. A cross-attention-based transformer block takes the obtained query, key and value as input and returns the features to be decoded into a clear face image, which is encouraged to be as consistent as possible with the corresponding ground truth." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.802, + 0.47, + 0.818 + ], + "angle": 0, + "content": "3.2. Latent Diffusion-based Feature Regularization" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.825, + 0.47, + 0.902 + ], + "angle": 0, + "content": "The structural information of an image with heavy degradation is typically disordered, and thus the preliminary features extracted by a generic encoder are potentially inadequate for capturing accurate semantics. Naively decoding the preliminary features may result in artifacts within the" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.431 + ], + "angle": 0, + "content": "The purpose of this section is to present a new method for the synthesis of the original content. To address this issue, we propose to regularize the preliminary features via a latent diffusion module. Specifically, a mapping network \\( E_{Q} \\) is adopted to take the feature \\( q \\) as input and produces a latent variable \\( u^{lq} \\) or \\( u^{hq} \\). Our objective is to construct a Markov Chain that incrementally approximates the HQ data distribution starting from a Gaussian prior. The regularization process attempts to restore the features from its noisy version while simultaneously preserving the low-frequency content inherent in the preliminary features. To attain this objective, we perform n-step perturbations to obtain probability \\( p_{\\pi}(u_{n}^{lq}|u^{lq}) \\), subsequently compute the transition probability \\( p_{\\theta}(u_{t - 1}^{hq}|u_t^{hq}) \\), and finally obtain \\( p_{\\theta}(u_s^{hq}|u_n^{lq}) \\), where \\( u_{n}^{lq}\\approx u_{n}^{hq} \\) and \\( s < t\\leq n \\). Finally, we can get \\( \\hat{u}_0^{hq} \\) by computing probability \\( p_{\\theta}(\\hat{u}_0^{hq}|u_s^{hq}) \\) directly. On the other hand, auxiliary information in the form of the low-frequency signals from \\( u_{t}^{lq} \\) are injected at multiple intermediate stages of the reverse diffusion process. We combine the multi-scale high-frequency signals from \\( u_{t}^{hq} \\) and the low-frequency signals from \\( u_{t}^{lq} \\) using Discrete Wavelet Transform (DWT) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.589, + 0.439, + 0.892, + 0.459 + ], + "angle": 0, + "content": "\\[\nu _ {t} ^ {h q} \\leftarrow \\phi^ {\\prime} \\left(\\phi^ {l f} \\left(u _ {t} ^ {l q}\\right), \\phi^ {h f} \\left(u _ {t} ^ {h q}\\right)\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.467, + 0.895, + 0.679 + ], + "angle": 0, + "content": "where \\(\\phi^{lf / hf}(\\cdot)\\) represents the DWT function that extracts the low/high-frequency information, and \\(\\phi^{\\prime}(\\cdot)\\) denotes the Inverse Discrete Wavelet Transform (IDWT). As will be demonstrated in the experiments, \\(\\hat{u}_0^{hq}\\) is less sensitive to degradation and can retain the primary semantics from \\(u^{lq}\\). Conditioned on the regularized variable, a mapping network \\(D_{Q}\\) is responsible for yielding degradation-irrelevant features \\(\\hat{q}\\) in the same space of \\(q\\). Considering that a latent space with excessively high variance could affect the training stability and the quality of sample generation in both the diffusion and reverse processes, we impose a Kullback-Leibler (KL) divergence-based penalty on the latent variable \\(u\\) to promote adherence to a standard normal distribution as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.624, + 0.69, + 0.891, + 0.708 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {K L} = K L \\left(p _ {u} \\| p _ {g}\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.717, + 0.894, + 0.777 + ], + "angle": 0, + "content": "where \\( p_u \\) and \\( p_g \\) denote a \\( u \\)'s distribution and a Gaussian distribution. Conditioned on \\( u \\), \\( D_Q \\) is trained to recover \\( q \\) as accurately as possible for reconstruction, and the consistency loss is defined as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.618, + 0.787, + 0.891, + 0.806 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {c o n s}} ^ {q} = \\mathbf {E} _ {q} [ | \\hat {q} - q | _ {1} ], \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.814, + 0.894, + 0.874 + ], + "angle": 0, + "content": "where \\(\\hat{q} = D_Q(u)\\) denotes the prediction. Given the training data in the form of HQ face image features \\(u^{hq}\\), our latent diffusion module is optimized by a standard mean-squared error loss as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.54, + 0.884, + 0.892, + 0.904 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {d i f} = \\mathbf {E} _ {\\epsilon} \\left[ | \\epsilon - \\epsilon_ {\\theta} \\left(\\sqrt {\\bar {a} _ {t}} u _ {t} ^ {h q} + \\sqrt {1 - \\bar {a} _ {t}} \\epsilon , t\\right) | _ {2} ^ {2} \\right], \\tag {4}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.971, + 0.516, + 0.984 + ], + "angle": 0, + "content": "9122" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.079, + 0.631, + 0.33 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.636, + 0.081, + 0.891, + 0.329 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.333, + 0.894, + 0.391 + ], + "angle": 0, + "content": "Figure 2. Overview of the proposed PLTrans framework. An encoder \\( E \\) extracts the preliminary feature \\( q \\) from a degraded face image \\( x \\). A latent diffusion-based regularization module is applied to \\( q \\) to obtain its degradation-irrelevant version \\( \\hat{q} \\) as query. On the other hand, a prior-based key-value module quantizes and transforms \\( q \\) to learn key \\( k \\) and value \\( v \\). We perform cross-attention computation over \\( \\hat{q}, k \\) and \\( v \\) in each transformer block, and feed the resulting feature into a generator \\( G \\) to synthesize a HQ face image." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.407, + 0.471, + 0.471 + ], + "angle": 0, + "content": "where \\(\\epsilon_{\\theta}(u_t^{hq},t)\\) is a U-net model used to predict the noise from \\(u_{t}^{hq}\\) at step \\(t,\\epsilon \\sim \\mathcal{N}(\\mathbf{0},\\mathbf{I})\\) and \\(\\bar{\\alpha}_{t} = \\prod_{m = 1}^{t}(1 - \\beta_{m})\\) in which \\(\\{\\beta_1,\\beta_2,\\dots,\\beta_t\\}\\) is the variance schedule used to control the degree of noise addition." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.48, + 0.29, + 0.496 + ], + "angle": 0, + "content": "3.3. Prior-based Key-Value" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.504, + 0.47, + 0.638 + ], + "angle": 0, + "content": "In addition to regularizing the preliminary features as query, we also learn key and value within our transformation by integrating HQ face priors via a latent dictionary \\(\\mathcal{V}\\). The elements in \\(\\mathcal{V}\\) are expected to offer a wealth of clear face details. Initially, we utilize the preliminary feature \\(q\\) to compute \\(z\\) through convolution and self-attention operations. Then, \\(z\\) is quantized by retrieving the \\(d\\) nearest elements from \\(\\mathcal{V}\\), which serve as the respective priors, as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.124, + 0.65, + 0.47, + 0.675 + ], + "angle": 0, + "content": "\\[\n\\left\\{e ^ {(1)}, \\dots , e ^ {(d)} \\right\\} _ {(i, j)} = \\arg \\min _ {e \\in \\mathcal {V}} \\| e - z _ {(i, j)} \\| _ {2} ^ {2}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.685, + 0.47, + 0.776 + ], + "angle": 0, + "content": "where \\( z_{(i,j)} \\) denotes the feature vector at the spatial location \\( (i,j) \\). Rather than replacing \\( z \\) with the most similar element, the retrieved top- \\( d \\) priors contain more richer information. Note that \\( \\mathcal{V} \\) may not generalize well to the reconstruction of degraded data. A global mapping over the top- \\( d \\) priors is performed as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.21, + 0.788, + 0.47, + 0.83 + ], + "angle": 0, + "content": "\\[\n\\widetilde {z} _ {(i, j)} = \\sum_ {l = 1} ^ {d} r _ {l} e ^ {(l)}, \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.471, + 0.902 + ], + "angle": 0, + "content": "where \\(\\mathbf{r} = [r_1, \\ldots, r_d]\\) denotes a learnable combination coefficient vector \\(e^{(l)} \\in \\{e^{(1)}, \\ldots, e^{(d)}\\}_{(i,j)}\\). Different from generic dictionary-based representation for data reconstruction, the global mapping is optimized for our restoration" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.409, + 0.893, + 0.468 + ], + "angle": 0, + "content": "task and thus its expressiveness of the retrieved elements can be enhanced. Building upon the priors \\(\\widetilde{z}\\), we learn \\(k, v\\) by utilizing a lightweight transformer module which can be formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.622, + 0.48, + 0.892, + 0.497 + ], + "angle": 0, + "content": "\\[\n\\{k, v \\} = \\Phi (\\widetilde {z}, z) + \\widetilde {z}, \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.507, + 0.893, + 0.568 + ], + "angle": 0, + "content": "where \\(\\Phi (\\cdot)\\) denotes the standard transformer operations. We compute the estimated features of the corresponding clear face image by performing cross-attention between \\(\\hat{q}\\) and \\(k,v\\) to promote adherence as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.557, + 0.578, + 0.892, + 0.62 + ], + "angle": 0, + "content": "\\[\n\\widehat {z} = \\operatorname {C o n v} \\left(\\operatorname {s o f t m a x} \\left(\\frac {Q K ^ {T}}{\\sqrt {N}}\\right) V\\right) + k, \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.628, + 0.892, + 0.658 + ], + "angle": 0, + "content": "where Conv represents the convolutional operation, \\(N\\) denotes the number of feature channels, and" + }, + { + "type": "equation", + "bbox": [ + 0.634, + 0.668, + 0.751, + 0.685 + ], + "angle": 0, + "content": "\\[\nQ = \\hat {q} W _ {Q} + b _ {Q},\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.636, + 0.687, + 0.891, + 0.704 + ], + "angle": 0, + "content": "\\[\nK = k W _ {K} + b _ {K}, \\tag {9}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.636, + 0.706, + 0.753, + 0.722 + ], + "angle": 0, + "content": "\\[\nV = v W _ {V} + b _ {V},\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.732, + 0.892, + 0.777 + ], + "angle": 0, + "content": "and \\( W_{Q / K / V} \\) and \\( b_{Q / K / V} \\) are learnable parameters. We then restore the clear face image \\( \\widehat{y} \\) by feeding \\( \\widehat{z} \\) into a decoder \\( G \\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.787, + 0.658, + 0.803 + ], + "angle": 0, + "content": "3.4. Model Training" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.81, + 0.892, + 0.871 + ], + "angle": 0, + "content": "Let \\(\\widehat{y}\\) denote the restored clear face image from a degraded input \\(x\\). We first adopt the widely used pixel-level loss to assess the consistency to the ground truth, and the corresponding function is defined as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.529, + 0.882, + 0.892, + 0.902 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {c o n s}} = \\mathbf {E} _ {(x, y)} \\left[ | \\widehat {y} - y | _ {1} + \\| \\varphi (\\widehat {y}) - \\varphi (y) \\| _ {2} ^ {2} \\right], \\tag {10}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.971, + 0.516, + 0.984 + ], + "angle": 0, + "content": "9123" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.168 + ], + "angle": 0, + "content": "where \\(y\\) denotes the ground-truth clear image with respect to \\(x\\), and \\(\\varphi(\\cdot)\\) represents the feature maps extracted by a pre-trained VGG [33]. We also adopt an adversarial training strategy to improve the visual quality of restored images, and the loss function is defined as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.17, + 0.179, + 0.47, + 0.203 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {a d v} ^ {\\text {r e a l}} = \\mathbf {E} _ {y} [ \\log D (y) ], \\tag {11}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.173, + 0.2, + 0.376, + 0.219 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {a d v} ^ {s y n c} = \\mathbf {E} _ {x} \\big [ \\log (1 - D (\\widehat {y})) \\big ],\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.232, + 0.471, + 0.293 + ], + "angle": 0, + "content": "where \\( D(\\cdot) \\) denotes the predicted probability of an input face image being real. By integrating the above training losses, we formulate the optimization problem of our restoration model as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.18, + 0.306, + 0.375, + 0.328 + ], + "angle": 0, + "content": "\\[\n\\min _ {R} \\mathcal {L} _ {c o n s} ^ {q} + \\lambda \\mathcal {L} _ {K L} + \\mathcal {L} _ {d i f},\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.174, + 0.33, + 0.469, + 0.353 + ], + "angle": 0, + "content": "\\[\n\\min _ {E, P, G} \\mathcal {L} _ {\\text {c o n s}} + \\mathcal {L} _ {\\text {a d v}} ^ {\\text {s y n c}}, \\tag {12}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.179, + 0.357, + 0.318, + 0.379 + ], + "angle": 0, + "content": "\\[\n\\max _ {D} \\mathcal {L} _ {a d v} ^ {r e a l} + \\mathcal {L} _ {a d v} ^ {s y n c},\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.394, + 0.47, + 0.47 + ], + "angle": 0, + "content": "where \\(\\lambda\\) denotes a weighting factor that controls the relative importance of the KL Divergence-based regularization term. Note that the latent dictionary \\(\\mathcal{V}\\) is learnt by performing vector quantization [36] in a clear face image reconstruction process." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.488, + 0.21, + 0.506 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.516, + 0.47, + 0.651 + ], + "angle": 0, + "content": "In this section, extensive experiments are performed to evaluate the proposed PLTrans on a variety of face restoration tasks. We first introduce the experimental settings including the training and test datasets, implementation details and evaluation protocol. Next, we show how the latent transformations benefit face restoration, followed by quantitative and qualitative comparison with state-of-the-art methods. Finally, we demonstrate the applicability of PLTrans to multiple vision tasks." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.666, + 0.285, + 0.683 + ], + "angle": 0, + "content": "4.1. Experimental Settings" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.691, + 0.231, + 0.707 + ], + "angle": 0, + "content": "4.1.1 Training Data" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.717, + 0.47, + 0.764 + ], + "angle": 0, + "content": "PLTrans was trained on FFHQ [19], which contains 70,000 HQ face images. To construct LQ training images, we follow [48] to degrade the FFHQ images as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.146, + 0.779, + 0.469, + 0.796 + ], + "angle": 0, + "content": "\\[\nI _ {L Q} = \\left(\\left(I _ {H Q} \\otimes \\mathcal {K} _ {\\rho}\\right) _ {\\downarrow b} + n _ {\\sigma}\\right) _ {J P E G _ {w}}. \\tag {13}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.81, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Each HQ image is first convoluted with the Gaussian blur kernel which has a standard deviation \\(\\rho \\in \\{0:0.1:5\\}\\). Afterwards, it is downsampled \\(b \\in \\{0.8:32\\}\\) times, and is corrupted by Gaussian noise with intensity parameter \\(\\sigma \\in \\{0:10\\}\\). Furthermore, the JPEG compression with quality factor \\(w \\in \\{50:100\\}\\) is then applied to the resulting image." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.092, + 0.622, + 0.106 + ], + "angle": 0, + "content": "4.1.2 Test Data" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.116, + 0.894, + 0.313 + ], + "angle": 0, + "content": "We assess the restoration performance of the proposed PLTrans and the competing methods on a well-known benchmark dataset: CelebA-HQ [28], and multiple in-the-wild datasets: WIDER FACE [47], LFW-Test [17] and WebPhoto-Test [41]. Specifically, we randomly sample 2,000 CelebA-HQ images and apply the degeneration operation defined in Eq.(13) to construct degraded images, and the resulting test dataset is referred to as CelebA-Test. WIDER-Hard/Medium are derived from the WIDER FACE dataset, and there are 13,890/3407 face images with heavy/medium degradations. In addition, LFW-Test and WebPhoto-Test contain 1,711 and 407 mildly degraded face images, respectively." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.332, + 0.719, + 0.347 + ], + "angle": 0, + "content": "4.1.3 Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.355, + 0.893, + 0.492 + ], + "angle": 0, + "content": "We adopt an encoder-transformer-decoder architecture together with a generic discriminator for the proposed PLTrans. We implement PLTrans using PyTorch with two NVIDIA GeForce RTX 3090s. For the optimizer, we adopt Adam [21] with a learning rate of \\(5 \\times 10^{-5}\\). There are a total of 30 training epochs with a batch size of 4. For the hyperparameters, we set the number of fetched elements \\(d\\) and the weighting factor \\(\\lambda\\) in Eq.(12) are set to 8 and \\(5 \\times 10^{-5}\\), respectively." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.511, + 0.694, + 0.525 + ], + "angle": 0, + "content": "4.1.4 Evaluation Protocol" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.535, + 0.892, + 0.732 + ], + "angle": 0, + "content": "We implement all the competing methods based on the open source codes, and both training and test images are resized to \\(512 \\times 512\\) for a fair comparison. The widely used metrics: Peak Signal-to-Noise Ratio (PSNR) and the Learned Perceptual Image Patch Similarity (LPIPS) are used to quantitatively evaluate the consistency between the restored face images and the corresponding ground truth. Considering that identity preservation is critical for BFR, we further report the IDentity Similarity (IDS) to the ground truth after restoration in the feature space of a well-trained face recognition model: CosFace [39]. In addition, we assess the diversity and the degree of realism of the synthesized data in terms of Fréchet Inception Distances (FID) [13]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.742, + 0.825, + 0.758 + ], + "angle": 0, + "content": "4.2. Degradation-unaware Representation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We begin by verifying the effectiveness of our latent diffusion module in producing degradation-irrelevant features. There are 500 HQ images and the corresponding 500 LQ images randomly sampled from CelebA-Test. For each HQ image and its degraded counterpart, we extract and denote their encoder features as \\( q_{hq} \\) and \\( q_{lq} \\). We apply the latent diffusion-based regularization on \\( q_{lq} \\), and denote the regularized version as \\( \\hat{q}_{lq} \\). In Figure 3, we visualize the feature distributions by using t-SNE [37], and can observe that the" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.972, + 0.516, + 0.983 + ], + "angle": 0, + "content": "9124" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.11, + 0.079, + 0.434, + 0.224 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.225, + 0.47, + 0.253 + ], + "angle": 0, + "content": "Figure 3. Distributions of HQ image features \\( q_{hq} \\), LQ image features \\( q_{lq} \\), and the regularized LQ image features \\( \\hat{q}_{lq} \\)" + }, + { + "type": "image", + "bbox": [ + 0.088, + 0.255, + 0.456, + 0.4 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.402, + 0.47, + 0.432 + ], + "angle": 0, + "content": "Figure 4. The average distances between the regularized LQ image features and the HQ counterparts in the training process." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.453, + 0.47, + 0.514 + ], + "angle": 0, + "content": "clusters of \\( q_{hq} \\) and \\( q_{lq} \\) are separable, while the data points of \\( \\hat{q}_{lq} \\) mix with those of \\( q_{hq} \\). This indicates that our regularization module is useful for mitigating degradations to a certain extent." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.529, + 0.426, + 0.546 + ], + "angle": 0, + "content": "4.3. Impact of the Number of Diffusion Steps" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.554, + 0.471, + 0.903 + ], + "angle": 0, + "content": "To obtain the degradation-unaware features, we regularize the preliminary features by performing \\( n \\)-step perturbations followed by a reverse diffusion process. It is nontrivial to determine the optimal number of diffusion steps for BFR. For a given image with heavy degradation, it typically takes more perturbation and denoising steps to restore it, and vice versa. To illustrate this point, we perform an experiment on the face images with four levels of degradations (\\( \\times 8/16/32/64 \\) downsampling). In Figure 4, we plot the average distances between the regularized features of LQ CelebA-Test images and the preliminary features of the HQ counterparts in the training process, and the shaded regions around these lines illustrate their variance. One can observe that the average distance to the HQ data quickly achieves the minimum value for the cases where the degree of degradation is low. This confirms that more diffusion steps are needed to restore the clean face image from a heavily degraded one. After the minima are attained, increasing the steps leads to a performance drop, since the relationship between the preliminary features and the corrupted features fades. In Figure 5, we visualize the restored face images at \\( \\times 32 \\) downsampling scale, showcasing the effects of using varying numbers of diffusion steps." + }, + { + "type": "image", + "bbox": [ + 0.532, + 0.092, + 0.859, + 0.153 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.155, + 0.892, + 0.182 + ], + "angle": 0, + "content": "Figure 5. The restoration results of PLTrans with different numbers of diffusion steps." + }, + { + "type": "table_caption", + "bbox": [ + 0.502, + 0.205, + 0.89, + 0.218 + ], + "angle": 0, + "content": "Table 1. Results of PLTrans and ablative models on CelebA-Test." + }, + { + "type": "table", + "bbox": [ + 0.529, + 0.22, + 0.86, + 0.304 + ], + "angle": 0, + "content": "
MethodsFID↓LPIPS↓PSNR↑IDS↑
PLTrans w/o V90.120.480818.810.2866
PLTrans w/o DIFF44.960.430418.890.4820
PLTrans w/o LT42.120.430119.110.5201
PLTrans w/o DWT41.570.448717.990.4672
PLTrans39.580.426019.360.5264
" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.326, + 0.654, + 0.342 + ], + "angle": 0, + "content": "4.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.358, + 0.895, + 0.903 + ], + "angle": 0, + "content": "We consider that the superior restoration performance of our PLTrans is mainly due to the latent diffusion-based regularization, HQ face prior, DWT-based low-frequency information injection and the prior-based key-value. To highlight the effectiveness of the four factors in BFR, we perform a number of ablative experiments. Specifically, we build four variants by disabling the diffusion module (DIFF), DWT, dictionary and Lightweight Transformer (LT) in the Prior-based Key-Value Module, and the resulting models are referred to as 'PLTrans w/o DIFF', 'PLTrans w/o DWT', 'PLTrans w/o V' and 'PLTrans w/o LT' respectively. The experiments are performed on CelebA-Test, and we summarize the results of the models in terms of FID, PSNR, LPIPS and IDS in Table 1. We can make the following observations: PLTrans outperforms its variants, yielding superior quantitative results across all the metrics. Without the latent diffusion-based regularization, it is difficult to restore the disordered structural information of degraded images, and the restoration performance reduces 5.38 in terms of FID. A number of artifacts in the resulting synthesized images are also observed as shown in Figure 6. When compared with 'PLTrans w/o V', the inclusion of the latent dictionary leads to 0.0548 improved performance in terms of LPIPS. This demonstrates that the HQ face prior is useful for synthesizing texture details. When disabling the lightweight transformer module, 'PLTrans w/o LT' learns the key and value vectors directly from the dictionary features, and we can observe a performance drop of 0.25 in terms of PSNR. We conclude that this module can infer a reasonable transformation to leverage the prior knowledge, which is useful for plausible synthesis. What's more, when disabling the DWT-based information injection module, 'PLTrans w/o DWT' leads to a significant performance drop of 0.0592 in terms of IDS. This suggests the information injection module is beneficial for preserving the semantics of the input image." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.972, + 0.516, + 0.984 + ], + "angle": 0, + "content": "9125" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.118, + 0.079, + 0.238, + 0.173 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.165, + 0.175, + 0.192, + 0.184 + ], + "angle": 0, + "content": "Input" + }, + { + "type": "image", + "bbox": [ + 0.24, + 0.079, + 0.361, + 0.173 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.264, + 0.175, + 0.338, + 0.184 + ], + "angle": 0, + "content": "PLTrans w/o \\(\\mathcal{V}\\)" + }, + { + "type": "image", + "bbox": [ + 0.363, + 0.079, + 0.483, + 0.173 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.375, + 0.175, + 0.469, + 0.184 + ], + "angle": 0, + "content": "PLTrans w/o DIFF" + }, + { + "type": "image", + "bbox": [ + 0.484, + 0.079, + 0.605, + 0.173 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.504, + 0.175, + 0.583, + 0.184 + ], + "angle": 0, + "content": "PLTrans w/o LT" + }, + { + "type": "image", + "bbox": [ + 0.606, + 0.079, + 0.726, + 0.173 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.611, + 0.175, + 0.703, + 0.184 + ], + "angle": 0, + "content": "PLTrans w/o DWT" + }, + { + "type": "image", + "bbox": [ + 0.728, + 0.079, + 0.848, + 0.173 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.766, + 0.175, + 0.808, + 0.184 + ], + "angle": 0, + "content": "PLTrans" + }, + { + "type": "image_caption", + "bbox": [ + 0.212, + 0.186, + 0.756, + 0.199 + ], + "angle": 0, + "content": "Figure 6. Visual comparison between PLTrans and ablative models on an in-the-wild image." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.214, + 0.358, + 0.23 + ], + "angle": 0, + "content": "4.5. Comparison to State-of-the-arts" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.238, + 0.468, + 0.343 + ], + "angle": 0, + "content": "To demonstrate the superiority of the proposed PLTrans, we perform quantitative and qualitative comparisons with state-of-the-arts, including generic image enhancement methods: Restormer [50] and DIL [23], BFR methods: GFP-GAN [41], GPEN [48], RestoreFormer [43] and Panini [42], and two diffusion-based methods: ILVR [5] and DR2 [44]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.365, + 0.294, + 0.379 + ], + "angle": 0, + "content": "4.5.1 Results on CelebA-Test" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.39, + 0.47, + 0.617 + ], + "angle": 0, + "content": "We adopt the same setting as [43] to perform the experiments, where PLTrans and the competing methods are used to restore the degraded face images across a spectrum of downsampling ratios \\((\\times 16, \\times 32, \\times 64)\\). The results of the methods are summarized in Table 2. GPEN, DR2 and RestoreFormer achieve lower FID/LPIPS and higher IDS scores than the other competing methods, which indicates that they perform better in terms of the precision and realism of the restored face images. On the other hand, PLTrans surpasses the competing methods in terms of all the metrics. In particular, for the most difficult case of downsampling \\(\\times 64\\), PLTrans is able to achieve the FID and PSNR scores of 39.58 and 19.36, which are lower and higher than the second best methods (GPEN: FID 45.12; DIL: PSNR 19.25) by 5.54 and 0.11, respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.617, + 0.47, + 0.783 + ], + "angle": 0, + "content": "Both ILVR and DR2 are diffusion-based methods, and DR2 outperforms ILVR in the above comparison. Different from DR2 which relies on a pre-trained DDPM model, PLTrans learns a latent diffusion module to regularize the preliminary features of degraded images. We perform an additional experiment to further highlight the advantage of PLTrans over DR2. We apply the methods to handle four types of degradation: Gaussian Noise, Blur, Downsample, and JPEG. Figure 7 shows the PLTrans is able to significantly outperform DR2. This suggests that the proposed latent diffusion strategy is more effective for our task." + }, + { + "type": "image", + "bbox": [ + 0.108, + 0.79, + 0.268, + 0.882 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.27, + 0.79, + 0.434, + 0.882 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.887, + 0.468, + 0.915 + ], + "angle": 0, + "content": "Figure 7. Comparison between PLTrans and DR2 over different types of degradations." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.215, + 0.773, + 0.229 + ], + "angle": 0, + "content": "4.5.2 User Study on In-the-wild Data" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.238, + 0.892, + 0.51 + ], + "angle": 0, + "content": "We further evaluate PLTrans and the competing methods on WIDER-Hard/Medium, LFW-Test and WebPhoto-Test. Please note that all the models are trained on FFHQ only. In Figure 8, we also present a number of representative restoration results to demonstrate the advantages of PLTrans in reducing artifacts, restoring realistic details, and preserving identity. A user study is performed to assess the restoration quality. We randomly sample 50 degraded face images from the four datasets, and there are 80 workers who are required to score the restoration results of the methods, ranging from 0 to 10. The maximum attainable score is 10 points. The high-score results should represent delightful content with realistic details, while at the same time properly preserving the basic information of the degraded ones. To ensure an unbiased evaluation, the results of the models are presented in a random order. Figure 9 shows the average scores of the models. Our PLTrans achieves the best performance in terms of the highest average scores with a small variance." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.521, + 0.71, + 0.537 + ], + "angle": 0, + "content": "4.6. Extended Applications" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.544, + 0.892, + 0.831 + ], + "angle": 0, + "content": "Due to the inclusion of the latent diffusion module, the proposed PLTrans is capable of performing various image synthesis and editing tasks. We impose Gaussian regularization on the latent variable \\( u \\) in Eq.(2), and is thus able to synthesize diverse face images by sampling \\( u \\) from the prior distribution. In addition, we apply linear interpolation to construct a path between two latent variables: \\( u_{1} \\) and \\( u_{2} \\), and decode the interpolated vectors. We find that PLTrans can produce continuously changing images along the path. By feeding out-of-domain images, such as cartoon, incomplete image, human scribble and segmentation map, the synthesized face images are realistic while at the same time preserving semantic consistency with the input to a certain extent. We can also edit face components by replacing the \\( u \\)'s subvector associated with the customized region with the counterparts of the reference. As shown in Figure 10, PLTrans produces realistic face images in different tasks. This demonstrates the greater capability of PLTrans in face image enhancement." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.845, + 0.619, + 0.861 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This paper presents a prior-based latent transformation approach for blind face restoration. We facilitate this task" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.972, + 0.516, + 0.983 + ], + "angle": 0, + "content": "9126" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.209, + 0.079, + 0.76, + 0.093 + ], + "angle": 0, + "content": "Table 2. Quantitative Comparison between PLTrans and competing methods on CelebA-Test." + }, + { + "type": "table", + "bbox": [ + 0.11, + 0.094, + 0.859, + 0.226 + ], + "angle": 0, + "content": "
Methods× 16× 32× 64
FID↓LPIPS↓PSNR↑IDS↑FID↓LPIPS↓PSNR↑IDS↑FID↓LPIPS↓PSNR↑IDS↑
GFPGAN [46]40.830.358321.000.6446107.650.433418.910.2523159.240.459018.410.1679
GPEN [48]25.820.378120.280.712636.220.433918.620.569845.120.451218.200.5011
ILVR [5]103.080.570821.080.576897.960.544619.760.5173107.830.573419.210.4627
Panini [42]47.140.393521.900.675444.230.483819.010.485752.370.486419.060.4272
Restormer [50]148.560.598122.120.3346185.250.630219.790.1771197.320.645919.240.1332
RestoreFormer [43]24.320.359221.990.737839.390.439719.410.537946.280.459719.110.4778
DIL [23]207.880.637521.910.3626406.170.683519.810.1697463.760.691819.250.1230
DR2 [44]35.180.411521.090.596543.410.427619.620.527349.640.456019.140.4721
PLTrans19.640.320722.130.741232.360.397819.910.596339.580.427019.360.5264
" + }, + { + "type": "image", + "bbox": [ + 0.118, + 0.228, + 0.849, + 0.38 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.162, + 0.383, + 0.804, + 0.397 + ], + "angle": 0, + "content": "Figure 8. Visual comparison between PLTrans and competing methods on representative in-the-wild images." + }, + { + "type": "image", + "bbox": [ + 0.116, + 0.408, + 0.426, + 0.572 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.089, + 0.575, + 0.456, + 0.588 + ], + "angle": 0, + "content": "Figure 9. The scoring result of user study on in-the-wild data." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.602, + 0.47, + 0.814 + ], + "angle": 0, + "content": "by improving the attention computation in a restoration transformer, which represents an effective attempt to transform query, key and value vectors to synthesize the clear face images from degraded ones. Toward this end, we incorporate a latent diffusion module to regularize the preliminary features, such that the regularized version becomes less sensitive to degradations. This is essential for enhancing the generalization performance over unknown degradations. We further incorporate a HQ face prior in the form of a latent dictionary to learn key and value, followed by cross-attention computation with the regularized features as query. Extensive experiments validate the effectiveness of our proposed framework PLTrans in restoring faithful details and preserving identity information." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.83, + 0.256, + 0.847 + ], + "angle": 0, + "content": "6. Acknowledgments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "This work was supported in part by the National Natural Science Foundation of China (Project No. 62072189, 62106136), in part by the Research Grants Coun" + }, + { + "type": "image", + "bbox": [ + 0.522, + 0.406, + 0.87, + 0.755 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.762, + 0.892, + 0.789 + ], + "angle": 0, + "content": "Figure 10. Representative results of PLTrans on different vision tasks." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.809, + 0.892, + 0.9 + ], + "angle": 0, + "content": "cil of the Hong Kong Special Administration Region (Project No. CityU 11206622), in part by the Guang-Dong Basic and Applied Basic Research Foundation (Project No. 2020A1515010484, 2022A1515011160, 2022A1515010434), and in part by TCL Science and Technology Innovation Fund (Project No. 20231752)." + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.971, + 0.516, + 0.983 + ], + "angle": 0, + "content": "9127" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.176, + 0.107 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.116, + 0.47, + 0.171 + ], + "angle": 0, + "content": "[1] Nicolas Carion, Francisco Massa, Gabriel Synnaeve, Nicolas Usunier, Alexander Kirillov, and Sergey Zagoruyko. End-to-end object detection with transformers. In Proc. 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In International Conference on Learning Representations, 2021. 3" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.883 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.972, + 0.516, + 0.983 + ], + "angle": 0, + "content": "9129" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_origin.pdf b/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..1db88c146124ddcb120b89da5d7cd48da45121df --- /dev/null +++ b/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/00121fc6-ccac-4774-942c-2646f683b09a_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:a9cbcaa11776e0e607c3742d300064855dcddb048a9283e7643936dfcb7ceb06 +size 8702855 diff --git a/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/full.md b/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/full.md new file mode 100644 index 0000000000000000000000000000000000000000..9fe0397b22f6e3eb1d1fb56b445028038af05369 --- /dev/null +++ b/2024/Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration/full.md @@ -0,0 +1,355 @@ +# Learning Degradation-unaware Representation with Prior-based Latent Transformations for Blind Face Restoration + +Lianxin Xie $^{1}$ , Csbingbing Zheng $^{1}$ , Wen Xue $^{1}$ , Le Jiang $^{1}$ , Cheng Liu $^{4}$ , Si Wu $^{1,2,3*}$ , Hau San Wong $^{5*}$ $^{1}$ School of Computer Science and Engineering, South China University of Technology + +$^{2}$ Peng Cheng Laboratory + +$^{3}$ PAZHOU LAB + +$^{4}$ Departent of Computer Science, Shantou University + +$^{5}$ Department of Computer Science, City University of Hong Kong + +{cslianxin.xie, 202321044369, csxuewen, 202220143385}@mail.scut.edu.cn + +cliu@stu.edu.cn, cswusi@scut.edu.cn, cshswong@cityu.edu.hk + +# Abstract + +Blind face restoration focuses on restoring high-fidelity details from images subjected to complex and unknown degradations, while preserving identity information. In this paper, we present a Prior-based Latent Transformation approach (PLTrans), which is specifically designed to learn a degradation-unaware representation, thereby allowing the restoration network to effectively generalize to real-world degradation. Toward this end, PLTrans learns a degradation-unaware query via a latent diffusion-based regularization module. Furthermore, conditioned on the features of a degraded face image, a latent dictionary that captures the priors of HQ face images is leveraged to refine the features by mapping the top-d nearest elements. The refined version will be used to build key and value for the cross-attention computation, which is tailored to each degraded image and exhibits reduced sensitivity to different degradation factors. Conditioned on the resulting representation, we train a decoding network that synthesizes face images with authentic details and identity preservation. Through extensive experiments, we verify the effectiveness of the design elements and demonstrate the generalization ability of our proposed approach for both synthetic and unknown degradations. We finally demonstrate the applicability of PLTrans in other vision tasks. + +# 1. Introduction + +Blind Face Restoration (BFR) aims to restore facial details while preserving the identity in degraded images that have been subjected to varying and unidentified degradations. Many CNN-based and Transformer-based BFR frameworks have been previously designed to enhance + +![](images/81087be5a85622a5a4659b4b08705c87a16946caf199a73e2bc134628984f508.jpg) +Figure 1. An example to illustrate that a better query empowers a generic model to generate HQ images, and vice versa. Enhancing the quality of key and value yields relatively slight effect. The restored image quality can be sorted as: $(\mathrm{b}) > (\mathrm{c}) > (\mathrm{d}) > (\mathrm{a})$ + +restoration performance, leading to significant advancements in the field. However, it is impractical to gather sufficient pairs of degraded-clean training data in real-world situations. In the pursuit of synthesizing clear and realistic face images from degraded ones, recent BFR methods have incorporated various face priors, including high-quality(HQ) exemplars with the same identity or geometric information. These methods often rely on capturing the correlation between degraded and clean images, making them susceptible to significant performance drops when handling unseen degradations. Additionally, there have been attempts to apply generative priors to BFR. Generative Adversarial Networks (GAN) [12] that are well-trained on face images represent strong priors due to their ability to generate high-fidelity samples, while GAN-based models are typically trained on specific datasets, thus limiting their generalization performance. + +The generic transformer-based model takes a high/low-quality (HQ/LQ) image as input and generates a set of corresponding HQ/LQ query, key and value in each block. The + +result shown in Figure 1 suggests that improving query and key-value leads to varying improvements for face restoration. Inspired by this observation, we propose a Prior-based Latent Transformation approach for BFR, which we refer to as PLTrans. The core idea behind PLTrans is to transform the preliminary features of degraded images to become degradation-unaware query, while at the same time to refine the preliminary feature to build key and value which are used in cross-attention computation. To achieve this, we incorporate a latent diffusion module to remove degradation from the features, in which various types of degradations become indistinguishable as Gaussian noise is added. In order to maintain the semantic similarity of the restored image to the degraded one, the features at each transition step is also combined with the input's low-frequency information obtained through a 2D discrete wavelet transform [49] during the reverse diffusion process. The resulting features are subsequently decoded into a query. Additionally, by incorporating a latent dictionary encoding rich details from the features of HQ face images via vector quantization [36], We learns a global mapping over the retrieved priors based on the top- $d$ elements that are nearest neighbors of the input features to build key and value. The cross-attention computation is performed over the obtained query, key and value for restoring the features of clean face. Extensive experiments are performed to demonstrate the effectiveness of the design elements and the improvement in generalization performance on real-world images with unknown degradation. We summarize the main contributions of this work as follows: + +- We address BFR from a new perspective of performing prior-based transformations on query, key and value for the attention computation in a latent transformer. +- By incorporating the wavelet-based low-frequency components of the degraded features as supplementary information into the intermediate stages, we can effectively guide the reverse diffusion process to synthesize the degradation-unaware features, while preserving essential semantics from the input. +- To restore the features of clean face, we further leverage a latent dictionary to refine the features of the degraded image, based on which we learn key and value to perform cross-attention computation with the degradation-unaware features as query. + +# 2. Related Work + +# 2.1. Blind Face Restoration + +Significant progress has been achieved in face image restoration recent years [8, 18, 20, 26]. A typical strategy is to regard the restoration as a domain translation task + +[10, 34, 45]. Considering facial structures, there have been many attempts to incorporate a variety of priors in the generation process. In [4, 16, 29], landmark estimation were used to recover clear face images from low-resolution ones based on facial geometry priors in the form of facial parsing maps. Given a HQ reference image of the same identity, a warping network was learnt to correct pose and expression for better recovery of fine details [7, 24, 25]. However, the reference-guided methods were only applicable in limited scenes. To effectively obtain the priors associated with the degraded images, a dictionary of semantic facial components was learnt in the feature space of a pretrained VGG [22], which was designed for face recognition. In addition, 3D morphable models explicitly modeled face attributes and can thus be applied to regularize the facial structures and identity information [15, 51]. + +Another research line is to exploit the priors encapsulated in the pre-trained generative models. The generative prior-based methods typically projected the degraded image back to the latent space of StyleGAN [19], and the resulting latent codes are transformed and decoded into a HQ face image [30]. To improve the efficiency of GAN inversion, a dedicated encoder was trained for latent code prediction, conditioned on the input image [31]. However, the restoration performance was limited by low dimensionality and poor spatial expression capability of the latent space. To address this issue, facial structural information was utilized by injecting the external features extracted from the degraded image into the generator of GFP-GAN [41], GPEN [48] and GLEAN [2]. Another effective approach is to perform progressive latent space extension across multiple intermediate layers of StyleGAN [32]. Based on a pre-trained Denoising Diffusion Probabilistic Model (DDPM) [14], different attempts were made to control the generation process. Choi et al. [5] proposed an Iterative Latent Variable Refinement (ILVR) method to condition the generative process on a given reference image. Further, Wang et al. [44] applied ILVR to BFR, and the proposed model is referred to as DR2, in which a degraded image was corrupted by Gaussian noise, and the corresponding HQ image could be recovered from its noisy version via an iterative denoising process. + +There are fundamental differences between the proposed PLTrans and the above methods. DDPM was designed for generic image synthesis, which differs from our restoration task. DR2 [44] utilized a pre-trained DDPM to perform sampling in the data space, while we learn a task-specific latent diffusion module to generate a degradation-unaware representation. Although RestoreFormer [43] captures clear face priors in the form of a latent dictionary, our model uses a dictionary to quantize the features of degraded images. We further learn a global mapping over the top- $d$ nearest elements to enhance the expressiveness of the resulting fea + +tures. + +# 2.2. Vision Transformer + +Transformers have emerged as powerful deep learning architectures for natural language processing [6,38]. Due to their excellent capability in capturing long-range dependencies between elements, the transformer-based models have been applied in a variety of vision tasks, including image classification [9], semantic segmentation [40], object detection [1, 52], and so on. Vision Transformers (ViTs) typically learnt to represent an image as a sequence of patches and estimate their underlying relationships [9, 35]. To deal with high-resolution images and visual objects with large variations in scale, SwinTransformer [27] adopted a shifted window strategy to enhance the modeling power of ViT and yield a hierarchical representation. By performing vector quantization in the latent space, a transformer was applied to high-resolution image generation by predicting the sequence of codebook indices [11]. In [50], a computationally efficient transformer was designed to perform multi-scale local-global representation learning for image restoration. On the other hand, a large-scale pre-trained transformer was also applied for multiple image processing tasks [3]. In this work, we apply a transformer architecture to BFR by modifying the intermediate feature as the query through a denoising diffusion process and learning the prior-based key and value for cross attention computation. + +# 3. Proposed Method + +# 3.1. Overview + +Our proposed PLTrans is built on an encoder-transformer-decoder architecture. As depicted in Figure 2, an encoder $E$ processes a degraded face image $x$ to extract preliminary features $q = E(x)$ . A Latent Diffusion-based Feature Regularization Module takes $q$ as input and returns the degradation-irrelevant feature $\hat{q}$ which is encouraged to be as consistent as possible with the corresponding ground truth. To recover rich face details, we utilize a pre-trained latent dictionary $\mathcal{V}$ , learned from HQ face images, to quantize $z$ . The resulting features $q$ are further refined and used to build the key and value vectors. A cross-attention-based transformer block takes the obtained query, key and value as input and returns the features to be decoded into a clear face image, which is encouraged to be as consistent as possible with the corresponding ground truth. + +# 3.2. Latent Diffusion-based Feature Regularization + +The structural information of an image with heavy degradation is typically disordered, and thus the preliminary features extracted by a generic encoder are potentially inadequate for capturing accurate semantics. Naively decoding the preliminary features may result in artifacts within the + +The purpose of this section is to present a new method for the synthesis of the original content. To address this issue, we propose to regularize the preliminary features via a latent diffusion module. Specifically, a mapping network $E_{Q}$ is adopted to take the feature $q$ as input and produces a latent variable $u^{lq}$ or $u^{hq}$ . Our objective is to construct a Markov Chain that incrementally approximates the HQ data distribution starting from a Gaussian prior. The regularization process attempts to restore the features from its noisy version while simultaneously preserving the low-frequency content inherent in the preliminary features. To attain this objective, we perform n-step perturbations to obtain probability $p_{\pi}(u_{n}^{lq}|u^{lq})$ , subsequently compute the transition probability $p_{\theta}(u_{t - 1}^{hq}|u_t^{hq})$ , and finally obtain $p_{\theta}(u_s^{hq}|u_n^{lq})$ , where $u_{n}^{lq}\approx u_{n}^{hq}$ and $s < t\leq n$ . Finally, we can get $\hat{u}_0^{hq}$ by computing probability $p_{\theta}(\hat{u}_0^{hq}|u_s^{hq})$ directly. On the other hand, auxiliary information in the form of the low-frequency signals from $u_{t}^{lq}$ are injected at multiple intermediate stages of the reverse diffusion process. We combine the multi-scale high-frequency signals from $u_{t}^{hq}$ and the low-frequency signals from $u_{t}^{lq}$ using Discrete Wavelet Transform (DWT) as follows: + +$$ +u _ {t} ^ {h q} \leftarrow \phi^ {\prime} \left(\phi^ {l f} \left(u _ {t} ^ {l q}\right), \phi^ {h f} \left(u _ {t} ^ {h q}\right)\right), \tag {1} +$$ + +where $\phi^{lf / hf}(\cdot)$ represents the DWT function that extracts the low/high-frequency information, and $\phi^{\prime}(\cdot)$ denotes the Inverse Discrete Wavelet Transform (IDWT). As will be demonstrated in the experiments, $\hat{u}_0^{hq}$ is less sensitive to degradation and can retain the primary semantics from $u^{lq}$ . Conditioned on the regularized variable, a mapping network $D_{Q}$ is responsible for yielding degradation-irrelevant features $\hat{q}$ in the same space of $q$ . Considering that a latent space with excessively high variance could affect the training stability and the quality of sample generation in both the diffusion and reverse processes, we impose a Kullback-Leibler (KL) divergence-based penalty on the latent variable $u$ to promote adherence to a standard normal distribution as follows: + +$$ +\mathcal {L} _ {K L} = K L \left(p _ {u} \| p _ {g}\right), \tag {2} +$$ + +where $p_u$ and $p_g$ denote a $u$ 's distribution and a Gaussian distribution. Conditioned on $u$ , $D_Q$ is trained to recover $q$ as accurately as possible for reconstruction, and the consistency loss is defined as follows: + +$$ +\mathcal {L} _ {\text {c o n s}} ^ {q} = \mathbf {E} _ {q} [ | \hat {q} - q | _ {1} ], \tag {3} +$$ + +where $\hat{q} = D_Q(u)$ denotes the prediction. Given the training data in the form of HQ face image features $u^{hq}$ , our latent diffusion module is optimized by a standard mean-squared error loss as follows: + +$$ +\mathcal {L} _ {d i f} = \mathbf {E} _ {\epsilon} \left[ | \epsilon - \epsilon_ {\theta} \left(\sqrt {\bar {a} _ {t}} u _ {t} ^ {h q} + \sqrt {1 - \bar {a} _ {t}} \epsilon , t\right) | _ {2} ^ {2} \right], \tag {4} +$$ + +![](images/86081e24704685b2755fae42c06267b0855d59e4a58dc2937f345d2d39901a82.jpg) +Figure 2. Overview of the proposed PLTrans framework. An encoder $E$ extracts the preliminary feature $q$ from a degraded face image $x$ . A latent diffusion-based regularization module is applied to $q$ to obtain its degradation-irrelevant version $\hat{q}$ as query. On the other hand, a prior-based key-value module quantizes and transforms $q$ to learn key $k$ and value $v$ . We perform cross-attention computation over $\hat{q}, k$ and $v$ in each transformer block, and feed the resulting feature into a generator $G$ to synthesize a HQ face image. + +![](images/24cedb48b5e9459fed255abea070798648a86f7612bc24c4ce2c9f2ca8d5feaf.jpg) + +where $\epsilon_{\theta}(u_t^{hq},t)$ is a U-net model used to predict the noise from $u_{t}^{hq}$ at step $t,\epsilon \sim \mathcal{N}(\mathbf{0},\mathbf{I})$ and $\bar{\alpha}_{t} = \prod_{m = 1}^{t}(1 - \beta_{m})$ in which $\{\beta_1,\beta_2,\dots,\beta_t\}$ is the variance schedule used to control the degree of noise addition. + +# 3.3. Prior-based Key-Value + +In addition to regularizing the preliminary features as query, we also learn key and value within our transformation by integrating HQ face priors via a latent dictionary $\mathcal{V}$ . The elements in $\mathcal{V}$ are expected to offer a wealth of clear face details. Initially, we utilize the preliminary feature $q$ to compute $z$ through convolution and self-attention operations. Then, $z$ is quantized by retrieving the $d$ nearest elements from $\mathcal{V}$ , which serve as the respective priors, as follows: + +$$ +\left\{e ^ {(1)}, \dots , e ^ {(d)} \right\} _ {(i, j)} = \arg \min _ {e \in \mathcal {V}} \| e - z _ {(i, j)} \| _ {2} ^ {2}, \tag {5} +$$ + +where $z_{(i,j)}$ denotes the feature vector at the spatial location $(i,j)$ . Rather than replacing $z$ with the most similar element, the retrieved top- $d$ priors contain more richer information. Note that $\mathcal{V}$ may not generalize well to the reconstruction of degraded data. A global mapping over the top- $d$ priors is performed as follows: + +$$ +\widetilde {z} _ {(i, j)} = \sum_ {l = 1} ^ {d} r _ {l} e ^ {(l)}, \tag {6} +$$ + +where $\mathbf{r} = [r_1, \ldots, r_d]$ denotes a learnable combination coefficient vector $e^{(l)} \in \{e^{(1)}, \ldots, e^{(d)}\}_{(i,j)}$ . Different from generic dictionary-based representation for data reconstruction, the global mapping is optimized for our restoration + +task and thus its expressiveness of the retrieved elements can be enhanced. Building upon the priors $\widetilde{z}$ , we learn $k, v$ by utilizing a lightweight transformer module which can be formulated as: + +$$ +\{k, v \} = \Phi (\widetilde {z}, z) + \widetilde {z}, \tag {7} +$$ + +where $\Phi (\cdot)$ denotes the standard transformer operations. We compute the estimated features of the corresponding clear face image by performing cross-attention between $\hat{q}$ and $k,v$ to promote adherence as follows: + +$$ +\widehat {z} = \operatorname {C o n v} \left(\operatorname {s o f t m a x} \left(\frac {Q K ^ {T}}{\sqrt {N}}\right) V\right) + k, \tag {8} +$$ + +where Conv represents the convolutional operation, $N$ denotes the number of feature channels, and + +$$ +Q = \hat {q} W _ {Q} + b _ {Q}, +$$ + +$$ +K = k W _ {K} + b _ {K}, \tag {9} +$$ + +$$ +V = v W _ {V} + b _ {V}, +$$ + +and $W_{Q / K / V}$ and $b_{Q / K / V}$ are learnable parameters. We then restore the clear face image $\widehat{y}$ by feeding $\widehat{z}$ into a decoder $G$ . + +# 3.4. Model Training + +Let $\widehat{y}$ denote the restored clear face image from a degraded input $x$ . We first adopt the widely used pixel-level loss to assess the consistency to the ground truth, and the corresponding function is defined as follows: + +$$ +\mathcal {L} _ {\text {c o n s}} = \mathbf {E} _ {(x, y)} \left[ | \widehat {y} - y | _ {1} + \| \varphi (\widehat {y}) - \varphi (y) \| _ {2} ^ {2} \right], \tag {10} +$$ + +where $y$ denotes the ground-truth clear image with respect to $x$ , and $\varphi(\cdot)$ represents the feature maps extracted by a pre-trained VGG [33]. We also adopt an adversarial training strategy to improve the visual quality of restored images, and the loss function is defined as follows: + +$$ +\mathcal {L} _ {a d v} ^ {\text {r e a l}} = \mathbf {E} _ {y} [ \log D (y) ], \tag {11} +$$ + +$$ +\mathcal {L} _ {a d v} ^ {s y n c} = \mathbf {E} _ {x} \big [ \log (1 - D (\widehat {y})) \big ], +$$ + +where $D(\cdot)$ denotes the predicted probability of an input face image being real. By integrating the above training losses, we formulate the optimization problem of our restoration model as follows: + +$$ +\min _ {R} \mathcal {L} _ {c o n s} ^ {q} + \lambda \mathcal {L} _ {K L} + \mathcal {L} _ {d i f}, +$$ + +$$ +\min _ {E, P, G} \mathcal {L} _ {\text {c o n s}} + \mathcal {L} _ {\text {a d v}} ^ {\text {s y n c}}, \tag {12} +$$ + +$$ +\max _ {D} \mathcal {L} _ {a d v} ^ {r e a l} + \mathcal {L} _ {a d v} ^ {s y n c}, +$$ + +where $\lambda$ denotes a weighting factor that controls the relative importance of the KL Divergence-based regularization term. Note that the latent dictionary $\mathcal{V}$ is learnt by performing vector quantization [36] in a clear face image reconstruction process. + +# 4. Experiments + +In this section, extensive experiments are performed to evaluate the proposed PLTrans on a variety of face restoration tasks. We first introduce the experimental settings including the training and test datasets, implementation details and evaluation protocol. Next, we show how the latent transformations benefit face restoration, followed by quantitative and qualitative comparison with state-of-the-art methods. Finally, we demonstrate the applicability of PLTrans to multiple vision tasks. + +# 4.1. Experimental Settings + +# 4.1.1 Training Data + +PLTrans was trained on FFHQ [19], which contains 70,000 HQ face images. To construct LQ training images, we follow [48] to degrade the FFHQ images as follows: + +$$ +I _ {L Q} = \left(\left(I _ {H Q} \otimes \mathcal {K} _ {\rho}\right) _ {\downarrow b} + n _ {\sigma}\right) _ {J P E G _ {w}}. \tag {13} +$$ + +Each HQ image is first convoluted with the Gaussian blur kernel which has a standard deviation $\rho \in \{0:0.1:5\}$ . Afterwards, it is downsampled $b \in \{0.8:32\}$ times, and is corrupted by Gaussian noise with intensity parameter $\sigma \in \{0:10\}$ . Furthermore, the JPEG compression with quality factor $w \in \{50:100\}$ is then applied to the resulting image. + +# 4.1.2 Test Data + +We assess the restoration performance of the proposed PLTrans and the competing methods on a well-known benchmark dataset: CelebA-HQ [28], and multiple in-the-wild datasets: WIDER FACE [47], LFW-Test [17] and WebPhoto-Test [41]. Specifically, we randomly sample 2,000 CelebA-HQ images and apply the degeneration operation defined in Eq.(13) to construct degraded images, and the resulting test dataset is referred to as CelebA-Test. WIDER-Hard/Medium are derived from the WIDER FACE dataset, and there are 13,890/3407 face images with heavy/medium degradations. In addition, LFW-Test and WebPhoto-Test contain 1,711 and 407 mildly degraded face images, respectively. + +# 4.1.3 Implementation Details + +We adopt an encoder-transformer-decoder architecture together with a generic discriminator for the proposed PLTrans. We implement PLTrans using PyTorch with two NVIDIA GeForce RTX 3090s. For the optimizer, we adopt Adam [21] with a learning rate of $5 \times 10^{-5}$ . There are a total of 30 training epochs with a batch size of 4. For the hyperparameters, we set the number of fetched elements $d$ and the weighting factor $\lambda$ in Eq.(12) are set to 8 and $5 \times 10^{-5}$ , respectively. + +# 4.1.4 Evaluation Protocol + +We implement all the competing methods based on the open source codes, and both training and test images are resized to $512 \times 512$ for a fair comparison. The widely used metrics: Peak Signal-to-Noise Ratio (PSNR) and the Learned Perceptual Image Patch Similarity (LPIPS) are used to quantitatively evaluate the consistency between the restored face images and the corresponding ground truth. Considering that identity preservation is critical for BFR, we further report the IDentity Similarity (IDS) to the ground truth after restoration in the feature space of a well-trained face recognition model: CosFace [39]. In addition, we assess the diversity and the degree of realism of the synthesized data in terms of Fréchet Inception Distances (FID) [13]. + +# 4.2. Degradation-unaware Representation + +We begin by verifying the effectiveness of our latent diffusion module in producing degradation-irrelevant features. There are 500 HQ images and the corresponding 500 LQ images randomly sampled from CelebA-Test. For each HQ image and its degraded counterpart, we extract and denote their encoder features as $q_{hq}$ and $q_{lq}$ . We apply the latent diffusion-based regularization on $q_{lq}$ , and denote the regularized version as $\hat{q}_{lq}$ . In Figure 3, we visualize the feature distributions by using t-SNE [37], and can observe that the + +![](images/e51848852e6dc174fd2166bb88b843b06d9b71d769242e219b0ec20861f044eb.jpg) +Figure 3. Distributions of HQ image features $q_{hq}$ , LQ image features $q_{lq}$ , and the regularized LQ image features $\hat{q}_{lq}$ + +![](images/83cec7c15c3a87fa0a68b2765f012dacec8ddea594d89e52a2928df0108d6378.jpg) +Figure 4. The average distances between the regularized LQ image features and the HQ counterparts in the training process. + +clusters of $q_{hq}$ and $q_{lq}$ are separable, while the data points of $\hat{q}_{lq}$ mix with those of $q_{hq}$ . This indicates that our regularization module is useful for mitigating degradations to a certain extent. + +# 4.3. Impact of the Number of Diffusion Steps + +To obtain the degradation-unaware features, we regularize the preliminary features by performing $n$ -step perturbations followed by a reverse diffusion process. It is nontrivial to determine the optimal number of diffusion steps for BFR. For a given image with heavy degradation, it typically takes more perturbation and denoising steps to restore it, and vice versa. To illustrate this point, we perform an experiment on the face images with four levels of degradations ( $\times 8/16/32/64$ downsampling). In Figure 4, we plot the average distances between the regularized features of LQ CelebA-Test images and the preliminary features of the HQ counterparts in the training process, and the shaded regions around these lines illustrate their variance. One can observe that the average distance to the HQ data quickly achieves the minimum value for the cases where the degree of degradation is low. This confirms that more diffusion steps are needed to restore the clean face image from a heavily degraded one. After the minima are attained, increasing the steps leads to a performance drop, since the relationship between the preliminary features and the corrupted features fades. In Figure 5, we visualize the restored face images at $\times 32$ downsampling scale, showcasing the effects of using varying numbers of diffusion steps. + +![](images/fe404441ff446860a7c6c5b9596ca2701c2786287d8c69ea3f5d0ebc703a1115.jpg) +Figure 5. The restoration results of PLTrans with different numbers of diffusion steps. + +Table 1. Results of PLTrans and ablative models on CelebA-Test. + +
MethodsFID↓LPIPS↓PSNR↑IDS↑
PLTrans w/o V90.120.480818.810.2866
PLTrans w/o DIFF44.960.430418.890.4820
PLTrans w/o LT42.120.430119.110.5201
PLTrans w/o DWT41.570.448717.990.4672
PLTrans39.580.426019.360.5264
+ +# 4.4. Ablation Study + +We consider that the superior restoration performance of our PLTrans is mainly due to the latent diffusion-based regularization, HQ face prior, DWT-based low-frequency information injection and the prior-based key-value. To highlight the effectiveness of the four factors in BFR, we perform a number of ablative experiments. Specifically, we build four variants by disabling the diffusion module (DIFF), DWT, dictionary and Lightweight Transformer (LT) in the Prior-based Key-Value Module, and the resulting models are referred to as 'PLTrans w/o DIFF', 'PLTrans w/o DWT', 'PLTrans w/o V' and 'PLTrans w/o LT' respectively. The experiments are performed on CelebA-Test, and we summarize the results of the models in terms of FID, PSNR, LPIPS and IDS in Table 1. We can make the following observations: PLTrans outperforms its variants, yielding superior quantitative results across all the metrics. Without the latent diffusion-based regularization, it is difficult to restore the disordered structural information of degraded images, and the restoration performance reduces 5.38 in terms of FID. A number of artifacts in the resulting synthesized images are also observed as shown in Figure 6. When compared with 'PLTrans w/o V', the inclusion of the latent dictionary leads to 0.0548 improved performance in terms of LPIPS. This demonstrates that the HQ face prior is useful for synthesizing texture details. When disabling the lightweight transformer module, 'PLTrans w/o LT' learns the key and value vectors directly from the dictionary features, and we can observe a performance drop of 0.25 in terms of PSNR. We conclude that this module can infer a reasonable transformation to leverage the prior knowledge, which is useful for plausible synthesis. What's more, when disabling the DWT-based information injection module, 'PLTrans w/o DWT' leads to a significant performance drop of 0.0592 in terms of IDS. This suggests the information injection module is beneficial for preserving the semantics of the input image. + +![](images/b4116cbe3d270c612e3f1c203f3388c28d0ee30867b3e3a30c391e66d42f246e.jpg) +Input + +![](images/03f50d58217954f5755426d76595e57eb6edc6e6e8bfcbaa1bc3466fd5e2bf7b.jpg) +PLTrans w/o $\mathcal{V}$ + +![](images/ada034fd33533eaeeb81bf795cd8205a9260be88258e1554031b07662cbccac5.jpg) +PLTrans w/o DIFF +Figure 6. Visual comparison between PLTrans and ablative models on an in-the-wild image. + +![](images/a02add26539532025428a810b580ec7eae4ad031487c853b07b60bd18b33af5a.jpg) +PLTrans w/o LT + +![](images/7ac751655b9254fce6baaa4f289827d29bd7d64a9e230b225857b8f159dbaa7b.jpg) +PLTrans w/o DWT + +![](images/265e491bd06f3c5cf13c3234255c0858a53eecce0bd206b3324ded1da8d75dbc.jpg) +PLTrans + +# 4.5. Comparison to State-of-the-arts + +To demonstrate the superiority of the proposed PLTrans, we perform quantitative and qualitative comparisons with state-of-the-arts, including generic image enhancement methods: Restormer [50] and DIL [23], BFR methods: GFP-GAN [41], GPEN [48], RestoreFormer [43] and Panini [42], and two diffusion-based methods: ILVR [5] and DR2 [44]. + +# 4.5.1 Results on CelebA-Test + +We adopt the same setting as [43] to perform the experiments, where PLTrans and the competing methods are used to restore the degraded face images across a spectrum of downsampling ratios $(\times 16, \times 32, \times 64)$ . The results of the methods are summarized in Table 2. GPEN, DR2 and RestoreFormer achieve lower FID/LPIPS and higher IDS scores than the other competing methods, which indicates that they perform better in terms of the precision and realism of the restored face images. On the other hand, PLTrans surpasses the competing methods in terms of all the metrics. In particular, for the most difficult case of downsampling $\times 64$ , PLTrans is able to achieve the FID and PSNR scores of 39.58 and 19.36, which are lower and higher than the second best methods (GPEN: FID 45.12; DIL: PSNR 19.25) by 5.54 and 0.11, respectively. + +Both ILVR and DR2 are diffusion-based methods, and DR2 outperforms ILVR in the above comparison. Different from DR2 which relies on a pre-trained DDPM model, PLTrans learns a latent diffusion module to regularize the preliminary features of degraded images. We perform an additional experiment to further highlight the advantage of PLTrans over DR2. We apply the methods to handle four types of degradation: Gaussian Noise, Blur, Downsample, and JPEG. Figure 7 shows the PLTrans is able to significantly outperform DR2. This suggests that the proposed latent diffusion strategy is more effective for our task. + +![](images/1aa2f7047b97914df1dd7fe3784af129616e7d9d68759c929ce53af8bd167768.jpg) +Figure 7. Comparison between PLTrans and DR2 over different types of degradations. + +![](images/1aaa3fa1a325004e267c477bfc70f71be36ea789a274af6a872a51d6f5356f00.jpg) + +# 4.5.2 User Study on In-the-wild Data + +We further evaluate PLTrans and the competing methods on WIDER-Hard/Medium, LFW-Test and WebPhoto-Test. Please note that all the models are trained on FFHQ only. In Figure 8, we also present a number of representative restoration results to demonstrate the advantages of PLTrans in reducing artifacts, restoring realistic details, and preserving identity. A user study is performed to assess the restoration quality. We randomly sample 50 degraded face images from the four datasets, and there are 80 workers who are required to score the restoration results of the methods, ranging from 0 to 10. The maximum attainable score is 10 points. The high-score results should represent delightful content with realistic details, while at the same time properly preserving the basic information of the degraded ones. To ensure an unbiased evaluation, the results of the models are presented in a random order. Figure 9 shows the average scores of the models. Our PLTrans achieves the best performance in terms of the highest average scores with a small variance. + +# 4.6. Extended Applications + +Due to the inclusion of the latent diffusion module, the proposed PLTrans is capable of performing various image synthesis and editing tasks. We impose Gaussian regularization on the latent variable $u$ in Eq.(2), and is thus able to synthesize diverse face images by sampling $u$ from the prior distribution. In addition, we apply linear interpolation to construct a path between two latent variables: $u_{1}$ and $u_{2}$ , and decode the interpolated vectors. We find that PLTrans can produce continuously changing images along the path. By feeding out-of-domain images, such as cartoon, incomplete image, human scribble and segmentation map, the synthesized face images are realistic while at the same time preserving semantic consistency with the input to a certain extent. We can also edit face components by replacing the $u$ 's subvector associated with the customized region with the counterparts of the reference. As shown in Figure 10, PLTrans produces realistic face images in different tasks. This demonstrates the greater capability of PLTrans in face image enhancement. + +# 5. Conclusion + +This paper presents a prior-based latent transformation approach for blind face restoration. We facilitate this task + +Table 2. Quantitative Comparison between PLTrans and competing methods on CelebA-Test. + +
Methods× 16× 32× 64
FID↓LPIPS↓PSNR↑IDS↑FID↓LPIPS↓PSNR↑IDS↑FID↓LPIPS↓PSNR↑IDS↑
GFPGAN [46]40.830.358321.000.6446107.650.433418.910.2523159.240.459018.410.1679
GPEN [48]25.820.378120.280.712636.220.433918.620.569845.120.451218.200.5011
ILVR [5]103.080.570821.080.576897.960.544619.760.5173107.830.573419.210.4627
Panini [42]47.140.393521.900.675444.230.483819.010.485752.370.486419.060.4272
Restormer [50]148.560.598122.120.3346185.250.630219.790.1771197.320.645919.240.1332
RestoreFormer [43]24.320.359221.990.737839.390.439719.410.537946.280.459719.110.4778
DIL [23]207.880.637521.910.3626406.170.683519.810.1697463.760.691819.250.1230
DR2 [44]35.180.411521.090.596543.410.427619.620.527349.640.456019.140.4721
PLTrans19.640.320722.130.741232.360.397819.910.596339.580.427019.360.5264
+ +![](images/0e092d063e80102937f318e8198b5592ad3d5f7579b028a1833fe5cb210e232b.jpg) +Figure 8. Visual comparison between PLTrans and competing methods on representative in-the-wild images. + +![](images/564b189c5fd09ddcad263bbda523f8294983989a48f237c31e8e0f2e8617a4bc.jpg) +Figure 9. The scoring result of user study on in-the-wild data. + +by improving the attention computation in a restoration transformer, which represents an effective attempt to transform query, key and value vectors to synthesize the clear face images from degraded ones. Toward this end, we incorporate a latent diffusion module to regularize the preliminary features, such that the regularized version becomes less sensitive to degradations. This is essential for enhancing the generalization performance over unknown degradations. We further incorporate a HQ face prior in the form of a latent dictionary to learn key and value, followed by cross-attention computation with the regularized features as query. Extensive experiments validate the effectiveness of our proposed framework PLTrans in restoring faithful details and preserving identity information. + +# 6. Acknowledgments + +This work was supported in part by the National Natural Science Foundation of China (Project No. 62072189, 62106136), in part by the Research Grants Coun + +![](images/551f5913e21724ff884b0336cb81aa00f569817624383cfa525bb9b9fc532a06.jpg) +Figure 10. Representative results of PLTrans on different vision tasks. + +cil of the Hong Kong Special Administration Region (Project No. CityU 11206622), in part by the Guang-Dong Basic and Applied Basic Research Foundation (Project No. 2020A1515010484, 2022A1515011160, 2022A1515010434), and in part by TCL Science and Technology Innovation Fund (Project No. 20231752). + +# References + +[1] Nicolas Carion, Francisco Massa, Gabriel Synnaeve, Nicolas Usunier, Alexander Kirillov, and Sergey Zagoruyko. End-to-end object detection with transformers. In Proc. 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+ 143, + 300, + 191, + 313 + ], + "spans": [ + { + "bbox": [ + 143, + 300, + 191, + 313 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 326, + 290, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 326, + 290, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 326, + 290, + 613 + ], + "type": "text", + "content": "Blind face restoration focuses on restoring high-fidelity details from images subjected to complex and unknown degradations, while preserving identity information. In this paper, we present a Prior-based Latent Transformation approach (PLTrans), which is specifically designed to learn a degradation-unaware representation, thereby allowing the restoration network to effectively generalize to real-world degradation. Toward this end, PLTrans learns a degradation-unaware query via a latent diffusion-based regularization module. Furthermore, conditioned on the features of a degraded face image, a latent dictionary that captures the priors of HQ face images is leveraged to refine the features by mapping the top-d nearest elements. The refined version will be used to build key and value for the cross-attention computation, which is tailored to each degraded image and exhibits reduced sensitivity to different degradation factors. Conditioned on the resulting representation, we train a decoding network that synthesizes face images with authentic details and identity preservation. Through extensive experiments, we verify the effectiveness of the design elements and demonstrate the generalization ability of our proposed approach for both synthetic and unknown degradations. We finally demonstrate the applicability of PLTrans in other vision tasks." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 634, + 128, + 646 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 634, + 128, + 646 + ], + "spans": [ + { + "bbox": [ + 47, + 634, + 128, + 646 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "content": "Blind Face Restoration (BFR) aims to restore facial details while preserving the identity in degraded images that have been subjected to varying and unidentified degradations. Many CNN-based and Transformer-based BFR frameworks have been previously designed to enhance" + } + ] + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 317, + 300, + 535, + 407 + ], + "blocks": [ + { + "bbox": [ + 317, + 300, + 535, + 407 + ], + "lines": [ + { + "bbox": [ + 317, + 300, + 535, + 407 + ], + "spans": [ + { + "bbox": [ + 317, + 300, + 535, + 407 + ], + "type": "image", + "image_path": "81087be5a85622a5a4659b4b08705c87a16946caf199a73e2bc134628984f508.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 411, + 547, + 455 + ], + "lines": [ + { + "bbox": [ + 305, + 411, + 547, + 455 + ], + "spans": [ + { + "bbox": [ + 305, + 411, + 547, + 455 + ], + "type": "text", + "content": "Figure 1. An example to illustrate that a better query empowers a generic model to generate HQ images, and vice versa. Enhancing the quality of key and value yields relatively slight effect. The restored image quality can be sorted as: " + }, + { + "bbox": [ + 305, + 411, + 547, + 455 + ], + "type": "inline_equation", + "content": "(\\mathrm{b}) > (\\mathrm{c}) > (\\mathrm{d}) > (\\mathrm{a})" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 471, + 546, + 674 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 471, + 546, + 674 + ], + "spans": [ + { + "bbox": [ + 304, + 471, + 546, + 674 + ], + "type": "text", + "content": "restoration performance, leading to significant advancements in the field. However, it is impractical to gather sufficient pairs of degraded-clean training data in real-world situations. In the pursuit of synthesizing clear and realistic face images from degraded ones, recent BFR methods have incorporated various face priors, including high-quality(HQ) exemplars with the same identity or geometric information. These methods often rely on capturing the correlation between degraded and clean images, making them susceptible to significant performance drops when handling unseen degradations. Additionally, there have been attempts to apply generative priors to BFR. Generative Adversarial Networks (GAN) [12] that are well-trained on face images represent strong priors due to their ability to generate high-fidelity samples, while GAN-based models are typically trained on specific datasets, thus limiting their generalization performance." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 677, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 677, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 305, + 677, + 547, + 715 + ], + "type": "text", + "content": "The generic transformer-based model takes a high/low-quality (HQ/LQ) image as input and generates a set of corresponding HQ/LQ query, key and value in each block. The" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 742, + 157, + 756 + ], + "type": "footer", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 742, + 157, + 756 + ], + "spans": [ + { + "bbox": [ + 47, + 742, + 157, + 756 + ], + "type": "text", + "content": "\\*Co-corresponding author." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "spans": [ + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "type": "text", + "content": "9120" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 430 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 430 + ], + "type": "text", + "content": "result shown in Figure 1 suggests that improving query and key-value leads to varying improvements for face restoration. Inspired by this observation, we propose a Prior-based Latent Transformation approach for BFR, which we refer to as PLTrans. The core idea behind PLTrans is to transform the preliminary features of degraded images to become degradation-unaware query, while at the same time to refine the preliminary feature to build key and value which are used in cross-attention computation. To achieve this, we incorporate a latent diffusion module to remove degradation from the features, in which various types of degradations become indistinguishable as Gaussian noise is added. In order to maintain the semantic similarity of the restored image to the degraded one, the features at each transition step is also combined with the input's low-frequency information obtained through a 2D discrete wavelet transform [49] during the reverse diffusion process. The resulting features are subsequently decoded into a query. Additionally, by incorporating a latent dictionary encoding rich details from the features of HQ face images via vector quantization [36], We learns a global mapping over the retrieved priors based on the top-" + }, + { + "bbox": [ + 47, + 72, + 289, + 430 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 47, + 72, + 289, + 430 + ], + "type": "text", + "content": " elements that are nearest neighbors of the input features to build key and value. The cross-attention computation is performed over the obtained query, key and value for restoring the features of clean face. Extensive experiments are performed to demonstrate the effectiveness of the design elements and the improvement in generalization performance on real-world images with unknown degradation. We summarize the main contributions of this work as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 59, + 440, + 287, + 627 + ], + "type": "list", + "angle": 0, + "index": 4, + "blocks": [ + { + "bbox": [ + 59, + 440, + 287, + 477 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 440, + 287, + 477 + ], + "spans": [ + { + "bbox": [ + 59, + 440, + 287, + 477 + ], + "type": "text", + "content": "- We address BFR from a new perspective of performing prior-based transformations on query, key and value for the attention computation in a latent transformer." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 59, + 486, + 287, + 558 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 486, + 287, + 558 + ], + "spans": [ + { + "bbox": [ + 59, + 486, + 287, + 558 + ], + "type": "text", + "content": "- By incorporating the wavelet-based low-frequency components of the degraded features as supplementary information into the intermediate stages, we can effectively guide the reverse diffusion process to synthesize the degradation-unaware features, while preserving essential semantics from the input." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 59, + 567, + 287, + 627 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 567, + 287, + 627 + ], + "spans": [ + { + "bbox": [ + 59, + 567, + 287, + 627 + ], + "type": "text", + "content": "- To restore the features of clean face, we further leverage a latent dictionary to refine the features of the degraded image, based on which we learn key and value to perform cross-attention computation with the degradation-unaware features as query." + } + ] + } + ], + "index": 3 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 639, + 134, + 651 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 639, + 134, + 651 + ], + "spans": [ + { + "bbox": [ + 47, + 639, + 134, + 651 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 658, + 178, + 670 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 658, + 178, + 670 + ], + "spans": [ + { + "bbox": [ + 47, + 658, + 178, + 670 + ], + "type": "text", + "content": "2.1. Blind Face Restoration" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "content": "Significant progress has been achieved in face image restoration recent years [8, 18, 20, 26]. A typical strategy is to regard the restoration as a domain translation task" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 545, + 263 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 263 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 263 + ], + "type": "text", + "content": "[10, 34, 45]. Considering facial structures, there have been many attempts to incorporate a variety of priors in the generation process. In [4, 16, 29], landmark estimation were used to recover clear face images from low-resolution ones based on facial geometry priors in the form of facial parsing maps. Given a HQ reference image of the same identity, a warping network was learnt to correct pose and expression for better recovery of fine details [7, 24, 25]. However, the reference-guided methods were only applicable in limited scenes. To effectively obtain the priors associated with the degraded images, a dictionary of semantic facial components was learnt in the feature space of a pretrained VGG [22], which was designed for face recognition. In addition, 3D morphable models explicitly modeled face attributes and can thus be applied to regularize the facial structures and identity information [15, 51]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 268, + 545, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 268, + 545, + 579 + ], + "spans": [ + { + "bbox": [ + 304, + 268, + 545, + 579 + ], + "type": "text", + "content": "Another research line is to exploit the priors encapsulated in the pre-trained generative models. The generative prior-based methods typically projected the degraded image back to the latent space of StyleGAN [19], and the resulting latent codes are transformed and decoded into a HQ face image [30]. To improve the efficiency of GAN inversion, a dedicated encoder was trained for latent code prediction, conditioned on the input image [31]. However, the restoration performance was limited by low dimensionality and poor spatial expression capability of the latent space. To address this issue, facial structural information was utilized by injecting the external features extracted from the degraded image into the generator of GFP-GAN [41], GPEN [48] and GLEAN [2]. Another effective approach is to perform progressive latent space extension across multiple intermediate layers of StyleGAN [32]. Based on a pre-trained Denoising Diffusion Probabilistic Model (DDPM) [14], different attempts were made to control the generation process. Choi et al. [5] proposed an Iterative Latent Variable Refinement (ILVR) method to condition the generative process on a given reference image. Further, Wang et al. [44] applied ILVR to BFR, and the proposed model is referred to as DR2, in which a degraded image was corrupted by Gaussian noise, and the corresponding HQ image could be recovered from its noisy version via an iterative denoising process." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "There are fundamental differences between the proposed PLTrans and the above methods. DDPM was designed for generic image synthesis, which differs from our restoration task. DR2 [44] utilized a pre-trained DDPM to perform sampling in the data space, while we learn a task-specific latent diffusion module to generate a degradation-unaware representation. Although RestoreFormer [43] captures clear face priors in the form of a latent dictionary, our model uses a dictionary to quantize the features of degraded images. We further learn a global mapping over the top- " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " nearest elements to enhance the expressiveness of the resulting fea" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 769, + 314, + 779 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 769, + 314, + 779 + ], + "spans": [ + { + "bbox": [ + 294, + 769, + 314, + 779 + ], + "type": "text", + "content": "9121" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 73, + 72, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 73, + 72, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 73, + 72, + 83 + ], + "type": "text", + "content": "tures." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 92, + 162, + 104 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 92, + 162, + 104 + ], + "spans": [ + { + "bbox": [ + 47, + 92, + 162, + 104 + ], + "type": "text", + "content": "2.2. Vision Transformer" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 111, + 289, + 399 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 111, + 289, + 399 + ], + "spans": [ + { + "bbox": [ + 47, + 111, + 289, + 399 + ], + "type": "text", + "content": "Transformers have emerged as powerful deep learning architectures for natural language processing [6,38]. Due to their excellent capability in capturing long-range dependencies between elements, the transformer-based models have been applied in a variety of vision tasks, including image classification [9], semantic segmentation [40], object detection [1, 52], and so on. Vision Transformers (ViTs) typically learnt to represent an image as a sequence of patches and estimate their underlying relationships [9, 35]. To deal with high-resolution images and visual objects with large variations in scale, SwinTransformer [27] adopted a shifted window strategy to enhance the modeling power of ViT and yield a hierarchical representation. By performing vector quantization in the latent space, a transformer was applied to high-resolution image generation by predicting the sequence of codebook indices [11]. In [50], a computationally efficient transformer was designed to perform multi-scale local-global representation learning for image restoration. On the other hand, a large-scale pre-trained transformer was also applied for multiple image processing tasks [3]. In this work, we apply a transformer architecture to BFR by modifying the intermediate feature as the query through a denoising diffusion process and learning the prior-based key and value for cross attention computation." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 409, + 153, + 422 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 409, + 153, + 422 + ], + "spans": [ + { + "bbox": [ + 47, + 409, + 153, + 422 + ], + "type": "text", + "content": "3. Proposed Method" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 429, + 115, + 441 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 429, + 115, + 441 + ], + "spans": [ + { + "bbox": [ + 47, + 429, + 115, + 441 + ], + "type": "text", + "content": "3.1. Overview" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "spans": [ + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": "Our proposed PLTrans is built on an encoder-transformer-decoder architecture. As depicted in Figure 2, an encoder " + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": " processes a degraded face image " + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": " to extract preliminary features " + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "inline_equation", + "content": "q = E(x)" + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": ". A Latent Diffusion-based Feature Regularization Module takes " + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": " as input and returns the degradation-irrelevant feature " + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "inline_equation", + "content": "\\hat{q}" + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": " which is encouraged to be as consistent as possible with the corresponding ground truth. To recover rich face details, we utilize a pre-trained latent dictionary " + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": ", learned from HQ face images, to quantize " + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "inline_equation", + "content": "z" + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": ". The resulting features " + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 47, + 448, + 289, + 628 + ], + "type": "text", + "content": " are further refined and used to build the key and value vectors. A cross-attention-based transformer block takes the obtained query, key and value as input and returns the features to be decoded into a clear face image, which is encouraged to be as consistent as possible with the corresponding ground truth." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 635, + 287, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 635, + 287, + 647 + ], + "spans": [ + { + "bbox": [ + 47, + 635, + 287, + 647 + ], + "type": "text", + "content": "3.2. Latent Diffusion-based Feature Regularization" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 653, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 653, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 653, + 287, + 714 + ], + "type": "text", + "content": "The structural information of an image with heavy degradation is typically disordered, and thus the preliminary features extracted by a generic encoder are potentially inadequate for capturing accurate semantics. Naively decoding the preliminary features may result in artifacts within the" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": "The purpose of this section is to present a new method for the synthesis of the original content. To address this issue, we propose to regularize the preliminary features via a latent diffusion module. Specifically, a mapping network " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "E_{Q}" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " is adopted to take the feature " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " as input and produces a latent variable " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "u^{lq}" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " or " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "u^{hq}" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": ". Our objective is to construct a Markov Chain that incrementally approximates the HQ data distribution starting from a Gaussian prior. The regularization process attempts to restore the features from its noisy version while simultaneously preserving the low-frequency content inherent in the preliminary features. To attain this objective, we perform n-step perturbations to obtain probability " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "p_{\\pi}(u_{n}^{lq}|u^{lq})" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": ", subsequently compute the transition probability " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "p_{\\theta}(u_{t - 1}^{hq}|u_t^{hq})" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": ", and finally obtain " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "p_{\\theta}(u_s^{hq}|u_n^{lq})" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "u_{n}^{lq}\\approx u_{n}^{hq}" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "s < t\\leq n" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": ". Finally, we can get " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "\\hat{u}_0^{hq}" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " by computing probability " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "p_{\\theta}(\\hat{u}_0^{hq}|u_s^{hq})" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " directly. On the other hand, auxiliary information in the form of the low-frequency signals from " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "u_{t}^{lq}" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " are injected at multiple intermediate stages of the reverse diffusion process. We combine the multi-scale high-frequency signals from " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "u_{t}^{hq}" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " and the low-frequency signals from " + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "inline_equation", + "content": "u_{t}^{lq}" + }, + { + "bbox": [ + 304, + 72, + 547, + 341 + ], + "type": "text", + "content": " using Discrete Wavelet Transform (DWT) as follows:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 360, + 347, + 545, + 363 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 360, + 347, + 545, + 363 + ], + "spans": [ + { + "bbox": [ + 360, + 347, + 545, + 363 + ], + "type": "interline_equation", + "content": "u _ {t} ^ {h q} \\leftarrow \\phi^ {\\prime} \\left(\\phi^ {l f} \\left(u _ {t} ^ {l q}\\right), \\phi^ {h f} \\left(u _ {t} ^ {h q}\\right)\\right), \\tag {1}", + "image_path": "411f829562219f23292cf10eae7da47ffecad875a919f087fd5555fbd77ce5f2.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "spans": [ + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "inline_equation", + "content": "\\phi^{lf / hf}(\\cdot)" + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": " represents the DWT function that extracts the low/high-frequency information, and " + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "inline_equation", + "content": "\\phi^{\\prime}(\\cdot)" + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": " denotes the Inverse Discrete Wavelet Transform (IDWT). As will be demonstrated in the experiments, " + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "inline_equation", + "content": "\\hat{u}_0^{hq}" + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": " is less sensitive to degradation and can retain the primary semantics from " + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "inline_equation", + "content": "u^{lq}" + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": ". Conditioned on the regularized variable, a mapping network " + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "inline_equation", + "content": "D_{Q}" + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": " is responsible for yielding degradation-irrelevant features " + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "inline_equation", + "content": "\\hat{q}" + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": " in the same space of " + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": ". Considering that a latent space with excessively high variance could affect the training stability and the quality of sample generation in both the diffusion and reverse processes, we impose a Kullback-Leibler (KL) divergence-based penalty on the latent variable " + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "inline_equation", + "content": "u" + }, + { + "bbox": [ + 304, + 369, + 547, + 537 + ], + "type": "text", + "content": " to promote adherence to a standard normal distribution as follows:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 381, + 546, + 545, + 560 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 381, + 546, + 545, + 560 + ], + "spans": [ + { + "bbox": [ + 381, + 546, + 545, + 560 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {K L} = K L \\left(p _ {u} \\| p _ {g}\\right), \\tag {2}", + "image_path": "c020740fa4078edd47afd4c35864bdd70eef151196be8e58233e41ca9cfa2cc9.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "spans": [ + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "inline_equation", + "content": "p_u" + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "inline_equation", + "content": "p_g" + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "text", + "content": " denote a " + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "inline_equation", + "content": "u" + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "text", + "content": "'s distribution and a Gaussian distribution. Conditioned on " + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "inline_equation", + "content": "u" + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "inline_equation", + "content": "D_Q" + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "text", + "content": " is trained to recover " + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 304, + 567, + 547, + 615 + ], + "type": "text", + "content": " as accurately as possible for reconstruction, and the consistency loss is defined as follows:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 378, + 623, + 545, + 638 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 378, + 623, + 545, + 638 + ], + "spans": [ + { + "bbox": [ + 378, + 623, + 545, + 638 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {c o n s}} ^ {q} = \\mathbf {E} _ {q} [ | \\hat {q} - q | _ {1} ], \\tag {3}", + "image_path": "adbd585ec7414b097a444bf73aa26fad1c37a51ab34e98bb46ec43fad0f4557d.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 644, + 547, + 692 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 644, + 547, + 692 + ], + "spans": [ + { + "bbox": [ + 304, + 644, + 547, + 692 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 644, + 547, + 692 + ], + "type": "inline_equation", + "content": "\\hat{q} = D_Q(u)" + }, + { + "bbox": [ + 304, + 644, + 547, + 692 + ], + "type": "text", + "content": " denotes the prediction. Given the training data in the form of HQ face image features " + }, + { + "bbox": [ + 304, + 644, + 547, + 692 + ], + "type": "inline_equation", + "content": "u^{hq}" + }, + { + "bbox": [ + 304, + 644, + 547, + 692 + ], + "type": "text", + "content": ", our latent diffusion module is optimized by a standard mean-squared error loss as follows:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 330, + 700, + 545, + 715 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 330, + 700, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 330, + 700, + 545, + 715 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {d i f} = \\mathbf {E} _ {\\epsilon} \\left[ | \\epsilon - \\epsilon_ {\\theta} \\left(\\sqrt {\\bar {a} _ {t}} u _ {t} ^ {h q} + \\sqrt {1 - \\bar {a} _ {t}} \\epsilon , t\\right) | _ {2} ^ {2} \\right], \\tag {4}", + "image_path": "a127245da3c3e2fda3b5a134527b3fd42af23152c69348712b38e0ab14076fd1.jpg" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "spans": [ + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "type": "text", + "content": "9122" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 62, + 386, + 261 + ], + "blocks": [ + { + "bbox": [ + 51, + 62, + 386, + 261 + ], + "lines": [ + { + "bbox": [ + 51, + 62, + 386, + 261 + ], + "spans": [ + { + "bbox": [ + 51, + 62, + 386, + 261 + ], + "type": "image", + "image_path": "86081e24704685b2755fae42c06267b0855d59e4a58dc2937f345d2d39901a82.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "lines": [ + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "spans": [ + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": "Figure 2. Overview of the proposed PLTrans framework. An encoder " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " extracts the preliminary feature " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " from a degraded face image " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": ". A latent diffusion-based regularization module is applied to " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " to obtain its degradation-irrelevant version " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "\\hat{q}" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " as query. On the other hand, a prior-based key-value module quantizes and transforms " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " to learn key " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " and value " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": ". We perform cross-attention computation over " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "\\hat{q}, k" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " in each transformer block, and feed the resulting feature into a generator " + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 263, + 547, + 309 + ], + "type": "text", + "content": " to synthesize a HQ face image." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 389, + 64, + 545, + 260 + ], + "blocks": [ + { + "bbox": [ + 389, + 64, + 545, + 260 + ], + "lines": [ + { + "bbox": [ + 389, + 64, + 545, + 260 + ], + "spans": [ + { + "bbox": [ + 389, + 64, + 545, + 260 + ], + "type": "image", + "image_path": "24cedb48b5e9459fed255abea070798648a86f7612bc24c4ce2c9f2ca8d5feaf.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "spans": [ + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "inline_equation", + "content": "\\epsilon_{\\theta}(u_t^{hq},t)" + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "text", + "content": " is a U-net model used to predict the noise from " + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "inline_equation", + "content": "u_{t}^{hq}" + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "text", + "content": " at step " + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "inline_equation", + "content": "t,\\epsilon \\sim \\mathcal{N}(\\mathbf{0},\\mathbf{I})" + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "inline_equation", + "content": "\\bar{\\alpha}_{t} = \\prod_{m = 1}^{t}(1 - \\beta_{m})" + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "text", + "content": " in which " + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "inline_equation", + "content": "\\{\\beta_1,\\beta_2,\\dots,\\beta_t\\}" + }, + { + "bbox": [ + 46, + 322, + 288, + 373 + ], + "type": "text", + "content": " is the variance schedule used to control the degree of noise addition." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 380, + 177, + 392 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 380, + 177, + 392 + ], + "spans": [ + { + "bbox": [ + 47, + 380, + 177, + 392 + ], + "type": "text", + "content": "3.3. Prior-based Key-Value" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "spans": [ + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "content": "In addition to regularizing the preliminary features as query, we also learn key and value within our transformation by integrating HQ face priors via a latent dictionary " + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "content": ". The elements in " + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "content": " are expected to offer a wealth of clear face details. Initially, we utilize the preliminary feature " + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "content": " to compute " + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "inline_equation", + "content": "z" + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "content": " through convolution and self-attention operations. Then, " + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "inline_equation", + "content": "z" + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "content": " is quantized by retrieving the " + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "content": " nearest elements from " + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 46, + 399, + 287, + 505 + ], + "type": "text", + "content": ", which serve as the respective priors, as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 75, + 514, + 287, + 534 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 75, + 514, + 287, + 534 + ], + "spans": [ + { + "bbox": [ + 75, + 514, + 287, + 534 + ], + "type": "interline_equation", + "content": "\\left\\{e ^ {(1)}, \\dots , e ^ {(d)} \\right\\} _ {(i, j)} = \\arg \\min _ {e \\in \\mathcal {V}} \\| e - z _ {(i, j)} \\| _ {2} ^ {2}, \\tag {5}", + "image_path": "6a0204dd88a556ae7d7ccea9f8fe6dc7020877453bc25bc4e1f2c5d96b8e5654.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "spans": [ + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "inline_equation", + "content": "z_{(i,j)}" + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "text", + "content": " denotes the feature vector at the spatial location " + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "inline_equation", + "content": "(i,j)" + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "text", + "content": ". Rather than replacing " + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "inline_equation", + "content": "z" + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "text", + "content": " with the most similar element, the retrieved top- " + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "text", + "content": " priors contain more richer information. Note that " + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "text", + "content": " may not generalize well to the reconstruction of degraded data. A global mapping over the top- " + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 542, + 287, + 614 + ], + "type": "text", + "content": " priors is performed as follows:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 128, + 624, + 287, + 657 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 128, + 624, + 287, + 657 + ], + "spans": [ + { + "bbox": [ + 128, + 624, + 287, + 657 + ], + "type": "interline_equation", + "content": "\\widetilde {z} _ {(i, j)} = \\sum_ {l = 1} ^ {d} r _ {l} e ^ {(l)}, \\tag {6}", + "image_path": "52740d9608984b0a446aee09e19b1014b001ba1950db87dd37085db6d67d1190.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{r} = [r_1, \\ldots, r_d]" + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "content": " denotes a learnable combination coefficient vector " + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "inline_equation", + "content": "e^{(l)} \\in \\{e^{(1)}, \\ldots, e^{(d)}\\}_{(i,j)}" + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "content": ". Different from generic dictionary-based representation for data reconstruction, the global mapping is optimized for our restoration" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 323, + 546, + 370 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 323, + 546, + 370 + ], + "spans": [ + { + "bbox": [ + 305, + 323, + 546, + 370 + ], + "type": "text", + "content": "task and thus its expressiveness of the retrieved elements can be enhanced. Building upon the priors " + }, + { + "bbox": [ + 305, + 323, + 546, + 370 + ], + "type": "inline_equation", + "content": "\\widetilde{z}" + }, + { + "bbox": [ + 305, + 323, + 546, + 370 + ], + "type": "text", + "content": ", we learn " + }, + { + "bbox": [ + 305, + 323, + 546, + 370 + ], + "type": "inline_equation", + "content": "k, v" + }, + { + "bbox": [ + 305, + 323, + 546, + 370 + ], + "type": "text", + "content": " by utilizing a lightweight transformer module which can be formulated as:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 380, + 380, + 545, + 393 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 380, + 380, + 545, + 393 + ], + "spans": [ + { + "bbox": [ + 380, + 380, + 545, + 393 + ], + "type": "interline_equation", + "content": "\\{k, v \\} = \\Phi (\\widetilde {z}, z) + \\widetilde {z}, \\tag {7}", + "image_path": "7150504d9c9ab9e81d1cf64fbe8d7771524080f3bc10dbc26337b9588ba6df43.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "spans": [ + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "type": "inline_equation", + "content": "\\Phi (\\cdot)" + }, + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "type": "text", + "content": " denotes the standard transformer operations. We compute the estimated features of the corresponding clear face image by performing cross-attention between " + }, + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "type": "inline_equation", + "content": "\\hat{q}" + }, + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "type": "inline_equation", + "content": "k,v" + }, + { + "bbox": [ + 305, + 401, + 546, + 449 + ], + "type": "text", + "content": " to promote adherence as follows:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 340, + 457, + 545, + 491 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 340, + 457, + 545, + 491 + ], + "spans": [ + { + "bbox": [ + 340, + 457, + 545, + 491 + ], + "type": "interline_equation", + "content": "\\widehat {z} = \\operatorname {C o n v} \\left(\\operatorname {s o f t m a x} \\left(\\frac {Q K ^ {T}}{\\sqrt {N}}\\right) V\\right) + k, \\tag {8}", + "image_path": "f98ac4660435ae49891f44dda5c60d5a899a07d8487f04bf1e299d3873883eb7.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 497, + 545, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 497, + 545, + 521 + ], + "spans": [ + { + "bbox": [ + 305, + 497, + 545, + 521 + ], + "type": "text", + "content": "where Conv represents the convolutional operation, " + }, + { + "bbox": [ + 305, + 497, + 545, + 521 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 305, + 497, + 545, + 521 + ], + "type": "text", + "content": " denotes the number of feature channels, and" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 388, + 529, + 459, + 542 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 388, + 529, + 459, + 542 + ], + "spans": [ + { + "bbox": [ + 388, + 529, + 459, + 542 + ], + "type": "interline_equation", + "content": "Q = \\hat {q} W _ {Q} + b _ {Q},", + "image_path": "4c54690777c796a057d74eb172bc85445ef4a6155f86a3dffeec01511b029868.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 389, + 544, + 545, + 557 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 389, + 544, + 545, + 557 + ], + "spans": [ + { + "bbox": [ + 389, + 544, + 545, + 557 + ], + "type": "interline_equation", + "content": "K = k W _ {K} + b _ {K}, \\tag {9}", + "image_path": "18c7b7b038eaf07c9ade7307212962629fcb8ac753e1710dc7bef06cb2446fcd.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 389, + 559, + 460, + 571 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 389, + 559, + 460, + 571 + ], + "spans": [ + { + "bbox": [ + 389, + 559, + 460, + 571 + ], + "type": "interline_equation", + "content": "V = v W _ {V} + b _ {V},", + "image_path": "f0de5f49041c688b216df1d91f338610850f7d6d720f5b99f224de62aebab2bb.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "spans": [ + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "text", + "content": "and " + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "inline_equation", + "content": "W_{Q / K / V}" + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "inline_equation", + "content": "b_{Q / K / V}" + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "text", + "content": " are learnable parameters. We then restore the clear face image " + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "inline_equation", + "content": "\\widehat{y}" + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "text", + "content": " by feeding " + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "inline_equation", + "content": "\\widehat{z}" + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "text", + "content": " into a decoder " + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 579, + 545, + 615 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 623, + 402, + 635 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 623, + 402, + 635 + ], + "spans": [ + { + "bbox": [ + 306, + 623, + 402, + 635 + ], + "type": "text", + "content": "3.4. Model Training" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 641, + 545, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 641, + 545, + 689 + ], + "spans": [ + { + "bbox": [ + 305, + 641, + 545, + 689 + ], + "type": "text", + "content": "Let " + }, + { + "bbox": [ + 305, + 641, + 545, + 689 + ], + "type": "inline_equation", + "content": "\\widehat{y}" + }, + { + "bbox": [ + 305, + 641, + 545, + 689 + ], + "type": "text", + "content": " denote the restored clear face image from a degraded input " + }, + { + "bbox": [ + 305, + 641, + 545, + 689 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 305, + 641, + 545, + 689 + ], + "type": "text", + "content": ". We first adopt the widely used pixel-level loss to assess the consistency to the ground truth, and the corresponding function is defined as follows:" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 323, + 698, + 545, + 714 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 323, + 698, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 323, + 698, + 545, + 714 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {c o n s}} = \\mathbf {E} _ {(x, y)} \\left[ | \\widehat {y} - y | _ {1} + \\| \\varphi (\\widehat {y}) - \\varphi (y) \\| _ {2} ^ {2} \\right], \\tag {10}", + "image_path": "ff2ba03843cbc54f6cec5a53827f304bde0e96fcfc2bf0b60d70db0d36c46fd4.jpg" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "spans": [ + { + "bbox": [ + 294, + 769, + 315, + 779 + ], + "type": "text", + "content": "9123" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "type": "text", + "content": " denotes the ground-truth clear image with respect to " + }, + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "type": "inline_equation", + "content": "\\varphi(\\cdot)" + }, + { + "bbox": [ + 46, + 72, + 289, + 133 + ], + "type": "text", + "content": " represents the feature maps extracted by a pre-trained VGG [33]. We also adopt an adversarial training strategy to improve the visual quality of restored images, and the loss function is defined as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 104, + 141, + 287, + 160 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 104, + 141, + 287, + 160 + ], + "spans": [ + { + "bbox": [ + 104, + 141, + 287, + 160 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {a d v} ^ {\\text {r e a l}} = \\mathbf {E} _ {y} [ \\log D (y) ], \\tag {11}", + "image_path": "c2de3d2310ed240e772509a62ba9b29bbdc5ac52e4665e159fec3e4b6e32a12c.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 105, + 158, + 230, + 173 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 105, + 158, + 230, + 173 + ], + "spans": [ + { + "bbox": [ + 105, + 158, + 230, + 173 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {a d v} ^ {s y n c} = \\mathbf {E} _ {x} \\big [ \\log (1 - D (\\widehat {y})) \\big ],", + "image_path": "644a635b2514a7abfa6420b2b1d7df9549af7f6a7c4d9145d51509f8c6487323.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 183, + 288, + 232 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 183, + 288, + 232 + ], + "spans": [ + { + "bbox": [ + 46, + 183, + 288, + 232 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 183, + 288, + 232 + ], + "type": "inline_equation", + "content": "D(\\cdot)" + }, + { + "bbox": [ + 46, + 183, + 288, + 232 + ], + "type": "text", + "content": " denotes the predicted probability of an input face image being real. By integrating the above training losses, we formulate the optimization problem of our restoration model as follows:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 110, + 242, + 229, + 259 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 110, + 242, + 229, + 259 + ], + "spans": [ + { + "bbox": [ + 110, + 242, + 229, + 259 + ], + "type": "interline_equation", + "content": "\\min _ {R} \\mathcal {L} _ {c o n s} ^ {q} + \\lambda \\mathcal {L} _ {K L} + \\mathcal {L} _ {d i f},", + "image_path": "c7689807d0069c5242559b99c7a2ffe36ff8dc5d0f56d31a56361d6402d252ea.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 106, + 261, + 287, + 279 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 106, + 261, + 287, + 279 + ], + "spans": [ + { + "bbox": [ + 106, + 261, + 287, + 279 + ], + "type": "interline_equation", + "content": "\\min _ {E, P, G} \\mathcal {L} _ {\\text {c o n s}} + \\mathcal {L} _ {\\text {a d v}} ^ {\\text {s y n c}}, \\tag {12}", + "image_path": "bd237cc5715bbc640f11105e9d50efe915355f2e46290404b2654be171195280.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 109, + 282, + 194, + 300 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 109, + 282, + 194, + 300 + ], + "spans": [ + { + "bbox": [ + 109, + 282, + 194, + 300 + ], + "type": "interline_equation", + "content": "\\max _ {D} \\mathcal {L} _ {a d v} ^ {r e a l} + \\mathcal {L} _ {a d v} ^ {s y n c},", + "image_path": "05c9f0ae3ef24d65a2904ba1c0c94b0af2d4e73a66bf933e2d0785207a346336.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 312, + 287, + 372 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 312, + 287, + 372 + ], + "spans": [ + { + "bbox": [ + 46, + 312, + 287, + 372 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 312, + 287, + 372 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 46, + 312, + 287, + 372 + ], + "type": "text", + "content": " denotes a weighting factor that controls the relative importance of the KL Divergence-based regularization term. Note that the latent dictionary " + }, + { + "bbox": [ + 46, + 312, + 287, + 372 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 46, + 312, + 287, + 372 + ], + "type": "text", + "content": " is learnt by performing vector quantization [36] in a clear face image reconstruction process." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 386, + 128, + 400 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 386, + 128, + 400 + ], + "spans": [ + { + "bbox": [ + 47, + 386, + 128, + 400 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 408, + 287, + 515 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 408, + 287, + 515 + ], + "spans": [ + { + "bbox": [ + 46, + 408, + 287, + 515 + ], + "type": "text", + "content": "In this section, extensive experiments are performed to evaluate the proposed PLTrans on a variety of face restoration tasks. We first introduce the experimental settings including the training and test datasets, implementation details and evaluation protocol. Next, we show how the latent transformations benefit face restoration, followed by quantitative and qualitative comparison with state-of-the-art methods. Finally, we demonstrate the applicability of PLTrans to multiple vision tasks." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 527, + 174, + 540 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 527, + 174, + 540 + ], + "spans": [ + { + "bbox": [ + 47, + 527, + 174, + 540 + ], + "type": "text", + "content": "4.1. Experimental Settings" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 547, + 141, + 559 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 547, + 141, + 559 + ], + "spans": [ + { + "bbox": [ + 47, + 547, + 141, + 559 + ], + "type": "text", + "content": "4.1.1 Training Data" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 567, + 287, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 567, + 287, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 567, + 287, + 605 + ], + "type": "text", + "content": "PLTrans was trained on FFHQ [19], which contains 70,000 HQ face images. To construct LQ training images, we follow [48] to degrade the FFHQ images as follows:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 89, + 616, + 287, + 630 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 89, + 616, + 287, + 630 + ], + "spans": [ + { + "bbox": [ + 89, + 616, + 287, + 630 + ], + "type": "interline_equation", + "content": "I _ {L Q} = \\left(\\left(I _ {H Q} \\otimes \\mathcal {K} _ {\\rho}\\right) _ {\\downarrow b} + n _ {\\sigma}\\right) _ {J P E G _ {w}}. \\tag {13}", + "image_path": "b7fba4e3a4177ae904891916a743a19d35e5198aba8bf4380056c2fa677913b4.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "text", + "content": "Each HQ image is first convoluted with the Gaussian blur kernel which has a standard deviation " + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\rho \\in \\{0:0.1:5\\}" + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "text", + "content": ". Afterwards, it is downsampled " + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "inline_equation", + "content": "b \\in \\{0.8:32\\}" + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "text", + "content": " times, and is corrupted by Gaussian noise with intensity parameter " + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\sigma \\in \\{0:10\\}" + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "text", + "content": ". Furthermore, the JPEG compression with quality factor " + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "inline_equation", + "content": "w \\in \\{50:100\\}" + }, + { + "bbox": [ + 47, + 641, + 288, + 714 + ], + "type": "text", + "content": " is then applied to the resulting image." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 72, + 380, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 380, + 83 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 380, + 83 + ], + "type": "text", + "content": "4.1.2 Test Data" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 91, + 547, + 247 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 547, + 247 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 547, + 247 + ], + "type": "text", + "content": "We assess the restoration performance of the proposed PLTrans and the competing methods on a well-known benchmark dataset: CelebA-HQ [28], and multiple in-the-wild datasets: WIDER FACE [47], LFW-Test [17] and WebPhoto-Test [41]. Specifically, we randomly sample 2,000 CelebA-HQ images and apply the degeneration operation defined in Eq.(13) to construct degraded images, and the resulting test dataset is referred to as CelebA-Test. WIDER-Hard/Medium are derived from the WIDER FACE dataset, and there are 13,890/3407 face images with heavy/medium degradations. In addition, LFW-Test and WebPhoto-Test contain 1,711 and 407 mildly degraded face images, respectively." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 262, + 440, + 274 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 262, + 440, + 274 + ], + "spans": [ + { + "bbox": [ + 305, + 262, + 440, + 274 + ], + "type": "text", + "content": "4.1.3 Implementation Details" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "spans": [ + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "text", + "content": "We adopt an encoder-transformer-decoder architecture together with a generic discriminator for the proposed PLTrans. We implement PLTrans using PyTorch with two NVIDIA GeForce RTX 3090s. For the optimizer, we adopt Adam [21] with a learning rate of " + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "inline_equation", + "content": "5 \\times 10^{-5}" + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "text", + "content": ". There are a total of 30 training epochs with a batch size of 4. For the hyperparameters, we set the number of fetched elements " + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "text", + "content": " and the weighting factor " + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "text", + "content": " in Eq.(12) are set to 8 and " + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "inline_equation", + "content": "5 \\times 10^{-5}" + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "text", + "content": ", respectively." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 404, + 424, + 415 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 404, + 424, + 415 + ], + "spans": [ + { + "bbox": [ + 306, + 404, + 424, + 415 + ], + "type": "text", + "content": "4.1.4 Evaluation Protocol" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 423, + 545, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 423, + 545, + 579 + ], + "spans": [ + { + "bbox": [ + 304, + 423, + 545, + 579 + ], + "type": "text", + "content": "We implement all the competing methods based on the open source codes, and both training and test images are resized to " + }, + { + "bbox": [ + 304, + 423, + 545, + 579 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 304, + 423, + 545, + 579 + ], + "type": "text", + "content": " for a fair comparison. The widely used metrics: Peak Signal-to-Noise Ratio (PSNR) and the Learned Perceptual Image Patch Similarity (LPIPS) are used to quantitatively evaluate the consistency between the restored face images and the corresponding ground truth. Considering that identity preservation is critical for BFR, we further report the IDentity Similarity (IDS) to the ground truth after restoration in the feature space of a well-trained face recognition model: CosFace [39]. In addition, we assess the diversity and the degree of realism of the synthesized data in terms of Fréchet Inception Distances (FID) [13]." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 587, + 504, + 600 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 587, + 504, + 600 + ], + "spans": [ + { + "bbox": [ + 306, + 587, + 504, + 600 + ], + "type": "text", + "content": "4.2. Degradation-unaware Representation" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": "We begin by verifying the effectiveness of our latent diffusion module in producing degradation-irrelevant features. There are 500 HQ images and the corresponding 500 LQ images randomly sampled from CelebA-Test. For each HQ image and its degraded counterpart, we extract and denote their encoder features as " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "q_{hq}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "q_{lq}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": ". We apply the latent diffusion-based regularization on " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "q_{lq}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": ", and denote the regularized version as " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\hat{q}_{lq}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": ". In Figure 3, we visualize the feature distributions by using t-SNE [37], and can observe that the" + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "spans": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "type": "text", + "content": "9124" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 67, + 62, + 265, + 177 + ], + "blocks": [ + { + "bbox": [ + 67, + 62, + 265, + 177 + ], + "lines": [ + { + "bbox": [ + 67, + 62, + 265, + 177 + ], + "spans": [ + { + "bbox": [ + 67, + 62, + 265, + 177 + ], + "type": "image", + "image_path": "e51848852e6dc174fd2166bb88b843b06d9b71d769242e219b0ec20861f044eb.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 178, + 287, + 200 + ], + "lines": [ + { + "bbox": [ + 47, + 178, + 287, + 200 + ], + "spans": [ + { + "bbox": [ + 47, + 178, + 287, + 200 + ], + "type": "text", + "content": "Figure 3. Distributions of HQ image features " + }, + { + "bbox": [ + 47, + 178, + 287, + 200 + ], + "type": "inline_equation", + "content": "q_{hq}" + }, + { + "bbox": [ + 47, + 178, + 287, + 200 + ], + "type": "text", + "content": ", LQ image features " + }, + { + "bbox": [ + 47, + 178, + 287, + 200 + ], + "type": "inline_equation", + "content": "q_{lq}" + }, + { + "bbox": [ + 47, + 178, + 287, + 200 + ], + "type": "text", + "content": ", and the regularized LQ image features " + }, + { + "bbox": [ + 47, + 178, + 287, + 200 + ], + "type": "inline_equation", + "content": "\\hat{q}_{lq}" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 53, + 201, + 279, + 316 + ], + "blocks": [ + { + "bbox": [ + 53, + 201, + 279, + 316 + ], + "lines": [ + { + "bbox": [ + 53, + 201, + 279, + 316 + ], + "spans": [ + { + "bbox": [ + 53, + 201, + 279, + 316 + ], + "type": "image", + "image_path": "83cec7c15c3a87fa0a68b2765f012dacec8ddea594d89e52a2928df0108d6378.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 318, + 287, + 342 + ], + "lines": [ + { + "bbox": [ + 47, + 318, + 287, + 342 + ], + "spans": [ + { + "bbox": [ + 47, + 318, + 287, + 342 + ], + "type": "text", + "content": "Figure 4. The average distances between the regularized LQ image features and the HQ counterparts in the training process." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "spans": [ + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "text", + "content": "clusters of " + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "inline_equation", + "content": "q_{hq}" + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "inline_equation", + "content": "q_{lq}" + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "text", + "content": " are separable, while the data points of " + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "inline_equation", + "content": "\\hat{q}_{lq}" + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "text", + "content": " mix with those of " + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "inline_equation", + "content": "q_{hq}" + }, + { + "bbox": [ + 46, + 358, + 287, + 407 + ], + "type": "text", + "content": ". This indicates that our regularization module is useful for mitigating degradations to a certain extent." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 418, + 260, + 432 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 418, + 260, + 432 + ], + "spans": [ + { + "bbox": [ + 47, + 418, + 260, + 432 + ], + "type": "text", + "content": "4.3. Impact of the Number of Diffusion Steps" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "type": "text", + "content": "To obtain the degradation-unaware features, we regularize the preliminary features by performing " + }, + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "type": "text", + "content": "-step perturbations followed by a reverse diffusion process. It is nontrivial to determine the optimal number of diffusion steps for BFR. For a given image with heavy degradation, it typically takes more perturbation and denoising steps to restore it, and vice versa. To illustrate this point, we perform an experiment on the face images with four levels of degradations (" + }, + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\times 8/16/32/64" + }, + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "type": "text", + "content": " downsampling). In Figure 4, we plot the average distances between the regularized features of LQ CelebA-Test images and the preliminary features of the HQ counterparts in the training process, and the shaded regions around these lines illustrate their variance. One can observe that the average distance to the HQ data quickly achieves the minimum value for the cases where the degree of degradation is low. This confirms that more diffusion steps are needed to restore the clean face image from a heavily degraded one. After the minima are attained, increasing the steps leads to a performance drop, since the relationship between the preliminary features and the corrupted features fades. In Figure 5, we visualize the restored face images at " + }, + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\times 32" + }, + { + "bbox": [ + 46, + 438, + 288, + 715 + ], + "type": "text", + "content": " downsampling scale, showcasing the effects of using varying numbers of diffusion steps." + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 325, + 72, + 525, + 121 + ], + "blocks": [ + { + "bbox": [ + 325, + 72, + 525, + 121 + ], + "lines": [ + { + "bbox": [ + 325, + 72, + 525, + 121 + ], + "spans": [ + { + "bbox": [ + 325, + 72, + 525, + 121 + ], + "type": "image", + "image_path": "fe404441ff446860a7c6c5b9596ca2701c2786287d8c69ea3f5d0ebc703a1115.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 122, + 545, + 144 + ], + "lines": [ + { + "bbox": [ + 306, + 122, + 545, + 144 + ], + "spans": [ + { + "bbox": [ + 306, + 122, + 545, + 144 + ], + "type": "text", + "content": "Figure 5. The restoration results of PLTrans with different numbers of diffusion steps." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 323, + 174, + 526, + 240 + ], + "blocks": [ + { + "bbox": [ + 307, + 162, + 544, + 172 + ], + "lines": [ + { + "bbox": [ + 307, + 162, + 544, + 172 + ], + "spans": [ + { + "bbox": [ + 307, + 162, + 544, + 172 + ], + "type": "text", + "content": "Table 1. Results of PLTrans and ablative models on CelebA-Test." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 323, + 174, + 526, + 240 + ], + "lines": [ + { + "bbox": [ + 323, + 174, + 526, + 240 + ], + "spans": [ + { + "bbox": [ + 323, + 174, + 526, + 240 + ], + "type": "table", + "html": "
MethodsFID↓LPIPS↓PSNR↑IDS↑
PLTrans w/o V90.120.480818.810.2866
PLTrans w/o DIFF44.960.430418.890.4820
PLTrans w/o LT42.120.430119.110.5201
PLTrans w/o DWT41.570.448717.990.4672
PLTrans39.580.426019.360.5264
", + "image_path": "d359acca2edb317be770bb48de34c753c965169e9a24eb2c24992051203bd8d3.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 258, + 400, + 270 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 258, + 400, + 270 + ], + "spans": [ + { + "bbox": [ + 306, + 258, + 400, + 270 + ], + "type": "text", + "content": "4.4. Ablation Study" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 283, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 283, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 283, + 547, + 715 + ], + "type": "text", + "content": "We consider that the superior restoration performance of our PLTrans is mainly due to the latent diffusion-based regularization, HQ face prior, DWT-based low-frequency information injection and the prior-based key-value. To highlight the effectiveness of the four factors in BFR, we perform a number of ablative experiments. Specifically, we build four variants by disabling the diffusion module (DIFF), DWT, dictionary and Lightweight Transformer (LT) in the Prior-based Key-Value Module, and the resulting models are referred to as 'PLTrans w/o DIFF', 'PLTrans w/o DWT', 'PLTrans w/o V' and 'PLTrans w/o LT' respectively. The experiments are performed on CelebA-Test, and we summarize the results of the models in terms of FID, PSNR, LPIPS and IDS in Table 1. We can make the following observations: PLTrans outperforms its variants, yielding superior quantitative results across all the metrics. Without the latent diffusion-based regularization, it is difficult to restore the disordered structural information of degraded images, and the restoration performance reduces 5.38 in terms of FID. A number of artifacts in the resulting synthesized images are also observed as shown in Figure 6. When compared with 'PLTrans w/o V', the inclusion of the latent dictionary leads to 0.0548 improved performance in terms of LPIPS. This demonstrates that the HQ face prior is useful for synthesizing texture details. When disabling the lightweight transformer module, 'PLTrans w/o LT' learns the key and value vectors directly from the dictionary features, and we can observe a performance drop of 0.25 in terms of PSNR. We conclude that this module can infer a reasonable transformation to leverage the prior knowledge, which is useful for plausible synthesis. What's more, when disabling the DWT-based information injection module, 'PLTrans w/o DWT' leads to a significant performance drop of 0.0592 in terms of IDS. This suggests the information injection module is beneficial for preserving the semantics of the input image." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 769, + 315, + 779 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 769, + 315, + 779 + ], + "spans": [ + { + "bbox": [ + 295, + 769, + 315, + 779 + ], + "type": "text", + "content": "9125" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 72, + 62, + 145, + 137 + ], + "blocks": [ + { + "bbox": [ + 72, + 62, + 145, + 137 + ], + "lines": [ + { + "bbox": [ + 72, + 62, + 145, + 137 + ], + "spans": [ + { + "bbox": [ + 72, + 62, + 145, + 137 + ], + "type": "image", + "image_path": "b4116cbe3d270c612e3f1c203f3388c28d0ee30867b3e3a30c391e66d42f246e.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 100, + 138, + 117, + 145 + ], + "lines": [ + { + "bbox": [ + 100, + 138, + 117, + 145 + ], + "spans": [ + { + "bbox": [ + 100, + 138, + 117, + 145 + ], + "type": "text", + "content": "Input" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 146, + 62, + 220, + 137 + ], + "blocks": [ + { + "bbox": [ + 146, + 62, + 220, + 137 + ], + "lines": [ + { + "bbox": [ + 146, + 62, + 220, + 137 + ], + "spans": [ + { + "bbox": [ + 146, + 62, + 220, + 137 + ], + "type": "image", + "image_path": "03f50d58217954f5755426d76595e57eb6edc6e6e8bfcbaa1bc3466fd5e2bf7b.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 161, + 138, + 206, + 145 + ], + "lines": [ + { + "bbox": [ + 161, + 138, + 206, + 145 + ], + "spans": [ + { + "bbox": [ + 161, + 138, + 206, + 145 + ], + "type": "text", + "content": "PLTrans w/o " + }, + { + "bbox": [ + 161, + 138, + 206, + 145 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 222, + 62, + 295, + 137 + ], + "blocks": [ + { + "bbox": [ + 222, + 62, + 295, + 137 + ], + "lines": [ + { + "bbox": [ + 222, + 62, + 295, + 137 + ], + "spans": [ + { + "bbox": [ + 222, + 62, + 295, + 137 + ], + "type": "image", + "image_path": "ada034fd33533eaeeb81bf795cd8205a9260be88258e1554031b07662cbccac5.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 229, + 138, + 287, + 145 + ], + "lines": [ + { + "bbox": [ + 229, + 138, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 229, + 138, + 287, + 145 + ], + "type": "text", + "content": "PLTrans w/o DIFF" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 129, + 147, + 462, + 157 + ], + "lines": [ + { + "bbox": [ + 129, + 147, + 462, + 157 + ], + "spans": [ + { + "bbox": [ + 129, + 147, + 462, + 157 + ], + "type": "text", + "content": "Figure 6. Visual comparison between PLTrans and ablative models on an in-the-wild image." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 296, + 62, + 370, + 137 + ], + "blocks": [ + { + "bbox": [ + 296, + 62, + 370, + 137 + ], + "lines": [ + { + "bbox": [ + 296, + 62, + 370, + 137 + ], + "spans": [ + { + "bbox": [ + 296, + 62, + 370, + 137 + ], + "type": "image", + "image_path": "a02add26539532025428a810b580ec7eae4ad031487c853b07b60bd18b33af5a.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 308, + 138, + 356, + 145 + ], + "lines": [ + { + "bbox": [ + 308, + 138, + 356, + 145 + ], + "spans": [ + { + "bbox": [ + 308, + 138, + 356, + 145 + ], + "type": "text", + "content": "PLTrans w/o LT" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 370, + 62, + 444, + 137 + ], + "blocks": [ + { + "bbox": [ + 370, + 62, + 444, + 137 + ], + "lines": [ + { + "bbox": [ + 370, + 62, + 444, + 137 + ], + "spans": [ + { + "bbox": [ + 370, + 62, + 444, + 137 + ], + "type": "image", + "image_path": "7ac751655b9254fce6baaa4f289827d29bd7d64a9e230b225857b8f159dbaa7b.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 373, + 138, + 430, + 145 + ], + "lines": [ + { + "bbox": [ + 373, + 138, + 430, + 145 + ], + "spans": [ + { + "bbox": [ + 373, + 138, + 430, + 145 + ], + "type": "text", + "content": "PLTrans w/o DWT" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 445, + 62, + 518, + 137 + ], + "blocks": [ + { + "bbox": [ + 445, + 62, + 518, + 137 + ], + "lines": [ + { + "bbox": [ + 445, + 62, + 518, + 137 + ], + "spans": [ + { + "bbox": [ + 445, + 62, + 518, + 137 + ], + "type": "image", + "image_path": "265e491bd06f3c5cf13c3234255c0858a53eecce0bd206b3324ded1da8d75dbc.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 468, + 138, + 494, + 145 + ], + "lines": [ + { + "bbox": [ + 468, + 138, + 494, + 145 + ], + "spans": [ + { + "bbox": [ + 468, + 138, + 494, + 145 + ], + "type": "text", + "content": "PLTrans" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 169, + 219, + 182 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 169, + 219, + 182 + ], + "spans": [ + { + "bbox": [ + 47, + 169, + 219, + 182 + ], + "type": "text", + "content": "4.5. Comparison to State-of-the-arts" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 188, + 286, + 271 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 188, + 286, + 271 + ], + "spans": [ + { + "bbox": [ + 46, + 188, + 286, + 271 + ], + "type": "text", + "content": "To demonstrate the superiority of the proposed PLTrans, we perform quantitative and qualitative comparisons with state-of-the-arts, including generic image enhancement methods: Restormer [50] and DIL [23], BFR methods: GFP-GAN [41], GPEN [48], RestoreFormer [43] and Panini [42], and two diffusion-based methods: ILVR [5] and DR2 [44]." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 47, + 289, + 179, + 300 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 289, + 179, + 300 + ], + "spans": [ + { + "bbox": [ + 47, + 289, + 179, + 300 + ], + "type": "text", + "content": "4.5.1 Results on CelebA-Test" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 46, + 308, + 287, + 488 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 308, + 287, + 488 + ], + "spans": [ + { + "bbox": [ + 46, + 308, + 287, + 488 + ], + "type": "text", + "content": "We adopt the same setting as [43] to perform the experiments, where PLTrans and the competing methods are used to restore the degraded face images across a spectrum of downsampling ratios " + }, + { + "bbox": [ + 46, + 308, + 287, + 488 + ], + "type": "inline_equation", + "content": "(\\times 16, \\times 32, \\times 64)" + }, + { + "bbox": [ + 46, + 308, + 287, + 488 + ], + "type": "text", + "content": ". The results of the methods are summarized in Table 2. GPEN, DR2 and RestoreFormer achieve lower FID/LPIPS and higher IDS scores than the other competing methods, which indicates that they perform better in terms of the precision and realism of the restored face images. On the other hand, PLTrans surpasses the competing methods in terms of all the metrics. In particular, for the most difficult case of downsampling " + }, + { + "bbox": [ + 46, + 308, + 287, + 488 + ], + "type": "inline_equation", + "content": "\\times 64" + }, + { + "bbox": [ + 46, + 308, + 287, + 488 + ], + "type": "text", + "content": ", PLTrans is able to achieve the FID and PSNR scores of 39.58 and 19.36, which are lower and higher than the second best methods (GPEN: FID 45.12; DIL: PSNR 19.25) by 5.54 and 0.11, respectively." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 46, + 488, + 287, + 620 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 488, + 287, + 620 + ], + "spans": [ + { + "bbox": [ + 46, + 488, + 287, + 620 + ], + "type": "text", + "content": "Both ILVR and DR2 are diffusion-based methods, and DR2 outperforms ILVR in the above comparison. Different from DR2 which relies on a pre-trained DDPM model, PLTrans learns a latent diffusion module to regularize the preliminary features of degraded images. We perform an additional experiment to further highlight the advantage of PLTrans over DR2. We apply the methods to handle four types of degradation: Gaussian Noise, Blur, Downsample, and JPEG. Figure 7 shows the PLTrans is able to significantly outperform DR2. This suggests that the proposed latent diffusion strategy is more effective for our task." + } + ] + } + ], + "index": 17 + }, + { + "type": "image", + "bbox": [ + 66, + 625, + 164, + 698 + ], + "blocks": [ + { + "bbox": [ + 66, + 625, + 164, + 698 + ], + "lines": [ + { + "bbox": [ + 66, + 625, + 164, + 698 + ], + "spans": [ + { + "bbox": [ + 66, + 625, + 164, + 698 + ], + "type": "image", + "image_path": "1aa2f7047b97914df1dd7fe3784af129616e7d9d68759c929ce53af8bd167768.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 702, + 286, + 724 + ], + "lines": [ + { + "bbox": [ + 46, + 702, + 286, + 724 + ], + "spans": [ + { + "bbox": [ + 46, + 702, + 286, + 724 + ], + "type": "text", + "content": "Figure 7. Comparison between PLTrans and DR2 over different types of degradations." + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "type": "image", + "bbox": [ + 165, + 625, + 265, + 698 + ], + "blocks": [ + { + "bbox": [ + 165, + 625, + 265, + 698 + ], + "lines": [ + { + "bbox": [ + 165, + 625, + 265, + 698 + ], + "spans": [ + { + "bbox": [ + 165, + 625, + 265, + 698 + ], + "type": "image", + "image_path": "1aaa3fa1a325004e267c477bfc70f71be36ea789a274af6a872a51d6f5356f00.jpg" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_body" + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 170, + 473, + 181 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 170, + 473, + 181 + ], + "spans": [ + { + "bbox": [ + 306, + 170, + 473, + 181 + ], + "type": "text", + "content": "4.5.2 User Study on In-the-wild Data" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 188, + 545, + 403 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 188, + 545, + 403 + ], + "spans": [ + { + "bbox": [ + 304, + 188, + 545, + 403 + ], + "type": "text", + "content": "We further evaluate PLTrans and the competing methods on WIDER-Hard/Medium, LFW-Test and WebPhoto-Test. Please note that all the models are trained on FFHQ only. In Figure 8, we also present a number of representative restoration results to demonstrate the advantages of PLTrans in reducing artifacts, restoring realistic details, and preserving identity. A user study is performed to assess the restoration quality. We randomly sample 50 degraded face images from the four datasets, and there are 80 workers who are required to score the restoration results of the methods, ranging from 0 to 10. The maximum attainable score is 10 points. The high-score results should represent delightful content with realistic details, while at the same time properly preserving the basic information of the degraded ones. To ensure an unbiased evaluation, the results of the models are presented in a random order. Figure 9 shows the average scores of the models. Our PLTrans achieves the best performance in terms of the highest average scores with a small variance." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 412, + 434, + 425 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 412, + 434, + 425 + ], + "spans": [ + { + "bbox": [ + 306, + 412, + 434, + 425 + ], + "type": "text", + "content": "4.6. Extended Applications" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "spans": [ + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "text", + "content": "Due to the inclusion of the latent diffusion module, the proposed PLTrans is capable of performing various image synthesis and editing tasks. We impose Gaussian regularization on the latent variable " + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "inline_equation", + "content": "u" + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "text", + "content": " in Eq.(2), and is thus able to synthesize diverse face images by sampling " + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "inline_equation", + "content": "u" + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "text", + "content": " from the prior distribution. In addition, we apply linear interpolation to construct a path between two latent variables: " + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "inline_equation", + "content": "u_{1}" + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "inline_equation", + "content": "u_{2}" + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "text", + "content": ", and decode the interpolated vectors. We find that PLTrans can produce continuously changing images along the path. By feeding out-of-domain images, such as cartoon, incomplete image, human scribble and segmentation map, the synthesized face images are realistic while at the same time preserving semantic consistency with the input to a certain extent. We can also edit face components by replacing the " + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "inline_equation", + "content": "u" + }, + { + "bbox": [ + 304, + 430, + 545, + 658 + ], + "type": "text", + "content": "'s subvector associated with the customized region with the counterparts of the reference. As shown in Figure 10, PLTrans produces realistic face images in different tasks. This demonstrates the greater capability of PLTrans in face image enhancement." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 306, + 669, + 378, + 681 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 669, + 378, + 681 + ], + "spans": [ + { + "bbox": [ + 306, + 669, + 378, + 681 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "This paper presents a prior-based latent transformation approach for blind face restoration. We facilitate this task" + } + ] + } + ], + "index": 26 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "spans": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "type": "text", + "content": "9126" + } + ] + } + ], + "index": 27 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 67, + 74, + 525, + 178 + ], + "blocks": [ + { + "bbox": [ + 127, + 62, + 465, + 73 + ], + "lines": [ + { + "bbox": [ + 127, + 62, + 465, + 73 + ], + "spans": [ + { + "bbox": [ + 127, + 62, + 465, + 73 + ], + "type": "text", + "content": "Table 2. Quantitative Comparison between PLTrans and competing methods on CelebA-Test." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 67, + 74, + 525, + 178 + ], + "lines": [ + { + "bbox": [ + 67, + 74, + 525, + 178 + ], + "spans": [ + { + "bbox": [ + 67, + 74, + 525, + 178 + ], + "type": "table", + "html": "
Methods× 16× 32× 64
FID↓LPIPS↓PSNR↑IDS↑FID↓LPIPS↓PSNR↑IDS↑FID↓LPIPS↓PSNR↑IDS↑
GFPGAN [46]40.830.358321.000.6446107.650.433418.910.2523159.240.459018.410.1679
GPEN [48]25.820.378120.280.712636.220.433918.620.569845.120.451218.200.5011
ILVR [5]103.080.570821.080.576897.960.544619.760.5173107.830.573419.210.4627
Panini [42]47.140.393521.900.675444.230.483819.010.485752.370.486419.060.4272
Restormer [50]148.560.598122.120.3346185.250.630219.790.1771197.320.645919.240.1332
RestoreFormer [43]24.320.359221.990.737839.390.439719.410.537946.280.459719.110.4778
DIL [23]207.880.637521.910.3626406.170.683519.810.1697463.760.691819.250.1230
DR2 [44]35.180.411521.090.596543.410.427619.620.527349.640.456019.140.4721
PLTrans19.640.320722.130.741232.360.397819.910.596339.580.427019.360.5264
", + "image_path": "c15a6811eeed02655b0ddb8f205b69595bc3431da4ddb71113fa58fa97248899.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 72, + 180, + 519, + 300 + ], + "blocks": [ + { + "bbox": [ + 72, + 180, + 519, + 300 + ], + "lines": [ + { + "bbox": [ + 72, + 180, + 519, + 300 + ], + "spans": [ + { + "bbox": [ + 72, + 180, + 519, + 300 + ], + "type": "image", + "image_path": "0e092d063e80102937f318e8198b5592ad3d5f7579b028a1833fe5cb210e232b.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 99, + 303, + 492, + 314 + ], + "lines": [ + { + "bbox": [ + 99, + 303, + 492, + 314 + ], + "spans": [ + { + "bbox": [ + 99, + 303, + 492, + 314 + ], + "type": "text", + "content": "Figure 8. Visual comparison between PLTrans and competing methods on representative in-the-wild images." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 70, + 323, + 260, + 453 + ], + "blocks": [ + { + "bbox": [ + 70, + 323, + 260, + 453 + ], + "lines": [ + { + "bbox": [ + 70, + 323, + 260, + 453 + ], + "spans": [ + { + "bbox": [ + 70, + 323, + 260, + 453 + ], + "type": "image", + "image_path": "564b189c5fd09ddcad263bbda523f8294983989a48f237c31e8e0f2e8617a4bc.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 54, + 455, + 279, + 465 + ], + "lines": [ + { + "bbox": [ + 54, + 455, + 279, + 465 + ], + "spans": [ + { + "bbox": [ + 54, + 455, + 279, + 465 + ], + "type": "text", + "content": "Figure 9. The scoring result of user study on in-the-wild data." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 476, + 287, + 644 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 476, + 287, + 644 + ], + "spans": [ + { + "bbox": [ + 46, + 476, + 287, + 644 + ], + "type": "text", + "content": "by improving the attention computation in a restoration transformer, which represents an effective attempt to transform query, key and value vectors to synthesize the clear face images from degraded ones. Toward this end, we incorporate a latent diffusion module to regularize the preliminary features, such that the regularized version becomes less sensitive to degradations. This is essential for enhancing the generalization performance over unknown degradations. We further incorporate a HQ face prior in the form of a latent dictionary to learn key and value, followed by cross-attention computation with the regularized features as query. Extensive experiments validate the effectiveness of our proposed framework PLTrans in restoring faithful details and preserving identity information." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 657, + 156, + 670 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 657, + 156, + 670 + ], + "spans": [ + { + "bbox": [ + 47, + 657, + 156, + 670 + ], + "type": "text", + "content": "6. Acknowledgments" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": "This work was supported in part by the National Natural Science Foundation of China (Project No. 62072189, 62106136), in part by the Research Grants Coun" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 319, + 321, + 532, + 597 + ], + "blocks": [ + { + "bbox": [ + 319, + 321, + 532, + 597 + ], + "lines": [ + { + "bbox": [ + 319, + 321, + 532, + 597 + ], + "spans": [ + { + "bbox": [ + 319, + 321, + 532, + 597 + ], + "type": "image", + "image_path": "551f5913e21724ff884b0336cb81aa00f569817624383cfa525bb9b9fc532a06.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 603, + 545, + 624 + ], + "lines": [ + { + "bbox": [ + 305, + 603, + 545, + 624 + ], + "spans": [ + { + "bbox": [ + 305, + 603, + 545, + 624 + ], + "type": "text", + "content": "Figure 10. Representative results of PLTrans on different vision tasks." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 640, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 640, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 640, + 545, + 712 + ], + "type": "text", + "content": "cil of the Hong Kong Special Administration Region (Project No. CityU 11206622), in part by the Guang-Dong Basic and Applied Basic Research Foundation (Project No. 2020A1515010484, 2022A1515011160, 2022A1515010434), and in part by TCL Science and Technology Innovation Fund (Project No. 20231752)." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "spans": [ + { + "bbox": [ + 294, + 769, + 315, + 778 + ], + "type": "text", + "content": "9127" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 91, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "type": "text", + "content": "[1] Nicolas Carion, Francisco Massa, Gabriel Synnaeve, Nicolas Usunier, Alexander Kirillov, and Sergey Zagoruyko. 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When adopting diffusion models for image restoration, the crucial challenge lies in how to preserve high-level image fidelity in the randomness diffusion process and generate accurate background structures and realistic texture details. In this paper, we propose a general framework and develop a Diffusion Texture Prior Model (DTPM) for image restoration tasks. DTPM explicitly models high-quality texture details through the diffusion process, rather than global contextual content. In phase one of the training stage, we pre-train DTPM on approximately 55K high-quality image samples, after which we freeze most of its parameters. In phase two, we insert conditional guidance adapters into DTPM and equip it with an initial predictor, thereby facilitating its rapid adaptation to downstream image restoration tasks. Our DTPM could mitigate the randomness of traditional diffusion models by utilizing encapsulated rich and diverse texture knowledge and background structural information provided by the initial predictor during the sampling process.", + "bbox": [ + 75, + 325, + 473, + 643 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 671, + 209, + 686 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Image Restoration tasks [37, 43, 70, 71] usually are ill-posed problems whose solutions are not unique. While existing methods [8, 70, 71] have achieved notable breakthroughs, they typically employ direct regression models to produce deterministic results. A persistent challenge is that these deterministic models [4, 70, 71] frequently yield unsatisfactory fine-grained details (See Figure 2), as they are trained to minimize pixel-level error, aligning output with ground truth by Norm-based losses [30]. The emergence of Diffusion Models (DMs) [14, 16, 51, 55] has revolutionized image generation, yielding realistic images replete with fine details. This advancement motivates our investigation", + "bbox": [ + 75, + 696, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/781aa095d4079ac5ae97581877cbcb9d653fcc3c4053d8d4c2964451738cff4e.jpg", + "image_caption": [ + "Figure 1. We use a coefficient $\\alpha$ ranging from 0.1 to 1 to control the intensity of texture removal. As $\\alpha$ increases, leading to richer textures from left to right in the images, we can observe a corresponding improvement in the scores of no-reference image quality metrics, specifically NIQE [42] and CLIP-IQA+ [57]. Regarding the NIQE, lower scores indicate better quality, while for CLIP-IQA+, higher scores represent better visual quality. This indicates that the quality of the image's texture details have a significant impact on the visual perceptual quality of the image." + ], + "image_footnote": [], + "bbox": [ + 501, + 290, + 890, + 357 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "into diffusion-based methods for image restoration, aiming to leverage conditional DMs [17, 45, 51] to produce perceptually appealing results that closely mimic natural, clean images.", + "bbox": [ + 496, + 536, + 892, + 597 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "However, directly applying diffusion image generation techniques [44, 51, 55] to image restoration tasks is often impractical [36, 45]. The high content fidelity required in image restoration clashes with the stochastic nature of diffusion models [44, 55]. A plausible solution involves integrating physical degradation models [5, 69] with neural networks or crafting hand-designed priors [20, 47] to mitigate the inherent randomness of the diffusion paradigm. While several previous studies [17, 68, 69] have adopted this approach with success, they lack versatility and show limited generalization capability on real-world scenes, as physical degradation models do not fully encompass real-world degradation scenarios [4, 66, 67]. Additionally, the iterative nature and complexity of the denoising process in diffusion models necessitate extensive data and lengthy training cycles for effective learning. The challenges and limitations outlined above necessitate a rethinking of the use of the diffusion paradigm in image restoration: (i) To preserve high-level fidelity in restoration, we propose using a diffusion model to recover only texture layers. This", + "bbox": [ + 496, + 598, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Lei Zhu (leizhu @ust.hk) is the corresponding author.", + "bbox": [ + 94, + 886, + 387, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "2524", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/3f92d8270648f6da63a7b5d5b5eeee7ae0006c76e03e603395810731d8a14f81.jpg", + "image_caption": [ + "Figure 2. (a) The input degraded image. (b) The result of Restormer [70]. Restormer is a representative image restoration method that can only produce deterministic results, which may lack promising details. (c) The result of RainHazeDiff [45]. (d) The result of our method. The content within the dashed rectangle represents the corresponding ground-truth details. It's worth noting that our approach excels in generating finer details, thanks to the incorporation of Diffusion Texture Priors we proposed." + ], + "image_footnote": [], + "bbox": [ + 78, + 88, + 467, + 268 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "approach emphasizes and highlights the importance of fine textures in visual perception (See Figure 1). By focusing diffusion on texture recovery, we minimize randomness of diffusion process and leverage its strength in generating realistic details. (ii) Recognizing the diffusion paradigm as a potent representation learning tool that requires extensive data for convergence, we pre-trained our model, named the Diffusion Texture Priors Model (DTPM), on a large-scale dataset of high-quality images. This model, trained on approximately $55K$ samples, is tailored to reconstruct texture layers, embedding texture priors within the diffusion process. Our DTPM framework is characterized by: (a) A novel approach in diffusion modeling that focuses on texture layers through residual learning, enhancing efficiency in downstream restoration tasks. (b) The incorporation of Semantic Code as a constraint, guiding the diffusion model to produce semantically coherent textures. (c) To preserve the integrity of the diffusion texture priors, most parameters of the DTPM remain fixed after pre-training. We introduce a Conditional Degradation Adapter to facilitate rapid adaptation to various restoration tasks without the risk of catastrophic forgetting.", + "bbox": [ + 75, + 448, + 472, + 781 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our extensive experiments across single-image defocus deblurring, image motion deblurring, desnowing, dehazing, deraining, and raindrop removal demonstrate that our method not only surpasses strong regression models and recent diffusion-based models in perceptual quality but also exhibits robust generalization across diverse restoration tasks.", + "bbox": [ + 75, + 795, + 468, + 898 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 500, + 89, + 650, + 106 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Evolution in Image Restoration. Image restoration [4, 15, 19, 25, 39, 67, 71, 77], a pivotal research domain within the computer vision community, has witnessed significant evolution over recent years. Traditionally regarded as an ill-posed problem, image restoration poses unique challenges due to the multitude of potential solutions derivable from a single degraded image. Over the last decade, there has been a notable shift in the computer vision field from conventional, handcrafted prior-based approaches [20, 47] to a more data-centric, deep learning-driven paradigm [4, 15, 59, 70]. This transition has led to the development of advanced deep learning techniques, characterized by complicated network structures [65, 70, 71] and extensive training on carefully collected datasets. These approaches excel in learning mappings from degraded to clean data, effectively tackling the complexities of image restoration. Initially, deep learning methods [9-11, 66, 67] in this area tended to produce deterministic outcomes, which starkly contrasted with the fundamentally probabilistic nature of image restoration tasks [18, 46, 70]. This discrepancy has increasingly brought generative methods [17, 27, 46, 64, 76] to the forefront, highlighting their potential to address the challenges inherent in image restoration.", + "bbox": [ + 496, + 114, + 893, + 462 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Generative image restoration methods. Recent developments [6, 7, 17, 41, 46, 61, 64, 74] have shed light on the fundamental flaws of earlier deep learning-driven image restoration techniques, specifically their (i) generate deterministic outputs and (ii) inability to restore high-quality, detailed textures, owing to their training focused on minimizing pixel-level discrepancies. Consequently, generative approaches are gaining traction. A notable strategy includes employing Generative Adversarial Networks (GANs) [24, 29, 48]. Nonetheless, GANs pose challenges due to their complex training procedures, instability during training, and occasional generation of unrealistic image attributes. The impressive efficacy of diffusion in image generation has introduced a promising avenue. Diffusion techniques adeptly tackle the aforementioned issues, offering a more stable training regimen and yielding images with realistic textures. Applications of diffusion-based methods in image super-resolution [52], shadow removal [17, 27], deblurring [60], and adverse weather removal [46] have shown promising results. However, there remains a need for comprehensive research to establish a consistent, reliable framework for diffusion-based image restoration tasks.", + "bbox": [ + 496, + 463, + 893, + 794 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. Our Framework", + "text_level": 1, + "bbox": [ + 500, + 806, + 663, + 821 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3.1. Preliminaries of Diffusion Models", + "text_level": 1, + "bbox": [ + 500, + 832, + 797, + 847 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Diffusion Models (DMs), as referenced in [22, 44], are a class of generative models that gradually infuse Gaussian noise into training data and then employ a denoiser to re", + "bbox": [ + 498, + 854, + 893, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "2525", + "bbox": [ + 482, + 944, + 514, + 957 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/1ca2c6e856e568cb347f98748ff494c6b183fe6145607f3d565c8539886d4286.jpg", + "image_caption": [ + "Stage I: Training a Conditional Diffusion Model for Learning Diffusion Texture Priors", + "Stage II : Fine-Tuning the Diffusion Model Using Task-Specific Adapters for Image Restoration Tasks" + ], + "image_footnote": [], + "bbox": [ + 99, + 101, + 658, + 241 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/11c8daa8588a39eed54754f2b1bd7bd566a7a6ff575b540f208a1d713fb89827.jpg", + "image_caption": [ + "(a) Overview of Our Framework", + "Figure 3. The overview of Our DTPM Framework. (a) Our method consists of two stages. In the stage I, under the guiding constraints of semantic code, the diffusion model learns texture layers through residual learning from a large amount of high-quality data, which allows us to encapsulate diverse and rich texture knowledge into the diffusion model. In the stage II, we fix most of the parameters of the trained diffusion model and insert Conditional Guidance Adapters between each layer for efficient fine-tuning and conditional guidance on image restoration tasks. (b) The overview of adapters and our denoising blocks.(c) The detailed design of our Conditional Guidance Adapter." + ], + "image_footnote": [], + "bbox": [ + 99, + 258, + 658, + 401 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/05bfec54f6d459768c6ca926c6152f54593948e735990833fbea0ded42544941.jpg", + "image_caption": [ + "(b) Overview of Adapters and Denoising Blocks" + ], + "image_footnote": [], + "bbox": [ + 658, + 101, + 870, + 234 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/802dacdd17a51cd338b9bb662b8ce78e58e3052c0b995ed718940b45a131ec6c.jpg", + "image_caption": [ + "(c) Conditional Guidance Adapter" + ], + "image_footnote": [], + "bbox": [ + 684, + 250, + 859, + 398 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "verse this noise addition. The process begins with the diffusion phase, where an initial image $\\pmb{x}_0$ evolves into Gaussian noise $\\pmb{x}_T \\sim \\mathcal{N}(0,1)$ through $T$ steps. Each step of this transformation is governed by:", + "bbox": [ + 75, + 520, + 468, + 580 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nq \\left(\\boldsymbol {x} _ {t} \\mid \\boldsymbol {x} _ {t - 1}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t}; \\sqrt {1 - \\beta_ {t}} \\boldsymbol {x} _ {t - 1}, \\beta_ {t} \\boldsymbol {I}\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 117, + 592, + 468, + 618 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\pmb{x}_t$ is the image with noise at step $t$ , $\\beta_t$ is a fixed scaling factor, and $\\mathcal{N}$ denotes the Gaussian distribution. Introducing $\\alpha_t = 1 - \\beta_t$ and $\\bar{\\alpha}_t = \\prod_{i=0}^t \\alpha_i$ simplifies Eq.1 to:", + "bbox": [ + 75, + 627, + 468, + 685 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nq \\left(\\boldsymbol {x} _ {t} \\mid \\boldsymbol {x} _ {0}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t}; \\sqrt {\\bar {\\alpha} _ {t}} \\boldsymbol {x} _ {0}, (1 - \\bar {\\alpha} _ {t}) \\boldsymbol {I}\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 130, + 686, + 468, + 705 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "During the inference stage's reverse process, DMs initiate with a random Gaussian noise map $\\boldsymbol{x}_T$ and progressively denoise it to reach the refined output $\\boldsymbol{x}_0$ .", + "bbox": [ + 75, + 710, + 468, + 756 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\np \\left(\\boldsymbol {x} _ {t - 1} \\mid \\boldsymbol {x} _ {t}, \\boldsymbol {x} _ {0}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t - 1}; \\boldsymbol {\\mu} _ {t} \\left(\\boldsymbol {x} _ {t}, \\boldsymbol {x} _ {0}\\right), \\sigma_ {t} ^ {2} \\boldsymbol {I}\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 99, + 767, + 468, + 785 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where the mean $\\pmb{\\mu}_t(\\pmb{x}_t,\\pmb{x}_0) = \\frac{1}{\\sqrt{\\alpha_t}}\\left(\\pmb{x}_t - \\epsilon \\frac{1 - \\alpha_t}{\\sqrt{1 - \\bar{\\alpha}_t}}\\right)$ and the variance $\\sigma_t^2 = \\frac{1 - \\bar{\\alpha}_{t-1}}{1 - \\bar{\\alpha}_t} \\beta_t$ .", + "bbox": [ + 75, + 797, + 468, + 840 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Overview of DTP-IR Framework", + "text_level": 1, + "bbox": [ + 76, + 847, + 367, + 862 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Our aim is to create a unified framework for image restoration tasks based on our Diffusion Texture Priors. As shown", + "bbox": [ + 75, + 869, + 468, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "in Figure 3, our DTPM framework comprises two stages: In Stage 1, we train a conditional diffusion model with semantic latent feature constraints using a large dataset of high-resolution, high-quality natural images. During Stage 2, we incorporate conditional guidance adapters into the conditional diffusion model to facilitate the model's adaptation to downstream image restoration tasks.", + "bbox": [ + 496, + 520, + 890, + 626 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.3. Stage I: Learning Diffusion Texture Priors", + "text_level": 1, + "bbox": [ + 498, + 633, + 862, + 648 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we will first briefly introduce the core motivation of our Diffusion Texture Priors, followed by the basic structure information of the diffusion model and the semantic code. Finally, we will discuss the training objective and training data.", + "bbox": [ + 496, + 656, + 890, + 733 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Motivation. Recent studies [52, 64, 74] have highlighted the pivotal role of texture quality in shaping subjective visual perception in the realm of image restoration. Traditional methodologies, however, encounter substantial difficulties in accurately restoring fine-grained textural details, which are crucial for realistic image reconstruction. While diffusion models have demonstrated excellence in generating lifelike images, their direct application to image restoration tasks has been less than ideal, yielding mediocre results. Our approach seeks to remedy this by integrating", + "bbox": [ + 496, + 750, + 892, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "2526", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/40be511639af5b759f78a8e90a9ef190a6dbea6e084547e99daa0cad713d4dc4.jpg", + "image_caption": [ + "Figure 4. The architecture of our fundamental denoising block incorporates \"Channel Attention\" (CA) and \"SimpleGate,\" a straightforward feature gating mechanism introduced by Chen et al.[8]. The current timestep $t$ is injected into the block with Adaptive Layer Normalization [3] (AdaLN), i.e., $AdaLN(f_{in} = \\gamma LayerNorm(f_{in}) + \\beta$ , where $f_{in}$ is the input features, $\\gamma$ and $\\beta$ are converted from the timestep embedding. The \"Shift&Scale\" block means shift and scale features by generated $\\gamma, \\beta$ ." + ], + "image_footnote": [], + "bbox": [ + 135, + 90, + 411, + 270 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "texture-specific priors into the diffusion model. This integration enables the diffusion model to specifically concentrate on reconstructing textures, as opposed to merely focusing on degradation elimination. Such a strategy leverages the diffusion model's inherent strengths and mitigates its weaknesses, allowing us to exploit a vast repository of high-quality natural images for prior knowledge. This method not only significantly enhances the model's generalization capabilities but also markedly improves the efficiency of the sampling process.", + "bbox": [ + 75, + 421, + 468, + 571 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Basic Denoising Block. We have engineered a denoising block based on NAFNet [8] block, designed to enhance model adaptability for a broad spectrum of natural image content. This block aims to balance peak model performance with reduced computational demands and easy-to-handle varying input resolutions. As delineated in Figure 4, our denoising block capitalizes on depth-wise convolution as its cornerstone, complemented by several $1 \\times 1$ convolution layers and LayerNorm [3], to facilitate efficient denoising. To incorporate the time condition, we utilize MLPs for transforming the time embedding into channel-specific scale and shift parameters. Additionally, to maintain the semantic consistency between $x_0$ and $y_s$ , we integrate an MLP layer for semantic condition, which amalgamates semantic code as a pivotal conditioning factor.", + "bbox": [ + 75, + 592, + 468, + 820 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Semantic code. To enable the diffusion model to produce realistically textured details, we utilize a pre-trained ResNet-18 [21] for extracting semantic embeddings as a global semantic code, which is then integrated into each de", + "bbox": [ + 75, + 839, + 468, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "noising block as shown in Figure 4. This approach of employing semantic code imposes robust semantic constraints, rather than solely depending on adjacent context information, allowing our model to generate textures in alignment with the contextual semantics. Consequently, this ensures high-fidelity results of our diffusion model.", + "bbox": [ + 496, + 90, + 890, + 181 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Training objective. To prioritize texture reconstruction over content of the image, our diffusion model is designed to capture the residual distribution of $y_{s}$ . The training objective for Stage I is thus defined as: $L_{\\mathrm{StageI}}(\\theta) =$", + "bbox": [ + 496, + 200, + 890, + 262 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbb {E} \\left\\| \\boldsymbol {\\epsilon} - f _ {\\theta} \\left(\\sqrt {\\gamma} \\left(\\underbrace {\\boldsymbol {x} _ {g} - \\boldsymbol {y} _ {s}} _ {\\text {r e s i d u a l}}\\right) + \\sqrt {1 - \\gamma} \\boldsymbol {\\epsilon}, \\boldsymbol {y} _ {s}, \\gamma\\right) \\right\\|, \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 524, + 282, + 890, + 335 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "here, $\\epsilon \\sim \\mathcal{N}(0,I)$ represents the noise vector, and $f_{\\theta}$ is our diffusion model. The term $\\gamma \\sim p(\\gamma)$ denotes a distribution associated with the noise schedule. In this context, $x_{g}$ symbolizes the high-quality input image, whereas $y_{s}$ denotes its corresponding smoothed image. $y_{s}$ is obtained by utilizing an edge-preserving smoothing method [63] to eliminate a majority of the texture while retaining the contextual content.", + "bbox": [ + 496, + 345, + 890, + 465 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Training data for Stage I. Inspired by previous codebook prior-based image restoration studies [61, 64, 74], our training stage I employs high-quality images from the widely-recognized DIV2K [2] and Flickr2K [35] datasets. Each image is cropped into multiple patches of $512 \\times 512$ resolution, followed by an edge-preserved smooth method [63] to diminish textural details. This process results in a training dataset comprising 55,558 paired instances $(x_{g}, y_{s})$ .", + "bbox": [ + 496, + 484, + 890, + 623 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.4. Stage II: Finetuning Diffusion Texture Priors Model with Adapters", + "text_level": 1, + "bbox": [ + 500, + 631, + 890, + 662 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "This section describes the initial predictor and the Conditional Guidance Adapter, along with the rationale behind their integration. We also detail the architecture of the adapters. Finally, the training objectives are outlined.", + "bbox": [ + 496, + 669, + 890, + 731 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Initial Predictor. In the pursuit of augmenting the diffusion model's adaptability for downstream tasks in its second stage (see Figure 3), we draw from the DvSR, integrating a compact and lightweight U-Net to generate an initial output. This initial step efficiently seizes deterministic components of the ultimate restored image, crucial for capturing essential structural information. Moreover, this initial output serves as a pivotal guiding element for the diffusion model, forming an effective complement with our Diffusion Texture Priors Model.", + "bbox": [ + 496, + 750, + 890, + 898 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "2527", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "table", + "img_path": "images/24e4896b11788f1f78fb7428b9e1dbcc93feff0b3ec6b2ba9a09c515b7da31cb.jpg", + "table_caption": [ + "Table 1. Image Desnowing." + ], + "table_footnote": [], + "table_body": "
MethodSnow100K-S [40]Snow100K-L [40]
PSNR ↑SSIM ↑LPIPS ↓PSNR ↑SSIM ↑LPIPS ↓
SPANet [58]29.920.82600.10423.700.79300.210
JSTASR [12]31.400.90120.05925.320.80760.152
RESCAN [34]31.510.90320.05426.080.81080.106
DesnowNet [40]32.330.95000.07027.170.89830.101
DDMSNet [72]34.340.94450.05828.850.87720.098
MPRNet [71]34.970.94570.04929.760.89490.091
NAFNet [8]34.790.94970.05130.060.90170.086
Restormer [70]35.030.94870.04730.520.90920.083
SnowDiff64[45]36.590.96260.03530.430.91450.069
SnowrDiff128[45]36.090.95450.03830.280.90000.067
DTPM-4 Step37.010.96630.03430.920.91740.063
DTPM-10 Step36.440.95210.03330.320.90240.055
DTPM-50 Step36.190.94830.02930.020.89010.053
", + "bbox": [ + 83, + 114, + 426, + 281 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/6f10136cc3c0251bfd387dd602cb26125daef5fbf5ef06f4b793eb526223ecd8.jpg", + "table_caption": [ + "Table 2. Image Deraining & Dehazing." + ], + "table_footnote": [], + "table_body": "
MethodOutdoor-Rain [33]
PSNR ↑SSIM ↑LPIPS ↓
CycleGAN [75]17.620.6560-
pix2pix [23]19.090.7100-
HRGAN [33]21.560.85500.154
PCNet [26]26.190.90150.132
MPRNet [71]28.030.91920.089
NAFNet [8]29.590.90270.085
Restormer [70]29.970.92150.074
RainHazeDiff64[45]28.380.93200.067
RainHazeDiff128[45]26.840.91520.071
DTPM-4 Step30.990.9340.0635
DTPM-10 Step30.920.9320.0617
DTPM-50 Step30.480.9210.0540
", + "bbox": [ + 431, + 114, + 658, + 280 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/67f6b786ce089cad0797abd47de17e4bc7775d92af469b806a462653f3dbd1a1.jpg", + "table_caption": [ + "Table 3. Removing Raindrops." + ], + "table_footnote": [], + "table_body": "
MethodRainDrop [48]
PSNR ↑SSIM ↑LPIPS ↓
pix2pix [23]28.020.8547-
DuRN [38]31.240.9259-
RaindropAttn [50]31.440.92630.068
AttentiveGAN [48]31.590.91700.055
CCN [49]31.340.92860.066
IDT [62]31.870.93130.059
RainDropDiff64[45]32.290.94220.058
RainDropDiff128[45]32.430.93340.058
DTPM-4 Step32.720.94400.0577
DTPM-10 Step31.840.93700.0477
DTPM-50 Step31.440.93200.0439
", + "bbox": [ + 661, + 118, + 888, + 277 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Conditional Guidance Adapter. DPTM encapsulates rich and diverse prior knowledge. We hope that DPTM can fully utilize this knowledge in adapting to downstream image restoration tasks, rather than forgetting it. Therefore, we freeze most of the parameters in DPTM and introduce a flexible and parameter-efficient adaptation mechanism through the Conditional Guidance Adapter as shown in Figure 3 (b) and (c). The design of the Conditional Guidance Adapter brings two benefits: (i) Parameter-efficient learning. Since most of the parameters of DPTM have been sufficiently trained, our model will converge faster and better on downstream tasks after introducing the adapter. (ii) Introducing additional conditions. Introduction of coarse structural information output by the initial predictor, providing the model with more flexible conditional information, thereby producing texture details that better align with expectations. Our Conditional Guidance Adapter could be formally written as:", + "bbox": [ + 75, + 306, + 472, + 580 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {C G - A d p a t e r} \\left(f _ {i n}, y _ {\\epsilon}\\right) = f _ {i n} + \\mathbf {M} _ {\\text {o u t}} \\left(\\mathbf {M} _ {i n} \\left(f _ {i n}\\right) + \\operatorname {C o n v} \\left(y _ {\\epsilon}\\right)\\right), \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 598, + 468, + 628 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathbf{M}$ denotes an MLP layer to scale the dimension $c$ of the input feature $f_{in}^{c}$ to dimension $r\\times c$ , and $y_{\\epsilon}$ denotes the output of initial predictor $\\epsilon_{\\theta}$ , thus $y_{\\epsilon} = \\epsilon_{\\theta}(y_d)$ .", + "bbox": [ + 75, + 630, + 468, + 676 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Training objective. The training objective for Stage II is defined as: $L_{\\mathrm{StageII}}(\\theta) =$", + "bbox": [ + 75, + 715, + 468, + 748 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbb {E} \\left\\| \\boldsymbol {\\epsilon} - f _ {\\theta} \\left(\\sqrt {\\gamma} \\left(\\boldsymbol {y} _ {g} - \\epsilon_ {\\theta} (\\boldsymbol {y} _ {d})\\right) + \\sqrt {1 - \\gamma} \\boldsymbol {\\epsilon}, \\boldsymbol {y} _ {d}, \\gamma\\right) \\right\\|. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 99, + 782, + 468, + 808 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\epsilon_{\\theta}$ represents the initial predictor, illustrated in Figure 3. It is important to note that $\\epsilon_{\\theta}$ does not necessitate additional supervisory loss or pre-training. This is because the gradient from the aforementioned loss propagates through $f_{\\theta}$ and subsequently influences $\\epsilon_{\\theta}$ .", + "bbox": [ + 76, + 824, + 470, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 305, + 632, + 321 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Settings", + "text_level": 1, + "bbox": [ + 500, + 330, + 596, + 347 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Our method is assessed on five specific image restoration tasks: image motion deblurring, single-image defocus deblurring, image deraining&dehazing, image desnowing, and image raindrop removal. In the initial stage, we develop a comprehensive Diffusion Texture Prior model, and in the subsequent stage, we fine-tune individual full models tailored to each task.", + "bbox": [ + 496, + 354, + 890, + 460 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets&Metrics. The GoPro dataset [43], as recommended by DvSR [60], is utilized for training and testing in the domain of image motion deblurring. Adhering to Restormer's approach [70], the DPDD dataset [1] is employed for single-image defocus deblurring. For image desnowing, we align with WeatherDiff [45] using the Snow100K dataset [40]. The Outdoor-Rain dataset [33] is used for image deraining&dehazing, following WeatherDiff [45]. Lastly, for single image raindrop removal, we adopt the practices from IDT [62] and WeatherDiff [45], employing the Raindrop dataset [48] for training and testing. We utilize PSNR, SSIM, and MAE as metrics for distortion-based image quality assessment, complemented by LPIPS [73] and FID for evaluating perceptual image quality. Adhering to the methodology outlined in Whang et al. [60], we extract image patches and compute FID at the patch level to ensure more consistent and reliable evaluation results.", + "bbox": [ + 496, + 484, + 892, + 755 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Training Details We implemented our DTPM using the Pytorch framework, leveraging four NVIDIA RTX 4090 GPUs. Training encompasses two stages: Stage I with 800K iterations and Stage II with 600K iterations. We employed the Adam optimizer, setting momentum values at 0.9 and 0.999. The initial learning rate was established at $1.5 \\times 10^{-4}$ , employing a cosine annealing strategy for gradual learning rate reduction. The diffusion process is", + "bbox": [ + 496, + 779, + 893, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "2528", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/164851ee9c8afbd8ab5a854a72d47995566696826c0a044301871ec7154c54b0.jpg", + "image_caption": [ + "Rain&Haze" + ], + "image_footnote": [], + "bbox": [ + 117, + 87, + 405, + 253 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/be65f41689e55a823e28d4db96fcac0c66d66e3096fe09bb302dbdaa561a484e.jpg", + "image_caption": [ + "Rain&Haze" + ], + "image_footnote": [], + "bbox": [ + 406, + 88, + 517, + 161 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/29a8c6905e4d5905a2e991fd9b88edc7d2c1653e40e2ea27e542d89445b61ebc.jpg", + "image_caption": [ + "Ground-truth" + ], + "image_footnote": [], + "bbox": [ + 517, + 89, + 629, + 161 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/7710880a0b509d8f391ae238cad49e71d6d99a4bf0d09b9324de9a4832b2fd0b.jpg", + "image_caption": [ + "MPRNet" + ], + "image_footnote": [], + "bbox": [ + 629, + 89, + 738, + 161 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/222e5336b90e8669932a3851520cbe7a233847794794735a725f9a72c8c048bc.jpg", + "image_caption": [ + "NAFNet" + ], + "image_footnote": [], + "bbox": [ + 738, + 89, + 849, + 161 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/4d1d959be606a2ae53763375d726e45244c3a4464660d2826b52c30e4806cfb4.jpg", + "image_caption": [ + "Restormer" + ], + "image_footnote": [], + "bbox": [ + 406, + 176, + 517, + 255 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/f183248aca4a424c22fef75a743f886ac87661915839b2dae180db4aeb558a4e.jpg", + "image_caption": [ + "RainHazeDiff" + ], + "image_footnote": [], + "bbox": [ + 517, + 176, + 629, + 255 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/b4ebb3ad4fa222ce9df41acc1f04412d01f838a1399cc3e8331fc3b36b37039c.jpg", + "image_caption": [ + "DTPM-4s" + ], + "image_footnote": [], + "bbox": [ + 629, + 176, + 738, + 255 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/a6ec7e9f8d87d904c9c015af6549bbad7801c625a14a6100483aead8b50d8822.jpg", + "image_caption": [ + "DTPM-50s" + ], + "image_footnote": [], + "bbox": [ + 738, + 176, + 849, + 256 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/d8a578087cc1efddee80302f05652c5770a09f716ecb25e37d2691cf43b9352f.jpg", + "image_caption": [ + "Figure 5. Image deraining&dehazing visual comparison on the Ourdoor-Rain dataset [48]. Our DTPM method generates rain-free and haze-free image with better details and without artifacts. The \"-4s\" and \"-50s\" denotes our DTPM method with a DDIM [55] sampling schedule of 4 steps and 50 steps.", + "Blurry Image" + ], + "image_footnote": [], + "bbox": [ + 117, + 334, + 364, + 458 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/7df9e91560fda996ebecaad8f546183016297b147a8ab7e828237fdf72cb3075.jpg", + "image_caption": [ + "Reference" + ], + "image_footnote": [], + "bbox": [ + 367, + 334, + 486, + 387 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/cc0f89ad37a0c4178af57597b36b425c8acb0f298dc6d25bde2c5792fb6a637b.jpg", + "image_caption": [ + "Blurry" + ], + "image_footnote": [], + "bbox": [ + 488, + 334, + 606, + 387 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/243198613ebc53f4b2861aea23b861a892c30376945354b199f926774f8df7f1.jpg", + "image_caption": [ + "MPRNet" + ], + "image_footnote": [], + "bbox": [ + 611, + 334, + 727, + 387 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/1f0ff91b7046e9c5cb24d05de78e2f967da7ea0d04fa83ee6be25f947409d2ca.jpg", + "image_caption": [ + "MIMO-UNet+" + ], + "image_footnote": [], + "bbox": [ + 728, + 334, + 846, + 387 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/d6119544b32be488db44dd4ce021738c35c4903f7d29e557f8294d0299f7665a.jpg", + "image_caption": [ + "Restormer", + "Figure 6. Single-image motion deblurring comparison on the GoPro Dataset [43]. Compared to the other methods, our DTPM more effectively removes blur and preserving better structural information. The \"-4s\" and \"-50s\" denotes our DTPM method with a DDIM sampling schedule of 4 steps and 50 steps." + ], + "image_footnote": [], + "bbox": [ + 369, + 407, + 486, + 459 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e2318682c5002ae6d20163b8d7c356864fba4992bf33b16842c457b2597728e6.jpg", + "image_caption": [ + "DvSR" + ], + "image_footnote": [], + "bbox": [ + 490, + 407, + 606, + 459 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/dd3bbf134beccbf78656c34e7b5a0b502a85282a833521e23d84e3f06e0472f2.jpg", + "image_caption": [ + "DTPM-4 steps" + ], + "image_footnote": [], + "bbox": [ + 611, + 407, + 728, + 458 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/6de8b9f4a9280b1ca2da6521e08a6c070568bef517131409beed8d91acb6f7e8.jpg", + "image_caption": [ + "DTPM-50 steps" + ], + "image_footnote": [], + "bbox": [ + 730, + 407, + 849, + 459 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "structured over 1,000 steps (denoted as $T$ ), incorporating a noise schedule $\\beta(t)$ that linearly escalates from 0.0001 to 0.02 throughout the training. Input data consistently utilized $256 \\times 256$ cropped patches. Data augmentation techniques, including horizontal flipping and random image rotation at $45^{\\circ}$ and $90^{\\circ}$ , were applied during training. We utilize Denoising Diffusion Implicit Models (DDIM) [55] to implement our diffusion model, thereby significantly enhancing our sampling speed.", + "bbox": [ + 75, + 537, + 468, + 674 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Main Results", + "text_level": 1, + "bbox": [ + 76, + 704, + 215, + 718 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Comparative Analysis of Deraining&Dehazing. As shown in Table 1 in outdoor hazy and rainy image restoration, DTPM's 4 Step variant outperforms RainHazeDiff's 25-step process, achieving higher PSNR (30.99), SSIM (0.934), and lower LPIPS (0.0635). DTPM demonstrates superior perceptual quality enhancement, as indicated by its LPIPS and PSNR metrics. The DTPM-10 and DTPM-50 Step versions further reduce LPIPS to 0.0617 and 0.0540, respectively, while maintaining high SSIM, establishing DTPM's methodological advantage and benchmark in high-fidelity restoration.", + "bbox": [ + 75, + 734, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Comparative Analysis of Single-image Defocus Deblurring. DTPM markedly outperforms other methods in defocus deblurring on the DPDD dataset as shown in Table 4, with its 4 Step iteration achieving high LPIPS (0.153) and SSIM (0.823) scores, thus maintaining image structural integrity. The DTPM-50 Step model further enhances perceived quality, achieving an LPIPS of 0.139, closely resembling ground truth. Visual evidence in Figure 7 corroborates DTPM's superior detail recovery and structural fidelity.", + "bbox": [ + 496, + 537, + 890, + 675 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Concise Analysis of DTPM in Single-image Motion Deblurring. As shown in Table 5, on the GoPro dataset, the DTPM 4 Step variant achieves a PSNR of 32.09, SSIM of 0.932, LPIPS of 0.084, and FID of 10.02, demonstrating a balance in distortion reduction and perceptual quality. The 10 Step version improves these metrics, with an LPIPS of 0.081 and a leading FID of 8.52, despite slight decreases in PSNR and SSIM. The DTPM-50 Step variant, achieving the best perceptual outcomes with the lowest LPIPS (0.073) and FID (7.69), slightly reduces PSNR to 31.11 and SSIM to 0.919, illustrating our method's ability to the best perceptual quality.", + "bbox": [ + 496, + 719, + 892, + 901 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "2529", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/07e84e3285fc2a450fb70d1433d9eb6c296a706a5023bccab4e159456d71121c.jpg", + "image_caption": [ + "Blurry Image" + ], + "image_footnote": [], + "bbox": [ + 119, + 87, + 377, + 244 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ee912a339bdb550112114fcd75486ae0b4b8f11ba729608bb1befc552ef0bf46.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 379, + 87, + 493, + 162 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/7a29ca79de64466ff4b9a24b0e989d75050e8583ec53a0cec27aac496d0865a4.jpg", + "image_caption": [ + "Reference", + "IFAN", + "Figure 7. Single-image defocus deblurring results on the DPDD dataset [1]. The \"-4s\" and \"-50s\" denotes our DTPM method with a DDIM sampling schedule of 4 steps and 50 steps. Compared to the other approaches, our DTPM generate better structures and details." + ], + "image_footnote": [], + "bbox": [ + 380, + 172, + 491, + 246 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9f9a3fc9441af6d557af4ddb109549332af74918d3d267a4e2f438bf3077ffa7.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 495, + 88, + 607, + 162 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/fa54b16391c1285535ced3e010da9e5e96d711626fa0d25cc773dd866f084c05.jpg", + "image_caption": [ + "Blurry", + "Restomer" + ], + "image_footnote": [], + "bbox": [ + 496, + 172, + 607, + 246 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/854b1d919072b917f29d1c57572f632ee0775b232b734dd20a96df895b42e799.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 616, + 88, + 728, + 162 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/f08a4706c6cae514dd47dbf53027a97846dd7b54f1c6aaa26e8f68ead430a239.jpg", + "image_caption": [ + "KPAC", + "DTPM-4s" + ], + "image_footnote": [], + "bbox": [ + 616, + 172, + 727, + 246 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/858eb06fc126be6ac9e9c133c64112383f0d5ac825c9dc2a39e161182543ea15.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 736, + 88, + 849, + 162 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/610652cd1194e508aad50a863e4f52482d1985960aec78c726213fa9be17a14d.jpg", + "image_caption": [ + "DeepRFT", + "DTPM-50s" + ], + "image_footnote": [], + "bbox": [ + 736, + 174, + 848, + 246 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/e82dea5c826a0582e8dd88325e8f5c639ece4c9b168962a8d506446f42cdf9e5.jpg", + "table_caption": [ + "Table 4. Single-image Defocus Deblurring comparisons on the DPDD testset [1]." + ], + "table_footnote": [], + "table_body": "
MethodDistortionPerceptual
PSNR ↑SSIM ↑MAE ↓LPIPS ↓
EBDB [28]23.450.6830.0490.336
DMENet [31]23.410.7140.0510.349
JNB [53]23.840.7150.0480.315
DPDNet [1]24.340.7470.0440.277
KPAC [54]25.220.7740.0400.227
IFAN [32]25.370.7890.0390.217
Restormer [70]25.980.8110.0380.178
DTPM-4 Step25.980.8230.0380.153
DTPM-10 Step25.760.8150.0390.140
DTPM-50 Step25.450.8030.0400.139
", + "bbox": [ + 114, + 362, + 434, + 489 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/cb35bdd07cd6d0277c02d1ea27921cedc68e703e2c13b4311effee55f26ed33c.jpg", + "table_caption": [ + "Table 5. Single-image Motion Deblurring comparisons on the GoPro testset [43]." + ], + "table_footnote": [], + "table_body": "
MethodDistortionPerceptual
PSNR ↑SSIM ↑LPIPS ↓FID ↓
MPRNet [71]32.660.9590.08920.18
MIMO-UNet+ [13]32.450.9570.09118.05
SAPHNet [56]31.890.9530.10119.06
Restomer [70]33.200.9630.08419.33
DvSR [60]30.660.9410.08412.20
DTPM-4 Step32.090.9320.08410.02
DTPM-10 Step31.820.9290.0777.52
DTPM-50 Step31.110.9190.0616.61
", + "bbox": [ + 117, + 546, + 431, + 652 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparative Analysis of Raindrop Removal. As illustrated in Table 2, we can observe that various versions of DTPM have demonstrated outstanding performance in the task of image raindrop removal. In comparison to RainDropDiff, our approach has achieved superior performance, with the LPIPS metric significantly outperforming that of RainDropDiff.", + "bbox": [ + 75, + 684, + 468, + 789 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparative Analysis of Snow Removal. As shown in Table 1, we can observe that various versions of DTPM have demonstrated excellent performance in the task of image desnowing. In comparison to SnowDiff, our approach has achieved superior LPIPS metrics.", + "bbox": [ + 75, + 824, + 467, + 898 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5. Discussion and Analysis", + "text_level": 1, + "bbox": [ + 500, + 325, + 723, + 343 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/b03d82b2b1cde98a50a18d9125e4ac59bf42cb6a5455f84d9c92f6e030cb32bd.jpg", + "image_caption": [ + "Figure 8. Trade-off between PSNR and LPIPS in DTPM: This plot illustrates the inverse relationship between PSNR (pixel-wise distortion) and LPIPS (perceptual similarity) across various sampling steps, highlighting the equilibrium achieved between distortion and perceptual quality in our method." + ], + "image_footnote": [], + "bbox": [ + 558, + 364, + 831, + 486 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "For the analysis of various aspects of our model, we perform our experiments on the image deraining& dehazing dataset as it's a more chanlenging settings than others.", + "bbox": [ + 496, + 583, + 890, + 628 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.1. Sampling Steps and Distortion-Perceptual Trade-off", + "text_level": 1, + "bbox": [ + 498, + 638, + 890, + 667 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In Figure 8, we evaluate the results of our DTPM through the lens of two critical image quality metrics: PSNR and LPIPS1. As the sampling steps increase, the PSNR values initially experience a precipitous drop, decreasing from just above 31 dB to below 30.70 dB by the 10th step. This substantial early decline indicates that sampling steps in the early phase degrade image fidelity. Beyond this point, the PSNR decline slows, entering a phase of more gradual descent before plateauing after the 30th step, suggesting that the method begins to stabilize in terms of distortion loss. In", + "bbox": [ + 496, + 676, + 890, + 828 + ], + "page_idx": 6 + }, + { + "type": "page_footnote", + "text": "1The PSNR, measured in decibels (dB), is a traditional metric for assessing the fidelity of the reconstructed images against an original high-quality image. The LPIPS metric, on the other hand, offers an assessment of perceptual similarity, which correlates more closely with human visual perception.", + "bbox": [ + 496, + 838, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "2530", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/beb7c5736bb10db29209052a5ba7f16f6f1f6e6de0348c3046ee7a82301d684f.jpg", + "image_caption": [ + "Figure 9. The first row in the figure shows the images, while the second row shows zoomed-in details. From left to right, they are: (a) input image, (b) the output of the initial predictor, (c) the final result of our method, (d) the ground-truth." + ], + "image_footnote": [], + "bbox": [ + 80, + 90, + 467, + 191 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "contrast, the LPIPS score improves markedly with each incremental sampling step, indicating that the perceived quality of the images is becoming more aligned with human visual perception. The steepness of the LPIPS improvement mirrors the PSNR decline, reflecting a pronounced trade-off between fidelity and perceptual quality up to the 10 step. After this inflection point, although the PSNR values level off, suggesting a saturation of fidelity loss, the LPIPS values continue to improve but at a diminished rate, plateauing around the 40 step. The intersecting trends of these metrics underscore a distinct trade-off: optimizing for perceptual likeness through more sampling steps comes at the expense of traditional fidelity measures. However, the stabilization of both metrics after a certain number of sampling steps suggests a convergence towards an equilibrium between the two qualities.", + "bbox": [ + 75, + 286, + 472, + 527 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.2. Output of the Initial Predictor", + "text_level": 1, + "bbox": [ + 76, + 539, + 346, + 555 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Given the significance of the initial predictor as a key component of our methodology, we have undertaken detailed explorations and analyses of it. Despite the absence of an explicit loss constraint in our initial predictor, it achieves results that closely resemble a clean background, as evidenced in Figure 9. The initial predictor, though not detailed in its finer aspects, effectively produces a reasonably clear image. This provides practical assurance for incorporating the output of the initial predictor as one of the enhanced, additional conditions for diffusion.", + "bbox": [ + 75, + 563, + 468, + 715 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.3. More Ablation Studies", + "text_level": 1, + "bbox": [ + 76, + 724, + 287, + 739 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this section, we conduct ablation studies to analyze the impact of different design choices in our DTPM framework. w/o Stage I Training. This variant, absent the initial training phase, exhibits a decrease in both image reconstruction quality and perceptual similarity relative to the complete model. This underscores the significance of the early training stage in establishing baseline performance.", + "bbox": [ + 75, + 748, + 467, + 854 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "w/o Initial Predictor: Removing the Initial Predictor results in a notable decline in both objective image quality and perceptual accuracy. This component's role is evidently", + "bbox": [ + 75, + 854, + 467, + 901 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/76518bfd5f33144c40d008d28439818cf212afbeb477e6637e1a39ea0052697f.jpg", + "table_caption": [ + "Table 6. The ablation studies on Image Deraining&Dehazing dataset [48]." + ], + "table_footnote": [], + "table_body": "
ModelPSNR ↑LPIPS ↓
w/o Stage I Training28.900.074
w/o Initial Predictor26.910.079
w/o Semantic Code29.790.0653
Fine-tune Enc. w/o Adapters29.200.0667
Fine-tune Dec. w/o Adapters28.910.0691
Fine-tune Enc.&Dec. w/o Adapters29.130.0712
Ours(DTPM-4S)30.990.0635
", + "bbox": [ + 560, + 128, + 834, + 231 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "crucial for enhancing the clarity and fidelity of the images. w/o Semantic Code. The removal of the Semantic Code somewhat improves both image quality and perceptual similarity. This could suggest that the Semantic Code potentially adding informative features.", + "bbox": [ + 496, + 256, + 890, + 330 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Fine-tune Enc. w/o Adapters. Fine-tuning just the encoder of DTPM without adapters leads to a slight reduction in performance. This indicates that while the encoder is a robust component, the adapters contribute to optimizing its function.", + "bbox": [ + 496, + 332, + 890, + 406 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Fine-tune Dec. w/o Adapters. Solely fine-tuning the decoder of DTPM without adapters also reduces model efficacy. The adapters appear more integral for the decoder, possibly enabling more nuanced adjustments that refine results.", + "bbox": [ + 496, + 407, + 890, + 481 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Fine-tune Enc.&Dec. w/o Adapters. Fine-tuning both the encoder and decoder without adapters does not match the performance of the complete model. This suggests a complex interplay between these components that adapters help to fine-tune effectively.", + "bbox": [ + 496, + 483, + 890, + 559 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion and Limitations", + "text_level": 1, + "bbox": [ + 498, + 571, + 756, + 588 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This study presents a comprehensive conditional framework for image restoration, integrating Diffusion Texture Priors for producing high-quality images with promising details. While achieving significant performance, it identifies potential improvements: accelerating sampling via advanced techniques and optimizing the model size.", + "bbox": [ + 496, + 597, + 890, + 688 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgment. This work is supported by the InnoHK funding launched by Innovation and Technology Commission, Hong Kong SAR, Guangzhou Municipal Science and Technology Project (Grant No. 2023A03J0671), and a grant of Innovation and Technology Fund under Guangdong-Hong Kong Technology Cooperation Funding Scheme (ITF-TCFS) (project no. GHP/051/20GD).", + "bbox": [ + 496, + 713, + 890, + 819 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "2531", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 106 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Abdullah Abuolaim and Michael S Brown. Defocus deblurring using dual-pixel data. In ECCV, 2020. 5, 7", + "[2] Eirikur Agustsson and Radu Timofte. Ntire 2017 challenge on single image super-resolution: Dataset and study. In Proceedings of the IEEE conference on computer vision and pattern recognition workshops, pages 126-135, 2017. 4", + "[3] Jimmy Lei Ba, Jamie Ryan Kiros, and Geoffrey E Hinton. Layer normalization. arXiv preprint arXiv:1607.06450, 2016. 4", + "[4] Bolun Cai, Xiangmin Xu, Kui Jia, Chunmei Qing, and Dacheng Tao. Dehazenet: An end-to-end system for single image haze removal. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 930-939, 2022. 2" + ], + "bbox": [ + 501, + 92, + 893, + 717 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "2534", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Diffusion Texture Priors for Image Restoration/c4fdbfda-8abc-47c5-aabf-b69c62343d36_model.json b/2024/Learning Diffusion Texture Priors for Image Restoration/c4fdbfda-8abc-47c5-aabf-b69c62343d36_model.json new file mode 100644 index 0000000000000000000000000000000000000000..cf173df0c33cdf3eb058cd44f1da6fa5d293ea91 --- /dev/null +++ b/2024/Learning Diffusion Texture Priors for Image Restoration/c4fdbfda-8abc-47c5-aabf-b69c62343d36_model.json @@ -0,0 +1,2983 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.198, + 0.131, + 0.773, + 0.154 + ], + "angle": 0, + "content": "Learning Diffusion Texture Priors for Image Restoration" + }, + { + "type": "text", + "bbox": [ + 0.289, + 0.18, + 0.708, + 0.218 + ], + "angle": 0, + "content": "Tian Ye1 Sixiang Chen1 Wenhao Chai2 \nZhaohu Xing1 Jing Qin3 Ge Lin1,4 Lei Zhu1,4*" + }, + { + "type": "text", + "bbox": [ + 0.086, + 0.223, + 0.89, + 0.26 + ], + "angle": 0, + "content": "1 The Hong Kong University of Science and Technology (Guangzhou) 2 University of Washington 3 The Hong Kong Polytechnic University 4 The Hong Kong University of Science and Technology" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.294, + 0.314, + 0.31 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.326, + 0.474, + 0.645 + ], + "angle": 0, + "content": "Diffusion Models have shown remarkable performance in image generation tasks, which are capable of generating diverse and realistic image content. When adopting diffusion models for image restoration, the crucial challenge lies in how to preserve high-level image fidelity in the randomness diffusion process and generate accurate background structures and realistic texture details. In this paper, we propose a general framework and develop a Diffusion Texture Prior Model (DTPM) for image restoration tasks. DTPM explicitly models high-quality texture details through the diffusion process, rather than global contextual content. In phase one of the training stage, we pre-train DTPM on approximately 55K high-quality image samples, after which we freeze most of its parameters. In phase two, we insert conditional guidance adapters into DTPM and equip it with an initial predictor, thereby facilitating its rapid adaptation to downstream image restoration tasks. Our DTPM could mitigate the randomness of traditional diffusion models by utilizing encapsulated rich and diverse texture knowledge and background structural information provided by the initial predictor during the sampling process." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.672, + 0.21, + 0.687 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.697, + 0.47, + 0.879 + ], + "angle": 0, + "content": "Image Restoration tasks [37, 43, 70, 71] usually are ill-posed problems whose solutions are not unique. While existing methods [8, 70, 71] have achieved notable breakthroughs, they typically employ direct regression models to produce deterministic results. A persistent challenge is that these deterministic models [4, 70, 71] frequently yield unsatisfactory fine-grained details (See Figure 2), as they are trained to minimize pixel-level error, aligning output with ground truth by Norm-based losses [30]. The emergence of Diffusion Models (DMs) [14, 16, 51, 55] has revolutionized image generation, yielding realistic images replete with fine details. This advancement motivates our investigation" + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.291, + 0.891, + 0.358 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.368, + 0.895, + 0.508 + ], + "angle": 0, + "content": "Figure 1. We use a coefficient \\(\\alpha\\) ranging from 0.1 to 1 to control the intensity of texture removal. As \\(\\alpha\\) increases, leading to richer textures from left to right in the images, we can observe a corresponding improvement in the scores of no-reference image quality metrics, specifically NIQE [42] and CLIP-IQA+ [57]. Regarding the NIQE, lower scores indicate better quality, while for CLIP-IQA+, higher scores represent better visual quality. This indicates that the quality of the image's texture details have a significant impact on the visual perceptual quality of the image." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.537, + 0.893, + 0.598 + ], + "angle": 0, + "content": "into diffusion-based methods for image restoration, aiming to leverage conditional DMs [17, 45, 51] to produce perceptually appealing results that closely mimic natural, clean images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.895, + 0.903 + ], + "angle": 0, + "content": "However, directly applying diffusion image generation techniques [44, 51, 55] to image restoration tasks is often impractical [36, 45]. The high content fidelity required in image restoration clashes with the stochastic nature of diffusion models [44, 55]. A plausible solution involves integrating physical degradation models [5, 69] with neural networks or crafting hand-designed priors [20, 47] to mitigate the inherent randomness of the diffusion paradigm. While several previous studies [17, 68, 69] have adopted this approach with success, they lack versatility and show limited generalization capability on real-world scenes, as physical degradation models do not fully encompass real-world degradation scenarios [4, 66, 67]. Additionally, the iterative nature and complexity of the denoising process in diffusion models necessitate extensive data and lengthy training cycles for effective learning. The challenges and limitations outlined above necessitate a rethinking of the use of the diffusion paradigm in image restoration: (i) To preserve high-level fidelity in restoration, we propose using a diffusion model to recover only texture layers. This" + }, + { + "type": "page_footnote", + "bbox": [ + 0.095, + 0.887, + 0.388, + 0.9 + ], + "angle": 0, + "content": "*Lei Zhu (leizhu @ust.hk) is the corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2524" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.08, + 0.089, + 0.468, + 0.27 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.281, + 0.473, + 0.395 + ], + "angle": 0, + "content": "Figure 2. (a) The input degraded image. (b) The result of Restormer [70]. Restormer is a representative image restoration method that can only produce deterministic results, which may lack promising details. (c) The result of RainHazeDiff [45]. (d) The result of our method. The content within the dashed rectangle represents the corresponding ground-truth details. It's worth noting that our approach excels in generating finer details, thanks to the incorporation of Diffusion Texture Priors we proposed." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.449, + 0.473, + 0.782 + ], + "angle": 0, + "content": "approach emphasizes and highlights the importance of fine textures in visual perception (See Figure 1). By focusing diffusion on texture recovery, we minimize randomness of diffusion process and leverage its strength in generating realistic details. (ii) Recognizing the diffusion paradigm as a potent representation learning tool that requires extensive data for convergence, we pre-trained our model, named the Diffusion Texture Priors Model (DTPM), on a large-scale dataset of high-quality images. This model, trained on approximately \\(55K\\) samples, is tailored to reconstruct texture layers, embedding texture priors within the diffusion process. Our DTPM framework is characterized by: (a) A novel approach in diffusion modeling that focuses on texture layers through residual learning, enhancing efficiency in downstream restoration tasks. (b) The incorporation of Semantic Code as a constraint, guiding the diffusion model to produce semantically coherent textures. (c) To preserve the integrity of the diffusion texture priors, most parameters of the DTPM remain fixed after pre-training. We introduce a Conditional Degradation Adapter to facilitate rapid adaptation to various restoration tasks without the risk of catastrophic forgetting." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.47, + 0.9 + ], + "angle": 0, + "content": "Our extensive experiments across single-image defocus deblurring, image motion deblurring, desnowing, dehazing, deraining, and raindrop removal demonstrate that our method not only surpasses strong regression models and recent diffusion-based models in perceptual quality but also exhibits robust generalization across diverse restoration tasks." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.09, + 0.651, + 0.107 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.115, + 0.895, + 0.463 + ], + "angle": 0, + "content": "Evolution in Image Restoration. Image restoration [4, 15, 19, 25, 39, 67, 71, 77], a pivotal research domain within the computer vision community, has witnessed significant evolution over recent years. Traditionally regarded as an ill-posed problem, image restoration poses unique challenges due to the multitude of potential solutions derivable from a single degraded image. Over the last decade, there has been a notable shift in the computer vision field from conventional, handcrafted prior-based approaches [20, 47] to a more data-centric, deep learning-driven paradigm [4, 15, 59, 70]. This transition has led to the development of advanced deep learning techniques, characterized by complicated network structures [65, 70, 71] and extensive training on carefully collected datasets. These approaches excel in learning mappings from degraded to clean data, effectively tackling the complexities of image restoration. Initially, deep learning methods [9-11, 66, 67] in this area tended to produce deterministic outcomes, which starkly contrasted with the fundamentally probabilistic nature of image restoration tasks [18, 46, 70]. This discrepancy has increasingly brought generative methods [17, 27, 46, 64, 76] to the forefront, highlighting their potential to address the challenges inherent in image restoration." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.464, + 0.895, + 0.795 + ], + "angle": 0, + "content": "Generative image restoration methods. Recent developments [6, 7, 17, 41, 46, 61, 64, 74] have shed light on the fundamental flaws of earlier deep learning-driven image restoration techniques, specifically their (i) generate deterministic outputs and (ii) inability to restore high-quality, detailed textures, owing to their training focused on minimizing pixel-level discrepancies. Consequently, generative approaches are gaining traction. A notable strategy includes employing Generative Adversarial Networks (GANs) [24, 29, 48]. Nonetheless, GANs pose challenges due to their complex training procedures, instability during training, and occasional generation of unrealistic image attributes. The impressive efficacy of diffusion in image generation has introduced a promising avenue. Diffusion techniques adeptly tackle the aforementioned issues, offering a more stable training regimen and yielding images with realistic textures. Applications of diffusion-based methods in image super-resolution [52], shadow removal [17, 27], deblurring [60], and adverse weather removal [46] have shown promising results. However, there remains a need for comprehensive research to establish a consistent, reliable framework for diffusion-based image restoration tasks." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.808, + 0.665, + 0.823 + ], + "angle": 0, + "content": "3. Our Framework" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.833, + 0.798, + 0.848 + ], + "angle": 0, + "content": "3.1. Preliminaries of Diffusion Models" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.856, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Diffusion Models (DMs), as referenced in [22, 44], are a class of generative models that gradually infuse Gaussian noise into training data and then employ a denoiser to re" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.958 + ], + "angle": 0, + "content": "2525" + } + ], + [ + { + "type": "image_caption", + "bbox": [ + 0.1, + 0.089, + 0.509, + 0.102 + ], + "angle": 0, + "content": "Stage I: Training a Conditional Diffusion Model for Learning Diffusion Texture Priors" + }, + { + "type": "image", + "bbox": [ + 0.1, + 0.102, + 0.659, + 0.242 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.1, + 0.244, + 0.583, + 0.257 + ], + "angle": 0, + "content": "Stage II : Fine-Tuning the Diffusion Model Using Task-Specific Adapters for Image Restoration Tasks" + }, + { + "type": "image", + "bbox": [ + 0.101, + 0.259, + 0.659, + 0.402 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.306, + 0.403, + 0.438, + 0.412 + ], + "angle": 0, + "content": "(a) Overview of Our Framework" + }, + { + "type": "image", + "bbox": [ + 0.66, + 0.102, + 0.872, + 0.235 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.679, + 0.237, + 0.872, + 0.246 + ], + "angle": 0, + "content": "(b) Overview of Adapters and Denoising Blocks" + }, + { + "type": "image", + "bbox": [ + 0.685, + 0.25, + 0.861, + 0.4 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.691, + 0.402, + 0.826, + 0.411 + ], + "angle": 0, + "content": "(c) Conditional Guidance Adapter" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.425, + 0.894, + 0.495 + ], + "angle": 0, + "content": "Figure 3. The overview of Our DTPM Framework. (a) Our method consists of two stages. In the stage I, under the guiding constraints of semantic code, the diffusion model learns texture layers through residual learning from a large amount of high-quality data, which allows us to encapsulate diverse and rich texture knowledge into the diffusion model. In the stage II, we fix most of the parameters of the trained diffusion model and insert Conditional Guidance Adapters between each layer for efficient fine-tuning and conditional guidance on image restoration tasks. (b) The overview of adapters and our denoising blocks.(c) The detailed design of our Conditional Guidance Adapter." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.521, + 0.47, + 0.582 + ], + "angle": 0, + "content": "verse this noise addition. The process begins with the diffusion phase, where an initial image \\( \\pmb{x}_0 \\) evolves into Gaussian noise \\( \\pmb{x}_T \\sim \\mathcal{N}(0,1) \\) through \\( T \\) steps. Each step of this transformation is governed by:" + }, + { + "type": "equation", + "bbox": [ + 0.119, + 0.593, + 0.47, + 0.619 + ], + "angle": 0, + "content": "\\[\nq \\left(\\boldsymbol {x} _ {t} \\mid \\boldsymbol {x} _ {t - 1}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t}; \\sqrt {1 - \\beta_ {t}} \\boldsymbol {x} _ {t - 1}, \\beta_ {t} \\boldsymbol {I}\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.628, + 0.469, + 0.686 + ], + "angle": 0, + "content": "where \\( \\pmb{x}_t \\) is the image with noise at step \\( t \\), \\( \\beta_t \\) is a fixed scaling factor, and \\( \\mathcal{N} \\) denotes the Gaussian distribution. Introducing \\( \\alpha_t = 1 - \\beta_t \\) and \\( \\bar{\\alpha}_t = \\prod_{i=0}^t \\alpha_i \\) simplifies Eq.1 to:" + }, + { + "type": "equation", + "bbox": [ + 0.131, + 0.687, + 0.469, + 0.706 + ], + "angle": 0, + "content": "\\[\nq \\left(\\boldsymbol {x} _ {t} \\mid \\boldsymbol {x} _ {0}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t}; \\sqrt {\\bar {\\alpha} _ {t}} \\boldsymbol {x} _ {0}, (1 - \\bar {\\alpha} _ {t}) \\boldsymbol {I}\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.711, + 0.47, + 0.757 + ], + "angle": 0, + "content": "During the inference stage's reverse process, DMs initiate with a random Gaussian noise map \\( \\boldsymbol{x}_T \\) and progressively denoise it to reach the refined output \\( \\boldsymbol{x}_0 \\)." + }, + { + "type": "equation", + "bbox": [ + 0.1, + 0.768, + 0.469, + 0.786 + ], + "angle": 0, + "content": "\\[\np \\left(\\boldsymbol {x} _ {t - 1} \\mid \\boldsymbol {x} _ {t}, \\boldsymbol {x} _ {0}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t - 1}; \\boldsymbol {\\mu} _ {t} \\left(\\boldsymbol {x} _ {t}, \\boldsymbol {x} _ {0}\\right), \\sigma_ {t} ^ {2} \\boldsymbol {I}\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.798, + 0.469, + 0.841 + ], + "angle": 0, + "content": "where the mean \\(\\pmb{\\mu}_t(\\pmb{x}_t,\\pmb{x}_0) = \\frac{1}{\\sqrt{\\alpha_t}}\\left(\\pmb{x}_t - \\epsilon \\frac{1 - \\alpha_t}{\\sqrt{1 - \\bar{\\alpha}_t}}\\right)\\) and the variance \\(\\sigma_t^2 = \\frac{1 - \\bar{\\alpha}_{t-1}}{1 - \\bar{\\alpha}_t} \\beta_t\\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.848, + 0.369, + 0.863 + ], + "angle": 0, + "content": "3.2. Overview of DTP-IR Framework" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Our aim is to create a unified framework for image restoration tasks based on our Diffusion Texture Priors. As shown" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.521, + 0.892, + 0.627 + ], + "angle": 0, + "content": "in Figure 3, our DTPM framework comprises two stages: In Stage 1, we train a conditional diffusion model with semantic latent feature constraints using a large dataset of high-resolution, high-quality natural images. During Stage 2, we incorporate conditional guidance adapters into the conditional diffusion model to facilitate the model's adaptation to downstream image restoration tasks." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.634, + 0.864, + 0.65 + ], + "angle": 0, + "content": "3.3. Stage I: Learning Diffusion Texture Priors" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.657, + 0.892, + 0.734 + ], + "angle": 0, + "content": "In this section, we will first briefly introduce the core motivation of our Diffusion Texture Priors, followed by the basic structure information of the diffusion model and the semantic code. Finally, we will discuss the training objective and training data." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.893, + 0.903 + ], + "angle": 0, + "content": "Motivation. Recent studies [52, 64, 74] have highlighted the pivotal role of texture quality in shaping subjective visual perception in the realm of image restoration. Traditional methodologies, however, encounter substantial difficulties in accurately restoring fine-grained textural details, which are crucial for realistic image reconstruction. While diffusion models have demonstrated excellence in generating lifelike images, their direct application to image restoration tasks has been less than ideal, yielding mediocre results. Our approach seeks to remedy this by integrating" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2526" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.136, + 0.091, + 0.413, + 0.271 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.283, + 0.472, + 0.396 + ], + "angle": 0, + "content": "Figure 4. The architecture of our fundamental denoising block incorporates \"Channel Attention\" (CA) and \"SimpleGate,\" a straightforward feature gating mechanism introduced by Chen et al.[8]. The current timestep \\( t \\) is injected into the block with Adaptive Layer Normalization [3] (AdaLN), i.e., \\( AdaLN(f_{in} = \\gamma LayerNorm(f_{in}) + \\beta \\), where \\( f_{in} \\) is the input features, \\( \\gamma \\) and \\( \\beta \\) are converted from the timestep embedding. The \"Shift&Scale\" block means shift and scale features by generated \\( \\gamma, \\beta \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.422, + 0.47, + 0.573 + ], + "angle": 0, + "content": "texture-specific priors into the diffusion model. This integration enables the diffusion model to specifically concentrate on reconstructing textures, as opposed to merely focusing on degradation elimination. Such a strategy leverages the diffusion model's inherent strengths and mitigates its weaknesses, allowing us to exploit a vast repository of high-quality natural images for prior knowledge. This method not only significantly enhances the model's generalization capabilities but also markedly improves the efficiency of the sampling process." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.593, + 0.47, + 0.821 + ], + "angle": 0, + "content": "Basic Denoising Block. We have engineered a denoising block based on NAFNet [8] block, designed to enhance model adaptability for a broad spectrum of natural image content. This block aims to balance peak model performance with reduced computational demands and easy-to-handle varying input resolutions. As delineated in Figure 4, our denoising block capitalizes on depth-wise convolution as its cornerstone, complemented by several \\(1 \\times 1\\) convolution layers and LayerNorm [3], to facilitate efficient denoising. To incorporate the time condition, we utilize MLPs for transforming the time embedding into channel-specific scale and shift parameters. Additionally, to maintain the semantic consistency between \\(x_0\\) and \\(y_s\\), we integrate an MLP layer for semantic condition, which amalgamates semantic code as a pivotal conditioning factor." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Semantic code. To enable the diffusion model to produce realistically textured details, we utilize a pre-trained ResNet-18 [21] for extracting semantic embeddings as a global semantic code, which is then integrated into each de" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.183 + ], + "angle": 0, + "content": "noising block as shown in Figure 4. This approach of employing semantic code imposes robust semantic constraints, rather than solely depending on adjacent context information, allowing our model to generate textures in alignment with the contextual semantics. Consequently, this ensures high-fidelity results of our diffusion model." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.201, + 0.892, + 0.263 + ], + "angle": 0, + "content": "Training objective. To prioritize texture reconstruction over content of the image, our diffusion model is designed to capture the residual distribution of \\( y_{s} \\). The training objective for Stage I is thus defined as: \\( L_{\\mathrm{StageI}}(\\theta) = \\)" + }, + { + "type": "equation", + "bbox": [ + 0.525, + 0.284, + 0.892, + 0.337 + ], + "angle": 0, + "content": "\\[\n\\mathbb {E} \\left\\| \\boldsymbol {\\epsilon} - f _ {\\theta} \\left(\\sqrt {\\gamma} \\left(\\underbrace {\\boldsymbol {x} _ {g} - \\boldsymbol {y} _ {s}} _ {\\text {r e s i d u a l}}\\right) + \\sqrt {1 - \\gamma} \\boldsymbol {\\epsilon}, \\boldsymbol {y} _ {s}, \\gamma\\right) \\right\\|, \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.347, + 0.892, + 0.466 + ], + "angle": 0, + "content": "here, \\(\\epsilon \\sim \\mathcal{N}(0,I)\\) represents the noise vector, and \\(f_{\\theta}\\) is our diffusion model. The term \\(\\gamma \\sim p(\\gamma)\\) denotes a distribution associated with the noise schedule. In this context, \\(x_{g}\\) symbolizes the high-quality input image, whereas \\(y_{s}\\) denotes its corresponding smoothed image. \\(y_{s}\\) is obtained by utilizing an edge-preserving smoothing method [63] to eliminate a majority of the texture while retaining the contextual content." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.486, + 0.892, + 0.624 + ], + "angle": 0, + "content": "Training data for Stage I. Inspired by previous codebook prior-based image restoration studies [61, 64, 74], our training stage I employs high-quality images from the widely-recognized DIV2K [2] and Flickr2K [35] datasets. Each image is cropped into multiple patches of \\(512 \\times 512\\) resolution, followed by an edge-preserved smooth method [63] to diminish textural details. This process results in a training dataset comprising 55,558 paired instances \\((x_{g}, y_{s})\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.632, + 0.892, + 0.663 + ], + "angle": 0, + "content": "3.4. Stage II: Finetuning Diffusion Texture Priors Model with Adapters" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.67, + 0.892, + 0.732 + ], + "angle": 0, + "content": "This section describes the initial predictor and the Conditional Guidance Adapter, along with the rationale behind their integration. We also detail the architecture of the adapters. Finally, the training objectives are outlined." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.9 + ], + "angle": 0, + "content": "Initial Predictor. In the pursuit of augmenting the diffusion model's adaptability for downstream tasks in its second stage (see Figure 3), we draw from the DvSR, integrating a compact and lightweight U-Net to generate an initial output. This initial step efficiently seizes deterministic components of the ultimate restored image, crucial for capturing essential structural information. Moreover, this initial output serves as a pivotal guiding element for the diffusion model, forming an effective complement with our Diffusion Texture Priors Model." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2527" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.172, + 0.09, + 0.33, + 0.104 + ], + "angle": 0, + "content": "Table 1. Image Desnowing." + }, + { + "type": "table", + "bbox": [ + 0.084, + 0.115, + 0.427, + 0.282 + ], + "angle": 0, + "content": "
MethodSnow100K-S [40]Snow100K-L [40]
PSNR ↑SSIM ↑LPIPS ↓PSNR ↑SSIM ↑LPIPS ↓
SPANet [58]29.920.82600.10423.700.79300.210
JSTASR [12]31.400.90120.05925.320.80760.152
RESCAN [34]31.510.90320.05426.080.81080.106
DesnowNet [40]32.330.95000.07027.170.89830.101
DDMSNet [72]34.340.94450.05828.850.87720.098
MPRNet [71]34.970.94570.04929.760.89490.091
NAFNet [8]34.790.94970.05130.060.90170.086
Restormer [70]35.030.94870.04730.520.90920.083
SnowDiff64[45]36.590.96260.03530.430.91450.069
SnowrDiff128[45]36.090.95450.03830.280.90000.067
DTPM-4 Step37.010.96630.03430.920.91740.063
DTPM-10 Step36.440.95210.03330.320.90240.055
DTPM-50 Step36.190.94830.02930.020.89010.053
" + }, + { + "type": "table_caption", + "bbox": [ + 0.427, + 0.09, + 0.648, + 0.104 + ], + "angle": 0, + "content": "Table 2. Image Deraining & Dehazing." + }, + { + "type": "table", + "bbox": [ + 0.432, + 0.115, + 0.66, + 0.281 + ], + "angle": 0, + "content": "
MethodOutdoor-Rain [33]
PSNR ↑SSIM ↑LPIPS ↓
CycleGAN [75]17.620.6560-
pix2pix [23]19.090.7100-
HRGAN [33]21.560.85500.154
PCNet [26]26.190.90150.132
MPRNet [71]28.030.91920.089
NAFNet [8]29.590.90270.085
Restormer [70]29.970.92150.074
RainHazeDiff64[45]28.380.93200.067
RainHazeDiff128[45]26.840.91520.071
DTPM-4 Step30.990.9340.0635
DTPM-10 Step30.920.9320.0617
DTPM-50 Step30.480.9210.0540
" + }, + { + "type": "table_caption", + "bbox": [ + 0.684, + 0.095, + 0.86, + 0.109 + ], + "angle": 0, + "content": "Table 3. Removing Raindrops." + }, + { + "type": "table", + "bbox": [ + 0.662, + 0.119, + 0.89, + 0.279 + ], + "angle": 0, + "content": "
MethodRainDrop [48]
PSNR ↑SSIM ↑LPIPS ↓
pix2pix [23]28.020.8547-
DuRN [38]31.240.9259-
RaindropAttn [50]31.440.92630.068
AttentiveGAN [48]31.590.91700.055
CCN [49]31.340.92860.066
IDT [62]31.870.93130.059
RainDropDiff64[45]32.290.94220.058
RainDropDiff128[45]32.430.93340.058
DTPM-4 Step32.720.94400.0577
DTPM-10 Step31.840.93700.0477
DTPM-50 Step31.440.93200.0439
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.307, + 0.473, + 0.581 + ], + "angle": 0, + "content": "Conditional Guidance Adapter. DPTM encapsulates rich and diverse prior knowledge. We hope that DPTM can fully utilize this knowledge in adapting to downstream image restoration tasks, rather than forgetting it. Therefore, we freeze most of the parameters in DPTM and introduce a flexible and parameter-efficient adaptation mechanism through the Conditional Guidance Adapter as shown in Figure 3 (b) and (c). The design of the Conditional Guidance Adapter brings two benefits: (i) Parameter-efficient learning. Since most of the parameters of DPTM have been sufficiently trained, our model will converge faster and better on downstream tasks after introducing the adapter. (ii) Introducing additional conditions. Introduction of coarse structural information output by the initial predictor, providing the model with more flexible conditional information, thereby producing texture details that better align with expectations. Our Conditional Guidance Adapter could be formally written as:" + }, + { + "type": "equation", + "bbox": [ + 0.077, + 0.599, + 0.47, + 0.63 + ], + "angle": 0, + "content": "\\[\n\\operatorname {C G - A d p a t e r} \\left(f _ {i n}, y _ {\\epsilon}\\right) = f _ {i n} + \\mathbf {M} _ {\\text {o u t}} \\left(\\mathbf {M} _ {i n} \\left(f _ {i n}\\right) + \\operatorname {C o n v} \\left(y _ {\\epsilon}\\right)\\right), \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.631, + 0.47, + 0.678 + ], + "angle": 0, + "content": "where \\(\\mathbf{M}\\) denotes an MLP layer to scale the dimension \\(c\\) of the input feature \\(f_{in}^{c}\\) to dimension \\(r\\times c\\), and \\(y_{\\epsilon}\\) denotes the output of initial predictor \\(\\epsilon_{\\theta}\\), thus \\(y_{\\epsilon} = \\epsilon_{\\theta}(y_d)\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.717, + 0.47, + 0.749 + ], + "angle": 0, + "content": "Training objective. The training objective for Stage II is defined as: \\( L_{\\mathrm{StageII}}(\\theta) = \\)" + }, + { + "type": "equation", + "bbox": [ + 0.101, + 0.784, + 0.47, + 0.809 + ], + "angle": 0, + "content": "\\[\n\\mathbb {E} \\left\\| \\boldsymbol {\\epsilon} - f _ {\\theta} \\left(\\sqrt {\\gamma} \\left(\\boldsymbol {y} _ {g} - \\epsilon_ {\\theta} (\\boldsymbol {y} _ {d})\\right) + \\sqrt {1 - \\gamma} \\boldsymbol {\\epsilon}, \\boldsymbol {y} _ {d}, \\gamma\\right) \\right\\|. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.825, + 0.471, + 0.903 + ], + "angle": 0, + "content": "where \\(\\epsilon_{\\theta}\\) represents the initial predictor, illustrated in Figure 3. It is important to note that \\(\\epsilon_{\\theta}\\) does not necessitate additional supervisory loss or pre-training. This is because the gradient from the aforementioned loss propagates through \\(f_{\\theta}\\) and subsequently influences \\(\\epsilon_{\\theta}\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.306, + 0.633, + 0.323 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.332, + 0.598, + 0.348 + ], + "angle": 0, + "content": "4.1. Settings" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.356, + 0.892, + 0.462 + ], + "angle": 0, + "content": "Our method is assessed on five specific image restoration tasks: image motion deblurring, single-image defocus deblurring, image deraining&dehazing, image desnowing, and image raindrop removal. In the initial stage, we develop a comprehensive Diffusion Texture Prior model, and in the subsequent stage, we fine-tune individual full models tailored to each task." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.485, + 0.893, + 0.756 + ], + "angle": 0, + "content": "Datasets&Metrics. The GoPro dataset [43], as recommended by DvSR [60], is utilized for training and testing in the domain of image motion deblurring. Adhering to Restormer's approach [70], the DPDD dataset [1] is employed for single-image defocus deblurring. For image desnowing, we align with WeatherDiff [45] using the Snow100K dataset [40]. The Outdoor-Rain dataset [33] is used for image deraining&dehazing, following WeatherDiff [45]. Lastly, for single image raindrop removal, we adopt the practices from IDT [62] and WeatherDiff [45], employing the Raindrop dataset [48] for training and testing. We utilize PSNR, SSIM, and MAE as metrics for distortion-based image quality assessment, complemented by LPIPS [73] and FID for evaluating perceptual image quality. Adhering to the methodology outlined in Whang et al. [60], we extract image patches and compute FID at the patch level to ensure more consistent and reliable evaluation results." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Training Details We implemented our DTPM using the Pytorch framework, leveraging four NVIDIA RTX 4090 GPUs. Training encompasses two stages: Stage I with 800K iterations and Stage II with 600K iterations. We employed the Adam optimizer, setting momentum values at 0.9 and 0.999. The initial learning rate was established at \\(1.5 \\times 10^{-4}\\), employing a cosine annealing strategy for gradual learning rate reduction. The diffusion process is" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2528" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.119, + 0.088, + 0.406, + 0.254 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.238, + 0.256, + 0.293, + 0.264 + ], + "angle": 0, + "content": "Rain&Haze" + }, + { + "type": "image", + "bbox": [ + 0.408, + 0.089, + 0.518, + 0.162 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.439, + 0.163, + 0.492, + 0.172 + ], + "angle": 0, + "content": "Rain&Haze" + }, + { + "type": "image", + "bbox": [ + 0.518, + 0.09, + 0.63, + 0.162 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.542, + 0.163, + 0.602, + 0.171 + ], + "angle": 0, + "content": "Ground-truth" + }, + { + "type": "image", + "bbox": [ + 0.63, + 0.09, + 0.74, + 0.162 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.665, + 0.163, + 0.704, + 0.17 + ], + "angle": 0, + "content": "MPRNet" + }, + { + "type": "image", + "bbox": [ + 0.74, + 0.09, + 0.851, + 0.162 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.783, + 0.163, + 0.82, + 0.17 + ], + "angle": 0, + "content": "NAFNet" + }, + { + "type": "image", + "bbox": [ + 0.408, + 0.178, + 0.518, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.442, + 0.258, + 0.489, + 0.266 + ], + "angle": 0, + "content": "Restormer" + }, + { + "type": "image", + "bbox": [ + 0.519, + 0.178, + 0.63, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.544, + 0.257, + 0.606, + 0.266 + ], + "angle": 0, + "content": "RainHazeDiff" + }, + { + "type": "image", + "bbox": [ + 0.63, + 0.178, + 0.74, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.665, + 0.257, + 0.708, + 0.265 + ], + "angle": 0, + "content": "DTPM-4s" + }, + { + "type": "image", + "bbox": [ + 0.74, + 0.178, + 0.851, + 0.257 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.777, + 0.258, + 0.826, + 0.266 + ], + "angle": 0, + "content": "DTPM-50s" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.279, + 0.895, + 0.321 + ], + "angle": 0, + "content": "Figure 5. Image deraining&dehazing visual comparison on the Ourdoor-Rain dataset [48]. Our DTPM method generates rain-free and haze-free image with better details and without artifacts. The \"-4s\" and \"-50s\" denotes our DTPM method with a DDIM [55] sampling schedule of 4 steps and 50 steps." + }, + { + "type": "image", + "bbox": [ + 0.119, + 0.335, + 0.366, + 0.459 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.195, + 0.461, + 0.27, + 0.473 + ], + "angle": 0, + "content": "Blurry Image" + }, + { + "type": "image", + "bbox": [ + 0.369, + 0.335, + 0.488, + 0.388 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.399, + 0.388, + 0.456, + 0.398 + ], + "angle": 0, + "content": "Reference" + }, + { + "type": "image", + "bbox": [ + 0.49, + 0.335, + 0.607, + 0.388 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.528, + 0.389, + 0.566, + 0.399 + ], + "angle": 0, + "content": "Blurry" + }, + { + "type": "image", + "bbox": [ + 0.612, + 0.335, + 0.728, + 0.388 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.643, + 0.389, + 0.693, + 0.398 + ], + "angle": 0, + "content": "MPRNet" + }, + { + "type": "image", + "bbox": [ + 0.73, + 0.335, + 0.848, + 0.388 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.747, + 0.389, + 0.828, + 0.399 + ], + "angle": 0, + "content": "MIMO-UNet+" + }, + { + "type": "image", + "bbox": [ + 0.37, + 0.409, + 0.488, + 0.46 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.404, + 0.461, + 0.463, + 0.471 + ], + "angle": 0, + "content": "Restormer" + }, + { + "type": "image", + "bbox": [ + 0.491, + 0.409, + 0.607, + 0.46 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.531, + 0.46, + 0.564, + 0.47 + ], + "angle": 0, + "content": "DvSR" + }, + { + "type": "image", + "bbox": [ + 0.612, + 0.409, + 0.729, + 0.459 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.635, + 0.459, + 0.716, + 0.47 + ], + "angle": 0, + "content": "DTPM-4 steps" + }, + { + "type": "image", + "bbox": [ + 0.731, + 0.409, + 0.851, + 0.46 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.747, + 0.46, + 0.834, + 0.471 + ], + "angle": 0, + "content": "DTPM-50 steps" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.484, + 0.893, + 0.527 + ], + "angle": 0, + "content": "Figure 6. Single-image motion deblurring comparison on the GoPro Dataset [43]. Compared to the other methods, our DTPM more effectively removes blur and preserving better structural information. The \"-4s\" and \"-50s\" denotes our DTPM method with a DDIM sampling schedule of 4 steps and 50 steps." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.539, + 0.47, + 0.675 + ], + "angle": 0, + "content": "structured over 1,000 steps (denoted as \\(T\\)), incorporating a noise schedule \\(\\beta(t)\\) that linearly escalates from 0.0001 to 0.02 throughout the training. Input data consistently utilized \\(256 \\times 256\\) cropped patches. Data augmentation techniques, including horizontal flipping and random image rotation at \\(45^{\\circ}\\) and \\(90^{\\circ}\\), were applied during training. We utilize Denoising Diffusion Implicit Models (DDIM) [55] to implement our diffusion model, thereby significantly enhancing our sampling speed." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.705, + 0.216, + 0.719 + ], + "angle": 0, + "content": "4.2. Main Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Comparative Analysis of Deraining&Dehazing. As shown in Table 1 in outdoor hazy and rainy image restoration, DTPM's 4 Step variant outperforms RainHazeDiff's 25-step process, achieving higher PSNR (30.99), SSIM (0.934), and lower LPIPS (0.0635). DTPM demonstrates superior perceptual quality enhancement, as indicated by its LPIPS and PSNR metrics. The DTPM-10 and DTPM-50 Step versions further reduce LPIPS to 0.0617 and 0.0540, respectively, while maintaining high SSIM, establishing DTPM's methodological advantage and benchmark in high-fidelity restoration." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.539, + 0.892, + 0.676 + ], + "angle": 0, + "content": "Comparative Analysis of Single-image Defocus Deblurring. DTPM markedly outperforms other methods in defocus deblurring on the DPDD dataset as shown in Table 4, with its 4 Step iteration achieving high LPIPS (0.153) and SSIM (0.823) scores, thus maintaining image structural integrity. The DTPM-50 Step model further enhances perceived quality, achieving an LPIPS of 0.139, closely resembling ground truth. Visual evidence in Figure 7 corroborates DTPM's superior detail recovery and structural fidelity." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.893, + 0.902 + ], + "angle": 0, + "content": "Concise Analysis of DTPM in Single-image Motion Deblurring. As shown in Table 5, on the GoPro dataset, the DTPM 4 Step variant achieves a PSNR of 32.09, SSIM of 0.932, LPIPS of 0.084, and FID of 10.02, demonstrating a balance in distortion reduction and perceptual quality. The 10 Step version improves these metrics, with an LPIPS of 0.081 and a leading FID of 8.52, despite slight decreases in PSNR and SSIM. The DTPM-50 Step variant, achieving the best perceptual outcomes with the lowest LPIPS (0.073) and FID (7.69), slightly reduces PSNR to 31.11 and SSIM to 0.919, illustrating our method's ability to the best perceptual quality." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2529" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.12, + 0.088, + 0.379, + 0.245 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.201, + 0.247, + 0.277, + 0.259 + ], + "angle": 0, + "content": "Blurry Image" + }, + { + "type": "image", + "bbox": [ + 0.38, + 0.088, + 0.495, + 0.164 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.409, + 0.165, + 0.465, + 0.174 + ], + "angle": 0, + "content": "Reference" + }, + { + "type": "image", + "bbox": [ + 0.381, + 0.174, + 0.493, + 0.247 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.425, + 0.248, + 0.456, + 0.258 + ], + "angle": 0, + "content": "IFAN" + }, + { + "type": "image", + "bbox": [ + 0.496, + 0.089, + 0.609, + 0.164 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.536, + 0.165, + 0.574, + 0.174 + ], + "angle": 0, + "content": "Blurry" + }, + { + "type": "image", + "bbox": [ + 0.497, + 0.174, + 0.609, + 0.247 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.53, + 0.249, + 0.591, + 0.259 + ], + "angle": 0, + "content": "Restomer" + }, + { + "type": "image", + "bbox": [ + 0.617, + 0.089, + 0.73, + 0.164 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.655, + 0.165, + 0.691, + 0.174 + ], + "angle": 0, + "content": "KPAC" + }, + { + "type": "image", + "bbox": [ + 0.617, + 0.174, + 0.728, + 0.247 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.648, + 0.248, + 0.703, + 0.258 + ], + "angle": 0, + "content": "DTPM-4s" + }, + { + "type": "image", + "bbox": [ + 0.738, + 0.089, + 0.851, + 0.164 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.765, + 0.165, + 0.824, + 0.175 + ], + "angle": 0, + "content": "DeepRFT" + }, + { + "type": "image", + "bbox": [ + 0.738, + 0.175, + 0.849, + 0.247 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.767, + 0.249, + 0.832, + 0.26 + ], + "angle": 0, + "content": "DTPM-50s" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.274, + 0.892, + 0.303 + ], + "angle": 0, + "content": "Figure 7. Single-image defocus deblurring results on the DPDD dataset [1]. The \"-4s\" and \"-50s\" denotes our DTPM method with a DDIM sampling schedule of 4 steps and 50 steps. Compared to the other approaches, our DTPM generate better structures and details." + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.327, + 0.468, + 0.352 + ], + "angle": 0, + "content": "Table 4. Single-image Defocus Deblurring comparisons on the DPDD testset [1]." + }, + { + "type": "table", + "bbox": [ + 0.116, + 0.363, + 0.435, + 0.491 + ], + "angle": 0, + "content": "
MethodDistortionPerceptual
PSNR ↑SSIM ↑MAE ↓LPIPS ↓
EBDB [28]23.450.6830.0490.336
DMENet [31]23.410.7140.0510.349
JNB [53]23.840.7150.0480.315
DPDNet [1]24.340.7470.0440.277
KPAC [54]25.220.7740.0400.227
IFAN [32]25.370.7890.0390.217
Restormer [70]25.980.8110.0380.178
DTPM-4 Step25.980.8230.0380.153
DTPM-10 Step25.760.8150.0390.140
DTPM-50 Step25.450.8030.0400.139
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.511, + 0.468, + 0.536 + ], + "angle": 0, + "content": "Table 5. Single-image Motion Deblurring comparisons on the GoPro testset [43]." + }, + { + "type": "table", + "bbox": [ + 0.118, + 0.547, + 0.433, + 0.654 + ], + "angle": 0, + "content": "
MethodDistortionPerceptual
PSNR ↑SSIM ↑LPIPS ↓FID ↓
MPRNet [71]32.660.9590.08920.18
MIMO-UNet+ [13]32.450.9570.09118.05
SAPHNet [56]31.890.9530.10119.06
Restomer [70]33.200.9630.08419.33
DvSR [60]30.660.9410.08412.20
DTPM-4 Step32.090.9320.08410.02
DTPM-10 Step31.820.9290.0777.52
DTPM-50 Step31.110.9190.0616.61
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.685, + 0.47, + 0.79 + ], + "angle": 0, + "content": "Comparative Analysis of Raindrop Removal. As illustrated in Table 2, we can observe that various versions of DTPM have demonstrated outstanding performance in the task of image raindrop removal. In comparison to RainDropDiff, our approach has achieved superior performance, with the LPIPS metric significantly outperforming that of RainDropDiff." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.468, + 0.9 + ], + "angle": 0, + "content": "Comparative Analysis of Snow Removal. As shown in Table 1, we can observe that various versions of DTPM have demonstrated excellent performance in the task of image desnowing. In comparison to SnowDiff, our approach has achieved superior LPIPS metrics." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.327, + 0.725, + 0.344 + ], + "angle": 0, + "content": "5. Discussion and Analysis" + }, + { + "type": "image", + "bbox": [ + 0.56, + 0.365, + 0.832, + 0.487 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.497, + 0.892, + 0.567 + ], + "angle": 0, + "content": "Figure 8. Trade-off between PSNR and LPIPS in DTPM: This plot illustrates the inverse relationship between PSNR (pixel-wise distortion) and LPIPS (perceptual similarity) across various sampling steps, highlighting the equilibrium achieved between distortion and perceptual quality in our method." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.584, + 0.891, + 0.629 + ], + "angle": 0, + "content": "For the analysis of various aspects of our model, we perform our experiments on the image deraining& dehazing dataset as it's a more chanlenging settings than others." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.639, + 0.891, + 0.669 + ], + "angle": 0, + "content": "5.1. Sampling Steps and Distortion-Perceptual Trade-off" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.678, + 0.892, + 0.829 + ], + "angle": 0, + "content": "In Figure 8, we evaluate the results of our DTPM through the lens of two critical image quality metrics: PSNR and LPIPS1. As the sampling steps increase, the PSNR values initially experience a precipitous drop, decreasing from just above 31 dB to below 30.70 dB by the 10th step. This substantial early decline indicates that sampling steps in the early phase degrade image fidelity. Beyond this point, the PSNR decline slows, entering a phase of more gradual descent before plateauing after the 30th step, suggesting that the method begins to stabilize in terms of distortion loss. In" + }, + { + "type": "page_footnote", + "bbox": [ + 0.498, + 0.839, + 0.892, + 0.901 + ], + "angle": 0, + "content": "1The PSNR, measured in decibels (dB), is a traditional metric for assessing the fidelity of the reconstructed images against an original high-quality image. The LPIPS metric, on the other hand, offers an assessment of perceptual similarity, which correlates more closely with human visual perception." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2530" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.091, + 0.468, + 0.192 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.203, + 0.47, + 0.26 + ], + "angle": 0, + "content": "Figure 9. The first row in the figure shows the images, while the second row shows zoomed-in details. From left to right, they are: (a) input image, (b) the output of the initial predictor, (c) the final result of our method, (d) the ground-truth." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.287, + 0.473, + 0.529 + ], + "angle": 0, + "content": "contrast, the LPIPS score improves markedly with each incremental sampling step, indicating that the perceived quality of the images is becoming more aligned with human visual perception. The steepness of the LPIPS improvement mirrors the PSNR decline, reflecting a pronounced trade-off between fidelity and perceptual quality up to the 10 step. After this inflection point, although the PSNR values level off, suggesting a saturation of fidelity loss, the LPIPS values continue to improve but at a diminished rate, plateauing around the 40 step. The intersecting trends of these metrics underscore a distinct trade-off: optimizing for perceptual likeness through more sampling steps comes at the expense of traditional fidelity measures. However, the stabilization of both metrics after a certain number of sampling steps suggests a convergence towards an equilibrium between the two qualities." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.54, + 0.347, + 0.556 + ], + "angle": 0, + "content": "5.2. Output of the Initial Predictor" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.564, + 0.47, + 0.716 + ], + "angle": 0, + "content": "Given the significance of the initial predictor as a key component of our methodology, we have undertaken detailed explorations and analyses of it. Despite the absence of an explicit loss constraint in our initial predictor, it achieves results that closely resemble a clean background, as evidenced in Figure 9. The initial predictor, though not detailed in its finer aspects, effectively produces a reasonably clear image. This provides practical assurance for incorporating the output of the initial predictor as one of the enhanced, additional conditions for diffusion." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.725, + 0.288, + 0.74 + ], + "angle": 0, + "content": "5.3. More Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.749, + 0.468, + 0.856 + ], + "angle": 0, + "content": "In this section, we conduct ablation studies to analyze the impact of different design choices in our DTPM framework. w/o Stage I Training. This variant, absent the initial training phase, exhibits a decrease in both image reconstruction quality and perceptual similarity relative to the complete model. This underscores the significance of the early training stage in establishing baseline performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.468, + 0.902 + ], + "angle": 0, + "content": "w/o Initial Predictor: Removing the Initial Predictor results in a notable decline in both objective image quality and perceptual accuracy. This component's role is evidently" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.089, + 0.892, + 0.118 + ], + "angle": 0, + "content": "Table 6. The ablation studies on Image Deraining&Dehazing dataset [48]." + }, + { + "type": "table", + "bbox": [ + 0.561, + 0.129, + 0.835, + 0.232 + ], + "angle": 0, + "content": "
ModelPSNR ↑LPIPS ↓
w/o Stage I Training28.900.074
w/o Initial Predictor26.910.079
w/o Semantic Code29.790.0653
Fine-tune Enc. w/o Adapters29.200.0667
Fine-tune Dec. w/o Adapters28.910.0691
Fine-tune Enc.&Dec. w/o Adapters29.130.0712
Ours(DTPM-4S)30.990.0635
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.257, + 0.892, + 0.332 + ], + "angle": 0, + "content": "crucial for enhancing the clarity and fidelity of the images. w/o Semantic Code. The removal of the Semantic Code somewhat improves both image quality and perceptual similarity. This could suggest that the Semantic Code potentially adding informative features." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.333, + 0.892, + 0.407 + ], + "angle": 0, + "content": "Fine-tune Enc. w/o Adapters. Fine-tuning just the encoder of DTPM without adapters leads to a slight reduction in performance. This indicates that while the encoder is a robust component, the adapters contribute to optimizing its function." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.408, + 0.892, + 0.482 + ], + "angle": 0, + "content": "Fine-tune Dec. w/o Adapters. Solely fine-tuning the decoder of DTPM without adapters also reduces model efficacy. The adapters appear more integral for the decoder, possibly enabling more nuanced adjustments that refine results." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.484, + 0.892, + 0.56 + ], + "angle": 0, + "content": "Fine-tune Enc.&Dec. w/o Adapters. Fine-tuning both the encoder and decoder without adapters does not match the performance of the complete model. This suggests a complex interplay between these components that adapters help to fine-tune effectively." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.573, + 0.757, + 0.589 + ], + "angle": 0, + "content": "6. Conclusion and Limitations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.892, + 0.689 + ], + "angle": 0, + "content": "This study presents a comprehensive conditional framework for image restoration, integrating Diffusion Texture Priors for producing high-quality images with promising details. While achieving significant performance, it identifies potential improvements: accelerating sampling via advanced techniques and optimizing the model size." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.714, + 0.892, + 0.82 + ], + "angle": 0, + "content": "Acknowledgment. This work is supported by the InnoHK funding launched by Innovation and Technology Commission, Hong Kong SAR, Guangzhou Municipal Science and Technology Project (Grant No. 2023A03J0671), and a grant of Innovation and Technology Fund under Guangdong-Hong Kong Technology Cooperation Funding Scheme (ITF-TCFS) (project no. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 930-939, 2022. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.894, + 0.718 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2534" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Diffusion Texture Priors for Image Restoration/c4fdbfda-8abc-47c5-aabf-b69c62343d36_origin.pdf b/2024/Learning Diffusion Texture Priors for Image Restoration/c4fdbfda-8abc-47c5-aabf-b69c62343d36_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..79716f4ab97857d064ba705b4b9e8ff1ff9c6723 --- /dev/null +++ b/2024/Learning Diffusion Texture Priors for Image Restoration/c4fdbfda-8abc-47c5-aabf-b69c62343d36_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:714f35c879f7393405da8252e0b74402b142f764f953a3d2dca389e471e0d96d +size 6204337 diff --git a/2024/Learning Diffusion Texture Priors for Image Restoration/full.md b/2024/Learning Diffusion Texture Priors for Image Restoration/full.md new file mode 100644 index 0000000000000000000000000000000000000000..491266402ef87453328f172acb3c3fb1c18ba232 --- /dev/null +++ b/2024/Learning Diffusion Texture Priors for Image Restoration/full.md @@ -0,0 +1,391 @@ +# Learning Diffusion Texture Priors for Image Restoration + +Tian Ye1 Sixiang Chen1 Wenhao Chai2 +Zhaohu Xing1 Jing Qin3 Ge Lin1,4 Lei Zhu1,4* + +1 The Hong Kong University of Science and Technology (Guangzhou) 2 University of Washington 3 The Hong Kong Polytechnic University 4 The Hong Kong University of Science and Technology + +# Abstract + +Diffusion Models have shown remarkable performance in image generation tasks, which are capable of generating diverse and realistic image content. When adopting diffusion models for image restoration, the crucial challenge lies in how to preserve high-level image fidelity in the randomness diffusion process and generate accurate background structures and realistic texture details. In this paper, we propose a general framework and develop a Diffusion Texture Prior Model (DTPM) for image restoration tasks. DTPM explicitly models high-quality texture details through the diffusion process, rather than global contextual content. In phase one of the training stage, we pre-train DTPM on approximately 55K high-quality image samples, after which we freeze most of its parameters. In phase two, we insert conditional guidance adapters into DTPM and equip it with an initial predictor, thereby facilitating its rapid adaptation to downstream image restoration tasks. Our DTPM could mitigate the randomness of traditional diffusion models by utilizing encapsulated rich and diverse texture knowledge and background structural information provided by the initial predictor during the sampling process. + +# 1. Introduction + +Image Restoration tasks [37, 43, 70, 71] usually are ill-posed problems whose solutions are not unique. While existing methods [8, 70, 71] have achieved notable breakthroughs, they typically employ direct regression models to produce deterministic results. A persistent challenge is that these deterministic models [4, 70, 71] frequently yield unsatisfactory fine-grained details (See Figure 2), as they are trained to minimize pixel-level error, aligning output with ground truth by Norm-based losses [30]. The emergence of Diffusion Models (DMs) [14, 16, 51, 55] has revolutionized image generation, yielding realistic images replete with fine details. This advancement motivates our investigation + +![](images/781aa095d4079ac5ae97581877cbcb9d653fcc3c4053d8d4c2964451738cff4e.jpg) +Figure 1. We use a coefficient $\alpha$ ranging from 0.1 to 1 to control the intensity of texture removal. As $\alpha$ increases, leading to richer textures from left to right in the images, we can observe a corresponding improvement in the scores of no-reference image quality metrics, specifically NIQE [42] and CLIP-IQA+ [57]. Regarding the NIQE, lower scores indicate better quality, while for CLIP-IQA+, higher scores represent better visual quality. This indicates that the quality of the image's texture details have a significant impact on the visual perceptual quality of the image. + +into diffusion-based methods for image restoration, aiming to leverage conditional DMs [17, 45, 51] to produce perceptually appealing results that closely mimic natural, clean images. + +However, directly applying diffusion image generation techniques [44, 51, 55] to image restoration tasks is often impractical [36, 45]. The high content fidelity required in image restoration clashes with the stochastic nature of diffusion models [44, 55]. A plausible solution involves integrating physical degradation models [5, 69] with neural networks or crafting hand-designed priors [20, 47] to mitigate the inherent randomness of the diffusion paradigm. While several previous studies [17, 68, 69] have adopted this approach with success, they lack versatility and show limited generalization capability on real-world scenes, as physical degradation models do not fully encompass real-world degradation scenarios [4, 66, 67]. Additionally, the iterative nature and complexity of the denoising process in diffusion models necessitate extensive data and lengthy training cycles for effective learning. The challenges and limitations outlined above necessitate a rethinking of the use of the diffusion paradigm in image restoration: (i) To preserve high-level fidelity in restoration, we propose using a diffusion model to recover only texture layers. This + +![](images/3f92d8270648f6da63a7b5d5b5eeee7ae0006c76e03e603395810731d8a14f81.jpg) +Figure 2. (a) The input degraded image. (b) The result of Restormer [70]. Restormer is a representative image restoration method that can only produce deterministic results, which may lack promising details. (c) The result of RainHazeDiff [45]. (d) The result of our method. The content within the dashed rectangle represents the corresponding ground-truth details. It's worth noting that our approach excels in generating finer details, thanks to the incorporation of Diffusion Texture Priors we proposed. + +approach emphasizes and highlights the importance of fine textures in visual perception (See Figure 1). By focusing diffusion on texture recovery, we minimize randomness of diffusion process and leverage its strength in generating realistic details. (ii) Recognizing the diffusion paradigm as a potent representation learning tool that requires extensive data for convergence, we pre-trained our model, named the Diffusion Texture Priors Model (DTPM), on a large-scale dataset of high-quality images. This model, trained on approximately $55K$ samples, is tailored to reconstruct texture layers, embedding texture priors within the diffusion process. Our DTPM framework is characterized by: (a) A novel approach in diffusion modeling that focuses on texture layers through residual learning, enhancing efficiency in downstream restoration tasks. (b) The incorporation of Semantic Code as a constraint, guiding the diffusion model to produce semantically coherent textures. (c) To preserve the integrity of the diffusion texture priors, most parameters of the DTPM remain fixed after pre-training. We introduce a Conditional Degradation Adapter to facilitate rapid adaptation to various restoration tasks without the risk of catastrophic forgetting. + +Our extensive experiments across single-image defocus deblurring, image motion deblurring, desnowing, dehazing, deraining, and raindrop removal demonstrate that our method not only surpasses strong regression models and recent diffusion-based models in perceptual quality but also exhibits robust generalization across diverse restoration tasks. + +# 2. Related Works + +Evolution in Image Restoration. Image restoration [4, 15, 19, 25, 39, 67, 71, 77], a pivotal research domain within the computer vision community, has witnessed significant evolution over recent years. Traditionally regarded as an ill-posed problem, image restoration poses unique challenges due to the multitude of potential solutions derivable from a single degraded image. Over the last decade, there has been a notable shift in the computer vision field from conventional, handcrafted prior-based approaches [20, 47] to a more data-centric, deep learning-driven paradigm [4, 15, 59, 70]. This transition has led to the development of advanced deep learning techniques, characterized by complicated network structures [65, 70, 71] and extensive training on carefully collected datasets. These approaches excel in learning mappings from degraded to clean data, effectively tackling the complexities of image restoration. Initially, deep learning methods [9-11, 66, 67] in this area tended to produce deterministic outcomes, which starkly contrasted with the fundamentally probabilistic nature of image restoration tasks [18, 46, 70]. This discrepancy has increasingly brought generative methods [17, 27, 46, 64, 76] to the forefront, highlighting their potential to address the challenges inherent in image restoration. + +Generative image restoration methods. Recent developments [6, 7, 17, 41, 46, 61, 64, 74] have shed light on the fundamental flaws of earlier deep learning-driven image restoration techniques, specifically their (i) generate deterministic outputs and (ii) inability to restore high-quality, detailed textures, owing to their training focused on minimizing pixel-level discrepancies. Consequently, generative approaches are gaining traction. A notable strategy includes employing Generative Adversarial Networks (GANs) [24, 29, 48]. Nonetheless, GANs pose challenges due to their complex training procedures, instability during training, and occasional generation of unrealistic image attributes. The impressive efficacy of diffusion in image generation has introduced a promising avenue. Diffusion techniques adeptly tackle the aforementioned issues, offering a more stable training regimen and yielding images with realistic textures. Applications of diffusion-based methods in image super-resolution [52], shadow removal [17, 27], deblurring [60], and adverse weather removal [46] have shown promising results. However, there remains a need for comprehensive research to establish a consistent, reliable framework for diffusion-based image restoration tasks. + +# 3. Our Framework + +# 3.1. Preliminaries of Diffusion Models + +Diffusion Models (DMs), as referenced in [22, 44], are a class of generative models that gradually infuse Gaussian noise into training data and then employ a denoiser to re + +![](images/1ca2c6e856e568cb347f98748ff494c6b183fe6145607f3d565c8539886d4286.jpg) +Stage I: Training a Conditional Diffusion Model for Learning Diffusion Texture Priors +Stage II : Fine-Tuning the Diffusion Model Using Task-Specific Adapters for Image Restoration Tasks + +![](images/11c8daa8588a39eed54754f2b1bd7bd566a7a6ff575b540f208a1d713fb89827.jpg) +(a) Overview of Our Framework +Figure 3. The overview of Our DTPM Framework. (a) Our method consists of two stages. In the stage I, under the guiding constraints of semantic code, the diffusion model learns texture layers through residual learning from a large amount of high-quality data, which allows us to encapsulate diverse and rich texture knowledge into the diffusion model. In the stage II, we fix most of the parameters of the trained diffusion model and insert Conditional Guidance Adapters between each layer for efficient fine-tuning and conditional guidance on image restoration tasks. (b) The overview of adapters and our denoising blocks.(c) The detailed design of our Conditional Guidance Adapter. + +![](images/05bfec54f6d459768c6ca926c6152f54593948e735990833fbea0ded42544941.jpg) +(b) Overview of Adapters and Denoising Blocks + +![](images/802dacdd17a51cd338b9bb662b8ce78e58e3052c0b995ed718940b45a131ec6c.jpg) +(c) Conditional Guidance Adapter + +verse this noise addition. The process begins with the diffusion phase, where an initial image $\pmb{x}_0$ evolves into Gaussian noise $\pmb{x}_T \sim \mathcal{N}(0,1)$ through $T$ steps. Each step of this transformation is governed by: + +$$ +q \left(\boldsymbol {x} _ {t} \mid \boldsymbol {x} _ {t - 1}\right) = \mathcal {N} \left(\boldsymbol {x} _ {t}; \sqrt {1 - \beta_ {t}} \boldsymbol {x} _ {t - 1}, \beta_ {t} \boldsymbol {I}\right), \tag {1} +$$ + +where $\pmb{x}_t$ is the image with noise at step $t$ , $\beta_t$ is a fixed scaling factor, and $\mathcal{N}$ denotes the Gaussian distribution. Introducing $\alpha_t = 1 - \beta_t$ and $\bar{\alpha}_t = \prod_{i=0}^t \alpha_i$ simplifies Eq.1 to: + +$$ +q \left(\boldsymbol {x} _ {t} \mid \boldsymbol {x} _ {0}\right) = \mathcal {N} \left(\boldsymbol {x} _ {t}; \sqrt {\bar {\alpha} _ {t}} \boldsymbol {x} _ {0}, (1 - \bar {\alpha} _ {t}) \boldsymbol {I}\right), \tag {2} +$$ + +During the inference stage's reverse process, DMs initiate with a random Gaussian noise map $\boldsymbol{x}_T$ and progressively denoise it to reach the refined output $\boldsymbol{x}_0$ . + +$$ +p \left(\boldsymbol {x} _ {t - 1} \mid \boldsymbol {x} _ {t}, \boldsymbol {x} _ {0}\right) = \mathcal {N} \left(\boldsymbol {x} _ {t - 1}; \boldsymbol {\mu} _ {t} \left(\boldsymbol {x} _ {t}, \boldsymbol {x} _ {0}\right), \sigma_ {t} ^ {2} \boldsymbol {I}\right), \tag {3} +$$ + +where the mean $\pmb{\mu}_t(\pmb{x}_t,\pmb{x}_0) = \frac{1}{\sqrt{\alpha_t}}\left(\pmb{x}_t - \epsilon \frac{1 - \alpha_t}{\sqrt{1 - \bar{\alpha}_t}}\right)$ and the variance $\sigma_t^2 = \frac{1 - \bar{\alpha}_{t-1}}{1 - \bar{\alpha}_t} \beta_t$ . + +# 3.2. Overview of DTP-IR Framework + +Our aim is to create a unified framework for image restoration tasks based on our Diffusion Texture Priors. As shown + +in Figure 3, our DTPM framework comprises two stages: In Stage 1, we train a conditional diffusion model with semantic latent feature constraints using a large dataset of high-resolution, high-quality natural images. During Stage 2, we incorporate conditional guidance adapters into the conditional diffusion model to facilitate the model's adaptation to downstream image restoration tasks. + +# 3.3. Stage I: Learning Diffusion Texture Priors + +In this section, we will first briefly introduce the core motivation of our Diffusion Texture Priors, followed by the basic structure information of the diffusion model and the semantic code. Finally, we will discuss the training objective and training data. + +Motivation. Recent studies [52, 64, 74] have highlighted the pivotal role of texture quality in shaping subjective visual perception in the realm of image restoration. Traditional methodologies, however, encounter substantial difficulties in accurately restoring fine-grained textural details, which are crucial for realistic image reconstruction. While diffusion models have demonstrated excellence in generating lifelike images, their direct application to image restoration tasks has been less than ideal, yielding mediocre results. Our approach seeks to remedy this by integrating + +![](images/40be511639af5b759f78a8e90a9ef190a6dbea6e084547e99daa0cad713d4dc4.jpg) +Figure 4. The architecture of our fundamental denoising block incorporates "Channel Attention" (CA) and "SimpleGate," a straightforward feature gating mechanism introduced by Chen et al.[8]. The current timestep $t$ is injected into the block with Adaptive Layer Normalization [3] (AdaLN), i.e., $AdaLN(f_{in} = \gamma LayerNorm(f_{in}) + \beta$ , where $f_{in}$ is the input features, $\gamma$ and $\beta$ are converted from the timestep embedding. The "Shift&Scale" block means shift and scale features by generated $\gamma, \beta$ . + +texture-specific priors into the diffusion model. This integration enables the diffusion model to specifically concentrate on reconstructing textures, as opposed to merely focusing on degradation elimination. Such a strategy leverages the diffusion model's inherent strengths and mitigates its weaknesses, allowing us to exploit a vast repository of high-quality natural images for prior knowledge. This method not only significantly enhances the model's generalization capabilities but also markedly improves the efficiency of the sampling process. + +Basic Denoising Block. We have engineered a denoising block based on NAFNet [8] block, designed to enhance model adaptability for a broad spectrum of natural image content. This block aims to balance peak model performance with reduced computational demands and easy-to-handle varying input resolutions. As delineated in Figure 4, our denoising block capitalizes on depth-wise convolution as its cornerstone, complemented by several $1 \times 1$ convolution layers and LayerNorm [3], to facilitate efficient denoising. To incorporate the time condition, we utilize MLPs for transforming the time embedding into channel-specific scale and shift parameters. Additionally, to maintain the semantic consistency between $x_0$ and $y_s$ , we integrate an MLP layer for semantic condition, which amalgamates semantic code as a pivotal conditioning factor. + +Semantic code. To enable the diffusion model to produce realistically textured details, we utilize a pre-trained ResNet-18 [21] for extracting semantic embeddings as a global semantic code, which is then integrated into each de + +noising block as shown in Figure 4. This approach of employing semantic code imposes robust semantic constraints, rather than solely depending on adjacent context information, allowing our model to generate textures in alignment with the contextual semantics. Consequently, this ensures high-fidelity results of our diffusion model. + +Training objective. To prioritize texture reconstruction over content of the image, our diffusion model is designed to capture the residual distribution of $y_{s}$ . The training objective for Stage I is thus defined as: $L_{\mathrm{StageI}}(\theta) =$ + +$$ +\mathbb {E} \left\| \boldsymbol {\epsilon} - f _ {\theta} \left(\sqrt {\gamma} \left(\underbrace {\boldsymbol {x} _ {g} - \boldsymbol {y} _ {s}} _ {\text {r e s i d u a l}}\right) + \sqrt {1 - \gamma} \boldsymbol {\epsilon}, \boldsymbol {y} _ {s}, \gamma\right) \right\|, \tag {4} +$$ + +here, $\epsilon \sim \mathcal{N}(0,I)$ represents the noise vector, and $f_{\theta}$ is our diffusion model. The term $\gamma \sim p(\gamma)$ denotes a distribution associated with the noise schedule. In this context, $x_{g}$ symbolizes the high-quality input image, whereas $y_{s}$ denotes its corresponding smoothed image. $y_{s}$ is obtained by utilizing an edge-preserving smoothing method [63] to eliminate a majority of the texture while retaining the contextual content. + +Training data for Stage I. Inspired by previous codebook prior-based image restoration studies [61, 64, 74], our training stage I employs high-quality images from the widely-recognized DIV2K [2] and Flickr2K [35] datasets. Each image is cropped into multiple patches of $512 \times 512$ resolution, followed by an edge-preserved smooth method [63] to diminish textural details. This process results in a training dataset comprising 55,558 paired instances $(x_{g}, y_{s})$ . + +# 3.4. Stage II: Finetuning Diffusion Texture Priors Model with Adapters + +This section describes the initial predictor and the Conditional Guidance Adapter, along with the rationale behind their integration. We also detail the architecture of the adapters. Finally, the training objectives are outlined. + +Initial Predictor. In the pursuit of augmenting the diffusion model's adaptability for downstream tasks in its second stage (see Figure 3), we draw from the DvSR, integrating a compact and lightweight U-Net to generate an initial output. This initial step efficiently seizes deterministic components of the ultimate restored image, crucial for capturing essential structural information. Moreover, this initial output serves as a pivotal guiding element for the diffusion model, forming an effective complement with our Diffusion Texture Priors Model. + +Table 1. Image Desnowing. + +
MethodSnow100K-S [40]Snow100K-L [40]
PSNR ↑SSIM ↑LPIPS ↓PSNR ↑SSIM ↑LPIPS ↓
SPANet [58]29.920.82600.10423.700.79300.210
JSTASR [12]31.400.90120.05925.320.80760.152
RESCAN [34]31.510.90320.05426.080.81080.106
DesnowNet [40]32.330.95000.07027.170.89830.101
DDMSNet [72]34.340.94450.05828.850.87720.098
MPRNet [71]34.970.94570.04929.760.89490.091
NAFNet [8]34.790.94970.05130.060.90170.086
Restormer [70]35.030.94870.04730.520.90920.083
SnowDiff64[45]36.590.96260.03530.430.91450.069
SnowrDiff128[45]36.090.95450.03830.280.90000.067
DTPM-4 Step37.010.96630.03430.920.91740.063
DTPM-10 Step36.440.95210.03330.320.90240.055
DTPM-50 Step36.190.94830.02930.020.89010.053
+ +Table 2. Image Deraining & Dehazing. + +
MethodOutdoor-Rain [33]
PSNR ↑SSIM ↑LPIPS ↓
CycleGAN [75]17.620.6560-
pix2pix [23]19.090.7100-
HRGAN [33]21.560.85500.154
PCNet [26]26.190.90150.132
MPRNet [71]28.030.91920.089
NAFNet [8]29.590.90270.085
Restormer [70]29.970.92150.074
RainHazeDiff64[45]28.380.93200.067
RainHazeDiff128[45]26.840.91520.071
DTPM-4 Step30.990.9340.0635
DTPM-10 Step30.920.9320.0617
DTPM-50 Step30.480.9210.0540
+ +Table 3. Removing Raindrops. + +
MethodRainDrop [48]
PSNR ↑SSIM ↑LPIPS ↓
pix2pix [23]28.020.8547-
DuRN [38]31.240.9259-
RaindropAttn [50]31.440.92630.068
AttentiveGAN [48]31.590.91700.055
CCN [49]31.340.92860.066
IDT [62]31.870.93130.059
RainDropDiff64[45]32.290.94220.058
RainDropDiff128[45]32.430.93340.058
DTPM-4 Step32.720.94400.0577
DTPM-10 Step31.840.93700.0477
DTPM-50 Step31.440.93200.0439
+ +Conditional Guidance Adapter. DPTM encapsulates rich and diverse prior knowledge. We hope that DPTM can fully utilize this knowledge in adapting to downstream image restoration tasks, rather than forgetting it. Therefore, we freeze most of the parameters in DPTM and introduce a flexible and parameter-efficient adaptation mechanism through the Conditional Guidance Adapter as shown in Figure 3 (b) and (c). The design of the Conditional Guidance Adapter brings two benefits: (i) Parameter-efficient learning. Since most of the parameters of DPTM have been sufficiently trained, our model will converge faster and better on downstream tasks after introducing the adapter. (ii) Introducing additional conditions. Introduction of coarse structural information output by the initial predictor, providing the model with more flexible conditional information, thereby producing texture details that better align with expectations. Our Conditional Guidance Adapter could be formally written as: + +$$ +\operatorname {C G - A d p a t e r} \left(f _ {i n}, y _ {\epsilon}\right) = f _ {i n} + \mathbf {M} _ {\text {o u t}} \left(\mathbf {M} _ {i n} \left(f _ {i n}\right) + \operatorname {C o n v} \left(y _ {\epsilon}\right)\right), \tag {5} +$$ + +where $\mathbf{M}$ denotes an MLP layer to scale the dimension $c$ of the input feature $f_{in}^{c}$ to dimension $r\times c$ , and $y_{\epsilon}$ denotes the output of initial predictor $\epsilon_{\theta}$ , thus $y_{\epsilon} = \epsilon_{\theta}(y_d)$ . + +Training objective. The training objective for Stage II is defined as: $L_{\mathrm{StageII}}(\theta) =$ + +$$ +\mathbb {E} \left\| \boldsymbol {\epsilon} - f _ {\theta} \left(\sqrt {\gamma} \left(\boldsymbol {y} _ {g} - \epsilon_ {\theta} (\boldsymbol {y} _ {d})\right) + \sqrt {1 - \gamma} \boldsymbol {\epsilon}, \boldsymbol {y} _ {d}, \gamma\right) \right\|. \tag {6} +$$ + +where $\epsilon_{\theta}$ represents the initial predictor, illustrated in Figure 3. It is important to note that $\epsilon_{\theta}$ does not necessitate additional supervisory loss or pre-training. This is because the gradient from the aforementioned loss propagates through $f_{\theta}$ and subsequently influences $\epsilon_{\theta}$ . + +# 4. Experiments + +# 4.1. Settings + +Our method is assessed on five specific image restoration tasks: image motion deblurring, single-image defocus deblurring, image deraining&dehazing, image desnowing, and image raindrop removal. In the initial stage, we develop a comprehensive Diffusion Texture Prior model, and in the subsequent stage, we fine-tune individual full models tailored to each task. + +Datasets&Metrics. The GoPro dataset [43], as recommended by DvSR [60], is utilized for training and testing in the domain of image motion deblurring. Adhering to Restormer's approach [70], the DPDD dataset [1] is employed for single-image defocus deblurring. For image desnowing, we align with WeatherDiff [45] using the Snow100K dataset [40]. The Outdoor-Rain dataset [33] is used for image deraining&dehazing, following WeatherDiff [45]. Lastly, for single image raindrop removal, we adopt the practices from IDT [62] and WeatherDiff [45], employing the Raindrop dataset [48] for training and testing. We utilize PSNR, SSIM, and MAE as metrics for distortion-based image quality assessment, complemented by LPIPS [73] and FID for evaluating perceptual image quality. Adhering to the methodology outlined in Whang et al. [60], we extract image patches and compute FID at the patch level to ensure more consistent and reliable evaluation results. + +Training Details We implemented our DTPM using the Pytorch framework, leveraging four NVIDIA RTX 4090 GPUs. Training encompasses two stages: Stage I with 800K iterations and Stage II with 600K iterations. We employed the Adam optimizer, setting momentum values at 0.9 and 0.999. The initial learning rate was established at $1.5 \times 10^{-4}$ , employing a cosine annealing strategy for gradual learning rate reduction. The diffusion process is + +![](images/164851ee9c8afbd8ab5a854a72d47995566696826c0a044301871ec7154c54b0.jpg) +Rain&Haze + +![](images/be65f41689e55a823e28d4db96fcac0c66d66e3096fe09bb302dbdaa561a484e.jpg) +Rain&Haze + +![](images/29a8c6905e4d5905a2e991fd9b88edc7d2c1653e40e2ea27e542d89445b61ebc.jpg) +Ground-truth + +![](images/7710880a0b509d8f391ae238cad49e71d6d99a4bf0d09b9324de9a4832b2fd0b.jpg) +MPRNet + +![](images/222e5336b90e8669932a3851520cbe7a233847794794735a725f9a72c8c048bc.jpg) +NAFNet + +![](images/4d1d959be606a2ae53763375d726e45244c3a4464660d2826b52c30e4806cfb4.jpg) +Restormer + +![](images/f183248aca4a424c22fef75a743f886ac87661915839b2dae180db4aeb558a4e.jpg) +RainHazeDiff + +![](images/b4ebb3ad4fa222ce9df41acc1f04412d01f838a1399cc3e8331fc3b36b37039c.jpg) +DTPM-4s + +![](images/a6ec7e9f8d87d904c9c015af6549bbad7801c625a14a6100483aead8b50d8822.jpg) +DTPM-50s + +![](images/d8a578087cc1efddee80302f05652c5770a09f716ecb25e37d2691cf43b9352f.jpg) +Figure 5. Image deraining&dehazing visual comparison on the Ourdoor-Rain dataset [48]. Our DTPM method generates rain-free and haze-free image with better details and without artifacts. The "-4s" and "-50s" denotes our DTPM method with a DDIM [55] sampling schedule of 4 steps and 50 steps. +Blurry Image + +![](images/7df9e91560fda996ebecaad8f546183016297b147a8ab7e828237fdf72cb3075.jpg) +Reference + +![](images/cc0f89ad37a0c4178af57597b36b425c8acb0f298dc6d25bde2c5792fb6a637b.jpg) +Blurry + +![](images/243198613ebc53f4b2861aea23b861a892c30376945354b199f926774f8df7f1.jpg) +MPRNet + +![](images/1f0ff91b7046e9c5cb24d05de78e2f967da7ea0d04fa83ee6be25f947409d2ca.jpg) +MIMO-UNet+ + +![](images/d6119544b32be488db44dd4ce021738c35c4903f7d29e557f8294d0299f7665a.jpg) +Restormer +Figure 6. Single-image motion deblurring comparison on the GoPro Dataset [43]. Compared to the other methods, our DTPM more effectively removes blur and preserving better structural information. The "-4s" and "-50s" denotes our DTPM method with a DDIM sampling schedule of 4 steps and 50 steps. + +![](images/e2318682c5002ae6d20163b8d7c356864fba4992bf33b16842c457b2597728e6.jpg) +DvSR + +![](images/dd3bbf134beccbf78656c34e7b5a0b502a85282a833521e23d84e3f06e0472f2.jpg) +DTPM-4 steps + +![](images/6de8b9f4a9280b1ca2da6521e08a6c070568bef517131409beed8d91acb6f7e8.jpg) +DTPM-50 steps + +structured over 1,000 steps (denoted as $T$ ), incorporating a noise schedule $\beta(t)$ that linearly escalates from 0.0001 to 0.02 throughout the training. Input data consistently utilized $256 \times 256$ cropped patches. Data augmentation techniques, including horizontal flipping and random image rotation at $45^{\circ}$ and $90^{\circ}$ , were applied during training. We utilize Denoising Diffusion Implicit Models (DDIM) [55] to implement our diffusion model, thereby significantly enhancing our sampling speed. + +# 4.2. Main Results + +Comparative Analysis of Deraining&Dehazing. As shown in Table 1 in outdoor hazy and rainy image restoration, DTPM's 4 Step variant outperforms RainHazeDiff's 25-step process, achieving higher PSNR (30.99), SSIM (0.934), and lower LPIPS (0.0635). DTPM demonstrates superior perceptual quality enhancement, as indicated by its LPIPS and PSNR metrics. The DTPM-10 and DTPM-50 Step versions further reduce LPIPS to 0.0617 and 0.0540, respectively, while maintaining high SSIM, establishing DTPM's methodological advantage and benchmark in high-fidelity restoration. + +Comparative Analysis of Single-image Defocus Deblurring. DTPM markedly outperforms other methods in defocus deblurring on the DPDD dataset as shown in Table 4, with its 4 Step iteration achieving high LPIPS (0.153) and SSIM (0.823) scores, thus maintaining image structural integrity. The DTPM-50 Step model further enhances perceived quality, achieving an LPIPS of 0.139, closely resembling ground truth. Visual evidence in Figure 7 corroborates DTPM's superior detail recovery and structural fidelity. + +Concise Analysis of DTPM in Single-image Motion Deblurring. As shown in Table 5, on the GoPro dataset, the DTPM 4 Step variant achieves a PSNR of 32.09, SSIM of 0.932, LPIPS of 0.084, and FID of 10.02, demonstrating a balance in distortion reduction and perceptual quality. The 10 Step version improves these metrics, with an LPIPS of 0.081 and a leading FID of 8.52, despite slight decreases in PSNR and SSIM. The DTPM-50 Step variant, achieving the best perceptual outcomes with the lowest LPIPS (0.073) and FID (7.69), slightly reduces PSNR to 31.11 and SSIM to 0.919, illustrating our method's ability to the best perceptual quality. + +![](images/07e84e3285fc2a450fb70d1433d9eb6c296a706a5023bccab4e159456d71121c.jpg) +Blurry Image + +![](images/ee912a339bdb550112114fcd75486ae0b4b8f11ba729608bb1befc552ef0bf46.jpg) + +![](images/7a29ca79de64466ff4b9a24b0e989d75050e8583ec53a0cec27aac496d0865a4.jpg) +Reference +IFAN +Figure 7. Single-image defocus deblurring results on the DPDD dataset [1]. The "-4s" and "-50s" denotes our DTPM method with a DDIM sampling schedule of 4 steps and 50 steps. Compared to the other approaches, our DTPM generate better structures and details. + +![](images/9f9a3fc9441af6d557af4ddb109549332af74918d3d267a4e2f438bf3077ffa7.jpg) + +![](images/fa54b16391c1285535ced3e010da9e5e96d711626fa0d25cc773dd866f084c05.jpg) +Blurry +Restomer + +![](images/854b1d919072b917f29d1c57572f632ee0775b232b734dd20a96df895b42e799.jpg) + +![](images/f08a4706c6cae514dd47dbf53027a97846dd7b54f1c6aaa26e8f68ead430a239.jpg) +KPAC +DTPM-4s + +![](images/858eb06fc126be6ac9e9c133c64112383f0d5ac825c9dc2a39e161182543ea15.jpg) + +![](images/610652cd1194e508aad50a863e4f52482d1985960aec78c726213fa9be17a14d.jpg) +DeepRFT +DTPM-50s + +Table 4. Single-image Defocus Deblurring comparisons on the DPDD testset [1]. + +
MethodDistortionPerceptual
PSNR ↑SSIM ↑MAE ↓LPIPS ↓
EBDB [28]23.450.6830.0490.336
DMENet [31]23.410.7140.0510.349
JNB [53]23.840.7150.0480.315
DPDNet [1]24.340.7470.0440.277
KPAC [54]25.220.7740.0400.227
IFAN [32]25.370.7890.0390.217
Restormer [70]25.980.8110.0380.178
DTPM-4 Step25.980.8230.0380.153
DTPM-10 Step25.760.8150.0390.140
DTPM-50 Step25.450.8030.0400.139
+ +Table 5. Single-image Motion Deblurring comparisons on the GoPro testset [43]. + +
MethodDistortionPerceptual
PSNR ↑SSIM ↑LPIPS ↓FID ↓
MPRNet [71]32.660.9590.08920.18
MIMO-UNet+ [13]32.450.9570.09118.05
SAPHNet [56]31.890.9530.10119.06
Restomer [70]33.200.9630.08419.33
DvSR [60]30.660.9410.08412.20
DTPM-4 Step32.090.9320.08410.02
DTPM-10 Step31.820.9290.0777.52
DTPM-50 Step31.110.9190.0616.61
+ +Comparative Analysis of Raindrop Removal. As illustrated in Table 2, we can observe that various versions of DTPM have demonstrated outstanding performance in the task of image raindrop removal. In comparison to RainDropDiff, our approach has achieved superior performance, with the LPIPS metric significantly outperforming that of RainDropDiff. + +Comparative Analysis of Snow Removal. As shown in Table 1, we can observe that various versions of DTPM have demonstrated excellent performance in the task of image desnowing. In comparison to SnowDiff, our approach has achieved superior LPIPS metrics. + +# 5. Discussion and Analysis + +![](images/b03d82b2b1cde98a50a18d9125e4ac59bf42cb6a5455f84d9c92f6e030cb32bd.jpg) +Figure 8. Trade-off between PSNR and LPIPS in DTPM: This plot illustrates the inverse relationship between PSNR (pixel-wise distortion) and LPIPS (perceptual similarity) across various sampling steps, highlighting the equilibrium achieved between distortion and perceptual quality in our method. + +For the analysis of various aspects of our model, we perform our experiments on the image deraining& dehazing dataset as it's a more chanlenging settings than others. + +# 5.1. Sampling Steps and Distortion-Perceptual Trade-off + +In Figure 8, we evaluate the results of our DTPM through the lens of two critical image quality metrics: PSNR and LPIPS1. As the sampling steps increase, the PSNR values initially experience a precipitous drop, decreasing from just above 31 dB to below 30.70 dB by the 10th step. This substantial early decline indicates that sampling steps in the early phase degrade image fidelity. Beyond this point, the PSNR decline slows, entering a phase of more gradual descent before plateauing after the 30th step, suggesting that the method begins to stabilize in terms of distortion loss. In + +![](images/beb7c5736bb10db29209052a5ba7f16f6f1f6e6de0348c3046ee7a82301d684f.jpg) +Figure 9. The first row in the figure shows the images, while the second row shows zoomed-in details. From left to right, they are: (a) input image, (b) the output of the initial predictor, (c) the final result of our method, (d) the ground-truth. + +contrast, the LPIPS score improves markedly with each incremental sampling step, indicating that the perceived quality of the images is becoming more aligned with human visual perception. The steepness of the LPIPS improvement mirrors the PSNR decline, reflecting a pronounced trade-off between fidelity and perceptual quality up to the 10 step. After this inflection point, although the PSNR values level off, suggesting a saturation of fidelity loss, the LPIPS values continue to improve but at a diminished rate, plateauing around the 40 step. The intersecting trends of these metrics underscore a distinct trade-off: optimizing for perceptual likeness through more sampling steps comes at the expense of traditional fidelity measures. However, the stabilization of both metrics after a certain number of sampling steps suggests a convergence towards an equilibrium between the two qualities. + +# 5.2. Output of the Initial Predictor + +Given the significance of the initial predictor as a key component of our methodology, we have undertaken detailed explorations and analyses of it. Despite the absence of an explicit loss constraint in our initial predictor, it achieves results that closely resemble a clean background, as evidenced in Figure 9. The initial predictor, though not detailed in its finer aspects, effectively produces a reasonably clear image. This provides practical assurance for incorporating the output of the initial predictor as one of the enhanced, additional conditions for diffusion. + +# 5.3. More Ablation Studies + +In this section, we conduct ablation studies to analyze the impact of different design choices in our DTPM framework. w/o Stage I Training. This variant, absent the initial training phase, exhibits a decrease in both image reconstruction quality and perceptual similarity relative to the complete model. This underscores the significance of the early training stage in establishing baseline performance. + +w/o Initial Predictor: Removing the Initial Predictor results in a notable decline in both objective image quality and perceptual accuracy. This component's role is evidently + +Table 6. The ablation studies on Image Deraining&Dehazing dataset [48]. + +
ModelPSNR ↑LPIPS ↓
w/o Stage I Training28.900.074
w/o Initial Predictor26.910.079
w/o Semantic Code29.790.0653
Fine-tune Enc. w/o Adapters29.200.0667
Fine-tune Dec. w/o Adapters28.910.0691
Fine-tune Enc.&Dec. w/o Adapters29.130.0712
Ours(DTPM-4S)30.990.0635
+ +crucial for enhancing the clarity and fidelity of the images. w/o Semantic Code. The removal of the Semantic Code somewhat improves both image quality and perceptual similarity. This could suggest that the Semantic Code potentially adding informative features. + +Fine-tune Enc. w/o Adapters. Fine-tuning just the encoder of DTPM without adapters leads to a slight reduction in performance. This indicates that while the encoder is a robust component, the adapters contribute to optimizing its function. + +Fine-tune Dec. w/o Adapters. Solely fine-tuning the decoder of DTPM without adapters also reduces model efficacy. The adapters appear more integral for the decoder, possibly enabling more nuanced adjustments that refine results. + +Fine-tune Enc.&Dec. w/o Adapters. Fine-tuning both the encoder and decoder without adapters does not match the performance of the complete model. This suggests a complex interplay between these components that adapters help to fine-tune effectively. + +# 6. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 930-939, 2022. 2 \ No newline at end of file diff --git a/2024/Learning Diffusion Texture Priors for Image Restoration/images.zip b/2024/Learning Diffusion Texture Priors for Image Restoration/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..6cac15384d3c88f2dc827d7a5cda9ed6b6a44d7d --- /dev/null +++ b/2024/Learning Diffusion Texture Priors for Image Restoration/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:fdc5e82aa1f660ae6356f253c9a4685dc28107ffa35b0920d29796bb2f85f989 +size 622503 diff --git a/2024/Learning Diffusion Texture Priors for Image Restoration/layout.json b/2024/Learning Diffusion Texture Priors for Image Restoration/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..7673cf19fc248559a44bda278fb1db22c31508d1 --- /dev/null +++ b/2024/Learning Diffusion Texture Priors for Image Restoration/layout.json @@ -0,0 +1,10466 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 121, + 103, + 473, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 121, + 103, + 473, + 121 + ], + "spans": [ + { + "bbox": [ + 121, + 103, + 473, + 121 + ], + "type": "text", + "content": "Learning Diffusion Texture Priors for Image Restoration" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 176, + 142, + 433, + 172 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 176, + 142, + 433, + 172 + ], + "spans": [ + { + "bbox": [ + 176, + 142, + 433, + 172 + ], + "type": "text", + "content": "Tian Ye1 Sixiang Chen1 Wenhao Chai2 \nZhaohu Xing1 Jing Qin3 Ge Lin1,4 Lei Zhu1,4*" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 52, + 176, + 544, + 205 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 176, + 544, + 205 + ], + "spans": [ + { + "bbox": [ + 52, + 176, + 544, + 205 + ], + "type": "text", + "content": "1 The Hong Kong University of Science and Technology (Guangzhou) 2 University of Washington 3 The Hong Kong Polytechnic University 4 The Hong Kong University of Science and Technology" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 232, + 192, + 245 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 232, + 192, + 245 + ], + "spans": [ + { + "bbox": [ + 143, + 232, + 192, + 245 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 258, + 290, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 258, + 290, + 510 + ], + "spans": [ + { + "bbox": [ + 46, + 258, + 290, + 510 + ], + "type": "text", + "content": "Diffusion Models have shown remarkable performance in image generation tasks, which are capable of generating diverse and realistic image content. When adopting diffusion models for image restoration, the crucial challenge lies in how to preserve high-level image fidelity in the randomness diffusion process and generate accurate background structures and realistic texture details. In this paper, we propose a general framework and develop a Diffusion Texture Prior Model (DTPM) for image restoration tasks. DTPM explicitly models high-quality texture details through the diffusion process, rather than global contextual content. In phase one of the training stage, we pre-train DTPM on approximately 55K high-quality image samples, after which we freeze most of its parameters. In phase two, we insert conditional guidance adapters into DTPM and equip it with an initial predictor, thereby facilitating its rapid adaptation to downstream image restoration tasks. Our DTPM could mitigate the randomness of traditional diffusion models by utilizing encapsulated rich and diverse texture knowledge and background structural information provided by the initial predictor during the sampling process." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 532, + 128, + 544 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 532, + 128, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 532, + 128, + 544 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 552, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 552, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 552, + 287, + 696 + ], + "type": "text", + "content": "Image Restoration tasks [37, 43, 70, 71] usually are ill-posed problems whose solutions are not unique. While existing methods [8, 70, 71] have achieved notable breakthroughs, they typically employ direct regression models to produce deterministic results. A persistent challenge is that these deterministic models [4, 70, 71] frequently yield unsatisfactory fine-grained details (See Figure 2), as they are trained to minimize pixel-level error, aligning output with ground truth by Norm-based losses [30]. The emergence of Diffusion Models (DMs) [14, 16, 51, 55] has revolutionized image generation, yielding realistic images replete with fine details. This advancement motivates our investigation" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 307, + 230, + 545, + 283 + ], + "blocks": [ + { + "bbox": [ + 307, + 230, + 545, + 283 + ], + "lines": [ + { + "bbox": [ + 307, + 230, + 545, + 283 + ], + "spans": [ + { + "bbox": [ + 307, + 230, + 545, + 283 + ], + "type": "image", + "image_path": "781aa095d4079ac5ae97581877cbcb9d653fcc3c4053d8d4c2964451738cff4e.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 291, + 547, + 402 + ], + "lines": [ + { + "bbox": [ + 305, + 291, + 547, + 402 + ], + "spans": [ + { + "bbox": [ + 305, + 291, + 547, + 402 + ], + "type": "text", + "content": "Figure 1. We use a coefficient " + }, + { + "bbox": [ + 305, + 291, + 547, + 402 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 305, + 291, + 547, + 402 + ], + "type": "text", + "content": " ranging from 0.1 to 1 to control the intensity of texture removal. As " + }, + { + "bbox": [ + 305, + 291, + 547, + 402 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 305, + 291, + 547, + 402 + ], + "type": "text", + "content": " increases, leading to richer textures from left to right in the images, we can observe a corresponding improvement in the scores of no-reference image quality metrics, specifically NIQE [42] and CLIP-IQA+ [57]. Regarding the NIQE, lower scores indicate better quality, while for CLIP-IQA+, higher scores represent better visual quality. This indicates that the quality of the image's texture details have a significant impact on the visual perceptual quality of the image." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 425, + 546, + 473 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 425, + 546, + 473 + ], + "spans": [ + { + "bbox": [ + 304, + 425, + 546, + 473 + ], + "type": "text", + "content": "into diffusion-based methods for image restoration, aiming to leverage conditional DMs [17, 45, 51] to produce perceptually appealing results that closely mimic natural, clean images." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 474, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 547, + 715 + ], + "type": "text", + "content": "However, directly applying diffusion image generation techniques [44, 51, 55] to image restoration tasks is often impractical [36, 45]. The high content fidelity required in image restoration clashes with the stochastic nature of diffusion models [44, 55]. A plausible solution involves integrating physical degradation models [5, 69] with neural networks or crafting hand-designed priors [20, 47] to mitigate the inherent randomness of the diffusion paradigm. While several previous studies [17, 68, 69] have adopted this approach with success, they lack versatility and show limited generalization capability on real-world scenes, as physical degradation models do not fully encompass real-world degradation scenarios [4, 66, 67]. Additionally, the iterative nature and complexity of the denoising process in diffusion models necessitate extensive data and lengthy training cycles for effective learning. The challenges and limitations outlined above necessitate a rethinking of the use of the diffusion paradigm in image restoration: (i) To preserve high-level fidelity in restoration, we propose using a diffusion model to recover only texture layers. This" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 237, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 237, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 237, + 712 + ], + "type": "text", + "content": "*Lei Zhu (leizhu @ust.hk) is the corresponding author." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2524" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 70, + 286, + 213 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 286, + 213 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 286, + 213 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 286, + 213 + ], + "type": "image", + "image_path": "3f92d8270648f6da63a7b5d5b5eeee7ae0006c76e03e603395810731d8a14f81.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 222, + 289, + 312 + ], + "lines": [ + { + "bbox": [ + 46, + 222, + 289, + 312 + ], + "spans": [ + { + "bbox": [ + 46, + 222, + 289, + 312 + ], + "type": "text", + "content": "Figure 2. (a) The input degraded image. (b) The result of Restormer [70]. Restormer is a representative image restoration method that can only produce deterministic results, which may lack promising details. (c) The result of RainHazeDiff [45]. (d) The result of our method. The content within the dashed rectangle represents the corresponding ground-truth details. It's worth noting that our approach excels in generating finer details, thanks to the incorporation of Diffusion Texture Priors we proposed." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 355, + 289, + 619 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 355, + 289, + 619 + ], + "spans": [ + { + "bbox": [ + 46, + 355, + 289, + 619 + ], + "type": "text", + "content": "approach emphasizes and highlights the importance of fine textures in visual perception (See Figure 1). By focusing diffusion on texture recovery, we minimize randomness of diffusion process and leverage its strength in generating realistic details. (ii) Recognizing the diffusion paradigm as a potent representation learning tool that requires extensive data for convergence, we pre-trained our model, named the Diffusion Texture Priors Model (DTPM), on a large-scale dataset of high-quality images. This model, trained on approximately " + }, + { + "bbox": [ + 46, + 355, + 289, + 619 + ], + "type": "inline_equation", + "content": "55K" + }, + { + "bbox": [ + 46, + 355, + 289, + 619 + ], + "type": "text", + "content": " samples, is tailored to reconstruct texture layers, embedding texture priors within the diffusion process. Our DTPM framework is characterized by: (a) A novel approach in diffusion modeling that focuses on texture layers through residual learning, enhancing efficiency in downstream restoration tasks. (b) The incorporation of Semantic Code as a constraint, guiding the diffusion model to produce semantically coherent textures. (c) To preserve the integrity of the diffusion texture priors, most parameters of the DTPM remain fixed after pre-training. We introduce a Conditional Degradation Adapter to facilitate rapid adaptation to various restoration tasks without the risk of catastrophic forgetting." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 630, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 287, + 712 + ], + "type": "text", + "content": "Our extensive experiments across single-image defocus deblurring, image motion deblurring, desnowing, dehazing, deraining, and raindrop removal demonstrate that our method not only surpasses strong regression models and recent diffusion-based models in perceptual quality but also exhibits robust generalization across diverse restoration tasks." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 306, + 71, + 398, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 71, + 398, + 84 + ], + "spans": [ + { + "bbox": [ + 306, + 71, + 398, + 84 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 91, + 547, + 366 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 547, + 366 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 547, + 366 + ], + "type": "text", + "content": "Evolution in Image Restoration. Image restoration [4, 15, 19, 25, 39, 67, 71, 77], a pivotal research domain within the computer vision community, has witnessed significant evolution over recent years. Traditionally regarded as an ill-posed problem, image restoration poses unique challenges due to the multitude of potential solutions derivable from a single degraded image. Over the last decade, there has been a notable shift in the computer vision field from conventional, handcrafted prior-based approaches [20, 47] to a more data-centric, deep learning-driven paradigm [4, 15, 59, 70]. This transition has led to the development of advanced deep learning techniques, characterized by complicated network structures [65, 70, 71] and extensive training on carefully collected datasets. These approaches excel in learning mappings from degraded to clean data, effectively tackling the complexities of image restoration. Initially, deep learning methods [9-11, 66, 67] in this area tended to produce deterministic outcomes, which starkly contrasted with the fundamentally probabilistic nature of image restoration tasks [18, 46, 70]. This discrepancy has increasingly brought generative methods [17, 27, 46, 64, 76] to the forefront, highlighting their potential to address the challenges inherent in image restoration." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 367, + 547, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 367, + 547, + 629 + ], + "spans": [ + { + "bbox": [ + 304, + 367, + 547, + 629 + ], + "type": "text", + "content": "Generative image restoration methods. Recent developments [6, 7, 17, 41, 46, 61, 64, 74] have shed light on the fundamental flaws of earlier deep learning-driven image restoration techniques, specifically their (i) generate deterministic outputs and (ii) inability to restore high-quality, detailed textures, owing to their training focused on minimizing pixel-level discrepancies. Consequently, generative approaches are gaining traction. A notable strategy includes employing Generative Adversarial Networks (GANs) [24, 29, 48]. Nonetheless, GANs pose challenges due to their complex training procedures, instability during training, and occasional generation of unrealistic image attributes. The impressive efficacy of diffusion in image generation has introduced a promising avenue. Diffusion techniques adeptly tackle the aforementioned issues, offering a more stable training regimen and yielding images with realistic textures. Applications of diffusion-based methods in image super-resolution [52], shadow removal [17, 27], deblurring [60], and adverse weather removal [46] have shown promising results. However, there remains a need for comprehensive research to establish a consistent, reliable framework for diffusion-based image restoration tasks." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 639, + 406, + 651 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 639, + 406, + 651 + ], + "spans": [ + { + "bbox": [ + 306, + 639, + 406, + 651 + ], + "type": "text", + "content": "3. Our Framework" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 659, + 488, + 671 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 659, + 488, + 671 + ], + "spans": [ + { + "bbox": [ + 306, + 659, + 488, + 671 + ], + "type": "text", + "content": "3.1. Preliminaries of Diffusion Models" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 677, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 677, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 677, + 547, + 713 + ], + "type": "text", + "content": "Diffusion Models (DMs), as referenced in [22, 44], are a class of generative models that gradually infuse Gaussian noise into training data and then employ a denoiser to re" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 758 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 758 + ], + "type": "text", + "content": "2525" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 61, + 80, + 403, + 191 + ], + "blocks": [ + { + "bbox": [ + 61, + 70, + 311, + 80 + ], + "lines": [ + { + "bbox": [ + 61, + 70, + 311, + 80 + ], + "spans": [ + { + "bbox": [ + 61, + 70, + 311, + 80 + ], + "type": "text", + "content": "Stage I: Training a Conditional Diffusion Model for Learning Diffusion Texture Priors" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 61, + 80, + 403, + 191 + ], + "lines": [ + { + "bbox": [ + 61, + 80, + 403, + 191 + ], + "spans": [ + { + "bbox": [ + 61, + 80, + 403, + 191 + ], + "type": "image", + "image_path": "1ca2c6e856e568cb347f98748ff494c6b183fe6145607f3d565c8539886d4286.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 61, + 193, + 356, + 203 + ], + "lines": [ + { + "bbox": [ + 61, + 193, + 356, + 203 + ], + "spans": [ + { + "bbox": [ + 61, + 193, + 356, + 203 + ], + "type": "text", + "content": "Stage II : Fine-Tuning the Diffusion Model Using Task-Specific Adapters for Image Restoration Tasks" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 61, + 205, + 403, + 318 + ], + "blocks": [ + { + "bbox": [ + 61, + 205, + 403, + 318 + ], + "lines": [ + { + "bbox": [ + 61, + 205, + 403, + 318 + ], + "spans": [ + { + "bbox": [ + 61, + 205, + 403, + 318 + ], + "type": "image", + "image_path": "11c8daa8588a39eed54754f2b1bd7bd566a7a6ff575b540f208a1d713fb89827.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 187, + 319, + 268, + 326 + ], + "lines": [ + { + "bbox": [ + 187, + 319, + 268, + 326 + ], + "spans": [ + { + "bbox": [ + 187, + 319, + 268, + 326 + ], + "type": "text", + "content": "(a) Overview of Our Framework" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 336, + 547, + 392 + ], + "lines": [ + { + "bbox": [ + 46, + 336, + 547, + 392 + ], + "spans": [ + { + "bbox": [ + 46, + 336, + 547, + 392 + ], + "type": "text", + "content": "Figure 3. The overview of Our DTPM Framework. (a) Our method consists of two stages. In the stage I, under the guiding constraints of semantic code, the diffusion model learns texture layers through residual learning from a large amount of high-quality data, which allows us to encapsulate diverse and rich texture knowledge into the diffusion model. In the stage II, we fix most of the parameters of the trained diffusion model and insert Conditional Guidance Adapters between each layer for efficient fine-tuning and conditional guidance on image restoration tasks. (b) The overview of adapters and our denoising blocks.(c) The detailed design of our Conditional Guidance Adapter." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 403, + 80, + 533, + 186 + ], + "blocks": [ + { + "bbox": [ + 403, + 80, + 533, + 186 + ], + "lines": [ + { + "bbox": [ + 403, + 80, + 533, + 186 + ], + "spans": [ + { + "bbox": [ + 403, + 80, + 533, + 186 + ], + "type": "image", + "image_path": "05bfec54f6d459768c6ca926c6152f54593948e735990833fbea0ded42544941.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 415, + 187, + 533, + 194 + ], + "lines": [ + { + "bbox": [ + 415, + 187, + 533, + 194 + ], + "spans": [ + { + "bbox": [ + 415, + 187, + 533, + 194 + ], + "type": "text", + "content": "(b) Overview of Adapters and Denoising Blocks" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 419, + 198, + 526, + 316 + ], + "blocks": [ + { + "bbox": [ + 419, + 198, + 526, + 316 + ], + "lines": [ + { + "bbox": [ + 419, + 198, + 526, + 316 + ], + "spans": [ + { + "bbox": [ + 419, + 198, + 526, + 316 + ], + "type": "image", + "image_path": "802dacdd17a51cd338b9bb662b8ce78e58e3052c0b995ed718940b45a131ec6c.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 422, + 318, + 505, + 325 + ], + "lines": [ + { + "bbox": [ + 422, + 318, + 505, + 325 + ], + "spans": [ + { + "bbox": [ + 422, + 318, + 505, + 325 + ], + "type": "text", + "content": "(c) Conditional Guidance Adapter" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "spans": [ + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "type": "text", + "content": "verse this noise addition. The process begins with the diffusion phase, where an initial image " + }, + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "type": "inline_equation", + "content": "\\pmb{x}_0" + }, + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "type": "text", + "content": " evolves into Gaussian noise " + }, + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "type": "inline_equation", + "content": "\\pmb{x}_T \\sim \\mathcal{N}(0,1)" + }, + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "type": "text", + "content": " through " + }, + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 412, + 287, + 460 + ], + "type": "text", + "content": " steps. Each step of this transformation is governed by:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 72, + 469, + 287, + 490 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 72, + 469, + 287, + 490 + ], + "spans": [ + { + "bbox": [ + 72, + 469, + 287, + 490 + ], + "type": "interline_equation", + "content": "q \\left(\\boldsymbol {x} _ {t} \\mid \\boldsymbol {x} _ {t - 1}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t}; \\sqrt {1 - \\beta_ {t}} \\boldsymbol {x} _ {t - 1}, \\beta_ {t} \\boldsymbol {I}\\right), \\tag {1}", + "image_path": "ce57160d32d97f460aa9d7fc23a95d6bc9a1ddf980d0bdebe12facb8385ffb45.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "spans": [ + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "inline_equation", + "content": "\\pmb{x}_t" + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "text", + "content": " is the image with noise at step " + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "inline_equation", + "content": "\\beta_t" + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "text", + "content": " is a fixed scaling factor, and " + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "inline_equation", + "content": "\\mathcal{N}" + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "text", + "content": " denotes the Gaussian distribution. Introducing " + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "inline_equation", + "content": "\\alpha_t = 1 - \\beta_t" + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "inline_equation", + "content": "\\bar{\\alpha}_t = \\prod_{i=0}^t \\alpha_i" + }, + { + "bbox": [ + 46, + 497, + 287, + 543 + ], + "type": "text", + "content": " simplifies Eq.1 to:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 80, + 544, + 287, + 559 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 80, + 544, + 287, + 559 + ], + "spans": [ + { + "bbox": [ + 80, + 544, + 287, + 559 + ], + "type": "interline_equation", + "content": "q \\left(\\boldsymbol {x} _ {t} \\mid \\boldsymbol {x} _ {0}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t}; \\sqrt {\\bar {\\alpha} _ {t}} \\boldsymbol {x} _ {0}, (1 - \\bar {\\alpha} _ {t}) \\boldsymbol {I}\\right), \\tag {2}", + "image_path": "634c6924fae9a5bcde3d115c56d1503da764df14fa78a38d4a17368b2b4962f7.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 563, + 287, + 599 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 563, + 287, + 599 + ], + "spans": [ + { + "bbox": [ + 46, + 563, + 287, + 599 + ], + "type": "text", + "content": "During the inference stage's reverse process, DMs initiate with a random Gaussian noise map " + }, + { + "bbox": [ + 46, + 563, + 287, + 599 + ], + "type": "inline_equation", + "content": "\\boldsymbol{x}_T" + }, + { + "bbox": [ + 46, + 563, + 287, + 599 + ], + "type": "text", + "content": " and progressively denoise it to reach the refined output " + }, + { + "bbox": [ + 46, + 563, + 287, + 599 + ], + "type": "inline_equation", + "content": "\\boldsymbol{x}_0" + }, + { + "bbox": [ + 46, + 563, + 287, + 599 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 61, + 608, + 287, + 622 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 608, + 287, + 622 + ], + "spans": [ + { + "bbox": [ + 61, + 608, + 287, + 622 + ], + "type": "interline_equation", + "content": "p \\left(\\boldsymbol {x} _ {t - 1} \\mid \\boldsymbol {x} _ {t}, \\boldsymbol {x} _ {0}\\right) = \\mathcal {N} \\left(\\boldsymbol {x} _ {t - 1}; \\boldsymbol {\\mu} _ {t} \\left(\\boldsymbol {x} _ {t}, \\boldsymbol {x} _ {0}\\right), \\sigma_ {t} ^ {2} \\boldsymbol {I}\\right), \\tag {3}", + "image_path": "d1ddba95a6a8b5a9f2cde2210d7b5787694d08c20728811e358b6c755f99da99.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "spans": [ + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "text", + "content": "where the mean " + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "inline_equation", + "content": "\\pmb{\\mu}_t(\\pmb{x}_t,\\pmb{x}_0) = \\frac{1}{\\sqrt{\\alpha_t}}\\left(\\pmb{x}_t - \\epsilon \\frac{1 - \\alpha_t}{\\sqrt{1 - \\bar{\\alpha}_t}}\\right)" + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "text", + "content": " and the variance " + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "inline_equation", + "content": "\\sigma_t^2 = \\frac{1 - \\bar{\\alpha}_{t-1}}{1 - \\bar{\\alpha}_t} \\beta_t" + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 47, + 671, + 225, + 683 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 671, + 225, + 683 + ], + "spans": [ + { + "bbox": [ + 47, + 671, + 225, + 683 + ], + "type": "text", + "content": "3.2. Overview of DTP-IR Framework" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "type": "text", + "content": "Our aim is to create a unified framework for image restoration tasks based on our Diffusion Texture Priors. As shown" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 412, + 545, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 412, + 545, + 496 + ], + "spans": [ + { + "bbox": [ + 304, + 412, + 545, + 496 + ], + "type": "text", + "content": "in Figure 3, our DTPM framework comprises two stages: In Stage 1, we train a conditional diffusion model with semantic latent feature constraints using a large dataset of high-resolution, high-quality natural images. During Stage 2, we incorporate conditional guidance adapters into the conditional diffusion model to facilitate the model's adaptation to downstream image restoration tasks." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 502, + 528, + 514 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 502, + 528, + 514 + ], + "spans": [ + { + "bbox": [ + 305, + 502, + 528, + 514 + ], + "type": "text", + "content": "3.3. Stage I: Learning Diffusion Texture Priors" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 520, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 520, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 520, + 545, + 581 + ], + "type": "text", + "content": "In this section, we will first briefly introduce the core motivation of our Diffusion Texture Priors, followed by the basic structure information of the diffusion model and the semantic code. Finally, we will discuss the training objective and training data." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 594, + 546, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 546, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 546, + 715 + ], + "type": "text", + "content": "Motivation. Recent studies [52, 64, 74] have highlighted the pivotal role of texture quality in shaping subjective visual perception in the realm of image restoration. Traditional methodologies, however, encounter substantial difficulties in accurately restoring fine-grained textural details, which are crucial for realistic image reconstruction. While diffusion models have demonstrated excellence in generating lifelike images, their direct application to image restoration tasks has been less than ideal, yielding mediocre results. Our approach seeks to remedy this by integrating" + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2526" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 83, + 72, + 252, + 214 + ], + "blocks": [ + { + "bbox": [ + 83, + 72, + 252, + 214 + ], + "lines": [ + { + "bbox": [ + 83, + 72, + 252, + 214 + ], + "spans": [ + { + "bbox": [ + 83, + 72, + 252, + 214 + ], + "type": "image", + "image_path": "40be511639af5b759f78a8e90a9ef190a6dbea6e084547e99daa0cad713d4dc4.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "lines": [ + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "spans": [ + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "text", + "content": "Figure 4. The architecture of our fundamental denoising block incorporates \"Channel Attention\" (CA) and \"SimpleGate,\" a straightforward feature gating mechanism introduced by Chen et al.[8]. The current timestep " + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "text", + "content": " is injected into the block with Adaptive Layer Normalization [3] (AdaLN), i.e., " + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "inline_equation", + "content": "AdaLN(f_{in} = \\gamma LayerNorm(f_{in}) + \\beta" + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "inline_equation", + "content": "f_{in}" + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "text", + "content": " is the input features, " + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "text", + "content": " are converted from the timestep embedding. The \"Shift&Scale\" block means shift and scale features by generated " + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "inline_equation", + "content": "\\gamma, \\beta" + }, + { + "bbox": [ + 46, + 224, + 288, + 313 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 334, + 287, + 453 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 334, + 287, + 453 + ], + "spans": [ + { + "bbox": [ + 46, + 334, + 287, + 453 + ], + "type": "text", + "content": "texture-specific priors into the diffusion model. This integration enables the diffusion model to specifically concentrate on reconstructing textures, as opposed to merely focusing on degradation elimination. Such a strategy leverages the diffusion model's inherent strengths and mitigates its weaknesses, allowing us to exploit a vast repository of high-quality natural images for prior knowledge. This method not only significantly enhances the model's generalization capabilities but also markedly improves the efficiency of the sampling process." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "spans": [ + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "type": "text", + "content": "Basic Denoising Block. We have engineered a denoising block based on NAFNet [8] block, designed to enhance model adaptability for a broad spectrum of natural image content. This block aims to balance peak model performance with reduced computational demands and easy-to-handle varying input resolutions. As delineated in Figure 4, our denoising block capitalizes on depth-wise convolution as its cornerstone, complemented by several " + }, + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "type": "inline_equation", + "content": "1 \\times 1" + }, + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "type": "text", + "content": " convolution layers and LayerNorm [3], to facilitate efficient denoising. To incorporate the time condition, we utilize MLPs for transforming the time embedding into channel-specific scale and shift parameters. Additionally, to maintain the semantic consistency between " + }, + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "type": "inline_equation", + "content": "x_0" + }, + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "type": "inline_equation", + "content": "y_s" + }, + { + "bbox": [ + 46, + 469, + 287, + 650 + ], + "type": "text", + "content": ", we integrate an MLP layer for semantic condition, which amalgamates semantic code as a pivotal conditioning factor." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "type": "text", + "content": "Semantic code. To enable the diffusion model to produce realistically textured details, we utilize a pre-trained ResNet-18 [21] for extracting semantic embeddings as a global semantic code, which is then integrated into each de" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": "noising block as shown in Figure 4. This approach of employing semantic code imposes robust semantic constraints, rather than solely depending on adjacent context information, allowing our model to generate textures in alignment with the contextual semantics. Consequently, this ensures high-fidelity results of our diffusion model." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 159, + 545, + 208 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 159, + 545, + 208 + ], + "spans": [ + { + "bbox": [ + 304, + 159, + 545, + 208 + ], + "type": "text", + "content": "Training objective. To prioritize texture reconstruction over content of the image, our diffusion model is designed to capture the residual distribution of " + }, + { + "bbox": [ + 304, + 159, + 545, + 208 + ], + "type": "inline_equation", + "content": "y_{s}" + }, + { + "bbox": [ + 304, + 159, + 545, + 208 + ], + "type": "text", + "content": ". The training objective for Stage I is thus defined as: " + }, + { + "bbox": [ + 304, + 159, + 545, + 208 + ], + "type": "inline_equation", + "content": "L_{\\mathrm{StageI}}(\\theta) =" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 321, + 224, + 545, + 266 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 321, + 224, + 545, + 266 + ], + "spans": [ + { + "bbox": [ + 321, + 224, + 545, + 266 + ], + "type": "interline_equation", + "content": "\\mathbb {E} \\left\\| \\boldsymbol {\\epsilon} - f _ {\\theta} \\left(\\sqrt {\\gamma} \\left(\\underbrace {\\boldsymbol {x} _ {g} - \\boldsymbol {y} _ {s}} _ {\\text {r e s i d u a l}}\\right) + \\sqrt {1 - \\gamma} \\boldsymbol {\\epsilon}, \\boldsymbol {y} _ {s}, \\gamma\\right) \\right\\|, \\tag {4}", + "image_path": "a3efa159588c7b9e0205ac95fc606925e0c1aebe08a468bfb09f229eadbadc61.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "spans": [ + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "text", + "content": "here, " + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "inline_equation", + "content": "\\epsilon \\sim \\mathcal{N}(0,I)" + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "text", + "content": " represents the noise vector, and " + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "inline_equation", + "content": "f_{\\theta}" + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "text", + "content": " is our diffusion model. The term " + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "inline_equation", + "content": "\\gamma \\sim p(\\gamma)" + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "text", + "content": " denotes a distribution associated with the noise schedule. In this context, " + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "inline_equation", + "content": "x_{g}" + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "text", + "content": " symbolizes the high-quality input image, whereas " + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "inline_equation", + "content": "y_{s}" + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "text", + "content": " denotes its corresponding smoothed image. " + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "inline_equation", + "content": "y_{s}" + }, + { + "bbox": [ + 304, + 274, + 545, + 369 + ], + "type": "text", + "content": " is obtained by utilizing an edge-preserving smoothing method [63] to eliminate a majority of the texture while retaining the contextual content." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 384, + 545, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 384, + 545, + 494 + ], + "spans": [ + { + "bbox": [ + 304, + 384, + 545, + 494 + ], + "type": "text", + "content": "Training data for Stage I. Inspired by previous codebook prior-based image restoration studies [61, 64, 74], our training stage I employs high-quality images from the widely-recognized DIV2K [2] and Flickr2K [35] datasets. Each image is cropped into multiple patches of " + }, + { + "bbox": [ + 304, + 384, + 545, + 494 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 304, + 384, + 545, + 494 + ], + "type": "text", + "content": " resolution, followed by an edge-preserved smooth method [63] to diminish textural details. This process results in a training dataset comprising 55,558 paired instances " + }, + { + "bbox": [ + 304, + 384, + 545, + 494 + ], + "type": "inline_equation", + "content": "(x_{g}, y_{s})" + }, + { + "bbox": [ + 304, + 384, + 545, + 494 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 500, + 545, + 525 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 500, + 545, + 525 + ], + "spans": [ + { + "bbox": [ + 306, + 500, + 545, + 525 + ], + "type": "text", + "content": "3.4. Stage II: Finetuning Diffusion Texture Priors Model with Adapters" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 530, + 545, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 530, + 545, + 579 + ], + "spans": [ + { + "bbox": [ + 304, + 530, + 545, + 579 + ], + "type": "text", + "content": "This section describes the initial predictor and the Conditional Guidance Adapter, along with the rationale behind their integration. We also detail the architecture of the adapters. Finally, the training objectives are outlined." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 594, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 712 + ], + "type": "text", + "content": "Initial Predictor. In the pursuit of augmenting the diffusion model's adaptability for downstream tasks in its second stage (see Figure 3), we draw from the DvSR, integrating a compact and lightweight U-Net to generate an initial output. This initial step efficiently seizes deterministic components of the ultimate restored image, crucial for capturing essential structural information. Moreover, this initial output serves as a pivotal guiding element for the diffusion model, forming an effective complement with our Diffusion Texture Priors Model." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2527" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 91, + 261, + 223 + ], + "blocks": [ + { + "bbox": [ + 105, + 71, + 201, + 82 + ], + "lines": [ + { + "bbox": [ + 105, + 71, + 201, + 82 + ], + "spans": [ + { + "bbox": [ + 105, + 71, + 201, + 82 + ], + "type": "text", + "content": "Table 1. Image Desnowing." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 51, + 91, + 261, + 223 + ], + "lines": [ + { + "bbox": [ + 51, + 91, + 261, + 223 + ], + "spans": [ + { + "bbox": [ + 51, + 91, + 261, + 223 + ], + "type": "table", + "html": "
MethodSnow100K-S [40]Snow100K-L [40]
PSNR ↑SSIM ↑LPIPS ↓PSNR ↑SSIM ↑LPIPS ↓
SPANet [58]29.920.82600.10423.700.79300.210
JSTASR [12]31.400.90120.05925.320.80760.152
RESCAN [34]31.510.90320.05426.080.81080.106
DesnowNet [40]32.330.95000.07027.170.89830.101
DDMSNet [72]34.340.94450.05828.850.87720.098
MPRNet [71]34.970.94570.04929.760.89490.091
NAFNet [8]34.790.94970.05130.060.90170.086
Restormer [70]35.030.94870.04730.520.90920.083
SnowDiff64[45]36.590.96260.03530.430.91450.069
SnowrDiff128[45]36.090.95450.03830.280.90000.067
DTPM-4 Step37.010.96630.03430.920.91740.063
DTPM-10 Step36.440.95210.03330.320.90240.055
DTPM-50 Step36.190.94830.02930.020.89010.053
", + "image_path": "24e4896b11788f1f78fb7428b9e1dbcc93feff0b3ec6b2ba9a09c515b7da31cb.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 264, + 91, + 403, + 222 + ], + "blocks": [ + { + "bbox": [ + 261, + 71, + 396, + 82 + ], + "lines": [ + { + "bbox": [ + 261, + 71, + 396, + 82 + ], + "spans": [ + { + "bbox": [ + 261, + 71, + 396, + 82 + ], + "type": "text", + "content": "Table 2. Image Deraining & Dehazing." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 264, + 91, + 403, + 222 + ], + "lines": [ + { + "bbox": [ + 264, + 91, + 403, + 222 + ], + "spans": [ + { + "bbox": [ + 264, + 91, + 403, + 222 + ], + "type": "table", + "html": "
MethodOutdoor-Rain [33]
PSNR ↑SSIM ↑LPIPS ↓
CycleGAN [75]17.620.6560-
pix2pix [23]19.090.7100-
HRGAN [33]21.560.85500.154
PCNet [26]26.190.90150.132
MPRNet [71]28.030.91920.089
NAFNet [8]29.590.90270.085
Restormer [70]29.970.92150.074
RainHazeDiff64[45]28.380.93200.067
RainHazeDiff128[45]26.840.91520.071
DTPM-4 Step30.990.9340.0635
DTPM-10 Step30.920.9320.0617
DTPM-50 Step30.480.9210.0540
", + "image_path": "6f10136cc3c0251bfd387dd602cb26125daef5fbf5ef06f4b793eb526223ecd8.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "type": "table", + "bbox": [ + 405, + 94, + 544, + 220 + ], + "blocks": [ + { + "bbox": [ + 418, + 75, + 526, + 86 + ], + "lines": [ + { + "bbox": [ + 418, + 75, + 526, + 86 + ], + "spans": [ + { + "bbox": [ + 418, + 75, + 526, + 86 + ], + "type": "text", + "content": "Table 3. Removing Raindrops." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 405, + 94, + 544, + 220 + ], + "lines": [ + { + "bbox": [ + 405, + 94, + 544, + 220 + ], + "spans": [ + { + "bbox": [ + 405, + 94, + 544, + 220 + ], + "type": "table", + "html": "
MethodRainDrop [48]
PSNR ↑SSIM ↑LPIPS ↓
pix2pix [23]28.020.8547-
DuRN [38]31.240.9259-
RaindropAttn [50]31.440.92630.068
AttentiveGAN [48]31.590.91700.055
CCN [49]31.340.92860.066
IDT [62]31.870.93130.059
RainDropDiff64[45]32.290.94220.058
RainDropDiff128[45]32.430.93340.058
DTPM-4 Step32.720.94400.0577
DTPM-10 Step31.840.93700.0477
DTPM-50 Step31.440.93200.0439
", + "image_path": "67f6b786ce089cad0797abd47de17e4bc7775d92af469b806a462653f3dbd1a1.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_body" + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 243, + 289, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 243, + 289, + 460 + ], + "spans": [ + { + "bbox": [ + 46, + 243, + 289, + 460 + ], + "type": "text", + "content": "Conditional Guidance Adapter. DPTM encapsulates rich and diverse prior knowledge. We hope that DPTM can fully utilize this knowledge in adapting to downstream image restoration tasks, rather than forgetting it. Therefore, we freeze most of the parameters in DPTM and introduce a flexible and parameter-efficient adaptation mechanism through the Conditional Guidance Adapter as shown in Figure 3 (b) and (c). The design of the Conditional Guidance Adapter brings two benefits: (i) Parameter-efficient learning. Since most of the parameters of DPTM have been sufficiently trained, our model will converge faster and better on downstream tasks after introducing the adapter. (ii) Introducing additional conditions. Introduction of coarse structural information output by the initial predictor, providing the model with more flexible conditional information, thereby producing texture details that better align with expectations. Our Conditional Guidance Adapter could be formally written as:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 474, + 287, + 498 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 474, + 287, + 498 + ], + "spans": [ + { + "bbox": [ + 47, + 474, + 287, + 498 + ], + "type": "interline_equation", + "content": "\\operatorname {C G - A d p a t e r} \\left(f _ {i n}, y _ {\\epsilon}\\right) = f _ {i n} + \\mathbf {M} _ {\\text {o u t}} \\left(\\mathbf {M} _ {i n} \\left(f _ {i n}\\right) + \\operatorname {C o n v} \\left(y _ {\\epsilon}\\right)\\right), \\tag {5}", + "image_path": "90c16c8f50a6683866e573e7da9fbb101cd13f93e2028c23df43452266a35fdc.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "spans": [ + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "inline_equation", + "content": "\\mathbf{M}" + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "content": " denotes an MLP layer to scale the dimension " + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "content": " of the input feature " + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "inline_equation", + "content": "f_{in}^{c}" + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "content": " to dimension " + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "inline_equation", + "content": "r\\times c" + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "inline_equation", + "content": "y_{\\epsilon}" + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "content": " denotes the output of initial predictor " + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "inline_equation", + "content": "\\epsilon_{\\theta}" + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "content": ", thus " + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "inline_equation", + "content": "y_{\\epsilon} = \\epsilon_{\\theta}(y_d)" + }, + { + "bbox": [ + 46, + 499, + 287, + 536 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 567, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 567, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 567, + 287, + 593 + ], + "type": "text", + "content": "Training objective. The training objective for Stage II is defined as: " + }, + { + "bbox": [ + 46, + 567, + 287, + 593 + ], + "type": "inline_equation", + "content": "L_{\\mathrm{StageII}}(\\theta) =" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 61, + 620, + 287, + 640 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 620, + 287, + 640 + ], + "spans": [ + { + "bbox": [ + 61, + 620, + 287, + 640 + ], + "type": "interline_equation", + "content": "\\mathbb {E} \\left\\| \\boldsymbol {\\epsilon} - f _ {\\theta} \\left(\\sqrt {\\gamma} \\left(\\boldsymbol {y} _ {g} - \\epsilon_ {\\theta} (\\boldsymbol {y} _ {d})\\right) + \\sqrt {1 - \\gamma} \\boldsymbol {\\epsilon}, \\boldsymbol {y} _ {d}, \\gamma\\right) \\right\\|. \\tag {6}", + "image_path": "801bd5645e9d3449cee2b942ee016c6ee4687186a5f7c61f6478499578566066.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\epsilon_{\\theta}" + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "text", + "content": " represents the initial predictor, illustrated in Figure 3. It is important to note that " + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\epsilon_{\\theta}" + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "text", + "content": " does not necessitate additional supervisory loss or pre-training. This is because the gradient from the aforementioned loss propagates through " + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "inline_equation", + "content": "f_{\\theta}" + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "text", + "content": " and subsequently influences " + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\epsilon_{\\theta}" + }, + { + "bbox": [ + 47, + 653, + 288, + 715 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 242, + 387, + 255 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 242, + 387, + 255 + ], + "spans": [ + { + "bbox": [ + 306, + 242, + 387, + 255 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 262, + 365, + 275 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 262, + 365, + 275 + ], + "spans": [ + { + "bbox": [ + 306, + 262, + 365, + 275 + ], + "type": "text", + "content": "4.1. Settings" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 281, + 545, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 281, + 545, + 365 + ], + "spans": [ + { + "bbox": [ + 304, + 281, + 545, + 365 + ], + "type": "text", + "content": "Our method is assessed on five specific image restoration tasks: image motion deblurring, single-image defocus deblurring, image deraining&dehazing, image desnowing, and image raindrop removal. In the initial stage, we develop a comprehensive Diffusion Texture Prior model, and in the subsequent stage, we fine-tune individual full models tailored to each task." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 384, + 546, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 384, + 546, + 598 + ], + "spans": [ + { + "bbox": [ + 304, + 384, + 546, + 598 + ], + "type": "text", + "content": "Datasets&Metrics. The GoPro dataset [43], as recommended by DvSR [60], is utilized for training and testing in the domain of image motion deblurring. Adhering to Restormer's approach [70], the DPDD dataset [1] is employed for single-image defocus deblurring. For image desnowing, we align with WeatherDiff [45] using the Snow100K dataset [40]. The Outdoor-Rain dataset [33] is used for image deraining&dehazing, following WeatherDiff [45]. Lastly, for single image raindrop removal, we adopt the practices from IDT [62] and WeatherDiff [45], employing the Raindrop dataset [48] for training and testing. We utilize PSNR, SSIM, and MAE as metrics for distortion-based image quality assessment, complemented by LPIPS [73] and FID for evaluating perceptual image quality. Adhering to the methodology outlined in Whang et al. [60], we extract image patches and compute FID at the patch level to ensure more consistent and reliable evaluation results." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": "Training Details We implemented our DTPM using the Pytorch framework, leveraging four NVIDIA RTX 4090 GPUs. Training encompasses two stages: Stage I with 800K iterations and Stage II with 600K iterations. We employed the Adam optimizer, setting momentum values at 0.9 and 0.999. The initial learning rate was established at " + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "inline_equation", + "content": "1.5 \\times 10^{-4}" + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": ", employing a cosine annealing strategy for gradual learning rate reduction. 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Image deraining&dehazing visual comparison on the Ourdoor-Rain dataset [48]. Our DTPM method generates rain-free and haze-free image with better details and without artifacts. 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Single-image motion deblurring comparison on the GoPro Dataset [43]. Compared to the other methods, our DTPM more effectively removes blur and preserving better structural information. 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Input data consistently utilized " + }, + { + "bbox": [ + 46, + 426, + 287, + 534 + ], + "type": "inline_equation", + "content": "256 \\times 256" + }, + { + "bbox": [ + 46, + 426, + 287, + 534 + ], + "type": "text", + "content": " cropped patches. Data augmentation techniques, including horizontal flipping and random image rotation at " + }, + { + "bbox": [ + 46, + 426, + 287, + 534 + ], + "type": "inline_equation", + "content": "45^{\\circ}" + }, + { + "bbox": [ + 46, + 426, + 287, + 534 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 426, + 287, + 534 + ], + "type": "inline_equation", + "content": "90^{\\circ}" + }, + { + "bbox": [ + 46, + 426, + 287, + 534 + ], + "type": "text", + "content": ", were applied during training. We utilize Denoising Diffusion Implicit Models (DDIM) [55] to implement our diffusion model, thereby significantly enhancing our sampling speed." + } + ] + } + ], + "index": 38 + }, + { + "bbox": [ + 47, + 558, + 132, + 569 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 558, + 132, + 569 + ], + "spans": [ + { + "bbox": [ + 47, + 558, + 132, + 569 + ], + "type": "text", + "content": "4.2. Main Results" + } + ] + } + ], + "index": 39 + }, + { + "bbox": [ + 46, + 582, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 287, + 713 + ], + "type": "text", + "content": "Comparative Analysis of Deraining&Dehazing. As shown in Table 1 in outdoor hazy and rainy image restoration, DTPM's 4 Step variant outperforms RainHazeDiff's 25-step process, achieving higher PSNR (30.99), SSIM (0.934), and lower LPIPS (0.0635). DTPM demonstrates superior perceptual quality enhancement, as indicated by its LPIPS and PSNR metrics. The DTPM-10 and DTPM-50 Step versions further reduce LPIPS to 0.0617 and 0.0540, respectively, while maintaining high SSIM, establishing DTPM's methodological advantage and benchmark in high-fidelity restoration." + } + ] + } + ], + "index": 40 + }, + { + "bbox": [ + 304, + 426, + 545, + 535 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 545, + 535 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 545, + 535 + ], + "type": "text", + "content": "Comparative Analysis of Single-image Defocus Deblurring. DTPM markedly outperforms other methods in defocus deblurring on the DPDD dataset as shown in Table 4, with its 4 Step iteration achieving high LPIPS (0.153) and SSIM (0.823) scores, thus maintaining image structural integrity. The DTPM-50 Step model further enhances perceived quality, achieving an LPIPS of 0.139, closely resembling ground truth. Visual evidence in Figure 7 corroborates DTPM's superior detail recovery and structural fidelity." + } + ] + } + ], + "index": 41 + }, + { + "bbox": [ + 304, + 570, + 546, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 546, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 546, + 714 + ], + "type": "text", + "content": "Concise Analysis of DTPM in Single-image Motion Deblurring. As shown in Table 5, on the GoPro dataset, the DTPM 4 Step variant achieves a PSNR of 32.09, SSIM of 0.932, LPIPS of 0.084, and FID of 10.02, demonstrating a balance in distortion reduction and perceptual quality. The 10 Step version improves these metrics, with an LPIPS of 0.081 and a leading FID of 8.52, despite slight decreases in PSNR and SSIM. The DTPM-50 Step variant, achieving the best perceptual outcomes with the lowest LPIPS (0.073) and FID (7.69), slightly reduces PSNR to 31.11 and SSIM to 0.919, illustrating our method's ability to the best perceptual quality." + } + ] + } + ], + "index": 42 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "2529" + } + ] + } + ], + "index": 43 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 73, + 69, + 231, + 194 + ], + "blocks": [ + { + "bbox": [ + 73, + 69, + 231, + 194 + ], + "lines": [ + { + "bbox": [ + 73, + 69, + 231, + 194 + ], + "spans": [ + { + "bbox": [ + 73, + 69, + 231, + 194 + ], + "type": "image", + "image_path": "07e84e3285fc2a450fb70d1433d9eb6c296a706a5023bccab4e159456d71121c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 123, + 195, + 169, + 205 + ], + "lines": [ + { + "bbox": [ + 123, + 195, + 169, + 205 + ], + "spans": [ + { + "bbox": [ + 123, + 195, + 169, + 205 + ], + "type": "text", + "content": "Blurry Image" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 232, + 69, + 302, + 129 + ], + "blocks": [ + { + "bbox": [ + 232, + 69, + 302, + 129 + ], + "lines": [ + { + "bbox": [ + 232, + 69, + 302, + 129 + ], + "spans": [ + { + "bbox": [ + 232, + 69, + 302, + 129 + ], + "type": "image", + "image_path": "ee912a339bdb550112114fcd75486ae0b4b8f11ba729608bb1befc552ef0bf46.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 233, + 137, + 301, + 195 + ], + "blocks": [ + { + "bbox": [ + 250, + 130, + 284, + 137 + ], + "lines": [ + { + "bbox": [ + 250, + 130, + 284, + 137 + ], + "spans": [ + { + "bbox": [ + 250, + 130, + 284, + 137 + ], + "type": "text", + "content": "Reference" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 233, + 137, + 301, + 195 + ], + "lines": [ + { + "bbox": [ + 233, + 137, + 301, + 195 + ], + "spans": [ + { + "bbox": [ + 233, + 137, + 301, + 195 + ], + "type": "image", + "image_path": "7a29ca79de64466ff4b9a24b0e989d75050e8583ec53a0cec27aac496d0865a4.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 260, + 196, + 279, + 204 + ], + "lines": [ + { + "bbox": [ + 260, + 196, + 279, + 204 + ], + "spans": [ + { + "bbox": [ + 260, + 196, + 279, + 204 + ], + "type": "text", + "content": "IFAN" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 217, + 545, + 239 + ], + "lines": [ + { + "bbox": [ + 46, + 217, + 545, + 239 + ], + "spans": [ + { + "bbox": [ + 46, + 217, + 545, + 239 + ], + "type": "text", + "content": "Figure 7. Single-image defocus deblurring results on the DPDD dataset [1]. The \"-4s\" and \"-50s\" denotes our DTPM method with a DDIM sampling schedule of 4 steps and 50 steps. Compared to the other approaches, our DTPM generate better structures and details." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 303, + 70, + 372, + 129 + ], + "blocks": [ + { + "bbox": [ + 303, + 70, + 372, + 129 + ], + "lines": [ + { + "bbox": [ + 303, + 70, + 372, + 129 + ], + "spans": [ + { + "bbox": [ + 303, + 70, + 372, + 129 + ], + "type": "image", + "image_path": "9f9a3fc9441af6d557af4ddb109549332af74918d3d267a4e2f438bf3077ffa7.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 304, + 137, + 372, + 195 + ], + "blocks": [ + { + "bbox": [ + 328, + 130, + 351, + 137 + ], + "lines": [ + { + "bbox": [ + 328, + 130, + 351, + 137 + ], + "spans": [ + { + "bbox": [ + 328, + 130, + 351, + 137 + ], + "type": "text", + "content": "Blurry" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 137, + 372, + 195 + ], + "lines": [ + { + "bbox": [ + 304, + 137, + 372, + 195 + ], + "spans": [ + { + "bbox": [ + 304, + 137, + 372, + 195 + ], + "type": "image", + "image_path": "fa54b16391c1285535ced3e010da9e5e96d711626fa0d25cc773dd866f084c05.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 324, + 197, + 361, + 205 + ], + "lines": [ + { + "bbox": [ + 324, + 197, + 361, + 205 + ], + "spans": [ + { + "bbox": [ + 324, + 197, + 361, + 205 + ], + "type": "text", + "content": "Restomer" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 377, + 70, + 446, + 129 + ], + "blocks": [ + { + "bbox": [ + 377, + 70, + 446, + 129 + ], + "lines": [ + { + "bbox": [ + 377, + 70, + 446, + 129 + ], + "spans": [ + { + "bbox": [ + 377, + 70, + 446, + 129 + ], + "type": "image", + "image_path": "854b1d919072b917f29d1c57572f632ee0775b232b734dd20a96df895b42e799.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 377, + 137, + 445, + 195 + ], + "blocks": [ + { + "bbox": [ + 400, + 130, + 422, + 137 + ], + "lines": [ + { + "bbox": [ + 400, + 130, + 422, + 137 + ], + "spans": [ + { + "bbox": [ + 400, + 130, + 422, + 137 + ], + "type": "text", + "content": "KPAC" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 377, + 137, + 445, + 195 + ], + "lines": [ + { + "bbox": [ + 377, + 137, + 445, + 195 + ], + "spans": [ + { + "bbox": [ + 377, + 137, + 445, + 195 + ], + "type": "image", + "image_path": "f08a4706c6cae514dd47dbf53027a97846dd7b54f1c6aaa26e8f68ead430a239.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 396, + 196, + 430, + 204 + ], + "lines": [ + { + "bbox": [ + 396, + 196, + 430, + 204 + ], + "spans": [ + { + "bbox": [ + 396, + 196, + 430, + 204 + ], + "type": "text", + "content": "DTPM-4s" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 451, + 70, + 520, + 129 + ], + "blocks": [ + { + "bbox": [ + 451, + 70, + 520, + 129 + ], + "lines": [ + { + "bbox": [ + 451, + 70, + 520, + 129 + ], + "spans": [ + { + "bbox": [ + 451, + 70, + 520, + 129 + ], + "type": "image", + "image_path": "858eb06fc126be6ac9e9c133c64112383f0d5ac825c9dc2a39e161182543ea15.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 451, + 138, + 519, + 195 + ], + "blocks": [ + { + "bbox": [ + 468, + 130, + 504, + 138 + ], + "lines": [ + { + "bbox": [ + 468, + 130, + 504, + 138 + ], + "spans": [ + { + "bbox": [ + 468, + 130, + 504, + 138 + ], + "type": "text", + "content": "DeepRFT" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 451, + 138, + 519, + 195 + ], + "lines": [ + { + "bbox": [ + 451, + 138, + 519, + 195 + ], + "spans": [ + { + "bbox": [ + 451, + 138, + 519, + 195 + ], + "type": "image", + "image_path": "610652cd1194e508aad50a863e4f52482d1985960aec78c726213fa9be17a14d.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 469, + 197, + 509, + 205 + ], + "lines": [ + { + "bbox": [ + 469, + 197, + 509, + 205 + ], + "spans": [ + { + "bbox": [ + 469, + 197, + 509, + 205 + ], + "type": "text", + "content": "DTPM-50s" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 16 + }, + { + "type": "table", + "bbox": [ + 70, + 287, + 266, + 388 + ], + "blocks": [ + { + "bbox": [ + 47, + 258, + 286, + 278 + ], + "lines": [ + { + "bbox": [ + 47, + 258, + 286, + 278 + ], + "spans": [ + { + "bbox": [ + 47, + 258, + 286, + 278 + ], + "type": "text", + "content": "Table 4. Single-image Defocus Deblurring comparisons on the DPDD testset [1]." + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 70, + 287, + 266, + 388 + ], + "lines": [ + { + "bbox": [ + 70, + 287, + 266, + 388 + ], + "spans": [ + { + "bbox": [ + 70, + 287, + 266, + 388 + ], + "type": "table", + "html": "
MethodDistortionPerceptual
PSNR ↑SSIM ↑MAE ↓LPIPS ↓
EBDB [28]23.450.6830.0490.336
DMENet [31]23.410.7140.0510.349
JNB [53]23.840.7150.0480.315
DPDNet [1]24.340.7470.0440.277
KPAC [54]25.220.7740.0400.227
IFAN [32]25.370.7890.0390.217
Restormer [70]25.980.8110.0380.178
DTPM-4 Step25.980.8230.0380.153
DTPM-10 Step25.760.8150.0390.140
DTPM-50 Step25.450.8030.0400.139
", + "image_path": "e82dea5c826a0582e8dd88325e8f5c639ece4c9b168962a8d506446f42cdf9e5.jpg" + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "table_body" + } + ], + "index": 20 + }, + { + "type": "table", + "bbox": [ + 72, + 433, + 264, + 517 + ], + "blocks": [ + { + "bbox": [ + 47, + 404, + 286, + 424 + ], + "lines": [ + { + "bbox": [ + 47, + 404, + 286, + 424 + ], + "spans": [ + { + "bbox": [ + 47, + 404, + 286, + 424 + ], + "type": "text", + "content": "Table 5. Single-image Motion Deblurring comparisons on the GoPro testset [43]." + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 72, + 433, + 264, + 517 + ], + "lines": [ + { + "bbox": [ + 72, + 433, + 264, + 517 + ], + "spans": [ + { + "bbox": [ + 72, + 433, + 264, + 517 + ], + "type": "table", + "html": "
MethodDistortionPerceptual
PSNR ↑SSIM ↑LPIPS ↓FID ↓
MPRNet [71]32.660.9590.08920.18
MIMO-UNet+ [13]32.450.9570.09118.05
SAPHNet [56]31.890.9530.10119.06
Restomer [70]33.200.9630.08419.33
DvSR [60]30.660.9410.08412.20
DTPM-4 Step32.090.9320.08410.02
DTPM-10 Step31.820.9290.0777.52
DTPM-50 Step31.110.9190.0616.61
", + "image_path": "cb35bdd07cd6d0277c02d1ea27921cedc68e703e2c13b4311effee55f26ed33c.jpg" + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "table_body" + } + ], + "index": 22 + }, + { + "bbox": [ + 46, + 542, + 287, + 625 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 542, + 287, + 625 + ], + "spans": [ + { + "bbox": [ + 46, + 542, + 287, + 625 + ], + "type": "text", + "content": "Comparative Analysis of Raindrop Removal. As illustrated in Table 2, we can observe that various versions of DTPM have demonstrated outstanding performance in the task of image raindrop removal. In comparison to RainDropDiff, our approach has achieved superior performance, with the LPIPS metric significantly outperforming that of RainDropDiff." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 46, + 653, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 286, + 712 + ], + "type": "text", + "content": "Comparative Analysis of Snow Removal. As shown in Table 1, we can observe that various versions of DTPM have demonstrated excellent performance in the task of image desnowing. In comparison to SnowDiff, our approach has achieved superior LPIPS metrics." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 306, + 258, + 443, + 272 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 258, + 443, + 272 + ], + "spans": [ + { + "bbox": [ + 306, + 258, + 443, + 272 + ], + "type": "text", + "content": "5. Discussion and Analysis" + } + ] + } + ], + "index": 25 + }, + { + "type": "image", + "bbox": [ + 342, + 289, + 509, + 385 + ], + "blocks": [ + { + "bbox": [ + 342, + 289, + 509, + 385 + ], + "lines": [ + { + "bbox": [ + 342, + 289, + 509, + 385 + ], + "spans": [ + { + "bbox": [ + 342, + 289, + 509, + 385 + ], + "type": "image", + "image_path": "b03d82b2b1cde98a50a18d9125e4ac59bf42cb6a5455f84d9c92f6e030cb32bd.jpg" + } + ] + } + ], + "index": 26, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 393, + 545, + 449 + ], + "lines": [ + { + "bbox": [ + 304, + 393, + 545, + 449 + ], + "spans": [ + { + "bbox": [ + 304, + 393, + 545, + 449 + ], + "type": "text", + "content": "Figure 8. Trade-off between PSNR and LPIPS in DTPM: This plot illustrates the inverse relationship between PSNR (pixel-wise distortion) and LPIPS (perceptual similarity) across various sampling steps, highlighting the equilibrium achieved between distortion and perceptual quality in our method." + } + ] + } + ], + "index": 27, + "angle": 0, + "type": "image_caption" + } + ], + "index": 26 + }, + { + "bbox": [ + 304, + 462, + 545, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 462, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 304, + 462, + 545, + 498 + ], + "type": "text", + "content": "For the analysis of various aspects of our model, we perform our experiments on the image deraining& dehazing dataset as it's a more chanlenging settings than others." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 305, + 506, + 545, + 529 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 506, + 545, + 529 + ], + "spans": [ + { + "bbox": [ + 305, + 506, + 545, + 529 + ], + "type": "text", + "content": "5.1. Sampling Steps and Distortion-Perceptual Trade-off" + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 304, + 536, + 545, + 656 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 536, + 545, + 656 + ], + "spans": [ + { + "bbox": [ + 304, + 536, + 545, + 656 + ], + "type": "text", + "content": "In Figure 8, we evaluate the results of our DTPM through the lens of two critical image quality metrics: PSNR and LPIPS1. As the sampling steps increase, the PSNR values initially experience a precipitous drop, decreasing from just above 31 dB to below 30.70 dB by the 10th step. This substantial early decline indicates that sampling steps in the early phase degrade image fidelity. Beyond this point, the PSNR decline slows, entering a phase of more gradual descent before plateauing after the 30th step, suggesting that the method begins to stabilize in terms of distortion loss. In" + } + ] + } + ], + "index": 30 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 304, + 664, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 664, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 664, + 545, + 713 + ], + "type": "text", + "content": "1The PSNR, measured in decibels (dB), is a traditional metric for assessing the fidelity of the reconstructed images against an original high-quality image. The LPIPS metric, on the other hand, offers an assessment of perceptual similarity, which correlates more closely with human visual perception." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2530" + } + ] + } + ], + "index": 32 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 72, + 286, + 152 + ], + "blocks": [ + { + "bbox": [ + 49, + 72, + 286, + 152 + ], + "lines": [ + { + "bbox": [ + 49, + 72, + 286, + 152 + ], + "spans": [ + { + "bbox": [ + 49, + 72, + 286, + 152 + ], + "type": "image", + "image_path": "beb7c5736bb10db29209052a5ba7f16f6f1f6e6de0348c3046ee7a82301d684f.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 160, + 287, + 205 + ], + "lines": [ + { + "bbox": [ + 46, + 160, + 287, + 205 + ], + "spans": [ + { + "bbox": [ + 46, + 160, + 287, + 205 + ], + "type": "text", + "content": "Figure 9. The first row in the figure shows the images, while the second row shows zoomed-in details. From left to right, they are: (a) input image, (b) the output of the initial predictor, (c) the final result of our method, (d) the ground-truth." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 227, + 289, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 227, + 289, + 418 + ], + "spans": [ + { + "bbox": [ + 46, + 227, + 289, + 418 + ], + "type": "text", + "content": "contrast, the LPIPS score improves markedly with each incremental sampling step, indicating that the perceived quality of the images is becoming more aligned with human visual perception. The steepness of the LPIPS improvement mirrors the PSNR decline, reflecting a pronounced trade-off between fidelity and perceptual quality up to the 10 step. After this inflection point, although the PSNR values level off, suggesting a saturation of fidelity loss, the LPIPS values continue to improve but at a diminished rate, plateauing around the 40 step. The intersecting trends of these metrics underscore a distinct trade-off: optimizing for perceptual likeness through more sampling steps comes at the expense of traditional fidelity measures. However, the stabilization of both metrics after a certain number of sampling steps suggests a convergence towards an equilibrium between the two qualities." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 427, + 212, + 440 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 427, + 212, + 440 + ], + "spans": [ + { + "bbox": [ + 47, + 427, + 212, + 440 + ], + "type": "text", + "content": "5.2. Output of the Initial Predictor" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 446, + 287, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 446, + 287, + 567 + ], + "spans": [ + { + "bbox": [ + 46, + 446, + 287, + 567 + ], + "type": "text", + "content": "Given the significance of the initial predictor as a key component of our methodology, we have undertaken detailed explorations and analyses of it. Despite the absence of an explicit loss constraint in our initial predictor, it achieves results that closely resemble a clean background, as evidenced in Figure 9. The initial predictor, though not detailed in its finer aspects, effectively produces a reasonably clear image. This provides practical assurance for incorporating the output of the initial predictor as one of the enhanced, additional conditions for diffusion." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 574, + 176, + 586 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 574, + 176, + 586 + ], + "spans": [ + { + "bbox": [ + 47, + 574, + 176, + 586 + ], + "type": "text", + "content": "5.3. More Ablation Studies" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 593, + 286, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 593, + 286, + 677 + ], + "spans": [ + { + "bbox": [ + 46, + 593, + 286, + 677 + ], + "type": "text", + "content": "In this section, we conduct ablation studies to analyze the impact of different design choices in our DTPM framework. w/o Stage I Training. This variant, absent the initial training phase, exhibits a decrease in both image reconstruction quality and perceptual similarity relative to the complete model. This underscores the significance of the early training stage in establishing baseline performance." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 677, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 286, + 714 + ], + "type": "text", + "content": "w/o Initial Predictor: Removing the Initial Predictor results in a notable decline in both objective image quality and perceptual accuracy. This component's role is evidently" + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 343, + 102, + 511, + 183 + ], + "blocks": [ + { + "bbox": [ + 305, + 70, + 545, + 93 + ], + "lines": [ + { + "bbox": [ + 305, + 70, + 545, + 93 + ], + "spans": [ + { + "bbox": [ + 305, + 70, + 545, + 93 + ], + "type": "text", + "content": "Table 6. The ablation studies on Image Deraining&Dehazing dataset [48]." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 343, + 102, + 511, + 183 + ], + "lines": [ + { + "bbox": [ + 343, + 102, + 511, + 183 + ], + "spans": [ + { + "bbox": [ + 343, + 102, + 511, + 183 + ], + "type": "table", + "html": "
ModelPSNR ↑LPIPS ↓
w/o Stage I Training28.900.074
w/o Initial Predictor26.910.079
w/o Semantic Code29.790.0653
Fine-tune Enc. w/o Adapters29.200.0667
Fine-tune Dec. w/o Adapters28.910.0691
Fine-tune Enc.&Dec. w/o Adapters29.130.0712
Ours(DTPM-4S)30.990.0635
", + "image_path": "76518bfd5f33144c40d008d28439818cf212afbeb477e6637e1a39ea0052697f.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 203, + 545, + 262 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 203, + 545, + 262 + ], + "spans": [ + { + "bbox": [ + 304, + 203, + 545, + 262 + ], + "type": "text", + "content": "crucial for enhancing the clarity and fidelity of the images. w/o Semantic Code. The removal of the Semantic Code somewhat improves both image quality and perceptual similarity. This could suggest that the Semantic Code potentially adding informative features." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 263, + 545, + 322 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 263, + 545, + 322 + ], + "spans": [ + { + "bbox": [ + 304, + 263, + 545, + 322 + ], + "type": "text", + "content": "Fine-tune Enc. w/o Adapters. Fine-tuning just the encoder of DTPM without adapters leads to a slight reduction in performance. This indicates that while the encoder is a robust component, the adapters contribute to optimizing its function." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 323, + 545, + 381 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 323, + 545, + 381 + ], + "spans": [ + { + "bbox": [ + 304, + 323, + 545, + 381 + ], + "type": "text", + "content": "Fine-tune Dec. w/o Adapters. Solely fine-tuning the decoder of DTPM without adapters also reduces model efficacy. The adapters appear more integral for the decoder, possibly enabling more nuanced adjustments that refine results." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 383, + 545, + 443 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 383, + 545, + 443 + ], + "spans": [ + { + "bbox": [ + 304, + 383, + 545, + 443 + ], + "type": "text", + "content": "Fine-tune Enc.&Dec. w/o Adapters. Fine-tuning both the encoder and decoder without adapters does not match the performance of the complete model. This suggests a complex interplay between these components that adapters help to fine-tune effectively." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 453, + 463, + 466 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 453, + 463, + 466 + ], + "spans": [ + { + "bbox": [ + 305, + 453, + 463, + 466 + ], + "type": "text", + "content": "6. Conclusion and Limitations" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 473, + 545, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 545, + 545 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 545, + 545 + ], + "type": "text", + "content": "This study presents a comprehensive conditional framework for image restoration, integrating Diffusion Texture Priors for producing high-quality images with promising details. While achieving significant performance, it identifies potential improvements: accelerating sampling via advanced techniques and optimizing the model size." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 565, + 545, + 649 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 565, + 545, + 649 + ], + "spans": [ + { + "bbox": [ + 304, + 565, + 545, + 649 + ], + "type": "text", + "content": "Acknowledgment. This work is supported by the InnoHK funding launched by Innovation and Technology Commission, Hong Kong SAR, Guangzhou Municipal Science and Technology Project (Grant No. 2023A03J0671), and a grant of Innovation and Technology Fund under Guangdong-Hong Kong Technology Cooperation Funding Scheme (ITF-TCFS) (project no. 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To effectively detect incorrectly labeled instances, previous works have mostly relied on distinguishable training signals, such as training loss, as indicators to differentiate between clean and noisy labels. However, they have limitations in that the training signals incompletely reveal the model's behavior and are not effectively generalized to various noise types, resulting in limited detection accuracy. In this paper, we propose DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones based on the dynamics of the training signals. To cope with the absence of supervision for clean and noisy labels, DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels, enabling indirect simulation of the model's behavior on noisy labels. Then, DynaCor learns to identify clean and noisy instances by inducing two clearly distinguishable clusters from the latent representations of training dynamics. Our comprehensive experiments show that DynaCor outperforms the state-of-the-art competitors and shows strong robustness to various noise types and noise rates.", + "bbox": [ + 76, + 323, + 473, + 656 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 685, + 209, + 700 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The remarkable success of deep neural networks (DNNs) is largely attributed to massive and accurately labeled datasets. However, creating such datasets is not only expensive but also time-consuming. As a cost-effective alternative, various methods have been employed for label collection, such as crowdsourcing [11] and extracting image labels from accompanying text on the web [27, 54]. Unfortunately, these approaches have led to the emergence of noise in real-world datasets, with reported noise rates ranging from $8.0\\%$ to $38.5\\%$ [25, 27, 54], which severely degrades the model's performance [1, 58].", + "bbox": [ + 75, + 710, + 470, + 878 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To cope with the detrimental effect of such noisy labels, a variety of approaches have been proposed, including noise robust learning that minimizes the impact of inaccurate information from noisy labels during the training process [7, 29, 49, 54] and data re-annotation through algorithmic methods [16, 39, 61]. Among them, the task of noisy label detection, which our work mainly focuses on, aims to identify incorrectly labeled instances in a training dataset [7, 22, 34]. This task has gained much attention in that it can be further utilized for improving the quality of the original dataset via cleansing or rectifying such instances.", + "bbox": [ + 500, + 292, + 893, + 459 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Motivated by the memorization effect, which refers to the phenomenon where DNNs initially grasp simple and generalized patterns in correctly labeled data and then gradually overfit to incorrectly labeled data [1], most existing studies have utilized distinguishable training signals as indicators of label quality to differentiate between clean and noisy labels. To elaborate, these training signals are derived from the model's behavior on individual instances during the training [42, 44], involving factors such as training loss or confidence scores. Note that it is impractical to acquire annotations explicitly indicating whether each instance is correctly labeled or not. Hence, numerous studies have crafted various heuristic training signals [12, 19, 22], designed based on human prior knowledge of the model's distinctive behaviors when faced with clean and noisy labels.", + "bbox": [ + 496, + 460, + 893, + 686 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Despite their effectiveness, the training signal-based detection methods still exhibit several limitations: (1) They only focus on a scalar signal at a single epoch (or a representative one across the entire training trajectory), which leads to limited detection accuracy (See Appendix B.2). Since the model's distinct behaviors on clean and noisy labels draw different temporal trajectories of training signals, a single scalar is insufficient to distinguish them by capturing temporal patterns within training dynamics. (2) Existing detection approaches based on heuristics are not effectively generalized to various types of label noise. Noisy labels can originate from diverse sources, including human annotator errors [33, 50], systematic biases [46], and unreliable annotations from web crawling [54], resulting in", + "bbox": [ + 496, + 688, + 895, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding authors", + "bbox": [ + 94, + 886, + 225, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "22477", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "different noise types and rates for each dataset; this eventually requires considerable efforts to tune hyperparameters for training recipes of DNNs [26, 29, 45].", + "bbox": [ + 75, + 90, + 468, + 136 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To tackle these challenges, our goal is to propose a fully data-driven approach that directly learns to distinguish the training dynamics of noisy labels from those of clean labels using a given dataset without solely relying on heuristics. The primary technical challenge in this data-driven approach arises from the absence of supervision for clean and noisy labels. As a solution, we introduce a label corruption strategy-image augmentation attaching intentionally corrupted labels via random label replacement. Since the augmented instances are highly likely to have incorrect labels, we can utilize them to capture the training dynamics of noisy labels. In other words, this allows us to simulate the model's behavior on noisy labels by leveraging the augmented instances with corrupted labels.", + "bbox": [ + 75, + 137, + 468, + 347 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this work, we present a novel framework, named DynaCor, that learns discriminative Dynamics with label Corruption for noisy label detection. To be specific, DynaCor identifies clean and noisy labels via clustering of latent representations of training dynamics. To this end, it first generates training dynamics of original instances and corrupted instances. Then, it computes the dynamics representations that encode discriminative patterns within the training trajectories by using a parametric dynamics encoder. The dynamics encoder is optimized to induce two clearly distinguishable clusters (i.e., each for clean and noisy instances) based on two different types of losses for (1) high cluster cohesion and (2) cluster alignment between original and corrupted instances. Furthermore, DynaCor adopts a simple validation metric for the dynamics encoder based on the clustering quality so as to indirectly estimate its detection performance where ground-truth annotations of clean and noisy labels are not available for validation as well.", + "bbox": [ + 75, + 347, + 470, + 618 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The contribution of this work is threefold as follows:", + "bbox": [ + 94, + 619, + 444, + 633 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We introduce a label corruption strategy that augments the original data with corrupted labels, which are highly likely to be noisy, enabling indirect simulation of the model's behavior on noisy labels during the training.", + "- We present a data-driven DynaCor framework to distinguish incorrectly labeled instances from correctly labeled ones via clustering of the training dynamics.", + "- Our extensive experiments on real-world datasets demonstrate that DynaCor achieves the highest accuracy in detecting incorrectly labeled instances and remarkable robustness to various noise types and noise rates." + ], + "bbox": [ + 76, + 635, + 468, + 800 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 814, + 218, + 830 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We provide a brief overview of the two primary research directions for addressing incorrectly labeled instances in a noisy dataset: (1) Noisy label detection focuses on identifying instances that are incorrectly labeled within a dataset,", + "bbox": [ + 75, + 839, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "aiming to enhance data quality. (2) Noise robust learning is centered on developing learning algorithms and models that are resilient to the impact of noisy labels, ensuring robust performance even in the presence of labeling errors.", + "bbox": [ + 496, + 90, + 890, + 151 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Noisy label detection. The main challenge in detecting noisy labels lies in defining a surrogate metric for label quality, essentially indicating how likely an instance is correctly labeled. The widely adopted option is the training loss, assessing the disparity between the model prediction and given labels [15, 19, 20], with higher loss often indicating incorrect labels. Various proxy measures, including gradient-based values [47, 60] and prediction-based metrics [31, 34, 39, 41] have been developed to differentiate between clean and noisy labels, utilizing methods like Gaussian mixture models [4, 22, 26, 64] or manually designed thresholds [15, 31, 34, 57, 63]. However, these approaches may overlook the potential benefits of adopting a data-driven (or learning-centric) detection model [7], which can be easily generalized to various noise types and levels. As a training-free alternative, a recent study [63] introduces a non-parametric KNN-based approach based on the assumption that instances situated closely in the input feature spaces derived from a pre-trained model are more likely to share the same clean label. However, its efficacy in detection heavily depends on the quality of the pre-trained model and may not be universally applicable across domains with specific fine-grained visual features.", + "bbox": [ + 496, + 156, + 892, + 503 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Noise robust learning. Extensive research have focused on creating noise robust methods: loss functions [47, 60], regularization [6, 8, 29], model architectures [2, 5, 9, 13, 21, 54, 56], and training strategies [23, 30, 52, 59]. Recent studies have endeavored to integrate the process of detecting noisy labels and appropriately addressing them into the training pipeline in various ways: re-weighting losses [20, 36, 38] or re-annotation [16, 39, 61]. Besides, several studies [4, 26, 45, 51] treat detected noisy labels as unlabeled and make use of established semi-supervised techniques [3, 16, 59, 61]. Current robust learning typically relies on clean data, i.e., test data, for validation, while noisy detection methods can function without it, making direct comparisons difficult [63]. In this sense, we will discuss how these noise robust learning approaches can be effectively combined with noisy detection methods (Sec. 5.5).", + "bbox": [ + 496, + 508, + 892, + 751 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. Problem Formulation", + "text_level": 1, + "bbox": [ + 500, + 768, + 705, + 784 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "For multi-class classification, let $\\mathcal{X}$ be an input feature space and $\\mathcal{Y} = \\{1,2,\\dots,C\\}$ be a label space. Consider a dataset $D = \\{(\\mathbf{x}_n,y_n)\\}_{n = 1}^N$ , where each sample is independently drawn from an unknown joint distribution over $\\mathcal{X}\\times \\mathcal{Y}$ . In real-world scenarios, we can only access a noisily labeled training set $\\widetilde{D} = \\{(\\mathbf{x}_n,\\tilde{y}_n)\\}_{n = 1}^N$ , where $\\tilde{y}$ denotes a noisy annotation, and there may exist $n\\in \\{1,\\ldots ,N\\}$ such", + "bbox": [ + 496, + 794, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "22478", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/7d1e5ee353fc116cfa7b179edb8cfd384243ad639f1677e0aabe5bd971495144.jpg", + "image_caption": [ + "1. Corrupted dataset construction" + ], + "image_footnote": [], + "bbox": [ + 86, + 109, + 271, + 282 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/fda0569deca210cb355d1eefa5409859148a34340d552cd3bd4ac62f9a3725c8.jpg", + "image_caption": [ + "2. Training dynamics generation", + "3. Noisy label detection via dynamics clustering" + ], + "image_footnote": [], + "bbox": [ + 292, + 109, + 473, + 281 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/ba4b97b564ffa7655c93daa3b1ea2ccd7b6f7dd2155e6249c3850eb0c793a1e8.jpg", + "image_caption": [ + "Figure 1. The proposed DynaCor framework consists of three steps: (1) Corrupted dataset construction generates the augmented images with corrupted labels, likely resulting in noisy labels, in order to provide guidance for discrimination between clean and noisy labels. (2) Training dynamics generation collects the trajectory of training signals for both the original and corrupted datasets by training a classifier. (3) Noisy label detection is performed by discovering two distinguishable clusters of dynamics representations, and for this, the dynamics encoder is optimized to enhance both cluster cohesion and alignment between the original and the corrupted datasets." + ], + "image_footnote": [], + "bbox": [ + 504, + 133, + 893, + 281 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "that $y_{n} \\neq \\tilde{y}_{n}$ . In this work, we focus on the task of noisy label detection, which aims to identify the incorrectly labeled instances, i.e., $\\{(x_{n},\\tilde{y}_{n}) \\in \\widetilde{D} \\mid y_{n} \\neq \\tilde{y}_{n}\\}$ . As an evaluation metric, we use F1 score [28], treating the incorrectly labeled instances as positive and the remainings as negative.", + "bbox": [ + 75, + 395, + 468, + 472 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Methodology", + "text_level": 1, + "bbox": [ + 76, + 493, + 210, + 510 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. Overview", + "text_level": 1, + "bbox": [ + 76, + 521, + 187, + 536 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "DynaCor (Dynamics learning with label Corruption for noisy label detection) framework learns discriminative patterns inherent in training dynamics, thereby distinguishing incorrectly labeled instances from clean ones. As illustrated in Figure 1, DynaCor consists of three major steps.", + "bbox": [ + 75, + 547, + 468, + 623 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Corrupted dataset construction (Sec. 4.2): To address the challenge arising from the lack of supervision for incorrectly labeled instances, we introduce a corrupted dataset that intentionally corrupts labels, providing guidance to identify incorrectly labeled instances.", + "- Training dynamics generation (Sec. 4.3): We generate training dynamics, which denote a model's behavior on individual instances during training, by training a classifier using both the original and the corrupted dataset.", + "- Noisy label detection via dynamics clustering (Sec. 4.4): We seek to discover underlying patterns in the training dynamics by learning representations that reflect the intrinsic similarities among data points, leveraging the characteristics of the corrupted dataset. For this, we encode the training dynamics via a dynamics encoder that learns discriminative representation using clustering and alignment losses. Then we find clusters using a robust validation metric designed for dynamics-based clustering." + ], + "bbox": [ + 76, + 625, + 470, + 898 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.2. Corrupted dataset construction", + "text_level": 1, + "bbox": [ + 500, + 395, + 777, + 411 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given the original dataset $\\widetilde{D}$ , we construct a corrupted dataset $\\bar{D}$ by intentionally corrupting labels for a randomly sampled subset of $\\widetilde{D}$ with a corruption rate $\\gamma \\in (0,1]$ . Specifically, to obtain a corrupted instance $(\\bar{\\mathbf{x}},\\bar{y})$ from an original data instance $(\\mathbf{x},\\tilde{y})$ , we transform an input image using weak augmentation such as horizontal flip or center crop, i.e., $\\bar{\\mathbf{x}} = \\mathrm{Aug}(\\mathbf{x})$ . Then, we randomly flip the class label to one of the other classes, i.e., $\\bar{y} \\in \\{1,\\dots,C\\} \\backslash \\{\\tilde{y}\\}$ . The corrupted dataset, guaranteed to exhibit symmetric noise at a higher rate than the original, provides additional signals for discerning incorrectly labeled instances in the clustering process, as detailed in the following analysis.", + "bbox": [ + 496, + 419, + 893, + 602 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Analysis: the noise rate of the corrupted dataset. We analyze the lower bound on the noise rate of the corrupted dataset $\\bar{D}$ . Let $\\eta \\in [0,1]$ denote the noise rate of the original dataset $\\widetilde{D}$ . Following the previous literature [14, 15, 40], we presume the diagonally dominant condition, i.e., $\\operatorname*{Pr}(\\tilde{y} = i|y = i) > \\operatorname*{Pr}(\\tilde{y} = j|y = i), \\forall i \\neq j$ , which indicates that correct labels should not be overwhelmed by the false ones. With this condition of $\\eta < 1 - \\frac{1}{C}$ , we have the following proposition.", + "bbox": [ + 496, + 607, + 893, + 748 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Proposition 1 (Lower bound of $\\eta_{\\gamma}$ ) Let $\\eta_{\\gamma}$ denote the noise rate of the corrupted dataset. Given the diagonally dominant condition, i.e., $\\eta < 1 - \\frac{1}{C}$ , for any $\\gamma \\in (0,1]$ , $\\eta_{\\gamma}$ has a lower bound of $1 - \\frac{1}{C}$ .", + "bbox": [ + 496, + 762, + 893, + 825 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The proof is presented in Appendix C, from which we can derive $\\eta < \\eta_{\\gamma}$ .", + "bbox": [ + 496, + 839, + 890, + 872 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n{ } ^ { 1 } \\eta = \\frac { 1 } { | \\widetilde { D } | } \\left| \\left\\{ ( \\mathbf { x } , \\widetilde { y } ) \\in \\widetilde { D } \\mid \\widetilde { y } \\neq y , ( \\mathbf { x } , y ) \\in D \\right\\} \\right|\n$$\n", + "text_format": "latex", + "bbox": [ + 514, + 883, + 774, + 904 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "22479", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.3. Training dynamics generation", + "text_level": 1, + "bbox": [ + 76, + 90, + 344, + 107 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.3.1 Training dynamics", + "text_level": 1, + "bbox": [ + 76, + 114, + 263, + 131 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The training dynamics indicates a model's behavior on individual instances during the training, quantitatively describing the training process [42, 44]. Concretely, the training dynamics is defined as the trajectory of training signals derived from a model's output across the training epochs. In the literature, various types of training signals [1, 42, 62] have been employed for analyzing the model's behavior.", + "bbox": [ + 75, + 140, + 467, + 244 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given a classifier $f$ , let $f(\\mathbf{x}) \\in \\mathbb{R}^C$ denote the output logits of an instance $\\mathbf{x}$ for $C$ classes. Let $t$ be a transformation function that maps $C$ logits to a scalar training signal. In this paper, we use quantized logit difference as the training signal. It quantizes the difference between a logit [34] of a given label and the largest logit among the remaining classes, i.e., $t(f(\\mathbf{x}),\\tilde{y}) = \\mathrm{sign}(f_{\\tilde{y}}(\\mathbf{x}) - \\max_{c\\neq \\tilde{y}}f_c(\\mathbf{x}))$ , where $f_{c}(\\mathbf{x})$ denotes the logit for class $c$ , and $\\mathrm{sign}(\\mathbf{x}) = 1$ or -1 if $\\mathbf{x} > = 0$ or $< 0$ , respectively. The training dynamics for an instance $\\mathbf{x}$ is defined as", + "bbox": [ + 75, + 247, + 468, + 398 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {t} _ {\\mathbf {x}} = \\left[ t ^ {(1)} \\left(f (\\mathbf {x}), \\tilde {y}\\right),.., t ^ {(E)} \\left(f (\\mathbf {x}), \\tilde {y}\\right) \\right], \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 145, + 411, + 468, + 431 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $t^{(e)}(f(\\mathbf{x}),\\tilde{y})$ denotes the training signal computed at epoch $e$ , and $E$ is the maximum number of training epochs. For the sake of convenience, we denote $\\mathbf{t}_{\\mathbf{x}}$ and $t_{\\mathbf{x}}^{(e)}$ as an abbreviation for $\\mathbf{t}(\\mathbf{x},\\tilde{y};f)$ and $t^{(e)}(f(\\mathbf{x}),\\tilde{y})$ , respectively.", + "bbox": [ + 75, + 443, + 468, + 508 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.3.2 Dynamics generation for noisy label detection", + "text_level": 1, + "bbox": [ + 76, + 532, + 447, + 547 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We generate training dynamics for both the original and the corrupted datasets. Specifically, we train a classifier by minimizing the classification loss on $\\widetilde{D}$ and $\\bar{D}$ :", + "bbox": [ + 75, + 558, + 468, + 603 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\frac {1}{| \\tilde {D} |} \\sum_ {(\\mathbf {x}, \\tilde {y}) \\in \\tilde {D}} \\ell_ {c e} (f (\\mathbf {x}), \\tilde {y}) + \\frac {1}{| \\bar {D} |} \\sum_ {(\\bar {\\mathbf {x}}, \\bar {y}) \\in \\bar {D}} \\ell_ {c e} (f (\\bar {\\mathbf {x}}), \\bar {y}), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 84, + 614, + 468, + 656 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\ell_{ce}$ is the softmax cross-entropy loss. For each instance $\\mathbf{x}$ , we obtain a training dynamics $\\mathbf{t}_{\\mathbf{x}} \\in \\mathbb{R}^{E}$ as specified in Eq. (1) by tracking $t_{\\mathbf{x}}^{(e)}$ over the course of training epochs $E$ . Training dynamics of the original and the corrupted datasets are denoted by $\\widetilde{T} := \\{\\mathbf{t}_{\\mathbf{x}} | (\\mathbf{x}, \\tilde{y}) \\in \\widetilde{D}\\}$ and $\\bar{T} := \\{\\mathbf{t}_{\\bar{\\mathbf{x}}} | (\\bar{\\mathbf{x}}, \\bar{y}) \\in \\bar{D}\\}$ , respectively.", + "bbox": [ + 75, + 669, + 468, + 763 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.4. Noisy label detection via dynamics clustering", + "text_level": 1, + "bbox": [ + 76, + 775, + 457, + 792 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We use a clustering approach to identify incorrectly labeled instances within the original dataset. Using a dynamics encoder, we encode the generated dynamics and progressively find clusters of correctly and incorrectly labeled instances", + "bbox": [ + 75, + 800, + 468, + 861 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "in the representation space. The dynamics clustering iterates two key processes: (1) identifications of incorrectly labeled instances (Sec. 4.4.1), and (2) learning distinct representations for each cluster (Sec. 4.4.2). The clustering quality is assessed by a newly introduced validation metric by leveraging the corrupted dataset without a clean validation dataset (Sec. 4.4.3).", + "bbox": [ + 500, + 90, + 890, + 196 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.4.1 Identification of incorrectly labeled instances", + "text_level": 1, + "bbox": [ + 500, + 220, + 866, + 234 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Cluster initialization. Given a training dynamics $\\mathbf{t}_{\\mathbf{x}}$ , a dynamics encoder generates its representation, i.e., $\\mathbf{z}_{\\mathbf{x}} = \\mathrm{Enc}(\\mathbf{t}_{\\mathbf{x}}) \\in \\mathbb{R}^{d_{\\mathbf{z}}}$ . Let $\\widetilde{Z}$ and $\\widetilde{Z}$ denote the set of dynamics representations of the original and the corrupted datasets, respectively. We first introduce trainable parameters for centroids of noisy and clean clusters, i.e., $\\mu_{noisy}$ , $\\mu_{clean} \\in \\mathbb{R}^{d_{\\mathbf{z}}}$ . We initialize $\\mu_{noisy}$ as the average representation of the corrupted instances $\\widetilde{Z}$ , while $\\mu_{clean}$ is initialized as the average representation of the original instances $\\widetilde{Z}$ . Note that this initialization is conducted only once at the beginning of the dynamics clustering step.", + "bbox": [ + 498, + 250, + 890, + 417 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Noisy label identification. We determine whether each instance $\\mathbf{x}$ has been incorrectly labeled based on its assignment probability to the noisy cluster. The assignment probability is computed based on the similarity between $\\mathbf{z}_{\\mathbf{x}}$ and the noisy cluster's centroid $\\pmb{\\mu}_{\\text {noisy }}$ . We employ a kernel function based on the Student's $t$ -distribution [43] with one degree of freedom as follows:", + "bbox": [ + 498, + 421, + 890, + 518 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nq _ {n o i s y} (\\mathbf {z} _ {\\mathbf {x}}) = \\frac {(1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {n o i s y})) ^ {- 1}}{(1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {n o i s y})) ^ {- 1} + (1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {c l e a n})) ^ {- 1}},\n$$\n", + "text_format": "latex", + "bbox": [ + 500, + 532, + 888, + 564 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nq _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) = 1 - q _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 501, + 566, + 890, + 582 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $d(\\mathbf{a},\\mathbf{b}) = 1 - \\frac{\\langle\\mathbf{a},\\mathbf{b}\\rangle}{||\\mathbf{a}||_2\\cdot||\\mathbf{b}||_2}$ . Based on the assignment probability, we regard an instance as incorrectly labeled when its probability to the noisy cluster is predominant.", + "bbox": [ + 498, + 595, + 890, + 645 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nv \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) := \\mathbb {1} \\left[ q _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) > q _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) \\right], \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 659, + 890, + 676 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "$v(\\mathbf{z}_{\\mathbf{x}}) = 1$ indicates that $\\mathbf{x}$ is predicted to have a noisy label.", + "bbox": [ + 500, + 690, + 888, + 705 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.4.2 Learning discriminative patterns in dynamics", + "text_level": 1, + "bbox": [ + 500, + 732, + 870, + 748 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We introduce the strategy of inducing two distinguishable clusters (each for correctly and incorrectly labeled instances) in the dynamics representation space. We propose two types of losses for (1) high cluster cohesion and (2) cluster alignment between original and corrupted instances.", + "bbox": [ + 498, + 758, + 890, + 834 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Clustering loss. We introduce a clustering loss to make the clusters more distinguishable. We enhance cluster cohesion by adjusting each instance's representation to be closer to a centroid through a self-enhancing target distribution.", + "bbox": [ + 498, + 839, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_footnote", + "text": "2We provide a detailed analysis of various training signals for identifying incorrectly labeled instances in Appendix B.3", + "bbox": [ + 76, + 875, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "footer", + "text": "22480", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The target distribution is constructed by amplifying the predicted assignment probability [55] as follows:", + "bbox": [ + 76, + 90, + 468, + 121 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\np _ {n o i s y} (\\mathbf {z _ {x}}) = \\frac {q _ {n o i s y} ^ {2} (\\mathbf {z _ {x}}) / s _ {n o i s y}}{q _ {n o i s y} ^ {2} (\\mathbf {z _ {x}}) / s _ {n o i s y} + q _ {c l e a n} ^ {2} (\\mathbf {z _ {x}}) / s _ {c l e a n}},\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 128, + 454, + 167 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\np _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) = 1 - p _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right), \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 91, + 170, + 468, + 186 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $s_{noisy} = \\sum_{\\mathbf{z} \\in \\widetilde{Z} \\cup \\bar{Z}} q_{noisy}(\\mathbf{z})$ and $s_{clean} = \\sum_{\\mathbf{z} \\in \\widetilde{Z} \\cup \\bar{Z}} q_{clean}(\\mathbf{z})$ . Then, we minimize the KL divergence between the cluster assignment distribution $\\mathbf{q}(\\mathbf{z}_{\\mathbf{x}}) = [q_{noisy}(\\mathbf{z}_{\\mathbf{x}}), q_{clean}(\\mathbf{z}_{\\mathbf{x}})]$ and the target distribution $\\mathbf{p}(\\mathbf{z}_{\\mathbf{x}}) = [p_{noisy}(\\mathbf{z}_{\\mathbf{x}}), p_{clean}(\\mathbf{z}_{\\mathbf{x}})]$ as follows:", + "bbox": [ + 76, + 195, + 468, + 272 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {c l u s t e r}} = \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\widetilde {\\tilde {Z}} \\cup \\bar {Z}} \\operatorname {K L} (\\mathbf {p} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) | | \\mathbf {q} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right)). \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 140, + 281, + 468, + 316 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Alignment loss. We introduce an alignment loss that aligns the representation from each cluster's original and corrupted datasets. We hypothesize3 that symmetric noise is relatively easy to identify among various noise types with diverse difficulty levels. Consequently, incorrectly labeled instances in the corrupted dataset exhibit more distinctive dynamics patterns than those in the original data, i.e., a red dashed line is farther away from blue lines than a red line in the 3rd step of Fig.1 (left). From this perspective, the mismatched noise types between the original and the corrupted datasets positively impact the clustering process by adopting alignment loss, which forces a red line to be aligned with a red dashed line in the 3rd step of Fig.1 (right).", + "bbox": [ + 75, + 329, + 468, + 525 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Instances in the original dataset predicted as noisy and clean are denoted by $\\widetilde{Z}_{noisy} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\widetilde{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 1\\}$ and $\\widetilde{Z}_{clean} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\widetilde{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 0\\}$ , respectively. Analogously, for the corrupted dataset, we obtain $\\bar{Z}_{noisy} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\bar{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 1\\}$ and $\\bar{Z}_{clean} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\bar{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 0\\}$ . Then, we employ the alignment loss to reduce the discrepancy between the representations of the original dataset and the corrupted dataset as follows:", + "bbox": [ + 76, + 525, + 468, + 648 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {a l i g n} ^ {n} = d \\Big (\\frac {1}{| \\tilde {\\bar {Z}} _ {n o i s y} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {\\bar {Z}} _ {n o i s y}} \\mathbf {z} _ {\\mathbf {x}}, \\frac {1}{| \\bar {Z} _ {n o i s y} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {n o i s y}} \\mathbf {z} _ {\\mathbf {x}} \\Big),\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 656, + 467, + 696 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {a l i g n}} ^ {c} = d \\Big (\\frac {1}{| \\tilde {Z} _ {\\text {c l e a n}} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {Z} _ {\\text {c l e a n}}} \\mathbf {z} _ {\\mathbf {x}}, \\frac {1}{| \\bar {Z} _ {\\text {c l e a n}} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {\\text {c l e a n}}} \\mathbf {z} _ {\\mathbf {x}} \\Big),\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 699, + 464, + 739 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {a l i g n}} = \\frac {1}{2} \\left(\\mathcal {L} _ {\\text {a l i g n}} ^ {n} + \\mathcal {L} _ {\\text {a l i g n}} ^ {c}\\right). \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 78, + 741, + 468, + 770 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Optimization. To sum up, the dynamics encoder is optimized by minimizing the following loss:", + "bbox": [ + 76, + 782, + 468, + 813 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {\\text {c l u s t e r}} + \\alpha \\mathcal {L} _ {\\text {a l i g n}}, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 189, + 823, + 468, + 839 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\alpha$ is a hyperparameter that controls the impact of the alignment loss.", + "bbox": [ + 76, + 848, + 468, + 878 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.4.3 Validation metric", + "text_level": 1, + "bbox": [ + 500, + 90, + 674, + 104 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "One practical challenge in training the dynamics encoder is determining an appropriate stopping point in the absence of ground-truth annotations of clean and noisy labels for validation. As a solution, we introduce a new validation metric for the dynamics encoder to estimate its detection performance indirectly. For noisy label detection, we aim to maximize (a) the assignment of incorrectly labeled instances to the noisy cluster while minimizing (b) the assignment of correctly labeled instances to the noisy cluster. Intuitively, in an ideally clustered space, the difference between (a) and (b) needs to be maximized.", + "bbox": [ + 496, + 114, + 890, + 280 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Since we cannot access the ground-truth annotations to compute (a) and (b), we use the most representative instances as a workaround. Considering the corrupted dataset has a higher noise rate than the original dataset, we emulate (a) using instances predicted as noisy among the corrupted dataset, i.e., $\\bar{Z}_{\\text{noise}}$ . Similarly, (b) is emulated using instances predicted as clean among the original dataset with a lower noise rate, i.e., $\\tilde{Z}_{\\text{clean}}$ . Our validation metric is defined as the difference between two emulated values as", + "bbox": [ + 496, + 281, + 890, + 416 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\left(\\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {\\text {n o i s y}}} \\frac {q _ {\\text {n o i s y}} (\\mathbf {z} _ {\\mathbf {x}})}{| \\bar {Z} _ {\\text {n o i s y}} |} - \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {Z} _ {\\text {c l e a n}}} \\frac {q _ {\\text {n o i s y}} (\\mathbf {z} _ {\\mathbf {x}})}{| \\tilde {Z} _ {\\text {c l e a n}} |}\\right) ^ {2}. \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 421, + 890, + 463 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The larger value indicates the better clustering quality for noisy label detection. Compared to the conventional metrics for assessing cluster separation [10, 37], this metric is tailored for our DynaCor framework and provides a more effective measure of noisy label detection efficacy.", + "bbox": [ + 496, + 469, + 890, + 546 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 558, + 633, + 574 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.1. Experiment setup", + "text_level": 1, + "bbox": [ + 500, + 582, + 671, + 599 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We evaluate the performance of DynaCor on benchmark datasets with different types of label noise, originating from diverse sources: (1) synthetic noise on CIFAR-10 and CIFAR-100 [24], (2) real-world human noise on CIFAR-10N and CIFAR-100N [50], and (3) systematic noise $^{4}$ on Clothing1M [54]. In the case of synthetic noise, following the previous experimental setup [63], we artificially introduce the noise by using different strategies with specific noise rates $\\eta$ as outlined below.", + "bbox": [ + 496, + 609, + 890, + 744 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Symmetric Noise (Sym., $\\eta = 0.6$ ) randomly replaces the label with one of the other classes.", + "- Asymmetric Noise (Asym., $\\eta = 0.3$ ) performs pairwise label flipping, where transition can only occur from a given class $i$ to the next class ( $i \\bmod C) + 1$ .", + "- Instance-dependent Noise (Inst., $\\eta = 0.4$ ) changes labels based on the transition probability calculated using instance's corresponding features [53]." + ], + "bbox": [ + 500, + 746, + 890, + 867 + ], + "page_idx": 4 + }, + { + "type": "page_footnote", + "text": "3It is theoretically proved in [32]", + "bbox": [ + 94, + 886, + 271, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_footnote", + "text": "4In case of Clothing1M, systematic noise is induced by automatic annotation from the keywords present in the surrounding text of each image.", + "bbox": [ + 500, + 875, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "22481", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/8cef2966658075e63c259f98de8d7f5e576eb06189fdd768f973a0b56a2fae05.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DatasetCIFAR-10CIFAR-100
Noise typeSym.Asym.Inst.Agg.WorstSym.Asym.Inst.HumanAvg.
Noise rate (η)0.60.30.40.090.40.60.30.40.4
Avg.Encoder98.0 ± 0.0389.7 ± 0.1422.4 ± 33.567.3 ± 0.4292.8 ± 0.1196.7 ± 0.0774.9 ± 0.1776.8 ± 0.5179.5 ± 0.3177.6
AUM95.7 ± 0.0786.5 ± 0.1881.9 ± 0.7274.0 ± 0.1688.7 ± 0.1996.4 ± 0.1074.7 ± 0.2181.2 ± 0.2574.6 ± 1.2583.7
CL96.6 ± 0.0494.0 ± 0.1082.0 ± 0.2168.6 ± 0.3388.3 ± 0.1188.0 ± 0.0868.6 ± 0.1675.9 ± 0.1271.9 ± 0.1081.5
CORES97.7 ± 0.035.00 ± 0.3319.2 ± 0.1080.5 ± 0.0977.5 ± 0.0983.9 ± 0.2021.9 ± 0.3236.7 ± 0.4136.0 ± 0.1250.9
SIMIFEAT-V95.1 ± 0.0689.4 ± 0.0888.1 ± 0.1179.6 ± 0.1391.6 ± 0.0686.0 ± 0.0973.8 ± 0.0780.5 ± 0.0977.1 ± 0.1284.6
SIMIFEAT-R96.1 ± 1.4188.9 ± 0.1491.2 ± 0.0779.6 ± 0.4091.7 ± 0.3590.3 ± 0.0768.0 ± 0.1077.3 ± 0.0979.3 ± 0.1184.7
DynaCor98.0 ± 0.0494.0 ± 0.1592.3 ± 0.3879.6 ± 0.3792.3 ± 0.1994.3 ± 0.3476.3 ± 0.2381.7 ± 0.2180.4 ± 0.1787.7
", + "bbox": [ + 78, + 88, + 893, + 218 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/f31cbacdadc988e4fff0b2246ffb9858455b509e5287d6f9f12488d224d159b5.jpg", + "table_caption": [ + "Table 1. Average F1 score (\\%) along with standard deviation across ten independent runs of DynaCor and baseline methods on CIFAR-10 and CIFAR-100. All methods except SIMIFEAT utilize the identical fixed image encoder from CLIP [35] and train only a subsequent MLP, while SIMIFEAT uses pre-trained CLIP as a feature extractor. The rightmost column averages the F1 scores across nine different settings. \"Agg.\", \"Worst\", and \"Human\" correspond to the real-world human label noises [50]. The best results are in bold." + ], + "table_footnote": [], + "table_body": "
DatasetCIFAR-10CIFAR-100
Noise typeSym.Asym.Inst.Agg.WorstSym.Asym.Inst.HumanAvg.
Avg.Encoder94.1 ± 0.1485.4 ± 0.1988.5 ± 0.2063.6 ± 0.7287.6 ± 0.1892.5 ± 0.3475.2 ± 0.3676.0 ± 0.4978.8 ± 0.1882.4
AUM75.4 ± 0.2246.4 ± 0.3057.7 ± 0.0316.7 ± 0.0157.8 ± 0.0475.8 ± 0.2146.7 ± 0.3257.8 ± 0.1058.0 ± 0.2154.7
CL88.7 ± 0.5691.9 ± 0.1282.5 ± 0.3757.0 ± 0.3180.0 ± 0.3277.9 ± 0.3962.4 ± 0.2467.3 ± 0.2865.2 ± 0.1974.8
CORES92.9 ± 0.1726.7 ± 0.4449.2 ± 1.1563.6 ± 0.5874.7 ± 0.3666.3 ± 0.3533.8 ± 0.4639.2 ± 0.4531.9 ± 0.4853.2
SIMIFEAT-V94.6 ± 0.0684.7 ± 0.1783.7 ± 0.0869.4 ± 0.1788.3 ± 0.0888.0 ± 0.0970.3 ± 0.1477.8 ± 0.1076.2 ± 0.1481.4
SIMIFEAT-R92.9 ± 1.8484.0 ± 0.1386.9 ± 0.0868.8 ± 0.3288.5 ± 0.3689.7 ± 0.0766.2 ± 0.1175.5 ± 0.0877.8 ± 0.1381.2
DynaCor93.6 ± 0.1894.2 ± 0.4591.5 ± 0.3172.6 ± 2.4687.8 ± 0.3791.3 ± 0.4679.2 ± 0.5979.5 ± 1.1477.3 ± 0.5485.2
", + "bbox": [ + 78, + 297, + 890, + 419 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Average F1 score (%) under identical settings to those in Table 1 except for the backbone model. All methods except SIMIFEAT utilize a randomly initialized Renset34 [17], while SIMIFEAT uses a pre-trained ResNet34 on ImageNet [11] as a feature extractor.", + "bbox": [ + 75, + 429, + 892, + 458 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In the case of human noise, we choose two noise subtypes for CIFAR-10N (denoted by Agg. and Worst) and a single noise subtype for CIFAR-100N (denoted by Human). More details of the datasets are presented in Appendix A.1.", + "bbox": [ + 75, + 484, + 468, + 546 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. We compare DynaCor with various noisy label detection methods. All the methods except SIMIFEAT use training signals to identify incorrectly labeled instances.", + "bbox": [ + 75, + 553, + 468, + 599 + ], + "page_idx": 5 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Avg.Encoder is a naive baseline that discriminates between clean and noisy labels by using a one-dimensional Gaussian mixture model [64] on the averaged training signals (i.e., logit difference) over the epochs.", + "- AUM [34] uses summation of training signals (i.e., logit difference) over the epochs and identifies correctly/incorrectly labeled instances based on a threshold.", + "- CL [31] uses a predicted probability of the given label (i.e., confidence) and filter out the instances with low confidence based on class-conditional thresholds.", + "- CORES [7] leverages a training loss for noisy label detection, progressively filtering out incorrectly labeled instances using its proposed sample sieve.", + "- SIMIFEAT [63] is a training-free approach that effectively detects noisy labels by utilizing $K$ -nearest neighbors in the feature space of a pre-trained model." + ], + "bbox": [ + 76, + 604, + 468, + 844 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation details. For our label corruption process, we use the corruption rate $\\gamma = 0.1$ as the default. To generate the training dynamics, we employ DNN classifiers:", + "bbox": [ + 75, + 854, + 468, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "ResNet34 [17] and the pre-trained ViT-B/32-CLIP [35] with a multi-layer perceptron (MLP) of two hidden layers. To encode the training dynamics, we use a three-layered 1D-CNN architecture [48] as the dynamics encoder. The hyperparameter $\\alpha$ is selected as either 0.05 or 0.5. For more details about implementation, please refer to Appendix A.2.", + "bbox": [ + 498, + 483, + 890, + 575 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Noisy label detection performance", + "text_level": 1, + "bbox": [ + 500, + 599, + 797, + 616 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We first evaluate DynaCor and the baseline methods for noisy label detection. Table 1 and Table 2 present their detection F1 scores for two classifiers, CLIP w/ MLP and ResNet34, across various noise types and rates. Notably, DynaCor achieves the best performance on average, i.e., $+3.0\\%$ in Table 1 and $+2.8\\%$ in Table 2, demonstrating its robustness to various types of noisy conditions. On the other hand, the baseline methods relying on training signals (i.e., Avg.Encoder, AUM, CL, and CORES) show considerable variations in performance across different noise types. For example, in the case of CIFAR-10, Avg.Encoder and CORES perform well for symmetric noises, whereas they struggle with identifying asymmetric or instance noises. It is worth noting that asymmetric and instance noise are more complex than symmetric noise in that they can have a more detrimental impact on model performance [32]. These results strongly support the superiority of our DynaCor framework in handling a wide range of label noise variations.", + "bbox": [ + 496, + 628, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "22482", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/786a3c7672bb4a46896858e0a71a21d3819e6e5e496c13848decb4f8afd1095e.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Validation metricCIFAR-10CIFAR-100
Inst.Agg.Inst.Human
Max epoch86.7 ± 6.7577.8 ± 3.3561.0 ± 10.364.3 ± 4.40
DBI86.3 ± 8.7576.7 ± 3.9160.0 ± 10.264.8 ± 9.70
Ours92.3 ± 0.3879.6 ± 0.3781.7 ± 0.2180.4 ± 0.17
Opt epoch92.6 ± 0.4080.40 ± 0.4481.8 ± 0.0880.5 ± 0.18
", + "bbox": [ + 84, + 88, + 464, + 170 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a18fee68b74a91ac2acf81bfc7b1a90f66a2f2b6eec9c5898a3ffcfdf9e5acc9.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 107, + 243, + 439, + 347 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/033ea5b06c659350d30247ddef95ff89b05ebd244d00162cb39e9509064a368e.jpg", + "image_caption": [ + "(a) Supervised setting", + "(b) Unsupervised setting: DynaCor.", + "Figure 2. F1 score $(\\%)$ changes with respect to corruption rate $(\\gamma)$ on CIFAR10 in supervised and unsupervised settings using CLIP w/ MLP (Left) and ResNet34 (Right) as classifiers." + ], + "image_footnote": [], + "bbox": [ + 107, + 364, + 437, + 467 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Effectiveness of validation metric", + "text_level": 1, + "bbox": [ + 76, + 569, + 367, + 584 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "To demonstrate the effectiveness of the proposed validation metric (Sec.4.4.3), we compare the detection performance of our dynamics encoder by employing our proposed metric and alternative criteria as stopping conditions during the training. Max epoch signifies the training over the maximum number of epochs. Davies-Bouldin Index (DBI) [10] assesses the quality of clustering results by calculating the ratio of intra-cluster distances to inter-cluster separations. A lower DBI value implies more compact and well-separated clusters, i.e., better clustering quality. In addition, Opt epoch selects the optimal training epoch that achieves the best detection results, providing the upper bound of detection performance.", + "bbox": [ + 75, + 595, + 468, + 792 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In Table 3, our performance is close to the optimal case across various noise types and datasets, whereas Max epoch and DBI fail to stop the training process at a proper epoch on CIFAR-100. In conclusion, using the proper validation metric is critical for achieving competitive detection performance, particularly in the scenario where ground-truth annotations are not available for validation.", + "bbox": [ + 75, + 795, + 467, + 898 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/f6050393630a6047a977b4089b683934a4593a6fc3aa3b3c3432f238a568ca60.jpg", + "table_caption": [ + "Table 3. F1 score (\\%) of our dynamics encoder over various validation metrics on CIFAR-10 and CIFAR-100 using CLIP w/ MLP as a classifier." + ], + "table_footnote": [], + "table_body": "
L_clusterL_alignAsym.Inst.Agg.
93.8 ± 0.1791.8 ± 0.3978.8 ± 0.37
✓93.2 ± 0.1192.7 ± 0.3676.8 ± 0.83
✓✓94.0 ± 0.1592.3 ± 0.3879.6 ± 0.37
", + "bbox": [ + 504, + 88, + 883, + 150 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 4. F1 score (\\%) of DynaCor that ablates the clustering and alignment loss on CIFAR10 using CLIP w/ MLP as a classifier. The first row reports the detection performance with a randomly initialized dynamics encoder.", + "bbox": [ + 498, + 161, + 890, + 217 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.4.Quantitative analyses", + "text_level": 1, + "bbox": [ + 500, + 246, + 700, + 262 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The effect of corruption rate. We analyze the effect of increasing the corruption rate, which in turn amplifies the overall noise level. For thorough analyses, we conduct a controlled experiment within a supervised framework using classification, assuming the availability of ground-truth annotations that indicate each instance as being correctly or incorrectly labeled. We then compare these results, generally regarded as the performance upper bound for unsupervised methods, with those obtained by an unsupervised approach. We focus on assessing the ability of our proposed unsupervised learning model, i.e., DynaCor, to discriminate training dynamics and how this discrimination is affected by increasing the overall noise level through corruption.", + "bbox": [ + 496, + 275, + 890, + 470 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "As shown in Figure 2, the detection F1 scores achieved by DynaCor (Figure 2b) approaches those of supervised learning (Figure 2a), demonstrating the effectiveness of training dynamics. This proximity is especially notable when utilizing a powerful image encoder, i.e., CLIP, which makes the training dynamics less susceptible to changes in the corruption rate. In contrast, the training dynamics from ResNet34 are more affected by increased corruption rate. Surprisingly, in the case of \"Inst.\" type label noise, the training dynamics from the CLIP w/ MLP classifier become even more distinguishable as the corruption rate increases to 0.5. It shows that a higher noise rate in the training dataset can enhance the discernibility of the training dynamics. We hypothesize that the symmetric noise introduced through our label corruption process may reduce the overall difficulty of the detection task. This is consistent with the assertion in Sec. 4.4.2 that the symmetric noise is relatively straightforward to identify and, in turn, contributes to improving the performance of noisy label detection.", + "bbox": [ + 496, + 473, + 892, + 760 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The effect of two losses. We examine the effect of the clustering and alignment losses within our DynaCor framework. In Table 4, both losses enhance detection performance. We also observe that the alignment loss effectively addresses the high imbalance between clean and noisy instances, particularly in scenarios with a low noise rate (e.g.,", + "bbox": [ + 496, + 765, + 890, + 857 + ], + "page_idx": 6 + }, + { + "type": "page_footnote", + "text": "The overall noise rate is formulated as $\\eta_{over} = \\frac{\\eta + \\gamma \\cdot \\eta_{\\gamma}}{1 + \\gamma}$ .", + "bbox": [ + 514, + 869, + 828, + 887 + ], + "page_idx": 6 + }, + { + "type": "page_footnote", + "text": "See Appendix B.1 for the details.", + "bbox": [ + 517, + 887, + 700, + 898 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "22483", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d56f4bc4a7c2c5e68e025c50aae2056520c5a6794e6a65da512f3687fe3e5972.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 107, + 89, + 436, + 193 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/41fa1a259a13be8d20db8b3b5964bf792b32ec8119a9dc60a44d4ef4ffba8dbd.jpg", + "image_caption": [ + "(a) Classification accuracy $(\\%)$ of robust learning", + "(b) Noisy label detection F1 score $(\\%)$", + "Figure 3. Compatibility analysis of Dividemix with DynaCor on CIFAR100 over \"Asym.\" and \"Inst.\" with respect to noise rate" + ], + "image_footnote": [], + "bbox": [ + 107, + 210, + 434, + 314 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "\"Agg.\" on CIFAR-10). Given that DynaCor intentionally increases the noise rate by augmenting instances with corrupted labels, its benefits become more pronounced when dealing with datasets featuring a small original noise rate. In such cases, the alignment loss is crucial in stabilizing the clustering process by aligning the distinct distributions of original and corrupted instances.", + "bbox": [ + 75, + 400, + 468, + 506 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.5. Compatibility analyses with robust learning", + "text_level": 1, + "bbox": [ + 76, + 520, + 447, + 537 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We investigate the compatibility and synergistic effects of integrating our framework with various robust learning techniques: a semi-supervised approach (Dividemix [26]), loss functions (GCE [61] and SCE [47]), and a regularization method (ELR [29]). Detailed analyses of incorporating the loss functions and regularization technique on the Clothing1M dataset are provided in Appendix D.", + "bbox": [ + 75, + 545, + 467, + 651 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "For the semi-supervised approach, we select Dividemix [26] that iteratively detects incorrectly labeled instances and treats them as unlabeled instances. We construct integrated models of Dividemix and DynaCor through two distinct approaches: (1) DDyna-L is leveraging Dividemix to obtain the training dynamics of both original and corrupted datasets within our framework, and (2) DDyna-S is substituting the original detection method in Dividemix, i.e., GMM, with DynaCor. For the base architecture, we employ an 18-layer PreAct ResNet [18], adhering to its default optimization settings and hyperparameters, as specified in the original paper [26].", + "bbox": [ + 75, + 652, + 467, + 834 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Classification accuracy. We explore the impact of our framework on the classifier's accuracy, specifically introducing a corrupted dataset (DDyna-L) and supplanting the existing noise detection method (DDyna-S). Figure 3a", + "bbox": [ + 75, + 839, + 467, + 901 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "demonstrates that both enhance classification performance. In essence, results obtained with DDyna-L demonstrate that instances with symmetric label noise introduced through our corruption process prove beneficial for noise robust learning, especially in scenarios featuring a low noise rate in the original dataset, pointed out as a challenging setting for Dividemix [50].", + "bbox": [ + 496, + 90, + 890, + 196 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Detection F1 score. To report the noisy label detection performance within robust learning framework, i.e., Dividemix and DDyna-S, we measure F1 score at every epoch and report the value when test classification accuracy is at its highest. Note that they leverage a clean test dataset to identify the optimal detection point; on the contrary, the noisy detection method (DDyna-L) operates without access to clean data, instead employing the procedure for model validation on the noisy dataset itself (Sec. 4.4.3), presenting a more challenging task. Figure 3b indicates that DDyna-S and DDyna-L further improves the detection F1 score of Dividemix, indicating the great compatibility of DynaCor with existing semi-supervised noise robust learning. In scenarios involving \"Inst.\" label noise, DDyna-L exhibits compelling synergistic effects across a wide range of noise rates.", + "bbox": [ + 496, + 202, + 890, + 429 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 449, + 617, + 464 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This paper proposes a new DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones via clustering of their training dynamics. DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels, enabling indirect simulation of the model's behavior on noisy labels. Subsequently, DynaCor learns to induce two clearly distinguishable clusters for clean and noisy instances by enhancing the cluster cohesion and alignment between the original and corrupted dataset. Furthermore, DynaCor adopts a simple yet effective validation metric to indirectly estimate its detection performance in the absence of annotations of clean and noisy labels. Our comprehensive experiments on real-world datasets demonstrate the detection efficacy of DynaCor, its remarkable robustness to various noise types and noise rates, and great compatibility with existing approaches to noise robust learning.", + "bbox": [ + 496, + 476, + 890, + 733 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "7. Acknowledgements", + "text_level": 1, + "bbox": [ + 500, + 752, + 686, + 768 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by the IITP grant funded by the MSIT (No.2018-0-00584, 2019-0-01906, 2020-0-01361), the NRF grant funded by the MSIT (No.2020R1A2B5B03097210, RS-2023-00217286), and the Digital Innovation Hub project supervised by the Daegu Digital Innovation Promotion Agency (DIP) grant funded by the Korea government (MSIT and Daegu Metropolitan City) in 2024 (No. DBSD1-07).", + "bbox": [ + 496, + 779, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "22484", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 106 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Devansh Arpit, Stanisław Jastrzebski, Nicolas Ballas, David Krueger, Emmanuel Bengio, Maxinder S Kanwal, Tegan Maharaj, Asja Fischer, Aaron Courville, Yoshua Bengio, et al. 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IEEE, 2011. 2, 6" + ], + "bbox": [ + 78, + 90, + 468, + 698 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "22487", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/9326fcaf-0cf3-4eae-8525-ad22e7243842_model.json b/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/9326fcaf-0cf3-4eae-8525-ad22e7243842_model.json new file mode 100644 index 0000000000000000000000000000000000000000..f422c12b4b56299d7d6ae5576417f7992ad0aa05 --- /dev/null +++ b/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/9326fcaf-0cf3-4eae-8525-ad22e7243842_model.json @@ -0,0 +1,2609 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.111, + 0.13, + 0.861, + 0.175 + ], + "angle": 0, + "content": "Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection" + }, + { + "type": "text", + "bbox": [ + 0.145, + 0.203, + 0.882, + 0.24 + ], + "angle": 0, + "content": "Suyeon Kim\\(^{1}\\), Dongha Lee\\(^{2*}\\), SeongKu Kang\\(^{3}\\), Sukang Chae\\(^{1}\\), Sanghwan Jang\\(^{1}\\), Hwanjo Yu\\(^{1*}\\) \n\\(^{1}\\) POSTECH, \\(^{2}\\) Yonsei University, \\(^{3}\\) University of Illinois at Urbana Champaign" + }, + { + "type": "text", + "bbox": [ + 0.089, + 0.242, + 0.92, + 0.258 + ], + "angle": 0, + "content": "{kimsu, chaesgng2, s.jang, hwanjoyu}@postech.ac.kr, donalee@yonsei.ac.kr, seongku@illinois.edu" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.292, + 0.314, + 0.308 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.324, + 0.474, + 0.657 + ], + "angle": 0, + "content": "Label noise, commonly found in real-world datasets, has a detrimental impact on a model's generalization. To effectively detect incorrectly labeled instances, previous works have mostly relied on distinguishable training signals, such as training loss, as indicators to differentiate between clean and noisy labels. However, they have limitations in that the training signals incompletely reveal the model's behavior and are not effectively generalized to various noise types, resulting in limited detection accuracy. In this paper, we propose DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones based on the dynamics of the training signals. To cope with the absence of supervision for clean and noisy labels, DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels, enabling indirect simulation of the model's behavior on noisy labels. Then, DynaCor learns to identify clean and noisy instances by inducing two clearly distinguishable clusters from the latent representations of training dynamics. Our comprehensive experiments show that DynaCor outperforms the state-of-the-art competitors and shows strong robustness to various noise types and noise rates." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.686, + 0.21, + 0.701 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.711, + 0.471, + 0.879 + ], + "angle": 0, + "content": "The remarkable success of deep neural networks (DNNs) is largely attributed to massive and accurately labeled datasets. However, creating such datasets is not only expensive but also time-consuming. As a cost-effective alternative, various methods have been employed for label collection, such as crowdsourcing [11] and extracting image labels from accompanying text on the web [27, 54]. Unfortunately, these approaches have led to the emergence of noise in real-world datasets, with reported noise rates ranging from \\(8.0\\%\\) to \\(38.5\\%\\) [25, 27, 54], which severely degrades the model's performance [1, 58]." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.293, + 0.895, + 0.46 + ], + "angle": 0, + "content": "To cope with the detrimental effect of such noisy labels, a variety of approaches have been proposed, including noise robust learning that minimizes the impact of inaccurate information from noisy labels during the training process [7, 29, 49, 54] and data re-annotation through algorithmic methods [16, 39, 61]. Among them, the task of noisy label detection, which our work mainly focuses on, aims to identify incorrectly labeled instances in a training dataset [7, 22, 34]. This task has gained much attention in that it can be further utilized for improving the quality of the original dataset via cleansing or rectifying such instances." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.461, + 0.895, + 0.688 + ], + "angle": 0, + "content": "Motivated by the memorization effect, which refers to the phenomenon where DNNs initially grasp simple and generalized patterns in correctly labeled data and then gradually overfit to incorrectly labeled data [1], most existing studies have utilized distinguishable training signals as indicators of label quality to differentiate between clean and noisy labels. To elaborate, these training signals are derived from the model's behavior on individual instances during the training [42, 44], involving factors such as training loss or confidence scores. Note that it is impractical to acquire annotations explicitly indicating whether each instance is correctly labeled or not. Hence, numerous studies have crafted various heuristic training signals [12, 19, 22], designed based on human prior knowledge of the model's distinctive behaviors when faced with clean and noisy labels." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.896, + 0.902 + ], + "angle": 0, + "content": "Despite their effectiveness, the training signal-based detection methods still exhibit several limitations: (1) They only focus on a scalar signal at a single epoch (or a representative one across the entire training trajectory), which leads to limited detection accuracy (See Appendix B.2). Since the model's distinct behaviors on clean and noisy labels draw different temporal trajectories of training signals, a single scalar is insufficient to distinguish them by capturing temporal patterns within training dynamics. (2) Existing detection approaches based on heuristics are not effectively generalized to various types of label noise. Noisy labels can originate from diverse sources, including human annotator errors [33, 50], systematic biases [46], and unreliable annotations from web crawling [54], resulting in" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.227, + 0.9 + ], + "angle": 0, + "content": "*Corresponding authors" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22477" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.137 + ], + "angle": 0, + "content": "different noise types and rates for each dataset; this eventually requires considerable efforts to tune hyperparameters for training recipes of DNNs [26, 29, 45]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.138, + 0.47, + 0.348 + ], + "angle": 0, + "content": "To tackle these challenges, our goal is to propose a fully data-driven approach that directly learns to distinguish the training dynamics of noisy labels from those of clean labels using a given dataset without solely relying on heuristics. The primary technical challenge in this data-driven approach arises from the absence of supervision for clean and noisy labels. As a solution, we introduce a label corruption strategy-image augmentation attaching intentionally corrupted labels via random label replacement. Since the augmented instances are highly likely to have incorrect labels, we can utilize them to capture the training dynamics of noisy labels. In other words, this allows us to simulate the model's behavior on noisy labels by leveraging the augmented instances with corrupted labels." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.348, + 0.471, + 0.619 + ], + "angle": 0, + "content": "In this work, we present a novel framework, named DynaCor, that learns discriminative Dynamics with label Corruption for noisy label detection. To be specific, DynaCor identifies clean and noisy labels via clustering of latent representations of training dynamics. To this end, it first generates training dynamics of original instances and corrupted instances. Then, it computes the dynamics representations that encode discriminative patterns within the training trajectories by using a parametric dynamics encoder. The dynamics encoder is optimized to induce two clearly distinguishable clusters (i.e., each for clean and noisy instances) based on two different types of losses for (1) high cluster cohesion and (2) cluster alignment between original and corrupted instances. Furthermore, DynaCor adopts a simple validation metric for the dynamics encoder based on the clustering quality so as to indirectly estimate its detection performance where ground-truth annotations of clean and noisy labels are not available for validation as well." + }, + { + "type": "text", + "bbox": [ + 0.096, + 0.62, + 0.446, + 0.635 + ], + "angle": 0, + "content": "The contribution of this work is threefold as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.636, + 0.469, + 0.696 + ], + "angle": 0, + "content": "- We introduce a label corruption strategy that augments the original data with corrupted labels, which are highly likely to be noisy, enabling indirect simulation of the model's behavior on noisy labels during the training." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.697, + 0.469, + 0.741 + ], + "angle": 0, + "content": "- We present a data-driven DynaCor framework to distinguish incorrectly labeled instances from correctly labeled ones via clustering of the training dynamics." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.741, + 0.469, + 0.801 + ], + "angle": 0, + "content": "- Our extensive experiments on real-world datasets demonstrate that DynaCor achieves the highest accuracy in detecting incorrectly labeled instances and remarkable robustness to various noise types and noise rates." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.636, + 0.469, + 0.801 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.815, + 0.219, + 0.831 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.469, + 0.901 + ], + "angle": 0, + "content": "We provide a brief overview of the two primary research directions for addressing incorrectly labeled instances in a noisy dataset: (1) Noisy label detection focuses on identifying instances that are incorrectly labeled within a dataset," + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.152 + ], + "angle": 0, + "content": "aiming to enhance data quality. (2) Noise robust learning is centered on developing learning algorithms and models that are resilient to the impact of noisy labels, ensuring robust performance even in the presence of labeling errors." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.157, + 0.893, + 0.504 + ], + "angle": 0, + "content": "Noisy label detection. The main challenge in detecting noisy labels lies in defining a surrogate metric for label quality, essentially indicating how likely an instance is correctly labeled. The widely adopted option is the training loss, assessing the disparity between the model prediction and given labels [15, 19, 20], with higher loss often indicating incorrect labels. Various proxy measures, including gradient-based values [47, 60] and prediction-based metrics [31, 34, 39, 41] have been developed to differentiate between clean and noisy labels, utilizing methods like Gaussian mixture models [4, 22, 26, 64] or manually designed thresholds [15, 31, 34, 57, 63]. However, these approaches may overlook the potential benefits of adopting a data-driven (or learning-centric) detection model [7], which can be easily generalized to various noise types and levels. As a training-free alternative, a recent study [63] introduces a non-parametric KNN-based approach based on the assumption that instances situated closely in the input feature spaces derived from a pre-trained model are more likely to share the same clean label. However, its efficacy in detection heavily depends on the quality of the pre-trained model and may not be universally applicable across domains with specific fine-grained visual features." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.51, + 0.893, + 0.752 + ], + "angle": 0, + "content": "Noise robust learning. Extensive research have focused on creating noise robust methods: loss functions [47, 60], regularization [6, 8, 29], model architectures [2, 5, 9, 13, 21, 54, 56], and training strategies [23, 30, 52, 59]. Recent studies have endeavored to integrate the process of detecting noisy labels and appropriately addressing them into the training pipeline in various ways: re-weighting losses [20, 36, 38] or re-annotation [16, 39, 61]. Besides, several studies [4, 26, 45, 51] treat detected noisy labels as unlabeled and make use of established semi-supervised techniques [3, 16, 59, 61]. Current robust learning typically relies on clean data, i.e., test data, for validation, while noisy detection methods can function without it, making direct comparisons difficult [63]. In this sense, we will discuss how these noise robust learning approaches can be effectively combined with noisy detection methods (Sec. 5.5)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.769, + 0.707, + 0.785 + ], + "angle": 0, + "content": "3. Problem Formulation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.901 + ], + "angle": 0, + "content": "For multi-class classification, let \\(\\mathcal{X}\\) be an input feature space and \\(\\mathcal{Y} = \\{1,2,\\dots,C\\}\\) be a label space. Consider a dataset \\(D = \\{(\\mathbf{x}_n,y_n)\\}_{n = 1}^N\\) , where each sample is independently drawn from an unknown joint distribution over \\(\\mathcal{X}\\times \\mathcal{Y}\\) . In real-world scenarios, we can only access a noisily labeled training set \\(\\widetilde{D} = \\{(\\mathbf{x}_n,\\tilde{y}_n)\\}_{n = 1}^N\\) , where \\(\\tilde{y}\\) denotes a noisy annotation, and there may exist \\(n\\in \\{1,\\ldots ,N\\}\\) such" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22478" + } + ], + [ + { + "type": "image_caption", + "bbox": [ + 0.086, + 0.091, + 0.273, + 0.104 + ], + "angle": 0, + "content": "1. Corrupted dataset construction" + }, + { + "type": "image", + "bbox": [ + 0.088, + 0.111, + 0.272, + 0.284 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.293, + 0.092, + 0.473, + 0.105 + ], + "angle": 0, + "content": "2. Training dynamics generation" + }, + { + "type": "image", + "bbox": [ + 0.293, + 0.111, + 0.474, + 0.282 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.511, + 0.092, + 0.773, + 0.105 + ], + "angle": 0, + "content": "3. Noisy label detection via dynamics clustering" + }, + { + "type": "image", + "bbox": [ + 0.506, + 0.134, + 0.894, + 0.282 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.3, + 0.894, + 0.37 + ], + "angle": 0, + "content": "Figure 1. The proposed DynaCor framework consists of three steps: (1) Corrupted dataset construction generates the augmented images with corrupted labels, likely resulting in noisy labels, in order to provide guidance for discrimination between clean and noisy labels. (2) Training dynamics generation collects the trajectory of training signals for both the original and corrupted datasets by training a classifier. (3) Noisy label detection is performed by discovering two distinguishable clusters of dynamics representations, and for this, the dynamics encoder is optimized to enhance both cluster cohesion and alignment between the original and the corrupted datasets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.396, + 0.47, + 0.473 + ], + "angle": 0, + "content": "that \\( y_{n} \\neq \\tilde{y}_{n} \\). In this work, we focus on the task of noisy label detection, which aims to identify the incorrectly labeled instances, i.e., \\( \\{(x_{n},\\tilde{y}_{n}) \\in \\widetilde{D} \\mid y_{n} \\neq \\tilde{y}_{n}\\} \\). As an evaluation metric, we use F1 score [28], treating the incorrectly labeled instances as positive and the remainings as negative." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.494, + 0.212, + 0.511 + ], + "angle": 0, + "content": "4. Methodology" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.522, + 0.188, + 0.537 + ], + "angle": 0, + "content": "4.1. Overview" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.548, + 0.47, + 0.624 + ], + "angle": 0, + "content": "DynaCor (Dynamics learning with label Corruption for noisy label detection) framework learns discriminative patterns inherent in training dynamics, thereby distinguishing incorrectly labeled instances from clean ones. As illustrated in Figure 1, DynaCor consists of three major steps." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.626, + 0.47, + 0.702 + ], + "angle": 0, + "content": "- Corrupted dataset construction (Sec. 4.2): To address the challenge arising from the lack of supervision for incorrectly labeled instances, we introduce a corrupted dataset that intentionally corrupts labels, providing guidance to identify incorrectly labeled instances." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.702, + 0.47, + 0.763 + ], + "angle": 0, + "content": "- Training dynamics generation (Sec. 4.3): We generate training dynamics, which denote a model's behavior on individual instances during training, by training a classifier using both the original and the corrupted dataset." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.762, + 0.471, + 0.9 + ], + "angle": 0, + "content": "- Noisy label detection via dynamics clustering (Sec. 4.4): We seek to discover underlying patterns in the training dynamics by learning representations that reflect the intrinsic similarities among data points, leveraging the characteristics of the corrupted dataset. For this, we encode the training dynamics via a dynamics encoder that learns discriminative representation using clustering and alignment losses. Then we find clusters using a robust validation metric designed for dynamics-based clustering." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.626, + 0.471, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.396, + 0.779, + 0.412 + ], + "angle": 0, + "content": "4.2. Corrupted dataset construction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.42, + 0.895, + 0.603 + ], + "angle": 0, + "content": "Given the original dataset \\(\\widetilde{D}\\), we construct a corrupted dataset \\(\\bar{D}\\) by intentionally corrupting labels for a randomly sampled subset of \\(\\widetilde{D}\\) with a corruption rate \\(\\gamma \\in (0,1]\\). Specifically, to obtain a corrupted instance \\((\\bar{\\mathbf{x}},\\bar{y})\\) from an original data instance \\((\\mathbf{x},\\tilde{y})\\), we transform an input image using weak augmentation such as horizontal flip or center crop, i.e., \\(\\bar{\\mathbf{x}} = \\mathrm{Aug}(\\mathbf{x})\\). Then, we randomly flip the class label to one of the other classes, i.e., \\(\\bar{y} \\in \\{1,\\dots,C\\} \\backslash \\{\\tilde{y}\\}\\). The corrupted dataset, guaranteed to exhibit symmetric noise at a higher rate than the original, provides additional signals for discerning incorrectly labeled instances in the clustering process, as detailed in the following analysis." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.608, + 0.894, + 0.749 + ], + "angle": 0, + "content": "Analysis: the noise rate of the corrupted dataset. We analyze the lower bound on the noise rate of the corrupted dataset \\(\\bar{D}\\). Let \\(\\eta \\in [0,1]\\) denote the noise rate of the original dataset \\(\\widetilde{D}\\). Following the previous literature [14, 15, 40], we presume the diagonally dominant condition, i.e., \\(\\operatorname*{Pr}(\\tilde{y} = i|y = i) > \\operatorname*{Pr}(\\tilde{y} = j|y = i), \\forall i \\neq j\\), which indicates that correct labels should not be overwhelmed by the false ones. With this condition of \\(\\eta < 1 - \\frac{1}{C}\\), we have the following proposition." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.763, + 0.894, + 0.827 + ], + "angle": 0, + "content": "Proposition 1 (Lower bound of \\(\\eta_{\\gamma}\\)) Let \\(\\eta_{\\gamma}\\) denote the noise rate of the corrupted dataset. Given the diagonally dominant condition, i.e., \\(\\eta < 1 - \\frac{1}{C}\\), for any \\(\\gamma \\in (0,1]\\), \\(\\eta_{\\gamma}\\) has a lower bound of \\(1 - \\frac{1}{C}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.873 + ], + "angle": 0, + "content": "The proof is presented in Appendix C, from which we can derive \\(\\eta < \\eta_{\\gamma}\\)." + }, + { + "type": "equation", + "bbox": [ + 0.516, + 0.884, + 0.776, + 0.905 + ], + "angle": 0, + "content": "\\[\n{ } ^ { 1 } \\eta = \\frac { 1 } { | \\widetilde { D } | } \\left| \\left\\{ ( \\mathbf { x } , \\widetilde { y } ) \\in \\widetilde { D } \\mid \\widetilde { y } \\neq y , ( \\mathbf { x } , y ) \\in D \\right\\} \\right|\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "22479" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.077, + 0.091, + 0.345, + 0.108 + ], + "angle": 0, + "content": "4.3. Training dynamics generation" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.115, + 0.264, + 0.132 + ], + "angle": 0, + "content": "4.3.1 Training dynamics" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.141, + 0.468, + 0.246 + ], + "angle": 0, + "content": "The training dynamics indicates a model's behavior on individual instances during the training, quantitatively describing the training process [42, 44]. Concretely, the training dynamics is defined as the trajectory of training signals derived from a model's output across the training epochs. In the literature, various types of training signals [1, 42, 62] have been employed for analyzing the model's behavior." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.248, + 0.47, + 0.399 + ], + "angle": 0, + "content": "Given a classifier \\( f \\), let \\( f(\\mathbf{x}) \\in \\mathbb{R}^C \\) denote the output logits of an instance \\( \\mathbf{x} \\) for \\( C \\) classes. Let \\( t \\) be a transformation function that maps \\( C \\) logits to a scalar training signal. In this paper, we use quantized logit difference as the training signal. It quantizes the difference between a logit [34] of a given label and the largest logit among the remaining classes, i.e., \\( t(f(\\mathbf{x}),\\tilde{y}) = \\mathrm{sign}(f_{\\tilde{y}}(\\mathbf{x}) - \\max_{c\\neq \\tilde{y}}f_c(\\mathbf{x})) \\), where \\( f_{c}(\\mathbf{x}) \\) denotes the logit for class \\( c \\), and \\( \\mathrm{sign}(\\mathbf{x}) = 1 \\) or -1 if \\( \\mathbf{x} > = 0 \\) or \\( < 0 \\), respectively. The training dynamics for an instance \\( \\mathbf{x} \\) is defined as" + }, + { + "type": "equation", + "bbox": [ + 0.146, + 0.412, + 0.47, + 0.432 + ], + "angle": 0, + "content": "\\[\n\\mathbf {t} _ {\\mathbf {x}} = \\left[ t ^ {(1)} \\left(f (\\mathbf {x}), \\tilde {y}\\right),.., t ^ {(E)} \\left(f (\\mathbf {x}), \\tilde {y}\\right) \\right], \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.444, + 0.469, + 0.509 + ], + "angle": 0, + "content": "where \\(t^{(e)}(f(\\mathbf{x}),\\tilde{y})\\) denotes the training signal computed at epoch \\(e\\), and \\(E\\) is the maximum number of training epochs. For the sake of convenience, we denote \\(\\mathbf{t}_{\\mathbf{x}}\\) and \\(t_{\\mathbf{x}}^{(e)}\\) as an abbreviation for \\(\\mathbf{t}(\\mathbf{x},\\tilde{y};f)\\) and \\(t^{(e)}(f(\\mathbf{x}),\\tilde{y})\\), respectively." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.533, + 0.449, + 0.549 + ], + "angle": 0, + "content": "4.3.2 Dynamics generation for noisy label detection" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.559, + 0.469, + 0.604 + ], + "angle": 0, + "content": "We generate training dynamics for both the original and the corrupted datasets. Specifically, we train a classifier by minimizing the classification loss on \\(\\widetilde{D}\\) and \\(\\bar{D}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.086, + 0.616, + 0.469, + 0.657 + ], + "angle": 0, + "content": "\\[\n\\frac {1}{| \\tilde {D} |} \\sum_ {(\\mathbf {x}, \\tilde {y}) \\in \\tilde {D}} \\ell_ {c e} (f (\\mathbf {x}), \\tilde {y}) + \\frac {1}{| \\bar {D} |} \\sum_ {(\\bar {\\mathbf {x}}, \\bar {y}) \\in \\bar {D}} \\ell_ {c e} (f (\\bar {\\mathbf {x}}), \\bar {y}), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.67, + 0.469, + 0.764 + ], + "angle": 0, + "content": "where \\(\\ell_{ce}\\) is the softmax cross-entropy loss. For each instance \\(\\mathbf{x}\\), we obtain a training dynamics \\(\\mathbf{t}_{\\mathbf{x}} \\in \\mathbb{R}^{E}\\) as specified in Eq. (1) by tracking \\(t_{\\mathbf{x}}^{(e)}\\) over the course of training epochs \\(E\\). Training dynamics of the original and the corrupted datasets are denoted by \\(\\widetilde{T} := \\{\\mathbf{t}_{\\mathbf{x}} | (\\mathbf{x}, \\tilde{y}) \\in \\widetilde{D}\\}\\) and \\(\\bar{T} := \\{\\mathbf{t}_{\\bar{\\mathbf{x}}} | (\\bar{\\mathbf{x}}, \\bar{y}) \\in \\bar{D}\\}\\), respectively." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.776, + 0.458, + 0.793 + ], + "angle": 0, + "content": "4.4. Noisy label detection via dynamics clustering" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.801, + 0.469, + 0.862 + ], + "angle": 0, + "content": "We use a clustering approach to identify incorrectly labeled instances within the original dataset. Using a dynamics encoder, we encode the generated dynamics and progressively find clusters of correctly and incorrectly labeled instances" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.198 + ], + "angle": 0, + "content": "in the representation space. The dynamics clustering iterates two key processes: (1) identifications of incorrectly labeled instances (Sec. 4.4.1), and (2) learning distinct representations for each cluster (Sec. 4.4.2). The clustering quality is assessed by a newly introduced validation metric by leveraging the corrupted dataset without a clean validation dataset (Sec. 4.4.3)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.221, + 0.867, + 0.236 + ], + "angle": 0, + "content": "4.4.1 Identification of incorrectly labeled instances" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.251, + 0.892, + 0.418 + ], + "angle": 0, + "content": "Cluster initialization. Given a training dynamics \\(\\mathbf{t}_{\\mathbf{x}}\\), a dynamics encoder generates its representation, i.e., \\(\\mathbf{z}_{\\mathbf{x}} = \\mathrm{Enc}(\\mathbf{t}_{\\mathbf{x}}) \\in \\mathbb{R}^{d_{\\mathbf{z}}}\\). Let \\(\\widetilde{Z}\\) and \\(\\widetilde{Z}\\) denote the set of dynamics representations of the original and the corrupted datasets, respectively. We first introduce trainable parameters for centroids of noisy and clean clusters, i.e., \\(\\mu_{noisy}\\), \\(\\mu_{clean} \\in \\mathbb{R}^{d_{\\mathbf{z}}}\\). We initialize \\(\\mu_{noisy}\\) as the average representation of the corrupted instances \\(\\widetilde{Z}\\), while \\(\\mu_{clean}\\) is initialized as the average representation of the original instances \\(\\widetilde{Z}\\). Note that this initialization is conducted only once at the beginning of the dynamics clustering step." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.422, + 0.892, + 0.52 + ], + "angle": 0, + "content": "Noisy label identification. We determine whether each instance \\(\\mathbf{x}\\) has been incorrectly labeled based on its assignment probability to the noisy cluster. The assignment probability is computed based on the similarity between \\(\\mathbf{z}_{\\mathbf{x}}\\) and the noisy cluster's centroid \\(\\pmb{\\mu}_{\\text {noisy }}\\). We employ a kernel function based on the Student's \\(t\\)-distribution [43] with one degree of freedom as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.5, + 0.534, + 0.89, + 0.565 + ], + "angle": 0, + "content": "\\[\nq _ {n o i s y} (\\mathbf {z} _ {\\mathbf {x}}) = \\frac {(1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {n o i s y})) ^ {- 1}}{(1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {n o i s y})) ^ {- 1} + (1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {c l e a n})) ^ {- 1}},\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.502, + 0.567, + 0.891, + 0.583 + ], + "angle": 0, + "content": "\\[\nq _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) = 1 - q _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.597, + 0.891, + 0.646 + ], + "angle": 0, + "content": "where \\(d(\\mathbf{a},\\mathbf{b}) = 1 - \\frac{\\langle\\mathbf{a},\\mathbf{b}\\rangle}{||\\mathbf{a}||_2\\cdot||\\mathbf{b}||_2}\\). Based on the assignment probability, we regard an instance as incorrectly labeled when its probability to the noisy cluster is predominant." + }, + { + "type": "equation", + "bbox": [ + 0.569, + 0.66, + 0.891, + 0.677 + ], + "angle": 0, + "content": "\\[\nv \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) := \\mathbb {1} \\left[ q _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) > q _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) \\right], \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.691, + 0.89, + 0.707 + ], + "angle": 0, + "content": "\\(v(\\mathbf{z}_{\\mathbf{x}}) = 1\\) indicates that \\(\\mathbf{x}\\) is predicted to have a noisy label." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.733, + 0.871, + 0.749 + ], + "angle": 0, + "content": "4.4.2 Learning discriminative patterns in dynamics" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.759, + 0.892, + 0.835 + ], + "angle": 0, + "content": "We introduce the strategy of inducing two distinguishable clusters (each for correctly and incorrectly labeled instances) in the dynamics representation space. We propose two types of losses for (1) high cluster cohesion and (2) cluster alignment between original and corrupted instances." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Clustering loss. We introduce a clustering loss to make the clusters more distinguishable. We enhance cluster cohesion by adjusting each instance's representation to be closer to a centroid through a self-enhancing target distribution." + }, + { + "type": "page_footnote", + "bbox": [ + 0.077, + 0.875, + 0.469, + 0.901 + ], + "angle": 0, + "content": "2We provide a detailed analysis of various training signals for identifying incorrectly labeled instances in Appendix B.3" + }, + { + "type": "footer", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22480" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.122 + ], + "angle": 0, + "content": "The target distribution is constructed by amplifying the predicted assignment probability [55] as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.091, + 0.13, + 0.455, + 0.168 + ], + "angle": 0, + "content": "\\[\np _ {n o i s y} (\\mathbf {z _ {x}}) = \\frac {q _ {n o i s y} ^ {2} (\\mathbf {z _ {x}}) / s _ {n o i s y}}{q _ {n o i s y} ^ {2} (\\mathbf {z _ {x}}) / s _ {n o i s y} + q _ {c l e a n} ^ {2} (\\mathbf {z _ {x}}) / s _ {c l e a n}},\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.093, + 0.171, + 0.469, + 0.188 + ], + "angle": 0, + "content": "\\[\np _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) = 1 - p _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right), \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.196, + 0.47, + 0.273 + ], + "angle": 0, + "content": "where \\( s_{noisy} = \\sum_{\\mathbf{z} \\in \\widetilde{Z} \\cup \\bar{Z}} q_{noisy}(\\mathbf{z}) \\) and \\( s_{clean} = \\sum_{\\mathbf{z} \\in \\widetilde{Z} \\cup \\bar{Z}} q_{clean}(\\mathbf{z}) \\). Then, we minimize the KL divergence between the cluster assignment distribution \\( \\mathbf{q}(\\mathbf{z}_{\\mathbf{x}}) = [q_{noisy}(\\mathbf{z}_{\\mathbf{x}}), q_{clean}(\\mathbf{z}_{\\mathbf{x}})] \\) and the target distribution \\( \\mathbf{p}(\\mathbf{z}_{\\mathbf{x}}) = [p_{noisy}(\\mathbf{z}_{\\mathbf{x}}), p_{clean}(\\mathbf{z}_{\\mathbf{x}})] \\) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.142, + 0.282, + 0.469, + 0.317 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {c l u s t e r}} = \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\widetilde {\\tilde {Z}} \\cup \\bar {Z}} \\operatorname {K L} (\\mathbf {p} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) | | \\mathbf {q} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right)). \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.33, + 0.469, + 0.526 + ], + "angle": 0, + "content": "Alignment loss. We introduce an alignment loss that aligns the representation from each cluster's original and corrupted datasets. We hypothesize3 that symmetric noise is relatively easy to identify among various noise types with diverse difficulty levels. Consequently, incorrectly labeled instances in the corrupted dataset exhibit more distinctive dynamics patterns than those in the original data, i.e., a red dashed line is farther away from blue lines than a red line in the 3rd step of Fig.1 (left). From this perspective, the mismatched noise types between the original and the corrupted datasets positively impact the clustering process by adopting alignment loss, which forces a red line to be aligned with a red dashed line in the 3rd step of Fig.1 (right)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.526, + 0.47, + 0.649 + ], + "angle": 0, + "content": "Instances in the original dataset predicted as noisy and clean are denoted by \\(\\widetilde{Z}_{noisy} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\widetilde{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 1\\}\\) and \\(\\widetilde{Z}_{clean} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\widetilde{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 0\\}\\), respectively. Analogously, for the corrupted dataset, we obtain \\(\\bar{Z}_{noisy} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\bar{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 1\\}\\) and \\(\\bar{Z}_{clean} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\bar{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 0\\}\\). Then, we employ the alignment loss to reduce the discrepancy between the representations of the original dataset and the corrupted dataset as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.078, + 0.657, + 0.468, + 0.697 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {a l i g n} ^ {n} = d \\Big (\\frac {1}{| \\tilde {\\bar {Z}} _ {n o i s y} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {\\bar {Z}} _ {n o i s y}} \\mathbf {z} _ {\\mathbf {x}}, \\frac {1}{| \\bar {Z} _ {n o i s y} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {n o i s y}} \\mathbf {z} _ {\\mathbf {x}} \\Big),\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.078, + 0.7, + 0.465, + 0.74 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {a l i g n}} ^ {c} = d \\Big (\\frac {1}{| \\tilde {Z} _ {\\text {c l e a n}} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {Z} _ {\\text {c l e a n}}} \\mathbf {z} _ {\\mathbf {x}}, \\frac {1}{| \\bar {Z} _ {\\text {c l e a n}} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {\\text {c l e a n}}} \\mathbf {z} _ {\\mathbf {x}} \\Big),\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.079, + 0.742, + 0.469, + 0.771 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {a l i g n}} = \\frac {1}{2} \\left(\\mathcal {L} _ {\\text {a l i g n}} ^ {n} + \\mathcal {L} _ {\\text {a l i g n}} ^ {c}\\right). \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.783, + 0.469, + 0.814 + ], + "angle": 0, + "content": "Optimization. To sum up, the dynamics encoder is optimized by minimizing the following loss:" + }, + { + "type": "equation", + "bbox": [ + 0.19, + 0.824, + 0.469, + 0.84 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {\\text {c l u s t e r}} + \\alpha \\mathcal {L} _ {\\text {a l i g n}}, \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.849, + 0.469, + 0.879 + ], + "angle": 0, + "content": "where \\(\\alpha\\) is a hyperparameter that controls the impact of the alignment loss." + }, + { + "type": "page_footnote", + "bbox": [ + 0.095, + 0.887, + 0.272, + 0.901 + ], + "angle": 0, + "content": "3It is theoretically proved in [32]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.092, + 0.676, + 0.105 + ], + "angle": 0, + "content": "4.4.3 Validation metric" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.115, + 0.892, + 0.281 + ], + "angle": 0, + "content": "One practical challenge in training the dynamics encoder is determining an appropriate stopping point in the absence of ground-truth annotations of clean and noisy labels for validation. As a solution, we introduce a new validation metric for the dynamics encoder to estimate its detection performance indirectly. For noisy label detection, we aim to maximize (a) the assignment of incorrectly labeled instances to the noisy cluster while minimizing (b) the assignment of correctly labeled instances to the noisy cluster. Intuitively, in an ideally clustered space, the difference between (a) and (b) needs to be maximized." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.282, + 0.892, + 0.417 + ], + "angle": 0, + "content": "Since we cannot access the ground-truth annotations to compute (a) and (b), we use the most representative instances as a workaround. Considering the corrupted dataset has a higher noise rate than the original dataset, we emulate (a) using instances predicted as noisy among the corrupted dataset, i.e., \\(\\bar{Z}_{\\text{noise}}\\). Similarly, (b) is emulated using instances predicted as clean among the original dataset with a lower noise rate, i.e., \\(\\tilde{Z}_{\\text{clean}}\\). Our validation metric is defined as the difference between two emulated values as" + }, + { + "type": "equation", + "bbox": [ + 0.52, + 0.422, + 0.892, + 0.464 + ], + "angle": 0, + "content": "\\[\n\\left(\\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {\\text {n o i s y}}} \\frac {q _ {\\text {n o i s y}} (\\mathbf {z} _ {\\mathbf {x}})}{| \\bar {Z} _ {\\text {n o i s y}} |} - \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {Z} _ {\\text {c l e a n}}} \\frac {q _ {\\text {n o i s y}} (\\mathbf {z} _ {\\mathbf {x}})}{| \\tilde {Z} _ {\\text {c l e a n}} |}\\right) ^ {2}. \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.47, + 0.892, + 0.547 + ], + "angle": 0, + "content": "The larger value indicates the better clustering quality for noisy label detection. Compared to the conventional metrics for assessing cluster separation [10, 37], this metric is tailored for our DynaCor framework and provides a more effective measure of noisy label detection efficacy." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.559, + 0.634, + 0.575 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.583, + 0.673, + 0.6 + ], + "angle": 0, + "content": "5.1. Experiment setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.611, + 0.892, + 0.746 + ], + "angle": 0, + "content": "Datasets. We evaluate the performance of DynaCor on benchmark datasets with different types of label noise, originating from diverse sources: (1) synthetic noise on CIFAR-10 and CIFAR-100 [24], (2) real-world human noise on CIFAR-10N and CIFAR-100N [50], and (3) systematic noise\\(^{4}\\) on Clothing1M [54]. In the case of synthetic noise, following the previous experimental setup [63], we artificially introduce the noise by using different strategies with specific noise rates \\(\\eta\\) as outlined below." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.747, + 0.89, + 0.775 + ], + "angle": 0, + "content": "- Symmetric Noise (Sym., \\(\\eta = 0.6\\)) randomly replaces the label with one of the other classes." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.777, + 0.891, + 0.822 + ], + "angle": 0, + "content": "- Asymmetric Noise (Asym., \\(\\eta = 0.3\\)) performs pairwise label flipping, where transition can only occur from a given class \\(i\\) to the next class (\\(i \\bmod C) + 1\\)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.822, + 0.891, + 0.868 + ], + "angle": 0, + "content": "- Instance-dependent Noise (Inst., \\(\\eta = 0.4\\)) changes labels based on the transition probability calculated using instance's corresponding features [53]." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.747, + 0.891, + 0.868 + ], + "angle": 0, + "content": null + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.875, + 0.892, + 0.901 + ], + "angle": 0, + "content": "4In case of Clothing1M, systematic noise is induced by automatic annotation from the keywords present in the surrounding text of each image." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "22481" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.08, + 0.089, + 0.894, + 0.219 + ], + "angle": 0, + "content": "
DatasetCIFAR-10CIFAR-100
Noise typeSym.Asym.Inst.Agg.WorstSym.Asym.Inst.HumanAvg.
Noise rate (η)0.60.30.40.090.40.60.30.40.4
Avg.Encoder98.0 ± 0.0389.7 ± 0.1422.4 ± 33.567.3 ± 0.4292.8 ± 0.1196.7 ± 0.0774.9 ± 0.1776.8 ± 0.5179.5 ± 0.3177.6
AUM95.7 ± 0.0786.5 ± 0.1881.9 ± 0.7274.0 ± 0.1688.7 ± 0.1996.4 ± 0.1074.7 ± 0.2181.2 ± 0.2574.6 ± 1.2583.7
CL96.6 ± 0.0494.0 ± 0.1082.0 ± 0.2168.6 ± 0.3388.3 ± 0.1188.0 ± 0.0868.6 ± 0.1675.9 ± 0.1271.9 ± 0.1081.5
CORES97.7 ± 0.035.00 ± 0.3319.2 ± 0.1080.5 ± 0.0977.5 ± 0.0983.9 ± 0.2021.9 ± 0.3236.7 ± 0.4136.0 ± 0.1250.9
SIMIFEAT-V95.1 ± 0.0689.4 ± 0.0888.1 ± 0.1179.6 ± 0.1391.6 ± 0.0686.0 ± 0.0973.8 ± 0.0780.5 ± 0.0977.1 ± 0.1284.6
SIMIFEAT-R96.1 ± 1.4188.9 ± 0.1491.2 ± 0.0779.6 ± 0.4091.7 ± 0.3590.3 ± 0.0768.0 ± 0.1077.3 ± 0.0979.3 ± 0.1184.7
DynaCor98.0 ± 0.0494.0 ± 0.1592.3 ± 0.3879.6 ± 0.3792.3 ± 0.1994.3 ± 0.3476.3 ± 0.2381.7 ± 0.2180.4 ± 0.1787.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.23, + 0.895, + 0.288 + ], + "angle": 0, + "content": "Table 1. Average F1 score (\\%) along with standard deviation across ten independent runs of DynaCor and baseline methods on CIFAR-10 and CIFAR-100. All methods except SIMIFEAT utilize the identical fixed image encoder from CLIP [35] and train only a subsequent MLP, while SIMIFEAT uses pre-trained CLIP as a feature extractor. The rightmost column averages the F1 scores across nine different settings. \"Agg.\", \"Worst\", and \"Human\" correspond to the real-world human label noises [50]. The best results are in bold." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.299, + 0.892, + 0.42 + ], + "angle": 0, + "content": "
DatasetCIFAR-10CIFAR-100
Noise typeSym.Asym.Inst.Agg.WorstSym.Asym.Inst.HumanAvg.
Avg.Encoder94.1 ± 0.1485.4 ± 0.1988.5 ± 0.2063.6 ± 0.7287.6 ± 0.1892.5 ± 0.3475.2 ± 0.3676.0 ± 0.4978.8 ± 0.1882.4
AUM75.4 ± 0.2246.4 ± 0.3057.7 ± 0.0316.7 ± 0.0157.8 ± 0.0475.8 ± 0.2146.7 ± 0.3257.8 ± 0.1058.0 ± 0.2154.7
CL88.7 ± 0.5691.9 ± 0.1282.5 ± 0.3757.0 ± 0.3180.0 ± 0.3277.9 ± 0.3962.4 ± 0.2467.3 ± 0.2865.2 ± 0.1974.8
CORES92.9 ± 0.1726.7 ± 0.4449.2 ± 1.1563.6 ± 0.5874.7 ± 0.3666.3 ± 0.3533.8 ± 0.4639.2 ± 0.4531.9 ± 0.4853.2
SIMIFEAT-V94.6 ± 0.0684.7 ± 0.1783.7 ± 0.0869.4 ± 0.1788.3 ± 0.0888.0 ± 0.0970.3 ± 0.1477.8 ± 0.1076.2 ± 0.1481.4
SIMIFEAT-R92.9 ± 1.8484.0 ± 0.1386.9 ± 0.0868.8 ± 0.3288.5 ± 0.3689.7 ± 0.0766.2 ± 0.1175.5 ± 0.0877.8 ± 0.1381.2
DynaCor93.6 ± 0.1894.2 ± 0.4591.5 ± 0.3172.6 ± 2.4687.8 ± 0.3791.3 ± 0.4679.2 ± 0.5979.5 ± 1.1477.3 ± 0.5485.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.43, + 0.893, + 0.459 + ], + "angle": 0, + "content": "Table 2. Average F1 score (%) under identical settings to those in Table 1 except for the backbone model. All methods except SIMIFEAT utilize a randomly initialized Renset34 [17], while SIMIFEAT uses a pre-trained ResNet34 on ImageNet [11] as a feature extractor." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.485, + 0.47, + 0.547 + ], + "angle": 0, + "content": "In the case of human noise, we choose two noise subtypes for CIFAR-10N (denoted by Agg. and Worst) and a single noise subtype for CIFAR-100N (denoted by Human). More details of the datasets are presented in Appendix A.1." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.554, + 0.47, + 0.601 + ], + "angle": 0, + "content": "Baselines. We compare DynaCor with various noisy label detection methods. All the methods except SIMIFEAT use training signals to identify incorrectly labeled instances." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.605, + 0.469, + 0.666 + ], + "angle": 0, + "content": "- Avg.Encoder is a naive baseline that discriminates between clean and noisy labels by using a one-dimensional Gaussian mixture model [64] on the averaged training signals (i.e., logit difference) over the epochs." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.666, + 0.469, + 0.71 + ], + "angle": 0, + "content": "- AUM [34] uses summation of training signals (i.e., logit difference) over the epochs and identifies correctly/incorrectly labeled instances based on a threshold." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.712, + 0.469, + 0.754 + ], + "angle": 0, + "content": "- CL [31] uses a predicted probability of the given label (i.e., confidence) and filter out the instances with low confidence based on class-conditional thresholds." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.755, + 0.469, + 0.8 + ], + "angle": 0, + "content": "- CORES [7] leverages a training loss for noisy label detection, progressively filtering out incorrectly labeled instances using its proposed sample sieve." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.801, + 0.469, + 0.845 + ], + "angle": 0, + "content": "- SIMIFEAT [63] is a training-free approach that effectively detects noisy labels by utilizing \\( K \\)-nearest neighbors in the feature space of a pre-trained model." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.605, + 0.469, + 0.845 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Implementation details. For our label corruption process, we use the corruption rate \\(\\gamma = 0.1\\) as the default. To generate the training dynamics, we employ DNN classifiers:" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.484, + 0.892, + 0.577 + ], + "angle": 0, + "content": "ResNet34 [17] and the pre-trained ViT-B/32-CLIP [35] with a multi-layer perceptron (MLP) of two hidden layers. To encode the training dynamics, we use a three-layered 1D-CNN architecture [48] as the dynamics encoder. The hyperparameter \\(\\alpha\\) is selected as either 0.05 or 0.5. For more details about implementation, please refer to Appendix A.2." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.601, + 0.799, + 0.617 + ], + "angle": 0, + "content": "5.2. Noisy label detection performance" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We first evaluate DynaCor and the baseline methods for noisy label detection. Table 1 and Table 2 present their detection F1 scores for two classifiers, CLIP w/ MLP and ResNet34, across various noise types and rates. Notably, DynaCor achieves the best performance on average, i.e., \\(+3.0\\%\\) in Table 1 and \\(+2.8\\%\\) in Table 2, demonstrating its robustness to various types of noisy conditions. On the other hand, the baseline methods relying on training signals (i.e., Avg.Encoder, AUM, CL, and CORES) show considerable variations in performance across different noise types. For example, in the case of CIFAR-10, Avg.Encoder and CORES perform well for symmetric noises, whereas they struggle with identifying asymmetric or instance noises. It is worth noting that asymmetric and instance noise are more complex than symmetric noise in that they can have a more detrimental impact on model performance [32]. These results strongly support the superiority of our DynaCor framework in handling a wide range of label noise variations." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22482" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.086, + 0.089, + 0.465, + 0.171 + ], + "angle": 0, + "content": "
Validation metricCIFAR-10CIFAR-100
Inst.Agg.Inst.Human
Max epoch86.7 ± 6.7577.8 ± 3.3561.0 ± 10.364.3 ± 4.40
DBI86.3 ± 8.7576.7 ± 3.9160.0 ± 10.264.8 ± 9.70
Ours92.3 ± 0.3879.6 ± 0.3781.7 ± 0.2180.4 ± 0.17
Opt epoch92.6 ± 0.4080.40 ± 0.4481.8 ± 0.0880.5 ± 0.18
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.181, + 0.471, + 0.222 + ], + "angle": 0, + "content": "Table 3. F1 score (\\%) of our dynamics encoder over various validation metrics on CIFAR-10 and CIFAR-100 using CLIP w/ MLP as a classifier." + }, + { + "type": "image", + "bbox": [ + 0.109, + 0.244, + 0.44, + 0.348 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.215, + 0.352, + 0.333, + 0.364 + ], + "angle": 0, + "content": "(a) Supervised setting" + }, + { + "type": "image", + "bbox": [ + 0.109, + 0.366, + 0.438, + 0.468 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.179, + 0.473, + 0.369, + 0.485 + ], + "angle": 0, + "content": "(b) Unsupervised setting: DynaCor." + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.497, + 0.47, + 0.539 + ], + "angle": 0, + "content": "Figure 2. F1 score \\((\\%)\\) changes with respect to corruption rate \\((\\gamma)\\) on CIFAR10 in supervised and unsupervised settings using CLIP w/ MLP (Left) and ResNet34 (Right) as classifiers." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.57, + 0.368, + 0.585 + ], + "angle": 0, + "content": "5.3. Effectiveness of validation metric" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.596, + 0.47, + 0.793 + ], + "angle": 0, + "content": "To demonstrate the effectiveness of the proposed validation metric (Sec.4.4.3), we compare the detection performance of our dynamics encoder by employing our proposed metric and alternative criteria as stopping conditions during the training. Max epoch signifies the training over the maximum number of epochs. Davies-Bouldin Index (DBI) [10] assesses the quality of clustering results by calculating the ratio of intra-cluster distances to inter-cluster separations. A lower DBI value implies more compact and well-separated clusters, i.e., better clustering quality. In addition, Opt epoch selects the optimal training epoch that achieves the best detection results, providing the upper bound of detection performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.468, + 0.9 + ], + "angle": 0, + "content": "In Table 3, our performance is close to the optimal case across various noise types and datasets, whereas Max epoch and DBI fail to stop the training process at a proper epoch on CIFAR-100. In conclusion, using the proper validation metric is critical for achieving competitive detection performance, particularly in the scenario where ground-truth annotations are not available for validation." + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.089, + 0.885, + 0.151 + ], + "angle": 0, + "content": "
L_clusterL_alignAsym.Inst.Agg.
93.8 ± 0.1791.8 ± 0.3978.8 ± 0.37
✓93.2 ± 0.1192.7 ± 0.3676.8 ± 0.83
✓✓94.0 ± 0.1592.3 ± 0.3879.6 ± 0.37
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.162, + 0.892, + 0.218 + ], + "angle": 0, + "content": "Table 4. F1 score (\\%) of DynaCor that ablates the clustering and alignment loss on CIFAR10 using CLIP w/ MLP as a classifier. The first row reports the detection performance with a randomly initialized dynamics encoder." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.247, + 0.702, + 0.263 + ], + "angle": 0, + "content": "5.4.Quantitative analyses" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.276, + 0.892, + 0.472 + ], + "angle": 0, + "content": "The effect of corruption rate. We analyze the effect of increasing the corruption rate, which in turn amplifies the overall noise level. For thorough analyses, we conduct a controlled experiment within a supervised framework using classification, assuming the availability of ground-truth annotations that indicate each instance as being correctly or incorrectly labeled. We then compare these results, generally regarded as the performance upper bound for unsupervised methods, with those obtained by an unsupervised approach. We focus on assessing the ability of our proposed unsupervised learning model, i.e., DynaCor, to discriminate training dynamics and how this discrimination is affected by increasing the overall noise level through corruption." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.474, + 0.893, + 0.761 + ], + "angle": 0, + "content": "As shown in Figure 2, the detection F1 scores achieved by DynaCor (Figure 2b) approaches those of supervised learning (Figure 2a), demonstrating the effectiveness of training dynamics. This proximity is especially notable when utilizing a powerful image encoder, i.e., CLIP, which makes the training dynamics less susceptible to changes in the corruption rate. In contrast, the training dynamics from ResNet34 are more affected by increased corruption rate. Surprisingly, in the case of \"Inst.\" type label noise, the training dynamics from the CLIP w/ MLP classifier become even more distinguishable as the corruption rate increases to 0.5. It shows that a higher noise rate in the training dataset can enhance the discernibility of the training dynamics. We hypothesize that the symmetric noise introduced through our label corruption process may reduce the overall difficulty of the detection task. This is consistent with the assertion in Sec. 4.4.2 that the symmetric noise is relatively straightforward to identify and, in turn, contributes to improving the performance of noisy label detection." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.766, + 0.892, + 0.858 + ], + "angle": 0, + "content": "The effect of two losses. We examine the effect of the clustering and alignment losses within our DynaCor framework. In Table 4, both losses enhance detection performance. We also observe that the alignment loss effectively addresses the high imbalance between clean and noisy instances, particularly in scenarios with a low noise rate (e.g.," + }, + { + "type": "page_footnote", + "bbox": [ + 0.516, + 0.871, + 0.829, + 0.888 + ], + "angle": 0, + "content": "The overall noise rate is formulated as \\(\\eta_{over} = \\frac{\\eta + \\gamma \\cdot \\eta_{\\gamma}}{1 + \\gamma}\\)." + }, + { + "type": "page_footnote", + "bbox": [ + 0.519, + 0.888, + 0.702, + 0.9 + ], + "angle": 0, + "content": "See Appendix B.1 for the details." + }, + { + "type": "list", + "bbox": [ + 0.516, + 0.871, + 0.829, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "22483" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.109, + 0.09, + 0.437, + 0.194 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.144, + 0.197, + 0.404, + 0.21 + ], + "angle": 0, + "content": "(a) Classification accuracy \\((\\%)\\) of robust learning" + }, + { + "type": "image", + "bbox": [ + 0.108, + 0.212, + 0.436, + 0.315 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.173, + 0.319, + 0.375, + 0.331 + ], + "angle": 0, + "content": "(b) Noisy label detection F1 score \\((\\%)\\)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.343, + 0.47, + 0.372 + ], + "angle": 0, + "content": "Figure 3. Compatibility analysis of Dividemix with DynaCor on CIFAR100 over \"Asym.\" and \"Inst.\" with respect to noise rate" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.401, + 0.47, + 0.507 + ], + "angle": 0, + "content": "\"Agg.\" on CIFAR-10). Given that DynaCor intentionally increases the noise rate by augmenting instances with corrupted labels, its benefits become more pronounced when dealing with datasets featuring a small original noise rate. In such cases, the alignment loss is crucial in stabilizing the clustering process by aligning the distinct distributions of original and corrupted instances." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.521, + 0.449, + 0.538 + ], + "angle": 0, + "content": "5.5. Compatibility analyses with robust learning" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.546, + 0.468, + 0.652 + ], + "angle": 0, + "content": "We investigate the compatibility and synergistic effects of integrating our framework with various robust learning techniques: a semi-supervised approach (Dividemix [26]), loss functions (GCE [61] and SCE [47]), and a regularization method (ELR [29]). Detailed analyses of incorporating the loss functions and regularization technique on the Clothing1M dataset are provided in Appendix D." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.653, + 0.468, + 0.835 + ], + "angle": 0, + "content": "For the semi-supervised approach, we select Dividemix [26] that iteratively detects incorrectly labeled instances and treats them as unlabeled instances. We construct integrated models of Dividemix and DynaCor through two distinct approaches: (1) DDyna-L is leveraging Dividemix to obtain the training dynamics of both original and corrupted datasets within our framework, and (2) DDyna-S is substituting the original detection method in Dividemix, i.e., GMM, with DynaCor. For the base architecture, we employ an 18-layer PreAct ResNet [18], adhering to its default optimization settings and hyperparameters, as specified in the original paper [26]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.468, + 0.902 + ], + "angle": 0, + "content": "Classification accuracy. We explore the impact of our framework on the classifier's accuracy, specifically introducing a corrupted dataset (DDyna-L) and supplanting the existing noise detection method (DDyna-S). Figure 3a" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.198 + ], + "angle": 0, + "content": "demonstrates that both enhance classification performance. In essence, results obtained with DDyna-L demonstrate that instances with symmetric label noise introduced through our corruption process prove beneficial for noise robust learning, especially in scenarios featuring a low noise rate in the original dataset, pointed out as a challenging setting for Dividemix [50]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.203, + 0.892, + 0.43 + ], + "angle": 0, + "content": "Detection F1 score. To report the noisy label detection performance within robust learning framework, i.e., Dividemix and DDyna-S, we measure F1 score at every epoch and report the value when test classification accuracy is at its highest. Note that they leverage a clean test dataset to identify the optimal detection point; on the contrary, the noisy detection method (DDyna-L) operates without access to clean data, instead employing the procedure for model validation on the noisy dataset itself (Sec. 4.4.3), presenting a more challenging task. Figure 3b indicates that DDyna-S and DDyna-L further improves the detection F1 score of Dividemix, indicating the great compatibility of DynaCor with existing semi-supervised noise robust learning. In scenarios involving \"Inst.\" label noise, DDyna-L exhibits compelling synergistic effects across a wide range of noise rates." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.45, + 0.618, + 0.465 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.477, + 0.892, + 0.734 + ], + "angle": 0, + "content": "This paper proposes a new DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones via clustering of their training dynamics. DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels, enabling indirect simulation of the model's behavior on noisy labels. Subsequently, DynaCor learns to induce two clearly distinguishable clusters for clean and noisy instances by enhancing the cluster cohesion and alignment between the original and corrupted dataset. Furthermore, DynaCor adopts a simple yet effective validation metric to indirectly estimate its detection performance in the absence of annotations of clean and noisy labels. Our comprehensive experiments on real-world datasets demonstrate the detection efficacy of DynaCor, its remarkable robustness to various noise types and noise rates, and great compatibility with existing approaches to noise robust learning." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.753, + 0.687, + 0.77 + ], + "angle": 0, + "content": "7. Acknowledgements" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This work was supported by the IITP grant funded by the MSIT (No.2018-0-00584, 2019-0-01906, 2020-0-01361), the NRF grant funded by the MSIT (No.2020R1A2B5B03097210, RS-2023-00217286), and the Digital Innovation Hub project supervised by the Daegu Digital Innovation Promotion Agency (DIP) grant funded by the Korea government (MSIT and Daegu Metropolitan City) in 2024 (No. DBSD1-07)." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22484" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.176, + 0.107 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.198 + ], + "angle": 0, + "content": "[1] Devansh Arpit, Stanisław Jastrzebski, Nicolas Ballas, David Krueger, Emmanuel Bengio, Maxinder S Kanwal, Tegan Maharaj, Asja Fischer, Aaron Courville, Yoshua Bengio, et al. 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IEEE, 2011. 2, 6" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.47, + 0.699 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22487" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/9326fcaf-0cf3-4eae-8525-ad22e7243842_origin.pdf b/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/9326fcaf-0cf3-4eae-8525-ad22e7243842_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..583e1cb8c2698245167ce8bb7e4958644ca9bfa7 --- /dev/null +++ b/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/9326fcaf-0cf3-4eae-8525-ad22e7243842_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:2c1b0d1f5576ab318a855b325781733a7a2b71ddb5e52ffc78a72fd2c429742d +size 1240405 diff --git a/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/full.md b/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/full.md new file mode 100644 index 0000000000000000000000000000000000000000..32a0ad907e2fc3cb422a05d97f6dfe28f5704bd0 --- /dev/null +++ b/2024/Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection/full.md @@ -0,0 +1,358 @@ +# Learning Discriminative Dynamics with Label Corruption for Noisy Label Detection + +Suyeon Kim $^{1}$ , Dongha Lee $^{2*}$ , SeongKu Kang $^{3}$ , Sukang Chae $^{1}$ , Sanghwan Jang $^{1}$ , Hwanjo Yu $^{1*}$ $^{1}$ POSTECH, $^{2}$ Yonsei University, $^{3}$ University of Illinois at Urbana Champaign + +{kimsu, chaesgng2, s.jang, hwanjoyu}@postech.ac.kr, donalee@yonsei.ac.kr, seongku@illinois.edu + +# Abstract + +Label noise, commonly found in real-world datasets, has a detrimental impact on a model's generalization. To effectively detect incorrectly labeled instances, previous works have mostly relied on distinguishable training signals, such as training loss, as indicators to differentiate between clean and noisy labels. However, they have limitations in that the training signals incompletely reveal the model's behavior and are not effectively generalized to various noise types, resulting in limited detection accuracy. In this paper, we propose DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones based on the dynamics of the training signals. To cope with the absence of supervision for clean and noisy labels, DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels, enabling indirect simulation of the model's behavior on noisy labels. Then, DynaCor learns to identify clean and noisy instances by inducing two clearly distinguishable clusters from the latent representations of training dynamics. Our comprehensive experiments show that DynaCor outperforms the state-of-the-art competitors and shows strong robustness to various noise types and noise rates. + +# 1. Introduction + +The remarkable success of deep neural networks (DNNs) is largely attributed to massive and accurately labeled datasets. However, creating such datasets is not only expensive but also time-consuming. As a cost-effective alternative, various methods have been employed for label collection, such as crowdsourcing [11] and extracting image labels from accompanying text on the web [27, 54]. Unfortunately, these approaches have led to the emergence of noise in real-world datasets, with reported noise rates ranging from $8.0\%$ to $38.5\%$ [25, 27, 54], which severely degrades the model's performance [1, 58]. + +To cope with the detrimental effect of such noisy labels, a variety of approaches have been proposed, including noise robust learning that minimizes the impact of inaccurate information from noisy labels during the training process [7, 29, 49, 54] and data re-annotation through algorithmic methods [16, 39, 61]. Among them, the task of noisy label detection, which our work mainly focuses on, aims to identify incorrectly labeled instances in a training dataset [7, 22, 34]. This task has gained much attention in that it can be further utilized for improving the quality of the original dataset via cleansing or rectifying such instances. + +Motivated by the memorization effect, which refers to the phenomenon where DNNs initially grasp simple and generalized patterns in correctly labeled data and then gradually overfit to incorrectly labeled data [1], most existing studies have utilized distinguishable training signals as indicators of label quality to differentiate between clean and noisy labels. To elaborate, these training signals are derived from the model's behavior on individual instances during the training [42, 44], involving factors such as training loss or confidence scores. Note that it is impractical to acquire annotations explicitly indicating whether each instance is correctly labeled or not. Hence, numerous studies have crafted various heuristic training signals [12, 19, 22], designed based on human prior knowledge of the model's distinctive behaviors when faced with clean and noisy labels. + +Despite their effectiveness, the training signal-based detection methods still exhibit several limitations: (1) They only focus on a scalar signal at a single epoch (or a representative one across the entire training trajectory), which leads to limited detection accuracy (See Appendix B.2). Since the model's distinct behaviors on clean and noisy labels draw different temporal trajectories of training signals, a single scalar is insufficient to distinguish them by capturing temporal patterns within training dynamics. (2) Existing detection approaches based on heuristics are not effectively generalized to various types of label noise. Noisy labels can originate from diverse sources, including human annotator errors [33, 50], systematic biases [46], and unreliable annotations from web crawling [54], resulting in + +different noise types and rates for each dataset; this eventually requires considerable efforts to tune hyperparameters for training recipes of DNNs [26, 29, 45]. + +To tackle these challenges, our goal is to propose a fully data-driven approach that directly learns to distinguish the training dynamics of noisy labels from those of clean labels using a given dataset without solely relying on heuristics. The primary technical challenge in this data-driven approach arises from the absence of supervision for clean and noisy labels. As a solution, we introduce a label corruption strategy-image augmentation attaching intentionally corrupted labels via random label replacement. Since the augmented instances are highly likely to have incorrect labels, we can utilize them to capture the training dynamics of noisy labels. In other words, this allows us to simulate the model's behavior on noisy labels by leveraging the augmented instances with corrupted labels. + +In this work, we present a novel framework, named DynaCor, that learns discriminative Dynamics with label Corruption for noisy label detection. To be specific, DynaCor identifies clean and noisy labels via clustering of latent representations of training dynamics. To this end, it first generates training dynamics of original instances and corrupted instances. Then, it computes the dynamics representations that encode discriminative patterns within the training trajectories by using a parametric dynamics encoder. The dynamics encoder is optimized to induce two clearly distinguishable clusters (i.e., each for clean and noisy instances) based on two different types of losses for (1) high cluster cohesion and (2) cluster alignment between original and corrupted instances. Furthermore, DynaCor adopts a simple validation metric for the dynamics encoder based on the clustering quality so as to indirectly estimate its detection performance where ground-truth annotations of clean and noisy labels are not available for validation as well. + +The contribution of this work is threefold as follows: + +- We introduce a label corruption strategy that augments the original data with corrupted labels, which are highly likely to be noisy, enabling indirect simulation of the model's behavior on noisy labels during the training. +- We present a data-driven DynaCor framework to distinguish incorrectly labeled instances from correctly labeled ones via clustering of the training dynamics. +- Our extensive experiments on real-world datasets demonstrate that DynaCor achieves the highest accuracy in detecting incorrectly labeled instances and remarkable robustness to various noise types and noise rates. + +# 2. Related Work + +We provide a brief overview of the two primary research directions for addressing incorrectly labeled instances in a noisy dataset: (1) Noisy label detection focuses on identifying instances that are incorrectly labeled within a dataset, + +aiming to enhance data quality. (2) Noise robust learning is centered on developing learning algorithms and models that are resilient to the impact of noisy labels, ensuring robust performance even in the presence of labeling errors. + +Noisy label detection. The main challenge in detecting noisy labels lies in defining a surrogate metric for label quality, essentially indicating how likely an instance is correctly labeled. The widely adopted option is the training loss, assessing the disparity between the model prediction and given labels [15, 19, 20], with higher loss often indicating incorrect labels. Various proxy measures, including gradient-based values [47, 60] and prediction-based metrics [31, 34, 39, 41] have been developed to differentiate between clean and noisy labels, utilizing methods like Gaussian mixture models [4, 22, 26, 64] or manually designed thresholds [15, 31, 34, 57, 63]. However, these approaches may overlook the potential benefits of adopting a data-driven (or learning-centric) detection model [7], which can be easily generalized to various noise types and levels. As a training-free alternative, a recent study [63] introduces a non-parametric KNN-based approach based on the assumption that instances situated closely in the input feature spaces derived from a pre-trained model are more likely to share the same clean label. However, its efficacy in detection heavily depends on the quality of the pre-trained model and may not be universally applicable across domains with specific fine-grained visual features. + +Noise robust learning. Extensive research have focused on creating noise robust methods: loss functions [47, 60], regularization [6, 8, 29], model architectures [2, 5, 9, 13, 21, 54, 56], and training strategies [23, 30, 52, 59]. Recent studies have endeavored to integrate the process of detecting noisy labels and appropriately addressing them into the training pipeline in various ways: re-weighting losses [20, 36, 38] or re-annotation [16, 39, 61]. Besides, several studies [4, 26, 45, 51] treat detected noisy labels as unlabeled and make use of established semi-supervised techniques [3, 16, 59, 61]. Current robust learning typically relies on clean data, i.e., test data, for validation, while noisy detection methods can function without it, making direct comparisons difficult [63]. In this sense, we will discuss how these noise robust learning approaches can be effectively combined with noisy detection methods (Sec. 5.5). + +# 3. Problem Formulation + +For multi-class classification, let $\mathcal{X}$ be an input feature space and $\mathcal{Y} = \{1,2,\dots,C\}$ be a label space. Consider a dataset $D = \{(\mathbf{x}_n,y_n)\}_{n = 1}^N$ , where each sample is independently drawn from an unknown joint distribution over $\mathcal{X}\times \mathcal{Y}$ . In real-world scenarios, we can only access a noisily labeled training set $\widetilde{D} = \{(\mathbf{x}_n,\tilde{y}_n)\}_{n = 1}^N$ , where $\tilde{y}$ denotes a noisy annotation, and there may exist $n\in \{1,\ldots ,N\}$ such + +![](images/7d1e5ee353fc116cfa7b179edb8cfd384243ad639f1677e0aabe5bd971495144.jpg) +1. Corrupted dataset construction + +![](images/fda0569deca210cb355d1eefa5409859148a34340d552cd3bd4ac62f9a3725c8.jpg) +2. Training dynamics generation +3. Noisy label detection via dynamics clustering + +![](images/ba4b97b564ffa7655c93daa3b1ea2ccd7b6f7dd2155e6249c3850eb0c793a1e8.jpg) +Figure 1. The proposed DynaCor framework consists of three steps: (1) Corrupted dataset construction generates the augmented images with corrupted labels, likely resulting in noisy labels, in order to provide guidance for discrimination between clean and noisy labels. (2) Training dynamics generation collects the trajectory of training signals for both the original and corrupted datasets by training a classifier. (3) Noisy label detection is performed by discovering two distinguishable clusters of dynamics representations, and for this, the dynamics encoder is optimized to enhance both cluster cohesion and alignment between the original and the corrupted datasets. + +that $y_{n} \neq \tilde{y}_{n}$ . In this work, we focus on the task of noisy label detection, which aims to identify the incorrectly labeled instances, i.e., $\{(x_{n},\tilde{y}_{n}) \in \widetilde{D} \mid y_{n} \neq \tilde{y}_{n}\}$ . As an evaluation metric, we use F1 score [28], treating the incorrectly labeled instances as positive and the remainings as negative. + +# 4. Methodology + +# 4.1. Overview + +DynaCor (Dynamics learning with label Corruption for noisy label detection) framework learns discriminative patterns inherent in training dynamics, thereby distinguishing incorrectly labeled instances from clean ones. As illustrated in Figure 1, DynaCor consists of three major steps. + +- Corrupted dataset construction (Sec. 4.2): To address the challenge arising from the lack of supervision for incorrectly labeled instances, we introduce a corrupted dataset that intentionally corrupts labels, providing guidance to identify incorrectly labeled instances. +- Training dynamics generation (Sec. 4.3): We generate training dynamics, which denote a model's behavior on individual instances during training, by training a classifier using both the original and the corrupted dataset. +- Noisy label detection via dynamics clustering (Sec. 4.4): We seek to discover underlying patterns in the training dynamics by learning representations that reflect the intrinsic similarities among data points, leveraging the characteristics of the corrupted dataset. For this, we encode the training dynamics via a dynamics encoder that learns discriminative representation using clustering and alignment losses. Then we find clusters using a robust validation metric designed for dynamics-based clustering. + +# 4.2. Corrupted dataset construction + +Given the original dataset $\widetilde{D}$ , we construct a corrupted dataset $\bar{D}$ by intentionally corrupting labels for a randomly sampled subset of $\widetilde{D}$ with a corruption rate $\gamma \in (0,1]$ . Specifically, to obtain a corrupted instance $(\bar{\mathbf{x}},\bar{y})$ from an original data instance $(\mathbf{x},\tilde{y})$ , we transform an input image using weak augmentation such as horizontal flip or center crop, i.e., $\bar{\mathbf{x}} = \mathrm{Aug}(\mathbf{x})$ . Then, we randomly flip the class label to one of the other classes, i.e., $\bar{y} \in \{1,\dots,C\} \backslash \{\tilde{y}\}$ . The corrupted dataset, guaranteed to exhibit symmetric noise at a higher rate than the original, provides additional signals for discerning incorrectly labeled instances in the clustering process, as detailed in the following analysis. + +Analysis: the noise rate of the corrupted dataset. We analyze the lower bound on the noise rate of the corrupted dataset $\bar{D}$ . Let $\eta \in [0,1]$ denote the noise rate of the original dataset $\widetilde{D}$ . Following the previous literature [14, 15, 40], we presume the diagonally dominant condition, i.e., $\operatorname*{Pr}(\tilde{y} = i|y = i) > \operatorname*{Pr}(\tilde{y} = j|y = i), \forall i \neq j$ , which indicates that correct labels should not be overwhelmed by the false ones. With this condition of $\eta < 1 - \frac{1}{C}$ , we have the following proposition. + +Proposition 1 (Lower bound of $\eta_{\gamma}$ ) Let $\eta_{\gamma}$ denote the noise rate of the corrupted dataset. Given the diagonally dominant condition, i.e., $\eta < 1 - \frac{1}{C}$ , for any $\gamma \in (0,1]$ , $\eta_{\gamma}$ has a lower bound of $1 - \frac{1}{C}$ . + +The proof is presented in Appendix C, from which we can derive $\eta < \eta_{\gamma}$ . + +$$ +{ } ^ { 1 } \eta = \frac { 1 } { | \widetilde { D } | } \left| \left\{ ( \mathbf { x } , \widetilde { y } ) \in \widetilde { D } \mid \widetilde { y } \neq y , ( \mathbf { x } , y ) \in D \right\} \right| +$$ + +# 4.3. Training dynamics generation + +# 4.3.1 Training dynamics + +The training dynamics indicates a model's behavior on individual instances during the training, quantitatively describing the training process [42, 44]. Concretely, the training dynamics is defined as the trajectory of training signals derived from a model's output across the training epochs. In the literature, various types of training signals [1, 42, 62] have been employed for analyzing the model's behavior. + +Given a classifier $f$ , let $f(\mathbf{x}) \in \mathbb{R}^C$ denote the output logits of an instance $\mathbf{x}$ for $C$ classes. Let $t$ be a transformation function that maps $C$ logits to a scalar training signal. In this paper, we use quantized logit difference as the training signal. It quantizes the difference between a logit [34] of a given label and the largest logit among the remaining classes, i.e., $t(f(\mathbf{x}),\tilde{y}) = \mathrm{sign}(f_{\tilde{y}}(\mathbf{x}) - \max_{c\neq \tilde{y}}f_c(\mathbf{x}))$ , where $f_{c}(\mathbf{x})$ denotes the logit for class $c$ , and $\mathrm{sign}(\mathbf{x}) = 1$ or -1 if $\mathbf{x} > = 0$ or $< 0$ , respectively. The training dynamics for an instance $\mathbf{x}$ is defined as + +$$ +\mathbf {t} _ {\mathbf {x}} = \left[ t ^ {(1)} \left(f (\mathbf {x}), \tilde {y}\right),.., t ^ {(E)} \left(f (\mathbf {x}), \tilde {y}\right) \right], \tag {1} +$$ + +where $t^{(e)}(f(\mathbf{x}),\tilde{y})$ denotes the training signal computed at epoch $e$ , and $E$ is the maximum number of training epochs. For the sake of convenience, we denote $\mathbf{t}_{\mathbf{x}}$ and $t_{\mathbf{x}}^{(e)}$ as an abbreviation for $\mathbf{t}(\mathbf{x},\tilde{y};f)$ and $t^{(e)}(f(\mathbf{x}),\tilde{y})$ , respectively. + +# 4.3.2 Dynamics generation for noisy label detection + +We generate training dynamics for both the original and the corrupted datasets. Specifically, we train a classifier by minimizing the classification loss on $\widetilde{D}$ and $\bar{D}$ : + +$$ +\frac {1}{| \tilde {D} |} \sum_ {(\mathbf {x}, \tilde {y}) \in \tilde {D}} \ell_ {c e} (f (\mathbf {x}), \tilde {y}) + \frac {1}{| \bar {D} |} \sum_ {(\bar {\mathbf {x}}, \bar {y}) \in \bar {D}} \ell_ {c e} (f (\bar {\mathbf {x}}), \bar {y}), \tag {2} +$$ + +where $\ell_{ce}$ is the softmax cross-entropy loss. For each instance $\mathbf{x}$ , we obtain a training dynamics $\mathbf{t}_{\mathbf{x}} \in \mathbb{R}^{E}$ as specified in Eq. (1) by tracking $t_{\mathbf{x}}^{(e)}$ over the course of training epochs $E$ . Training dynamics of the original and the corrupted datasets are denoted by $\widetilde{T} := \{\mathbf{t}_{\mathbf{x}} | (\mathbf{x}, \tilde{y}) \in \widetilde{D}\}$ and $\bar{T} := \{\mathbf{t}_{\bar{\mathbf{x}}} | (\bar{\mathbf{x}}, \bar{y}) \in \bar{D}\}$ , respectively. + +# 4.4. Noisy label detection via dynamics clustering + +We use a clustering approach to identify incorrectly labeled instances within the original dataset. Using a dynamics encoder, we encode the generated dynamics and progressively find clusters of correctly and incorrectly labeled instances + +in the representation space. The dynamics clustering iterates two key processes: (1) identifications of incorrectly labeled instances (Sec. 4.4.1), and (2) learning distinct representations for each cluster (Sec. 4.4.2). The clustering quality is assessed by a newly introduced validation metric by leveraging the corrupted dataset without a clean validation dataset (Sec. 4.4.3). + +# 4.4.1 Identification of incorrectly labeled instances + +Cluster initialization. Given a training dynamics $\mathbf{t}_{\mathbf{x}}$ , a dynamics encoder generates its representation, i.e., $\mathbf{z}_{\mathbf{x}} = \mathrm{Enc}(\mathbf{t}_{\mathbf{x}}) \in \mathbb{R}^{d_{\mathbf{z}}}$ . Let $\widetilde{Z}$ and $\widetilde{Z}$ denote the set of dynamics representations of the original and the corrupted datasets, respectively. We first introduce trainable parameters for centroids of noisy and clean clusters, i.e., $\mu_{noisy}$ , $\mu_{clean} \in \mathbb{R}^{d_{\mathbf{z}}}$ . We initialize $\mu_{noisy}$ as the average representation of the corrupted instances $\widetilde{Z}$ , while $\mu_{clean}$ is initialized as the average representation of the original instances $\widetilde{Z}$ . Note that this initialization is conducted only once at the beginning of the dynamics clustering step. + +Noisy label identification. We determine whether each instance $\mathbf{x}$ has been incorrectly labeled based on its assignment probability to the noisy cluster. The assignment probability is computed based on the similarity between $\mathbf{z}_{\mathbf{x}}$ and the noisy cluster's centroid $\pmb{\mu}_{\text {noisy }}$ . We employ a kernel function based on the Student's $t$ -distribution [43] with one degree of freedom as follows: + +$$ +q _ {n o i s y} (\mathbf {z} _ {\mathbf {x}}) = \frac {(1 + d (\mathbf {z} _ {\mathbf {x}} , \boldsymbol {\mu} _ {n o i s y})) ^ {- 1}}{(1 + d (\mathbf {z} _ {\mathbf {x}} , \boldsymbol {\mu} _ {n o i s y})) ^ {- 1} + (1 + d (\mathbf {z} _ {\mathbf {x}} , \boldsymbol {\mu} _ {c l e a n})) ^ {- 1}}, +$$ + +$$ +q _ {\text {c l e a n}} \left(\mathbf {z} _ {\mathbf {x}}\right) = 1 - q _ {\text {n o i s y}} \left(\mathbf {z} _ {\mathbf {x}}\right), \tag {3} +$$ + +where $d(\mathbf{a},\mathbf{b}) = 1 - \frac{\langle\mathbf{a},\mathbf{b}\rangle}{||\mathbf{a}||_2\cdot||\mathbf{b}||_2}$ . Based on the assignment probability, we regard an instance as incorrectly labeled when its probability to the noisy cluster is predominant. + +$$ +v \left(\mathbf {z} _ {\mathbf {x}}\right) := \mathbb {1} \left[ q _ {\text {n o i s y}} \left(\mathbf {z} _ {\mathbf {x}}\right) > q _ {\text {c l e a n}} \left(\mathbf {z} _ {\mathbf {x}}\right) \right], \tag {4} +$$ + +$v(\mathbf{z}_{\mathbf{x}}) = 1$ indicates that $\mathbf{x}$ is predicted to have a noisy label. + +# 4.4.2 Learning discriminative patterns in dynamics + +We introduce the strategy of inducing two distinguishable clusters (each for correctly and incorrectly labeled instances) in the dynamics representation space. We propose two types of losses for (1) high cluster cohesion and (2) cluster alignment between original and corrupted instances. + +Clustering loss. We introduce a clustering loss to make the clusters more distinguishable. We enhance cluster cohesion by adjusting each instance's representation to be closer to a centroid through a self-enhancing target distribution. + +The target distribution is constructed by amplifying the predicted assignment probability [55] as follows: + +$$ +p _ {n o i s y} (\mathbf {z _ {x}}) = \frac {q _ {n o i s y} ^ {2} (\mathbf {z _ {x}}) / s _ {n o i s y}}{q _ {n o i s y} ^ {2} (\mathbf {z _ {x}}) / s _ {n o i s y} + q _ {c l e a n} ^ {2} (\mathbf {z _ {x}}) / s _ {c l e a n}}, +$$ + +$$ +p _ {\text {c l e a n}} \left(\mathbf {z} _ {\mathbf {x}}\right) = 1 - p _ {\text {n o i s y}} \left(\mathbf {z} _ {\mathbf {x}}\right), \tag {5} +$$ + +where $s_{noisy} = \sum_{\mathbf{z} \in \widetilde{Z} \cup \bar{Z}} q_{noisy}(\mathbf{z})$ and $s_{clean} = \sum_{\mathbf{z} \in \widetilde{Z} \cup \bar{Z}} q_{clean}(\mathbf{z})$ . Then, we minimize the KL divergence between the cluster assignment distribution $\mathbf{q}(\mathbf{z}_{\mathbf{x}}) = [q_{noisy}(\mathbf{z}_{\mathbf{x}}), q_{clean}(\mathbf{z}_{\mathbf{x}})]$ and the target distribution $\mathbf{p}(\mathbf{z}_{\mathbf{x}}) = [p_{noisy}(\mathbf{z}_{\mathbf{x}}), p_{clean}(\mathbf{z}_{\mathbf{x}})]$ as follows: + +$$ +\mathcal {L} _ {\text {c l u s t e r}} = \sum_ {\mathbf {z} _ {\mathbf {x}} \in \widetilde {\tilde {Z}} \cup \bar {Z}} \operatorname {K L} (\mathbf {p} \left(\mathbf {z} _ {\mathbf {x}}\right) | | \mathbf {q} \left(\mathbf {z} _ {\mathbf {x}}\right)). \tag {6} +$$ + +Alignment loss. We introduce an alignment loss that aligns the representation from each cluster's original and corrupted datasets. We hypothesize3 that symmetric noise is relatively easy to identify among various noise types with diverse difficulty levels. Consequently, incorrectly labeled instances in the corrupted dataset exhibit more distinctive dynamics patterns than those in the original data, i.e., a red dashed line is farther away from blue lines than a red line in the 3rd step of Fig.1 (left). From this perspective, the mismatched noise types between the original and the corrupted datasets positively impact the clustering process by adopting alignment loss, which forces a red line to be aligned with a red dashed line in the 3rd step of Fig.1 (right). + +Instances in the original dataset predicted as noisy and clean are denoted by $\widetilde{Z}_{noisy} = \{\mathbf{z}_{\mathbf{x}} \in \widetilde{Z} | v(\mathbf{z}_{\mathbf{x}}) = 1\}$ and $\widetilde{Z}_{clean} = \{\mathbf{z}_{\mathbf{x}} \in \widetilde{Z} | v(\mathbf{z}_{\mathbf{x}}) = 0\}$ , respectively. Analogously, for the corrupted dataset, we obtain $\bar{Z}_{noisy} = \{\mathbf{z}_{\mathbf{x}} \in \bar{Z} | v(\mathbf{z}_{\mathbf{x}}) = 1\}$ and $\bar{Z}_{clean} = \{\mathbf{z}_{\mathbf{x}} \in \bar{Z} | v(\mathbf{z}_{\mathbf{x}}) = 0\}$ . Then, we employ the alignment loss to reduce the discrepancy between the representations of the original dataset and the corrupted dataset as follows: + +$$ +\mathcal {L} _ {a l i g n} ^ {n} = d \Big (\frac {1}{| \tilde {\bar {Z}} _ {n o i s y} |} \sum_ {\mathbf {z} _ {\mathbf {x}} \in \tilde {\bar {Z}} _ {n o i s y}} \mathbf {z} _ {\mathbf {x}}, \frac {1}{| \bar {Z} _ {n o i s y} |} \sum_ {\mathbf {z} _ {\mathbf {x}} \in \bar {Z} _ {n o i s y}} \mathbf {z} _ {\mathbf {x}} \Big), +$$ + +$$ +\mathcal {L} _ {\text {a l i g n}} ^ {c} = d \Big (\frac {1}{| \tilde {Z} _ {\text {c l e a n}} |} \sum_ {\mathbf {z} _ {\mathbf {x}} \in \tilde {Z} _ {\text {c l e a n}}} \mathbf {z} _ {\mathbf {x}}, \frac {1}{| \bar {Z} _ {\text {c l e a n}} |} \sum_ {\mathbf {z} _ {\mathbf {x}} \in \bar {Z} _ {\text {c l e a n}}} \mathbf {z} _ {\mathbf {x}} \Big), +$$ + +$$ +\mathcal {L} _ {\text {a l i g n}} = \frac {1}{2} \left(\mathcal {L} _ {\text {a l i g n}} ^ {n} + \mathcal {L} _ {\text {a l i g n}} ^ {c}\right). \tag {7} +$$ + +Optimization. To sum up, the dynamics encoder is optimized by minimizing the following loss: + +$$ +\mathcal {L} = \mathcal {L} _ {\text {c l u s t e r}} + \alpha \mathcal {L} _ {\text {a l i g n}}, \tag {8} +$$ + +where $\alpha$ is a hyperparameter that controls the impact of the alignment loss. + +# 4.4.3 Validation metric + +One practical challenge in training the dynamics encoder is determining an appropriate stopping point in the absence of ground-truth annotations of clean and noisy labels for validation. As a solution, we introduce a new validation metric for the dynamics encoder to estimate its detection performance indirectly. For noisy label detection, we aim to maximize (a) the assignment of incorrectly labeled instances to the noisy cluster while minimizing (b) the assignment of correctly labeled instances to the noisy cluster. Intuitively, in an ideally clustered space, the difference between (a) and (b) needs to be maximized. + +Since we cannot access the ground-truth annotations to compute (a) and (b), we use the most representative instances as a workaround. Considering the corrupted dataset has a higher noise rate than the original dataset, we emulate (a) using instances predicted as noisy among the corrupted dataset, i.e., $\bar{Z}_{\text{noise}}$ . Similarly, (b) is emulated using instances predicted as clean among the original dataset with a lower noise rate, i.e., $\tilde{Z}_{\text{clean}}$ . Our validation metric is defined as the difference between two emulated values as + +$$ +\left(\sum_ {\mathbf {z} _ {\mathbf {x}} \in \bar {Z} _ {\text {n o i s y}}} \frac {q _ {\text {n o i s y}} (\mathbf {z} _ {\mathbf {x}})}{| \bar {Z} _ {\text {n o i s y}} |} - \sum_ {\mathbf {z} _ {\mathbf {x}} \in \tilde {Z} _ {\text {c l e a n}}} \frac {q _ {\text {n o i s y}} (\mathbf {z} _ {\mathbf {x}})}{| \tilde {Z} _ {\text {c l e a n}} |}\right) ^ {2}. \tag {9} +$$ + +The larger value indicates the better clustering quality for noisy label detection. Compared to the conventional metrics for assessing cluster separation [10, 37], this metric is tailored for our DynaCor framework and provides a more effective measure of noisy label detection efficacy. + +# 5. Experiments + +# 5.1. Experiment setup + +Datasets. We evaluate the performance of DynaCor on benchmark datasets with different types of label noise, originating from diverse sources: (1) synthetic noise on CIFAR-10 and CIFAR-100 [24], (2) real-world human noise on CIFAR-10N and CIFAR-100N [50], and (3) systematic noise $^{4}$ on Clothing1M [54]. In the case of synthetic noise, following the previous experimental setup [63], we artificially introduce the noise by using different strategies with specific noise rates $\eta$ as outlined below. + +- Symmetric Noise (Sym., $\eta = 0.6$ ) randomly replaces the label with one of the other classes. +- Asymmetric Noise (Asym., $\eta = 0.3$ ) performs pairwise label flipping, where transition can only occur from a given class $i$ to the next class ( $i \bmod C) + 1$ . +- Instance-dependent Noise (Inst., $\eta = 0.4$ ) changes labels based on the transition probability calculated using instance's corresponding features [53]. + +
DatasetCIFAR-10CIFAR-100
Noise typeSym.Asym.Inst.Agg.WorstSym.Asym.Inst.HumanAvg.
Noise rate (η)0.60.30.40.090.40.60.30.40.4
Avg.Encoder98.0 ± 0.0389.7 ± 0.1422.4 ± 33.567.3 ± 0.4292.8 ± 0.1196.7 ± 0.0774.9 ± 0.1776.8 ± 0.5179.5 ± 0.3177.6
AUM95.7 ± 0.0786.5 ± 0.1881.9 ± 0.7274.0 ± 0.1688.7 ± 0.1996.4 ± 0.1074.7 ± 0.2181.2 ± 0.2574.6 ± 1.2583.7
CL96.6 ± 0.0494.0 ± 0.1082.0 ± 0.2168.6 ± 0.3388.3 ± 0.1188.0 ± 0.0868.6 ± 0.1675.9 ± 0.1271.9 ± 0.1081.5
CORES97.7 ± 0.035.00 ± 0.3319.2 ± 0.1080.5 ± 0.0977.5 ± 0.0983.9 ± 0.2021.9 ± 0.3236.7 ± 0.4136.0 ± 0.1250.9
SIMIFEAT-V95.1 ± 0.0689.4 ± 0.0888.1 ± 0.1179.6 ± 0.1391.6 ± 0.0686.0 ± 0.0973.8 ± 0.0780.5 ± 0.0977.1 ± 0.1284.6
SIMIFEAT-R96.1 ± 1.4188.9 ± 0.1491.2 ± 0.0779.6 ± 0.4091.7 ± 0.3590.3 ± 0.0768.0 ± 0.1077.3 ± 0.0979.3 ± 0.1184.7
DynaCor98.0 ± 0.0494.0 ± 0.1592.3 ± 0.3879.6 ± 0.3792.3 ± 0.1994.3 ± 0.3476.3 ± 0.2381.7 ± 0.2180.4 ± 0.1787.7
+ +Table 1. Average F1 score (\%) along with standard deviation across ten independent runs of DynaCor and baseline methods on CIFAR-10 and CIFAR-100. All methods except SIMIFEAT utilize the identical fixed image encoder from CLIP [35] and train only a subsequent MLP, while SIMIFEAT uses pre-trained CLIP as a feature extractor. The rightmost column averages the F1 scores across nine different settings. "Agg.", "Worst", and "Human" correspond to the real-world human label noises [50]. The best results are in bold. + +
DatasetCIFAR-10CIFAR-100
Noise typeSym.Asym.Inst.Agg.WorstSym.Asym.Inst.HumanAvg.
Avg.Encoder94.1 ± 0.1485.4 ± 0.1988.5 ± 0.2063.6 ± 0.7287.6 ± 0.1892.5 ± 0.3475.2 ± 0.3676.0 ± 0.4978.8 ± 0.1882.4
AUM75.4 ± 0.2246.4 ± 0.3057.7 ± 0.0316.7 ± 0.0157.8 ± 0.0475.8 ± 0.2146.7 ± 0.3257.8 ± 0.1058.0 ± 0.2154.7
CL88.7 ± 0.5691.9 ± 0.1282.5 ± 0.3757.0 ± 0.3180.0 ± 0.3277.9 ± 0.3962.4 ± 0.2467.3 ± 0.2865.2 ± 0.1974.8
CORES92.9 ± 0.1726.7 ± 0.4449.2 ± 1.1563.6 ± 0.5874.7 ± 0.3666.3 ± 0.3533.8 ± 0.4639.2 ± 0.4531.9 ± 0.4853.2
SIMIFEAT-V94.6 ± 0.0684.7 ± 0.1783.7 ± 0.0869.4 ± 0.1788.3 ± 0.0888.0 ± 0.0970.3 ± 0.1477.8 ± 0.1076.2 ± 0.1481.4
SIMIFEAT-R92.9 ± 1.8484.0 ± 0.1386.9 ± 0.0868.8 ± 0.3288.5 ± 0.3689.7 ± 0.0766.2 ± 0.1175.5 ± 0.0877.8 ± 0.1381.2
DynaCor93.6 ± 0.1894.2 ± 0.4591.5 ± 0.3172.6 ± 2.4687.8 ± 0.3791.3 ± 0.4679.2 ± 0.5979.5 ± 1.1477.3 ± 0.5485.2
+ +Table 2. Average F1 score (%) under identical settings to those in Table 1 except for the backbone model. All methods except SIMIFEAT utilize a randomly initialized Renset34 [17], while SIMIFEAT uses a pre-trained ResNet34 on ImageNet [11] as a feature extractor. + +In the case of human noise, we choose two noise subtypes for CIFAR-10N (denoted by Agg. and Worst) and a single noise subtype for CIFAR-100N (denoted by Human). More details of the datasets are presented in Appendix A.1. + +Baselines. We compare DynaCor with various noisy label detection methods. All the methods except SIMIFEAT use training signals to identify incorrectly labeled instances. + +- Avg.Encoder is a naive baseline that discriminates between clean and noisy labels by using a one-dimensional Gaussian mixture model [64] on the averaged training signals (i.e., logit difference) over the epochs. +- AUM [34] uses summation of training signals (i.e., logit difference) over the epochs and identifies correctly/incorrectly labeled instances based on a threshold. +- CL [31] uses a predicted probability of the given label (i.e., confidence) and filter out the instances with low confidence based on class-conditional thresholds. +- CORES [7] leverages a training loss for noisy label detection, progressively filtering out incorrectly labeled instances using its proposed sample sieve. +- SIMIFEAT [63] is a training-free approach that effectively detects noisy labels by utilizing $K$ -nearest neighbors in the feature space of a pre-trained model. + +Implementation details. For our label corruption process, we use the corruption rate $\gamma = 0.1$ as the default. To generate the training dynamics, we employ DNN classifiers: + +ResNet34 [17] and the pre-trained ViT-B/32-CLIP [35] with a multi-layer perceptron (MLP) of two hidden layers. To encode the training dynamics, we use a three-layered 1D-CNN architecture [48] as the dynamics encoder. The hyperparameter $\alpha$ is selected as either 0.05 or 0.5. For more details about implementation, please refer to Appendix A.2. + +# 5.2. Noisy label detection performance + +We first evaluate DynaCor and the baseline methods for noisy label detection. Table 1 and Table 2 present their detection F1 scores for two classifiers, CLIP w/ MLP and ResNet34, across various noise types and rates. Notably, DynaCor achieves the best performance on average, i.e., $+3.0\%$ in Table 1 and $+2.8\%$ in Table 2, demonstrating its robustness to various types of noisy conditions. On the other hand, the baseline methods relying on training signals (i.e., Avg.Encoder, AUM, CL, and CORES) show considerable variations in performance across different noise types. For example, in the case of CIFAR-10, Avg.Encoder and CORES perform well for symmetric noises, whereas they struggle with identifying asymmetric or instance noises. It is worth noting that asymmetric and instance noise are more complex than symmetric noise in that they can have a more detrimental impact on model performance [32]. These results strongly support the superiority of our DynaCor framework in handling a wide range of label noise variations. + +
Validation metricCIFAR-10CIFAR-100
Inst.Agg.Inst.Human
Max epoch86.7 ± 6.7577.8 ± 3.3561.0 ± 10.364.3 ± 4.40
DBI86.3 ± 8.7576.7 ± 3.9160.0 ± 10.264.8 ± 9.70
Ours92.3 ± 0.3879.6 ± 0.3781.7 ± 0.2180.4 ± 0.17
Opt epoch92.6 ± 0.4080.40 ± 0.4481.8 ± 0.0880.5 ± 0.18
+ +![](images/a18fee68b74a91ac2acf81bfc7b1a90f66a2f2b6eec9c5898a3ffcfdf9e5acc9.jpg) + +![](images/033ea5b06c659350d30247ddef95ff89b05ebd244d00162cb39e9509064a368e.jpg) +(a) Supervised setting +(b) Unsupervised setting: DynaCor. +Figure 2. F1 score $(\%)$ changes with respect to corruption rate $(\gamma)$ on CIFAR10 in supervised and unsupervised settings using CLIP w/ MLP (Left) and ResNet34 (Right) as classifiers. + +# 5.3. Effectiveness of validation metric + +To demonstrate the effectiveness of the proposed validation metric (Sec.4.4.3), we compare the detection performance of our dynamics encoder by employing our proposed metric and alternative criteria as stopping conditions during the training. Max epoch signifies the training over the maximum number of epochs. Davies-Bouldin Index (DBI) [10] assesses the quality of clustering results by calculating the ratio of intra-cluster distances to inter-cluster separations. A lower DBI value implies more compact and well-separated clusters, i.e., better clustering quality. In addition, Opt epoch selects the optimal training epoch that achieves the best detection results, providing the upper bound of detection performance. + +In Table 3, our performance is close to the optimal case across various noise types and datasets, whereas Max epoch and DBI fail to stop the training process at a proper epoch on CIFAR-100. In conclusion, using the proper validation metric is critical for achieving competitive detection performance, particularly in the scenario where ground-truth annotations are not available for validation. + +Table 3. F1 score (\%) of our dynamics encoder over various validation metrics on CIFAR-10 and CIFAR-100 using CLIP w/ MLP as a classifier. + +
L_clusterL_alignAsym.Inst.Agg.
93.8 ± 0.1791.8 ± 0.3978.8 ± 0.37
✓93.2 ± 0.1192.7 ± 0.3676.8 ± 0.83
✓✓94.0 ± 0.1592.3 ± 0.3879.6 ± 0.37
+ +Table 4. F1 score (\%) of DynaCor that ablates the clustering and alignment loss on CIFAR10 using CLIP w/ MLP as a classifier. The first row reports the detection performance with a randomly initialized dynamics encoder. + +# 5.4.Quantitative analyses + +The effect of corruption rate. We analyze the effect of increasing the corruption rate, which in turn amplifies the overall noise level. For thorough analyses, we conduct a controlled experiment within a supervised framework using classification, assuming the availability of ground-truth annotations that indicate each instance as being correctly or incorrectly labeled. We then compare these results, generally regarded as the performance upper bound for unsupervised methods, with those obtained by an unsupervised approach. We focus on assessing the ability of our proposed unsupervised learning model, i.e., DynaCor, to discriminate training dynamics and how this discrimination is affected by increasing the overall noise level through corruption. + +As shown in Figure 2, the detection F1 scores achieved by DynaCor (Figure 2b) approaches those of supervised learning (Figure 2a), demonstrating the effectiveness of training dynamics. This proximity is especially notable when utilizing a powerful image encoder, i.e., CLIP, which makes the training dynamics less susceptible to changes in the corruption rate. In contrast, the training dynamics from ResNet34 are more affected by increased corruption rate. Surprisingly, in the case of "Inst." type label noise, the training dynamics from the CLIP w/ MLP classifier become even more distinguishable as the corruption rate increases to 0.5. It shows that a higher noise rate in the training dataset can enhance the discernibility of the training dynamics. We hypothesize that the symmetric noise introduced through our label corruption process may reduce the overall difficulty of the detection task. This is consistent with the assertion in Sec. 4.4.2 that the symmetric noise is relatively straightforward to identify and, in turn, contributes to improving the performance of noisy label detection. + +The effect of two losses. We examine the effect of the clustering and alignment losses within our DynaCor framework. In Table 4, both losses enhance detection performance. We also observe that the alignment loss effectively addresses the high imbalance between clean and noisy instances, particularly in scenarios with a low noise rate (e.g., + +![](images/d56f4bc4a7c2c5e68e025c50aae2056520c5a6794e6a65da512f3687fe3e5972.jpg) + +![](images/41fa1a259a13be8d20db8b3b5964bf792b32ec8119a9dc60a44d4ef4ffba8dbd.jpg) +(a) Classification accuracy $(\%)$ of robust learning +(b) Noisy label detection F1 score $(\%)$ +Figure 3. Compatibility analysis of Dividemix with DynaCor on CIFAR100 over "Asym." and "Inst." with respect to noise rate + +"Agg." on CIFAR-10). Given that DynaCor intentionally increases the noise rate by augmenting instances with corrupted labels, its benefits become more pronounced when dealing with datasets featuring a small original noise rate. In such cases, the alignment loss is crucial in stabilizing the clustering process by aligning the distinct distributions of original and corrupted instances. + +# 5.5. Compatibility analyses with robust learning + +We investigate the compatibility and synergistic effects of integrating our framework with various robust learning techniques: a semi-supervised approach (Dividemix [26]), loss functions (GCE [61] and SCE [47]), and a regularization method (ELR [29]). Detailed analyses of incorporating the loss functions and regularization technique on the Clothing1M dataset are provided in Appendix D. + +For the semi-supervised approach, we select Dividemix [26] that iteratively detects incorrectly labeled instances and treats them as unlabeled instances. We construct integrated models of Dividemix and DynaCor through two distinct approaches: (1) DDyna-L is leveraging Dividemix to obtain the training dynamics of both original and corrupted datasets within our framework, and (2) DDyna-S is substituting the original detection method in Dividemix, i.e., GMM, with DynaCor. For the base architecture, we employ an 18-layer PreAct ResNet [18], adhering to its default optimization settings and hyperparameters, as specified in the original paper [26]. + +Classification accuracy. We explore the impact of our framework on the classifier's accuracy, specifically introducing a corrupted dataset (DDyna-L) and supplanting the existing noise detection method (DDyna-S). Figure 3a + +demonstrates that both enhance classification performance. In essence, results obtained with DDyna-L demonstrate that instances with symmetric label noise introduced through our corruption process prove beneficial for noise robust learning, especially in scenarios featuring a low noise rate in the original dataset, pointed out as a challenging setting for Dividemix [50]. + +Detection F1 score. To report the noisy label detection performance within robust learning framework, i.e., Dividemix and DDyna-S, we measure F1 score at every epoch and report the value when test classification accuracy is at its highest. Note that they leverage a clean test dataset to identify the optimal detection point; on the contrary, the noisy detection method (DDyna-L) operates without access to clean data, instead employing the procedure for model validation on the noisy dataset itself (Sec. 4.4.3), presenting a more challenging task. Figure 3b indicates that DDyna-S and DDyna-L further improves the detection F1 score of Dividemix, indicating the great compatibility of DynaCor with existing semi-supervised noise robust learning. In scenarios involving "Inst." label noise, DDyna-L exhibits compelling synergistic effects across a wide range of noise rates. + +# 6. Conclusion + +This paper proposes a new DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones via clustering of their training dynamics. DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels, enabling indirect simulation of the model's behavior on noisy labels. Subsequently, DynaCor learns to induce two clearly distinguishable clusters for clean and noisy instances by enhancing the cluster cohesion and alignment between the original and corrupted dataset. Furthermore, DynaCor adopts a simple yet effective validation metric to indirectly estimate its detection performance in the absence of annotations of clean and noisy labels. Our comprehensive experiments on real-world datasets demonstrate the detection efficacy of DynaCor, its remarkable robustness to various noise types and noise rates, and great compatibility with existing approaches to noise robust learning. + +# 7. Acknowledgements + +This work was supported by the IITP grant funded by the MSIT (No.2018-0-00584, 2019-0-01906, 2020-0-01361), the NRF grant funded by the MSIT (No.2020R1A2B5B03097210, RS-2023-00217286), and the Digital Innovation Hub project supervised by the Daegu Digital Innovation Promotion Agency (DIP) grant funded by the Korea government (MSIT and Daegu Metropolitan City) in 2024 (No. DBSD1-07). + +# References + +[1] Devansh Arpit, Stanisław Jastrzebski, Nicolas Ballas, David Krueger, Emmanuel Bengio, Maxinder S Kanwal, Tegan Maharaj, Asja Fischer, Aaron Courville, Yoshua Bengio, et al. A closer look at memorization in deep networks. In International conference on machine learning, pages 233-242. PMLR, 2017. 1, 4 +[2] Alan Joseph Bekker and Jacob Goldberger. Training deep neural-networks based on unreliable labels. In 2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), pages 2682-2686. 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To effectively detect incorrectly labeled instances, previous works have mostly relied on distinguishable training signals, such as training loss, as indicators to differentiate between clean and noisy labels. However, they have limitations in that the training signals incompletely reveal the model's behavior and are not effectively generalized to various noise types, resulting in limited detection accuracy. In this paper, we propose DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones based on the dynamics of the training signals. To cope with the absence of supervision for clean and noisy labels, DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels, enabling indirect simulation of the model's behavior on noisy labels. Then, DynaCor learns to identify clean and noisy instances by inducing two clearly distinguishable clusters from the latent representations of training dynamics. Our comprehensive experiments show that DynaCor outperforms the state-of-the-art competitors and shows strong robustness to various noise types and noise rates." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 543, + 128, + 555 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 543, + 128, + 555 + ], + "spans": [ + { + "bbox": [ + 47, + 543, + 128, + 555 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 563, + 288, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 563, + 288, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 563, + 288, + 696 + ], + "type": "text", + "content": "The remarkable success of deep neural networks (DNNs) is largely attributed to massive and accurately labeled datasets. However, creating such datasets is not only expensive but also time-consuming. As a cost-effective alternative, various methods have been employed for label collection, such as crowdsourcing [11] and extracting image labels from accompanying text on the web [27, 54]. 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Among them, the task of noisy label detection, which our work mainly focuses on, aims to identify incorrectly labeled instances in a training dataset [7, 22, 34]. This task has gained much attention in that it can be further utilized for improving the quality of the original dataset via cleansing or rectifying such instances." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 365, + 547, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 365, + 547, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 365, + 547, + 544 + ], + "type": "text", + "content": "Motivated by the memorization effect, which refers to the phenomenon where DNNs initially grasp simple and generalized patterns in correctly labeled data and then gradually overfit to incorrectly labeled data [1], most existing studies have utilized distinguishable training signals as indicators of label quality to differentiate between clean and noisy labels. To elaborate, these training signals are derived from the model's behavior on individual instances during the training [42, 44], involving factors such as training loss or confidence scores. Note that it is impractical to acquire annotations explicitly indicating whether each instance is correctly labeled or not. Hence, numerous studies have crafted various heuristic training signals [12, 19, 22], designed based on human prior knowledge of the model's distinctive behaviors when faced with clean and noisy labels." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 545, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 548, + 714 + ], + "type": "text", + "content": "Despite their effectiveness, the training signal-based detection methods still exhibit several limitations: (1) They only focus on a scalar signal at a single epoch (or a representative one across the entire training trajectory), which leads to limited detection accuracy (See Appendix B.2). Since the model's distinct behaviors on clean and noisy labels draw different temporal trajectories of training signals, a single scalar is insufficient to distinguish them by capturing temporal patterns within training dynamics. (2) Existing detection approaches based on heuristics are not effectively generalized to various types of label noise. Noisy labels can originate from diverse sources, including human annotator errors [33, 50], systematic biases [46], and unreliable annotations from web crawling [54], resulting in" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 138, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 138, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 138, + 712 + ], + "type": "text", + "content": "*Corresponding authors" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22477" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 108 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 108 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 108 + ], + "type": "text", + "content": "different noise types and rates for each dataset; this eventually requires considerable efforts to tune hyperparameters for training recipes of DNNs [26, 29, 45]." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 109, + 287, + 275 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 109, + 287, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 109, + 287, + 275 + ], + "type": "text", + "content": "To tackle these challenges, our goal is to propose a fully data-driven approach that directly learns to distinguish the training dynamics of noisy labels from those of clean labels using a given dataset without solely relying on heuristics. The primary technical challenge in this data-driven approach arises from the absence of supervision for clean and noisy labels. As a solution, we introduce a label corruption strategy-image augmentation attaching intentionally corrupted labels via random label replacement. Since the augmented instances are highly likely to have incorrect labels, we can utilize them to capture the training dynamics of noisy labels. In other words, this allows us to simulate the model's behavior on noisy labels by leveraging the augmented instances with corrupted labels." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 275, + 288, + 490 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 275, + 288, + 490 + ], + "spans": [ + { + "bbox": [ + 46, + 275, + 288, + 490 + ], + "type": "text", + "content": "In this work, we present a novel framework, named DynaCor, that learns discriminative Dynamics with label Corruption for noisy label detection. To be specific, DynaCor identifies clean and noisy labels via clustering of latent representations of training dynamics. To this end, it first generates training dynamics of original instances and corrupted instances. Then, it computes the dynamics representations that encode discriminative patterns within the training trajectories by using a parametric dynamics encoder. The dynamics encoder is optimized to induce two clearly distinguishable clusters (i.e., each for clean and noisy instances) based on two different types of losses for (1) high cluster cohesion and (2) cluster alignment between original and corrupted instances. Furthermore, DynaCor adopts a simple validation metric for the dynamics encoder based on the clustering quality so as to indirectly estimate its detection performance where ground-truth annotations of clean and noisy labels are not available for validation as well." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 58, + 491, + 272, + 502 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 491, + 272, + 502 + ], + "spans": [ + { + "bbox": [ + 58, + 491, + 272, + 502 + ], + "type": "text", + "content": "The contribution of this work is threefold as follows:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 503, + 287, + 634 + ], + "type": "list", + "angle": 0, + "index": 7, + "blocks": [ + { + "bbox": [ + 47, + 503, + 287, + 551 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 503, + 287, + 551 + ], + "spans": [ + { + "bbox": [ + 47, + 503, + 287, + 551 + ], + "type": "text", + "content": "- We introduce a label corruption strategy that augments the original data with corrupted labels, which are highly likely to be noisy, enabling indirect simulation of the model's behavior on noisy labels during the training." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 552, + 287, + 586 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 552, + 287, + 586 + ], + "spans": [ + { + "bbox": [ + 47, + 552, + 287, + 586 + ], + "type": "text", + "content": "- We present a data-driven DynaCor framework to distinguish incorrectly labeled instances from correctly labeled ones via clustering of the training dynamics." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 586, + 287, + 634 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 586, + 287, + 634 + ], + "spans": [ + { + "bbox": [ + 47, + 586, + 287, + 634 + ], + "type": "text", + "content": "- Our extensive experiments on real-world datasets demonstrate that DynaCor achieves the highest accuracy in detecting incorrectly labeled instances and remarkable robustness to various noise types and noise rates." + } + ] + } + ], + "index": 6 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 645, + 134, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 645, + 134, + 658 + ], + "spans": [ + { + "bbox": [ + 47, + 645, + 134, + 658 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "type": "text", + "content": "We provide a brief overview of the two primary research directions for addressing incorrectly labeled instances in a noisy dataset: (1) Noisy label detection focuses on identifying instances that are incorrectly labeled within a dataset," + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "content": "aiming to enhance data quality. (2) Noise robust learning is centered on developing learning algorithms and models that are resilient to the impact of noisy labels, ensuring robust performance even in the presence of labeling errors." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 124, + 546, + 399 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 124, + 546, + 399 + ], + "spans": [ + { + "bbox": [ + 304, + 124, + 546, + 399 + ], + "type": "text", + "content": "Noisy label detection. The main challenge in detecting noisy labels lies in defining a surrogate metric for label quality, essentially indicating how likely an instance is correctly labeled. The widely adopted option is the training loss, assessing the disparity between the model prediction and given labels [15, 19, 20], with higher loss often indicating incorrect labels. Various proxy measures, including gradient-based values [47, 60] and prediction-based metrics [31, 34, 39, 41] have been developed to differentiate between clean and noisy labels, utilizing methods like Gaussian mixture models [4, 22, 26, 64] or manually designed thresholds [15, 31, 34, 57, 63]. However, these approaches may overlook the potential benefits of adopting a data-driven (or learning-centric) detection model [7], which can be easily generalized to various noise types and levels. As a training-free alternative, a recent study [63] introduces a non-parametric KNN-based approach based on the assumption that instances situated closely in the input feature spaces derived from a pre-trained model are more likely to share the same clean label. However, its efficacy in detection heavily depends on the quality of the pre-trained model and may not be universally applicable across domains with specific fine-grained visual features." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 403, + 546, + 595 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 546, + 595 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 546, + 595 + ], + "type": "text", + "content": "Noise robust learning. Extensive research have focused on creating noise robust methods: loss functions [47, 60], regularization [6, 8, 29], model architectures [2, 5, 9, 13, 21, 54, 56], and training strategies [23, 30, 52, 59]. Recent studies have endeavored to integrate the process of detecting noisy labels and appropriately addressing them into the training pipeline in various ways: re-weighting losses [20, 36, 38] or re-annotation [16, 39, 61]. Besides, several studies [4, 26, 45, 51] treat detected noisy labels as unlabeled and make use of established semi-supervised techniques [3, 16, 59, 61]. Current robust learning typically relies on clean data, i.e., test data, for validation, while noisy detection methods can function without it, making direct comparisons difficult [63]. In this sense, we will discuss how these noise robust learning approaches can be effectively combined with noisy detection methods (Sec. 5.5)." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 609, + 432, + 621 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 609, + 432, + 621 + ], + "spans": [ + { + "bbox": [ + 306, + 609, + 432, + 621 + ], + "type": "text", + "content": "3. Problem Formulation" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": "For multi-class classification, let " + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{X}" + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": " be an input feature space and " + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{Y} = \\{1,2,\\dots,C\\}" + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": " be a label space. Consider a dataset " + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "D = \\{(\\mathbf{x}_n,y_n)\\}_{n = 1}^N" + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": " , where each sample is independently drawn from an unknown joint distribution over " + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{X}\\times \\mathcal{Y}" + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": " . In real-world scenarios, we can only access a noisily labeled training set " + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\widetilde{D} = \\{(\\mathbf{x}_n,\\tilde{y}_n)\\}_{n = 1}^N" + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": " , where " + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\tilde{y}" + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": " denotes a noisy annotation, and there may exist " + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "n\\in \\{1,\\ldots ,N\\}" + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": " such" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22478" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 87, + 166, + 224 + ], + "blocks": [ + { + "bbox": [ + 52, + 72, + 167, + 82 + ], + "lines": [ + { + "bbox": [ + 52, + 72, + 167, + 82 + ], + "spans": [ + { + "bbox": [ + 52, + 72, + 167, + 82 + ], + "type": "text", + "content": "1. Corrupted dataset construction" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 53, + 87, + 166, + 224 + ], + "lines": [ + { + "bbox": [ + 53, + 87, + 166, + 224 + ], + "spans": [ + { + "bbox": [ + 53, + 87, + 166, + 224 + ], + "type": "image", + "image_path": "7d1e5ee353fc116cfa7b179edb8cfd384243ad639f1677e0aabe5bd971495144.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 179, + 87, + 290, + 223 + ], + "blocks": [ + { + "bbox": [ + 179, + 72, + 289, + 83 + ], + "lines": [ + { + "bbox": [ + 179, + 72, + 289, + 83 + ], + "spans": [ + { + "bbox": [ + 179, + 72, + 289, + 83 + ], + "type": "text", + "content": "2. Training dynamics generation" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 179, + 87, + 290, + 223 + ], + "lines": [ + { + "bbox": [ + 179, + 87, + 290, + 223 + ], + "spans": [ + { + "bbox": [ + 179, + 87, + 290, + 223 + ], + "type": "image", + "image_path": "fda0569deca210cb355d1eefa5409859148a34340d552cd3bd4ac62f9a3725c8.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 312, + 72, + 473, + 83 + ], + "lines": [ + { + "bbox": [ + 312, + 72, + 473, + 83 + ], + "spans": [ + { + "bbox": [ + 312, + 72, + 473, + 83 + ], + "type": "text", + "content": "3. Noisy label detection via dynamics clustering" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 309, + 106, + 547, + 223 + ], + "blocks": [ + { + "bbox": [ + 309, + 106, + 547, + 223 + ], + "lines": [ + { + "bbox": [ + 309, + 106, + 547, + 223 + ], + "spans": [ + { + "bbox": [ + 309, + 106, + 547, + 223 + ], + "type": "image", + "image_path": "ba4b97b564ffa7655c93daa3b1ea2ccd7b6f7dd2155e6249c3850eb0c793a1e8.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 237, + 547, + 293 + ], + "lines": [ + { + "bbox": [ + 46, + 237, + 547, + 293 + ], + "spans": [ + { + "bbox": [ + 46, + 237, + 547, + 293 + ], + "type": "text", + "content": "Figure 1. The proposed DynaCor framework consists of three steps: (1) Corrupted dataset construction generates the augmented images with corrupted labels, likely resulting in noisy labels, in order to provide guidance for discrimination between clean and noisy labels. (2) Training dynamics generation collects the trajectory of training signals for both the original and corrupted datasets by training a classifier. (3) Noisy label detection is performed by discovering two distinguishable clusters of dynamics representations, and for this, the dynamics encoder is optimized to enhance both cluster cohesion and alignment between the original and the corrupted datasets." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 313, + 287, + 374 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 313, + 287, + 374 + ], + "spans": [ + { + "bbox": [ + 46, + 313, + 287, + 374 + ], + "type": "text", + "content": "that " + }, + { + "bbox": [ + 46, + 313, + 287, + 374 + ], + "type": "inline_equation", + "content": "y_{n} \\neq \\tilde{y}_{n}" + }, + { + "bbox": [ + 46, + 313, + 287, + 374 + ], + "type": "text", + "content": ". In this work, we focus on the task of noisy label detection, which aims to identify the incorrectly labeled instances, i.e., " + }, + { + "bbox": [ + 46, + 313, + 287, + 374 + ], + "type": "inline_equation", + "content": "\\{(x_{n},\\tilde{y}_{n}) \\in \\widetilde{D} \\mid y_{n} \\neq \\tilde{y}_{n}\\}" + }, + { + "bbox": [ + 46, + 313, + 287, + 374 + ], + "type": "text", + "content": ". As an evaluation metric, we use F1 score [28], treating the incorrectly labeled instances as positive and the remainings as negative." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 391, + 129, + 404 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 391, + 129, + 404 + ], + "spans": [ + { + "bbox": [ + 47, + 391, + 129, + 404 + ], + "type": "text", + "content": "4. Methodology" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 413, + 115, + 425 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 413, + 115, + 425 + ], + "spans": [ + { + "bbox": [ + 47, + 413, + 115, + 425 + ], + "type": "text", + "content": "4.1. Overview" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 434, + 287, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 434, + 287, + 494 + ], + "spans": [ + { + "bbox": [ + 46, + 434, + 287, + 494 + ], + "type": "text", + "content": "DynaCor (Dynamics learning with label Corruption for noisy label detection) framework learns discriminative patterns inherent in training dynamics, thereby distinguishing incorrectly labeled instances from clean ones. As illustrated in Figure 1, DynaCor consists of three major steps." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 495, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 47, + 495, + 287, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 495, + 287, + 555 + ], + "spans": [ + { + "bbox": [ + 47, + 495, + 287, + 555 + ], + "type": "text", + "content": "- Corrupted dataset construction (Sec. 4.2): To address the challenge arising from the lack of supervision for incorrectly labeled instances, we introduce a corrupted dataset that intentionally corrupts labels, providing guidance to identify incorrectly labeled instances." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 555, + 287, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 555, + 287, + 604 + ], + "spans": [ + { + "bbox": [ + 47, + 555, + 287, + 604 + ], + "type": "text", + "content": "- Training dynamics generation (Sec. 4.3): We generate training dynamics, which denote a model's behavior on individual instances during training, by training a classifier using both the original and the corrupted dataset." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 47, + 603, + 288, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 603, + 288, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 603, + 288, + 712 + ], + "type": "text", + "content": "- Noisy label detection via dynamics clustering (Sec. 4.4): We seek to discover underlying patterns in the training dynamics by learning representations that reflect the intrinsic similarities among data points, leveraging the characteristics of the corrupted dataset. For this, we encode the training dynamics via a dynamics encoder that learns discriminative representation using clustering and alignment losses. Then we find clusters using a robust validation metric designed for dynamics-based clustering." + } + ] + } + ], + "index": 13 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 313, + 476, + 326 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 313, + 476, + 326 + ], + "spans": [ + { + "bbox": [ + 306, + 313, + 476, + 326 + ], + "type": "text", + "content": "4.2. Corrupted dataset construction" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "spans": [ + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": "Given the original dataset " + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "inline_equation", + "content": "\\widetilde{D}" + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": ", we construct a corrupted dataset " + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "inline_equation", + "content": "\\bar{D}" + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": " by intentionally corrupting labels for a randomly sampled subset of " + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "inline_equation", + "content": "\\widetilde{D}" + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": " with a corruption rate " + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "inline_equation", + "content": "\\gamma \\in (0,1]" + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": ". Specifically, to obtain a corrupted instance " + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "inline_equation", + "content": "(\\bar{\\mathbf{x}},\\bar{y})" + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": " from an original data instance " + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "inline_equation", + "content": "(\\mathbf{x},\\tilde{y})" + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": ", we transform an input image using weak augmentation such as horizontal flip or center crop, i.e., " + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "inline_equation", + "content": "\\bar{\\mathbf{x}} = \\mathrm{Aug}(\\mathbf{x})" + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": ". Then, we randomly flip the class label to one of the other classes, i.e., " + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "inline_equation", + "content": "\\bar{y} \\in \\{1,\\dots,C\\} \\backslash \\{\\tilde{y}\\}" + }, + { + "bbox": [ + 304, + 332, + 547, + 477 + ], + "type": "text", + "content": ". The corrupted dataset, guaranteed to exhibit symmetric noise at a higher rate than the original, provides additional signals for discerning incorrectly labeled instances in the clustering process, as detailed in the following analysis." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "spans": [ + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "text", + "content": "Analysis: the noise rate of the corrupted dataset. We analyze the lower bound on the noise rate of the corrupted dataset " + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\bar{D}" + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "text", + "content": ". Let " + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\eta \\in [0,1]" + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "text", + "content": " denote the noise rate of the original dataset " + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\widetilde{D}" + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "text", + "content": ". Following the previous literature [14, 15, 40], we presume the diagonally dominant condition, i.e., " + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\operatorname*{Pr}(\\tilde{y} = i|y = i) > \\operatorname*{Pr}(\\tilde{y} = j|y = i), \\forall i \\neq j" + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "text", + "content": ", which indicates that correct labels should not be overwhelmed by the false ones. With this condition of " + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\eta < 1 - \\frac{1}{C}" + }, + { + "bbox": [ + 304, + 481, + 547, + 593 + ], + "type": "text", + "content": ", we have the following proposition." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "spans": [ + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "text", + "content": "Proposition 1 (Lower bound of " + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "inline_equation", + "content": "\\eta_{\\gamma}" + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "text", + "content": ") Let " + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "inline_equation", + "content": "\\eta_{\\gamma}" + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "text", + "content": " denote the noise rate of the corrupted dataset. Given the diagonally dominant condition, i.e., " + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "inline_equation", + "content": "\\eta < 1 - \\frac{1}{C}" + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "text", + "content": ", for any " + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "inline_equation", + "content": "\\gamma \\in (0,1]" + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "inline_equation", + "content": "\\eta_{\\gamma}" + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "text", + "content": " has a lower bound of " + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "inline_equation", + "content": "1 - \\frac{1}{C}" + }, + { + "bbox": [ + 304, + 604, + 547, + 654 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 665, + 545, + 691 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 691 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 691 + ], + "type": "text", + "content": "The proof is presented in Appendix C, from which we can derive " + }, + { + "bbox": [ + 304, + 665, + 545, + 691 + ], + "type": "inline_equation", + "content": "\\eta < \\eta_{\\gamma}" + }, + { + "bbox": [ + 304, + 665, + 545, + 691 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 315, + 700, + 474, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 700, + 474, + 716 + ], + "spans": [ + { + "bbox": [ + 315, + 700, + 474, + 716 + ], + "type": "interline_equation", + "content": "{ } ^ { 1 } \\eta = \\frac { 1 } { | \\widetilde { D } | } \\left| \\left\\{ ( \\mathbf { x } , \\widetilde { y } ) \\in \\widetilde { D } \\mid \\widetilde { y } \\neq y , ( \\mathbf { x } , y ) \\in D \\right\\} \\right|", + "image_path": "403d5a7615aeee98aedc83a3e17caa3b5d849f56c91e34e7877b361dcc360a52.jpg" + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22479" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 211, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 211, + 85 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 211, + 85 + ], + "type": "text", + "content": "4.3. Training dynamics generation" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 91, + 161, + 104 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 91, + 161, + 104 + ], + "spans": [ + { + "bbox": [ + 47, + 91, + 161, + 104 + ], + "type": "text", + "content": "4.3.1 Training dynamics" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 111, + 286, + 194 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 111, + 286, + 194 + ], + "spans": [ + { + "bbox": [ + 46, + 111, + 286, + 194 + ], + "type": "text", + "content": "The training dynamics indicates a model's behavior on individual instances during the training, quantitatively describing the training process [42, 44]. Concretely, the training dynamics is defined as the trajectory of training signals derived from a model's output across the training epochs. In the literature, various types of training signals [1, 42, 62] have been employed for analyzing the model's behavior." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "spans": [ + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": "Given a classifier " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": ", let " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "f(\\mathbf{x}) \\in \\mathbb{R}^C" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " denote the output logits of an instance " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " classes. Let " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " be a transformation function that maps " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " logits to a scalar training signal. In this paper, we use quantized logit difference as the training signal. It quantizes the difference between a logit [34] of a given label and the largest logit among the remaining classes, i.e., " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "t(f(\\mathbf{x}),\\tilde{y}) = \\mathrm{sign}(f_{\\tilde{y}}(\\mathbf{x}) - \\max_{c\\neq \\tilde{y}}f_c(\\mathbf{x}))" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "f_{c}(\\mathbf{x})" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " denotes the logit for class " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "\\mathrm{sign}(\\mathbf{x}) = 1" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " or -1 if " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "\\mathbf{x} > = 0" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " or " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "< 0" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": ", respectively. The training dynamics for an instance " + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 46, + 196, + 287, + 316 + ], + "type": "text", + "content": " is defined as" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 89, + 326, + 287, + 342 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 89, + 326, + 287, + 342 + ], + "spans": [ + { + "bbox": [ + 89, + 326, + 287, + 342 + ], + "type": "interline_equation", + "content": "\\mathbf {t} _ {\\mathbf {x}} = \\left[ t ^ {(1)} \\left(f (\\mathbf {x}), \\tilde {y}\\right),.., t ^ {(E)} \\left(f (\\mathbf {x}), \\tilde {y}\\right) \\right], \\tag {1}", + "image_path": "59e47960234014c17ce8d4463557ce05fe68366300bd4933d0bb8557677d49f3.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "spans": [ + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "inline_equation", + "content": "t^{(e)}(f(\\mathbf{x}),\\tilde{y})" + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "content": " denotes the training signal computed at epoch " + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "inline_equation", + "content": "e" + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "content": " is the maximum number of training epochs. For the sake of convenience, we denote " + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{\\mathbf{x}}" + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "inline_equation", + "content": "t_{\\mathbf{x}}^{(e)}" + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "content": " as an abbreviation for " + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "inline_equation", + "content": "\\mathbf{t}(\\mathbf{x},\\tilde{y};f)" + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "inline_equation", + "content": "t^{(e)}(f(\\mathbf{x}),\\tilde{y})" + }, + { + "bbox": [ + 46, + 351, + 287, + 403 + ], + "type": "text", + "content": ", respectively." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 422, + 274, + 434 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 422, + 274, + 434 + ], + "spans": [ + { + "bbox": [ + 47, + 422, + 274, + 434 + ], + "type": "text", + "content": "4.3.2 Dynamics generation for noisy label detection" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 442, + 287, + 478 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 442, + 287, + 478 + ], + "spans": [ + { + "bbox": [ + 46, + 442, + 287, + 478 + ], + "type": "text", + "content": "We generate training dynamics for both the original and the corrupted datasets. Specifically, we train a classifier by minimizing the classification loss on " + }, + { + "bbox": [ + 46, + 442, + 287, + 478 + ], + "type": "inline_equation", + "content": "\\widetilde{D}" + }, + { + "bbox": [ + 46, + 442, + 287, + 478 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 442, + 287, + 478 + ], + "type": "inline_equation", + "content": "\\bar{D}" + }, + { + "bbox": [ + 46, + 442, + 287, + 478 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 52, + 487, + 287, + 520 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 487, + 287, + 520 + ], + "spans": [ + { + "bbox": [ + 52, + 487, + 287, + 520 + ], + "type": "interline_equation", + "content": "\\frac {1}{| \\tilde {D} |} \\sum_ {(\\mathbf {x}, \\tilde {y}) \\in \\tilde {D}} \\ell_ {c e} (f (\\mathbf {x}), \\tilde {y}) + \\frac {1}{| \\bar {D} |} \\sum_ {(\\bar {\\mathbf {x}}, \\bar {y}) \\in \\bar {D}} \\ell_ {c e} (f (\\bar {\\mathbf {x}}), \\bar {y}), \\tag {2}", + "image_path": "928b3cd94d341f8eafd55068a40ebfb52708cc00cdf84d1b8740eb56c2f75f53.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "inline_equation", + "content": "\\ell_{ce}" + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "content": " is the softmax cross-entropy loss. For each instance " + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "content": ", we obtain a training dynamics " + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{\\mathbf{x}} \\in \\mathbb{R}^{E}" + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "content": " as specified in Eq. (1) by tracking " + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "inline_equation", + "content": "t_{\\mathbf{x}}^{(e)}" + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "content": " over the course of training epochs " + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "content": ". Training dynamics of the original and the corrupted datasets are denoted by " + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "inline_equation", + "content": "\\widetilde{T} := \\{\\mathbf{t}_{\\mathbf{x}} | (\\mathbf{x}, \\tilde{y}) \\in \\widetilde{D}\\}" + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "inline_equation", + "content": "\\bar{T} := \\{\\mathbf{t}_{\\bar{\\mathbf{x}}} | (\\bar{\\mathbf{x}}, \\bar{y}) \\in \\bar{D}\\}" + }, + { + "bbox": [ + 46, + 530, + 287, + 605 + ], + "type": "text", + "content": ", respectively." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 614, + 280, + 628 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 614, + 280, + 628 + ], + "spans": [ + { + "bbox": [ + 47, + 614, + 280, + 628 + ], + "type": "text", + "content": "4.4. Noisy label detection via dynamics clustering" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 634, + 287, + 682 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 634, + 287, + 682 + ], + "spans": [ + { + "bbox": [ + 46, + 634, + 287, + 682 + ], + "type": "text", + "content": "We use a clustering approach to identify incorrectly labeled instances within the original dataset. Using a dynamics encoder, we encode the generated dynamics and progressively find clusters of correctly and incorrectly labeled instances" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 72, + 545, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 156 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 156 + ], + "type": "text", + "content": "in the representation space. The dynamics clustering iterates two key processes: (1) identifications of incorrectly labeled instances (Sec. 4.4.1), and (2) learning distinct representations for each cluster (Sec. 4.4.2). The clustering quality is assessed by a newly introduced validation metric by leveraging the corrupted dataset without a clean validation dataset (Sec. 4.4.3)." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 175, + 530, + 186 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 175, + 530, + 186 + ], + "spans": [ + { + "bbox": [ + 306, + 175, + 530, + 186 + ], + "type": "text", + "content": "4.4.1 Identification of incorrectly labeled instances" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "spans": [ + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": "Cluster initialization. Given a training dynamics " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{\\mathbf{x}}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": ", a dynamics encoder generates its representation, i.e., " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\mathbf{z}_{\\mathbf{x}} = \\mathrm{Enc}(\\mathbf{t}_{\\mathbf{x}}) \\in \\mathbb{R}^{d_{\\mathbf{z}}}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": ". Let " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\widetilde{Z}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\widetilde{Z}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": " denote the set of dynamics representations of the original and the corrupted datasets, respectively. We first introduce trainable parameters for centroids of noisy and clean clusters, i.e., " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\mu_{noisy}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\mu_{clean} \\in \\mathbb{R}^{d_{\\mathbf{z}}}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": ". We initialize " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\mu_{noisy}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": " as the average representation of the corrupted instances " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\widetilde{Z}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": ", while " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\mu_{clean}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": " is initialized as the average representation of the original instances " + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "inline_equation", + "content": "\\widetilde{Z}" + }, + { + "bbox": [ + 305, + 198, + 545, + 331 + ], + "type": "text", + "content": ". Note that this initialization is conducted only once at the beginning of the dynamics clustering step." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "spans": [ + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "text", + "content": "Noisy label identification. We determine whether each instance " + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "text", + "content": " has been incorrectly labeled based on its assignment probability to the noisy cluster. The assignment probability is computed based on the similarity between " + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "inline_equation", + "content": "\\mathbf{z}_{\\mathbf{x}}" + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "text", + "content": " and the noisy cluster's centroid " + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "inline_equation", + "content": "\\pmb{\\mu}_{\\text {noisy }}" + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "text", + "content": ". We employ a kernel function based on the Student's " + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 305, + 334, + 545, + 411 + ], + "type": "text", + "content": "-distribution [43] with one degree of freedom as follows:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 422, + 544, + 447 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 422, + 544, + 447 + ], + "spans": [ + { + "bbox": [ + 306, + 422, + 544, + 447 + ], + "type": "interline_equation", + "content": "q _ {n o i s y} (\\mathbf {z} _ {\\mathbf {x}}) = \\frac {(1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {n o i s y})) ^ {- 1}}{(1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {n o i s y})) ^ {- 1} + (1 + d (\\mathbf {z} _ {\\mathbf {x}} , \\boldsymbol {\\mu} _ {c l e a n})) ^ {- 1}},", + "image_path": "f265de5e310c5c8838b84f86e9a71fd0aee19917dd5df4488a6dd881209c42a2.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 307, + 449, + 545, + 461 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 307, + 449, + 545, + 461 + ], + "spans": [ + { + "bbox": [ + 307, + 449, + 545, + 461 + ], + "type": "interline_equation", + "content": "q _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) = 1 - q _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right), \\tag {3}", + "image_path": "69ffd89a39c8eda71b0d36abf8a3a1afa7ada4f8b227242e17a2e0be147eacd0.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 472, + 545, + 511 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 472, + 545, + 511 + ], + "spans": [ + { + "bbox": [ + 305, + 472, + 545, + 511 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 472, + 545, + 511 + ], + "type": "inline_equation", + "content": "d(\\mathbf{a},\\mathbf{b}) = 1 - \\frac{\\langle\\mathbf{a},\\mathbf{b}\\rangle}{||\\mathbf{a}||_2\\cdot||\\mathbf{b}||_2}" + }, + { + "bbox": [ + 305, + 472, + 545, + 511 + ], + "type": "text", + "content": ". Based on the assignment probability, we regard an instance as incorrectly labeled when its probability to the noisy cluster is predominant." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 348, + 522, + 545, + 536 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 522, + 545, + 536 + ], + "spans": [ + { + "bbox": [ + 348, + 522, + 545, + 536 + ], + "type": "interline_equation", + "content": "v \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) := \\mathbb {1} \\left[ q _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) > q _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) \\right], \\tag {4}", + "image_path": "476e10122c325f077d15b54d8384bae84b64cd16efdad90dfd23263a9d5e0794.jpg" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 547, + 544, + 559 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 547, + 544, + 559 + ], + "spans": [ + { + "bbox": [ + 306, + 547, + 544, + 559 + ], + "type": "inline_equation", + "content": "v(\\mathbf{z}_{\\mathbf{x}}) = 1" + }, + { + "bbox": [ + 306, + 547, + 544, + 559 + ], + "type": "text", + "content": " indicates that " + }, + { + "bbox": [ + 306, + 547, + 544, + 559 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 306, + 547, + 544, + 559 + ], + "type": "text", + "content": " is predicted to have a noisy label." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 580, + 533, + 593 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 580, + 533, + 593 + ], + "spans": [ + { + "bbox": [ + 306, + 580, + 533, + 593 + ], + "type": "text", + "content": "4.4.2 Learning discriminative patterns in dynamics" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 305, + 601, + 545, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 601, + 545, + 661 + ], + "spans": [ + { + "bbox": [ + 305, + 601, + 545, + 661 + ], + "type": "text", + "content": "We introduce the strategy of inducing two distinguishable clusters (each for correctly and incorrectly labeled instances) in the dynamics representation space. We propose two types of losses for (1) high cluster cohesion and (2) cluster alignment between original and corrupted instances." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "content": "Clustering loss. We introduce a clustering loss to make the clusters more distinguishable. We enhance cluster cohesion by adjusting each instance's representation to be closer to a centroid through a self-enhancing target distribution." + } + ] + } + ], + "index": 23 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "type": "text", + "content": "2We provide a detailed analysis of various training signals for identifying incorrectly labeled instances in Appendix B.3" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "footer", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22480" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "content": "The target distribution is constructed by amplifying the predicted assignment probability [55] as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 55, + 102, + 278, + 133 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 102, + 278, + 133 + ], + "spans": [ + { + "bbox": [ + 55, + 102, + 278, + 133 + ], + "type": "interline_equation", + "content": "p _ {n o i s y} (\\mathbf {z _ {x}}) = \\frac {q _ {n o i s y} ^ {2} (\\mathbf {z _ {x}}) / s _ {n o i s y}}{q _ {n o i s y} ^ {2} (\\mathbf {z _ {x}}) / s _ {n o i s y} + q _ {c l e a n} ^ {2} (\\mathbf {z _ {x}}) / s _ {c l e a n}},", + "image_path": "eef9e090d1c6b4c11e76e8f953f0d1a7c78de1c2ca129c41528800c56d1ee536.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 56, + 135, + 287, + 148 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 56, + 135, + 287, + 148 + ], + "spans": [ + { + "bbox": [ + 56, + 135, + 287, + 148 + ], + "type": "interline_equation", + "content": "p _ {\\text {c l e a n}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) = 1 - p _ {\\text {n o i s y}} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right), \\tag {5}", + "image_path": "74ad49bbd30d0b66f075d4d0e6dbe0b9cc1c47fdf00650c8039f011f36da1bdb.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "spans": [ + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "inline_equation", + "content": "s_{noisy} = \\sum_{\\mathbf{z} \\in \\widetilde{Z} \\cup \\bar{Z}} q_{noisy}(\\mathbf{z})" + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "inline_equation", + "content": "s_{clean} = \\sum_{\\mathbf{z} \\in \\widetilde{Z} \\cup \\bar{Z}} q_{clean}(\\mathbf{z})" + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "text", + "content": ". Then, we minimize the KL divergence between the cluster assignment distribution " + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{q}(\\mathbf{z}_{\\mathbf{x}}) = [q_{noisy}(\\mathbf{z}_{\\mathbf{x}}), q_{clean}(\\mathbf{z}_{\\mathbf{x}})]" + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "text", + "content": " and the target distribution " + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{p}(\\mathbf{z}_{\\mathbf{x}}) = [p_{noisy}(\\mathbf{z}_{\\mathbf{x}}), p_{clean}(\\mathbf{z}_{\\mathbf{x}})]" + }, + { + "bbox": [ + 47, + 155, + 287, + 216 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 86, + 223, + 287, + 251 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 86, + 223, + 287, + 251 + ], + "spans": [ + { + "bbox": [ + 86, + 223, + 287, + 251 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {c l u s t e r}} = \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\widetilde {\\tilde {Z}} \\cup \\bar {Z}} \\operatorname {K L} (\\mathbf {p} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right) | | \\mathbf {q} \\left(\\mathbf {z} _ {\\mathbf {x}}\\right)). \\tag {6}", + "image_path": "5db4e152da3cd05483f7ccb3b17be8adc8764102298dcba82e6151f3aa5c11da.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 261, + 287, + 416 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 261, + 287, + 416 + ], + "spans": [ + { + "bbox": [ + 46, + 261, + 287, + 416 + ], + "type": "text", + "content": "Alignment loss. We introduce an alignment loss that aligns the representation from each cluster's original and corrupted datasets. We hypothesize3 that symmetric noise is relatively easy to identify among various noise types with diverse difficulty levels. Consequently, incorrectly labeled instances in the corrupted dataset exhibit more distinctive dynamics patterns than those in the original data, i.e., a red dashed line is farther away from blue lines than a red line in the 3rd step of Fig.1 (left). From this perspective, the mismatched noise types between the original and the corrupted datasets positively impact the clustering process by adopting alignment loss, which forces a red line to be aligned with a red dashed line in the 3rd step of Fig.1 (right)." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "spans": [ + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "text", + "content": "Instances in the original dataset predicted as noisy and clean are denoted by " + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "inline_equation", + "content": "\\widetilde{Z}_{noisy} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\widetilde{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 1\\}" + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "inline_equation", + "content": "\\widetilde{Z}_{clean} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\widetilde{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 0\\}" + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "text", + "content": ", respectively. Analogously, for the corrupted dataset, we obtain " + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "inline_equation", + "content": "\\bar{Z}_{noisy} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\bar{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 1\\}" + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "inline_equation", + "content": "\\bar{Z}_{clean} = \\{\\mathbf{z}_{\\mathbf{x}} \\in \\bar{Z} | v(\\mathbf{z}_{\\mathbf{x}}) = 0\\}" + }, + { + "bbox": [ + 47, + 416, + 287, + 514 + ], + "type": "text", + "content": ". Then, we employ the alignment loss to reduce the discrepancy between the representations of the original dataset and the corrupted dataset as follows:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 520, + 286, + 552 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 520, + 286, + 552 + ], + "spans": [ + { + "bbox": [ + 47, + 520, + 286, + 552 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {a l i g n} ^ {n} = d \\Big (\\frac {1}{| \\tilde {\\bar {Z}} _ {n o i s y} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {\\bar {Z}} _ {n o i s y}} \\mathbf {z} _ {\\mathbf {x}}, \\frac {1}{| \\bar {Z} _ {n o i s y} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {n o i s y}} \\mathbf {z} _ {\\mathbf {x}} \\Big),", + "image_path": "d0bfb9316bcba6a89ec8a4a08900fe16f77222dc1e5794d5816fcdb35bb32c62.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 554, + 284, + 586 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 554, + 284, + 586 + ], + "spans": [ + { + "bbox": [ + 47, + 554, + 284, + 586 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {a l i g n}} ^ {c} = d \\Big (\\frac {1}{| \\tilde {Z} _ {\\text {c l e a n}} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {Z} _ {\\text {c l e a n}}} \\mathbf {z} _ {\\mathbf {x}}, \\frac {1}{| \\bar {Z} _ {\\text {c l e a n}} |} \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {\\text {c l e a n}}} \\mathbf {z} _ {\\mathbf {x}} \\Big),", + "image_path": "9abb88a90f2f66e7a454123dcb756016e544697ed6d6abe25359d7e20a9a6d08.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 48, + 587, + 287, + 610 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 587, + 287, + 610 + ], + "spans": [ + { + "bbox": [ + 48, + 587, + 287, + 610 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {a l i g n}} = \\frac {1}{2} \\left(\\mathcal {L} _ {\\text {a l i g n}} ^ {n} + \\mathcal {L} _ {\\text {a l i g n}} ^ {c}\\right). \\tag {7}", + "image_path": "6bd48d0a391bcccda0e5e3f086dd3bc9cedcc8b5c4c3ae08432c5241895992f5.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 620, + 287, + 644 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 620, + 287, + 644 + ], + "spans": [ + { + "bbox": [ + 47, + 620, + 287, + 644 + ], + "type": "text", + "content": "Optimization. To sum up, the dynamics encoder is optimized by minimizing the following loss:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 116, + 652, + 287, + 665 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 116, + 652, + 287, + 665 + ], + "spans": [ + { + "bbox": [ + 116, + 652, + 287, + 665 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {\\text {c l u s t e r}} + \\alpha \\mathcal {L} _ {\\text {a l i g n}}, \\tag {8}", + "image_path": "47a9c6f95dc400c0f7127b024dc8c1b90a1db3410bf44a72810761beeac3e1c9.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 672, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 672, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 47, + 672, + 287, + 696 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 672, + 287, + 696 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 47, + 672, + 287, + 696 + ], + "type": "text", + "content": " is a hyperparameter that controls the impact of the alignment loss." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 72, + 413, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 413, + 83 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 413, + 83 + ], + "type": "text", + "content": "4.4.3 Validation metric" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 91, + 545, + 222 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 545, + 222 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 545, + 222 + ], + "type": "text", + "content": "One practical challenge in training the dynamics encoder is determining an appropriate stopping point in the absence of ground-truth annotations of clean and noisy labels for validation. As a solution, we introduce a new validation metric for the dynamics encoder to estimate its detection performance indirectly. For noisy label detection, we aim to maximize (a) the assignment of incorrectly labeled instances to the noisy cluster while minimizing (b) the assignment of correctly labeled instances to the noisy cluster. Intuitively, in an ideally clustered space, the difference between (a) and (b) needs to be maximized." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 223, + 545, + 330 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 223, + 545, + 330 + ], + "spans": [ + { + "bbox": [ + 304, + 223, + 545, + 330 + ], + "type": "text", + "content": "Since we cannot access the ground-truth annotations to compute (a) and (b), we use the most representative instances as a workaround. Considering the corrupted dataset has a higher noise rate than the original dataset, we emulate (a) using instances predicted as noisy among the corrupted dataset, i.e., " + }, + { + "bbox": [ + 304, + 223, + 545, + 330 + ], + "type": "inline_equation", + "content": "\\bar{Z}_{\\text{noise}}" + }, + { + "bbox": [ + 304, + 223, + 545, + 330 + ], + "type": "text", + "content": ". Similarly, (b) is emulated using instances predicted as clean among the original dataset with a lower noise rate, i.e., " + }, + { + "bbox": [ + 304, + 223, + 545, + 330 + ], + "type": "inline_equation", + "content": "\\tilde{Z}_{\\text{clean}}" + }, + { + "bbox": [ + 304, + 223, + 545, + 330 + ], + "type": "text", + "content": ". Our validation metric is defined as the difference between two emulated values as" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 318, + 334, + 545, + 367 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 334, + 545, + 367 + ], + "spans": [ + { + "bbox": [ + 318, + 334, + 545, + 367 + ], + "type": "interline_equation", + "content": "\\left(\\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\bar {Z} _ {\\text {n o i s y}}} \\frac {q _ {\\text {n o i s y}} (\\mathbf {z} _ {\\mathbf {x}})}{| \\bar {Z} _ {\\text {n o i s y}} |} - \\sum_ {\\mathbf {z} _ {\\mathbf {x}} \\in \\tilde {Z} _ {\\text {c l e a n}}} \\frac {q _ {\\text {n o i s y}} (\\mathbf {z} _ {\\mathbf {x}})}{| \\tilde {Z} _ {\\text {c l e a n}} |}\\right) ^ {2}. \\tag {9}", + "image_path": "2083025e3b135dc7e1ddc0ca29dfa966c3b847ea94039fdbe08ec1e54b29c2e1.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 372, + 545, + 433 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 372, + 545, + 433 + ], + "spans": [ + { + "bbox": [ + 304, + 372, + 545, + 433 + ], + "type": "text", + "content": "The larger value indicates the better clustering quality for noisy label detection. Compared to the conventional metrics for assessing cluster separation [10, 37], this metric is tailored for our DynaCor framework and provides a more effective measure of noisy label detection efficacy." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 442, + 388, + 455 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 442, + 388, + 455 + ], + "spans": [ + { + "bbox": [ + 306, + 442, + 388, + 455 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 461, + 411, + 475 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 461, + 411, + 475 + ], + "spans": [ + { + "bbox": [ + 306, + 461, + 411, + 475 + ], + "type": "text", + "content": "5.1. Experiment setup" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 483, + 545, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 483, + 545, + 590 + ], + "spans": [ + { + "bbox": [ + 304, + 483, + 545, + 590 + ], + "type": "text", + "content": "Datasets. We evaluate the performance of DynaCor on benchmark datasets with different types of label noise, originating from diverse sources: (1) synthetic noise on CIFAR-10 and CIFAR-100 [24], (2) real-world human noise on CIFAR-10N and CIFAR-100N [50], and (3) systematic noise" + }, + { + "bbox": [ + 304, + 483, + 545, + 590 + ], + "type": "inline_equation", + "content": "^{4}" + }, + { + "bbox": [ + 304, + 483, + 545, + 590 + ], + "type": "text", + "content": " on Clothing1M [54]. In the case of synthetic noise, following the previous experimental setup [63], we artificially introduce the noise by using different strategies with specific noise rates " + }, + { + "bbox": [ + 304, + 483, + 545, + 590 + ], + "type": "inline_equation", + "content": "\\eta" + }, + { + "bbox": [ + 304, + 483, + 545, + 590 + ], + "type": "text", + "content": " as outlined below." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 306, + 591, + 545, + 687 + ], + "type": "list", + "angle": 0, + "index": 25, + "blocks": [ + { + "bbox": [ + 306, + 591, + 544, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 591, + 544, + 613 + ], + "spans": [ + { + "bbox": [ + 306, + 591, + 544, + 613 + ], + "type": "text", + "content": "- Symmetric Noise (Sym., " + }, + { + "bbox": [ + 306, + 591, + 544, + 613 + ], + "type": "inline_equation", + "content": "\\eta = 0.6" + }, + { + "bbox": [ + 306, + 591, + 544, + 613 + ], + "type": "text", + "content": ") randomly replaces the label with one of the other classes." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "spans": [ + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "type": "text", + "content": "- Asymmetric Noise (Asym., " + }, + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "type": "inline_equation", + "content": "\\eta = 0.3" + }, + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "type": "text", + "content": ") performs pairwise label flipping, where transition can only occur from a given class " + }, + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "type": "text", + "content": " to the next class (" + }, + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "type": "inline_equation", + "content": "i \\bmod C) + 1" + }, + { + "bbox": [ + 306, + 615, + 545, + 651 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 306, + 651, + 545, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 651, + 545, + 687 + ], + "spans": [ + { + "bbox": [ + 306, + 651, + 545, + 687 + ], + "type": "text", + "content": "- Instance-dependent Noise (Inst., " + }, + { + "bbox": [ + 306, + 651, + 545, + 687 + ], + "type": "inline_equation", + "content": "\\eta = 0.4" + }, + { + "bbox": [ + 306, + 651, + 545, + 687 + ], + "type": "text", + "content": ") changes labels based on the transition probability calculated using instance's corresponding features [53]." + } + ] + } + ], + "index": 24 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 58, + 702, + 166, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 166, + 713 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 166, + 713 + ], + "type": "text", + "content": "3It is theoretically proved in [32]" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "text", + "content": "4In case of Clothing1M, systematic noise is induced by automatic annotation from the keywords present in the surrounding text of each image." + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22481" + } + ] + } + ], + "index": 27 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 70, + 547, + 173 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 547, + 173 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 547, + 173 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 547, + 173 + ], + "type": "table", + "html": "
DatasetCIFAR-10CIFAR-100
Noise typeSym.Asym.Inst.Agg.WorstSym.Asym.Inst.HumanAvg.
Noise rate (η)0.60.30.40.090.40.60.30.40.4
Avg.Encoder98.0 ± 0.0389.7 ± 0.1422.4 ± 33.567.3 ± 0.4292.8 ± 0.1196.7 ± 0.0774.9 ± 0.1776.8 ± 0.5179.5 ± 0.3177.6
AUM95.7 ± 0.0786.5 ± 0.1881.9 ± 0.7274.0 ± 0.1688.7 ± 0.1996.4 ± 0.1074.7 ± 0.2181.2 ± 0.2574.6 ± 1.2583.7
CL96.6 ± 0.0494.0 ± 0.1082.0 ± 0.2168.6 ± 0.3388.3 ± 0.1188.0 ± 0.0868.6 ± 0.1675.9 ± 0.1271.9 ± 0.1081.5
CORES97.7 ± 0.035.00 ± 0.3319.2 ± 0.1080.5 ± 0.0977.5 ± 0.0983.9 ± 0.2021.9 ± 0.3236.7 ± 0.4136.0 ± 0.1250.9
SIMIFEAT-V95.1 ± 0.0689.4 ± 0.0888.1 ± 0.1179.6 ± 0.1391.6 ± 0.0686.0 ± 0.0973.8 ± 0.0780.5 ± 0.0977.1 ± 0.1284.6
SIMIFEAT-R96.1 ± 1.4188.9 ± 0.1491.2 ± 0.0779.6 ± 0.4091.7 ± 0.3590.3 ± 0.0768.0 ± 0.1077.3 ± 0.0979.3 ± 0.1184.7
DynaCor98.0 ± 0.0494.0 ± 0.1592.3 ± 0.3879.6 ± 0.3792.3 ± 0.1994.3 ± 0.3476.3 ± 0.2381.7 ± 0.2180.4 ± 0.1787.7
", + "image_path": "8cef2966658075e63c259f98de8d7f5e576eb06189fdd768f973a0b56a2fae05.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 48, + 236, + 545, + 332 + ], + "blocks": [ + { + "bbox": [ + 46, + 182, + 547, + 228 + ], + "lines": [ + { + "bbox": [ + 46, + 182, + 547, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 182, + 547, + 228 + ], + "type": "text", + "content": "Table 1. Average F1 score (\\%) along with standard deviation across ten independent runs of DynaCor and baseline methods on CIFAR-10 and CIFAR-100. All methods except SIMIFEAT utilize the identical fixed image encoder from CLIP [35] and train only a subsequent MLP, while SIMIFEAT uses pre-trained CLIP as a feature extractor. The rightmost column averages the F1 scores across nine different settings. \"Agg.\", \"Worst\", and \"Human\" correspond to the real-world human label noises [50]. The best results are in bold." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 236, + 545, + 332 + ], + "lines": [ + { + "bbox": [ + 48, + 236, + 545, + 332 + ], + "spans": [ + { + "bbox": [ + 48, + 236, + 545, + 332 + ], + "type": "table", + "html": "
DatasetCIFAR-10CIFAR-100
Noise typeSym.Asym.Inst.Agg.WorstSym.Asym.Inst.HumanAvg.
Avg.Encoder94.1 ± 0.1485.4 ± 0.1988.5 ± 0.2063.6 ± 0.7287.6 ± 0.1892.5 ± 0.3475.2 ± 0.3676.0 ± 0.4978.8 ± 0.1882.4
AUM75.4 ± 0.2246.4 ± 0.3057.7 ± 0.0316.7 ± 0.0157.8 ± 0.0475.8 ± 0.2146.7 ± 0.3257.8 ± 0.1058.0 ± 0.2154.7
CL88.7 ± 0.5691.9 ± 0.1282.5 ± 0.3757.0 ± 0.3180.0 ± 0.3277.9 ± 0.3962.4 ± 0.2467.3 ± 0.2865.2 ± 0.1974.8
CORES92.9 ± 0.1726.7 ± 0.4449.2 ± 1.1563.6 ± 0.5874.7 ± 0.3666.3 ± 0.3533.8 ± 0.4639.2 ± 0.4531.9 ± 0.4853.2
SIMIFEAT-V94.6 ± 0.0684.7 ± 0.1783.7 ± 0.0869.4 ± 0.1788.3 ± 0.0888.0 ± 0.0970.3 ± 0.1477.8 ± 0.1076.2 ± 0.1481.4
SIMIFEAT-R92.9 ± 1.8484.0 ± 0.1386.9 ± 0.0868.8 ± 0.3288.5 ± 0.3689.7 ± 0.0766.2 ± 0.1175.5 ± 0.0877.8 ± 0.1381.2
DynaCor93.6 ± 0.1894.2 ± 0.4591.5 ± 0.3172.6 ± 2.4687.8 ± 0.3791.3 ± 0.4679.2 ± 0.5979.5 ± 1.1477.3 ± 0.5485.2
", + "image_path": "f31cbacdadc988e4fff0b2246ffb9858455b509e5287d6f9f12488d224d159b5.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 340, + 546, + 363 + ], + "lines": [ + { + "bbox": [ + 46, + 340, + 546, + 363 + ], + "spans": [ + { + "bbox": [ + 46, + 340, + 546, + 363 + ], + "type": "text", + "content": "Table 2. Average F1 score (%) under identical settings to those in Table 1 except for the backbone model. All methods except SIMIFEAT utilize a randomly initialized Renset34 [17], while SIMIFEAT uses a pre-trained ResNet34 on ImageNet [11] as a feature extractor." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 384, + 287, + 433 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 384, + 287, + 433 + ], + "spans": [ + { + "bbox": [ + 46, + 384, + 287, + 433 + ], + "type": "text", + "content": "In the case of human noise, we choose two noise subtypes for CIFAR-10N (denoted by Agg. and Worst) and a single noise subtype for CIFAR-100N (denoted by Human). More details of the datasets are presented in Appendix A.1." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 438, + 287, + 475 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 438, + 287, + 475 + ], + "spans": [ + { + "bbox": [ + 46, + 438, + 287, + 475 + ], + "type": "text", + "content": "Baselines. We compare DynaCor with various noisy label detection methods. All the methods except SIMIFEAT use training signals to identify incorrectly labeled instances." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 479, + 287, + 669 + ], + "type": "list", + "angle": 0, + "index": 11, + "blocks": [ + { + "bbox": [ + 47, + 479, + 287, + 527 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 479, + 287, + 527 + ], + "spans": [ + { + "bbox": [ + 47, + 479, + 287, + 527 + ], + "type": "text", + "content": "- Avg.Encoder is a naive baseline that discriminates between clean and noisy labels by using a one-dimensional Gaussian mixture model [64] on the averaged training signals (i.e., logit difference) over the epochs." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 527, + 287, + 562 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 527, + 287, + 562 + ], + "spans": [ + { + "bbox": [ + 47, + 527, + 287, + 562 + ], + "type": "text", + "content": "- AUM [34] uses summation of training signals (i.e., logit difference) over the epochs and identifies correctly/incorrectly labeled instances based on a threshold." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 563, + 287, + 597 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 563, + 287, + 597 + ], + "spans": [ + { + "bbox": [ + 47, + 563, + 287, + 597 + ], + "type": "text", + "content": "- CL [31] uses a predicted probability of the given label (i.e., confidence) and filter out the instances with low confidence based on class-conditional thresholds." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 597, + 287, + 633 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 597, + 287, + 633 + ], + "spans": [ + { + "bbox": [ + 47, + 597, + 287, + 633 + ], + "type": "text", + "content": "- CORES [7] leverages a training loss for noisy label detection, progressively filtering out incorrectly labeled instances using its proposed sample sieve." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 634, + 287, + 669 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 634, + 287, + 669 + ], + "spans": [ + { + "bbox": [ + 47, + 634, + 287, + 669 + ], + "type": "text", + "content": "- SIMIFEAT [63] is a training-free approach that effectively detects noisy labels by utilizing " + }, + { + "bbox": [ + 47, + 634, + 287, + 669 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 47, + 634, + 287, + 669 + ], + "type": "text", + "content": "-nearest neighbors in the feature space of a pre-trained model." + } + ] + } + ], + "index": 10 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "content": "Implementation details. For our label corruption process, we use the corruption rate " + }, + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\gamma = 0.1" + }, + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "content": " as the default. To generate the training dynamics, we employ DNN classifiers:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 383, + 545, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 383, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 305, + 383, + 545, + 456 + ], + "type": "text", + "content": "ResNet34 [17] and the pre-trained ViT-B/32-CLIP [35] with a multi-layer perceptron (MLP) of two hidden layers. To encode the training dynamics, we use a three-layered 1D-CNN architecture [48] as the dynamics encoder. The hyperparameter " + }, + { + "bbox": [ + 305, + 383, + 545, + 456 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 305, + 383, + 545, + 456 + ], + "type": "text", + "content": " is selected as either 0.05 or 0.5. For more details about implementation, please refer to Appendix A.2." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 475, + 488, + 488 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 475, + 488, + 488 + ], + "spans": [ + { + "bbox": [ + 306, + 475, + 488, + 488 + ], + "type": "text", + "content": "5.2. Noisy label detection performance" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 498, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 545, + 713 + ], + "type": "text", + "content": "We first evaluate DynaCor and the baseline methods for noisy label detection. Table 1 and Table 2 present their detection F1 scores for two classifiers, CLIP w/ MLP and ResNet34, across various noise types and rates. Notably, DynaCor achieves the best performance on average, i.e., " + }, + { + "bbox": [ + 304, + 498, + 545, + 713 + ], + "type": "inline_equation", + "content": "+3.0\\%" + }, + { + "bbox": [ + 304, + 498, + 545, + 713 + ], + "type": "text", + "content": " in Table 1 and " + }, + { + "bbox": [ + 304, + 498, + 545, + 713 + ], + "type": "inline_equation", + "content": "+2.8\\%" + }, + { + "bbox": [ + 304, + 498, + 545, + 713 + ], + "type": "text", + "content": " in Table 2, demonstrating its robustness to various types of noisy conditions. On the other hand, the baseline methods relying on training signals (i.e., Avg.Encoder, AUM, CL, and CORES) show considerable variations in performance across different noise types. For example, in the case of CIFAR-10, Avg.Encoder and CORES perform well for symmetric noises, whereas they struggle with identifying asymmetric or instance noises. It is worth noting that asymmetric and instance noise are more complex than symmetric noise in that they can have a more detrimental impact on model performance [32]. These results strongly support the superiority of our DynaCor framework in handling a wide range of label noise variations." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22482" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 52, + 70, + 284, + 135 + ], + "blocks": [ + { + "bbox": [ + 52, + 70, + 284, + 135 + ], + "lines": [ + { + "bbox": [ + 52, + 70, + 284, + 135 + ], + "spans": [ + { + "bbox": [ + 52, + 70, + 284, + 135 + ], + "type": "table", + "html": "
Validation metricCIFAR-10CIFAR-100
Inst.Agg.Inst.Human
Max epoch86.7 ± 6.7577.8 ± 3.3561.0 ± 10.364.3 ± 4.40
DBI86.3 ± 8.7576.7 ± 3.9160.0 ± 10.264.8 ± 9.70
Ours92.3 ± 0.3879.6 ± 0.3781.7 ± 0.2180.4 ± 0.17
Opt epoch92.6 ± 0.4080.40 ± 0.4481.8 ± 0.0880.5 ± 0.18
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F1 score " + }, + { + "bbox": [ + 46, + 393, + 287, + 426 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 46, + 393, + 287, + 426 + ], + "type": "text", + "content": " changes with respect to corruption rate " + }, + { + "bbox": [ + 46, + 393, + 287, + 426 + ], + "type": "inline_equation", + "content": "(\\gamma)" + }, + { + "bbox": [ + 46, + 393, + 287, + 426 + ], + "type": "text", + "content": " on CIFAR10 in supervised and unsupervised settings using CLIP w/ MLP (Left) and ResNet34 (Right) as classifiers." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 451, + 225, + 463 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 451, + 225, + 463 + ], + "spans": [ + { + "bbox": [ + 47, + 451, + 225, + 463 + ], + "type": "text", + "content": "5.3. Effectiveness of validation metric" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 472, + 287, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 472, + 287, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 472, + 287, + 628 + ], + "type": "text", + "content": "To demonstrate the effectiveness of the proposed validation metric (Sec.4.4.3), we compare the detection performance of our dynamics encoder by employing our proposed metric and alternative criteria as stopping conditions during the training. Max epoch signifies the training over the maximum number of epochs. Davies-Bouldin Index (DBI) [10] assesses the quality of clustering results by calculating the ratio of intra-cluster distances to inter-cluster separations. A lower DBI value implies more compact and well-separated clusters, i.e., better clustering quality. In addition, Opt epoch selects the optimal training epoch that achieves the best detection results, providing the upper bound of detection performance." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 630, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 286, + 712 + ], + "type": "text", + "content": "In Table 3, our performance is close to the optimal case across various noise types and datasets, whereas Max epoch and DBI fail to stop the training process at a proper epoch on CIFAR-100. In conclusion, using the proper validation metric is critical for achieving competitive detection performance, particularly in the scenario where ground-truth annotations are not available for validation." + } + ] + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 309, + 70, + 541, + 119 + ], + "blocks": [ + { + "bbox": [ + 46, + 143, + 288, + 175 + ], + "lines": [ + { + "bbox": [ + 46, + 143, + 288, + 175 + ], + "spans": [ + { + "bbox": [ + 46, + 143, + 288, + 175 + ], + "type": "text", + "content": "Table 3. F1 score (\\%) of our dynamics encoder over various validation metrics on CIFAR-10 and CIFAR-100 using CLIP w/ MLP as a classifier." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 70, + 541, + 119 + ], + "lines": [ + { + "bbox": [ + 309, + 70, + 541, + 119 + ], + "spans": [ + { + "bbox": [ + 309, + 70, + 541, + 119 + ], + "type": "table", + "html": "
L_clusterL_alignAsym.Inst.Agg.
93.8 ± 0.1791.8 ± 0.3978.8 ± 0.37
✓93.2 ± 0.1192.7 ± 0.3676.8 ± 0.83
✓✓94.0 ± 0.1592.3 ± 0.3879.6 ± 0.37
", + "image_path": "f6050393630a6047a977b4089b683934a4593a6fc3aa3b3c3432f238a568ca60.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 128, + 545, + 172 + ], + "lines": [ + { + "bbox": [ + 305, + 128, + 545, + 172 + ], + "spans": [ + { + "bbox": [ + 305, + 128, + 545, + 172 + ], + "type": "text", + "content": "Table 4. F1 score (\\%) of DynaCor that ablates the clustering and alignment loss on CIFAR10 using CLIP w/ MLP as a classifier. The first row reports the detection performance with a randomly initialized dynamics encoder." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 306, + 195, + 429, + 208 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 195, + 429, + 208 + ], + "spans": [ + { + "bbox": [ + 306, + 195, + 429, + 208 + ], + "type": "text", + "content": "5.4.Quantitative analyses" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 218, + 545, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 218, + 545, + 373 + ], + "spans": [ + { + "bbox": [ + 304, + 218, + 545, + 373 + ], + "type": "text", + "content": "The effect of corruption rate. We analyze the effect of increasing the corruption rate, which in turn amplifies the overall noise level. For thorough analyses, we conduct a controlled experiment within a supervised framework using classification, assuming the availability of ground-truth annotations that indicate each instance as being correctly or incorrectly labeled. We then compare these results, generally regarded as the performance upper bound for unsupervised methods, with those obtained by an unsupervised approach. We focus on assessing the ability of our proposed unsupervised learning model, i.e., DynaCor, to discriminate training dynamics and how this discrimination is affected by increasing the overall noise level through corruption." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 375, + 546, + 602 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 375, + 546, + 602 + ], + "spans": [ + { + "bbox": [ + 304, + 375, + 546, + 602 + ], + "type": "text", + "content": "As shown in Figure 2, the detection F1 scores achieved by DynaCor (Figure 2b) approaches those of supervised learning (Figure 2a), demonstrating the effectiveness of training dynamics. This proximity is especially notable when utilizing a powerful image encoder, i.e., CLIP, which makes the training dynamics less susceptible to changes in the corruption rate. In contrast, the training dynamics from ResNet34 are more affected by increased corruption rate. Surprisingly, in the case of \"Inst.\" type label noise, the training dynamics from the CLIP w/ MLP classifier become even more distinguishable as the corruption rate increases to 0.5. It shows that a higher noise rate in the training dataset can enhance the discernibility of the training dynamics. We hypothesize that the symmetric noise introduced through our label corruption process may reduce the overall difficulty of the detection task. This is consistent with the assertion in Sec. 4.4.2 that the symmetric noise is relatively straightforward to identify and, in turn, contributes to improving the performance of noisy label detection." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 606, + 545, + 679 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 606, + 545, + 679 + ], + "spans": [ + { + "bbox": [ + 304, + 606, + 545, + 679 + ], + "type": "text", + "content": "The effect of two losses. We examine the effect of the clustering and alignment losses within our DynaCor framework. In Table 4, both losses enhance detection performance. We also observe that the alignment loss effectively addresses the high imbalance between clean and noisy instances, particularly in scenarios with a low noise rate (e.g.," + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 315, + 689, + 507, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 689, + 507, + 703 + ], + "spans": [ + { + "bbox": [ + 315, + 689, + 507, + 703 + ], + "type": "text", + "content": "The overall noise rate is formulated as " + }, + { + "bbox": [ + 315, + 689, + 507, + 703 + ], + "type": "inline_equation", + "content": "\\eta_{over} = \\frac{\\eta + \\gamma \\cdot \\eta_{\\gamma}}{1 + \\gamma}" + }, + { + "bbox": [ + 315, + 689, + 507, + 703 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 317, + 703, + 429, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 703, + 429, + 712 + ], + "spans": [ + { + "bbox": [ + 317, + 703, + 429, + 712 + ], + "type": "text", + "content": "See Appendix B.1 for the details." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22483" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 66, + 71, + 267, + 153 + ], + "blocks": [ + { + "bbox": [ + 66, + 71, + 267, + 153 + ], + "lines": [ + { + "bbox": [ + 66, + 71, + 267, + 153 + ], + "spans": [ + { + "bbox": [ + 66, + 71, + 267, + 153 + ], + "type": "image", + "image_path": "d56f4bc4a7c2c5e68e025c50aae2056520c5a6794e6a65da512f3687fe3e5972.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 66, + 167, + 266, + 249 + ], + "blocks": [ + { + "bbox": [ + 88, + 156, + 247, + 166 + ], + "lines": [ + { + "bbox": [ + 88, + 156, + 247, + 166 + ], + "spans": [ + { + "bbox": [ + 88, + 156, + 247, + 166 + ], + "type": "text", + "content": "(a) Classification accuracy " + }, + { + "bbox": [ + 88, + 156, + 247, + 166 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 88, + 156, + 247, + 166 + ], + "type": "text", + "content": " of robust learning" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 66, + 167, + 266, + 249 + ], + "lines": [ + { + "bbox": [ + 66, + 167, + 266, + 249 + ], + "spans": [ + { + "bbox": [ + 66, + 167, + 266, + 249 + ], + "type": "image", + "image_path": "41fa1a259a13be8d20db8b3b5964bf792b32ec8119a9dc60a44d4ef4ffba8dbd.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 105, + 252, + 229, + 262 + ], + "lines": [ + { + "bbox": [ + 105, + 252, + 229, + 262 + ], + "spans": [ + { + "bbox": [ + 105, + 252, + 229, + 262 + ], + "type": "text", + "content": "(b) Noisy label detection F1 score " + }, + { + "bbox": [ + 105, + 252, + 229, + 262 + ], + "type": "inline_equation", + "content": "(\\%)" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 271, + 287, + 294 + ], + "lines": [ + { + "bbox": [ + 46, + 271, + 287, + 294 + ], + "spans": [ + { + "bbox": [ + 46, + 271, + 287, + 294 + ], + "type": "text", + "content": "Figure 3. Compatibility analysis of Dividemix with DynaCor on CIFAR100 over \"Asym.\" and \"Inst.\" with respect to noise rate" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 317, + 287, + 401 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 317, + 287, + 401 + ], + "spans": [ + { + "bbox": [ + 46, + 317, + 287, + 401 + ], + "type": "text", + "content": "\"Agg.\" on CIFAR-10). Given that DynaCor intentionally increases the noise rate by augmenting instances with corrupted labels, its benefits become more pronounced when dealing with datasets featuring a small original noise rate. In such cases, the alignment loss is crucial in stabilizing the clustering process by aligning the distinct distributions of original and corrupted instances." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 412, + 274, + 426 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 412, + 274, + 426 + ], + "spans": [ + { + "bbox": [ + 47, + 412, + 274, + 426 + ], + "type": "text", + "content": "5.5. Compatibility analyses with robust learning" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 432, + 286, + 516 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 432, + 286, + 516 + ], + "spans": [ + { + "bbox": [ + 46, + 432, + 286, + 516 + ], + "type": "text", + "content": "We investigate the compatibility and synergistic effects of integrating our framework with various robust learning techniques: a semi-supervised approach (Dividemix [26]), loss functions (GCE [61] and SCE [47]), and a regularization method (ELR [29]). Detailed analyses of incorporating the loss functions and regularization technique on the Clothing1M dataset are provided in Appendix D." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 517, + 286, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 517, + 286, + 661 + ], + "spans": [ + { + "bbox": [ + 46, + 517, + 286, + 661 + ], + "type": "text", + "content": "For the semi-supervised approach, we select Dividemix [26] that iteratively detects incorrectly labeled instances and treats them as unlabeled instances. We construct integrated models of Dividemix and DynaCor through two distinct approaches: (1) DDyna-L is leveraging Dividemix to obtain the training dynamics of both original and corrupted datasets within our framework, and (2) DDyna-S is substituting the original detection method in Dividemix, i.e., GMM, with DynaCor. For the base architecture, we employ an 18-layer PreAct ResNet [18], adhering to its default optimization settings and hyperparameters, as specified in the original paper [26]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 665, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 286, + 714 + ], + "type": "text", + "content": "Classification accuracy. We explore the impact of our framework on the classifier's accuracy, specifically introducing a corrupted dataset (DDyna-L) and supplanting the existing noise detection method (DDyna-S). Figure 3a" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": "demonstrates that both enhance classification performance. In essence, results obtained with DDyna-L demonstrate that instances with symmetric label noise introduced through our corruption process prove beneficial for noise robust learning, especially in scenarios featuring a low noise rate in the original dataset, pointed out as a challenging setting for Dividemix [50]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 160, + 545, + 340 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 160, + 545, + 340 + ], + "spans": [ + { + "bbox": [ + 304, + 160, + 545, + 340 + ], + "type": "text", + "content": "Detection F1 score. To report the noisy label detection performance within robust learning framework, i.e., Dividemix and DDyna-S, we measure F1 score at every epoch and report the value when test classification accuracy is at its highest. Note that they leverage a clean test dataset to identify the optimal detection point; on the contrary, the noisy detection method (DDyna-L) operates without access to clean data, instead employing the procedure for model validation on the noisy dataset itself (Sec. 4.4.3), presenting a more challenging task. Figure 3b indicates that DDyna-S and DDyna-L further improves the detection F1 score of Dividemix, indicating the great compatibility of DynaCor with existing semi-supervised noise robust learning. In scenarios involving \"Inst.\" label noise, DDyna-L exhibits compelling synergistic effects across a wide range of noise rates." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 356, + 378, + 368 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 356, + 378, + 368 + ], + "spans": [ + { + "bbox": [ + 306, + 356, + 378, + 368 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 377, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 377, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 377, + 545, + 581 + ], + "type": "text", + "content": "This paper proposes a new DynaCor framework that distinguishes incorrectly labeled instances from correctly labeled ones via clustering of their training dynamics. DynaCor first introduces a label corruption strategy that augments the original dataset with intentionally corrupted labels, enabling indirect simulation of the model's behavior on noisy labels. Subsequently, DynaCor learns to induce two clearly distinguishable clusters for clean and noisy instances by enhancing the cluster cohesion and alignment between the original and corrupted dataset. Furthermore, DynaCor adopts a simple yet effective validation metric to indirectly estimate its detection performance in the absence of annotations of clean and noisy labels. Our comprehensive experiments on real-world datasets demonstrate the detection efficacy of DynaCor, its remarkable robustness to various noise types and noise rates, and great compatibility with existing approaches to noise robust learning." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 596, + 420, + 609 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 596, + 420, + 609 + ], + "spans": [ + { + "bbox": [ + 306, + 596, + 420, + 609 + ], + "type": "text", + "content": "7. Acknowledgements" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "content": "This work was supported by the IITP grant funded by the MSIT (No.2018-0-00584, 2019-0-01906, 2020-0-01361), the NRF grant funded by the MSIT (No.2020R1A2B5B03097210, RS-2023-00217286), and the Digital Innovation Hub project supervised by the Daegu Digital Innovation Promotion Agency (DIP) grant funded by the Korea government (MSIT and Daegu Metropolitan City) in 2024 (No. DBSD1-07)." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22484" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 15, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "text", + "content": "[1] Devansh Arpit, Stanisław Jastrzebski, Nicolas Ballas, David Krueger, Emmanuel Bengio, Maxinder S Kanwal, Tegan Maharaj, Asja Fischer, Aaron Courville, Yoshua Bengio, et al. 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Action customization results of our ADI method. By inverting representative action-related features, the learned identifiers “” can be paired with a variety of characters and animals to contribute to the generation of accurate, diverse and high-quality images." + ], + "image_footnote": [], + "bbox": [ + 76, + 316, + 895, + 618 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 667, + 313, + 684 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "This study focuses on a novel task in text-to-image (T2I) generation, namely action customization. The objective of this task is to learn the co-existing action from limited data and generalize it to unseen humans or even animals. Experimental results show that existing subject-driven customization methods fail to learn the representative characteristics of actions and struggle in decoupling actions from context features, including appearance. To overcome the preference for low-level features and the entanglement of high-level features, we propose an inversion-based method ActionDisentangled Identifier (ADI) to learn action-specific iden", + "bbox": [ + 73, + 700, + 470, + 866 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "tifiers from the exemplar images. ADI first expands the semantic conditioning space by introducing layer-wise identifier tokens, thereby increasing the representational richness while distributing the inversion across different features. Then, to block the inversion of action-agnostic features, ADI extracts the gradient invariance from the constructed sample triples and masks the updates of irrelevant channels. To comprehensively evaluate the task, we present an Action-Bench that includes a variety of actions, each accompanied by meticulously selected samples. Both quantitative and qualitative results show that our ADI outperforms existing baselines in action-customized T2I generation. Our project page is at https://adi-t2i.github.io/ADI.", + "bbox": [ + 496, + 666, + 893, + 863 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Work done during internship at Alibaba Group.", + "bbox": [ + 99, + 875, + 357, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "†Corresponding author.", + "bbox": [ + 99, + 887, + 228, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "7797", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/41555498ad9d5719b3ceed0a2a902191d2ff1e37128baf59f8d116ab7ca598e3.jpg", + "image_caption": [ + "Figure 2. Action customization results of existing subject-driven customization methods. Due to the preference to search for low-level invariants when asked to learn high-level action features, some methods fail to generate the specified actions, while others confuse the animals with human appearances." + ], + "image_footnote": [], + "bbox": [ + 137, + 89, + 830, + 244 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 301, + 209, + 316 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Thanks to the remarkable advances in text-to-image generation models [3, 10, 18, 20], in particular the recent diffusion model [22, 26], high-quality and diverse images can be synthesized under the control of text descriptions. However, it is difficult to provide precise descriptions of the desired actions, which are highly abstracted and summarized concepts. Therefore, relying solely on textual descriptions to generate actions tends to reduce fidelity to user requirements. Additionally, controllable generation methods [14, 35] that rely on the conditioning of a skeleton or sketch image suffer from limited diversity and freedom, and they show difficulty generalizing to unseen subjects without retraining. In this paper, we study the action customization task, capturing the common action in the given images to generate new images with various new subjects.", + "bbox": [ + 75, + 334, + 472, + 561 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To better understand the challenge of action customization, we start by examining existing subject-driven customization methods. Observations shown in Fig. 2 can be divided into two categories. Several methods including DreamBooth [25], Textual Inversion [5], and ReVersion [7], generate images that are unrelated to specific actions, suggesting that they fail to capture the representative characteristics of the actions. Since most of them are designed to invert appearance features with a pixel-level reconstruction loss, low-level details are emphasized during optimization while high-level action features are neglected. Benefiting from fine-tuning cross-attention or utilizing per-layer tokens, Custom Diffusion [9] and $\\mathrm{P + }$ [30] offer a larger semantic conditioning space for learning new concepts. Consequently, they are capable of encoding action-related knowledge such as \"raises one finger\" or \"raises both arms for cheering\" from exemplar images. However, they fail to decouple the focus from action-agnostic features, such as the appearance of the human body. These pieces of information are also encoded into the learned identifiers and \"contaminate\" the generation of animals during inference. As a result, the intended gorilla is replaced by a", + "bbox": [ + 75, + 568, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "woman, and the tigers generated by the two methods exhibit human arms instead.", + "bbox": [ + 498, + 303, + 890, + 333 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To avoid the appearance leakage while accurately modeling the target action, we propose Action-Disentangled Identifier (ADI) to learn the optimal action-specific identifiers. Firstly, we expand the semantic conditioning space by applying layer-wise identifier tokens. Since existing works have analyzed that different layers have varying degrees of control over low-level and high-level features [30], such an expansion increases the accommodation of various features, making it easier to invert action-related features. Furthermore, we would like to decouple the action-agnostic features from the learning of action identifiers. To achieve this, we discover invariant mechanisms in the data that are difficult to vary across examples. Specifically, given an exemplar image with the specific action, another same-action image can be randomly sampled from the training data, forming a context-different pair. Meanwhile, leveraging mature subject-driven customization techniques, an image that shares the similar context can be quickly synthesized to form an action-different pair. To decouple the highly-coupled features, we disentangle action-agnostic features at the gradient level, and construct two context gradient masks by comparing the difference on the gradients over the input pairs. By overwriting the merged gradient mask to the gradient of the anchor image, the update of action-agnostic channels on the identifiers is discarded.", + "bbox": [ + 496, + 335, + 892, + 712 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Moreover, as a pioneering effort in this direction, we also contribute to a new benchmark named ActionBench, which provides a testbed of unique actions with diverse images for the under-explored task. We conduct extensive experiments on ActionBench, and a quick glance at the performance of ADI is illustrated in Fig. 1, where users can freely combine the designated action identifiers with various unseen humans and even animals. In summary, the main contributions of our work are three-fold:", + "bbox": [ + 496, + 715, + 893, + 851 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "- We propose a novel action customization task, which requires learning the desired action from limited data for future generation. While existing customization fo", + "bbox": [ + 503, + 854, + 893, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "7798", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "cuses on reprinting appearances, we highlight this understudied but important problem.", + "bbox": [ + 91, + 90, + 467, + 119 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We contribute the ActionBench, where a variety of unique actions with manually filtered images provide the evaluation conditions for the task.", + "- We devise the Action-Disentangled Identifier (ADI) method, which successfully inverts action-related features into the learned identifiers that can be freely combined with various characters and animals to generate high-quality images." + ], + "bbox": [ + 81, + 121, + 468, + 242 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 256, + 217, + 272 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Text-to-Image (T2I) Generation. Generating high-quality and diverse images from textual conditions has received considerable attention from both the research community and the general public. The previous dominant generative adversarial networks (GANs) [20, 28, 31, 38], consisting of a generator and a discriminator, suffer from unstable optimization and less diverse generations due to the adversarial training [2]. And variational autoencoders (VAEs) [8], which apply a probabilistic encoder-decoder architecture, are also prone to posterior collapse and over-smoothed generations [37]. Text-conditional auto-regressive models [3, 4, 18, 34] have shown more impressive results, but require time-consuming iterative processes to achieve high-quality image sampling. More recently, diffusion models have emerged as a promising alternative, achieving impressive results with open-vocabulary text descriptions through their natural fitting to inductive biases of image data [15, 19, 22, 26]. GLIDE [15] introduces text conditions into the diffusion process through the use of an unclassified guide. DALL-E 2 [19] employs a diffusion prior module and cascading diffusion decoders to generate high-resolution images based on the CLIP [17] text encoder. Imagen [26] focuses on language understanding by using a large T5 language model to better represent semantics. The latent diffusion model [22] improves computational efficiency by performing the diffusion process in low-dimension latent space with an autoencoder. Finally, Stable Diffusion (SD) [22] employs a cross-attention mechanism to inject textual conditions into the diffusion generation process, aligning with the provided textual input. However, it is difficult to provide precise action descriptions in text, since user intent and machine understanding are not aligned. Furthermore, experimental results in Fig. 4 show that some actions are difficult to generate correctly without re-training, e.g., \"performs a handstand\".", + "bbox": [ + 76, + 280, + 468, + 809 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Controllable Action Generation. The paper focuses on transferring the desired action from exemplar images to unseen people, characters, and even animals for photorealistic image generation. Existing efforts take source images and pose information (e.g., skeletal images or body parsing) as conditions to control the generation. Previous controllable", + "bbox": [ + 76, + 810, + 467, + 898 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "solutions based on GANs [12, 13, 36] and VAEs [21, 33] suffer from training difficulties and poor generation results. Some subsequent works [24, 32] introduce text conditions to guide the action generation, yet fail with open vocabulary due to the small size of the vocabulary pools. Thanks to the significant advances of T2I diffusion models, recent methods [10, 14, 29], in particular the popular ControlNet [35], add arbitrary conditions to improve the versatility and controllability. While gaining a tremendous amount of traction from the community, ControlNet refers to the provided skeleton image to generate the action, which reduces flexibility and diversity. In addition, the objective of designing a general framework with additional trainable modules makes it not well-targeted to animals. In this work, we investigate customization solutions for action generation.", + "bbox": [ + 496, + 90, + 890, + 316 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Subject-Driven Customization. Due to the demand for generating images with user-specified subjects, customization methods [5, 9, 25, 30] tailored to the appearance have been studied in the context of T2I generation. Specifically, DreamBooth [25] binds rare new words with specific subjects through fine-tuning the whole T2I generator. Textual Inversion [5] learns an extra identifier to represent the subject and adds the identifier as a new word to the dictionary of the text encoder. Custom Diffusion [9] only fine-tunes the key and value matrices of the cross-attention to represent new concepts. $\\mathrm{P + }$ [30] extends the textual-conditioning space with per-layer tokens to allow for greater disentangling and control. Despite the success achieved, the experimental results in Fig. 2 show their failure in action customization. A recent work ReVersion [7] makes progress in learning specific relations including some interactions from exemplar images. However, the design of the method, which specializes in learning spatial relations, makes it difficult to invert action information.", + "bbox": [ + 496, + 316, + 890, + 603 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Action Customization Benchmark", + "text_level": 1, + "bbox": [ + 500, + 618, + 808, + 633 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given a set of exemplar images $\\mathcal{X} = \\{\\mathbf{x}_1, \\mathbf{x}_2, \\dots, \\mathbf{x}_N\\}$ , we assume that all images contain the same action performed by different people. The action-agnostic descriptions associated to the exemplar images are also provided, which can be used as prompt templates during training. The objective of the action customization task is to extract the co-existing action and transfer it to the synthesis of action-specific images with different new subjects. In order to provide suitable conditions for systematic comparisons on this task, we present a new ActionBench, which consists of diverse actions accompanied by meticulously selected sample images. The benchmark can be used for both quantitative and qualitative comparisons.", + "bbox": [ + 496, + 643, + 890, + 839 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Action Categories. To determine the involved actions, we first request GPT-4 [16] to provide 50 candidate action categories, and then attempt to collect images for these candidates. Only actions that can collect sufficient high-quality", + "bbox": [ + 496, + 839, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "7799", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/cf97c55f9103fcf6e70eb9df14326331e9d00fde0719b3fcabe2488fa81d66dd.jpg", + "image_caption": [ + "Figure 3. Overview of our ADI method. ADI learns more efficient action identifiers by extending the semantic conditioning space and masking gradient updates to action-agnostic channels." + ], + "image_footnote": [], + "bbox": [ + 84, + 89, + 883, + 321 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "images are preserved. We finally define eight unique actions, ranging from single-handed (e.g., “raises one finger”) to full-body movements (e.g., “performs a handstand”).", + "bbox": [ + 75, + 369, + 468, + 415 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Exemplar Images and Prompts. For each action, we collect ten example images with corresponding textual descriptions, featuring different people. We manually remove action-related descriptions from the textual content to make them suitable as prompt templates.", + "bbox": [ + 75, + 416, + 468, + 492 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Evaluation Subjects. We provide a list containing 23 subjects, including generic humans (e.g., \"An old man\"), well-known personalities (e.g., \"David Beckham\"), and animals (e.g., \"A panda\"). The latter two are guaranteed to be completely unseen, which tests the generalization of methods.", + "bbox": [ + 75, + 492, + 468, + 570 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Methodology", + "text_level": 1, + "bbox": [ + 76, + 585, + 212, + 603 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We start with the technical background in Sec. 4.1. Then, we provide a comprehensive description of our proposed ADI in Sec. 4.2.", + "bbox": [ + 75, + 612, + 468, + 657 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Preliminaries", + "text_level": 1, + "bbox": [ + 76, + 670, + 217, + 686 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Our study is based on the Stable Diffusion (SD) [22] model, which is considered to be the public state-of-the-art text-to-image generator. Specifically, to operate the diffusion process [6] in a low-dimensional latent space, SD employs a hierarchical VAE that consists of an encoder $\\mathcal{E}$ and a decoder $\\mathcal{D}$ . The encoder $\\mathcal{E}$ is tasked with encoding the given image $\\mathbf{x}$ into latent features $\\mathbf{z}$ , and the decoder $\\mathcal{D}$ reconstructs the image $\\widehat{\\mathbf{x}}$ from the latent, i.e., $\\widehat{\\mathbf{x}} = \\mathcal{D}(\\mathbf{z}) = \\mathcal{D}(\\mathcal{E}(\\mathbf{x}))$ . To control the generation with the textual conditions, given the noisy latent $\\mathbf{z}_t$ , current time step $t$ and text tokens $\\mathbf{y}$ , a conditional U-Net [23] denoiser is trained to predict the noise $\\epsilon$ added to the latent $\\mathbf{z}$ :", + "bbox": [ + 75, + 695, + 470, + 875 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathbb {E} _ {\\mathbf {z} \\sim \\mathcal {E} (\\mathbf {x}), \\mathbf {y}, \\epsilon \\sim \\mathcal {N} (0, 1), t} \\left[ \\| \\epsilon - \\epsilon_ {\\theta} (\\mathbf {z} _ {t}, t, \\mathbf {y}) \\| _ {2} ^ {2} \\right], \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 102, + 878, + 468, + 905 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathbf{y}$ is obtained by feeding the prompt into a CLIP [17] text encoder. During inference, the pre-trained SD first samples a latent $\\mathbf{z}_T$ from the standard normal distribution $\\mathcal{N}(0,1)$ . Iteratively, $\\mathbf{z}_{t-1}$ can be obtained by removing noise from $\\mathbf{z}_t$ conditioned on $\\mathbf{y}$ . After the final denoising step, the latent $\\mathbf{z}_0$ is mapped to generate an image $\\widehat{\\mathbf{x}}$ with the decoder $\\mathcal{D}$ .", + "bbox": [ + 496, + 369, + 890, + 474 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.2. Action-Disentangled Identifier (ADI)", + "text_level": 1, + "bbox": [ + 498, + 484, + 818, + 501 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given exemplar images that all contain a specific entity, existing subject-driven inversion methods [5, 9] learn to represent the entity as an identifier token $v \\in \\mathbb{R}^d$ . And the learned $v$ can then be employed in text prompts to produce diverse and novel images, where the entity can be generated with different contexts. In this paper, we continue the vein of capturing the common action in exemplar images by finding the optimal identifiers. An overview of our proposed ADI is illustrated in Fig. 3.", + "bbox": [ + 496, + 508, + 890, + 643 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Expanding Semantic Inversion. To overcome the preference to low-level appearance features, we apply layer-wise identifier tokens to increase the accommodation of various features. Specifically, for the $l$ -th layer where $l \\in [1, L]$ and $L$ is the number of cross-attention layers in the T2I model, a new identifier token $v_l \\in \\mathbb{R}^d$ is initialized. Feeding the prompt with $v_l$ into the text encoder, the output tokens $\\mathbf{y}_l$ control the update of the latents in the $l$ -th layer, thus influencing the generation of the visual content. And the learned tokens from all layers can form a token set $\\mathcal{V}$ , which can then be paired with different subjects for generation. Rather than having a single identifier token take on the responsibility of reconstruction, having separate identifiers at different layers effectively ensures that more features are converted, including the action-related features we care about.", + "bbox": [ + 496, + 643, + 892, + 869 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Learning Gradient Mask with Context-Different Pair. The next step is to prevent the identifiers from inverting fea", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "7800", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "tures that are not relevant to the action and thus contaminating the subsequent image generation. Given $\\mathbf{x}^{(a,c)}\\in \\mathcal{X}$ as an anchor sample, where $a$ denotes the specific action, and $c$ denotes the action-agnostic context contained in the image including human appearance and background, we can randomly sample another image $\\mathbf{x}^{(a,\\overline{c})}$ from $\\mathcal{X}$ , where $\\overline{c}$ represents that the context is different from $c$ . Taking the context-different pair $\\mathbf{x}^{(a,c)}$ and $\\mathbf{x}^{(a,\\overline{c})}$ as the input, we can calculate two gradients of the denoising loss $\\mathcal{L}$ with respect to the identifier token $v$ :", + "bbox": [ + 75, + 90, + 472, + 241 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\ng ^ {(a, c)} = \\frac {\\partial \\mathcal {L} ^ {(a , c)}}{\\partial v}, \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 212, + 244, + 468, + 277 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\ng ^ {(a, \\bar {c})} = \\frac {\\partial \\mathcal {L} ^ {(a , \\bar {c})}}{\\partial v}. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 212, + 277, + 468, + 310 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Note that the subscript $l$ is omitted for the sake of uniformity and clarity. Each identifier token contains multiple channels, each carrying semantically distinct and independent information. And the gradient consistency of a channel indicates that the channel is likely to carry information about the specific action. Therefore, we calculate the absolute value of the difference between the two gradients:", + "bbox": [ + 75, + 314, + 468, + 420 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\triangle g ^ {\\overline {{c}}} = \\left| g ^ {(a, c)} - g ^ {(a, \\overline {{c}})} \\right|, \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 191, + 436, + 468, + 454 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where the semantic channels with a small difference can be regarded as action-related channels of the action $a$ , which are expected to be preserved. Specifically, we sort the difference from the largest to the smallest, taking the value at $\\beta$ percent $\\gamma^{\\beta}$ as a threshold. In other words, $\\beta \\%$ of the channels are masked. Then, the mask that shares the same dimension as $v$ can be calculated. For the $k$ -th channel,", + "bbox": [ + 75, + 460, + 468, + 566 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nm _ {k} ^ {\\bar {c}} = \\left\\{ \\begin{array}{l l} 0, & \\triangle g _ {k} ^ {\\bar {c}} \\geqslant \\gamma^ {\\beta} \\\\ 1, & \\triangle g _ {k} ^ {\\bar {c}} < \\gamma^ {\\beta} \\end{array} . \\right. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 181, + 570, + 468, + 604 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "By overwriting the mask to the gradient of the anchor sample, the action-related knowledge is preserved and incorporated into the update of $v$ , while the updates on action-agnostic channels are ignored. Note that since the specific visual invariance about the action changes slightly depending on the sample pair, the masked channels may not be exactly the same each time. Furthermore, both samples use the prompt of the anchor sample $\\mathbf{x}^{(a,c)}$ when calculating the gradients. Since the visual context of $\\mathbf{x}^{(a,\\bar{c})}$ is inconsistent with the description in the prompt, the reconstruction loss favours larger gradients in the context-related channels. In this way, the action-related channels found through the threshold will be more accurate.", + "bbox": [ + 75, + 609, + 468, + 804 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Learning Gradient Mask with Action-Different Pair. Although the context-different pairs have the same action semantics, there may be differences in the visualization of the actions, and therefore the channels associated with the most representative action features do not necessarily have a smaller gradient difference. Since learning the gradient", + "bbox": [ + 75, + 809, + 470, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "mask with the context-different only pair is not stable and effective enough, we also construct action-different pairs to generate the gradient mask from another perspective. For each sample $\\mathbf{x}^{(a,c)}$ in $\\mathcal{X}$ , we can use it to quickly train a subject-driven customization model (e.g., DreamBooth) that effectively inverts the most of the low-level context information. Therefore, by filling the prompt template of $\\mathbf{x}^{(a,c)}$ with action descriptions that are different from $a$ , the trained customization model can generate various action images as $\\mathcal{X}^{(\\overline{a},c)}$ . Note that this step is not necessary if the users can compile a dataset of varied actions by the same individual using pre-captured images. However, the data collection is usually arduous and lengthy, making fast training of a subject-driven customization a more convenient solution. Due to the one-shot training and the concise text, the generated images $\\mathcal{X}^{(\\overline{a},c)}$ may not be consistent with the action descriptions, or the context may differ from the original $\\mathbf{x}^{(a,c)}$ , but in practice, we have found that the quality is sufficient to diversify the action variation. In this way, when $\\mathbf{x}^{(a,c)}$ is sampled during training, we can randomly sample a image $\\mathbf{x}^{(\\overline{a},c)}$ from $\\mathcal{X}^{(\\overline{a},c)}$ to construct the action-different pair. And the gradient of $\\mathbf{x}^{(\\overline{a},c)}$ with respect to the token $v$ can be calculated as", + "bbox": [ + 496, + 90, + 890, + 436 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\ng ^ {(\\bar {a}, c)} = \\frac {\\partial \\mathcal {L} ^ {(\\bar {a} , c)}}{\\partial v}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 635, + 441, + 890, + 472 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Similarly, both samples use the prompt of the anchor sample $\\mathbf{x}^{(a,c)}$ . We can also calculate the absolute value of the gradient difference:", + "bbox": [ + 496, + 477, + 890, + 521 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\triangle g ^ {\\bar {a}} = \\left| g ^ {(a, c)} - g ^ {(\\bar {a}, c)} \\right|, \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 614, + 527, + 890, + 545 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where the semantic channels with small difference can be regarded as context-related channels of the action $a$ , which are expected to be masked. Therefore, we have", + "bbox": [ + 496, + 551, + 890, + 597 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nm _ {k} ^ {\\bar {a}} = \\left\\{ \\begin{array}{l l} 0, & \\triangle g _ {k} ^ {\\bar {a}} < \\lambda^ {\\beta} \\\\ 1, & \\triangle g _ {k} ^ {\\bar {a}} \\geqslant \\lambda^ {\\beta} \\end{array} , \\right. \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 601, + 602, + 890, + 636 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\lambda^{\\beta}$ is the threshold here to mask $\\beta \\%$ of the channels.", + "bbox": [ + 496, + 642, + 888, + 657 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Merging Gradient Masks for Context. Due to the noise introduced by context variations, identifying action-relevant channels using only context-different or action-different pairs would be difficult and unreliable. As an evidence, the average overlap rate of channels preserved by both masks at each training step is $30.26\\%$ . Therefore, given the input triple $\\mathcal{I} = \\{\\mathbf{x}^{(a,\\overline{c})},\\mathbf{x}^{(a,c)},\\mathbf{x}^{(\\overline{a},c)}\\}$ , we can merge the two obtained masks $m^{\\overline{a}}$ and $m^{\\overline{c}}$ to get the final context mask $m$ . In practice, we keep only the intersection of the unmasked channels as unmasked, as we find this merging strategy performs better. Formally, we have", + "bbox": [ + 496, + 661, + 890, + 827 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nm = m ^ {\\overline {{c}}} \\cap m ^ {\\overline {{a}}}, \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 640, + 834, + 890, + 849 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "which is overwritten to the gradient of the anchor sample:", + "bbox": [ + 500, + 857, + 888, + 872 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\widetilde {g} ^ {(a, c)} = m \\odot g ^ {(a, c)}. \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 625, + 878, + 890, + 896 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "7801", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/1232d370776c7eca185f2f101c5fb640294d877449bbf3723348b8f0c965115c.jpg", + "image_caption": [ + "Sample Image", + "Stable Diffusion ControlNet", + "DreamBooth Textual Inversion", + "ReVersion Custom Diffusion", + "P+", + "Ours", + "Figure 4. Visual comparisons of all methods. For each action, we present the generated results showcasing its pairing with a human character and an animal." + ], + "image_footnote": [], + "bbox": [ + 81, + 103, + 888, + 531 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "", + "bbox": [ + 799, + 103, + 887, + 241 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Note that the masked gradient $\\widetilde{g}^{(a,c)}$ , where action-agnostic channels are considered to be masked, is the only gradient used to update $v$ . Therefore, our identifiers can adequately invert action-related features.", + "bbox": [ + 75, + 577, + 468, + 638 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 76, + 654, + 209, + 671 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Experiment Setup", + "text_level": 1, + "bbox": [ + 76, + 679, + 253, + 695 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. For the baselines included in the comparison, we select Stable Diffusion [22], ControlNet [35], Dream-Booth [25], Textual Inversion [5], ReVersion [7], Custom Diffusion [9] and $\\mathrm{P + }$ [30].", + "bbox": [ + 75, + 703, + 468, + 763 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation Details. For ADI, we set the masking ratio $\\beta$ to 0.6 and use the AdamW [11] optimizer with a learning rate of 2e-4, while the training takes 3000 steps. For efficiency, DreamBooth for action-different pairs does not generate class-preservation images. While only one image is used for training, the initial learning rate is 1e-6, and the training takes 2000 steps. For a fair comparison, we use 50 steps of the DDIM [27] sampler with a scale of 7.5 for all methods. Unless otherwise specified, Stable Diffusion", + "bbox": [ + 75, + 763, + 470, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "v2-1-base is selected as the default pre-trained model, and images are generated at a resolution of $512 \\times 512$ . All experiments are conducted on a NVIDIA A100 GPU.", + "bbox": [ + 496, + 577, + 892, + 623 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Quantitative Comparison", + "text_level": 1, + "bbox": [ + 500, + 633, + 732, + 650 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We perform the quantitative comparison with human evaluators to assess the quantitative performance. For each subject-action pair, four images are randomly sampled from the images generated by different methods. Given (1) the exemplar images of a specific action, and (2) the textual name of the subjects, human evaluators are asked to determine whether (1) the generated action is consistent with those in the exemplar images, and (2) the generated character corresponds with the name without obvious deformations, defects, or abnormalities. A generated image will only be considered totally correct if both the action and the character are correctly generated.", + "bbox": [ + 496, + 657, + 892, + 839 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Tab. 1 reports the action, subject and total accuracy for all methods. Some observations are worth highlighting: (1) Given the textual descriptions of the actions, Stable Diffusion yields the highest total accuracy of all baseline meth", + "bbox": [ + 496, + 840, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "7802", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/33408aa4e675ea453b5dced91fbf503c97c18077006155f14cd39b3870653552.jpg", + "image_caption": [ + "Figure 5. Ablation study. We remove or revise one implementation at a time to demonstrate the effects of the identifier extension and the gradient masking." + ], + "image_footnote": [], + "bbox": [ + 165, + 89, + 803, + 324 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/6f24877c0503dabc265a5b8aaa10ec959ab750a69f65207c69c0eb97eea91930.jpg", + "table_caption": [ + "Table 1. Quantitative comparisons with competing methods. Action, subject and total accuracies $(\\%)$ are reported." + ], + "table_footnote": [], + "table_body": "
MethodsActionSubjectTotal
Stable Diffusion [22]30.7184.5127.17
ControlNet [35]41.3042.6619.29
DreamBooth [25]2.4595.652.45
Textual Inversion [5]2.1786.141.90
ReVersion [7]1.6384.511.63
Custom Diffusion [9]29.6253.537.07
P+ [30]26.9080.1620.92
ADI (Ours)60.3385.8751.09
", + "bbox": [ + 120, + 398, + 426, + 525 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ods. This suggests that the existing baselines do not take full advantage of the exemplar images. (2) Despite relying on the skeleton as the condition to improve the action generation, ControlNet fail to maintain the performance of subject generation, resulting in an unsatisfactory total accuracy. (3) The action accuracy of DreamBooth, Textual Inversion, and ReVersion is incredibly low, reflecting their complete failure to invert the action-related features. (4) Custom Diffusion and $\\mathrm{P + }$ improve action accuracy at more or less the expense of subject accuracy. (5) Attribute to the extended semantic conditioning space and the gradient masking strategy, our ADI dramatically improves the accuracy of action generation while maintaining excellent subject accuracy. As a result, ADI achieves the best total accuracy, outperforming the baselines by $23.92\\%$ .", + "bbox": [ + 75, + 534, + 472, + 762 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Qualitative Comparison", + "text_level": 1, + "bbox": [ + 76, + 770, + 299, + 787 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Fig. 4 illustrates the qualitative comparison of all methods involved. It can be observed that although text descriptions of the actions are provided, the actions generated by Stable Diffusion still differ from the examples. ControlNet can only maintain a rough consistency in posture and struggles to match the generated subjects to the desired requirements, resulting in incomplete or distorted body structures, while", + "bbox": [ + 75, + 794, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "sacrificing diversity. And the subject-driven customization methods, as discussed earlier, fail to generate the actions or exhibit appearance characteristics that differ from the specified subjects. This suggests that they are unable to convert only the features associated with the actions. Giving the credit to the design from a perspective of gradient, our ADI decouples action-related features from action-agnostic information and blocks the inversion of the latter. This allows ADI to effectively model the invariance of the action and transfer it to different characters and animals without sacrificing image quality and variety.", + "bbox": [ + 496, + 369, + 893, + 537 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.4. Ablation Study", + "text_level": 1, + "bbox": [ + 498, + 544, + 653, + 560 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We conduct ablation experiments on ActionBench to verify the individual effects of the proposed contributions. From the generation results in Fig. 5, it can be observed that (1) The removal of the extension to the semantic conditioning space diminishes the inversion ability of ADI. (2) Both the gradient masks learned from the context-different and the action-different pairs are essential. Removing either one can lead to inadequate learning of action knowledge or a degradation in the quality of the subject's appearance. We attribute this to the fact that learning from a single pair is inherently noisy due to varied action visuals and the interference of action-irrelevant information. (3) We also attempt to reverse the gradient masks, i.e., updates to channels that should have been masked are preserved, and updates to other channels are cancelled. Obviously, this will result in action-related features not being inverted.", + "bbox": [ + 496, + 566, + 893, + 811 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.5. Further Analysis", + "text_level": 1, + "bbox": [ + 498, + 816, + 668, + 833 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Impact of Masking Strategy. To validate the masking strategy in our ADI, we compare it with four other strategies in Fig. 6. Specifically, on the gradients for each update: (1) Uniform: we uniformly mask $\\beta$ percent of channels. (2)", + "bbox": [ + 496, + 839, + 893, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "7803", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/3de6cce6cba2819735dc0c8f5dabaa52fd0eb2b239e501a62f207f1ab5bad95d.jpg", + "image_caption": [ + "Figure 6. Visual comparison of masking strategies. The four compared strategies fail to mask the updates from agnostic channels and invert the action-related features." + ], + "image_footnote": [], + "bbox": [ + 165, + 89, + 803, + 251 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c98390fb2b0d368c9d47c621b27a7ec205bdc61c26b70fee07e5fe9b0e528d74.jpg", + "image_caption": [ + "Figure 7. Effect of gradient mask merging strategy. Preserving the intersection of gradient masks can better invert the representative action features." + ], + "image_footnote": [], + "bbox": [ + 80, + 295, + 468, + 428 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Random: we randomly mask $\\beta$ percent of channels. (3) Min: we mask $\\beta$ percent of channels with the lowest value. (4) Max: we mask $\\beta$ percent of channels with the highest value. We observe that none of these four strategies successfully captures high-level features related to actions, since the images they generate are independent of the specified action. And the comparison also shows that the effectiveness of our ADI not only depends on the masking itself, but also requires learning action-agnostic channels by modeling the invariance of action and context.", + "bbox": [ + 75, + 489, + 468, + 641 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Impact of Gradient Mask Merging Strategy. As shown in Eq. (9), ADI takes the intersection of the two gradient masks as the default merging strategy. We compare this with selecting the union of the two masks, and illustrate the generation results in Fig. 7. Since only channels that are preserved on both masks are updated, taking the intersection can effectively filter out action-agnostic features, leading to better customization of the actions. In contrast, taking the intersection may dilute the most representative action features due to the preserved context information.", + "bbox": [ + 75, + 643, + 468, + 792 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Impact of Masking Ratio $\\beta$ . In Fig. 8, we vary the masking ratio $\\beta$ from 0.2 to 0.8. When $\\beta$ is small, fewer dimensions of the gradient are masked, and more action-agnostic features are retained to hinder the generation of the subject's appearance. This situation improves as $\\beta$ is gradually increased. However, when $\\beta$ is relatively large, due to the large number of masked dimensions, some of the most dis", + "bbox": [ + 75, + 795, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ec6bd2fc4bc6fe6905244b4dd8aeccf1bf4012025b8212b1fc6bb5894fef0357.jpg", + "image_caption": [ + "Figure 8. Effect of the masking ratio $\\beta$ . A value close to 0.5 can balance the inversion of action-related features and the removal of action-agnostic features." + ], + "image_footnote": [], + "bbox": [ + 501, + 295, + 890, + 426 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "criminative features of actions may not be inverted, resulting in incomplete learning of actions. Note that the optimal value of $\\beta$ may be different for different actions.", + "bbox": [ + 498, + 488, + 890, + 532 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 547, + 619, + 563 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we investigate an under-explored text-to-image generation task, namely action customization. To understand the challenge of the task, we first visualize the inadequacy of existing subject-driven methods in extracting action-related features from the entanglement of action-agnostic context features. Then, we propose a novel method named ADI to learn action-specific identifiers from the given images. To increase the accommodation of knowledge relevant to the action, ADI extends the inversion process with layer-wise identifier tokens. Furthermore, ADI generates gradient masks to block the contamination of action-agnostic features at the gradient level. We also contribute the ActionBench for evaluating performance on the task. Since there is a growing need to synthesize action-specific images with various new subjects, we hope that our work can highlight this important direction.", + "bbox": [ + 496, + 571, + 890, + 813 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement This work was supported by STI 2030—Major Projects (2022ZD0208800), NSFC General Program (Grant No. 62176215). 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 5802-5810, 2019. 3" + ], + "bbox": [ + 501, + 92, + 890, + 261 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "7806", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/9257612f-7f23-4c8a-85fd-19ebf525ae6f_model.json b/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/9257612f-7f23-4c8a-85fd-19ebf525ae6f_model.json new file mode 100644 index 0000000000000000000000000000000000000000..c30750db631d1529f7fea9dc8f063f237e2303d1 --- /dev/null +++ b/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/9257612f-7f23-4c8a-85fd-19ebf525ae6f_model.json @@ -0,0 +1,1892 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.198, + 0.131, + 0.775, + 0.176 + ], + "angle": 0, + "content": "Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation" + }, + { + "type": "text", + "bbox": [ + 0.11, + 0.203, + 0.861, + 0.24 + ], + "angle": 0, + "content": "Siteng Huang\\(^{1,4*}\\), Biao Gong\\(^{2}\\), Yutong Feng\\(^{2}\\), Xi Chen\\(^{2}\\), Yuqian Fu\\(^{3}\\), Yu Liu\\(^{2}\\), Donglin Wang\\(^{4\\dagger}\\), Zhejiang University \\({}^{2}\\)Alibaba Group \\({}^{3}\\)ETH Zürich" + }, + { + "type": "text", + "bbox": [ + 0.11, + 0.24, + 0.86, + 0.258 + ], + "angle": 0, + "content": "4Machine Intelligence Lab (MiLAB), AI Division, School of Engineering, Westlake University" + }, + { + "type": "text", + "bbox": [ + 0.26, + 0.258, + 0.714, + 0.272 + ], + "angle": 0, + "content": "{siteng.huang, a.biao.gong, yuqianfu0207}@gmail.com" + }, + { + "type": "text", + "bbox": [ + 0.13, + 0.272, + 0.837, + 0.286 + ], + "angle": 0, + "content": "{fengyutong.fyt, xizhi.cx, ly103369}@alibaba-inc.com wangdonglin@westlake.edu.cn" + }, + { + "type": "image", + "bbox": [ + 0.078, + 0.318, + 0.896, + 0.619 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.624, + 0.895, + 0.654 + ], + "angle": 0, + "content": "Figure 1. Action customization results of our ADI method. By inverting representative action-related features, the learned identifiers “
” can be paired with a variety of characters and animals to contribute to the generation of accurate, diverse and high-quality images." + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.669, + 0.314, + 0.685 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.701, + 0.472, + 0.867 + ], + "angle": 0, + "content": "This study focuses on a novel task in text-to-image (T2I) generation, namely action customization. The objective of this task is to learn the co-existing action from limited data and generalize it to unseen humans or even animals. Experimental results show that existing subject-driven customization methods fail to learn the representative characteristics of actions and struggle in decoupling actions from context features, including appearance. To overcome the preference for low-level features and the entanglement of high-level features, we propose an inversion-based method ActionDisentangled Identifier (ADI) to learn action-specific iden" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.667, + 0.895, + 0.864 + ], + "angle": 0, + "content": "tifiers from the exemplar images. ADI first expands the semantic conditioning space by introducing layer-wise identifier tokens, thereby increasing the representational richness while distributing the inversion across different features. Then, to block the inversion of action-agnostic features, ADI extracts the gradient invariance from the constructed sample triples and masks the updates of irrelevant channels. To comprehensively evaluate the task, we present an Action-Bench that includes a variety of actions, each accompanied by meticulously selected samples. Both quantitative and qualitative results show that our ADI outperforms existing baselines in action-customized T2I generation. Our project page is at https://adi-t2i.github.io/ADI." + }, + { + "type": "page_footnote", + "bbox": [ + 0.1, + 0.875, + 0.359, + 0.888 + ], + "angle": 0, + "content": "*Work done during internship at Alibaba Group." + }, + { + "type": "page_footnote", + "bbox": [ + 0.1, + 0.888, + 0.23, + 0.901 + ], + "angle": 0, + "content": "†Corresponding author." + }, + { + "type": "list", + "bbox": [ + 0.1, + 0.875, + 0.359, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7797" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.138, + 0.09, + 0.831, + 0.245 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.25, + 0.895, + 0.293 + ], + "angle": 0, + "content": "Figure 2. Action customization results of existing subject-driven customization methods. Due to the preference to search for low-level invariants when asked to learn high-level action features, some methods fail to generate the specified actions, while others confuse the animals with human appearances." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.303, + 0.21, + 0.318 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.335, + 0.473, + 0.562 + ], + "angle": 0, + "content": "Thanks to the remarkable advances in text-to-image generation models [3, 10, 18, 20], in particular the recent diffusion model [22, 26], high-quality and diverse images can be synthesized under the control of text descriptions. However, it is difficult to provide precise descriptions of the desired actions, which are highly abstracted and summarized concepts. Therefore, relying solely on textual descriptions to generate actions tends to reduce fidelity to user requirements. Additionally, controllable generation methods [14, 35] that rely on the conditioning of a skeleton or sketch image suffer from limited diversity and freedom, and they show difficulty generalizing to unseen subjects without retraining. In this paper, we study the action customization task, capturing the common action in the given images to generate new images with various new subjects." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.569, + 0.473, + 0.903 + ], + "angle": 0, + "content": "To better understand the challenge of action customization, we start by examining existing subject-driven customization methods. Observations shown in Fig. 2 can be divided into two categories. Several methods including DreamBooth [25], Textual Inversion [5], and ReVersion [7], generate images that are unrelated to specific actions, suggesting that they fail to capture the representative characteristics of the actions. Since most of them are designed to invert appearance features with a pixel-level reconstruction loss, low-level details are emphasized during optimization while high-level action features are neglected. Benefiting from fine-tuning cross-attention or utilizing per-layer tokens, Custom Diffusion [9] and \\(\\mathrm{P + }\\) [30] offer a larger semantic conditioning space for learning new concepts. Consequently, they are capable of encoding action-related knowledge such as \"raises one finger\" or \"raises both arms for cheering\" from exemplar images. However, they fail to decouple the focus from action-agnostic features, such as the appearance of the human body. These pieces of information are also encoded into the learned identifiers and \"contaminate\" the generation of animals during inference. As a result, the intended gorilla is replaced by a" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.304, + 0.892, + 0.334 + ], + "angle": 0, + "content": "woman, and the tigers generated by the two methods exhibit human arms instead." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.337, + 0.893, + 0.713 + ], + "angle": 0, + "content": "To avoid the appearance leakage while accurately modeling the target action, we propose Action-Disentangled Identifier (ADI) to learn the optimal action-specific identifiers. Firstly, we expand the semantic conditioning space by applying layer-wise identifier tokens. Since existing works have analyzed that different layers have varying degrees of control over low-level and high-level features [30], such an expansion increases the accommodation of various features, making it easier to invert action-related features. Furthermore, we would like to decouple the action-agnostic features from the learning of action identifiers. To achieve this, we discover invariant mechanisms in the data that are difficult to vary across examples. Specifically, given an exemplar image with the specific action, another same-action image can be randomly sampled from the training data, forming a context-different pair. Meanwhile, leveraging mature subject-driven customization techniques, an image that shares the similar context can be quickly synthesized to form an action-different pair. To decouple the highly-coupled features, we disentangle action-agnostic features at the gradient level, and construct two context gradient masks by comparing the difference on the gradients over the input pairs. By overwriting the merged gradient mask to the gradient of the anchor image, the update of action-agnostic channels on the identifiers is discarded." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.717, + 0.895, + 0.852 + ], + "angle": 0, + "content": "Moreover, as a pioneering effort in this direction, we also contribute to a new benchmark named ActionBench, which provides a testbed of unique actions with diverse images for the under-explored task. We conduct extensive experiments on ActionBench, and a quick glance at the performance of ADI is illustrated in Fig. 1, where users can freely combine the designated action identifiers with various unseen humans and even animals. In summary, the main contributions of our work are three-fold:" + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.856, + 0.895, + 0.901 + ], + "angle": 0, + "content": "- We propose a novel action customization task, which requires learning the desired action from limited data for future generation. While existing customization fo" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7798" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.093, + 0.092, + 0.468, + 0.121 + ], + "angle": 0, + "content": "cuses on reprinting appearances, we highlight this understudied but important problem." + }, + { + "type": "text", + "bbox": [ + 0.082, + 0.122, + 0.47, + 0.167 + ], + "angle": 0, + "content": "- We contribute the ActionBench, where a variety of unique actions with manually filtered images provide the evaluation conditions for the task." + }, + { + "type": "text", + "bbox": [ + 0.082, + 0.167, + 0.468, + 0.243 + ], + "angle": 0, + "content": "- We devise the Action-Disentangled Identifier (ADI) method, which successfully inverts action-related features into the learned identifiers that can be freely combined with various characters and animals to generate high-quality images." + }, + { + "type": "list", + "bbox": [ + 0.082, + 0.122, + 0.47, + 0.243 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.257, + 0.218, + 0.273 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.281, + 0.47, + 0.81 + ], + "angle": 0, + "content": "Text-to-Image (T2I) Generation. Generating high-quality and diverse images from textual conditions has received considerable attention from both the research community and the general public. The previous dominant generative adversarial networks (GANs) [20, 28, 31, 38], consisting of a generator and a discriminator, suffer from unstable optimization and less diverse generations due to the adversarial training [2]. And variational autoencoders (VAEs) [8], which apply a probabilistic encoder-decoder architecture, are also prone to posterior collapse and over-smoothed generations [37]. Text-conditional auto-regressive models [3, 4, 18, 34] have shown more impressive results, but require time-consuming iterative processes to achieve high-quality image sampling. More recently, diffusion models have emerged as a promising alternative, achieving impressive results with open-vocabulary text descriptions through their natural fitting to inductive biases of image data [15, 19, 22, 26]. GLIDE [15] introduces text conditions into the diffusion process through the use of an unclassified guide. DALL-E 2 [19] employs a diffusion prior module and cascading diffusion decoders to generate high-resolution images based on the CLIP [17] text encoder. Imagen [26] focuses on language understanding by using a large T5 language model to better represent semantics. The latent diffusion model [22] improves computational efficiency by performing the diffusion process in low-dimension latent space with an autoencoder. Finally, Stable Diffusion (SD) [22] employs a cross-attention mechanism to inject textual conditions into the diffusion generation process, aligning with the provided textual input. However, it is difficult to provide precise action descriptions in text, since user intent and machine understanding are not aligned. Furthermore, experimental results in Fig. 4 show that some actions are difficult to generate correctly without re-training, e.g., \"performs a handstand\"." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.811, + 0.468, + 0.9 + ], + "angle": 0, + "content": "Controllable Action Generation. The paper focuses on transferring the desired action from exemplar images to unseen people, characters, and even animals for photorealistic image generation. Existing efforts take source images and pose information (e.g., skeletal images or body parsing) as conditions to control the generation. Previous controllable" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.317 + ], + "angle": 0, + "content": "solutions based on GANs [12, 13, 36] and VAEs [21, 33] suffer from training difficulties and poor generation results. Some subsequent works [24, 32] introduce text conditions to guide the action generation, yet fail with open vocabulary due to the small size of the vocabulary pools. Thanks to the significant advances of T2I diffusion models, recent methods [10, 14, 29], in particular the popular ControlNet [35], add arbitrary conditions to improve the versatility and controllability. While gaining a tremendous amount of traction from the community, ControlNet refers to the provided skeleton image to generate the action, which reduces flexibility and diversity. In addition, the objective of designing a general framework with additional trainable modules makes it not well-targeted to animals. In this work, we investigate customization solutions for action generation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.318, + 0.892, + 0.604 + ], + "angle": 0, + "content": "Subject-Driven Customization. Due to the demand for generating images with user-specified subjects, customization methods [5, 9, 25, 30] tailored to the appearance have been studied in the context of T2I generation. Specifically, DreamBooth [25] binds rare new words with specific subjects through fine-tuning the whole T2I generator. Textual Inversion [5] learns an extra identifier to represent the subject and adds the identifier as a new word to the dictionary of the text encoder. Custom Diffusion [9] only fine-tunes the key and value matrices of the cross-attention to represent new concepts. \\(\\mathrm{P + }\\) [30] extends the textual-conditioning space with per-layer tokens to allow for greater disentangling and control. Despite the success achieved, the experimental results in Fig. 2 show their failure in action customization. A recent work ReVersion [7] makes progress in learning specific relations including some interactions from exemplar images. However, the design of the method, which specializes in learning spatial relations, makes it difficult to invert action information." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.619, + 0.809, + 0.634 + ], + "angle": 0, + "content": "3. Action Customization Benchmark" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.892, + 0.84 + ], + "angle": 0, + "content": "Given a set of exemplar images \\(\\mathcal{X} = \\{\\mathbf{x}_1, \\mathbf{x}_2, \\dots, \\mathbf{x}_N\\}\\), we assume that all images contain the same action performed by different people. The action-agnostic descriptions associated to the exemplar images are also provided, which can be used as prompt templates during training. The objective of the action customization task is to extract the co-existing action and transfer it to the synthesis of action-specific images with different new subjects. In order to provide suitable conditions for systematic comparisons on this task, we present a new ActionBench, which consists of diverse actions accompanied by meticulously selected sample images. The benchmark can be used for both quantitative and qualitative comparisons." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Action Categories. To determine the involved actions, we first request GPT-4 [16] to provide 50 candidate action categories, and then attempt to collect images for these candidates. Only actions that can collect sufficient high-quality" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7799" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.086, + 0.09, + 0.885, + 0.322 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.326, + 0.895, + 0.357 + ], + "angle": 0, + "content": "Figure 3. Overview of our ADI method. ADI learns more efficient action identifiers by extending the semantic conditioning space and masking gradient updates to action-agnostic channels." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.371, + 0.47, + 0.416 + ], + "angle": 0, + "content": "images are preserved. We finally define eight unique actions, ranging from single-handed (e.g., “raises one finger”) to full-body movements (e.g., “performs a handstand”)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.417, + 0.47, + 0.493 + ], + "angle": 0, + "content": "Exemplar Images and Prompts. For each action, we collect ten example images with corresponding textual descriptions, featuring different people. We manually remove action-related descriptions from the textual content to make them suitable as prompt templates." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.493, + 0.47, + 0.571 + ], + "angle": 0, + "content": "Evaluation Subjects. We provide a list containing 23 subjects, including generic humans (e.g., \"An old man\"), well-known personalities (e.g., \"David Beckham\"), and animals (e.g., \"A panda\"). The latter two are guaranteed to be completely unseen, which tests the generalization of methods." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.587, + 0.214, + 0.604 + ], + "angle": 0, + "content": "4. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.613, + 0.47, + 0.658 + ], + "angle": 0, + "content": "We start with the technical background in Sec. 4.1. Then, we provide a comprehensive description of our proposed ADI in Sec. 4.2." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.671, + 0.218, + 0.687 + ], + "angle": 0, + "content": "4.1. Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.696, + 0.471, + 0.876 + ], + "angle": 0, + "content": "Our study is based on the Stable Diffusion (SD) [22] model, which is considered to be the public state-of-the-art text-to-image generator. Specifically, to operate the diffusion process [6] in a low-dimensional latent space, SD employs a hierarchical VAE that consists of an encoder \\(\\mathcal{E}\\) and a decoder \\(\\mathcal{D}\\). The encoder \\(\\mathcal{E}\\) is tasked with encoding the given image \\(\\mathbf{x}\\) into latent features \\(\\mathbf{z}\\), and the decoder \\(\\mathcal{D}\\) reconstructs the image \\(\\widehat{\\mathbf{x}}\\) from the latent, i.e., \\(\\widehat{\\mathbf{x}} = \\mathcal{D}(\\mathbf{z}) = \\mathcal{D}(\\mathcal{E}(\\mathbf{x}))\\). To control the generation with the textual conditions, given the noisy latent \\(\\mathbf{z}_t\\), current time step \\(t\\) and text tokens \\(\\mathbf{y}\\), a conditional U-Net [23] denoiser is trained to predict the noise \\(\\epsilon\\) added to the latent \\(\\mathbf{z}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.103, + 0.879, + 0.47, + 0.906 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathbb {E} _ {\\mathbf {z} \\sim \\mathcal {E} (\\mathbf {x}), \\mathbf {y}, \\epsilon \\sim \\mathcal {N} (0, 1), t} \\left[ \\| \\epsilon - \\epsilon_ {\\theta} (\\mathbf {z} _ {t}, t, \\mathbf {y}) \\| _ {2} ^ {2} \\right], \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.371, + 0.892, + 0.476 + ], + "angle": 0, + "content": "where \\(\\mathbf{y}\\) is obtained by feeding the prompt into a CLIP [17] text encoder. During inference, the pre-trained SD first samples a latent \\(\\mathbf{z}_T\\) from the standard normal distribution \\(\\mathcal{N}(0,1)\\). Iteratively, \\(\\mathbf{z}_{t-1}\\) can be obtained by removing noise from \\(\\mathbf{z}_t\\) conditioned on \\(\\mathbf{y}\\). After the final denoising step, the latent \\(\\mathbf{z}_0\\) is mapped to generate an image \\(\\widehat{\\mathbf{x}}\\) with the decoder \\(\\mathcal{D}\\)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.485, + 0.82, + 0.502 + ], + "angle": 0, + "content": "4.2. Action-Disentangled Identifier (ADI)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.509, + 0.892, + 0.644 + ], + "angle": 0, + "content": "Given exemplar images that all contain a specific entity, existing subject-driven inversion methods [5, 9] learn to represent the entity as an identifier token \\( v \\in \\mathbb{R}^d \\). And the learned \\( v \\) can then be employed in text prompts to produce diverse and novel images, where the entity can be generated with different contexts. In this paper, we continue the vein of capturing the common action in exemplar images by finding the optimal identifiers. An overview of our proposed ADI is illustrated in Fig. 3." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.645, + 0.893, + 0.87 + ], + "angle": 0, + "content": "Expanding Semantic Inversion. To overcome the preference to low-level appearance features, we apply layer-wise identifier tokens to increase the accommodation of various features. Specifically, for the \\(l\\)-th layer where \\(l \\in [1, L]\\) and \\(L\\) is the number of cross-attention layers in the T2I model, a new identifier token \\(v_l \\in \\mathbb{R}^d\\) is initialized. Feeding the prompt with \\(v_l\\) into the text encoder, the output tokens \\(\\mathbf{y}_l\\) control the update of the latents in the \\(l\\)-th layer, thus influencing the generation of the visual content. And the learned tokens from all layers can form a token set \\(\\mathcal{V}\\), which can then be paired with different subjects for generation. Rather than having a single identifier token take on the responsibility of reconstruction, having separate identifiers at different layers effectively ensures that more features are converted, including the action-related features we care about." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Learning Gradient Mask with Context-Different Pair. The next step is to prevent the identifiers from inverting fea" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7800" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.242 + ], + "angle": 0, + "content": "tures that are not relevant to the action and thus contaminating the subsequent image generation. Given \\(\\mathbf{x}^{(a,c)}\\in \\mathcal{X}\\) as an anchor sample, where \\(a\\) denotes the specific action, and \\(c\\) denotes the action-agnostic context contained in the image including human appearance and background, we can randomly sample another image \\(\\mathbf{x}^{(a,\\overline{c})}\\) from \\(\\mathcal{X}\\), where \\(\\overline{c}\\) represents that the context is different from \\(c\\). Taking the context-different pair \\(\\mathbf{x}^{(a,c)}\\) and \\(\\mathbf{x}^{(a,\\overline{c})}\\) as the input, we can calculate two gradients of the denoising loss \\(\\mathcal{L}\\) with respect to the identifier token \\(v\\):" + }, + { + "type": "equation", + "bbox": [ + 0.213, + 0.246, + 0.47, + 0.278 + ], + "angle": 0, + "content": "\\[\ng ^ {(a, c)} = \\frac {\\partial \\mathcal {L} ^ {(a , c)}}{\\partial v}, \\tag {2}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.214, + 0.279, + 0.469, + 0.311 + ], + "angle": 0, + "content": "\\[\ng ^ {(a, \\bar {c})} = \\frac {\\partial \\mathcal {L} ^ {(a , \\bar {c})}}{\\partial v}. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.315, + 0.47, + 0.421 + ], + "angle": 0, + "content": "Note that the subscript \\( l \\) is omitted for the sake of uniformity and clarity. Each identifier token contains multiple channels, each carrying semantically distinct and independent information. And the gradient consistency of a channel indicates that the channel is likely to carry information about the specific action. Therefore, we calculate the absolute value of the difference between the two gradients:" + }, + { + "type": "equation", + "bbox": [ + 0.192, + 0.437, + 0.469, + 0.455 + ], + "angle": 0, + "content": "\\[\n\\triangle g ^ {\\overline {{c}}} = \\left| g ^ {(a, c)} - g ^ {(a, \\overline {{c}})} \\right|, \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.462, + 0.469, + 0.567 + ], + "angle": 0, + "content": "where the semantic channels with a small difference can be regarded as action-related channels of the action \\(a\\), which are expected to be preserved. Specifically, we sort the difference from the largest to the smallest, taking the value at \\(\\beta\\) percent \\(\\gamma^{\\beta}\\) as a threshold. In other words, \\(\\beta \\%\\) of the channels are masked. Then, the mask that shares the same dimension as \\(v\\) can be calculated. For the \\(k\\)-th channel," + }, + { + "type": "equation", + "bbox": [ + 0.182, + 0.571, + 0.469, + 0.605 + ], + "angle": 0, + "content": "\\[\nm _ {k} ^ {\\bar {c}} = \\left\\{ \\begin{array}{l l} 0, & \\triangle g _ {k} ^ {\\bar {c}} \\geqslant \\gamma^ {\\beta} \\\\ 1, & \\triangle g _ {k} ^ {\\bar {c}} < \\gamma^ {\\beta} \\end{array} . \\right. \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.61, + 0.47, + 0.805 + ], + "angle": 0, + "content": "By overwriting the mask to the gradient of the anchor sample, the action-related knowledge is preserved and incorporated into the update of \\( v \\), while the updates on action-agnostic channels are ignored. Note that since the specific visual invariance about the action changes slightly depending on the sample pair, the masked channels may not be exactly the same each time. Furthermore, both samples use the prompt of the anchor sample \\( \\mathbf{x}^{(a,c)} \\) when calculating the gradients. Since the visual context of \\( \\mathbf{x}^{(a,\\bar{c})} \\) is inconsistent with the description in the prompt, the reconstruction loss favours larger gradients in the context-related channels. In this way, the action-related channels found through the threshold will be more accurate." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Learning Gradient Mask with Action-Different Pair. Although the context-different pairs have the same action semantics, there may be differences in the visualization of the actions, and therefore the channels associated with the most representative action features do not necessarily have a smaller gradient difference. Since learning the gradient" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.438 + ], + "angle": 0, + "content": "mask with the context-different only pair is not stable and effective enough, we also construct action-different pairs to generate the gradient mask from another perspective. For each sample \\(\\mathbf{x}^{(a,c)}\\) in \\(\\mathcal{X}\\), we can use it to quickly train a subject-driven customization model (e.g., DreamBooth) that effectively inverts the most of the low-level context information. Therefore, by filling the prompt template of \\(\\mathbf{x}^{(a,c)}\\) with action descriptions that are different from \\(a\\), the trained customization model can generate various action images as \\(\\mathcal{X}^{(\\overline{a},c)}\\). Note that this step is not necessary if the users can compile a dataset of varied actions by the same individual using pre-captured images. However, the data collection is usually arduous and lengthy, making fast training of a subject-driven customization a more convenient solution. Due to the one-shot training and the concise text, the generated images \\(\\mathcal{X}^{(\\overline{a},c)}\\) may not be consistent with the action descriptions, or the context may differ from the original \\(\\mathbf{x}^{(a,c)}\\), but in practice, we have found that the quality is sufficient to diversify the action variation. In this way, when \\(\\mathbf{x}^{(a,c)}\\) is sampled during training, we can randomly sample a image \\(\\mathbf{x}^{(\\overline{a},c)}\\) from \\(\\mathcal{X}^{(\\overline{a},c)}\\) to construct the action-different pair. And the gradient of \\(\\mathbf{x}^{(\\overline{a},c)}\\) with respect to the token \\(v\\) can be calculated as" + }, + { + "type": "equation", + "bbox": [ + 0.636, + 0.442, + 0.891, + 0.473 + ], + "angle": 0, + "content": "\\[\ng ^ {(\\bar {a}, c)} = \\frac {\\partial \\mathcal {L} ^ {(\\bar {a} , c)}}{\\partial v}. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.478, + 0.891, + 0.522 + ], + "angle": 0, + "content": "Similarly, both samples use the prompt of the anchor sample \\(\\mathbf{x}^{(a,c)}\\). We can also calculate the absolute value of the gradient difference:" + }, + { + "type": "equation", + "bbox": [ + 0.615, + 0.528, + 0.891, + 0.546 + ], + "angle": 0, + "content": "\\[\n\\triangle g ^ {\\bar {a}} = \\left| g ^ {(a, c)} - g ^ {(\\bar {a}, c)} \\right|, \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.552, + 0.891, + 0.598 + ], + "angle": 0, + "content": "where the semantic channels with small difference can be regarded as context-related channels of the action \\(a\\), which are expected to be masked. Therefore, we have" + }, + { + "type": "equation", + "bbox": [ + 0.602, + 0.603, + 0.891, + 0.637 + ], + "angle": 0, + "content": "\\[\nm _ {k} ^ {\\bar {a}} = \\left\\{ \\begin{array}{l l} 0, & \\triangle g _ {k} ^ {\\bar {a}} < \\lambda^ {\\beta} \\\\ 1, & \\triangle g _ {k} ^ {\\bar {a}} \\geqslant \\lambda^ {\\beta} \\end{array} , \\right. \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.89, + 0.658 + ], + "angle": 0, + "content": "where \\(\\lambda^{\\beta}\\) is the threshold here to mask \\(\\beta \\%\\) of the channels." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.662, + 0.892, + 0.828 + ], + "angle": 0, + "content": "Merging Gradient Masks for Context. Due to the noise introduced by context variations, identifying action-relevant channels using only context-different or action-different pairs would be difficult and unreliable. As an evidence, the average overlap rate of channels preserved by both masks at each training step is \\(30.26\\%\\). Therefore, given the input triple \\(\\mathcal{I} = \\{\\mathbf{x}^{(a,\\overline{c})},\\mathbf{x}^{(a,c)},\\mathbf{x}^{(\\overline{a},c)}\\}\\), we can merge the two obtained masks \\(m^{\\overline{a}}\\) and \\(m^{\\overline{c}}\\) to get the final context mask \\(m\\). In practice, we keep only the intersection of the unmasked channels as unmasked, as we find this merging strategy performs better. Formally, we have" + }, + { + "type": "equation", + "bbox": [ + 0.642, + 0.835, + 0.891, + 0.851 + ], + "angle": 0, + "content": "\\[\nm = m ^ {\\overline {{c}}} \\cap m ^ {\\overline {{a}}}, \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.858, + 0.89, + 0.873 + ], + "angle": 0, + "content": "which is overwritten to the gradient of the anchor sample:" + }, + { + "type": "equation", + "bbox": [ + 0.626, + 0.879, + 0.891, + 0.897 + ], + "angle": 0, + "content": "\\[\n\\widetilde {g} ^ {(a, c)} = m \\odot g ^ {(a, c)}. \\tag {10}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.514, + 0.957 + ], + "angle": 0, + "content": "7801" + } + ], + [ + { + "type": "image_caption", + "bbox": [ + 0.084, + 0.093, + 0.163, + 0.104 + ], + "angle": 0, + "content": "Sample Image" + }, + { + "type": "image_caption", + "bbox": [ + 0.186, + 0.093, + 0.348, + 0.103 + ], + "angle": 0, + "content": "Stable Diffusion ControlNet" + }, + { + "type": "image_caption", + "bbox": [ + 0.368, + 0.093, + 0.536, + 0.103 + ], + "angle": 0, + "content": "DreamBooth Textual Inversion" + }, + { + "type": "image_caption", + "bbox": [ + 0.551, + 0.093, + 0.712, + 0.103 + ], + "angle": 0, + "content": "ReVersion Custom Diffusion" + }, + { + "type": "image_caption", + "bbox": [ + 0.743, + 0.093, + 0.761, + 0.103 + ], + "angle": 0, + "content": "P+" + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.104, + 0.89, + 0.532 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.824, + 0.093, + 0.862, + 0.104 + ], + "angle": 0, + "content": "Ours" + }, + { + "type": "image", + "bbox": [ + 0.8, + 0.104, + 0.888, + 0.242 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.538, + 0.893, + 0.565 + ], + "angle": 0, + "content": "Figure 4. Visual comparisons of all methods. For each action, we present the generated results showcasing its pairing with a human character and an animal." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.578, + 0.47, + 0.639 + ], + "angle": 0, + "content": "Note that the masked gradient \\(\\widetilde{g}^{(a,c)}\\), where action-agnostic channels are considered to be masked, is the only gradient used to update \\(v\\). Therefore, our identifiers can adequately invert action-related features." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.655, + 0.21, + 0.672 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.68, + 0.254, + 0.696 + ], + "angle": 0, + "content": "5.1. Experiment Setup" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.704, + 0.47, + 0.764 + ], + "angle": 0, + "content": "Baselines. For the baselines included in the comparison, we select Stable Diffusion [22], ControlNet [35], Dream-Booth [25], Textual Inversion [5], ReVersion [7], Custom Diffusion [9] and \\(\\mathrm{P + }\\) [30]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Implementation Details. For ADI, we set the masking ratio \\(\\beta\\) to 0.6 and use the AdamW [11] optimizer with a learning rate of 2e-4, while the training takes 3000 steps. For efficiency, DreamBooth for action-different pairs does not generate class-preservation images. While only one image is used for training, the initial learning rate is 1e-6, and the training takes 2000 steps. For a fair comparison, we use 50 steps of the DDIM [27] sampler with a scale of 7.5 for all methods. Unless otherwise specified, Stable Diffusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.578, + 0.893, + 0.624 + ], + "angle": 0, + "content": "v2-1-base is selected as the default pre-trained model, and images are generated at a resolution of \\(512 \\times 512\\). All experiments are conducted on a NVIDIA A100 GPU." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.635, + 0.733, + 0.651 + ], + "angle": 0, + "content": "5.2. Quantitative Comparison" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.893, + 0.84 + ], + "angle": 0, + "content": "We perform the quantitative comparison with human evaluators to assess the quantitative performance. For each subject-action pair, four images are randomly sampled from the images generated by different methods. Given (1) the exemplar images of a specific action, and (2) the textual name of the subjects, human evaluators are asked to determine whether (1) the generated action is consistent with those in the exemplar images, and (2) the generated character corresponds with the name without obvious deformations, defects, or abnormalities. A generated image will only be considered totally correct if both the action and the character are correctly generated." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.841, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Tab. 1 reports the action, subject and total accuracy for all methods. Some observations are worth highlighting: (1) Given the textual descriptions of the actions, Stable Diffusion yields the highest total accuracy of all baseline meth" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7802" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.166, + 0.09, + 0.805, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.33, + 0.895, + 0.361 + ], + "angle": 0, + "content": "Figure 5. Ablation study. We remove or revise one implementation at a time to demonstrate the effects of the identifier extension and the gradient masking." + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.369, + 0.471, + 0.397 + ], + "angle": 0, + "content": "Table 1. Quantitative comparisons with competing methods. Action, subject and total accuracies \\((\\%)\\) are reported." + }, + { + "type": "table", + "bbox": [ + 0.122, + 0.4, + 0.428, + 0.526 + ], + "angle": 0, + "content": "
MethodsActionSubjectTotal
Stable Diffusion [22]30.7184.5127.17
ControlNet [35]41.3042.6619.29
DreamBooth [25]2.4595.652.45
Textual Inversion [5]2.1786.141.90
ReVersion [7]1.6384.511.63
Custom Diffusion [9]29.6253.537.07
P+ [30]26.9080.1620.92
ADI (Ours)60.3385.8751.09
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.535, + 0.473, + 0.763 + ], + "angle": 0, + "content": "ods. This suggests that the existing baselines do not take full advantage of the exemplar images. (2) Despite relying on the skeleton as the condition to improve the action generation, ControlNet fail to maintain the performance of subject generation, resulting in an unsatisfactory total accuracy. (3) The action accuracy of DreamBooth, Textual Inversion, and ReVersion is incredibly low, reflecting their complete failure to invert the action-related features. (4) Custom Diffusion and \\(\\mathrm{P + }\\) improve action accuracy at more or less the expense of subject accuracy. (5) Attribute to the extended semantic conditioning space and the gradient masking strategy, our ADI dramatically improves the accuracy of action generation while maintaining excellent subject accuracy. As a result, ADI achieves the best total accuracy, outperforming the baselines by \\(23.92\\%\\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.771, + 0.3, + 0.789 + ], + "angle": 0, + "content": "5.3. Qualitative Comparison" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Fig. 4 illustrates the qualitative comparison of all methods involved. It can be observed that although text descriptions of the actions are provided, the actions generated by Stable Diffusion still differ from the examples. ControlNet can only maintain a rough consistency in posture and struggles to match the generated subjects to the desired requirements, resulting in incomplete or distorted body structures, while" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.371, + 0.895, + 0.538 + ], + "angle": 0, + "content": "sacrificing diversity. And the subject-driven customization methods, as discussed earlier, fail to generate the actions or exhibit appearance characteristics that differ from the specified subjects. This suggests that they are unable to convert only the features associated with the actions. Giving the credit to the design from a perspective of gradient, our ADI decouples action-related features from action-agnostic information and blocks the inversion of the latter. This allows ADI to effectively model the invariance of the action and transfer it to different characters and animals without sacrificing image quality and variety." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.545, + 0.655, + 0.561 + ], + "angle": 0, + "content": "5.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.568, + 0.895, + 0.812 + ], + "angle": 0, + "content": "We conduct ablation experiments on ActionBench to verify the individual effects of the proposed contributions. From the generation results in Fig. 5, it can be observed that (1) The removal of the extension to the semantic conditioning space diminishes the inversion ability of ADI. (2) Both the gradient masks learned from the context-different and the action-different pairs are essential. Removing either one can lead to inadequate learning of action knowledge or a degradation in the quality of the subject's appearance. We attribute this to the fact that learning from a single pair is inherently noisy due to varied action visuals and the interference of action-irrelevant information. (3) We also attempt to reverse the gradient masks, i.e., updates to channels that should have been masked are preserved, and updates to other channels are cancelled. Obviously, this will result in action-related features not being inverted." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.818, + 0.669, + 0.834 + ], + "angle": 0, + "content": "5.5. Further Analysis" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Impact of Masking Strategy. To validate the masking strategy in our ADI, we compare it with four other strategies in Fig. 6. Specifically, on the gradients for each update: (1) Uniform: we uniformly mask \\(\\beta\\) percent of channels. (2)" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7803" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.166, + 0.09, + 0.805, + 0.252 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.257, + 0.895, + 0.286 + ], + "angle": 0, + "content": "Figure 6. Visual comparison of masking strategies. The four compared strategies fail to mask the updates from agnostic channels and invert the action-related features." + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.296, + 0.47, + 0.429 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.435, + 0.471, + 0.476 + ], + "angle": 0, + "content": "Figure 7. Effect of gradient mask merging strategy. Preserving the intersection of gradient masks can better invert the representative action features." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.491, + 0.47, + 0.642 + ], + "angle": 0, + "content": "Random: we randomly mask \\(\\beta\\) percent of channels. (3) Min: we mask \\(\\beta\\) percent of channels with the lowest value. (4) Max: we mask \\(\\beta\\) percent of channels with the highest value. We observe that none of these four strategies successfully captures high-level features related to actions, since the images they generate are independent of the specified action. And the comparison also shows that the effectiveness of our ADI not only depends on the masking itself, but also requires learning action-agnostic channels by modeling the invariance of action and context." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.644, + 0.47, + 0.794 + ], + "angle": 0, + "content": "Impact of Gradient Mask Merging Strategy. As shown in Eq. (9), ADI takes the intersection of the two gradient masks as the default merging strategy. We compare this with selecting the union of the two masks, and illustrate the generation results in Fig. 7. Since only channels that are preserved on both masks are updated, taking the intersection can effectively filter out action-agnostic features, leading to better customization of the actions. In contrast, taking the intersection may dilute the most representative action features due to the preserved context information." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Impact of Masking Ratio \\(\\beta\\). In Fig. 8, we vary the masking ratio \\(\\beta\\) from 0.2 to 0.8. When \\(\\beta\\) is small, fewer dimensions of the gradient are masked, and more action-agnostic features are retained to hinder the generation of the subject's appearance. This situation improves as \\(\\beta\\) is gradually increased. However, when \\(\\beta\\) is relatively large, due to the large number of masked dimensions, some of the most dis" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.296, + 0.892, + 0.428 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.434, + 0.895, + 0.476 + ], + "angle": 0, + "content": "Figure 8. Effect of the masking ratio \\(\\beta\\). A value close to 0.5 can balance the inversion of action-related features and the removal of action-agnostic features." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.489, + 0.892, + 0.534 + ], + "angle": 0, + "content": "criminative features of actions may not be inverted, resulting in incomplete learning of actions. Note that the optimal value of \\(\\beta\\) may be different for different actions." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.548, + 0.62, + 0.564 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.573, + 0.892, + 0.814 + ], + "angle": 0, + "content": "In this paper, we investigate an under-explored text-to-image generation task, namely action customization. To understand the challenge of the task, we first visualize the inadequacy of existing subject-driven methods in extracting action-related features from the entanglement of action-agnostic context features. Then, we propose a novel method named ADI to learn action-specific identifiers from the given images. To increase the accommodation of knowledge relevant to the action, ADI extends the inversion process with layer-wise identifier tokens. Furthermore, ADI generates gradient masks to block the contamination of action-agnostic features at the gradient level. We also contribute the ActionBench for evaluating performance on the task. Since there is a growing need to synthesize action-specific images with various new subjects, we hope that our work can highlight this important direction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.815, + 0.892, + 0.89 + ], + "angle": 0, + "content": "Acknowledgement This work was supported by STI 2030—Major Projects (2022ZD0208800), NSFC General Program (Grant No. 62176215). 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 5802-5810, 2019. 3" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.262 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.516, + 0.956 + ], + "angle": 0, + "content": "7806" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/9257612f-7f23-4c8a-85fd-19ebf525ae6f_origin.pdf b/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/9257612f-7f23-4c8a-85fd-19ebf525ae6f_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..efa2cee16dc3c7d6288b6fdfb527de4ead02d537 --- /dev/null +++ b/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/9257612f-7f23-4c8a-85fd-19ebf525ae6f_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:6bb38cfdb45173c960d359ad284f655c75e38f04333dfaef2c1a53a8d9713650 +size 8122209 diff --git a/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/full.md b/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/full.md new file mode 100644 index 0000000000000000000000000000000000000000..05e2bac359d2ac0415b6c4d43e5def1036af1815 --- /dev/null +++ b/2024/Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation/full.md @@ -0,0 +1,265 @@ +# Learning Disentangled Identifiers for Action-Customized Text-to-Image Generation + +Siteng Huang $^{1,4*}$ , Biao Gong $^{2}$ , Yutong Feng $^{2}$ , Xi Chen $^{2}$ , Yuqian Fu $^{3}$ , Yu Liu $^{2}$ , Donglin Wang $^{4\dagger}$ , Zhejiang University ${}^{2}$ Alibaba Group ${}^{3}$ ETH Zürich + +4Machine Intelligence Lab (MiLAB), AI Division, School of Engineering, Westlake University + +{siteng.huang, a.biao.gong, yuqianfu0207}@gmail.com + +{fengyutong.fyt, xizhi.cx, ly103369}@alibaba-inc.com wangdonglin@westlake.edu.cn + +![](images/1341c58f489a73dc469f1352fa544c5e02cd13b356c927db2a92a8d732197dd2.jpg) +Figure 1. Action customization results of our ADI method. By inverting representative action-related features, the learned identifiers “
” can be paired with a variety of characters and animals to contribute to the generation of accurate, diverse and high-quality images. + +# Abstract + +This study focuses on a novel task in text-to-image (T2I) generation, namely action customization. The objective of this task is to learn the co-existing action from limited data and generalize it to unseen humans or even animals. Experimental results show that existing subject-driven customization methods fail to learn the representative characteristics of actions and struggle in decoupling actions from context features, including appearance. To overcome the preference for low-level features and the entanglement of high-level features, we propose an inversion-based method ActionDisentangled Identifier (ADI) to learn action-specific iden + +tifiers from the exemplar images. ADI first expands the semantic conditioning space by introducing layer-wise identifier tokens, thereby increasing the representational richness while distributing the inversion across different features. Then, to block the inversion of action-agnostic features, ADI extracts the gradient invariance from the constructed sample triples and masks the updates of irrelevant channels. To comprehensively evaluate the task, we present an Action-Bench that includes a variety of actions, each accompanied by meticulously selected samples. Both quantitative and qualitative results show that our ADI outperforms existing baselines in action-customized T2I generation. Our project page is at https://adi-t2i.github.io/ADI. + +![](images/41555498ad9d5719b3ceed0a2a902191d2ff1e37128baf59f8d116ab7ca598e3.jpg) +Figure 2. Action customization results of existing subject-driven customization methods. Due to the preference to search for low-level invariants when asked to learn high-level action features, some methods fail to generate the specified actions, while others confuse the animals with human appearances. + +# 1. Introduction + +Thanks to the remarkable advances in text-to-image generation models [3, 10, 18, 20], in particular the recent diffusion model [22, 26], high-quality and diverse images can be synthesized under the control of text descriptions. However, it is difficult to provide precise descriptions of the desired actions, which are highly abstracted and summarized concepts. Therefore, relying solely on textual descriptions to generate actions tends to reduce fidelity to user requirements. Additionally, controllable generation methods [14, 35] that rely on the conditioning of a skeleton or sketch image suffer from limited diversity and freedom, and they show difficulty generalizing to unseen subjects without retraining. In this paper, we study the action customization task, capturing the common action in the given images to generate new images with various new subjects. + +To better understand the challenge of action customization, we start by examining existing subject-driven customization methods. Observations shown in Fig. 2 can be divided into two categories. Several methods including DreamBooth [25], Textual Inversion [5], and ReVersion [7], generate images that are unrelated to specific actions, suggesting that they fail to capture the representative characteristics of the actions. Since most of them are designed to invert appearance features with a pixel-level reconstruction loss, low-level details are emphasized during optimization while high-level action features are neglected. Benefiting from fine-tuning cross-attention or utilizing per-layer tokens, Custom Diffusion [9] and $\mathrm{P + }$ [30] offer a larger semantic conditioning space for learning new concepts. Consequently, they are capable of encoding action-related knowledge such as "raises one finger" or "raises both arms for cheering" from exemplar images. However, they fail to decouple the focus from action-agnostic features, such as the appearance of the human body. These pieces of information are also encoded into the learned identifiers and "contaminate" the generation of animals during inference. As a result, the intended gorilla is replaced by a + +woman, and the tigers generated by the two methods exhibit human arms instead. + +To avoid the appearance leakage while accurately modeling the target action, we propose Action-Disentangled Identifier (ADI) to learn the optimal action-specific identifiers. Firstly, we expand the semantic conditioning space by applying layer-wise identifier tokens. Since existing works have analyzed that different layers have varying degrees of control over low-level and high-level features [30], such an expansion increases the accommodation of various features, making it easier to invert action-related features. Furthermore, we would like to decouple the action-agnostic features from the learning of action identifiers. To achieve this, we discover invariant mechanisms in the data that are difficult to vary across examples. Specifically, given an exemplar image with the specific action, another same-action image can be randomly sampled from the training data, forming a context-different pair. Meanwhile, leveraging mature subject-driven customization techniques, an image that shares the similar context can be quickly synthesized to form an action-different pair. To decouple the highly-coupled features, we disentangle action-agnostic features at the gradient level, and construct two context gradient masks by comparing the difference on the gradients over the input pairs. By overwriting the merged gradient mask to the gradient of the anchor image, the update of action-agnostic channels on the identifiers is discarded. + +Moreover, as a pioneering effort in this direction, we also contribute to a new benchmark named ActionBench, which provides a testbed of unique actions with diverse images for the under-explored task. We conduct extensive experiments on ActionBench, and a quick glance at the performance of ADI is illustrated in Fig. 1, where users can freely combine the designated action identifiers with various unseen humans and even animals. In summary, the main contributions of our work are three-fold: + +- We propose a novel action customization task, which requires learning the desired action from limited data for future generation. While existing customization fo + +cuses on reprinting appearances, we highlight this understudied but important problem. + +- We contribute the ActionBench, where a variety of unique actions with manually filtered images provide the evaluation conditions for the task. +- We devise the Action-Disentangled Identifier (ADI) method, which successfully inverts action-related features into the learned identifiers that can be freely combined with various characters and animals to generate high-quality images. + +# 2. Related Work + +Text-to-Image (T2I) Generation. Generating high-quality and diverse images from textual conditions has received considerable attention from both the research community and the general public. The previous dominant generative adversarial networks (GANs) [20, 28, 31, 38], consisting of a generator and a discriminator, suffer from unstable optimization and less diverse generations due to the adversarial training [2]. And variational autoencoders (VAEs) [8], which apply a probabilistic encoder-decoder architecture, are also prone to posterior collapse and over-smoothed generations [37]. Text-conditional auto-regressive models [3, 4, 18, 34] have shown more impressive results, but require time-consuming iterative processes to achieve high-quality image sampling. More recently, diffusion models have emerged as a promising alternative, achieving impressive results with open-vocabulary text descriptions through their natural fitting to inductive biases of image data [15, 19, 22, 26]. GLIDE [15] introduces text conditions into the diffusion process through the use of an unclassified guide. DALL-E 2 [19] employs a diffusion prior module and cascading diffusion decoders to generate high-resolution images based on the CLIP [17] text encoder. Imagen [26] focuses on language understanding by using a large T5 language model to better represent semantics. The latent diffusion model [22] improves computational efficiency by performing the diffusion process in low-dimension latent space with an autoencoder. Finally, Stable Diffusion (SD) [22] employs a cross-attention mechanism to inject textual conditions into the diffusion generation process, aligning with the provided textual input. However, it is difficult to provide precise action descriptions in text, since user intent and machine understanding are not aligned. Furthermore, experimental results in Fig. 4 show that some actions are difficult to generate correctly without re-training, e.g., "performs a handstand". + +Controllable Action Generation. The paper focuses on transferring the desired action from exemplar images to unseen people, characters, and even animals for photorealistic image generation. Existing efforts take source images and pose information (e.g., skeletal images or body parsing) as conditions to control the generation. Previous controllable + +solutions based on GANs [12, 13, 36] and VAEs [21, 33] suffer from training difficulties and poor generation results. Some subsequent works [24, 32] introduce text conditions to guide the action generation, yet fail with open vocabulary due to the small size of the vocabulary pools. Thanks to the significant advances of T2I diffusion models, recent methods [10, 14, 29], in particular the popular ControlNet [35], add arbitrary conditions to improve the versatility and controllability. While gaining a tremendous amount of traction from the community, ControlNet refers to the provided skeleton image to generate the action, which reduces flexibility and diversity. In addition, the objective of designing a general framework with additional trainable modules makes it not well-targeted to animals. In this work, we investigate customization solutions for action generation. + +Subject-Driven Customization. Due to the demand for generating images with user-specified subjects, customization methods [5, 9, 25, 30] tailored to the appearance have been studied in the context of T2I generation. Specifically, DreamBooth [25] binds rare new words with specific subjects through fine-tuning the whole T2I generator. Textual Inversion [5] learns an extra identifier to represent the subject and adds the identifier as a new word to the dictionary of the text encoder. Custom Diffusion [9] only fine-tunes the key and value matrices of the cross-attention to represent new concepts. $\mathrm{P + }$ [30] extends the textual-conditioning space with per-layer tokens to allow for greater disentangling and control. Despite the success achieved, the experimental results in Fig. 2 show their failure in action customization. A recent work ReVersion [7] makes progress in learning specific relations including some interactions from exemplar images. However, the design of the method, which specializes in learning spatial relations, makes it difficult to invert action information. + +# 3. Action Customization Benchmark + +Given a set of exemplar images $\mathcal{X} = \{\mathbf{x}_1, \mathbf{x}_2, \dots, \mathbf{x}_N\}$ , we assume that all images contain the same action performed by different people. The action-agnostic descriptions associated to the exemplar images are also provided, which can be used as prompt templates during training. The objective of the action customization task is to extract the co-existing action and transfer it to the synthesis of action-specific images with different new subjects. In order to provide suitable conditions for systematic comparisons on this task, we present a new ActionBench, which consists of diverse actions accompanied by meticulously selected sample images. The benchmark can be used for both quantitative and qualitative comparisons. + +Action Categories. To determine the involved actions, we first request GPT-4 [16] to provide 50 candidate action categories, and then attempt to collect images for these candidates. Only actions that can collect sufficient high-quality + +![](images/cf97c55f9103fcf6e70eb9df14326331e9d00fde0719b3fcabe2488fa81d66dd.jpg) +Figure 3. Overview of our ADI method. ADI learns more efficient action identifiers by extending the semantic conditioning space and masking gradient updates to action-agnostic channels. + +images are preserved. We finally define eight unique actions, ranging from single-handed (e.g., “raises one finger”) to full-body movements (e.g., “performs a handstand”). + +Exemplar Images and Prompts. For each action, we collect ten example images with corresponding textual descriptions, featuring different people. We manually remove action-related descriptions from the textual content to make them suitable as prompt templates. + +Evaluation Subjects. We provide a list containing 23 subjects, including generic humans (e.g., "An old man"), well-known personalities (e.g., "David Beckham"), and animals (e.g., "A panda"). The latter two are guaranteed to be completely unseen, which tests the generalization of methods. + +# 4. Methodology + +We start with the technical background in Sec. 4.1. Then, we provide a comprehensive description of our proposed ADI in Sec. 4.2. + +# 4.1. Preliminaries + +Our study is based on the Stable Diffusion (SD) [22] model, which is considered to be the public state-of-the-art text-to-image generator. Specifically, to operate the diffusion process [6] in a low-dimensional latent space, SD employs a hierarchical VAE that consists of an encoder $\mathcal{E}$ and a decoder $\mathcal{D}$ . The encoder $\mathcal{E}$ is tasked with encoding the given image $\mathbf{x}$ into latent features $\mathbf{z}$ , and the decoder $\mathcal{D}$ reconstructs the image $\widehat{\mathbf{x}}$ from the latent, i.e., $\widehat{\mathbf{x}} = \mathcal{D}(\mathbf{z}) = \mathcal{D}(\mathcal{E}(\mathbf{x}))$ . To control the generation with the textual conditions, given the noisy latent $\mathbf{z}_t$ , current time step $t$ and text tokens $\mathbf{y}$ , a conditional U-Net [23] denoiser is trained to predict the noise $\epsilon$ added to the latent $\mathbf{z}$ : + +$$ +\mathcal {L} = \mathbb {E} _ {\mathbf {z} \sim \mathcal {E} (\mathbf {x}), \mathbf {y}, \epsilon \sim \mathcal {N} (0, 1), t} \left[ \| \epsilon - \epsilon_ {\theta} (\mathbf {z} _ {t}, t, \mathbf {y}) \| _ {2} ^ {2} \right], \tag {1} +$$ + +where $\mathbf{y}$ is obtained by feeding the prompt into a CLIP [17] text encoder. During inference, the pre-trained SD first samples a latent $\mathbf{z}_T$ from the standard normal distribution $\mathcal{N}(0,1)$ . Iteratively, $\mathbf{z}_{t-1}$ can be obtained by removing noise from $\mathbf{z}_t$ conditioned on $\mathbf{y}$ . After the final denoising step, the latent $\mathbf{z}_0$ is mapped to generate an image $\widehat{\mathbf{x}}$ with the decoder $\mathcal{D}$ . + +# 4.2. Action-Disentangled Identifier (ADI) + +Given exemplar images that all contain a specific entity, existing subject-driven inversion methods [5, 9] learn to represent the entity as an identifier token $v \in \mathbb{R}^d$ . And the learned $v$ can then be employed in text prompts to produce diverse and novel images, where the entity can be generated with different contexts. In this paper, we continue the vein of capturing the common action in exemplar images by finding the optimal identifiers. An overview of our proposed ADI is illustrated in Fig. 3. + +Expanding Semantic Inversion. To overcome the preference to low-level appearance features, we apply layer-wise identifier tokens to increase the accommodation of various features. Specifically, for the $l$ -th layer where $l \in [1, L]$ and $L$ is the number of cross-attention layers in the T2I model, a new identifier token $v_l \in \mathbb{R}^d$ is initialized. Feeding the prompt with $v_l$ into the text encoder, the output tokens $\mathbf{y}_l$ control the update of the latents in the $l$ -th layer, thus influencing the generation of the visual content. And the learned tokens from all layers can form a token set $\mathcal{V}$ , which can then be paired with different subjects for generation. Rather than having a single identifier token take on the responsibility of reconstruction, having separate identifiers at different layers effectively ensures that more features are converted, including the action-related features we care about. + +Learning Gradient Mask with Context-Different Pair. The next step is to prevent the identifiers from inverting fea + +tures that are not relevant to the action and thus contaminating the subsequent image generation. Given $\mathbf{x}^{(a,c)}\in \mathcal{X}$ as an anchor sample, where $a$ denotes the specific action, and $c$ denotes the action-agnostic context contained in the image including human appearance and background, we can randomly sample another image $\mathbf{x}^{(a,\overline{c})}$ from $\mathcal{X}$ , where $\overline{c}$ represents that the context is different from $c$ . Taking the context-different pair $\mathbf{x}^{(a,c)}$ and $\mathbf{x}^{(a,\overline{c})}$ as the input, we can calculate two gradients of the denoising loss $\mathcal{L}$ with respect to the identifier token $v$ : + +$$ +g ^ {(a, c)} = \frac {\partial \mathcal {L} ^ {(a , c)}}{\partial v}, \tag {2} +$$ + +$$ +g ^ {(a, \bar {c})} = \frac {\partial \mathcal {L} ^ {(a , \bar {c})}}{\partial v}. \tag {3} +$$ + +Note that the subscript $l$ is omitted for the sake of uniformity and clarity. Each identifier token contains multiple channels, each carrying semantically distinct and independent information. And the gradient consistency of a channel indicates that the channel is likely to carry information about the specific action. Therefore, we calculate the absolute value of the difference between the two gradients: + +$$ +\triangle g ^ {\overline {{c}}} = \left| g ^ {(a, c)} - g ^ {(a, \overline {{c}})} \right|, \tag {4} +$$ + +where the semantic channels with a small difference can be regarded as action-related channels of the action $a$ , which are expected to be preserved. Specifically, we sort the difference from the largest to the smallest, taking the value at $\beta$ percent $\gamma^{\beta}$ as a threshold. In other words, $\beta \%$ of the channels are masked. Then, the mask that shares the same dimension as $v$ can be calculated. For the $k$ -th channel, + +$$ +m _ {k} ^ {\bar {c}} = \left\{ \begin{array}{l l} 0, & \triangle g _ {k} ^ {\bar {c}} \geqslant \gamma^ {\beta} \\ 1, & \triangle g _ {k} ^ {\bar {c}} < \gamma^ {\beta} \end{array} . \right. \tag {5} +$$ + +By overwriting the mask to the gradient of the anchor sample, the action-related knowledge is preserved and incorporated into the update of $v$ , while the updates on action-agnostic channels are ignored. Note that since the specific visual invariance about the action changes slightly depending on the sample pair, the masked channels may not be exactly the same each time. Furthermore, both samples use the prompt of the anchor sample $\mathbf{x}^{(a,c)}$ when calculating the gradients. Since the visual context of $\mathbf{x}^{(a,\bar{c})}$ is inconsistent with the description in the prompt, the reconstruction loss favours larger gradients in the context-related channels. In this way, the action-related channels found through the threshold will be more accurate. + +Learning Gradient Mask with Action-Different Pair. Although the context-different pairs have the same action semantics, there may be differences in the visualization of the actions, and therefore the channels associated with the most representative action features do not necessarily have a smaller gradient difference. Since learning the gradient + +mask with the context-different only pair is not stable and effective enough, we also construct action-different pairs to generate the gradient mask from another perspective. For each sample $\mathbf{x}^{(a,c)}$ in $\mathcal{X}$ , we can use it to quickly train a subject-driven customization model (e.g., DreamBooth) that effectively inverts the most of the low-level context information. Therefore, by filling the prompt template of $\mathbf{x}^{(a,c)}$ with action descriptions that are different from $a$ , the trained customization model can generate various action images as $\mathcal{X}^{(\overline{a},c)}$ . Note that this step is not necessary if the users can compile a dataset of varied actions by the same individual using pre-captured images. However, the data collection is usually arduous and lengthy, making fast training of a subject-driven customization a more convenient solution. Due to the one-shot training and the concise text, the generated images $\mathcal{X}^{(\overline{a},c)}$ may not be consistent with the action descriptions, or the context may differ from the original $\mathbf{x}^{(a,c)}$ , but in practice, we have found that the quality is sufficient to diversify the action variation. In this way, when $\mathbf{x}^{(a,c)}$ is sampled during training, we can randomly sample a image $\mathbf{x}^{(\overline{a},c)}$ from $\mathcal{X}^{(\overline{a},c)}$ to construct the action-different pair. And the gradient of $\mathbf{x}^{(\overline{a},c)}$ with respect to the token $v$ can be calculated as + +$$ +g ^ {(\bar {a}, c)} = \frac {\partial \mathcal {L} ^ {(\bar {a} , c)}}{\partial v}. \tag {6} +$$ + +Similarly, both samples use the prompt of the anchor sample $\mathbf{x}^{(a,c)}$ . We can also calculate the absolute value of the gradient difference: + +$$ +\triangle g ^ {\bar {a}} = \left| g ^ {(a, c)} - g ^ {(\bar {a}, c)} \right|, \tag {7} +$$ + +where the semantic channels with small difference can be regarded as context-related channels of the action $a$ , which are expected to be masked. Therefore, we have + +$$ +m _ {k} ^ {\bar {a}} = \left\{ \begin{array}{l l} 0, & \triangle g _ {k} ^ {\bar {a}} < \lambda^ {\beta} \\ 1, & \triangle g _ {k} ^ {\bar {a}} \geqslant \lambda^ {\beta} \end{array} , \right. \tag {8} +$$ + +where $\lambda^{\beta}$ is the threshold here to mask $\beta \%$ of the channels. + +Merging Gradient Masks for Context. Due to the noise introduced by context variations, identifying action-relevant channels using only context-different or action-different pairs would be difficult and unreliable. As an evidence, the average overlap rate of channels preserved by both masks at each training step is $30.26\%$ . Therefore, given the input triple $\mathcal{I} = \{\mathbf{x}^{(a,\overline{c})},\mathbf{x}^{(a,c)},\mathbf{x}^{(\overline{a},c)}\}$ , we can merge the two obtained masks $m^{\overline{a}}$ and $m^{\overline{c}}$ to get the final context mask $m$ . In practice, we keep only the intersection of the unmasked channels as unmasked, as we find this merging strategy performs better. Formally, we have + +$$ +m = m ^ {\overline {{c}}} \cap m ^ {\overline {{a}}}, \tag {9} +$$ + +which is overwritten to the gradient of the anchor sample: + +$$ +\widetilde {g} ^ {(a, c)} = m \odot g ^ {(a, c)}. \tag {10} +$$ + +![](images/1232d370776c7eca185f2f101c5fb640294d877449bbf3723348b8f0c965115c.jpg) +Sample Image +Stable Diffusion ControlNet +DreamBooth Textual Inversion +ReVersion Custom Diffusion +P+ +Ours +Figure 4. Visual comparisons of all methods. For each action, we present the generated results showcasing its pairing with a human character and an animal. + +Note that the masked gradient $\widetilde{g}^{(a,c)}$ , where action-agnostic channels are considered to be masked, is the only gradient used to update $v$ . Therefore, our identifiers can adequately invert action-related features. + +# 5. Experiments + +# 5.1. Experiment Setup + +Baselines. For the baselines included in the comparison, we select Stable Diffusion [22], ControlNet [35], Dream-Booth [25], Textual Inversion [5], ReVersion [7], Custom Diffusion [9] and $\mathrm{P + }$ [30]. + +Implementation Details. For ADI, we set the masking ratio $\beta$ to 0.6 and use the AdamW [11] optimizer with a learning rate of 2e-4, while the training takes 3000 steps. For efficiency, DreamBooth for action-different pairs does not generate class-preservation images. While only one image is used for training, the initial learning rate is 1e-6, and the training takes 2000 steps. For a fair comparison, we use 50 steps of the DDIM [27] sampler with a scale of 7.5 for all methods. Unless otherwise specified, Stable Diffusion + +v2-1-base is selected as the default pre-trained model, and images are generated at a resolution of $512 \times 512$ . All experiments are conducted on a NVIDIA A100 GPU. + +# 5.2. Quantitative Comparison + +We perform the quantitative comparison with human evaluators to assess the quantitative performance. For each subject-action pair, four images are randomly sampled from the images generated by different methods. Given (1) the exemplar images of a specific action, and (2) the textual name of the subjects, human evaluators are asked to determine whether (1) the generated action is consistent with those in the exemplar images, and (2) the generated character corresponds with the name without obvious deformations, defects, or abnormalities. A generated image will only be considered totally correct if both the action and the character are correctly generated. + +Tab. 1 reports the action, subject and total accuracy for all methods. Some observations are worth highlighting: (1) Given the textual descriptions of the actions, Stable Diffusion yields the highest total accuracy of all baseline meth + +![](images/33408aa4e675ea453b5dced91fbf503c97c18077006155f14cd39b3870653552.jpg) +Figure 5. Ablation study. We remove or revise one implementation at a time to demonstrate the effects of the identifier extension and the gradient masking. + +Table 1. Quantitative comparisons with competing methods. Action, subject and total accuracies $(\%)$ are reported. + +
MethodsActionSubjectTotal
Stable Diffusion [22]30.7184.5127.17
ControlNet [35]41.3042.6619.29
DreamBooth [25]2.4595.652.45
Textual Inversion [5]2.1786.141.90
ReVersion [7]1.6384.511.63
Custom Diffusion [9]29.6253.537.07
P+ [30]26.9080.1620.92
ADI (Ours)60.3385.8751.09
+ +ods. This suggests that the existing baselines do not take full advantage of the exemplar images. (2) Despite relying on the skeleton as the condition to improve the action generation, ControlNet fail to maintain the performance of subject generation, resulting in an unsatisfactory total accuracy. (3) The action accuracy of DreamBooth, Textual Inversion, and ReVersion is incredibly low, reflecting their complete failure to invert the action-related features. (4) Custom Diffusion and $\mathrm{P + }$ improve action accuracy at more or less the expense of subject accuracy. (5) Attribute to the extended semantic conditioning space and the gradient masking strategy, our ADI dramatically improves the accuracy of action generation while maintaining excellent subject accuracy. As a result, ADI achieves the best total accuracy, outperforming the baselines by $23.92\%$ . + +# 5.3. Qualitative Comparison + +Fig. 4 illustrates the qualitative comparison of all methods involved. It can be observed that although text descriptions of the actions are provided, the actions generated by Stable Diffusion still differ from the examples. ControlNet can only maintain a rough consistency in posture and struggles to match the generated subjects to the desired requirements, resulting in incomplete or distorted body structures, while + +sacrificing diversity. And the subject-driven customization methods, as discussed earlier, fail to generate the actions or exhibit appearance characteristics that differ from the specified subjects. This suggests that they are unable to convert only the features associated with the actions. Giving the credit to the design from a perspective of gradient, our ADI decouples action-related features from action-agnostic information and blocks the inversion of the latter. This allows ADI to effectively model the invariance of the action and transfer it to different characters and animals without sacrificing image quality and variety. + +# 5.4. Ablation Study + +We conduct ablation experiments on ActionBench to verify the individual effects of the proposed contributions. From the generation results in Fig. 5, it can be observed that (1) The removal of the extension to the semantic conditioning space diminishes the inversion ability of ADI. (2) Both the gradient masks learned from the context-different and the action-different pairs are essential. Removing either one can lead to inadequate learning of action knowledge or a degradation in the quality of the subject's appearance. We attribute this to the fact that learning from a single pair is inherently noisy due to varied action visuals and the interference of action-irrelevant information. (3) We also attempt to reverse the gradient masks, i.e., updates to channels that should have been masked are preserved, and updates to other channels are cancelled. Obviously, this will result in action-related features not being inverted. + +# 5.5. Further Analysis + +Impact of Masking Strategy. To validate the masking strategy in our ADI, we compare it with four other strategies in Fig. 6. Specifically, on the gradients for each update: (1) Uniform: we uniformly mask $\beta$ percent of channels. (2) + +![](images/3de6cce6cba2819735dc0c8f5dabaa52fd0eb2b239e501a62f207f1ab5bad95d.jpg) +Figure 6. Visual comparison of masking strategies. The four compared strategies fail to mask the updates from agnostic channels and invert the action-related features. + +![](images/c98390fb2b0d368c9d47c621b27a7ec205bdc61c26b70fee07e5fe9b0e528d74.jpg) +Figure 7. Effect of gradient mask merging strategy. Preserving the intersection of gradient masks can better invert the representative action features. + +Random: we randomly mask $\beta$ percent of channels. (3) Min: we mask $\beta$ percent of channels with the lowest value. (4) Max: we mask $\beta$ percent of channels with the highest value. We observe that none of these four strategies successfully captures high-level features related to actions, since the images they generate are independent of the specified action. And the comparison also shows that the effectiveness of our ADI not only depends on the masking itself, but also requires learning action-agnostic channels by modeling the invariance of action and context. + +Impact of Gradient Mask Merging Strategy. As shown in Eq. (9), ADI takes the intersection of the two gradient masks as the default merging strategy. We compare this with selecting the union of the two masks, and illustrate the generation results in Fig. 7. Since only channels that are preserved on both masks are updated, taking the intersection can effectively filter out action-agnostic features, leading to better customization of the actions. In contrast, taking the intersection may dilute the most representative action features due to the preserved context information. + +Impact of Masking Ratio $\beta$ . In Fig. 8, we vary the masking ratio $\beta$ from 0.2 to 0.8. When $\beta$ is small, fewer dimensions of the gradient are masked, and more action-agnostic features are retained to hinder the generation of the subject's appearance. This situation improves as $\beta$ is gradually increased. However, when $\beta$ is relatively large, due to the large number of masked dimensions, some of the most dis + +![](images/ec6bd2fc4bc6fe6905244b4dd8aeccf1bf4012025b8212b1fc6bb5894fef0357.jpg) +Figure 8. Effect of the masking ratio $\beta$ . A value close to 0.5 can balance the inversion of action-related features and the removal of action-agnostic features. + +criminative features of actions may not be inverted, resulting in incomplete learning of actions. Note that the optimal value of $\beta$ may be different for different actions. + +# 6. Conclusion + +In this paper, we investigate an under-explored text-to-image generation task, namely action customization. To understand the challenge of the task, we first visualize the inadequacy of existing subject-driven methods in extracting action-related features from the entanglement of action-agnostic context features. Then, we propose a novel method named ADI to learn action-specific identifiers from the given images. To increase the accommodation of knowledge relevant to the action, ADI extends the inversion process with layer-wise identifier tokens. Furthermore, ADI generates gradient masks to block the contamination of action-agnostic features at the gradient level. We also contribute the ActionBench for evaluating performance on the task. Since there is a growing need to synthesize action-specific images with various new subjects, we hope that our work can highlight this important direction. + +Acknowledgement This work was supported by STI 2030—Major Projects (2022ZD0208800), NSFC General Program (Grant No. 62176215). This work was supported by Alibaba Group through Alibaba Research Intern Program. + +# References + +[1] Zhe Cao, Gines Hidalgo, Tomas Simon, Shih-En Wei, and Yaser Sheikh. OpenPose: Realtime multi-person 2d pose estimation using part affinity fields. IEEE Transactions on Pattern Analysis and Machine Intelligence, pages 172–186, 2021. 1 +[2] Prafulla Dhariwal and Alexander Quinn Nichol. Diffusion models beat GANs on image synthesis. In Proceedings of the Advances in Neural Information Processing Systems, pages 8780-8794, 2021. 3 +[3] Ming Ding, Zhuoyi Yang, Wenyi Hong, Wendi Zheng, Chang Zhou, Da Yin, Junyang Lin, Xu Zou, Zhou Shao, Hongxia Yang, and Jie Tang. 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Action customization results of our ADI method. By inverting representative action-related features, the learned identifiers “
” can be paired with a variety of characters and animals to contribute to the generation of accurate, diverse and high-quality images." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 143, + 529, + 192, + 542 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 529, + 192, + 542 + ], + "spans": [ + { + "bbox": [ + 143, + 529, + 192, + 542 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 45, + 555, + 288, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 555, + 288, + 686 + ], + "spans": [ + { + "bbox": [ + 45, + 555, + 288, + 686 + ], + "type": "text", + "content": "This study focuses on a novel task in text-to-image (T2I) generation, namely action customization. The objective of this task is to learn the co-existing action from limited data and generalize it to unseen humans or even animals. Experimental results show that existing subject-driven customization methods fail to learn the representative characteristics of actions and struggle in decoupling actions from context features, including appearance. To overcome the preference for low-level features and the entanglement of high-level features, we propose an inversion-based method ActionDisentangled Identifier (ADI) to learn action-specific iden" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 528, + 547, + 684 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 528, + 547, + 684 + ], + "spans": [ + { + "bbox": [ + 304, + 528, + 547, + 684 + ], + "type": "text", + "content": "tifiers from the exemplar images. ADI first expands the semantic conditioning space by introducing layer-wise identifier tokens, thereby increasing the representational richness while distributing the inversion across different features. Then, to block the inversion of action-agnostic features, ADI extracts the gradient invariance from the constructed sample triples and masks the updates of irrelevant channels. To comprehensively evaluate the task, we present an Action-Bench that includes a variety of actions, each accompanied by meticulously selected samples. Both quantitative and qualitative results show that our ADI outperforms existing baselines in action-customized T2I generation. Our project page is at https://adi-t2i.github.io/ADI." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 61, + 693, + 219, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 693, + 219, + 703 + ], + "spans": [ + { + "bbox": [ + 61, + 693, + 219, + 703 + ], + "type": "text", + "content": "*Work done during internship at Alibaba Group." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 61, + 703, + 140, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 703, + 140, + 713 + ], + "spans": [ + { + "bbox": [ + 61, + 703, + 140, + 713 + ], + "type": "text", + "content": "†Corresponding author." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7797" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 84, + 71, + 508, + 194 + ], + "blocks": [ + { + "bbox": [ + 84, + 71, + 508, + 194 + ], + "lines": [ + { + "bbox": [ + 84, + 71, + 508, + 194 + ], + "spans": [ + { + "bbox": [ + 84, + 71, + 508, + 194 + ], + "type": "image", + "image_path": "41555498ad9d5719b3ceed0a2a902191d2ff1e37128baf59f8d116ab7ca598e3.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 198, + 547, + 232 + ], + "lines": [ + { + "bbox": [ + 46, + 198, + 547, + 232 + ], + "spans": [ + { + "bbox": [ + 46, + 198, + 547, + 232 + ], + "type": "text", + "content": "Figure 2. Action customization results of existing subject-driven customization methods. Due to the preference to search for low-level invariants when asked to learn high-level action features, some methods fail to generate the specified actions, while others confuse the animals with human appearances." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 239, + 128, + 251 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 239, + 128, + 251 + ], + "spans": [ + { + "bbox": [ + 47, + 239, + 128, + 251 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 265, + 289, + 445 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 265, + 289, + 445 + ], + "spans": [ + { + "bbox": [ + 46, + 265, + 289, + 445 + ], + "type": "text", + "content": "Thanks to the remarkable advances in text-to-image generation models [3, 10, 18, 20], in particular the recent diffusion model [22, 26], high-quality and diverse images can be synthesized under the control of text descriptions. However, it is difficult to provide precise descriptions of the desired actions, which are highly abstracted and summarized concepts. Therefore, relying solely on textual descriptions to generate actions tends to reduce fidelity to user requirements. Additionally, controllable generation methods [14, 35] that rely on the conditioning of a skeleton or sketch image suffer from limited diversity and freedom, and they show difficulty generalizing to unseen subjects without retraining. In this paper, we study the action customization task, capturing the common action in the given images to generate new images with various new subjects." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 450, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 450, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 450, + 289, + 715 + ], + "type": "text", + "content": "To better understand the challenge of action customization, we start by examining existing subject-driven customization methods. Observations shown in Fig. 2 can be divided into two categories. Several methods including DreamBooth [25], Textual Inversion [5], and ReVersion [7], generate images that are unrelated to specific actions, suggesting that they fail to capture the representative characteristics of the actions. Since most of them are designed to invert appearance features with a pixel-level reconstruction loss, low-level details are emphasized during optimization while high-level action features are neglected. Benefiting from fine-tuning cross-attention or utilizing per-layer tokens, Custom Diffusion [9] and " + }, + { + "bbox": [ + 46, + 450, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathrm{P + }" + }, + { + "bbox": [ + 46, + 450, + 289, + 715 + ], + "type": "text", + "content": " [30] offer a larger semantic conditioning space for learning new concepts. Consequently, they are capable of encoding action-related knowledge such as \"raises one finger\" or \"raises both arms for cheering\" from exemplar images. However, they fail to decouple the focus from action-agnostic features, such as the appearance of the human body. These pieces of information are also encoded into the learned identifiers and \"contaminate\" the generation of animals during inference. As a result, the intended gorilla is replaced by a" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 305, + 240, + 545, + 264 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 240, + 545, + 264 + ], + "spans": [ + { + "bbox": [ + 305, + 240, + 545, + 264 + ], + "type": "text", + "content": "woman, and the tigers generated by the two methods exhibit human arms instead." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 266, + 546, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 266, + 546, + 564 + ], + "spans": [ + { + "bbox": [ + 304, + 266, + 546, + 564 + ], + "type": "text", + "content": "To avoid the appearance leakage while accurately modeling the target action, we propose Action-Disentangled Identifier (ADI) to learn the optimal action-specific identifiers. Firstly, we expand the semantic conditioning space by applying layer-wise identifier tokens. Since existing works have analyzed that different layers have varying degrees of control over low-level and high-level features [30], such an expansion increases the accommodation of various features, making it easier to invert action-related features. Furthermore, we would like to decouple the action-agnostic features from the learning of action identifiers. To achieve this, we discover invariant mechanisms in the data that are difficult to vary across examples. Specifically, given an exemplar image with the specific action, another same-action image can be randomly sampled from the training data, forming a context-different pair. Meanwhile, leveraging mature subject-driven customization techniques, an image that shares the similar context can be quickly synthesized to form an action-different pair. To decouple the highly-coupled features, we disentangle action-agnostic features at the gradient level, and construct two context gradient masks by comparing the difference on the gradients over the input pairs. By overwriting the merged gradient mask to the gradient of the anchor image, the update of action-agnostic channels on the identifiers is discarded." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 567, + 547, + 674 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 567, + 547, + 674 + ], + "spans": [ + { + "bbox": [ + 304, + 567, + 547, + 674 + ], + "type": "text", + "content": "Moreover, as a pioneering effort in this direction, we also contribute to a new benchmark named ActionBench, which provides a testbed of unique actions with diverse images for the under-explored task. We conduct extensive experiments on ActionBench, and a quick glance at the performance of ADI is illustrated in Fig. 1, where users can freely combine the designated action identifiers with various unseen humans and even animals. In summary, the main contributions of our work are three-fold:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 308, + 677, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 677, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 308, + 677, + 547, + 713 + ], + "type": "text", + "content": "- We propose a novel action customization task, which requires learning the desired action from limited data for future generation. While existing customization fo" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7798" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 56, + 72, + 286, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 56, + 72, + 286, + 95 + ], + "spans": [ + { + "bbox": [ + 56, + 72, + 286, + 95 + ], + "type": "text", + "content": "cuses on reprinting appearances, we highlight this understudied but important problem." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 50, + 96, + 287, + 192 + ], + "type": "list", + "angle": 0, + "index": 3, + "blocks": [ + { + "bbox": [ + 50, + 96, + 287, + 132 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 50, + 96, + 287, + 132 + ], + "spans": [ + { + "bbox": [ + 50, + 96, + 287, + 132 + ], + "type": "text", + "content": "- We contribute the ActionBench, where a variety of unique actions with manually filtered images provide the evaluation conditions for the task." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 50, + 132, + 286, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 50, + 132, + 286, + 192 + ], + "spans": [ + { + "bbox": [ + 50, + 132, + 286, + 192 + ], + "type": "text", + "content": "- We devise the Action-Disentangled Identifier (ADI) method, which successfully inverts action-related features into the learned identifiers that can be freely combined with various characters and animals to generate high-quality images." + } + ] + } + ], + "index": 2 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 203, + 133, + 216 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 203, + 133, + 216 + ], + "spans": [ + { + "bbox": [ + 47, + 203, + 133, + 216 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 222, + 287, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 222, + 287, + 641 + ], + "spans": [ + { + "bbox": [ + 47, + 222, + 287, + 641 + ], + "type": "text", + "content": "Text-to-Image (T2I) Generation. Generating high-quality and diverse images from textual conditions has received considerable attention from both the research community and the general public. The previous dominant generative adversarial networks (GANs) [20, 28, 31, 38], consisting of a generator and a discriminator, suffer from unstable optimization and less diverse generations due to the adversarial training [2]. And variational autoencoders (VAEs) [8], which apply a probabilistic encoder-decoder architecture, are also prone to posterior collapse and over-smoothed generations [37]. Text-conditional auto-regressive models [3, 4, 18, 34] have shown more impressive results, but require time-consuming iterative processes to achieve high-quality image sampling. More recently, diffusion models have emerged as a promising alternative, achieving impressive results with open-vocabulary text descriptions through their natural fitting to inductive biases of image data [15, 19, 22, 26]. GLIDE [15] introduces text conditions into the diffusion process through the use of an unclassified guide. DALL-E 2 [19] employs a diffusion prior module and cascading diffusion decoders to generate high-resolution images based on the CLIP [17] text encoder. Imagen [26] focuses on language understanding by using a large T5 language model to better represent semantics. The latent diffusion model [22] improves computational efficiency by performing the diffusion process in low-dimension latent space with an autoencoder. Finally, Stable Diffusion (SD) [22] employs a cross-attention mechanism to inject textual conditions into the diffusion generation process, aligning with the provided textual input. However, it is difficult to provide precise action descriptions in text, since user intent and machine understanding are not aligned. Furthermore, experimental results in Fig. 4 show that some actions are difficult to generate correctly without re-training, e.g., \"performs a handstand\"." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 642, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 642, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 642, + 286, + 712 + ], + "type": "text", + "content": "Controllable Action Generation. The paper focuses on transferring the desired action from exemplar images to unseen people, characters, and even animals for photorealistic image generation. Existing efforts take source images and pose information (e.g., skeletal images or body parsing) as conditions to control the generation. Previous controllable" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 251 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 251 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 251 + ], + "type": "text", + "content": "solutions based on GANs [12, 13, 36] and VAEs [21, 33] suffer from training difficulties and poor generation results. Some subsequent works [24, 32] introduce text conditions to guide the action generation, yet fail with open vocabulary due to the small size of the vocabulary pools. Thanks to the significant advances of T2I diffusion models, recent methods [10, 14, 29], in particular the popular ControlNet [35], add arbitrary conditions to improve the versatility and controllability. While gaining a tremendous amount of traction from the community, ControlNet refers to the provided skeleton image to generate the action, which reduces flexibility and diversity. In addition, the objective of designing a general framework with additional trainable modules makes it not well-targeted to animals. In this work, we investigate customization solutions for action generation." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 251, + 545, + 478 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 251, + 545, + 478 + ], + "spans": [ + { + "bbox": [ + 304, + 251, + 545, + 478 + ], + "type": "text", + "content": "Subject-Driven Customization. Due to the demand for generating images with user-specified subjects, customization methods [5, 9, 25, 30] tailored to the appearance have been studied in the context of T2I generation. Specifically, DreamBooth [25] binds rare new words with specific subjects through fine-tuning the whole T2I generator. Textual Inversion [5] learns an extra identifier to represent the subject and adds the identifier as a new word to the dictionary of the text encoder. Custom Diffusion [9] only fine-tunes the key and value matrices of the cross-attention to represent new concepts. " + }, + { + "bbox": [ + 304, + 251, + 545, + 478 + ], + "type": "inline_equation", + "content": "\\mathrm{P + }" + }, + { + "bbox": [ + 304, + 251, + 545, + 478 + ], + "type": "text", + "content": " [30] extends the textual-conditioning space with per-layer tokens to allow for greater disentangling and control. Despite the success achieved, the experimental results in Fig. 2 show their failure in action customization. A recent work ReVersion [7] makes progress in learning specific relations including some interactions from exemplar images. However, the design of the method, which specializes in learning spatial relations, makes it difficult to invert action information." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 490, + 495, + 502 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 490, + 495, + 502 + ], + "spans": [ + { + "bbox": [ + 306, + 490, + 495, + 502 + ], + "type": "text", + "content": "3. Action Customization Benchmark" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 510, + 545, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 545, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 545, + 665 + ], + "type": "text", + "content": "Given a set of exemplar images " + }, + { + "bbox": [ + 304, + 510, + 545, + 665 + ], + "type": "inline_equation", + "content": "\\mathcal{X} = \\{\\mathbf{x}_1, \\mathbf{x}_2, \\dots, \\mathbf{x}_N\\}" + }, + { + "bbox": [ + 304, + 510, + 545, + 665 + ], + "type": "text", + "content": ", we assume that all images contain the same action performed by different people. The action-agnostic descriptions associated to the exemplar images are also provided, which can be used as prompt templates during training. The objective of the action customization task is to extract the co-existing action and transfer it to the synthesis of action-specific images with different new subjects. In order to provide suitable conditions for systematic comparisons on this task, we present a new ActionBench, which consists of diverse actions accompanied by meticulously selected sample images. The benchmark can be used for both quantitative and qualitative comparisons." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": "Action Categories. To determine the involved actions, we first request GPT-4 [16] to provide 50 candidate action categories, and then attempt to collect images for these candidates. Only actions that can collect sufficient high-quality" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "7799" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 52, + 71, + 541, + 255 + ], + "blocks": [ + { + "bbox": [ + 52, + 71, + 541, + 255 + ], + "lines": [ + { + "bbox": [ + 52, + 71, + 541, + 255 + ], + "spans": [ + { + "bbox": [ + 52, + 71, + 541, + 255 + ], + "type": "image", + "image_path": "cf97c55f9103fcf6e70eb9df14326331e9d00fde0719b3fcabe2488fa81d66dd.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 258, + 547, + 282 + ], + "lines": [ + { + "bbox": [ + 46, + 258, + 547, + 282 + ], + "spans": [ + { + "bbox": [ + 46, + 258, + 547, + 282 + ], + "type": "text", + "content": "Figure 3. Overview of our ADI method. ADI learns more efficient action identifiers by extending the semantic conditioning space and masking gradient updates to action-agnostic channels." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 293, + 287, + 329 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 293, + 287, + 329 + ], + "spans": [ + { + "bbox": [ + 46, + 293, + 287, + 329 + ], + "type": "text", + "content": "images are preserved. We finally define eight unique actions, ranging from single-handed (e.g., “raises one finger”) to full-body movements (e.g., “performs a handstand”)." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 330, + 287, + 390 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 330, + 287, + 390 + ], + "spans": [ + { + "bbox": [ + 46, + 330, + 287, + 390 + ], + "type": "text", + "content": "Exemplar Images and Prompts. For each action, we collect ten example images with corresponding textual descriptions, featuring different people. We manually remove action-related descriptions from the textual content to make them suitable as prompt templates." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 390, + 287, + 452 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 390, + 287, + 452 + ], + "spans": [ + { + "bbox": [ + 46, + 390, + 287, + 452 + ], + "type": "text", + "content": "Evaluation Subjects. We provide a list containing 23 subjects, including generic humans (e.g., \"An old man\"), well-known personalities (e.g., \"David Beckham\"), and animals (e.g., \"A panda\"). The latter two are guaranteed to be completely unseen, which tests the generalization of methods." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 464, + 130, + 478 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 464, + 130, + 478 + ], + "spans": [ + { + "bbox": [ + 47, + 464, + 130, + 478 + ], + "type": "text", + "content": "4. Methodology" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 485, + 287, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 485, + 287, + 521 + ], + "spans": [ + { + "bbox": [ + 46, + 485, + 287, + 521 + ], + "type": "text", + "content": "We start with the technical background in Sec. 4.1. Then, we provide a comprehensive description of our proposed ADI in Sec. 4.2." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 531, + 133, + 544 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 531, + 133, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 531, + 133, + 544 + ], + "type": "text", + "content": "4.1. Preliminaries" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "spans": [ + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": "Our study is based on the Stable Diffusion (SD) [22] model, which is considered to be the public state-of-the-art text-to-image generator. Specifically, to operate the diffusion process [6] in a low-dimensional latent space, SD employs a hierarchical VAE that consists of an encoder " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": " and a decoder " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": ". The encoder " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": " is tasked with encoding the given image " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": " into latent features " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathbf{z}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": ", and the decoder " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": " reconstructs the image " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathbf{x}}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": " from the latent, i.e., " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathbf{x}} = \\mathcal{D}(\\mathbf{z}) = \\mathcal{D}(\\mathcal{E}(\\mathbf{x}))" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": ". To control the generation with the textual conditions, given the noisy latent " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathbf{z}_t" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": ", current time step " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": " and text tokens " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": ", a conditional U-Net [23] denoiser is trained to predict the noise " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": " added to the latent " + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "inline_equation", + "content": "\\mathbf{z}" + }, + { + "bbox": [ + 46, + 551, + 288, + 693 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 63, + 696, + 287, + 717 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 63, + 696, + 287, + 717 + ], + "spans": [ + { + "bbox": [ + 63, + 696, + 287, + 717 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathbb {E} _ {\\mathbf {z} \\sim \\mathcal {E} (\\mathbf {x}), \\mathbf {y}, \\epsilon \\sim \\mathcal {N} (0, 1), t} \\left[ \\| \\epsilon - \\epsilon_ {\\theta} (\\mathbf {z} _ {t}, t, \\mathbf {y}) \\| _ {2} ^ {2} \\right], \\tag {1}", + "image_path": "d9844ffffdeb66585def735d90ad5b23fd98ae49d0f95fddd116855f30a84c08.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "spans": [ + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": " is obtained by feeding the prompt into a CLIP [17] text encoder. During inference, the pre-trained SD first samples a latent " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{z}_T" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": " from the standard normal distribution " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\mathcal{N}(0,1)" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": ". Iteratively, " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{z}_{t-1}" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": " can be obtained by removing noise from " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{z}_t" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": " conditioned on " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": ". After the final denoising step, the latent " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{z}_0" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": " is mapped to generate an image " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathbf{x}}" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": " with the decoder " + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 304, + 293, + 545, + 376 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 384, + 501, + 397 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 384, + 501, + 397 + ], + "spans": [ + { + "bbox": [ + 305, + 384, + 501, + 397 + ], + "type": "text", + "content": "4.2. Action-Disentangled Identifier (ADI)" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 403, + 545, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 545, + 510 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 545, + 510 + ], + "type": "text", + "content": "Given exemplar images that all contain a specific entity, existing subject-driven inversion methods [5, 9] learn to represent the entity as an identifier token " + }, + { + "bbox": [ + 304, + 403, + 545, + 510 + ], + "type": "inline_equation", + "content": "v \\in \\mathbb{R}^d" + }, + { + "bbox": [ + 304, + 403, + 545, + 510 + ], + "type": "text", + "content": ". And the learned " + }, + { + "bbox": [ + 304, + 403, + 545, + 510 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 304, + 403, + 545, + 510 + ], + "type": "text", + "content": " can then be employed in text prompts to produce diverse and novel images, where the entity can be generated with different contexts. In this paper, we continue the vein of capturing the common action in exemplar images by finding the optimal identifiers. An overview of our proposed ADI is illustrated in Fig. 3." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": "Expanding Semantic Inversion. To overcome the preference to low-level appearance features, we apply layer-wise identifier tokens to increase the accommodation of various features. Specifically, for the " + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": "-th layer where " + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "inline_equation", + "content": "l \\in [1, L]" + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": " is the number of cross-attention layers in the T2I model, a new identifier token " + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "inline_equation", + "content": "v_l \\in \\mathbb{R}^d" + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": " is initialized. Feeding the prompt with " + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "inline_equation", + "content": "v_l" + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": " into the text encoder, the output tokens " + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "inline_equation", + "content": "\\mathbf{y}_l" + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": " control the update of the latents in the " + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": "-th layer, thus influencing the generation of the visual content. And the learned tokens from all layers can form a token set " + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 304, + 510, + 546, + 689 + ], + "type": "text", + "content": ", which can then be paired with different subjects for generation. Rather than having a single identifier token take on the responsibility of reconstruction, having separate identifiers at different layers effectively ensures that more features are converted, including the action-related features we care about." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "Learning Gradient Mask with Context-Different Pair. The next step is to prevent the identifiers from inverting fea" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7800" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": "tures that are not relevant to the action and thus contaminating the subsequent image generation. Given " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,c)}\\in \\mathcal{X}" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": " as an anchor sample, where " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": " denotes the specific action, and " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": " denotes the action-agnostic context contained in the image including human appearance and background, we can randomly sample another image " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,\\overline{c})}" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "\\mathcal{X}" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "\\overline{c}" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": " represents that the context is different from " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": ". Taking the context-different pair " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,c)}" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,\\overline{c})}" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": " as the input, we can calculate two gradients of the denoising loss " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": " with respect to the identifier token " + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 130, + 194, + 287, + 220 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 130, + 194, + 287, + 220 + ], + "spans": [ + { + "bbox": [ + 130, + 194, + 287, + 220 + ], + "type": "interline_equation", + "content": "g ^ {(a, c)} = \\frac {\\partial \\mathcal {L} ^ {(a , c)}}{\\partial v}, \\tag {2}", + "image_path": "d1021023507d23a0451758b4d7c78fa7ef0c4fb1dd53cda3d38dc0747878b9e6.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 130, + 220, + 287, + 246 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 130, + 220, + 287, + 246 + ], + "spans": [ + { + "bbox": [ + 130, + 220, + 287, + 246 + ], + "type": "interline_equation", + "content": "g ^ {(a, \\bar {c})} = \\frac {\\partial \\mathcal {L} ^ {(a , \\bar {c})}}{\\partial v}. \\tag {3}", + "image_path": "0a06924178b09e78c3d7a8c2733fed06ab091e8ff79cfbada5acac2e4caf789a.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 249, + 287, + 333 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 249, + 287, + 333 + ], + "spans": [ + { + "bbox": [ + 46, + 249, + 287, + 333 + ], + "type": "text", + "content": "Note that the subscript " + }, + { + "bbox": [ + 46, + 249, + 287, + 333 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 46, + 249, + 287, + 333 + ], + "type": "text", + "content": " is omitted for the sake of uniformity and clarity. Each identifier token contains multiple channels, each carrying semantically distinct and independent information. And the gradient consistency of a channel indicates that the channel is likely to carry information about the specific action. Therefore, we calculate the absolute value of the difference between the two gradients:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 117, + 346, + 287, + 360 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 117, + 346, + 287, + 360 + ], + "spans": [ + { + "bbox": [ + 117, + 346, + 287, + 360 + ], + "type": "interline_equation", + "content": "\\triangle g ^ {\\overline {{c}}} = \\left| g ^ {(a, c)} - g ^ {(a, \\overline {{c}})} \\right|, \\tag {4}", + "image_path": "d89fa1d1b9b0f05aa62303531e0d579831425b3b5b2389bd837953f417005d0e.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "spans": [ + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "text", + "content": "where the semantic channels with a small difference can be regarded as action-related channels of the action " + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "text", + "content": ", which are expected to be preserved. Specifically, we sort the difference from the largest to the smallest, taking the value at " + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "text", + "content": " percent " + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "inline_equation", + "content": "\\gamma^{\\beta}" + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "text", + "content": " as a threshold. In other words, " + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "inline_equation", + "content": "\\beta \\%" + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "text", + "content": " of the channels are masked. Then, the mask that shares the same dimension as " + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "text", + "content": " can be calculated. For the " + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 365, + 287, + 449 + ], + "type": "text", + "content": "-th channel," + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 111, + 452, + 287, + 479 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 111, + 452, + 287, + 479 + ], + "spans": [ + { + "bbox": [ + 111, + 452, + 287, + 479 + ], + "type": "interline_equation", + "content": "m _ {k} ^ {\\bar {c}} = \\left\\{ \\begin{array}{l l} 0, & \\triangle g _ {k} ^ {\\bar {c}} \\geqslant \\gamma^ {\\beta} \\\\ 1, & \\triangle g _ {k} ^ {\\bar {c}} < \\gamma^ {\\beta} \\end{array} . \\right. \\tag {5}", + "image_path": "219b2dd6956138bc35f8bac025b22b687bf19dcad305b3a04c85771d62b86d9a.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "spans": [ + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "type": "text", + "content": "By overwriting the mask to the gradient of the anchor sample, the action-related knowledge is preserved and incorporated into the update of " + }, + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "type": "text", + "content": ", while the updates on action-agnostic channels are ignored. Note that since the specific visual invariance about the action changes slightly depending on the sample pair, the masked channels may not be exactly the same each time. Furthermore, both samples use the prompt of the anchor sample " + }, + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,c)}" + }, + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "type": "text", + "content": " when calculating the gradients. Since the visual context of " + }, + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,\\bar{c})}" + }, + { + "bbox": [ + 46, + 483, + 287, + 637 + ], + "type": "text", + "content": " is inconsistent with the description in the prompt, the reconstruction loss favours larger gradients in the context-related channels. In this way, the action-related channels found through the threshold will be more accurate." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 288, + 714 + ], + "type": "text", + "content": "Learning Gradient Mask with Action-Different Pair. Although the context-different pairs have the same action semantics, there may be differences in the visualization of the actions, and therefore the channels associated with the most representative action features do not necessarily have a smaller gradient difference. Since learning the gradient" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": "mask with the context-different only pair is not stable and effective enough, we also construct action-different pairs to generate the gradient mask from another perspective. For each sample " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathcal{X}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": ", we can use it to quickly train a subject-driven customization model (e.g., DreamBooth) that effectively inverts the most of the low-level context information. Therefore, by filling the prompt template of " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": " with action descriptions that are different from " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": ", the trained customization model can generate various action images as " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathcal{X}^{(\\overline{a},c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": ". Note that this step is not necessary if the users can compile a dataset of varied actions by the same individual using pre-captured images. However, the data collection is usually arduous and lengthy, making fast training of a subject-driven customization a more convenient solution. Due to the one-shot training and the concise text, the generated images " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathcal{X}^{(\\overline{a},c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": " may not be consistent with the action descriptions, or the context may differ from the original " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": ", but in practice, we have found that the quality is sufficient to diversify the action variation. In this way, when " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": " is sampled during training, we can randomly sample a image " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(\\overline{a},c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathcal{X}^{(\\overline{a},c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": " to construct the action-different pair. And the gradient of " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(\\overline{a},c)}" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": " with respect to the token " + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 304, + 72, + 545, + 346 + ], + "type": "text", + "content": " can be calculated as" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 389, + 350, + 545, + 374 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 389, + 350, + 545, + 374 + ], + "spans": [ + { + "bbox": [ + 389, + 350, + 545, + 374 + ], + "type": "interline_equation", + "content": "g ^ {(\\bar {a}, c)} = \\frac {\\partial \\mathcal {L} ^ {(\\bar {a} , c)}}{\\partial v}. \\tag {6}", + "image_path": "c73e0f50f0a8336461cf386e9d44ef133c2e08047ce352bc81ca9176003cac2e.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 378, + 545, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 378, + 545, + 413 + ], + "spans": [ + { + "bbox": [ + 304, + 378, + 545, + 413 + ], + "type": "text", + "content": "Similarly, both samples use the prompt of the anchor sample " + }, + { + "bbox": [ + 304, + 378, + 545, + 413 + ], + "type": "inline_equation", + "content": "\\mathbf{x}^{(a,c)}" + }, + { + "bbox": [ + 304, + 378, + 545, + 413 + ], + "type": "text", + "content": ". We can also calculate the absolute value of the gradient difference:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 376, + 418, + 545, + 432 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 376, + 418, + 545, + 432 + ], + "spans": [ + { + "bbox": [ + 376, + 418, + 545, + 432 + ], + "type": "interline_equation", + "content": "\\triangle g ^ {\\bar {a}} = \\left| g ^ {(a, c)} - g ^ {(\\bar {a}, c)} \\right|, \\tag {7}", + "image_path": "8f8c74086968f7ceea7b6ebbe872a77f21e773224446bfebf2d4cf6d18189e11.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 437, + 545, + 473 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 437, + 545, + 473 + ], + "spans": [ + { + "bbox": [ + 304, + 437, + 545, + 473 + ], + "type": "text", + "content": "where the semantic channels with small difference can be regarded as context-related channels of the action " + }, + { + "bbox": [ + 304, + 437, + 545, + 473 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 304, + 437, + 545, + 473 + ], + "type": "text", + "content": ", which are expected to be masked. Therefore, we have" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 368, + 477, + 545, + 504 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 368, + 477, + 545, + 504 + ], + "spans": [ + { + "bbox": [ + 368, + 477, + 545, + 504 + ], + "type": "interline_equation", + "content": "m _ {k} ^ {\\bar {a}} = \\left\\{ \\begin{array}{l l} 0, & \\triangle g _ {k} ^ {\\bar {a}} < \\lambda^ {\\beta} \\\\ 1, & \\triangle g _ {k} ^ {\\bar {a}} \\geqslant \\lambda^ {\\beta} \\end{array} , \\right. \\tag {8}", + "image_path": "3f36da5a75c67b0c9e8c53da3f7c19277f69a859fdea44248f3de936293f6815.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 509, + 544, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 544, + 521 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 544, + 521 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 509, + 544, + 521 + ], + "type": "inline_equation", + "content": "\\lambda^{\\beta}" + }, + { + "bbox": [ + 304, + 509, + 544, + 521 + ], + "type": "text", + "content": " is the threshold here to mask " + }, + { + "bbox": [ + 304, + 509, + 544, + 521 + ], + "type": "inline_equation", + "content": "\\beta \\%" + }, + { + "bbox": [ + 304, + 509, + 544, + 521 + ], + "type": "text", + "content": " of the channels." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "spans": [ + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "text", + "content": "Merging Gradient Masks for Context. Due to the noise introduced by context variations, identifying action-relevant channels using only context-different or action-different pairs would be difficult and unreliable. As an evidence, the average overlap rate of channels preserved by both masks at each training step is " + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "inline_equation", + "content": "30.26\\%" + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "text", + "content": ". Therefore, given the input triple " + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "inline_equation", + "content": "\\mathcal{I} = \\{\\mathbf{x}^{(a,\\overline{c})},\\mathbf{x}^{(a,c)},\\mathbf{x}^{(\\overline{a},c)}\\}" + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "text", + "content": ", we can merge the two obtained masks " + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "inline_equation", + "content": "m^{\\overline{a}}" + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "inline_equation", + "content": "m^{\\overline{c}}" + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "text", + "content": " to get the final context mask " + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 304, + 524, + 545, + 655 + ], + "type": "text", + "content": ". In practice, we keep only the intersection of the unmasked channels as unmasked, as we find this merging strategy performs better. Formally, we have" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 392, + 661, + 545, + 673 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 392, + 661, + 545, + 673 + ], + "spans": [ + { + "bbox": [ + 392, + 661, + 545, + 673 + ], + "type": "interline_equation", + "content": "m = m ^ {\\overline {{c}}} \\cap m ^ {\\overline {{a}}}, \\tag {9}", + "image_path": "f4c629d5f74b9edbaed93ae7ed37338bb0bb6af4c4792eead84d02526e15cf18.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 679, + 544, + 691 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 679, + 544, + 691 + ], + "spans": [ + { + "bbox": [ + 306, + 679, + 544, + 691 + ], + "type": "text", + "content": "which is overwritten to the gradient of the anchor sample:" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 383, + 696, + 545, + 710 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 383, + 696, + 545, + 710 + ], + "spans": [ + { + "bbox": [ + 383, + 696, + 545, + 710 + ], + "type": "interline_equation", + "content": "\\widetilde {g} ^ {(a, c)} = m \\odot g ^ {(a, c)}. \\tag {10}", + "image_path": "4f0188dc6bb4bd8710a02a3acdf67abb72afe7e765325a2979e04b00dc964870.jpg" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "text", + "content": "7801" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 82, + 544, + 421 + ], + "blocks": [ + { + "bbox": [ + 51, + 73, + 99, + 82 + ], + "lines": [ + { + "bbox": [ + 51, + 73, + 99, + 82 + ], + "spans": [ + { + "bbox": [ + 51, + 73, + 99, + 82 + ], + "type": "text", + "content": "Sample Image" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 113, + 73, + 212, + 81 + ], + "lines": [ + { + "bbox": [ + 113, + 73, + 212, + 81 + ], + "spans": [ + { + "bbox": [ + 113, + 73, + 212, + 81 + ], + "type": "text", + "content": "Stable Diffusion ControlNet" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 225, + 73, + 328, + 81 + ], + "lines": [ + { + "bbox": [ + 225, + 73, + 328, + 81 + ], + "spans": [ + { + "bbox": [ + 225, + 73, + 328, + 81 + ], + "type": "text", + "content": "DreamBooth Textual Inversion" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 337, + 73, + 435, + 81 + ], + "lines": [ + { + "bbox": [ + 337, + 73, + 435, + 81 + ], + "spans": [ + { + "bbox": [ + 337, + 73, + 435, + 81 + ], + "type": "text", + "content": "ReVersion Custom Diffusion" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 454, + 73, + 465, + 81 + ], + "lines": [ + { + "bbox": [ + 454, + 73, + 465, + 81 + ], + "spans": [ + { + "bbox": [ + 454, + 73, + 465, + 81 + ], + "type": "text", + "content": "P+" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 50, + 82, + 544, + 421 + ], + "lines": [ + { + "bbox": [ + 50, + 82, + 544, + 421 + ], + "spans": [ + { + "bbox": [ + 50, + 82, + 544, + 421 + ], + "type": "image", + "image_path": "1232d370776c7eca185f2f101c5fb640294d877449bbf3723348b8f0c965115c.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 504, + 73, + 527, + 82 + ], + "lines": [ + { + "bbox": [ + 504, + 73, + 527, + 82 + ], + "spans": [ + { + "bbox": [ + 504, + 73, + 527, + 82 + ], + "type": "text", + "content": "Ours" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 426, + 546, + 447 + ], + "lines": [ + { + "bbox": [ + 46, + 426, + 546, + 447 + ], + "spans": [ + { + "bbox": [ + 46, + 426, + 546, + 447 + ], + "type": "text", + "content": "Figure 4. Visual comparisons of all methods. For each action, we present the generated results showcasing its pairing with a human character and an animal." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "bbox": [ + 489, + 82, + 543, + 191 + ], + "angle": 0, + "lines": [ + { + "bbox": [ + 489, + 82, + 543, + 191 + ], + "spans": [ + { + "bbox": [ + 489, + 82, + 543, + 191 + ], + "type": "image", + "image_path": "da0f6d97df588907cde1a59bb81f0a94630a68b74ebce91f0baa390482058bda.jpg" + } + ] + } + ], + "index": 7, + "type": "text" + }, + { + "bbox": [ + 46, + 457, + 287, + 506 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 457, + 287, + 506 + ], + "spans": [ + { + "bbox": [ + 46, + 457, + 287, + 506 + ], + "type": "text", + "content": "Note that the masked gradient " + }, + { + "bbox": [ + 46, + 457, + 287, + 506 + ], + "type": "inline_equation", + "content": "\\widetilde{g}^{(a,c)}" + }, + { + "bbox": [ + 46, + 457, + 287, + 506 + ], + "type": "text", + "content": ", where action-agnostic channels are considered to be masked, is the only gradient used to update " + }, + { + "bbox": [ + 46, + 457, + 287, + 506 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 457, + 287, + 506 + ], + "type": "text", + "content": ". Therefore, our identifiers can adequately invert action-related features." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 518, + 128, + 532 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 518, + 128, + 532 + ], + "spans": [ + { + "bbox": [ + 47, + 518, + 128, + 532 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 538, + 155, + 551 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 538, + 155, + 551 + ], + "spans": [ + { + "bbox": [ + 47, + 538, + 155, + 551 + ], + "type": "text", + "content": "5.1. Experiment Setup" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 557, + 287, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 557, + 287, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 557, + 287, + 605 + ], + "type": "text", + "content": "Baselines. For the baselines included in the comparison, we select Stable Diffusion [22], ControlNet [35], Dream-Booth [25], Textual Inversion [5], ReVersion [7], Custom Diffusion [9] and " + }, + { + "bbox": [ + 46, + 557, + 287, + 605 + ], + "type": "inline_equation", + "content": "\\mathrm{P + }" + }, + { + "bbox": [ + 46, + 557, + 287, + 605 + ], + "type": "text", + "content": " [30]." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 605, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 288, + 713 + ], + "type": "text", + "content": "Implementation Details. For ADI, we set the masking ratio " + }, + { + "bbox": [ + 46, + 605, + 288, + 713 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 605, + 288, + 713 + ], + "type": "text", + "content": " to 0.6 and use the AdamW [11] optimizer with a learning rate of 2e-4, while the training takes 3000 steps. For efficiency, DreamBooth for action-different pairs does not generate class-preservation images. While only one image is used for training, the initial learning rate is 1e-6, and the training takes 2000 steps. For a fair comparison, we use 50 steps of the DDIM [27] sampler with a scale of 7.5 for all methods. Unless otherwise specified, Stable Diffusion" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 457, + 546, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 457, + 546, + 494 + ], + "spans": [ + { + "bbox": [ + 304, + 457, + 546, + 494 + ], + "type": "text", + "content": "v2-1-base is selected as the default pre-trained model, and images are generated at a resolution of " + }, + { + "bbox": [ + 304, + 457, + 546, + 494 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 304, + 457, + 546, + 494 + ], + "type": "text", + "content": ". All experiments are conducted on a NVIDIA A100 GPU." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 502, + 448, + 515 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 502, + 448, + 515 + ], + "spans": [ + { + "bbox": [ + 306, + 502, + 448, + 515 + ], + "type": "text", + "content": "5.2. Quantitative Comparison" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 521, + 546, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 546, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 546, + 665 + ], + "type": "text", + "content": "We perform the quantitative comparison with human evaluators to assess the quantitative performance. For each subject-action pair, four images are randomly sampled from the images generated by different methods. Given (1) the exemplar images of a specific action, and (2) the textual name of the subjects, human evaluators are asked to determine whether (1) the generated action is consistent with those in the exemplar images, and (2) the generated character corresponds with the name without obvious deformations, defects, or abnormalities. A generated image will only be considered totally correct if both the action and the character are correctly generated." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "type": "text", + "content": "Tab. 1 reports the action, subject and total accuracy for all methods. Some observations are worth highlighting: (1) Given the textual descriptions of the actions, Stable Diffusion yields the highest total accuracy of all baseline meth" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7802" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 101, + 71, + 492, + 257 + ], + "blocks": [ + { + "bbox": [ + 101, + 71, + 492, + 257 + ], + "lines": [ + { + "bbox": [ + 101, + 71, + 492, + 257 + ], + "spans": [ + { + "bbox": [ + 101, + 71, + 492, + 257 + ], + "type": "image", + "image_path": "33408aa4e675ea453b5dced91fbf503c97c18077006155f14cd39b3870653552.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 261, + 547, + 285 + ], + "lines": [ + { + "bbox": [ + 46, + 261, + 547, + 285 + ], + "spans": [ + { + "bbox": [ + 46, + 261, + 547, + 285 + ], + "type": "text", + "content": "Figure 5. Ablation study. We remove or revise one implementation at a time to demonstrate the effects of the identifier extension and the gradient masking." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 74, + 316, + 261, + 416 + ], + "blocks": [ + { + "bbox": [ + 47, + 292, + 288, + 314 + ], + "lines": [ + { + "bbox": [ + 47, + 292, + 288, + 314 + ], + "spans": [ + { + "bbox": [ + 47, + 292, + 288, + 314 + ], + "type": "text", + "content": "Table 1. Quantitative comparisons with competing methods. Action, subject and total accuracies " + }, + { + "bbox": [ + 47, + 292, + 288, + 314 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 47, + 292, + 288, + 314 + ], + "type": "text", + "content": " are reported." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 74, + 316, + 261, + 416 + ], + "lines": [ + { + "bbox": [ + 74, + 316, + 261, + 416 + ], + "spans": [ + { + "bbox": [ + 74, + 316, + 261, + 416 + ], + "type": "table", + "html": "
MethodsActionSubjectTotal
Stable Diffusion [22]30.7184.5127.17
ControlNet [35]41.3042.6619.29
DreamBooth [25]2.4595.652.45
Textual Inversion [5]2.1786.141.90
ReVersion [7]1.6384.511.63
Custom Diffusion [9]29.6253.537.07
P+ [30]26.9080.1620.92
ADI (Ours)60.3385.8751.09
", + "image_path": "6f24877c0503dabc265a5b8aaa10ec959ab750a69f65207c69c0eb97eea91930.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "type": "text", + "content": "ods. This suggests that the existing baselines do not take full advantage of the exemplar images. (2) Despite relying on the skeleton as the condition to improve the action generation, ControlNet fail to maintain the performance of subject generation, resulting in an unsatisfactory total accuracy. (3) The action accuracy of DreamBooth, Textual Inversion, and ReVersion is incredibly low, reflecting their complete failure to invert the action-related features. (4) Custom Diffusion and " + }, + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "type": "inline_equation", + "content": "\\mathrm{P + }" + }, + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "type": "text", + "content": " improve action accuracy at more or less the expense of subject accuracy. (5) Attribute to the extended semantic conditioning space and the gradient masking strategy, our ADI dramatically improves the accuracy of action generation while maintaining excellent subject accuracy. As a result, ADI achieves the best total accuracy, outperforming the baselines by " + }, + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "type": "inline_equation", + "content": "23.92\\%" + }, + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 610, + 183, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 610, + 183, + 624 + ], + "spans": [ + { + "bbox": [ + 47, + 610, + 183, + 624 + ], + "type": "text", + "content": "5.3. Qualitative Comparison" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": "Fig. 4 illustrates the qualitative comparison of all methods involved. It can be observed that although text descriptions of the actions are provided, the actions generated by Stable Diffusion still differ from the examples. ControlNet can only maintain a rough consistency in posture and struggles to match the generated subjects to the desired requirements, resulting in incomplete or distorted body structures, while" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 293, + 547, + 426 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 293, + 547, + 426 + ], + "spans": [ + { + "bbox": [ + 304, + 293, + 547, + 426 + ], + "type": "text", + "content": "sacrificing diversity. And the subject-driven customization methods, as discussed earlier, fail to generate the actions or exhibit appearance characteristics that differ from the specified subjects. This suggests that they are unable to convert only the features associated with the actions. Giving the credit to the design from a perspective of gradient, our ADI decouples action-related features from action-agnostic information and blocks the inversion of the latter. This allows ADI to effectively model the invariance of the action and transfer it to different characters and animals without sacrificing image quality and variety." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 431, + 400, + 444 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 431, + 400, + 444 + ], + "spans": [ + { + "bbox": [ + 305, + 431, + 400, + 444 + ], + "type": "text", + "content": "5.4. Ablation Study" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 449, + 547, + 643 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 449, + 547, + 643 + ], + "spans": [ + { + "bbox": [ + 304, + 449, + 547, + 643 + ], + "type": "text", + "content": "We conduct ablation experiments on ActionBench to verify the individual effects of the proposed contributions. From the generation results in Fig. 5, it can be observed that (1) The removal of the extension to the semantic conditioning space diminishes the inversion ability of ADI. (2) Both the gradient masks learned from the context-different and the action-different pairs are essential. Removing either one can lead to inadequate learning of action knowledge or a degradation in the quality of the subject's appearance. We attribute this to the fact that learning from a single pair is inherently noisy due to varied action visuals and the interference of action-irrelevant information. (3) We also attempt to reverse the gradient masks, i.e., updates to channels that should have been masked are preserved, and updates to other channels are cancelled. Obviously, this will result in action-related features not being inverted." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 647, + 409, + 660 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 647, + 409, + 660 + ], + "spans": [ + { + "bbox": [ + 305, + 647, + 409, + 660 + ], + "type": "text", + "content": "5.5. Further Analysis" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": "Impact of Masking Strategy. To validate the masking strategy in our ADI, we compare it with four other strategies in Fig. 6. Specifically, on the gradients for each update: (1) Uniform: we uniformly mask " + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": " percent of channels. (2)" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7803" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 101, + 71, + 492, + 199 + ], + "blocks": [ + { + "bbox": [ + 101, + 71, + 492, + 199 + ], + "lines": [ + { + "bbox": [ + 101, + 71, + 492, + 199 + ], + "spans": [ + { + "bbox": [ + 101, + 71, + 492, + 199 + ], + "type": "image", + "image_path": "3de6cce6cba2819735dc0c8f5dabaa52fd0eb2b239e501a62f207f1ab5bad95d.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 203, + 547, + 226 + ], + "lines": [ + { + "bbox": [ + 46, + 203, + 547, + 226 + ], + "spans": [ + { + "bbox": [ + 46, + 203, + 547, + 226 + ], + "type": "text", + "content": "Figure 6. Visual comparison of masking strategies. The four compared strategies fail to mask the updates from agnostic channels and invert the action-related features." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 49, + 234, + 287, + 339 + ], + "blocks": [ + { + "bbox": [ + 49, + 234, + 287, + 339 + ], + "lines": [ + { + "bbox": [ + 49, + 234, + 287, + 339 + ], + "spans": [ + { + "bbox": [ + 49, + 234, + 287, + 339 + ], + "type": "image", + "image_path": "c98390fb2b0d368c9d47c621b27a7ec205bdc61c26b70fee07e5fe9b0e528d74.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 344, + 288, + 376 + ], + "lines": [ + { + "bbox": [ + 46, + 344, + 288, + 376 + ], + "spans": [ + { + "bbox": [ + 46, + 344, + 288, + 376 + ], + "type": "text", + "content": "Figure 7. Effect of gradient mask merging strategy. Preserving the intersection of gradient masks can better invert the representative action features." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "spans": [ + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "type": "text", + "content": "Random: we randomly mask " + }, + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "type": "text", + "content": " percent of channels. (3) Min: we mask " + }, + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "type": "text", + "content": " percent of channels with the lowest value. (4) Max: we mask " + }, + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 388, + 287, + 508 + ], + "type": "text", + "content": " percent of channels with the highest value. We observe that none of these four strategies successfully captures high-level features related to actions, since the images they generate are independent of the specified action. And the comparison also shows that the effectiveness of our ADI not only depends on the masking itself, but also requires learning action-agnostic channels by modeling the invariance of action and context." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 510, + 287, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 287, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 287, + 628 + ], + "type": "text", + "content": "Impact of Gradient Mask Merging Strategy. As shown in Eq. (9), ADI takes the intersection of the two gradient masks as the default merging strategy. We compare this with selecting the union of the two masks, and illustrate the generation results in Fig. 7. Since only channels that are preserved on both masks are updated, taking the intersection can effectively filter out action-agnostic features, leading to better customization of the actions. In contrast, taking the intersection may dilute the most representative action features due to the preserved context information." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "content": "Impact of Masking Ratio " + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "content": ". In Fig. 8, we vary the masking ratio " + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "content": " from 0.2 to 0.8. When " + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "content": " is small, fewer dimensions of the gradient are masked, and more action-agnostic features are retained to hinder the generation of the subject's appearance. This situation improves as " + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "content": " is gradually increased. However, when " + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 630, + 288, + 715 + ], + "type": "text", + "content": " is relatively large, due to the large number of masked dimensions, some of the most dis" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 307, + 234, + 545, + 338 + ], + "blocks": [ + { + "bbox": [ + 307, + 234, + 545, + 338 + ], + "lines": [ + { + "bbox": [ + 307, + 234, + 545, + 338 + ], + "spans": [ + { + "bbox": [ + 307, + 234, + 545, + 338 + ], + "type": "image", + "image_path": "ec6bd2fc4bc6fe6905244b4dd8aeccf1bf4012025b8212b1fc6bb5894fef0357.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 343, + 547, + 376 + ], + "lines": [ + { + "bbox": [ + 305, + 343, + 547, + 376 + ], + "spans": [ + { + "bbox": [ + 305, + 343, + 547, + 376 + ], + "type": "text", + "content": "Figure 8. Effect of the masking ratio " + }, + { + "bbox": [ + 305, + 343, + 547, + 376 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 305, + 343, + 547, + 376 + ], + "type": "text", + "content": ". A value close to 0.5 can balance the inversion of action-related features and the removal of action-agnostic features." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 387, + 545, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 387, + 545, + 422 + ], + "spans": [ + { + "bbox": [ + 305, + 387, + 545, + 422 + ], + "type": "text", + "content": "criminative features of actions may not be inverted, resulting in incomplete learning of actions. Note that the optimal value of " + }, + { + "bbox": [ + 305, + 387, + 545, + 422 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 305, + 387, + 545, + 422 + ], + "type": "text", + "content": " may be different for different actions." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 434, + 379, + 446 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 434, + 379, + 446 + ], + "spans": [ + { + "bbox": [ + 306, + 434, + 379, + 446 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 453, + 545, + 644 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 453, + 545, + 644 + ], + "spans": [ + { + "bbox": [ + 304, + 453, + 545, + 644 + ], + "type": "text", + "content": "In this paper, we investigate an under-explored text-to-image generation task, namely action customization. To understand the challenge of the task, we first visualize the inadequacy of existing subject-driven methods in extracting action-related features from the entanglement of action-agnostic context features. Then, we propose a novel method named ADI to learn action-specific identifiers from the given images. To increase the accommodation of knowledge relevant to the action, ADI extends the inversion process with layer-wise identifier tokens. Furthermore, ADI generates gradient masks to block the contamination of action-agnostic features at the gradient level. We also contribute the ActionBench for evaluating performance on the task. Since there is a growing need to synthesize action-specific images with various new subjects, we hope that our work can highlight this important direction." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 645, + 545, + 704 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 645, + 545, + 704 + ], + "spans": [ + { + "bbox": [ + 304, + 645, + 545, + 704 + ], + "type": "text", + "content": "Acknowledgement This work was supported by STI 2030—Major Projects (2022ZD0208800), NSFC General Program (Grant No. 62176215). This work was supported by Alibaba Group through Alibaba Research Intern Program." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7804" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Zhe Cao, Gines Hidalgo, Tomas Simon, Shih-En Wei, and Yaser Sheikh. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 5802-5810, 2019. 3" + } + ] + } + ], + "index": 15 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "7806" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Dynamic Tetrahedra for High-Quality Talking Head Synthesis/53f925b0-849e-40c5-8f29-bb11fe50f467_content_list.json b/2024/Learning Dynamic Tetrahedra for High-Quality Talking Head Synthesis/53f925b0-849e-40c5-8f29-bb11fe50f467_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..bddeea9ebdedb9d2f1528ca1c1bce62353178544 --- /dev/null +++ b/2024/Learning Dynamic Tetrahedra for High-Quality Talking Head Synthesis/53f925b0-849e-40c5-8f29-bb11fe50f467_content_list.json @@ -0,0 +1,1648 @@ +[ + { + "type": "text", + "text": "Learning Dynamic Tetrahedra for High-Quality Talking Head Synthesis", + "text_level": 1, + "bbox": [ + 120, + 130, + 849, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Zicheng Zhang $^{1}$ Ruobing Zheng $^{2}$ Bonan Li $^{1}$ Congying Han $^{1*}$ Tianqi Li $^{2}$ Meng Wang $^{2}$ Tiande Guo $^{1}$ Jingdong Chen $^{2}$ Ziwen Liu $^{1}$ Ming Yang $^{2}$ $^{1}$ University of Chinese Academy of Sciences $^{2}$ Ant Group", + "bbox": [ + 161, + 179, + 805, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 268, + 313, + 284 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Recent works in implicit representations, such as Neural Radiance Fields (NeRF), have advanced the generation of realistic and animatable head avatars from video sequences. These implicit methods are still confronted by visual artifacts and jitters, since the lack of explicit geometric constraints poses a fundamental challenge in accurately modeling complex facial deformations. In this paper, we introduce Dynamic Tetrahedra (DynTet), a novel hybrid representation that encodes explicit dynamic meshes by neural networks to ensure geometric consistency across various motions and viewpoints. DynTet is parameterized by the coordinate-based networks which learn signed distance, deformation, and material texture, anchoring the training data into a predefined tetrahedra grid. Leveraging Marching Tetrahedra, DynTet efficiently decodes textured meshes with a consistent topology, enabling fast rendering through a differentiable rasterizer and supervision via a pixel loss. To enhance training efficiency, we incorporate classical 3D Morphable Models to facilitate geometry learning and define a canonical space for simplifying texture learning. These advantages are readily achievable owing to the effective geometric representation employed in DynTet. Compared with prior works, DynTet demonstrates significant improvements in fidelity, lip synchronization, and real-time performance according to various metrics. Beyond producing stable and visually appealing synthesis videos, our method also outputs the dynamic meshes which is promising to enable many emerging applications. Code is available at https://github.com/zhangzc21/DynTet.", + "bbox": [ + 76, + 301, + 473, + 741 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 771, + 209, + 787 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Talking head synthesis is a long-standing task with a wide range of applications, such as digital humans, metaverse and filmmaking. The set up of this task can be roughly categorized to two lines: 1) learning from a large-scale dataset to drive arbitrary portrait images by the motion sig-", + "bbox": [ + 75, + 797, + 468, + 875 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "nal [7, 40, 41, 50, 62, 70, 77, 78]; and 2) building a personalized animatable head model from a several-minute video of a specific person [23, 31, 37, 53, 60, 61, 64, 67, 74]. We concentrate on the latter one, since it generally delivers high-quality synthesis results with intricate details and 3D naturalness, suitable for professional scenarios.", + "bbox": [ + 500, + 268, + 890, + 361 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Building such an exquisite talking head avatar from video data poses challenges in faithful appearance, motion control, as well as low running cost. One line of methods [14, 19, 20, 28, 30, 61, 67] explicitly rely on 3D Morphable Models (3DMM) [3] to reconstruct and animate human faces by estimating the person-specific parameters. While these methods allow for efficient rendering and dynamic deformation, the fixed face topology makes them often fall short in generating characteristic details, e.g., hairstyle, glasses, and inner mouth. Recently, neural implicit representations, especially Neural Radiance Fields (NeRF) [43], provide a new way to realize faithful generation. Some seminal work [16, 23, 37, 53, 64] learn a direct mapping from the control signal to the talking head, meanwhile the efficient neural representations like voxel grid [15, 34, 57] and hash encoding [44] have been introduced to improve training and inference speed.", + "bbox": [ + 496, + 364, + 892, + 621 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Despite the expressive capabilities, these implicit methods still need to improve many subtle issues in realism, e.g., head jitters, motionless mouths, and occasional artifacts. Researchers have discussed these issues from various aspects, e.g., introducing a canonical space for easier appearance learning [1, 49], developing compact models for more efficient training [31, 60], and using expressive driving conditions for better control [64, 65], against the naive baseline of NeRF. Essentially, the implicit definition for 3D objects complicates the analytical alternation of the underlying object geometry, leading to ineffective disentanglement of static appearance and motion from dynamic data, as opposed to the explicit meshes and vertex displacements for 3DMM. In viewing of this, it is appealing to incorporate the expressivity of implicit methods with an effective geometric control to take advantage of both lines of works.", + "bbox": [ + 496, + 625, + 893, + 866 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We introduce Dynamic Tetrahedra (DynTet), a novel hybrid approach that encodes dynamic meshes within neural", + "bbox": [ + 498, + 869, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author", + "bbox": [ + 94, + 887, + 220, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "5209", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "networks to assist explicit deformation. In essence, DynTet employs neural networks to predict attributes of underlying surfaces, from which explicit meshes can be extracted to fast render images with a differentiable rasterizer. On one hand, distinguished from implicit methods, the explicit geometry enables DynTet to learn a consistent 3D model across frames and directly express deformation as vertex displacement, thus DynTet is convenient to model the dynamics of talking head. On the other hand, unlike 3DMM with a preset topology, DynTet end-to-end learns personalized meshes and texture suitable for the given video.", + "bbox": [ + 75, + 90, + 472, + 257 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Technically, the proposed DynTex is inspired by recent advancements in tetrahedral techniques [17], originally developed for 3D reconstruction [45] and synthesis [18, 54]. The key insight is a parameterized tetrahedral grid: Coordinate-based networks are used to learn the signed distance field (SDF) and refinement for the grid, then the meshes are subsequently decoded through the Marching Tetrahedra algorithm. Since these prior methods [17, 18, 45, 54] primarily work for static scenes, they can hardly render images with deformation, nor keep the mesh topology under different conditions [18]. This also largely prevents the parallelized rendering and training processes. In contrast, we redesign the framework that exclusively determines the mesh topology with SDF, while a new branch controls the geometric variations with deformation signals. We also estimate the elastic score of each vertex to specify the rigid (e.g., forehead) and non-rigid regions (e.g., mouth) of the head, so as to achieve precise deformations in local regions while maintaining stability in other parts. These designs ensure the topological consistency and expressivity across all decoded meshes, enabling a customized dynamic mesh beyond 3DMM. To improve training efficiency, we introduce geometry losses that supervise shape and motion using the 3DMM priors. This replenishes the limited depth information available in frontal talking videos. Moreover, we establish an interpretable canonical space for the dynamic mesh, reducing the complexity of texture learning. In summary, our contributions include:", + "bbox": [ + 75, + 258, + 472, + 683 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "(1). We propose DynTet, a novel hybrid representation that encodes dynamic head meshes in neural networks, where the explicit geometry delineated by tetrahedra facilitates appearance and motion learning.", + "(2). This is the first work that successfully extends the static tetrahedral representation to dynamic head avatars by a new elaborated architecture, a canonical space, and 3DMM guidance for modeling dynamic meshes.", + "(3). DynTet presents evident advantages in terms of fidelity, lip-sync precision, stability and runtime by thorough evaluation compared with prior works." + ], + "bbox": [ + 76, + 685, + 468, + 852 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The learned dynamic head meshes are promising together with existing 3D assets or AR/VR techniques for emerging applications such as human avatar and the meta", + "bbox": [ + 76, + 854, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "verse, which may inspire further study on the hybrid representation for dynamic 3D objects.", + "bbox": [ + 500, + 90, + 890, + 121 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 150, + 640, + 166 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Talking head synthesis. Most existing methods for talking head synthesis can be classified into three categories in terms of the modeling approaches. 2D-based methods [50, 68, 69, 76, 78] utilized generative models [21, 26, 29] as renderers to produce photorealistic portraits. While, these methods often fall short in achieving 3D naturalness and consistent pose control due to the absence of an explicit 3D model. 3DMM-based methods [14, 19, 20, 28, 30, 61, 67] leveraged 3D face knowledge to drive facial expression, resulting in quite natural talking style. As a trade-off, due to the lack of complete head topology they cannot guarantee consistency or fidelity beyond the facial region such as hair and inner mouth. Neural head avatar [22, 74, 75] has emerged as an attractive way for automatically creating 3D facial models. While earlier approaches [51, 66] required detailed scanning data, NeRFs [5, 43, 49] offer a solution to learn models from video clips, driven by the factors like 3DMM coefficients [16], audio feature [23], or facial landmarks [65]. Several recent works have enhanced control effects [1, 37, 64], system efficiency [31, 60] and few-shot training [32, 53]. Despite great progress, neural avatars still face challenges in realism and plausible motion, not to mention that NeRF rendering is computationally expensive when generating high-resolution images.", + "bbox": [ + 496, + 181, + 893, + 544 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Neural 3D representation. Neural implicit functions are emerging as an effective representation of 3D object [35, 42, 43, 48, 55] using coordinate-based MLPs [44, 56, 59]. While prior methods [42, 48] required 3D supervision, several recent works [33, 36, 43, 47] demonstrated differentiable rendering for training directly from images. Meanwhile, NeRF [43] and followups [15, 44, 57, 73] performed volume rendering [27] on a continuous field for density and color, achieving impressive results for multi-view synthesis. As density is ambiguous to depict geometric details [63], they cannot explicitly edit shape or extract a high-quality surface with Marching Cubes [39], which makes it challenging in formulating deformation for dynamic scenes. Recent works [17, 54] proposed to convert deformable tetrahedral grid into surface meshes via the differentiable Marching Tetrahedral algorithm [11], where the SDF values are implicitly learned. The following methods [18, 45] further extended to jointly learn geometry and texture from image data. They can render photorealistic images competitive with NeRF in real-time. However, as these methods only work for static scenes, they cannot learn dynamics for modeling head avatars. We present an original effort to address this issue to learn dynamic tetrahedral meshes.", + "bbox": [ + 496, + 553, + 893, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "5210", + "bbox": [ + 482, + 944, + 516, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. Preliminaries", + "text_level": 1, + "bbox": [ + 76, + 89, + 217, + 104 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We provide some background concepts and notations. At first, we define operations between sets as element-wise operations, and functions are mapped element-wise as well.", + "bbox": [ + 75, + 118, + 468, + 162 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Tetrahedral meshes have been studied in deep learning [17, 54] as a hybrid representation for 3D shape modeling. Consider an object lying in a unit cube, a tetrahedral grid denoted as $(\\mathbf{V}_{tet},\\mathbf{T}_{tet})$ is pre-defined to tetrahedralize the cube into $r^3$ resolution. Each tetrahedron $T_{k}\\in \\mathbf{T}_{tet}$ is defined by four vertices $\\{\\mathbf{v}_{a_k},\\mathbf{v}_{b_k},\\mathbf{v}_{c_k},\\mathbf{v}_{d_k}\\}$ , where $K$ is the total number of tetrahedra. Additionally, each vertex $\\mathbf{v}_i$ contains a learnable SDF value $s_i\\in \\mathbb{R}$ to express the distance away from the underlying surface, and a small offset $\\Delta \\mathbf{v}_i\\in [-\\frac{1}{r},\\frac{1}{r}]^3$ from its initial coordinates to refine the grid as $\\mathbf{v}_i' = \\mathbf{v}_i + \\Delta \\mathbf{v}_i$ . We let $S = \\{s_i\\}_{i = 1}^K$ and $\\Delta \\mathbf{V} = \\{\\Delta \\mathbf{v}_i\\}_{i = 1}^K$ . Notably, the surface shape within the tetrahedral grid is primarily determined by the SDF values $S$ as $\\Delta \\mathbf{V}$ is confined within the resolution boundaries.", + "bbox": [ + 75, + 167, + 472, + 378 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Marching Tetrahedra $(MT)$ is an iso-surface extraction algorithm [11] to generate triangular meshes from tetrahedral meshes. Given SDF values $\\{s_a, s_b, s_c, s_d\\}$ of a tetrahedron, $MT$ determines the surface topology inside the tetrahedron based on the signs of these values, where the $2^4$ configurations in total fall into 3 unique cases after considering rotation symmetry [54]. A simplified 2D example can be found in Figure 1. Once the topology is identified, a new vertex denoted as $\\mathbf{v}_{ab}$ by example, is located at the zero crossings of linear interpolation along the tetrahedral edges:", + "bbox": [ + 75, + 381, + 472, + 532 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {l e r p} \\left(\\mathbf {v} _ {a}, \\mathbf {v} _ {b}, s _ {a}, s _ {b}\\right) = \\frac {s _ {a} \\cdot \\mathbf {v} _ {a} - s _ {b} \\cdot \\mathbf {v} _ {b}}{s _ {a} - s _ {b}}, \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 137, + 537, + 468, + 566 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "the same for other vertices. Note that this equation is evaluated only when signs differ $(\\mathrm{sign}(s_a)\\neq \\mathrm{sign}(s_b))$ to prevent singularity. Leveraging $MT$ on the deformed tetrahedral grid $(\\mathbf{V}_{tet} + \\Delta \\mathbf{V},\\mathbf{T}_{tet})$ , the triangular surface of the encoded object can be acquired in a differentiable manner. We omit constant symbols and represent this process as", + "bbox": [ + 75, + 570, + 468, + 661 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {V} _ {t r i}, \\mathbf {T} _ {t r i} = \\operatorname {M a r T e t} (\\mathcal {S}, \\Delta \\mathbf {V}), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 166, + 666, + 468, + 683 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathbf{V}_{tri}$ and $\\mathbf{T}_{tri}$ are the sets of vertices and connectivity of the triangular meshes, respectively.", + "bbox": [ + 75, + 688, + 468, + 718 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3D Morphable Models provide generic parametric models [3] for synthesizing face shapes, usually expressed as", + "bbox": [ + 75, + 722, + 468, + 753 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {V} _ {3 d m m} = \\bar {\\mathbf {V}} _ {3 d m m} + \\mathbf {U} _ {i d} \\gamma + \\mathbf {U} _ {e x p} \\boldsymbol {\\alpha}. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 142, + 776, + 468, + 794 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Here $\\bar{\\mathbf{V}}_{3dmm}$ denotes a mean shape, $\\mathbf{U}_{id}$ and $\\mathbf{U}_{exp}$ are the matrices of basis vectors in the identity and expression space, respectively. $\\gamma$ and $\\alpha$ are coefficients for the identity and expression, allowing for a tractable control over facial variations. The parameter $\\alpha$ has been served as a versatile representation for driving facial deformation [13].", + "bbox": [ + 75, + 809, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Methodology", + "text_level": 1, + "bbox": [ + 500, + 89, + 635, + 107 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we introduce a framework called Dynamic Tetrahedra (DynTet) to rapidly learn 3D head avatars from short video sequences, and enable real-time rendering of high-quality talking heads. Generally, DynTet upgrades recent tetrahedral representation [17, 18, 45] tailored for dynamic head modeling. As shown in Figure 1, neural networks are trained to encode head shapes within a tetrahedral grid [54], and then the Marching Tetrahedra (MT) [11] decodes the meshes for photorealistic rasterization rendering. In the following, we delineate the talking head task through the lens of tetrahedral representation (Sec.4.1), and elucidate our improvements in the geometry model (Sec.4.2), rendering process (Sec.4.3), and training losses (Sec.4.4).", + "bbox": [ + 496, + 116, + 893, + 313 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. Problem statement", + "text_level": 1, + "bbox": [ + 498, + 325, + 681, + 339 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given a sequence of head images $\\{\\mathbf{I}_i\\}_{i=1}^n$ , we aim to reenact the specific head driven by motion signals, which typically includes camera parameters $\\{\\mathbf{P}_i\\}_{i=1}^n$ for rigid motion, and talking signals which we represent using 3DMM expression coefficients $\\{\\alpha_i\\}_{i=1}^n$ for non-rigid facial expressions.", + "bbox": [ + 496, + 349, + 893, + 426 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "**Formulation.** Drawing inspiration from the seminal work of [54], which applied tetrahedral meshes for multi-view reconstruction, we propose a basic paradigm for talking head modeling: (1) A geometry mapping $\\mathbf{F}$ first predicts $S$ and $\\Delta \\mathbf{V}$ from $\\alpha$ and $\\mathbf{V}_{tet}$ . (2) The outputs from $\\mathbf{F}$ are processed based on Eq. (2) to obtain the triangular mesh, which are then rasterized given camera pose $\\mathbf{P}$ to get the coordinates of image pixels in the model space. (3) An appearance mapping $\\mathbf{G}$ predicts the materials, which is incorporated with a lighting model $L$ for the physically-based rendering (PBR) [4]. We summarize the overall process as", + "bbox": [ + 496, + 436, + 890, + 603 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\min _ {\\boldsymbol {F}, \\boldsymbol {G}, \\boldsymbol {L}} \\frac {1}{n} \\sum_ {i = 1} ^ {n} L o s s (\\hat {\\mathbf {I}} _ {i}, \\mathbf {I} _ {i}) \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 557, + 604, + 890, + 642 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\hat{\\mathbf{I}}_i = \\mathrm{Rendering}(\\pmb {F},\\pmb {G},\\pmb {L},\\pmb {\\alpha}_i,\\mathbf{P}_i)$", + "bbox": [ + 553, + 645, + 836, + 661 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Herein, Rendering denotes the PBR procedure, and the loss function comprises a set of constraints on the predictions.", + "bbox": [ + 496, + 662, + 890, + 691 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Challenges. Prior works [17, 18, 54] commonly parameterize $\\pmb{F}$ using a neural network $f$ to predict SDF values and relative offsets, i.e., $\\mathcal{S},\\Delta \\mathbf{V} = f(\\mathbf{V}_{tet})$ , while introducing the talking signal $\\alpha$ to $f$ as a condition will bring several problems. First, once SDF values vary along with the conditions, it is difficult to learn the intricate deformation of the facial area with a simple MLP. Second, modern GPUs do not support parallelization for meshes with a variable topology, resulting in inefficient training and running processes. Lastly, previous approaches were designed for $360^{\\circ}$ data, while our training data only includes frontal head images. Consequently, this inaccurate estimation of geometry leads to evident artifacts in the rendered videos.", + "bbox": [ + 496, + 704, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "5211", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/058501d2bab3f2c8bdb0df2da62fe9db9d045826b3b5cc12f36b534bab40274c.jpg", + "image_caption": [ + "Figure 1. Illustration of the proposed DynTet for modeling a talking head. Left panel: The top branch predicts topology-related information, including SDF values $s$ and elastic scores. The bottom branch, conditioned by talking signals, predicts the offset vectors scaled by the elastic scores to yield deformation vectors $\\Delta \\mathbf{v}$ for driving the tetrahedral grid. Then, the Marching Tetrahedra (MT) algorithm decodes the meshes. Right panel: The pixel coordinates are projected into a canonical space. Then the physically-based materials and lighting are sampled for rendering images." + ], + "image_footnote": [], + "bbox": [ + 81, + 89, + 890, + 287 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.2. Geometry modeling", + "text_level": 1, + "bbox": [ + 76, + 383, + 267, + 401 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To address the mentioned challenges, we initially disentangle topology and geometry from head shapes within the tetrahedra grid, allowing for generating dynamic meshes with a consistent topology. Furthermore, we enhance the tetrahedral attributes by introducing a novel elastic score, facilitating precise control over deformation. These improvements are incorporated by modifying the internal structure of the geometry mapping as", + "bbox": [ + 75, + 407, + 470, + 529 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {F}: \\mathbf {V} _ {t e t}, \\boldsymbol {\\alpha} \\rightarrow \\mathcal {S}, \\Delta \\mathbf {V} \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 98, + 539, + 468, + 563 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathcal{S},\\mathcal{E} = f_1(\\mathbf{V}_{tet}),\\Delta \\mathbf{V} = \\mathcal{E}\\cdot f_2(\\mathbf{V}_{tet},\\boldsymbol {\\alpha})$", + "bbox": [ + 99, + 558, + 428, + 574 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Here, $f_{1}$ and $f_{2}$ are coordinate-based MLPs, while $\\mathcal{E} \\coloneqq [f_1(\\mathbf{V}_{tet})]_e$ represents the set of non-negative elastic scores.", + "bbox": [ + 76, + 583, + 468, + 614 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Shape representation. Ideal face models exhibit topological invariance regardless of deformation. While implicit SDF representations present challenges in fulfilling this property, it is clear for explicit meshes like 3DMM [3] to maintain the number of vertices and their relationship. By employing Eq. (1) within $MT$ algorithm, we have", + "bbox": [ + 75, + 619, + 468, + 710 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {v} _ {a b} ^ {\\prime} = \\underbrace {\\operatorname {l e r p} \\left(\\mathbf {v} _ {a} , \\mathbf {v} _ {b} , s _ {a} , s _ {b}\\right)} _ {\\text {t o p o l o g y a n d i d e n t i t y}} + \\underbrace {\\operatorname {l e r p} \\left(\\Delta \\mathbf {v} _ {a} , \\Delta \\mathbf {v} _ {b} , s _ {a} , s _ {b}\\right)} _ {\\text {g e o m e t r y a n d e x p r e s s i o n}}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 84, + 719, + 468, + 756 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given that vertices $\\mathbf{v}_a$ and $\\mathbf{v}_b$ are pre-defined in the tetrahedral grid, the first term is just affected by the SDF values. Hence, our design in Eq.(5), which segregates SDF from the talking signal, results in a topologically invariant mesh. Meanwhile, the second term indicates that the geometry of mesh explicitly relies on the tetrahedral grid offsets. Additionally, a comparison with Eq. (3) reveals that DynTet functions as a quasi-3DMM hybrid model, enabling additive changes to facial shapes driven by neural networks.", + "bbox": [ + 75, + 763, + 470, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Elastic estimation. Our design necessitates relaxing the range of $\\Delta \\mathbf{v}_i\\in [-\\frac{1}{r},\\frac{1}{r}]^3$ to allow greater flexibility in geometric variations. However, this relaxation potentially leads to local jitters that significantly impact visual quality. We introduce an elastic scoring mechanism for each vertex within the tetrahedral grid to regulate deformation. These scores $\\mathcal{E}$ are predicted by the neural network $f_{1}$ to quantify the non-rigid properties across different regions of the human head. For instance, areas like the forehead and nose exhibit near-rigid behavior with minimal changes during talking, while regions like the mouth and eyes are more flexible and primarily contribute to deformations. In this way, the offset vectors are scaled using the elastic scores to determine the deformable vectors $\\Delta \\mathbf{V}$ .", + "bbox": [ + 496, + 383, + 893, + 597 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Architecture details. As shown in Figure 1, we formulate neural networks $f_{1}$ and $f_{2}$ as a composition of regular lightweight MLPs and a frequency positional encoding [59]", + "bbox": [ + 496, + 602, + 893, + 650 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\gamma (\\mathbf {v}) = < \\left(\\sin \\left(2 ^ {l} \\pi \\mathbf {v}\\right), \\cos \\left(2 ^ {l} \\pi \\mathbf {v}\\right)\\right) > _ {l = 0} ^ {L - 1}. \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 547, + 660, + 890, + 680 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We find that the simple frequency coding outperforms hash grid encoding [44] which tends to generate surfaces with significant noise. To maintain temporal consistency, we follow [41, 52] to represent the deformation of any timestamp by the window of adjacent 27 frames of expression coefficients, which are averaged into a 256-dimensional feature vector by a trainable convolutional encoder.", + "bbox": [ + 496, + 685, + 893, + 791 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.3. Neural rendering", + "text_level": 1, + "bbox": [ + 500, + 800, + 669, + 816 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "This procedure aims to automatically texture the triangular meshes $(\\mathbf{V}_{tri},\\mathbf{T}_{tri})$ extracted by $MT$ algorithm, and generate photorealistic images $\\hat{\\mathbf{I}}$ given camera pose $\\mathbf{P}$ and talking signal $\\alpha$ . In the realm of deformable reconstruction [38, 38, 46, 49], the canonical or template model", + "bbox": [ + 496, + 823, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "5212", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "serves an important role in reducing the complexity of texture parametrization. Thanks to the well-designed geometry model in DynTet, defining a canonical space becomes straightforward. We upgrade the vanilla rendering process by incorporating a canonical projection, thereby unifying both shading and lighting within a single space.", + "bbox": [ + 75, + 90, + 468, + 181 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Canonical projection. We propose the canonical projection CanProj to map the pixel coordinates $\\mathcal{C}_{2d}$ from an arbitrary camera pose $\\mathbf{P}$ into a canonical 3D space where the mean expression lies. This process is expressed as", + "bbox": [ + 75, + 186, + 470, + 247 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\bar {\\mathcal {C}} _ {3 d} = \\operatorname {C a n P r o j} \\left(\\mathcal {C} _ {2 d}, \\mathbf {V} _ {t r i}, \\mathbf {P}; \\bar {\\mathbf {V}} _ {t r i}, \\mathbf {T} _ {t r i}\\right),\n$$\n", + "text_format": "latex", + "bbox": [ + 129, + 255, + 413, + 272 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\bar{\\alpha} = \\Sigma_{i=1}^{n} \\alpha_{i} / n$ , (8)", + "bbox": [ + 132, + 275, + 468, + 291 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "and $\\bar{\\mathbf{V}}_{tri},\\mathbf{T}_{tri} = \\mathrm{MatTet}(\\pmb {F}(\\mathbf{V}_{tet},\\bar{\\alpha}))$", + "bbox": [ + 132, + 294, + 411, + 310 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In practical implementation, CanProj can be executed readily using a modern mesh rasterizer to derive coordinates $\\mathcal{C}_{3d}$ and 2D barycentric coordinates within $(\\mathbf{V}_{tri},\\mathbf{T}_{tri})$ . Then, $\\bar{\\mathcal{C}}_{3d}$ positioned in the canonical space, is computed through barycentric interpolation over $(\\bar{\\mathbf{V}}_{tri},\\mathbf{T}_{tri})$ .", + "bbox": [ + 75, + 319, + 468, + 395 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Appearance model. We follow previous work [4, 45] to adopt a physically-base material model, which allows easy integration of 3D assets within existing engines. To parameterize the appearance mapping $G$ , we employ a coordinate-based neural network comprising a hash grid encoder [44] for querying spatial features and a lightweight MLP for predicting materials. This network takes the projected coordinates and talking signal as inputs:", + "bbox": [ + 75, + 400, + 468, + 521 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {K} _ {d}, \\mathcal {K} _ {\\text {o r m}} = \\boldsymbol {G} (\\bar {\\mathcal {C}} _ {3 d}, \\boldsymbol {\\alpha}). \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 189, + 531, + 468, + 546 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Here, $\\mathcal{K}_d$ comprises three-channel diffuse albedo, and $\\mathcal{K}_{orm}$ is the set of occupancy $k_{o}$ , roughness $k_{r}$ , and metalness factors $k_{m}$ for the GGX normal distribution function [9]. Unlike prior works, we do not predict normals, but instead compute them directly using the triangular mesh in the model space, which yields similar results.", + "bbox": [ + 75, + 556, + 468, + 647 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Lighting model. We leverage the image based lighting model, where the environment light is given by a trainable mapping $\\pmb{L}$ . For each position $\\mathbf{v} \\in \\mathcal{C}_{3d}$ with a normal vector $\\mathbf{n}$ , the color along direction $\\omega_{o}$ is computed by", + "bbox": [ + 75, + 651, + 468, + 713 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}) = L _ {d} (\\mathbf {v}) + L _ {s} (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}), \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 161, + 722, + 468, + 738 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $L_{d}$ is the diffuse intensity and $L_{s}$ is the specular intensity. Consider a hemisphere with the incident direction $\\Omega = \\{\\pmb {\\omega}_i:\\pmb {\\omega}_i^T\\mathbf{n}\\geq 0\\}$ , the first diffuse term is computed by", + "bbox": [ + 75, + 748, + 468, + 794 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {d} (\\mathbf {v}) = \\left(1 - k _ {m}\\right) \\boldsymbol {k} _ {d} \\int_ {\\Omega} \\boldsymbol {L} _ {i} \\left(\\mathbf {v}, \\boldsymbol {\\omega} _ {i}\\right) \\left(\\boldsymbol {\\omega} _ {i} ^ {T} \\mathbf {n}\\right) \\mathrm {d} \\boldsymbol {\\omega} _ {i}. \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 109, + 804, + 468, + 832 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "And the second term is based on Cook-Torrance microfacet specular shading mode model [9] $r(\\omega_o,\\omega_i)$ to compute", + "bbox": [ + 75, + 835, + 468, + 867 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {s} (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}) = \\boldsymbol {k} _ {s} \\int_ {\\Omega} r \\left(\\boldsymbol {\\omega} _ {o}, \\boldsymbol {\\omega} _ {i}\\right) \\boldsymbol {L} _ {i} (\\mathbf {v}, \\boldsymbol {\\omega} _ {i}) \\left(\\boldsymbol {\\omega} _ {i} ^ {T} \\mathbf {n}\\right) \\mathrm {d} \\boldsymbol {\\omega} _ {i}, \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 875, + 468, + 904 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where the specular color $\\pmb{k}_s = (1 - k_m) \\cdot 0.04 + k_m \\pmb{k}_d$ . Following [45], we parameterize $\\pmb{L}$ with a cube map with resolution $6 \\times 512 \\times 512$ , and the calculate the hemisphere integration by the split-sum method [25]. By aggregating the rendered pixel colors along the camera pose, we obtain the rendered image $\\hat{\\mathbf{I}} = \\{k_o \\cdot L(\\mathbf{v}, \\pmb{\\omega}_o) | \\mathbf{v} \\in \\mathcal{C}_{3d}\\}$ .", + "bbox": [ + 496, + 90, + 890, + 181 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.4. Training losses", + "text_level": 1, + "bbox": [ + 500, + 189, + 650, + 205 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Thanks to its hybrid representation, DynTet possesses an interpretable SDF space and a cost-efficient rendering procedure. This unique combination allows us to supervise its training in both image and geometry space, facilitating the estimation of reasonable 3D models from frontal images.", + "bbox": [ + 496, + 213, + 890, + 289 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Image supervision. Given an image $\\mathbf{I}$ and its prediction $\\hat{\\mathbf{I}}$ , we train DynTet with the MSE loss for pixel-level reconstruction, and apply the overall LPIPS loss [71] for enhancing sharp details [31]. Besides, we find silhouette loss is important to provide shape guidance. The image loss is", + "bbox": [ + 496, + 292, + 890, + 369 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {i m g} = \\mathcal {L} _ {m s e} (\\hat {\\mathbf {I}}, \\mathbf {I}) + \\mathcal {L} _ {m s e} (\\hat {\\mathbf {I}} _ {o}, \\mathbf {I} _ {o}) + \\lambda_ {1} \\mathcal {L} _ {L P I P S} (\\hat {\\mathbf {I}}, \\mathbf {I}), \\tag {13}\n$$\n", + "text_format": "latex", + "bbox": [ + 511, + 375, + 890, + 392 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\hat{\\mathbf{I}}_o$ and $\\mathbf{I}_o$ denote the binary masks of head regions. We combine the head, background and torso together to train in practice to prevent noise around the facial contours.", + "bbox": [ + 496, + 398, + 890, + 444 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3DMM supervision. Frontal head views in talking videos often lack adequate depth information, resulting in flawed geometry estimation and artifacts in synthesized profile face. To counter this, we leverage 3DMM [3] as a geometry prior to mitigate these issues in the SDF space. We introduce two key losses to incorporate 3DMM. First, the normal distance loss $\\mathcal{L}_{ndl}$ constrains the canonical model:", + "bbox": [ + 496, + 449, + 890, + 554 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {n d l} = \\mathbb {E} _ {s \\sim U (- a, a)} \\| f _ {1} \\left(\\mathbf {V} _ {3 d m m} ^ {\\bar {\\alpha}} + s \\cdot \\mathbf {N} _ {3 d m m} ^ {\\bar {\\alpha}}\\right) - s \\| _ {2} ^ {2}, \\tag {14}\n$$\n", + "text_format": "latex", + "bbox": [ + 514, + 561, + 890, + 577 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathbf{V}_{3dmm}^{\\bar{\\alpha}}$ and $\\mathbf{N}_{3dmm}^{\\bar{\\alpha}}$ represent 3DMM vertices and normal vectors generated by coefficient $\\bar{\\alpha}$ , while $a$ is a small value which we set to 0.1. $\\mathcal{L}_{ndl}$ injects facial prior into $f_{1}$ , affecting the SDF values around 3DMM surface. Consequently, it avoids excessive restraint compared to full-space supervision [48], enabling adaptive learning in other regions. The second facial deformation loss is expressed as", + "bbox": [ + 496, + 584, + 890, + 690 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {f d l} = \\left\\| \\left[ f _ {1} \\left(\\mathbf {V} _ {3 d m m}\\right) \\right] _ {e} f _ {2} \\left(\\mathbf {V} _ {3 d m m}, \\boldsymbol {\\alpha}\\right) - \\mathbf {U} _ {e x p} (\\boldsymbol {\\alpha} - \\bar {\\boldsymbol {\\alpha}}) \\right\\| _ {2} ^ {2}. \\tag {15}\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 710, + 890, + 728 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "This loss helps the tetrahedral grid to mimic the 3DMM deformation. Although these losses target 3DMM vertices, the tetrahedral vertices are appropriately constrained due to their spatial density covering the 3DMM vertices.", + "bbox": [ + 496, + 734, + 890, + 795 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Loss function. We introduce a regularization term for the elastic score, denoted as $\\mathcal{R}_{es} = \\| [f_1(\\mathbf{V}_{3dmm})]_e\\| _2^2$ , to reinforce the rigid property. We incorporate the weighted combination of the above constraints as follows to formulate the loss function described in Eq. (4)", + "bbox": [ + 496, + 800, + 890, + 876 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL o s s = \\mathcal {L} _ {i m g} + \\lambda_ {2} \\mathcal {L} _ {n d l} + \\lambda_ {3} \\mathcal {L} _ {f d l} + \\lambda_ {4} \\mathcal {R} _ {e s}. \\tag {16}\n$$\n", + "text_format": "latex", + "bbox": [ + 531, + 885, + 890, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "5213", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/31e376b995de3ccefea3c82e9d161f2eff2e29427ddac14373c9f712e10f28d8.jpg", + "image_caption": [ + "Figure 2. Qualitative comparison of DynTet with the prior methods [31, 50, 60, 77]. Some representative defects are marked with red arrows, around which the generated eyes, mouths or wrinkles highlight discrepancies with real ones. The right panel presents the details of the mouth and eye area. The results show the superior realism and motion accuracy achieved by DynTet compared to existing methods." + ], + "image_footnote": [], + "bbox": [ + 81, + 90, + 496, + 470 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/a70e0b5814e559fc9a122431d7e6af9ae672e14157c4415b735a047dd7a6f47f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 503, + 90, + 885, + 469 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiment", + "text_level": 1, + "bbox": [ + 76, + 541, + 200, + 558 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Experimental settings", + "text_level": 1, + "bbox": [ + 76, + 566, + 279, + 583 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Dataset and pre-processing. For a fair comparison, we follow recent works [23, 31, 53] to conduct experiments on a publicly-released video dataset, which includes four high-definition talking videos with an average length of about 6500 frames at 25 FPS. Each raw video is cropped and resized to $512 \\times 512$ , except for the Obama data with the resolution $448 \\times 448$ . Each video is divided into training and test sets at a ratio of 10:1. We ensure strict alignment with the pre-processing steps outlined in AD-NeRF [23]. In order to extract the 3DMM coefficients efficiently, we utilize a pre-trained model from Deng et al. [10].", + "bbox": [ + 75, + 590, + 468, + 758 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation details. We implement DynTet based on the code of Nvdiffrec1 [45] for differentiable Marching Tetrahedra and rasterization. We use a tetrahedral grid with a resolution of $128^3$ [12], which is a commonly used setting [18, 45]. For the MLPs, we equip each one with ReLU-Linear layers. The geometry model utilizes a frequency positional encoder [59] with $L = 6$ and a 3-layer MLP with", + "bbox": [ + 75, + 768, + 468, + 875 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "128 middle neurons. Additionally, a 4-layer convolutional encoder [52] is used for the 3DMM coefficients. The appearance model consists of a 5-layer MLP with 256 middle neurons. During training, we perform 20,000 iterations with a batch size of 4. We employ the Adam optimizer with an initial learning rate of $1 \\times 10^{-3}$ , which exponentially decayed to $1 \\times 10^{-5}$ . The default hyperparameters are $\\lambda_{1} = 0.1$ , $\\lambda_{2} = 100$ , $\\lambda_{3} = 100$ , and $\\lambda_{4} = 100$ . All experiments are conducted on a single NVIDIA Tesla V100.", + "bbox": [ + 500, + 542, + 890, + 679 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Comparison baselines. We compare our method with several recent representative one-shot and person-specific models, including Wav2Lip [50], PC-AVS [77], NVP [62], SynObama [58], SadTalker [72]. In addition, we also compare our method with three end-to-end NeRF-based models: ADNeRF [23], RAD-NeRF [60] and ER-NeRF [31]. All these methods are implemented with their official code.", + "bbox": [ + 496, + 685, + 890, + 791 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Quantitative results", + "text_level": 1, + "bbox": [ + 500, + 801, + 687, + 816 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Comparison settings. We follow recent works to organize our comparisons into two settings: 1) Self-driven head reconstruction setting, in which we train a model for each video clip and evaluate the reconstruction quality on its respective test set. 2) Cross-driven lip synchronization set-", + "bbox": [ + 496, + 824, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_footnote", + "text": "1https://github.com/NVlabs/nvdiffrec", + "bbox": [ + 94, + 886, + 379, + 898 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "5214", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/35522e772a0c9237ec0587bc6ea50e492aaefb6dd7a31411c407f82eaf496151.jpg", + "table_caption": [], + "table_footnote": [ + "$\\dagger$ supervised by overall LPIPS [71].", + "Table 1. Quantitative results of the self-driven head reconstruction. The best and second results are in bold and underline. Wav2Lip takes ground truth as input, thus its PSNR and LPIPS values are biased. The FPS values are tested on the resolution of $512 \\times 512$ ." + ], + "table_body": "
MethodsPSNR ↑LPIPS ↓FID ↓CSIM ↑LMDm ↓LMDe ↓AUE ↓Sync ↑TimeFPS
Ground Truth∞001.0000007.899--
Wav2Lip [50]31.150.073020.700.9703.0722.1472.0598.256-20
PC-AVS [77]22.060.134547.530.8022.4963.6094.2838.540-32
AD-NeRF [23]30.410.079914.920.9264.3172.4054.3745.01518h0.08
RAD-NeRF [60]31.510.067511.140.9513.0062.2853.3174.4095h23
ER-NeRF† [31]32.500.03456.440.9602.9242.2202.7734.9442h23
DynTet35.150.061912.230.9752.4182.1371.8337.4072h46
DynTet†34.840.02234.720.9782.2842.1291.7127.6463h46
", + "bbox": [ + 84, + 88, + 890, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9805d245dd0e5491b41b089ac3d3042b135517a12618b4aa8152dc48540a098f.jpg", + "image_caption": [ + "Figure 3. The triangular meshes from 3DMM [3], ER-NeRF [31] and DynTet. The surfaces extracted from ER-NeRF using the Marching Cubes [39] exhibit noise and undesirable topology. Note that the backs of the meshes may have some defects due to limited training data, but it does not impact the rendering results." + ], + "image_footnote": [], + "bbox": [ + 81, + 262, + 467, + 431 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ting, where we use clips from unseen videos to drive all methods for comparisons in lip synchronization. We extract two video clips from the public demos of SynObama [58] and NVP [62], which we refer to as Testset A and Testset B.", + "bbox": [ + 75, + 526, + 468, + 588 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Evaluation metrics. We assess the methods with several metrics: We evaluate the reconstruction quality using PSNR and LPIPS metrics [71]. Realism and identity preservation are measured using Fréchet Inception Distance (FID) [24] and Cosine Similarity of Identity Embedding (CSIM) [41]. Driving accuracy is assessed by calculating the landmark distances for the mouth $(\\mathrm{LMD}^m)$ and eyes $(\\mathrm{LMD}^e)$ [6], while face motion accuracy is quantified by action units error (AUE) [2]. Temporal lip synchronization is evaluated using the SyncNet confidence score (Sync) [8]. Additionally, we report training time and frame-per-second (FPS) to evaluate the running efficiency of the methods.", + "bbox": [ + 75, + 592, + 470, + 773 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Head reconstruction. The results of the head reconstruction setting are presented in Table 1. For fairness, we provide DynTet with and without LPIPS supervision, both of which demonstrate significant advantages in reconstructing accurate details and precisely controlling facial movements. While 2D-based methods such as Wav2Lip [50] and PC-AVS [77] excel in the lip synchronization due to the pretraining on the large-scale dataset, they fall short in the", + "bbox": [ + 75, + 779, + 472, + 901 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/c649d234a2a205e1eb0a24e092a00830e3034aecdac626741c297cde3019575d.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodsTestset ATestset B
AUE ↓Sync ↑AUE ↓Sync ↑
Ground Truth07.38606.676
SynObama [58]5.5747.419--
NVP [62]--7.9546.562
Wav2Lip [50]5.0298.3947.4159.072
PC-AVS [77]4.3598.0877.4509.964
SadTalker [72]4.7327.2076.7607.932
AD-NeRF [23]4.2776.0416.7315.567
RAD-NeRF [60]4.1726.5416.7336.786
ER-NeRF [31]4.2106.8776.6697.401
DynTet3.6725.0556.0296.401
Audio2Exp + DynTet4.3167.0556.5417.335
", + "bbox": [ + 506, + 261, + 890, + 431 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Quantitative results of cross-driven lip synchronization. The best and second results are in **bold** and **underline**. To drive DynTet with audios, we utilize an off-the-shelf model Audio2Exp [72] to convert audios into 3DMM coefficients.", + "bbox": [ + 496, + 441, + 892, + 497 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "faithful appearance. Among NeRF-based methods, the recent work ER-NeRF [31] achieves top performance in the evaluation. As the first tetrahedra representation for talking heads, DynTet notably outperforms on all metrics compared to NeRF-based approaches, showcasing its advancements in faithful reconstruction and accurate mapping from conditions to facial deformation. This further validates the great potential of tetrahedra meshes for dynamic modeling.", + "bbox": [ + 496, + 512, + 893, + 635 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Lip synchronization. DynTet offers both frame-driven and audio-driven approaches to accomplish this task. In the frame-driven approach, 3DMM coefficients are directly extracted from the target videos. On the other hand, the audio-driven approach utilizes an off-the-shelf model, specifically the Audio2Exp model in SadTalker [72], to convert audi-los into the 3DMM coefficients. It is worth noting that the target coefficients, denoted as $\\alpha^{\\prime}$ , and the training co-efficients $\\alpha$ , may have different distributions according to speaking habits. We find that a re-center process, expressed as $\\alpha^{\\prime} + (\\bar{\\alpha} - \\bar{\\alpha}^{\\prime})$ is crucial to rectificate the talking style. As shown in Table 2, the frame-driven approach of DynTet unsurprisingly achieves the best AUE performance among all methods. Furthermore, the audio-driven approach of DynTet also achieves comparable results with ER-NeRF and SadTalker, indicating its flexibility and strong generalization properties for various applications.", + "bbox": [ + 496, + 643, + 893, + 901 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "5215", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The rain will gradually sink its way slowly southward into England", + "bbox": [ + 127, + 89, + 421, + 101 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5af55b6a2e47b201e01563469e7a6fe5d0bf92d0f58b05e335693bdf51bc69c7.jpg", + "image_caption": [ + "Figure 4. Qualitative results of the cross-driven setting. The top and bottom panels show the frame- and audio-driven results, respectively. We attach the estimated 3DMM shapes for reference." + ], + "image_footnote": [], + "bbox": [ + 81, + 103, + 460, + 308 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Running efficiency. Table 1 shows that DynTet achieves fast training speed and real-time inference at $512 \\times 512$ resolution. Notably, DynTet maintains the same 46 FPS even at $1024 \\times 1024$ resolution, thanks to the cost-efficient rasterization rendering. In contrast, ER-NeRF and RAD-NeRF experience a half drop in FPS. This highlights our efficiency advantage in challenging high-resolution scenes.", + "bbox": [ + 76, + 367, + 468, + 474 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.3. Qualitative results", + "text_level": 1, + "bbox": [ + 76, + 482, + 254, + 498 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Figure 2 demonstrates that DynTet effectively addresses challenges faced by prior methods. It generates photorealistic images with intricate details in non-rigid areas and achieves precise control of mouth, blinks, and even wrinkles. Our supplementary videos showcase the impressive temporal stability of DynTet, resulting in smooth and stable motion. In Figure 3, the comparison of meshes obtained by different methods reveals that DynTet outperforms 3DMM and NeRF in terms of topology. Additionally, Figure 4 showcases the accurate expression control achieved by frame-driven DynTet, while audio-driven DynTet surpasses SadTalker in producing realistic and expressive results. These advancements firmly establish DynTet as a promising approach for modeling talking heads.", + "bbox": [ + 75, + 505, + 470, + 718 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Ablation study", + "text_level": 1, + "bbox": [ + 76, + 726, + 227, + 742 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We present the results of different structures in Table 3 and Figure 5. It is evident that the removal of canonical projection (C.P.) has a quite negative impact, resulting in increased LPIPS and LMD values. This is because the absence of the canonical projection increases the difficulty of texture learning and consequently hinders the supervision of loss on the geometry model. Similarly, removing 3DMM supervision leads to flawed meshes and introduces artifacts into the images. The visualization of elastic scores (E.S.) highlights its function in quantifying the non-rigid property, and", + "bbox": [ + 75, + 750, + 470, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ccc76b52adc76b697fb6e0d8c6bf29ce1cdc065e680b5cc5dbba3f7607eb0af9.jpg", + "image_caption": [ + "Figure 5. The validation of key components in DynTet. (a) Result of DynTet. (b) Replacing frequency encoding with hash encoding [44]. (c) Removing 3DMM supervision. (d) Removing canonical projection. (e) Groundtruth. (f) Visualization of elastic scores." + ], + "image_footnote": [], + "bbox": [ + 506, + 97, + 883, + 244 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/5abe14859986f98011d60644ab9b1e0317704e6563b451ce1d9486e0e572dab5.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DynTet-3DMM-C.P.-E.S.3264128512
FPS↑46---103928023
#Param1.41M---1.11M1.13M1.19M2.28M
PSNR↑34.8433.6534.3734.8132.2234.2035.1535.06
LPIPS↓0.02230.06860.05290.02470.05390.02540.02370.0219
LMDm↓2.2842.4532.5722.3362.8752.6362.4492.201
", + "bbox": [ + 506, + 313, + 888, + 387 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. Quantitative ablation of DynTet via removing 3DMM supervision, canonical projection, elastic score or changing the number of middle neurons in appearance mapping from 32 to 512. #Param denotes the parameter number of DynTet.", + "bbox": [ + 498, + 393, + 890, + 450 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "its removal affects the temporal stability of the results (see the supplementary videos). Interestingly, we find replacing frequency encoding with hash encoding leads to a cluttered mesh, indicating that it is desirable to encode coordinates as low-frequency signals in geometry learning. In addition, we explore the impact of middle neuron channels within the appearance mapping, and find that dimensions ranging from 64 to 256 strike a balance between expressivity and inference speed. These findings underscore the reasonable designs of DynTet for achieving desirable results.", + "bbox": [ + 496, + 464, + 890, + 616 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 640, + 617, + 656 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We introduce Dynamic Tetrahedra (DynTet), a novel hybrid representation for realistic and expressive talking heads. DynTet upgrades tetrahedral meshes from statics to dynamics with a new architecture, a canonical space and guidance from geometry prior. DynTet can efficiently generate high-resolution talking videos with realism and precise motion control beyond prior works. Our work may inspire future research in the direction of Dynamic Tetrahedra.", + "bbox": [ + 496, + 670, + 890, + 790 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements. This paper is supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDA27000000), the National key research and development program of China (2021YFA1000403), the National Natural Science Foundation of China (Nos. U23B2012, 11991022) and the Fundamental Research Funds for the Central Universities (E3E41904).", + "bbox": [ + 496, + 795, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "5216", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] ShahRukh Athar. Rignerf: Fully controllable neural 3d portraits. In CVPR, 2022. 1, 2", + "[2] Tadas Baltrusaitis, Amir Zadeh, Yao Chong Lim, and Louis-Philippe Morency. Openface 2.0: Facial behavior analysis toolkit. In FG, 2018. 7", + "[3] Volker Blanz and Thomas Vetter. 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ACM TOG, 2020. 1, 2" + ], + "bbox": [ + 78, + 90, + 470, + 797 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "5219", + "bbox": [ + 482, + 944, + 516, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Dynamic Tetrahedra for High-Quality Talking Head Synthesis/53f925b0-849e-40c5-8f29-bb11fe50f467_model.json b/2024/Learning Dynamic Tetrahedra for High-Quality Talking Head Synthesis/53f925b0-849e-40c5-8f29-bb11fe50f467_model.json new file mode 100644 index 0000000000000000000000000000000000000000..6e43ddbb41b0b8751baffe141996b0c35ed14be3 --- /dev/null +++ b/2024/Learning Dynamic Tetrahedra for High-Quality Talking Head Synthesis/53f925b0-849e-40c5-8f29-bb11fe50f467_model.json @@ -0,0 +1,2499 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.122, + 0.131, + 0.85, + 0.154 + ], + "angle": 0, + "content": "Learning Dynamic Tetrahedra for High-Quality Talking Head Synthesis" + }, + { + "type": "text", + "bbox": [ + 0.163, + 0.18, + 0.806, + 0.234 + ], + "angle": 0, + "content": "Zicheng Zhang\\(^{1}\\) Ruobing Zheng\\(^{2}\\) Bonan Li\\(^{1}\\) Congying Han\\(^{1*}\\) Tianqi Li\\(^{2}\\) Meng Wang\\(^{2}\\) Tiande Guo\\(^{1}\\) Jingdong Chen\\(^{2}\\) Ziwen Liu\\(^{1}\\) Ming Yang\\(^{2}\\) \\(^{1}\\)University of Chinese Academy of Sciences \\(^{2}\\)Ant Group" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.302, + 0.474, + 0.742 + ], + "angle": 0, + "content": "Recent works in implicit representations, such as Neural Radiance Fields (NeRF), have advanced the generation of realistic and animatable head avatars from video sequences. These implicit methods are still confronted by visual artifacts and jitters, since the lack of explicit geometric constraints poses a fundamental challenge in accurately modeling complex facial deformations. In this paper, we introduce Dynamic Tetrahedra (DynTet), a novel hybrid representation that encodes explicit dynamic meshes by neural networks to ensure geometric consistency across various motions and viewpoints. DynTet is parameterized by the coordinate-based networks which learn signed distance, deformation, and material texture, anchoring the training data into a predefined tetrahedra grid. Leveraging Marching Tetrahedra, DynTet efficiently decodes textured meshes with a consistent topology, enabling fast rendering through a differentiable rasterizer and supervision via a pixel loss. To enhance training efficiency, we incorporate classical 3D Morphable Models to facilitate geometry learning and define a canonical space for simplifying texture learning. These advantages are readily achievable owing to the effective geometric representation employed in DynTet. Compared with prior works, DynTet demonstrates significant improvements in fidelity, lip synchronization, and real-time performance according to various metrics. Beyond producing stable and visually appealing synthesis videos, our method also outputs the dynamic meshes which is promising to enable many emerging applications. Code is available at https://github.com/zhangzc21/DynTet." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.772, + 0.21, + 0.789 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.798, + 0.47, + 0.875 + ], + "angle": 0, + "content": "Talking head synthesis is a long-standing task with a wide range of applications, such as digital humans, metaverse and filmmaking. The set up of this task can be roughly categorized to two lines: 1) learning from a large-scale dataset to drive arbitrary portrait images by the motion sig-" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.27, + 0.892, + 0.362 + ], + "angle": 0, + "content": "nal [7, 40, 41, 50, 62, 70, 77, 78]; and 2) building a personalized animatable head model from a several-minute video of a specific person [23, 31, 37, 53, 60, 61, 64, 67, 74]. We concentrate on the latter one, since it generally delivers high-quality synthesis results with intricate details and 3D naturalness, suitable for professional scenarios." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.365, + 0.893, + 0.622 + ], + "angle": 0, + "content": "Building such an exquisite talking head avatar from video data poses challenges in faithful appearance, motion control, as well as low running cost. One line of methods [14, 19, 20, 28, 30, 61, 67] explicitly rely on 3D Morphable Models (3DMM) [3] to reconstruct and animate human faces by estimating the person-specific parameters. While these methods allow for efficient rendering and dynamic deformation, the fixed face topology makes them often fall short in generating characteristic details, e.g., hairstyle, glasses, and inner mouth. Recently, neural implicit representations, especially Neural Radiance Fields (NeRF) [43], provide a new way to realize faithful generation. Some seminal work [16, 23, 37, 53, 64] learn a direct mapping from the control signal to the talking head, meanwhile the efficient neural representations like voxel grid [15, 34, 57] and hash encoding [44] have been introduced to improve training and inference speed." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.625, + 0.895, + 0.867 + ], + "angle": 0, + "content": "Despite the expressive capabilities, these implicit methods still need to improve many subtle issues in realism, e.g., head jitters, motionless mouths, and occasional artifacts. Researchers have discussed these issues from various aspects, e.g., introducing a canonical space for easier appearance learning [1, 49], developing compact models for more efficient training [31, 60], and using expressive driving conditions for better control [64, 65], against the naive baseline of NeRF. Essentially, the implicit definition for 3D objects complicates the analytical alternation of the underlying object geometry, leading to ineffective disentanglement of static appearance and motion from dynamic data, as opposed to the explicit meshes and vertex displacements for 3DMM. In viewing of this, it is appealing to incorporate the expressivity of implicit methods with an effective geometric control to take advantage of both lines of works." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.895, + 0.902 + ], + "angle": 0, + "content": "We introduce Dynamic Tetrahedra (DynTet), a novel hybrid approach that encodes dynamic meshes within neural" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.888, + 0.221, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5209" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.258 + ], + "angle": 0, + "content": "networks to assist explicit deformation. In essence, DynTet employs neural networks to predict attributes of underlying surfaces, from which explicit meshes can be extracted to fast render images with a differentiable rasterizer. On one hand, distinguished from implicit methods, the explicit geometry enables DynTet to learn a consistent 3D model across frames and directly express deformation as vertex displacement, thus DynTet is convenient to model the dynamics of talking head. On the other hand, unlike 3DMM with a preset topology, DynTet end-to-end learns personalized meshes and texture suitable for the given video." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.26, + 0.473, + 0.684 + ], + "angle": 0, + "content": "Technically, the proposed DynTex is inspired by recent advancements in tetrahedral techniques [17], originally developed for 3D reconstruction [45] and synthesis [18, 54]. The key insight is a parameterized tetrahedral grid: Coordinate-based networks are used to learn the signed distance field (SDF) and refinement for the grid, then the meshes are subsequently decoded through the Marching Tetrahedra algorithm. Since these prior methods [17, 18, 45, 54] primarily work for static scenes, they can hardly render images with deformation, nor keep the mesh topology under different conditions [18]. This also largely prevents the parallelized rendering and training processes. In contrast, we redesign the framework that exclusively determines the mesh topology with SDF, while a new branch controls the geometric variations with deformation signals. We also estimate the elastic score of each vertex to specify the rigid (e.g., forehead) and non-rigid regions (e.g., mouth) of the head, so as to achieve precise deformations in local regions while maintaining stability in other parts. These designs ensure the topological consistency and expressivity across all decoded meshes, enabling a customized dynamic mesh beyond 3DMM. To improve training efficiency, we introduce geometry losses that supervise shape and motion using the 3DMM priors. This replenishes the limited depth information available in frontal talking videos. Moreover, we establish an interpretable canonical space for the dynamic mesh, reducing the complexity of texture learning. In summary, our contributions include:" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.686, + 0.47, + 0.746 + ], + "angle": 0, + "content": "(1). We propose DynTet, a novel hybrid representation that encodes dynamic head meshes in neural networks, where the explicit geometry delineated by tetrahedra facilitates appearance and motion learning." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.747, + 0.47, + 0.807 + ], + "angle": 0, + "content": "(2). This is the first work that successfully extends the static tetrahedral representation to dynamic head avatars by a new elaborated architecture, a canonical space, and 3DMM guidance for modeling dynamic meshes." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.808, + 0.47, + 0.853 + ], + "angle": 0, + "content": "(3). DynTet presents evident advantages in terms of fidelity, lip-sync precision, stability and runtime by thorough evaluation compared with prior works." + }, + { + "type": "list", + "bbox": [ + 0.077, + 0.686, + 0.47, + 0.853 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "The learned dynamic head meshes are promising together with existing 3D assets or AR/VR techniques for emerging applications such as human avatar and the meta" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.122 + ], + "angle": 0, + "content": "verse, which may inspire further study on the hybrid representation for dynamic 3D objects." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.151, + 0.642, + 0.167 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.182, + 0.895, + 0.545 + ], + "angle": 0, + "content": "Talking head synthesis. Most existing methods for talking head synthesis can be classified into three categories in terms of the modeling approaches. 2D-based methods [50, 68, 69, 76, 78] utilized generative models [21, 26, 29] as renderers to produce photorealistic portraits. While, these methods often fall short in achieving 3D naturalness and consistent pose control due to the absence of an explicit 3D model. 3DMM-based methods [14, 19, 20, 28, 30, 61, 67] leveraged 3D face knowledge to drive facial expression, resulting in quite natural talking style. As a trade-off, due to the lack of complete head topology they cannot guarantee consistency or fidelity beyond the facial region such as hair and inner mouth. Neural head avatar [22, 74, 75] has emerged as an attractive way for automatically creating 3D facial models. While earlier approaches [51, 66] required detailed scanning data, NeRFs [5, 43, 49] offer a solution to learn models from video clips, driven by the factors like 3DMM coefficients [16], audio feature [23], or facial landmarks [65]. Several recent works have enhanced control effects [1, 37, 64], system efficiency [31, 60] and few-shot training [32, 53]. Despite great progress, neural avatars still face challenges in realism and plausible motion, not to mention that NeRF rendering is computationally expensive when generating high-resolution images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.554, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Neural 3D representation. Neural implicit functions are emerging as an effective representation of 3D object [35, 42, 43, 48, 55] using coordinate-based MLPs [44, 56, 59]. While prior methods [42, 48] required 3D supervision, several recent works [33, 36, 43, 47] demonstrated differentiable rendering for training directly from images. Meanwhile, NeRF [43] and followups [15, 44, 57, 73] performed volume rendering [27] on a continuous field for density and color, achieving impressive results for multi-view synthesis. As density is ambiguous to depict geometric details [63], they cannot explicitly edit shape or extract a high-quality surface with Marching Cubes [39], which makes it challenging in formulating deformation for dynamic scenes. Recent works [17, 54] proposed to convert deformable tetrahedral grid into surface meshes via the differentiable Marching Tetrahedral algorithm [11], where the SDF values are implicitly learned. The following methods [18, 45] further extended to jointly learn geometry and texture from image data. They can render photorealistic images competitive with NeRF in real-time. However, as these methods only work for static scenes, they cannot learn dynamics for modeling head avatars. We present an original effort to address this issue to learn dynamic tetrahedral meshes." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.517, + 0.957 + ], + "angle": 0, + "content": "5210" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.078, + 0.09, + 0.218, + 0.106 + ], + "angle": 0, + "content": "3. Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.119, + 0.47, + 0.164 + ], + "angle": 0, + "content": "We provide some background concepts and notations. At first, we define operations between sets as element-wise operations, and functions are mapped element-wise as well." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.168, + 0.473, + 0.379 + ], + "angle": 0, + "content": "Tetrahedral meshes have been studied in deep learning [17, 54] as a hybrid representation for 3D shape modeling. Consider an object lying in a unit cube, a tetrahedral grid denoted as \\((\\mathbf{V}_{tet},\\mathbf{T}_{tet})\\) is pre-defined to tetrahedralize the cube into \\(r^3\\) resolution. Each tetrahedron \\(T_{k}\\in \\mathbf{T}_{tet}\\) is defined by four vertices \\(\\{\\mathbf{v}_{a_k},\\mathbf{v}_{b_k},\\mathbf{v}_{c_k},\\mathbf{v}_{d_k}\\}\\), where \\(K\\) is the total number of tetrahedra. Additionally, each vertex \\(\\mathbf{v}_i\\) contains a learnable SDF value \\(s_i\\in \\mathbb{R}\\) to express the distance away from the underlying surface, and a small offset \\(\\Delta \\mathbf{v}_i\\in [-\\frac{1}{r},\\frac{1}{r}]^3\\) from its initial coordinates to refine the grid as \\(\\mathbf{v}_i' = \\mathbf{v}_i + \\Delta \\mathbf{v}_i\\). We let \\(S = \\{s_i\\}_{i = 1}^K\\) and \\(\\Delta \\mathbf{V} = \\{\\Delta \\mathbf{v}_i\\}_{i = 1}^K\\). Notably, the surface shape within the tetrahedral grid is primarily determined by the SDF values \\(S\\) as \\(\\Delta \\mathbf{V}\\) is confined within the resolution boundaries." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.382, + 0.473, + 0.534 + ], + "angle": 0, + "content": "Marching Tetrahedra \\((MT)\\) is an iso-surface extraction algorithm [11] to generate triangular meshes from tetrahedral meshes. Given SDF values \\(\\{s_a, s_b, s_c, s_d\\}\\) of a tetrahedron, \\(MT\\) determines the surface topology inside the tetrahedron based on the signs of these values, where the \\(2^4\\) configurations in total fall into 3 unique cases after considering rotation symmetry [54]. A simplified 2D example can be found in Figure 1. Once the topology is identified, a new vertex denoted as \\(\\mathbf{v}_{ab}\\) by example, is located at the zero crossings of linear interpolation along the tetrahedral edges:" + }, + { + "type": "equation", + "bbox": [ + 0.138, + 0.538, + 0.47, + 0.568 + ], + "angle": 0, + "content": "\\[\n\\operatorname {l e r p} \\left(\\mathbf {v} _ {a}, \\mathbf {v} _ {b}, s _ {a}, s _ {b}\\right) = \\frac {s _ {a} \\cdot \\mathbf {v} _ {a} - s _ {b} \\cdot \\mathbf {v} _ {b}}{s _ {a} - s _ {b}}, \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.571, + 0.47, + 0.662 + ], + "angle": 0, + "content": "the same for other vertices. Note that this equation is evaluated only when signs differ \\((\\mathrm{sign}(s_a)\\neq \\mathrm{sign}(s_b))\\) to prevent singularity. Leveraging \\(MT\\) on the deformed tetrahedral grid \\((\\mathbf{V}_{tet} + \\Delta \\mathbf{V},\\mathbf{T}_{tet})\\), the triangular surface of the encoded object can be acquired in a differentiable manner. We omit constant symbols and represent this process as" + }, + { + "type": "equation", + "bbox": [ + 0.167, + 0.667, + 0.469, + 0.684 + ], + "angle": 0, + "content": "\\[\n\\mathbf {V} _ {t r i}, \\mathbf {T} _ {t r i} = \\operatorname {M a r T e t} (\\mathcal {S}, \\Delta \\mathbf {V}), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.469, + 0.719 + ], + "angle": 0, + "content": "where \\(\\mathbf{V}_{tri}\\) and \\(\\mathbf{T}_{tri}\\) are the sets of vertices and connectivity of the triangular meshes, respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.723, + 0.47, + 0.754 + ], + "angle": 0, + "content": "3D Morphable Models provide generic parametric models [3] for synthesizing face shapes, usually expressed as" + }, + { + "type": "equation", + "bbox": [ + 0.143, + 0.777, + 0.469, + 0.795 + ], + "angle": 0, + "content": "\\[\n\\mathbf {V} _ {3 d m m} = \\bar {\\mathbf {V}} _ {3 d m m} + \\mathbf {U} _ {i d} \\gamma + \\mathbf {U} _ {e x p} \\boldsymbol {\\alpha}. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Here \\(\\bar{\\mathbf{V}}_{3dmm}\\) denotes a mean shape, \\(\\mathbf{U}_{id}\\) and \\(\\mathbf{U}_{exp}\\) are the matrices of basis vectors in the identity and expression space, respectively. \\(\\gamma\\) and \\(\\alpha\\) are coefficients for the identity and expression, allowing for a tractable control over facial variations. The parameter \\(\\alpha\\) has been served as a versatile representation for driving facial deformation [13]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.09, + 0.636, + 0.108 + ], + "angle": 0, + "content": "4. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.117, + 0.894, + 0.314 + ], + "angle": 0, + "content": "In this section, we introduce a framework called Dynamic Tetrahedra (DynTet) to rapidly learn 3D head avatars from short video sequences, and enable real-time rendering of high-quality talking heads. Generally, DynTet upgrades recent tetrahedral representation [17, 18, 45] tailored for dynamic head modeling. As shown in Figure 1, neural networks are trained to encode head shapes within a tetrahedral grid [54], and then the Marching Tetrahedra (MT) [11] decodes the meshes for photorealistic rasterization rendering. In the following, we delineate the talking head task through the lens of tetrahedral representation (Sec.4.1), and elucidate our improvements in the geometry model (Sec.4.2), rendering process (Sec.4.3), and training losses (Sec.4.4)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.326, + 0.682, + 0.34 + ], + "angle": 0, + "content": "4.1. Problem statement" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.35, + 0.894, + 0.428 + ], + "angle": 0, + "content": "Given a sequence of head images \\(\\{\\mathbf{I}_i\\}_{i=1}^n\\), we aim to reenact the specific head driven by motion signals, which typically includes camera parameters \\(\\{\\mathbf{P}_i\\}_{i=1}^n\\) for rigid motion, and talking signals which we represent using 3DMM expression coefficients \\(\\{\\alpha_i\\}_{i=1}^n\\) for non-rigid facial expressions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.438, + 0.892, + 0.604 + ], + "angle": 0, + "content": "**Formulation.** Drawing inspiration from the seminal work of [54], which applied tetrahedral meshes for multi-view reconstruction, we propose a basic paradigm for talking head modeling: (1) A geometry mapping \\( \\mathbf{F} \\) first predicts \\( S \\) and \\( \\Delta \\mathbf{V} \\) from \\( \\alpha \\) and \\( \\mathbf{V}_{tet} \\). (2) The outputs from \\( \\mathbf{F} \\) are processed based on Eq. (2) to obtain the triangular mesh, which are then rasterized given camera pose \\( \\mathbf{P} \\) to get the coordinates of image pixels in the model space. (3) An appearance mapping \\( \\mathbf{G} \\) predicts the materials, which is incorporated with a lighting model \\( L \\) for the physically-based rendering (PBR) [4]. We summarize the overall process as" + }, + { + "type": "equation", + "bbox": [ + 0.558, + 0.605, + 0.891, + 0.643 + ], + "angle": 0, + "content": "\\[\n\\min _ {\\boldsymbol {F}, \\boldsymbol {G}, \\boldsymbol {L}} \\frac {1}{n} \\sum_ {i = 1} ^ {n} L o s s (\\hat {\\mathbf {I}} _ {i}, \\mathbf {I} _ {i}) \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.555, + 0.646, + 0.838, + 0.662 + ], + "angle": 0, + "content": "where \\(\\hat{\\mathbf{I}}_i = \\mathrm{Rendering}(\\pmb {F},\\pmb {G},\\pmb {L},\\pmb {\\alpha}_i,\\mathbf{P}_i)\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.663, + 0.892, + 0.693 + ], + "angle": 0, + "content": "Herein, Rendering denotes the PBR procedure, and the loss function comprises a set of constraints on the predictions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Challenges. Prior works [17, 18, 54] commonly parameterize \\(\\pmb{F}\\) using a neural network \\(f\\) to predict SDF values and relative offsets, i.e., \\(\\mathcal{S},\\Delta \\mathbf{V} = f(\\mathbf{V}_{tet})\\), while introducing the talking signal \\(\\alpha\\) to \\(f\\) as a condition will bring several problems. First, once SDF values vary along with the conditions, it is difficult to learn the intricate deformation of the facial area with a simple MLP. Second, modern GPUs do not support parallelization for meshes with a variable topology, resulting in inefficient training and running processes. Lastly, previous approaches were designed for \\(360^{\\circ}\\) data, while our training data only includes frontal head images. Consequently, this inaccurate estimation of geometry leads to evident artifacts in the rendered videos." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.514, + 0.957 + ], + "angle": 0, + "content": "5211" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.09, + 0.891, + 0.288 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.3, + 0.896, + 0.373 + ], + "angle": 0, + "content": "Figure 1. Illustration of the proposed DynTet for modeling a talking head. Left panel: The top branch predicts topology-related information, including SDF values \\( s \\) and elastic scores. The bottom branch, conditioned by talking signals, predicts the offset vectors scaled by the elastic scores to yield deformation vectors \\( \\Delta \\mathbf{v} \\) for driving the tetrahedral grid. Then, the Marching Tetrahedra (MT) algorithm decodes the meshes. Right panel: The pixel coordinates are projected into a canonical space. Then the physically-based materials and lighting are sampled for rendering images." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.385, + 0.269, + 0.402 + ], + "angle": 0, + "content": "4.2. Geometry modeling" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.408, + 0.471, + 0.53 + ], + "angle": 0, + "content": "To address the mentioned challenges, we initially disentangle topology and geometry from head shapes within the tetrahedra grid, allowing for generating dynamic meshes with a consistent topology. Furthermore, we enhance the tetrahedral attributes by introducing a novel elastic score, facilitating precise control over deformation. These improvements are incorporated by modifying the internal structure of the geometry mapping as" + }, + { + "type": "equation", + "bbox": [ + 0.099, + 0.54, + 0.47, + 0.564 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {F}: \\mathbf {V} _ {t e t}, \\boldsymbol {\\alpha} \\rightarrow \\mathcal {S}, \\Delta \\mathbf {V} \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.1, + 0.559, + 0.429, + 0.575 + ], + "angle": 0, + "content": "where \\(\\mathcal{S},\\mathcal{E} = f_1(\\mathbf{V}_{tet}),\\Delta \\mathbf{V} = \\mathcal{E}\\cdot f_2(\\mathbf{V}_{tet},\\boldsymbol {\\alpha})\\)" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.584, + 0.47, + 0.616 + ], + "angle": 0, + "content": "Here, \\( f_{1} \\) and \\( f_{2} \\) are coordinate-based MLPs, while \\( \\mathcal{E} \\coloneqq [f_1(\\mathbf{V}_{tet})]_e \\) represents the set of non-negative elastic scores." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.62, + 0.47, + 0.711 + ], + "angle": 0, + "content": "Shape representation. Ideal face models exhibit topological invariance regardless of deformation. While implicit SDF representations present challenges in fulfilling this property, it is clear for explicit meshes like 3DMM [3] to maintain the number of vertices and their relationship. By employing Eq. (1) within \\(MT\\) algorithm, we have" + }, + { + "type": "equation", + "bbox": [ + 0.086, + 0.72, + 0.469, + 0.757 + ], + "angle": 0, + "content": "\\[\n\\mathbf {v} _ {a b} ^ {\\prime} = \\underbrace {\\operatorname {l e r p} \\left(\\mathbf {v} _ {a} , \\mathbf {v} _ {b} , s _ {a} , s _ {b}\\right)} _ {\\text {t o p o l o g y a n d i d e n t i t y}} + \\underbrace {\\operatorname {l e r p} \\left(\\Delta \\mathbf {v} _ {a} , \\Delta \\mathbf {v} _ {b} , s _ {a} , s _ {b}\\right)} _ {\\text {g e o m e t r y a n d e x p r e s s i o n}}. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Given that vertices \\(\\mathbf{v}_a\\) and \\(\\mathbf{v}_b\\) are pre-defined in the tetrahedral grid, the first term is just affected by the SDF values. Hence, our design in Eq.(5), which segregates SDF from the talking signal, results in a topologically invariant mesh. Meanwhile, the second term indicates that the geometry of mesh explicitly relies on the tetrahedral grid offsets. Additionally, a comparison with Eq. (3) reveals that DynTet functions as a quasi-3DMM hybrid model, enabling additive changes to facial shapes driven by neural networks." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.385, + 0.895, + 0.598 + ], + "angle": 0, + "content": "Elastic estimation. Our design necessitates relaxing the range of \\(\\Delta \\mathbf{v}_i\\in [-\\frac{1}{r},\\frac{1}{r}]^3\\) to allow greater flexibility in geometric variations. However, this relaxation potentially leads to local jitters that significantly impact visual quality. We introduce an elastic scoring mechanism for each vertex within the tetrahedral grid to regulate deformation. These scores \\(\\mathcal{E}\\) are predicted by the neural network \\(f_{1}\\) to quantify the non-rigid properties across different regions of the human head. For instance, areas like the forehead and nose exhibit near-rigid behavior with minimal changes during talking, while regions like the mouth and eyes are more flexible and primarily contribute to deformations. In this way, the offset vectors are scaled using the elastic scores to determine the deformable vectors \\(\\Delta \\mathbf{V}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.603, + 0.895, + 0.651 + ], + "angle": 0, + "content": "Architecture details. As shown in Figure 1, we formulate neural networks \\( f_{1} \\) and \\( f_{2} \\) as a composition of regular lightweight MLPs and a frequency positional encoding [59]" + }, + { + "type": "equation", + "bbox": [ + 0.549, + 0.661, + 0.892, + 0.681 + ], + "angle": 0, + "content": "\\[\n\\gamma (\\mathbf {v}) = < \\left(\\sin \\left(2 ^ {l} \\pi \\mathbf {v}\\right), \\cos \\left(2 ^ {l} \\pi \\mathbf {v}\\right)\\right) > _ {l = 0} ^ {L - 1}. \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.686, + 0.894, + 0.792 + ], + "angle": 0, + "content": "We find that the simple frequency coding outperforms hash grid encoding [44] which tends to generate surfaces with significant noise. To maintain temporal consistency, we follow [41, 52] to represent the deformation of any timestamp by the window of adjacent 27 frames of expression coefficients, which are averaged into a 256-dimensional feature vector by a trainable convolutional encoder." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.801, + 0.671, + 0.818 + ], + "angle": 0, + "content": "4.3. Neural rendering" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.824, + 0.894, + 0.903 + ], + "angle": 0, + "content": "This procedure aims to automatically texture the triangular meshes \\((\\mathbf{V}_{tri},\\mathbf{T}_{tri})\\) extracted by \\(MT\\) algorithm, and generate photorealistic images \\(\\hat{\\mathbf{I}}\\) given camera pose \\(\\mathbf{P}\\) and talking signal \\(\\alpha\\). In the realm of deformable reconstruction [38, 38, 46, 49], the canonical or template model" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5212" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.183 + ], + "angle": 0, + "content": "serves an important role in reducing the complexity of texture parametrization. Thanks to the well-designed geometry model in DynTet, defining a canonical space becomes straightforward. We upgrade the vanilla rendering process by incorporating a canonical projection, thereby unifying both shading and lighting within a single space." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.187, + 0.471, + 0.248 + ], + "angle": 0, + "content": "Canonical projection. We propose the canonical projection CanProj to map the pixel coordinates \\(\\mathcal{C}_{2d}\\) from an arbitrary camera pose \\(\\mathbf{P}\\) into a canonical 3D space where the mean expression lies. This process is expressed as" + }, + { + "type": "equation", + "bbox": [ + 0.13, + 0.256, + 0.414, + 0.273 + ], + "angle": 0, + "content": "\\[\n\\bar {\\mathcal {C}} _ {3 d} = \\operatorname {C a n P r o j} \\left(\\mathcal {C} _ {2 d}, \\mathbf {V} _ {t r i}, \\mathbf {P}; \\bar {\\mathbf {V}} _ {t r i}, \\mathbf {T} _ {t r i}\\right),\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.133, + 0.276, + 0.469, + 0.292 + ], + "angle": 0, + "content": "where \\(\\bar{\\alpha} = \\Sigma_{i=1}^{n} \\alpha_{i} / n\\), (8)" + }, + { + "type": "text", + "bbox": [ + 0.133, + 0.295, + 0.413, + 0.311 + ], + "angle": 0, + "content": "and \\(\\bar{\\mathbf{V}}_{tri},\\mathbf{T}_{tri} = \\mathrm{MatTet}(\\pmb {F}(\\mathbf{V}_{tet},\\bar{\\alpha}))\\)" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.32, + 0.469, + 0.396 + ], + "angle": 0, + "content": "In practical implementation, CanProj can be executed readily using a modern mesh rasterizer to derive coordinates \\(\\mathcal{C}_{3d}\\) and 2D barycentric coordinates within \\((\\mathbf{V}_{tri},\\mathbf{T}_{tri})\\). Then, \\(\\bar{\\mathcal{C}}_{3d}\\) positioned in the canonical space, is computed through barycentric interpolation over \\((\\bar{\\mathbf{V}}_{tri},\\mathbf{T}_{tri})\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.401, + 0.469, + 0.522 + ], + "angle": 0, + "content": "Appearance model. We follow previous work [4, 45] to adopt a physically-base material model, which allows easy integration of 3D assets within existing engines. To parameterize the appearance mapping \\( G \\), we employ a coordinate-based neural network comprising a hash grid encoder [44] for querying spatial features and a lightweight MLP for predicting materials. This network takes the projected coordinates and talking signal as inputs:" + }, + { + "type": "equation", + "bbox": [ + 0.19, + 0.532, + 0.469, + 0.547 + ], + "angle": 0, + "content": "\\[\n\\mathcal {K} _ {d}, \\mathcal {K} _ {\\text {o r m}} = \\boldsymbol {G} (\\bar {\\mathcal {C}} _ {3 d}, \\boldsymbol {\\alpha}). \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.557, + 0.469, + 0.648 + ], + "angle": 0, + "content": "Here, \\(\\mathcal{K}_d\\) comprises three-channel diffuse albedo, and \\(\\mathcal{K}_{orm}\\) is the set of occupancy \\(k_{o}\\), roughness \\(k_{r}\\), and metalness factors \\(k_{m}\\) for the GGX normal distribution function [9]. Unlike prior works, we do not predict normals, but instead compute them directly using the triangular mesh in the model space, which yields similar results." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.652, + 0.469, + 0.714 + ], + "angle": 0, + "content": "Lighting model. We leverage the image based lighting model, where the environment light is given by a trainable mapping \\( \\pmb{L} \\). For each position \\( \\mathbf{v} \\in \\mathcal{C}_{3d} \\) with a normal vector \\( \\mathbf{n} \\), the color along direction \\( \\omega_{o} \\) is computed by" + }, + { + "type": "equation", + "bbox": [ + 0.163, + 0.723, + 0.469, + 0.739 + ], + "angle": 0, + "content": "\\[\nL (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}) = L _ {d} (\\mathbf {v}) + L _ {s} (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}), \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.749, + 0.469, + 0.795 + ], + "angle": 0, + "content": "where \\(L_{d}\\) is the diffuse intensity and \\(L_{s}\\) is the specular intensity. Consider a hemisphere with the incident direction \\(\\Omega = \\{\\pmb {\\omega}_i:\\pmb {\\omega}_i^T\\mathbf{n}\\geq 0\\}\\), the first diffuse term is computed by" + }, + { + "type": "equation", + "bbox": [ + 0.11, + 0.805, + 0.469, + 0.833 + ], + "angle": 0, + "content": "\\[\nL _ {d} (\\mathbf {v}) = \\left(1 - k _ {m}\\right) \\boldsymbol {k} _ {d} \\int_ {\\Omega} \\boldsymbol {L} _ {i} \\left(\\mathbf {v}, \\boldsymbol {\\omega} _ {i}\\right) \\left(\\boldsymbol {\\omega} _ {i} ^ {T} \\mathbf {n}\\right) \\mathrm {d} \\boldsymbol {\\omega} _ {i}. \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.837, + 0.469, + 0.868 + ], + "angle": 0, + "content": "And the second term is based on Cook-Torrance microfacet specular shading mode model [9] \\(r(\\omega_o,\\omega_i)\\) to compute" + }, + { + "type": "equation", + "bbox": [ + 0.09, + 0.876, + 0.469, + 0.905 + ], + "angle": 0, + "content": "\\[\nL _ {s} (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}) = \\boldsymbol {k} _ {s} \\int_ {\\Omega} r \\left(\\boldsymbol {\\omega} _ {o}, \\boldsymbol {\\omega} _ {i}\\right) \\boldsymbol {L} _ {i} (\\mathbf {v}, \\boldsymbol {\\omega} _ {i}) \\left(\\boldsymbol {\\omega} _ {i} ^ {T} \\mathbf {n}\\right) \\mathrm {d} \\boldsymbol {\\omega} _ {i}, \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.183 + ], + "angle": 0, + "content": "where the specular color \\( \\pmb{k}_s = (1 - k_m) \\cdot 0.04 + k_m \\pmb{k}_d \\). Following [45], we parameterize \\( \\pmb{L} \\) with a cube map with resolution \\( 6 \\times 512 \\times 512 \\), and the calculate the hemisphere integration by the split-sum method [25]. By aggregating the rendered pixel colors along the camera pose, we obtain the rendered image \\( \\hat{\\mathbf{I}} = \\{k_o \\cdot L(\\mathbf{v}, \\pmb{\\omega}_o) | \\mathbf{v} \\in \\mathcal{C}_{3d}\\} \\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.19, + 0.651, + 0.206 + ], + "angle": 0, + "content": "4.4. Training losses" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.214, + 0.892, + 0.29 + ], + "angle": 0, + "content": "Thanks to its hybrid representation, DynTet possesses an interpretable SDF space and a cost-efficient rendering procedure. This unique combination allows us to supervise its training in both image and geometry space, facilitating the estimation of reasonable 3D models from frontal images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.294, + 0.892, + 0.37 + ], + "angle": 0, + "content": "Image supervision. Given an image \\(\\mathbf{I}\\) and its prediction \\(\\hat{\\mathbf{I}}\\), we train DynTet with the MSE loss for pixel-level reconstruction, and apply the overall LPIPS loss [71] for enhancing sharp details [31]. Besides, we find silhouette loss is important to provide shape guidance. The image loss is" + }, + { + "type": "equation", + "bbox": [ + 0.512, + 0.376, + 0.892, + 0.393 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {i m g} = \\mathcal {L} _ {m s e} (\\hat {\\mathbf {I}}, \\mathbf {I}) + \\mathcal {L} _ {m s e} (\\hat {\\mathbf {I}} _ {o}, \\mathbf {I} _ {o}) + \\lambda_ {1} \\mathcal {L} _ {L P I P S} (\\hat {\\mathbf {I}}, \\mathbf {I}), \\tag {13}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.399, + 0.891, + 0.445 + ], + "angle": 0, + "content": "where \\(\\hat{\\mathbf{I}}_o\\) and \\(\\mathbf{I}_o\\) denote the binary masks of head regions. We combine the head, background and torso together to train in practice to prevent noise around the facial contours." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.45, + 0.892, + 0.555 + ], + "angle": 0, + "content": "3DMM supervision. Frontal head views in talking videos often lack adequate depth information, resulting in flawed geometry estimation and artifacts in synthesized profile face. To counter this, we leverage 3DMM [3] as a geometry prior to mitigate these issues in the SDF space. We introduce two key losses to incorporate 3DMM. First, the normal distance loss \\(\\mathcal{L}_{ndl}\\) constrains the canonical model:" + }, + { + "type": "equation", + "bbox": [ + 0.516, + 0.562, + 0.891, + 0.578 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {n d l} = \\mathbb {E} _ {s \\sim U (- a, a)} \\| f _ {1} \\left(\\mathbf {V} _ {3 d m m} ^ {\\bar {\\alpha}} + s \\cdot \\mathbf {N} _ {3 d m m} ^ {\\bar {\\alpha}}\\right) - s \\| _ {2} ^ {2}, \\tag {14}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.585, + 0.892, + 0.691 + ], + "angle": 0, + "content": "where \\(\\mathbf{V}_{3dmm}^{\\bar{\\alpha}}\\) and \\(\\mathbf{N}_{3dmm}^{\\bar{\\alpha}}\\) represent 3DMM vertices and normal vectors generated by coefficient \\(\\bar{\\alpha}\\), while \\(a\\) is a small value which we set to 0.1. \\(\\mathcal{L}_{ndl}\\) injects facial prior into \\(f_{1}\\), affecting the SDF values around 3DMM surface. Consequently, it avoids excessive restraint compared to full-space supervision [48], enabling adaptive learning in other regions. The second facial deformation loss is expressed as" + }, + { + "type": "equation", + "bbox": [ + 0.508, + 0.712, + 0.891, + 0.729 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {f d l} = \\left\\| \\left[ f _ {1} \\left(\\mathbf {V} _ {3 d m m}\\right) \\right] _ {e} f _ {2} \\left(\\mathbf {V} _ {3 d m m}, \\boldsymbol {\\alpha}\\right) - \\mathbf {U} _ {e x p} (\\boldsymbol {\\alpha} - \\bar {\\boldsymbol {\\alpha}}) \\right\\| _ {2} ^ {2}. \\tag {15}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.736, + 0.891, + 0.796 + ], + "angle": 0, + "content": "This loss helps the tetrahedral grid to mimic the 3DMM deformation. Although these losses target 3DMM vertices, the tetrahedral vertices are appropriately constrained due to their spatial density covering the 3DMM vertices." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.801, + 0.892, + 0.877 + ], + "angle": 0, + "content": "Loss function. We introduce a regularization term for the elastic score, denoted as \\(\\mathcal{R}_{es} = \\| [f_1(\\mathbf{V}_{3dmm})]_e\\| _2^2\\), to reinforce the rigid property. We incorporate the weighted combination of the above constraints as follows to formulate the loss function described in Eq. (4)" + }, + { + "type": "equation", + "bbox": [ + 0.532, + 0.886, + 0.891, + 0.902 + ], + "angle": 0, + "content": "\\[\nL o s s = \\mathcal {L} _ {i m g} + \\lambda_ {2} \\mathcal {L} _ {n d l} + \\lambda_ {3} \\mathcal {L} _ {f d l} + \\lambda_ {4} \\mathcal {R} _ {e s}. \\tag {16}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5213" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.092, + 0.498, + 0.471 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.092, + 0.887, + 0.47 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.486, + 0.895, + 0.529 + ], + "angle": 0, + "content": "Figure 2. Qualitative comparison of DynTet with the prior methods [31, 50, 60, 77]. Some representative defects are marked with red arrows, around which the generated eyes, mouths or wrinkles highlight discrepancies with real ones. The right panel presents the details of the mouth and eye area. The results show the superior realism and motion accuracy achieved by DynTet compared to existing methods." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.542, + 0.202, + 0.559 + ], + "angle": 0, + "content": "5. Experiment" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.568, + 0.281, + 0.584 + ], + "angle": 0, + "content": "5.1. Experimental settings" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.592, + 0.47, + 0.759 + ], + "angle": 0, + "content": "Dataset and pre-processing. For a fair comparison, we follow recent works [23, 31, 53] to conduct experiments on a publicly-released video dataset, which includes four high-definition talking videos with an average length of about 6500 frames at 25 FPS. Each raw video is cropped and resized to \\(512 \\times 512\\), except for the Obama data with the resolution \\(448 \\times 448\\). Each video is divided into training and test sets at a ratio of 10:1. We ensure strict alignment with the pre-processing steps outlined in AD-NeRF [23]. In order to extract the 3DMM coefficients efficiently, we utilize a pre-trained model from Deng et al. [10]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.769, + 0.47, + 0.875 + ], + "angle": 0, + "content": "Implementation details. We implement DynTet based on the code of Nvdiffrec1 [45] for differentiable Marching Tetrahedra and rasterization. We use a tetrahedral grid with a resolution of \\(128^3\\) [12], which is a commonly used setting [18, 45]. For the MLPs, we equip each one with ReLU-Linear layers. The geometry model utilizes a frequency positional encoder [59] with \\(L = 6\\) and a 3-layer MLP with" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.543, + 0.892, + 0.68 + ], + "angle": 0, + "content": "128 middle neurons. Additionally, a 4-layer convolutional encoder [52] is used for the 3DMM coefficients. The appearance model consists of a 5-layer MLP with 256 middle neurons. During training, we perform 20,000 iterations with a batch size of 4. We employ the Adam optimizer with an initial learning rate of \\(1 \\times 10^{-3}\\), which exponentially decayed to \\(1 \\times 10^{-5}\\). The default hyperparameters are \\(\\lambda_{1} = 0.1\\), \\(\\lambda_{2} = 100\\), \\(\\lambda_{3} = 100\\), and \\(\\lambda_{4} = 100\\). All experiments are conducted on a single NVIDIA Tesla V100." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.686, + 0.892, + 0.792 + ], + "angle": 0, + "content": "Comparison baselines. We compare our method with several recent representative one-shot and person-specific models, including Wav2Lip [50], PC-AVS [77], NVP [62], SynObama [58], SadTalker [72]. In addition, we also compare our method with three end-to-end NeRF-based models: ADNeRF [23], RAD-NeRF [60] and ER-NeRF [31]. All these methods are implemented with their official code." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.802, + 0.689, + 0.818 + ], + "angle": 0, + "content": "5.2. Quantitative results" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Comparison settings. We follow recent works to organize our comparisons into two settings: 1) Self-driven head reconstruction setting, in which we train a model for each video clip and evaluate the reconstruction quality on its respective test set. 2) Cross-driven lip synchronization set-" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.38, + 0.9 + ], + "angle": 0, + "content": "1https://github.com/NVlabs/nvdiffrec" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5214" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.085, + 0.089, + 0.891, + 0.212 + ], + "angle": 0, + "content": "
MethodsPSNR ↑LPIPS ↓FID ↓CSIM ↑LMDm ↓LMDe ↓AUE ↓Sync ↑TimeFPS
Ground Truth∞001.0000007.899--
Wav2Lip [50]31.150.073020.700.9703.0722.1472.0598.256-20
PC-AVS [77]22.060.134547.530.8022.4963.6094.2838.540-32
AD-NeRF [23]30.410.079914.920.9264.3172.4054.3745.01518h0.08
RAD-NeRF [60]31.510.067511.140.9513.0062.2853.3174.4095h23
ER-NeRF† [31]32.500.03456.440.9602.9242.2202.7734.9442h23
DynTet35.150.061912.230.9752.4182.1371.8337.4072h46
DynTet†34.840.02234.720.9782.2842.1291.7127.6463h46
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.099, + 0.211, + 0.28, + 0.223 + ], + "angle": 0, + "content": "\\(\\dagger\\) supervised by overall LPIPS [71]." + }, + { + "type": "table_footnote", + "bbox": [ + 0.077, + 0.224, + 0.893, + 0.253 + ], + "angle": 0, + "content": "Table 1. Quantitative results of the self-driven head reconstruction. The best and second results are in bold and underline. Wav2Lip takes ground truth as input, thus its PSNR and LPIPS values are biased. The FPS values are tested on the resolution of \\(512 \\times 512\\)." + }, + { + "type": "list", + "bbox": [ + 0.077, + 0.211, + 0.893, + 0.253 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.263, + 0.468, + 0.432 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.443, + 0.471, + 0.514 + ], + "angle": 0, + "content": "Figure 3. The triangular meshes from 3DMM [3], ER-NeRF [31] and DynTet. The surfaces extracted from ER-NeRF using the Marching Cubes [39] exhibit noise and undesirable topology. Note that the backs of the meshes may have some defects due to limited training data, but it does not impact the rendering results." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.527, + 0.47, + 0.589 + ], + "angle": 0, + "content": "ting, where we use clips from unseen videos to drive all methods for comparisons in lip synchronization. We extract two video clips from the public demos of SynObama [58] and NVP [62], which we refer to as Testset A and Testset B." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.593, + 0.471, + 0.775 + ], + "angle": 0, + "content": "Evaluation metrics. We assess the methods with several metrics: We evaluate the reconstruction quality using PSNR and LPIPS metrics [71]. Realism and identity preservation are measured using Fréchet Inception Distance (FID) [24] and Cosine Similarity of Identity Embedding (CSIM) [41]. Driving accuracy is assessed by calculating the landmark distances for the mouth \\((\\mathrm{LMD}^m)\\) and eyes \\((\\mathrm{LMD}^e)\\) [6], while face motion accuracy is quantified by action units error (AUE) [2]. Temporal lip synchronization is evaluated using the SyncNet confidence score (Sync) [8]. Additionally, we report training time and frame-per-second (FPS) to evaluate the running efficiency of the methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.473, + 0.902 + ], + "angle": 0, + "content": "Head reconstruction. The results of the head reconstruction setting are presented in Table 1. For fairness, we provide DynTet with and without LPIPS supervision, both of which demonstrate significant advantages in reconstructing accurate details and precisely controlling facial movements. While 2D-based methods such as Wav2Lip [50] and PC-AVS [77] excel in the lip synchronization due to the pretraining on the large-scale dataset, they fall short in the" + }, + { + "type": "table", + "bbox": [ + 0.508, + 0.262, + 0.891, + 0.432 + ], + "angle": 0, + "content": "
MethodsTestset ATestset B
AUE ↓Sync ↑AUE ↓Sync ↑
Ground Truth07.38606.676
SynObama [58]5.5747.419--
NVP [62]--7.9546.562
Wav2Lip [50]5.0298.3947.4159.072
PC-AVS [77]4.3598.0877.4509.964
SadTalker [72]4.7327.2076.7607.932
AD-NeRF [23]4.2776.0416.7315.567
RAD-NeRF [60]4.1726.5416.7336.786
ER-NeRF [31]4.2106.8776.6697.401
DynTet3.6725.0556.0296.401
Audio2Exp + DynTet4.3167.0556.5417.335
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.442, + 0.893, + 0.498 + ], + "angle": 0, + "content": "Table 2. Quantitative results of cross-driven lip synchronization. The best and second results are in **bold** and **underline**. To drive DynTet with audios, we utilize an off-the-shelf model Audio2Exp [72] to convert audios into 3DMM coefficients." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.513, + 0.894, + 0.636 + ], + "angle": 0, + "content": "faithful appearance. Among NeRF-based methods, the recent work ER-NeRF [31] achieves top performance in the evaluation. As the first tetrahedra representation for talking heads, DynTet notably outperforms on all metrics compared to NeRF-based approaches, showcasing its advancements in faithful reconstruction and accurate mapping from conditions to facial deformation. This further validates the great potential of tetrahedra meshes for dynamic modeling." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.895, + 0.902 + ], + "angle": 0, + "content": "Lip synchronization. DynTet offers both frame-driven and audio-driven approaches to accomplish this task. In the frame-driven approach, 3DMM coefficients are directly extracted from the target videos. On the other hand, the audio-driven approach utilizes an off-the-shelf model, specifically the Audio2Exp model in SadTalker [72], to convert audi-los into the 3DMM coefficients. It is worth noting that the target coefficients, denoted as \\(\\alpha^{\\prime}\\), and the training co-efficients \\(\\alpha\\), may have different distributions according to speaking habits. We find that a re-center process, expressed as \\(\\alpha^{\\prime} + (\\bar{\\alpha} - \\bar{\\alpha}^{\\prime})\\) is crucial to rectificate the talking style. As shown in Table 2, the frame-driven approach of DynTet unsurprisingly achieves the best AUE performance among all methods. Furthermore, the audio-driven approach of DynTet also achieves comparable results with ER-NeRF and SadTalker, indicating its flexibility and strong generalization properties for various applications." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5215" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.128, + 0.09, + 0.422, + 0.102 + ], + "angle": 0, + "content": "The rain will gradually sink its way slowly southward into England" + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.104, + 0.462, + 0.309 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.313, + 0.47, + 0.356 + ], + "angle": 0, + "content": "Figure 4. Qualitative results of the cross-driven setting. The top and bottom panels show the frame- and audio-driven results, respectively. We attach the estimated 3DMM shapes for reference." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.368, + 0.47, + 0.475 + ], + "angle": 0, + "content": "Running efficiency. Table 1 shows that DynTet achieves fast training speed and real-time inference at \\(512 \\times 512\\) resolution. Notably, DynTet maintains the same 46 FPS even at \\(1024 \\times 1024\\) resolution, thanks to the cost-efficient rasterization rendering. In contrast, ER-NeRF and RAD-NeRF experience a half drop in FPS. This highlights our efficiency advantage in challenging high-resolution scenes." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.483, + 0.255, + 0.499 + ], + "angle": 0, + "content": "5.3. Qualitative results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.506, + 0.471, + 0.719 + ], + "angle": 0, + "content": "Figure 2 demonstrates that DynTet effectively addresses challenges faced by prior methods. It generates photorealistic images with intricate details in non-rigid areas and achieves precise control of mouth, blinks, and even wrinkles. Our supplementary videos showcase the impressive temporal stability of DynTet, resulting in smooth and stable motion. In Figure 3, the comparison of meshes obtained by different methods reveals that DynTet outperforms 3DMM and NeRF in terms of topology. Additionally, Figure 4 showcases the accurate expression control achieved by frame-driven DynTet, while audio-driven DynTet surpasses SadTalker in producing realistic and expressive results. These advancements firmly establish DynTet as a promising approach for modeling talking heads." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.727, + 0.228, + 0.743 + ], + "angle": 0, + "content": "5.4. Ablation study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.902 + ], + "angle": 0, + "content": "We present the results of different structures in Table 3 and Figure 5. It is evident that the removal of canonical projection (C.P.) has a quite negative impact, resulting in increased LPIPS and LMD values. This is because the absence of the canonical projection increases the difficulty of texture learning and consequently hinders the supervision of loss on the geometry model. Similarly, removing 3DMM supervision leads to flawed meshes and introduces artifacts into the images. The visualization of elastic scores (E.S.) highlights its function in quantifying the non-rigid property, and" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.098, + 0.885, + 0.245 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.25, + 0.892, + 0.306 + ], + "angle": 0, + "content": "Figure 5. The validation of key components in DynTet. (a) Result of DynTet. (b) Replacing frequency encoding with hash encoding [44]. (c) Removing 3DMM supervision. (d) Removing canonical projection. (e) Groundtruth. (f) Visualization of elastic scores." + }, + { + "type": "table", + "bbox": [ + 0.507, + 0.314, + 0.89, + 0.388 + ], + "angle": 0, + "content": "
DynTet-3DMM-C.P.-E.S.3264128512
FPS↑46---103928023
#Param1.41M---1.11M1.13M1.19M2.28M
PSNR↑34.8433.6534.3734.8132.2234.2035.1535.06
LPIPS↓0.02230.06860.05290.02470.05390.02540.02370.0219
LMDm↓2.2842.4532.5722.3362.8752.6362.4492.201
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.394, + 0.892, + 0.451 + ], + "angle": 0, + "content": "Table 3. Quantitative ablation of DynTet via removing 3DMM supervision, canonical projection, elastic score or changing the number of middle neurons in appearance mapping from 32 to 512. #Param denotes the parameter number of DynTet." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.465, + 0.892, + 0.617 + ], + "angle": 0, + "content": "its removal affects the temporal stability of the results (see the supplementary videos). Interestingly, we find replacing frequency encoding with hash encoding leads to a cluttered mesh, indicating that it is desirable to encode coordinates as low-frequency signals in geometry learning. In addition, we explore the impact of middle neuron channels within the appearance mapping, and find that dimensions ranging from 64 to 256 strike a balance between expressivity and inference speed. These findings underscore the reasonable designs of DynTet for achieving desirable results." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.641, + 0.619, + 0.657 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.671, + 0.892, + 0.791 + ], + "angle": 0, + "content": "We introduce Dynamic Tetrahedra (DynTet), a novel hybrid representation for realistic and expressive talking heads. DynTet upgrades tetrahedral meshes from statics to dynamics with a new architecture, a canonical space and guidance from geometry prior. DynTet can efficiently generate high-resolution talking videos with realism and precise motion control beyond prior works. Our work may inspire future research in the direction of Dynamic Tetrahedra." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Acknowledgements. This paper is supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDA27000000), the National key research and development program of China (2021YFA1000403), the National Natural Science Foundation of China (Nos. U23B2012, 11991022) and the Fundamental Research Funds for the Central Universities (E3E41904)." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5216" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.468, + 0.142 + ], + "angle": 0, + "content": "[1] ShahRukh Athar. Rignerf: Fully controllable neural 3d portraits. In CVPR, 2022. 1, 2" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.145, + 0.468, + 0.185 + ], + "angle": 0, + "content": "[2] Tadas Baltrusaitis, Amir Zadeh, Yao Chong Lim, and Louis-Philippe Morency. 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These implicit methods are still confronted by visual artifacts and jitters, since the lack of explicit geometric constraints poses a fundamental challenge in accurately modeling complex facial deformations. In this paper, we introduce Dynamic Tetrahedra (DynTet), a novel hybrid representation that encodes explicit dynamic meshes by neural networks to ensure geometric consistency across various motions and viewpoints. DynTet is parameterized by the coordinate-based networks which learn signed distance, deformation, and material texture, anchoring the training data into a predefined tetrahedra grid. Leveraging Marching Tetrahedra, DynTet efficiently decodes textured meshes with a consistent topology, enabling fast rendering through a differentiable rasterizer and supervision via a pixel loss. To enhance training efficiency, we incorporate classical 3D Morphable Models to facilitate geometry learning and define a canonical space for simplifying texture learning. These advantages are readily achievable owing to the effective geometric representation employed in DynTet. Compared with prior works, DynTet demonstrates significant improvements in fidelity, lip synchronization, and real-time performance according to various metrics. Beyond producing stable and visually appealing synthesis videos, our method also outputs the dynamic meshes which is promising to enable many emerging applications. Code is available at https://github.com/zhangzc21/DynTet. + +# 1. Introduction + +Talking head synthesis is a long-standing task with a wide range of applications, such as digital humans, metaverse and filmmaking. The set up of this task can be roughly categorized to two lines: 1) learning from a large-scale dataset to drive arbitrary portrait images by the motion sig- + +nal [7, 40, 41, 50, 62, 70, 77, 78]; and 2) building a personalized animatable head model from a several-minute video of a specific person [23, 31, 37, 53, 60, 61, 64, 67, 74]. We concentrate on the latter one, since it generally delivers high-quality synthesis results with intricate details and 3D naturalness, suitable for professional scenarios. + +Building such an exquisite talking head avatar from video data poses challenges in faithful appearance, motion control, as well as low running cost. One line of methods [14, 19, 20, 28, 30, 61, 67] explicitly rely on 3D Morphable Models (3DMM) [3] to reconstruct and animate human faces by estimating the person-specific parameters. While these methods allow for efficient rendering and dynamic deformation, the fixed face topology makes them often fall short in generating characteristic details, e.g., hairstyle, glasses, and inner mouth. Recently, neural implicit representations, especially Neural Radiance Fields (NeRF) [43], provide a new way to realize faithful generation. Some seminal work [16, 23, 37, 53, 64] learn a direct mapping from the control signal to the talking head, meanwhile the efficient neural representations like voxel grid [15, 34, 57] and hash encoding [44] have been introduced to improve training and inference speed. + +Despite the expressive capabilities, these implicit methods still need to improve many subtle issues in realism, e.g., head jitters, motionless mouths, and occasional artifacts. Researchers have discussed these issues from various aspects, e.g., introducing a canonical space for easier appearance learning [1, 49], developing compact models for more efficient training [31, 60], and using expressive driving conditions for better control [64, 65], against the naive baseline of NeRF. Essentially, the implicit definition for 3D objects complicates the analytical alternation of the underlying object geometry, leading to ineffective disentanglement of static appearance and motion from dynamic data, as opposed to the explicit meshes and vertex displacements for 3DMM. In viewing of this, it is appealing to incorporate the expressivity of implicit methods with an effective geometric control to take advantage of both lines of works. + +We introduce Dynamic Tetrahedra (DynTet), a novel hybrid approach that encodes dynamic meshes within neural + +networks to assist explicit deformation. In essence, DynTet employs neural networks to predict attributes of underlying surfaces, from which explicit meshes can be extracted to fast render images with a differentiable rasterizer. On one hand, distinguished from implicit methods, the explicit geometry enables DynTet to learn a consistent 3D model across frames and directly express deformation as vertex displacement, thus DynTet is convenient to model the dynamics of talking head. On the other hand, unlike 3DMM with a preset topology, DynTet end-to-end learns personalized meshes and texture suitable for the given video. + +Technically, the proposed DynTex is inspired by recent advancements in tetrahedral techniques [17], originally developed for 3D reconstruction [45] and synthesis [18, 54]. The key insight is a parameterized tetrahedral grid: Coordinate-based networks are used to learn the signed distance field (SDF) and refinement for the grid, then the meshes are subsequently decoded through the Marching Tetrahedra algorithm. Since these prior methods [17, 18, 45, 54] primarily work for static scenes, they can hardly render images with deformation, nor keep the mesh topology under different conditions [18]. This also largely prevents the parallelized rendering and training processes. In contrast, we redesign the framework that exclusively determines the mesh topology with SDF, while a new branch controls the geometric variations with deformation signals. We also estimate the elastic score of each vertex to specify the rigid (e.g., forehead) and non-rigid regions (e.g., mouth) of the head, so as to achieve precise deformations in local regions while maintaining stability in other parts. These designs ensure the topological consistency and expressivity across all decoded meshes, enabling a customized dynamic mesh beyond 3DMM. To improve training efficiency, we introduce geometry losses that supervise shape and motion using the 3DMM priors. This replenishes the limited depth information available in frontal talking videos. Moreover, we establish an interpretable canonical space for the dynamic mesh, reducing the complexity of texture learning. In summary, our contributions include: + +(1). We propose DynTet, a novel hybrid representation that encodes dynamic head meshes in neural networks, where the explicit geometry delineated by tetrahedra facilitates appearance and motion learning. +(2). This is the first work that successfully extends the static tetrahedral representation to dynamic head avatars by a new elaborated architecture, a canonical space, and 3DMM guidance for modeling dynamic meshes. +(3). DynTet presents evident advantages in terms of fidelity, lip-sync precision, stability and runtime by thorough evaluation compared with prior works. + +The learned dynamic head meshes are promising together with existing 3D assets or AR/VR techniques for emerging applications such as human avatar and the meta + +verse, which may inspire further study on the hybrid representation for dynamic 3D objects. + +# 2. Related Work + +Talking head synthesis. Most existing methods for talking head synthesis can be classified into three categories in terms of the modeling approaches. 2D-based methods [50, 68, 69, 76, 78] utilized generative models [21, 26, 29] as renderers to produce photorealistic portraits. While, these methods often fall short in achieving 3D naturalness and consistent pose control due to the absence of an explicit 3D model. 3DMM-based methods [14, 19, 20, 28, 30, 61, 67] leveraged 3D face knowledge to drive facial expression, resulting in quite natural talking style. As a trade-off, due to the lack of complete head topology they cannot guarantee consistency or fidelity beyond the facial region such as hair and inner mouth. Neural head avatar [22, 74, 75] has emerged as an attractive way for automatically creating 3D facial models. While earlier approaches [51, 66] required detailed scanning data, NeRFs [5, 43, 49] offer a solution to learn models from video clips, driven by the factors like 3DMM coefficients [16], audio feature [23], or facial landmarks [65]. Several recent works have enhanced control effects [1, 37, 64], system efficiency [31, 60] and few-shot training [32, 53]. Despite great progress, neural avatars still face challenges in realism and plausible motion, not to mention that NeRF rendering is computationally expensive when generating high-resolution images. + +Neural 3D representation. Neural implicit functions are emerging as an effective representation of 3D object [35, 42, 43, 48, 55] using coordinate-based MLPs [44, 56, 59]. While prior methods [42, 48] required 3D supervision, several recent works [33, 36, 43, 47] demonstrated differentiable rendering for training directly from images. Meanwhile, NeRF [43] and followups [15, 44, 57, 73] performed volume rendering [27] on a continuous field for density and color, achieving impressive results for multi-view synthesis. As density is ambiguous to depict geometric details [63], they cannot explicitly edit shape or extract a high-quality surface with Marching Cubes [39], which makes it challenging in formulating deformation for dynamic scenes. Recent works [17, 54] proposed to convert deformable tetrahedral grid into surface meshes via the differentiable Marching Tetrahedral algorithm [11], where the SDF values are implicitly learned. The following methods [18, 45] further extended to jointly learn geometry and texture from image data. They can render photorealistic images competitive with NeRF in real-time. However, as these methods only work for static scenes, they cannot learn dynamics for modeling head avatars. We present an original effort to address this issue to learn dynamic tetrahedral meshes. + +# 3. Preliminaries + +We provide some background concepts and notations. At first, we define operations between sets as element-wise operations, and functions are mapped element-wise as well. + +Tetrahedral meshes have been studied in deep learning [17, 54] as a hybrid representation for 3D shape modeling. Consider an object lying in a unit cube, a tetrahedral grid denoted as $(\mathbf{V}_{tet},\mathbf{T}_{tet})$ is pre-defined to tetrahedralize the cube into $r^3$ resolution. Each tetrahedron $T_{k}\in \mathbf{T}_{tet}$ is defined by four vertices $\{\mathbf{v}_{a_k},\mathbf{v}_{b_k},\mathbf{v}_{c_k},\mathbf{v}_{d_k}\}$ , where $K$ is the total number of tetrahedra. Additionally, each vertex $\mathbf{v}_i$ contains a learnable SDF value $s_i\in \mathbb{R}$ to express the distance away from the underlying surface, and a small offset $\Delta \mathbf{v}_i\in [-\frac{1}{r},\frac{1}{r}]^3$ from its initial coordinates to refine the grid as $\mathbf{v}_i' = \mathbf{v}_i + \Delta \mathbf{v}_i$ . We let $S = \{s_i\}_{i = 1}^K$ and $\Delta \mathbf{V} = \{\Delta \mathbf{v}_i\}_{i = 1}^K$ . Notably, the surface shape within the tetrahedral grid is primarily determined by the SDF values $S$ as $\Delta \mathbf{V}$ is confined within the resolution boundaries. + +Marching Tetrahedra $(MT)$ is an iso-surface extraction algorithm [11] to generate triangular meshes from tetrahedral meshes. Given SDF values $\{s_a, s_b, s_c, s_d\}$ of a tetrahedron, $MT$ determines the surface topology inside the tetrahedron based on the signs of these values, where the $2^4$ configurations in total fall into 3 unique cases after considering rotation symmetry [54]. A simplified 2D example can be found in Figure 1. Once the topology is identified, a new vertex denoted as $\mathbf{v}_{ab}$ by example, is located at the zero crossings of linear interpolation along the tetrahedral edges: + +$$ +\operatorname {l e r p} \left(\mathbf {v} _ {a}, \mathbf {v} _ {b}, s _ {a}, s _ {b}\right) = \frac {s _ {a} \cdot \mathbf {v} _ {a} - s _ {b} \cdot \mathbf {v} _ {b}}{s _ {a} - s _ {b}}, \tag {1} +$$ + +the same for other vertices. Note that this equation is evaluated only when signs differ $(\mathrm{sign}(s_a)\neq \mathrm{sign}(s_b))$ to prevent singularity. Leveraging $MT$ on the deformed tetrahedral grid $(\mathbf{V}_{tet} + \Delta \mathbf{V},\mathbf{T}_{tet})$ , the triangular surface of the encoded object can be acquired in a differentiable manner. We omit constant symbols and represent this process as + +$$ +\mathbf {V} _ {t r i}, \mathbf {T} _ {t r i} = \operatorname {M a r T e t} (\mathcal {S}, \Delta \mathbf {V}), \tag {2} +$$ + +where $\mathbf{V}_{tri}$ and $\mathbf{T}_{tri}$ are the sets of vertices and connectivity of the triangular meshes, respectively. + +3D Morphable Models provide generic parametric models [3] for synthesizing face shapes, usually expressed as + +$$ +\mathbf {V} _ {3 d m m} = \bar {\mathbf {V}} _ {3 d m m} + \mathbf {U} _ {i d} \gamma + \mathbf {U} _ {e x p} \boldsymbol {\alpha}. \tag {3} +$$ + +Here $\bar{\mathbf{V}}_{3dmm}$ denotes a mean shape, $\mathbf{U}_{id}$ and $\mathbf{U}_{exp}$ are the matrices of basis vectors in the identity and expression space, respectively. $\gamma$ and $\alpha$ are coefficients for the identity and expression, allowing for a tractable control over facial variations. The parameter $\alpha$ has been served as a versatile representation for driving facial deformation [13]. + +# 4. Methodology + +In this section, we introduce a framework called Dynamic Tetrahedra (DynTet) to rapidly learn 3D head avatars from short video sequences, and enable real-time rendering of high-quality talking heads. Generally, DynTet upgrades recent tetrahedral representation [17, 18, 45] tailored for dynamic head modeling. As shown in Figure 1, neural networks are trained to encode head shapes within a tetrahedral grid [54], and then the Marching Tetrahedra (MT) [11] decodes the meshes for photorealistic rasterization rendering. In the following, we delineate the talking head task through the lens of tetrahedral representation (Sec.4.1), and elucidate our improvements in the geometry model (Sec.4.2), rendering process (Sec.4.3), and training losses (Sec.4.4). + +# 4.1. Problem statement + +Given a sequence of head images $\{\mathbf{I}_i\}_{i=1}^n$ , we aim to reenact the specific head driven by motion signals, which typically includes camera parameters $\{\mathbf{P}_i\}_{i=1}^n$ for rigid motion, and talking signals which we represent using 3DMM expression coefficients $\{\alpha_i\}_{i=1}^n$ for non-rigid facial expressions. + +**Formulation.** Drawing inspiration from the seminal work of [54], which applied tetrahedral meshes for multi-view reconstruction, we propose a basic paradigm for talking head modeling: (1) A geometry mapping $\mathbf{F}$ first predicts $S$ and $\Delta \mathbf{V}$ from $\alpha$ and $\mathbf{V}_{tet}$ . (2) The outputs from $\mathbf{F}$ are processed based on Eq. (2) to obtain the triangular mesh, which are then rasterized given camera pose $\mathbf{P}$ to get the coordinates of image pixels in the model space. (3) An appearance mapping $\mathbf{G}$ predicts the materials, which is incorporated with a lighting model $L$ for the physically-based rendering (PBR) [4]. We summarize the overall process as + +$$ +\min _ {\boldsymbol {F}, \boldsymbol {G}, \boldsymbol {L}} \frac {1}{n} \sum_ {i = 1} ^ {n} L o s s (\hat {\mathbf {I}} _ {i}, \mathbf {I} _ {i}) \tag {4} +$$ + +where $\hat{\mathbf{I}}_i = \mathrm{Rendering}(\pmb {F},\pmb {G},\pmb {L},\pmb {\alpha}_i,\mathbf{P}_i)$ + +Herein, Rendering denotes the PBR procedure, and the loss function comprises a set of constraints on the predictions. + +Challenges. Prior works [17, 18, 54] commonly parameterize $\pmb{F}$ using a neural network $f$ to predict SDF values and relative offsets, i.e., $\mathcal{S},\Delta \mathbf{V} = f(\mathbf{V}_{tet})$ , while introducing the talking signal $\alpha$ to $f$ as a condition will bring several problems. First, once SDF values vary along with the conditions, it is difficult to learn the intricate deformation of the facial area with a simple MLP. Second, modern GPUs do not support parallelization for meshes with a variable topology, resulting in inefficient training and running processes. Lastly, previous approaches were designed for $360^{\circ}$ data, while our training data only includes frontal head images. Consequently, this inaccurate estimation of geometry leads to evident artifacts in the rendered videos. + +![](images/058501d2bab3f2c8bdb0df2da62fe9db9d045826b3b5cc12f36b534bab40274c.jpg) +Figure 1. Illustration of the proposed DynTet for modeling a talking head. Left panel: The top branch predicts topology-related information, including SDF values $s$ and elastic scores. The bottom branch, conditioned by talking signals, predicts the offset vectors scaled by the elastic scores to yield deformation vectors $\Delta \mathbf{v}$ for driving the tetrahedral grid. Then, the Marching Tetrahedra (MT) algorithm decodes the meshes. Right panel: The pixel coordinates are projected into a canonical space. Then the physically-based materials and lighting are sampled for rendering images. + +# 4.2. Geometry modeling + +To address the mentioned challenges, we initially disentangle topology and geometry from head shapes within the tetrahedra grid, allowing for generating dynamic meshes with a consistent topology. Furthermore, we enhance the tetrahedral attributes by introducing a novel elastic score, facilitating precise control over deformation. These improvements are incorporated by modifying the internal structure of the geometry mapping as + +$$ +\boldsymbol {F}: \mathbf {V} _ {t e t}, \boldsymbol {\alpha} \rightarrow \mathcal {S}, \Delta \mathbf {V} \tag {5} +$$ + +where $\mathcal{S},\mathcal{E} = f_1(\mathbf{V}_{tet}),\Delta \mathbf{V} = \mathcal{E}\cdot f_2(\mathbf{V}_{tet},\boldsymbol {\alpha})$ + +Here, $f_{1}$ and $f_{2}$ are coordinate-based MLPs, while $\mathcal{E} \coloneqq [f_1(\mathbf{V}_{tet})]_e$ represents the set of non-negative elastic scores. + +Shape representation. Ideal face models exhibit topological invariance regardless of deformation. While implicit SDF representations present challenges in fulfilling this property, it is clear for explicit meshes like 3DMM [3] to maintain the number of vertices and their relationship. By employing Eq. (1) within $MT$ algorithm, we have + +$$ +\mathbf {v} _ {a b} ^ {\prime} = \underbrace {\operatorname {l e r p} \left(\mathbf {v} _ {a} , \mathbf {v} _ {b} , s _ {a} , s _ {b}\right)} _ {\text {t o p o l o g y a n d i d e n t i t y}} + \underbrace {\operatorname {l e r p} \left(\Delta \mathbf {v} _ {a} , \Delta \mathbf {v} _ {b} , s _ {a} , s _ {b}\right)} _ {\text {g e o m e t r y a n d e x p r e s s i o n}}. \tag {6} +$$ + +Given that vertices $\mathbf{v}_a$ and $\mathbf{v}_b$ are pre-defined in the tetrahedral grid, the first term is just affected by the SDF values. Hence, our design in Eq.(5), which segregates SDF from the talking signal, results in a topologically invariant mesh. Meanwhile, the second term indicates that the geometry of mesh explicitly relies on the tetrahedral grid offsets. Additionally, a comparison with Eq. (3) reveals that DynTet functions as a quasi-3DMM hybrid model, enabling additive changes to facial shapes driven by neural networks. + +Elastic estimation. Our design necessitates relaxing the range of $\Delta \mathbf{v}_i\in [-\frac{1}{r},\frac{1}{r}]^3$ to allow greater flexibility in geometric variations. However, this relaxation potentially leads to local jitters that significantly impact visual quality. We introduce an elastic scoring mechanism for each vertex within the tetrahedral grid to regulate deformation. These scores $\mathcal{E}$ are predicted by the neural network $f_{1}$ to quantify the non-rigid properties across different regions of the human head. For instance, areas like the forehead and nose exhibit near-rigid behavior with minimal changes during talking, while regions like the mouth and eyes are more flexible and primarily contribute to deformations. In this way, the offset vectors are scaled using the elastic scores to determine the deformable vectors $\Delta \mathbf{V}$ . + +Architecture details. As shown in Figure 1, we formulate neural networks $f_{1}$ and $f_{2}$ as a composition of regular lightweight MLPs and a frequency positional encoding [59] + +$$ +\gamma (\mathbf {v}) = < \left(\sin \left(2 ^ {l} \pi \mathbf {v}\right), \cos \left(2 ^ {l} \pi \mathbf {v}\right)\right) > _ {l = 0} ^ {L - 1}. \tag {7} +$$ + +We find that the simple frequency coding outperforms hash grid encoding [44] which tends to generate surfaces with significant noise. To maintain temporal consistency, we follow [41, 52] to represent the deformation of any timestamp by the window of adjacent 27 frames of expression coefficients, which are averaged into a 256-dimensional feature vector by a trainable convolutional encoder. + +# 4.3. Neural rendering + +This procedure aims to automatically texture the triangular meshes $(\mathbf{V}_{tri},\mathbf{T}_{tri})$ extracted by $MT$ algorithm, and generate photorealistic images $\hat{\mathbf{I}}$ given camera pose $\mathbf{P}$ and talking signal $\alpha$ . In the realm of deformable reconstruction [38, 38, 46, 49], the canonical or template model + +serves an important role in reducing the complexity of texture parametrization. Thanks to the well-designed geometry model in DynTet, defining a canonical space becomes straightforward. We upgrade the vanilla rendering process by incorporating a canonical projection, thereby unifying both shading and lighting within a single space. + +Canonical projection. We propose the canonical projection CanProj to map the pixel coordinates $\mathcal{C}_{2d}$ from an arbitrary camera pose $\mathbf{P}$ into a canonical 3D space where the mean expression lies. This process is expressed as + +$$ +\bar {\mathcal {C}} _ {3 d} = \operatorname {C a n P r o j} \left(\mathcal {C} _ {2 d}, \mathbf {V} _ {t r i}, \mathbf {P}; \bar {\mathbf {V}} _ {t r i}, \mathbf {T} _ {t r i}\right), +$$ + +where $\bar{\alpha} = \Sigma_{i=1}^{n} \alpha_{i} / n$ , (8) + +and $\bar{\mathbf{V}}_{tri},\mathbf{T}_{tri} = \mathrm{MatTet}(\pmb {F}(\mathbf{V}_{tet},\bar{\alpha}))$ + +In practical implementation, CanProj can be executed readily using a modern mesh rasterizer to derive coordinates $\mathcal{C}_{3d}$ and 2D barycentric coordinates within $(\mathbf{V}_{tri},\mathbf{T}_{tri})$ . Then, $\bar{\mathcal{C}}_{3d}$ positioned in the canonical space, is computed through barycentric interpolation over $(\bar{\mathbf{V}}_{tri},\mathbf{T}_{tri})$ . + +Appearance model. We follow previous work [4, 45] to adopt a physically-base material model, which allows easy integration of 3D assets within existing engines. To parameterize the appearance mapping $G$ , we employ a coordinate-based neural network comprising a hash grid encoder [44] for querying spatial features and a lightweight MLP for predicting materials. This network takes the projected coordinates and talking signal as inputs: + +$$ +\mathcal {K} _ {d}, \mathcal {K} _ {\text {o r m}} = \boldsymbol {G} (\bar {\mathcal {C}} _ {3 d}, \boldsymbol {\alpha}). \tag {9} +$$ + +Here, $\mathcal{K}_d$ comprises three-channel diffuse albedo, and $\mathcal{K}_{orm}$ is the set of occupancy $k_{o}$ , roughness $k_{r}$ , and metalness factors $k_{m}$ for the GGX normal distribution function [9]. Unlike prior works, we do not predict normals, but instead compute them directly using the triangular mesh in the model space, which yields similar results. + +Lighting model. We leverage the image based lighting model, where the environment light is given by a trainable mapping $\pmb{L}$ . For each position $\mathbf{v} \in \mathcal{C}_{3d}$ with a normal vector $\mathbf{n}$ , the color along direction $\omega_{o}$ is computed by + +$$ +L (\mathbf {v}, \boldsymbol {\omega} _ {o}) = L _ {d} (\mathbf {v}) + L _ {s} (\mathbf {v}, \boldsymbol {\omega} _ {o}), \tag {10} +$$ + +where $L_{d}$ is the diffuse intensity and $L_{s}$ is the specular intensity. Consider a hemisphere with the incident direction $\Omega = \{\pmb {\omega}_i:\pmb {\omega}_i^T\mathbf{n}\geq 0\}$ , the first diffuse term is computed by + +$$ +L _ {d} (\mathbf {v}) = \left(1 - k _ {m}\right) \boldsymbol {k} _ {d} \int_ {\Omega} \boldsymbol {L} _ {i} \left(\mathbf {v}, \boldsymbol {\omega} _ {i}\right) \left(\boldsymbol {\omega} _ {i} ^ {T} \mathbf {n}\right) \mathrm {d} \boldsymbol {\omega} _ {i}. \tag {11} +$$ + +And the second term is based on Cook-Torrance microfacet specular shading mode model [9] $r(\omega_o,\omega_i)$ to compute + +$$ +L _ {s} (\mathbf {v}, \boldsymbol {\omega} _ {o}) = \boldsymbol {k} _ {s} \int_ {\Omega} r \left(\boldsymbol {\omega} _ {o}, \boldsymbol {\omega} _ {i}\right) \boldsymbol {L} _ {i} (\mathbf {v}, \boldsymbol {\omega} _ {i}) \left(\boldsymbol {\omega} _ {i} ^ {T} \mathbf {n}\right) \mathrm {d} \boldsymbol {\omega} _ {i}, \tag {12} +$$ + +where the specular color $\pmb{k}_s = (1 - k_m) \cdot 0.04 + k_m \pmb{k}_d$ . Following [45], we parameterize $\pmb{L}$ with a cube map with resolution $6 \times 512 \times 512$ , and the calculate the hemisphere integration by the split-sum method [25]. By aggregating the rendered pixel colors along the camera pose, we obtain the rendered image $\hat{\mathbf{I}} = \{k_o \cdot L(\mathbf{v}, \pmb{\omega}_o) | \mathbf{v} \in \mathcal{C}_{3d}\}$ . + +# 4.4. Training losses + +Thanks to its hybrid representation, DynTet possesses an interpretable SDF space and a cost-efficient rendering procedure. This unique combination allows us to supervise its training in both image and geometry space, facilitating the estimation of reasonable 3D models from frontal images. + +Image supervision. Given an image $\mathbf{I}$ and its prediction $\hat{\mathbf{I}}$ , we train DynTet with the MSE loss for pixel-level reconstruction, and apply the overall LPIPS loss [71] for enhancing sharp details [31]. Besides, we find silhouette loss is important to provide shape guidance. The image loss is + +$$ +\mathcal {L} _ {i m g} = \mathcal {L} _ {m s e} (\hat {\mathbf {I}}, \mathbf {I}) + \mathcal {L} _ {m s e} (\hat {\mathbf {I}} _ {o}, \mathbf {I} _ {o}) + \lambda_ {1} \mathcal {L} _ {L P I P S} (\hat {\mathbf {I}}, \mathbf {I}), \tag {13} +$$ + +where $\hat{\mathbf{I}}_o$ and $\mathbf{I}_o$ denote the binary masks of head regions. We combine the head, background and torso together to train in practice to prevent noise around the facial contours. + +3DMM supervision. Frontal head views in talking videos often lack adequate depth information, resulting in flawed geometry estimation and artifacts in synthesized profile face. To counter this, we leverage 3DMM [3] as a geometry prior to mitigate these issues in the SDF space. We introduce two key losses to incorporate 3DMM. First, the normal distance loss $\mathcal{L}_{ndl}$ constrains the canonical model: + +$$ +\mathcal {L} _ {n d l} = \mathbb {E} _ {s \sim U (- a, a)} \| f _ {1} \left(\mathbf {V} _ {3 d m m} ^ {\bar {\alpha}} + s \cdot \mathbf {N} _ {3 d m m} ^ {\bar {\alpha}}\right) - s \| _ {2} ^ {2}, \tag {14} +$$ + +where $\mathbf{V}_{3dmm}^{\bar{\alpha}}$ and $\mathbf{N}_{3dmm}^{\bar{\alpha}}$ represent 3DMM vertices and normal vectors generated by coefficient $\bar{\alpha}$ , while $a$ is a small value which we set to 0.1. $\mathcal{L}_{ndl}$ injects facial prior into $f_{1}$ , affecting the SDF values around 3DMM surface. Consequently, it avoids excessive restraint compared to full-space supervision [48], enabling adaptive learning in other regions. The second facial deformation loss is expressed as + +$$ +\mathcal {L} _ {f d l} = \left\| \left[ f _ {1} \left(\mathbf {V} _ {3 d m m}\right) \right] _ {e} f _ {2} \left(\mathbf {V} _ {3 d m m}, \boldsymbol {\alpha}\right) - \mathbf {U} _ {e x p} (\boldsymbol {\alpha} - \bar {\boldsymbol {\alpha}}) \right\| _ {2} ^ {2}. \tag {15} +$$ + +This loss helps the tetrahedral grid to mimic the 3DMM deformation. Although these losses target 3DMM vertices, the tetrahedral vertices are appropriately constrained due to their spatial density covering the 3DMM vertices. + +Loss function. We introduce a regularization term for the elastic score, denoted as $\mathcal{R}_{es} = \| [f_1(\mathbf{V}_{3dmm})]_e\| _2^2$ , to reinforce the rigid property. We incorporate the weighted combination of the above constraints as follows to formulate the loss function described in Eq. (4) + +$$ +L o s s = \mathcal {L} _ {i m g} + \lambda_ {2} \mathcal {L} _ {n d l} + \lambda_ {3} \mathcal {L} _ {f d l} + \lambda_ {4} \mathcal {R} _ {e s}. \tag {16} +$$ + +![](images/31e376b995de3ccefea3c82e9d161f2eff2e29427ddac14373c9f712e10f28d8.jpg) +Figure 2. Qualitative comparison of DynTet with the prior methods [31, 50, 60, 77]. Some representative defects are marked with red arrows, around which the generated eyes, mouths or wrinkles highlight discrepancies with real ones. The right panel presents the details of the mouth and eye area. The results show the superior realism and motion accuracy achieved by DynTet compared to existing methods. + +![](images/a70e0b5814e559fc9a122431d7e6af9ae672e14157c4415b735a047dd7a6f47f.jpg) + +# 5. Experiment + +# 5.1. Experimental settings + +Dataset and pre-processing. For a fair comparison, we follow recent works [23, 31, 53] to conduct experiments on a publicly-released video dataset, which includes four high-definition talking videos with an average length of about 6500 frames at 25 FPS. Each raw video is cropped and resized to $512 \times 512$ , except for the Obama data with the resolution $448 \times 448$ . Each video is divided into training and test sets at a ratio of 10:1. We ensure strict alignment with the pre-processing steps outlined in AD-NeRF [23]. In order to extract the 3DMM coefficients efficiently, we utilize a pre-trained model from Deng et al. [10]. + +Implementation details. We implement DynTet based on the code of Nvdiffrec1 [45] for differentiable Marching Tetrahedra and rasterization. We use a tetrahedral grid with a resolution of $128^3$ [12], which is a commonly used setting [18, 45]. For the MLPs, we equip each one with ReLU-Linear layers. The geometry model utilizes a frequency positional encoder [59] with $L = 6$ and a 3-layer MLP with + +128 middle neurons. Additionally, a 4-layer convolutional encoder [52] is used for the 3DMM coefficients. The appearance model consists of a 5-layer MLP with 256 middle neurons. During training, we perform 20,000 iterations with a batch size of 4. We employ the Adam optimizer with an initial learning rate of $1 \times 10^{-3}$ , which exponentially decayed to $1 \times 10^{-5}$ . The default hyperparameters are $\lambda_{1} = 0.1$ , $\lambda_{2} = 100$ , $\lambda_{3} = 100$ , and $\lambda_{4} = 100$ . All experiments are conducted on a single NVIDIA Tesla V100. + +Comparison baselines. We compare our method with several recent representative one-shot and person-specific models, including Wav2Lip [50], PC-AVS [77], NVP [62], SynObama [58], SadTalker [72]. In addition, we also compare our method with three end-to-end NeRF-based models: ADNeRF [23], RAD-NeRF [60] and ER-NeRF [31]. All these methods are implemented with their official code. + +# 5.2. Quantitative results + +Comparison settings. We follow recent works to organize our comparisons into two settings: 1) Self-driven head reconstruction setting, in which we train a model for each video clip and evaluate the reconstruction quality on its respective test set. 2) Cross-driven lip synchronization set- + +
MethodsPSNR ↑LPIPS ↓FID ↓CSIM ↑LMDm ↓LMDe ↓AUE ↓Sync ↑TimeFPS
Ground Truth∞001.0000007.899--
Wav2Lip [50]31.150.073020.700.9703.0722.1472.0598.256-20
PC-AVS [77]22.060.134547.530.8022.4963.6094.2838.540-32
AD-NeRF [23]30.410.079914.920.9264.3172.4054.3745.01518h0.08
RAD-NeRF [60]31.510.067511.140.9513.0062.2853.3174.4095h23
ER-NeRF† [31]32.500.03456.440.9602.9242.2202.7734.9442h23
DynTet35.150.061912.230.9752.4182.1371.8337.4072h46
DynTet†34.840.02234.720.9782.2842.1291.7127.6463h46
+ +$\dagger$ supervised by overall LPIPS [71]. +Table 1. Quantitative results of the self-driven head reconstruction. The best and second results are in bold and underline. Wav2Lip takes ground truth as input, thus its PSNR and LPIPS values are biased. The FPS values are tested on the resolution of $512 \times 512$ . + +![](images/9805d245dd0e5491b41b089ac3d3042b135517a12618b4aa8152dc48540a098f.jpg) +Figure 3. The triangular meshes from 3DMM [3], ER-NeRF [31] and DynTet. The surfaces extracted from ER-NeRF using the Marching Cubes [39] exhibit noise and undesirable topology. Note that the backs of the meshes may have some defects due to limited training data, but it does not impact the rendering results. + +ting, where we use clips from unseen videos to drive all methods for comparisons in lip synchronization. We extract two video clips from the public demos of SynObama [58] and NVP [62], which we refer to as Testset A and Testset B. + +Evaluation metrics. We assess the methods with several metrics: We evaluate the reconstruction quality using PSNR and LPIPS metrics [71]. Realism and identity preservation are measured using Fréchet Inception Distance (FID) [24] and Cosine Similarity of Identity Embedding (CSIM) [41]. Driving accuracy is assessed by calculating the landmark distances for the mouth $(\mathrm{LMD}^m)$ and eyes $(\mathrm{LMD}^e)$ [6], while face motion accuracy is quantified by action units error (AUE) [2]. Temporal lip synchronization is evaluated using the SyncNet confidence score (Sync) [8]. Additionally, we report training time and frame-per-second (FPS) to evaluate the running efficiency of the methods. + +Head reconstruction. The results of the head reconstruction setting are presented in Table 1. For fairness, we provide DynTet with and without LPIPS supervision, both of which demonstrate significant advantages in reconstructing accurate details and precisely controlling facial movements. While 2D-based methods such as Wav2Lip [50] and PC-AVS [77] excel in the lip synchronization due to the pretraining on the large-scale dataset, they fall short in the + +
MethodsTestset ATestset B
AUE ↓Sync ↑AUE ↓Sync ↑
Ground Truth07.38606.676
SynObama [58]5.5747.419--
NVP [62]--7.9546.562
Wav2Lip [50]5.0298.3947.4159.072
PC-AVS [77]4.3598.0877.4509.964
SadTalker [72]4.7327.2076.7607.932
AD-NeRF [23]4.2776.0416.7315.567
RAD-NeRF [60]4.1726.5416.7336.786
ER-NeRF [31]4.2106.8776.6697.401
DynTet3.6725.0556.0296.401
Audio2Exp + DynTet4.3167.0556.5417.335
+ +Table 2. Quantitative results of cross-driven lip synchronization. The best and second results are in **bold** and **underline**. To drive DynTet with audios, we utilize an off-the-shelf model Audio2Exp [72] to convert audios into 3DMM coefficients. + +faithful appearance. Among NeRF-based methods, the recent work ER-NeRF [31] achieves top performance in the evaluation. As the first tetrahedra representation for talking heads, DynTet notably outperforms on all metrics compared to NeRF-based approaches, showcasing its advancements in faithful reconstruction and accurate mapping from conditions to facial deformation. This further validates the great potential of tetrahedra meshes for dynamic modeling. + +Lip synchronization. DynTet offers both frame-driven and audio-driven approaches to accomplish this task. In the frame-driven approach, 3DMM coefficients are directly extracted from the target videos. On the other hand, the audio-driven approach utilizes an off-the-shelf model, specifically the Audio2Exp model in SadTalker [72], to convert audi-los into the 3DMM coefficients. It is worth noting that the target coefficients, denoted as $\alpha^{\prime}$ , and the training co-efficients $\alpha$ , may have different distributions according to speaking habits. We find that a re-center process, expressed as $\alpha^{\prime} + (\bar{\alpha} - \bar{\alpha}^{\prime})$ is crucial to rectificate the talking style. As shown in Table 2, the frame-driven approach of DynTet unsurprisingly achieves the best AUE performance among all methods. Furthermore, the audio-driven approach of DynTet also achieves comparable results with ER-NeRF and SadTalker, indicating its flexibility and strong generalization properties for various applications. + +The rain will gradually sink its way slowly southward into England + +![](images/5af55b6a2e47b201e01563469e7a6fe5d0bf92d0f58b05e335693bdf51bc69c7.jpg) +Figure 4. Qualitative results of the cross-driven setting. The top and bottom panels show the frame- and audio-driven results, respectively. We attach the estimated 3DMM shapes for reference. + +Running efficiency. Table 1 shows that DynTet achieves fast training speed and real-time inference at $512 \times 512$ resolution. Notably, DynTet maintains the same 46 FPS even at $1024 \times 1024$ resolution, thanks to the cost-efficient rasterization rendering. In contrast, ER-NeRF and RAD-NeRF experience a half drop in FPS. This highlights our efficiency advantage in challenging high-resolution scenes. + +# 5.3. Qualitative results + +Figure 2 demonstrates that DynTet effectively addresses challenges faced by prior methods. It generates photorealistic images with intricate details in non-rigid areas and achieves precise control of mouth, blinks, and even wrinkles. Our supplementary videos showcase the impressive temporal stability of DynTet, resulting in smooth and stable motion. In Figure 3, the comparison of meshes obtained by different methods reveals that DynTet outperforms 3DMM and NeRF in terms of topology. Additionally, Figure 4 showcases the accurate expression control achieved by frame-driven DynTet, while audio-driven DynTet surpasses SadTalker in producing realistic and expressive results. These advancements firmly establish DynTet as a promising approach for modeling talking heads. + +# 5.4. Ablation study + +We present the results of different structures in Table 3 and Figure 5. It is evident that the removal of canonical projection (C.P.) has a quite negative impact, resulting in increased LPIPS and LMD values. This is because the absence of the canonical projection increases the difficulty of texture learning and consequently hinders the supervision of loss on the geometry model. Similarly, removing 3DMM supervision leads to flawed meshes and introduces artifacts into the images. The visualization of elastic scores (E.S.) highlights its function in quantifying the non-rigid property, and + +![](images/ccc76b52adc76b697fb6e0d8c6bf29ce1cdc065e680b5cc5dbba3f7607eb0af9.jpg) +Figure 5. The validation of key components in DynTet. (a) Result of DynTet. (b) Replacing frequency encoding with hash encoding [44]. (c) Removing 3DMM supervision. (d) Removing canonical projection. (e) Groundtruth. (f) Visualization of elastic scores. + +
DynTet-3DMM-C.P.-E.S.3264128512
FPS↑46---103928023
#Param1.41M---1.11M1.13M1.19M2.28M
PSNR↑34.8433.6534.3734.8132.2234.2035.1535.06
LPIPS↓0.02230.06860.05290.02470.05390.02540.02370.0219
LMDm↓2.2842.4532.5722.3362.8752.6362.4492.201
+ +Table 3. Quantitative ablation of DynTet via removing 3DMM supervision, canonical projection, elastic score or changing the number of middle neurons in appearance mapping from 32 to 512. #Param denotes the parameter number of DynTet. + +its removal affects the temporal stability of the results (see the supplementary videos). Interestingly, we find replacing frequency encoding with hash encoding leads to a cluttered mesh, indicating that it is desirable to encode coordinates as low-frequency signals in geometry learning. In addition, we explore the impact of middle neuron channels within the appearance mapping, and find that dimensions ranging from 64 to 256 strike a balance between expressivity and inference speed. These findings underscore the reasonable designs of DynTet for achieving desirable results. + +# 6. Conclusion + +We introduce Dynamic Tetrahedra (DynTet), a novel hybrid representation for realistic and expressive talking heads. DynTet upgrades tetrahedral meshes from statics to dynamics with a new architecture, a canonical space and guidance from geometry prior. DynTet can efficiently generate high-resolution talking videos with realism and precise motion control beyond prior works. Our work may inspire future research in the direction of Dynamic Tetrahedra. + +Acknowledgements. This paper is supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDA27000000), the National key research and development program of China (2021YFA1000403), the National Natural Science Foundation of China (Nos. U23B2012, 11991022) and the Fundamental Research Funds for the Central Universities (E3E41904). + +# References + +[1] ShahRukh Athar. Rignerf: Fully controllable neural 3d portraits. In CVPR, 2022. 1, 2 +[2] Tadas Baltrusaitis, Amir Zadeh, Yao Chong Lim, and Louis-Philippe Morency. Openface 2.0: Facial behavior analysis toolkit. In FG, 2018. 7 +[3] Volker Blanz and Thomas Vetter. 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These implicit methods are still confronted by visual artifacts and jitters, since the lack of explicit geometric constraints poses a fundamental challenge in accurately modeling complex facial deformations. In this paper, we introduce Dynamic Tetrahedra (DynTet), a novel hybrid representation that encodes explicit dynamic meshes by neural networks to ensure geometric consistency across various motions and viewpoints. DynTet is parameterized by the coordinate-based networks which learn signed distance, deformation, and material texture, anchoring the training data into a predefined tetrahedra grid. Leveraging Marching Tetrahedra, DynTet efficiently decodes textured meshes with a consistent topology, enabling fast rendering through a differentiable rasterizer and supervision via a pixel loss. To enhance training efficiency, we incorporate classical 3D Morphable Models to facilitate geometry learning and define a canonical space for simplifying texture learning. These advantages are readily achievable owing to the effective geometric representation employed in DynTet. Compared with prior works, DynTet demonstrates significant improvements in fidelity, lip synchronization, and real-time performance according to various metrics. Beyond producing stable and visually appealing synthesis videos, our method also outputs the dynamic meshes which is promising to enable many emerging applications. Code is available at https://github.com/zhangzc21/DynTet." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 611, + 128, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 611, + 128, + 624 + ], + "spans": [ + { + "bbox": [ + 47, + 611, + 128, + 624 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 632, + 287, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 632, + 287, + 693 + ], + "spans": [ + { + "bbox": [ + 46, + 632, + 287, + 693 + ], + "type": "text", + "content": "Talking head synthesis is a long-standing task with a wide range of applications, such as digital humans, metaverse and filmmaking. The set up of this task can be roughly categorized to two lines: 1) learning from a large-scale dataset to drive arbitrary portrait images by the motion sig-" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 213, + 545, + 286 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 213, + 545, + 286 + ], + "spans": [ + { + "bbox": [ + 306, + 213, + 545, + 286 + ], + "type": "text", + "content": "nal [7, 40, 41, 50, 62, 70, 77, 78]; and 2) building a personalized animatable head model from a several-minute video of a specific person [23, 31, 37, 53, 60, 61, 64, 67, 74]. We concentrate on the latter one, since it generally delivers high-quality synthesis results with intricate details and 3D naturalness, suitable for professional scenarios." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 289, + 546, + 492 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 289, + 546, + 492 + ], + "spans": [ + { + "bbox": [ + 304, + 289, + 546, + 492 + ], + "type": "text", + "content": "Building such an exquisite talking head avatar from video data poses challenges in faithful appearance, motion control, as well as low running cost. One line of methods [14, 19, 20, 28, 30, 61, 67] explicitly rely on 3D Morphable Models (3DMM) [3] to reconstruct and animate human faces by estimating the person-specific parameters. While these methods allow for efficient rendering and dynamic deformation, the fixed face topology makes them often fall short in generating characteristic details, e.g., hairstyle, glasses, and inner mouth. Recently, neural implicit representations, especially Neural Radiance Fields (NeRF) [43], provide a new way to realize faithful generation. Some seminal work [16, 23, 37, 53, 64] learn a direct mapping from the control signal to the talking head, meanwhile the efficient neural representations like voxel grid [15, 34, 57] and hash encoding [44] have been introduced to improve training and inference speed." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 495, + 547, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 495, + 547, + 686 + ], + "spans": [ + { + "bbox": [ + 304, + 495, + 547, + 686 + ], + "type": "text", + "content": "Despite the expressive capabilities, these implicit methods still need to improve many subtle issues in realism, e.g., head jitters, motionless mouths, and occasional artifacts. Researchers have discussed these issues from various aspects, e.g., introducing a canonical space for easier appearance learning [1, 49], developing compact models for more efficient training [31, 60], and using expressive driving conditions for better control [64, 65], against the naive baseline of NeRF. Essentially, the implicit definition for 3D objects complicates the analytical alternation of the underlying object geometry, leading to ineffective disentanglement of static appearance and motion from dynamic data, as opposed to the explicit meshes and vertex displacements for 3DMM. In viewing of this, it is appealing to incorporate the expressivity of implicit methods with an effective geometric control to take advantage of both lines of works." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 689, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 547, + 714 + ], + "type": "text", + "content": "We introduce Dynamic Tetrahedra (DynTet), a novel hybrid approach that encodes dynamic meshes within neural" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "type": "text", + "content": "*Corresponding author" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5209" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "content": "networks to assist explicit deformation. In essence, DynTet employs neural networks to predict attributes of underlying surfaces, from which explicit meshes can be extracted to fast render images with a differentiable rasterizer. On one hand, distinguished from implicit methods, the explicit geometry enables DynTet to learn a consistent 3D model across frames and directly express deformation as vertex displacement, thus DynTet is convenient to model the dynamics of talking head. On the other hand, unlike 3DMM with a preset topology, DynTet end-to-end learns personalized meshes and texture suitable for the given video." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 205, + 289, + 541 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 205, + 289, + 541 + ], + "spans": [ + { + "bbox": [ + 46, + 205, + 289, + 541 + ], + "type": "text", + "content": "Technically, the proposed DynTex is inspired by recent advancements in tetrahedral techniques [17], originally developed for 3D reconstruction [45] and synthesis [18, 54]. The key insight is a parameterized tetrahedral grid: Coordinate-based networks are used to learn the signed distance field (SDF) and refinement for the grid, then the meshes are subsequently decoded through the Marching Tetrahedra algorithm. Since these prior methods [17, 18, 45, 54] primarily work for static scenes, they can hardly render images with deformation, nor keep the mesh topology under different conditions [18]. This also largely prevents the parallelized rendering and training processes. In contrast, we redesign the framework that exclusively determines the mesh topology with SDF, while a new branch controls the geometric variations with deformation signals. We also estimate the elastic score of each vertex to specify the rigid (e.g., forehead) and non-rigid regions (e.g., mouth) of the head, so as to achieve precise deformations in local regions while maintaining stability in other parts. These designs ensure the topological consistency and expressivity across all decoded meshes, enabling a customized dynamic mesh beyond 3DMM. To improve training efficiency, we introduce geometry losses that supervise shape and motion using the 3DMM priors. This replenishes the limited depth information available in frontal talking videos. Moreover, we establish an interpretable canonical space for the dynamic mesh, reducing the complexity of texture learning. In summary, our contributions include:" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 543, + 287, + 675 + ], + "type": "list", + "angle": 0, + "index": 5, + "blocks": [ + { + "bbox": [ + 47, + 543, + 287, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 543, + 287, + 590 + ], + "spans": [ + { + "bbox": [ + 47, + 543, + 287, + 590 + ], + "type": "text", + "content": "(1). We propose DynTet, a novel hybrid representation that encodes dynamic head meshes in neural networks, where the explicit geometry delineated by tetrahedra facilitates appearance and motion learning." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 591, + 287, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 591, + 287, + 639 + ], + "spans": [ + { + "bbox": [ + 47, + 591, + 287, + 639 + ], + "type": "text", + "content": "(2). This is the first work that successfully extends the static tetrahedral representation to dynamic head avatars by a new elaborated architecture, a canonical space, and 3DMM guidance for modeling dynamic meshes." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 639, + 287, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 639, + 287, + 675 + ], + "spans": [ + { + "bbox": [ + 47, + 639, + 287, + 675 + ], + "type": "text", + "content": "(3). DynTet presents evident advantages in terms of fidelity, lip-sync precision, stability and runtime by thorough evaluation compared with prior works." + } + ] + } + ], + "index": 4 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "content": "The learned dynamic head meshes are promising together with existing 3D assets or AR/VR techniques for emerging applications such as human avatar and the meta" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 96 + ], + "type": "text", + "content": "verse, which may inspire further study on the hybrid representation for dynamic 3D objects." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 119, + 392, + 132 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 119, + 392, + 132 + ], + "spans": [ + { + "bbox": [ + 306, + 119, + 392, + 132 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 144, + 547, + 431 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 144, + 547, + 431 + ], + "spans": [ + { + "bbox": [ + 304, + 144, + 547, + 431 + ], + "type": "text", + "content": "Talking head synthesis. Most existing methods for talking head synthesis can be classified into three categories in terms of the modeling approaches. 2D-based methods [50, 68, 69, 76, 78] utilized generative models [21, 26, 29] as renderers to produce photorealistic portraits. While, these methods often fall short in achieving 3D naturalness and consistent pose control due to the absence of an explicit 3D model. 3DMM-based methods [14, 19, 20, 28, 30, 61, 67] leveraged 3D face knowledge to drive facial expression, resulting in quite natural talking style. As a trade-off, due to the lack of complete head topology they cannot guarantee consistency or fidelity beyond the facial region such as hair and inner mouth. Neural head avatar [22, 74, 75] has emerged as an attractive way for automatically creating 3D facial models. While earlier approaches [51, 66] required detailed scanning data, NeRFs [5, 43, 49] offer a solution to learn models from video clips, driven by the factors like 3DMM coefficients [16], audio feature [23], or facial landmarks [65]. Several recent works have enhanced control effects [1, 37, 64], system efficiency [31, 60] and few-shot training [32, 53]. Despite great progress, neural avatars still face challenges in realism and plausible motion, not to mention that NeRF rendering is computationally expensive when generating high-resolution images." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 438, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 438, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 438, + 547, + 715 + ], + "type": "text", + "content": "Neural 3D representation. Neural implicit functions are emerging as an effective representation of 3D object [35, 42, 43, 48, 55] using coordinate-based MLPs [44, 56, 59]. While prior methods [42, 48] required 3D supervision, several recent works [33, 36, 43, 47] demonstrated differentiable rendering for training directly from images. Meanwhile, NeRF [43] and followups [15, 44, 57, 73] performed volume rendering [27] on a continuous field for density and color, achieving impressive results for multi-view synthesis. As density is ambiguous to depict geometric details [63], they cannot explicitly edit shape or extract a high-quality surface with Marching Cubes [39], which makes it challenging in formulating deformation for dynamic scenes. Recent works [17, 54] proposed to convert deformable tetrahedral grid into surface meshes via the differentiable Marching Tetrahedral algorithm [11], where the SDF values are implicitly learned. The following methods [18, 45] further extended to jointly learn geometry and texture from image data. They can render photorealistic images competitive with NeRF in real-time. However, as these methods only work for static scenes, they cannot learn dynamics for modeling head avatars. We present an original effort to address this issue to learn dynamic tetrahedral meshes." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "type": "text", + "content": "5210" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 71, + 133, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 71, + 133, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 71, + 133, + 83 + ], + "type": "text", + "content": "3. Preliminaries" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 94, + 287, + 129 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 94, + 287, + 129 + ], + "spans": [ + { + "bbox": [ + 46, + 94, + 287, + 129 + ], + "type": "text", + "content": "We provide some background concepts and notations. At first, we define operations between sets as element-wise operations, and functions are mapped element-wise as well." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "spans": [ + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": "Tetrahedral meshes have been studied in deep learning [17, 54] as a hybrid representation for 3D shape modeling. Consider an object lying in a unit cube, a tetrahedral grid denoted as " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "(\\mathbf{V}_{tet},\\mathbf{T}_{tet})" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " is pre-defined to tetrahedralize the cube into " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "r^3" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " resolution. Each tetrahedron " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "T_{k}\\in \\mathbf{T}_{tet}" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " is defined by four vertices " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{v}_{a_k},\\mathbf{v}_{b_k},\\mathbf{v}_{c_k},\\mathbf{v}_{d_k}\\}" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " is the total number of tetrahedra. Additionally, each vertex " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "\\mathbf{v}_i" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " contains a learnable SDF value " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "s_i\\in \\mathbb{R}" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " to express the distance away from the underlying surface, and a small offset " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "\\Delta \\mathbf{v}_i\\in [-\\frac{1}{r},\\frac{1}{r}]^3" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " from its initial coordinates to refine the grid as " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "\\mathbf{v}_i' = \\mathbf{v}_i + \\Delta \\mathbf{v}_i" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": ". We let " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "S = \\{s_i\\}_{i = 1}^K" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "\\Delta \\mathbf{V} = \\{\\Delta \\mathbf{v}_i\\}_{i = 1}^K" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": ". Notably, the surface shape within the tetrahedral grid is primarily determined by the SDF values " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " as " + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "inline_equation", + "content": "\\Delta \\mathbf{V}" + }, + { + "bbox": [ + 46, + 133, + 289, + 300 + ], + "type": "text", + "content": " is confined within the resolution boundaries." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "text", + "content": "Marching Tetrahedra " + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "inline_equation", + "content": "(MT)" + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "text", + "content": " is an iso-surface extraction algorithm [11] to generate triangular meshes from tetrahedral meshes. Given SDF values " + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "inline_equation", + "content": "\\{s_a, s_b, s_c, s_d\\}" + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "text", + "content": " of a tetrahedron, " + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "inline_equation", + "content": "MT" + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "text", + "content": " determines the surface topology inside the tetrahedron based on the signs of these values, where the " + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "inline_equation", + "content": "2^4" + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "text", + "content": " configurations in total fall into 3 unique cases after considering rotation symmetry [54]. A simplified 2D example can be found in Figure 1. Once the topology is identified, a new vertex denoted as " + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "inline_equation", + "content": "\\mathbf{v}_{ab}" + }, + { + "bbox": [ + 46, + 302, + 289, + 422 + ], + "type": "text", + "content": " by example, is located at the zero crossings of linear interpolation along the tetrahedral edges:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 84, + 426, + 287, + 449 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 84, + 426, + 287, + 449 + ], + "spans": [ + { + "bbox": [ + 84, + 426, + 287, + 449 + ], + "type": "interline_equation", + "content": "\\operatorname {l e r p} \\left(\\mathbf {v} _ {a}, \\mathbf {v} _ {b}, s _ {a}, s _ {b}\\right) = \\frac {s _ {a} \\cdot \\mathbf {v} _ {a} - s _ {b} \\cdot \\mathbf {v} _ {b}}{s _ {a} - s _ {b}}, \\tag {1}", + "image_path": "b5286db420c727fde16afdeea2ca513759d32e24302dbc3e7a8805792b36345b.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "spans": [ + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "type": "text", + "content": "the same for other vertices. Note that this equation is evaluated only when signs differ " + }, + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "type": "inline_equation", + "content": "(\\mathrm{sign}(s_a)\\neq \\mathrm{sign}(s_b))" + }, + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "type": "text", + "content": " to prevent singularity. Leveraging " + }, + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "type": "inline_equation", + "content": "MT" + }, + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "type": "text", + "content": " on the deformed tetrahedral grid " + }, + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "type": "inline_equation", + "content": "(\\mathbf{V}_{tet} + \\Delta \\mathbf{V},\\mathbf{T}_{tet})" + }, + { + "bbox": [ + 46, + 452, + 287, + 524 + ], + "type": "text", + "content": ", the triangular surface of the encoded object can be acquired in a differentiable manner. We omit constant symbols and represent this process as" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 102, + 528, + 287, + 541 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 102, + 528, + 287, + 541 + ], + "spans": [ + { + "bbox": [ + 102, + 528, + 287, + 541 + ], + "type": "interline_equation", + "content": "\\mathbf {V} _ {t r i}, \\mathbf {T} _ {t r i} = \\operatorname {M a r T e t} (\\mathcal {S}, \\Delta \\mathbf {V}), \\tag {2}", + "image_path": "f1da953b8ef4f1a2b8a110d45223550339d9ce0f652b122405cfff22324652b9.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "type": "inline_equation", + "content": "\\mathbf{V}_{tri}" + }, + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_{tri}" + }, + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "type": "text", + "content": " are the sets of vertices and connectivity of the triangular meshes, respectively." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 572, + 287, + 597 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 572, + 287, + 597 + ], + "spans": [ + { + "bbox": [ + 46, + 572, + 287, + 597 + ], + "type": "text", + "content": "3D Morphable Models provide generic parametric models [3] for synthesizing face shapes, usually expressed as" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 87, + 615, + 287, + 629 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 87, + 615, + 287, + 629 + ], + "spans": [ + { + "bbox": [ + 87, + 615, + 287, + 629 + ], + "type": "interline_equation", + "content": "\\mathbf {V} _ {3 d m m} = \\bar {\\mathbf {V}} _ {3 d m m} + \\mathbf {U} _ {i d} \\gamma + \\mathbf {U} _ {e x p} \\boldsymbol {\\alpha}. \\tag {3}", + "image_path": "179576cff98e416602c3211ac820b59e5f01772ddc1d2dcb3c736f35128e47b8.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": "Here " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\bar{\\mathbf{V}}_{3dmm}" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": " denotes a mean shape, " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{U}_{id}" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{U}_{exp}" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": " are the matrices of basis vectors in the identity and expression space, respectively. " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": " are coefficients for the identity and expression, allowing for a tractable control over facial variations. The parameter " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": " has been served as a versatile representation for driving facial deformation [13]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 71, + 389, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 71, + 389, + 85 + ], + "spans": [ + { + "bbox": [ + 306, + 71, + 389, + 85 + ], + "type": "text", + "content": "4. Methodology" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 92, + 547, + 248 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 92, + 547, + 248 + ], + "spans": [ + { + "bbox": [ + 304, + 92, + 547, + 248 + ], + "type": "text", + "content": "In this section, we introduce a framework called Dynamic Tetrahedra (DynTet) to rapidly learn 3D head avatars from short video sequences, and enable real-time rendering of high-quality talking heads. Generally, DynTet upgrades recent tetrahedral representation [17, 18, 45] tailored for dynamic head modeling. As shown in Figure 1, neural networks are trained to encode head shapes within a tetrahedral grid [54], and then the Marching Tetrahedra (MT) [11] decodes the meshes for photorealistic rasterization rendering. In the following, we delineate the talking head task through the lens of tetrahedral representation (Sec.4.1), and elucidate our improvements in the geometry model (Sec.4.2), rendering process (Sec.4.3), and training losses (Sec.4.4)." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 258, + 417, + 269 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 258, + 417, + 269 + ], + "spans": [ + { + "bbox": [ + 305, + 258, + 417, + 269 + ], + "type": "text", + "content": "4.1. Problem statement" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "spans": [ + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "type": "text", + "content": "Given a sequence of head images " + }, + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{I}_i\\}_{i=1}^n" + }, + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "type": "text", + "content": ", we aim to reenact the specific head driven by motion signals, which typically includes camera parameters " + }, + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{P}_i\\}_{i=1}^n" + }, + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "type": "text", + "content": " for rigid motion, and talking signals which we represent using 3DMM expression coefficients " + }, + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "type": "inline_equation", + "content": "\\{\\alpha_i\\}_{i=1}^n" + }, + { + "bbox": [ + 304, + 277, + 547, + 338 + ], + "type": "text", + "content": " for non-rigid facial expressions." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "spans": [ + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": "**Formulation.** Drawing inspiration from the seminal work of [54], which applied tetrahedral meshes for multi-view reconstruction, we propose a basic paradigm for talking head modeling: (1) A geometry mapping " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "\\mathbf{F}" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": " first predicts " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "\\Delta \\mathbf{V}" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "\\mathbf{V}_{tet}" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": ". (2) The outputs from " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "\\mathbf{F}" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": " are processed based on Eq. (2) to obtain the triangular mesh, which are then rasterized given camera pose " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": " to get the coordinates of image pixels in the model space. (3) An appearance mapping " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "\\mathbf{G}" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": " predicts the materials, which is incorporated with a lighting model " + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 346, + 545, + 478 + ], + "type": "text", + "content": " for the physically-based rendering (PBR) [4]. We summarize the overall process as" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 341, + 479, + 545, + 509 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 341, + 479, + 545, + 509 + ], + "spans": [ + { + "bbox": [ + 341, + 479, + 545, + 509 + ], + "type": "interline_equation", + "content": "\\min _ {\\boldsymbol {F}, \\boldsymbol {G}, \\boldsymbol {L}} \\frac {1}{n} \\sum_ {i = 1} ^ {n} L o s s (\\hat {\\mathbf {I}} _ {i}, \\mathbf {I} _ {i}) \\tag {4}", + "image_path": "c64ce7a7705623d4d8e6a3e7978fc1e3b3cf2c94c5365df720c40b79c38472f1.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 339, + 511, + 512, + 524 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 339, + 511, + 512, + 524 + ], + "spans": [ + { + "bbox": [ + 339, + 511, + 512, + 524 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 339, + 511, + 512, + 524 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}_i = \\mathrm{Rendering}(\\pmb {F},\\pmb {G},\\pmb {L},\\pmb {\\alpha}_i,\\mathbf{P}_i)" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 525, + 545, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 525, + 545, + 548 + ], + "spans": [ + { + "bbox": [ + 304, + 525, + 545, + 548 + ], + "type": "text", + "content": "Herein, Rendering denotes the PBR procedure, and the loss function comprises a set of constraints on the predictions." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": "Challenges. Prior works [17, 18, 54] commonly parameterize " + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{F}" + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": " using a neural network " + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": " to predict SDF values and relative offsets, i.e., " + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{S},\\Delta \\mathbf{V} = f(\\mathbf{V}_{tet})" + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": ", while introducing the talking signal " + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": " as a condition will bring several problems. First, once SDF values vary along with the conditions, it is difficult to learn the intricate deformation of the facial area with a simple MLP. Second, modern GPUs do not support parallelization for meshes with a variable topology, resulting in inefficient training and running processes. Lastly, previous approaches were designed for " + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": " data, while our training data only includes frontal head images. Consequently, this inaccurate estimation of geometry leads to evident artifacts in the rendered videos." + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "text", + "content": "5211" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 71, + 545, + 228 + ], + "blocks": [ + { + "bbox": [ + 50, + 71, + 545, + 228 + ], + "lines": [ + { + "bbox": [ + 50, + 71, + 545, + 228 + ], + "spans": [ + { + "bbox": [ + 50, + 71, + 545, + 228 + ], + "type": "image", + "image_path": "058501d2bab3f2c8bdb0df2da62fe9db9d045826b3b5cc12f36b534bab40274c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 237, + 548, + 295 + ], + "lines": [ + { + "bbox": [ + 46, + 237, + 548, + 295 + ], + "spans": [ + { + "bbox": [ + 46, + 237, + 548, + 295 + ], + "type": "text", + "content": "Figure 1. Illustration of the proposed DynTet for modeling a talking head. Left panel: The top branch predicts topology-related information, including SDF values " + }, + { + "bbox": [ + 46, + 237, + 548, + 295 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 46, + 237, + 548, + 295 + ], + "type": "text", + "content": " and elastic scores. The bottom branch, conditioned by talking signals, predicts the offset vectors scaled by the elastic scores to yield deformation vectors " + }, + { + "bbox": [ + 46, + 237, + 548, + 295 + ], + "type": "inline_equation", + "content": "\\Delta \\mathbf{v}" + }, + { + "bbox": [ + 46, + 237, + 548, + 295 + ], + "type": "text", + "content": " for driving the tetrahedral grid. Then, the Marching Tetrahedra (MT) algorithm decodes the meshes. Right panel: The pixel coordinates are projected into a canonical space. Then the physically-based materials and lighting are sampled for rendering images." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 304, + 164, + 318 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 304, + 164, + 318 + ], + "spans": [ + { + "bbox": [ + 47, + 304, + 164, + 318 + ], + "type": "text", + "content": "4.2. Geometry modeling" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 323, + 288, + 419 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 323, + 288, + 419 + ], + "spans": [ + { + "bbox": [ + 46, + 323, + 288, + 419 + ], + "type": "text", + "content": "To address the mentioned challenges, we initially disentangle topology and geometry from head shapes within the tetrahedra grid, allowing for generating dynamic meshes with a consistent topology. Furthermore, we enhance the tetrahedral attributes by introducing a novel elastic score, facilitating precise control over deformation. These improvements are incorporated by modifying the internal structure of the geometry mapping as" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 60, + 427, + 287, + 446 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 60, + 427, + 287, + 446 + ], + "spans": [ + { + "bbox": [ + 60, + 427, + 287, + 446 + ], + "type": "interline_equation", + "content": "\\boldsymbol {F}: \\mathbf {V} _ {t e t}, \\boldsymbol {\\alpha} \\rightarrow \\mathcal {S}, \\Delta \\mathbf {V} \\tag {5}", + "image_path": "2a0789418177341cdf140e00e3d3ca1749d35cda5c227821fcdb59eaaf3b9aef.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 61, + 442, + 262, + 455 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 442, + 262, + 455 + ], + "spans": [ + { + "bbox": [ + 61, + 442, + 262, + 455 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 61, + 442, + 262, + 455 + ], + "type": "inline_equation", + "content": "\\mathcal{S},\\mathcal{E} = f_1(\\mathbf{V}_{tet}),\\Delta \\mathbf{V} = \\mathcal{E}\\cdot f_2(\\mathbf{V}_{tet},\\boldsymbol {\\alpha})" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "spans": [ + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "type": "text", + "content": "Here, " + }, + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "type": "inline_equation", + "content": "f_{1}" + }, + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "type": "inline_equation", + "content": "f_{2}" + }, + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "type": "text", + "content": " are coordinate-based MLPs, while " + }, + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "type": "inline_equation", + "content": "\\mathcal{E} \\coloneqq [f_1(\\mathbf{V}_{tet})]_e" + }, + { + "bbox": [ + 47, + 462, + 287, + 487 + ], + "type": "text", + "content": " represents the set of non-negative elastic scores." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 491, + 287, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 491, + 287, + 563 + ], + "spans": [ + { + "bbox": [ + 46, + 491, + 287, + 563 + ], + "type": "text", + "content": "Shape representation. Ideal face models exhibit topological invariance regardless of deformation. While implicit SDF representations present challenges in fulfilling this property, it is clear for explicit meshes like 3DMM [3] to maintain the number of vertices and their relationship. By employing Eq. (1) within " + }, + { + "bbox": [ + 46, + 491, + 287, + 563 + ], + "type": "inline_equation", + "content": "MT" + }, + { + "bbox": [ + 46, + 491, + 287, + 563 + ], + "type": "text", + "content": " algorithm, we have" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 52, + 570, + 287, + 599 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 570, + 287, + 599 + ], + "spans": [ + { + "bbox": [ + 52, + 570, + 287, + 599 + ], + "type": "interline_equation", + "content": "\\mathbf {v} _ {a b} ^ {\\prime} = \\underbrace {\\operatorname {l e r p} \\left(\\mathbf {v} _ {a} , \\mathbf {v} _ {b} , s _ {a} , s _ {b}\\right)} _ {\\text {t o p o l o g y a n d i d e n t i t y}} + \\underbrace {\\operatorname {l e r p} \\left(\\Delta \\mathbf {v} _ {a} , \\Delta \\mathbf {v} _ {b} , s _ {a} , s _ {b}\\right)} _ {\\text {g e o m e t r y a n d e x p r e s s i o n}}. \\tag {6}", + "image_path": "dc9dcc6dd78dde672381d45fcce8a80ad267fe36eba4d84a9f69761b0162d245.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 605, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 288, + 714 + ], + "type": "text", + "content": "Given that vertices " + }, + { + "bbox": [ + 46, + 605, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{v}_a" + }, + { + "bbox": [ + 46, + 605, + 288, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 605, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{v}_b" + }, + { + "bbox": [ + 46, + 605, + 288, + 714 + ], + "type": "text", + "content": " are pre-defined in the tetrahedral grid, the first term is just affected by the SDF values. Hence, our design in Eq.(5), which segregates SDF from the talking signal, results in a topologically invariant mesh. Meanwhile, the second term indicates that the geometry of mesh explicitly relies on the tetrahedral grid offsets. Additionally, a comparison with Eq. (3) reveals that DynTet functions as a quasi-3DMM hybrid model, enabling additive changes to facial shapes driven by neural networks." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "spans": [ + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "text", + "content": "Elastic estimation. Our design necessitates relaxing the range of " + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "inline_equation", + "content": "\\Delta \\mathbf{v}_i\\in [-\\frac{1}{r},\\frac{1}{r}]^3" + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "text", + "content": " to allow greater flexibility in geometric variations. However, this relaxation potentially leads to local jitters that significantly impact visual quality. We introduce an elastic scoring mechanism for each vertex within the tetrahedral grid to regulate deformation. These scores " + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "text", + "content": " are predicted by the neural network " + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "inline_equation", + "content": "f_{1}" + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "text", + "content": " to quantify the non-rigid properties across different regions of the human head. For instance, areas like the forehead and nose exhibit near-rigid behavior with minimal changes during talking, while regions like the mouth and eyes are more flexible and primarily contribute to deformations. In this way, the offset vectors are scaled using the elastic scores to determine the deformable vectors " + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "inline_equation", + "content": "\\Delta \\mathbf{V}" + }, + { + "bbox": [ + 304, + 304, + 547, + 473 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 477, + 547, + 515 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 477, + 547, + 515 + ], + "spans": [ + { + "bbox": [ + 304, + 477, + 547, + 515 + ], + "type": "text", + "content": "Architecture details. As shown in Figure 1, we formulate neural networks " + }, + { + "bbox": [ + 304, + 477, + 547, + 515 + ], + "type": "inline_equation", + "content": "f_{1}" + }, + { + "bbox": [ + 304, + 477, + 547, + 515 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 477, + 547, + 515 + ], + "type": "inline_equation", + "content": "f_{2}" + }, + { + "bbox": [ + 304, + 477, + 547, + 515 + ], + "type": "text", + "content": " as a composition of regular lightweight MLPs and a frequency positional encoding [59]" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 335, + 523, + 545, + 539 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 335, + 523, + 545, + 539 + ], + "spans": [ + { + "bbox": [ + 335, + 523, + 545, + 539 + ], + "type": "interline_equation", + "content": "\\gamma (\\mathbf {v}) = < \\left(\\sin \\left(2 ^ {l} \\pi \\mathbf {v}\\right), \\cos \\left(2 ^ {l} \\pi \\mathbf {v}\\right)\\right) > _ {l = 0} ^ {L - 1}. \\tag {7}", + "image_path": "b239586e357b7dbd6f5f0493f2d710f46abe4eb872f49aa8462b7756f5b10f65.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 543, + 547, + 627 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 543, + 547, + 627 + ], + "spans": [ + { + "bbox": [ + 304, + 543, + 547, + 627 + ], + "type": "text", + "content": "We find that the simple frequency coding outperforms hash grid encoding [44] which tends to generate surfaces with significant noise. To maintain temporal consistency, we follow [41, 52] to represent the deformation of any timestamp by the window of adjacent 27 frames of expression coefficients, which are averaged into a 256-dimensional feature vector by a trainable convolutional encoder." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 634, + 410, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 634, + 410, + 647 + ], + "spans": [ + { + "bbox": [ + 306, + 634, + 410, + 647 + ], + "type": "text", + "content": "4.3. Neural rendering" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "text", + "content": "This procedure aims to automatically texture the triangular meshes " + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "inline_equation", + "content": "(\\mathbf{V}_{tri},\\mathbf{T}_{tri})" + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "text", + "content": " extracted by " + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "inline_equation", + "content": "MT" + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "text", + "content": " algorithm, and generate photorealistic images " + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}" + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "text", + "content": " given camera pose " + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "text", + "content": " and talking signal " + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 652, + 547, + 715 + ], + "type": "text", + "content": ". In the realm of deformable reconstruction [38, 38, 46, 49], the canonical or template model" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5212" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "content": "serves an important role in reducing the complexity of texture parametrization. Thanks to the well-designed geometry model in DynTet, defining a canonical space becomes straightforward. We upgrade the vanilla rendering process by incorporating a canonical projection, thereby unifying both shading and lighting within a single space." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 148, + 288, + 196 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 148, + 288, + 196 + ], + "spans": [ + { + "bbox": [ + 46, + 148, + 288, + 196 + ], + "type": "text", + "content": "Canonical projection. We propose the canonical projection CanProj to map the pixel coordinates " + }, + { + "bbox": [ + 46, + 148, + 288, + 196 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_{2d}" + }, + { + "bbox": [ + 46, + 148, + 288, + 196 + ], + "type": "text", + "content": " from an arbitrary camera pose " + }, + { + "bbox": [ + 46, + 148, + 288, + 196 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 46, + 148, + 288, + 196 + ], + "type": "text", + "content": " into a canonical 3D space where the mean expression lies. This process is expressed as" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 79, + 202, + 253, + 216 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 79, + 202, + 253, + 216 + ], + "spans": [ + { + "bbox": [ + 79, + 202, + 253, + 216 + ], + "type": "interline_equation", + "content": "\\bar {\\mathcal {C}} _ {3 d} = \\operatorname {C a n P r o j} \\left(\\mathcal {C} _ {2 d}, \\mathbf {V} _ {t r i}, \\mathbf {P}; \\bar {\\mathbf {V}} _ {t r i}, \\mathbf {T} _ {t r i}\\right),", + "image_path": "6597da5d4bb777619aaeaa844b139287e238066b44dab71ad0f2e01f056a4ebe.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 81, + 218, + 287, + 231 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 81, + 218, + 287, + 231 + ], + "spans": [ + { + "bbox": [ + 81, + 218, + 287, + 231 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 81, + 218, + 287, + 231 + ], + "type": "inline_equation", + "content": "\\bar{\\alpha} = \\Sigma_{i=1}^{n} \\alpha_{i} / n" + }, + { + "bbox": [ + 81, + 218, + 287, + 231 + ], + "type": "text", + "content": ", (8)" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 81, + 233, + 252, + 246 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 81, + 233, + 252, + 246 + ], + "spans": [ + { + "bbox": [ + 81, + 233, + 252, + 246 + ], + "type": "text", + "content": "and " + }, + { + "bbox": [ + 81, + 233, + 252, + 246 + ], + "type": "inline_equation", + "content": "\\bar{\\mathbf{V}}_{tri},\\mathbf{T}_{tri} = \\mathrm{MatTet}(\\pmb {F}(\\mathbf{V}_{tet},\\bar{\\alpha}))" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "spans": [ + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "text", + "content": "In practical implementation, CanProj can be executed readily using a modern mesh rasterizer to derive coordinates " + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_{3d}" + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "text", + "content": " and 2D barycentric coordinates within " + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "inline_equation", + "content": "(\\mathbf{V}_{tri},\\mathbf{T}_{tri})" + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "text", + "content": ". Then, " + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "inline_equation", + "content": "\\bar{\\mathcal{C}}_{3d}" + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "text", + "content": " positioned in the canonical space, is computed through barycentric interpolation over " + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "inline_equation", + "content": "(\\bar{\\mathbf{V}}_{tri},\\mathbf{T}_{tri})" + }, + { + "bbox": [ + 46, + 253, + 287, + 313 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 317, + 287, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 317, + 287, + 413 + ], + "spans": [ + { + "bbox": [ + 46, + 317, + 287, + 413 + ], + "type": "text", + "content": "Appearance model. We follow previous work [4, 45] to adopt a physically-base material model, which allows easy integration of 3D assets within existing engines. To parameterize the appearance mapping " + }, + { + "bbox": [ + 46, + 317, + 287, + 413 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 317, + 287, + 413 + ], + "type": "text", + "content": ", we employ a coordinate-based neural network comprising a hash grid encoder [44] for querying spatial features and a lightweight MLP for predicting materials. This network takes the projected coordinates and talking signal as inputs:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 116, + 421, + 287, + 433 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 116, + 421, + 287, + 433 + ], + "spans": [ + { + "bbox": [ + 116, + 421, + 287, + 433 + ], + "type": "interline_equation", + "content": "\\mathcal {K} _ {d}, \\mathcal {K} _ {\\text {o r m}} = \\boldsymbol {G} (\\bar {\\mathcal {C}} _ {3 d}, \\boldsymbol {\\alpha}). \\tag {9}", + "image_path": "64fe6481b547e2648848e1a29dfdb239b9541fb44903e49cdb3b5eda18a9d038.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "spans": [ + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "text", + "content": "Here, " + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "inline_equation", + "content": "\\mathcal{K}_d" + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "text", + "content": " comprises three-channel diffuse albedo, and " + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "inline_equation", + "content": "\\mathcal{K}_{orm}" + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "text", + "content": " is the set of occupancy " + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "inline_equation", + "content": "k_{o}" + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "text", + "content": ", roughness " + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "inline_equation", + "content": "k_{r}" + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "text", + "content": ", and metalness factors " + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "inline_equation", + "content": "k_{m}" + }, + { + "bbox": [ + 46, + 441, + 287, + 513 + ], + "type": "text", + "content": " for the GGX normal distribution function [9]. Unlike prior works, we do not predict normals, but instead compute them directly using the triangular mesh in the model space, which yields similar results." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "spans": [ + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "text", + "content": "Lighting model. We leverage the image based lighting model, where the environment light is given by a trainable mapping " + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "inline_equation", + "content": "\\pmb{L}" + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "text", + "content": ". For each position " + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "inline_equation", + "content": "\\mathbf{v} \\in \\mathcal{C}_{3d}" + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "text", + "content": " with a normal vector " + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "inline_equation", + "content": "\\mathbf{n}" + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "text", + "content": ", the color along direction " + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "inline_equation", + "content": "\\omega_{o}" + }, + { + "bbox": [ + 46, + 516, + 287, + 565 + ], + "type": "text", + "content": " is computed by" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 99, + 572, + 287, + 585 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 99, + 572, + 287, + 585 + ], + "spans": [ + { + "bbox": [ + 99, + 572, + 287, + 585 + ], + "type": "interline_equation", + "content": "L (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}) = L _ {d} (\\mathbf {v}) + L _ {s} (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}), \\tag {10}", + "image_path": "e89e02bd0e6b3f8c83ec96121c5b1f18637f2a7d19771360e73eb37ea1550c55.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "spans": [ + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "type": "inline_equation", + "content": "L_{d}" + }, + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "type": "text", + "content": " is the diffuse intensity and " + }, + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "type": "inline_equation", + "content": "L_{s}" + }, + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "type": "text", + "content": " is the specular intensity. Consider a hemisphere with the incident direction " + }, + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "type": "inline_equation", + "content": "\\Omega = \\{\\pmb {\\omega}_i:\\pmb {\\omega}_i^T\\mathbf{n}\\geq 0\\}" + }, + { + "bbox": [ + 46, + 593, + 287, + 629 + ], + "type": "text", + "content": ", the first diffuse term is computed by" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 67, + 637, + 287, + 659 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 637, + 287, + 659 + ], + "spans": [ + { + "bbox": [ + 67, + 637, + 287, + 659 + ], + "type": "interline_equation", + "content": "L _ {d} (\\mathbf {v}) = \\left(1 - k _ {m}\\right) \\boldsymbol {k} _ {d} \\int_ {\\Omega} \\boldsymbol {L} _ {i} \\left(\\mathbf {v}, \\boldsymbol {\\omega} _ {i}\\right) \\left(\\boldsymbol {\\omega} _ {i} ^ {T} \\mathbf {n}\\right) \\mathrm {d} \\boldsymbol {\\omega} _ {i}. \\tag {11}", + "image_path": "d4ec5fc2c00d1861f87c259aac23eed35f6fcb845316a8dcf157492724aee102.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 662, + 287, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 662, + 287, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 662, + 287, + 687 + ], + "type": "text", + "content": "And the second term is based on Cook-Torrance microfacet specular shading mode model [9] " + }, + { + "bbox": [ + 46, + 662, + 287, + 687 + ], + "type": "inline_equation", + "content": "r(\\omega_o,\\omega_i)" + }, + { + "bbox": [ + 46, + 662, + 287, + 687 + ], + "type": "text", + "content": " to compute" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 55, + 693, + 287, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 693, + 287, + 716 + ], + "spans": [ + { + "bbox": [ + 55, + 693, + 287, + 716 + ], + "type": "interline_equation", + "content": "L _ {s} (\\mathbf {v}, \\boldsymbol {\\omega} _ {o}) = \\boldsymbol {k} _ {s} \\int_ {\\Omega} r \\left(\\boldsymbol {\\omega} _ {o}, \\boldsymbol {\\omega} _ {i}\\right) \\boldsymbol {L} _ {i} (\\mathbf {v}, \\boldsymbol {\\omega} _ {i}) \\left(\\boldsymbol {\\omega} _ {i} ^ {T} \\mathbf {n}\\right) \\mathrm {d} \\boldsymbol {\\omega} _ {i}, \\tag {12}", + "image_path": "6215a0f8d547bdf282323e711557690c86f8b41a4aa554ff79f2e33069a1d537.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": "where the specular color " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "\\pmb{k}_s = (1 - k_m) \\cdot 0.04 + k_m \\pmb{k}_d" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": ". Following [45], we parameterize " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "\\pmb{L}" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " with a cube map with resolution " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "6 \\times 512 \\times 512" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": ", and the calculate the hemisphere integration by the split-sum method [25]. By aggregating the rendered pixel colors along the camera pose, we obtain the rendered image " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}} = \\{k_o \\cdot L(\\mathbf{v}, \\pmb{\\omega}_o) | \\mathbf{v} \\in \\mathcal{C}_{3d}\\}" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 150, + 398, + 163 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 150, + 398, + 163 + ], + "spans": [ + { + "bbox": [ + 306, + 150, + 398, + 163 + ], + "type": "text", + "content": "4.4. Training losses" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 169, + 545, + 229 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 169, + 545, + 229 + ], + "spans": [ + { + "bbox": [ + 304, + 169, + 545, + 229 + ], + "type": "text", + "content": "Thanks to its hybrid representation, DynTet possesses an interpretable SDF space and a cost-efficient rendering procedure. This unique combination allows us to supervise its training in both image and geometry space, facilitating the estimation of reasonable 3D models from frontal images." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 232, + 545, + 293 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 232, + 545, + 293 + ], + "spans": [ + { + "bbox": [ + 304, + 232, + 545, + 293 + ], + "type": "text", + "content": "Image supervision. Given an image " + }, + { + "bbox": [ + 304, + 232, + 545, + 293 + ], + "type": "inline_equation", + "content": "\\mathbf{I}" + }, + { + "bbox": [ + 304, + 232, + 545, + 293 + ], + "type": "text", + "content": " and its prediction " + }, + { + "bbox": [ + 304, + 232, + 545, + 293 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}" + }, + { + "bbox": [ + 304, + 232, + 545, + 293 + ], + "type": "text", + "content": ", we train DynTet with the MSE loss for pixel-level reconstruction, and apply the overall LPIPS loss [71] for enhancing sharp details [31]. Besides, we find silhouette loss is important to provide shape guidance. The image loss is" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 313, + 297, + 545, + 311 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 297, + 545, + 311 + ], + "spans": [ + { + "bbox": [ + 313, + 297, + 545, + 311 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {i m g} = \\mathcal {L} _ {m s e} (\\hat {\\mathbf {I}}, \\mathbf {I}) + \\mathcal {L} _ {m s e} (\\hat {\\mathbf {I}} _ {o}, \\mathbf {I} _ {o}) + \\lambda_ {1} \\mathcal {L} _ {L P I P S} (\\hat {\\mathbf {I}}, \\mathbf {I}), \\tag {13}", + "image_path": "9ec03e73721c1b92f45b0d66bffa6e7c01b5f13d2c2e7d791552125a98f61d21.jpg" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 316, + 545, + 352 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 316, + 545, + 352 + ], + "spans": [ + { + "bbox": [ + 304, + 316, + 545, + 352 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 316, + 545, + 352 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}_o" + }, + { + "bbox": [ + 304, + 316, + 545, + 352 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 316, + 545, + 352 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_o" + }, + { + "bbox": [ + 304, + 316, + 545, + 352 + ], + "type": "text", + "content": " denote the binary masks of head regions. We combine the head, background and torso together to train in practice to prevent noise around the facial contours." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 356, + 545, + 439 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 356, + 545, + 439 + ], + "spans": [ + { + "bbox": [ + 304, + 356, + 545, + 439 + ], + "type": "text", + "content": "3DMM supervision. Frontal head views in talking videos often lack adequate depth information, resulting in flawed geometry estimation and artifacts in synthesized profile face. To counter this, we leverage 3DMM [3] as a geometry prior to mitigate these issues in the SDF space. We introduce two key losses to incorporate 3DMM. First, the normal distance loss " + }, + { + "bbox": [ + 304, + 356, + 545, + 439 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ndl}" + }, + { + "bbox": [ + 304, + 356, + 545, + 439 + ], + "type": "text", + "content": " constrains the canonical model:" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 315, + 445, + 545, + 457 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 445, + 545, + 457 + ], + "spans": [ + { + "bbox": [ + 315, + 445, + 545, + 457 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {n d l} = \\mathbb {E} _ {s \\sim U (- a, a)} \\| f _ {1} \\left(\\mathbf {V} _ {3 d m m} ^ {\\bar {\\alpha}} + s \\cdot \\mathbf {N} _ {3 d m m} ^ {\\bar {\\alpha}}\\right) - s \\| _ {2} ^ {2}, \\tag {14}", + "image_path": "52337c958190c77a4e1833e5d07de32f04c791333f4946740a9bcab3bf2129b7.jpg" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "spans": [ + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\mathbf{V}_{3dmm}^{\\bar{\\alpha}}" + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\mathbf{N}_{3dmm}^{\\bar{\\alpha}}" + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "text", + "content": " represent 3DMM vertices and normal vectors generated by coefficient " + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\bar{\\alpha}" + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "text", + "content": ", while " + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "text", + "content": " is a small value which we set to 0.1. " + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ndl}" + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "text", + "content": " injects facial prior into " + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "inline_equation", + "content": "f_{1}" + }, + { + "bbox": [ + 304, + 463, + 545, + 547 + ], + "type": "text", + "content": ", affecting the SDF values around 3DMM surface. Consequently, it avoids excessive restraint compared to full-space supervision [48], enabling adaptive learning in other regions. The second facial deformation loss is expressed as" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 310, + 563, + 545, + 577 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 563, + 545, + 577 + ], + "spans": [ + { + "bbox": [ + 310, + 563, + 545, + 577 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {f d l} = \\left\\| \\left[ f _ {1} \\left(\\mathbf {V} _ {3 d m m}\\right) \\right] _ {e} f _ {2} \\left(\\mathbf {V} _ {3 d m m}, \\boldsymbol {\\alpha}\\right) - \\mathbf {U} _ {e x p} (\\boldsymbol {\\alpha} - \\bar {\\boldsymbol {\\alpha}}) \\right\\| _ {2} ^ {2}. \\tag {15}", + "image_path": "f8e722ce8ad36bfbf4a730894533a8005224bdbfe2094f66823114f7b9de4f76.jpg" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 582, + 545, + 630 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 630 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 630 + ], + "type": "text", + "content": "This loss helps the tetrahedral grid to mimic the 3DMM deformation. Although these losses target 3DMM vertices, the tetrahedral vertices are appropriately constrained due to their spatial density covering the 3DMM vertices." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 304, + 634, + 545, + 694 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 634, + 545, + 694 + ], + "spans": [ + { + "bbox": [ + 304, + 634, + 545, + 694 + ], + "type": "text", + "content": "Loss function. We introduce a regularization term for the elastic score, denoted as " + }, + { + "bbox": [ + 304, + 634, + 545, + 694 + ], + "type": "inline_equation", + "content": "\\mathcal{R}_{es} = \\| [f_1(\\mathbf{V}_{3dmm})]_e\\| _2^2" + }, + { + "bbox": [ + 304, + 634, + 545, + 694 + ], + "type": "text", + "content": ", to reinforce the rigid property. We incorporate the weighted combination of the above constraints as follows to formulate the loss function described in Eq. (4)" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 325, + 701, + 545, + 714 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 325, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 325, + 701, + 545, + 714 + ], + "type": "interline_equation", + "content": "L o s s = \\mathcal {L} _ {i m g} + \\lambda_ {2} \\mathcal {L} _ {n d l} + \\lambda_ {3} \\mathcal {L} _ {f d l} + \\lambda_ {4} \\mathcal {R} _ {e s}. \\tag {16}", + "image_path": "d6bef2edbf8ce5d63ee09de4e4dd8da08f5b9806d32bbcb38bc8282d66b4e6e8.jpg" + } + ] + } + ], + "index": 27 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5213" + } + ] + } + ], + "index": 28 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 72, + 304, + 373 + ], + "blocks": [ + { + "bbox": [ + 50, + 72, + 304, + 373 + ], + "lines": [ + { + "bbox": [ + 50, + 72, + 304, + 373 + ], + "spans": [ + { + "bbox": [ + 50, + 72, + 304, + 373 + ], + "type": "image", + "image_path": "31e376b995de3ccefea3c82e9d161f2eff2e29427ddac14373c9f712e10f28d8.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 384, + 547, + 418 + ], + "lines": [ + { + "bbox": [ + 46, + 384, + 547, + 418 + ], + "spans": [ + { + "bbox": [ + 46, + 384, + 547, + 418 + ], + "type": "text", + "content": "Figure 2. Qualitative comparison of DynTet with the prior methods [31, 50, 60, 77]. Some representative defects are marked with red arrows, around which the generated eyes, mouths or wrinkles highlight discrepancies with real ones. The right panel presents the details of the mouth and eye area. The results show the superior realism and motion accuracy achieved by DynTet compared to existing methods." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 308, + 72, + 542, + 372 + ], + "blocks": [ + { + "bbox": [ + 308, + 72, + 542, + 372 + ], + "lines": [ + { + "bbox": [ + 308, + 72, + 542, + 372 + ], + "spans": [ + { + "bbox": [ + 308, + 72, + 542, + 372 + ], + "type": "image", + "image_path": "a70e0b5814e559fc9a122431d7e6af9ae672e14157c4415b735a047dd7a6f47f.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 429, + 123, + 442 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 429, + 123, + 442 + ], + "spans": [ + { + "bbox": [ + 47, + 429, + 123, + 442 + ], + "type": "text", + "content": "5. Experiment" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 449, + 171, + 462 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 449, + 171, + 462 + ], + "spans": [ + { + "bbox": [ + 47, + 449, + 171, + 462 + ], + "type": "text", + "content": "5.1. Experimental settings" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 468, + 287, + 601 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 468, + 287, + 601 + ], + "spans": [ + { + "bbox": [ + 46, + 468, + 287, + 601 + ], + "type": "text", + "content": "Dataset and pre-processing. For a fair comparison, we follow recent works [23, 31, 53] to conduct experiments on a publicly-released video dataset, which includes four high-definition talking videos with an average length of about 6500 frames at 25 FPS. Each raw video is cropped and resized to " + }, + { + "bbox": [ + 46, + 468, + 287, + 601 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 46, + 468, + 287, + 601 + ], + "type": "text", + "content": ", except for the Obama data with the resolution " + }, + { + "bbox": [ + 46, + 468, + 287, + 601 + ], + "type": "inline_equation", + "content": "448 \\times 448" + }, + { + "bbox": [ + 46, + 468, + 287, + 601 + ], + "type": "text", + "content": ". Each video is divided into training and test sets at a ratio of 10:1. We ensure strict alignment with the pre-processing steps outlined in AD-NeRF [23]. In order to extract the 3DMM coefficients efficiently, we utilize a pre-trained model from Deng et al. [10]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 609, + 287, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 609, + 287, + 693 + ], + "spans": [ + { + "bbox": [ + 46, + 609, + 287, + 693 + ], + "type": "text", + "content": "Implementation details. We implement DynTet based on the code of Nvdiffrec1 [45] for differentiable Marching Tetrahedra and rasterization. We use a tetrahedral grid with a resolution of " + }, + { + "bbox": [ + 46, + 609, + 287, + 693 + ], + "type": "inline_equation", + "content": "128^3" + }, + { + "bbox": [ + 46, + 609, + 287, + 693 + ], + "type": "text", + "content": " [12], which is a commonly used setting [18, 45]. For the MLPs, we equip each one with ReLU-Linear layers. The geometry model utilizes a frequency positional encoder [59] with " + }, + { + "bbox": [ + 46, + 609, + 287, + 693 + ], + "type": "inline_equation", + "content": "L = 6" + }, + { + "bbox": [ + 46, + 609, + 287, + 693 + ], + "type": "text", + "content": " and a 3-layer MLP with" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "spans": [ + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "text", + "content": "128 middle neurons. Additionally, a 4-layer convolutional encoder [52] is used for the 3DMM coefficients. The appearance model consists of a 5-layer MLP with 256 middle neurons. During training, we perform 20,000 iterations with a batch size of 4. We employ the Adam optimizer with an initial learning rate of " + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "inline_equation", + "content": "1 \\times 10^{-3}" + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "text", + "content": ", which exponentially decayed to " + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "inline_equation", + "content": "1 \\times 10^{-5}" + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "text", + "content": ". The default hyperparameters are " + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "inline_equation", + "content": "\\lambda_{1} = 0.1" + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "inline_equation", + "content": "\\lambda_{2} = 100" + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "inline_equation", + "content": "\\lambda_{3} = 100" + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "inline_equation", + "content": "\\lambda_{4} = 100" + }, + { + "bbox": [ + 306, + 430, + 545, + 538 + ], + "type": "text", + "content": ". All experiments are conducted on a single NVIDIA Tesla V100." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 543, + 545, + 627 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 543, + 545, + 627 + ], + "spans": [ + { + "bbox": [ + 304, + 543, + 545, + 627 + ], + "type": "text", + "content": "Comparison baselines. We compare our method with several recent representative one-shot and person-specific models, including Wav2Lip [50], PC-AVS [77], NVP [62], SynObama [58], SadTalker [72]. In addition, we also compare our method with three end-to-end NeRF-based models: ADNeRF [23], RAD-NeRF [60] and ER-NeRF [31]. All these methods are implemented with their official code." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 635, + 421, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 635, + 421, + 647 + ], + "spans": [ + { + "bbox": [ + 306, + 635, + 421, + 647 + ], + "type": "text", + "content": "5.2. Quantitative results" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "type": "text", + "content": "Comparison settings. We follow recent works to organize our comparisons into two settings: 1) Self-driven head reconstruction setting, in which we train a model for each video clip and evaluate the reconstruction quality on its respective test set. 2) Cross-driven lip synchronization set-" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 58, + 702, + 232, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 232, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 232, + 712 + ], + "type": "text", + "content": "1https://github.com/NVlabs/nvdiffrec" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5214" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 52, + 70, + 545, + 167 + ], + "blocks": [ + { + "bbox": [ + 52, + 70, + 545, + 167 + ], + "lines": [ + { + "bbox": [ + 52, + 70, + 545, + 167 + ], + "spans": [ + { + "bbox": [ + 52, + 70, + 545, + 167 + ], + "type": "table", + "html": "
MethodsPSNR ↑LPIPS ↓FID ↓CSIM ↑LMDm ↓LMDe ↓AUE ↓Sync ↑TimeFPS
Ground Truth∞001.0000007.899--
Wav2Lip [50]31.150.073020.700.9703.0722.1472.0598.256-20
PC-AVS [77]22.060.134547.530.8022.4963.6094.2838.540-32
AD-NeRF [23]30.410.079914.920.9264.3172.4054.3745.01518h0.08
RAD-NeRF [60]31.510.067511.140.9513.0062.2853.3174.4095h23
ER-NeRF† [31]32.500.03456.440.9602.9242.2202.7734.9442h23
DynTet35.150.061912.230.9752.4182.1371.8337.4072h46
DynTet†34.840.02234.720.9782.2842.1291.7127.6463h46
", + "image_path": "35522e772a0c9237ec0587bc6ea50e492aaefb6dd7a31411c407f82eaf496151.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 60, + 167, + 171, + 176 + ], + "lines": [ + { + "bbox": [ + 60, + 167, + 171, + 176 + ], + "spans": [ + { + "bbox": [ + 60, + 167, + 171, + 176 + ], + "type": "inline_equation", + "content": "\\dagger" + }, + { + "bbox": [ + 60, + 167, + 171, + 176 + ], + "type": "text", + "content": " supervised by overall LPIPS [71]." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_footnote" + }, + { + "bbox": [ + 47, + 177, + 546, + 200 + ], + "lines": [ + { + "bbox": [ + 47, + 177, + 546, + 200 + ], + "spans": [ + { + "bbox": [ + 47, + 177, + 546, + 200 + ], + "type": "text", + "content": "Table 1. Quantitative results of the self-driven head reconstruction. The best and second results are in bold and underline. Wav2Lip takes ground truth as input, thus its PSNR and LPIPS values are biased. The FPS values are tested on the resolution of " + }, + { + "bbox": [ + 47, + 177, + 546, + 200 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 47, + 177, + 546, + 200 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 50, + 208, + 286, + 342 + ], + "blocks": [ + { + "bbox": [ + 50, + 208, + 286, + 342 + ], + "lines": [ + { + "bbox": [ + 50, + 208, + 286, + 342 + ], + "spans": [ + { + "bbox": [ + 50, + 208, + 286, + 342 + ], + "type": "image", + "image_path": "9805d245dd0e5491b41b089ac3d3042b135517a12618b4aa8152dc48540a098f.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 350, + 288, + 407 + ], + "lines": [ + { + "bbox": [ + 46, + 350, + 288, + 407 + ], + "spans": [ + { + "bbox": [ + 46, + 350, + 288, + 407 + ], + "type": "text", + "content": "Figure 3. The triangular meshes from 3DMM [3], ER-NeRF [31] and DynTet. The surfaces extracted from ER-NeRF using the Marching Cubes [39] exhibit noise and undesirable topology. Note that the backs of the meshes may have some defects due to limited training data, but it does not impact the rendering results." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 417, + 287, + 466 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 417, + 287, + 466 + ], + "spans": [ + { + "bbox": [ + 46, + 417, + 287, + 466 + ], + "type": "text", + "content": "ting, where we use clips from unseen videos to drive all methods for comparisons in lip synchronization. We extract two video clips from the public demos of SynObama [58] and NVP [62], which we refer to as Testset A and Testset B." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 469, + 288, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 469, + 288, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 469, + 288, + 613 + ], + "type": "text", + "content": "Evaluation metrics. We assess the methods with several metrics: We evaluate the reconstruction quality using PSNR and LPIPS metrics [71]. Realism and identity preservation are measured using Fréchet Inception Distance (FID) [24] and Cosine Similarity of Identity Embedding (CSIM) [41]. Driving accuracy is assessed by calculating the landmark distances for the mouth " + }, + { + "bbox": [ + 46, + 469, + 288, + 613 + ], + "type": "inline_equation", + "content": "(\\mathrm{LMD}^m)" + }, + { + "bbox": [ + 46, + 469, + 288, + 613 + ], + "type": "text", + "content": " and eyes " + }, + { + "bbox": [ + 46, + 469, + 288, + 613 + ], + "type": "inline_equation", + "content": "(\\mathrm{LMD}^e)" + }, + { + "bbox": [ + 46, + 469, + 288, + 613 + ], + "type": "text", + "content": " [6], while face motion accuracy is quantified by action units error (AUE) [2]. Temporal lip synchronization is evaluated using the SyncNet confidence score (Sync) [8]. Additionally, we report training time and frame-per-second (FPS) to evaluate the running efficiency of the methods." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 617, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 289, + 714 + ], + "type": "text", + "content": "Head reconstruction. The results of the head reconstruction setting are presented in Table 1. For fairness, we provide DynTet with and without LPIPS supervision, both of which demonstrate significant advantages in reconstructing accurate details and precisely controlling facial movements. While 2D-based methods such as Wav2Lip [50] and PC-AVS [77] excel in the lip synchronization due to the pretraining on the large-scale dataset, they fall short in the" + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 310, + 207, + 545, + 342 + ], + "blocks": [ + { + "bbox": [ + 310, + 207, + 545, + 342 + ], + "lines": [ + { + "bbox": [ + 310, + 207, + 545, + 342 + ], + "spans": [ + { + "bbox": [ + 310, + 207, + 545, + 342 + ], + "type": "table", + "html": "
MethodsTestset ATestset B
AUE ↓Sync ↑AUE ↓Sync ↑
Ground Truth07.38606.676
SynObama [58]5.5747.419--
NVP [62]--7.9546.562
Wav2Lip [50]5.0298.3947.4159.072
PC-AVS [77]4.3598.0877.4509.964
SadTalker [72]4.7327.2076.7607.932
AD-NeRF [23]4.2776.0416.7315.567
RAD-NeRF [60]4.1726.5416.7336.786
ER-NeRF [31]4.2106.8776.6697.401
DynTet3.6725.0556.0296.401
Audio2Exp + DynTet4.3167.0556.5417.335
", + "image_path": "c649d234a2a205e1eb0a24e092a00830e3034aecdac626741c297cde3019575d.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 350, + 546, + 394 + ], + "lines": [ + { + "bbox": [ + 304, + 350, + 546, + 394 + ], + "spans": [ + { + "bbox": [ + 304, + 350, + 546, + 394 + ], + "type": "text", + "content": "Table 2. Quantitative results of cross-driven lip synchronization. The best and second results are in **bold** and **underline**. To drive DynTet with audios, we utilize an off-the-shelf model Audio2Exp [72] to convert audios into 3DMM coefficients." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 406, + 547, + 503 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 406, + 547, + 503 + ], + "spans": [ + { + "bbox": [ + 304, + 406, + 547, + 503 + ], + "type": "text", + "content": "faithful appearance. Among NeRF-based methods, the recent work ER-NeRF [31] achieves top performance in the evaluation. As the first tetrahedra representation for talking heads, DynTet notably outperforms on all metrics compared to NeRF-based approaches, showcasing its advancements in faithful reconstruction and accurate mapping from conditions to facial deformation. This further validates the great potential of tetrahedra meshes for dynamic modeling." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "type": "text", + "content": "Lip synchronization. DynTet offers both frame-driven and audio-driven approaches to accomplish this task. In the frame-driven approach, 3DMM coefficients are directly extracted from the target videos. On the other hand, the audio-driven approach utilizes an off-the-shelf model, specifically the Audio2Exp model in SadTalker [72], to convert audi-los into the 3DMM coefficients. It is worth noting that the target coefficients, denoted as " + }, + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "type": "inline_equation", + "content": "\\alpha^{\\prime}" + }, + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "type": "text", + "content": ", and the training co-efficients " + }, + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "type": "text", + "content": ", may have different distributions according to speaking habits. We find that a re-center process, expressed as " + }, + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "type": "inline_equation", + "content": "\\alpha^{\\prime} + (\\bar{\\alpha} - \\bar{\\alpha}^{\\prime})" + }, + { + "bbox": [ + 304, + 510, + 547, + 714 + ], + "type": "text", + "content": " is crucial to rectificate the talking style. As shown in Table 2, the frame-driven approach of DynTet unsurprisingly achieves the best AUE performance among all methods. Furthermore, the audio-driven approach of DynTet also achieves comparable results with ER-NeRF and SadTalker, indicating its flexibility and strong generalization properties for various applications." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5215" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "bbox": [ + 78, + 71, + 258, + 80 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 78, + 71, + 258, + 80 + ], + "spans": [ + { + "bbox": [ + 78, + 71, + 258, + 80 + ], + "type": "text", + "content": "The rain will gradually sink its way slowly southward into England" + } + ] + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 50, + 82, + 282, + 244 + ], + "blocks": [ + { + "bbox": [ + 50, + 82, + 282, + 244 + ], + "lines": [ + { + "bbox": [ + 50, + 82, + 282, + 244 + ], + "spans": [ + { + "bbox": [ + 50, + 82, + 282, + 244 + ], + "type": "image", + "image_path": "5af55b6a2e47b201e01563469e7a6fe5d0bf92d0f58b05e335693bdf51bc69c7.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 247, + 287, + 281 + ], + "lines": [ + { + "bbox": [ + 47, + 247, + 287, + 281 + ], + "spans": [ + { + "bbox": [ + 47, + 247, + 287, + 281 + ], + "type": "text", + "content": "Figure 4. Qualitative results of the cross-driven setting. The top and bottom panels show the frame- and audio-driven results, respectively. We attach the estimated 3DMM shapes for reference." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 291, + 287, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 291, + 287, + 376 + ], + "spans": [ + { + "bbox": [ + 47, + 291, + 287, + 376 + ], + "type": "text", + "content": "Running efficiency. Table 1 shows that DynTet achieves fast training speed and real-time inference at " + }, + { + "bbox": [ + 47, + 291, + 287, + 376 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 47, + 291, + 287, + 376 + ], + "type": "text", + "content": " resolution. Notably, DynTet maintains the same 46 FPS even at " + }, + { + "bbox": [ + 47, + 291, + 287, + 376 + ], + "type": "inline_equation", + "content": "1024 \\times 1024" + }, + { + "bbox": [ + 47, + 291, + 287, + 376 + ], + "type": "text", + "content": " resolution, thanks to the cost-efficient rasterization rendering. In contrast, ER-NeRF and RAD-NeRF experience a half drop in FPS. This highlights our efficiency advantage in challenging high-resolution scenes." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 382, + 156, + 395 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 382, + 156, + 395 + ], + "spans": [ + { + "bbox": [ + 47, + 382, + 156, + 395 + ], + "type": "text", + "content": "5.3. Qualitative results" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 400, + 288, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 400, + 288, + 569 + ], + "spans": [ + { + "bbox": [ + 46, + 400, + 288, + 569 + ], + "type": "text", + "content": "Figure 2 demonstrates that DynTet effectively addresses challenges faced by prior methods. It generates photorealistic images with intricate details in non-rigid areas and achieves precise control of mouth, blinks, and even wrinkles. Our supplementary videos showcase the impressive temporal stability of DynTet, resulting in smooth and stable motion. In Figure 3, the comparison of meshes obtained by different methods reveals that DynTet outperforms 3DMM and NeRF in terms of topology. Additionally, Figure 4 showcases the accurate expression control achieved by frame-driven DynTet, while audio-driven DynTet surpasses SadTalker in producing realistic and expressive results. These advancements firmly establish DynTet as a promising approach for modeling talking heads." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 575, + 139, + 588 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 575, + 139, + 588 + ], + "spans": [ + { + "bbox": [ + 47, + 575, + 139, + 588 + ], + "type": "text", + "content": "5.4. Ablation study" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": "We present the results of different structures in Table 3 and Figure 5. It is evident that the removal of canonical projection (C.P.) has a quite negative impact, resulting in increased LPIPS and LMD values. This is because the absence of the canonical projection increases the difficulty of texture learning and consequently hinders the supervision of loss on the geometry model. Similarly, removing 3DMM supervision leads to flawed meshes and introduces artifacts into the images. The visualization of elastic scores (E.S.) highlights its function in quantifying the non-rigid property, and" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 310, + 77, + 541, + 194 + ], + "blocks": [ + { + "bbox": [ + 310, + 77, + 541, + 194 + ], + "lines": [ + { + "bbox": [ + 310, + 77, + 541, + 194 + ], + "spans": [ + { + "bbox": [ + 310, + 77, + 541, + 194 + ], + "type": "image", + "image_path": "ccc76b52adc76b697fb6e0d8c6bf29ce1cdc065e680b5cc5dbba3f7607eb0af9.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 198, + 545, + 242 + ], + "lines": [ + { + "bbox": [ + 305, + 198, + 545, + 242 + ], + "spans": [ + { + "bbox": [ + 305, + 198, + 545, + 242 + ], + "type": "text", + "content": "Figure 5. The validation of key components in DynTet. (a) Result of DynTet. (b) Replacing frequency encoding with hash encoding [44]. (c) Removing 3DMM supervision. (d) Removing canonical projection. (e) Groundtruth. (f) Visualization of elastic scores." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 310, + 248, + 544, + 307 + ], + "blocks": [ + { + "bbox": [ + 310, + 248, + 544, + 307 + ], + "lines": [ + { + "bbox": [ + 310, + 248, + 544, + 307 + ], + "spans": [ + { + "bbox": [ + 310, + 248, + 544, + 307 + ], + "type": "table", + "html": "
DynTet-3DMM-C.P.-E.S.3264128512
FPS↑46---103928023
#Param1.41M---1.11M1.13M1.19M2.28M
PSNR↑34.8433.6534.3734.8132.2234.2035.1535.06
LPIPS↓0.02230.06860.05290.02470.05390.02540.02370.0219
LMDm↓2.2842.4532.5722.3362.8752.6362.4492.201
", + "image_path": "5abe14859986f98011d60644ab9b1e0317704e6563b451ce1d9486e0e572dab5.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 312, + 545, + 357 + ], + "lines": [ + { + "bbox": [ + 305, + 312, + 545, + 357 + ], + "spans": [ + { + "bbox": [ + 305, + 312, + 545, + 357 + ], + "type": "text", + "content": "Table 3. Quantitative ablation of DynTet via removing 3DMM supervision, canonical projection, elastic score or changing the number of middle neurons in appearance mapping from 32 to 512. #Param denotes the parameter number of DynTet." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 368, + 545, + 488 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 368, + 545, + 488 + ], + "spans": [ + { + "bbox": [ + 304, + 368, + 545, + 488 + ], + "type": "text", + "content": "its removal affects the temporal stability of the results (see the supplementary videos). Interestingly, we find replacing frequency encoding with hash encoding leads to a cluttered mesh, indicating that it is desirable to encode coordinates as low-frequency signals in geometry learning. In addition, we explore the impact of middle neuron channels within the appearance mapping, and find that dimensions ranging from 64 to 256 strike a balance between expressivity and inference speed. These findings underscore the reasonable designs of DynTet for achieving desirable results." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 507, + 378, + 520 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 507, + 378, + 520 + ], + "spans": [ + { + "bbox": [ + 306, + 507, + 378, + 520 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 531, + 545, + 626 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 531, + 545, + 626 + ], + "spans": [ + { + "bbox": [ + 304, + 531, + 545, + 626 + ], + "type": "text", + "content": "We introduce Dynamic Tetrahedra (DynTet), a novel hybrid representation for realistic and expressive talking heads. DynTet upgrades tetrahedral meshes from statics to dynamics with a new architecture, a canonical space and guidance from geometry prior. DynTet can efficiently generate high-resolution talking videos with realism and precise motion control beyond prior works. Our work may inspire future research in the direction of Dynamic Tetrahedra." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "content": "Acknowledgements. This paper is supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDA27000000), the National key research and development program of China (2021YFA1000403), the National Natural Science Foundation of China (Nos. U23B2012, 11991022) and the Fundamental Research Funds for the Central Universities (E3E41904)." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5216" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 286, + 713 + ], + "type": "list", + "angle": 0, + "index": 19, + "blocks": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "type": "text", + "content": "[1] ShahRukh Athar. 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ACM TOG, 2020. 1, 2" + } + ] + } + ], + "index": 12 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "type": "text", + "content": "5219" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_content_list.json b/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..cf6d4bd6437a067099cc8ea4a8562626e90cfed9 --- /dev/null +++ b/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_content_list.json @@ -0,0 +1,1572 @@ +[ + { + "type": "text", + "text": "Learning Equi-angular Representations for Online Continual Learning", + "text_level": 1, + "bbox": [ + 125, + 130, + 844, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Minhyuk Seo $^{1,\\dagger}$ Hyunseo Koh $^{1}$ Wonje Jeung $^{1}$ Minjae Lee $^{1}$ San Kim $^{1}$ Hankook Lee $^{2,3}$ Sungjun Cho $^{2}$ Sungik Choi $^{2}$ Hyunwoo Kim $^{4,*}$ Jonghyun Choi $^{5,*}$", + "bbox": [ + 125, + 179, + 843, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{1}$ Yonsei Univ. $^{2}$ LG AI Research $^{3}$ Sungkyunkwan Univ. $^{4}$ Zhejiang Lab $^{5}$ Seoul National Univ. {dbd0508, specific0924, reccos1020, nasmik419}@yonsei.ac.kr khs8157@gmail.com, {sungik.choi,sungjun.cho}@lgresearch.ai hankook.lee@skku.edu, hwkim@zhejianglab.com, jonghyunchoi@snu.ac.kr", + "bbox": [ + 107, + 222, + 861, + 292 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 329, + 313, + 345 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Online continual learning suffers from an underfitted solution due to insufficient training for prompt model update (e.g., single-epoch training). To address the challenge, we propose an efficient online continual learning method using the neural collapse phenomenon. In particular, we induce neural collapse to form a simplex equiangular tight frame (ETF) structure in the representation space so that the continuously learned model with a single epoch can better fit to the streamed data by proposing preparatory data training and residual correction in the representation space. With an extensive set of empirical validations using CIFAR10/100, TinyImageNet, ImageNet-200, and ImageNet-1K, we show that our proposed method outperforms state-of-the-art methods by a noticeable margin in various online continual learning scenarios such as disjoint and Gaussian scheduled continuous (i.e., boundary-free) data setups. Code is available at https://github.com/yonseivnl/earl.", + "bbox": [ + 75, + 359, + 473, + 632 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 660, + 209, + 676 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "A growing interest in continuous learning (CL) involves training the model using continuous data streams. Mostly, CL research has focused on the offline scenario that assumes the model can be trained in multiple epochs for the current task [8, 42, 54]. However, substantial storage and computational complexity are required to store all data to train a model for multiple epochs. Recently, there has been significant interest in online CL as a more realistic set-up with a lower computational overhead of allowing a single training pass through the data stream [1, 7, 27]. Learning a model in streamed data by a single training pass is challenging, since the temporal distribution at each intermediate", + "bbox": [ + 75, + 685, + 470, + 867 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "time point is likely imbalanced, even if the overall distribution of a dataset is balanced. Imbalanced data distributions would cause several problems, such as bias towards the major classes [24, 61] and the hindrance to generalization [53].", + "bbox": [ + 500, + 329, + 890, + 392 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Recently, minority collapse [14], the phenomenon in which the angles between classifier vectors for minor classes (i.e., the classes that have a relatively small number of samples) become narrow, has been proposed as a fundamental issue in training with imbalanced data, making the classification of minor classes considerably more challenging. In contrast, for balanced data sets, it was proven that classifier vectors and the last layer activations for all classes converge into an optimal geometric structure, named the simplex equiangular tight frame (ETF) structure, where all pairwise angles between classes are equal and maximally widened when using cross entropy (CE) [23, 30, 52, 65] or mean squared error (MSE) [32, 41, 48, 64] loss. This phenomenon is called neural collapse [34].", + "bbox": [ + 496, + 393, + 892, + 606 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Although neural collapse naturally occurs only in balanced training, several recent studies attempted to induce neural collapse in imbalanced training to address the minority collapse problem using a fixed ETF classifier [55, 62]. When employing a fixed ETF classifier, the output features are pulled toward the corresponding classifier vector during training, since the classifier is fixed. More recently, research has also been extended to induce neural collapse in offline CL using a fixed ETF classifier [56].", + "bbox": [ + 496, + 609, + 893, + 747 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "However, unlike offline CL, there are a number of challenges in inducing neural collapse in online CL, even with a fixed ETF classifier. The prerequisite for neural collapse is reaching the terminal phase of training (TPT) by sufficient training [34]. In offline CL, the model can reach the TPT phase for each task by multi-epoch training. In contrast, a single-pass training constraint often prevents the online CL from reaching TPT. As shown in Fig. 1, the offline CL quickly reaches TPT shortly after the arrival of novel task data, while online CL (vanilla ETF) does not.", + "bbox": [ + 496, + 750, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "†: Work done while interning at LG AI Research.", + "bbox": [ + 78, + 875, + 344, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*: Indicates corresponding authors.", + "bbox": [ + 81, + 888, + 269, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "23933", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/286fe80ac345fa2b15e206b235117ac50ec9c21f64780bd5db4f6faefd35e08f.jpg", + "image_caption": [ + "Figure 1. Comparison of training error rates between online CL and offline CL in the CIFAR-10 disjoint setup, where two novel classes are added every 10k samples. Vanilla ETF refers to a method where both preparatory data training and residual correction are removed from our proposed EARL." + ], + "image_footnote": [], + "bbox": [ + 76, + 88, + 893, + 250 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Recently, the importance of anytime inference in online CL has been emphasized [6, 17, 27, 36], since a model should be available for inference not only at the end of a task, but also at any point during training to be practical for real-world applications. Hence, not only reaching TPT but also achieving faster convergence is necessary when using neural collapse in online CL.", + "bbox": [ + 75, + 306, + 470, + 412 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "However, we observe that the phenomenon in which the features of the new class become biased toward the features of the existing classes [5] hinders fast convergence of the last-layer features into the ETF structure, which we call the 'bias problem.' When features of old and new classes overlap (i.e., biased) and are trained with the same objective, well-clustered features of old classes disperse (or perturb) [5], leading to destruction of the ETF structure formed by features of the old classes.", + "bbox": [ + 75, + 414, + 468, + 551 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Contributions. To address the bias problem, we train the model to distinguish out-of-distribution (OOD) samples from existing classes' samples. Specifically, we synthesize preparatory data that play the role of OOD data, by applying negative data augmentation [25, 47, 50] to samples from existing classes, refer to Sec. 4.2 for details. Since samples from new classes are OOD in the perspective of existing classes, training with preparatory data encourages the representation of new classes to be distinguished from existing classes in advance, thereby mitigating the bias problem. This promotes fast and stable convergence into the ETF structure.", + "bbox": [ + 75, + 565, + 468, + 744 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Despite these efforts, however, the continuous stream of new samples cause ongoing data distribution shifts, which prevent the model from reaching the TPT and fully converging to the ETF structure. To address this, we propose to store the residuals between the target ETF classifier and the features during training. During inference, we correct the inference output using the stored residual to compensate for insufficient convergence in the training.", + "bbox": [ + 75, + 748, + 468, + 868 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "By accelerating convergence by preparatory data training and additional correction using residual, we noticeably", + "bbox": [ + 76, + 869, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "improve anytime inference performance than state of the arts. We name our method Equi-Angular Representation Learning (EARL). We empirically demonstrate the effectiveness of our framework on CIFAR-10, CIFAR-100, TinyImageNet,Imagenet-200,and ImageNet-1K.In particular, our framework outperforms various CL methods by a significant margin $(+4.0\\%)$ gain of $A_{\\mathrm{auc}}$ in ImageNet-1K).", + "bbox": [ + 496, + 306, + 893, + 412 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We summarize our contributions as follows:", + "bbox": [ + 517, + 414, + 812, + 428 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Proposing to induce neural collapse for online CL.", + "- Proposing 'preparatory data training' to address the 'bias problem' that the new classes are biased toward the existing classes, promoting faster induction of neural collapse.", + "- Proposing 'residual correction' scheme to compensate for not fully reaching neural collapse at inference to further improve anytime inference accuracy." + ], + "bbox": [ + 509, + 431, + 890, + 553 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related work", + "text_level": 1, + "bbox": [ + 500, + 571, + 637, + 585 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Continual learning methods. Various continual learning methods are being researched to prevent forgetting past tasks, broadly categorized into replay, parameter isolation, and regularization. Replay methods involve storing a small portion of data from previous tasks in episodic memory [1, 2, 20, 27, 60] or storing a generative model trained on data from previous tasks [39, 46]. By replaying the samples stored in episodic memory or generated from the stored generative model, the model prevents forgetting past tasks during subsequent learning of novel tasks. Furthermore, Boschini et al. [3], Buzzega et al. [4], Li and Hoiem [29], Wu et al. [54] used replay samples to distill information about past tasks.", + "bbox": [ + 496, + 597, + 890, + 792 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Regularization methods [26, 28] apply a penalty to the change of important model parameters during the process of learning new tasks, allowing the model to retain information about previous tasks. Parameter isolation methods [10, 44, 63] expand the network by allocating specific layers for each task. This enables the network to store information about individual tasks and preserves their knowl-", + "bbox": [ + 496, + 795, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "23934", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "edge without forgetting.", + "bbox": [ + 76, + 90, + 238, + 107 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Neural collapse. Neural collapse is a phenomenon in which the activations of the last layer and the classifier vectors form a simplex equiangular tight frame (ETF) structure at the terminal phase of training (TPT) in a balanced dataset. [34]. Neural collapse has been demonstrated as the global optimum of balanced training using cross entropy (CE) loss [23, 30, 52, 65] and MSE [32, 41, 48, 64] loss functions, within a simplified model focused solely on last-layer optimization. Inducing neural collapse in imbalanced datasets poses challenges due to minority collapse [14] where minor classes are not well distinguished.", + "bbox": [ + 75, + 109, + 468, + 276 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "However, using a fixed ETF classifier, it is empirically and theoretically shown that neural collapse is induced even in imbalanced datasets [55]. Continual learning also needs to address imbalanced data since there is an imbalance in the data between novel classes and existing classes. Therefore, in offline CL, NC-FSCIL [38, 56] used a fixed ETF classifier to induce neural collapse. Meanwhile, online CL often fails to induce neural collapse compared to offline CL, e.g., FSCIL, since it lacks sufficient training in multiple epochs, causing failure to reach TPT.", + "bbox": [ + 75, + 277, + 468, + 428 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Please refer to the supplementary material for more comprehensive literature reviews including topics related to anytime inference.", + "bbox": [ + 76, + 428, + 468, + 473 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Preliminaries", + "text_level": 1, + "bbox": [ + 76, + 484, + 215, + 500 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We here describe the problem statement for the online continual learning (Sec. 3.1), neural collapse (Sec. 3.2), and the equiangular tight frame classifier (Sec. 3.3).", + "bbox": [ + 76, + 511, + 468, + 556 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Problem Statement of Online CL", + "text_level": 1, + "bbox": [ + 76, + 563, + 366, + 578 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Continual learning (CL) aims to learn from a stream of data, rather than a fixed dataset as in standard learning. Formally, given a sequence of tasks $\\mathcal{T} = (T_1,T_2,\\ldots)$ where each task $T_{i}$ is a training dataset $D_{i} = \\{(x_{1}^{(i)},y_{1}^{(i)}),(x_{2}^{(i)},y_{2}^{(i)}),\\ldots \\}$ , an offline CL algorithm $A_{\\mathrm{CL}}$ updates the model parameter $\\theta$ based on the current task $D_{k}$ , i.e., $\\theta_{k} = A_{\\mathrm{CL}}(\\theta_{k - 1},D_{k})$ , starting from the initial parameter $\\theta_0$ .", + "bbox": [ + 76, + 585, + 468, + 695 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To avoid the forgetting issue in CL, many CL setups allow the use of episodic memory $M_{k}$ , which is a limited-size subset of training data from previous tasks, i.e., $(\\theta_k,M_k) = A_{\\mathrm{CL}}(\\theta_{k - 1},M_{k - 1},D_k)$ . The objective is to minimize the error of $\\theta_{k}$ in all observed tasks $\\{T_i\\}_{i = 1}^k$", + "bbox": [ + 76, + 695, + 468, + 770 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Unlike offline CL where all training samples in $D_{k}$ are given as input, in online CL, the input is provided as a stream of samples $(x_{1}^{(k)}, y_{1}^{(k)}), (x_{2}^{(k)}, y_{2}^{(k)}), \\dots$ . Therefore, an online CL algorithm $A_{\\mathrm{OCL}}$ is defined as:", + "bbox": [ + 76, + 770, + 468, + 832 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\left(\\theta_ {k, t}, M _ {k, t}\\right) = A _ {\\mathrm {O C L}} \\left(\\theta_ {k, t - 1}, M _ {k, t - 1}, \\left(x _ {t} ^ {(k)}, y _ {t} ^ {(k)}\\right)\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 839, + 468, + 864 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "with the same objective of minimizing the error of $\\theta_{k,t}$ on $\\{T_i\\}_{i = 1}^k$ . Since the algorithm does not have access to pre", + "bbox": [ + 76, + 869, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "vious samples $\\{(x_s^{(k)},y_s^{(k)}),s < t\\}$ at time $t$ , multi-epoch training with $D_{k}$ is unavailable in online CL.", + "bbox": [ + 498, + 88, + 890, + 121 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Neural Collapse", + "text_level": 1, + "bbox": [ + 500, + 130, + 660, + 146 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Neural collapse [34] is a phenomenon of the penultimate features after the convergence of training on a balanced dataset. When neural collapse (NC) occurs, the collection of $K$ classifier vectors $\\mathbf{W}_{\\mathrm{ETF}} = [\\mathbf{w}_1,\\mathbf{w}_2,\\dots,\\mathbf{w}_K]\\in \\mathbb{R}^{d\\times K}$ forms a simplex equiangular tight frame (ETF), which satisfies:", + "bbox": [ + 498, + 152, + 890, + 242 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {w} _ {i} ^ {T} \\mathbf {w} _ {j} = \\left\\{ \\begin{array}{l l} 1, & i = j \\\\ - \\frac {1}{K - 1}, & i \\neq j \\end{array} , \\forall i, j \\in [ 1, \\dots , K ], \\right. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 250, + 890, + 290 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $K - 1 \\leq d$ , and the penultimate feature of a training sample collapses into an ETF vector $\\mathbf{w}_i$ .", + "bbox": [ + 498, + 297, + 890, + 329 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.3. Equiangular Tight Frame (ETF) Classifier", + "text_level": 1, + "bbox": [ + 498, + 335, + 861, + 353 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Inspired by neural collapse as described in Sec. 3.2, a fixed ETF classifier has been utilized for inducing neural collapse in imbalanced datasets [55, 56, 65]. Here, the classifier is initialized by the ETF structure $\\mathbf{W}_{\\mathrm{ETF}}$ at the beginning of training and fixed during training to induce the penultimate feature $f(x)$ to converge to the ideal balanced scenario. For training $f(x)$ , it is only required to attract $f(x)$ to the corresponding classifier vector for convergence, since the classifier is fixed during training. Therefore, following Yang et al. [55], we use the dot regression (DR) loss as a training objective, as it shows to outperform cross entropy (CE) loss when using a fixed ETF classifier in imbalanced datasets [55]. The DR loss can be written as follows:", + "bbox": [ + 498, + 359, + 890, + 555 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {D R}} (\\hat {f} (x), y; \\mathbf {W} _ {\\text {E T F}}) = \\frac {1}{2} \\left(\\mathbf {w} _ {y} \\hat {f} (x) - 1\\right) ^ {2}, \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 550, + 561, + 890, + 590 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\hat{f} (x) = f(x) / \\| f(x)\\| _2$ is the $L_{2}$ normalized feature of the model $f$ , $y$ is the label of the input $x$ , and $\\mathbf{w}_y$ is a classifier vector in $\\mathbf{W}_{\\mathrm{ETF}}$ for the label $y$ .", + "bbox": [ + 498, + 599, + 890, + 647 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Approach", + "text_level": 1, + "bbox": [ + 500, + 660, + 607, + 676 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Despite the success of the fixed ETF classifier in both imbalanced training [55, 62] and offline CL [56], the ETF classifier has not yet been explored for online CL due to the necessity of sufficient training for neural collapse. To be specific, streamed data are trained only once in online CL, which makes it harder to induce neural collapse than in offline CL which supports multi-epoch training.", + "bbox": [ + 498, + 685, + 890, + 791 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To learn a better converged model without multi-epoch training for online CL, we propose two novel methods, each for the training phase and the inference phase, respectively. In the training phase, we accelerate convergence by proposing preparatory data training (Sec. 4.2). In the inference", + "bbox": [ + 498, + 791, + 890, + 867 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "1If the training objective includes a contrastive term between different classes like cross entropy, it could cause incorrect gradients [55].", + "bbox": [ + 500, + 875, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "23935", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/2b82eece2a6f75f774eccd89b2b2db38f906fc55e473e2cbb59d5e1a6020feeb.jpg", + "image_caption": [ + "Figure 2. Overview of EARL. $\\mathbf{w}_i$ denotes the ETF classifier vector for class $i$ . $h_a$ denotes the output of the model. The colors of the data denote the class to which the data belong. The arrow $\\mathbf{r}_i$ denotes the residual between the last layer activation $h_i$ and the classifier vector $\\mathbf{w}_i$ for class $i$ . During training, both memory and preparatory data are used for replaying, and the residuals between $h_i$ and $\\mathbf{w}_i$ are stored in feature-residual memory. During inference, using the similarity between $f(x_{\\mathrm{eval}})$ and $h_i$ in feature-residual memory, $\\mathbf{r}_{\\mathrm{eval}}$ is obtained by a weighted sum of $\\mathbf{r}_i$ 's. Finally, by adding $\\mathbf{r}_{\\mathrm{eval}}$ , $f(x_{\\mathrm{eval}})$ is corrected. The purple arrow indicates 'residual correction' (Sec. 4.3)." + ], + "image_footnote": [], + "bbox": [ + 80, + 88, + 893, + 292 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/a35fba741b9772f294b8d2a04435ef928c8e2b090cda6ff1dc2da925b6dfdb8c.jpg", + "image_caption": [ + "Figure 3. Illustrative effects for each component of EARL. (a) In online CL, features of novel classes are biased towards the features of the previous class. (b) By training with preparatory data (w/ Prep. Data, Sec. 4.2), we address the bias problem. (c) In inference, for features that do not fully converge to an ETF classifier, we add residuals (w/ Res. Corr., Sec. 4.3) to features that have not yet reached the corresponding classifier vectors, making features aligned with them. Purple arrow: the 'residual correction', Colors: classes." + ], + "image_footnote": [], + "bbox": [ + 84, + 385, + 455, + 508 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "phase, we propose to correct the remaining discrepancy between the classifiers and the features using residual correction (Sec. 4.3). We illustrate an overview of EARL in Fig. 2 and the effect of EARL in Fig. 3.", + "bbox": [ + 75, + 650, + 468, + 710 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Inducing Neural Collapse for Online CL", + "text_level": 1, + "bbox": [ + 76, + 723, + 421, + 739 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For online CL, we first try to induce neural collapse with a fixed ETF classifier: $\\mathbf{W}_{\\mathrm{ETF}} \\in R^{d \\times K}$ where $d$ is the dimension of the embedding space and $K$ is the number of ETF vectors. While prior works [55, 56] use prior knowledge of the total number of classes that will be encountered for setting $K$ , it is unrealistic to know the knowledge (i.e., the exact number of classes) as it evolves continuously over time under realistic CL scenarios.", + "bbox": [ + 75, + 748, + 468, + 867 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To address the challenge, we propose using the maximum possible number of classifier vectors for $K$ . Based", + "bbox": [ + 76, + 869, + 470, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "on the simplex ETF property that the maximum number of ETF vectors is $d + 1$ [16, 55], we define our ETF classifier $\\mathbf{W}_{\\mathrm{ETF}} \\in \\mathbb{R}^{d \\times (d + 1)}$ by letting $K := d + 1$ .", + "bbox": [ + 498, + 387, + 893, + 434 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.2. Preparatory data at training", + "text_level": 1, + "bbox": [ + 498, + 446, + 756, + 463 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Since novel classes continuously arrive in CL, both the data from previous tasks $(x_{\\mathrm{old}})$ and the current task $(x_{\\mathrm{new}})$ coexist. While $\\hat{f}(x_{\\mathrm{old}})$ are placed closer to their corresponding ETF classifier vectors $w_{\\mathrm{new}}$ by training, $\\hat{f}(x_{\\mathrm{new}})$ are biased toward the cluster of $\\hat{f}(x_{\\mathrm{old}})$ , as we can see in Fig. 4-(a), where $\\hat{f}(x_{\\mathrm{new}})$ and $\\hat{f}(x_{\\mathrm{old}})$ are the outputs of the model for inputs $x_{\\mathrm{new}}$ and $x_{\\mathrm{old}}$ , respectively. We call this 'bias problem.' When $\\hat{f}(x_{\\mathrm{new}})$ and $\\hat{f}(x_{\\mathrm{old}})$ overlap due to bias and are optimized with the same objective function, training on the new class interferes with the representations of the old classes, dispersing the well-clustered $\\hat{f}(x_{\\mathrm{old}})$ [5]. It destroys the ETF structure formed by $\\hat{f}(x_{\\mathrm{old}})$ , which hinders convergence towards neural collapse. Although the bias problem exists even without a fixed ETF classifier [5, 12, 54], it poses a greater problem when using a fixed ETF classifier, since the dispersed feature of old classes has to be restored to the corresponding fixed classifier vector. In contrast, when using a learnable classifier, the dispersed representation of the old classes does not have to be restored to the original position, since the learnable classifier vector will be re-optimized from the dispersed feature. However, the angles between the classifier vector may become narrow, i.e., minority collapse occurs.", + "bbox": [ + 496, + 470, + 890, + 824 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To accelerate convergence in the ETF structure, we propose to prevent novel classes from being biased towards existing classes when introduced, mitigating the bias problem. Specifically, we train the model to avoid making predictions in favor of the existing classes for images that do not be", + "bbox": [ + 496, + 825, + 893, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "23936", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/398d95752bcf26ed3d242ed8d9f8d52b7f79e369528685f4c796db1aa8abb21c.jpg", + "image_caption": [ + "Figure 4. t-SNE visualization of 'bias-problem' in data distributions (class 0 to 3). (a) Only after 100 iterations of training after task 1 appears, learning is likely insufficient, and we can see that the features of new classes (class 2, 3) are biased towards the feature cluster of the existing class (i.e., class 1). (b) With more training iterations (10,000 iter), the features are well clustered by class." + ], + "image_footnote": [], + "bbox": [ + 89, + 98, + 452, + 233 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "long to them. To this end, we propose to use preparatory data $x_{p}$ that is different from existing classes, obtained by transforming the samples in the episodic memory. By training with the preparatory data so that their representations differ from existing classes, we prevent biased predictions towards existing classes when a new class arrives.", + "bbox": [ + 75, + 353, + 467, + 443 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For preparatory data to have a different representation from existing classes when trained, their image semantics should be distinguishable from existing classes, provided that they contain enough semantic information to be considered as an image (i.e., not noise). There are various approaches to synthesize images with modified semantics, such as using generative models [11, 19, 58] or negative transformations [47, 50]. We use negative transformations, as generative models are expensive in computation and storage [13], which is undesirable for CL scenarios with limited memory and computations. On the contrary, negative transformations are relatively efficient in computation and storage [33] and is reported to create images with semantics different from the original image [50]. We empirically observed that data generated through negative transformations have a distinct semantic class from the original class while preserving its semantic information as an image (i.e., not as random noise), and we summarize the results in the supplementary material.", + "bbox": [ + 75, + 446, + 467, + 733 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Formally, for a set of existing classes $Y$ and the set of possible transformations $G$ , we randomly select $y \\in Y$ and $g \\in G$ , and randomly retrieve a sample of class $y$ from memory and apply the transformation $g$ to obtain preparatory data $x_{p}$ . We assign labels of the unseen classes to the preparatory data by a mapping function $m: Y \\times G \\to Y'$ where $Y'$ denotes a set of unseen classes, i.e., $Y' = \\{y | y \\notin Y, 1 \\leq y \\leq K\\}$ and $K$ is the total number of classifier vectors in $\\mathbf{W}_{\\mathrm{ETF}} \\in \\mathbb{R}^{d \\times K}$ . Thus, preparatory data $x_{p}$ from class $y$ and transformation $g$ is pulled towards the classifier vector $\\mathbf{w}_{p}$ , where $p = m(y, g)$ . When a new class $y_{\\mathrm{new}}$", + "bbox": [ + 75, + 734, + 467, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "is added to $Y$ , we update $m$ by randomly assigning a new mapping $m(y_{\\mathrm{new}}, g)$ for $y_{\\mathrm{new}}$ and $g \\in G$ .", + "bbox": [ + 498, + 90, + 888, + 121 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We compose the transformation set $G$ as a negative transformation that can modify semantic information (i.e., change the label), used in the self-supervised literature [15, 18] and out-of-distribution (OOD) detection [25, 47, 50]. Specifically, we use rotation by 90, 180, and 270 degrees [15, 18] as our negative transformation. Since the vertical information of the image is more important than the horizontal information [22, 49], e.g., images of a car facing left or right are common, but a car flipped upside down is very rare compared to a car standing right, rotation by a large angle causes loss of semantic information of images [50]. Thus, we can use rotated data as semantically different images from images of existing classes, i.e., suitable for preparatory data. A more detailed analysis of various negative transformations is provided in the Supple.", + "bbox": [ + 498, + 121, + 890, + 347 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We jointly train the model using real data (i.e., samples of existing classes) and preparatory data. Formally, we write the objective for the model parameter $\\theta$ as:", + "bbox": [ + 498, + 347, + 890, + 393 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\underset {\\theta} {\\arg \\min } \\left[ \\mathbb {E} _ {(x, y) \\sim \\mathcal {M}} \\mathcal {L} _ {\\mathrm {D R}} \\left(\\hat {f} _ {\\theta} (x), y; \\mathbf {W} _ {\\text {E T F}}\\right) \\right. \\tag {4} \\\\ \\left. \\right.\\left. + \\lambda \\mathbb {E} _ {\\left(x ^ {\\prime}, y ^ {\\prime}\\right) \\sim \\mathcal {M}, g \\sim G} \\mathcal {L} _ {\\mathrm {D R}} \\left(\\hat {f} _ {\\theta} (g \\left(x ^ {\\prime}\\right)), m \\left(y ^ {\\prime}, g\\right); \\mathbf {W} _ {\\text {E T F}}\\right)\\right], \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 500, + 400, + 903, + 469 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{M}$ denotes episodic memory, $(x,y)$ and $(x',y')$ denote the samples in $\\mathcal{M}$ , $G$ denotes the set of possible transformations, $g$ denotes a transformation in $G$ , $m$ denotes the mapping function, and $\\lambda$ is a hyperparameter for balancing real data and preparatory data.", + "bbox": [ + 498, + 476, + 890, + 551 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3. Residual correction at inference", + "text_level": 1, + "bbox": [ + 500, + 560, + 779, + 574 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Despite preparatory data training that accelerates convergence towards ETF, in online CL, new samples in a data stream hinder models from reaching the Terminal Phase of Training (TPT) and fully converging to the ETF during single-epoch training. When the output of the model $f(x)$ does not fully converge to the ETF classifier, the model would not perform well at all times, leading to poor anytime inference accuracy ( $A_{\\mathrm{AUC}}$ ).", + "bbox": [ + 498, + 583, + 890, + 703 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To address this issue, we want to correct the residual between $f(x)$ and the corresponding classifier vector $\\mathbf{w}_y$ during inference, where $y$ is label of input $x$ .", + "bbox": [ + 498, + 704, + 888, + 750 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "However, the discrepancy between the prediction on test data $x_{\\mathrm{eval}}$ and the ground-truth ETF classifier vector is not available in the inference phase. In a similar situation, ResMem [57] stores the residual obtained from training data and uses them during inference, but they assume two-stage learning algorithms, i.e., standard training and inference rather than incremental learning and anytime inference.", + "bbox": [ + 496, + 750, + 890, + 854 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Inspired by ResMem [57], which uses residuals from the training in the inference stage, we propose to use the residual obtained from the training process to compensate for the", + "bbox": [ + 498, + 854, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "23937", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/a7c115f190f9210571617b661e4d4406938133cb087dd8120eb1d917fe9cebd5.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodCIFAR-10CIFAR-100
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)75.25±0.7860.80±2.2059.62±0.3164.24±1.9752.08±0.8341.55±0.8538.22±0.5042.52±0.58
ER (Rolnick et al., 2019)75.94±0.8663.56±1.3260.13±0.5664.81±2.7052.95±1.2542.82±0.0541.12±0.5642.74±1.09
ER-MIR (Aljundi et al., 2019)75.89±1.0261.93±0.9360.39±0.4861.64±3.8652.93±1.4442.47±0.1341.19±0.6342.93±1.18
REMIND (Hayes et al., 2020)69.55±0.9153.34±1.0158.01±0.7259.27±1.8640.87±0.7636.17±1.8323.40±2.2528.78±1.71
DER++ (Buzzega et al., 2020)74.78±0.7259.20±0.9559.44±0.2866.11±1.8038.16±1.5738.55±2.1129.38±2.5838.20±3.13
SCR (Mai et al., 2021)75.61±0.9356.52±0.5260.62±0.4358.41±2.3941.84±0.7436.00±0.8331.33±0.4132.11±0.39
ODDL (Ye et al., 2022)75.03±1.0061.61±3.5565.46±0.4666.19±2.0840.26±0.5041.88±4.5238.82±0.4941.35±1.08
MEMO (Zhou et al., 2023)73.21±0.4962.47±3.3859.26±0.9062.01±1.1740.60±1.1139.87±0.4623.41±1.6332.74±2.11
X-DER (Boschini et al., 2023)77.59±0.6265.40±4.7958.28±1.1759.76±4.2852.80±1.6143.73±0.8641.94±0.5746.00±1.04
EARL (Ours)78.31±0.7265.71±2.2669.52±0.1970.41±1.9757.12±1.2244.40±0.6847.89±0.6146.09±0.26
", + "bbox": [ + 78, + 88, + 893, + 277 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/7f31bf504023dff07cdaf10d49311d56658ca7aa529299a96d29a5e2cedf8e32.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodTinyImageNetImageNet-200
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)37.95±0.9327.50±0.8025.29±0.8126.06±0.5241.84±0.6431.57±0.8030.71±0.2733.33±0.98
ER (Rolnick et al., 2019)37.43±1.0527.47±0.6326.37±0.8925.79±0.4441.51±0.7630.87±0.7232.39±0.3633.09±0.37
ER-MIR (Aljundi et al., 2019)37.81±1.0626.72±0.8626.22±0.6925.11±1.0438.28±0.3833.12±0.7332.17±0.4433.85±0.93
REMIND (Hayes et al., 2020)28.37±0.1327.68±0.4510.19±0.6014.90±1.4939.25±0.9331.98±0.8430.23±0.6233.98±0.09
DER++ (Buzzega et al., 2020)39.38±0.6029.36±0.8127.23±1.9431.53±0.8043.50±0.3134.56±0.5035.22±0.2638.38±0.97
SCR (Mai et al., 2021)34.65±1.0822.18±0.3225.86±0.9422.54±0.5941.90±0.4028.92±0.4033.24±0.3230.98±0.28
MEMO (Zhou et al., 2023)27.36±0.6127.57±0.5210.82±1.2318.03±1.3641.55±0.2334.19±1.4732.54±0.3936.11±1.06
X-DER (Boschini et al., 2023)35.15±2.1226.67±0.5229.71±0.8628.10±0.5043.41±0.4734.14±0.9836.31±0.1738.61±0.55
EARL (Ours)41.77±1.2629.65±0.2035.08±0.7032.49±1.2144.88±0.2934.79±0.5539.14±0.4738.83±0.35
", + "bbox": [ + 78, + 286, + 890, + 463 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Comparison of online CL methods on Disjoint and Gaussian Scheduled Setup for CIFAR-10, CIFAR-100, TinyImageNet and ImageNet-200.", + "bbox": [ + 75, + 473, + 892, + 502 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "remaining discrepancy between the classifiers and the features at inference.", + "bbox": [ + 75, + 508, + 468, + 539 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To select which of the stored residuals to use during inference, we not only store the residual, but also $f(x)$ to choose the stored residual closest to $f(x_{\\mathrm{infer}})$ . Therefore, we retain 'feature-residual' pairs in a 'feature-residual memory' $M = \\{(\\hat{h}_i,\\mathbf{r}_i)\\}_{i = 1}^N$ , where $\\hat{h}_i = \\hat{f} (x_i)$ , $\\mathbf{r}_i = \\mathbf{w}_{y_i} - \\hat{f} (x_i)$ , where $N$ is the size of feature-residual memory, and $\\mathbf{w}_{y_i}$ is the classifier vector for class $y_i$ .", + "bbox": [ + 75, + 542, + 468, + 651 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "During inference, we select the $k$ nearest neighbor $\\hat{h}$ 's, i.e., $\\{\\hat{h}_{n_1},\\hat{h}_{n_1},\\dots ,\\hat{h}_{n_k}\\}$ from $\\{\\hat{h}_i\\}_{i = 1}^N$ , since using only the nearest residual for correction may lead to incorrect inference predictions if a wrong residual is selected from a different class. Finally, following ResMem [57], we calculate the residual correction term $\\mathbf{r}_{\\mathrm{eval}}$ by a weighted average of the corresponding residuals $\\{\\mathbf{r}_{n_1},\\mathbf{r}_{n_2},\\dots ,\\mathbf{r}_{n_k}\\}$ , with weights $\\{s_1,s_2,\\ldots ,s_k\\}$ that are inversely proportional to the distance from $\\hat{f} (x_{\\mathrm{eval}})$ , as:", + "bbox": [ + 75, + 654, + 468, + 792 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {r} _ {\\text {e v a l}} = \\sum_ {i = 1} ^ {k} s _ {i} \\mathbf {r} _ {i}, \\quad s _ {i} = \\frac {e ^ {- (\\hat {f} (x _ {\\text {e v a l}}) - \\hat {h} _ {i}) / \\tau}}{\\sum_ {j = 1} ^ {k} e ^ {- (\\hat {f} (x _ {\\text {e v a l}}) - \\hat {h} _ {j}) / \\tau}}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 101, + 811, + 468, + 854 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $\\tau$ is a temperature hyperparameter. We add the residual-correcting term $\\mathbf{r}_{\\mathrm{eval}}$ to the model output $\\hat{f} (x_{\\mathrm{eval}})$", + "bbox": [ + 75, + 869, + 468, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "to obtain the corrected output $\\hat{f} (x_{\\mathrm{eval}})_{\\mathrm{corrected}}$ as:", + "bbox": [ + 498, + 508, + 816, + 526 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {f} \\left(x _ {\\text {e v a l}}\\right) _ {\\text {c o r r e c t e d}} = \\hat {f} \\left(x _ {\\text {e v a l}}\\right) + \\mathbf {r} _ {\\text {e v a l}}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 583, + 537, + 890, + 558 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 498, + 573, + 633, + 590 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Experimental setup", + "text_level": 1, + "bbox": [ + 498, + 599, + 687, + 616 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We perform experiments on four datasets: CIFAR-10, CIFAR-100, TinyImageNet, ImageNet-200, and ImageNet-1K. For all datasets, our experiments are conducted on both a disjoint setup [35] and a Gaussian scheduled setup [45, 51]. We report the average and standard deviation results in three different seeds, except ImageNet-1k due to computational resource constraints [2, 27].", + "bbox": [ + 496, + 623, + 890, + 729 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To evaluate anytime inference performance, we use the area under the curve accuracy $(A_{auc})$ [6, 27], which measures the area under the accuracy curve. We also use last accuracy $(A_{last})$ which measures accuracy at the end of training. For detailed information about the experimental setup, refer to the Supplementary.", + "bbox": [ + 496, + 731, + 890, + 821 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. We compare EARL with various CL methods in different categories: regularization (EWC [26]), network expansion (MEMO [63]), replay (ER [43], ER-MIR [1], REMIND [20], SCR [31], ODDL [3]), and distillation", + "bbox": [ + 496, + 839, + 892, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "23938", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/4a92afd0f76460ee44d8922823af0b9d29866dc167005430069c9ea3c666b109.jpg", + "table_caption": [], + "table_footnote": [ + "Table 2. Comparison of online CL methods on Disjoint and Gaussian Scheduled Setup for ImageNet-1K." + ], + "table_body": "
MethodImageNet-1K
DisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)30.1718.7817.0920.15
ER (Rolnick et al., 2019)30.1818.9617.1718.39
ER-MIR (Aljundi et al., 2019)31.6819.8719.3716.30
REMIND (Hayes et al., 2020)32.4724.5917.4219.79
DER++ (Buzzega et al., 2020)31.0818.9823.7323.14
SCR (Mai et al., 2021)26.7213.6019.8215.84
MEMO (Zhou et al., 2023)30.4519.0814.0620.12
X-DER (Boschini et al., 2023)31.6718.1825.1812.51
EARL (Ours)34.3323.1930.5329.48
", + "bbox": [ + 80, + 89, + 467, + 253 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "$(\\mathrm{DER} + + [4], \\mathrm{X - DER}[3])$ . For more details on the implementation of these methods and a comparison with NCFSCIL [56], which attempts to induce neural collapse in the context of few-shot class incremental learning, please refer to the supplementary material.", + "bbox": [ + 75, + 291, + 467, + 367 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Implementation details. We use three components to architect our model: a backbone network $g(\\cdot)$ , a projection MLP $p(\\cdot)$ , and a fixed ETF classifier $\\mathbf{W}_{\\mathrm{ETF}}$ (i.e., our model $f$ can be defined as $f(x) = p \\circ g(x)$ ). For the projection layer, we attach an MLP projection layer $p_{\\theta_p}$ to the output of the backbone network $g_{\\theta_g}$ , where $\\theta_g$ and $\\theta_p$ denote the parameters of the backbone network and the projection layer, respectively (i.e., the model $f$ can be defined as $f(x) = p \\circ g(x)$ ), following [9, 37, 56]. For all methods, we use ResNet-18 [21] as the backbone network.", + "bbox": [ + 75, + 382, + 467, + 532 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Following [27, 59], we employ memory-only training, where a random batch is selected from memory at each iteration. Furthermore, for episodic memory sampling, EARL uses the Greedy Balanced Sampling strategy [40]. We describe the details about hyperparameters and the pseudocode of EARL in Supplementary for the sake of space.", + "bbox": [ + 75, + 532, + 467, + 623 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.2. Results", + "text_level": 1, + "bbox": [ + 76, + 633, + 169, + 648 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We first compare the accuracy of online continual learning methods, including EARL, and summarize the results in Table 1. As shown in the table, EARL outperforms other baselines on all benchmarks, both in disjoint and Gaussian-scheduled setups, except $A_{\\mathrm{last}}$ in ImageNet-1K disjoint setup. In particular, high $A_{\\mathrm{AUC}}$ suggests that EARL outperforms other methods for all the time that the data stream is provided to the model, which implies that it can be used for inference at anytime.", + "bbox": [ + 75, + 657, + 467, + 792 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Furthermore, EARL, SCR, ER, MIR, DER, and ODDL do not use task boundary information during training, i.e., task-free, in contrast to EWC, X-DER, MEMO, and REMIND which use task-boundary information, i.e., task-aware. Nevertheless, EARL outperforms these methods even in the disjoint setup where utilizing task boundary information is advantageous due to abrupt distribution shifts", + "bbox": [ + 75, + 794, + 467, + 898 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "at the task boundaries, except MEMO in ImageNet-1K disjoint. Since MEMO not only uses the task boundary information but also expands the network per task, this extra advantage of using a larger model is emphasized in largescale datasets such as ImageNet which require a large learning capacity of the model. Please refer to the supplementary material for details of the computational budget comparison among the baseline methods.", + "bbox": [ + 496, + 90, + 890, + 210 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Memory budget. We consider not only the size of episodic memory, but also the size of the model, logits, and other components, following MEMO [63]. In the case of the memory budget for CIFAR-10 and the architecture of ResNet-18 (size of 42.6MB), EARL incurs an additional memory cost of 0.2MB to store feature-residual pairs. EWC requires an additional cost of 85.2MB due to the need to store Fisher Information per parameter and the previous model. MEMO, which expands the network per task, incurs an additional cost of 32MB per task. DER also requires an additional cost of 0.1MB to store logits during distillation.", + "bbox": [ + 496, + 215, + 890, + 381 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Ablation study", + "text_level": 1, + "bbox": [ + 500, + 392, + 648, + 407 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We conduct an ablation study on the two components of EARL, preparatory data training and residual correction, and summarize the results in Table 3. Although both components contribute to performance improvement, preparatory data training shows a larger gain in performance. Training with preparatory data improves the baseline by $2.7\\% \\sim 3.3\\%$ in $A_{auc}$ and $2.1\\% \\sim 4.4\\%$ in $A_{last}$ . When combined with residual correction, we observe further gains across all metrics in both disjoint and Gaussian-scheduled setups.", + "bbox": [ + 496, + 415, + 890, + 550 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5ec652ff9bfca509aaf3d5de8627a380793ab48d2e58d806828c8db6872f8c63.jpg", + "image_caption": [ + "Figure 5. Average similarity between features of the most recently added class's samples and the closest classifier vectors of the old classes (CIFAR-10, Gaussian Scheduled). Baseline is a vanilla ETF model trained only using episodic memory." + ], + "image_footnote": [], + "bbox": [ + 545, + 563, + 823, + 726 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "For further analysis, Fig. 6 visualizes the cosine similarity between the output features of 50 randomly selected test set samples of novel class '4' and the classifier vectors $\\mathbf{w}_i$ . In baseline (a), the features of the class 4 are strongly biased towards the classifier vectors of the old classes (i.e., $\\mathbf{w}_0$ , $\\mathbf{w}_1$ , $\\mathbf{w}_2$ , $\\mathbf{w}_3$ ), rather than the correct classifier, $\\mathbf{w}_4$ . (c)", + "bbox": [ + 496, + 809, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "23939", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/91716e7bf6d09db1e5161c74dcb538b16eeaa3438f4750be450e1a49d0242171.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
METHODCIFAR-10CIFAR-100
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EARL (Ours)78.61±0.7266.01±2.2669.62±0.1970.91±1.9757.42±1.2444.60±0.6548.19±0.6146.10±0.26
(-) RC77.78±0.5265.52±1.6368.37±0.1070.17±1.0856.28±1.4044.29±1.0447.05±0.7146.07±0.52
(-) RC & PDT74.77±0.7761.10±3.1265.60±0.2567.39±0.7852.91±1.0541.08±0.6044.34±0.5544.45±0.48
", + "bbox": [ + 83, + 75, + 885, + 178 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. Ablation Study. RC and PDT refer to preparatory data training (Sec. 4.2) and the residual correction (Sec. 4.3), respectively.", + "bbox": [ + 91, + 183, + 875, + 198 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/bb4af209ee29559e28e20df0cd9d4917e821b0cefa5027490e79b3335dce7a7c.jpg", + "image_caption": [ + "Figure 6. Cosine similarity between features $\\hat{f}(x)$ for class 4 and the ETF classifier vectors $\\mathbf{w}_i$ at the $50^{th}$ iteration after the introduction of class 4 in the Gaussian Scheduled CIFAR-10 setup. As we can see in the cyan highlighted box, EARL promotes the convergence of $\\hat{f}(x)$ for class 4 toward the ground truth classifier vector $\\mathbf{w}_4$ ." + ], + "image_footnote": [], + "bbox": [ + 107, + 203, + 864, + 431 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "When residual correction is used, some samples show high similarity with $\\mathbf{w}_4$ compared to the baseline.", + "bbox": [ + 75, + 492, + 468, + 522 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "However, since incorrect residuals can be added due to the bias problem, more samples have high similarity with $\\mathbf{w}_2$ than the baseline (i.e., wrong residuals are added). (b) When using preparatory data training, the bias toward $\\mathbf{w}_0$ and $\\mathbf{w}_1$ classes significantly decreases compared to the baseline. Fig. 5 also shows the effect of preparatory data, which reduces the similarity between the novel class features and existing classes. (d) Using both residual correction and preparatory data training shows a remarkable alignment with the ground truth classifier $\\mathbf{w}_4$ . A more detailed analysis of the ablation results is provided in the Supple.", + "bbox": [ + 75, + 523, + 470, + 691 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 76, + 707, + 194, + 722 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To better learn online data in a continuous data stream without multiple epoch training, we propose to induce neural collapse, which aligns last layer activations to the corresponding classifier vectors in the representation space. Unlike in offline CL, it is challenging to induce neural collapse in online CL due to insufficient training epochs and continuously streamed new data. We first observe that the bias of the new class towards existing classes slows the convergence of features toward neural collapse.", + "bbox": [ + 75, + 733, + 468, + 868 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To mitigate the bias, we propose synthesizing preparatory data for unseen classes by transforming the samples", + "bbox": [ + 75, + 869, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "of existing classes. Using the preparatory data for training, we accelerate neural collapse in an online CL scenario. Additionally, we propose residual correction to resolve the remaining discrepancy toward neural collapse at inference, which arises due to the continuous stream of new data. In our empirical evaluations, the proposed methods outperform state-of-the-art online CL methods in various datasets and setups, especially with high performance on anytime inference.", + "bbox": [ + 496, + 492, + 890, + 628 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Limitations and Future Work. Since our work uses ETF structure, it has an inherent limitation that the number of possible classifier vectors in the ETF classifier is limited by the dimension of the embedding space. Considering lifelong learning, where the number of new classes goes to infinity, it is interesting to explore the idea of dynamically expanding the ETF structure so that the model can continually learn the ever-increasing number of concepts in the real world.", + "bbox": [ + 496, + 643, + 892, + 779 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement. This work was partly supported by the NRF grant (No.2022R1A2C4002300, $20\\%$ ) and IITP grants (No.2022-0-00077 $(10\\%)$ , No.2022-0-00113 $(25\\%)$ , No.2022-0-00959 $(10\\%)$ , No.2022-0- 00871 $(10\\%)$ , No.2020-0-01361 $(5\\%)$ , Yonsei AI), No.2021-0-01343 $(5\\%)$ SNU AI), No.2021-0-02068 $(5\\%)$ , AI Innov. Hub), No.2022-0-00951 $(5\\%)$ ) funded by the Korea government (MSIT) and CARAI grant funded by DAPA and ADD (UD230017TD) $5 \\%$ . This work was done while J. Choi was with Yonsei University and partially while H. Lee, M. Seo and H. Kim was with LG AI Research.", + "bbox": [ + 496, + 790, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "23940", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Rahaf Aljundi, Klaas Kelchtermans, and Tinne Tuytelaars. Task-free continual learning. In CVPR, 2019. 1, 2, 6", + "[2] Jihwan Bang, Heesu Kim, YoungJoon Yoo, Jung-Woo Ha, and Jonghyun Choi. Rainbow memory: Continual learning with a memory of diverse samples. In CVPR, 2021. 2, 6", + "[3] Matteo Boschini, Lorenzo Bonicelli, Pietro Buzzega, Angelo Porrello, and Simone Calderara. Class-incremental continual learning into the extended der-verse. IEEE TPAMI, 45(5): 5497-5512, 2022. 2, 6, 7", + "[4] Pietro Buzzega, Matteo Boschini, Angelo Porrello, Davide Abati, and Simone Calderara. 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In NeurIPS, 2021. 1, 3" + ], + "bbox": [ + 501, + 92, + 890, + 811 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "23942", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_model.json b/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_model.json new file mode 100644 index 0000000000000000000000000000000000000000..4aeb114405a3df1120f69fa6a7cd91554b061436 --- /dev/null +++ b/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_model.json @@ -0,0 +1,2288 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.127, + 0.131, + 0.846, + 0.154 + ], + "angle": 0, + "content": "Learning Equi-angular Representations for Online Continual Learning" + }, + { + "type": "text", + "bbox": [ + 0.126, + 0.18, + 0.844, + 0.218 + ], + "angle": 0, + "content": "Minhyuk Seo\\(^{1,\\dagger}\\) Hyunseo Koh\\(^{1}\\) Wonje Jeung\\(^{1}\\) Minjae Lee\\(^{1}\\) San Kim\\(^{1}\\) Hankook Lee\\(^{2,3}\\) Sungjun Cho\\(^{2}\\) Sungik Choi\\(^{2}\\) Hyunwoo Kim\\(^{4,*}\\) Jonghyun Choi\\(^{5,*}\\)" + }, + { + "type": "text", + "bbox": [ + 0.108, + 0.223, + 0.862, + 0.294 + ], + "angle": 0, + "content": "\\(^{1}\\)Yonsei Univ. \\(^{2}\\)LG AI Research \\(^{3}\\)Sungkyunkwan Univ. \\(^{4}\\)Zhejiang Lab \\(^{5}\\)Seoul National Univ. {dbd0508, specific0924, reccos1020, nasmik419}@yonsei.ac.kr khs8157@gmail.com, {sungik.choi,sungjun.cho}@lgresearch.ai hankook.lee@skku.edu, hwkim@zhejianglab.com, jonghyunchoi@snu.ac.kr" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.33, + 0.314, + 0.346 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.361, + 0.474, + 0.633 + ], + "angle": 0, + "content": "Online continual learning suffers from an underfitted solution due to insufficient training for prompt model update (e.g., single-epoch training). To address the challenge, we propose an efficient online continual learning method using the neural collapse phenomenon. In particular, we induce neural collapse to form a simplex equiangular tight frame (ETF) structure in the representation space so that the continuously learned model with a single epoch can better fit to the streamed data by proposing preparatory data training and residual correction in the representation space. With an extensive set of empirical validations using CIFAR10/100, TinyImageNet, ImageNet-200, and ImageNet-1K, we show that our proposed method outperforms state-of-the-art methods by a noticeable margin in various online continual learning scenarios such as disjoint and Gaussian scheduled continuous (i.e., boundary-free) data setups. Code is available at https://github.com/yonseivnl/earl." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.661, + 0.21, + 0.677 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.686, + 0.471, + 0.868 + ], + "angle": 0, + "content": "A growing interest in continuous learning (CL) involves training the model using continuous data streams. Mostly, CL research has focused on the offline scenario that assumes the model can be trained in multiple epochs for the current task [8, 42, 54]. However, substantial storage and computational complexity are required to store all data to train a model for multiple epochs. Recently, there has been significant interest in online CL as a more realistic set-up with a lower computational overhead of allowing a single training pass through the data stream [1, 7, 27]. Learning a model in streamed data by a single training pass is challenging, since the temporal distribution at each intermediate" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.33, + 0.892, + 0.393 + ], + "angle": 0, + "content": "time point is likely imbalanced, even if the overall distribution of a dataset is balanced. Imbalanced data distributions would cause several problems, such as bias towards the major classes [24, 61] and the hindrance to generalization [53]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.395, + 0.893, + 0.607 + ], + "angle": 0, + "content": "Recently, minority collapse [14], the phenomenon in which the angles between classifier vectors for minor classes (i.e., the classes that have a relatively small number of samples) become narrow, has been proposed as a fundamental issue in training with imbalanced data, making the classification of minor classes considerably more challenging. In contrast, for balanced data sets, it was proven that classifier vectors and the last layer activations for all classes converge into an optimal geometric structure, named the simplex equiangular tight frame (ETF) structure, where all pairwise angles between classes are equal and maximally widened when using cross entropy (CE) [23, 30, 52, 65] or mean squared error (MSE) [32, 41, 48, 64] loss. This phenomenon is called neural collapse [34]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.61, + 0.895, + 0.748 + ], + "angle": 0, + "content": "Although neural collapse naturally occurs only in balanced training, several recent studies attempted to induce neural collapse in imbalanced training to address the minority collapse problem using a fixed ETF classifier [55, 62]. When employing a fixed ETF classifier, the output features are pulled toward the corresponding classifier vector during training, since the classifier is fixed. More recently, research has also been extended to induce neural collapse in offline CL using a fixed ETF classifier [56]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.895, + 0.902 + ], + "angle": 0, + "content": "However, unlike offline CL, there are a number of challenges in inducing neural collapse in online CL, even with a fixed ETF classifier. The prerequisite for neural collapse is reaching the terminal phase of training (TPT) by sufficient training [34]. In offline CL, the model can reach the TPT phase for each task by multi-epoch training. In contrast, a single-pass training constraint often prevents the online CL from reaching TPT. As shown in Fig. 1, the offline CL quickly reaches TPT shortly after the arrival of novel task data, while online CL (vanilla ETF) does not." + }, + { + "type": "page_footnote", + "bbox": [ + 0.08, + 0.875, + 0.345, + 0.888 + ], + "angle": 0, + "content": "†: Work done while interning at LG AI Research." + }, + { + "type": "page_footnote", + "bbox": [ + 0.083, + 0.889, + 0.27, + 0.9 + ], + "angle": 0, + "content": "*: Indicates corresponding authors." + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.875, + 0.345, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23933" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.089, + 0.895, + 0.25 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.258, + 0.895, + 0.302 + ], + "angle": 0, + "content": "Figure 1. Comparison of training error rates between online CL and offline CL in the CIFAR-10 disjoint setup, where two novel classes are added every 10k samples. Vanilla ETF refers to a method where both preparatory data training and residual correction are removed from our proposed EARL." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.308, + 0.471, + 0.414 + ], + "angle": 0, + "content": "Recently, the importance of anytime inference in online CL has been emphasized [6, 17, 27, 36], since a model should be available for inference not only at the end of a task, but also at any point during training to be practical for real-world applications. Hence, not only reaching TPT but also achieving faster convergence is necessary when using neural collapse in online CL." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.415, + 0.47, + 0.552 + ], + "angle": 0, + "content": "However, we observe that the phenomenon in which the features of the new class become biased toward the features of the existing classes [5] hinders fast convergence of the last-layer features into the ETF structure, which we call the 'bias problem.' When features of old and new classes overlap (i.e., biased) and are trained with the same objective, well-clustered features of old classes disperse (or perturb) [5], leading to destruction of the ETF structure formed by features of the old classes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.566, + 0.47, + 0.746 + ], + "angle": 0, + "content": "Contributions. To address the bias problem, we train the model to distinguish out-of-distribution (OOD) samples from existing classes' samples. Specifically, we synthesize preparatory data that play the role of OOD data, by applying negative data augmentation [25, 47, 50] to samples from existing classes, refer to Sec. 4.2 for details. Since samples from new classes are OOD in the perspective of existing classes, training with preparatory data encourages the representation of new classes to be distinguished from existing classes in advance, thereby mitigating the bias problem. This promotes fast and stable convergence into the ETF structure." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.749, + 0.47, + 0.869 + ], + "angle": 0, + "content": "Despite these efforts, however, the continuous stream of new samples cause ongoing data distribution shifts, which prevent the model from reaching the TPT and fully converging to the ETF structure. To address this, we propose to store the residuals between the target ETF classifier and the features during training. During inference, we correct the inference output using the stored residual to compensate for insufficient convergence in the training." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.902 + ], + "angle": 0, + "content": "By accelerating convergence by preparatory data training and additional correction using residual, we noticeably" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.308, + 0.895, + 0.414 + ], + "angle": 0, + "content": "improve anytime inference performance than state of the arts. We name our method Equi-Angular Representation Learning (EARL). We empirically demonstrate the effectiveness of our framework on CIFAR-10, CIFAR-100, TinyImageNet,Imagenet-200,and ImageNet-1K.In particular, our framework outperforms various CL methods by a significant margin \\((+4.0\\%)\\) gain of \\(A_{\\mathrm{auc}}\\) in ImageNet-1K)." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.415, + 0.813, + 0.429 + ], + "angle": 0, + "content": "We summarize our contributions as follows:" + }, + { + "type": "text", + "bbox": [ + 0.511, + 0.432, + 0.858, + 0.446 + ], + "angle": 0, + "content": "- Proposing to induce neural collapse for online CL." + }, + { + "type": "text", + "bbox": [ + 0.511, + 0.448, + 0.892, + 0.507 + ], + "angle": 0, + "content": "- Proposing 'preparatory data training' to address the 'bias problem' that the new classes are biased toward the existing classes, promoting faster induction of neural collapse." + }, + { + "type": "text", + "bbox": [ + 0.511, + 0.509, + 0.892, + 0.554 + ], + "angle": 0, + "content": "- Proposing 'residual correction' scheme to compensate for not fully reaching neural collapse at inference to further improve anytime inference accuracy." + }, + { + "type": "list", + "bbox": [ + 0.511, + 0.432, + 0.892, + 0.554 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.572, + 0.638, + 0.587 + ], + "angle": 0, + "content": "2. Related work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.892, + 0.794 + ], + "angle": 0, + "content": "Continual learning methods. Various continual learning methods are being researched to prevent forgetting past tasks, broadly categorized into replay, parameter isolation, and regularization. Replay methods involve storing a small portion of data from previous tasks in episodic memory [1, 2, 20, 27, 60] or storing a generative model trained on data from previous tasks [39, 46]. By replaying the samples stored in episodic memory or generated from the stored generative model, the model prevents forgetting past tasks during subsequent learning of novel tasks. Furthermore, Boschini et al. [3], Buzzega et al. [4], Li and Hoiem [29], Wu et al. [54] used replay samples to distill information about past tasks." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Regularization methods [26, 28] apply a penalty to the change of important model parameters during the process of learning new tasks, allowing the model to retain information about previous tasks. Parameter isolation methods [10, 44, 63] expand the network by allocating specific layers for each task. This enables the network to store information about individual tasks and preserves their knowl-" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "23934" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.24, + 0.108 + ], + "angle": 0, + "content": "edge without forgetting." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.111, + 0.469, + 0.277 + ], + "angle": 0, + "content": "Neural collapse. Neural collapse is a phenomenon in which the activations of the last layer and the classifier vectors form a simplex equiangular tight frame (ETF) structure at the terminal phase of training (TPT) in a balanced dataset. [34]. Neural collapse has been demonstrated as the global optimum of balanced training using cross entropy (CE) loss [23, 30, 52, 65] and MSE [32, 41, 48, 64] loss functions, within a simplified model focused solely on last-layer optimization. Inducing neural collapse in imbalanced datasets poses challenges due to minority collapse [14] where minor classes are not well distinguished." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.278, + 0.469, + 0.429 + ], + "angle": 0, + "content": "However, using a fixed ETF classifier, it is empirically and theoretically shown that neural collapse is induced even in imbalanced datasets [55]. Continual learning also needs to address imbalanced data since there is an imbalance in the data between novel classes and existing classes. Therefore, in offline CL, NC-FSCIL [38, 56] used a fixed ETF classifier to induce neural collapse. Meanwhile, online CL often fails to induce neural collapse compared to offline CL, e.g., FSCIL, since it lacks sufficient training in multiple epochs, causing failure to reach TPT." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.429, + 0.469, + 0.474 + ], + "angle": 0, + "content": "Please refer to the supplementary material for more comprehensive literature reviews including topics related to anytime inference." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.486, + 0.216, + 0.501 + ], + "angle": 0, + "content": "3. Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.512, + 0.469, + 0.557 + ], + "angle": 0, + "content": "We here describe the problem statement for the online continual learning (Sec. 3.1), neural collapse (Sec. 3.2), and the equiangular tight frame classifier (Sec. 3.3)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.564, + 0.367, + 0.579 + ], + "angle": 0, + "content": "3.1. Problem Statement of Online CL" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.587, + 0.469, + 0.696 + ], + "angle": 0, + "content": "Continual learning (CL) aims to learn from a stream of data, rather than a fixed dataset as in standard learning. Formally, given a sequence of tasks \\(\\mathcal{T} = (T_1,T_2,\\ldots)\\) where each task \\(T_{i}\\) is a training dataset \\(D_{i} = \\{(x_{1}^{(i)},y_{1}^{(i)}),(x_{2}^{(i)},y_{2}^{(i)}),\\ldots \\}\\), an offline CL algorithm \\(A_{\\mathrm{CL}}\\) updates the model parameter \\(\\theta\\) based on the current task \\(D_{k}\\), i.e., \\(\\theta_{k} = A_{\\mathrm{CL}}(\\theta_{k - 1},D_{k})\\), starting from the initial parameter \\(\\theta_0\\)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.696, + 0.469, + 0.771 + ], + "angle": 0, + "content": "To avoid the forgetting issue in CL, many CL setups allow the use of episodic memory \\(M_{k}\\), which is a limited-size subset of training data from previous tasks, i.e., \\((\\theta_k,M_k) = A_{\\mathrm{CL}}(\\theta_{k - 1},M_{k - 1},D_k)\\). The objective is to minimize the error of \\(\\theta_{k}\\) in all observed tasks \\(\\{T_i\\}_{i = 1}^k\\)" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.771, + 0.469, + 0.833 + ], + "angle": 0, + "content": "Unlike offline CL where all training samples in \\( D_{k} \\) are given as input, in online CL, the input is provided as a stream of samples \\( (x_{1}^{(k)}, y_{1}^{(k)}), (x_{2}^{(k)}, y_{2}^{(k)}), \\dots \\). Therefore, an online CL algorithm \\( A_{\\mathrm{OCL}} \\) is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.09, + 0.84, + 0.469, + 0.865 + ], + "angle": 0, + "content": "\\[\n\\left(\\theta_ {k, t}, M _ {k, t}\\right) = A _ {\\mathrm {O C L}} \\left(\\theta_ {k, t - 1}, M _ {k, t - 1}, \\left(x _ {t} ^ {(k)}, y _ {t} ^ {(k)}\\right)\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.871, + 0.469, + 0.902 + ], + "angle": 0, + "content": "with the same objective of minimizing the error of \\(\\theta_{k,t}\\) on \\(\\{T_i\\}_{i = 1}^k\\). Since the algorithm does not have access to pre" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.089, + 0.892, + 0.122 + ], + "angle": 0, + "content": "vious samples \\(\\{(x_s^{(k)},y_s^{(k)}),s < t\\}\\) at time \\(t\\) , multi-epoch training with \\(D_{k}\\) is unavailable in online CL." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.131, + 0.661, + 0.147 + ], + "angle": 0, + "content": "3.2. Neural Collapse" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.154, + 0.892, + 0.243 + ], + "angle": 0, + "content": "Neural collapse [34] is a phenomenon of the penultimate features after the convergence of training on a balanced dataset. When neural collapse (NC) occurs, the collection of \\(K\\) classifier vectors \\(\\mathbf{W}_{\\mathrm{ETF}} = [\\mathbf{w}_1,\\mathbf{w}_2,\\dots,\\mathbf{w}_K]\\in \\mathbb{R}^{d\\times K}\\) forms a simplex equiangular tight frame (ETF), which satisfies:" + }, + { + "type": "equation", + "bbox": [ + 0.508, + 0.251, + 0.892, + 0.291 + ], + "angle": 0, + "content": "\\[\n\\mathbf {w} _ {i} ^ {T} \\mathbf {w} _ {j} = \\left\\{ \\begin{array}{l l} 1, & i = j \\\\ - \\frac {1}{K - 1}, & i \\neq j \\end{array} , \\forall i, j \\in [ 1, \\dots , K ], \\right. \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.299, + 0.892, + 0.33 + ], + "angle": 0, + "content": "where \\(K - 1 \\leq d\\), and the penultimate feature of a training sample collapses into an ETF vector \\(\\mathbf{w}_i\\)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.337, + 0.862, + 0.354 + ], + "angle": 0, + "content": "3.3. Equiangular Tight Frame (ETF) Classifier" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.361, + 0.892, + 0.556 + ], + "angle": 0, + "content": "Inspired by neural collapse as described in Sec. 3.2, a fixed ETF classifier has been utilized for inducing neural collapse in imbalanced datasets [55, 56, 65]. Here, the classifier is initialized by the ETF structure \\(\\mathbf{W}_{\\mathrm{ETF}}\\) at the beginning of training and fixed during training to induce the penultimate feature \\(f(x)\\) to converge to the ideal balanced scenario. For training \\(f(x)\\), it is only required to attract \\(f(x)\\) to the corresponding classifier vector for convergence, since the classifier is fixed during training. Therefore, following Yang et al. [55], we use the dot regression (DR) loss as a training objective, as it shows to outperform cross entropy (CE) loss when using a fixed ETF classifier in imbalanced datasets [55]. The DR loss can be written as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.552, + 0.563, + 0.891, + 0.592 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {D R}} (\\hat {f} (x), y; \\mathbf {W} _ {\\text {E T F}}) = \\frac {1}{2} \\left(\\mathbf {w} _ {y} \\hat {f} (x) - 1\\right) ^ {2}, \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.601, + 0.892, + 0.648 + ], + "angle": 0, + "content": "where \\(\\hat{f} (x) = f(x) / \\| f(x)\\| _2\\) is the \\(L_{2}\\) normalized feature of the model \\(f\\), \\(y\\) is the label of the input \\(x\\), and \\(\\mathbf{w}_y\\) is a classifier vector in \\(\\mathbf{W}_{\\mathrm{ETF}}\\) for the label \\(y\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.661, + 0.609, + 0.678 + ], + "angle": 0, + "content": "4. Approach" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.686, + 0.892, + 0.792 + ], + "angle": 0, + "content": "Despite the success of the fixed ETF classifier in both imbalanced training [55, 62] and offline CL [56], the ETF classifier has not yet been explored for online CL due to the necessity of sufficient training for neural collapse. To be specific, streamed data are trained only once in online CL, which makes it harder to induce neural collapse than in offline CL which supports multi-epoch training." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.792, + 0.892, + 0.868 + ], + "angle": 0, + "content": "To learn a better converged model without multi-epoch training for online CL, we propose two novel methods, each for the training phase and the inference phase, respectively. In the training phase, we accelerate convergence by proposing preparatory data training (Sec. 4.2). In the inference" + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.875, + 0.892, + 0.901 + ], + "angle": 0, + "content": "1If the training objective includes a contrastive term between different classes like cross entropy, it could cause incorrect gradients [55]." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "23935" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.895, + 0.293 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.298, + 0.895, + 0.37 + ], + "angle": 0, + "content": "Figure 2. Overview of EARL. \\(\\mathbf{w}_i\\) denotes the ETF classifier vector for class \\(i\\). \\(h_a\\) denotes the output of the model. The colors of the data denote the class to which the data belong. The arrow \\(\\mathbf{r}_i\\) denotes the residual between the last layer activation \\(h_i\\) and the classifier vector \\(\\mathbf{w}_i\\) for class \\(i\\). During training, both memory and preparatory data are used for replaying, and the residuals between \\(h_i\\) and \\(\\mathbf{w}_i\\) are stored in feature-residual memory. During inference, using the similarity between \\(f(x_{\\mathrm{eval}})\\) and \\(h_i\\) in feature-residual memory, \\(\\mathbf{r}_{\\mathrm{eval}}\\) is obtained by a weighted sum of \\(\\mathbf{r}_i\\)'s. Finally, by adding \\(\\mathbf{r}_{\\mathrm{eval}}\\), \\(f(x_{\\mathrm{eval}})\\) is corrected. The purple arrow indicates 'residual correction' (Sec. 4.3)." + }, + { + "type": "image", + "bbox": [ + 0.086, + 0.386, + 0.457, + 0.51 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.515, + 0.473, + 0.64 + ], + "angle": 0, + "content": "Figure 3. Illustrative effects for each component of EARL. (a) In online CL, features of novel classes are biased towards the features of the previous class. (b) By training with preparatory data (w/ Prep. Data, Sec. 4.2), we address the bias problem. (c) In inference, for features that do not fully converge to an ETF classifier, we add residuals (w/ Res. Corr., Sec. 4.3) to features that have not yet reached the corresponding classifier vectors, making features aligned with them. Purple arrow: the 'residual correction', Colors: classes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.651, + 0.47, + 0.711 + ], + "angle": 0, + "content": "phase, we propose to correct the remaining discrepancy between the classifiers and the features using residual correction (Sec. 4.3). We illustrate an overview of EARL in Fig. 2 and the effect of EARL in Fig. 3." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.724, + 0.423, + 0.741 + ], + "angle": 0, + "content": "4.1. Inducing Neural Collapse for Online CL" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.749, + 0.47, + 0.868 + ], + "angle": 0, + "content": "For online CL, we first try to induce neural collapse with a fixed ETF classifier: \\(\\mathbf{W}_{\\mathrm{ETF}} \\in R^{d \\times K}\\) where \\(d\\) is the dimension of the embedding space and \\(K\\) is the number of ETF vectors. While prior works [55, 56] use prior knowledge of the total number of classes that will be encountered for setting \\(K\\), it is unrealistic to know the knowledge (i.e., the exact number of classes) as it evolves continuously over time under realistic CL scenarios." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.471, + 0.901 + ], + "angle": 0, + "content": "To address the challenge, we propose using the maximum possible number of classifier vectors for \\( K \\). Based" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.388, + 0.895, + 0.435 + ], + "angle": 0, + "content": "on the simplex ETF property that the maximum number of ETF vectors is \\(d + 1\\) [16, 55], we define our ETF classifier \\(\\mathbf{W}_{\\mathrm{ETF}} \\in \\mathbb{R}^{d \\times (d + 1)}\\) by letting \\(K := d + 1\\)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.447, + 0.757, + 0.464 + ], + "angle": 0, + "content": "4.2. Preparatory data at training" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.471, + 0.892, + 0.825 + ], + "angle": 0, + "content": "Since novel classes continuously arrive in CL, both the data from previous tasks \\((x_{\\mathrm{old}})\\) and the current task \\((x_{\\mathrm{new}})\\) coexist. While \\(\\hat{f}(x_{\\mathrm{old}})\\) are placed closer to their corresponding ETF classifier vectors \\(w_{\\mathrm{new}}\\) by training, \\(\\hat{f}(x_{\\mathrm{new}})\\) are biased toward the cluster of \\(\\hat{f}(x_{\\mathrm{old}})\\), as we can see in Fig. 4-(a), where \\(\\hat{f}(x_{\\mathrm{new}})\\) and \\(\\hat{f}(x_{\\mathrm{old}})\\) are the outputs of the model for inputs \\(x_{\\mathrm{new}}\\) and \\(x_{\\mathrm{old}}\\), respectively. We call this 'bias problem.' When \\(\\hat{f}(x_{\\mathrm{new}})\\) and \\(\\hat{f}(x_{\\mathrm{old}})\\) overlap due to bias and are optimized with the same objective function, training on the new class interferes with the representations of the old classes, dispersing the well-clustered \\(\\hat{f}(x_{\\mathrm{old}})\\) [5]. It destroys the ETF structure formed by \\(\\hat{f}(x_{\\mathrm{old}})\\), which hinders convergence towards neural collapse. Although the bias problem exists even without a fixed ETF classifier [5, 12, 54], it poses a greater problem when using a fixed ETF classifier, since the dispersed feature of old classes has to be restored to the corresponding fixed classifier vector. In contrast, when using a learnable classifier, the dispersed representation of the old classes does not have to be restored to the original position, since the learnable classifier vector will be re-optimized from the dispersed feature. However, the angles between the classifier vector may become narrow, i.e., minority collapse occurs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.894, + 0.901 + ], + "angle": 0, + "content": "To accelerate convergence in the ETF structure, we propose to prevent novel classes from being biased towards existing classes when introduced, mitigating the bias problem. Specifically, we train the model to avoid making predictions in favor of the existing classes for images that do not be" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23936" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.091, + 0.099, + 0.454, + 0.234 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.239, + 0.47, + 0.336 + ], + "angle": 0, + "content": "Figure 4. t-SNE visualization of 'bias-problem' in data distributions (class 0 to 3). (a) Only after 100 iterations of training after task 1 appears, learning is likely insufficient, and we can see that the features of new classes (class 2, 3) are biased towards the feature cluster of the existing class (i.e., class 1). (b) With more training iterations (10,000 iter), the features are well clustered by class." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.354, + 0.468, + 0.444 + ], + "angle": 0, + "content": "long to them. To this end, we propose to use preparatory data \\( x_{p} \\) that is different from existing classes, obtained by transforming the samples in the episodic memory. By training with the preparatory data so that their representations differ from existing classes, we prevent biased predictions towards existing classes when a new class arrives." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.447, + 0.468, + 0.734 + ], + "angle": 0, + "content": "For preparatory data to have a different representation from existing classes when trained, their image semantics should be distinguishable from existing classes, provided that they contain enough semantic information to be considered as an image (i.e., not noise). There are various approaches to synthesize images with modified semantics, such as using generative models [11, 19, 58] or negative transformations [47, 50]. We use negative transformations, as generative models are expensive in computation and storage [13], which is undesirable for CL scenarios with limited memory and computations. On the contrary, negative transformations are relatively efficient in computation and storage [33] and is reported to create images with semantics different from the original image [50]. We empirically observed that data generated through negative transformations have a distinct semantic class from the original class while preserving its semantic information as an image (i.e., not as random noise), and we summarize the results in the supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.468, + 0.902 + ], + "angle": 0, + "content": "Formally, for a set of existing classes \\( Y \\) and the set of possible transformations \\( G \\), we randomly select \\( y \\in Y \\) and \\( g \\in G \\), and randomly retrieve a sample of class \\( y \\) from memory and apply the transformation \\( g \\) to obtain preparatory data \\( x_{p} \\). We assign labels of the unseen classes to the preparatory data by a mapping function \\( m: Y \\times G \\to Y' \\) where \\( Y' \\) denotes a set of unseen classes, i.e., \\( Y' = \\{y | y \\notin Y, 1 \\leq y \\leq K\\} \\) and \\( K \\) is the total number of classifier vectors in \\( \\mathbf{W}_{\\mathrm{ETF}} \\in \\mathbb{R}^{d \\times K} \\). Thus, preparatory data \\( x_{p} \\) from class \\( y \\) and transformation \\( g \\) is pulled towards the classifier vector \\( \\mathbf{w}_{p} \\), where \\( p = m(y, g) \\). When a new class \\( y_{\\mathrm{new}} \\)" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.89, + 0.122 + ], + "angle": 0, + "content": "is added to \\( Y \\), we update \\( m \\) by randomly assigning a new mapping \\( m(y_{\\mathrm{new}}, g) \\) for \\( y_{\\mathrm{new}} \\) and \\( g \\in G \\)." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.122, + 0.892, + 0.348 + ], + "angle": 0, + "content": "We compose the transformation set \\( G \\) as a negative transformation that can modify semantic information (i.e., change the label), used in the self-supervised literature [15, 18] and out-of-distribution (OOD) detection [25, 47, 50]. Specifically, we use rotation by 90, 180, and 270 degrees [15, 18] as our negative transformation. Since the vertical information of the image is more important than the horizontal information [22, 49], e.g., images of a car facing left or right are common, but a car flipped upside down is very rare compared to a car standing right, rotation by a large angle causes loss of semantic information of images [50]. Thus, we can use rotated data as semantically different images from images of existing classes, i.e., suitable for preparatory data. A more detailed analysis of various negative transformations is provided in the Supple." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.348, + 0.892, + 0.394 + ], + "angle": 0, + "content": "We jointly train the model using real data (i.e., samples of existing classes) and preparatory data. Formally, we write the objective for the model parameter \\(\\theta\\) as:" + }, + { + "type": "equation", + "bbox": [ + 0.5, + 0.401, + 0.904, + 0.47 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\underset {\\theta} {\\arg \\min } \\left[ \\mathbb {E} _ {(x, y) \\sim \\mathcal {M}} \\mathcal {L} _ {\\mathrm {D R}} \\left(\\hat {f} _ {\\theta} (x), y; \\mathbf {W} _ {\\text {E T F}}\\right) \\right. \\tag {4} \\\\ \\left. \\right.\\left. + \\lambda \\mathbb {E} _ {\\left(x ^ {\\prime}, y ^ {\\prime}\\right) \\sim \\mathcal {M}, g \\sim G} \\mathcal {L} _ {\\mathrm {D R}} \\left(\\hat {f} _ {\\theta} (g \\left(x ^ {\\prime}\\right)), m \\left(y ^ {\\prime}, g\\right); \\mathbf {W} _ {\\text {E T F}}\\right)\\right], \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.477, + 0.892, + 0.553 + ], + "angle": 0, + "content": "where \\(\\mathcal{M}\\) denotes episodic memory, \\((x,y)\\) and \\((x',y')\\) denote the samples in \\(\\mathcal{M}\\), \\(G\\) denotes the set of possible transformations, \\(g\\) denotes a transformation in \\(G\\), \\(m\\) denotes the mapping function, and \\(\\lambda\\) is a hyperparameter for balancing real data and preparatory data." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.561, + 0.78, + 0.575 + ], + "angle": 0, + "content": "4.3. Residual correction at inference" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.584, + 0.892, + 0.704 + ], + "angle": 0, + "content": "Despite preparatory data training that accelerates convergence towards ETF, in online CL, new samples in a data stream hinder models from reaching the Terminal Phase of Training (TPT) and fully converging to the ETF during single-epoch training. When the output of the model \\( f(x) \\) does not fully converge to the ETF classifier, the model would not perform well at all times, leading to poor anytime inference accuracy (\\( A_{\\mathrm{AUC}} \\))." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.705, + 0.89, + 0.75 + ], + "angle": 0, + "content": "To address this issue, we want to correct the residual between \\( f(x) \\) and the corresponding classifier vector \\( \\mathbf{w}_y \\) during inference, where \\( y \\) is label of input \\( x \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.856 + ], + "angle": 0, + "content": "However, the discrepancy between the prediction on test data \\( x_{\\mathrm{eval}} \\) and the ground-truth ETF classifier vector is not available in the inference phase. In a similar situation, ResMem [57] stores the residual obtained from training data and uses them during inference, but they assume two-stage learning algorithms, i.e., standard training and inference rather than incremental learning and anytime inference." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Inspired by ResMem [57], which uses residuals from the training in the inference stage, we propose to use the residual obtained from the training process to compensate for the" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "23937" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.08, + 0.089, + 0.895, + 0.278 + ], + "angle": 0, + "content": "
MethodCIFAR-10CIFAR-100
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)75.25±0.7860.80±2.2059.62±0.3164.24±1.9752.08±0.8341.55±0.8538.22±0.5042.52±0.58
ER (Rolnick et al., 2019)75.94±0.8663.56±1.3260.13±0.5664.81±2.7052.95±1.2542.82±0.0541.12±0.5642.74±1.09
ER-MIR (Aljundi et al., 2019)75.89±1.0261.93±0.9360.39±0.4861.64±3.8652.93±1.4442.47±0.1341.19±0.6342.93±1.18
REMIND (Hayes et al., 2020)69.55±0.9153.34±1.0158.01±0.7259.27±1.8640.87±0.7636.17±1.8323.40±2.2528.78±1.71
DER++ (Buzzega et al., 2020)74.78±0.7259.20±0.9559.44±0.2866.11±1.8038.16±1.5738.55±2.1129.38±2.5838.20±3.13
SCR (Mai et al., 2021)75.61±0.9356.52±0.5260.62±0.4358.41±2.3941.84±0.7436.00±0.8331.33±0.4132.11±0.39
ODDL (Ye et al., 2022)75.03±1.0061.61±3.5565.46±0.4666.19±2.0840.26±0.5041.88±4.5238.82±0.4941.35±1.08
MEMO (Zhou et al., 2023)73.21±0.4962.47±3.3859.26±0.9062.01±1.1740.60±1.1139.87±0.4623.41±1.6332.74±2.11
X-DER (Boschini et al., 2023)77.59±0.6265.40±4.7958.28±1.1759.76±4.2852.80±1.6143.73±0.8641.94±0.5746.00±1.04
EARL (Ours)78.31±0.7265.71±2.2669.52±0.1970.41±1.9757.12±1.2244.40±0.6847.89±0.6146.09±0.26
" + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.287, + 0.891, + 0.464 + ], + "angle": 0, + "content": "
MethodTinyImageNetImageNet-200
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)37.95±0.9327.50±0.8025.29±0.8126.06±0.5241.84±0.6431.57±0.8030.71±0.2733.33±0.98
ER (Rolnick et al., 2019)37.43±1.0527.47±0.6326.37±0.8925.79±0.4441.51±0.7630.87±0.7232.39±0.3633.09±0.37
ER-MIR (Aljundi et al., 2019)37.81±1.0626.72±0.8626.22±0.6925.11±1.0438.28±0.3833.12±0.7332.17±0.4433.85±0.93
REMIND (Hayes et al., 2020)28.37±0.1327.68±0.4510.19±0.6014.90±1.4939.25±0.9331.98±0.8430.23±0.6233.98±0.09
DER++ (Buzzega et al., 2020)39.38±0.6029.36±0.8127.23±1.9431.53±0.8043.50±0.3134.56±0.5035.22±0.2638.38±0.97
SCR (Mai et al., 2021)34.65±1.0822.18±0.3225.86±0.9422.54±0.5941.90±0.4028.92±0.4033.24±0.3230.98±0.28
MEMO (Zhou et al., 2023)27.36±0.6127.57±0.5210.82±1.2318.03±1.3641.55±0.2334.19±1.4732.54±0.3936.11±1.06
X-DER (Boschini et al., 2023)35.15±2.1226.67±0.5229.71±0.8628.10±0.5043.41±0.4734.14±0.9836.31±0.1738.61±0.55
EARL (Ours)41.77±1.2629.65±0.2035.08±0.7032.49±1.2144.88±0.2934.79±0.5539.14±0.4738.83±0.35
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.474, + 0.893, + 0.503 + ], + "angle": 0, + "content": "Table 1. Comparison of online CL methods on Disjoint and Gaussian Scheduled Setup for CIFAR-10, CIFAR-100, TinyImageNet and ImageNet-200." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.51, + 0.47, + 0.54 + ], + "angle": 0, + "content": "remaining discrepancy between the classifiers and the features at inference." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.544, + 0.47, + 0.652 + ], + "angle": 0, + "content": "To select which of the stored residuals to use during inference, we not only store the residual, but also \\( f(x) \\) to choose the stored residual closest to \\( f(x_{\\mathrm{infer}}) \\). Therefore, we retain 'feature-residual' pairs in a 'feature-residual memory' \\( M = \\{(\\hat{h}_i,\\mathbf{r}_i)\\}_{i = 1}^N \\), where \\( \\hat{h}_i = \\hat{f} (x_i) \\), \\( \\mathbf{r}_i = \\mathbf{w}_{y_i} - \\hat{f} (x_i) \\), where \\( N \\) is the size of feature-residual memory, and \\( \\mathbf{w}_{y_i} \\) is the classifier vector for class \\( y_i \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.655, + 0.47, + 0.794 + ], + "angle": 0, + "content": "During inference, we select the \\(k\\) nearest neighbor \\(\\hat{h}\\)'s, i.e., \\(\\{\\hat{h}_{n_1},\\hat{h}_{n_1},\\dots ,\\hat{h}_{n_k}\\}\\) from \\(\\{\\hat{h}_i\\}_{i = 1}^N\\), since using only the nearest residual for correction may lead to incorrect inference predictions if a wrong residual is selected from a different class. Finally, following ResMem [57], we calculate the residual correction term \\(\\mathbf{r}_{\\mathrm{eval}}\\) by a weighted average of the corresponding residuals \\(\\{\\mathbf{r}_{n_1},\\mathbf{r}_{n_2},\\dots ,\\mathbf{r}_{n_k}\\}\\), with weights \\(\\{s_1,s_2,\\ldots ,s_k\\}\\) that are inversely proportional to the distance from \\(\\hat{f} (x_{\\mathrm{eval}})\\), as:" + }, + { + "type": "equation", + "bbox": [ + 0.102, + 0.812, + 0.47, + 0.856 + ], + "angle": 0, + "content": "\\[\n\\mathbf {r} _ {\\text {e v a l}} = \\sum_ {i = 1} ^ {k} s _ {i} \\mathbf {r} _ {i}, \\quad s _ {i} = \\frac {e ^ {- (\\hat {f} (x _ {\\text {e v a l}}) - \\hat {h} _ {i}) / \\tau}}{\\sum_ {j = 1} ^ {k} e ^ {- (\\hat {f} (x _ {\\text {e v a l}}) - \\hat {h} _ {j}) / \\tau}}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.47, + 0.903 + ], + "angle": 0, + "content": "where \\(\\tau\\) is a temperature hyperparameter. We add the residual-correcting term \\(\\mathbf{r}_{\\mathrm{eval}}\\) to the model output \\(\\hat{f} (x_{\\mathrm{eval}})\\)" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.509, + 0.818, + 0.527 + ], + "angle": 0, + "content": "to obtain the corrected output \\(\\hat{f} (x_{\\mathrm{eval}})_{\\mathrm{corrected}}\\) as:" + }, + { + "type": "equation", + "bbox": [ + 0.584, + 0.539, + 0.892, + 0.559 + ], + "angle": 0, + "content": "\\[\n\\hat {f} \\left(x _ {\\text {e v a l}}\\right) _ {\\text {c o r r e c t e d}} = \\hat {f} \\left(x _ {\\text {e v a l}}\\right) + \\mathbf {r} _ {\\text {e v a l}}. \\tag {6}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.574, + 0.634, + 0.591 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.6, + 0.688, + 0.617 + ], + "angle": 0, + "content": "5.1. Experimental setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.624, + 0.892, + 0.731 + ], + "angle": 0, + "content": "We perform experiments on four datasets: CIFAR-10, CIFAR-100, TinyImageNet, ImageNet-200, and ImageNet-1K. For all datasets, our experiments are conducted on both a disjoint setup [35] and a Gaussian scheduled setup [45, 51]. We report the average and standard deviation results in three different seeds, except ImageNet-1k due to computational resource constraints [2, 27]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.732, + 0.892, + 0.822 + ], + "angle": 0, + "content": "To evaluate anytime inference performance, we use the area under the curve accuracy \\((A_{auc})\\) [6, 27], which measures the area under the accuracy curve. We also use last accuracy \\((A_{last})\\) which measures accuracy at the end of training. For detailed information about the experimental setup, refer to the Supplementary." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Baselines. We compare EARL with various CL methods in different categories: regularization (EWC [26]), network expansion (MEMO [63]), replay (ER [43], ER-MIR [1], REMIND [20], SCR [31], ODDL [3]), and distillation" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23938" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.081, + 0.09, + 0.468, + 0.255 + ], + "angle": 0, + "content": "
MethodImageNet-1K
DisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)30.1718.7817.0920.15
ER (Rolnick et al., 2019)30.1818.9617.1718.39
ER-MIR (Aljundi et al., 2019)31.6819.8719.3716.30
REMIND (Hayes et al., 2020)32.4724.5917.4219.79
DER++ (Buzzega et al., 2020)31.0818.9823.7323.14
SCR (Mai et al., 2021)26.7213.6019.8215.84
MEMO (Zhou et al., 2023)30.4519.0814.0620.12
X-DER (Boschini et al., 2023)31.6718.1825.1812.51
EARL (Ours)34.3323.1930.5329.48
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.076, + 0.256, + 0.47, + 0.283 + ], + "angle": 0, + "content": "Table 2. Comparison of online CL methods on Disjoint and Gaussian Scheduled Setup for ImageNet-1K." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.292, + 0.468, + 0.368 + ], + "angle": 0, + "content": "\\((\\mathrm{DER} + + [4], \\mathrm{X - DER}[3])\\). For more details on the implementation of these methods and a comparison with NCFSCIL [56], which attempts to induce neural collapse in the context of few-shot class incremental learning, please refer to the supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.383, + 0.468, + 0.533 + ], + "angle": 0, + "content": "Implementation details. We use three components to architect our model: a backbone network \\( g(\\cdot) \\), a projection MLP \\( p(\\cdot) \\), and a fixed ETF classifier \\( \\mathbf{W}_{\\mathrm{ETF}} \\) (i.e., our model \\( f \\) can be defined as \\( f(x) = p \\circ g(x) \\)). For the projection layer, we attach an MLP projection layer \\( p_{\\theta_p} \\) to the output of the backbone network \\( g_{\\theta_g} \\), where \\( \\theta_g \\) and \\( \\theta_p \\) denote the parameters of the backbone network and the projection layer, respectively (i.e., the model \\( f \\) can be defined as \\( f(x) = p \\circ g(x) \\)), following [9, 37, 56]. For all methods, we use ResNet-18 [21] as the backbone network." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.534, + 0.468, + 0.624 + ], + "angle": 0, + "content": "Following [27, 59], we employ memory-only training, where a random batch is selected from memory at each iteration. Furthermore, for episodic memory sampling, EARL uses the Greedy Balanced Sampling strategy [40]. We describe the details about hyperparameters and the pseudocode of EARL in Supplementary for the sake of space." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.635, + 0.17, + 0.649 + ], + "angle": 0, + "content": "5.2. Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.659, + 0.468, + 0.794 + ], + "angle": 0, + "content": "We first compare the accuracy of online continual learning methods, including EARL, and summarize the results in Table 1. As shown in the table, EARL outperforms other baselines on all benchmarks, both in disjoint and Gaussian-scheduled setups, except \\( A_{\\mathrm{last}} \\) in ImageNet-1K disjoint setup. In particular, high \\( A_{\\mathrm{AUC}} \\) suggests that EARL outperforms other methods for all the time that the data stream is provided to the model, which implies that it can be used for inference at anytime." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.468, + 0.9 + ], + "angle": 0, + "content": "Furthermore, EARL, SCR, ER, MIR, DER, and ODDL do not use task boundary information during training, i.e., task-free, in contrast to EWC, X-DER, MEMO, and REMIND which use task-boundary information, i.e., task-aware. Nevertheless, EARL outperforms these methods even in the disjoint setup where utilizing task boundary information is advantageous due to abrupt distribution shifts" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.212 + ], + "angle": 0, + "content": "at the task boundaries, except MEMO in ImageNet-1K disjoint. Since MEMO not only uses the task boundary information but also expands the network per task, this extra advantage of using a larger model is emphasized in largescale datasets such as ImageNet which require a large learning capacity of the model. Please refer to the supplementary material for details of the computational budget comparison among the baseline methods." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.216, + 0.892, + 0.382 + ], + "angle": 0, + "content": "Memory budget. We consider not only the size of episodic memory, but also the size of the model, logits, and other components, following MEMO [63]. In the case of the memory budget for CIFAR-10 and the architecture of ResNet-18 (size of 42.6MB), EARL incurs an additional memory cost of 0.2MB to store feature-residual pairs. EWC requires an additional cost of 85.2MB due to the need to store Fisher Information per parameter and the previous model. MEMO, which expands the network per task, incurs an additional cost of 32MB per task. DER also requires an additional cost of 0.1MB to store logits during distillation." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.393, + 0.65, + 0.408 + ], + "angle": 0, + "content": "5.3. Ablation study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.416, + 0.892, + 0.551 + ], + "angle": 0, + "content": "We conduct an ablation study on the two components of EARL, preparatory data training and residual correction, and summarize the results in Table 3. Although both components contribute to performance improvement, preparatory data training shows a larger gain in performance. Training with preparatory data improves the baseline by \\(2.7\\% \\sim 3.3\\%\\) in \\(A_{auc}\\) and \\(2.1\\% \\sim 4.4\\%\\) in \\(A_{last}\\). When combined with residual correction, we observe further gains across all metrics in both disjoint and Gaussian-scheduled setups." + }, + { + "type": "image", + "bbox": [ + 0.546, + 0.564, + 0.824, + 0.727 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.738, + 0.892, + 0.794 + ], + "angle": 0, + "content": "Figure 5. Average similarity between features of the most recently added class's samples and the closest classifier vectors of the old classes (CIFAR-10, Gaussian Scheduled). Baseline is a vanilla ETF model trained only using episodic memory." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.81, + 0.892, + 0.901 + ], + "angle": 0, + "content": "For further analysis, Fig. 6 visualizes the cosine similarity between the output features of 50 randomly selected test set samples of novel class '4' and the classifier vectors \\(\\mathbf{w}_i\\). In baseline (a), the features of the class 4 are strongly biased towards the classifier vectors of the old classes (i.e., \\(\\mathbf{w}_0\\), \\(\\mathbf{w}_1\\), \\(\\mathbf{w}_2\\), \\(\\mathbf{w}_3\\)), rather than the correct classifier, \\(\\mathbf{w}_4\\). (c)" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "23939" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.084, + 0.077, + 0.887, + 0.179 + ], + "angle": 0, + "content": "
METHODCIFAR-10CIFAR-100
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EARL (Ours)78.61±0.7266.01±2.2669.62±0.1970.91±1.9757.42±1.2444.60±0.6548.19±0.6146.10±0.26
(-) RC77.78±0.5265.52±1.6368.37±0.1070.17±1.0856.28±1.4044.29±1.0447.05±0.7146.07±0.52
(-) RC & PDT74.77±0.7761.10±3.1265.60±0.2567.39±0.7852.91±1.0541.08±0.6044.34±0.5544.45±0.48
" + }, + { + "type": "table_caption", + "bbox": [ + 0.093, + 0.184, + 0.877, + 0.199 + ], + "angle": 0, + "content": "Table 3. Ablation Study. RC and PDT refer to preparatory data training (Sec. 4.2) and the residual correction (Sec. 4.3), respectively." + }, + { + "type": "image", + "bbox": [ + 0.109, + 0.204, + 0.865, + 0.433 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.437, + 0.895, + 0.482 + ], + "angle": 0, + "content": "Figure 6. Cosine similarity between features \\(\\hat{f}(x)\\) for class 4 and the ETF classifier vectors \\(\\mathbf{w}_i\\) at the \\(50^{th}\\) iteration after the introduction of class 4 in the Gaussian Scheduled CIFAR-10 setup. As we can see in the cyan highlighted box, EARL promotes the convergence of \\(\\hat{f}(x)\\) for class 4 toward the ground truth classifier vector \\(\\mathbf{w}_4\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.493, + 0.47, + 0.523 + ], + "angle": 0, + "content": "When residual correction is used, some samples show high similarity with \\(\\mathbf{w}_4\\) compared to the baseline." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.524, + 0.471, + 0.692 + ], + "angle": 0, + "content": "However, since incorrect residuals can be added due to the bias problem, more samples have high similarity with \\(\\mathbf{w}_2\\) than the baseline (i.e., wrong residuals are added). (b) When using preparatory data training, the bias toward \\(\\mathbf{w}_0\\) and \\(\\mathbf{w}_1\\) classes significantly decreases compared to the baseline. Fig. 5 also shows the effect of preparatory data, which reduces the similarity between the novel class features and existing classes. (d) Using both residual correction and preparatory data training shows a remarkable alignment with the ground truth classifier \\(\\mathbf{w}_4\\). A more detailed analysis of the ablation results is provided in the Supple." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.708, + 0.196, + 0.723 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.734, + 0.47, + 0.869 + ], + "angle": 0, + "content": "To better learn online data in a continuous data stream without multiple epoch training, we propose to induce neural collapse, which aligns last layer activations to the corresponding classifier vectors in the representation space. Unlike in offline CL, it is challenging to induce neural collapse in online CL due to insufficient training epochs and continuously streamed new data. We first observe that the bias of the new class towards existing classes slows the convergence of features toward neural collapse." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.471, + 0.903 + ], + "angle": 0, + "content": "To mitigate the bias, we propose synthesizing preparatory data for unseen classes by transforming the samples" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.493, + 0.892, + 0.629 + ], + "angle": 0, + "content": "of existing classes. Using the preparatory data for training, we accelerate neural collapse in an online CL scenario. Additionally, we propose residual correction to resolve the remaining discrepancy toward neural collapse at inference, which arises due to the continuous stream of new data. In our empirical evaluations, the proposed methods outperform state-of-the-art online CL methods in various datasets and setups, especially with high performance on anytime inference." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.645, + 0.893, + 0.78 + ], + "angle": 0, + "content": "Limitations and Future Work. Since our work uses ETF structure, it has an inherent limitation that the number of possible classifier vectors in the ETF classifier is limited by the dimension of the embedding space. Considering lifelong learning, where the number of new classes goes to infinity, it is interesting to explore the idea of dynamically expanding the ETF structure so that the model can continually learn the ever-increasing number of concepts in the real world." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.791, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Acknowledgement. This work was partly supported by the NRF grant (No.2022R1A2C4002300, \\(20\\%\\) ) and IITP grants (No.2022-0-00077 \\((10\\%)\\) , No.2022-0-00113 \\((25\\%)\\) , No.2022-0-00959 \\((10\\%)\\) , No.2022-0- 00871 \\((10\\%)\\) , No.2020-0-01361 \\((5\\%)\\) , Yonsei AI), No.2021-0-01343 \\((5\\%)\\) SNU AI), No.2021-0-02068 \\((5\\%)\\) , AI Innov. Hub), No.2022-0-00951 \\((5\\%)\\) ) funded by the Korea government (MSIT) and CARAI grant funded by DAPA and ADD (UD230017TD) \\(5 \\%\\) . This work was done while J. Choi was with Yonsei University and partially while H. Lee, M. Seo and H. 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In NeurIPS, 2021. 1, 3" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.813 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.52, + 0.957 + ], + "angle": 0, + "content": "23942" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_origin.pdf b/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..eed0017864e7ae09f42b3b2d5cc44279a72caf39 --- /dev/null +++ b/2024/Learning Equi-angular Representations for Online Continual Learning/1f2bf4e3-a137-4287-b431-b0fd185698d5_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:d348ac42eba3fd20bc4df4c01bf5335d94a938390f81433dceb471592ebb51a0 +size 1108684 diff --git a/2024/Learning Equi-angular Representations for Online Continual Learning/full.md b/2024/Learning Equi-angular Representations for Online Continual Learning/full.md new file mode 100644 index 0000000000000000000000000000000000000000..82730f4b3aa9dc6aaf0f37242a0e38f48e226a1d --- /dev/null +++ b/2024/Learning Equi-angular Representations for Online Continual Learning/full.md @@ -0,0 +1,312 @@ +# Learning Equi-angular Representations for Online Continual Learning + +Minhyuk Seo $^{1,\dagger}$ Hyunseo Koh $^{1}$ Wonje Jeung $^{1}$ Minjae Lee $^{1}$ San Kim $^{1}$ Hankook Lee $^{2,3}$ Sungjun Cho $^{2}$ Sungik Choi $^{2}$ Hyunwoo Kim $^{4,*}$ Jonghyun Choi $^{5,*}$ + +$^{1}$ Yonsei Univ. $^{2}$ LG AI Research $^{3}$ Sungkyunkwan Univ. $^{4}$ Zhejiang Lab $^{5}$ Seoul National Univ. {dbd0508, specific0924, reccos1020, nasmik419}@yonsei.ac.kr khs8157@gmail.com, {sungik.choi,sungjun.cho}@lgresearch.ai hankook.lee@skku.edu, hwkim@zhejianglab.com, jonghyunchoi@snu.ac.kr + +# Abstract + +Online continual learning suffers from an underfitted solution due to insufficient training for prompt model update (e.g., single-epoch training). To address the challenge, we propose an efficient online continual learning method using the neural collapse phenomenon. In particular, we induce neural collapse to form a simplex equiangular tight frame (ETF) structure in the representation space so that the continuously learned model with a single epoch can better fit to the streamed data by proposing preparatory data training and residual correction in the representation space. With an extensive set of empirical validations using CIFAR10/100, TinyImageNet, ImageNet-200, and ImageNet-1K, we show that our proposed method outperforms state-of-the-art methods by a noticeable margin in various online continual learning scenarios such as disjoint and Gaussian scheduled continuous (i.e., boundary-free) data setups. Code is available at https://github.com/yonseivnl/earl. + +# 1. Introduction + +A growing interest in continuous learning (CL) involves training the model using continuous data streams. Mostly, CL research has focused on the offline scenario that assumes the model can be trained in multiple epochs for the current task [8, 42, 54]. However, substantial storage and computational complexity are required to store all data to train a model for multiple epochs. Recently, there has been significant interest in online CL as a more realistic set-up with a lower computational overhead of allowing a single training pass through the data stream [1, 7, 27]. Learning a model in streamed data by a single training pass is challenging, since the temporal distribution at each intermediate + +time point is likely imbalanced, even if the overall distribution of a dataset is balanced. Imbalanced data distributions would cause several problems, such as bias towards the major classes [24, 61] and the hindrance to generalization [53]. + +Recently, minority collapse [14], the phenomenon in which the angles between classifier vectors for minor classes (i.e., the classes that have a relatively small number of samples) become narrow, has been proposed as a fundamental issue in training with imbalanced data, making the classification of minor classes considerably more challenging. In contrast, for balanced data sets, it was proven that classifier vectors and the last layer activations for all classes converge into an optimal geometric structure, named the simplex equiangular tight frame (ETF) structure, where all pairwise angles between classes are equal and maximally widened when using cross entropy (CE) [23, 30, 52, 65] or mean squared error (MSE) [32, 41, 48, 64] loss. This phenomenon is called neural collapse [34]. + +Although neural collapse naturally occurs only in balanced training, several recent studies attempted to induce neural collapse in imbalanced training to address the minority collapse problem using a fixed ETF classifier [55, 62]. When employing a fixed ETF classifier, the output features are pulled toward the corresponding classifier vector during training, since the classifier is fixed. More recently, research has also been extended to induce neural collapse in offline CL using a fixed ETF classifier [56]. + +However, unlike offline CL, there are a number of challenges in inducing neural collapse in online CL, even with a fixed ETF classifier. The prerequisite for neural collapse is reaching the terminal phase of training (TPT) by sufficient training [34]. In offline CL, the model can reach the TPT phase for each task by multi-epoch training. In contrast, a single-pass training constraint often prevents the online CL from reaching TPT. As shown in Fig. 1, the offline CL quickly reaches TPT shortly after the arrival of novel task data, while online CL (vanilla ETF) does not. + +![](images/286fe80ac345fa2b15e206b235117ac50ec9c21f64780bd5db4f6faefd35e08f.jpg) +Figure 1. Comparison of training error rates between online CL and offline CL in the CIFAR-10 disjoint setup, where two novel classes are added every 10k samples. Vanilla ETF refers to a method where both preparatory data training and residual correction are removed from our proposed EARL. + +Recently, the importance of anytime inference in online CL has been emphasized [6, 17, 27, 36], since a model should be available for inference not only at the end of a task, but also at any point during training to be practical for real-world applications. Hence, not only reaching TPT but also achieving faster convergence is necessary when using neural collapse in online CL. + +However, we observe that the phenomenon in which the features of the new class become biased toward the features of the existing classes [5] hinders fast convergence of the last-layer features into the ETF structure, which we call the 'bias problem.' When features of old and new classes overlap (i.e., biased) and are trained with the same objective, well-clustered features of old classes disperse (or perturb) [5], leading to destruction of the ETF structure formed by features of the old classes. + +Contributions. To address the bias problem, we train the model to distinguish out-of-distribution (OOD) samples from existing classes' samples. Specifically, we synthesize preparatory data that play the role of OOD data, by applying negative data augmentation [25, 47, 50] to samples from existing classes, refer to Sec. 4.2 for details. Since samples from new classes are OOD in the perspective of existing classes, training with preparatory data encourages the representation of new classes to be distinguished from existing classes in advance, thereby mitigating the bias problem. This promotes fast and stable convergence into the ETF structure. + +Despite these efforts, however, the continuous stream of new samples cause ongoing data distribution shifts, which prevent the model from reaching the TPT and fully converging to the ETF structure. To address this, we propose to store the residuals between the target ETF classifier and the features during training. During inference, we correct the inference output using the stored residual to compensate for insufficient convergence in the training. + +By accelerating convergence by preparatory data training and additional correction using residual, we noticeably + +improve anytime inference performance than state of the arts. We name our method Equi-Angular Representation Learning (EARL). We empirically demonstrate the effectiveness of our framework on CIFAR-10, CIFAR-100, TinyImageNet,Imagenet-200,and ImageNet-1K.In particular, our framework outperforms various CL methods by a significant margin $(+4.0\%)$ gain of $A_{\mathrm{auc}}$ in ImageNet-1K). + +We summarize our contributions as follows: + +- Proposing to induce neural collapse for online CL. +- Proposing 'preparatory data training' to address the 'bias problem' that the new classes are biased toward the existing classes, promoting faster induction of neural collapse. +- Proposing 'residual correction' scheme to compensate for not fully reaching neural collapse at inference to further improve anytime inference accuracy. + +# 2. Related work + +Continual learning methods. Various continual learning methods are being researched to prevent forgetting past tasks, broadly categorized into replay, parameter isolation, and regularization. Replay methods involve storing a small portion of data from previous tasks in episodic memory [1, 2, 20, 27, 60] or storing a generative model trained on data from previous tasks [39, 46]. By replaying the samples stored in episodic memory or generated from the stored generative model, the model prevents forgetting past tasks during subsequent learning of novel tasks. Furthermore, Boschini et al. [3], Buzzega et al. [4], Li and Hoiem [29], Wu et al. [54] used replay samples to distill information about past tasks. + +Regularization methods [26, 28] apply a penalty to the change of important model parameters during the process of learning new tasks, allowing the model to retain information about previous tasks. Parameter isolation methods [10, 44, 63] expand the network by allocating specific layers for each task. This enables the network to store information about individual tasks and preserves their knowl- + +edge without forgetting. + +Neural collapse. Neural collapse is a phenomenon in which the activations of the last layer and the classifier vectors form a simplex equiangular tight frame (ETF) structure at the terminal phase of training (TPT) in a balanced dataset. [34]. Neural collapse has been demonstrated as the global optimum of balanced training using cross entropy (CE) loss [23, 30, 52, 65] and MSE [32, 41, 48, 64] loss functions, within a simplified model focused solely on last-layer optimization. Inducing neural collapse in imbalanced datasets poses challenges due to minority collapse [14] where minor classes are not well distinguished. + +However, using a fixed ETF classifier, it is empirically and theoretically shown that neural collapse is induced even in imbalanced datasets [55]. Continual learning also needs to address imbalanced data since there is an imbalance in the data between novel classes and existing classes. Therefore, in offline CL, NC-FSCIL [38, 56] used a fixed ETF classifier to induce neural collapse. Meanwhile, online CL often fails to induce neural collapse compared to offline CL, e.g., FSCIL, since it lacks sufficient training in multiple epochs, causing failure to reach TPT. + +Please refer to the supplementary material for more comprehensive literature reviews including topics related to anytime inference. + +# 3. Preliminaries + +We here describe the problem statement for the online continual learning (Sec. 3.1), neural collapse (Sec. 3.2), and the equiangular tight frame classifier (Sec. 3.3). + +# 3.1. Problem Statement of Online CL + +Continual learning (CL) aims to learn from a stream of data, rather than a fixed dataset as in standard learning. Formally, given a sequence of tasks $\mathcal{T} = (T_1,T_2,\ldots)$ where each task $T_{i}$ is a training dataset $D_{i} = \{(x_{1}^{(i)},y_{1}^{(i)}),(x_{2}^{(i)},y_{2}^{(i)}),\ldots \}$ , an offline CL algorithm $A_{\mathrm{CL}}$ updates the model parameter $\theta$ based on the current task $D_{k}$ , i.e., $\theta_{k} = A_{\mathrm{CL}}(\theta_{k - 1},D_{k})$ , starting from the initial parameter $\theta_0$ . + +To avoid the forgetting issue in CL, many CL setups allow the use of episodic memory $M_{k}$ , which is a limited-size subset of training data from previous tasks, i.e., $(\theta_k,M_k) = A_{\mathrm{CL}}(\theta_{k - 1},M_{k - 1},D_k)$ . The objective is to minimize the error of $\theta_{k}$ in all observed tasks $\{T_i\}_{i = 1}^k$ + +Unlike offline CL where all training samples in $D_{k}$ are given as input, in online CL, the input is provided as a stream of samples $(x_{1}^{(k)}, y_{1}^{(k)}), (x_{2}^{(k)}, y_{2}^{(k)}), \dots$ . Therefore, an online CL algorithm $A_{\mathrm{OCL}}$ is defined as: + +$$ +\left(\theta_ {k, t}, M _ {k, t}\right) = A _ {\mathrm {O C L}} \left(\theta_ {k, t - 1}, M _ {k, t - 1}, \left(x _ {t} ^ {(k)}, y _ {t} ^ {(k)}\right)\right), \tag {1} +$$ + +with the same objective of minimizing the error of $\theta_{k,t}$ on $\{T_i\}_{i = 1}^k$ . Since the algorithm does not have access to pre + +vious samples $\{(x_s^{(k)},y_s^{(k)}),s < t\}$ at time $t$ , multi-epoch training with $D_{k}$ is unavailable in online CL. + +# 3.2. Neural Collapse + +Neural collapse [34] is a phenomenon of the penultimate features after the convergence of training on a balanced dataset. When neural collapse (NC) occurs, the collection of $K$ classifier vectors $\mathbf{W}_{\mathrm{ETF}} = [\mathbf{w}_1,\mathbf{w}_2,\dots,\mathbf{w}_K]\in \mathbb{R}^{d\times K}$ forms a simplex equiangular tight frame (ETF), which satisfies: + +$$ +\mathbf {w} _ {i} ^ {T} \mathbf {w} _ {j} = \left\{ \begin{array}{l l} 1, & i = j \\ - \frac {1}{K - 1}, & i \neq j \end{array} , \forall i, j \in [ 1, \dots , K ], \right. \tag {2} +$$ + +where $K - 1 \leq d$ , and the penultimate feature of a training sample collapses into an ETF vector $\mathbf{w}_i$ . + +# 3.3. Equiangular Tight Frame (ETF) Classifier + +Inspired by neural collapse as described in Sec. 3.2, a fixed ETF classifier has been utilized for inducing neural collapse in imbalanced datasets [55, 56, 65]. Here, the classifier is initialized by the ETF structure $\mathbf{W}_{\mathrm{ETF}}$ at the beginning of training and fixed during training to induce the penultimate feature $f(x)$ to converge to the ideal balanced scenario. For training $f(x)$ , it is only required to attract $f(x)$ to the corresponding classifier vector for convergence, since the classifier is fixed during training. Therefore, following Yang et al. [55], we use the dot regression (DR) loss as a training objective, as it shows to outperform cross entropy (CE) loss when using a fixed ETF classifier in imbalanced datasets [55]. The DR loss can be written as follows: + +$$ +\mathcal {L} _ {\mathrm {D R}} (\hat {f} (x), y; \mathbf {W} _ {\text {E T F}}) = \frac {1}{2} \left(\mathbf {w} _ {y} \hat {f} (x) - 1\right) ^ {2}, \tag {3} +$$ + +where $\hat{f} (x) = f(x) / \| f(x)\| _2$ is the $L_{2}$ normalized feature of the model $f$ , $y$ is the label of the input $x$ , and $\mathbf{w}_y$ is a classifier vector in $\mathbf{W}_{\mathrm{ETF}}$ for the label $y$ . + +# 4. Approach + +Despite the success of the fixed ETF classifier in both imbalanced training [55, 62] and offline CL [56], the ETF classifier has not yet been explored for online CL due to the necessity of sufficient training for neural collapse. To be specific, streamed data are trained only once in online CL, which makes it harder to induce neural collapse than in offline CL which supports multi-epoch training. + +To learn a better converged model without multi-epoch training for online CL, we propose two novel methods, each for the training phase and the inference phase, respectively. In the training phase, we accelerate convergence by proposing preparatory data training (Sec. 4.2). In the inference + +![](images/2b82eece2a6f75f774eccd89b2b2db38f906fc55e473e2cbb59d5e1a6020feeb.jpg) +Figure 2. Overview of EARL. $\mathbf{w}_i$ denotes the ETF classifier vector for class $i$ . $h_a$ denotes the output of the model. The colors of the data denote the class to which the data belong. The arrow $\mathbf{r}_i$ denotes the residual between the last layer activation $h_i$ and the classifier vector $\mathbf{w}_i$ for class $i$ . During training, both memory and preparatory data are used for replaying, and the residuals between $h_i$ and $\mathbf{w}_i$ are stored in feature-residual memory. During inference, using the similarity between $f(x_{\mathrm{eval}})$ and $h_i$ in feature-residual memory, $\mathbf{r}_{\mathrm{eval}}$ is obtained by a weighted sum of $\mathbf{r}_i$ 's. Finally, by adding $\mathbf{r}_{\mathrm{eval}}$ , $f(x_{\mathrm{eval}})$ is corrected. The purple arrow indicates 'residual correction' (Sec. 4.3). + +![](images/a35fba741b9772f294b8d2a04435ef928c8e2b090cda6ff1dc2da925b6dfdb8c.jpg) +Figure 3. Illustrative effects for each component of EARL. (a) In online CL, features of novel classes are biased towards the features of the previous class. (b) By training with preparatory data (w/ Prep. Data, Sec. 4.2), we address the bias problem. (c) In inference, for features that do not fully converge to an ETF classifier, we add residuals (w/ Res. Corr., Sec. 4.3) to features that have not yet reached the corresponding classifier vectors, making features aligned with them. Purple arrow: the 'residual correction', Colors: classes. + +phase, we propose to correct the remaining discrepancy between the classifiers and the features using residual correction (Sec. 4.3). We illustrate an overview of EARL in Fig. 2 and the effect of EARL in Fig. 3. + +# 4.1. Inducing Neural Collapse for Online CL + +For online CL, we first try to induce neural collapse with a fixed ETF classifier: $\mathbf{W}_{\mathrm{ETF}} \in R^{d \times K}$ where $d$ is the dimension of the embedding space and $K$ is the number of ETF vectors. While prior works [55, 56] use prior knowledge of the total number of classes that will be encountered for setting $K$ , it is unrealistic to know the knowledge (i.e., the exact number of classes) as it evolves continuously over time under realistic CL scenarios. + +To address the challenge, we propose using the maximum possible number of classifier vectors for $K$ . Based + +on the simplex ETF property that the maximum number of ETF vectors is $d + 1$ [16, 55], we define our ETF classifier $\mathbf{W}_{\mathrm{ETF}} \in \mathbb{R}^{d \times (d + 1)}$ by letting $K := d + 1$ . + +# 4.2. Preparatory data at training + +Since novel classes continuously arrive in CL, both the data from previous tasks $(x_{\mathrm{old}})$ and the current task $(x_{\mathrm{new}})$ coexist. While $\hat{f}(x_{\mathrm{old}})$ are placed closer to their corresponding ETF classifier vectors $w_{\mathrm{new}}$ by training, $\hat{f}(x_{\mathrm{new}})$ are biased toward the cluster of $\hat{f}(x_{\mathrm{old}})$ , as we can see in Fig. 4-(a), where $\hat{f}(x_{\mathrm{new}})$ and $\hat{f}(x_{\mathrm{old}})$ are the outputs of the model for inputs $x_{\mathrm{new}}$ and $x_{\mathrm{old}}$ , respectively. We call this 'bias problem.' When $\hat{f}(x_{\mathrm{new}})$ and $\hat{f}(x_{\mathrm{old}})$ overlap due to bias and are optimized with the same objective function, training on the new class interferes with the representations of the old classes, dispersing the well-clustered $\hat{f}(x_{\mathrm{old}})$ [5]. It destroys the ETF structure formed by $\hat{f}(x_{\mathrm{old}})$ , which hinders convergence towards neural collapse. Although the bias problem exists even without a fixed ETF classifier [5, 12, 54], it poses a greater problem when using a fixed ETF classifier, since the dispersed feature of old classes has to be restored to the corresponding fixed classifier vector. In contrast, when using a learnable classifier, the dispersed representation of the old classes does not have to be restored to the original position, since the learnable classifier vector will be re-optimized from the dispersed feature. However, the angles between the classifier vector may become narrow, i.e., minority collapse occurs. + +To accelerate convergence in the ETF structure, we propose to prevent novel classes from being biased towards existing classes when introduced, mitigating the bias problem. Specifically, we train the model to avoid making predictions in favor of the existing classes for images that do not be + +![](images/398d95752bcf26ed3d242ed8d9f8d52b7f79e369528685f4c796db1aa8abb21c.jpg) +Figure 4. t-SNE visualization of 'bias-problem' in data distributions (class 0 to 3). (a) Only after 100 iterations of training after task 1 appears, learning is likely insufficient, and we can see that the features of new classes (class 2, 3) are biased towards the feature cluster of the existing class (i.e., class 1). (b) With more training iterations (10,000 iter), the features are well clustered by class. + +long to them. To this end, we propose to use preparatory data $x_{p}$ that is different from existing classes, obtained by transforming the samples in the episodic memory. By training with the preparatory data so that their representations differ from existing classes, we prevent biased predictions towards existing classes when a new class arrives. + +For preparatory data to have a different representation from existing classes when trained, their image semantics should be distinguishable from existing classes, provided that they contain enough semantic information to be considered as an image (i.e., not noise). There are various approaches to synthesize images with modified semantics, such as using generative models [11, 19, 58] or negative transformations [47, 50]. We use negative transformations, as generative models are expensive in computation and storage [13], which is undesirable for CL scenarios with limited memory and computations. On the contrary, negative transformations are relatively efficient in computation and storage [33] and is reported to create images with semantics different from the original image [50]. We empirically observed that data generated through negative transformations have a distinct semantic class from the original class while preserving its semantic information as an image (i.e., not as random noise), and we summarize the results in the supplementary material. + +Formally, for a set of existing classes $Y$ and the set of possible transformations $G$ , we randomly select $y \in Y$ and $g \in G$ , and randomly retrieve a sample of class $y$ from memory and apply the transformation $g$ to obtain preparatory data $x_{p}$ . We assign labels of the unseen classes to the preparatory data by a mapping function $m: Y \times G \to Y'$ where $Y'$ denotes a set of unseen classes, i.e., $Y' = \{y | y \notin Y, 1 \leq y \leq K\}$ and $K$ is the total number of classifier vectors in $\mathbf{W}_{\mathrm{ETF}} \in \mathbb{R}^{d \times K}$ . Thus, preparatory data $x_{p}$ from class $y$ and transformation $g$ is pulled towards the classifier vector $\mathbf{w}_{p}$ , where $p = m(y, g)$ . When a new class $y_{\mathrm{new}}$ + +is added to $Y$ , we update $m$ by randomly assigning a new mapping $m(y_{\mathrm{new}}, g)$ for $y_{\mathrm{new}}$ and $g \in G$ . + +We compose the transformation set $G$ as a negative transformation that can modify semantic information (i.e., change the label), used in the self-supervised literature [15, 18] and out-of-distribution (OOD) detection [25, 47, 50]. Specifically, we use rotation by 90, 180, and 270 degrees [15, 18] as our negative transformation. Since the vertical information of the image is more important than the horizontal information [22, 49], e.g., images of a car facing left or right are common, but a car flipped upside down is very rare compared to a car standing right, rotation by a large angle causes loss of semantic information of images [50]. Thus, we can use rotated data as semantically different images from images of existing classes, i.e., suitable for preparatory data. A more detailed analysis of various negative transformations is provided in the Supple. + +We jointly train the model using real data (i.e., samples of existing classes) and preparatory data. Formally, we write the objective for the model parameter $\theta$ as: + +$$ +\begin{array}{l} \underset {\theta} {\arg \min } \left[ \mathbb {E} _ {(x, y) \sim \mathcal {M}} \mathcal {L} _ {\mathrm {D R}} \left(\hat {f} _ {\theta} (x), y; \mathbf {W} _ {\text {E T F}}\right) \right. \tag {4} \\ \left. \right.\left. + \lambda \mathbb {E} _ {\left(x ^ {\prime}, y ^ {\prime}\right) \sim \mathcal {M}, g \sim G} \mathcal {L} _ {\mathrm {D R}} \left(\hat {f} _ {\theta} (g \left(x ^ {\prime}\right)), m \left(y ^ {\prime}, g\right); \mathbf {W} _ {\text {E T F}}\right)\right], \\ \end{array} +$$ + +where $\mathcal{M}$ denotes episodic memory, $(x,y)$ and $(x',y')$ denote the samples in $\mathcal{M}$ , $G$ denotes the set of possible transformations, $g$ denotes a transformation in $G$ , $m$ denotes the mapping function, and $\lambda$ is a hyperparameter for balancing real data and preparatory data. + +# 4.3. Residual correction at inference + +Despite preparatory data training that accelerates convergence towards ETF, in online CL, new samples in a data stream hinder models from reaching the Terminal Phase of Training (TPT) and fully converging to the ETF during single-epoch training. When the output of the model $f(x)$ does not fully converge to the ETF classifier, the model would not perform well at all times, leading to poor anytime inference accuracy ( $A_{\mathrm{AUC}}$ ). + +To address this issue, we want to correct the residual between $f(x)$ and the corresponding classifier vector $\mathbf{w}_y$ during inference, where $y$ is label of input $x$ . + +However, the discrepancy between the prediction on test data $x_{\mathrm{eval}}$ and the ground-truth ETF classifier vector is not available in the inference phase. In a similar situation, ResMem [57] stores the residual obtained from training data and uses them during inference, but they assume two-stage learning algorithms, i.e., standard training and inference rather than incremental learning and anytime inference. + +Inspired by ResMem [57], which uses residuals from the training in the inference stage, we propose to use the residual obtained from the training process to compensate for the + +
MethodCIFAR-10CIFAR-100
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)
EWC (Kirkpatrick et al., 2017)75.25±0.7860.80±2.2059.62±0.3164.24±1.9752.08±0.8341.55±0.8538.22±0.5042.52±0.58
ER (Rolnick et al., 2019)75.94±0.8663.56±1.3260.13±0.5664.81±2.7052.95±1.2542.82±0.0541.12±0.5642.74±1.09
ER-MIR (Aljundi et al., 2019)75.89±1.0261.93±0.9360.39±0.4861.64±3.8652.93±1.4442.47±0.1341.19±0.6342.93±1.18
REMIND (Hayes et al., 2020)69.55±0.9153.34±1.0158.01±0.7259.27±1.8640.87±0.7636.17±1.8323.40±2.2528.78±1.71
DER++ (Buzzega et al., 2020)74.78±0.7259.20±0.9559.44±0.2866.11±1.8038.16±1.5738.55±2.1129.38±2.5838.20±3.13
SCR (Mai et al., 2021)75.61±0.9356.52±0.5260.62±0.4358.41±2.3941.84±0.7436.00±0.8331.33±0.4132.11±0.39
ODDL (Ye et al., 2022)75.03±1.0061.61±3.5565.46±0.4666.19±2.0840.26±0.5041.88±4.5238.82±0.4941.35±1.08
MEMO (Zhou et al., 2023)73.21±0.4962.47±3.3859.26±0.9062.01±1.1740.60±1.1139.87±0.4623.41±1.6332.74±2.11
X-DER (Boschini et al., 2023)77.59±0.6265.40±4.7958.28±1.1759.76±4.2852.80±1.6143.73±0.8641.94±0.5746.00±1.04
EARL (Ours)78.31±0.7265.71±2.2669.52±0.1970.41±1.9757.12±1.2244.40±0.6847.89±0.6146.09±0.26
+ +
MethodTinyImageNetImageNet-200
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)
EWC (Kirkpatrick et al., 2017)37.95±0.9327.50±0.8025.29±0.8126.06±0.5241.84±0.6431.57±0.8030.71±0.2733.33±0.98
ER (Rolnick et al., 2019)37.43±1.0527.47±0.6326.37±0.8925.79±0.4441.51±0.7630.87±0.7232.39±0.3633.09±0.37
ER-MIR (Aljundi et al., 2019)37.81±1.0626.72±0.8626.22±0.6925.11±1.0438.28±0.3833.12±0.7332.17±0.4433.85±0.93
REMIND (Hayes et al., 2020)28.37±0.1327.68±0.4510.19±0.6014.90±1.4939.25±0.9331.98±0.8430.23±0.6233.98±0.09
DER++ (Buzzega et al., 2020)39.38±0.6029.36±0.8127.23±1.9431.53±0.8043.50±0.3134.56±0.5035.22±0.2638.38±0.97
SCR (Mai et al., 2021)34.65±1.0822.18±0.3225.86±0.9422.54±0.5941.90±0.4028.92±0.4033.24±0.3230.98±0.28
MEMO (Zhou et al., 2023)27.36±0.6127.57±0.5210.82±1.2318.03±1.3641.55±0.2334.19±1.4732.54±0.3936.11±1.06
X-DER (Boschini et al., 2023)35.15±2.1226.67±0.5229.71±0.8628.10±0.5043.41±0.4734.14±0.9836.31±0.1738.61±0.55
EARL (Ours)41.77±1.2629.65±0.2035.08±0.7032.49±1.2144.88±0.2934.79±0.5539.14±0.4738.83±0.35
+ +Table 1. Comparison of online CL methods on Disjoint and Gaussian Scheduled Setup for CIFAR-10, CIFAR-100, TinyImageNet and ImageNet-200. + +remaining discrepancy between the classifiers and the features at inference. + +To select which of the stored residuals to use during inference, we not only store the residual, but also $f(x)$ to choose the stored residual closest to $f(x_{\mathrm{infer}})$ . Therefore, we retain 'feature-residual' pairs in a 'feature-residual memory' $M = \{(\hat{h}_i,\mathbf{r}_i)\}_{i = 1}^N$ , where $\hat{h}_i = \hat{f} (x_i)$ , $\mathbf{r}_i = \mathbf{w}_{y_i} - \hat{f} (x_i)$ , where $N$ is the size of feature-residual memory, and $\mathbf{w}_{y_i}$ is the classifier vector for class $y_i$ . + +During inference, we select the $k$ nearest neighbor $\hat{h}$ 's, i.e., $\{\hat{h}_{n_1},\hat{h}_{n_1},\dots ,\hat{h}_{n_k}\}$ from $\{\hat{h}_i\}_{i = 1}^N$ , since using only the nearest residual for correction may lead to incorrect inference predictions if a wrong residual is selected from a different class. Finally, following ResMem [57], we calculate the residual correction term $\mathbf{r}_{\mathrm{eval}}$ by a weighted average of the corresponding residuals $\{\mathbf{r}_{n_1},\mathbf{r}_{n_2},\dots ,\mathbf{r}_{n_k}\}$ , with weights $\{s_1,s_2,\ldots ,s_k\}$ that are inversely proportional to the distance from $\hat{f} (x_{\mathrm{eval}})$ , as: + +$$ +\mathbf {r} _ {\text {e v a l}} = \sum_ {i = 1} ^ {k} s _ {i} \mathbf {r} _ {i}, \quad s _ {i} = \frac {e ^ {- (\hat {f} (x _ {\text {e v a l}}) - \hat {h} _ {i}) / \tau}}{\sum_ {j = 1} ^ {k} e ^ {- (\hat {f} (x _ {\text {e v a l}}) - \hat {h} _ {j}) / \tau}}, \tag {5} +$$ + +where $\tau$ is a temperature hyperparameter. We add the residual-correcting term $\mathbf{r}_{\mathrm{eval}}$ to the model output $\hat{f} (x_{\mathrm{eval}})$ + +to obtain the corrected output $\hat{f} (x_{\mathrm{eval}})_{\mathrm{corrected}}$ as: + +$$ +\hat {f} \left(x _ {\text {e v a l}}\right) _ {\text {c o r r e c t e d}} = \hat {f} \left(x _ {\text {e v a l}}\right) + \mathbf {r} _ {\text {e v a l}}. \tag {6} +$$ + +# 5. Experiments + +# 5.1. Experimental setup + +We perform experiments on four datasets: CIFAR-10, CIFAR-100, TinyImageNet, ImageNet-200, and ImageNet-1K. For all datasets, our experiments are conducted on both a disjoint setup [35] and a Gaussian scheduled setup [45, 51]. We report the average and standard deviation results in three different seeds, except ImageNet-1k due to computational resource constraints [2, 27]. + +To evaluate anytime inference performance, we use the area under the curve accuracy $(A_{auc})$ [6, 27], which measures the area under the accuracy curve. We also use last accuracy $(A_{last})$ which measures accuracy at the end of training. For detailed information about the experimental setup, refer to the Supplementary. + +Baselines. We compare EARL with various CL methods in different categories: regularization (EWC [26]), network expansion (MEMO [63]), replay (ER [43], ER-MIR [1], REMIND [20], SCR [31], ODDL [3]), and distillation + +
MethodImageNet-1K
DisjointGaussian-Scheduled
\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)
EWC (Kirkpatrick et al., 2017)30.1718.7817.0920.15
ER (Rolnick et al., 2019)30.1818.9617.1718.39
ER-MIR (Aljundi et al., 2019)31.6819.8719.3716.30
REMIND (Hayes et al., 2020)32.4724.5917.4219.79
DER++ (Buzzega et al., 2020)31.0818.9823.7323.14
SCR (Mai et al., 2021)26.7213.6019.8215.84
MEMO (Zhou et al., 2023)30.4519.0814.0620.12
X-DER (Boschini et al., 2023)31.6718.1825.1812.51
EARL (Ours)34.3323.1930.5329.48
+ +Table 2. Comparison of online CL methods on Disjoint and Gaussian Scheduled Setup for ImageNet-1K. + +$(\mathrm{DER} + + [4], \mathrm{X - DER}[3])$ . For more details on the implementation of these methods and a comparison with NCFSCIL [56], which attempts to induce neural collapse in the context of few-shot class incremental learning, please refer to the supplementary material. + +Implementation details. We use three components to architect our model: a backbone network $g(\cdot)$ , a projection MLP $p(\cdot)$ , and a fixed ETF classifier $\mathbf{W}_{\mathrm{ETF}}$ (i.e., our model $f$ can be defined as $f(x) = p \circ g(x)$ ). For the projection layer, we attach an MLP projection layer $p_{\theta_p}$ to the output of the backbone network $g_{\theta_g}$ , where $\theta_g$ and $\theta_p$ denote the parameters of the backbone network and the projection layer, respectively (i.e., the model $f$ can be defined as $f(x) = p \circ g(x)$ ), following [9, 37, 56]. For all methods, we use ResNet-18 [21] as the backbone network. + +Following [27, 59], we employ memory-only training, where a random batch is selected from memory at each iteration. Furthermore, for episodic memory sampling, EARL uses the Greedy Balanced Sampling strategy [40]. We describe the details about hyperparameters and the pseudocode of EARL in Supplementary for the sake of space. + +# 5.2. Results + +We first compare the accuracy of online continual learning methods, including EARL, and summarize the results in Table 1. As shown in the table, EARL outperforms other baselines on all benchmarks, both in disjoint and Gaussian-scheduled setups, except $A_{\mathrm{last}}$ in ImageNet-1K disjoint setup. In particular, high $A_{\mathrm{AUC}}$ suggests that EARL outperforms other methods for all the time that the data stream is provided to the model, which implies that it can be used for inference at anytime. + +Furthermore, EARL, SCR, ER, MIR, DER, and ODDL do not use task boundary information during training, i.e., task-free, in contrast to EWC, X-DER, MEMO, and REMIND which use task-boundary information, i.e., task-aware. Nevertheless, EARL outperforms these methods even in the disjoint setup where utilizing task boundary information is advantageous due to abrupt distribution shifts + +at the task boundaries, except MEMO in ImageNet-1K disjoint. Since MEMO not only uses the task boundary information but also expands the network per task, this extra advantage of using a larger model is emphasized in largescale datasets such as ImageNet which require a large learning capacity of the model. Please refer to the supplementary material for details of the computational budget comparison among the baseline methods. + +Memory budget. We consider not only the size of episodic memory, but also the size of the model, logits, and other components, following MEMO [63]. In the case of the memory budget for CIFAR-10 and the architecture of ResNet-18 (size of 42.6MB), EARL incurs an additional memory cost of 0.2MB to store feature-residual pairs. EWC requires an additional cost of 85.2MB due to the need to store Fisher Information per parameter and the previous model. MEMO, which expands the network per task, incurs an additional cost of 32MB per task. DER also requires an additional cost of 0.1MB to store logits during distillation. + +# 5.3. Ablation study + +We conduct an ablation study on the two components of EARL, preparatory data training and residual correction, and summarize the results in Table 3. Although both components contribute to performance improvement, preparatory data training shows a larger gain in performance. Training with preparatory data improves the baseline by $2.7\% \sim 3.3\%$ in $A_{auc}$ and $2.1\% \sim 4.4\%$ in $A_{last}$ . When combined with residual correction, we observe further gains across all metrics in both disjoint and Gaussian-scheduled setups. + +![](images/5ec652ff9bfca509aaf3d5de8627a380793ab48d2e58d806828c8db6872f8c63.jpg) +Figure 5. Average similarity between features of the most recently added class's samples and the closest classifier vectors of the old classes (CIFAR-10, Gaussian Scheduled). Baseline is a vanilla ETF model trained only using episodic memory. + +For further analysis, Fig. 6 visualizes the cosine similarity between the output features of 50 randomly selected test set samples of novel class '4' and the classifier vectors $\mathbf{w}_i$ . In baseline (a), the features of the class 4 are strongly biased towards the classifier vectors of the old classes (i.e., $\mathbf{w}_0$ , $\mathbf{w}_1$ , $\mathbf{w}_2$ , $\mathbf{w}_3$ ), rather than the correct classifier, $\mathbf{w}_4$ . (c) + +
METHODCIFAR-10CIFAR-100
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)\(A_{\text{AUC}} \uparrow\)\(A_{\text{last}} \uparrow\)
EARL (Ours)78.61±0.7266.01±2.2669.62±0.1970.91±1.9757.42±1.2444.60±0.6548.19±0.6146.10±0.26
(-) RC77.78±0.5265.52±1.6368.37±0.1070.17±1.0856.28±1.4044.29±1.0447.05±0.7146.07±0.52
(-) RC & PDT74.77±0.7761.10±3.1265.60±0.2567.39±0.7852.91±1.0541.08±0.6044.34±0.5544.45±0.48
+ +Table 3. Ablation Study. RC and PDT refer to preparatory data training (Sec. 4.2) and the residual correction (Sec. 4.3), respectively. + +![](images/bb4af209ee29559e28e20df0cd9d4917e821b0cefa5027490e79b3335dce7a7c.jpg) +Figure 6. Cosine similarity between features $\hat{f}(x)$ for class 4 and the ETF classifier vectors $\mathbf{w}_i$ at the $50^{th}$ iteration after the introduction of class 4 in the Gaussian Scheduled CIFAR-10 setup. As we can see in the cyan highlighted box, EARL promotes the convergence of $\hat{f}(x)$ for class 4 toward the ground truth classifier vector $\mathbf{w}_4$ . + +When residual correction is used, some samples show high similarity with $\mathbf{w}_4$ compared to the baseline. + +However, since incorrect residuals can be added due to the bias problem, more samples have high similarity with $\mathbf{w}_2$ than the baseline (i.e., wrong residuals are added). (b) When using preparatory data training, the bias toward $\mathbf{w}_0$ and $\mathbf{w}_1$ classes significantly decreases compared to the baseline. Fig. 5 also shows the effect of preparatory data, which reduces the similarity between the novel class features and existing classes. (d) Using both residual correction and preparatory data training shows a remarkable alignment with the ground truth classifier $\mathbf{w}_4$ . A more detailed analysis of the ablation results is provided in the Supple. + +# 6. Conclusion + +To better learn online data in a continuous data stream without multiple epoch training, we propose to induce neural collapse, which aligns last layer activations to the corresponding classifier vectors in the representation space. Unlike in offline CL, it is challenging to induce neural collapse in online CL due to insufficient training epochs and continuously streamed new data. We first observe that the bias of the new class towards existing classes slows the convergence of features toward neural collapse. + +To mitigate the bias, we propose synthesizing preparatory data for unseen classes by transforming the samples + +of existing classes. Using the preparatory data for training, we accelerate neural collapse in an online CL scenario. Additionally, we propose residual correction to resolve the remaining discrepancy toward neural collapse at inference, which arises due to the continuous stream of new data. In our empirical evaluations, the proposed methods outperform state-of-the-art online CL methods in various datasets and setups, especially with high performance on anytime inference. + +Limitations and Future Work. Since our work uses ETF structure, it has an inherent limitation that the number of possible classifier vectors in the ETF classifier is limited by the dimension of the embedding space. Considering lifelong learning, where the number of new classes goes to infinity, it is interesting to explore the idea of dynamically expanding the ETF structure so that the model can continually learn the ever-increasing number of concepts in the real world. + +Acknowledgement. This work was partly supported by the NRF grant (No.2022R1A2C4002300, $20\%$ ) and IITP grants (No.2022-0-00077 $(10\%)$ , No.2022-0-00113 $(25\%)$ , No.2022-0-00959 $(10\%)$ , No.2022-0- 00871 $(10\%)$ , No.2020-0-01361 $(5\%)$ , Yonsei AI), No.2021-0-01343 $(5\%)$ SNU AI), No.2021-0-02068 $(5\%)$ , AI Innov. Hub), No.2022-0-00951 $(5\%)$ ) funded by the Korea government (MSIT) and CARAI grant funded by DAPA and ADD (UD230017TD) $5 \%$ . This work was done while J. Choi was with Yonsei University and partially while H. Lee, M. Seo and H. Kim was with LG AI Research. + +# References + +[1] Rahaf Aljundi, Klaas Kelchtermans, and Tinne Tuytelaars. Task-free continual learning. 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In NeurIPS, 2021. 1, 3 \ No newline at end of file diff --git a/2024/Learning Equi-angular Representations for Online Continual Learning/images.zip b/2024/Learning Equi-angular Representations for Online Continual Learning/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..3d4a7328161303e27c9bcd65cf2ef3f2e5f2cfd1 --- /dev/null +++ b/2024/Learning Equi-angular Representations for Online Continual Learning/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:100937dffb54f54f7a48b47a2f7c0fd7bd37ab5f7b8f3d3dd18b3ea57be5e256 +size 675003 diff --git a/2024/Learning Equi-angular Representations for Online Continual Learning/layout.json b/2024/Learning Equi-angular Representations for Online Continual Learning/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..8c3cf4073d49308fa464c77e288720e1299c266b --- /dev/null +++ b/2024/Learning Equi-angular Representations for Online Continual Learning/layout.json @@ -0,0 +1,10816 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 77, + 103, + 517, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 77, + 103, + 517, + 121 + ], + "spans": [ + { + "bbox": [ + 77, + 103, + 517, + 121 + ], + "type": "text", + "content": "Learning Equi-angular Representations for Online Continual Learning" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "spans": [ + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": "Minhyuk Seo" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{1,\\dagger}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " Hyunseo Koh" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " Wonje Jeung" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " Minjae Lee" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " San Kim" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " Hankook Lee" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{2,3}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " Sungjun Cho" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " Sungik Choi" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " Hyunwoo Kim" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{4,*}" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "text", + "content": " Jonghyun Choi" + }, + { + "bbox": [ + 77, + 142, + 516, + 172 + ], + "type": "inline_equation", + "content": "^{5,*}" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 66, + 176, + 527, + 232 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 66, + 176, + 527, + 232 + ], + "spans": [ + { + "bbox": [ + 66, + 176, + 527, + 232 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 66, + 176, + 527, + 232 + ], + "type": "text", + "content": "Yonsei Univ. 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" + }, + { + "bbox": [ + 66, + 176, + 527, + 232 + ], + "type": "inline_equation", + "content": "^{4}" + }, + { + "bbox": [ + 66, + 176, + 527, + 232 + ], + "type": "text", + "content": "Zhejiang Lab " + }, + { + "bbox": [ + 66, + 176, + 527, + 232 + ], + "type": "inline_equation", + "content": "^{5}" + }, + { + "bbox": [ + 66, + 176, + 527, + 232 + ], + "type": "text", + "content": "Seoul National Univ. {dbd0508, specific0924, reccos1020, nasmik419}@yonsei.ac.kr khs8157@gmail.com, {sungik.choi,sungjun.cho}@lgresearch.ai hankook.lee@skku.edu, hwkim@zhejianglab.com, jonghyunchoi@snu.ac.kr" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 261, + 192, + 274 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 261, + 192, + 274 + ], + "spans": [ + { + "bbox": [ + 143, + 261, + 192, + 274 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 285, + 290, + 501 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 285, + 290, + 501 + ], + "spans": [ + { + "bbox": [ + 46, + 285, + 290, + 501 + ], + "type": "text", + "content": "Online continual learning suffers from an underfitted solution due to insufficient training for prompt model update (e.g., single-epoch training). To address the challenge, we propose an efficient online continual learning method using the neural collapse phenomenon. In particular, we induce neural collapse to form a simplex equiangular tight frame (ETF) structure in the representation space so that the continuously learned model with a single epoch can better fit to the streamed data by proposing preparatory data training and residual correction in the representation space. With an extensive set of empirical validations using CIFAR10/100, TinyImageNet, ImageNet-200, and ImageNet-1K, we show that our proposed method outperforms state-of-the-art methods by a noticeable margin in various online continual learning scenarios such as disjoint and Gaussian scheduled continuous (i.e., boundary-free) data setups. Code is available at https://github.com/yonseivnl/earl." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 523, + 128, + 536 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 523, + 128, + 536 + ], + "spans": [ + { + "bbox": [ + 47, + 523, + 128, + 536 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 543, + 288, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 543, + 288, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 543, + 288, + 687 + ], + "type": "text", + "content": "A growing interest in continuous learning (CL) involves training the model using continuous data streams. Mostly, CL research has focused on the offline scenario that assumes the model can be trained in multiple epochs for the current task [8, 42, 54]. However, substantial storage and computational complexity are required to store all data to train a model for multiple epochs. Recently, there has been significant interest in online CL as a more realistic set-up with a lower computational overhead of allowing a single training pass through the data stream [1, 7, 27]. Learning a model in streamed data by a single training pass is challenging, since the temporal distribution at each intermediate" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 261, + 545, + 311 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 261, + 545, + 311 + ], + "spans": [ + { + "bbox": [ + 306, + 261, + 545, + 311 + ], + "type": "text", + "content": "time point is likely imbalanced, even if the overall distribution of a dataset is balanced. Imbalanced data distributions would cause several problems, such as bias towards the major classes [24, 61] and the hindrance to generalization [53]." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 312, + 546, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 312, + 546, + 480 + ], + "spans": [ + { + "bbox": [ + 304, + 312, + 546, + 480 + ], + "type": "text", + "content": "Recently, minority collapse [14], the phenomenon in which the angles between classifier vectors for minor classes (i.e., the classes that have a relatively small number of samples) become narrow, has been proposed as a fundamental issue in training with imbalanced data, making the classification of minor classes considerably more challenging. In contrast, for balanced data sets, it was proven that classifier vectors and the last layer activations for all classes converge into an optimal geometric structure, named the simplex equiangular tight frame (ETF) structure, where all pairwise angles between classes are equal and maximally widened when using cross entropy (CE) [23, 30, 52, 65] or mean squared error (MSE) [32, 41, 48, 64] loss. This phenomenon is called neural collapse [34]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 483, + 547, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 483, + 547, + 592 + ], + "spans": [ + { + "bbox": [ + 304, + 483, + 547, + 592 + ], + "type": "text", + "content": "Although neural collapse naturally occurs only in balanced training, several recent studies attempted to induce neural collapse in imbalanced training to address the minority collapse problem using a fixed ETF classifier [55, 62]. When employing a fixed ETF classifier, the output features are pulled toward the corresponding classifier vector during training, since the classifier is fixed. More recently, research has also been extended to induce neural collapse in offline CL using a fixed ETF classifier [56]." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 594, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 547, + 714 + ], + "type": "text", + "content": "However, unlike offline CL, there are a number of challenges in inducing neural collapse in online CL, even with a fixed ETF classifier. The prerequisite for neural collapse is reaching the terminal phase of training (TPT) by sufficient training [34]. In offline CL, the model can reach the TPT phase for each task by multi-epoch training. In contrast, a single-pass training constraint often prevents the online CL from reaching TPT. As shown in Fig. 1, the offline CL quickly reaches TPT shortly after the arrival of novel task data, while online CL (vanilla ETF) does not." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 48, + 693, + 211, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 693, + 211, + 703 + ], + "spans": [ + { + "bbox": [ + 48, + 693, + 211, + 703 + ], + "type": "text", + "content": "†: Work done while interning at LG AI Research." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 50, + 704, + 165, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 50, + 704, + 165, + 712 + ], + "spans": [ + { + "bbox": [ + 50, + 704, + 165, + 712 + ], + "type": "text", + "content": "*: Indicates corresponding authors." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23933" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 70, + 547, + 198 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 547, + 198 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 547, + 198 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 547, + 198 + ], + "type": "image", + "image_path": "286fe80ac345fa2b15e206b235117ac50ec9c21f64780bd5db4f6faefd35e08f.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 204, + 547, + 239 + ], + "lines": [ + { + "bbox": [ + 46, + 204, + 547, + 239 + ], + "spans": [ + { + "bbox": [ + 46, + 204, + 547, + 239 + ], + "type": "text", + "content": "Figure 1. Comparison of training error rates between online CL and offline CL in the CIFAR-10 disjoint setup, where two novel classes are added every 10k samples. Vanilla ETF refers to a method where both preparatory data training and residual correction are removed from our proposed EARL." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 243, + 288, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 243, + 288, + 327 + ], + "spans": [ + { + "bbox": [ + 46, + 243, + 288, + 327 + ], + "type": "text", + "content": "Recently, the importance of anytime inference in online CL has been emphasized [6, 17, 27, 36], since a model should be available for inference not only at the end of a task, but also at any point during training to be practical for real-world applications. Hence, not only reaching TPT but also achieving faster convergence is necessary when using neural collapse in online CL." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 328, + 287, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 328, + 287, + 437 + ], + "spans": [ + { + "bbox": [ + 46, + 328, + 287, + 437 + ], + "type": "text", + "content": "However, we observe that the phenomenon in which the features of the new class become biased toward the features of the existing classes [5] hinders fast convergence of the last-layer features into the ETF structure, which we call the 'bias problem.' When features of old and new classes overlap (i.e., biased) and are trained with the same objective, well-clustered features of old classes disperse (or perturb) [5], leading to destruction of the ETF structure formed by features of the old classes." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 448, + 287, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 448, + 287, + 590 + ], + "spans": [ + { + "bbox": [ + 46, + 448, + 287, + 590 + ], + "type": "text", + "content": "Contributions. To address the bias problem, we train the model to distinguish out-of-distribution (OOD) samples from existing classes' samples. Specifically, we synthesize preparatory data that play the role of OOD data, by applying negative data augmentation [25, 47, 50] to samples from existing classes, refer to Sec. 4.2 for details. Since samples from new classes are OOD in the perspective of existing classes, training with preparatory data encourages the representation of new classes to be distinguished from existing classes in advance, thereby mitigating the bias problem. This promotes fast and stable convergence into the ETF structure." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 593, + 287, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 593, + 287, + 688 + ], + "spans": [ + { + "bbox": [ + 46, + 593, + 287, + 688 + ], + "type": "text", + "content": "Despite these efforts, however, the continuous stream of new samples cause ongoing data distribution shifts, which prevent the model from reaching the TPT and fully converging to the ETF structure. To address this, we propose to store the residuals between the target ETF classifier and the features during training. During inference, we correct the inference output using the stored residual to compensate for insufficient convergence in the training." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": "By accelerating convergence by preparatory data training and additional correction using residual, we noticeably" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 243, + 547, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 243, + 547, + 327 + ], + "spans": [ + { + "bbox": [ + 304, + 243, + 547, + 327 + ], + "type": "text", + "content": "improve anytime inference performance than state of the arts. We name our method Equi-Angular Representation Learning (EARL). We empirically demonstrate the effectiveness of our framework on CIFAR-10, CIFAR-100, TinyImageNet,Imagenet-200,and ImageNet-1K.In particular, our framework outperforms various CL methods by a significant margin " + }, + { + "bbox": [ + 304, + 243, + 547, + 327 + ], + "type": "inline_equation", + "content": "(+4.0\\%)" + }, + { + "bbox": [ + 304, + 243, + 547, + 327 + ], + "type": "text", + "content": " gain of " + }, + { + "bbox": [ + 304, + 243, + 547, + 327 + ], + "type": "inline_equation", + "content": "A_{\\mathrm{auc}}" + }, + { + "bbox": [ + 304, + 243, + 547, + 327 + ], + "type": "text", + "content": " in ImageNet-1K)." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 317, + 328, + 497, + 339 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 328, + 497, + 339 + ], + "spans": [ + { + "bbox": [ + 317, + 328, + 497, + 339 + ], + "type": "text", + "content": "We summarize our contributions as follows:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 312, + 342, + 545, + 438 + ], + "type": "list", + "angle": 0, + "index": 12, + "blocks": [ + { + "bbox": [ + 312, + 342, + 525, + 353 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 342, + 525, + 353 + ], + "spans": [ + { + "bbox": [ + 312, + 342, + 525, + 353 + ], + "type": "text", + "content": "- Proposing to induce neural collapse for online CL." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 312, + 354, + 545, + 401 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 354, + 545, + 401 + ], + "spans": [ + { + "bbox": [ + 312, + 354, + 545, + 401 + ], + "type": "text", + "content": "- Proposing 'preparatory data training' to address the 'bias problem' that the new classes are biased toward the existing classes, promoting faster induction of neural collapse." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 312, + 403, + 545, + 438 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 403, + 545, + 438 + ], + "spans": [ + { + "bbox": [ + 312, + 403, + 545, + 438 + ], + "type": "text", + "content": "- Proposing 'residual correction' scheme to compensate for not fully reaching neural collapse at inference to further improve anytime inference accuracy." + } + ] + } + ], + "index": 11 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 453, + 390, + 464 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 453, + 390, + 464 + ], + "spans": [ + { + "bbox": [ + 306, + 453, + 390, + 464 + ], + "type": "text", + "content": "2. Related work" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 473, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 545, + 628 + ], + "type": "text", + "content": "Continual learning methods. Various continual learning methods are being researched to prevent forgetting past tasks, broadly categorized into replay, parameter isolation, and regularization. Replay methods involve storing a small portion of data from previous tasks in episodic memory [1, 2, 20, 27, 60] or storing a generative model trained on data from previous tasks [39, 46]. By replaying the samples stored in episodic memory or generated from the stored generative model, the model prevents forgetting past tasks during subsequent learning of novel tasks. Furthermore, Boschini et al. [3], Buzzega et al. [4], Li and Hoiem [29], Wu et al. [54] used replay samples to distill information about past tasks." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "content": "Regularization methods [26, 28] apply a penalty to the change of important model parameters during the process of learning new tasks, allowing the model to retain information about previous tasks. Parameter isolation methods [10, 44, 63] expand the network by allocating specific layers for each task. This enables the network to store information about individual tasks and preserves their knowl-" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "23934" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 146, + 85 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 146, + 85 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 146, + 85 + ], + "type": "text", + "content": "edge without forgetting." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 87, + 287, + 219 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 87, + 287, + 219 + ], + "spans": [ + { + "bbox": [ + 46, + 87, + 287, + 219 + ], + "type": "text", + "content": "Neural collapse. Neural collapse is a phenomenon in which the activations of the last layer and the classifier vectors form a simplex equiangular tight frame (ETF) structure at the terminal phase of training (TPT) in a balanced dataset. [34]. Neural collapse has been demonstrated as the global optimum of balanced training using cross entropy (CE) loss [23, 30, 52, 65] and MSE [32, 41, 48, 64] loss functions, within a simplified model focused solely on last-layer optimization. Inducing neural collapse in imbalanced datasets poses challenges due to minority collapse [14] where minor classes are not well distinguished." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 220, + 287, + 339 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 220, + 287, + 339 + ], + "spans": [ + { + "bbox": [ + 46, + 220, + 287, + 339 + ], + "type": "text", + "content": "However, using a fixed ETF classifier, it is empirically and theoretically shown that neural collapse is induced even in imbalanced datasets [55]. Continual learning also needs to address imbalanced data since there is an imbalance in the data between novel classes and existing classes. Therefore, in offline CL, NC-FSCIL [38, 56] used a fixed ETF classifier to induce neural collapse. Meanwhile, online CL often fails to induce neural collapse compared to offline CL, e.g., FSCIL, since it lacks sufficient training in multiple epochs, causing failure to reach TPT." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 339, + 287, + 375 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 339, + 287, + 375 + ], + "spans": [ + { + "bbox": [ + 47, + 339, + 287, + 375 + ], + "type": "text", + "content": "Please refer to the supplementary material for more comprehensive literature reviews including topics related to anytime inference." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 384, + 132, + 396 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 384, + 132, + 396 + ], + "spans": [ + { + "bbox": [ + 47, + 384, + 132, + 396 + ], + "type": "text", + "content": "3. Preliminaries" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 405, + 287, + 441 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 405, + 287, + 441 + ], + "spans": [ + { + "bbox": [ + 47, + 405, + 287, + 441 + ], + "type": "text", + "content": "We here describe the problem statement for the online continual learning (Sec. 3.1), neural collapse (Sec. 3.2), and the equiangular tight frame classifier (Sec. 3.3)." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 446, + 224, + 458 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 446, + 224, + 458 + ], + "spans": [ + { + "bbox": [ + 47, + 446, + 224, + 458 + ], + "type": "text", + "content": "3.1. Problem Statement of Online CL" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "spans": [ + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": "Continual learning (CL) aims to learn from a stream of data, rather than a fixed dataset as in standard learning. Formally, given a sequence of tasks " + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "inline_equation", + "content": "\\mathcal{T} = (T_1,T_2,\\ldots)" + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": " where each task " + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "inline_equation", + "content": "T_{i}" + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": " is a training dataset " + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "inline_equation", + "content": "D_{i} = \\{(x_{1}^{(i)},y_{1}^{(i)}),(x_{2}^{(i)},y_{2}^{(i)}),\\ldots \\}" + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": ", an offline CL algorithm " + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "inline_equation", + "content": "A_{\\mathrm{CL}}" + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": " updates the model parameter " + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": " based on the current task " + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "inline_equation", + "content": "D_{k}" + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": ", i.e., " + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "inline_equation", + "content": "\\theta_{k} = A_{\\mathrm{CL}}(\\theta_{k - 1},D_{k})" + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": ", starting from the initial parameter " + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "inline_equation", + "content": "\\theta_0" + }, + { + "bbox": [ + 47, + 464, + 287, + 551 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "spans": [ + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "text", + "content": "To avoid the forgetting issue in CL, many CL setups allow the use of episodic memory " + }, + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "inline_equation", + "content": "M_{k}" + }, + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "text", + "content": ", which is a limited-size subset of training data from previous tasks, i.e., " + }, + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "inline_equation", + "content": "(\\theta_k,M_k) = A_{\\mathrm{CL}}(\\theta_{k - 1},M_{k - 1},D_k)" + }, + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "text", + "content": ". The objective is to minimize the error of " + }, + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "inline_equation", + "content": "\\theta_{k}" + }, + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "text", + "content": " in all observed tasks " + }, + { + "bbox": [ + 47, + 551, + 287, + 610 + ], + "type": "inline_equation", + "content": "\\{T_i\\}_{i = 1}^k" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "spans": [ + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "type": "text", + "content": "Unlike offline CL where all training samples in " + }, + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "type": "inline_equation", + "content": "D_{k}" + }, + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "type": "text", + "content": " are given as input, in online CL, the input is provided as a stream of samples " + }, + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "type": "inline_equation", + "content": "(x_{1}^{(k)}, y_{1}^{(k)}), (x_{2}^{(k)}, y_{2}^{(k)}), \\dots" + }, + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "type": "text", + "content": ". Therefore, an online CL algorithm " + }, + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "type": "inline_equation", + "content": "A_{\\mathrm{OCL}}" + }, + { + "bbox": [ + 47, + 610, + 287, + 659 + ], + "type": "text", + "content": " is defined as:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 55, + 665, + 287, + 685 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 665, + 287, + 685 + ], + "spans": [ + { + "bbox": [ + 55, + 665, + 287, + 685 + ], + "type": "interline_equation", + "content": "\\left(\\theta_ {k, t}, M _ {k, t}\\right) = A _ {\\mathrm {O C L}} \\left(\\theta_ {k, t - 1}, M _ {k, t - 1}, \\left(x _ {t} ^ {(k)}, y _ {t} ^ {(k)}\\right)\\right), \\tag {1}", + "image_path": "ddd693e38aa90d73937ab9c0c08f6777e75544fc049744e263317b4e739bb83e.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": "with the same objective of minimizing the error of " + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\theta_{k,t}" + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": " on " + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\{T_i\\}_{i = 1}^k" + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": ". Since the algorithm does not have access to pre" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "spans": [ + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "type": "text", + "content": "vious samples " + }, + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "type": "inline_equation", + "content": "\\{(x_s^{(k)},y_s^{(k)}),s < t\\}" + }, + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "type": "text", + "content": " at time " + }, + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "type": "text", + "content": " , multi-epoch training with " + }, + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "type": "inline_equation", + "content": "D_{k}" + }, + { + "bbox": [ + 305, + 70, + 545, + 96 + ], + "type": "text", + "content": " is unavailable in online CL." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 103, + 404, + 116 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 103, + 404, + 116 + ], + "spans": [ + { + "bbox": [ + 306, + 103, + 404, + 116 + ], + "type": "text", + "content": "3.2. Neural Collapse" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 121, + 545, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 121, + 545, + 192 + ], + "spans": [ + { + "bbox": [ + 305, + 121, + 545, + 192 + ], + "type": "text", + "content": "Neural collapse [34] is a phenomenon of the penultimate features after the convergence of training on a balanced dataset. When neural collapse (NC) occurs, the collection of " + }, + { + "bbox": [ + 305, + 121, + 545, + 192 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 305, + 121, + 545, + 192 + ], + "type": "text", + "content": " classifier vectors " + }, + { + "bbox": [ + 305, + 121, + 545, + 192 + ], + "type": "inline_equation", + "content": "\\mathbf{W}_{\\mathrm{ETF}} = [\\mathbf{w}_1,\\mathbf{w}_2,\\dots,\\mathbf{w}_K]\\in \\mathbb{R}^{d\\times K}" + }, + { + "bbox": [ + 305, + 121, + 545, + 192 + ], + "type": "text", + "content": " forms a simplex equiangular tight frame (ETF), which satisfies:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 310, + 198, + 545, + 230 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 198, + 545, + 230 + ], + "spans": [ + { + "bbox": [ + 310, + 198, + 545, + 230 + ], + "type": "interline_equation", + "content": "\\mathbf {w} _ {i} ^ {T} \\mathbf {w} _ {j} = \\left\\{ \\begin{array}{l l} 1, & i = j \\\\ - \\frac {1}{K - 1}, & i \\neq j \\end{array} , \\forall i, j \\in [ 1, \\dots , K ], \\right. \\tag {2}", + "image_path": "b1d316d0770da0e4e06146f85570e029298178e99665847a4842b639839579f3.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 236, + 545, + 261 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 236, + 545, + 261 + ], + "spans": [ + { + "bbox": [ + 305, + 236, + 545, + 261 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 236, + 545, + 261 + ], + "type": "inline_equation", + "content": "K - 1 \\leq d" + }, + { + "bbox": [ + 305, + 236, + 545, + 261 + ], + "type": "text", + "content": ", and the penultimate feature of a training sample collapses into an ETF vector " + }, + { + "bbox": [ + 305, + 236, + 545, + 261 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_i" + }, + { + "bbox": [ + 305, + 236, + 545, + 261 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 266, + 527, + 280 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 266, + 527, + 280 + ], + "spans": [ + { + "bbox": [ + 305, + 266, + 527, + 280 + ], + "type": "text", + "content": "3.3. Equiangular Tight Frame (ETF) Classifier" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "spans": [ + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "text", + "content": "Inspired by neural collapse as described in Sec. 3.2, a fixed ETF classifier has been utilized for inducing neural collapse in imbalanced datasets [55, 56, 65]. Here, the classifier is initialized by the ETF structure " + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "inline_equation", + "content": "\\mathbf{W}_{\\mathrm{ETF}}" + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "text", + "content": " at the beginning of training and fixed during training to induce the penultimate feature " + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "inline_equation", + "content": "f(x)" + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "text", + "content": " to converge to the ideal balanced scenario. For training " + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "inline_equation", + "content": "f(x)" + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "text", + "content": ", it is only required to attract " + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "inline_equation", + "content": "f(x)" + }, + { + "bbox": [ + 305, + 285, + 545, + 440 + ], + "type": "text", + "content": " to the corresponding classifier vector for convergence, since the classifier is fixed during training. Therefore, following Yang et al. [55], we use the dot regression (DR) loss as a training objective, as it shows to outperform cross entropy (CE) loss when using a fixed ETF classifier in imbalanced datasets [55]. The DR loss can be written as follows:" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 337, + 445, + 545, + 468 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 337, + 445, + 545, + 468 + ], + "spans": [ + { + "bbox": [ + 337, + 445, + 545, + 468 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {D R}} (\\hat {f} (x), y; \\mathbf {W} _ {\\text {E T F}}) = \\frac {1}{2} \\left(\\mathbf {w} _ {y} \\hat {f} (x) - 1\\right) ^ {2}, \\tag {3}", + "image_path": "e9bf895ca7d0104a0f8167547eae4298c2d3c9f27c67c0b18b2fc1694ffa301e.jpg" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "spans": [ + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "inline_equation", + "content": "\\hat{f} (x) = f(x) / \\| f(x)\\| _2" + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": " is the " + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "inline_equation", + "content": "L_{2}" + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": " normalized feature of the model " + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": " is the label of the input " + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_y" + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": " is a classifier vector in " + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "inline_equation", + "content": "\\mathbf{W}_{\\mathrm{ETF}}" + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": " for the label " + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 305, + 475, + 545, + 513 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 523, + 372, + 536 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 523, + 372, + 536 + ], + "spans": [ + { + "bbox": [ + 306, + 523, + 372, + 536 + ], + "type": "text", + "content": "4. Approach" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 305, + 543, + 545, + 627 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 543, + 545, + 627 + ], + "spans": [ + { + "bbox": [ + 305, + 543, + 545, + 627 + ], + "type": "text", + "content": "Despite the success of the fixed ETF classifier in both imbalanced training [55, 62] and offline CL [56], the ETF classifier has not yet been explored for online CL due to the necessity of sufficient training for neural collapse. To be specific, streamed data are trained only once in online CL, which makes it harder to induce neural collapse than in offline CL which supports multi-epoch training." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 305, + 627, + 545, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 627, + 545, + 687 + ], + "spans": [ + { + "bbox": [ + 305, + 627, + 545, + 687 + ], + "type": "text", + "content": "To learn a better converged model without multi-epoch training for online CL, we propose two novel methods, each for the training phase and the inference phase, respectively. In the training phase, we accelerate convergence by proposing preparatory data training (Sec. 4.2). In the inference" + } + ] + } + ], + "index": 23 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "text", + "content": "1If the training objective includes a contrastive term between different classes like cross entropy, it could cause incorrect gradients [55]." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "23935" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 70, + 547, + 232 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 547, + 232 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 547, + 232 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 547, + 232 + ], + "type": "image", + "image_path": "2b82eece2a6f75f774eccd89b2b2db38f906fc55e473e2cbb59d5e1a6020feeb.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "lines": [ + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "spans": [ + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": "Figure 2. Overview of EARL. " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " denotes the ETF classifier vector for class " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "h_a" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " denotes the output of the model. The colors of the data denote the class to which the data belong. The arrow " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " denotes the residual between the last layer activation " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "h_i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " and the classifier vector " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " for class " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": ". During training, both memory and preparatory data are used for replaying, and the residuals between " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "h_i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " are stored in feature-residual memory. During inference, using the similarity between " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "f(x_{\\mathrm{eval}})" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "h_i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " in feature-residual memory, " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_{\\mathrm{eval}}" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " is obtained by a weighted sum of " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_i" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": "'s. Finally, by adding " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_{\\mathrm{eval}}" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "inline_equation", + "content": "f(x_{\\mathrm{eval}})" + }, + { + "bbox": [ + 46, + 236, + 547, + 293 + ], + "type": "text", + "content": " is corrected. The purple arrow indicates 'residual correction' (Sec. 4.3)." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 52, + 305, + 279, + 403 + ], + "blocks": [ + { + "bbox": [ + 52, + 305, + 279, + 403 + ], + "lines": [ + { + "bbox": [ + 52, + 305, + 279, + 403 + ], + "spans": [ + { + "bbox": [ + 52, + 305, + 279, + 403 + ], + "type": "image", + "image_path": "a35fba741b9772f294b8d2a04435ef928c8e2b090cda6ff1dc2da925b6dfdb8c.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 407, + 289, + 506 + ], + "lines": [ + { + "bbox": [ + 46, + 407, + 289, + 506 + ], + "spans": [ + { + "bbox": [ + 46, + 407, + 289, + 506 + ], + "type": "text", + "content": "Figure 3. Illustrative effects for each component of EARL. (a) In online CL, features of novel classes are biased towards the features of the previous class. (b) By training with preparatory data (w/ Prep. Data, Sec. 4.2), we address the bias problem. (c) In inference, for features that do not fully converge to an ETF classifier, we add residuals (w/ Res. Corr., Sec. 4.3) to features that have not yet reached the corresponding classifier vectors, making features aligned with them. Purple arrow: the 'residual correction', Colors: classes." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 515, + 287, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 515, + 287, + 563 + ], + "spans": [ + { + "bbox": [ + 46, + 515, + 287, + 563 + ], + "type": "text", + "content": "phase, we propose to correct the remaining discrepancy between the classifiers and the features using residual correction (Sec. 4.3). We illustrate an overview of EARL in Fig. 2 and the effect of EARL in Fig. 3." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 573, + 258, + 586 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 573, + 258, + 586 + ], + "spans": [ + { + "bbox": [ + 47, + 573, + 258, + 586 + ], + "type": "text", + "content": "4.1. Inducing Neural Collapse for Online CL" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "text", + "content": "For online CL, we first try to induce neural collapse with a fixed ETF classifier: " + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "inline_equation", + "content": "\\mathbf{W}_{\\mathrm{ETF}} \\in R^{d \\times K}" + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "text", + "content": " is the dimension of the embedding space and " + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "text", + "content": " is the number of ETF vectors. While prior works [55, 56] use prior knowledge of the total number of classes that will be encountered for setting " + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 593, + 287, + 687 + ], + "type": "text", + "content": ", it is unrealistic to know the knowledge (i.e., the exact number of classes) as it evolves continuously over time under realistic CL scenarios." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "content": "To address the challenge, we propose using the maximum possible number of classifier vectors for " + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "content": ". Based" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "spans": [ + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "type": "text", + "content": "on the simplex ETF property that the maximum number of ETF vectors is " + }, + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "type": "inline_equation", + "content": "d + 1" + }, + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "type": "text", + "content": " [16, 55], we define our ETF classifier " + }, + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "type": "inline_equation", + "content": "\\mathbf{W}_{\\mathrm{ETF}} \\in \\mathbb{R}^{d \\times (d + 1)}" + }, + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "type": "text", + "content": " by letting " + }, + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "type": "inline_equation", + "content": "K := d + 1" + }, + { + "bbox": [ + 305, + 307, + 547, + 344 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 354, + 463, + 367 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 354, + 463, + 367 + ], + "spans": [ + { + "bbox": [ + 305, + 354, + 463, + 367 + ], + "type": "text", + "content": "4.2. Preparatory data at training" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": "Since novel classes continuously arrive in CL, both the data from previous tasks " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "(x_{\\mathrm{old}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " and the current task " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "(x_{\\mathrm{new}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " coexist. While " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{old}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " are placed closer to their corresponding ETF classifier vectors " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "w_{\\mathrm{new}}" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " by training, " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{new}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " are biased toward the cluster of " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{old}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": ", as we can see in Fig. 4-(a), where " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{new}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{old}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " are the outputs of the model for inputs " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "x_{\\mathrm{new}}" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "x_{\\mathrm{old}}" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": ", respectively. We call this 'bias problem.' When " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{new}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{old}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " overlap due to bias and are optimized with the same objective function, training on the new class interferes with the representations of the old classes, dispersing the well-clustered " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{old}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": " [5]. It destroys the ETF structure formed by " + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{f}(x_{\\mathrm{old}})" + }, + { + "bbox": [ + 304, + 373, + 545, + 653 + ], + "type": "text", + "content": ", which hinders convergence towards neural collapse. Although the bias problem exists even without a fixed ETF classifier [5, 12, 54], it poses a greater problem when using a fixed ETF classifier, since the dispersed feature of old classes has to be restored to the corresponding fixed classifier vector. In contrast, when using a learnable classifier, the dispersed representation of the old classes does not have to be restored to the original position, since the learnable classifier vector will be re-optimized from the dispersed feature. However, the angles between the classifier vector may become narrow, i.e., minority collapse occurs." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": "To accelerate convergence in the ETF structure, we propose to prevent novel classes from being biased towards existing classes when introduced, mitigating the bias problem. Specifically, we train the model to avoid making predictions in favor of the existing classes for images that do not be" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23936" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 55, + 78, + 277, + 185 + ], + "blocks": [ + { + "bbox": [ + 55, + 78, + 277, + 185 + ], + "lines": [ + { + "bbox": [ + 55, + 78, + 277, + 185 + ], + "spans": [ + { + "bbox": [ + 55, + 78, + 277, + 185 + ], + "type": "image", + "image_path": "398d95752bcf26ed3d242ed8d9f8d52b7f79e369528685f4c796db1aa8abb21c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 189, + 287, + 266 + ], + "lines": [ + { + "bbox": [ + 46, + 189, + 287, + 266 + ], + "spans": [ + { + "bbox": [ + 46, + 189, + 287, + 266 + ], + "type": "text", + "content": "Figure 4. t-SNE visualization of 'bias-problem' in data distributions (class 0 to 3). (a) Only after 100 iterations of training after task 1 appears, learning is likely insufficient, and we can see that the features of new classes (class 2, 3) are biased towards the feature cluster of the existing class (i.e., class 1). (b) With more training iterations (10,000 iter), the features are well clustered by class." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 280, + 286, + 351 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 280, + 286, + 351 + ], + "spans": [ + { + "bbox": [ + 46, + 280, + 286, + 351 + ], + "type": "text", + "content": "long to them. To this end, we propose to use preparatory data " + }, + { + "bbox": [ + 46, + 280, + 286, + 351 + ], + "type": "inline_equation", + "content": "x_{p}" + }, + { + "bbox": [ + 46, + 280, + 286, + 351 + ], + "type": "text", + "content": " that is different from existing classes, obtained by transforming the samples in the episodic memory. By training with the preparatory data so that their representations differ from existing classes, we prevent biased predictions towards existing classes when a new class arrives." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 354, + 286, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 354, + 286, + 581 + ], + "spans": [ + { + "bbox": [ + 46, + 354, + 286, + 581 + ], + "type": "text", + "content": "For preparatory data to have a different representation from existing classes when trained, their image semantics should be distinguishable from existing classes, provided that they contain enough semantic information to be considered as an image (i.e., not noise). There are various approaches to synthesize images with modified semantics, such as using generative models [11, 19, 58] or negative transformations [47, 50]. We use negative transformations, as generative models are expensive in computation and storage [13], which is undesirable for CL scenarios with limited memory and computations. On the contrary, negative transformations are relatively efficient in computation and storage [33] and is reported to create images with semantics different from the original image [50]. We empirically observed that data generated through negative transformations have a distinct semantic class from the original class while preserving its semantic information as an image (i.e., not as random noise), and we summarize the results in the supplementary material." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": "Formally, for a set of existing classes " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "Y" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " and the set of possible transformations " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": ", we randomly select " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "y \\in Y" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "g \\in G" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": ", and randomly retrieve a sample of class " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " from memory and apply the transformation " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " to obtain preparatory data " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "x_{p}" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": ". We assign labels of the unseen classes to the preparatory data by a mapping function " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "m: Y \\times G \\to Y'" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "Y'" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " denotes a set of unseen classes, i.e., " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "Y' = \\{y | y \\notin Y, 1 \\leq y \\leq K\\}" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " is the total number of classifier vectors in " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{W}_{\\mathrm{ETF}} \\in \\mathbb{R}^{d \\times K}" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": ". Thus, preparatory data " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "x_{p}" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " from class " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " and transformation " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " is pulled towards the classifier vector " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_{p}" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "p = m(y, g)" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": ". When a new class " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "y_{\\mathrm{new}}" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "text", + "content": "is added to " + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "inline_equation", + "content": "Y" + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "text", + "content": ", we update " + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "text", + "content": " by randomly assigning a new mapping " + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "inline_equation", + "content": "m(y_{\\mathrm{new}}, g)" + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "inline_equation", + "content": "y_{\\mathrm{new}}" + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "inline_equation", + "content": "g \\in G" + }, + { + "bbox": [ + 305, + 72, + 544, + 96 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 96, + 545, + 275 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 96, + 545, + 275 + ], + "spans": [ + { + "bbox": [ + 305, + 96, + 545, + 275 + ], + "type": "text", + "content": "We compose the transformation set " + }, + { + "bbox": [ + 305, + 96, + 545, + 275 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 96, + 545, + 275 + ], + "type": "text", + "content": " as a negative transformation that can modify semantic information (i.e., change the label), used in the self-supervised literature [15, 18] and out-of-distribution (OOD) detection [25, 47, 50]. Specifically, we use rotation by 90, 180, and 270 degrees [15, 18] as our negative transformation. Since the vertical information of the image is more important than the horizontal information [22, 49], e.g., images of a car facing left or right are common, but a car flipped upside down is very rare compared to a car standing right, rotation by a large angle causes loss of semantic information of images [50]. Thus, we can use rotated data as semantically different images from images of existing classes, i.e., suitable for preparatory data. A more detailed analysis of various negative transformations is provided in the Supple." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 275, + 545, + 312 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 275, + 545, + 312 + ], + "spans": [ + { + "bbox": [ + 305, + 275, + 545, + 312 + ], + "type": "text", + "content": "We jointly train the model using real data (i.e., samples of existing classes) and preparatory data. Formally, we write the objective for the model parameter " + }, + { + "bbox": [ + 305, + 275, + 545, + 312 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 305, + 275, + 545, + 312 + ], + "type": "text", + "content": " as:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 317, + 553, + 372 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 317, + 553, + 372 + ], + "spans": [ + { + "bbox": [ + 306, + 317, + 553, + 372 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\underset {\\theta} {\\arg \\min } \\left[ \\mathbb {E} _ {(x, y) \\sim \\mathcal {M}} \\mathcal {L} _ {\\mathrm {D R}} \\left(\\hat {f} _ {\\theta} (x), y; \\mathbf {W} _ {\\text {E T F}}\\right) \\right. \\tag {4} \\\\ \\left. \\right.\\left. + \\lambda \\mathbb {E} _ {\\left(x ^ {\\prime}, y ^ {\\prime}\\right) \\sim \\mathcal {M}, g \\sim G} \\mathcal {L} _ {\\mathrm {D R}} \\left(\\hat {f} _ {\\theta} (g \\left(x ^ {\\prime}\\right)), m \\left(y ^ {\\prime}, g\\right); \\mathbf {W} _ {\\text {E T F}}\\right)\\right], \\\\ \\end{array}", + "image_path": "880196ad1ef2c9d661d82975aca23a539c98bc70d300feb352cb58fd8d59e5ce.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "spans": [ + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "\\mathcal{M}" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": " denotes episodic memory, " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "(x,y)" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "(x',y')" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": " denote the samples in " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "\\mathcal{M}" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": " denotes the set of possible transformations, " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": " denotes a transformation in " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": " denotes the mapping function, and " + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 305, + 377, + 545, + 437 + ], + "type": "text", + "content": " is a hyperparameter for balancing real data and preparatory data." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 444, + 477, + 455 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 444, + 477, + 455 + ], + "spans": [ + { + "bbox": [ + 306, + 444, + 477, + 455 + ], + "type": "text", + "content": "4.3. Residual correction at inference" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 462, + 545, + 557 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 462, + 545, + 557 + ], + "spans": [ + { + "bbox": [ + 305, + 462, + 545, + 557 + ], + "type": "text", + "content": "Despite preparatory data training that accelerates convergence towards ETF, in online CL, new samples in a data stream hinder models from reaching the Terminal Phase of Training (TPT) and fully converging to the ETF during single-epoch training. When the output of the model " + }, + { + "bbox": [ + 305, + 462, + 545, + 557 + ], + "type": "inline_equation", + "content": "f(x)" + }, + { + "bbox": [ + 305, + 462, + 545, + 557 + ], + "type": "text", + "content": " does not fully converge to the ETF classifier, the model would not perform well at all times, leading to poor anytime inference accuracy (" + }, + { + "bbox": [ + 305, + 462, + 545, + 557 + ], + "type": "inline_equation", + "content": "A_{\\mathrm{AUC}}" + }, + { + "bbox": [ + 305, + 462, + 545, + 557 + ], + "type": "text", + "content": ")." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "spans": [ + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "text", + "content": "To address this issue, we want to correct the residual between " + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "inline_equation", + "content": "f(x)" + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "text", + "content": " and the corresponding classifier vector " + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_y" + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "text", + "content": " during inference, where " + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "text", + "content": " is label of input " + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 305, + 558, + 544, + 594 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 594, + 545, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 677 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 677 + ], + "type": "text", + "content": "However, the discrepancy between the prediction on test data " + }, + { + "bbox": [ + 304, + 594, + 545, + 677 + ], + "type": "inline_equation", + "content": "x_{\\mathrm{eval}}" + }, + { + "bbox": [ + 304, + 594, + 545, + 677 + ], + "type": "text", + "content": " and the ground-truth ETF classifier vector is not available in the inference phase. In a similar situation, ResMem [57] stores the residual obtained from training data and uses them during inference, but they assume two-stage learning algorithms, i.e., standard training and inference rather than incremental learning and anytime inference." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "type": "text", + "content": "Inspired by ResMem [57], which uses residuals from the training in the inference stage, we propose to use the residual obtained from the training process to compensate for the" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "23937" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 70, + 547, + 220 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 547, + 220 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 547, + 220 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 547, + 220 + ], + "type": "table", + "html": "
MethodCIFAR-10CIFAR-100
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)75.25±0.7860.80±2.2059.62±0.3164.24±1.9752.08±0.8341.55±0.8538.22±0.5042.52±0.58
ER (Rolnick et al., 2019)75.94±0.8663.56±1.3260.13±0.5664.81±2.7052.95±1.2542.82±0.0541.12±0.5642.74±1.09
ER-MIR (Aljundi et al., 2019)75.89±1.0261.93±0.9360.39±0.4861.64±3.8652.93±1.4442.47±0.1341.19±0.6342.93±1.18
REMIND (Hayes et al., 2020)69.55±0.9153.34±1.0158.01±0.7259.27±1.8640.87±0.7636.17±1.8323.40±2.2528.78±1.71
DER++ (Buzzega et al., 2020)74.78±0.7259.20±0.9559.44±0.2866.11±1.8038.16±1.5738.55±2.1129.38±2.5838.20±3.13
SCR (Mai et al., 2021)75.61±0.9356.52±0.5260.62±0.4358.41±2.3941.84±0.7436.00±0.8331.33±0.4132.11±0.39
ODDL (Ye et al., 2022)75.03±1.0061.61±3.5565.46±0.4666.19±2.0840.26±0.5041.88±4.5238.82±0.4941.35±1.08
MEMO (Zhou et al., 2023)73.21±0.4962.47±3.3859.26±0.9062.01±1.1740.60±1.1139.87±0.4623.41±1.6332.74±2.11
X-DER (Boschini et al., 2023)77.59±0.6265.40±4.7958.28±1.1759.76±4.2852.80±1.6143.73±0.8641.94±0.5746.00±1.04
EARL (Ours)78.31±0.7265.71±2.2669.52±0.1970.41±1.9757.12±1.2244.40±0.6847.89±0.6146.09±0.26
", + "image_path": "a7c115f190f9210571617b661e4d4406938133cb087dd8120eb1d917fe9cebd5.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 48, + 227, + 545, + 367 + ], + "blocks": [ + { + "bbox": [ + 48, + 227, + 545, + 367 + ], + "lines": [ + { + "bbox": [ + 48, + 227, + 545, + 367 + ], + "spans": [ + { + "bbox": [ + 48, + 227, + 545, + 367 + ], + "type": "table", + "html": "
MethodTinyImageNetImageNet-200
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)37.95±0.9327.50±0.8025.29±0.8126.06±0.5241.84±0.6431.57±0.8030.71±0.2733.33±0.98
ER (Rolnick et al., 2019)37.43±1.0527.47±0.6326.37±0.8925.79±0.4441.51±0.7630.87±0.7232.39±0.3633.09±0.37
ER-MIR (Aljundi et al., 2019)37.81±1.0626.72±0.8626.22±0.6925.11±1.0438.28±0.3833.12±0.7332.17±0.4433.85±0.93
REMIND (Hayes et al., 2020)28.37±0.1327.68±0.4510.19±0.6014.90±1.4939.25±0.9331.98±0.8430.23±0.6233.98±0.09
DER++ (Buzzega et al., 2020)39.38±0.6029.36±0.8127.23±1.9431.53±0.8043.50±0.3134.56±0.5035.22±0.2638.38±0.97
SCR (Mai et al., 2021)34.65±1.0822.18±0.3225.86±0.9422.54±0.5941.90±0.4028.92±0.4033.24±0.3230.98±0.28
MEMO (Zhou et al., 2023)27.36±0.6127.57±0.5210.82±1.2318.03±1.3641.55±0.2334.19±1.4732.54±0.3936.11±1.06
X-DER (Boschini et al., 2023)35.15±2.1226.67±0.5229.71±0.8628.10±0.5043.41±0.4734.14±0.9836.31±0.1738.61±0.55
EARL (Ours)41.77±1.2629.65±0.2035.08±0.7032.49±1.2144.88±0.2934.79±0.5539.14±0.4738.83±0.35
", + "image_path": "7f31bf504023dff07cdaf10d49311d56658ca7aa529299a96d29a5e2cedf8e32.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 375, + 546, + 398 + ], + "lines": [ + { + "bbox": [ + 46, + 375, + 546, + 398 + ], + "spans": [ + { + "bbox": [ + 46, + 375, + 546, + 398 + ], + "type": "text", + "content": "Table 1. Comparison of online CL methods on Disjoint and Gaussian Scheduled Setup for CIFAR-10, CIFAR-100, TinyImageNet and ImageNet-200." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 403, + 287, + 427 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 403, + 287, + 427 + ], + "spans": [ + { + "bbox": [ + 46, + 403, + 287, + 427 + ], + "type": "text", + "content": "remaining discrepancy between the classifiers and the features at inference." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "spans": [ + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": "To select which of the stored residuals to use during inference, we not only store the residual, but also " + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "inline_equation", + "content": "f(x)" + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": " to choose the stored residual closest to " + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "inline_equation", + "content": "f(x_{\\mathrm{infer}})" + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": ". Therefore, we retain 'feature-residual' pairs in a 'feature-residual memory' " + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "inline_equation", + "content": "M = \\{(\\hat{h}_i,\\mathbf{r}_i)\\}_{i = 1}^N" + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "inline_equation", + "content": "\\hat{h}_i = \\hat{f} (x_i)" + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_i = \\mathbf{w}_{y_i} - \\hat{f} (x_i)" + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": " is the size of feature-residual memory, and " + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_{y_i}" + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": " is the classifier vector for class " + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "inline_equation", + "content": "y_i" + }, + { + "bbox": [ + 46, + 430, + 287, + 516 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": "During inference, we select the " + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": " nearest neighbor " + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "inline_equation", + "content": "\\hat{h}" + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": "'s, i.e., " + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "inline_equation", + "content": "\\{\\hat{h}_{n_1},\\hat{h}_{n_1},\\dots ,\\hat{h}_{n_k}\\}" + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "inline_equation", + "content": "\\{\\hat{h}_i\\}_{i = 1}^N" + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": ", since using only the nearest residual for correction may lead to incorrect inference predictions if a wrong residual is selected from a different class. Finally, following ResMem [57], we calculate the residual correction term " + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_{\\mathrm{eval}}" + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": " by a weighted average of the corresponding residuals " + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{r}_{n_1},\\mathbf{r}_{n_2},\\dots ,\\mathbf{r}_{n_k}\\}" + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": ", with weights " + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "inline_equation", + "content": "\\{s_1,s_2,\\ldots ,s_k\\}" + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": " that are inversely proportional to the distance from " + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "inline_equation", + "content": "\\hat{f} (x_{\\mathrm{eval}})" + }, + { + "bbox": [ + 46, + 518, + 287, + 628 + ], + "type": "text", + "content": ", as:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 62, + 643, + 287, + 677 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 62, + 643, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 62, + 643, + 287, + 677 + ], + "type": "interline_equation", + "content": "\\mathbf {r} _ {\\text {e v a l}} = \\sum_ {i = 1} ^ {k} s _ {i} \\mathbf {r} _ {i}, \\quad s _ {i} = \\frac {e ^ {- (\\hat {f} (x _ {\\text {e v a l}}) - \\hat {h} _ {i}) / \\tau}}{\\sum_ {j = 1} ^ {k} e ^ {- (\\hat {f} (x _ {\\text {e v a l}}) - \\hat {h} _ {j}) / \\tau}}, \\tag {5}", + "image_path": "04b39a20097d9a06aa53b7a8b4e19495f521cddab24e9ad0b5b5fc5a44284134.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 689, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 715 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 689, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 46, + 689, + 287, + 715 + ], + "type": "text", + "content": " is a temperature hyperparameter. We add the residual-correcting term " + }, + { + "bbox": [ + 46, + 689, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_{\\mathrm{eval}}" + }, + { + "bbox": [ + 46, + 689, + 287, + 715 + ], + "type": "text", + "content": " to the model output " + }, + { + "bbox": [ + 46, + 689, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\hat{f} (x_{\\mathrm{eval}})" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 403, + 500, + 417 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 403, + 500, + 417 + ], + "spans": [ + { + "bbox": [ + 305, + 403, + 500, + 417 + ], + "type": "text", + "content": "to obtain the corrected output " + }, + { + "bbox": [ + 305, + 403, + 500, + 417 + ], + "type": "inline_equation", + "content": "\\hat{f} (x_{\\mathrm{eval}})_{\\mathrm{corrected}}" + }, + { + "bbox": [ + 305, + 403, + 500, + 417 + ], + "type": "text", + "content": " as:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 357, + 426, + 545, + 442 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 357, + 426, + 545, + 442 + ], + "spans": [ + { + "bbox": [ + 357, + 426, + 545, + 442 + ], + "type": "interline_equation", + "content": "\\hat {f} \\left(x _ {\\text {e v a l}}\\right) _ {\\text {c o r r e c t e d}} = \\hat {f} \\left(x _ {\\text {e v a l}}\\right) + \\mathbf {r} _ {\\text {e v a l}}. \\tag {6}", + "image_path": "0930e031a2226f223906bf821288c360e6def32627b0c6fcc2f003f4c1daab12.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 454, + 388, + 468 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 454, + 388, + 468 + ], + "spans": [ + { + "bbox": [ + 305, + 454, + 388, + 468 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 475, + 421, + 488 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 475, + 421, + 488 + ], + "spans": [ + { + "bbox": [ + 305, + 475, + 421, + 488 + ], + "type": "text", + "content": "5.1. Experimental setup" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 494, + 545, + 578 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 494, + 545, + 578 + ], + "spans": [ + { + "bbox": [ + 304, + 494, + 545, + 578 + ], + "type": "text", + "content": "We perform experiments on four datasets: CIFAR-10, CIFAR-100, TinyImageNet, ImageNet-200, and ImageNet-1K. For all datasets, our experiments are conducted on both a disjoint setup [35] and a Gaussian scheduled setup [45, 51]. We report the average and standard deviation results in three different seeds, except ImageNet-1k due to computational resource constraints [2, 27]." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 579, + 545, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 579, + 545, + 651 + ], + "spans": [ + { + "bbox": [ + 304, + 579, + 545, + 651 + ], + "type": "text", + "content": "To evaluate anytime inference performance, we use the area under the curve accuracy " + }, + { + "bbox": [ + 304, + 579, + 545, + 651 + ], + "type": "inline_equation", + "content": "(A_{auc})" + }, + { + "bbox": [ + 304, + 579, + 545, + 651 + ], + "type": "text", + "content": " [6, 27], which measures the area under the accuracy curve. We also use last accuracy " + }, + { + "bbox": [ + 304, + 579, + 545, + 651 + ], + "type": "inline_equation", + "content": "(A_{last})" + }, + { + "bbox": [ + 304, + 579, + 545, + 651 + ], + "type": "text", + "content": " which measures accuracy at the end of training. For detailed information about the experimental setup, refer to the Supplementary." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 665, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 546, + 713 + ], + "type": "text", + "content": "Baselines. We compare EARL with various CL methods in different categories: regularization (EWC [26]), network expansion (MEMO [63]), replay (ER [43], ER-MIR [1], REMIND [20], SCR [31], ODDL [3]), and distillation" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23938" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 49, + 71, + 286, + 201 + ], + "blocks": [ + { + "bbox": [ + 49, + 71, + 286, + 201 + ], + "lines": [ + { + "bbox": [ + 49, + 71, + 286, + 201 + ], + "spans": [ + { + "bbox": [ + 49, + 71, + 286, + 201 + ], + "type": "table", + "html": "
MethodImageNet-1K
DisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EWC (Kirkpatrick et al., 2017)30.1718.7817.0920.15
ER (Rolnick et al., 2019)30.1818.9617.1718.39
ER-MIR (Aljundi et al., 2019)31.6819.8719.3716.30
REMIND (Hayes et al., 2020)32.4724.5917.4219.79
DER++ (Buzzega et al., 2020)31.0818.9823.7323.14
SCR (Mai et al., 2021)26.7213.6019.8215.84
MEMO (Zhou et al., 2023)30.4519.0814.0620.12
X-DER (Boschini et al., 2023)31.6718.1825.1812.51
EARL (Ours)34.3323.1930.5329.48
", + "image_path": "4a92afd0f76460ee44d8922823af0b9d29866dc167005430069c9ea3c666b109.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 46, + 202, + 287, + 224 + ], + "lines": [ + { + "bbox": [ + 46, + 202, + 287, + 224 + ], + "spans": [ + { + "bbox": [ + 46, + 202, + 287, + 224 + ], + "type": "text", + "content": "Table 2. Comparison of online CL methods on Disjoint and Gaussian Scheduled Setup for ImageNet-1K." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 231, + 286, + 291 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 231, + 286, + 291 + ], + "spans": [ + { + "bbox": [ + 46, + 231, + 286, + 291 + ], + "type": "inline_equation", + "content": "(\\mathrm{DER} + + [4], \\mathrm{X - DER}[3])" + }, + { + "bbox": [ + 46, + 231, + 286, + 291 + ], + "type": "text", + "content": ". For more details on the implementation of these methods and a comparison with NCFSCIL [56], which attempts to induce neural collapse in the context of few-shot class incremental learning, please refer to the supplementary material." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": "Implementation details. We use three components to architect our model: a backbone network " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "g(\\cdot)" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": ", a projection MLP " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "p(\\cdot)" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": ", and a fixed ETF classifier " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "\\mathbf{W}_{\\mathrm{ETF}}" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": " (i.e., our model " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": " can be defined as " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "f(x) = p \\circ g(x)" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": "). For the projection layer, we attach an MLP projection layer " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "p_{\\theta_p}" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": " to the output of the backbone network " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "g_{\\theta_g}" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "\\theta_g" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "\\theta_p" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": " denote the parameters of the backbone network and the projection layer, respectively (i.e., the model " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": " can be defined as " + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "inline_equation", + "content": "f(x) = p \\circ g(x)" + }, + { + "bbox": [ + 46, + 303, + 286, + 422 + ], + "type": "text", + "content": "), following [9, 37, 56]. For all methods, we use ResNet-18 [21] as the backbone network." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 422, + 286, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 422, + 286, + 494 + ], + "spans": [ + { + "bbox": [ + 46, + 422, + 286, + 494 + ], + "type": "text", + "content": "Following [27, 59], we employ memory-only training, where a random batch is selected from memory at each iteration. Furthermore, for episodic memory sampling, EARL uses the Greedy Balanced Sampling strategy [40]. We describe the details about hyperparameters and the pseudocode of EARL in Supplementary for the sake of space." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 502, + 104, + 514 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 502, + 104, + 514 + ], + "spans": [ + { + "bbox": [ + 47, + 502, + 104, + 514 + ], + "type": "text", + "content": "5.2. Results" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 521, + 286, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 521, + 286, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 521, + 286, + 628 + ], + "type": "text", + "content": "We first compare the accuracy of online continual learning methods, including EARL, and summarize the results in Table 1. As shown in the table, EARL outperforms other baselines on all benchmarks, both in disjoint and Gaussian-scheduled setups, except " + }, + { + "bbox": [ + 46, + 521, + 286, + 628 + ], + "type": "inline_equation", + "content": "A_{\\mathrm{last}}" + }, + { + "bbox": [ + 46, + 521, + 286, + 628 + ], + "type": "text", + "content": " in ImageNet-1K disjoint setup. In particular, high " + }, + { + "bbox": [ + 46, + 521, + 286, + 628 + ], + "type": "inline_equation", + "content": "A_{\\mathrm{AUC}}" + }, + { + "bbox": [ + 46, + 521, + 286, + 628 + ], + "type": "text", + "content": " suggests that EARL outperforms other methods for all the time that the data stream is provided to the model, which implies that it can be used for inference at anytime." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 629, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 286, + 712 + ], + "type": "text", + "content": "Furthermore, EARL, SCR, ER, MIR, DER, and ODDL do not use task boundary information during training, i.e., task-free, in contrast to EWC, X-DER, MEMO, and REMIND which use task-boundary information, i.e., task-aware. Nevertheless, EARL outperforms these methods even in the disjoint setup where utilizing task boundary information is advantageous due to abrupt distribution shifts" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "type": "text", + "content": "at the task boundaries, except MEMO in ImageNet-1K disjoint. Since MEMO not only uses the task boundary information but also expands the network per task, this extra advantage of using a larger model is emphasized in largescale datasets such as ImageNet which require a large learning capacity of the model. Please refer to the supplementary material for details of the computational budget comparison among the baseline methods." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 171, + 545, + 302 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 171, + 545, + 302 + ], + "spans": [ + { + "bbox": [ + 304, + 171, + 545, + 302 + ], + "type": "text", + "content": "Memory budget. We consider not only the size of episodic memory, but also the size of the model, logits, and other components, following MEMO [63]. In the case of the memory budget for CIFAR-10 and the architecture of ResNet-18 (size of 42.6MB), EARL incurs an additional memory cost of 0.2MB to store feature-residual pairs. EWC requires an additional cost of 85.2MB due to the need to store Fisher Information per parameter and the previous model. MEMO, which expands the network per task, incurs an additional cost of 32MB per task. DER also requires an additional cost of 0.1MB to store logits during distillation." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 311, + 397, + 323 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 311, + 397, + 323 + ], + "spans": [ + { + "bbox": [ + 306, + 311, + 397, + 323 + ], + "type": "text", + "content": "5.3. Ablation study" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "spans": [ + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "text", + "content": "We conduct an ablation study on the two components of EARL, preparatory data training and residual correction, and summarize the results in Table 3. Although both components contribute to performance improvement, preparatory data training shows a larger gain in performance. Training with preparatory data improves the baseline by " + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "inline_equation", + "content": "2.7\\% \\sim 3.3\\%" + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "inline_equation", + "content": "A_{auc}" + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "inline_equation", + "content": "2.1\\% \\sim 4.4\\%" + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "inline_equation", + "content": "A_{last}" + }, + { + "bbox": [ + 304, + 329, + 545, + 436 + ], + "type": "text", + "content": ". When combined with residual correction, we observe further gains across all metrics in both disjoint and Gaussian-scheduled setups." + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 334, + 446, + 504, + 575 + ], + "blocks": [ + { + "bbox": [ + 334, + 446, + 504, + 575 + ], + "lines": [ + { + "bbox": [ + 334, + 446, + 504, + 575 + ], + "spans": [ + { + "bbox": [ + 334, + 446, + 504, + 575 + ], + "type": "image", + "image_path": "5ec652ff9bfca509aaf3d5de8627a380793ab48d2e58d806828c8db6872f8c63.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 584, + 545, + 628 + ], + "lines": [ + { + "bbox": [ + 304, + 584, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 584, + 545, + 628 + ], + "type": "text", + "content": "Figure 5. Average similarity between features of the most recently added class's samples and the closest classifier vectors of the old classes (CIFAR-10, Gaussian Scheduled). Baseline is a vanilla ETF model trained only using episodic memory." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": "For further analysis, Fig. 6 visualizes the cosine similarity between the output features of 50 randomly selected test set samples of novel class '4' and the classifier vectors " + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_i" + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": ". In baseline (a), the features of the class 4 are strongly biased towards the classifier vectors of the old classes (i.e., " + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_0" + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_1" + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_2" + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_3" + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": "), rather than the correct classifier, " + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_4" + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": ". (c)" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "23939" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 60, + 542, + 141 + ], + "blocks": [ + { + "bbox": [ + 51, + 60, + 542, + 141 + ], + "lines": [ + { + "bbox": [ + 51, + 60, + 542, + 141 + ], + "spans": [ + { + "bbox": [ + 51, + 60, + 542, + 141 + ], + "type": "table", + "html": "
METHODCIFAR-10CIFAR-100
DisjointGaussian-ScheduledDisjointGaussian-Scheduled
\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)\\(A_{\\text{AUC}} \\uparrow\\)\\(A_{\\text{last}} \\uparrow\\)
EARL (Ours)78.61±0.7266.01±2.2669.62±0.1970.91±1.9757.42±1.2444.60±0.6548.19±0.6146.10±0.26
(-) RC77.78±0.5265.52±1.6368.37±0.1070.17±1.0856.28±1.4044.29±1.0447.05±0.7146.07±0.52
(-) RC & PDT74.77±0.7761.10±3.1265.60±0.2567.39±0.7852.91±1.0541.08±0.6044.34±0.5544.45±0.48
", + "image_path": "91716e7bf6d09db1e5161c74dcb538b16eeaa3438f4750be450e1a49d0242171.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 56, + 145, + 536, + 157 + ], + "lines": [ + { + "bbox": [ + 56, + 145, + 536, + 157 + ], + "spans": [ + { + "bbox": [ + 56, + 145, + 536, + 157 + ], + "type": "text", + "content": "Table 3. Ablation Study. RC and PDT refer to preparatory data training (Sec. 4.2) and the residual correction (Sec. 4.3), respectively." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 66, + 161, + 529, + 342 + ], + "blocks": [ + { + "bbox": [ + 66, + 161, + 529, + 342 + ], + "lines": [ + { + "bbox": [ + 66, + 161, + 529, + 342 + ], + "spans": [ + { + "bbox": [ + 66, + 161, + 529, + 342 + ], + "type": "image", + "image_path": "bb4af209ee29559e28e20df0cd9d4917e821b0cefa5027490e79b3335dce7a7c.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "lines": [ + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "spans": [ + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "text", + "content": "Figure 6. Cosine similarity between features " + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "inline_equation", + "content": "\\hat{f}(x)" + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "text", + "content": " for class 4 and the ETF classifier vectors " + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_i" + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "text", + "content": " at the " + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "inline_equation", + "content": "50^{th}" + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "text", + "content": " iteration after the introduction of class 4 in the Gaussian Scheduled CIFAR-10 setup. As we can see in the cyan highlighted box, EARL promotes the convergence of " + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "inline_equation", + "content": "\\hat{f}(x)" + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "text", + "content": " for class 4 toward the ground truth classifier vector " + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_4" + }, + { + "bbox": [ + 46, + 346, + 547, + 381 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 390, + 287, + 414 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 390, + 287, + 414 + ], + "spans": [ + { + "bbox": [ + 46, + 390, + 287, + 414 + ], + "type": "text", + "content": "When residual correction is used, some samples show high similarity with " + }, + { + "bbox": [ + 46, + 390, + 287, + 414 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_4" + }, + { + "bbox": [ + 46, + 390, + 287, + 414 + ], + "type": "text", + "content": " compared to the baseline." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "spans": [ + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "text", + "content": "However, since incorrect residuals can be added due to the bias problem, more samples have high similarity with " + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_2" + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "text", + "content": " than the baseline (i.e., wrong residuals are added). (b) When using preparatory data training, the bias toward " + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_0" + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_1" + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "text", + "content": " classes significantly decreases compared to the baseline. Fig. 5 also shows the effect of preparatory data, which reduces the similarity between the novel class features and existing classes. (d) Using both residual correction and preparatory data training shows a remarkable alignment with the ground truth classifier " + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_4" + }, + { + "bbox": [ + 46, + 415, + 288, + 548 + ], + "type": "text", + "content": ". A more detailed analysis of the ablation results is provided in the Supple." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 560, + 119, + 572 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 560, + 119, + 572 + ], + "spans": [ + { + "bbox": [ + 47, + 560, + 119, + 572 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 581, + 287, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 581, + 287, + 688 + ], + "spans": [ + { + "bbox": [ + 46, + 581, + 287, + 688 + ], + "type": "text", + "content": "To better learn online data in a continuous data stream without multiple epoch training, we propose to induce neural collapse, which aligns last layer activations to the corresponding classifier vectors in the representation space. Unlike in offline CL, it is challenging to induce neural collapse in online CL due to insufficient training epochs and continuously streamed new data. We first observe that the bias of the new class towards existing classes slows the convergence of features toward neural collapse." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "content": "To mitigate the bias, we propose synthesizing preparatory data for unseen classes by transforming the samples" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 390, + 545, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 390, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 304, + 390, + 545, + 498 + ], + "type": "text", + "content": "of existing classes. Using the preparatory data for training, we accelerate neural collapse in an online CL scenario. Additionally, we propose residual correction to resolve the remaining discrepancy toward neural collapse at inference, which arises due to the continuous stream of new data. In our empirical evaluations, the proposed methods outperform state-of-the-art online CL methods in various datasets and setups, especially with high performance on anytime inference." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 510, + 546, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 546, + 617 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 546, + 617 + ], + "type": "text", + "content": "Limitations and Future Work. Since our work uses ETF structure, it has an inherent limitation that the number of possible classifier vectors in the ETF classifier is limited by the dimension of the embedding space. Considering lifelong learning, where the number of new classes goes to infinity, it is interesting to explore the idea of dynamically expanding the ETF structure so that the model can continually learn the ever-increasing number of concepts in the real world." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": "Acknowledgement. This work was partly supported by the NRF grant (No.2022R1A2C4002300, " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " ) and IITP grants (No.2022-0-00077 " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "(10\\%)" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " , No.2022-0-00113 " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "(25\\%)" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " , No.2022-0-00959 " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "(10\\%)" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " , No.2022-0- 00871 " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "(10\\%)" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " , No.2020-0-01361 " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "(5\\%)" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " , Yonsei AI), No.2021-0-01343 " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "(5\\%)" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " SNU AI), No.2021-0-02068 " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "(5\\%)" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " , AI Innov. Hub), No.2022-0-00951 " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "(5\\%)" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " ) funded by the Korea government (MSIT) and CARAI grant funded by DAPA and ADD (UD230017TD) " + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "inline_equation", + "content": "5 \\%" + }, + { + "bbox": [ + 304, + 626, + 547, + 713 + ], + "type": "text", + "content": " . This work was done while J. Choi was with Yonsei University and partially while H. Lee, M. Seo and H. Kim was with LG AI Research." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23940" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 712 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "type": "text", + "content": "[1] Rahaf Aljundi, Klaas Kelchtermans, and Tinne Tuytelaars. 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In NeurIPS, 2021. 1, 3" + } + ] + } + ], + "index": 31 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "text", + "content": "23942" + } + ] + } + ], + "index": 33 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_content_list.json b/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..d2a77259ea8f9379c520ec1081dfa60b39a91f19 --- /dev/null +++ b/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_content_list.json @@ -0,0 +1,1580 @@ +[ + { + "type": "text", + "text": "Learning Group Activity Features Through Person Attribute Prediction", + "text_level": 1, + "bbox": [ + 122, + 130, + 846, + 151 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Chihiro Nakatani1 Hiroaki Kawashima2 Norimichi Ukita1", + "bbox": [ + 238, + 179, + 727, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{1}$ Toyota Technological Institute, Japan $^{2}$ University of Hyogo, Japan", + "bbox": [ + 204, + 198, + 764, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 251, + 312, + 266 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "This paper proposes Group Activity Feature (GAF) learning in which features of multi-person activity are learned as a compact latent vector. Unlike prior work in which the manual annotation of group activities is required for supervised learning, our method learns the GAF through person attribute prediction without group activity annotations. By learning the whole network in an end-to-end manner so that the GAF is required for predicting the person attributes of people in a group, the GAF is trained as the features of multi-person activity. As a person attribute, we propose to use a person's action class and appearance features because the former is easy to annotate due to its simplicity, and the latter requires no manual annotation. In addition, we introduce a location-guided attribute prediction to disentangle the complex GAF for extracting the features of each target person properly. Various experimental results validate that our method outperforms SOTA methods quantitatively and qualitatively on two public datasets. Visualization of our GAF also demonstrates that our method learns the GAF representing fined-grained group activity classes. Code: https://github.com/ chihina/GAFL-CVPR2024.", + "bbox": [ + 75, + 282, + 473, + 614 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 647, + 207, + 662 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "A group activity is defined as what multiple people jointly engage in. Group activities are important targets in image and video understanding, such as team plays in sports [36], conversations in social scenes [3], and people flows in surveillance cameras [28].", + "bbox": [ + 75, + 672, + 468, + 748 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Group Activity Recognition (GAR), in which a frame or video is classified into either of the predefined group activity classes, has been widely investigated in recent years [2, 3, 6, 9, 11, 14, 16, 19, 21, 25, 29, 37-40, 42, 45]. All of these GAR methods are based on supervised learning that requires the ground-truth group activities, as shown in Fig. 1 (a). In addition, it is known that person action recognition, which is also achieved based on a supervised learning manner, supports GAR [2, 3, 6, 9, 11, 14, 19, 21, 25, 29, 37, 38, 40, 45].", + "bbox": [ + 75, + 750, + 470, + 900 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/7f6601462bd530010594814630216b53bcf9b9f5b9341342e5dd96c348038b2e.jpg", + "image_caption": [ + "(b) Ours (group activity feature learning with person attribute)", + "Figure 1. Difference between annotations for GAR and our group activity feature learning. (a) Supervised GAR employs group activity annotations that are difficult due to various similar group activities. (b-1) Our GAF learning employs person action annotations that are easy due to their simplicity. (b-2) We further propose annotation-free GAF learning with person appearance features." + ], + "image_footnote": [], + "bbox": [ + 501, + 250, + 880, + 445 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Such supervised learning requires manually-annotated training data. For GAR, group activity annotations are required. In addition to labor-intensive and erroneous annotations, a difficulty peculiar to GAR is the complexity of the group activities. For example, while only four elemental group activity classes are annotated in a widely-used team-sport dataset [15], they may be insufficient for practical purposes such as tactical analysis (e.g., 200 or more plays are defined in American Football [8]). That is, more fine-grained activity classes are required for several applications of group activity analysis. It is, however, difficult to correctly define and annotate such complex, fine-grained activity classes, even manually, because of visually minor but highly contextual differences among those classes.", + "bbox": [ + 496, + 582, + 892, + 792 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Such difficulty in manual annotations of group activities motivates us to learn a Group Activity Feature (GAF) in which features of multi-person activity are learned as a compact latent vector without group activity annotations. We note here that GAFs, which represent the complex features of multi-person activity, may have enough information to predict the attributes of each person in a group.", + "bbox": [ + 496, + 795, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "18233", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "With this regard, this paper proposes GAF learning using person attribute (e.g., action and appearance), which is easier to provide compared with the complex group activity annotation, as shown in Fig. 1 (b). With the person attribute related to the group activity, the GAF can narrow down the possible attribute of each person. For example, Fig. 2, in which a spike is observed, shows that the possible person action enclosed by the purple rectangle (i.e., digging) can be narrowed down by the GAF representing the scene context (i.e., spike group activity) with the person's location.", + "bbox": [ + 75, + 90, + 472, + 242 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "As a person attribute for our GAF learning, person action can be used as shown in Fig. 1 (b-1). This is because person action is strongly related to the group activities and is essential to support GAR as mentioned above. However, manual annotations are still required to use person action. While the annotations of person action are easier than the one of group activities defined with complex people interaction, such action annotations are still labor-intensive.", + "bbox": [ + 75, + 243, + 468, + 364 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To alleviate such difficulty in manual annotations, we also propose to learn GAF through the task of appearance feature prediction of each person in a group without manual annotations, as shown in Fig. 1 (b-2). While the reduction of annotation cost have been studied widely, including active learning [13, 26], few-shot learning [35, 44], and self-supervised learning [4, 5, 7, 10, 18, 23, 24, 32, 33, 41, 43], we follows the framework of self-supervised learning, where supervision signals are derived from the input data and any manual annotations are unnecessary.", + "bbox": [ + 75, + 364, + 470, + 516 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our novel contributions are summarized as follows:", + "bbox": [ + 96, + 517, + 437, + 531 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- GAF learning through person attribute prediction: Unlike supervised GAR, we propose GAF learning through person attribute prediction without group activity annotations. This paper proposes its two variants:", + "- GAF Learning with Person Action Classes (GAFL-PAC): As a person attribute, we utilize person action classes, which are more easily annotated than group activities defined with complex inter-people interactions (Fig. 1 (b-1)). In addition, for practical use of GAR and other group-related applications, the annotations of person actions are already given in general [3, 14].", + "- GAF Learning with Person Appearance Features (GAFL-PAF): We also utilize person appearance features that can be obtained by a pre-trained model (e.g., VGG) without manual annotation (Fig. 1 (b-2)). The appearance features are suitable as a person attribute due to the high relationship with multi-person activity.", + "- Fine granularity of our GAF: With the GAF learning through person attribute prediction, our method can learn fine-grained GAF that represents visual-subtle but important differences that are not represented in a manually-defined activity class, as shown in Fig. 6.", + "- Location-Guided Person Attribute Prediction Using GAF: While predicting the person attribute using the" + ], + "bbox": [ + 76, + 537, + 470, + 901 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/6935fa9b6710768106f1d178a1f279956a3a1f84aa75ce6d259eefa88ef4fc8c.jpg", + "image_caption": [ + "Figure 2. Example of our group activity feature learning. In this example, a group activity feature is learned to extract the scene context (i.e., spike group activity) through prediction of person attribute (e.g., digging). See Fig. 3 for the detailed architecture." + ], + "image_footnote": [], + "bbox": [ + 501, + 89, + 883, + 181 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "GAF is required in our method, extracting the features of each target person from the GAF is difficult. This is because the GAF represents complex features of multi-person activity. This feature extraction is achieved by location guidance in which each person's location feature is embedded into the GAF with positional encoding.", + "bbox": [ + 511, + 275, + 890, + 367 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 381, + 640, + 396 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Group Activity Recognition", + "text_level": 1, + "bbox": [ + 500, + 406, + 748, + 422 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Supervision by group activity labels. While we propose the GAF learning without group activity annotations (Fig. 1 (b)), various GAR methods supervised by group activity annotations (i.e., Fig. 1 (a)) have been proposed. In [16, 40, 42], only the labels of group activity are required for training. In [16], a group activity is recognized from a whole image without any person features. Kim et al [42] and Yan et al [40] employ the set of person features as input for a Graph Neural Network (GNN) as with [6, 37].", + "bbox": [ + 496, + 429, + 890, + 565 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Supervision by the labels of person action and group activity. Different from the aforementioned methods only with group activity supervision, the GAR network is jointly trained with the person action recognition network in [2, 3, 6, 9, 11, 14, 19, 21, 25, 29, 37, 45] for augmenting GAR. In [6, 37], GNN models the interactions between person features. In [9, 11, 19, 29, 45], Transformer [31] improves modeling the interactions between person features for GAR.", + "bbox": [ + 496, + 566, + 890, + 686 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "While all of the methods introduced in Sec. 2.1 employ the annotation of group activities, our method learns GAF without group activity labels. Following the success of interaction modeling in [9, 11, 19, 29, 45], we also learn the GAF with Transformer.", + "bbox": [ + 496, + 686, + 890, + 761 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.2. Self-supervised Representation Learning", + "text_level": 1, + "bbox": [ + 500, + 771, + 848, + 787 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Image-based pretext tasks. Most pretext tasks for self-supervised image representation utilize the transformation of original images. In Gidaris et al. [10], Zhang et al. [43], and Larsson et al. [18], each original image is rotated, affinely- and projectively-transformed, and grayscale, respectively. The image representation model is trained so that the model undoes each image. While these meth", + "bbox": [ + 496, + 794, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "18234", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "ods [10, 18, 43] employ a whole image, patches extracted from the image are used in [4, 23, 24]. Doersch et al. [4] predict the spatial configuration (i.e., relative positions) of randomly-sampled patches. In Noroozi et al. [23], jigsaw puzzles in which all patches of an image are shuffled are solved. Pathak et al. [24] inpaint partially-erased images.", + "bbox": [ + 75, + 90, + 468, + 181 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Video-based pretext tasks. While the image-based methods can be applied to a video, video-specific pretext tasks are also proposed in [5, 7, 32, 33, 41]. In Yao et al. [41] and Wang et al. [33], the paces of video clips are arbitrarily changed (e.g., normal, half, and double speeds), and video representation is learned by solving a pace prediction problem. In Fernando et al. [7], sequential video clips are randomly reordered, and video representation is learned so that these reordered and original clips can be classified. Wang et al. [32] employ appearance cues as well as motion statistics for spatial-temporal representation learning.", + "bbox": [ + 75, + 184, + 470, + 349 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "While all of the representation learning methods introduced above extract low-level image features for various downstream tasks such as general image/video classification and prediction, our method focuses on features useful for group-related tasks (e.g., group scene retrieval and clustering). As with our method, Ibrahim et al. [14] aims to extract multi-person scene features through GNN in an unsupervised manner, while the relation of each person to a group activity is not fully captured. Our method incorporates such intimate relations between individuals and group activity (e.g., digging in a spike scene) using the task of location-guided person attribute prediction from a GAF.", + "bbox": [ + 75, + 353, + 468, + 534 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Proposed Method", + "text_level": 1, + "bbox": [ + 76, + 556, + 250, + 573 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Our GAF learning network consists of three stages, (a), (b), and (c) (Fig. 3). In stage (a), the features of each person are extracted (Sec. 3.1). In stage (b), the features of several people are masked (i.e., removed) during training for GAF enhancement (Sec. 3.2). Then, the masked person features are fed into the transformer-based GAF learning network (Sec. 3.3). In stage (c), the attribute of each person is predicted from the GAF with location guidance (Sec. 3.4).", + "bbox": [ + 75, + 584, + 468, + 705 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Person Feature Extractor", + "text_level": 1, + "bbox": [ + 76, + 723, + 308, + 738 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Overview. As shown in Fig. 3 (a), the set of person features $\\pmb{F}_{set} \\in \\mathbb{R}^{T \\times N \\times C}$ are extracted from images. $\\pmb{F}_{set}$ is composed of the features of $N$ people obtained from $T$ frames in a video. $C$ is the dimension of person $p$ 's feature vector, $\\pmb{F}_{ind}^p \\in \\mathbb{R}^C$ , indicated by a blue cuboid in Fig. 3 (a). $\\pmb{F}_{ind}^p$ consists of appearance features (denoted by $\\pmb{F}_{app}^p \\in \\mathbb{R}^C$ ) and location features (denoted by $\\pmb{F}_{loc}^p \\in \\mathbb{R}^C$ ) in our implementation because their effectiveness is validated for GAR [9, 11, 19, 25, 45], while other features (e.g., body keypoints) can also be used.", + "bbox": [ + 75, + 750, + 468, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Detail. $F_{app}^{p}$ is extracted by the following three steps, as with [42]. First, a feature map is extracted from the whole image by VGG [27]. Then, RoIAlign [12] is applied with the bounding box of each person to obtain the feature map for each person. Finally, the feature map of each person is embedded into $C$ -dimensional appearance features with a linear transformation. From the $F_{app}^{p}$ of $N$ people between $T$ frames, we construct $F_{app} \\in \\mathbb{R}^{T \\times N \\times C}$ . In addition to $F_{app}$ , $F_{loc}^{p}$ is also essential to understand the spatial structure of a group, as $F_{loc}^{p}$ is used for GAR [9, 11, 25, 37, 45]. As with [11], the center point of each person bounding box, $(x,y)$ , is embedded into $F_{loc}^{p}$ by a spatial positional encoding so that $F_{loc} \\in \\mathbb{R}^{T \\times N \\times C}$ whose dimension is equal to $F_{app}$ . Finally, $F_{loc}$ is elementwise added with $F_{app}$ to obtain the set of person features, $F_{set}$ . Here, we denote person $p$ 's features in $T$ frames (i.e., a slice of $F_{set}$ ) as $F_{ind}^{p} \\in \\mathbb{R}^{T \\times C}$ ( $p \\in \\{1,\\dots,N\\}$ ) and, similarly, person $p$ 's location features in $T$ frames (i.e., a slice of $F_{loc}$ ) as $F_{loc}^{p} \\in \\mathbb{R}^{T \\times C}$ ( $p \\in \\{1,\\dots,N\\}$ ).", + "bbox": [ + 496, + 90, + 890, + 381 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Masked Person Modeling (MPM)", + "text_level": 1, + "bbox": [ + 498, + 388, + 792, + 404 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Overview. In the set of person features $\\mathbf{F}_{\\text{set}}$ , the features of randomly sampled people are masked (e.g., $\\mathbf{F}_{\\text{ind}}^{1}$ indicated by a black cuboid in Fig. 3(b)) during training. By extracting such features with our Masked Person Modeling (MPM), our network is expected to learn the features of the interaction between unmasked people for predicting the attribute of the masked person.", + "bbox": [ + 496, + 411, + 890, + 517 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Detail. The binary mask for $p$ -th person (denoted by $M^p \\in \\mathbb{R}^{T \\times C}$ ) is initialized by filling 1 in all values. Then, $N_{mask}$ people to be masked are randomly sampled from all $N$ people in a scene. All values in $M^p$ for the randomly sampled people are updated with 0.", + "bbox": [ + 498, + 536, + 890, + 611 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "From the all $M^p$ of $N$ people, we construct $M = [M^1,\\dots ,M^N ]\\in \\mathbb{R}^{T\\times N\\times C}$ . Then, $M$ is elementwise multiplied by $\\pmb{F}_{set}$ to obtain the masked person features $\\pmb{F}_{mask}$ for our GAF training. Note that all values in $M$ are set to be 0 during inference to preserve features of all people in a GAF.", + "bbox": [ + 498, + 611, + 890, + 700 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.3. Group Activity Feature Learning Network", + "text_level": 1, + "bbox": [ + 498, + 710, + 861, + 727 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Overview. The GAF $G$ is extracted from the set of masked person features $\\pmb{F}_{mask}$ obtained in Sec. 3.2. For this GAF learning, we employ Transformer to model spatial- and temporal-interactions between people in accordance with [11, 19]. Our transformer-based GAF learning network consists of two branches (i.e., TS and ST branches) similar to [11]. As shown in Fig. 3, the Temporal Transformer encoder $(T^T)$ and the Spatial Transformer encoder $(T^S)$ are used in both branches, but they are placed in reverse order in the two branches. The combination of these two branches can model the spatial-temporal interactions", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "18235", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/9acc36c397b402613e00111436e8561dca356b09e9d7cacf7bb8ba65e83d93c2.jpg", + "image_caption": [ + "Figure 3. Overview of our GAF learning network. (a) Person feature extractor. The person feature is composed of appearance and location features. (b) GAF learning network. The GAF is learned from extracted people features. (c) Location-guided attribute prediction network with the GAF. The attribute of each person is predicted from the location feature of the person and the GAF extracted in (b)." + ], + "image_footnote": [], + "bbox": [ + 76, + 85, + 890, + 281 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "between people, as proven in GAR [11, 19]. While the transformer-based network is used in our method, the network can be replaced with any SOTA network without difficulties because the stage (i.e., Fig. 3 (b)) is modularized.", + "bbox": [ + 75, + 366, + 468, + 428 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Detail. $\\mathbf{F}_{mask}$ is independently fed into the TS and ST branches to acquire $\\mathbf{F}_{mask}^{TS}$ and $\\mathbf{F}_{mask}^{ST}$ , respectively:", + "bbox": [ + 75, + 445, + 468, + 477 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {F} _ {\\text {m a s k}} ^ {T S} = T ^ {S} \\left(\\boldsymbol {F} _ {\\text {m a s k}} + M L P \\left(T ^ {T} \\left(\\boldsymbol {F} _ {\\text {m a s k}}\\right)\\right)\\right) \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 120, + 481, + 468, + 500 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {F} _ {\\text {m a s k}} ^ {S T} = T ^ {T} \\left(\\boldsymbol {F} _ {\\text {m a s k}} + M L P \\left(T ^ {S} \\left(\\boldsymbol {F} _ {\\text {m a s k}}\\right)\\right)\\right) \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 122, + 502, + 468, + 520 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $MLP$ denotes the multi-layer perceptron. $G^{TS} \\in \\mathbb{R}^C$ and $G^{ST} \\in \\mathbb{R}^C$ are obtained from $F_{mask}^{TS}$ and $F_{mask}^{ST}$ , respectively, by the Temporal Max Pooling (denoted by $P^{TM}$ ) and the Spatial Max Pooling (denoted by $P^{SM}$ ), as with previous methods [9, 37]:", + "bbox": [ + 76, + 527, + 468, + 604 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {G} ^ {T S} = P ^ {S M} \\left(P ^ {T M} \\left(\\boldsymbol {F} _ {\\text {m a s k}} ^ {T S}\\right)\\right) \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 169, + 609, + 468, + 628 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {G} ^ {S T} = P ^ {S M} \\left(P ^ {T M} \\left(\\boldsymbol {F} _ {\\text {m a s k}} ^ {S T}\\right)\\right) \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 173, + 630, + 468, + 648 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Finally, $G^{TS}$ and $G^{ST}$ are concatenated to obtain the final GAF $G\\in \\mathbb{R}^{2C}$ as follows:", + "bbox": [ + 75, + 656, + 468, + 686 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {G} = \\boldsymbol {G} ^ {T S} \\oplus \\boldsymbol {G} ^ {S T} \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 207, + 693, + 468, + 710 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "During training, $G$ is fed into the attribute prediction network (denoted by $APN$ ), as shown in Fig. 3 (c). By backpropagating a loss used in this person attribute prediction not only inside $APN$ but also across the whole network shown in Fig. 3, $G$ can be trained as the GAF. The details of person attribute prediction and the loss used in this prediction are described in Sec. 3.4 and Sec.3.5, respectively.", + "bbox": [ + 75, + 719, + 468, + 824 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "After predicting $G$ in inference, $G$ can be used in various ways such as a pretrained model for downstream supervised tasks and unsupervised learning tasks (e.g., retrieval and clustering), as mentioned in Sec. 1. The effectiveness of $G$ in these tasks is validated in Sec. 4.", + "bbox": [ + 75, + 825, + 468, + 898 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.4. Attribute Prediction with GAF", + "text_level": 1, + "bbox": [ + 500, + 366, + 772, + 381 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Overview. Using $G$ obtained in Sec. 3.3, the attribute of each person is predicted by the $APN$ (Fig. 3 (c)). To predict the attribute of $p$ -th person, we use their location features (i.e., $F_{loc}^{p}$ ) as guidance for attribute prediction from $G$ .", + "bbox": [ + 498, + 393, + 892, + 455 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Detail. $G$ is fed into the attribute prediction network with the location of each person as follows:", + "bbox": [ + 498, + 493, + 890, + 523 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {A} _ {P R E D} ^ {p} = A P N (\\boldsymbol {G}, \\boldsymbol {F} _ {l o c} ^ {p}) \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 602, + 542, + 890, + 560 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $A_{PRED}^p \\in \\mathbb{R}^{T \\times R}$ denotes the predicted attribute of each person obtained from $G$ with their location. The dimension of $R$ changes depending on the type of the predicted person attribute as follows:", + "bbox": [ + 498, + 579, + 890, + 640 + ], + "page_idx": 3 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "(i) Person action: $R$ is the number of action classes and the $A_{PRED}^{p}$ represents predicted action probabilities.", + "(ii) Person appearance features: $R$ is the dimension of the appearance features (i.e., $C$ ) extracted in Sec. 3.1." + ], + "bbox": [ + 500, + 643, + 888, + 709 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.5. Loss Function", + "text_level": 1, + "bbox": [ + 500, + 729, + 643, + 743 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The whole network is trained with a loss function (denoted by $\\mathcal{L}$ ) for attribute prediction as a pretext task as follows:", + "bbox": [ + 498, + 757, + 890, + 787 + ], + "page_idx": 3 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "(i) Person action: When the person attribute is the action, $\\mathcal{L}$ is the cross-entropy loss: $\\mathcal{L} = \\mathcal{L}_{CE}(\\pmb{A}_{PRED}^{p},\\pmb{A}_{GT}^{p})$ , where $\\pmb{A}_{GT}^{p}$ denotes the ground-truth one-hot vector for action.", + "(ii) Person appearance features: For appearance features, $\\mathcal{L}$ is the mean squared loss function: $\\mathcal{L} = \\mathcal{L}_{MSE}(A_{PRED}^p, A_{GT}^p)$ , where $A_{GT}^p$ denotes the extracted appearance features (i.e., $F_{app}$ ) shown in Sec. 3.1." + ], + "bbox": [ + 500, + 790, + 890, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "18236", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 89, + 209, + 107 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Datasets", + "text_level": 1, + "bbox": [ + 76, + 114, + 179, + 128 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The Volleyball dataset, which contains highly correlated players, is mainly used to validate the effectiveness of our GAF learning. The Collective Activity dataset is also used to validate the generality of our method in Sec. 4.4, while people in this dataset are not highly related to each other compared with the Volleyball dataset.", + "bbox": [ + 75, + 138, + 468, + 228 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "VolleyBall Dataset (VBD) [15] consists of 4,830 sequences extracted from 55 games. Each sequence is annotated with one of the predefined eight group activity classes, i.e., Left-spike, Right-spike, Left-set, Right-set, Left-pass, Right-pass, Left-winpoint, and Right-winpoint. While each sequence has 41 frames, its center 20 frames have annotations with the full-body bounding boxes of all players and their action classes, i.e., Waiting, Setting, Digging, Falling, Spiking, Jumping, Moving, Blocking, and Standing.", + "bbox": [ + 75, + 229, + 468, + 364 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Collective Activity Dataset (CAD) [3] contains 44 videos. In each video, every ten frames are annotated with person action classes, i.e., NA, Crossing, Waiting, Queuing, Walking, and Talking, and their bounding boxes. The group activity class is determined by the largest number of person actions in each frame, while the NA class is not included as a group activity class. We follow the previous methods [34, 42] to merge the Crossing and Walking into Moving.", + "bbox": [ + 75, + 364, + 468, + 501 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Evaluation Protocols", + "text_level": 1, + "bbox": [ + 76, + 511, + 272, + 526 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2.1 Evaluation Tasks", + "text_level": 1, + "bbox": [ + 76, + 535, + 250, + 549 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The quality of the estimated GAF is verified with the following two types of retrieval tasks.", + "bbox": [ + 75, + 559, + 468, + 589 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Action set retrieval. We employ the same action set retrieval task as in [14]. Action IoU in [14] evaluates the similarity of action structures between query and retrieved images based on the overlap of action distributions. If the IoU exceeds a predefined threshold (e.g., 0.5), the query and retrieved images are regarded as matched. However, in this action IoU, all action classes are counted equally without weights, although the action class distribution is imbalanced (e.g., the percentage of \"standing\" people, who are less informative for tactics, is over $68\\%$ in VBD).", + "bbox": [ + 75, + 590, + 468, + 739 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To resolve this class imbalanced problem, we propose Action Frequency-Inverse Scene Frequency (AF-ISF) inspired by Term Frequency-Inverse Document Frequency (TF-IDF [1]) that evaluates the importance of a word in a document. In AF-ISF, each scene is represented by a feature vector in which each value is computed from frequency statics of action classes as follows:", + "bbox": [ + 75, + 741, + 468, + 845 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {F} \\boldsymbol {V} ^ {i} = \\left[ F V _ {1} ^ {i}, F V _ {m} ^ {i}, \\dots , F V _ {M} ^ {i} \\right] \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 163, + 858, + 468, + 877 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nF V _ {m} ^ {i} = A F _ {m} ^ {i} \\cdot I S F _ {m} \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 233, + 878, + 468, + 897 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $i$ and $M$ denote the image index and the number of actions, respectively. $AF_{m}^{i}$ is the frequency of $m$ -th action class in each image. $ISF_{M}$ is the inverse frequency of each action class in the dataset. In AF-ISF, the similarity between $\\pmb{F}\\pmb{V}^{j}$ and $\\pmb{F}\\pmb{V}^{k}$ , where $j$ and $k$ denote the IDs of query and retrieved images, evaluates the similarity of action structure of the two images. If the cosine similarity exceeds a predefined threshold (e.g., 0.5), the query and retrieved images are regarded as matched as with the Action IoU.", + "bbox": [ + 500, + 90, + 890, + 226 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "While AF-ISF alleviates the action class imbalanced problem, several action classes are distinctive for representing a group scene even if the action distribution is balanced (e.g., \"Spiking\" is more important than \"Falling\" in VBD). Due to this problem, AF-ISF is still improper for the contextual representation of group scenes.", + "bbox": [ + 498, + 229, + 890, + 320 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Group activity retrieval. Based on the discussion above, we propose to further evaluate whether or not the group activity class of a query scene matches that of the retrieved scene. Note that the group activity annotations are given to the test data (i.e., all query and retrieved images) only for this evaluation and are not used in our GAF learning.", + "bbox": [ + 498, + 323, + 890, + 414 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2.2 Evaluation Metrics", + "text_level": 1, + "bbox": [ + 500, + 449, + 687, + 463 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "With IoU and AF-ISF in the action set retrieval and group activity matching in the group activity retrieval, we compute the Hit@K used in [14]. In addition, the mean Average Precision (mAP) is used in the action set retrieval as with [14]. For mAP, the Euclidean distance of $G$ between query and retrieved images is used as the confidence indicator.", + "bbox": [ + 498, + 478, + 890, + 569 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3. Training Details", + "text_level": 1, + "bbox": [ + 500, + 587, + 661, + 604 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Our network is optimized by Adam [17] with $\\beta_{1} = 0.9$ , $\\beta_{2} = 0.999$ , and $\\epsilon = 10^{-8}$ . The whole image is resized into $320 \\times 640$ and $240 \\times 360$ for VBD and CAD, respectively. We employ the VGG-19 and Inception-v3 models as a person feature extractor (Fig. 3 (a)) for VBD and CAD, respectively. While the person feature extractor trained on person action recognition is fine-tuned through our GAF learning in GAFL-PAC, we freeze the person feature extractor trained on ImageNet in GAFL-PAF following the previous method [14]. Our APN consists of three fully-connected layers. As for the other details, we follow the widely used setting [42]. See the details in the supplementary material.", + "bbox": [ + 498, + 613, + 890, + 795 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.4. Comparative Experiments", + "text_level": 1, + "bbox": [ + 500, + 814, + 738, + 830 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We compare our methods with other methods by the following three types of experimental results: (1) the results of retrieval (Sec. 4.4.1), (2) the results of GAR (Sec. 4.4.2), and (3) the visualized distributions of GAFs (Sec. 4.4.3).", + "bbox": [ + 498, + 839, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "18237", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/bc50dac7a5ba55030a33129854b8b39817aa2af514cbb7208010bb1facd3a163.jpg", + "table_caption": [ + "Table 1. Quantitative comparison of retrieval on the VolleyBall Dataset (VBD). The results obtained in two experimental settings (i.g., GAFL-PAC and GAFL-PAF) are separated by double lines. The best result in each column is colored in red. Results obtained by the concatenation of output features (i.e., $\\mathbf{F}_{grp}^{TS}$ and $\\mathbf{F}_{grp}^{ST}$ ) and $\\mathbf{G}$ are denoted as \"Ours-ind\" and \"Ours-grp\", respectively." + ], + "table_footnote": [], + "table_body": "
Retrieval typeAction set (IoU [14])Action set (AF-IDF)Group activity
MethodHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3
GAFL-PACHiGCIN [40]74.384.989.555.759.873.680.330.550.066.374.5
DIN [42]79.790.193.460.274.585.288.339.357.073.181.1
Dual-AI [11]67.684.791.656.972.683.788.653.064.476.582.0
Ours-ind82.791.695.059.179.086.889.845.682.788.891.3
Ours-grp83.092.795.564.280.188.491.559.984.889.691.8
GAFL-PAFB1-Compact128 [14]57.975.784.345.841.360.871.429.330.348.059.9
B2-VGG19 [14]63.880.686.846.846.765.875.729.435.453.665.0
HRN [14]60.978.686.046.940.860.972.928.731.247.057.6
Ours-ind64.280.888.345.050.469.377.630.155.072.379.2
Ours-grp64.882.790.346.452.371.481.031.461.175.182.4
", + "bbox": [ + 76, + 135, + 919, + 311 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/a0344f132ec27e7a8c82916ba43d49717bbfabf421484d2088d96b59dbd8aed2.jpg", + "table_caption": [ + "Table 2. Quantitative comparison of retrieval on the Collective Activity Dataset (CAD)." + ], + "table_footnote": [], + "table_body": "
Retrieval typeAction set (IoU [14])Action set (AF-IDF)Group activity
MethodHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3
GAFL-PACHiGCIN [40]80.885.489.757.981.085.289.361.686.188.891.9
DIN [42]71.474.174.951.590.192.794.052.890.892.593.2
Dual-AI [11]61.072.576.761.585.586.988.182.782.184.184.7
Ours-ind76.282.689.478.994.895.695.982.294.995.495.7
Ours-grp81.890.793.569.996.196.596.693.994.995.696.3
GAFL-PAFB1-Compact128 [14]48.860.368.238.081.888.289.752.682.488.490.1
B2-VGG19 [14]53.661.666.135.371.180.383.846.772.280.884.2
HRN [14]37.150.158.622.253.264.872.534.254.064.872.4
Ours-ind67.681.385.953.383.788.990.257.588.591.291.9
Ours-grp52.770.374.146.474.080.582.660.179.281.082.0
", + "bbox": [ + 76, + 334, + 919, + 512 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.4.1 Retrieval", + "text_level": 1, + "bbox": [ + 76, + 537, + 194, + 551 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To validate the effectiveness of the GAF for group representation, the set of person features (i.e., the concatenation of $\\pmb{F}_{\\text{grp}}^{TS}$ and $\\pmb{F}_{\\text{grp}}^{ST}$ in Fig. 3 (b)) is also evaluated. Specifically, the output features of $P^{TM}$ in the TS and ST branches $(\\pmb{F}_{\\text{grp}}^{TS}$ and $\\pmb{F}_{\\text{grp}}^{ST}$ in Fig. 3) are concatenated and also used for retrieval in our method. Results obtained by the concatenation of output features (i.e., $\\pmb{F}_{\\text{grp}}^{TS}$ and $\\pmb{F}_{\\text{grp}}^{ST}$ ) and $\\pmb{G}$ are denoted as \"Ours-ind\" and \"Ours-grp\", respectively.", + "bbox": [ + 75, + 563, + 468, + 686 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Volleyball dataset (GAFL-PAC). Our method is compared with the SOTA GAR methods [11, 40, 42] which are only trained with person action labels as with our method. Table 1 (top) shows that our method is best in action set and group activity retrieval. The results validate that our method learns features about the action structure and the group activity of a scene into the compact latent vector (i.e., $\\pmb{G}$ ) efficiently. The large gain in the group activity retrieval shows that the features of multi-person activity are learned in our GAF in contrast to the SOTA GAR methods [11, 40, 42] where the set of person features is used for the retrieval.", + "bbox": [ + 75, + 686, + 468, + 852 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Volleyball dataset (GAFL-PAF). Our method is compared with the SOTA method [14], the only existing GAF learning method using no person-action and group-activity an", + "bbox": [ + 76, + 854, + 468, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "notations, and baseline methods as with [14]. From Table 1 (bottom), we see that our method performs best in all metrics except that \"HRN\" is better than our method in mAP of Action set (IoU). However, the performance difference is small (i.e., 46.9 and 46.4 in \"HRN\" and \"Ours-grp,\" respectively). Furthermore, our method is better than \"HRN\" in Action set (AF-IDF). From these results, we can say that our GAF is better even in the action set retrieval. Regarding group activity retrieval, our method significantly outperforms the SOTA method. The results validate that our method learns the contextual features of multi-person activity better than the SOTA method.", + "bbox": [ + 496, + 537, + 890, + 717 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Collective activity dataset (GAFL-PAC). The results in GAFL-PAC on CAD are shown in Table 2 (top). The results validate that our method is better than Dual-AI [11] in all metrics. While \"Ours-grp\" is better than \"Ours-ind\" in most metrics, \"Ours-ind\" is better in mAP of Action set (IoU). The action set (IoU) evaluates the similarity of the number of people, so the results may come from that the change in the number of people between scenes on this dataset is addressed well in \"Ours-ind.\" Specifically, we can consider that such information about the number of people may be preserved well in \"Ours-ind.\" where the set of person features is used for retrieval.", + "bbox": [ + 496, + 719, + 892, + 898 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "18238", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/9af64f66df6e96ff08ba693cb82ee26ef20019adc78b472895718d2f1ef77618.jpg", + "image_caption": [ + "Figure 4. Confusion matrices of GAR by nearest neighbor retrieval on VBD and CAD in GAFL-PAF. Each row and column show the ground-truth and recognized group activity, respectively. Results of the other methods are shown in the supplementary material." + ], + "image_footnote": [], + "bbox": [ + 83, + 88, + 472, + 291 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Collective activity dataset (GAFL-PAF). Table 2 (bottom) shows that our method is the best in all metrics among the other methods. The results validate the wide applicability of GAF learned even in general scenes included in CAD. While \"Ours-grp\" is better than \"Ours-ind\" on VBD, \"Ours-ind\" is better on CAD. These opposite results may come from the difference between the number of people in each image. While $N = 12$ people are observed in most images in VBD, around five people on average on CAD. As the number of features in $F_{grp}^{TS}$ and $F_{grp}^{ST}$ increase in proportion to the number of observed people, the difficulty in learning $F_{grp}^{TS}$ and $F_{grp}^{ST}$ becomes higher. Since this learning difficulty might occur on VBD, spatial max pooling used in \"Ours-grp\" is effective for reducing the feature dimension from $NC$ of $F_{grp}^{TS}$ and $F_{grp}^{ST}$ to $C$ of $G^{TS}$ and $G^{ST}$ .", + "bbox": [ + 75, + 382, + 470, + 612 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4.2 Group Activity Recognition", + "text_level": 1, + "bbox": [ + 76, + 632, + 323, + 648 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "While no group annotation is used in our GAF learning, the group activity class retrieved by Hit@1, which is equal to 1-nearest neighbor classification, can be regarded as the result of GAR, as done in [20]. While results only in GAFL-PAF are shown in this section, results in GAFL-PAC are available in the supplementary material.", + "bbox": [ + 75, + 657, + 468, + 748 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Volleyball dataset (GAFL-PAF). As shown in Fig. 4, our method outperforms \"B2-VGG19\" in all group activity classes except for L-winpoint. While \"B2-VGG19\" is better than \"Ours\" in L-winpoint shown at the bottom right of each confusion matrix, \"B2-VGG19\" often misrecognizes the R-winpoint scene as L-winpoint, as shown in the red rectangle cells. Left-spike and Right-spike are especially recognized better in our method than the others. This superiority of our method can be interpreted as follows. In Left-spike and Right-spike, spiking and blocking players who", + "bbox": [ + 75, + 750, + 468, + 901 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/22d15987b9bc3a75c7db44d5cccc4d438f711c63d78cbde5416d33d00843aca8.jpg", + "image_caption": [ + "Figure 5. Visualization of the learned GAF on VBD and CAD in GAFL-PAF. The color of each sample shows the ground-truth of the group activity label corresponding to each test sample." + ], + "image_footnote": [], + "bbox": [ + 504, + 88, + 890, + 241 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/88c1db0cd07774cdcc5ba7eec9dadbb3256f7fecb28dbbcceb272d86020c7e7c.jpg", + "image_caption": [ + "Figure 6. Visualization of the learned GAF on VBD in GAFL-PAC. The magenta data points (i.e., \"L-pass\") are divided into two sub-categories based on the context (i.e., whether the receiving is caused by the spiking or serving of the opposite player)." + ], + "image_footnote": [], + "bbox": [ + 503, + 308, + 890, + 506 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "are distinctive both in appearance and location cues are always observed. Since these distinctive people are important in predicting not only their attributes but also the attributes of other people, the features of these distinctive people are extracted well even in the compact latent vector (i.e., GAF). Collective activity dataset (GAFL-PAF). The confusion matrices are shown in Fig. 4. The results show that our method is the best in all activity classes. In particular, while VGG19 gets many false negatives in Moving, the number of false negatives in Moving of our method is almost zero.", + "bbox": [ + 496, + 598, + 890, + 750 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4.3 Visualization of Learned GAFs", + "text_level": 1, + "bbox": [ + 498, + 770, + 769, + 784 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The distribution of learned GAFs in all test images is visualized in a 2D space by t-SNE [30]. The color of each point shows its annotated group activity class. Figure 5 shows that our method can learn the GAFs better than the other methods because (1) while the inner-class variance is small, the inter-class variance is large, and (2) the data points of similar group activities (e.g., Left-pass and Left-set) are closer.", + "bbox": [ + 496, + 794, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "18239", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/b992a116519be9053f9443dce951db86c642ca3cacf38c22de7be0e001c06311.jpg", + "image_caption": [ + "Figure 7. Performance changes depending on the number of masking people on VBD." + ], + "image_footnote": [], + "bbox": [ + 81, + 89, + 464, + 186 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/69bd9e093cd5450e1f4fa0d40bb9189f12ebd235115ce2c33dcb24b03d28c549.jpg", + "table_caption": [ + "Table 3. Effectiveness of our location-guidance on VBD. Results obtained by \"Ours-grp\" are shown as \"Ours.\"" + ], + "table_footnote": [], + "table_body": "
Retrieval typeAction set (IoU)Action set (AF-IDF)Group activity
MethodHit@1Hit@1Hit@1
GAFL-PACOurs w/o Floc80.075.669.5
Ours83.080.184.8
GAFL-PAFOurs w/o Floc64.151.753.2
Ours64.852.361.1
", + "bbox": [ + 78, + 281, + 470, + 395 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Our GAFs in GAL-PAC on VBD are also shown in Fig. 6. This figure shows that data points with the same group activity labels are divided into sub-activities. For example, L-pass indicated by magenta data points are divided into two clusters. While the cluster enclosed by the orange rectangle represents L-pass where the person is receiving a ball from the opposite spiker, the other cluster enclosed by the light blue rectangle represents L-pass where the person is receiving a ball from the opposite server. As shown in this example, our GAFs are learned well enough to represent visually subtle but important differences that are not represented in the manually defined activity classes.", + "bbox": [ + 75, + 422, + 467, + 603 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.5. Detailed analysis", + "text_level": 1, + "bbox": [ + 76, + 617, + 241, + 633 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Comparison of the number of masked persons. We explore the optimal number of masked people (i.e., $N_{mask}$ ) for our MPM. For this comparison, we change $N_{mask}$ from 0 to $N - 1$ . $N_{mask} = 0$ means that $F_{set}$ is directly fed into the transformer encoder without the MPM.", + "bbox": [ + 75, + 642, + 467, + 715 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Figure 7 shows that the performance changes depending on $N_{mask}$ on VBD. The best performance is obtained when $N_{mask}$ is the middle number (i.e., 5 and 6 in the GAFL-PAC and GAFL-PAF, respectively), while the performance gain from $N_{mask} = 0$ is insignificant. On the other hand, we can also see that the performance with a large masking ratio (i.e., $N_{mask} \\in \\{10, 11\\}$ ) drops. These results reveal that the extreme difficulty in the attribute prediction of the masked person from a few non-masked people leads GAF learning to failure.", + "bbox": [ + 75, + 718, + 467, + 867 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effect of location-guidance in GAF learning. We ablate $F_{loc}^{p}$ which is used for guidance to extract the features of", + "bbox": [ + 76, + 869, + 467, + 901 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/48e72d2d1b73f0a94eecbde58dd8a3f5246101155e203cac81c82b581f819ef1.jpg", + "table_caption": [ + "Table 4. Comparison with supervised GAR. Double lines separate the results obtained by VBD and CAD." + ], + "table_footnote": [], + "table_body": "
DatasetMethodAccuracy
VBDDual-AI [11]92.1
Ours w/ group activity labels92.4
CADDual-AI [11]94.1
Ours w/ group activity labels96.6
", + "bbox": [ + 513, + 125, + 874, + 210 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "each person in the action prediction network in Fig. 3 (c) (see also Sec. 3.4) on VBD.", + "bbox": [ + 498, + 236, + 888, + 263 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In GAFL-PAC, \"Ours\" is better than \"Ours w/o $F_{loc}^{p}$ \" in the all metrics. In particular, the performance gain in the group activity retrieval is large. We can interpret the reason as follows. In \"Ours w/o $F_{loc}^{p}$ ,\" only $G$ is used to predict the attribute of each person in a scene. It makes the model predict not the attribute of each person but the attribute distribution of people in a scene. Therefore, the GAF can be used for action set retrieval to some extent because the similarity of action distribution is evaluated in this retrieval. However, spatial interaction between people is not learned in the GAF. It causes a significant performance drop in the group activity retrieval. In GAFL-PAF, we can also see the high-performance gain of \"Ours\" in the group activity retrieval. From these results, we can conclude that our location guidance is important for learning group activity.", + "bbox": [ + 496, + 265, + 888, + 491 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Fine-tuning for Group Activity Recognition. Table 4 shows that the comparison of \"Dual-AI\" and \"Ours\" with group activity labels on VBD and CAD. In \"Dual-AI,\" the network is trained with group activity labels from scratch. In \"Ours,\" after the pretraining by our GAF learning without the group activity supervision, the network is fine-tuned for GAR with group activity labels.", + "bbox": [ + 496, + 492, + 888, + 597 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "On both datasets, our method is better than \"Dual-AI.\" In particular, on CAD, the GAR accuracy obtained by our method is $2.5\\%$ better than the GAR accuracy obtained by \"Dual-AI.\" The results demonstrate that our GAF learning is effective as a pre-training for supervised GAR.", + "bbox": [ + 498, + 598, + 888, + 672 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Concluding Remarks", + "text_level": 1, + "bbox": [ + 500, + 686, + 700, + 704 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Instead of group activity annotations which is difficult due to a variety of similar group activities, our method learns GAF through person attribute prediction without group activity annotations. Quantitative comparisons and visualized results show that our method can learn informative GAF compared with other methods on the two public datasets.", + "bbox": [ + 496, + 713, + 888, + 801 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "While our method outperforms all the other methods in our experiments not only for GAF learning but also for GAR, our method is understandably inferior to GAR supervised by group activity annotations. Exploring other pretext tasks such as predicting the joint attention of a group (e.g., [22]) is important future work for further GAF enhancement.", + "bbox": [ + 496, + 801, + 888, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "18240", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 122, + 173, + 137 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Akiko N. Aizawa. 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In ECCV, 2022. 1, 2, 3" + ], + "bbox": [ + 78, + 90, + 467, + 573 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "18242", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_model.json b/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_model.json new file mode 100644 index 0000000000000000000000000000000000000000..2db5fbec45f2d04f37d5ad2e78b5fadf47d1891c --- /dev/null +++ b/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_model.json @@ -0,0 +1,2178 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.123, + 0.131, + 0.848, + 0.152 + ], + "angle": 0, + "content": "Learning Group Activity Features Through Person Attribute Prediction" + }, + { + "type": "text", + "bbox": [ + 0.24, + 0.18, + 0.728, + 0.198 + ], + "angle": 0, + "content": "Chihiro Nakatani1 Hiroaki Kawashima2 Norimichi Ukita1" + }, + { + "type": "text", + "bbox": [ + 0.205, + 0.199, + 0.765, + 0.218 + ], + "angle": 0, + "content": "\\(^{1}\\) Toyota Technological Institute, Japan \\(^{2}\\) University of Hyogo, Japan" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.252, + 0.313, + 0.267 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.284, + 0.474, + 0.616 + ], + "angle": 0, + "content": "This paper proposes Group Activity Feature (GAF) learning in which features of multi-person activity are learned as a compact latent vector. Unlike prior work in which the manual annotation of group activities is required for supervised learning, our method learns the GAF through person attribute prediction without group activity annotations. By learning the whole network in an end-to-end manner so that the GAF is required for predicting the person attributes of people in a group, the GAF is trained as the features of multi-person activity. As a person attribute, we propose to use a person's action class and appearance features because the former is easy to annotate due to its simplicity, and the latter requires no manual annotation. In addition, we introduce a location-guided attribute prediction to disentangle the complex GAF for extracting the features of each target person properly. Various experimental results validate that our method outperforms SOTA methods quantitatively and qualitatively on two public datasets. Visualization of our GAF also demonstrates that our method learns the GAF representing fined-grained group activity classes. Code: https://github.com/ chihina/GAFL-CVPR2024." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.648, + 0.208, + 0.663 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.673, + 0.47, + 0.749 + ], + "angle": 0, + "content": "A group activity is defined as what multiple people jointly engage in. Group activities are important targets in image and video understanding, such as team plays in sports [36], conversations in social scenes [3], and people flows in surveillance cameras [28]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Group Activity Recognition (GAR), in which a frame or video is classified into either of the predefined group activity classes, has been widely investigated in recent years [2, 3, 6, 9, 11, 14, 16, 19, 21, 25, 29, 37-40, 42, 45]. All of these GAR methods are based on supervised learning that requires the ground-truth group activities, as shown in Fig. 1 (a). In addition, it is known that person action recognition, which is also achieved based on a supervised learning manner, supports GAR [2, 3, 6, 9, 11, 14, 19, 21, 25, 29, 37, 38, 40, 45]." + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.25, + 0.882, + 0.446 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.59, + 0.447, + 0.885, + 0.457 + ], + "angle": 0, + "content": "(b) Ours (group activity feature learning with person attribute)" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.472, + 0.892, + 0.556 + ], + "angle": 0, + "content": "Figure 1. Difference between annotations for GAR and our group activity feature learning. (a) Supervised GAR employs group activity annotations that are difficult due to various similar group activities. (b-1) Our GAF learning employs person action annotations that are easy due to their simplicity. (b-2) We further propose annotation-free GAF learning with person appearance features." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.583, + 0.893, + 0.794 + ], + "angle": 0, + "content": "Such supervised learning requires manually-annotated training data. For GAR, group activity annotations are required. In addition to labor-intensive and erroneous annotations, a difficulty peculiar to GAR is the complexity of the group activities. For example, while only four elemental group activity classes are annotated in a widely-used team-sport dataset [15], they may be insufficient for practical purposes such as tactical analysis (e.g., 200 or more plays are defined in American Football [8]). That is, more fine-grained activity classes are required for several applications of group activity analysis. It is, however, difficult to correctly define and annotate such complex, fine-grained activity classes, even manually, because of visually minor but highly contextual differences among those classes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.894, + 0.902 + ], + "angle": 0, + "content": "Such difficulty in manual annotations of group activities motivates us to learn a Group Activity Feature (GAF) in which features of multi-person activity are learned as a compact latent vector without group activity annotations. We note here that GAFs, which represent the complex features of multi-person activity, may have enough information to predict the attributes of each person in a group." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18233" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.243 + ], + "angle": 0, + "content": "With this regard, this paper proposes GAF learning using person attribute (e.g., action and appearance), which is easier to provide compared with the complex group activity annotation, as shown in Fig. 1 (b). With the person attribute related to the group activity, the GAF can narrow down the possible attribute of each person. For example, Fig. 2, in which a spike is observed, shows that the possible person action enclosed by the purple rectangle (i.e., digging) can be narrowed down by the GAF representing the scene context (i.e., spike group activity) with the person's location." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.244, + 0.47, + 0.365 + ], + "angle": 0, + "content": "As a person attribute for our GAF learning, person action can be used as shown in Fig. 1 (b-1). This is because person action is strongly related to the group activities and is essential to support GAR as mentioned above. However, manual annotations are still required to use person action. While the annotations of person action are easier than the one of group activities defined with complex people interaction, such action annotations are still labor-intensive." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.366, + 0.471, + 0.517 + ], + "angle": 0, + "content": "To alleviate such difficulty in manual annotations, we also propose to learn GAF through the task of appearance feature prediction of each person in a group without manual annotations, as shown in Fig. 1 (b-2). While the reduction of annotation cost have been studied widely, including active learning [13, 26], few-shot learning [35, 44], and self-supervised learning [4, 5, 7, 10, 18, 23, 24, 32, 33, 41, 43], we follows the framework of self-supervised learning, where supervision signals are derived from the input data and any manual annotations are unnecessary." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.518, + 0.439, + 0.532 + ], + "angle": 0, + "content": "Our novel contributions are summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.539, + 0.47, + 0.599 + ], + "angle": 0, + "content": "- GAF learning through person attribute prediction: Unlike supervised GAR, we propose GAF learning through person attribute prediction without group activity annotations. This paper proposes its two variants:" + }, + { + "type": "text", + "bbox": [ + 0.09, + 0.599, + 0.472, + 0.705 + ], + "angle": 0, + "content": "- GAF Learning with Person Action Classes (GAFL-PAC): As a person attribute, we utilize person action classes, which are more easily annotated than group activities defined with complex inter-people interactions (Fig. 1 (b-1)). In addition, for practical use of GAR and other group-related applications, the annotations of person actions are already given in general [3, 14]." + }, + { + "type": "text", + "bbox": [ + 0.091, + 0.706, + 0.47, + 0.796 + ], + "angle": 0, + "content": "- GAF Learning with Person Appearance Features (GAFL-PAF): We also utilize person appearance features that can be obtained by a pre-trained model (e.g., VGG) without manual annotation (Fig. 1 (b-2)). The appearance features are suitable as a person attribute due to the high relationship with multi-person activity." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.796, + 0.47, + 0.871 + ], + "angle": 0, + "content": "- Fine granularity of our GAF: With the GAF learning through person attribute prediction, our method can learn fine-grained GAF that represents visual-subtle but important differences that are not represented in a manually-defined activity class, as shown in Fig. 6." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.871, + 0.47, + 0.902 + ], + "angle": 0, + "content": "- Location-Guided Person Attribute Prediction Using GAF: While predicting the person attribute using the" + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.539, + 0.472, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.09, + 0.885, + 0.182 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.193, + 0.892, + 0.249 + ], + "angle": 0, + "content": "Figure 2. Example of our group activity feature learning. In this example, a group activity feature is learned to extract the scene context (i.e., spike group activity) through prediction of person attribute (e.g., digging). See Fig. 3 for the detailed architecture." + }, + { + "type": "text", + "bbox": [ + 0.512, + 0.276, + 0.892, + 0.368 + ], + "angle": 0, + "content": "GAF is required in our method, extracting the features of each target person from the GAF is difficult. This is because the GAF represents complex features of multi-person activity. This feature extraction is achieved by location guidance in which each person's location feature is embedded into the GAF with positional encoding." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.382, + 0.642, + 0.397 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.407, + 0.749, + 0.423 + ], + "angle": 0, + "content": "2.1. Group Activity Recognition" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.43, + 0.892, + 0.566 + ], + "angle": 0, + "content": "Supervision by group activity labels. While we propose the GAF learning without group activity annotations (Fig. 1 (b)), various GAR methods supervised by group activity annotations (i.e., Fig. 1 (a)) have been proposed. In [16, 40, 42], only the labels of group activity are required for training. In [16], a group activity is recognized from a whole image without any person features. Kim et al [42] and Yan et al [40] employ the set of person features as input for a Graph Neural Network (GNN) as with [6, 37]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.567, + 0.892, + 0.687 + ], + "angle": 0, + "content": "Supervision by the labels of person action and group activity. Different from the aforementioned methods only with group activity supervision, the GAR network is jointly trained with the person action recognition network in [2, 3, 6, 9, 11, 14, 19, 21, 25, 29, 37, 45] for augmenting GAR. In [6, 37], GNN models the interactions between person features. In [9, 11, 19, 29, 45], Transformer [31] improves modeling the interactions between person features for GAR." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.687, + 0.892, + 0.762 + ], + "angle": 0, + "content": "While all of the methods introduced in Sec. 2.1 employ the annotation of group activities, our method learns GAF without group activity labels. Following the success of interaction modeling in [9, 11, 19, 29, 45], we also learn the GAF with Transformer." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.772, + 0.849, + 0.789 + ], + "angle": 0, + "content": "2.2. Self-supervised Representation Learning" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Image-based pretext tasks. Most pretext tasks for self-supervised image representation utilize the transformation of original images. In Gidaris et al. [10], Zhang et al. [43], and Larsson et al. [18], each original image is rotated, affinely- and projectively-transformed, and grayscale, respectively. The image representation model is trained so that the model undoes each image. While these meth" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18234" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.183 + ], + "angle": 0, + "content": "ods [10, 18, 43] employ a whole image, patches extracted from the image are used in [4, 23, 24]. Doersch et al. [4] predict the spatial configuration (i.e., relative positions) of randomly-sampled patches. In Noroozi et al. [23], jigsaw puzzles in which all patches of an image are shuffled are solved. Pathak et al. [24] inpaint partially-erased images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.185, + 0.471, + 0.351 + ], + "angle": 0, + "content": "Video-based pretext tasks. While the image-based methods can be applied to a video, video-specific pretext tasks are also proposed in [5, 7, 32, 33, 41]. In Yao et al. [41] and Wang et al. [33], the paces of video clips are arbitrarily changed (e.g., normal, half, and double speeds), and video representation is learned by solving a pace prediction problem. In Fernando et al. [7], sequential video clips are randomly reordered, and video representation is learned so that these reordered and original clips can be classified. Wang et al. [32] employ appearance cues as well as motion statistics for spatial-temporal representation learning." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.354, + 0.47, + 0.535 + ], + "angle": 0, + "content": "While all of the representation learning methods introduced above extract low-level image features for various downstream tasks such as general image/video classification and prediction, our method focuses on features useful for group-related tasks (e.g., group scene retrieval and clustering). As with our method, Ibrahim et al. [14] aims to extract multi-person scene features through GNN in an unsupervised manner, while the relation of each person to a group activity is not fully captured. Our method incorporates such intimate relations between individuals and group activity (e.g., digging in a spike scene) using the task of location-guided person attribute prediction from a GAF." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.557, + 0.251, + 0.574 + ], + "angle": 0, + "content": "3. Proposed Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.585, + 0.469, + 0.706 + ], + "angle": 0, + "content": "Our GAF learning network consists of three stages, (a), (b), and (c) (Fig. 3). In stage (a), the features of each person are extracted (Sec. 3.1). In stage (b), the features of several people are masked (i.e., removed) during training for GAF enhancement (Sec. 3.2). Then, the masked person features are fed into the transformer-based GAF learning network (Sec. 3.3). In stage (c), the attribute of each person is predicted from the GAF with location guidance (Sec. 3.4)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.724, + 0.31, + 0.739 + ], + "angle": 0, + "content": "3.1. Person Feature Extractor" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Overview. As shown in Fig. 3 (a), the set of person features \\( \\pmb{F}_{set} \\in \\mathbb{R}^{T \\times N \\times C} \\) are extracted from images. \\( \\pmb{F}_{set} \\) is composed of the features of \\( N \\) people obtained from \\( T \\) frames in a video. \\( C \\) is the dimension of person \\( p \\)'s feature vector, \\( \\pmb{F}_{ind}^p \\in \\mathbb{R}^C \\), indicated by a blue cuboid in Fig. 3 (a). \\( \\pmb{F}_{ind}^p \\) consists of appearance features (denoted by \\( \\pmb{F}_{app}^p \\in \\mathbb{R}^C \\)) and location features (denoted by \\( \\pmb{F}_{loc}^p \\in \\mathbb{R}^C \\)) in our implementation because their effectiveness is validated for GAR [9, 11, 19, 25, 45], while other features (e.g., body keypoints) can also be used." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.382 + ], + "angle": 0, + "content": "Detail. \\(F_{app}^{p}\\) is extracted by the following three steps, as with [42]. First, a feature map is extracted from the whole image by VGG [27]. Then, RoIAlign [12] is applied with the bounding box of each person to obtain the feature map for each person. Finally, the feature map of each person is embedded into \\(C\\)-dimensional appearance features with a linear transformation. From the \\(F_{app}^{p}\\) of \\(N\\) people between \\(T\\) frames, we construct \\(F_{app} \\in \\mathbb{R}^{T \\times N \\times C}\\). In addition to \\(F_{app}\\), \\(F_{loc}^{p}\\) is also essential to understand the spatial structure of a group, as \\(F_{loc}^{p}\\) is used for GAR [9, 11, 25, 37, 45]. As with [11], the center point of each person bounding box, \\((x,y)\\), is embedded into \\(F_{loc}^{p}\\) by a spatial positional encoding so that \\(F_{loc} \\in \\mathbb{R}^{T \\times N \\times C}\\) whose dimension is equal to \\(F_{app}\\). Finally, \\(F_{loc}\\) is elementwise added with \\(F_{app}\\) to obtain the set of person features, \\(F_{set}\\). Here, we denote person \\(p\\)'s features in \\(T\\) frames (i.e., a slice of \\(F_{set}\\)) as \\(F_{ind}^{p} \\in \\mathbb{R}^{T \\times C}\\) (\\(p \\in \\{1,\\dots,N\\}\\)) and, similarly, person \\(p\\)'s location features in \\(T\\) frames (i.e., a slice of \\(F_{loc}\\)) as \\(F_{loc}^{p} \\in \\mathbb{R}^{T \\times C}\\) (\\(p \\in \\{1,\\dots,N\\}\\))." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.389, + 0.794, + 0.405 + ], + "angle": 0, + "content": "3.2. Masked Person Modeling (MPM)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.412, + 0.892, + 0.518 + ], + "angle": 0, + "content": "Overview. In the set of person features \\( \\mathbf{F}_{\\text{set}} \\), the features of randomly sampled people are masked (e.g., \\( \\mathbf{F}_{\\text{ind}}^{1} \\) indicated by a black cuboid in Fig. 3(b)) during training. By extracting such features with our Masked Person Modeling (MPM), our network is expected to learn the features of the interaction between unmasked people for predicting the attribute of the masked person." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.537, + 0.892, + 0.612 + ], + "angle": 0, + "content": "Detail. The binary mask for \\( p \\)-th person (denoted by \\( M^p \\in \\mathbb{R}^{T \\times C} \\)) is initialized by filling 1 in all values. Then, \\( N_{mask} \\) people to be masked are randomly sampled from all \\( N \\) people in a scene. All values in \\( M^p \\) for the randomly sampled people are updated with 0." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.612, + 0.892, + 0.702 + ], + "angle": 0, + "content": "From the all \\(M^p\\) of \\(N\\) people, we construct \\(M = [M^1,\\dots ,M^N ]\\in \\mathbb{R}^{T\\times N\\times C}\\). Then, \\(M\\) is elementwise multiplied by \\(\\pmb{F}_{set}\\) to obtain the masked person features \\(\\pmb{F}_{mask}\\) for our GAF training. Note that all values in \\(M\\) are set to be 0 during inference to preserve features of all people in a GAF." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.712, + 0.862, + 0.728 + ], + "angle": 0, + "content": "3.3. Group Activity Feature Learning Network" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Overview. The GAF \\(G\\) is extracted from the set of masked person features \\(\\pmb{F}_{mask}\\) obtained in Sec. 3.2. For this GAF learning, we employ Transformer to model spatial- and temporal-interactions between people in accordance with [11, 19]. Our transformer-based GAF learning network consists of two branches (i.e., TS and ST branches) similar to [11]. As shown in Fig. 3, the Temporal Transformer encoder \\((T^T)\\) and the Spatial Transformer encoder \\((T^S)\\) are used in both branches, but they are placed in reverse order in the two branches. The combination of these two branches can model the spatial-temporal interactions" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18235" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.087, + 0.891, + 0.282 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.299, + 0.893, + 0.342 + ], + "angle": 0, + "content": "Figure 3. Overview of our GAF learning network. (a) Person feature extractor. The person feature is composed of appearance and location features. (b) GAF learning network. The GAF is learned from extracted people features. (c) Location-guided attribute prediction network with the GAF. The attribute of each person is predicted from the location feature of the person and the GAF extracted in (b)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.367, + 0.47, + 0.429 + ], + "angle": 0, + "content": "between people, as proven in GAR [11, 19]. While the transformer-based network is used in our method, the network can be replaced with any SOTA network without difficulties because the stage (i.e., Fig. 3 (b)) is modularized." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.446, + 0.47, + 0.478 + ], + "angle": 0, + "content": "Detail. \\( \\mathbf{F}_{mask} \\) is independently fed into the TS and ST branches to acquire \\( \\mathbf{F}_{mask}^{TS} \\) and \\( \\mathbf{F}_{mask}^{ST} \\), respectively:" + }, + { + "type": "equation", + "bbox": [ + 0.122, + 0.482, + 0.469, + 0.5 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {F} _ {\\text {m a s k}} ^ {T S} = T ^ {S} \\left(\\boldsymbol {F} _ {\\text {m a s k}} + M L P \\left(T ^ {T} \\left(\\boldsymbol {F} _ {\\text {m a s k}}\\right)\\right)\\right) \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.124, + 0.503, + 0.469, + 0.521 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {F} _ {\\text {m a s k}} ^ {S T} = T ^ {T} \\left(\\boldsymbol {F} _ {\\text {m a s k}} + M L P \\left(T ^ {S} \\left(\\boldsymbol {F} _ {\\text {m a s k}}\\right)\\right)\\right) \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.528, + 0.47, + 0.605 + ], + "angle": 0, + "content": "where \\( MLP \\) denotes the multi-layer perceptron. \\( G^{TS} \\in \\mathbb{R}^C \\) and \\( G^{ST} \\in \\mathbb{R}^C \\) are obtained from \\( F_{mask}^{TS} \\) and \\( F_{mask}^{ST} \\), respectively, by the Temporal Max Pooling (denoted by \\( P^{TM} \\)) and the Spatial Max Pooling (denoted by \\( P^{SM} \\)), as with previous methods [9, 37]:" + }, + { + "type": "equation", + "bbox": [ + 0.171, + 0.61, + 0.469, + 0.629 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {G} ^ {T S} = P ^ {S M} \\left(P ^ {T M} \\left(\\boldsymbol {F} _ {\\text {m a s k}} ^ {T S}\\right)\\right) \\tag {3}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.174, + 0.631, + 0.469, + 0.65 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {G} ^ {S T} = P ^ {S M} \\left(P ^ {T M} \\left(\\boldsymbol {F} _ {\\text {m a s k}} ^ {S T}\\right)\\right) \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.657, + 0.469, + 0.687 + ], + "angle": 0, + "content": "Finally, \\(G^{TS}\\) and \\(G^{ST}\\) are concatenated to obtain the final GAF \\(G\\in \\mathbb{R}^{2C}\\) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.209, + 0.694, + 0.469, + 0.712 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {G} = \\boldsymbol {G} ^ {T S} \\oplus \\boldsymbol {G} ^ {S T} \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.469, + 0.825 + ], + "angle": 0, + "content": "During training, \\( G \\) is fed into the attribute prediction network (denoted by \\( APN \\)), as shown in Fig. 3 (c). By backpropagating a loss used in this person attribute prediction not only inside \\( APN \\) but also across the whole network shown in Fig. 3, \\( G \\) can be trained as the GAF. The details of person attribute prediction and the loss used in this prediction are described in Sec. 3.4 and Sec.3.5, respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.826, + 0.469, + 0.899 + ], + "angle": 0, + "content": "After predicting \\( G \\) in inference, \\( G \\) can be used in various ways such as a pretrained model for downstream supervised tasks and unsupervised learning tasks (e.g., retrieval and clustering), as mentioned in Sec. 1. The effectiveness of \\( G \\) in these tasks is validated in Sec. 4." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.367, + 0.774, + 0.382 + ], + "angle": 0, + "content": "3.4. Attribute Prediction with GAF" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.394, + 0.893, + 0.456 + ], + "angle": 0, + "content": "Overview. Using \\( G \\) obtained in Sec. 3.3, the attribute of each person is predicted by the \\( APN \\) (Fig. 3 (c)). To predict the attribute of \\( p \\)-th person, we use their location features (i.e., \\( F_{loc}^{p} \\)) as guidance for attribute prediction from \\( G \\)." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.494, + 0.892, + 0.525 + ], + "angle": 0, + "content": "Detail. \\(G\\) is fed into the attribute prediction network with the location of each person as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.604, + 0.544, + 0.892, + 0.561 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {A} _ {P R E D} ^ {p} = A P N (\\boldsymbol {G}, \\boldsymbol {F} _ {l o c} ^ {p}) \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.58, + 0.892, + 0.641 + ], + "angle": 0, + "content": "where \\(A_{PRED}^p \\in \\mathbb{R}^{T \\times R}\\) denotes the predicted attribute of each person obtained from \\(G\\) with their location. The dimension of \\(R\\) changes depending on the type of the predicted person attribute as follows:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.645, + 0.89, + 0.676 + ], + "angle": 0, + "content": "(i) Person action: \\( R \\) is the number of action classes and the \\( A_{PRED}^{p} \\) represents predicted action probabilities." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.679, + 0.89, + 0.71 + ], + "angle": 0, + "content": "(ii) Person appearance features: \\( R \\) is the dimension of the appearance features (i.e., \\( C \\)) extracted in Sec. 3.1." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.645, + 0.89, + 0.71 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.731, + 0.645, + 0.744 + ], + "angle": 0, + "content": "3.5. Loss Function" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.758, + 0.892, + 0.788 + ], + "angle": 0, + "content": "The whole network is trained with a loss function (denoted by \\(\\mathcal{L}\\)) for attribute prediction as a pretext task as follows:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.791, + 0.892, + 0.838 + ], + "angle": 0, + "content": "(i) Person action: When the person attribute is the action, \\(\\mathcal{L}\\) is the cross-entropy loss: \\(\\mathcal{L} = \\mathcal{L}_{CE}(\\pmb{A}_{PRED}^{p},\\pmb{A}_{GT}^{p})\\), where \\(\\pmb{A}_{GT}^{p}\\) denotes the ground-truth one-hot vector for action." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.84, + 0.892, + 0.902 + ], + "angle": 0, + "content": "(ii) Person appearance features: For appearance features, \\(\\mathcal{L}\\) is the mean squared loss function: \\(\\mathcal{L} = \\mathcal{L}_{MSE}(A_{PRED}^p, A_{GT}^p)\\), where \\(A_{GT}^p\\) denotes the extracted appearance features (i.e., \\(F_{app}\\)) shown in Sec. 3.1." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.791, + 0.892, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18236" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.077, + 0.09, + 0.21, + 0.108 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.115, + 0.181, + 0.13 + ], + "angle": 0, + "content": "4.1. Datasets" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.139, + 0.47, + 0.229 + ], + "angle": 0, + "content": "The Volleyball dataset, which contains highly correlated players, is mainly used to validate the effectiveness of our GAF learning. The Collective Activity dataset is also used to validate the generality of our method in Sec. 4.4, while people in this dataset are not highly related to each other compared with the Volleyball dataset." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.23, + 0.469, + 0.365 + ], + "angle": 0, + "content": "VolleyBall Dataset (VBD) [15] consists of 4,830 sequences extracted from 55 games. Each sequence is annotated with one of the predefined eight group activity classes, i.e., Left-spike, Right-spike, Left-set, Right-set, Left-pass, Right-pass, Left-winpoint, and Right-winpoint. While each sequence has 41 frames, its center 20 frames have annotations with the full-body bounding boxes of all players and their action classes, i.e., Waiting, Setting, Digging, Falling, Spiking, Jumping, Moving, Blocking, and Standing." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.366, + 0.47, + 0.502 + ], + "angle": 0, + "content": "Collective Activity Dataset (CAD) [3] contains 44 videos. In each video, every ten frames are annotated with person action classes, i.e., NA, Crossing, Waiting, Queuing, Walking, and Talking, and their bounding boxes. The group activity class is determined by the largest number of person actions in each frame, while the NA class is not included as a group activity class. We follow the previous methods [34, 42] to merge the Crossing and Walking into Moving." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.512, + 0.274, + 0.527 + ], + "angle": 0, + "content": "4.2. Evaluation Protocols" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.536, + 0.251, + 0.55 + ], + "angle": 0, + "content": "4.2.1 Evaluation Tasks" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.56, + 0.469, + 0.59 + ], + "angle": 0, + "content": "The quality of the estimated GAF is verified with the following two types of retrieval tasks." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.591, + 0.469, + 0.741 + ], + "angle": 0, + "content": "Action set retrieval. We employ the same action set retrieval task as in [14]. Action IoU in [14] evaluates the similarity of action structures between query and retrieved images based on the overlap of action distributions. If the IoU exceeds a predefined threshold (e.g., 0.5), the query and retrieved images are regarded as matched. However, in this action IoU, all action classes are counted equally without weights, although the action class distribution is imbalanced (e.g., the percentage of \"standing\" people, who are less informative for tactics, is over \\(68\\%\\) in VBD)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.742, + 0.469, + 0.846 + ], + "angle": 0, + "content": "To resolve this class imbalanced problem, we propose Action Frequency-Inverse Scene Frequency (AF-ISF) inspired by Term Frequency-Inverse Document Frequency (TF-IDF [1]) that evaluates the importance of a word in a document. In AF-ISF, each scene is represented by a feature vector in which each value is computed from frequency statics of action classes as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.164, + 0.859, + 0.469, + 0.878 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {F} \\boldsymbol {V} ^ {i} = \\left[ F V _ {1} ^ {i}, F V _ {m} ^ {i}, \\dots , F V _ {M} ^ {i} \\right] \\tag {7}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.234, + 0.88, + 0.469, + 0.898 + ], + "angle": 0, + "content": "\\[\nF V _ {m} ^ {i} = A F _ {m} ^ {i} \\cdot I S F _ {m} \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.227 + ], + "angle": 0, + "content": "where \\(i\\) and \\(M\\) denote the image index and the number of actions, respectively. \\(AF_{m}^{i}\\) is the frequency of \\(m\\)-th action class in each image. \\(ISF_{M}\\) is the inverse frequency of each action class in the dataset. In AF-ISF, the similarity between \\(\\pmb{F}\\pmb{V}^{j}\\) and \\(\\pmb{F}\\pmb{V}^{k}\\), where \\(j\\) and \\(k\\) denote the IDs of query and retrieved images, evaluates the similarity of action structure of the two images. If the cosine similarity exceeds a predefined threshold (e.g., 0.5), the query and retrieved images are regarded as matched as with the Action IoU." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.23, + 0.892, + 0.321 + ], + "angle": 0, + "content": "While AF-ISF alleviates the action class imbalanced problem, several action classes are distinctive for representing a group scene even if the action distribution is balanced (e.g., \"Spiking\" is more important than \"Falling\" in VBD). Due to this problem, AF-ISF is still improper for the contextual representation of group scenes." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.324, + 0.892, + 0.415 + ], + "angle": 0, + "content": "Group activity retrieval. Based on the discussion above, we propose to further evaluate whether or not the group activity class of a query scene matches that of the retrieved scene. Note that the group activity annotations are given to the test data (i.e., all query and retrieved images) only for this evaluation and are not used in our GAF learning." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.45, + 0.688, + 0.464 + ], + "angle": 0, + "content": "4.2.2 Evaluation Metrics" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.479, + 0.892, + 0.57 + ], + "angle": 0, + "content": "With IoU and AF-ISF in the action set retrieval and group activity matching in the group activity retrieval, we compute the Hit@K used in [14]. In addition, the mean Average Precision (mAP) is used in the action set retrieval as with [14]. For mAP, the Euclidean distance of \\( G \\) between query and retrieved images is used as the confidence indicator." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.588, + 0.662, + 0.605 + ], + "angle": 0, + "content": "4.3. Training Details" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.614, + 0.892, + 0.796 + ], + "angle": 0, + "content": "Our network is optimized by Adam [17] with \\(\\beta_{1} = 0.9\\), \\(\\beta_{2} = 0.999\\), and \\(\\epsilon = 10^{-8}\\). The whole image is resized into \\(320 \\times 640\\) and \\(240 \\times 360\\) for VBD and CAD, respectively. We employ the VGG-19 and Inception-v3 models as a person feature extractor (Fig. 3 (a)) for VBD and CAD, respectively. While the person feature extractor trained on person action recognition is fine-tuned through our GAF learning in GAFL-PAC, we freeze the person feature extractor trained on ImageNet in GAFL-PAF following the previous method [14]. Our APN consists of three fully-connected layers. As for the other details, we follow the widely used setting [42]. See the details in the supplementary material." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.815, + 0.74, + 0.831 + ], + "angle": 0, + "content": "4.4. Comparative Experiments" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We compare our methods with other methods by the following three types of experimental results: (1) the results of retrieval (Sec. 4.4.1), (2) the results of GAR (Sec. 4.4.2), and (3) the visualized distributions of GAFs (Sec. 4.4.3)." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18237" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.089, + 0.892, + 0.134 + ], + "angle": 0, + "content": "Table 1. Quantitative comparison of retrieval on the VolleyBall Dataset (VBD). The results obtained in two experimental settings (i.g., GAFL-PAC and GAFL-PAF) are separated by double lines. The best result in each column is colored in red. Results obtained by the concatenation of output features (i.e., \\( \\mathbf{F}_{grp}^{TS} \\) and \\( \\mathbf{F}_{grp}^{ST} \\)) and \\( \\mathbf{G} \\) are denoted as \"Ours-ind\" and \"Ours-grp\", respectively." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.136, + 0.92, + 0.313 + ], + "angle": 0, + "content": "
Retrieval typeAction set (IoU [14])Action set (AF-IDF)Group activity
MethodHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3
GAFL-PACHiGCIN [40]74.384.989.555.759.873.680.330.550.066.374.5
DIN [42]79.790.193.460.274.585.288.339.357.073.181.1
Dual-AI [11]67.684.791.656.972.683.788.653.064.476.582.0
Ours-ind82.791.695.059.179.086.889.845.682.788.891.3
Ours-grp83.092.795.564.280.188.491.559.984.889.691.8
GAFL-PAFB1-Compact128 [14]57.975.784.345.841.360.871.429.330.348.059.9
B2-VGG19 [14]63.880.686.846.846.765.875.729.435.453.665.0
HRN [14]60.978.686.046.940.860.972.928.731.247.057.6
Ours-ind64.280.888.345.050.469.377.630.155.072.379.2
Ours-grp64.882.790.346.452.371.481.031.461.175.182.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.225, + 0.32, + 0.744, + 0.334 + ], + "angle": 0, + "content": "Table 2. Quantitative comparison of retrieval on the Collective Activity Dataset (CAD)." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.335, + 0.921, + 0.513 + ], + "angle": 0, + "content": "
Retrieval typeAction set (IoU [14])Action set (AF-IDF)Group activity
MethodHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3
GAFL-PACHiGCIN [40]80.885.489.757.981.085.289.361.686.188.891.9
DIN [42]71.474.174.951.590.192.794.052.890.892.593.2
Dual-AI [11]61.072.576.761.585.586.988.182.782.184.184.7
Ours-ind76.282.689.478.994.895.695.982.294.995.495.7
Ours-grp81.890.793.569.996.196.596.693.994.995.696.3
GAFL-PAFB1-Compact128 [14]48.860.368.238.081.888.289.752.682.488.490.1
B2-VGG19 [14]53.661.666.135.371.180.383.846.772.280.884.2
HRN [14]37.150.158.622.253.264.872.534.254.064.872.4
Ours-ind67.681.385.953.383.788.990.257.588.591.291.9
Ours-grp52.770.374.146.474.080.582.660.179.281.082.0
" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.538, + 0.196, + 0.552 + ], + "angle": 0, + "content": "4.4.1 Retrieval" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.564, + 0.47, + 0.687 + ], + "angle": 0, + "content": "To validate the effectiveness of the GAF for group representation, the set of person features (i.e., the concatenation of \\( \\pmb{F}_{\\text{grp}}^{TS} \\) and \\( \\pmb{F}_{\\text{grp}}^{ST} \\) in Fig. 3 (b)) is also evaluated. Specifically, the output features of \\( P^{TM} \\) in the TS and ST branches \\( (\\pmb{F}_{\\text{grp}}^{TS} \\) and \\( \\pmb{F}_{\\text{grp}}^{ST} \\) in Fig. 3) are concatenated and also used for retrieval in our method. Results obtained by the concatenation of output features (i.e., \\( \\pmb{F}_{\\text{grp}}^{TS} \\) and \\( \\pmb{F}_{\\text{grp}}^{ST} \\)) and \\( \\pmb{G} \\) are denoted as \"Ours-ind\" and \"Ours-grp\", respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.688, + 0.47, + 0.853 + ], + "angle": 0, + "content": "Volleyball dataset (GAFL-PAC). Our method is compared with the SOTA GAR methods [11, 40, 42] which are only trained with person action labels as with our method. Table 1 (top) shows that our method is best in action set and group activity retrieval. The results validate that our method learns features about the action structure and the group activity of a scene into the compact latent vector (i.e., \\(\\pmb{G}\\)) efficiently. The large gain in the group activity retrieval shows that the features of multi-person activity are learned in our GAF in contrast to the SOTA GAR methods [11, 40, 42] where the set of person features is used for the retrieval." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Volleyball dataset (GAFL-PAF). Our method is compared with the SOTA method [14], the only existing GAF learning method using no person-action and group-activity an" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.538, + 0.892, + 0.718 + ], + "angle": 0, + "content": "notations, and baseline methods as with [14]. From Table 1 (bottom), we see that our method performs best in all metrics except that \"HRN\" is better than our method in mAP of Action set (IoU). However, the performance difference is small (i.e., 46.9 and 46.4 in \"HRN\" and \"Ours-grp,\" respectively). Furthermore, our method is better than \"HRN\" in Action set (AF-IDF). From these results, we can say that our GAF is better even in the action set retrieval. Regarding group activity retrieval, our method significantly outperforms the SOTA method. The results validate that our method learns the contextual features of multi-person activity better than the SOTA method." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.893, + 0.9 + ], + "angle": 0, + "content": "Collective activity dataset (GAFL-PAC). The results in GAFL-PAC on CAD are shown in Table 2 (top). The results validate that our method is better than Dual-AI [11] in all metrics. While \"Ours-grp\" is better than \"Ours-ind\" in most metrics, \"Ours-ind\" is better in mAP of Action set (IoU). The action set (IoU) evaluates the similarity of the number of people, so the results may come from that the change in the number of people between scenes on this dataset is addressed well in \"Ours-ind.\" Specifically, we can consider that such information about the number of people may be preserved well in \"Ours-ind.\" where the set of person features is used for retrieval." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18238" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.089, + 0.473, + 0.292 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.299, + 0.471, + 0.356 + ], + "angle": 0, + "content": "Figure 4. Confusion matrices of GAR by nearest neighbor retrieval on VBD and CAD in GAFL-PAF. Each row and column show the ground-truth and recognized group activity, respectively. Results of the other methods are shown in the supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.383, + 0.471, + 0.613 + ], + "angle": 0, + "content": "Collective activity dataset (GAFL-PAF). Table 2 (bottom) shows that our method is the best in all metrics among the other methods. The results validate the wide applicability of GAF learned even in general scenes included in CAD. While \"Ours-grp\" is better than \"Ours-ind\" on VBD, \"Ours-ind\" is better on CAD. These opposite results may come from the difference between the number of people in each image. While \\( N = 12 \\) people are observed in most images in VBD, around five people on average on CAD. As the number of features in \\( F_{grp}^{TS} \\) and \\( F_{grp}^{ST} \\) increase in proportion to the number of observed people, the difficulty in learning \\( F_{grp}^{TS} \\) and \\( F_{grp}^{ST} \\) becomes higher. Since this learning difficulty might occur on VBD, spatial max pooling used in \"Ours-grp\" is effective for reducing the feature dimension from \\( NC \\) of \\( F_{grp}^{TS} \\) and \\( F_{grp}^{ST} \\) to \\( C \\) of \\( G^{TS} \\) and \\( G^{ST} \\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.633, + 0.325, + 0.649 + ], + "angle": 0, + "content": "4.4.2 Group Activity Recognition" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.659, + 0.469, + 0.749 + ], + "angle": 0, + "content": "While no group annotation is used in our GAF learning, the group activity class retrieved by Hit@1, which is equal to 1-nearest neighbor classification, can be regarded as the result of GAR, as done in [20]. While results only in GAFL-PAF are shown in this section, results in GAFL-PAC are available in the supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Volleyball dataset (GAFL-PAF). As shown in Fig. 4, our method outperforms \"B2-VGG19\" in all group activity classes except for L-winpoint. While \"B2-VGG19\" is better than \"Ours\" in L-winpoint shown at the bottom right of each confusion matrix, \"B2-VGG19\" often misrecognizes the R-winpoint scene as L-winpoint, as shown in the red rectangle cells. Left-spike and Right-spike are especially recognized better in our method than the others. This superiority of our method can be interpreted as follows. In Left-spike and Right-spike, spiking and blocking players who" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.089, + 0.891, + 0.242 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.25, + 0.894, + 0.293 + ], + "angle": 0, + "content": "Figure 5. Visualization of the learned GAF on VBD and CAD in GAFL-PAF. The color of each sample shows the ground-truth of the group activity label corresponding to each test sample." + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.309, + 0.891, + 0.507 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.515, + 0.893, + 0.573 + ], + "angle": 0, + "content": "Figure 6. Visualization of the learned GAF on VBD in GAFL-PAC. The magenta data points (i.e., \"L-pass\") are divided into two sub-categories based on the context (i.e., whether the receiving is caused by the spiking or serving of the opposite player)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.892, + 0.751 + ], + "angle": 0, + "content": "are distinctive both in appearance and location cues are always observed. Since these distinctive people are important in predicting not only their attributes but also the attributes of other people, the features of these distinctive people are extracted well even in the compact latent vector (i.e., GAF). Collective activity dataset (GAFL-PAF). The confusion matrices are shown in Fig. 4. The results show that our method is the best in all activity classes. In particular, while VGG19 gets many false negatives in Moving, the number of false negatives in Moving of our method is almost zero." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.771, + 0.771, + 0.785 + ], + "angle": 0, + "content": "4.4.3 Visualization of Learned GAFs" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.901 + ], + "angle": 0, + "content": "The distribution of learned GAFs in all test images is visualized in a 2D space by t-SNE [30]. The color of each point shows its annotated group activity class. Figure 5 shows that our method can learn the GAFs better than the other methods because (1) while the inner-class variance is small, the inter-class variance is large, and (2) the data points of similar group activities (e.g., Left-pass and Left-set) are closer." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18239" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.09, + 0.465, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.201, + 0.468, + 0.228 + ], + "angle": 0, + "content": "Figure 7. Performance changes depending on the number of masking people on VBD." + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.246, + 0.468, + 0.273 + ], + "angle": 0, + "content": "Table 3. Effectiveness of our location-guidance on VBD. Results obtained by \"Ours-grp\" are shown as \"Ours.\"" + }, + { + "type": "table", + "bbox": [ + 0.079, + 0.282, + 0.472, + 0.396 + ], + "angle": 0, + "content": "
Retrieval typeAction set (IoU)Action set (AF-IDF)Group activity
MethodHit@1Hit@1Hit@1
GAFL-PACOurs w/o Floc80.075.669.5
Ours83.080.184.8
GAFL-PAFOurs w/o Floc64.151.753.2
Ours64.852.361.1
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.424, + 0.468, + 0.604 + ], + "angle": 0, + "content": "Our GAFs in GAL-PAC on VBD are also shown in Fig. 6. This figure shows that data points with the same group activity labels are divided into sub-activities. For example, L-pass indicated by magenta data points are divided into two clusters. While the cluster enclosed by the orange rectangle represents L-pass where the person is receiving a ball from the opposite spiker, the other cluster enclosed by the light blue rectangle represents L-pass where the person is receiving a ball from the opposite server. As shown in this example, our GAFs are learned well enough to represent visually subtle but important differences that are not represented in the manually defined activity classes." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.618, + 0.242, + 0.634 + ], + "angle": 0, + "content": "4.5. Detailed analysis" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.643, + 0.468, + 0.716 + ], + "angle": 0, + "content": "Comparison of the number of masked persons. We explore the optimal number of masked people (i.e., \\( N_{mask} \\)) for our MPM. For this comparison, we change \\( N_{mask} \\) from 0 to \\( N - 1 \\). \\( N_{mask} = 0 \\) means that \\( F_{set} \\) is directly fed into the transformer encoder without the MPM." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.719, + 0.468, + 0.868 + ], + "angle": 0, + "content": "Figure 7 shows that the performance changes depending on \\( N_{mask} \\) on VBD. The best performance is obtained when \\( N_{mask} \\) is the middle number (i.e., 5 and 6 in the GAFL-PAC and GAFL-PAF, respectively), while the performance gain from \\( N_{mask} = 0 \\) is insignificant. On the other hand, we can also see that the performance with a large masking ratio (i.e., \\( N_{mask} \\in \\{10, 11\\} \\)) drops. These results reveal that the extreme difficulty in the attribute prediction of the masked person from a few non-masked people leads GAF learning to failure." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.468, + 0.902 + ], + "angle": 0, + "content": "Effect of location-guidance in GAF learning. We ablate \\(F_{loc}^{p}\\) which is used for guidance to extract the features of" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.09, + 0.89, + 0.117 + ], + "angle": 0, + "content": "Table 4. Comparison with supervised GAR. Double lines separate the results obtained by VBD and CAD." + }, + { + "type": "table", + "bbox": [ + 0.514, + 0.125, + 0.875, + 0.211 + ], + "angle": 0, + "content": "
DatasetMethodAccuracy
VBDDual-AI [11]92.1
Ours w/ group activity labels92.4
CADDual-AI [11]94.1
Ours w/ group activity labels96.6
" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.237, + 0.89, + 0.265 + ], + "angle": 0, + "content": "each person in the action prediction network in Fig. 3 (c) (see also Sec. 3.4) on VBD." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.266, + 0.89, + 0.492 + ], + "angle": 0, + "content": "In GAFL-PAC, \"Ours\" is better than \"Ours w/o \\( F_{loc}^{p} \\)\" in the all metrics. In particular, the performance gain in the group activity retrieval is large. We can interpret the reason as follows. In \"Ours w/o \\( F_{loc}^{p} \\),\" only \\( G \\) is used to predict the attribute of each person in a scene. It makes the model predict not the attribute of each person but the attribute distribution of people in a scene. Therefore, the GAF can be used for action set retrieval to some extent because the similarity of action distribution is evaluated in this retrieval. However, spatial interaction between people is not learned in the GAF. It causes a significant performance drop in the group activity retrieval. In GAFL-PAF, we can also see the high-performance gain of \"Ours\" in the group activity retrieval. From these results, we can conclude that our location guidance is important for learning group activity." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.493, + 0.89, + 0.598 + ], + "angle": 0, + "content": "Fine-tuning for Group Activity Recognition. Table 4 shows that the comparison of \"Dual-AI\" and \"Ours\" with group activity labels on VBD and CAD. In \"Dual-AI,\" the network is trained with group activity labels from scratch. In \"Ours,\" after the pretraining by our GAF learning without the group activity supervision, the network is fine-tuned for GAR with group activity labels." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.599, + 0.89, + 0.674 + ], + "angle": 0, + "content": "On both datasets, our method is better than \"Dual-AI.\" In particular, on CAD, the GAR accuracy obtained by our method is \\(2.5\\%\\) better than the GAR accuracy obtained by \"Dual-AI.\" The results demonstrate that our GAF learning is effective as a pre-training for supervised GAR." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.688, + 0.702, + 0.705 + ], + "angle": 0, + "content": "5. Concluding Remarks" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.714, + 0.89, + 0.803 + ], + "angle": 0, + "content": "Instead of group activity annotations which is difficult due to a variety of similar group activities, our method learns GAF through person attribute prediction without group activity annotations. Quantitative comparisons and visualized results show that our method can learn informative GAF compared with other methods on the two public datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.803, + 0.89, + 0.9 + ], + "angle": 0, + "content": "While our method outperforms all the other methods in our experiments not only for GAF learning but also for GAR, our method is understandably inferior to GAR supervised by group activity annotations. Exploring other pretext tasks such as predicting the joint attention of a group (e.g., [22]) is important future work for further GAF enhancement." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.956 + ], + "angle": 0, + "content": "18240" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.123, + 0.174, + 0.138 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.148, + 0.47, + 0.175 + ], + "angle": 0, + "content": "[1] Akiko N. Aizawa. 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In ECCV, 2022. 1, 2, 3" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.468, + 0.574 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.946, + 0.519, + 0.956 + ], + "angle": 0, + "content": "18242" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_origin.pdf b/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..71cfe6c62ade7f485652369ee2872f7d8a6a7634 --- /dev/null +++ b/2024/Learning Group Activity Features Through Person Attribute Prediction/58724bbe-6f1a-4e5e-a5d2-557cd815fe3c_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:a45de0c7343e70e178292fe661ef2648c58c423c5bfe7f4396368500876fc33d +size 4353777 diff --git a/2024/Learning Group Activity Features Through Person Attribute Prediction/full.md b/2024/Learning Group Activity Features Through Person Attribute Prediction/full.md new file mode 100644 index 0000000000000000000000000000000000000000..87c9e922cb5ed53c84b1536b33c021778d742242 --- /dev/null +++ b/2024/Learning Group Activity Features Through Person Attribute Prediction/full.md @@ -0,0 +1,315 @@ +# Learning Group Activity Features Through Person Attribute Prediction + +Chihiro Nakatani1 Hiroaki Kawashima2 Norimichi Ukita1 + +$^{1}$ Toyota Technological Institute, Japan $^{2}$ University of Hyogo, Japan + +# Abstract + +This paper proposes Group Activity Feature (GAF) learning in which features of multi-person activity are learned as a compact latent vector. Unlike prior work in which the manual annotation of group activities is required for supervised learning, our method learns the GAF through person attribute prediction without group activity annotations. By learning the whole network in an end-to-end manner so that the GAF is required for predicting the person attributes of people in a group, the GAF is trained as the features of multi-person activity. As a person attribute, we propose to use a person's action class and appearance features because the former is easy to annotate due to its simplicity, and the latter requires no manual annotation. In addition, we introduce a location-guided attribute prediction to disentangle the complex GAF for extracting the features of each target person properly. Various experimental results validate that our method outperforms SOTA methods quantitatively and qualitatively on two public datasets. Visualization of our GAF also demonstrates that our method learns the GAF representing fined-grained group activity classes. Code: https://github.com/ chihina/GAFL-CVPR2024. + +# 1. Introduction + +A group activity is defined as what multiple people jointly engage in. Group activities are important targets in image and video understanding, such as team plays in sports [36], conversations in social scenes [3], and people flows in surveillance cameras [28]. + +Group Activity Recognition (GAR), in which a frame or video is classified into either of the predefined group activity classes, has been widely investigated in recent years [2, 3, 6, 9, 11, 14, 16, 19, 21, 25, 29, 37-40, 42, 45]. All of these GAR methods are based on supervised learning that requires the ground-truth group activities, as shown in Fig. 1 (a). In addition, it is known that person action recognition, which is also achieved based on a supervised learning manner, supports GAR [2, 3, 6, 9, 11, 14, 19, 21, 25, 29, 37, 38, 40, 45]. + +![](images/7f6601462bd530010594814630216b53bcf9b9f5b9341342e5dd96c348038b2e.jpg) +(b) Ours (group activity feature learning with person attribute) +Figure 1. Difference between annotations for GAR and our group activity feature learning. (a) Supervised GAR employs group activity annotations that are difficult due to various similar group activities. (b-1) Our GAF learning employs person action annotations that are easy due to their simplicity. (b-2) We further propose annotation-free GAF learning with person appearance features. + +Such supervised learning requires manually-annotated training data. For GAR, group activity annotations are required. In addition to labor-intensive and erroneous annotations, a difficulty peculiar to GAR is the complexity of the group activities. For example, while only four elemental group activity classes are annotated in a widely-used team-sport dataset [15], they may be insufficient for practical purposes such as tactical analysis (e.g., 200 or more plays are defined in American Football [8]). That is, more fine-grained activity classes are required for several applications of group activity analysis. It is, however, difficult to correctly define and annotate such complex, fine-grained activity classes, even manually, because of visually minor but highly contextual differences among those classes. + +Such difficulty in manual annotations of group activities motivates us to learn a Group Activity Feature (GAF) in which features of multi-person activity are learned as a compact latent vector without group activity annotations. We note here that GAFs, which represent the complex features of multi-person activity, may have enough information to predict the attributes of each person in a group. + +With this regard, this paper proposes GAF learning using person attribute (e.g., action and appearance), which is easier to provide compared with the complex group activity annotation, as shown in Fig. 1 (b). With the person attribute related to the group activity, the GAF can narrow down the possible attribute of each person. For example, Fig. 2, in which a spike is observed, shows that the possible person action enclosed by the purple rectangle (i.e., digging) can be narrowed down by the GAF representing the scene context (i.e., spike group activity) with the person's location. + +As a person attribute for our GAF learning, person action can be used as shown in Fig. 1 (b-1). This is because person action is strongly related to the group activities and is essential to support GAR as mentioned above. However, manual annotations are still required to use person action. While the annotations of person action are easier than the one of group activities defined with complex people interaction, such action annotations are still labor-intensive. + +To alleviate such difficulty in manual annotations, we also propose to learn GAF through the task of appearance feature prediction of each person in a group without manual annotations, as shown in Fig. 1 (b-2). While the reduction of annotation cost have been studied widely, including active learning [13, 26], few-shot learning [35, 44], and self-supervised learning [4, 5, 7, 10, 18, 23, 24, 32, 33, 41, 43], we follows the framework of self-supervised learning, where supervision signals are derived from the input data and any manual annotations are unnecessary. + +Our novel contributions are summarized as follows: + +- GAF learning through person attribute prediction: Unlike supervised GAR, we propose GAF learning through person attribute prediction without group activity annotations. This paper proposes its two variants: +- GAF Learning with Person Action Classes (GAFL-PAC): As a person attribute, we utilize person action classes, which are more easily annotated than group activities defined with complex inter-people interactions (Fig. 1 (b-1)). In addition, for practical use of GAR and other group-related applications, the annotations of person actions are already given in general [3, 14]. +- GAF Learning with Person Appearance Features (GAFL-PAF): We also utilize person appearance features that can be obtained by a pre-trained model (e.g., VGG) without manual annotation (Fig. 1 (b-2)). The appearance features are suitable as a person attribute due to the high relationship with multi-person activity. +- Fine granularity of our GAF: With the GAF learning through person attribute prediction, our method can learn fine-grained GAF that represents visual-subtle but important differences that are not represented in a manually-defined activity class, as shown in Fig. 6. +- Location-Guided Person Attribute Prediction Using GAF: While predicting the person attribute using the + +![](images/6935fa9b6710768106f1d178a1f279956a3a1f84aa75ce6d259eefa88ef4fc8c.jpg) +Figure 2. Example of our group activity feature learning. In this example, a group activity feature is learned to extract the scene context (i.e., spike group activity) through prediction of person attribute (e.g., digging). See Fig. 3 for the detailed architecture. + +GAF is required in our method, extracting the features of each target person from the GAF is difficult. This is because the GAF represents complex features of multi-person activity. This feature extraction is achieved by location guidance in which each person's location feature is embedded into the GAF with positional encoding. + +# 2. Related Work + +# 2.1. Group Activity Recognition + +Supervision by group activity labels. While we propose the GAF learning without group activity annotations (Fig. 1 (b)), various GAR methods supervised by group activity annotations (i.e., Fig. 1 (a)) have been proposed. In [16, 40, 42], only the labels of group activity are required for training. In [16], a group activity is recognized from a whole image without any person features. Kim et al [42] and Yan et al [40] employ the set of person features as input for a Graph Neural Network (GNN) as with [6, 37]. + +Supervision by the labels of person action and group activity. Different from the aforementioned methods only with group activity supervision, the GAR network is jointly trained with the person action recognition network in [2, 3, 6, 9, 11, 14, 19, 21, 25, 29, 37, 45] for augmenting GAR. In [6, 37], GNN models the interactions between person features. In [9, 11, 19, 29, 45], Transformer [31] improves modeling the interactions between person features for GAR. + +While all of the methods introduced in Sec. 2.1 employ the annotation of group activities, our method learns GAF without group activity labels. Following the success of interaction modeling in [9, 11, 19, 29, 45], we also learn the GAF with Transformer. + +# 2.2. Self-supervised Representation Learning + +Image-based pretext tasks. Most pretext tasks for self-supervised image representation utilize the transformation of original images. In Gidaris et al. [10], Zhang et al. [43], and Larsson et al. [18], each original image is rotated, affinely- and projectively-transformed, and grayscale, respectively. The image representation model is trained so that the model undoes each image. While these meth + +ods [10, 18, 43] employ a whole image, patches extracted from the image are used in [4, 23, 24]. Doersch et al. [4] predict the spatial configuration (i.e., relative positions) of randomly-sampled patches. In Noroozi et al. [23], jigsaw puzzles in which all patches of an image are shuffled are solved. Pathak et al. [24] inpaint partially-erased images. + +Video-based pretext tasks. While the image-based methods can be applied to a video, video-specific pretext tasks are also proposed in [5, 7, 32, 33, 41]. In Yao et al. [41] and Wang et al. [33], the paces of video clips are arbitrarily changed (e.g., normal, half, and double speeds), and video representation is learned by solving a pace prediction problem. In Fernando et al. [7], sequential video clips are randomly reordered, and video representation is learned so that these reordered and original clips can be classified. Wang et al. [32] employ appearance cues as well as motion statistics for spatial-temporal representation learning. + +While all of the representation learning methods introduced above extract low-level image features for various downstream tasks such as general image/video classification and prediction, our method focuses on features useful for group-related tasks (e.g., group scene retrieval and clustering). As with our method, Ibrahim et al. [14] aims to extract multi-person scene features through GNN in an unsupervised manner, while the relation of each person to a group activity is not fully captured. Our method incorporates such intimate relations between individuals and group activity (e.g., digging in a spike scene) using the task of location-guided person attribute prediction from a GAF. + +# 3. Proposed Method + +Our GAF learning network consists of three stages, (a), (b), and (c) (Fig. 3). In stage (a), the features of each person are extracted (Sec. 3.1). In stage (b), the features of several people are masked (i.e., removed) during training for GAF enhancement (Sec. 3.2). Then, the masked person features are fed into the transformer-based GAF learning network (Sec. 3.3). In stage (c), the attribute of each person is predicted from the GAF with location guidance (Sec. 3.4). + +# 3.1. Person Feature Extractor + +Overview. As shown in Fig. 3 (a), the set of person features $\pmb{F}_{set} \in \mathbb{R}^{T \times N \times C}$ are extracted from images. $\pmb{F}_{set}$ is composed of the features of $N$ people obtained from $T$ frames in a video. $C$ is the dimension of person $p$ 's feature vector, $\pmb{F}_{ind}^p \in \mathbb{R}^C$ , indicated by a blue cuboid in Fig. 3 (a). $\pmb{F}_{ind}^p$ consists of appearance features (denoted by $\pmb{F}_{app}^p \in \mathbb{R}^C$ ) and location features (denoted by $\pmb{F}_{loc}^p \in \mathbb{R}^C$ ) in our implementation because their effectiveness is validated for GAR [9, 11, 19, 25, 45], while other features (e.g., body keypoints) can also be used. + +Detail. $F_{app}^{p}$ is extracted by the following three steps, as with [42]. First, a feature map is extracted from the whole image by VGG [27]. Then, RoIAlign [12] is applied with the bounding box of each person to obtain the feature map for each person. Finally, the feature map of each person is embedded into $C$ -dimensional appearance features with a linear transformation. From the $F_{app}^{p}$ of $N$ people between $T$ frames, we construct $F_{app} \in \mathbb{R}^{T \times N \times C}$ . In addition to $F_{app}$ , $F_{loc}^{p}$ is also essential to understand the spatial structure of a group, as $F_{loc}^{p}$ is used for GAR [9, 11, 25, 37, 45]. As with [11], the center point of each person bounding box, $(x,y)$ , is embedded into $F_{loc}^{p}$ by a spatial positional encoding so that $F_{loc} \in \mathbb{R}^{T \times N \times C}$ whose dimension is equal to $F_{app}$ . Finally, $F_{loc}$ is elementwise added with $F_{app}$ to obtain the set of person features, $F_{set}$ . Here, we denote person $p$ 's features in $T$ frames (i.e., a slice of $F_{set}$ ) as $F_{ind}^{p} \in \mathbb{R}^{T \times C}$ ( $p \in \{1,\dots,N\}$ ) and, similarly, person $p$ 's location features in $T$ frames (i.e., a slice of $F_{loc}$ ) as $F_{loc}^{p} \in \mathbb{R}^{T \times C}$ ( $p \in \{1,\dots,N\}$ ). + +# 3.2. Masked Person Modeling (MPM) + +Overview. In the set of person features $\mathbf{F}_{\text{set}}$ , the features of randomly sampled people are masked (e.g., $\mathbf{F}_{\text{ind}}^{1}$ indicated by a black cuboid in Fig. 3(b)) during training. By extracting such features with our Masked Person Modeling (MPM), our network is expected to learn the features of the interaction between unmasked people for predicting the attribute of the masked person. + +Detail. The binary mask for $p$ -th person (denoted by $M^p \in \mathbb{R}^{T \times C}$ ) is initialized by filling 1 in all values. Then, $N_{mask}$ people to be masked are randomly sampled from all $N$ people in a scene. All values in $M^p$ for the randomly sampled people are updated with 0. + +From the all $M^p$ of $N$ people, we construct $M = [M^1,\dots ,M^N ]\in \mathbb{R}^{T\times N\times C}$ . Then, $M$ is elementwise multiplied by $\pmb{F}_{set}$ to obtain the masked person features $\pmb{F}_{mask}$ for our GAF training. Note that all values in $M$ are set to be 0 during inference to preserve features of all people in a GAF. + +# 3.3. Group Activity Feature Learning Network + +Overview. The GAF $G$ is extracted from the set of masked person features $\pmb{F}_{mask}$ obtained in Sec. 3.2. For this GAF learning, we employ Transformer to model spatial- and temporal-interactions between people in accordance with [11, 19]. Our transformer-based GAF learning network consists of two branches (i.e., TS and ST branches) similar to [11]. As shown in Fig. 3, the Temporal Transformer encoder $(T^T)$ and the Spatial Transformer encoder $(T^S)$ are used in both branches, but they are placed in reverse order in the two branches. The combination of these two branches can model the spatial-temporal interactions + +![](images/9acc36c397b402613e00111436e8561dca356b09e9d7cacf7bb8ba65e83d93c2.jpg) +Figure 3. Overview of our GAF learning network. (a) Person feature extractor. The person feature is composed of appearance and location features. (b) GAF learning network. The GAF is learned from extracted people features. (c) Location-guided attribute prediction network with the GAF. The attribute of each person is predicted from the location feature of the person and the GAF extracted in (b). + +between people, as proven in GAR [11, 19]. While the transformer-based network is used in our method, the network can be replaced with any SOTA network without difficulties because the stage (i.e., Fig. 3 (b)) is modularized. + +Detail. $\mathbf{F}_{mask}$ is independently fed into the TS and ST branches to acquire $\mathbf{F}_{mask}^{TS}$ and $\mathbf{F}_{mask}^{ST}$ , respectively: + +$$ +\boldsymbol {F} _ {\text {m a s k}} ^ {T S} = T ^ {S} \left(\boldsymbol {F} _ {\text {m a s k}} + M L P \left(T ^ {T} \left(\boldsymbol {F} _ {\text {m a s k}}\right)\right)\right) \tag {1} +$$ + +$$ +\boldsymbol {F} _ {\text {m a s k}} ^ {S T} = T ^ {T} \left(\boldsymbol {F} _ {\text {m a s k}} + M L P \left(T ^ {S} \left(\boldsymbol {F} _ {\text {m a s k}}\right)\right)\right) \tag {2} +$$ + +where $MLP$ denotes the multi-layer perceptron. $G^{TS} \in \mathbb{R}^C$ and $G^{ST} \in \mathbb{R}^C$ are obtained from $F_{mask}^{TS}$ and $F_{mask}^{ST}$ , respectively, by the Temporal Max Pooling (denoted by $P^{TM}$ ) and the Spatial Max Pooling (denoted by $P^{SM}$ ), as with previous methods [9, 37]: + +$$ +\boldsymbol {G} ^ {T S} = P ^ {S M} \left(P ^ {T M} \left(\boldsymbol {F} _ {\text {m a s k}} ^ {T S}\right)\right) \tag {3} +$$ + +$$ +\boldsymbol {G} ^ {S T} = P ^ {S M} \left(P ^ {T M} \left(\boldsymbol {F} _ {\text {m a s k}} ^ {S T}\right)\right) \tag {4} +$$ + +Finally, $G^{TS}$ and $G^{ST}$ are concatenated to obtain the final GAF $G\in \mathbb{R}^{2C}$ as follows: + +$$ +\boldsymbol {G} = \boldsymbol {G} ^ {T S} \oplus \boldsymbol {G} ^ {S T} \tag {5} +$$ + +During training, $G$ is fed into the attribute prediction network (denoted by $APN$ ), as shown in Fig. 3 (c). By backpropagating a loss used in this person attribute prediction not only inside $APN$ but also across the whole network shown in Fig. 3, $G$ can be trained as the GAF. The details of person attribute prediction and the loss used in this prediction are described in Sec. 3.4 and Sec.3.5, respectively. + +After predicting $G$ in inference, $G$ can be used in various ways such as a pretrained model for downstream supervised tasks and unsupervised learning tasks (e.g., retrieval and clustering), as mentioned in Sec. 1. The effectiveness of $G$ in these tasks is validated in Sec. 4. + +# 3.4. Attribute Prediction with GAF + +Overview. Using $G$ obtained in Sec. 3.3, the attribute of each person is predicted by the $APN$ (Fig. 3 (c)). To predict the attribute of $p$ -th person, we use their location features (i.e., $F_{loc}^{p}$ ) as guidance for attribute prediction from $G$ . + +Detail. $G$ is fed into the attribute prediction network with the location of each person as follows: + +$$ +\boldsymbol {A} _ {P R E D} ^ {p} = A P N (\boldsymbol {G}, \boldsymbol {F} _ {l o c} ^ {p}) \tag {6} +$$ + +where $A_{PRED}^p \in \mathbb{R}^{T \times R}$ denotes the predicted attribute of each person obtained from $G$ with their location. The dimension of $R$ changes depending on the type of the predicted person attribute as follows: + +(i) Person action: $R$ is the number of action classes and the $A_{PRED}^{p}$ represents predicted action probabilities. +(ii) Person appearance features: $R$ is the dimension of the appearance features (i.e., $C$ ) extracted in Sec. 3.1. + +# 3.5. Loss Function + +The whole network is trained with a loss function (denoted by $\mathcal{L}$ ) for attribute prediction as a pretext task as follows: + +(i) Person action: When the person attribute is the action, $\mathcal{L}$ is the cross-entropy loss: $\mathcal{L} = \mathcal{L}_{CE}(\pmb{A}_{PRED}^{p},\pmb{A}_{GT}^{p})$ , where $\pmb{A}_{GT}^{p}$ denotes the ground-truth one-hot vector for action. +(ii) Person appearance features: For appearance features, $\mathcal{L}$ is the mean squared loss function: $\mathcal{L} = \mathcal{L}_{MSE}(A_{PRED}^p, A_{GT}^p)$ , where $A_{GT}^p$ denotes the extracted appearance features (i.e., $F_{app}$ ) shown in Sec. 3.1. + +# 4. Experiments + +# 4.1. Datasets + +The Volleyball dataset, which contains highly correlated players, is mainly used to validate the effectiveness of our GAF learning. The Collective Activity dataset is also used to validate the generality of our method in Sec. 4.4, while people in this dataset are not highly related to each other compared with the Volleyball dataset. + +VolleyBall Dataset (VBD) [15] consists of 4,830 sequences extracted from 55 games. Each sequence is annotated with one of the predefined eight group activity classes, i.e., Left-spike, Right-spike, Left-set, Right-set, Left-pass, Right-pass, Left-winpoint, and Right-winpoint. While each sequence has 41 frames, its center 20 frames have annotations with the full-body bounding boxes of all players and their action classes, i.e., Waiting, Setting, Digging, Falling, Spiking, Jumping, Moving, Blocking, and Standing. + +Collective Activity Dataset (CAD) [3] contains 44 videos. In each video, every ten frames are annotated with person action classes, i.e., NA, Crossing, Waiting, Queuing, Walking, and Talking, and their bounding boxes. The group activity class is determined by the largest number of person actions in each frame, while the NA class is not included as a group activity class. We follow the previous methods [34, 42] to merge the Crossing and Walking into Moving. + +# 4.2. Evaluation Protocols + +# 4.2.1 Evaluation Tasks + +The quality of the estimated GAF is verified with the following two types of retrieval tasks. + +Action set retrieval. We employ the same action set retrieval task as in [14]. Action IoU in [14] evaluates the similarity of action structures between query and retrieved images based on the overlap of action distributions. If the IoU exceeds a predefined threshold (e.g., 0.5), the query and retrieved images are regarded as matched. However, in this action IoU, all action classes are counted equally without weights, although the action class distribution is imbalanced (e.g., the percentage of "standing" people, who are less informative for tactics, is over $68\%$ in VBD). + +To resolve this class imbalanced problem, we propose Action Frequency-Inverse Scene Frequency (AF-ISF) inspired by Term Frequency-Inverse Document Frequency (TF-IDF [1]) that evaluates the importance of a word in a document. In AF-ISF, each scene is represented by a feature vector in which each value is computed from frequency statics of action classes as follows: + +$$ +\boldsymbol {F} \boldsymbol {V} ^ {i} = \left[ F V _ {1} ^ {i}, F V _ {m} ^ {i}, \dots , F V _ {M} ^ {i} \right] \tag {7} +$$ + +$$ +F V _ {m} ^ {i} = A F _ {m} ^ {i} \cdot I S F _ {m} \tag {8} +$$ + +where $i$ and $M$ denote the image index and the number of actions, respectively. $AF_{m}^{i}$ is the frequency of $m$ -th action class in each image. $ISF_{M}$ is the inverse frequency of each action class in the dataset. In AF-ISF, the similarity between $\pmb{F}\pmb{V}^{j}$ and $\pmb{F}\pmb{V}^{k}$ , where $j$ and $k$ denote the IDs of query and retrieved images, evaluates the similarity of action structure of the two images. If the cosine similarity exceeds a predefined threshold (e.g., 0.5), the query and retrieved images are regarded as matched as with the Action IoU. + +While AF-ISF alleviates the action class imbalanced problem, several action classes are distinctive for representing a group scene even if the action distribution is balanced (e.g., "Spiking" is more important than "Falling" in VBD). Due to this problem, AF-ISF is still improper for the contextual representation of group scenes. + +Group activity retrieval. Based on the discussion above, we propose to further evaluate whether or not the group activity class of a query scene matches that of the retrieved scene. Note that the group activity annotations are given to the test data (i.e., all query and retrieved images) only for this evaluation and are not used in our GAF learning. + +# 4.2.2 Evaluation Metrics + +With IoU and AF-ISF in the action set retrieval and group activity matching in the group activity retrieval, we compute the Hit@K used in [14]. In addition, the mean Average Precision (mAP) is used in the action set retrieval as with [14]. For mAP, the Euclidean distance of $G$ between query and retrieved images is used as the confidence indicator. + +# 4.3. Training Details + +Our network is optimized by Adam [17] with $\beta_{1} = 0.9$ , $\beta_{2} = 0.999$ , and $\epsilon = 10^{-8}$ . The whole image is resized into $320 \times 640$ and $240 \times 360$ for VBD and CAD, respectively. We employ the VGG-19 and Inception-v3 models as a person feature extractor (Fig. 3 (a)) for VBD and CAD, respectively. While the person feature extractor trained on person action recognition is fine-tuned through our GAF learning in GAFL-PAC, we freeze the person feature extractor trained on ImageNet in GAFL-PAF following the previous method [14]. Our APN consists of three fully-connected layers. As for the other details, we follow the widely used setting [42]. See the details in the supplementary material. + +# 4.4. Comparative Experiments + +We compare our methods with other methods by the following three types of experimental results: (1) the results of retrieval (Sec. 4.4.1), (2) the results of GAR (Sec. 4.4.2), and (3) the visualized distributions of GAFs (Sec. 4.4.3). + +Table 1. Quantitative comparison of retrieval on the VolleyBall Dataset (VBD). The results obtained in two experimental settings (i.g., GAFL-PAC and GAFL-PAF) are separated by double lines. The best result in each column is colored in red. Results obtained by the concatenation of output features (i.e., $\mathbf{F}_{grp}^{TS}$ and $\mathbf{F}_{grp}^{ST}$ ) and $\mathbf{G}$ are denoted as "Ours-ind" and "Ours-grp", respectively. + +
Retrieval typeAction set (IoU [14])Action set (AF-IDF)Group activity
MethodHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3
GAFL-PACHiGCIN [40]74.384.989.555.759.873.680.330.550.066.374.5
DIN [42]79.790.193.460.274.585.288.339.357.073.181.1
Dual-AI [11]67.684.791.656.972.683.788.653.064.476.582.0
Ours-ind82.791.695.059.179.086.889.845.682.788.891.3
Ours-grp83.092.795.564.280.188.491.559.984.889.691.8
GAFL-PAFB1-Compact128 [14]57.975.784.345.841.360.871.429.330.348.059.9
B2-VGG19 [14]63.880.686.846.846.765.875.729.435.453.665.0
HRN [14]60.978.686.046.940.860.972.928.731.247.057.6
Ours-ind64.280.888.345.050.469.377.630.155.072.379.2
Ours-grp64.882.790.346.452.371.481.031.461.175.182.4
+ +Table 2. Quantitative comparison of retrieval on the Collective Activity Dataset (CAD). + +
Retrieval typeAction set (IoU [14])Action set (AF-IDF)Group activity
MethodHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3
GAFL-PACHiGCIN [40]80.885.489.757.981.085.289.361.686.188.891.9
DIN [42]71.474.174.951.590.192.794.052.890.892.593.2
Dual-AI [11]61.072.576.761.585.586.988.182.782.184.184.7
Ours-ind76.282.689.478.994.895.695.982.294.995.495.7
Ours-grp81.890.793.569.996.196.596.693.994.995.696.3
GAFL-PAFB1-Compact128 [14]48.860.368.238.081.888.289.752.682.488.490.1
B2-VGG19 [14]53.661.666.135.371.180.383.846.772.280.884.2
HRN [14]37.150.158.622.253.264.872.534.254.064.872.4
Ours-ind67.681.385.953.383.788.990.257.588.591.291.9
Ours-grp52.770.374.146.474.080.582.660.179.281.082.0
+ +# 4.4.1 Retrieval + +To validate the effectiveness of the GAF for group representation, the set of person features (i.e., the concatenation of $\pmb{F}_{\text{grp}}^{TS}$ and $\pmb{F}_{\text{grp}}^{ST}$ in Fig. 3 (b)) is also evaluated. Specifically, the output features of $P^{TM}$ in the TS and ST branches $(\pmb{F}_{\text{grp}}^{TS}$ and $\pmb{F}_{\text{grp}}^{ST}$ in Fig. 3) are concatenated and also used for retrieval in our method. Results obtained by the concatenation of output features (i.e., $\pmb{F}_{\text{grp}}^{TS}$ and $\pmb{F}_{\text{grp}}^{ST}$ ) and $\pmb{G}$ are denoted as "Ours-ind" and "Ours-grp", respectively. + +Volleyball dataset (GAFL-PAC). Our method is compared with the SOTA GAR methods [11, 40, 42] which are only trained with person action labels as with our method. Table 1 (top) shows that our method is best in action set and group activity retrieval. The results validate that our method learns features about the action structure and the group activity of a scene into the compact latent vector (i.e., $\pmb{G}$ ) efficiently. The large gain in the group activity retrieval shows that the features of multi-person activity are learned in our GAF in contrast to the SOTA GAR methods [11, 40, 42] where the set of person features is used for the retrieval. + +Volleyball dataset (GAFL-PAF). Our method is compared with the SOTA method [14], the only existing GAF learning method using no person-action and group-activity an + +notations, and baseline methods as with [14]. From Table 1 (bottom), we see that our method performs best in all metrics except that "HRN" is better than our method in mAP of Action set (IoU). However, the performance difference is small (i.e., 46.9 and 46.4 in "HRN" and "Ours-grp," respectively). Furthermore, our method is better than "HRN" in Action set (AF-IDF). From these results, we can say that our GAF is better even in the action set retrieval. Regarding group activity retrieval, our method significantly outperforms the SOTA method. The results validate that our method learns the contextual features of multi-person activity better than the SOTA method. + +Collective activity dataset (GAFL-PAC). The results in GAFL-PAC on CAD are shown in Table 2 (top). The results validate that our method is better than Dual-AI [11] in all metrics. While "Ours-grp" is better than "Ours-ind" in most metrics, "Ours-ind" is better in mAP of Action set (IoU). The action set (IoU) evaluates the similarity of the number of people, so the results may come from that the change in the number of people between scenes on this dataset is addressed well in "Ours-ind." Specifically, we can consider that such information about the number of people may be preserved well in "Ours-ind." where the set of person features is used for retrieval. + +![](images/9af64f66df6e96ff08ba693cb82ee26ef20019adc78b472895718d2f1ef77618.jpg) +Figure 4. Confusion matrices of GAR by nearest neighbor retrieval on VBD and CAD in GAFL-PAF. Each row and column show the ground-truth and recognized group activity, respectively. Results of the other methods are shown in the supplementary material. + +Collective activity dataset (GAFL-PAF). Table 2 (bottom) shows that our method is the best in all metrics among the other methods. The results validate the wide applicability of GAF learned even in general scenes included in CAD. While "Ours-grp" is better than "Ours-ind" on VBD, "Ours-ind" is better on CAD. These opposite results may come from the difference between the number of people in each image. While $N = 12$ people are observed in most images in VBD, around five people on average on CAD. As the number of features in $F_{grp}^{TS}$ and $F_{grp}^{ST}$ increase in proportion to the number of observed people, the difficulty in learning $F_{grp}^{TS}$ and $F_{grp}^{ST}$ becomes higher. Since this learning difficulty might occur on VBD, spatial max pooling used in "Ours-grp" is effective for reducing the feature dimension from $NC$ of $F_{grp}^{TS}$ and $F_{grp}^{ST}$ to $C$ of $G^{TS}$ and $G^{ST}$ . + +# 4.4.2 Group Activity Recognition + +While no group annotation is used in our GAF learning, the group activity class retrieved by Hit@1, which is equal to 1-nearest neighbor classification, can be regarded as the result of GAR, as done in [20]. While results only in GAFL-PAF are shown in this section, results in GAFL-PAC are available in the supplementary material. + +Volleyball dataset (GAFL-PAF). As shown in Fig. 4, our method outperforms "B2-VGG19" in all group activity classes except for L-winpoint. While "B2-VGG19" is better than "Ours" in L-winpoint shown at the bottom right of each confusion matrix, "B2-VGG19" often misrecognizes the R-winpoint scene as L-winpoint, as shown in the red rectangle cells. Left-spike and Right-spike are especially recognized better in our method than the others. This superiority of our method can be interpreted as follows. In Left-spike and Right-spike, spiking and blocking players who + +![](images/22d15987b9bc3a75c7db44d5cccc4d438f711c63d78cbde5416d33d00843aca8.jpg) +Figure 5. Visualization of the learned GAF on VBD and CAD in GAFL-PAF. The color of each sample shows the ground-truth of the group activity label corresponding to each test sample. + +![](images/88c1db0cd07774cdcc5ba7eec9dadbb3256f7fecb28dbbcceb272d86020c7e7c.jpg) +Figure 6. Visualization of the learned GAF on VBD in GAFL-PAC. The magenta data points (i.e., "L-pass") are divided into two sub-categories based on the context (i.e., whether the receiving is caused by the spiking or serving of the opposite player). + +are distinctive both in appearance and location cues are always observed. Since these distinctive people are important in predicting not only their attributes but also the attributes of other people, the features of these distinctive people are extracted well even in the compact latent vector (i.e., GAF). Collective activity dataset (GAFL-PAF). The confusion matrices are shown in Fig. 4. The results show that our method is the best in all activity classes. In particular, while VGG19 gets many false negatives in Moving, the number of false negatives in Moving of our method is almost zero. + +# 4.4.3 Visualization of Learned GAFs + +The distribution of learned GAFs in all test images is visualized in a 2D space by t-SNE [30]. The color of each point shows its annotated group activity class. Figure 5 shows that our method can learn the GAFs better than the other methods because (1) while the inner-class variance is small, the inter-class variance is large, and (2) the data points of similar group activities (e.g., Left-pass and Left-set) are closer. + +![](images/b992a116519be9053f9443dce951db86c642ca3cacf38c22de7be0e001c06311.jpg) +Figure 7. Performance changes depending on the number of masking people on VBD. + +Table 3. Effectiveness of our location-guidance on VBD. Results obtained by "Ours-grp" are shown as "Ours." + +
Retrieval typeAction set (IoU)Action set (AF-IDF)Group activity
MethodHit@1Hit@1Hit@1
GAFL-PACOurs w/o Floc80.075.669.5
Ours83.080.184.8
GAFL-PAFOurs w/o Floc64.151.753.2
Ours64.852.361.1
+ +Our GAFs in GAL-PAC on VBD are also shown in Fig. 6. This figure shows that data points with the same group activity labels are divided into sub-activities. For example, L-pass indicated by magenta data points are divided into two clusters. While the cluster enclosed by the orange rectangle represents L-pass where the person is receiving a ball from the opposite spiker, the other cluster enclosed by the light blue rectangle represents L-pass where the person is receiving a ball from the opposite server. As shown in this example, our GAFs are learned well enough to represent visually subtle but important differences that are not represented in the manually defined activity classes. + +# 4.5. Detailed analysis + +Comparison of the number of masked persons. We explore the optimal number of masked people (i.e., $N_{mask}$ ) for our MPM. For this comparison, we change $N_{mask}$ from 0 to $N - 1$ . $N_{mask} = 0$ means that $F_{set}$ is directly fed into the transformer encoder without the MPM. + +Figure 7 shows that the performance changes depending on $N_{mask}$ on VBD. The best performance is obtained when $N_{mask}$ is the middle number (i.e., 5 and 6 in the GAFL-PAC and GAFL-PAF, respectively), while the performance gain from $N_{mask} = 0$ is insignificant. On the other hand, we can also see that the performance with a large masking ratio (i.e., $N_{mask} \in \{10, 11\}$ ) drops. These results reveal that the extreme difficulty in the attribute prediction of the masked person from a few non-masked people leads GAF learning to failure. + +Effect of location-guidance in GAF learning. We ablate $F_{loc}^{p}$ which is used for guidance to extract the features of + +Table 4. Comparison with supervised GAR. Double lines separate the results obtained by VBD and CAD. + +
DatasetMethodAccuracy
VBDDual-AI [11]92.1
Ours w/ group activity labels92.4
CADDual-AI [11]94.1
Ours w/ group activity labels96.6
+ +each person in the action prediction network in Fig. 3 (c) (see also Sec. 3.4) on VBD. + +In GAFL-PAC, "Ours" is better than "Ours w/o $F_{loc}^{p}$ " in the all metrics. In particular, the performance gain in the group activity retrieval is large. We can interpret the reason as follows. In "Ours w/o $F_{loc}^{p}$ ," only $G$ is used to predict the attribute of each person in a scene. It makes the model predict not the attribute of each person but the attribute distribution of people in a scene. Therefore, the GAF can be used for action set retrieval to some extent because the similarity of action distribution is evaluated in this retrieval. However, spatial interaction between people is not learned in the GAF. It causes a significant performance drop in the group activity retrieval. In GAFL-PAF, we can also see the high-performance gain of "Ours" in the group activity retrieval. From these results, we can conclude that our location guidance is important for learning group activity. + +Fine-tuning for Group Activity Recognition. Table 4 shows that the comparison of "Dual-AI" and "Ours" with group activity labels on VBD and CAD. In "Dual-AI," the network is trained with group activity labels from scratch. In "Ours," after the pretraining by our GAF learning without the group activity supervision, the network is fine-tuned for GAR with group activity labels. + +On both datasets, our method is better than "Dual-AI." In particular, on CAD, the GAR accuracy obtained by our method is $2.5\%$ better than the GAR accuracy obtained by "Dual-AI." The results demonstrate that our GAF learning is effective as a pre-training for supervised GAR. + +# 5. Concluding Remarks + +Instead of group activity annotations which is difficult due to a variety of similar group activities, our method learns GAF through person attribute prediction without group activity annotations. 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COMPOSER: compositional reasoning of group activity in videos with keypoint-only modality. 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Unlike prior work in which the manual annotation of group activities is required for supervised learning, our method learns the GAF through person attribute prediction without group activity annotations. By learning the whole network in an end-to-end manner so that the GAF is required for predicting the person attributes of people in a group, the GAF is trained as the features of multi-person activity. As a person attribute, we propose to use a person's action class and appearance features because the former is easy to annotate due to its simplicity, and the latter requires no manual annotation. In addition, we introduce a location-guided attribute prediction to disentangle the complex GAF for extracting the features of each target person properly. Various experimental results validate that our method outperforms SOTA methods quantitatively and qualitatively on two public datasets. Visualization of our GAF also demonstrates that our method learns the GAF representing fined-grained group activity classes. Code: https://github.com/ chihina/GAFL-CVPR2024." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 513, + 127, + 525 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 513, + 127, + 525 + ], + "spans": [ + { + "bbox": [ + 47, + 513, + 127, + 525 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 533, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 533, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 533, + 287, + 593 + ], + "type": "text", + "content": "A group activity is defined as what multiple people jointly engage in. Group activities are important targets in image and video understanding, such as team plays in sports [36], conversations in social scenes [3], and people flows in surveillance cameras [28]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 594, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 713 + ], + "type": "text", + "content": "Group Activity Recognition (GAR), in which a frame or video is classified into either of the predefined group activity classes, has been widely investigated in recent years [2, 3, 6, 9, 11, 14, 16, 19, 21, 25, 29, 37-40, 42, 45]. All of these GAR methods are based on supervised learning that requires the ground-truth group activities, as shown in Fig. 1 (a). In addition, it is known that person action recognition, which is also achieved based on a supervised learning manner, supports GAR [2, 3, 6, 9, 11, 14, 19, 21, 25, 29, 37, 38, 40, 45]." + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 307, + 198, + 539, + 353 + ], + "blocks": [ + { + "bbox": [ + 307, + 198, + 539, + 353 + ], + "lines": [ + { + "bbox": [ + 307, + 198, + 539, + 353 + ], + "spans": [ + { + "bbox": [ + 307, + 198, + 539, + 353 + ], + "type": "image", + "image_path": "7f6601462bd530010594814630216b53bcf9b9f5b9341342e5dd96c348038b2e.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 361, + 354, + 541, + 361 + ], + "lines": [ + { + "bbox": [ + 361, + 354, + 541, + 361 + ], + "spans": [ + { + "bbox": [ + 361, + 354, + 541, + 361 + ], + "type": "text", + "content": "(b) Ours (group activity feature learning with person attribute)" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 373, + 545, + 440 + ], + "lines": [ + { + "bbox": [ + 304, + 373, + 545, + 440 + ], + "spans": [ + { + "bbox": [ + 304, + 373, + 545, + 440 + ], + "type": "text", + "content": "Figure 1. Difference between annotations for GAR and our group activity feature learning. (a) Supervised GAR employs group activity annotations that are difficult due to various similar group activities. (b-1) Our GAF learning employs person action annotations that are easy due to their simplicity. (b-2) We further propose annotation-free GAF learning with person appearance features." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 461, + 546, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 461, + 546, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 461, + 546, + 628 + ], + "type": "text", + "content": "Such supervised learning requires manually-annotated training data. For GAR, group activity annotations are required. In addition to labor-intensive and erroneous annotations, a difficulty peculiar to GAR is the complexity of the group activities. For example, while only four elemental group activity classes are annotated in a widely-used team-sport dataset [15], they may be insufficient for practical purposes such as tactical analysis (e.g., 200 or more plays are defined in American Football [8]). That is, more fine-grained activity classes are required for several applications of group activity analysis. It is, however, difficult to correctly define and annotate such complex, fine-grained activity classes, even manually, because of visually minor but highly contextual differences among those classes." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 630, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 547, + 714 + ], + "type": "text", + "content": "Such difficulty in manual annotations of group activities motivates us to learn a Group Activity Feature (GAF) in which features of multi-person activity are learned as a compact latent vector without group activity annotations. We note here that GAFs, which represent the complex features of multi-person activity, may have enough information to predict the attributes of each person in a group." + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18233" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "content": "With this regard, this paper proposes GAF learning using person attribute (e.g., action and appearance), which is easier to provide compared with the complex group activity annotation, as shown in Fig. 1 (b). With the person attribute related to the group activity, the GAF can narrow down the possible attribute of each person. For example, Fig. 2, in which a spike is observed, shows that the possible person action enclosed by the purple rectangle (i.e., digging) can be narrowed down by the GAF representing the scene context (i.e., spike group activity) with the person's location." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 193, + 287, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 193, + 287, + 289 + ], + "spans": [ + { + "bbox": [ + 46, + 193, + 287, + 289 + ], + "type": "text", + "content": "As a person attribute for our GAF learning, person action can be used as shown in Fig. 1 (b-1). This is because person action is strongly related to the group activities and is essential to support GAR as mentioned above. However, manual annotations are still required to use person action. While the annotations of person action are easier than the one of group activities defined with complex people interaction, such action annotations are still labor-intensive." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 289, + 288, + 409 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 289, + 288, + 409 + ], + "spans": [ + { + "bbox": [ + 46, + 289, + 288, + 409 + ], + "type": "text", + "content": "To alleviate such difficulty in manual annotations, we also propose to learn GAF through the task of appearance feature prediction of each person in a group without manual annotations, as shown in Fig. 1 (b-2). While the reduction of annotation cost have been studied widely, including active learning [13, 26], few-shot learning [35, 44], and self-supervised learning [4, 5, 7, 10, 18, 23, 24, 32, 33, 41, 43], we follows the framework of self-supervised learning, where supervision signals are derived from the input data and any manual annotations are unnecessary." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 59, + 410, + 268, + 421 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 410, + 268, + 421 + ], + "spans": [ + { + "bbox": [ + 59, + 410, + 268, + 421 + ], + "type": "text", + "content": "Our novel contributions are summarized as follows:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 426, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 47, + 426, + 287, + 474 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 426, + 287, + 474 + ], + "spans": [ + { + "bbox": [ + 47, + 426, + 287, + 474 + ], + "type": "text", + "content": "- GAF learning through person attribute prediction: Unlike supervised GAR, we propose GAF learning through person attribute prediction without group activity annotations. This paper proposes its two variants:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 55, + 474, + 288, + 558 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 474, + 288, + 558 + ], + "spans": [ + { + "bbox": [ + 55, + 474, + 288, + 558 + ], + "type": "text", + "content": "- GAF Learning with Person Action Classes (GAFL-PAC): As a person attribute, we utilize person action classes, which are more easily annotated than group activities defined with complex inter-people interactions (Fig. 1 (b-1)). In addition, for practical use of GAR and other group-related applications, the annotations of person actions are already given in general [3, 14]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 55, + 559, + 287, + 630 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 559, + 287, + 630 + ], + "spans": [ + { + "bbox": [ + 55, + 559, + 287, + 630 + ], + "type": "text", + "content": "- GAF Learning with Person Appearance Features (GAFL-PAF): We also utilize person appearance features that can be obtained by a pre-trained model (e.g., VGG) without manual annotation (Fig. 1 (b-2)). The appearance features are suitable as a person attribute due to the high relationship with multi-person activity." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 630, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 630, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 47, + 630, + 287, + 689 + ], + "type": "text", + "content": "- Fine granularity of our GAF: With the GAF learning through person attribute prediction, our method can learn fine-grained GAF that represents visual-subtle but important differences that are not represented in a manually-defined activity class, as shown in Fig. 6." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": "- Location-Guided Person Attribute Prediction Using GAF: While predicting the person attribute using the" + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "type": "image", + "bbox": [ + 307, + 71, + 541, + 144 + ], + "blocks": [ + { + "bbox": [ + 307, + 71, + 541, + 144 + ], + "lines": [ + { + "bbox": [ + 307, + 71, + 541, + 144 + ], + "spans": [ + { + "bbox": [ + 307, + 71, + 541, + 144 + ], + "type": "image", + "image_path": "6935fa9b6710768106f1d178a1f279956a3a1f84aa75ce6d259eefa88ef4fc8c.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 152, + 545, + 197 + ], + "lines": [ + { + "bbox": [ + 304, + 152, + 545, + 197 + ], + "spans": [ + { + "bbox": [ + 304, + 152, + 545, + 197 + ], + "type": "text", + "content": "Figure 2. Example of our group activity feature learning. In this example, a group activity feature is learned to extract the scene context (i.e., spike group activity) through prediction of person attribute (e.g., digging). See Fig. 3 for the detailed architecture." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 313, + 218, + 545, + 291 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 218, + 545, + 291 + ], + "spans": [ + { + "bbox": [ + 313, + 218, + 545, + 291 + ], + "type": "text", + "content": "GAF is required in our method, extracting the features of each target person from the GAF is difficult. This is because the GAF represents complex features of multi-person activity. This feature extraction is achieved by location guidance in which each person's location feature is embedded into the GAF with positional encoding." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 302, + 392, + 314 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 302, + 392, + 314 + ], + "spans": [ + { + "bbox": [ + 306, + 302, + 392, + 314 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 322, + 458, + 335 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 322, + 458, + 335 + ], + "spans": [ + { + "bbox": [ + 306, + 322, + 458, + 335 + ], + "type": "text", + "content": "2.1. Group Activity Recognition" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 340, + 545, + 448 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 340, + 545, + 448 + ], + "spans": [ + { + "bbox": [ + 304, + 340, + 545, + 448 + ], + "type": "text", + "content": "Supervision by group activity labels. While we propose the GAF learning without group activity annotations (Fig. 1 (b)), various GAR methods supervised by group activity annotations (i.e., Fig. 1 (a)) have been proposed. In [16, 40, 42], only the labels of group activity are required for training. In [16], a group activity is recognized from a whole image without any person features. Kim et al [42] and Yan et al [40] employ the set of person features as input for a Graph Neural Network (GNN) as with [6, 37]." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 449, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 449, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 449, + 545, + 544 + ], + "type": "text", + "content": "Supervision by the labels of person action and group activity. Different from the aforementioned methods only with group activity supervision, the GAR network is jointly trained with the person action recognition network in [2, 3, 6, 9, 11, 14, 19, 21, 25, 29, 37, 45] for augmenting GAR. In [6, 37], GNN models the interactions between person features. In [9, 11, 19, 29, 45], Transformer [31] improves modeling the interactions between person features for GAR." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 544, + 545, + 603 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 544, + 545, + 603 + ], + "spans": [ + { + "bbox": [ + 304, + 544, + 545, + 603 + ], + "type": "text", + "content": "While all of the methods introduced in Sec. 2.1 employ the annotation of group activities, our method learns GAF without group activity labels. Following the success of interaction modeling in [9, 11, 19, 29, 45], we also learn the GAF with Transformer." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 611, + 519, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 611, + 519, + 624 + ], + "spans": [ + { + "bbox": [ + 306, + 611, + 519, + 624 + ], + "type": "text", + "content": "2.2. Self-supervised Representation Learning" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": "Image-based pretext tasks. Most pretext tasks for self-supervised image representation utilize the transformation of original images. In Gidaris et al. [10], Zhang et al. [43], and Larsson et al. [18], each original image is rotated, affinely- and projectively-transformed, and grayscale, respectively. The image representation model is trained so that the model undoes each image. While these meth" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18234" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "content": "ods [10, 18, 43] employ a whole image, patches extracted from the image are used in [4, 23, 24]. Doersch et al. [4] predict the spatial configuration (i.e., relative positions) of randomly-sampled patches. In Noroozi et al. [23], jigsaw puzzles in which all patches of an image are shuffled are solved. Pathak et al. [24] inpaint partially-erased images." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 146, + 288, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 146, + 288, + 277 + ], + "spans": [ + { + "bbox": [ + 46, + 146, + 288, + 277 + ], + "type": "text", + "content": "Video-based pretext tasks. While the image-based methods can be applied to a video, video-specific pretext tasks are also proposed in [5, 7, 32, 33, 41]. In Yao et al. [41] and Wang et al. [33], the paces of video clips are arbitrarily changed (e.g., normal, half, and double speeds), and video representation is learned by solving a pace prediction problem. In Fernando et al. [7], sequential video clips are randomly reordered, and video representation is learned so that these reordered and original clips can be classified. Wang et al. [32] employ appearance cues as well as motion statistics for spatial-temporal representation learning." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 280, + 287, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 280, + 287, + 423 + ], + "spans": [ + { + "bbox": [ + 46, + 280, + 287, + 423 + ], + "type": "text", + "content": "While all of the representation learning methods introduced above extract low-level image features for various downstream tasks such as general image/video classification and prediction, our method focuses on features useful for group-related tasks (e.g., group scene retrieval and clustering). As with our method, Ibrahim et al. [14] aims to extract multi-person scene features through GNN in an unsupervised manner, while the relation of each person to a group activity is not fully captured. Our method incorporates such intimate relations between individuals and group activity (e.g., digging in a spike scene) using the task of location-guided person attribute prediction from a GAF." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 441, + 153, + 454 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 441, + 153, + 454 + ], + "spans": [ + { + "bbox": [ + 47, + 441, + 153, + 454 + ], + "type": "text", + "content": "3. Proposed Method" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 463, + 287, + 559 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 463, + 287, + 559 + ], + "spans": [ + { + "bbox": [ + 46, + 463, + 287, + 559 + ], + "type": "text", + "content": "Our GAF learning network consists of three stages, (a), (b), and (c) (Fig. 3). In stage (a), the features of each person are extracted (Sec. 3.1). In stage (b), the features of several people are masked (i.e., removed) during training for GAF enhancement (Sec. 3.2). Then, the masked person features are fed into the transformer-based GAF learning network (Sec. 3.3). In stage (c), the attribute of each person is predicted from the GAF with location guidance (Sec. 3.4)." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 573, + 189, + 585 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 573, + 189, + 585 + ], + "spans": [ + { + "bbox": [ + 47, + 573, + 189, + 585 + ], + "type": "text", + "content": "3.1. Person Feature Extractor" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": "Overview. As shown in Fig. 3 (a), the set of person features " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{set} \\in \\mathbb{R}^{T \\times N \\times C}" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": " are extracted from images. " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{set}" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": " is composed of the features of " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": " people obtained from " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": " frames in a video. " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": " is the dimension of person " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": "'s feature vector, " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{ind}^p \\in \\mathbb{R}^C" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": ", indicated by a blue cuboid in Fig. 3 (a). " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{ind}^p" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": " consists of appearance features (denoted by " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{app}^p \\in \\mathbb{R}^C" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": ") and location features (denoted by " + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{loc}^p \\in \\mathbb{R}^C" + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": ") in our implementation because their effectiveness is validated for GAR [9, 11, 19, 25, 45], while other features (e.g., body keypoints) can also be used." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": "Detail. " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{app}^{p}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " is extracted by the following three steps, as with [42]. First, a feature map is extracted from the whole image by VGG [27]. Then, RoIAlign [12] is applied with the bounding box of each person to obtain the feature map for each person. Finally, the feature map of each person is embedded into " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": "-dimensional appearance features with a linear transformation. From the " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{app}^{p}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " people between " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " frames, we construct " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{app} \\in \\mathbb{R}^{T \\times N \\times C}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ". In addition to " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{app}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{loc}^{p}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " is also essential to understand the spatial structure of a group, as " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{loc}^{p}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " is used for GAR [9, 11, 25, 37, 45]. As with [11], the center point of each person bounding box, " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "(x,y)" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ", is embedded into " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{loc}^{p}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " by a spatial positional encoding so that " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{loc} \\in \\mathbb{R}^{T \\times N \\times C}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " whose dimension is equal to " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{app}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ". Finally, " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{loc}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " is elementwise added with " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{app}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " to obtain the set of person features, " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{set}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ". Here, we denote person " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": "'s features in " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " frames (i.e., a slice of " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{set}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ") as " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{ind}^{p} \\in \\mathbb{R}^{T \\times C}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "p \\in \\{1,\\dots,N\\}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ") and, similarly, person " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": "'s location features in " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " frames (i.e., a slice of " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{loc}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ") as " + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "F_{loc}^{p} \\in \\mathbb{R}^{T \\times C}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "inline_equation", + "content": "p \\in \\{1,\\dots,N\\}" + }, + { + "bbox": [ + 304, + 72, + 545, + 302 + ], + "type": "text", + "content": ")." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 308, + 485, + 320 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 308, + 485, + 320 + ], + "spans": [ + { + "bbox": [ + 305, + 308, + 485, + 320 + ], + "type": "text", + "content": "3.2. Masked Person Modeling (MPM)" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 326, + 545, + 410 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 326, + 545, + 410 + ], + "spans": [ + { + "bbox": [ + 304, + 326, + 545, + 410 + ], + "type": "text", + "content": "Overview. In the set of person features " + }, + { + "bbox": [ + 304, + 326, + 545, + 410 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\text{set}}" + }, + { + "bbox": [ + 304, + 326, + 545, + 410 + ], + "type": "text", + "content": ", the features of randomly sampled people are masked (e.g., " + }, + { + "bbox": [ + 304, + 326, + 545, + 410 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\text{ind}}^{1}" + }, + { + "bbox": [ + 304, + 326, + 545, + 410 + ], + "type": "text", + "content": " indicated by a black cuboid in Fig. 3(b)) during training. By extracting such features with our Masked Person Modeling (MPM), our network is expected to learn the features of the interaction between unmasked people for predicting the attribute of the masked person." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "spans": [ + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "text", + "content": "Detail. The binary mask for " + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "text", + "content": "-th person (denoted by " + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "inline_equation", + "content": "M^p \\in \\mathbb{R}^{T \\times C}" + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "text", + "content": ") is initialized by filling 1 in all values. Then, " + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "inline_equation", + "content": "N_{mask}" + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "text", + "content": " people to be masked are randomly sampled from all " + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "text", + "content": " people in a scene. All values in " + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "inline_equation", + "content": "M^p" + }, + { + "bbox": [ + 305, + 425, + 545, + 484 + ], + "type": "text", + "content": " for the randomly sampled people are updated with 0." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "content": "From the all " + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "inline_equation", + "content": "M^p" + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "content": " people, we construct " + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "inline_equation", + "content": "M = [M^1,\\dots ,M^N ]\\in \\mathbb{R}^{T\\times N\\times C}" + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "content": ". Then, " + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "content": " is elementwise multiplied by " + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{set}" + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "content": " to obtain the masked person features " + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{mask}" + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "content": " for our GAF training. Note that all values in " + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 305, + 484, + 545, + 555 + ], + "type": "text", + "content": " are set to be 0 during inference to preserve features of all people in a GAF." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 563, + 527, + 576 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 563, + 527, + 576 + ], + "spans": [ + { + "bbox": [ + 305, + 563, + 527, + 576 + ], + "type": "text", + "content": "3.3. Group Activity Feature Learning Network" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "Overview. The GAF " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " is extracted from the set of masked person features " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{mask}" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " obtained in Sec. 3.2. For this GAF learning, we employ Transformer to model spatial- and temporal-interactions between people in accordance with [11, 19]. Our transformer-based GAF learning network consists of two branches (i.e., TS and ST branches) similar to [11]. As shown in Fig. 3, the Temporal Transformer encoder " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "(T^T)" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " and the Spatial Transformer encoder " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "(T^S)" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " are used in both branches, but they are placed in reverse order in the two branches. The combination of these two branches can model the spatial-temporal interactions" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18235" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 68, + 545, + 223 + ], + "blocks": [ + { + "bbox": [ + 47, + 68, + 545, + 223 + ], + "lines": [ + { + "bbox": [ + 47, + 68, + 545, + 223 + ], + "spans": [ + { + "bbox": [ + 47, + 68, + 545, + 223 + ], + "type": "image", + "image_path": "9acc36c397b402613e00111436e8561dca356b09e9d7cacf7bb8ba65e83d93c2.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 236, + 546, + 270 + ], + "lines": [ + { + "bbox": [ + 46, + 236, + 546, + 270 + ], + "spans": [ + { + "bbox": [ + 46, + 236, + 546, + 270 + ], + "type": "text", + "content": "Figure 3. Overview of our GAF learning network. (a) Person feature extractor. The person feature is composed of appearance and location features. (b) GAF learning network. The GAF is learned from extracted people features. (c) Location-guided attribute prediction network with the GAF. The attribute of each person is predicted from the location feature of the person and the GAF extracted in (b)." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 290, + 287, + 339 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 290, + 287, + 339 + ], + "spans": [ + { + "bbox": [ + 46, + 290, + 287, + 339 + ], + "type": "text", + "content": "between people, as proven in GAR [11, 19]. While the transformer-based network is used in our method, the network can be replaced with any SOTA network without difficulties because the stage (i.e., Fig. 3 (b)) is modularized." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "spans": [ + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "type": "text", + "content": "Detail. " + }, + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{mask}" + }, + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "type": "text", + "content": " is independently fed into the TS and ST branches to acquire " + }, + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{mask}^{TS}" + }, + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{mask}^{ST}" + }, + { + "bbox": [ + 46, + 353, + 287, + 378 + ], + "type": "text", + "content": ", respectively:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 74, + 381, + 287, + 396 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 74, + 381, + 287, + 396 + ], + "spans": [ + { + "bbox": [ + 74, + 381, + 287, + 396 + ], + "type": "interline_equation", + "content": "\\boldsymbol {F} _ {\\text {m a s k}} ^ {T S} = T ^ {S} \\left(\\boldsymbol {F} _ {\\text {m a s k}} + M L P \\left(T ^ {T} \\left(\\boldsymbol {F} _ {\\text {m a s k}}\\right)\\right)\\right) \\tag {1}", + "image_path": "b00fe01bd7ba61be1c3e71c51b39f725368deaffb8c4f3545f14309a20a1ea61.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 75, + 398, + 287, + 412 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 75, + 398, + 287, + 412 + ], + "spans": [ + { + "bbox": [ + 75, + 398, + 287, + 412 + ], + "type": "interline_equation", + "content": "\\boldsymbol {F} _ {\\text {m a s k}} ^ {S T} = T ^ {T} \\left(\\boldsymbol {F} _ {\\text {m a s k}} + M L P \\left(T ^ {S} \\left(\\boldsymbol {F} _ {\\text {m a s k}}\\right)\\right)\\right) \\tag {2}", + "image_path": "e09ed3a38ff800e6cfebd807307cdf9e9469a2e12c6eedf8b230feef3a7a69bf.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "spans": [ + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "inline_equation", + "content": "MLP" + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "content": " denotes the multi-layer perceptron. " + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "inline_equation", + "content": "G^{TS} \\in \\mathbb{R}^C" + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "inline_equation", + "content": "G^{ST} \\in \\mathbb{R}^C" + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "content": " are obtained from " + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "inline_equation", + "content": "F_{mask}^{TS}" + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "inline_equation", + "content": "F_{mask}^{ST}" + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "content": ", respectively, by the Temporal Max Pooling (denoted by " + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "inline_equation", + "content": "P^{TM}" + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "content": ") and the Spatial Max Pooling (denoted by " + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "inline_equation", + "content": "P^{SM}" + }, + { + "bbox": [ + 47, + 418, + 287, + 479 + ], + "type": "text", + "content": "), as with previous methods [9, 37]:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 104, + 483, + 287, + 498 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 104, + 483, + 287, + 498 + ], + "spans": [ + { + "bbox": [ + 104, + 483, + 287, + 498 + ], + "type": "interline_equation", + "content": "\\boldsymbol {G} ^ {T S} = P ^ {S M} \\left(P ^ {T M} \\left(\\boldsymbol {F} _ {\\text {m a s k}} ^ {T S}\\right)\\right) \\tag {3}", + "image_path": "dbd1648a50cc161d6ff08e36e3ac01a6aacc79bae5dde776e66b377d5b9c34df.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 106, + 499, + 287, + 514 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 106, + 499, + 287, + 514 + ], + "spans": [ + { + "bbox": [ + 106, + 499, + 287, + 514 + ], + "type": "interline_equation", + "content": "\\boldsymbol {G} ^ {S T} = P ^ {S M} \\left(P ^ {T M} \\left(\\boldsymbol {F} _ {\\text {m a s k}} ^ {S T}\\right)\\right) \\tag {4}", + "image_path": "d4dcec9f9517367558650cd25f47b74e3243dab85c196953a61c3209a0c6db65.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "type": "text", + "content": "Finally, " + }, + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "type": "inline_equation", + "content": "G^{TS}" + }, + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "type": "inline_equation", + "content": "G^{ST}" + }, + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "type": "text", + "content": " are concatenated to obtain the final GAF " + }, + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "type": "inline_equation", + "content": "G\\in \\mathbb{R}^{2C}" + }, + { + "bbox": [ + 46, + 520, + 287, + 544 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 127, + 549, + 287, + 563 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 127, + 549, + 287, + 563 + ], + "spans": [ + { + "bbox": [ + 127, + 549, + 287, + 563 + ], + "type": "interline_equation", + "content": "\\boldsymbol {G} = \\boldsymbol {G} ^ {T S} \\oplus \\boldsymbol {G} ^ {S T} \\tag {5}", + "image_path": "129c4a26801094dca3a94bc5601fa0b52a0e87efe66c3b35b720d1088cd1d64c.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "text", + "content": "During training, " + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "text", + "content": " is fed into the attribute prediction network (denoted by " + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "inline_equation", + "content": "APN" + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "text", + "content": "), as shown in Fig. 3 (c). By backpropagating a loss used in this person attribute prediction not only inside " + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "inline_equation", + "content": "APN" + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "text", + "content": " but also across the whole network shown in Fig. 3, " + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 570, + 287, + 653 + ], + "type": "text", + "content": " can be trained as the GAF. The details of person attribute prediction and the loss used in this prediction are described in Sec. 3.4 and Sec.3.5, respectively." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "text", + "content": "After predicting " + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "text", + "content": " in inference, " + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "text", + "content": " can be used in various ways such as a pretrained model for downstream supervised tasks and unsupervised learning tasks (e.g., retrieval and clustering), as mentioned in Sec. 1. The effectiveness of " + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 654, + 287, + 712 + ], + "type": "text", + "content": " in these tasks is validated in Sec. 4." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 290, + 473, + 302 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 290, + 473, + 302 + ], + "spans": [ + { + "bbox": [ + 306, + 290, + 473, + 302 + ], + "type": "text", + "content": "3.4. Attribute Prediction with GAF" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "spans": [ + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "text", + "content": "Overview. Using " + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "text", + "content": " obtained in Sec. 3.3, the attribute of each person is predicted by the " + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "inline_equation", + "content": "APN" + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "text", + "content": " (Fig. 3 (c)). To predict the attribute of " + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "text", + "content": "-th person, we use their location features (i.e., " + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "inline_equation", + "content": "F_{loc}^{p}" + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "text", + "content": ") as guidance for attribute prediction from " + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 312, + 546, + 361 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 391, + 545, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 391, + 545, + 415 + ], + "spans": [ + { + "bbox": [ + 305, + 391, + 545, + 415 + ], + "type": "text", + "content": "Detail. " + }, + { + "bbox": [ + 305, + 391, + 545, + 415 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 391, + 545, + 415 + ], + "type": "text", + "content": " is fed into the attribute prediction network with the location of each person as follows:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 369, + 430, + 545, + 444 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 369, + 430, + 545, + 444 + ], + "spans": [ + { + "bbox": [ + 369, + 430, + 545, + 444 + ], + "type": "interline_equation", + "content": "\\boldsymbol {A} _ {P R E D} ^ {p} = A P N (\\boldsymbol {G}, \\boldsymbol {F} _ {l o c} ^ {p}) \\tag {6}", + "image_path": "d05badda30a648759452ac3ecf49b907d95f4578c0316473ebaac5ee57d2caaa.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "spans": [ + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "type": "inline_equation", + "content": "A_{PRED}^p \\in \\mathbb{R}^{T \\times R}" + }, + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "type": "text", + "content": " denotes the predicted attribute of each person obtained from " + }, + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "type": "text", + "content": " with their location. The dimension of " + }, + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "type": "inline_equation", + "content": "R" + }, + { + "bbox": [ + 305, + 459, + 545, + 507 + ], + "type": "text", + "content": " changes depending on the type of the predicted person attribute as follows:" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 510, + 544, + 562 + ], + "type": "list", + "angle": 0, + "index": 20, + "blocks": [ + { + "bbox": [ + 306, + 510, + 544, + 535 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 510, + 544, + 535 + ], + "spans": [ + { + "bbox": [ + 306, + 510, + 544, + 535 + ], + "type": "text", + "content": "(i) Person action: " + }, + { + "bbox": [ + 306, + 510, + 544, + 535 + ], + "type": "inline_equation", + "content": "R" + }, + { + "bbox": [ + 306, + 510, + 544, + 535 + ], + "type": "text", + "content": " is the number of action classes and the " + }, + { + "bbox": [ + 306, + 510, + 544, + 535 + ], + "type": "inline_equation", + "content": "A_{PRED}^{p}" + }, + { + "bbox": [ + 306, + 510, + 544, + 535 + ], + "type": "text", + "content": " represents predicted action probabilities." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 537, + 544, + 562 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 537, + 544, + 562 + ], + "spans": [ + { + "bbox": [ + 306, + 537, + 544, + 562 + ], + "type": "text", + "content": "(ii) Person appearance features: " + }, + { + "bbox": [ + 306, + 537, + 544, + 562 + ], + "type": "inline_equation", + "content": "R" + }, + { + "bbox": [ + 306, + 537, + 544, + 562 + ], + "type": "text", + "content": " is the dimension of the appearance features (i.e., " + }, + { + "bbox": [ + 306, + 537, + 544, + 562 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 306, + 537, + 544, + 562 + ], + "type": "text", + "content": ") extracted in Sec. 3.1." + } + ] + } + ], + "index": 19 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 578, + 394, + 589 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 578, + 394, + 589 + ], + "spans": [ + { + "bbox": [ + 306, + 578, + 394, + 589 + ], + "type": "text", + "content": "3.5. Loss Function" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 305, + 600, + 545, + 624 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 600, + 545, + 624 + ], + "spans": [ + { + "bbox": [ + 305, + 600, + 545, + 624 + ], + "type": "text", + "content": "The whole network is trained with a loss function (denoted by " + }, + { + "bbox": [ + 305, + 600, + 545, + 624 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 305, + 600, + 545, + 624 + ], + "type": "text", + "content": ") for attribute prediction as a pretext task as follows:" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 626, + 545, + 714 + ], + "type": "list", + "angle": 0, + "index": 25, + "blocks": [ + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "spans": [ + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "type": "text", + "content": "(i) Person action: When the person attribute is the action, " + }, + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "type": "text", + "content": " is the cross-entropy loss: " + }, + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "type": "inline_equation", + "content": "\\mathcal{L} = \\mathcal{L}_{CE}(\\pmb{A}_{PRED}^{p},\\pmb{A}_{GT}^{p})" + }, + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "type": "inline_equation", + "content": "\\pmb{A}_{GT}^{p}" + }, + { + "bbox": [ + 306, + 626, + 545, + 663 + ], + "type": "text", + "content": " denotes the ground-truth one-hot vector for action." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "text", + "content": "(ii) Person appearance features: For appearance features, " + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "text", + "content": " is the mean squared loss function: " + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{L} = \\mathcal{L}_{MSE}(A_{PRED}^p, A_{GT}^p)" + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "inline_equation", + "content": "A_{GT}^p" + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "text", + "content": " denotes the extracted appearance features (i.e., " + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "inline_equation", + "content": "F_{app}" + }, + { + "bbox": [ + 306, + 665, + 545, + 714 + ], + "type": "text", + "content": ") shown in Sec. 3.1." + } + ] + } + ], + "index": 24 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18236" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 71, + 128, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 71, + 128, + 85 + ], + "spans": [ + { + "bbox": [ + 47, + 71, + 128, + 85 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 91, + 110, + 102 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 91, + 110, + 102 + ], + "spans": [ + { + "bbox": [ + 47, + 91, + 110, + 102 + ], + "type": "text", + "content": "4.1. Datasets" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 110, + 287, + 181 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 110, + 287, + 181 + ], + "spans": [ + { + "bbox": [ + 46, + 110, + 287, + 181 + ], + "type": "text", + "content": "The Volleyball dataset, which contains highly correlated players, is mainly used to validate the effectiveness of our GAF learning. The Collective Activity dataset is also used to validate the generality of our method in Sec. 4.4, while people in this dataset are not highly related to each other compared with the Volleyball dataset." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 182, + 287, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 182, + 287, + 289 + ], + "spans": [ + { + "bbox": [ + 46, + 182, + 287, + 289 + ], + "type": "text", + "content": "VolleyBall Dataset (VBD) [15] consists of 4,830 sequences extracted from 55 games. Each sequence is annotated with one of the predefined eight group activity classes, i.e., Left-spike, Right-spike, Left-set, Right-set, Left-pass, Right-pass, Left-winpoint, and Right-winpoint. While each sequence has 41 frames, its center 20 frames have annotations with the full-body bounding boxes of all players and their action classes, i.e., Waiting, Setting, Digging, Falling, Spiking, Jumping, Moving, Blocking, and Standing." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 289, + 287, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 289, + 287, + 397 + ], + "spans": [ + { + "bbox": [ + 46, + 289, + 287, + 397 + ], + "type": "text", + "content": "Collective Activity Dataset (CAD) [3] contains 44 videos. In each video, every ten frames are annotated with person action classes, i.e., NA, Crossing, Waiting, Queuing, Walking, and Talking, and their bounding boxes. The group activity class is determined by the largest number of person actions in each frame, while the NA class is not included as a group activity class. We follow the previous methods [34, 42] to merge the Crossing and Walking into Moving." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 405, + 167, + 417 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 405, + 167, + 417 + ], + "spans": [ + { + "bbox": [ + 47, + 405, + 167, + 417 + ], + "type": "text", + "content": "4.2. Evaluation Protocols" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 424, + 153, + 435 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 424, + 153, + 435 + ], + "spans": [ + { + "bbox": [ + 47, + 424, + 153, + 435 + ], + "type": "text", + "content": "4.2.1 Evaluation Tasks" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 443, + 287, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 443, + 287, + 467 + ], + "spans": [ + { + "bbox": [ + 46, + 443, + 287, + 467 + ], + "type": "text", + "content": "The quality of the estimated GAF is verified with the following two types of retrieval tasks." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 468, + 287, + 586 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 468, + 287, + 586 + ], + "spans": [ + { + "bbox": [ + 46, + 468, + 287, + 586 + ], + "type": "text", + "content": "Action set retrieval. We employ the same action set retrieval task as in [14]. Action IoU in [14] evaluates the similarity of action structures between query and retrieved images based on the overlap of action distributions. If the IoU exceeds a predefined threshold (e.g., 0.5), the query and retrieved images are regarded as matched. However, in this action IoU, all action classes are counted equally without weights, although the action class distribution is imbalanced (e.g., the percentage of \"standing\" people, who are less informative for tactics, is over " + }, + { + "bbox": [ + 46, + 468, + 287, + 586 + ], + "type": "inline_equation", + "content": "68\\%" + }, + { + "bbox": [ + 46, + 468, + 287, + 586 + ], + "type": "text", + "content": " in VBD)." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 587, + 287, + 670 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 587, + 287, + 670 + ], + "spans": [ + { + "bbox": [ + 46, + 587, + 287, + 670 + ], + "type": "text", + "content": "To resolve this class imbalanced problem, we propose Action Frequency-Inverse Scene Frequency (AF-ISF) inspired by Term Frequency-Inverse Document Frequency (TF-IDF [1]) that evaluates the importance of a word in a document. In AF-ISF, each scene is represented by a feature vector in which each value is computed from frequency statics of action classes as follows:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 100, + 680, + 287, + 695 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 100, + 680, + 287, + 695 + ], + "spans": [ + { + "bbox": [ + 100, + 680, + 287, + 695 + ], + "type": "interline_equation", + "content": "\\boldsymbol {F} \\boldsymbol {V} ^ {i} = \\left[ F V _ {1} ^ {i}, F V _ {m} ^ {i}, \\dots , F V _ {M} ^ {i} \\right] \\tag {7}", + "image_path": "0ad29c1832290b158a010b2f92d6932c4e8cab37818f1bb75de47b91b058bebe.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 143, + 696, + 287, + 711 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 696, + 287, + 711 + ], + "spans": [ + { + "bbox": [ + 143, + 696, + 287, + 711 + ], + "type": "interline_equation", + "content": "F V _ {m} ^ {i} = A F _ {m} ^ {i} \\cdot I S F _ {m} \\tag {8}", + "image_path": "7f41045b52296f50e05e504bf3bb842aa02221fed8c9dec231eecad42321ad07.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": " denote the image index and the number of actions, respectively. " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "AF_{m}^{i}" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": " is the frequency of " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": "-th action class in each image. " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "ISF_{M}" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": " is the inverse frequency of each action class in the dataset. In AF-ISF, the similarity between " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "\\pmb{F}\\pmb{V}^{j}" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "\\pmb{F}\\pmb{V}^{k}" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 306, + 72, + 545, + 179 + ], + "type": "text", + "content": " denote the IDs of query and retrieved images, evaluates the similarity of action structure of the two images. If the cosine similarity exceeds a predefined threshold (e.g., 0.5), the query and retrieved images are regarded as matched as with the Action IoU." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 182, + 545, + 254 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 182, + 545, + 254 + ], + "spans": [ + { + "bbox": [ + 305, + 182, + 545, + 254 + ], + "type": "text", + "content": "While AF-ISF alleviates the action class imbalanced problem, several action classes are distinctive for representing a group scene even if the action distribution is balanced (e.g., \"Spiking\" is more important than \"Falling\" in VBD). Due to this problem, AF-ISF is still improper for the contextual representation of group scenes." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 256, + 545, + 328 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 256, + 545, + 328 + ], + "spans": [ + { + "bbox": [ + 305, + 256, + 545, + 328 + ], + "type": "text", + "content": "Group activity retrieval. Based on the discussion above, we propose to further evaluate whether or not the group activity class of a query scene matches that of the retrieved scene. Note that the group activity annotations are given to the test data (i.e., all query and retrieved images) only for this evaluation and are not used in our GAF learning." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 356, + 421, + 367 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 356, + 421, + 367 + ], + "spans": [ + { + "bbox": [ + 306, + 356, + 421, + 367 + ], + "type": "text", + "content": "4.2.2 Evaluation Metrics" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 379, + 545, + 451 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 379, + 545, + 451 + ], + "spans": [ + { + "bbox": [ + 305, + 379, + 545, + 451 + ], + "type": "text", + "content": "With IoU and AF-ISF in the action set retrieval and group activity matching in the group activity retrieval, we compute the Hit@K used in [14]. In addition, the mean Average Precision (mAP) is used in the action set retrieval as with [14]. For mAP, the Euclidean distance of " + }, + { + "bbox": [ + 305, + 379, + 545, + 451 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 305, + 379, + 545, + 451 + ], + "type": "text", + "content": " between query and retrieved images is used as the confidence indicator." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 465, + 405, + 479 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 465, + 405, + 479 + ], + "spans": [ + { + "bbox": [ + 306, + 465, + 405, + 479 + ], + "type": "text", + "content": "4.3. Training Details" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "spans": [ + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "text", + "content": "Our network is optimized by Adam [17] with " + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "inline_equation", + "content": "\\beta_{1} = 0.9" + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "inline_equation", + "content": "\\beta_{2} = 0.999" + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "inline_equation", + "content": "\\epsilon = 10^{-8}" + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "text", + "content": ". The whole image is resized into " + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "inline_equation", + "content": "320 \\times 640" + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "inline_equation", + "content": "240 \\times 360" + }, + { + "bbox": [ + 305, + 486, + 545, + 630 + ], + "type": "text", + "content": " for VBD and CAD, respectively. We employ the VGG-19 and Inception-v3 models as a person feature extractor (Fig. 3 (a)) for VBD and CAD, respectively. While the person feature extractor trained on person action recognition is fine-tuned through our GAF learning in GAFL-PAC, we freeze the person feature extractor trained on ImageNet in GAFL-PAF following the previous method [14]. Our APN consists of three fully-connected layers. As for the other details, we follow the widely used setting [42]. See the details in the supplementary material." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 645, + 452, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 645, + 452, + 658 + ], + "spans": [ + { + "bbox": [ + 306, + 645, + 452, + 658 + ], + "type": "text", + "content": "4.4. Comparative Experiments" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "content": "We compare our methods with other methods by the following three types of experimental results: (1) the results of retrieval (Sec. 4.4.1), (2) the results of GAR (Sec. 4.4.2), and (3) the visualized distributions of GAFs (Sec. 4.4.3)." + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18237" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 47, + 107, + 563, + 247 + ], + "blocks": [ + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "lines": [ + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "spans": [ + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "type": "text", + "content": "Table 1. Quantitative comparison of retrieval on the VolleyBall Dataset (VBD). The results obtained in two experimental settings (i.g., GAFL-PAC and GAFL-PAF) are separated by double lines. The best result in each column is colored in red. Results obtained by the concatenation of output features (i.e., " + }, + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{grp}^{TS}" + }, + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{grp}^{ST}" + }, + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "type": "text", + "content": ") and " + }, + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "type": "inline_equation", + "content": "\\mathbf{G}" + }, + { + "bbox": [ + 46, + 70, + 545, + 106 + ], + "type": "text", + "content": " are denoted as \"Ours-ind\" and \"Ours-grp\", respectively." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 107, + 563, + 247 + ], + "lines": [ + { + "bbox": [ + 47, + 107, + 563, + 247 + ], + "spans": [ + { + "bbox": [ + 47, + 107, + 563, + 247 + ], + "type": "table", + "html": "
Retrieval typeAction set (IoU [14])Action set (AF-IDF)Group activity
MethodHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3
GAFL-PACHiGCIN [40]74.384.989.555.759.873.680.330.550.066.374.5
DIN [42]79.790.193.460.274.585.288.339.357.073.181.1
Dual-AI [11]67.684.791.656.972.683.788.653.064.476.582.0
Ours-ind82.791.695.059.179.086.889.845.682.788.891.3
Ours-grp83.092.795.564.280.188.491.559.984.889.691.8
GAFL-PAFB1-Compact128 [14]57.975.784.345.841.360.871.429.330.348.059.9
B2-VGG19 [14]63.880.686.846.846.765.875.729.435.453.665.0
HRN [14]60.978.686.046.940.860.972.928.731.247.057.6
Ours-ind64.280.888.345.050.469.377.630.155.072.379.2
Ours-grp64.882.790.346.452.371.481.031.461.175.182.4
", + "image_path": "bc50dac7a5ba55030a33129854b8b39817aa2af514cbb7208010bb1facd3a163.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 47, + 265, + 563, + 406 + ], + "blocks": [ + { + "bbox": [ + 137, + 253, + 455, + 264 + ], + "lines": [ + { + "bbox": [ + 137, + 253, + 455, + 264 + ], + "spans": [ + { + "bbox": [ + 137, + 253, + 455, + 264 + ], + "type": "text", + "content": "Table 2. Quantitative comparison of retrieval on the Collective Activity Dataset (CAD)." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 265, + 563, + 406 + ], + "lines": [ + { + "bbox": [ + 47, + 265, + 563, + 406 + ], + "spans": [ + { + "bbox": [ + 47, + 265, + 563, + 406 + ], + "type": "table", + "html": "
Retrieval typeAction set (IoU [14])Action set (AF-IDF)Group activity
MethodHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3mAPHit@1Hit@2Hit@3
GAFL-PACHiGCIN [40]80.885.489.757.981.085.289.361.686.188.891.9
DIN [42]71.474.174.951.590.192.794.052.890.892.593.2
Dual-AI [11]61.072.576.761.585.586.988.182.782.184.184.7
Ours-ind76.282.689.478.994.895.695.982.294.995.495.7
Ours-grp81.890.793.569.996.196.596.693.994.995.696.3
GAFL-PAFB1-Compact128 [14]48.860.368.238.081.888.289.752.682.488.490.1
B2-VGG19 [14]53.661.666.135.371.180.383.846.772.280.884.2
HRN [14]37.150.158.622.253.264.872.534.254.064.872.4
Ours-ind67.681.385.953.383.788.990.257.588.591.291.9
Ours-grp52.770.374.146.474.080.582.660.179.281.082.0
", + "image_path": "a0344f132ec27e7a8c82916ba43d49717bbfabf421484d2088d96b59dbd8aed2.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 426, + 119, + 437 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 426, + 119, + 437 + ], + "spans": [ + { + "bbox": [ + 47, + 426, + 119, + 437 + ], + "type": "text", + "content": "4.4.1 Retrieval" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": "To validate the effectiveness of the GAF for group representation, the set of person features (i.e., the concatenation of " + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{\\text{grp}}^{TS}" + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{\\text{grp}}^{ST}" + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": " in Fig. 3 (b)) is also evaluated. Specifically, the output features of " + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "inline_equation", + "content": "P^{TM}" + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": " in the TS and ST branches " + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "inline_equation", + "content": "(\\pmb{F}_{\\text{grp}}^{TS}" + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{\\text{grp}}^{ST}" + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": " in Fig. 3) are concatenated and also used for retrieval in our method. Results obtained by the concatenation of output features (i.e., " + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{\\text{grp}}^{TS}" + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\pmb{F}_{\\text{grp}}^{ST}" + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": ") and " + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\pmb{G}" + }, + { + "bbox": [ + 46, + 446, + 287, + 544 + ], + "type": "text", + "content": " are denoted as \"Ours-ind\" and \"Ours-grp\", respectively." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 544, + 287, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 287, + 675 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 287, + 675 + ], + "type": "text", + "content": "Volleyball dataset (GAFL-PAC). Our method is compared with the SOTA GAR methods [11, 40, 42] which are only trained with person action labels as with our method. Table 1 (top) shows that our method is best in action set and group activity retrieval. The results validate that our method learns features about the action structure and the group activity of a scene into the compact latent vector (i.e., " + }, + { + "bbox": [ + 46, + 544, + 287, + 675 + ], + "type": "inline_equation", + "content": "\\pmb{G}" + }, + { + "bbox": [ + 46, + 544, + 287, + 675 + ], + "type": "text", + "content": ") efficiently. The large gain in the group activity retrieval shows that the features of multi-person activity are learned in our GAF in contrast to the SOTA GAR methods [11, 40, 42] where the set of person features is used for the retrieval." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 677, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 715 + ], + "type": "text", + "content": "Volleyball dataset (GAFL-PAF). Our method is compared with the SOTA method [14], the only existing GAF learning method using no person-action and group-activity an" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 426, + 545, + 568 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 545, + 568 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 545, + 568 + ], + "type": "text", + "content": "notations, and baseline methods as with [14]. From Table 1 (bottom), we see that our method performs best in all metrics except that \"HRN\" is better than our method in mAP of Action set (IoU). However, the performance difference is small (i.e., 46.9 and 46.4 in \"HRN\" and \"Ours-grp,\" respectively). Furthermore, our method is better than \"HRN\" in Action set (AF-IDF). From these results, we can say that our GAF is better even in the action set retrieval. Regarding group activity retrieval, our method significantly outperforms the SOTA method. The results validate that our method learns the contextual features of multi-person activity better than the SOTA method." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 570, + 546, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 546, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 546, + 712 + ], + "type": "text", + "content": "Collective activity dataset (GAFL-PAC). The results in GAFL-PAC on CAD are shown in Table 2 (top). The results validate that our method is better than Dual-AI [11] in all metrics. While \"Ours-grp\" is better than \"Ours-ind\" in most metrics, \"Ours-ind\" is better in mAP of Action set (IoU). The action set (IoU) evaluates the similarity of the number of people, so the results may come from that the change in the number of people between scenes on this dataset is addressed well in \"Ours-ind.\" Specifically, we can consider that such information about the number of people may be preserved well in \"Ours-ind.\" where the set of person features is used for retrieval." + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18238" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 70, + 289, + 231 + ], + "blocks": [ + { + "bbox": [ + 51, + 70, + 289, + 231 + ], + "lines": [ + { + "bbox": [ + 51, + 70, + 289, + 231 + ], + "spans": [ + { + "bbox": [ + 51, + 70, + 289, + 231 + ], + "type": "image", + "image_path": "9af64f66df6e96ff08ba693cb82ee26ef20019adc78b472895718d2f1ef77618.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 236, + 288, + 281 + ], + "lines": [ + { + "bbox": [ + 46, + 236, + 288, + 281 + ], + "spans": [ + { + "bbox": [ + 46, + 236, + 288, + 281 + ], + "type": "text", + "content": "Figure 4. Confusion matrices of GAR by nearest neighbor retrieval on VBD and CAD in GAFL-PAF. Each row and column show the ground-truth and recognized group activity, respectively. Results of the other methods are shown in the supplementary material." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "spans": [ + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": "Collective activity dataset (GAFL-PAF). Table 2 (bottom) shows that our method is the best in all metrics among the other methods. The results validate the wide applicability of GAF learned even in general scenes included in CAD. While \"Ours-grp\" is better than \"Ours-ind\" on VBD, \"Ours-ind\" is better on CAD. These opposite results may come from the difference between the number of people in each image. While " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "N = 12" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " people are observed in most images in VBD, around five people on average on CAD. As the number of features in " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "F_{grp}^{TS}" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "F_{grp}^{ST}" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " increase in proportion to the number of observed people, the difficulty in learning " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "F_{grp}^{TS}" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "F_{grp}^{ST}" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " becomes higher. Since this learning difficulty might occur on VBD, spatial max pooling used in \"Ours-grp\" is effective for reducing the feature dimension from " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "NC" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "F_{grp}^{TS}" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "F_{grp}^{ST}" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "G^{TS}" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "inline_equation", + "content": "G^{ST}" + }, + { + "bbox": [ + 46, + 303, + 288, + 485 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 501, + 198, + 514 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 501, + 198, + 514 + ], + "spans": [ + { + "bbox": [ + 47, + 501, + 198, + 514 + ], + "type": "text", + "content": "4.4.2 Group Activity Recognition" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 521, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 521, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 521, + 287, + 593 + ], + "type": "text", + "content": "While no group annotation is used in our GAF learning, the group activity class retrieved by Hit@1, which is equal to 1-nearest neighbor classification, can be regarded as the result of GAR, as done in [20]. While results only in GAFL-PAF are shown in this section, results in GAFL-PAC are available in the supplementary material." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "type": "text", + "content": "Volleyball dataset (GAFL-PAF). As shown in Fig. 4, our method outperforms \"B2-VGG19\" in all group activity classes except for L-winpoint. While \"B2-VGG19\" is better than \"Ours\" in L-winpoint shown at the bottom right of each confusion matrix, \"B2-VGG19\" often misrecognizes the R-winpoint scene as L-winpoint, as shown in the red rectangle cells. Left-spike and Right-spike are especially recognized better in our method than the others. This superiority of our method can be interpreted as follows. In Left-spike and Right-spike, spiking and blocking players who" + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 309, + 70, + 545, + 191 + ], + "blocks": [ + { + "bbox": [ + 309, + 70, + 545, + 191 + ], + "lines": [ + { + "bbox": [ + 309, + 70, + 545, + 191 + ], + "spans": [ + { + "bbox": [ + 309, + 70, + 545, + 191 + ], + "type": "image", + "image_path": "22d15987b9bc3a75c7db44d5cccc4d438f711c63d78cbde5416d33d00843aca8.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 198, + 547, + 232 + ], + "lines": [ + { + "bbox": [ + 305, + 198, + 547, + 232 + ], + "spans": [ + { + "bbox": [ + 305, + 198, + 547, + 232 + ], + "type": "text", + "content": "Figure 5. Visualization of the learned GAF on VBD and CAD in GAFL-PAF. The color of each sample shows the ground-truth of the group activity label corresponding to each test sample." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 308, + 244, + 545, + 401 + ], + "blocks": [ + { + "bbox": [ + 308, + 244, + 545, + 401 + ], + "lines": [ + { + "bbox": [ + 308, + 244, + 545, + 401 + ], + "spans": [ + { + "bbox": [ + 308, + 244, + 545, + 401 + ], + "type": "image", + "image_path": "88c1db0cd07774cdcc5ba7eec9dadbb3256f7fecb28dbbcceb272d86020c7e7c.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 407, + 546, + 453 + ], + "lines": [ + { + "bbox": [ + 305, + 407, + 546, + 453 + ], + "spans": [ + { + "bbox": [ + 305, + 407, + 546, + 453 + ], + "type": "text", + "content": "Figure 6. Visualization of the learned GAF on VBD in GAFL-PAC. The magenta data points (i.e., \"L-pass\") are divided into two sub-categories based on the context (i.e., whether the receiving is caused by the spiking or serving of the opposite player)." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 474, + 545, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 545, + 594 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 545, + 594 + ], + "type": "text", + "content": "are distinctive both in appearance and location cues are always observed. Since these distinctive people are important in predicting not only their attributes but also the attributes of other people, the features of these distinctive people are extracted well even in the compact latent vector (i.e., GAF). Collective activity dataset (GAFL-PAF). The confusion matrices are shown in Fig. 4. The results show that our method is the best in all activity classes. In particular, while VGG19 gets many false negatives in Moving, the number of false negatives in Moving of our method is almost zero." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 610, + 471, + 621 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 610, + 471, + 621 + ], + "spans": [ + { + "bbox": [ + 305, + 610, + 471, + 621 + ], + "type": "text", + "content": "4.4.3 Visualization of Learned GAFs" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": "The distribution of learned GAFs in all test images is visualized in a 2D space by t-SNE [30]. The color of each point shows its annotated group activity class. Figure 5 shows that our method can learn the GAFs better than the other methods because (1) while the inner-class variance is small, the inter-class variance is large, and (2) the data points of similar group activities (e.g., Left-pass and Left-set) are closer." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18239" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 71, + 284, + 148 + ], + "blocks": [ + { + "bbox": [ + 50, + 71, + 284, + 148 + ], + "lines": [ + { + "bbox": [ + 50, + 71, + 284, + 148 + ], + "spans": [ + { + "bbox": [ + 50, + 71, + 284, + 148 + ], + "type": "image", + "image_path": "b992a116519be9053f9443dce951db86c642ca3cacf38c22de7be0e001c06311.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 159, + 286, + 180 + ], + "lines": [ + { + "bbox": [ + 46, + 159, + 286, + 180 + ], + "spans": [ + { + "bbox": [ + 46, + 159, + 286, + 180 + ], + "type": "text", + "content": "Figure 7. Performance changes depending on the number of masking people on VBD." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 48, + 223, + 288, + 313 + ], + "blocks": [ + { + "bbox": [ + 46, + 194, + 286, + 216 + ], + "lines": [ + { + "bbox": [ + 46, + 194, + 286, + 216 + ], + "spans": [ + { + "bbox": [ + 46, + 194, + 286, + 216 + ], + "type": "text", + "content": "Table 3. Effectiveness of our location-guidance on VBD. Results obtained by \"Ours-grp\" are shown as \"Ours.\"" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 223, + 288, + 313 + ], + "lines": [ + { + "bbox": [ + 48, + 223, + 288, + 313 + ], + "spans": [ + { + "bbox": [ + 48, + 223, + 288, + 313 + ], + "type": "table", + "html": "
Retrieval typeAction set (IoU)Action set (AF-IDF)Group activity
MethodHit@1Hit@1Hit@1
GAFL-PACOurs w/o Floc80.075.669.5
Ours83.080.184.8
GAFL-PAFOurs w/o Floc64.151.753.2
Ours64.852.361.1
", + "image_path": "69bd9e093cd5450e1f4fa0d40bb9189f12ebd235115ce2c33dcb24b03d28c549.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 335, + 286, + 478 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 335, + 286, + 478 + ], + "spans": [ + { + "bbox": [ + 46, + 335, + 286, + 478 + ], + "type": "text", + "content": "Our GAFs in GAL-PAC on VBD are also shown in Fig. 6. This figure shows that data points with the same group activity labels are divided into sub-activities. For example, L-pass indicated by magenta data points are divided into two clusters. While the cluster enclosed by the orange rectangle represents L-pass where the person is receiving a ball from the opposite spiker, the other cluster enclosed by the light blue rectangle represents L-pass where the person is receiving a ball from the opposite server. As shown in this example, our GAFs are learned well enough to represent visually subtle but important differences that are not represented in the manually defined activity classes." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 489, + 148, + 502 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 489, + 148, + 502 + ], + "spans": [ + { + "bbox": [ + 47, + 489, + 148, + 502 + ], + "type": "text", + "content": "4.5. Detailed analysis" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "spans": [ + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "text", + "content": "Comparison of the number of masked persons. We explore the optimal number of masked people (i.e., " + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "inline_equation", + "content": "N_{mask}" + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "text", + "content": ") for our MPM. For this comparison, we change " + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "inline_equation", + "content": "N_{mask}" + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "text", + "content": " from 0 to " + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "inline_equation", + "content": "N - 1" + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "inline_equation", + "content": "N_{mask} = 0" + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "text", + "content": " means that " + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "inline_equation", + "content": "F_{set}" + }, + { + "bbox": [ + 46, + 509, + 286, + 567 + ], + "type": "text", + "content": " is directly fed into the transformer encoder without the MPM." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "text", + "content": "Figure 7 shows that the performance changes depending on " + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "inline_equation", + "content": "N_{mask}" + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "text", + "content": " on VBD. The best performance is obtained when " + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "inline_equation", + "content": "N_{mask}" + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "text", + "content": " is the middle number (i.e., 5 and 6 in the GAFL-PAC and GAFL-PAF, respectively), while the performance gain from " + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "inline_equation", + "content": "N_{mask} = 0" + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "text", + "content": " is insignificant. On the other hand, we can also see that the performance with a large masking ratio (i.e., " + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "inline_equation", + "content": "N_{mask} \\in \\{10, 11\\}" + }, + { + "bbox": [ + 46, + 569, + 286, + 687 + ], + "type": "text", + "content": ") drops. These results reveal that the extreme difficulty in the attribute prediction of the masked person from a few non-masked people leads GAF learning to failure." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 689, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 286, + 714 + ], + "type": "text", + "content": "Effect of location-guidance in GAF learning. We ablate " + }, + { + "bbox": [ + 47, + 689, + 286, + 714 + ], + "type": "inline_equation", + "content": "F_{loc}^{p}" + }, + { + "bbox": [ + 47, + 689, + 286, + 714 + ], + "type": "text", + "content": " which is used for guidance to extract the features of" + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 314, + 99, + 535, + 167 + ], + "blocks": [ + { + "bbox": [ + 306, + 71, + 544, + 92 + ], + "lines": [ + { + "bbox": [ + 306, + 71, + 544, + 92 + ], + "spans": [ + { + "bbox": [ + 306, + 71, + 544, + 92 + ], + "type": "text", + "content": "Table 4. Comparison with supervised GAR. Double lines separate the results obtained by VBD and CAD." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 314, + 99, + 535, + 167 + ], + "lines": [ + { + "bbox": [ + 314, + 99, + 535, + 167 + ], + "spans": [ + { + "bbox": [ + 314, + 99, + 535, + 167 + ], + "type": "table", + "html": "
DatasetMethodAccuracy
VBDDual-AI [11]92.1
Ours w/ group activity labels92.4
CADDual-AI [11]94.1
Ours w/ group activity labels96.6
", + "image_path": "48e72d2d1b73f0a94eecbde58dd8a3f5246101155e203cac81c82b581f819ef1.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 187, + 544, + 209 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 187, + 544, + 209 + ], + "spans": [ + { + "bbox": [ + 305, + 187, + 544, + 209 + ], + "type": "text", + "content": "each person in the action prediction network in Fig. 3 (c) (see also Sec. 3.4) on VBD." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "spans": [ + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "type": "text", + "content": "In GAFL-PAC, \"Ours\" is better than \"Ours w/o " + }, + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "type": "inline_equation", + "content": "F_{loc}^{p}" + }, + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "type": "text", + "content": "\" in the all metrics. In particular, the performance gain in the group activity retrieval is large. We can interpret the reason as follows. In \"Ours w/o " + }, + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "type": "inline_equation", + "content": "F_{loc}^{p}" + }, + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "type": "text", + "content": ",\" only " + }, + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 304, + 210, + 544, + 389 + ], + "type": "text", + "content": " is used to predict the attribute of each person in a scene. It makes the model predict not the attribute of each person but the attribute distribution of people in a scene. Therefore, the GAF can be used for action set retrieval to some extent because the similarity of action distribution is evaluated in this retrieval. However, spatial interaction between people is not learned in the GAF. It causes a significant performance drop in the group activity retrieval. In GAFL-PAF, we can also see the high-performance gain of \"Ours\" in the group activity retrieval. From these results, we can conclude that our location guidance is important for learning group activity." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 390, + 544, + 473 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 390, + 544, + 473 + ], + "spans": [ + { + "bbox": [ + 304, + 390, + 544, + 473 + ], + "type": "text", + "content": "Fine-tuning for Group Activity Recognition. Table 4 shows that the comparison of \"Dual-AI\" and \"Ours\" with group activity labels on VBD and CAD. In \"Dual-AI,\" the network is trained with group activity labels from scratch. In \"Ours,\" after the pretraining by our GAF learning without the group activity supervision, the network is fine-tuned for GAR with group activity labels." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 474, + 544, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 474, + 544, + 533 + ], + "spans": [ + { + "bbox": [ + 305, + 474, + 544, + 533 + ], + "type": "text", + "content": "On both datasets, our method is better than \"Dual-AI.\" In particular, on CAD, the GAR accuracy obtained by our method is " + }, + { + "bbox": [ + 305, + 474, + 544, + 533 + ], + "type": "inline_equation", + "content": "2.5\\%" + }, + { + "bbox": [ + 305, + 474, + 544, + 533 + ], + "type": "text", + "content": " better than the GAR accuracy obtained by \"Dual-AI.\" The results demonstrate that our GAF learning is effective as a pre-training for supervised GAR." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 544, + 429, + 558 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 544, + 429, + 558 + ], + "spans": [ + { + "bbox": [ + 306, + 544, + 429, + 558 + ], + "type": "text", + "content": "5. Concluding Remarks" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 565, + 544, + 635 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 565, + 544, + 635 + ], + "spans": [ + { + "bbox": [ + 304, + 565, + 544, + 635 + ], + "type": "text", + "content": "Instead of group activity annotations which is difficult due to a variety of similar group activities, our method learns GAF through person attribute prediction without group activity annotations. Quantitative comparisons and visualized results show that our method can learn informative GAF compared with other methods on the two public datasets." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 635, + 544, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 635, + 544, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 635, + 544, + 712 + ], + "type": "text", + "content": "While our method outperforms all the other methods in our experiments not only for GAF learning but also for GAR, our method is understandably inferior to GAR supervised by group activity annotations. Exploring other pretext tasks such as predicting the joint attention of a group (e.g., [22]) is important future work for further GAF enhancement." + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18240" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 97, + 106, + 109 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 97, + 106, + 109 + ], + "spans": [ + { + "bbox": [ + 48, + 97, + 106, + 109 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 117, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 18, + "blocks": [ + { + "bbox": [ + 53, + 117, + 287, + 138 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 117, + 287, + 138 + ], + "spans": [ + { + "bbox": [ + 53, + 117, + 287, + 138 + ], + "type": "text", + "content": "[1] Akiko N. 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In ECCV, 2022. 1, 2, 3" + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "text", + "content": "18242" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_content_list.json b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..e3b49887c464a3efb479dc4635418ced2855c418 --- /dev/null +++ b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_content_list.json @@ -0,0 +1,1450 @@ +[ + { + "type": "text", + "text": "Learning Inclusion Matching for Animation Paint Bucket Colorization", + "text_level": 1, + "bbox": [ + 127, + 130, + 841, + 151 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yuekun Dai Shangchen Zhou Qinyue Li Chongyi Li Chen Change Loy S-Lab, Nanyang Technological University", + "bbox": [ + 168, + 180, + 800, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "https://ykdai.github.io/projects/InclusionMatching", + "bbox": [ + 259, + 219, + 705, + 233 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/64a68f6eb1e062dcd1e9ec1ff4b94358ecd1bbab9aeb55d2fa4b457d93d22f7a.jpg", + "image_caption": [ + "Figure 1. In the animation industry, digital painters use paint bucket tool to colorize drawn line arts frame by frame. Our proposed pipeline streamlines this process by requiring the painters to colorize just one frame, after which the algorithm autonomously propagates the color to subsequent frames, enabling automatic colorization. Compared with optical-flow-based method RAFT [35] and segment-matching-based method AnT [8], our method can achieve more robust results on challenging cases such as one-to-many matching, large deformation, and tiny region colorization. In this figure, RAFT is trained on Sintel dataset [5] and finetuned on AnimeRun [30]. We use the most frequent color in each segment to colorize each line-enclosed region. ©drawn by Nicca (Sriprachum Kongwisawamit), used with artist permission." + ], + "image_footnote": [], + "bbox": [ + 84, + 241, + 890, + 458 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 560, + 313, + 574 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Colorizing line art is a pivotal task in the production of hand-drawn cel animation. This typically involves digital painters using a paint bucket tool to manually color each segment enclosed by lines, based on RGB values predetermined by a color designer. This frame-by-frame process is both arduous and time-intensive. Current automated methods mainly focus on segment matching. This technique migrates colors from a reference to the target frame by aligning features within line-enclosed segments across frames. However, issues like occlusion and wrinkles in animations often disrupt these direct correspondences, leading to mismatches. In this work, we introduce a new learning-based inclusion matching pipeline, which directs the network to comprehend the inclusion relationships between segments rather than relying solely on direct visual correspondences. Our method features a two-stage pipeline that integrates a coarse color warping module with an inclusion matching module, enabling more nuanced and accurate colorization. To facilitate the training of our network, we also develop a unique dataset, referred to as PaintBucket-Character. This", + "bbox": [ + 75, + 598, + 473, + 902 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "dataset includes rendered line arts alongside their colorized counterparts, featuring various 3D characters. Extensive experiments demonstrate the effectiveness and superiority of our method over existing techniques.", + "bbox": [ + 498, + 560, + 893, + 623 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 500, + 645, + 632, + 660 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Colorizing line art is a critical step in hand-drawn animation production. Initially, key animators create the characters' keyframes, followed by in-between animators who generate intermediate frames and refine keyframes for seamless connection between each stroke, as described in [31]. These line arts are then scanned into binary images, featuring a primary color palette of red, blue, green, and black, which represents highlights, shadows, special instructions (e.g., eye irises), and normal lines respectively. These scanned images, with regions of transparent background as shown in Fig. 1, are forwarded to digital painters. The painters use a paint bucket tool and a designated color palette to fill each line-enclosed segment, including the color lines, which is known as paint bucket colorization. Finally, special effect artists add visual enhancements, such as anti-aliasing, to", + "bbox": [ + 496, + 672, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "25544", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "blend character animations with backgrounds, culminating in the final video composition, detailed in [20].", + "bbox": [ + 75, + 90, + 468, + 119 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Line art colorization is a notably laborious process. For instance, even the relatively simple scenario in Fig. 1, involving 93 segments, still requires hundreds of manual clicks. To mitigate this demanding task, several commercial software applications like Retas Studio Paintman, OpenToonz, and CLIP Studio Paint have been developed. These tools provide helpful features that allow users to easily adjust assigned colors, fill small areas, and aid in line colorization. Despite these advancements, fully automated colorization has yet to be realized.", + "bbox": [ + 75, + 123, + 467, + 273 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To address the challenges of line art colorization, numerous segment-matching methods have been developed for identifying corresponding segments in reference and target frames. Traditional graph-based approaches [17-19, 39, 44] consider each segment as a graph node and establish edges based on adjacency relationships. These methods employ optimization techniques to minimize topological similarity loss among corresponding nodes. However, they are time-intensive, often taking several minutes to process a single image with around 100 segments. Casey et al. [8] introduced the Animation Transformer (AnT) and its application Cadmium, which significantly improved segment matching. AnT standardizes the size of each segment and employs convolutional neural networks (CNNs) to extract features, transforming the image into a segment sequence. This converts segment matching into a sequence-to-sequence problem. Although AnT excels in aligning segments between adjacent frames featuring minimal motion, it struggles in more complex scenarios, particularly those with occlusion or pronounced motion. During occlusions, interlaced lines tend to fragment segments into multiple pieces, as depicted in Fig. 2. This fragmentation disrupts the strict correspondence between segments, rendering the task of segment matching inherently problematic and poorly defined.", + "bbox": [ + 75, + 277, + 468, + 638 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this study, we introduce the novel notion of 'inclusion matching', which obviates the necessity for exact segment-to-segment correspondence. Instead of direct segment matching, our approach computes the likelihood of each segment in a target frame being included within a specific region of a reference frame. Our methodology is unique in that it follows a coarse-to-fine colorization pipeline, inspired by the approach of skilled digital painters. This approach typically begins with coloring larger, more noticeable segments across all frames before filling in details of smaller segments in each frame. Motivated by this workflow, our pipeline first computes optical flow between line sketches, warping colors from a reference to a target frame to achieve a preliminary, coarse colorization. This is followed by the application of an inclusion matching module, which refines the colorization result of tiny segments.", + "bbox": [ + 75, + 642, + 467, + 882 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The sparse nature of line art requires special formula", + "bbox": [ + 96, + 885, + 467, + 898 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/8e896adca3dc90fadbbb9c687f5e54dc73f98b22406890693cef3f5838eea213.jpg", + "image_caption": [ + "Figure 2. Methods relying on segment matching typically seek the most similar segment across frames, yet challenges arise in scenarios involving occlusion and wrinkles. This is particularly evident in tiny segments, as highlighted in the red box, where disruptions in correspondence lead to mismatches. Our innovative approach, based on inclusion matching, addresses this issue by estimating the inclusion relationship rather than pursuing direct correspondence, as illustrated by the comparison of red and blue matching lines." + ], + "image_footnote": [], + "bbox": [ + 506, + 87, + 883, + 257 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "tion in our approach. Specifically, recognizing the necessity for a large receptive field in extracting line art features, we employ a U-Net structure [25] to process concatenated color and line features. To address the difficulty in matching segments under large deformations, we extract line semantic features using CLIP [23] and concatenate them with features from the U-Net's bottleneck. This allows the network to match the region with the same semantic information across frames. Finally, we introduce super-pixel pooling at each segment to transfer the image into tokens for sequence-to-sequence matching.", + "bbox": [ + 498, + 385, + 890, + 551 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Dataset plays a key role in the success of our method. To train and evaluate our method, we select 22 character models from Mixamo [3] and Aplaybox [1]. We mimic real intermediate line art data on the animation coloring production line. We disable the anti-aliasing and provide the color lines which is quite common in animation production. Then we use 3D software Cinema 4D to synthesize a specially-designed cartoon character colorization dataset named PaintBucket-Character.", + "bbox": [ + 498, + 560, + 890, + 694 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The contributions of our work include the introduction of the PaintBucket-Character dataset tailored for paint bucket colorization tasks, the novel inclusion matching pipeline addressing the challenge of lacking strict segment correspondence, and a new coarse-to-fine baseline that outperforms existing solutions, particularly in scenes with occlusion. Our experiments demonstrate that our method surpasses the performance of recent AnT application Cadmium, and outperforms the results presented by Li et al. [30]. Notably, the advantages of our approach extend beyond dataset improvements, highlighting the effectiveness of our newly designed inclusion matching pipeline and the coarse-to-fine baseline in the context of animation colorization.", + "bbox": [ + 498, + 704, + 890, + 898 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "25545", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/e3c167aff20d190f42a038d09f18e1f8361a9e78314bf00331ea9eeae025417e.jpg", + "image_caption": [ + "Figure 3. Several examples of our rendered characters in PaintBucket-Character dataset." + ], + "image_footnote": [], + "bbox": [ + 117, + 85, + 851, + 263 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 281, + 218, + 296 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Line Art Colorization. Line art colorization aims to create reasonable colors in the sketch's blank regions. To achieve precise control, many user guidance types are designed including text [15, 45], scribble [6, 33, 40, 41], colored reference [4, 7, 9, 16, 32, 34, 37, 42, 43]. These methods mainly focus on pixel-wise estimation and cannot fill flat accurate RGB values assigned by the color designer in line arts' segments, which always leads to flickering and color bleeding. Besides, in the post-processing, the special effect artists often need to select specific colors to create various effects such as ramp or glow for the character's specific region. Thus, current line art colorization methods are still difficult to be merged into animation industrial processes.", + "bbox": [ + 75, + 318, + 470, + 513 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Animation-related Dataset. To facilitate hand-drawn animation production, many real and rendered datasets are proposed. To boost video interpolation performance, Li et al. [29] propose the ATD-12K dataset which consists of triplet frames from 30 real animation movies. Due to the absence of correspondence labels for real animation, addressing this challenge has led to the adoption of 3D rendering techniques. MPI-Sintel [5] and CreativeFlow+ [28] provide different annotations such as optical flow, segmentation labels, and depth maps for multiple applications using Blender. To overcome the domain gap between rendered images and real 2D cartoons, Li et al. [30] developed the AnimeRun dataset using open-source 3D animations and their rendered optical flow. It improves segment matching accuracy and handles complex scenes.", + "bbox": [ + 75, + 526, + 468, + 752 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Segment-based Animation Colorization. In the cleaning-up process of the animation industry, animators enclose each line manually, making segments serve as basic units for colorization. Thus, how to calculate segment-level semantic information and correspondence becomes the key in animation colorization. Traditional methods [17-19, 39, 44] regards segment as node and adjacency relationship as edge which transfer the segment matching to the graph optimization problem. Recently, Dang et al. [12] use Hu mo", + "bbox": [ + 75, + 763, + 468, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ments [14] to extract each segment's feature to replace the RGB value and apply a UNet structure [25] to obtain the feature map. Subsequently, the feature is averaged in each segment to calculate the distance across frames for matching. Referring to the success of Transformer [36] in image matching [27], Casey et al. [8] apply multiplex transformer to aggregate information across frames to obtain more accurate results. Besides, Casey et al. replace the Hu moments algorithm with a segment feature extraction CNN which crop and resize each segment to fixed resolution first. Since both Dang et al. and Casey et al.'s methods and dataset are not publicly available, AnimeRun [30] remains the sole benchmark for segment matching available to researchers.", + "bbox": [ + 496, + 282, + 893, + 479 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Paint Bucket Colorization Dataset", + "text_level": 1, + "bbox": [ + 498, + 494, + 808, + 511 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "AnimeRun [30] employs rendered optical flow to calculate segment correspondence, leading to frequent one-to-many and many-to-one matching in the dataset. This results in inaccurate benchmark evaluations, as each segment may have multiple potential ground-truth correspondences. Furthermore, the limited dataset provided by AnimeRun, consisting of only 1,760 training images, increases the risk of network overfitting. Meanwhile, due to the anti-aliasing processing of AnimeRun's rendered images, accurate color labels cannot be obtained in each segment. Consequently, AnimeRun faces difficulties in serving as a paint bucket colorization dataset directly.", + "bbox": [ + 496, + 522, + 890, + 702 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To address these challenges, we introduce a new dataset PaintBucket-Character, comprising 11,345 training images and 3,200 test images. The test set includes 3,000 3D rendered frames and 200 hand-drawn frames. Notably, our dataset focuses solely on character animations, with consideration for the common practice among animators of just drawing foreground character animations while employing 3D models or separate paintings for the background. Our dataset focuses on character animations, considering the industry practice where animators typically sketch only the foreground character movements, while backgrounds are created using separate 3D models or paintings. Different from AnimeRun, our evaluation focuses on", + "bbox": [ + 496, + 704, + 892, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "25546", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 2 + }, + { + "type": "table", + "img_path": "images/37823a2f4bb435cb03a777c2b11c9fefe1bd77dabf39d140a8f030411c8ab462.jpg", + "table_caption": [ + "Table 1. A comparison between our PaintBucket-Character dataset and previous segment matching datasets. Since AnT [8]'s dataset is not publicly available, we use $-$ to mark the unknown information. AnT does possess a private hand-drawn dataset with 3578 frames; however, it does not provide train-test-split information, indicated by $+^{\\prime}$ . Compared with previous open-source datasets, our dataset is more diverse and provides color lines that are closer to real hand-drawn animation. No anti-aliasing provides extra semantic information for each segment, which enables the network to learn better semantic information rather than segment shape similarity." + ], + "table_footnote": [], + "table_body": "
DatasetStatisticsAnnotations
TrainTestClipsSeg per Fr.No anti-aliasingOptical flowIndex labelColor labelColor line
AnimeRun [30]1,7601,05920+10237×✓×××
AnT [8] (private)9,900+1,100+-< 50-×✓✓×
Ours11,3453,200180+170169✓×✓✓✓
", + "bbox": [ + 99, + 148, + 867, + 227 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/970f272193153fbf4488dfb423d57052c6738e655df40842fd0b426d52a73c74.jpg", + "image_caption": [ + "(a) UV Map" + ], + "image_footnote": [], + "bbox": [ + 117, + 234, + 196, + 294 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/023bfcde80c5f48632e91bb33f3e1f06da79c3f3ce099268e56f0086aab57f15.jpg", + "image_caption": [ + "(b)Color label" + ], + "image_footnote": [], + "bbox": [ + 117, + 301, + 196, + 359 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/52d18fca425efed10eea89b6694d65719e6fce96c98de30ed5444aa9ed97eab6.jpg", + "image_caption": [ + "(c) Index label", + "Figure 4. Overview of our synthetic data generation pipeline. We extract the UV map (a) and the used UV region from the character. Then, we use a paint bucket tool to fill the used UV region, creating color label (b) and index label (c). Label images (b) and (c) are then pasted back to the 3D meshes to create flat color characters (d) and (e), respectively. Finally, we post-process the index image (e) to obtain the rendered line art image (f)." + ], + "image_footnote": [], + "bbox": [ + 120, + 368, + 196, + 425 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/0d59492cef147a596941d7452d90e435d36cf72767e8d8b99c183dd617b5703f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 199, + 238, + 267, + 285 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/96a04cf44555c229894628d7b9070c1083ed484d84a02f49b1820b0fdb51db95.jpg", + "image_caption": [ + "(d) Color image" + ], + "image_footnote": [], + "bbox": [ + 199, + 285, + 267, + 422 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/1d64e731a10fd6c9f82a6e3d1739cec1d982f559e7c1c210e45582d2d59266a2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 269, + 238, + 339, + 285 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/3223d83b19642418e094c95d2834b8a36221bcb1e5eb9aa5b45c93f8f89bc870.jpg", + "image_caption": [ + "(e) Index image" + ], + "image_footnote": [], + "bbox": [ + 269, + 285, + 339, + 422 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/7565642f43845ffb189e0dbb6e8033322bc30fd0f03b1894e8998f919d8eb1d7.jpg", + "image_caption": [ + "(f) Line art image" + ], + "image_footnote": [], + "bbox": [ + 343, + 238, + 418, + 422 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "segments' color accuracy rather than traditional matching accuracy. To build our dataset, we sample 22 characters from Mixamo [3] and Aplaybox [1] and set 12 characters for training and 10 for testing. Then, we replot the UV map for these character models in flat color style and use Cinema 4D's Sketch and Toon Effect to produce the line art. To ensure consistent color in each segment, we disable the anti-aliasing and change the texture sampling method to the nearest. As depicted in Fig. 3, our dataset showcases a diverse array of characters encompassing both Japanese and Western cartoon styles.", + "bbox": [ + 75, + 546, + 468, + 713 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.1. Synthetic Dataset Construction", + "text_level": 1, + "bbox": [ + 76, + 724, + 354, + 742 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To include temporal and occlusion relationships in our dataset, we apply Mixamo's actions to our characters. For each character, we add five types of actions and animate the camera motion to capture different viewpoints of the character in each sequence. We classify the camera positions into three types: face shot, long shot, and close-up, in which we separately focus on the face, whole body, and other parts of the body. Following this pipeline, we obtain 15 clips for each character and form 180 clips for training and 150 clips for test. In the animation industry, keyframes always have a", + "bbox": [ + 75, + 750, + 470, + 902 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/d7f5669e14ae1be98ed42dc25e3d498d21def9f4d68255a0e365c7c180878318.jpg", + "image_caption": [ + "Real hand-drawn line art", + "Figure 5. Our simulation method can generate color lines that closely mimic hand-drawn line arts. Red, blue, and green lines represent highlights, shadows, and other instructions respectively. low frame rate [29]. Thus, in each clip, we set the frame rate to 10 to mimic real animation and bring larger motion and deformation. Meanwhile, to address the fine scale of character details such as pupils and buttons, we use $1920 \\times 1920$ as our training size and $1024 \\times 1024$ as our test set size to provide clear segments in these areas." + ], + "image_footnote": [], + "bbox": [ + 506, + 231, + 656, + 321 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/1c4ea5cd06ef16f532b0f83bff026a9e23ac3238ffdfdaacaf7e833138775f9b.jpg", + "image_caption": [ + "Our synthetic line art" + ], + "image_footnote": [], + "bbox": [ + 663, + 233, + 776, + 321 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/ddec8b21ea3bab60cebc8f75f9a2f1293c6dddd42af5a97cb0516f2f6c3ae1e8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 777, + 233, + 885, + 321 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Flat Color Style Rendering. To render characters in a flat color style, we use Cinema 4D to extract a UV mesh map and set unused regions as black. Then, we draw contour lines of character details such as pockets and shoelace on the UV mesh. Based on this original UV map, we use a paint bucket tool to colorize the mesh as the color label. To obtain a more precise matching relationship for training, we connect the label with the same semantic information (such as palm and back of the hand) and use the connected components algorithm for each color to extract the index label as shown in Fig. 4. Since we aim to achieve accurate line art to separate each segment, we calculate the difference between each color's segment and its erosion as the black lines. This operation ensures that each line-enclosed segment contains clear semantic information and comprises only one color.", + "bbox": [ + 496, + 473, + 892, + 698 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Color Line Extraction. To simulate color lines which are common in real hand-drawn animation's shadow and highlight regions, we mark these highlight and shadow colors and erode these regions to create color lines, as shown in Fig. 5. Compared with AnimeRun [30], our dataset features more realistic line art and provides clear semantic information for each segment. Since our characters are rendered with discrete colors, we can easily obtain specific meanings for each segment.", + "bbox": [ + 496, + 699, + 890, + 835 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Hand-drawn Dataset Collection", + "text_level": 1, + "bbox": [ + 500, + 845, + 779, + 861 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Obtaining intermediate unprocessed data poses a challenge, as common commercial animations undergo post", + "bbox": [ + 498, + 869, + 890, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "25547", + "bbox": [ + 478, + 944, + 517, + 957 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "processing techniques including anti-aliasing. To address this challenge, we invite some professional animators to draw line art animation clips with different characters. Then, we use the paint bucket tool to colorize these line arts as our ground truth to synthesize paired line art and colorized data. Besides, animation creation software such as Retas Studio Paintman and CLIP Studio Paint all provide animation production tutorials. We collect animations in these tutorials and use the color line extraction method to synthesize the paired data. Finally, we collect a hand-drawn test dataset with 200 frames and 20 clips for evaluation.", + "bbox": [ + 75, + 90, + 472, + 257 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Method", + "text_level": 1, + "bbox": [ + 76, + 271, + 168, + 286 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Inclusion Matching", + "text_level": 1, + "bbox": [ + 76, + 304, + 250, + 319 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Given two line art images $L_{i}, L_{j} \\in \\mathbb{R}^{H \\times W \\times 3}$ , lines separate the blank area into $N_{i}$ and $N_{j}$ 's line-enclosed segments. In the reference frame $L_{i}$ , each segment is colorized with $M$ colors whose color labels can be represented as one-hot representation $c_{i} \\in \\mathbb{R}^{N_{i} \\times M}$ . To estimate the $L_{j}$ 's color label $\\hat{c}_{j} \\in \\mathbb{R}^{N_{j} \\times M}$ , previous segment-matching-based methods [8, 30] mainly focus on calculating segments' visual correspondence with the matching $\\mathbf{m}^{j \\rightarrow i} \\in \\mathbb{R}^{N_{j} \\times N_{i}}$ . Nevertheless, the absence of strict correspondence among segments imposes limitations on the model's learning capacity.", + "bbox": [ + 75, + 325, + 468, + 477 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To tackle this challenge, we introduce a novel method called inclusion matching. In the reference frame, segments with identical semantic information are merged, creating $K_{i}$ large regions with different labels. As each line-enclosed segment in the target frame can only possess one color with a specific meaning, it can be identified as a subset of one of the $K_{i}$ regions. Specifically, in the training process, the index label stated in Fig. 4 separates the reference frame into $K_{i}$ region. We train a network to estimate each segment's index label $\\mathbb{R}^{N_j\\times K_i}$ . To enrich the diversity, we randomly merge the adjacent labels in the reference frame to create larger regions to guide the network to learn a more robust inclusion relationship, as shown in Fig. 6.", + "bbox": [ + 75, + 479, + 470, + 675 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. PaintBucket Colorization Pipeline", + "text_level": 1, + "bbox": [ + 76, + 685, + 351, + 700 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Color Warping Module. Colorized line art carries substantial information about how segments are grouped, making it crucial for inclusion matching. However, previous segment matching methods [8, 30] exclusively leverage the line art's features for matching and do not incorporate the colorized reference. To encode the color feature, we recolorize the index label image. Specifically, we partition the RGB space into $K_{i}$ cubes, each with a side length of $255 \\times K_{i}^{-\\frac{1}{3}}$ . Subsequently, we select the RGB value at the center of each cube and randomly assign them to index labels as the reference color image $C_{i}$ . We employ the optical flow estimation model RAFT [35], fine-tuned on AnimeRun [30], to esti", + "bbox": [ + 75, + 715, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/458fb955574b1d0d61a4a48511c0747ec0d183422dd81dc91ccb1df151cd3eaf.jpg", + "image_caption": [ + "Figure 6. Our inclusion matching training pipeline employs index labels to partition the reference frame into $K_{i}$ regions, which are then randomly merged with adjacent index labels with a probability of $20\\%$ . Subsequently, the model estimates the affiliation of each line-enclosed segment in the target frame with a specific region in the reference, thereby facilitating the learning of the inclusion relationship." + ], + "image_footnote": [], + "bbox": [ + 555, + 87, + 839, + 244 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "mate the optical flow between the reference line art $L_{i}$ and the target line art $L_{j}$ . Utilizing this optical flow, we warp the reference color image $C_i$ to generate the coarse color estimation $C_j$ for the target frame.", + "bbox": [ + 496, + 349, + 890, + 409 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Feature Extraction Module. Lacking textual information and large deformation in animation make warped color image $C_j$ hard to precisely align with the line art in the target frame. To address this, we employ deformable convolution [11] on the warped color $C_j$ to extract aligned features. For a given deformable convolution kernel of $K$ sampling positions, we use $\\omega_k$ and $\\mathbf{p}_k$ to represent the weight and prespecified offset. The aligned features $F_a$ at each position $\\mathbf{p}_0$ can be expressed as:", + "bbox": [ + 496, + 409, + 890, + 545 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nF _ {a} \\left(\\mathbf {p} _ {0}\\right) = \\sum_ {k = 1} ^ {K} \\omega_ {k} \\cdot F _ {a} \\left(\\mathbf {p} _ {0} + \\mathbf {p} _ {k} + \\Delta \\mathbf {p} _ {k}\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 557, + 555, + 890, + 597 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where learnable offset $\\Delta \\mathbf{p}_k$ can be predicted from the offset estimation network as depicted in Fig. 8. This network, designed as a lightweight U-Net [25] denoted as $\\Phi$ , is employed to expand the receptive field:", + "bbox": [ + 496, + 606, + 890, + 667 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\Delta \\mathbf {p} _ {k} = \\Phi ([ L _ {j}, C _ {j} ]). \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 624, + 676, + 890, + 694 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For the reference frame, we deactivate the offset estimation module and set the offset to zero. Subsequently, the aligned color feature is concatenated with the line feature and passed through a feature encoder network. To guide the network in learning semantic information matching, we resize the line art image to $320 \\times 320$ and utilize CLIP [23]'s image encoder to extract features. To preserve the feature's positional information, we choose to use the ConvNext-Large model from OpenCLIP [10]. We only selected the initial layers of CLIP, which downsample the feature to a resolution of $40 \\times 40$ . The CLIP feature is interpolated to concatenate with the encoded features. Finally, the feature decoder decodes these concatenated features to the input's", + "bbox": [ + 496, + 704, + 892, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "25548", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/843f66a024d950a4747c5a3c7ebcb8a854c13bc49289b2c6715b93fa64220720.jpg", + "image_caption": [ + "Figure 7. Our paint bucket colorization architecture. Initially, we estimate the optical flow based on the line arts and warp the reference color as the coarse colorization result. The mask and position embedding module tokenizes the segments and features extracted by the feature extraction module into a sequence, which is then fed into the multiplex transformer for information aggregation. Finally, we compute a similarity matrix between reference and target tokens to calculate matching loss and predict the final color." + ], + "image_footnote": [], + "bbox": [ + 86, + 88, + 885, + 286 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/0cd9736962cc67bd204883b6c9330e0d6284da4779d5cdd009f09429de7d7093.jpg", + "image_caption": [ + "Figure 8. Overall pipeline of our feature extraction module. Deformable convolution is applied to align the color features of the target frame to the line image. Then, the line features and aligned color features are concatenated and fed to the feature extraction network in a U-Net structure. Line art's CLIP features are also concatenated to the bottleneck of the feature extraction network." + ], + "image_footnote": [], + "bbox": [ + 81, + 351, + 460, + 470 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "resolution with $C$ channels. To preserve features in high resolution, shortcuts are added between the network's encoder and decoder, following the structure of the U-Net.", + "bbox": [ + 75, + 561, + 468, + 606 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Mask + Position Embedding Module. To transform different segments into tokens, we employ super-pixel pooling to average the features within each segment's mask, resulting in a $C$ -dimensional visual token, denoted as $\\mathbf{d}_i$ . Subsequently, a Multilayer Perceptron (MLP) layer is utilized to encode the segment's bounding box's four-dimensional coordinates, denoted as $p_i$ , into a $C$ -dimensional positional embedding. The token $\\mathbf{x}_i$ for matching is obtained by adding the positional embedding and visual token:", + "bbox": [ + 75, + 608, + 470, + 744 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {x} _ {i} = \\mathbf {d} _ {i} + \\mathbf {M L P} \\left(p _ {i}\\right). \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 199, + 761, + 468, + 779 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Differing from previous segment matching pipelines [8, 30], our approach matches each line-enclosed segment in the target frame with a specific index label in the reference frame, rather than employing label-to-label matching.", + "bbox": [ + 75, + 792, + 468, + 853 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Multiplex Transformer. Building upon [8, 27], we employ multiplex self- and cross-attention layers to aggregate tokenized features. In a self-attention layer, queries, keys, and", + "bbox": [ + 75, + 854, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "values are derived from a single source feature:", + "bbox": [ + 500, + 352, + 812, + 367 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {s e l f - a t t e n t i o n} \\left(\\mathbf {x} _ {i}\\right) = \\operatorname {s o f t m a x} \\left(\\frac {\\mathbf {Q} _ {i} \\mathbf {K} _ {i}}{\\sqrt {D}}\\right) \\mathbf {V} _ {i}, \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 545, + 377, + 890, + 412 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $\\mathbf{Q}_i$ , $\\mathbf{K}_i$ , and $\\mathbf{V}_i$ represent $\\mathbf{x}_i$ processed by MLPs for query, key, and value. In contrast, the cross-attention layer computes keys and values from another feature:", + "bbox": [ + 498, + 420, + 892, + 465 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {c r o s s - a t t e n t i o n} \\left(\\mathbf {x} _ {i} ^ {\\prime}, \\mathbf {x} _ {j} ^ {\\prime}\\right) = \\operatorname {s o f t m a x} \\left(\\frac {\\mathbf {Q} _ {i} ^ {\\prime} \\mathbf {K} _ {j} ^ {\\prime}}{\\sqrt {D}}\\right) \\mathbf {V} _ {j} ^ {\\prime}. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 514, + 477, + 890, + 523 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Following each self- or cross-attention layer, the output is added to the original $\\mathbf{x}_i$ or $\\mathbf{x}'_i$ , and then processed with a feed-forward MLP. After repeating these operations $N$ times, as illustrated in Fig. 7, we obtain the final aggregated features $\\hat{\\mathbf{x}}_i \\in \\mathbb{R}^{K_i \\times C}$ and $\\hat{\\mathbf{x}}_j \\in \\mathbb{R}^{N_j \\times C}$ .", + "bbox": [ + 498, + 523, + 890, + 598 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Loss function. After the propagation step, the similarity matrix $\\mathbf{S} \\in \\mathbb{R}^{N_j \\times K_i}$ is represented as follows:", + "bbox": [ + 500, + 599, + 890, + 628 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {S} _ {m n} = \\frac {\\exp \\left(\\hat {\\mathbf {x}} _ {i m} \\cdot \\hat {\\mathbf {x}} _ {j n}\\right)}{\\sum_ {m = 1} ^ {N _ {j}} \\exp \\left(\\hat {\\mathbf {x}} _ {i m} \\cdot \\hat {\\mathbf {x}} _ {j n}\\right)}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 586, + 638, + 890, + 676 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "This matrix can be interpreted as the color probability $\\hat{\\mathbf{y}}_m\\in \\mathbb{R}^{K_i}$ for segment $m$ in the target frame. Given that each frame has a one-hot ground truth index label $\\mathbf{y}_m$ , the loss function is derived from the cross-entropy loss:", + "bbox": [ + 498, + 686, + 890, + 747 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nL _ {c e} = - \\sum_ {m = 1} ^ {K _ {i}} \\mathbf {y} _ {m} \\log (\\hat {\\mathbf {y}} _ {m}). \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 604, + 757, + 890, + 799 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Inference Pipeline. Since real animation's colors have an obvious domain gap with our randomly generated colors, we adopt a color redistribution strategy to reassign randomly generated colors to replace the original colors during the warping and matching pipeline. This strategy can avoid the mismatching problem when several predefined colors", + "bbox": [ + 498, + 809, + 892, + 901 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "25549", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/8e756080549693a7b5ddef8fb66e2b88fec6aeef01c3a5f6d961c425146d575a.jpg", + "image_caption": [ + "Figure 9. The visualization results of our proposed methods and other approaches on real hand-drawn animation. Compared with previous methods, our proposed approach demonstrates enhanced robustness in handling occlusion situations (e.g., hand of the running girl and shadow near eyebrows of the girl in the second row.)", + "Table 2. Quantitative comparison of our method with different methods. 'Acc' and 'Acc-Thres' denote segment-wise accuracy, providing insights into the potential workload reduction for digital painters. In 'Acc-Thres,' segments smaller than 10 pixels are filtered out. 'Pix-Acc,' 'Pix-F-Acc,' and 'Pix-B-MIoU' represent pixel-wise accuracy, foreground pixel-wise accuracy, and pixel-wise background MIoU, respectively, reflecting the visualization performance. All RAFT models undergo training on MPI-Sintel [5], and 'F/C' indicates the models fine-tuned on AnimeRun's colorized frames and contours." + ], + "image_footnote": [], + "bbox": [ + 122, + 79, + 848, + 335 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/69d591b6074aefa4e2830a8ccbd1c3acf850c439e69c450c8a0f749f5b8feb82.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
TypeMethod3D rendered test setHand-drawn test set
AccAcc-ThresPix-AccPix-F-AccPix-B-MIoUAccAcc-ThresPix-AccPix-F-AccPix-B-MIoU
Reference-basedControlNet0.17090.18560.42740.26530.46000.17150.18120.24490.22980.2260
Segment matchingAnT(AnimeRun)0.55840.59300.87340.65370.89540.67790.70430.91930.73770.9429
AnT(Cadmium)0.66340.77130.97650.94710.98010.72240.78790.97920.93030.9899
Optical flowRAFT0.65890.74560.97240.90990.97630.75280.80930.98190.91900.9898
RAFT (F)0.71330.80540.98180.94490.98520.77580.84240.98600.94250.9922
RAFT (C)0.70280.79440.97230.94110.96900.77180.83560.98330.93750.9916
Inclusion matchingOurs0.82660.87260.99050.97240.99480.85930.89290.99000.96380.9984
", + "bbox": [ + 78, + 449, + 890, + 547 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "are too closed. Finally, the estimated color for each line-enclosed segment $\\hat{\\mathbf{c}}_j\\in \\mathbb{R}^{N_j\\times M}$ can be derived by:", + "bbox": [ + 75, + 553, + 468, + 583 + ], + "page_idx": 6 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\mathbf {c}} _ {j} = \\hat {\\mathbf {S}} \\mathbf {c} _ {i}, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 236, + 589, + 468, + 608 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "where $\\hat{\\mathbf{S}}\\in \\mathbb{R}^{N_j\\times N_i}$ is the similarity matrix for each line-enclosed segment in reference and target frames. In this paper, we set the match threshold as 0.2 to filter out all the segments which are unmatched.", + "bbox": [ + 75, + 613, + 468, + 675 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 76, + 686, + 209, + 703 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.1. Implementation Details", + "text_level": 1, + "bbox": [ + 76, + 710, + 294, + 727 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "During the training stage, our model undergoes 300,000 iterations with a batch size of 2, utilizing NVIDIA GeForce RTX 3090 GPUs. We employ the Adam optimizer with a learning rate of $10^{-4}$ and no weight decay. Throughout the training process, we keep the weights of the pretrained optical flow estimation module and the CLIP image encoder fixed. In the feature extraction module, the offset estimation module is structured as a lightweight U-Net with three down-sampling layers and a bottleneck featuring 128 features. Simultaneously, the feature extraction network is implemented as a U-Net with four down-sampling layers and a", + "bbox": [ + 75, + 734, + 470, + 901 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "bottleneck containing 512 features. The channel number $C$ for our extracted feature is set to 128. Within the multiplex transformer, the layer number $N$ is set to nine, and the number of heads is configured as four. The data augmentation pipeline is shown in the supplementary material.", + "bbox": [ + 496, + 553, + 890, + 628 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.2. Comparisons with Previous Methods", + "text_level": 1, + "bbox": [ + 498, + 635, + 818, + 651 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Since there is no existing paint bucket colorization method, we mainly compare our method with reference-based line art colorization [42], segment matching methods [8, 30], and optical flow estimation methods [35]. The quantitative comparison is shown in Table 2. The visual comparison of real hand-drawn animation and rendered 3D test sets are shown in Fig. 9 and Fig. 10.", + "bbox": [ + 496, + 659, + 890, + 763 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Reference-based Line Art Colorization. The saturated luminance of the blank regions within line art impedes the application of reference-based methods for natural gray-scale image colorization. Thus, we choose ControlNet [42] as our reference-based line art colorization method. We use Stable Diffusion v1.5 [24] as our base model and employ the ControlNet's line art checkpoint to encode the line art condition. Then, we adopt the IP-Adapter [38] to encode the reference image. We set the number of steps to 50 and use", + "bbox": [ + 496, + 763, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "25550", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/7911eee26b666dae8a017c3b68737a52f87e9f63ed77d249dc7f36f30c6095e0.jpg", + "table_caption": [ + "Table 3. Quantitative comparison of different datasets, different network structures, and different methods on test data. 'IM' signifies the inclusion matching pipeline, which incorporates adjacent index label merging and segment-label matching strategies. Since the inclusion matching pipeline and coarse warping module with RAFT can also be applied to other networks, we also adopt them to AnT for comparison to illustrate the generalization of these methods." + ], + "table_footnote": [], + "table_body": "
TypeMethod3D rendered test setHand-drawn test set
AccAcc-ThresPix-AccPix-F-AccPix-B-MIoUAccAcc-ThresPix-AccPix-F-AccPix-B-MIoU
BaselineOurs0.82660.87260.99050.97240.99480.85930.89290.99000.96380.9984
DatasetAnimeRun0.73590.79580.96930.92010.97650.82780.86340.98180.93990.9906
Modelw/o CLIP0.81800.86530.98730.96850.99100.84890.88430.98780.95700.9925
w/o RAFT0.80010.84470.98240.94810.98780.84460.87500.98040.94040.9851
w/o DConv0.82470.86850.98940.97090.99280.85250.88330.98750.95490.9937
MethodOurs w/o IM0.76370.83520.97210.95730.96880.83480.87630.97770.94950.9822
AnT0.74500.79300.97080.93610.97580.81620.84970.98170.93740.9905
AnT with IM0.80630.84470.98370.95510.98870.83880.86980.98390.93880.9943
AnT with IM/RAFT0.81770.85870.98790.96810.99320.84830.88280.98860.95980.9946
", + "bbox": [ + 78, + 133, + 890, + 260 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "the text prompt 'A character in the white background'. We calculate the average RGB value per segment and match the average color with the nearest color in the reference image for evaluation.", + "bbox": [ + 75, + 263, + 468, + 324 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Optical Flow Estimation. Since optical flow methods cannot produce segment-wise estimation without postprocessing, we warp the color and calculate the colors that appear most frequently in each segment as the baseline of optical estimation method. Since finetuning RAFT on AnimeRun can promote the optical flow's performance effectively, we use the finetuned RAFT in the following sessions. Segment Matching. We also compare our method with the Cadmium application, the official implementation of AnT [8], and AnimenRun's reimplemented AnT [30]. The visual comparison shown in Fig. 9 and Fig. 10 demonstrate the robust performance of our proposed method, particularly in scenarios where strict segment correspondence is absent, and challenges with large motion and complex deformations. More visual results are presented in the suppl. material.", + "bbox": [ + 75, + 324, + 473, + 566 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.3. Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 575, + 230, + 590 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Dataset. To demonstrate the effectiveness of our proposed dataset, we also train the proposed method on the AnimeRun. In the training process, we adopt the inclusion matching strategy by merging the segments in the reference frames. The quantitative results reported in Table 3 suggest the positive influence of our proposed dataset.", + "bbox": [ + 75, + 598, + 468, + 688 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Model. We conduct an ablation study on our model design to examine the necessity of each structure. In our experiments, we explore alternative configurations by replacing the deformable convolution and offset estimation module with the original convolution, eliminating the coarse warping module, and omitting the CLIP image encoder for ablation. The results presented in Table 3 underscore the significance of each module, highlighting the crucial role of the coarse warping module.", + "bbox": [ + 75, + 688, + 468, + 824 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Method. The results in Table 3 further highlight the efficacy of our inclusion matching pipeline. Its application to AnT [8] yields a substantial improvement in network performance, suggesting the broad applicability and generalization of our inclusion matching pipeline. Ablation study", + "bbox": [ + 75, + 824, + 468, + 902 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/8846974929558ba6d43b465c9e50b19fac81994c5682c440460bb3f8fcc8b0a2.jpg", + "image_caption": [ + "Figure 10. Visual comparison of different methods on our 3D rendered test set. Our proposed method produces satisfactory results in the presence of occlusion, significant motion, and substantial changes in viewing angles." + ], + "image_footnote": [], + "bbox": [ + 506, + 263, + 888, + 525 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "visualizations are available in the supplementary material.", + "bbox": [ + 500, + 583, + 883, + 598 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 614, + 619, + 631 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We have introduced a new approach for line art paint bucket colorization. Departing from traditional segment matching methods that struggle with one-to-one correspondence, we proposed a novel inclusion matching pipeline that estimates each segment's inclusion relationship rather than the direct correspondence. To facilitate the learning of this inclusion relationship, we presented a dedicated dataset, PaintBucket-Character, and a two-stage colorization pipeline. Our pipeline incorporates a coarse color warping module and an inclusion matching module. The experimental results demonstrate the superior performance of our method in handling occlusion and accommodating large movements within challenging scenarios.", + "bbox": [ + 496, + 642, + 893, + 839 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement. This study is supported under the RIE2020 Industry Alignment Fund Industry Collaboration Projects (IAF-ICP) Funding Initiative, as well as cash and in-kind contribution from the industry partner(s).", + "bbox": [ + 496, + 839, + 893, + 902 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "25551", + "bbox": [ + 478, + 944, + 517, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Aplaybox. https://www.aplaybox.com/.2,4", + "[2] Cadmium. https://cadmium.app/. 2", + "[3] Mixamo. https://www MIXamo.com/.2,4", + "[4] Kenta Akita, Yuki Morimoto, and Reiji Tsuruno. Handdrawn anime line drawing colorization of faces with texture details. Computer Animation and Virtual Worlds, 2023. 3", + "[5] D. J. Butler, J. Wulff, G. B. Stanley, and M. J. Black. 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ACM TOG, 38(6), 2019. 3" + ], + "bbox": [ + 78, + 90, + 468, + 545 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "25553", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_model.json b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_model.json new file mode 100644 index 0000000000000000000000000000000000000000..ef6e88e19e617d44e2bdcd5cb926f9c54ac516de --- /dev/null +++ b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_model.json @@ -0,0 +1,2035 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.129, + 0.131, + 0.842, + 0.152 + ], + "angle": 0, + "content": "Learning Inclusion Matching for Animation Paint Bucket Colorization" + }, + { + "type": "text", + "bbox": [ + 0.169, + 0.181, + 0.801, + 0.218 + ], + "angle": 0, + "content": "Yuekun Dai Shangchen Zhou Qinyue Li Chongyi Li Chen Change Loy S-Lab, Nanyang Technological University" + }, + { + "type": "text", + "bbox": [ + 0.26, + 0.22, + 0.706, + 0.234 + ], + "angle": 0, + "content": "https://ykdai.github.io/projects/InclusionMatching" + }, + { + "type": "image", + "bbox": [ + 0.086, + 0.242, + 0.891, + 0.459 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.464, + 0.893, + 0.549 + ], + "angle": 0, + "content": "Figure 1. In the animation industry, digital painters use paint bucket tool to colorize drawn line arts frame by frame. Our proposed pipeline streamlines this process by requiring the painters to colorize just one frame, after which the algorithm autonomously propagates the color to subsequent frames, enabling automatic colorization. Compared with optical-flow-based method RAFT [35] and segment-matching-based method AnT [8], our method can achieve more robust results on challenging cases such as one-to-many matching, large deformation, and tiny region colorization. In this figure, RAFT is trained on Sintel dataset [5] and finetuned on AnimeRun [30]. We use the most frequent color in each segment to colorize each line-enclosed region. ©drawn by Nicca (Sriprachum Kongwisawamit), used with artist permission." + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.561, + 0.314, + 0.575 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.599, + 0.474, + 0.903 + ], + "angle": 0, + "content": "Colorizing line art is a pivotal task in the production of hand-drawn cel animation. This typically involves digital painters using a paint bucket tool to manually color each segment enclosed by lines, based on RGB values predetermined by a color designer. This frame-by-frame process is both arduous and time-intensive. Current automated methods mainly focus on segment matching. This technique migrates colors from a reference to the target frame by aligning features within line-enclosed segments across frames. However, issues like occlusion and wrinkles in animations often disrupt these direct correspondences, leading to mismatches. In this work, we introduce a new learning-based inclusion matching pipeline, which directs the network to comprehend the inclusion relationships between segments rather than relying solely on direct visual correspondences. Our method features a two-stage pipeline that integrates a coarse color warping module with an inclusion matching module, enabling more nuanced and accurate colorization. To facilitate the training of our network, we also develop a unique dataset, referred to as PaintBucket-Character. This" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.561, + 0.895, + 0.624 + ], + "angle": 0, + "content": "dataset includes rendered line arts alongside their colorized counterparts, featuring various 3D characters. Extensive experiments demonstrate the effectiveness and superiority of our method over existing techniques." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.646, + 0.633, + 0.661 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.674, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Colorizing line art is a critical step in hand-drawn animation production. Initially, key animators create the characters' keyframes, followed by in-between animators who generate intermediate frames and refine keyframes for seamless connection between each stroke, as described in [31]. These line arts are then scanned into binary images, featuring a primary color palette of red, blue, green, and black, which represents highlights, shadows, special instructions (e.g., eye irises), and normal lines respectively. These scanned images, with regions of transparent background as shown in Fig. 1, are forwarded to digital painters. The painters use a paint bucket tool and a designated color palette to fill each line-enclosed segment, including the color lines, which is known as paint bucket colorization. Finally, special effect artists add visual enhancements, such as anti-aliasing, to" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25544" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.121 + ], + "angle": 0, + "content": "blend character animations with backgrounds, culminating in the final video composition, detailed in [20]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.124, + 0.468, + 0.274 + ], + "angle": 0, + "content": "Line art colorization is a notably laborious process. For instance, even the relatively simple scenario in Fig. 1, involving 93 segments, still requires hundreds of manual clicks. To mitigate this demanding task, several commercial software applications like Retas Studio Paintman, OpenToonz, and CLIP Studio Paint have been developed. These tools provide helpful features that allow users to easily adjust assigned colors, fill small areas, and aid in line colorization. Despite these advancements, fully automated colorization has yet to be realized." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.278, + 0.47, + 0.639 + ], + "angle": 0, + "content": "To address the challenges of line art colorization, numerous segment-matching methods have been developed for identifying corresponding segments in reference and target frames. Traditional graph-based approaches [17-19, 39, 44] consider each segment as a graph node and establish edges based on adjacency relationships. These methods employ optimization techniques to minimize topological similarity loss among corresponding nodes. However, they are time-intensive, often taking several minutes to process a single image with around 100 segments. Casey et al. [8] introduced the Animation Transformer (AnT) and its application Cadmium, which significantly improved segment matching. AnT standardizes the size of each segment and employs convolutional neural networks (CNNs) to extract features, transforming the image into a segment sequence. This converts segment matching into a sequence-to-sequence problem. Although AnT excels in aligning segments between adjacent frames featuring minimal motion, it struggles in more complex scenarios, particularly those with occlusion or pronounced motion. During occlusions, interlaced lines tend to fragment segments into multiple pieces, as depicted in Fig. 2. This fragmentation disrupts the strict correspondence between segments, rendering the task of segment matching inherently problematic and poorly defined." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.643, + 0.468, + 0.883 + ], + "angle": 0, + "content": "In this study, we introduce the novel notion of 'inclusion matching', which obviates the necessity for exact segment-to-segment correspondence. Instead of direct segment matching, our approach computes the likelihood of each segment in a target frame being included within a specific region of a reference frame. Our methodology is unique in that it follows a coarse-to-fine colorization pipeline, inspired by the approach of skilled digital painters. This approach typically begins with coloring larger, more noticeable segments across all frames before filling in details of smaller segments in each frame. Motivated by this workflow, our pipeline first computes optical flow between line sketches, warping colors from a reference to a target frame to achieve a preliminary, coarse colorization. This is followed by the application of an inclusion matching module, which refines the colorization result of tiny segments." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.886, + 0.468, + 0.9 + ], + "angle": 0, + "content": "The sparse nature of line art requires special formula" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.088, + 0.885, + 0.258 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.263, + 0.892, + 0.375 + ], + "angle": 0, + "content": "Figure 2. Methods relying on segment matching typically seek the most similar segment across frames, yet challenges arise in scenarios involving occlusion and wrinkles. This is particularly evident in tiny segments, as highlighted in the red box, where disruptions in correspondence lead to mismatches. Our innovative approach, based on inclusion matching, addresses this issue by estimating the inclusion relationship rather than pursuing direct correspondence, as illustrated by the comparison of red and blue matching lines." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.386, + 0.892, + 0.552 + ], + "angle": 0, + "content": "tion in our approach. Specifically, recognizing the necessity for a large receptive field in extracting line art features, we employ a U-Net structure [25] to process concatenated color and line features. To address the difficulty in matching segments under large deformations, we extract line semantic features using CLIP [23] and concatenate them with features from the U-Net's bottleneck. This allows the network to match the region with the same semantic information across frames. Finally, we introduce super-pixel pooling at each segment to transfer the image into tokens for sequence-to-sequence matching." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.561, + 0.892, + 0.695 + ], + "angle": 0, + "content": "Dataset plays a key role in the success of our method. To train and evaluate our method, we select 22 character models from Mixamo [3] and Aplaybox [1]. We mimic real intermediate line art data on the animation coloring production line. We disable the anti-aliasing and provide the color lines which is quite common in animation production. Then we use 3D software Cinema 4D to synthesize a specially-designed cartoon character colorization dataset named PaintBucket-Character." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.705, + 0.892, + 0.9 + ], + "angle": 0, + "content": "The contributions of our work include the introduction of the PaintBucket-Character dataset tailored for paint bucket colorization tasks, the novel inclusion matching pipeline addressing the challenge of lacking strict segment correspondence, and a new coarse-to-fine baseline that outperforms existing solutions, particularly in scenes with occlusion. Our experiments demonstrate that our method surpasses the performance of recent AnT application Cadmium, and outperforms the results presented by Li et al. [30]. Notably, the advantages of our approach extend beyond dataset improvements, highlighting the effectiveness of our newly designed inclusion matching pipeline and the coarse-to-fine baseline in the context of animation colorization." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "25545" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.119, + 0.087, + 0.852, + 0.264 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.221, + 0.268, + 0.746, + 0.281 + ], + "angle": 0, + "content": "Figure 3. Several examples of our rendered characters in PaintBucket-Character dataset." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.282, + 0.22, + 0.297 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.319, + 0.471, + 0.515 + ], + "angle": 0, + "content": "Line Art Colorization. Line art colorization aims to create reasonable colors in the sketch's blank regions. To achieve precise control, many user guidance types are designed including text [15, 45], scribble [6, 33, 40, 41], colored reference [4, 7, 9, 16, 32, 34, 37, 42, 43]. These methods mainly focus on pixel-wise estimation and cannot fill flat accurate RGB values assigned by the color designer in line arts' segments, which always leads to flickering and color bleeding. Besides, in the post-processing, the special effect artists often need to select specific colors to create various effects such as ramp or glow for the character's specific region. Thus, current line art colorization methods are still difficult to be merged into animation industrial processes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.527, + 0.47, + 0.753 + ], + "angle": 0, + "content": "Animation-related Dataset. To facilitate hand-drawn animation production, many real and rendered datasets are proposed. To boost video interpolation performance, Li et al. [29] propose the ATD-12K dataset which consists of triplet frames from 30 real animation movies. Due to the absence of correspondence labels for real animation, addressing this challenge has led to the adoption of 3D rendering techniques. MPI-Sintel [5] and CreativeFlow+ [28] provide different annotations such as optical flow, segmentation labels, and depth maps for multiple applications using Blender. To overcome the domain gap between rendered images and real 2D cartoons, Li et al. [30] developed the AnimeRun dataset using open-source 3D animations and their rendered optical flow. It improves segment matching accuracy and handles complex scenes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Segment-based Animation Colorization. In the cleaning-up process of the animation industry, animators enclose each line manually, making segments serve as basic units for colorization. Thus, how to calculate segment-level semantic information and correspondence becomes the key in animation colorization. Traditional methods [17-19, 39, 44] regards segment as node and adjacency relationship as edge which transfer the segment matching to the graph optimization problem. Recently, Dang et al. [12] use Hu mo" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.284, + 0.895, + 0.48 + ], + "angle": 0, + "content": "ments [14] to extract each segment's feature to replace the RGB value and apply a UNet structure [25] to obtain the feature map. Subsequently, the feature is averaged in each segment to calculate the distance across frames for matching. Referring to the success of Transformer [36] in image matching [27], Casey et al. [8] apply multiplex transformer to aggregate information across frames to obtain more accurate results. Besides, Casey et al. replace the Hu moments algorithm with a segment feature extraction CNN which crop and resize each segment to fixed resolution first. Since both Dang et al. and Casey et al.'s methods and dataset are not publicly available, AnimeRun [30] remains the sole benchmark for segment matching available to researchers." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.496, + 0.81, + 0.512 + ], + "angle": 0, + "content": "3. Paint Bucket Colorization Dataset" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.523, + 0.892, + 0.703 + ], + "angle": 0, + "content": "AnimeRun [30] employs rendered optical flow to calculate segment correspondence, leading to frequent one-to-many and many-to-one matching in the dataset. This results in inaccurate benchmark evaluations, as each segment may have multiple potential ground-truth correspondences. Furthermore, the limited dataset provided by AnimeRun, consisting of only 1,760 training images, increases the risk of network overfitting. Meanwhile, due to the anti-aliasing processing of AnimeRun's rendered images, accurate color labels cannot be obtained in each segment. Consequently, AnimeRun faces difficulties in serving as a paint bucket colorization dataset directly." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.893, + 0.901 + ], + "angle": 0, + "content": "To address these challenges, we introduce a new dataset PaintBucket-Character, comprising 11,345 training images and 3,200 test images. The test set includes 3,000 3D rendered frames and 200 hand-drawn frames. Notably, our dataset focuses solely on character animations, with consideration for the common practice among animators of just drawing foreground character animations while employing 3D models or separate paintings for the background. Our dataset focuses on character animations, considering the industry practice where animators typically sketch only the foreground character movements, while backgrounds are created using separate 3D models or paintings. Different from AnimeRun, our evaluation focuses on" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "25546" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.079, + 0.895, + 0.149 + ], + "angle": 0, + "content": "Table 1. A comparison between our PaintBucket-Character dataset and previous segment matching datasets. Since AnT [8]'s dataset is not publicly available, we use \\(-\\) to mark the unknown information. AnT does possess a private hand-drawn dataset with 3578 frames; however, it does not provide train-test-split information, indicated by \\(+^{\\prime}\\) . Compared with previous open-source datasets, our dataset is more diverse and provides color lines that are closer to real hand-drawn animation. No anti-aliasing provides extra semantic information for each segment, which enables the network to learn better semantic information rather than segment shape similarity." + }, + { + "type": "table", + "bbox": [ + 0.1, + 0.15, + 0.868, + 0.228 + ], + "angle": 0, + "content": "
DatasetStatisticsAnnotations
TrainTestClipsSeg per Fr.No anti-aliasingOptical flowIndex labelColor labelColor line
AnimeRun [30]1,7601,05920+10237×✓×××
AnT [8] (private)9,900+1,100+-< 50-×✓✓×
Ours11,3453,200180+170169✓×✓✓✓
" + }, + { + "type": "image", + "bbox": [ + 0.119, + 0.236, + 0.197, + 0.295 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.119, + 0.295, + 0.197, + 0.303 + ], + "angle": 0, + "content": "(a) UV Map" + }, + { + "type": "image", + "bbox": [ + 0.119, + 0.303, + 0.197, + 0.36 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.119, + 0.36, + 0.185, + 0.368 + ], + "angle": 0, + "content": "(b)Color label" + }, + { + "type": "image", + "bbox": [ + 0.122, + 0.369, + 0.197, + 0.426 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.132, + 0.427, + 0.187, + 0.436 + ], + "angle": 0, + "content": "(c) Index label" + }, + { + "type": "image", + "bbox": [ + 0.2, + 0.239, + 0.269, + 0.286 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.2, + 0.286, + 0.269, + 0.423 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.207, + 0.427, + 0.268, + 0.436 + ], + "angle": 0, + "content": "(d) Color image" + }, + { + "type": "image", + "bbox": [ + 0.271, + 0.239, + 0.341, + 0.286 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.271, + 0.286, + 0.341, + 0.423 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.277, + 0.427, + 0.337, + 0.436 + ], + "angle": 0, + "content": "(e) Index image" + }, + { + "type": "image", + "bbox": [ + 0.344, + 0.239, + 0.419, + 0.423 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.347, + 0.427, + 0.413, + 0.436 + ], + "angle": 0, + "content": "(f) Line art image" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.443, + 0.473, + 0.541 + ], + "angle": 0, + "content": "Figure 4. Overview of our synthetic data generation pipeline. We extract the UV map (a) and the used UV region from the character. Then, we use a paint bucket tool to fill the used UV region, creating color label (b) and index label (c). Label images (b) and (c) are then pasted back to the 3D meshes to create flat color characters (d) and (e), respectively. Finally, we post-process the index image (e) to obtain the rendered line art image (f)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.547, + 0.47, + 0.714 + ], + "angle": 0, + "content": "segments' color accuracy rather than traditional matching accuracy. To build our dataset, we sample 22 characters from Mixamo [3] and Aplaybox [1] and set 12 characters for training and 10 for testing. Then, we replot the UV map for these character models in flat color style and use Cinema 4D's Sketch and Toon Effect to produce the line art. To ensure consistent color in each segment, we disable the anti-aliasing and change the texture sampling method to the nearest. As depicted in Fig. 3, our dataset showcases a diverse array of characters encompassing both Japanese and Western cartoon styles." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.726, + 0.355, + 0.743 + ], + "angle": 0, + "content": "3.1. Synthetic Dataset Construction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.903 + ], + "angle": 0, + "content": "To include temporal and occlusion relationships in our dataset, we apply Mixamo's actions to our characters. For each character, we add five types of actions and animate the camera motion to capture different viewpoints of the character in each sequence. We classify the camera positions into three types: face shot, long shot, and close-up, in which we separately focus on the face, whole body, and other parts of the body. Following this pipeline, we obtain 15 clips for each character and form 180 clips for training and 150 clips for test. In the animation industry, keyframes always have a" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.232, + 0.657, + 0.322 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.525, + 0.323, + 0.64, + 0.333 + ], + "angle": 0, + "content": "Real hand-drawn line art" + }, + { + "type": "image", + "bbox": [ + 0.665, + 0.234, + 0.777, + 0.323 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.721, + 0.325, + 0.818, + 0.335 + ], + "angle": 0, + "content": "Our synthetic line art" + }, + { + "type": "image", + "bbox": [ + 0.778, + 0.234, + 0.887, + 0.323 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.338, + 0.892, + 0.473 + ], + "angle": 0, + "content": "Figure 5. Our simulation method can generate color lines that closely mimic hand-drawn line arts. Red, blue, and green lines represent highlights, shadows, and other instructions respectively. low frame rate [29]. Thus, in each clip, we set the frame rate to 10 to mimic real animation and bring larger motion and deformation. Meanwhile, to address the fine scale of character details such as pupils and buttons, we use \\(1920 \\times 1920\\) as our training size and \\(1024 \\times 1024\\) as our test set size to provide clear segments in these areas." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.474, + 0.893, + 0.699 + ], + "angle": 0, + "content": "Flat Color Style Rendering. To render characters in a flat color style, we use Cinema 4D to extract a UV mesh map and set unused regions as black. Then, we draw contour lines of character details such as pockets and shoelace on the UV mesh. Based on this original UV map, we use a paint bucket tool to colorize the mesh as the color label. To obtain a more precise matching relationship for training, we connect the label with the same semantic information (such as palm and back of the hand) and use the connected components algorithm for each color to extract the index label as shown in Fig. 4. Since we aim to achieve accurate line art to separate each segment, we calculate the difference between each color's segment and its erosion as the black lines. This operation ensures that each line-enclosed segment contains clear semantic information and comprises only one color." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.7, + 0.892, + 0.837 + ], + "angle": 0, + "content": "Color Line Extraction. To simulate color lines which are common in real hand-drawn animation's shadow and highlight regions, we mark these highlight and shadow colors and erode these regions to create color lines, as shown in Fig. 5. Compared with AnimeRun [30], our dataset features more realistic line art and provides clear semantic information for each segment. Since our characters are rendered with discrete colors, we can easily obtain specific meanings for each segment." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.847, + 0.78, + 0.862 + ], + "angle": 0, + "content": "3.2. Hand-drawn Dataset Collection" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Obtaining intermediate unprocessed data poses a challenge, as common commercial animations undergo post" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.958 + ], + "angle": 0, + "content": "25547" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.258 + ], + "angle": 0, + "content": "processing techniques including anti-aliasing. To address this challenge, we invite some professional animators to draw line art animation clips with different characters. Then, we use the paint bucket tool to colorize these line arts as our ground truth to synthesize paired line art and colorized data. Besides, animation creation software such as Retas Studio Paintman and CLIP Studio Paint all provide animation production tutorials. We collect animations in these tutorials and use the color line extraction method to synthesize the paired data. Finally, we collect a hand-drawn test dataset with 200 frames and 20 clips for evaluation." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.272, + 0.169, + 0.287 + ], + "angle": 0, + "content": "4. Method" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.305, + 0.25, + 0.32 + ], + "angle": 0, + "content": "4.1. Inclusion Matching" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.326, + 0.47, + 0.478 + ], + "angle": 0, + "content": "Given two line art images \\(L_{i}, L_{j} \\in \\mathbb{R}^{H \\times W \\times 3}\\), lines separate the blank area into \\(N_{i}\\) and \\(N_{j}\\)'s line-enclosed segments. In the reference frame \\(L_{i}\\), each segment is colorized with \\(M\\) colors whose color labels can be represented as one-hot representation \\(c_{i} \\in \\mathbb{R}^{N_{i} \\times M}\\). To estimate the \\(L_{j}\\)'s color label \\(\\hat{c}_{j} \\in \\mathbb{R}^{N_{j} \\times M}\\), previous segment-matching-based methods [8, 30] mainly focus on calculating segments' visual correspondence with the matching \\(\\mathbf{m}^{j \\rightarrow i} \\in \\mathbb{R}^{N_{j} \\times N_{i}}\\). Nevertheless, the absence of strict correspondence among segments imposes limitations on the model's learning capacity." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.48, + 0.471, + 0.676 + ], + "angle": 0, + "content": "To tackle this challenge, we introduce a novel method called inclusion matching. In the reference frame, segments with identical semantic information are merged, creating \\( K_{i} \\) large regions with different labels. As each line-enclosed segment in the target frame can only possess one color with a specific meaning, it can be identified as a subset of one of the \\( K_{i} \\) regions. Specifically, in the training process, the index label stated in Fig. 4 separates the reference frame into \\( K_{i} \\) region. We train a network to estimate each segment's index label \\( \\mathbb{R}^{N_j\\times K_i} \\). To enrich the diversity, we randomly merge the adjacent labels in the reference frame to create larger regions to guide the network to learn a more robust inclusion relationship, as shown in Fig. 6." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.686, + 0.352, + 0.701 + ], + "angle": 0, + "content": "4.2. PaintBucket Colorization Pipeline" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.716, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Color Warping Module. Colorized line art carries substantial information about how segments are grouped, making it crucial for inclusion matching. However, previous segment matching methods [8, 30] exclusively leverage the line art's features for matching and do not incorporate the colorized reference. To encode the color feature, we recolorize the index label image. Specifically, we partition the RGB space into \\( K_{i} \\) cubes, each with a side length of \\( 255 \\times K_{i}^{-\\frac{1}{3}} \\). Subsequently, we select the RGB value at the center of each cube and randomly assign them to index labels as the reference color image \\( C_{i} \\). We employ the optical flow estimation model RAFT [35], fine-tuned on AnimeRun [30], to esti" + }, + { + "type": "image", + "bbox": [ + 0.557, + 0.088, + 0.84, + 0.245 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.249, + 0.892, + 0.346 + ], + "angle": 0, + "content": "Figure 6. Our inclusion matching training pipeline employs index labels to partition the reference frame into \\( K_{i} \\) regions, which are then randomly merged with adjacent index labels with a probability of \\( 20\\% \\). Subsequently, the model estimates the affiliation of each line-enclosed segment in the target frame with a specific region in the reference, thereby facilitating the learning of the inclusion relationship." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.35, + 0.892, + 0.41 + ], + "angle": 0, + "content": "mate the optical flow between the reference line art \\(L_{i}\\) and the target line art \\(L_{j}\\). Utilizing this optical flow, we warp the reference color image \\(C_i\\) to generate the coarse color estimation \\(C_j\\) for the target frame." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.41, + 0.892, + 0.546 + ], + "angle": 0, + "content": "Feature Extraction Module. Lacking textual information and large deformation in animation make warped color image \\(C_j\\) hard to precisely align with the line art in the target frame. To address this, we employ deformable convolution [11] on the warped color \\(C_j\\) to extract aligned features. For a given deformable convolution kernel of \\(K\\) sampling positions, we use \\(\\omega_k\\) and \\(\\mathbf{p}_k\\) to represent the weight and prespecified offset. The aligned features \\(F_a\\) at each position \\(\\mathbf{p}_0\\) can be expressed as:" + }, + { + "type": "equation", + "bbox": [ + 0.558, + 0.556, + 0.892, + 0.598 + ], + "angle": 0, + "content": "\\[\nF _ {a} \\left(\\mathbf {p} _ {0}\\right) = \\sum_ {k = 1} ^ {K} \\omega_ {k} \\cdot F _ {a} \\left(\\mathbf {p} _ {0} + \\mathbf {p} _ {k} + \\Delta \\mathbf {p} _ {k}\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.607, + 0.891, + 0.668 + ], + "angle": 0, + "content": "where learnable offset \\(\\Delta \\mathbf{p}_k\\) can be predicted from the offset estimation network as depicted in Fig. 8. This network, designed as a lightweight U-Net [25] denoted as \\(\\Phi\\), is employed to expand the receptive field:" + }, + { + "type": "equation", + "bbox": [ + 0.625, + 0.678, + 0.891, + 0.695 + ], + "angle": 0, + "content": "\\[\n\\Delta \\mathbf {p} _ {k} = \\Phi ([ L _ {j}, C _ {j} ]). \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.893, + 0.901 + ], + "angle": 0, + "content": "For the reference frame, we deactivate the offset estimation module and set the offset to zero. Subsequently, the aligned color feature is concatenated with the line feature and passed through a feature encoder network. To guide the network in learning semantic information matching, we resize the line art image to \\(320 \\times 320\\) and utilize CLIP [23]'s image encoder to extract features. To preserve the feature's positional information, we choose to use the ConvNext-Large model from OpenCLIP [10]. We only selected the initial layers of CLIP, which downsample the feature to a resolution of \\(40 \\times 40\\). The CLIP feature is interpolated to concatenate with the encoded features. Finally, the feature decoder decodes these concatenated features to the input's" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25548" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.087, + 0.089, + 0.887, + 0.287 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.291, + 0.895, + 0.348 + ], + "angle": 0, + "content": "Figure 7. Our paint bucket colorization architecture. Initially, we estimate the optical flow based on the line arts and warp the reference color as the coarse colorization result. The mask and position embedding module tokenizes the segments and features extracted by the feature extraction module into a sequence, which is then fed into the multiplex transformer for information aggregation. Finally, we compute a similarity matrix between reference and target tokens to calculate matching loss and predict the final color." + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.352, + 0.462, + 0.472 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.474, + 0.47, + 0.557 + ], + "angle": 0, + "content": "Figure 8. Overall pipeline of our feature extraction module. Deformable convolution is applied to align the color features of the target frame to the line image. Then, the line features and aligned color features are concatenated and fed to the feature extraction network in a U-Net structure. Line art's CLIP features are also concatenated to the bottleneck of the feature extraction network." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.562, + 0.47, + 0.607 + ], + "angle": 0, + "content": "resolution with \\( C \\) channels. To preserve features in high resolution, shortcuts are added between the network's encoder and decoder, following the structure of the U-Net." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.609, + 0.471, + 0.746 + ], + "angle": 0, + "content": "Mask + Position Embedding Module. To transform different segments into tokens, we employ super-pixel pooling to average the features within each segment's mask, resulting in a \\(C\\)-dimensional visual token, denoted as \\(\\mathbf{d}_i\\). Subsequently, a Multilayer Perceptron (MLP) layer is utilized to encode the segment's bounding box's four-dimensional coordinates, denoted as \\(p_i\\), into a \\(C\\)-dimensional positional embedding. The token \\(\\mathbf{x}_i\\) for matching is obtained by adding the positional embedding and visual token:" + }, + { + "type": "equation", + "bbox": [ + 0.2, + 0.762, + 0.47, + 0.78 + ], + "angle": 0, + "content": "\\[\n\\mathbf {x} _ {i} = \\mathbf {d} _ {i} + \\mathbf {M L P} \\left(p _ {i}\\right). \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.793, + 0.469, + 0.854 + ], + "angle": 0, + "content": "Differing from previous segment matching pipelines [8, 30], our approach matches each line-enclosed segment in the target frame with a specific index label in the reference frame, rather than employing label-to-label matching." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Multiplex Transformer. Building upon [8, 27], we employ multiplex self- and cross-attention layers to aggregate tokenized features. In a self-attention layer, queries, keys, and" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.353, + 0.813, + 0.368 + ], + "angle": 0, + "content": "values are derived from a single source feature:" + }, + { + "type": "equation", + "bbox": [ + 0.547, + 0.378, + 0.892, + 0.413 + ], + "angle": 0, + "content": "\\[\n\\operatorname {s e l f - a t t e n t i o n} \\left(\\mathbf {x} _ {i}\\right) = \\operatorname {s o f t m a x} \\left(\\frac {\\mathbf {Q} _ {i} \\mathbf {K} _ {i}}{\\sqrt {D}}\\right) \\mathbf {V} _ {i}, \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.421, + 0.893, + 0.467 + ], + "angle": 0, + "content": "where \\(\\mathbf{Q}_i\\), \\(\\mathbf{K}_i\\), and \\(\\mathbf{V}_i\\) represent \\(\\mathbf{x}_i\\) processed by MLPs for query, key, and value. In contrast, the cross-attention layer computes keys and values from another feature:" + }, + { + "type": "equation", + "bbox": [ + 0.516, + 0.478, + 0.892, + 0.524 + ], + "angle": 0, + "content": "\\[\n\\operatorname {c r o s s - a t t e n t i o n} \\left(\\mathbf {x} _ {i} ^ {\\prime}, \\mathbf {x} _ {j} ^ {\\prime}\\right) = \\operatorname {s o f t m a x} \\left(\\frac {\\mathbf {Q} _ {i} ^ {\\prime} \\mathbf {K} _ {j} ^ {\\prime}}{\\sqrt {D}}\\right) \\mathbf {V} _ {j} ^ {\\prime}. \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.524, + 0.892, + 0.599 + ], + "angle": 0, + "content": "Following each self- or cross-attention layer, the output is added to the original \\(\\mathbf{x}_i\\) or \\(\\mathbf{x}'_i\\), and then processed with a feed-forward MLP. After repeating these operations \\(N\\) times, as illustrated in Fig. 7, we obtain the final aggregated features \\(\\hat{\\mathbf{x}}_i \\in \\mathbb{R}^{K_i \\times C}\\) and \\(\\hat{\\mathbf{x}}_j \\in \\mathbb{R}^{N_j \\times C}\\)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.6, + 0.891, + 0.63 + ], + "angle": 0, + "content": "Loss function. After the propagation step, the similarity matrix \\(\\mathbf{S} \\in \\mathbb{R}^{N_j \\times K_i}\\) is represented as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.587, + 0.64, + 0.892, + 0.678 + ], + "angle": 0, + "content": "\\[\n\\mathbf {S} _ {m n} = \\frac {\\exp \\left(\\hat {\\mathbf {x}} _ {i m} \\cdot \\hat {\\mathbf {x}} _ {j n}\\right)}{\\sum_ {m = 1} ^ {N _ {j}} \\exp \\left(\\hat {\\mathbf {x}} _ {i m} \\cdot \\hat {\\mathbf {x}} _ {j n}\\right)}. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.687, + 0.892, + 0.748 + ], + "angle": 0, + "content": "This matrix can be interpreted as the color probability \\(\\hat{\\mathbf{y}}_m\\in \\mathbb{R}^{K_i}\\) for segment \\(m\\) in the target frame. Given that each frame has a one-hot ground truth index label \\(\\mathbf{y}_m\\), the loss function is derived from the cross-entropy loss:" + }, + { + "type": "equation", + "bbox": [ + 0.605, + 0.758, + 0.892, + 0.8 + ], + "angle": 0, + "content": "\\[\nL _ {c e} = - \\sum_ {m = 1} ^ {K _ {i}} \\mathbf {y} _ {m} \\log (\\hat {\\mathbf {y}} _ {m}). \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.81, + 0.893, + 0.902 + ], + "angle": 0, + "content": "Inference Pipeline. Since real animation's colors have an obvious domain gap with our randomly generated colors, we adopt a color redistribution strategy to reassign randomly generated colors to replace the original colors during the warping and matching pipeline. This strategy can avoid the mismatching problem when several predefined colors" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "25549" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.123, + 0.08, + 0.849, + 0.336 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.338, + 0.892, + 0.379 + ], + "angle": 0, + "content": "Figure 9. The visualization results of our proposed methods and other approaches on real hand-drawn animation. Compared with previous methods, our proposed approach demonstrates enhanced robustness in handling occlusion situations (e.g., hand of the running girl and shadow near eyebrows of the girl in the second row.)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.38, + 0.892, + 0.448 + ], + "angle": 0, + "content": "Table 2. Quantitative comparison of our method with different methods. 'Acc' and 'Acc-Thres' denote segment-wise accuracy, providing insights into the potential workload reduction for digital painters. In 'Acc-Thres,' segments smaller than 10 pixels are filtered out. 'Pix-Acc,' 'Pix-F-Acc,' and 'Pix-B-MIoU' represent pixel-wise accuracy, foreground pixel-wise accuracy, and pixel-wise background MIoU, respectively, reflecting the visualization performance. All RAFT models undergo training on MPI-Sintel [5], and 'F/C' indicates the models fine-tuned on AnimeRun's colorized frames and contours." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.45, + 0.891, + 0.549 + ], + "angle": 0, + "content": "
TypeMethod3D rendered test setHand-drawn test set
AccAcc-ThresPix-AccPix-F-AccPix-B-MIoUAccAcc-ThresPix-AccPix-F-AccPix-B-MIoU
Reference-basedControlNet0.17090.18560.42740.26530.46000.17150.18120.24490.22980.2260
Segment matchingAnT(AnimeRun)0.55840.59300.87340.65370.89540.67790.70430.91930.73770.9429
AnT(Cadmium)0.66340.77130.97650.94710.98010.72240.78790.97920.93030.9899
Optical flowRAFT0.65890.74560.97240.90990.97630.75280.80930.98190.91900.9898
RAFT (F)0.71330.80540.98180.94490.98520.77580.84240.98600.94250.9922
RAFT (C)0.70280.79440.97230.94110.96900.77180.83560.98330.93750.9916
Inclusion matchingOurs0.82660.87260.99050.97240.99480.85930.89290.99000.96380.9984
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.554, + 0.47, + 0.584 + ], + "angle": 0, + "content": "are too closed. Finally, the estimated color for each line-enclosed segment \\(\\hat{\\mathbf{c}}_j\\in \\mathbb{R}^{N_j\\times M}\\) can be derived by:" + }, + { + "type": "equation", + "bbox": [ + 0.238, + 0.59, + 0.469, + 0.609 + ], + "angle": 0, + "content": "\\[\n\\hat {\\mathbf {c}} _ {j} = \\hat {\\mathbf {S}} \\mathbf {c} _ {i}, \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.614, + 0.47, + 0.676 + ], + "angle": 0, + "content": "where \\(\\hat{\\mathbf{S}}\\in \\mathbb{R}^{N_j\\times N_i}\\) is the similarity matrix for each line-enclosed segment in reference and target frames. In this paper, we set the match threshold as 0.2 to filter out all the segments which are unmatched." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.687, + 0.21, + 0.704 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.712, + 0.295, + 0.728 + ], + "angle": 0, + "content": "5.1. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.471, + 0.902 + ], + "angle": 0, + "content": "During the training stage, our model undergoes 300,000 iterations with a batch size of 2, utilizing NVIDIA GeForce RTX 3090 GPUs. We employ the Adam optimizer with a learning rate of \\(10^{-4}\\) and no weight decay. Throughout the training process, we keep the weights of the pretrained optical flow estimation module and the CLIP image encoder fixed. In the feature extraction module, the offset estimation module is structured as a lightweight U-Net with three down-sampling layers and a bottleneck featuring 128 features. Simultaneously, the feature extraction network is implemented as a U-Net with four down-sampling layers and a" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.554, + 0.892, + 0.63 + ], + "angle": 0, + "content": "bottleneck containing 512 features. The channel number \\( C \\) for our extracted feature is set to 128. Within the multiplex transformer, the layer number \\( N \\) is set to nine, and the number of heads is configured as four. The data augmentation pipeline is shown in the supplementary material." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.636, + 0.819, + 0.652 + ], + "angle": 0, + "content": "5.2. Comparisons with Previous Methods" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.66, + 0.892, + 0.765 + ], + "angle": 0, + "content": "Since there is no existing paint bucket colorization method, we mainly compare our method with reference-based line art colorization [42], segment matching methods [8, 30], and optical flow estimation methods [35]. The quantitative comparison is shown in Table 2. The visual comparison of real hand-drawn animation and rendered 3D test sets are shown in Fig. 9 and Fig. 10." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Reference-based Line Art Colorization. The saturated luminance of the blank regions within line art impedes the application of reference-based methods for natural gray-scale image colorization. Thus, we choose ControlNet [42] as our reference-based line art colorization method. We use Stable Diffusion v1.5 [24] as our base model and employ the ControlNet's line art checkpoint to encode the line art condition. Then, we adopt the IP-Adapter [38] to encode the reference image. We set the number of steps to 50 and use" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25550" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.079, + 0.895, + 0.135 + ], + "angle": 0, + "content": "Table 3. Quantitative comparison of different datasets, different network structures, and different methods on test data. 'IM' signifies the inclusion matching pipeline, which incorporates adjacent index label merging and segment-label matching strategies. Since the inclusion matching pipeline and coarse warping module with RAFT can also be applied to other networks, we also adopt them to AnT for comparison to illustrate the generalization of these methods." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.135, + 0.891, + 0.261 + ], + "angle": 0, + "content": "
TypeMethod3D rendered test setHand-drawn test set
AccAcc-ThresPix-AccPix-F-AccPix-B-MIoUAccAcc-ThresPix-AccPix-F-AccPix-B-MIoU
BaselineOurs0.82660.87260.99050.97240.99480.85930.89290.99000.96380.9984
DatasetAnimeRun0.73590.79580.96930.92010.97650.82780.86340.98180.93990.9906
Modelw/o CLIP0.81800.86530.98730.96850.99100.84890.88430.98780.95700.9925
w/o RAFT0.80010.84470.98240.94810.98780.84460.87500.98040.94040.9851
w/o DConv0.82470.86850.98940.97090.99280.85250.88330.98750.95490.9937
MethodOurs w/o IM0.76370.83520.97210.95730.96880.83480.87630.97770.94950.9822
AnT0.74500.79300.97080.93610.97580.81620.84970.98170.93740.9905
AnT with IM0.80630.84470.98370.95510.98870.83880.86980.98390.93880.9943
AnT with IM/RAFT0.81770.85870.98790.96810.99320.84830.88280.98860.95980.9946
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.265, + 0.47, + 0.325 + ], + "angle": 0, + "content": "the text prompt 'A character in the white background'. We calculate the average RGB value per segment and match the average color with the nearest color in the reference image for evaluation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.325, + 0.474, + 0.568 + ], + "angle": 0, + "content": "Optical Flow Estimation. Since optical flow methods cannot produce segment-wise estimation without postprocessing, we warp the color and calculate the colors that appear most frequently in each segment as the baseline of optical estimation method. Since finetuning RAFT on AnimeRun can promote the optical flow's performance effectively, we use the finetuned RAFT in the following sessions. Segment Matching. We also compare our method with the Cadmium application, the official implementation of AnT [8], and AnimenRun's reimplemented AnT [30]. The visual comparison shown in Fig. 9 and Fig. 10 demonstrate the robust performance of our proposed method, particularly in scenarios where strict segment correspondence is absent, and challenges with large motion and complex deformations. More visual results are presented in the suppl. material." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.576, + 0.232, + 0.592 + ], + "angle": 0, + "content": "5.3. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.599, + 0.47, + 0.689 + ], + "angle": 0, + "content": "Dataset. To demonstrate the effectiveness of our proposed dataset, we also train the proposed method on the AnimeRun. In the training process, we adopt the inclusion matching strategy by merging the segments in the reference frames. The quantitative results reported in Table 3 suggest the positive influence of our proposed dataset." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.47, + 0.825 + ], + "angle": 0, + "content": "Model. We conduct an ablation study on our model design to examine the necessity of each structure. In our experiments, we explore alternative configurations by replacing the deformable convolution and offset estimation module with the original convolution, eliminating the coarse warping module, and omitting the CLIP image encoder for ablation. The results presented in Table 3 underscore the significance of each module, highlighting the crucial role of the coarse warping module." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Method. The results in Table 3 further highlight the efficacy of our inclusion matching pipeline. Its application to AnT [8] yields a substantial improvement in network performance, suggesting the broad applicability and generalization of our inclusion matching pipeline. Ablation study" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.264, + 0.889, + 0.526 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.527, + 0.895, + 0.583 + ], + "angle": 0, + "content": "Figure 10. Visual comparison of different methods on our 3D rendered test set. Our proposed method produces satisfactory results in the presence of occlusion, significant motion, and substantial changes in viewing angles." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.584, + 0.884, + 0.599 + ], + "angle": 0, + "content": "visualizations are available in the supplementary material." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.616, + 0.62, + 0.632 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.895, + 0.84 + ], + "angle": 0, + "content": "We have introduced a new approach for line art paint bucket colorization. Departing from traditional segment matching methods that struggle with one-to-one correspondence, we proposed a novel inclusion matching pipeline that estimates each segment's inclusion relationship rather than the direct correspondence. To facilitate the learning of this inclusion relationship, we presented a dedicated dataset, PaintBucket-Character, and a two-stage colorization pipeline. Our pipeline incorporates a coarse color warping module and an inclusion matching module. The experimental results demonstrate the superior performance of our method in handling occlusion and accommodating large movements within challenging scenarios." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Acknowledgement. This study is supported under the RIE2020 Industry Alignment Fund Industry Collaboration Projects (IAF-ICP) Funding Initiative, as well as cash and in-kind contribution from the industry partner(s)." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.958 + ], + "angle": 0, + "content": "25551" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.175, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.116, + 0.433, + 0.129 + ], + "angle": 0, + "content": "[1] Aplaybox. https://www.aplaybox.com/.2,4" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.131, + 0.375, + 0.144 + ], + "angle": 0, + "content": "[2] Cadmium. https://cadmium.app/. 2" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.146, + 0.407, + 0.16 + ], + "angle": 0, + "content": "[3] Mixamo. https://www MIXamo.com/.2,4" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.161, + 0.469, + 0.202 + ], + "angle": 0, + "content": "[4] Kenta Akita, Yuki Morimoto, and Reiji Tsuruno. 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ACM TOG, 38(6), 2019. 3" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.469, + 0.546 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.518, + 0.956 + ], + "angle": 0, + "content": "25553" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_origin.pdf b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..c1f71ddcd5113c575f8fd038165bf5f5a3450b0a --- /dev/null +++ b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/3a58aaab-2a4a-445b-9bfe-6c6c88da7d90_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:129614e4411b15ec087cb42cc509164a201589288c8f5edb972f79c6ab9e7846 +size 2970476 diff --git a/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/full.md b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/full.md new file mode 100644 index 0000000000000000000000000000000000000000..68896b064cb5abdfeb7f8ece9f093c75eb8666b5 --- /dev/null +++ b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/full.md @@ -0,0 +1,290 @@ +# Learning Inclusion Matching for Animation Paint Bucket Colorization + +Yuekun Dai Shangchen Zhou Qinyue Li Chongyi Li Chen Change Loy S-Lab, Nanyang Technological University + +https://ykdai.github.io/projects/InclusionMatching + +![](images/64a68f6eb1e062dcd1e9ec1ff4b94358ecd1bbab9aeb55d2fa4b457d93d22f7a.jpg) +Figure 1. In the animation industry, digital painters use paint bucket tool to colorize drawn line arts frame by frame. Our proposed pipeline streamlines this process by requiring the painters to colorize just one frame, after which the algorithm autonomously propagates the color to subsequent frames, enabling automatic colorization. Compared with optical-flow-based method RAFT [35] and segment-matching-based method AnT [8], our method can achieve more robust results on challenging cases such as one-to-many matching, large deformation, and tiny region colorization. In this figure, RAFT is trained on Sintel dataset [5] and finetuned on AnimeRun [30]. We use the most frequent color in each segment to colorize each line-enclosed region. ©drawn by Nicca (Sriprachum Kongwisawamit), used with artist permission. + +# Abstract + +Colorizing line art is a pivotal task in the production of hand-drawn cel animation. This typically involves digital painters using a paint bucket tool to manually color each segment enclosed by lines, based on RGB values predetermined by a color designer. This frame-by-frame process is both arduous and time-intensive. Current automated methods mainly focus on segment matching. This technique migrates colors from a reference to the target frame by aligning features within line-enclosed segments across frames. However, issues like occlusion and wrinkles in animations often disrupt these direct correspondences, leading to mismatches. In this work, we introduce a new learning-based inclusion matching pipeline, which directs the network to comprehend the inclusion relationships between segments rather than relying solely on direct visual correspondences. Our method features a two-stage pipeline that integrates a coarse color warping module with an inclusion matching module, enabling more nuanced and accurate colorization. To facilitate the training of our network, we also develop a unique dataset, referred to as PaintBucket-Character. This + +dataset includes rendered line arts alongside their colorized counterparts, featuring various 3D characters. Extensive experiments demonstrate the effectiveness and superiority of our method over existing techniques. + +# 1. Introduction + +Colorizing line art is a critical step in hand-drawn animation production. Initially, key animators create the characters' keyframes, followed by in-between animators who generate intermediate frames and refine keyframes for seamless connection between each stroke, as described in [31]. These line arts are then scanned into binary images, featuring a primary color palette of red, blue, green, and black, which represents highlights, shadows, special instructions (e.g., eye irises), and normal lines respectively. These scanned images, with regions of transparent background as shown in Fig. 1, are forwarded to digital painters. The painters use a paint bucket tool and a designated color palette to fill each line-enclosed segment, including the color lines, which is known as paint bucket colorization. Finally, special effect artists add visual enhancements, such as anti-aliasing, to + +blend character animations with backgrounds, culminating in the final video composition, detailed in [20]. + +Line art colorization is a notably laborious process. For instance, even the relatively simple scenario in Fig. 1, involving 93 segments, still requires hundreds of manual clicks. To mitigate this demanding task, several commercial software applications like Retas Studio Paintman, OpenToonz, and CLIP Studio Paint have been developed. These tools provide helpful features that allow users to easily adjust assigned colors, fill small areas, and aid in line colorization. Despite these advancements, fully automated colorization has yet to be realized. + +To address the challenges of line art colorization, numerous segment-matching methods have been developed for identifying corresponding segments in reference and target frames. Traditional graph-based approaches [17-19, 39, 44] consider each segment as a graph node and establish edges based on adjacency relationships. These methods employ optimization techniques to minimize topological similarity loss among corresponding nodes. However, they are time-intensive, often taking several minutes to process a single image with around 100 segments. Casey et al. [8] introduced the Animation Transformer (AnT) and its application Cadmium, which significantly improved segment matching. AnT standardizes the size of each segment and employs convolutional neural networks (CNNs) to extract features, transforming the image into a segment sequence. This converts segment matching into a sequence-to-sequence problem. Although AnT excels in aligning segments between adjacent frames featuring minimal motion, it struggles in more complex scenarios, particularly those with occlusion or pronounced motion. During occlusions, interlaced lines tend to fragment segments into multiple pieces, as depicted in Fig. 2. This fragmentation disrupts the strict correspondence between segments, rendering the task of segment matching inherently problematic and poorly defined. + +In this study, we introduce the novel notion of 'inclusion matching', which obviates the necessity for exact segment-to-segment correspondence. Instead of direct segment matching, our approach computes the likelihood of each segment in a target frame being included within a specific region of a reference frame. Our methodology is unique in that it follows a coarse-to-fine colorization pipeline, inspired by the approach of skilled digital painters. This approach typically begins with coloring larger, more noticeable segments across all frames before filling in details of smaller segments in each frame. Motivated by this workflow, our pipeline first computes optical flow between line sketches, warping colors from a reference to a target frame to achieve a preliminary, coarse colorization. This is followed by the application of an inclusion matching module, which refines the colorization result of tiny segments. + +The sparse nature of line art requires special formula + +![](images/8e896adca3dc90fadbbb9c687f5e54dc73f98b22406890693cef3f5838eea213.jpg) +Figure 2. Methods relying on segment matching typically seek the most similar segment across frames, yet challenges arise in scenarios involving occlusion and wrinkles. This is particularly evident in tiny segments, as highlighted in the red box, where disruptions in correspondence lead to mismatches. Our innovative approach, based on inclusion matching, addresses this issue by estimating the inclusion relationship rather than pursuing direct correspondence, as illustrated by the comparison of red and blue matching lines. + +tion in our approach. Specifically, recognizing the necessity for a large receptive field in extracting line art features, we employ a U-Net structure [25] to process concatenated color and line features. To address the difficulty in matching segments under large deformations, we extract line semantic features using CLIP [23] and concatenate them with features from the U-Net's bottleneck. This allows the network to match the region with the same semantic information across frames. Finally, we introduce super-pixel pooling at each segment to transfer the image into tokens for sequence-to-sequence matching. + +Dataset plays a key role in the success of our method. To train and evaluate our method, we select 22 character models from Mixamo [3] and Aplaybox [1]. We mimic real intermediate line art data on the animation coloring production line. We disable the anti-aliasing and provide the color lines which is quite common in animation production. Then we use 3D software Cinema 4D to synthesize a specially-designed cartoon character colorization dataset named PaintBucket-Character. + +The contributions of our work include the introduction of the PaintBucket-Character dataset tailored for paint bucket colorization tasks, the novel inclusion matching pipeline addressing the challenge of lacking strict segment correspondence, and a new coarse-to-fine baseline that outperforms existing solutions, particularly in scenes with occlusion. Our experiments demonstrate that our method surpasses the performance of recent AnT application Cadmium, and outperforms the results presented by Li et al. [30]. Notably, the advantages of our approach extend beyond dataset improvements, highlighting the effectiveness of our newly designed inclusion matching pipeline and the coarse-to-fine baseline in the context of animation colorization. + +![](images/e3c167aff20d190f42a038d09f18e1f8361a9e78314bf00331ea9eeae025417e.jpg) +Figure 3. Several examples of our rendered characters in PaintBucket-Character dataset. + +# 2. Related Work + +Line Art Colorization. Line art colorization aims to create reasonable colors in the sketch's blank regions. To achieve precise control, many user guidance types are designed including text [15, 45], scribble [6, 33, 40, 41], colored reference [4, 7, 9, 16, 32, 34, 37, 42, 43]. These methods mainly focus on pixel-wise estimation and cannot fill flat accurate RGB values assigned by the color designer in line arts' segments, which always leads to flickering and color bleeding. Besides, in the post-processing, the special effect artists often need to select specific colors to create various effects such as ramp or glow for the character's specific region. Thus, current line art colorization methods are still difficult to be merged into animation industrial processes. + +Animation-related Dataset. To facilitate hand-drawn animation production, many real and rendered datasets are proposed. To boost video interpolation performance, Li et al. [29] propose the ATD-12K dataset which consists of triplet frames from 30 real animation movies. Due to the absence of correspondence labels for real animation, addressing this challenge has led to the adoption of 3D rendering techniques. MPI-Sintel [5] and CreativeFlow+ [28] provide different annotations such as optical flow, segmentation labels, and depth maps for multiple applications using Blender. To overcome the domain gap between rendered images and real 2D cartoons, Li et al. [30] developed the AnimeRun dataset using open-source 3D animations and their rendered optical flow. It improves segment matching accuracy and handles complex scenes. + +Segment-based Animation Colorization. In the cleaning-up process of the animation industry, animators enclose each line manually, making segments serve as basic units for colorization. Thus, how to calculate segment-level semantic information and correspondence becomes the key in animation colorization. Traditional methods [17-19, 39, 44] regards segment as node and adjacency relationship as edge which transfer the segment matching to the graph optimization problem. Recently, Dang et al. [12] use Hu mo + +ments [14] to extract each segment's feature to replace the RGB value and apply a UNet structure [25] to obtain the feature map. Subsequently, the feature is averaged in each segment to calculate the distance across frames for matching. Referring to the success of Transformer [36] in image matching [27], Casey et al. [8] apply multiplex transformer to aggregate information across frames to obtain more accurate results. Besides, Casey et al. replace the Hu moments algorithm with a segment feature extraction CNN which crop and resize each segment to fixed resolution first. Since both Dang et al. and Casey et al.'s methods and dataset are not publicly available, AnimeRun [30] remains the sole benchmark for segment matching available to researchers. + +# 3. Paint Bucket Colorization Dataset + +AnimeRun [30] employs rendered optical flow to calculate segment correspondence, leading to frequent one-to-many and many-to-one matching in the dataset. This results in inaccurate benchmark evaluations, as each segment may have multiple potential ground-truth correspondences. Furthermore, the limited dataset provided by AnimeRun, consisting of only 1,760 training images, increases the risk of network overfitting. Meanwhile, due to the anti-aliasing processing of AnimeRun's rendered images, accurate color labels cannot be obtained in each segment. Consequently, AnimeRun faces difficulties in serving as a paint bucket colorization dataset directly. + +To address these challenges, we introduce a new dataset PaintBucket-Character, comprising 11,345 training images and 3,200 test images. The test set includes 3,000 3D rendered frames and 200 hand-drawn frames. Notably, our dataset focuses solely on character animations, with consideration for the common practice among animators of just drawing foreground character animations while employing 3D models or separate paintings for the background. Our dataset focuses on character animations, considering the industry practice where animators typically sketch only the foreground character movements, while backgrounds are created using separate 3D models or paintings. Different from AnimeRun, our evaluation focuses on + +Table 1. A comparison between our PaintBucket-Character dataset and previous segment matching datasets. Since AnT [8]'s dataset is not publicly available, we use $-$ to mark the unknown information. AnT does possess a private hand-drawn dataset with 3578 frames; however, it does not provide train-test-split information, indicated by $+^{\prime}$ . Compared with previous open-source datasets, our dataset is more diverse and provides color lines that are closer to real hand-drawn animation. No anti-aliasing provides extra semantic information for each segment, which enables the network to learn better semantic information rather than segment shape similarity. + +
DatasetStatisticsAnnotations
TrainTestClipsSeg per Fr.No anti-aliasingOptical flowIndex labelColor labelColor line
AnimeRun [30]1,7601,05920+10237×✓×××
AnT [8] (private)9,900+1,100+-< 50-×✓✓×
Ours11,3453,200180+170169✓×✓✓✓
+ +![](images/970f272193153fbf4488dfb423d57052c6738e655df40842fd0b426d52a73c74.jpg) +(a) UV Map + +![](images/023bfcde80c5f48632e91bb33f3e1f06da79c3f3ce099268e56f0086aab57f15.jpg) +(b)Color label + +![](images/52d18fca425efed10eea89b6694d65719e6fce96c98de30ed5444aa9ed97eab6.jpg) +(c) Index label +Figure 4. Overview of our synthetic data generation pipeline. We extract the UV map (a) and the used UV region from the character. Then, we use a paint bucket tool to fill the used UV region, creating color label (b) and index label (c). Label images (b) and (c) are then pasted back to the 3D meshes to create flat color characters (d) and (e), respectively. Finally, we post-process the index image (e) to obtain the rendered line art image (f). + +![](images/0d59492cef147a596941d7452d90e435d36cf72767e8d8b99c183dd617b5703f.jpg) + +![](images/96a04cf44555c229894628d7b9070c1083ed484d84a02f49b1820b0fdb51db95.jpg) +(d) Color image + +![](images/1d64e731a10fd6c9f82a6e3d1739cec1d982f559e7c1c210e45582d2d59266a2.jpg) + +![](images/3223d83b19642418e094c95d2834b8a36221bcb1e5eb9aa5b45c93f8f89bc870.jpg) +(e) Index image + +![](images/7565642f43845ffb189e0dbb6e8033322bc30fd0f03b1894e8998f919d8eb1d7.jpg) +(f) Line art image + +segments' color accuracy rather than traditional matching accuracy. To build our dataset, we sample 22 characters from Mixamo [3] and Aplaybox [1] and set 12 characters for training and 10 for testing. Then, we replot the UV map for these character models in flat color style and use Cinema 4D's Sketch and Toon Effect to produce the line art. To ensure consistent color in each segment, we disable the anti-aliasing and change the texture sampling method to the nearest. As depicted in Fig. 3, our dataset showcases a diverse array of characters encompassing both Japanese and Western cartoon styles. + +# 3.1. Synthetic Dataset Construction + +To include temporal and occlusion relationships in our dataset, we apply Mixamo's actions to our characters. For each character, we add five types of actions and animate the camera motion to capture different viewpoints of the character in each sequence. We classify the camera positions into three types: face shot, long shot, and close-up, in which we separately focus on the face, whole body, and other parts of the body. Following this pipeline, we obtain 15 clips for each character and form 180 clips for training and 150 clips for test. In the animation industry, keyframes always have a + +![](images/d7f5669e14ae1be98ed42dc25e3d498d21def9f4d68255a0e365c7c180878318.jpg) +Real hand-drawn line art +Figure 5. Our simulation method can generate color lines that closely mimic hand-drawn line arts. Red, blue, and green lines represent highlights, shadows, and other instructions respectively. low frame rate [29]. Thus, in each clip, we set the frame rate to 10 to mimic real animation and bring larger motion and deformation. Meanwhile, to address the fine scale of character details such as pupils and buttons, we use $1920 \times 1920$ as our training size and $1024 \times 1024$ as our test set size to provide clear segments in these areas. + +![](images/1c4ea5cd06ef16f532b0f83bff026a9e23ac3238ffdfdaacaf7e833138775f9b.jpg) +Our synthetic line art + +![](images/ddec8b21ea3bab60cebc8f75f9a2f1293c6dddd42af5a97cb0516f2f6c3ae1e8.jpg) + +Flat Color Style Rendering. To render characters in a flat color style, we use Cinema 4D to extract a UV mesh map and set unused regions as black. Then, we draw contour lines of character details such as pockets and shoelace on the UV mesh. Based on this original UV map, we use a paint bucket tool to colorize the mesh as the color label. To obtain a more precise matching relationship for training, we connect the label with the same semantic information (such as palm and back of the hand) and use the connected components algorithm for each color to extract the index label as shown in Fig. 4. Since we aim to achieve accurate line art to separate each segment, we calculate the difference between each color's segment and its erosion as the black lines. This operation ensures that each line-enclosed segment contains clear semantic information and comprises only one color. + +Color Line Extraction. To simulate color lines which are common in real hand-drawn animation's shadow and highlight regions, we mark these highlight and shadow colors and erode these regions to create color lines, as shown in Fig. 5. Compared with AnimeRun [30], our dataset features more realistic line art and provides clear semantic information for each segment. Since our characters are rendered with discrete colors, we can easily obtain specific meanings for each segment. + +# 3.2. Hand-drawn Dataset Collection + +Obtaining intermediate unprocessed data poses a challenge, as common commercial animations undergo post + +processing techniques including anti-aliasing. To address this challenge, we invite some professional animators to draw line art animation clips with different characters. Then, we use the paint bucket tool to colorize these line arts as our ground truth to synthesize paired line art and colorized data. Besides, animation creation software such as Retas Studio Paintman and CLIP Studio Paint all provide animation production tutorials. We collect animations in these tutorials and use the color line extraction method to synthesize the paired data. Finally, we collect a hand-drawn test dataset with 200 frames and 20 clips for evaluation. + +# 4. Method + +# 4.1. Inclusion Matching + +Given two line art images $L_{i}, L_{j} \in \mathbb{R}^{H \times W \times 3}$ , lines separate the blank area into $N_{i}$ and $N_{j}$ 's line-enclosed segments. In the reference frame $L_{i}$ , each segment is colorized with $M$ colors whose color labels can be represented as one-hot representation $c_{i} \in \mathbb{R}^{N_{i} \times M}$ . To estimate the $L_{j}$ 's color label $\hat{c}_{j} \in \mathbb{R}^{N_{j} \times M}$ , previous segment-matching-based methods [8, 30] mainly focus on calculating segments' visual correspondence with the matching $\mathbf{m}^{j \rightarrow i} \in \mathbb{R}^{N_{j} \times N_{i}}$ . Nevertheless, the absence of strict correspondence among segments imposes limitations on the model's learning capacity. + +To tackle this challenge, we introduce a novel method called inclusion matching. In the reference frame, segments with identical semantic information are merged, creating $K_{i}$ large regions with different labels. As each line-enclosed segment in the target frame can only possess one color with a specific meaning, it can be identified as a subset of one of the $K_{i}$ regions. Specifically, in the training process, the index label stated in Fig. 4 separates the reference frame into $K_{i}$ region. We train a network to estimate each segment's index label $\mathbb{R}^{N_j\times K_i}$ . To enrich the diversity, we randomly merge the adjacent labels in the reference frame to create larger regions to guide the network to learn a more robust inclusion relationship, as shown in Fig. 6. + +# 4.2. PaintBucket Colorization Pipeline + +Color Warping Module. Colorized line art carries substantial information about how segments are grouped, making it crucial for inclusion matching. However, previous segment matching methods [8, 30] exclusively leverage the line art's features for matching and do not incorporate the colorized reference. To encode the color feature, we recolorize the index label image. Specifically, we partition the RGB space into $K_{i}$ cubes, each with a side length of $255 \times K_{i}^{-\frac{1}{3}}$ . Subsequently, we select the RGB value at the center of each cube and randomly assign them to index labels as the reference color image $C_{i}$ . We employ the optical flow estimation model RAFT [35], fine-tuned on AnimeRun [30], to esti + +![](images/458fb955574b1d0d61a4a48511c0747ec0d183422dd81dc91ccb1df151cd3eaf.jpg) +Figure 6. Our inclusion matching training pipeline employs index labels to partition the reference frame into $K_{i}$ regions, which are then randomly merged with adjacent index labels with a probability of $20\%$ . Subsequently, the model estimates the affiliation of each line-enclosed segment in the target frame with a specific region in the reference, thereby facilitating the learning of the inclusion relationship. + +mate the optical flow between the reference line art $L_{i}$ and the target line art $L_{j}$ . Utilizing this optical flow, we warp the reference color image $C_i$ to generate the coarse color estimation $C_j$ for the target frame. + +Feature Extraction Module. Lacking textual information and large deformation in animation make warped color image $C_j$ hard to precisely align with the line art in the target frame. To address this, we employ deformable convolution [11] on the warped color $C_j$ to extract aligned features. For a given deformable convolution kernel of $K$ sampling positions, we use $\omega_k$ and $\mathbf{p}_k$ to represent the weight and prespecified offset. The aligned features $F_a$ at each position $\mathbf{p}_0$ can be expressed as: + +$$ +F _ {a} \left(\mathbf {p} _ {0}\right) = \sum_ {k = 1} ^ {K} \omega_ {k} \cdot F _ {a} \left(\mathbf {p} _ {0} + \mathbf {p} _ {k} + \Delta \mathbf {p} _ {k}\right), \tag {1} +$$ + +where learnable offset $\Delta \mathbf{p}_k$ can be predicted from the offset estimation network as depicted in Fig. 8. This network, designed as a lightweight U-Net [25] denoted as $\Phi$ , is employed to expand the receptive field: + +$$ +\Delta \mathbf {p} _ {k} = \Phi ([ L _ {j}, C _ {j} ]). \tag {2} +$$ + +For the reference frame, we deactivate the offset estimation module and set the offset to zero. Subsequently, the aligned color feature is concatenated with the line feature and passed through a feature encoder network. To guide the network in learning semantic information matching, we resize the line art image to $320 \times 320$ and utilize CLIP [23]'s image encoder to extract features. To preserve the feature's positional information, we choose to use the ConvNext-Large model from OpenCLIP [10]. We only selected the initial layers of CLIP, which downsample the feature to a resolution of $40 \times 40$ . The CLIP feature is interpolated to concatenate with the encoded features. Finally, the feature decoder decodes these concatenated features to the input's + +![](images/843f66a024d950a4747c5a3c7ebcb8a854c13bc49289b2c6715b93fa64220720.jpg) +Figure 7. Our paint bucket colorization architecture. Initially, we estimate the optical flow based on the line arts and warp the reference color as the coarse colorization result. The mask and position embedding module tokenizes the segments and features extracted by the feature extraction module into a sequence, which is then fed into the multiplex transformer for information aggregation. Finally, we compute a similarity matrix between reference and target tokens to calculate matching loss and predict the final color. + +![](images/0cd9736962cc67bd204883b6c9330e0d6284da4779d5cdd009f09429de7d7093.jpg) +Figure 8. Overall pipeline of our feature extraction module. Deformable convolution is applied to align the color features of the target frame to the line image. Then, the line features and aligned color features are concatenated and fed to the feature extraction network in a U-Net structure. Line art's CLIP features are also concatenated to the bottleneck of the feature extraction network. + +resolution with $C$ channels. To preserve features in high resolution, shortcuts are added between the network's encoder and decoder, following the structure of the U-Net. + +Mask + Position Embedding Module. To transform different segments into tokens, we employ super-pixel pooling to average the features within each segment's mask, resulting in a $C$ -dimensional visual token, denoted as $\mathbf{d}_i$ . Subsequently, a Multilayer Perceptron (MLP) layer is utilized to encode the segment's bounding box's four-dimensional coordinates, denoted as $p_i$ , into a $C$ -dimensional positional embedding. The token $\mathbf{x}_i$ for matching is obtained by adding the positional embedding and visual token: + +$$ +\mathbf {x} _ {i} = \mathbf {d} _ {i} + \mathbf {M L P} \left(p _ {i}\right). \tag {3} +$$ + +Differing from previous segment matching pipelines [8, 30], our approach matches each line-enclosed segment in the target frame with a specific index label in the reference frame, rather than employing label-to-label matching. + +Multiplex Transformer. Building upon [8, 27], we employ multiplex self- and cross-attention layers to aggregate tokenized features. In a self-attention layer, queries, keys, and + +values are derived from a single source feature: + +$$ +\operatorname {s e l f - a t t e n t i o n} \left(\mathbf {x} _ {i}\right) = \operatorname {s o f t m a x} \left(\frac {\mathbf {Q} _ {i} \mathbf {K} _ {i}}{\sqrt {D}}\right) \mathbf {V} _ {i}, \tag {4} +$$ + +where $\mathbf{Q}_i$ , $\mathbf{K}_i$ , and $\mathbf{V}_i$ represent $\mathbf{x}_i$ processed by MLPs for query, key, and value. In contrast, the cross-attention layer computes keys and values from another feature: + +$$ +\operatorname {c r o s s - a t t e n t i o n} \left(\mathbf {x} _ {i} ^ {\prime}, \mathbf {x} _ {j} ^ {\prime}\right) = \operatorname {s o f t m a x} \left(\frac {\mathbf {Q} _ {i} ^ {\prime} \mathbf {K} _ {j} ^ {\prime}}{\sqrt {D}}\right) \mathbf {V} _ {j} ^ {\prime}. \tag {5} +$$ + +Following each self- or cross-attention layer, the output is added to the original $\mathbf{x}_i$ or $\mathbf{x}'_i$ , and then processed with a feed-forward MLP. After repeating these operations $N$ times, as illustrated in Fig. 7, we obtain the final aggregated features $\hat{\mathbf{x}}_i \in \mathbb{R}^{K_i \times C}$ and $\hat{\mathbf{x}}_j \in \mathbb{R}^{N_j \times C}$ . + +Loss function. After the propagation step, the similarity matrix $\mathbf{S} \in \mathbb{R}^{N_j \times K_i}$ is represented as follows: + +$$ +\mathbf {S} _ {m n} = \frac {\exp \left(\hat {\mathbf {x}} _ {i m} \cdot \hat {\mathbf {x}} _ {j n}\right)}{\sum_ {m = 1} ^ {N _ {j}} \exp \left(\hat {\mathbf {x}} _ {i m} \cdot \hat {\mathbf {x}} _ {j n}\right)}. \tag {6} +$$ + +This matrix can be interpreted as the color probability $\hat{\mathbf{y}}_m\in \mathbb{R}^{K_i}$ for segment $m$ in the target frame. Given that each frame has a one-hot ground truth index label $\mathbf{y}_m$ , the loss function is derived from the cross-entropy loss: + +$$ +L _ {c e} = - \sum_ {m = 1} ^ {K _ {i}} \mathbf {y} _ {m} \log (\hat {\mathbf {y}} _ {m}). \tag {7} +$$ + +Inference Pipeline. Since real animation's colors have an obvious domain gap with our randomly generated colors, we adopt a color redistribution strategy to reassign randomly generated colors to replace the original colors during the warping and matching pipeline. This strategy can avoid the mismatching problem when several predefined colors + +![](images/8e756080549693a7b5ddef8fb66e2b88fec6aeef01c3a5f6d961c425146d575a.jpg) +Figure 9. The visualization results of our proposed methods and other approaches on real hand-drawn animation. Compared with previous methods, our proposed approach demonstrates enhanced robustness in handling occlusion situations (e.g., hand of the running girl and shadow near eyebrows of the girl in the second row.) +Table 2. Quantitative comparison of our method with different methods. 'Acc' and 'Acc-Thres' denote segment-wise accuracy, providing insights into the potential workload reduction for digital painters. In 'Acc-Thres,' segments smaller than 10 pixels are filtered out. 'Pix-Acc,' 'Pix-F-Acc,' and 'Pix-B-MIoU' represent pixel-wise accuracy, foreground pixel-wise accuracy, and pixel-wise background MIoU, respectively, reflecting the visualization performance. All RAFT models undergo training on MPI-Sintel [5], and 'F/C' indicates the models fine-tuned on AnimeRun's colorized frames and contours. + +
TypeMethod3D rendered test setHand-drawn test set
AccAcc-ThresPix-AccPix-F-AccPix-B-MIoUAccAcc-ThresPix-AccPix-F-AccPix-B-MIoU
Reference-basedControlNet0.17090.18560.42740.26530.46000.17150.18120.24490.22980.2260
Segment matchingAnT(AnimeRun)0.55840.59300.87340.65370.89540.67790.70430.91930.73770.9429
AnT(Cadmium)0.66340.77130.97650.94710.98010.72240.78790.97920.93030.9899
Optical flowRAFT0.65890.74560.97240.90990.97630.75280.80930.98190.91900.9898
RAFT (F)0.71330.80540.98180.94490.98520.77580.84240.98600.94250.9922
RAFT (C)0.70280.79440.97230.94110.96900.77180.83560.98330.93750.9916
Inclusion matchingOurs0.82660.87260.99050.97240.99480.85930.89290.99000.96380.9984
+ +are too closed. Finally, the estimated color for each line-enclosed segment $\hat{\mathbf{c}}_j\in \mathbb{R}^{N_j\times M}$ can be derived by: + +$$ +\hat {\mathbf {c}} _ {j} = \hat {\mathbf {S}} \mathbf {c} _ {i}, \tag {8} +$$ + +where $\hat{\mathbf{S}}\in \mathbb{R}^{N_j\times N_i}$ is the similarity matrix for each line-enclosed segment in reference and target frames. In this paper, we set the match threshold as 0.2 to filter out all the segments which are unmatched. + +# 5. Experiments + +# 5.1. Implementation Details + +During the training stage, our model undergoes 300,000 iterations with a batch size of 2, utilizing NVIDIA GeForce RTX 3090 GPUs. We employ the Adam optimizer with a learning rate of $10^{-4}$ and no weight decay. Throughout the training process, we keep the weights of the pretrained optical flow estimation module and the CLIP image encoder fixed. In the feature extraction module, the offset estimation module is structured as a lightweight U-Net with three down-sampling layers and a bottleneck featuring 128 features. Simultaneously, the feature extraction network is implemented as a U-Net with four down-sampling layers and a + +bottleneck containing 512 features. The channel number $C$ for our extracted feature is set to 128. Within the multiplex transformer, the layer number $N$ is set to nine, and the number of heads is configured as four. The data augmentation pipeline is shown in the supplementary material. + +# 5.2. Comparisons with Previous Methods + +Since there is no existing paint bucket colorization method, we mainly compare our method with reference-based line art colorization [42], segment matching methods [8, 30], and optical flow estimation methods [35]. The quantitative comparison is shown in Table 2. The visual comparison of real hand-drawn animation and rendered 3D test sets are shown in Fig. 9 and Fig. 10. + +Reference-based Line Art Colorization. The saturated luminance of the blank regions within line art impedes the application of reference-based methods for natural gray-scale image colorization. Thus, we choose ControlNet [42] as our reference-based line art colorization method. We use Stable Diffusion v1.5 [24] as our base model and employ the ControlNet's line art checkpoint to encode the line art condition. Then, we adopt the IP-Adapter [38] to encode the reference image. We set the number of steps to 50 and use + +Table 3. Quantitative comparison of different datasets, different network structures, and different methods on test data. 'IM' signifies the inclusion matching pipeline, which incorporates adjacent index label merging and segment-label matching strategies. Since the inclusion matching pipeline and coarse warping module with RAFT can also be applied to other networks, we also adopt them to AnT for comparison to illustrate the generalization of these methods. + +
TypeMethod3D rendered test setHand-drawn test set
AccAcc-ThresPix-AccPix-F-AccPix-B-MIoUAccAcc-ThresPix-AccPix-F-AccPix-B-MIoU
BaselineOurs0.82660.87260.99050.97240.99480.85930.89290.99000.96380.9984
DatasetAnimeRun0.73590.79580.96930.92010.97650.82780.86340.98180.93990.9906
Modelw/o CLIP0.81800.86530.98730.96850.99100.84890.88430.98780.95700.9925
w/o RAFT0.80010.84470.98240.94810.98780.84460.87500.98040.94040.9851
w/o DConv0.82470.86850.98940.97090.99280.85250.88330.98750.95490.9937
MethodOurs w/o IM0.76370.83520.97210.95730.96880.83480.87630.97770.94950.9822
AnT0.74500.79300.97080.93610.97580.81620.84970.98170.93740.9905
AnT with IM0.80630.84470.98370.95510.98870.83880.86980.98390.93880.9943
AnT with IM/RAFT0.81770.85870.98790.96810.99320.84830.88280.98860.95980.9946
+ +the text prompt 'A character in the white background'. We calculate the average RGB value per segment and match the average color with the nearest color in the reference image for evaluation. + +Optical Flow Estimation. Since optical flow methods cannot produce segment-wise estimation without postprocessing, we warp the color and calculate the colors that appear most frequently in each segment as the baseline of optical estimation method. Since finetuning RAFT on AnimeRun can promote the optical flow's performance effectively, we use the finetuned RAFT in the following sessions. Segment Matching. We also compare our method with the Cadmium application, the official implementation of AnT [8], and AnimenRun's reimplemented AnT [30]. The visual comparison shown in Fig. 9 and Fig. 10 demonstrate the robust performance of our proposed method, particularly in scenarios where strict segment correspondence is absent, and challenges with large motion and complex deformations. More visual results are presented in the suppl. material. + +# 5.3. Ablation Study + +Dataset. To demonstrate the effectiveness of our proposed dataset, we also train the proposed method on the AnimeRun. In the training process, we adopt the inclusion matching strategy by merging the segments in the reference frames. The quantitative results reported in Table 3 suggest the positive influence of our proposed dataset. + +Model. We conduct an ablation study on our model design to examine the necessity of each structure. In our experiments, we explore alternative configurations by replacing the deformable convolution and offset estimation module with the original convolution, eliminating the coarse warping module, and omitting the CLIP image encoder for ablation. The results presented in Table 3 underscore the significance of each module, highlighting the crucial role of the coarse warping module. + +Method. The results in Table 3 further highlight the efficacy of our inclusion matching pipeline. Its application to AnT [8] yields a substantial improvement in network performance, suggesting the broad applicability and generalization of our inclusion matching pipeline. Ablation study + +![](images/8846974929558ba6d43b465c9e50b19fac81994c5682c440460bb3f8fcc8b0a2.jpg) +Figure 10. Visual comparison of different methods on our 3D rendered test set. Our proposed method produces satisfactory results in the presence of occlusion, significant motion, and substantial changes in viewing angles. + +visualizations are available in the supplementary material. + +# 6. Conclusion + +We have introduced a new approach for line art paint bucket colorization. Departing from traditional segment matching methods that struggle with one-to-one correspondence, we proposed a novel inclusion matching pipeline that estimates each segment's inclusion relationship rather than the direct correspondence. 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ACM TOG, 38(6), 2019. 3 \ No newline at end of file diff --git a/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/images.zip b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..c4cd99648b8b7972bcb09a3e132f3e32fcd8d59f --- /dev/null +++ b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:ddd47f49555248e5d485c2269e0de160d5993be96784b64e34b7894787e881cc +size 900701 diff --git a/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/layout.json b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..712bc7f56e6685f1a4e31644d1a7c2d0b3bd164d --- /dev/null +++ b/2024/Learning Inclusion Matching for Animation Paint Bucket Colorization/layout.json @@ -0,0 +1,7593 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 78, + 103, + 515, + 120 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 78, + 103, + 515, + 120 + ], + "spans": [ + { + "bbox": [ + 78, + 103, + 515, + 120 + ], + "type": "text", + "content": "Learning Inclusion Matching for Animation Paint Bucket Colorization" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 103, + 143, + 490, + 172 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 103, + 143, + 490, + 172 + ], + "spans": [ + { + "bbox": [ + 103, + 143, + 490, + 172 + ], + "type": "text", + "content": "Yuekun Dai Shangchen Zhou Qinyue Li Chongyi Li Chen Change Loy S-Lab, Nanyang Technological University" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 159, + 174, + 432, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 159, + 174, + 432, + 185 + ], + "spans": [ + { + "bbox": [ + 159, + 174, + 432, + 185 + ], + "type": "text", + "content": "https://ykdai.github.io/projects/InclusionMatching" + } + ] + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 52, + 191, + 545, + 363 + ], + "blocks": [ + { + "bbox": [ + 52, + 191, + 545, + 363 + ], + "lines": [ + { + "bbox": [ + 52, + 191, + 545, + 363 + ], + "spans": [ + { + "bbox": [ + 52, + 191, + 545, + 363 + ], + "type": "image", + "image_path": "64a68f6eb1e062dcd1e9ec1ff4b94358ecd1bbab9aeb55d2fa4b457d93d22f7a.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 367, + 546, + 434 + ], + "lines": [ + { + "bbox": [ + 46, + 367, + 546, + 434 + ], + "spans": [ + { + "bbox": [ + 46, + 367, + 546, + 434 + ], + "type": "text", + "content": "Figure 1. In the animation industry, digital painters use paint bucket tool to colorize drawn line arts frame by frame. Our proposed pipeline streamlines this process by requiring the painters to colorize just one frame, after which the algorithm autonomously propagates the color to subsequent frames, enabling automatic colorization. Compared with optical-flow-based method RAFT [35] and segment-matching-based method AnT [8], our method can achieve more robust results on challenging cases such as one-to-many matching, large deformation, and tiny region colorization. In this figure, RAFT is trained on Sintel dataset [5] and finetuned on AnimeRun [30]. We use the most frequent color in each segment to colorize each line-enclosed region. ©drawn by Nicca (Sriprachum Kongwisawamit), used with artist permission." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "bbox": [ + 143, + 444, + 192, + 455 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 444, + 192, + 455 + ], + "spans": [ + { + "bbox": [ + 143, + 444, + 192, + 455 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 474, + 290, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 474, + 290, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 474, + 290, + 715 + ], + "type": "text", + "content": "Colorizing line art is a pivotal task in the production of hand-drawn cel animation. This typically involves digital painters using a paint bucket tool to manually color each segment enclosed by lines, based on RGB values predetermined by a color designer. This frame-by-frame process is both arduous and time-intensive. Current automated methods mainly focus on segment matching. This technique migrates colors from a reference to the target frame by aligning features within line-enclosed segments across frames. However, issues like occlusion and wrinkles in animations often disrupt these direct correspondences, leading to mismatches. In this work, we introduce a new learning-based inclusion matching pipeline, which directs the network to comprehend the inclusion relationships between segments rather than relying solely on direct visual correspondences. Our method features a two-stage pipeline that integrates a coarse color warping module with an inclusion matching module, enabling more nuanced and accurate colorization. To facilitate the training of our network, we also develop a unique dataset, referred to as PaintBucket-Character. This" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 444, + 547, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 444, + 547, + 494 + ], + "spans": [ + { + "bbox": [ + 305, + 444, + 547, + 494 + ], + "type": "text", + "content": "dataset includes rendered line arts alongside their colorized counterparts, featuring various 3D characters. Extensive experiments demonstrate the effectiveness and superiority of our method over existing techniques." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 511, + 387, + 523 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 511, + 387, + 523 + ], + "spans": [ + { + "bbox": [ + 306, + 511, + 387, + 523 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 533, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 547, + 715 + ], + "type": "text", + "content": "Colorizing line art is a critical step in hand-drawn animation production. Initially, key animators create the characters' keyframes, followed by in-between animators who generate intermediate frames and refine keyframes for seamless connection between each stroke, as described in [31]. These line arts are then scanned into binary images, featuring a primary color palette of red, blue, green, and black, which represents highlights, shadows, special instructions (e.g., eye irises), and normal lines respectively. These scanned images, with regions of transparent background as shown in Fig. 1, are forwarded to digital painters. The painters use a paint bucket tool and a designated color palette to fill each line-enclosed segment, including the color lines, which is known as paint bucket colorization. Finally, special effect artists add visual enhancements, such as anti-aliasing, to" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25544" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 95 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 95 + ], + "type": "text", + "content": "blend character animations with backgrounds, culminating in the final video composition, detailed in [20]." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 98, + 286, + 217 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 98, + 286, + 217 + ], + "spans": [ + { + "bbox": [ + 46, + 98, + 286, + 217 + ], + "type": "text", + "content": "Line art colorization is a notably laborious process. For instance, even the relatively simple scenario in Fig. 1, involving 93 segments, still requires hundreds of manual clicks. To mitigate this demanding task, several commercial software applications like Retas Studio Paintman, OpenToonz, and CLIP Studio Paint have been developed. These tools provide helpful features that allow users to easily adjust assigned colors, fill small areas, and aid in line colorization. Despite these advancements, fully automated colorization has yet to be realized." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 220, + 287, + 506 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 220, + 287, + 506 + ], + "spans": [ + { + "bbox": [ + 46, + 220, + 287, + 506 + ], + "type": "text", + "content": "To address the challenges of line art colorization, numerous segment-matching methods have been developed for identifying corresponding segments in reference and target frames. Traditional graph-based approaches [17-19, 39, 44] consider each segment as a graph node and establish edges based on adjacency relationships. These methods employ optimization techniques to minimize topological similarity loss among corresponding nodes. However, they are time-intensive, often taking several minutes to process a single image with around 100 segments. Casey et al. [8] introduced the Animation Transformer (AnT) and its application Cadmium, which significantly improved segment matching. AnT standardizes the size of each segment and employs convolutional neural networks (CNNs) to extract features, transforming the image into a segment sequence. This converts segment matching into a sequence-to-sequence problem. Although AnT excels in aligning segments between adjacent frames featuring minimal motion, it struggles in more complex scenarios, particularly those with occlusion or pronounced motion. During occlusions, interlaced lines tend to fragment segments into multiple pieces, as depicted in Fig. 2. This fragmentation disrupts the strict correspondence between segments, rendering the task of segment matching inherently problematic and poorly defined." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 509, + 286, + 699 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 509, + 286, + 699 + ], + "spans": [ + { + "bbox": [ + 46, + 509, + 286, + 699 + ], + "type": "text", + "content": "In this study, we introduce the novel notion of 'inclusion matching', which obviates the necessity for exact segment-to-segment correspondence. Instead of direct segment matching, our approach computes the likelihood of each segment in a target frame being included within a specific region of a reference frame. Our methodology is unique in that it follows a coarse-to-fine colorization pipeline, inspired by the approach of skilled digital painters. This approach typically begins with coloring larger, more noticeable segments across all frames before filling in details of smaller segments in each frame. Motivated by this workflow, our pipeline first computes optical flow between line sketches, warping colors from a reference to a target frame to achieve a preliminary, coarse colorization. This is followed by the application of an inclusion matching module, which refines the colorization result of tiny segments." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 59, + 701, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 701, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 701, + 286, + 712 + ], + "type": "text", + "content": "The sparse nature of line art requires special formula" + } + ] + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 310, + 69, + 541, + 204 + ], + "blocks": [ + { + "bbox": [ + 310, + 69, + 541, + 204 + ], + "lines": [ + { + "bbox": [ + 310, + 69, + 541, + 204 + ], + "spans": [ + { + "bbox": [ + 310, + 69, + 541, + 204 + ], + "type": "image", + "image_path": "8e896adca3dc90fadbbb9c687f5e54dc73f98b22406890693cef3f5838eea213.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 208, + 545, + 297 + ], + "lines": [ + { + "bbox": [ + 305, + 208, + 545, + 297 + ], + "spans": [ + { + "bbox": [ + 305, + 208, + 545, + 297 + ], + "type": "text", + "content": "Figure 2. Methods relying on segment matching typically seek the most similar segment across frames, yet challenges arise in scenarios involving occlusion and wrinkles. This is particularly evident in tiny segments, as highlighted in the red box, where disruptions in correspondence lead to mismatches. Our innovative approach, based on inclusion matching, addresses this issue by estimating the inclusion relationship rather than pursuing direct correspondence, as illustrated by the comparison of red and blue matching lines." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 305, + 545, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 305, + 545, + 437 + ], + "spans": [ + { + "bbox": [ + 305, + 305, + 545, + 437 + ], + "type": "text", + "content": "tion in our approach. Specifically, recognizing the necessity for a large receptive field in extracting line art features, we employ a U-Net structure [25] to process concatenated color and line features. To address the difficulty in matching segments under large deformations, we extract line semantic features using CLIP [23] and concatenate them with features from the U-Net's bottleneck. This allows the network to match the region with the same semantic information across frames. Finally, we introduce super-pixel pooling at each segment to transfer the image into tokens for sequence-to-sequence matching." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 444, + 545, + 550 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 444, + 545, + 550 + ], + "spans": [ + { + "bbox": [ + 305, + 444, + 545, + 550 + ], + "type": "text", + "content": "Dataset plays a key role in the success of our method. To train and evaluate our method, we select 22 character models from Mixamo [3] and Aplaybox [1]. We mimic real intermediate line art data on the animation coloring production line. We disable the anti-aliasing and provide the color lines which is quite common in animation production. Then we use 3D software Cinema 4D to synthesize a specially-designed cartoon character colorization dataset named PaintBucket-Character." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 558, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 558, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 305, + 558, + 545, + 712 + ], + "type": "text", + "content": "The contributions of our work include the introduction of the PaintBucket-Character dataset tailored for paint bucket colorization tasks, the novel inclusion matching pipeline addressing the challenge of lacking strict segment correspondence, and a new coarse-to-fine baseline that outperforms existing solutions, particularly in scenes with occlusion. Our experiments demonstrate that our method surpasses the performance of recent AnT application Cadmium, and outperforms the results presented by Li et al. [30]. Notably, the advantages of our approach extend beyond dataset improvements, highlighting the effectiveness of our newly designed inclusion matching pipeline and the coarse-to-fine baseline in the context of animation colorization." + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25545" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 72, + 68, + 521, + 209 + ], + "blocks": [ + { + "bbox": [ + 72, + 68, + 521, + 209 + ], + "lines": [ + { + "bbox": [ + 72, + 68, + 521, + 209 + ], + "spans": [ + { + "bbox": [ + 72, + 68, + 521, + 209 + ], + "type": "image", + "image_path": "e3c167aff20d190f42a038d09f18e1f8361a9e78314bf00331ea9eeae025417e.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 135, + 212, + 456, + 222 + ], + "lines": [ + { + "bbox": [ + 135, + 212, + 456, + 222 + ], + "spans": [ + { + "bbox": [ + 135, + 212, + 456, + 222 + ], + "type": "text", + "content": "Figure 3. Several examples of our rendered characters in PaintBucket-Character dataset." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 223, + 134, + 235 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 223, + 134, + 235 + ], + "spans": [ + { + "bbox": [ + 47, + 223, + 134, + 235 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 252, + 288, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 252, + 288, + 407 + ], + "spans": [ + { + "bbox": [ + 46, + 252, + 288, + 407 + ], + "type": "text", + "content": "Line Art Colorization. Line art colorization aims to create reasonable colors in the sketch's blank regions. To achieve precise control, many user guidance types are designed including text [15, 45], scribble [6, 33, 40, 41], colored reference [4, 7, 9, 16, 32, 34, 37, 42, 43]. These methods mainly focus on pixel-wise estimation and cannot fill flat accurate RGB values assigned by the color designer in line arts' segments, which always leads to flickering and color bleeding. Besides, in the post-processing, the special effect artists often need to select specific colors to create various effects such as ramp or glow for the character's specific region. Thus, current line art colorization methods are still difficult to be merged into animation industrial processes." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 417, + 287, + 596 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 417, + 287, + 596 + ], + "spans": [ + { + "bbox": [ + 46, + 417, + 287, + 596 + ], + "type": "text", + "content": "Animation-related Dataset. To facilitate hand-drawn animation production, many real and rendered datasets are proposed. To boost video interpolation performance, Li et al. [29] propose the ATD-12K dataset which consists of triplet frames from 30 real animation movies. Due to the absence of correspondence labels for real animation, addressing this challenge has led to the adoption of 3D rendering techniques. MPI-Sintel [5] and CreativeFlow+ [28] provide different annotations such as optical flow, segmentation labels, and depth maps for multiple applications using Blender. To overcome the domain gap between rendered images and real 2D cartoons, Li et al. [30] developed the AnimeRun dataset using open-source 3D animations and their rendered optical flow. It improves segment matching accuracy and handles complex scenes." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "type": "text", + "content": "Segment-based Animation Colorization. In the cleaning-up process of the animation industry, animators enclose each line manually, making segments serve as basic units for colorization. Thus, how to calculate segment-level semantic information and correspondence becomes the key in animation colorization. Traditional methods [17-19, 39, 44] regards segment as node and adjacency relationship as edge which transfer the segment matching to the graph optimization problem. Recently, Dang et al. [12] use Hu mo" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 224, + 547, + 380 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 224, + 547, + 380 + ], + "spans": [ + { + "bbox": [ + 304, + 224, + 547, + 380 + ], + "type": "text", + "content": "ments [14] to extract each segment's feature to replace the RGB value and apply a UNet structure [25] to obtain the feature map. Subsequently, the feature is averaged in each segment to calculate the distance across frames for matching. Referring to the success of Transformer [36] in image matching [27], Casey et al. [8] apply multiplex transformer to aggregate information across frames to obtain more accurate results. Besides, Casey et al. replace the Hu moments algorithm with a segment feature extraction CNN which crop and resize each segment to fixed resolution first. Since both Dang et al. and Casey et al.'s methods and dataset are not publicly available, AnimeRun [30] remains the sole benchmark for segment matching available to researchers." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 392, + 495, + 405 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 392, + 495, + 405 + ], + "spans": [ + { + "bbox": [ + 305, + 392, + 495, + 405 + ], + "type": "text", + "content": "3. Paint Bucket Colorization Dataset" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 414, + 545, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 414, + 545, + 556 + ], + "spans": [ + { + "bbox": [ + 304, + 414, + 545, + 556 + ], + "type": "text", + "content": "AnimeRun [30] employs rendered optical flow to calculate segment correspondence, leading to frequent one-to-many and many-to-one matching in the dataset. This results in inaccurate benchmark evaluations, as each segment may have multiple potential ground-truth correspondences. Furthermore, the limited dataset provided by AnimeRun, consisting of only 1,760 training images, increases the risk of network overfitting. Meanwhile, due to the anti-aliasing processing of AnimeRun's rendered images, accurate color labels cannot be obtained in each segment. Consequently, AnimeRun faces difficulties in serving as a paint bucket colorization dataset directly." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": "To address these challenges, we introduce a new dataset PaintBucket-Character, comprising 11,345 training images and 3,200 test images. The test set includes 3,000 3D rendered frames and 200 hand-drawn frames. Notably, our dataset focuses solely on character animations, with consideration for the common practice among animators of just drawing foreground character animations while employing 3D models or separate paintings for the background. Our dataset focuses on character animations, considering the industry practice where animators typically sketch only the foreground character movements, while backgrounds are created using separate 3D models or paintings. Different from AnimeRun, our evaluation focuses on" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "25546" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 61, + 118, + 531, + 180 + ], + "blocks": [ + { + "bbox": [ + 46, + 62, + 547, + 118 + ], + "lines": [ + { + "bbox": [ + 46, + 62, + 547, + 118 + ], + "spans": [ + { + "bbox": [ + 46, + 62, + 547, + 118 + ], + "type": "text", + "content": "Table 1. A comparison between our PaintBucket-Character dataset and previous segment matching datasets. Since AnT [8]'s dataset is not publicly available, we use " + }, + { + "bbox": [ + 46, + 62, + 547, + 118 + ], + "type": "inline_equation", + "content": "-" + }, + { + "bbox": [ + 46, + 62, + 547, + 118 + ], + "type": "text", + "content": " to mark the unknown information. AnT does possess a private hand-drawn dataset with 3578 frames; however, it does not provide train-test-split information, indicated by " + }, + { + "bbox": [ + 46, + 62, + 547, + 118 + ], + "type": "inline_equation", + "content": "+^{\\prime}" + }, + { + "bbox": [ + 46, + 62, + 547, + 118 + ], + "type": "text", + "content": " . Compared with previous open-source datasets, our dataset is more diverse and provides color lines that are closer to real hand-drawn animation. No anti-aliasing provides extra semantic information for each segment, which enables the network to learn better semantic information rather than segment shape similarity." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 61, + 118, + 531, + 180 + ], + "lines": [ + { + "bbox": [ + 61, + 118, + 531, + 180 + ], + "spans": [ + { + "bbox": [ + 61, + 118, + 531, + 180 + ], + "type": "table", + "html": "
DatasetStatisticsAnnotations
TrainTestClipsSeg per Fr.No anti-aliasingOptical flowIndex labelColor labelColor line
AnimeRun [30]1,7601,05920+10237×✓×××
AnT [8] (private)9,900+1,100+-< 50-×✓✓×
Ours11,3453,200180+170169✓×✓✓✓
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Overview of our synthetic data generation pipeline. We extract the UV map (a) and the used UV region from the character. Then, we use a paint bucket tool to fill the used UV region, creating color label (b) and index label (c). Label images (b) and (c) are then pasted back to the 3D meshes to create flat color characters (d) and (e), respectively. 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To build our dataset, we sample 22 characters from Mixamo [3] and Aplaybox [1] and set 12 characters for training and 10 for testing. Then, we replot the UV map for these character models in flat color style and use Cinema 4D's Sketch and Toon Effect to produce the line art. To ensure consistent color in each segment, we disable the anti-aliasing and change the texture sampling method to the nearest. As depicted in Fig. 3, our dataset showcases a diverse array of characters encompassing both Japanese and Western cartoon styles." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 47, + 574, + 217, + 588 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 574, + 217, + 588 + ], + "spans": [ + { + "bbox": [ + 47, + 574, + 217, + 588 + ], + "type": "text", + "content": "3.1. Synthetic Dataset Construction" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "type": "text", + "content": "To include temporal and occlusion relationships in our dataset, we apply Mixamo's actions to our characters. For each character, we add five types of actions and animate the camera motion to capture different viewpoints of the character in each sequence. We classify the camera positions into three types: face shot, long shot, and close-up, in which we separately focus on the face, whole body, and other parts of the body. Following this pipeline, we obtain 15 clips for each character and form 180 clips for training and 150 clips for test. In the animation industry, keyframes always have a" + } + ] + } + ], + "index": 19 + }, + { + "type": "image", + "bbox": [ + 310, + 183, + 402, + 255 + ], + "blocks": [ + { + "bbox": [ + 310, + 183, + 402, + 255 + ], + "lines": [ + { + "bbox": [ + 310, + 183, + 402, + 255 + ], + "spans": [ + { + "bbox": [ + 310, + 183, + 402, + 255 + ], + "type": "image", + "image_path": "d7f5669e14ae1be98ed42dc25e3d498d21def9f4d68255a0e365c7c180878318.jpg" + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 321, + 255, + 391, + 263 + ], + "lines": [ + { + "bbox": [ + 321, + 255, + 391, + 263 + ], + "spans": [ + { + "bbox": [ + 321, + 255, + 391, + 263 + ], + "type": "text", + "content": "Real hand-drawn line art" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 267, + 545, + 374 + ], + "lines": [ + { + "bbox": [ + 304, + 267, + 545, + 374 + ], + "spans": [ + { + "bbox": [ + 304, + 267, + 545, + 374 + ], + "type": "text", + "content": "Figure 5. Our simulation method can generate color lines that closely mimic hand-drawn line arts. Red, blue, and green lines represent highlights, shadows, and other instructions respectively. low frame rate [29]. Thus, in each clip, we set the frame rate to 10 to mimic real animation and bring larger motion and deformation. Meanwhile, to address the fine scale of character details such as pupils and buttons, we use " + }, + { + "bbox": [ + 304, + 267, + 545, + 374 + ], + "type": "inline_equation", + "content": "1920 \\times 1920" + }, + { + "bbox": [ + 304, + 267, + 545, + 374 + ], + "type": "text", + "content": " as our training size and " + }, + { + "bbox": [ + 304, + 267, + 545, + 374 + ], + "type": "inline_equation", + "content": "1024 \\times 1024" + }, + { + "bbox": [ + 304, + 267, + 545, + 374 + ], + "type": "text", + "content": " as our test set size to provide clear segments in these areas." + } + ] + } + ], + "index": 25, + "angle": 0, + "type": "image_caption" + } + ], + "index": 20 + }, + { + "type": "image", + "bbox": [ + 406, + 185, + 475, + 255 + ], + "blocks": [ + { + "bbox": [ + 406, + 185, + 475, + 255 + ], + "lines": [ + { + "bbox": [ + 406, + 185, + 475, + 255 + ], + "spans": [ + { + "bbox": [ + 406, + 185, + 475, + 255 + ], + "type": "image", + "image_path": "1c4ea5cd06ef16f532b0f83bff026a9e23ac3238ffdfdaacaf7e833138775f9b.jpg" + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 441, + 257, + 500, + 265 + ], + "lines": [ + { + "bbox": [ + 441, + 257, + 500, + 265 + ], + "spans": [ + { + "bbox": [ + 441, + 257, + 500, + 265 + ], + "type": "text", + "content": "Our synthetic line art" + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_caption" + } + ], + "index": 22 + }, + { + "type": "image", + "bbox": [ + 476, + 185, + 542, + 255 + ], + "blocks": [ + { + "bbox": [ + 476, + 185, + 542, + 255 + ], + "lines": [ + { + "bbox": [ + 476, + 185, + 542, + 255 + ], + "spans": [ + { + "bbox": [ + 476, + 185, + 542, + 255 + ], + "type": "image", + "image_path": "ddec8b21ea3bab60cebc8f75f9a2f1293c6dddd42af5a97cb0516f2f6c3ae1e8.jpg" + } + ] + } + ], + "index": 24, + "angle": 0, + "type": "image_body" + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 375, + 546, + 553 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 375, + 546, + 553 + ], + "spans": [ + { + "bbox": [ + 304, + 375, + 546, + 553 + ], + "type": "text", + "content": "Flat Color Style Rendering. To render characters in a flat color style, we use Cinema 4D to extract a UV mesh map and set unused regions as black. Then, we draw contour lines of character details such as pockets and shoelace on the UV mesh. Based on this original UV map, we use a paint bucket tool to colorize the mesh as the color label. To obtain a more precise matching relationship for training, we connect the label with the same semantic information (such as palm and back of the hand) and use the connected components algorithm for each color to extract the index label as shown in Fig. 4. Since we aim to achieve accurate line art to separate each segment, we calculate the difference between each color's segment and its erosion as the black lines. This operation ensures that each line-enclosed segment contains clear semantic information and comprises only one color." + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 304, + 554, + 545, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 554, + 545, + 662 + ], + "spans": [ + { + "bbox": [ + 304, + 554, + 545, + 662 + ], + "type": "text", + "content": "Color Line Extraction. To simulate color lines which are common in real hand-drawn animation's shadow and highlight regions, we mark these highlight and shadow colors and erode these regions to create color lines, as shown in Fig. 5. Compared with AnimeRun [30], our dataset features more realistic line art and provides clear semantic information for each segment. Since our characters are rendered with discrete colors, we can easily obtain specific meanings for each segment." + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 306, + 670, + 477, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 670, + 477, + 682 + ], + "spans": [ + { + "bbox": [ + 306, + 670, + 477, + 682 + ], + "type": "text", + "content": "3.2. Hand-drawn Dataset Collection" + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 305, + 689, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 715 + ], + "type": "text", + "content": "Obtaining intermediate unprocessed data poses a challenge, as common commercial animations undergo post" + } + ] + } + ], + "index": 29 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "text", + "content": "25547" + } + ] + } + ], + "index": 30 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "content": "processing techniques including anti-aliasing. To address this challenge, we invite some professional animators to draw line art animation clips with different characters. Then, we use the paint bucket tool to colorize these line arts as our ground truth to synthesize paired line art and colorized data. Besides, animation creation software such as Retas Studio Paintman and CLIP Studio Paint all provide animation production tutorials. We collect animations in these tutorials and use the color line extraction method to synthesize the paired data. Finally, we collect a hand-drawn test dataset with 200 frames and 20 clips for evaluation." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 215, + 103, + 227 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 215, + 103, + 227 + ], + "spans": [ + { + "bbox": [ + 47, + 215, + 103, + 227 + ], + "type": "text", + "content": "4. Method" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 241, + 153, + 253 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 241, + 153, + 253 + ], + "spans": [ + { + "bbox": [ + 47, + 241, + 153, + 253 + ], + "type": "text", + "content": "4.1. Inclusion Matching" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "spans": [ + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": "Given two line art images " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "L_{i}, L_{j} \\in \\mathbb{R}^{H \\times W \\times 3}" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": ", lines separate the blank area into " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "N_{i}" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "N_{j}" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": "'s line-enclosed segments. In the reference frame " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "L_{i}" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": ", each segment is colorized with " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": " colors whose color labels can be represented as one-hot representation " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "c_{i} \\in \\mathbb{R}^{N_{i} \\times M}" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": ". To estimate the " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "L_{j}" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": "'s color label " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "\\hat{c}_{j} \\in \\mathbb{R}^{N_{j} \\times M}" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": ", previous segment-matching-based methods [8, 30] mainly focus on calculating segments' visual correspondence with the matching " + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "inline_equation", + "content": "\\mathbf{m}^{j \\rightarrow i} \\in \\mathbb{R}^{N_{j} \\times N_{i}}" + }, + { + "bbox": [ + 46, + 258, + 287, + 378 + ], + "type": "text", + "content": ". Nevertheless, the absence of strict correspondence among segments imposes limitations on the model's learning capacity." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "spans": [ + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "text", + "content": "To tackle this challenge, we introduce a novel method called inclusion matching. In the reference frame, segments with identical semantic information are merged, creating " + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "inline_equation", + "content": "K_{i}" + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "text", + "content": " large regions with different labels. As each line-enclosed segment in the target frame can only possess one color with a specific meaning, it can be identified as a subset of one of the " + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "inline_equation", + "content": "K_{i}" + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "text", + "content": " regions. Specifically, in the training process, the index label stated in Fig. 4 separates the reference frame into " + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "inline_equation", + "content": "K_{i}" + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "text", + "content": " region. We train a network to estimate each segment's index label " + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{N_j\\times K_i}" + }, + { + "bbox": [ + 46, + 380, + 288, + 535 + ], + "type": "text", + "content": ". To enrich the diversity, we randomly merge the adjacent labels in the reference frame to create larger regions to guide the network to learn a more robust inclusion relationship, as shown in Fig. 6." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 543, + 215, + 555 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 543, + 215, + 555 + ], + "spans": [ + { + "bbox": [ + 47, + 543, + 215, + 555 + ], + "type": "text", + "content": "4.2. PaintBucket Colorization Pipeline" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": "Color Warping Module. Colorized line art carries substantial information about how segments are grouped, making it crucial for inclusion matching. However, previous segment matching methods [8, 30] exclusively leverage the line art's features for matching and do not incorporate the colorized reference. To encode the color feature, we recolorize the index label image. Specifically, we partition the RGB space into " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "K_{i}" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": " cubes, each with a side length of " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "255 \\times K_{i}^{-\\frac{1}{3}}" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": ". Subsequently, we select the RGB value at the center of each cube and randomly assign them to index labels as the reference color image " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "C_{i}" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": ". We employ the optical flow estimation model RAFT [35], fine-tuned on AnimeRun [30], to esti" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 340, + 69, + 514, + 194 + ], + "blocks": [ + { + "bbox": [ + 340, + 69, + 514, + 194 + ], + "lines": [ + { + "bbox": [ + 340, + 69, + 514, + 194 + ], + "spans": [ + { + "bbox": [ + 340, + 69, + 514, + 194 + ], + "type": "image", + "image_path": "458fb955574b1d0d61a4a48511c0747ec0d183422dd81dc91ccb1df151cd3eaf.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 197, + 545, + 274 + ], + "lines": [ + { + "bbox": [ + 304, + 197, + 545, + 274 + ], + "spans": [ + { + "bbox": [ + 304, + 197, + 545, + 274 + ], + "type": "text", + "content": "Figure 6. Our inclusion matching training pipeline employs index labels to partition the reference frame into " + }, + { + "bbox": [ + 304, + 197, + 545, + 274 + ], + "type": "inline_equation", + "content": "K_{i}" + }, + { + "bbox": [ + 304, + 197, + 545, + 274 + ], + "type": "text", + "content": " regions, which are then randomly merged with adjacent index labels with a probability of " + }, + { + "bbox": [ + 304, + 197, + 545, + 274 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 304, + 197, + 545, + 274 + ], + "type": "text", + "content": ". Subsequently, the model estimates the affiliation of each line-enclosed segment in the target frame with a specific region in the reference, thereby facilitating the learning of the inclusion relationship." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "spans": [ + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "text", + "content": "mate the optical flow between the reference line art " + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "inline_equation", + "content": "L_{i}" + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "text", + "content": " and the target line art " + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "inline_equation", + "content": "L_{j}" + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "text", + "content": ". Utilizing this optical flow, we warp the reference color image " + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "inline_equation", + "content": "C_i" + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "text", + "content": " to generate the coarse color estimation " + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "inline_equation", + "content": "C_j" + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "text", + "content": " for the target frame." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "spans": [ + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "content": "Feature Extraction Module. Lacking textual information and large deformation in animation make warped color image " + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "inline_equation", + "content": "C_j" + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "content": " hard to precisely align with the line art in the target frame. To address this, we employ deformable convolution [11] on the warped color " + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "inline_equation", + "content": "C_j" + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "content": " to extract aligned features. For a given deformable convolution kernel of " + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "content": " sampling positions, we use " + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "inline_equation", + "content": "\\omega_k" + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_k" + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "content": " to represent the weight and prespecified offset. The aligned features " + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "inline_equation", + "content": "F_a" + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "content": " at each position " + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_0" + }, + { + "bbox": [ + 304, + 324, + 545, + 432 + ], + "type": "text", + "content": " can be expressed as:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 341, + 440, + 545, + 473 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 341, + 440, + 545, + 473 + ], + "spans": [ + { + "bbox": [ + 341, + 440, + 545, + 473 + ], + "type": "interline_equation", + "content": "F _ {a} \\left(\\mathbf {p} _ {0}\\right) = \\sum_ {k = 1} ^ {K} \\omega_ {k} \\cdot F _ {a} \\left(\\mathbf {p} _ {0} + \\mathbf {p} _ {k} + \\Delta \\mathbf {p} _ {k}\\right), \\tag {1}", + "image_path": "0ece283d4769a6e768dbd8e4ec0032415ecf1ee2651d53cbede4f53db03d7312.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 480, + 545, + 529 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 480, + 545, + 529 + ], + "spans": [ + { + "bbox": [ + 304, + 480, + 545, + 529 + ], + "type": "text", + "content": "where learnable offset " + }, + { + "bbox": [ + 304, + 480, + 545, + 529 + ], + "type": "inline_equation", + "content": "\\Delta \\mathbf{p}_k" + }, + { + "bbox": [ + 304, + 480, + 545, + 529 + ], + "type": "text", + "content": " can be predicted from the offset estimation network as depicted in Fig. 8. This network, designed as a lightweight U-Net [25] denoted as " + }, + { + "bbox": [ + 304, + 480, + 545, + 529 + ], + "type": "inline_equation", + "content": "\\Phi" + }, + { + "bbox": [ + 304, + 480, + 545, + 529 + ], + "type": "text", + "content": ", is employed to expand the receptive field:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 382, + 536, + 545, + 550 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 382, + 536, + 545, + 550 + ], + "spans": [ + { + "bbox": [ + 382, + 536, + 545, + 550 + ], + "type": "interline_equation", + "content": "\\Delta \\mathbf {p} _ {k} = \\Phi ([ L _ {j}, C _ {j} ]). \\tag {2}", + "image_path": "95579e5ea876417731704187061b892d2993cef4d3f96e1edebf5b6dac9e5cf8.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": "For the reference frame, we deactivate the offset estimation module and set the offset to zero. Subsequently, the aligned color feature is concatenated with the line feature and passed through a feature encoder network. To guide the network in learning semantic information matching, we resize the line art image to " + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "inline_equation", + "content": "320 \\times 320" + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": " and utilize CLIP [23]'s image encoder to extract features. To preserve the feature's positional information, we choose to use the ConvNext-Large model from OpenCLIP [10]. We only selected the initial layers of CLIP, which downsample the feature to a resolution of " + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "inline_equation", + "content": "40 \\times 40" + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": ". The CLIP feature is interpolated to concatenate with the encoded features. Finally, the feature decoder decodes these concatenated features to the input's" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25548" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 70, + 542, + 227 + ], + "blocks": [ + { + "bbox": [ + 53, + 70, + 542, + 227 + ], + "lines": [ + { + "bbox": [ + 53, + 70, + 542, + 227 + ], + "spans": [ + { + "bbox": [ + 53, + 70, + 542, + 227 + ], + "type": "image", + "image_path": "843f66a024d950a4747c5a3c7ebcb8a854c13bc49289b2c6715b93fa64220720.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 230, + 547, + 275 + ], + "lines": [ + { + "bbox": [ + 46, + 230, + 547, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 230, + 547, + 275 + ], + "type": "text", + "content": "Figure 7. Our paint bucket colorization architecture. Initially, we estimate the optical flow based on the line arts and warp the reference color as the coarse colorization result. The mask and position embedding module tokenizes the segments and features extracted by the feature extraction module into a sequence, which is then fed into the multiplex transformer for information aggregation. Finally, we compute a similarity matrix between reference and target tokens to calculate matching loss and predict the final color." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 50, + 278, + 282, + 373 + ], + "blocks": [ + { + "bbox": [ + 50, + 278, + 282, + 373 + ], + "lines": [ + { + "bbox": [ + 50, + 278, + 282, + 373 + ], + "spans": [ + { + "bbox": [ + 50, + 278, + 282, + 373 + ], + "type": "image", + "image_path": "0cd9736962cc67bd204883b6c9330e0d6284da4779d5cdd009f09429de7d7093.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 375, + 287, + 441 + ], + "lines": [ + { + "bbox": [ + 46, + 375, + 287, + 441 + ], + "spans": [ + { + "bbox": [ + 46, + 375, + 287, + 441 + ], + "type": "text", + "content": "Figure 8. Overall pipeline of our feature extraction module. Deformable convolution is applied to align the color features of the target frame to the line image. Then, the line features and aligned color features are concatenated and fed to the feature extraction network in a U-Net structure. Line art's CLIP features are also concatenated to the bottleneck of the feature extraction network." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 445, + 287, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 445, + 287, + 480 + ], + "spans": [ + { + "bbox": [ + 46, + 445, + 287, + 480 + ], + "type": "text", + "content": "resolution with " + }, + { + "bbox": [ + 46, + 445, + 287, + 480 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 445, + 287, + 480 + ], + "type": "text", + "content": " channels. To preserve features in high resolution, shortcuts are added between the network's encoder and decoder, following the structure of the U-Net." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "spans": [ + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "text", + "content": "Mask + Position Embedding Module. To transform different segments into tokens, we employ super-pixel pooling to average the features within each segment's mask, resulting in a " + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "text", + "content": "-dimensional visual token, denoted as " + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "inline_equation", + "content": "\\mathbf{d}_i" + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "text", + "content": ". Subsequently, a Multilayer Perceptron (MLP) layer is utilized to encode the segment's bounding box's four-dimensional coordinates, denoted as " + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "inline_equation", + "content": "p_i" + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "text", + "content": ", into a " + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "text", + "content": "-dimensional positional embedding. The token " + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_i" + }, + { + "bbox": [ + 46, + 482, + 288, + 590 + ], + "type": "text", + "content": " for matching is obtained by adding the positional embedding and visual token:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 122, + 603, + 287, + 617 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 122, + 603, + 287, + 617 + ], + "spans": [ + { + "bbox": [ + 122, + 603, + 287, + 617 + ], + "type": "interline_equation", + "content": "\\mathbf {x} _ {i} = \\mathbf {d} _ {i} + \\mathbf {M L P} \\left(p _ {i}\\right). \\tag {3}", + "image_path": "43165722d19e9f89a72956dbf661ff769191ac912925b7d8bd8824499efbbbc5.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 628, + 287, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 628, + 287, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 628, + 287, + 676 + ], + "type": "text", + "content": "Differing from previous segment matching pipelines [8, 30], our approach matches each line-enclosed segment in the target frame with a specific index label in the reference frame, rather than employing label-to-label matching." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 677, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 288, + 714 + ], + "type": "text", + "content": "Multiplex Transformer. Building upon [8, 27], we employ multiplex self- and cross-attention layers to aggregate tokenized features. In a self-attention layer, queries, keys, and" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 279, + 497, + 291 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 279, + 497, + 291 + ], + "spans": [ + { + "bbox": [ + 306, + 279, + 497, + 291 + ], + "type": "text", + "content": "values are derived from a single source feature:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 334, + 299, + 545, + 327 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 334, + 299, + 545, + 327 + ], + "spans": [ + { + "bbox": [ + 334, + 299, + 545, + 327 + ], + "type": "interline_equation", + "content": "\\operatorname {s e l f - a t t e n t i o n} \\left(\\mathbf {x} _ {i}\\right) = \\operatorname {s o f t m a x} \\left(\\frac {\\mathbf {Q} _ {i} \\mathbf {K} _ {i}}{\\sqrt {D}}\\right) \\mathbf {V} _ {i}, \\tag {4}", + "image_path": "745fcf052d8c58774ee464fb935cec11419783ae761616be385f6a0b93773d46.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "spans": [ + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "inline_equation", + "content": "\\mathbf{Q}_i" + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "inline_equation", + "content": "\\mathbf{K}_i" + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "inline_equation", + "content": "\\mathbf{V}_i" + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "text", + "content": " represent " + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_i" + }, + { + "bbox": [ + 305, + 333, + 546, + 369 + ], + "type": "text", + "content": " processed by MLPs for query, key, and value. In contrast, the cross-attention layer computes keys and values from another feature:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 315, + 378, + 545, + 415 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 378, + 545, + 415 + ], + "spans": [ + { + "bbox": [ + 315, + 378, + 545, + 415 + ], + "type": "interline_equation", + "content": "\\operatorname {c r o s s - a t t e n t i o n} \\left(\\mathbf {x} _ {i} ^ {\\prime}, \\mathbf {x} _ {j} ^ {\\prime}\\right) = \\operatorname {s o f t m a x} \\left(\\frac {\\mathbf {Q} _ {i} ^ {\\prime} \\mathbf {K} _ {j} ^ {\\prime}}{\\sqrt {D}}\\right) \\mathbf {V} _ {j} ^ {\\prime}. \\tag {5}", + "image_path": "fe47684d51fe0270027a3d20349deb6e4f946ae9572cf334066e245619073247.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "spans": [ + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "text", + "content": "Following each self- or cross-attention layer, the output is added to the original " + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_i" + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "text", + "content": " or " + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "inline_equation", + "content": "\\mathbf{x}'_i" + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "text", + "content": ", and then processed with a feed-forward MLP. After repeating these operations " + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "text", + "content": " times, as illustrated in Fig. 7, we obtain the final aggregated features " + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{x}}_i \\in \\mathbb{R}^{K_i \\times C}" + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{x}}_j \\in \\mathbb{R}^{N_j \\times C}" + }, + { + "bbox": [ + 305, + 415, + 545, + 474 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 475, + 545, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 475, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 306, + 475, + 545, + 498 + ], + "type": "text", + "content": "Loss function. After the propagation step, the similarity matrix " + }, + { + "bbox": [ + 306, + 475, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\mathbf{S} \\in \\mathbb{R}^{N_j \\times K_i}" + }, + { + "bbox": [ + 306, + 475, + 545, + 498 + ], + "type": "text", + "content": " is represented as follows:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 359, + 506, + 545, + 536 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 359, + 506, + 545, + 536 + ], + "spans": [ + { + "bbox": [ + 359, + 506, + 545, + 536 + ], + "type": "interline_equation", + "content": "\\mathbf {S} _ {m n} = \\frac {\\exp \\left(\\hat {\\mathbf {x}} _ {i m} \\cdot \\hat {\\mathbf {x}} _ {j n}\\right)}{\\sum_ {m = 1} ^ {N _ {j}} \\exp \\left(\\hat {\\mathbf {x}} _ {i m} \\cdot \\hat {\\mathbf {x}} _ {j n}\\right)}. \\tag {6}", + "image_path": "f8645d2fd2c0c1f811345e82fea922b83d0772e9cb63466d11966533832368bf.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "spans": [ + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "type": "text", + "content": "This matrix can be interpreted as the color probability " + }, + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{y}}_m\\in \\mathbb{R}^{K_i}" + }, + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "type": "text", + "content": " for segment " + }, + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "type": "text", + "content": " in the target frame. Given that each frame has a one-hot ground truth index label " + }, + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "type": "inline_equation", + "content": "\\mathbf{y}_m" + }, + { + "bbox": [ + 305, + 544, + 545, + 592 + ], + "type": "text", + "content": ", the loss function is derived from the cross-entropy loss:" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 370, + 600, + 545, + 633 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 370, + 600, + 545, + 633 + ], + "spans": [ + { + "bbox": [ + 370, + 600, + 545, + 633 + ], + "type": "interline_equation", + "content": "L _ {c e} = - \\sum_ {m = 1} ^ {K _ {i}} \\mathbf {y} _ {m} \\log (\\hat {\\mathbf {y}} _ {m}). \\tag {7}", + "image_path": "b94fb73cf804a25652152baa6a6bc1b7f4b9251c9a8a15e5084991c9db8419d9.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 641, + 546, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 641, + 546, + 714 + ], + "spans": [ + { + "bbox": [ + 305, + 641, + 546, + 714 + ], + "type": "text", + "content": "Inference Pipeline. Since real animation's colors have an obvious domain gap with our randomly generated colors, we adopt a color redistribution strategy to reassign randomly generated colors to replace the original colors during the warping and matching pipeline. This strategy can avoid the mismatching problem when several predefined colors" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "25549" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 75, + 63, + 519, + 266 + ], + "blocks": [ + { + "bbox": [ + 75, + 63, + 519, + 266 + ], + "lines": [ + { + "bbox": [ + 75, + 63, + 519, + 266 + ], + "spans": [ + { + "bbox": [ + 75, + 63, + 519, + 266 + ], + "type": "image", + "image_path": "8e756080549693a7b5ddef8fb66e2b88fec6aeef01c3a5f6d961c425146d575a.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 267, + 545, + 300 + ], + "lines": [ + { + "bbox": [ + 46, + 267, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 46, + 267, + 545, + 300 + ], + "type": "text", + "content": "Figure 9. The visualization results of our proposed methods and other approaches on real hand-drawn animation. Compared with previous methods, our proposed approach demonstrates enhanced robustness in handling occlusion situations (e.g., hand of the running girl and shadow near eyebrows of the girl in the second row.)" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 300, + 545, + 354 + ], + "lines": [ + { + "bbox": [ + 46, + 300, + 545, + 354 + ], + "spans": [ + { + "bbox": [ + 46, + 300, + 545, + 354 + ], + "type": "text", + "content": "Table 2. Quantitative comparison of our method with different methods. 'Acc' and 'Acc-Thres' denote segment-wise accuracy, providing insights into the potential workload reduction for digital painters. In 'Acc-Thres,' segments smaller than 10 pixels are filtered out. 'Pix-Acc,' 'Pix-F-Acc,' and 'Pix-B-MIoU' represent pixel-wise accuracy, foreground pixel-wise accuracy, and pixel-wise background MIoU, respectively, reflecting the visualization performance. All RAFT models undergo training on MPI-Sintel [5], and 'F/C' indicates the models fine-tuned on AnimeRun's colorized frames and contours." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 48, + 356, + 545, + 434 + ], + "blocks": [ + { + "bbox": [ + 48, + 356, + 545, + 434 + ], + "lines": [ + { + "bbox": [ + 48, + 356, + 545, + 434 + ], + "spans": [ + { + "bbox": [ + 48, + 356, + 545, + 434 + ], + "type": "table", + "html": "
TypeMethod3D rendered test setHand-drawn test set
AccAcc-ThresPix-AccPix-F-AccPix-B-MIoUAccAcc-ThresPix-AccPix-F-AccPix-B-MIoU
Reference-basedControlNet0.17090.18560.42740.26530.46000.17150.18120.24490.22980.2260
Segment matchingAnT(AnimeRun)0.55840.59300.87340.65370.89540.67790.70430.91930.73770.9429
AnT(Cadmium)0.66340.77130.97650.94710.98010.72240.78790.97920.93030.9899
Optical flowRAFT0.65890.74560.97240.90990.97630.75280.80930.98190.91900.9898
RAFT (F)0.71330.80540.98180.94490.98520.77580.84240.98600.94250.9922
RAFT (C)0.70280.79440.97230.94110.96900.77180.83560.98330.93750.9916
Inclusion matchingOurs0.82660.87260.99050.97240.99480.85930.89290.99000.96380.9984
", + "image_path": "69d591b6074aefa4e2830a8ccbd1c3acf850c439e69c450c8a0f749f5b8feb82.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 438, + 287, + 462 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 438, + 287, + 462 + ], + "spans": [ + { + "bbox": [ + 46, + 438, + 287, + 462 + ], + "type": "text", + "content": "are too closed. Finally, the estimated color for each line-enclosed segment " + }, + { + "bbox": [ + 46, + 438, + 287, + 462 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{c}}_j\\in \\mathbb{R}^{N_j\\times M}" + }, + { + "bbox": [ + 46, + 438, + 287, + 462 + ], + "type": "text", + "content": " can be derived by:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 145, + 467, + 287, + 482 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 467, + 287, + 482 + ], + "spans": [ + { + "bbox": [ + 145, + 467, + 287, + 482 + ], + "type": "interline_equation", + "content": "\\hat {\\mathbf {c}} _ {j} = \\hat {\\mathbf {S}} \\mathbf {c} _ {i}, \\tag {8}", + "image_path": "23a40f52dcd9852a2958abe29f78f768f62fa76e20e6115cd34d3288a371a6fe.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 486, + 287, + 535 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 486, + 287, + 535 + ], + "spans": [ + { + "bbox": [ + 46, + 486, + 287, + 535 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 486, + 287, + 535 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{S}}\\in \\mathbb{R}^{N_j\\times N_i}" + }, + { + "bbox": [ + 46, + 486, + 287, + 535 + ], + "type": "text", + "content": " is the similarity matrix for each line-enclosed segment in reference and target frames. In this paper, we set the match threshold as 0.2 to filter out all the segments which are unmatched." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 544, + 128, + 557 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 544, + 128, + 557 + ], + "spans": [ + { + "bbox": [ + 47, + 544, + 128, + 557 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 563, + 180, + 576 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 563, + 180, + 576 + ], + "spans": [ + { + "bbox": [ + 47, + 563, + 180, + 576 + ], + "type": "text", + "content": "5.1. Implementation Details" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "type": "text", + "content": "During the training stage, our model undergoes 300,000 iterations with a batch size of 2, utilizing NVIDIA GeForce RTX 3090 GPUs. We employ the Adam optimizer with a learning rate of " + }, + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "type": "inline_equation", + "content": "10^{-4}" + }, + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "type": "text", + "content": " and no weight decay. Throughout the training process, we keep the weights of the pretrained optical flow estimation module and the CLIP image encoder fixed. In the feature extraction module, the offset estimation module is structured as a lightweight U-Net with three down-sampling layers and a bottleneck featuring 128 features. Simultaneously, the feature extraction network is implemented as a U-Net with four down-sampling layers and a" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 438, + 545, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 438, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 304, + 438, + 545, + 498 + ], + "type": "text", + "content": "bottleneck containing 512 features. The channel number " + }, + { + "bbox": [ + 304, + 438, + 545, + 498 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 438, + 545, + 498 + ], + "type": "text", + "content": " for our extracted feature is set to 128. Within the multiplex transformer, the layer number " + }, + { + "bbox": [ + 304, + 438, + 545, + 498 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 438, + 545, + 498 + ], + "type": "text", + "content": " is set to nine, and the number of heads is configured as four. The data augmentation pipeline is shown in the supplementary material." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 503, + 501, + 516 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 503, + 501, + 516 + ], + "spans": [ + { + "bbox": [ + 305, + 503, + 501, + 516 + ], + "type": "text", + "content": "5.2. Comparisons with Previous Methods" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 522, + 545, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 522, + 545, + 605 + ], + "spans": [ + { + "bbox": [ + 304, + 522, + 545, + 605 + ], + "type": "text", + "content": "Since there is no existing paint bucket colorization method, we mainly compare our method with reference-based line art colorization [42], segment matching methods [8, 30], and optical flow estimation methods [35]. The quantitative comparison is shown in Table 2. The visual comparison of real hand-drawn animation and rendered 3D test sets are shown in Fig. 9 and Fig. 10." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": "Reference-based Line Art Colorization. The saturated luminance of the blank regions within line art impedes the application of reference-based methods for natural gray-scale image colorization. Thus, we choose ControlNet [42] as our reference-based line art colorization method. We use Stable Diffusion v1.5 [24] as our base model and employ the ControlNet's line art checkpoint to encode the line art condition. Then, we adopt the IP-Adapter [38] to encode the reference image. We set the number of steps to 50 and use" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25550" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 106, + 545, + 206 + ], + "blocks": [ + { + "bbox": [ + 46, + 62, + 547, + 106 + ], + "lines": [ + { + "bbox": [ + 46, + 62, + 547, + 106 + ], + "spans": [ + { + "bbox": [ + 46, + 62, + 547, + 106 + ], + "type": "text", + "content": "Table 3. Quantitative comparison of different datasets, different network structures, and different methods on test data. 'IM' signifies the inclusion matching pipeline, which incorporates adjacent index label merging and segment-label matching strategies. Since the inclusion matching pipeline and coarse warping module with RAFT can also be applied to other networks, we also adopt them to AnT for comparison to illustrate the generalization of these methods." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 106, + 545, + 206 + ], + "lines": [ + { + "bbox": [ + 48, + 106, + 545, + 206 + ], + "spans": [ + { + "bbox": [ + 48, + 106, + 545, + 206 + ], + "type": "table", + "html": "
TypeMethod3D rendered test setHand-drawn test set
AccAcc-ThresPix-AccPix-F-AccPix-B-MIoUAccAcc-ThresPix-AccPix-F-AccPix-B-MIoU
BaselineOurs0.82660.87260.99050.97240.99480.85930.89290.99000.96380.9984
DatasetAnimeRun0.73590.79580.96930.92010.97650.82780.86340.98180.93990.9906
Modelw/o CLIP0.81800.86530.98730.96850.99100.84890.88430.98780.95700.9925
w/o RAFT0.80010.84470.98240.94810.98780.84460.87500.98040.94040.9851
w/o DConv0.82470.86850.98940.97090.99280.85250.88330.98750.95490.9937
MethodOurs w/o IM0.76370.83520.97210.95730.96880.83480.87630.97770.94950.9822
AnT0.74500.79300.97080.93610.97580.81620.84970.98170.93740.9905
AnT with IM0.80630.84470.98370.95510.98870.83880.86980.98390.93880.9943
AnT with IM/RAFT0.81770.85870.98790.96810.99320.84830.88280.98860.95980.9946
", + "image_path": "7911eee26b666dae8a017c3b68737a52f87e9f63ed77d249dc7f36f30c6095e0.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 209, + 287, + 257 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 209, + 287, + 257 + ], + "spans": [ + { + "bbox": [ + 46, + 209, + 287, + 257 + ], + "type": "text", + "content": "the text prompt 'A character in the white background'. We calculate the average RGB value per segment and match the average color with the nearest color in the reference image for evaluation." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 257, + 290, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 257, + 290, + 449 + ], + "spans": [ + { + "bbox": [ + 46, + 257, + 290, + 449 + ], + "type": "text", + "content": "Optical Flow Estimation. Since optical flow methods cannot produce segment-wise estimation without postprocessing, we warp the color and calculate the colors that appear most frequently in each segment as the baseline of optical estimation method. Since finetuning RAFT on AnimeRun can promote the optical flow's performance effectively, we use the finetuned RAFT in the following sessions. Segment Matching. We also compare our method with the Cadmium application, the official implementation of AnT [8], and AnimenRun's reimplemented AnT [30]. The visual comparison shown in Fig. 9 and Fig. 10 demonstrate the robust performance of our proposed method, particularly in scenarios where strict segment correspondence is absent, and challenges with large motion and complex deformations. More visual results are presented in the suppl. material." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 456, + 141, + 468 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 456, + 141, + 468 + ], + "spans": [ + { + "bbox": [ + 47, + 456, + 141, + 468 + ], + "type": "text", + "content": "5.3. Ablation Study" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 474, + 287, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 474, + 287, + 545 + ], + "spans": [ + { + "bbox": [ + 46, + 474, + 287, + 545 + ], + "type": "text", + "content": "Dataset. To demonstrate the effectiveness of our proposed dataset, we also train the proposed method on the AnimeRun. In the training process, we adopt the inclusion matching strategy by merging the segments in the reference frames. The quantitative results reported in Table 3 suggest the positive influence of our proposed dataset." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 545, + 287, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 287, + 653 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 287, + 653 + ], + "type": "text", + "content": "Model. We conduct an ablation study on our model design to examine the necessity of each structure. In our experiments, we explore alternative configurations by replacing the deformable convolution and offset estimation module with the original convolution, eliminating the coarse warping module, and omitting the CLIP image encoder for ablation. The results presented in Table 3 underscore the significance of each module, highlighting the crucial role of the coarse warping module." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "content": "Method. The results in Table 3 further highlight the efficacy of our inclusion matching pipeline. Its application to AnT [8] yields a substantial improvement in network performance, suggesting the broad applicability and generalization of our inclusion matching pipeline. Ablation study" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 310, + 209, + 544, + 416 + ], + "blocks": [ + { + "bbox": [ + 310, + 209, + 544, + 416 + ], + "lines": [ + { + "bbox": [ + 310, + 209, + 544, + 416 + ], + "spans": [ + { + "bbox": [ + 310, + 209, + 544, + 416 + ], + "type": "image", + "image_path": "8846974929558ba6d43b465c9e50b19fac81994c5682c440460bb3f8fcc8b0a2.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 417, + 547, + 461 + ], + "lines": [ + { + "bbox": [ + 304, + 417, + 547, + 461 + ], + "spans": [ + { + "bbox": [ + 304, + 417, + 547, + 461 + ], + "type": "text", + "content": "Figure 10. Visual comparison of different methods on our 3D rendered test set. Our proposed method produces satisfactory results in the presence of occlusion, significant motion, and substantial changes in viewing angles." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 462, + 541, + 474 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 462, + 541, + 474 + ], + "spans": [ + { + "bbox": [ + 306, + 462, + 541, + 474 + ], + "type": "text", + "content": "visualizations are available in the supplementary material." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 487, + 379, + 500 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 487, + 379, + 500 + ], + "spans": [ + { + "bbox": [ + 306, + 487, + 379, + 500 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 509, + 547, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 547, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 547, + 665 + ], + "type": "text", + "content": "We have introduced a new approach for line art paint bucket colorization. Departing from traditional segment matching methods that struggle with one-to-one correspondence, we proposed a novel inclusion matching pipeline that estimates each segment's inclusion relationship rather than the direct correspondence. To facilitate the learning of this inclusion relationship, we presented a dedicated dataset, PaintBucket-Character, and a two-stage colorization pipeline. Our pipeline incorporates a coarse color warping module and an inclusion matching module. The experimental results demonstrate the superior performance of our method in handling occlusion and accommodating large movements within challenging scenarios." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": "Acknowledgement. This study is supported under the RIE2020 Industry Alignment Fund Industry Collaboration Projects (IAF-ICP) Funding Initiative, as well as cash and in-kind contribution from the industry partner(s)." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "text", + "content": "25551" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 712 + ], + "type": "list", + "angle": 0, + "index": 19, + "blocks": [ + { + "bbox": [ + 53, + 91, + 264, + 102 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 264, + 102 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 264, + 102 + ], + "type": "text", + "content": "[1] Aplaybox. https://www.aplaybox.com/.2,4" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 53, + 103, + 229, + 114 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 103, + 229, + 114 + ], + "spans": [ + { + "bbox": [ + 53, + 103, + 229, + 114 + ], + "type": "text", + "content": "[2] Cadmium. https://cadmium.app/. 2" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 53, + 115, + 249, + 126 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 115, + 249, + 126 + ], + "spans": [ + { + "bbox": [ + 53, + 115, + 249, + 126 + ], + "type": "text", + "content": "[3] Mixamo. https://www MIXamo.com/.2,4" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 53, + 127, + 287, + 159 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 127, + 287, + 159 + ], + "spans": [ + { + "bbox": [ + 53, + 127, + 287, + 159 + ], + "type": "text", + "content": "[4] Kenta Akita, Yuki Morimoto, and Reiji Tsuruno. 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ACM TOG, 38(6), 2019. 3" + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "25553" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/2ddc8710-2e01-4d04-9c1a-627c67a89c1a_content_list.json b/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/2ddc8710-2e01-4d04-9c1a-627c67a89c1a_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..2851a59b9af3d151433e78cbc2ab0b228bce9a0f --- /dev/null +++ b/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/2ddc8710-2e01-4d04-9c1a-627c67a89c1a_content_list.json @@ -0,0 +1,2014 @@ +[ + { + "type": "text", + "text": "Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes", + "text_level": 1, + "bbox": [ + 102, + 128, + 867, + 174 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Zhiyuan Yu1 Zheng Qin2 Lintao Zheng1 Kai Xu1*", + "bbox": [ + 276, + 202, + 697, + 220 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{1}$ National University of Defense Technology", + "bbox": [ + 305, + 220, + 661, + 239 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "2 Defense Innovation Institute, Academy of Military Sciences", + "bbox": [ + 238, + 239, + 723, + 256 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 291, + 312, + 306 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Multi-instance point cloud registration estimates the poses of multiple instances of a model point cloud in a scene point cloud. Extracting accurate point correspondences is to the center of the problem. Existing approaches usually treat the scene point cloud as a whole, overlooking the separation of instances. Therefore, point features could be easily polluted by other points from the background or different instances, leading to inaccurate correspondences oblivious to separate instances, especially in cluttered scenes. In this work, we propose MIRETR, Multi-Instance REgistration TRansformer, a coarse-to-fine approach to the extraction of instance-aware correspondences. At the coarse level, it jointly learns instance-aware superpoint features and predicts per-instance masks. With instance masks, the influence from outside of the instance being concerned is minimized, such that highly reliable superpoint correspondences can be extracted. The superpoint correspondences are then extended to instance candidates at the fine level according to the instance masks. At last, an efficient candidate selection and refinement algorithm is devised to obtain the final registrations. Extensive experiments on three public benchmarks demonstrate the efficacy of our approach. In particular, MIRETR outperforms the state of the arts by 16.6 points on $F_{1}$ score on the challenging ROBI benchmark. Code and models are available at https://github.com/zhiyuanYU134/MIRETR.", + "bbox": [ + 76, + 323, + 473, + 717 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 733, + 209, + 748 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Point cloud registration aims at estimating a rigid transformation that aligns two point clouds. In real-world application scenarios such as robotic bin picking, there is often the requirement of multi-instance registration where the point cloud of a model needs to be registered against multiple instances of the model in the target scene. Multi-instance point cloud registration is challenging due to the unknown number of instances and inter-instance occlusions", + "bbox": [ + 75, + 758, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/4e3233d8ef36aaf966956864326cf4843320fcc8584ebcc900975e170f9989a3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 501, + 286, + 702, + 429 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/00be69d5bf270e5c38962f7ae76f9870d92c0d3d8b7e6c7ddb2e2018720a0531.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 707, + 286, + 890, + 430 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/5d5753b9c79caf849264974067eb6e9ab1282f7bd930789ee42af60941679459.jpg", + "image_caption": [ + "GeoTransformer", + "Figure 1. MIRETR significantly improves the multi-instance registration results in cluttered scenes compared to the state-of-the-art GeoTransformer [38]. Benefiting from the instance-aware correspondences, our method can generate more accurate registrations (see the yellow boxes) and register the heavily-occluded instances with severe geometric deficiency (see the red boxes)." + ], + "image_footnote": [], + "bbox": [ + 501, + 431, + 702, + 575 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/58acc35d0b23e9c36e8cc7256f026a2e6cc6e4b36fa6eb0703816a6b5c4c0e26.jpg", + "image_caption": [ + "MIRETR" + ], + "image_footnote": [], + "bbox": [ + 707, + 431, + 890, + 575 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "especially in a cluttered scene.", + "bbox": [ + 500, + 700, + 702, + 714 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Existing approaches to multi-instance registration are mostly two-stage: They first extract point correspondences between the model and the scene point clouds and then recover per-instance transformations with multi-model fitting [28, 44, 55]. Clearly, the performance of such approach highly depends on the quality of the correspondences. Unlike pair-wise registration that can be pinned down by a small number of correspondences, multi-instance registration poses unique challenges. First, the correspondences should widely spread over the scene point cloud to cover as many instances as possible so that more instances can be found and registered. Second, the correspondences should", + "bbox": [ + 496, + 719, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author: Kai Xu (kevin.kai.xu@gmail.com).", + "bbox": [ + 94, + 886, + 410, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "19605", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "be accurately clustered into individual instances to estimate per-instance pose transformations.", + "bbox": [ + 75, + 90, + 468, + 121 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Existing point correspondence methods can be broadly classified into keypoint-based and keypoint-free ones. Albeit successful in pairwise registration, these methods fail to effectively tackle the aforementioned challenges. On the one hand, keypoint-based methods [4, 14, 25] first detect keypoints and then match them to form correspondences. In the multi-instance setting, however, it is common that an instance is severely occluded so that too few keypoints can be detected to guarantee a successful registration.", + "bbox": [ + 75, + 123, + 467, + 258 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "On the other hand, keypoint-free methods [38, 54] bypass keypoint detection with a coarse-to-fine pipeline. They first extract correspondences between sparse superpoints and then refine them to dense point correspondences. To achieve reliable superpoint matching, they encode global context with feature correlation [54] or geometric structure [38] to learn distinctive superpoint features. When used in multi-instance registration, such approach may overlook the separation of individual instances and lead to the following two drawbacks. First, the superpoint features of an instance may be contaminated by the global context from the background or other instances, making the extracted features less informative. Thus, the features of a severely occluded instance could be overwhelmed by those more complete neighboring ones, making the occluded instances hard to registered (see Fig. 1 (left)). Second, they cannot discriminate correspondences into different instances and have to rely on multi-model fitting [28, 44, 55] to cluster correspondences. Multi-model fitting needs to sample numerous hypotheses and finds difficulty in handling heavy occlusion.", + "bbox": [ + 75, + 261, + 467, + 561 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We propose MIRETR, Multi-Instance REgistration Transformer, which learns to extract instance-aware correspondences in a coarse-to-fine fashion. Our key motivation is to restrict the contextual feature encoding within the instance scope. An Instance-aware Geometric Transformer module is devised to jointly extract reliable superpoint features and predict instance masks in the scene. We resolve this chicken-and-egg problem with an iterative process. In each iteration, we first encode intra-instance geometric structure based on the instance mask of the previous iteration and then learn geometric consistency between the model and the scene. Next, the instance masks are refined based on the instance-aware features. As the iteration goes, the superpoint features gradually improve with increasingly relevant context and accurate instance masks, resulting in reliable registrations even for heavily-occluded instances (see Fig. 1 (right)).", + "bbox": [ + 75, + 566, + 467, + 821 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Having obtained superpoint correspondences, we extend them to instance candidates based on instance masks. This allows us to directly extract instance-wise point correspondences and estimate a transformation for each instance candidate. An efficient candidate selection and refinement", + "bbox": [ + 75, + 825, + 467, + 898 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "method is proposed to eliminate duplicated instances and obtain the final registrations. Thanks to the instance-aware correspondences, our method bypasses the need of multimodel fitting, achieving superior efficiency and accuracy. Extensive experiments on three benchmarks [2, 10, 52] demonstrate the efficacy of our method. Our method surpasses the previous state-of-the-art methods [38, 55] by 16.6 points on $\\mathrm{F_1}$ score on the cluttered ROBI benchmark. Our main contributions include:", + "bbox": [ + 496, + 90, + 890, + 224 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- A multi-instance point cloud registration method which extracts instance-wise correspondences and estimates transformations without multi-model fitting.", + "- An instance-aware geometric transformer module which jointly learns instance-aware superpoint features and predicts instance masks.", + "- An efficient instance candidate selection and refinement method which removes duplicated candidates and generates the final registrations." + ], + "bbox": [ + 500, + 227, + 890, + 361 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related work", + "text_level": 1, + "bbox": [ + 500, + 376, + 635, + 391 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Point cloud registration. State-of-the-art point cloud registration methods can be categorized into direct registration methods and correspondence-based methods. Direct registration methods [1, 18, 26, 48, 49, 51, 53] use a neural network to estimate the transformation in an end-to-end manner. Correspondence-based methods [4, 14, 16, 17, 19, 25, 38, 54] extract point correspondences and estimate the rigid transformation with a robust pose estimator. Early point correspondence methods [4, 25] adopt a detect-then-match pipeline, where keypoints are first detected and then matched. Recent advances [38, 54] have bypassed keypoint detection by extracting correspondences in a coarse-to-fine fashion. However, existing methods mainly focus on pairwise registration and little attention has been paid to multi-instance registration, which faces new challenges such as unknown number of instances and heavy intra-instance occlusion. In this paper, we fill this gap by directly extracting instance-aware correspondences.", + "bbox": [ + 496, + 402, + 890, + 672 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Multi-model fitting. Multi-model fitting aims at recovering multiple models from noisy data, which is an important step in multi-instance registration. Multi-model fitting methods can be classified into RANSAC-based methods and clustering-based methods. RANSAC-based methods [6, 7, 27, 28] adopt a hypothesize-and-verify manner to sequentially fit multiple models. Clustering-based methods [33-35, 44, 55] sample a huge set of hypotheses and cluster the correspondences according to their residuals under these hypotheses. However, these methods suffer from huge memory usage or long convergence time. In this work, we achieve accurate and efficient multi-instance registration without multi-model fitting.", + "bbox": [ + 496, + 674, + 890, + 869 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Open-set pose estimation. Model retrieval [2, 3, 8, 9, 13, 20, 24, 29] and image-based pose estimation [11, 12,", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "19606", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "22, 23, 31, 32, 37, 41-43, 47, 50] are two highly-related tasks to multi-instance registration. Model retrieval aims at estimating the 9-DoF pose parameters of the CAD models from a pre-built database that appears in a given scene. And image-based pose estimation recovers the 6-DoF poses for certain objects [12, 22, 23, 37, 41-43, 50] or categories [11, 31, 32, 47] in an RGB or RGB-D image. However, both tasks are based on the close-set assumption, where the training and testing data follow the same distribution. Model retrieval can only retrieve the CAD models in the database while image-based pose estimation can only handle known objects or categories in the training data. On the contrary, multi-instance registration is an open-set problem. It is based on geometric matching and thus can generalize well to novel objects and categories. We discuss the generality of MIRETR in Sec. 5.3.", + "bbox": [ + 75, + 90, + 472, + 333 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Problem Statement", + "text_level": 1, + "bbox": [ + 76, + 347, + 264, + 363 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given a model point cloud $\\mathcal{P} = \\{\\mathbf{p}_i\\in \\mathbb{R}^3 |i = 1,\\dots,N\\}$ and a scene point cloud $\\mathcal{Q} = \\{\\mathbf{q}_i\\in \\mathbb{R}^3 |i = 1,\\dots,M\\}$ , where $\\mathcal{Q}$ could contain multiple instances of $\\mathcal{P}$ , the goal of multi-instance registration is to register all instances of $\\mathcal{P}$ in $\\mathcal{Q}$ . Specifically, $\\mathcal{Q}$ is represented as $\\mathcal{Q} = \\mathcal{Q}_0\\cup \\mathcal{Q}_1\\cup \\ldots \\cup \\mathcal{Q}_K$ where $\\mathcal{Q}_0$ is the background points and $\\{\\mathcal{Q}_1,\\dots,\\mathcal{Q}_K\\}$ are the $K$ instances of $\\mathcal{P}$ . For each instance $\\mathcal{Q}_k$ , we estimate a 6-DoF pose $\\mathbf{T}_k\\in \\mathcal{SE}(3)$ aligning $\\mathcal{P}$ to $\\mathcal{Q}_k$ , which consists of a 3D rotation $\\mathbf{R}_k\\in \\mathcal{SO}(3)$ and a 3D translation $\\mathbf{t}_k\\in \\mathbb{R}^3$ . To solve this problem, one usually first extracts a set of correspondences $\\mathcal{C} = \\{(\\mathbf{p}_i,\\mathbf{q}_i)|\\mathbf{p}_i\\in \\mathcal{P},\\mathbf{q}_i\\in \\mathcal{Q}\\}$ between the two point clouds. The correspondences are then clustered into different groups $\\{\\mathcal{C}_1,\\dots,\\mathcal{C}_K\\}$ , and each group recovers the pose of one instance by solving the following problem:", + "bbox": [ + 75, + 372, + 472, + 585 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\min _ {\\mathbf {R} _ {k}, \\mathbf {t} _ {k}} \\sum_ {\\left(\\mathbf {p} _ {i}, \\mathbf {q} _ {i}\\right) \\in \\mathcal {C} _ {k}} \\left\\| \\mathbf {R} _ {k} \\cdot \\mathbf {p} _ {i} + \\mathbf {t} _ {k} - \\mathbf {q} _ {i} \\right\\| _ {2} ^ {2}. \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 133, + 595, + 468, + 625 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "This problem is very challenging as the number of instances is unknown and it is difficult to cluster the correspondences to the correct instances. In this work, we deal with this problem by extracting instance-aware correspondences.", + "bbox": [ + 75, + 633, + 468, + 695 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Method", + "text_level": 1, + "bbox": [ + 76, + 709, + 168, + 724 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "MIRETR extracts correspondences in a coarse-to-fine fashion similar to keypoint-free registration methods. The overall pipeline of our method is illustrated in Fig. 2. At the coarse level, we establish correspondences between down-sampled superpoints with an Instance-aware Geometric Transformer module (Sec. 4.1). At the fine level, each superpoint correspondence is extended to form an instance candidate, where instance-wise point correspondences are extracted for pose estimation (Sec. 4.2). At last, we merge similar instance candidates and refine the resultant poses to obtain the final registrations (Sec. 4.3).", + "bbox": [ + 75, + 734, + 468, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given the input point clouds $\\mathcal{P}$ and $\\mathcal{Q}$ , we progressively downsample them into sparse superpoints, denoted as $\\hat{\\mathcal{P}}$ and $\\hat{\\mathcal{Q}}$ , using grid subsampling [45]. KPFCNN [45] is adopted to extract multi-level point features. Let us denote the features of $\\mathcal{P}$ , $\\mathcal{Q}$ , $\\hat{\\mathcal{P}}$ and $\\hat{\\mathcal{Q}}$ as $\\mathbf{F}^{\\mathcal{P}}$ , $\\mathbf{F}^{\\mathcal{Q}}$ , $\\hat{\\mathbf{F}}^{\\mathcal{P}}$ and $\\hat{\\mathbf{F}}^{\\mathcal{Q}}$ , respectively. Following [38, 54], each superpoint $\\hat{\\mathbf{p}}_i \\in \\hat{\\mathcal{P}}$ ( $\\hat{\\mathbf{q}}_i \\in \\hat{\\mathcal{Q}}$ ) is associated with a local patch $\\mathcal{G}_i^{\\mathcal{P}}$ ( $\\mathcal{G}_i^{\\mathcal{Q}}$ ) by the point-to-node partition strategy [30] where each point is assigned to its nearest superpoint.", + "bbox": [ + 496, + 90, + 893, + 227 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. Instance-aware Geometric Transformer", + "text_level": 1, + "bbox": [ + 498, + 239, + 841, + 255 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given the superpoints $\\hat{\\mathcal{P}}$ and $\\hat{\\mathcal{Q}}$ , as well as their features $\\hat{\\mathbf{F}}^{\\mathcal{P}}$ and $\\hat{\\mathbf{F}}^{\\mathcal{Q}}$ , we first extract a set of superpoint correspondences whose local patches overlap with each other. Accurate superpoint matching relies on learning the geometric consistency between the two point clouds. To this end, previous works [38, 54] adopt transformer [46] to encode intra- and inter-point-cloud context in the global scope, as shown in Fig. 3 (a). Albeit successful in pairwise registration, this is problematic in multi-instance registration. In the scene point cloud, the superpoints from the background or other instances are de facto noises for modeling the geometric consistency and severely pollute the superpoint features. This becomes more severe in cluttered scenes. Considering an heavily-occluded instance, as its geometric structure is incomplete, the features of its superpoints could be easily overwhelmed by those from the background or nearby instances. As a result, it can hardly be registered.", + "bbox": [ + 496, + 262, + 890, + 520 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To address these issues, we propose to make the superpoint features instance-aware with a novel Instance-aware Geometric Transformer module. The key insight is to restrict the intra-point-cloud context encoding in the scene point cloud within each individual instance. To this end, we first extract the $k$ -nearest neighbors for each superpoint and conduct context aggregation within local regions. However, as shown in Fig. 3 (b), nearby superpoints do not necessarily reside in the same instance, and the feature pollution problem still exists. For this reason, we further design an instance masking mechanism by predicting an instance mask for each superpoint to select the neighbors in the same instance as it, and only aggregate the context among them. Fig. 3 (c) illustrates our instance masking mechanism.", + "bbox": [ + 496, + 521, + 890, + 733 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As shown in Fig. 2 (bottom), the instance-aware geometric transformer contains three blocks. First, a geometric encoding block encodes intra-instance geometric structure based on the instance masks. Next, a cross-attention block enhances the superpoint features by modeling inter-point-cloud geometric consistency. At last, an instance masking block predicts new instance masks with the instance-aware superpoint features. We adopt $N_{t}$ instance-aware geometric transformer modules to progressively refine the superpoint features and the instance masks.", + "bbox": [ + 496, + 734, + 890, + 883 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Geometric encoding block. This block encodes the intra-", + "bbox": [ + 500, + 885, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "19607", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/3b7392b09c5d7484addd23a021cbc0ab02df234b1100bb360f33a433492f01cb.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 80, + 890, + 193 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/52277569e5bee28670850f75f127e1a769c8fc1da2d6cf9a671fe014504afb6b.jpg", + "image_caption": [ + "Geometric Embedding", + "Geodesic Embedding" + ], + "image_footnote": [], + "bbox": [ + 80, + 196, + 480, + 349 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/198ab56572b2efb94d1dea75798e9498348125d5d6c19e0b4037aebedff7f7f3.jpg", + "image_caption": [ + "Figure 2. Overall pipeline of MIRETR. The backbone progressively downsamples two point clouds and extracts multi-level features. At the coarse level, the Instance-aware Geometric Transformer module extracts instance-aware superpoint features and establishes reliable superpoint correspondences. At the fine level, the superpoint correspondences are extended to instance candidates, where instance-wise point correspondences are extracted to estimate per-candidate poses. At last, a simple but effective candidate selection and refinement algorithm is adopted to generate the final registrations." + ], + "image_footnote": [], + "bbox": [ + 89, + 349, + 104, + 358 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/72bd292598fd3f57848a6fdcfcf195b9ac2d811ebe60d3a447c403bfcc003618.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 196, + 349, + 207, + 358 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/b2fce553568a448c42ce0a4fffcda0bc34c065c03b263199c38bdd5d131f20c5.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 488, + 195, + 888, + 349 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "instance geometric context within each point cloud. Given an anchor superpoint $\\hat{\\mathbf{q}}_i\\in \\hat{\\mathcal{Q}}$ , its $k$ -nearest superpoints $\\mathcal{N}_i^{\\mathcal{Q}} = \\{\\hat{\\mathbf{q}}_{i_1},\\dots,\\hat{\\mathbf{q}}_{i_k}\\}$ , the input feature matrix $\\mathbf{X}^{\\mathcal{Q}}\\in$ $\\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times d}$ , and the instance mask matrix $\\mathbf{M}^{\\mathcal{Q}}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times k}$ , the output feature matrix $\\mathbf{Z}^{\\mathcal{Q}}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times d}$ is computed as:", + "bbox": [ + 76, + 438, + 468, + 516 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {z} _ {i} ^ {\\mathcal {Q}} = \\sum_ {j = 1} ^ {k} \\frac {\\exp \\left(e _ {i , j}\\right)}{\\sum_ {l = 1} ^ {k} \\exp \\left(e _ {i , l}\\right)} \\left(\\mathbf {x} _ {i _ {j}} ^ {\\mathcal {Q}} \\mathbf {W} ^ {V}\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 148, + 527, + 468, + 570 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the attention score $e_{i,j}$ is computed as:", + "bbox": [ + 76, + 580, + 377, + 597 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ne _ {i, j} = \\frac {\\left(\\mathbf {x} _ {i} ^ {\\mathcal {Q}} \\mathbf {W} ^ {\\mathcal {Q}}\\right) \\left(\\mathbf {x} _ {i j} ^ {\\mathcal {Q}} \\mathbf {W} ^ {K} + \\mathbf {r} _ {i , j} \\mathbf {W} ^ {R}\\right) ^ {\\top}}{\\sqrt {d}} + m _ {i, j} ^ {\\mathcal {Q}}, \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 99, + 606, + 468, + 643 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathbf{W}^Q, \\mathbf{W}^K, \\mathbf{W}^V, \\mathbf{W}^R \\in \\mathbb{R}^{d \\times d}$ are the projection weights for query, key, value and geometric embedding, respectively. $\\mathbf{r}_{i,j}$ is the geometric structure embedding [38] encoding the transformation-invariant geometric information among the superpoints. For the instance mask $\\mathbf{M}^Q$ , we set $m_{i,j}^Q = 0$ if $\\hat{\\mathbf{q}}_i$ and $\\hat{\\mathbf{q}}_{i_j}$ are in the same instance, while $m_{i,j}^Q = -\\infty$ otherwise. $\\mathbf{M}^Q$ is initialized with all zeros and refined by the instance masking block described later. Benefiting from the instance masks, the superpoint features are instance-aware by encoding the feature correlation and the geometric context within their belonging instances. For the computation in $\\hat{\\mathcal{P}}$ , we ignore the mask term in Eq. (3) and aggregate the features from all neighbors.", + "bbox": [ + 75, + 654, + 468, + 854 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Cross-attention block. After encoding the intra-instance geometric context, we further learn the inter-point-cloud geometric consistency with a cross-attention block inspired", + "bbox": [ + 75, + 854, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/c78b66be2db0dedf0a3adb2415281fc822852d19df4a1b7986ae17ae8d9b739f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 501, + 435, + 629, + 540 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/09a848ec848c99caed909ec564f47b049240a2c8ee2429b97cfe85cec67732ee.jpg", + "image_caption": [ + "(a) Global attention" + ], + "image_footnote": [], + "bbox": [ + 501, + 541, + 629, + 647 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/ee2a80afa38ded4b7aa7bd7bd407fba887b5b40cff38a87b2eca348f1c1c2ffe.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 630, + 435, + 759, + 540 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/8c993a1786492cbe44ecd9b922c68ae3aafe952b9213d852b298883392da4c54.jpg", + "image_caption": [ + "(b) Local attention" + ], + "image_footnote": [], + "bbox": [ + 630, + 541, + 759, + 647 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/d7e014254b2b4da6199dface4ee16daa2b19b3923f9abf661baeb54d11babae1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 761, + 436, + 888, + 540 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/1a513c39b4baf070960b0f7d1d21541028d3b9b2680d9b1294156640f056c829.jpg", + "image_caption": [ + "(c) Instance-aware attention" + ], + "image_footnote": [], + "bbox": [ + 761, + 541, + 888, + 647 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Figure 3. Comparison of (a) global attention, (b) local attention, and (c) instance-aware attention. The superpoints (patches) participating in the attention computation are color-coded. The anchor superpoints are in red. The $k$ -nearest neighbors of the anchor are enclosed by the purple line.", + "bbox": [ + 496, + 659, + 890, + 728 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "by [38, 54]. Given the feature matrices $\\mathbf{X}^{\\mathcal{P}}\\in \\mathbb{R}^{|\\hat{\\mathcal{P}} |\\times d}$ of $\\hat{\\mathcal{P}}$ and $\\mathbf{X}^{\\mathcal{Q}}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times d}$ of $\\hat{\\mathcal{Q}}$ from the geometric encoding block, the output feature matrix $\\mathbf{Z}^{\\mathcal{P}}\\in \\mathbb{R}^{|\\hat{\\mathcal{P}} |\\times d}$ of $\\hat{\\mathcal{P}}$ is computed as:", + "bbox": [ + 496, + 732, + 893, + 782 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {z} _ {i} ^ {\\mathcal {P}} = \\sum_ {j = 1} ^ {| \\hat {\\mathcal {Q}} |} \\frac {\\exp \\left(e _ {i , j}\\right)}{\\sum_ {k = 1} ^ {| \\hat {\\mathcal {Q}} |} \\exp \\left(e _ {i , k}\\right)} \\left(\\mathbf {x} _ {k} ^ {\\mathcal {Q}} \\mathbf {W} ^ {V}\\right), \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 791, + 890, + 839 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the attention score $e_{i,j}$ is computed as:", + "bbox": [ + 500, + 844, + 800, + 859 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ne _ {i, j} = \\frac {\\left(\\mathbf {x} _ {i} ^ {\\mathcal {P}} \\mathbf {W} ^ {Q}\\right) \\left(\\mathbf {x} _ {j} ^ {\\mathcal {Q}} \\mathbf {W} ^ {K}\\right) ^ {\\top}}{\\sqrt {d}}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 594, + 867, + 890, + 904 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "19608", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/3ada87a13994500c9e9f1cff06f7ac5ccc4037d8889262b56faad03e71531af0.jpg", + "image_caption": [ + "Figure 4. Structure of the Instance masking block." + ], + "image_footnote": [], + "bbox": [ + 78, + 85, + 467, + 258 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathbf{W}^Q, \\mathbf{W}^K, \\mathbf{W}^V \\in \\mathbb{R}^{d \\times d}$ are the respective projection weights for query, key and value. The same computation goes for $\\mathbf{Z}^Q$ . Benefiting from the cross-attention block, the superpoint features in one point cloud are aware of the geometric structure of the other one, which facilitates modeling the geometric consistency between two point clouds.", + "bbox": [ + 75, + 281, + 468, + 375 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Instance masking block. At last, this block consumes the cross-attention features $\\mathbf{X}^{\\mathcal{Q}}$ of $\\hat{\\mathcal{Q}}$ as well as the previous instance mask $\\mathbf{M}_{(t - 1)}^{\\mathcal{Q}}$ to predict a refined instance mask $\\mathbf{M}_{(t)}^{\\mathcal{Q}}$ . We observe that two superpoints from different instances tend to be distant in the geodesic space. To this end, we design a geodesic self-attention mechanism by replacing the geometric structure embedding in Eq. (3) with a similar geodesic distance embedding to enhance the superpoint features. Please refer to the appendix for more details. The resultant superpoint features are denoted as $\\mathbf{Y}$ . At last, we adopt an MLP to predict a confidence score $u_{i,j}$ for each neighbor $\\hat{\\mathbf{q}}_{i_j} \\in \\mathcal{N}_i^{\\mathcal{Q}}$ indicating whether it belongs to the same instance as $\\hat{\\mathbf{q}}_i$ based on the feature discrepancy between $\\mathbf{y}_i$ and $\\mathbf{y}_{i_j}$ and the geodesic distance embedding $\\mathbf{g}_{i,j}$ between $\\hat{\\mathbf{q}}_i$ and $\\hat{\\mathbf{q}}_{i_j}$ :", + "bbox": [ + 75, + 375, + 468, + 604 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nu _ {i, j} = \\sigma \\left(\\operatorname {M L P} \\left(\\left[ \\mathbf {y} _ {i j} - \\mathbf {y} _ {i}; \\mathbf {g} _ {i, j} \\right]\\right)\\right), \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 151, + 616, + 468, + 642 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\sigma (\\cdot)$ is the sigmoid function and $[\\cdot ]$ is the concatenation operator. At last, the confidence matrix $\\mathbf{U}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times k}$ is converted into $\\mathbf{M}_{(t)}^{\\mathcal{Q}}$ with a thresholding function:", + "bbox": [ + 76, + 652, + 468, + 704 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nm _ {i, j} ^ {\\mathcal {Q}} = \\left\\{ \\begin{array}{l l} - \\infty & u _ {i, j} < \\tau \\\\ 0 & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 178, + 713, + 468, + 753 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\tau$ is the confidence threshold. Thanks to the instance mask, our model can effectively learn instance-aware superpoint features and extract accurate superpoint correspondences covering more instances. Furthermore, the instance masks also help extract instance-aware dense point correspondences as described in Sec. 4.2.", + "bbox": [ + 75, + 763, + 468, + 854 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Superpoint matching. We extract superpoint correspondences $\\hat{\\mathcal{C}}$ by matching the superpoint features from the last cross-attention block. As in [38], we select the top $N_{c}$ su", + "bbox": [ + 75, + 854, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "perpoint pairs with the highest cosine feature similarity as the superpoint correspondences.", + "bbox": [ + 498, + 90, + 890, + 121 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Instance Candidate Generation", + "text_level": 1, + "bbox": [ + 500, + 131, + 777, + 145 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "After obtaining the superpoint correspondences, we then refine them to dense point correspondences at the fine level. Previous methods [38, 54] opt to match the points within the local patches of two matched superpoints with an optimal transport layer [40]. Nonetheless, the local correspondences extracted in this manner often cluster closely, which could lead to unstable pose estimation as noted in [25]. This is aggravated in multi-instance registration, especially in cluttered scenes, as each instance is typically small and thus its pose cannot be globally optimized as in [38].", + "bbox": [ + 496, + 154, + 890, + 305 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To address this issue, we propose to extract dense point correspondences within the instance scope by leveraging the instance masks from the coarse level. For each superpoint correspondence $\\hat{\\mathcal{C}}_k = (\\hat{\\mathbf{p}}_i,\\hat{\\mathbf{q}}_j)$ , we collect their neighboring superpoints $\\mathcal{N}_i^{\\mathcal{P}}$ and $\\mathcal{N}_j^{\\mathcal{Q}}$ . The superpoints from different instances of $\\hat{\\mathbf{q}}_j$ are removed from $\\mathcal{N}_j^{\\mathcal{Q}}$ based on the instance mask $\\mathbf{M}_j$ . The points in the local patches of all superpoints in $\\mathcal{N}_i^{\\mathcal{P}}$ and $\\mathcal{N}_j^{\\mathcal{Q}}$ imply a potential occurrence of $\\mathcal{P}$ in $\\mathcal{Q}$ , i.e., an instance candidate, denoted as $\\mathcal{I}_k$ . Next, instance-wise point correspondences are extracted within $\\mathcal{I}_k$ with an optimal transport layer and mutual top- $k$ selection following [38], denoted as $\\mathcal{C}_k$ . At last, we estimate a pose $\\mathbf{T}_k = \\{\\mathbf{R}_k,\\mathbf{t}_k\\}$ for $\\mathcal{I}_k$ by solving Eq. (1) with weighted SVD [8]. Thanks to the powerful instance-aware geometric transformer, an instance candidate can cover a relatively large portion of an instance, with few points from the background or other instances, so the poses obtained in this step have already been very accurate.", + "bbox": [ + 496, + 306, + 892, + 580 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3. Candidate Selection and Refinement", + "text_level": 1, + "bbox": [ + 500, + 590, + 815, + 604 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "As several superpoint correspondences could belong to the same instance, there are commonly duplicated instances in the instance candidates. For this reason, we further design a simple but effective algorithm for duplicate removal and candidate refinement.", + "bbox": [ + 496, + 613, + 890, + 686 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Inspired by non-maximum suppression (NMS) [39], we first sort the instance candidates by the inlier ratio on the global point correspondences $\\mathcal{C} = \\bigcup_{i=1}^{N_c} \\mathcal{C}_i$ . The inlier ratio of the instance candidate $\\mathcal{I}_k$ is:", + "bbox": [ + 496, + 688, + 890, + 750 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\gamma_ {k} = \\frac {1}{| \\mathcal {C} |} \\sum_ {(\\mathbf {p}, \\mathbf {q}) \\in \\mathcal {C}} [ [ \\| \\mathbf {R} _ {k} \\mathbf {p} + \\mathbf {t} _ {k} - \\mathbf {q} \\| < \\tau_ {2} ] ], \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 553, + 758, + 890, + 797 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\llbracket \\cdot \\rrbracket$ is the Iverson bracket and $\\tau_{2}$ is the acceptance radius. Next, we select the instance candidate with the highest inlier ratio as the anchor candidate. All remaining candidates similar with the anchor are merged with it and removed from future computation. We define the similarity between two candidates $\\mathcal{I}_i$ and $\\mathcal{I}_j$ by the average distance", + "bbox": [ + 496, + 809, + 890, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "19609", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "(ADD) [21] between their estimated poses:", + "bbox": [ + 76, + 90, + 362, + 106 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\ns _ {i, j} = 1 - \\frac {\\operatorname {A D D} \\left(\\mathbf {T} _ {i} , \\mathbf {T} _ {j}\\right)}{r}, \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 187, + 113, + 468, + 143 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $r$ is the diameter of $\\mathcal{P}$ . And $\\mathcal{I}_i$ and $\\mathcal{I}_j$ are considered similar if $s_{i,j}$ is above $\\tau_s$ . To merge two candidates, we combine their point correspondences and recompute the pose by solving Eq. (1). At last, the preserved pose is iteratively refined with the surviving inliers as in [5, 38], leading to a final instance registration. The anchor is then removed from future computation. The above process repeats until there are no candidates left and we omit the instance registrations with too few inliers.", + "bbox": [ + 75, + 151, + 468, + 286 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Compared to multi-model fitting methods [44, 55], the advantages of our MIRETR are two-fold. First, by learning instance-aware superpoint features, the influence from the background and other instances is minimized, thus the correspondences are more accurate and can cover more instances. Second, correspondence clustering-based methods tend to lose heavily-occluded instances as there are few correspondences on them, especially in cluttered scenes. On the contrary, our method can better recognize these hard instances as we bypass the clustering process by directly extracting instance candidates and merging similar ones.", + "bbox": [ + 75, + 287, + 470, + 454 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.4. Loss Functions", + "text_level": 1, + "bbox": [ + 76, + 462, + 230, + 477 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We adopt three loss functions to train MIRETR: an overlap-aware circle loss [38] $\\mathcal{L}_{\\mathrm{circle}}$ to supervise the superpoint features, a negative log-likelihood loss [40] $\\mathcal{L}_{\\mathrm{nll}}$ to supervise the point matching, and a mask prediction loss [36] $\\mathcal{L}_{\\mathrm{mask}}$ to supervise the instance masks. The overall loss is computed as $\\mathcal{L} = \\mathcal{L}_{\\mathrm{circle}} + \\mathcal{L}_{\\mathrm{nll}} + \\mathcal{L}_{\\mathrm{mask}}$ . Please refer to the supplementary material for more details.", + "bbox": [ + 75, + 484, + 468, + 590 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 76, + 603, + 209, + 619 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We evaluate MIRETR on indoor Scan2CAD [2, 44, 55], industrial ROBI [52] and synthetic ShapeNet [10] benchmarks. And we also introduce the implementation details and more experiments in the supplementary material.", + "bbox": [ + 75, + 628, + 468, + 688 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. We compare with three state-of-the-art point cloud correspondence methods, FCGF [14], CoFiNet [54] and GeoTransformer [38], and four recent multi-model fitting methods, T-linkage [33], RansaCov [34], ECC [44], and PointCLM [55]. The point cloud correspondence methods and the multi-model fitting methods are pairwise integrated for a comprehensive comparison.", + "bbox": [ + 75, + 688, + 468, + 794 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Metrics. Following [44, 55], we evaluate our method with three registration metrics: (1) Mean Recall (MR), the ratio of registered instances over all ground-truth instances, (2) Mean Precision (MP), the ratio of registered instances over all predicted instances, and (3) Mean $F_{1}$ score (MF), the harmonic mean of MP and MR. We also report Inlier Ratio (IR), the ratio of inliers over all extracted correspondences.", + "bbox": [ + 75, + 795, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/6861a70b9f788145571310bf2c171c61f4a4da672434117e90d1d85f2b30f5c4.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelIR(%)MR(%)MP(%)MF(%)
FCGF [14] + T-Linkage [33]54.7522.7632.15
FCGF [14] + RansaCov [34]36.2773.5045.0155.83
FCGF [14] + PointCLM [55]86.9970.0577.60
FCGF [14] + ECC [44]92.6073.7982.13
CoFiNet [54] + T-Linkage [33]28.175.098.62
CoFiNet [54] + RansaCov [34]18.5238.2913.6920.16
CoFiNet [54] + PointCLM [55]36.1524.7029.34
CoFiNet [54] + ECC [44]57.2617.2426.50
GeoTransformer [38] + T-Linkage [33]72.6844.8055.43
GeoTransformer [38] + RansaCov [34]44.0278.8467.1672.53
GeoTransformer [38] + PointCLM [55]82.8181.9082.35
GeoTransformer [38] + ECC [44]94.6374.8383.57
MIRETR (ours) + T-Linkage [33]77.1246.0457.65
MIRETR (ours) + RansaCov [34]84.7871.3477.48
MIRETR (ours) + PointCLM [55]56.5991.8591.0891.46
MIRETR (ours) + ECC [44]96.5289.0392.62
MIRETR (ours, full pipeline)95.7091.2193.40
", + "bbox": [ + 501, + 88, + 888, + 305 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Evaluation results on Scan2CAD benchmark.", + "bbox": [ + 532, + 309, + 854, + 321 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Evaluations on Scan2CAD", + "text_level": 1, + "bbox": [ + 500, + 330, + 741, + 345 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Dataset. Scan2CAD [2] is a scene-to-CAD alignment dataset build upon ScanNet [15] and ShapeNet [10]. It consists of 1506 scenes from ScanNet annotated with 14225 CAD models from ShapeNet and their poses in the scenes. Following [55], we replace the objects in the scenes with the corresponding aligned CAD models. We select the scene-model pairs which the scene contain multiple instances of the model for multi-instance registration. As last, we obtain 2184 point cloud pairs and use $70\\%$ pairs for training, $10\\%$ for validation and $20\\%$ for testing.", + "bbox": [ + 496, + 354, + 890, + 503 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Quantitative results. As shown in Tab. 1, our MIRETR achieves consistent improvements over the baseline correspondence models. Notably, our method surpasses the previous best GeoTransformer on IR by 12 percentage points (pp). When coupled with PointCLM, it outperforms GeoTransformer by over 9 pp on the three registration metrics.", + "bbox": [ + 496, + 505, + 890, + 595 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Moreover, our full pipeline surpasses all models with the baseline multi-model fitting methods. Although the ECC-based model performs slightly better than full MIRETR on MR, its MP is significantly worse. This indicates that ECC achieves high MR by predicting more registrations, which is impractical in real-world applications. And our method outperforms PointCLM on all three registration metrics, which demonstrates the strong effectiveness of our method.", + "bbox": [ + 496, + 595, + 890, + 715 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Evaluations on ROBI", + "text_level": 1, + "bbox": [ + 500, + 726, + 700, + 739 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Dataset. ROBI [52] is a recent dataset for industrial bin-picking. It includes 7 reflective metallic industrial objects and 63 bin-picking scenes. Each scene contains cluttered instances of one industrial object. For each point cloud pair, the scene point cloud is backprojected from a depth image and the model point cloud is sampled from the CAD model of its corresponding industrial object. We obtain 4880 pairs in total, and we split the scenes for training, validation and testing according to the ratio of $6:1:2$ for each object.", + "bbox": [ + 496, + 750, + 890, + 885 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Quantitative results. As in Tab. 2, our method outper", + "bbox": [ + 500, + 886, + 890, + 901 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "19610", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/1abb0532efa0b1f690a72759bce9d97f471e82cd995a9373c97e80cf534597da.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 85, + 179, + 164 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/704b66b88c6729d9e6d53705b971c818475de3b48203da143327ec604af1982b.jpg", + "image_caption": [ + "Inst:12" + ], + "image_footnote": [], + "bbox": [ + 204, + 85, + 303, + 164 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/644149e1b7874c39a7f61a04f1fbf69b621909165d2e10ea50794c9885073d18.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 326, + 85, + 426, + 162 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/802cd1095a9446fc722eebc795ebfe0682251baab7a87e94de02204906d214f5.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 450, + 85, + 550, + 162 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/98d47ff7e66ebf5c4a5024041eec2b8facef842f7d79a9b042ef23194aeed501.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 563, + 85, + 718, + 162 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/dcf490464ac34f05aef2449727051e01a1176447869aa82803f6a3b80d6ebae8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 730, + 85, + 885, + 164 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/69bf9dfd46a5d4c4b990e3f08d9f2ceea561adb39a0152fe649cafaaf2d4b944.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 178, + 179, + 255 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a51edfd444ebd817b90e9e521858ae6e30c964e1c3b3c8b17636ec74df0ec497.jpg", + "image_caption": [ + "Inst:22" + ], + "image_footnote": [], + "bbox": [ + 202, + 178, + 303, + 255 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/61f2e6e3fb21f46a27a0863d5a0a1fe1e21d5f959140175d540a28ac1c232176.jpg", + "image_caption": [ + "Inst:3" + ], + "image_footnote": [], + "bbox": [ + 328, + 178, + 426, + 255 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/47222ca7df42dc2273d530c4ccfaf40b595aeb40c9ba23287a6c505bda959a24.jpg", + "image_caption": [ + "Inst:9" + ], + "image_footnote": [], + "bbox": [ + 450, + 178, + 550, + 255 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9a7fcfb515a5db074b12478da6599137d1ac11a0ae2da99a77456ceb4d27c2a0.jpg", + "image_caption": [ + "IR:39.42%", + "IR:49.91%" + ], + "image_footnote": [], + "bbox": [ + 576, + 178, + 705, + 255 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/251cbcaee9afec1b852c631e6866a3942684bba4cd67373ccb205ee2290cc1e5.jpg", + "image_caption": [ + "IR:54.21%", + "IR:56.90%" + ], + "image_footnote": [], + "bbox": [ + 743, + 178, + 872, + 255 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/b69c08aeb868cc2fad1379dd2651a4718e7043dc9f9bed2dccc4cd7a2d810a69.jpg", + "image_caption": [ + "(a) Input" + ], + "image_footnote": [], + "bbox": [ + 78, + 271, + 181, + 351 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/88ba29007d8ff52a2871dd70323d5b0a20822679cfaf53c00c1570e020f5dcf1.jpg", + "image_caption": [ + "Inst:18", + "(b) Ground Truth" + ], + "image_footnote": [], + "bbox": [ + 202, + 272, + 303, + 351 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d018345a684d4f108de169b40602c60da8d37b88e7b148d84d70253f3f89d44f.jpg", + "image_caption": [ + "Inst:4", + "Inst:4", + "(c) GeoTrans" + ], + "image_footnote": [], + "bbox": [ + 326, + 272, + 428, + 349 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/4e921912da9654eb7fc66703f378cf70ad42ea341c3022fb1f929244e3610718.jpg", + "image_caption": [ + "Inst:11", + "Inst:8", + "(d) Ours" + ], + "image_footnote": [], + "bbox": [ + 450, + 272, + 552, + 349 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1c725f11c388f00e1a1af134e30d50ede5a2a17ff74c64aca2d5f3b1480fa8b4.jpg", + "image_caption": [ + "IR:48.03%", + "(e) GeoTrans (corr)" + ], + "image_footnote": [], + "bbox": [ + 563, + 272, + 715, + 349 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/289dc0081fe5c9ddbfe53c9c7fbf6005030cc6947efdd95e0d5d9d14a572b8ed.jpg", + "image_caption": [ + "IR:72.40%", + "(f) Ours (corr)" + ], + "image_footnote": [], + "bbox": [ + 730, + 272, + 883, + 349 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/b12e836e86784d456a97df0e8d248d366226a281417fc839953ffa70b7175de9.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelIR(%)MR(%)MP(%)MF(%)
CoFiNet [54] + T-Linkage [33]10.351.340.720.93
CoFiNet [54] + RansaCov [34]1.251.391.31
CoFiNet [54] + PointCLM [55]1.172.111.50
CoFiNet [54] + ECC [44]3.218.504.66
GeoTransformer [38] + T-Linkage [33]39.647.714.575.73
GeoTransformer [38] + RansaCov [34]8.9913.5810.81
GeoTransformer [38] + PointCLM [55]13.9826.6418.33
GeoTransformer [38] + ECC [44]18.5530.9923.20
MIRETR (ours) + T-Linkage [33]45.1412.0410.4711.20
MIRETR (ours) + RansaCov [34]14.1426.2918.38
MIRETR (ours) + PointCLM [55]18.6840.1125.48
MIRETR (ours) + ECC [44]24.6534.8528.91
MIRETR (ours, full pipeline)38.5141.1939.80
", + "bbox": [ + 78, + 433, + 465, + 602 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Evaluation results on ROBI benchmark.", + "bbox": [ + 127, + 607, + 416, + 619 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "forms the baseline correspondence methods by a large margin on all four metrics. Compared to Scan2CAD, ROBI is more challenging due to the more cluttered scenes, where instance-aware information is more important. Benefiting from the instance-aware geometric transformer module, our method extracts reliable instance-aware correspondences, which contributes to more accurate instance registrations.", + "bbox": [ + 75, + 627, + 467, + 732 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our full model achieves significant improvements over the ECC-based model on MR, MP and MF. The PointCLM-based model achieves comparable MP with the full model, but significantly worse MR, which means it can register only several easy instances but misses most heavily-occluded instances. Specifically, it can register on average only 6.2 instances per scene, while the number of our method is 13.7. Our method achieves both high MR and MP, showing strong robustness in cluttered scenes.", + "bbox": [ + 75, + 734, + 467, + 869 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Qualitative results. Fig. 5 visualizes the registration results of GeoTransformer and MIRETR. Our method can", + "bbox": [ + 75, + 869, + 467, + 898 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/391ca0191f955cb9a6ce937cf227c2f26566bf36dc2ed686e4e35c93a389f6c0.jpg", + "image_caption": [ + "Figure 5. Registration results on ROBI benchmark. We visualize the successfully registered instances in (c) and (d). MIRETR registers more instances in the cluttered scenes (the $2^{\\text{nd}}$ and the $3^{\\text{rd}}$ rows) and with incomplete geometry (all three rows). And it extracts more accurate correspondences benefiting from the instance-aware correspondence learning mechanism." + ], + "image_footnote": [], + "bbox": [ + 501, + 431, + 625, + 529 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/b6485a00d3b1d395f9bd361f2487dcd38fa3167e21cd81dbb7ffe8c613cfcf55.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 630, + 431, + 756, + 529 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d5503b738ba1ee730cc57be49e2512510deae3912135aa643abd992b3e952ba8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 761, + 431, + 888, + 529 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/8d3df5aa3f8921044baebe2827a67c205e342787a90d0bc6f09a89fe3001a9b0.jpg", + "image_caption": [ + "(a) Anchor's neighbors", + "Figure 6. Visualizations of the predicted instance masks. The anchor superpoint (patch) is in red and the selected neighbors are color-coded. Our method can effectively reject the patches outside the interested instance while preserving most of those inside." + ], + "image_footnote": [], + "bbox": [ + 501, + 531, + 627, + 628 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d5e8662215981f9b8f3c9bdfbf1940a9049c4a266abfef58d8dc728417113bbf.jpg", + "image_caption": [ + "(b) Ground Truth Mask" + ], + "image_footnote": [], + "bbox": [ + 630, + 531, + 756, + 628 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/96232d5edff7c4e3fb917f7bd8549b8ca128637140de62e2cc227b322af338d4.jpg", + "image_caption": [ + "(c) Our Prediceted Mask" + ], + "image_footnote": [], + "bbox": [ + 761, + 531, + 888, + 628 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "register more instances in cluttered scenes (see the $2^{\\text{nd}}$ and the $3^{\\text{rd}}$ rows) and with severe geometric deficiency (see all three rows). And MIRETR attains more high-quality correspondences thanks to our instance-aware design.", + "bbox": [ + 500, + 702, + 890, + 762 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We further visualize the predicted instance masks Fig. 6. The instance masks effectively reject the patches out of the interested instance while preserving most of those inside. Specifically, our method achieves the instance mIoU of 69.26 pp while the result of the model without masking is merely 38.13 pp. The high-quality masks allow us to effectively encode intra-instance context and contribute to accurate registrations.", + "bbox": [ + 500, + 763, + 890, + 883 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Fig. 7 compares the results under different overlap ratios.", + "bbox": [ + 517, + 885, + 888, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "19611", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/47fd1ca19d7110631edeade7b18fcf7f75922bb74cb3687da7de3747fb0f468c.jpg", + "image_caption": [ + "Figure 7. Results in different overlap levels on ROBI benchmark." + ], + "image_footnote": [], + "bbox": [ + 76, + 85, + 472, + 263 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "MIRETR consistently outperforms the baselines at all overlap levels, and the improvements are more significant when the overlap ratio is below $50\\%$ . This proves the strong capability of our method to handle low-overlap instances.", + "bbox": [ + 76, + 287, + 468, + 349 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.3. Evaluations on ShapeNet", + "text_level": 1, + "bbox": [ + 76, + 358, + 307, + 375 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Dataset. ShapeNet [10] is a large CAD model dataset which contains 51300 models from 55 categories. We use the models from first 30 categories for training and those from the rest 25 categories for testing to evaluate the generality to novel categories. We randomly sample at most 500 models from each category to avoid class imbalance. For each point cloud pair, the model point cloud is a random CAD model and the scene one is constructed by applying $4\\sim 16$ random poses on the model. At last, we obtain 8634 pairs for training, 900 for validation, and 7683 for testing.", + "bbox": [ + 75, + 382, + 468, + 532 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Quantitative results. As shown in Tab. 3, our MIRETR achieves the best results on all four metrics, surpassing the baselines by a large margin. GeoTransformer significantly outperforms CoFiNet, which proves the importance of geometric structure to achieving generality. And our method achieves improvements of more than 10 pp over GeoTransformer on all registration metrics with PointCLM and ECC. Thanks to the instance-ware geometric transformer, the correspondences extracted by our method provide strong instance information, facilitating the correspondence clustering process. At last, our full model surpasses the previous best ECC-based baseline by around 2 pp on MR, 11 pp on MP and 7 pp on MF, demonstrating the strong generality of MIRETR to unseen objects.", + "bbox": [ + 75, + 534, + 470, + 744 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Ablation Studies", + "text_level": 1, + "bbox": [ + 76, + 756, + 240, + 770 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We conduct extensive ablation studies on ROBI benchmark to better understand our design choices in Tab. 4. We first ablate the instance-aware point matching and extract point correspondences within only the patches of the superpoint correspondences in Tab. 4 (b), which is significantly worse than the full model. The poses estimated by this method is unstable due to clustered correspondences, thus the duplicated candidates cannot be effectively removed by NMS.", + "bbox": [ + 75, + 779, + 468, + 902 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/843107ec916c96881858bfb81362e9325f0099639ec1d5bd81622569773569d0.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelIR(%)MR(%)MP(%)MF(%)
CoFiNet [54] + T-Linkage [33]4.593.243.79
CoFiNet [54] + RansaCov [34]39.537.355.336.17
CoFiNet [54] + PointCLM [55]23.4019.6621.36
CoFiNet [54] + ECC [44]41.4926.6032.41
GeoTransformer [38] + T-Linkage [33]27.6826.4027.02
GeoTransformer [38] + RansaCov [34]69.6541.8648.1644.78
GeoTransformer [38] + PointCLM [55]68.0969.0968.58
GeoTransformer [38] + ECC [44]78.0364.0870.37
MIRETR (ours) + T-Linkage [33]29.4028.6729.03
MIRETR (ours) + RansaCov [34]45.6346.8546.23
MIRETR (ours) + PointCLM [55]77.1385.6385.8185.71
MIRETR (ours) + ECC [44]92.5682.0887.01
MIRETR (ours, full pipeline)94.9593.9494.44
", + "bbox": [ + 501, + 88, + 888, + 258 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/1cff5e45d9ef139c4870cf53a0bfdeb7a6a006cc885ea66901caa584aa79197f.jpg", + "table_caption": [ + "Table 3. Evaluation results on ShapeNet benchmark." + ], + "table_footnote": [], + "table_body": "
ModelIR(%)MR(%)MP(%)MF(%)
(a) full MIRETR45.1438.5141.1939.80
(b) w/o instance-aware point matching40.5218.1527.5421.88
(c) w/o instance masking block36.7817.0745.3724.80
(d) w/o both38.8114.1327.4418.65
(e) w/ global attention25.987.7218.8610.96
", + "bbox": [ + 504, + 279, + 885, + 354 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4. Ablation studies on ROBI benchmark.", + "bbox": [ + 553, + 359, + 834, + 373 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Next, we remove the instance masking blocks in Tab. 4 (c) and the instance-aware point matching gathers the points from all neighbor superpoints. This model achieves a good MP, but a significantly worse MR, which means it can register only few instances (2.9 vs. 13.7 average instances per scene). We then ablate both modules in Tab. 4 (d), which further degrades the performance. At last, we replace the geometric encoding block with the global geometric self-attention [38] in Tab. 4 (e), which achieves the worst results. This indicates that the superpoint features can be polluted if global context is encoded. These results have proven the strong efficacy of our designs. More ablation studies are presented in the supplementary material.", + "bbox": [ + 496, + 378, + 890, + 575 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 588, + 617, + 604 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We have proposed MIRETR, a coarse-to-fine method to extract instance-aware correspondences for multi-instance registration. At the coarse level, an instance-aware geometric transformer module jointly learns instance-aware superpoint features and predicts per-instance masks. At the fine level, the superpoint correspondences are extended to instance candidates according to the instance masks, where instance-wise point correspondences are extracted. At last, we devise a simple but effective candidate selection and refinement algorithm to obtain the final registrations, bypassing the need of multi-model fitting methods. Extensive experiments on three public benchmarks have demonstrated the efficacy of our method. For future work, we would like to extend MIRETR to multi-modal multi-instance registration to boost more applications.", + "bbox": [ + 496, + 613, + 890, + 839 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement. This work is in part supported by the NSFC (62325211, 62132021, 62102435), the Major Program of Xiangjiang Laboratory (23XJ01009), and the National Key R&D Program of China (2018AAA0102200).", + "bbox": [ + 496, + 839, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "19612", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Yasuhiro Aoki, Hunter Goforth, Rangaprasad Arun Srivatsan, and Simon Lucey. 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Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.104, + 0.13, + 0.868, + 0.175 + ], + "angle": 0, + "content": "Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes" + }, + { + "type": "text", + "bbox": [ + 0.277, + 0.203, + 0.699, + 0.221 + ], + "angle": 0, + "content": "Zhiyuan Yu1 Zheng Qin2 Lintao Zheng1 Kai Xu1*" + }, + { + "type": "text", + "bbox": [ + 0.307, + 0.222, + 0.663, + 0.24 + ], + "angle": 0, + "content": "\\(^{1}\\) National University of Defense Technology" + }, + { + "type": "text", + "bbox": [ + 0.24, + 0.24, + 0.725, + 0.257 + ], + "angle": 0, + "content": "2 Defense Innovation Institute, Academy of Military Sciences" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.292, + 0.313, + 0.307 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.324, + 0.474, + 0.718 + ], + "angle": 0, + "content": "Multi-instance point cloud registration estimates the poses of multiple instances of a model point cloud in a scene point cloud. Extracting accurate point correspondences is to the center of the problem. Existing approaches usually treat the scene point cloud as a whole, overlooking the separation of instances. Therefore, point features could be easily polluted by other points from the background or different instances, leading to inaccurate correspondences oblivious to separate instances, especially in cluttered scenes. In this work, we propose MIRETR, Multi-Instance REgistration TRansformer, a coarse-to-fine approach to the extraction of instance-aware correspondences. At the coarse level, it jointly learns instance-aware superpoint features and predicts per-instance masks. With instance masks, the influence from outside of the instance being concerned is minimized, such that highly reliable superpoint correspondences can be extracted. The superpoint correspondences are then extended to instance candidates at the fine level according to the instance masks. At last, an efficient candidate selection and refinement algorithm is devised to obtain the final registrations. Extensive experiments on three public benchmarks demonstrate the efficacy of our approach. In particular, MIRETR outperforms the state of the arts by 16.6 points on \\( F_{1} \\) score on the challenging ROBI benchmark. Code and models are available at https://github.com/zhiyuanYU134/MIRETR." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.734, + 0.21, + 0.749 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.759, + 0.47, + 0.879 + ], + "angle": 0, + "content": "Point cloud registration aims at estimating a rigid transformation that aligns two point clouds. In real-world application scenarios such as robotic bin picking, there is often the requirement of multi-instance registration where the point cloud of a model needs to be registered against multiple instances of the model in the target scene. Multi-instance point cloud registration is challenging due to the unknown number of instances and inter-instance occlusions" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.287, + 0.703, + 0.43 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.708, + 0.287, + 0.892, + 0.431 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.433, + 0.703, + 0.576 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.708, + 0.433, + 0.892, + 0.576 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.56, + 0.577, + 0.645, + 0.586 + ], + "angle": 0, + "content": "GeoTransformer" + }, + { + "type": "image_caption", + "bbox": [ + 0.773, + 0.577, + 0.822, + 0.586 + ], + "angle": 0, + "content": "MIRETR" + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.599, + 0.892, + 0.682 + ], + "angle": 0, + "content": "Figure 1. MIRETR significantly improves the multi-instance registration results in cluttered scenes compared to the state-of-the-art GeoTransformer [38]. Benefiting from the instance-aware correspondences, our method can generate more accurate registrations (see the yellow boxes) and register the heavily-occluded instances with severe geometric deficiency (see the red boxes)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.701, + 0.704, + 0.715 + ], + "angle": 0, + "content": "especially in a cluttered scene." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Existing approaches to multi-instance registration are mostly two-stage: They first extract point correspondences between the model and the scene point clouds and then recover per-instance transformations with multi-model fitting [28, 44, 55]. Clearly, the performance of such approach highly depends on the quality of the correspondences. Unlike pair-wise registration that can be pinned down by a small number of correspondences, multi-instance registration poses unique challenges. First, the correspondences should widely spread over the scene point cloud to cover as many instances as possible so that more instances can be found and registered. Second, the correspondences should" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.411, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author: Kai Xu (kevin.kai.xu@gmail.com)." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19605" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.122 + ], + "angle": 0, + "content": "be accurately clustered into individual instances to estimate per-instance pose transformations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.124, + 0.468, + 0.26 + ], + "angle": 0, + "content": "Existing point correspondence methods can be broadly classified into keypoint-based and keypoint-free ones. Albeit successful in pairwise registration, these methods fail to effectively tackle the aforementioned challenges. On the one hand, keypoint-based methods [4, 14, 25] first detect keypoints and then match them to form correspondences. In the multi-instance setting, however, it is common that an instance is severely occluded so that too few keypoints can be detected to guarantee a successful registration." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.262, + 0.468, + 0.563 + ], + "angle": 0, + "content": "On the other hand, keypoint-free methods [38, 54] bypass keypoint detection with a coarse-to-fine pipeline. They first extract correspondences between sparse superpoints and then refine them to dense point correspondences. To achieve reliable superpoint matching, they encode global context with feature correlation [54] or geometric structure [38] to learn distinctive superpoint features. When used in multi-instance registration, such approach may overlook the separation of individual instances and lead to the following two drawbacks. First, the superpoint features of an instance may be contaminated by the global context from the background or other instances, making the extracted features less informative. Thus, the features of a severely occluded instance could be overwhelmed by those more complete neighboring ones, making the occluded instances hard to registered (see Fig. 1 (left)). Second, they cannot discriminate correspondences into different instances and have to rely on multi-model fitting [28, 44, 55] to cluster correspondences. Multi-model fitting needs to sample numerous hypotheses and finds difficulty in handling heavy occlusion." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.567, + 0.468, + 0.822 + ], + "angle": 0, + "content": "We propose MIRETR, Multi-Instance REgistration Transformer, which learns to extract instance-aware correspondences in a coarse-to-fine fashion. Our key motivation is to restrict the contextual feature encoding within the instance scope. An Instance-aware Geometric Transformer module is devised to jointly extract reliable superpoint features and predict instance masks in the scene. We resolve this chicken-and-egg problem with an iterative process. In each iteration, we first encode intra-instance geometric structure based on the instance mask of the previous iteration and then learn geometric consistency between the model and the scene. Next, the instance masks are refined based on the instance-aware features. As the iteration goes, the superpoint features gradually improve with increasingly relevant context and accurate instance masks, resulting in reliable registrations even for heavily-occluded instances (see Fig. 1 (right))." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.826, + 0.468, + 0.899 + ], + "angle": 0, + "content": "Having obtained superpoint correspondences, we extend them to instance candidates based on instance masks. This allows us to directly extract instance-wise point correspondences and estimate a transformation for each instance candidate. An efficient candidate selection and refinement" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.226 + ], + "angle": 0, + "content": "method is proposed to eliminate duplicated instances and obtain the final registrations. Thanks to the instance-aware correspondences, our method bypasses the need of multimodel fitting, achieving superior efficiency and accuracy. Extensive experiments on three benchmarks [2, 10, 52] demonstrate the efficacy of our method. Our method surpasses the previous state-of-the-art methods [38, 55] by 16.6 points on \\(\\mathrm{F_1}\\) score on the cluttered ROBI benchmark. Our main contributions include:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.228, + 0.891, + 0.272 + ], + "angle": 0, + "content": "- A multi-instance point cloud registration method which extracts instance-wise correspondences and estimates transformations without multi-model fitting." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.273, + 0.891, + 0.317 + ], + "angle": 0, + "content": "- An instance-aware geometric transformer module which jointly learns instance-aware superpoint features and predicts instance masks." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.318, + 0.891, + 0.362 + ], + "angle": 0, + "content": "- An efficient instance candidate selection and refinement method which removes duplicated candidates and generates the final registrations." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.228, + 0.891, + 0.362 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.377, + 0.637, + 0.392 + ], + "angle": 0, + "content": "2. Related work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.403, + 0.892, + 0.674 + ], + "angle": 0, + "content": "Point cloud registration. State-of-the-art point cloud registration methods can be categorized into direct registration methods and correspondence-based methods. Direct registration methods [1, 18, 26, 48, 49, 51, 53] use a neural network to estimate the transformation in an end-to-end manner. Correspondence-based methods [4, 14, 16, 17, 19, 25, 38, 54] extract point correspondences and estimate the rigid transformation with a robust pose estimator. Early point correspondence methods [4, 25] adopt a detect-then-match pipeline, where keypoints are first detected and then matched. Recent advances [38, 54] have bypassed keypoint detection by extracting correspondences in a coarse-to-fine fashion. However, existing methods mainly focus on pairwise registration and little attention has been paid to multi-instance registration, which faces new challenges such as unknown number of instances and heavy intra-instance occlusion. In this paper, we fill this gap by directly extracting instance-aware correspondences." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.892, + 0.87 + ], + "angle": 0, + "content": "Multi-model fitting. Multi-model fitting aims at recovering multiple models from noisy data, which is an important step in multi-instance registration. Multi-model fitting methods can be classified into RANSAC-based methods and clustering-based methods. RANSAC-based methods [6, 7, 27, 28] adopt a hypothesize-and-verify manner to sequentially fit multiple models. Clustering-based methods [33-35, 44, 55] sample a huge set of hypotheses and cluster the correspondences according to their residuals under these hypotheses. However, these methods suffer from huge memory usage or long convergence time. In this work, we achieve accurate and efficient multi-instance registration without multi-model fitting." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Open-set pose estimation. Model retrieval [2, 3, 8, 9, 13, 20, 24, 29] and image-based pose estimation [11, 12," + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19606" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.091, + 0.473, + 0.334 + ], + "angle": 0, + "content": "22, 23, 31, 32, 37, 41-43, 47, 50] are two highly-related tasks to multi-instance registration. Model retrieval aims at estimating the 9-DoF pose parameters of the CAD models from a pre-built database that appears in a given scene. And image-based pose estimation recovers the 6-DoF poses for certain objects [12, 22, 23, 37, 41-43, 50] or categories [11, 31, 32, 47] in an RGB or RGB-D image. However, both tasks are based on the close-set assumption, where the training and testing data follow the same distribution. Model retrieval can only retrieve the CAD models in the database while image-based pose estimation can only handle known objects or categories in the training data. On the contrary, multi-instance registration is an open-set problem. It is based on geometric matching and thus can generalize well to novel objects and categories. We discuss the generality of MIRETR in Sec. 5.3." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.348, + 0.266, + 0.364 + ], + "angle": 0, + "content": "3. Problem Statement" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.373, + 0.473, + 0.587 + ], + "angle": 0, + "content": "Given a model point cloud \\(\\mathcal{P} = \\{\\mathbf{p}_i\\in \\mathbb{R}^3 |i = 1,\\dots,N\\}\\) and a scene point cloud \\(\\mathcal{Q} = \\{\\mathbf{q}_i\\in \\mathbb{R}^3 |i = 1,\\dots,M\\}\\), where \\(\\mathcal{Q}\\) could contain multiple instances of \\(\\mathcal{P}\\), the goal of multi-instance registration is to register all instances of \\(\\mathcal{P}\\) in \\(\\mathcal{Q}\\). Specifically, \\(\\mathcal{Q}\\) is represented as \\(\\mathcal{Q} = \\mathcal{Q}_0\\cup \\mathcal{Q}_1\\cup \\ldots \\cup \\mathcal{Q}_K\\) where \\(\\mathcal{Q}_0\\) is the background points and \\(\\{\\mathcal{Q}_1,\\dots,\\mathcal{Q}_K\\}\\) are the \\(K\\) instances of \\(\\mathcal{P}\\). For each instance \\(\\mathcal{Q}_k\\), we estimate a 6-DoF pose \\(\\mathbf{T}_k\\in \\mathcal{SE}(3)\\) aligning \\(\\mathcal{P}\\) to \\(\\mathcal{Q}_k\\), which consists of a 3D rotation \\(\\mathbf{R}_k\\in \\mathcal{SO}(3)\\) and a 3D translation \\(\\mathbf{t}_k\\in \\mathbb{R}^3\\). To solve this problem, one usually first extracts a set of correspondences \\(\\mathcal{C} = \\{(\\mathbf{p}_i,\\mathbf{q}_i)|\\mathbf{p}_i\\in \\mathcal{P},\\mathbf{q}_i\\in \\mathcal{Q}\\}\\) between the two point clouds. The correspondences are then clustered into different groups \\(\\{\\mathcal{C}_1,\\dots,\\mathcal{C}_K\\}\\), and each group recovers the pose of one instance by solving the following problem:" + }, + { + "type": "equation", + "bbox": [ + 0.135, + 0.597, + 0.47, + 0.625 + ], + "angle": 0, + "content": "\\[\n\\min _ {\\mathbf {R} _ {k}, \\mathbf {t} _ {k}} \\sum_ {\\left(\\mathbf {p} _ {i}, \\mathbf {q} _ {i}\\right) \\in \\mathcal {C} _ {k}} \\left\\| \\mathbf {R} _ {k} \\cdot \\mathbf {p} _ {i} + \\mathbf {t} _ {k} - \\mathbf {q} _ {i} \\right\\| _ {2} ^ {2}. \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.634, + 0.47, + 0.696 + ], + "angle": 0, + "content": "This problem is very challenging as the number of instances is unknown and it is difficult to cluster the correspondences to the correct instances. In this work, we deal with this problem by extracting instance-aware correspondences." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.71, + 0.169, + 0.725 + ], + "angle": 0, + "content": "4. Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.47, + 0.903 + ], + "angle": 0, + "content": "MIRETR extracts correspondences in a coarse-to-fine fashion similar to keypoint-free registration methods. The overall pipeline of our method is illustrated in Fig. 2. At the coarse level, we establish correspondences between down-sampled superpoints with an Instance-aware Geometric Transformer module (Sec. 4.1). At the fine level, each superpoint correspondence is extended to form an instance candidate, where instance-wise point correspondences are extracted for pose estimation (Sec. 4.2). At last, we merge similar instance candidates and refine the resultant poses to obtain the final registrations (Sec. 4.3)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.228 + ], + "angle": 0, + "content": "Given the input point clouds \\(\\mathcal{P}\\) and \\(\\mathcal{Q}\\), we progressively downsample them into sparse superpoints, denoted as \\(\\hat{\\mathcal{P}}\\) and \\(\\hat{\\mathcal{Q}}\\), using grid subsampling [45]. KPFCNN [45] is adopted to extract multi-level point features. Let us denote the features of \\(\\mathcal{P}\\), \\(\\mathcal{Q}\\), \\(\\hat{\\mathcal{P}}\\) and \\(\\hat{\\mathcal{Q}}\\) as \\(\\mathbf{F}^{\\mathcal{P}}\\), \\(\\mathbf{F}^{\\mathcal{Q}}\\), \\(\\hat{\\mathbf{F}}^{\\mathcal{P}}\\) and \\(\\hat{\\mathbf{F}}^{\\mathcal{Q}}\\), respectively. Following [38, 54], each superpoint \\(\\hat{\\mathbf{p}}_i \\in \\hat{\\mathcal{P}}\\) (\\(\\hat{\\mathbf{q}}_i \\in \\hat{\\mathcal{Q}}\\)) is associated with a local patch \\(\\mathcal{G}_i^{\\mathcal{P}}\\) (\\(\\mathcal{G}_i^{\\mathcal{Q}}\\)) by the point-to-node partition strategy [30] where each point is assigned to its nearest superpoint." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.24, + 0.842, + 0.256 + ], + "angle": 0, + "content": "4.1. Instance-aware Geometric Transformer" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.263, + 0.892, + 0.521 + ], + "angle": 0, + "content": "Given the superpoints \\(\\hat{\\mathcal{P}}\\) and \\(\\hat{\\mathcal{Q}}\\), as well as their features \\(\\hat{\\mathbf{F}}^{\\mathcal{P}}\\) and \\(\\hat{\\mathbf{F}}^{\\mathcal{Q}}\\), we first extract a set of superpoint correspondences whose local patches overlap with each other. Accurate superpoint matching relies on learning the geometric consistency between the two point clouds. To this end, previous works [38, 54] adopt transformer [46] to encode intra- and inter-point-cloud context in the global scope, as shown in Fig. 3 (a). Albeit successful in pairwise registration, this is problematic in multi-instance registration. In the scene point cloud, the superpoints from the background or other instances are de facto noises for modeling the geometric consistency and severely pollute the superpoint features. This becomes more severe in cluttered scenes. Considering an heavily-occluded instance, as its geometric structure is incomplete, the features of its superpoints could be easily overwhelmed by those from the background or nearby instances. As a result, it can hardly be registered." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.522, + 0.892, + 0.734 + ], + "angle": 0, + "content": "To address these issues, we propose to make the superpoint features instance-aware with a novel Instance-aware Geometric Transformer module. The key insight is to restrict the intra-point-cloud context encoding in the scene point cloud within each individual instance. To this end, we first extract the \\(k\\)-nearest neighbors for each superpoint and conduct context aggregation within local regions. However, as shown in Fig. 3 (b), nearby superpoints do not necessarily reside in the same instance, and the feature pollution problem still exists. For this reason, we further design an instance masking mechanism by predicting an instance mask for each superpoint to select the neighbors in the same instance as it, and only aggregate the context among them. Fig. 3 (c) illustrates our instance masking mechanism." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.884 + ], + "angle": 0, + "content": "As shown in Fig. 2 (bottom), the instance-aware geometric transformer contains three blocks. First, a geometric encoding block encodes intra-instance geometric structure based on the instance masks. Next, a cross-attention block enhances the superpoint features by modeling inter-point-cloud geometric consistency. At last, an instance masking block predicts new instance masks with the instance-aware superpoint features. We adopt \\( N_{t} \\) instance-aware geometric transformer modules to progressively refine the superpoint features and the instance masks." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.886, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Geometric encoding block. This block encodes the intra-" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "19607" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.082, + 0.892, + 0.194 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.197, + 0.482, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.091, + 0.35, + 0.105, + 0.359 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.107, + 0.35, + 0.181, + 0.359 + ], + "angle": 0, + "content": "Geometric Embedding" + }, + { + "type": "image", + "bbox": [ + 0.197, + 0.35, + 0.209, + 0.359 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.218, + 0.35, + 0.287, + 0.359 + ], + "angle": 0, + "content": "Geodesic Embedding" + }, + { + "type": "image", + "bbox": [ + 0.489, + 0.196, + 0.89, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.361, + 0.894, + 0.432 + ], + "angle": 0, + "content": "Figure 2. Overall pipeline of MIRETR. The backbone progressively downsamples two point clouds and extracts multi-level features. At the coarse level, the Instance-aware Geometric Transformer module extracts instance-aware superpoint features and establishes reliable superpoint correspondences. At the fine level, the superpoint correspondences are extended to instance candidates, where instance-wise point correspondences are extracted to estimate per-candidate poses. At last, a simple but effective candidate selection and refinement algorithm is adopted to generate the final registrations." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.439, + 0.47, + 0.517 + ], + "angle": 0, + "content": "instance geometric context within each point cloud. Given an anchor superpoint \\(\\hat{\\mathbf{q}}_i\\in \\hat{\\mathcal{Q}}\\) , its \\(k\\) -nearest superpoints \\(\\mathcal{N}_i^{\\mathcal{Q}} = \\{\\hat{\\mathbf{q}}_{i_1},\\dots,\\hat{\\mathbf{q}}_{i_k}\\}\\) , the input feature matrix \\(\\mathbf{X}^{\\mathcal{Q}}\\in\\) \\(\\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times d}\\) , and the instance mask matrix \\(\\mathbf{M}^{\\mathcal{Q}}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times k}\\) , the output feature matrix \\(\\mathbf{Z}^{\\mathcal{Q}}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times d}\\) is computed as:" + }, + { + "type": "equation", + "bbox": [ + 0.149, + 0.528, + 0.47, + 0.571 + ], + "angle": 0, + "content": "\\[\n\\mathbf {z} _ {i} ^ {\\mathcal {Q}} = \\sum_ {j = 1} ^ {k} \\frac {\\exp \\left(e _ {i , j}\\right)}{\\sum_ {l = 1} ^ {k} \\exp \\left(e _ {i , l}\\right)} \\left(\\mathbf {x} _ {i _ {j}} ^ {\\mathcal {Q}} \\mathbf {W} ^ {V}\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.582, + 0.379, + 0.598 + ], + "angle": 0, + "content": "where the attention score \\( e_{i,j} \\) is computed as:" + }, + { + "type": "equation", + "bbox": [ + 0.101, + 0.607, + 0.47, + 0.645 + ], + "angle": 0, + "content": "\\[\ne _ {i, j} = \\frac {\\left(\\mathbf {x} _ {i} ^ {\\mathcal {Q}} \\mathbf {W} ^ {\\mathcal {Q}}\\right) \\left(\\mathbf {x} _ {i j} ^ {\\mathcal {Q}} \\mathbf {W} ^ {K} + \\mathbf {r} _ {i , j} \\mathbf {W} ^ {R}\\right) ^ {\\top}}{\\sqrt {d}} + m _ {i, j} ^ {\\mathcal {Q}}, \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.655, + 0.47, + 0.856 + ], + "angle": 0, + "content": "where \\(\\mathbf{W}^Q, \\mathbf{W}^K, \\mathbf{W}^V, \\mathbf{W}^R \\in \\mathbb{R}^{d \\times d}\\) are the projection weights for query, key, value and geometric embedding, respectively. \\(\\mathbf{r}_{i,j}\\) is the geometric structure embedding [38] encoding the transformation-invariant geometric information among the superpoints. For the instance mask \\(\\mathbf{M}^Q\\), we set \\(m_{i,j}^Q = 0\\) if \\(\\hat{\\mathbf{q}}_i\\) and \\(\\hat{\\mathbf{q}}_{i_j}\\) are in the same instance, while \\(m_{i,j}^Q = -\\infty\\) otherwise. \\(\\mathbf{M}^Q\\) is initialized with all zeros and refined by the instance masking block described later. Benefiting from the instance masks, the superpoint features are instance-aware by encoding the feature correlation and the geometric context within their belonging instances. For the computation in \\(\\hat{\\mathcal{P}}\\), we ignore the mask term in Eq. (3) and aggregate the features from all neighbors." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Cross-attention block. After encoding the intra-instance geometric context, we further learn the inter-point-cloud geometric consistency with a cross-attention block inspired" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.436, + 0.63, + 0.541 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.542, + 0.63, + 0.648 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.524, + 0.65, + 0.602, + 0.658 + ], + "angle": 0, + "content": "(a) Global attention" + }, + { + "type": "image", + "bbox": [ + 0.632, + 0.436, + 0.76, + 0.541 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.632, + 0.542, + 0.76, + 0.648 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.657, + 0.65, + 0.73, + 0.658 + ], + "angle": 0, + "content": "(b) Local attention" + }, + { + "type": "image", + "bbox": [ + 0.763, + 0.437, + 0.89, + 0.541 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.763, + 0.542, + 0.89, + 0.648 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.766, + 0.65, + 0.875, + 0.658 + ], + "angle": 0, + "content": "(c) Instance-aware attention" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.66, + 0.892, + 0.729 + ], + "angle": 0, + "content": "Figure 3. Comparison of (a) global attention, (b) local attention, and (c) instance-aware attention. The superpoints (patches) participating in the attention computation are color-coded. The anchor superpoints are in red. The \\(k\\)-nearest neighbors of the anchor are enclosed by the purple line." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.733, + 0.894, + 0.784 + ], + "angle": 0, + "content": "by [38, 54]. Given the feature matrices \\(\\mathbf{X}^{\\mathcal{P}}\\in \\mathbb{R}^{|\\hat{\\mathcal{P}} |\\times d}\\) of \\(\\hat{\\mathcal{P}}\\) and \\(\\mathbf{X}^{\\mathcal{Q}}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times d}\\) of \\(\\hat{\\mathcal{Q}}\\) from the geometric encoding block, the output feature matrix \\(\\mathbf{Z}^{\\mathcal{P}}\\in \\mathbb{R}^{|\\hat{\\mathcal{P}} |\\times d}\\) of \\(\\hat{\\mathcal{P}}\\) is computed as:" + }, + { + "type": "equation", + "bbox": [ + 0.569, + 0.792, + 0.892, + 0.84 + ], + "angle": 0, + "content": "\\[\n\\mathbf {z} _ {i} ^ {\\mathcal {P}} = \\sum_ {j = 1} ^ {| \\hat {\\mathcal {Q}} |} \\frac {\\exp \\left(e _ {i , j}\\right)}{\\sum_ {k = 1} ^ {| \\hat {\\mathcal {Q}} |} \\exp \\left(e _ {i , k}\\right)} \\left(\\mathbf {x} _ {k} ^ {\\mathcal {Q}} \\mathbf {W} ^ {V}\\right), \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.845, + 0.802, + 0.861 + ], + "angle": 0, + "content": "where the attention score \\( e_{i,j} \\) is computed as:" + }, + { + "type": "equation", + "bbox": [ + 0.595, + 0.868, + 0.892, + 0.905 + ], + "angle": 0, + "content": "\\[\ne _ {i, j} = \\frac {\\left(\\mathbf {x} _ {i} ^ {\\mathcal {P}} \\mathbf {W} ^ {Q}\\right) \\left(\\mathbf {x} _ {j} ^ {\\mathcal {Q}} \\mathbf {W} ^ {K}\\right) ^ {\\top}}{\\sqrt {d}}, \\tag {5}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19608" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.079, + 0.087, + 0.468, + 0.259 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.123, + 0.262, + 0.423, + 0.276 + ], + "angle": 0, + "content": "Figure 4. Structure of the Instance masking block." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.282, + 0.469, + 0.375 + ], + "angle": 0, + "content": "where \\(\\mathbf{W}^Q, \\mathbf{W}^K, \\mathbf{W}^V \\in \\mathbb{R}^{d \\times d}\\) are the respective projection weights for query, key and value. The same computation goes for \\(\\mathbf{Z}^Q\\). Benefiting from the cross-attention block, the superpoint features in one point cloud are aware of the geometric structure of the other one, which facilitates modeling the geometric consistency between two point clouds." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.375, + 0.47, + 0.606 + ], + "angle": 0, + "content": "Instance masking block. At last, this block consumes the cross-attention features \\(\\mathbf{X}^{\\mathcal{Q}}\\) of \\(\\hat{\\mathcal{Q}}\\) as well as the previous instance mask \\(\\mathbf{M}_{(t - 1)}^{\\mathcal{Q}}\\) to predict a refined instance mask \\(\\mathbf{M}_{(t)}^{\\mathcal{Q}}\\). We observe that two superpoints from different instances tend to be distant in the geodesic space. To this end, we design a geodesic self-attention mechanism by replacing the geometric structure embedding in Eq. (3) with a similar geodesic distance embedding to enhance the superpoint features. Please refer to the appendix for more details. The resultant superpoint features are denoted as \\(\\mathbf{Y}\\). At last, we adopt an MLP to predict a confidence score \\(u_{i,j}\\) for each neighbor \\(\\hat{\\mathbf{q}}_{i_j} \\in \\mathcal{N}_i^{\\mathcal{Q}}\\) indicating whether it belongs to the same instance as \\(\\hat{\\mathbf{q}}_i\\) based on the feature discrepancy between \\(\\mathbf{y}_i\\) and \\(\\mathbf{y}_{i_j}\\) and the geodesic distance embedding \\(\\mathbf{g}_{i,j}\\) between \\(\\hat{\\mathbf{q}}_i\\) and \\(\\hat{\\mathbf{q}}_{i_j}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.153, + 0.617, + 0.47, + 0.643 + ], + "angle": 0, + "content": "\\[\nu _ {i, j} = \\sigma \\left(\\operatorname {M L P} \\left(\\left[ \\mathbf {y} _ {i j} - \\mathbf {y} _ {i}; \\mathbf {g} _ {i, j} \\right]\\right)\\right), \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.653, + 0.47, + 0.705 + ], + "angle": 0, + "content": "where \\(\\sigma (\\cdot)\\) is the sigmoid function and \\([\\cdot ]\\) is the concatenation operator. At last, the confidence matrix \\(\\mathbf{U}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times k}\\) is converted into \\(\\mathbf{M}_{(t)}^{\\mathcal{Q}}\\) with a thresholding function:" + }, + { + "type": "equation", + "bbox": [ + 0.179, + 0.714, + 0.469, + 0.755 + ], + "angle": 0, + "content": "\\[\nm _ {i, j} ^ {\\mathcal {Q}} = \\left\\{ \\begin{array}{l l} - \\infty & u _ {i, j} < \\tau \\\\ 0 & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.469, + 0.856 + ], + "angle": 0, + "content": "where \\(\\tau\\) is the confidence threshold. Thanks to the instance mask, our model can effectively learn instance-aware superpoint features and extract accurate superpoint correspondences covering more instances. Furthermore, the instance masks also help extract instance-aware dense point correspondences as described in Sec. 4.2." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Superpoint matching. We extract superpoint correspondences \\(\\hat{\\mathcal{C}}\\) by matching the superpoint features from the last cross-attention block. As in [38], we select the top \\(N_{c}\\) su" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.892, + 0.122 + ], + "angle": 0, + "content": "perpoint pairs with the highest cosine feature similarity as the superpoint correspondences." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.132, + 0.779, + 0.146 + ], + "angle": 0, + "content": "4.2. Instance Candidate Generation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.155, + 0.892, + 0.306 + ], + "angle": 0, + "content": "After obtaining the superpoint correspondences, we then refine them to dense point correspondences at the fine level. Previous methods [38, 54] opt to match the points within the local patches of two matched superpoints with an optimal transport layer [40]. Nonetheless, the local correspondences extracted in this manner often cluster closely, which could lead to unstable pose estimation as noted in [25]. This is aggravated in multi-instance registration, especially in cluttered scenes, as each instance is typically small and thus its pose cannot be globally optimized as in [38]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.307, + 0.893, + 0.581 + ], + "angle": 0, + "content": "To address this issue, we propose to extract dense point correspondences within the instance scope by leveraging the instance masks from the coarse level. For each superpoint correspondence \\(\\hat{\\mathcal{C}}_k = (\\hat{\\mathbf{p}}_i,\\hat{\\mathbf{q}}_j)\\), we collect their neighboring superpoints \\(\\mathcal{N}_i^{\\mathcal{P}}\\) and \\(\\mathcal{N}_j^{\\mathcal{Q}}\\). The superpoints from different instances of \\(\\hat{\\mathbf{q}}_j\\) are removed from \\(\\mathcal{N}_j^{\\mathcal{Q}}\\) based on the instance mask \\(\\mathbf{M}_j\\). The points in the local patches of all superpoints in \\(\\mathcal{N}_i^{\\mathcal{P}}\\) and \\(\\mathcal{N}_j^{\\mathcal{Q}}\\) imply a potential occurrence of \\(\\mathcal{P}\\) in \\(\\mathcal{Q}\\), i.e., an instance candidate, denoted as \\(\\mathcal{I}_k\\). Next, instance-wise point correspondences are extracted within \\(\\mathcal{I}_k\\) with an optimal transport layer and mutual top-\\(k\\) selection following [38], denoted as \\(\\mathcal{C}_k\\). At last, we estimate a pose \\(\\mathbf{T}_k = \\{\\mathbf{R}_k,\\mathbf{t}_k\\}\\) for \\(\\mathcal{I}_k\\) by solving Eq. (1) with weighted SVD [8]. Thanks to the powerful instance-aware geometric transformer, an instance candidate can cover a relatively large portion of an instance, with few points from the background or other instances, so the poses obtained in this step have already been very accurate." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.591, + 0.816, + 0.605 + ], + "angle": 0, + "content": "4.3. Candidate Selection and Refinement" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.614, + 0.892, + 0.688 + ], + "angle": 0, + "content": "As several superpoint correspondences could belong to the same instance, there are commonly duplicated instances in the instance candidates. For this reason, we further design a simple but effective algorithm for duplicate removal and candidate refinement." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.892, + 0.75 + ], + "angle": 0, + "content": "Inspired by non-maximum suppression (NMS) [39], we first sort the instance candidates by the inlier ratio on the global point correspondences \\(\\mathcal{C} = \\bigcup_{i=1}^{N_c} \\mathcal{C}_i\\). The inlier ratio of the instance candidate \\(\\mathcal{I}_k\\) is:" + }, + { + "type": "equation", + "bbox": [ + 0.554, + 0.76, + 0.892, + 0.799 + ], + "angle": 0, + "content": "\\[\n\\gamma_ {k} = \\frac {1}{| \\mathcal {C} |} \\sum_ {(\\mathbf {p}, \\mathbf {q}) \\in \\mathcal {C}} [ [ \\| \\mathbf {R} _ {k} \\mathbf {p} + \\mathbf {t} _ {k} - \\mathbf {q} \\| < \\tau_ {2} ] ], \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.81, + 0.892, + 0.902 + ], + "angle": 0, + "content": "where \\(\\llbracket \\cdot \\rrbracket\\) is the Iverson bracket and \\(\\tau_{2}\\) is the acceptance radius. Next, we select the instance candidate with the highest inlier ratio as the anchor candidate. All remaining candidates similar with the anchor are merged with it and removed from future computation. We define the similarity between two candidates \\(\\mathcal{I}_i\\) and \\(\\mathcal{I}_j\\) by the average distance" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19609" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.078, + 0.092, + 0.364, + 0.107 + ], + "angle": 0, + "content": "(ADD) [21] between their estimated poses:" + }, + { + "type": "equation", + "bbox": [ + 0.188, + 0.114, + 0.469, + 0.145 + ], + "angle": 0, + "content": "\\[\ns _ {i, j} = 1 - \\frac {\\operatorname {A D D} \\left(\\mathbf {T} _ {i} , \\mathbf {T} _ {j}\\right)}{r}, \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.152, + 0.47, + 0.287 + ], + "angle": 0, + "content": "where \\( r \\) is the diameter of \\( \\mathcal{P} \\). And \\( \\mathcal{I}_i \\) and \\( \\mathcal{I}_j \\) are considered similar if \\( s_{i,j} \\) is above \\( \\tau_s \\). To merge two candidates, we combine their point correspondences and recompute the pose by solving Eq. (1). At last, the preserved pose is iteratively refined with the surviving inliers as in [5, 38], leading to a final instance registration. The anchor is then removed from future computation. The above process repeats until there are no candidates left and we omit the instance registrations with too few inliers." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.288, + 0.471, + 0.455 + ], + "angle": 0, + "content": "Compared to multi-model fitting methods [44, 55], the advantages of our MIRETR are two-fold. First, by learning instance-aware superpoint features, the influence from the background and other instances is minimized, thus the correspondences are more accurate and can cover more instances. Second, correspondence clustering-based methods tend to lose heavily-occluded instances as there are few correspondences on them, especially in cluttered scenes. On the contrary, our method can better recognize these hard instances as we bypass the clustering process by directly extracting instance candidates and merging similar ones." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.463, + 0.231, + 0.478 + ], + "angle": 0, + "content": "4.4. Loss Functions" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.485, + 0.47, + 0.592 + ], + "angle": 0, + "content": "We adopt three loss functions to train MIRETR: an overlap-aware circle loss [38] \\(\\mathcal{L}_{\\mathrm{circle}}\\) to supervise the superpoint features, a negative log-likelihood loss [40] \\(\\mathcal{L}_{\\mathrm{nll}}\\) to supervise the point matching, and a mask prediction loss [36] \\(\\mathcal{L}_{\\mathrm{mask}}\\) to supervise the instance masks. The overall loss is computed as \\(\\mathcal{L} = \\mathcal{L}_{\\mathrm{circle}} + \\mathcal{L}_{\\mathrm{nll}} + \\mathcal{L}_{\\mathrm{mask}}\\). Please refer to the supplementary material for more details." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.604, + 0.21, + 0.621 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.469, + 0.689 + ], + "angle": 0, + "content": "We evaluate MIRETR on indoor Scan2CAD [2, 44, 55], industrial ROBI [52] and synthetic ShapeNet [10] benchmarks. And we also introduce the implementation details and more experiments in the supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.469, + 0.795 + ], + "angle": 0, + "content": "Baselines. We compare with three state-of-the-art point cloud correspondence methods, FCGF [14], CoFiNet [54] and GeoTransformer [38], and four recent multi-model fitting methods, T-linkage [33], RansaCov [34], ECC [44], and PointCLM [55]. The point cloud correspondence methods and the multi-model fitting methods are pairwise integrated for a comprehensive comparison." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Metrics. Following [44, 55], we evaluate our method with three registration metrics: (1) Mean Recall (MR), the ratio of registered instances over all ground-truth instances, (2) Mean Precision (MP), the ratio of registered instances over all predicted instances, and (3) Mean \\( F_{1} \\) score (MF), the harmonic mean of MP and MR. We also report Inlier Ratio (IR), the ratio of inliers over all extracted correspondences." + }, + { + "type": "table", + "bbox": [ + 0.503, + 0.089, + 0.89, + 0.306 + ], + "angle": 0, + "content": "
ModelIR(%)MR(%)MP(%)MF(%)
FCGF [14] + T-Linkage [33]54.7522.7632.15
FCGF [14] + RansaCov [34]36.2773.5045.0155.83
FCGF [14] + PointCLM [55]86.9970.0577.60
FCGF [14] + ECC [44]92.6073.7982.13
CoFiNet [54] + T-Linkage [33]28.175.098.62
CoFiNet [54] + RansaCov [34]18.5238.2913.6920.16
CoFiNet [54] + PointCLM [55]36.1524.7029.34
CoFiNet [54] + ECC [44]57.2617.2426.50
GeoTransformer [38] + T-Linkage [33]72.6844.8055.43
GeoTransformer [38] + RansaCov [34]44.0278.8467.1672.53
GeoTransformer [38] + PointCLM [55]82.8181.9082.35
GeoTransformer [38] + ECC [44]94.6374.8383.57
MIRETR (ours) + T-Linkage [33]77.1246.0457.65
MIRETR (ours) + RansaCov [34]84.7871.3477.48
MIRETR (ours) + PointCLM [55]56.5991.8591.0891.46
MIRETR (ours) + ECC [44]96.5289.0392.62
MIRETR (ours, full pipeline)95.7091.2193.40
" + }, + { + "type": "table_caption", + "bbox": [ + 0.534, + 0.31, + 0.856, + 0.323 + ], + "angle": 0, + "content": "Table 1. Evaluation results on Scan2CAD benchmark." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.332, + 0.742, + 0.346 + ], + "angle": 0, + "content": "5.1. Evaluations on Scan2CAD" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.355, + 0.892, + 0.505 + ], + "angle": 0, + "content": "Dataset. Scan2CAD [2] is a scene-to-CAD alignment dataset build upon ScanNet [15] and ShapeNet [10]. It consists of 1506 scenes from ScanNet annotated with 14225 CAD models from ShapeNet and their poses in the scenes. Following [55], we replace the objects in the scenes with the corresponding aligned CAD models. We select the scene-model pairs which the scene contain multiple instances of the model for multi-instance registration. As last, we obtain 2184 point cloud pairs and use \\(70\\%\\) pairs for training, \\(10\\%\\) for validation and \\(20\\%\\) for testing." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.506, + 0.892, + 0.597 + ], + "angle": 0, + "content": "Quantitative results. As shown in Tab. 1, our MIRETR achieves consistent improvements over the baseline correspondence models. Notably, our method surpasses the previous best GeoTransformer on IR by 12 percentage points (pp). When coupled with PointCLM, it outperforms GeoTransformer by over 9 pp on the three registration metrics." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.597, + 0.892, + 0.717 + ], + "angle": 0, + "content": "Moreover, our full pipeline surpasses all models with the baseline multi-model fitting methods. Although the ECC-based model performs slightly better than full MIRETR on MR, its MP is significantly worse. This indicates that ECC achieves high MR by predicting more registrations, which is impractical in real-world applications. And our method outperforms PointCLM on all three registration metrics, which demonstrates the strong effectiveness of our method." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.727, + 0.702, + 0.741 + ], + "angle": 0, + "content": "5.2. Evaluations on ROBI" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.886 + ], + "angle": 0, + "content": "Dataset. ROBI [52] is a recent dataset for industrial bin-picking. It includes 7 reflective metallic industrial objects and 63 bin-picking scenes. Each scene contains cluttered instances of one industrial object. For each point cloud pair, the scene point cloud is backprojected from a depth image and the model point cloud is sampled from the CAD model of its corresponding industrial object. We obtain 4880 pairs in total, and we split the scenes for training, validation and testing according to the ratio of \\( 6:1:2 \\) for each object." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.887, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Quantitative results. As in Tab. 2, our method outper" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "19610" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.087, + 0.181, + 0.165 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.205, + 0.087, + 0.304, + 0.165 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.23, + 0.167, + 0.278, + 0.177 + ], + "angle": 0, + "content": "Inst:12" + }, + { + "type": "image", + "bbox": [ + 0.328, + 0.087, + 0.428, + 0.164 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.358, + 0.167, + 0.398, + 0.177 + ], + "angle": 0, + "content": "Inst:3" + }, + { + "type": "image", + "bbox": [ + 0.452, + 0.087, + 0.552, + 0.164 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.482, + 0.167, + 0.522, + 0.177 + ], + "angle": 0, + "content": "Inst:9" + }, + { + "type": "image", + "bbox": [ + 0.564, + 0.087, + 0.72, + 0.164 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.611, + 0.167, + 0.669, + 0.177 + ], + "angle": 0, + "content": "IR:39.42%" + }, + { + "type": "image", + "bbox": [ + 0.731, + 0.087, + 0.886, + 0.165 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.78, + 0.167, + 0.838, + 0.177 + ], + "angle": 0, + "content": "IR:54.21%" + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.179, + 0.18, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.204, + 0.179, + 0.304, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.23, + 0.259, + 0.278, + 0.269 + ], + "angle": 0, + "content": "Inst:22" + }, + { + "type": "image", + "bbox": [ + 0.329, + 0.179, + 0.428, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.358, + 0.259, + 0.398, + 0.269 + ], + "angle": 0, + "content": "Inst:4" + }, + { + "type": "image", + "bbox": [ + 0.452, + 0.179, + 0.552, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.479, + 0.259, + 0.524, + 0.27 + ], + "angle": 0, + "content": "Inst:11" + }, + { + "type": "image", + "bbox": [ + 0.578, + 0.179, + 0.706, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.611, + 0.26, + 0.668, + 0.27 + ], + "angle": 0, + "content": "IR:49.91%" + }, + { + "type": "image", + "bbox": [ + 0.745, + 0.179, + 0.874, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.78, + 0.26, + 0.838, + 0.27 + ], + "angle": 0, + "content": "IR:56.90%" + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.272, + 0.182, + 0.352 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.107, + 0.371, + 0.153, + 0.382 + ], + "angle": 0, + "content": "(a) Input" + }, + { + "type": "image", + "bbox": [ + 0.203, + 0.273, + 0.304, + 0.352 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.23, + 0.354, + 0.278, + 0.364 + ], + "angle": 0, + "content": "Inst:18" + }, + { + "type": "image_caption", + "bbox": [ + 0.209, + 0.371, + 0.298, + 0.381 + ], + "angle": 0, + "content": "(b) Ground Truth" + }, + { + "type": "image", + "bbox": [ + 0.328, + 0.273, + 0.429, + 0.351 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.358, + 0.354, + 0.398, + 0.364 + ], + "angle": 0, + "content": "Inst:4" + }, + { + "type": "image_caption", + "bbox": [ + 0.344, + 0.371, + 0.412, + 0.381 + ], + "angle": 0, + "content": "(c) GeoTrans" + }, + { + "type": "image", + "bbox": [ + 0.452, + 0.273, + 0.553, + 0.351 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.482, + 0.354, + 0.522, + 0.364 + ], + "angle": 0, + "content": "Inst:8" + }, + { + "type": "image_caption", + "bbox": [ + 0.48, + 0.371, + 0.525, + 0.381 + ], + "angle": 0, + "content": "(d) Ours" + }, + { + "type": "image", + "bbox": [ + 0.565, + 0.273, + 0.716, + 0.351 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.611, + 0.354, + 0.668, + 0.364 + ], + "angle": 0, + "content": "IR:48.03%" + }, + { + "type": "image_caption", + "bbox": [ + 0.59, + 0.371, + 0.69, + 0.381 + ], + "angle": 0, + "content": "(e) GeoTrans (corr)" + }, + { + "type": "image", + "bbox": [ + 0.732, + 0.273, + 0.884, + 0.351 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.78, + 0.354, + 0.838, + 0.364 + ], + "angle": 0, + "content": "IR:72.40%" + }, + { + "type": "image_caption", + "bbox": [ + 0.771, + 0.371, + 0.845, + 0.381 + ], + "angle": 0, + "content": "(f) Ours (corr)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.386, + 0.891, + 0.428 + ], + "angle": 0, + "content": "Figure 5. Registration results on ROBI benchmark. We visualize the successfully registered instances in (c) and (d). MIRETR registers more instances in the cluttered scenes (the \\(2^{\\text{nd}}\\) and the \\(3^{\\text{rd}}\\) rows) and with incomplete geometry (all three rows). And it extracts more accurate correspondences benefiting from the instance-aware correspondence learning mechanism." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.434, + 0.466, + 0.603 + ], + "angle": 0, + "content": "
ModelIR(%)MR(%)MP(%)MF(%)
CoFiNet [54] + T-Linkage [33]10.351.340.720.93
CoFiNet [54] + RansaCov [34]1.251.391.31
CoFiNet [54] + PointCLM [55]1.172.111.50
CoFiNet [54] + ECC [44]3.218.504.66
GeoTransformer [38] + T-Linkage [33]39.647.714.575.73
GeoTransformer [38] + RansaCov [34]8.9913.5810.81
GeoTransformer [38] + PointCLM [55]13.9826.6418.33
GeoTransformer [38] + ECC [44]18.5530.9923.20
MIRETR (ours) + T-Linkage [33]45.1412.0410.4711.20
MIRETR (ours) + RansaCov [34]14.1426.2918.38
MIRETR (ours) + PointCLM [55]18.6840.1125.48
MIRETR (ours) + ECC [44]24.6534.8528.91
MIRETR (ours, full pipeline)38.5141.1939.80
" + }, + { + "type": "table_caption", + "bbox": [ + 0.128, + 0.608, + 0.417, + 0.62 + ], + "angle": 0, + "content": "Table 2. Evaluation results on ROBI benchmark." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.628, + 0.468, + 0.733 + ], + "angle": 0, + "content": "forms the baseline correspondence methods by a large margin on all four metrics. Compared to Scan2CAD, ROBI is more challenging due to the more cluttered scenes, where instance-aware information is more important. Benefiting from the instance-aware geometric transformer module, our method extracts reliable instance-aware correspondences, which contributes to more accurate instance registrations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.468, + 0.87 + ], + "angle": 0, + "content": "Our full model achieves significant improvements over the ECC-based model on MR, MP and MF. The PointCLM-based model achieves comparable MP with the full model, but significantly worse MR, which means it can register only several easy instances but misses most heavily-occluded instances. Specifically, it can register on average only 6.2 instances per scene, while the number of our method is 13.7. Our method achieves both high MR and MP, showing strong robustness in cluttered scenes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.468, + 0.899 + ], + "angle": 0, + "content": "Qualitative results. Fig. 5 visualizes the registration results of GeoTransformer and MIRETR. Our method can" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.433, + 0.627, + 0.53 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.631, + 0.433, + 0.757, + 0.53 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.763, + 0.433, + 0.889, + 0.53 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.532, + 0.629, + 0.629 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.507, + 0.63, + 0.625, + 0.64 + ], + "angle": 0, + "content": "(a) Anchor's neighbors" + }, + { + "type": "image", + "bbox": [ + 0.632, + 0.532, + 0.758, + 0.629 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.637, + 0.63, + 0.755, + 0.64 + ], + "angle": 0, + "content": "(b) Ground Truth Mask" + }, + { + "type": "image", + "bbox": [ + 0.762, + 0.532, + 0.889, + 0.629 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.764, + 0.63, + 0.89, + 0.64 + ], + "angle": 0, + "content": "(c) Our Prediceted Mask" + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.642, + 0.891, + 0.698 + ], + "angle": 0, + "content": "Figure 6. Visualizations of the predicted instance masks. The anchor superpoint (patch) is in red and the selected neighbors are color-coded. Our method can effectively reject the patches outside the interested instance while preserving most of those inside." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.703, + 0.891, + 0.763 + ], + "angle": 0, + "content": "register more instances in cluttered scenes (see the \\(2^{\\text{nd}}\\) and the \\(3^{\\text{rd}}\\) rows) and with severe geometric deficiency (see all three rows). And MIRETR attains more high-quality correspondences thanks to our instance-aware design." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.765, + 0.891, + 0.884 + ], + "angle": 0, + "content": "We further visualize the predicted instance masks Fig. 6. The instance masks effectively reject the patches out of the interested instance while preserving most of those inside. Specifically, our method achieves the instance mIoU of 69.26 pp while the result of the model without masking is merely 38.13 pp. The high-quality masks allow us to effectively encode intra-instance context and contribute to accurate registrations." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.886, + 0.89, + 0.901 + ], + "angle": 0, + "content": "Fig. 7 compares the results under different overlap ratios." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "19611" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.087, + 0.473, + 0.265 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.078, + 0.266, + 0.468, + 0.28 + ], + "angle": 0, + "content": "Figure 7. Results in different overlap levels on ROBI benchmark." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.288, + 0.47, + 0.35 + ], + "angle": 0, + "content": "MIRETR consistently outperforms the baselines at all overlap levels, and the improvements are more significant when the overlap ratio is below \\(50\\%\\). This proves the strong capability of our method to handle low-overlap instances." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.359, + 0.308, + 0.376 + ], + "angle": 0, + "content": "5.3. Evaluations on ShapeNet" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.383, + 0.47, + 0.534 + ], + "angle": 0, + "content": "Dataset. ShapeNet [10] is a large CAD model dataset which contains 51300 models from 55 categories. We use the models from first 30 categories for training and those from the rest 25 categories for testing to evaluate the generality to novel categories. We randomly sample at most 500 models from each category to avoid class imbalance. For each point cloud pair, the model point cloud is a random CAD model and the scene one is constructed by applying \\(4\\sim 16\\) random poses on the model. At last, we obtain 8634 pairs for training, 900 for validation, and 7683 for testing." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.535, + 0.471, + 0.746 + ], + "angle": 0, + "content": "Quantitative results. As shown in Tab. 3, our MIRETR achieves the best results on all four metrics, surpassing the baselines by a large margin. GeoTransformer significantly outperforms CoFiNet, which proves the importance of geometric structure to achieving generality. And our method achieves improvements of more than 10 pp over GeoTransformer on all registration metrics with PointCLM and ECC. Thanks to the instance-ware geometric transformer, the correspondences extracted by our method provide strong instance information, facilitating the correspondence clustering process. At last, our full model surpasses the previous best ECC-based baseline by around 2 pp on MR, 11 pp on MP and 7 pp on MF, demonstrating the strong generality of MIRETR to unseen objects." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.757, + 0.241, + 0.771 + ], + "angle": 0, + "content": "5.4. Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.47, + 0.903 + ], + "angle": 0, + "content": "We conduct extensive ablation studies on ROBI benchmark to better understand our design choices in Tab. 4. We first ablate the instance-aware point matching and extract point correspondences within only the patches of the superpoint correspondences in Tab. 4 (b), which is significantly worse than the full model. The poses estimated by this method is unstable due to clustered correspondences, thus the duplicated candidates cannot be effectively removed by NMS." + }, + { + "type": "table", + "bbox": [ + 0.503, + 0.089, + 0.89, + 0.259 + ], + "angle": 0, + "content": "
ModelIR(%)MR(%)MP(%)MF(%)
CoFiNet [54] + T-Linkage [33]4.593.243.79
CoFiNet [54] + RansaCov [34]39.537.355.336.17
CoFiNet [54] + PointCLM [55]23.4019.6621.36
CoFiNet [54] + ECC [44]41.4926.6032.41
GeoTransformer [38] + T-Linkage [33]27.6826.4027.02
GeoTransformer [38] + RansaCov [34]69.6541.8648.1644.78
GeoTransformer [38] + PointCLM [55]68.0969.0968.58
GeoTransformer [38] + ECC [44]78.0364.0870.37
MIRETR (ours) + T-Linkage [33]29.4028.6729.03
MIRETR (ours) + RansaCov [34]45.6346.8546.23
MIRETR (ours) + PointCLM [55]77.1385.6385.8185.71
MIRETR (ours) + ECC [44]92.5682.0887.01
MIRETR (ours, full pipeline)94.9593.9494.44
" + }, + { + "type": "table_caption", + "bbox": [ + 0.54, + 0.264, + 0.851, + 0.277 + ], + "angle": 0, + "content": "Table 3. Evaluation results on ShapeNet benchmark." + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.28, + 0.887, + 0.356 + ], + "angle": 0, + "content": "
ModelIR(%)MR(%)MP(%)MF(%)
(a) full MIRETR45.1438.5141.1939.80
(b) w/o instance-aware point matching40.5218.1527.5421.88
(c) w/o instance masking block36.7817.0745.3724.80
(d) w/o both38.8114.1327.4418.65
(e) w/ global attention25.987.7218.8610.96
" + }, + { + "type": "table_caption", + "bbox": [ + 0.555, + 0.361, + 0.836, + 0.374 + ], + "angle": 0, + "content": "Table 4. Ablation studies on ROBI benchmark." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.379, + 0.892, + 0.576 + ], + "angle": 0, + "content": "Next, we remove the instance masking blocks in Tab. 4 (c) and the instance-aware point matching gathers the points from all neighbor superpoints. This model achieves a good MP, but a significantly worse MR, which means it can register only few instances (2.9 vs. 13.7 average instances per scene). We then ablate both modules in Tab. 4 (d), which further degrades the performance. At last, we replace the geometric encoding block with the global geometric self-attention [38] in Tab. 4 (e), which achieves the worst results. This indicates that the superpoint features can be polluted if global context is encoded. These results have proven the strong efficacy of our designs. More ablation studies are presented in the supplementary material." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.589, + 0.619, + 0.605 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.614, + 0.892, + 0.84 + ], + "angle": 0, + "content": "We have proposed MIRETR, a coarse-to-fine method to extract instance-aware correspondences for multi-instance registration. At the coarse level, an instance-aware geometric transformer module jointly learns instance-aware superpoint features and predicts per-instance masks. At the fine level, the superpoint correspondences are extended to instance candidates according to the instance masks, where instance-wise point correspondences are extracted. At last, we devise a simple but effective candidate selection and refinement algorithm to obtain the final registrations, bypassing the need of multi-model fitting methods. Extensive experiments on three public benchmarks have demonstrated the efficacy of our method. For future work, we would like to extend MIRETR to multi-modal multi-instance registration to boost more applications." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Acknowledgement. This work is in part supported by the NSFC (62325211, 62132021, 62102435), the Major Program of Xiangjiang Laboratory (23XJ01009), and the National Key R&D Program of China (2018AAA0102200)." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19612" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.175, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.17 + ], + "angle": 0, + "content": "[1] Yasuhiro Aoki, Hunter Goforth, Rangaprasad Arun Srivatsan, and Simon Lucey. 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In ECCV, pages 595-611, 2022. 1, 2, 6, 7, 8" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.092, + 0.892, + 0.545 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "19614" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/2ddc8710-2e01-4d04-9c1a-627c67a89c1a_origin.pdf b/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/2ddc8710-2e01-4d04-9c1a-627c67a89c1a_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..aa482d4f78f20d5e7ebbc0f1f4e12c9aac5a432d --- /dev/null +++ b/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/2ddc8710-2e01-4d04-9c1a-627c67a89c1a_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:3d273985ce8e40593dcefc5d361249562014f3f2b9c2942ffd7ece9872d0f399 +size 8661463 diff --git a/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/full.md b/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/full.md new file mode 100644 index 0000000000000000000000000000000000000000..b1aa3c6bb16e4c0d0dfaf2f9483b95d2361e69d8 --- /dev/null +++ b/2024/Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes/full.md @@ -0,0 +1,403 @@ +# Learning Instance-Aware Correspondences for Robust Multi-Instance Point Cloud Registration in Cluttered Scenes + +Zhiyuan Yu1 Zheng Qin2 Lintao Zheng1 Kai Xu1* + +$^{1}$ National University of Defense Technology + +2 Defense Innovation Institute, Academy of Military Sciences + +# Abstract + +Multi-instance point cloud registration estimates the poses of multiple instances of a model point cloud in a scene point cloud. Extracting accurate point correspondences is to the center of the problem. Existing approaches usually treat the scene point cloud as a whole, overlooking the separation of instances. Therefore, point features could be easily polluted by other points from the background or different instances, leading to inaccurate correspondences oblivious to separate instances, especially in cluttered scenes. In this work, we propose MIRETR, Multi-Instance REgistration TRansformer, a coarse-to-fine approach to the extraction of instance-aware correspondences. At the coarse level, it jointly learns instance-aware superpoint features and predicts per-instance masks. With instance masks, the influence from outside of the instance being concerned is minimized, such that highly reliable superpoint correspondences can be extracted. The superpoint correspondences are then extended to instance candidates at the fine level according to the instance masks. At last, an efficient candidate selection and refinement algorithm is devised to obtain the final registrations. Extensive experiments on three public benchmarks demonstrate the efficacy of our approach. In particular, MIRETR outperforms the state of the arts by 16.6 points on $F_{1}$ score on the challenging ROBI benchmark. Code and models are available at https://github.com/zhiyuanYU134/MIRETR. + +# 1. Introduction + +Point cloud registration aims at estimating a rigid transformation that aligns two point clouds. In real-world application scenarios such as robotic bin picking, there is often the requirement of multi-instance registration where the point cloud of a model needs to be registered against multiple instances of the model in the target scene. Multi-instance point cloud registration is challenging due to the unknown number of instances and inter-instance occlusions + +![](images/4e3233d8ef36aaf966956864326cf4843320fcc8584ebcc900975e170f9989a3.jpg) + +![](images/00be69d5bf270e5c38962f7ae76f9870d92c0d3d8b7e6c7ddb2e2018720a0531.jpg) + +![](images/5d5753b9c79caf849264974067eb6e9ab1282f7bd930789ee42af60941679459.jpg) +GeoTransformer +Figure 1. MIRETR significantly improves the multi-instance registration results in cluttered scenes compared to the state-of-the-art GeoTransformer [38]. Benefiting from the instance-aware correspondences, our method can generate more accurate registrations (see the yellow boxes) and register the heavily-occluded instances with severe geometric deficiency (see the red boxes). + +![](images/58acc35d0b23e9c36e8cc7256f026a2e6cc6e4b36fa6eb0703816a6b5c4c0e26.jpg) +MIRETR + +especially in a cluttered scene. + +Existing approaches to multi-instance registration are mostly two-stage: They first extract point correspondences between the model and the scene point clouds and then recover per-instance transformations with multi-model fitting [28, 44, 55]. Clearly, the performance of such approach highly depends on the quality of the correspondences. Unlike pair-wise registration that can be pinned down by a small number of correspondences, multi-instance registration poses unique challenges. First, the correspondences should widely spread over the scene point cloud to cover as many instances as possible so that more instances can be found and registered. Second, the correspondences should + +be accurately clustered into individual instances to estimate per-instance pose transformations. + +Existing point correspondence methods can be broadly classified into keypoint-based and keypoint-free ones. Albeit successful in pairwise registration, these methods fail to effectively tackle the aforementioned challenges. On the one hand, keypoint-based methods [4, 14, 25] first detect keypoints and then match them to form correspondences. In the multi-instance setting, however, it is common that an instance is severely occluded so that too few keypoints can be detected to guarantee a successful registration. + +On the other hand, keypoint-free methods [38, 54] bypass keypoint detection with a coarse-to-fine pipeline. They first extract correspondences between sparse superpoints and then refine them to dense point correspondences. To achieve reliable superpoint matching, they encode global context with feature correlation [54] or geometric structure [38] to learn distinctive superpoint features. When used in multi-instance registration, such approach may overlook the separation of individual instances and lead to the following two drawbacks. First, the superpoint features of an instance may be contaminated by the global context from the background or other instances, making the extracted features less informative. Thus, the features of a severely occluded instance could be overwhelmed by those more complete neighboring ones, making the occluded instances hard to registered (see Fig. 1 (left)). Second, they cannot discriminate correspondences into different instances and have to rely on multi-model fitting [28, 44, 55] to cluster correspondences. Multi-model fitting needs to sample numerous hypotheses and finds difficulty in handling heavy occlusion. + +We propose MIRETR, Multi-Instance REgistration Transformer, which learns to extract instance-aware correspondences in a coarse-to-fine fashion. Our key motivation is to restrict the contextual feature encoding within the instance scope. An Instance-aware Geometric Transformer module is devised to jointly extract reliable superpoint features and predict instance masks in the scene. We resolve this chicken-and-egg problem with an iterative process. In each iteration, we first encode intra-instance geometric structure based on the instance mask of the previous iteration and then learn geometric consistency between the model and the scene. Next, the instance masks are refined based on the instance-aware features. As the iteration goes, the superpoint features gradually improve with increasingly relevant context and accurate instance masks, resulting in reliable registrations even for heavily-occluded instances (see Fig. 1 (right)). + +Having obtained superpoint correspondences, we extend them to instance candidates based on instance masks. This allows us to directly extract instance-wise point correspondences and estimate a transformation for each instance candidate. An efficient candidate selection and refinement + +method is proposed to eliminate duplicated instances and obtain the final registrations. Thanks to the instance-aware correspondences, our method bypasses the need of multimodel fitting, achieving superior efficiency and accuracy. Extensive experiments on three benchmarks [2, 10, 52] demonstrate the efficacy of our method. Our method surpasses the previous state-of-the-art methods [38, 55] by 16.6 points on $\mathrm{F_1}$ score on the cluttered ROBI benchmark. Our main contributions include: + +- A multi-instance point cloud registration method which extracts instance-wise correspondences and estimates transformations without multi-model fitting. +- An instance-aware geometric transformer module which jointly learns instance-aware superpoint features and predicts instance masks. +- An efficient instance candidate selection and refinement method which removes duplicated candidates and generates the final registrations. + +# 2. Related work + +Point cloud registration. State-of-the-art point cloud registration methods can be categorized into direct registration methods and correspondence-based methods. Direct registration methods [1, 18, 26, 48, 49, 51, 53] use a neural network to estimate the transformation in an end-to-end manner. Correspondence-based methods [4, 14, 16, 17, 19, 25, 38, 54] extract point correspondences and estimate the rigid transformation with a robust pose estimator. Early point correspondence methods [4, 25] adopt a detect-then-match pipeline, where keypoints are first detected and then matched. Recent advances [38, 54] have bypassed keypoint detection by extracting correspondences in a coarse-to-fine fashion. However, existing methods mainly focus on pairwise registration and little attention has been paid to multi-instance registration, which faces new challenges such as unknown number of instances and heavy intra-instance occlusion. In this paper, we fill this gap by directly extracting instance-aware correspondences. + +Multi-model fitting. Multi-model fitting aims at recovering multiple models from noisy data, which is an important step in multi-instance registration. Multi-model fitting methods can be classified into RANSAC-based methods and clustering-based methods. RANSAC-based methods [6, 7, 27, 28] adopt a hypothesize-and-verify manner to sequentially fit multiple models. Clustering-based methods [33-35, 44, 55] sample a huge set of hypotheses and cluster the correspondences according to their residuals under these hypotheses. However, these methods suffer from huge memory usage or long convergence time. In this work, we achieve accurate and efficient multi-instance registration without multi-model fitting. + +Open-set pose estimation. Model retrieval [2, 3, 8, 9, 13, 20, 24, 29] and image-based pose estimation [11, 12, + +22, 23, 31, 32, 37, 41-43, 47, 50] are two highly-related tasks to multi-instance registration. Model retrieval aims at estimating the 9-DoF pose parameters of the CAD models from a pre-built database that appears in a given scene. And image-based pose estimation recovers the 6-DoF poses for certain objects [12, 22, 23, 37, 41-43, 50] or categories [11, 31, 32, 47] in an RGB or RGB-D image. However, both tasks are based on the close-set assumption, where the training and testing data follow the same distribution. Model retrieval can only retrieve the CAD models in the database while image-based pose estimation can only handle known objects or categories in the training data. On the contrary, multi-instance registration is an open-set problem. It is based on geometric matching and thus can generalize well to novel objects and categories. We discuss the generality of MIRETR in Sec. 5.3. + +# 3. Problem Statement + +Given a model point cloud $\mathcal{P} = \{\mathbf{p}_i\in \mathbb{R}^3 |i = 1,\dots,N\}$ and a scene point cloud $\mathcal{Q} = \{\mathbf{q}_i\in \mathbb{R}^3 |i = 1,\dots,M\}$ , where $\mathcal{Q}$ could contain multiple instances of $\mathcal{P}$ , the goal of multi-instance registration is to register all instances of $\mathcal{P}$ in $\mathcal{Q}$ . Specifically, $\mathcal{Q}$ is represented as $\mathcal{Q} = \mathcal{Q}_0\cup \mathcal{Q}_1\cup \ldots \cup \mathcal{Q}_K$ where $\mathcal{Q}_0$ is the background points and $\{\mathcal{Q}_1,\dots,\mathcal{Q}_K\}$ are the $K$ instances of $\mathcal{P}$ . For each instance $\mathcal{Q}_k$ , we estimate a 6-DoF pose $\mathbf{T}_k\in \mathcal{SE}(3)$ aligning $\mathcal{P}$ to $\mathcal{Q}_k$ , which consists of a 3D rotation $\mathbf{R}_k\in \mathcal{SO}(3)$ and a 3D translation $\mathbf{t}_k\in \mathbb{R}^3$ . To solve this problem, one usually first extracts a set of correspondences $\mathcal{C} = \{(\mathbf{p}_i,\mathbf{q}_i)|\mathbf{p}_i\in \mathcal{P},\mathbf{q}_i\in \mathcal{Q}\}$ between the two point clouds. The correspondences are then clustered into different groups $\{\mathcal{C}_1,\dots,\mathcal{C}_K\}$ , and each group recovers the pose of one instance by solving the following problem: + +$$ +\min _ {\mathbf {R} _ {k}, \mathbf {t} _ {k}} \sum_ {\left(\mathbf {p} _ {i}, \mathbf {q} _ {i}\right) \in \mathcal {C} _ {k}} \left\| \mathbf {R} _ {k} \cdot \mathbf {p} _ {i} + \mathbf {t} _ {k} - \mathbf {q} _ {i} \right\| _ {2} ^ {2}. \tag {1} +$$ + +This problem is very challenging as the number of instances is unknown and it is difficult to cluster the correspondences to the correct instances. In this work, we deal with this problem by extracting instance-aware correspondences. + +# 4. Method + +MIRETR extracts correspondences in a coarse-to-fine fashion similar to keypoint-free registration methods. The overall pipeline of our method is illustrated in Fig. 2. At the coarse level, we establish correspondences between down-sampled superpoints with an Instance-aware Geometric Transformer module (Sec. 4.1). At the fine level, each superpoint correspondence is extended to form an instance candidate, where instance-wise point correspondences are extracted for pose estimation (Sec. 4.2). At last, we merge similar instance candidates and refine the resultant poses to obtain the final registrations (Sec. 4.3). + +Given the input point clouds $\mathcal{P}$ and $\mathcal{Q}$ , we progressively downsample them into sparse superpoints, denoted as $\hat{\mathcal{P}}$ and $\hat{\mathcal{Q}}$ , using grid subsampling [45]. KPFCNN [45] is adopted to extract multi-level point features. Let us denote the features of $\mathcal{P}$ , $\mathcal{Q}$ , $\hat{\mathcal{P}}$ and $\hat{\mathcal{Q}}$ as $\mathbf{F}^{\mathcal{P}}$ , $\mathbf{F}^{\mathcal{Q}}$ , $\hat{\mathbf{F}}^{\mathcal{P}}$ and $\hat{\mathbf{F}}^{\mathcal{Q}}$ , respectively. Following [38, 54], each superpoint $\hat{\mathbf{p}}_i \in \hat{\mathcal{P}}$ ( $\hat{\mathbf{q}}_i \in \hat{\mathcal{Q}}$ ) is associated with a local patch $\mathcal{G}_i^{\mathcal{P}}$ ( $\mathcal{G}_i^{\mathcal{Q}}$ ) by the point-to-node partition strategy [30] where each point is assigned to its nearest superpoint. + +# 4.1. Instance-aware Geometric Transformer + +Given the superpoints $\hat{\mathcal{P}}$ and $\hat{\mathcal{Q}}$ , as well as their features $\hat{\mathbf{F}}^{\mathcal{P}}$ and $\hat{\mathbf{F}}^{\mathcal{Q}}$ , we first extract a set of superpoint correspondences whose local patches overlap with each other. Accurate superpoint matching relies on learning the geometric consistency between the two point clouds. To this end, previous works [38, 54] adopt transformer [46] to encode intra- and inter-point-cloud context in the global scope, as shown in Fig. 3 (a). Albeit successful in pairwise registration, this is problematic in multi-instance registration. In the scene point cloud, the superpoints from the background or other instances are de facto noises for modeling the geometric consistency and severely pollute the superpoint features. This becomes more severe in cluttered scenes. Considering an heavily-occluded instance, as its geometric structure is incomplete, the features of its superpoints could be easily overwhelmed by those from the background or nearby instances. As a result, it can hardly be registered. + +To address these issues, we propose to make the superpoint features instance-aware with a novel Instance-aware Geometric Transformer module. The key insight is to restrict the intra-point-cloud context encoding in the scene point cloud within each individual instance. To this end, we first extract the $k$ -nearest neighbors for each superpoint and conduct context aggregation within local regions. However, as shown in Fig. 3 (b), nearby superpoints do not necessarily reside in the same instance, and the feature pollution problem still exists. For this reason, we further design an instance masking mechanism by predicting an instance mask for each superpoint to select the neighbors in the same instance as it, and only aggregate the context among them. Fig. 3 (c) illustrates our instance masking mechanism. + +As shown in Fig. 2 (bottom), the instance-aware geometric transformer contains three blocks. First, a geometric encoding block encodes intra-instance geometric structure based on the instance masks. Next, a cross-attention block enhances the superpoint features by modeling inter-point-cloud geometric consistency. At last, an instance masking block predicts new instance masks with the instance-aware superpoint features. We adopt $N_{t}$ instance-aware geometric transformer modules to progressively refine the superpoint features and the instance masks. + +Geometric encoding block. This block encodes the intra- + +![](images/3b7392b09c5d7484addd23a021cbc0ab02df234b1100bb360f33a433492f01cb.jpg) + +![](images/52277569e5bee28670850f75f127e1a769c8fc1da2d6cf9a671fe014504afb6b.jpg) +Geometric Embedding +Geodesic Embedding + +![](images/198ab56572b2efb94d1dea75798e9498348125d5d6c19e0b4037aebedff7f7f3.jpg) +Figure 2. Overall pipeline of MIRETR. The backbone progressively downsamples two point clouds and extracts multi-level features. At the coarse level, the Instance-aware Geometric Transformer module extracts instance-aware superpoint features and establishes reliable superpoint correspondences. At the fine level, the superpoint correspondences are extended to instance candidates, where instance-wise point correspondences are extracted to estimate per-candidate poses. At last, a simple but effective candidate selection and refinement algorithm is adopted to generate the final registrations. + +![](images/72bd292598fd3f57848a6fdcfcf195b9ac2d811ebe60d3a447c403bfcc003618.jpg) + +![](images/b2fce553568a448c42ce0a4fffcda0bc34c065c03b263199c38bdd5d131f20c5.jpg) + +instance geometric context within each point cloud. Given an anchor superpoint $\hat{\mathbf{q}}_i\in \hat{\mathcal{Q}}$ , its $k$ -nearest superpoints $\mathcal{N}_i^{\mathcal{Q}} = \{\hat{\mathbf{q}}_{i_1},\dots,\hat{\mathbf{q}}_{i_k}\}$ , the input feature matrix $\mathbf{X}^{\mathcal{Q}}\in$ $\mathbb{R}^{|\hat{\mathcal{Q}} |\times d}$ , and the instance mask matrix $\mathbf{M}^{\mathcal{Q}}\in \mathbb{R}^{|\hat{\mathcal{Q}} |\times k}$ , the output feature matrix $\mathbf{Z}^{\mathcal{Q}}\in \mathbb{R}^{|\hat{\mathcal{Q}} |\times d}$ is computed as: + +$$ +\mathbf {z} _ {i} ^ {\mathcal {Q}} = \sum_ {j = 1} ^ {k} \frac {\exp \left(e _ {i , j}\right)}{\sum_ {l = 1} ^ {k} \exp \left(e _ {i , l}\right)} \left(\mathbf {x} _ {i _ {j}} ^ {\mathcal {Q}} \mathbf {W} ^ {V}\right), \tag {2} +$$ + +where the attention score $e_{i,j}$ is computed as: + +$$ +e _ {i, j} = \frac {\left(\mathbf {x} _ {i} ^ {\mathcal {Q}} \mathbf {W} ^ {\mathcal {Q}}\right) \left(\mathbf {x} _ {i j} ^ {\mathcal {Q}} \mathbf {W} ^ {K} + \mathbf {r} _ {i , j} \mathbf {W} ^ {R}\right) ^ {\top}}{\sqrt {d}} + m _ {i, j} ^ {\mathcal {Q}}, \tag {3} +$$ + +where $\mathbf{W}^Q, \mathbf{W}^K, \mathbf{W}^V, \mathbf{W}^R \in \mathbb{R}^{d \times d}$ are the projection weights for query, key, value and geometric embedding, respectively. $\mathbf{r}_{i,j}$ is the geometric structure embedding [38] encoding the transformation-invariant geometric information among the superpoints. For the instance mask $\mathbf{M}^Q$ , we set $m_{i,j}^Q = 0$ if $\hat{\mathbf{q}}_i$ and $\hat{\mathbf{q}}_{i_j}$ are in the same instance, while $m_{i,j}^Q = -\infty$ otherwise. $\mathbf{M}^Q$ is initialized with all zeros and refined by the instance masking block described later. Benefiting from the instance masks, the superpoint features are instance-aware by encoding the feature correlation and the geometric context within their belonging instances. For the computation in $\hat{\mathcal{P}}$ , we ignore the mask term in Eq. (3) and aggregate the features from all neighbors. + +Cross-attention block. After encoding the intra-instance geometric context, we further learn the inter-point-cloud geometric consistency with a cross-attention block inspired + +![](images/c78b66be2db0dedf0a3adb2415281fc822852d19df4a1b7986ae17ae8d9b739f.jpg) + +![](images/09a848ec848c99caed909ec564f47b049240a2c8ee2429b97cfe85cec67732ee.jpg) +(a) Global attention + +![](images/ee2a80afa38ded4b7aa7bd7bd407fba887b5b40cff38a87b2eca348f1c1c2ffe.jpg) + +![](images/8c993a1786492cbe44ecd9b922c68ae3aafe952b9213d852b298883392da4c54.jpg) +(b) Local attention + +![](images/d7e014254b2b4da6199dface4ee16daa2b19b3923f9abf661baeb54d11babae1.jpg) + +![](images/1a513c39b4baf070960b0f7d1d21541028d3b9b2680d9b1294156640f056c829.jpg) +(c) Instance-aware attention + +Figure 3. Comparison of (a) global attention, (b) local attention, and (c) instance-aware attention. The superpoints (patches) participating in the attention computation are color-coded. The anchor superpoints are in red. The $k$ -nearest neighbors of the anchor are enclosed by the purple line. + +by [38, 54]. Given the feature matrices $\mathbf{X}^{\mathcal{P}}\in \mathbb{R}^{|\hat{\mathcal{P}} |\times d}$ of $\hat{\mathcal{P}}$ and $\mathbf{X}^{\mathcal{Q}}\in \mathbb{R}^{|\hat{\mathcal{Q}} |\times d}$ of $\hat{\mathcal{Q}}$ from the geometric encoding block, the output feature matrix $\mathbf{Z}^{\mathcal{P}}\in \mathbb{R}^{|\hat{\mathcal{P}} |\times d}$ of $\hat{\mathcal{P}}$ is computed as: + +$$ +\mathbf {z} _ {i} ^ {\mathcal {P}} = \sum_ {j = 1} ^ {| \hat {\mathcal {Q}} |} \frac {\exp \left(e _ {i , j}\right)}{\sum_ {k = 1} ^ {| \hat {\mathcal {Q}} |} \exp \left(e _ {i , k}\right)} \left(\mathbf {x} _ {k} ^ {\mathcal {Q}} \mathbf {W} ^ {V}\right), \tag {4} +$$ + +where the attention score $e_{i,j}$ is computed as: + +$$ +e _ {i, j} = \frac {\left(\mathbf {x} _ {i} ^ {\mathcal {P}} \mathbf {W} ^ {Q}\right) \left(\mathbf {x} _ {j} ^ {\mathcal {Q}} \mathbf {W} ^ {K}\right) ^ {\top}}{\sqrt {d}}, \tag {5} +$$ + +![](images/3ada87a13994500c9e9f1cff06f7ac5ccc4037d8889262b56faad03e71531af0.jpg) +Figure 4. Structure of the Instance masking block. + +where $\mathbf{W}^Q, \mathbf{W}^K, \mathbf{W}^V \in \mathbb{R}^{d \times d}$ are the respective projection weights for query, key and value. The same computation goes for $\mathbf{Z}^Q$ . Benefiting from the cross-attention block, the superpoint features in one point cloud are aware of the geometric structure of the other one, which facilitates modeling the geometric consistency between two point clouds. + +Instance masking block. At last, this block consumes the cross-attention features $\mathbf{X}^{\mathcal{Q}}$ of $\hat{\mathcal{Q}}$ as well as the previous instance mask $\mathbf{M}_{(t - 1)}^{\mathcal{Q}}$ to predict a refined instance mask $\mathbf{M}_{(t)}^{\mathcal{Q}}$ . We observe that two superpoints from different instances tend to be distant in the geodesic space. To this end, we design a geodesic self-attention mechanism by replacing the geometric structure embedding in Eq. (3) with a similar geodesic distance embedding to enhance the superpoint features. Please refer to the appendix for more details. The resultant superpoint features are denoted as $\mathbf{Y}$ . At last, we adopt an MLP to predict a confidence score $u_{i,j}$ for each neighbor $\hat{\mathbf{q}}_{i_j} \in \mathcal{N}_i^{\mathcal{Q}}$ indicating whether it belongs to the same instance as $\hat{\mathbf{q}}_i$ based on the feature discrepancy between $\mathbf{y}_i$ and $\mathbf{y}_{i_j}$ and the geodesic distance embedding $\mathbf{g}_{i,j}$ between $\hat{\mathbf{q}}_i$ and $\hat{\mathbf{q}}_{i_j}$ : + +$$ +u _ {i, j} = \sigma \left(\operatorname {M L P} \left(\left[ \mathbf {y} _ {i j} - \mathbf {y} _ {i}; \mathbf {g} _ {i, j} \right]\right)\right), \tag {6} +$$ + +where $\sigma (\cdot)$ is the sigmoid function and $[\cdot ]$ is the concatenation operator. At last, the confidence matrix $\mathbf{U}\in \mathbb{R}^{|\hat{\mathcal{Q}} |\times k}$ is converted into $\mathbf{M}_{(t)}^{\mathcal{Q}}$ with a thresholding function: + +$$ +m _ {i, j} ^ {\mathcal {Q}} = \left\{ \begin{array}{l l} - \infty & u _ {i, j} < \tau \\ 0 & \text {o t h e r w i s e} \end{array} , \right. \tag {7} +$$ + +where $\tau$ is the confidence threshold. Thanks to the instance mask, our model can effectively learn instance-aware superpoint features and extract accurate superpoint correspondences covering more instances. Furthermore, the instance masks also help extract instance-aware dense point correspondences as described in Sec. 4.2. + +Superpoint matching. We extract superpoint correspondences $\hat{\mathcal{C}}$ by matching the superpoint features from the last cross-attention block. As in [38], we select the top $N_{c}$ su + +perpoint pairs with the highest cosine feature similarity as the superpoint correspondences. + +# 4.2. Instance Candidate Generation + +After obtaining the superpoint correspondences, we then refine them to dense point correspondences at the fine level. Previous methods [38, 54] opt to match the points within the local patches of two matched superpoints with an optimal transport layer [40]. Nonetheless, the local correspondences extracted in this manner often cluster closely, which could lead to unstable pose estimation as noted in [25]. This is aggravated in multi-instance registration, especially in cluttered scenes, as each instance is typically small and thus its pose cannot be globally optimized as in [38]. + +To address this issue, we propose to extract dense point correspondences within the instance scope by leveraging the instance masks from the coarse level. For each superpoint correspondence $\hat{\mathcal{C}}_k = (\hat{\mathbf{p}}_i,\hat{\mathbf{q}}_j)$ , we collect their neighboring superpoints $\mathcal{N}_i^{\mathcal{P}}$ and $\mathcal{N}_j^{\mathcal{Q}}$ . The superpoints from different instances of $\hat{\mathbf{q}}_j$ are removed from $\mathcal{N}_j^{\mathcal{Q}}$ based on the instance mask $\mathbf{M}_j$ . The points in the local patches of all superpoints in $\mathcal{N}_i^{\mathcal{P}}$ and $\mathcal{N}_j^{\mathcal{Q}}$ imply a potential occurrence of $\mathcal{P}$ in $\mathcal{Q}$ , i.e., an instance candidate, denoted as $\mathcal{I}_k$ . Next, instance-wise point correspondences are extracted within $\mathcal{I}_k$ with an optimal transport layer and mutual top- $k$ selection following [38], denoted as $\mathcal{C}_k$ . At last, we estimate a pose $\mathbf{T}_k = \{\mathbf{R}_k,\mathbf{t}_k\}$ for $\mathcal{I}_k$ by solving Eq. (1) with weighted SVD [8]. Thanks to the powerful instance-aware geometric transformer, an instance candidate can cover a relatively large portion of an instance, with few points from the background or other instances, so the poses obtained in this step have already been very accurate. + +# 4.3. Candidate Selection and Refinement + +As several superpoint correspondences could belong to the same instance, there are commonly duplicated instances in the instance candidates. For this reason, we further design a simple but effective algorithm for duplicate removal and candidate refinement. + +Inspired by non-maximum suppression (NMS) [39], we first sort the instance candidates by the inlier ratio on the global point correspondences $\mathcal{C} = \bigcup_{i=1}^{N_c} \mathcal{C}_i$ . The inlier ratio of the instance candidate $\mathcal{I}_k$ is: + +$$ +\gamma_ {k} = \frac {1}{| \mathcal {C} |} \sum_ {(\mathbf {p}, \mathbf {q}) \in \mathcal {C}} [ [ \| \mathbf {R} _ {k} \mathbf {p} + \mathbf {t} _ {k} - \mathbf {q} \| < \tau_ {2} ] ], \tag {8} +$$ + +where $\llbracket \cdot \rrbracket$ is the Iverson bracket and $\tau_{2}$ is the acceptance radius. Next, we select the instance candidate with the highest inlier ratio as the anchor candidate. All remaining candidates similar with the anchor are merged with it and removed from future computation. We define the similarity between two candidates $\mathcal{I}_i$ and $\mathcal{I}_j$ by the average distance + +(ADD) [21] between their estimated poses: + +$$ +s _ {i, j} = 1 - \frac {\operatorname {A D D} \left(\mathbf {T} _ {i} , \mathbf {T} _ {j}\right)}{r}, \tag {9} +$$ + +where $r$ is the diameter of $\mathcal{P}$ . And $\mathcal{I}_i$ and $\mathcal{I}_j$ are considered similar if $s_{i,j}$ is above $\tau_s$ . To merge two candidates, we combine their point correspondences and recompute the pose by solving Eq. (1). At last, the preserved pose is iteratively refined with the surviving inliers as in [5, 38], leading to a final instance registration. The anchor is then removed from future computation. The above process repeats until there are no candidates left and we omit the instance registrations with too few inliers. + +Compared to multi-model fitting methods [44, 55], the advantages of our MIRETR are two-fold. First, by learning instance-aware superpoint features, the influence from the background and other instances is minimized, thus the correspondences are more accurate and can cover more instances. Second, correspondence clustering-based methods tend to lose heavily-occluded instances as there are few correspondences on them, especially in cluttered scenes. On the contrary, our method can better recognize these hard instances as we bypass the clustering process by directly extracting instance candidates and merging similar ones. + +# 4.4. Loss Functions + +We adopt three loss functions to train MIRETR: an overlap-aware circle loss [38] $\mathcal{L}_{\mathrm{circle}}$ to supervise the superpoint features, a negative log-likelihood loss [40] $\mathcal{L}_{\mathrm{nll}}$ to supervise the point matching, and a mask prediction loss [36] $\mathcal{L}_{\mathrm{mask}}$ to supervise the instance masks. The overall loss is computed as $\mathcal{L} = \mathcal{L}_{\mathrm{circle}} + \mathcal{L}_{\mathrm{nll}} + \mathcal{L}_{\mathrm{mask}}$ . Please refer to the supplementary material for more details. + +# 5. Experiments + +We evaluate MIRETR on indoor Scan2CAD [2, 44, 55], industrial ROBI [52] and synthetic ShapeNet [10] benchmarks. And we also introduce the implementation details and more experiments in the supplementary material. + +Baselines. We compare with three state-of-the-art point cloud correspondence methods, FCGF [14], CoFiNet [54] and GeoTransformer [38], and four recent multi-model fitting methods, T-linkage [33], RansaCov [34], ECC [44], and PointCLM [55]. The point cloud correspondence methods and the multi-model fitting methods are pairwise integrated for a comprehensive comparison. + +Metrics. Following [44, 55], we evaluate our method with three registration metrics: (1) Mean Recall (MR), the ratio of registered instances over all ground-truth instances, (2) Mean Precision (MP), the ratio of registered instances over all predicted instances, and (3) Mean $F_{1}$ score (MF), the harmonic mean of MP and MR. We also report Inlier Ratio (IR), the ratio of inliers over all extracted correspondences. + +
ModelIR(%)MR(%)MP(%)MF(%)
FCGF [14] + T-Linkage [33]54.7522.7632.15
FCGF [14] + RansaCov [34]36.2773.5045.0155.83
FCGF [14] + PointCLM [55]86.9970.0577.60
FCGF [14] + ECC [44]92.6073.7982.13
CoFiNet [54] + T-Linkage [33]28.175.098.62
CoFiNet [54] + RansaCov [34]18.5238.2913.6920.16
CoFiNet [54] + PointCLM [55]36.1524.7029.34
CoFiNet [54] + ECC [44]57.2617.2426.50
GeoTransformer [38] + T-Linkage [33]72.6844.8055.43
GeoTransformer [38] + RansaCov [34]44.0278.8467.1672.53
GeoTransformer [38] + PointCLM [55]82.8181.9082.35
GeoTransformer [38] + ECC [44]94.6374.8383.57
MIRETR (ours) + T-Linkage [33]77.1246.0457.65
MIRETR (ours) + RansaCov [34]84.7871.3477.48
MIRETR (ours) + PointCLM [55]56.5991.8591.0891.46
MIRETR (ours) + ECC [44]96.5289.0392.62
MIRETR (ours, full pipeline)95.7091.2193.40
+ +Table 1. Evaluation results on Scan2CAD benchmark. + +# 5.1. Evaluations on Scan2CAD + +Dataset. Scan2CAD [2] is a scene-to-CAD alignment dataset build upon ScanNet [15] and ShapeNet [10]. It consists of 1506 scenes from ScanNet annotated with 14225 CAD models from ShapeNet and their poses in the scenes. Following [55], we replace the objects in the scenes with the corresponding aligned CAD models. We select the scene-model pairs which the scene contain multiple instances of the model for multi-instance registration. As last, we obtain 2184 point cloud pairs and use $70\%$ pairs for training, $10\%$ for validation and $20\%$ for testing. + +Quantitative results. As shown in Tab. 1, our MIRETR achieves consistent improvements over the baseline correspondence models. Notably, our method surpasses the previous best GeoTransformer on IR by 12 percentage points (pp). When coupled with PointCLM, it outperforms GeoTransformer by over 9 pp on the three registration metrics. + +Moreover, our full pipeline surpasses all models with the baseline multi-model fitting methods. Although the ECC-based model performs slightly better than full MIRETR on MR, its MP is significantly worse. This indicates that ECC achieves high MR by predicting more registrations, which is impractical in real-world applications. And our method outperforms PointCLM on all three registration metrics, which demonstrates the strong effectiveness of our method. + +# 5.2. Evaluations on ROBI + +Dataset. ROBI [52] is a recent dataset for industrial bin-picking. It includes 7 reflective metallic industrial objects and 63 bin-picking scenes. Each scene contains cluttered instances of one industrial object. For each point cloud pair, the scene point cloud is backprojected from a depth image and the model point cloud is sampled from the CAD model of its corresponding industrial object. We obtain 4880 pairs in total, and we split the scenes for training, validation and testing according to the ratio of $6:1:2$ for each object. + +Quantitative results. As in Tab. 2, our method outper + +![](images/1abb0532efa0b1f690a72759bce9d97f471e82cd995a9373c97e80cf534597da.jpg) + +![](images/704b66b88c6729d9e6d53705b971c818475de3b48203da143327ec604af1982b.jpg) +Inst:12 + +![](images/644149e1b7874c39a7f61a04f1fbf69b621909165d2e10ea50794c9885073d18.jpg) + +![](images/802cd1095a9446fc722eebc795ebfe0682251baab7a87e94de02204906d214f5.jpg) + +![](images/98d47ff7e66ebf5c4a5024041eec2b8facef842f7d79a9b042ef23194aeed501.jpg) + +![](images/dcf490464ac34f05aef2449727051e01a1176447869aa82803f6a3b80d6ebae8.jpg) + +![](images/69bf9dfd46a5d4c4b990e3f08d9f2ceea561adb39a0152fe649cafaaf2d4b944.jpg) + +![](images/a51edfd444ebd817b90e9e521858ae6e30c964e1c3b3c8b17636ec74df0ec497.jpg) +Inst:22 + +![](images/61f2e6e3fb21f46a27a0863d5a0a1fe1e21d5f959140175d540a28ac1c232176.jpg) +Inst:3 + +![](images/47222ca7df42dc2273d530c4ccfaf40b595aeb40c9ba23287a6c505bda959a24.jpg) +Inst:9 + +![](images/9a7fcfb515a5db074b12478da6599137d1ac11a0ae2da99a77456ceb4d27c2a0.jpg) +IR:39.42% +IR:49.91% + +![](images/251cbcaee9afec1b852c631e6866a3942684bba4cd67373ccb205ee2290cc1e5.jpg) +IR:54.21% +IR:56.90% + +![](images/b69c08aeb868cc2fad1379dd2651a4718e7043dc9f9bed2dccc4cd7a2d810a69.jpg) +(a) Input + +![](images/88ba29007d8ff52a2871dd70323d5b0a20822679cfaf53c00c1570e020f5dcf1.jpg) +Inst:18 +(b) Ground Truth + +![](images/d018345a684d4f108de169b40602c60da8d37b88e7b148d84d70253f3f89d44f.jpg) +Inst:4 +Inst:4 +(c) GeoTrans + +![](images/4e921912da9654eb7fc66703f378cf70ad42ea341c3022fb1f929244e3610718.jpg) +Inst:11 +Inst:8 +(d) Ours + +![](images/1c725f11c388f00e1a1af134e30d50ede5a2a17ff74c64aca2d5f3b1480fa8b4.jpg) +IR:48.03% +(e) GeoTrans (corr) + +![](images/289dc0081fe5c9ddbfe53c9c7fbf6005030cc6947efdd95e0d5d9d14a572b8ed.jpg) +IR:72.40% +(f) Ours (corr) + +
ModelIR(%)MR(%)MP(%)MF(%)
CoFiNet [54] + T-Linkage [33]10.351.340.720.93
CoFiNet [54] + RansaCov [34]1.251.391.31
CoFiNet [54] + PointCLM [55]1.172.111.50
CoFiNet [54] + ECC [44]3.218.504.66
GeoTransformer [38] + T-Linkage [33]39.647.714.575.73
GeoTransformer [38] + RansaCov [34]8.9913.5810.81
GeoTransformer [38] + PointCLM [55]13.9826.6418.33
GeoTransformer [38] + ECC [44]18.5530.9923.20
MIRETR (ours) + T-Linkage [33]45.1412.0410.4711.20
MIRETR (ours) + RansaCov [34]14.1426.2918.38
MIRETR (ours) + PointCLM [55]18.6840.1125.48
MIRETR (ours) + ECC [44]24.6534.8528.91
MIRETR (ours, full pipeline)38.5141.1939.80
+ +Table 2. Evaluation results on ROBI benchmark. + +forms the baseline correspondence methods by a large margin on all four metrics. Compared to Scan2CAD, ROBI is more challenging due to the more cluttered scenes, where instance-aware information is more important. Benefiting from the instance-aware geometric transformer module, our method extracts reliable instance-aware correspondences, which contributes to more accurate instance registrations. + +Our full model achieves significant improvements over the ECC-based model on MR, MP and MF. The PointCLM-based model achieves comparable MP with the full model, but significantly worse MR, which means it can register only several easy instances but misses most heavily-occluded instances. Specifically, it can register on average only 6.2 instances per scene, while the number of our method is 13.7. Our method achieves both high MR and MP, showing strong robustness in cluttered scenes. + +Qualitative results. Fig. 5 visualizes the registration results of GeoTransformer and MIRETR. Our method can + +![](images/391ca0191f955cb9a6ce937cf227c2f26566bf36dc2ed686e4e35c93a389f6c0.jpg) +Figure 5. Registration results on ROBI benchmark. We visualize the successfully registered instances in (c) and (d). MIRETR registers more instances in the cluttered scenes (the $2^{\text{nd}}$ and the $3^{\text{rd}}$ rows) and with incomplete geometry (all three rows). And it extracts more accurate correspondences benefiting from the instance-aware correspondence learning mechanism. + +![](images/b6485a00d3b1d395f9bd361f2487dcd38fa3167e21cd81dbb7ffe8c613cfcf55.jpg) + +![](images/d5503b738ba1ee730cc57be49e2512510deae3912135aa643abd992b3e952ba8.jpg) + +![](images/8d3df5aa3f8921044baebe2827a67c205e342787a90d0bc6f09a89fe3001a9b0.jpg) +(a) Anchor's neighbors +Figure 6. Visualizations of the predicted instance masks. The anchor superpoint (patch) is in red and the selected neighbors are color-coded. Our method can effectively reject the patches outside the interested instance while preserving most of those inside. + +![](images/d5e8662215981f9b8f3c9bdfbf1940a9049c4a266abfef58d8dc728417113bbf.jpg) +(b) Ground Truth Mask + +![](images/96232d5edff7c4e3fb917f7bd8549b8ca128637140de62e2cc227b322af338d4.jpg) +(c) Our Prediceted Mask + +register more instances in cluttered scenes (see the $2^{\text{nd}}$ and the $3^{\text{rd}}$ rows) and with severe geometric deficiency (see all three rows). And MIRETR attains more high-quality correspondences thanks to our instance-aware design. + +We further visualize the predicted instance masks Fig. 6. The instance masks effectively reject the patches out of the interested instance while preserving most of those inside. Specifically, our method achieves the instance mIoU of 69.26 pp while the result of the model without masking is merely 38.13 pp. The high-quality masks allow us to effectively encode intra-instance context and contribute to accurate registrations. + +Fig. 7 compares the results under different overlap ratios. + +![](images/47fd1ca19d7110631edeade7b18fcf7f75922bb74cb3687da7de3747fb0f468c.jpg) +Figure 7. Results in different overlap levels on ROBI benchmark. + +MIRETR consistently outperforms the baselines at all overlap levels, and the improvements are more significant when the overlap ratio is below $50\%$ . This proves the strong capability of our method to handle low-overlap instances. + +# 5.3. Evaluations on ShapeNet + +Dataset. ShapeNet [10] is a large CAD model dataset which contains 51300 models from 55 categories. We use the models from first 30 categories for training and those from the rest 25 categories for testing to evaluate the generality to novel categories. We randomly sample at most 500 models from each category to avoid class imbalance. For each point cloud pair, the model point cloud is a random CAD model and the scene one is constructed by applying $4\sim 16$ random poses on the model. At last, we obtain 8634 pairs for training, 900 for validation, and 7683 for testing. + +Quantitative results. As shown in Tab. 3, our MIRETR achieves the best results on all four metrics, surpassing the baselines by a large margin. GeoTransformer significantly outperforms CoFiNet, which proves the importance of geometric structure to achieving generality. And our method achieves improvements of more than 10 pp over GeoTransformer on all registration metrics with PointCLM and ECC. Thanks to the instance-ware geometric transformer, the correspondences extracted by our method provide strong instance information, facilitating the correspondence clustering process. At last, our full model surpasses the previous best ECC-based baseline by around 2 pp on MR, 11 pp on MP and 7 pp on MF, demonstrating the strong generality of MIRETR to unseen objects. + +# 5.4. Ablation Studies + +We conduct extensive ablation studies on ROBI benchmark to better understand our design choices in Tab. 4. We first ablate the instance-aware point matching and extract point correspondences within only the patches of the superpoint correspondences in Tab. 4 (b), which is significantly worse than the full model. The poses estimated by this method is unstable due to clustered correspondences, thus the duplicated candidates cannot be effectively removed by NMS. + +
ModelIR(%)MR(%)MP(%)MF(%)
CoFiNet [54] + T-Linkage [33]4.593.243.79
CoFiNet [54] + RansaCov [34]39.537.355.336.17
CoFiNet [54] + PointCLM [55]23.4019.6621.36
CoFiNet [54] + ECC [44]41.4926.6032.41
GeoTransformer [38] + T-Linkage [33]27.6826.4027.02
GeoTransformer [38] + RansaCov [34]69.6541.8648.1644.78
GeoTransformer [38] + PointCLM [55]68.0969.0968.58
GeoTransformer [38] + ECC [44]78.0364.0870.37
MIRETR (ours) + T-Linkage [33]29.4028.6729.03
MIRETR (ours) + RansaCov [34]45.6346.8546.23
MIRETR (ours) + PointCLM [55]77.1385.6385.8185.71
MIRETR (ours) + ECC [44]92.5682.0887.01
MIRETR (ours, full pipeline)94.9593.9494.44
+ +Table 3. Evaluation results on ShapeNet benchmark. + +
ModelIR(%)MR(%)MP(%)MF(%)
(a) full MIRETR45.1438.5141.1939.80
(b) w/o instance-aware point matching40.5218.1527.5421.88
(c) w/o instance masking block36.7817.0745.3724.80
(d) w/o both38.8114.1327.4418.65
(e) w/ global attention25.987.7218.8610.96
+ +Table 4. Ablation studies on ROBI benchmark. + +Next, we remove the instance masking blocks in Tab. 4 (c) and the instance-aware point matching gathers the points from all neighbor superpoints. This model achieves a good MP, but a significantly worse MR, which means it can register only few instances (2.9 vs. 13.7 average instances per scene). We then ablate both modules in Tab. 4 (d), which further degrades the performance. At last, we replace the geometric encoding block with the global geometric self-attention [38] in Tab. 4 (e), which achieves the worst results. This indicates that the superpoint features can be polluted if global context is encoded. These results have proven the strong efficacy of our designs. More ablation studies are presented in the supplementary material. + +# 6. Conclusion + +We have proposed MIRETR, a coarse-to-fine method to extract instance-aware correspondences for multi-instance registration. At the coarse level, an instance-aware geometric transformer module jointly learns instance-aware superpoint features and predicts per-instance masks. At the fine level, the superpoint correspondences are extended to instance candidates according to the instance masks, where instance-wise point correspondences are extracted. At last, we devise a simple but effective candidate selection and refinement algorithm to obtain the final registrations, bypassing the need of multi-model fitting methods. Extensive experiments on three public benchmarks have demonstrated the efficacy of our method. For future work, we would like to extend MIRETR to multi-modal multi-instance registration to boost more applications. + +Acknowledgement. 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In ICCV, pages 3132-3141, 2021. 2 +[52] Jun Yang, Yizhou Gao, Dong Li, and Steven L Waslander. Robi: A multi-view dataset for reflective objects in robotic bin-picking. In IROS, pages 9788-9795, 2021. 2, 6 +[53] Zi Jian Yew and Gim Hee Lee. RPM-net: Robust point matching using learned features. In CVPR, pages 11824-11833, 2020. 2 +[54] Hao Yu, Fu Li, Mahdi Saleh, Benjamin Busam, and Slobodan Ilic. Cofinet: Reliable coarse-to-fine correspondences for robust point cloud registration. arXiv preprint arXiv:2110.14076, 2021. 2, 3, 4, 5, 6, 7, 8 +[55] Mingzhi Yuan, Zhihao Li, Qiuye Jin, Xinrong Chen, and Manning Wang. Pointclm: A contrastive learning-based framework for multi-instance point cloud registration. 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Extracting accurate point correspondences is to the center of the problem. Existing approaches usually treat the scene point cloud as a whole, overlooking the separation of instances. Therefore, point features could be easily polluted by other points from the background or different instances, leading to inaccurate correspondences oblivious to separate instances, especially in cluttered scenes. In this work, we propose MIRETR, Multi-Instance REgistration TRansformer, a coarse-to-fine approach to the extraction of instance-aware correspondences. At the coarse level, it jointly learns instance-aware superpoint features and predicts per-instance masks. With instance masks, the influence from outside of the instance being concerned is minimized, such that highly reliable superpoint correspondences can be extracted. The superpoint correspondences are then extended to instance candidates at the fine level according to the instance masks. 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Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 601, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 601, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 601, + 287, + 696 + ], + "type": "text", + "content": "Point cloud registration aims at estimating a rigid transformation that aligns two point clouds. In real-world application scenarios such as robotic bin picking, there is often the requirement of multi-instance registration where the point cloud of a model needs to be registered against multiple instances of the model in the target scene. 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MIRETR significantly improves the multi-instance registration results in cluttered scenes compared to the state-of-the-art GeoTransformer [38]. Benefiting from the instance-aware correspondences, our method can generate more accurate registrations (see the yellow boxes) and register the heavily-occluded instances with severe geometric deficiency (see the red boxes)." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 433, + 342, + 545, + 456 + ], + "blocks": [ + { + "bbox": [ + 433, + 342, + 545, + 456 + ], + "lines": [ + { + "bbox": [ + 433, + 342, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 433, + 342, + 545, + 456 + ], + "type": "image", + "image_path": "58acc35d0b23e9c36e8cc7256f026a2e6cc6e4b36fa6eb0703816a6b5c4c0e26.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 473, + 456, + 503, + 464 + ], + "lines": [ + { + "bbox": [ + 473, + 456, + 503, + 464 + ], + "spans": [ + { + "bbox": [ + 473, + 456, + 503, + 464 + ], + "type": "text", + "content": "MIRETR" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 555, + 430, + 566 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 555, + 430, + 566 + ], + "spans": [ + { + "bbox": [ + 306, + 555, + 430, + 566 + ], + "type": "text", + "content": "especially in a cluttered scene." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": "Existing approaches to multi-instance registration are mostly two-stage: They first extract point correspondences between the model and the scene point clouds and then recover per-instance transformations with multi-model fitting [28, 44, 55]. Clearly, the performance of such approach highly depends on the quality of the correspondences. Unlike pair-wise registration that can be pinned down by a small number of correspondences, multi-instance registration poses unique challenges. First, the correspondences should widely spread over the scene point cloud to cover as many instances as possible so that more instances can be found and registered. Second, the correspondences should" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 251, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 251, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 251, + 712 + ], + "type": "text", + "content": "*Corresponding author: Kai Xu (kevin.kai.xu@gmail.com)." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19605" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 96 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 96 + ], + "type": "text", + "content": "be accurately clustered into individual instances to estimate per-instance pose transformations." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 98, + 286, + 205 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 98, + 286, + 205 + ], + "spans": [ + { + "bbox": [ + 46, + 98, + 286, + 205 + ], + "type": "text", + "content": "Existing point correspondence methods can be broadly classified into keypoint-based and keypoint-free ones. Albeit successful in pairwise registration, these methods fail to effectively tackle the aforementioned challenges. On the one hand, keypoint-based methods [4, 14, 25] first detect keypoints and then match them to form correspondences. In the multi-instance setting, however, it is common that an instance is severely occluded so that too few keypoints can be detected to guarantee a successful registration." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 207, + 286, + 445 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 207, + 286, + 445 + ], + "spans": [ + { + "bbox": [ + 46, + 207, + 286, + 445 + ], + "type": "text", + "content": "On the other hand, keypoint-free methods [38, 54] bypass keypoint detection with a coarse-to-fine pipeline. They first extract correspondences between sparse superpoints and then refine them to dense point correspondences. To achieve reliable superpoint matching, they encode global context with feature correlation [54] or geometric structure [38] to learn distinctive superpoint features. When used in multi-instance registration, such approach may overlook the separation of individual instances and lead to the following two drawbacks. First, the superpoint features of an instance may be contaminated by the global context from the background or other instances, making the extracted features less informative. Thus, the features of a severely occluded instance could be overwhelmed by those more complete neighboring ones, making the occluded instances hard to registered (see Fig. 1 (left)). Second, they cannot discriminate correspondences into different instances and have to rely on multi-model fitting [28, 44, 55] to cluster correspondences. Multi-model fitting needs to sample numerous hypotheses and finds difficulty in handling heavy occlusion." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 449, + 286, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 449, + 286, + 651 + ], + "spans": [ + { + "bbox": [ + 46, + 449, + 286, + 651 + ], + "type": "text", + "content": "We propose MIRETR, Multi-Instance REgistration Transformer, which learns to extract instance-aware correspondences in a coarse-to-fine fashion. Our key motivation is to restrict the contextual feature encoding within the instance scope. An Instance-aware Geometric Transformer module is devised to jointly extract reliable superpoint features and predict instance masks in the scene. We resolve this chicken-and-egg problem with an iterative process. In each iteration, we first encode intra-instance geometric structure based on the instance mask of the previous iteration and then learn geometric consistency between the model and the scene. Next, the instance masks are refined based on the instance-aware features. As the iteration goes, the superpoint features gradually improve with increasingly relevant context and accurate instance masks, resulting in reliable registrations even for heavily-occluded instances (see Fig. 1 (right))." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 654, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 654, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 654, + 286, + 712 + ], + "type": "text", + "content": "Having obtained superpoint correspondences, we extend them to instance candidates based on instance masks. This allows us to directly extract instance-wise point correspondences and estimate a transformation for each instance candidate. An efficient candidate selection and refinement" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 545, + 178 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 178 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 178 + ], + "type": "text", + "content": "method is proposed to eliminate duplicated instances and obtain the final registrations. Thanks to the instance-aware correspondences, our method bypasses the need of multimodel fitting, achieving superior efficiency and accuracy. Extensive experiments on three benchmarks [2, 10, 52] demonstrate the efficacy of our method. Our method surpasses the previous state-of-the-art methods [38, 55] by 16.6 points on " + }, + { + "bbox": [ + 304, + 72, + 545, + 178 + ], + "type": "inline_equation", + "content": "\\mathrm{F_1}" + }, + { + "bbox": [ + 304, + 72, + 545, + 178 + ], + "type": "text", + "content": " score on the cluttered ROBI benchmark. Our main contributions include:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 180, + 545, + 286 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 306, + 180, + 545, + 215 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 180, + 545, + 215 + ], + "spans": [ + { + "bbox": [ + 306, + 180, + 545, + 215 + ], + "type": "text", + "content": "- A multi-instance point cloud registration method which extracts instance-wise correspondences and estimates transformations without multi-model fitting." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 216, + 545, + 251 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 216, + 545, + 251 + ], + "spans": [ + { + "bbox": [ + 306, + 216, + 545, + 251 + ], + "type": "text", + "content": "- An instance-aware geometric transformer module which jointly learns instance-aware superpoint features and predicts instance masks." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 251, + 545, + 286 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 251, + 545, + 286 + ], + "spans": [ + { + "bbox": [ + 306, + 251, + 545, + 286 + ], + "type": "text", + "content": "- An efficient instance candidate selection and refinement method which removes duplicated candidates and generates the final registrations." + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 298, + 389, + 310 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 298, + 389, + 310 + ], + "spans": [ + { + "bbox": [ + 306, + 298, + 389, + 310 + ], + "type": "text", + "content": "2. Related work" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 319, + 545, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 319, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 304, + 319, + 545, + 533 + ], + "type": "text", + "content": "Point cloud registration. State-of-the-art point cloud registration methods can be categorized into direct registration methods and correspondence-based methods. Direct registration methods [1, 18, 26, 48, 49, 51, 53] use a neural network to estimate the transformation in an end-to-end manner. Correspondence-based methods [4, 14, 16, 17, 19, 25, 38, 54] extract point correspondences and estimate the rigid transformation with a robust pose estimator. Early point correspondence methods [4, 25] adopt a detect-then-match pipeline, where keypoints are first detected and then matched. Recent advances [38, 54] have bypassed keypoint detection by extracting correspondences in a coarse-to-fine fashion. However, existing methods mainly focus on pairwise registration and little attention has been paid to multi-instance registration, which faces new challenges such as unknown number of instances and heavy intra-instance occlusion. In this paper, we fill this gap by directly extracting instance-aware correspondences." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 534, + 545, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 545, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 545, + 689 + ], + "type": "text", + "content": "Multi-model fitting. Multi-model fitting aims at recovering multiple models from noisy data, which is an important step in multi-instance registration. Multi-model fitting methods can be classified into RANSAC-based methods and clustering-based methods. RANSAC-based methods [6, 7, 27, 28] adopt a hypothesize-and-verify manner to sequentially fit multiple models. Clustering-based methods [33-35, 44, 55] sample a huge set of hypotheses and cluster the correspondences according to their residuals under these hypotheses. However, these methods suffer from huge memory usage or long convergence time. In this work, we achieve accurate and efficient multi-instance registration without multi-model fitting." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "Open-set pose estimation. Model retrieval [2, 3, 8, 9, 13, 20, 24, 29] and image-based pose estimation [11, 12," + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "text", + "content": "19606" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 264 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 264 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 264 + ], + "type": "text", + "content": "22, 23, 31, 32, 37, 41-43, 47, 50] are two highly-related tasks to multi-instance registration. Model retrieval aims at estimating the 9-DoF pose parameters of the CAD models from a pre-built database that appears in a given scene. And image-based pose estimation recovers the 6-DoF poses for certain objects [12, 22, 23, 37, 41-43, 50] or categories [11, 31, 32, 47] in an RGB or RGB-D image. However, both tasks are based on the close-set assumption, where the training and testing data follow the same distribution. Model retrieval can only retrieve the CAD models in the database while image-based pose estimation can only handle known objects or categories in the training data. On the contrary, multi-instance registration is an open-set problem. It is based on geometric matching and thus can generalize well to novel objects and categories. We discuss the generality of MIRETR in Sec. 5.3." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 275, + 162, + 288 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 275, + 162, + 288 + ], + "spans": [ + { + "bbox": [ + 47, + 275, + 162, + 288 + ], + "type": "text", + "content": "3. Problem Statement" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "spans": [ + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": "Given a model point cloud " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{P} = \\{\\mathbf{p}_i\\in \\mathbb{R}^3 |i = 1,\\dots,N\\}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " and a scene point cloud " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{Q} = \\{\\mathbf{q}_i\\in \\mathbb{R}^3 |i = 1,\\dots,M\\}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " could contain multiple instances of " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": ", the goal of multi-instance registration is to register all instances of " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": ". Specifically, " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " is represented as " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{Q} = \\mathcal{Q}_0\\cup \\mathcal{Q}_1\\cup \\ldots \\cup \\mathcal{Q}_K" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}_0" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " is the background points and " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{Q}_1,\\dots,\\mathcal{Q}_K\\}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " are the " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " instances of " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": ". For each instance " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}_k" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": ", we estimate a 6-DoF pose " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_k\\in \\mathcal{SE}(3)" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " aligning " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}_k" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": ", which consists of a 3D rotation " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathbf{R}_k\\in \\mathcal{SO}(3)" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " and a 3D translation " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_k\\in \\mathbb{R}^3" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": ". To solve this problem, one usually first extracts a set of correspondences " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{C} = \\{(\\mathbf{p}_i,\\mathbf{q}_i)|\\mathbf{p}_i\\in \\mathcal{P},\\mathbf{q}_i\\in \\mathcal{Q}\\}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": " between the two point clouds. The correspondences are then clustered into different groups " + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{C}_1,\\dots,\\mathcal{C}_K\\}" + }, + { + "bbox": [ + 46, + 295, + 289, + 464 + ], + "type": "text", + "content": ", and each group recovers the pose of one instance by solving the following problem:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 82, + 472, + 287, + 495 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 82, + 472, + 287, + 495 + ], + "spans": [ + { + "bbox": [ + 82, + 472, + 287, + 495 + ], + "type": "interline_equation", + "content": "\\min _ {\\mathbf {R} _ {k}, \\mathbf {t} _ {k}} \\sum_ {\\left(\\mathbf {p} _ {i}, \\mathbf {q} _ {i}\\right) \\in \\mathcal {C} _ {k}} \\left\\| \\mathbf {R} _ {k} \\cdot \\mathbf {p} _ {i} + \\mathbf {t} _ {k} - \\mathbf {q} _ {i} \\right\\| _ {2} ^ {2}. \\tag {1}", + "image_path": "dad69e6596ef322cf8e108eab594f87cb7f27ad07dc944cc95ff6532e6f8a9f2.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 502, + 287, + 551 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 502, + 287, + 551 + ], + "spans": [ + { + "bbox": [ + 46, + 502, + 287, + 551 + ], + "type": "text", + "content": "This problem is very challenging as the number of instances is unknown and it is difficult to cluster the correspondences to the correct instances. In this work, we deal with this problem by extracting instance-aware correspondences." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 562, + 103, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 562, + 103, + 574 + ], + "spans": [ + { + "bbox": [ + 47, + 562, + 103, + 574 + ], + "type": "text", + "content": "4. Method" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 582, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 287, + 715 + ], + "type": "text", + "content": "MIRETR extracts correspondences in a coarse-to-fine fashion similar to keypoint-free registration methods. The overall pipeline of our method is illustrated in Fig. 2. At the coarse level, we establish correspondences between down-sampled superpoints with an Instance-aware Geometric Transformer module (Sec. 4.1). At the fine level, each superpoint correspondence is extended to form an instance candidate, where instance-wise point correspondences are extracted for pose estimation (Sec. 4.2). At last, we merge similar instance candidates and refine the resultant poses to obtain the final registrations (Sec. 4.3)." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": "Given the input point clouds " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ", we progressively downsample them into sparse superpoints, denoted as " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ", using grid subsampling [45]. KPFCNN [45] is adopted to extract multi-level point features. Let us denote the features of " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": " as " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\mathbf{F}^{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\mathbf{F}^{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}^{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}^{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ", respectively. Following [38, 54], each superpoint " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_i \\in \\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{q}}_i \\in \\hat{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ") is associated with a local patch " + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_i^{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_i^{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": ") by the point-to-node partition strategy [30] where each point is assigned to its nearest superpoint." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 190, + 515, + 202 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 190, + 515, + 202 + ], + "spans": [ + { + "bbox": [ + 305, + 190, + 515, + 202 + ], + "type": "text", + "content": "4.1. Instance-aware Geometric Transformer" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "spans": [ + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "text", + "content": "Given the superpoints " + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "text", + "content": ", as well as their features " + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}^{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}^{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 208, + 545, + 412 + ], + "type": "text", + "content": ", we first extract a set of superpoint correspondences whose local patches overlap with each other. Accurate superpoint matching relies on learning the geometric consistency between the two point clouds. To this end, previous works [38, 54] adopt transformer [46] to encode intra- and inter-point-cloud context in the global scope, as shown in Fig. 3 (a). Albeit successful in pairwise registration, this is problematic in multi-instance registration. In the scene point cloud, the superpoints from the background or other instances are de facto noises for modeling the geometric consistency and severely pollute the superpoint features. This becomes more severe in cluttered scenes. Considering an heavily-occluded instance, as its geometric structure is incomplete, the features of its superpoints could be easily overwhelmed by those from the background or nearby instances. As a result, it can hardly be registered." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 413, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 413, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 413, + 545, + 581 + ], + "type": "text", + "content": "To address these issues, we propose to make the superpoint features instance-aware with a novel Instance-aware Geometric Transformer module. The key insight is to restrict the intra-point-cloud context encoding in the scene point cloud within each individual instance. To this end, we first extract the " + }, + { + "bbox": [ + 304, + 413, + 545, + 581 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 413, + 545, + 581 + ], + "type": "text", + "content": "-nearest neighbors for each superpoint and conduct context aggregation within local regions. However, as shown in Fig. 3 (b), nearby superpoints do not necessarily reside in the same instance, and the feature pollution problem still exists. For this reason, we further design an instance masking mechanism by predicting an instance mask for each superpoint to select the neighbors in the same instance as it, and only aggregate the context among them. Fig. 3 (c) illustrates our instance masking mechanism." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 582, + 545, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 700 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 700 + ], + "type": "text", + "content": "As shown in Fig. 2 (bottom), the instance-aware geometric transformer contains three blocks. First, a geometric encoding block encodes intra-instance geometric structure based on the instance masks. Next, a cross-attention block enhances the superpoint features by modeling inter-point-cloud geometric consistency. At last, an instance masking block predicts new instance masks with the instance-aware superpoint features. We adopt " + }, + { + "bbox": [ + 304, + 582, + 545, + 700 + ], + "type": "inline_equation", + "content": "N_{t}" + }, + { + "bbox": [ + 304, + 582, + 545, + 700 + ], + "type": "text", + "content": " instance-aware geometric transformer modules to progressively refine the superpoint features and the instance masks." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 701, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 701, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 701, + 545, + 713 + ], + "type": "text", + "content": "Geometric encoding block. 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Overall pipeline of MIRETR. The backbone progressively downsamples two point clouds and extracts multi-level features. At the coarse level, the Instance-aware Geometric Transformer module extracts instance-aware superpoint features and establishes reliable superpoint correspondences. At the fine level, the superpoint correspondences are extended to instance candidates, where instance-wise point correspondences are extracted to estimate per-candidate poses. 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" + }, + { + "bbox": [ + 46, + 518, + 287, + 677 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_{i,j}" + }, + { + "bbox": [ + 46, + 518, + 287, + 677 + ], + "type": "text", + "content": " is the geometric structure embedding [38] encoding the transformation-invariant geometric information among the superpoints. 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" + }, + { + "bbox": [ + 46, + 518, + 287, + 677 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^Q" + }, + { + "bbox": [ + 46, + 518, + 287, + 677 + ], + "type": "text", + "content": " is initialized with all zeros and refined by the instance masking block described later. Benefiting from the instance masks, the superpoint features are instance-aware by encoding the feature correlation and the geometric context within their belonging instances. For the computation in " + }, + { + "bbox": [ + 46, + 518, + 287, + 677 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 46, + 518, + 287, + 677 + ], + "type": "text", + "content": ", we ignore the mask term in Eq. 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Comparison of (a) global attention, (b) local attention, and (c) instance-aware attention. The superpoints (patches) participating in the attention computation are color-coded. The anchor superpoints are in red. The " + }, + { + "bbox": [ + 304, + 522, + 545, + 577 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 522, + 545, + 577 + ], + "type": "text", + "content": "-nearest neighbors of the anchor are enclosed by the purple line." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "spans": [ + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "text", + "content": "by [38, 54]. Given the feature matrices " + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "inline_equation", + "content": "\\mathbf{X}^{\\mathcal{P}}\\in \\mathbb{R}^{|\\hat{\\mathcal{P}} |\\times d}" + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "inline_equation", + "content": "\\mathbf{X}^{\\mathcal{Q}}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times d}" + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "text", + "content": " from the geometric encoding block, the output feature matrix " + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}^{\\mathcal{P}}\\in \\mathbb{R}^{|\\hat{\\mathcal{P}} |\\times d}" + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 580, + 547, + 620 + ], + "type": "text", + "content": " is computed as:" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 348, + 627, + 545, + 665 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 627, + 545, + 665 + ], + "spans": [ + { + "bbox": [ + 348, + 627, + 545, + 665 + ], + "type": "interline_equation", + "content": "\\mathbf {z} _ {i} ^ {\\mathcal {P}} = \\sum_ {j = 1} ^ {| \\hat {\\mathcal {Q}} |} \\frac {\\exp \\left(e _ {i , j}\\right)}{\\sum_ {k = 1} ^ {| \\hat {\\mathcal {Q}} |} \\exp \\left(e _ {i , k}\\right)} \\left(\\mathbf {x} _ {k} ^ {\\mathcal {Q}} \\mathbf {W} ^ {V}\\right), \\tag {4}", + "image_path": "011b5590ad5268a908a48c02a0baf8766ad66a2e4cb15b53ace04e53c178f80e.jpg" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 306, + 669, + 490, + 681 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 669, + 490, + 681 + ], + "spans": [ + { + "bbox": [ + 306, + 669, + 490, + 681 + ], + "type": "text", + "content": "where the attention score " + }, + { + "bbox": [ + 306, + 669, + 490, + 681 + ], + "type": "inline_equation", + "content": "e_{i,j}" + }, + { + "bbox": [ + 306, + 669, + 490, + 681 + ], + "type": "text", + "content": " is computed as:" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 364, + 687, + 545, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 364, + 687, + 545, + 716 + ], + "spans": [ + { + "bbox": [ + 364, + 687, + 545, + 716 + ], + "type": "interline_equation", + "content": "e _ {i, j} = \\frac {\\left(\\mathbf {x} _ {i} ^ {\\mathcal {P}} \\mathbf {W} ^ {Q}\\right) \\left(\\mathbf {x} _ {j} ^ {\\mathcal {Q}} \\mathbf {W} ^ {K}\\right) ^ {\\top}}{\\sqrt {d}}, \\tag {5}", + "image_path": "a4d44b105eb94b4acbeefc5cc9ec2306a02fc2a40a7e53c758d56f7fa49befe2.jpg" + } + ] + } + ], + "index": 27 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19608" + } + ] + } + ], + "index": 28 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 68, + 286, + 205 + ], + "blocks": [ + { + "bbox": [ + 48, + 68, + 286, + 205 + ], + "lines": [ + { + "bbox": [ + 48, + 68, + 286, + 205 + ], + "spans": [ + { + "bbox": [ + 48, + 68, + 286, + 205 + ], + "type": "image", + "image_path": "3ada87a13994500c9e9f1cff06f7ac5ccc4037d8889262b56faad03e71531af0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 75, + 207, + 258, + 218 + ], + "lines": [ + { + "bbox": [ + 75, + 207, + 258, + 218 + ], + "spans": [ + { + "bbox": [ + 75, + 207, + 258, + 218 + ], + "type": "text", + "content": "Figure 4. Structure of the Instance masking block." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 223, + 287, + 297 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 223, + 287, + 297 + ], + "spans": [ + { + "bbox": [ + 46, + 223, + 287, + 297 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 223, + 287, + 297 + ], + "type": "inline_equation", + "content": "\\mathbf{W}^Q, \\mathbf{W}^K, \\mathbf{W}^V \\in \\mathbb{R}^{d \\times d}" + }, + { + "bbox": [ + 46, + 223, + 287, + 297 + ], + "type": "text", + "content": " are the respective projection weights for query, key and value. The same computation goes for " + }, + { + "bbox": [ + 46, + 223, + 287, + 297 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}^Q" + }, + { + "bbox": [ + 46, + 223, + 287, + 297 + ], + "type": "text", + "content": ". Benefiting from the cross-attention block, the superpoint features in one point cloud are aware of the geometric structure of the other one, which facilitates modeling the geometric consistency between two point clouds." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "spans": [ + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": "Instance masking block. At last, this block consumes the cross-attention features " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\mathbf{X}^{\\mathcal{Q}}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{Q}}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " as well as the previous instance mask " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_{(t - 1)}^{\\mathcal{Q}}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " to predict a refined instance mask " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_{(t)}^{\\mathcal{Q}}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": ". We observe that two superpoints from different instances tend to be distant in the geodesic space. To this end, we design a geodesic self-attention mechanism by replacing the geometric structure embedding in Eq. (3) with a similar geodesic distance embedding to enhance the superpoint features. Please refer to the appendix for more details. The resultant superpoint features are denoted as " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\mathbf{Y}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": ". At last, we adopt an MLP to predict a confidence score " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "u_{i,j}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " for each neighbor " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{q}}_{i_j} \\in \\mathcal{N}_i^{\\mathcal{Q}}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " indicating whether it belongs to the same instance as " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{q}}_i" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " based on the feature discrepancy between " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\mathbf{y}_i" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\mathbf{y}_{i_j}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " and the geodesic distance embedding " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\mathbf{g}_{i,j}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " between " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{q}}_i" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{q}}_{i_j}" + }, + { + "bbox": [ + 46, + 297, + 287, + 479 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 93, + 488, + 287, + 509 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 93, + 488, + 287, + 509 + ], + "spans": [ + { + "bbox": [ + 93, + 488, + 287, + 509 + ], + "type": "interline_equation", + "content": "u _ {i, j} = \\sigma \\left(\\operatorname {M L P} \\left(\\left[ \\mathbf {y} _ {i j} - \\mathbf {y} _ {i}; \\mathbf {g} _ {i, j} \\right]\\right)\\right), \\tag {6}", + "image_path": "90e00aa41f8832ba62c5da92a1a6babb023059c8b57d38022f75ab87f1e9dac6.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "spans": [ + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "inline_equation", + "content": "\\sigma (\\cdot)" + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "text", + "content": " is the sigmoid function and " + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "inline_equation", + "content": "[\\cdot ]" + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "text", + "content": " is the concatenation operator. At last, the confidence matrix " + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "inline_equation", + "content": "\\mathbf{U}\\in \\mathbb{R}^{|\\hat{\\mathcal{Q}} |\\times k}" + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "text", + "content": " is converted into " + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_{(t)}^{\\mathcal{Q}}" + }, + { + "bbox": [ + 47, + 517, + 287, + 558 + ], + "type": "text", + "content": " with a thresholding function:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 109, + 565, + 287, + 597 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 109, + 565, + 287, + 597 + ], + "spans": [ + { + "bbox": [ + 109, + 565, + 287, + 597 + ], + "type": "interline_equation", + "content": "m _ {i, j} ^ {\\mathcal {Q}} = \\left\\{ \\begin{array}{l l} - \\infty & u _ {i, j} < \\tau \\\\ 0 & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {7}", + "image_path": "c11ec5fb6318ea6a207642793e7066f466e02b3dfdfaf86c7722d0f9cffc60a6.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 605, + 287, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 677 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 605, + 287, + 677 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 46, + 605, + 287, + 677 + ], + "type": "text", + "content": " is the confidence threshold. Thanks to the instance mask, our model can effectively learn instance-aware superpoint features and extract accurate superpoint correspondences covering more instances. Furthermore, the instance masks also help extract instance-aware dense point correspondences as described in Sec. 4.2." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": "Superpoint matching. We extract superpoint correspondences " + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{C}}" + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": " by matching the superpoint features from the last cross-attention block. As in [38], we select the top " + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "N_{c}" + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": " su" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "text", + "content": "perpoint pairs with the highest cosine feature similarity as the superpoint correspondences." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 104, + 476, + 115 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 104, + 476, + 115 + ], + "spans": [ + { + "bbox": [ + 306, + 104, + 476, + 115 + ], + "type": "text", + "content": "4.2. Instance Candidate Generation" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 122, + 545, + 242 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 122, + 545, + 242 + ], + "spans": [ + { + "bbox": [ + 304, + 122, + 545, + 242 + ], + "type": "text", + "content": "After obtaining the superpoint correspondences, we then refine them to dense point correspondences at the fine level. Previous methods [38, 54] opt to match the points within the local patches of two matched superpoints with an optimal transport layer [40]. Nonetheless, the local correspondences extracted in this manner often cluster closely, which could lead to unstable pose estimation as noted in [25]. This is aggravated in multi-instance registration, especially in cluttered scenes, as each instance is typically small and thus its pose cannot be globally optimized as in [38]." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "spans": [ + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": "To address this issue, we propose to extract dense point correspondences within the instance scope by leveraging the instance masks from the coarse level. For each superpoint correspondence " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{C}}_k = (\\hat{\\mathbf{p}}_i,\\hat{\\mathbf{q}}_j)" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": ", we collect their neighboring superpoints " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_i^{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_j^{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": ". The superpoints from different instances of " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{q}}_j" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " are removed from " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_j^{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " based on the instance mask " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_j" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": ". The points in the local patches of all superpoints in " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_i^{\\mathcal{P}}" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_j^{\\mathcal{Q}}" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " imply a potential occurrence of " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{Q}" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": ", i.e., an instance candidate, denoted as " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_k" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": ". Next, instance-wise point correspondences are extracted within " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_k" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " with an optimal transport layer and mutual top-" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " selection following [38], denoted as " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_k" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": ". At last, we estimate a pose " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_k = \\{\\mathbf{R}_k,\\mathbf{t}_k\\}" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_k" + }, + { + "bbox": [ + 304, + 243, + 546, + 460 + ], + "type": "text", + "content": " by solving Eq. (1) with weighted SVD [8]. Thanks to the powerful instance-aware geometric transformer, an instance candidate can cover a relatively large portion of an instance, with few points from the background or other instances, so the poses obtained in this step have already been very accurate." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 468, + 499, + 479 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 468, + 499, + 479 + ], + "spans": [ + { + "bbox": [ + 306, + 468, + 499, + 479 + ], + "type": "text", + "content": "4.3. Candidate Selection and Refinement" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 486, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 486, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 486, + 545, + 544 + ], + "type": "text", + "content": "As several superpoint correspondences could belong to the same instance, there are commonly duplicated instances in the instance candidates. For this reason, we further design a simple but effective algorithm for duplicate removal and candidate refinement." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 545, + 545, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 545, + 594 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 545, + 594 + ], + "type": "text", + "content": "Inspired by non-maximum suppression (NMS) [39], we first sort the instance candidates by the inlier ratio on the global point correspondences " + }, + { + "bbox": [ + 304, + 545, + 545, + 594 + ], + "type": "inline_equation", + "content": "\\mathcal{C} = \\bigcup_{i=1}^{N_c} \\mathcal{C}_i" + }, + { + "bbox": [ + 304, + 545, + 545, + 594 + ], + "type": "text", + "content": ". The inlier ratio of the instance candidate " + }, + { + "bbox": [ + 304, + 545, + 545, + 594 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_k" + }, + { + "bbox": [ + 304, + 545, + 545, + 594 + ], + "type": "text", + "content": " is:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 339, + 601, + 545, + 632 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 339, + 601, + 545, + 632 + ], + "spans": [ + { + "bbox": [ + 339, + 601, + 545, + 632 + ], + "type": "interline_equation", + "content": "\\gamma_ {k} = \\frac {1}{| \\mathcal {C} |} \\sum_ {(\\mathbf {p}, \\mathbf {q}) \\in \\mathcal {C}} [ [ \\| \\mathbf {R} _ {k} \\mathbf {p} + \\mathbf {t} _ {k} - \\mathbf {q} \\| < \\tau_ {2} ] ], \\tag {8}", + "image_path": "8ecedc5d9f0c98d2063ee6f67b8a10689e964cfddc0816f604d44238506f7b69.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\llbracket \\cdot \\rrbracket" + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "text", + "content": " is the Iverson bracket and " + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\tau_{2}" + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "text", + "content": " is the acceptance radius. Next, we select the instance candidate with the highest inlier ratio as the anchor candidate. All remaining candidates similar with the anchor are merged with it and removed from future computation. We define the similarity between two candidates " + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_i" + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_j" + }, + { + "bbox": [ + 304, + 641, + 545, + 714 + ], + "type": "text", + "content": " by the average distance" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19609" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 222, + 84 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 222, + 84 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 222, + 84 + ], + "type": "text", + "content": "(ADD) [21] between their estimated poses:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 115, + 90, + 287, + 114 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 115, + 90, + 287, + 114 + ], + "spans": [ + { + "bbox": [ + 115, + 90, + 287, + 114 + ], + "type": "interline_equation", + "content": "s _ {i, j} = 1 - \\frac {\\operatorname {A D D} \\left(\\mathbf {T} _ {i} , \\mathbf {T} _ {j}\\right)}{r}, \\tag {9}", + "image_path": "8eed0204ccc9ba40874cff41c055ec1f7b12729829f0d198c25f2ba09f9ee9ff.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "spans": [ + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "inline_equation", + "content": "r" + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "text", + "content": " is the diameter of " + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "text", + "content": ". And " + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_i" + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_j" + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "text", + "content": " are considered similar if " + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "inline_equation", + "content": "s_{i,j}" + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "text", + "content": " is above " + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "inline_equation", + "content": "\\tau_s" + }, + { + "bbox": [ + 46, + 120, + 287, + 227 + ], + "type": "text", + "content": ". To merge two candidates, we combine their point correspondences and recompute the pose by solving Eq. (1). At last, the preserved pose is iteratively refined with the surviving inliers as in [5, 38], leading to a final instance registration. The anchor is then removed from future computation. The above process repeats until there are no candidates left and we omit the instance registrations with too few inliers." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 228, + 288, + 360 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 228, + 288, + 360 + ], + "spans": [ + { + "bbox": [ + 46, + 228, + 288, + 360 + ], + "type": "text", + "content": "Compared to multi-model fitting methods [44, 55], the advantages of our MIRETR are two-fold. First, by learning instance-aware superpoint features, the influence from the background and other instances is minimized, thus the correspondences are more accurate and can cover more instances. Second, correspondence clustering-based methods tend to lose heavily-occluded instances as there are few correspondences on them, especially in cluttered scenes. On the contrary, our method can better recognize these hard instances as we bypass the clustering process by directly extracting instance candidates and merging similar ones." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 366, + 141, + 378 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 366, + 141, + 378 + ], + "spans": [ + { + "bbox": [ + 47, + 366, + 141, + 378 + ], + "type": "text", + "content": "4.4. Loss Functions" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "spans": [ + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "text", + "content": "We adopt three loss functions to train MIRETR: an overlap-aware circle loss [38] " + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{circle}}" + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "text", + "content": " to supervise the superpoint features, a negative log-likelihood loss [40] " + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{nll}}" + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "text", + "content": " to supervise the point matching, and a mask prediction loss [36] " + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{mask}}" + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "text", + "content": " to supervise the instance masks. The overall loss is computed as " + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "inline_equation", + "content": "\\mathcal{L} = \\mathcal{L}_{\\mathrm{circle}} + \\mathcal{L}_{\\mathrm{nll}} + \\mathcal{L}_{\\mathrm{mask}}" + }, + { + "bbox": [ + 46, + 384, + 287, + 468 + ], + "type": "text", + "content": ". Please refer to the supplementary material for more details." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 478, + 128, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 478, + 128, + 491 + ], + "spans": [ + { + "bbox": [ + 47, + 478, + 128, + 491 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 498, + 287, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 287, + 545 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 287, + 545 + ], + "type": "text", + "content": "We evaluate MIRETR on indoor Scan2CAD [2, 44, 55], industrial ROBI [52] and synthetic ShapeNet [10] benchmarks. And we also introduce the implementation details and more experiments in the supplementary material." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 545, + 287, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 287, + 629 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 287, + 629 + ], + "type": "text", + "content": "Baselines. We compare with three state-of-the-art point cloud correspondence methods, FCGF [14], CoFiNet [54] and GeoTransformer [38], and four recent multi-model fitting methods, T-linkage [33], RansaCov [34], ECC [44], and PointCLM [55]. The point cloud correspondence methods and the multi-model fitting methods are pairwise integrated for a comprehensive comparison." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 630, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 287, + 713 + ], + "type": "text", + "content": "Metrics. Following [44, 55], we evaluate our method with three registration metrics: (1) Mean Recall (MR), the ratio of registered instances over all ground-truth instances, (2) Mean Precision (MP), the ratio of registered instances over all predicted instances, and (3) Mean " + }, + { + "bbox": [ + 46, + 630, + 287, + 713 + ], + "type": "inline_equation", + "content": "F_{1}" + }, + { + "bbox": [ + 46, + 630, + 287, + 713 + ], + "type": "text", + "content": " score (MF), the harmonic mean of MP and MR. We also report Inlier Ratio (IR), the ratio of inliers over all extracted correspondences." + } + ] + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 307, + 70, + 544, + 242 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 544, + 242 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 544, + 242 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 544, + 242 + ], + "type": "table", + "html": "
ModelIR(%)MR(%)MP(%)MF(%)
FCGF [14] + T-Linkage [33]54.7522.7632.15
FCGF [14] + RansaCov [34]36.2773.5045.0155.83
FCGF [14] + PointCLM [55]86.9970.0577.60
FCGF [14] + ECC [44]92.6073.7982.13
CoFiNet [54] + T-Linkage [33]28.175.098.62
CoFiNet [54] + RansaCov [34]18.5238.2913.6920.16
CoFiNet [54] + PointCLM [55]36.1524.7029.34
CoFiNet [54] + ECC [44]57.2617.2426.50
GeoTransformer [38] + T-Linkage [33]72.6844.8055.43
GeoTransformer [38] + RansaCov [34]44.0278.8467.1672.53
GeoTransformer [38] + PointCLM [55]82.8181.9082.35
GeoTransformer [38] + ECC [44]94.6374.8383.57
MIRETR (ours) + T-Linkage [33]77.1246.0457.65
MIRETR (ours) + RansaCov [34]84.7871.3477.48
MIRETR (ours) + PointCLM [55]56.5991.8591.0891.46
MIRETR (ours) + ECC [44]96.5289.0392.62
MIRETR (ours, full pipeline)95.7091.2193.40
", + "image_path": "6861a70b9f788145571310bf2c171c61f4a4da672434117e90d1d85f2b30f5c4.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 326, + 245, + 523, + 255 + ], + "lines": [ + { + "bbox": [ + 326, + 245, + 523, + 255 + ], + "spans": [ + { + "bbox": [ + 326, + 245, + 523, + 255 + ], + "type": "text", + "content": "Table 1. Evaluation results on Scan2CAD benchmark." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 306, + 262, + 454, + 274 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 262, + 454, + 274 + ], + "spans": [ + { + "bbox": [ + 306, + 262, + 454, + 274 + ], + "type": "text", + "content": "5.1. Evaluations on Scan2CAD" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "spans": [ + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "type": "text", + "content": "Dataset. Scan2CAD [2] is a scene-to-CAD alignment dataset build upon ScanNet [15] and ShapeNet [10]. It consists of 1506 scenes from ScanNet annotated with 14225 CAD models from ShapeNet and their poses in the scenes. Following [55], we replace the objects in the scenes with the corresponding aligned CAD models. We select the scene-model pairs which the scene contain multiple instances of the model for multi-instance registration. As last, we obtain 2184 point cloud pairs and use " + }, + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "type": "inline_equation", + "content": "70\\%" + }, + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "type": "text", + "content": " pairs for training, " + }, + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "type": "text", + "content": " for validation and " + }, + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 304, + 281, + 545, + 399 + ], + "type": "text", + "content": " for testing." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 400, + 545, + 472 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 400, + 545, + 472 + ], + "spans": [ + { + "bbox": [ + 304, + 400, + 545, + 472 + ], + "type": "text", + "content": "Quantitative results. As shown in Tab. 1, our MIRETR achieves consistent improvements over the baseline correspondence models. Notably, our method surpasses the previous best GeoTransformer on IR by 12 percentage points (pp). When coupled with PointCLM, it outperforms GeoTransformer by over 9 pp on the three registration metrics." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 472, + 545, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 472, + 545, + 567 + ], + "spans": [ + { + "bbox": [ + 304, + 472, + 545, + 567 + ], + "type": "text", + "content": "Moreover, our full pipeline surpasses all models with the baseline multi-model fitting methods. Although the ECC-based model performs slightly better than full MIRETR on MR, its MP is significantly worse. This indicates that ECC achieves high MR by predicting more registrations, which is impractical in real-world applications. And our method outperforms PointCLM on all three registration metrics, which demonstrates the strong effectiveness of our method." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 575, + 429, + 586 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 575, + 429, + 586 + ], + "spans": [ + { + "bbox": [ + 306, + 575, + 429, + 586 + ], + "type": "text", + "content": "5.2. Evaluations on ROBI" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "content": "Dataset. ROBI [52] is a recent dataset for industrial bin-picking. It includes 7 reflective metallic industrial objects and 63 bin-picking scenes. Each scene contains cluttered instances of one industrial object. 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ModelIR(%)MR(%)MP(%)MF(%)
CoFiNet [54] + T-Linkage [33]10.351.340.720.93
CoFiNet [54] + RansaCov [34]1.251.391.31
CoFiNet [54] + PointCLM [55]1.172.111.50
CoFiNet [54] + ECC [44]3.218.504.66
GeoTransformer [38] + T-Linkage [33]39.647.714.575.73
GeoTransformer [38] + RansaCov [34]8.9913.5810.81
GeoTransformer [38] + PointCLM [55]13.9826.6418.33
GeoTransformer [38] + ECC [44]18.5530.9923.20
MIRETR (ours) + T-Linkage [33]45.1412.0410.4711.20
MIRETR (ours) + RansaCov [34]14.1426.2918.38
MIRETR (ours) + PointCLM [55]18.6840.1125.48
MIRETR (ours) + ECC [44]24.6534.8528.91
MIRETR (ours, full pipeline)38.5141.1939.80
", + "image_path": "b12e836e86784d456a97df0e8d248d366226a281417fc839953ffa70b7175de9.jpg" + } + ] + } + ], + "index": 40, + "angle": 0, + "type": "table_body" + } + ], + "index": 40 + }, + { + "bbox": [ + 78, + 481, + 255, + 491 + ], + "lines": [ + { + "bbox": [ + 78, + 481, + 255, + 491 + ], + "spans": [ + { + "bbox": [ + 78, + 481, + 255, + 491 + ], + "type": "text", + "content": "Table 2. Evaluation results on ROBI benchmark." + } + ] + } + ], + "index": 41, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 497, + 286, + 580 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 497, + 286, + 580 + ], + "spans": [ + { + "bbox": [ + 46, + 497, + 286, + 580 + ], + "type": "text", + "content": "forms the baseline correspondence methods by a large margin on all four metrics. Compared to Scan2CAD, ROBI is more challenging due to the more cluttered scenes, where instance-aware information is more important. Benefiting from the instance-aware geometric transformer module, our method extracts reliable instance-aware correspondences, which contributes to more accurate instance registrations." + } + ] + } + ], + "index": 42 + }, + { + "bbox": [ + 46, + 582, + 286, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 286, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 286, + 689 + ], + "type": "text", + "content": "Our full model achieves significant improvements over the ECC-based model on MR, MP and MF. The PointCLM-based model achieves comparable MP with the full model, but significantly worse MR, which means it can register only several easy instances but misses most heavily-occluded instances. Specifically, it can register on average only 6.2 instances per scene, while the number of our method is 13.7. Our method achieves both high MR and MP, showing strong robustness in cluttered scenes." + } + ] + } + ], + "index": 43 + }, + { + "bbox": [ + 46, + 689, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 286, + 712 + ], + "type": "text", + "content": "Qualitative results. Fig. 5 visualizes the registration results of GeoTransformer and MIRETR. Our method can" + } + ] + } + ], + "index": 44 + }, + { + "type": "image", + "bbox": [ + 307, + 342, + 383, + 419 + ], + "blocks": [ + { + "bbox": [ + 46, + 305, + 545, + 338 + ], + "lines": [ + { + "bbox": [ + 46, + 305, + 545, + 338 + ], + "spans": [ + { + "bbox": [ + 46, + 305, + 545, + 338 + ], + "type": "text", + "content": "Figure 5. Registration results on ROBI benchmark. We visualize the successfully registered instances in (c) and (d). MIRETR registers more instances in the cluttered scenes (the " + }, + { + "bbox": [ + 46, + 305, + 545, + 338 + ], + "type": "inline_equation", + "content": "2^{\\text{nd}}" + }, + { + "bbox": [ + 46, + 305, + 545, + 338 + ], + "type": "text", + "content": " and the " + }, + { + "bbox": [ + 46, + 305, + 545, + 338 + ], + "type": "inline_equation", + "content": "3^{\\text{rd}}" + }, + { + "bbox": [ + 46, + 305, + 545, + 338 + ], + "type": "text", + "content": " rows) and with incomplete geometry (all three rows). And it extracts more accurate correspondences benefiting from the instance-aware correspondence learning mechanism." + } + ] + } + ], + "index": 39, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 307, + 342, + 383, + 419 + ], + "lines": [ + { + "bbox": [ + 307, + 342, + 383, + 419 + ], + "spans": [ + { + "bbox": [ + 307, + 342, + 383, + 419 + ], + "type": "image", + "image_path": "391ca0191f955cb9a6ce937cf227c2f26566bf36dc2ed686e4e35c93a389f6c0.jpg" + } + ] + } + ], + "index": 45, + "angle": 0, + "type": "image_body" + } + ], + "index": 45 + }, + { + "type": "image", + "bbox": [ + 386, + 342, + 463, + 419 + ], + "blocks": [ + { + "bbox": [ + 386, + 342, + 463, + 419 + ], + "lines": [ + { + "bbox": [ + 386, + 342, + 463, + 419 + ], + "spans": [ + { + "bbox": [ + 386, + 342, + 463, + 419 + ], + "type": "image", + "image_path": "b6485a00d3b1d395f9bd361f2487dcd38fa3167e21cd81dbb7ffe8c613cfcf55.jpg" + } + ] + } + ], + "index": 46, + "angle": 0, + "type": "image_body" + } + ], + "index": 46 + }, + { + "type": "image", + "bbox": [ + 466, + 342, + 544, + 419 + ], + "blocks": [ + { + "bbox": [ + 466, + 342, + 544, + 419 + ], + "lines": [ + { + "bbox": [ + 466, + 342, + 544, + 419 + ], + "spans": [ + { + "bbox": [ + 466, + 342, + 544, + 419 + ], + "type": "image", + "image_path": "d5503b738ba1ee730cc57be49e2512510deae3912135aa643abd992b3e952ba8.jpg" + } + ] + } + ], + "index": 47, + "angle": 0, + "type": "image_body" + } + ], + "index": 47 + }, + { + "type": "image", + "bbox": [ + 307, + 421, + 384, + 498 + ], + "blocks": [ + { + "bbox": [ + 307, + 421, + 384, + 498 + ], + "lines": [ + { + "bbox": [ + 307, + 421, + 384, + 498 + ], + "spans": [ + { + "bbox": [ + 307, + 421, + 384, + 498 + ], + "type": "image", + "image_path": "8d3df5aa3f8921044baebe2827a67c205e342787a90d0bc6f09a89fe3001a9b0.jpg" + } + ] + } + ], + "index": 48, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 310, + 498, + 382, + 506 + ], + "lines": [ + { + "bbox": [ + 310, + 498, + 382, + 506 + ], + "spans": [ + { + "bbox": [ + 310, + 498, + 382, + 506 + ], + "type": "text", + "content": "(a) Anchor's neighbors" + } + ] + } + ], + "index": 49, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 306, + 508, + 545, + 552 + ], + "lines": [ + { + "bbox": [ + 306, + 508, + 545, + 552 + ], + "spans": [ + { + "bbox": [ + 306, + 508, + 545, + 552 + ], + "type": "text", + "content": "Figure 6. Visualizations of the predicted instance masks. The anchor superpoint (patch) is in red and the selected neighbors are color-coded. Our method can effectively reject the patches outside the interested instance while preserving most of those inside." + } + ] + } + ], + "index": 54, + "angle": 0, + "type": "image_caption" + } + ], + "index": 48 + }, + { + "type": "image", + "bbox": [ + 386, + 421, + 463, + 498 + ], + "blocks": [ + { + "bbox": [ + 386, + 421, + 463, + 498 + ], + "lines": [ + { + "bbox": [ + 386, + 421, + 463, + 498 + ], + "spans": [ + { + "bbox": [ + 386, + 421, + 463, + 498 + ], + "type": "image", + "image_path": "d5e8662215981f9b8f3c9bdfbf1940a9049c4a266abfef58d8dc728417113bbf.jpg" + } + ] + } + ], + "index": 50, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 389, + 498, + 462, + 506 + ], + "lines": [ + { + "bbox": [ + 389, + 498, + 462, + 506 + ], + "spans": [ + { + "bbox": [ + 389, + 498, + 462, + 506 + ], + "type": "text", + "content": "(b) Ground Truth Mask" + } + ] + } + ], + "index": 51, + "angle": 0, + "type": "image_caption" + } + ], + "index": 50 + }, + { + "type": "image", + "bbox": [ + 466, + 421, + 544, + 498 + ], + "blocks": [ + { + "bbox": [ + 466, + 421, + 544, + 498 + ], + "lines": [ + { + "bbox": [ + 466, + 421, + 544, + 498 + ], + "spans": [ + { + "bbox": [ + 466, + 421, + 544, + 498 + ], + "type": "image", + "image_path": "96232d5edff7c4e3fb917f7bd8549b8ca128637140de62e2cc227b322af338d4.jpg" + } + ] + } + ], + "index": 52, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 467, + 498, + 544, + 506 + ], + "lines": [ + { + "bbox": [ + 467, + 498, + 544, + 506 + ], + "spans": [ + { + "bbox": [ + 467, + 498, + 544, + 506 + ], + "type": "text", + "content": "(c) Our Prediceted Mask" + } + ] + } + ], + "index": 53, + "angle": 0, + "type": "image_caption" + } + ], + "index": 52 + }, + { + "bbox": [ + 306, + 556, + 545, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 556, + 545, + 604 + ], + "spans": [ + { + "bbox": [ + 306, + 556, + 545, + 604 + ], + "type": "text", + "content": "register more instances in cluttered scenes (see the " + }, + { + "bbox": [ + 306, + 556, + 545, + 604 + ], + "type": "inline_equation", + "content": "2^{\\text{nd}}" + }, + { + "bbox": [ + 306, + 556, + 545, + 604 + ], + "type": "text", + "content": " and the " + }, + { + "bbox": [ + 306, + 556, + 545, + 604 + ], + "type": "inline_equation", + "content": "3^{\\text{rd}}" + }, + { + "bbox": [ + 306, + 556, + 545, + 604 + ], + "type": "text", + "content": " rows) and with severe geometric deficiency (see all three rows). And MIRETR attains more high-quality correspondences thanks to our instance-aware design." + } + ] + } + ], + "index": 55 + }, + { + "bbox": [ + 306, + 605, + 545, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 605, + 545, + 700 + ], + "spans": [ + { + "bbox": [ + 306, + 605, + 545, + 700 + ], + "type": "text", + "content": "We further visualize the predicted instance masks Fig. 6. The instance masks effectively reject the patches out of the interested instance while preserving most of those inside. Specifically, our method achieves the instance mIoU of 69.26 pp while the result of the model without masking is merely 38.13 pp. The high-quality masks allow us to effectively encode intra-instance context and contribute to accurate registrations." + } + ] + } + ], + "index": 56 + }, + { + "bbox": [ + 317, + 701, + 544, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 701, + 544, + 713 + ], + "spans": [ + { + "bbox": [ + 317, + 701, + 544, + 713 + ], + "type": "text", + "content": "Fig. 7 compares the results under different overlap ratios." + } + ] + } + ], + "index": 57 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19611" + } + ] + } + ], + "index": 58 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 68, + 289, + 209 + ], + "blocks": [ + { + "bbox": [ + 47, + 68, + 289, + 209 + ], + "lines": [ + { + "bbox": [ + 47, + 68, + 289, + 209 + ], + "spans": [ + { + "bbox": [ + 47, + 68, + 289, + 209 + ], + "type": "image", + "image_path": "47fd1ca19d7110631edeade7b18fcf7f75922bb74cb3687da7de3747fb0f468c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 210, + 286, + 221 + ], + "lines": [ + { + "bbox": [ + 47, + 210, + 286, + 221 + ], + "spans": [ + { + "bbox": [ + 47, + 210, + 286, + 221 + ], + "type": "text", + "content": "Figure 7. Results in different overlap levels on ROBI benchmark." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 228, + 287, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 228, + 287, + 277 + ], + "spans": [ + { + "bbox": [ + 47, + 228, + 287, + 277 + ], + "type": "text", + "content": "MIRETR consistently outperforms the baselines at all overlap levels, and the improvements are more significant when the overlap ratio is below " + }, + { + "bbox": [ + 47, + 228, + 287, + 277 + ], + "type": "inline_equation", + "content": "50\\%" + }, + { + "bbox": [ + 47, + 228, + 287, + 277 + ], + "type": "text", + "content": ". This proves the strong capability of our method to handle low-overlap instances." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 284, + 188, + 297 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 284, + 188, + 297 + ], + "spans": [ + { + "bbox": [ + 47, + 284, + 188, + 297 + ], + "type": "text", + "content": "5.3. Evaluations on ShapeNet" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 303, + 287, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 303, + 287, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 303, + 287, + 422 + ], + "type": "text", + "content": "Dataset. ShapeNet [10] is a large CAD model dataset which contains 51300 models from 55 categories. We use the models from first 30 categories for training and those from the rest 25 categories for testing to evaluate the generality to novel categories. We randomly sample at most 500 models from each category to avoid class imbalance. For each point cloud pair, the model point cloud is a random CAD model and the scene one is constructed by applying " + }, + { + "bbox": [ + 46, + 303, + 287, + 422 + ], + "type": "inline_equation", + "content": "4\\sim 16" + }, + { + "bbox": [ + 46, + 303, + 287, + 422 + ], + "type": "text", + "content": " random poses on the model. At last, we obtain 8634 pairs for training, 900 for validation, and 7683 for testing." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 423, + 288, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 423, + 288, + 590 + ], + "spans": [ + { + "bbox": [ + 46, + 423, + 288, + 590 + ], + "type": "text", + "content": "Quantitative results. As shown in Tab. 3, our MIRETR achieves the best results on all four metrics, surpassing the baselines by a large margin. GeoTransformer significantly outperforms CoFiNet, which proves the importance of geometric structure to achieving generality. And our method achieves improvements of more than 10 pp over GeoTransformer on all registration metrics with PointCLM and ECC. Thanks to the instance-ware geometric transformer, the correspondences extracted by our method provide strong instance information, facilitating the correspondence clustering process. At last, our full model surpasses the previous best ECC-based baseline by around 2 pp on MR, 11 pp on MP and 7 pp on MF, demonstrating the strong generality of MIRETR to unseen objects." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 599, + 147, + 610 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 599, + 147, + 610 + ], + "spans": [ + { + "bbox": [ + 47, + 599, + 147, + 610 + ], + "type": "text", + "content": "5.4. Ablation Studies" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 617, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 287, + 715 + ], + "type": "text", + "content": "We conduct extensive ablation studies on ROBI benchmark to better understand our design choices in Tab. 4. We first ablate the instance-aware point matching and extract point correspondences within only the patches of the superpoint correspondences in Tab. 4 (b), which is significantly worse than the full model. The poses estimated by this method is unstable due to clustered correspondences, thus the duplicated candidates cannot be effectively removed by NMS." + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 307, + 70, + 544, + 205 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 544, + 205 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 544, + 205 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 544, + 205 + ], + "type": "table", + "html": "
ModelIR(%)MR(%)MP(%)MF(%)
CoFiNet [54] + T-Linkage [33]4.593.243.79
CoFiNet [54] + RansaCov [34]39.537.355.336.17
CoFiNet [54] + PointCLM [55]23.4019.6621.36
CoFiNet [54] + ECC [44]41.4926.6032.41
GeoTransformer [38] + T-Linkage [33]27.6826.4027.02
GeoTransformer [38] + RansaCov [34]69.6541.8648.1644.78
GeoTransformer [38] + PointCLM [55]68.0969.0968.58
GeoTransformer [38] + ECC [44]78.0364.0870.37
MIRETR (ours) + T-Linkage [33]29.4028.6729.03
MIRETR (ours) + RansaCov [34]45.6346.8546.23
MIRETR (ours) + PointCLM [55]77.1385.6385.8185.71
MIRETR (ours) + ECC [44]92.5682.0887.01
MIRETR (ours, full pipeline)94.9593.9494.44
", + "image_path": "843107ec916c96881858bfb81362e9325f0099639ec1d5bd81622569773569d0.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 309, + 221, + 542, + 281 + ], + "blocks": [ + { + "bbox": [ + 330, + 209, + 520, + 219 + ], + "lines": [ + { + "bbox": [ + 330, + 209, + 520, + 219 + ], + "spans": [ + { + "bbox": [ + 330, + 209, + 520, + 219 + ], + "type": "text", + "content": "Table 3. Evaluation results on ShapeNet benchmark." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 221, + 542, + 281 + ], + "lines": [ + { + "bbox": [ + 309, + 221, + 542, + 281 + ], + "spans": [ + { + "bbox": [ + 309, + 221, + 542, + 281 + ], + "type": "table", + "html": "
ModelIR(%)MR(%)MP(%)MF(%)
(a) full MIRETR45.1438.5141.1939.80
(b) w/o instance-aware point matching40.5218.1527.5421.88
(c) w/o instance masking block36.7817.0745.3724.80
(d) w/o both38.8114.1327.4418.65
(e) w/ global attention25.987.7218.8610.96
", + "image_path": "1cff5e45d9ef139c4870cf53a0bfdeb7a6a006cc885ea66901caa584aa79197f.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 339, + 285, + 511, + 296 + ], + "lines": [ + { + "bbox": [ + 339, + 285, + 511, + 296 + ], + "spans": [ + { + "bbox": [ + 339, + 285, + 511, + 296 + ], + "type": "text", + "content": "Table 4. Ablation studies on ROBI benchmark." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 300, + 545, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 300, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 304, + 300, + 545, + 456 + ], + "type": "text", + "content": "Next, we remove the instance masking blocks in Tab. 4 (c) and the instance-aware point matching gathers the points from all neighbor superpoints. This model achieves a good MP, but a significantly worse MR, which means it can register only few instances (2.9 vs. 13.7 average instances per scene). We then ablate both modules in Tab. 4 (d), which further degrades the performance. At last, we replace the geometric encoding block with the global geometric self-attention [38] in Tab. 4 (e), which achieves the worst results. This indicates that the superpoint features can be polluted if global context is encoded. These results have proven the strong efficacy of our designs. More ablation studies are presented in the supplementary material." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 466, + 378, + 479 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 466, + 378, + 479 + ], + "spans": [ + { + "bbox": [ + 306, + 466, + 378, + 479 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 486, + 545, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 486, + 545, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 486, + 545, + 665 + ], + "type": "text", + "content": "We have proposed MIRETR, a coarse-to-fine method to extract instance-aware correspondences for multi-instance registration. At the coarse level, an instance-aware geometric transformer module jointly learns instance-aware superpoint features and predicts per-instance masks. At the fine level, the superpoint correspondences are extended to instance candidates according to the instance masks, where instance-wise point correspondences are extracted. At last, we devise a simple but effective candidate selection and refinement algorithm to obtain the final registrations, bypassing the need of multi-model fitting methods. Extensive experiments on three public benchmarks have demonstrated the efficacy of our method. For future work, we would like to extend MIRETR to multi-modal multi-instance registration to boost more applications." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": "Acknowledgement. This work is in part supported by the NSFC (62325211, 62132021, 62102435), the Major Program of Xiangjiang Laboratory (23XJ01009), and the National Key R&D Program of China (2018AAA0102200)." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19612" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "text", + "content": "[1] Yasuhiro Aoki, Hunter Goforth, Rangaprasad Arun Srivatsan, and Simon Lucey. 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However, prior attempts to integrate geometric insights into stereo matching algorithms have largely focused on geometric knowledge from single images while crucial cross-view factors such as occlusion and matching uniqueness have been overlooked. To address this gap, we propose a novel Intra-view and Cross-view Geometric knowledge learning Network (ICGNet), specifically crafted to assimilate both intra-view and cross-view geometric knowledge. ICGNet harnesses the power of interest points to serve as a channel for intra-view geometric understanding. Simultaneously, it employs the correspondences among these points to capture cross-view geometric relationships. This dual incorporation empowers the proposed ICGNet to leverage both intra-view and cross-view geometric knowledge in its learning process, substantially improving its ability to estimate disparities. Our extensive experiments demonstrate the superiority of the ICGNet over contemporary leading models. The code will be available at https://github.com/DFSDDDDD1199/ICGNet.", + "bbox": [ + 75, + 335, + 473, + 638 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 667, + 209, + 684 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Stereo matching is the task of estimating a disparity map from a pair of rectified images. It stands as one of the cornerstone challenges in a range of computer vision tasks, including augmented reality, autonomous driving, and robotics [18]. With the rapid development of deep learning techniques and network structures in computer vision scenarios, deep stereo matching networks have achieved great success in stereo matching.", + "bbox": [ + 75, + 695, + 468, + 815 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Geometric knowledge plays a crucial role in the overall performance of stereo matching networks [21, 45, 55, 69] due to the existence of repeated patterns, textureless ar", + "bbox": [ + 75, + 816, + 468, + 862 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e4322bd310dd5ac8e01bf179132a8e43fb4227ec535028a88a0f20b4b1d7811f.jpg", + "image_caption": [ + "Figure 1. An illustration of our overall framework using synthetic shapes. We leverage intra-view geometric knowledge which is the knowledge of extracting geometric structures, and cross-view geometric knowledge which is the knowledge of the correspondences of these structures, to aid the stereo matching task. Note that the dotted lines are used for illustration and are not used in the method." + ], + "image_footnote": [], + "bbox": [ + 511, + 301, + 883, + 415 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "eas, and reflective surfaces, which make simple texture-based matching methods ineffective. Consequently, several methods were proposed to introduce geometric knowledge into stereo matching networks through kinds of geometric structures. EdgeStereo [45] proposed a learning network that incorporates edges and edge-disparity relations into the stereo matching network. Normal assisted stereo matching [21, 69] leverages surface normal as geometric constraints to reduce the matching ambiguity for textureless regions. However, the geometric knowledge employed in these studies is mainly intra-view, lacking the cross-view geometric knowledge such as matching uniqueness and occlusion.", + "bbox": [ + 496, + 537, + 890, + 718 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To address the absence of cross-view geometric knowledge, we have identified that the local feature matching task [12, 34, 40] can serve as a suitable source of cross-view geometric knowledge for stereo matching. Local feature matching involves the identification of correspondences between two images, typically achieved by initially detecting sparse, geometrically meaningful interest points within each view and then extracting descriptors for these interest points encoded with their visual attributes [12]. Subsequently, cross-view matching is carried out by comparing the interest points between the two images [40]. This matching process solves a partial assignment problem be", + "bbox": [ + 496, + 719, + 892, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*The work was done during an internship at I²R, A*STAR.", + "bbox": [ + 93, + 875, + 410, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "$\\dagger$ cheng-jun@i2r.a-star.edu.sg", + "bbox": [ + 98, + 887, + 251, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "20752", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "tween the points which takes matching uniqueness and occlusion into account. Moreover, we also find that the interest points from each image also provide intra-view knowledge of the image. Building upon these insights, we introduce our ICGNet framework to take both the intra-view and cross-view geometric knowledge contained in local feature matching models into the stereo matching network. We leverage a pre-trained local feature matching pipeline, comprising an interest point detector and a point matcher. We propose an intra-view constraint that the features we extract from stereo matching backbone preserve the same interest point information as the pre-trained interest point detector to gain intra-view geometric knowledge. Additionally, we propose a cross-view constraint that these features are compelled to serve as descriptors for the interest points, facilitating the matching process between these points. The matching outcome is then constrained to align with both the ground-truth matching labels provided by ground-truth disparity maps and the matching results obtained from the pretrained interest point matcher, in order to gain cross-view geometric knowledge. Compared to EdgeStereo [45] and normal assisted stereo matching [21, 69], our method not only additionally introduces cross-view geometric knowledge but also keeps zero overhead when inference.", + "bbox": [ + 76, + 90, + 472, + 453 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our experiments show that our method effectively improves the performance across both the seen and unseen domains. The contributions are summarized as follows:", + "bbox": [ + 76, + 454, + 470, + 500 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. We propose to learn intra-view geometric knowledge for stereo matching networks from an interest point detector by introducing a novel intra-view geometric constraint computed from the interest point detection outcomes.", + "2. We propose to learn cross-view geometric knowledge for stereo matching networks from an interest point matcher by introducing a novel cross-view geometric constraint. We compute both soft cross-view and hard cross-view geometric losses using pretrained interest point matcher and disparity ground truth.", + "3. We conduct a series of comprehensive experiments that consistently demonstrate the proposed framework's ability to enhance the overall performance of state-of-the-art stereo matching networks. Our ICGNet achieves state-of-the-art performance on the SceneFlow dataset and ranks $1^{st}$ on the KITTI 2015 stereo matching benchmark among published peer-reviewed methods at the time of submission, and improves cross-domain generalization of baseline methods on KITTI 2012, KITTI 2015, and Middlebury 2014 datasets." + ], + "bbox": [ + 76, + 501, + 470, + 801 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 76, + 819, + 227, + 835 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Deep Stereo Matching", + "text_level": 1, + "bbox": [ + 76, + 845, + 284, + 862 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Deep-learning-based deep stereo matching techniques have gained widespread adoption and demonstrated promis", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "ing outcomes [7, 9, 16, 24, 25, 28, 37, 52, 53, 57, 58, 61]. The initial instance of such an approach is DispNetC [35], which presents an end-to-end trainable stereo matching framework. This framework employs the dot product of feature maps from left and right images as correspondence to build a cost volume of three dimensions. However, the drawback of this computational-friendly methodology is its inability to capture sufficient information to achieve satisfactory results. In the pursuit of improved performance, subsequent methods like GC-Net [20] have emerged. Numerous works [3, 65] have followed this trend and incorporated 3D hourglass convolutions to aggregate a 4D cost volume. This volume is created by concatenating features from left and right images. Unfortunately, this approach demands substantial memory usage and computational complexity. A notable enhancement arrives with GwcNet [17], which introduces the concept of group-wise correlation. This innovation enables the construction of a more compact cost volume. Recently, iterative optimization-based methods [23, 27, 63] have achieved splendid performance. Inspired by RAFT [48], RAFT-Stereo [27] iteratively updates the disparity using all-pairs correlation between features extracted. IGEV-Stereo [55] further boosts the performance of stereo matching network by combining cost-volume modules with iterative updating modules. Uncertainty-based methods [8, 51] also gained attention these years. ELFNet [33] leverage uncertainty to fuse multi-scale disparity and stereo network with different structures. SEDNet [6] proposes a soft-histogramming technique to align the distribution of prediction error and prediction uncertainty. Other works focus on improving the domain generalization performance [4, 11, 29, 38, 68] and domain adaptation performance [31, 46, 64, 66] of stereo matching networks.", + "bbox": [ + 496, + 90, + 893, + 589 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Recognizing the need for increased efficiency and the integration of richer semantic information, multi-scale cost volume is used in stereo matching networks. HSMNet [59] employs a pyramid of volumes to enable high-resolution stereo matching. AANet [56] takes a lightweight approach, incorporating a feature pyramid and interactions with multi-scale correlation volumes. In a recent development, PCWNet [43] introduces a volume fusion module that directly combines multi-scale 4D volumes. This innovation calculates a multi-level loss, ultimately expediting the model's convergence speed.", + "bbox": [ + 496, + 590, + 893, + 757 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.2. Geometric Structure Guided Stereo Matching", + "text_level": 1, + "bbox": [ + 500, + 770, + 887, + 786 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Geometric structures have been used to guide stereo matching networks in previous works. EdgeStereo [45] introduced an edge branch, integrating edge features into the stereo matching branch. Yang et al. [60] also advocated the use of edges for supervising stereo matching through multitask learning. Additionally, surface normals have been another employed geometric structure to guide stereo match", + "bbox": [ + 496, + 795, + 893, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "20753", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "ing. Zhang et al. [69] suggested a joint prediction of a surface normal map and a raw disparity map, iteratively refining the disparity map with guidance from the surface normal map. Kusupati et al. [21] incorporated an extra surface normal branch to predict raw surface normals and employed an independently trained consistency module for refinement of both surface normals and raw disparities.", + "bbox": [ + 75, + 90, + 470, + 196 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "However, these approaches have two limitations. Firstly, they heavily depend on additional branches during inference to improve their performance, which impacts efficiency. In contrast, our proposed framework leverages geometric structures as constraints during training without incurring any overhead in inference, and shows improved performance. Secondly, the previous methods only made use of intra-view geometric structures, whereas our framework takes into account both intra-view and cross-view geometric knowledge through both geometric structure and their correspondences.", + "bbox": [ + 75, + 198, + 468, + 364 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.3. Local Feature Matching", + "text_level": 1, + "bbox": [ + 76, + 376, + 299, + 393 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Local feature matching aims at matching images that depict the same scene or object. This is usually done in a two-stage manner: first, detect interest points each associated with a visual descriptor from both images, and then match the detected interest points.", + "bbox": [ + 75, + 400, + 468, + 474 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Traditional interest points detection and description algorithms [1, 19, 34, 39] rely on hand-crafted features. Recent research turns to Convolutional Neural Networks (CNN) for both interest point detection and description [22, 30, 32, 49]. SuperPoint [12] is a representative work of CNN-based interest point detector and descriptor, trained in a self-supervised manner. It constructs a synthetic shape dataset by rendering simplified 2D geometries, such as triangles, quadrilaterals, lines, and ellipses. The junctions of lines are labeled as interest points. These labels are then transferred to substantial real-world image datasets using a MagicPoint model and homographic adaptation. The self-supervised training process equips SuperPoint with the ability to be trained on various domains, enabling it to encode geometric information across diverse domains.", + "bbox": [ + 75, + 477, + 468, + 702 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Traditional algorithms employ nearest-neighbor classifiers for matching interest points. Lowe's test [34], inlier classifiers [62, 67], or geometric model fitting [2, 13] techniques are subsequently used to filter out unmatched points and incorrect correspondences. However, these methods are highly domain-specific and struggle to handle particularly challenging conditions. In contrast, deep learning-based matchers are trained to simultaneously match interest points and reject outliers. A notable example of this approach is SuperGlue [40], which leverages Transformers [50] to conduct self-attention among interest points within the same view and cross-attention between interest points in different views. The final matching step involves solving an op", + "bbox": [ + 75, + 704, + 470, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "timal transport problem. This approach allows SuperGlue to acquire robust insights into scene geometry and camera motion, rendering it resilient to extreme changes and effective in generalizing across various data domains. Subsequent works [5, 26, 44] focused on making it more efficient and digging into its design details while keeping its strong matching capability. Consequently, these matchers are great sources of cross-view geometric knowledge. We set up constraints to let the stereo matching network learn geometric knowledge from a pre-trained interest point detector and a pre-trained interest point matcher.", + "bbox": [ + 496, + 90, + 893, + 258 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 500, + 268, + 591, + 286 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We propose ICGNet to introduce geometric knowledge into stereo matching networks through geometric constraints. Intra-view geometric knowledge refers to the understanding that uncovers the geometric structures contained within a single image. Cross-view geometric knowledge refers to the comprehension that enables the alignment of geometric structures from one image to another. Models capable of uncovering and matching geometric structures harness the potential to convey intra-view and cross-view knowledge. Therefore, as depicted in Fig. 2, our framework introduces intra-view and cross-view geometric knowledge into the stereo matching network by aligning our network with intra-view and cross-view geometric knowledge sources. Although there are multiple choices (e.g., edges, points) to extract intra-view knowledge, we choose interest points as it is easy to further compute cross-view knowledge from these points using well-established methods [40] while it is more challenging to match the edges for cross-view knowledge computation. We denote the left-view stereo image as $I_{l}$ and right-view stereo image as $I_{r}$ , and the extracted left feature and right feature as $F_{l}$ and $F_{r}$ .", + "bbox": [ + 496, + 295, + 893, + 613 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Intra-view Geometric Knowledge", + "text_level": 1, + "bbox": [ + 500, + 619, + 794, + 638 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Intra-view Geometric Knowledge Decoder is to introduce intra-view geometric knowledge into the stereo matching network. We propose to leverage a pre-trained interest point detector $\\mathcal{IP}_{\\mathrm{det}}$ [12] in our method. It takes the left-view image $I_{l}$ and the right-view image $I_{r}$ as input and generates interest maps $\\mathbf{M}_l$ and $\\mathbf{M}_r$ , where each pixel is either labeled as interest point or non-interest point. These maps convey the intra-view geometric characteristics of the two images. We expect that the backbone features $F_{l}$ and $F_{r}$ preserve and unveil the intra-view geometric details present in both the left and right view images, akin to what the pretrained interest point detector accomplishes. Consequently, we aim to extract two interest point maps, $\\mathbf{M}_l^{\\prime}$ and $\\mathbf{M}_r^{\\prime}$ , from $F_{l}$ and $F_{r}$ using a trainable intra-view decoder $D_{\\mathrm{intra}}$ , aligning with $\\mathbf{M}_l$ and $\\mathbf{M}_r$ respectively. For the design of $D_{\\mathrm{intra}}$ , we use a stack of two bottleneck convolutional blocks. Note that decoder $D_{\\mathrm{intra}}$ is discarded during the test stage.", + "bbox": [ + 496, + 643, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "20754", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/c525551cd5238e96fc656ac5c96421dc22f5a0f75d144a35232d007023aa2769.jpg", + "image_caption": [ + "Figure 2. Overall structure of our proposed framework. The model architecture comprises three parts: stereo matching network, cross-view knowledge learning network, and intra-view knowledge learning network. The cross-view knowledge learning network introduces cross-view geometric knowledge by aligning the interest point correspondences $\\mathbf{P}'$ , $\\mathbf{P}$ and $\\mathcal{P}^{gt}$ using $\\mathcal{L}_{\\mathrm{cross - hard}}$ and $\\mathcal{L}_{\\mathrm{cross - soft}}$ . The intra-view knowledge learning network introduces intra-view geometric knowledge through aligning the interest point maps $\\mathbf{M}'$ and $\\mathbf{M}$ using $\\mathcal{L}_{\\mathrm{intra}}$ . Note that the dotted lines are used just for clear illustration and are not used in our work." + ], + "image_footnote": [], + "bbox": [ + 99, + 87, + 872, + 390 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Intra-view geometric loss $\\mathcal{L}_{\\mathrm{intra}}$ is computed to enforce this alignment:", + "bbox": [ + 76, + 494, + 470, + 526 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {i n t r a}} = \\frac {1}{2} \\mathcal {L} \\left(\\mathbf {M} _ {l} ^ {\\prime}, \\mathbf {M} _ {l}\\right) + \\frac {1}{2} \\mathcal {L} \\left(\\mathbf {M} _ {r} ^ {\\prime}, \\mathbf {M} _ {r}\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 138, + 539, + 468, + 570 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where we compute a focal loss $\\mathcal{L}$ due to unbalanced positive and negative samples of interest points.", + "bbox": [ + 76, + 575, + 468, + 607 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Cross-view Geometric Knowledge", + "text_level": 1, + "bbox": [ + 76, + 619, + 375, + 635 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Cross-view Geometric Knowledge Decoder enables the stereo matching network to acquire cross-view geometric knowledge by framing it as a learning task. This task is to align the stereo matching network with two complementary knowledge sources: a pre-trained interest point matcher denoted as $\\mathcal{IP}_{\\mathrm{match}}$ where we use [40] in our method, and the ground truth matching between interest points.", + "bbox": [ + 75, + 643, + 468, + 748 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The pre-trained matcher processes two sets of interest points extracted from stereo image pair $I_{l}$ and $I_{r}$ , denoted as $p_l$ and $p_r$ , each containing $m$ and $n$ points respectively, along with their associated descriptors. It outputs an assignment matrix $\\mathbf{P} \\in [0,1]^{(m + 1)\\times (n + 1)}$ . This matrix includes an extra row and column to account for the possibility that some points do not match any counterpart in the other view. The assignment matrix $\\mathbf{P}$ elucidates the cross-view geometric knowledge via the relations between the matching probabilities of the two sets of points.", + "bbox": [ + 75, + 750, + 470, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Furthermore, the ground truth disparities can serve as another source of knowledge since it provide accurate matching between these points. Ground truth matching pairs between the points $\\mathcal{P}^{gt} = \\{(i,j)\\} \\subset p_l \\times p_r$ ( $x$ refers to Cartesian product) and unmatched points in left image $\\mathcal{U}_l^{gt} \\subseteq p_l$ and right image $\\mathcal{U}_r^{gt} \\subseteq p_r$ are formed by warping interest points from the left image to the right image using the disparity.", + "bbox": [ + 496, + 494, + 890, + 617 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The ground truth is more precise compared to the assignment matrix provided by the interest point matcher. In the ground truth, the relationships between points are binary, classified simply as either a match or a mismatch. On the other hand, the assignment matrix presents matching scores as continuous values ranging from 0 to 1, implicitly indicating the degree of similarity between the points. This makes the two approaches complementary: one provides precise matching categorization, which is 'harder', while the other offers a fine-grained assessment of similarity, which is 'softer'.", + "bbox": [ + 496, + 622, + 892, + 787 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To align the stereo matching network with these two sources of cross-view geometric knowledge, a trainable cross-view decoder denoted as $D_{\\mathrm{cross}}$ is proposed. $D_{\\mathrm{cross}}$ first use as an Multilayer Perceptron (MLP) encoder [14, 50] followed by four alternative self-attention and cross-attention layers [50]. The self attention layers operate on points within the same image, while the cross-attention", + "bbox": [ + 496, + 794, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "20755", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "layer operate on points within different images. The decoder is responsible for decoding an assignment matrix $\\mathbf{P}'$ . This decoded matrix is trained to closely match its corresponding reference assignment matrix $\\mathbf{P}$ created by a pretrained interest point matcher $\\mathcal{IP}_{\\mathrm{match}}$ and the ground truth matching pairs $\\mathcal{P}^{gt}$ and unmatched points $\\mathcal{U}_l^{gt}$ , $\\mathcal{U}_r^{gt}$ from left and right images respectively, serving as the supervision pseudo ground truth during training. The points input $p_l$ and $p_r$ to the decoder $D_{\\mathrm{cross}}$ are identical to the input to $\\mathcal{IP}_{\\mathrm{match}}$ , but with different descriptors bi-linearly sampled from features $F_l$ and $F_r$ extracted by stereo backbone such that the gradient can flow back to the stereo network. Note that decoder $D_{\\mathrm{cross}}$ is discarded during the test stage.", + "bbox": [ + 75, + 90, + 472, + 287 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Soft cross-view geometric loss $\\mathcal{L}_{\\mathrm{cross - soft}}$ is proposed to introduce the cross-view geometric knowledge from the reference assignment matrix $\\mathbf{P}$ into the predicted assignment matrix $\\mathbf{P}'$ .", + "bbox": [ + 76, + 287, + 472, + 348 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {\\text {c r o s s - s o f t}} = \\frac {1}{m} \\sum_ {i = 1} ^ {m} \\mathcal {K L} \\left(\\mathbf {P} _ {i, \\cdot} / | | \\mathbf {P} _ {i, \\cdot} | | _ {1}, \\mathbf {P} _ {i, \\cdot} ^ {\\prime} / | | \\mathbf {P} _ {i, \\cdot} ^ {\\prime} | | _ {1}\\right) \\\\ + \\frac {1}{n} \\sum_ {j = 1} ^ {n} \\mathcal {K L} \\left(\\mathbf {P} _ {\\cdot , j} / \\left\\| \\mathbf {P} _ {\\cdot , j} \\right\\| _ {1}, \\mathbf {P} _ {\\cdot , j} ^ {\\prime} / \\left\\| \\mathbf {P} _ {\\cdot , j} ^ {\\prime} \\right\\| _ {1}\\right), \\tag {2} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 98, + 375, + 468, + 469 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{KL}$ stands for KL-divergence, and $\\mathbf{P}_{i,\\cdot}$ stands for the $i^{th}$ row of $\\mathbf{P}$ , $\\mathbf{P}_{\\cdot,j}$ stands for the $j^{th}$ column of $\\mathbf{P}$ . In this work, we use the interest points filtered from interest point maps $\\mathbf{M}_l$ , $\\mathbf{M}_r$ extracted by pre-trained interest point detector [12] by non maximum suppression as $p_l$ and $p_r$ .", + "bbox": [ + 75, + 482, + 468, + 558 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Hard cross-view geometric loss is further computed based on the ground truth matching between interest points $\\mathcal{P}^{gt}$ , unmatched points in the left image $\\mathcal{U}_l^{gt}$ , and unmatched points in the right image $\\mathcal{U}_r^{gt}$ . Hard cross-view geometric loss is utilized as a negative log-likelihood loss balanced between matched points and unmatched points to align $\\mathbf{P}'$ and $\\mathcal{P}^{gt}, \\mathcal{U}_l^{gt}, \\mathcal{U}_r^{gt}$ :", + "bbox": [ + 75, + 559, + 472, + 665 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {\\text {c r o s s - h a r d}} = - \\frac {1}{| \\mathcal {P} ^ {g t} |} \\sum_ {(i, j) \\in \\mathcal {P} ^ {g t}} \\log \\mathbf {P} _ {i, j} ^ {\\prime} \\\\ - \\frac {1}{\\left| \\mathcal {U} _ {l} ^ {g t} \\right|} \\sum_ {i \\in \\mathcal {U} _ {l}} \\log \\mathbf {P} _ {i, n + 1} ^ {\\prime} \\tag {3} \\\\ - \\frac {1}{\\left| \\mathcal {U} _ {r} ^ {g t} \\right|} \\sum_ {j \\in \\mathcal {U} _ {r}} \\log \\mathbf {P} _ {m + 1, j} ^ {\\prime}. \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 150, + 688, + 468, + 804 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Loss", + "text_level": 1, + "bbox": [ + 76, + 816, + 148, + 830 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We integrate our proposed $\\mathcal{L}_{\\mathrm{intra}}$ , $\\mathcal{L}_{\\mathrm{cross - soft}}$ , and $\\mathcal{L}_{\\mathrm{cross - hard}}$ with disparity loss $L_{\\mathrm{disp}}$ , enabling simultaneously estimating disparity and learning intra-view and cross-view geometric structure knowledge from local feature matching", + "bbox": [ + 75, + 839, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "models. The disparity loss, $L_{\\mathrm{disp}}$ , is determined by the loss function utilized by the base models. The total loss is defined as:", + "bbox": [ + 498, + 90, + 890, + 135 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {\\text {t o t a l}} = \\mathcal {L} _ {\\text {d i s p}} + \\lambda_ {\\text {i n t r a}} \\cdot \\mathcal {L} _ {\\text {i n t r a}} + \\lambda_ {\\text {c r o s s - s o f t}} \\cdot \\mathcal {L} _ {\\text {c r o s s - s o f t}} \\tag {4} \\\\ + \\lambda_ {\\text {c r o s s - h a r d}} \\cdot \\mathcal {L} _ {\\text {c r o s s - h a r d}}, \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 524, + 143, + 890, + 175 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{L}_{\\mathrm{intra}}$ , $\\mathcal{L}_{\\mathrm{cross - soft}}$ , $\\mathcal{L}_{\\mathrm{cross - hard}}$ are weighting terms. The loss weights are empirically set as $\\mathcal{L}_{\\mathrm{intra}} = 100$ , $\\mathcal{L}_{\\mathrm{cross - soft}} = 0.5$ , $\\mathcal{L}_{\\mathrm{cross - hard}} = 0.5$ such that they are comparable and none of the items would dominate the results.", + "bbox": [ + 498, + 183, + 893, + 243 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 255, + 633, + 272 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "SceneFlow dataset [35] constitutes a synthetic dataset featuring diverse random objects. It contains 35,454 training pairs and 4,370 test pairs with dense disparity labels. Finalpass of the SceneFlow dataset that contains motion blur and defocuses is used.", + "bbox": [ + 498, + 280, + 890, + 354 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "KITTI 2012 [15] & KITTI 2015 [36] datasets consist of stereo image pairs of real-world driving scenarios. KITTI 2012 contains 194 training and 195 testing image pairs. KITTI 2015 comprises 200 training and 200 testing image pairs. The stereo pairs in both KITTI 2012 and KITTI 2015 possess resolutions of $1226 \\times 370$ and $1242 \\times 375$ , respectively. Notably, both datasets furnish sparse disparity maps as part of their annotations.", + "bbox": [ + 498, + 356, + 890, + 476 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Middlebury 2014 [41] is an stereo dataset consisted of indoor stereo images. It comprises 15 training and 15 testing pairs. All the images are available in three different resolutions. We use the Middlebury 2014 dataset with half resolution to test cross-domain generalization performance.", + "bbox": [ + 498, + 477, + 890, + 551 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Evaluation metrics. We use end point error (EPE), the percentage of errors larger than 3px ( $>3\\mathrm{px}$ ) on the Scene-Flow dataset, and use EPE and D1-3px on KITTI datasets as evaluation metrics for disparity prediction. D1-3px refers to the percentage of disparity estimations with both absolute larger than 3px and relative error greater than $5\\%$ . We use EPE and the percentage of errors larger than 2px ( $>2\\mathrm{px}$ ) on Middlebury 2014 dataset.", + "bbox": [ + 498, + 553, + 890, + 672 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Implementation Details", + "text_level": 1, + "bbox": [ + 500, + 681, + 718, + 696 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Our ICGNet is inherently compatible with most stereo matching models since we do not change the structure of the network during inference. Specifically, our framework's compatibility expands to encompass all stereo matching models incorporating a common feature extractor and a disparity decoder. We experiment with our ICGNet on different baseline models GwcNet [17] and IGEV-Stereo [55]. We train the models end-to-end for all experiments. We pre-train the models on the SceneFlow training set. For the evaluation of cross-domain generalization, we directly test the sceneflow pre-trained models' performance on the KITTI 2012 training set, KITTI 2015 training set, and Middlebury 2014 training set. For evaluation of KITTI 2012", + "bbox": [ + 498, + 704, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "20756", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/6c1a9f9c8733ac282d101b1766957cc286c59d048d73832554f77b7f68d2c0a5.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodPSMNet [3]GANet [65]ACVNet [54]DLNR [71]GwcNet [17]IGEV-Stereo [55]Ours
EPE(px)↓1.090.840.480.480.7650.4790.447
", + "bbox": [ + 124, + 89, + 846, + 127 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/f917cd0704c7e4a642f62e5146f206a5d09ea55ccbe26cd00c12e4d1c57ebeed.jpg", + "table_caption": [ + "Table 1. Comparison with state-of-the-art models on the SceneFlow dataset. Our method outperforms most of the state-of-the-art methods." + ], + "table_footnote": [], + "table_body": "
MethodKITTI 2012KITTI 2015 (all pixels)KITTI 2015 (noc pixels)
2-noc↓2-all↓3-noc↓3-all↓D1-bg↓D1-fg↓D1-all↓D1-bg↓D1-fg↓D1-all↓
EdgeStereo [45]2.322.881.461.831.843.302.081.692.941.89
LEAStereo [10]1.902.391.131.451.402.911.651.292.651.51
ACVNet [54]1.832.351.131.471.373.071.651.262.841.52
CREStereo [23]1.722.181.141.461.452.861.691.332.601.54
RAFT-Stereo [27]1.922.421.301.661.583.051.821.452.941.69
AcfNet [70]1.832.351.171.541.513.801.891.363.491.72
HITNet [47]2.002.651.411.891.743.201.981.542.721.74
GANet [65]1.892.501.191.601.483.461.811.343.111.63
GwcNet [17]2.162.711.321.701.743.932.111.613.491.92
IGEV-Stereo [55]1.712.171.121.441.382.671.591.272.621.49
Ours1.702.141.101.411.382.551.571.262.561.47
", + "bbox": [ + 114, + 165, + 857, + 359 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Finetuning results on KITTI 2012 and KITTI 2015 benchmarks. Our ICGNet achieves state-of-the-art performance on both benchmarks and ranks $1^{st}$ on the KITTI 2015 stereo matching benchmark at the time of submission.", + "bbox": [ + 75, + 369, + 892, + 398 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "and KITTI 2015 benchmarks, we finetune SceneFlow pretrained model on the mix of KITTI 2012 and KITTI 2015 training sets. For GwcNet, we use the GwcNet-g setting for KITTI 2015 pre-training and the GwcNet-gc setting for other experiments, consistent with the original work for a fair comparison. We train the model for 64 epochs on SceneFlow and 1000 epochs on KITTI. The initial learning rate is set to 0.001. The learning rate is decayed by a factor of 2 after epochs 20, 32, 40, 48, and 56 on SceneFlow, and decayed by a factor of 2 after epochs 200, 400, 600, 700, and 800 on KITTI. For IGEV-Stereo, we train the model for 80 epochs on SceneFlow and 1000 epochs on KITTI. The initial learning rate is set as 0.0002 and a one-cycle learning rate schedule is used. We maintain all other settings consistent with the original works for both models. All the codes in this paper would be released in Github.", + "bbox": [ + 75, + 424, + 472, + 667 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Comparison with State-of-the-art", + "text_level": 1, + "bbox": [ + 76, + 678, + 370, + 695 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To evaluate the effectiveness of our proposed method, we use the latest IGEV-Stereo [55] as the base model and integrate it with ICGNet to compare with state-of-the-art stereo mathing methods. Tab. 1 presents a comparison of our method with state-of-the-art on SceneFlow. Our proposed method achieved state-of-the-art performance on the SceneFlow dataset. We further finetune the SceneFlow pretrained model on KITTI12 [15] and KITTI15 [36] datasets, and compare the performance of ICGNet with state-of-the-art methods on KITTI 2012 and KITTI 2015 benchmarks. Results are shown in Tab. 2. Our ICGNet outperforms state-of-the-art methods in most scenarios.", + "bbox": [ + 75, + 702, + 468, + 883 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Besides quantitative results, qualitative experiments are", + "bbox": [ + 96, + 885, + 468, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "conducted to show the effectiveness of our proposed method. Fig. 3 visualizes the disparity predictions of our methods. Compared to the state-of-the-art method IGEV-Stereo, our method performs better in reflective regions and unlabelled backgrounds.", + "bbox": [ + 496, + 424, + 893, + 501 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Cross-domain Generalization", + "text_level": 1, + "bbox": [ + 498, + 510, + 764, + 526 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We carry out experiments to demonstrate that our approach enhances the domain-generalization capacity of base models, transitioning from the synthetic SceneFlow dataset to real-world datasets. As illustrated in Tab. 3, our proposed ICGNet method boosts the cross-domain generalization performance for IGEV-Stereo which is a strong baseline for cross-domain generalization. Our ICGNet outperforms IGEV-Stereo by $4.8\\%$ on EPE in KITTI 2012 and $4.1\\%$ in KITTI 2015. Furthermore, from the qualitative results in Fig. 4, we can see that our method outperforms IGEV-Stereo in reflective regions and occluded regions.", + "bbox": [ + 496, + 534, + 893, + 702 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.4. Ablation Studies", + "text_level": 1, + "bbox": [ + 500, + 710, + 665, + 726 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We conduct ablation studies to evaluate the effectiveness of our proposed method. To show the generalization of the intra-view and cross-view knowledge learning, two base methods are used: GwcNet [17] and IGEV-Stereo [55].", + "bbox": [ + 496, + 733, + 893, + 794 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Effectiveness of Intra-view and Cross-view Knowledge. To verify that our proposed components all contribute to improving the performance, we provide quantitative results on the SceneFlow dataset in Tab. 4. The proposed ICGNet framework introduces an intra-view geometric loss $\\mathcal{L}_{\\mathrm{intra}}$ , a soft cross-view geometric loss $\\mathcal{L}_{\\mathrm{cross - soft}}$ and a hard cross-view geometric loss $\\mathcal{L}_{\\mathrm{cross - hard}}$ . The intra-view geo", + "bbox": [ + 496, + 795, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "20757", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/17d7d39358fb65389ffb88ec4d07cca926fe9ce345eb5f7a5a4b88656add1347.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodKITTI 2012KITTI 2015Middlebury 2014(H)
EPE(px)↓>3px(%)↓EPE(px)↓>3px(%)↓EPE(px)↓>2px(%)↓
PSMNet [3]2.6915.13.1716.37.6534.2
CFNet [42]1.045.21.716.03.2415.4
GANet [65]1.9310.12.3111.75.4120.3
DSMNet [66]1.266.21.466.52.6213.8
IGEV-Stereo [55]1.045.181.216.030.917.27
Ours0.994.871.165.960.826.73
", + "bbox": [ + 179, + 88, + 794, + 215 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/731eacf9df2e37bc1db684b0b9ccf25ac997de4bdde05f1fce4ee755fb9db6fa.jpg", + "image_caption": [ + "Figure 3. Qualitative results of ICGNet (ours) compared with the state-of-the-art method IGEV-Stereo." + ], + "image_footnote": [], + "bbox": [ + 98, + 252, + 870, + 443 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/0c22e3bc9a6828ae72495f8f8c56e081264e411b8814f1052793bb477d24144f.jpg", + "table_caption": [ + "Table 3. Cross-domain generalization from SceneFlow to real-world datasets." + ], + "table_footnote": [], + "table_body": "
BaselineComponentsSceneFlow
\\( \\mathcal{L}_{\\text{intra}} \\)\\( \\mathcal{L}_{\\text{cross-soft}} \\)\\( \\mathcal{L}_{\\text{cross-hard}} \\)EPEpx)\\( \\downarrow \\)>3px(\\%)↓
GwcNet0.7653.30
✓0.6152.61
✓✓0.6082.56
✓✓✓0.5972.55
IGEV-Stereo0.4792.48
✓0.4522.37
✓✓0.4492.36
✓✓✓0.4472.34
", + "bbox": [ + 78, + 491, + 468, + 606 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 4. Ablation studies of proposed components on SceneFlow dataset on two baseline approaches GwcNet and IGEV-Stereo.", + "bbox": [ + 76, + 616, + 470, + 645 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "metric loss allows the model to learn intra-image geometric knowledge, and the soft cross-view geometric loss and hard cross-view geometric loss allow the model to learn cross-view geometric knowledge. Notably, our method demonstrates an improvement of over $20\\%$ (0.597 vs 0.765) in EPE and over $20\\%$ improvement in 3px-error. When applied to the strong base model IGEV-Stereo, our method still shows solid improvements over both EPE and 3px-error. The SceneFlow pre-trained full models of both base models are then finetuned on KITTI 2012 and KITTI 2015 datasets and results are shown in Tab. 5. Our method consistently outperforms the performance of baseline models.", + "bbox": [ + 75, + 672, + 468, + 853 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Impact on Occluded and Non-occluded Regions. We further conduct experiments on our method's impact on occluded pixels and non-occluded pixels separately. Tab. 6", + "bbox": [ + 76, + 854, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "shows that our method consistently improves disparity quality in both occluded regions and non-occluded regions. Furthermore, since occluded regions are areas without correspondence in the other figures, intuitively the prediction of disparities on such pixels relies more on intra-view geometric knowledge; on the contrary, predicting disparities at non-occluded pixels relies more on cross-view geometric knowledge [55]. Our experiment results are consistent with this intuition, validating our formulation of the process of extracting interest points as intra-view geometric knowledge and the process of extracting their correspondences as cross-view geometric knowledge.", + "bbox": [ + 496, + 493, + 893, + 676 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Complexity of intra-view decoder and cross-view decoder. We conduct experiments to evaluate the impact of the complexity of the intra-view decoder $D_{\\mathrm{intra}}$ and cross-view decoder $D_{\\mathrm{cross}}$ on the models' performance. We keep GwcNet as the base model and change the number of layers of the decoders. The number of layers of the intra-view decoder refers to the number of stacked bottleneck convolutional blocks, and the number of layers of the cross-view decoder refers to the number of alternating attention layers. For the cross-view decoder with zero layers, we are directly using cosine similarities between the interest point features plus a softmax layer to form an assignment matrix $\\mathbf{P}'$ . Results on the SceneFlow dataset with GwcNet [17] as baseline are shown in Tab. 7. Results have shown that an", + "bbox": [ + 496, + 688, + 893, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "20758", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/b99b8b560909e2e3e41e45664a42afe34c3af5001b9337bfd5d1badcdb62bfb7.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
BaselineICGNetKITTI 2012KITTI 2015 (all pixels)KITTI 2015 (noc pixels)
2-noc↓2-all↓3-noc↓3-all↓D1-bg↓D1-fg↓D1-all↓D1-bg↓D1-fg↓D1-all↓
GwcNet [17]✓2.162.711.321.701.743.932.111.613.491.92
1.982.541.251.631.623.902.001.503.561.84
IGEV-Stereo [55]✓1.712.171.121.441.382.671.591.272.621.49
1.702.141.101.411.382.551.571.262.561.47
", + "bbox": [ + 83, + 89, + 888, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5efce1c2a8a69da46e8d6167dbcffb896dbfd81f74c89d133ea7910179135948.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 101, + 224, + 305, + 325 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/4d4374ca6d3af06b41e8d7445d6815ad8991a9aec22d635a1b688a8998f153e7.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 101, + 325, + 305, + 371 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5f6f606c98c7eba6f8a0ce7742dc79aa14fd3b9d8eeea1d6583d68a945b62e86.jpg", + "image_caption": [ + "Left Image" + ], + "image_footnote": [], + "bbox": [ + 101, + 372, + 305, + 417 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ac2a3a8eaa7c2213989ce270c16bfe736e102714bbe25584bfd465f61842d1db.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 307, + 224, + 493, + 325 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/dad635d27cd1538e1a9a23846b94cae000ff1ebfa28532fa6501ed3b388016e1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 307, + 325, + 493, + 372 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9b8c5a17008d67a4a3700f83928d43c7a273c6f9f2c4d04b29dffacbf771afd1.jpg", + "image_caption": [ + "Disparity Labels", + "Figure 4. Qualitative results of cross-domain generalization of ICGNet (ours) compared with state-of-the-art baseline IGEV-Stereo [55]." + ], + "image_footnote": [], + "bbox": [ + 307, + 372, + 493, + 417 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/23f438ec92a8be8f5e7b575ba79e2fb512f20dfa2f510e69f5b0af0c05b5e1bd.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 495, + 224, + 681, + 325 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/936d28b859e674aa7a8031f1a11350a505d31955ca3b11a7dce476d91fea56e1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 495, + 325, + 681, + 372 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ffd5c2f360d0506468d2e8d61ca21ef5d88e54a47d7c635afc6b7a1b183fdf6b.jpg", + "image_caption": [ + "IGEV-Stereo" + ], + "image_footnote": [], + "bbox": [ + 495, + 372, + 681, + 417 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/0b1c3b86dc7f3ca7cd8b81b55686a6ac8e9c055868735fd7c4eed02cfbaa5d5e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 683, + 224, + 870, + 325 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/690a22fc978c60d920640c295939a3764e9466d7901c0589b8e27056bcf3d84e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 683, + 325, + 870, + 371 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/cf621a204ad2874f573ee6203c36573ab97261fbad9d28cdb6551251358b2760.jpg", + "image_caption": [ + "ICGNet (ours)" + ], + "image_footnote": [], + "bbox": [ + 683, + 372, + 870, + 417 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/8c626e29ed6bf501696725ba2cffcb8b2a7e0903dbcc401c2bff5c1793bfb984.jpg", + "table_caption": [ + "Table 5. Ablation studies on KITTI 2012 and KITTI 2015 benchmarks." + ], + "table_footnote": [], + "table_body": "
Intra-view\nL_intraCross-view\nL CROSS-soft + L cross-hardSceneFlow EPE
noc(px)↓occ(px)↓Δnoc/Δocc
0.4132.58/
✓0.3342.086.33
✓✓0.3182.023.75
", + "bbox": [ + 78, + 483, + 493, + 565 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/022dcfc2a01a1f4eb4a47703fd67ba68cf67020b9e3699301c738fd6c24eb253.jpg", + "table_caption": [ + "Table 6. Ablation studies on occluded and non-occluded areas on the SceneFlow dataset using GwcNet baseline model. Our method improves disparity prediction accuracy in both occluded areas and non-occluded areas. Compared with cross-view geometric knowledge, intra-view geometric knowledge improves more in occluded regions, consistent with the intuition that occluded areas rely on their surrounding geometric relations to infer their disparities." + ], + "table_footnote": [], + "table_body": "
DecoderLayersSceneFlow
EPE(px)↓>3px↓
intra-view10.6312.74
20.6152.61
40.6232.68
cross-view00.6172.61
40.5972.55
60.6062.58
", + "bbox": [ + 130, + 691, + 416, + 816 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 7. Comparison of performance of different decoder complexities.", + "bbox": [ + 75, + 825, + 468, + 854 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "intermediate number of decoder layers for both intra-view and cross-view decoder yields the best results. This may be due to a too-complex decoder will take up too much of the task of learning the geometric knowledge, making the feature backbone not learn sufficient knowledge, while a too-simple decoder is not sufficient to map the features into the geometric structures, leaving too much for the feature backbone and make it sub-optimal in disparity prediction task.", + "bbox": [ + 498, + 486, + 890, + 608 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 625, + 617, + 638 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we introduce ICGNet, a novel approach designed to infuse stereo matching networks with both intraview and cross-view geometric knowledge. Utilizing interest points and their corresponding matches derived from local feature matching models, we provide rich sources of geometric knowledge to educate the stereo matching network. Our extensive experimental evaluations demonstrate that this methodology enhances the performance of state-of-the-art stereo matching models, boosting both their accuracy and their ability to generalize across diverse domains.", + "bbox": [ + 496, + 650, + 890, + 801 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement", + "text_level": 1, + "bbox": [ + 500, + 818, + 660, + 835 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by the Agency for Science, Technology and Research (A*STAR) under its MTC Programmatic Funds (Grant No. M23L7b0021).", + "bbox": [ + 498, + 844, + 890, + 887 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "20759", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Herbert Bay, Tinne Tuytelaars, and Luc Van Gool. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 1327-1336, 2023. 6" + ], + "bbox": [ + 503, + 92, + 890, + 821 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "20762", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/2798eade-4610-47df-96d1-47a92d0431fb_model.json b/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/2798eade-4610-47df-96d1-47a92d0431fb_model.json new file mode 100644 index 0000000000000000000000000000000000000000..1ba99c3736ec217f770639735db18f01a9911069 --- /dev/null +++ b/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/2798eade-4610-47df-96d1-47a92d0431fb_model.json @@ -0,0 +1,2389 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.084, + 0.131, + 0.888, + 0.154 + ], + "angle": 0, + "content": "Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching" + }, + { + "type": "text", + "bbox": [ + 0.206, + 0.193, + 0.761, + 0.213 + ], + "angle": 0, + "content": "Rui Gong\\*1, Weide Liu?, Zaiwang Gu?, Xulei Yang?, and Jun Cheng" + }, + { + "type": "text", + "bbox": [ + 0.151, + 0.223, + 0.819, + 0.259 + ], + "angle": 0, + "content": "\\(^{1}\\)School of Electrical and Electronic Engineering, Nanyang Technological University \\(^{2}\\)Institute for Infocomm Research, A*STAR" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.304, + 0.314, + 0.32 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.336, + 0.474, + 0.64 + ], + "angle": 0, + "content": "Geometric knowledge has been shown to be beneficial for the stereo matching task. However, prior attempts to integrate geometric insights into stereo matching algorithms have largely focused on geometric knowledge from single images while crucial cross-view factors such as occlusion and matching uniqueness have been overlooked. To address this gap, we propose a novel Intra-view and Cross-view Geometric knowledge learning Network (ICGNet), specifically crafted to assimilate both intra-view and cross-view geometric knowledge. ICGNet harnesses the power of interest points to serve as a channel for intra-view geometric understanding. Simultaneously, it employs the correspondences among these points to capture cross-view geometric relationships. This dual incorporation empowers the proposed ICGNet to leverage both intra-view and cross-view geometric knowledge in its learning process, substantially improving its ability to estimate disparities. Our extensive experiments demonstrate the superiority of the ICGNet over contemporary leading models. The code will be available at https://github.com/DFSDDDDD1199/ICGNet." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.669, + 0.21, + 0.685 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.696, + 0.47, + 0.816 + ], + "angle": 0, + "content": "Stereo matching is the task of estimating a disparity map from a pair of rectified images. It stands as one of the cornerstone challenges in a range of computer vision tasks, including augmented reality, autonomous driving, and robotics [18]. With the rapid development of deep learning techniques and network structures in computer vision scenarios, deep stereo matching networks have achieved great success in stereo matching." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.817, + 0.47, + 0.863 + ], + "angle": 0, + "content": "Geometric knowledge plays a crucial role in the overall performance of stereo matching networks [21, 45, 55, 69] due to the existence of repeated patterns, textureless ar" + }, + { + "type": "image", + "bbox": [ + 0.512, + 0.302, + 0.885, + 0.416 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.426, + 0.892, + 0.511 + ], + "angle": 0, + "content": "Figure 1. An illustration of our overall framework using synthetic shapes. We leverage intra-view geometric knowledge which is the knowledge of extracting geometric structures, and cross-view geometric knowledge which is the knowledge of the correspondences of these structures, to aid the stereo matching task. Note that the dotted lines are used for illustration and are not used in the method." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.538, + 0.892, + 0.719 + ], + "angle": 0, + "content": "eas, and reflective surfaces, which make simple texture-based matching methods ineffective. Consequently, several methods were proposed to introduce geometric knowledge into stereo matching networks through kinds of geometric structures. EdgeStereo [45] proposed a learning network that incorporates edges and edge-disparity relations into the stereo matching network. Normal assisted stereo matching [21, 69] leverages surface normal as geometric constraints to reduce the matching ambiguity for textureless regions. However, the geometric knowledge employed in these studies is mainly intra-view, lacking the cross-view geometric knowledge such as matching uniqueness and occlusion." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.893, + 0.902 + ], + "angle": 0, + "content": "To address the absence of cross-view geometric knowledge, we have identified that the local feature matching task [12, 34, 40] can serve as a suitable source of cross-view geometric knowledge for stereo matching. Local feature matching involves the identification of correspondences between two images, typically achieved by initially detecting sparse, geometrically meaningful interest points within each view and then extracting descriptors for these interest points encoded with their visual attributes [12]. Subsequently, cross-view matching is carried out by comparing the interest points between the two images [40]. This matching process solves a partial assignment problem be" + }, + { + "type": "page_footnote", + "bbox": [ + 0.094, + 0.875, + 0.411, + 0.888 + ], + "angle": 0, + "content": "*The work was done during an internship at I²R, A*STAR." + }, + { + "type": "page_footnote", + "bbox": [ + 0.099, + 0.888, + 0.253, + 0.901 + ], + "angle": 0, + "content": "\\(\\dagger\\) cheng-jun@i2r.a-star.edu.sg" + }, + { + "type": "list", + "bbox": [ + 0.094, + 0.875, + 0.411, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20752" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.454 + ], + "angle": 0, + "content": "tween the points which takes matching uniqueness and occlusion into account. Moreover, we also find that the interest points from each image also provide intra-view knowledge of the image. Building upon these insights, we introduce our ICGNet framework to take both the intra-view and cross-view geometric knowledge contained in local feature matching models into the stereo matching network. We leverage a pre-trained local feature matching pipeline, comprising an interest point detector and a point matcher. We propose an intra-view constraint that the features we extract from stereo matching backbone preserve the same interest point information as the pre-trained interest point detector to gain intra-view geometric knowledge. Additionally, we propose a cross-view constraint that these features are compelled to serve as descriptors for the interest points, facilitating the matching process between these points. The matching outcome is then constrained to align with both the ground-truth matching labels provided by ground-truth disparity maps and the matching results obtained from the pretrained interest point matcher, in order to gain cross-view geometric knowledge. Compared to EdgeStereo [45] and normal assisted stereo matching [21, 69], our method not only additionally introduces cross-view geometric knowledge but also keeps zero overhead when inference." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.455, + 0.472, + 0.5 + ], + "angle": 0, + "content": "Our experiments show that our method effectively improves the performance across both the seen and unseen domains. The contributions are summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.502, + 0.47, + 0.561 + ], + "angle": 0, + "content": "1. We propose to learn intra-view geometric knowledge for stereo matching networks from an interest point detector by introducing a novel intra-view geometric constraint computed from the interest point detection outcomes." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.562, + 0.47, + 0.652 + ], + "angle": 0, + "content": "2. We propose to learn cross-view geometric knowledge for stereo matching networks from an interest point matcher by introducing a novel cross-view geometric constraint. We compute both soft cross-view and hard cross-view geometric losses using pretrained interest point matcher and disparity ground truth." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.653, + 0.471, + 0.803 + ], + "angle": 0, + "content": "3. We conduct a series of comprehensive experiments that consistently demonstrate the proposed framework's ability to enhance the overall performance of state-of-the-art stereo matching networks. Our ICGNet achieves state-of-the-art performance on the SceneFlow dataset and ranks \\(1^{st}\\) on the KITTI 2015 stereo matching benchmark among published peer-reviewed methods at the time of submission, and improves cross-domain generalization of baseline methods on KITTI 2012, KITTI 2015, and Middlebury 2014 datasets." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.502, + 0.471, + 0.803 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.82, + 0.228, + 0.836 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.846, + 0.285, + 0.863 + ], + "angle": 0, + "content": "2.1. Deep Stereo Matching" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Deep-learning-based deep stereo matching techniques have gained widespread adoption and demonstrated promis" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.59 + ], + "angle": 0, + "content": "ing outcomes [7, 9, 16, 24, 25, 28, 37, 52, 53, 57, 58, 61]. The initial instance of such an approach is DispNetC [35], which presents an end-to-end trainable stereo matching framework. This framework employs the dot product of feature maps from left and right images as correspondence to build a cost volume of three dimensions. However, the drawback of this computational-friendly methodology is its inability to capture sufficient information to achieve satisfactory results. In the pursuit of improved performance, subsequent methods like GC-Net [20] have emerged. Numerous works [3, 65] have followed this trend and incorporated 3D hourglass convolutions to aggregate a 4D cost volume. This volume is created by concatenating features from left and right images. Unfortunately, this approach demands substantial memory usage and computational complexity. A notable enhancement arrives with GwcNet [17], which introduces the concept of group-wise correlation. This innovation enables the construction of a more compact cost volume. Recently, iterative optimization-based methods [23, 27, 63] have achieved splendid performance. Inspired by RAFT [48], RAFT-Stereo [27] iteratively updates the disparity using all-pairs correlation between features extracted. IGEV-Stereo [55] further boosts the performance of stereo matching network by combining cost-volume modules with iterative updating modules. Uncertainty-based methods [8, 51] also gained attention these years. ELFNet [33] leverage uncertainty to fuse multi-scale disparity and stereo network with different structures. SEDNet [6] proposes a soft-histogramming technique to align the distribution of prediction error and prediction uncertainty. Other works focus on improving the domain generalization performance [4, 11, 29, 38, 68] and domain adaptation performance [31, 46, 64, 66] of stereo matching networks." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.592, + 0.895, + 0.758 + ], + "angle": 0, + "content": "Recognizing the need for increased efficiency and the integration of richer semantic information, multi-scale cost volume is used in stereo matching networks. HSMNet [59] employs a pyramid of volumes to enable high-resolution stereo matching. AANet [56] takes a lightweight approach, incorporating a feature pyramid and interactions with multi-scale correlation volumes. In a recent development, PCWNet [43] introduces a volume fusion module that directly combines multi-scale 4D volumes. This innovation calculates a multi-level loss, ultimately expediting the model's convergence speed." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.771, + 0.888, + 0.787 + ], + "angle": 0, + "content": "2.2. Geometric Structure Guided Stereo Matching" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Geometric structures have been used to guide stereo matching networks in previous works. EdgeStereo [45] introduced an edge branch, integrating edge features into the stereo matching branch. Yang et al. [60] also advocated the use of edges for supervising stereo matching through multitask learning. Additionally, surface normals have been another employed geometric structure to guide stereo match" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20753" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.198 + ], + "angle": 0, + "content": "ing. Zhang et al. [69] suggested a joint prediction of a surface normal map and a raw disparity map, iteratively refining the disparity map with guidance from the surface normal map. Kusupati et al. [21] incorporated an extra surface normal branch to predict raw surface normals and employed an independently trained consistency module for refinement of both surface normals and raw disparities." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.199, + 0.47, + 0.365 + ], + "angle": 0, + "content": "However, these approaches have two limitations. Firstly, they heavily depend on additional branches during inference to improve their performance, which impacts efficiency. In contrast, our proposed framework leverages geometric structures as constraints during training without incurring any overhead in inference, and shows improved performance. Secondly, the previous methods only made use of intra-view geometric structures, whereas our framework takes into account both intra-view and cross-view geometric knowledge through both geometric structure and their correspondences." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.377, + 0.3, + 0.394 + ], + "angle": 0, + "content": "2.3. Local Feature Matching" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.401, + 0.47, + 0.476 + ], + "angle": 0, + "content": "Local feature matching aims at matching images that depict the same scene or object. This is usually done in a two-stage manner: first, detect interest points each associated with a visual descriptor from both images, and then match the detected interest points." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.478, + 0.47, + 0.703 + ], + "angle": 0, + "content": "Traditional interest points detection and description algorithms [1, 19, 34, 39] rely on hand-crafted features. Recent research turns to Convolutional Neural Networks (CNN) for both interest point detection and description [22, 30, 32, 49]. SuperPoint [12] is a representative work of CNN-based interest point detector and descriptor, trained in a self-supervised manner. It constructs a synthetic shape dataset by rendering simplified 2D geometries, such as triangles, quadrilaterals, lines, and ellipses. The junctions of lines are labeled as interest points. These labels are then transferred to substantial real-world image datasets using a MagicPoint model and homographic adaptation. The self-supervised training process equips SuperPoint with the ability to be trained on various domains, enabling it to encode geometric information across diverse domains." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.705, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Traditional algorithms employ nearest-neighbor classifiers for matching interest points. Lowe's test [34], inlier classifiers [62, 67], or geometric model fitting [2, 13] techniques are subsequently used to filter out unmatched points and incorrect correspondences. However, these methods are highly domain-specific and struggle to handle particularly challenging conditions. In contrast, deep learning-based matchers are trained to simultaneously match interest points and reject outliers. A notable example of this approach is SuperGlue [40], which leverages Transformers [50] to conduct self-attention among interest points within the same view and cross-attention between interest points in different views. The final matching step involves solving an op" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.259 + ], + "angle": 0, + "content": "timal transport problem. This approach allows SuperGlue to acquire robust insights into scene geometry and camera motion, rendering it resilient to extreme changes and effective in generalizing across various data domains. Subsequent works [5, 26, 44] focused on making it more efficient and digging into its design details while keeping its strong matching capability. Consequently, these matchers are great sources of cross-view geometric knowledge. We set up constraints to let the stereo matching network learn geometric knowledge from a pre-trained interest point detector and a pre-trained interest point matcher." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.27, + 0.593, + 0.287 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.296, + 0.895, + 0.614 + ], + "angle": 0, + "content": "We propose ICGNet to introduce geometric knowledge into stereo matching networks through geometric constraints. Intra-view geometric knowledge refers to the understanding that uncovers the geometric structures contained within a single image. Cross-view geometric knowledge refers to the comprehension that enables the alignment of geometric structures from one image to another. Models capable of uncovering and matching geometric structures harness the potential to convey intra-view and cross-view knowledge. Therefore, as depicted in Fig. 2, our framework introduces intra-view and cross-view geometric knowledge into the stereo matching network by aligning our network with intra-view and cross-view geometric knowledge sources. Although there are multiple choices (e.g., edges, points) to extract intra-view knowledge, we choose interest points as it is easy to further compute cross-view knowledge from these points using well-established methods [40] while it is more challenging to match the edges for cross-view knowledge computation. We denote the left-view stereo image as \\(I_{l}\\) and right-view stereo image as \\(I_{r}\\), and the extracted left feature and right feature as \\(F_{l}\\) and \\(F_{r}\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.621, + 0.795, + 0.639 + ], + "angle": 0, + "content": "3.1. Intra-view Geometric Knowledge" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Intra-view Geometric Knowledge Decoder is to introduce intra-view geometric knowledge into the stereo matching network. We propose to leverage a pre-trained interest point detector \\(\\mathcal{IP}_{\\mathrm{det}}\\) [12] in our method. It takes the left-view image \\(I_{l}\\) and the right-view image \\(I_{r}\\) as input and generates interest maps \\(\\mathbf{M}_l\\) and \\(\\mathbf{M}_r\\), where each pixel is either labeled as interest point or non-interest point. These maps convey the intra-view geometric characteristics of the two images. We expect that the backbone features \\(F_{l}\\) and \\(F_{r}\\) preserve and unveil the intra-view geometric details present in both the left and right view images, akin to what the pretrained interest point detector accomplishes. Consequently, we aim to extract two interest point maps, \\(\\mathbf{M}_l^{\\prime}\\) and \\(\\mathbf{M}_r^{\\prime}\\), from \\(F_{l}\\) and \\(F_{r}\\) using a trainable intra-view decoder \\(D_{\\mathrm{intra}}\\), aligning with \\(\\mathbf{M}_l\\) and \\(\\mathbf{M}_r\\) respectively. For the design of \\(D_{\\mathrm{intra}}\\), we use a stack of two bottleneck convolutional blocks. Note that decoder \\(D_{\\mathrm{intra}}\\) is discarded during the test stage." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20754" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.101, + 0.088, + 0.873, + 0.391 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.4, + 0.895, + 0.471 + ], + "angle": 0, + "content": "Figure 2. Overall structure of our proposed framework. The model architecture comprises three parts: stereo matching network, cross-view knowledge learning network, and intra-view knowledge learning network. The cross-view knowledge learning network introduces cross-view geometric knowledge by aligning the interest point correspondences \\(\\mathbf{P}'\\), \\(\\mathbf{P}\\) and \\(\\mathcal{P}^{gt}\\) using \\(\\mathcal{L}_{\\mathrm{cross - hard}}\\) and \\(\\mathcal{L}_{\\mathrm{cross - soft}}\\). The intra-view knowledge learning network introduces intra-view geometric knowledge through aligning the interest point maps \\(\\mathbf{M}'\\) and \\(\\mathbf{M}\\) using \\(\\mathcal{L}_{\\mathrm{intra}}\\). Note that the dotted lines are used just for clear illustration and are not used in our work." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.496, + 0.471, + 0.527 + ], + "angle": 0, + "content": "Intra-view geometric loss \\(\\mathcal{L}_{\\mathrm{intra}}\\) is computed to enforce this alignment:" + }, + { + "type": "equation", + "bbox": [ + 0.14, + 0.54, + 0.47, + 0.571 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {i n t r a}} = \\frac {1}{2} \\mathcal {L} \\left(\\mathbf {M} _ {l} ^ {\\prime}, \\mathbf {M} _ {l}\\right) + \\frac {1}{2} \\mathcal {L} \\left(\\mathbf {M} _ {r} ^ {\\prime}, \\mathbf {M} _ {r}\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.577, + 0.47, + 0.608 + ], + "angle": 0, + "content": "where we compute a focal loss \\(\\mathcal{L}\\) due to unbalanced positive and negative samples of interest points." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.62, + 0.377, + 0.636 + ], + "angle": 0, + "content": "3.2. Cross-view Geometric Knowledge" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.644, + 0.47, + 0.749 + ], + "angle": 0, + "content": "Cross-view Geometric Knowledge Decoder enables the stereo matching network to acquire cross-view geometric knowledge by framing it as a learning task. This task is to align the stereo matching network with two complementary knowledge sources: a pre-trained interest point matcher denoted as \\(\\mathcal{IP}_{\\mathrm{match}}\\) where we use [40] in our method, and the ground truth matching between interest points." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.902 + ], + "angle": 0, + "content": "The pre-trained matcher processes two sets of interest points extracted from stereo image pair \\( I_{l} \\) and \\( I_{r} \\), denoted as \\( p_l \\) and \\( p_r \\), each containing \\( m \\) and \\( n \\) points respectively, along with their associated descriptors. It outputs an assignment matrix \\( \\mathbf{P} \\in [0,1]^{(m + 1)\\times (n + 1)} \\). This matrix includes an extra row and column to account for the possibility that some points do not match any counterpart in the other view. The assignment matrix \\( \\mathbf{P} \\) elucidates the cross-view geometric knowledge via the relations between the matching probabilities of the two sets of points." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.496, + 0.892, + 0.618 + ], + "angle": 0, + "content": "Furthermore, the ground truth disparities can serve as another source of knowledge since it provide accurate matching between these points. Ground truth matching pairs between the points \\(\\mathcal{P}^{gt} = \\{(i,j)\\} \\subset p_l \\times p_r\\) (\\(x\\) refers to Cartesian product) and unmatched points in left image \\(\\mathcal{U}_l^{gt} \\subseteq p_l\\) and right image \\(\\mathcal{U}_r^{gt} \\subseteq p_r\\) are formed by warping interest points from the left image to the right image using the disparity." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.623, + 0.893, + 0.789 + ], + "angle": 0, + "content": "The ground truth is more precise compared to the assignment matrix provided by the interest point matcher. In the ground truth, the relationships between points are binary, classified simply as either a match or a mismatch. On the other hand, the assignment matrix presents matching scores as continuous values ranging from 0 to 1, implicitly indicating the degree of similarity between the points. This makes the two approaches complementary: one provides precise matching categorization, which is 'harder', while the other offers a fine-grained assessment of similarity, which is 'softer'." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.895, + 0.903 + ], + "angle": 0, + "content": "To align the stereo matching network with these two sources of cross-view geometric knowledge, a trainable cross-view decoder denoted as \\( D_{\\mathrm{cross}} \\) is proposed. \\( D_{\\mathrm{cross}} \\) first use as an Multilayer Perceptron (MLP) encoder [14, 50] followed by four alternative self-attention and cross-attention layers [50]. The self attention layers operate on points within the same image, while the cross-attention" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20755" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.288 + ], + "angle": 0, + "content": "layer operate on points within different images. The decoder is responsible for decoding an assignment matrix \\(\\mathbf{P}'\\). This decoded matrix is trained to closely match its corresponding reference assignment matrix \\(\\mathbf{P}\\) created by a pretrained interest point matcher \\(\\mathcal{IP}_{\\mathrm{match}}\\) and the ground truth matching pairs \\(\\mathcal{P}^{gt}\\) and unmatched points \\(\\mathcal{U}_l^{gt}\\), \\(\\mathcal{U}_r^{gt}\\) from left and right images respectively, serving as the supervision pseudo ground truth during training. The points input \\(p_l\\) and \\(p_r\\) to the decoder \\(D_{\\mathrm{cross}}\\) are identical to the input to \\(\\mathcal{IP}_{\\mathrm{match}}\\), but with different descriptors bi-linearly sampled from features \\(F_l\\) and \\(F_r\\) extracted by stereo backbone such that the gradient can flow back to the stereo network. Note that decoder \\(D_{\\mathrm{cross}}\\) is discarded during the test stage." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.289, + 0.473, + 0.349 + ], + "angle": 0, + "content": "Soft cross-view geometric loss \\(\\mathcal{L}_{\\mathrm{cross - soft}}\\) is proposed to introduce the cross-view geometric knowledge from the reference assignment matrix \\(\\mathbf{P}\\) into the predicted assignment matrix \\(\\mathbf{P}'\\)." + }, + { + "type": "equation", + "bbox": [ + 0.099, + 0.375, + 0.469, + 0.47 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {\\text {c r o s s - s o f t}} = \\frac {1}{m} \\sum_ {i = 1} ^ {m} \\mathcal {K L} \\left(\\mathbf {P} _ {i, \\cdot} / | | \\mathbf {P} _ {i, \\cdot} | | _ {1}, \\mathbf {P} _ {i, \\cdot} ^ {\\prime} / | | \\mathbf {P} _ {i, \\cdot} ^ {\\prime} | | _ {1}\\right) \\\\ + \\frac {1}{n} \\sum_ {j = 1} ^ {n} \\mathcal {K L} \\left(\\mathbf {P} _ {\\cdot , j} / \\left\\| \\mathbf {P} _ {\\cdot , j} \\right\\| _ {1}, \\mathbf {P} _ {\\cdot , j} ^ {\\prime} / \\left\\| \\mathbf {P} _ {\\cdot , j} ^ {\\prime} \\right\\| _ {1}\\right), \\tag {2} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.483, + 0.47, + 0.559 + ], + "angle": 0, + "content": "where \\(\\mathcal{KL}\\) stands for KL-divergence, and \\(\\mathbf{P}_{i,\\cdot}\\) stands for the \\(i^{th}\\) row of \\(\\mathbf{P}\\), \\(\\mathbf{P}_{\\cdot,j}\\) stands for the \\(j^{th}\\) column of \\(\\mathbf{P}\\). In this work, we use the interest points filtered from interest point maps \\(\\mathbf{M}_l\\), \\(\\mathbf{M}_r\\) extracted by pre-trained interest point detector [12] by non maximum suppression as \\(p_l\\) and \\(p_r\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.56, + 0.473, + 0.666 + ], + "angle": 0, + "content": "Hard cross-view geometric loss is further computed based on the ground truth matching between interest points \\(\\mathcal{P}^{gt}\\), unmatched points in the left image \\(\\mathcal{U}_l^{gt}\\), and unmatched points in the right image \\(\\mathcal{U}_r^{gt}\\). Hard cross-view geometric loss is utilized as a negative log-likelihood loss balanced between matched points and unmatched points to align \\(\\mathbf{P}'\\) and \\(\\mathcal{P}^{gt}, \\mathcal{U}_l^{gt}, \\mathcal{U}_r^{gt}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.151, + 0.689, + 0.469, + 0.805 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {\\text {c r o s s - h a r d}} = - \\frac {1}{| \\mathcal {P} ^ {g t} |} \\sum_ {(i, j) \\in \\mathcal {P} ^ {g t}} \\log \\mathbf {P} _ {i, j} ^ {\\prime} \\\\ - \\frac {1}{\\left| \\mathcal {U} _ {l} ^ {g t} \\right|} \\sum_ {i \\in \\mathcal {U} _ {l}} \\log \\mathbf {P} _ {i, n + 1} ^ {\\prime} \\tag {3} \\\\ - \\frac {1}{\\left| \\mathcal {U} _ {r} ^ {g t} \\right|} \\sum_ {j \\in \\mathcal {U} _ {r}} \\log \\mathbf {P} _ {m + 1, j} ^ {\\prime}. \\\\ \\end{array}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.817, + 0.15, + 0.832 + ], + "angle": 0, + "content": "3.3. Loss" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.47, + 0.902 + ], + "angle": 0, + "content": "We integrate our proposed \\(\\mathcal{L}_{\\mathrm{intra}}\\), \\(\\mathcal{L}_{\\mathrm{cross - soft}}\\), and \\(\\mathcal{L}_{\\mathrm{cross - hard}}\\) with disparity loss \\(L_{\\mathrm{disp}}\\), enabling simultaneously estimating disparity and learning intra-view and cross-view geometric structure knowledge from local feature matching" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.892, + 0.136 + ], + "angle": 0, + "content": "models. The disparity loss, \\( L_{\\mathrm{disp}} \\), is determined by the loss function utilized by the base models. The total loss is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.525, + 0.144, + 0.892, + 0.176 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {\\text {t o t a l}} = \\mathcal {L} _ {\\text {d i s p}} + \\lambda_ {\\text {i n t r a}} \\cdot \\mathcal {L} _ {\\text {i n t r a}} + \\lambda_ {\\text {c r o s s - s o f t}} \\cdot \\mathcal {L} _ {\\text {c r o s s - s o f t}} \\tag {4} \\\\ + \\lambda_ {\\text {c r o s s - h a r d}} \\cdot \\mathcal {L} _ {\\text {c r o s s - h a r d}}, \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.184, + 0.894, + 0.244 + ], + "angle": 0, + "content": "where \\(\\mathcal{L}_{\\mathrm{intra}}\\), \\(\\mathcal{L}_{\\mathrm{cross - soft}}\\), \\(\\mathcal{L}_{\\mathrm{cross - hard}}\\) are weighting terms. The loss weights are empirically set as \\(\\mathcal{L}_{\\mathrm{intra}} = 100\\), \\(\\mathcal{L}_{\\mathrm{cross - soft}} = 0.5\\), \\(\\mathcal{L}_{\\mathrm{cross - hard}} = 0.5\\) such that they are comparable and none of the items would dominate the results." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.256, + 0.634, + 0.273 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.281, + 0.892, + 0.356 + ], + "angle": 0, + "content": "SceneFlow dataset [35] constitutes a synthetic dataset featuring diverse random objects. It contains 35,454 training pairs and 4,370 test pairs with dense disparity labels. Finalpass of the SceneFlow dataset that contains motion blur and defocuses is used." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.357, + 0.892, + 0.477 + ], + "angle": 0, + "content": "KITTI 2012 [15] & KITTI 2015 [36] datasets consist of stereo image pairs of real-world driving scenarios. KITTI 2012 contains 194 training and 195 testing image pairs. KITTI 2015 comprises 200 training and 200 testing image pairs. The stereo pairs in both KITTI 2012 and KITTI 2015 possess resolutions of \\(1226 \\times 370\\) and \\(1242 \\times 375\\), respectively. Notably, both datasets furnish sparse disparity maps as part of their annotations." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.478, + 0.892, + 0.553 + ], + "angle": 0, + "content": "Middlebury 2014 [41] is an stereo dataset consisted of indoor stereo images. It comprises 15 training and 15 testing pairs. All the images are available in three different resolutions. We use the Middlebury 2014 dataset with half resolution to test cross-domain generalization performance." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.554, + 0.892, + 0.674 + ], + "angle": 0, + "content": "Evaluation metrics. We use end point error (EPE), the percentage of errors larger than 3px (\\(>3\\mathrm{px}\\)) on the Scene-Flow dataset, and use EPE and D1-3px on KITTI datasets as evaluation metrics for disparity prediction. D1-3px refers to the percentage of disparity estimations with both absolute larger than 3px and relative error greater than \\(5\\%\\). We use EPE and the percentage of errors larger than 2px (\\(>2\\mathrm{px}\\)) on Middlebury 2014 dataset." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.682, + 0.719, + 0.698 + ], + "angle": 0, + "content": "4.1. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.705, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Our ICGNet is inherently compatible with most stereo matching models since we do not change the structure of the network during inference. Specifically, our framework's compatibility expands to encompass all stereo matching models incorporating a common feature extractor and a disparity decoder. We experiment with our ICGNet on different baseline models GwcNet [17] and IGEV-Stereo [55]. We train the models end-to-end for all experiments. We pre-train the models on the SceneFlow training set. For the evaluation of cross-domain generalization, we directly test the sceneflow pre-trained models' performance on the KITTI 2012 training set, KITTI 2015 training set, and Middlebury 2014 training set. For evaluation of KITTI 2012" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20756" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.125, + 0.09, + 0.847, + 0.128 + ], + "angle": 0, + "content": "
MethodPSMNet [3]GANet [65]ACVNet [54]DLNR [71]GwcNet [17]IGEV-Stereo [55]Ours
EPE(px)↓1.090.840.480.480.7650.4790.447
" + }, + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.138, + 0.892, + 0.152 + ], + "angle": 0, + "content": "Table 1. Comparison with state-of-the-art models on the SceneFlow dataset. Our method outperforms most of the state-of-the-art methods." + }, + { + "type": "table", + "bbox": [ + 0.115, + 0.166, + 0.859, + 0.361 + ], + "angle": 0, + "content": "
MethodKITTI 2012KITTI 2015 (all pixels)KITTI 2015 (noc pixels)
2-noc↓2-all↓3-noc↓3-all↓D1-bg↓D1-fg↓D1-all↓D1-bg↓D1-fg↓D1-all↓
EdgeStereo [45]2.322.881.461.831.843.302.081.692.941.89
LEAStereo [10]1.902.391.131.451.402.911.651.292.651.51
ACVNet [54]1.832.351.131.471.373.071.651.262.841.52
CREStereo [23]1.722.181.141.461.452.861.691.332.601.54
RAFT-Stereo [27]1.922.421.301.661.583.051.821.452.941.69
AcfNet [70]1.832.351.171.541.513.801.891.363.491.72
HITNet [47]2.002.651.411.891.743.201.981.542.721.74
GANet [65]1.892.501.191.601.483.461.811.343.111.63
GwcNet [17]2.162.711.321.701.743.932.111.613.491.92
IGEV-Stereo [55]1.712.171.121.441.382.671.591.272.621.49
Ours1.702.141.101.411.382.551.571.262.561.47
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.371, + 0.893, + 0.399 + ], + "angle": 0, + "content": "Table 2. Finetuning results on KITTI 2012 and KITTI 2015 benchmarks. Our ICGNet achieves state-of-the-art performance on both benchmarks and ranks \\(1^{st}\\) on the KITTI 2015 stereo matching benchmark at the time of submission." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.425, + 0.473, + 0.669 + ], + "angle": 0, + "content": "and KITTI 2015 benchmarks, we finetune SceneFlow pretrained model on the mix of KITTI 2012 and KITTI 2015 training sets. For GwcNet, we use the GwcNet-g setting for KITTI 2015 pre-training and the GwcNet-gc setting for other experiments, consistent with the original work for a fair comparison. We train the model for 64 epochs on SceneFlow and 1000 epochs on KITTI. The initial learning rate is set to 0.001. The learning rate is decayed by a factor of 2 after epochs 20, 32, 40, 48, and 56 on SceneFlow, and decayed by a factor of 2 after epochs 200, 400, 600, 700, and 800 on KITTI. For IGEV-Stereo, we train the model for 80 epochs on SceneFlow and 1000 epochs on KITTI. The initial learning rate is set as 0.0002 and a one-cycle learning rate schedule is used. We maintain all other settings consistent with the original works for both models. All the codes in this paper would be released in Github." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.679, + 0.371, + 0.696 + ], + "angle": 0, + "content": "4.2. Comparison with State-of-the-art" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.703, + 0.47, + 0.884 + ], + "angle": 0, + "content": "To evaluate the effectiveness of our proposed method, we use the latest IGEV-Stereo [55] as the base model and integrate it with ICGNet to compare with state-of-the-art stereo mathing methods. Tab. 1 presents a comparison of our method with state-of-the-art on SceneFlow. Our proposed method achieved state-of-the-art performance on the SceneFlow dataset. We further finetune the SceneFlow pretrained model on KITTI12 [15] and KITTI15 [36] datasets, and compare the performance of ICGNet with state-of-the-art methods on KITTI 2012 and KITTI 2015 benchmarks. Results are shown in Tab. 2. Our ICGNet outperforms state-of-the-art methods in most scenarios." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.886, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Besides quantitative results, qualitative experiments are" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.425, + 0.895, + 0.502 + ], + "angle": 0, + "content": "conducted to show the effectiveness of our proposed method. Fig. 3 visualizes the disparity predictions of our methods. Compared to the state-of-the-art method IGEV-Stereo, our method performs better in reflective regions and unlabelled backgrounds." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.511, + 0.766, + 0.527 + ], + "angle": 0, + "content": "4.3. Cross-domain Generalization" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.535, + 0.895, + 0.703 + ], + "angle": 0, + "content": "We carry out experiments to demonstrate that our approach enhances the domain-generalization capacity of base models, transitioning from the synthetic SceneFlow dataset to real-world datasets. As illustrated in Tab. 3, our proposed ICGNet method boosts the cross-domain generalization performance for IGEV-Stereo which is a strong baseline for cross-domain generalization. Our ICGNet outperforms IGEV-Stereo by \\(4.8\\%\\) on EPE in KITTI 2012 and \\(4.1\\%\\) in KITTI 2015. Furthermore, from the qualitative results in Fig. 4, we can see that our method outperforms IGEV-Stereo in reflective regions and occluded regions." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.711, + 0.666, + 0.727 + ], + "angle": 0, + "content": "4.4. Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.734, + 0.894, + 0.795 + ], + "angle": 0, + "content": "We conduct ablation studies to evaluate the effectiveness of our proposed method. To show the generalization of the intra-view and cross-view knowledge learning, two base methods are used: GwcNet [17] and IGEV-Stereo [55]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Effectiveness of Intra-view and Cross-view Knowledge. To verify that our proposed components all contribute to improving the performance, we provide quantitative results on the SceneFlow dataset in Tab. 4. The proposed ICGNet framework introduces an intra-view geometric loss \\(\\mathcal{L}_{\\mathrm{intra}}\\), a soft cross-view geometric loss \\(\\mathcal{L}_{\\mathrm{cross - soft}}\\) and a hard cross-view geometric loss \\(\\mathcal{L}_{\\mathrm{cross - hard}}\\). The intra-view geo" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20757" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.18, + 0.089, + 0.795, + 0.216 + ], + "angle": 0, + "content": "
MethodKITTI 2012KITTI 2015Middlebury 2014(H)
EPE(px)↓>3px(%)↓EPE(px)↓>3px(%)↓EPE(px)↓>2px(%)↓
PSMNet [3]2.6915.13.1716.37.6534.2
CFNet [42]1.045.21.716.03.2415.4
GANet [65]1.9310.12.3111.75.4120.3
DSMNet [66]1.266.21.466.52.6213.8
IGEV-Stereo [55]1.045.181.216.030.917.27
Ours0.994.871.165.960.826.73
" + }, + { + "type": "table_caption", + "bbox": [ + 0.254, + 0.224, + 0.715, + 0.239 + ], + "angle": 0, + "content": "Table 3. Cross-domain generalization from SceneFlow to real-world datasets." + }, + { + "type": "image", + "bbox": [ + 0.099, + 0.253, + 0.872, + 0.444 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.18, + 0.454, + 0.79, + 0.469 + ], + "angle": 0, + "content": "Figure 3. Qualitative results of ICGNet (ours) compared with the state-of-the-art method IGEV-Stereo." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.492, + 0.47, + 0.607 + ], + "angle": 0, + "content": "
BaselineComponentsSceneFlow
\\( \\mathcal{L}_{\\text{intra}} \\)\\( \\mathcal{L}_{\\text{cross-soft}} \\)\\( \\mathcal{L}_{\\text{cross-hard}} \\)EPEpx)\\( \\downarrow \\)>3px(\\%)↓
GwcNet0.7653.30
✓0.6152.61
✓✓0.6082.56
✓✓✓0.5972.55
IGEV-Stereo0.4792.48
✓0.4522.37
✓✓0.4492.36
✓✓✓0.4472.34
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.617, + 0.471, + 0.646 + ], + "angle": 0, + "content": "Table 4. Ablation studies of proposed components on SceneFlow dataset on two baseline approaches GwcNet and IGEV-Stereo." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.673, + 0.47, + 0.854 + ], + "angle": 0, + "content": "metric loss allows the model to learn intra-image geometric knowledge, and the soft cross-view geometric loss and hard cross-view geometric loss allow the model to learn cross-view geometric knowledge. Notably, our method demonstrates an improvement of over \\(20\\%\\) (0.597 vs 0.765) in EPE and over \\(20\\%\\) improvement in 3px-error. When applied to the strong base model IGEV-Stereo, our method still shows solid improvements over both EPE and 3px-error. The SceneFlow pre-trained full models of both base models are then finetuned on KITTI 2012 and KITTI 2015 datasets and results are shown in Tab. 5. Our method consistently outperforms the performance of baseline models." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Impact on Occluded and Non-occluded Regions. We further conduct experiments on our method's impact on occluded pixels and non-occluded pixels separately. Tab. 6" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.494, + 0.895, + 0.678 + ], + "angle": 0, + "content": "shows that our method consistently improves disparity quality in both occluded regions and non-occluded regions. Furthermore, since occluded regions are areas without correspondence in the other figures, intuitively the prediction of disparities on such pixels relies more on intra-view geometric knowledge; on the contrary, predicting disparities at non-occluded pixels relies more on cross-view geometric knowledge [55]. Our experiment results are consistent with this intuition, validating our formulation of the process of extracting interest points as intra-view geometric knowledge and the process of extracting their correspondences as cross-view geometric knowledge." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Complexity of intra-view decoder and cross-view decoder. We conduct experiments to evaluate the impact of the complexity of the intra-view decoder \\( D_{\\mathrm{intra}} \\) and cross-view decoder \\( D_{\\mathrm{cross}} \\) on the models' performance. We keep GwcNet as the base model and change the number of layers of the decoders. The number of layers of the intra-view decoder refers to the number of stacked bottleneck convolutional blocks, and the number of layers of the cross-view decoder refers to the number of alternating attention layers. For the cross-view decoder with zero layers, we are directly using cosine similarities between the interest point features plus a softmax layer to form an assignment matrix \\( \\mathbf{P}' \\). Results on the SceneFlow dataset with GwcNet [17] as baseline are shown in Tab. 7. Results have shown that an" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20758" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.084, + 0.09, + 0.889, + 0.187 + ], + "angle": 0, + "content": "
BaselineICGNetKITTI 2012KITTI 2015 (all pixels)KITTI 2015 (noc pixels)
2-noc↓2-all↓3-noc↓3-all↓D1-bg↓D1-fg↓D1-all↓D1-bg↓D1-fg↓D1-all↓
GwcNet [17]✓2.162.711.321.701.743.932.111.613.491.92
1.982.541.251.631.623.902.001.503.561.84
IGEV-Stereo [55]✓1.712.171.121.441.382.671.591.272.621.49
1.702.141.101.411.382.551.571.262.561.47
" + }, + { + "type": "table_caption", + "bbox": [ + 0.273, + 0.196, + 0.696, + 0.21 + ], + "angle": 0, + "content": "Table 5. Ablation studies on KITTI 2012 and KITTI 2015 benchmarks." + }, + { + "type": "image", + "bbox": [ + 0.102, + 0.226, + 0.306, + 0.326 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.102, + 0.327, + 0.306, + 0.372 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.102, + 0.373, + 0.306, + 0.419 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.186, + 0.421, + 0.24, + 0.432 + ], + "angle": 0, + "content": "Left Image" + }, + { + "type": "image", + "bbox": [ + 0.308, + 0.226, + 0.495, + 0.326 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.308, + 0.327, + 0.494, + 0.373 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.308, + 0.373, + 0.494, + 0.419 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.363, + 0.421, + 0.443, + 0.432 + ], + "angle": 0, + "content": "Disparity Labels" + }, + { + "type": "image", + "bbox": [ + 0.496, + 0.226, + 0.682, + 0.326 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.496, + 0.327, + 0.682, + 0.373 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.496, + 0.373, + 0.682, + 0.419 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.557, + 0.421, + 0.621, + 0.432 + ], + "angle": 0, + "content": "IGEV-Stereo" + }, + { + "type": "image", + "bbox": [ + 0.684, + 0.226, + 0.871, + 0.326 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.684, + 0.327, + 0.871, + 0.372 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.684, + 0.373, + 0.871, + 0.419 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.741, + 0.421, + 0.812, + 0.432 + ], + "angle": 0, + "content": "ICGNet (ours)" + }, + { + "type": "image_caption", + "bbox": [ + 0.082, + 0.445, + 0.886, + 0.461 + ], + "angle": 0, + "content": "Figure 4. Qualitative results of cross-domain generalization of ICGNet (ours) compared with state-of-the-art baseline IGEV-Stereo [55]." + }, + { + "type": "table", + "bbox": [ + 0.079, + 0.484, + 0.495, + 0.566 + ], + "angle": 0, + "content": "
Intra-view\nL_intraCross-view\nL CROSS-soft + L cross-hardSceneFlow EPE
noc(px)↓occ(px)↓Δnoc/Δocc
0.4132.58/
✓0.3342.086.33
✓✓0.3182.023.75
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.577, + 0.47, + 0.675 + ], + "angle": 0, + "content": "Table 6. Ablation studies on occluded and non-occluded areas on the SceneFlow dataset using GwcNet baseline model. Our method improves disparity prediction accuracy in both occluded areas and non-occluded areas. Compared with cross-view geometric knowledge, intra-view geometric knowledge improves more in occluded regions, consistent with the intuition that occluded areas rely on their surrounding geometric relations to infer their disparities." + }, + { + "type": "table", + "bbox": [ + 0.132, + 0.692, + 0.418, + 0.817 + ], + "angle": 0, + "content": "
DecoderLayersSceneFlow
EPE(px)↓>3px↓
intra-view10.6312.74
20.6152.61
40.6232.68
cross-view00.6172.61
40.5972.55
60.6062.58
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.827, + 0.47, + 0.856 + ], + "angle": 0, + "content": "Table 7. Comparison of performance of different decoder complexities." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.487, + 0.892, + 0.609 + ], + "angle": 0, + "content": "intermediate number of decoder layers for both intra-view and cross-view decoder yields the best results. This may be due to a too-complex decoder will take up too much of the task of learning the geometric knowledge, making the feature backbone not learn sufficient knowledge, while a too-simple decoder is not sufficient to map the features into the geometric structures, leaving too much for the feature backbone and make it sub-optimal in disparity prediction task." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.625, + 0.619, + 0.64 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.651, + 0.892, + 0.803 + ], + "angle": 0, + "content": "In this work, we introduce ICGNet, a novel approach designed to infuse stereo matching networks with both intraview and cross-view geometric knowledge. Utilizing interest points and their corresponding matches derived from local feature matching models, we provide rich sources of geometric knowledge to educate the stereo matching network. Our extensive experimental evaluations demonstrate that this methodology enhances the performance of state-of-the-art stereo matching models, boosting both their accuracy and their ability to generalize across diverse domains." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.819, + 0.661, + 0.837 + ], + "angle": 0, + "content": "Acknowledgement" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.845, + 0.892, + 0.888 + ], + "angle": 0, + "content": "This work was supported by the Agency for Science, Technology and Research (A*STAR) under its MTC Programmatic Funds (Grant No. M23L7b0021)." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "20759" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Herbert Bay, Tinne Tuytelaars, and Luc Van Gool. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 1327-1336, 2023. 6" + }, + { + "type": "list", + "bbox": [ + 0.504, + 0.093, + 0.892, + 0.823 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.52, + 0.957 + ], + "angle": 0, + "content": "20762" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/2798eade-4610-47df-96d1-47a92d0431fb_origin.pdf b/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/2798eade-4610-47df-96d1-47a92d0431fb_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..e7209f9b3eb71810982ab14fcfb13f8a3adc930a --- /dev/null +++ b/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/2798eade-4610-47df-96d1-47a92d0431fb_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:e9a3f52d40a12ab514df4e95c7eb33b05509202648534c29f081cfa7fce9955e +size 7590874 diff --git a/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/full.md b/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/full.md new file mode 100644 index 0000000000000000000000000000000000000000..fac79d6a87b7661b4b8da08a177e3c7f1809edaf --- /dev/null +++ b/2024/Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching/full.md @@ -0,0 +1,314 @@ +# Learning Intra-view and Cross-view Geometric Knowledge for Stereo Matching + +Rui Gong\*1, Weide Liu?, Zaiwang Gu?, Xulei Yang?, and Jun Cheng + +$^{1}$ School of Electrical and Electronic Engineering, Nanyang Technological University $^{2}$ Institute for Infocomm Research, A*STAR + +# Abstract + +Geometric knowledge has been shown to be beneficial for the stereo matching task. However, prior attempts to integrate geometric insights into stereo matching algorithms have largely focused on geometric knowledge from single images while crucial cross-view factors such as occlusion and matching uniqueness have been overlooked. To address this gap, we propose a novel Intra-view and Cross-view Geometric knowledge learning Network (ICGNet), specifically crafted to assimilate both intra-view and cross-view geometric knowledge. ICGNet harnesses the power of interest points to serve as a channel for intra-view geometric understanding. Simultaneously, it employs the correspondences among these points to capture cross-view geometric relationships. This dual incorporation empowers the proposed ICGNet to leverage both intra-view and cross-view geometric knowledge in its learning process, substantially improving its ability to estimate disparities. Our extensive experiments demonstrate the superiority of the ICGNet over contemporary leading models. The code will be available at https://github.com/DFSDDDDD1199/ICGNet. + +# 1. Introduction + +Stereo matching is the task of estimating a disparity map from a pair of rectified images. It stands as one of the cornerstone challenges in a range of computer vision tasks, including augmented reality, autonomous driving, and robotics [18]. With the rapid development of deep learning techniques and network structures in computer vision scenarios, deep stereo matching networks have achieved great success in stereo matching. + +Geometric knowledge plays a crucial role in the overall performance of stereo matching networks [21, 45, 55, 69] due to the existence of repeated patterns, textureless ar + +![](images/e4322bd310dd5ac8e01bf179132a8e43fb4227ec535028a88a0f20b4b1d7811f.jpg) +Figure 1. An illustration of our overall framework using synthetic shapes. We leverage intra-view geometric knowledge which is the knowledge of extracting geometric structures, and cross-view geometric knowledge which is the knowledge of the correspondences of these structures, to aid the stereo matching task. Note that the dotted lines are used for illustration and are not used in the method. + +eas, and reflective surfaces, which make simple texture-based matching methods ineffective. Consequently, several methods were proposed to introduce geometric knowledge into stereo matching networks through kinds of geometric structures. EdgeStereo [45] proposed a learning network that incorporates edges and edge-disparity relations into the stereo matching network. Normal assisted stereo matching [21, 69] leverages surface normal as geometric constraints to reduce the matching ambiguity for textureless regions. However, the geometric knowledge employed in these studies is mainly intra-view, lacking the cross-view geometric knowledge such as matching uniqueness and occlusion. + +To address the absence of cross-view geometric knowledge, we have identified that the local feature matching task [12, 34, 40] can serve as a suitable source of cross-view geometric knowledge for stereo matching. Local feature matching involves the identification of correspondences between two images, typically achieved by initially detecting sparse, geometrically meaningful interest points within each view and then extracting descriptors for these interest points encoded with their visual attributes [12]. Subsequently, cross-view matching is carried out by comparing the interest points between the two images [40]. This matching process solves a partial assignment problem be + +tween the points which takes matching uniqueness and occlusion into account. Moreover, we also find that the interest points from each image also provide intra-view knowledge of the image. Building upon these insights, we introduce our ICGNet framework to take both the intra-view and cross-view geometric knowledge contained in local feature matching models into the stereo matching network. We leverage a pre-trained local feature matching pipeline, comprising an interest point detector and a point matcher. We propose an intra-view constraint that the features we extract from stereo matching backbone preserve the same interest point information as the pre-trained interest point detector to gain intra-view geometric knowledge. Additionally, we propose a cross-view constraint that these features are compelled to serve as descriptors for the interest points, facilitating the matching process between these points. The matching outcome is then constrained to align with both the ground-truth matching labels provided by ground-truth disparity maps and the matching results obtained from the pretrained interest point matcher, in order to gain cross-view geometric knowledge. Compared to EdgeStereo [45] and normal assisted stereo matching [21, 69], our method not only additionally introduces cross-view geometric knowledge but also keeps zero overhead when inference. + +Our experiments show that our method effectively improves the performance across both the seen and unseen domains. The contributions are summarized as follows: + +1. We propose to learn intra-view geometric knowledge for stereo matching networks from an interest point detector by introducing a novel intra-view geometric constraint computed from the interest point detection outcomes. +2. We propose to learn cross-view geometric knowledge for stereo matching networks from an interest point matcher by introducing a novel cross-view geometric constraint. We compute both soft cross-view and hard cross-view geometric losses using pretrained interest point matcher and disparity ground truth. +3. We conduct a series of comprehensive experiments that consistently demonstrate the proposed framework's ability to enhance the overall performance of state-of-the-art stereo matching networks. Our ICGNet achieves state-of-the-art performance on the SceneFlow dataset and ranks $1^{st}$ on the KITTI 2015 stereo matching benchmark among published peer-reviewed methods at the time of submission, and improves cross-domain generalization of baseline methods on KITTI 2012, KITTI 2015, and Middlebury 2014 datasets. + +# 2. Related Works + +# 2.1. Deep Stereo Matching + +Deep-learning-based deep stereo matching techniques have gained widespread adoption and demonstrated promis + +ing outcomes [7, 9, 16, 24, 25, 28, 37, 52, 53, 57, 58, 61]. The initial instance of such an approach is DispNetC [35], which presents an end-to-end trainable stereo matching framework. This framework employs the dot product of feature maps from left and right images as correspondence to build a cost volume of three dimensions. However, the drawback of this computational-friendly methodology is its inability to capture sufficient information to achieve satisfactory results. In the pursuit of improved performance, subsequent methods like GC-Net [20] have emerged. Numerous works [3, 65] have followed this trend and incorporated 3D hourglass convolutions to aggregate a 4D cost volume. This volume is created by concatenating features from left and right images. Unfortunately, this approach demands substantial memory usage and computational complexity. A notable enhancement arrives with GwcNet [17], which introduces the concept of group-wise correlation. This innovation enables the construction of a more compact cost volume. Recently, iterative optimization-based methods [23, 27, 63] have achieved splendid performance. Inspired by RAFT [48], RAFT-Stereo [27] iteratively updates the disparity using all-pairs correlation between features extracted. IGEV-Stereo [55] further boosts the performance of stereo matching network by combining cost-volume modules with iterative updating modules. Uncertainty-based methods [8, 51] also gained attention these years. ELFNet [33] leverage uncertainty to fuse multi-scale disparity and stereo network with different structures. SEDNet [6] proposes a soft-histogramming technique to align the distribution of prediction error and prediction uncertainty. Other works focus on improving the domain generalization performance [4, 11, 29, 38, 68] and domain adaptation performance [31, 46, 64, 66] of stereo matching networks. + +Recognizing the need for increased efficiency and the integration of richer semantic information, multi-scale cost volume is used in stereo matching networks. HSMNet [59] employs a pyramid of volumes to enable high-resolution stereo matching. AANet [56] takes a lightweight approach, incorporating a feature pyramid and interactions with multi-scale correlation volumes. In a recent development, PCWNet [43] introduces a volume fusion module that directly combines multi-scale 4D volumes. This innovation calculates a multi-level loss, ultimately expediting the model's convergence speed. + +# 2.2. Geometric Structure Guided Stereo Matching + +Geometric structures have been used to guide stereo matching networks in previous works. EdgeStereo [45] introduced an edge branch, integrating edge features into the stereo matching branch. Yang et al. [60] also advocated the use of edges for supervising stereo matching through multitask learning. Additionally, surface normals have been another employed geometric structure to guide stereo match + +ing. Zhang et al. [69] suggested a joint prediction of a surface normal map and a raw disparity map, iteratively refining the disparity map with guidance from the surface normal map. Kusupati et al. [21] incorporated an extra surface normal branch to predict raw surface normals and employed an independently trained consistency module for refinement of both surface normals and raw disparities. + +However, these approaches have two limitations. Firstly, they heavily depend on additional branches during inference to improve their performance, which impacts efficiency. In contrast, our proposed framework leverages geometric structures as constraints during training without incurring any overhead in inference, and shows improved performance. Secondly, the previous methods only made use of intra-view geometric structures, whereas our framework takes into account both intra-view and cross-view geometric knowledge through both geometric structure and their correspondences. + +# 2.3. Local Feature Matching + +Local feature matching aims at matching images that depict the same scene or object. This is usually done in a two-stage manner: first, detect interest points each associated with a visual descriptor from both images, and then match the detected interest points. + +Traditional interest points detection and description algorithms [1, 19, 34, 39] rely on hand-crafted features. Recent research turns to Convolutional Neural Networks (CNN) for both interest point detection and description [22, 30, 32, 49]. SuperPoint [12] is a representative work of CNN-based interest point detector and descriptor, trained in a self-supervised manner. It constructs a synthetic shape dataset by rendering simplified 2D geometries, such as triangles, quadrilaterals, lines, and ellipses. The junctions of lines are labeled as interest points. These labels are then transferred to substantial real-world image datasets using a MagicPoint model and homographic adaptation. The self-supervised training process equips SuperPoint with the ability to be trained on various domains, enabling it to encode geometric information across diverse domains. + +Traditional algorithms employ nearest-neighbor classifiers for matching interest points. Lowe's test [34], inlier classifiers [62, 67], or geometric model fitting [2, 13] techniques are subsequently used to filter out unmatched points and incorrect correspondences. However, these methods are highly domain-specific and struggle to handle particularly challenging conditions. In contrast, deep learning-based matchers are trained to simultaneously match interest points and reject outliers. A notable example of this approach is SuperGlue [40], which leverages Transformers [50] to conduct self-attention among interest points within the same view and cross-attention between interest points in different views. The final matching step involves solving an op + +timal transport problem. This approach allows SuperGlue to acquire robust insights into scene geometry and camera motion, rendering it resilient to extreme changes and effective in generalizing across various data domains. Subsequent works [5, 26, 44] focused on making it more efficient and digging into its design details while keeping its strong matching capability. Consequently, these matchers are great sources of cross-view geometric knowledge. We set up constraints to let the stereo matching network learn geometric knowledge from a pre-trained interest point detector and a pre-trained interest point matcher. + +# 3. Method + +We propose ICGNet to introduce geometric knowledge into stereo matching networks through geometric constraints. Intra-view geometric knowledge refers to the understanding that uncovers the geometric structures contained within a single image. Cross-view geometric knowledge refers to the comprehension that enables the alignment of geometric structures from one image to another. Models capable of uncovering and matching geometric structures harness the potential to convey intra-view and cross-view knowledge. Therefore, as depicted in Fig. 2, our framework introduces intra-view and cross-view geometric knowledge into the stereo matching network by aligning our network with intra-view and cross-view geometric knowledge sources. Although there are multiple choices (e.g., edges, points) to extract intra-view knowledge, we choose interest points as it is easy to further compute cross-view knowledge from these points using well-established methods [40] while it is more challenging to match the edges for cross-view knowledge computation. We denote the left-view stereo image as $I_{l}$ and right-view stereo image as $I_{r}$ , and the extracted left feature and right feature as $F_{l}$ and $F_{r}$ . + +# 3.1. Intra-view Geometric Knowledge + +Intra-view Geometric Knowledge Decoder is to introduce intra-view geometric knowledge into the stereo matching network. We propose to leverage a pre-trained interest point detector $\mathcal{IP}_{\mathrm{det}}$ [12] in our method. It takes the left-view image $I_{l}$ and the right-view image $I_{r}$ as input and generates interest maps $\mathbf{M}_l$ and $\mathbf{M}_r$ , where each pixel is either labeled as interest point or non-interest point. These maps convey the intra-view geometric characteristics of the two images. We expect that the backbone features $F_{l}$ and $F_{r}$ preserve and unveil the intra-view geometric details present in both the left and right view images, akin to what the pretrained interest point detector accomplishes. Consequently, we aim to extract two interest point maps, $\mathbf{M}_l^{\prime}$ and $\mathbf{M}_r^{\prime}$ , from $F_{l}$ and $F_{r}$ using a trainable intra-view decoder $D_{\mathrm{intra}}$ , aligning with $\mathbf{M}_l$ and $\mathbf{M}_r$ respectively. For the design of $D_{\mathrm{intra}}$ , we use a stack of two bottleneck convolutional blocks. Note that decoder $D_{\mathrm{intra}}$ is discarded during the test stage. + +![](images/c525551cd5238e96fc656ac5c96421dc22f5a0f75d144a35232d007023aa2769.jpg) +Figure 2. Overall structure of our proposed framework. The model architecture comprises three parts: stereo matching network, cross-view knowledge learning network, and intra-view knowledge learning network. The cross-view knowledge learning network introduces cross-view geometric knowledge by aligning the interest point correspondences $\mathbf{P}'$ , $\mathbf{P}$ and $\mathcal{P}^{gt}$ using $\mathcal{L}_{\mathrm{cross - hard}}$ and $\mathcal{L}_{\mathrm{cross - soft}}$ . The intra-view knowledge learning network introduces intra-view geometric knowledge through aligning the interest point maps $\mathbf{M}'$ and $\mathbf{M}$ using $\mathcal{L}_{\mathrm{intra}}$ . Note that the dotted lines are used just for clear illustration and are not used in our work. + +Intra-view geometric loss $\mathcal{L}_{\mathrm{intra}}$ is computed to enforce this alignment: + +$$ +\mathcal {L} _ {\text {i n t r a}} = \frac {1}{2} \mathcal {L} \left(\mathbf {M} _ {l} ^ {\prime}, \mathbf {M} _ {l}\right) + \frac {1}{2} \mathcal {L} \left(\mathbf {M} _ {r} ^ {\prime}, \mathbf {M} _ {r}\right), \tag {1} +$$ + +where we compute a focal loss $\mathcal{L}$ due to unbalanced positive and negative samples of interest points. + +# 3.2. Cross-view Geometric Knowledge + +Cross-view Geometric Knowledge Decoder enables the stereo matching network to acquire cross-view geometric knowledge by framing it as a learning task. This task is to align the stereo matching network with two complementary knowledge sources: a pre-trained interest point matcher denoted as $\mathcal{IP}_{\mathrm{match}}$ where we use [40] in our method, and the ground truth matching between interest points. + +The pre-trained matcher processes two sets of interest points extracted from stereo image pair $I_{l}$ and $I_{r}$ , denoted as $p_l$ and $p_r$ , each containing $m$ and $n$ points respectively, along with their associated descriptors. It outputs an assignment matrix $\mathbf{P} \in [0,1]^{(m + 1)\times (n + 1)}$ . This matrix includes an extra row and column to account for the possibility that some points do not match any counterpart in the other view. The assignment matrix $\mathbf{P}$ elucidates the cross-view geometric knowledge via the relations between the matching probabilities of the two sets of points. + +Furthermore, the ground truth disparities can serve as another source of knowledge since it provide accurate matching between these points. Ground truth matching pairs between the points $\mathcal{P}^{gt} = \{(i,j)\} \subset p_l \times p_r$ ( $x$ refers to Cartesian product) and unmatched points in left image $\mathcal{U}_l^{gt} \subseteq p_l$ and right image $\mathcal{U}_r^{gt} \subseteq p_r$ are formed by warping interest points from the left image to the right image using the disparity. + +The ground truth is more precise compared to the assignment matrix provided by the interest point matcher. In the ground truth, the relationships between points are binary, classified simply as either a match or a mismatch. On the other hand, the assignment matrix presents matching scores as continuous values ranging from 0 to 1, implicitly indicating the degree of similarity between the points. This makes the two approaches complementary: one provides precise matching categorization, which is 'harder', while the other offers a fine-grained assessment of similarity, which is 'softer'. + +To align the stereo matching network with these two sources of cross-view geometric knowledge, a trainable cross-view decoder denoted as $D_{\mathrm{cross}}$ is proposed. $D_{\mathrm{cross}}$ first use as an Multilayer Perceptron (MLP) encoder [14, 50] followed by four alternative self-attention and cross-attention layers [50]. The self attention layers operate on points within the same image, while the cross-attention + +layer operate on points within different images. The decoder is responsible for decoding an assignment matrix $\mathbf{P}'$ . This decoded matrix is trained to closely match its corresponding reference assignment matrix $\mathbf{P}$ created by a pretrained interest point matcher $\mathcal{IP}_{\mathrm{match}}$ and the ground truth matching pairs $\mathcal{P}^{gt}$ and unmatched points $\mathcal{U}_l^{gt}$ , $\mathcal{U}_r^{gt}$ from left and right images respectively, serving as the supervision pseudo ground truth during training. The points input $p_l$ and $p_r$ to the decoder $D_{\mathrm{cross}}$ are identical to the input to $\mathcal{IP}_{\mathrm{match}}$ , but with different descriptors bi-linearly sampled from features $F_l$ and $F_r$ extracted by stereo backbone such that the gradient can flow back to the stereo network. Note that decoder $D_{\mathrm{cross}}$ is discarded during the test stage. + +Soft cross-view geometric loss $\mathcal{L}_{\mathrm{cross - soft}}$ is proposed to introduce the cross-view geometric knowledge from the reference assignment matrix $\mathbf{P}$ into the predicted assignment matrix $\mathbf{P}'$ . + +$$ +\begin{array}{l} \mathcal {L} _ {\text {c r o s s - s o f t}} = \frac {1}{m} \sum_ {i = 1} ^ {m} \mathcal {K L} \left(\mathbf {P} _ {i, \cdot} / | | \mathbf {P} _ {i, \cdot} | | _ {1}, \mathbf {P} _ {i, \cdot} ^ {\prime} / | | \mathbf {P} _ {i, \cdot} ^ {\prime} | | _ {1}\right) \\ + \frac {1}{n} \sum_ {j = 1} ^ {n} \mathcal {K L} \left(\mathbf {P} _ {\cdot , j} / \left\| \mathbf {P} _ {\cdot , j} \right\| _ {1}, \mathbf {P} _ {\cdot , j} ^ {\prime} / \left\| \mathbf {P} _ {\cdot , j} ^ {\prime} \right\| _ {1}\right), \tag {2} \\ \end{array} +$$ + +where $\mathcal{KL}$ stands for KL-divergence, and $\mathbf{P}_{i,\cdot}$ stands for the $i^{th}$ row of $\mathbf{P}$ , $\mathbf{P}_{\cdot,j}$ stands for the $j^{th}$ column of $\mathbf{P}$ . In this work, we use the interest points filtered from interest point maps $\mathbf{M}_l$ , $\mathbf{M}_r$ extracted by pre-trained interest point detector [12] by non maximum suppression as $p_l$ and $p_r$ . + +Hard cross-view geometric loss is further computed based on the ground truth matching between interest points $\mathcal{P}^{gt}$ , unmatched points in the left image $\mathcal{U}_l^{gt}$ , and unmatched points in the right image $\mathcal{U}_r^{gt}$ . Hard cross-view geometric loss is utilized as a negative log-likelihood loss balanced between matched points and unmatched points to align $\mathbf{P}'$ and $\mathcal{P}^{gt}, \mathcal{U}_l^{gt}, \mathcal{U}_r^{gt}$ : + +$$ +\begin{array}{l} \mathcal {L} _ {\text {c r o s s - h a r d}} = - \frac {1}{| \mathcal {P} ^ {g t} |} \sum_ {(i, j) \in \mathcal {P} ^ {g t}} \log \mathbf {P} _ {i, j} ^ {\prime} \\ - \frac {1}{\left| \mathcal {U} _ {l} ^ {g t} \right|} \sum_ {i \in \mathcal {U} _ {l}} \log \mathbf {P} _ {i, n + 1} ^ {\prime} \tag {3} \\ - \frac {1}{\left| \mathcal {U} _ {r} ^ {g t} \right|} \sum_ {j \in \mathcal {U} _ {r}} \log \mathbf {P} _ {m + 1, j} ^ {\prime}. \\ \end{array} +$$ + +# 3.3. Loss + +We integrate our proposed $\mathcal{L}_{\mathrm{intra}}$ , $\mathcal{L}_{\mathrm{cross - soft}}$ , and $\mathcal{L}_{\mathrm{cross - hard}}$ with disparity loss $L_{\mathrm{disp}}$ , enabling simultaneously estimating disparity and learning intra-view and cross-view geometric structure knowledge from local feature matching + +models. The disparity loss, $L_{\mathrm{disp}}$ , is determined by the loss function utilized by the base models. The total loss is defined as: + +$$ +\begin{array}{l} \mathcal {L} _ {\text {t o t a l}} = \mathcal {L} _ {\text {d i s p}} + \lambda_ {\text {i n t r a}} \cdot \mathcal {L} _ {\text {i n t r a}} + \lambda_ {\text {c r o s s - s o f t}} \cdot \mathcal {L} _ {\text {c r o s s - s o f t}} \tag {4} \\ + \lambda_ {\text {c r o s s - h a r d}} \cdot \mathcal {L} _ {\text {c r o s s - h a r d}}, \\ \end{array} +$$ + +where $\mathcal{L}_{\mathrm{intra}}$ , $\mathcal{L}_{\mathrm{cross - soft}}$ , $\mathcal{L}_{\mathrm{cross - hard}}$ are weighting terms. The loss weights are empirically set as $\mathcal{L}_{\mathrm{intra}} = 100$ , $\mathcal{L}_{\mathrm{cross - soft}} = 0.5$ , $\mathcal{L}_{\mathrm{cross - hard}} = 0.5$ such that they are comparable and none of the items would dominate the results. + +# 4. Experiments + +SceneFlow dataset [35] constitutes a synthetic dataset featuring diverse random objects. It contains 35,454 training pairs and 4,370 test pairs with dense disparity labels. Finalpass of the SceneFlow dataset that contains motion blur and defocuses is used. + +KITTI 2012 [15] & KITTI 2015 [36] datasets consist of stereo image pairs of real-world driving scenarios. KITTI 2012 contains 194 training and 195 testing image pairs. KITTI 2015 comprises 200 training and 200 testing image pairs. The stereo pairs in both KITTI 2012 and KITTI 2015 possess resolutions of $1226 \times 370$ and $1242 \times 375$ , respectively. Notably, both datasets furnish sparse disparity maps as part of their annotations. + +Middlebury 2014 [41] is an stereo dataset consisted of indoor stereo images. It comprises 15 training and 15 testing pairs. All the images are available in three different resolutions. We use the Middlebury 2014 dataset with half resolution to test cross-domain generalization performance. + +Evaluation metrics. We use end point error (EPE), the percentage of errors larger than 3px ( $>3\mathrm{px}$ ) on the Scene-Flow dataset, and use EPE and D1-3px on KITTI datasets as evaluation metrics for disparity prediction. D1-3px refers to the percentage of disparity estimations with both absolute larger than 3px and relative error greater than $5\%$ . We use EPE and the percentage of errors larger than 2px ( $>2\mathrm{px}$ ) on Middlebury 2014 dataset. + +# 4.1. Implementation Details + +Our ICGNet is inherently compatible with most stereo matching models since we do not change the structure of the network during inference. Specifically, our framework's compatibility expands to encompass all stereo matching models incorporating a common feature extractor and a disparity decoder. We experiment with our ICGNet on different baseline models GwcNet [17] and IGEV-Stereo [55]. We train the models end-to-end for all experiments. We pre-train the models on the SceneFlow training set. For the evaluation of cross-domain generalization, we directly test the sceneflow pre-trained models' performance on the KITTI 2012 training set, KITTI 2015 training set, and Middlebury 2014 training set. For evaluation of KITTI 2012 + +
MethodPSMNet [3]GANet [65]ACVNet [54]DLNR [71]GwcNet [17]IGEV-Stereo [55]Ours
EPE(px)↓1.090.840.480.480.7650.4790.447
+ +Table 1. Comparison with state-of-the-art models on the SceneFlow dataset. Our method outperforms most of the state-of-the-art methods. + +
MethodKITTI 2012KITTI 2015 (all pixels)KITTI 2015 (noc pixels)
2-noc↓2-all↓3-noc↓3-all↓D1-bg↓D1-fg↓D1-all↓D1-bg↓D1-fg↓D1-all↓
EdgeStereo [45]2.322.881.461.831.843.302.081.692.941.89
LEAStereo [10]1.902.391.131.451.402.911.651.292.651.51
ACVNet [54]1.832.351.131.471.373.071.651.262.841.52
CREStereo [23]1.722.181.141.461.452.861.691.332.601.54
RAFT-Stereo [27]1.922.421.301.661.583.051.821.452.941.69
AcfNet [70]1.832.351.171.541.513.801.891.363.491.72
HITNet [47]2.002.651.411.891.743.201.981.542.721.74
GANet [65]1.892.501.191.601.483.461.811.343.111.63
GwcNet [17]2.162.711.321.701.743.932.111.613.491.92
IGEV-Stereo [55]1.712.171.121.441.382.671.591.272.621.49
Ours1.702.141.101.411.382.551.571.262.561.47
+ +Table 2. Finetuning results on KITTI 2012 and KITTI 2015 benchmarks. Our ICGNet achieves state-of-the-art performance on both benchmarks and ranks $1^{st}$ on the KITTI 2015 stereo matching benchmark at the time of submission. + +and KITTI 2015 benchmarks, we finetune SceneFlow pretrained model on the mix of KITTI 2012 and KITTI 2015 training sets. For GwcNet, we use the GwcNet-g setting for KITTI 2015 pre-training and the GwcNet-gc setting for other experiments, consistent with the original work for a fair comparison. We train the model for 64 epochs on SceneFlow and 1000 epochs on KITTI. The initial learning rate is set to 0.001. The learning rate is decayed by a factor of 2 after epochs 20, 32, 40, 48, and 56 on SceneFlow, and decayed by a factor of 2 after epochs 200, 400, 600, 700, and 800 on KITTI. For IGEV-Stereo, we train the model for 80 epochs on SceneFlow and 1000 epochs on KITTI. The initial learning rate is set as 0.0002 and a one-cycle learning rate schedule is used. We maintain all other settings consistent with the original works for both models. All the codes in this paper would be released in Github. + +# 4.2. Comparison with State-of-the-art + +To evaluate the effectiveness of our proposed method, we use the latest IGEV-Stereo [55] as the base model and integrate it with ICGNet to compare with state-of-the-art stereo mathing methods. Tab. 1 presents a comparison of our method with state-of-the-art on SceneFlow. Our proposed method achieved state-of-the-art performance on the SceneFlow dataset. We further finetune the SceneFlow pretrained model on KITTI12 [15] and KITTI15 [36] datasets, and compare the performance of ICGNet with state-of-the-art methods on KITTI 2012 and KITTI 2015 benchmarks. Results are shown in Tab. 2. Our ICGNet outperforms state-of-the-art methods in most scenarios. + +Besides quantitative results, qualitative experiments are + +conducted to show the effectiveness of our proposed method. Fig. 3 visualizes the disparity predictions of our methods. Compared to the state-of-the-art method IGEV-Stereo, our method performs better in reflective regions and unlabelled backgrounds. + +# 4.3. Cross-domain Generalization + +We carry out experiments to demonstrate that our approach enhances the domain-generalization capacity of base models, transitioning from the synthetic SceneFlow dataset to real-world datasets. As illustrated in Tab. 3, our proposed ICGNet method boosts the cross-domain generalization performance for IGEV-Stereo which is a strong baseline for cross-domain generalization. Our ICGNet outperforms IGEV-Stereo by $4.8\%$ on EPE in KITTI 2012 and $4.1\%$ in KITTI 2015. Furthermore, from the qualitative results in Fig. 4, we can see that our method outperforms IGEV-Stereo in reflective regions and occluded regions. + +# 4.4. Ablation Studies + +We conduct ablation studies to evaluate the effectiveness of our proposed method. To show the generalization of the intra-view and cross-view knowledge learning, two base methods are used: GwcNet [17] and IGEV-Stereo [55]. + +Effectiveness of Intra-view and Cross-view Knowledge. To verify that our proposed components all contribute to improving the performance, we provide quantitative results on the SceneFlow dataset in Tab. 4. The proposed ICGNet framework introduces an intra-view geometric loss $\mathcal{L}_{\mathrm{intra}}$ , a soft cross-view geometric loss $\mathcal{L}_{\mathrm{cross - soft}}$ and a hard cross-view geometric loss $\mathcal{L}_{\mathrm{cross - hard}}$ . The intra-view geo + +
MethodKITTI 2012KITTI 2015Middlebury 2014(H)
EPE(px)↓>3px(%)↓EPE(px)↓>3px(%)↓EPE(px)↓>2px(%)↓
PSMNet [3]2.6915.13.1716.37.6534.2
CFNet [42]1.045.21.716.03.2415.4
GANet [65]1.9310.12.3111.75.4120.3
DSMNet [66]1.266.21.466.52.6213.8
IGEV-Stereo [55]1.045.181.216.030.917.27
Ours0.994.871.165.960.826.73
+ +![](images/731eacf9df2e37bc1db684b0b9ccf25ac997de4bdde05f1fce4ee755fb9db6fa.jpg) +Figure 3. Qualitative results of ICGNet (ours) compared with the state-of-the-art method IGEV-Stereo. + +Table 3. Cross-domain generalization from SceneFlow to real-world datasets. + +
BaselineComponentsSceneFlow
\( \mathcal{L}_{\text{intra}} \)\( \mathcal{L}_{\text{cross-soft}} \)\( \mathcal{L}_{\text{cross-hard}} \)EPEpx)\( \downarrow \)>3px(\%)↓
GwcNet0.7653.30
✓0.6152.61
✓✓0.6082.56
✓✓✓0.5972.55
IGEV-Stereo0.4792.48
✓0.4522.37
✓✓0.4492.36
✓✓✓0.4472.34
+ +Table 4. Ablation studies of proposed components on SceneFlow dataset on two baseline approaches GwcNet and IGEV-Stereo. + +metric loss allows the model to learn intra-image geometric knowledge, and the soft cross-view geometric loss and hard cross-view geometric loss allow the model to learn cross-view geometric knowledge. Notably, our method demonstrates an improvement of over $20\%$ (0.597 vs 0.765) in EPE and over $20\%$ improvement in 3px-error. When applied to the strong base model IGEV-Stereo, our method still shows solid improvements over both EPE and 3px-error. The SceneFlow pre-trained full models of both base models are then finetuned on KITTI 2012 and KITTI 2015 datasets and results are shown in Tab. 5. Our method consistently outperforms the performance of baseline models. + +Impact on Occluded and Non-occluded Regions. We further conduct experiments on our method's impact on occluded pixels and non-occluded pixels separately. Tab. 6 + +shows that our method consistently improves disparity quality in both occluded regions and non-occluded regions. Furthermore, since occluded regions are areas without correspondence in the other figures, intuitively the prediction of disparities on such pixels relies more on intra-view geometric knowledge; on the contrary, predicting disparities at non-occluded pixels relies more on cross-view geometric knowledge [55]. Our experiment results are consistent with this intuition, validating our formulation of the process of extracting interest points as intra-view geometric knowledge and the process of extracting their correspondences as cross-view geometric knowledge. + +Complexity of intra-view decoder and cross-view decoder. We conduct experiments to evaluate the impact of the complexity of the intra-view decoder $D_{\mathrm{intra}}$ and cross-view decoder $D_{\mathrm{cross}}$ on the models' performance. We keep GwcNet as the base model and change the number of layers of the decoders. The number of layers of the intra-view decoder refers to the number of stacked bottleneck convolutional blocks, and the number of layers of the cross-view decoder refers to the number of alternating attention layers. For the cross-view decoder with zero layers, we are directly using cosine similarities between the interest point features plus a softmax layer to form an assignment matrix $\mathbf{P}'$ . Results on the SceneFlow dataset with GwcNet [17] as baseline are shown in Tab. 7. Results have shown that an + +
BaselineICGNetKITTI 2012KITTI 2015 (all pixels)KITTI 2015 (noc pixels)
2-noc↓2-all↓3-noc↓3-all↓D1-bg↓D1-fg↓D1-all↓D1-bg↓D1-fg↓D1-all↓
GwcNet [17]✓2.162.711.321.701.743.932.111.613.491.92
1.982.541.251.631.623.902.001.503.561.84
IGEV-Stereo [55]✓1.712.171.121.441.382.671.591.272.621.49
1.702.141.101.411.382.551.571.262.561.47
+ +![](images/5efce1c2a8a69da46e8d6167dbcffb896dbfd81f74c89d133ea7910179135948.jpg) + +![](images/4d4374ca6d3af06b41e8d7445d6815ad8991a9aec22d635a1b688a8998f153e7.jpg) + +![](images/5f6f606c98c7eba6f8a0ce7742dc79aa14fd3b9d8eeea1d6583d68a945b62e86.jpg) +Left Image + +![](images/ac2a3a8eaa7c2213989ce270c16bfe736e102714bbe25584bfd465f61842d1db.jpg) + +![](images/dad635d27cd1538e1a9a23846b94cae000ff1ebfa28532fa6501ed3b388016e1.jpg) + +![](images/9b8c5a17008d67a4a3700f83928d43c7a273c6f9f2c4d04b29dffacbf771afd1.jpg) +Disparity Labels +Figure 4. Qualitative results of cross-domain generalization of ICGNet (ours) compared with state-of-the-art baseline IGEV-Stereo [55]. + +![](images/23f438ec92a8be8f5e7b575ba79e2fb512f20dfa2f510e69f5b0af0c05b5e1bd.jpg) + +![](images/936d28b859e674aa7a8031f1a11350a505d31955ca3b11a7dce476d91fea56e1.jpg) + +![](images/ffd5c2f360d0506468d2e8d61ca21ef5d88e54a47d7c635afc6b7a1b183fdf6b.jpg) +IGEV-Stereo + +![](images/0b1c3b86dc7f3ca7cd8b81b55686a6ac8e9c055868735fd7c4eed02cfbaa5d5e.jpg) + +![](images/690a22fc978c60d920640c295939a3764e9466d7901c0589b8e27056bcf3d84e.jpg) + +![](images/cf621a204ad2874f573ee6203c36573ab97261fbad9d28cdb6551251358b2760.jpg) +ICGNet (ours) + +Table 5. Ablation studies on KITTI 2012 and KITTI 2015 benchmarks. + +
Intra-view +L_intraCross-view +L CROSS-soft + L cross-hardSceneFlow EPE
noc(px)↓occ(px)↓Δnoc/Δocc
0.4132.58/
✓0.3342.086.33
✓✓0.3182.023.75
+ +Table 6. Ablation studies on occluded and non-occluded areas on the SceneFlow dataset using GwcNet baseline model. Our method improves disparity prediction accuracy in both occluded areas and non-occluded areas. Compared with cross-view geometric knowledge, intra-view geometric knowledge improves more in occluded regions, consistent with the intuition that occluded areas rely on their surrounding geometric relations to infer their disparities. + +
DecoderLayersSceneFlow
EPE(px)↓>3px↓
intra-view10.6312.74
20.6152.61
40.6232.68
cross-view00.6172.61
40.5972.55
60.6062.58
+ +Table 7. Comparison of performance of different decoder complexities. + +intermediate number of decoder layers for both intra-view and cross-view decoder yields the best results. This may be due to a too-complex decoder will take up too much of the task of learning the geometric knowledge, making the feature backbone not learn sufficient knowledge, while a too-simple decoder is not sufficient to map the features into the geometric structures, leaving too much for the feature backbone and make it sub-optimal in disparity prediction task. + +# 5. Conclusion + +In this work, we introduce ICGNet, a novel approach designed to infuse stereo matching networks with both intraview and cross-view geometric knowledge. Utilizing interest points and their corresponding matches derived from local feature matching models, we provide rich sources of geometric knowledge to educate the stereo matching network. 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However, prior attempts to integrate geometric insights into stereo matching algorithms have largely focused on geometric knowledge from single images while crucial cross-view factors such as occlusion and matching uniqueness have been overlooked. To address this gap, we propose a novel Intra-view and Cross-view Geometric knowledge learning Network (ICGNet), specifically crafted to assimilate both intra-view and cross-view geometric knowledge. ICGNet harnesses the power of interest points to serve as a channel for intra-view geometric understanding. Simultaneously, it employs the correspondences among these points to capture cross-view geometric relationships. This dual incorporation empowers the proposed ICGNet to leverage both intra-view and cross-view geometric knowledge in its learning process, substantially improving its ability to estimate disparities. Our extensive experiments demonstrate the superiority of the ICGNet over contemporary leading models. 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With the rapid development of deep learning techniques and network structures in computer vision scenarios, deep stereo matching networks have achieved great success in stereo matching." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 647, + 287, + 683 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 647, + 287, + 683 + ], + "spans": [ + { + "bbox": [ + 46, + 647, + 287, + 683 + ], + "type": "text", + "content": "Geometric knowledge plays a crucial role in the overall performance of stereo matching networks [21, 45, 55, 69] due to the existence of repeated patterns, textureless ar" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 313, + 239, + 541, + 329 + ], + "blocks": [ + { + "bbox": [ + 313, + 239, + 541, + 329 + ], + "lines": [ + { + "bbox": [ + 313, + 239, + 541, + 329 + ], + "spans": [ + { + "bbox": [ + 313, + 239, + 541, + 329 + ], + "type": "image", + "image_path": "e4322bd310dd5ac8e01bf179132a8e43fb4227ec535028a88a0f20b4b1d7811f.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 337, + 545, + 404 + ], + "lines": [ + { + "bbox": [ + 304, + 337, + 545, + 404 + ], + "spans": [ + { + "bbox": [ + 304, + 337, + 545, + 404 + ], + "type": "text", + "content": "Figure 1. An illustration of our overall framework using synthetic shapes. We leverage intra-view geometric knowledge which is the knowledge of extracting geometric structures, and cross-view geometric knowledge which is the knowledge of the correspondences of these structures, to aid the stereo matching task. Note that the dotted lines are used for illustration and are not used in the method." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 426, + 545, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 545, + 569 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 545, + 569 + ], + "type": "text", + "content": "eas, and reflective surfaces, which make simple texture-based matching methods ineffective. Consequently, several methods were proposed to introduce geometric knowledge into stereo matching networks through kinds of geometric structures. EdgeStereo [45] proposed a learning network that incorporates edges and edge-disparity relations into the stereo matching network. Normal assisted stereo matching [21, 69] leverages surface normal as geometric constraints to reduce the matching ambiguity for textureless regions. However, the geometric knowledge employed in these studies is mainly intra-view, lacking the cross-view geometric knowledge such as matching uniqueness and occlusion." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 570, + 546, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 546, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 546, + 714 + ], + "type": "text", + "content": "To address the absence of cross-view geometric knowledge, we have identified that the local feature matching task [12, 34, 40] can serve as a suitable source of cross-view geometric knowledge for stereo matching. Local feature matching involves the identification of correspondences between two images, typically achieved by initially detecting sparse, geometrically meaningful interest points within each view and then extracting descriptors for these interest points encoded with their visual attributes [12]. Subsequently, cross-view matching is carried out by comparing the interest points between the two images [40]. This matching process solves a partial assignment problem be" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 57, + 693, + 251, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 693, + 251, + 703 + ], + "spans": [ + { + "bbox": [ + 57, + 693, + 251, + 703 + ], + "type": "text", + "content": "*The work was done during an internship at I²R, A*STAR." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 60, + 703, + 154, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 60, + 703, + 154, + 713 + ], + "spans": [ + { + "bbox": [ + 60, + 703, + 154, + 713 + ], + "type": "inline_equation", + "content": "\\dagger" + }, + { + "bbox": [ + 60, + 703, + 154, + 713 + ], + "type": "text", + "content": " cheng-jun@i2r.a-star.edu.sg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20752" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 359 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 359 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 359 + ], + "type": "text", + "content": "tween the points which takes matching uniqueness and occlusion into account. Moreover, we also find that the interest points from each image also provide intra-view knowledge of the image. Building upon these insights, we introduce our ICGNet framework to take both the intra-view and cross-view geometric knowledge contained in local feature matching models into the stereo matching network. We leverage a pre-trained local feature matching pipeline, comprising an interest point detector and a point matcher. We propose an intra-view constraint that the features we extract from stereo matching backbone preserve the same interest point information as the pre-trained interest point detector to gain intra-view geometric knowledge. Additionally, we propose a cross-view constraint that these features are compelled to serve as descriptors for the interest points, facilitating the matching process between these points. The matching outcome is then constrained to align with both the ground-truth matching labels provided by ground-truth disparity maps and the matching results obtained from the pretrained interest point matcher, in order to gain cross-view geometric knowledge. Compared to EdgeStereo [45] and normal assisted stereo matching [21, 69], our method not only additionally introduces cross-view geometric knowledge but also keeps zero overhead when inference." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 360, + 288, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 360, + 288, + 396 + ], + "spans": [ + { + "bbox": [ + 47, + 360, + 288, + 396 + ], + "type": "text", + "content": "Our experiments show that our method effectively improves the performance across both the seen and unseen domains. The contributions are summarized as follows:" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 397, + 288, + 635 + ], + "type": "list", + "angle": 0, + "index": 5, + "blocks": [ + { + "bbox": [ + 47, + 397, + 287, + 444 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 397, + 287, + 444 + ], + "spans": [ + { + "bbox": [ + 47, + 397, + 287, + 444 + ], + "type": "text", + "content": "1. We propose to learn intra-view geometric knowledge for stereo matching networks from an interest point detector by introducing a novel intra-view geometric constraint computed from the interest point detection outcomes." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 445, + 287, + 516 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 445, + 287, + 516 + ], + "spans": [ + { + "bbox": [ + 47, + 445, + 287, + 516 + ], + "type": "text", + "content": "2. We propose to learn cross-view geometric knowledge for stereo matching networks from an interest point matcher by introducing a novel cross-view geometric constraint. We compute both soft cross-view and hard cross-view geometric losses using pretrained interest point matcher and disparity ground truth." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 517, + 288, + 635 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 517, + 288, + 635 + ], + "spans": [ + { + "bbox": [ + 47, + 517, + 288, + 635 + ], + "type": "text", + "content": "3. We conduct a series of comprehensive experiments that consistently demonstrate the proposed framework's ability to enhance the overall performance of state-of-the-art stereo matching networks. Our ICGNet achieves state-of-the-art performance on the SceneFlow dataset and ranks " + }, + { + "bbox": [ + 47, + 517, + 288, + 635 + ], + "type": "inline_equation", + "content": "1^{st}" + }, + { + "bbox": [ + 47, + 517, + 288, + 635 + ], + "type": "text", + "content": " on the KITTI 2015 stereo matching benchmark among published peer-reviewed methods at the time of submission, and improves cross-domain generalization of baseline methods on KITTI 2012, KITTI 2015, and Middlebury 2014 datasets." + } + ] + } + ], + "index": 4 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 649, + 139, + 662 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 649, + 139, + 662 + ], + "spans": [ + { + "bbox": [ + 47, + 649, + 139, + 662 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 670, + 174, + 683 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 174, + 683 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 174, + 683 + ], + "type": "text", + "content": "2.1. Deep Stereo Matching" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "Deep-learning-based deep stereo matching techniques have gained widespread adoption and demonstrated promis" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 547, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 467 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 467 + ], + "type": "text", + "content": "ing outcomes [7, 9, 16, 24, 25, 28, 37, 52, 53, 57, 58, 61]. The initial instance of such an approach is DispNetC [35], which presents an end-to-end trainable stereo matching framework. This framework employs the dot product of feature maps from left and right images as correspondence to build a cost volume of three dimensions. However, the drawback of this computational-friendly methodology is its inability to capture sufficient information to achieve satisfactory results. In the pursuit of improved performance, subsequent methods like GC-Net [20] have emerged. Numerous works [3, 65] have followed this trend and incorporated 3D hourglass convolutions to aggregate a 4D cost volume. This volume is created by concatenating features from left and right images. Unfortunately, this approach demands substantial memory usage and computational complexity. A notable enhancement arrives with GwcNet [17], which introduces the concept of group-wise correlation. This innovation enables the construction of a more compact cost volume. Recently, iterative optimization-based methods [23, 27, 63] have achieved splendid performance. Inspired by RAFT [48], RAFT-Stereo [27] iteratively updates the disparity using all-pairs correlation between features extracted. IGEV-Stereo [55] further boosts the performance of stereo matching network by combining cost-volume modules with iterative updating modules. Uncertainty-based methods [8, 51] also gained attention these years. ELFNet [33] leverage uncertainty to fuse multi-scale disparity and stereo network with different structures. SEDNet [6] proposes a soft-histogramming technique to align the distribution of prediction error and prediction uncertainty. Other works focus on improving the domain generalization performance [4, 11, 29, 38, 68] and domain adaptation performance [31, 46, 64, 66] of stereo matching networks." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 468, + 547, + 600 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 468, + 547, + 600 + ], + "spans": [ + { + "bbox": [ + 304, + 468, + 547, + 600 + ], + "type": "text", + "content": "Recognizing the need for increased efficiency and the integration of richer semantic information, multi-scale cost volume is used in stereo matching networks. HSMNet [59] employs a pyramid of volumes to enable high-resolution stereo matching. AANet [56] takes a lightweight approach, incorporating a feature pyramid and interactions with multi-scale correlation volumes. In a recent development, PCWNet [43] introduces a volume fusion module that directly combines multi-scale 4D volumes. This innovation calculates a multi-level loss, ultimately expediting the model's convergence speed." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 610, + 543, + 623 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 610, + 543, + 623 + ], + "spans": [ + { + "bbox": [ + 306, + 610, + 543, + 623 + ], + "type": "text", + "content": "2.2. Geometric Structure Guided Stereo Matching" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 630, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 547, + 713 + ], + "type": "text", + "content": "Geometric structures have been used to guide stereo matching networks in previous works. EdgeStereo [45] introduced an edge branch, integrating edge features into the stereo matching branch. Yang et al. [60] also advocated the use of edges for supervising stereo matching through multitask learning. Additionally, surface normals have been another employed geometric structure to guide stereo match" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20753" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 156 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 156 + ], + "type": "text", + "content": "ing. Zhang et al. [69] suggested a joint prediction of a surface normal map and a raw disparity map, iteratively refining the disparity map with guidance from the surface normal map. Kusupati et al. [21] incorporated an extra surface normal branch to predict raw surface normals and employed an independently trained consistency module for refinement of both surface normals and raw disparities." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 157, + 287, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 157, + 287, + 289 + ], + "spans": [ + { + "bbox": [ + 46, + 157, + 287, + 289 + ], + "type": "text", + "content": "However, these approaches have two limitations. Firstly, they heavily depend on additional branches during inference to improve their performance, which impacts efficiency. In contrast, our proposed framework leverages geometric structures as constraints during training without incurring any overhead in inference, and shows improved performance. Secondly, the previous methods only made use of intra-view geometric structures, whereas our framework takes into account both intra-view and cross-view geometric knowledge through both geometric structure and their correspondences." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 298, + 183, + 312 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 298, + 183, + 312 + ], + "spans": [ + { + "bbox": [ + 47, + 298, + 183, + 312 + ], + "type": "text", + "content": "2.3. Local Feature Matching" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 317, + 287, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 317, + 287, + 376 + ], + "spans": [ + { + "bbox": [ + 46, + 317, + 287, + 376 + ], + "type": "text", + "content": "Local feature matching aims at matching images that depict the same scene or object. This is usually done in a two-stage manner: first, detect interest points each associated with a visual descriptor from both images, and then match the detected interest points." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 378, + 287, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 378, + 287, + 556 + ], + "spans": [ + { + "bbox": [ + 46, + 378, + 287, + 556 + ], + "type": "text", + "content": "Traditional interest points detection and description algorithms [1, 19, 34, 39] rely on hand-crafted features. Recent research turns to Convolutional Neural Networks (CNN) for both interest point detection and description [22, 30, 32, 49]. SuperPoint [12] is a representative work of CNN-based interest point detector and descriptor, trained in a self-supervised manner. It constructs a synthetic shape dataset by rendering simplified 2D geometries, such as triangles, quadrilaterals, lines, and ellipses. The junctions of lines are labeled as interest points. These labels are then transferred to substantial real-world image datasets using a MagicPoint model and homographic adaptation. The self-supervised training process equips SuperPoint with the ability to be trained on various domains, enabling it to encode geometric information across diverse domains." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 558, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 558, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 558, + 288, + 714 + ], + "type": "text", + "content": "Traditional algorithms employ nearest-neighbor classifiers for matching interest points. Lowe's test [34], inlier classifiers [62, 67], or geometric model fitting [2, 13] techniques are subsequently used to filter out unmatched points and incorrect correspondences. However, these methods are highly domain-specific and struggle to handle particularly challenging conditions. In contrast, deep learning-based matchers are trained to simultaneously match interest points and reject outliers. A notable example of this approach is SuperGlue [40], which leverages Transformers [50] to conduct self-attention among interest points within the same view and cross-attention between interest points in different views. The final matching step involves solving an op" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "content": "timal transport problem. This approach allows SuperGlue to acquire robust insights into scene geometry and camera motion, rendering it resilient to extreme changes and effective in generalizing across various data domains. Subsequent works [5, 26, 44] focused on making it more efficient and digging into its design details while keeping its strong matching capability. Consequently, these matchers are great sources of cross-view geometric knowledge. We set up constraints to let the stereo matching network learn geometric knowledge from a pre-trained interest point detector and a pre-trained interest point matcher." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 213, + 362, + 227 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 213, + 362, + 227 + ], + "spans": [ + { + "bbox": [ + 306, + 213, + 362, + 227 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "spans": [ + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "text", + "content": "We propose ICGNet to introduce geometric knowledge into stereo matching networks through geometric constraints. Intra-view geometric knowledge refers to the understanding that uncovers the geometric structures contained within a single image. Cross-view geometric knowledge refers to the comprehension that enables the alignment of geometric structures from one image to another. Models capable of uncovering and matching geometric structures harness the potential to convey intra-view and cross-view knowledge. Therefore, as depicted in Fig. 2, our framework introduces intra-view and cross-view geometric knowledge into the stereo matching network by aligning our network with intra-view and cross-view geometric knowledge sources. Although there are multiple choices (e.g., edges, points) to extract intra-view knowledge, we choose interest points as it is easy to further compute cross-view knowledge from these points using well-established methods [40] while it is more challenging to match the edges for cross-view knowledge computation. We denote the left-view stereo image as " + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "inline_equation", + "content": "I_{l}" + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "text", + "content": " and right-view stereo image as " + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "inline_equation", + "content": "I_{r}" + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "text", + "content": ", and the extracted left feature and right feature as " + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "inline_equation", + "content": "F_{l}" + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "inline_equation", + "content": "F_{r}" + }, + { + "bbox": [ + 304, + 234, + 547, + 486 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 491, + 486, + 506 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 491, + 486, + 506 + ], + "spans": [ + { + "bbox": [ + 306, + 491, + 486, + 506 + ], + "type": "text", + "content": "3.1. Intra-view Geometric Knowledge" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": "Intra-view Geometric Knowledge Decoder is to introduce intra-view geometric knowledge into the stereo matching network. We propose to leverage a pre-trained interest point detector " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{IP}_{\\mathrm{det}}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " [12] in our method. It takes the left-view image " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "I_{l}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " and the right-view image " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "I_{r}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " as input and generates interest maps " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_l" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_r" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": ", where each pixel is either labeled as interest point or non-interest point. These maps convey the intra-view geometric characteristics of the two images. We expect that the backbone features " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "F_{l}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "F_{r}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " preserve and unveil the intra-view geometric details present in both the left and right view images, akin to what the pretrained interest point detector accomplishes. Consequently, we aim to extract two interest point maps, " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_l^{\\prime}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_r^{\\prime}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": ", from " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "F_{l}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "F_{r}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " using a trainable intra-view decoder " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{intra}}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": ", aligning with " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_l" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_r" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " respectively. For the design of " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{intra}}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": ", we use a stack of two bottleneck convolutional blocks. Note that decoder " + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{intra}}" + }, + { + "bbox": [ + 304, + 510, + 547, + 715 + ], + "type": "text", + "content": " is discarded during the test stage." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20754" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 61, + 69, + 534, + 309 + ], + "blocks": [ + { + "bbox": [ + 61, + 69, + 534, + 309 + ], + "lines": [ + { + "bbox": [ + 61, + 69, + 534, + 309 + ], + "spans": [ + { + "bbox": [ + 61, + 69, + 534, + 309 + ], + "type": "image", + "image_path": "c525551cd5238e96fc656ac5c96421dc22f5a0f75d144a35232d007023aa2769.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "lines": [ + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "spans": [ + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": "Figure 2. Overall structure of our proposed framework. The model architecture comprises three parts: stereo matching network, cross-view knowledge learning network, and intra-view knowledge learning network. The cross-view knowledge learning network introduces cross-view geometric knowledge by aligning the interest point correspondences " + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "inline_equation", + "content": "\\mathbf{P}'" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "inline_equation", + "content": "\\mathcal{P}^{gt}" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": " using " + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - hard}}" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - soft}}" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": ". The intra-view knowledge learning network introduces intra-view geometric knowledge through aligning the interest point maps " + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "inline_equation", + "content": "\\mathbf{M}'" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "inline_equation", + "content": "\\mathbf{M}" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": " using " + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{intra}}" + }, + { + "bbox": [ + 46, + 316, + 547, + 373 + ], + "type": "text", + "content": ". Note that the dotted lines are used just for clear illustration and are not used in our work." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 392, + 288, + 417 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 392, + 288, + 417 + ], + "spans": [ + { + "bbox": [ + 47, + 392, + 288, + 417 + ], + "type": "text", + "content": "Intra-view geometric loss " + }, + { + "bbox": [ + 47, + 392, + 288, + 417 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{intra}}" + }, + { + "bbox": [ + 47, + 392, + 288, + 417 + ], + "type": "text", + "content": " is computed to enforce this alignment:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 85, + 427, + 287, + 452 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 85, + 427, + 287, + 452 + ], + "spans": [ + { + "bbox": [ + 85, + 427, + 287, + 452 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {i n t r a}} = \\frac {1}{2} \\mathcal {L} \\left(\\mathbf {M} _ {l} ^ {\\prime}, \\mathbf {M} _ {l}\\right) + \\frac {1}{2} \\mathcal {L} \\left(\\mathbf {M} _ {r} ^ {\\prime}, \\mathbf {M} _ {r}\\right), \\tag {1}", + "image_path": "e7d2169c40aa094f0d59c33f489d1237b44d23124bf68d26300e2a97ce5d4f35.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 456, + 287, + 481 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 456, + 287, + 481 + ], + "spans": [ + { + "bbox": [ + 47, + 456, + 287, + 481 + ], + "type": "text", + "content": "where we compute a focal loss " + }, + { + "bbox": [ + 47, + 456, + 287, + 481 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 47, + 456, + 287, + 481 + ], + "type": "text", + "content": " due to unbalanced positive and negative samples of interest points." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 491, + 230, + 503 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 491, + 230, + 503 + ], + "spans": [ + { + "bbox": [ + 47, + 491, + 230, + 503 + ], + "type": "text", + "content": "3.2. Cross-view Geometric Knowledge" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 510, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 287, + 593 + ], + "type": "text", + "content": "Cross-view Geometric Knowledge Decoder enables the stereo matching network to acquire cross-view geometric knowledge by framing it as a learning task. This task is to align the stereo matching network with two complementary knowledge sources: a pre-trained interest point matcher denoted as " + }, + { + "bbox": [ + 46, + 510, + 287, + 593 + ], + "type": "inline_equation", + "content": "\\mathcal{IP}_{\\mathrm{match}}" + }, + { + "bbox": [ + 46, + 510, + 287, + 593 + ], + "type": "text", + "content": " where we use [40] in our method, and the ground truth matching between interest points." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": "The pre-trained matcher processes two sets of interest points extracted from stereo image pair " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "I_{l}" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "I_{r}" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": ", denoted as " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "p_l" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "p_r" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": ", each containing " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " points respectively, along with their associated descriptors. It outputs an assignment matrix " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{P} \\in [0,1]^{(m + 1)\\times (n + 1)}" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": ". This matrix includes an extra row and column to account for the possibility that some points do not match any counterpart in the other view. The assignment matrix " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " elucidates the cross-view geometric knowledge via the relations between the matching probabilities of the two sets of points." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "spans": [ + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "text", + "content": "Furthermore, the ground truth disparities can serve as another source of knowledge since it provide accurate matching between these points. Ground truth matching pairs between the points " + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "inline_equation", + "content": "\\mathcal{P}^{gt} = \\{(i,j)\\} \\subset p_l \\times p_r" + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "text", + "content": " refers to Cartesian product) and unmatched points in left image " + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "inline_equation", + "content": "\\mathcal{U}_l^{gt} \\subseteq p_l" + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "text", + "content": " and right image " + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "inline_equation", + "content": "\\mathcal{U}_r^{gt} \\subseteq p_r" + }, + { + "bbox": [ + 304, + 392, + 545, + 489 + ], + "type": "text", + "content": " are formed by warping interest points from the left image to the right image using the disparity." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 493, + 546, + 624 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 493, + 546, + 624 + ], + "spans": [ + { + "bbox": [ + 304, + 493, + 546, + 624 + ], + "type": "text", + "content": "The ground truth is more precise compared to the assignment matrix provided by the interest point matcher. In the ground truth, the relationships between points are binary, classified simply as either a match or a mismatch. On the other hand, the assignment matrix presents matching scores as continuous values ranging from 0 to 1, implicitly indicating the degree of similarity between the points. This makes the two approaches complementary: one provides precise matching categorization, which is 'harder', while the other offers a fine-grained assessment of similarity, which is 'softer'." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": "To align the stereo matching network with these two sources of cross-view geometric knowledge, a trainable cross-view decoder denoted as " + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cross}}" + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": " is proposed. " + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cross}}" + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": " first use as an Multilayer Perceptron (MLP) encoder [14, 50] followed by four alternative self-attention and cross-attention layers [50]. The self attention layers operate on points within the same image, while the cross-attention" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20755" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": "layer operate on points within different images. The decoder is responsible for decoding an assignment matrix " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{P}'" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": ". This decoded matrix is trained to closely match its corresponding reference assignment matrix " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " created by a pretrained interest point matcher " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "\\mathcal{IP}_{\\mathrm{match}}" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " and the ground truth matching pairs " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "\\mathcal{P}^{gt}" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " and unmatched points " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "\\mathcal{U}_l^{gt}" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "\\mathcal{U}_r^{gt}" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " from left and right images respectively, serving as the supervision pseudo ground truth during training. The points input " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "p_l" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "p_r" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " to the decoder " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cross}}" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " are identical to the input to " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "\\mathcal{IP}_{\\mathrm{match}}" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": ", but with different descriptors bi-linearly sampled from features " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "F_l" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "F_r" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " extracted by stereo backbone such that the gradient can flow back to the stereo network. Note that decoder " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cross}}" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " is discarded during the test stage." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "spans": [ + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "type": "text", + "content": "Soft cross-view geometric loss " + }, + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - soft}}" + }, + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "type": "text", + "content": " is proposed to introduce the cross-view geometric knowledge from the reference assignment matrix " + }, + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "type": "text", + "content": " into the predicted assignment matrix " + }, + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "type": "inline_equation", + "content": "\\mathbf{P}'" + }, + { + "bbox": [ + 47, + 228, + 289, + 276 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 60, + 297, + 287, + 372 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 60, + 297, + 287, + 372 + ], + "spans": [ + { + "bbox": [ + 60, + 297, + 287, + 372 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {\\text {c r o s s - s o f t}} = \\frac {1}{m} \\sum_ {i = 1} ^ {m} \\mathcal {K L} \\left(\\mathbf {P} _ {i, \\cdot} / | | \\mathbf {P} _ {i, \\cdot} | | _ {1}, \\mathbf {P} _ {i, \\cdot} ^ {\\prime} / | | \\mathbf {P} _ {i, \\cdot} ^ {\\prime} | | _ {1}\\right) \\\\ + \\frac {1}{n} \\sum_ {j = 1} ^ {n} \\mathcal {K L} \\left(\\mathbf {P} _ {\\cdot , j} / \\left\\| \\mathbf {P} _ {\\cdot , j} \\right\\| _ {1}, \\mathbf {P} _ {\\cdot , j} ^ {\\prime} / \\left\\| \\mathbf {P} _ {\\cdot , j} ^ {\\prime} \\right\\| _ {1}\\right), \\tag {2} \\\\ \\end{array}", + "image_path": "6d0b554f975cd4137a7c1033e0c51b8b44dc9908702ecc1bdcd99533ca6d16b3.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "spans": [ + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "\\mathcal{KL}" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": " stands for KL-divergence, and " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_{i,\\cdot}" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": " stands for the " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "i^{th}" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": " row of " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_{\\cdot,j}" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": " stands for the " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "j^{th}" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": " column of " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": ". In this work, we use the interest points filtered from interest point maps " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_l" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_r" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": " extracted by pre-trained interest point detector [12] by non maximum suppression as " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "p_l" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "inline_equation", + "content": "p_r" + }, + { + "bbox": [ + 46, + 382, + 287, + 442 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "spans": [ + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "text", + "content": "Hard cross-view geometric loss is further computed based on the ground truth matching between interest points " + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "inline_equation", + "content": "\\mathcal{P}^{gt}" + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "text", + "content": ", unmatched points in the left image " + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "inline_equation", + "content": "\\mathcal{U}_l^{gt}" + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "text", + "content": ", and unmatched points in the right image " + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "inline_equation", + "content": "\\mathcal{U}_r^{gt}" + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "text", + "content": ". Hard cross-view geometric loss is utilized as a negative log-likelihood loss balanced between matched points and unmatched points to align " + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "inline_equation", + "content": "\\mathbf{P}'" + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "inline_equation", + "content": "\\mathcal{P}^{gt}, \\mathcal{U}_l^{gt}, \\mathcal{U}_r^{gt}" + }, + { + "bbox": [ + 46, + 443, + 289, + 527 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 92, + 545, + 287, + 637 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 92, + 545, + 287, + 637 + ], + "spans": [ + { + "bbox": [ + 92, + 545, + 287, + 637 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {\\text {c r o s s - h a r d}} = - \\frac {1}{| \\mathcal {P} ^ {g t} |} \\sum_ {(i, j) \\in \\mathcal {P} ^ {g t}} \\log \\mathbf {P} _ {i, j} ^ {\\prime} \\\\ - \\frac {1}{\\left| \\mathcal {U} _ {l} ^ {g t} \\right|} \\sum_ {i \\in \\mathcal {U} _ {l}} \\log \\mathbf {P} _ {i, n + 1} ^ {\\prime} \\tag {3} \\\\ - \\frac {1}{\\left| \\mathcal {U} _ {r} ^ {g t} \\right|} \\sum_ {j \\in \\mathcal {U} _ {r}} \\log \\mathbf {P} _ {m + 1, j} ^ {\\prime}. \\\\ \\end{array}", + "image_path": "16b8e8b8c1aad216d730734d481da17158ee798021d97179fe0d091c0c28c55b.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 647, + 91, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 647, + 91, + 658 + ], + "spans": [ + { + "bbox": [ + 47, + 647, + 91, + 658 + ], + "type": "text", + "content": "3.3. Loss" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "content": "We integrate our proposed " + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{intra}}" + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - soft}}" + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - hard}}" + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "content": " with disparity loss " + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "inline_equation", + "content": "L_{\\mathrm{disp}}" + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "content": ", enabling simultaneously estimating disparity and learning intra-view and cross-view geometric structure knowledge from local feature matching" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 72, + 545, + 107 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 545, + 107 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 545, + 107 + ], + "type": "text", + "content": "models. The disparity loss, " + }, + { + "bbox": [ + 305, + 72, + 545, + 107 + ], + "type": "inline_equation", + "content": "L_{\\mathrm{disp}}" + }, + { + "bbox": [ + 305, + 72, + 545, + 107 + ], + "type": "text", + "content": ", is determined by the loss function utilized by the base models. The total loss is defined as:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 321, + 114, + 545, + 139 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 321, + 114, + 545, + 139 + ], + "spans": [ + { + "bbox": [ + 321, + 114, + 545, + 139 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {\\text {t o t a l}} = \\mathcal {L} _ {\\text {d i s p}} + \\lambda_ {\\text {i n t r a}} \\cdot \\mathcal {L} _ {\\text {i n t r a}} + \\lambda_ {\\text {c r o s s - s o f t}} \\cdot \\mathcal {L} _ {\\text {c r o s s - s o f t}} \\tag {4} \\\\ + \\lambda_ {\\text {c r o s s - h a r d}} \\cdot \\mathcal {L} _ {\\text {c r o s s - h a r d}}, \\\\ \\end{array}", + "image_path": "989a4fdb1f1cf8ab6d2b89e5f643cf1d6b5240c78cfdafe44f6ee679326867b2.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "spans": [ + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{intra}}" + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - soft}}" + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - hard}}" + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "text", + "content": " are weighting terms. The loss weights are empirically set as " + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{intra}} = 100" + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - soft}} = 0.5" + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - hard}} = 0.5" + }, + { + "bbox": [ + 305, + 145, + 547, + 193 + ], + "type": "text", + "content": " such that they are comparable and none of the items would dominate the results." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 202, + 388, + 216 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 202, + 388, + 216 + ], + "spans": [ + { + "bbox": [ + 306, + 202, + 388, + 216 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 222, + 545, + 281 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 222, + 545, + 281 + ], + "spans": [ + { + "bbox": [ + 305, + 222, + 545, + 281 + ], + "type": "text", + "content": "SceneFlow dataset [35] constitutes a synthetic dataset featuring diverse random objects. It contains 35,454 training pairs and 4,370 test pairs with dense disparity labels. Finalpass of the SceneFlow dataset that contains motion blur and defocuses is used." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 282, + 545, + 377 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 282, + 545, + 377 + ], + "spans": [ + { + "bbox": [ + 305, + 282, + 545, + 377 + ], + "type": "text", + "content": "KITTI 2012 [15] & KITTI 2015 [36] datasets consist of stereo image pairs of real-world driving scenarios. KITTI 2012 contains 194 training and 195 testing image pairs. KITTI 2015 comprises 200 training and 200 testing image pairs. The stereo pairs in both KITTI 2012 and KITTI 2015 possess resolutions of " + }, + { + "bbox": [ + 305, + 282, + 545, + 377 + ], + "type": "inline_equation", + "content": "1226 \\times 370" + }, + { + "bbox": [ + 305, + 282, + 545, + 377 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 282, + 545, + 377 + ], + "type": "inline_equation", + "content": "1242 \\times 375" + }, + { + "bbox": [ + 305, + 282, + 545, + 377 + ], + "type": "text", + "content": ", respectively. Notably, both datasets furnish sparse disparity maps as part of their annotations." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 378, + 545, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 378, + 545, + 437 + ], + "spans": [ + { + "bbox": [ + 305, + 378, + 545, + 437 + ], + "type": "text", + "content": "Middlebury 2014 [41] is an stereo dataset consisted of indoor stereo images. It comprises 15 training and 15 testing pairs. All the images are available in three different resolutions. We use the Middlebury 2014 dataset with half resolution to test cross-domain generalization performance." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "type": "text", + "content": "Evaluation metrics. We use end point error (EPE), the percentage of errors larger than 3px (" + }, + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "type": "inline_equation", + "content": ">3\\mathrm{px}" + }, + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "type": "text", + "content": ") on the Scene-Flow dataset, and use EPE and D1-3px on KITTI datasets as evaluation metrics for disparity prediction. D1-3px refers to the percentage of disparity estimations with both absolute larger than 3px and relative error greater than " + }, + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "type": "inline_equation", + "content": "5\\%" + }, + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "type": "text", + "content": ". We use EPE and the percentage of errors larger than 2px (" + }, + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "type": "inline_equation", + "content": ">2\\mathrm{px}" + }, + { + "bbox": [ + 305, + 438, + 545, + 533 + ], + "type": "text", + "content": ") on Middlebury 2014 dataset." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 540, + 440, + 552 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 540, + 440, + 552 + ], + "spans": [ + { + "bbox": [ + 306, + 540, + 440, + 552 + ], + "type": "text", + "content": "4.1. Implementation Details" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 558, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 558, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 558, + 545, + 713 + ], + "type": "text", + "content": "Our ICGNet is inherently compatible with most stereo matching models since we do not change the structure of the network during inference. Specifically, our framework's compatibility expands to encompass all stereo matching models incorporating a common feature extractor and a disparity decoder. We experiment with our ICGNet on different baseline models GwcNet [17] and IGEV-Stereo [55]. We train the models end-to-end for all experiments. We pre-train the models on the SceneFlow training set. For the evaluation of cross-domain generalization, we directly test the sceneflow pre-trained models' performance on the KITTI 2012 training set, KITTI 2015 training set, and Middlebury 2014 training set. For evaluation of KITTI 2012" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20756" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 76, + 71, + 518, + 101 + ], + "blocks": [ + { + "bbox": [ + 76, + 71, + 518, + 101 + ], + "lines": [ + { + "bbox": [ + 76, + 71, + 518, + 101 + ], + "spans": [ + { + "bbox": [ + 76, + 71, + 518, + 101 + ], + "type": "table", + "html": "
MethodPSMNet [3]GANet [65]ACVNet [54]DLNR [71]GwcNet [17]IGEV-Stereo [55]Ours
EPE(px)↓1.090.840.480.480.7650.4790.447
", + "image_path": "6c1a9f9c8733ac282d101b1766957cc286c59d048d73832554f77b7f68d2c0a5.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 70, + 131, + 525, + 285 + ], + "blocks": [ + { + "bbox": [ + 47, + 109, + 545, + 120 + ], + "lines": [ + { + "bbox": [ + 47, + 109, + 545, + 120 + ], + "spans": [ + { + "bbox": [ + 47, + 109, + 545, + 120 + ], + "type": "text", + "content": "Table 1. Comparison with state-of-the-art models on the SceneFlow dataset. Our method outperforms most of the state-of-the-art methods." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 70, + 131, + 525, + 285 + ], + "lines": [ + { + "bbox": [ + 70, + 131, + 525, + 285 + ], + "spans": [ + { + "bbox": [ + 70, + 131, + 525, + 285 + ], + "type": "table", + "html": "
MethodKITTI 2012KITTI 2015 (all pixels)KITTI 2015 (noc pixels)
2-noc↓2-all↓3-noc↓3-all↓D1-bg↓D1-fg↓D1-all↓D1-bg↓D1-fg↓D1-all↓
EdgeStereo [45]2.322.881.461.831.843.302.081.692.941.89
LEAStereo [10]1.902.391.131.451.402.911.651.292.651.51
ACVNet [54]1.832.351.131.471.373.071.651.262.841.52
CREStereo [23]1.722.181.141.461.452.861.691.332.601.54
RAFT-Stereo [27]1.922.421.301.661.583.051.821.452.941.69
AcfNet [70]1.832.351.171.541.513.801.891.363.491.72
HITNet [47]2.002.651.411.891.743.201.981.542.721.74
GANet [65]1.892.501.191.601.483.461.811.343.111.63
GwcNet [17]2.162.711.321.701.743.932.111.613.491.92
IGEV-Stereo [55]1.712.171.121.441.382.671.591.272.621.49
Ours1.702.141.101.411.382.551.571.262.561.47
", + "image_path": "f917cd0704c7e4a642f62e5146f206a5d09ea55ccbe26cd00c12e4d1c57ebeed.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 293, + 546, + 316 + ], + "lines": [ + { + "bbox": [ + 46, + 293, + 546, + 316 + ], + "spans": [ + { + "bbox": [ + 46, + 293, + 546, + 316 + ], + "type": "text", + "content": "Table 2. Finetuning results on KITTI 2012 and KITTI 2015 benchmarks. Our ICGNet achieves state-of-the-art performance on both benchmarks and ranks " + }, + { + "bbox": [ + 46, + 293, + 546, + 316 + ], + "type": "inline_equation", + "content": "1^{st}" + }, + { + "bbox": [ + 46, + 293, + 546, + 316 + ], + "type": "text", + "content": " on the KITTI 2015 stereo matching benchmark at the time of submission." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 336, + 289, + 529 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 336, + 289, + 529 + ], + "spans": [ + { + "bbox": [ + 46, + 336, + 289, + 529 + ], + "type": "text", + "content": "and KITTI 2015 benchmarks, we finetune SceneFlow pretrained model on the mix of KITTI 2012 and KITTI 2015 training sets. For GwcNet, we use the GwcNet-g setting for KITTI 2015 pre-training and the GwcNet-gc setting for other experiments, consistent with the original work for a fair comparison. We train the model for 64 epochs on SceneFlow and 1000 epochs on KITTI. The initial learning rate is set to 0.001. The learning rate is decayed by a factor of 2 after epochs 20, 32, 40, 48, and 56 on SceneFlow, and decayed by a factor of 2 after epochs 200, 400, 600, 700, and 800 on KITTI. For IGEV-Stereo, we train the model for 80 epochs on SceneFlow and 1000 epochs on KITTI. The initial learning rate is set as 0.0002 and a one-cycle learning rate schedule is used. We maintain all other settings consistent with the original works for both models. All the codes in this paper would be released in Github." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 537, + 227, + 551 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 537, + 227, + 551 + ], + "spans": [ + { + "bbox": [ + 47, + 537, + 227, + 551 + ], + "type": "text", + "content": "4.2. Comparison with State-of-the-art" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 556, + 287, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 556, + 287, + 700 + ], + "spans": [ + { + "bbox": [ + 46, + 556, + 287, + 700 + ], + "type": "text", + "content": "To evaluate the effectiveness of our proposed method, we use the latest IGEV-Stereo [55] as the base model and integrate it with ICGNet to compare with state-of-the-art stereo mathing methods. Tab. 1 presents a comparison of our method with state-of-the-art on SceneFlow. Our proposed method achieved state-of-the-art performance on the SceneFlow dataset. We further finetune the SceneFlow pretrained model on KITTI12 [15] and KITTI15 [36] datasets, and compare the performance of ICGNet with state-of-the-art methods on KITTI 2012 and KITTI 2015 benchmarks. Results are shown in Tab. 2. Our ICGNet outperforms state-of-the-art methods in most scenarios." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 59, + 701, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 701, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 59, + 701, + 287, + 714 + ], + "type": "text", + "content": "Besides quantitative results, qualitative experiments are" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 336, + 547, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 336, + 547, + 397 + ], + "spans": [ + { + "bbox": [ + 304, + 336, + 547, + 397 + ], + "type": "text", + "content": "conducted to show the effectiveness of our proposed method. Fig. 3 visualizes the disparity predictions of our methods. Compared to the state-of-the-art method IGEV-Stereo, our method performs better in reflective regions and unlabelled backgrounds." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 404, + 468, + 417 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 404, + 468, + 417 + ], + "spans": [ + { + "bbox": [ + 305, + 404, + 468, + 417 + ], + "type": "text", + "content": "4.3. Cross-domain Generalization" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 423, + 547, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 423, + 547, + 556 + ], + "spans": [ + { + "bbox": [ + 304, + 423, + 547, + 556 + ], + "type": "text", + "content": "We carry out experiments to demonstrate that our approach enhances the domain-generalization capacity of base models, transitioning from the synthetic SceneFlow dataset to real-world datasets. As illustrated in Tab. 3, our proposed ICGNet method boosts the cross-domain generalization performance for IGEV-Stereo which is a strong baseline for cross-domain generalization. Our ICGNet outperforms IGEV-Stereo by " + }, + { + "bbox": [ + 304, + 423, + 547, + 556 + ], + "type": "inline_equation", + "content": "4.8\\%" + }, + { + "bbox": [ + 304, + 423, + 547, + 556 + ], + "type": "text", + "content": " on EPE in KITTI 2012 and " + }, + { + "bbox": [ + 304, + 423, + 547, + 556 + ], + "type": "inline_equation", + "content": "4.1\\%" + }, + { + "bbox": [ + 304, + 423, + 547, + 556 + ], + "type": "text", + "content": " in KITTI 2015. Furthermore, from the qualitative results in Fig. 4, we can see that our method outperforms IGEV-Stereo in reflective regions and occluded regions." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 563, + 407, + 575 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 563, + 407, + 575 + ], + "spans": [ + { + "bbox": [ + 306, + 563, + 407, + 575 + ], + "type": "text", + "content": "4.4. Ablation Studies" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 581, + 547, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 581, + 547, + 629 + ], + "spans": [ + { + "bbox": [ + 304, + 581, + 547, + 629 + ], + "type": "text", + "content": "We conduct ablation studies to evaluate the effectiveness of our proposed method. To show the generalization of the intra-view and cross-view knowledge learning, two base methods are used: GwcNet [17] and IGEV-Stereo [55]." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "content": "Effectiveness of Intra-view and Cross-view Knowledge. To verify that our proposed components all contribute to improving the performance, we provide quantitative results on the SceneFlow dataset in Tab. 4. The proposed ICGNet framework introduces an intra-view geometric loss " + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{intra}}" + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "content": ", a soft cross-view geometric loss " + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - soft}}" + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "content": " and a hard cross-view geometric loss " + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{cross - hard}}" + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "content": ". The intra-view geo" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20757" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 110, + 70, + 486, + 171 + ], + "blocks": [ + { + "bbox": [ + 110, + 70, + 486, + 171 + ], + "lines": [ + { + "bbox": [ + 110, + 70, + 486, + 171 + ], + "spans": [ + { + "bbox": [ + 110, + 70, + 486, + 171 + ], + "type": "table", + "html": "
MethodKITTI 2012KITTI 2015Middlebury 2014(H)
EPE(px)↓>3px(%)↓EPE(px)↓>3px(%)↓EPE(px)↓>2px(%)↓
PSMNet [3]2.6915.13.1716.37.6534.2
CFNet [42]1.045.21.716.03.2415.4
GANet [65]1.9310.12.3111.75.4120.3
DSMNet [66]1.266.21.466.52.6213.8
IGEV-Stereo [55]1.045.181.216.030.917.27
Ours0.994.871.165.960.826.73
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BaselineComponentsSceneFlow
\\( \\mathcal{L}_{\\text{intra}} \\)\\( \\mathcal{L}_{\\text{cross-soft}} \\)\\( \\mathcal{L}_{\\text{cross-hard}} \\)EPEpx)\\( \\downarrow \\)>3px(\\%)↓
GwcNet0.7653.30
✓0.6152.61
✓✓0.6082.56
✓✓✓0.5972.55
IGEV-Stereo0.4792.48
✓0.4522.37
✓✓0.4492.36
✓✓✓0.4472.34
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Ablation studies of proposed components on SceneFlow dataset on two baseline approaches GwcNet and IGEV-Stereo." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 533, + 287, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 533, + 287, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 533, + 287, + 676 + ], + "type": "text", + "content": "metric loss allows the model to learn intra-image geometric knowledge, and the soft cross-view geometric loss and hard cross-view geometric loss allow the model to learn cross-view geometric knowledge. Notably, our method demonstrates an improvement of over " + }, + { + "bbox": [ + 46, + 533, + 287, + 676 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 46, + 533, + 287, + 676 + ], + "type": "text", + "content": " (0.597 vs 0.765) in EPE and over " + }, + { + "bbox": [ + 46, + 533, + 287, + 676 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 46, + 533, + 287, + 676 + ], + "type": "text", + "content": " improvement in 3px-error. When applied to the strong base model IGEV-Stereo, our method still shows solid improvements over both EPE and 3px-error. The SceneFlow pre-trained full models of both base models are then finetuned on KITTI 2012 and KITTI 2015 datasets and results are shown in Tab. 5. Our method consistently outperforms the performance of baseline models." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 677, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 288, + 715 + ], + "type": "text", + "content": "Impact on Occluded and Non-occluded Regions. We further conduct experiments on our method's impact on occluded pixels and non-occluded pixels separately. Tab. 6" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 391, + 547, + 536 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 391, + 547, + 536 + ], + "spans": [ + { + "bbox": [ + 304, + 391, + 547, + 536 + ], + "type": "text", + "content": "shows that our method consistently improves disparity quality in both occluded regions and non-occluded regions. Furthermore, since occluded regions are areas without correspondence in the other figures, intuitively the prediction of disparities on such pixels relies more on intra-view geometric knowledge; on the contrary, predicting disparities at non-occluded pixels relies more on cross-view geometric knowledge [55]. Our experiment results are consistent with this intuition, validating our formulation of the process of extracting interest points as intra-view geometric knowledge and the process of extracting their correspondences as cross-view geometric knowledge." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "type": "text", + "content": "Complexity of intra-view decoder and cross-view decoder. We conduct experiments to evaluate the impact of the complexity of the intra-view decoder " + }, + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{intra}}" + }, + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "type": "text", + "content": " and cross-view decoder " + }, + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cross}}" + }, + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "type": "text", + "content": " on the models' performance. We keep GwcNet as the base model and change the number of layers of the decoders. The number of layers of the intra-view decoder refers to the number of stacked bottleneck convolutional blocks, and the number of layers of the cross-view decoder refers to the number of alternating attention layers. For the cross-view decoder with zero layers, we are directly using cosine similarities between the interest point features plus a softmax layer to form an assignment matrix " + }, + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{P}'" + }, + { + "bbox": [ + 304, + 545, + 547, + 713 + ], + "type": "text", + "content": ". Results on the SceneFlow dataset with GwcNet [17] as baseline are shown in Tab. 7. Results have shown that an" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20758" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 71, + 544, + 148 + ], + "blocks": [ + { + "bbox": [ + 51, + 71, + 544, + 148 + ], + "lines": [ + { + "bbox": [ + 51, + 71, + 544, + 148 + ], + "spans": [ + { + "bbox": [ + 51, + 71, + 544, + 148 + ], + "type": "table", + "html": "
BaselineICGNetKITTI 2012KITTI 2015 (all pixels)KITTI 2015 (noc pixels)
2-noc↓2-all↓3-noc↓3-all↓D1-bg↓D1-fg↓D1-all↓D1-bg↓D1-fg↓D1-all↓
GwcNet [17]✓2.162.711.321.701.743.932.111.613.491.92
1.982.541.251.631.623.902.001.503.561.84
IGEV-Stereo [55]✓1.712.171.121.441.382.671.591.272.621.49
1.702.141.101.411.382.551.571.262.561.47
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Qualitative results of cross-domain generalization of ICGNet (ours) compared with state-of-the-art baseline IGEV-Stereo [55]." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 303, + 178, + 417, + 258 + ], + "blocks": [ + { + "bbox": [ + 303, + 178, + 417, + 258 + ], + "lines": [ + { + "bbox": [ + 303, + 178, + 417, + 258 + ], + "spans": [ + { + "bbox": [ + 303, + 178, + 417, + 258 + ], + "type": "image", + "image_path": "23f438ec92a8be8f5e7b575ba79e2fb512f20dfa2f510e69f5b0af0c05b5e1bd.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 303, + 258, + 417, + 295 + ], + "blocks": [ + { + "bbox": [ + 303, + 258, + 417, + 295 + ], + "lines": [ + { + "bbox": [ + 303, + 258, + 417, + 295 + ], + "spans": [ + { + "bbox": [ + 303, + 258, + 417, + 295 + ], + "type": "image", + "image_path": "936d28b859e674aa7a8031f1a11350a505d31955ca3b11a7dce476d91fea56e1.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 303, + 295, + 417, + 331 + ], + "blocks": [ + { + "bbox": [ + 303, + 295, + 417, + 331 + ], + "lines": [ + { + "bbox": [ + 303, + 295, + 417, + 331 + ], + "spans": [ + { + "bbox": [ + 303, + 295, + 417, + 331 + ], + "type": "image", + "image_path": "ffd5c2f360d0506468d2e8d61ca21ef5d88e54a47d7c635afc6b7a1b183fdf6b.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 340, + 333, + 380, + 342 + ], + "lines": [ + { + "bbox": [ + 340, + 333, + 380, + 342 + ], + "spans": [ + { + "bbox": [ + 340, + 333, + 380, + 342 + ], + "type": "text", + "content": "IGEV-Stereo" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 418, + 178, + 533, + 258 + ], + "blocks": [ + { + "bbox": [ + 418, + 178, + 533, + 258 + ], + "lines": [ + { + "bbox": [ + 418, + 178, + 533, + 258 + ], + "spans": [ + { + "bbox": [ + 418, + 178, + 533, + 258 + ], + "type": "image", + "image_path": "0b1c3b86dc7f3ca7cd8b81b55686a6ac8e9c055868735fd7c4eed02cfbaa5d5e.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 418, + 258, + 533, + 294 + ], + "blocks": [ + { + "bbox": [ + 418, + 258, + 533, + 294 + ], + "lines": [ + { + "bbox": [ + 418, + 258, + 533, + 294 + ], + "spans": [ + { + "bbox": [ + 418, + 258, + 533, + 294 + ], + "type": "image", + "image_path": "690a22fc978c60d920640c295939a3764e9466d7901c0589b8e27056bcf3d84e.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + } + ], + "index": 15 + }, + { + "type": "image", + "bbox": [ + 418, + 295, + 533, + 331 + ], + "blocks": [ + { + "bbox": [ + 418, + 295, + 533, + 331 + ], + "lines": [ + { + "bbox": [ + 418, + 295, + 533, + 331 + ], + "spans": [ + { + "bbox": [ + 418, + 295, + 533, + 331 + ], + "type": "image", + "image_path": "cf621a204ad2874f573ee6203c36573ab97261fbad9d28cdb6551251358b2760.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 453, + 333, + 496, + 342 + ], + "lines": [ + { + "bbox": [ + 453, + 333, + 496, + 342 + ], + "spans": [ + { + "bbox": [ + 453, + 333, + 496, + 342 + ], + "type": "text", + "content": "ICGNet (ours)" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 16 + }, + { + "type": "table", + "bbox": [ + 48, + 383, + 302, + 448 + ], + "blocks": [ + { + "bbox": [ + 167, + 155, + 425, + 166 + ], + "lines": [ + { + "bbox": [ + 167, + 155, + 425, + 166 + ], + "spans": [ + { + "bbox": [ + 167, + 155, + 425, + 166 + ], + "type": "text", + "content": "Table 5. Ablation studies on KITTI 2012 and KITTI 2015 benchmarks." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 383, + 302, + 448 + ], + "lines": [ + { + "bbox": [ + 48, + 383, + 302, + 448 + ], + "spans": [ + { + "bbox": [ + 48, + 383, + 302, + 448 + ], + "type": "table", + "html": "
Intra-view\nL_intraCross-view\nL CROSS-soft + L cross-hardSceneFlow EPE
noc(px)↓occ(px)↓Δnoc/Δocc
0.4132.58/
✓0.3342.086.33
✓✓0.3182.023.75
", + "image_path": "8c626e29ed6bf501696725ba2cffcb8b2a7e0903dbcc401c2bff5c1793bfb984.jpg" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "table_body" + } + ], + "index": 19 + }, + { + "type": "table", + "bbox": [ + 80, + 548, + 255, + 647 + ], + "blocks": [ + { + "bbox": [ + 46, + 456, + 287, + 534 + ], + "lines": [ + { + "bbox": [ + 46, + 456, + 287, + 534 + ], + "spans": [ + { + "bbox": [ + 46, + 456, + 287, + 534 + ], + "type": "text", + "content": "Table 6. Ablation studies on occluded and non-occluded areas on the SceneFlow dataset using GwcNet baseline model. Our method improves disparity prediction accuracy in both occluded areas and non-occluded areas. Compared with cross-view geometric knowledge, intra-view geometric knowledge improves more in occluded regions, consistent with the intuition that occluded areas rely on their surrounding geometric relations to infer their disparities." + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 80, + 548, + 255, + 647 + ], + "lines": [ + { + "bbox": [ + 80, + 548, + 255, + 647 + ], + "spans": [ + { + "bbox": [ + 80, + 548, + 255, + 647 + ], + "type": "table", + "html": "
DecoderLayersSceneFlow
EPE(px)↓>3px↓
intra-view10.6312.74
20.6152.61
40.6232.68
cross-view00.6172.61
40.5972.55
60.6062.58
", + "image_path": "022dcfc2a01a1f4eb4a47703fd67ba68cf67020b9e3699301c738fd6c24eb253.jpg" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "table_body" + } + ], + "index": 21 + }, + { + "bbox": [ + 46, + 654, + 287, + 677 + ], + "lines": [ + { + "bbox": [ + 46, + 654, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 46, + 654, + 287, + 677 + ], + "type": "text", + "content": "Table 7. Comparison of performance of different decoder complexities." + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 305, + 385, + 545, + 482 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 385, + 545, + 482 + ], + "spans": [ + { + "bbox": [ + 305, + 385, + 545, + 482 + ], + "type": "text", + "content": "intermediate number of decoder layers for both intra-view and cross-view decoder yields the best results. This may be due to a too-complex decoder will take up too much of the task of learning the geometric knowledge, making the feature backbone not learn sufficient knowledge, while a too-simple decoder is not sufficient to map the features into the geometric structures, leaving too much for the feature backbone and make it sub-optimal in disparity prediction task." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 306, + 495, + 378, + 506 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 495, + 378, + 506 + ], + "spans": [ + { + "bbox": [ + 306, + 495, + 378, + 506 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 515, + 545, + 635 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 515, + 545, + 635 + ], + "spans": [ + { + "bbox": [ + 304, + 515, + 545, + 635 + ], + "type": "text", + "content": "In this work, we introduce ICGNet, a novel approach designed to infuse stereo matching networks with both intraview and cross-view geometric knowledge. Utilizing interest points and their corresponding matches derived from local feature matching models, we provide rich sources of geometric knowledge to educate the stereo matching network. Our extensive experimental evaluations demonstrate that this methodology enhances the performance of state-of-the-art stereo matching models, boosting both their accuracy and their ability to generalize across diverse domains." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 306, + 648, + 404, + 662 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 648, + 404, + 662 + ], + "spans": [ + { + "bbox": [ + 306, + 648, + 404, + 662 + ], + "type": "text", + "content": "Acknowledgement" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 305, + 669, + 545, + 703 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 669, + 545, + 703 + ], + "spans": [ + { + "bbox": [ + 305, + 669, + 545, + 703 + ], + "type": "text", + "content": "This work was supported by the Agency for Science, Technology and Research (A*STAR) under its MTC Programmatic Funds (Grant No. M23L7b0021)." + } + ] + } + ], + "index": 27 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20759" + } + ] + } + ], + "index": 28 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Herbert Bay, Tinne Tuytelaars, and Luc Van Gool. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 1327-1336, 2023. 6" + } + ] + } + ], + "index": 24 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "text", + "content": "20762" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_content_list.json b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..6dabc569a735f6a9a21baa0c8fada1c90bda5138 --- /dev/null +++ b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_content_list.json @@ -0,0 +1,1542 @@ +[ + { + "type": "text", + "text": "Learning Large-Factor EM Image Super-Resolution with Generative Priors", + "text_level": 1, + "bbox": [ + 104, + 130, + 867, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Jiateng Shou1 Zeyu Xiao1 Shiyu Deng1 Wei Huang1 Peiyao Shi3 Ruobing Zhang3,2 Zhiwei Xiong1,2 Feng Wu1,2,†", + "bbox": [ + 196, + 179, + 772, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1 MoE Key Laboratory of Brain-inspired Intelligent Perception and Cognition, University of Science and Technology of China", + "bbox": [ + 112, + 218, + 857, + 234 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ Institute of Artificial Intelligence, Hefei Comprehensive National Science Center", + "bbox": [ + 241, + 234, + 728, + 250 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{3}$ Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences", + "bbox": [ + 207, + 253, + 759, + 268 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "shoujt@mail.ustc.edu.cn {zwxiong,fengwu}@ustc.edu.cn", + "bbox": [ + 246, + 272, + 715, + 286 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 321, + 313, + 338 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "As the mainstream technique for capturing images of biological specimens at nanometer resolution, electron microscopy (EM) is extremely time-consuming for scanning wide field-of-view (FOV) specimens. In this paper, we investigate a challenging task of large-factor EM image super-resolution (EMSR), which holds great promise for reducing scanning time, relaxing acquisition conditions, and expanding imaging FOV. By exploiting the repetitive structures and volumetric coherence of EM images, we propose the first generative learning-based framework for large-factor EMSR. Specifically, motivated by the predictability of repetitive structures and textures in EM images, we first learn a discrete codebook in the latent space to represent high-resolution (HR) cell-specific priors and a latent vector indexer to map low-resolution (LR) EM images to their corresponding latent vectors in a generative manner. By incorporating the generative cell-specific priors from HR EM images through a multi-scale prior fusion module, we then deploy multi-image feature alignment and fusion to further exploit the inter-section coherence in the volumetric EM data. Extensive experiments demonstrate that our proposed framework outperforms advanced single-image and video super-resolution methods for $8 \\times$ and $16 \\times$ EMSR (i.e., with 64 times and 256 times less data acquired, respectively), achieving superior visual reconstruction quality and downstream segmentation accuracy on benchmark EM datasets. Code is available at https://github.com/jtshou/GPEMSR.", + "bbox": [ + 75, + 349, + 473, + 772 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 792, + 209, + 808 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Electron microscopy (EM) is a commonly used imaging technique in life sciences to investigate the ultrastructure of cells, tissues, organelles, and macromolecular complexes, which captures images of biological specimens at nanome", + "bbox": [ + 75, + 814, + 468, + 876 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ter resolution. However, high-quality EM image acquisition typically requires a strict and time-consuming process, involving careful adjustments of beam current, aperture size, and detector settings. This process may take up to years to scan wide field-of-view (FOV) specimens. For example, Zheng et al. [57] spent approximately 16 months to acquire a $\\sim 106\\mathrm{TB}$ whole-brain dataset of an adult drosophila melanogaster. The long acquisition time greatly limits the application of EM imaging in analyzing complete biological structures in large specimens, such as neuron connections in mammalian brains.", + "bbox": [ + 500, + 323, + 890, + 487 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Image super-resolution (SR), which is capable of restoring high-resolution (HR) images from their corresponding low-resolution (LR) observations, has the potential to revolutionize EM imaging by allowing for faster and less restrictive data acquisition, while also providing high-quality images with a wide field of view. By applying SR to EM images (shorted as EMSR hereafter), the capturing time can be significantly reduced, and the strict capturing conditions can be relaxed. By deploying a simple ResNet-based UNet model, Fang et al. [13] have demonstrated the promising performance of EMSR for $4\\times$ magnification (i.e., with 16 times less data acquired). However, achieving even larger-factor EMSR to further reduce capturing time remains challenging. This is in accordance with existing methods [5, 18, 30, 35, 50, 58] for natural images, which can achieve satisfactory results for up to $4\\times$ magnification, but fail to meet the demand for larger factors.", + "bbox": [ + 496, + 489, + 892, + 747 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "On the other hand, recent advances in generative models, such as ChatGPT and diffusion-based models [9, 16, 21, 43], reveal powerful capability in automatic content generation, including natural languages and images. This motivates us to consider the EMSR task from a generative perspective. Especially, compared with natural images that possess diverse structures and textures, EM images often exhibit repetitive structures and textures due to the predictability of imaging specimens, making it more suitable to leverage generative learning for accurate reconstruction. In", + "bbox": [ + 496, + 750, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "†Corresponding author.", + "bbox": [ + 102, + 886, + 228, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "11313", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "this paper, we propose a novel deep learning-based framework tailored to the challenging task of large-factor EMSR, by 1) exploiting the repetitive structures and textures in EM images with generative cell-specific priors learned from HR EM images, and 2) exploiting the inter-section coherence in the volumetric EM data by aggregating features learned from multiple consecutive images.", + "bbox": [ + 75, + 90, + 468, + 196 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Specifically, our framework explores cell-specific priors using a VQGAN-Indexer network, consisting of VQGAN [12] and our proposed latent vector indexer. We first learn a discrete codebook to represent the distribution of HR EM images in the latent space. The codebook captures both structure and texture information, while the decoder establishes relationships between latent vectors and image patches. We then train a latent vector indexer to acquire the corresponding latent vectors and integrate the indexer with the codebook and the decoder for generating HR EM images. By treating the generation process as an indexing task, we can match LR EM images with their corresponding HR feature representations from the latent space, thereby obtaining priors solely derived from HR EM images.", + "bbox": [ + 75, + 199, + 470, + 411 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To maintain reconstruction quality while prioritizing downstream segmentation accuracy, we propose a MultiScale Prior Fusion (MPF) module for incorporating the above learned cell-specific priors in EMSR. We use the VQGAN-Indexer output as reference images and learn a mask for fusing reference features based on the patch-level cosine similarity between LR EM images and corresponding reference images. To fully utilize the latent vectors and relationships learned by the decoder, we use multi-scale reference features from different layers of the decoder with varying resolutions. Following the MPF module, our framework includes two key steps for exploiting inter-section coherence in the volumetric EM data: multi-image feature alignment (along the axial direction) and multi-image feature fusion. To this end, we introduce a Pyramid Optical-flow-based Deformable convolution alignment (POD) module and a 3D Spatial-Attention fusion (3DA) module. The former leverages a pre-trained optical-flow network SPyNet [42] and deformable convolutions [6, 60], while the latter leverages the spatial attention mechanism and 3D convolutions. Both improve reconstruction quality and downstream segmentation accuracy for large-factor EMSR.", + "bbox": [ + 75, + 414, + 468, + 747 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In summary, this paper offers the following contributions. 1) We present the first generative learning-based framework for the challenging task of large-factor EMSR. 2) We introduce the VQGAN-Indexer network to explore generative cell-specific prior information from HR EM images. 3) We propose the MPF module to effectively utilize the generative priors while preserving image fidelity with LR observations, followed by the POD and 3DA modules for multi-image feature alignment and fusion. 4) Extensive experiments demonstrate the superiority of our framework", + "bbox": [ + 75, + 750, + 470, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "in terms of both reconstruction quality and downstream segmentation accuracy for $8 \\times$ and $16 \\times$ EMSR.", + "bbox": [ + 498, + 90, + 890, + 121 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 128, + 640, + 143 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Electron microscopy image super-resolution. Existing EMSR methods can be categorized into two types: restoring isotropic volumes from anisotropic ones, i.e., SR along the axial dimension [8, 20], and reconstructing HR images from corresponding LR observations in the lateral dimensions [7, 13, 40, 46, 53]. We focus on the latter task in this paper, while our proposed framework may also apply to the former task. As a pioneering work in the field of EMSR, Sreehari et al. [46] introduce a Bayesian framework and utilize a library-based non-local means (LB-NLM) algorithm to achieve up to $16 \\times$ EMSR without requiring a training process. However, this non-learning-based method limits performance and is not specifically designed for large-factor EMSR. Along the deep learning line, Nehme et al. [40] train a fully convolutional encoder-decoder network on simulated data to reconstruct super-resolved images. Hann et al. [7] train a GAN model using pairs of test specimens captured from the same region of interest. Xie et al. [53] leverage the attention mechanism to capture inter-section dependencies and shared features among adjacent images. Compared to previous EMSR methods, our framework not only utilizes adjacent EM images but also explores and integrates generative cell-specific priors to tackle the challenging task of large-factor EMSR.", + "bbox": [ + 496, + 150, + 890, + 512 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Video super-resolution. Video super-resolution (VSR) aims to restore HR frames by leveraging adjacent temporal information in multiple LR frames. To align temporal features, optical flow [3, 5, 26, 44, 49, 52, 54] and deformable convolution [47, 50], have been widely adopted. Recently, transformer-based approaches [4, 36] yield remarkable advancements in VSR, owing to the utilization of diverse attention mechanisms. Inspired by these VSR methods, to exploit the inter-section coherence in the volumetric EM data, we utilize optical-flow networks and deformable convolutions for multi-image feature alignment, and spatial attention mechanisms for multi-image feature fusion.", + "bbox": [ + 496, + 518, + 890, + 699 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Generative priors in image restoration. Generative image restoration methods [11, 31-33] employ the priors from the pre-trained generative adversarial network (GAN), such as StyleGAN [24] and BigGAN [2], to approximate the natural image manifold and synthesize high-quality images. Given the superior performance of discrete codebook-based generative methods in semantic image synthesis, structure-to-image, and stochastic super-resolution tasks [12, 48], recent methods explore codebook-based facial priors [17, 59] by leveraging VQGAN [12] for training. Different from these methods, we propose a latent vector indexer to exploit the information contained within the input LR images, and the MPF module to fuse generative priors.", + "bbox": [ + 496, + 704, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "11314", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 89, + 168, + 104 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Overview", + "text_level": 1, + "bbox": [ + 76, + 107, + 187, + 121 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As illustrated in Figure 1, the goal of large-factor EMSR is to obtain the super-resolved $I_{SR}^{0} \\in \\mathbb{R}^{rH \\times rW \\times 1}$ , given a sequence of $2N + 1$ consecutive LR EM images, $I_{LR}^{z} \\in \\mathbb{R}^{H \\times W \\times 1}$ , which should be close to the ground truth image $I_{GT}^{0} \\in \\mathbb{R}^{rH \\times rW \\times 1}$ , where $z \\in \\{-N, -N + 1, \\dots, 0, \\dots, N - 1, N\\}$ and $r$ is the large scale factor. In this paper, we set $N = 2$ and $r = 8, 16$ .", + "bbox": [ + 76, + 123, + 468, + 228 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To achieve this, we propose a generative learning-based framework consisting of three stages. Stage I involves exploring generative cell-specific priors through the VQGAN model, which identifies a discrete latent space of HR EM images and generates the HR EM image $I_{\\mathrm{HRref}}$ from the latent space. This latent space is represented using vectors from the VQGAN codebook $C$ . In Stage II, we train a latent vector indexer and connect it with the VQGAN codebook $C$ and VQGAN decoder $Q$ obtained from Stage I. This connection allows us to generate the reference HR EM image $I_{\\mathrm{Ref}}$ and its corresponding multi-scale generative features $F_{\\mathrm{Ref}}^{l}$ from the LR EM image $I_{\\mathrm{LR}}$ . Finally, in Stage III, we fuse the multi-scale generative features $F_{\\mathrm{Ref}}^{l}$ using the MPF module, align adjacent image features in the axial direction using the POD module, and fuse the adjacent image features using the 3DA module. We finally use sub-pixel convolution to reconstruct the HR output $I_{SR}^{0}$ .", + "bbox": [ + 75, + 229, + 470, + 488 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Exploring Generative Cell-Specific Priors", + "text_level": 1, + "bbox": [ + 76, + 491, + 431, + 507 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "EM images are characterized by their repetitive structures and textures, such as cellular membranes and subcellular organelles. These features offer an opportunity to exploit their regularity and predictability, motivating our exploration of the generative cell-specific prior in EM images for large-factor EMSR. As shown in Figure 1 (a), our framework for exploring generative cell-specific prior exploration consists of two main steps. First, we identify a discrete latent space that represents the features of HR EM images. Then, we generate the HR EM images from this latent space, leveraging its compact and representative nature.", + "bbox": [ + 75, + 508, + 468, + 675 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Identifying a discrete latent space. We aim to identify a discrete latent space that represents HR EM images. To achieve this, we utilize an encoder $\\pmb{E}$ to parameterize the posterior categorical distribution of HR EM images $q_{\\phi}(\\xi \\mid o)$ , where $\\xi$ represents the variable for latent vectors, $o$ represents the variable for HR EM images and $\\phi$ represents the encoder's parameters. Specifically, we quantize the output feature $Z_{e}$ from $\\pmb{E}$ by mapping it to its closest latent vector in $C$ and obtain the quantified feature $Z_{d}$ and one-hot index of each mapped HR patch, denoted as $s^{m,n}$", + "bbox": [ + 75, + 678, + 468, + 830 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} Z _ {d} ^ {m, n} = \\arg \\min _ {Z _ {q} [ j ]} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2}, \\\\ s ^ {m, n} [ k ] = \\left\\{ \\begin{array}{l l} 1, & k = \\arg \\min _ {j} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2} \\\\ 0, & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {1} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 94, + 840, + 468, + 904 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $Z_{q}[j]$ denotes the $j$ -th latent vector stored in $C$ . $Z_{e}^{m,n}$ denotes the encoder output feature element at position $(m,n)$ within $Z_{e}$ , while $Z_{d}^{m,n}$ denotes the quantified feature element at position $(m,n)$ within $Z_{d}$ . $s^{m,n}$ is a v-dimensional vector and $s^{m,n}[k]$ denotes the $k$ -th element in $s^{m,n}$ . The codebook $C$ consists of $v$ latent vectors, each with a dimensionality of $d$ . Thus, the posterior categorical distribution $q_{\\phi}(\\xi | o)$ is defined as", + "bbox": [ + 498, + 90, + 893, + 213 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nq _ {\\phi} (\\xi = k \\mid o) = \\left\\{ \\begin{array}{l l} 1, & Z _ {q} [ k ] = \\arg \\min _ {Z _ {q} [ j ]} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2} \\\\ 0, & \\text {o t h e r w i s e} \\end{array} . \\right. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 498, + 224, + 924, + 277 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Generating the HR EM image. Given the quantified feature $Z_{d}$ , we can generate HR EM image $I_{\\mathrm{HRref}}$ through the decoder. We parameterize the prior distribution of HR EM images $p_{\\theta}(o \\mid \\xi)$ through the decoder $Q$ , where $\\theta$ is the parameters of the decoder.", + "bbox": [ + 496, + 286, + 890, + 361 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The encoder is composed of multiple Res-blocks [19] and convolution blocks for downsampling, while the decoder is composed of multiple Res-blocks and deconvolution blocks for upsampling. The compression patch size for downsampling is set to $p$ . Both the encoder and decoder leverage self-attention mechanisms to enhance generalization quality. We optimize the latent vector $Z_{q}[j]$ along with the encoder $E$ and decoder $Q$ .", + "bbox": [ + 496, + 362, + 890, + 483 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.3. Generating LR Reference", + "text_level": 1, + "bbox": [ + 498, + 488, + 733, + 503 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "With the parameterization of the latent space using $C$ and the prior distribution of HR EM images using $Q$ , we can generate HR EM images given real HR EM images as input. However, in the large-factor EMSR task, only highly degraded LR images are available as input. Hence, we need to map the LR images to their corresponding quantified feature $Z_{d}$ to utilize the generative cell-prior stored in $C$ .", + "bbox": [ + 496, + 506, + 890, + 611 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To achieve this, one straightforward approach is to interpolate the LR images and feed them into the encoder [17]. This straightforward approach approximates the posterior categorical distribution of LR EM images $q(\\xi \\mid o_{\\downarrow})$ by utilizing the parameterized posterior categorical distribution of HR EM images $q_{\\phi}(\\xi \\mid [o_{\\downarrow}]_{\\uparrow})$ with the interpolation operation. Here, $o_{\\downarrow}$ represents the LR image variable, and $[\\cdot]_{\\uparrow}$ denotes the interpolation operation. However, in scenarios where significant degradation occurs in LR input images, the interpolation operation struggles to restore the rich details and textures in HR EM images. Consequently, this mismatch leads to discrepancies between the real HR EM image distribution $p(o)$ and the interpolated HR EM image distribution $p([o_{\\downarrow}]_{\\uparrow})$ , thereby resulting in disparities between $q(\\xi \\mid o_{\\downarrow})$ and $q_{\\phi}(\\xi \\mid [o_{\\downarrow}]_{\\uparrow})$ . Despite the loss of fine-grained details in LR images, the partial preservation of information enables the utilization of such details as priors in mapping LR images to their corresponding quantified feature $Z_{d}$ . To fully utilize these priors, we propose a latent", + "bbox": [ + 496, + 612, + 892, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "11315", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/493cf8d2b9ae46d437915f0bcf6293001b84ec8dc47095e1395fd1bdf2bbf203.jpg", + "image_caption": [ + "Figure 1. Overview of our framework. The proposed generative learning-based framework consists of three stages. In Stage I, the encoder, the codebook, and the decoder are trained by self-generating the input HR EM image. In Stage II, a latent vector indexer is trained and connected with the codebook and the decoder with fixed parameters to generate the reference HR EM image and multi-scale generative features from the LR EM image. In Stage III, the HR output is reconstructed by fusing multi-scale generative features and exploiting inter-section coherence in volumetric EM data with the POD module and the 3DA module. Rec denotes reconstruction layers composed of convolution layers and pixel shuffle operation." + ], + "image_footnote": [], + "bbox": [ + 86, + 93, + 645, + 465 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/358f9753f2980d2ad4eb765d8f95c343cd5679b7a63d68805e26d2601ffff839.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 650, + 93, + 880, + 465 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "vector indexer $W$ to predict probabilities of corresponding latent vectors in $C$ given LR EM images as input, as shown in Figure 1 (b). We denote the output of the latent vector indexer as $Z_{w}$ , where the element at position $(m,n)$ is denoted as $Z_{w}^{m,n}$ and represents a $v$ -dimensional vector. Then, by selecting the latent vector with the highest probability, we can effectively model the posterior categorical distribution $q(\\xi \\mid o_{\\downarrow})$ as", + "bbox": [ + 75, + 561, + 472, + 683 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nq _ {\\varphi} (\\xi = k \\mid o _ {\\downarrow}) = \\left\\{ \\begin{array}{l l} 1, & k = \\arg \\max _ {i \\in \\{1, 2, 3, \\dots , v \\}} Z _ {w} ^ {m, n} [ i ] \\\\ 0, & \\text {o t h e r w i s e} \\end{array} \\right., \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 696, + 478, + 747 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\varphi$ denotes the parameters of the latent vector indexer $W$ . $Z_{w}^{m,n}[i]$ denotes the $i$ -th element of the vector $Z_{w}^{m,n}$ .", + "bbox": [ + 76, + 750, + 470, + 780 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "This quantization operation allows us to capture the most representative latent vector that corresponds to the LR image. Then the predicted quantified feature $Z_{d}^{pre}$ is obtained and fed into the decoder to generate the reference HR EM image $I_{\\mathrm{Ref}}$ and its corresponding multi-scale generative features $F_{\\mathrm{Ref}}^{l}$ through the decoder. Note that all the latent vectors used to generate $I_{\\mathrm{Ref}}$ and $F_{\\mathrm{Ref}}^{l}$ are obtained from the codebook, which contains the generative cell-specific pri", + "bbox": [ + 75, + 780, + 470, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "ors of HR EM images.", + "bbox": [ + 498, + 561, + 653, + 577 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.4. Reconstructing HR Image", + "text_level": 1, + "bbox": [ + 498, + 580, + 736, + 595 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "MPF module. The complete process of reconstructing HR image is depicted in Figure 1 (c). The discrepancies between the generated HR image $I_{\\mathrm{Ref}}$ and real EM image $I_{\\mathrm{GT}}$ pose a challenge in achieving accurate multi-scale generative feature fusion. To overcome this challenge, we propose the MPF module, which focuses on identifying and fusing the multi-scale generative features. The MPF module comprises two essential processes: a mask-learning process and a multi-scale fusion process.", + "bbox": [ + 496, + 598, + 890, + 734 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The mask-learning mechanism within the MPF module enables us to identify and mask out multi-scale generative features in regions that show significant boundary differences compared to real HR images. As shown in Figure 1 (d), we first embed the interpolated LR image $[I_{LR}]_{\\uparrow}$ and the reference image $I_{Ref}$ from the decoder into the feature space by a pre-trained VGG19 encoder [45]. We extract $16\\times 16$ patches from LR feature maps and reference (Ref) feature maps without overlap. Then, We calculate cosine similarity vector $CS$ between LR feature patches and Ref feature patches, where $CS_{i}$ denotes cosine similarity be", + "bbox": [ + 496, + 734, + 892, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "11316", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "tween the $i$ -th LR feature patch and the $i$ -th Ref feature patch. We refine the mask by employing three 2D convolutions. Finally, we apply a sigmoid function to obtain the mask $M$ with the same spatial resolution as LR features.", + "bbox": [ + 75, + 90, + 468, + 151 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To effectively fuse features from different layers of the decoder across $L$ levels, we employ a multi-scale fusion scheme, as illustrated in Figure 1 (e). As the decoder learns the relationship between latent vectors, each layer of the decoder contains varying levels of detailed information about EM images. Additionally, since the decoder is responsible for reconstructing HR EM images, layers closer to the output represent shallower features. Given these considerations, we begin fusing features from $F_{Ref}^{0}$ and its corresponding LR features $F_{LR}^{0}$ with the same resolution and gradually incorporate features with lower resolution", + "bbox": [ + 75, + 151, + 472, + 319 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\tilde {F} ^ {1} = R _ {D} ^ {0} \\left(R _ {F} ^ {0} \\left(\\left\\langle F _ {L R} ^ {0}, F _ {R e f} ^ {0} \\right\\rangle\\right) \\otimes [ M ] _ {\\uparrow 2 ^ {L - 1}}\\right), \\\\ \\tilde {F} ^ {l + 1} = R _ {D} ^ {l} \\left(\\langle R _ {F} ^ {l} \\left(\\langle \\tilde {F} ^ {l}, F _ {L R} ^ {l}, F _ {R e f} ^ {l} \\rangle\\right) \\otimes [ M ] _ {\\uparrow 2 ^ {L - l - 1}}, \\tilde {F} ^ {l} \\rangle\\right), \\\\ \\hat {F} = R _ {F} ^ {L - 1} \\left(\\langle \\tilde {F} ^ {L - 1}, F _ {L R} ^ {L - 1}, F _ {R e f} ^ {L - 1} \\rangle\\right) \\otimes M, \\\\ F ^ {O u t} = R _ {O} ^ {L - 1} \\left(\\langle \\hat {F}, \\tilde {F} ^ {L - 1}, F _ {L R} ^ {L - 1} \\rangle\\right), \\tag {4} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 80, + 329, + 485, + 448 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\otimes$ denotes element-wise multiplication, $\\langle \\cdot \\rangle$ denotes concatenation operation, and $[\\cdot ]_{\\uparrow}$ denotes interpolation operation. $\\tilde{F}^l$ denotes output features from downsample convolution at the $l$ -th level. $R_D^l,R_F^l$ ,and $R_O^{L - 1}$ denote downsample convolution, fusion convolution, and output convolution, respectively. $\\hat{F}$ denotes the output feature of the last fusion convolution. $F^{Out}$ represents the final multi-scale fusion feature.", + "bbox": [ + 75, + 449, + 468, + 571 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "POD module and 3DA module. To exploit the intersection coherence in volumetric EM data and leverage the correlation between adjacent EM images, we design two modules: the POD module and the 3DA module. The POD module is responsible for aligning the adjacent EM image output features from the MPF module in a coarse-to-fine manner. It utilizes a pyramid architecture and incorporates a pre-trained optical-flow network SPyNet and deformable convolutions to achieve accurate feature alignment. The 3DA module employs spatial attention mechanisms and 3D convolutions to effectively fuse the aligned features. More detailed information about the POD module and 3DA module can be found in the supplementary material.", + "bbox": [ + 75, + 577, + 468, + 773 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.5. Training Strategy", + "text_level": 1, + "bbox": [ + 76, + 777, + 250, + 792 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In Stage I, we adopt three loss functions: a reconstruction loss $L_{r - I}$ , a codebook learning loss $L_{c}$ , and an adversarial loss $L_{adv}$", + "bbox": [ + 75, + 795, + 468, + 840 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} L _ {r - I} = \\left\\| I _ {\\mathrm {H R r e f}} - I _ {\\mathrm {G T}} \\right\\| _ {1}, L _ {a d v} = D \\left(I _ {\\mathrm {G T}}\\right) + D \\left(- I _ {\\mathrm {H R r e f}}\\right), \\\\ L _ {c} = \\left\\| \\operatorname {s g} \\left[ Z _ {d} \\right] - Z _ {e} \\right\\| _ {2} ^ {2} + \\left\\| \\operatorname {s g} \\left[ Z _ {e} \\right] - Z _ {d} \\right\\| _ {2} ^ {2}, \\tag {5} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 86, + 849, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $D$ represents a PatchGAN discriminator [23] and $\\mathrm{sg}[\\cdot ]$ denotes the stop-gradient operation. As Eq. 1 is non-differentiable, we propagate the gradients from the decoder to the encoder [12, 48]. We utilize R1 regularization [39] for GAN training stability. The complete objective of the first stage is", + "bbox": [ + 496, + 90, + 890, + 181 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {s - I} = L _ {r - I} + \\lambda_ {c} L _ {c} + \\lambda_ {a d v} L _ {a d v}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 576, + 191, + 890, + 208 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In Stage II, we optimize the latent vector indexer $W$ while keeping the parameters of $C$ and $Q$ fixed. The objective of the second stage is", + "bbox": [ + 496, + 217, + 890, + 263 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {s - I I} = - \\sum_ {m, n, i} s ^ {m, n} [ i ] \\log \\frac {\\exp \\left(Z _ {w} ^ {m , n} [ i ]\\right)}{\\sum_ {j} \\exp \\left(Z _ {w} ^ {m , n} [ j ]\\right)}. \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 524, + 271, + 890, + 310 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In Stage III, we train our network with two loss functions: a reconstruction loss $L_{r - III}$ and a multi-Ref fidelity loss $L_{Mfid}$ [28]. The objective of the third stage is", + "bbox": [ + 496, + 319, + 890, + 364 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} L _ {r - I I I} = \\left\\| I _ {S R} ^ {0} - I _ {G T} ^ {0} \\right\\| _ {1}, \\\\ L _ {M f i d} = \\frac {\\sum_ {z ^ {\\prime} \\in \\Omega} \\sum_ {i} \\delta_ {i} \\left(I _ {S R} ^ {0} , I _ {R e f} ^ {z ^ {\\prime}}\\right) \\cdot c _ {z ^ {\\prime} , i}}{\\sum_ {z ^ {\\prime} \\in \\Omega} \\sum_ {i} c _ {z ^ {\\prime} , i}}, \\tag {8} \\\\ L _ {s - I I I} = L _ {r - I I I} + \\lambda_ {M f i d} L _ {M f i d}, \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 547, + 375, + 890, + 458 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\Omega = \\{-N, -N + 1, \\dots, 0, \\dots, N - 1, N\\}$ , $\\delta_i(\\cdot, \\cdot)$ denotes contextual loss in [38] and $c_{z', i}$ is the matching confidence weight based on cosine similarity.", + "bbox": [ + 496, + 465, + 890, + 513 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 518, + 632, + 535 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Settings", + "text_level": 1, + "bbox": [ + 500, + 539, + 596, + 555 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We conduct experiments under two different settings to demonstrate the superior performance of our framework in both reconstruction quality and downstream segmentation accuracy. For the first setting, we select the adult drosophila melanogaster brain dataset FAFB [57] and its subset CREMI [14] acquired at $4 \\times 4 \\times 40\\mathrm{nm}^3$ resolution. In Stage I and Stage II, we train our framework on a subset ( $\\sim 38\\mathrm{G}$ ) of FAFB to obtain a cell-specific prior. In Stage III, we utilize the padded version of the CREMI dataset, excluding the CREMI C subset, to train for large-factor EMSR. We use the cropped version of CREMI C, which has segmentation labels, as the test set consisting of 125 images. We fine-tune two pre-trained segmentation networks, Superhuman [29] and MALA [15], on the first 75 images of CREMI C. Therefore, we test all 125 images for reconstruction evaluation metrics and the last 50 for segmentation evaluation metrics. For the second setting, we select the mouse somatosensory cortex dataset Kasthuri15 [25] and its subset AC3/AC4 dataset [25] acquired at $3 \\times 3 \\times 29\\mathrm{nm}^3$ resolution. As the AC3/AC4 datasets are too small, we use the data partitioning strategy from [22] and train three stages on a subset ( $\\sim 11.2\\mathrm{G}$ , i.e., Subset3 in [22]) of Kasthuri15 and AC3. We fine-tune two pre-trained segmentation networks on AC3 and test them on AC4.", + "bbox": [ + 496, + 559, + 890, + 921 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "11317", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/96206aaa147bd712d822acb6757606d89ed77b944d2aeecfeda1bc40e4dc5343.jpg", + "table_caption": [ + "Table 1. Quantitative comparison of reconstruction quality and EM image segmentation results on CREMI C for ${16} \\times$ and $8 \\times$ EMSR. The best and the second-best results are highlighted in bold and underline. * Parameters optimized in Stage III." + ], + "table_footnote": [], + "table_body": "
MethodsScaleReconstruction MetricsSegmentation MetricsParams/M
FidelityPerceptualSuperhumanMALA
PSNR↑SSIM↑LPIPS↓DISTS↓VOI↓ARAND↓VOI↓ARAND↓
Bicubic16×21.55570.48010.73380.48426.66270.70436.55990.8830-
RCAN [56]16×23.12380.57790.53360.34295.27620.61932.93530.232512.9080
SwinIR [35]16×23.10980.57810.53320.34165.12540.49552.93020.231712.1426
BSRN [34]16×22.91610.56450.54530.34025.57280.68093.20340.26940.4719
Real-ESRGAN [51]16×22.76310.55370.53330.31344.08230.48903.38060.297316.6957
EDVR [50]16×23.88940.61470.50220.31824.17090.41322.32290.19693.4455
BasicVSR [5]16×23.38770.59240.51070.31764.58250.50532.54280.21153.9339
Ours16×23.67670.60200.47900.29272.96390.30752.25710.17865.4627*
Bicubic8×25.58970.66070.47790.29825.93040.87542.47480.2036-
RCAN [56]8×29.39260.79140.37290.23393.38580.32881.56340.133312.7603
SwinIR [35]8×29.43340.79210.37240.23403.34940.32671.54000.130611.9949
BSRN [34]8×29.14640.78320.37910.23133.59280.34611.56210.13150.3611
Real-ESRGAN [51]8×29.14570.78430.37740.23173.57400.33631.55550.130916.6957
EDVR [50]8×29.73260.80160.36420.23163.17390.31591.51070.13243.2978
BasicVSR [5]8×29.08280.78310.37740.23053.46190.33361.58790.13494.0445
Ours8×29.70270.80020.35680.22912.93760.30761.50110.12984.4257*
", + "bbox": [ + 125, + 121, + 841, + 356 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/a42b5236ff061bfc0cd5cd0cc14648cc5af8b9db16be4511461744cfc2d6f656.jpg", + "table_caption": [ + "Table 2. Quantitative comparison of reconstruction quality and EM image segmentation results on AC4 for ${16} \\times$ and $8 \\times$ EMSR. The best and the second-best results are highlighted in bold and underline. * Parameters optimized in Stage III." + ], + "table_footnote": [], + "table_body": "
MethodsScaleReconstruction MetricsSegmentation MetricsParams/M
FidelityPerceptualSuperhumanMALA
PSNR↑SSIM↑LPIPS↓DISTS↓VOI↓ARAND↓VOI↓ARAND↓
Bicubic16×19.00780.25180.77580.46396.93000.96886.81440.9664-
RCAN [56]16×19.59380.29810.66610.39706.45350.93516.47160.929412.9080
SwinIR [35]16×19.59490.29560.66710.38936.87960.94966.54170.932212.1426
BSRN [34]16×19.56130.29280.67250.39147.19610.96156.61680.93950.4719
Real-ESRGAN [51]16×19.42540.28930.64270.37066.38530.87456.06590.914016.6957
EDVR [50]16×19.93740.32830.62320.37314.81780.71585.00290.82823.4455
BasicVSR [5]16×19.42930.28880.67470.37476.86080.95986.75480.95133.9339
Ours16×19.74680.31140.57480.35844.36550.61264.83620.82335.4627*
Bicubic8×21.09790.37200.58960.33616.76940.96756.13460.9157-
RCAN [56]8×22.31670.47730.52000.31622.21010.28262.35710.388612.7603
SwinIR [35]8×22.49090.49310.51040.32131.78670.21072.36350.524211.9949
BSRN [34]8×22.27360.47360.52310.31322.26300.28602.51200.37460.3611
Real-ESRGAN [51]8×22.34390.48890.50000.31271.88390.25842.06800.344516.6957
EDVR [50]8×22.93140.52700.48900.31761.29460.25321.64860.40273.2978
BasicVSR [5]8×22.24440.47570.51800.31142.17160.32422.51170.49534.0445
Ours8×22.92510.52700.46540.30751.15010.13771.58620.31344.4257*
", + "bbox": [ + 125, + 391, + 841, + 626 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Metrics. To evaluate the difference between SR results and ground truth, we use various reconstruction metrics. These encompass two fidelity metrics, PSNR and SSIM, alongside two perceptual metrics, LPIPS [55] and DISTS [10]. For EM image segmentation evaluation, we use VOI [41] and ARAND [1] as our metrics. In our segmentation evaluation, we consider both split error and merge error to ensure a comprehensive and accurate assessment.", + "bbox": [ + 75, + 628, + 468, + 750 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Training setting. We train the networks in three stages using Adam [27] optimizer with $\\beta_{1} = 0.9$ , $\\beta_{2} = 0.99$ and employ Cosine Annealing scheme [37]. In our experiments, we set all initial learning rates to $4\\times 10^{-4}$ except for Stage III on the mouse somatosensory cortex training dataset, where we adjust the initial learning rate to $1\\times 10^{-4}$ to ensure the convergence of deformable convolution layer. To generate paired data, we use bicubic downsampling to reduce the image resolution by factors of 8 and 16. The LR patch size is set to $16\\times 16$ for $16\\times$ EMSR and $32\\times 32$", + "bbox": [ + 75, + 750, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "for $8 \\times$ EMSR during Stage III training phase. The compression patch size $p$ is set to 16 based on our ablation studies. We select the weights for our loss functions as follows: $\\lambda_{c} = 10$ , $\\lambda_{adv} = 0.05$ , and $\\lambda_{MFid} = 0.01$ for $16 \\times$ EMSR, and $\\lambda_{MFid} = 0.001$ for $8 \\times$ EMSR. These weights are chosen through empirical experimentation aimed at striking the right balance for optimal performance. We also set the number of latent vectors to $v = 1024$ and their dimension to $d = 512$ in the codebook based on our ablation studies.", + "bbox": [ + 496, + 628, + 890, + 765 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Comparisons with Existing Methods", + "text_level": 1, + "bbox": [ + 498, + 776, + 815, + 792 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We compare our framework with (1) single-image SR methods including RCAN [56], SwinIR [35], BSRN [34], and Real-ESRGAN [51], (2) video SR methods including EDVR [50] and BasicVSR [5]. All these models are pretrained on the same EM datasets for fair comparisons. The quantitative results of image reconstruction and EM image segmentation are summarized in Table 1 and Table 2.", + "bbox": [ + 496, + 794, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "11318", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/ab0bc3ef16e34c4218f80b2e9993eab993d88cd815de43e4133ce5dc9df647c0.jpg", + "image_caption": [ + "Figure 2. Top: Qualitative comparison for $16 \\times$ EMSR. Our framework exhibits sharper boundaries and preserves a more complete structure. Bottom: Qualitative comparison for $16 \\times$ EMSR in terms of segmentation." + ], + "image_footnote": [], + "bbox": [ + 83, + 92, + 261, + 229 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/41483e2cd87305aa907cc85843fa1734a4b90bee0d91fc7130ffec6a49e2161a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 261, + 92, + 349, + 238 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/7a2fb841ff92e6f3131a6fc1e491e96f2bf694b771432fb080dc8ec7376497ed.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 351, + 92, + 437, + 238 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ce6a810af5dc4c60b30bfe48c24f839936b49afe8379046441dab9c5b7cdc58c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 439, + 92, + 527, + 239 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/85af61c2f2875bce49d6635eff3e03fa945b0a8e4c6f710da37d1b64cfb40ac1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 527, + 92, + 616, + 239 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/7ee40a7c1ecb434accea76b28b575755a4ec41588459985cecba1e9d952cfd5c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 616, + 92, + 705, + 239 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/95877bf9cdfb719cdcf9d9762777aef4773a6583552246182f8a08c597d48f3a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 705, + 92, + 792, + 239 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/260d8d01c3d0c2179684afc552e41b87206b3ba3a4e2d462f5874a758b069069.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 794, + 92, + 883, + 239 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/b4ec9d36b8502c46f22b6411480603ebb8d8f228dc5393d7ac6e7bdcb85b6805.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 83, + 287, + 261, + 425 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/545101d11cbd46ff61a8a3e1e9de8ecfb697b6ed60d66480254688011fb812c2.jpg", + "image_caption": [ + "Figure 3. Top: Qualitative comparison for $8 \\times$ EMSR. Our framework exhibits sharper boundaries and preserves a more complete structure. Bottom: Qualitative comparison for $8 \\times$ EMSR in terms of segmentation." + ], + "image_footnote": [], + "bbox": [ + 261, + 287, + 349, + 436 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a22aed93f768eac5d392afa88e8e2e12b5de2db81cb1a97ea662b44278299e9d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 351, + 287, + 437, + 436 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/bf56ce122694153570fa1a267c8763130e2b0181d85ee2b3e30a72a89279d76e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 439, + 287, + 527, + 436 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/c576b278bc678464332604850da700166e1d68d140719d27b7bcc41967b84bf8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 527, + 287, + 616, + 436 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ea6553e5d093b497bd25066f27fc0e38cb6752aded82afd797a985778b1b047d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 617, + 287, + 705, + 436 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/b9963105a2a475613e10bef6e906ace68ff39f75d23c04528cba6715dc18782a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 705, + 287, + 794, + 436 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/405795ed7ab59a8dfb924abeceb9638e2fb4ca9b5ddfe07c6cdaee66ac2d7aaa.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 794, + 287, + 883, + 436 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Reconstruction quality. While our framework performs the second-best in terms of PSNR and SSIM, slightly behind EDVR, these fidelity metrics do not necessarily align with human perception of image quality. On the other hand, our framework surpasses all other methods in terms of perceptual metrics LPIPS [55] and DISTS [10]. As shown in Figure 2 and Figure 3, our framework produces images with sharper boundaries, richer texture details, and more complete structures for $16 \\times$ and $8 \\times$ EMSR. This demonstrates that our cell-specific generative priors and the MPF module can effectively incorporate fine-grained details from HR EM images instead of producing smoothed results at the pixel level. It is noteworthy that although Real-ESRGAN [51] partially alleviates over-smoothing by incorporating the adversarial loss, it introduces noticeable noise-like artifacts in the super-resolved images. Additionally, a general comparison between single-image and video SR methods supports the effectiveness of incorporating adjacent EM images in the context of large-factor EMSR.", + "bbox": [ + 75, + 481, + 472, + 770 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "EM image segmentation accuracy. We evaluate the accuracy of two pre-trained segmentation networks by using the super-resolved EM images as inputs. Our framework outperforms all other methods with two different segmentation networks, demonstrating exceptional image fidelity in terms of downstream tasks achieved by our framework. Moreover, our framework effectively addresses the issue of over-segmentation caused by excessive smoothing of ex", + "bbox": [ + 75, + 780, + 468, + 902 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/84ea49445c463ae22037afc430b0a208b639d30306f0b6e0688322ec6d315e16.jpg", + "table_caption": [ + "Table 3. Ablation studies on prior exploration and prior indexing trade-off. p denotes the compression patch size." + ], + "table_footnote": [], + "table_body": "
PStage IStage IIΔPSNRΔLPIPS
PSNR↑LPIPS↓PSNR↑LPIPS↓
835.07310.261820.12120.5240-14.95190.2622
1628.68760.371521.74230.4996-6.94530.1281
3223.18790.469321.52910.5024-1.65880.0331
6420.28320.622620.16090.6263-0.12230.0037
", + "bbox": [ + 504, + 512, + 887, + 589 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "isting methods, which is particularly prominent in the Superhuman segmentation network (see supplementary material for detail). Visualization examples of segmentation, as shown in Figure 2 and Figure 3, confirm the superiority of our framework over existing methods.", + "bbox": [ + 496, + 611, + 890, + 686 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Ablation Studies", + "text_level": 1, + "bbox": [ + 500, + 691, + 663, + 707 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effectiveness of prior exploration. Table 3 presents a quantitative analysis of the prior exploration process. As the mapping from the HR space to the latent space involves a compression process, the size of the compression patch is a crucial hyperparameter. In Stage I, a smaller compression patch size captures more detailed information and leads to more realistic generated images. We observe a significant improvement in both PSNR and LPIPS as the compression patch size decreases, indicating improvements in reconstruction quality and fidelity.", + "bbox": [ + 496, + 712, + 890, + 864 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Trade-off between prior exploration and prior indexing. There exists a trade-off between the quality of generated im", + "bbox": [ + 500, + 869, + 890, + 901 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "11319", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/2a08bf77344d9368af2ce66b228506636199ece61cb52c7f8b08735acba7a86d.jpg", + "image_caption": [ + "Figure 4. Qualitative comparison of prior indexing results and the effectiveness of the latent vector indexer. $p$ denotes the compression patch size." + ], + "image_footnote": [], + "bbox": [ + 84, + 95, + 464, + 166 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/58e3f1b2c6bbeb599ab8e72918a79d558a3dbeebd0d0fba629691096d2ece0a9.jpg", + "table_caption": [ + "Table 4. Ablation studies on the quantity $v$ and dimensions $d$ of latent vectors in the codebook on prior exploration." + ], + "table_footnote": [], + "table_body": "
vdPSNR↑LPIPS↓
51251228.31650.3806
102425628.52270.3728
102451228.68760.3715
204851228.71590.3712
1024102428.75740.3743
", + "bbox": [ + 163, + 257, + 379, + 337 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ages in Stage I and the accuracy of predicting latent vectors through the latent vector indexer in Stage II. This trade-off arises from the fact that as the compression patch size decreases and less information is available when feeding LR images into the latent vector indexer in Stage II, the learned posterior distribution of LR EM images $q_{\\varphi}(\\xi \\mid o_{\\downarrow})$ deviates further from the true posterior distribution $q(\\xi \\mid o_{\\downarrow})$ . Consequently, reducing the compression patch size allows the first stage network to preserve more image details, but it poses challenges for the indexing task in Stage II. This can be observed from the changes in $\\Delta PSNR$ and $\\Delta LPIPS$ values presented in Table 3, which indicate a decrease in the indexing accuracy as the compression patch size decreases. In consideration of the trade-off between prior exploration and prior indexing, we set $p = 16$ , as depicted in Table 3 and Figure 4. Moreover, as illustrated in Figure 4, removing the latent vector indexer and directly utilizing bicubic interpolation along with the decoder in Stage I leads to notably blurry $I_{Ref}$ outcomes.", + "bbox": [ + 73, + 358, + 468, + 648 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Impact of the quantity and dimensions of latent vectors in the codebook. We systematically investigate the impact of the quantity and dimensions of latent vectors in the codebook by selecting several sets of representative parameters. The results are summarized in Table 4. From the experimental results, we observe that augmenting $v$ to 2048 or $d$ to 1024 does not yield significant improvements in prior exploration, despite doubling the codebook's size. Conversely, reducing $v$ to 512 or $d$ to 256 results in a noticeable performance decline. Based on these insightful results, we set $v = 1024$ and $d = 512$ for our codebook. This decision strikes an optimal balance between computational efficiency and performance.", + "bbox": [ + 75, + 652, + 468, + 849 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effectiveness of POD module and 3DA module. We evaluate the effectiveness of the proposed POD and 3DA modules for multi-image feature alignment and multi-image", + "bbox": [ + 75, + 854, + 468, + 902 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/0bafb0dc4d59920758da2187ed9502e65e2c4f241f2e23ed83cb8e1a85772158.jpg", + "table_caption": [ + "Table 5. Ablation studies of our proposed modules. VOI-S and VOI-M denote segmentation using Superhuman and MALA, respectively." + ], + "table_footnote": [], + "table_body": "
MPFPOD3DAPSNR↑LPIPS↓VOI-S↓VOI-M↓
XXX23.52870.51684.59122.7265
X✓✓23.73540.50634.24292.3410
✓X✓23.54220.48583.15002.5144
✓✓X23.55480.48153.01932.3794
✓✓✓23.67670.47902.96392.2571
", + "bbox": [ + 514, + 133, + 874, + 220 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "feature fusion, respectively. To ensure a fair comparison, we replace these modules with residual blocks with comparable parameters. Table 5 shows the results of our ablation study. We observe that even without incorporating generative prior, the introduction of the POD module or 3DA module leads to improvements in both reconstruction evaluation metrics and segmentation metrics, as demonstrated in row 1 and row 2. Furthermore, when the generative prior is introduced, both the POD module and the 3DA module provide additional gains in reconstruction and segmentation metrics, as shown in rows 3 to 5. Notably, the POD module exhibits a larger improvement compared to the 3DA module, indicating its significance in multi-image feature alignment for large-factor EMSR. These results demonstrate the effectiveness of the proposed POD and 3DA modules in enhancing visual reconstruction quality and segmentation accuracy.", + "bbox": [ + 496, + 243, + 890, + 484 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effectiveness of MPF module. The effectiveness of our MPF module is further demonstrated in row 2 and row 5 of Table 5, where it exhibits substantial improvements in perceptual metric LPIPS and segmentation metric VOI. It is important to note that the introduction of $L_{Mfd}$ in Stage III leads to a decrease in PSNR. This observation highlights the inconsistency between PSNR and visual quality as well as segmentation outcomes and reinforces the importance of using perceptual metrics and segmentation metrics to evaluate reconstruction quality.", + "bbox": [ + 496, + 494, + 892, + 647 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 659, + 619, + 674 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we present a generative learning-based framework for large-factor EMSR. By exploring and indexing cell-specific priors using a VQGAN-Indexer network, our framework leverages generative learning to capture the repetitive structures and textures of EM images. The MPF module effectively fuses generative priors obtained from the VQGAN-Indexer network while ensuring the image fidelity. Extensive experiments demonstrate the superiority of our framework in terms of both reconstruction quality and segmentation accuracy for $8 \\times$ and $16 \\times$ EMSR.", + "bbox": [ + 496, + 683, + 890, + 834 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgment", + "text_level": 1, + "bbox": [ + 500, + 847, + 651, + 864 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported in part by the National Natural Science Foundation of China under Grant 62021001.", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "11320", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 106 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Ignacio Arganda-Carreras, Srinivas C Turaga, Daniel R Berger, Dan Ciresan, Alessandro Giusti, Luca M Gambardella, Jürgen Schmidhuber, Dmitry Laptev, Sarvesh Dwivedi, Joachim M Buhmann, et al. 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In CVPR, 2019. 2" + ], + "bbox": [ + 501, + 92, + 890, + 728 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "11322", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_model.json b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_model.json new file mode 100644 index 0000000000000000000000000000000000000000..0bab9bf5eccff0beb9afc70abd9bc013f7e57b00 --- /dev/null +++ b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_model.json @@ -0,0 +1,2167 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.105, + 0.131, + 0.868, + 0.154 + ], + "angle": 0, + "content": "Learning Large-Factor EM Image Super-Resolution with Generative Priors" + }, + { + "type": "text", + "bbox": [ + 0.197, + 0.18, + 0.773, + 0.218 + ], + "angle": 0, + "content": "Jiateng Shou1 Zeyu Xiao1 Shiyu Deng1 Wei Huang1 Peiyao Shi3 Ruobing Zhang3,2 Zhiwei Xiong1,2 Feng Wu1,2,†" + }, + { + "type": "text", + "bbox": [ + 0.113, + 0.219, + 0.858, + 0.235 + ], + "angle": 0, + "content": "1 MoE Key Laboratory of Brain-inspired Intelligent Perception and Cognition, University of Science and Technology of China" + }, + { + "type": "text", + "bbox": [ + 0.242, + 0.236, + 0.729, + 0.251 + ], + "angle": 0, + "content": "\\(^{2}\\)Institute of Artificial Intelligence, Hefei Comprehensive National Science Center" + }, + { + "type": "text", + "bbox": [ + 0.208, + 0.254, + 0.761, + 0.269 + ], + "angle": 0, + "content": "\\(^{3}\\)Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences" + }, + { + "type": "text", + "bbox": [ + 0.248, + 0.273, + 0.717, + 0.287 + ], + "angle": 0, + "content": "shoujt@mail.ustc.edu.cn {zwxiong,fengwu}@ustc.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.322, + 0.314, + 0.339 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.351, + 0.474, + 0.773 + ], + "angle": 0, + "content": "As the mainstream technique for capturing images of biological specimens at nanometer resolution, electron microscopy (EM) is extremely time-consuming for scanning wide field-of-view (FOV) specimens. In this paper, we investigate a challenging task of large-factor EM image super-resolution (EMSR), which holds great promise for reducing scanning time, relaxing acquisition conditions, and expanding imaging FOV. By exploiting the repetitive structures and volumetric coherence of EM images, we propose the first generative learning-based framework for large-factor EMSR. Specifically, motivated by the predictability of repetitive structures and textures in EM images, we first learn a discrete codebook in the latent space to represent high-resolution (HR) cell-specific priors and a latent vector indexer to map low-resolution (LR) EM images to their corresponding latent vectors in a generative manner. By incorporating the generative cell-specific priors from HR EM images through a multi-scale prior fusion module, we then deploy multi-image feature alignment and fusion to further exploit the inter-section coherence in the volumetric EM data. Extensive experiments demonstrate that our proposed framework outperforms advanced single-image and video super-resolution methods for \\(8 \\times\\) and \\(16 \\times\\) EMSR (i.e., with 64 times and 256 times less data acquired, respectively), achieving superior visual reconstruction quality and downstream segmentation accuracy on benchmark EM datasets. Code is available at https://github.com/jtshou/GPEMSR." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.793, + 0.21, + 0.809 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.815, + 0.47, + 0.877 + ], + "angle": 0, + "content": "Electron microscopy (EM) is a commonly used imaging technique in life sciences to investigate the ultrastructure of cells, tissues, organelles, and macromolecular complexes, which captures images of biological specimens at nanome" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.324, + 0.892, + 0.488 + ], + "angle": 0, + "content": "ter resolution. However, high-quality EM image acquisition typically requires a strict and time-consuming process, involving careful adjustments of beam current, aperture size, and detector settings. This process may take up to years to scan wide field-of-view (FOV) specimens. For example, Zheng et al. [57] spent approximately 16 months to acquire a \\(\\sim 106\\mathrm{TB}\\) whole-brain dataset of an adult drosophila melanogaster. The long acquisition time greatly limits the application of EM imaging in analyzing complete biological structures in large specimens, such as neuron connections in mammalian brains." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.491, + 0.893, + 0.748 + ], + "angle": 0, + "content": "Image super-resolution (SR), which is capable of restoring high-resolution (HR) images from their corresponding low-resolution (LR) observations, has the potential to revolutionize EM imaging by allowing for faster and less restrictive data acquisition, while also providing high-quality images with a wide field of view. By applying SR to EM images (shorted as EMSR hereafter), the capturing time can be significantly reduced, and the strict capturing conditions can be relaxed. By deploying a simple ResNet-based UNet model, Fang et al. [13] have demonstrated the promising performance of EMSR for \\(4\\times\\) magnification (i.e., with 16 times less data acquired). However, achieving even larger-factor EMSR to further reduce capturing time remains challenging. This is in accordance with existing methods [5, 18, 30, 35, 50, 58] for natural images, which can achieve satisfactory results for up to \\(4\\times\\) magnification, but fail to meet the demand for larger factors." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.895, + 0.902 + ], + "angle": 0, + "content": "On the other hand, recent advances in generative models, such as ChatGPT and diffusion-based models [9, 16, 21, 43], reveal powerful capability in automatic content generation, including natural languages and images. This motivates us to consider the EMSR task from a generative perspective. Especially, compared with natural images that possess diverse structures and textures, EM images often exhibit repetitive structures and textures due to the predictability of imaging specimens, making it more suitable to leverage generative learning for accurate reconstruction. In" + }, + { + "type": "page_footnote", + "bbox": [ + 0.103, + 0.887, + 0.229, + 0.901 + ], + "angle": 0, + "content": "†Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "11313" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.198 + ], + "angle": 0, + "content": "this paper, we propose a novel deep learning-based framework tailored to the challenging task of large-factor EMSR, by 1) exploiting the repetitive structures and textures in EM images with generative cell-specific priors learned from HR EM images, and 2) exploiting the inter-section coherence in the volumetric EM data by aggregating features learned from multiple consecutive images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.2, + 0.471, + 0.412 + ], + "angle": 0, + "content": "Specifically, our framework explores cell-specific priors using a VQGAN-Indexer network, consisting of VQGAN [12] and our proposed latent vector indexer. We first learn a discrete codebook to represent the distribution of HR EM images in the latent space. The codebook captures both structure and texture information, while the decoder establishes relationships between latent vectors and image patches. We then train a latent vector indexer to acquire the corresponding latent vectors and integrate the indexer with the codebook and the decoder for generating HR EM images. By treating the generation process as an indexing task, we can match LR EM images with their corresponding HR feature representations from the latent space, thereby obtaining priors solely derived from HR EM images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.415, + 0.47, + 0.748 + ], + "angle": 0, + "content": "To maintain reconstruction quality while prioritizing downstream segmentation accuracy, we propose a MultiScale Prior Fusion (MPF) module for incorporating the above learned cell-specific priors in EMSR. We use the VQGAN-Indexer output as reference images and learn a mask for fusing reference features based on the patch-level cosine similarity between LR EM images and corresponding reference images. To fully utilize the latent vectors and relationships learned by the decoder, we use multi-scale reference features from different layers of the decoder with varying resolutions. Following the MPF module, our framework includes two key steps for exploiting inter-section coherence in the volumetric EM data: multi-image feature alignment (along the axial direction) and multi-image feature fusion. To this end, we introduce a Pyramid Optical-flow-based Deformable convolution alignment (POD) module and a 3D Spatial-Attention fusion (3DA) module. The former leverages a pre-trained optical-flow network SPyNet [42] and deformable convolutions [6, 60], while the latter leverages the spatial attention mechanism and 3D convolutions. Both improve reconstruction quality and downstream segmentation accuracy for large-factor EMSR." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.903 + ], + "angle": 0, + "content": "In summary, this paper offers the following contributions. 1) We present the first generative learning-based framework for the challenging task of large-factor EMSR. 2) We introduce the VQGAN-Indexer network to explore generative cell-specific prior information from HR EM images. 3) We propose the MPF module to effectively utilize the generative priors while preserving image fidelity with LR observations, followed by the POD and 3DA modules for multi-image feature alignment and fusion. 4) Extensive experiments demonstrate the superiority of our framework" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.892, + 0.122 + ], + "angle": 0, + "content": "in terms of both reconstruction quality and downstream segmentation accuracy for \\(8 \\times\\) and \\(16 \\times\\) EMSR." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.129, + 0.642, + 0.144 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.151, + 0.892, + 0.513 + ], + "angle": 0, + "content": "Electron microscopy image super-resolution. Existing EMSR methods can be categorized into two types: restoring isotropic volumes from anisotropic ones, i.e., SR along the axial dimension [8, 20], and reconstructing HR images from corresponding LR observations in the lateral dimensions [7, 13, 40, 46, 53]. We focus on the latter task in this paper, while our proposed framework may also apply to the former task. As a pioneering work in the field of EMSR, Sreehari et al. [46] introduce a Bayesian framework and utilize a library-based non-local means (LB-NLM) algorithm to achieve up to \\(16 \\times\\) EMSR without requiring a training process. However, this non-learning-based method limits performance and is not specifically designed for large-factor EMSR. Along the deep learning line, Nehme et al. [40] train a fully convolutional encoder-decoder network on simulated data to reconstruct super-resolved images. Hann et al. [7] train a GAN model using pairs of test specimens captured from the same region of interest. Xie et al. [53] leverage the attention mechanism to capture inter-section dependencies and shared features among adjacent images. Compared to previous EMSR methods, our framework not only utilizes adjacent EM images but also explores and integrates generative cell-specific priors to tackle the challenging task of large-factor EMSR." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.519, + 0.892, + 0.7 + ], + "angle": 0, + "content": "Video super-resolution. Video super-resolution (VSR) aims to restore HR frames by leveraging adjacent temporal information in multiple LR frames. To align temporal features, optical flow [3, 5, 26, 44, 49, 52, 54] and deformable convolution [47, 50], have been widely adopted. Recently, transformer-based approaches [4, 36] yield remarkable advancements in VSR, owing to the utilization of diverse attention mechanisms. Inspired by these VSR methods, to exploit the inter-section coherence in the volumetric EM data, we utilize optical-flow networks and deformable convolutions for multi-image feature alignment, and spatial attention mechanisms for multi-image feature fusion." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Generative priors in image restoration. Generative image restoration methods [11, 31-33] employ the priors from the pre-trained generative adversarial network (GAN), such as StyleGAN [24] and BigGAN [2], to approximate the natural image manifold and synthesize high-quality images. Given the superior performance of discrete codebook-based generative methods in semantic image synthesis, structure-to-image, and stochastic super-resolution tasks [12, 48], recent methods explore codebook-based facial priors [17, 59] by leveraging VQGAN [12] for training. Different from these methods, we propose a latent vector indexer to exploit the information contained within the input LR images, and the MPF module to fuse generative priors." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "11314" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.078, + 0.09, + 0.169, + 0.105 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.108, + 0.188, + 0.122 + ], + "angle": 0, + "content": "3.1. Overview" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.124, + 0.47, + 0.229 + ], + "angle": 0, + "content": "As illustrated in Figure 1, the goal of large-factor EMSR is to obtain the super-resolved \\( I_{SR}^{0} \\in \\mathbb{R}^{rH \\times rW \\times 1} \\), given a sequence of \\( 2N + 1 \\) consecutive LR EM images, \\( I_{LR}^{z} \\in \\mathbb{R}^{H \\times W \\times 1} \\), which should be close to the ground truth image \\( I_{GT}^{0} \\in \\mathbb{R}^{rH \\times rW \\times 1} \\), where \\( z \\in \\{-N, -N + 1, \\dots, 0, \\dots, N - 1, N\\} \\) and \\( r \\) is the large scale factor. In this paper, we set \\( N = 2 \\) and \\( r = 8, 16 \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.23, + 0.471, + 0.489 + ], + "angle": 0, + "content": "To achieve this, we propose a generative learning-based framework consisting of three stages. Stage I involves exploring generative cell-specific priors through the VQGAN model, which identifies a discrete latent space of HR EM images and generates the HR EM image \\(I_{\\mathrm{HRref}}\\) from the latent space. This latent space is represented using vectors from the VQGAN codebook \\(C\\). In Stage II, we train a latent vector indexer and connect it with the VQGAN codebook \\(C\\) and VQGAN decoder \\(Q\\) obtained from Stage I. This connection allows us to generate the reference HR EM image \\(I_{\\mathrm{Ref}}\\) and its corresponding multi-scale generative features \\(F_{\\mathrm{Ref}}^{l}\\) from the LR EM image \\(I_{\\mathrm{LR}}\\). Finally, in Stage III, we fuse the multi-scale generative features \\(F_{\\mathrm{Ref}}^{l}\\) using the MPF module, align adjacent image features in the axial direction using the POD module, and fuse the adjacent image features using the 3DA module. We finally use sub-pixel convolution to reconstruct the HR output \\(I_{SR}^{0}\\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.492, + 0.433, + 0.508 + ], + "angle": 0, + "content": "3.2. Exploring Generative Cell-Specific Priors" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.51, + 0.47, + 0.676 + ], + "angle": 0, + "content": "EM images are characterized by their repetitive structures and textures, such as cellular membranes and subcellular organelles. These features offer an opportunity to exploit their regularity and predictability, motivating our exploration of the generative cell-specific prior in EM images for large-factor EMSR. As shown in Figure 1 (a), our framework for exploring generative cell-specific prior exploration consists of two main steps. First, we identify a discrete latent space that represents the features of HR EM images. Then, we generate the HR EM images from this latent space, leveraging its compact and representative nature." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.679, + 0.47, + 0.831 + ], + "angle": 0, + "content": "Identifying a discrete latent space. We aim to identify a discrete latent space that represents HR EM images. To achieve this, we utilize an encoder \\( \\pmb{E} \\) to parameterize the posterior categorical distribution of HR EM images \\( q_{\\phi}(\\xi \\mid o) \\), where \\( \\xi \\) represents the variable for latent vectors, \\( o \\) represents the variable for HR EM images and \\( \\phi \\) represents the encoder's parameters. Specifically, we quantize the output feature \\( Z_{e} \\) from \\( \\pmb{E} \\) by mapping it to its closest latent vector in \\( C \\) and obtain the quantified feature \\( Z_{d} \\) and one-hot index of each mapped HR patch, denoted as \\( s^{m,n} \\)" + }, + { + "type": "equation", + "bbox": [ + 0.096, + 0.841, + 0.469, + 0.905 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} Z _ {d} ^ {m, n} = \\arg \\min _ {Z _ {q} [ j ]} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2}, \\\\ s ^ {m, n} [ k ] = \\left\\{ \\begin{array}{l l} 1, & k = \\arg \\min _ {j} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2} \\\\ 0, & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {1} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.091, + 0.895, + 0.214 + ], + "angle": 0, + "content": "where \\( Z_{q}[j] \\) denotes the \\( j \\)-th latent vector stored in \\( C \\). \\( Z_{e}^{m,n} \\) denotes the encoder output feature element at position \\( (m,n) \\) within \\( Z_{e} \\), while \\( Z_{d}^{m,n} \\) denotes the quantified feature element at position \\( (m,n) \\) within \\( Z_{d} \\). \\( s^{m,n} \\) is a v-dimensional vector and \\( s^{m,n}[k] \\) denotes the \\( k \\)-th element in \\( s^{m,n} \\). The codebook \\( C \\) consists of \\( v \\) latent vectors, each with a dimensionality of \\( d \\). Thus, the posterior categorical distribution \\( q_{\\phi}(\\xi | o) \\) is defined as" + }, + { + "type": "equation", + "bbox": [ + 0.499, + 0.225, + 0.925, + 0.278 + ], + "angle": 0, + "content": "\\[\nq _ {\\phi} (\\xi = k \\mid o) = \\left\\{ \\begin{array}{l l} 1, & Z _ {q} [ k ] = \\arg \\min _ {Z _ {q} [ j ]} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2} \\\\ 0, & \\text {o t h e r w i s e} \\end{array} . \\right. \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.287, + 0.892, + 0.362 + ], + "angle": 0, + "content": "Generating the HR EM image. Given the quantified feature \\( Z_{d} \\), we can generate HR EM image \\( I_{\\mathrm{HRref}} \\) through the decoder. We parameterize the prior distribution of HR EM images \\( p_{\\theta}(o \\mid \\xi) \\) through the decoder \\( Q \\), where \\( \\theta \\) is the parameters of the decoder." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.363, + 0.892, + 0.484 + ], + "angle": 0, + "content": "The encoder is composed of multiple Res-blocks [19] and convolution blocks for downsampling, while the decoder is composed of multiple Res-blocks and deconvolution blocks for upsampling. The compression patch size for downsampling is set to \\( p \\). Both the encoder and decoder leverage self-attention mechanisms to enhance generalization quality. We optimize the latent vector \\( Z_{q}[j] \\) along with the encoder \\( E \\) and decoder \\( Q \\)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.489, + 0.734, + 0.505 + ], + "angle": 0, + "content": "3.3. Generating LR Reference" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.507, + 0.892, + 0.612 + ], + "angle": 0, + "content": "With the parameterization of the latent space using \\( C \\) and the prior distribution of HR EM images using \\( Q \\), we can generate HR EM images given real HR EM images as input. However, in the large-factor EMSR task, only highly degraded LR images are available as input. Hence, we need to map the LR images to their corresponding quantified feature \\( Z_{d} \\) to utilize the generative cell-prior stored in \\( C \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.613, + 0.893, + 0.901 + ], + "angle": 0, + "content": "To achieve this, one straightforward approach is to interpolate the LR images and feed them into the encoder [17]. This straightforward approach approximates the posterior categorical distribution of LR EM images \\( q(\\xi \\mid o_{\\downarrow}) \\) by utilizing the parameterized posterior categorical distribution of HR EM images \\( q_{\\phi}(\\xi \\mid [o_{\\downarrow}]_{\\uparrow}) \\) with the interpolation operation. Here, \\( o_{\\downarrow} \\) represents the LR image variable, and \\( [\\cdot]_{\\uparrow} \\) denotes the interpolation operation. However, in scenarios where significant degradation occurs in LR input images, the interpolation operation struggles to restore the rich details and textures in HR EM images. Consequently, this mismatch leads to discrepancies between the real HR EM image distribution \\( p(o) \\) and the interpolated HR EM image distribution \\( p([o_{\\downarrow}]_{\\uparrow}) \\), thereby resulting in disparities between \\( q(\\xi \\mid o_{\\downarrow}) \\) and \\( q_{\\phi}(\\xi \\mid [o_{\\downarrow}]_{\\uparrow}) \\). Despite the loss of fine-grained details in LR images, the partial preservation of information enables the utilization of such details as priors in mapping LR images to their corresponding quantified feature \\( Z_{d} \\). To fully utilize these priors, we propose a latent" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "11315" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.088, + 0.094, + 0.647, + 0.467 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.651, + 0.094, + 0.882, + 0.466 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.475, + 0.896, + 0.559 + ], + "angle": 0, + "content": "Figure 1. Overview of our framework. The proposed generative learning-based framework consists of three stages. In Stage I, the encoder, the codebook, and the decoder are trained by self-generating the input HR EM image. In Stage II, a latent vector indexer is trained and connected with the codebook and the decoder with fixed parameters to generate the reference HR EM image and multi-scale generative features from the LR EM image. In Stage III, the HR output is reconstructed by fusing multi-scale generative features and exploiting inter-section coherence in volumetric EM data with the POD module and the 3DA module. Rec denotes reconstruction layers composed of convolution layers and pixel shuffle operation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.562, + 0.473, + 0.684 + ], + "angle": 0, + "content": "vector indexer \\( W \\) to predict probabilities of corresponding latent vectors in \\( C \\) given LR EM images as input, as shown in Figure 1 (b). We denote the output of the latent vector indexer as \\( Z_{w} \\), where the element at position \\( (m,n) \\) is denoted as \\( Z_{w}^{m,n} \\) and represents a \\( v \\)-dimensional vector. Then, by selecting the latent vector with the highest probability, we can effectively model the posterior categorical distribution \\( q(\\xi \\mid o_{\\downarrow}) \\) as" + }, + { + "type": "equation", + "bbox": [ + 0.077, + 0.697, + 0.479, + 0.748 + ], + "angle": 0, + "content": "\\[\nq _ {\\varphi} (\\xi = k \\mid o _ {\\downarrow}) = \\left\\{ \\begin{array}{l l} 1, & k = \\arg \\max _ {i \\in \\{1, 2, 3, \\dots , v \\}} Z _ {w} ^ {m, n} [ i ] \\\\ 0, & \\text {o t h e r w i s e} \\end{array} \\right., \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.75, + 0.471, + 0.781 + ], + "angle": 0, + "content": "where \\(\\varphi\\) denotes the parameters of the latent vector indexer \\(W\\). \\(Z_{w}^{m,n}[i]\\) denotes the \\(i\\)-th element of the vector \\(Z_{w}^{m,n}\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.471, + 0.902 + ], + "angle": 0, + "content": "This quantization operation allows us to capture the most representative latent vector that corresponds to the LR image. Then the predicted quantified feature \\( Z_{d}^{pre} \\) is obtained and fed into the decoder to generate the reference HR EM image \\( I_{\\mathrm{Ref}} \\) and its corresponding multi-scale generative features \\( F_{\\mathrm{Ref}}^{l} \\) through the decoder. Note that all the latent vectors used to generate \\( I_{\\mathrm{Ref}} \\) and \\( F_{\\mathrm{Ref}}^{l} \\) are obtained from the codebook, which contains the generative cell-specific pri" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.562, + 0.654, + 0.578 + ], + "angle": 0, + "content": "ors of HR EM images." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.581, + 0.738, + 0.597 + ], + "angle": 0, + "content": "3.4. Reconstructing HR Image" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.892, + 0.735 + ], + "angle": 0, + "content": "MPF module. The complete process of reconstructing HR image is depicted in Figure 1 (c). The discrepancies between the generated HR image \\( I_{\\mathrm{Ref}} \\) and real EM image \\( I_{\\mathrm{GT}} \\) pose a challenge in achieving accurate multi-scale generative feature fusion. To overcome this challenge, we propose the MPF module, which focuses on identifying and fusing the multi-scale generative features. The MPF module comprises two essential processes: a mask-learning process and a multi-scale fusion process." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.893, + 0.901 + ], + "angle": 0, + "content": "The mask-learning mechanism within the MPF module enables us to identify and mask out multi-scale generative features in regions that show significant boundary differences compared to real HR images. As shown in Figure 1 (d), we first embed the interpolated LR image \\([I_{LR}]_{\\uparrow}\\) and the reference image \\(I_{Ref}\\) from the decoder into the feature space by a pre-trained VGG19 encoder [45]. We extract \\(16\\times 16\\) patches from LR feature maps and reference (Ref) feature maps without overlap. Then, We calculate cosine similarity vector \\(CS\\) between LR feature patches and Ref feature patches, where \\(CS_{i}\\) denotes cosine similarity be" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "11316" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.152 + ], + "angle": 0, + "content": "tween the \\(i\\)-th LR feature patch and the \\(i\\)-th Ref feature patch. We refine the mask by employing three 2D convolutions. Finally, we apply a sigmoid function to obtain the mask \\(M\\) with the same spatial resolution as LR features." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.152, + 0.473, + 0.32 + ], + "angle": 0, + "content": "To effectively fuse features from different layers of the decoder across \\(L\\) levels, we employ a multi-scale fusion scheme, as illustrated in Figure 1 (e). As the decoder learns the relationship between latent vectors, each layer of the decoder contains varying levels of detailed information about EM images. Additionally, since the decoder is responsible for reconstructing HR EM images, layers closer to the output represent shallower features. Given these considerations, we begin fusing features from \\(F_{Ref}^{0}\\) and its corresponding LR features \\(F_{LR}^{0}\\) with the same resolution and gradually incorporate features with lower resolution" + }, + { + "type": "equation", + "bbox": [ + 0.081, + 0.33, + 0.486, + 0.449 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\tilde {F} ^ {1} = R _ {D} ^ {0} \\left(R _ {F} ^ {0} \\left(\\left\\langle F _ {L R} ^ {0}, F _ {R e f} ^ {0} \\right\\rangle\\right) \\otimes [ M ] _ {\\uparrow 2 ^ {L - 1}}\\right), \\\\ \\tilde {F} ^ {l + 1} = R _ {D} ^ {l} \\left(\\langle R _ {F} ^ {l} \\left(\\langle \\tilde {F} ^ {l}, F _ {L R} ^ {l}, F _ {R e f} ^ {l} \\rangle\\right) \\otimes [ M ] _ {\\uparrow 2 ^ {L - l - 1}}, \\tilde {F} ^ {l} \\rangle\\right), \\\\ \\hat {F} = R _ {F} ^ {L - 1} \\left(\\langle \\tilde {F} ^ {L - 1}, F _ {L R} ^ {L - 1}, F _ {R e f} ^ {L - 1} \\rangle\\right) \\otimes M, \\\\ F ^ {O u t} = R _ {O} ^ {L - 1} \\left(\\langle \\hat {F}, \\tilde {F} ^ {L - 1}, F _ {L R} ^ {L - 1} \\rangle\\right), \\tag {4} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.45, + 0.47, + 0.573 + ], + "angle": 0, + "content": "where \\(\\otimes\\) denotes element-wise multiplication, \\(\\langle \\cdot \\rangle\\) denotes concatenation operation, and \\([\\cdot ]_{\\uparrow}\\) denotes interpolation operation. \\(\\tilde{F}^l\\) denotes output features from downsample convolution at the \\(l\\) -th level. \\(R_D^l,R_F^l\\) ,and \\(R_O^{L - 1}\\) denote downsample convolution, fusion convolution, and output convolution, respectively. \\(\\hat{F}\\) denotes the output feature of the last fusion convolution. \\(F^{Out}\\) represents the final multi-scale fusion feature." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.578, + 0.47, + 0.775 + ], + "angle": 0, + "content": "POD module and 3DA module. To exploit the intersection coherence in volumetric EM data and leverage the correlation between adjacent EM images, we design two modules: the POD module and the 3DA module. The POD module is responsible for aligning the adjacent EM image output features from the MPF module in a coarse-to-fine manner. It utilizes a pyramid architecture and incorporates a pre-trained optical-flow network SPyNet and deformable convolutions to achieve accurate feature alignment. The 3DA module employs spatial attention mechanisms and 3D convolutions to effectively fuse the aligned features. More detailed information about the POD module and 3DA module can be found in the supplementary material." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.778, + 0.25, + 0.794 + ], + "angle": 0, + "content": "3.5. Training Strategy" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.469, + 0.841 + ], + "angle": 0, + "content": "In Stage I, we adopt three loss functions: a reconstruction loss \\( L_{r - I} \\), a codebook learning loss \\( L_{c} \\), and an adversarial loss \\( L_{adv} \\)" + }, + { + "type": "equation", + "bbox": [ + 0.087, + 0.851, + 0.469, + 0.901 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} L _ {r - I} = \\left\\| I _ {\\mathrm {H R r e f}} - I _ {\\mathrm {G T}} \\right\\| _ {1}, L _ {a d v} = D \\left(I _ {\\mathrm {G T}}\\right) + D \\left(- I _ {\\mathrm {H R r e f}}\\right), \\\\ L _ {c} = \\left\\| \\operatorname {s g} \\left[ Z _ {d} \\right] - Z _ {e} \\right\\| _ {2} ^ {2} + \\left\\| \\operatorname {s g} \\left[ Z _ {e} \\right] - Z _ {d} \\right\\| _ {2} ^ {2}, \\tag {5} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.182 + ], + "angle": 0, + "content": "where \\(D\\) represents a PatchGAN discriminator [23] and \\(\\mathrm{sg}[\\cdot ]\\) denotes the stop-gradient operation. As Eq. 1 is non-differentiable, we propagate the gradients from the decoder to the encoder [12, 48]. We utilize R1 regularization [39] for GAN training stability. The complete objective of the first stage is" + }, + { + "type": "equation", + "bbox": [ + 0.577, + 0.193, + 0.892, + 0.209 + ], + "angle": 0, + "content": "\\[\nL _ {s - I} = L _ {r - I} + \\lambda_ {c} L _ {c} + \\lambda_ {a d v} L _ {a d v}. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.218, + 0.892, + 0.264 + ], + "angle": 0, + "content": "In Stage II, we optimize the latent vector indexer \\( W \\) while keeping the parameters of \\( C \\) and \\( Q \\) fixed. The objective of the second stage is" + }, + { + "type": "equation", + "bbox": [ + 0.525, + 0.272, + 0.892, + 0.311 + ], + "angle": 0, + "content": "\\[\nL _ {s - I I} = - \\sum_ {m, n, i} s ^ {m, n} [ i ] \\log \\frac {\\exp \\left(Z _ {w} ^ {m , n} [ i ]\\right)}{\\sum_ {j} \\exp \\left(Z _ {w} ^ {m , n} [ j ]\\right)}. \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.32, + 0.892, + 0.366 + ], + "angle": 0, + "content": "In Stage III, we train our network with two loss functions: a reconstruction loss \\( L_{r - III} \\) and a multi-Ref fidelity loss \\( L_{Mfid} \\) [28]. The objective of the third stage is" + }, + { + "type": "equation", + "bbox": [ + 0.549, + 0.375, + 0.891, + 0.459 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} L _ {r - I I I} = \\left\\| I _ {S R} ^ {0} - I _ {G T} ^ {0} \\right\\| _ {1}, \\\\ L _ {M f i d} = \\frac {\\sum_ {z ^ {\\prime} \\in \\Omega} \\sum_ {i} \\delta_ {i} \\left(I _ {S R} ^ {0} , I _ {R e f} ^ {z ^ {\\prime}}\\right) \\cdot c _ {z ^ {\\prime} , i}}{\\sum_ {z ^ {\\prime} \\in \\Omega} \\sum_ {i} c _ {z ^ {\\prime} , i}}, \\tag {8} \\\\ L _ {s - I I I} = L _ {r - I I I} + \\lambda_ {M f i d} L _ {M f i d}, \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.467, + 0.892, + 0.514 + ], + "angle": 0, + "content": "where \\(\\Omega = \\{-N, -N + 1, \\dots, 0, \\dots, N - 1, N\\}\\), \\(\\delta_i(\\cdot, \\cdot)\\) denotes contextual loss in [38] and \\(c_{z', i}\\) is the matching confidence weight based on cosine similarity." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.52, + 0.633, + 0.536 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.54, + 0.598, + 0.556 + ], + "angle": 0, + "content": "4.1. Settings" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.56, + 0.892, + 0.922 + ], + "angle": 0, + "content": "Datasets. We conduct experiments under two different settings to demonstrate the superior performance of our framework in both reconstruction quality and downstream segmentation accuracy. For the first setting, we select the adult drosophila melanogaster brain dataset FAFB [57] and its subset CREMI [14] acquired at \\(4 \\times 4 \\times 40\\mathrm{nm}^3\\) resolution. In Stage I and Stage II, we train our framework on a subset (\\(\\sim 38\\mathrm{G}\\)) of FAFB to obtain a cell-specific prior. In Stage III, we utilize the padded version of the CREMI dataset, excluding the CREMI C subset, to train for large-factor EMSR. We use the cropped version of CREMI C, which has segmentation labels, as the test set consisting of 125 images. We fine-tune two pre-trained segmentation networks, Superhuman [29] and MALA [15], on the first 75 images of CREMI C. Therefore, we test all 125 images for reconstruction evaluation metrics and the last 50 for segmentation evaluation metrics. For the second setting, we select the mouse somatosensory cortex dataset Kasthuri15 [25] and its subset AC3/AC4 dataset [25] acquired at \\(3 \\times 3 \\times 29\\mathrm{nm}^3\\) resolution. As the AC3/AC4 datasets are too small, we use the data partitioning strategy from [22] and train three stages on a subset (\\(\\sim 11.2\\mathrm{G}\\), i.e., Subset3 in [22]) of Kasthuri15 and AC3. We fine-tune two pre-trained segmentation networks on AC3 and test them on AC4." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "11317" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.089, + 0.894, + 0.119 + ], + "angle": 0, + "content": "Table 1. Quantitative comparison of reconstruction quality and EM image segmentation results on CREMI C for \\( {16} \\times \\) and \\( 8 \\times \\) EMSR. The best and the second-best results are highlighted in bold and underline. * Parameters optimized in Stage III." + }, + { + "type": "table", + "bbox": [ + 0.127, + 0.122, + 0.842, + 0.357 + ], + "angle": 0, + "content": "
MethodsScaleReconstruction MetricsSegmentation MetricsParams/M
FidelityPerceptualSuperhumanMALA
PSNR↑SSIM↑LPIPS↓DISTS↓VOI↓ARAND↓VOI↓ARAND↓
Bicubic16×21.55570.48010.73380.48426.66270.70436.55990.8830-
RCAN [56]16×23.12380.57790.53360.34295.27620.61932.93530.232512.9080
SwinIR [35]16×23.10980.57810.53320.34165.12540.49552.93020.231712.1426
BSRN [34]16×22.91610.56450.54530.34025.57280.68093.20340.26940.4719
Real-ESRGAN [51]16×22.76310.55370.53330.31344.08230.48903.38060.297316.6957
EDVR [50]16×23.88940.61470.50220.31824.17090.41322.32290.19693.4455
BasicVSR [5]16×23.38770.59240.51070.31764.58250.50532.54280.21153.9339
Ours16×23.67670.60200.47900.29272.96390.30752.25710.17865.4627*
Bicubic8×25.58970.66070.47790.29825.93040.87542.47480.2036-
RCAN [56]8×29.39260.79140.37290.23393.38580.32881.56340.133312.7603
SwinIR [35]8×29.43340.79210.37240.23403.34940.32671.54000.130611.9949
BSRN [34]8×29.14640.78320.37910.23133.59280.34611.56210.13150.3611
Real-ESRGAN [51]8×29.14570.78430.37740.23173.57400.33631.55550.130916.6957
EDVR [50]8×29.73260.80160.36420.23163.17390.31591.51070.13243.2978
BasicVSR [5]8×29.08280.78310.37740.23053.46190.33361.58790.13494.0445
Ours8×29.70270.80020.35680.22912.93760.30761.50110.12984.4257*
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.36, + 0.893, + 0.389 + ], + "angle": 0, + "content": "Table 2. Quantitative comparison of reconstruction quality and EM image segmentation results on AC4 for \\( {16} \\times \\) and \\( 8 \\times \\) EMSR. The best and the second-best results are highlighted in bold and underline. * Parameters optimized in Stage III." + }, + { + "type": "table", + "bbox": [ + 0.127, + 0.392, + 0.842, + 0.627 + ], + "angle": 0, + "content": "
MethodsScaleReconstruction MetricsSegmentation MetricsParams/M
FidelityPerceptualSuperhumanMALA
PSNR↑SSIM↑LPIPS↓DISTS↓VOI↓ARAND↓VOI↓ARAND↓
Bicubic16×19.00780.25180.77580.46396.93000.96886.81440.9664-
RCAN [56]16×19.59380.29810.66610.39706.45350.93516.47160.929412.9080
SwinIR [35]16×19.59490.29560.66710.38936.87960.94966.54170.932212.1426
BSRN [34]16×19.56130.29280.67250.39147.19610.96156.61680.93950.4719
Real-ESRGAN [51]16×19.42540.28930.64270.37066.38530.87456.06590.914016.6957
EDVR [50]16×19.93740.32830.62320.37314.81780.71585.00290.82823.4455
BasicVSR [5]16×19.42930.28880.67470.37476.86080.95986.75480.95133.9339
Ours16×19.74680.31140.57480.35844.36550.61264.83620.82335.4627*
Bicubic8×21.09790.37200.58960.33616.76940.96756.13460.9157-
RCAN [56]8×22.31670.47730.52000.31622.21010.28262.35710.388612.7603
SwinIR [35]8×22.49090.49310.51040.32131.78670.21072.36350.524211.9949
BSRN [34]8×22.27360.47360.52310.31322.26300.28602.51200.37460.3611
Real-ESRGAN [51]8×22.34390.48890.50000.31271.88390.25842.06800.344516.6957
EDVR [50]8×22.93140.52700.48900.31761.29460.25321.64860.40273.2978
BasicVSR [5]8×22.24440.47570.51800.31142.17160.32422.51170.49534.0445
Ours8×22.92510.52700.46540.30751.15010.13771.58620.31344.4257*
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.63, + 0.47, + 0.75 + ], + "angle": 0, + "content": "Metrics. To evaluate the difference between SR results and ground truth, we use various reconstruction metrics. These encompass two fidelity metrics, PSNR and SSIM, alongside two perceptual metrics, LPIPS [55] and DISTS [10]. For EM image segmentation evaluation, we use VOI [41] and ARAND [1] as our metrics. In our segmentation evaluation, we consider both split error and merge error to ensure a comprehensive and accurate assessment." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.751, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Training setting. We train the networks in three stages using Adam [27] optimizer with \\(\\beta_{1} = 0.9\\), \\(\\beta_{2} = 0.99\\) and employ Cosine Annealing scheme [37]. In our experiments, we set all initial learning rates to \\(4\\times 10^{-4}\\) except for Stage III on the mouse somatosensory cortex training dataset, where we adjust the initial learning rate to \\(1\\times 10^{-4}\\) to ensure the convergence of deformable convolution layer. To generate paired data, we use bicubic downsampling to reduce the image resolution by factors of 8 and 16. The LR patch size is set to \\(16\\times 16\\) for \\(16\\times\\) EMSR and \\(32\\times 32\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.63, + 0.892, + 0.766 + ], + "angle": 0, + "content": "for \\(8 \\times\\) EMSR during Stage III training phase. The compression patch size \\(p\\) is set to 16 based on our ablation studies. We select the weights for our loss functions as follows: \\(\\lambda_{c} = 10\\), \\(\\lambda_{adv} = 0.05\\), and \\(\\lambda_{MFid} = 0.01\\) for \\(16 \\times\\) EMSR, and \\(\\lambda_{MFid} = 0.001\\) for \\(8 \\times\\) EMSR. These weights are chosen through empirical experimentation aimed at striking the right balance for optimal performance. We also set the number of latent vectors to \\(v = 1024\\) and their dimension to \\(d = 512\\) in the codebook based on our ablation studies." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.777, + 0.816, + 0.793 + ], + "angle": 0, + "content": "4.2. Comparisons with Existing Methods" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We compare our framework with (1) single-image SR methods including RCAN [56], SwinIR [35], BSRN [34], and Real-ESRGAN [51], (2) video SR methods including EDVR [50] and BasicVSR [5]. All these models are pretrained on the same EM datasets for fair comparisons. The quantitative results of image reconstruction and EM image segmentation are summarized in Table 1 and Table 2." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "11318" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.093, + 0.263, + 0.231 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.263, + 0.093, + 0.351, + 0.239 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.352, + 0.093, + 0.439, + 0.239 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.44, + 0.093, + 0.528, + 0.24 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.529, + 0.093, + 0.617, + 0.24 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.617, + 0.093, + 0.706, + 0.24 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.706, + 0.093, + 0.794, + 0.24 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.795, + 0.093, + 0.885, + 0.24 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.247, + 0.892, + 0.275 + ], + "angle": 0, + "content": "Figure 2. Top: Qualitative comparison for \\(16 \\times\\) EMSR. Our framework exhibits sharper boundaries and preserves a more complete structure. Bottom: Qualitative comparison for \\(16 \\times\\) EMSR in terms of segmentation." + }, + { + "type": "image", + "bbox": [ + 0.084, + 0.288, + 0.262, + 0.426 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.263, + 0.288, + 0.351, + 0.437 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.352, + 0.288, + 0.439, + 0.437 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.44, + 0.288, + 0.528, + 0.437 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.529, + 0.288, + 0.617, + 0.437 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.618, + 0.288, + 0.706, + 0.437 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.706, + 0.288, + 0.795, + 0.437 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.795, + 0.288, + 0.885, + 0.437 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.442, + 0.89, + 0.471 + ], + "angle": 0, + "content": "Figure 3. Top: Qualitative comparison for \\(8 \\times\\) EMSR. Our framework exhibits sharper boundaries and preserves a more complete structure. Bottom: Qualitative comparison for \\(8 \\times\\) EMSR in terms of segmentation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.482, + 0.473, + 0.771 + ], + "angle": 0, + "content": "Reconstruction quality. While our framework performs the second-best in terms of PSNR and SSIM, slightly behind EDVR, these fidelity metrics do not necessarily align with human perception of image quality. On the other hand, our framework surpasses all other methods in terms of perceptual metrics LPIPS [55] and DISTS [10]. As shown in Figure 2 and Figure 3, our framework produces images with sharper boundaries, richer texture details, and more complete structures for \\(16 \\times\\) and \\(8 \\times\\) EMSR. This demonstrates that our cell-specific generative priors and the MPF module can effectively incorporate fine-grained details from HR EM images instead of producing smoothed results at the pixel level. It is noteworthy that although Real-ESRGAN [51] partially alleviates over-smoothing by incorporating the adversarial loss, it introduces noticeable noise-like artifacts in the super-resolved images. Additionally, a general comparison between single-image and video SR methods supports the effectiveness of incorporating adjacent EM images in the context of large-factor EMSR." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.47, + 0.903 + ], + "angle": 0, + "content": "EM image segmentation accuracy. We evaluate the accuracy of two pre-trained segmentation networks by using the super-resolved EM images as inputs. Our framework outperforms all other methods with two different segmentation networks, demonstrating exceptional image fidelity in terms of downstream tasks achieved by our framework. Moreover, our framework effectively addresses the issue of over-segmentation caused by excessive smoothing of ex" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.481, + 0.89, + 0.509 + ], + "angle": 0, + "content": "Table 3. Ablation studies on prior exploration and prior indexing trade-off. p denotes the compression patch size." + }, + { + "type": "table", + "bbox": [ + 0.506, + 0.513, + 0.888, + 0.59 + ], + "angle": 0, + "content": "
PStage IStage IIΔPSNRΔLPIPS
PSNR↑LPIPS↓PSNR↑LPIPS↓
835.07310.261820.12120.5240-14.95190.2622
1628.68760.371521.74230.4996-6.94530.1281
3223.18790.469321.52910.5024-1.65880.0331
6420.28320.622620.16090.6263-0.12230.0037
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.612, + 0.892, + 0.688 + ], + "angle": 0, + "content": "isting methods, which is particularly prominent in the Superhuman segmentation network (see supplementary material for detail). Visualization examples of segmentation, as shown in Figure 2 and Figure 3, confirm the superiority of our framework over existing methods." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.693, + 0.665, + 0.708 + ], + "angle": 0, + "content": "4.3. Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.713, + 0.892, + 0.865 + ], + "angle": 0, + "content": "Effectiveness of prior exploration. Table 3 presents a quantitative analysis of the prior exploration process. As the mapping from the HR space to the latent space involves a compression process, the size of the compression patch is a crucial hyperparameter. In Stage I, a smaller compression patch size captures more detailed information and leads to more realistic generated images. We observe a significant improvement in both PSNR and LPIPS as the compression patch size decreases, indicating improvements in reconstruction quality and fidelity." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Trade-off between prior exploration and prior indexing. There exists a trade-off between the quality of generated im" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "11319" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.086, + 0.096, + 0.465, + 0.167 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.172, + 0.47, + 0.214 + ], + "angle": 0, + "content": "Figure 4. Qualitative comparison of prior indexing results and the effectiveness of the latent vector indexer. \\( p \\) denotes the compression patch size." + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.225, + 0.471, + 0.253 + ], + "angle": 0, + "content": "Table 4. Ablation studies on the quantity \\( v \\) and dimensions \\( d \\) of latent vectors in the codebook on prior exploration." + }, + { + "type": "table", + "bbox": [ + 0.165, + 0.258, + 0.38, + 0.338 + ], + "angle": 0, + "content": "
vdPSNR↑LPIPS↓
51251228.31650.3806
102425628.52270.3728
102451228.68760.3715
204851228.71590.3712
1024102428.75740.3743
" + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.359, + 0.47, + 0.649 + ], + "angle": 0, + "content": "ages in Stage I and the accuracy of predicting latent vectors through the latent vector indexer in Stage II. This trade-off arises from the fact that as the compression patch size decreases and less information is available when feeding LR images into the latent vector indexer in Stage II, the learned posterior distribution of LR EM images \\( q_{\\varphi}(\\xi \\mid o_{\\downarrow}) \\) deviates further from the true posterior distribution \\( q(\\xi \\mid o_{\\downarrow}) \\). Consequently, reducing the compression patch size allows the first stage network to preserve more image details, but it poses challenges for the indexing task in Stage II. This can be observed from the changes in \\( \\Delta PSNR \\) and \\( \\Delta LPIPS \\) values presented in Table 3, which indicate a decrease in the indexing accuracy as the compression patch size decreases. In consideration of the trade-off between prior exploration and prior indexing, we set \\( p = 16 \\), as depicted in Table 3 and Figure 4. Moreover, as illustrated in Figure 4, removing the latent vector indexer and directly utilizing bicubic interpolation along with the decoder in Stage I leads to notably blurry \\( I_{Ref} \\) outcomes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.653, + 0.47, + 0.851 + ], + "angle": 0, + "content": "Impact of the quantity and dimensions of latent vectors in the codebook. We systematically investigate the impact of the quantity and dimensions of latent vectors in the codebook by selecting several sets of representative parameters. The results are summarized in Table 4. From the experimental results, we observe that augmenting \\( v \\) to 2048 or \\( d \\) to 1024 does not yield significant improvements in prior exploration, despite doubling the codebook's size. Conversely, reducing \\( v \\) to 512 or \\( d \\) to 256 results in a noticeable performance decline. Based on these insightful results, we set \\( v = 1024 \\) and \\( d = 512 \\) for our codebook. This decision strikes an optimal balance between computational efficiency and performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Effectiveness of POD module and 3DA module. We evaluate the effectiveness of the proposed POD and 3DA modules for multi-image feature alignment and multi-image" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.089, + 0.892, + 0.132 + ], + "angle": 0, + "content": "Table 5. Ablation studies of our proposed modules. VOI-S and VOI-M denote segmentation using Superhuman and MALA, respectively." + }, + { + "type": "table", + "bbox": [ + 0.515, + 0.135, + 0.875, + 0.221 + ], + "angle": 0, + "content": "
MPFPOD3DAPSNR↑LPIPS↓VOI-S↓VOI-M↓
XXX23.52870.51684.59122.7265
X✓✓23.73540.50634.24292.3410
✓X✓23.54220.48583.15002.5144
✓✓X23.55480.48153.01932.3794
✓✓✓23.67670.47902.96392.2571
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.244, + 0.892, + 0.486 + ], + "angle": 0, + "content": "feature fusion, respectively. To ensure a fair comparison, we replace these modules with residual blocks with comparable parameters. Table 5 shows the results of our ablation study. We observe that even without incorporating generative prior, the introduction of the POD module or 3DA module leads to improvements in both reconstruction evaluation metrics and segmentation metrics, as demonstrated in row 1 and row 2. Furthermore, when the generative prior is introduced, both the POD module and the 3DA module provide additional gains in reconstruction and segmentation metrics, as shown in rows 3 to 5. Notably, the POD module exhibits a larger improvement compared to the 3DA module, indicating its significance in multi-image feature alignment for large-factor EMSR. These results demonstrate the effectiveness of the proposed POD and 3DA modules in enhancing visual reconstruction quality and segmentation accuracy." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.496, + 0.893, + 0.648 + ], + "angle": 0, + "content": "Effectiveness of MPF module. The effectiveness of our MPF module is further demonstrated in row 2 and row 5 of Table 5, where it exhibits substantial improvements in perceptual metric LPIPS and segmentation metric VOI. It is important to note that the introduction of \\(L_{Mfd}\\) in Stage III leads to a decrease in PSNR. This observation highlights the inconsistency between PSNR and visual quality as well as segmentation outcomes and reinforces the importance of using perceptual metrics and segmentation metrics to evaluate reconstruction quality." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.66, + 0.62, + 0.675 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.684, + 0.892, + 0.835 + ], + "angle": 0, + "content": "In this paper, we present a generative learning-based framework for large-factor EMSR. By exploring and indexing cell-specific priors using a VQGAN-Indexer network, our framework leverages generative learning to capture the repetitive structures and textures of EM images. The MPF module effectively fuses generative priors obtained from the VQGAN-Indexer network while ensuring the image fidelity. Extensive experiments demonstrate the superiority of our framework in terms of both reconstruction quality and segmentation accuracy for \\(8 \\times\\) and \\(16 \\times\\) EMSR." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.848, + 0.652, + 0.866 + ], + "angle": 0, + "content": "Acknowledgment" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This work was supported in part by the National Natural Science Foundation of China under Grant 62021001." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "11320" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.176, + 0.107 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.198 + ], + "angle": 0, + "content": "[1] Ignacio Arganda-Carreras, Srinivas C Turaga, Daniel R Berger, Dan Ciresan, Alessandro Giusti, Luca M Gambardella, Jürgen Schmidhuber, Dmitry Laptev, Sarvesh Dwivedi, Joachim M Buhmann, et al. 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In CVPR, 2019. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.729 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "11322" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_origin.pdf b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..8b9b32dd10bb40260a50d1b7e474b0772fa84bd7 --- /dev/null +++ b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/246e675a-bddb-4921-a098-1fe2784b0d78_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:e4c96e21a42939ae8cdd95e828df53e3f41b210cba08dd1c41b3b4a3bb9fe79c +size 903106 diff --git a/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/full.md b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/full.md new file mode 100644 index 0000000000000000000000000000000000000000..433ead6bd4be6f668991ac5f0c6590240d1dbad0 --- /dev/null +++ b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/full.md @@ -0,0 +1,310 @@ +# Learning Large-Factor EM Image Super-Resolution with Generative Priors + +Jiateng Shou1 Zeyu Xiao1 Shiyu Deng1 Wei Huang1 Peiyao Shi3 Ruobing Zhang3,2 Zhiwei Xiong1,2 Feng Wu1,2,† + +1 MoE Key Laboratory of Brain-inspired Intelligent Perception and Cognition, University of Science and Technology of China + +$^{2}$ Institute of Artificial Intelligence, Hefei Comprehensive National Science Center + +$^{3}$ Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences + +shoujt@mail.ustc.edu.cn {zwxiong,fengwu}@ustc.edu.cn + +# Abstract + +As the mainstream technique for capturing images of biological specimens at nanometer resolution, electron microscopy (EM) is extremely time-consuming for scanning wide field-of-view (FOV) specimens. In this paper, we investigate a challenging task of large-factor EM image super-resolution (EMSR), which holds great promise for reducing scanning time, relaxing acquisition conditions, and expanding imaging FOV. By exploiting the repetitive structures and volumetric coherence of EM images, we propose the first generative learning-based framework for large-factor EMSR. Specifically, motivated by the predictability of repetitive structures and textures in EM images, we first learn a discrete codebook in the latent space to represent high-resolution (HR) cell-specific priors and a latent vector indexer to map low-resolution (LR) EM images to their corresponding latent vectors in a generative manner. By incorporating the generative cell-specific priors from HR EM images through a multi-scale prior fusion module, we then deploy multi-image feature alignment and fusion to further exploit the inter-section coherence in the volumetric EM data. Extensive experiments demonstrate that our proposed framework outperforms advanced single-image and video super-resolution methods for $8 \times$ and $16 \times$ EMSR (i.e., with 64 times and 256 times less data acquired, respectively), achieving superior visual reconstruction quality and downstream segmentation accuracy on benchmark EM datasets. Code is available at https://github.com/jtshou/GPEMSR. + +# 1. Introduction + +Electron microscopy (EM) is a commonly used imaging technique in life sciences to investigate the ultrastructure of cells, tissues, organelles, and macromolecular complexes, which captures images of biological specimens at nanome + +ter resolution. However, high-quality EM image acquisition typically requires a strict and time-consuming process, involving careful adjustments of beam current, aperture size, and detector settings. This process may take up to years to scan wide field-of-view (FOV) specimens. For example, Zheng et al. [57] spent approximately 16 months to acquire a $\sim 106\mathrm{TB}$ whole-brain dataset of an adult drosophila melanogaster. The long acquisition time greatly limits the application of EM imaging in analyzing complete biological structures in large specimens, such as neuron connections in mammalian brains. + +Image super-resolution (SR), which is capable of restoring high-resolution (HR) images from their corresponding low-resolution (LR) observations, has the potential to revolutionize EM imaging by allowing for faster and less restrictive data acquisition, while also providing high-quality images with a wide field of view. By applying SR to EM images (shorted as EMSR hereafter), the capturing time can be significantly reduced, and the strict capturing conditions can be relaxed. By deploying a simple ResNet-based UNet model, Fang et al. [13] have demonstrated the promising performance of EMSR for $4\times$ magnification (i.e., with 16 times less data acquired). However, achieving even larger-factor EMSR to further reduce capturing time remains challenging. This is in accordance with existing methods [5, 18, 30, 35, 50, 58] for natural images, which can achieve satisfactory results for up to $4\times$ magnification, but fail to meet the demand for larger factors. + +On the other hand, recent advances in generative models, such as ChatGPT and diffusion-based models [9, 16, 21, 43], reveal powerful capability in automatic content generation, including natural languages and images. This motivates us to consider the EMSR task from a generative perspective. Especially, compared with natural images that possess diverse structures and textures, EM images often exhibit repetitive structures and textures due to the predictability of imaging specimens, making it more suitable to leverage generative learning for accurate reconstruction. In + +this paper, we propose a novel deep learning-based framework tailored to the challenging task of large-factor EMSR, by 1) exploiting the repetitive structures and textures in EM images with generative cell-specific priors learned from HR EM images, and 2) exploiting the inter-section coherence in the volumetric EM data by aggregating features learned from multiple consecutive images. + +Specifically, our framework explores cell-specific priors using a VQGAN-Indexer network, consisting of VQGAN [12] and our proposed latent vector indexer. We first learn a discrete codebook to represent the distribution of HR EM images in the latent space. The codebook captures both structure and texture information, while the decoder establishes relationships between latent vectors and image patches. We then train a latent vector indexer to acquire the corresponding latent vectors and integrate the indexer with the codebook and the decoder for generating HR EM images. By treating the generation process as an indexing task, we can match LR EM images with their corresponding HR feature representations from the latent space, thereby obtaining priors solely derived from HR EM images. + +To maintain reconstruction quality while prioritizing downstream segmentation accuracy, we propose a MultiScale Prior Fusion (MPF) module for incorporating the above learned cell-specific priors in EMSR. We use the VQGAN-Indexer output as reference images and learn a mask for fusing reference features based on the patch-level cosine similarity between LR EM images and corresponding reference images. To fully utilize the latent vectors and relationships learned by the decoder, we use multi-scale reference features from different layers of the decoder with varying resolutions. Following the MPF module, our framework includes two key steps for exploiting inter-section coherence in the volumetric EM data: multi-image feature alignment (along the axial direction) and multi-image feature fusion. To this end, we introduce a Pyramid Optical-flow-based Deformable convolution alignment (POD) module and a 3D Spatial-Attention fusion (3DA) module. The former leverages a pre-trained optical-flow network SPyNet [42] and deformable convolutions [6, 60], while the latter leverages the spatial attention mechanism and 3D convolutions. Both improve reconstruction quality and downstream segmentation accuracy for large-factor EMSR. + +In summary, this paper offers the following contributions. 1) We present the first generative learning-based framework for the challenging task of large-factor EMSR. 2) We introduce the VQGAN-Indexer network to explore generative cell-specific prior information from HR EM images. 3) We propose the MPF module to effectively utilize the generative priors while preserving image fidelity with LR observations, followed by the POD and 3DA modules for multi-image feature alignment and fusion. 4) Extensive experiments demonstrate the superiority of our framework + +in terms of both reconstruction quality and downstream segmentation accuracy for $8 \times$ and $16 \times$ EMSR. + +# 2. Related Work + +Electron microscopy image super-resolution. Existing EMSR methods can be categorized into two types: restoring isotropic volumes from anisotropic ones, i.e., SR along the axial dimension [8, 20], and reconstructing HR images from corresponding LR observations in the lateral dimensions [7, 13, 40, 46, 53]. We focus on the latter task in this paper, while our proposed framework may also apply to the former task. As a pioneering work in the field of EMSR, Sreehari et al. [46] introduce a Bayesian framework and utilize a library-based non-local means (LB-NLM) algorithm to achieve up to $16 \times$ EMSR without requiring a training process. However, this non-learning-based method limits performance and is not specifically designed for large-factor EMSR. Along the deep learning line, Nehme et al. [40] train a fully convolutional encoder-decoder network on simulated data to reconstruct super-resolved images. Hann et al. [7] train a GAN model using pairs of test specimens captured from the same region of interest. Xie et al. [53] leverage the attention mechanism to capture inter-section dependencies and shared features among adjacent images. Compared to previous EMSR methods, our framework not only utilizes adjacent EM images but also explores and integrates generative cell-specific priors to tackle the challenging task of large-factor EMSR. + +Video super-resolution. Video super-resolution (VSR) aims to restore HR frames by leveraging adjacent temporal information in multiple LR frames. To align temporal features, optical flow [3, 5, 26, 44, 49, 52, 54] and deformable convolution [47, 50], have been widely adopted. Recently, transformer-based approaches [4, 36] yield remarkable advancements in VSR, owing to the utilization of diverse attention mechanisms. Inspired by these VSR methods, to exploit the inter-section coherence in the volumetric EM data, we utilize optical-flow networks and deformable convolutions for multi-image feature alignment, and spatial attention mechanisms for multi-image feature fusion. + +Generative priors in image restoration. Generative image restoration methods [11, 31-33] employ the priors from the pre-trained generative adversarial network (GAN), such as StyleGAN [24] and BigGAN [2], to approximate the natural image manifold and synthesize high-quality images. Given the superior performance of discrete codebook-based generative methods in semantic image synthesis, structure-to-image, and stochastic super-resolution tasks [12, 48], recent methods explore codebook-based facial priors [17, 59] by leveraging VQGAN [12] for training. Different from these methods, we propose a latent vector indexer to exploit the information contained within the input LR images, and the MPF module to fuse generative priors. + +# 3. Method + +# 3.1. Overview + +As illustrated in Figure 1, the goal of large-factor EMSR is to obtain the super-resolved $I_{SR}^{0} \in \mathbb{R}^{rH \times rW \times 1}$ , given a sequence of $2N + 1$ consecutive LR EM images, $I_{LR}^{z} \in \mathbb{R}^{H \times W \times 1}$ , which should be close to the ground truth image $I_{GT}^{0} \in \mathbb{R}^{rH \times rW \times 1}$ , where $z \in \{-N, -N + 1, \dots, 0, \dots, N - 1, N\}$ and $r$ is the large scale factor. In this paper, we set $N = 2$ and $r = 8, 16$ . + +To achieve this, we propose a generative learning-based framework consisting of three stages. Stage I involves exploring generative cell-specific priors through the VQGAN model, which identifies a discrete latent space of HR EM images and generates the HR EM image $I_{\mathrm{HRref}}$ from the latent space. This latent space is represented using vectors from the VQGAN codebook $C$ . In Stage II, we train a latent vector indexer and connect it with the VQGAN codebook $C$ and VQGAN decoder $Q$ obtained from Stage I. This connection allows us to generate the reference HR EM image $I_{\mathrm{Ref}}$ and its corresponding multi-scale generative features $F_{\mathrm{Ref}}^{l}$ from the LR EM image $I_{\mathrm{LR}}$ . Finally, in Stage III, we fuse the multi-scale generative features $F_{\mathrm{Ref}}^{l}$ using the MPF module, align adjacent image features in the axial direction using the POD module, and fuse the adjacent image features using the 3DA module. We finally use sub-pixel convolution to reconstruct the HR output $I_{SR}^{0}$ . + +# 3.2. Exploring Generative Cell-Specific Priors + +EM images are characterized by their repetitive structures and textures, such as cellular membranes and subcellular organelles. These features offer an opportunity to exploit their regularity and predictability, motivating our exploration of the generative cell-specific prior in EM images for large-factor EMSR. As shown in Figure 1 (a), our framework for exploring generative cell-specific prior exploration consists of two main steps. First, we identify a discrete latent space that represents the features of HR EM images. Then, we generate the HR EM images from this latent space, leveraging its compact and representative nature. + +Identifying a discrete latent space. We aim to identify a discrete latent space that represents HR EM images. To achieve this, we utilize an encoder $\pmb{E}$ to parameterize the posterior categorical distribution of HR EM images $q_{\phi}(\xi \mid o)$ , where $\xi$ represents the variable for latent vectors, $o$ represents the variable for HR EM images and $\phi$ represents the encoder's parameters. Specifically, we quantize the output feature $Z_{e}$ from $\pmb{E}$ by mapping it to its closest latent vector in $C$ and obtain the quantified feature $Z_{d}$ and one-hot index of each mapped HR patch, denoted as $s^{m,n}$ + +$$ +\begin{array}{l} Z _ {d} ^ {m, n} = \arg \min _ {Z _ {q} [ j ]} \| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \| _ {2} ^ {2}, \\ s ^ {m, n} [ k ] = \left\{ \begin{array}{l l} 1, & k = \arg \min _ {j} \| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \| _ {2} ^ {2} \\ 0, & \text {o t h e r w i s e} \end{array} , \right. \tag {1} \\ \end{array} +$$ + +where $Z_{q}[j]$ denotes the $j$ -th latent vector stored in $C$ . $Z_{e}^{m,n}$ denotes the encoder output feature element at position $(m,n)$ within $Z_{e}$ , while $Z_{d}^{m,n}$ denotes the quantified feature element at position $(m,n)$ within $Z_{d}$ . $s^{m,n}$ is a v-dimensional vector and $s^{m,n}[k]$ denotes the $k$ -th element in $s^{m,n}$ . The codebook $C$ consists of $v$ latent vectors, each with a dimensionality of $d$ . Thus, the posterior categorical distribution $q_{\phi}(\xi | o)$ is defined as + +$$ +q _ {\phi} (\xi = k \mid o) = \left\{ \begin{array}{l l} 1, & Z _ {q} [ k ] = \arg \min _ {Z _ {q} [ j ]} \| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \| _ {2} ^ {2} \\ 0, & \text {o t h e r w i s e} \end{array} . \right. \tag {2} +$$ + +Generating the HR EM image. Given the quantified feature $Z_{d}$ , we can generate HR EM image $I_{\mathrm{HRref}}$ through the decoder. We parameterize the prior distribution of HR EM images $p_{\theta}(o \mid \xi)$ through the decoder $Q$ , where $\theta$ is the parameters of the decoder. + +The encoder is composed of multiple Res-blocks [19] and convolution blocks for downsampling, while the decoder is composed of multiple Res-blocks and deconvolution blocks for upsampling. The compression patch size for downsampling is set to $p$ . Both the encoder and decoder leverage self-attention mechanisms to enhance generalization quality. We optimize the latent vector $Z_{q}[j]$ along with the encoder $E$ and decoder $Q$ . + +# 3.3. Generating LR Reference + +With the parameterization of the latent space using $C$ and the prior distribution of HR EM images using $Q$ , we can generate HR EM images given real HR EM images as input. However, in the large-factor EMSR task, only highly degraded LR images are available as input. Hence, we need to map the LR images to their corresponding quantified feature $Z_{d}$ to utilize the generative cell-prior stored in $C$ . + +To achieve this, one straightforward approach is to interpolate the LR images and feed them into the encoder [17]. This straightforward approach approximates the posterior categorical distribution of LR EM images $q(\xi \mid o_{\downarrow})$ by utilizing the parameterized posterior categorical distribution of HR EM images $q_{\phi}(\xi \mid [o_{\downarrow}]_{\uparrow})$ with the interpolation operation. Here, $o_{\downarrow}$ represents the LR image variable, and $[\cdot]_{\uparrow}$ denotes the interpolation operation. However, in scenarios where significant degradation occurs in LR input images, the interpolation operation struggles to restore the rich details and textures in HR EM images. Consequently, this mismatch leads to discrepancies between the real HR EM image distribution $p(o)$ and the interpolated HR EM image distribution $p([o_{\downarrow}]_{\uparrow})$ , thereby resulting in disparities between $q(\xi \mid o_{\downarrow})$ and $q_{\phi}(\xi \mid [o_{\downarrow}]_{\uparrow})$ . Despite the loss of fine-grained details in LR images, the partial preservation of information enables the utilization of such details as priors in mapping LR images to their corresponding quantified feature $Z_{d}$ . To fully utilize these priors, we propose a latent + +![](images/493cf8d2b9ae46d437915f0bcf6293001b84ec8dc47095e1395fd1bdf2bbf203.jpg) +Figure 1. Overview of our framework. The proposed generative learning-based framework consists of three stages. In Stage I, the encoder, the codebook, and the decoder are trained by self-generating the input HR EM image. In Stage II, a latent vector indexer is trained and connected with the codebook and the decoder with fixed parameters to generate the reference HR EM image and multi-scale generative features from the LR EM image. In Stage III, the HR output is reconstructed by fusing multi-scale generative features and exploiting inter-section coherence in volumetric EM data with the POD module and the 3DA module. Rec denotes reconstruction layers composed of convolution layers and pixel shuffle operation. + +![](images/358f9753f2980d2ad4eb765d8f95c343cd5679b7a63d68805e26d2601ffff839.jpg) + +vector indexer $W$ to predict probabilities of corresponding latent vectors in $C$ given LR EM images as input, as shown in Figure 1 (b). We denote the output of the latent vector indexer as $Z_{w}$ , where the element at position $(m,n)$ is denoted as $Z_{w}^{m,n}$ and represents a $v$ -dimensional vector. Then, by selecting the latent vector with the highest probability, we can effectively model the posterior categorical distribution $q(\xi \mid o_{\downarrow})$ as + +$$ +q _ {\varphi} (\xi = k \mid o _ {\downarrow}) = \left\{ \begin{array}{l l} 1, & k = \arg \max _ {i \in \{1, 2, 3, \dots , v \}} Z _ {w} ^ {m, n} [ i ] \\ 0, & \text {o t h e r w i s e} \end{array} \right., \tag {3} +$$ + +where $\varphi$ denotes the parameters of the latent vector indexer $W$ . $Z_{w}^{m,n}[i]$ denotes the $i$ -th element of the vector $Z_{w}^{m,n}$ . + +This quantization operation allows us to capture the most representative latent vector that corresponds to the LR image. Then the predicted quantified feature $Z_{d}^{pre}$ is obtained and fed into the decoder to generate the reference HR EM image $I_{\mathrm{Ref}}$ and its corresponding multi-scale generative features $F_{\mathrm{Ref}}^{l}$ through the decoder. Note that all the latent vectors used to generate $I_{\mathrm{Ref}}$ and $F_{\mathrm{Ref}}^{l}$ are obtained from the codebook, which contains the generative cell-specific pri + +ors of HR EM images. + +# 3.4. Reconstructing HR Image + +MPF module. The complete process of reconstructing HR image is depicted in Figure 1 (c). The discrepancies between the generated HR image $I_{\mathrm{Ref}}$ and real EM image $I_{\mathrm{GT}}$ pose a challenge in achieving accurate multi-scale generative feature fusion. To overcome this challenge, we propose the MPF module, which focuses on identifying and fusing the multi-scale generative features. The MPF module comprises two essential processes: a mask-learning process and a multi-scale fusion process. + +The mask-learning mechanism within the MPF module enables us to identify and mask out multi-scale generative features in regions that show significant boundary differences compared to real HR images. As shown in Figure 1 (d), we first embed the interpolated LR image $[I_{LR}]_{\uparrow}$ and the reference image $I_{Ref}$ from the decoder into the feature space by a pre-trained VGG19 encoder [45]. We extract $16\times 16$ patches from LR feature maps and reference (Ref) feature maps without overlap. Then, We calculate cosine similarity vector $CS$ between LR feature patches and Ref feature patches, where $CS_{i}$ denotes cosine similarity be + +tween the $i$ -th LR feature patch and the $i$ -th Ref feature patch. We refine the mask by employing three 2D convolutions. Finally, we apply a sigmoid function to obtain the mask $M$ with the same spatial resolution as LR features. + +To effectively fuse features from different layers of the decoder across $L$ levels, we employ a multi-scale fusion scheme, as illustrated in Figure 1 (e). As the decoder learns the relationship between latent vectors, each layer of the decoder contains varying levels of detailed information about EM images. Additionally, since the decoder is responsible for reconstructing HR EM images, layers closer to the output represent shallower features. Given these considerations, we begin fusing features from $F_{Ref}^{0}$ and its corresponding LR features $F_{LR}^{0}$ with the same resolution and gradually incorporate features with lower resolution + +$$ +\begin{array}{l} \tilde {F} ^ {1} = R _ {D} ^ {0} \left(R _ {F} ^ {0} \left(\left\langle F _ {L R} ^ {0}, F _ {R e f} ^ {0} \right\rangle\right) \otimes [ M ] _ {\uparrow 2 ^ {L - 1}}\right), \\ \tilde {F} ^ {l + 1} = R _ {D} ^ {l} \left(\langle R _ {F} ^ {l} \left(\langle \tilde {F} ^ {l}, F _ {L R} ^ {l}, F _ {R e f} ^ {l} \rangle\right) \otimes [ M ] _ {\uparrow 2 ^ {L - l - 1}}, \tilde {F} ^ {l} \rangle\right), \\ \hat {F} = R _ {F} ^ {L - 1} \left(\langle \tilde {F} ^ {L - 1}, F _ {L R} ^ {L - 1}, F _ {R e f} ^ {L - 1} \rangle\right) \otimes M, \\ F ^ {O u t} = R _ {O} ^ {L - 1} \left(\langle \hat {F}, \tilde {F} ^ {L - 1}, F _ {L R} ^ {L - 1} \rangle\right), \tag {4} \\ \end{array} +$$ + +where $\otimes$ denotes element-wise multiplication, $\langle \cdot \rangle$ denotes concatenation operation, and $[\cdot ]_{\uparrow}$ denotes interpolation operation. $\tilde{F}^l$ denotes output features from downsample convolution at the $l$ -th level. $R_D^l,R_F^l$ ,and $R_O^{L - 1}$ denote downsample convolution, fusion convolution, and output convolution, respectively. $\hat{F}$ denotes the output feature of the last fusion convolution. $F^{Out}$ represents the final multi-scale fusion feature. + +POD module and 3DA module. To exploit the intersection coherence in volumetric EM data and leverage the correlation between adjacent EM images, we design two modules: the POD module and the 3DA module. The POD module is responsible for aligning the adjacent EM image output features from the MPF module in a coarse-to-fine manner. It utilizes a pyramid architecture and incorporates a pre-trained optical-flow network SPyNet and deformable convolutions to achieve accurate feature alignment. The 3DA module employs spatial attention mechanisms and 3D convolutions to effectively fuse the aligned features. More detailed information about the POD module and 3DA module can be found in the supplementary material. + +# 3.5. Training Strategy + +In Stage I, we adopt three loss functions: a reconstruction loss $L_{r - I}$ , a codebook learning loss $L_{c}$ , and an adversarial loss $L_{adv}$ + +$$ +\begin{array}{l} L _ {r - I} = \left\| I _ {\mathrm {H R r e f}} - I _ {\mathrm {G T}} \right\| _ {1}, L _ {a d v} = D \left(I _ {\mathrm {G T}}\right) + D \left(- I _ {\mathrm {H R r e f}}\right), \\ L _ {c} = \left\| \operatorname {s g} \left[ Z _ {d} \right] - Z _ {e} \right\| _ {2} ^ {2} + \left\| \operatorname {s g} \left[ Z _ {e} \right] - Z _ {d} \right\| _ {2} ^ {2}, \tag {5} \\ \end{array} +$$ + +where $D$ represents a PatchGAN discriminator [23] and $\mathrm{sg}[\cdot ]$ denotes the stop-gradient operation. As Eq. 1 is non-differentiable, we propagate the gradients from the decoder to the encoder [12, 48]. We utilize R1 regularization [39] for GAN training stability. The complete objective of the first stage is + +$$ +L _ {s - I} = L _ {r - I} + \lambda_ {c} L _ {c} + \lambda_ {a d v} L _ {a d v}. \tag {6} +$$ + +In Stage II, we optimize the latent vector indexer $W$ while keeping the parameters of $C$ and $Q$ fixed. The objective of the second stage is + +$$ +L _ {s - I I} = - \sum_ {m, n, i} s ^ {m, n} [ i ] \log \frac {\exp \left(Z _ {w} ^ {m , n} [ i ]\right)}{\sum_ {j} \exp \left(Z _ {w} ^ {m , n} [ j ]\right)}. \tag {7} +$$ + +In Stage III, we train our network with two loss functions: a reconstruction loss $L_{r - III}$ and a multi-Ref fidelity loss $L_{Mfid}$ [28]. The objective of the third stage is + +$$ +\begin{array}{l} L _ {r - I I I} = \left\| I _ {S R} ^ {0} - I _ {G T} ^ {0} \right\| _ {1}, \\ L _ {M f i d} = \frac {\sum_ {z ^ {\prime} \in \Omega} \sum_ {i} \delta_ {i} \left(I _ {S R} ^ {0} , I _ {R e f} ^ {z ^ {\prime}}\right) \cdot c _ {z ^ {\prime} , i}}{\sum_ {z ^ {\prime} \in \Omega} \sum_ {i} c _ {z ^ {\prime} , i}}, \tag {8} \\ L _ {s - I I I} = L _ {r - I I I} + \lambda_ {M f i d} L _ {M f i d}, \\ \end{array} +$$ + +where $\Omega = \{-N, -N + 1, \dots, 0, \dots, N - 1, N\}$ , $\delta_i(\cdot, \cdot)$ denotes contextual loss in [38] and $c_{z', i}$ is the matching confidence weight based on cosine similarity. + +# 4. Experiments + +# 4.1. Settings + +Datasets. We conduct experiments under two different settings to demonstrate the superior performance of our framework in both reconstruction quality and downstream segmentation accuracy. For the first setting, we select the adult drosophila melanogaster brain dataset FAFB [57] and its subset CREMI [14] acquired at $4 \times 4 \times 40\mathrm{nm}^3$ resolution. In Stage I and Stage II, we train our framework on a subset ( $\sim 38\mathrm{G}$ ) of FAFB to obtain a cell-specific prior. In Stage III, we utilize the padded version of the CREMI dataset, excluding the CREMI C subset, to train for large-factor EMSR. We use the cropped version of CREMI C, which has segmentation labels, as the test set consisting of 125 images. We fine-tune two pre-trained segmentation networks, Superhuman [29] and MALA [15], on the first 75 images of CREMI C. Therefore, we test all 125 images for reconstruction evaluation metrics and the last 50 for segmentation evaluation metrics. For the second setting, we select the mouse somatosensory cortex dataset Kasthuri15 [25] and its subset AC3/AC4 dataset [25] acquired at $3 \times 3 \times 29\mathrm{nm}^3$ resolution. As the AC3/AC4 datasets are too small, we use the data partitioning strategy from [22] and train three stages on a subset ( $\sim 11.2\mathrm{G}$ , i.e., Subset3 in [22]) of Kasthuri15 and AC3. We fine-tune two pre-trained segmentation networks on AC3 and test them on AC4. + +Table 1. Quantitative comparison of reconstruction quality and EM image segmentation results on CREMI C for ${16} \times$ and $8 \times$ EMSR. The best and the second-best results are highlighted in bold and underline. * Parameters optimized in Stage III. + +
MethodsScaleReconstruction MetricsSegmentation MetricsParams/M
FidelityPerceptualSuperhumanMALA
PSNR↑SSIM↑LPIPS↓DISTS↓VOI↓ARAND↓VOI↓ARAND↓
Bicubic16×21.55570.48010.73380.48426.66270.70436.55990.8830-
RCAN [56]16×23.12380.57790.53360.34295.27620.61932.93530.232512.9080
SwinIR [35]16×23.10980.57810.53320.34165.12540.49552.93020.231712.1426
BSRN [34]16×22.91610.56450.54530.34025.57280.68093.20340.26940.4719
Real-ESRGAN [51]16×22.76310.55370.53330.31344.08230.48903.38060.297316.6957
EDVR [50]16×23.88940.61470.50220.31824.17090.41322.32290.19693.4455
BasicVSR [5]16×23.38770.59240.51070.31764.58250.50532.54280.21153.9339
Ours16×23.67670.60200.47900.29272.96390.30752.25710.17865.4627*
Bicubic8×25.58970.66070.47790.29825.93040.87542.47480.2036-
RCAN [56]8×29.39260.79140.37290.23393.38580.32881.56340.133312.7603
SwinIR [35]8×29.43340.79210.37240.23403.34940.32671.54000.130611.9949
BSRN [34]8×29.14640.78320.37910.23133.59280.34611.56210.13150.3611
Real-ESRGAN [51]8×29.14570.78430.37740.23173.57400.33631.55550.130916.6957
EDVR [50]8×29.73260.80160.36420.23163.17390.31591.51070.13243.2978
BasicVSR [5]8×29.08280.78310.37740.23053.46190.33361.58790.13494.0445
Ours8×29.70270.80020.35680.22912.93760.30761.50110.12984.4257*
+ +Table 2. Quantitative comparison of reconstruction quality and EM image segmentation results on AC4 for ${16} \times$ and $8 \times$ EMSR. The best and the second-best results are highlighted in bold and underline. * Parameters optimized in Stage III. + +
MethodsScaleReconstruction MetricsSegmentation MetricsParams/M
FidelityPerceptualSuperhumanMALA
PSNR↑SSIM↑LPIPS↓DISTS↓VOI↓ARAND↓VOI↓ARAND↓
Bicubic16×19.00780.25180.77580.46396.93000.96886.81440.9664-
RCAN [56]16×19.59380.29810.66610.39706.45350.93516.47160.929412.9080
SwinIR [35]16×19.59490.29560.66710.38936.87960.94966.54170.932212.1426
BSRN [34]16×19.56130.29280.67250.39147.19610.96156.61680.93950.4719
Real-ESRGAN [51]16×19.42540.28930.64270.37066.38530.87456.06590.914016.6957
EDVR [50]16×19.93740.32830.62320.37314.81780.71585.00290.82823.4455
BasicVSR [5]16×19.42930.28880.67470.37476.86080.95986.75480.95133.9339
Ours16×19.74680.31140.57480.35844.36550.61264.83620.82335.4627*
Bicubic8×21.09790.37200.58960.33616.76940.96756.13460.9157-
RCAN [56]8×22.31670.47730.52000.31622.21010.28262.35710.388612.7603
SwinIR [35]8×22.49090.49310.51040.32131.78670.21072.36350.524211.9949
BSRN [34]8×22.27360.47360.52310.31322.26300.28602.51200.37460.3611
Real-ESRGAN [51]8×22.34390.48890.50000.31271.88390.25842.06800.344516.6957
EDVR [50]8×22.93140.52700.48900.31761.29460.25321.64860.40273.2978
BasicVSR [5]8×22.24440.47570.51800.31142.17160.32422.51170.49534.0445
Ours8×22.92510.52700.46540.30751.15010.13771.58620.31344.4257*
+ +Metrics. To evaluate the difference between SR results and ground truth, we use various reconstruction metrics. These encompass two fidelity metrics, PSNR and SSIM, alongside two perceptual metrics, LPIPS [55] and DISTS [10]. For EM image segmentation evaluation, we use VOI [41] and ARAND [1] as our metrics. In our segmentation evaluation, we consider both split error and merge error to ensure a comprehensive and accurate assessment. + +Training setting. We train the networks in three stages using Adam [27] optimizer with $\beta_{1} = 0.9$ , $\beta_{2} = 0.99$ and employ Cosine Annealing scheme [37]. In our experiments, we set all initial learning rates to $4\times 10^{-4}$ except for Stage III on the mouse somatosensory cortex training dataset, where we adjust the initial learning rate to $1\times 10^{-4}$ to ensure the convergence of deformable convolution layer. To generate paired data, we use bicubic downsampling to reduce the image resolution by factors of 8 and 16. The LR patch size is set to $16\times 16$ for $16\times$ EMSR and $32\times 32$ + +for $8 \times$ EMSR during Stage III training phase. The compression patch size $p$ is set to 16 based on our ablation studies. We select the weights for our loss functions as follows: $\lambda_{c} = 10$ , $\lambda_{adv} = 0.05$ , and $\lambda_{MFid} = 0.01$ for $16 \times$ EMSR, and $\lambda_{MFid} = 0.001$ for $8 \times$ EMSR. These weights are chosen through empirical experimentation aimed at striking the right balance for optimal performance. We also set the number of latent vectors to $v = 1024$ and their dimension to $d = 512$ in the codebook based on our ablation studies. + +# 4.2. Comparisons with Existing Methods + +We compare our framework with (1) single-image SR methods including RCAN [56], SwinIR [35], BSRN [34], and Real-ESRGAN [51], (2) video SR methods including EDVR [50] and BasicVSR [5]. All these models are pretrained on the same EM datasets for fair comparisons. The quantitative results of image reconstruction and EM image segmentation are summarized in Table 1 and Table 2. + +![](images/ab0bc3ef16e34c4218f80b2e9993eab993d88cd815de43e4133ce5dc9df647c0.jpg) +Figure 2. Top: Qualitative comparison for $16 \times$ EMSR. Our framework exhibits sharper boundaries and preserves a more complete structure. Bottom: Qualitative comparison for $16 \times$ EMSR in terms of segmentation. + +![](images/41483e2cd87305aa907cc85843fa1734a4b90bee0d91fc7130ffec6a49e2161a.jpg) + +![](images/7a2fb841ff92e6f3131a6fc1e491e96f2bf694b771432fb080dc8ec7376497ed.jpg) + +![](images/ce6a810af5dc4c60b30bfe48c24f839936b49afe8379046441dab9c5b7cdc58c.jpg) + +![](images/85af61c2f2875bce49d6635eff3e03fa945b0a8e4c6f710da37d1b64cfb40ac1.jpg) + +![](images/7ee40a7c1ecb434accea76b28b575755a4ec41588459985cecba1e9d952cfd5c.jpg) + +![](images/95877bf9cdfb719cdcf9d9762777aef4773a6583552246182f8a08c597d48f3a.jpg) + +![](images/260d8d01c3d0c2179684afc552e41b87206b3ba3a4e2d462f5874a758b069069.jpg) + +![](images/b4ec9d36b8502c46f22b6411480603ebb8d8f228dc5393d7ac6e7bdcb85b6805.jpg) + +![](images/545101d11cbd46ff61a8a3e1e9de8ecfb697b6ed60d66480254688011fb812c2.jpg) +Figure 3. Top: Qualitative comparison for $8 \times$ EMSR. Our framework exhibits sharper boundaries and preserves a more complete structure. Bottom: Qualitative comparison for $8 \times$ EMSR in terms of segmentation. + +![](images/a22aed93f768eac5d392afa88e8e2e12b5de2db81cb1a97ea662b44278299e9d.jpg) + +![](images/bf56ce122694153570fa1a267c8763130e2b0181d85ee2b3e30a72a89279d76e.jpg) + +![](images/c576b278bc678464332604850da700166e1d68d140719d27b7bcc41967b84bf8.jpg) + +![](images/ea6553e5d093b497bd25066f27fc0e38cb6752aded82afd797a985778b1b047d.jpg) + +![](images/b9963105a2a475613e10bef6e906ace68ff39f75d23c04528cba6715dc18782a.jpg) + +![](images/405795ed7ab59a8dfb924abeceb9638e2fb4ca9b5ddfe07c6cdaee66ac2d7aaa.jpg) + +Reconstruction quality. While our framework performs the second-best in terms of PSNR and SSIM, slightly behind EDVR, these fidelity metrics do not necessarily align with human perception of image quality. On the other hand, our framework surpasses all other methods in terms of perceptual metrics LPIPS [55] and DISTS [10]. As shown in Figure 2 and Figure 3, our framework produces images with sharper boundaries, richer texture details, and more complete structures for $16 \times$ and $8 \times$ EMSR. This demonstrates that our cell-specific generative priors and the MPF module can effectively incorporate fine-grained details from HR EM images instead of producing smoothed results at the pixel level. It is noteworthy that although Real-ESRGAN [51] partially alleviates over-smoothing by incorporating the adversarial loss, it introduces noticeable noise-like artifacts in the super-resolved images. Additionally, a general comparison between single-image and video SR methods supports the effectiveness of incorporating adjacent EM images in the context of large-factor EMSR. + +EM image segmentation accuracy. We evaluate the accuracy of two pre-trained segmentation networks by using the super-resolved EM images as inputs. Our framework outperforms all other methods with two different segmentation networks, demonstrating exceptional image fidelity in terms of downstream tasks achieved by our framework. Moreover, our framework effectively addresses the issue of over-segmentation caused by excessive smoothing of ex + +Table 3. Ablation studies on prior exploration and prior indexing trade-off. p denotes the compression patch size. + +
PStage IStage IIΔPSNRΔLPIPS
PSNR↑LPIPS↓PSNR↑LPIPS↓
835.07310.261820.12120.5240-14.95190.2622
1628.68760.371521.74230.4996-6.94530.1281
3223.18790.469321.52910.5024-1.65880.0331
6420.28320.622620.16090.6263-0.12230.0037
+ +isting methods, which is particularly prominent in the Superhuman segmentation network (see supplementary material for detail). Visualization examples of segmentation, as shown in Figure 2 and Figure 3, confirm the superiority of our framework over existing methods. + +# 4.3. Ablation Studies + +Effectiveness of prior exploration. Table 3 presents a quantitative analysis of the prior exploration process. As the mapping from the HR space to the latent space involves a compression process, the size of the compression patch is a crucial hyperparameter. In Stage I, a smaller compression patch size captures more detailed information and leads to more realistic generated images. We observe a significant improvement in both PSNR and LPIPS as the compression patch size decreases, indicating improvements in reconstruction quality and fidelity. + +Trade-off between prior exploration and prior indexing. There exists a trade-off between the quality of generated im + +![](images/2a08bf77344d9368af2ce66b228506636199ece61cb52c7f8b08735acba7a86d.jpg) +Figure 4. Qualitative comparison of prior indexing results and the effectiveness of the latent vector indexer. $p$ denotes the compression patch size. + +Table 4. Ablation studies on the quantity $v$ and dimensions $d$ of latent vectors in the codebook on prior exploration. + +
vdPSNR↑LPIPS↓
51251228.31650.3806
102425628.52270.3728
102451228.68760.3715
204851228.71590.3712
1024102428.75740.3743
+ +ages in Stage I and the accuracy of predicting latent vectors through the latent vector indexer in Stage II. This trade-off arises from the fact that as the compression patch size decreases and less information is available when feeding LR images into the latent vector indexer in Stage II, the learned posterior distribution of LR EM images $q_{\varphi}(\xi \mid o_{\downarrow})$ deviates further from the true posterior distribution $q(\xi \mid o_{\downarrow})$ . Consequently, reducing the compression patch size allows the first stage network to preserve more image details, but it poses challenges for the indexing task in Stage II. This can be observed from the changes in $\Delta PSNR$ and $\Delta LPIPS$ values presented in Table 3, which indicate a decrease in the indexing accuracy as the compression patch size decreases. In consideration of the trade-off between prior exploration and prior indexing, we set $p = 16$ , as depicted in Table 3 and Figure 4. Moreover, as illustrated in Figure 4, removing the latent vector indexer and directly utilizing bicubic interpolation along with the decoder in Stage I leads to notably blurry $I_{Ref}$ outcomes. + +Impact of the quantity and dimensions of latent vectors in the codebook. We systematically investigate the impact of the quantity and dimensions of latent vectors in the codebook by selecting several sets of representative parameters. The results are summarized in Table 4. From the experimental results, we observe that augmenting $v$ to 2048 or $d$ to 1024 does not yield significant improvements in prior exploration, despite doubling the codebook's size. Conversely, reducing $v$ to 512 or $d$ to 256 results in a noticeable performance decline. Based on these insightful results, we set $v = 1024$ and $d = 512$ for our codebook. This decision strikes an optimal balance between computational efficiency and performance. + +Effectiveness of POD module and 3DA module. We evaluate the effectiveness of the proposed POD and 3DA modules for multi-image feature alignment and multi-image + +Table 5. Ablation studies of our proposed modules. VOI-S and VOI-M denote segmentation using Superhuman and MALA, respectively. + +
MPFPOD3DAPSNR↑LPIPS↓VOI-S↓VOI-M↓
XXX23.52870.51684.59122.7265
X✓✓23.73540.50634.24292.3410
✓X✓23.54220.48583.15002.5144
✓✓X23.55480.48153.01932.3794
✓✓✓23.67670.47902.96392.2571
+ +feature fusion, respectively. To ensure a fair comparison, we replace these modules with residual blocks with comparable parameters. Table 5 shows the results of our ablation study. We observe that even without incorporating generative prior, the introduction of the POD module or 3DA module leads to improvements in both reconstruction evaluation metrics and segmentation metrics, as demonstrated in row 1 and row 2. Furthermore, when the generative prior is introduced, both the POD module and the 3DA module provide additional gains in reconstruction and segmentation metrics, as shown in rows 3 to 5. Notably, the POD module exhibits a larger improvement compared to the 3DA module, indicating its significance in multi-image feature alignment for large-factor EMSR. These results demonstrate the effectiveness of the proposed POD and 3DA modules in enhancing visual reconstruction quality and segmentation accuracy. + +Effectiveness of MPF module. The effectiveness of our MPF module is further demonstrated in row 2 and row 5 of Table 5, where it exhibits substantial improvements in perceptual metric LPIPS and segmentation metric VOI. It is important to note that the introduction of $L_{Mfd}$ in Stage III leads to a decrease in PSNR. This observation highlights the inconsistency between PSNR and visual quality as well as segmentation outcomes and reinforces the importance of using perceptual metrics and segmentation metrics to evaluate reconstruction quality. + +# 5. Conclusion + +In this paper, we present a generative learning-based framework for large-factor EMSR. By exploring and indexing cell-specific priors using a VQGAN-Indexer network, our framework leverages generative learning to capture the repetitive structures and textures of EM images. The MPF module effectively fuses generative priors obtained from the VQGAN-Indexer network while ensuring the image fidelity. 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In CVPR, 2019. 2 \ No newline at end of file diff --git a/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/images.zip b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..60aa6f159ed957c7a2617d1b98dcde333db30edd --- /dev/null +++ b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:6131bd87295576842376bf9e4a611fef6ed985b13d75078acb3b46202fadbccb +size 771812 diff --git a/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/layout.json b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..cd1c8005bbbf6b8aff7b0b64ecdb33e544e560b0 --- /dev/null +++ b/2024/Learning Large-Factor EM Image Super-Resolution with Generative Priors/layout.json @@ -0,0 +1,10266 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 64, + 103, + 531, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 64, + 103, + 531, + 121 + ], + "spans": [ + { + "bbox": [ + 64, + 103, + 531, + 121 + ], + "type": "text", + "content": "Learning Large-Factor EM Image Super-Resolution with Generative Priors" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 120, + 142, + 473, + 172 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 120, + 142, + 473, + 172 + ], + "spans": [ + { + "bbox": [ + 120, + 142, + 473, + 172 + ], + "type": "text", + "content": "Jiateng Shou1 Zeyu Xiao1 Shiyu Deng1 Wei Huang1 Peiyao Shi3 Ruobing Zhang3,2 Zhiwei Xiong1,2 Feng Wu1,2,†" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 69, + 173, + 525, + 186 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 173, + 525, + 186 + ], + "spans": [ + { + "bbox": [ + 69, + 173, + 525, + 186 + ], + "type": "text", + "content": "1 MoE Key Laboratory of Brain-inspired Intelligent Perception and Cognition, University of Science and Technology of China" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 148, + 186, + 446, + 198 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 148, + 186, + 446, + 198 + ], + "spans": [ + { + "bbox": [ + 148, + 186, + 446, + 198 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 148, + 186, + 446, + 198 + ], + "type": "text", + "content": "Institute of Artificial Intelligence, Hefei Comprehensive National Science Center" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 127, + 201, + 465, + 213 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 127, + 201, + 465, + 213 + ], + "spans": [ + { + "bbox": [ + 127, + 201, + 465, + 213 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 127, + 201, + 465, + 213 + ], + "type": "text", + "content": "Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 151, + 216, + 438, + 227 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 151, + 216, + 438, + 227 + ], + "spans": [ + { + "bbox": [ + 151, + 216, + 438, + 227 + ], + "type": "text", + "content": "shoujt@mail.ustc.edu.cn {zwxiong,fengwu}@ustc.edu.cn" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 143, + 255, + 192, + 268 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 255, + 192, + 268 + ], + "spans": [ + { + "bbox": [ + 143, + 255, + 192, + 268 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 277, + 290, + 612 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 277, + 290, + 612 + ], + "spans": [ + { + "bbox": [ + 46, + 277, + 290, + 612 + ], + "type": "text", + "content": "As the mainstream technique for capturing images of biological specimens at nanometer resolution, electron microscopy (EM) is extremely time-consuming for scanning wide field-of-view (FOV) specimens. In this paper, we investigate a challenging task of large-factor EM image super-resolution (EMSR), which holds great promise for reducing scanning time, relaxing acquisition conditions, and expanding imaging FOV. By exploiting the repetitive structures and volumetric coherence of EM images, we propose the first generative learning-based framework for large-factor EMSR. Specifically, motivated by the predictability of repetitive structures and textures in EM images, we first learn a discrete codebook in the latent space to represent high-resolution (HR) cell-specific priors and a latent vector indexer to map low-resolution (LR) EM images to their corresponding latent vectors in a generative manner. By incorporating the generative cell-specific priors from HR EM images through a multi-scale prior fusion module, we then deploy multi-image feature alignment and fusion to further exploit the inter-section coherence in the volumetric EM data. Extensive experiments demonstrate that our proposed framework outperforms advanced single-image and video super-resolution methods for " + }, + { + "bbox": [ + 46, + 277, + 290, + 612 + ], + "type": "inline_equation", + "content": "8 \\times" + }, + { + "bbox": [ + 46, + 277, + 290, + 612 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 277, + 290, + 612 + ], + "type": "inline_equation", + "content": "16 \\times" + }, + { + "bbox": [ + 46, + 277, + 290, + 612 + ], + "type": "text", + "content": " EMSR (i.e., with 64 times and 256 times less data acquired, respectively), achieving superior visual reconstruction quality and downstream segmentation accuracy on benchmark EM datasets. Code is available at https://github.com/jtshou/GPEMSR." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 628, + 128, + 640 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 628, + 128, + 640 + ], + "spans": [ + { + "bbox": [ + 47, + 628, + 128, + 640 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 645, + 287, + 694 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 645, + 287, + 694 + ], + "spans": [ + { + "bbox": [ + 46, + 645, + 287, + 694 + ], + "type": "text", + "content": "Electron microscopy (EM) is a commonly used imaging technique in life sciences to investigate the ultrastructure of cells, tissues, organelles, and macromolecular complexes, which captures images of biological specimens at nanome" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 256, + 545, + 386 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 256, + 545, + 386 + ], + "spans": [ + { + "bbox": [ + 306, + 256, + 545, + 386 + ], + "type": "text", + "content": "ter resolution. However, high-quality EM image acquisition typically requires a strict and time-consuming process, involving careful adjustments of beam current, aperture size, and detector settings. This process may take up to years to scan wide field-of-view (FOV) specimens. For example, Zheng et al. [57] spent approximately 16 months to acquire a " + }, + { + "bbox": [ + 306, + 256, + 545, + 386 + ], + "type": "inline_equation", + "content": "\\sim 106\\mathrm{TB}" + }, + { + "bbox": [ + 306, + 256, + 545, + 386 + ], + "type": "text", + "content": " whole-brain dataset of an adult drosophila melanogaster. The long acquisition time greatly limits the application of EM imaging in analyzing complete biological structures in large specimens, such as neuron connections in mammalian brains." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 388, + 546, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 388, + 546, + 592 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 546, + 592 + ], + "type": "text", + "content": "Image super-resolution (SR), which is capable of restoring high-resolution (HR) images from their corresponding low-resolution (LR) observations, has the potential to revolutionize EM imaging by allowing for faster and less restrictive data acquisition, while also providing high-quality images with a wide field of view. By applying SR to EM images (shorted as EMSR hereafter), the capturing time can be significantly reduced, and the strict capturing conditions can be relaxed. By deploying a simple ResNet-based UNet model, Fang et al. [13] have demonstrated the promising performance of EMSR for " + }, + { + "bbox": [ + 304, + 388, + 546, + 592 + ], + "type": "inline_equation", + "content": "4\\times" + }, + { + "bbox": [ + 304, + 388, + 546, + 592 + ], + "type": "text", + "content": " magnification (i.e., with 16 times less data acquired). However, achieving even larger-factor EMSR to further reduce capturing time remains challenging. This is in accordance with existing methods [5, 18, 30, 35, 50, 58] for natural images, which can achieve satisfactory results for up to " + }, + { + "bbox": [ + 304, + 388, + 546, + 592 + ], + "type": "inline_equation", + "content": "4\\times" + }, + { + "bbox": [ + 304, + 388, + 546, + 592 + ], + "type": "text", + "content": " magnification, but fail to meet the demand for larger factors." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 594, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 547, + 714 + ], + "type": "text", + "content": "On the other hand, recent advances in generative models, such as ChatGPT and diffusion-based models [9, 16, 21, 43], reveal powerful capability in automatic content generation, including natural languages and images. This motivates us to consider the EMSR task from a generative perspective. Especially, compared with natural images that possess diverse structures and textures, EM images often exhibit repetitive structures and textures due to the predictability of imaging specimens, making it more suitable to leverage generative learning for accurate reconstruction. In" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 63, + 702, + 140, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 63, + 702, + 140, + 713 + ], + "spans": [ + { + "bbox": [ + 63, + 702, + 140, + 713 + ], + "type": "text", + "content": "†Corresponding author." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "11313" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 156 + ], + "type": "text", + "content": "this paper, we propose a novel deep learning-based framework tailored to the challenging task of large-factor EMSR, by 1) exploiting the repetitive structures and textures in EM images with generative cell-specific priors learned from HR EM images, and 2) exploiting the inter-section coherence in the volumetric EM data by aggregating features learned from multiple consecutive images." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 158, + 288, + 326 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 158, + 288, + 326 + ], + "spans": [ + { + "bbox": [ + 46, + 158, + 288, + 326 + ], + "type": "text", + "content": "Specifically, our framework explores cell-specific priors using a VQGAN-Indexer network, consisting of VQGAN [12] and our proposed latent vector indexer. We first learn a discrete codebook to represent the distribution of HR EM images in the latent space. The codebook captures both structure and texture information, while the decoder establishes relationships between latent vectors and image patches. We then train a latent vector indexer to acquire the corresponding latent vectors and integrate the indexer with the codebook and the decoder for generating HR EM images. By treating the generation process as an indexing task, we can match LR EM images with their corresponding HR feature representations from the latent space, thereby obtaining priors solely derived from HR EM images." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 328, + 287, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 328, + 287, + 592 + ], + "spans": [ + { + "bbox": [ + 46, + 328, + 287, + 592 + ], + "type": "text", + "content": "To maintain reconstruction quality while prioritizing downstream segmentation accuracy, we propose a MultiScale Prior Fusion (MPF) module for incorporating the above learned cell-specific priors in EMSR. We use the VQGAN-Indexer output as reference images and learn a mask for fusing reference features based on the patch-level cosine similarity between LR EM images and corresponding reference images. To fully utilize the latent vectors and relationships learned by the decoder, we use multi-scale reference features from different layers of the decoder with varying resolutions. Following the MPF module, our framework includes two key steps for exploiting inter-section coherence in the volumetric EM data: multi-image feature alignment (along the axial direction) and multi-image feature fusion. To this end, we introduce a Pyramid Optical-flow-based Deformable convolution alignment (POD) module and a 3D Spatial-Attention fusion (3DA) module. The former leverages a pre-trained optical-flow network SPyNet [42] and deformable convolutions [6, 60], while the latter leverages the spatial attention mechanism and 3D convolutions. Both improve reconstruction quality and downstream segmentation accuracy for large-factor EMSR." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "type": "text", + "content": "In summary, this paper offers the following contributions. 1) We present the first generative learning-based framework for the challenging task of large-factor EMSR. 2) We introduce the VQGAN-Indexer network to explore generative cell-specific prior information from HR EM images. 3) We propose the MPF module to effectively utilize the generative priors while preserving image fidelity with LR observations, followed by the POD and 3DA modules for multi-image feature alignment and fusion. 4) Extensive experiments demonstrate the superiority of our framework" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "text", + "content": "in terms of both reconstruction quality and downstream segmentation accuracy for " + }, + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "inline_equation", + "content": "8 \\times" + }, + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "inline_equation", + "content": "16 \\times" + }, + { + "bbox": [ + 305, + 72, + 545, + 96 + ], + "type": "text", + "content": " EMSR." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 102, + 392, + 114 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 102, + 392, + 114 + ], + "spans": [ + { + "bbox": [ + 306, + 102, + 392, + 114 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 119, + 545, + 406 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 119, + 545, + 406 + ], + "spans": [ + { + "bbox": [ + 304, + 119, + 545, + 406 + ], + "type": "text", + "content": "Electron microscopy image super-resolution. Existing EMSR methods can be categorized into two types: restoring isotropic volumes from anisotropic ones, i.e., SR along the axial dimension [8, 20], and reconstructing HR images from corresponding LR observations in the lateral dimensions [7, 13, 40, 46, 53]. We focus on the latter task in this paper, while our proposed framework may also apply to the former task. As a pioneering work in the field of EMSR, Sreehari et al. [46] introduce a Bayesian framework and utilize a library-based non-local means (LB-NLM) algorithm to achieve up to " + }, + { + "bbox": [ + 304, + 119, + 545, + 406 + ], + "type": "inline_equation", + "content": "16 \\times" + }, + { + "bbox": [ + 304, + 119, + 545, + 406 + ], + "type": "text", + "content": " EMSR without requiring a training process. However, this non-learning-based method limits performance and is not specifically designed for large-factor EMSR. Along the deep learning line, Nehme et al. [40] train a fully convolutional encoder-decoder network on simulated data to reconstruct super-resolved images. Hann et al. [7] train a GAN model using pairs of test specimens captured from the same region of interest. Xie et al. [53] leverage the attention mechanism to capture inter-section dependencies and shared features among adjacent images. Compared to previous EMSR methods, our framework not only utilizes adjacent EM images but also explores and integrates generative cell-specific priors to tackle the challenging task of large-factor EMSR." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 411, + 545, + 554 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 411, + 545, + 554 + ], + "spans": [ + { + "bbox": [ + 304, + 411, + 545, + 554 + ], + "type": "text", + "content": "Video super-resolution. Video super-resolution (VSR) aims to restore HR frames by leveraging adjacent temporal information in multiple LR frames. To align temporal features, optical flow [3, 5, 26, 44, 49, 52, 54] and deformable convolution [47, 50], have been widely adopted. Recently, transformer-based approaches [4, 36] yield remarkable advancements in VSR, owing to the utilization of diverse attention mechanisms. Inspired by these VSR methods, to exploit the inter-section coherence in the volumetric EM data, we utilize optical-flow networks and deformable convolutions for multi-image feature alignment, and spatial attention mechanisms for multi-image feature fusion." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": "Generative priors in image restoration. Generative image restoration methods [11, 31-33] employ the priors from the pre-trained generative adversarial network (GAN), such as StyleGAN [24] and BigGAN [2], to approximate the natural image manifold and synthesize high-quality images. Given the superior performance of discrete codebook-based generative methods in semantic image synthesis, structure-to-image, and stochastic super-resolution tasks [12, 48], recent methods explore codebook-based facial priors [17, 59] by leveraging VQGAN [12] for training. Different from these methods, we propose a latent vector indexer to exploit the information contained within the input LR images, and the MPF module to fuse generative priors." + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "11314" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 71, + 103, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 71, + 103, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 71, + 103, + 83 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 85, + 115, + 96 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 85, + 115, + 96 + ], + "spans": [ + { + "bbox": [ + 47, + 85, + 115, + 96 + ], + "type": "text", + "content": "3.1. Overview" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "spans": [ + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": "As illustrated in Figure 1, the goal of large-factor EMSR is to obtain the super-resolved " + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "inline_equation", + "content": "I_{SR}^{0} \\in \\mathbb{R}^{rH \\times rW \\times 1}" + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": ", given a sequence of " + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "inline_equation", + "content": "2N + 1" + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": " consecutive LR EM images, " + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "inline_equation", + "content": "I_{LR}^{z} \\in \\mathbb{R}^{H \\times W \\times 1}" + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": ", which should be close to the ground truth image " + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "inline_equation", + "content": "I_{GT}^{0} \\in \\mathbb{R}^{rH \\times rW \\times 1}" + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "inline_equation", + "content": "z \\in \\{-N, -N + 1, \\dots, 0, \\dots, N - 1, N\\}" + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "inline_equation", + "content": "r" + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": " is the large scale factor. In this paper, we set " + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "inline_equation", + "content": "N = 2" + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "inline_equation", + "content": "r = 8, 16" + }, + { + "bbox": [ + 47, + 98, + 287, + 181 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "spans": [ + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": "To achieve this, we propose a generative learning-based framework consisting of three stages. Stage I involves exploring generative cell-specific priors through the VQGAN model, which identifies a discrete latent space of HR EM images and generates the HR EM image " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{HRref}}" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": " from the latent space. This latent space is represented using vectors from the VQGAN codebook " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": ". In Stage II, we train a latent vector indexer and connect it with the VQGAN codebook " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": " and VQGAN decoder " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "Q" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": " obtained from Stage I. This connection allows us to generate the reference HR EM image " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{Ref}}" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": " and its corresponding multi-scale generative features " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "F_{\\mathrm{Ref}}^{l}" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": " from the LR EM image " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{LR}}" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": ". Finally, in Stage III, we fuse the multi-scale generative features " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "F_{\\mathrm{Ref}}^{l}" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": " using the MPF module, align adjacent image features in the axial direction using the POD module, and fuse the adjacent image features using the 3DA module. We finally use sub-pixel convolution to reconstruct the HR output " + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "inline_equation", + "content": "I_{SR}^{0}" + }, + { + "bbox": [ + 46, + 182, + 288, + 387 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 389, + 264, + 402 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 389, + 264, + 402 + ], + "spans": [ + { + "bbox": [ + 47, + 389, + 264, + 402 + ], + "type": "text", + "content": "3.2. Exploring Generative Cell-Specific Priors" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 403, + 287, + 535 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 403, + 287, + 535 + ], + "spans": [ + { + "bbox": [ + 46, + 403, + 287, + 535 + ], + "type": "text", + "content": "EM images are characterized by their repetitive structures and textures, such as cellular membranes and subcellular organelles. These features offer an opportunity to exploit their regularity and predictability, motivating our exploration of the generative cell-specific prior in EM images for large-factor EMSR. As shown in Figure 1 (a), our framework for exploring generative cell-specific prior exploration consists of two main steps. First, we identify a discrete latent space that represents the features of HR EM images. Then, we generate the HR EM images from this latent space, leveraging its compact and representative nature." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "spans": [ + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": "Identifying a discrete latent space. We aim to identify a discrete latent space that represents HR EM images. To achieve this, we utilize an encoder " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "\\pmb{E}" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": " to parameterize the posterior categorical distribution of HR EM images " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "q_{\\phi}(\\xi \\mid o)" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "\\xi" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": " represents the variable for latent vectors, " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "o" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": " represents the variable for HR EM images and " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": " represents the encoder's parameters. Specifically, we quantize the output feature " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "Z_{e}" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "\\pmb{E}" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": " by mapping it to its closest latent vector in " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": " and obtain the quantified feature " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "Z_{d}" + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "text", + "content": " and one-hot index of each mapped HR patch, denoted as " + }, + { + "bbox": [ + 46, + 537, + 287, + 658 + ], + "type": "inline_equation", + "content": "s^{m,n}" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 58, + 666, + 287, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 666, + 287, + 716 + ], + "spans": [ + { + "bbox": [ + 58, + 666, + 287, + 716 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} Z _ {d} ^ {m, n} = \\arg \\min _ {Z _ {q} [ j ]} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2}, \\\\ s ^ {m, n} [ k ] = \\left\\{ \\begin{array}{l l} 1, & k = \\arg \\min _ {j} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2} \\\\ 0, & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {1} \\\\ \\end{array}", + "image_path": "c4b5d260118121d7f29cdd9e99d4774a242071b8b74cfc580651c13d7fd3b167.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "Z_{q}[j]" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " denotes the " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": "-th latent vector stored in " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "Z_{e}^{m,n}" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " denotes the encoder output feature element at position " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "(m,n)" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " within " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "Z_{e}" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": ", while " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "Z_{d}^{m,n}" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " denotes the quantified feature element at position " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "(m,n)" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " within " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "Z_{d}" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "s^{m,n}" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " is a v-dimensional vector and " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "s^{m,n}[k]" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " denotes the " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": "-th element in " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "s^{m,n}" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": ". The codebook " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " consists of " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " latent vectors, each with a dimensionality of " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": ". Thus, the posterior categorical distribution " + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "inline_equation", + "content": "q_{\\phi}(\\xi | o)" + }, + { + "bbox": [ + 305, + 72, + 547, + 169 + ], + "type": "text", + "content": " is defined as" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 178, + 566, + 220 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 178, + 566, + 220 + ], + "spans": [ + { + "bbox": [ + 305, + 178, + 566, + 220 + ], + "type": "interline_equation", + "content": "q _ {\\phi} (\\xi = k \\mid o) = \\left\\{ \\begin{array}{l l} 1, & Z _ {q} [ k ] = \\arg \\min _ {Z _ {q} [ j ]} \\| Z _ {q} [ j ] - Z _ {e} ^ {m, n} \\| _ {2} ^ {2} \\\\ 0, & \\text {o t h e r w i s e} \\end{array} . \\right. \\tag {2}", + "image_path": "d462fab5c435e95138bdcf21e3672d8e4b252dbfd92113e7fddbf7865acc8e3b.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "spans": [ + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "text", + "content": "Generating the HR EM image. Given the quantified feature " + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "inline_equation", + "content": "Z_{d}" + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "text", + "content": ", we can generate HR EM image " + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{HRref}}" + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "text", + "content": " through the decoder. We parameterize the prior distribution of HR EM images " + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "inline_equation", + "content": "p_{\\theta}(o \\mid \\xi)" + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "text", + "content": " through the decoder " + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "inline_equation", + "content": "Q" + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 304, + 227, + 545, + 286 + ], + "type": "text", + "content": " is the parameters of the decoder." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "spans": [ + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "text", + "content": "The encoder is composed of multiple Res-blocks [19] and convolution blocks for downsampling, while the decoder is composed of multiple Res-blocks and deconvolution blocks for upsampling. The compression patch size for downsampling is set to " + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "text", + "content": ". Both the encoder and decoder leverage self-attention mechanisms to enhance generalization quality. We optimize the latent vector " + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "inline_equation", + "content": "Z_{q}[j]" + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "text", + "content": " along with the encoder " + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "text", + "content": " and decoder " + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "inline_equation", + "content": "Q" + }, + { + "bbox": [ + 304, + 287, + 545, + 383 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 387, + 449, + 399 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 387, + 449, + 399 + ], + "spans": [ + { + "bbox": [ + 305, + 387, + 449, + 399 + ], + "type": "text", + "content": "3.3. Generating LR Reference" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "spans": [ + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "text", + "content": "With the parameterization of the latent space using " + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "text", + "content": " and the prior distribution of HR EM images using " + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "inline_equation", + "content": "Q" + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "text", + "content": ", we can generate HR EM images given real HR EM images as input. However, in the large-factor EMSR task, only highly degraded LR images are available as input. Hence, we need to map the LR images to their corresponding quantified feature " + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "inline_equation", + "content": "Z_{d}" + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "text", + "content": " to utilize the generative cell-prior stored in " + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 401, + 545, + 484 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": "To achieve this, one straightforward approach is to interpolate the LR images and feed them into the encoder [17]. This straightforward approach approximates the posterior categorical distribution of LR EM images " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "q(\\xi \\mid o_{\\downarrow})" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": " by utilizing the parameterized posterior categorical distribution of HR EM images " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "q_{\\phi}(\\xi \\mid [o_{\\downarrow}]_{\\uparrow})" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": " with the interpolation operation. Here, " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "o_{\\downarrow}" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": " represents the LR image variable, and " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "[\\cdot]_{\\uparrow}" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": " denotes the interpolation operation. However, in scenarios where significant degradation occurs in LR input images, the interpolation operation struggles to restore the rich details and textures in HR EM images. Consequently, this mismatch leads to discrepancies between the real HR EM image distribution " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "p(o)" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": " and the interpolated HR EM image distribution " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "p([o_{\\downarrow}]_{\\uparrow})" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": ", thereby resulting in disparities between " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "q(\\xi \\mid o_{\\downarrow})" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "q_{\\phi}(\\xi \\mid [o_{\\downarrow}]_{\\uparrow})" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": ". Despite the loss of fine-grained details in LR images, the partial preservation of information enables the utilization of such details as priors in mapping LR images to their corresponding quantified feature " + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "inline_equation", + "content": "Z_{d}" + }, + { + "bbox": [ + 304, + 485, + 546, + 713 + ], + "type": "text", + "content": ". To fully utilize these priors, we propose a latent" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "11315" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 74, + 395, + 369 + ], + "blocks": [ + { + "bbox": [ + 53, + 74, + 395, + 369 + ], + "lines": [ + { + "bbox": [ + 53, + 74, + 395, + 369 + ], + "spans": [ + { + "bbox": [ + 53, + 74, + 395, + 369 + ], + "type": "image", + "image_path": "493cf8d2b9ae46d437915f0bcf6293001b84ec8dc47095e1395fd1bdf2bbf203.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 376, + 548, + 442 + ], + "lines": [ + { + "bbox": [ + 46, + 376, + 548, + 442 + ], + "spans": [ + { + "bbox": [ + 46, + 376, + 548, + 442 + ], + "type": "text", + "content": "Figure 1. Overview of our framework. The proposed generative learning-based framework consists of three stages. In Stage I, the encoder, the codebook, and the decoder are trained by self-generating the input HR EM image. In Stage II, a latent vector indexer is trained and connected with the codebook and the decoder with fixed parameters to generate the reference HR EM image and multi-scale generative features from the LR EM image. In Stage III, the HR output is reconstructed by fusing multi-scale generative features and exploiting inter-section coherence in volumetric EM data with the POD module and the 3DA module. Rec denotes reconstruction layers composed of convolution layers and pixel shuffle operation." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 398, + 74, + 539, + 369 + ], + "blocks": [ + { + "bbox": [ + 398, + 74, + 539, + 369 + ], + "lines": [ + { + "bbox": [ + 398, + 74, + 539, + 369 + ], + "spans": [ + { + "bbox": [ + 398, + 74, + 539, + 369 + ], + "type": "image", + "image_path": "358f9753f2980d2ad4eb765d8f95c343cd5679b7a63d68805e26d2601ffff839.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "spans": [ + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "content": "vector indexer " + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "inline_equation", + "content": "W" + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "content": " to predict probabilities of corresponding latent vectors in " + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "content": " given LR EM images as input, as shown in Figure 1 (b). We denote the output of the latent vector indexer as " + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "inline_equation", + "content": "Z_{w}" + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "content": ", where the element at position " + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "inline_equation", + "content": "(m,n)" + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "content": " is denoted as " + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "inline_equation", + "content": "Z_{w}^{m,n}" + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "content": " and represents a " + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "content": "-dimensional vector. Then, by selecting the latent vector with the highest probability, we can effectively model the posterior categorical distribution " + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "inline_equation", + "content": "q(\\xi \\mid o_{\\downarrow})" + }, + { + "bbox": [ + 46, + 445, + 289, + 541 + ], + "type": "text", + "content": " as" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 552, + 293, + 592 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 552, + 293, + 592 + ], + "spans": [ + { + "bbox": [ + 47, + 552, + 293, + 592 + ], + "type": "interline_equation", + "content": "q _ {\\varphi} (\\xi = k \\mid o _ {\\downarrow}) = \\left\\{ \\begin{array}{l l} 1, & k = \\arg \\max _ {i \\in \\{1, 2, 3, \\dots , v \\}} Z _ {w} ^ {m, n} [ i ] \\\\ 0, & \\text {o t h e r w i s e} \\end{array} \\right., \\tag {3}", + "image_path": "fee145ab6fab6264fa51f461ed3b4685405d7f084f596ef777390c1b128f85be.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "spans": [ + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "inline_equation", + "content": "\\varphi" + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "text", + "content": " denotes the parameters of the latent vector indexer " + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "inline_equation", + "content": "W" + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "inline_equation", + "content": "Z_{w}^{m,n}[i]" + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "text", + "content": " denotes the " + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "text", + "content": "-th element of the vector " + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "inline_equation", + "content": "Z_{w}^{m,n}" + }, + { + "bbox": [ + 47, + 594, + 288, + 618 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": "This quantization operation allows us to capture the most representative latent vector that corresponds to the LR image. Then the predicted quantified feature " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "Z_{d}^{pre}" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " is obtained and fed into the decoder to generate the reference HR EM image " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{Ref}}" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " and its corresponding multi-scale generative features " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "F_{\\mathrm{Ref}}^{l}" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " through the decoder. Note that all the latent vectors used to generate " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{Ref}}" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "F_{\\mathrm{Ref}}^{l}" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " are obtained from the codebook, which contains the generative cell-specific pri" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 445, + 400, + 457 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 445, + 400, + 457 + ], + "spans": [ + { + "bbox": [ + 305, + 445, + 400, + 457 + ], + "type": "text", + "content": "ors of HR EM images." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 460, + 451, + 472 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 460, + 451, + 472 + ], + "spans": [ + { + "bbox": [ + 305, + 460, + 451, + 472 + ], + "type": "text", + "content": "3.4. Reconstructing HR Image" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 474, + 545, + 582 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 545, + 582 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 545, + 582 + ], + "type": "text", + "content": "MPF module. The complete process of reconstructing HR image is depicted in Figure 1 (c). The discrepancies between the generated HR image " + }, + { + "bbox": [ + 304, + 474, + 545, + 582 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{Ref}}" + }, + { + "bbox": [ + 304, + 474, + 545, + 582 + ], + "type": "text", + "content": " and real EM image " + }, + { + "bbox": [ + 304, + 474, + 545, + 582 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{GT}}" + }, + { + "bbox": [ + 304, + 474, + 545, + 582 + ], + "type": "text", + "content": " pose a challenge in achieving accurate multi-scale generative feature fusion. To overcome this challenge, we propose the MPF module, which focuses on identifying and fusing the multi-scale generative features. The MPF module comprises two essential processes: a mask-learning process and a multi-scale fusion process." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "content": "The mask-learning mechanism within the MPF module enables us to identify and mask out multi-scale generative features in regions that show significant boundary differences compared to real HR images. As shown in Figure 1 (d), we first embed the interpolated LR image " + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "inline_equation", + "content": "[I_{LR}]_{\\uparrow}" + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "content": " and the reference image " + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "inline_equation", + "content": "I_{Ref}" + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "content": " from the decoder into the feature space by a pre-trained VGG19 encoder [45]. We extract " + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "inline_equation", + "content": "16\\times 16" + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "content": " patches from LR feature maps and reference (Ref) feature maps without overlap. Then, We calculate cosine similarity vector " + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "inline_equation", + "content": "CS" + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "content": " between LR feature patches and Ref feature patches, where " + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "inline_equation", + "content": "CS_{i}" + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "content": " denotes cosine similarity be" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "11316" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "text", + "content": "tween the " + }, + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "text", + "content": "-th LR feature patch and the " + }, + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "text", + "content": "-th Ref feature patch. We refine the mask by employing three 2D convolutions. Finally, we apply a sigmoid function to obtain the mask " + }, + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "text", + "content": " with the same spatial resolution as LR features." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "spans": [ + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "type": "text", + "content": "To effectively fuse features from different layers of the decoder across " + }, + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "type": "text", + "content": " levels, we employ a multi-scale fusion scheme, as illustrated in Figure 1 (e). As the decoder learns the relationship between latent vectors, each layer of the decoder contains varying levels of detailed information about EM images. Additionally, since the decoder is responsible for reconstructing HR EM images, layers closer to the output represent shallower features. Given these considerations, we begin fusing features from " + }, + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "type": "inline_equation", + "content": "F_{Ref}^{0}" + }, + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "type": "text", + "content": " and its corresponding LR features " + }, + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "type": "inline_equation", + "content": "F_{LR}^{0}" + }, + { + "bbox": [ + 46, + 120, + 289, + 253 + ], + "type": "text", + "content": " with the same resolution and gradually incorporate features with lower resolution" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 49, + 261, + 297, + 355 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 261, + 297, + 355 + ], + "spans": [ + { + "bbox": [ + 49, + 261, + 297, + 355 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\tilde {F} ^ {1} = R _ {D} ^ {0} \\left(R _ {F} ^ {0} \\left(\\left\\langle F _ {L R} ^ {0}, F _ {R e f} ^ {0} \\right\\rangle\\right) \\otimes [ M ] _ {\\uparrow 2 ^ {L - 1}}\\right), \\\\ \\tilde {F} ^ {l + 1} = R _ {D} ^ {l} \\left(\\langle R _ {F} ^ {l} \\left(\\langle \\tilde {F} ^ {l}, F _ {L R} ^ {l}, F _ {R e f} ^ {l} \\rangle\\right) \\otimes [ M ] _ {\\uparrow 2 ^ {L - l - 1}}, \\tilde {F} ^ {l} \\rangle\\right), \\\\ \\hat {F} = R _ {F} ^ {L - 1} \\left(\\langle \\tilde {F} ^ {L - 1}, F _ {L R} ^ {L - 1}, F _ {R e f} ^ {L - 1} \\rangle\\right) \\otimes M, \\\\ F ^ {O u t} = R _ {O} ^ {L - 1} \\left(\\langle \\hat {F}, \\tilde {F} ^ {L - 1}, F _ {L R} ^ {L - 1} \\rangle\\right), \\tag {4} \\\\ \\end{array}", + "image_path": "676966c2e3ad148ba41176fe1137c41285cd87f4f94666e2b593508e18ab28dc.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "spans": [ + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\otimes" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " denotes element-wise multiplication, " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\langle \\cdot \\rangle" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " denotes concatenation operation, and " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "[\\cdot ]_{\\uparrow}" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " denotes interpolation operation. " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\tilde{F}^l" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " denotes output features from downsample convolution at the " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " -th level. " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "R_D^l,R_F^l" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " ,and " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "R_O^{L - 1}" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " denote downsample convolution, fusion convolution, and output convolution, respectively. " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\hat{F}" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " denotes the output feature of the last fusion convolution. " + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "inline_equation", + "content": "F^{Out}" + }, + { + "bbox": [ + 46, + 356, + 287, + 453 + ], + "type": "text", + "content": " represents the final multi-scale fusion feature." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 457, + 287, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 457, + 287, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 457, + 287, + 613 + ], + "type": "text", + "content": "POD module and 3DA module. To exploit the intersection coherence in volumetric EM data and leverage the correlation between adjacent EM images, we design two modules: the POD module and the 3DA module. The POD module is responsible for aligning the adjacent EM image output features from the MPF module in a coarse-to-fine manner. It utilizes a pyramid architecture and incorporates a pre-trained optical-flow network SPyNet and deformable convolutions to achieve accurate feature alignment. The 3DA module employs spatial attention mechanisms and 3D convolutions to effectively fuse the aligned features. More detailed information about the POD module and 3DA module can be found in the supplementary material." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 616, + 153, + 628 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 616, + 153, + 628 + ], + "spans": [ + { + "bbox": [ + 47, + 616, + 153, + 628 + ], + "type": "text", + "content": "3.5. Training Strategy" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 630, + 287, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 287, + 666 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 287, + 666 + ], + "type": "text", + "content": "In Stage I, we adopt three loss functions: a reconstruction loss " + }, + { + "bbox": [ + 46, + 630, + 287, + 666 + ], + "type": "inline_equation", + "content": "L_{r - I}" + }, + { + "bbox": [ + 46, + 630, + 287, + 666 + ], + "type": "text", + "content": ", a codebook learning loss " + }, + { + "bbox": [ + 46, + 630, + 287, + 666 + ], + "type": "inline_equation", + "content": "L_{c}" + }, + { + "bbox": [ + 46, + 630, + 287, + 666 + ], + "type": "text", + "content": ", and an adversarial loss " + }, + { + "bbox": [ + 46, + 630, + 287, + 666 + ], + "type": "inline_equation", + "content": "L_{adv}" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 53, + 673, + 287, + 713 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 673, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 53, + 673, + 287, + 713 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} L _ {r - I} = \\left\\| I _ {\\mathrm {H R r e f}} - I _ {\\mathrm {G T}} \\right\\| _ {1}, L _ {a d v} = D \\left(I _ {\\mathrm {G T}}\\right) + D \\left(- I _ {\\mathrm {H R r e f}}\\right), \\\\ L _ {c} = \\left\\| \\operatorname {s g} \\left[ Z _ {d} \\right] - Z _ {e} \\right\\| _ {2} ^ {2} + \\left\\| \\operatorname {s g} \\left[ Z _ {e} \\right] - Z _ {d} \\right\\| _ {2} ^ {2}, \\tag {5} \\\\ \\end{array}", + "image_path": "166167416d66c2fe53b3559a3cc634b50097c8b3816b1dc046bedfcb012bce1b.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " represents a PatchGAN discriminator [23] and " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "\\mathrm{sg}[\\cdot ]" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " denotes the stop-gradient operation. As Eq. 1 is non-differentiable, we propagate the gradients from the decoder to the encoder [12, 48]. We utilize R1 regularization [39] for GAN training stability. The complete objective of the first stage is" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 353, + 152, + 545, + 165 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 353, + 152, + 545, + 165 + ], + "spans": [ + { + "bbox": [ + 353, + 152, + 545, + 165 + ], + "type": "interline_equation", + "content": "L _ {s - I} = L _ {r - I} + \\lambda_ {c} L _ {c} + \\lambda_ {a d v} L _ {a d v}. \\tag {6}", + "image_path": "1a26c2d96dc8de1f167569145b18966f519ebdefd0c935e94195ddef1887b880.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "spans": [ + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "type": "text", + "content": "In Stage II, we optimize the latent vector indexer " + }, + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "type": "inline_equation", + "content": "W" + }, + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "type": "text", + "content": " while keeping the parameters of " + }, + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "type": "inline_equation", + "content": "Q" + }, + { + "bbox": [ + 304, + 172, + 545, + 209 + ], + "type": "text", + "content": " fixed. The objective of the second stage is" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 321, + 215, + 545, + 246 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 321, + 215, + 545, + 246 + ], + "spans": [ + { + "bbox": [ + 321, + 215, + 545, + 246 + ], + "type": "interline_equation", + "content": "L _ {s - I I} = - \\sum_ {m, n, i} s ^ {m, n} [ i ] \\log \\frac {\\exp \\left(Z _ {w} ^ {m , n} [ i ]\\right)}{\\sum_ {j} \\exp \\left(Z _ {w} ^ {m , n} [ j ]\\right)}. \\tag {7}", + "image_path": "8470c222c470441d5e4469d21fe7d3a09a40cdea5a393c1444e256665101f795.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "spans": [ + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "type": "text", + "content": "In Stage III, we train our network with two loss functions: a reconstruction loss " + }, + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "type": "inline_equation", + "content": "L_{r - III}" + }, + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "type": "text", + "content": " and a multi-Ref fidelity loss " + }, + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "type": "inline_equation", + "content": "L_{Mfid}" + }, + { + "bbox": [ + 304, + 253, + 545, + 289 + ], + "type": "text", + "content": " [28]. The objective of the third stage is" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 335, + 297, + 545, + 363 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 335, + 297, + 545, + 363 + ], + "spans": [ + { + "bbox": [ + 335, + 297, + 545, + 363 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} L _ {r - I I I} = \\left\\| I _ {S R} ^ {0} - I _ {G T} ^ {0} \\right\\| _ {1}, \\\\ L _ {M f i d} = \\frac {\\sum_ {z ^ {\\prime} \\in \\Omega} \\sum_ {i} \\delta_ {i} \\left(I _ {S R} ^ {0} , I _ {R e f} ^ {z ^ {\\prime}}\\right) \\cdot c _ {z ^ {\\prime} , i}}{\\sum_ {z ^ {\\prime} \\in \\Omega} \\sum_ {i} c _ {z ^ {\\prime} , i}}, \\tag {8} \\\\ L _ {s - I I I} = L _ {r - I I I} + \\lambda_ {M f i d} L _ {M f i d}, \\\\ \\end{array}", + "image_path": "923d081f2aeaced5d3ebd0ce830057154379885383856d464548b9792963244e.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "spans": [ + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "type": "inline_equation", + "content": "\\Omega = \\{-N, -N + 1, \\dots, 0, \\dots, N - 1, N\\}" + }, + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "type": "inline_equation", + "content": "\\delta_i(\\cdot, \\cdot)" + }, + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "type": "text", + "content": " denotes contextual loss in [38] and " + }, + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "type": "inline_equation", + "content": "c_{z', i}" + }, + { + "bbox": [ + 304, + 369, + 545, + 407 + ], + "type": "text", + "content": " is the matching confidence weight based on cosine similarity." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 411, + 387, + 424 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 411, + 387, + 424 + ], + "spans": [ + { + "bbox": [ + 306, + 411, + 387, + 424 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 427, + 365, + 440 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 427, + 365, + 440 + ], + "spans": [ + { + "bbox": [ + 306, + 427, + 365, + 440 + ], + "type": "text", + "content": "4.1. Settings" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "spans": [ + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "text", + "content": "Datasets. We conduct experiments under two different settings to demonstrate the superior performance of our framework in both reconstruction quality and downstream segmentation accuracy. For the first setting, we select the adult drosophila melanogaster brain dataset FAFB [57] and its subset CREMI [14] acquired at " + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "inline_equation", + "content": "4 \\times 4 \\times 40\\mathrm{nm}^3" + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "text", + "content": " resolution. In Stage I and Stage II, we train our framework on a subset (" + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "inline_equation", + "content": "\\sim 38\\mathrm{G}" + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "text", + "content": ") of FAFB to obtain a cell-specific prior. In Stage III, we utilize the padded version of the CREMI dataset, excluding the CREMI C subset, to train for large-factor EMSR. We use the cropped version of CREMI C, which has segmentation labels, as the test set consisting of 125 images. We fine-tune two pre-trained segmentation networks, Superhuman [29] and MALA [15], on the first 75 images of CREMI C. Therefore, we test all 125 images for reconstruction evaluation metrics and the last 50 for segmentation evaluation metrics. For the second setting, we select the mouse somatosensory cortex dataset Kasthuri15 [25] and its subset AC3/AC4 dataset [25] acquired at " + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "inline_equation", + "content": "3 \\times 3 \\times 29\\mathrm{nm}^3" + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "text", + "content": " resolution. As the AC3/AC4 datasets are too small, we use the data partitioning strategy from [22] and train three stages on a subset (" + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "inline_equation", + "content": "\\sim 11.2\\mathrm{G}" + }, + { + "bbox": [ + 304, + 443, + 545, + 730 + ], + "type": "text", + "content": ", i.e., Subset3 in [22]) of Kasthuri15 and AC3. We fine-tune two pre-trained segmentation networks on AC3 and test them on AC4." + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "11317" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 77, + 96, + 515, + 282 + ], + "blocks": [ + { + "bbox": [ + 46, + 70, + 547, + 94 + ], + "lines": [ + { + "bbox": [ + 46, + 70, + 547, + 94 + ], + "spans": [ + { + "bbox": [ + 46, + 70, + 547, + 94 + ], + "type": "text", + "content": "Table 1. Quantitative comparison of reconstruction quality and EM image segmentation results on CREMI C for " + }, + { + "bbox": [ + 46, + 70, + 547, + 94 + ], + "type": "inline_equation", + "content": "{16} \\times" + }, + { + "bbox": [ + 46, + 70, + 547, + 94 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 70, + 547, + 94 + ], + "type": "inline_equation", + "content": "8 \\times" + }, + { + "bbox": [ + 46, + 70, + 547, + 94 + ], + "type": "text", + "content": " EMSR. The best and the second-best results are highlighted in bold and underline. * Parameters optimized in Stage III." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 77, + 96, + 515, + 282 + ], + "lines": [ + { + "bbox": [ + 77, + 96, + 515, + 282 + ], + "spans": [ + { + "bbox": [ + 77, + 96, + 515, + 282 + ], + "type": "table", + "html": "
MethodsScaleReconstruction MetricsSegmentation MetricsParams/M
FidelityPerceptualSuperhumanMALA
PSNR↑SSIM↑LPIPS↓DISTS↓VOI↓ARAND↓VOI↓ARAND↓
Bicubic16×21.55570.48010.73380.48426.66270.70436.55990.8830-
RCAN [56]16×23.12380.57790.53360.34295.27620.61932.93530.232512.9080
SwinIR [35]16×23.10980.57810.53320.34165.12540.49552.93020.231712.1426
BSRN [34]16×22.91610.56450.54530.34025.57280.68093.20340.26940.4719
Real-ESRGAN [51]16×22.76310.55370.53330.31344.08230.48903.38060.297316.6957
EDVR [50]16×23.88940.61470.50220.31824.17090.41322.32290.19693.4455
BasicVSR [5]16×23.38770.59240.51070.31764.58250.50532.54280.21153.9339
Ours16×23.67670.60200.47900.29272.96390.30752.25710.17865.4627*
Bicubic8×25.58970.66070.47790.29825.93040.87542.47480.2036-
RCAN [56]8×29.39260.79140.37290.23393.38580.32881.56340.133312.7603
SwinIR [35]8×29.43340.79210.37240.23403.34940.32671.54000.130611.9949
BSRN [34]8×29.14640.78320.37910.23133.59280.34611.56210.13150.3611
Real-ESRGAN [51]8×29.14570.78430.37740.23173.57400.33631.55550.130916.6957
EDVR [50]8×29.73260.80160.36420.23163.17390.31591.51070.13243.2978
BasicVSR [5]8×29.08280.78310.37740.23053.46190.33361.58790.13494.0445
Ours8×29.70270.80020.35680.22912.93760.30761.50110.12984.4257*
", + "image_path": "96206aaa147bd712d822acb6757606d89ed77b944d2aeecfeda1bc40e4dc5343.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 77, + 310, + 515, + 496 + ], + "blocks": [ + { + "bbox": [ + 46, + 285, + 546, + 308 + ], + "lines": [ + { + "bbox": [ + 46, + 285, + 546, + 308 + ], + "spans": [ + { + "bbox": [ + 46, + 285, + 546, + 308 + ], + "type": "text", + "content": "Table 2. Quantitative comparison of reconstruction quality and EM image segmentation results on AC4 for " + }, + { + "bbox": [ + 46, + 285, + 546, + 308 + ], + "type": "inline_equation", + "content": "{16} \\times" + }, + { + "bbox": [ + 46, + 285, + 546, + 308 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 285, + 546, + 308 + ], + "type": "inline_equation", + "content": "8 \\times" + }, + { + "bbox": [ + 46, + 285, + 546, + 308 + ], + "type": "text", + "content": " EMSR. The best and the second-best results are highlighted in bold and underline. * Parameters optimized in Stage III." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 77, + 310, + 515, + 496 + ], + "lines": [ + { + "bbox": [ + 77, + 310, + 515, + 496 + ], + "spans": [ + { + "bbox": [ + 77, + 310, + 515, + 496 + ], + "type": "table", + "html": "
MethodsScaleReconstruction MetricsSegmentation MetricsParams/M
FidelityPerceptualSuperhumanMALA
PSNR↑SSIM↑LPIPS↓DISTS↓VOI↓ARAND↓VOI↓ARAND↓
Bicubic16×19.00780.25180.77580.46396.93000.96886.81440.9664-
RCAN [56]16×19.59380.29810.66610.39706.45350.93516.47160.929412.9080
SwinIR [35]16×19.59490.29560.66710.38936.87960.94966.54170.932212.1426
BSRN [34]16×19.56130.29280.67250.39147.19610.96156.61680.93950.4719
Real-ESRGAN [51]16×19.42540.28930.64270.37066.38530.87456.06590.914016.6957
EDVR [50]16×19.93740.32830.62320.37314.81780.71585.00290.82823.4455
BasicVSR [5]16×19.42930.28880.67470.37476.86080.95986.75480.95133.9339
Ours16×19.74680.31140.57480.35844.36550.61264.83620.82335.4627*
Bicubic8×21.09790.37200.58960.33616.76940.96756.13460.9157-
RCAN [56]8×22.31670.47730.52000.31622.21010.28262.35710.388612.7603
SwinIR [35]8×22.49090.49310.51040.32131.78670.21072.36350.524211.9949
BSRN [34]8×22.27360.47360.52310.31322.26300.28602.51200.37460.3611
Real-ESRGAN [51]8×22.34390.48890.50000.31271.88390.25842.06800.344516.6957
EDVR [50]8×22.93140.52700.48900.31761.29460.25321.64860.40273.2978
BasicVSR [5]8×22.24440.47570.51800.31142.17160.32422.51170.49534.0445
Ours8×22.92510.52700.46540.30751.15010.13771.58620.31344.4257*
", + "image_path": "a42b5236ff061bfc0cd5cd0cc14648cc5af8b9db16be4511461744cfc2d6f656.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 498, + 287, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 287, + 594 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 287, + 594 + ], + "type": "text", + "content": "Metrics. To evaluate the difference between SR results and ground truth, we use various reconstruction metrics. These encompass two fidelity metrics, PSNR and SSIM, alongside two perceptual metrics, LPIPS [55] and DISTS [10]. For EM image segmentation evaluation, we use VOI [41] and ARAND [1] as our metrics. In our segmentation evaluation, we consider both split error and merge error to ensure a comprehensive and accurate assessment." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": "Training setting. We train the networks in three stages using Adam [27] optimizer with " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\beta_{1} = 0.9" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\beta_{2} = 0.99" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " and employ Cosine Annealing scheme [37]. In our experiments, we set all initial learning rates to " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "4\\times 10^{-4}" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " except for Stage III on the mouse somatosensory cortex training dataset, where we adjust the initial learning rate to " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "1\\times 10^{-4}" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " to ensure the convergence of deformable convolution layer. To generate paired data, we use bicubic downsampling to reduce the image resolution by factors of 8 and 16. The LR patch size is set to " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "16\\times 16" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "16\\times" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " EMSR and " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "32\\times 32" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": "for " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "8 \\times" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": " EMSR during Stage III training phase. The compression patch size " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": " is set to 16 based on our ablation studies. We select the weights for our loss functions as follows: " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\lambda_{c} = 10" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\lambda_{adv} = 0.05" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\lambda_{MFid} = 0.01" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "16 \\times" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": " EMSR, and " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "\\lambda_{MFid} = 0.001" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "8 \\times" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": " EMSR. These weights are chosen through empirical experimentation aimed at striking the right balance for optimal performance. We also set the number of latent vectors to " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "v = 1024" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": " and their dimension to " + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "inline_equation", + "content": "d = 512" + }, + { + "bbox": [ + 304, + 498, + 545, + 606 + ], + "type": "text", + "content": " in the codebook based on our ablation studies." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 615, + 499, + 628 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 615, + 499, + 628 + ], + "spans": [ + { + "bbox": [ + 305, + 615, + 499, + 628 + ], + "type": "text", + "content": "4.2. Comparisons with Existing Methods" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": "We compare our framework with (1) single-image SR methods including RCAN [56], SwinIR [35], BSRN [34], and Real-ESRGAN [51], (2) video SR methods including EDVR [50] and BasicVSR [5]. All these models are pretrained on the same EM datasets for fair comparisons. The quantitative results of image reconstruction and EM image segmentation are summarized in Table 1 and Table 2." + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "11318" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 73, + 160, + 182 + ], + "blocks": [ + { + "bbox": [ + 51, + 73, + 160, + 182 + ], + "lines": [ + { + "bbox": [ + 51, + 73, + 160, + 182 + ], + "spans": [ + { + "bbox": [ + 51, + 73, + 160, + 182 + ], + "type": "image", + "image_path": "ab0bc3ef16e34c4218f80b2e9993eab993d88cd815de43e4133ce5dc9df647c0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 195, + 545, + 217 + ], + "lines": [ + { + "bbox": [ + 46, + 195, + 545, + 217 + ], + "spans": [ + { + "bbox": [ + 46, + 195, + 545, + 217 + ], + "type": "text", + "content": "Figure 2. Top: Qualitative comparison for " + }, + { + "bbox": [ + 46, + 195, + 545, + 217 + ], + "type": "inline_equation", + "content": "16 \\times" + }, + { + "bbox": [ + 46, + 195, + 545, + 217 + ], + "type": "text", + "content": " EMSR. Our framework exhibits sharper boundaries and preserves a more complete structure. 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While our framework performs the second-best in terms of PSNR and SSIM, slightly behind EDVR, these fidelity metrics do not necessarily align with human perception of image quality. On the other hand, our framework surpasses all other methods in terms of perceptual metrics LPIPS [55] and DISTS [10]. As shown in Figure 2 and Figure 3, our framework produces images with sharper boundaries, richer texture details, and more complete structures for " + }, + { + "bbox": [ + 46, + 381, + 289, + 610 + ], + "type": "inline_equation", + "content": "16 \\times" + }, + { + "bbox": [ + 46, + 381, + 289, + 610 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 381, + 289, + 610 + ], + "type": "inline_equation", + "content": "8 \\times" + }, + { + "bbox": [ + 46, + 381, + 289, + 610 + ], + "type": "text", + "content": " EMSR. This demonstrates that our cell-specific generative priors and the MPF module can effectively incorporate fine-grained details from HR EM images instead of producing smoothed results at the pixel level. It is noteworthy that although Real-ESRGAN [51] partially alleviates over-smoothing by incorporating the adversarial loss, it introduces noticeable noise-like artifacts in the super-resolved images. Additionally, a general comparison between single-image and video SR methods supports the effectiveness of incorporating adjacent EM images in the context of large-factor EMSR." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 46, + 618, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 287, + 715 + ], + "type": "text", + "content": "EM image segmentation accuracy. We evaluate the accuracy of two pre-trained segmentation networks by using the super-resolved EM images as inputs. Our framework outperforms all other methods with two different segmentation networks, demonstrating exceptional image fidelity in terms of downstream tasks achieved by our framework. Moreover, our framework effectively addresses the issue of over-segmentation caused by excessive smoothing of ex" + } + ] + } + ], + "index": 19 + }, + { + "type": "table", + "bbox": [ + 309, + 406, + 543, + 467 + ], + "blocks": [ + { + "bbox": [ + 306, + 380, + 544, + 403 + ], + "lines": [ + { + "bbox": [ + 306, + 380, + 544, + 403 + ], + "spans": [ + { + "bbox": [ + 306, + 380, + 544, + 403 + ], + "type": "text", + "content": "Table 3. Ablation studies on prior exploration and prior indexing trade-off. p denotes the compression patch size." + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 406, + 543, + 467 + ], + "lines": [ + { + "bbox": [ + 309, + 406, + 543, + 467 + ], + "spans": [ + { + "bbox": [ + 309, + 406, + 543, + 467 + ], + "type": "table", + "html": "
PStage IStage IIΔPSNRΔLPIPS
PSNR↑LPIPS↓PSNR↑LPIPS↓
835.07310.261820.12120.5240-14.95190.2622
1628.68760.371521.74230.4996-6.94530.1281
3223.18790.469321.52910.5024-1.65880.0331
6420.28320.622620.16090.6263-0.12230.0037
", + "image_path": "84ea49445c463ae22037afc430b0a208b639d30306f0b6e0688322ec6d315e16.jpg" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "table_body" + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 484, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 484, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 484, + 545, + 544 + ], + "type": "text", + "content": "isting methods, which is particularly prominent in the Superhuman segmentation network (see supplementary material for detail). Visualization examples of segmentation, as shown in Figure 2 and Figure 3, confirm the superiority of our framework over existing methods." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 548, + 406, + 560 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 548, + 406, + 560 + ], + "spans": [ + { + "bbox": [ + 306, + 548, + 406, + 560 + ], + "type": "text", + "content": "4.3. Ablation Studies" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 564, + 545, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 564, + 545, + 685 + ], + "spans": [ + { + "bbox": [ + 304, + 564, + 545, + 685 + ], + "type": "text", + "content": "Effectiveness of prior exploration. Table 3 presents a quantitative analysis of the prior exploration process. As the mapping from the HR space to the latent space involves a compression process, the size of the compression patch is a crucial hyperparameter. In Stage I, a smaller compression patch size captures more detailed information and leads to more realistic generated images. We observe a significant improvement in both PSNR and LPIPS as the compression patch size decreases, indicating improvements in reconstruction quality and fidelity." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 306, + 689, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 714 + ], + "type": "text", + "content": "Trade-off between prior exploration and prior indexing. There exists a trade-off between the quality of generated im" + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "11319" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 52, + 76, + 284, + 132 + ], + "blocks": [ + { + "bbox": [ + 52, + 76, + 284, + 132 + ], + "lines": [ + { + "bbox": [ + 52, + 76, + 284, + 132 + ], + "spans": [ + { + "bbox": [ + 52, + 76, + 284, + 132 + ], + "type": "image", + "image_path": "2a08bf77344d9368af2ce66b228506636199ece61cb52c7f8b08735acba7a86d.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 136, + 287, + 169 + ], + "lines": [ + { + "bbox": [ + 46, + 136, + 287, + 169 + ], + "spans": [ + { + "bbox": [ + 46, + 136, + 287, + 169 + ], + "type": "text", + "content": "Figure 4. Qualitative comparison of prior indexing results and the effectiveness of the latent vector indexer. " + }, + { + "bbox": [ + 46, + 136, + 287, + 169 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 46, + 136, + 287, + 169 + ], + "type": "text", + "content": " denotes the compression patch size." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 100, + 204, + 232, + 267 + ], + "blocks": [ + { + "bbox": [ + 46, + 178, + 288, + 200 + ], + "lines": [ + { + "bbox": [ + 46, + 178, + 288, + 200 + ], + "spans": [ + { + "bbox": [ + 46, + 178, + 288, + 200 + ], + "type": "text", + "content": "Table 4. Ablation studies on the quantity " + }, + { + "bbox": [ + 46, + 178, + 288, + 200 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 178, + 288, + 200 + ], + "type": "text", + "content": " and dimensions " + }, + { + "bbox": [ + 46, + 178, + 288, + 200 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 178, + 288, + 200 + ], + "type": "text", + "content": " of latent vectors in the codebook on prior exploration." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 100, + 204, + 232, + 267 + ], + "lines": [ + { + "bbox": [ + 100, + 204, + 232, + 267 + ], + "spans": [ + { + "bbox": [ + 100, + 204, + 232, + 267 + ], + "type": "table", + "html": "
vdPSNR↑LPIPS↓
51251228.31650.3806
102425628.52270.3728
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1024102428.75740.3743
", + "image_path": "58e3f1b2c6bbeb599ab8e72918a79d558a3dbeebd0d0fba629691096d2ece0a9.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "spans": [ + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "text", + "content": "ages in Stage I and the accuracy of predicting latent vectors through the latent vector indexer in Stage II. This trade-off arises from the fact that as the compression patch size decreases and less information is available when feeding LR images into the latent vector indexer in Stage II, the learned posterior distribution of LR EM images " + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "inline_equation", + "content": "q_{\\varphi}(\\xi \\mid o_{\\downarrow})" + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "text", + "content": " deviates further from the true posterior distribution " + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "inline_equation", + "content": "q(\\xi \\mid o_{\\downarrow})" + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "text", + "content": ". Consequently, reducing the compression patch size allows the first stage network to preserve more image details, but it poses challenges for the indexing task in Stage II. This can be observed from the changes in " + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "inline_equation", + "content": "\\Delta PSNR" + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "inline_equation", + "content": "\\Delta LPIPS" + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "text", + "content": " values presented in Table 3, which indicate a decrease in the indexing accuracy as the compression patch size decreases. In consideration of the trade-off between prior exploration and prior indexing, we set " + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "inline_equation", + "content": "p = 16" + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "text", + "content": ", as depicted in Table 3 and Figure 4. Moreover, as illustrated in Figure 4, removing the latent vector indexer and directly utilizing bicubic interpolation along with the decoder in Stage I leads to notably blurry " + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "inline_equation", + "content": "I_{Ref}" + }, + { + "bbox": [ + 45, + 284, + 287, + 514 + ], + "type": "text", + "content": " outcomes." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "spans": [ + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "text", + "content": "Impact of the quantity and dimensions of latent vectors in the codebook. We systematically investigate the impact of the quantity and dimensions of latent vectors in the codebook by selecting several sets of representative parameters. The results are summarized in Table 4. From the experimental results, we observe that augmenting " + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "text", + "content": " to 2048 or " + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "text", + "content": " to 1024 does not yield significant improvements in prior exploration, despite doubling the codebook's size. Conversely, reducing " + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "text", + "content": " to 512 or " + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "text", + "content": " to 256 results in a noticeable performance decline. Based on these insightful results, we set " + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "inline_equation", + "content": "v = 1024" + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "inline_equation", + "content": "d = 512" + }, + { + "bbox": [ + 46, + 517, + 287, + 673 + ], + "type": "text", + "content": " for our codebook. This decision strikes an optimal balance between computational efficiency and performance." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "content": "Effectiveness of POD module and 3DA module. We evaluate the effectiveness of the proposed POD and 3DA modules for multi-image feature alignment and multi-image" + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 315, + 106, + 535, + 175 + ], + "blocks": [ + { + "bbox": [ + 305, + 70, + 545, + 104 + ], + "lines": [ + { + "bbox": [ + 305, + 70, + 545, + 104 + ], + "spans": [ + { + "bbox": [ + 305, + 70, + 545, + 104 + ], + "type": "text", + "content": "Table 5. Ablation studies of our proposed modules. VOI-S and VOI-M denote segmentation using Superhuman and MALA, respectively." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 315, + 106, + 535, + 175 + ], + "lines": [ + { + "bbox": [ + 315, + 106, + 535, + 175 + ], + "spans": [ + { + "bbox": [ + 315, + 106, + 535, + 175 + ], + "type": "table", + "html": "
MPFPOD3DAPSNR↑LPIPS↓VOI-S↓VOI-M↓
XXX23.52870.51684.59122.7265
X✓✓23.73540.50634.24292.3410
✓X✓23.54220.48583.15002.5144
✓✓X23.55480.48153.01932.3794
✓✓✓23.67670.47902.96392.2571
", + "image_path": "0bafb0dc4d59920758da2187ed9502e65e2c4f241f2e23ed83cb8e1a85772158.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 193, + 545, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 193, + 545, + 384 + ], + "spans": [ + { + "bbox": [ + 304, + 193, + 545, + 384 + ], + "type": "text", + "content": "feature fusion, respectively. To ensure a fair comparison, we replace these modules with residual blocks with comparable parameters. Table 5 shows the results of our ablation study. We observe that even without incorporating generative prior, the introduction of the POD module or 3DA module leads to improvements in both reconstruction evaluation metrics and segmentation metrics, as demonstrated in row 1 and row 2. Furthermore, when the generative prior is introduced, both the POD module and the 3DA module provide additional gains in reconstruction and segmentation metrics, as shown in rows 3 to 5. Notably, the POD module exhibits a larger improvement compared to the 3DA module, indicating its significance in multi-image feature alignment for large-factor EMSR. These results demonstrate the effectiveness of the proposed POD and 3DA modules in enhancing visual reconstruction quality and segmentation accuracy." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 392, + 546, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 392, + 546, + 513 + ], + "spans": [ + { + "bbox": [ + 304, + 392, + 546, + 513 + ], + "type": "text", + "content": "Effectiveness of MPF module. The effectiveness of our MPF module is further demonstrated in row 2 and row 5 of Table 5, where it exhibits substantial improvements in perceptual metric LPIPS and segmentation metric VOI. It is important to note that the introduction of " + }, + { + "bbox": [ + 304, + 392, + 546, + 513 + ], + "type": "inline_equation", + "content": "L_{Mfd}" + }, + { + "bbox": [ + 304, + 392, + 546, + 513 + ], + "type": "text", + "content": " in Stage III leads to a decrease in PSNR. This observation highlights the inconsistency between PSNR and visual quality as well as segmentation outcomes and reinforces the importance of using perceptual metrics and segmentation metrics to evaluate reconstruction quality." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 522, + 379, + 534 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 522, + 379, + 534 + ], + "spans": [ + { + "bbox": [ + 306, + 522, + 379, + 534 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "spans": [ + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "type": "text", + "content": "In this paper, we present a generative learning-based framework for large-factor EMSR. By exploring and indexing cell-specific priors using a VQGAN-Indexer network, our framework leverages generative learning to capture the repetitive structures and textures of EM images. The MPF module effectively fuses generative priors obtained from the VQGAN-Indexer network while ensuring the image fidelity. Extensive experiments demonstrate the superiority of our framework in terms of both reconstruction quality and segmentation accuracy for " + }, + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "type": "inline_equation", + "content": "8 \\times" + }, + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "type": "inline_equation", + "content": "16 \\times" + }, + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "type": "text", + "content": " EMSR." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 671, + 399, + 685 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 671, + 399, + 685 + ], + "spans": [ + { + "bbox": [ + 306, + 671, + 399, + 685 + ], + "type": "text", + "content": "Acknowledgment" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "This work was supported in part by the National Natural Science Foundation of China under Grant 62021001." + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "11320" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 713 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "text", + "content": "[1] Ignacio Arganda-Carreras, Srinivas C Turaga, Daniel R Berger, Dan Ciresan, Alessandro Giusti, Luca M Gambardella, Jürgen Schmidhuber, Dmitry Laptev, Sarvesh Dwivedi, Joachim M Buhmann, et al. 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In CVPR, 2019. 2" + } + ] + } + ], + "index": 30 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "11322" + } + ] + } + ], + "index": 32 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_content_list.json b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..0b94db879a8bc203e8fc2b44da53b093c47105e1 --- /dev/null +++ b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_content_list.json @@ -0,0 +1,1428 @@ +[ + { + "type": "text", + "text": "Learning Multi-dimensional Human Preference for Text-to-Image Generation", + "text_level": 1, + "bbox": [ + 93, + 130, + 875, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Sixian Zhang,\\* Bohan Wang\\* Junqiang Wu\\* Yan Li\\* Tingting Gao, Di Zhang, Zhongyuan Wang Kuaishou Technology", + "text_level": 1, + "bbox": [ + 112, + 180, + 854, + 218 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 251, + 313, + 266 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Current metrics for text-to-image models typically rely on statistical metrics which inadequately represent the real preference of humans. Although recent work attempts to learn these preferences via human annotated images, they reduce the rich tapestry of human preference to a single overall score. However, the preference results vary when humans evaluate images with different aspects. Therefore, to learn the multi-dimensional human preferences, we propose the Multi-dimensional Preference Score (MPS), the first multi-dimensional preference scoring model for the evaluation of text-to-image models. The MPS introduces the preference condition module upon CLIP model to learn these diverse preferences. It is trained based on our Multi-dimensional Human Preference (MHP) Dataset, which comprises 918,315 human preference choices across four dimensions (i.e., aesthetics, semantic alignment, detail quality and overall assessment) on 607,541 images. The images are generated by a wide range of latest text-to-image models. The MPS outperforms existing scoring methods across 3 datasets in 4 dimensions, enabling it a promising metric for evaluating and improving text-to-image generation. The model and dataset will be made publicly available to facilitate future research. Project page: https://wangbohan97.github.io/MPS/.", + "bbox": [ + 75, + 282, + 473, + 648 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 78, + 676, + 209, + 691 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "\"There are a thousand Hamlets in a thousand people's eyes.\"", + "bbox": [ + 88, + 704, + 452, + 719 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "-Vissarion Belinsky", + "bbox": [ + 351, + 727, + 459, + 739 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Text-to-image generative models [10, 14, 15] have achieved remarkable advancements in recent years, and these models have the capability to generate high-fidelity and contextually relevant images based on textual descriptions (i.e., prompts). To evaluate the quality of generated images, several evaluation metrics are proposed, including Inception Score (IS) [16], Fréchet Inception Distance (FID)", + "bbox": [ + 75, + 757, + 468, + 863 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/1027e4b711ed6d283ca76f98b3b2de0a85ed2bf9fad8020b5f186e7c7d0c033f.jpg", + "image_caption": [], + "image_footnote": [ + "Prompt: A picture depicting the Grand Canal of Venice, with a row of houses on both sides of the canal and boatman rowing two boats on the river, illustration, vivid colors, high-contrast." + ], + "bbox": [ + 509, + 253, + 622, + 340 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/873bbab20c2820637a11a37993c96c6fefa059a84bdd9f11244827c23d5079d0.jpg", + "image_caption": [], + "image_footnote": [ + "mal of Venice, with a row of houses on \nng two boats on the river, illustration," + ], + "bbox": [ + 625, + 253, + 738, + 339 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e6ff0ffa3974bc5035eaba5ccfc0f0ca35a0ac04c917e762a4562891451cadc7.jpg", + "image_caption": [], + "image_footnote": [ + "" + ], + "bbox": [ + 743, + 256, + 880, + 340 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/a286e4f56162a05986c22a4d27fc06e816f38febc3d4544f25e3fb9f492e3dc2.jpg", + "image_caption": [ + "Figure 1. As humans evaluate images from different perspectives, their preference for the images also varies. Specifically, when examining the images in the top row, the image on the left stands out in terms of aesthetic appeal, though it falls short in semantic alignment (e.g., two boats on the river) compared to its counterpart on the right. In the case of the bottom row, both images are aesthetically pleasing, yet the image on the right is marred by poor detail quality (e.g., as signified by the red bounding boxes around the distorted hand and foot)." + ], + "image_footnote": [ + "Prompt: A family of three poses in the Grand Canyon, with the main wearing sunglasses and smiling, 4k resolution, extremely detailed" + ], + "bbox": [ + 509, + 373, + 622, + 460 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/1325e2359ffdc1c66038a0f5a812ee4b168f3e28c59fcf0fd417d8807efdc20b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 625, + 373, + 738, + 460 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "nd Canyon, with the man wearing emely detailed", + "bbox": [ + 625, + 462, + 715, + 478 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ae2c264553da446934d054e36dfe392213d464a1beed5450cb3fb8a4ff5ae573.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 745, + 372, + 879, + 455 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "[5], and CLIP Score [12]. However, these statistical metrics fall short of aligning with human perceptual preferences. For instance, metrics like the IS or the FID, although indicative of image quality to some extent, might not necessarily reflect how a human observer would rate the image in terms of fidelity, coherence, or aesthetic appeal.", + "bbox": [ + 496, + 641, + 893, + 733 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Contrary to these statistical metrics, several approaches [6, 20-22, 24] turn towards human-centric evaluations, where generated images are manually annotated according to human preferences. Subsequently, models are trained with these annotations to predict preference scores. However, these approaches typically utilize a single score to summarize all human preferences, overlooking the multidimensionality of human preferences. As Fig. 1 shows, the preference results differ when humans evaluate images from various perspectives. Therefore, using a single-dimensional evaluation method is insufficient in capturing the broad", + "bbox": [ + 496, + 734, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation.", + "bbox": [ + 236, + 1, + 807, + 18 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "Except for this watermark, it is identical to the accepted version;", + "bbox": [ + 323, + 16, + 722, + 30 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 292, + 31, + 754, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*These authors contributed equally to this work.", + "bbox": [ + 94, + 875, + 351, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "† Corresponding author.", + "bbox": [ + 96, + 887, + 222, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "8018", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "table", + "img_path": "images/17eb6dcfb4561a35d90b4a96dacb901987ffbcdcb5739290e4ebdc54cdea9d63.jpg", + "table_caption": [ + "Table 1. Comparisons of text-to-image models quality databases. Our Multi-dimensional Human Preference (MHP) dataset achieves significant advancements over existing work in three aspects, including prompt collection, image generation, and preference annotation. Moreover, it constitutes the largest dataset both in generated images and preference annotations. Note that the Diffusion DB only contains generated images but lacks annotations of human preferences. Besides, KOKORS is an internal dataset derived from in-house platform for designer, which provides $\\sim 10\\mathrm{w}$ prompts." + ], + "table_footnote": [], + "table_body": "
DatasetPrompt collectionImage GenerationPreference annotation
SourceAnnotationSourceNumberRatingDimension
DiffusionDB [19]DiffusionDB×Diffusion (1)1,819,8080None
AGIQA-1K [24]DiffusionDB×Diffusion (2)1,08023,760Overall
PickScore [6]Web Application×Diffusion (3)583,747583,747Overall
ImageReward [22]DiffusionDB×Auto Regressive; Diffusion (6)136,892410,676Overall
HPS [21]DiffusionDB×Diffusion (1)98,80798,807Overall
HPS v2 [20]DiffusionDB, COCO✓GAN; Auto Regressive; Diffusion, COCO (9)430,060798,090Overall
AGIQA-3K [7]DiffusionDB×GAN; Auto Regressive; Diffusion (6)2,982125,244Overall; Alignment
MHPDiffusionDB, PromptHero, KOLORS, GPT4✓GAN; Auto Regressive; Diffusion (9)607,541918,315Aesthetics, Detail, Alignment, Overall
", + "bbox": [ + 84, + 169, + 883, + 369 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "range of personalized needs and preferences. To ensure a comprehensive evaluation of text-to-image synthesis outputs, it is crucial to learn and utilize multi-dimensional human preferences.", + "bbox": [ + 75, + 383, + 470, + 445 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To learn the multi-dimensional human preferences, we propose the Multi-dimensional Human Preference (MHP) dataset. Compared to prior efforts [6, 20-22], the MHP dataset offers significant enhancements in prompts collection, image generation, and preference annotation. For the prompt collection, previous work [6, 21, 22] directly utilizes existing open-source datasets (e.g., Diffusion DB [19]) or datasets collated from the internet [6], overlooking the potential data bias of long-tail distribution. To this end, based on the categories schema of Parti [23], we annotate the collected prompts into 7 category labels (e.g., characters, scenes, objects, animals, etc.). For the underrepresented tail categories, we employ Large Language Models (LLMs) (e.g., GPT-4 [9]) to generate additional prompts. This process results in a balanced prompt collection across various categories, which is used for later image generation. For image generation, following previous work [7, 20], we not only utilize existing open-source Diffusion models and their variants, but also employ GANs and auto-regressive models to generate images. Consequently, we generate a dataset of 607,541 images, which are further used to create 918,315 pairwise comparisons of images for preference annotation. The quantity of image data constitutes the largest dataset of its kind. For the annotation of human preferences, contrary to the single annotation of existing work [6, 20, 21, 24], we consider a broader range of dimensions for human preferences and employ human annotators to label each image pair across four dimensions, including aesthetics, detail quality, semantic alignment, and overall score.", + "bbox": [ + 75, + 446, + 470, + 883 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To learn human preferences, existing methods employ", + "bbox": [ + 96, + 885, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "the pre-trained vision-language models (e.g., CLIP [11], BLIP [8]) to extract features from images and prompts independently, followed by computing the similarity between them. These methods then fine-tune the network utilizing the collected preference data. For learning the multidimensional preferences, a straightforward strategy is to train separate models for different preferences. However, such a simple strategy requires data re-collection and model re-training for the new preference. Moreover, due to the potential bias in single-preference data, a model trained under one preference condition often exhibits diminished performance when evaluated against other preferences. Therefore, we propose the Multi-dimensional Preference Score (MPS), a unified model capable of predicting scores under various preference conditions. Specifically, a certain preference is denoted by a series of descriptive words. For instance, the 'aesthetic' condition is decomposed into words such as 'light', 'color', and 'clarity' to describe the attributes of this condition. These attribute words are used to compute similarities with the prompt, resulting in a similarity matrix that reflects the correspondence between words in the prompt and the specified condition. On the other hand, features from images and text are extracted using a pre-trained vision-language model. Subsequently, two modalities are fused through a multimodal cross-attention layer. The similarity matrix serves as a mask merged into the cross-attention layer, which ensures that the text only related to the condition is attended to by the visual modality. Then the fused features are used to predict the preference scores. We evaluate our MPS model on both the existing human preference datasets (i.e., ImageReward [22] and HPS v2 [20]) and our MHP dataset. The experimental results indicate that our MPS model surpasses existing benchmarks in evaluating both overall and multi-dimensional prefer", + "bbox": [ + 496, + 383, + 893, + 898 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "8019", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "ences, establishing a new state-of-the-art in comparison with related work.", + "bbox": [ + 76, + 90, + 468, + 119 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In summary, our main contributions are as follows:", + "bbox": [ + 96, + 122, + 433, + 136 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We introduce the Multi-dimensional Human Preference (MHP) datasets for evaluating text-to-image models. The MHP contains balanced prompts and the largest collection of images with multi-dimensional annotations. Based on MHP, we propose a standard test benchmark to evaluate existing text-to-image synthesis models.", + "- We propose the MPS model, which learns multidimensional human preferences and evaluates the scores of generated images under different preference conditions.", + "- Our MPS exhibits superior performance compared to existing methods across three datasets in predicting the overall preferences and multi-dimensional preferences." + ], + "bbox": [ + 76, + 137, + 467, + 333 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2. Related work", + "text_level": 1, + "bbox": [ + 76, + 348, + 212, + 364 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.1. Text-to-image Generation and Evaluation", + "text_level": 1, + "bbox": [ + 76, + 373, + 431, + 388 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The text-to-image task aims to synthesize realistic images from natural language description (i.e., prompt). Several work attempts to tackle this problem, including GANs [4, 25], auto-regressive [2, 3, 23] and diffusion models [10, 14, 15]. Among the previously mentioned methods, diffusion models gain significant attention for their exceptional performance. These methods are principally divided into two categories: latent-based and pixel-based approaches. The Latent Diffusion Model (LDM) [14] is notable as the first to introduce a latent-based diffusion model, leveraging an auto-encoder to map images into a latent space where the diffusion process is executed. Following this, Stable Diffusion has notably propelled the field forward by open-sourcing SD series [10]. In contrast, DALL-E 2 [13] and Imagen [15] are predicated on pixel-based diffusion models. Besides, the Imagen [15] integrates the large language model T5 XXL to achieve a text-to-image super-resolution diffusion model capable of producing highly realistic images. Current text-to-image models excel in creating high-quality images but often miss aligning with human preferences in real-world applications. For evaluating text-to-image models, several evaluation metrics are proposed to evaluate the quality of generated images, including Inception Score (IS) [16], Fréchet Inception Distance (FID) [5], and CLIP Score [12]. However, these statistical metrics fall short of aligning with human perceptual preferences. Our MPS provides a comprehensive evaluation for text-to-image generations, facilitating the evaluation of alignment with multi-dimensional human preference.", + "bbox": [ + 76, + 397, + 468, + 835 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Learning human preferences", + "text_level": 1, + "bbox": [ + 76, + 845, + 334, + 863 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Currently, several studies attempt to collect and learn human preferences for the evaluation of text-to-image gen", + "bbox": [ + 76, + 869, + 467, + 900 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/d353a47d6c6d83dc4c757bfcce712d067a429789e9da4cfb07202e28edbb42ec.jpg", + "image_caption": [ + "Figure 2. Prompt collection. The initially collected prompts exhibit a long-tail distribution across various categories. After prompt augmentation with GPT, we obtain a relatively balanced prompt dataset, which contains 66,389 prompts." + ], + "image_footnote": [], + "bbox": [ + 513, + 97, + 890, + 214 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "eration. They use the collected data to fine-tune visual-language models (VLMs) to align with human selections.", + "bbox": [ + 498, + 301, + 890, + 330 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "HPS [21] introduces the HPD dataset of human preference choices. The images are generated solely using the Stable Diffusion model with prompts from Diffusion DB. They train HPS model utilizing the human preference annotations of HPD to align it with human preference. Subsequently, they fine-tune the Stable Diffusion model under the guidance of HPS, leading to better generated images that are more preferred by human users. However, HPS is limited to a single generation model and a relatively small number of images. Furthermore, HPS v2 [20] introduces a larger dataset, employing 8 generative models, including Diffusion models, GANs, and Auto regressive models, and also incorporating captions from the COCO dataset. However, both HPS and HPS v2 primarily focus on overall human preferences, not considering the diversity of human tastes.", + "bbox": [ + 496, + 333, + 890, + 559 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "PickScore [6] proposes a web application designed to collect prompts and human preference annotations from real users. Unlike previous methods adopting prompts from existing datasets (e.g. DiffusionDB), the prompts of PickScore are directly generated by actual users. The dataset of PickScore is sizeable, however, it focuses only on the overall preferences, lacking detailed annotations for multi-dimension preferences.", + "bbox": [ + 496, + 561, + 890, + 681 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ImageReward [22] employs four types of Diffusion models along with an auto-regression-based model. Their annotation of generated images is more detailed with scoring ranging from 0 to 7. Beyond overall satisfaction, they also consider annotations for alignment and fidelity. However, they merge alignment and fidelity into a single overall score, inadequately capturing the multi-dimensional dimensions of human preferences.", + "bbox": [ + 496, + 684, + 890, + 805 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "AGIQA-1k [24] and AGIQA-3k [7] utilize a range of generative models, including Diffusion, GAN, and Auto regressive models, to produce images. They consider both overall and alignment preferences. However, their dataset size is considerably smaller compared to existing work.", + "bbox": [ + 498, + 806, + 890, + 883 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Our MHP dataset represents an advancement over previ", + "bbox": [ + 519, + 885, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "8020", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "table", + "img_path": "images/e3c2010a480f778cbf2f178ecddca0795649d8927f8a1339cdb9c9db9a176d42.jpg", + "table_caption": [ + "Table 2. Image generation. The image sources of the MHP dataset consist of the images generated from 9 text-to-image generative models. Note that KOKORS is an internal model for in-house designer platform." + ], + "table_footnote": [], + "table_body": "
SourceTypeImagesSplit
KOKORSDiffusion211,707Train and test
DeepFloyd IFDiffusion27,311Train and test
Stable Diffusion XLDiffusion89,176Train and test
Openjourney v4Diffusion133,875Train and test
Stable Diffusion v2.0Diffusion84,590Train and test
Stable Diffusion v1.5Diffusion56,882Train and test
VQGAN+CLIPGAN1,000Test
LAFITEGAN1,000Test
CogView2Autoregressive2,000Test
", + "bbox": [ + 83, + 155, + 460, + 311 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "ous work in terms of prompt collection, image generation, and preference annotation.", + "bbox": [ + 76, + 334, + 467, + 364 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3. MHP Dataset", + "text_level": 1, + "bbox": [ + 76, + 388, + 215, + 402 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.1. Prompt collection and annotation", + "text_level": 1, + "bbox": [ + 76, + 417, + 369, + 431 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Our prompts are carefully collected from several databases, including PromptHero[1], DiffusionDB[19] and KOKORS-dataset (an internal dataset derived from in-house platform for designers). Following the category schema from Parti[23], we further merge some categories, and finally determine 7 categories as illustrated in Fig. 2. The definitions and merging rules are detailed in the supplementary material. Based on these defined categories, we employ human annotators to label the initially collected 59,396 prompts. Additionally, the annotators are also required to filter out anomalous prompts, such as those that are incoherent, incomprehensible, or have punctuation errors. After annotation, we obtain 52,057 prompts. The distribution of these prompts, based on their categories, is depicted in Fig. 2. As the figure shows, the initially collected prompts exhibit a long-tail distribution across categories. Such category imbalances might lead to imbalanced generated images. Consequently, the human preferences learned from these imbalanced data could also be biased. As a result, we further expand our prompts.", + "bbox": [ + 75, + 443, + 468, + 746 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "By employing the GPT-4[9], we obtain additional prompts to supplement categories with initially low quantities (see supplementary materials for more examples of the generated prompts). These generated prompts are further refined by annotators to remove those incoherent or incomprehensible items. As shown in Figure 2, after supplementation, we obtain 66,389 prompts and the distribution of prompts across categories is balanced. These balanced prompts help us in learning more representative human preferences.", + "bbox": [ + 75, + 750, + 470, + 901 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/37a1111427a93b60ed21499121cb4d5f7261e1b1d3d29c0a892689fc276e3638.jpg", + "image_caption": [ + "Figure 3. Annotation interface. Annotators are required to evaluate the preference for the given image pair on four dimensions, including aesthetics, detail quality (detail), semantic alignment (alignment) and overall score (overall). Annotation scores are discrete values ranging from 1 to 5, which are subsequently normalized to Boolean values of 0 or 1. When the scores are tied, the normalized score is set to 0.5." + ], + "image_footnote": [], + "bbox": [ + 517, + 89, + 869, + 344 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Image collection and annotation", + "text_level": 1, + "bbox": [ + 500, + 473, + 782, + 489 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "As shown in Table 2, we utilize Diffusion models (such as the Stable Diffusion series and DeepFloyd IF), GANs, and AutoRegressive models to generate images based on the obtained prompts. Each model produces 2-4 images for every single prompt. The generated images come from a variety of model architectures, with various image resolution scales (e.g., $512 \\times 512$ , $1024 \\times 1024$ , $1366 \\times 768$ ), and aspect ratios (e.g., 1:1, 16:9). This diversity ensures a comprehensive representation of the text-to-image models' generalization capability.", + "bbox": [ + 496, + 500, + 890, + 651 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Images generated from the same prompt are paired together for comparison. To enhance the representativeness of these image pairs, the construction of image pairs sources not only from images generated by different models but also includes those produced by the same model using different random seeds. Based on these contrastive image pairs, we employ human annotators to evaluate the image pairs with our annotation interface as shown in Fig. 3. The annotators are required to evaluate the quality of the generated image pairs based on three sub-dimensions (i.e., aesthetics, text-image consistency, and detail) and one overall dimension (i.e., overall score). These four dimensions are defined as follows:", + "bbox": [ + 496, + 652, + 890, + 848 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "1. Aesthetics: annotators should measure the aesthetic quality of a generated image pair in terms of composition, light contrast, color matching, clarity, tone, style,", + "bbox": [ + 500, + 854, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "8021", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "depth of field, atmosphere, and artistry of the image.", + "bbox": [ + 96, + 90, + 442, + 106 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "2. Detail quality: annotators should focus on the delicacy of image details such as texture, hair, and light and shadow, whether there is distortion in the face, hands, and limbs of the characters, whether there is a blurry overall view, object distortion, severe deformation.", + "3. Semantic alignment: annotators should evaluate the semantic consistency of the generated images with the prompts, and the evaluation includes measuring whether the generated image accurately matches the textual description (e.g., quantity, attributes, location, positional relationships) and whether there is missing or redundant content in the generated image.", + "4. Overall assessment: Based on the combination of above aspects and subjective preferences, the annotators assess the quality of each generated image from a holistic perspective." + ], + "bbox": [ + 76, + 107, + 467, + 347 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The annotators rate all these scores of each image in the pair into five distinct levels (from 1 to 5), and the scores are eventually normalized to [0, 1]. The image annotation is completed by a crowdsourced team of 210 members. Before the official annotation, each member needs to perform pre-annotation, where any member whose annotation results have a high degree of inconsistency with that of the majority is disqualified. Eventually, 198 members participate in the annotation of generated image pairs, of which 170 members act as annotators and 28 members act as quality inspectors. Each image pair is annotated by three annotators respectively and the final result is averaged from these three annotation results. $20\\%$ of the annotated data is extracted and sent to the quality inspector for inspection. If there is significant difference in annotation results between annotators and inspectors, the annotated data is considered invalid and will be relabeled.", + "bbox": [ + 75, + 356, + 468, + 609 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Statistics", + "text_level": 1, + "bbox": [ + 76, + 630, + 181, + 643 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In summary, we collect 66,389 prompts and employ 9 recent text-to-image models to generate 607,541 images. Based on these images, we construct 918,315 image pairs. Notably, $20\\%$ of these pairs are created using the same model but with different settings, while the other $80\\%$ are produced by different models, allowing for a wide range of comparisons. Each image pair is then annotated by 3 distinct annotators across 4 dimensions to enable the study of diversity in human preference.", + "bbox": [ + 75, + 656, + 467, + 792 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We divide the annotated data into training, validation and test sets. The training and validation set contains 898,315 and 10,000 image pairs and the test set comprises 10,000 pairs. To ensure that the data distribution is representative, the test set includes not only images generated by Diffusion models but also those produced by GAN and Autoregressive models.", + "bbox": [ + 75, + 795, + 467, + 898 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/b5d4020d89159312c02e7298fa5c03b2144bbc0dd73c853ef3766d38d44d0e6b.jpg", + "image_caption": [ + "Figure 4. The framework of Multi-dimensional Preference Score (MPS). The MPS takes the generated image, prompt and preference condition as the input, and predicts the quality (i.e. human preference) of the generated image under the given preference condition." + ], + "image_footnote": [], + "bbox": [ + 516, + 89, + 875, + 344 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Multi-dimensional Preference Prediction", + "text_level": 1, + "bbox": [ + 500, + 440, + 864, + 455 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Model Structure of MPS", + "text_level": 1, + "bbox": [ + 500, + 465, + 723, + 481 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "As shown in Fig. 4, we adopt CLIP [11] to initially extract features from images and prompts. Given a prompt $x$ , a generated image $y$ and a preference condition $c$ , the visual feature of $y$ is obtained by the vision encoder of the CLIP by $X_{v} = E_{v}(y)$ , where $X_{v} \\in \\mathbb{R}^{n_{v} \\times n_{d}}$ . $n_{v}$ is the token number of the image and $n_{d}$ is the feature dimension. $X_{t} = E_{t}(x)$ where $X_{t} \\in \\mathbb{R}^{n_{p} \\times n_{d}}$ and $n_{p}$ is the token number of the text. $X_{c} = E_{c}(c)$ , where $X_{c} \\in \\mathbb{R}^{n_{c} \\times n_{d}}$ and $n_{p}$ is the token number of word sets representing the preference. For the setup of word sets for each preference, please refer to Sec. 5.1. Previous works [6, 21, 22] typically utilize the first dimension of $X_{v}$ and the last dimension of $X_{t}$ to calculate the preference score, which loses a lot of detailed information of both image and text. Alternatively, we employ the full range of $X_{v}$ and $X_{t}$ and fuse two modalities through the Cross Attention (CA) module", + "bbox": [ + 498, + 489, + 890, + 731 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nC A \\left(X _ {v}, X _ {t}\\right) = \\sigma \\left(\\frac {X _ {v} W _ {q} \\left(X _ {t} W _ {k}\\right) ^ {T}}{\\sqrt {n _ {d}}}\\right) X _ {t} W _ {v} \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 537, + 742, + 890, + 782 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\sigma$ is the SoftMax activation function, and $W_{*} \\in \\mathbb{R}^{n_d \\times n_d}$ are parameters and biases are omitted. Our motivation is computing the preference scores in different preference conditions. Specific words in the prompt should be given more attention based on different conditions, e.g., when aesthetics is considered as a condition, words in the prompt related to color, light, and clarity should be taken", + "bbox": [ + 498, + 794, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "8022", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/e819749a37e22634eaeee4b272cc314c42a6a1fb75575cbba828d45c82189799.jpg", + "table_caption": [ + "Table 3. Main results of MPS and comparison methods on human preference evaluation. Preference accuracy (\\%) is calculated on ImageReward, HPD v2, and our MHP dataset." + ], + "table_footnote": [], + "table_body": "
IDPreference ModelImageRewardHPD v2MHP (Overall)
1CLIP score [11]54.371.263.7
2Aesthetic Score [17]57.472.662.9
3ImageReward [22]65.170.667.5
4HPS [21]61.273.165.5
5PickScore [6]62.979.869.5
6HPS v2 [20]65.783.365.5
7MPS (Ours)67.583.574.2
", + "bbox": [ + 76, + 142, + 480, + 292 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "into account more when calculating the score. Therefore, we propose a condition mask to highlight the relevant tokens while suppressing the irrelevant tokens. The condition is represented by a series of attribute words, e.g. the preference condition of 'Aesthetic' is represented by a set of words, including light, color and clarity. The relevance of prompt and condition is computed by $R_{p,c} = X_cX_t^T W_c + b_c$ , where $R_{p,c} \\in \\mathbb{R}^{n_c \\times n_p}$ and $W_c$ and $b_c$ are learnable parameters. The $R_{p,c}$ is averaged along the dimension $n_c$ and then repeated $n_v$ times to obtain the mask $M_c \\in \\mathbb{R}^{n_v \\times n_p}$ . The $M_c$ is further binarized to $\\bar{M}_c$ , where elements below the similarity threshold are assigned to negative infinity and others are set to zero. Based on the condition mask $\\bar{M}_c$ , the Eq. 1 is further improved as", + "bbox": [ + 75, + 308, + 473, + 521 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nC A \\left(X _ {v}, X _ {t} \\mid X _ {c}\\right) = \\sigma \\left(\\frac {X _ {v} W _ {q} \\left(X _ {t} W _ {k}\\right) ^ {T}}{\\sqrt {d}} + \\bar {M} _ {c}\\right) X _ {t} W _ {v} \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 80, + 530, + 468, + 583 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The Eq. 2 ensures that the parts of the prompt that are relevant to the condition information receive more attention when computing the preference score. We adopt the first dimension (i.e. the cls token) of fused feature $CA(X_v, X_t | X_c)$ for further prediction, which is denoted as $f_{v,t}$ and $s \\in \\mathbb{R}^{1 \\times n_d}$ . Additionally, to prevent the issue of excessively short prompts leading to a scenario where no words of the prompt are related to the condition. In such a scenario, the cross-attention layer would be unable to capture the information from the prompt. Therefore, we supplement the $f_{v,t}$ with additional prompt feature $f_t$ , where $f_t$ is the last dimension of $X_t$ . Consequently, the MPS is obtained by", + "bbox": [ + 75, + 584, + 468, + 779 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nS (x, y \\mid c) = \\alpha f _ {v, t} \\cdot f _ {t} \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 197, + 781, + 468, + 797 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $\\alpha$ is a learned scalar while $x, y$ and $c$ denote the prompt, image and preference condition, respectively.", + "bbox": [ + 76, + 805, + 468, + 837 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Training", + "text_level": 1, + "bbox": [ + 76, + 845, + 181, + 863 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The input for our objective includes our scoring function MPS $S(x, y|c)$ , a prompt $x$ , two generated image $y_1, y_2$ , a", + "bbox": [ + 76, + 869, + 468, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "preference condition $c$ and the preference score (annotated by human) $p$ , where $p$ takes a value of [1, 0] for $y_{1}$ is preferred, [0, 1] if $y_{2}$ is preferred, or [0.5, 0.5] for ties. Following previous work [6], the training objective minimizes the KL-divergence between the annotation $p$ and the softmax-normalized prediction", + "bbox": [ + 496, + 90, + 890, + 181 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {p} _ {i, c} = \\frac {\\exp S (x , y _ {i} | c)}{\\sum_ {i = 1} ^ {2} \\exp S (x , y _ {i} | c)} \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 189, + 890, + 234 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nL _ {P} = \\sum_ {c} \\sum_ {i = 1} ^ {\\bar {}} p _ {i, c} (l o g p _ {i, c} - l o g \\hat {p} _ {i, c})\n$$\n", + "text_format": "latex", + "bbox": [ + 573, + 234, + 818, + 268 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We initialize the text and vision encoders, $E_{t}$ and $E_{v}$ , with parameters from the pre-trained CLIP-H model, while the remaining parameters are subject to random initialization. We train our MPS on MHP datasets for 30,000 steps, with a batch size of 128, a learning rate of 3e-6, and a warmup period of 500 steps.", + "bbox": [ + 496, + 276, + 890, + 367 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 380, + 633, + 397 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 500, + 404, + 689, + 421 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Preference condition setting. We utilize the following collection of word sets to represent human preferences: 1) Aesthetics: light, color, clarity, tone, style, ambiance, artistry; 2) Detail quality: shape, face, hair, hands, limbs, structure, instance, texture; 3) Semantic alignment: quantity, attributes, position, number, location; 4) Overall: light, color, clarity, tone, style, ambiance, artistry, shape, face, hair, hands, limbs, structure, instance, texture, quantity, attributes, position, number, location.", + "bbox": [ + 496, + 428, + 890, + 564 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation setting. We select widely used statistical metrics for evaluating text-to-image models, namely the CLIP score [12] and Aesthetic score [17] for comparison. Additionally, we also choose methods that align with human preferences for evaluating text-to-image models, including Image Reward [22], HPS [20, 21] and PickScore [6]. Following previous works [6, 20], we utilize publicly available pre-trained models without finetuning for evaluation.", + "bbox": [ + 496, + 580, + 890, + 703 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Evaluation Results", + "text_level": 1, + "bbox": [ + 500, + 710, + 679, + 724 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Overall Preference accuracy. Previous works on learning human preferences mostly focus on a singular, overall preference, i.e., summarizing human preferences with an overall score. For a fair comparison, we choose existing publicly available human preference datasets: the ImageReward test set [22] and the HPD v2 test set [20], along with our MHP dataset (using only data annotated with overall scores) to compare our method with relevant baselines. As shown in Tab. 3, our MPS demonstrates a better accuracy across these three datasets, indicating the strong generalization capability of our method.", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "8023", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/e976c34c70d582028fd2562a1bb2ccac17144a14de06b13efccd77c9e35db754.jpg", + "table_caption": [ + "Table 4. The evaluation of MPS and related scoring functions for the prediction of multi-dimensional human preferences(%)" + ], + "table_footnote": [], + "table_body": "
IDPreference ModelOverallAestheticsAlignmentDetail
1CLIP score [11]63.6768.1482.6961.71
2Aesthetic Score [17]62.8582.8569.3660.34
3ImageReward [22]67.4574.7975.2758.31
4HPS [21]65.5173.8673.8662.05
5PickScore [6]69.5270.9570.9256.74
6HPS v2 [20]65.5173.8673.8762.06
7MPS (Ours)74.2483.8683.8785.18
", + "bbox": [ + 76, + 128, + 480, + 277 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Multinational Preference accuracy. In addition to the overall score, we also compare the performance of previous works and our method in predicting multi-dimensional human preferences based on our MHP dataset. As Tab. 4 illustrates, the CLIP Score and Aesthetic score focus on specific types of preferences, only perform well in certain preferences (e.g., semantic alignment or aesthetics). However, they fall short in predicting other preferences compared to models trained on human preferences. Additionally, preference models [6, 20-22] generally perform better in overall score and some other dimensions but lack generalization in certain specific preferences (e.g., details)*. We illustrate the Fig. 5 to reveal the underlying reasons for this poor generalization. In the first and second rows of Fig. 5, the score functions exhibit a high correlation only with the trained preferences (e.g. semantic alignment and overall score), but perform poorly on other preferences. It is important to note that the prediction of different preferences is based on the same data, albeit with different preference annotations. This indicates that not all preferences are strongly correlated, which results in that improvements in one preference might come at the expense of others. Therefore, only learning a single score is inadequate in fully reflecting the complexity of human preferences. In contrast, our MPS learns human preferences with the condition mask from multiple dimensions and maintains high consistency across all dimensions of human preferences, as shown in the third row of Fig. 5. Besides, as Tab. 4 indicated, MPS outperforms the related works by a large margin in predicting the multi-dimensional human preference on the MHP dataset.", + "bbox": [ + 76, + 295, + 472, + 750 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Visualization Results. Further, we aim to explore why our MPS exhibits strong generalization across various dimensions of human preferences, even some preferences (e.g., detail quantity) are not highly correlated with others. To this end, we visualized the attention map of images and prompts that MPS focuses on when predicting hu", + "bbox": [ + 75, + 771, + 468, + 864 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/05ce8b5a3070af49bee5a1b330805ac69759a5b3256a3b9a44ac722525e74295.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 500, + 88, + 901, + 151 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/216ced121ee7889a6afb654c3c0f044c24c0689ea311d0ed314b6af64d3a694f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 500, + 152, + 900, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/095bbabf4bc7c2525ba001d0d085c15aa113ddc765eaf24a3108c99c193bf911.jpg", + "image_caption": [ + "Figure 5. Correlation between real user preferences and model predictions. The x-axis of each subplot represents the annotated real human preferences, and the y-axis denotes the model's predictions. We examine three models: CLIP score, PickScore, and MPS (ours). Each subplot is annotated with the calculated correlation coefficient R-value, where a higher R-value indicates a closer alignment of the model's predictions with actual human preferences." + ], + "image_footnote": [], + "bbox": [ + 500, + 210, + 900, + 268 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "man preferences. As shown in Fig. 6, we employ Grad-CAM [18] and $f_{v,t}$ to generate attention heatmaps of the image, and utilize the values of $M_c$ to represent the attention heatmap of the prompt. The visualization results indicate that our HPS attends to different regions of prompts and images depending on the specific preference condition. This is attributed to the condition mask, which allows only those words in the prompt related to the preference condition to be observed by the image. The condition mask ensures that the model predicts the preference with different inputs, and the model only needs to calculate the similarity between patches in the image and the retained partial prompt to determine the final score. Therefore, the selective focus enabled by the condition mask allows utilizing a unified model to predict multinational preferences effectively, even if some preferences have weak correlations with others.", + "bbox": [ + 496, + 409, + 893, + 665 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Ablation study. We conduct ablation studies to verify the effectiveness of each component, as illustrated in Tab. 5. Compared to the baseline† (i.e., PickScore), the cross-attention module enables more comprehensive integration between image and prompt, leading to improvement of prediction accuracy in overall score, aesthetics, and semantic alignment. However, the model still underperforms in detail quantity, which is less correlated with other preferences. The addition of the condition mask $M_{c}$ alleviates this issue and improves the prediction performance across various preferences, especially in the detail quantity. Furthermore, we train separate models for different preferences.", + "bbox": [ + 496, + 684, + 893, + 866 + ], + "page_idx": 6 + }, + { + "type": "page_footnote", + "text": "*Since these methods have been trained solely to generate an overall score, we could only duplicate it for multinational preferences.", + "bbox": [ + 76, + 875, + 468, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_footnote", + "text": "†Note that the baseline shares the same network architecture with PickScore in Tab. 3 and 4, but is trained on our MHP dataset.", + "bbox": [ + 500, + 875, + 890, + 898 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "8024", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d574610aed709865fa4e5b496868957fc34d260e63b0f2a287de029af19fcae1.jpg", + "image_caption": [ + "Figure 6. Visualization. We leverage Grad-CAM and the condition mask $M_{c}$ to visualize attention heatmaps for the image and prompt. The condition mask results in the prompt focusing on words related to the preference condition. For Aesthetic, the model tends to focus on colors (e.g., pink) and lighting (e.g., bright). In the case of semantic alignment, the focus shifts to attributes (e.g., pink suit) and position (e.g., inside, background). For detail quantity, the model's attention is on instances (e.g., alpaca, machine, fancy food). On the image side, the model also tends to focus on areas of the image that correlate with the parts of the prompt receiving attention." + ], + "image_footnote": [], + "bbox": [ + 84, + 89, + 883, + 334 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/bc896c7835d4c84c92d39168b32459a940d0a220be4999dcf7dc3bad7237e81e.jpg", + "table_caption": [ + "Table 5. Ablation study for different modules used in MPS. Base: PickScore is employed as the baseline model. CA: Cross-attention module. Mask: Preference condition mask $M_{c}$ . Row 4 illustrates the models that have identical structures but are trained separately for each preference type." + ], + "table_footnote": [], + "table_body": "
IDModuleOverallAestheticsAlignmentDetail
BaseCAMask
1✓70.6571.0570.8157.46
2✓✓74.1171.8373.0258.79
3✓✓✓74.2483.8683.8785.18
4Separately trained MPS73.5180.5479.6876.81
", + "bbox": [ + 78, + 508, + 468, + 623 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Experimental results indicate that models trained separately for each preference do not perform as well as those trained to learn multiple preferences simultaneously. We infer that more extensive annotations and unified training contribute to better model generalization. Ablation studies validate the effectiveness of each module, particularly the condition mask, in learning multiple preferences.", + "bbox": [ + 75, + 640, + 468, + 747 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.3. MPS Benchmark", + "text_level": 1, + "bbox": [ + 76, + 756, + 246, + 771 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Based on the MPS model and the collected MHP dataset, we introduce the MPS benchmark for evaluating text-to-image models across multiple dimensions. The MPS benchmark includes a set of evaluation prompts designed to assess the models on a total of 4,000 prompts, covering seven categories: characters, scenes, objects, animals, plants, arts, and food. Each category comprises 500 prompts. Our MPS assesses the images generated by the text-to-image mod", + "bbox": [ + 75, + 779, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "els across four dimensions: Aesthetic, Semantic Alignment, Detail Quantity, and Overall Score. The scoring results can assist users in selecting superior models based on their personal preferences. Additionally, the scoring results can also enhance the generative models' performance by selecting more preferable images with higher MPS scores.", + "bbox": [ + 496, + 430, + 893, + 522 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusions", + "text_level": 1, + "bbox": [ + 500, + 537, + 627, + 553 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we introduce the Multi-dimensional Human Preference (MHP) dataset and Multi-dimensional Preference Score (MPS) to evaluate text-to-image models from multi-dimensional human preferences. The MHP dataset offers improvements over previous methods in prompt collection, image generation, and preference annotation, which comprises 918,315 human preference choices across four dimensions. These preferences include aesthetics, semantic alignment, detail quantity, and overall score. Additionally, to align the multi-dimensional human preferences, we propose the MPS, which employs a unified network to score generated images based on varying preference conditions. The MPS introduces a condition mask that retains words in the prompt related to the preference condition. Subsequently, the model integrates only the retained prompt with the image to compute the final score. MPS outperforms related works in predicting multi-dimensional human preferences across three datasets, which demonstrates the generalization of our method.", + "bbox": [ + 496, + 563, + 893, + 849 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements: We sincerely thank Zhuang Li, Lingyu Zou, and Peihan Li for their valuable discussions and feedback.", + "bbox": [ + 498, + 872, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "8025", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Prompthero. https://prompthero.com/.4", + "[2] Ming Ding, Zhuoyi Yang, Wenyi Hong, Wendi Zheng, Chang Zhou, Da Yin, Junyang Lin, Xu Zou, Zhou Shao, Hongxia Yang, and Jie Tang. 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Res., 2022, 2, 3, 4", + "[24] Zicheng Zhang, Chunyi Li, Wei Sun, Xiaohong Liu, Xiongkuo Min, and Guangtao Zhai. A perceptual quality assessment exploration for aigc images. arXiv preprint arXiv:2303.12618, 2023. 1, 2, 3", + "[25] Yufan Zhou, Ruiyi Zhang, Changyou Chen, Chunyuan Li, Chris Tensmeyer, Tong Yu, Jiuming Gu, Jinhui Xu, and Tong Sun. Lafite: Towards language-free training for text-to-image generation. arXiv preprint arXiv:2111.13792, 2021. 3" + ], + "bbox": [ + 78, + 90, + 468, + 330 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "8027", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_model.json b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_model.json new file mode 100644 index 0000000000000000000000000000000000000000..12e17e1f430a5b72c973d48075bf4988c674b656 --- /dev/null +++ b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_model.json @@ -0,0 +1,1848 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.002, + 0.808, + 0.02 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation." + }, + { + "type": "header", + "bbox": [ + 0.325, + 0.017, + 0.723, + 0.031 + ], + "angle": 0, + "content": "Except for this watermark, it is identical to the accepted version;" + }, + { + "type": "header", + "bbox": [ + 0.294, + 0.032, + 0.755, + 0.047 + ], + "angle": 0, + "content": "the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.094, + 0.131, + 0.877, + 0.154 + ], + "angle": 0, + "content": "Learning Multi-dimensional Human Preference for Text-to-Image Generation" + }, + { + "type": "title", + "bbox": [ + 0.113, + 0.181, + 0.856, + 0.219 + ], + "angle": 0, + "content": "Sixian Zhang,\\* Bohan Wang\\* Junqiang Wu\\* Yan Li\\* Tingting Gao, Di Zhang, Zhongyuan Wang Kuaishou Technology" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.252, + 0.314, + 0.267 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.284, + 0.474, + 0.649 + ], + "angle": 0, + "content": "Current metrics for text-to-image models typically rely on statistical metrics which inadequately represent the real preference of humans. Although recent work attempts to learn these preferences via human annotated images, they reduce the rich tapestry of human preference to a single overall score. However, the preference results vary when humans evaluate images with different aspects. Therefore, to learn the multi-dimensional human preferences, we propose the Multi-dimensional Preference Score (MPS), the first multi-dimensional preference scoring model for the evaluation of text-to-image models. The MPS introduces the preference condition module upon CLIP model to learn these diverse preferences. It is trained based on our Multi-dimensional Human Preference (MHP) Dataset, which comprises 918,315 human preference choices across four dimensions (i.e., aesthetics, semantic alignment, detail quality and overall assessment) on 607,541 images. The images are generated by a wide range of latest text-to-image models. The MPS outperforms existing scoring methods across 3 datasets in 4 dimensions, enabling it a promising metric for evaluating and improving text-to-image generation. The model and dataset will be made publicly available to facilitate future research. Project page: https://wangbohan97.github.io/MPS/." + }, + { + "type": "title", + "bbox": [ + 0.079, + 0.677, + 0.21, + 0.693 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.089, + 0.705, + 0.454, + 0.72 + ], + "angle": 0, + "content": "\"There are a thousand Hamlets in a thousand people's eyes.\"" + }, + { + "type": "text", + "bbox": [ + 0.352, + 0.728, + 0.46, + 0.741 + ], + "angle": 0, + "content": "-Vissarion Belinsky" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.758, + 0.47, + 0.864 + ], + "angle": 0, + "content": "Text-to-image generative models [10, 14, 15] have achieved remarkable advancements in recent years, and these models have the capability to generate high-fidelity and contextually relevant images based on textual descriptions (i.e., prompts). To evaluate the quality of generated images, several evaluation metrics are proposed, including Inception Score (IS) [16], Fréchet Inception Distance (FID)" + }, + { + "type": "image", + "bbox": [ + 0.511, + 0.254, + 0.623, + 0.341 + ], + "angle": 0, + "content": null + }, + { + "type": "image_footnote", + "bbox": [ + 0.513, + 0.343, + 0.73, + 0.364 + ], + "angle": 0, + "content": "Prompt: A picture depicting the Grand Canal of Venice, with a row of houses on both sides of the canal and boatman rowing two boats on the river, illustration, vivid colors, high-contrast." + }, + { + "type": "image", + "bbox": [ + 0.627, + 0.254, + 0.739, + 0.34 + ], + "angle": 0, + "content": null + }, + { + "type": "image_footnote", + "bbox": [ + 0.627, + 0.343, + 0.739, + 0.364 + ], + "angle": 0, + "content": "mal of Venice, with a row of houses on \nng two boats on the river, illustration," + }, + { + "type": "image", + "bbox": [ + 0.745, + 0.257, + 0.882, + 0.342 + ], + "angle": 0, + "content": null + }, + { + "type": "image_footnote", + "bbox": [ + 0.746, + 0.343, + 0.875, + 0.364 + ], + "angle": 0, + "content": "" + }, + { + "type": "image", + "bbox": [ + 0.511, + 0.374, + 0.623, + 0.461 + ], + "angle": 0, + "content": null + }, + { + "type": "image_footnote", + "bbox": [ + 0.513, + 0.463, + 0.717, + 0.479 + ], + "angle": 0, + "content": "Prompt: A family of three poses in the Grand Canyon, with the main wearing sunglasses and smiling, 4k resolution, extremely detailed" + }, + { + "type": "image", + "bbox": [ + 0.627, + 0.374, + 0.739, + 0.461 + ], + "angle": 0, + "content": null + }, + { + "type": "image_footnote", + "bbox": [ + 0.627, + 0.463, + 0.717, + 0.479 + ], + "angle": 0, + "content": "nd Canyon, with the man wearing emely detailed" + }, + { + "type": "image", + "bbox": [ + 0.746, + 0.373, + 0.88, + 0.456 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.496, + 0.895, + 0.621 + ], + "angle": 0, + "content": "Figure 1. As humans evaluate images from different perspectives, their preference for the images also varies. Specifically, when examining the images in the top row, the image on the left stands out in terms of aesthetic appeal, though it falls short in semantic alignment (e.g., two boats on the river) compared to its counterpart on the right. In the case of the bottom row, both images are aesthetically pleasing, yet the image on the right is marred by poor detail quality (e.g., as signified by the red bounding boxes around the distorted hand and foot)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.642, + 0.894, + 0.734 + ], + "angle": 0, + "content": "[5], and CLIP Score [12]. However, these statistical metrics fall short of aligning with human perceptual preferences. For instance, metrics like the IS or the FID, although indicative of image quality to some extent, might not necessarily reflect how a human observer would rate the image in terms of fidelity, coherence, or aesthetic appeal." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.902 + ], + "angle": 0, + "content": "Contrary to these statistical metrics, several approaches [6, 20-22, 24] turn towards human-centric evaluations, where generated images are manually annotated according to human preferences. Subsequently, models are trained with these annotations to predict preference scores. However, these approaches typically utilize a single score to summarize all human preferences, overlooking the multidimensionality of human preferences. As Fig. 1 shows, the preference results differ when humans evaluate images from various perspectives. Therefore, using a single-dimensional evaluation method is insufficient in capturing the broad" + }, + { + "type": "page_footnote", + "bbox": [ + 0.095, + 0.875, + 0.352, + 0.888 + ], + "angle": 0, + "content": "*These authors contributed equally to this work." + }, + { + "type": "page_footnote", + "bbox": [ + 0.098, + 0.888, + 0.223, + 0.9 + ], + "angle": 0, + "content": "† Corresponding author." + }, + { + "type": "list", + "bbox": [ + 0.095, + 0.875, + 0.352, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "8018" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.089, + 0.895, + 0.16 + ], + "angle": 0, + "content": "Table 1. Comparisons of text-to-image models quality databases. Our Multi-dimensional Human Preference (MHP) dataset achieves significant advancements over existing work in three aspects, including prompt collection, image generation, and preference annotation. Moreover, it constitutes the largest dataset both in generated images and preference annotations. Note that the Diffusion DB only contains generated images but lacks annotations of human preferences. Besides, KOKORS is an internal dataset derived from in-house platform for designer, which provides \\(\\sim 10\\mathrm{w}\\) prompts." + }, + { + "type": "table", + "bbox": [ + 0.086, + 0.17, + 0.885, + 0.371 + ], + "angle": 0, + "content": "
DatasetPrompt collectionImage GenerationPreference annotation
SourceAnnotationSourceNumberRatingDimension
DiffusionDB [19]DiffusionDB×Diffusion (1)1,819,8080None
AGIQA-1K [24]DiffusionDB×Diffusion (2)1,08023,760Overall
PickScore [6]Web Application×Diffusion (3)583,747583,747Overall
ImageReward [22]DiffusionDB×Auto Regressive; Diffusion (6)136,892410,676Overall
HPS [21]DiffusionDB×Diffusion (1)98,80798,807Overall
HPS v2 [20]DiffusionDB, COCO✓GAN; Auto Regressive; Diffusion, COCO (9)430,060798,090Overall
AGIQA-3K [7]DiffusionDB×GAN; Auto Regressive; Diffusion (6)2,982125,244Overall; Alignment
MHPDiffusionDB, PromptHero, KOLORS, GPT4✓GAN; Auto Regressive; Diffusion (9)607,541918,315Aesthetics, Detail, Alignment, Overall
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.385, + 0.471, + 0.446 + ], + "angle": 0, + "content": "range of personalized needs and preferences. To ensure a comprehensive evaluation of text-to-image synthesis outputs, it is crucial to learn and utilize multi-dimensional human preferences." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.447, + 0.471, + 0.884 + ], + "angle": 0, + "content": "To learn the multi-dimensional human preferences, we propose the Multi-dimensional Human Preference (MHP) dataset. Compared to prior efforts [6, 20-22], the MHP dataset offers significant enhancements in prompts collection, image generation, and preference annotation. For the prompt collection, previous work [6, 21, 22] directly utilizes existing open-source datasets (e.g., Diffusion DB [19]) or datasets collated from the internet [6], overlooking the potential data bias of long-tail distribution. To this end, based on the categories schema of Parti [23], we annotate the collected prompts into 7 category labels (e.g., characters, scenes, objects, animals, etc.). For the underrepresented tail categories, we employ Large Language Models (LLMs) (e.g., GPT-4 [9]) to generate additional prompts. This process results in a balanced prompt collection across various categories, which is used for later image generation. For image generation, following previous work [7, 20], we not only utilize existing open-source Diffusion models and their variants, but also employ GANs and auto-regressive models to generate images. Consequently, we generate a dataset of 607,541 images, which are further used to create 918,315 pairwise comparisons of images for preference annotation. The quantity of image data constitutes the largest dataset of its kind. For the annotation of human preferences, contrary to the single annotation of existing work [6, 20, 21, 24], we consider a broader range of dimensions for human preferences and employ human annotators to label each image pair across four dimensions, including aesthetics, detail quality, semantic alignment, and overall score." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.886, + 0.47, + 0.902 + ], + "angle": 0, + "content": "To learn human preferences, existing methods employ" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.385, + 0.895, + 0.899 + ], + "angle": 0, + "content": "the pre-trained vision-language models (e.g., CLIP [11], BLIP [8]) to extract features from images and prompts independently, followed by computing the similarity between them. These methods then fine-tune the network utilizing the collected preference data. For learning the multidimensional preferences, a straightforward strategy is to train separate models for different preferences. However, such a simple strategy requires data re-collection and model re-training for the new preference. Moreover, due to the potential bias in single-preference data, a model trained under one preference condition often exhibits diminished performance when evaluated against other preferences. Therefore, we propose the Multi-dimensional Preference Score (MPS), a unified model capable of predicting scores under various preference conditions. Specifically, a certain preference is denoted by a series of descriptive words. For instance, the 'aesthetic' condition is decomposed into words such as 'light', 'color', and 'clarity' to describe the attributes of this condition. These attribute words are used to compute similarities with the prompt, resulting in a similarity matrix that reflects the correspondence between words in the prompt and the specified condition. On the other hand, features from images and text are extracted using a pre-trained vision-language model. Subsequently, two modalities are fused through a multimodal cross-attention layer. The similarity matrix serves as a mask merged into the cross-attention layer, which ensures that the text only related to the condition is attended to by the visual modality. Then the fused features are used to predict the preference scores. We evaluate our MPS model on both the existing human preference datasets (i.e., ImageReward [22] and HPS v2 [20]) and our MHP dataset. The experimental results indicate that our MPS model surpasses existing benchmarks in evaluating both overall and multi-dimensional prefer" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "8019" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.12 + ], + "angle": 0, + "content": "ences, establishing a new state-of-the-art in comparison with related work." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.123, + 0.434, + 0.137 + ], + "angle": 0, + "content": "In summary, our main contributions are as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.138, + 0.468, + 0.228 + ], + "angle": 0, + "content": "- We introduce the Multi-dimensional Human Preference (MHP) datasets for evaluating text-to-image models. The MHP contains balanced prompts and the largest collection of images with multi-dimensional annotations. Based on MHP, we propose a standard test benchmark to evaluate existing text-to-image synthesis models." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.229, + 0.468, + 0.287 + ], + "angle": 0, + "content": "- We propose the MPS model, which learns multidimensional human preferences and evaluates the scores of generated images under different preference conditions." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.289, + 0.468, + 0.334 + ], + "angle": 0, + "content": "- Our MPS exhibits superior performance compared to existing methods across three datasets in predicting the overall preferences and multi-dimensional preferences." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.138, + 0.468, + 0.334 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.349, + 0.214, + 0.365 + ], + "angle": 0, + "content": "2. Related work" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.374, + 0.433, + 0.39 + ], + "angle": 0, + "content": "2.1. Text-to-image Generation and Evaluation" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.398, + 0.47, + 0.837 + ], + "angle": 0, + "content": "The text-to-image task aims to synthesize realistic images from natural language description (i.e., prompt). Several work attempts to tackle this problem, including GANs [4, 25], auto-regressive [2, 3, 23] and diffusion models [10, 14, 15]. Among the previously mentioned methods, diffusion models gain significant attention for their exceptional performance. These methods are principally divided into two categories: latent-based and pixel-based approaches. The Latent Diffusion Model (LDM) [14] is notable as the first to introduce a latent-based diffusion model, leveraging an auto-encoder to map images into a latent space where the diffusion process is executed. Following this, Stable Diffusion has notably propelled the field forward by open-sourcing SD series [10]. In contrast, DALL-E 2 [13] and Imagen [15] are predicated on pixel-based diffusion models. Besides, the Imagen [15] integrates the large language model T5 XXL to achieve a text-to-image super-resolution diffusion model capable of producing highly realistic images. Current text-to-image models excel in creating high-quality images but often miss aligning with human preferences in real-world applications. For evaluating text-to-image models, several evaluation metrics are proposed to evaluate the quality of generated images, including Inception Score (IS) [16], Fréchet Inception Distance (FID) [5], and CLIP Score [12]. However, these statistical metrics fall short of aligning with human perceptual preferences. Our MPS provides a comprehensive evaluation for text-to-image generations, facilitating the evaluation of alignment with multi-dimensional human preference." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.847, + 0.336, + 0.864 + ], + "angle": 0, + "content": "2.2. Learning human preferences" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Currently, several studies attempt to collect and learn human preferences for the evaluation of text-to-image gen" + }, + { + "type": "image", + "bbox": [ + 0.514, + 0.098, + 0.891, + 0.215 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.225, + 0.892, + 0.281 + ], + "angle": 0, + "content": "Figure 2. Prompt collection. The initially collected prompts exhibit a long-tail distribution across various categories. After prompt augmentation with GPT, we obtain a relatively balanced prompt dataset, which contains 66,389 prompts." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.302, + 0.891, + 0.332 + ], + "angle": 0, + "content": "eration. They use the collected data to fine-tune visual-language models (VLMs) to align with human selections." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.334, + 0.892, + 0.56 + ], + "angle": 0, + "content": "HPS [21] introduces the HPD dataset of human preference choices. The images are generated solely using the Stable Diffusion model with prompts from Diffusion DB. They train HPS model utilizing the human preference annotations of HPD to align it with human preference. Subsequently, they fine-tune the Stable Diffusion model under the guidance of HPS, leading to better generated images that are more preferred by human users. However, HPS is limited to a single generation model and a relatively small number of images. Furthermore, HPS v2 [20] introduces a larger dataset, employing 8 generative models, including Diffusion models, GANs, and Auto regressive models, and also incorporating captions from the COCO dataset. However, both HPS and HPS v2 primarily focus on overall human preferences, not considering the diversity of human tastes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.563, + 0.892, + 0.683 + ], + "angle": 0, + "content": "PickScore [6] proposes a web application designed to collect prompts and human preference annotations from real users. Unlike previous methods adopting prompts from existing datasets (e.g. DiffusionDB), the prompts of PickScore are directly generated by actual users. The dataset of PickScore is sizeable, however, it focuses only on the overall preferences, lacking detailed annotations for multi-dimension preferences." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.685, + 0.892, + 0.806 + ], + "angle": 0, + "content": "ImageReward [22] employs four types of Diffusion models along with an auto-regression-based model. Their annotation of generated images is more detailed with scoring ranging from 0 to 7. Beyond overall satisfaction, they also consider annotations for alignment and fidelity. However, they merge alignment and fidelity into a single overall score, inadequately capturing the multi-dimensional dimensions of human preferences." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.808, + 0.892, + 0.884 + ], + "angle": 0, + "content": "AGIQA-1k [24] and AGIQA-3k [7] utilize a range of generative models, including Diffusion, GAN, and Auto regressive models, to produce images. They consider both overall and alignment preferences. However, their dataset size is considerably smaller compared to existing work." + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.886, + 0.891, + 0.901 + ], + "angle": 0, + "content": "Our MHP dataset represents an advancement over previ" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "8020" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.471, + 0.146 + ], + "angle": 0, + "content": "Table 2. Image generation. The image sources of the MHP dataset consist of the images generated from 9 text-to-image generative models. Note that KOKORS is an internal model for in-house designer platform." + }, + { + "type": "table", + "bbox": [ + 0.084, + 0.156, + 0.462, + 0.312 + ], + "angle": 0, + "content": "
SourceTypeImagesSplit
KOKORSDiffusion211,707Train and test
DeepFloyd IFDiffusion27,311Train and test
Stable Diffusion XLDiffusion89,176Train and test
Openjourney v4Diffusion133,875Train and test
Stable Diffusion v2.0Diffusion84,590Train and test
Stable Diffusion v1.5Diffusion56,882Train and test
VQGAN+CLIPGAN1,000Test
LAFITEGAN1,000Test
CogView2Autoregressive2,000Test
" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.335, + 0.468, + 0.365 + ], + "angle": 0, + "content": "ous work in terms of prompt collection, image generation, and preference annotation." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.389, + 0.216, + 0.404 + ], + "angle": 0, + "content": "3. MHP Dataset" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.418, + 0.37, + 0.433 + ], + "angle": 0, + "content": "3.1. Prompt collection and annotation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.444, + 0.47, + 0.747 + ], + "angle": 0, + "content": "Our prompts are carefully collected from several databases, including PromptHero[1], DiffusionDB[19] and KOKORS-dataset (an internal dataset derived from in-house platform for designers). Following the category schema from Parti[23], we further merge some categories, and finally determine 7 categories as illustrated in Fig. 2. The definitions and merging rules are detailed in the supplementary material. Based on these defined categories, we employ human annotators to label the initially collected 59,396 prompts. Additionally, the annotators are also required to filter out anomalous prompts, such as those that are incoherent, incomprehensible, or have punctuation errors. After annotation, we obtain 52,057 prompts. The distribution of these prompts, based on their categories, is depicted in Fig. 2. As the figure shows, the initially collected prompts exhibit a long-tail distribution across categories. Such category imbalances might lead to imbalanced generated images. Consequently, the human preferences learned from these imbalanced data could also be biased. As a result, we further expand our prompts." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.902 + ], + "angle": 0, + "content": "By employing the GPT-4[9], we obtain additional prompts to supplement categories with initially low quantities (see supplementary materials for more examples of the generated prompts). These generated prompts are further refined by annotators to remove those incoherent or incomprehensible items. As shown in Figure 2, after supplementation, we obtain 66,389 prompts and the distribution of prompts across categories is balanced. These balanced prompts help us in learning more representative human preferences." + }, + { + "type": "image", + "bbox": [ + 0.518, + 0.09, + 0.87, + 0.345 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.357, + 0.892, + 0.454 + ], + "angle": 0, + "content": "Figure 3. Annotation interface. Annotators are required to evaluate the preference for the given image pair on four dimensions, including aesthetics, detail quality (detail), semantic alignment (alignment) and overall score (overall). Annotation scores are discrete values ranging from 1 to 5, which are subsequently normalized to Boolean values of 0 or 1. When the scores are tied, the normalized score is set to 0.5." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.474, + 0.783, + 0.49 + ], + "angle": 0, + "content": "3.2. Image collection and annotation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.5, + 0.892, + 0.652 + ], + "angle": 0, + "content": "As shown in Table 2, we utilize Diffusion models (such as the Stable Diffusion series and DeepFloyd IF), GANs, and AutoRegressive models to generate images based on the obtained prompts. Each model produces 2-4 images for every single prompt. The generated images come from a variety of model architectures, with various image resolution scales (e.g., \\(512 \\times 512\\), \\(1024 \\times 1024\\), \\(1366 \\times 768\\)), and aspect ratios (e.g., 1:1, 16:9). This diversity ensures a comprehensive representation of the text-to-image models' generalization capability." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.653, + 0.892, + 0.849 + ], + "angle": 0, + "content": "Images generated from the same prompt are paired together for comparison. To enhance the representativeness of these image pairs, the construction of image pairs sources not only from images generated by different models but also includes those produced by the same model using different random seeds. Based on these contrastive image pairs, we employ human annotators to evaluate the image pairs with our annotation interface as shown in Fig. 3. The annotators are required to evaluate the quality of the generated image pairs based on three sub-dimensions (i.e., aesthetics, text-image consistency, and detail) and one overall dimension (i.e., overall score). These four dimensions are defined as follows:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "1. Aesthetics: annotators should measure the aesthetic quality of a generated image pair in terms of composition, light contrast, color matching, clarity, tone, style," + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.514, + 0.957 + ], + "angle": 0, + "content": "8021" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.097, + 0.092, + 0.443, + 0.107 + ], + "angle": 0, + "content": "depth of field, atmosphere, and artistry of the image." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.108, + 0.468, + 0.182 + ], + "angle": 0, + "content": "2. Detail quality: annotators should focus on the delicacy of image details such as texture, hair, and light and shadow, whether there is distortion in the face, hands, and limbs of the characters, whether there is a blurry overall view, object distortion, severe deformation." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.183, + 0.468, + 0.287 + ], + "angle": 0, + "content": "3. Semantic alignment: annotators should evaluate the semantic consistency of the generated images with the prompts, and the evaluation includes measuring whether the generated image accurately matches the textual description (e.g., quantity, attributes, location, positional relationships) and whether there is missing or redundant content in the generated image." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.288, + 0.468, + 0.348 + ], + "angle": 0, + "content": "4. Overall assessment: Based on the combination of above aspects and subjective preferences, the annotators assess the quality of each generated image from a holistic perspective." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.108, + 0.468, + 0.348 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.357, + 0.47, + 0.611 + ], + "angle": 0, + "content": "The annotators rate all these scores of each image in the pair into five distinct levels (from 1 to 5), and the scores are eventually normalized to [0, 1]. The image annotation is completed by a crowdsourced team of 210 members. Before the official annotation, each member needs to perform pre-annotation, where any member whose annotation results have a high degree of inconsistency with that of the majority is disqualified. Eventually, 198 members participate in the annotation of generated image pairs, of which 170 members act as annotators and 28 members act as quality inspectors. Each image pair is annotated by three annotators respectively and the final result is averaged from these three annotation results. \\(20\\%\\) of the annotated data is extracted and sent to the quality inspector for inspection. If there is significant difference in annotation results between annotators and inspectors, the annotated data is considered invalid and will be relabeled." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.631, + 0.183, + 0.645 + ], + "angle": 0, + "content": "3.3. Statistics" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.657, + 0.468, + 0.793 + ], + "angle": 0, + "content": "In summary, we collect 66,389 prompts and employ 9 recent text-to-image models to generate 607,541 images. Based on these images, we construct 918,315 image pairs. Notably, \\(20\\%\\) of these pairs are created using the same model but with different settings, while the other \\(80\\%\\) are produced by different models, allowing for a wide range of comparisons. Each image pair is then annotated by 3 distinct annotators across 4 dimensions to enable the study of diversity in human preference." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.468, + 0.9 + ], + "angle": 0, + "content": "We divide the annotated data into training, validation and test sets. The training and validation set contains 898,315 and 10,000 image pairs and the test set comprises 10,000 pairs. To ensure that the data distribution is representative, the test set includes not only images generated by Diffusion models but also those produced by GAN and Autoregressive models." + }, + { + "type": "image", + "bbox": [ + 0.517, + 0.09, + 0.877, + 0.345 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.356, + 0.892, + 0.425 + ], + "angle": 0, + "content": "Figure 4. The framework of Multi-dimensional Preference Score (MPS). The MPS takes the generated image, prompt and preference condition as the input, and predicts the quality (i.e. human preference) of the generated image under the given preference condition." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.441, + 0.865, + 0.457 + ], + "angle": 0, + "content": "4. Multi-dimensional Preference Prediction" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.467, + 0.725, + 0.482 + ], + "angle": 0, + "content": "4.1. Model Structure of MPS" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.491, + 0.892, + 0.732 + ], + "angle": 0, + "content": "As shown in Fig. 4, we adopt CLIP [11] to initially extract features from images and prompts. Given a prompt \\( x \\), a generated image \\( y \\) and a preference condition \\( c \\), the visual feature of \\( y \\) is obtained by the vision encoder of the CLIP by \\( X_{v} = E_{v}(y) \\), where \\( X_{v} \\in \\mathbb{R}^{n_{v} \\times n_{d}} \\). \\( n_{v} \\) is the token number of the image and \\( n_{d} \\) is the feature dimension. \\( X_{t} = E_{t}(x) \\) where \\( X_{t} \\in \\mathbb{R}^{n_{p} \\times n_{d}} \\) and \\( n_{p} \\) is the token number of the text. \\( X_{c} = E_{c}(c) \\), where \\( X_{c} \\in \\mathbb{R}^{n_{c} \\times n_{d}} \\) and \\( n_{p} \\) is the token number of word sets representing the preference. For the setup of word sets for each preference, please refer to Sec. 5.1. Previous works [6, 21, 22] typically utilize the first dimension of \\( X_{v} \\) and the last dimension of \\( X_{t} \\) to calculate the preference score, which loses a lot of detailed information of both image and text. Alternatively, we employ the full range of \\( X_{v} \\) and \\( X_{t} \\) and fuse two modalities through the Cross Attention (CA) module" + }, + { + "type": "equation", + "bbox": [ + 0.538, + 0.743, + 0.892, + 0.784 + ], + "angle": 0, + "content": "\\[\nC A \\left(X _ {v}, X _ {t}\\right) = \\sigma \\left(\\frac {X _ {v} W _ {q} \\left(X _ {t} W _ {k}\\right) ^ {T}}{\\sqrt {n _ {d}}}\\right) X _ {t} W _ {v} \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.795, + 0.892, + 0.901 + ], + "angle": 0, + "content": "where \\(\\sigma\\) is the SoftMax activation function, and \\(W_{*} \\in \\mathbb{R}^{n_d \\times n_d}\\) are parameters and biases are omitted. Our motivation is computing the preference scores in different preference conditions. Specific words in the prompt should be given more attention based on different conditions, e.g., when aesthetics is considered as a condition, words in the prompt related to color, light, and clarity should be taken" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "8022" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.472, + 0.132 + ], + "angle": 0, + "content": "Table 3. Main results of MPS and comparison methods on human preference evaluation. Preference accuracy (\\%) is calculated on ImageReward, HPD v2, and our MHP dataset." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.143, + 0.481, + 0.294 + ], + "angle": 0, + "content": "
IDPreference ModelImageRewardHPD v2MHP (Overall)
1CLIP score [11]54.371.263.7
2Aesthetic Score [17]57.472.662.9
3ImageReward [22]65.170.667.5
4HPS [21]61.273.165.5
5PickScore [6]62.979.869.5
6HPS v2 [20]65.783.365.5
7MPS (Ours)67.583.574.2
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.309, + 0.474, + 0.522 + ], + "angle": 0, + "content": "into account more when calculating the score. Therefore, we propose a condition mask to highlight the relevant tokens while suppressing the irrelevant tokens. The condition is represented by a series of attribute words, e.g. the preference condition of 'Aesthetic' is represented by a set of words, including light, color and clarity. The relevance of prompt and condition is computed by \\( R_{p,c} = X_cX_t^T W_c + b_c \\), where \\( R_{p,c} \\in \\mathbb{R}^{n_c \\times n_p} \\) and \\( W_c \\) and \\( b_c \\) are learnable parameters. The \\( R_{p,c} \\) is averaged along the dimension \\( n_c \\) and then repeated \\( n_v \\) times to obtain the mask \\( M_c \\in \\mathbb{R}^{n_v \\times n_p} \\). The \\( M_c \\) is further binarized to \\( \\bar{M}_c \\), where elements below the similarity threshold are assigned to negative infinity and others are set to zero. Based on the condition mask \\( \\bar{M}_c \\), the Eq. 1 is further improved as" + }, + { + "type": "equation", + "bbox": [ + 0.081, + 0.531, + 0.469, + 0.584 + ], + "angle": 0, + "content": "\\[\nC A \\left(X _ {v}, X _ {t} \\mid X _ {c}\\right) = \\sigma \\left(\\frac {X _ {v} W _ {q} \\left(X _ {t} W _ {k}\\right) ^ {T}}{\\sqrt {d}} + \\bar {M} _ {c}\\right) X _ {t} W _ {v} \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.585, + 0.47, + 0.78 + ], + "angle": 0, + "content": "The Eq. 2 ensures that the parts of the prompt that are relevant to the condition information receive more attention when computing the preference score. We adopt the first dimension (i.e. the cls token) of fused feature \\(CA(X_v, X_t | X_c)\\) for further prediction, which is denoted as \\(f_{v,t}\\) and \\(s \\in \\mathbb{R}^{1 \\times n_d}\\). Additionally, to prevent the issue of excessively short prompts leading to a scenario where no words of the prompt are related to the condition. In such a scenario, the cross-attention layer would be unable to capture the information from the prompt. Therefore, we supplement the \\(f_{v,t}\\) with additional prompt feature \\(f_t\\), where \\(f_t\\) is the last dimension of \\(X_t\\). Consequently, the MPS is obtained by" + }, + { + "type": "equation", + "bbox": [ + 0.199, + 0.782, + 0.469, + 0.799 + ], + "angle": 0, + "content": "\\[\nS (x, y \\mid c) = \\alpha f _ {v, t} \\cdot f _ {t} \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.806, + 0.47, + 0.838 + ], + "angle": 0, + "content": "where \\(\\alpha\\) is a learned scalar while \\(x, y\\) and \\(c\\) denote the prompt, image and preference condition, respectively." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.847, + 0.182, + 0.864 + ], + "angle": 0, + "content": "4.2. Training" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.903 + ], + "angle": 0, + "content": "The input for our objective includes our scoring function MPS \\( S(x, y|c) \\), a prompt \\( x \\), two generated image \\( y_1, y_2 \\), a" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.183 + ], + "angle": 0, + "content": "preference condition \\( c \\) and the preference score (annotated by human) \\( p \\), where \\( p \\) takes a value of [1, 0] for \\( y_{1} \\) is preferred, [0, 1] if \\( y_{2} \\) is preferred, or [0.5, 0.5] for ties. Following previous work [6], the training objective minimizes the KL-divergence between the annotation \\( p \\) and the softmax-normalized prediction" + }, + { + "type": "equation", + "bbox": [ + 0.57, + 0.19, + 0.892, + 0.236 + ], + "angle": 0, + "content": "\\[\n\\hat {p} _ {i, c} = \\frac {\\exp S (x , y _ {i} | c)}{\\sum_ {i = 1} ^ {2} \\exp S (x , y _ {i} | c)} \\tag {4}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.574, + 0.236, + 0.82, + 0.269 + ], + "angle": 0, + "content": "\\[\nL _ {P} = \\sum_ {c} \\sum_ {i = 1} ^ {\\bar {}} p _ {i, c} (l o g p _ {i, c} - l o g \\hat {p} _ {i, c})\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.277, + 0.892, + 0.368 + ], + "angle": 0, + "content": "We initialize the text and vision encoders, \\( E_{t} \\) and \\( E_{v} \\), with parameters from the pre-trained CLIP-H model, while the remaining parameters are subject to random initialization. We train our MPS on MHP datasets for 30,000 steps, with a batch size of 128, a learning rate of 3e-6, and a warmup period of 500 steps." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.381, + 0.634, + 0.398 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.405, + 0.691, + 0.422 + ], + "angle": 0, + "content": "5.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.429, + 0.892, + 0.565 + ], + "angle": 0, + "content": "Preference condition setting. We utilize the following collection of word sets to represent human preferences: 1) Aesthetics: light, color, clarity, tone, style, ambiance, artistry; 2) Detail quality: shape, face, hair, hands, limbs, structure, instance, texture; 3) Semantic alignment: quantity, attributes, position, number, location; 4) Overall: light, color, clarity, tone, style, ambiance, artistry, shape, face, hair, hands, limbs, structure, instance, texture, quantity, attributes, position, number, location." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.582, + 0.892, + 0.704 + ], + "angle": 0, + "content": "Evaluation setting. We select widely used statistical metrics for evaluating text-to-image models, namely the CLIP score [12] and Aesthetic score [17] for comparison. Additionally, we also choose methods that align with human preferences for evaluating text-to-image models, including Image Reward [22], HPS [20, 21] and PickScore [6]. Following previous works [6, 20], we utilize publicly available pre-trained models without finetuning for evaluation." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.712, + 0.681, + 0.726 + ], + "angle": 0, + "content": "5.2. Evaluation Results" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Overall Preference accuracy. Previous works on learning human preferences mostly focus on a singular, overall preference, i.e., summarizing human preferences with an overall score. For a fair comparison, we choose existing publicly available human preference datasets: the ImageReward test set [22] and the HPD v2 test set [20], along with our MHP dataset (using only data annotated with overall scores) to compare our method with relevant baselines. As shown in Tab. 3, our MPS demonstrates a better accuracy across these three datasets, indicating the strong generalization capability of our method." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "8023" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.472, + 0.119 + ], + "angle": 0, + "content": "Table 4. The evaluation of MPS and related scoring functions for the prediction of multi-dimensional human preferences(%)" + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.129, + 0.481, + 0.279 + ], + "angle": 0, + "content": "
IDPreference ModelOverallAestheticsAlignmentDetail
1CLIP score [11]63.6768.1482.6961.71
2Aesthetic Score [17]62.8582.8569.3660.34
3ImageReward [22]67.4574.7975.2758.31
4HPS [21]65.5173.8673.8662.05
5PickScore [6]69.5270.9570.9256.74
6HPS v2 [20]65.5173.8673.8762.06
7MPS (Ours)74.2483.8683.8785.18
" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.296, + 0.473, + 0.751 + ], + "angle": 0, + "content": "Multinational Preference accuracy. In addition to the overall score, we also compare the performance of previous works and our method in predicting multi-dimensional human preferences based on our MHP dataset. As Tab. 4 illustrates, the CLIP Score and Aesthetic score focus on specific types of preferences, only perform well in certain preferences (e.g., semantic alignment or aesthetics). However, they fall short in predicting other preferences compared to models trained on human preferences. Additionally, preference models [6, 20-22] generally perform better in overall score and some other dimensions but lack generalization in certain specific preferences (e.g., details)*. We illustrate the Fig. 5 to reveal the underlying reasons for this poor generalization. In the first and second rows of Fig. 5, the score functions exhibit a high correlation only with the trained preferences (e.g. semantic alignment and overall score), but perform poorly on other preferences. It is important to note that the prediction of different preferences is based on the same data, albeit with different preference annotations. This indicates that not all preferences are strongly correlated, which results in that improvements in one preference might come at the expense of others. Therefore, only learning a single score is inadequate in fully reflecting the complexity of human preferences. In contrast, our MPS learns human preferences with the condition mask from multiple dimensions and maintains high consistency across all dimensions of human preferences, as shown in the third row of Fig. 5. Besides, as Tab. 4 indicated, MPS outperforms the related works by a large margin in predicting the multi-dimensional human preference on the MHP dataset." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.772, + 0.47, + 0.866 + ], + "angle": 0, + "content": "Visualization Results. Further, we aim to explore why our MPS exhibits strong generalization across various dimensions of human preferences, even some preferences (e.g., detail quantity) are not highly correlated with others. To this end, we visualized the attention map of images and prompts that MPS focuses on when predicting hu" + }, + { + "type": "image", + "bbox": [ + 0.501, + 0.089, + 0.902, + 0.152 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.501, + 0.153, + 0.901, + 0.211 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.501, + 0.212, + 0.901, + 0.27 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.281, + 0.895, + 0.392 + ], + "angle": 0, + "content": "Figure 5. Correlation between real user preferences and model predictions. The x-axis of each subplot represents the annotated real human preferences, and the y-axis denotes the model's predictions. We examine three models: CLIP score, PickScore, and MPS (ours). Each subplot is annotated with the calculated correlation coefficient R-value, where a higher R-value indicates a closer alignment of the model's predictions with actual human preferences." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.41, + 0.895, + 0.666 + ], + "angle": 0, + "content": "man preferences. As shown in Fig. 6, we employ Grad-CAM [18] and \\( f_{v,t} \\) to generate attention heatmaps of the image, and utilize the values of \\( M_c \\) to represent the attention heatmap of the prompt. The visualization results indicate that our HPS attends to different regions of prompts and images depending on the specific preference condition. This is attributed to the condition mask, which allows only those words in the prompt related to the preference condition to be observed by the image. The condition mask ensures that the model predicts the preference with different inputs, and the model only needs to calculate the similarity between patches in the image and the retained partial prompt to determine the final score. Therefore, the selective focus enabled by the condition mask allows utilizing a unified model to predict multinational preferences effectively, even if some preferences have weak correlations with others." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.685, + 0.895, + 0.867 + ], + "angle": 0, + "content": "Ablation study. We conduct ablation studies to verify the effectiveness of each component, as illustrated in Tab. 5. Compared to the baseline† (i.e., PickScore), the cross-attention module enables more comprehensive integration between image and prompt, leading to improvement of prediction accuracy in overall score, aesthetics, and semantic alignment. However, the model still underperforms in detail quantity, which is less correlated with other preferences. The addition of the condition mask \\( M_{c} \\) alleviates this issue and improves the prediction performance across various preferences, especially in the detail quantity. Furthermore, we train separate models for different preferences." + }, + { + "type": "page_footnote", + "bbox": [ + 0.077, + 0.875, + 0.47, + 0.903 + ], + "angle": 0, + "content": "*Since these methods have been trained solely to generate an overall score, we could only duplicate it for multinational preferences." + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.875, + 0.892, + 0.9 + ], + "angle": 0, + "content": "†Note that the baseline shares the same network architecture with PickScore in Tab. 3 and 4, but is trained on our MHP dataset." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "8024" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.086, + 0.09, + 0.885, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.345, + 0.896, + 0.416 + ], + "angle": 0, + "content": "Figure 6. Visualization. We leverage Grad-CAM and the condition mask \\( M_{c} \\) to visualize attention heatmaps for the image and prompt. The condition mask results in the prompt focusing on words related to the preference condition. For Aesthetic, the model tends to focus on colors (e.g., pink) and lighting (e.g., bright). In the case of semantic alignment, the focus shifts to attributes (e.g., pink suit) and position (e.g., inside, background). For detail quantity, the model's attention is on instances (e.g., alpaca, machine, fancy food). On the image side, the model also tends to focus on areas of the image that correlate with the parts of the prompt receiving attention." + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.43, + 0.47, + 0.5 + ], + "angle": 0, + "content": "Table 5. Ablation study for different modules used in MPS. Base: PickScore is employed as the baseline model. CA: Cross-attention module. Mask: Preference condition mask \\( M_{c} \\). Row 4 illustrates the models that have identical structures but are trained separately for each preference type." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.51, + 0.47, + 0.624 + ], + "angle": 0, + "content": "
IDModuleOverallAestheticsAlignmentDetail
BaseCAMask
1✓70.6571.0570.8157.46
2✓✓74.1171.8373.0258.79
3✓✓✓74.2483.8683.8785.18
4Separately trained MPS73.5180.5479.6876.81
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.641, + 0.47, + 0.748 + ], + "angle": 0, + "content": "Experimental results indicate that models trained separately for each preference do not perform as well as those trained to learn multiple preferences simultaneously. We infer that more extensive annotations and unified training contribute to better model generalization. Ablation studies validate the effectiveness of each module, particularly the condition mask, in learning multiple preferences." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.757, + 0.248, + 0.772 + ], + "angle": 0, + "content": "5.3. MPS Benchmark" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Based on the MPS model and the collected MHP dataset, we introduce the MPS benchmark for evaluating text-to-image models across multiple dimensions. The MPS benchmark includes a set of evaluation prompts designed to assess the models on a total of 4,000 prompts, covering seven categories: characters, scenes, objects, animals, plants, arts, and food. Each category comprises 500 prompts. Our MPS assesses the images generated by the text-to-image mod" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.431, + 0.895, + 0.523 + ], + "angle": 0, + "content": "els across four dimensions: Aesthetic, Semantic Alignment, Detail Quantity, and Overall Score. The scoring results can assist users in selecting superior models based on their personal preferences. Additionally, the scoring results can also enhance the generative models' performance by selecting more preferable images with higher MPS scores." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.538, + 0.628, + 0.554 + ], + "angle": 0, + "content": "6. Conclusions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.564, + 0.895, + 0.851 + ], + "angle": 0, + "content": "In this work, we introduce the Multi-dimensional Human Preference (MHP) dataset and Multi-dimensional Preference Score (MPS) to evaluate text-to-image models from multi-dimensional human preferences. The MHP dataset offers improvements over previous methods in prompt collection, image generation, and preference annotation, which comprises 918,315 human preference choices across four dimensions. These preferences include aesthetics, semantic alignment, detail quantity, and overall score. Additionally, to align the multi-dimensional human preferences, we propose the MPS, which employs a unified network to score generated images based on varying preference conditions. The MPS introduces a condition mask that retains words in the prompt related to the preference condition. Subsequently, the model integrates only the retained prompt with the image to compute the final score. MPS outperforms related works in predicting multi-dimensional human preferences across three datasets, which demonstrates the generalization of our method." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.873, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Acknowledgements: We sincerely thank Zhuang Li, Lingyu Zou, and Peihan Li for their valuable discussions and feedback." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "8025" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.116, + 0.414, + 0.129 + ], + "angle": 0, + "content": "[1] Prompthero. https://prompthero.com/.4" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.131, + 0.47, + 0.2 + ], + "angle": 0, + "content": "[2] Ming Ding, Zhuoyi Yang, Wenyi Hong, Wendi Zheng, Chang Zhou, Da Yin, Junyang Lin, Xu Zou, Zhou Shao, Hongxia Yang, and Jie Tang. 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Lafite: Towards language-free training for text-to-image generation. arXiv preprint arXiv:2111.13792, 2021. 3" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.469, + 0.332 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "8027" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_origin.pdf b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..741a88de13a94ca0b820c28fa299212f96be28ff --- /dev/null +++ b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/0686b0c0-a9d4-4259-972e-6fc4bad8bf88_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:261665ed66ff342b9488f8baee88b3447898c18c814b3b4b320982ec6c736d31 +size 2337209 diff --git a/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/full.md b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/full.md new file mode 100644 index 0000000000000000000000000000000000000000..fad11b2cd12f01fb9c1878795fc717b5219c2fa5 --- /dev/null +++ b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/full.md @@ -0,0 +1,255 @@ +# Learning Multi-dimensional Human Preference for Text-to-Image Generation + +# Sixian Zhang,\* Bohan Wang\* Junqiang Wu\* Yan Li\* Tingting Gao, Di Zhang, Zhongyuan Wang Kuaishou Technology + +# Abstract + +Current metrics for text-to-image models typically rely on statistical metrics which inadequately represent the real preference of humans. Although recent work attempts to learn these preferences via human annotated images, they reduce the rich tapestry of human preference to a single overall score. However, the preference results vary when humans evaluate images with different aspects. Therefore, to learn the multi-dimensional human preferences, we propose the Multi-dimensional Preference Score (MPS), the first multi-dimensional preference scoring model for the evaluation of text-to-image models. The MPS introduces the preference condition module upon CLIP model to learn these diverse preferences. It is trained based on our Multi-dimensional Human Preference (MHP) Dataset, which comprises 918,315 human preference choices across four dimensions (i.e., aesthetics, semantic alignment, detail quality and overall assessment) on 607,541 images. The images are generated by a wide range of latest text-to-image models. The MPS outperforms existing scoring methods across 3 datasets in 4 dimensions, enabling it a promising metric for evaluating and improving text-to-image generation. The model and dataset will be made publicly available to facilitate future research. Project page: https://wangbohan97.github.io/MPS/. + +# 1. Introduction + +"There are a thousand Hamlets in a thousand people's eyes." + +-Vissarion Belinsky + +Text-to-image generative models [10, 14, 15] have achieved remarkable advancements in recent years, and these models have the capability to generate high-fidelity and contextually relevant images based on textual descriptions (i.e., prompts). To evaluate the quality of generated images, several evaluation metrics are proposed, including Inception Score (IS) [16], Fréchet Inception Distance (FID) + +![](images/1027e4b711ed6d283ca76f98b3b2de0a85ed2bf9fad8020b5f186e7c7d0c033f.jpg) +Prompt: A picture depicting the Grand Canal of Venice, with a row of houses on both sides of the canal and boatman rowing two boats on the river, illustration, vivid colors, high-contrast. + +![](images/873bbab20c2820637a11a37993c96c6fefa059a84bdd9f11244827c23d5079d0.jpg) +mal of Venice, with a row of houses on +ng two boats on the river, illustration, + +![](images/e6ff0ffa3974bc5035eaba5ccfc0f0ca35a0ac04c917e762a4562891451cadc7.jpg) + +Figure 1. As humans evaluate images from different perspectives, their preference for the images also varies. Specifically, when examining the images in the top row, the image on the left stands out in terms of aesthetic appeal, though it falls short in semantic alignment (e.g., two boats on the river) compared to its counterpart on the right. In the case of the bottom row, both images are aesthetically pleasing, yet the image on the right is marred by poor detail quality (e.g., as signified by the red bounding boxes around the distorted hand and foot). +![](images/a286e4f56162a05986c22a4d27fc06e816f38febc3d4544f25e3fb9f492e3dc2.jpg) +Prompt: A family of three poses in the Grand Canyon, with the main wearing sunglasses and smiling, 4k resolution, extremely detailed + +![](images/1325e2359ffdc1c66038a0f5a812ee4b168f3e28c59fcf0fd417d8807efdc20b.jpg) + +nd Canyon, with the man wearing emely detailed + +![](images/ae2c264553da446934d054e36dfe392213d464a1beed5450cb3fb8a4ff5ae573.jpg) + +[5], and CLIP Score [12]. However, these statistical metrics fall short of aligning with human perceptual preferences. For instance, metrics like the IS or the FID, although indicative of image quality to some extent, might not necessarily reflect how a human observer would rate the image in terms of fidelity, coherence, or aesthetic appeal. + +Contrary to these statistical metrics, several approaches [6, 20-22, 24] turn towards human-centric evaluations, where generated images are manually annotated according to human preferences. Subsequently, models are trained with these annotations to predict preference scores. However, these approaches typically utilize a single score to summarize all human preferences, overlooking the multidimensionality of human preferences. As Fig. 1 shows, the preference results differ when humans evaluate images from various perspectives. Therefore, using a single-dimensional evaluation method is insufficient in capturing the broad + +Table 1. Comparisons of text-to-image models quality databases. Our Multi-dimensional Human Preference (MHP) dataset achieves significant advancements over existing work in three aspects, including prompt collection, image generation, and preference annotation. Moreover, it constitutes the largest dataset both in generated images and preference annotations. Note that the Diffusion DB only contains generated images but lacks annotations of human preferences. Besides, KOKORS is an internal dataset derived from in-house platform for designer, which provides $\sim 10\mathrm{w}$ prompts. + +
DatasetPrompt collectionImage GenerationPreference annotation
SourceAnnotationSourceNumberRatingDimension
DiffusionDB [19]DiffusionDB×Diffusion (1)1,819,8080None
AGIQA-1K [24]DiffusionDB×Diffusion (2)1,08023,760Overall
PickScore [6]Web Application×Diffusion (3)583,747583,747Overall
ImageReward [22]DiffusionDB×Auto Regressive; Diffusion (6)136,892410,676Overall
HPS [21]DiffusionDB×Diffusion (1)98,80798,807Overall
HPS v2 [20]DiffusionDB, COCO✓GAN; Auto Regressive; Diffusion, COCO (9)430,060798,090Overall
AGIQA-3K [7]DiffusionDB×GAN; Auto Regressive; Diffusion (6)2,982125,244Overall; Alignment
MHPDiffusionDB, PromptHero, KOLORS, GPT4✓GAN; Auto Regressive; Diffusion (9)607,541918,315Aesthetics, Detail, Alignment, Overall
+ +range of personalized needs and preferences. To ensure a comprehensive evaluation of text-to-image synthesis outputs, it is crucial to learn and utilize multi-dimensional human preferences. + +To learn the multi-dimensional human preferences, we propose the Multi-dimensional Human Preference (MHP) dataset. Compared to prior efforts [6, 20-22], the MHP dataset offers significant enhancements in prompts collection, image generation, and preference annotation. For the prompt collection, previous work [6, 21, 22] directly utilizes existing open-source datasets (e.g., Diffusion DB [19]) or datasets collated from the internet [6], overlooking the potential data bias of long-tail distribution. To this end, based on the categories schema of Parti [23], we annotate the collected prompts into 7 category labels (e.g., characters, scenes, objects, animals, etc.). For the underrepresented tail categories, we employ Large Language Models (LLMs) (e.g., GPT-4 [9]) to generate additional prompts. This process results in a balanced prompt collection across various categories, which is used for later image generation. For image generation, following previous work [7, 20], we not only utilize existing open-source Diffusion models and their variants, but also employ GANs and auto-regressive models to generate images. Consequently, we generate a dataset of 607,541 images, which are further used to create 918,315 pairwise comparisons of images for preference annotation. The quantity of image data constitutes the largest dataset of its kind. For the annotation of human preferences, contrary to the single annotation of existing work [6, 20, 21, 24], we consider a broader range of dimensions for human preferences and employ human annotators to label each image pair across four dimensions, including aesthetics, detail quality, semantic alignment, and overall score. + +To learn human preferences, existing methods employ + +the pre-trained vision-language models (e.g., CLIP [11], BLIP [8]) to extract features from images and prompts independently, followed by computing the similarity between them. These methods then fine-tune the network utilizing the collected preference data. For learning the multidimensional preferences, a straightforward strategy is to train separate models for different preferences. However, such a simple strategy requires data re-collection and model re-training for the new preference. Moreover, due to the potential bias in single-preference data, a model trained under one preference condition often exhibits diminished performance when evaluated against other preferences. Therefore, we propose the Multi-dimensional Preference Score (MPS), a unified model capable of predicting scores under various preference conditions. Specifically, a certain preference is denoted by a series of descriptive words. For instance, the 'aesthetic' condition is decomposed into words such as 'light', 'color', and 'clarity' to describe the attributes of this condition. These attribute words are used to compute similarities with the prompt, resulting in a similarity matrix that reflects the correspondence between words in the prompt and the specified condition. On the other hand, features from images and text are extracted using a pre-trained vision-language model. Subsequently, two modalities are fused through a multimodal cross-attention layer. The similarity matrix serves as a mask merged into the cross-attention layer, which ensures that the text only related to the condition is attended to by the visual modality. Then the fused features are used to predict the preference scores. We evaluate our MPS model on both the existing human preference datasets (i.e., ImageReward [22] and HPS v2 [20]) and our MHP dataset. The experimental results indicate that our MPS model surpasses existing benchmarks in evaluating both overall and multi-dimensional prefer + +ences, establishing a new state-of-the-art in comparison with related work. + +In summary, our main contributions are as follows: + +- We introduce the Multi-dimensional Human Preference (MHP) datasets for evaluating text-to-image models. The MHP contains balanced prompts and the largest collection of images with multi-dimensional annotations. Based on MHP, we propose a standard test benchmark to evaluate existing text-to-image synthesis models. +- We propose the MPS model, which learns multidimensional human preferences and evaluates the scores of generated images under different preference conditions. +- Our MPS exhibits superior performance compared to existing methods across three datasets in predicting the overall preferences and multi-dimensional preferences. + +# 2. Related work + +# 2.1. Text-to-image Generation and Evaluation + +The text-to-image task aims to synthesize realistic images from natural language description (i.e., prompt). Several work attempts to tackle this problem, including GANs [4, 25], auto-regressive [2, 3, 23] and diffusion models [10, 14, 15]. Among the previously mentioned methods, diffusion models gain significant attention for their exceptional performance. These methods are principally divided into two categories: latent-based and pixel-based approaches. The Latent Diffusion Model (LDM) [14] is notable as the first to introduce a latent-based diffusion model, leveraging an auto-encoder to map images into a latent space where the diffusion process is executed. Following this, Stable Diffusion has notably propelled the field forward by open-sourcing SD series [10]. In contrast, DALL-E 2 [13] and Imagen [15] are predicated on pixel-based diffusion models. Besides, the Imagen [15] integrates the large language model T5 XXL to achieve a text-to-image super-resolution diffusion model capable of producing highly realistic images. Current text-to-image models excel in creating high-quality images but often miss aligning with human preferences in real-world applications. For evaluating text-to-image models, several evaluation metrics are proposed to evaluate the quality of generated images, including Inception Score (IS) [16], Fréchet Inception Distance (FID) [5], and CLIP Score [12]. However, these statistical metrics fall short of aligning with human perceptual preferences. Our MPS provides a comprehensive evaluation for text-to-image generations, facilitating the evaluation of alignment with multi-dimensional human preference. + +# 2.2. Learning human preferences + +Currently, several studies attempt to collect and learn human preferences for the evaluation of text-to-image gen + +![](images/d353a47d6c6d83dc4c757bfcce712d067a429789e9da4cfb07202e28edbb42ec.jpg) +Figure 2. Prompt collection. The initially collected prompts exhibit a long-tail distribution across various categories. After prompt augmentation with GPT, we obtain a relatively balanced prompt dataset, which contains 66,389 prompts. + +eration. They use the collected data to fine-tune visual-language models (VLMs) to align with human selections. + +HPS [21] introduces the HPD dataset of human preference choices. The images are generated solely using the Stable Diffusion model with prompts from Diffusion DB. They train HPS model utilizing the human preference annotations of HPD to align it with human preference. Subsequently, they fine-tune the Stable Diffusion model under the guidance of HPS, leading to better generated images that are more preferred by human users. However, HPS is limited to a single generation model and a relatively small number of images. Furthermore, HPS v2 [20] introduces a larger dataset, employing 8 generative models, including Diffusion models, GANs, and Auto regressive models, and also incorporating captions from the COCO dataset. However, both HPS and HPS v2 primarily focus on overall human preferences, not considering the diversity of human tastes. + +PickScore [6] proposes a web application designed to collect prompts and human preference annotations from real users. Unlike previous methods adopting prompts from existing datasets (e.g. DiffusionDB), the prompts of PickScore are directly generated by actual users. The dataset of PickScore is sizeable, however, it focuses only on the overall preferences, lacking detailed annotations for multi-dimension preferences. + +ImageReward [22] employs four types of Diffusion models along with an auto-regression-based model. Their annotation of generated images is more detailed with scoring ranging from 0 to 7. Beyond overall satisfaction, they also consider annotations for alignment and fidelity. However, they merge alignment and fidelity into a single overall score, inadequately capturing the multi-dimensional dimensions of human preferences. + +AGIQA-1k [24] and AGIQA-3k [7] utilize a range of generative models, including Diffusion, GAN, and Auto regressive models, to produce images. They consider both overall and alignment preferences. However, their dataset size is considerably smaller compared to existing work. + +Our MHP dataset represents an advancement over previ + +Table 2. Image generation. The image sources of the MHP dataset consist of the images generated from 9 text-to-image generative models. Note that KOKORS is an internal model for in-house designer platform. + +
SourceTypeImagesSplit
KOKORSDiffusion211,707Train and test
DeepFloyd IFDiffusion27,311Train and test
Stable Diffusion XLDiffusion89,176Train and test
Openjourney v4Diffusion133,875Train and test
Stable Diffusion v2.0Diffusion84,590Train and test
Stable Diffusion v1.5Diffusion56,882Train and test
VQGAN+CLIPGAN1,000Test
LAFITEGAN1,000Test
CogView2Autoregressive2,000Test
+ +ous work in terms of prompt collection, image generation, and preference annotation. + +# 3. MHP Dataset + +# 3.1. Prompt collection and annotation + +Our prompts are carefully collected from several databases, including PromptHero[1], DiffusionDB[19] and KOKORS-dataset (an internal dataset derived from in-house platform for designers). Following the category schema from Parti[23], we further merge some categories, and finally determine 7 categories as illustrated in Fig. 2. The definitions and merging rules are detailed in the supplementary material. Based on these defined categories, we employ human annotators to label the initially collected 59,396 prompts. Additionally, the annotators are also required to filter out anomalous prompts, such as those that are incoherent, incomprehensible, or have punctuation errors. After annotation, we obtain 52,057 prompts. The distribution of these prompts, based on their categories, is depicted in Fig. 2. As the figure shows, the initially collected prompts exhibit a long-tail distribution across categories. Such category imbalances might lead to imbalanced generated images. Consequently, the human preferences learned from these imbalanced data could also be biased. As a result, we further expand our prompts. + +By employing the GPT-4[9], we obtain additional prompts to supplement categories with initially low quantities (see supplementary materials for more examples of the generated prompts). These generated prompts are further refined by annotators to remove those incoherent or incomprehensible items. As shown in Figure 2, after supplementation, we obtain 66,389 prompts and the distribution of prompts across categories is balanced. These balanced prompts help us in learning more representative human preferences. + +![](images/37a1111427a93b60ed21499121cb4d5f7261e1b1d3d29c0a892689fc276e3638.jpg) +Figure 3. Annotation interface. Annotators are required to evaluate the preference for the given image pair on four dimensions, including aesthetics, detail quality (detail), semantic alignment (alignment) and overall score (overall). Annotation scores are discrete values ranging from 1 to 5, which are subsequently normalized to Boolean values of 0 or 1. When the scores are tied, the normalized score is set to 0.5. + +# 3.2. Image collection and annotation + +As shown in Table 2, we utilize Diffusion models (such as the Stable Diffusion series and DeepFloyd IF), GANs, and AutoRegressive models to generate images based on the obtained prompts. Each model produces 2-4 images for every single prompt. The generated images come from a variety of model architectures, with various image resolution scales (e.g., $512 \times 512$ , $1024 \times 1024$ , $1366 \times 768$ ), and aspect ratios (e.g., 1:1, 16:9). This diversity ensures a comprehensive representation of the text-to-image models' generalization capability. + +Images generated from the same prompt are paired together for comparison. To enhance the representativeness of these image pairs, the construction of image pairs sources not only from images generated by different models but also includes those produced by the same model using different random seeds. Based on these contrastive image pairs, we employ human annotators to evaluate the image pairs with our annotation interface as shown in Fig. 3. The annotators are required to evaluate the quality of the generated image pairs based on three sub-dimensions (i.e., aesthetics, text-image consistency, and detail) and one overall dimension (i.e., overall score). These four dimensions are defined as follows: + +1. Aesthetics: annotators should measure the aesthetic quality of a generated image pair in terms of composition, light contrast, color matching, clarity, tone, style, + +depth of field, atmosphere, and artistry of the image. + +2. Detail quality: annotators should focus on the delicacy of image details such as texture, hair, and light and shadow, whether there is distortion in the face, hands, and limbs of the characters, whether there is a blurry overall view, object distortion, severe deformation. +3. Semantic alignment: annotators should evaluate the semantic consistency of the generated images with the prompts, and the evaluation includes measuring whether the generated image accurately matches the textual description (e.g., quantity, attributes, location, positional relationships) and whether there is missing or redundant content in the generated image. +4. Overall assessment: Based on the combination of above aspects and subjective preferences, the annotators assess the quality of each generated image from a holistic perspective. + +The annotators rate all these scores of each image in the pair into five distinct levels (from 1 to 5), and the scores are eventually normalized to [0, 1]. The image annotation is completed by a crowdsourced team of 210 members. Before the official annotation, each member needs to perform pre-annotation, where any member whose annotation results have a high degree of inconsistency with that of the majority is disqualified. Eventually, 198 members participate in the annotation of generated image pairs, of which 170 members act as annotators and 28 members act as quality inspectors. Each image pair is annotated by three annotators respectively and the final result is averaged from these three annotation results. $20\%$ of the annotated data is extracted and sent to the quality inspector for inspection. If there is significant difference in annotation results between annotators and inspectors, the annotated data is considered invalid and will be relabeled. + +# 3.3. Statistics + +In summary, we collect 66,389 prompts and employ 9 recent text-to-image models to generate 607,541 images. Based on these images, we construct 918,315 image pairs. Notably, $20\%$ of these pairs are created using the same model but with different settings, while the other $80\%$ are produced by different models, allowing for a wide range of comparisons. Each image pair is then annotated by 3 distinct annotators across 4 dimensions to enable the study of diversity in human preference. + +We divide the annotated data into training, validation and test sets. The training and validation set contains 898,315 and 10,000 image pairs and the test set comprises 10,000 pairs. To ensure that the data distribution is representative, the test set includes not only images generated by Diffusion models but also those produced by GAN and Autoregressive models. + +![](images/b5d4020d89159312c02e7298fa5c03b2144bbc0dd73c853ef3766d38d44d0e6b.jpg) +Figure 4. The framework of Multi-dimensional Preference Score (MPS). The MPS takes the generated image, prompt and preference condition as the input, and predicts the quality (i.e. human preference) of the generated image under the given preference condition. + +# 4. Multi-dimensional Preference Prediction + +# 4.1. Model Structure of MPS + +As shown in Fig. 4, we adopt CLIP [11] to initially extract features from images and prompts. Given a prompt $x$ , a generated image $y$ and a preference condition $c$ , the visual feature of $y$ is obtained by the vision encoder of the CLIP by $X_{v} = E_{v}(y)$ , where $X_{v} \in \mathbb{R}^{n_{v} \times n_{d}}$ . $n_{v}$ is the token number of the image and $n_{d}$ is the feature dimension. $X_{t} = E_{t}(x)$ where $X_{t} \in \mathbb{R}^{n_{p} \times n_{d}}$ and $n_{p}$ is the token number of the text. $X_{c} = E_{c}(c)$ , where $X_{c} \in \mathbb{R}^{n_{c} \times n_{d}}$ and $n_{p}$ is the token number of word sets representing the preference. For the setup of word sets for each preference, please refer to Sec. 5.1. Previous works [6, 21, 22] typically utilize the first dimension of $X_{v}$ and the last dimension of $X_{t}$ to calculate the preference score, which loses a lot of detailed information of both image and text. Alternatively, we employ the full range of $X_{v}$ and $X_{t}$ and fuse two modalities through the Cross Attention (CA) module + +$$ +C A \left(X _ {v}, X _ {t}\right) = \sigma \left(\frac {X _ {v} W _ {q} \left(X _ {t} W _ {k}\right) ^ {T}}{\sqrt {n _ {d}}}\right) X _ {t} W _ {v} \tag {1} +$$ + +where $\sigma$ is the SoftMax activation function, and $W_{*} \in \mathbb{R}^{n_d \times n_d}$ are parameters and biases are omitted. Our motivation is computing the preference scores in different preference conditions. Specific words in the prompt should be given more attention based on different conditions, e.g., when aesthetics is considered as a condition, words in the prompt related to color, light, and clarity should be taken + +Table 3. Main results of MPS and comparison methods on human preference evaluation. Preference accuracy (\%) is calculated on ImageReward, HPD v2, and our MHP dataset. + +
IDPreference ModelImageRewardHPD v2MHP (Overall)
1CLIP score [11]54.371.263.7
2Aesthetic Score [17]57.472.662.9
3ImageReward [22]65.170.667.5
4HPS [21]61.273.165.5
5PickScore [6]62.979.869.5
6HPS v2 [20]65.783.365.5
7MPS (Ours)67.583.574.2
+ +into account more when calculating the score. Therefore, we propose a condition mask to highlight the relevant tokens while suppressing the irrelevant tokens. The condition is represented by a series of attribute words, e.g. the preference condition of 'Aesthetic' is represented by a set of words, including light, color and clarity. The relevance of prompt and condition is computed by $R_{p,c} = X_cX_t^T W_c + b_c$ , where $R_{p,c} \in \mathbb{R}^{n_c \times n_p}$ and $W_c$ and $b_c$ are learnable parameters. The $R_{p,c}$ is averaged along the dimension $n_c$ and then repeated $n_v$ times to obtain the mask $M_c \in \mathbb{R}^{n_v \times n_p}$ . The $M_c$ is further binarized to $\bar{M}_c$ , where elements below the similarity threshold are assigned to negative infinity and others are set to zero. Based on the condition mask $\bar{M}_c$ , the Eq. 1 is further improved as + +$$ +C A \left(X _ {v}, X _ {t} \mid X _ {c}\right) = \sigma \left(\frac {X _ {v} W _ {q} \left(X _ {t} W _ {k}\right) ^ {T}}{\sqrt {d}} + \bar {M} _ {c}\right) X _ {t} W _ {v} \tag {2} +$$ + +The Eq. 2 ensures that the parts of the prompt that are relevant to the condition information receive more attention when computing the preference score. We adopt the first dimension (i.e. the cls token) of fused feature $CA(X_v, X_t | X_c)$ for further prediction, which is denoted as $f_{v,t}$ and $s \in \mathbb{R}^{1 \times n_d}$ . Additionally, to prevent the issue of excessively short prompts leading to a scenario where no words of the prompt are related to the condition. In such a scenario, the cross-attention layer would be unable to capture the information from the prompt. Therefore, we supplement the $f_{v,t}$ with additional prompt feature $f_t$ , where $f_t$ is the last dimension of $X_t$ . Consequently, the MPS is obtained by + +$$ +S (x, y \mid c) = \alpha f _ {v, t} \cdot f _ {t} \tag {3} +$$ + +where $\alpha$ is a learned scalar while $x, y$ and $c$ denote the prompt, image and preference condition, respectively. + +# 4.2. Training + +The input for our objective includes our scoring function MPS $S(x, y|c)$ , a prompt $x$ , two generated image $y_1, y_2$ , a + +preference condition $c$ and the preference score (annotated by human) $p$ , where $p$ takes a value of [1, 0] for $y_{1}$ is preferred, [0, 1] if $y_{2}$ is preferred, or [0.5, 0.5] for ties. Following previous work [6], the training objective minimizes the KL-divergence between the annotation $p$ and the softmax-normalized prediction + +$$ +\hat {p} _ {i, c} = \frac {\exp S (x , y _ {i} | c)}{\sum_ {i = 1} ^ {2} \exp S (x , y _ {i} | c)} \tag {4} +$$ + +$$ +L _ {P} = \sum_ {c} \sum_ {i = 1} ^ {\bar {}} p _ {i, c} (l o g p _ {i, c} - l o g \hat {p} _ {i, c}) +$$ + +We initialize the text and vision encoders, $E_{t}$ and $E_{v}$ , with parameters from the pre-trained CLIP-H model, while the remaining parameters are subject to random initialization. We train our MPS on MHP datasets for 30,000 steps, with a batch size of 128, a learning rate of 3e-6, and a warmup period of 500 steps. + +# 5. Experiments + +# 5.1. Experimental Setup + +Preference condition setting. We utilize the following collection of word sets to represent human preferences: 1) Aesthetics: light, color, clarity, tone, style, ambiance, artistry; 2) Detail quality: shape, face, hair, hands, limbs, structure, instance, texture; 3) Semantic alignment: quantity, attributes, position, number, location; 4) Overall: light, color, clarity, tone, style, ambiance, artistry, shape, face, hair, hands, limbs, structure, instance, texture, quantity, attributes, position, number, location. + +Evaluation setting. We select widely used statistical metrics for evaluating text-to-image models, namely the CLIP score [12] and Aesthetic score [17] for comparison. Additionally, we also choose methods that align with human preferences for evaluating text-to-image models, including Image Reward [22], HPS [20, 21] and PickScore [6]. Following previous works [6, 20], we utilize publicly available pre-trained models without finetuning for evaluation. + +# 5.2. Evaluation Results + +Overall Preference accuracy. Previous works on learning human preferences mostly focus on a singular, overall preference, i.e., summarizing human preferences with an overall score. For a fair comparison, we choose existing publicly available human preference datasets: the ImageReward test set [22] and the HPD v2 test set [20], along with our MHP dataset (using only data annotated with overall scores) to compare our method with relevant baselines. As shown in Tab. 3, our MPS demonstrates a better accuracy across these three datasets, indicating the strong generalization capability of our method. + +Table 4. The evaluation of MPS and related scoring functions for the prediction of multi-dimensional human preferences(%) + +
IDPreference ModelOverallAestheticsAlignmentDetail
1CLIP score [11]63.6768.1482.6961.71
2Aesthetic Score [17]62.8582.8569.3660.34
3ImageReward [22]67.4574.7975.2758.31
4HPS [21]65.5173.8673.8662.05
5PickScore [6]69.5270.9570.9256.74
6HPS v2 [20]65.5173.8673.8762.06
7MPS (Ours)74.2483.8683.8785.18
+ +Multinational Preference accuracy. In addition to the overall score, we also compare the performance of previous works and our method in predicting multi-dimensional human preferences based on our MHP dataset. As Tab. 4 illustrates, the CLIP Score and Aesthetic score focus on specific types of preferences, only perform well in certain preferences (e.g., semantic alignment or aesthetics). However, they fall short in predicting other preferences compared to models trained on human preferences. Additionally, preference models [6, 20-22] generally perform better in overall score and some other dimensions but lack generalization in certain specific preferences (e.g., details)*. We illustrate the Fig. 5 to reveal the underlying reasons for this poor generalization. In the first and second rows of Fig. 5, the score functions exhibit a high correlation only with the trained preferences (e.g. semantic alignment and overall score), but perform poorly on other preferences. It is important to note that the prediction of different preferences is based on the same data, albeit with different preference annotations. This indicates that not all preferences are strongly correlated, which results in that improvements in one preference might come at the expense of others. Therefore, only learning a single score is inadequate in fully reflecting the complexity of human preferences. In contrast, our MPS learns human preferences with the condition mask from multiple dimensions and maintains high consistency across all dimensions of human preferences, as shown in the third row of Fig. 5. Besides, as Tab. 4 indicated, MPS outperforms the related works by a large margin in predicting the multi-dimensional human preference on the MHP dataset. + +Visualization Results. Further, we aim to explore why our MPS exhibits strong generalization across various dimensions of human preferences, even some preferences (e.g., detail quantity) are not highly correlated with others. To this end, we visualized the attention map of images and prompts that MPS focuses on when predicting hu + +![](images/05ce8b5a3070af49bee5a1b330805ac69759a5b3256a3b9a44ac722525e74295.jpg) + +![](images/216ced121ee7889a6afb654c3c0f044c24c0689ea311d0ed314b6af64d3a694f.jpg) + +![](images/095bbabf4bc7c2525ba001d0d085c15aa113ddc765eaf24a3108c99c193bf911.jpg) +Figure 5. Correlation between real user preferences and model predictions. The x-axis of each subplot represents the annotated real human preferences, and the y-axis denotes the model's predictions. We examine three models: CLIP score, PickScore, and MPS (ours). Each subplot is annotated with the calculated correlation coefficient R-value, where a higher R-value indicates a closer alignment of the model's predictions with actual human preferences. + +man preferences. As shown in Fig. 6, we employ Grad-CAM [18] and $f_{v,t}$ to generate attention heatmaps of the image, and utilize the values of $M_c$ to represent the attention heatmap of the prompt. The visualization results indicate that our HPS attends to different regions of prompts and images depending on the specific preference condition. This is attributed to the condition mask, which allows only those words in the prompt related to the preference condition to be observed by the image. The condition mask ensures that the model predicts the preference with different inputs, and the model only needs to calculate the similarity between patches in the image and the retained partial prompt to determine the final score. Therefore, the selective focus enabled by the condition mask allows utilizing a unified model to predict multinational preferences effectively, even if some preferences have weak correlations with others. + +Ablation study. We conduct ablation studies to verify the effectiveness of each component, as illustrated in Tab. 5. Compared to the baseline† (i.e., PickScore), the cross-attention module enables more comprehensive integration between image and prompt, leading to improvement of prediction accuracy in overall score, aesthetics, and semantic alignment. However, the model still underperforms in detail quantity, which is less correlated with other preferences. The addition of the condition mask $M_{c}$ alleviates this issue and improves the prediction performance across various preferences, especially in the detail quantity. Furthermore, we train separate models for different preferences. + +![](images/d574610aed709865fa4e5b496868957fc34d260e63b0f2a287de029af19fcae1.jpg) +Figure 6. Visualization. We leverage Grad-CAM and the condition mask $M_{c}$ to visualize attention heatmaps for the image and prompt. The condition mask results in the prompt focusing on words related to the preference condition. For Aesthetic, the model tends to focus on colors (e.g., pink) and lighting (e.g., bright). In the case of semantic alignment, the focus shifts to attributes (e.g., pink suit) and position (e.g., inside, background). For detail quantity, the model's attention is on instances (e.g., alpaca, machine, fancy food). On the image side, the model also tends to focus on areas of the image that correlate with the parts of the prompt receiving attention. + +Table 5. Ablation study for different modules used in MPS. Base: PickScore is employed as the baseline model. CA: Cross-attention module. Mask: Preference condition mask $M_{c}$ . Row 4 illustrates the models that have identical structures but are trained separately for each preference type. + +
IDModuleOverallAestheticsAlignmentDetail
BaseCAMask
1✓70.6571.0570.8157.46
2✓✓74.1171.8373.0258.79
3✓✓✓74.2483.8683.8785.18
4Separately trained MPS73.5180.5479.6876.81
+ +Experimental results indicate that models trained separately for each preference do not perform as well as those trained to learn multiple preferences simultaneously. We infer that more extensive annotations and unified training contribute to better model generalization. Ablation studies validate the effectiveness of each module, particularly the condition mask, in learning multiple preferences. + +# 5.3. MPS Benchmark + +Based on the MPS model and the collected MHP dataset, we introduce the MPS benchmark for evaluating text-to-image models across multiple dimensions. The MPS benchmark includes a set of evaluation prompts designed to assess the models on a total of 4,000 prompts, covering seven categories: characters, scenes, objects, animals, plants, arts, and food. Each category comprises 500 prompts. Our MPS assesses the images generated by the text-to-image mod + +els across four dimensions: Aesthetic, Semantic Alignment, Detail Quantity, and Overall Score. The scoring results can assist users in selecting superior models based on their personal preferences. Additionally, the scoring results can also enhance the generative models' performance by selecting more preferable images with higher MPS scores. + +# 6. Conclusions + +In this work, we introduce the Multi-dimensional Human Preference (MHP) dataset and Multi-dimensional Preference Score (MPS) to evaluate text-to-image models from multi-dimensional human preferences. The MHP dataset offers improvements over previous methods in prompt collection, image generation, and preference annotation, which comprises 918,315 human preference choices across four dimensions. These preferences include aesthetics, semantic alignment, detail quantity, and overall score. Additionally, to align the multi-dimensional human preferences, we propose the MPS, which employs a unified network to score generated images based on varying preference conditions. The MPS introduces a condition mask that retains words in the prompt related to the preference condition. Subsequently, the model integrates only the retained prompt with the image to compute the final score. MPS outperforms related works in predicting multi-dimensional human preferences across three datasets, which demonstrates the generalization of our method. + +Acknowledgements: We sincerely thank Zhuang Li, Lingyu Zou, and Peihan Li for their valuable discussions and feedback. + +# References + +[1] Prompthero. https://prompthero.com/.4 +[2] Ming Ding, Zhuoyi Yang, Wenyi Hong, Wendi Zheng, Chang Zhou, Da Yin, Junyang Lin, Xu Zou, Zhou Shao, Hongxia Yang, and Jie Tang. Cogview: Mastering text-to-image generation via transformers. arXiv preprint arXiv:2105.13290, 2021. 3 +[3] Ming Ding, Wendi Zheng, Wenyi Hong, and Jie Tang. Cogview2: Faster and better text-to-image generation via hierarchical transformers. Advances in Neural Information Processing Systems, 35:16890-16902, 2022. 3 +[4] Patrick Esser, Robin Rombach, and Björn Ommer. Taming transformers for high-resolution image synthesis, 2020. 3 +[5] Martin Heusel, Hubert Ramsauer, Thomas Unterthiner, Bernhard Nessler, and Sepp Hochreiter. Gans trained by a two time-scale update rule converge to a local nash equilibrium. In Advances in Neural Information Processing Systems 30: Annual Conference on Neural Information Processing Systems 2017, December 4-9, 2017, Long Beach, CA, USA, pages 6626-6637, 2017. 1, 3 +[6] Yuval Kirstain, Adam Polyak, Uriel Singer, Shahbuland Matiana, Joe Penna, and Omer Levy. Pick-a-pic: An open dataset of user preferences for text-to-image generation. arXiv preprint arXiv:2305.01569, 2023. 1, 2, 3, 5, 6, 7 +[7] Chunyi Li, Zicheng Zhang, Haoning Wu, Wei Sun, Xiongkuo Min, Xiaohong Liu, Guangtao Zhai, and Weisi Lin. Agiqa-3k: An open database for ai-generated image quality assessment. arXiv preprint arXiv:2306.04717, 2023. 2, 3 +[8] Junnan Li, Dongxu Li, Caiming Xiong, and Steven C. H. Hoi. BLIP: bootstrapping language-image pre-training for unified vision-language understanding and generation. In International Conference on Machine Learning, ICML 2022, 17-23 July 2022, Baltimore, Maryland, USA, pages 12888-12900. PMLR, 2022. 2 +[9] OpenAI. GPT-4 technical report. CoRR, abs/2303.08774, 2023. 2, 4 +[10] Dustin Podell, Zion English, Kyle Lacey, Andreas Blattmann, Tim Dockhorn, Jonas Müller, Joe Penna, and Robin Rombach. Sdxl: Improving latent diffusion models for high-resolution image synthesis. arXiv preprint arXiv:2307.01952, 2023. 1, 3 +[11] Alec Radford, Jong Wook Kim, Chris Hallacy, Aditya Ramesh, Gabriel Goh, Sandhini Agarwal, Girish Sastry, Amanda Askell, Pamela Mishkin, Jack Clark, Gretchen Krueger, and Ilya Sutskever. Learning transferable visual models from natural language supervision. In Proceedings of the 38th International Conference on Machine Learning, ICML 2021, 18-24 July 2021, Virtual Event, pages 8748-8763. PMLR, 2021. 2, 5, 6, 7 +[12] Alec Radford, Jong Wook Kim, Chris Hallacy, Aditya Ramesh, Gabriel Goh, Sandhini Agarwal, Girish Sastry, Amanda Askell, Pamela Mishkin, Jack Clark, Gretchen Krueger, and Ilya Sutskever. Learning transferable visual models from natural language supervision. In Proceedings of the 38th International Conference on Machine Learning, + +ICML 2021, 18-24 July 2021, Virtual Event, pages 8748-8763. PMLR, 2021. 1, 3, 6 +[13] Aditya Ramesh, Prafulla Dhariwal, Alex Nichol, Casey Chu, and Mark Chen. Hierarchical text-conditional image generation with clip latents, 2022. URL https://arxiv.org/abs/2204.06125, 7, 2022. 3 +[14] Robin Rombach, Andreas Blattmann, Dominik Lorenz, Patrick Esser, and Björn Ommer. High-resolution image synthesis with latent diffusion models. 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In Advances in Neural Information Processing Systems 29: Annual Conference on Neural Information Processing Systems 2016, December 5-10, 2016, Barcelona, Spain, pages 2226-2234, 2016. 1, 3 +[17] Christoph Schuhmann, Romain Beaumont, Richard Vencu, Cade Gordon, Ross Wightman, Mehdi Cherti, Theo Coombes, Aarush Katta, Clayton Mullis, Mitchell Wortsman, Patrick Schramowski, Srivatsa Kundurthy, Katherine Crowson, Ludwig Schmidt, Robert Kaczmarczyk, and Jenia Jitsev. LAION-5B: an open large-scale dataset for training next generation image-text models. In NeurIPS, 2022. 6, 7 +[18] Ramprasaath R. Selvaraju, Michael Cogswell, Abhishek Das, Ramakrishna Vedantam, Devi Parikh, and Dhruv Batra. Grad-cam: Visual explanations from deep networks via gradient-based localization. In IEEE International Conference on Computer Vision, ICCV 2017, Venice, Italy, October 22-29, 2017, pages 618-626. IEEE Computer Society, 2017. 7 +[19] Zijie J. Wang, Evan Montoya, David Munechika, Haoyang Yang, Benjamin Hoover, and Duen Horng Chau. Diffusiondb: A large-scale prompt gallery dataset for text-to-image generative models. In Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), ACL 2023, Toronto, Canada, July 9-14, 2023, pages 893-911. Association for Computational Linguistics, 2023. 2, 4 +[20] Xiaoshi Wu, Yiming Hao, Keqiang Sun, Yixiong Chen, Feng Zhu, Rui Zhao, and Hongsheng Li. Human preference score v2: A solid benchmark for evaluating human preferences of text-to-image synthesis. CoRR, abs/2306.09341, 2023. 1, 2, 3, 6, 7 +[21] Xiaoshi Wu, Keqiang Sun, Feng Zhu, Rui Zhao, and Hongsheng Li. Better aligning text-to-image models with human preference. arXiv preprint arXiv:2303.14420, 2023. 2, 3, 5, 6, 7 +[22] Jiazheng Xu, Xiao Liu, Yuchen Wu, Yuxuan Tong, Qinkai Li, Ming Ding, Jie Tang, and Yuxiao Dong. Imagereward: Learning and evaluating human preferences for text- + +to-image generation. arXiv preprint arXiv:2304.05977, 2023.1,2,3,5,6,7 +[23] Jiahui Yu, Yuanzhong Xu, Jing Yu Koh, Thang Luong, Gunjan Baid, Zirui Wang, Vijay Vasudevan, Alexander Ku, Yinfei Yang, Burcu Karagol Ayan, Ben Hutchinson, Wei Han, Zarana Parekh, Xin Li, Han Zhang, Jason Baldridge, and Yonghui Wu. Scaling autoregressive models for content-rich text-to-image generation. Trans. Mach. Learn. Res., 2022, 2, 3, 4 +[24] Zicheng Zhang, Chunyi Li, Wei Sun, Xiaohong Liu, Xiongkuo Min, and Guangtao Zhai. A perceptual quality assessment exploration for aigc images. arXiv preprint arXiv:2303.12618, 2023. 1, 2, 3 +[25] Yufan Zhou, Ruiyi Zhang, Changyou Chen, Chunyuan Li, Chris Tensmeyer, Tong Yu, Jiuming Gu, Jinhui Xu, and Tong Sun. Lafite: Towards language-free training for text-to-image generation. arXiv preprint arXiv:2111.13792, 2021. 3 \ No newline at end of file diff --git a/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/images.zip b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..4b77e93a4100019b3f02b81bd87fb1073ecc9e9d --- /dev/null +++ b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:b9bb10c43b766bf6796cc09f9ce0ba1f057cd57ba8f4518db8f7e031d5d3a5c5 +size 626038 diff --git a/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/layout.json b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..0a5265ebe87f91940249fc80dcadc4f8894fae4e --- /dev/null +++ b/2024/Learning Multi-Dimensional Human Preference for Text-to-Image Generation/layout.json @@ -0,0 +1,6972 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 57, + 103, + 536, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 103, + 536, + 121 + ], + "spans": [ + { + "bbox": [ + 57, + 103, + 536, + 121 + ], + "type": "text", + "content": "Learning Multi-dimensional Human Preference for Text-to-Image Generation" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 69, + 143, + 523, + 173 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 143, + 523, + 173 + ], + "spans": [ + { + "bbox": [ + 69, + 143, + 523, + 173 + ], + "type": "text", + "content": "Sixian Zhang,\\* Bohan Wang\\* Junqiang Wu\\* Yan Li\\* Tingting Gao, Di Zhang, Zhongyuan Wang Kuaishou Technology" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 143, + 199, + 192, + 211 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 199, + 192, + 211 + ], + "spans": [ + { + "bbox": [ + 143, + 199, + 192, + 211 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 224, + 290, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 224, + 290, + 514 + ], + "spans": [ + { + "bbox": [ + 46, + 224, + 290, + 514 + ], + "type": "text", + "content": "Current metrics for text-to-image models typically rely on statistical metrics which inadequately represent the real preference of humans. Although recent work attempts to learn these preferences via human annotated images, they reduce the rich tapestry of human preference to a single overall score. However, the preference results vary when humans evaluate images with different aspects. Therefore, to learn the multi-dimensional human preferences, we propose the Multi-dimensional Preference Score (MPS), the first multi-dimensional preference scoring model for the evaluation of text-to-image models. The MPS introduces the preference condition module upon CLIP model to learn these diverse preferences. It is trained based on our Multi-dimensional Human Preference (MHP) Dataset, which comprises 918,315 human preference choices across four dimensions (i.e., aesthetics, semantic alignment, detail quality and overall assessment) on 607,541 images. The images are generated by a wide range of latest text-to-image models. The MPS outperforms existing scoring methods across 3 datasets in 4 dimensions, enabling it a promising metric for evaluating and improving text-to-image generation. The model and dataset will be made publicly available to facilitate future research. Project page: https://wangbohan97.github.io/MPS/." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 48, + 536, + 128, + 548 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 536, + 128, + 548 + ], + "spans": [ + { + "bbox": [ + 48, + 536, + 128, + 548 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 54, + 558, + 277, + 570 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 54, + 558, + 277, + 570 + ], + "spans": [ + { + "bbox": [ + 54, + 558, + 277, + 570 + ], + "type": "text", + "content": "\"There are a thousand Hamlets in a thousand people's eyes.\"" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 215, + 576, + 281, + 586 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 215, + 576, + 281, + 586 + ], + "spans": [ + { + "bbox": [ + 215, + 576, + 281, + 586 + ], + "type": "text", + "content": "-Vissarion Belinsky" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 600, + 287, + 684 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 600, + 287, + 684 + ], + "spans": [ + { + "bbox": [ + 46, + 600, + 287, + 684 + ], + "type": "text", + "content": "Text-to-image generative models [10, 14, 15] have achieved remarkable advancements in recent years, and these models have the capability to generate high-fidelity and contextually relevant images based on textual descriptions (i.e., prompts). To evaluate the quality of generated images, several evaluation metrics are proposed, including Inception Score (IS) [16], Fréchet Inception Distance (FID)" + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 312, + 201, + 381, + 270 + ], + "blocks": [ + { + "bbox": [ + 312, + 201, + 381, + 270 + ], + "lines": [ + { + "bbox": [ + 312, + 201, + 381, + 270 + ], + "spans": [ + { + "bbox": [ + 312, + 201, + 381, + 270 + ], + "type": "image", + "image_path": "1027e4b711ed6d283ca76f98b3b2de0a85ed2bf9fad8020b5f186e7c7d0c033f.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 313, + 271, + 446, + 288 + ], + "lines": [ + { + "bbox": [ + 313, + 271, + 446, + 288 + ], + "spans": [ + { + "bbox": [ + 313, + 271, + 446, + 288 + ], + "type": "text", + "content": "Prompt: A picture depicting the Grand Canal of Venice, with a row of houses on both sides of the canal and boatman rowing two boats on the river, illustration, vivid colors, high-contrast." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_footnote" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 383, + 201, + 452, + 269 + ], + "blocks": [ + { + "bbox": [ + 383, + 201, + 452, + 269 + ], + "lines": [ + { + "bbox": [ + 383, + 201, + 452, + 269 + ], + "spans": [ + { + "bbox": [ + 383, + 201, + 452, + 269 + ], + "type": "image", + "image_path": "873bbab20c2820637a11a37993c96c6fefa059a84bdd9f11244827c23d5079d0.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 383, + 271, + 452, + 288 + ], + "lines": [ + { + "bbox": [ + 383, + 271, + 452, + 288 + ], + "spans": [ + { + "bbox": [ + 383, + 271, + 452, + 288 + ], + "type": "text", + "content": "mal of Venice, with a row of houses on \nng two boats on the river, illustration," + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_footnote" + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 455, + 203, + 539, + 270 + ], + "blocks": [ + { + "bbox": [ + 455, + 203, + 539, + 270 + ], + "lines": [ + { + "bbox": [ + 455, + 203, + 539, + 270 + ], + "spans": [ + { + "bbox": [ + 455, + 203, + 539, + 270 + ], + "type": "image", + "image_path": "e6ff0ffa3974bc5035eaba5ccfc0f0ca35a0ac04c917e762a4562891451cadc7.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 456, + 271, + 535, + 288 + ], + "lines": [ + { + "bbox": [ + 456, + 271, + 535, + 288 + ], + "spans": [ + { + "bbox": [ + 456, + 271, + 535, + 288 + ], + "type": "text", + "content": "" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_footnote" + } + ], + "index": 16 + }, + { + "type": "image", + "bbox": [ + 312, + 296, + 381, + 365 + ], + "blocks": [ + { + "bbox": [ + 312, + 296, + 381, + 365 + ], + "lines": [ + { + "bbox": [ + 312, + 296, + 381, + 365 + ], + "spans": [ + { + "bbox": [ + 312, + 296, + 381, + 365 + ], + "type": "image", + "image_path": "a286e4f56162a05986c22a4d27fc06e816f38febc3d4544f25e3fb9f492e3dc2.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 313, + 366, + 438, + 379 + ], + "lines": [ + { + "bbox": [ + 313, + 366, + 438, + 379 + ], + "spans": [ + { + "bbox": [ + 313, + 366, + 438, + 379 + ], + "type": "text", + "content": "Prompt: A family of three poses in the Grand Canyon, with the main wearing sunglasses and smiling, 4k resolution, extremely detailed" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_footnote" + }, + { + "bbox": [ + 304, + 392, + 547, + 491 + ], + "lines": [ + { + "bbox": [ + 304, + 392, + 547, + 491 + ], + "spans": [ + { + "bbox": [ + 304, + 392, + 547, + 491 + ], + "type": "text", + "content": "Figure 1. As humans evaluate images from different perspectives, their preference for the images also varies. Specifically, when examining the images in the top row, the image on the left stands out in terms of aesthetic appeal, though it falls short in semantic alignment (e.g., two boats on the river) compared to its counterpart on the right. In the case of the bottom row, both images are aesthetically pleasing, yet the image on the right is marred by poor detail quality (e.g., as signified by the red bounding boxes around the distorted hand and foot)." + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "type": "image", + "bbox": [ + 383, + 296, + 452, + 365 + ], + "blocks": [ + { + "bbox": [ + 383, + 296, + 452, + 365 + ], + "lines": [ + { + "bbox": [ + 383, + 296, + 452, + 365 + ], + "spans": [ + { + "bbox": [ + 383, + 296, + 452, + 365 + ], + "type": "image", + "image_path": "1325e2359ffdc1c66038a0f5a812ee4b168f3e28c59fcf0fd417d8807efdc20b.jpg" + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_body" + } + ], + "index": 20 + }, + { + "bbox": [ + 383, + 366, + 438, + 379 + ], + "angle": 0, + "lines": [ + { + "bbox": [ + 383, + 366, + 438, + 379 + ], + "spans": [ + { + "bbox": [ + 383, + 366, + 438, + 379 + ], + "type": "text", + "content": "nd Canyon, with the man wearing emely detailed" + } + ] + } + ], + "index": 21, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 456, + 295, + 538, + 361 + ], + "blocks": [ + { + "bbox": [ + 456, + 295, + 538, + 361 + ], + "lines": [ + { + "bbox": [ + 456, + 295, + 538, + 361 + ], + "spans": [ + { + "bbox": [ + 456, + 295, + 538, + 361 + ], + "type": "image", + "image_path": "ae2c264553da446934d054e36dfe392213d464a1beed5450cb3fb8a4ff5ae573.jpg" + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_body" + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 508, + 547, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 508, + 547, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 508, + 547, + 581 + ], + "type": "text", + "content": "[5], and CLIP Score [12]. However, these statistical metrics fall short of aligning with human perceptual preferences. For instance, metrics like the IS or the FID, although indicative of image quality to some extent, might not necessarily reflect how a human observer would rate the image in terms of fidelity, coherence, or aesthetic appeal." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "type": "text", + "content": "Contrary to these statistical metrics, several approaches [6, 20-22, 24] turn towards human-centric evaluations, where generated images are manually annotated according to human preferences. Subsequently, models are trained with these annotations to predict preference scores. However, these approaches typically utilize a single score to summarize all human preferences, overlooking the multidimensionality of human preferences. As Fig. 1 shows, the preference results differ when humans evaluate images from various perspectives. Therefore, using a single-dimensional evaluation method is insufficient in capturing the broad" + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 1, + 494, + 15 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 1, + 494, + 15 + ], + "spans": [ + { + "bbox": [ + 145, + 1, + 494, + 15 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 198, + 13, + 442, + 24 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 198, + 13, + 442, + 24 + ], + "spans": [ + { + "bbox": [ + 198, + 13, + 442, + 24 + ], + "type": "text", + "content": "Except for this watermark, it is identical to the accepted version;" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 179, + 25, + 462, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 179, + 25, + 462, + 37 + ], + "spans": [ + { + "bbox": [ + 179, + 25, + 462, + 37 + ], + "type": "text", + "content": "the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 58, + 693, + 215, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 693, + 215, + 703 + ], + "spans": [ + { + "bbox": [ + 58, + 693, + 215, + 703 + ], + "type": "text", + "content": "*These authors contributed equally to this work." + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 59, + 703, + 136, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 136, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 136, + 712 + ], + "type": "text", + "content": "† Corresponding author." + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "8018" + } + ] + } + ], + "index": 29 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 52, + 134, + 541, + 293 + ], + "blocks": [ + { + "bbox": [ + 46, + 70, + 547, + 126 + ], + "lines": [ + { + "bbox": [ + 46, + 70, + 547, + 126 + ], + "spans": [ + { + "bbox": [ + 46, + 70, + 547, + 126 + ], + "type": "text", + "content": "Table 1. Comparisons of text-to-image models quality databases. Our Multi-dimensional Human Preference (MHP) dataset achieves significant advancements over existing work in three aspects, including prompt collection, image generation, and preference annotation. Moreover, it constitutes the largest dataset both in generated images and preference annotations. Note that the Diffusion DB only contains generated images but lacks annotations of human preferences. Besides, KOKORS is an internal dataset derived from in-house platform for designer, which provides " + }, + { + "bbox": [ + 46, + 70, + 547, + 126 + ], + "type": "inline_equation", + "content": "\\sim 10\\mathrm{w}" + }, + { + "bbox": [ + 46, + 70, + 547, + 126 + ], + "type": "text", + "content": " prompts." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 52, + 134, + 541, + 293 + ], + "lines": [ + { + "bbox": [ + 52, + 134, + 541, + 293 + ], + "spans": [ + { + "bbox": [ + 52, + 134, + 541, + 293 + ], + "type": "table", + "html": "
DatasetPrompt collectionImage GenerationPreference annotation
SourceAnnotationSourceNumberRatingDimension
DiffusionDB [19]DiffusionDB×Diffusion (1)1,819,8080None
AGIQA-1K [24]DiffusionDB×Diffusion (2)1,08023,760Overall
PickScore [6]Web Application×Diffusion (3)583,747583,747Overall
ImageReward [22]DiffusionDB×Auto Regressive; Diffusion (6)136,892410,676Overall
HPS [21]DiffusionDB×Diffusion (1)98,80798,807Overall
HPS v2 [20]DiffusionDB, COCO✓GAN; Auto Regressive; Diffusion, COCO (9)430,060798,090Overall
AGIQA-3K [7]DiffusionDB×GAN; Auto Regressive; Diffusion (6)2,982125,244Overall; Alignment
MHPDiffusionDB, PromptHero, KOLORS, GPT4✓GAN; Auto Regressive; Diffusion (9)607,541918,315Aesthetics, Detail, Alignment, Overall
", + "image_path": "17eb6dcfb4561a35d90b4a96dacb901987ffbcdcb5739290e4ebdc54cdea9d63.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 304, + 288, + 353 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 304, + 288, + 353 + ], + "spans": [ + { + "bbox": [ + 46, + 304, + 288, + 353 + ], + "type": "text", + "content": "range of personalized needs and preferences. To ensure a comprehensive evaluation of text-to-image synthesis outputs, it is crucial to learn and utilize multi-dimensional human preferences." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 354, + 288, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 354, + 288, + 700 + ], + "spans": [ + { + "bbox": [ + 46, + 354, + 288, + 700 + ], + "type": "text", + "content": "To learn the multi-dimensional human preferences, we propose the Multi-dimensional Human Preference (MHP) dataset. Compared to prior efforts [6, 20-22], the MHP dataset offers significant enhancements in prompts collection, image generation, and preference annotation. For the prompt collection, previous work [6, 21, 22] directly utilizes existing open-source datasets (e.g., Diffusion DB [19]) or datasets collated from the internet [6], overlooking the potential data bias of long-tail distribution. To this end, based on the categories schema of Parti [23], we annotate the collected prompts into 7 category labels (e.g., characters, scenes, objects, animals, etc.). For the underrepresented tail categories, we employ Large Language Models (LLMs) (e.g., GPT-4 [9]) to generate additional prompts. This process results in a balanced prompt collection across various categories, which is used for later image generation. For image generation, following previous work [7, 20], we not only utilize existing open-source Diffusion models and their variants, but also employ GANs and auto-regressive models to generate images. Consequently, we generate a dataset of 607,541 images, which are further used to create 918,315 pairwise comparisons of images for preference annotation. The quantity of image data constitutes the largest dataset of its kind. For the annotation of human preferences, contrary to the single annotation of existing work [6, 20, 21, 24], we consider a broader range of dimensions for human preferences and employ human annotators to label each image pair across four dimensions, including aesthetics, detail quality, semantic alignment, and overall score." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 59, + 701, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 701, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 59, + 701, + 287, + 714 + ], + "type": "text", + "content": "To learn human preferences, existing methods employ" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 304, + 547, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 304, + 547, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 304, + 547, + 712 + ], + "type": "text", + "content": "the pre-trained vision-language models (e.g., CLIP [11], BLIP [8]) to extract features from images and prompts independently, followed by computing the similarity between them. These methods then fine-tune the network utilizing the collected preference data. For learning the multidimensional preferences, a straightforward strategy is to train separate models for different preferences. However, such a simple strategy requires data re-collection and model re-training for the new preference. Moreover, due to the potential bias in single-preference data, a model trained under one preference condition often exhibits diminished performance when evaluated against other preferences. Therefore, we propose the Multi-dimensional Preference Score (MPS), a unified model capable of predicting scores under various preference conditions. Specifically, a certain preference is denoted by a series of descriptive words. For instance, the 'aesthetic' condition is decomposed into words such as 'light', 'color', and 'clarity' to describe the attributes of this condition. These attribute words are used to compute similarities with the prompt, resulting in a similarity matrix that reflects the correspondence between words in the prompt and the specified condition. On the other hand, features from images and text are extracted using a pre-trained vision-language model. Subsequently, two modalities are fused through a multimodal cross-attention layer. The similarity matrix serves as a mask merged into the cross-attention layer, which ensures that the text only related to the condition is attended to by the visual modality. Then the fused features are used to predict the preference scores. We evaluate our MPS model on both the existing human preference datasets (i.e., ImageReward [22] and HPS v2 [20]) and our MHP dataset. The experimental results indicate that our MPS model surpasses existing benchmarks in evaluating both overall and multi-dimensional prefer" + } + ] + } + ], + "index": 5 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "8019" + } + ] + } + ], + "index": 6 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "type": "text", + "content": "ences, establishing a new state-of-the-art in comparison with related work." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 59, + 97, + 265, + 108 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 97, + 265, + 108 + ], + "spans": [ + { + "bbox": [ + 59, + 97, + 265, + 108 + ], + "type": "text", + "content": "In summary, our main contributions are as follows:" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 109, + 286, + 264 + ], + "type": "list", + "angle": 0, + "index": 5, + "blocks": [ + { + "bbox": [ + 47, + 109, + 286, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 109, + 286, + 180 + ], + "spans": [ + { + "bbox": [ + 47, + 109, + 286, + 180 + ], + "type": "text", + "content": "- We introduce the Multi-dimensional Human Preference (MHP) datasets for evaluating text-to-image models. The MHP contains balanced prompts and the largest collection of images with multi-dimensional annotations. Based on MHP, we propose a standard test benchmark to evaluate existing text-to-image synthesis models." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 181, + 286, + 227 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 181, + 286, + 227 + ], + "spans": [ + { + "bbox": [ + 47, + 181, + 286, + 227 + ], + "type": "text", + "content": "- We propose the MPS model, which learns multidimensional human preferences and evaluates the scores of generated images under different preference conditions." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 228, + 286, + 264 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 228, + 286, + 264 + ], + "spans": [ + { + "bbox": [ + 47, + 228, + 286, + 264 + ], + "type": "text", + "content": "- Our MPS exhibits superior performance compared to existing methods across three datasets in predicting the overall preferences and multi-dimensional preferences." + } + ] + } + ], + "index": 4 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 276, + 130, + 289 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 276, + 130, + 289 + ], + "spans": [ + { + "bbox": [ + 47, + 276, + 130, + 289 + ], + "type": "text", + "content": "2. Related work" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 296, + 264, + 308 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 296, + 264, + 308 + ], + "spans": [ + { + "bbox": [ + 47, + 296, + 264, + 308 + ], + "type": "text", + "content": "2.1. Text-to-image Generation and Evaluation" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 315, + 287, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 315, + 287, + 662 + ], + "spans": [ + { + "bbox": [ + 47, + 315, + 287, + 662 + ], + "type": "text", + "content": "The text-to-image task aims to synthesize realistic images from natural language description (i.e., prompt). Several work attempts to tackle this problem, including GANs [4, 25], auto-regressive [2, 3, 23] and diffusion models [10, 14, 15]. Among the previously mentioned methods, diffusion models gain significant attention for their exceptional performance. These methods are principally divided into two categories: latent-based and pixel-based approaches. The Latent Diffusion Model (LDM) [14] is notable as the first to introduce a latent-based diffusion model, leveraging an auto-encoder to map images into a latent space where the diffusion process is executed. Following this, Stable Diffusion has notably propelled the field forward by open-sourcing SD series [10]. In contrast, DALL-E 2 [13] and Imagen [15] are predicated on pixel-based diffusion models. Besides, the Imagen [15] integrates the large language model T5 XXL to achieve a text-to-image super-resolution diffusion model capable of producing highly realistic images. Current text-to-image models excel in creating high-quality images but often miss aligning with human preferences in real-world applications. For evaluating text-to-image models, several evaluation metrics are proposed to evaluate the quality of generated images, including Inception Score (IS) [16], Fréchet Inception Distance (FID) [5], and CLIP Score [12]. However, these statistical metrics fall short of aligning with human perceptual preferences. Our MPS provides a comprehensive evaluation for text-to-image generations, facilitating the evaluation of alignment with multi-dimensional human preference." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 670, + 205, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 205, + 684 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 205, + 684 + ], + "type": "text", + "content": "2.2. Learning human preferences" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "type": "text", + "content": "Currently, several studies attempt to collect and learn human preferences for the evaluation of text-to-image gen" + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 314, + 77, + 545, + 170 + ], + "blocks": [ + { + "bbox": [ + 314, + 77, + 545, + 170 + ], + "lines": [ + { + "bbox": [ + 314, + 77, + 545, + 170 + ], + "spans": [ + { + "bbox": [ + 314, + 77, + 545, + 170 + ], + "type": "image", + "image_path": "d353a47d6c6d83dc4c757bfcce712d067a429789e9da4cfb07202e28edbb42ec.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 178, + 545, + 222 + ], + "lines": [ + { + "bbox": [ + 305, + 178, + 545, + 222 + ], + "spans": [ + { + "bbox": [ + 305, + 178, + 545, + 222 + ], + "type": "text", + "content": "Figure 2. Prompt collection. The initially collected prompts exhibit a long-tail distribution across various categories. After prompt augmentation with GPT, we obtain a relatively balanced prompt dataset, which contains 66,389 prompts." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 239, + 545, + 262 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 239, + 545, + 262 + ], + "spans": [ + { + "bbox": [ + 305, + 239, + 545, + 262 + ], + "type": "text", + "content": "eration. They use the collected data to fine-tune visual-language models (VLMs) to align with human selections." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 264, + 545, + 443 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 264, + 545, + 443 + ], + "spans": [ + { + "bbox": [ + 304, + 264, + 545, + 443 + ], + "type": "text", + "content": "HPS [21] introduces the HPD dataset of human preference choices. The images are generated solely using the Stable Diffusion model with prompts from Diffusion DB. They train HPS model utilizing the human preference annotations of HPD to align it with human preference. Subsequently, they fine-tune the Stable Diffusion model under the guidance of HPS, leading to better generated images that are more preferred by human users. However, HPS is limited to a single generation model and a relatively small number of images. Furthermore, HPS v2 [20] introduces a larger dataset, employing 8 generative models, including Diffusion models, GANs, and Auto regressive models, and also incorporating captions from the COCO dataset. However, both HPS and HPS v2 primarily focus on overall human preferences, not considering the diversity of human tastes." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 445, + 545, + 540 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 445, + 545, + 540 + ], + "spans": [ + { + "bbox": [ + 304, + 445, + 545, + 540 + ], + "type": "text", + "content": "PickScore [6] proposes a web application designed to collect prompts and human preference annotations from real users. Unlike previous methods adopting prompts from existing datasets (e.g. DiffusionDB), the prompts of PickScore are directly generated by actual users. The dataset of PickScore is sizeable, however, it focuses only on the overall preferences, lacking detailed annotations for multi-dimension preferences." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 542, + 545, + 638 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 542, + 545, + 638 + ], + "spans": [ + { + "bbox": [ + 304, + 542, + 545, + 638 + ], + "type": "text", + "content": "ImageReward [22] employs four types of Diffusion models along with an auto-regression-based model. Their annotation of generated images is more detailed with scoring ranging from 0 to 7. Beyond overall satisfaction, they also consider annotations for alignment and fidelity. However, they merge alignment and fidelity into a single overall score, inadequately capturing the multi-dimensional dimensions of human preferences." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 639, + 545, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 639, + 545, + 700 + ], + "spans": [ + { + "bbox": [ + 305, + 639, + 545, + 700 + ], + "type": "text", + "content": "AGIQA-1k [24] and AGIQA-3k [7] utilize a range of generative models, including Diffusion, GAN, and Auto regressive models, to produce images. They consider both overall and alignment preferences. However, their dataset size is considerably smaller compared to existing work." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 318, + 701, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 701, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 318, + 701, + 545, + 713 + ], + "type": "text", + "content": "Our MHP dataset represents an advancement over previ" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "8020" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 123, + 282, + 247 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 288, + 115 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 288, + 115 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 288, + 115 + ], + "type": "text", + "content": "Table 2. Image generation. The image sources of the MHP dataset consist of the images generated from 9 text-to-image generative models. Note that KOKORS is an internal model for in-house designer platform." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 51, + 123, + 282, + 247 + ], + "lines": [ + { + "bbox": [ + 51, + 123, + 282, + 247 + ], + "spans": [ + { + "bbox": [ + 51, + 123, + 282, + 247 + ], + "type": "table", + "html": "
SourceTypeImagesSplit
KOKORSDiffusion211,707Train and test
DeepFloyd IFDiffusion27,311Train and test
Stable Diffusion XLDiffusion89,176Train and test
Openjourney v4Diffusion133,875Train and test
Stable Diffusion v2.0Diffusion84,590Train and test
Stable Diffusion v1.5Diffusion56,882Train and test
VQGAN+CLIPGAN1,000Test
LAFITEGAN1,000Test
CogView2Autoregressive2,000Test
", + "image_path": "e3c2010a480f778cbf2f178ecddca0795649d8927f8a1339cdb9c9db9a176d42.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 265, + 286, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 265, + 286, + 289 + ], + "spans": [ + { + "bbox": [ + 47, + 265, + 286, + 289 + ], + "type": "text", + "content": "ous work in terms of prompt collection, image generation, and preference annotation." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 308, + 132, + 319 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 308, + 132, + 319 + ], + "spans": [ + { + "bbox": [ + 47, + 308, + 132, + 319 + ], + "type": "text", + "content": "3. MHP Dataset" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 331, + 226, + 342 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 331, + 226, + 342 + ], + "spans": [ + { + "bbox": [ + 47, + 331, + 226, + 342 + ], + "type": "text", + "content": "3.1. Prompt collection and annotation" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 351, + 287, + 591 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 351, + 287, + 591 + ], + "spans": [ + { + "bbox": [ + 46, + 351, + 287, + 591 + ], + "type": "text", + "content": "Our prompts are carefully collected from several databases, including PromptHero[1], DiffusionDB[19] and KOKORS-dataset (an internal dataset derived from in-house platform for designers). Following the category schema from Parti[23], we further merge some categories, and finally determine 7 categories as illustrated in Fig. 2. The definitions and merging rules are detailed in the supplementary material. Based on these defined categories, we employ human annotators to label the initially collected 59,396 prompts. Additionally, the annotators are also required to filter out anomalous prompts, such as those that are incoherent, incomprehensible, or have punctuation errors. After annotation, we obtain 52,057 prompts. The distribution of these prompts, based on their categories, is depicted in Fig. 2. As the figure shows, the initially collected prompts exhibit a long-tail distribution across categories. Such category imbalances might lead to imbalanced generated images. Consequently, the human preferences learned from these imbalanced data could also be biased. As a result, we further expand our prompts." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": "By employing the GPT-4[9], we obtain additional prompts to supplement categories with initially low quantities (see supplementary materials for more examples of the generated prompts). These generated prompts are further refined by annotators to remove those incoherent or incomprehensible items. As shown in Figure 2, after supplementation, we obtain 66,389 prompts and the distribution of prompts across categories is balanced. These balanced prompts help us in learning more representative human preferences." + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 317, + 71, + 532, + 273 + ], + "blocks": [ + { + "bbox": [ + 317, + 71, + 532, + 273 + ], + "lines": [ + { + "bbox": [ + 317, + 71, + 532, + 273 + ], + "spans": [ + { + "bbox": [ + 317, + 71, + 532, + 273 + ], + "type": "image", + "image_path": "37a1111427a93b60ed21499121cb4d5f7261e1b1d3d29c0a892689fc276e3638.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 282, + 545, + 359 + ], + "lines": [ + { + "bbox": [ + 305, + 282, + 545, + 359 + ], + "spans": [ + { + "bbox": [ + 305, + 282, + 545, + 359 + ], + "type": "text", + "content": "Figure 3. Annotation interface. Annotators are required to evaluate the preference for the given image pair on four dimensions, including aesthetics, detail quality (detail), semantic alignment (alignment) and overall score (overall). Annotation scores are discrete values ranging from 1 to 5, which are subsequently normalized to Boolean values of 0 or 1. When the scores are tied, the normalized score is set to 0.5." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 375, + 479, + 388 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 375, + 479, + 388 + ], + "spans": [ + { + "bbox": [ + 306, + 375, + 479, + 388 + ], + "type": "text", + "content": "3.2. Image collection and annotation" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "spans": [ + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "type": "text", + "content": "As shown in Table 2, we utilize Diffusion models (such as the Stable Diffusion series and DeepFloyd IF), GANs, and AutoRegressive models to generate images based on the obtained prompts. Each model produces 2-4 images for every single prompt. The generated images come from a variety of model architectures, with various image resolution scales (e.g., " + }, + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "type": "inline_equation", + "content": "1024 \\times 1024" + }, + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "type": "inline_equation", + "content": "1366 \\times 768" + }, + { + "bbox": [ + 304, + 396, + 545, + 516 + ], + "type": "text", + "content": "), and aspect ratios (e.g., 1:1, 16:9). This diversity ensures a comprehensive representation of the text-to-image models' generalization capability." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 517, + 545, + 672 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 517, + 545, + 672 + ], + "spans": [ + { + "bbox": [ + 304, + 517, + 545, + 672 + ], + "type": "text", + "content": "Images generated from the same prompt are paired together for comparison. To enhance the representativeness of these image pairs, the construction of image pairs sources not only from images generated by different models but also includes those produced by the same model using different random seeds. Based on these contrastive image pairs, we employ human annotators to evaluate the image pairs with our annotation interface as shown in Fig. 3. The annotators are required to evaluate the quality of the generated image pairs based on three sub-dimensions (i.e., aesthetics, text-image consistency, and detail) and one overall dimension (i.e., overall score). These four dimensions are defined as follows:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "content": "1. Aesthetics: annotators should measure the aesthetic quality of a generated image pair in terms of composition, light contrast, color matching, clarity, tone, style," + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "text", + "content": "8021" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 59, + 72, + 271, + 84 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 72, + 271, + 84 + ], + "spans": [ + { + "bbox": [ + 59, + 72, + 271, + 84 + ], + "type": "text", + "content": "depth of field, atmosphere, and artistry of the image." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 85, + 286, + 275 + ], + "type": "list", + "angle": 0, + "index": 4, + "blocks": [ + { + "bbox": [ + 47, + 85, + 286, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 85, + 286, + 144 + ], + "spans": [ + { + "bbox": [ + 47, + 85, + 286, + 144 + ], + "type": "text", + "content": "2. Detail quality: annotators should focus on the delicacy of image details such as texture, hair, and light and shadow, whether there is distortion in the face, hands, and limbs of the characters, whether there is a blurry overall view, object distortion, severe deformation." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 144, + 286, + 227 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 144, + 286, + 227 + ], + "spans": [ + { + "bbox": [ + 47, + 144, + 286, + 227 + ], + "type": "text", + "content": "3. Semantic alignment: annotators should evaluate the semantic consistency of the generated images with the prompts, and the evaluation includes measuring whether the generated image accurately matches the textual description (e.g., quantity, attributes, location, positional relationships) and whether there is missing or redundant content in the generated image." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 228, + 286, + 275 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 228, + 286, + 275 + ], + "spans": [ + { + "bbox": [ + 47, + 228, + 286, + 275 + ], + "type": "text", + "content": "4. Overall assessment: Based on the combination of above aspects and subjective preferences, the annotators assess the quality of each generated image from a holistic perspective." + } + ] + } + ], + "index": 3 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 46, + 282, + 287, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 282, + 287, + 483 + ], + "spans": [ + { + "bbox": [ + 46, + 282, + 287, + 483 + ], + "type": "text", + "content": "The annotators rate all these scores of each image in the pair into five distinct levels (from 1 to 5), and the scores are eventually normalized to [0, 1]. The image annotation is completed by a crowdsourced team of 210 members. Before the official annotation, each member needs to perform pre-annotation, where any member whose annotation results have a high degree of inconsistency with that of the majority is disqualified. Eventually, 198 members participate in the annotation of generated image pairs, of which 170 members act as annotators and 28 members act as quality inspectors. Each image pair is annotated by three annotators respectively and the final result is averaged from these three annotation results. " + }, + { + "bbox": [ + 46, + 282, + 287, + 483 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 46, + 282, + 287, + 483 + ], + "type": "text", + "content": " of the annotated data is extracted and sent to the quality inspector for inspection. If there is significant difference in annotation results between annotators and inspectors, the annotated data is considered invalid and will be relabeled." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 499, + 111, + 510 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 499, + 111, + 510 + ], + "spans": [ + { + "bbox": [ + 47, + 499, + 111, + 510 + ], + "type": "text", + "content": "3.3. Statistics" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 520, + 286, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 520, + 286, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 520, + 286, + 628 + ], + "type": "text", + "content": "In summary, we collect 66,389 prompts and employ 9 recent text-to-image models to generate 607,541 images. Based on these images, we construct 918,315 image pairs. Notably, " + }, + { + "bbox": [ + 46, + 520, + 286, + 628 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 46, + 520, + 286, + 628 + ], + "type": "text", + "content": " of these pairs are created using the same model but with different settings, while the other " + }, + { + "bbox": [ + 46, + 520, + 286, + 628 + ], + "type": "inline_equation", + "content": "80\\%" + }, + { + "bbox": [ + 46, + 520, + 286, + 628 + ], + "type": "text", + "content": " are produced by different models, allowing for a wide range of comparisons. Each image pair is then annotated by 3 distinct annotators across 4 dimensions to enable the study of diversity in human preference." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 630, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 286, + 712 + ], + "type": "text", + "content": "We divide the annotated data into training, validation and test sets. The training and validation set contains 898,315 and 10,000 image pairs and the test set comprises 10,000 pairs. To ensure that the data distribution is representative, the test set includes not only images generated by Diffusion models but also those produced by GAN and Autoregressive models." + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 316, + 71, + 536, + 273 + ], + "blocks": [ + { + "bbox": [ + 316, + 71, + 536, + 273 + ], + "lines": [ + { + "bbox": [ + 316, + 71, + 536, + 273 + ], + "spans": [ + { + "bbox": [ + 316, + 71, + 536, + 273 + ], + "type": "image", + "image_path": "b5d4020d89159312c02e7298fa5c03b2144bbc0dd73c853ef3766d38d44d0e6b.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 281, + 545, + 336 + ], + "lines": [ + { + "bbox": [ + 305, + 281, + 545, + 336 + ], + "spans": [ + { + "bbox": [ + 305, + 281, + 545, + 336 + ], + "type": "text", + "content": "Figure 4. The framework of Multi-dimensional Preference Score (MPS). The MPS takes the generated image, prompt and preference condition as the input, and predicts the quality (i.e. human preference) of the generated image under the given preference condition." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 349, + 529, + 361 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 349, + 529, + 361 + ], + "spans": [ + { + "bbox": [ + 306, + 349, + 529, + 361 + ], + "type": "text", + "content": "4. Multi-dimensional Preference Prediction" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 369, + 443, + 381 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 369, + 443, + 381 + ], + "spans": [ + { + "bbox": [ + 306, + 369, + 443, + 381 + ], + "type": "text", + "content": "4.1. Model Structure of MPS" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "spans": [ + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": "As shown in Fig. 4, we adopt CLIP [11] to initially extract features from images and prompts. Given a prompt " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": ", a generated image " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " and a preference condition " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": ", the visual feature of " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " is obtained by the vision encoder of the CLIP by " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{v} = E_{v}(y)" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{v} \\in \\mathbb{R}^{n_{v} \\times n_{d}}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "n_{v}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " is the token number of the image and " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "n_{d}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " is the feature dimension. " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{t} = E_{t}(x)" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{t} \\in \\mathbb{R}^{n_{p} \\times n_{d}}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "n_{p}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " is the token number of the text. " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{c} = E_{c}(c)" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{c} \\in \\mathbb{R}^{n_{c} \\times n_{d}}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "n_{p}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " is the token number of word sets representing the preference. For the setup of word sets for each preference, please refer to Sec. 5.1. Previous works [6, 21, 22] typically utilize the first dimension of " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{v}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " and the last dimension of " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{t}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " to calculate the preference score, which loses a lot of detailed information of both image and text. Alternatively, we employ the full range of " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{v}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "inline_equation", + "content": "X_{t}" + }, + { + "bbox": [ + 305, + 388, + 545, + 579 + ], + "type": "text", + "content": " and fuse two modalities through the Cross Attention (CA) module" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 329, + 588, + 545, + 620 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 329, + 588, + 545, + 620 + ], + "spans": [ + { + "bbox": [ + 329, + 588, + 545, + 620 + ], + "type": "interline_equation", + "content": "C A \\left(X _ {v}, X _ {t}\\right) = \\sigma \\left(\\frac {X _ {v} W _ {q} \\left(X _ {t} W _ {k}\\right) ^ {T}}{\\sqrt {n _ {d}}}\\right) X _ {t} W _ {v} \\tag {1}", + "image_path": "78af12f343d6916eba4c8af129184d2bd1f6c8a735de2ee8358a62a74411a01b.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 629, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 629, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 629, + 545, + 713 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 305, + 629, + 545, + 713 + ], + "type": "text", + "content": " is the SoftMax activation function, and " + }, + { + "bbox": [ + 305, + 629, + 545, + 713 + ], + "type": "inline_equation", + "content": "W_{*} \\in \\mathbb{R}^{n_d \\times n_d}" + }, + { + "bbox": [ + 305, + 629, + 545, + 713 + ], + "type": "text", + "content": " are parameters and biases are omitted. Our motivation is computing the preference scores in different preference conditions. Specific words in the prompt should be given more attention based on different conditions, e.g., when aesthetics is considered as a condition, words in the prompt related to color, light, and clarity should be taken" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "8022" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 47, + 113, + 294, + 232 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 288, + 104 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 288, + 104 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 288, + 104 + ], + "type": "text", + "content": "Table 3. Main results of MPS and comparison methods on human preference evaluation. Preference accuracy (\\%) is calculated on ImageReward, HPD v2, and our MHP dataset." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 113, + 294, + 232 + ], + "lines": [ + { + "bbox": [ + 47, + 113, + 294, + 232 + ], + "spans": [ + { + "bbox": [ + 47, + 113, + 294, + 232 + ], + "type": "table", + "html": "
IDPreference ModelImageRewardHPD v2MHP (Overall)
1CLIP score [11]54.371.263.7
2Aesthetic Score [17]57.472.662.9
3ImageReward [22]65.170.667.5
4HPS [21]61.273.165.5
5PickScore [6]62.979.869.5
6HPS v2 [20]65.783.365.5
7MPS (Ours)67.583.574.2
", + "image_path": "e819749a37e22634eaeee4b272cc314c42a6a1fb75575cbba828d45c82189799.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "spans": [ + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": "into account more when calculating the score. Therefore, we propose a condition mask to highlight the relevant tokens while suppressing the irrelevant tokens. The condition is represented by a series of attribute words, e.g. the preference condition of 'Aesthetic' is represented by a set of words, including light, color and clarity. The relevance of prompt and condition is computed by " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "R_{p,c} = X_cX_t^T W_c + b_c" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "R_{p,c} \\in \\mathbb{R}^{n_c \\times n_p}" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "W_c" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "b_c" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": " are learnable parameters. The " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "R_{p,c}" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": " is averaged along the dimension " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "n_c" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": " and then repeated " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "n_v" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": " times to obtain the mask " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "M_c \\in \\mathbb{R}^{n_v \\times n_p}" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": ". The " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "M_c" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": " is further binarized to " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "\\bar{M}_c" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": ", where elements below the similarity threshold are assigned to negative infinity and others are set to zero. Based on the condition mask " + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "inline_equation", + "content": "\\bar{M}_c" + }, + { + "bbox": [ + 46, + 244, + 290, + 413 + ], + "type": "text", + "content": ", the Eq. 1 is further improved as" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 49, + 420, + 287, + 462 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 420, + 287, + 462 + ], + "spans": [ + { + "bbox": [ + 49, + 420, + 287, + 462 + ], + "type": "interline_equation", + "content": "C A \\left(X _ {v}, X _ {t} \\mid X _ {c}\\right) = \\sigma \\left(\\frac {X _ {v} W _ {q} \\left(X _ {t} W _ {k}\\right) ^ {T}}{\\sqrt {d}} + \\bar {M} _ {c}\\right) X _ {t} W _ {v} \\tag {2}", + "image_path": "a74191b54119a555785ac8935e83b87dd40fd3cc1b9e76c24e6f107e68ff2384.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "spans": [ + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "content": "The Eq. 2 ensures that the parts of the prompt that are relevant to the condition information receive more attention when computing the preference score. We adopt the first dimension (i.e. the cls token) of fused feature " + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "inline_equation", + "content": "CA(X_v, X_t | X_c)" + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "content": " for further prediction, which is denoted as " + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "inline_equation", + "content": "f_{v,t}" + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "inline_equation", + "content": "s \\in \\mathbb{R}^{1 \\times n_d}" + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "content": ". Additionally, to prevent the issue of excessively short prompts leading to a scenario where no words of the prompt are related to the condition. In such a scenario, the cross-attention layer would be unable to capture the information from the prompt. Therefore, we supplement the " + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "inline_equation", + "content": "f_{v,t}" + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "content": " with additional prompt feature " + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "inline_equation", + "content": "f_t" + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "inline_equation", + "content": "f_t" + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "content": " is the last dimension of " + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "inline_equation", + "content": "X_t" + }, + { + "bbox": [ + 46, + 463, + 287, + 617 + ], + "type": "text", + "content": ". Consequently, the MPS is obtained by" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 121, + 619, + 287, + 632 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 121, + 619, + 287, + 632 + ], + "spans": [ + { + "bbox": [ + 121, + 619, + 287, + 632 + ], + "type": "interline_equation", + "content": "S (x, y \\mid c) = \\alpha f _ {v, t} \\cdot f _ {t} \\tag {3}", + "image_path": "7e0dc1a01a08b4e89a2101b3504a78da03dbd5c824c749329eb8e785fe574ac1.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "spans": [ + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "type": "text", + "content": " is a learned scalar while " + }, + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "type": "inline_equation", + "content": "x, y" + }, + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 47, + 638, + 287, + 663 + ], + "type": "text", + "content": " denote the prompt, image and preference condition, respectively." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 670, + 111, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 111, + 684 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 111, + 684 + ], + "type": "text", + "content": "4.2. Training" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": "The input for our objective includes our scoring function MPS " + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "inline_equation", + "content": "S(x, y|c)" + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": ", a prompt " + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": ", two generated image " + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "inline_equation", + "content": "y_1, y_2" + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": ", a" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": "preference condition " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " and the preference score (annotated by human) " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " takes a value of [1, 0] for " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "y_{1}" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " is preferred, [0, 1] if " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "y_{2}" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " is preferred, or [0.5, 0.5] for ties. Following previous work [6], the training objective minimizes the KL-divergence between the annotation " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " and the softmax-normalized prediction" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 348, + 150, + 545, + 186 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 150, + 545, + 186 + ], + "spans": [ + { + "bbox": [ + 348, + 150, + 545, + 186 + ], + "type": "interline_equation", + "content": "\\hat {p} _ {i, c} = \\frac {\\exp S (x , y _ {i} | c)}{\\sum_ {i = 1} ^ {2} \\exp S (x , y _ {i} | c)} \\tag {4}", + "image_path": "1c1d157a7fca572c5056f61f0b9abe2b13c4d11a23defcfd57ae6c189b95a1e2.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 351, + 186, + 501, + 213 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 351, + 186, + 501, + 213 + ], + "spans": [ + { + "bbox": [ + 351, + 186, + 501, + 213 + ], + "type": "interline_equation", + "content": "L _ {P} = \\sum_ {c} \\sum_ {i = 1} ^ {\\bar {}} p _ {i, c} (l o g p _ {i, c} - l o g \\hat {p} _ {i, c})", + "image_path": "5eb01e4245e11d5e103d814b4a5e09789a24f23e22fd13d07913e590ed4cc6b8.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 219, + 545, + 291 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 219, + 545, + 291 + ], + "spans": [ + { + "bbox": [ + 304, + 219, + 545, + 291 + ], + "type": "text", + "content": "We initialize the text and vision encoders, " + }, + { + "bbox": [ + 304, + 219, + 545, + 291 + ], + "type": "inline_equation", + "content": "E_{t}" + }, + { + "bbox": [ + 304, + 219, + 545, + 291 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 219, + 545, + 291 + ], + "type": "inline_equation", + "content": "E_{v}" + }, + { + "bbox": [ + 304, + 219, + 545, + 291 + ], + "type": "text", + "content": ", with parameters from the pre-trained CLIP-H model, while the remaining parameters are subject to random initialization. We train our MPS on MHP datasets for 30,000 steps, with a batch size of 128, a learning rate of 3e-6, and a warmup period of 500 steps." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 301, + 388, + 315 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 301, + 388, + 315 + ], + "spans": [ + { + "bbox": [ + 306, + 301, + 388, + 315 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 320, + 422, + 334 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 320, + 422, + 334 + ], + "spans": [ + { + "bbox": [ + 306, + 320, + 422, + 334 + ], + "type": "text", + "content": "5.1. Experimental Setup" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 339, + 545, + 447 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 339, + 545, + 447 + ], + "spans": [ + { + "bbox": [ + 304, + 339, + 545, + 447 + ], + "type": "text", + "content": "Preference condition setting. We utilize the following collection of word sets to represent human preferences: 1) Aesthetics: light, color, clarity, tone, style, ambiance, artistry; 2) Detail quality: shape, face, hair, hands, limbs, structure, instance, texture; 3) Semantic alignment: quantity, attributes, position, number, location; 4) Overall: light, color, clarity, tone, style, ambiance, artistry, shape, face, hair, hands, limbs, structure, instance, texture, quantity, attributes, position, number, location." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 460, + 545, + 557 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 545, + 557 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 545, + 557 + ], + "type": "text", + "content": "Evaluation setting. We select widely used statistical metrics for evaluating text-to-image models, namely the CLIP score [12] and Aesthetic score [17] for comparison. Additionally, we also choose methods that align with human preferences for evaluating text-to-image models, including Image Reward [22], HPS [20, 21] and PickScore [6]. Following previous works [6, 20], we utilize publicly available pre-trained models without finetuning for evaluation." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 563, + 416, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 563, + 416, + 574 + ], + "spans": [ + { + "bbox": [ + 306, + 563, + 416, + 574 + ], + "type": "text", + "content": "5.2. Evaluation Results" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "Overall Preference accuracy. Previous works on learning human preferences mostly focus on a singular, overall preference, i.e., summarizing human preferences with an overall score. For a fair comparison, we choose existing publicly available human preference datasets: the ImageReward test set [22] and the HPD v2 test set [20], along with our MHP dataset (using only data annotated with overall scores) to compare our method with relevant baselines. As shown in Tab. 3, our MPS demonstrates a better accuracy across these three datasets, indicating the strong generalization capability of our method." + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "8023" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 47, + 102, + 294, + 220 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 288, + 94 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 288, + 94 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 288, + 94 + ], + "type": "text", + "content": "Table 4. The evaluation of MPS and related scoring functions for the prediction of multi-dimensional human preferences(%)" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 102, + 294, + 220 + ], + "lines": [ + { + "bbox": [ + 47, + 102, + 294, + 220 + ], + "spans": [ + { + "bbox": [ + 47, + 102, + 294, + 220 + ], + "type": "table", + "html": "
IDPreference ModelOverallAestheticsAlignmentDetail
1CLIP score [11]63.6768.1482.6961.71
2Aesthetic Score [17]62.8582.8569.3660.34
3ImageReward [22]67.4574.7975.2758.31
4HPS [21]65.5173.8673.8662.05
5PickScore [6]69.5270.9570.9256.74
6HPS v2 [20]65.5173.8673.8762.06
7MPS (Ours)74.2483.8683.8785.18
", + "image_path": "e976c34c70d582028fd2562a1bb2ccac17144a14de06b13efccd77c9e35db754.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 234, + 289, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 234, + 289, + 594 + ], + "spans": [ + { + "bbox": [ + 47, + 234, + 289, + 594 + ], + "type": "text", + "content": "Multinational Preference accuracy. In addition to the overall score, we also compare the performance of previous works and our method in predicting multi-dimensional human preferences based on our MHP dataset. As Tab. 4 illustrates, the CLIP Score and Aesthetic score focus on specific types of preferences, only perform well in certain preferences (e.g., semantic alignment or aesthetics). However, they fall short in predicting other preferences compared to models trained on human preferences. Additionally, preference models [6, 20-22] generally perform better in overall score and some other dimensions but lack generalization in certain specific preferences (e.g., details)*. We illustrate the Fig. 5 to reveal the underlying reasons for this poor generalization. In the first and second rows of Fig. 5, the score functions exhibit a high correlation only with the trained preferences (e.g. semantic alignment and overall score), but perform poorly on other preferences. It is important to note that the prediction of different preferences is based on the same data, albeit with different preference annotations. This indicates that not all preferences are strongly correlated, which results in that improvements in one preference might come at the expense of others. Therefore, only learning a single score is inadequate in fully reflecting the complexity of human preferences. In contrast, our MPS learns human preferences with the condition mask from multiple dimensions and maintains high consistency across all dimensions of human preferences, as shown in the third row of Fig. 5. Besides, as Tab. 4 indicated, MPS outperforms the related works by a large margin in predicting the multi-dimensional human preference on the MHP dataset." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 611, + 287, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 611, + 287, + 685 + ], + "spans": [ + { + "bbox": [ + 46, + 611, + 287, + 685 + ], + "type": "text", + "content": "Visualization Results. Further, we aim to explore why our MPS exhibits strong generalization across various dimensions of human preferences, even some preferences (e.g., detail quantity) are not highly correlated with others. To this end, we visualized the attention map of images and prompts that MPS focuses on when predicting hu" + } + ] + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 306, + 70, + 552, + 120 + ], + "blocks": [ + { + "bbox": [ + 306, + 70, + 552, + 120 + ], + "lines": [ + { + "bbox": [ + 306, + 70, + 552, + 120 + ], + "spans": [ + { + "bbox": [ + 306, + 70, + 552, + 120 + ], + "type": "image", + "image_path": "05ce8b5a3070af49bee5a1b330805ac69759a5b3256a3b9a44ac722525e74295.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 306, + 121, + 551, + 167 + ], + "blocks": [ + { + "bbox": [ + 306, + 121, + 551, + 167 + ], + "lines": [ + { + "bbox": [ + 306, + 121, + 551, + 167 + ], + "spans": [ + { + "bbox": [ + 306, + 121, + 551, + 167 + ], + "type": "image", + "image_path": "216ced121ee7889a6afb654c3c0f044c24c0689ea311d0ed314b6af64d3a694f.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 306, + 167, + 551, + 213 + ], + "blocks": [ + { + "bbox": [ + 306, + 167, + 551, + 213 + ], + "lines": [ + { + "bbox": [ + 306, + 167, + 551, + 213 + ], + "spans": [ + { + "bbox": [ + 306, + 167, + 551, + 213 + ], + "type": "image", + "image_path": "095bbabf4bc7c2525ba001d0d085c15aa113ddc765eaf24a3108c99c193bf911.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 222, + 547, + 310 + ], + "lines": [ + { + "bbox": [ + 304, + 222, + 547, + 310 + ], + "spans": [ + { + "bbox": [ + 304, + 222, + 547, + 310 + ], + "type": "text", + "content": "Figure 5. Correlation between real user preferences and model predictions. The x-axis of each subplot represents the annotated real human preferences, and the y-axis denotes the model's predictions. We examine three models: CLIP score, PickScore, and MPS (ours). Each subplot is annotated with the calculated correlation coefficient R-value, where a higher R-value indicates a closer alignment of the model's predictions with actual human preferences." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 324, + 547, + 527 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 324, + 547, + 527 + ], + "spans": [ + { + "bbox": [ + 304, + 324, + 547, + 527 + ], + "type": "text", + "content": "man preferences. As shown in Fig. 6, we employ Grad-CAM [18] and " + }, + { + "bbox": [ + 304, + 324, + 547, + 527 + ], + "type": "inline_equation", + "content": "f_{v,t}" + }, + { + "bbox": [ + 304, + 324, + 547, + 527 + ], + "type": "text", + "content": " to generate attention heatmaps of the image, and utilize the values of " + }, + { + "bbox": [ + 304, + 324, + 547, + 527 + ], + "type": "inline_equation", + "content": "M_c" + }, + { + "bbox": [ + 304, + 324, + 547, + 527 + ], + "type": "text", + "content": " to represent the attention heatmap of the prompt. The visualization results indicate that our HPS attends to different regions of prompts and images depending on the specific preference condition. This is attributed to the condition mask, which allows only those words in the prompt related to the preference condition to be observed by the image. The condition mask ensures that the model predicts the preference with different inputs, and the model only needs to calculate the similarity between patches in the image and the retained partial prompt to determine the final score. Therefore, the selective focus enabled by the condition mask allows utilizing a unified model to predict multinational preferences effectively, even if some preferences have weak correlations with others." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 542, + 547, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 542, + 547, + 686 + ], + "spans": [ + { + "bbox": [ + 304, + 542, + 547, + 686 + ], + "type": "text", + "content": "Ablation study. We conduct ablation studies to verify the effectiveness of each component, as illustrated in Tab. 5. Compared to the baseline† (i.e., PickScore), the cross-attention module enables more comprehensive integration between image and prompt, leading to improvement of prediction accuracy in overall score, aesthetics, and semantic alignment. However, the model still underperforms in detail quantity, which is less correlated with other preferences. The addition of the condition mask " + }, + { + "bbox": [ + 304, + 542, + 547, + 686 + ], + "type": "inline_equation", + "content": "M_{c}" + }, + { + "bbox": [ + 304, + 542, + 547, + 686 + ], + "type": "text", + "content": " alleviates this issue and improves the prediction performance across various preferences, especially in the detail quantity. Furthermore, we train separate models for different preferences." + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 47, + 693, + 287, + 715 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 287, + 715 + ], + "type": "text", + "content": "*Since these methods have been trained solely to generate an overall score, we could only duplicate it for multinational preferences." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 693, + 545, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 545, + 712 + ], + "type": "text", + "content": "†Note that the baseline shares the same network architecture with PickScore in Tab. 3 and 4, but is trained on our MHP dataset." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "8024" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 52, + 71, + 541, + 265 + ], + "blocks": [ + { + "bbox": [ + 52, + 71, + 541, + 265 + ], + "lines": [ + { + "bbox": [ + 52, + 71, + 541, + 265 + ], + "spans": [ + { + "bbox": [ + 52, + 71, + 541, + 265 + ], + "type": "image", + "image_path": "d574610aed709865fa4e5b496868957fc34d260e63b0f2a287de029af19fcae1.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 273, + 548, + 329 + ], + "lines": [ + { + "bbox": [ + 46, + 273, + 548, + 329 + ], + "spans": [ + { + "bbox": [ + 46, + 273, + 548, + 329 + ], + "type": "text", + "content": "Figure 6. Visualization. We leverage Grad-CAM and the condition mask " + }, + { + "bbox": [ + 46, + 273, + 548, + 329 + ], + "type": "inline_equation", + "content": "M_{c}" + }, + { + "bbox": [ + 46, + 273, + 548, + 329 + ], + "type": "text", + "content": " to visualize attention heatmaps for the image and prompt. The condition mask results in the prompt focusing on words related to the preference condition. For Aesthetic, the model tends to focus on colors (e.g., pink) and lighting (e.g., bright). In the case of semantic alignment, the focus shifts to attributes (e.g., pink suit) and position (e.g., inside, background). For detail quantity, the model's attention is on instances (e.g., alpaca, machine, fancy food). On the image side, the model also tends to focus on areas of the image that correlate with the parts of the prompt receiving attention." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 48, + 403, + 287, + 494 + ], + "blocks": [ + { + "bbox": [ + 46, + 340, + 287, + 396 + ], + "lines": [ + { + "bbox": [ + 46, + 340, + 287, + 396 + ], + "spans": [ + { + "bbox": [ + 46, + 340, + 287, + 396 + ], + "type": "text", + "content": "Table 5. Ablation study for different modules used in MPS. Base: PickScore is employed as the baseline model. CA: Cross-attention module. Mask: Preference condition mask " + }, + { + "bbox": [ + 46, + 340, + 287, + 396 + ], + "type": "inline_equation", + "content": "M_{c}" + }, + { + "bbox": [ + 46, + 340, + 287, + 396 + ], + "type": "text", + "content": ". Row 4 illustrates the models that have identical structures but are trained separately for each preference type." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 403, + 287, + 494 + ], + "lines": [ + { + "bbox": [ + 48, + 403, + 287, + 494 + ], + "spans": [ + { + "bbox": [ + 48, + 403, + 287, + 494 + ], + "type": "table", + "html": "
IDModuleOverallAestheticsAlignmentDetail
BaseCAMask
1✓70.6571.0570.8157.46
2✓✓74.1171.8373.0258.79
3✓✓✓74.2483.8683.8785.18
4Separately trained MPS73.5180.5479.6876.81
", + "image_path": "bc896c7835d4c84c92d39168b32459a940d0a220be4999dcf7dc3bad7237e81e.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 507, + 287, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 507, + 287, + 592 + ], + "spans": [ + { + "bbox": [ + 46, + 507, + 287, + 592 + ], + "type": "text", + "content": "Experimental results indicate that models trained separately for each preference do not perform as well as those trained to learn multiple preferences simultaneously. We infer that more extensive annotations and unified training contribute to better model generalization. Ablation studies validate the effectiveness of each module, particularly the condition mask, in learning multiple preferences." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 599, + 151, + 611 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 599, + 151, + 611 + ], + "spans": [ + { + "bbox": [ + 47, + 599, + 151, + 611 + ], + "type": "text", + "content": "5.3. MPS Benchmark" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": "Based on the MPS model and the collected MHP dataset, we introduce the MPS benchmark for evaluating text-to-image models across multiple dimensions. The MPS benchmark includes a set of evaluation prompts designed to assess the models on a total of 4,000 prompts, covering seven categories: characters, scenes, objects, animals, plants, arts, and food. Each category comprises 500 prompts. Our MPS assesses the images generated by the text-to-image mod" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 341, + 547, + 414 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 341, + 547, + 414 + ], + "spans": [ + { + "bbox": [ + 304, + 341, + 547, + 414 + ], + "type": "text", + "content": "els across four dimensions: Aesthetic, Semantic Alignment, Detail Quantity, and Overall Score. The scoring results can assist users in selecting superior models based on their personal preferences. Additionally, the scoring results can also enhance the generative models' performance by selecting more preferable images with higher MPS scores." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 426, + 384, + 438 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 426, + 384, + 438 + ], + "spans": [ + { + "bbox": [ + 306, + 426, + 384, + 438 + ], + "type": "text", + "content": "6. Conclusions" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 446, + 547, + 673 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 446, + 547, + 673 + ], + "spans": [ + { + "bbox": [ + 304, + 446, + 547, + 673 + ], + "type": "text", + "content": "In this work, we introduce the Multi-dimensional Human Preference (MHP) dataset and Multi-dimensional Preference Score (MPS) to evaluate text-to-image models from multi-dimensional human preferences. The MHP dataset offers improvements over previous methods in prompt collection, image generation, and preference annotation, which comprises 918,315 human preference choices across four dimensions. These preferences include aesthetics, semantic alignment, detail quantity, and overall score. Additionally, to align the multi-dimensional human preferences, we propose the MPS, which employs a unified network to score generated images based on varying preference conditions. The MPS introduces a condition mask that retains words in the prompt related to the preference condition. Subsequently, the model integrates only the retained prompt with the image to compute the final score. MPS outperforms related works in predicting multi-dimensional human preferences across three datasets, which demonstrates the generalization of our method." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 691, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 691, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 691, + 545, + 713 + ], + "type": "text", + "content": "Acknowledgements: We sincerely thank Zhuang Li, Lingyu Zou, and Peihan Li for their valuable discussions and feedback." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "8025" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 253, + 102 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 253, + 102 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 253, + 102 + ], + "type": "text", + "content": "[1] Prompthero. https://prompthero.com/.4" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 53, + 103, + 287, + 158 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 103, + 287, + 158 + ], + "spans": [ + { + "bbox": [ + 53, + 103, + 287, + 158 + ], + "type": "text", + "content": "[2] Ming Ding, Zhuoyi Yang, Wenyi Hong, Wendi Zheng, Chang Zhou, Da Yin, Junyang Lin, Xu Zou, Zhou Shao, Hongxia Yang, and Jie Tang. 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Lafite: Towards language-free training for text-to-image generation. arXiv preprint arXiv:2111.13792, 2021. 3" + } + ] + } + ], + "index": 3 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "8027" + } + ] + } + ], + "index": 5 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_content_list.json b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..de743b15e439af86b046d4dea3b7f04f96badb1f --- /dev/null +++ b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_content_list.json @@ -0,0 +1,1450 @@ +[ + { + "type": "text", + "text": "Learning Object State Changes in Videos: An Open-World Perspective", + "text_level": 1, + "bbox": [ + 127, + 130, + 841, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Zihui Xue1,2", + "bbox": [ + 238, + 179, + 343, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Kumar Ashutosh1,2", + "bbox": [ + 377, + 180, + 531, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Kristen Grauman $^{1,2}$", + "bbox": [ + 571, + 179, + 727, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1The University of Texas at Austin", + "bbox": [ + 276, + 198, + 550, + 215 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ FAIR, Meta", + "bbox": [ + 589, + 198, + 694, + 215 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 251, + 313, + 266 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Object State Changes (OSCs) are pivotal for video understanding. While humans can effortlessly generalize OSC understanding from familiar to unknown objects, current approaches are confined to a closed vocabulary. Addressing this gap, we introduce a novel open-world formulation for the video OSC problem. The goal is to temporally localize the three stages of an OSC—the object's initial state, its transitioning state, and its end state—whether or not the object has been observed during training. Towards this end, we develop VIDOSC, a holistic learning approach that: (1) leverages text and vision-language models for supervisory signals to obviate manually labeling OSC training data, and (2) abstracts fine-grained shared state representations from objects to enhance generalization. Furthermore, we present HowToChange, the first open-world benchmark for video OSC localization, which offers an order of magnitude increase in the label space and annotation volume compared to the best existing benchmark. Experimental results demonstrate the efficacy of our approach, in both traditional closed-world and open-world scenarios. $^{1}$", + "bbox": [ + 73, + 282, + 473, + 585 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 613, + 209, + 628 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In video understanding, the study of objects primarily revolves around tasks like recognition [16], detection [24], and tracking [8, 62], with the assumption that objects maintain a consistent visual appearance throughout the video. Yet, objects in video are often dynamic. They can undergo transformations that change their appearance, shape, and even topology. For example, a pineapple goes from whole to peeled to sliced, or wood is carved into a new shape.", + "bbox": [ + 75, + 638, + 468, + 758 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Object State Changes (OSCs) [2, 15, 17, 22, 47, 50-52, 60, 64] add a critical dimension to video understanding. On the one hand, they provide insights into human actions—observing a piece of metal being shaped into a hook, for instance, implies the action of bending; observing an egg shell go from whole to broken implies the action of cracking. On the other hand, OSCs are essential", + "bbox": [ + 75, + 760, + 470, + 864 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/85f72c82d0ff670f54b9eb4f496b733dc97e95e3bcec96d6967775bb1b1a4d34.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 506, + 252, + 885, + 334 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e49abcaa07332c67ed714d89c2ec36e0026b413512f6c05d00a99d3b2d38241f.jpg", + "image_caption": [ + "Figure 1. Top: The video OSC objective is to temporally localize an object's three states (i.e., initial, transitioning, end). Bottom: OSCs naturally exhibit a long tail. Certain OSCs, such as melting butter or marshmallow, are frequently showcased in instructional videos while others like melting jaggery might be rarely seen. We introduce an innovative open-world formulation that requires extrapolating to novel objects never encountered during training." + ], + "image_footnote": [], + "bbox": [ + 506, + 335, + 885, + 460 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "for assessing goal completion, in a way that is invariant to the specific procedure used. For instance, the readiness of cake batter signifies the completion of a mixing task, regardless of whether it was stirred by hand or a mechanical mixer. These core functionalities are instrumental for various real-world applications [5, 6, 12, 13, 20, 21, 66], ranging from AR/VR assistants [42] that guide users through complex tasks by monitoring object states, to robotic manipulation [9, 55] where understanding the state of objects is critical for task planning and failure recovery.", + "bbox": [ + 496, + 580, + 892, + 733 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "However, the development of video OSC is still at a primitive stage. Existing approaches [1, 2, 15, 46, 50, 51, 58] assume a closed vocabulary, where each state transformation is associated with a limited set of objects—often just 1 or 2. For example, the concept of “melting” might be limited to familiar items like butter and marshmallow. Consequently, the learned models are only capable of identifying state changes for objects observed during training and stumble when presented with novel objects. In contrast, in real-world situations a single state transition like “melting” can be linked with a plethora of objects—some ubiquitous and", + "bbox": [ + 496, + 734, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "1Project webpage: https://vision.cs.utexas.edu/projects/VidOSC/.", + "bbox": [ + 76, + 875, + 467, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "18493", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "others rare. Importantly, there is an intrinsic connection that threads these OSC processes together. As humans, even if we have never encountered an unusual substance (e.g., jaggery) before, we can still understand that it is experiencing a \"melting\" process based on its visual transformation cues (see Fig. 1, bottom).", + "bbox": [ + 75, + 90, + 468, + 181 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In light of these limitations, we propose a novel open-world formulation of the video OSC problem. We formally characterize OSCs in videos in terms of three states that must be temporally localized: initial, transitioning, and end (see Fig. 1, top). In our open-world setting, there are known objects and novel objects. The model is only presented with known objects during training (e.g., frying chicken, frying onions). Then, it is evaluated on both known and novel objects (e.g., frying cauliflower). In addition to this fundamental open-world generalization, we also tackle a more comprehensive notion of the transitioning state. Specifically, our transitioning states encapsulate not only action-induced modifications to the object (e.g., peeling), but also passive transformations the object undergoes without human interference (e.g., melting) and edited-out transformations (e.g., the cake goes from raw to baked even if baked off camera). Though largely overlooked in existing approaches [1, 15, 46, 58], these cases are both common and technically interesting, since they force a model to reason about the effects of the core state change rather than search for evidence of a human actor carrying out the action.", + "bbox": [ + 75, + 181, + 470, + 500 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Armed with this new problem formulation, we propose a holistic video OSC learning approach, anchored by two innovative ideas. First, we explore text and vision-language models (VLMs) for supervisory signals during training. We pioneer the use of textual state descriptions to generate a long tail of object state pseudo-labels, by leveraging the remarkable capabilities of VLMs [23, 44, 63] and large language models (LLMs) [40, 53, 54]. This strategy eliminates the need for exhaustive label collection for training data, facilitating large-scale model training. Second, to confront the open-world challenge, we propose object-agnostic state prediction, consisting of three key techniques: a shared state vocabulary to unify the label space across objects sharing the same state transition (e.g., melting butter and melting marshmallow), temporal modeling to grasp the progression of state changes over time, and object-centric features that better represent the objects during an OSC. These designs equip our model with the ability to generalize state understanding from known objects to novel ones. We term our approach VIDOSC.", + "bbox": [ + 75, + 500, + 468, + 801 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Complementing this, we present a large-scale real-world dataset HowToChange. Sourced from the HowTo100M collection [36], it sets a new benchmark in the field of unprecedented scale and an authentic long-tail distribution, setting", + "bbox": [ + 75, + 801, + 468, + 864 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "it apart from the constrained scope and closed-world setting of earlier benchmarks (see Table 1). Finally, experimental results demonstrate the efficacy of VIDOsc, surpassing the state-of-the-art in both traditional closed-world and novel open-world scenarios by a great margin.", + "bbox": [ + 500, + 90, + 890, + 167 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 180, + 640, + 196 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Object State Changes Image-based methods explore the compositional nature of objects and their attributes, including zero-shot recognition of unseen combinations [22, 29, 33, 37-39, 41, 43], but do not consider the temporal progression of OSCs in video, which brings new challenges. Video-based methods develop human-centric models that leverage state change cues to facilitate action recognition [1, 15, 46, 58], or explore joint discovery of object states and actions [2, 50, 51]. Notably, all the existing methods assume a closed world, recognizing only the OSC categories (\"known\" objects) seen during training. Our approach distinguishes itself in three crucial ways: (1) we introduce a novel open-world3 formulation, where the objects encountered during evaluation can be entirely unseen during training; (2) we adopt an object-centric perspective, allowing for scenarios where OSCs occur with no observable human actions in the video; and (3) we propose to utilize the text modality and VLMs as supervisory signals, greatly scaling up model training and boosting performance.", + "bbox": [ + 496, + 208, + 890, + 496 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Early datasets for video OSC capture a limited array of OSCs in fewer than 1,000 videos [2, 31]. The more recent ChangeIt dataset [50] marks an advance in dataset scale (34K videos), yet is still restricted to a small OSC vocabulary of 44 total object-state transitions. It lacks the scope to adequately test unseen objects, since most state changes coincide with only 1 or 2 objects across all the videos (see Table 1). Other datasets explore different aspects of video OSCs, including object state recognition [47], point-of-noreturn (PNR) frame localization [17], and object segmentation [52, 64], but they lack any temporal annotations of fine-grained OSC states needed for our task's evaluation. Our HowToChange dataset increases the OSC vocabulary space by an order of magnitude and allows for the first time rigorous study of the open-world temporal OSC challenge.", + "bbox": [ + 496, + 496, + 892, + 723 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Vision and Language LLMs [40, 53, 54] have revolutionized various research fields with their exceptional performance across diverse applications. Building on this momentum, the use of web-scale image-text data has emerged as a powerful paradigm in computer vision, with powerful VLMs now advancing an array of image tasks, including zero-shot classification [44], detection [18], segmentation [32] and visual question answering [27, 28]. Similarly, joint video-text representation learning [3, 30, 36, 67] has been advanced by multimodal datasets like", + "bbox": [ + 496, + 724, + 890, + 876 + ], + "page_idx": 1 + }, + { + "type": "page_footnote", + "text": "2Note that at test time, our model requires only the video, with no need for additional text, ensuring utmost flexibility and applicability.", + "bbox": [ + 75, + 875, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_footnote", + "text": "also called \"unseen compositions\" in object-attribute learning [34, 37].", + "bbox": [ + 514, + 886, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "18494", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "HowTo100M [36] and Ego4D [17], which offer large-scale collections of videos paired with their corresponding narratives. These datasets have also facilitated tasks like step discovery [11], localization in procedural activities [35] and long egocentric videos [45]. The vision-language multimodal cycle consistency loss proposed in [14] helps discover long-term temporal dynamics in video. In line with these developments, we propose to leverage the text accompanying instructional videos as well as existing high-performing VLMs to provide supervisory signals that guide the training of our video OSC model and allow learning for the open world.", + "bbox": [ + 75, + 90, + 472, + 272 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Learning in an Open World The open world setting has received increasing attention, predominantly within the image domain for object recognition [4, 48], detection [10, 18, 25, 65] and object-attribute compositionality [29, 33, 37-39, 41, 43]. In the video domain, compositionality is advanced by the Something-Else dataset [34], where the training combinations of verbs and nouns do not overlap with the test set, sparking work on the dynamics of subject-object interactions [7, 34, 47]. More recent efforts leverage VLMs for zero-shot action recognition [7, 26, 57]. Concurrent work explores video object segmentation with state-changing objects [64] and recognition of novel object-state compositions for food chopped in different styles [47]. Despite these advances, temporal video OSC understanding in the open world remains unexplored. Our open-world formulation requires generalizing the temporal localization of fine-grained object states from known to novel objects.", + "bbox": [ + 75, + 275, + 472, + 532 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Approach", + "text_level": 1, + "bbox": [ + 76, + 542, + 187, + 559 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We present the VIDOSC framework for learning video OSCs, detailing the open-world formulation (Sec. 3.1), model design for object-agnostic state prediction (Sec. 3.2), and text-guided training scheme (Sec. 3.3).", + "bbox": [ + 75, + 568, + 468, + 628 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Video OSC in the Open World", + "text_level": 1, + "bbox": [ + 76, + 636, + 346, + 652 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We begin by formally defining an object state change (OSC) in videos as a visually detectable transformation, where an object experiences a change that is not easily reversible, in line with [17]. We characterize an OSC category as an object combined with a specific state transition, such as \"chicken + shredding\", and delineate an OSC process through three distinct states: initial (precondition state), transitioning, and end (postcondition state).4 It is essential to highlight that we take an object-centric perspective: the \"transitioning state\" accounts for instances where the video depicts an active action applied to the object, as well as scenarios where the object undergoes a passive transformation absent of human intervention (e.g., melting, drying).", + "bbox": [ + 75, + 659, + 468, + 857 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4Due to real-world data variation, some videos may lack one of the OSC states, and there may be multiple segments in a video corresponding to the same state. Our formulation accounts for all these scenarios.", + "bbox": [ + 75, + 862, + 468, + 898 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given a video in which an object may be changing state, the objective is to temporally localize each of the three OSC states. Consistent with prior work [50, 51], we formulate the task as a frame-wise classification problem. Formally, a video sequence is represented by a temporal sequence of $T$ feature vectors $\\mathbf{X} = \\{\\mathbf{x}_1,\\mathbf{x}_2,\\dots ,\\mathbf{x}_T\\}$ , where $T$ denotes the video duration. The goal is to predict the OSC state label for each timepoint, denoted by $\\mathbf{Y} = \\{\\mathbf{y}_1,\\mathbf{y}_2,\\dots ,\\mathbf{y}_T\\}$ , $\\mathbf{y}_t\\in \\{1,\\dots ,K + 1\\}$ , where $K$ is the total number of OSC states, and there is one additional category representing the background class not associated with any OSC state.", + "bbox": [ + 496, + 90, + 890, + 257 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Next, we propose an open-world problem formulation, capturing the intrinsic long-tail distribution observed in real-world scenarios. Consider $N$ state transitions, each paired with a set of associated objects, denoted by $\\mathbf{O}^n = \\{o_1^n,o_2^n,\\dots ,o_{m(n)}^n\\}$ , for $n = \\{1,2,\\dots ,N\\}$ , where $m(n)$ denotes the number of objects linked with the $n$ -th state transition. Within a specific state transition (like frying), certain objects in the set (such as chicken or onions) are frequently observed, while the combination of the same state transition with other objects (such as cauliflower) appear less often. Motivated by this inherent long-tail, we propose to split $\\mathbf{O}^n$ into two distinct subsets: $\\mathbf{O}_{\\mathrm{known}}^n$ covering the common combinations observed during training, and $\\mathbf{O}_{\\mathrm{novel}}^n$ comprising the infrequent combinations, which are unseen during training due to their rarity. During inference, the model is evaluated on the entire object set $\\mathbf{O}^n$ for a comprehensive reflection of the open-world setting.", + "bbox": [ + 496, + 257, + 892, + 513 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Object-Agnostic State Prediction", + "text_level": 1, + "bbox": [ + 500, + 521, + 790, + 537 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To address the open-world challenges and ensure robust generalization to novel objects, VIDOSC integrates three key techniques: (1) a shared state vocabulary that consolidates the state label space; (2) temporal modeling within the video OSC model design; and (3) object-centric features.", + "bbox": [ + 496, + 545, + 890, + 619 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Shared State Vocabulary The inherent link among different OSC categories is overlooked in prior work. Common practice involves developing separate models for each OSC category [2, 50] (e.g., one model exclusively for melting butter and another for melting chocolate), or using one single model that still treats every OSC as a distinct entity in the label space [51] (e.g., considering melted butter and melted chocolate as two separate end states). Such a formulation results in an extensive label set with $K = 3 \\times \\sum_{n=1}^{N} m(n)$ , where 3 denotes the number of OSC states (i.e., initial, transitioning and end) and $\\sum_{n=1}^{N} m(n)$ is the total number of OSC categories. This compartmentalized view can inadvertently hinder the model's generalization ability. Yet, on closer inspection, states across varied objects are intrinsically related. For instance, the \"melting\" principle remains consistent, even when applied to visually", + "bbox": [ + 496, + 623, + 892, + 867 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "5Not all training videos may feature an OSC due to data collection noise, yet all evaluation videos are manually verified to include one.", + "bbox": [ + 500, + 875, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "18495", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/cd72c8c8e56e856913a378b48dd2543d852b875733f4176b2040f195b13f267f.jpg", + "image_caption": [ + "Figure 2. Our proposed VIDOSC framework: (a) Mining for OSC examples (Sec. 3.3): We leverage ASR transcriptions paired with videos and the capabilities of LLM to automatically mine OSC examples. (b) Pseudo Label Generation (Sec. 3.3): We utilize textual state descriptions and a VLM for supervisory signals during training; (c) Model Training (Sec. 3.2): We develop a video model for object-agnostic state prediction. (d) Model Testing (Sec. 3.1): We propose an open-world formulation, evaluating on both known and novel OSCs. Notably, while we employ the text modality to guide model training, our model is purely video-based and requires no text input at the test phase, ensuring maximum flexibility and applicability. Ground truth for the test set is manually annotated." + ], + "image_footnote": [], + "bbox": [ + 96, + 88, + 872, + 400 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "distinct objects like butter and chocolate. This motivates us to group OSC labels that share the same state transition as one, and train a single model per state transition.6 By adopting object-agnostic OSC labels, we encourage the model to learn state representations shared by visually different objects, and thus facilitate the transfer from known to novel objects.", + "bbox": [ + 75, + 520, + 470, + 626 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Temporal Modeling Recognizing that state changes unfold over time, it is important to capture the temporal dynamics in videos. An object's state at any frame, be it initial, transitioning, or end, is often best understood in the context of preceding and succeeding frames. Contrary to prior works [2, 50, 51] that rely on isolated frameswise modeling without considering the temporal progression of video OSCs, we address this gap by proposing a temporally-aware model design. As illustrated in Fig. 2(c), we adopt an encoder-decoder architecture. For the encoding phase, input video features $\\mathbf{X} = \\{\\mathbf{x}_1,\\mathbf{x}_2,\\dots ,\\mathbf{x}_T\\}$ are first projected using an MLP $f_{\\mathrm{project}}$ and augmented with sinusoidal positional embeddings, $\\mathbf{Z}_{\\mathrm{pos}}$ . Subsequently, a transformer encoder [56] $f_{\\mathrm{transformer}}$ is adopted to capture the temporal dynamics among these features, yield", + "bbox": [ + 75, + 630, + 468, + 857 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "ing $\\mathbf{Z} = f_{\\mathrm{transformer}}(f_{\\mathrm{project}}(\\mathbf{X}) + \\mathbf{Z}_{\\mathrm{pos}})$ . For the decoding phase, a MLP decoder $g$ , maps these temporally-aware hidden representations to OSC state predictions: $\\tilde{\\mathbf{Y}} = g(\\mathbf{Z})$ . See Sec. 5 for architecture and training details. This design ensures that when predicting the state for a frame, the model has assimilated temporal context from the entire sequence. Essentially, our model exploits the fact that the dynamics of the state change has greater invariance to the object category than how the object looks, emphasizing temporal object transformations over objects' static appearances, and thereby enhancing generalization to novel OSCs.", + "bbox": [ + 504, + 520, + 890, + 686 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Object-Centric Features Finally, we discuss how to better represent \"object\" features in the problem. In many scenarios, due to camera placement and framing, the object going through a state transition might only occupy a small portion of the frame, surrounded by other visual elements such as background, people, or bystander objects. Recognizing this challenge, we introduce an enhancement to our model's input features $\\mathbf{X}$ to emphasize the object of interest. To be specific, we leverage an off-the-shelf detector [49] to identify the active object (i.e., the object being manipulated) region at each timepoint $t$ , yielding feature $\\mathbf{x}_t^{obj}$ that centers on the object (see bounding boxes in Fig. 2(c)). The input feature is then constructed as a concatenation of the original global feature and the localized object-centric feature,", + "bbox": [ + 500, + 688, + 892, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_footnote", + "text": "See Supp. for the multi-task model variant, where we develop one unified model for all state transitions.", + "bbox": [ + 76, + 875, + 468, + 898 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "18496", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "i.e., $\\mathbf{X} = \\{\\left[\\mathbf{x}_t,\\mathbf{x}_t^{obj}\\right]\\}_{t = 1}^T$ . By emphasizing the object in this manner, our model is better positioned to discern the intricate state changes and provide more informed predictions.", + "bbox": [ + 75, + 89, + 468, + 137 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Text and VLMs as Supervision", + "text_level": 1, + "bbox": [ + 76, + 145, + 349, + 162 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To scale up training and ensure broad generalization, we propose a novel training pipeline that leverages LLMs and VLMs for OSC mining and pseudo-labeling.", + "bbox": [ + 75, + 167, + 468, + 214 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Mining for OSC examples Utilizing a vast collection of \"how-to\" instructional videos as the training source, we develop an automated mining process to capture the rich, real-world variability of OSCs. The motivation is that instructional videos usually have accompanying Automatic Speech Recognition (ASR) transcriptions that offer valuable OSC cues. For example, a speaker mentioning, \"so just get your rotisserie chicken and shred it up\" suggests that the chicken may undergo a state transition of shredding in the video. Leveraging this fact, we employ LLAMA2 [54] to analyze ASR transcriptions for identifying candidate videos and their associated OSC categories. This text mining stage allows us to corral a long tail of OSCs, discovering likely state change terms—even if rare—from the free-form natural language narrations given by how-to instructors in the training videos. See Fig. 2 (a).", + "bbox": [ + 75, + 215, + 470, + 455 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Pseudo Label Generation Next, to negate the need of manually labeling large-scale training data, we propose a novel pseudo-labeling pipeline facilitated by VLMs. From the identified OSC category (e.g., shredding chicken), we form three textual state descriptions for its initial, transitioning, and end states (e.g., whole chicken, shredding chicken, and shredded chicken). We then adopt both the vision and language encoder from a well-trained VLM (we experiment with CLIP [44] and VideoClip [61]) to compute the cross-modal similarity between every frame in training video and the three state descriptions, producing a score matrix $\\mathbf{S} \\in \\mathbb{R}^{T \\times 3}$ . The pseudo label $\\hat{y}_t$ at timepoint $t$ is then assigned based on this score matrix:", + "bbox": [ + 75, + 460, + 470, + 656 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {y} _ {t} = \\left\\{ \\begin{array}{l l} \\text {B a c k g r o u n d} & \\text {i f} \\sum (\\mathbf {S} [ t,: ]) < \\tau \\\\ \\text {I n i t i a l} & \\text {e l i f} \\mathbf {S} [ t, 0 ] - \\mathbf {S} [ t, 1 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 0 ] - \\mathbf {S} [ t, 2 ] > \\delta \\\\ \\text {T r a n s i t i o n i n g} & \\text {e l i f} \\mathbf {S} [ t, 1 ] - \\mathbf {S} [ t, 0 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 1 ] - \\mathbf {S} [ t, 2 ] > \\delta \\\\ \\text {E n d} & \\text {e l i f} \\mathbf {S} [ t, 2 ] - \\mathbf {S} [ t, 0 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 2 ] - \\mathbf {S} [ t, 1 ] > \\delta \\\\ \\text {A m b i g u o u s} & \\text {o t h e r w i s e} \\end{array} \\right.\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 672, + 478, + 743 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\delta$ is the threshold that separates states and $\\tau$ is the threshold that differentiates between states and background. Essentially if the VLM scores some state more strongly than the other two—and the cumulative confidence score of all states is high—then it is adopted as the pseudo label. Otherwise it is omitted as ambiguous. See Fig. 2(b).", + "bbox": [ + 75, + 750, + 467, + 839 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To further refine these labels, we enforce a causal ordering constraint. Given the inherent progression of OSCs, the anticipated order is initial states followed by transitioning states, and finally, the end states. Any frame whose pseudo", + "bbox": [ + 75, + 839, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/e01633ea3975b12a759c00349c03523047c529023ee3c4bf9aacc2d2f5d4d340.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 509, + 95, + 883, + 198 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/4da85303989aab31667cb729883906822b1a233cff069012172f5a3b7eed6a67.jpg", + "image_caption": [ + "Figure 3. Ground truth annotation distribution across 20 state transitions (top) and 134 objects (bottom) in HowToChange (Evaluation). In line with our open-world formulation, annotations cover a diverse range of object-state transition combinations, categorized into known and novel OSCs." + ], + "image_footnote": [], + "bbox": [ + 509, + 215, + 880, + 321 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "label does not respect this natural progression is re-assigned to the ambiguous category. Our training employs a cross-entropy loss between pseudo label $\\hat{y}_t$ and the corresponding model prediction $\\tilde{y}_t$ , with ambiguous frames excluded to maintain clarity and distinction among the state labels. See Section 4.2 in Supp. for detailed pseudo label analysis.", + "bbox": [ + 498, + 416, + 890, + 507 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. The HowToChange Dataset", + "text_level": 1, + "bbox": [ + 500, + 523, + 756, + 540 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Existing OSC datasets fall short in capturing the open-world's diversity and long-tail distribution of OSCs. To address this gap, we introduce HowToChange. It encompasses varied state transitions coupled with a diverse range of objects, providing an authentic reflection of their real-world frequency—from the commonplace to the rare.", + "bbox": [ + 496, + 550, + 890, + 640 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Data Collection The HowTo100M collection [36] contains a wealth of instructional videos that often feature OSCs and is particularly suitable for this task. We specifically focus on the HowTo100M Food & Entertaining category because (1) it constitutes a third of the entire HowTo100M videos, (2) cooking tasks offer a wealth of objects, tools, and state changes, providing an excellent test bed for open-world OSC, and (3) in cooking activities a single state transition can often be associated with a varied range of objects, opening the door to learning compositionality. (Note, we also experiment with non-cooking domains below.) We process a total of 498,475 videos and 11,390,287 ASR transcriptions with LLAMA2. From the responses, we identify the most frequently seen state transitions and objects associated with them to establish an OSC vocabulary, resulting in 134 objects, 20 state transitions, and 409 unique OSCs. The number of objects associated with each state transition $(m(n))$", + "bbox": [ + 496, + 643, + 892, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "18497", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/e1882e341191d5592c5849e00edc0d8ed6d967dd54696108d8d3182670d9d8b0.jpg", + "table_caption": [], + "table_footnote": [ + "Table 1. Comparison with existing video datasets focusing on object states. 'Obj' and 'ST' represent objects and state transitions, respectively. 'ObjPer' denotes the average number of objects associated with each state transition; higher values indicate more need to generalization across objects. We present the first open-world benchmark for temporal video OSC, with an order of magnitude increase in OSC vocabulary and annotation volume." + ], + "table_body": "
Datasets# Obj# ST# OSCObjPer# VideosGT Label?
Alayrac et al. [2]5671.2630✓
Task-Fluent [31]2514322.3809✓
ChangeIt (Training) [50]4227441.634,428✗
ChangeIt (Evaluation) [50]4227441.6667✓
HowToChange (Training)1222031815.936,075✗
HowToChange (Evaluation)1342040920.55,424✓
", + "bbox": [ + 78, + 88, + 470, + 204 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "spans from 6 for “zesting” to 55 for “chopping”. The state transitions applied to each object vary from 1 to 15, with onions being the most versatile. In total, we identify 36,075 videos for the training set of HowToChange, with an average duration of 41.2 seconds.", + "bbox": [ + 75, + 321, + 468, + 398 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Data Splits In line with our open-world formulation, we divide the 409 identified OSCs into two disjoint subsets based on their frequency of occurrence. Within each state transition, we categorize the top $75\\%$ frequent objects as known and the bottom $25\\%$ as novel. This yields a total of 318 known OSCs that are seen during training and testing, spanning 20 state transitions associated with 122 objects, and 91 novel OSCs that are only seen during testing, encompassing the same transitions across 58 objects.", + "bbox": [ + 75, + 401, + 468, + 537 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Ground Truth Label Collection (Evaluation Set) To facilitate thorough evaluation, we obtain manual annotations for a subset of 5,424 videos from the collected dataset. The annotation workflow is as follows: each annotator is presented with a video segment along with an OSC category that was previously identified by LLAMA2. The annotator has the option to reject the video segment if it does not contain the specified OSC. Otherwise, they label the time ranges corresponding to the initial, transitioning, and end states of the OSC. Adhering to our object-centric emphasis, annotators are instructed to label based on the visual changes of the object, rather than human-centric actions, and exclude time ranges where the object of interest is not visible, ensuring clean and focused temporal labels. Fig. 3 provides the distribution of annotated videos. On average, we collect 271 annotations per state transition, with a video duration of 41.5 seconds, and $12.9\\%$ of videos belong to the novel category. The entire annotation process required around 1,507 hours by 30 professional annotators.", + "bbox": [ + 75, + 540, + 468, + 828 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Dataset Comparison Table 1 compares HowToChange with existing video datasets on temporal OSC understand-", + "bbox": [ + 76, + 830, + 468, + 862 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "ing. HowToChange offers an unprecedented scale—with 9.3x more OSC categories and 8.1x more annotated video instances compared to the previous largest collection [50]. Furthermore, notably, in prior datasets, each state transition is typically coupled with 1 or 2 objects, preventing subsequent models from generalizing to new objects, as we will see in results. In contrast, HowToChange pioneers the open-world formulation, presenting a much broader range of objects associated with each state transition—from 6 to 55 objects per state transition, and averaging 20. This facilitates the development of models with generalized OSC understanding. Please see Supp. for full data collection and annotation details.", + "bbox": [ + 500, + 90, + 890, + 287 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 301, + 632, + 319 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Datasets In addition to our new HowToChange dataset, we also evaluate on ChangeIt [50] due to its expansive data scale (34K videos spanning many activities) and high relevance to our task. Beyond the conventional split of ChangeIt, we propose a new split tailored to our open-world formulation. Specifically, from the 44 available OSC categories in ChangeIt, we concentrate on the 25 categories where each state transition is paired with more than one object. With those, we form the \"ChangeIt (open-world)\" subset that comprises 8 state transitions and 25 objects. Within each state transition, objects are randomly divided into known and novel categories, yielding 13 known OSC categories for training and 12 novel OSC categories exclusively reserved for evaluation. A detailed breakdown of this split can be found in Supp. To sum up, our evaluation encompasses: ChangeIt; ChangeIt (open-world); and How-ToChange, offering a comprehensive setup in both closed-world and open-world scenarios.", + "bbox": [ + 496, + 329, + 890, + 601 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation For ChangeIt and ChangeIt (open-world), we adhere to the original dataset's evaluation protocol [50], reporting action and state precision@1 as the evaluation metrics. For our dataset, besides precision@1, which evaluates a single frame for each state within a video, we advocate for the use of F1 score and precision over all frames to ensure a more holistic evaluation.", + "bbox": [ + 496, + 604, + 890, + 709 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines We compare our approach with four baselines across two categories: (a) self-supervised approaches on identifying object states enforced by the causal ordering constraint: LookForTheChange [50] trains a dedicated model for each OSC category, while MultiTaskChange [51] evolves this into a multi-task approach8, catering to several OSCs concurrently; (b) zero-shot VLMs: image-based CLIP [44], video-based VideoCLIP [61] and InternVideo [59]. All baselines in (a) use the same training data as our model, whereas the zero-shot models (b) are directly", + "bbox": [ + 496, + 713, + 890, + 864 + ], + "page_idx": 5 + }, + { + "type": "page_footnote", + "text": "Our training is purely guided by a VLM and requires no ground truth labels. The annotations are reserved exclusively for evaluation.", + "bbox": [ + 76, + 875, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_footnote", + "text": "To ensure a thorough evaluation, we train both single-task and multitask variants of our approach. See Supp. for a detailed discussion.", + "bbox": [ + 500, + 875, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "18498", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/b0dfeba61b83d83f2d110f421e9d96d3eebe3c208056ca3a60e2807d1b1fbefb.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodChangeItChangeIt (open-world)HowToChange
State Prec.@1Action Prec.@1State Prec.@1 known@1 novelAction Prec.@1 known@1 novelF1 (%)Prec (%)Prec.@1 (%)
knownnovelknownnovelknownnovel
CLIP [44]0.300.630.290.290.710.7026.925.427.326.647.547.5
VideoCLIP [61]0.330.590.250.240.620.5536.634.339.738.548.344.8
InternVideo [59]0.270.570.290.250.600.6129.929.531.430.846.946.3
LookForTheChange [50]0.350.680.360.250.770.6830.328.732.530.037.236.1
MultiTaskChange [51]0.490.800.410.220.720.6233.929.938.534.143.138.8
VIDOSC (ours)0.570.840.560.480.890.8246.443.146.643.760.758.2
", + "bbox": [ + 124, + 88, + 846, + 212 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Results on ChangeIt, ChangeIt (open-world), and HowToChange. VIDOSC outperforms all approaches in both closed-world and open-world scenarios, across known and novel OSCs.", + "bbox": [ + 75, + 222, + 893, + 251 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a4de4c0b17e3f8aa325e58f3a72965853b684d32c79cfd0dcd3eebf335dfd28e.jpg", + "image_caption": [ + "Figure 4. Top-1 frame predictions given by VIDOSC for the initial, transitioning, and end states, on ChangeIt (open-world) (first 2 rows) and HowToChange (last 2 rows). VIDOSC not only accurately localizes the three fine-grained states for known OSCs, but also generalizes this understanding to novel objects, such as cauliflower and capsicum, which are not observed during training." + ], + "image_footnote": [], + "bbox": [ + 99, + 263, + 867, + 518 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "evaluated on the test set with no training.", + "bbox": [ + 75, + 607, + 349, + 622 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Implementation Videos are sampled at one frame per second. Each one-second video segment gets assigned to an OSC state label, and is encoded by InternVideo [59], a general video foundation model (which is kept frozen for training efficiency). Our video model consists of a 3-layer transformer with a hidden dimension of 512 and 4 attention heads as the encoder and a 1-layer MLP as the decoder. Consistent with prior work [50, 51], our model predicts the OSC state label (i.e., initial, transitioning, end state, or background) for a video, assuming the video OSC category is known (say from a recognition model's output or a user's specific query). While the standard output does not include the state transition name, our multi-task version detailed in Supp. is capable of this.", + "bbox": [ + 75, + 625, + 470, + 835 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Main Results Table 2 presents results on all three datasets. VIDOSC outperforms all approaches in both traditional closed-world and our newly introduced open-world settings. The large performance gains—as much as $9.6\\%$", + "bbox": [ + 75, + 839, + 468, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "jumps in precision vs. the next best method—underscore the effectiveness of two pivotal components in VIDOSC. First, its use of text and VLMs for supervisory signals during training: particularly on novel OSCs, VIDOSC extracts meaningful cues from the video modality to refine pseudo labels from VLMs, and ultimately surpasses the VLM baselines. Second, our model for object-agnostic state prediction, designed for the open-world context, effectively narrows the gap between known and novel OSCs. For instance, on ChangeIt (open-world), MultiTaskChange [51] experiences a $19\\%$ decline in state precision@1 while VIDOSC has only a $8\\%$ drop. Note that we observe a more pronounced performance drop of all approaches on ChangeIt (open-world) than on HowToChange due to its limited number of objects available per state transition. These results also point to the potential for future development in bridging the known and novel OSC performance gap.", + "bbox": [ + 496, + 607, + 890, + 864 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Qualitative Results Fig. 4 presents VIDOSC's top-1 frame predictions on ChangeIt (open-world) and HowToChange,", + "bbox": [ + 496, + 869, + 890, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "18499", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/052c79eb56d0e2490c4c61368a040adef20b2425421b7bb9ad80c0a81cf123c1.jpg", + "image_caption": [ + "Figure 5. Comparison of model predictions across a test video depicting the OSC of \"slicing shallot\" on HowToChange. The x-axis represents temporal progression through the video. VIDOSC gives temporally smooth and coherent predictions that best align with the ground truth, significantly outperforming baselines in capturing the video's global temporal context." + ], + "image_footnote": [], + "bbox": [ + 80, + 88, + 468, + 229 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/4ad900709227f4128abf657df0aa04b0eca6a8256818d8f6b3f57481b97d342a.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Shared StateTemporal ModelingObject CentricPrec.@1 (%)
knownnovelΔ
X✓✓58.553.35.2
✓X✓52.948.24.7
✓✓X59.856.73.1
✓✓✓60.758.22.5
", + "bbox": [ + 109, + 330, + 437, + 428 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. Ablation Study. $\\Delta$ denotes the performance gap between known OSCs and novel OSCs.", + "bbox": [ + 75, + 438, + 468, + 465 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "across both known and novel OSCs. Notably, despite never seeing objects such as cauliflower and capsicum during training, VIDOSC effectively leverages visual state change cues and correctly localizes the three states of these objects going through OSCs, demonstrating its strong generalization capability. For a more holistic view, Fig. 5 compares VIDOSC's frame-by-frame predictions with all baselines for a given test video. VIDOSC provides temporally coherent predictions, smoothly progressing through the OSC states in the natural order (i.e., from initial to transitioning then end). In contrast, baseline approaches often yield fragmented and inconsistent predictions, indicating a lack of understanding of the video's global temporal context, primarily due to their reliance on frame-wise modeling. See Supp. and Supp. video for more qualitative examples and VIDOSC's interpretability on object relations.", + "bbox": [ + 75, + 474, + 470, + 717 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Ablation To further dissect the performance gains brought by our three model design techniques (i.e., shared state vocabulary, temporal modeling, and object-centric features), we conduct an ablation study, removing one component at a time. Table 3 confirms the essential role of each element. A shared state vocabulary is particularly crucial in the open-world context, as its absence increases the gap between known and novel OSCs from $2.5\\%$ to $5.2\\%$ . Furthermore, temporal modeling provides a substantial performance boost, and object-centric features offer further gains. See Supp. for an additional analysis of VIDOSC's performance with different pseudo labels.", + "bbox": [ + 75, + 719, + 468, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9d1f32e0778c6df3c3e7faeacd7aacc43fb180db810cdae57d06f58d29ee3056.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 504, + 89, + 630, + 165 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d89bd13c9576ccd67aa20a3fa41ada55cb08132f5feb3318e28edb545b528211.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 633, + 90, + 756, + 165 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a3095c4a99ce8a77e781dfab0a0c1613c254747cddaa7fb10ab02a0e869a0f60.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 761, + 90, + 883, + 165 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5e899bce65443ad6d413bb490e5e7e1e760d018cb93e860bd9525f99ce79f28b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 506, + 166, + 630, + 229 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f49e65cdda0833b854e58f203dced4b1d98da138bcfc32f653ee03b85079de69.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 633, + 167, + 756, + 229 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/b724d6f0c51be04b39124d41241ba2036473264517014d40a6f5b6708e8c0441.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 761, + 167, + 883, + 229 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/013cfe0bda99f477cca63a310e917ddb576e9060509a0ff8aa44711c37e7e5a0.jpg", + "image_caption": [ + "Figure 6. Frame retrieval on the HowToChange test set. Given a query frame showcasing a novel OSC at its initial state, VIDOSC retrieves the nearest and furthest frame among all known OSCs at their end states. The closest post-OSC frame follows the transition trajectory of the query while the furthest post-OSC frame depicts a substantially different object, demonstrating VIDOSC's capability to generalize the OSC progression for novel objects." + ], + "image_footnote": [], + "bbox": [ + 506, + 229, + 630, + 296 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/adafb4bc491b3895ee43dbc17069ef2a26cfe7e46c75842abd0cb14dffbc32c4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 633, + 229, + 756, + 296 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/eb50f5874b135d3d270464d6d3aa53859288f43ba6f45000c48bb6c349d473e0.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 759, + 229, + 883, + 296 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Frame Retrieval VIDOSC learns features that accurately characterize the evolution of an OSC process. To illustrate, we consider a novel frame retrieval setting. Within the HowToChange test set, when presented with a query video featuring a novel OSC at its initial state, VIDOSC seeks the most similar and most contrasting video from a pool of candidates at their end states. The frame triplets with the smallest and largest feature distance are shown in Fig. 6. Remarkably, the retrieved nearest post-OSC frames correspond to the query's anticipated state transition trajectory, despite the object and state gap. Conversely, the furthest frames exhibit end states of markedly different objects. These results further lend support to VIDOSC's capability to understand the evolution of an OSC process, even for novel objects it has never encountered during training.", + "bbox": [ + 496, + 412, + 892, + 638 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 651, + 617, + 666 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work aims at a comprehensive exploration of video OSCs, with a novel open-world formulation. To address the challenges, we leverage text and VLMs to assist the training of a video OSC model at scale and design three modeling techniques to achieve object-agnostic state prediction for better generalization to novel OSCs. Furthermore, we present the most expansive video OSC dataset collection HowToChange, which echoes the natural long-tail of state transitions coupled with varied objects, fostering a realistic representation of real-world scenarios. As for future work, we will consider extending VIDOSC to video sequences featuring concurrent OSC processes, and integrating spatial understanding of OSC within our open-world framework.", + "bbox": [ + 496, + 676, + 890, + 872 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements: UT Austin is supported in part by the IFML NSF AI Institute. KG is paid as a research scientist by Meta.", + "bbox": [ + 500, + 873, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "18500", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Nachwa Aboubakr, James L Crowley, and Rémi Ronfard. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 6586-6597, 2023. 2" + ], + "bbox": [ + 501, + 92, + 890, + 315 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "18503", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_model.json b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_model.json new file mode 100644 index 0000000000000000000000000000000000000000..599af094bf545b2cfd9e0c039a020b2d327aba8c --- /dev/null +++ b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_model.json @@ -0,0 +1,2169 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.128, + 0.131, + 0.843, + 0.154 + ], + "angle": 0, + "content": "Learning Object State Changes in Videos: An Open-World Perspective" + }, + { + "type": "text", + "bbox": [ + 0.24, + 0.18, + 0.344, + 0.198 + ], + "angle": 0, + "content": "Zihui Xue1,2" + }, + { + "type": "text", + "bbox": [ + 0.379, + 0.181, + 0.532, + 0.198 + ], + "angle": 0, + "content": "Kumar Ashutosh1,2" + }, + { + "type": "text", + "bbox": [ + 0.572, + 0.18, + 0.728, + 0.198 + ], + "angle": 0, + "content": "Kristen Grauman\\(^{1,2}\\)" + }, + { + "type": "text", + "bbox": [ + 0.277, + 0.199, + 0.551, + 0.217 + ], + "angle": 0, + "content": "1The University of Texas at Austin" + }, + { + "type": "text", + "bbox": [ + 0.59, + 0.199, + 0.696, + 0.216 + ], + "angle": 0, + "content": "\\(^{2}\\)FAIR, Meta" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.252, + 0.314, + 0.267 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.283, + 0.474, + 0.587 + ], + "angle": 0, + "content": "Object State Changes (OSCs) are pivotal for video understanding. While humans can effortlessly generalize OSC understanding from familiar to unknown objects, current approaches are confined to a closed vocabulary. Addressing this gap, we introduce a novel open-world formulation for the video OSC problem. The goal is to temporally localize the three stages of an OSC—the object's initial state, its transitioning state, and its end state—whether or not the object has been observed during training. Towards this end, we develop VIDOSC, a holistic learning approach that: (1) leverages text and vision-language models for supervisory signals to obviate manually labeling OSC training data, and (2) abstracts fine-grained shared state representations from objects to enhance generalization. Furthermore, we present HowToChange, the first open-world benchmark for video OSC localization, which offers an order of magnitude increase in the label space and annotation volume compared to the best existing benchmark. Experimental results demonstrate the efficacy of our approach, in both traditional closed-world and open-world scenarios.\\(^{1}\\)" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.614, + 0.21, + 0.63 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.639, + 0.47, + 0.76 + ], + "angle": 0, + "content": "In video understanding, the study of objects primarily revolves around tasks like recognition [16], detection [24], and tracking [8, 62], with the assumption that objects maintain a consistent visual appearance throughout the video. Yet, objects in video are often dynamic. They can undergo transformations that change their appearance, shape, and even topology. For example, a pineapple goes from whole to peeled to sliced, or wood is carved into a new shape." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.761, + 0.471, + 0.866 + ], + "angle": 0, + "content": "Object State Changes (OSCs) [2, 15, 17, 22, 47, 50-52, 60, 64] add a critical dimension to video understanding. On the one hand, they provide insights into human actions—observing a piece of metal being shaped into a hook, for instance, implies the action of bending; observing an egg shell go from whole to broken implies the action of cracking. On the other hand, OSCs are essential" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.253, + 0.887, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.337, + 0.887, + 0.462 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.473, + 0.893, + 0.572 + ], + "angle": 0, + "content": "Figure 1. Top: The video OSC objective is to temporally localize an object's three states (i.e., initial, transitioning, end). Bottom: OSCs naturally exhibit a long tail. Certain OSCs, such as melting butter or marshmallow, are frequently showcased in instructional videos while others like melting jaggery might be rarely seen. We introduce an innovative open-world formulation that requires extrapolating to novel objects never encountered during training." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.582, + 0.893, + 0.734 + ], + "angle": 0, + "content": "for assessing goal completion, in a way that is invariant to the specific procedure used. For instance, the readiness of cake batter signifies the completion of a mixing task, regardless of whether it was stirred by hand or a mechanical mixer. These core functionalities are instrumental for various real-world applications [5, 6, 12, 13, 20, 21, 66], ranging from AR/VR assistants [42] that guide users through complex tasks by monitoring object states, to robotic manipulation [9, 55] where understanding the state of objects is critical for task planning and failure recovery." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.901 + ], + "angle": 0, + "content": "However, the development of video OSC is still at a primitive stage. Existing approaches [1, 2, 15, 46, 50, 51, 58] assume a closed vocabulary, where each state transformation is associated with a limited set of objects—often just 1 or 2. For example, the concept of “melting” might be limited to familiar items like butter and marshmallow. Consequently, the learned models are only capable of identifying state changes for objects observed during training and stumble when presented with novel objects. In contrast, in real-world situations a single state transition like “melting” can be linked with a plethora of objects—some ubiquitous and" + }, + { + "type": "page_footnote", + "bbox": [ + 0.077, + 0.875, + 0.468, + 0.901 + ], + "angle": 0, + "content": "1Project webpage: https://vision.cs.utexas.edu/projects/VidOSC/." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18493" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.182 + ], + "angle": 0, + "content": "others rare. Importantly, there is an intrinsic connection that threads these OSC processes together. As humans, even if we have never encountered an unusual substance (e.g., jaggery) before, we can still understand that it is experiencing a \"melting\" process based on its visual transformation cues (see Fig. 1, bottom)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.183, + 0.471, + 0.501 + ], + "angle": 0, + "content": "In light of these limitations, we propose a novel open-world formulation of the video OSC problem. We formally characterize OSCs in videos in terms of three states that must be temporally localized: initial, transitioning, and end (see Fig. 1, top). In our open-world setting, there are known objects and novel objects. The model is only presented with known objects during training (e.g., frying chicken, frying onions). Then, it is evaluated on both known and novel objects (e.g., frying cauliflower). In addition to this fundamental open-world generalization, we also tackle a more comprehensive notion of the transitioning state. Specifically, our transitioning states encapsulate not only action-induced modifications to the object (e.g., peeling), but also passive transformations the object undergoes without human interference (e.g., melting) and edited-out transformations (e.g., the cake goes from raw to baked even if baked off camera). Though largely overlooked in existing approaches [1, 15, 46, 58], these cases are both common and technically interesting, since they force a model to reason about the effects of the core state change rather than search for evidence of a human actor carrying out the action." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.501, + 0.47, + 0.802 + ], + "angle": 0, + "content": "Armed with this new problem formulation, we propose a holistic video OSC learning approach, anchored by two innovative ideas. First, we explore text and vision-language models (VLMs) for supervisory signals during training. We pioneer the use of textual state descriptions to generate a long tail of object state pseudo-labels, by leveraging the remarkable capabilities of VLMs [23, 44, 63] and large language models (LLMs) [40, 53, 54]. This strategy eliminates the need for exhaustive label collection for training data, facilitating large-scale model training. Second, to confront the open-world challenge, we propose object-agnostic state prediction, consisting of three key techniques: a shared state vocabulary to unify the label space across objects sharing the same state transition (e.g., melting butter and melting marshmallow), temporal modeling to grasp the progression of state changes over time, and object-centric features that better represent the objects during an OSC. These designs equip our model with the ability to generalize state understanding from known objects to novel ones. We term our approach VIDOSC." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.803, + 0.47, + 0.866 + ], + "angle": 0, + "content": "Complementing this, we present a large-scale real-world dataset HowToChange. Sourced from the HowTo100M collection [36], it sets a new benchmark in the field of unprecedented scale and an authentic long-tail distribution, setting" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.168 + ], + "angle": 0, + "content": "it apart from the constrained scope and closed-world setting of earlier benchmarks (see Table 1). Finally, experimental results demonstrate the efficacy of VIDOsc, surpassing the state-of-the-art in both traditional closed-world and novel open-world scenarios by a great margin." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.181, + 0.642, + 0.198 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.209, + 0.892, + 0.497 + ], + "angle": 0, + "content": "Object State Changes Image-based methods explore the compositional nature of objects and their attributes, including zero-shot recognition of unseen combinations [22, 29, 33, 37-39, 41, 43], but do not consider the temporal progression of OSCs in video, which brings new challenges. Video-based methods develop human-centric models that leverage state change cues to facilitate action recognition [1, 15, 46, 58], or explore joint discovery of object states and actions [2, 50, 51]. Notably, all the existing methods assume a closed world, recognizing only the OSC categories (\"known\" objects) seen during training. Our approach distinguishes itself in three crucial ways: (1) we introduce a novel open-world3 formulation, where the objects encountered during evaluation can be entirely unseen during training; (2) we adopt an object-centric perspective, allowing for scenarios where OSCs occur with no observable human actions in the video; and (3) we propose to utilize the text modality and VLMs as supervisory signals, greatly scaling up model training and boosting performance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.497, + 0.893, + 0.724 + ], + "angle": 0, + "content": "Early datasets for video OSC capture a limited array of OSCs in fewer than 1,000 videos [2, 31]. The more recent ChangeIt dataset [50] marks an advance in dataset scale (34K videos), yet is still restricted to a small OSC vocabulary of 44 total object-state transitions. It lacks the scope to adequately test unseen objects, since most state changes coincide with only 1 or 2 objects across all the videos (see Table 1). Other datasets explore different aspects of video OSCs, including object state recognition [47], point-of-noreturn (PNR) frame localization [17], and object segmentation [52, 64], but they lack any temporal annotations of fine-grained OSC states needed for our task's evaluation. Our HowToChange dataset increases the OSC vocabulary space by an order of magnitude and allows for the first time rigorous study of the open-world temporal OSC challenge." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.726, + 0.892, + 0.877 + ], + "angle": 0, + "content": "Vision and Language LLMs [40, 53, 54] have revolutionized various research fields with their exceptional performance across diverse applications. Building on this momentum, the use of web-scale image-text data has emerged as a powerful paradigm in computer vision, with powerful VLMs now advancing an array of image tasks, including zero-shot classification [44], detection [18], segmentation [32] and visual question answering [27, 28]. Similarly, joint video-text representation learning [3, 30, 36, 67] has been advanced by multimodal datasets like" + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.875, + 0.47, + 0.901 + ], + "angle": 0, + "content": "2Note that at test time, our model requires only the video, with no need for additional text, ensuring utmost flexibility and applicability." + }, + { + "type": "page_footnote", + "bbox": [ + 0.516, + 0.887, + 0.891, + 0.901 + ], + "angle": 0, + "content": "also called \"unseen compositions\" in object-attribute learning [34, 37]." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18494" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.091, + 0.473, + 0.273 + ], + "angle": 0, + "content": "HowTo100M [36] and Ego4D [17], which offer large-scale collections of videos paired with their corresponding narratives. These datasets have also facilitated tasks like step discovery [11], localization in procedural activities [35] and long egocentric videos [45]. The vision-language multimodal cycle consistency loss proposed in [14] helps discover long-term temporal dynamics in video. In line with these developments, we propose to leverage the text accompanying instructional videos as well as existing high-performing VLMs to provide supervisory signals that guide the training of our video OSC model and allow learning for the open world." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.276, + 0.473, + 0.534 + ], + "angle": 0, + "content": "Learning in an Open World The open world setting has received increasing attention, predominantly within the image domain for object recognition [4, 48], detection [10, 18, 25, 65] and object-attribute compositionality [29, 33, 37-39, 41, 43]. In the video domain, compositionality is advanced by the Something-Else dataset [34], where the training combinations of verbs and nouns do not overlap with the test set, sparking work on the dynamics of subject-object interactions [7, 34, 47]. More recent efforts leverage VLMs for zero-shot action recognition [7, 26, 57]. Concurrent work explores video object segmentation with state-changing objects [64] and recognition of novel object-state compositions for food chopped in different styles [47]. Despite these advances, temporal video OSC understanding in the open world remains unexplored. Our open-world formulation requires generalizing the temporal localization of fine-grained object states from known to novel objects." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.544, + 0.188, + 0.56 + ], + "angle": 0, + "content": "3. Approach" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.569, + 0.47, + 0.63 + ], + "angle": 0, + "content": "We present the VIDOSC framework for learning video OSCs, detailing the open-world formulation (Sec. 3.1), model design for object-agnostic state prediction (Sec. 3.2), and text-guided training scheme (Sec. 3.3)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.637, + 0.348, + 0.653 + ], + "angle": 0, + "content": "3.1. Video OSC in the Open World" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.66, + 0.47, + 0.858 + ], + "angle": 0, + "content": "We begin by formally defining an object state change (OSC) in videos as a visually detectable transformation, where an object experiences a change that is not easily reversible, in line with [17]. We characterize an OSC category as an object combined with a specific state transition, such as \"chicken + shredding\", and delineate an OSC process through three distinct states: initial (precondition state), transitioning, and end (postcondition state).4 It is essential to highlight that we take an object-centric perspective: the \"transitioning state\" accounts for instances where the video depicts an active action applied to the object, as well as scenarios where the object undergoes a passive transformation absent of human intervention (e.g., melting, drying)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.863, + 0.47, + 0.9 + ], + "angle": 0, + "content": "4Due to real-world data variation, some videos may lack one of the OSC states, and there may be multiple segments in a video corresponding to the same state. Our formulation accounts for all these scenarios." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.258 + ], + "angle": 0, + "content": "Given a video in which an object may be changing state, the objective is to temporally localize each of the three OSC states. Consistent with prior work [50, 51], we formulate the task as a frame-wise classification problem. Formally, a video sequence is represented by a temporal sequence of \\( T \\) feature vectors \\( \\mathbf{X} = \\{\\mathbf{x}_1,\\mathbf{x}_2,\\dots ,\\mathbf{x}_T\\} \\), where \\( T \\) denotes the video duration. The goal is to predict the OSC state label for each timepoint, denoted by \\( \\mathbf{Y} = \\{\\mathbf{y}_1,\\mathbf{y}_2,\\dots ,\\mathbf{y}_T\\} \\), \\( \\mathbf{y}_t\\in \\{1,\\dots ,K + 1\\} \\), where \\( K \\) is the total number of OSC states, and there is one additional category representing the background class not associated with any OSC state." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.258, + 0.893, + 0.515 + ], + "angle": 0, + "content": "Next, we propose an open-world problem formulation, capturing the intrinsic long-tail distribution observed in real-world scenarios. Consider \\(N\\) state transitions, each paired with a set of associated objects, denoted by \\(\\mathbf{O}^n = \\{o_1^n,o_2^n,\\dots ,o_{m(n)}^n\\}\\), for \\(n = \\{1,2,\\dots ,N\\}\\), where \\(m(n)\\) denotes the number of objects linked with the \\(n\\)-th state transition. Within a specific state transition (like frying), certain objects in the set (such as chicken or onions) are frequently observed, while the combination of the same state transition with other objects (such as cauliflower) appear less often. Motivated by this inherent long-tail, we propose to split \\(\\mathbf{O}^n\\) into two distinct subsets: \\(\\mathbf{O}_{\\mathrm{known}}^n\\) covering the common combinations observed during training, and \\(\\mathbf{O}_{\\mathrm{novel}}^n\\) comprising the infrequent combinations, which are unseen during training due to their rarity. During inference, the model is evaluated on the entire object set \\(\\mathbf{O}^n\\) for a comprehensive reflection of the open-world setting." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.522, + 0.792, + 0.538 + ], + "angle": 0, + "content": "3.2. Object-Agnostic State Prediction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.546, + 0.892, + 0.621 + ], + "angle": 0, + "content": "To address the open-world challenges and ensure robust generalization to novel objects, VIDOSC integrates three key techniques: (1) a shared state vocabulary that consolidates the state label space; (2) temporal modeling within the video OSC model design; and (3) object-centric features." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.624, + 0.893, + 0.868 + ], + "angle": 0, + "content": "Shared State Vocabulary The inherent link among different OSC categories is overlooked in prior work. Common practice involves developing separate models for each OSC category [2, 50] (e.g., one model exclusively for melting butter and another for melting chocolate), or using one single model that still treats every OSC as a distinct entity in the label space [51] (e.g., considering melted butter and melted chocolate as two separate end states). Such a formulation results in an extensive label set with \\( K = 3 \\times \\sum_{n=1}^{N} m(n) \\), where 3 denotes the number of OSC states (i.e., initial, transitioning and end) and \\( \\sum_{n=1}^{N} m(n) \\) is the total number of OSC categories. This compartmentalized view can inadvertently hinder the model's generalization ability. Yet, on closer inspection, states across varied objects are intrinsically related. For instance, the \"melting\" principle remains consistent, even when applied to visually" + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.875, + 0.892, + 0.901 + ], + "angle": 0, + "content": "5Not all training videos may feature an OSC due to data collection noise, yet all evaluation videos are manually verified to include one." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18495" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.098, + 0.089, + 0.873, + 0.401 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.41, + 0.896, + 0.496 + ], + "angle": 0, + "content": "Figure 2. Our proposed VIDOSC framework: (a) Mining for OSC examples (Sec. 3.3): We leverage ASR transcriptions paired with videos and the capabilities of LLM to automatically mine OSC examples. (b) Pseudo Label Generation (Sec. 3.3): We utilize textual state descriptions and a VLM for supervisory signals during training; (c) Model Training (Sec. 3.2): We develop a video model for object-agnostic state prediction. (d) Model Testing (Sec. 3.1): We propose an open-world formulation, evaluating on both known and novel OSCs. Notably, while we employ the text modality to guide model training, our model is purely video-based and requires no text input at the test phase, ensuring maximum flexibility and applicability. Ground truth for the test set is manually annotated." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.521, + 0.471, + 0.627 + ], + "angle": 0, + "content": "distinct objects like butter and chocolate. This motivates us to group OSC labels that share the same state transition as one, and train a single model per state transition.6 By adopting object-agnostic OSC labels, we encourage the model to learn state representations shared by visually different objects, and thus facilitate the transfer from known to novel objects." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.631, + 0.47, + 0.858 + ], + "angle": 0, + "content": "Temporal Modeling Recognizing that state changes unfold over time, it is important to capture the temporal dynamics in videos. An object's state at any frame, be it initial, transitioning, or end, is often best understood in the context of preceding and succeeding frames. Contrary to prior works [2, 50, 51] that rely on isolated frameswise modeling without considering the temporal progression of video OSCs, we address this gap by proposing a temporally-aware model design. As illustrated in Fig. 2(c), we adopt an encoder-decoder architecture. For the encoding phase, input video features \\(\\mathbf{X} = \\{\\mathbf{x}_1,\\mathbf{x}_2,\\dots ,\\mathbf{x}_T\\}\\) are first projected using an MLP \\(f_{\\mathrm{project}}\\) and augmented with sinusoidal positional embeddings, \\(\\mathbf{Z}_{\\mathrm{pos}}\\). Subsequently, a transformer encoder [56] \\(f_{\\mathrm{transformer}}\\) is adopted to capture the temporal dynamics among these features, yield" + }, + { + "type": "text", + "bbox": [ + 0.506, + 0.521, + 0.892, + 0.687 + ], + "angle": 0, + "content": "ing \\(\\mathbf{Z} = f_{\\mathrm{transformer}}(f_{\\mathrm{project}}(\\mathbf{X}) + \\mathbf{Z}_{\\mathrm{pos}})\\). For the decoding phase, a MLP decoder \\(g\\), maps these temporally-aware hidden representations to OSC state predictions: \\(\\tilde{\\mathbf{Y}} = g(\\mathbf{Z})\\). See Sec. 5 for architecture and training details. This design ensures that when predicting the state for a frame, the model has assimilated temporal context from the entire sequence. Essentially, our model exploits the fact that the dynamics of the state change has greater invariance to the object category than how the object looks, emphasizing temporal object transformations over objects' static appearances, and thereby enhancing generalization to novel OSCs." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.689, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Object-Centric Features Finally, we discuss how to better represent \"object\" features in the problem. In many scenarios, due to camera placement and framing, the object going through a state transition might only occupy a small portion of the frame, surrounded by other visual elements such as background, people, or bystander objects. Recognizing this challenge, we introduce an enhancement to our model's input features \\(\\mathbf{X}\\) to emphasize the object of interest. To be specific, we leverage an off-the-shelf detector [49] to identify the active object (i.e., the object being manipulated) region at each timepoint \\(t\\), yielding feature \\(\\mathbf{x}_t^{obj}\\) that centers on the object (see bounding boxes in Fig. 2(c)). The input feature is then constructed as a concatenation of the original global feature and the localized object-centric feature," + }, + { + "type": "page_footnote", + "bbox": [ + 0.077, + 0.875, + 0.47, + 0.9 + ], + "angle": 0, + "content": "See Supp. for the multi-task model variant, where we develop one unified model for all state transitions." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18496" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.09, + 0.47, + 0.138 + ], + "angle": 0, + "content": "i.e., \\(\\mathbf{X} = \\{\\left[\\mathbf{x}_t,\\mathbf{x}_t^{obj}\\right]\\}_{t = 1}^T\\). By emphasizing the object in this manner, our model is better positioned to discern the intricate state changes and provide more informed predictions." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.146, + 0.35, + 0.163 + ], + "angle": 0, + "content": "3.3. Text and VLMs as Supervision" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.169, + 0.47, + 0.215 + ], + "angle": 0, + "content": "To scale up training and ensure broad generalization, we propose a novel training pipeline that leverages LLMs and VLMs for OSC mining and pseudo-labeling." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.217, + 0.471, + 0.457 + ], + "angle": 0, + "content": "Mining for OSC examples Utilizing a vast collection of \"how-to\" instructional videos as the training source, we develop an automated mining process to capture the rich, real-world variability of OSCs. The motivation is that instructional videos usually have accompanying Automatic Speech Recognition (ASR) transcriptions that offer valuable OSC cues. For example, a speaker mentioning, \"so just get your rotisserie chicken and shred it up\" suggests that the chicken may undergo a state transition of shredding in the video. Leveraging this fact, we employ LLAMA2 [54] to analyze ASR transcriptions for identifying candidate videos and their associated OSC categories. This text mining stage allows us to corral a long tail of OSCs, discovering likely state change terms—even if rare—from the free-form natural language narrations given by how-to instructors in the training videos. See Fig. 2 (a)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.461, + 0.471, + 0.657 + ], + "angle": 0, + "content": "Pseudo Label Generation Next, to negate the need of manually labeling large-scale training data, we propose a novel pseudo-labeling pipeline facilitated by VLMs. From the identified OSC category (e.g., shredding chicken), we form three textual state descriptions for its initial, transitioning, and end states (e.g., whole chicken, shredding chicken, and shredded chicken). We then adopt both the vision and language encoder from a well-trained VLM (we experiment with CLIP [44] and VideoClip [61]) to compute the cross-modal similarity between every frame in training video and the three state descriptions, producing a score matrix \\(\\mathbf{S} \\in \\mathbb{R}^{T \\times 3}\\). The pseudo label \\(\\hat{y}_t\\) at timepoint \\(t\\) is then assigned based on this score matrix:" + }, + { + "type": "equation", + "bbox": [ + 0.077, + 0.673, + 0.479, + 0.744 + ], + "angle": 0, + "content": "\\[\n\\hat {y} _ {t} = \\left\\{ \\begin{array}{l l} \\text {B a c k g r o u n d} & \\text {i f} \\sum (\\mathbf {S} [ t,: ]) < \\tau \\\\ \\text {I n i t i a l} & \\text {e l i f} \\mathbf {S} [ t, 0 ] - \\mathbf {S} [ t, 1 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 0 ] - \\mathbf {S} [ t, 2 ] > \\delta \\\\ \\text {T r a n s i t i o n i n g} & \\text {e l i f} \\mathbf {S} [ t, 1 ] - \\mathbf {S} [ t, 0 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 1 ] - \\mathbf {S} [ t, 2 ] > \\delta \\\\ \\text {E n d} & \\text {e l i f} \\mathbf {S} [ t, 2 ] - \\mathbf {S} [ t, 0 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 2 ] - \\mathbf {S} [ t, 1 ] > \\delta \\\\ \\text {A m b i g u o u s} & \\text {o t h e r w i s e} \\end{array} \\right.\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.468, + 0.84 + ], + "angle": 0, + "content": "where \\(\\delta\\) is the threshold that separates states and \\(\\tau\\) is the threshold that differentiates between states and background. Essentially if the VLM scores some state more strongly than the other two—and the cumulative confidence score of all states is high—then it is adopted as the pseudo label. Otherwise it is omitted as ambiguous. See Fig. 2(b)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.469, + 0.901 + ], + "angle": 0, + "content": "To further refine these labels, we enforce a causal ordering constraint. Given the inherent progression of OSCs, the anticipated order is initial states followed by transitioning states, and finally, the end states. Any frame whose pseudo" + }, + { + "type": "image", + "bbox": [ + 0.51, + 0.096, + 0.885, + 0.199 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.511, + 0.216, + 0.882, + 0.322 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.338, + 0.892, + 0.407 + ], + "angle": 0, + "content": "Figure 3. Ground truth annotation distribution across 20 state transitions (top) and 134 objects (bottom) in HowToChange (Evaluation). In line with our open-world formulation, annotations cover a diverse range of object-state transition combinations, categorized into known and novel OSCs." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.417, + 0.892, + 0.508 + ], + "angle": 0, + "content": "label does not respect this natural progression is re-assigned to the ambiguous category. Our training employs a cross-entropy loss between pseudo label \\(\\hat{y}_t\\) and the corresponding model prediction \\(\\tilde{y}_t\\), with ambiguous frames excluded to maintain clarity and distinction among the state labels. See Section 4.2 in Supp. for detailed pseudo label analysis." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.524, + 0.757, + 0.541 + ], + "angle": 0, + "content": "4. The HowToChange Dataset" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.551, + 0.892, + 0.641 + ], + "angle": 0, + "content": "Existing OSC datasets fall short in capturing the open-world's diversity and long-tail distribution of OSCs. To address this gap, we introduce HowToChange. It encompasses varied state transitions coupled with a diverse range of objects, providing an authentic reflection of their real-world frequency—from the commonplace to the rare." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Data Collection The HowTo100M collection [36] contains a wealth of instructional videos that often feature OSCs and is particularly suitable for this task. We specifically focus on the HowTo100M Food & Entertaining category because (1) it constitutes a third of the entire HowTo100M videos, (2) cooking tasks offer a wealth of objects, tools, and state changes, providing an excellent test bed for open-world OSC, and (3) in cooking activities a single state transition can often be associated with a varied range of objects, opening the door to learning compositionality. (Note, we also experiment with non-cooking domains below.) We process a total of 498,475 videos and 11,390,287 ASR transcriptions with LLAMA2. From the responses, we identify the most frequently seen state transitions and objects associated with them to establish an OSC vocabulary, resulting in 134 objects, 20 state transitions, and 409 unique OSCs. The number of objects associated with each state transition \\((m(n))\\)" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18497" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.079, + 0.089, + 0.472, + 0.205 + ], + "angle": 0, + "content": "
Datasets# Obj# ST# OSCObjPer# VideosGT Label?
Alayrac et al. [2]5671.2630✓
Task-Fluent [31]2514322.3809✓
ChangeIt (Training) [50]4227441.634,428✗
ChangeIt (Evaluation) [50]4227441.6667✓
HowToChange (Training)1222031815.936,075✗
HowToChange (Evaluation)1342040920.55,424✓
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.076, + 0.215, + 0.47, + 0.313 + ], + "angle": 0, + "content": "Table 1. Comparison with existing video datasets focusing on object states. 'Obj' and 'ST' represent objects and state transitions, respectively. 'ObjPer' denotes the average number of objects associated with each state transition; higher values indicate more need to generalization across objects. We present the first open-world benchmark for temporal video OSC, with an order of magnitude increase in OSC vocabulary and annotation volume." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.322, + 0.47, + 0.399 + ], + "angle": 0, + "content": "spans from 6 for “zesting” to 55 for “chopping”. The state transitions applied to each object vary from 1 to 15, with onions being the most versatile. In total, we identify 36,075 videos for the training set of HowToChange, with an average duration of 41.2 seconds." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.402, + 0.47, + 0.538 + ], + "angle": 0, + "content": "Data Splits In line with our open-world formulation, we divide the 409 identified OSCs into two disjoint subsets based on their frequency of occurrence. Within each state transition, we categorize the top \\(75\\%\\) frequent objects as known and the bottom \\(25\\%\\) as novel. This yields a total of 318 known OSCs that are seen during training and testing, spanning 20 state transitions associated with 122 objects, and 91 novel OSCs that are only seen during testing, encompassing the same transitions across 58 objects." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.541, + 0.47, + 0.829 + ], + "angle": 0, + "content": "Ground Truth Label Collection (Evaluation Set) To facilitate thorough evaluation, we obtain manual annotations for a subset of 5,424 videos from the collected dataset. The annotation workflow is as follows: each annotator is presented with a video segment along with an OSC category that was previously identified by LLAMA2. The annotator has the option to reject the video segment if it does not contain the specified OSC. Otherwise, they label the time ranges corresponding to the initial, transitioning, and end states of the OSC. Adhering to our object-centric emphasis, annotators are instructed to label based on the visual changes of the object, rather than human-centric actions, and exclude time ranges where the object of interest is not visible, ensuring clean and focused temporal labels. Fig. 3 provides the distribution of annotated videos. On average, we collect 271 annotations per state transition, with a video duration of 41.5 seconds, and \\(12.9\\%\\) of videos belong to the novel category. The entire annotation process required around 1,507 hours by 30 professional annotators." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.832, + 0.47, + 0.863 + ], + "angle": 0, + "content": "Dataset Comparison Table 1 compares HowToChange with existing video datasets on temporal OSC understand-" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.288 + ], + "angle": 0, + "content": "ing. HowToChange offers an unprecedented scale—with 9.3x more OSC categories and 8.1x more annotated video instances compared to the previous largest collection [50]. Furthermore, notably, in prior datasets, each state transition is typically coupled with 1 or 2 objects, preventing subsequent models from generalizing to new objects, as we will see in results. In contrast, HowToChange pioneers the open-world formulation, presenting a much broader range of objects associated with each state transition—from 6 to 55 objects per state transition, and averaging 20. This facilitates the development of models with generalized OSC understanding. Please see Supp. for full data collection and annotation details." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.303, + 0.633, + 0.32 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.33, + 0.892, + 0.602 + ], + "angle": 0, + "content": "Datasets In addition to our new HowToChange dataset, we also evaluate on ChangeIt [50] due to its expansive data scale (34K videos spanning many activities) and high relevance to our task. Beyond the conventional split of ChangeIt, we propose a new split tailored to our open-world formulation. Specifically, from the 44 available OSC categories in ChangeIt, we concentrate on the 25 categories where each state transition is paired with more than one object. With those, we form the \"ChangeIt (open-world)\" subset that comprises 8 state transitions and 25 objects. Within each state transition, objects are randomly divided into known and novel categories, yielding 13 known OSC categories for training and 12 novel OSC categories exclusively reserved for evaluation. A detailed breakdown of this split can be found in Supp. To sum up, our evaluation encompasses: ChangeIt; ChangeIt (open-world); and How-ToChange, offering a comprehensive setup in both closed-world and open-world scenarios." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.605, + 0.892, + 0.71 + ], + "angle": 0, + "content": "Evaluation For ChangeIt and ChangeIt (open-world), we adhere to the original dataset's evaluation protocol [50], reporting action and state precision@1 as the evaluation metrics. For our dataset, besides precision@1, which evaluates a single frame for each state within a video, we advocate for the use of F1 score and precision over all frames to ensure a more holistic evaluation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.714, + 0.892, + 0.866 + ], + "angle": 0, + "content": "Baselines We compare our approach with four baselines across two categories: (a) self-supervised approaches on identifying object states enforced by the causal ordering constraint: LookForTheChange [50] trains a dedicated model for each OSC category, while MultiTaskChange [51] evolves this into a multi-task approach8, catering to several OSCs concurrently; (b) zero-shot VLMs: image-based CLIP [44], video-based VideoCLIP [61] and InternVideo [59]. All baselines in (a) use the same training data as our model, whereas the zero-shot models (b) are directly" + }, + { + "type": "page_footnote", + "bbox": [ + 0.077, + 0.875, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Our training is purely guided by a VLM and requires no ground truth labels. The annotations are reserved exclusively for evaluation." + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.875, + 0.892, + 0.901 + ], + "angle": 0, + "content": "To ensure a thorough evaluation, we train both single-task and multitask variants of our approach. See Supp. for a detailed discussion." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18498" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.125, + 0.089, + 0.848, + 0.213 + ], + "angle": 0, + "content": "
MethodChangeItChangeIt (open-world)HowToChange
State Prec.@1Action Prec.@1State Prec.@1 known@1 novelAction Prec.@1 known@1 novelF1 (%)Prec (%)Prec.@1 (%)
knownnovelknownnovelknownnovel
CLIP [44]0.300.630.290.290.710.7026.925.427.326.647.547.5
VideoCLIP [61]0.330.590.250.240.620.5536.634.339.738.548.344.8
InternVideo [59]0.270.570.290.250.600.6129.929.531.430.846.946.3
LookForTheChange [50]0.350.680.360.250.770.6830.328.732.530.037.236.1
MultiTaskChange [51]0.490.800.410.220.720.6233.929.938.534.143.138.8
VIDOSC (ours)0.570.840.560.480.890.8246.443.146.643.760.758.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.223, + 0.895, + 0.252 + ], + "angle": 0, + "content": "Table 2. Results on ChangeIt, ChangeIt (open-world), and HowToChange. VIDOSC outperforms all approaches in both closed-world and open-world scenarios, across known and novel OSCs." + }, + { + "type": "image", + "bbox": [ + 0.1, + 0.265, + 0.868, + 0.519 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.538, + 0.893, + 0.583 + ], + "angle": 0, + "content": "Figure 4. Top-1 frame predictions given by VIDOSC for the initial, transitioning, and end states, on ChangeIt (open-world) (first 2 rows) and HowToChange (last 2 rows). VIDOSC not only accurately localizes the three fine-grained states for known OSCs, but also generalizes this understanding to novel objects, such as cauliflower and capsicum, which are not observed during training." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.608, + 0.351, + 0.623 + ], + "angle": 0, + "content": "evaluated on the test set with no training." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.626, + 0.471, + 0.837 + ], + "angle": 0, + "content": "Implementation Videos are sampled at one frame per second. Each one-second video segment gets assigned to an OSC state label, and is encoded by InternVideo [59], a general video foundation model (which is kept frozen for training efficiency). Our video model consists of a 3-layer transformer with a hidden dimension of 512 and 4 attention heads as the encoder and a 1-layer MLP as the decoder. Consistent with prior work [50, 51], our model predicts the OSC state label (i.e., initial, transitioning, end state, or background) for a video, assuming the video OSC category is known (say from a recognition model's output or a user's specific query). While the standard output does not include the state transition name, our multi-task version detailed in Supp. is capable of this." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Main Results Table 2 presents results on all three datasets. VIDOSC outperforms all approaches in both traditional closed-world and our newly introduced open-world settings. The large performance gains—as much as \\(9.6\\%\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.608, + 0.892, + 0.865 + ], + "angle": 0, + "content": "jumps in precision vs. the next best method—underscore the effectiveness of two pivotal components in VIDOSC. First, its use of text and VLMs for supervisory signals during training: particularly on novel OSCs, VIDOSC extracts meaningful cues from the video modality to refine pseudo labels from VLMs, and ultimately surpasses the VLM baselines. Second, our model for object-agnostic state prediction, designed for the open-world context, effectively narrows the gap between known and novel OSCs. For instance, on ChangeIt (open-world), MultiTaskChange [51] experiences a \\(19\\%\\) decline in state precision@1 while VIDOSC has only a \\(8\\%\\) drop. Note that we observe a more pronounced performance drop of all approaches on ChangeIt (open-world) than on HowToChange due to its limited number of objects available per state transition. These results also point to the potential for future development in bridging the known and novel OSC performance gap." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Qualitative Results Fig. 4 presents VIDOSC's top-1 frame predictions on ChangeIt (open-world) and HowToChange," + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18499" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.47, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.242, + 0.471, + 0.326 + ], + "angle": 0, + "content": "Figure 5. Comparison of model predictions across a test video depicting the OSC of \"slicing shallot\" on HowToChange. The x-axis represents temporal progression through the video. VIDOSC gives temporally smooth and coherent predictions that best align with the ground truth, significantly outperforming baselines in capturing the video's global temporal context." + }, + { + "type": "table", + "bbox": [ + 0.111, + 0.331, + 0.438, + 0.429 + ], + "angle": 0, + "content": "
Shared StateTemporal ModelingObject CentricPrec.@1 (%)
knownnovelΔ
X✓✓58.553.35.2
✓X✓52.948.24.7
✓✓X59.856.73.1
✓✓✓60.758.22.5
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.439, + 0.47, + 0.467 + ], + "angle": 0, + "content": "Table 3. Ablation Study. \\(\\Delta\\) denotes the performance gap between known OSCs and novel OSCs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.475, + 0.471, + 0.718 + ], + "angle": 0, + "content": "across both known and novel OSCs. Notably, despite never seeing objects such as cauliflower and capsicum during training, VIDOSC effectively leverages visual state change cues and correctly localizes the three states of these objects going through OSCs, demonstrating its strong generalization capability. For a more holistic view, Fig. 5 compares VIDOSC's frame-by-frame predictions with all baselines for a given test video. VIDOSC provides temporally coherent predictions, smoothly progressing through the OSC states in the natural order (i.e., from initial to transitioning then end). In contrast, baseline approaches often yield fragmented and inconsistent predictions, indicating a lack of understanding of the video's global temporal context, primarily due to their reliance on frame-wise modeling. See Supp. and Supp. video for more qualitative examples and VIDOSC's interpretability on object relations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Ablation To further dissect the performance gains brought by our three model design techniques (i.e., shared state vocabulary, temporal modeling, and object-centric features), we conduct an ablation study, removing one component at a time. Table 3 confirms the essential role of each element. A shared state vocabulary is particularly crucial in the open-world context, as its absence increases the gap between known and novel OSCs from \\(2.5\\%\\) to \\(5.2\\%\\). Furthermore, temporal modeling provides a substantial performance boost, and object-centric features offer further gains. See Supp. for an additional analysis of VIDOSC's performance with different pseudo labels." + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.09, + 0.631, + 0.166 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.635, + 0.092, + 0.757, + 0.166 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.762, + 0.092, + 0.885, + 0.166 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.167, + 0.631, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.635, + 0.168, + 0.757, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.762, + 0.168, + 0.885, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.23, + 0.631, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.635, + 0.23, + 0.757, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.761, + 0.23, + 0.885, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.308, + 0.892, + 0.406 + ], + "angle": 0, + "content": "Figure 6. Frame retrieval on the HowToChange test set. Given a query frame showcasing a novel OSC at its initial state, VIDOSC retrieves the nearest and furthest frame among all known OSCs at their end states. The closest post-OSC frame follows the transition trajectory of the query while the furthest post-OSC frame depicts a substantially different object, demonstrating VIDOSC's capability to generalize the OSC progression for novel objects." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.413, + 0.893, + 0.64 + ], + "angle": 0, + "content": "Frame Retrieval VIDOSC learns features that accurately characterize the evolution of an OSC process. To illustrate, we consider a novel frame retrieval setting. Within the HowToChange test set, when presented with a query video featuring a novel OSC at its initial state, VIDOSC seeks the most similar and most contrasting video from a pool of candidates at their end states. The frame triplets with the smallest and largest feature distance are shown in Fig. 6. Remarkably, the retrieved nearest post-OSC frames correspond to the query's anticipated state transition trajectory, despite the object and state gap. Conversely, the furthest frames exhibit end states of markedly different objects. These results further lend support to VIDOSC's capability to understand the evolution of an OSC process, even for novel objects it has never encountered during training." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.652, + 0.619, + 0.667 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.677, + 0.892, + 0.873 + ], + "angle": 0, + "content": "This work aims at a comprehensive exploration of video OSCs, with a novel open-world formulation. To address the challenges, we leverage text and VLMs to assist the training of a video OSC model at scale and design three modeling techniques to achieve object-agnostic state prediction for better generalization to novel OSCs. Furthermore, we present the most expansive video OSC dataset collection HowToChange, which echoes the natural long-tail of state transitions coupled with varied objects, fostering a realistic representation of real-world scenarios. As for future work, we will consider extending VIDOSC to video sequences featuring concurrent OSC processes, and integrating spatial understanding of OSC within our open-world framework." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.874, + 0.891, + 0.901 + ], + "angle": 0, + "content": "Acknowledgements: UT Austin is supported in part by the IFML NSF AI Institute. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 6586-6597, 2023. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.316 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.946, + 0.519, + 0.956 + ], + "angle": 0, + "content": "18503" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_origin.pdf b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..fbf8da3afefe592a11e31a76d3575d537c1677eb --- /dev/null +++ b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/fe5e8aba-0eb4-418b-9856-ff82ba536a86_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:469552aff2d4f81196e67194fae41561ebe85943cba707c51064fe51bed962ac +size 8228825 diff --git a/2024/Learning Object State Changes in Videos_ An Open-World Perspective/full.md b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/full.md new file mode 100644 index 0000000000000000000000000000000000000000..ff9ebe656ab97959d780dfd882993f909a4bcd5d --- /dev/null +++ b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/full.md @@ -0,0 +1,269 @@ +# Learning Object State Changes in Videos: An Open-World Perspective + +Zihui Xue1,2 + +Kumar Ashutosh1,2 + +Kristen Grauman $^{1,2}$ + +1The University of Texas at Austin + +$^{2}$ FAIR, Meta + +# Abstract + +Object State Changes (OSCs) are pivotal for video understanding. While humans can effortlessly generalize OSC understanding from familiar to unknown objects, current approaches are confined to a closed vocabulary. Addressing this gap, we introduce a novel open-world formulation for the video OSC problem. The goal is to temporally localize the three stages of an OSC—the object's initial state, its transitioning state, and its end state—whether or not the object has been observed during training. Towards this end, we develop VIDOSC, a holistic learning approach that: (1) leverages text and vision-language models for supervisory signals to obviate manually labeling OSC training data, and (2) abstracts fine-grained shared state representations from objects to enhance generalization. Furthermore, we present HowToChange, the first open-world benchmark for video OSC localization, which offers an order of magnitude increase in the label space and annotation volume compared to the best existing benchmark. Experimental results demonstrate the efficacy of our approach, in both traditional closed-world and open-world scenarios. $^{1}$ + +# 1. Introduction + +In video understanding, the study of objects primarily revolves around tasks like recognition [16], detection [24], and tracking [8, 62], with the assumption that objects maintain a consistent visual appearance throughout the video. Yet, objects in video are often dynamic. They can undergo transformations that change their appearance, shape, and even topology. For example, a pineapple goes from whole to peeled to sliced, or wood is carved into a new shape. + +Object State Changes (OSCs) [2, 15, 17, 22, 47, 50-52, 60, 64] add a critical dimension to video understanding. On the one hand, they provide insights into human actions—observing a piece of metal being shaped into a hook, for instance, implies the action of bending; observing an egg shell go from whole to broken implies the action of cracking. On the other hand, OSCs are essential + +![](images/85f72c82d0ff670f54b9eb4f496b733dc97e95e3bcec96d6967775bb1b1a4d34.jpg) + +![](images/e49abcaa07332c67ed714d89c2ec36e0026b413512f6c05d00a99d3b2d38241f.jpg) +Figure 1. Top: The video OSC objective is to temporally localize an object's three states (i.e., initial, transitioning, end). Bottom: OSCs naturally exhibit a long tail. Certain OSCs, such as melting butter or marshmallow, are frequently showcased in instructional videos while others like melting jaggery might be rarely seen. We introduce an innovative open-world formulation that requires extrapolating to novel objects never encountered during training. + +for assessing goal completion, in a way that is invariant to the specific procedure used. For instance, the readiness of cake batter signifies the completion of a mixing task, regardless of whether it was stirred by hand or a mechanical mixer. These core functionalities are instrumental for various real-world applications [5, 6, 12, 13, 20, 21, 66], ranging from AR/VR assistants [42] that guide users through complex tasks by monitoring object states, to robotic manipulation [9, 55] where understanding the state of objects is critical for task planning and failure recovery. + +However, the development of video OSC is still at a primitive stage. Existing approaches [1, 2, 15, 46, 50, 51, 58] assume a closed vocabulary, where each state transformation is associated with a limited set of objects—often just 1 or 2. For example, the concept of “melting” might be limited to familiar items like butter and marshmallow. Consequently, the learned models are only capable of identifying state changes for objects observed during training and stumble when presented with novel objects. In contrast, in real-world situations a single state transition like “melting” can be linked with a plethora of objects—some ubiquitous and + +others rare. Importantly, there is an intrinsic connection that threads these OSC processes together. As humans, even if we have never encountered an unusual substance (e.g., jaggery) before, we can still understand that it is experiencing a "melting" process based on its visual transformation cues (see Fig. 1, bottom). + +In light of these limitations, we propose a novel open-world formulation of the video OSC problem. We formally characterize OSCs in videos in terms of three states that must be temporally localized: initial, transitioning, and end (see Fig. 1, top). In our open-world setting, there are known objects and novel objects. The model is only presented with known objects during training (e.g., frying chicken, frying onions). Then, it is evaluated on both known and novel objects (e.g., frying cauliflower). In addition to this fundamental open-world generalization, we also tackle a more comprehensive notion of the transitioning state. Specifically, our transitioning states encapsulate not only action-induced modifications to the object (e.g., peeling), but also passive transformations the object undergoes without human interference (e.g., melting) and edited-out transformations (e.g., the cake goes from raw to baked even if baked off camera). Though largely overlooked in existing approaches [1, 15, 46, 58], these cases are both common and technically interesting, since they force a model to reason about the effects of the core state change rather than search for evidence of a human actor carrying out the action. + +Armed with this new problem formulation, we propose a holistic video OSC learning approach, anchored by two innovative ideas. First, we explore text and vision-language models (VLMs) for supervisory signals during training. We pioneer the use of textual state descriptions to generate a long tail of object state pseudo-labels, by leveraging the remarkable capabilities of VLMs [23, 44, 63] and large language models (LLMs) [40, 53, 54]. This strategy eliminates the need for exhaustive label collection for training data, facilitating large-scale model training. Second, to confront the open-world challenge, we propose object-agnostic state prediction, consisting of three key techniques: a shared state vocabulary to unify the label space across objects sharing the same state transition (e.g., melting butter and melting marshmallow), temporal modeling to grasp the progression of state changes over time, and object-centric features that better represent the objects during an OSC. These designs equip our model with the ability to generalize state understanding from known objects to novel ones. We term our approach VIDOSC. + +Complementing this, we present a large-scale real-world dataset HowToChange. Sourced from the HowTo100M collection [36], it sets a new benchmark in the field of unprecedented scale and an authentic long-tail distribution, setting + +it apart from the constrained scope and closed-world setting of earlier benchmarks (see Table 1). Finally, experimental results demonstrate the efficacy of VIDOsc, surpassing the state-of-the-art in both traditional closed-world and novel open-world scenarios by a great margin. + +# 2. Related Work + +Object State Changes Image-based methods explore the compositional nature of objects and their attributes, including zero-shot recognition of unseen combinations [22, 29, 33, 37-39, 41, 43], but do not consider the temporal progression of OSCs in video, which brings new challenges. Video-based methods develop human-centric models that leverage state change cues to facilitate action recognition [1, 15, 46, 58], or explore joint discovery of object states and actions [2, 50, 51]. Notably, all the existing methods assume a closed world, recognizing only the OSC categories ("known" objects) seen during training. Our approach distinguishes itself in three crucial ways: (1) we introduce a novel open-world3 formulation, where the objects encountered during evaluation can be entirely unseen during training; (2) we adopt an object-centric perspective, allowing for scenarios where OSCs occur with no observable human actions in the video; and (3) we propose to utilize the text modality and VLMs as supervisory signals, greatly scaling up model training and boosting performance. + +Early datasets for video OSC capture a limited array of OSCs in fewer than 1,000 videos [2, 31]. The more recent ChangeIt dataset [50] marks an advance in dataset scale (34K videos), yet is still restricted to a small OSC vocabulary of 44 total object-state transitions. It lacks the scope to adequately test unseen objects, since most state changes coincide with only 1 or 2 objects across all the videos (see Table 1). Other datasets explore different aspects of video OSCs, including object state recognition [47], point-of-noreturn (PNR) frame localization [17], and object segmentation [52, 64], but they lack any temporal annotations of fine-grained OSC states needed for our task's evaluation. Our HowToChange dataset increases the OSC vocabulary space by an order of magnitude and allows for the first time rigorous study of the open-world temporal OSC challenge. + +Vision and Language LLMs [40, 53, 54] have revolutionized various research fields with their exceptional performance across diverse applications. Building on this momentum, the use of web-scale image-text data has emerged as a powerful paradigm in computer vision, with powerful VLMs now advancing an array of image tasks, including zero-shot classification [44], detection [18], segmentation [32] and visual question answering [27, 28]. Similarly, joint video-text representation learning [3, 30, 36, 67] has been advanced by multimodal datasets like + +HowTo100M [36] and Ego4D [17], which offer large-scale collections of videos paired with their corresponding narratives. These datasets have also facilitated tasks like step discovery [11], localization in procedural activities [35] and long egocentric videos [45]. The vision-language multimodal cycle consistency loss proposed in [14] helps discover long-term temporal dynamics in video. In line with these developments, we propose to leverage the text accompanying instructional videos as well as existing high-performing VLMs to provide supervisory signals that guide the training of our video OSC model and allow learning for the open world. + +Learning in an Open World The open world setting has received increasing attention, predominantly within the image domain for object recognition [4, 48], detection [10, 18, 25, 65] and object-attribute compositionality [29, 33, 37-39, 41, 43]. In the video domain, compositionality is advanced by the Something-Else dataset [34], where the training combinations of verbs and nouns do not overlap with the test set, sparking work on the dynamics of subject-object interactions [7, 34, 47]. More recent efforts leverage VLMs for zero-shot action recognition [7, 26, 57]. Concurrent work explores video object segmentation with state-changing objects [64] and recognition of novel object-state compositions for food chopped in different styles [47]. Despite these advances, temporal video OSC understanding in the open world remains unexplored. Our open-world formulation requires generalizing the temporal localization of fine-grained object states from known to novel objects. + +# 3. Approach + +We present the VIDOSC framework for learning video OSCs, detailing the open-world formulation (Sec. 3.1), model design for object-agnostic state prediction (Sec. 3.2), and text-guided training scheme (Sec. 3.3). + +# 3.1. Video OSC in the Open World + +We begin by formally defining an object state change (OSC) in videos as a visually detectable transformation, where an object experiences a change that is not easily reversible, in line with [17]. We characterize an OSC category as an object combined with a specific state transition, such as "chicken + shredding", and delineate an OSC process through three distinct states: initial (precondition state), transitioning, and end (postcondition state).4 It is essential to highlight that we take an object-centric perspective: the "transitioning state" accounts for instances where the video depicts an active action applied to the object, as well as scenarios where the object undergoes a passive transformation absent of human intervention (e.g., melting, drying). + +4Due to real-world data variation, some videos may lack one of the OSC states, and there may be multiple segments in a video corresponding to the same state. Our formulation accounts for all these scenarios. + +Given a video in which an object may be changing state, the objective is to temporally localize each of the three OSC states. Consistent with prior work [50, 51], we formulate the task as a frame-wise classification problem. Formally, a video sequence is represented by a temporal sequence of $T$ feature vectors $\mathbf{X} = \{\mathbf{x}_1,\mathbf{x}_2,\dots ,\mathbf{x}_T\}$ , where $T$ denotes the video duration. The goal is to predict the OSC state label for each timepoint, denoted by $\mathbf{Y} = \{\mathbf{y}_1,\mathbf{y}_2,\dots ,\mathbf{y}_T\}$ , $\mathbf{y}_t\in \{1,\dots ,K + 1\}$ , where $K$ is the total number of OSC states, and there is one additional category representing the background class not associated with any OSC state. + +Next, we propose an open-world problem formulation, capturing the intrinsic long-tail distribution observed in real-world scenarios. Consider $N$ state transitions, each paired with a set of associated objects, denoted by $\mathbf{O}^n = \{o_1^n,o_2^n,\dots ,o_{m(n)}^n\}$ , for $n = \{1,2,\dots ,N\}$ , where $m(n)$ denotes the number of objects linked with the $n$ -th state transition. Within a specific state transition (like frying), certain objects in the set (such as chicken or onions) are frequently observed, while the combination of the same state transition with other objects (such as cauliflower) appear less often. Motivated by this inherent long-tail, we propose to split $\mathbf{O}^n$ into two distinct subsets: $\mathbf{O}_{\mathrm{known}}^n$ covering the common combinations observed during training, and $\mathbf{O}_{\mathrm{novel}}^n$ comprising the infrequent combinations, which are unseen during training due to their rarity. During inference, the model is evaluated on the entire object set $\mathbf{O}^n$ for a comprehensive reflection of the open-world setting. + +# 3.2. Object-Agnostic State Prediction + +To address the open-world challenges and ensure robust generalization to novel objects, VIDOSC integrates three key techniques: (1) a shared state vocabulary that consolidates the state label space; (2) temporal modeling within the video OSC model design; and (3) object-centric features. + +Shared State Vocabulary The inherent link among different OSC categories is overlooked in prior work. Common practice involves developing separate models for each OSC category [2, 50] (e.g., one model exclusively for melting butter and another for melting chocolate), or using one single model that still treats every OSC as a distinct entity in the label space [51] (e.g., considering melted butter and melted chocolate as two separate end states). Such a formulation results in an extensive label set with $K = 3 \times \sum_{n=1}^{N} m(n)$ , where 3 denotes the number of OSC states (i.e., initial, transitioning and end) and $\sum_{n=1}^{N} m(n)$ is the total number of OSC categories. This compartmentalized view can inadvertently hinder the model's generalization ability. Yet, on closer inspection, states across varied objects are intrinsically related. For instance, the "melting" principle remains consistent, even when applied to visually + +![](images/cd72c8c8e56e856913a378b48dd2543d852b875733f4176b2040f195b13f267f.jpg) +Figure 2. Our proposed VIDOSC framework: (a) Mining for OSC examples (Sec. 3.3): We leverage ASR transcriptions paired with videos and the capabilities of LLM to automatically mine OSC examples. (b) Pseudo Label Generation (Sec. 3.3): We utilize textual state descriptions and a VLM for supervisory signals during training; (c) Model Training (Sec. 3.2): We develop a video model for object-agnostic state prediction. (d) Model Testing (Sec. 3.1): We propose an open-world formulation, evaluating on both known and novel OSCs. Notably, while we employ the text modality to guide model training, our model is purely video-based and requires no text input at the test phase, ensuring maximum flexibility and applicability. Ground truth for the test set is manually annotated. + +distinct objects like butter and chocolate. This motivates us to group OSC labels that share the same state transition as one, and train a single model per state transition.6 By adopting object-agnostic OSC labels, we encourage the model to learn state representations shared by visually different objects, and thus facilitate the transfer from known to novel objects. + +Temporal Modeling Recognizing that state changes unfold over time, it is important to capture the temporal dynamics in videos. An object's state at any frame, be it initial, transitioning, or end, is often best understood in the context of preceding and succeeding frames. Contrary to prior works [2, 50, 51] that rely on isolated frameswise modeling without considering the temporal progression of video OSCs, we address this gap by proposing a temporally-aware model design. As illustrated in Fig. 2(c), we adopt an encoder-decoder architecture. For the encoding phase, input video features $\mathbf{X} = \{\mathbf{x}_1,\mathbf{x}_2,\dots ,\mathbf{x}_T\}$ are first projected using an MLP $f_{\mathrm{project}}$ and augmented with sinusoidal positional embeddings, $\mathbf{Z}_{\mathrm{pos}}$ . Subsequently, a transformer encoder [56] $f_{\mathrm{transformer}}$ is adopted to capture the temporal dynamics among these features, yield + +ing $\mathbf{Z} = f_{\mathrm{transformer}}(f_{\mathrm{project}}(\mathbf{X}) + \mathbf{Z}_{\mathrm{pos}})$ . For the decoding phase, a MLP decoder $g$ , maps these temporally-aware hidden representations to OSC state predictions: $\tilde{\mathbf{Y}} = g(\mathbf{Z})$ . See Sec. 5 for architecture and training details. This design ensures that when predicting the state for a frame, the model has assimilated temporal context from the entire sequence. Essentially, our model exploits the fact that the dynamics of the state change has greater invariance to the object category than how the object looks, emphasizing temporal object transformations over objects' static appearances, and thereby enhancing generalization to novel OSCs. + +Object-Centric Features Finally, we discuss how to better represent "object" features in the problem. In many scenarios, due to camera placement and framing, the object going through a state transition might only occupy a small portion of the frame, surrounded by other visual elements such as background, people, or bystander objects. Recognizing this challenge, we introduce an enhancement to our model's input features $\mathbf{X}$ to emphasize the object of interest. To be specific, we leverage an off-the-shelf detector [49] to identify the active object (i.e., the object being manipulated) region at each timepoint $t$ , yielding feature $\mathbf{x}_t^{obj}$ that centers on the object (see bounding boxes in Fig. 2(c)). The input feature is then constructed as a concatenation of the original global feature and the localized object-centric feature, + +i.e., $\mathbf{X} = \{\left[\mathbf{x}_t,\mathbf{x}_t^{obj}\right]\}_{t = 1}^T$ . By emphasizing the object in this manner, our model is better positioned to discern the intricate state changes and provide more informed predictions. + +# 3.3. Text and VLMs as Supervision + +To scale up training and ensure broad generalization, we propose a novel training pipeline that leverages LLMs and VLMs for OSC mining and pseudo-labeling. + +Mining for OSC examples Utilizing a vast collection of "how-to" instructional videos as the training source, we develop an automated mining process to capture the rich, real-world variability of OSCs. The motivation is that instructional videos usually have accompanying Automatic Speech Recognition (ASR) transcriptions that offer valuable OSC cues. For example, a speaker mentioning, "so just get your rotisserie chicken and shred it up" suggests that the chicken may undergo a state transition of shredding in the video. Leveraging this fact, we employ LLAMA2 [54] to analyze ASR transcriptions for identifying candidate videos and their associated OSC categories. This text mining stage allows us to corral a long tail of OSCs, discovering likely state change terms—even if rare—from the free-form natural language narrations given by how-to instructors in the training videos. See Fig. 2 (a). + +Pseudo Label Generation Next, to negate the need of manually labeling large-scale training data, we propose a novel pseudo-labeling pipeline facilitated by VLMs. From the identified OSC category (e.g., shredding chicken), we form three textual state descriptions for its initial, transitioning, and end states (e.g., whole chicken, shredding chicken, and shredded chicken). We then adopt both the vision and language encoder from a well-trained VLM (we experiment with CLIP [44] and VideoClip [61]) to compute the cross-modal similarity between every frame in training video and the three state descriptions, producing a score matrix $\mathbf{S} \in \mathbb{R}^{T \times 3}$ . The pseudo label $\hat{y}_t$ at timepoint $t$ is then assigned based on this score matrix: + +$$ +\hat {y} _ {t} = \left\{ \begin{array}{l l} \text {B a c k g r o u n d} & \text {i f} \sum (\mathbf {S} [ t,: ]) < \tau \\ \text {I n i t i a l} & \text {e l i f} \mathbf {S} [ t, 0 ] - \mathbf {S} [ t, 1 ] > \delta \text {a n d} \mathbf {S} [ t, 0 ] - \mathbf {S} [ t, 2 ] > \delta \\ \text {T r a n s i t i o n i n g} & \text {e l i f} \mathbf {S} [ t, 1 ] - \mathbf {S} [ t, 0 ] > \delta \text {a n d} \mathbf {S} [ t, 1 ] - \mathbf {S} [ t, 2 ] > \delta \\ \text {E n d} & \text {e l i f} \mathbf {S} [ t, 2 ] - \mathbf {S} [ t, 0 ] > \delta \text {a n d} \mathbf {S} [ t, 2 ] - \mathbf {S} [ t, 1 ] > \delta \\ \text {A m b i g u o u s} & \text {o t h e r w i s e} \end{array} \right. +$$ + +where $\delta$ is the threshold that separates states and $\tau$ is the threshold that differentiates between states and background. Essentially if the VLM scores some state more strongly than the other two—and the cumulative confidence score of all states is high—then it is adopted as the pseudo label. Otherwise it is omitted as ambiguous. See Fig. 2(b). + +To further refine these labels, we enforce a causal ordering constraint. Given the inherent progression of OSCs, the anticipated order is initial states followed by transitioning states, and finally, the end states. Any frame whose pseudo + +![](images/e01633ea3975b12a759c00349c03523047c529023ee3c4bf9aacc2d2f5d4d340.jpg) + +![](images/4da85303989aab31667cb729883906822b1a233cff069012172f5a3b7eed6a67.jpg) +Figure 3. Ground truth annotation distribution across 20 state transitions (top) and 134 objects (bottom) in HowToChange (Evaluation). In line with our open-world formulation, annotations cover a diverse range of object-state transition combinations, categorized into known and novel OSCs. + +label does not respect this natural progression is re-assigned to the ambiguous category. Our training employs a cross-entropy loss between pseudo label $\hat{y}_t$ and the corresponding model prediction $\tilde{y}_t$ , with ambiguous frames excluded to maintain clarity and distinction among the state labels. See Section 4.2 in Supp. for detailed pseudo label analysis. + +# 4. The HowToChange Dataset + +Existing OSC datasets fall short in capturing the open-world's diversity and long-tail distribution of OSCs. To address this gap, we introduce HowToChange. It encompasses varied state transitions coupled with a diverse range of objects, providing an authentic reflection of their real-world frequency—from the commonplace to the rare. + +Data Collection The HowTo100M collection [36] contains a wealth of instructional videos that often feature OSCs and is particularly suitable for this task. We specifically focus on the HowTo100M Food & Entertaining category because (1) it constitutes a third of the entire HowTo100M videos, (2) cooking tasks offer a wealth of objects, tools, and state changes, providing an excellent test bed for open-world OSC, and (3) in cooking activities a single state transition can often be associated with a varied range of objects, opening the door to learning compositionality. (Note, we also experiment with non-cooking domains below.) We process a total of 498,475 videos and 11,390,287 ASR transcriptions with LLAMA2. From the responses, we identify the most frequently seen state transitions and objects associated with them to establish an OSC vocabulary, resulting in 134 objects, 20 state transitions, and 409 unique OSCs. The number of objects associated with each state transition $(m(n))$ + +
Datasets# Obj# ST# OSCObjPer# VideosGT Label?
Alayrac et al. [2]5671.2630✓
Task-Fluent [31]2514322.3809✓
ChangeIt (Training) [50]4227441.634,428✗
ChangeIt (Evaluation) [50]4227441.6667✓
HowToChange (Training)1222031815.936,075✗
HowToChange (Evaluation)1342040920.55,424✓
+ +Table 1. Comparison with existing video datasets focusing on object states. 'Obj' and 'ST' represent objects and state transitions, respectively. 'ObjPer' denotes the average number of objects associated with each state transition; higher values indicate more need to generalization across objects. We present the first open-world benchmark for temporal video OSC, with an order of magnitude increase in OSC vocabulary and annotation volume. + +spans from 6 for “zesting” to 55 for “chopping”. The state transitions applied to each object vary from 1 to 15, with onions being the most versatile. In total, we identify 36,075 videos for the training set of HowToChange, with an average duration of 41.2 seconds. + +Data Splits In line with our open-world formulation, we divide the 409 identified OSCs into two disjoint subsets based on their frequency of occurrence. Within each state transition, we categorize the top $75\%$ frequent objects as known and the bottom $25\%$ as novel. This yields a total of 318 known OSCs that are seen during training and testing, spanning 20 state transitions associated with 122 objects, and 91 novel OSCs that are only seen during testing, encompassing the same transitions across 58 objects. + +Ground Truth Label Collection (Evaluation Set) To facilitate thorough evaluation, we obtain manual annotations for a subset of 5,424 videos from the collected dataset. The annotation workflow is as follows: each annotator is presented with a video segment along with an OSC category that was previously identified by LLAMA2. The annotator has the option to reject the video segment if it does not contain the specified OSC. Otherwise, they label the time ranges corresponding to the initial, transitioning, and end states of the OSC. Adhering to our object-centric emphasis, annotators are instructed to label based on the visual changes of the object, rather than human-centric actions, and exclude time ranges where the object of interest is not visible, ensuring clean and focused temporal labels. Fig. 3 provides the distribution of annotated videos. On average, we collect 271 annotations per state transition, with a video duration of 41.5 seconds, and $12.9\%$ of videos belong to the novel category. The entire annotation process required around 1,507 hours by 30 professional annotators. + +Dataset Comparison Table 1 compares HowToChange with existing video datasets on temporal OSC understand- + +ing. HowToChange offers an unprecedented scale—with 9.3x more OSC categories and 8.1x more annotated video instances compared to the previous largest collection [50]. Furthermore, notably, in prior datasets, each state transition is typically coupled with 1 or 2 objects, preventing subsequent models from generalizing to new objects, as we will see in results. In contrast, HowToChange pioneers the open-world formulation, presenting a much broader range of objects associated with each state transition—from 6 to 55 objects per state transition, and averaging 20. This facilitates the development of models with generalized OSC understanding. Please see Supp. for full data collection and annotation details. + +# 5. Experiments + +Datasets In addition to our new HowToChange dataset, we also evaluate on ChangeIt [50] due to its expansive data scale (34K videos spanning many activities) and high relevance to our task. Beyond the conventional split of ChangeIt, we propose a new split tailored to our open-world formulation. Specifically, from the 44 available OSC categories in ChangeIt, we concentrate on the 25 categories where each state transition is paired with more than one object. With those, we form the "ChangeIt (open-world)" subset that comprises 8 state transitions and 25 objects. Within each state transition, objects are randomly divided into known and novel categories, yielding 13 known OSC categories for training and 12 novel OSC categories exclusively reserved for evaluation. A detailed breakdown of this split can be found in Supp. To sum up, our evaluation encompasses: ChangeIt; ChangeIt (open-world); and How-ToChange, offering a comprehensive setup in both closed-world and open-world scenarios. + +Evaluation For ChangeIt and ChangeIt (open-world), we adhere to the original dataset's evaluation protocol [50], reporting action and state precision@1 as the evaluation metrics. For our dataset, besides precision@1, which evaluates a single frame for each state within a video, we advocate for the use of F1 score and precision over all frames to ensure a more holistic evaluation. + +Baselines We compare our approach with four baselines across two categories: (a) self-supervised approaches on identifying object states enforced by the causal ordering constraint: LookForTheChange [50] trains a dedicated model for each OSC category, while MultiTaskChange [51] evolves this into a multi-task approach8, catering to several OSCs concurrently; (b) zero-shot VLMs: image-based CLIP [44], video-based VideoCLIP [61] and InternVideo [59]. All baselines in (a) use the same training data as our model, whereas the zero-shot models (b) are directly + +
MethodChangeItChangeIt (open-world)HowToChange
State Prec.@1Action Prec.@1State Prec.@1 known@1 novelAction Prec.@1 known@1 novelF1 (%)Prec (%)Prec.@1 (%)
knownnovelknownnovelknownnovel
CLIP [44]0.300.630.290.290.710.7026.925.427.326.647.547.5
VideoCLIP [61]0.330.590.250.240.620.5536.634.339.738.548.344.8
InternVideo [59]0.270.570.290.250.600.6129.929.531.430.846.946.3
LookForTheChange [50]0.350.680.360.250.770.6830.328.732.530.037.236.1
MultiTaskChange [51]0.490.800.410.220.720.6233.929.938.534.143.138.8
VIDOSC (ours)0.570.840.560.480.890.8246.443.146.643.760.758.2
+ +Table 2. Results on ChangeIt, ChangeIt (open-world), and HowToChange. VIDOSC outperforms all approaches in both closed-world and open-world scenarios, across known and novel OSCs. + +![](images/a4de4c0b17e3f8aa325e58f3a72965853b684d32c79cfd0dcd3eebf335dfd28e.jpg) +Figure 4. Top-1 frame predictions given by VIDOSC for the initial, transitioning, and end states, on ChangeIt (open-world) (first 2 rows) and HowToChange (last 2 rows). VIDOSC not only accurately localizes the three fine-grained states for known OSCs, but also generalizes this understanding to novel objects, such as cauliflower and capsicum, which are not observed during training. + +evaluated on the test set with no training. + +Implementation Videos are sampled at one frame per second. Each one-second video segment gets assigned to an OSC state label, and is encoded by InternVideo [59], a general video foundation model (which is kept frozen for training efficiency). Our video model consists of a 3-layer transformer with a hidden dimension of 512 and 4 attention heads as the encoder and a 1-layer MLP as the decoder. Consistent with prior work [50, 51], our model predicts the OSC state label (i.e., initial, transitioning, end state, or background) for a video, assuming the video OSC category is known (say from a recognition model's output or a user's specific query). While the standard output does not include the state transition name, our multi-task version detailed in Supp. is capable of this. + +Main Results Table 2 presents results on all three datasets. VIDOSC outperforms all approaches in both traditional closed-world and our newly introduced open-world settings. The large performance gains—as much as $9.6\%$ + +jumps in precision vs. the next best method—underscore the effectiveness of two pivotal components in VIDOSC. First, its use of text and VLMs for supervisory signals during training: particularly on novel OSCs, VIDOSC extracts meaningful cues from the video modality to refine pseudo labels from VLMs, and ultimately surpasses the VLM baselines. Second, our model for object-agnostic state prediction, designed for the open-world context, effectively narrows the gap between known and novel OSCs. For instance, on ChangeIt (open-world), MultiTaskChange [51] experiences a $19\%$ decline in state precision@1 while VIDOSC has only a $8\%$ drop. Note that we observe a more pronounced performance drop of all approaches on ChangeIt (open-world) than on HowToChange due to its limited number of objects available per state transition. These results also point to the potential for future development in bridging the known and novel OSC performance gap. + +Qualitative Results Fig. 4 presents VIDOSC's top-1 frame predictions on ChangeIt (open-world) and HowToChange, + +![](images/052c79eb56d0e2490c4c61368a040adef20b2425421b7bb9ad80c0a81cf123c1.jpg) +Figure 5. Comparison of model predictions across a test video depicting the OSC of "slicing shallot" on HowToChange. The x-axis represents temporal progression through the video. VIDOSC gives temporally smooth and coherent predictions that best align with the ground truth, significantly outperforming baselines in capturing the video's global temporal context. + +
Shared StateTemporal ModelingObject CentricPrec.@1 (%)
knownnovelΔ
X✓✓58.553.35.2
✓X✓52.948.24.7
✓✓X59.856.73.1
✓✓✓60.758.22.5
+ +Table 3. Ablation Study. $\Delta$ denotes the performance gap between known OSCs and novel OSCs. + +across both known and novel OSCs. Notably, despite never seeing objects such as cauliflower and capsicum during training, VIDOSC effectively leverages visual state change cues and correctly localizes the three states of these objects going through OSCs, demonstrating its strong generalization capability. For a more holistic view, Fig. 5 compares VIDOSC's frame-by-frame predictions with all baselines for a given test video. VIDOSC provides temporally coherent predictions, smoothly progressing through the OSC states in the natural order (i.e., from initial to transitioning then end). In contrast, baseline approaches often yield fragmented and inconsistent predictions, indicating a lack of understanding of the video's global temporal context, primarily due to their reliance on frame-wise modeling. See Supp. and Supp. video for more qualitative examples and VIDOSC's interpretability on object relations. + +Ablation To further dissect the performance gains brought by our three model design techniques (i.e., shared state vocabulary, temporal modeling, and object-centric features), we conduct an ablation study, removing one component at a time. Table 3 confirms the essential role of each element. A shared state vocabulary is particularly crucial in the open-world context, as its absence increases the gap between known and novel OSCs from $2.5\%$ to $5.2\%$ . Furthermore, temporal modeling provides a substantial performance boost, and object-centric features offer further gains. See Supp. for an additional analysis of VIDOSC's performance with different pseudo labels. + +![](images/9d1f32e0778c6df3c3e7faeacd7aacc43fb180db810cdae57d06f58d29ee3056.jpg) + +![](images/d89bd13c9576ccd67aa20a3fa41ada55cb08132f5feb3318e28edb545b528211.jpg) + +![](images/a3095c4a99ce8a77e781dfab0a0c1613c254747cddaa7fb10ab02a0e869a0f60.jpg) + +![](images/5e899bce65443ad6d413bb490e5e7e1e760d018cb93e860bd9525f99ce79f28b.jpg) + +![](images/f49e65cdda0833b854e58f203dced4b1d98da138bcfc32f653ee03b85079de69.jpg) + +![](images/b724d6f0c51be04b39124d41241ba2036473264517014d40a6f5b6708e8c0441.jpg) + +![](images/013cfe0bda99f477cca63a310e917ddb576e9060509a0ff8aa44711c37e7e5a0.jpg) +Figure 6. Frame retrieval on the HowToChange test set. Given a query frame showcasing a novel OSC at its initial state, VIDOSC retrieves the nearest and furthest frame among all known OSCs at their end states. The closest post-OSC frame follows the transition trajectory of the query while the furthest post-OSC frame depicts a substantially different object, demonstrating VIDOSC's capability to generalize the OSC progression for novel objects. + +![](images/adafb4bc491b3895ee43dbc17069ef2a26cfe7e46c75842abd0cb14dffbc32c4.jpg) + +![](images/eb50f5874b135d3d270464d6d3aa53859288f43ba6f45000c48bb6c349d473e0.jpg) + +Frame Retrieval VIDOSC learns features that accurately characterize the evolution of an OSC process. To illustrate, we consider a novel frame retrieval setting. Within the HowToChange test set, when presented with a query video featuring a novel OSC at its initial state, VIDOSC seeks the most similar and most contrasting video from a pool of candidates at their end states. The frame triplets with the smallest and largest feature distance are shown in Fig. 6. Remarkably, the retrieved nearest post-OSC frames correspond to the query's anticipated state transition trajectory, despite the object and state gap. Conversely, the furthest frames exhibit end states of markedly different objects. These results further lend support to VIDOSC's capability to understand the evolution of an OSC process, even for novel objects it has never encountered during training. + +# 6. Conclusion + +This work aims at a comprehensive exploration of video OSCs, with a novel open-world formulation. To address the challenges, we leverage text and VLMs to assist the training of a video OSC model at scale and design three modeling techniques to achieve object-agnostic state prediction for better generalization to novel OSCs. Furthermore, we present the most expansive video OSC dataset collection HowToChange, which echoes the natural long-tail of state transitions coupled with varied objects, fostering a realistic representation of real-world scenarios. As for future work, we will consider extending VIDOSC to video sequences featuring concurrent OSC processes, and integrating spatial understanding of OSC within our open-world framework. + +Acknowledgements: UT Austin is supported in part by the IFML NSF AI Institute. KG is paid as a research scientist by Meta. + +# References + +[1] Nachwa Aboubakr, James L Crowley, and Rémi Ronfard. Recognizing manipulation actions from state-transformations. arXiv preprint arXiv:1906.05147, 2019. 1, 2 +[2] Jean-Baptiste Alayrac, Ivan Laptev, Josef Sivic, and Simon Lacoste-Julien. Joint discovery of object states and manipulation actions. In Proceedings of the IEEE International Conference on Computer Vision, pages 2127-2136, 2017. 1, 2, 3, 4, 6 +[3] Kumar Ashutosh, Rohit Girdhar, Lorenzo Torresani, and Kristen Grauman. Hiervl: Learning hierarchical videolanguage embeddings. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 6586-6597, 2023. 2 \ No newline at end of file diff --git a/2024/Learning Object State Changes in Videos_ An Open-World Perspective/images.zip b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..15d4700469d34d752aa18a1dcfa300309ba04250 --- /dev/null +++ b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:ce676a0dbe06f6607b689d2bcf0f77c5c79de85c6416520fdcc52b0da0fcf75f +size 531511 diff --git a/2024/Learning Object State Changes in Videos_ An Open-World Perspective/layout.json b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..b871a68d6edf3779351be754c1070276301ee491 --- /dev/null +++ b/2024/Learning Object State Changes in Videos_ An Open-World Perspective/layout.json @@ -0,0 +1,7590 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 78, + 103, + 515, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 78, + 103, + 515, + 121 + ], + "spans": [ + { + "bbox": [ + 78, + 103, + 515, + 121 + ], + "type": "text", + "content": "Learning Object State Changes in Videos: An Open-World Perspective" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 146, + 142, + 210, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 146, + 142, + 210, + 156 + ], + "spans": [ + { + "bbox": [ + 146, + 142, + 210, + 156 + ], + "type": "text", + "content": "Zihui Xue1,2" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 231, + 143, + 325, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 231, + 143, + 325, + 156 + ], + "spans": [ + { + "bbox": [ + 231, + 143, + 325, + 156 + ], + "type": "text", + "content": "Kumar Ashutosh1,2" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 350, + 142, + 445, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 350, + 142, + 445, + 156 + ], + "spans": [ + { + "bbox": [ + 350, + 142, + 445, + 156 + ], + "type": "text", + "content": "Kristen Grauman" + }, + { + "bbox": [ + 350, + 142, + 445, + 156 + ], + "type": "inline_equation", + "content": "^{1,2}" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 169, + 157, + 337, + 171 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 169, + 157, + 337, + 171 + ], + "spans": [ + { + "bbox": [ + 169, + 157, + 337, + 171 + ], + "type": "text", + "content": "1The University of Texas at Austin" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 361, + 157, + 425, + 171 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 361, + 157, + 425, + 171 + ], + "spans": [ + { + "bbox": [ + 361, + 157, + 425, + 171 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 361, + 157, + 425, + 171 + ], + "type": "text", + "content": "FAIR, Meta" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 143, + 199, + 192, + 211 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 199, + 192, + 211 + ], + "spans": [ + { + "bbox": [ + 143, + 199, + 192, + 211 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 45, + 224, + 290, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 224, + 290, + 464 + ], + "spans": [ + { + "bbox": [ + 45, + 224, + 290, + 464 + ], + "type": "text", + "content": "Object State Changes (OSCs) are pivotal for video understanding. While humans can effortlessly generalize OSC understanding from familiar to unknown objects, current approaches are confined to a closed vocabulary. Addressing this gap, we introduce a novel open-world formulation for the video OSC problem. The goal is to temporally localize the three stages of an OSC—the object's initial state, its transitioning state, and its end state—whether or not the object has been observed during training. Towards this end, we develop VIDOSC, a holistic learning approach that: (1) leverages text and vision-language models for supervisory signals to obviate manually labeling OSC training data, and (2) abstracts fine-grained shared state representations from objects to enhance generalization. Furthermore, we present HowToChange, the first open-world benchmark for video OSC localization, which offers an order of magnitude increase in the label space and annotation volume compared to the best existing benchmark. 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Introduction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 506, + 287, + 601 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 506, + 287, + 601 + ], + "spans": [ + { + "bbox": [ + 46, + 506, + 287, + 601 + ], + "type": "text", + "content": "In video understanding, the study of objects primarily revolves around tasks like recognition [16], detection [24], and tracking [8, 62], with the assumption that objects maintain a consistent visual appearance throughout the video. Yet, objects in video are often dynamic. They can undergo transformations that change their appearance, shape, and even topology. For example, a pineapple goes from whole to peeled to sliced, or wood is carved into a new shape." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 602, + 288, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 602, + 288, + 685 + ], + "spans": [ + { + "bbox": [ + 46, + 602, + 288, + 685 + ], + "type": "text", + "content": "Object State Changes (OSCs) [2, 15, 17, 22, 47, 50-52, 60, 64] add a critical dimension to video understanding. On the one hand, they provide insights into human actions—observing a piece of metal being shaped into a hook, for instance, implies the action of bending; observing an egg shell go from whole to broken implies the action of cracking. On the other hand, OSCs are essential" + } + ] + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 310, + 200, + 542, + 265 + ], + "blocks": [ + { + "bbox": [ + 310, + 200, + 542, + 265 + ], + "lines": [ + { + "bbox": [ + 310, + 200, + 542, + 265 + ], + "spans": [ + { + "bbox": [ + 310, + 200, + 542, + 265 + ], + "type": "image", + "image_path": "85f72c82d0ff670f54b9eb4f496b733dc97e95e3bcec96d6967775bb1b1a4d34.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 310, + 266, + 542, + 365 + ], + "blocks": [ + { + "bbox": [ + 310, + 266, + 542, + 365 + ], + "lines": [ + { + "bbox": [ + 310, + 266, + 542, + 365 + ], + "spans": [ + { + "bbox": [ + 310, + 266, + 542, + 365 + ], + "type": "image", + "image_path": "e49abcaa07332c67ed714d89c2ec36e0026b413512f6c05d00a99d3b2d38241f.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 374, + 546, + 453 + ], + "lines": [ + { + "bbox": [ + 304, + 374, + 546, + 453 + ], + "spans": [ + { + "bbox": [ + 304, + 374, + 546, + 453 + ], + "type": "text", + "content": "Figure 1. Top: The video OSC objective is to temporally localize an object's three states (i.e., initial, transitioning, end). Bottom: OSCs naturally exhibit a long tail. Certain OSCs, such as melting butter or marshmallow, are frequently showcased in instructional videos while others like melting jaggery might be rarely seen. We introduce an innovative open-world formulation that requires extrapolating to novel objects never encountered during training." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 460, + 546, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 546, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 546, + 581 + ], + "type": "text", + "content": "for assessing goal completion, in a way that is invariant to the specific procedure used. For instance, the readiness of cake batter signifies the completion of a mixing task, regardless of whether it was stirred by hand or a mechanical mixer. These core functionalities are instrumental for various real-world applications [5, 6, 12, 13, 20, 21, 66], ranging from AR/VR assistants [42] that guide users through complex tasks by monitoring object states, to robotic manipulation [9, 55] where understanding the state of objects is critical for task planning and failure recovery." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "type": "text", + "content": "However, the development of video OSC is still at a primitive stage. Existing approaches [1, 2, 15, 46, 50, 51, 58] assume a closed vocabulary, where each state transformation is associated with a limited set of objects—often just 1 or 2. For example, the concept of “melting” might be limited to familiar items like butter and marshmallow. Consequently, the learned models are only capable of identifying state changes for objects observed during training and stumble when presented with novel objects. In contrast, in real-world situations a single state transition like “melting” can be linked with a plethora of objects—some ubiquitous and" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 693, + 286, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 286, + 713 + ], + "type": "text", + "content": "1Project webpage: https://vision.cs.utexas.edu/projects/VidOSC/." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18493" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "content": "others rare. Importantly, there is an intrinsic connection that threads these OSC processes together. As humans, even if we have never encountered an unusual substance (e.g., jaggery) before, we can still understand that it is experiencing a \"melting\" process based on its visual transformation cues (see Fig. 1, bottom)." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 144, + 288, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 144, + 288, + 396 + ], + "spans": [ + { + "bbox": [ + 46, + 144, + 288, + 396 + ], + "type": "text", + "content": "In light of these limitations, we propose a novel open-world formulation of the video OSC problem. We formally characterize OSCs in videos in terms of three states that must be temporally localized: initial, transitioning, and end (see Fig. 1, top). In our open-world setting, there are known objects and novel objects. The model is only presented with known objects during training (e.g., frying chicken, frying onions). Then, it is evaluated on both known and novel objects (e.g., frying cauliflower). In addition to this fundamental open-world generalization, we also tackle a more comprehensive notion of the transitioning state. Specifically, our transitioning states encapsulate not only action-induced modifications to the object (e.g., peeling), but also passive transformations the object undergoes without human interference (e.g., melting) and edited-out transformations (e.g., the cake goes from raw to baked even if baked off camera). Though largely overlooked in existing approaches [1, 15, 46, 58], these cases are both common and technically interesting, since they force a model to reason about the effects of the core state change rather than search for evidence of a human actor carrying out the action." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 396, + 287, + 635 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 396, + 287, + 635 + ], + "spans": [ + { + "bbox": [ + 46, + 396, + 287, + 635 + ], + "type": "text", + "content": "Armed with this new problem formulation, we propose a holistic video OSC learning approach, anchored by two innovative ideas. First, we explore text and vision-language models (VLMs) for supervisory signals during training. We pioneer the use of textual state descriptions to generate a long tail of object state pseudo-labels, by leveraging the remarkable capabilities of VLMs [23, 44, 63] and large language models (LLMs) [40, 53, 54]. This strategy eliminates the need for exhaustive label collection for training data, facilitating large-scale model training. Second, to confront the open-world challenge, we propose object-agnostic state prediction, consisting of three key techniques: a shared state vocabulary to unify the label space across objects sharing the same state transition (e.g., melting butter and melting marshmallow), temporal modeling to grasp the progression of state changes over time, and object-centric features that better represent the objects during an OSC. These designs equip our model with the ability to generalize state understanding from known objects to novel ones. We term our approach VIDOSC." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 635, + 287, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 635, + 287, + 685 + ], + "spans": [ + { + "bbox": [ + 46, + 635, + 287, + 685 + ], + "type": "text", + "content": "Complementing this, we present a large-scale real-world dataset HowToChange. Sourced from the HowTo100M collection [36], it sets a new benchmark in the field of unprecedented scale and an authentic long-tail distribution, setting" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 306, + 72, + 545, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 133 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 133 + ], + "type": "text", + "content": "it apart from the constrained scope and closed-world setting of earlier benchmarks (see Table 1). Finally, experimental results demonstrate the efficacy of VIDOsc, surpassing the state-of-the-art in both traditional closed-world and novel open-world scenarios by a great margin." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 143, + 392, + 156 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 143, + 392, + 156 + ], + "spans": [ + { + "bbox": [ + 306, + 143, + 392, + 156 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 165, + 545, + 393 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 165, + 545, + 393 + ], + "spans": [ + { + "bbox": [ + 304, + 165, + 545, + 393 + ], + "type": "text", + "content": "Object State Changes Image-based methods explore the compositional nature of objects and their attributes, including zero-shot recognition of unseen combinations [22, 29, 33, 37-39, 41, 43], but do not consider the temporal progression of OSCs in video, which brings new challenges. Video-based methods develop human-centric models that leverage state change cues to facilitate action recognition [1, 15, 46, 58], or explore joint discovery of object states and actions [2, 50, 51]. Notably, all the existing methods assume a closed world, recognizing only the OSC categories (\"known\" objects) seen during training. Our approach distinguishes itself in three crucial ways: (1) we introduce a novel open-world3 formulation, where the objects encountered during evaluation can be entirely unseen during training; (2) we adopt an object-centric perspective, allowing for scenarios where OSCs occur with no observable human actions in the video; and (3) we propose to utilize the text modality and VLMs as supervisory signals, greatly scaling up model training and boosting performance." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 393, + 546, + 573 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 393, + 546, + 573 + ], + "spans": [ + { + "bbox": [ + 304, + 393, + 546, + 573 + ], + "type": "text", + "content": "Early datasets for video OSC capture a limited array of OSCs in fewer than 1,000 videos [2, 31]. The more recent ChangeIt dataset [50] marks an advance in dataset scale (34K videos), yet is still restricted to a small OSC vocabulary of 44 total object-state transitions. It lacks the scope to adequately test unseen objects, since most state changes coincide with only 1 or 2 objects across all the videos (see Table 1). Other datasets explore different aspects of video OSCs, including object state recognition [47], point-of-noreturn (PNR) frame localization [17], and object segmentation [52, 64], but they lack any temporal annotations of fine-grained OSC states needed for our task's evaluation. Our HowToChange dataset increases the OSC vocabulary space by an order of magnitude and allows for the first time rigorous study of the open-world temporal OSC challenge." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 574, + 545, + 694 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 574, + 545, + 694 + ], + "spans": [ + { + "bbox": [ + 304, + 574, + 545, + 694 + ], + "type": "text", + "content": "Vision and Language LLMs [40, 53, 54] have revolutionized various research fields with their exceptional performance across diverse applications. Building on this momentum, the use of web-scale image-text data has emerged as a powerful paradigm in computer vision, with powerful VLMs now advancing an array of image tasks, including zero-shot classification [44], detection [18], segmentation [32] and visual question answering [27, 28]. Similarly, joint video-text representation learning [3, 30, 36, 67] has been advanced by multimodal datasets like" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 46, + 693, + 287, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 693, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 693, + 287, + 713 + ], + "type": "text", + "content": "2Note that at test time, our model requires only the video, with no need for additional text, ensuring utmost flexibility and applicability." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 315, + 702, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 702, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 315, + 702, + 545, + 713 + ], + "type": "text", + "content": "also called \"unseen compositions\" in object-attribute learning [34, 37]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18494" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": "HowTo100M [36] and Ego4D [17], which offer large-scale collections of videos paired with their corresponding narratives. These datasets have also facilitated tasks like step discovery [11], localization in procedural activities [35] and long egocentric videos [45]. The vision-language multimodal cycle consistency loss proposed in [14] helps discover long-term temporal dynamics in video. In line with these developments, we propose to leverage the text accompanying instructional videos as well as existing high-performing VLMs to provide supervisory signals that guide the training of our video OSC model and allow learning for the open world." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 218, + 289, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 218, + 289, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 218, + 289, + 422 + ], + "type": "text", + "content": "Learning in an Open World The open world setting has received increasing attention, predominantly within the image domain for object recognition [4, 48], detection [10, 18, 25, 65] and object-attribute compositionality [29, 33, 37-39, 41, 43]. In the video domain, compositionality is advanced by the Something-Else dataset [34], where the training combinations of verbs and nouns do not overlap with the test set, sparking work on the dynamics of subject-object interactions [7, 34, 47]. More recent efforts leverage VLMs for zero-shot action recognition [7, 26, 57]. Concurrent work explores video object segmentation with state-changing objects [64] and recognition of novel object-state compositions for food chopped in different styles [47]. Despite these advances, temporal video OSC understanding in the open world remains unexplored. Our open-world formulation requires generalizing the temporal localization of fine-grained object states from known to novel objects." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 430, + 115, + 443 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 430, + 115, + 443 + ], + "spans": [ + { + "bbox": [ + 47, + 430, + 115, + 443 + ], + "type": "text", + "content": "3. Approach" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 450, + 287, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 450, + 287, + 498 + ], + "spans": [ + { + "bbox": [ + 46, + 450, + 287, + 498 + ], + "type": "text", + "content": "We present the VIDOSC framework for learning video OSCs, detailing the open-world formulation (Sec. 3.1), model design for object-agnostic state prediction (Sec. 3.2), and text-guided training scheme (Sec. 3.3)." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 504, + 212, + 517 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 504, + 212, + 517 + ], + "spans": [ + { + "bbox": [ + 47, + 504, + 212, + 517 + ], + "type": "text", + "content": "3.1. Video OSC in the Open World" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 522, + 287, + 679 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 522, + 287, + 679 + ], + "spans": [ + { + "bbox": [ + 46, + 522, + 287, + 679 + ], + "type": "text", + "content": "We begin by formally defining an object state change (OSC) in videos as a visually detectable transformation, where an object experiences a change that is not easily reversible, in line with [17]. We characterize an OSC category as an object combined with a specific state transition, such as \"chicken + shredding\", and delineate an OSC process through three distinct states: initial (precondition state), transitioning, and end (postcondition state).4 It is essential to highlight that we take an object-centric perspective: the \"transitioning state\" accounts for instances where the video depicts an active action applied to the object, as well as scenarios where the object undergoes a passive transformation absent of human intervention (e.g., melting, drying)." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 683, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 683, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 683, + 287, + 712 + ], + "type": "text", + "content": "4Due to real-world data variation, some videos may lack one of the OSC states, and there may be multiple segments in a video corresponding to the same state. Our formulation accounts for all these scenarios." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "text", + "content": "Given a video in which an object may be changing state, the objective is to temporally localize each of the three OSC states. Consistent with prior work [50, 51], we formulate the task as a frame-wise classification problem. Formally, a video sequence is represented by a temporal sequence of " + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "text", + "content": " feature vectors " + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "inline_equation", + "content": "\\mathbf{X} = \\{\\mathbf{x}_1,\\mathbf{x}_2,\\dots ,\\mathbf{x}_T\\}" + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "text", + "content": " denotes the video duration. The goal is to predict the OSC state label for each timepoint, denoted by " + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "inline_equation", + "content": "\\mathbf{Y} = \\{\\mathbf{y}_1,\\mathbf{y}_2,\\dots ,\\mathbf{y}_T\\}" + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "inline_equation", + "content": "\\mathbf{y}_t\\in \\{1,\\dots ,K + 1\\}" + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 72, + 545, + 204 + ], + "type": "text", + "content": " is the total number of OSC states, and there is one additional category representing the background class not associated with any OSC state." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "spans": [ + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": "Next, we propose an open-world problem formulation, capturing the intrinsic long-tail distribution observed in real-world scenarios. Consider " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": " state transitions, each paired with a set of associated objects, denoted by " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "\\mathbf{O}^n = \\{o_1^n,o_2^n,\\dots ,o_{m(n)}^n\\}" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": ", for " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "n = \\{1,2,\\dots ,N\\}" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "m(n)" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": " denotes the number of objects linked with the " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": "-th state transition. Within a specific state transition (like frying), certain objects in the set (such as chicken or onions) are frequently observed, while the combination of the same state transition with other objects (such as cauliflower) appear less often. Motivated by this inherent long-tail, we propose to split " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "\\mathbf{O}^n" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": " into two distinct subsets: " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathrm{known}}^n" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": " covering the common combinations observed during training, and " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathrm{novel}}^n" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": " comprising the infrequent combinations, which are unseen during training due to their rarity. During inference, the model is evaluated on the entire object set " + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "inline_equation", + "content": "\\mathbf{O}^n" + }, + { + "bbox": [ + 304, + 204, + 546, + 407 + ], + "type": "text", + "content": " for a comprehensive reflection of the open-world setting." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 413, + 484, + 426 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 413, + 484, + 426 + ], + "spans": [ + { + "bbox": [ + 306, + 413, + 484, + 426 + ], + "type": "text", + "content": "3.2. Object-Agnostic State Prediction" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 432, + 545, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 432, + 545, + 491 + ], + "spans": [ + { + "bbox": [ + 304, + 432, + 545, + 491 + ], + "type": "text", + "content": "To address the open-world challenges and ensure robust generalization to novel objects, VIDOSC integrates three key techniques: (1) a shared state vocabulary that consolidates the state label space; (2) temporal modeling within the video OSC model design; and (3) object-centric features." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 494, + 546, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 494, + 546, + 687 + ], + "spans": [ + { + "bbox": [ + 304, + 494, + 546, + 687 + ], + "type": "text", + "content": "Shared State Vocabulary The inherent link among different OSC categories is overlooked in prior work. Common practice involves developing separate models for each OSC category [2, 50] (e.g., one model exclusively for melting butter and another for melting chocolate), or using one single model that still treats every OSC as a distinct entity in the label space [51] (e.g., considering melted butter and melted chocolate as two separate end states). Such a formulation results in an extensive label set with " + }, + { + "bbox": [ + 304, + 494, + 546, + 687 + ], + "type": "inline_equation", + "content": "K = 3 \\times \\sum_{n=1}^{N} m(n)" + }, + { + "bbox": [ + 304, + 494, + 546, + 687 + ], + "type": "text", + "content": ", where 3 denotes the number of OSC states (i.e., initial, transitioning and end) and " + }, + { + "bbox": [ + 304, + 494, + 546, + 687 + ], + "type": "inline_equation", + "content": "\\sum_{n=1}^{N} m(n)" + }, + { + "bbox": [ + 304, + 494, + 546, + 687 + ], + "type": "text", + "content": " is the total number of OSC categories. This compartmentalized view can inadvertently hinder the model's generalization ability. Yet, on closer inspection, states across varied objects are intrinsically related. For instance, the \"melting\" principle remains consistent, even when applied to visually" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "text", + "content": "5Not all training videos may feature an OSC due to data collection noise, yet all evaluation videos are manually verified to include one." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18495" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 59, + 70, + 534, + 317 + ], + "blocks": [ + { + "bbox": [ + 59, + 70, + 534, + 317 + ], + "lines": [ + { + "bbox": [ + 59, + 70, + 534, + 317 + ], + "spans": [ + { + "bbox": [ + 59, + 70, + 534, + 317 + ], + "type": "image", + "image_path": "cd72c8c8e56e856913a378b48dd2543d852b875733f4176b2040f195b13f267f.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 324, + 548, + 392 + ], + "lines": [ + { + "bbox": [ + 46, + 324, + 548, + 392 + ], + "spans": [ + { + "bbox": [ + 46, + 324, + 548, + 392 + ], + "type": "text", + "content": "Figure 2. Our proposed VIDOSC framework: (a) Mining for OSC examples (Sec. 3.3): We leverage ASR transcriptions paired with videos and the capabilities of LLM to automatically mine OSC examples. (b) Pseudo Label Generation (Sec. 3.3): We utilize textual state descriptions and a VLM for supervisory signals during training; (c) Model Training (Sec. 3.2): We develop a video model for object-agnostic state prediction. (d) Model Testing (Sec. 3.1): We propose an open-world formulation, evaluating on both known and novel OSCs. Notably, while we employ the text modality to guide model training, our model is purely video-based and requires no text input at the test phase, ensuring maximum flexibility and applicability. Ground truth for the test set is manually annotated." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 412, + 288, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 412, + 288, + 496 + ], + "spans": [ + { + "bbox": [ + 46, + 412, + 288, + 496 + ], + "type": "text", + "content": "distinct objects like butter and chocolate. This motivates us to group OSC labels that share the same state transition as one, and train a single model per state transition.6 By adopting object-agnostic OSC labels, we encourage the model to learn state representations shared by visually different objects, and thus facilitate the transfer from known to novel objects." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "spans": [ + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "text", + "content": "Temporal Modeling Recognizing that state changes unfold over time, it is important to capture the temporal dynamics in videos. An object's state at any frame, be it initial, transitioning, or end, is often best understood in the context of preceding and succeeding frames. Contrary to prior works [2, 50, 51] that rely on isolated frameswise modeling without considering the temporal progression of video OSCs, we address this gap by proposing a temporally-aware model design. As illustrated in Fig. 2(c), we adopt an encoder-decoder architecture. For the encoding phase, input video features " + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "inline_equation", + "content": "\\mathbf{X} = \\{\\mathbf{x}_1,\\mathbf{x}_2,\\dots ,\\mathbf{x}_T\\}" + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "text", + "content": " are first projected using an MLP " + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{project}}" + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "text", + "content": " and augmented with sinusoidal positional embeddings, " + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}_{\\mathrm{pos}}" + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "text", + "content": ". Subsequently, a transformer encoder [56] " + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{transformer}}" + }, + { + "bbox": [ + 46, + 499, + 287, + 679 + ], + "type": "text", + "content": " is adopted to capture the temporal dynamics among these features, yield" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "type": "text", + "content": "ing " + }, + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "type": "inline_equation", + "content": "\\mathbf{Z} = f_{\\mathrm{transformer}}(f_{\\mathrm{project}}(\\mathbf{X}) + \\mathbf{Z}_{\\mathrm{pos}})" + }, + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "type": "text", + "content": ". For the decoding phase, a MLP decoder " + }, + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "type": "text", + "content": ", maps these temporally-aware hidden representations to OSC state predictions: " + }, + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "type": "inline_equation", + "content": "\\tilde{\\mathbf{Y}} = g(\\mathbf{Z})" + }, + { + "bbox": [ + 309, + 412, + 545, + 544 + ], + "type": "text", + "content": ". See Sec. 5 for architecture and training details. This design ensures that when predicting the state for a frame, the model has assimilated temporal context from the entire sequence. Essentially, our model exploits the fact that the dynamics of the state change has greater invariance to the object category than how the object looks, emphasizing temporal object transformations over objects' static appearances, and thereby enhancing generalization to novel OSCs." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "type": "text", + "content": "Object-Centric Features Finally, we discuss how to better represent \"object\" features in the problem. In many scenarios, due to camera placement and framing, the object going through a state transition might only occupy a small portion of the frame, surrounded by other visual elements such as background, people, or bystander objects. Recognizing this challenge, we introduce an enhancement to our model's input features " + }, + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{X}" + }, + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "type": "text", + "content": " to emphasize the object of interest. To be specific, we leverage an off-the-shelf detector [49] to identify the active object (i.e., the object being manipulated) region at each timepoint " + }, + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "type": "text", + "content": ", yielding feature " + }, + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_t^{obj}" + }, + { + "bbox": [ + 306, + 545, + 546, + 713 + ], + "type": "text", + "content": " that centers on the object (see bounding boxes in Fig. 2(c)). The input feature is then constructed as a concatenation of the original global feature and the localized object-centric feature," + } + ] + } + ], + "index": 5 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 47, + 693, + 287, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 287, + 712 + ], + "type": "text", + "content": "See Supp. for the multi-task model variant, where we develop one unified model for all state transitions." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18496" + } + ] + } + ], + "index": 7 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 71, + 287, + 109 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 71, + 287, + 109 + ], + "spans": [ + { + "bbox": [ + 46, + 71, + 287, + 109 + ], + "type": "text", + "content": "i.e., " + }, + { + "bbox": [ + 46, + 71, + 287, + 109 + ], + "type": "inline_equation", + "content": "\\mathbf{X} = \\{\\left[\\mathbf{x}_t,\\mathbf{x}_t^{obj}\\right]\\}_{t = 1}^T" + }, + { + "bbox": [ + 46, + 71, + 287, + 109 + ], + "type": "text", + "content": ". By emphasizing the object in this manner, our model is better positioned to discern the intricate state changes and provide more informed predictions." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 115, + 214, + 129 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 115, + 214, + 129 + ], + "spans": [ + { + "bbox": [ + 47, + 115, + 214, + 129 + ], + "type": "text", + "content": "3.3. Text and VLMs as Supervision" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 133, + 287, + 170 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 133, + 287, + 170 + ], + "spans": [ + { + "bbox": [ + 46, + 133, + 287, + 170 + ], + "type": "text", + "content": "To scale up training and ensure broad generalization, we propose a novel training pipeline that leverages LLMs and VLMs for OSC mining and pseudo-labeling." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 171, + 288, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 171, + 288, + 361 + ], + "spans": [ + { + "bbox": [ + 46, + 171, + 288, + 361 + ], + "type": "text", + "content": "Mining for OSC examples Utilizing a vast collection of \"how-to\" instructional videos as the training source, we develop an automated mining process to capture the rich, real-world variability of OSCs. The motivation is that instructional videos usually have accompanying Automatic Speech Recognition (ASR) transcriptions that offer valuable OSC cues. For example, a speaker mentioning, \"so just get your rotisserie chicken and shred it up\" suggests that the chicken may undergo a state transition of shredding in the video. Leveraging this fact, we employ LLAMA2 [54] to analyze ASR transcriptions for identifying candidate videos and their associated OSC categories. This text mining stage allows us to corral a long tail of OSCs, discovering likely state change terms—even if rare—from the free-form natural language narrations given by how-to instructors in the training videos. See Fig. 2 (a)." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "spans": [ + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "type": "text", + "content": "Pseudo Label Generation Next, to negate the need of manually labeling large-scale training data, we propose a novel pseudo-labeling pipeline facilitated by VLMs. From the identified OSC category (e.g., shredding chicken), we form three textual state descriptions for its initial, transitioning, and end states (e.g., whole chicken, shredding chicken, and shredded chicken). We then adopt both the vision and language encoder from a well-trained VLM (we experiment with CLIP [44] and VideoClip [61]) to compute the cross-modal similarity between every frame in training video and the three state descriptions, producing a score matrix " + }, + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "type": "inline_equation", + "content": "\\mathbf{S} \\in \\mathbb{R}^{T \\times 3}" + }, + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "type": "text", + "content": ". The pseudo label " + }, + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "type": "inline_equation", + "content": "\\hat{y}_t" + }, + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "type": "text", + "content": " at timepoint " + }, + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 365, + 288, + 520 + ], + "type": "text", + "content": " is then assigned based on this score matrix:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 533, + 293, + 589 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 533, + 293, + 589 + ], + "spans": [ + { + "bbox": [ + 47, + 533, + 293, + 589 + ], + "type": "interline_equation", + "content": "\\hat {y} _ {t} = \\left\\{ \\begin{array}{l l} \\text {B a c k g r o u n d} & \\text {i f} \\sum (\\mathbf {S} [ t,: ]) < \\tau \\\\ \\text {I n i t i a l} & \\text {e l i f} \\mathbf {S} [ t, 0 ] - \\mathbf {S} [ t, 1 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 0 ] - \\mathbf {S} [ t, 2 ] > \\delta \\\\ \\text {T r a n s i t i o n i n g} & \\text {e l i f} \\mathbf {S} [ t, 1 ] - \\mathbf {S} [ t, 0 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 1 ] - \\mathbf {S} [ t, 2 ] > \\delta \\\\ \\text {E n d} & \\text {e l i f} \\mathbf {S} [ t, 2 ] - \\mathbf {S} [ t, 0 ] > \\delta \\text {a n d} \\mathbf {S} [ t, 2 ] - \\mathbf {S} [ t, 1 ] > \\delta \\\\ \\text {A m b i g u o u s} & \\text {o t h e r w i s e} \\end{array} \\right.", + "image_path": "e9fa79bd7f333737867c4b4940b6f8d20414791a405701654cbbde720bc027fe.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 594, + 286, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 286, + 665 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 286, + 665 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 594, + 286, + 665 + ], + "type": "inline_equation", + "content": "\\delta" + }, + { + "bbox": [ + 46, + 594, + 286, + 665 + ], + "type": "text", + "content": " is the threshold that separates states and " + }, + { + "bbox": [ + 46, + 594, + 286, + 665 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 46, + 594, + 286, + 665 + ], + "type": "text", + "content": " is the threshold that differentiates between states and background. Essentially if the VLM scores some state more strongly than the other two—and the cumulative confidence score of all states is high—then it is adopted as the pseudo label. Otherwise it is omitted as ambiguous. See Fig. 2(b)." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "type": "text", + "content": "To further refine these labels, we enforce a causal ordering constraint. Given the inherent progression of OSCs, the anticipated order is initial states followed by transitioning states, and finally, the end states. Any frame whose pseudo" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 312, + 76, + 541, + 157 + ], + "blocks": [ + { + "bbox": [ + 312, + 76, + 541, + 157 + ], + "lines": [ + { + "bbox": [ + 312, + 76, + 541, + 157 + ], + "spans": [ + { + "bbox": [ + 312, + 76, + 541, + 157 + ], + "type": "image", + "image_path": "e01633ea3975b12a759c00349c03523047c529023ee3c4bf9aacc2d2f5d4d340.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 312, + 171, + 539, + 255 + ], + "blocks": [ + { + "bbox": [ + 312, + 171, + 539, + 255 + ], + "lines": [ + { + "bbox": [ + 312, + 171, + 539, + 255 + ], + "spans": [ + { + "bbox": [ + 312, + 171, + 539, + 255 + ], + "type": "image", + "image_path": "4da85303989aab31667cb729883906822b1a233cff069012172f5a3b7eed6a67.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 267, + 545, + 322 + ], + "lines": [ + { + "bbox": [ + 305, + 267, + 545, + 322 + ], + "spans": [ + { + "bbox": [ + 305, + 267, + 545, + 322 + ], + "type": "text", + "content": "Figure 3. Ground truth annotation distribution across 20 state transitions (top) and 134 objects (bottom) in HowToChange (Evaluation). In line with our open-world formulation, annotations cover a diverse range of object-state transition combinations, categorized into known and novel OSCs." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 330, + 545, + 402 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 330, + 545, + 402 + ], + "spans": [ + { + "bbox": [ + 305, + 330, + 545, + 402 + ], + "type": "text", + "content": "label does not respect this natural progression is re-assigned to the ambiguous category. Our training employs a cross-entropy loss between pseudo label " + }, + { + "bbox": [ + 305, + 330, + 545, + 402 + ], + "type": "inline_equation", + "content": "\\hat{y}_t" + }, + { + "bbox": [ + 305, + 330, + 545, + 402 + ], + "type": "text", + "content": " and the corresponding model prediction " + }, + { + "bbox": [ + 305, + 330, + 545, + 402 + ], + "type": "inline_equation", + "content": "\\tilde{y}_t" + }, + { + "bbox": [ + 305, + 330, + 545, + 402 + ], + "type": "text", + "content": ", with ambiguous frames excluded to maintain clarity and distinction among the state labels. See Section 4.2 in Supp. for detailed pseudo label analysis." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 415, + 463, + 428 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 415, + 463, + 428 + ], + "spans": [ + { + "bbox": [ + 306, + 415, + 463, + 428 + ], + "type": "text", + "content": "4. The HowToChange Dataset" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 436, + 545, + 507 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 436, + 545, + 507 + ], + "spans": [ + { + "bbox": [ + 304, + 436, + 545, + 507 + ], + "type": "text", + "content": "Existing OSC datasets fall short in capturing the open-world's diversity and long-tail distribution of OSCs. To address this gap, we introduce HowToChange. It encompasses varied state transitions coupled with a diverse range of objects, providing an authentic reflection of their real-world frequency—from the commonplace to the rare." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 510, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 546, + 713 + ], + "type": "text", + "content": "Data Collection The HowTo100M collection [36] contains a wealth of instructional videos that often feature OSCs and is particularly suitable for this task. We specifically focus on the HowTo100M Food & Entertaining category because (1) it constitutes a third of the entire HowTo100M videos, (2) cooking tasks offer a wealth of objects, tools, and state changes, providing an excellent test bed for open-world OSC, and (3) in cooking activities a single state transition can often be associated with a varied range of objects, opening the door to learning compositionality. (Note, we also experiment with non-cooking domains below.) We process a total of 498,475 videos and 11,390,287 ASR transcriptions with LLAMA2. From the responses, we identify the most frequently seen state transitions and objects associated with them to establish an OSC vocabulary, resulting in 134 objects, 20 state transitions, and 409 unique OSCs. The number of objects associated with each state transition " + }, + { + "bbox": [ + 304, + 510, + 546, + 713 + ], + "type": "inline_equation", + "content": "(m(n))" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18497" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 70, + 288, + 162 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 288, + 162 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 288, + 162 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 288, + 162 + ], + "type": "table", + "html": "
Datasets# Obj# ST# OSCObjPer# VideosGT Label?
Alayrac et al. [2]5671.2630✓
Task-Fluent [31]2514322.3809✓
ChangeIt (Training) [50]4227441.634,428✗
ChangeIt (Evaluation) [50]4227441.6667✓
HowToChange (Training)1222031815.936,075✗
HowToChange (Evaluation)1342040920.55,424✓
", + "image_path": "e1882e341191d5592c5849e00edc0d8ed6d967dd54696108d8d3182670d9d8b0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 46, + 170, + 287, + 247 + ], + "lines": [ + { + "bbox": [ + 46, + 170, + 287, + 247 + ], + "spans": [ + { + "bbox": [ + 46, + 170, + 287, + 247 + ], + "type": "text", + "content": "Table 1. Comparison with existing video datasets focusing on object states. 'Obj' and 'ST' represent objects and state transitions, respectively. 'ObjPer' denotes the average number of objects associated with each state transition; higher values indicate more need to generalization across objects. We present the first open-world benchmark for temporal video OSC, with an order of magnitude increase in OSC vocabulary and annotation volume." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 255, + 287, + 316 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 255, + 287, + 316 + ], + "spans": [ + { + "bbox": [ + 46, + 255, + 287, + 316 + ], + "type": "text", + "content": "spans from 6 for “zesting” to 55 for “chopping”. The state transitions applied to each object vary from 1 to 15, with onions being the most versatile. In total, we identify 36,075 videos for the training set of HowToChange, with an average duration of 41.2 seconds." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 318, + 287, + 426 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 318, + 287, + 426 + ], + "spans": [ + { + "bbox": [ + 46, + 318, + 287, + 426 + ], + "type": "text", + "content": "Data Splits In line with our open-world formulation, we divide the 409 identified OSCs into two disjoint subsets based on their frequency of occurrence. Within each state transition, we categorize the top " + }, + { + "bbox": [ + 46, + 318, + 287, + 426 + ], + "type": "inline_equation", + "content": "75\\%" + }, + { + "bbox": [ + 46, + 318, + 287, + 426 + ], + "type": "text", + "content": " frequent objects as known and the bottom " + }, + { + "bbox": [ + 46, + 318, + 287, + 426 + ], + "type": "inline_equation", + "content": "25\\%" + }, + { + "bbox": [ + 46, + 318, + 287, + 426 + ], + "type": "text", + "content": " as novel. This yields a total of 318 known OSCs that are seen during training and testing, spanning 20 state transitions associated with 122 objects, and 91 novel OSCs that are only seen during testing, encompassing the same transitions across 58 objects." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 428, + 287, + 656 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 428, + 287, + 656 + ], + "spans": [ + { + "bbox": [ + 46, + 428, + 287, + 656 + ], + "type": "text", + "content": "Ground Truth Label Collection (Evaluation Set) To facilitate thorough evaluation, we obtain manual annotations for a subset of 5,424 videos from the collected dataset. The annotation workflow is as follows: each annotator is presented with a video segment along with an OSC category that was previously identified by LLAMA2. The annotator has the option to reject the video segment if it does not contain the specified OSC. Otherwise, they label the time ranges corresponding to the initial, transitioning, and end states of the OSC. Adhering to our object-centric emphasis, annotators are instructed to label based on the visual changes of the object, rather than human-centric actions, and exclude time ranges where the object of interest is not visible, ensuring clean and focused temporal labels. Fig. 3 provides the distribution of annotated videos. On average, we collect 271 annotations per state transition, with a video duration of 41.5 seconds, and " + }, + { + "bbox": [ + 46, + 428, + 287, + 656 + ], + "type": "inline_equation", + "content": "12.9\\%" + }, + { + "bbox": [ + 46, + 428, + 287, + 656 + ], + "type": "text", + "content": " of videos belong to the novel category. The entire annotation process required around 1,507 hours by 30 professional annotators." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 658, + 287, + 683 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 658, + 287, + 683 + ], + "spans": [ + { + "bbox": [ + 47, + 658, + 287, + 683 + ], + "type": "text", + "content": "Dataset Comparison Table 1 compares HowToChange with existing video datasets on temporal OSC understand-" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 72, + 545, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 228 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 228 + ], + "type": "text", + "content": "ing. HowToChange offers an unprecedented scale—with 9.3x more OSC categories and 8.1x more annotated video instances compared to the previous largest collection [50]. Furthermore, notably, in prior datasets, each state transition is typically coupled with 1 or 2 objects, preventing subsequent models from generalizing to new objects, as we will see in results. In contrast, HowToChange pioneers the open-world formulation, presenting a much broader range of objects associated with each state transition—from 6 to 55 objects per state transition, and averaging 20. This facilitates the development of models with generalized OSC understanding. Please see Supp. for full data collection and annotation details." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 239, + 387, + 253 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 239, + 387, + 253 + ], + "spans": [ + { + "bbox": [ + 306, + 239, + 387, + 253 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 261, + 545, + 476 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 261, + 545, + 476 + ], + "spans": [ + { + "bbox": [ + 304, + 261, + 545, + 476 + ], + "type": "text", + "content": "Datasets In addition to our new HowToChange dataset, we also evaluate on ChangeIt [50] due to its expansive data scale (34K videos spanning many activities) and high relevance to our task. Beyond the conventional split of ChangeIt, we propose a new split tailored to our open-world formulation. Specifically, from the 44 available OSC categories in ChangeIt, we concentrate on the 25 categories where each state transition is paired with more than one object. With those, we form the \"ChangeIt (open-world)\" subset that comprises 8 state transitions and 25 objects. Within each state transition, objects are randomly divided into known and novel categories, yielding 13 known OSC categories for training and 12 novel OSC categories exclusively reserved for evaluation. A detailed breakdown of this split can be found in Supp. To sum up, our evaluation encompasses: ChangeIt; ChangeIt (open-world); and How-ToChange, offering a comprehensive setup in both closed-world and open-world scenarios." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 479, + 545, + 562 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 479, + 545, + 562 + ], + "spans": [ + { + "bbox": [ + 304, + 479, + 545, + 562 + ], + "type": "text", + "content": "Evaluation For ChangeIt and ChangeIt (open-world), we adhere to the original dataset's evaluation protocol [50], reporting action and state precision@1 as the evaluation metrics. For our dataset, besides precision@1, which evaluates a single frame for each state within a video, we advocate for the use of F1 score and precision over all frames to ensure a more holistic evaluation." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 565, + 545, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 565, + 545, + 685 + ], + "spans": [ + { + "bbox": [ + 304, + 565, + 545, + 685 + ], + "type": "text", + "content": "Baselines We compare our approach with four baselines across two categories: (a) self-supervised approaches on identifying object states enforced by the causal ordering constraint: LookForTheChange [50] trains a dedicated model for each OSC category, while MultiTaskChange [51] evolves this into a multi-task approach8, catering to several OSCs concurrently; (b) zero-shot VLMs: image-based CLIP [44], video-based VideoCLIP [61] and InternVideo [59]. All baselines in (a) use the same training data as our model, whereas the zero-shot models (b) are directly" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "type": "text", + "content": "Our training is purely guided by a VLM and requires no ground truth labels. The annotations are reserved exclusively for evaluation." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "text", + "content": "To ensure a thorough evaluation, we train both single-task and multitask variants of our approach. See Supp. for a detailed discussion." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18498" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 76, + 70, + 518, + 168 + ], + "blocks": [ + { + "bbox": [ + 76, + 70, + 518, + 168 + ], + "lines": [ + { + "bbox": [ + 76, + 70, + 518, + 168 + ], + "spans": [ + { + "bbox": [ + 76, + 70, + 518, + 168 + ], + "type": "table", + "html": "
MethodChangeItChangeIt (open-world)HowToChange
State Prec.@1Action Prec.@1State Prec.@1 known@1 novelAction Prec.@1 known@1 novelF1 (%)Prec (%)Prec.@1 (%)
knownnovelknownnovelknownnovel
CLIP [44]0.300.630.290.290.710.7026.925.427.326.647.547.5
VideoCLIP [61]0.330.590.250.240.620.5536.634.339.738.548.344.8
InternVideo [59]0.270.570.290.250.600.6129.929.531.430.846.946.3
LookForTheChange [50]0.350.680.360.250.770.6830.328.732.530.037.236.1
MultiTaskChange [51]0.490.800.410.220.720.6233.929.938.534.143.138.8
VIDOSC (ours)0.570.840.560.480.890.8246.443.146.643.760.758.2
", + "image_path": "b0dfeba61b83d83f2d110f421e9d96d3eebe3c208056ca3a60e2807d1b1fbefb.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 176, + 547, + 199 + ], + "lines": [ + { + "bbox": [ + 46, + 176, + 547, + 199 + ], + "spans": [ + { + "bbox": [ + 46, + 176, + 547, + 199 + ], + "type": "text", + "content": "Table 2. Results on ChangeIt, ChangeIt (open-world), and HowToChange. VIDOSC outperforms all approaches in both closed-world and open-world scenarios, across known and novel OSCs." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 61, + 209, + 531, + 411 + ], + "blocks": [ + { + "bbox": [ + 61, + 209, + 531, + 411 + ], + "lines": [ + { + "bbox": [ + 61, + 209, + 531, + 411 + ], + "spans": [ + { + "bbox": [ + 61, + 209, + 531, + 411 + ], + "type": "image", + "image_path": "a4de4c0b17e3f8aa325e58f3a72965853b684d32c79cfd0dcd3eebf335dfd28e.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 426, + 546, + 461 + ], + "lines": [ + { + "bbox": [ + 46, + 426, + 546, + 461 + ], + "spans": [ + { + "bbox": [ + 46, + 426, + 546, + 461 + ], + "type": "text", + "content": "Figure 4. Top-1 frame predictions given by VIDOSC for the initial, transitioning, and end states, on ChangeIt (open-world) (first 2 rows) and HowToChange (last 2 rows). VIDOSC not only accurately localizes the three fine-grained states for known OSCs, but also generalizes this understanding to novel objects, such as cauliflower and capsicum, which are not observed during training." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 481, + 214, + 493 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 481, + 214, + 493 + ], + "spans": [ + { + "bbox": [ + 46, + 481, + 214, + 493 + ], + "type": "text", + "content": "evaluated on the test set with no training." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 495, + 288, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 495, + 288, + 662 + ], + "spans": [ + { + "bbox": [ + 46, + 495, + 288, + 662 + ], + "type": "text", + "content": "Implementation Videos are sampled at one frame per second. Each one-second video segment gets assigned to an OSC state label, and is encoded by InternVideo [59], a general video foundation model (which is kept frozen for training efficiency). Our video model consists of a 3-layer transformer with a hidden dimension of 512 and 4 attention heads as the encoder and a 1-layer MLP as the decoder. Consistent with prior work [50, 51], our model predicts the OSC state label (i.e., initial, transitioning, end state, or background) for a video, assuming the video OSC category is known (say from a recognition model's output or a user's specific query). While the standard output does not include the state transition name, our multi-task version detailed in Supp. is capable of this." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "type": "text", + "content": "Main Results Table 2 presents results on all three datasets. VIDOSC outperforms all approaches in both traditional closed-world and our newly introduced open-world settings. The large performance gains—as much as " + }, + { + "bbox": [ + 46, + 665, + 287, + 715 + ], + "type": "inline_equation", + "content": "9.6\\%" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 481, + 545, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 481, + 545, + 685 + ], + "spans": [ + { + "bbox": [ + 304, + 481, + 545, + 685 + ], + "type": "text", + "content": "jumps in precision vs. the next best method—underscore the effectiveness of two pivotal components in VIDOSC. First, its use of text and VLMs for supervisory signals during training: particularly on novel OSCs, VIDOSC extracts meaningful cues from the video modality to refine pseudo labels from VLMs, and ultimately surpasses the VLM baselines. Second, our model for object-agnostic state prediction, designed for the open-world context, effectively narrows the gap between known and novel OSCs. For instance, on ChangeIt (open-world), MultiTaskChange [51] experiences a " + }, + { + "bbox": [ + 304, + 481, + 545, + 685 + ], + "type": "inline_equation", + "content": "19\\%" + }, + { + "bbox": [ + 304, + 481, + 545, + 685 + ], + "type": "text", + "content": " decline in state precision@1 while VIDOSC has only a " + }, + { + "bbox": [ + 304, + 481, + 545, + 685 + ], + "type": "inline_equation", + "content": "8\\%" + }, + { + "bbox": [ + 304, + 481, + 545, + 685 + ], + "type": "text", + "content": " drop. Note that we observe a more pronounced performance drop of all approaches on ChangeIt (open-world) than on HowToChange due to its limited number of objects available per state transition. These results also point to the potential for future development in bridging the known and novel OSC performance gap." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 689, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 545, + 715 + ], + "type": "text", + "content": "Qualitative Results Fig. 4 presents VIDOSC's top-1 frame predictions on ChangeIt (open-world) and HowToChange," + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18499" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 70, + 287, + 182 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 287, + 182 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 287, + 182 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 287, + 182 + ], + "type": "image", + "image_path": "052c79eb56d0e2490c4c61368a040adef20b2425421b7bb9ad80c0a81cf123c1.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 191, + 288, + 258 + ], + "lines": [ + { + "bbox": [ + 46, + 191, + 288, + 258 + ], + "spans": [ + { + "bbox": [ + 46, + 191, + 288, + 258 + ], + "type": "text", + "content": "Figure 5. Comparison of model predictions across a test video depicting the OSC of \"slicing shallot\" on HowToChange. The x-axis represents temporal progression through the video. VIDOSC gives temporally smooth and coherent predictions that best align with the ground truth, significantly outperforming baselines in capturing the video's global temporal context." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 67, + 262, + 268, + 339 + ], + "blocks": [ + { + "bbox": [ + 67, + 262, + 268, + 339 + ], + "lines": [ + { + "bbox": [ + 67, + 262, + 268, + 339 + ], + "spans": [ + { + "bbox": [ + 67, + 262, + 268, + 339 + ], + "type": "table", + "html": "
Shared StateTemporal ModelingObject CentricPrec.@1 (%)
knownnovelΔ
X✓✓58.553.35.2
✓X✓52.948.24.7
✓✓X59.856.73.1
✓✓✓60.758.22.5
", + "image_path": "4ad900709227f4128abf657df0aa04b0eca6a8256818d8f6b3f57481b97d342a.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 347, + 287, + 369 + ], + "lines": [ + { + "bbox": [ + 46, + 347, + 287, + 369 + ], + "spans": [ + { + "bbox": [ + 46, + 347, + 287, + 369 + ], + "type": "text", + "content": "Table 3. Ablation Study. " + }, + { + "bbox": [ + 46, + 347, + 287, + 369 + ], + "type": "inline_equation", + "content": "\\Delta" + }, + { + "bbox": [ + 46, + 347, + 287, + 369 + ], + "type": "text", + "content": " denotes the performance gap between known OSCs and novel OSCs." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 376, + 288, + 568 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 376, + 288, + 568 + ], + "spans": [ + { + "bbox": [ + 46, + 376, + 288, + 568 + ], + "type": "text", + "content": "across both known and novel OSCs. Notably, despite never seeing objects such as cauliflower and capsicum during training, VIDOSC effectively leverages visual state change cues and correctly localizes the three states of these objects going through OSCs, demonstrating its strong generalization capability. For a more holistic view, Fig. 5 compares VIDOSC's frame-by-frame predictions with all baselines for a given test video. VIDOSC provides temporally coherent predictions, smoothly progressing through the OSC states in the natural order (i.e., from initial to transitioning then end). In contrast, baseline approaches often yield fragmented and inconsistent predictions, indicating a lack of understanding of the video's global temporal context, primarily due to their reliance on frame-wise modeling. See Supp. and Supp. video for more qualitative examples and VIDOSC's interpretability on object relations." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "text", + "content": "Ablation To further dissect the performance gains brought by our three model design techniques (i.e., shared state vocabulary, temporal modeling, and object-centric features), we conduct an ablation study, removing one component at a time. Table 3 confirms the essential role of each element. A shared state vocabulary is particularly crucial in the open-world context, as its absence increases the gap between known and novel OSCs from " + }, + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "inline_equation", + "content": "2.5\\%" + }, + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "inline_equation", + "content": "5.2\\%" + }, + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "text", + "content": ". Furthermore, temporal modeling provides a substantial performance boost, and object-centric features offer further gains. See Supp. for an additional analysis of VIDOSC's performance with different pseudo labels." + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 309, + 71, + 386, + 131 + ], + "blocks": [ + { + "bbox": [ + 309, + 71, + 386, + 131 + ], + "lines": [ + { + "bbox": [ + 309, + 71, + 386, + 131 + ], + "spans": [ + { + "bbox": [ + 309, + 71, + 386, + 131 + ], + "type": "image", + "image_path": "9d1f32e0778c6df3c3e7faeacd7aacc43fb180db810cdae57d06f58d29ee3056.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 388, + 72, + 463, + 131 + ], + "blocks": [ + { + "bbox": [ + 388, + 72, + 463, + 131 + ], + "lines": [ + { + "bbox": [ + 388, + 72, + 463, + 131 + ], + "spans": [ + { + "bbox": [ + 388, + 72, + 463, + 131 + ], + "type": "image", + "image_path": "d89bd13c9576ccd67aa20a3fa41ada55cb08132f5feb3318e28edb545b528211.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 466, + 72, + 541, + 131 + ], + "blocks": [ + { + "bbox": [ + 466, + 72, + 541, + 131 + ], + "lines": [ + { + "bbox": [ + 466, + 72, + 541, + 131 + ], + "spans": [ + { + "bbox": [ + 466, + 72, + 541, + 131 + ], + "type": "image", + "image_path": "a3095c4a99ce8a77e781dfab0a0c1613c254747cddaa7fb10ab02a0e869a0f60.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 310, + 132, + 386, + 182 + ], + "blocks": [ + { + "bbox": [ + 310, + 132, + 386, + 182 + ], + "lines": [ + { + "bbox": [ + 310, + 132, + 386, + 182 + ], + "spans": [ + { + "bbox": [ + 310, + 132, + 386, + 182 + ], + "type": "image", + "image_path": "5e899bce65443ad6d413bb490e5e7e1e760d018cb93e860bd9525f99ce79f28b.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 388, + 133, + 463, + 182 + ], + "blocks": [ + { + "bbox": [ + 388, + 133, + 463, + 182 + ], + "lines": [ + { + "bbox": [ + 388, + 133, + 463, + 182 + ], + "spans": [ + { + "bbox": [ + 388, + 133, + 463, + 182 + ], + "type": "image", + "image_path": "f49e65cdda0833b854e58f203dced4b1d98da138bcfc32f653ee03b85079de69.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 466, + 133, + 541, + 182 + ], + "blocks": [ + { + "bbox": [ + 466, + 133, + 541, + 182 + ], + "lines": [ + { + "bbox": [ + 466, + 133, + 541, + 182 + ], + "spans": [ + { + "bbox": [ + 466, + 133, + 541, + 182 + ], + "type": "image", + "image_path": "b724d6f0c51be04b39124d41241ba2036473264517014d40a6f5b6708e8c0441.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 310, + 182, + 386, + 235 + ], + "blocks": [ + { + "bbox": [ + 310, + 182, + 386, + 235 + ], + "lines": [ + { + "bbox": [ + 310, + 182, + 386, + 235 + ], + "spans": [ + { + "bbox": [ + 310, + 182, + 386, + 235 + ], + "type": "image", + "image_path": "013cfe0bda99f477cca63a310e917ddb576e9060509a0ff8aa44711c37e7e5a0.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 243, + 545, + 321 + ], + "lines": [ + { + "bbox": [ + 304, + 243, + 545, + 321 + ], + "spans": [ + { + "bbox": [ + 304, + 243, + 545, + 321 + ], + "type": "text", + "content": "Figure 6. Frame retrieval on the HowToChange test set. Given a query frame showcasing a novel OSC at its initial state, VIDOSC retrieves the nearest and furthest frame among all known OSCs at their end states. The closest post-OSC frame follows the transition trajectory of the query while the furthest post-OSC frame depicts a substantially different object, demonstrating VIDOSC's capability to generalize the OSC progression for novel objects." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 388, + 182, + 463, + 235 + ], + "blocks": [ + { + "bbox": [ + 388, + 182, + 463, + 235 + ], + "lines": [ + { + "bbox": [ + 388, + 182, + 463, + 235 + ], + "spans": [ + { + "bbox": [ + 388, + 182, + 463, + 235 + ], + "type": "image", + "image_path": "adafb4bc491b3895ee43dbc17069ef2a26cfe7e46c75842abd0cb14dffbc32c4.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 465, + 182, + 541, + 235 + ], + "blocks": [ + { + "bbox": [ + 465, + 182, + 541, + 235 + ], + "lines": [ + { + "bbox": [ + 465, + 182, + 541, + 235 + ], + "spans": [ + { + "bbox": [ + 465, + 182, + 541, + 235 + ], + "type": "image", + "image_path": "eb50f5874b135d3d270464d6d3aa53859288f43ba6f45000c48bb6c349d473e0.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 327, + 546, + 506 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 327, + 546, + 506 + ], + "spans": [ + { + "bbox": [ + 304, + 327, + 546, + 506 + ], + "type": "text", + "content": "Frame Retrieval VIDOSC learns features that accurately characterize the evolution of an OSC process. To illustrate, we consider a novel frame retrieval setting. Within the HowToChange test set, when presented with a query video featuring a novel OSC at its initial state, VIDOSC seeks the most similar and most contrasting video from a pool of candidates at their end states. The frame triplets with the smallest and largest feature distance are shown in Fig. 6. Remarkably, the retrieved nearest post-OSC frames correspond to the query's anticipated state transition trajectory, despite the object and state gap. Conversely, the furthest frames exhibit end states of markedly different objects. These results further lend support to VIDOSC's capability to understand the evolution of an OSC process, even for novel objects it has never encountered during training." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 516, + 378, + 528 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 516, + 378, + 528 + ], + "spans": [ + { + "bbox": [ + 306, + 516, + 378, + 528 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 536, + 545, + 691 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 536, + 545, + 691 + ], + "spans": [ + { + "bbox": [ + 304, + 536, + 545, + 691 + ], + "type": "text", + "content": "This work aims at a comprehensive exploration of video OSCs, with a novel open-world formulation. To address the challenges, we leverage text and VLMs to assist the training of a video OSC model at scale and design three modeling techniques to achieve object-agnostic state prediction for better generalization to novel OSCs. Furthermore, we present the most expansive video OSC dataset collection HowToChange, which echoes the natural long-tail of state transitions coupled with varied objects, fostering a realistic representation of real-world scenarios. As for future work, we will consider extending VIDOSC to video sequences featuring concurrent OSC processes, and integrating spatial understanding of OSC within our open-world framework." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 692, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 692, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 692, + 545, + 713 + ], + "type": "text", + "content": "Acknowledgements: UT Austin is supported in part by the IFML NSF AI Institute. KG is paid as a research scientist by Meta." + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18500" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 133 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 133 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 133 + ], + "type": "text", + "content": "[1] Nachwa Aboubakr, James L Crowley, and Rémi Ronfard. 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Existing approaches typically rely on geometry constraints and dense depth estimates to facilitate the learning, but often fail to fully exploit the benefits of three-dimensional feature extraction in frustum and 3D space. In this paper, we propose OccupancyM3D, a method of learning occupancy for monocular 3D detection. It directly learns occupancy in frustum and 3D space, leading to more discriminative and informative 3D features and representations. Specifically, by using synchronized raw sparse LiDAR point clouds, we define the space status and generate voxel-based occupancy labels. We formulate occupancy prediction as a simple classification problem and design associated occupancy losses. Resulting occupancy estimates are employed to enhance original frustum/3D features. As a result, experiments on KITTI and Waymo open datasets demonstrate that the proposed method achieves a new state of the art and surpasses other methods by a significant margin.", + "bbox": [ + 75, + 353, + 473, + 642 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 669, + 209, + 686 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Three dimensional object detection is a critical task in many real-world applications, such as self-driving and robot navigation. Early methods [52, 58, 78] typically rely on Li-DAR sensors because they can produce sparse yet accurate 3D point measurements. In contrast, cameras provide dense texture features but lack 3D information. Recently, monocular-based methods [36, 39, 49, 53] for 3D detection, also known as monocular 3D detection, have gained significant attention from both industry and academia due to their cost-effectiveness and deployment-friendly nature.", + "bbox": [ + 75, + 694, + 468, + 845 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Recovering accurate 3D information from a single RGB image poses a challenge. While previous researches have", + "bbox": [ + 76, + 845, + 468, + 877 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/7740132d172103cf8f14111b792745cf9ae39a039ffa88b95e5eb7d3a2920860.jpg", + "image_caption": [ + "Figure 1. Overall design. We introduce occupancy learning for monocular 3D detection. Best viewed in color." + ], + "image_footnote": [], + "bbox": [ + 519, + 320, + 870, + 417 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "employed geometry constraints [7, 27, 36, 45] and dense depth estimates [38, 53, 67] to facilitate 3D reasoning, they often overlook the importance of discriminative and informative 3D features in 3D space, which are essential for effective 3D detection. They mainly focus on improving features in 2D space, with little attention paid to better feature encoding and representation in the frustum and 3D space.", + "bbox": [ + 496, + 460, + 892, + 566 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Towards this goal, in this paper we propose to learn occupancy in frustum and 3D space, to obtain more discriminative and informative 3D features/representations for monocular 3D detection. Specifically, we employ synchronized raw sparse LiDAR point clouds to generate voxel-based occupancy labels in frustum and 3D space during the training stage. Concerning the sparsity of LiDAR points, we define three occupancy statuses: free, occupied, and unknown. Based on this, we voxelize the 3D space and use ray tracing on each LiDAR point to obtain occupancy labels. With the occupancy labels, we can enforce explicit 3D supervision on intermediate 3D features. It allows the network to learn voxelized occupancy for current 3D space, which enhances the original 3D features. This process is also performed in the frustum space, enabling a more fine-grained manner in extracting three-dimensional features for near objects due to the perspective nature of camera imagery. Overall, we call the proposed occupancy learning method OccupancyM3D, and illustrate the framework overview in Figure 1.", + "bbox": [ + 496, + 568, + 893, + 853 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To demonstrate the effectiveness of our method, we conduct experiments on the competitive KITTI and Waymo open datasets. As a result, the proposed method achieves", + "bbox": [ + 496, + 854, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author.", + "bbox": [ + 94, + 886, + 220, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "10281", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "state-of-the-art results with a significant margin over other methods. Our contributions can be summarized as follows:", + "bbox": [ + 76, + 90, + 468, + 119 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We emphasize the importance of feature encoding and representation in the frustum and 3D space for monocular 3D detection, and we propose to learn occupancy in both space.", + "- We propose a method to generate occupancy labels using synchronized raw sparse LiDAR points and introduce corresponding occupancy losses, enabling the network to learn voxelized occupancy in both frustum and 3D space. This occupancy learning process facilitates the extraction of discriminative 3D features in the network.", + "- Experiments demonstrate the superiority of the proposed method. Evaluated on challenging KITTI and Waymo open datasets, our method achieves new state-of-the-art (SOTA) results and outperforms other methods by a significant margin." + ], + "bbox": [ + 76, + 125, + 467, + 349 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 364, + 217, + 380 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. LiDAR Based 3D Object Detection", + "text_level": 1, + "bbox": [ + 76, + 388, + 377, + 405 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "LiDAR-based methods [19, 26, 56, 68, 69, 71, 77] currently dominate 3D object detection accuracy because of their precise depth measurements. Due to the unordered nature of point clouds, LiDAR-based methods are required to organize the input data. There are four main streams based on the input data representation: point-based, voxel-based, range-view-based, and hybrid-based. PointNet families [50, 51] are effective methods for feature extraction from raw point clouds, allowing point-based methods [52, 55, 59, 72] to directly perform 3D detection. Voxel-based methods [13, 70, 73, 77, 78] organize point clouds into voxel grids, making them compatible with regular convolutional neural networks. Range-view-based methods [1, 5, 15] convert point clouds into range-view to accommodate the LiDAR scanning mode. Hybrid-based methods [8, 46, 57, 71] use a combination of different representations to leverage their individual strengths. There is still a significant performance gap between monocular and LiDAR-based methods, which encourages researchers to advance monocular 3D detection.", + "bbox": [ + 76, + 412, + 468, + 715 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.2. Monocular 3D Object Detection", + "text_level": 1, + "bbox": [ + 76, + 726, + 357, + 741 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Significant progress has been made in advancing monocular 3D detection in recent years. The ill-posed problem of recovering instance level 3D information from a single image is challenging and important, attracting many researches. This is also the core sub-problem in monocular 3D detection. Early works [9, 45] resort to using scene priors and geometric projections to resolve objects' 3D locations. More recent monocular methods [2, 27, 29, 31, 35, 40, 76] employ more geometry constraints and extra priors like CAD models to achieve this goal. AutoShape [35] incorporates shape", + "bbox": [ + 76, + 750, + 467, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "aware 2D/3D constraints into the 3D detection framework by learning distinguished 2D and 3D keypoints. MonoJSG [31] reformulates the instance depth estimation as a progressive refinement problem and propose a joint semantic and geometric cost volume to model the depth error. As RGB images lack explicit depth information, many works rely on dense depth estimates. Some methods [37, 38, 67] directly convert depth map to pseudo LiDAR or 3D coordinate patches, and some works [53] use depth distributions to lift 2D image features to 3D space. Therefore, previous well-designed LiDAR 3D detectors can be easily employed on such explicit 3D features. Other researches [11, 12, 14, 47, 49, 64] also take advantage of depth maps or LiDAR point clouds as guidance for feature extraction and auxiliary information. While previous works have leveraged geometry constraints and dense depth estimates, they have not fully explored feature encoding and representation in the frustum and 3D space. To address this, our method focuses on learning occupancy for monocular 3D detection.", + "bbox": [ + 496, + 90, + 890, + 378 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.3. 3D Scene Representations", + "text_level": 1, + "bbox": [ + 500, + 391, + 733, + 406 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Recent researches [41, 43, 75] rapidly advance implicit representations. Implicit representations have the advantage of arbitrary-resolution on modeling the 3D scene. This nature is beneficial for fine-grained tasks such as 3D reconstruction and semantic segmentation. Different from them, monocular 3D detection is an instance level task, and we explore explicit occupancy learning using fixed-sized voxels. Implicit occupancy representations for this task can be explored in future works, which is an interesting and promising topic. Additionally, many bird's-eye-view (BEV) based works [20, 28, 30, 34, 53, 54] have been proposed recently. These works commonly employ BEV representations and obtain great success, especially for multi-camera BEV detection. The most related work to ours is CaDDN [53]. We follow its architecture design except for the proposed occupancy learning module, and we replace its 2D backbone with lightweight DLA34 [74].", + "bbox": [ + 496, + 415, + 890, + 672 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Since occupancy can serve as a general representation for scene perception and understanding. There is a burst of related works recently. SimpleOccupancy [16] adopts occupancy for better depth estimation. OccDepth [42] explores the occupancy in a stereo setting for semantic occupancy prediction. TPVFormer [22] employs sparse 3D occupancy labels from LiDAR as the supervision to obtain 3D features. OccNet [63] uses a decoder with various voxel based attention to reconstruct height information, accumulating occupancy labels from point cloud sequences. Different from them, we concentrate on 3D detection and takes a step farther to explore the effectiveness of occupancy in monocular 3D detection. Please note that our work focuses on the monocular setting, and extending the method to the multicamera setup is a potential avenue for future researches.", + "bbox": [ + 496, + 674, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "10282", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/064ce3d686db6f2539309f688845ef6d8eef2037a453ef3cb398e10788932f2e.jpg", + "image_caption": [ + "Figure 2. Network overview. Compared to previous works, our method employs two newly-proposed components for learning occupancy in frustum and 3D space. All network blocks in the proposed parts consist of vanilla 3D convolutions. Please refer to Section 3.1 for detailed feature passing description. For occupancy in frustum and 3D space and their network blocks, please see Section 3.2.1; For occupancy label generation, please see Section 3.2.2; For occupancy losses, please see Section 3.2.3; Best viewed in color with zoom in." + ], + "image_footnote": [], + "bbox": [ + 101, + 88, + 877, + 359 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. OccupancyM3D", + "text_level": 1, + "bbox": [ + 76, + 431, + 238, + 450 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Preliminary and Overview", + "text_level": 1, + "bbox": [ + 76, + 459, + 316, + 476 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Task Definition. We first describe the preliminary of this task and the method. At inference, monocular 3D detection takes only a single RGB image and outputs interested amodal 3D bounding boxes in the current scene. At the training stage, our method requires RGB images, 3D box labels annotated on LiDAR points and synchronized LiDAR data. It is worth noting that the system has been calibrated, and the camera intrinsics and extrinsics between the camera and LiDAR are available.", + "bbox": [ + 75, + 486, + 470, + 621 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Network Overview. We present the network overview of our method in Figure 2. First, a single RGB image is fed into the DLA34 [74] backbone network to extract features. Then, we use these features to produce categorical depth distributions [53], which lifts 2D features to frustum space. After that, we employ the depth predictions and backbone features to generate frustum features. They are used for learning occupancy in frustum space, and then are transformed to voxelized 3D features using grid-sampling. Such voxelized 3D features are employed to study occupancy in 3D space. Occupancy learning in both frustum and 3D spaces can produce reasonable occupancy estimates that enhance the original features. The final enhanced voxelized 3D features are passed to the detection module to obtain final 3D detection results.", + "bbox": [ + 75, + 626, + 468, + 851 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "At the training stage, occupancy estimates are supervised by the generated occupancy labels in frustum and 3D space, respectively, using the proposed occupancy losses. We de", + "bbox": [ + 75, + 854, + 470, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "tail the occupancy learning in following sections.", + "bbox": [ + 498, + 433, + 823, + 450 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Occupancy Learning", + "text_level": 1, + "bbox": [ + 500, + 455, + 697, + 472 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We consider a frustum voxel or regular 3D voxel to be occupied if it contains part of an object. We denote the resulting voxel states as frustum occupancy and 3D occupancy, respectively. In this section, we introduce occupancy learning for monocular 3D detection. It is organized as four parts: occupancy in frustum/3D space, occupancy labels, occupancy losses, and occupancy and depth.", + "bbox": [ + 496, + 479, + 890, + 585 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2.1 Occupancy in Frustum Space and 3D Space", + "text_level": 1, + "bbox": [ + 498, + 603, + 859, + 619 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "After extracting backbone features, we employ a depth head to obtain dense category depth [53]. To save GPU memory, we use a convolution layer to reduce the number of feature channels, and the resulting feature is lifted to a frustum feature $\\mathbf{Fru}_1 \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times C}$ with the assistance of depth estimates. Then we extract frustum feature $\\mathbf{Fru}_2 \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times C}$ as follows:", + "bbox": [ + 496, + 626, + 890, + 733 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {F r u} _ {\\mathbf {2}} = f _ {1} \\left(\\mathbf {F r u} _ {\\mathbf {1}}\\right) \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 630, + 739, + 890, + 756 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $f_{1}$ denotes two 3D convolutions followed by ReLU activate functions. Then we use a 3D convolution layer $f_{2}$ and sigmoid function to obtain frustum occupancy $\\mathbf{O}_{\\mathbf{fru}} \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times 1}$ , which is supervised by corresponding labels $\\mathbf{O}_{\\mathbf{fru}}^*$ as described in Section 3.2.2 and Section 3.2.3.", + "bbox": [ + 496, + 763, + 890, + 840 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {O} _ {\\mathbf {f r u}} = \\operatorname {S i g m o i d} \\left(f _ {2} \\left(\\mathbf {F r u} _ {2}\\right)\\right) \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 596, + 845, + 890, + 864 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The frustum occupancy indicates the feature density in the frustum space, thus inherently can be employed to weight", + "bbox": [ + 496, + 869, + 890, + 901 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "10283", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "original frustum features for achieving enhanced frustum feature $\\mathbf{Fru}_3\\in \\mathbb{R}^{W_F\\times H_F\\times D\\times C}$ as follows:", + "bbox": [ + 76, + 90, + 468, + 121 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {F r u} _ {3} = \\mathbf {O} _ {\\mathbf {f r u}} \\odot \\mathbf {F r u} _ {2} \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 194, + 133, + 468, + 150 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\odot$ denotes the Hadamard product (element-wise multiplication). The resulted frustum feature $\\mathbf{Fru}_3$ is transformed to regular voxelized feature $\\mathbf{V}_1 \\in \\mathbb{R}^{X \\times Y \\times Z \\times C}$ via grid-sampling [53]. The occupancy learning process is then repeated in the regular 3D space.", + "bbox": [ + 76, + 162, + 468, + 238 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {V} _ {\\mathbf {2}} = f _ {3} \\left(\\mathbf {V} _ {\\mathbf {1}}\\right); \\mathbf {O} _ {\\mathbf {3 d}} = \\text {S i g m o i d} \\left(f _ {4} \\left(\\mathbf {V} _ {\\mathbf {2}}\\right)\\right); \\mathbf {V} _ {\\mathbf {3}} = \\mathbf {O} _ {\\mathbf {3 d}} \\odot \\mathbf {V} _ {\\mathbf {2}} \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 251, + 472, + 280 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To better encode 3D features in the regular 3D space, we use a 3D hourglass-like design [6] in $f_{3}$ , and $f_{4}$ is a 3D convolution. Finally, we have more informative 3D voxel feature $\\mathbf{V}_3 \\in \\mathbb{R}^{X \\times Y \\times Z \\times C}$ for the detection module.", + "bbox": [ + 75, + 281, + 468, + 340 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "What is the rationale behind learning occupancy in both frustum and 3D space? Occupancy learning in both frustum and 3D space is beneficial because they have different nature. Frustum space has a resolution that depends on camera intrinsics and the downsample factor of the backbone network, while voxelized 3D space has a resolution that is decided by the pre-defined voxel size and detection range. Frustum voxels are irregular and vary in size based on the distance to the camera, which results in fine-grained voxels for objects that are closer and coarse-grained voxels for objects that are far away. In contrast, regular 3D voxels have the same size throughout the 3D space. On the other hand, frustum space is more fit to camera imagery, but objects in the frustum space cannot precisely represent the real 3D geometry. Thus the feature extraction and occupancy in frustum space have distortion for objects/scenes. Therefore, occupancy learning in both frustum and 3D space is complementary, and can result in more informative representations and features.", + "bbox": [ + 73, + 342, + 468, + 628 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2.2 Occupancy Labels", + "text_level": 1, + "bbox": [ + 76, + 648, + 259, + 665 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given a set of sparse LiDAR points $\\mathbf{P} \\in \\mathbb{R}^{N \\times 3}$ , where $N$ is the number of points and 3 is the coordinate dimension $(X, Y, Z)$ , we generate corresponding occupancy labels. The process is illustrated in Figure 3, and is operated on every LiDAR point. More formally, we first define three space status and represent them with numbers: free:0, occupied:1, unknown:-1. We then describe the occupancy label generation process in the frustum and 3D space, respectively.", + "bbox": [ + 75, + 672, + 468, + 808 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Occupancy label in frustum space: Let us denote the frustum occupancy label as $\\mathbf{O}_{\\mathrm{fru}}^{*} \\in \\mathbb{R}^{W_{F} \\times H_{F} \\times D}$ , where $W_{F}$ and $H_{F}$ are feature resolution, and $D$ is the depth category. We first project LiDAR points onto the image plane to form a category depth index map. Each valid projected point has a category depth index, while invalid points (no", + "bbox": [ + 75, + 810, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/7759ed541f59d86c294c8e6b60ffd67312cd7c7ac9426e83cbb9ab575ac278d3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 529, + 87, + 859, + 229 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/c0e052a59b9eb03aef75e60353dcc9758dce073f74590c52ab97bd7695c4f675.jpg", + "image_caption": [ + "Figure 3. Occupancy label generation in frustum and 3D space. Best viewed in color with zoom in." + ], + "image_footnote": [], + "bbox": [ + 527, + 231, + 859, + 366 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "LiDAR points projections) are given negative indexes of $-1$ . This index map is then downsampled to fit the feature resolution, resulting in $\\mathbf{Ind} \\in \\mathbb{R}^{W_F \\times H_F}$ . Benefit from the camera projection nature, we can easily distinguish the space status as follows:", + "bbox": [ + 498, + 407, + 890, + 482 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {O} _ {\\mathbf {f r u} i, j, d} ^ {*} = \\left\\{ \\begin{array}{l l} 1 & \\text {i f} \\mathbf {I n d} _ {i, j} > - 1 \\text {a n d} d = \\mathbf {I n d} _ {i, j}, \\\\ 0 & \\text {i f} \\mathbf {I n d} _ {i, j} > - 1 \\text {a n d} d < \\mathbf {I n d} _ {i, j}, \\\\ - 1 & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 500, + 488, + 888, + 571 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $i,j,d\\in W_F,H_F,D$ .Note that we do not consider unknown voxels in both the occupancy labels and occupancy losses. We use the known voxels, i.e., the free and occupied voxels, to perform occupancy learning.", + "bbox": [ + 498, + 571, + 890, + 632 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Occupancy label in 3D space: We denote $\\mathbf{O}_{\\mathbf{3d}}^{*} \\in \\mathbb{R}^{X \\times Y \\times Z}$ as the 3D occupancy label, where $X, Y, Z$ are determined by the pre-defined voxel size and detection range. We voxelize LiDAR points within the grid and set the voxels containing points to 1, and those without points to $-1$ . In this way, occupied voxels can be easily achieved. To obtain the free voxels, we utilize ray tracing from each LiDAR point to the camera, where intersected voxels are set as free, filled by 0. We summarize the occupancy label in 3D space as follows:", + "bbox": [ + 498, + 632, + 890, + 781 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {O} _ {\\mathbf {3 d} x, y, z} ^ {*} = \\left\\{\\begin{array}{l l}1&\\text {i f V o l} _ {\\mathbf {3 d} x, y, z} > 0,\\\\0&\\text {i f R} \\left(\\mathbf {O} _ {\\mathbf {3 d} x, y, z} ^ {*}\\right) \\cap \\operatorname {R a y} _ {\\text {p o i n t} \\rightarrow \\text {c a m}}\\\\- 1&\\text {o t h e r w i s e .}\\end{array}\\right. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 500, + 786, + 890, + 869 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $x,y,z\\in X,Y,Z$ .In this equation, $\\mathbf{Vol}_{3d}$ denotes the voxelized grid. $\\mathbf{Vol}_{3d} > 0$ when it is occu", + "bbox": [ + 498, + 869, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "10284", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "table", + "img_path": "images/c5c6e7eb1422e7dd3b5c7cc94a39dbb866c888c481c5771216052d54d2e6a9fa.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ApproachesVenueInputAPBEV(IoU=0.7)|R40AP3D(IoU=0.7)|R40
EasyModerateHardEasyModerateHard
Kinematic3D [3]ECCV20Video26.6917.5213.1019.0712.729.17
DfM [66]ECCV22Video31.7122.8919.9722.9416.8214.65
Monodle [39]CVPR21Image24.7918.8916.0017.2312.2610.29
MonoFlex [76]CVPR21Image28.2319.7516.8919.9413.8912.07
CaDDN [53]CVPR21Image27.9418.9117.1919.1713.4111.46
GUP Net [36]ICCV21Image30.2921.1918.2022.2615.0213.12
AutoShape [35]ICCV21Image30.6620.0815.9522.4714.1711.36
PCT [65]NeurIPS21Image29.6519.0315.9221.0013.3711.31
MonoDTR [21]CVPR22Image28.5920.3817.1421.9915.3912.73
MonoJSG [31]CVPR22Image32.5921.2618.1824.6916.1413.64
DEVIANT [25]ECCV22Image29.6520.4417.4321.8814.4611.89
DID-M3D [49]ECCV22Image32.9522.7619.8324.4016.2913.75
MonoDDE [29]CVPR22Image33.5823.4620.3724.9317.1415.10
Cube R-CNN [4]CVPR23Image31.7021.2018.4323.5915.0112.56
NeuROCS†[44]CVPR23Image37.2724.4920.8929.8918.9415.90
MonoUNI [23]NeurlPS23Image33.2823.0519.3924.7516.7313.49
OccupancyM3D-Image35.3824.1821.3725.5517.0214.79
", + "bbox": [ + 168, + 88, + 802, + 381 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Table 1. Comparisons on KITTI test set for Car category. The red refers to the highest result and blue is the second-highest result. Our method outperforms other methods including monocular and video-based methods.", + "bbox": [ + 75, + 383, + 893, + 412 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "pied by LiDAR points. $\\mathrm{R}(\\cdot)$ refers to the voxel range and $\\mathrm{R}(\\mathbf{O}_{3\\mathbf{d}i,j,d})\\cap \\mathrm{Ray}_{\\mathrm{point}\\to \\mathrm{cam}}$ denotes that the voxel at index $i,j,d$ intersects with a ray from LiDAR points to the camera. In this way, 3D occupancy labels are generated.", + "bbox": [ + 75, + 439, + 468, + 500 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "When generating voxel-based occupancy labels, there is a quantization error that arises due to the discretization process. A smaller voxel size results in lower quantization error, providing more fine-grained and accurate information. However, it requires more computation and GPU resources.", + "bbox": [ + 75, + 500, + 468, + 575 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.2.3 Occupancy Losses", + "text_level": 1, + "bbox": [ + 76, + 592, + 259, + 607 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We use generated occupancy labels $\\mathbf{O}_{\\mathbf{fru}}^{*}$ and $\\mathbf{O}_{3\\mathbf{d}}^{*}$ to supervised the predicted occupancy $\\mathbf{O}_{\\mathbf{fru}}$ and $\\mathbf{O}_{3\\mathbf{d}}$ , respectively. We regard occupancy prediction as a simple classification problem and use focal loss [32] as the classification loss. Only valid voxels, i.e., free and occupied voxels, contribute to the loss, and unknown voxels are ignored. We first obtain valid masks $\\mathbf{M}_{\\mathbf{fru}} \\in \\mathbb{R}^{W_F \\times H_F \\times D}$ and $\\mathbf{M}_{3\\mathbf{d}} \\in \\mathbb{R}^{X \\times Y \\times Z}$ . $\\mathbf{M}_{\\mathbf{fru}} = true$ if $\\mathbf{O}_{\\mathbf{fru}}^{*} > -1$ otherwise false. $\\mathbf{M}_{3\\mathbf{d}}$ is obtained using the similar way.", + "bbox": [ + 75, + 614, + 468, + 752 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Therefore, the occupancy loss in frustum space is:", + "bbox": [ + 96, + 752, + 428, + 767 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {f r u} = \\operatorname {F L} \\left(\\mathbf {O} _ {\\mathbf {f r u}} ^ {*} \\left[ \\mathbf {M} _ {\\mathbf {f r u}} \\right], \\mathbf {O} _ {\\mathbf {f r u}} \\left[ \\mathbf {M} _ {\\mathbf {f r u}} \\right]\\right) \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 140, + 773, + 468, + 792 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathrm{FL}(\\cdot)$ refers to focal loss and $[\\cdot]$ is the selection via mask. Similarly, we can obtain 3D occupancy loss as follows:", + "bbox": [ + 75, + 797, + 468, + 840 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {3 d} = \\operatorname {F L} \\left(\\mathrm {O} _ {\\mathbf {3 d}} ^ {*} \\left[ \\mathrm {M} _ {\\mathbf {3 d}} \\right], \\mathrm {O} _ {\\mathbf {3 d}} \\left[ \\mathrm {M} _ {\\mathbf {3 d}} \\right]\\right) \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 151, + 842, + 468, + 859 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The final occupancy loss is their sum:", + "bbox": [ + 76, + 862, + 328, + 877 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {o c c u p a n c y}} = \\mathcal {L} _ {f r u} + \\mathcal {L} _ {3 d} \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 183, + 885, + 468, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The occupancy loss allows the network to learn informative and discriminative features and representations, thus benefit downstream tasks. Therefore, the final loss of the network is:", + "bbox": [ + 496, + 439, + 892, + 497 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {\\text {o r g}} + \\lambda \\mathcal {L} _ {\\text {o c c u p a n c y}} \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 609, + 500, + 892, + 517 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{L}_{org}$ denotes the original detection and depth losses in CaDDN [53] and $\\lambda$ is the occupancy loss weighting factor, which is set to 1 by default.", + "bbox": [ + 496, + 523, + 890, + 569 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.2.4 Occupancy and Depth", + "text_level": 1, + "bbox": [ + 500, + 589, + 709, + 604 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Occupancy has some similarities with 2D depth map, especially the frustum occupancy. They both can represent object geometry surface in the space. However, depth map is two-dimensional while occupancy is three-dimensional. Occupancy is beyond the depth and can base on it. It is able to express dense features of objects but not only the surface. For unknown space due to occlusion, the occupancy can infer reasonable results. Moreover, learning occupancy in frustum and 3D space allows the network to study more informative features under a higher dimension compared to 2D space.", + "bbox": [ + 496, + 613, + 890, + 779 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Occupancy and depth are not mutually exclusive representations. In fact, they complement each other in the 3D object detection task. Without depth, the network has to deal with a large search space, making it challenging to learn reasonable occupancy features. Incorporating depth estimation provides the network with a good starting point and facilitates learning the occupancy features. Therefore, it is recommended to utilize both depth and occupancy in-", + "bbox": [ + 496, + 780, + 892, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "10285", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/264d554e3a5c20a740a9ba41129f099e3a8eeef26c33dc237afb853adf50fc60.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodsVenue3D mAP / mAPH (IoU = 0.7)3D mAP / mAPH (IoU = 0.5)
Overall0 - 30m30 - 50m50m - ∞Overall0 - 30m30 - 50m50m - ∞
Comparison on LEVEL 1
PatchNet[38]ECCV200.39/0.371.67/1.630.13/0.120.03/0.032.92/2.7410.03/9.751.09/0.960.23/0.18
CaDDN [53]CVPR215.03/4.9914.54/14.431.47/1.450.10/0.1017.54/17.3145.00/44.469.24/9.110.64/0.62
PCT [65]NeurlIPS210.89/0.883.18/3.150.27/0.270.07/0.074.20/4.1514.70/14.541.78/1.750.39/0.39
MonoJSG [31]CVPR220.97/0.954.65/4.590.55/0.530.10/0.095.65/5.4720.86/20.263.91/3.790.97/0.92
DEVIANT [25]ECCV222.69/2.676.95/6.900.99/0.980.02/0.0210.98/10.8926.85/26.645.13/5.080.18/0.18
DID-M3D [49]ECCV22-/--/--/--/-20.66/20.4740.92/40.6015.63/15.485.35/5.24
NeuROCS†[44]CVPR232.44/2.436.35/6.310.97/0.970.04/0.04-/--/--/--/-
MonoUNI [23]NeurlIPS233.20/3.168.61/8.500.87/0.860.13/0.1210.98/10.7326.63/26.304.04/3.980.57/0.55
OccupancyM3D-10.61/10.5329.18/28.964.49/4.460.41/0.4028.99/28.6661.24/60.6323.25/23.003.65/3.59
Comparison on LEVEL 2
PatchNet[38]ECCV200.38/0.361.67/1.630.13/0.110.03/0.032.42/2.2810.01/9.731.07/0.940.22/0.16
CaDDN [53]CVPR214.49/4.4514.50/14.381.42/1.410.09/0.0916.51/16.2844.87/44.338.99/8.860.58/0.55
PCT [65]NeurlIPS210.66/0.663.18/3.150.27/0.260.07/0.074.03/3.9914.67/14.511.74/1.710.36/0.35
MonoJSG [31]CVPR220.91/0.894.64/4.650.55/0.530.09/0.095.34/5.1720.79/20.193.79/3.670.85/0.82
DEVIANT [25]ECCV222.52/2.506.93/6.870.95/0.940.02/0.0210.29/10.2026.75/26.544.95/4.900.16/0.16
DID-M3D[49]ECCV22-/--/--/--/-19.37/19.1940.77/40.4615.18/15.044.69/4.59
NeuROCS†[44]CVPR232.29/2.286.32/6.290.94/0.930.03/0.03-/--/--/--/-
MonoUNI [23]NeurlIPS233.04/3.008.59/8.480.85/0.840.12/0.1210.38/10.2426.57/26.243.95/3.890.53/0.51
OccupancyM3D-10.02/9.9428.38/28.174.38/4.340.36/0.3627.21/26.9061.09/60.4922.59/22.343.18/3.13
", + "bbox": [ + 106, + 88, + 859, + 441 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Results on WaymoOD val set for Vehicle category. The red refers to the highest result and blue is the second-highest result. Our method outperforms other methods by significant margins on most metrics. Note that our method has the detection range limitation of [2, 59.6](meters), while the perspective-view based method DID-M3D [49] does not have this shortcoming. Thus our method performs worse for objects within $[50m,\\infty ]$ under IoU=0.5 criterion.", + "bbox": [ + 75, + 445, + 893, + 503 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "formation to achieve better representations and features for monocular 3D detection.", + "bbox": [ + 75, + 527, + 470, + 558 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 595, + 209, + 612 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.1. Implementation Details", + "text_level": 1, + "bbox": [ + 76, + 627, + 294, + 643 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We employ PyTorch [48] for implementation. The network is trained on 4 NVIDIA 3080Ti (12G) GPUs, with a total batch size of 8 for 80 epochs. We use Adam [24] optimizer with initial learning rate 0.001 and employ the one-cycle learning rate policy [61]. We use pre-trained DLA34 [74] backbone from [47]. We employ flip and crop data augmentation [36]. For KITTI [17], we fix the input image to $1280 \\times 384$ , detection range $[2,46.8] \\times [-30.08,30.08] \\times [-3.0,1.0]$ (meter) for $x,y,z$ axes under the LiDAR coordinate system, respectively. We use voxel size $[0.16,0.16,0.16]$ (meter). For Waymo [62], we downsample the input RGB image from $1920 \\times 1280$ to $960 \\times 640$ to meet GPU memory. We use detection range $[2,59.6] \\times [-25.6,25.6] \\times [-2.0,2.0]$ (meter) for $x,y,z$ axes due to the larger depth domain on Waymo. We use voxel size $[0.16,0.16,0.16]$ (meter).", + "bbox": [ + 75, + 657, + 472, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Datasets and Metrics", + "text_level": 1, + "bbox": [ + 500, + 527, + 697, + 542 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Following the fashion in previous works, we conduct experiments on competitive KITTI and Waymo open datasets.", + "bbox": [ + 498, + 551, + 890, + 580 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "KITTI: KITTI [17] is a widely employed benchmark for autonomous driving. KITTI3D object dataset consists of 7,481 training samples and 7,518 testing samples, where labels on test set keep secret and the final performance is evaluated on KITTI official website. To conduct ablations, the training samples are further divided into a train set and a val set [10]. They individually contain 3,512 and 3,769 samples, respectively. KITTI has three categories: Car, Pedestrian, and Cyclist. According to difficulties (2D box height, occlusion and truncation levels), KITTI divides objects into Easy, Moderate, and Hard. Following common practice [35, 53, 60], we use $\\mathrm{AP}_{BEV}|_{R_{40}}$ and $\\mathrm{AP}_{3D}|_{R_{40}}$ under IoU threshold of 0.7 to evaluate the performance.", + "bbox": [ + 496, + 582, + 892, + 777 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Waymo: Waymo open dataset (WaymoOD) [62] is a large modern dataset for autonomous driving. It has 798 sequences for training and 202 sequences for validation. Following previous works [49, 53], we use the front camera of the multi-camera rig and provide performance comparison on val set for the vehicle category. To make fair comparisons, we use one third samples of training sequences to train the network due to the large-scale and high frame rate", + "bbox": [ + 496, + 779, + 893, + 901 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "10286", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/d14cae5a0dc2f4ba306b2936a95071670802488cf307f0433a56834cdf325a3d.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ApproachesVenueInputPedestrian APBEV/AP3D(IoU=0.5)|R40Cyclist APBEV/AP3D(IoU=0.5)|R40
EasyModerateHardEasyModerateHard
DfM [66]ECCV22Video-13.70-8.71-7.32-8.98-5.75-4.88
Monodle [39]CVPR21Image10.73/9.646.96/6.556.20/5.445.34/4.593.28/2.662.83/2.45
DDMP-3D [64]CVPR21Image5.53/4.934.02/3.553.36/3.014.92/4.183.14/2.502.44/2.32
MonoRUn [7]CVPR21Image11.70/10.887.59/6.786.34/5.831.14/1.010.73/0.610.66/0.48
MonoEF [79]CVPR21Image4.61/4.273.05/2.792.85/2.212.36/1.801.18/0.921.15/0.71
MonoFlex [76]CVPR21Image10.36/9.437.36/6.316.29/5.264.41/4.172.67/2.352.50/2.04
CaDDN [53]CVPR21Image14.72/12.879.41/8.148.17/6.769.67/7.005.38/3.414.75/3.30
GUP Net [36]ICCV21Image15.62/14.9510.37/9.768.79/8.416.94/5.583.85/3.213.64/2.66
AutoShape [35]ICCV21Image-5.46-3.74-3.03-5.99-3.06-2.70
MonoCon [33]AAAI22Image-13.10-8.41-6.94-2.80-1.92-1.55
HomoLoss [18]CVPR22Image13.26/11.878.81/7.667.41/6.826.81/5.484.09/3.503.78/2.99
MonoJSG [31]CVPR22Image-11.02-7.49-6.41-5.45-3.21-2.57
DEVIANT [25]ECCV22Image14.49/13.439.77/8.658.28/7.696.42/5.053.97/3.133.51/2.59
Cube R-CNN [4]CVPR23Image11.67/11.177.65/6.956.60/5.875.01/3.653.35/2.673.23/2.28
MonoUNI [23]NeurlPS23Image16.54/15.7810.90/10.349.17/8.748.25/7.345.03/4.284.50/3.78
OccupancyM3D-Image16.54/14.6810.65/9.159.16/7.808.58/7.374.35/3.563.55/2.84
", + "bbox": [ + 102, + 88, + 862, + 364 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 3. Comparisons on KITTI test set for Pedestrian and Cyclist categories. The red refers to the highest result and blue is the second-highest result. Our method achieves new state-of-the-art results.", + "bbox": [ + 75, + 369, + 888, + 398 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "of this dataset. Waymo divides objects to LEVEL 1 and LEVEL 2 according to the LiDAR point number within objects. For metrics, we employ the official mAP and mAPH under LEVEL 1 and LEVEL 2.", + "bbox": [ + 75, + 424, + 468, + 484 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Results on KITTI and Waymo Datasets", + "text_level": 1, + "bbox": [ + 76, + 497, + 413, + 513 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We provide the performance comparisons on KITTI and WaymoOD. Table 1 shows the results of Car category on KITTI test set. Our method outperforms other methods including video-based methods. For example, the proposed method exceeds CaDDN [53] under all metrics, e.g., 25.55/17.02/14.79 vs. 19.17/13.41/11.46 $\\mathrm{AP}_{3D}$ . Please note that NeuROCS [44] requires instance masks for training and does not report results of Pedestrian and Cyclist on KITTI test set. Such irregularly shaped objects are challenging to NOCS prediction. Our method outperforms DID-M3D [49] by a margin of $2.43 / 1.42 / 1.54\\mathrm{AP}_{BEV}$ , and performs better than Cube R-CNN [4] and MonoUNI [23]. When compared to the video-based method DfM [66], OccupancyM3D also shows better performance, e.g., 24.18 vs. 22.89 $\\mathrm{AP}_{BEV}$ under the moderate setting. In Table 3, we provide comparisons on other categories, namely, Pedestrian and Cyclist. The results demonstrate the superiority of our method on different categories. Concerning the overall performance on all categories, our method achieves a state-of-the-art on KITTI test set for monocular 3D detection.", + "bbox": [ + 75, + 521, + 468, + 823 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We also evaluate our method on Waymo open dataset (WaymoOD) [62] and obtain promising results. As shown in Table 2, our method surpasses other methods with a significant margin. For example, under LEVEL 1 setting, OccupancyM3D outperforms CaDDN [53] by 5.58/5.54", + "bbox": [ + 75, + 824, + 468, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "mAP/mAPH (10.61/10.53 vs. 5.03/4.99) and 11.55/11.35 mAP/mAPH (28.99/28.66 vs. 17.54/17.31) with IoU 0.7 and 0.5 criterions, respectively. Compared to DID-M3D [49], under IoU criterion 0.5, our method outperforms it by $8.33 / 8.19\\mathrm{mAP / mAPH}$ (28.99/28.66 vs. 20.66/20.47) and 7.84/7.71 mAP/mAPH (27.21/26.90 vs. 19.37/19.19) with LEVEL 1 and 2 settings, respectively. This success can be attributed to the fact that occupancy learning benefits from the diverse scenes present in large datasets. In other words, large datasets especially favor the proposed occupancy learning method. Interestingly, concerning objects within $[50m,\\infty ]$ , our method performs worse than DID-M3D [49]. It is because our method is voxel-based, which has a detection range limitation ([2, 59.6](meters) in our method). By contrast, DID-M3D is a perspectivebased method, indicating that it does not have this limitation and can detect more faraway objects. We encourage future works to address this range limitation in our method.", + "bbox": [ + 496, + 424, + 890, + 696 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Ablations", + "text_level": 1, + "bbox": [ + 500, + 709, + 609, + 724 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Following common practice in previous works, we perform ablations on KITTI val set to validate the effectiveness of each component. We compare the performance on Car category under IoU criterion 0.7.", + "bbox": [ + 496, + 733, + 890, + 792 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We provide the main ablation in Table 4. It can be easily seen that occupancy learning significantly benefit the final detection performance. When enforcing occupancy learning in frustum space, the detection $\\mathrm{AP}_{3D}$ increases from 21.04/17.05/15.01 to 24.69/17.79/15.16 (Exp. (a) $\\rightarrow$ (b)). On the other hand, when enforcing occupancy learning in 3D space, the detection $\\mathrm{AP}_{3D}$ is boosted to", + "bbox": [ + 496, + 794, + 890, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "10287", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/7e51f782f242a681009176fec3ee4432dea98614bc8f8e498ce2d3f9074d3dc4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 88, + 356, + 165 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c2addf750a3519ed96714e57ebf5cd88d914759e0450f0f7e23c69dbab038400.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 362, + 98, + 624, + 170 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/44b295e4483676b68badfd55723d74a0cc170480ff11ddb5e9a50236c3b90294.jpg", + "image_caption": [ + "3D detections", + "Figure 4. Qualitative results of occupancy predictions and 3D detections on KITTI val set. In 3D detections, Red boxes are our results and Green boxes denote ground-truths. The LiDAR point clouds in 3D detections are used only for visualization. We can see that the proposed method generates reasonable occupancy predictions for the current scene, which benefits downstream monocular 3D detection task. However, our method may fail to estimate heavily occluded objects (see right objects of the bottom picture). Most monocular 3D detection failure cases stem from the poor occupancy estimation. Best viewed in color with zoom in." + ], + "image_footnote": [], + "bbox": [ + 640, + 85, + 893, + 284 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f279047a4216fa30d8bbaba1d95555bdce69e0931fd761e223c8689b0c4d9d41.jpg", + "image_caption": [ + "Input RGB images" + ], + "image_footnote": [], + "bbox": [ + 80, + 196, + 356, + 272 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/cf7e2bdc0f9d0e88f82060881c1ab10ed792c212da768f6790bca31673d05ed1.jpg", + "image_caption": [ + "Occupancy predictions" + ], + "image_footnote": [], + "bbox": [ + 372, + 204, + 637, + 268 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/5c6ac2e50840e6cd8df26874d480044fa58acc2d3b61bccf1ca1729104fef08f.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
E.OL-FSOL-3DSAPBEV/AP3D(IoU=0.7)|R40
EasyModerateHard
(a)30.32/21.0424.58/17.0522.02/15.01
(b)✓35.46/24.6925.46/17.7922.96/15.16
(c)✓33.15/24.6425.45/18.8822.68/16.38
(d)✓✓35.72/26.8726.60/19.9623.68/17.15
", + "bbox": [ + 78, + 391, + 480, + 479 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4. Main ablation. \"E.\" in the table is the experiment ID; \"OL-FS\" refers to occupancy learning in frustum space; \"OL-3DS\" denotes occupancy learning in 3D space.", + "bbox": [ + 76, + 484, + 470, + 526 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "24.64/18.88/16.38 (Exp. (c)). Finally, the model obtains $5.83 / 2.91 / 2.14\\mathrm{AP}_{3D}$ gains (Exp. $(a)\\rightarrow (d))$ by employing occupancy learning in both frustum and 3D space. This main ablation demonstrates the effectiveness of our method.", + "bbox": [ + 76, + 542, + 468, + 604 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.5. Qualitative Results", + "text_level": 1, + "bbox": [ + 76, + 612, + 261, + 628 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We present qualitative results of occupancy predictions and 3D detections in Figure 4. Our method can predict reasonable occupancy for the current scene, especially for foreground objects. This indicates the potential of occupancy learning in downstream tasks. Nevertheless, we can see that the occupancy estimates are not very accurate for heavily occluded objects (see right objects of the bottom picture), which leaves room for improvement in future works.", + "bbox": [ + 75, + 635, + 468, + 756 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Limitation and Future Work", + "text_level": 1, + "bbox": [ + 76, + 768, + 341, + 786 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "One significant drawback of this work is the voxel size limitation. Large voxels in explicit voxel-based representation can reduce computation overhead and GPU memory, but at the cost of failing to precisely describe the 3D geometry of the scene due to quantization errors. Conversely, smaller voxel sizes are able to express fine-grained 3D geometry but come at the significant expense of increased computation", + "bbox": [ + 75, + 794, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "overhead and GPU memory usage. On the other hand, the voxel-based method has limited detection ranges and most detection failure cases stem from poor occupancy estimation. This work mainly focuses on occupancy learning in the monocular 3D detection task, and the exploration of its application in more downstream tasks such as multi-camera detection/segmentation and indoor 3D detection is less explored. We believe that it is an interesting and promising topic and encourage future works to alleviate the above limitations to advance the self-driving community.", + "bbox": [ + 496, + 393, + 893, + 546 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 566, + 617, + 582 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we propose to learn occupancy for monocular 3D detection, to obtain more discriminative and informative 3D features. To perform occupancy learning, we design occupancy labels by using synchronized raw sparse LiDAR point clouds and introduce corresponding occupancy losses. Ablations verify the effectiveness of each proposed component. To the best of our knowledge, this is the first work that introduces occupancy learning to monocular 3D detection. We conduct experiments on the challenging KITTI and Waymo open datasets. The results demonstrate that the proposed method achieves new state-of-the-art results and outperforms other methods by a large margin.", + "bbox": [ + 496, + 594, + 893, + 776 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments", + "text_level": 1, + "bbox": [ + 500, + 797, + 658, + 814 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported in part by The National Nature Science Foundation of China (Grant Nos: 62273302, 62036009, 61936006, 62303406) and in part by Yongjiang Talent Introduction Programme (Grant No: 2023A-197-G, 2023A-194-G).", + "bbox": [ + 496, + 824, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "10288", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Alex Bewley, Pei Sun, Thomas Mensink, Dragomir Anguelov, and Cristian Sminchisescu. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 7556-7566, 2021. 7" + ], + "bbox": [ + 78, + 90, + 470, + 218 + ], + "page_idx": 11 + }, + { + "type": "page_number", + "text": "10292", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 11 + } +] \ No newline at end of file diff --git a/2024/Learning Occupancy for Monocular 3D Object Detection/9f9633e2-2ceb-4ed8-94da-20b12a33cfae_model.json b/2024/Learning Occupancy for Monocular 3D Object Detection/9f9633e2-2ceb-4ed8-94da-20b12a33cfae_model.json new file mode 100644 index 0000000000000000000000000000000000000000..90828e9722245767bdc60db47e32f23bb43a5924 --- /dev/null +++ b/2024/Learning Occupancy for Monocular 3D Object Detection/9f9633e2-2ceb-4ed8-94da-20b12a33cfae_model.json @@ -0,0 +1,2479 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.197, + 0.131, + 0.775, + 0.154 + ], + "angle": 0, + "content": "Learning Occupancy for Monocular 3D Object Detection" + }, + { + "type": "text", + "bbox": [ + 0.167, + 0.179, + 0.803, + 0.29 + ], + "angle": 0, + "content": "Liang Peng\\(^{3}\\) Junkai Xu\\(^{1,3}\\) Haoran Cheng\\(^{1,3}\\) Zheng Yang\\(^{3}\\) Xiaopei Wu\\(^{1}\\) Wei Qian\\(^{3}\\) Wenxiao Wang\\(^{2}\\) Boxi Wu\\(^{2*}\\) Deng Cai\\(^{1}\\) \\(^{1}\\)State Key Lab of CAD&CG, Zhejiang University \\(^{2}\\)School of Software Technology, Zhejiang University \\(^{3}\\)FABU Inc. {pengliang, xujunkai, haorancheng}@zju.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.322, + 0.314, + 0.339 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.354, + 0.474, + 0.643 + ], + "angle": 0, + "content": "Monocular 3D detection is a challenging task due to the lack of accurate 3D information. Existing approaches typically rely on geometry constraints and dense depth estimates to facilitate the learning, but often fail to fully exploit the benefits of three-dimensional feature extraction in frustum and 3D space. In this paper, we propose OccupancyM3D, a method of learning occupancy for monocular 3D detection. It directly learns occupancy in frustum and 3D space, leading to more discriminative and informative 3D features and representations. Specifically, by using synchronized raw sparse LiDAR point clouds, we define the space status and generate voxel-based occupancy labels. We formulate occupancy prediction as a simple classification problem and design associated occupancy losses. Resulting occupancy estimates are employed to enhance original frustum/3D features. As a result, experiments on KITTI and Waymo open datasets demonstrate that the proposed method achieves a new state of the art and surpasses other methods by a significant margin." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.67, + 0.21, + 0.687 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.695, + 0.47, + 0.846 + ], + "angle": 0, + "content": "Three dimensional object detection is a critical task in many real-world applications, such as self-driving and robot navigation. Early methods [52, 58, 78] typically rely on Li-DAR sensors because they can produce sparse yet accurate 3D point measurements. In contrast, cameras provide dense texture features but lack 3D information. Recently, monocular-based methods [36, 39, 49, 53] for 3D detection, also known as monocular 3D detection, have gained significant attention from both industry and academia due to their cost-effectiveness and deployment-friendly nature." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.847, + 0.47, + 0.878 + ], + "angle": 0, + "content": "Recovering accurate 3D information from a single RGB image poses a challenge. While previous researches have" + }, + { + "type": "image", + "bbox": [ + 0.52, + 0.321, + 0.871, + 0.419 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.421, + 0.892, + 0.449 + ], + "angle": 0, + "content": "Figure 1. Overall design. We introduce occupancy learning for monocular 3D detection. Best viewed in color." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.462, + 0.893, + 0.568 + ], + "angle": 0, + "content": "employed geometry constraints [7, 27, 36, 45] and dense depth estimates [38, 53, 67] to facilitate 3D reasoning, they often overlook the importance of discriminative and informative 3D features in 3D space, which are essential for effective 3D detection. They mainly focus on improving features in 2D space, with little attention paid to better feature encoding and representation in the frustum and 3D space." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.569, + 0.895, + 0.854 + ], + "angle": 0, + "content": "Towards this goal, in this paper we propose to learn occupancy in frustum and 3D space, to obtain more discriminative and informative 3D features/representations for monocular 3D detection. Specifically, we employ synchronized raw sparse LiDAR point clouds to generate voxel-based occupancy labels in frustum and 3D space during the training stage. Concerning the sparsity of LiDAR points, we define three occupancy statuses: free, occupied, and unknown. Based on this, we voxelize the 3D space and use ray tracing on each LiDAR point to obtain occupancy labels. With the occupancy labels, we can enforce explicit 3D supervision on intermediate 3D features. It allows the network to learn voxelized occupancy for current 3D space, which enhances the original 3D features. This process is also performed in the frustum space, enabling a more fine-grained manner in extracting three-dimensional features for near objects due to the perspective nature of camera imagery. Overall, we call the proposed occupancy learning method OccupancyM3D, and illustrate the framework overview in Figure 1." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.895, + 0.901 + ], + "angle": 0, + "content": "To demonstrate the effectiveness of our method, we conduct experiments on the competitive KITTI and Waymo open datasets. As a result, the proposed method achieves" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.222, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "10281" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.121 + ], + "angle": 0, + "content": "state-of-the-art results with a significant margin over other methods. Our contributions can be summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.125, + 0.468, + 0.184 + ], + "angle": 0, + "content": "- We emphasize the importance of feature encoding and representation in the frustum and 3D space for monocular 3D detection, and we propose to learn occupancy in both space." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.186, + 0.468, + 0.274 + ], + "angle": 0, + "content": "- We propose a method to generate occupancy labels using synchronized raw sparse LiDAR points and introduce corresponding occupancy losses, enabling the network to learn voxelized occupancy in both frustum and 3D space. This occupancy learning process facilitates the extraction of discriminative 3D features in the network." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.277, + 0.468, + 0.351 + ], + "angle": 0, + "content": "- Experiments demonstrate the superiority of the proposed method. Evaluated on challenging KITTI and Waymo open datasets, our method achieves new state-of-the-art (SOTA) results and outperforms other methods by a significant margin." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.125, + 0.468, + 0.351 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.366, + 0.218, + 0.381 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.39, + 0.379, + 0.406 + ], + "angle": 0, + "content": "2.1. LiDAR Based 3D Object Detection" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.414, + 0.47, + 0.716 + ], + "angle": 0, + "content": "LiDAR-based methods [19, 26, 56, 68, 69, 71, 77] currently dominate 3D object detection accuracy because of their precise depth measurements. Due to the unordered nature of point clouds, LiDAR-based methods are required to organize the input data. There are four main streams based on the input data representation: point-based, voxel-based, range-view-based, and hybrid-based. PointNet families [50, 51] are effective methods for feature extraction from raw point clouds, allowing point-based methods [52, 55, 59, 72] to directly perform 3D detection. Voxel-based methods [13, 70, 73, 77, 78] organize point clouds into voxel grids, making them compatible with regular convolutional neural networks. Range-view-based methods [1, 5, 15] convert point clouds into range-view to accommodate the LiDAR scanning mode. Hybrid-based methods [8, 46, 57, 71] use a combination of different representations to leverage their individual strengths. There is still a significant performance gap between monocular and LiDAR-based methods, which encourages researchers to advance monocular 3D detection." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.727, + 0.358, + 0.742 + ], + "angle": 0, + "content": "2.2. Monocular 3D Object Detection" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.75, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Significant progress has been made in advancing monocular 3D detection in recent years. The ill-posed problem of recovering instance level 3D information from a single image is challenging and important, attracting many researches. This is also the core sub-problem in monocular 3D detection. Early works [9, 45] resort to using scene priors and geometric projections to resolve objects' 3D locations. More recent monocular methods [2, 27, 29, 31, 35, 40, 76] employ more geometry constraints and extra priors like CAD models to achieve this goal. AutoShape [35] incorporates shape" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.379 + ], + "angle": 0, + "content": "aware 2D/3D constraints into the 3D detection framework by learning distinguished 2D and 3D keypoints. MonoJSG [31] reformulates the instance depth estimation as a progressive refinement problem and propose a joint semantic and geometric cost volume to model the depth error. As RGB images lack explicit depth information, many works rely on dense depth estimates. Some methods [37, 38, 67] directly convert depth map to pseudo LiDAR or 3D coordinate patches, and some works [53] use depth distributions to lift 2D image features to 3D space. Therefore, previous well-designed LiDAR 3D detectors can be easily employed on such explicit 3D features. Other researches [11, 12, 14, 47, 49, 64] also take advantage of depth maps or LiDAR point clouds as guidance for feature extraction and auxiliary information. While previous works have leveraged geometry constraints and dense depth estimates, they have not fully explored feature encoding and representation in the frustum and 3D space. To address this, our method focuses on learning occupancy for monocular 3D detection." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.392, + 0.734, + 0.407 + ], + "angle": 0, + "content": "2.3. 3D Scene Representations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.416, + 0.892, + 0.674 + ], + "angle": 0, + "content": "Recent researches [41, 43, 75] rapidly advance implicit representations. Implicit representations have the advantage of arbitrary-resolution on modeling the 3D scene. This nature is beneficial for fine-grained tasks such as 3D reconstruction and semantic segmentation. Different from them, monocular 3D detection is an instance level task, and we explore explicit occupancy learning using fixed-sized voxels. Implicit occupancy representations for this task can be explored in future works, which is an interesting and promising topic. Additionally, many bird's-eye-view (BEV) based works [20, 28, 30, 34, 53, 54] have been proposed recently. These works commonly employ BEV representations and obtain great success, especially for multi-camera BEV detection. The most related work to ours is CaDDN [53]. We follow its architecture design except for the proposed occupancy learning module, and we replace its 2D backbone with lightweight DLA34 [74]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Since occupancy can serve as a general representation for scene perception and understanding. There is a burst of related works recently. SimpleOccupancy [16] adopts occupancy for better depth estimation. OccDepth [42] explores the occupancy in a stereo setting for semantic occupancy prediction. TPVFormer [22] employs sparse 3D occupancy labels from LiDAR as the supervision to obtain 3D features. OccNet [63] uses a decoder with various voxel based attention to reconstruct height information, accumulating occupancy labels from point cloud sequences. Different from them, we concentrate on 3D detection and takes a step farther to explore the effectiveness of occupancy in monocular 3D detection. Please note that our work focuses on the monocular setting, and extending the method to the multicamera setup is a potential avenue for future researches." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "10282" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.102, + 0.089, + 0.878, + 0.361 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.366, + 0.895, + 0.424 + ], + "angle": 0, + "content": "Figure 2. Network overview. Compared to previous works, our method employs two newly-proposed components for learning occupancy in frustum and 3D space. All network blocks in the proposed parts consist of vanilla 3D convolutions. Please refer to Section 3.1 for detailed feature passing description. For occupancy in frustum and 3D space and their network blocks, please see Section 3.2.1; For occupancy label generation, please see Section 3.2.2; For occupancy losses, please see Section 3.2.3; Best viewed in color with zoom in." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.433, + 0.24, + 0.451 + ], + "angle": 0, + "content": "3. OccupancyM3D" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.46, + 0.318, + 0.477 + ], + "angle": 0, + "content": "3.1. Preliminary and Overview" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.487, + 0.471, + 0.622 + ], + "angle": 0, + "content": "Task Definition. We first describe the preliminary of this task and the method. At inference, monocular 3D detection takes only a single RGB image and outputs interested amodal 3D bounding boxes in the current scene. At the training stage, our method requires RGB images, 3D box labels annotated on LiDAR points and synchronized LiDAR data. It is worth noting that the system has been calibrated, and the camera intrinsics and extrinsics between the camera and LiDAR are available." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.627, + 0.47, + 0.852 + ], + "angle": 0, + "content": "Network Overview. We present the network overview of our method in Figure 2. First, a single RGB image is fed into the DLA34 [74] backbone network to extract features. Then, we use these features to produce categorical depth distributions [53], which lifts 2D features to frustum space. After that, we employ the depth predictions and backbone features to generate frustum features. They are used for learning occupancy in frustum space, and then are transformed to voxelized 3D features using grid-sampling. Such voxelized 3D features are employed to study occupancy in 3D space. Occupancy learning in both frustum and 3D spaces can produce reasonable occupancy estimates that enhance the original features. The final enhanced voxelized 3D features are passed to the detection module to obtain final 3D detection results." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.471, + 0.903 + ], + "angle": 0, + "content": "At the training stage, occupancy estimates are supervised by the generated occupancy labels in frustum and 3D space, respectively, using the proposed occupancy losses. We de" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.434, + 0.825, + 0.451 + ], + "angle": 0, + "content": "tail the occupancy learning in following sections." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.457, + 0.699, + 0.473 + ], + "angle": 0, + "content": "3.2. Occupancy Learning" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.48, + 0.892, + 0.587 + ], + "angle": 0, + "content": "We consider a frustum voxel or regular 3D voxel to be occupied if it contains part of an object. We denote the resulting voxel states as frustum occupancy and 3D occupancy, respectively. In this section, we introduce occupancy learning for monocular 3D detection. It is organized as four parts: occupancy in frustum/3D space, occupancy labels, occupancy losses, and occupancy and depth." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.604, + 0.86, + 0.62 + ], + "angle": 0, + "content": "3.2.1 Occupancy in Frustum Space and 3D Space" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.627, + 0.892, + 0.734 + ], + "angle": 0, + "content": "After extracting backbone features, we employ a depth head to obtain dense category depth [53]. To save GPU memory, we use a convolution layer to reduce the number of feature channels, and the resulting feature is lifted to a frustum feature \\(\\mathbf{Fru}_1 \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times C}\\) with the assistance of depth estimates. Then we extract frustum feature \\(\\mathbf{Fru}_2 \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times C}\\) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.631, + 0.741, + 0.892, + 0.757 + ], + "angle": 0, + "content": "\\[\n\\mathbf {F r u} _ {\\mathbf {2}} = f _ {1} \\left(\\mathbf {F r u} _ {\\mathbf {1}}\\right) \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.764, + 0.892, + 0.842 + ], + "angle": 0, + "content": "where \\(f_{1}\\) denotes two 3D convolutions followed by ReLU activate functions. Then we use a 3D convolution layer \\(f_{2}\\) and sigmoid function to obtain frustum occupancy \\(\\mathbf{O}_{\\mathbf{fru}} \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times 1}\\), which is supervised by corresponding labels \\(\\mathbf{O}_{\\mathbf{fru}}^*\\) as described in Section 3.2.2 and Section 3.2.3." + }, + { + "type": "equation", + "bbox": [ + 0.598, + 0.847, + 0.892, + 0.865 + ], + "angle": 0, + "content": "\\[\n\\mathbf {O} _ {\\mathbf {f r u}} = \\operatorname {S i g m o i d} \\left(f _ {2} \\left(\\mathbf {F r u} _ {2}\\right)\\right) \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.892, + 0.902 + ], + "angle": 0, + "content": "The frustum occupancy indicates the feature density in the frustum space, thus inherently can be employed to weight" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "10283" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.122 + ], + "angle": 0, + "content": "original frustum features for achieving enhanced frustum feature \\(\\mathbf{Fru}_3\\in \\mathbb{R}^{W_F\\times H_F\\times D\\times C}\\) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.196, + 0.135, + 0.469, + 0.151 + ], + "angle": 0, + "content": "\\[\n\\mathbf {F r u} _ {3} = \\mathbf {O} _ {\\mathbf {f r u}} \\odot \\mathbf {F r u} _ {2} \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.164, + 0.47, + 0.239 + ], + "angle": 0, + "content": "where \\(\\odot\\) denotes the Hadamard product (element-wise multiplication). The resulted frustum feature \\(\\mathbf{Fru}_3\\) is transformed to regular voxelized feature \\(\\mathbf{V}_1 \\in \\mathbb{R}^{X \\times Y \\times Z \\times C}\\) via grid-sampling [53]. The occupancy learning process is then repeated in the regular 3D space." + }, + { + "type": "equation", + "bbox": [ + 0.078, + 0.252, + 0.473, + 0.281 + ], + "angle": 0, + "content": "\\[\n\\mathbf {V} _ {\\mathbf {2}} = f _ {3} \\left(\\mathbf {V} _ {\\mathbf {1}}\\right); \\mathbf {O} _ {\\mathbf {3 d}} = \\text {S i g m o i d} \\left(f _ {4} \\left(\\mathbf {V} _ {\\mathbf {2}}\\right)\\right); \\mathbf {V} _ {\\mathbf {3}} = \\mathbf {O} _ {\\mathbf {3 d}} \\odot \\mathbf {V} _ {\\mathbf {2}} \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.282, + 0.469, + 0.342 + ], + "angle": 0, + "content": "To better encode 3D features in the regular 3D space, we use a 3D hourglass-like design [6] in \\( f_{3} \\), and \\( f_{4} \\) is a 3D convolution. Finally, we have more informative 3D voxel feature \\( \\mathbf{V}_3 \\in \\mathbb{R}^{X \\times Y \\times Z \\times C} \\) for the detection module." + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.343, + 0.47, + 0.629 + ], + "angle": 0, + "content": "What is the rationale behind learning occupancy in both frustum and 3D space? Occupancy learning in both frustum and 3D space is beneficial because they have different nature. Frustum space has a resolution that depends on camera intrinsics and the downsample factor of the backbone network, while voxelized 3D space has a resolution that is decided by the pre-defined voxel size and detection range. Frustum voxels are irregular and vary in size based on the distance to the camera, which results in fine-grained voxels for objects that are closer and coarse-grained voxels for objects that are far away. In contrast, regular 3D voxels have the same size throughout the 3D space. On the other hand, frustum space is more fit to camera imagery, but objects in the frustum space cannot precisely represent the real 3D geometry. Thus the feature extraction and occupancy in frustum space have distortion for objects/scenes. Therefore, occupancy learning in both frustum and 3D space is complementary, and can result in more informative representations and features." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.65, + 0.26, + 0.666 + ], + "angle": 0, + "content": "3.2.2 Occupancy Labels" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.673, + 0.469, + 0.809 + ], + "angle": 0, + "content": "Given a set of sparse LiDAR points \\(\\mathbf{P} \\in \\mathbb{R}^{N \\times 3}\\), where \\(N\\) is the number of points and 3 is the coordinate dimension \\((X, Y, Z)\\), we generate corresponding occupancy labels. The process is illustrated in Figure 3, and is operated on every LiDAR point. More formally, we first define three space status and represent them with numbers: free:0, occupied:1, unknown:-1. We then describe the occupancy label generation process in the frustum and 3D space, respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Occupancy label in frustum space: Let us denote the frustum occupancy label as \\(\\mathbf{O}_{\\mathrm{fru}}^{*} \\in \\mathbb{R}^{W_{F} \\times H_{F} \\times D}\\), where \\(W_{F}\\) and \\(H_{F}\\) are feature resolution, and \\(D\\) is the depth category. We first project LiDAR points onto the image plane to form a category depth index map. Each valid projected point has a category depth index, while invalid points (no" + }, + { + "type": "image", + "bbox": [ + 0.53, + 0.088, + 0.86, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.529, + 0.232, + 0.86, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.372, + 0.89, + 0.4 + ], + "angle": 0, + "content": "Figure 3. Occupancy label generation in frustum and 3D space. Best viewed in color with zoom in." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.408, + 0.892, + 0.483 + ], + "angle": 0, + "content": "LiDAR points projections) are given negative indexes of \\(-1\\). This index map is then downsampled to fit the feature resolution, resulting in \\(\\mathbf{Ind} \\in \\mathbb{R}^{W_F \\times H_F}\\). Benefit from the camera projection nature, we can easily distinguish the space status as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.5, + 0.489, + 0.89, + 0.572 + ], + "angle": 0, + "content": "\\[\n\\mathbf {O} _ {\\mathbf {f r u} i, j, d} ^ {*} = \\left\\{ \\begin{array}{l l} 1 & \\text {i f} \\mathbf {I n d} _ {i, j} > - 1 \\text {a n d} d = \\mathbf {I n d} _ {i, j}, \\\\ 0 & \\text {i f} \\mathbf {I n d} _ {i, j} > - 1 \\text {a n d} d < \\mathbf {I n d} _ {i, j}, \\\\ - 1 & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.573, + 0.891, + 0.633 + ], + "angle": 0, + "content": "where \\(i,j,d\\in W_F,H_F,D\\) .Note that we do not consider unknown voxels in both the occupancy labels and occupancy losses. We use the known voxels, i.e., the free and occupied voxels, to perform occupancy learning." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.633, + 0.892, + 0.782 + ], + "angle": 0, + "content": "Occupancy label in 3D space: We denote \\(\\mathbf{O}_{\\mathbf{3d}}^{*} \\in \\mathbb{R}^{X \\times Y \\times Z}\\) as the 3D occupancy label, where \\(X, Y, Z\\) are determined by the pre-defined voxel size and detection range. We voxelize LiDAR points within the grid and set the voxels containing points to 1, and those without points to \\(-1\\). In this way, occupied voxels can be easily achieved. To obtain the free voxels, we utilize ray tracing from each LiDAR point to the camera, where intersected voxels are set as free, filled by 0. We summarize the occupancy label in 3D space as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.5, + 0.787, + 0.891, + 0.87 + ], + "angle": 0, + "content": "\\[\n\\mathbf {O} _ {\\mathbf {3 d} x, y, z} ^ {*} = \\left\\{\\begin{array}{l l}1&\\text {i f V o l} _ {\\mathbf {3 d} x, y, z} > 0,\\\\0&\\text {i f R} \\left(\\mathbf {O} _ {\\mathbf {3 d} x, y, z} ^ {*}\\right) \\cap \\operatorname {R a y} _ {\\text {p o i n t} \\rightarrow \\text {c a m}}\\\\- 1&\\text {o t h e r w i s e .}\\end{array}\\right. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.891, + 0.901 + ], + "angle": 0, + "content": "where \\(x,y,z\\in X,Y,Z\\) .In this equation, \\(\\mathbf{Vol}_{3d}\\) denotes the voxelized grid. \\(\\mathbf{Vol}_{3d} > 0\\) when it is occu" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "10284" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.169, + 0.089, + 0.803, + 0.382 + ], + "angle": 0, + "content": "
ApproachesVenueInputAPBEV(IoU=0.7)|R40AP3D(IoU=0.7)|R40
EasyModerateHardEasyModerateHard
Kinematic3D [3]ECCV20Video26.6917.5213.1019.0712.729.17
DfM [66]ECCV22Video31.7122.8919.9722.9416.8214.65
Monodle [39]CVPR21Image24.7918.8916.0017.2312.2610.29
MonoFlex [76]CVPR21Image28.2319.7516.8919.9413.8912.07
CaDDN [53]CVPR21Image27.9418.9117.1919.1713.4111.46
GUP Net [36]ICCV21Image30.2921.1918.2022.2615.0213.12
AutoShape [35]ICCV21Image30.6620.0815.9522.4714.1711.36
PCT [65]NeurIPS21Image29.6519.0315.9221.0013.3711.31
MonoDTR [21]CVPR22Image28.5920.3817.1421.9915.3912.73
MonoJSG [31]CVPR22Image32.5921.2618.1824.6916.1413.64
DEVIANT [25]ECCV22Image29.6520.4417.4321.8814.4611.89
DID-M3D [49]ECCV22Image32.9522.7619.8324.4016.2913.75
MonoDDE [29]CVPR22Image33.5823.4620.3724.9317.1415.10
Cube R-CNN [4]CVPR23Image31.7021.2018.4323.5915.0112.56
NeuROCS†[44]CVPR23Image37.2724.4920.8929.8918.9415.90
MonoUNI [23]NeurlPS23Image33.2823.0519.3924.7516.7313.49
OccupancyM3D-Image35.3824.1821.3725.5517.0214.79
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.385, + 0.895, + 0.414 + ], + "angle": 0, + "content": "Table 1. Comparisons on KITTI test set for Car category. The red refers to the highest result and blue is the second-highest result. Our method outperforms other methods including monocular and video-based methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.44, + 0.47, + 0.5 + ], + "angle": 0, + "content": "pied by LiDAR points. \\(\\mathrm{R}(\\cdot)\\) refers to the voxel range and \\(\\mathrm{R}(\\mathbf{O}_{3\\mathbf{d}i,j,d})\\cap \\mathrm{Ray}_{\\mathrm{point}\\to \\mathrm{cam}}\\) denotes that the voxel at index \\(i,j,d\\) intersects with a ray from LiDAR points to the camera. In this way, 3D occupancy labels are generated." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.5, + 0.47, + 0.577 + ], + "angle": 0, + "content": "When generating voxel-based occupancy labels, there is a quantization error that arises due to the discretization process. A smaller voxel size results in lower quantization error, providing more fine-grained and accurate information. However, it requires more computation and GPU resources." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.593, + 0.26, + 0.608 + ], + "angle": 0, + "content": "3.2.3 Occupancy Losses" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.616, + 0.47, + 0.753 + ], + "angle": 0, + "content": "We use generated occupancy labels \\(\\mathbf{O}_{\\mathbf{fru}}^{*}\\) and \\(\\mathbf{O}_{3\\mathbf{d}}^{*}\\) to supervised the predicted occupancy \\(\\mathbf{O}_{\\mathbf{fru}}\\) and \\(\\mathbf{O}_{3\\mathbf{d}}\\), respectively. We regard occupancy prediction as a simple classification problem and use focal loss [32] as the classification loss. Only valid voxels, i.e., free and occupied voxels, contribute to the loss, and unknown voxels are ignored. We first obtain valid masks \\(\\mathbf{M}_{\\mathbf{fru}} \\in \\mathbb{R}^{W_F \\times H_F \\times D}\\) and \\(\\mathbf{M}_{3\\mathbf{d}} \\in \\mathbb{R}^{X \\times Y \\times Z}\\). \\(\\mathbf{M}_{\\mathbf{fru}} = true\\) if \\(\\mathbf{O}_{\\mathbf{fru}}^{*} > -1\\) otherwise false. \\(\\mathbf{M}_{3\\mathbf{d}}\\) is obtained using the similar way." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.753, + 0.429, + 0.768 + ], + "angle": 0, + "content": "Therefore, the occupancy loss in frustum space is:" + }, + { + "type": "equation", + "bbox": [ + 0.142, + 0.775, + 0.47, + 0.793 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {f r u} = \\operatorname {F L} \\left(\\mathbf {O} _ {\\mathbf {f r u}} ^ {*} \\left[ \\mathbf {M} _ {\\mathbf {f r u}} \\right], \\mathbf {O} _ {\\mathbf {f r u}} \\left[ \\mathbf {M} _ {\\mathbf {f r u}} \\right]\\right) \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.798, + 0.47, + 0.841 + ], + "angle": 0, + "content": "where \\(\\mathrm{FL}(\\cdot)\\) refers to focal loss and \\([\\cdot]\\) is the selection via mask. Similarly, we can obtain 3D occupancy loss as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.152, + 0.843, + 0.469, + 0.861 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {3 d} = \\operatorname {F L} \\left(\\mathrm {O} _ {\\mathbf {3 d}} ^ {*} \\left[ \\mathrm {M} _ {\\mathbf {3 d}} \\right], \\mathrm {O} _ {\\mathbf {3 d}} \\left[ \\mathrm {M} _ {\\mathbf {3 d}} \\right]\\right) \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.863, + 0.329, + 0.878 + ], + "angle": 0, + "content": "The final occupancy loss is their sum:" + }, + { + "type": "equation", + "bbox": [ + 0.184, + 0.886, + 0.47, + 0.903 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {o c c u p a n c y}} = \\mathcal {L} _ {f r u} + \\mathcal {L} _ {3 d} \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.44, + 0.893, + 0.498 + ], + "angle": 0, + "content": "The occupancy loss allows the network to learn informative and discriminative features and representations, thus benefit downstream tasks. Therefore, the final loss of the network is:" + }, + { + "type": "equation", + "bbox": [ + 0.61, + 0.501, + 0.893, + 0.518 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {\\text {o r g}} + \\lambda \\mathcal {L} _ {\\text {o c c u p a n c y}} \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.524, + 0.892, + 0.57 + ], + "angle": 0, + "content": "where \\(\\mathcal{L}_{org}\\) denotes the original detection and depth losses in CaDDN [53] and \\(\\lambda\\) is the occupancy loss weighting factor, which is set to 1 by default." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.59, + 0.71, + 0.606 + ], + "angle": 0, + "content": "3.2.4 Occupancy and Depth" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.614, + 0.892, + 0.78 + ], + "angle": 0, + "content": "Occupancy has some similarities with 2D depth map, especially the frustum occupancy. They both can represent object geometry surface in the space. However, depth map is two-dimensional while occupancy is three-dimensional. Occupancy is beyond the depth and can base on it. It is able to express dense features of objects but not only the surface. For unknown space due to occlusion, the occupancy can infer reasonable results. Moreover, learning occupancy in frustum and 3D space allows the network to study more informative features under a higher dimension compared to 2D space." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.781, + 0.893, + 0.902 + ], + "angle": 0, + "content": "Occupancy and depth are not mutually exclusive representations. In fact, they complement each other in the 3D object detection task. Without depth, the network has to deal with a large search space, making it challenging to learn reasonable occupancy features. Incorporating depth estimation provides the network with a good starting point and facilitates learning the occupancy features. Therefore, it is recommended to utilize both depth and occupancy in-" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "10285" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.107, + 0.089, + 0.861, + 0.442 + ], + "angle": 0, + "content": "
MethodsVenue3D mAP / mAPH (IoU = 0.7)3D mAP / mAPH (IoU = 0.5)
Overall0 - 30m30 - 50m50m - ∞Overall0 - 30m30 - 50m50m - ∞
Comparison on LEVEL 1
PatchNet[38]ECCV200.39/0.371.67/1.630.13/0.120.03/0.032.92/2.7410.03/9.751.09/0.960.23/0.18
CaDDN [53]CVPR215.03/4.9914.54/14.431.47/1.450.10/0.1017.54/17.3145.00/44.469.24/9.110.64/0.62
PCT [65]NeurlIPS210.89/0.883.18/3.150.27/0.270.07/0.074.20/4.1514.70/14.541.78/1.750.39/0.39
MonoJSG [31]CVPR220.97/0.954.65/4.590.55/0.530.10/0.095.65/5.4720.86/20.263.91/3.790.97/0.92
DEVIANT [25]ECCV222.69/2.676.95/6.900.99/0.980.02/0.0210.98/10.8926.85/26.645.13/5.080.18/0.18
DID-M3D [49]ECCV22-/--/--/--/-20.66/20.4740.92/40.6015.63/15.485.35/5.24
NeuROCS†[44]CVPR232.44/2.436.35/6.310.97/0.970.04/0.04-/--/--/--/-
MonoUNI [23]NeurlIPS233.20/3.168.61/8.500.87/0.860.13/0.1210.98/10.7326.63/26.304.04/3.980.57/0.55
OccupancyM3D-10.61/10.5329.18/28.964.49/4.460.41/0.4028.99/28.6661.24/60.6323.25/23.003.65/3.59
Comparison on LEVEL 2
PatchNet[38]ECCV200.38/0.361.67/1.630.13/0.110.03/0.032.42/2.2810.01/9.731.07/0.940.22/0.16
CaDDN [53]CVPR214.49/4.4514.50/14.381.42/1.410.09/0.0916.51/16.2844.87/44.338.99/8.860.58/0.55
PCT [65]NeurlIPS210.66/0.663.18/3.150.27/0.260.07/0.074.03/3.9914.67/14.511.74/1.710.36/0.35
MonoJSG [31]CVPR220.91/0.894.64/4.650.55/0.530.09/0.095.34/5.1720.79/20.193.79/3.670.85/0.82
DEVIANT [25]ECCV222.52/2.506.93/6.870.95/0.940.02/0.0210.29/10.2026.75/26.544.95/4.900.16/0.16
DID-M3D[49]ECCV22-/--/--/--/-19.37/19.1940.77/40.4615.18/15.044.69/4.59
NeuROCS†[44]CVPR232.29/2.286.32/6.290.94/0.930.03/0.03-/--/--/--/-
MonoUNI [23]NeurlIPS233.04/3.008.59/8.480.85/0.840.12/0.1210.38/10.2426.57/26.243.95/3.890.53/0.51
OccupancyM3D-10.02/9.9428.38/28.174.38/4.340.36/0.3627.21/26.9061.09/60.4922.59/22.343.18/3.13
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.446, + 0.895, + 0.504 + ], + "angle": 0, + "content": "Table 2. Results on WaymoOD val set for Vehicle category. The red refers to the highest result and blue is the second-highest result. Our method outperforms other methods by significant margins on most metrics. Note that our method has the detection range limitation of [2, 59.6](meters), while the perspective-view based method DID-M3D [49] does not have this shortcoming. Thus our method performs worse for objects within \\([50m,\\infty ]\\) under IoU=0.5 criterion." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.528, + 0.471, + 0.559 + ], + "angle": 0, + "content": "formation to achieve better representations and features for monocular 3D detection." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.596, + 0.21, + 0.613 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.628, + 0.295, + 0.645 + ], + "angle": 0, + "content": "4.1. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.659, + 0.473, + 0.903 + ], + "angle": 0, + "content": "We employ PyTorch [48] for implementation. The network is trained on 4 NVIDIA 3080Ti (12G) GPUs, with a total batch size of 8 for 80 epochs. We use Adam [24] optimizer with initial learning rate 0.001 and employ the one-cycle learning rate policy [61]. We use pre-trained DLA34 [74] backbone from [47]. We employ flip and crop data augmentation [36]. For KITTI [17], we fix the input image to \\(1280 \\times 384\\), detection range \\([2,46.8] \\times [-30.08,30.08] \\times [-3.0,1.0]\\) (meter) for \\(x,y,z\\) axes under the LiDAR coordinate system, respectively. We use voxel size \\([0.16,0.16,0.16]\\) (meter). For Waymo [62], we downsample the input RGB image from \\(1920 \\times 1280\\) to \\(960 \\times 640\\) to meet GPU memory. We use detection range \\([2,59.6] \\times [-25.6,25.6] \\times [-2.0,2.0]\\) (meter) for \\(x,y,z\\) axes due to the larger depth domain on Waymo. We use voxel size \\([0.16,0.16,0.16]\\) (meter)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.528, + 0.698, + 0.543 + ], + "angle": 0, + "content": "4.2. Datasets and Metrics" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.552, + 0.892, + 0.581 + ], + "angle": 0, + "content": "Following the fashion in previous works, we conduct experiments on competitive KITTI and Waymo open datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.583, + 0.893, + 0.779 + ], + "angle": 0, + "content": "KITTI: KITTI [17] is a widely employed benchmark for autonomous driving. KITTI3D object dataset consists of 7,481 training samples and 7,518 testing samples, where labels on test set keep secret and the final performance is evaluated on KITTI official website. To conduct ablations, the training samples are further divided into a train set and a val set [10]. They individually contain 3,512 and 3,769 samples, respectively. KITTI has three categories: Car, Pedestrian, and Cyclist. According to difficulties (2D box height, occlusion and truncation levels), KITTI divides objects into Easy, Moderate, and Hard. Following common practice [35, 53, 60], we use \\(\\mathrm{AP}_{BEV}|_{R_{40}}\\) and \\(\\mathrm{AP}_{3D}|_{R_{40}}\\) under IoU threshold of 0.7 to evaluate the performance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.895, + 0.902 + ], + "angle": 0, + "content": "Waymo: Waymo open dataset (WaymoOD) [62] is a large modern dataset for autonomous driving. It has 798 sequences for training and 202 sequences for validation. Following previous works [49, 53], we use the front camera of the multi-camera rig and provide performance comparison on val set for the vehicle category. To make fair comparisons, we use one third samples of training sequences to train the network due to the large-scale and high frame rate" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "10286" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.104, + 0.089, + 0.863, + 0.366 + ], + "angle": 0, + "content": "
ApproachesVenueInputPedestrian APBEV/AP3D(IoU=0.5)|R40Cyclist APBEV/AP3D(IoU=0.5)|R40
EasyModerateHardEasyModerateHard
DfM [66]ECCV22Video-13.70-8.71-7.32-8.98-5.75-4.88
Monodle [39]CVPR21Image10.73/9.646.96/6.556.20/5.445.34/4.593.28/2.662.83/2.45
DDMP-3D [64]CVPR21Image5.53/4.934.02/3.553.36/3.014.92/4.183.14/2.502.44/2.32
MonoRUn [7]CVPR21Image11.70/10.887.59/6.786.34/5.831.14/1.010.73/0.610.66/0.48
MonoEF [79]CVPR21Image4.61/4.273.05/2.792.85/2.212.36/1.801.18/0.921.15/0.71
MonoFlex [76]CVPR21Image10.36/9.437.36/6.316.29/5.264.41/4.172.67/2.352.50/2.04
CaDDN [53]CVPR21Image14.72/12.879.41/8.148.17/6.769.67/7.005.38/3.414.75/3.30
GUP Net [36]ICCV21Image15.62/14.9510.37/9.768.79/8.416.94/5.583.85/3.213.64/2.66
AutoShape [35]ICCV21Image-5.46-3.74-3.03-5.99-3.06-2.70
MonoCon [33]AAAI22Image-13.10-8.41-6.94-2.80-1.92-1.55
HomoLoss [18]CVPR22Image13.26/11.878.81/7.667.41/6.826.81/5.484.09/3.503.78/2.99
MonoJSG [31]CVPR22Image-11.02-7.49-6.41-5.45-3.21-2.57
DEVIANT [25]ECCV22Image14.49/13.439.77/8.658.28/7.696.42/5.053.97/3.133.51/2.59
Cube R-CNN [4]CVPR23Image11.67/11.177.65/6.956.60/5.875.01/3.653.35/2.673.23/2.28
MonoUNI [23]NeurlPS23Image16.54/15.7810.90/10.349.17/8.748.25/7.345.03/4.284.50/3.78
OccupancyM3D-Image16.54/14.6810.65/9.159.16/7.808.58/7.374.35/3.563.55/2.84
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.371, + 0.89, + 0.399 + ], + "angle": 0, + "content": "Table 3. Comparisons on KITTI test set for Pedestrian and Cyclist categories. The red refers to the highest result and blue is the second-highest result. Our method achieves new state-of-the-art results." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.425, + 0.47, + 0.485 + ], + "angle": 0, + "content": "of this dataset. Waymo divides objects to LEVEL 1 and LEVEL 2 according to the LiDAR point number within objects. For metrics, we employ the official mAP and mAPH under LEVEL 1 and LEVEL 2." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.498, + 0.415, + 0.515 + ], + "angle": 0, + "content": "4.3. Results on KITTI and Waymo Datasets" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.522, + 0.47, + 0.824 + ], + "angle": 0, + "content": "We provide the performance comparisons on KITTI and WaymoOD. Table 1 shows the results of Car category on KITTI test set. Our method outperforms other methods including video-based methods. For example, the proposed method exceeds CaDDN [53] under all metrics, e.g., 25.55/17.02/14.79 vs. 19.17/13.41/11.46 \\(\\mathrm{AP}_{3D}\\). Please note that NeuROCS [44] requires instance masks for training and does not report results of Pedestrian and Cyclist on KITTI test set. Such irregularly shaped objects are challenging to NOCS prediction. Our method outperforms DID-M3D [49] by a margin of \\(2.43 / 1.42 / 1.54\\mathrm{AP}_{BEV}\\), and performs better than Cube R-CNN [4] and MonoUNI [23]. When compared to the video-based method DfM [66], OccupancyM3D also shows better performance, e.g., 24.18 vs. 22.89 \\(\\mathrm{AP}_{BEV}\\) under the moderate setting. In Table 3, we provide comparisons on other categories, namely, Pedestrian and Cyclist. The results demonstrate the superiority of our method on different categories. Concerning the overall performance on all categories, our method achieves a state-of-the-art on KITTI test set for monocular 3D detection." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.47, + 0.903 + ], + "angle": 0, + "content": "We also evaluate our method on Waymo open dataset (WaymoOD) [62] and obtain promising results. As shown in Table 2, our method surpasses other methods with a significant margin. For example, under LEVEL 1 setting, OccupancyM3D outperforms CaDDN [53] by 5.58/5.54" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.425, + 0.892, + 0.698 + ], + "angle": 0, + "content": "mAP/mAPH (10.61/10.53 vs. 5.03/4.99) and 11.55/11.35 mAP/mAPH (28.99/28.66 vs. 17.54/17.31) with IoU 0.7 and 0.5 criterions, respectively. Compared to DID-M3D [49], under IoU criterion 0.5, our method outperforms it by \\(8.33 / 8.19\\mathrm{mAP / mAPH}\\) (28.99/28.66 vs. 20.66/20.47) and 7.84/7.71 mAP/mAPH (27.21/26.90 vs. 19.37/19.19) with LEVEL 1 and 2 settings, respectively. This success can be attributed to the fact that occupancy learning benefits from the diverse scenes present in large datasets. In other words, large datasets especially favor the proposed occupancy learning method. Interestingly, concerning objects within \\([50m,\\infty ]\\) , our method performs worse than DID-M3D [49]. It is because our method is voxel-based, which has a detection range limitation ([2, 59.6](meters) in our method). By contrast, DID-M3D is a perspectivebased method, indicating that it does not have this limitation and can detect more faraway objects. We encourage future works to address this range limitation in our method." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.71, + 0.611, + 0.725 + ], + "angle": 0, + "content": "4.4. Ablations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.734, + 0.892, + 0.794 + ], + "angle": 0, + "content": "Following common practice in previous works, we perform ablations on KITTI val set to validate the effectiveness of each component. We compare the performance on Car category under IoU criterion 0.7." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.903 + ], + "angle": 0, + "content": "We provide the main ablation in Table 4. It can be easily seen that occupancy learning significantly benefit the final detection performance. When enforcing occupancy learning in frustum space, the detection \\(\\mathrm{AP}_{3D}\\) increases from 21.04/17.05/15.01 to 24.69/17.79/15.16 (Exp. (a) \\(\\rightarrow\\) (b)). On the other hand, when enforcing occupancy learning in 3D space, the detection \\(\\mathrm{AP}_{3D}\\) is boosted to" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "10287" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.357, + 0.166 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.364, + 0.099, + 0.625, + 0.171 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.642, + 0.087, + 0.895, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.197, + 0.357, + 0.273 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.179, + 0.287, + 0.277, + 0.299 + ], + "angle": 0, + "content": "Input RGB images" + }, + { + "type": "image", + "bbox": [ + 0.373, + 0.205, + 0.638, + 0.269 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.434, + 0.287, + 0.558, + 0.299 + ], + "angle": 0, + "content": "Occupancy predictions" + }, + { + "type": "image_caption", + "bbox": [ + 0.741, + 0.287, + 0.817, + 0.298 + ], + "angle": 0, + "content": "3D detections" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.305, + 0.894, + 0.377 + ], + "angle": 0, + "content": "Figure 4. Qualitative results of occupancy predictions and 3D detections on KITTI val set. In 3D detections, Red boxes are our results and Green boxes denote ground-truths. The LiDAR point clouds in 3D detections are used only for visualization. We can see that the proposed method generates reasonable occupancy predictions for the current scene, which benefits downstream monocular 3D detection task. However, our method may fail to estimate heavily occluded objects (see right objects of the bottom picture). Most monocular 3D detection failure cases stem from the poor occupancy estimation. Best viewed in color with zoom in." + }, + { + "type": "table", + "bbox": [ + 0.079, + 0.392, + 0.482, + 0.48 + ], + "angle": 0, + "content": "
E.OL-FSOL-3DSAPBEV/AP3D(IoU=0.7)|R40
EasyModerateHard
(a)30.32/21.0424.58/17.0522.02/15.01
(b)✓35.46/24.6925.46/17.7922.96/15.16
(c)✓33.15/24.6425.45/18.8822.68/16.38
(d)✓✓35.72/26.8726.60/19.9623.68/17.15
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.485, + 0.471, + 0.527 + ], + "angle": 0, + "content": "Table 4. Main ablation. \"E.\" in the table is the experiment ID; \"OL-FS\" refers to occupancy learning in frustum space; \"OL-3DS\" denotes occupancy learning in 3D space." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.544, + 0.47, + 0.605 + ], + "angle": 0, + "content": "24.64/18.88/16.38 (Exp. (c)). Finally, the model obtains \\(5.83 / 2.91 / 2.14\\mathrm{AP}_{3D}\\) gains (Exp. \\((a)\\rightarrow (d))\\) by employing occupancy learning in both frustum and 3D space. This main ablation demonstrates the effectiveness of our method." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.613, + 0.262, + 0.63 + ], + "angle": 0, + "content": "4.5. Qualitative Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.636, + 0.47, + 0.757 + ], + "angle": 0, + "content": "We present qualitative results of occupancy predictions and 3D detections in Figure 4. Our method can predict reasonable occupancy for the current scene, especially for foreground objects. This indicates the potential of occupancy learning in downstream tasks. Nevertheless, we can see that the occupancy estimates are not very accurate for heavily occluded objects (see right objects of the bottom picture), which leaves room for improvement in future works." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.77, + 0.342, + 0.787 + ], + "angle": 0, + "content": "5. Limitation and Future Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.903 + ], + "angle": 0, + "content": "One significant drawback of this work is the voxel size limitation. Large voxels in explicit voxel-based representation can reduce computation overhead and GPU memory, but at the cost of failing to precisely describe the 3D geometry of the scene due to quantization errors. Conversely, smaller voxel sizes are able to express fine-grained 3D geometry but come at the significant expense of increased computation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.394, + 0.895, + 0.547 + ], + "angle": 0, + "content": "overhead and GPU memory usage. On the other hand, the voxel-based method has limited detection ranges and most detection failure cases stem from poor occupancy estimation. This work mainly focuses on occupancy learning in the monocular 3D detection task, and the exploration of its application in more downstream tasks such as multi-camera detection/segmentation and indoor 3D detection is less explored. We believe that it is an interesting and promising topic and encourage future works to alleviate the above limitations to advance the self-driving community." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.567, + 0.619, + 0.583 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.595, + 0.894, + 0.777 + ], + "angle": 0, + "content": "In this paper, we propose to learn occupancy for monocular 3D detection, to obtain more discriminative and informative 3D features. To perform occupancy learning, we design occupancy labels by using synchronized raw sparse LiDAR point clouds and introduce corresponding occupancy losses. Ablations verify the effectiveness of each proposed component. To the best of our knowledge, this is the first work that introduces occupancy learning to monocular 3D detection. We conduct experiments on the challenging KITTI and Waymo open datasets. The results demonstrate that the proposed method achieves new state-of-the-art results and outperforms other methods by a large margin." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.798, + 0.66, + 0.815 + ], + "angle": 0, + "content": "Acknowledgments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.894, + 0.901 + ], + "angle": 0, + "content": "This work was supported in part by The National Nature Science Foundation of China (Grant Nos: 62273302, 62036009, 61936006, 62303406) and in part by Yongjiang Talent Introduction Programme (Grant No: 2023A-197-G, 2023A-194-G)." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "10288" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.17 + ], + "angle": 0, + "content": "[1] Alex Bewley, Pei Sun, Thomas Mensink, Dragomir Anguelov, and Cristian Sminchisescu. 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Existing approaches typically rely on geometry constraints and dense depth estimates to facilitate the learning, but often fail to fully exploit the benefits of three-dimensional feature extraction in frustum and 3D space. In this paper, we propose OccupancyM3D, a method of learning occupancy for monocular 3D detection. It directly learns occupancy in frustum and 3D space, leading to more discriminative and informative 3D features and representations. Specifically, by using synchronized raw sparse LiDAR point clouds, we define the space status and generate voxel-based occupancy labels. We formulate occupancy prediction as a simple classification problem and design associated occupancy losses. Resulting occupancy estimates are employed to enhance original frustum/3D features. As a result, experiments on KITTI and Waymo open datasets demonstrate that the proposed method achieves a new state of the art and surpasses other methods by a significant margin. + +# 1. Introduction + +Three dimensional object detection is a critical task in many real-world applications, such as self-driving and robot navigation. Early methods [52, 58, 78] typically rely on Li-DAR sensors because they can produce sparse yet accurate 3D point measurements. In contrast, cameras provide dense texture features but lack 3D information. Recently, monocular-based methods [36, 39, 49, 53] for 3D detection, also known as monocular 3D detection, have gained significant attention from both industry and academia due to their cost-effectiveness and deployment-friendly nature. + +Recovering accurate 3D information from a single RGB image poses a challenge. While previous researches have + +![](images/7740132d172103cf8f14111b792745cf9ae39a039ffa88b95e5eb7d3a2920860.jpg) +Figure 1. Overall design. We introduce occupancy learning for monocular 3D detection. Best viewed in color. + +employed geometry constraints [7, 27, 36, 45] and dense depth estimates [38, 53, 67] to facilitate 3D reasoning, they often overlook the importance of discriminative and informative 3D features in 3D space, which are essential for effective 3D detection. They mainly focus on improving features in 2D space, with little attention paid to better feature encoding and representation in the frustum and 3D space. + +Towards this goal, in this paper we propose to learn occupancy in frustum and 3D space, to obtain more discriminative and informative 3D features/representations for monocular 3D detection. Specifically, we employ synchronized raw sparse LiDAR point clouds to generate voxel-based occupancy labels in frustum and 3D space during the training stage. Concerning the sparsity of LiDAR points, we define three occupancy statuses: free, occupied, and unknown. Based on this, we voxelize the 3D space and use ray tracing on each LiDAR point to obtain occupancy labels. With the occupancy labels, we can enforce explicit 3D supervision on intermediate 3D features. It allows the network to learn voxelized occupancy for current 3D space, which enhances the original 3D features. This process is also performed in the frustum space, enabling a more fine-grained manner in extracting three-dimensional features for near objects due to the perspective nature of camera imagery. Overall, we call the proposed occupancy learning method OccupancyM3D, and illustrate the framework overview in Figure 1. + +To demonstrate the effectiveness of our method, we conduct experiments on the competitive KITTI and Waymo open datasets. As a result, the proposed method achieves + +state-of-the-art results with a significant margin over other methods. Our contributions can be summarized as follows: + +- We emphasize the importance of feature encoding and representation in the frustum and 3D space for monocular 3D detection, and we propose to learn occupancy in both space. +- We propose a method to generate occupancy labels using synchronized raw sparse LiDAR points and introduce corresponding occupancy losses, enabling the network to learn voxelized occupancy in both frustum and 3D space. This occupancy learning process facilitates the extraction of discriminative 3D features in the network. +- Experiments demonstrate the superiority of the proposed method. Evaluated on challenging KITTI and Waymo open datasets, our method achieves new state-of-the-art (SOTA) results and outperforms other methods by a significant margin. + +# 2. Related Work + +# 2.1. LiDAR Based 3D Object Detection + +LiDAR-based methods [19, 26, 56, 68, 69, 71, 77] currently dominate 3D object detection accuracy because of their precise depth measurements. Due to the unordered nature of point clouds, LiDAR-based methods are required to organize the input data. There are four main streams based on the input data representation: point-based, voxel-based, range-view-based, and hybrid-based. PointNet families [50, 51] are effective methods for feature extraction from raw point clouds, allowing point-based methods [52, 55, 59, 72] to directly perform 3D detection. Voxel-based methods [13, 70, 73, 77, 78] organize point clouds into voxel grids, making them compatible with regular convolutional neural networks. Range-view-based methods [1, 5, 15] convert point clouds into range-view to accommodate the LiDAR scanning mode. Hybrid-based methods [8, 46, 57, 71] use a combination of different representations to leverage their individual strengths. There is still a significant performance gap between monocular and LiDAR-based methods, which encourages researchers to advance monocular 3D detection. + +# 2.2. Monocular 3D Object Detection + +Significant progress has been made in advancing monocular 3D detection in recent years. The ill-posed problem of recovering instance level 3D information from a single image is challenging and important, attracting many researches. This is also the core sub-problem in monocular 3D detection. Early works [9, 45] resort to using scene priors and geometric projections to resolve objects' 3D locations. More recent monocular methods [2, 27, 29, 31, 35, 40, 76] employ more geometry constraints and extra priors like CAD models to achieve this goal. AutoShape [35] incorporates shape + +aware 2D/3D constraints into the 3D detection framework by learning distinguished 2D and 3D keypoints. MonoJSG [31] reformulates the instance depth estimation as a progressive refinement problem and propose a joint semantic and geometric cost volume to model the depth error. As RGB images lack explicit depth information, many works rely on dense depth estimates. Some methods [37, 38, 67] directly convert depth map to pseudo LiDAR or 3D coordinate patches, and some works [53] use depth distributions to lift 2D image features to 3D space. Therefore, previous well-designed LiDAR 3D detectors can be easily employed on such explicit 3D features. Other researches [11, 12, 14, 47, 49, 64] also take advantage of depth maps or LiDAR point clouds as guidance for feature extraction and auxiliary information. While previous works have leveraged geometry constraints and dense depth estimates, they have not fully explored feature encoding and representation in the frustum and 3D space. To address this, our method focuses on learning occupancy for monocular 3D detection. + +# 2.3. 3D Scene Representations + +Recent researches [41, 43, 75] rapidly advance implicit representations. Implicit representations have the advantage of arbitrary-resolution on modeling the 3D scene. This nature is beneficial for fine-grained tasks such as 3D reconstruction and semantic segmentation. Different from them, monocular 3D detection is an instance level task, and we explore explicit occupancy learning using fixed-sized voxels. Implicit occupancy representations for this task can be explored in future works, which is an interesting and promising topic. Additionally, many bird's-eye-view (BEV) based works [20, 28, 30, 34, 53, 54] have been proposed recently. These works commonly employ BEV representations and obtain great success, especially for multi-camera BEV detection. The most related work to ours is CaDDN [53]. We follow its architecture design except for the proposed occupancy learning module, and we replace its 2D backbone with lightweight DLA34 [74]. + +Since occupancy can serve as a general representation for scene perception and understanding. There is a burst of related works recently. SimpleOccupancy [16] adopts occupancy for better depth estimation. OccDepth [42] explores the occupancy in a stereo setting for semantic occupancy prediction. TPVFormer [22] employs sparse 3D occupancy labels from LiDAR as the supervision to obtain 3D features. OccNet [63] uses a decoder with various voxel based attention to reconstruct height information, accumulating occupancy labels from point cloud sequences. Different from them, we concentrate on 3D detection and takes a step farther to explore the effectiveness of occupancy in monocular 3D detection. Please note that our work focuses on the monocular setting, and extending the method to the multicamera setup is a potential avenue for future researches. + +![](images/064ce3d686db6f2539309f688845ef6d8eef2037a453ef3cb398e10788932f2e.jpg) +Figure 2. Network overview. Compared to previous works, our method employs two newly-proposed components for learning occupancy in frustum and 3D space. All network blocks in the proposed parts consist of vanilla 3D convolutions. Please refer to Section 3.1 for detailed feature passing description. For occupancy in frustum and 3D space and their network blocks, please see Section 3.2.1; For occupancy label generation, please see Section 3.2.2; For occupancy losses, please see Section 3.2.3; Best viewed in color with zoom in. + +# 3. OccupancyM3D + +# 3.1. Preliminary and Overview + +Task Definition. We first describe the preliminary of this task and the method. At inference, monocular 3D detection takes only a single RGB image and outputs interested amodal 3D bounding boxes in the current scene. At the training stage, our method requires RGB images, 3D box labels annotated on LiDAR points and synchronized LiDAR data. It is worth noting that the system has been calibrated, and the camera intrinsics and extrinsics between the camera and LiDAR are available. + +Network Overview. We present the network overview of our method in Figure 2. First, a single RGB image is fed into the DLA34 [74] backbone network to extract features. Then, we use these features to produce categorical depth distributions [53], which lifts 2D features to frustum space. After that, we employ the depth predictions and backbone features to generate frustum features. They are used for learning occupancy in frustum space, and then are transformed to voxelized 3D features using grid-sampling. Such voxelized 3D features are employed to study occupancy in 3D space. Occupancy learning in both frustum and 3D spaces can produce reasonable occupancy estimates that enhance the original features. The final enhanced voxelized 3D features are passed to the detection module to obtain final 3D detection results. + +At the training stage, occupancy estimates are supervised by the generated occupancy labels in frustum and 3D space, respectively, using the proposed occupancy losses. We de + +tail the occupancy learning in following sections. + +# 3.2. Occupancy Learning + +We consider a frustum voxel or regular 3D voxel to be occupied if it contains part of an object. We denote the resulting voxel states as frustum occupancy and 3D occupancy, respectively. In this section, we introduce occupancy learning for monocular 3D detection. It is organized as four parts: occupancy in frustum/3D space, occupancy labels, occupancy losses, and occupancy and depth. + +# 3.2.1 Occupancy in Frustum Space and 3D Space + +After extracting backbone features, we employ a depth head to obtain dense category depth [53]. To save GPU memory, we use a convolution layer to reduce the number of feature channels, and the resulting feature is lifted to a frustum feature $\mathbf{Fru}_1 \in \mathbb{R}^{W_F \times H_F \times D \times C}$ with the assistance of depth estimates. Then we extract frustum feature $\mathbf{Fru}_2 \in \mathbb{R}^{W_F \times H_F \times D \times C}$ as follows: + +$$ +\mathbf {F r u} _ {\mathbf {2}} = f _ {1} \left(\mathbf {F r u} _ {\mathbf {1}}\right) \tag {1} +$$ + +where $f_{1}$ denotes two 3D convolutions followed by ReLU activate functions. Then we use a 3D convolution layer $f_{2}$ and sigmoid function to obtain frustum occupancy $\mathbf{O}_{\mathbf{fru}} \in \mathbb{R}^{W_F \times H_F \times D \times 1}$ , which is supervised by corresponding labels $\mathbf{O}_{\mathbf{fru}}^*$ as described in Section 3.2.2 and Section 3.2.3. + +$$ +\mathbf {O} _ {\mathbf {f r u}} = \operatorname {S i g m o i d} \left(f _ {2} \left(\mathbf {F r u} _ {2}\right)\right) \tag {2} +$$ + +The frustum occupancy indicates the feature density in the frustum space, thus inherently can be employed to weight + +original frustum features for achieving enhanced frustum feature $\mathbf{Fru}_3\in \mathbb{R}^{W_F\times H_F\times D\times C}$ as follows: + +$$ +\mathbf {F r u} _ {3} = \mathbf {O} _ {\mathbf {f r u}} \odot \mathbf {F r u} _ {2} \tag {3} +$$ + +where $\odot$ denotes the Hadamard product (element-wise multiplication). The resulted frustum feature $\mathbf{Fru}_3$ is transformed to regular voxelized feature $\mathbf{V}_1 \in \mathbb{R}^{X \times Y \times Z \times C}$ via grid-sampling [53]. The occupancy learning process is then repeated in the regular 3D space. + +$$ +\mathbf {V} _ {\mathbf {2}} = f _ {3} \left(\mathbf {V} _ {\mathbf {1}}\right); \mathbf {O} _ {\mathbf {3 d}} = \text {S i g m o i d} \left(f _ {4} \left(\mathbf {V} _ {\mathbf {2}}\right)\right); \mathbf {V} _ {\mathbf {3}} = \mathbf {O} _ {\mathbf {3 d}} \odot \mathbf {V} _ {\mathbf {2}} \tag {4} +$$ + +To better encode 3D features in the regular 3D space, we use a 3D hourglass-like design [6] in $f_{3}$ , and $f_{4}$ is a 3D convolution. Finally, we have more informative 3D voxel feature $\mathbf{V}_3 \in \mathbb{R}^{X \times Y \times Z \times C}$ for the detection module. + +What is the rationale behind learning occupancy in both frustum and 3D space? Occupancy learning in both frustum and 3D space is beneficial because they have different nature. Frustum space has a resolution that depends on camera intrinsics and the downsample factor of the backbone network, while voxelized 3D space has a resolution that is decided by the pre-defined voxel size and detection range. Frustum voxels are irregular and vary in size based on the distance to the camera, which results in fine-grained voxels for objects that are closer and coarse-grained voxels for objects that are far away. In contrast, regular 3D voxels have the same size throughout the 3D space. On the other hand, frustum space is more fit to camera imagery, but objects in the frustum space cannot precisely represent the real 3D geometry. Thus the feature extraction and occupancy in frustum space have distortion for objects/scenes. Therefore, occupancy learning in both frustum and 3D space is complementary, and can result in more informative representations and features. + +# 3.2.2 Occupancy Labels + +Given a set of sparse LiDAR points $\mathbf{P} \in \mathbb{R}^{N \times 3}$ , where $N$ is the number of points and 3 is the coordinate dimension $(X, Y, Z)$ , we generate corresponding occupancy labels. The process is illustrated in Figure 3, and is operated on every LiDAR point. More formally, we first define three space status and represent them with numbers: free:0, occupied:1, unknown:-1. We then describe the occupancy label generation process in the frustum and 3D space, respectively. + +Occupancy label in frustum space: Let us denote the frustum occupancy label as $\mathbf{O}_{\mathrm{fru}}^{*} \in \mathbb{R}^{W_{F} \times H_{F} \times D}$ , where $W_{F}$ and $H_{F}$ are feature resolution, and $D$ is the depth category. We first project LiDAR points onto the image plane to form a category depth index map. Each valid projected point has a category depth index, while invalid points (no + +![](images/7759ed541f59d86c294c8e6b60ffd67312cd7c7ac9426e83cbb9ab575ac278d3.jpg) + +![](images/c0e052a59b9eb03aef75e60353dcc9758dce073f74590c52ab97bd7695c4f675.jpg) +Figure 3. Occupancy label generation in frustum and 3D space. Best viewed in color with zoom in. + +LiDAR points projections) are given negative indexes of $-1$ . This index map is then downsampled to fit the feature resolution, resulting in $\mathbf{Ind} \in \mathbb{R}^{W_F \times H_F}$ . Benefit from the camera projection nature, we can easily distinguish the space status as follows: + +$$ +\mathbf {O} _ {\mathbf {f r u} i, j, d} ^ {*} = \left\{ \begin{array}{l l} 1 & \text {i f} \mathbf {I n d} _ {i, j} > - 1 \text {a n d} d = \mathbf {I n d} _ {i, j}, \\ 0 & \text {i f} \mathbf {I n d} _ {i, j} > - 1 \text {a n d} d < \mathbf {I n d} _ {i, j}, \\ - 1 & \text {o t h e r w i s e .} \end{array} \right. \tag {5} +$$ + +where $i,j,d\in W_F,H_F,D$ .Note that we do not consider unknown voxels in both the occupancy labels and occupancy losses. We use the known voxels, i.e., the free and occupied voxels, to perform occupancy learning. + +Occupancy label in 3D space: We denote $\mathbf{O}_{\mathbf{3d}}^{*} \in \mathbb{R}^{X \times Y \times Z}$ as the 3D occupancy label, where $X, Y, Z$ are determined by the pre-defined voxel size and detection range. We voxelize LiDAR points within the grid and set the voxels containing points to 1, and those without points to $-1$ . In this way, occupied voxels can be easily achieved. To obtain the free voxels, we utilize ray tracing from each LiDAR point to the camera, where intersected voxels are set as free, filled by 0. We summarize the occupancy label in 3D space as follows: + +$$ +\mathbf {O} _ {\mathbf {3 d} x, y, z} ^ {*} = \left\{\begin{array}{l l}1&\text {i f V o l} _ {\mathbf {3 d} x, y, z} > 0,\\0&\text {i f R} \left(\mathbf {O} _ {\mathbf {3 d} x, y, z} ^ {*}\right) \cap \operatorname {R a y} _ {\text {p o i n t} \rightarrow \text {c a m}}\\- 1&\text {o t h e r w i s e .}\end{array}\right. \tag {6} +$$ + +where $x,y,z\in X,Y,Z$ .In this equation, $\mathbf{Vol}_{3d}$ denotes the voxelized grid. $\mathbf{Vol}_{3d} > 0$ when it is occu + +
ApproachesVenueInputAPBEV(IoU=0.7)|R40AP3D(IoU=0.7)|R40
EasyModerateHardEasyModerateHard
Kinematic3D [3]ECCV20Video26.6917.5213.1019.0712.729.17
DfM [66]ECCV22Video31.7122.8919.9722.9416.8214.65
Monodle [39]CVPR21Image24.7918.8916.0017.2312.2610.29
MonoFlex [76]CVPR21Image28.2319.7516.8919.9413.8912.07
CaDDN [53]CVPR21Image27.9418.9117.1919.1713.4111.46
GUP Net [36]ICCV21Image30.2921.1918.2022.2615.0213.12
AutoShape [35]ICCV21Image30.6620.0815.9522.4714.1711.36
PCT [65]NeurIPS21Image29.6519.0315.9221.0013.3711.31
MonoDTR [21]CVPR22Image28.5920.3817.1421.9915.3912.73
MonoJSG [31]CVPR22Image32.5921.2618.1824.6916.1413.64
DEVIANT [25]ECCV22Image29.6520.4417.4321.8814.4611.89
DID-M3D [49]ECCV22Image32.9522.7619.8324.4016.2913.75
MonoDDE [29]CVPR22Image33.5823.4620.3724.9317.1415.10
Cube R-CNN [4]CVPR23Image31.7021.2018.4323.5915.0112.56
NeuROCS†[44]CVPR23Image37.2724.4920.8929.8918.9415.90
MonoUNI [23]NeurlPS23Image33.2823.0519.3924.7516.7313.49
OccupancyM3D-Image35.3824.1821.3725.5517.0214.79
+ +Table 1. Comparisons on KITTI test set for Car category. The red refers to the highest result and blue is the second-highest result. Our method outperforms other methods including monocular and video-based methods. + +pied by LiDAR points. $\mathrm{R}(\cdot)$ refers to the voxel range and $\mathrm{R}(\mathbf{O}_{3\mathbf{d}i,j,d})\cap \mathrm{Ray}_{\mathrm{point}\to \mathrm{cam}}$ denotes that the voxel at index $i,j,d$ intersects with a ray from LiDAR points to the camera. In this way, 3D occupancy labels are generated. + +When generating voxel-based occupancy labels, there is a quantization error that arises due to the discretization process. A smaller voxel size results in lower quantization error, providing more fine-grained and accurate information. However, it requires more computation and GPU resources. + +# 3.2.3 Occupancy Losses + +We use generated occupancy labels $\mathbf{O}_{\mathbf{fru}}^{*}$ and $\mathbf{O}_{3\mathbf{d}}^{*}$ to supervised the predicted occupancy $\mathbf{O}_{\mathbf{fru}}$ and $\mathbf{O}_{3\mathbf{d}}$ , respectively. We regard occupancy prediction as a simple classification problem and use focal loss [32] as the classification loss. Only valid voxels, i.e., free and occupied voxels, contribute to the loss, and unknown voxels are ignored. We first obtain valid masks $\mathbf{M}_{\mathbf{fru}} \in \mathbb{R}^{W_F \times H_F \times D}$ and $\mathbf{M}_{3\mathbf{d}} \in \mathbb{R}^{X \times Y \times Z}$ . $\mathbf{M}_{\mathbf{fru}} = true$ if $\mathbf{O}_{\mathbf{fru}}^{*} > -1$ otherwise false. $\mathbf{M}_{3\mathbf{d}}$ is obtained using the similar way. + +Therefore, the occupancy loss in frustum space is: + +$$ +\mathcal {L} _ {f r u} = \operatorname {F L} \left(\mathbf {O} _ {\mathbf {f r u}} ^ {*} \left[ \mathbf {M} _ {\mathbf {f r u}} \right], \mathbf {O} _ {\mathbf {f r u}} \left[ \mathbf {M} _ {\mathbf {f r u}} \right]\right) \tag {7} +$$ + +where $\mathrm{FL}(\cdot)$ refers to focal loss and $[\cdot]$ is the selection via mask. Similarly, we can obtain 3D occupancy loss as follows: + +$$ +\mathcal {L} _ {3 d} = \operatorname {F L} \left(\mathrm {O} _ {\mathbf {3 d}} ^ {*} \left[ \mathrm {M} _ {\mathbf {3 d}} \right], \mathrm {O} _ {\mathbf {3 d}} \left[ \mathrm {M} _ {\mathbf {3 d}} \right]\right) \tag {8} +$$ + +The final occupancy loss is their sum: + +$$ +\mathcal {L} _ {\text {o c c u p a n c y}} = \mathcal {L} _ {f r u} + \mathcal {L} _ {3 d} \tag {9} +$$ + +The occupancy loss allows the network to learn informative and discriminative features and representations, thus benefit downstream tasks. Therefore, the final loss of the network is: + +$$ +\mathcal {L} = \mathcal {L} _ {\text {o r g}} + \lambda \mathcal {L} _ {\text {o c c u p a n c y}} \tag {10} +$$ + +where $\mathcal{L}_{org}$ denotes the original detection and depth losses in CaDDN [53] and $\lambda$ is the occupancy loss weighting factor, which is set to 1 by default. + +# 3.2.4 Occupancy and Depth + +Occupancy has some similarities with 2D depth map, especially the frustum occupancy. They both can represent object geometry surface in the space. However, depth map is two-dimensional while occupancy is three-dimensional. Occupancy is beyond the depth and can base on it. It is able to express dense features of objects but not only the surface. For unknown space due to occlusion, the occupancy can infer reasonable results. Moreover, learning occupancy in frustum and 3D space allows the network to study more informative features under a higher dimension compared to 2D space. + +Occupancy and depth are not mutually exclusive representations. In fact, they complement each other in the 3D object detection task. Without depth, the network has to deal with a large search space, making it challenging to learn reasonable occupancy features. Incorporating depth estimation provides the network with a good starting point and facilitates learning the occupancy features. Therefore, it is recommended to utilize both depth and occupancy in- + +
MethodsVenue3D mAP / mAPH (IoU = 0.7)3D mAP / mAPH (IoU = 0.5)
Overall0 - 30m30 - 50m50m - ∞Overall0 - 30m30 - 50m50m - ∞
Comparison on LEVEL 1
PatchNet[38]ECCV200.39/0.371.67/1.630.13/0.120.03/0.032.92/2.7410.03/9.751.09/0.960.23/0.18
CaDDN [53]CVPR215.03/4.9914.54/14.431.47/1.450.10/0.1017.54/17.3145.00/44.469.24/9.110.64/0.62
PCT [65]NeurlIPS210.89/0.883.18/3.150.27/0.270.07/0.074.20/4.1514.70/14.541.78/1.750.39/0.39
MonoJSG [31]CVPR220.97/0.954.65/4.590.55/0.530.10/0.095.65/5.4720.86/20.263.91/3.790.97/0.92
DEVIANT [25]ECCV222.69/2.676.95/6.900.99/0.980.02/0.0210.98/10.8926.85/26.645.13/5.080.18/0.18
DID-M3D [49]ECCV22-/--/--/--/-20.66/20.4740.92/40.6015.63/15.485.35/5.24
NeuROCS†[44]CVPR232.44/2.436.35/6.310.97/0.970.04/0.04-/--/--/--/-
MonoUNI [23]NeurlIPS233.20/3.168.61/8.500.87/0.860.13/0.1210.98/10.7326.63/26.304.04/3.980.57/0.55
OccupancyM3D-10.61/10.5329.18/28.964.49/4.460.41/0.4028.99/28.6661.24/60.6323.25/23.003.65/3.59
Comparison on LEVEL 2
PatchNet[38]ECCV200.38/0.361.67/1.630.13/0.110.03/0.032.42/2.2810.01/9.731.07/0.940.22/0.16
CaDDN [53]CVPR214.49/4.4514.50/14.381.42/1.410.09/0.0916.51/16.2844.87/44.338.99/8.860.58/0.55
PCT [65]NeurlIPS210.66/0.663.18/3.150.27/0.260.07/0.074.03/3.9914.67/14.511.74/1.710.36/0.35
MonoJSG [31]CVPR220.91/0.894.64/4.650.55/0.530.09/0.095.34/5.1720.79/20.193.79/3.670.85/0.82
DEVIANT [25]ECCV222.52/2.506.93/6.870.95/0.940.02/0.0210.29/10.2026.75/26.544.95/4.900.16/0.16
DID-M3D[49]ECCV22-/--/--/--/-19.37/19.1940.77/40.4615.18/15.044.69/4.59
NeuROCS†[44]CVPR232.29/2.286.32/6.290.94/0.930.03/0.03-/--/--/--/-
MonoUNI [23]NeurlIPS233.04/3.008.59/8.480.85/0.840.12/0.1210.38/10.2426.57/26.243.95/3.890.53/0.51
OccupancyM3D-10.02/9.9428.38/28.174.38/4.340.36/0.3627.21/26.9061.09/60.4922.59/22.343.18/3.13
+ +Table 2. Results on WaymoOD val set for Vehicle category. The red refers to the highest result and blue is the second-highest result. Our method outperforms other methods by significant margins on most metrics. Note that our method has the detection range limitation of [2, 59.6](meters), while the perspective-view based method DID-M3D [49] does not have this shortcoming. Thus our method performs worse for objects within $[50m,\infty ]$ under IoU=0.5 criterion. + +formation to achieve better representations and features for monocular 3D detection. + +# 4. Experiments + +# 4.1. Implementation Details + +We employ PyTorch [48] for implementation. The network is trained on 4 NVIDIA 3080Ti (12G) GPUs, with a total batch size of 8 for 80 epochs. We use Adam [24] optimizer with initial learning rate 0.001 and employ the one-cycle learning rate policy [61]. We use pre-trained DLA34 [74] backbone from [47]. We employ flip and crop data augmentation [36]. For KITTI [17], we fix the input image to $1280 \times 384$ , detection range $[2,46.8] \times [-30.08,30.08] \times [-3.0,1.0]$ (meter) for $x,y,z$ axes under the LiDAR coordinate system, respectively. We use voxel size $[0.16,0.16,0.16]$ (meter). For Waymo [62], we downsample the input RGB image from $1920 \times 1280$ to $960 \times 640$ to meet GPU memory. We use detection range $[2,59.6] \times [-25.6,25.6] \times [-2.0,2.0]$ (meter) for $x,y,z$ axes due to the larger depth domain on Waymo. We use voxel size $[0.16,0.16,0.16]$ (meter). + +# 4.2. Datasets and Metrics + +Following the fashion in previous works, we conduct experiments on competitive KITTI and Waymo open datasets. + +KITTI: KITTI [17] is a widely employed benchmark for autonomous driving. KITTI3D object dataset consists of 7,481 training samples and 7,518 testing samples, where labels on test set keep secret and the final performance is evaluated on KITTI official website. To conduct ablations, the training samples are further divided into a train set and a val set [10]. They individually contain 3,512 and 3,769 samples, respectively. KITTI has three categories: Car, Pedestrian, and Cyclist. According to difficulties (2D box height, occlusion and truncation levels), KITTI divides objects into Easy, Moderate, and Hard. Following common practice [35, 53, 60], we use $\mathrm{AP}_{BEV}|_{R_{40}}$ and $\mathrm{AP}_{3D}|_{R_{40}}$ under IoU threshold of 0.7 to evaluate the performance. + +Waymo: Waymo open dataset (WaymoOD) [62] is a large modern dataset for autonomous driving. It has 798 sequences for training and 202 sequences for validation. Following previous works [49, 53], we use the front camera of the multi-camera rig and provide performance comparison on val set for the vehicle category. To make fair comparisons, we use one third samples of training sequences to train the network due to the large-scale and high frame rate + +
ApproachesVenueInputPedestrian APBEV/AP3D(IoU=0.5)|R40Cyclist APBEV/AP3D(IoU=0.5)|R40
EasyModerateHardEasyModerateHard
DfM [66]ECCV22Video-13.70-8.71-7.32-8.98-5.75-4.88
Monodle [39]CVPR21Image10.73/9.646.96/6.556.20/5.445.34/4.593.28/2.662.83/2.45
DDMP-3D [64]CVPR21Image5.53/4.934.02/3.553.36/3.014.92/4.183.14/2.502.44/2.32
MonoRUn [7]CVPR21Image11.70/10.887.59/6.786.34/5.831.14/1.010.73/0.610.66/0.48
MonoEF [79]CVPR21Image4.61/4.273.05/2.792.85/2.212.36/1.801.18/0.921.15/0.71
MonoFlex [76]CVPR21Image10.36/9.437.36/6.316.29/5.264.41/4.172.67/2.352.50/2.04
CaDDN [53]CVPR21Image14.72/12.879.41/8.148.17/6.769.67/7.005.38/3.414.75/3.30
GUP Net [36]ICCV21Image15.62/14.9510.37/9.768.79/8.416.94/5.583.85/3.213.64/2.66
AutoShape [35]ICCV21Image-5.46-3.74-3.03-5.99-3.06-2.70
MonoCon [33]AAAI22Image-13.10-8.41-6.94-2.80-1.92-1.55
HomoLoss [18]CVPR22Image13.26/11.878.81/7.667.41/6.826.81/5.484.09/3.503.78/2.99
MonoJSG [31]CVPR22Image-11.02-7.49-6.41-5.45-3.21-2.57
DEVIANT [25]ECCV22Image14.49/13.439.77/8.658.28/7.696.42/5.053.97/3.133.51/2.59
Cube R-CNN [4]CVPR23Image11.67/11.177.65/6.956.60/5.875.01/3.653.35/2.673.23/2.28
MonoUNI [23]NeurlPS23Image16.54/15.7810.90/10.349.17/8.748.25/7.345.03/4.284.50/3.78
OccupancyM3D-Image16.54/14.6810.65/9.159.16/7.808.58/7.374.35/3.563.55/2.84
+ +Table 3. Comparisons on KITTI test set for Pedestrian and Cyclist categories. The red refers to the highest result and blue is the second-highest result. Our method achieves new state-of-the-art results. + +of this dataset. Waymo divides objects to LEVEL 1 and LEVEL 2 according to the LiDAR point number within objects. For metrics, we employ the official mAP and mAPH under LEVEL 1 and LEVEL 2. + +# 4.3. Results on KITTI and Waymo Datasets + +We provide the performance comparisons on KITTI and WaymoOD. Table 1 shows the results of Car category on KITTI test set. Our method outperforms other methods including video-based methods. For example, the proposed method exceeds CaDDN [53] under all metrics, e.g., 25.55/17.02/14.79 vs. 19.17/13.41/11.46 $\mathrm{AP}_{3D}$ . Please note that NeuROCS [44] requires instance masks for training and does not report results of Pedestrian and Cyclist on KITTI test set. Such irregularly shaped objects are challenging to NOCS prediction. Our method outperforms DID-M3D [49] by a margin of $2.43 / 1.42 / 1.54\mathrm{AP}_{BEV}$ , and performs better than Cube R-CNN [4] and MonoUNI [23]. When compared to the video-based method DfM [66], OccupancyM3D also shows better performance, e.g., 24.18 vs. 22.89 $\mathrm{AP}_{BEV}$ under the moderate setting. In Table 3, we provide comparisons on other categories, namely, Pedestrian and Cyclist. The results demonstrate the superiority of our method on different categories. Concerning the overall performance on all categories, our method achieves a state-of-the-art on KITTI test set for monocular 3D detection. + +We also evaluate our method on Waymo open dataset (WaymoOD) [62] and obtain promising results. As shown in Table 2, our method surpasses other methods with a significant margin. For example, under LEVEL 1 setting, OccupancyM3D outperforms CaDDN [53] by 5.58/5.54 + +mAP/mAPH (10.61/10.53 vs. 5.03/4.99) and 11.55/11.35 mAP/mAPH (28.99/28.66 vs. 17.54/17.31) with IoU 0.7 and 0.5 criterions, respectively. Compared to DID-M3D [49], under IoU criterion 0.5, our method outperforms it by $8.33 / 8.19\mathrm{mAP / mAPH}$ (28.99/28.66 vs. 20.66/20.47) and 7.84/7.71 mAP/mAPH (27.21/26.90 vs. 19.37/19.19) with LEVEL 1 and 2 settings, respectively. This success can be attributed to the fact that occupancy learning benefits from the diverse scenes present in large datasets. In other words, large datasets especially favor the proposed occupancy learning method. Interestingly, concerning objects within $[50m,\infty ]$ , our method performs worse than DID-M3D [49]. It is because our method is voxel-based, which has a detection range limitation ([2, 59.6](meters) in our method). By contrast, DID-M3D is a perspectivebased method, indicating that it does not have this limitation and can detect more faraway objects. We encourage future works to address this range limitation in our method. + +# 4.4. Ablations + +Following common practice in previous works, we perform ablations on KITTI val set to validate the effectiveness of each component. We compare the performance on Car category under IoU criterion 0.7. + +We provide the main ablation in Table 4. It can be easily seen that occupancy learning significantly benefit the final detection performance. When enforcing occupancy learning in frustum space, the detection $\mathrm{AP}_{3D}$ increases from 21.04/17.05/15.01 to 24.69/17.79/15.16 (Exp. (a) $\rightarrow$ (b)). On the other hand, when enforcing occupancy learning in 3D space, the detection $\mathrm{AP}_{3D}$ is boosted to + +![](images/7e51f782f242a681009176fec3ee4432dea98614bc8f8e498ce2d3f9074d3dc4.jpg) + +![](images/c2addf750a3519ed96714e57ebf5cd88d914759e0450f0f7e23c69dbab038400.jpg) + +![](images/44b295e4483676b68badfd55723d74a0cc170480ff11ddb5e9a50236c3b90294.jpg) +3D detections +Figure 4. Qualitative results of occupancy predictions and 3D detections on KITTI val set. In 3D detections, Red boxes are our results and Green boxes denote ground-truths. The LiDAR point clouds in 3D detections are used only for visualization. We can see that the proposed method generates reasonable occupancy predictions for the current scene, which benefits downstream monocular 3D detection task. However, our method may fail to estimate heavily occluded objects (see right objects of the bottom picture). Most monocular 3D detection failure cases stem from the poor occupancy estimation. Best viewed in color with zoom in. + +![](images/f279047a4216fa30d8bbaba1d95555bdce69e0931fd761e223c8689b0c4d9d41.jpg) +Input RGB images + +![](images/cf7e2bdc0f9d0e88f82060881c1ab10ed792c212da768f6790bca31673d05ed1.jpg) +Occupancy predictions + +
E.OL-FSOL-3DSAPBEV/AP3D(IoU=0.7)|R40
EasyModerateHard
(a)30.32/21.0424.58/17.0522.02/15.01
(b)✓35.46/24.6925.46/17.7922.96/15.16
(c)✓33.15/24.6425.45/18.8822.68/16.38
(d)✓✓35.72/26.8726.60/19.9623.68/17.15
+ +Table 4. Main ablation. "E." in the table is the experiment ID; "OL-FS" refers to occupancy learning in frustum space; "OL-3DS" denotes occupancy learning in 3D space. + +24.64/18.88/16.38 (Exp. (c)). Finally, the model obtains $5.83 / 2.91 / 2.14\mathrm{AP}_{3D}$ gains (Exp. $(a)\rightarrow (d))$ by employing occupancy learning in both frustum and 3D space. This main ablation demonstrates the effectiveness of our method. + +# 4.5. Qualitative Results + +We present qualitative results of occupancy predictions and 3D detections in Figure 4. Our method can predict reasonable occupancy for the current scene, especially for foreground objects. This indicates the potential of occupancy learning in downstream tasks. Nevertheless, we can see that the occupancy estimates are not very accurate for heavily occluded objects (see right objects of the bottom picture), which leaves room for improvement in future works. + +# 5. Limitation and Future Work + +One significant drawback of this work is the voxel size limitation. Large voxels in explicit voxel-based representation can reduce computation overhead and GPU memory, but at the cost of failing to precisely describe the 3D geometry of the scene due to quantization errors. Conversely, smaller voxel sizes are able to express fine-grained 3D geometry but come at the significant expense of increased computation + +overhead and GPU memory usage. On the other hand, the voxel-based method has limited detection ranges and most detection failure cases stem from poor occupancy estimation. This work mainly focuses on occupancy learning in the monocular 3D detection task, and the exploration of its application in more downstream tasks such as multi-camera detection/segmentation and indoor 3D detection is less explored. We believe that it is an interesting and promising topic and encourage future works to alleviate the above limitations to advance the self-driving community. + +# 6. Conclusion + +In this paper, we propose to learn occupancy for monocular 3D detection, to obtain more discriminative and informative 3D features. To perform occupancy learning, we design occupancy labels by using synchronized raw sparse LiDAR point clouds and introduce corresponding occupancy losses. Ablations verify the effectiveness of each proposed component. To the best of our knowledge, this is the first work that introduces occupancy learning to monocular 3D detection. We conduct experiments on the challenging KITTI and Waymo open datasets. The results demonstrate that the proposed method achieves new state-of-the-art results and outperforms other methods by a large margin. + +# Acknowledgments + +This work was supported in part by The National Nature Science Foundation of China (Grant Nos: 62273302, 62036009, 61936006, 62303406) and in part by Yongjiang Talent Introduction Programme (Grant No: 2023A-197-G, 2023A-194-G). + +# References + +[1] Alex Bewley, Pei Sun, Thomas Mensink, Dragomir Anguelov, and Cristian Sminchisescu. Range conditioned dilated convolutions for scale invariant 3d object detection. arXiv preprint arXiv:2005.09927, 2020. 2 +[2] Garrick Brazil and Xiaoming Liu. M3d-rpn: Monocular 3d region proposal network for object detection. In Proceedings of the IEEE International Conference on Computer Vision, pages 9287-9296, 2019. 2 +[3] Garrick Brazil, Gerard Pons-Moll, Xiaoming Liu, and Bernt Schiele. Kinematic 3d object detection in monocular video. In European Conference on Computer Vision, pages 135-152. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 7556-7566, 2021. 7 \ No newline at end of file diff --git a/2024/Learning Occupancy for Monocular 3D Object Detection/images.zip b/2024/Learning Occupancy for Monocular 3D Object Detection/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..f110b5bc2b8d37e42507f1336e49bfbab773c6b7 --- /dev/null +++ b/2024/Learning Occupancy for Monocular 3D Object Detection/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:f2022e6064f9e55ef55f73a93f1fce07ff8af76b59b97d07e9a279d150075bd1 +size 837243 diff --git a/2024/Learning Occupancy for Monocular 3D Object Detection/layout.json b/2024/Learning Occupancy for Monocular 3D Object Detection/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..8016c810415437cb8c1bb28f49312bd3a87ab456 --- /dev/null +++ b/2024/Learning Occupancy for Monocular 3D Object Detection/layout.json @@ -0,0 +1,9085 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 120, + 103, + 474, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 120, + 103, + 474, + 121 + ], + "spans": [ + { + "bbox": [ + 120, + 103, + 474, + 121 + ], + "type": "text", + "content": "Learning Occupancy for Monocular 3D Object Detection" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "spans": [ + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": "Liang Peng" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": " Junkai Xu" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{1,3}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": " Haoran Cheng" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{1,3}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": " Zheng Yang" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": " Xiaopei Wu" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": " Wei Qian" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": " Wenxiao Wang" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": " Boxi Wu" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{2*}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": " Deng Cai" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": "State Key Lab of CAD&CG, Zhejiang University " + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": "School of Software Technology, Zhejiang University " + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 102, + 141, + 491, + 229 + ], + "type": "text", + "content": "FABU Inc. {pengliang, xujunkai, haorancheng}@zju.edu.cn" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 143, + 255, + 192, + 268 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 255, + 192, + 268 + ], + "spans": [ + { + "bbox": [ + 143, + 255, + 192, + 268 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 280, + 290, + 509 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 280, + 290, + 509 + ], + "spans": [ + { + "bbox": [ + 46, + 280, + 290, + 509 + ], + "type": "text", + "content": "Monocular 3D detection is a challenging task due to the lack of accurate 3D information. Existing approaches typically rely on geometry constraints and dense depth estimates to facilitate the learning, but often fail to fully exploit the benefits of three-dimensional feature extraction in frustum and 3D space. In this paper, we propose OccupancyM3D, a method of learning occupancy for monocular 3D detection. It directly learns occupancy in frustum and 3D space, leading to more discriminative and informative 3D features and representations. Specifically, by using synchronized raw sparse LiDAR point clouds, we define the space status and generate voxel-based occupancy labels. We formulate occupancy prediction as a simple classification problem and design associated occupancy losses. Resulting occupancy estimates are employed to enhance original frustum/3D features. As a result, experiments on KITTI and Waymo open datasets demonstrate that the proposed method achieves a new state of the art and surpasses other methods by a significant margin." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 530, + 128, + 544 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 530, + 128, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 530, + 128, + 544 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 550, + 287, + 670 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 550, + 287, + 670 + ], + "spans": [ + { + "bbox": [ + 46, + 550, + 287, + 670 + ], + "type": "text", + "content": "Three dimensional object detection is a critical task in many real-world applications, such as self-driving and robot navigation. Early methods [52, 58, 78] typically rely on Li-DAR sensors because they can produce sparse yet accurate 3D point measurements. In contrast, cameras provide dense texture features but lack 3D information. Recently, monocular-based methods [36, 39, 49, 53] for 3D detection, also known as monocular 3D detection, have gained significant attention from both industry and academia due to their cost-effectiveness and deployment-friendly nature." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 670, + 287, + 695 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 287, + 695 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 287, + 695 + ], + "type": "text", + "content": "Recovering accurate 3D information from a single RGB image poses a challenge. While previous researches have" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 318, + 254, + 533, + 331 + ], + "blocks": [ + { + "bbox": [ + 318, + 254, + 533, + 331 + ], + "lines": [ + { + "bbox": [ + 318, + 254, + 533, + 331 + ], + "spans": [ + { + "bbox": [ + 318, + 254, + 533, + 331 + ], + "type": "image", + "image_path": "7740132d172103cf8f14111b792745cf9ae39a039ffa88b95e5eb7d3a2920860.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 333, + 545, + 355 + ], + "lines": [ + { + "bbox": [ + 306, + 333, + 545, + 355 + ], + "spans": [ + { + "bbox": [ + 306, + 333, + 545, + 355 + ], + "type": "text", + "content": "Figure 1. Overall design. We introduce occupancy learning for monocular 3D detection. Best viewed in color." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 365, + 546, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 365, + 546, + 449 + ], + "spans": [ + { + "bbox": [ + 304, + 365, + 546, + 449 + ], + "type": "text", + "content": "employed geometry constraints [7, 27, 36, 45] and dense depth estimates [38, 53, 67] to facilitate 3D reasoning, they often overlook the importance of discriminative and informative 3D features in 3D space, which are essential for effective 3D detection. They mainly focus on improving features in 2D space, with little attention paid to better feature encoding and representation in the frustum and 3D space." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 450, + 547, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 450, + 547, + 676 + ], + "spans": [ + { + "bbox": [ + 304, + 450, + 547, + 676 + ], + "type": "text", + "content": "Towards this goal, in this paper we propose to learn occupancy in frustum and 3D space, to obtain more discriminative and informative 3D features/representations for monocular 3D detection. Specifically, we employ synchronized raw sparse LiDAR point clouds to generate voxel-based occupancy labels in frustum and 3D space during the training stage. Concerning the sparsity of LiDAR points, we define three occupancy statuses: free, occupied, and unknown. Based on this, we voxelize the 3D space and use ray tracing on each LiDAR point to obtain occupancy labels. With the occupancy labels, we can enforce explicit 3D supervision on intermediate 3D features. It allows the network to learn voxelized occupancy for current 3D space, which enhances the original 3D features. This process is also performed in the frustum space, enabling a more fine-grained manner in extracting three-dimensional features for near objects due to the perspective nature of camera imagery. Overall, we call the proposed occupancy learning method OccupancyM3D, and illustrate the framework overview in Figure 1." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "type": "text", + "content": "To demonstrate the effectiveness of our method, we conduct experiments on the competitive KITTI and Waymo open datasets. As a result, the proposed method achieves" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 135, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 135, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 135, + 712 + ], + "type": "text", + "content": "*Corresponding author." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "10281" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "type": "text", + "content": "state-of-the-art results with a significant margin over other methods. Our contributions can be summarized as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 99, + 286, + 277 + ], + "type": "list", + "angle": 0, + "index": 4, + "blocks": [ + { + "bbox": [ + 47, + 99, + 286, + 145 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 99, + 286, + 145 + ], + "spans": [ + { + "bbox": [ + 47, + 99, + 286, + 145 + ], + "type": "text", + "content": "- We emphasize the importance of feature encoding and representation in the frustum and 3D space for monocular 3D detection, and we propose to learn occupancy in both space." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 147, + 286, + 217 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 147, + 286, + 217 + ], + "spans": [ + { + "bbox": [ + 47, + 147, + 286, + 217 + ], + "type": "text", + "content": "- We propose a method to generate occupancy labels using synchronized raw sparse LiDAR points and introduce corresponding occupancy losses, enabling the network to learn voxelized occupancy in both frustum and 3D space. This occupancy learning process facilitates the extraction of discriminative 3D features in the network." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 219, + 286, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 219, + 286, + 277 + ], + "spans": [ + { + "bbox": [ + 47, + 219, + 286, + 277 + ], + "type": "text", + "content": "- Experiments demonstrate the superiority of the proposed method. Evaluated on challenging KITTI and Waymo open datasets, our method achieves new state-of-the-art (SOTA) results and outperforms other methods by a significant margin." + } + ] + } + ], + "index": 3 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 289, + 133, + 301 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 289, + 133, + 301 + ], + "spans": [ + { + "bbox": [ + 47, + 289, + 133, + 301 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 308, + 231, + 321 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 308, + 231, + 321 + ], + "spans": [ + { + "bbox": [ + 47, + 308, + 231, + 321 + ], + "type": "text", + "content": "2.1. LiDAR Based 3D Object Detection" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 327, + 287, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 327, + 287, + 567 + ], + "spans": [ + { + "bbox": [ + 47, + 327, + 287, + 567 + ], + "type": "text", + "content": "LiDAR-based methods [19, 26, 56, 68, 69, 71, 77] currently dominate 3D object detection accuracy because of their precise depth measurements. Due to the unordered nature of point clouds, LiDAR-based methods are required to organize the input data. There are four main streams based on the input data representation: point-based, voxel-based, range-view-based, and hybrid-based. PointNet families [50, 51] are effective methods for feature extraction from raw point clouds, allowing point-based methods [52, 55, 59, 72] to directly perform 3D detection. Voxel-based methods [13, 70, 73, 77, 78] organize point clouds into voxel grids, making them compatible with regular convolutional neural networks. Range-view-based methods [1, 5, 15] convert point clouds into range-view to accommodate the LiDAR scanning mode. Hybrid-based methods [8, 46, 57, 71] use a combination of different representations to leverage their individual strengths. There is still a significant performance gap between monocular and LiDAR-based methods, which encourages researchers to advance monocular 3D detection." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 575, + 219, + 587 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 575, + 219, + 587 + ], + "spans": [ + { + "bbox": [ + 47, + 575, + 219, + 587 + ], + "type": "text", + "content": "2.2. Monocular 3D Object Detection" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 594, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 594, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 594, + 286, + 713 + ], + "type": "text", + "content": "Significant progress has been made in advancing monocular 3D detection in recent years. The ill-posed problem of recovering instance level 3D information from a single image is challenging and important, attracting many researches. This is also the core sub-problem in monocular 3D detection. Early works [9, 45] resort to using scene priors and geometric projections to resolve objects' 3D locations. More recent monocular methods [2, 27, 29, 31, 35, 40, 76] employ more geometry constraints and extra priors like CAD models to achieve this goal. AutoShape [35] incorporates shape" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 72, + 545, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 300 + ], + "type": "text", + "content": "aware 2D/3D constraints into the 3D detection framework by learning distinguished 2D and 3D keypoints. MonoJSG [31] reformulates the instance depth estimation as a progressive refinement problem and propose a joint semantic and geometric cost volume to model the depth error. As RGB images lack explicit depth information, many works rely on dense depth estimates. Some methods [37, 38, 67] directly convert depth map to pseudo LiDAR or 3D coordinate patches, and some works [53] use depth distributions to lift 2D image features to 3D space. Therefore, previous well-designed LiDAR 3D detectors can be easily employed on such explicit 3D features. Other researches [11, 12, 14, 47, 49, 64] also take advantage of depth maps or LiDAR point clouds as guidance for feature extraction and auxiliary information. While previous works have leveraged geometry constraints and dense depth estimates, they have not fully explored feature encoding and representation in the frustum and 3D space. To address this, our method focuses on learning occupancy for monocular 3D detection." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 310, + 449, + 322 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 310, + 449, + 322 + ], + "spans": [ + { + "bbox": [ + 306, + 310, + 449, + 322 + ], + "type": "text", + "content": "2.3. 3D Scene Representations" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 329, + 545, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 329, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 304, + 329, + 545, + 533 + ], + "type": "text", + "content": "Recent researches [41, 43, 75] rapidly advance implicit representations. Implicit representations have the advantage of arbitrary-resolution on modeling the 3D scene. This nature is beneficial for fine-grained tasks such as 3D reconstruction and semantic segmentation. Different from them, monocular 3D detection is an instance level task, and we explore explicit occupancy learning using fixed-sized voxels. Implicit occupancy representations for this task can be explored in future works, which is an interesting and promising topic. Additionally, many bird's-eye-view (BEV) based works [20, 28, 30, 34, 53, 54] have been proposed recently. These works commonly employ BEV representations and obtain great success, especially for multi-camera BEV detection. The most related work to ours is CaDDN [53]. We follow its architecture design except for the proposed occupancy learning module, and we replace its 2D backbone with lightweight DLA34 [74]." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 534, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 545, + 713 + ], + "type": "text", + "content": "Since occupancy can serve as a general representation for scene perception and understanding. There is a burst of related works recently. SimpleOccupancy [16] adopts occupancy for better depth estimation. OccDepth [42] explores the occupancy in a stereo setting for semantic occupancy prediction. TPVFormer [22] employs sparse 3D occupancy labels from LiDAR as the supervision to obtain 3D features. OccNet [63] uses a decoder with various voxel based attention to reconstruct height information, accumulating occupancy labels from point cloud sequences. Different from them, we concentrate on 3D detection and takes a step farther to explore the effectiveness of occupancy in monocular 3D detection. Please note that our work focuses on the monocular setting, and extending the method to the multicamera setup is a potential avenue for future researches." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "10282" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 62, + 70, + 537, + 285 + ], + "blocks": [ + { + "bbox": [ + 62, + 70, + 537, + 285 + ], + "lines": [ + { + "bbox": [ + 62, + 70, + 537, + 285 + ], + "spans": [ + { + "bbox": [ + 62, + 70, + 537, + 285 + ], + "type": "image", + "image_path": "064ce3d686db6f2539309f688845ef6d8eef2037a453ef3cb398e10788932f2e.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 289, + 547, + 335 + ], + "lines": [ + { + "bbox": [ + 46, + 289, + 547, + 335 + ], + "spans": [ + { + "bbox": [ + 46, + 289, + 547, + 335 + ], + "type": "text", + "content": "Figure 2. Network overview. Compared to previous works, our method employs two newly-proposed components for learning occupancy in frustum and 3D space. All network blocks in the proposed parts consist of vanilla 3D convolutions. Please refer to Section 3.1 for detailed feature passing description. For occupancy in frustum and 3D space and their network blocks, please see Section 3.2.1; For occupancy label generation, please see Section 3.2.2; For occupancy losses, please see Section 3.2.3; Best viewed in color with zoom in." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 342, + 146, + 357 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 342, + 146, + 357 + ], + "spans": [ + { + "bbox": [ + 47, + 342, + 146, + 357 + ], + "type": "text", + "content": "3. OccupancyM3D" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 364, + 194, + 377 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 364, + 194, + 377 + ], + "spans": [ + { + "bbox": [ + 47, + 364, + 194, + 377 + ], + "type": "text", + "content": "3.1. Preliminary and Overview" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 385, + 288, + 492 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 385, + 288, + 492 + ], + "spans": [ + { + "bbox": [ + 46, + 385, + 288, + 492 + ], + "type": "text", + "content": "Task Definition. We first describe the preliminary of this task and the method. At inference, monocular 3D detection takes only a single RGB image and outputs interested amodal 3D bounding boxes in the current scene. At the training stage, our method requires RGB images, 3D box labels annotated on LiDAR points and synchronized LiDAR data. It is worth noting that the system has been calibrated, and the camera intrinsics and extrinsics between the camera and LiDAR are available." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 496, + 287, + 674 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 496, + 287, + 674 + ], + "spans": [ + { + "bbox": [ + 46, + 496, + 287, + 674 + ], + "type": "text", + "content": "Network Overview. We present the network overview of our method in Figure 2. First, a single RGB image is fed into the DLA34 [74] backbone network to extract features. Then, we use these features to produce categorical depth distributions [53], which lifts 2D features to frustum space. After that, we employ the depth predictions and backbone features to generate frustum features. They are used for learning occupancy in frustum space, and then are transformed to voxelized 3D features using grid-sampling. Such voxelized 3D features are employed to study occupancy in 3D space. Occupancy learning in both frustum and 3D spaces can produce reasonable occupancy estimates that enhance the original features. The final enhanced voxelized 3D features are passed to the detection module to obtain final 3D detection results." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "text", + "content": "At the training stage, occupancy estimates are supervised by the generated occupancy labels in frustum and 3D space, respectively, using the proposed occupancy losses. We de" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 343, + 504, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 343, + 504, + 357 + ], + "spans": [ + { + "bbox": [ + 305, + 343, + 504, + 357 + ], + "type": "text", + "content": "tail the occupancy learning in following sections." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 361, + 427, + 374 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 361, + 427, + 374 + ], + "spans": [ + { + "bbox": [ + 306, + 361, + 427, + 374 + ], + "type": "text", + "content": "3.2. Occupancy Learning" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 380, + 545, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 380, + 545, + 464 + ], + "spans": [ + { + "bbox": [ + 304, + 380, + 545, + 464 + ], + "type": "text", + "content": "We consider a frustum voxel or regular 3D voxel to be occupied if it contains part of an object. We denote the resulting voxel states as frustum occupancy and 3D occupancy, respectively. In this section, we introduce occupancy learning for monocular 3D detection. It is organized as four parts: occupancy in frustum/3D space, occupancy labels, occupancy losses, and occupancy and depth." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 478, + 526, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 478, + 526, + 491 + ], + "spans": [ + { + "bbox": [ + 305, + 478, + 526, + 491 + ], + "type": "text", + "content": "3.2.1 Occupancy in Frustum Space and 3D Space" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 496, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 496, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 496, + 545, + 581 + ], + "type": "text", + "content": "After extracting backbone features, we employ a depth head to obtain dense category depth [53]. To save GPU memory, we use a convolution layer to reduce the number of feature channels, and the resulting feature is lifted to a frustum feature " + }, + { + "bbox": [ + 304, + 496, + 545, + 581 + ], + "type": "inline_equation", + "content": "\\mathbf{Fru}_1 \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times C}" + }, + { + "bbox": [ + 304, + 496, + 545, + 581 + ], + "type": "text", + "content": " with the assistance of depth estimates. Then we extract frustum feature " + }, + { + "bbox": [ + 304, + 496, + 545, + 581 + ], + "type": "inline_equation", + "content": "\\mathbf{Fru}_2 \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times C}" + }, + { + "bbox": [ + 304, + 496, + 545, + 581 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 386, + 586, + 545, + 599 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 386, + 586, + 545, + 599 + ], + "spans": [ + { + "bbox": [ + 386, + 586, + 545, + 599 + ], + "type": "interline_equation", + "content": "\\mathbf {F r u} _ {\\mathbf {2}} = f _ {1} \\left(\\mathbf {F r u} _ {\\mathbf {1}}\\right) \\tag {1}", + "image_path": "220c9c97d666987940501b007ad333c0b5ac0d56911e02680d770817a8bcd4eb.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "inline_equation", + "content": "f_{1}" + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "text", + "content": " denotes two 3D convolutions followed by ReLU activate functions. Then we use a 3D convolution layer " + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "inline_equation", + "content": "f_{2}" + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "text", + "content": " and sigmoid function to obtain frustum occupancy " + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathbf{fru}} \\in \\mathbb{R}^{W_F \\times H_F \\times D \\times 1}" + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "text", + "content": ", which is supervised by corresponding labels " + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathbf{fru}}^*" + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "text", + "content": " as described in Section 3.2.2 and Section 3.2.3." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 365, + 670, + 545, + 685 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 365, + 670, + 545, + 685 + ], + "spans": [ + { + "bbox": [ + 365, + 670, + 545, + 685 + ], + "type": "interline_equation", + "content": "\\mathbf {O} _ {\\mathbf {f r u}} = \\operatorname {S i g m o i d} \\left(f _ {2} \\left(\\mathbf {F r u} _ {2}\\right)\\right) \\tag {2}", + "image_path": "8122eea4df61b8bda41b1c33af74842f56429fd400ec181d4b1417793a973d79.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "content": "The frustum occupancy indicates the feature density in the frustum space, thus inherently can be employed to weight" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "10283" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "content": "original frustum features for achieving enhanced frustum feature " + }, + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "inline_equation", + "content": "\\mathbf{Fru}_3\\in \\mathbb{R}^{W_F\\times H_F\\times D\\times C}" + }, + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 119, + 106, + 287, + 119 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 119, + 106, + 287, + 119 + ], + "spans": [ + { + "bbox": [ + 119, + 106, + 287, + 119 + ], + "type": "interline_equation", + "content": "\\mathbf {F r u} _ {3} = \\mathbf {O} _ {\\mathbf {f r u}} \\odot \\mathbf {F r u} _ {2} \\tag {3}", + "image_path": "9032d8a9e50269f28b0afdd14f04619cebff1f57cfe59d25b6b9a74db830da06.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "spans": [ + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "type": "inline_equation", + "content": "\\odot" + }, + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "type": "text", + "content": " denotes the Hadamard product (element-wise multiplication). The resulted frustum feature " + }, + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "type": "inline_equation", + "content": "\\mathbf{Fru}_3" + }, + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "type": "text", + "content": " is transformed to regular voxelized feature " + }, + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "type": "inline_equation", + "content": "\\mathbf{V}_1 \\in \\mathbb{R}^{X \\times Y \\times Z \\times C}" + }, + { + "bbox": [ + 47, + 129, + 287, + 189 + ], + "type": "text", + "content": " via grid-sampling [53]. The occupancy learning process is then repeated in the regular 3D space." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 199, + 289, + 222 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 199, + 289, + 222 + ], + "spans": [ + { + "bbox": [ + 47, + 199, + 289, + 222 + ], + "type": "interline_equation", + "content": "\\mathbf {V} _ {\\mathbf {2}} = f _ {3} \\left(\\mathbf {V} _ {\\mathbf {1}}\\right); \\mathbf {O} _ {\\mathbf {3 d}} = \\text {S i g m o i d} \\left(f _ {4} \\left(\\mathbf {V} _ {\\mathbf {2}}\\right)\\right); \\mathbf {V} _ {\\mathbf {3}} = \\mathbf {O} _ {\\mathbf {3 d}} \\odot \\mathbf {V} _ {\\mathbf {2}} \\tag {4}", + "image_path": "606df31144ec99e334c0089e46e4f943fe3e2301e1c509fcf9e8c3b7247ff71a.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "spans": [ + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "type": "text", + "content": "To better encode 3D features in the regular 3D space, we use a 3D hourglass-like design [6] in " + }, + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "type": "inline_equation", + "content": "f_{3}" + }, + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "type": "inline_equation", + "content": "f_{4}" + }, + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "type": "text", + "content": " is a 3D convolution. Finally, we have more informative 3D voxel feature " + }, + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "type": "inline_equation", + "content": "\\mathbf{V}_3 \\in \\mathbb{R}^{X \\times Y \\times Z \\times C}" + }, + { + "bbox": [ + 46, + 223, + 287, + 270 + ], + "type": "text", + "content": " for the detection module." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 45, + 271, + 287, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 271, + 287, + 498 + ], + "spans": [ + { + "bbox": [ + 45, + 271, + 287, + 498 + ], + "type": "text", + "content": "What is the rationale behind learning occupancy in both frustum and 3D space? Occupancy learning in both frustum and 3D space is beneficial because they have different nature. Frustum space has a resolution that depends on camera intrinsics and the downsample factor of the backbone network, while voxelized 3D space has a resolution that is decided by the pre-defined voxel size and detection range. Frustum voxels are irregular and vary in size based on the distance to the camera, which results in fine-grained voxels for objects that are closer and coarse-grained voxels for objects that are far away. In contrast, regular 3D voxels have the same size throughout the 3D space. On the other hand, frustum space is more fit to camera imagery, but objects in the frustum space cannot precisely represent the real 3D geometry. Thus the feature extraction and occupancy in frustum space have distortion for objects/scenes. Therefore, occupancy learning in both frustum and 3D space is complementary, and can result in more informative representations and features." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 514, + 159, + 527 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 514, + 159, + 527 + ], + "spans": [ + { + "bbox": [ + 47, + 514, + 159, + 527 + ], + "type": "text", + "content": "3.2.2 Occupancy Labels" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "spans": [ + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "type": "text", + "content": "Given a set of sparse LiDAR points " + }, + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "type": "inline_equation", + "content": "\\mathbf{P} \\in \\mathbb{R}^{N \\times 3}" + }, + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "type": "text", + "content": " is the number of points and 3 is the coordinate dimension " + }, + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "type": "inline_equation", + "content": "(X, Y, Z)" + }, + { + "bbox": [ + 46, + 533, + 287, + 640 + ], + "type": "text", + "content": ", we generate corresponding occupancy labels. The process is illustrated in Figure 3, and is operated on every LiDAR point. More formally, we first define three space status and represent them with numbers: free:0, occupied:1, unknown:-1. We then describe the occupancy label generation process in the frustum and 3D space, respectively." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": "Occupancy label in frustum space: Let us denote the frustum occupancy label as " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathrm{fru}}^{*} \\in \\mathbb{R}^{W_{F} \\times H_{F} \\times D}" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "W_{F}" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "H_{F}" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": " are feature resolution, and " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": " is the depth category. We first project LiDAR points onto the image plane to form a category depth index map. Each valid projected point has a category depth index, while invalid points (no" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 324, + 69, + 526, + 182 + ], + "blocks": [ + { + "bbox": [ + 324, + 69, + 526, + 182 + ], + "lines": [ + { + "bbox": [ + 324, + 69, + 526, + 182 + ], + "spans": [ + { + "bbox": [ + 324, + 69, + 526, + 182 + ], + "type": "image", + "image_path": "7759ed541f59d86c294c8e6b60ffd67312cd7c7ac9426e83cbb9ab575ac278d3.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 323, + 183, + 526, + 290 + ], + "blocks": [ + { + "bbox": [ + 323, + 183, + 526, + 290 + ], + "lines": [ + { + "bbox": [ + 323, + 183, + 526, + 290 + ], + "spans": [ + { + "bbox": [ + 323, + 183, + 526, + 290 + ], + "type": "image", + "image_path": "c0e052a59b9eb03aef75e60353dcc9758dce073f74590c52ab97bd7695c4f675.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 294, + 544, + 316 + ], + "lines": [ + { + "bbox": [ + 305, + 294, + 544, + 316 + ], + "spans": [ + { + "bbox": [ + 305, + 294, + 544, + 316 + ], + "type": "text", + "content": "Figure 3. Occupancy label generation in frustum and 3D space. Best viewed in color with zoom in." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 323, + 545, + 382 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 323, + 545, + 382 + ], + "spans": [ + { + "bbox": [ + 305, + 323, + 545, + 382 + ], + "type": "text", + "content": "LiDAR points projections) are given negative indexes of " + }, + { + "bbox": [ + 305, + 323, + 545, + 382 + ], + "type": "inline_equation", + "content": "-1" + }, + { + "bbox": [ + 305, + 323, + 545, + 382 + ], + "type": "text", + "content": ". This index map is then downsampled to fit the feature resolution, resulting in " + }, + { + "bbox": [ + 305, + 323, + 545, + 382 + ], + "type": "inline_equation", + "content": "\\mathbf{Ind} \\in \\mathbb{R}^{W_F \\times H_F}" + }, + { + "bbox": [ + 305, + 323, + 545, + 382 + ], + "type": "text", + "content": ". Benefit from the camera projection nature, we can easily distinguish the space status as follows:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 387, + 544, + 453 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 387, + 544, + 453 + ], + "spans": [ + { + "bbox": [ + 306, + 387, + 544, + 453 + ], + "type": "interline_equation", + "content": "\\mathbf {O} _ {\\mathbf {f r u} i, j, d} ^ {*} = \\left\\{ \\begin{array}{l l} 1 & \\text {i f} \\mathbf {I n d} _ {i, j} > - 1 \\text {a n d} d = \\mathbf {I n d} _ {i, j}, \\\\ 0 & \\text {i f} \\mathbf {I n d} _ {i, j} > - 1 \\text {a n d} d < \\mathbf {I n d} _ {i, j}, \\\\ - 1 & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {5}", + "image_path": "ccc666e0f98d0b78b912820281b925bd5214dfdd1660a0828405e8952ff2758b.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 453, + 545, + 501 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 453, + 545, + 501 + ], + "spans": [ + { + "bbox": [ + 305, + 453, + 545, + 501 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 453, + 545, + 501 + ], + "type": "inline_equation", + "content": "i,j,d\\in W_F,H_F,D" + }, + { + "bbox": [ + 305, + 453, + 545, + 501 + ], + "type": "text", + "content": " .Note that we do not consider unknown voxels in both the occupancy labels and occupancy losses. We use the known voxels, i.e., the free and occupied voxels, to perform occupancy learning." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "spans": [ + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "type": "text", + "content": "Occupancy label in 3D space: We denote " + }, + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathbf{3d}}^{*} \\in \\mathbb{R}^{X \\times Y \\times Z}" + }, + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "type": "text", + "content": " as the 3D occupancy label, where " + }, + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "type": "inline_equation", + "content": "X, Y, Z" + }, + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "type": "text", + "content": " are determined by the pre-defined voxel size and detection range. We voxelize LiDAR points within the grid and set the voxels containing points to 1, and those without points to " + }, + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "type": "inline_equation", + "content": "-1" + }, + { + "bbox": [ + 305, + 501, + 545, + 619 + ], + "type": "text", + "content": ". In this way, occupied voxels can be easily achieved. To obtain the free voxels, we utilize ray tracing from each LiDAR point to the camera, where intersected voxels are set as free, filled by 0. We summarize the occupancy label in 3D space as follows:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 623, + 545, + 689 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 623, + 545, + 689 + ], + "spans": [ + { + "bbox": [ + 306, + 623, + 545, + 689 + ], + "type": "interline_equation", + "content": "\\mathbf {O} _ {\\mathbf {3 d} x, y, z} ^ {*} = \\left\\{\\begin{array}{l l}1&\\text {i f V o l} _ {\\mathbf {3 d} x, y, z} > 0,\\\\0&\\text {i f R} \\left(\\mathbf {O} _ {\\mathbf {3 d} x, y, z} ^ {*}\\right) \\cap \\operatorname {R a y} _ {\\text {p o i n t} \\rightarrow \\text {c a m}}\\\\- 1&\\text {o t h e r w i s e .}\\end{array}\\right. \\tag {6}", + "image_path": "5544220e9bf7fe117f8121174e5cd6ee07c58487c9c698c90abac4a90f7ee3cf.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "inline_equation", + "content": "x,y,z\\in X,Y,Z" + }, + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "content": " .In this equation, " + }, + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{Vol}_{3d}" + }, + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "content": " denotes the voxelized grid. 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ApproachesVenueInputAPBEV(IoU=0.7)|R40AP3D(IoU=0.7)|R40
EasyModerateHardEasyModerateHard
Kinematic3D [3]ECCV20Video26.6917.5213.1019.0712.729.17
DfM [66]ECCV22Video31.7122.8919.9722.9416.8214.65
Monodle [39]CVPR21Image24.7918.8916.0017.2312.2610.29
MonoFlex [76]CVPR21Image28.2319.7516.8919.9413.8912.07
CaDDN [53]CVPR21Image27.9418.9117.1919.1713.4111.46
GUP Net [36]ICCV21Image30.2921.1918.2022.2615.0213.12
AutoShape [35]ICCV21Image30.6620.0815.9522.4714.1711.36
PCT [65]NeurIPS21Image29.6519.0315.9221.0013.3711.31
MonoDTR [21]CVPR22Image28.5920.3817.1421.9915.3912.73
MonoJSG [31]CVPR22Image32.5921.2618.1824.6916.1413.64
DEVIANT [25]ECCV22Image29.6520.4417.4321.8814.4611.89
DID-M3D [49]ECCV22Image32.9522.7619.8324.4016.2913.75
MonoDDE [29]CVPR22Image33.5823.4620.3724.9317.1415.10
Cube R-CNN [4]CVPR23Image31.7021.2018.4323.5915.0112.56
NeuROCS†[44]CVPR23Image37.2724.4920.8929.8918.9415.90
MonoUNI [23]NeurlPS23Image33.2823.0519.3924.7516.7313.49
OccupancyM3D-Image35.3824.1821.3725.5517.0214.79
", + "image_path": "c5c6e7eb1422e7dd3b5c7cc94a39dbb866c888c481c5771216052d54d2e6a9fa.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 304, + 547, + 327 + ], + "lines": [ + { + "bbox": [ + 46, + 304, + 547, + 327 + ], + "spans": [ + { + "bbox": [ + 46, + 304, + 547, + 327 + ], + "type": "text", + "content": "Table 1. Comparisons on KITTI test set for Car category. The red refers to the highest result and blue is the second-highest result. Our method outperforms other methods including monocular and video-based methods." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "spans": [ + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "type": "text", + "content": "pied by LiDAR points. " + }, + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "type": "inline_equation", + "content": "\\mathrm{R}(\\cdot)" + }, + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "type": "text", + "content": " refers to the voxel range and " + }, + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "type": "inline_equation", + "content": "\\mathrm{R}(\\mathbf{O}_{3\\mathbf{d}i,j,d})\\cap \\mathrm{Ray}_{\\mathrm{point}\\to \\mathrm{cam}}" + }, + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "type": "text", + "content": " denotes that the voxel at index " + }, + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "type": "inline_equation", + "content": "i,j,d" + }, + { + "bbox": [ + 46, + 348, + 287, + 396 + ], + "type": "text", + "content": " intersects with a ray from LiDAR points to the camera. In this way, 3D occupancy labels are generated." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "spans": [ + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "content": "When generating voxel-based occupancy labels, there is a quantization error that arises due to the discretization process. A smaller voxel size results in lower quantization error, providing more fine-grained and accurate information. However, it requires more computation and GPU resources." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 469, + 159, + 481 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 469, + 159, + 481 + ], + "spans": [ + { + "bbox": [ + 47, + 469, + 159, + 481 + ], + "type": "text", + "content": "3.2.3 Occupancy Losses" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "spans": [ + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": "We use generated occupancy labels " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathbf{fru}}^{*}" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{3\\mathbf{d}}^{*}" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": " to supervised the predicted occupancy " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathbf{fru}}" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{3\\mathbf{d}}" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": ", respectively. We regard occupancy prediction as a simple classification problem and use focal loss [32] as the classification loss. Only valid voxels, i.e., free and occupied voxels, contribute to the loss, and unknown voxels are ignored. We first obtain valid masks " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_{\\mathbf{fru}} \\in \\mathbb{R}^{W_F \\times H_F \\times D}" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_{3\\mathbf{d}} \\in \\mathbb{R}^{X \\times Y \\times Z}" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_{\\mathbf{fru}} = true" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": " if " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{\\mathbf{fru}}^{*} > -1" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": " otherwise false. " + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "inline_equation", + "content": "\\mathbf{M}_{3\\mathbf{d}}" + }, + { + "bbox": [ + 46, + 487, + 287, + 596 + ], + "type": "text", + "content": " is obtained using the similar way." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 59, + 596, + 262, + 608 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 596, + 262, + 608 + ], + "spans": [ + { + "bbox": [ + 59, + 596, + 262, + 608 + ], + "type": "text", + "content": "Therefore, the occupancy loss in frustum space is:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 86, + 613, + 287, + 628 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 86, + 613, + 287, + 628 + ], + "spans": [ + { + "bbox": [ + 86, + 613, + 287, + 628 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {f r u} = \\operatorname {F L} \\left(\\mathbf {O} _ {\\mathbf {f r u}} ^ {*} \\left[ \\mathbf {M} _ {\\mathbf {f r u}} \\right], \\mathbf {O} _ {\\mathbf {f r u}} \\left[ \\mathbf {M} _ {\\mathbf {f r u}} \\right]\\right) \\tag {7}", + "image_path": "f7ad153f0f0eb13fb09ad4e516cf2133dd10919e93e7a47ad27ffc16452f2124.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "spans": [ + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "inline_equation", + "content": "\\mathrm{FL}(\\cdot)" + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "text", + "content": " refers to focal loss and " + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "inline_equation", + "content": "[\\cdot]" + }, + { + "bbox": [ + 46, + 632, + 287, + 666 + ], + "type": "text", + "content": " is the selection via mask. Similarly, we can obtain 3D occupancy loss as follows:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 93, + 667, + 287, + 681 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 93, + 667, + 287, + 681 + ], + "spans": [ + { + "bbox": [ + 93, + 667, + 287, + 681 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {3 d} = \\operatorname {F L} \\left(\\mathrm {O} _ {\\mathbf {3 d}} ^ {*} \\left[ \\mathrm {M} _ {\\mathbf {3 d}} \\right], \\mathrm {O} _ {\\mathbf {3 d}} \\left[ \\mathrm {M} _ {\\mathbf {3 d}} \\right]\\right) \\tag {8}", + "image_path": "9ff2619b4fe160a65e46757c8f9dc426fd1b73cf8c1fdbedc12b80cdd224bbde.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 683, + 201, + 695 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 683, + 201, + 695 + ], + "spans": [ + { + "bbox": [ + 47, + 683, + 201, + 695 + ], + "type": "text", + "content": "The final occupancy loss is their sum:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 112, + 701, + 287, + 715 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 112, + 701, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 112, + 701, + 287, + 715 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {o c c u p a n c y}} = \\mathcal {L} _ {f r u} + \\mathcal {L} _ {3 d} \\tag {9}", + "image_path": "e45bacb4fc3ba9a5820c171a68fbf944749cdef27de450ca254e7a826c30f111.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 348, + 546, + 394 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 348, + 546, + 394 + ], + "spans": [ + { + "bbox": [ + 304, + 348, + 546, + 394 + ], + "type": "text", + "content": "The occupancy loss allows the network to learn informative and discriminative features and representations, thus benefit downstream tasks. Therefore, the final loss of the network is:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 373, + 396, + 546, + 410 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 373, + 396, + 546, + 410 + ], + "spans": [ + { + "bbox": [ + 373, + 396, + 546, + 410 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {\\text {o r g}} + \\lambda \\mathcal {L} _ {\\text {o c c u p a n c y}} \\tag {10}", + "image_path": "978318ba47e12b67b2e4840456ac6ff72e43fcbbd36b95e7d986101a8bbce19b.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 415, + 545, + 451 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 415, + 545, + 451 + ], + "spans": [ + { + "bbox": [ + 304, + 415, + 545, + 451 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 415, + 545, + 451 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{org}" + }, + { + "bbox": [ + 304, + 415, + 545, + 451 + ], + "type": "text", + "content": " denotes the original detection and depth losses in CaDDN [53] and " + }, + { + "bbox": [ + 304, + 415, + 545, + 451 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 304, + 415, + 545, + 451 + ], + "type": "text", + "content": " is the occupancy loss weighting factor, which is set to 1 by default." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 467, + 434, + 479 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 467, + 434, + 479 + ], + "spans": [ + { + "bbox": [ + 306, + 467, + 434, + 479 + ], + "type": "text", + "content": "3.2.4 Occupancy and Depth" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 486, + 545, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 486, + 545, + 617 + ], + "spans": [ + { + "bbox": [ + 304, + 486, + 545, + 617 + ], + "type": "text", + "content": "Occupancy has some similarities with 2D depth map, especially the frustum occupancy. They both can represent object geometry surface in the space. However, depth map is two-dimensional while occupancy is three-dimensional. Occupancy is beyond the depth and can base on it. It is able to express dense features of objects but not only the surface. For unknown space due to occlusion, the occupancy can infer reasonable results. Moreover, learning occupancy in frustum and 3D space allows the network to study more informative features under a higher dimension compared to 2D space." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 618, + 546, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 618, + 546, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 618, + 546, + 714 + ], + "type": "text", + "content": "Occupancy and depth are not mutually exclusive representations. In fact, they complement each other in the 3D object detection task. Without depth, the network has to deal with a large search space, making it challenging to learn reasonable occupancy features. Incorporating depth estimation provides the network with a good starting point and facilitates learning the occupancy features. Therefore, it is recommended to utilize both depth and occupancy in-" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "10285" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 65, + 70, + 526, + 350 + ], + "blocks": [ + { + "bbox": [ + 65, + 70, + 526, + 350 + ], + "lines": [ + { + "bbox": [ + 65, + 70, + 526, + 350 + ], + "spans": [ + { + "bbox": [ + 65, + 70, + 526, + 350 + ], + "type": "table", + "html": "
MethodsVenue3D mAP / mAPH (IoU = 0.7)3D mAP / mAPH (IoU = 0.5)
Overall0 - 30m30 - 50m50m - ∞Overall0 - 30m30 - 50m50m - ∞
Comparison on LEVEL 1
PatchNet[38]ECCV200.39/0.371.67/1.630.13/0.120.03/0.032.92/2.7410.03/9.751.09/0.960.23/0.18
CaDDN [53]CVPR215.03/4.9914.54/14.431.47/1.450.10/0.1017.54/17.3145.00/44.469.24/9.110.64/0.62
PCT [65]NeurlIPS210.89/0.883.18/3.150.27/0.270.07/0.074.20/4.1514.70/14.541.78/1.750.39/0.39
MonoJSG [31]CVPR220.97/0.954.65/4.590.55/0.530.10/0.095.65/5.4720.86/20.263.91/3.790.97/0.92
DEVIANT [25]ECCV222.69/2.676.95/6.900.99/0.980.02/0.0210.98/10.8926.85/26.645.13/5.080.18/0.18
DID-M3D [49]ECCV22-/--/--/--/-20.66/20.4740.92/40.6015.63/15.485.35/5.24
NeuROCS†[44]CVPR232.44/2.436.35/6.310.97/0.970.04/0.04-/--/--/--/-
MonoUNI [23]NeurlIPS233.20/3.168.61/8.500.87/0.860.13/0.1210.98/10.7326.63/26.304.04/3.980.57/0.55
OccupancyM3D-10.61/10.5329.18/28.964.49/4.460.41/0.4028.99/28.6661.24/60.6323.25/23.003.65/3.59
Comparison on LEVEL 2
PatchNet[38]ECCV200.38/0.361.67/1.630.13/0.110.03/0.032.42/2.2810.01/9.731.07/0.940.22/0.16
CaDDN [53]CVPR214.49/4.4514.50/14.381.42/1.410.09/0.0916.51/16.2844.87/44.338.99/8.860.58/0.55
PCT [65]NeurlIPS210.66/0.663.18/3.150.27/0.260.07/0.074.03/3.9914.67/14.511.74/1.710.36/0.35
MonoJSG [31]CVPR220.91/0.894.64/4.650.55/0.530.09/0.095.34/5.1720.79/20.193.79/3.670.85/0.82
DEVIANT [25]ECCV222.52/2.506.93/6.870.95/0.940.02/0.0210.29/10.2026.75/26.544.95/4.900.16/0.16
DID-M3D[49]ECCV22-/--/--/--/-19.37/19.1940.77/40.4615.18/15.044.69/4.59
NeuROCS†[44]CVPR232.29/2.286.32/6.290.94/0.930.03/0.03-/--/--/--/-
MonoUNI [23]NeurlIPS233.04/3.008.59/8.480.85/0.840.12/0.1210.38/10.2426.57/26.243.95/3.890.53/0.51
OccupancyM3D-10.02/9.9428.38/28.174.38/4.340.36/0.3627.21/26.9061.09/60.4922.59/22.343.18/3.13
", + "image_path": "264d554e3a5c20a740a9ba41129f099e3a8eeef26c33dc237afb853adf50fc60.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 353, + 547, + 399 + ], + "lines": [ + { + "bbox": [ + 46, + 353, + 547, + 399 + ], + "spans": [ + { + "bbox": [ + 46, + 353, + 547, + 399 + ], + "type": "text", + "content": "Table 2. Results on WaymoOD val set for Vehicle category. The red refers to the highest result and blue is the second-highest result. Our method outperforms other methods by significant margins on most metrics. Note that our method has the detection range limitation of [2, 59.6](meters), while the perspective-view based method DID-M3D [49] does not have this shortcoming. Thus our method performs worse for objects within " + }, + { + "bbox": [ + 46, + 353, + 547, + 399 + ], + "type": "inline_equation", + "content": "[50m,\\infty ]" + }, + { + "bbox": [ + 46, + 353, + 547, + 399 + ], + "type": "text", + "content": " under IoU=0.5 criterion." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 418, + 288, + 442 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 418, + 288, + 442 + ], + "spans": [ + { + "bbox": [ + 46, + 418, + 288, + 442 + ], + "type": "text", + "content": "formation to achieve better representations and features for monocular 3D detection." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 472, + 128, + 485 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 472, + 128, + 485 + ], + "spans": [ + { + "bbox": [ + 47, + 472, + 128, + 485 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 497, + 180, + 510 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 497, + 180, + 510 + ], + "spans": [ + { + "bbox": [ + 47, + 497, + 180, + 510 + ], + "type": "text", + "content": "4.1. Implementation Details" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": "We employ PyTorch [48] for implementation. The network is trained on 4 NVIDIA 3080Ti (12G) GPUs, with a total batch size of 8 for 80 epochs. We use Adam [24] optimizer with initial learning rate 0.001 and employ the one-cycle learning rate policy [61]. We use pre-trained DLA34 [74] backbone from [47]. We employ flip and crop data augmentation [36]. For KITTI [17], we fix the input image to " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "1280 \\times 384" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": ", detection range " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "[2,46.8] \\times [-30.08,30.08] \\times [-3.0,1.0]" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": " (meter) for " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "x,y,z" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": " axes under the LiDAR coordinate system, respectively. We use voxel size " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "[0.16,0.16,0.16]" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": " (meter). For Waymo [62], we downsample the input RGB image from " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "1920 \\times 1280" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "960 \\times 640" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": " to meet GPU memory. We use detection range " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "[2,59.6] \\times [-25.6,25.6] \\times [-2.0,2.0]" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": " (meter) for " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "x,y,z" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": " axes due to the larger depth domain on Waymo. We use voxel size " + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "inline_equation", + "content": "[0.16,0.16,0.16]" + }, + { + "bbox": [ + 46, + 521, + 289, + 715 + ], + "type": "text", + "content": " (meter)." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 418, + 427, + 430 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 418, + 427, + 430 + ], + "spans": [ + { + "bbox": [ + 306, + 418, + 427, + 430 + ], + "type": "text", + "content": "4.2. Datasets and Metrics" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 437, + 545, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 437, + 545, + 460 + ], + "spans": [ + { + "bbox": [ + 305, + 437, + 545, + 460 + ], + "type": "text", + "content": "Following the fashion in previous works, we conduct experiments on competitive KITTI and Waymo open datasets." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 461, + 546, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 461, + 546, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 461, + 546, + 616 + ], + "type": "text", + "content": "KITTI: KITTI [17] is a widely employed benchmark for autonomous driving. KITTI3D object dataset consists of 7,481 training samples and 7,518 testing samples, where labels on test set keep secret and the final performance is evaluated on KITTI official website. To conduct ablations, the training samples are further divided into a train set and a val set [10]. They individually contain 3,512 and 3,769 samples, respectively. KITTI has three categories: Car, Pedestrian, and Cyclist. According to difficulties (2D box height, occlusion and truncation levels), KITTI divides objects into Easy, Moderate, and Hard. Following common practice [35, 53, 60], we use " + }, + { + "bbox": [ + 304, + 461, + 546, + 616 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{BEV}|_{R_{40}}" + }, + { + "bbox": [ + 304, + 461, + 546, + 616 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 461, + 546, + 616 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{3D}|_{R_{40}}" + }, + { + "bbox": [ + 304, + 461, + 546, + 616 + ], + "type": "text", + "content": " under IoU threshold of 0.7 to evaluate the performance." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "type": "text", + "content": "Waymo: Waymo open dataset (WaymoOD) [62] is a large modern dataset for autonomous driving. It has 798 sequences for training and 202 sequences for validation. Following previous works [49, 53], we use the front camera of the multi-camera rig and provide performance comparison on val set for the vehicle category. To make fair comparisons, we use one third samples of training sequences to train the network due to the large-scale and high frame rate" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "10286" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 63, + 70, + 528, + 289 + ], + "blocks": [ + { + "bbox": [ + 63, + 70, + 528, + 289 + ], + "lines": [ + { + "bbox": [ + 63, + 70, + 528, + 289 + ], + "spans": [ + { + "bbox": [ + 63, + 70, + 528, + 289 + ], + "type": "table", + "html": "
ApproachesVenueInputPedestrian APBEV/AP3D(IoU=0.5)|R40Cyclist APBEV/AP3D(IoU=0.5)|R40
EasyModerateHardEasyModerateHard
DfM [66]ECCV22Video-13.70-8.71-7.32-8.98-5.75-4.88
Monodle [39]CVPR21Image10.73/9.646.96/6.556.20/5.445.34/4.593.28/2.662.83/2.45
DDMP-3D [64]CVPR21Image5.53/4.934.02/3.553.36/3.014.92/4.183.14/2.502.44/2.32
MonoRUn [7]CVPR21Image11.70/10.887.59/6.786.34/5.831.14/1.010.73/0.610.66/0.48
MonoEF [79]CVPR21Image4.61/4.273.05/2.792.85/2.212.36/1.801.18/0.921.15/0.71
MonoFlex [76]CVPR21Image10.36/9.437.36/6.316.29/5.264.41/4.172.67/2.352.50/2.04
CaDDN [53]CVPR21Image14.72/12.879.41/8.148.17/6.769.67/7.005.38/3.414.75/3.30
GUP Net [36]ICCV21Image15.62/14.9510.37/9.768.79/8.416.94/5.583.85/3.213.64/2.66
AutoShape [35]ICCV21Image-5.46-3.74-3.03-5.99-3.06-2.70
MonoCon [33]AAAI22Image-13.10-8.41-6.94-2.80-1.92-1.55
HomoLoss [18]CVPR22Image13.26/11.878.81/7.667.41/6.826.81/5.484.09/3.503.78/2.99
MonoJSG [31]CVPR22Image-11.02-7.49-6.41-5.45-3.21-2.57
DEVIANT [25]ECCV22Image14.49/13.439.77/8.658.28/7.696.42/5.053.97/3.133.51/2.59
Cube R-CNN [4]CVPR23Image11.67/11.177.65/6.956.60/5.875.01/3.653.35/2.673.23/2.28
MonoUNI [23]NeurlPS23Image16.54/15.7810.90/10.349.17/8.748.25/7.345.03/4.284.50/3.78
OccupancyM3D-Image16.54/14.6810.65/9.159.16/7.808.58/7.374.35/3.563.55/2.84
", + "image_path": "d14cae5a0dc2f4ba306b2936a95071670802488cf307f0433a56834cdf325a3d.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 293, + 544, + 316 + ], + "lines": [ + { + "bbox": [ + 46, + 293, + 544, + 316 + ], + "spans": [ + { + "bbox": [ + 46, + 293, + 544, + 316 + ], + "type": "text", + "content": "Table 3. Comparisons on KITTI test set for Pedestrian and Cyclist categories. The red refers to the highest result and blue is the second-highest result. Our method achieves new state-of-the-art results." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 336, + 287, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 336, + 287, + 384 + ], + "spans": [ + { + "bbox": [ + 46, + 336, + 287, + 384 + ], + "type": "text", + "content": "of this dataset. Waymo divides objects to LEVEL 1 and LEVEL 2 according to the LiDAR point number within objects. For metrics, we employ the official mAP and mAPH under LEVEL 1 and LEVEL 2." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 394, + 253, + 407 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 394, + 253, + 407 + ], + "spans": [ + { + "bbox": [ + 47, + 394, + 253, + 407 + ], + "type": "text", + "content": "4.3. Results on KITTI and Waymo Datasets" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "spans": [ + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "type": "text", + "content": "We provide the performance comparisons on KITTI and WaymoOD. Table 1 shows the results of Car category on KITTI test set. Our method outperforms other methods including video-based methods. For example, the proposed method exceeds CaDDN [53] under all metrics, e.g., 25.55/17.02/14.79 vs. 19.17/13.41/11.46 " + }, + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{3D}" + }, + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "type": "text", + "content": ". Please note that NeuROCS [44] requires instance masks for training and does not report results of Pedestrian and Cyclist on KITTI test set. Such irregularly shaped objects are challenging to NOCS prediction. Our method outperforms DID-M3D [49] by a margin of " + }, + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "type": "inline_equation", + "content": "2.43 / 1.42 / 1.54\\mathrm{AP}_{BEV}" + }, + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "type": "text", + "content": ", and performs better than Cube R-CNN [4] and MonoUNI [23]. When compared to the video-based method DfM [66], OccupancyM3D also shows better performance, e.g., 24.18 vs. 22.89 " + }, + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{BEV}" + }, + { + "bbox": [ + 46, + 413, + 287, + 652 + ], + "type": "text", + "content": " under the moderate setting. In Table 3, we provide comparisons on other categories, namely, Pedestrian and Cyclist. The results demonstrate the superiority of our method on different categories. Concerning the overall performance on all categories, our method achieves a state-of-the-art on KITTI test set for monocular 3D detection." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 287, + 715 + ], + "type": "text", + "content": "We also evaluate our method on Waymo open dataset (WaymoOD) [62] and obtain promising results. As shown in Table 2, our method surpasses other methods with a significant margin. For example, under LEVEL 1 setting, OccupancyM3D outperforms CaDDN [53] by 5.58/5.54" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 336, + 545, + 552 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 336, + 545, + 552 + ], + "spans": [ + { + "bbox": [ + 304, + 336, + 545, + 552 + ], + "type": "text", + "content": "mAP/mAPH (10.61/10.53 vs. 5.03/4.99) and 11.55/11.35 mAP/mAPH (28.99/28.66 vs. 17.54/17.31) with IoU 0.7 and 0.5 criterions, respectively. Compared to DID-M3D [49], under IoU criterion 0.5, our method outperforms it by " + }, + { + "bbox": [ + 304, + 336, + 545, + 552 + ], + "type": "inline_equation", + "content": "8.33 / 8.19\\mathrm{mAP / mAPH}" + }, + { + "bbox": [ + 304, + 336, + 545, + 552 + ], + "type": "text", + "content": " (28.99/28.66 vs. 20.66/20.47) and 7.84/7.71 mAP/mAPH (27.21/26.90 vs. 19.37/19.19) with LEVEL 1 and 2 settings, respectively. This success can be attributed to the fact that occupancy learning benefits from the diverse scenes present in large datasets. In other words, large datasets especially favor the proposed occupancy learning method. Interestingly, concerning objects within " + }, + { + "bbox": [ + 304, + 336, + 545, + 552 + ], + "type": "inline_equation", + "content": "[50m,\\infty ]" + }, + { + "bbox": [ + 304, + 336, + 545, + 552 + ], + "type": "text", + "content": " , our method performs worse than DID-M3D [49]. It is because our method is voxel-based, which has a detection range limitation ([2, 59.6](meters) in our method). By contrast, DID-M3D is a perspectivebased method, indicating that it does not have this limitation and can detect more faraway objects. We encourage future works to address this range limitation in our method." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 562, + 373, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 562, + 373, + 574 + ], + "spans": [ + { + "bbox": [ + 306, + 562, + 373, + 574 + ], + "type": "text", + "content": "4.4. Ablations" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 581, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 581, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 581, + 545, + 628 + ], + "type": "text", + "content": "Following common practice in previous works, we perform ablations on KITTI val set to validate the effectiveness of each component. We compare the performance on Car category under IoU criterion 0.7." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 629, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 715 + ], + "type": "text", + "content": "We provide the main ablation in Table 4. It can be easily seen that occupancy learning significantly benefit the final detection performance. When enforcing occupancy learning in frustum space, the detection " + }, + { + "bbox": [ + 304, + 629, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\mathrm{AP}_{3D}" + }, + { + "bbox": [ + 304, + 629, + 545, + 715 + ], + "type": "text", + "content": " increases from 21.04/17.05/15.01 to 24.69/17.79/15.16 (Exp. 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Qualitative results of occupancy predictions and 3D detections on KITTI val set. In 3D detections, Red boxes are our results and Green boxes denote ground-truths. The LiDAR point clouds in 3D detections are used only for visualization. We can see that the proposed method generates reasonable occupancy predictions for the current scene, which benefits downstream monocular 3D detection task. However, our method may fail to estimate heavily occluded objects (see right objects of the bottom picture). Most monocular 3D detection failure cases stem from the poor occupancy estimation. Best viewed in color with zoom in." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 49, + 156, + 218, + 216 + ], + "blocks": [ + { + "bbox": [ + 49, + 156, + 218, + 216 + ], + "lines": [ + { + "bbox": [ + 49, + 156, + 218, + 216 + ], + "spans": [ + { + "bbox": [ + 49, + 156, + 218, + 216 + ], + "type": "image", + "image_path": "f279047a4216fa30d8bbaba1d95555bdce69e0931fd761e223c8689b0c4d9d41.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 109, + 227, + 169, + 236 + ], + "lines": [ + { + "bbox": [ + 109, + 227, + 169, + 236 + ], + "spans": [ + { + "bbox": [ + 109, + 227, + 169, + 236 + ], + "type": "text", + "content": "Input RGB images" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 228, + 162, + 390, + 213 + ], + "blocks": [ + { + "bbox": [ + 228, + 162, + 390, + 213 + ], + "lines": [ + { + "bbox": [ + 228, + 162, + 390, + 213 + ], + "spans": [ + { + "bbox": [ + 228, + 162, + 390, + 213 + ], + "type": "image", + "image_path": "cf7e2bdc0f9d0e88f82060881c1ab10ed792c212da768f6790bca31673d05ed1.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 265, + 227, + 341, + 236 + ], + "lines": [ + { + "bbox": [ + 265, + 227, + 341, + 236 + ], + "spans": [ + { + "bbox": [ + 265, + 227, + 341, + 236 + ], + "type": "text", + "content": "Occupancy predictions" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 48, + 310, + 294, + 380 + ], + "blocks": [ + { + "bbox": [ + 48, + 310, + 294, + 380 + ], + "lines": [ + { + "bbox": [ + 48, + 310, + 294, + 380 + ], + "spans": [ + { + "bbox": [ + 48, + 310, + 294, + 380 + ], + "type": "table", + "html": "
E.OL-FSOL-3DSAPBEV/AP3D(IoU=0.7)|R40
EasyModerateHard
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", + "image_path": "5c6ac2e50840e6cd8df26874d480044fa58acc2d3b61bccf1ca1729104fef08f.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 384, + 288, + 417 + ], + "lines": [ + { + "bbox": [ + 47, + 384, + 288, + 417 + ], + "spans": [ + { + "bbox": [ + 47, + 384, + 288, + 417 + ], + "type": "text", + "content": "Table 4. Main ablation. \"E.\" in the table is the experiment ID; \"OL-FS\" refers to occupancy learning in frustum space; \"OL-3DS\" denotes occupancy learning in 3D space." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 47, + 430, + 287, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 430, + 287, + 479 + ], + "spans": [ + { + "bbox": [ + 47, + 430, + 287, + 479 + ], + "type": "text", + "content": "24.64/18.88/16.38 (Exp. (c)). Finally, the model obtains " + }, + { + "bbox": [ + 47, + 430, + 287, + 479 + ], + "type": "inline_equation", + "content": "5.83 / 2.91 / 2.14\\mathrm{AP}_{3D}" + }, + { + "bbox": [ + 47, + 430, + 287, + 479 + ], + "type": "text", + "content": " gains (Exp. " + }, + { + "bbox": [ + 47, + 430, + 287, + 479 + ], + "type": "inline_equation", + "content": "(a)\\rightarrow (d))" + }, + { + "bbox": [ + 47, + 430, + 287, + 479 + ], + "type": "text", + "content": " by employing occupancy learning in both frustum and 3D space. This main ablation demonstrates the effectiveness of our method." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 485, + 160, + 498 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 485, + 160, + 498 + ], + "spans": [ + { + "bbox": [ + 47, + 485, + 160, + 498 + ], + "type": "text", + "content": "4.5. Qualitative Results" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 503, + 287, + 599 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 503, + 287, + 599 + ], + "spans": [ + { + "bbox": [ + 46, + 503, + 287, + 599 + ], + "type": "text", + "content": "We present qualitative results of occupancy predictions and 3D detections in Figure 4. Our method can predict reasonable occupancy for the current scene, especially for foreground objects. This indicates the potential of occupancy learning in downstream tasks. Nevertheless, we can see that the occupancy estimates are not very accurate for heavily occluded objects (see right objects of the bottom picture), which leaves room for improvement in future works." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 609, + 209, + 623 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 609, + 209, + 623 + ], + "spans": [ + { + "bbox": [ + 47, + 609, + 209, + 623 + ], + "type": "text", + "content": "5. Limitation and Future Work" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": "One significant drawback of this work is the voxel size limitation. Large voxels in explicit voxel-based representation can reduce computation overhead and GPU memory, but at the cost of failing to precisely describe the 3D geometry of the scene due to quantization errors. Conversely, smaller voxel sizes are able to express fine-grained 3D geometry but come at the significant expense of increased computation" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 312, + 547, + 433 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 312, + 547, + 433 + ], + "spans": [ + { + "bbox": [ + 304, + 312, + 547, + 433 + ], + "type": "text", + "content": "overhead and GPU memory usage. On the other hand, the voxel-based method has limited detection ranges and most detection failure cases stem from poor occupancy estimation. This work mainly focuses on occupancy learning in the monocular 3D detection task, and the exploration of its application in more downstream tasks such as multi-camera detection/segmentation and indoor 3D detection is less explored. We believe that it is an interesting and promising topic and encourage future works to alleviate the above limitations to advance the self-driving community." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 449, + 378, + 461 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 449, + 378, + 461 + ], + "spans": [ + { + "bbox": [ + 306, + 449, + 378, + 461 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 471, + 547, + 615 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 471, + 547, + 615 + ], + "spans": [ + { + "bbox": [ + 304, + 471, + 547, + 615 + ], + "type": "text", + "content": "In this paper, we propose to learn occupancy for monocular 3D detection, to obtain more discriminative and informative 3D features. To perform occupancy learning, we design occupancy labels by using synchronized raw sparse LiDAR point clouds and introduce corresponding occupancy losses. Ablations verify the effectiveness of each proposed component. To the best of our knowledge, this is the first work that introduces occupancy learning to monocular 3D detection. We conduct experiments on the challenging KITTI and Waymo open datasets. The results demonstrate that the proposed method achieves new state-of-the-art results and outperforms other methods by a large margin." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 632, + 403, + 645 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 632, + 403, + 645 + ], + "spans": [ + { + "bbox": [ + 306, + 632, + 403, + 645 + ], + "type": "text", + "content": "Acknowledgments" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "content": "This work was supported in part by The National Nature Science Foundation of China (Grant Nos: 62273302, 62036009, 61936006, 62303406) and in part by Yongjiang Talent Introduction Programme (Grant No: 2023A-197-G, 2023A-194-G)." + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "10288" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "text", + "content": "[1] Alex Bewley, Pei Sun, Thomas Mensink, Dragomir Anguelov, and Cristian Sminchisescu. 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However, existing self-supervised methods for this problem assume perfect input shape alignment, restricting their real-world applicability. In this work, we introduce a novel self-supervised Rotation-Invariant 3D correspondence learner with local Shape Transform, dubbed RIST, that learns to establish dense correspondences between shapes even under challenging intra-class variations and arbitrary orientations. Specifically, RIST learns to dynamically formulate an SO(3)-invariant local shape transform for each point, which maps the SO(3)-equivariant global shape descriptor of the input shape to a local shape descriptor. These local shape descriptors are provided as inputs to our decoder to facilitate point cloud self- and cross-reconstruction. Our proposed self-supervised training pipeline encourages semantically corresponding points from different shapes to be mapped to similar local shape descriptors, enabling RIST to establish dense point-wise correspondences. RIST demonstrates state-of-the-art performances on 3D part label transfer and semantic keypoint transfer given arbitrarily rotated point cloud pairs of the same category, outperforming existing methods by significant margins.", + "bbox": [ + 75, + 316, + 473, + 680 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 710, + 209, + 724 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Establishing dense 3D correspondences between different shapes is foundational to numerous applications across computer vision, graphics, and robotics [9, 22, 28, 41]. One of the primary challenges hindering advancements in this domain is the difficulty of annotating dense inter-shape correspondences, which limits the leverage of strongly-supervised learning paradigms.", + "bbox": [ + 75, + 736, + 468, + 843 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Recently, self-supervised learning methods have been proposed to address this issue [3, 21], showing promis", + "bbox": [ + 76, + 843, + 468, + 875 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/56c299036b6cb72d2b28b7f19ce12f3bb92b344acdbe6005bd26952d1c329d41.jpg", + "image_caption": [ + "Figure 1. Semantic correspondence between rotated shapes. We visualize the semantic correspondence results of the previous SOTA [3] and ours, given two randomly rotated airplanes from the ShapeNetPart dataset [39]. Green and red lines indicate the correct and incorrect matches, respectively. For each method, 100 source points are randomly selected from the source (yellow) for correspondence visualization1. Ours predicts SO(3)-invariant correspondences, showing superior accuracy and robustness in comparison to the previous SOTA [3]." + ], + "image_footnote": [], + "bbox": [ + 504, + 282, + 893, + 435 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ing directions for 3D correspondence estimation. Nonetheless, a significant limitation in existing approaches is their stringent assumption about the alignment of input shape pairs; these methods strongly assume that the input point cloud pair to establish correspondences between is precisely aligned. This assumption is rarely met in practice, where object scans and shape instances can be arbitrarily oriented. We find that the performance of existing methods degrades significantly when confronted with rotated input shapes, restricting their real-world applicability (Figure 1).", + "bbox": [ + 496, + 585, + 892, + 736 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To address this challenge, we introduce a novel self-supervised learning approach, dubbed RIST, designed to reliably determine dense $SO(3)$ -invariant correspondences between shapes via local shape transform. In essence, RIST learns to formulate SO(3)-invariant local shape transform for each point in a dynamic and input-dependent manner. Each point-wise local shape transform maps the SO(3)-equivariant global shape descriptor of the input shape to a local shape descriptor, which is passed to the decoder to re", + "bbox": [ + 496, + 737, + 893, + 875 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal contribution", + "bbox": [ + 94, + 886, + 202, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "For the details of the inference algorithm, please refer to Appendix A.", + "bbox": [ + 517, + 886, + 890, + 901 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "22978", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "construct the shape and pose of the input shape. By training RIST via self- and cross-reconstruction of input shapes, true semantically corresponding points are trained to yield similar local shape descriptors, enabling us to determine dense shape correspondences.", + "bbox": [ + 75, + 90, + 470, + 167 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "RIST demonstrates state-of-the-art performance on part segmentation label transfer when evaluated on the ShapeNetPart [39] and ScanObjectNN [35] datasets. In particular, significant improvements over existing baselines are observed when our method is applied to randomly oriented shape pair inputs. Furthermore, our approach also proves to be more effective compared to existing methods at semantic keypoint transfer when evaluated on the Keypoint-Net dataset [40]. This showcases not only the applicability of RIST across a diverse range of tasks, but also its potential to be utilized for efficient dense annotation of 3D shapes. These results highlight the efficacy of RIST in addressing the challenges posed by real-world scenarios where existing methods fail to perform effectively.", + "bbox": [ + 75, + 169, + 468, + 380 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The main contributions of our work are as follows:", + "bbox": [ + 94, + 382, + 433, + 397 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We introduce RIST, a novel self-supervised approach for determining dense SO(3)-invariant correspondences between arbitrarily aligned 3D objects.", + "- We propose to formulate the local shape information of each point as a novel function called local shape transform with dynamic input-dependent parameters, which effectively maps the global shape descriptor of input shapes to local shape descriptors.", + "- RIST achieves state-of-the-art performance on 3D part segmentation label transfer and 3D keypoint transfer under arbitrary rotations, indicating its potential for application in a wide range of practical tasks in computer vision." + ], + "bbox": [ + 76, + 400, + 468, + 580 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 601, + 218, + 616 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Point cloud understanding via self-supervised learning.", + "text_level": 1, + "bbox": [ + 75, + 628, + 468, + 643 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "While traditional methods for point cloud processing involving hand-crafted features [27, 33] have shown impressive performance, with the advent of deep learning, substantial research efforts have been directed towards developing learning-based algorithms capable of effectively processing and understanding point clouds [5, 24-26, 42]. Due to limited large-scale datasets with rich annotations, self-supervised learning approaches emerged as a viable alternative. One of the most prominent directions to learn point cloud representations in a self-supervised manner is learning through self-reconstruction [23, 38, 43] of the point cloud. Primarily inspired by the efficacy of point cloud reconstruction as a self-supervised representation learning scheme, we train RIST to establish 3D correspondences in a self-supervised manner via self- and cross-reconstruction of point clouds by leveraging SO(3)-invariant dynamic local shape transform.", + "bbox": [ + 75, + 643, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Equivariance and invariance to rotation. The conventional method to improve a neural network's robustness to rotation is by employing rotation augmentations during training or inference. However, this tends to increase the resources required for training and still shows unsatisfactory results when confronted with an unseen rotation [14, 18]. In recent years, various methods have been proposed to yield point cloud representations, which are equivariant [2, 6, 29, 32] or invariant [14, 18, 19, 31, 37] to the rotation of the input, demonstrating enhanced performances under arbitrary input rotations. To facilitate the rotation-robust establishment of 3D dense correspondences, we utilize SO(3)-equivariant networks in building RIST, leveraging SO(3)-equivariant and -invariant representations to guarantee robustness to rotation by design.", + "bbox": [ + 496, + 90, + 890, + 318 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Semantic correspondences under intra-class variations.", + "text_level": 1, + "bbox": [ + 496, + 325, + 890, + 338 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Finding correspondences between images or shapes under intra-class variations - manifesting as differences in shape, size, and orientation within the same category of objects - poses significant challenges over photometric or viewpoint variations. This task has been widely studied in the domain of images, where existing methods make use of sparsely annotated image pair datasets to train their method in a strongly- or a weakly-supervised manner [4, 11, 13, 15, 34]. However, learning to establish dense yet reliable 3D correspondences between 3D shapes remains challenging, as it is infeasible to label dense correspondence annotations across point cloud pairs with intra-class variations. Self-supervised methods have been proposed to address this issue [3, 21], but they strongly assume that the input point clouds are aligned, leading to considerable significant degradation when confronted with arbitrarily rotated point clouds. Additionally, the functional map-based approach introduced by Huang et al. [10] for non-rigid registration struggles with topological changes and efficiency. To this end, we propose RIST to establish reliable 3D dense correspondences irrespective of the input point clouds' poses.", + "bbox": [ + 496, + 339, + 890, + 657 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. RIST for 3D Semantic Correspondence", + "text_level": 1, + "bbox": [ + 498, + 685, + 852, + 703 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this section, we detail the components of RIST, which come together to facilitate the end-to-end self-supervised training for 3D semantic correspondence establishment. The objective of 3D semantic correspondence is as follows; given two different point clouds instances $\\mathbf{P}_1 \\in \\mathbb{R}^{N \\times 3}$ and $\\mathbf{P}_2 \\in \\mathbb{R}^{N \\times 3}$ belonging to the same semantic category, we aim to find all semantically corresponding point pairs $\\{\\mathbf{p}_i, \\mathbf{q}_i\\}_{i=1}^{N'}$ such that $\\mathbf{p}_i \\in \\mathbf{P}_1$ and $\\mathbf{q}_i \\in \\mathbf{P}_2$ . To achieve this, we claim it is crucial to identify the local shape information i.e. local semantics and geometry, which is generalizable across different instances within the same category.", + "bbox": [ + 496, + 710, + 890, + 878 + ], + "page_idx": 1 + }, + { + "type": "page_footnote", + "text": "$2N^{\\prime}\\leq N$ ; there could be points with no matches.", + "bbox": [ + 514, + 886, + 782, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "22979", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/55a1493eec5b7723a871631a691b1297b59c8927f3ef3ff84cbd2ee63fec328d.jpg", + "image_caption": [ + "SO(3)-Equivariant Encoding" + ], + "image_footnote": [], + "bbox": [ + 81, + 88, + 357, + 308 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/17d8d70677f49d572052a748b3192b37696a056e24887b272c9ae668387f5e68.jpg", + "image_caption": [ + "Figure 2. Overview: Self-supervised training of RIST. The input point clouds are independently encoded to SO(3)-equivariant global shape descriptor $\\mathbf{Z}$ and dynamic SO(3)-invariant point-wise local shape transforms $\\{f_{\\theta_i}\\}$ . The local shape transforms map the global shape descriptor to local shape descriptors by infusing local semantics and geometry, which are used as inputs to the decoder for self-reconstruction. For cross-reconstruction, we apply the local shape transforms formulated from another point cloud to reconstruct the point cloud, ensuring that the local shape descriptors successfully capture generalizable local semantics and geometries. We supervise RIST via penalizing errors in self- and cross-reconstructions. At inference, we can leverage the local shape transforms for obtaining local shape descriptors, to identify the dense correspondences." + ], + "image_footnote": [], + "bbox": [ + 367, + 97, + 614, + 309 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/3d6ac63acf794569ad63819e321ee21bf2906d5dfcf4812f60fb89566ad0c2f1.jpg", + "image_caption": [ + "SO(3)-Equivariant Decoding" + ], + "image_footnote": [], + "bbox": [ + 614, + 98, + 892, + 308 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Therefore, the main idea of RIST is to dynamically generate a SO(3)-invariant local shape transform as a function for each point, such that each local shape transform can map the SO(3)-equivariant global shape descriptor of the input point cloud to its respective local shape descriptor. In the following, we elaborate on the network architecture of RIST, in particular how we leverage SO(3)-equivariant and invariant representations to facilitate the dynamic formulation of pointwise SO(3)-invariant local shape transforms and the reconstruction of pose-preserved point clouds (Sec. 3.1). Subsequently, we introduce our self-supervisory objective function, which trains RIST to self- and cross-reconstruct the input point clouds in a rotation-equivariant manner (Sec. 3.2), finally enabling the establishment of 3D dense correspondences (Sec. 3.3) via corresponding local shape descriptors. Figure 2 illustrates the outline of the training scheme of RIST.", + "bbox": [ + 75, + 455, + 472, + 712 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Network Design of RIST", + "text_level": 1, + "bbox": [ + 76, + 727, + 302, + 742 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1.1 Preliminary: SO(3)-Equivariant Representation", + "text_level": 1, + "bbox": [ + 76, + 752, + 465, + 768 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "One of the main motivations of RIST is to establish reliable and accurate 3D dense correspondences given arbitrarily rotated shapes, a setting where existing work shows to be brittle. This requires our encoder to formulate the pointwise local shape transforms not only effectively to capture the local shape semantics and geometry, but also robustly against transformations in the SO(3) space. To this end, we integrate SO(3)-equivariant networks into RIST to facilitate", + "bbox": [ + 75, + 779, + 468, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "robustness to SO(3) transformations of the input. In this work, we choose VNNs [7] to build our SO(3)-equivariant layers for their simplicity and efficacy. In VNNs, a single neuron, which is represented by a scalar-list of values, is lifted to a vector-list feature $\\mathbf{V} \\in \\mathbb{R}^{C \\times 3}$ , which is essentially a sequence of 3D vectors. The layers of VNNs handle batches of such vector-list features such that equivariance with respect to rotation $R \\in \\mathrm{SO}(3)$ is satisfied i.e. $f(\\mathbf{V}R) = f(\\mathbf{V})R^3$ . Notably, we can yield an SO(3)-invariant output by performing a product of an equivariant vector-list feature $\\mathbf{V}R \\in \\mathbb{R}^{C \\times 3}$ with the transpose of another consistently equivariant vector-list feature $\\mathbf{U}R \\in \\mathbb{R}^{C' \\times 3}$ as follows: $(\\mathbf{V}R)(\\mathbf{U}R)^{\\top} = \\mathbf{V}RR^{\\top}\\mathbf{U}^{\\top} = \\mathbf{V}\\mathbf{U}^{\\top}$ . This serves as a critical functionality when constructing our SO(3)-invariant local shape transform of our encoder (Sec. 3.1.2).", + "bbox": [ + 496, + 455, + 893, + 681 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1.2 SO(3)-Equivariant Encoder", + "text_level": 1, + "bbox": [ + 500, + 700, + 746, + 715 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We design our encoder architecture to take as input a point cloud $\\mathbf{P} \\in \\mathbb{R}^{N \\times 3}$ , and simultaneously output an SO(3)-equivariant global shape descriptor and formulate pointwise SO(3)-invariant local shape transforms.", + "bbox": [ + 496, + 724, + 892, + 786 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "SO(3)-equivariant global shape descriptor. Given a point cloud, we first aim to obtain the SO(3)-equivariant global shape descriptor $\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}$ , which captures the pose and the global shape characteristics of the input point cloud. We leverage VN-DGCNN [7] as our encoder architecture,", + "bbox": [ + 496, + 789, + 893, + 866 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "3We refer the readers to the original paper [7] for further information and detailed formulations of VNNs.", + "bbox": [ + 500, + 875, + 892, + 898 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "22980", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "which consists of 4 edge convolutional VN-layers to capture local semantics at a progressively larger receptive field, and a FPN [20] to aggregate the multi-level features. Then, we apply the global average pooling to the aggregated SO(3)-equivariant point-wise features $\\mathbf{V}^{\\mathrm{equi}}\\in \\mathbb{R}^{C\\times 3\\times N}$ to encode SO(3)-equivariant global shape descriptor $\\mathbf{Z}$ of the input point cloud. The global shape descriptor can be used subsequently as the input for our SO(3)-invariant point-wise local shape transform, to be mapped to their respective local shape descriptors, as shown in Figure 2.", + "bbox": [ + 75, + 90, + 472, + 243 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "SO(3)-invariant local shape transform. Alongside the extraction of SO(3)-equivariant global shape descriptors, we also formulate the SO(3)-invariant local shape transform $f_{\\theta_i}:\\mathbb{R}^{C\\times 3}\\mapsto \\mathbb{R}^{C'\\times 3}$ for each point $\\mathbf{p}_i\\in \\mathbb{R}^3$ of the input point cloud $\\mathbf{P}\\in \\mathbb{R}^{N\\times 3}$ . The parameters of each local shape transform $\\theta_{i}\\in \\mathbb{R}^{C^{\\prime}\\times C}$ are input-dependent - thus, dynamic since they are predicted by our encoder for the $i$ -th point of the point cloud. To predict $\\theta_{i}$ , we first obtain SO(3)-invariant point-wise features $\\mathbf{V}^{\\mathrm{in}}\\in \\mathbb{R}^{C^{\\prime}\\times 3\\times N}$ as described in Sec. 3.1.1. Then, we transform each vectorized SO(3)-invariant point-wise feature $\\operatorname {vec}(\\mathbf{v}_i^{\\mathrm{in}})\\in \\mathbb{R}^{3C'}$ to the vectorized parameter of the local shape transform $\\operatorname {vec}(\\theta_i)\\in \\mathbb{R}^{C'C}$ by using a multi-layer perceptron. By reshaping $\\operatorname {vec}(\\theta_i)$ to $\\theta_{i}\\in \\mathbb{R}^{C^{\\prime}\\times C}$ , we finally obtain the dynamic and SO(3)-invariant local shape transform $f_{\\theta_i}$ for the point $\\mathbf{p}_i$ .", + "bbox": [ + 75, + 247, + 472, + 474 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The role of these local shape transforms is to map the SO(3)-equivariant global shape descriptor $\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}$ to their respective local shape descriptors $\\mathbf{v}_i' := f_{\\theta_i}(\\mathbf{Z}) \\in \\mathbb{R}^{C' \\times 3}$ , which is provided as the input to our decoder for reconstruction. Our self-supervised training scheme encourages the point-wise dynamic local shape transform to encapsulate the local shape information e.g. semantics and geometry, to enhance the reconstruction performance.", + "bbox": [ + 75, + 476, + 472, + 598 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.1.3 SO(3)-Equivariant Decoder", + "text_level": 1, + "bbox": [ + 76, + 618, + 323, + 633 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Our decoder aims to reconstruct the initial input shapes using the obtained SO(3)-equivariant global shape descriptors $\\mathbf{Z}$ and the SO(3)-invariant local shape transforms $\\{f_{\\theta_i}\\}_{i = 1}^N$ . To reconstruct the point clouds aligned to their initial poses, we leverage SO(3)-equivariant layers as the building blocks of our decoder architecture. We first train our decoder to perform self-reconstruction, using the local shape descriptors $\\mathbf{V}'$ , i.e. $\\mathbf{P} \\leftrightarrow \\mathbf{P}' := \\mathrm{Decoder}(\\mathbf{V}') = \\mathrm{Decoder}(\\{f_{\\theta_i}(\\mathbf{Z})\\}_{i = 1}^N)$ . We also train our decoder to perform cross-reconstruction, where we use the local shape descriptors obtained using global shape descriptors and local shape transforms from different point clouds. Specifically, assume we are given two point clouds $\\mathbf{P}_1, \\mathbf{P}_2 \\in \\mathbb{R}^{N \\times 3}$ , with SO(3)-equivariant global shape descriptors $\\mathbf{Z}_1, \\mathbf{Z}_2 \\in \\mathbb{R}^{C \\times 3}$ and SO(3)-invariant local shape transforms $\\{f_{\\theta_i}^1\\}_{i = 1}^N, \\{f_{\\theta_i}^2\\}_{i = 1}^N$ . As shown in Figure 2, we then can perform cross-reconstruction from $\\mathbf{P}_2$ to $\\mathbf{P}_1$ as follows:", + "bbox": [ + 75, + 643, + 472, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "$\\mathbf{P}_1 \\leftrightarrow \\mathbf{P}_{2 \\mapsto 1}' := \\mathrm{Decoder}(\\{f_{\\theta_i}^2(\\mathbf{Z_1})\\}_{i=1}^N)$ . Intuitively, for the above cross-reconstruction to be carried out successfully, the local shape transforms for points of a true correspondence should hold similar dynamic parameters, mapping global shape descriptors to similar local shape descriptors. By training RIST to cross-reconstruct point clouds, we are supervising local shape transforms to map corresponding points between shapes to similar local shape descriptors, which encode local semantics and geometry that are generalizable across different instances within a category.", + "bbox": [ + 496, + 90, + 893, + 244 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Self-Supervised Objective", + "text_level": 1, + "bbox": [ + 498, + 261, + 736, + 277 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Due to the lack of annotated datasets for dense 3D intershape correspondences, we train RIST in a self-supervised manner by penalizing inaccurate shape reconstructions. First, we supervise RIST for self-reconstruction using the following loss:", + "bbox": [ + 496, + 287, + 893, + 364 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {S R}} = \\lambda_ {\\mathrm {M S E}} \\operatorname {M S E} \\left(\\mathbf {P}, \\mathbf {P} ^ {\\prime}\\right) + \\lambda_ {\\mathrm {E M D}} \\operatorname {E M D} \\left(\\mathbf {P}, \\mathbf {P} ^ {\\prime}\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 516, + 381, + 890, + 398 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where MSE is the Mean Squared Error, EMD stands for the Earth Mover's Distance, and both $\\lambda_{\\mathrm{MSE}}$ and $\\lambda_{\\mathrm{EMD}}$ are weight coefficients. In essence, we are trying to minimize the difference between the input and reconstructed point cloud. We also supervise RIST for cross-reconstruction as follows: $\\mathcal{L}_{\\mathrm{CR}} = \\lambda_{\\mathrm{CD}}\\mathrm{CD}(\\mathbf{P}_1,\\mathbf{P}_{2\\mapsto 1}')$ , where CD stands for the Chamfer distance, and $\\lambda_{\\mathrm{CD}}$ is a weight coefficient. Finally, our total loss $\\mathcal{L}_{\\mathrm{total}}$ is defined as: $\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{SR}} + \\mathcal{L}_{\\mathrm{CR}}$ . We omit the CD loss from self-reconstruction, as we can directly use the input point cloud to provide supervision using the MSE loss. We also omit the EMD loss from cross-reconstruction, as EMD tends to overlook the fidelity of detailed structures [36], which is crucial in cross-reconstruction of shapes under intra-class variations.", + "bbox": [ + 496, + 416, + 893, + 628 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. SO(3)-Invariant Correspondence", + "text_level": 1, + "bbox": [ + 498, + 647, + 790, + 664 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this section, given two randomly rotated point clouds $\\mathbf{P}_1$ and $\\mathbf{P}_2$ , we elaborate on how our RIST establishes the 3D dense correspondence from $\\mathbf{P}_1$ to $\\mathbf{P}_2$ . As shown in Figure 2, we first encode the SO(3)-equivariant global shape descriptor of $\\mathbf{P}_1$ , $\\mathbf{Z}_1 \\in \\mathbb{R}^{C \\times 3}$ , and the SO(3)-invariant local shape transform functions of $\\mathbf{P}_2$ , $\\{f_{\\theta_i}^2\\}_{i=1}^N$ . Then, we cross-reconstruct $\\mathbf{P}_1$ as follows: $\\mathbf{P}_{2 \\mapsto 1}' := \\mathrm{Decoder}(\\{f_{\\theta_i}^2(\\mathbf{Z}_1)\\}_{i=1}^N)$ . Finally, we define the 3D dense correspondence from $\\mathbf{P}_2$ to $\\mathbf{P}_1$ as the nearest point pairs among all possible pairs between $\\mathbf{P}_1$ and $\\mathbf{P}_{2 \\mapsto 1}'$ . Since both encoder and decoder are SO(3)-equivariant, the cross-reconstructed point cloud $\\mathbf{P}_{2 \\mapsto 1}'$ is aligned to $\\mathbf{P}_1$ . As a result, our RIST can predict 3D dense correspondences between randomly rotated point clouds, while previous approaches [3, 21] experience a high rate of failure.", + "bbox": [ + 496, + 674, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "22981", + "bbox": [ + 478, + 944, + 517, + 957 + ], + "page_idx": 3 + }, + { + "type": "table", + "img_path": "images/419fb37df3c3faf145ae1ad1dfbe4c4432cdab0da24945a97a4346d7039a3d4c.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
TrainingMethodAirplaneCapChairGuitarLaptopMotorcycleMugTableAverage
w/o RotationsFoldingNet [38]17.834.722.522.136.212.650.034.628.8
AtlasNetV2 [8]19.731.423.622.736.013.149.735.228.9
DPC [17]22.737.125.631.935.017.551.336.832.2
CPAE [3]21.038.026.022.734.914.751.435.530.5
RIST (ours)52.154.558.374.156.548.675.041.357.6
w/ RotationsFoldingNet [38]22.533.224.031.035.913.549.937.030.9
AtlasNetV2 [8]21.132.725.228.835.514.549.941.031.1
DPC [17]24.638.525.640.234.919.351.837.334.0
CPAE [3]17.036.624.539.437.415.851.936.732.4
RIST (ours)51.257.055.073.560.648.572.244.457.8
", + "bbox": [ + 119, + 88, + 854, + 263 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 327, + 209, + 343 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We present evaluations of RIST on the tasks of 3D part segmentation label transfer and 3D semantic keypoint transfer, following prior work [3, 21]. For both tasks, each method is trained with and without rotation augmentations, and tested on arbitrarily rotated inputs to validate its rotation robustness in predicting semantic correspondences between the rotated inputs. Note that previous approaches [3, 8, 21, 38] used aligned point clouds or slightly rotated point clouds with a subset of SO(3), not the full SO(3), for testing - which is unrealistic in practice, as described in Appendix H.", + "bbox": [ + 75, + 353, + 468, + 503 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We use the ShapeNetPart [39] and ScanObjectNN [35] datasets to evaluate RIST on the task of 3D part segmentation label transfer, which requires 3D dense semantic correspondence. The ShapeNetPart dataset [39] consists of 16,880 synthetic 3D data from 16 categories. The ScanObjectNN dataset [35] contains real-world scanned data, and provides part label annotations for the chair category. Following the previous work [3], we use the same pre-processed KeypointNet [40] dataset for the 3D semantic keypoint transfer task. Since both KeypointNet and ShapeNetPart are based on the ShapeNet dataset [1], we use the eight overlapping categories between the ShapeNetPart and KeypointNet [40] datasets to evaluate each method on both tasks without fine-tuning the method on each dataset. For all tasks, we follow the experiment setting of the previous work [3].", + "bbox": [ + 75, + 506, + 470, + 748 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Baseline methods. Throughout the evaluation section, we mainly compare RIST against CPAE [3], the state-of-the-art self-supervised method to establish 3D dense correspondence by exploiting an intermediate UV canonical space. When open-sourced pre-trained models or codes are applicable, we also compare RIST with AtlasNetV2 [8], FoldingNet [38] and DPC [17]. AtlasNetV2 proposes to represent shapes as the deformation and combination of learnable elementary 3D structures, which can be extended to 3D correspondence establishment. FoldingNet introduces", + "bbox": [ + 75, + 750, + 470, + 901 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/85735000c5d2b24249f949874b7ffc3b375767f41b4b19c35643b94bd41305fd.jpg", + "table_caption": [ + "Table 1. Average IoU (%) of part label transfer for eight categories in the ShapeNetPart dataset [39]. Ours consistently outperforms previous approaches [3, 8, 17, 38] both with and without rotation augmentations during training, achieving the state-of-the-art IoU. We also provide results of the other classes in Appendix I." + ], + "table_footnote": [], + "table_body": "
Methodw/o Rotationsw/ Rotations
FoldingNet [38]23.223.3
AtlasNetV2 [8]23.624.1
DPC [17]23.923.9
CPAE [3]24.423.9
RIST (ours)39.637.9
", + "bbox": [ + 540, + 325, + 854, + 425 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Table 2. Average IoU (\\%) of part label transfer for the chair category in the ScanObjectNN dataset [35]. Ours shows the best IoU both with and without rotation augmentations during training.", + "bbox": [ + 498, + 434, + 893, + 477 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "a folding-based decoder to 'fold' a canonical 2D grid into the 3D object surface, where the canonical 2D grid can be applied to identify cross-shape correspondences. DPC predicts 3D dense correspondence between non-rigidly deformed 3D humans, meaning that it can be a powerful baseline for both 3D part segmentation label transfer and 3D keypoint transfer tasks as well.", + "bbox": [ + 496, + 488, + 890, + 594 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Implementation details. We use VN-DGCNN [7] as our SO(3)-equivariant encoder, and VN-based multi-layer perception as our SO(3)-equivariant decoder. For a fair comparison, we set the dimension, $C$ , of SO(3)-equivariant global shape descriptor $\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}$ as $170 \\ (\\approx 512/3)$ since CPAE [3] uses 512-dimensional global shape descriptors. Following the training setup of CPAE [3], we use $\\lambda_{\\mathrm{MSE}}$ , $\\lambda_{\\mathrm{EMD}}$ , and $\\lambda_{\\mathrm{CD}}$ as 1000, 1, and 10, respectively. RIST is implemented in PyTorch, and is optimized with the Adam [16] optimizer at a constant learning rate of $1e^{-3}$ .", + "bbox": [ + 496, + 595, + 892, + 748 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Part Segmentation Label Transfer", + "text_level": 1, + "bbox": [ + 498, + 756, + 799, + 772 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We compare RIST with the state of the art in 3D part segmentation label transfer on ShapeNetPart [39] and ScanObjectNN [35]. For both datasets, we use the average of instance-wise IoU scores as the evaluation metric.", + "bbox": [ + 496, + 779, + 893, + 839 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "ShapeNetPart [39]. The quantitative results are presented in Table 1, where RIST outperforms CPAE [3], DPC [17], AtlasNetV2 [8], and FoldingNet [38] on all classes by a large margin with and without rotation augmentations dur", + "bbox": [ + 496, + 839, + 893, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "22982", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/4ee986b5c6538bee1a428ddcd1c50994be351da87421719e93dc99cac977f3c2.jpg", + "image_caption": [ + "Figure 3. Qualitative results of part label transfer on the ShapeNetPart dataset [39]. We visualize the label transfer results via learned correspondences of each method with the ground truth labels of targets. Note that the input shapes were arbitrarily rotated at evaluation, differently for both the source and targets of each row, but have been aligned in the above figure for better visibility of part label transfer results. RIST shows to outperform CPAE [3] consistently, showing a high resemblance to ground truth results." + ], + "image_footnote": [], + "bbox": [ + 117, + 87, + 854, + 420 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "ing training. We also provide the qualitative results of the part segmentation label transfer experiments on ShapeNetPart in Figure 3. Attributing to the SO(3)-invariant nature of correspondences established by RIST, we are able to transfer part labels significantly more accurately given randomly rotated shape pairs.", + "bbox": [ + 75, + 513, + 468, + 604 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "ScanObjectNN [35]. We evaluate each method trained on synthetic chair data of ShapeNet [1] on the real chair data of ScanObjectNN [35], which is partial and more challenging than ShapeNetPart [39], without fine-tuning. As shown in Table 2, RIST consistently outperforms previous approaches [3, 8, 17, 38] both with and without rotation augmentations during training. The qualitative results presented in Figure 4 show that RIST can predict rotation-robust 3D semantic correspondence between real and partial chair shapes, while CPAE [3] fails.", + "bbox": [ + 75, + 604, + 470, + 755 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2.3D Semantic Keypoint Transfer", + "text_level": 1, + "bbox": [ + 76, + 763, + 357, + 780 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Following the previous work [3], we compute the distances from the transferred $M$ keypoints to the ground truth keypoints, and report PCK (Percentage of Correct keypoints) of our transferred keypoints, which is computed by:", + "bbox": [ + 75, + 787, + 468, + 848 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {P C K} = \\frac {1}{M} \\sum_ {m = 1} ^ {M} \\mathbb {1} \\left[ \\left\\| \\mathbf {k} _ {m} - \\hat {\\mathbf {k}} _ {m} \\right\\| \\leq \\tau \\right], \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 147, + 856, + 468, + 897 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/c237da1af5b71c1714543729148195284a6ec599dfc63a24a0e9931e0c0c0eaa.jpg", + "image_caption": [ + "Figure 4. Qualitative results of part label transfer on ScanObjectNN [35]. Note that both source and target point clouds were arbitrarily rotated at evaluation, but have been aligned in the figure for better visibility of part label transfer results. The results show that RIST reasonably predicts the semantic correspondences between arbitrarily rotated and partial real point clouds." + ], + "image_footnote": [], + "bbox": [ + 501, + 508, + 890, + 710 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $\\tau$ , $\\mathbf{k}_m$ , and $\\hat{\\mathbf{k}}_m$ are a distance threshold, $m$ -th ground truth keypoint, and $m$ -th transferred keypoint, respectively. The results on the KeypointNet dataset [40] are illustrated in Figure 5 for varying distance thresholds $\\tau$ . It can be seen that RIST consistently outperforms baseline methods with", + "bbox": [ + 496, + 824, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "22983", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/1a4608f16826200b6932369e0f2d0964c6ff0c908e89b5cc1ec42cd5ccc237d3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 90, + 284, + 191 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/90eedb8370dda8ae124a88bddab1c89996c4c6042d9cae96c9221bc4beff9a60.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 282, + 90, + 486, + 191 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/90317cb062f207bf8d15a78e37a352e8a109fbfa9c9e36a7037a1b43ab6de593.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 486, + 90, + 687, + 191 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ea3423924f4c04f5f750a206c0add192befa7e9f76f60c90af4eca4618adb7a2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 689, + 90, + 888, + 191 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/02a7a8f1c0cbd7dfd5753dd36db1732598ac9e160507e865b03f883cfc2b8b49.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 78, + 196, + 284, + 299 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/554738b6f0ef160714c62537a663413f80b08131069d20d8900c1ecd806bf095.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 282, + 196, + 486, + 299 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/558a328480ff168bd7ea3672f4c34d781f6355892348bd8ad200615cfb582d22.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 486, + 196, + 687, + 299 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ad40310dc543bcd72f00872ce0963e9074ca6a36b36572131cdafab7c3c5369e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 687, + 196, + 888, + 299 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/6328a4059450af8dfb48fca40a75106407ecadeacfb88ad9a4c4ea6277782148.jpg", + "image_caption": [ + "Figure 5. Percentage of Correct Keypoints (PCK) for the 12 categories of the KeypointNet dataset [40] with and without rotation augmentations during training. RIST consistently outperforms previous approaches on all classes and thresholds in both settings." + ], + "image_footnote": [], + "bbox": [ + 78, + 303, + 284, + 405 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5471e74130eea9d0498d5feab29d79178a6afb97aafbbd4a41186cbe510ee87a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 282, + 303, + 486, + 406 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/046c1e7edf3d796f8865d254196865040fd7a4580494b86e5cf3dc099c4306eb.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 486, + 303, + 687, + 406 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/af7f0aa42b8055cbf7794ff194b1b450e78c20ee5be4e30f4ef943c289569b53.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 687, + 303, + 888, + 406 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d5facbb8dc74061c51c0c544bb8e03b21aff5ab63d7e9bdb5950ce096ee217e3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 178, + 409, + 792, + 435 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "and without rotation augmentations during training for all classes, by up to $10 \\times$ on certain classes and thresholds. This substantiates RIST's superior efficacy at establishing dense 3D correspondences between varying shapes. However, for certain classes such as Bathtub or Table, the performance is noticeably low, outperforming baseline methods only by a tight margin. We speculate this to be due to the prevalent rotational symmetry of those classes, making it especially challenging to establish accurate 3D correspondences under arbitrary rotations. The qualitative results of RIST in comparison to baseline methods are presented in Figure 6. It can also be seen that RIST can identify more accurate keypoint correspondences compared to CPAE [3] under arbitrary rotations, confirming the results of Figure 5.", + "bbox": [ + 75, + 508, + 472, + 720 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Ablation Study and Analyses", + "text_level": 1, + "bbox": [ + 76, + 734, + 334, + 750 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We perform an ablation study to justify the design choice of RIST, and evidence the efficacy of each component.", + "bbox": [ + 75, + 757, + 468, + 789 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Self- and cross-reconstruction. We train RIST in a self-supervised manner via penalizing errors in self- and cross-reconstruction of input point clouds. We conduct an ablation study on RIST's reconstruction, providing comparative results for scenarios with and without its use. The results are illustrated in the first graph of Figure 7. It can be seen that with and without rotation augmentations during training, in", + "bbox": [ + 75, + 794, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "corporating both self- and cross-reconstruction yields the best results. Removing self-reconstruction results in a much dramatic drop in performance; we conjecture this is because without self-reconstruction, the dynamic local shape transform (Sec. 3.1.2) fails to capture the required locality of its own point cloud in the first place, being unsuitable to establish correspondences.", + "bbox": [ + 496, + 508, + 890, + 614 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Encoder outputs and SO(3)-equivariance. RIST uses VNNs [7] as the SO(3)-equivariant layers to facilitate 3D dense correspondence establishment between arbitrarily rotated point cloud pairs, leveraging local shape transform to map global shape descriptors to local shape descriptors which encode the pointwise semantics and local geometry. We perform an ablation study to demonstrate the efficacy of local shape transforms and SO(3)-equivariant and -invariant representations in RIST on the motorcycle class of the KeypointNet dataset [40]. We start our comparison from the architecture of CPAE [3], given that they also employ an encoder-decoder architecture to self-supervise their network via shape reconstruction. The results are presented in the two rightmost graphs of Figure 7, showing the evaluation results with and without rotation augmentations during training in order. It can be seen that our design choice of using equivariant encoders and decoders shows consistent improvements over using an SO(3)-variant counterpart. Also,", + "bbox": [ + 496, + 628, + 892, + 901 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "22984", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d8e9b29f7921f50e2faad0528d2b65a612fdb0df8a05f8c37e27aed98a5b9fd8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 91, + 88, + 880, + 304 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e4717c30df69ec05eec18202f2947c497c9660585a2e1af74a642248e4fec04e.jpg", + "image_caption": [ + "Figure 7. Ablation study on losses (the leftmost) and the components of model architecture (the others); self-reconstruction loss (SR), cross-reconstruction loss (CR), equivariant decoder (ED), local shape transform (LST), and local feature (LF). When excluding the equivariant decoder, local shape transforms, or local features, the default is to use an SO(3)-variant decoder, UV coordinates [3], or global features for encoding, respectively." + ], + "image_footnote": [], + "bbox": [ + 78, + 376, + 344, + 556 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/4dda6a506ded8115f9f7e42d9863f601064997c1e4cde5d653e8ce1c6e5d6092.jpg", + "image_caption": [ + "Figure 6. Keypoint transfer results for airplane and motorcycle categories of KeypointNet [40]. Each row contains a shape pair, each with ground-truth keypoints and the keypoint transfer results. Note that the input shapes were arbitrarily rotated at evaluation, but have been aligned in the above figure for better visibility of keypoint transfer results. RIST shows to transfer the keypoints more accurately." + ], + "image_footnote": [], + "bbox": [ + 352, + 375, + 614, + 547 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/34e976bc2e6186abbbd01417b7278fb48852fcceb61aa730419b94cd03799438.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 627, + 375, + 890, + 545 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "using UV coordinates as proposed in CPAE [3] performs worse compared to our dynamic local shape transform, evidencing the comparatively better efficacy of transforming each point to their local shape descriptors via our dynamic SO(3)-invariant shape transform. While using local features as inputs to the encoder shows varied trends across with and without augmentation settings, using the point-wise local feature as input is a key component that facilitates the learning of point-wise dynamic local shape transform that is essential in establishing the 3D correspondences in RIST.", + "bbox": [ + 75, + 646, + 472, + 797 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 76, + 814, + 194, + 829 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We've introduced RIST, a novel self-supervised learner for dense 3D semantic matching across shapes of the same category, even with arbitrary rotations. Its robustness stems from our innovative use of SO(3)-equivariant and -invariant", + "bbox": [ + 75, + 839, + 470, + 901 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "representations, enabling dynamic local shape transforms that preserve rotation equivariance. These transforms map global descriptors to local ones, facilitating the establishment of dense correspondences. Our method outperforms existing ones on tasks like part label and keypoint transfer, enhancing applicability in computer vision and robotics, e.g., AR/VR and texture mapping. Future research could focus on improving robustness under common corruption.", + "bbox": [ + 496, + 646, + 890, + 768 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement. This work was supported by IITP grants (No.2021-0-02068: AI Innovation Hub $(50\\%)$ , No. 2022-0-00290: Visual Intelligence for Space-Time Understanding and Generation $(40\\%)$ , No.2019-0-01906: Artificial Intelligence Graduate School Program at POSTECH $(5\\%)$ , NO.2021-0-01343, Artificial Intelligence Graduate School Program at Seoul National University $(5\\%)$ ) funded by the Korea government (MSIT). 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In ICCV, 2023. 3" + ], + "bbox": [ + 78, + 90, + 468, + 628 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "22987", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/6e54c33e-941d-421a-b1b4-ad1a347fd128_model.json b/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/6e54c33e-941d-421a-b1b4-ad1a347fd128_model.json new file mode 100644 index 0000000000000000000000000000000000000000..73551241c02e3c946b236e72d85124450808fe20 --- /dev/null +++ b/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/6e54c33e-941d-421a-b1b4-ad1a347fd128_model.json @@ -0,0 +1,1914 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.081, + 0.131, + 0.89, + 0.152 + ], + "angle": 0, + "content": "Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform" + }, + { + "type": "text", + "bbox": [ + 0.178, + 0.18, + 0.79, + 0.225 + ], + "angle": 0, + "content": "Chunghyun Park\\(^{1*}\\) Seungwook Kim\\(^{1*}\\) Jaesik Park\\(^{2}\\) Minsu Cho\\(^{1}\\) \n\\(^{1}\\)POSTECH Seoul National University" + }, + { + "type": "text", + "bbox": [ + 0.303, + 0.234, + 0.661, + 0.248 + ], + "angle": 0, + "content": "http://cvlab.postech.ac.kr/research/RIST" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.283, + 0.314, + 0.3 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.317, + 0.474, + 0.681 + ], + "angle": 0, + "content": "Establishing accurate 3D correspondences between shapes stands as a pivotal challenge with profound implications for computer vision and robotics. However, existing self-supervised methods for this problem assume perfect input shape alignment, restricting their real-world applicability. In this work, we introduce a novel self-supervised Rotation-Invariant 3D correspondence learner with local Shape Transform, dubbed RIST, that learns to establish dense correspondences between shapes even under challenging intra-class variations and arbitrary orientations. Specifically, RIST learns to dynamically formulate an SO(3)-invariant local shape transform for each point, which maps the SO(3)-equivariant global shape descriptor of the input shape to a local shape descriptor. These local shape descriptors are provided as inputs to our decoder to facilitate point cloud self- and cross-reconstruction. Our proposed self-supervised training pipeline encourages semantically corresponding points from different shapes to be mapped to similar local shape descriptors, enabling RIST to establish dense point-wise correspondences. RIST demonstrates state-of-the-art performances on 3D part label transfer and semantic keypoint transfer given arbitrarily rotated point cloud pairs of the same category, outperforming existing methods by significant margins." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.711, + 0.21, + 0.726 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.737, + 0.47, + 0.844 + ], + "angle": 0, + "content": "Establishing dense 3D correspondences between different shapes is foundational to numerous applications across computer vision, graphics, and robotics [9, 22, 28, 41]. One of the primary challenges hindering advancements in this domain is the difficulty of annotating dense inter-shape correspondences, which limits the leverage of strongly-supervised learning paradigms." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.844, + 0.47, + 0.875 + ], + "angle": 0, + "content": "Recently, self-supervised learning methods have been proposed to address this issue [3, 21], showing promis" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.283, + 0.895, + 0.436 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.446, + 0.895, + 0.572 + ], + "angle": 0, + "content": "Figure 1. Semantic correspondence between rotated shapes. We visualize the semantic correspondence results of the previous SOTA [3] and ours, given two randomly rotated airplanes from the ShapeNetPart dataset [39]. Green and red lines indicate the correct and incorrect matches, respectively. For each method, 100 source points are randomly selected from the source (yellow) for correspondence visualization1. Ours predicts SO(3)-invariant correspondences, showing superior accuracy and robustness in comparison to the previous SOTA [3]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.586, + 0.893, + 0.737 + ], + "angle": 0, + "content": "ing directions for 3D correspondence estimation. Nonetheless, a significant limitation in existing approaches is their stringent assumption about the alignment of input shape pairs; these methods strongly assume that the input point cloud pair to establish correspondences between is precisely aligned. This assumption is rarely met in practice, where object scans and shape instances can be arbitrarily oriented. We find that the performance of existing methods degrades significantly when confronted with rotated input shapes, restricting their real-world applicability (Figure 1)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.738, + 0.894, + 0.875 + ], + "angle": 0, + "content": "To address this challenge, we introduce a novel self-supervised learning approach, dubbed RIST, designed to reliably determine dense \\( SO(3) \\)-invariant correspondences between shapes via local shape transform. In essence, RIST learns to formulate SO(3)-invariant local shape transform for each point in a dynamic and input-dependent manner. Each point-wise local shape transform maps the SO(3)-equivariant global shape descriptor of the input shape to a local shape descriptor, which is passed to the decoder to re" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.204, + 0.9 + ], + "angle": 0, + "content": "*Equal contribution" + }, + { + "type": "page_footnote", + "bbox": [ + 0.518, + 0.887, + 0.892, + 0.902 + ], + "angle": 0, + "content": "For the details of the inference algorithm, please refer to Appendix A." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22978" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.168 + ], + "angle": 0, + "content": "construct the shape and pose of the input shape. By training RIST via self- and cross-reconstruction of input shapes, true semantically corresponding points are trained to yield similar local shape descriptors, enabling us to determine dense shape correspondences." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.17, + 0.47, + 0.381 + ], + "angle": 0, + "content": "RIST demonstrates state-of-the-art performance on part segmentation label transfer when evaluated on the ShapeNetPart [39] and ScanObjectNN [35] datasets. In particular, significant improvements over existing baselines are observed when our method is applied to randomly oriented shape pair inputs. Furthermore, our approach also proves to be more effective compared to existing methods at semantic keypoint transfer when evaluated on the Keypoint-Net dataset [40]. This showcases not only the applicability of RIST across a diverse range of tasks, but also its potential to be utilized for efficient dense annotation of 3D shapes. These results highlight the efficacy of RIST in addressing the challenges posed by real-world scenarios where existing methods fail to perform effectively." + }, + { + "type": "text", + "bbox": [ + 0.096, + 0.383, + 0.434, + 0.398 + ], + "angle": 0, + "content": "The main contributions of our work are as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.401, + 0.469, + 0.445 + ], + "angle": 0, + "content": "- We introduce RIST, a novel self-supervised approach for determining dense SO(3)-invariant correspondences between arbitrarily aligned 3D objects." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.446, + 0.469, + 0.52 + ], + "angle": 0, + "content": "- We propose to formulate the local shape information of each point as a novel function called local shape transform with dynamic input-dependent parameters, which effectively maps the global shape descriptor of input shapes to local shape descriptors." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.521, + 0.469, + 0.581 + ], + "angle": 0, + "content": "- RIST achieves state-of-the-art performance on 3D part segmentation label transfer and 3D keypoint transfer under arbitrary rotations, indicating its potential for application in a wide range of practical tasks in computer vision." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.401, + 0.469, + 0.581 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.602, + 0.219, + 0.617 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.076, + 0.629, + 0.469, + 0.644 + ], + "angle": 0, + "content": "Point cloud understanding via self-supervised learning." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.644, + 0.47, + 0.901 + ], + "angle": 0, + "content": "While traditional methods for point cloud processing involving hand-crafted features [27, 33] have shown impressive performance, with the advent of deep learning, substantial research efforts have been directed towards developing learning-based algorithms capable of effectively processing and understanding point clouds [5, 24-26, 42]. Due to limited large-scale datasets with rich annotations, self-supervised learning approaches emerged as a viable alternative. One of the most prominent directions to learn point cloud representations in a self-supervised manner is learning through self-reconstruction [23, 38, 43] of the point cloud. Primarily inspired by the efficacy of point cloud reconstruction as a self-supervised representation learning scheme, we train RIST to establish 3D correspondences in a self-supervised manner via self- and cross-reconstruction of point clouds by leveraging SO(3)-invariant dynamic local shape transform." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.319 + ], + "angle": 0, + "content": "Equivariance and invariance to rotation. The conventional method to improve a neural network's robustness to rotation is by employing rotation augmentations during training or inference. However, this tends to increase the resources required for training and still shows unsatisfactory results when confronted with an unseen rotation [14, 18]. In recent years, various methods have been proposed to yield point cloud representations, which are equivariant [2, 6, 29, 32] or invariant [14, 18, 19, 31, 37] to the rotation of the input, demonstrating enhanced performances under arbitrary input rotations. To facilitate the rotation-robust establishment of 3D dense correspondences, we utilize SO(3)-equivariant networks in building RIST, leveraging SO(3)-equivariant and -invariant representations to guarantee robustness to rotation by design." + }, + { + "type": "title", + "bbox": [ + 0.498, + 0.326, + 0.892, + 0.339 + ], + "angle": 0, + "content": "Semantic correspondences under intra-class variations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.34, + 0.892, + 0.658 + ], + "angle": 0, + "content": "Finding correspondences between images or shapes under intra-class variations - manifesting as differences in shape, size, and orientation within the same category of objects - poses significant challenges over photometric or viewpoint variations. This task has been widely studied in the domain of images, where existing methods make use of sparsely annotated image pair datasets to train their method in a strongly- or a weakly-supervised manner [4, 11, 13, 15, 34]. However, learning to establish dense yet reliable 3D correspondences between 3D shapes remains challenging, as it is infeasible to label dense correspondence annotations across point cloud pairs with intra-class variations. Self-supervised methods have been proposed to address this issue [3, 21], but they strongly assume that the input point clouds are aligned, leading to considerable significant degradation when confronted with arbitrarily rotated point clouds. Additionally, the functional map-based approach introduced by Huang et al. [10] for non-rigid registration struggles with topological changes and efficiency. To this end, we propose RIST to establish reliable 3D dense correspondences irrespective of the input point clouds' poses." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.686, + 0.854, + 0.704 + ], + "angle": 0, + "content": "3. RIST for 3D Semantic Correspondence" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.712, + 0.892, + 0.879 + ], + "angle": 0, + "content": "In this section, we detail the components of RIST, which come together to facilitate the end-to-end self-supervised training for 3D semantic correspondence establishment. The objective of 3D semantic correspondence is as follows; given two different point clouds instances \\(\\mathbf{P}_1 \\in \\mathbb{R}^{N \\times 3}\\) and \\(\\mathbf{P}_2 \\in \\mathbb{R}^{N \\times 3}\\) belonging to the same semantic category, we aim to find all semantically corresponding point pairs \\(\\{\\mathbf{p}_i, \\mathbf{q}_i\\}_{i=1}^{N'}\\) such that \\(\\mathbf{p}_i \\in \\mathbf{P}_1\\) and \\(\\mathbf{q}_i \\in \\mathbf{P}_2\\). To achieve this, we claim it is crucial to identify the local shape information i.e. local semantics and geometry, which is generalizable across different instances within the same category." + }, + { + "type": "page_footnote", + "bbox": [ + 0.516, + 0.887, + 0.783, + 0.901 + ], + "angle": 0, + "content": "\\(2N^{\\prime}\\leq N\\) ; there could be points with no matches." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22979" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.089, + 0.359, + 0.309 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.141, + 0.311, + 0.295, + 0.324 + ], + "angle": 0, + "content": "SO(3)-Equivariant Encoding" + }, + { + "type": "image", + "bbox": [ + 0.369, + 0.098, + 0.615, + 0.31 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.616, + 0.099, + 0.893, + 0.309 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.68, + 0.311, + 0.836, + 0.324 + ], + "angle": 0, + "content": "SO(3)-Equivariant Decoding" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.346, + 0.895, + 0.445 + ], + "angle": 0, + "content": "Figure 2. Overview: Self-supervised training of RIST. The input point clouds are independently encoded to SO(3)-equivariant global shape descriptor \\(\\mathbf{Z}\\) and dynamic SO(3)-invariant point-wise local shape transforms \\(\\{f_{\\theta_i}\\}\\). The local shape transforms map the global shape descriptor to local shape descriptors by infusing local semantics and geometry, which are used as inputs to the decoder for self-reconstruction. For cross-reconstruction, we apply the local shape transforms formulated from another point cloud to reconstruct the point cloud, ensuring that the local shape descriptors successfully capture generalizable local semantics and geometries. We supervise RIST via penalizing errors in self- and cross-reconstructions. At inference, we can leverage the local shape transforms for obtaining local shape descriptors, to identify the dense correspondences." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.456, + 0.473, + 0.713 + ], + "angle": 0, + "content": "Therefore, the main idea of RIST is to dynamically generate a SO(3)-invariant local shape transform as a function for each point, such that each local shape transform can map the SO(3)-equivariant global shape descriptor of the input point cloud to its respective local shape descriptor. In the following, we elaborate on the network architecture of RIST, in particular how we leverage SO(3)-equivariant and invariant representations to facilitate the dynamic formulation of pointwise SO(3)-invariant local shape transforms and the reconstruction of pose-preserved point clouds (Sec. 3.1). Subsequently, we introduce our self-supervisory objective function, which trains RIST to self- and cross-reconstruct the input point clouds in a rotation-equivariant manner (Sec. 3.2), finally enabling the establishment of 3D dense correspondences (Sec. 3.3) via corresponding local shape descriptors. Figure 2 illustrates the outline of the training scheme of RIST." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.728, + 0.303, + 0.743 + ], + "angle": 0, + "content": "3.1. Network Design of RIST" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.753, + 0.466, + 0.769 + ], + "angle": 0, + "content": "3.1.1 Preliminary: SO(3)-Equivariant Representation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.47, + 0.901 + ], + "angle": 0, + "content": "One of the main motivations of RIST is to establish reliable and accurate 3D dense correspondences given arbitrarily rotated shapes, a setting where existing work shows to be brittle. This requires our encoder to formulate the pointwise local shape transforms not only effectively to capture the local shape semantics and geometry, but also robustly against transformations in the SO(3) space. To this end, we integrate SO(3)-equivariant networks into RIST to facilitate" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.456, + 0.895, + 0.683 + ], + "angle": 0, + "content": "robustness to SO(3) transformations of the input. In this work, we choose VNNs [7] to build our SO(3)-equivariant layers for their simplicity and efficacy. In VNNs, a single neuron, which is represented by a scalar-list of values, is lifted to a vector-list feature \\(\\mathbf{V} \\in \\mathbb{R}^{C \\times 3}\\), which is essentially a sequence of 3D vectors. The layers of VNNs handle batches of such vector-list features such that equivariance with respect to rotation \\(R \\in \\mathrm{SO}(3)\\) is satisfied i.e. \\(f(\\mathbf{V}R) = f(\\mathbf{V})R^3\\). Notably, we can yield an SO(3)-invariant output by performing a product of an equivariant vector-list feature \\(\\mathbf{V}R \\in \\mathbb{R}^{C \\times 3}\\) with the transpose of another consistently equivariant vector-list feature \\(\\mathbf{U}R \\in \\mathbb{R}^{C' \\times 3}\\) as follows: \\((\\mathbf{V}R)(\\mathbf{U}R)^{\\top} = \\mathbf{V}RR^{\\top}\\mathbf{U}^{\\top} = \\mathbf{V}\\mathbf{U}^{\\top}\\). This serves as a critical functionality when constructing our SO(3)-invariant local shape transform of our encoder (Sec. 3.1.2)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.702, + 0.748, + 0.717 + ], + "angle": 0, + "content": "3.1.2 SO(3)-Equivariant Encoder" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.726, + 0.893, + 0.787 + ], + "angle": 0, + "content": "We design our encoder architecture to take as input a point cloud \\(\\mathbf{P} \\in \\mathbb{R}^{N \\times 3}\\), and simultaneously output an SO(3)-equivariant global shape descriptor and formulate pointwise SO(3)-invariant local shape transforms." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.79, + 0.894, + 0.867 + ], + "angle": 0, + "content": "SO(3)-equivariant global shape descriptor. Given a point cloud, we first aim to obtain the SO(3)-equivariant global shape descriptor \\(\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}\\), which captures the pose and the global shape characteristics of the input point cloud. We leverage VN-DGCNN [7] as our encoder architecture," + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.875, + 0.893, + 0.9 + ], + "angle": 0, + "content": "3We refer the readers to the original paper [7] for further information and detailed formulations of VNNs." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22980" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.244 + ], + "angle": 0, + "content": "which consists of 4 edge convolutional VN-layers to capture local semantics at a progressively larger receptive field, and a FPN [20] to aggregate the multi-level features. Then, we apply the global average pooling to the aggregated SO(3)-equivariant point-wise features \\(\\mathbf{V}^{\\mathrm{equi}}\\in \\mathbb{R}^{C\\times 3\\times N}\\) to encode SO(3)-equivariant global shape descriptor \\(\\mathbf{Z}\\) of the input point cloud. The global shape descriptor can be used subsequently as the input for our SO(3)-invariant point-wise local shape transform, to be mapped to their respective local shape descriptors, as shown in Figure 2." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.248, + 0.473, + 0.476 + ], + "angle": 0, + "content": "SO(3)-invariant local shape transform. Alongside the extraction of SO(3)-equivariant global shape descriptors, we also formulate the SO(3)-invariant local shape transform \\(f_{\\theta_i}:\\mathbb{R}^{C\\times 3}\\mapsto \\mathbb{R}^{C'\\times 3}\\) for each point \\(\\mathbf{p}_i\\in \\mathbb{R}^3\\) of the input point cloud \\(\\mathbf{P}\\in \\mathbb{R}^{N\\times 3}\\). The parameters of each local shape transform \\(\\theta_{i}\\in \\mathbb{R}^{C^{\\prime}\\times C}\\) are input-dependent - thus, dynamic since they are predicted by our encoder for the \\(i\\)-th point of the point cloud. To predict \\(\\theta_{i}\\), we first obtain SO(3)-invariant point-wise features \\(\\mathbf{V}^{\\mathrm{in}}\\in \\mathbb{R}^{C^{\\prime}\\times 3\\times N}\\) as described in Sec. 3.1.1. Then, we transform each vectorized SO(3)-invariant point-wise feature \\(\\operatorname {vec}(\\mathbf{v}_i^{\\mathrm{in}})\\in \\mathbb{R}^{3C'}\\) to the vectorized parameter of the local shape transform \\(\\operatorname {vec}(\\theta_i)\\in \\mathbb{R}^{C'C}\\) by using a multi-layer perceptron. By reshaping \\(\\operatorname {vec}(\\theta_i)\\) to \\(\\theta_{i}\\in \\mathbb{R}^{C^{\\prime}\\times C}\\), we finally obtain the dynamic and SO(3)-invariant local shape transform \\(f_{\\theta_i}\\) for the point \\(\\mathbf{p}_i\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.477, + 0.473, + 0.599 + ], + "angle": 0, + "content": "The role of these local shape transforms is to map the SO(3)-equivariant global shape descriptor \\(\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}\\) to their respective local shape descriptors \\(\\mathbf{v}_i' := f_{\\theta_i}(\\mathbf{Z}) \\in \\mathbb{R}^{C' \\times 3}\\), which is provided as the input to our decoder for reconstruction. Our self-supervised training scheme encourages the point-wise dynamic local shape transform to encapsulate the local shape information e.g. semantics and geometry, to enhance the reconstruction performance." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.619, + 0.325, + 0.635 + ], + "angle": 0, + "content": "3.1.3 SO(3)-Equivariant Decoder" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.645, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Our decoder aims to reconstruct the initial input shapes using the obtained SO(3)-equivariant global shape descriptors \\(\\mathbf{Z}\\) and the SO(3)-invariant local shape transforms \\(\\{f_{\\theta_i}\\}_{i = 1}^N\\). To reconstruct the point clouds aligned to their initial poses, we leverage SO(3)-equivariant layers as the building blocks of our decoder architecture. We first train our decoder to perform self-reconstruction, using the local shape descriptors \\(\\mathbf{V}'\\), i.e. \\(\\mathbf{P} \\leftrightarrow \\mathbf{P}' := \\mathrm{Decoder}(\\mathbf{V}') = \\mathrm{Decoder}(\\{f_{\\theta_i}(\\mathbf{Z})\\}_{i = 1}^N)\\). We also train our decoder to perform cross-reconstruction, where we use the local shape descriptors obtained using global shape descriptors and local shape transforms from different point clouds. Specifically, assume we are given two point clouds \\(\\mathbf{P}_1, \\mathbf{P}_2 \\in \\mathbb{R}^{N \\times 3}\\), with SO(3)-equivariant global shape descriptors \\(\\mathbf{Z}_1, \\mathbf{Z}_2 \\in \\mathbb{R}^{C \\times 3}\\) and SO(3)-invariant local shape transforms \\(\\{f_{\\theta_i}^1\\}_{i = 1}^N, \\{f_{\\theta_i}^2\\}_{i = 1}^N\\). As shown in Figure 2, we then can perform cross-reconstruction from \\(\\mathbf{P}_2\\) to \\(\\mathbf{P}_1\\) as follows:" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.091, + 0.895, + 0.245 + ], + "angle": 0, + "content": "\\(\\mathbf{P}_1 \\leftrightarrow \\mathbf{P}_{2 \\mapsto 1}' := \\mathrm{Decoder}(\\{f_{\\theta_i}^2(\\mathbf{Z_1})\\}_{i=1}^N)\\). Intuitively, for the above cross-reconstruction to be carried out successfully, the local shape transforms for points of a true correspondence should hold similar dynamic parameters, mapping global shape descriptors to similar local shape descriptors. By training RIST to cross-reconstruct point clouds, we are supervising local shape transforms to map corresponding points between shapes to similar local shape descriptors, which encode local semantics and geometry that are generalizable across different instances within a category." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.262, + 0.737, + 0.279 + ], + "angle": 0, + "content": "3.2. Self-Supervised Objective" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.289, + 0.895, + 0.366 + ], + "angle": 0, + "content": "Due to the lack of annotated datasets for dense 3D intershape correspondences, we train RIST in a self-supervised manner by penalizing inaccurate shape reconstructions. First, we supervise RIST for self-reconstruction using the following loss:" + }, + { + "type": "equation", + "bbox": [ + 0.517, + 0.382, + 0.892, + 0.4 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {S R}} = \\lambda_ {\\mathrm {M S E}} \\operatorname {M S E} \\left(\\mathbf {P}, \\mathbf {P} ^ {\\prime}\\right) + \\lambda_ {\\mathrm {E M D}} \\operatorname {E M D} \\left(\\mathbf {P}, \\mathbf {P} ^ {\\prime}\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.417, + 0.895, + 0.63 + ], + "angle": 0, + "content": "where MSE is the Mean Squared Error, EMD stands for the Earth Mover's Distance, and both \\(\\lambda_{\\mathrm{MSE}}\\) and \\(\\lambda_{\\mathrm{EMD}}\\) are weight coefficients. In essence, we are trying to minimize the difference between the input and reconstructed point cloud. We also supervise RIST for cross-reconstruction as follows: \\(\\mathcal{L}_{\\mathrm{CR}} = \\lambda_{\\mathrm{CD}}\\mathrm{CD}(\\mathbf{P}_1,\\mathbf{P}_{2\\mapsto 1}')\\), where CD stands for the Chamfer distance, and \\(\\lambda_{\\mathrm{CD}}\\) is a weight coefficient. Finally, our total loss \\(\\mathcal{L}_{\\mathrm{total}}\\) is defined as: \\(\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{SR}} + \\mathcal{L}_{\\mathrm{CR}}\\). We omit the CD loss from self-reconstruction, as we can directly use the input point cloud to provide supervision using the MSE loss. We also omit the EMD loss from cross-reconstruction, as EMD tends to overlook the fidelity of detailed structures [36], which is crucial in cross-reconstruction of shapes under intra-class variations." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.648, + 0.792, + 0.665 + ], + "angle": 0, + "content": "3.3. SO(3)-Invariant Correspondence" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.895, + 0.903 + ], + "angle": 0, + "content": "In this section, given two randomly rotated point clouds \\(\\mathbf{P}_1\\) and \\(\\mathbf{P}_2\\), we elaborate on how our RIST establishes the 3D dense correspondence from \\(\\mathbf{P}_1\\) to \\(\\mathbf{P}_2\\). As shown in Figure 2, we first encode the SO(3)-equivariant global shape descriptor of \\(\\mathbf{P}_1\\), \\(\\mathbf{Z}_1 \\in \\mathbb{R}^{C \\times 3}\\), and the SO(3)-invariant local shape transform functions of \\(\\mathbf{P}_2\\), \\(\\{f_{\\theta_i}^2\\}_{i=1}^N\\). Then, we cross-reconstruct \\(\\mathbf{P}_1\\) as follows: \\(\\mathbf{P}_{2 \\mapsto 1}' := \\mathrm{Decoder}(\\{f_{\\theta_i}^2(\\mathbf{Z}_1)\\}_{i=1}^N)\\). Finally, we define the 3D dense correspondence from \\(\\mathbf{P}_2\\) to \\(\\mathbf{P}_1\\) as the nearest point pairs among all possible pairs between \\(\\mathbf{P}_1\\) and \\(\\mathbf{P}_{2 \\mapsto 1}'\\). Since both encoder and decoder are SO(3)-equivariant, the cross-reconstructed point cloud \\(\\mathbf{P}_{2 \\mapsto 1}'\\) is aligned to \\(\\mathbf{P}_1\\). As a result, our RIST can predict 3D dense correspondences between randomly rotated point clouds, while previous approaches [3, 21] experience a high rate of failure." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.958 + ], + "angle": 0, + "content": "22981" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.12, + 0.089, + 0.855, + 0.265 + ], + "angle": 0, + "content": "
TrainingMethodAirplaneCapChairGuitarLaptopMotorcycleMugTableAverage
w/o RotationsFoldingNet [38]17.834.722.522.136.212.650.034.628.8
AtlasNetV2 [8]19.731.423.622.736.013.149.735.228.9
DPC [17]22.737.125.631.935.017.551.336.832.2
CPAE [3]21.038.026.022.734.914.751.435.530.5
RIST (ours)52.154.558.374.156.548.675.041.357.6
w/ RotationsFoldingNet [38]22.533.224.031.035.913.549.937.030.9
AtlasNetV2 [8]21.132.725.228.835.514.549.941.031.1
DPC [17]24.638.525.640.234.919.351.837.334.0
CPAE [3]17.036.624.539.437.415.851.936.732.4
RIST (ours)51.257.055.073.560.648.572.244.457.8
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.274, + 0.895, + 0.318 + ], + "angle": 0, + "content": "Table 1. Average IoU (%) of part label transfer for eight categories in the ShapeNetPart dataset [39]. Ours consistently outperforms previous approaches [3, 8, 17, 38] both with and without rotation augmentations during training, achieving the state-of-the-art IoU. We also provide results of the other classes in Appendix I." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.328, + 0.21, + 0.344 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.354, + 0.47, + 0.505 + ], + "angle": 0, + "content": "We present evaluations of RIST on the tasks of 3D part segmentation label transfer and 3D semantic keypoint transfer, following prior work [3, 21]. For both tasks, each method is trained with and without rotation augmentations, and tested on arbitrarily rotated inputs to validate its rotation robustness in predicting semantic correspondences between the rotated inputs. Note that previous approaches [3, 8, 21, 38] used aligned point clouds or slightly rotated point clouds with a subset of SO(3), not the full SO(3), for testing - which is unrealistic in practice, as described in Appendix H." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.507, + 0.471, + 0.749 + ], + "angle": 0, + "content": "Datasets. We use the ShapeNetPart [39] and ScanObjectNN [35] datasets to evaluate RIST on the task of 3D part segmentation label transfer, which requires 3D dense semantic correspondence. The ShapeNetPart dataset [39] consists of 16,880 synthetic 3D data from 16 categories. The ScanObjectNN dataset [35] contains real-world scanned data, and provides part label annotations for the chair category. Following the previous work [3], we use the same pre-processed KeypointNet [40] dataset for the 3D semantic keypoint transfer task. Since both KeypointNet and ShapeNetPart are based on the ShapeNet dataset [1], we use the eight overlapping categories between the ShapeNetPart and KeypointNet [40] datasets to evaluate each method on both tasks without fine-tuning the method on each dataset. For all tasks, we follow the experiment setting of the previous work [3]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Baseline methods. Throughout the evaluation section, we mainly compare RIST against CPAE [3], the state-of-the-art self-supervised method to establish 3D dense correspondence by exploiting an intermediate UV canonical space. When open-sourced pre-trained models or codes are applicable, we also compare RIST with AtlasNetV2 [8], FoldingNet [38] and DPC [17]. AtlasNetV2 proposes to represent shapes as the deformation and combination of learnable elementary 3D structures, which can be extended to 3D correspondence establishment. FoldingNet introduces" + }, + { + "type": "table", + "bbox": [ + 0.541, + 0.326, + 0.855, + 0.426 + ], + "angle": 0, + "content": "
Methodw/o Rotationsw/ Rotations
FoldingNet [38]23.223.3
AtlasNetV2 [8]23.624.1
DPC [17]23.923.9
CPAE [3]24.423.9
RIST (ours)39.637.9
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.435, + 0.895, + 0.478 + ], + "angle": 0, + "content": "Table 2. Average IoU (\\%) of part label transfer for the chair category in the ScanObjectNN dataset [35]. Ours shows the best IoU both with and without rotation augmentations during training." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.489, + 0.892, + 0.595 + ], + "angle": 0, + "content": "a folding-based decoder to 'fold' a canonical 2D grid into the 3D object surface, where the canonical 2D grid can be applied to identify cross-shape correspondences. DPC predicts 3D dense correspondence between non-rigidly deformed 3D humans, meaning that it can be a powerful baseline for both 3D part segmentation label transfer and 3D keypoint transfer tasks as well." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.596, + 0.893, + 0.749 + ], + "angle": 0, + "content": "Implementation details. We use VN-DGCNN [7] as our SO(3)-equivariant encoder, and VN-based multi-layer perception as our SO(3)-equivariant decoder. For a fair comparison, we set the dimension, \\(C\\), of SO(3)-equivariant global shape descriptor \\(\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}\\) as \\(170 \\ (\\approx 512/3)\\) since CPAE [3] uses 512-dimensional global shape descriptors. Following the training setup of CPAE [3], we use \\(\\lambda_{\\mathrm{MSE}}\\), \\(\\lambda_{\\mathrm{EMD}}\\), and \\(\\lambda_{\\mathrm{CD}}\\) as 1000, 1, and 10, respectively. RIST is implemented in PyTorch, and is optimized with the Adam [16] optimizer at a constant learning rate of \\(1e^{-3}\\)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.757, + 0.8, + 0.773 + ], + "angle": 0, + "content": "4.1. Part Segmentation Label Transfer" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.894, + 0.84 + ], + "angle": 0, + "content": "We compare RIST with the state of the art in 3D part segmentation label transfer on ShapeNetPart [39] and ScanObjectNN [35]. For both datasets, we use the average of instance-wise IoU scores as the evaluation metric." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.894, + 0.902 + ], + "angle": 0, + "content": "ShapeNetPart [39]. The quantitative results are presented in Table 1, where RIST outperforms CPAE [3], DPC [17], AtlasNetV2 [8], and FoldingNet [38] on all classes by a large margin with and without rotation augmentations dur" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22982" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.119, + 0.088, + 0.856, + 0.421 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.439, + 0.895, + 0.496 + ], + "angle": 0, + "content": "Figure 3. Qualitative results of part label transfer on the ShapeNetPart dataset [39]. We visualize the label transfer results via learned correspondences of each method with the ground truth labels of targets. Note that the input shapes were arbitrarily rotated at evaluation, differently for both the source and targets of each row, but have been aligned in the above figure for better visibility of part label transfer results. RIST shows to outperform CPAE [3] consistently, showing a high resemblance to ground truth results." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.515, + 0.47, + 0.605 + ], + "angle": 0, + "content": "ing training. We also provide the qualitative results of the part segmentation label transfer experiments on ShapeNetPart in Figure 3. Attributing to the SO(3)-invariant nature of correspondences established by RIST, we are able to transfer part labels significantly more accurately given randomly rotated shape pairs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.605, + 0.471, + 0.756 + ], + "angle": 0, + "content": "ScanObjectNN [35]. We evaluate each method trained on synthetic chair data of ShapeNet [1] on the real chair data of ScanObjectNN [35], which is partial and more challenging than ShapeNetPart [39], without fine-tuning. As shown in Table 2, RIST consistently outperforms previous approaches [3, 8, 17, 38] both with and without rotation augmentations during training. The qualitative results presented in Figure 4 show that RIST can predict rotation-robust 3D semantic correspondence between real and partial chair shapes, while CPAE [3] fails." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.764, + 0.358, + 0.781 + ], + "angle": 0, + "content": "4.2.3D Semantic Keypoint Transfer" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.788, + 0.47, + 0.849 + ], + "angle": 0, + "content": "Following the previous work [3], we compute the distances from the transferred \\(M\\) keypoints to the ground truth keypoints, and report PCK (Percentage of Correct keypoints) of our transferred keypoints, which is computed by:" + }, + { + "type": "equation", + "bbox": [ + 0.148, + 0.857, + 0.47, + 0.898 + ], + "angle": 0, + "content": "\\[\n\\mathrm {P C K} = \\frac {1}{M} \\sum_ {m = 1} ^ {M} \\mathbb {1} \\left[ \\left\\| \\mathbf {k} _ {m} - \\hat {\\mathbf {k}} _ {m} \\right\\| \\leq \\tau \\right], \\tag {2}\n\\]" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.509, + 0.892, + 0.711 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.719, + 0.895, + 0.803 + ], + "angle": 0, + "content": "Figure 4. Qualitative results of part label transfer on ScanObjectNN [35]. Note that both source and target point clouds were arbitrarily rotated at evaluation, but have been aligned in the figure for better visibility of part label transfer results. The results show that RIST reasonably predicts the semantic correspondences between arbitrarily rotated and partial real point clouds." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.895, + 0.903 + ], + "angle": 0, + "content": "where \\(\\tau\\), \\(\\mathbf{k}_m\\), and \\(\\hat{\\mathbf{k}}_m\\) are a distance threshold, \\(m\\)-th ground truth keypoint, and \\(m\\)-th transferred keypoint, respectively. The results on the KeypointNet dataset [40] are illustrated in Figure 5 for varying distance thresholds \\(\\tau\\). It can be seen that RIST consistently outperforms baseline methods with" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22983" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.091, + 0.285, + 0.193 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.091, + 0.487, + 0.193 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.487, + 0.091, + 0.688, + 0.193 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.69, + 0.092, + 0.889, + 0.193 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.197, + 0.285, + 0.3 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.197, + 0.487, + 0.3 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.487, + 0.197, + 0.688, + 0.3 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.688, + 0.197, + 0.889, + 0.3 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.304, + 0.285, + 0.406 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.304, + 0.487, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.487, + 0.304, + 0.688, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.688, + 0.304, + 0.889, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.179, + 0.41, + 0.793, + 0.436 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.462, + 0.893, + 0.491 + ], + "angle": 0, + "content": "Figure 5. Percentage of Correct Keypoints (PCK) for the 12 categories of the KeypointNet dataset [40] with and without rotation augmentations during training. RIST consistently outperforms previous approaches on all classes and thresholds in both settings." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.51, + 0.473, + 0.722 + ], + "angle": 0, + "content": "and without rotation augmentations during training for all classes, by up to \\(10 \\times\\) on certain classes and thresholds. This substantiates RIST's superior efficacy at establishing dense 3D correspondences between varying shapes. However, for certain classes such as Bathtub or Table, the performance is noticeably low, outperforming baseline methods only by a tight margin. We speculate this to be due to the prevalent rotational symmetry of those classes, making it especially challenging to establish accurate 3D correspondences under arbitrary rotations. The qualitative results of RIST in comparison to baseline methods are presented in Figure 6. It can also be seen that RIST can identify more accurate keypoint correspondences compared to CPAE [3] under arbitrary rotations, confirming the results of Figure 5." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.735, + 0.336, + 0.751 + ], + "angle": 0, + "content": "4.3. Ablation Study and Analyses" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.758, + 0.47, + 0.79 + ], + "angle": 0, + "content": "We perform an ablation study to justify the design choice of RIST, and evidence the efficacy of each component." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Self- and cross-reconstruction. We train RIST in a self-supervised manner via penalizing errors in self- and cross-reconstruction of input point clouds. We conduct an ablation study on RIST's reconstruction, providing comparative results for scenarios with and without its use. The results are illustrated in the first graph of Figure 7. It can be seen that with and without rotation augmentations during training, in" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.51, + 0.892, + 0.616 + ], + "angle": 0, + "content": "corporating both self- and cross-reconstruction yields the best results. Removing self-reconstruction results in a much dramatic drop in performance; we conjecture this is because without self-reconstruction, the dynamic local shape transform (Sec. 3.1.2) fails to capture the required locality of its own point cloud in the first place, being unsuitable to establish correspondences." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.893, + 0.902 + ], + "angle": 0, + "content": "Encoder outputs and SO(3)-equivariance. RIST uses VNNs [7] as the SO(3)-equivariant layers to facilitate 3D dense correspondence establishment between arbitrarily rotated point cloud pairs, leveraging local shape transform to map global shape descriptors to local shape descriptors which encode the pointwise semantics and local geometry. We perform an ablation study to demonstrate the efficacy of local shape transforms and SO(3)-equivariant and -invariant representations in RIST on the motorcycle class of the KeypointNet dataset [40]. We start our comparison from the architecture of CPAE [3], given that they also employ an encoder-decoder architecture to self-supervise their network via shape reconstruction. The results are presented in the two rightmost graphs of Figure 7, showing the evaluation results with and without rotation augmentations during training in order. It can be seen that our design choice of using equivariant encoders and decoders shows consistent improvements over using an SO(3)-variant counterpart. Also," + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22984" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.092, + 0.089, + 0.882, + 0.305 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.325, + 0.895, + 0.369 + ], + "angle": 0, + "content": "Figure 6. Keypoint transfer results for airplane and motorcycle categories of KeypointNet [40]. Each row contains a shape pair, each with ground-truth keypoints and the keypoint transfer results. Note that the input shapes were arbitrarily rotated at evaluation, but have been aligned in the above figure for better visibility of keypoint transfer results. RIST shows to transfer the keypoints more accurately." + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.377, + 0.345, + 0.558 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.354, + 0.376, + 0.615, + 0.548 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.629, + 0.376, + 0.891, + 0.546 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.571, + 0.895, + 0.629 + ], + "angle": 0, + "content": "Figure 7. Ablation study on losses (the leftmost) and the components of model architecture (the others); self-reconstruction loss (SR), cross-reconstruction loss (CR), equivariant decoder (ED), local shape transform (LST), and local feature (LF). When excluding the equivariant decoder, local shape transforms, or local features, the default is to use an SO(3)-variant decoder, UV coordinates [3], or global features for encoding, respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.647, + 0.473, + 0.799 + ], + "angle": 0, + "content": "using UV coordinates as proposed in CPAE [3] performs worse compared to our dynamic local shape transform, evidencing the comparatively better efficacy of transforming each point to their local shape descriptors via our dynamic SO(3)-invariant shape transform. While using local features as inputs to the encoder shows varied trends across with and without augmentation settings, using the point-wise local feature as input is a key component that facilitates the learning of point-wise dynamic local shape transform that is essential in establishing the 3D correspondences in RIST." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.815, + 0.196, + 0.83 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.471, + 0.902 + ], + "angle": 0, + "content": "We've introduced RIST, a novel self-supervised learner for dense 3D semantic matching across shapes of the same category, even with arbitrary rotations. Its robustness stems from our innovative use of SO(3)-equivariant and -invariant" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.647, + 0.892, + 0.769 + ], + "angle": 0, + "content": "representations, enabling dynamic local shape transforms that preserve rotation equivariance. These transforms map global descriptors to local ones, facilitating the establishment of dense correspondences. Our method outperforms existing ones on tasks like part label and keypoint transfer, enhancing applicability in computer vision and robotics, e.g., AR/VR and texture mapping. Future research could focus on improving robustness under common corruption." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.776, + 0.893, + 0.896 + ], + "angle": 0, + "content": "Acknowledgement. This work was supported by IITP grants (No.2021-0-02068: AI Innovation Hub \\((50\\%)\\), No. 2022-0-00290: Visual Intelligence for Space-Time Understanding and Generation \\((40\\%)\\), No.2019-0-01906: Artificial Intelligence Graduate School Program at POSTECH \\((5\\%)\\), NO.2021-0-01343, Artificial Intelligence Graduate School Program at Seoul National University \\((5\\%)\\)) funded by the Korea government (MSIT). Seungwook was supported by the Hyundai-Motor Chung Mong-koo Foundation." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22985" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.175, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Angel X. Chang, Thomas Funkhouser, Leonidas Guibas, Pat Hanrahan, Qixing Huang, Zimo Li, Silvio Savarese, Manolis Savva, Shuran Song, Hao Su, Jianxiong Xiao, Li Yi, and Fisher Yu. Shapenet: An information-rich 3d model repository. arXiv, 2015. 5, 6, 3, 4" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.186, + 0.47, + 0.227 + ], + "angle": 0, + "content": "[2] Haiwei Chen, Shichen Liu, Weikai Chen, Hao Li, and Randall Hill. Equivariant point network for 3d point cloud analysis. 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However, existing self-supervised methods for this problem assume perfect input shape alignment, restricting their real-world applicability. In this work, we introduce a novel self-supervised Rotation-Invariant 3D correspondence learner with local Shape Transform, dubbed RIST, that learns to establish dense correspondences between shapes even under challenging intra-class variations and arbitrary orientations. Specifically, RIST learns to dynamically formulate an SO(3)-invariant local shape transform for each point, which maps the SO(3)-equivariant global shape descriptor of the input shape to a local shape descriptor. These local shape descriptors are provided as inputs to our decoder to facilitate point cloud self- and cross-reconstruction. Our proposed self-supervised training pipeline encourages semantically corresponding points from different shapes to be mapped to similar local shape descriptors, enabling RIST to establish dense point-wise correspondences. RIST demonstrates state-of-the-art performances on 3D part label transfer and semantic keypoint transfer given arbitrarily rotated point cloud pairs of the same category, outperforming existing methods by significant margins. + +# 1. Introduction + +Establishing dense 3D correspondences between different shapes is foundational to numerous applications across computer vision, graphics, and robotics [9, 22, 28, 41]. One of the primary challenges hindering advancements in this domain is the difficulty of annotating dense inter-shape correspondences, which limits the leverage of strongly-supervised learning paradigms. + +Recently, self-supervised learning methods have been proposed to address this issue [3, 21], showing promis + +![](images/56c299036b6cb72d2b28b7f19ce12f3bb92b344acdbe6005bd26952d1c329d41.jpg) +Figure 1. Semantic correspondence between rotated shapes. We visualize the semantic correspondence results of the previous SOTA [3] and ours, given two randomly rotated airplanes from the ShapeNetPart dataset [39]. Green and red lines indicate the correct and incorrect matches, respectively. For each method, 100 source points are randomly selected from the source (yellow) for correspondence visualization1. Ours predicts SO(3)-invariant correspondences, showing superior accuracy and robustness in comparison to the previous SOTA [3]. + +ing directions for 3D correspondence estimation. Nonetheless, a significant limitation in existing approaches is their stringent assumption about the alignment of input shape pairs; these methods strongly assume that the input point cloud pair to establish correspondences between is precisely aligned. This assumption is rarely met in practice, where object scans and shape instances can be arbitrarily oriented. We find that the performance of existing methods degrades significantly when confronted with rotated input shapes, restricting their real-world applicability (Figure 1). + +To address this challenge, we introduce a novel self-supervised learning approach, dubbed RIST, designed to reliably determine dense $SO(3)$ -invariant correspondences between shapes via local shape transform. In essence, RIST learns to formulate SO(3)-invariant local shape transform for each point in a dynamic and input-dependent manner. Each point-wise local shape transform maps the SO(3)-equivariant global shape descriptor of the input shape to a local shape descriptor, which is passed to the decoder to re + +construct the shape and pose of the input shape. By training RIST via self- and cross-reconstruction of input shapes, true semantically corresponding points are trained to yield similar local shape descriptors, enabling us to determine dense shape correspondences. + +RIST demonstrates state-of-the-art performance on part segmentation label transfer when evaluated on the ShapeNetPart [39] and ScanObjectNN [35] datasets. In particular, significant improvements over existing baselines are observed when our method is applied to randomly oriented shape pair inputs. Furthermore, our approach also proves to be more effective compared to existing methods at semantic keypoint transfer when evaluated on the Keypoint-Net dataset [40]. This showcases not only the applicability of RIST across a diverse range of tasks, but also its potential to be utilized for efficient dense annotation of 3D shapes. These results highlight the efficacy of RIST in addressing the challenges posed by real-world scenarios where existing methods fail to perform effectively. + +The main contributions of our work are as follows: + +- We introduce RIST, a novel self-supervised approach for determining dense SO(3)-invariant correspondences between arbitrarily aligned 3D objects. +- We propose to formulate the local shape information of each point as a novel function called local shape transform with dynamic input-dependent parameters, which effectively maps the global shape descriptor of input shapes to local shape descriptors. +- RIST achieves state-of-the-art performance on 3D part segmentation label transfer and 3D keypoint transfer under arbitrary rotations, indicating its potential for application in a wide range of practical tasks in computer vision. + +# 2. Related Work + +# Point cloud understanding via self-supervised learning. + +While traditional methods for point cloud processing involving hand-crafted features [27, 33] have shown impressive performance, with the advent of deep learning, substantial research efforts have been directed towards developing learning-based algorithms capable of effectively processing and understanding point clouds [5, 24-26, 42]. Due to limited large-scale datasets with rich annotations, self-supervised learning approaches emerged as a viable alternative. One of the most prominent directions to learn point cloud representations in a self-supervised manner is learning through self-reconstruction [23, 38, 43] of the point cloud. Primarily inspired by the efficacy of point cloud reconstruction as a self-supervised representation learning scheme, we train RIST to establish 3D correspondences in a self-supervised manner via self- and cross-reconstruction of point clouds by leveraging SO(3)-invariant dynamic local shape transform. + +Equivariance and invariance to rotation. The conventional method to improve a neural network's robustness to rotation is by employing rotation augmentations during training or inference. However, this tends to increase the resources required for training and still shows unsatisfactory results when confronted with an unseen rotation [14, 18]. In recent years, various methods have been proposed to yield point cloud representations, which are equivariant [2, 6, 29, 32] or invariant [14, 18, 19, 31, 37] to the rotation of the input, demonstrating enhanced performances under arbitrary input rotations. To facilitate the rotation-robust establishment of 3D dense correspondences, we utilize SO(3)-equivariant networks in building RIST, leveraging SO(3)-equivariant and -invariant representations to guarantee robustness to rotation by design. + +# Semantic correspondences under intra-class variations. + +Finding correspondences between images or shapes under intra-class variations - manifesting as differences in shape, size, and orientation within the same category of objects - poses significant challenges over photometric or viewpoint variations. This task has been widely studied in the domain of images, where existing methods make use of sparsely annotated image pair datasets to train their method in a strongly- or a weakly-supervised manner [4, 11, 13, 15, 34]. However, learning to establish dense yet reliable 3D correspondences between 3D shapes remains challenging, as it is infeasible to label dense correspondence annotations across point cloud pairs with intra-class variations. Self-supervised methods have been proposed to address this issue [3, 21], but they strongly assume that the input point clouds are aligned, leading to considerable significant degradation when confronted with arbitrarily rotated point clouds. Additionally, the functional map-based approach introduced by Huang et al. [10] for non-rigid registration struggles with topological changes and efficiency. To this end, we propose RIST to establish reliable 3D dense correspondences irrespective of the input point clouds' poses. + +# 3. RIST for 3D Semantic Correspondence + +In this section, we detail the components of RIST, which come together to facilitate the end-to-end self-supervised training for 3D semantic correspondence establishment. The objective of 3D semantic correspondence is as follows; given two different point clouds instances $\mathbf{P}_1 \in \mathbb{R}^{N \times 3}$ and $\mathbf{P}_2 \in \mathbb{R}^{N \times 3}$ belonging to the same semantic category, we aim to find all semantically corresponding point pairs $\{\mathbf{p}_i, \mathbf{q}_i\}_{i=1}^{N'}$ such that $\mathbf{p}_i \in \mathbf{P}_1$ and $\mathbf{q}_i \in \mathbf{P}_2$ . To achieve this, we claim it is crucial to identify the local shape information i.e. local semantics and geometry, which is generalizable across different instances within the same category. + +![](images/55a1493eec5b7723a871631a691b1297b59c8927f3ef3ff84cbd2ee63fec328d.jpg) +SO(3)-Equivariant Encoding + +![](images/17d8d70677f49d572052a748b3192b37696a056e24887b272c9ae668387f5e68.jpg) +Figure 2. Overview: Self-supervised training of RIST. The input point clouds are independently encoded to SO(3)-equivariant global shape descriptor $\mathbf{Z}$ and dynamic SO(3)-invariant point-wise local shape transforms $\{f_{\theta_i}\}$ . The local shape transforms map the global shape descriptor to local shape descriptors by infusing local semantics and geometry, which are used as inputs to the decoder for self-reconstruction. For cross-reconstruction, we apply the local shape transforms formulated from another point cloud to reconstruct the point cloud, ensuring that the local shape descriptors successfully capture generalizable local semantics and geometries. We supervise RIST via penalizing errors in self- and cross-reconstructions. At inference, we can leverage the local shape transforms for obtaining local shape descriptors, to identify the dense correspondences. + +![](images/3d6ac63acf794569ad63819e321ee21bf2906d5dfcf4812f60fb89566ad0c2f1.jpg) +SO(3)-Equivariant Decoding + +Therefore, the main idea of RIST is to dynamically generate a SO(3)-invariant local shape transform as a function for each point, such that each local shape transform can map the SO(3)-equivariant global shape descriptor of the input point cloud to its respective local shape descriptor. In the following, we elaborate on the network architecture of RIST, in particular how we leverage SO(3)-equivariant and invariant representations to facilitate the dynamic formulation of pointwise SO(3)-invariant local shape transforms and the reconstruction of pose-preserved point clouds (Sec. 3.1). Subsequently, we introduce our self-supervisory objective function, which trains RIST to self- and cross-reconstruct the input point clouds in a rotation-equivariant manner (Sec. 3.2), finally enabling the establishment of 3D dense correspondences (Sec. 3.3) via corresponding local shape descriptors. Figure 2 illustrates the outline of the training scheme of RIST. + +# 3.1. Network Design of RIST + +# 3.1.1 Preliminary: SO(3)-Equivariant Representation + +One of the main motivations of RIST is to establish reliable and accurate 3D dense correspondences given arbitrarily rotated shapes, a setting where existing work shows to be brittle. This requires our encoder to formulate the pointwise local shape transforms not only effectively to capture the local shape semantics and geometry, but also robustly against transformations in the SO(3) space. To this end, we integrate SO(3)-equivariant networks into RIST to facilitate + +robustness to SO(3) transformations of the input. In this work, we choose VNNs [7] to build our SO(3)-equivariant layers for their simplicity and efficacy. In VNNs, a single neuron, which is represented by a scalar-list of values, is lifted to a vector-list feature $\mathbf{V} \in \mathbb{R}^{C \times 3}$ , which is essentially a sequence of 3D vectors. The layers of VNNs handle batches of such vector-list features such that equivariance with respect to rotation $R \in \mathrm{SO}(3)$ is satisfied i.e. $f(\mathbf{V}R) = f(\mathbf{V})R^3$ . Notably, we can yield an SO(3)-invariant output by performing a product of an equivariant vector-list feature $\mathbf{V}R \in \mathbb{R}^{C \times 3}$ with the transpose of another consistently equivariant vector-list feature $\mathbf{U}R \in \mathbb{R}^{C' \times 3}$ as follows: $(\mathbf{V}R)(\mathbf{U}R)^{\top} = \mathbf{V}RR^{\top}\mathbf{U}^{\top} = \mathbf{V}\mathbf{U}^{\top}$ . This serves as a critical functionality when constructing our SO(3)-invariant local shape transform of our encoder (Sec. 3.1.2). + +# 3.1.2 SO(3)-Equivariant Encoder + +We design our encoder architecture to take as input a point cloud $\mathbf{P} \in \mathbb{R}^{N \times 3}$ , and simultaneously output an SO(3)-equivariant global shape descriptor and formulate pointwise SO(3)-invariant local shape transforms. + +SO(3)-equivariant global shape descriptor. Given a point cloud, we first aim to obtain the SO(3)-equivariant global shape descriptor $\mathbf{Z} \in \mathbb{R}^{C \times 3}$ , which captures the pose and the global shape characteristics of the input point cloud. We leverage VN-DGCNN [7] as our encoder architecture, + +which consists of 4 edge convolutional VN-layers to capture local semantics at a progressively larger receptive field, and a FPN [20] to aggregate the multi-level features. Then, we apply the global average pooling to the aggregated SO(3)-equivariant point-wise features $\mathbf{V}^{\mathrm{equi}}\in \mathbb{R}^{C\times 3\times N}$ to encode SO(3)-equivariant global shape descriptor $\mathbf{Z}$ of the input point cloud. The global shape descriptor can be used subsequently as the input for our SO(3)-invariant point-wise local shape transform, to be mapped to their respective local shape descriptors, as shown in Figure 2. + +SO(3)-invariant local shape transform. Alongside the extraction of SO(3)-equivariant global shape descriptors, we also formulate the SO(3)-invariant local shape transform $f_{\theta_i}:\mathbb{R}^{C\times 3}\mapsto \mathbb{R}^{C'\times 3}$ for each point $\mathbf{p}_i\in \mathbb{R}^3$ of the input point cloud $\mathbf{P}\in \mathbb{R}^{N\times 3}$ . The parameters of each local shape transform $\theta_{i}\in \mathbb{R}^{C^{\prime}\times C}$ are input-dependent - thus, dynamic since they are predicted by our encoder for the $i$ -th point of the point cloud. To predict $\theta_{i}$ , we first obtain SO(3)-invariant point-wise features $\mathbf{V}^{\mathrm{in}}\in \mathbb{R}^{C^{\prime}\times 3\times N}$ as described in Sec. 3.1.1. Then, we transform each vectorized SO(3)-invariant point-wise feature $\operatorname {vec}(\mathbf{v}_i^{\mathrm{in}})\in \mathbb{R}^{3C'}$ to the vectorized parameter of the local shape transform $\operatorname {vec}(\theta_i)\in \mathbb{R}^{C'C}$ by using a multi-layer perceptron. By reshaping $\operatorname {vec}(\theta_i)$ to $\theta_{i}\in \mathbb{R}^{C^{\prime}\times C}$ , we finally obtain the dynamic and SO(3)-invariant local shape transform $f_{\theta_i}$ for the point $\mathbf{p}_i$ . + +The role of these local shape transforms is to map the SO(3)-equivariant global shape descriptor $\mathbf{Z} \in \mathbb{R}^{C \times 3}$ to their respective local shape descriptors $\mathbf{v}_i' := f_{\theta_i}(\mathbf{Z}) \in \mathbb{R}^{C' \times 3}$ , which is provided as the input to our decoder for reconstruction. Our self-supervised training scheme encourages the point-wise dynamic local shape transform to encapsulate the local shape information e.g. semantics and geometry, to enhance the reconstruction performance. + +# 3.1.3 SO(3)-Equivariant Decoder + +Our decoder aims to reconstruct the initial input shapes using the obtained SO(3)-equivariant global shape descriptors $\mathbf{Z}$ and the SO(3)-invariant local shape transforms $\{f_{\theta_i}\}_{i = 1}^N$ . To reconstruct the point clouds aligned to their initial poses, we leverage SO(3)-equivariant layers as the building blocks of our decoder architecture. We first train our decoder to perform self-reconstruction, using the local shape descriptors $\mathbf{V}'$ , i.e. $\mathbf{P} \leftrightarrow \mathbf{P}' := \mathrm{Decoder}(\mathbf{V}') = \mathrm{Decoder}(\{f_{\theta_i}(\mathbf{Z})\}_{i = 1}^N)$ . We also train our decoder to perform cross-reconstruction, where we use the local shape descriptors obtained using global shape descriptors and local shape transforms from different point clouds. Specifically, assume we are given two point clouds $\mathbf{P}_1, \mathbf{P}_2 \in \mathbb{R}^{N \times 3}$ , with SO(3)-equivariant global shape descriptors $\mathbf{Z}_1, \mathbf{Z}_2 \in \mathbb{R}^{C \times 3}$ and SO(3)-invariant local shape transforms $\{f_{\theta_i}^1\}_{i = 1}^N, \{f_{\theta_i}^2\}_{i = 1}^N$ . As shown in Figure 2, we then can perform cross-reconstruction from $\mathbf{P}_2$ to $\mathbf{P}_1$ as follows: + +$\mathbf{P}_1 \leftrightarrow \mathbf{P}_{2 \mapsto 1}' := \mathrm{Decoder}(\{f_{\theta_i}^2(\mathbf{Z_1})\}_{i=1}^N)$ . Intuitively, for the above cross-reconstruction to be carried out successfully, the local shape transforms for points of a true correspondence should hold similar dynamic parameters, mapping global shape descriptors to similar local shape descriptors. By training RIST to cross-reconstruct point clouds, we are supervising local shape transforms to map corresponding points between shapes to similar local shape descriptors, which encode local semantics and geometry that are generalizable across different instances within a category. + +# 3.2. Self-Supervised Objective + +Due to the lack of annotated datasets for dense 3D intershape correspondences, we train RIST in a self-supervised manner by penalizing inaccurate shape reconstructions. First, we supervise RIST for self-reconstruction using the following loss: + +$$ +\mathcal {L} _ {\mathrm {S R}} = \lambda_ {\mathrm {M S E}} \operatorname {M S E} \left(\mathbf {P}, \mathbf {P} ^ {\prime}\right) + \lambda_ {\mathrm {E M D}} \operatorname {E M D} \left(\mathbf {P}, \mathbf {P} ^ {\prime}\right), \tag {1} +$$ + +where MSE is the Mean Squared Error, EMD stands for the Earth Mover's Distance, and both $\lambda_{\mathrm{MSE}}$ and $\lambda_{\mathrm{EMD}}$ are weight coefficients. In essence, we are trying to minimize the difference between the input and reconstructed point cloud. We also supervise RIST for cross-reconstruction as follows: $\mathcal{L}_{\mathrm{CR}} = \lambda_{\mathrm{CD}}\mathrm{CD}(\mathbf{P}_1,\mathbf{P}_{2\mapsto 1}')$ , where CD stands for the Chamfer distance, and $\lambda_{\mathrm{CD}}$ is a weight coefficient. Finally, our total loss $\mathcal{L}_{\mathrm{total}}$ is defined as: $\mathcal{L}_{\mathrm{total}} = \mathcal{L}_{\mathrm{SR}} + \mathcal{L}_{\mathrm{CR}}$ . We omit the CD loss from self-reconstruction, as we can directly use the input point cloud to provide supervision using the MSE loss. We also omit the EMD loss from cross-reconstruction, as EMD tends to overlook the fidelity of detailed structures [36], which is crucial in cross-reconstruction of shapes under intra-class variations. + +# 3.3. SO(3)-Invariant Correspondence + +In this section, given two randomly rotated point clouds $\mathbf{P}_1$ and $\mathbf{P}_2$ , we elaborate on how our RIST establishes the 3D dense correspondence from $\mathbf{P}_1$ to $\mathbf{P}_2$ . As shown in Figure 2, we first encode the SO(3)-equivariant global shape descriptor of $\mathbf{P}_1$ , $\mathbf{Z}_1 \in \mathbb{R}^{C \times 3}$ , and the SO(3)-invariant local shape transform functions of $\mathbf{P}_2$ , $\{f_{\theta_i}^2\}_{i=1}^N$ . Then, we cross-reconstruct $\mathbf{P}_1$ as follows: $\mathbf{P}_{2 \mapsto 1}' := \mathrm{Decoder}(\{f_{\theta_i}^2(\mathbf{Z}_1)\}_{i=1}^N)$ . Finally, we define the 3D dense correspondence from $\mathbf{P}_2$ to $\mathbf{P}_1$ as the nearest point pairs among all possible pairs between $\mathbf{P}_1$ and $\mathbf{P}_{2 \mapsto 1}'$ . Since both encoder and decoder are SO(3)-equivariant, the cross-reconstructed point cloud $\mathbf{P}_{2 \mapsto 1}'$ is aligned to $\mathbf{P}_1$ . As a result, our RIST can predict 3D dense correspondences between randomly rotated point clouds, while previous approaches [3, 21] experience a high rate of failure. + +
TrainingMethodAirplaneCapChairGuitarLaptopMotorcycleMugTableAverage
w/o RotationsFoldingNet [38]17.834.722.522.136.212.650.034.628.8
AtlasNetV2 [8]19.731.423.622.736.013.149.735.228.9
DPC [17]22.737.125.631.935.017.551.336.832.2
CPAE [3]21.038.026.022.734.914.751.435.530.5
RIST (ours)52.154.558.374.156.548.675.041.357.6
w/ RotationsFoldingNet [38]22.533.224.031.035.913.549.937.030.9
AtlasNetV2 [8]21.132.725.228.835.514.549.941.031.1
DPC [17]24.638.525.640.234.919.351.837.334.0
CPAE [3]17.036.624.539.437.415.851.936.732.4
RIST (ours)51.257.055.073.560.648.572.244.457.8
+ +# 4. Experiments + +We present evaluations of RIST on the tasks of 3D part segmentation label transfer and 3D semantic keypoint transfer, following prior work [3, 21]. For both tasks, each method is trained with and without rotation augmentations, and tested on arbitrarily rotated inputs to validate its rotation robustness in predicting semantic correspondences between the rotated inputs. Note that previous approaches [3, 8, 21, 38] used aligned point clouds or slightly rotated point clouds with a subset of SO(3), not the full SO(3), for testing - which is unrealistic in practice, as described in Appendix H. + +Datasets. We use the ShapeNetPart [39] and ScanObjectNN [35] datasets to evaluate RIST on the task of 3D part segmentation label transfer, which requires 3D dense semantic correspondence. The ShapeNetPart dataset [39] consists of 16,880 synthetic 3D data from 16 categories. The ScanObjectNN dataset [35] contains real-world scanned data, and provides part label annotations for the chair category. Following the previous work [3], we use the same pre-processed KeypointNet [40] dataset for the 3D semantic keypoint transfer task. Since both KeypointNet and ShapeNetPart are based on the ShapeNet dataset [1], we use the eight overlapping categories between the ShapeNetPart and KeypointNet [40] datasets to evaluate each method on both tasks without fine-tuning the method on each dataset. For all tasks, we follow the experiment setting of the previous work [3]. + +Baseline methods. Throughout the evaluation section, we mainly compare RIST against CPAE [3], the state-of-the-art self-supervised method to establish 3D dense correspondence by exploiting an intermediate UV canonical space. When open-sourced pre-trained models or codes are applicable, we also compare RIST with AtlasNetV2 [8], FoldingNet [38] and DPC [17]. AtlasNetV2 proposes to represent shapes as the deformation and combination of learnable elementary 3D structures, which can be extended to 3D correspondence establishment. FoldingNet introduces + +Table 1. Average IoU (%) of part label transfer for eight categories in the ShapeNetPart dataset [39]. Ours consistently outperforms previous approaches [3, 8, 17, 38] both with and without rotation augmentations during training, achieving the state-of-the-art IoU. We also provide results of the other classes in Appendix I. + +
Methodw/o Rotationsw/ Rotations
FoldingNet [38]23.223.3
AtlasNetV2 [8]23.624.1
DPC [17]23.923.9
CPAE [3]24.423.9
RIST (ours)39.637.9
+ +Table 2. Average IoU (\%) of part label transfer for the chair category in the ScanObjectNN dataset [35]. Ours shows the best IoU both with and without rotation augmentations during training. + +a folding-based decoder to 'fold' a canonical 2D grid into the 3D object surface, where the canonical 2D grid can be applied to identify cross-shape correspondences. DPC predicts 3D dense correspondence between non-rigidly deformed 3D humans, meaning that it can be a powerful baseline for both 3D part segmentation label transfer and 3D keypoint transfer tasks as well. + +Implementation details. We use VN-DGCNN [7] as our SO(3)-equivariant encoder, and VN-based multi-layer perception as our SO(3)-equivariant decoder. For a fair comparison, we set the dimension, $C$ , of SO(3)-equivariant global shape descriptor $\mathbf{Z} \in \mathbb{R}^{C \times 3}$ as $170 \ (\approx 512/3)$ since CPAE [3] uses 512-dimensional global shape descriptors. Following the training setup of CPAE [3], we use $\lambda_{\mathrm{MSE}}$ , $\lambda_{\mathrm{EMD}}$ , and $\lambda_{\mathrm{CD}}$ as 1000, 1, and 10, respectively. RIST is implemented in PyTorch, and is optimized with the Adam [16] optimizer at a constant learning rate of $1e^{-3}$ . + +# 4.1. Part Segmentation Label Transfer + +We compare RIST with the state of the art in 3D part segmentation label transfer on ShapeNetPart [39] and ScanObjectNN [35]. For both datasets, we use the average of instance-wise IoU scores as the evaluation metric. + +ShapeNetPart [39]. The quantitative results are presented in Table 1, where RIST outperforms CPAE [3], DPC [17], AtlasNetV2 [8], and FoldingNet [38] on all classes by a large margin with and without rotation augmentations dur + +![](images/4ee986b5c6538bee1a428ddcd1c50994be351da87421719e93dc99cac977f3c2.jpg) +Figure 3. Qualitative results of part label transfer on the ShapeNetPart dataset [39]. We visualize the label transfer results via learned correspondences of each method with the ground truth labels of targets. Note that the input shapes were arbitrarily rotated at evaluation, differently for both the source and targets of each row, but have been aligned in the above figure for better visibility of part label transfer results. RIST shows to outperform CPAE [3] consistently, showing a high resemblance to ground truth results. + +ing training. We also provide the qualitative results of the part segmentation label transfer experiments on ShapeNetPart in Figure 3. Attributing to the SO(3)-invariant nature of correspondences established by RIST, we are able to transfer part labels significantly more accurately given randomly rotated shape pairs. + +ScanObjectNN [35]. We evaluate each method trained on synthetic chair data of ShapeNet [1] on the real chair data of ScanObjectNN [35], which is partial and more challenging than ShapeNetPart [39], without fine-tuning. As shown in Table 2, RIST consistently outperforms previous approaches [3, 8, 17, 38] both with and without rotation augmentations during training. The qualitative results presented in Figure 4 show that RIST can predict rotation-robust 3D semantic correspondence between real and partial chair shapes, while CPAE [3] fails. + +# 4.2.3D Semantic Keypoint Transfer + +Following the previous work [3], we compute the distances from the transferred $M$ keypoints to the ground truth keypoints, and report PCK (Percentage of Correct keypoints) of our transferred keypoints, which is computed by: + +$$ +\mathrm {P C K} = \frac {1}{M} \sum_ {m = 1} ^ {M} \mathbb {1} \left[ \left\| \mathbf {k} _ {m} - \hat {\mathbf {k}} _ {m} \right\| \leq \tau \right], \tag {2} +$$ + +![](images/c237da1af5b71c1714543729148195284a6ec599dfc63a24a0e9931e0c0c0eaa.jpg) +Figure 4. Qualitative results of part label transfer on ScanObjectNN [35]. Note that both source and target point clouds were arbitrarily rotated at evaluation, but have been aligned in the figure for better visibility of part label transfer results. The results show that RIST reasonably predicts the semantic correspondences between arbitrarily rotated and partial real point clouds. + +where $\tau$ , $\mathbf{k}_m$ , and $\hat{\mathbf{k}}_m$ are a distance threshold, $m$ -th ground truth keypoint, and $m$ -th transferred keypoint, respectively. The results on the KeypointNet dataset [40] are illustrated in Figure 5 for varying distance thresholds $\tau$ . It can be seen that RIST consistently outperforms baseline methods with + +![](images/1a4608f16826200b6932369e0f2d0964c6ff0c908e89b5cc1ec42cd5ccc237d3.jpg) + +![](images/90eedb8370dda8ae124a88bddab1c89996c4c6042d9cae96c9221bc4beff9a60.jpg) + +![](images/90317cb062f207bf8d15a78e37a352e8a109fbfa9c9e36a7037a1b43ab6de593.jpg) + +![](images/ea3423924f4c04f5f750a206c0add192befa7e9f76f60c90af4eca4618adb7a2.jpg) + +![](images/02a7a8f1c0cbd7dfd5753dd36db1732598ac9e160507e865b03f883cfc2b8b49.jpg) + +![](images/554738b6f0ef160714c62537a663413f80b08131069d20d8900c1ecd806bf095.jpg) + +![](images/558a328480ff168bd7ea3672f4c34d781f6355892348bd8ad200615cfb582d22.jpg) + +![](images/ad40310dc543bcd72f00872ce0963e9074ca6a36b36572131cdafab7c3c5369e.jpg) + +![](images/6328a4059450af8dfb48fca40a75106407ecadeacfb88ad9a4c4ea6277782148.jpg) +Figure 5. Percentage of Correct Keypoints (PCK) for the 12 categories of the KeypointNet dataset [40] with and without rotation augmentations during training. RIST consistently outperforms previous approaches on all classes and thresholds in both settings. + +![](images/5471e74130eea9d0498d5feab29d79178a6afb97aafbbd4a41186cbe510ee87a.jpg) + +![](images/046c1e7edf3d796f8865d254196865040fd7a4580494b86e5cf3dc099c4306eb.jpg) + +![](images/af7f0aa42b8055cbf7794ff194b1b450e78c20ee5be4e30f4ef943c289569b53.jpg) + +![](images/d5facbb8dc74061c51c0c544bb8e03b21aff5ab63d7e9bdb5950ce096ee217e3.jpg) + +and without rotation augmentations during training for all classes, by up to $10 \times$ on certain classes and thresholds. This substantiates RIST's superior efficacy at establishing dense 3D correspondences between varying shapes. However, for certain classes such as Bathtub or Table, the performance is noticeably low, outperforming baseline methods only by a tight margin. We speculate this to be due to the prevalent rotational symmetry of those classes, making it especially challenging to establish accurate 3D correspondences under arbitrary rotations. The qualitative results of RIST in comparison to baseline methods are presented in Figure 6. It can also be seen that RIST can identify more accurate keypoint correspondences compared to CPAE [3] under arbitrary rotations, confirming the results of Figure 5. + +# 4.3. Ablation Study and Analyses + +We perform an ablation study to justify the design choice of RIST, and evidence the efficacy of each component. + +Self- and cross-reconstruction. We train RIST in a self-supervised manner via penalizing errors in self- and cross-reconstruction of input point clouds. We conduct an ablation study on RIST's reconstruction, providing comparative results for scenarios with and without its use. The results are illustrated in the first graph of Figure 7. It can be seen that with and without rotation augmentations during training, in + +corporating both self- and cross-reconstruction yields the best results. Removing self-reconstruction results in a much dramatic drop in performance; we conjecture this is because without self-reconstruction, the dynamic local shape transform (Sec. 3.1.2) fails to capture the required locality of its own point cloud in the first place, being unsuitable to establish correspondences. + +Encoder outputs and SO(3)-equivariance. RIST uses VNNs [7] as the SO(3)-equivariant layers to facilitate 3D dense correspondence establishment between arbitrarily rotated point cloud pairs, leveraging local shape transform to map global shape descriptors to local shape descriptors which encode the pointwise semantics and local geometry. We perform an ablation study to demonstrate the efficacy of local shape transforms and SO(3)-equivariant and -invariant representations in RIST on the motorcycle class of the KeypointNet dataset [40]. We start our comparison from the architecture of CPAE [3], given that they also employ an encoder-decoder architecture to self-supervise their network via shape reconstruction. The results are presented in the two rightmost graphs of Figure 7, showing the evaluation results with and without rotation augmentations during training in order. It can be seen that our design choice of using equivariant encoders and decoders shows consistent improvements over using an SO(3)-variant counterpart. Also, + +![](images/d8e9b29f7921f50e2faad0528d2b65a612fdb0df8a05f8c37e27aed98a5b9fd8.jpg) + +![](images/e4717c30df69ec05eec18202f2947c497c9660585a2e1af74a642248e4fec04e.jpg) +Figure 7. Ablation study on losses (the leftmost) and the components of model architecture (the others); self-reconstruction loss (SR), cross-reconstruction loss (CR), equivariant decoder (ED), local shape transform (LST), and local feature (LF). When excluding the equivariant decoder, local shape transforms, or local features, the default is to use an SO(3)-variant decoder, UV coordinates [3], or global features for encoding, respectively. + +![](images/4dda6a506ded8115f9f7e42d9863f601064997c1e4cde5d653e8ce1c6e5d6092.jpg) +Figure 6. Keypoint transfer results for airplane and motorcycle categories of KeypointNet [40]. Each row contains a shape pair, each with ground-truth keypoints and the keypoint transfer results. Note that the input shapes were arbitrarily rotated at evaluation, but have been aligned in the above figure for better visibility of keypoint transfer results. RIST shows to transfer the keypoints more accurately. + +![](images/34e976bc2e6186abbbd01417b7278fb48852fcceb61aa730419b94cd03799438.jpg) + +using UV coordinates as proposed in CPAE [3] performs worse compared to our dynamic local shape transform, evidencing the comparatively better efficacy of transforming each point to their local shape descriptors via our dynamic SO(3)-invariant shape transform. While using local features as inputs to the encoder shows varied trends across with and without augmentation settings, using the point-wise local feature as input is a key component that facilitates the learning of point-wise dynamic local shape transform that is essential in establishing the 3D correspondences in RIST. + +# 5. Conclusion + +We've introduced RIST, a novel self-supervised learner for dense 3D semantic matching across shapes of the same category, even with arbitrary rotations. Its robustness stems from our innovative use of SO(3)-equivariant and -invariant + +representations, enabling dynamic local shape transforms that preserve rotation equivariance. These transforms map global descriptors to local ones, facilitating the establishment of dense correspondences. Our method outperforms existing ones on tasks like part label and keypoint transfer, enhancing applicability in computer vision and robotics, e.g., AR/VR and texture mapping. Future research could focus on improving robustness under common corruption. + +Acknowledgement. This work was supported by IITP grants (No.2021-0-02068: AI Innovation Hub $(50\%)$ , No. 2022-0-00290: Visual Intelligence for Space-Time Understanding and Generation $(40\%)$ , No.2019-0-01906: Artificial Intelligence Graduate School Program at POSTECH $(5\%)$ , NO.2021-0-01343, Artificial Intelligence Graduate School Program at Seoul National University $(5\%)$ ) funded by the Korea government (MSIT). 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ACM TOG, 35(6): 1-12, 2016. 1, 2, 5, 6, 3, 4 +[40] Yang You, Yujing Lou, Chengkun Li, Zhoujun Cheng, Liangwei Li, Lizhuang Ma, Cewu Lu, and Weiming Wang. Keypointnet: A large-scale 3d keypoint dataset aggregated from numerous human annotations. In CVPR, 2020. 2, 5, 6, 7, 8, 1, 3 +[41] Wang Zeng, Wanli Ouyang, Ping Luo, Wentao Liu, and Xiaogang Wang. 3d human mesh regression with dense correspondence. In CVPR, 2020. 1 +[42] Hengshuang Zhao, Li Jiang, Chi-Wing Fu, and Jiaya Jia. Point transformer. In ICCV, 2021. 2 +[43] Yongheng Zhao, Tolga Birdal, Haowen Deng, and Federico Tombari. 3d point capsule networks. In CVPR, 2019. 2 +[44] Zerong Zheng, Tao Yu, Qionghai Dai, and Yebin Liu. Deep implicit templates for 3d shape representation. In CVPR, 2021. 3, 4 +[45] Mohammad Zohaib and Alessio Del Bue. Sc3k: Self-supervised and coherent 3d keypoints estimation from rotated, noisy, and decimated point cloud data. In ICCV, 2023. 3 \ No newline at end of file diff --git a/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/images.zip b/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..ce3cffb5847adebb43c7281aaa8f104cd0fd6c2f --- /dev/null +++ b/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:097c2b6a23fdbbb3f00bae448c825915172d4ff1914c73be16308d94df667f17 +size 697717 diff --git a/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/layout.json b/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..6f72f40da89b902e68689f5a03e54b597d530c1e --- /dev/null +++ b/2024/Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform/layout.json @@ -0,0 +1,7790 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 49, + 103, + 544, + 120 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 103, + 544, + 120 + ], + "spans": [ + { + "bbox": [ + 49, + 103, + 544, + 120 + ], + "type": "text", + "content": "Learning SO(3)-Invariant Semantic Correspondence via Local Shape Transform" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "spans": [ + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "text", + "content": "Chunghyun Park" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "inline_equation", + "content": "^{1*}" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "text", + "content": " Seungwook Kim" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "inline_equation", + "content": "^{1*}" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "text", + "content": " Jaesik Park" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "text", + "content": " Minsu Cho" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 108, + 142, + 483, + 178 + ], + "type": "text", + "content": "POSTECH Seoul National University" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 185, + 185, + 404, + 196 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 185, + 185, + 404, + 196 + ], + "spans": [ + { + "bbox": [ + 185, + 185, + 404, + 196 + ], + "type": "text", + "content": "http://cvlab.postech.ac.kr/research/RIST" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 224, + 192, + 237 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 224, + 192, + 237 + ], + "spans": [ + { + "bbox": [ + 143, + 224, + 192, + 237 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 251, + 290, + 539 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 251, + 290, + 539 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 290, + 539 + ], + "type": "text", + "content": "Establishing accurate 3D correspondences between shapes stands as a pivotal challenge with profound implications for computer vision and robotics. However, existing self-supervised methods for this problem assume perfect input shape alignment, restricting their real-world applicability. In this work, we introduce a novel self-supervised Rotation-Invariant 3D correspondence learner with local Shape Transform, dubbed RIST, that learns to establish dense correspondences between shapes even under challenging intra-class variations and arbitrary orientations. Specifically, RIST learns to dynamically formulate an SO(3)-invariant local shape transform for each point, which maps the SO(3)-equivariant global shape descriptor of the input shape to a local shape descriptor. These local shape descriptors are provided as inputs to our decoder to facilitate point cloud self- and cross-reconstruction. Our proposed self-supervised training pipeline encourages semantically corresponding points from different shapes to be mapped to similar local shape descriptors, enabling RIST to establish dense point-wise correspondences. RIST demonstrates state-of-the-art performances on 3D part label transfer and semantic keypoint transfer given arbitrarily rotated point cloud pairs of the same category, outperforming existing methods by significant margins." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 563, + 128, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 563, + 128, + 574 + ], + "spans": [ + { + "bbox": [ + 47, + 563, + 128, + 574 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 583, + 287, + 668 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 583, + 287, + 668 + ], + "spans": [ + { + "bbox": [ + 46, + 583, + 287, + 668 + ], + "type": "text", + "content": "Establishing dense 3D correspondences between different shapes is foundational to numerous applications across computer vision, graphics, and robotics [9, 22, 28, 41]. One of the primary challenges hindering advancements in this domain is the difficulty of annotating dense inter-shape correspondences, which limits the leverage of strongly-supervised learning paradigms." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 668, + 287, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 668, + 287, + 693 + ], + "spans": [ + { + "bbox": [ + 47, + 668, + 287, + 693 + ], + "type": "text", + "content": "Recently, self-supervised learning methods have been proposed to address this issue [3, 21], showing promis" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 309, + 224, + 547, + 345 + ], + "blocks": [ + { + "bbox": [ + 309, + 224, + 547, + 345 + ], + "lines": [ + { + "bbox": [ + 309, + 224, + 547, + 345 + ], + "spans": [ + { + "bbox": [ + 309, + 224, + 547, + 345 + ], + "type": "image", + "image_path": "56c299036b6cb72d2b28b7f19ce12f3bb92b344acdbe6005bd26952d1c329d41.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 353, + 547, + 453 + ], + "lines": [ + { + "bbox": [ + 304, + 353, + 547, + 453 + ], + "spans": [ + { + "bbox": [ + 304, + 353, + 547, + 453 + ], + "type": "text", + "content": "Figure 1. Semantic correspondence between rotated shapes. We visualize the semantic correspondence results of the previous SOTA [3] and ours, given two randomly rotated airplanes from the ShapeNetPart dataset [39]. Green and red lines indicate the correct and incorrect matches, respectively. For each method, 100 source points are randomly selected from the source (yellow) for correspondence visualization1. Ours predicts SO(3)-invariant correspondences, showing superior accuracy and robustness in comparison to the previous SOTA [3]." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 464, + 546, + 583 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 464, + 546, + 583 + ], + "spans": [ + { + "bbox": [ + 304, + 464, + 546, + 583 + ], + "type": "text", + "content": "ing directions for 3D correspondence estimation. Nonetheless, a significant limitation in existing approaches is their stringent assumption about the alignment of input shape pairs; these methods strongly assume that the input point cloud pair to establish correspondences between is precisely aligned. This assumption is rarely met in practice, where object scans and shape instances can be arbitrarily oriented. We find that the performance of existing methods degrades significantly when confronted with rotated input shapes, restricting their real-world applicability (Figure 1)." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 584, + 547, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 584, + 547, + 693 + ], + "spans": [ + { + "bbox": [ + 304, + 584, + 547, + 693 + ], + "type": "text", + "content": "To address this challenge, we introduce a novel self-supervised learning approach, dubbed RIST, designed to reliably determine dense " + }, + { + "bbox": [ + 304, + 584, + 547, + 693 + ], + "type": "inline_equation", + "content": "SO(3)" + }, + { + "bbox": [ + 304, + 584, + 547, + 693 + ], + "type": "text", + "content": "-invariant correspondences between shapes via local shape transform. In essence, RIST learns to formulate SO(3)-invariant local shape transform for each point in a dynamic and input-dependent manner. Each point-wise local shape transform maps the SO(3)-equivariant global shape descriptor of the input shape to a local shape descriptor, which is passed to the decoder to re" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 124, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 124, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 124, + 712 + ], + "type": "text", + "content": "*Equal contribution" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 317, + 702, + 545, + 714 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 702, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 317, + 702, + 545, + 714 + ], + "type": "text", + "content": "For the details of the inference algorithm, please refer to Appendix A." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22978" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "type": "text", + "content": "construct the shape and pose of the input shape. By training RIST via self- and cross-reconstruction of input shapes, true semantically corresponding points are trained to yield similar local shape descriptors, enabling us to determine dense shape correspondences." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 134, + 287, + 301 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 134, + 287, + 301 + ], + "spans": [ + { + "bbox": [ + 46, + 134, + 287, + 301 + ], + "type": "text", + "content": "RIST demonstrates state-of-the-art performance on part segmentation label transfer when evaluated on the ShapeNetPart [39] and ScanObjectNN [35] datasets. In particular, significant improvements over existing baselines are observed when our method is applied to randomly oriented shape pair inputs. Furthermore, our approach also proves to be more effective compared to existing methods at semantic keypoint transfer when evaluated on the Keypoint-Net dataset [40]. This showcases not only the applicability of RIST across a diverse range of tasks, but also its potential to be utilized for efficient dense annotation of 3D shapes. These results highlight the efficacy of RIST in addressing the challenges posed by real-world scenarios where existing methods fail to perform effectively." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 303, + 265, + 315 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 303, + 265, + 315 + ], + "spans": [ + { + "bbox": [ + 58, + 303, + 265, + 315 + ], + "type": "text", + "content": "The main contributions of our work are as follows:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 317, + 287, + 460 + ], + "type": "list", + "angle": 0, + "index": 6, + "blocks": [ + { + "bbox": [ + 47, + 317, + 287, + 352 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 317, + 287, + 352 + ], + "spans": [ + { + "bbox": [ + 47, + 317, + 287, + 352 + ], + "type": "text", + "content": "- We introduce RIST, a novel self-supervised approach for determining dense SO(3)-invariant correspondences between arbitrarily aligned 3D objects." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 353, + 287, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 353, + 287, + 411 + ], + "spans": [ + { + "bbox": [ + 47, + 353, + 287, + 411 + ], + "type": "text", + "content": "- We propose to formulate the local shape information of each point as a novel function called local shape transform with dynamic input-dependent parameters, which effectively maps the global shape descriptor of input shapes to local shape descriptors." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 412, + 287, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 412, + 287, + 460 + ], + "spans": [ + { + "bbox": [ + 47, + 412, + 287, + 460 + ], + "type": "text", + "content": "- RIST achieves state-of-the-art performance on 3D part segmentation label transfer and 3D keypoint transfer under arbitrary rotations, indicating its potential for application in a wide range of practical tasks in computer vision." + } + ] + } + ], + "index": 5 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 476, + 134, + 488 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 476, + 134, + 488 + ], + "spans": [ + { + "bbox": [ + 47, + 476, + 134, + 488 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 498, + 287, + 510 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 287, + 510 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 287, + 510 + ], + "type": "text", + "content": "Point cloud understanding via self-supervised learning." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 510, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 287, + 713 + ], + "type": "text", + "content": "While traditional methods for point cloud processing involving hand-crafted features [27, 33] have shown impressive performance, with the advent of deep learning, substantial research efforts have been directed towards developing learning-based algorithms capable of effectively processing and understanding point clouds [5, 24-26, 42]. Due to limited large-scale datasets with rich annotations, self-supervised learning approaches emerged as a viable alternative. One of the most prominent directions to learn point cloud representations in a self-supervised manner is learning through self-reconstruction [23, 38, 43] of the point cloud. Primarily inspired by the efficacy of point cloud reconstruction as a self-supervised representation learning scheme, we train RIST to establish 3D correspondences in a self-supervised manner via self- and cross-reconstruction of point clouds by leveraging SO(3)-invariant dynamic local shape transform." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 72, + 545, + 252 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 252 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 252 + ], + "type": "text", + "content": "Equivariance and invariance to rotation. The conventional method to improve a neural network's robustness to rotation is by employing rotation augmentations during training or inference. However, this tends to increase the resources required for training and still shows unsatisfactory results when confronted with an unseen rotation [14, 18]. In recent years, various methods have been proposed to yield point cloud representations, which are equivariant [2, 6, 29, 32] or invariant [14, 18, 19, 31, 37] to the rotation of the input, demonstrating enhanced performances under arbitrary input rotations. To facilitate the rotation-robust establishment of 3D dense correspondences, we utilize SO(3)-equivariant networks in building RIST, leveraging SO(3)-equivariant and -invariant representations to guarantee robustness to rotation by design." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 258, + 545, + 268 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 258, + 545, + 268 + ], + "spans": [ + { + "bbox": [ + 304, + 258, + 545, + 268 + ], + "type": "text", + "content": "Semantic correspondences under intra-class variations." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 269, + 545, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 269, + 545, + 521 + ], + "spans": [ + { + "bbox": [ + 304, + 269, + 545, + 521 + ], + "type": "text", + "content": "Finding correspondences between images or shapes under intra-class variations - manifesting as differences in shape, size, and orientation within the same category of objects - poses significant challenges over photometric or viewpoint variations. This task has been widely studied in the domain of images, where existing methods make use of sparsely annotated image pair datasets to train their method in a strongly- or a weakly-supervised manner [4, 11, 13, 15, 34]. However, learning to establish dense yet reliable 3D correspondences between 3D shapes remains challenging, as it is infeasible to label dense correspondence annotations across point cloud pairs with intra-class variations. Self-supervised methods have been proposed to address this issue [3, 21], but they strongly assume that the input point clouds are aligned, leading to considerable significant degradation when confronted with arbitrarily rotated point clouds. Additionally, the functional map-based approach introduced by Huang et al. [10] for non-rigid registration struggles with topological changes and efficiency. To this end, we propose RIST to establish reliable 3D dense correspondences irrespective of the input point clouds' poses." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 543, + 522, + 557 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 543, + 522, + 557 + ], + "spans": [ + { + "bbox": [ + 305, + 543, + 522, + 557 + ], + "type": "text", + "content": "3. RIST for 3D Semantic Correspondence" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "spans": [ + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "text", + "content": "In this section, we detail the components of RIST, which come together to facilitate the end-to-end self-supervised training for 3D semantic correspondence establishment. The objective of 3D semantic correspondence is as follows; given two different point clouds instances " + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1 \\in \\mathbb{R}^{N \\times 3}" + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_2 \\in \\mathbb{R}^{N \\times 3}" + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "text", + "content": " belonging to the same semantic category, we aim to find all semantically corresponding point pairs " + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{p}_i, \\mathbf{q}_i\\}_{i=1}^{N'}" + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "text", + "content": " such that " + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_i \\in \\mathbf{P}_1" + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "inline_equation", + "content": "\\mathbf{q}_i \\in \\mathbf{P}_2" + }, + { + "bbox": [ + 304, + 563, + 545, + 696 + ], + "type": "text", + "content": ". To achieve this, we claim it is crucial to identify the local shape information i.e. local semantics and geometry, which is generalizable across different instances within the same category." + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 315, + 702, + 479, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 702, + 479, + 713 + ], + "spans": [ + { + "bbox": [ + 315, + 702, + 479, + 713 + ], + "type": "inline_equation", + "content": "2N^{\\prime}\\leq N" + }, + { + "bbox": [ + 315, + 702, + 479, + 713 + ], + "type": "text", + "content": " ; there could be points with no matches." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22979" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 70, + 219, + 244 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 219, + 244 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 219, + 244 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 219, + 244 + ], + "type": "image", + "image_path": "55a1493eec5b7723a871631a691b1297b59c8927f3ef3ff84cbd2ee63fec328d.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 86, + 246, + 180, + 256 + ], + "lines": [ + { + "bbox": [ + 86, + 246, + 180, + 256 + ], + "spans": [ + { + "bbox": [ + 86, + 246, + 180, + 256 + ], + "type": "text", + "content": "SO(3)-Equivariant Encoding" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 225, + 77, + 376, + 245 + ], + "blocks": [ + { + "bbox": [ + 225, + 77, + 376, + 245 + ], + "lines": [ + { + "bbox": [ + 225, + 77, + 376, + 245 + ], + "spans": [ + { + "bbox": [ + 225, + 77, + 376, + 245 + ], + "type": "image", + "image_path": "17d8d70677f49d572052a748b3192b37696a056e24887b272c9ae668387f5e68.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 274, + 547, + 352 + ], + "lines": [ + { + "bbox": [ + 46, + 274, + 547, + 352 + ], + "spans": [ + { + "bbox": [ + 46, + 274, + 547, + 352 + ], + "type": "text", + "content": "Figure 2. Overview: Self-supervised training of RIST. The input point clouds are independently encoded to SO(3)-equivariant global shape descriptor " + }, + { + "bbox": [ + 46, + 274, + 547, + 352 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}" + }, + { + "bbox": [ + 46, + 274, + 547, + 352 + ], + "type": "text", + "content": " and dynamic SO(3)-invariant point-wise local shape transforms " + }, + { + "bbox": [ + 46, + 274, + 547, + 352 + ], + "type": "inline_equation", + "content": "\\{f_{\\theta_i}\\}" + }, + { + "bbox": [ + 46, + 274, + 547, + 352 + ], + "type": "text", + "content": ". The local shape transforms map the global shape descriptor to local shape descriptors by infusing local semantics and geometry, which are used as inputs to the decoder for self-reconstruction. For cross-reconstruction, we apply the local shape transforms formulated from another point cloud to reconstruct the point cloud, ensuring that the local shape descriptors successfully capture generalizable local semantics and geometries. We supervise RIST via penalizing errors in self- and cross-reconstructions. At inference, we can leverage the local shape transforms for obtaining local shape descriptors, to identify the dense correspondences." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 376, + 78, + 546, + 244 + ], + "blocks": [ + { + "bbox": [ + 376, + 78, + 546, + 244 + ], + "lines": [ + { + "bbox": [ + 376, + 78, + 546, + 244 + ], + "spans": [ + { + "bbox": [ + 376, + 78, + 546, + 244 + ], + "type": "image", + "image_path": "3d6ac63acf794569ad63819e321ee21bf2906d5dfcf4812f60fb89566ad0c2f1.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 416, + 246, + 511, + 256 + ], + "lines": [ + { + "bbox": [ + 416, + 246, + 511, + 256 + ], + "spans": [ + { + "bbox": [ + 416, + 246, + 511, + 256 + ], + "type": "text", + "content": "SO(3)-Equivariant Decoding" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 361, + 289, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 361, + 289, + 564 + ], + "spans": [ + { + "bbox": [ + 46, + 361, + 289, + 564 + ], + "type": "text", + "content": "Therefore, the main idea of RIST is to dynamically generate a SO(3)-invariant local shape transform as a function for each point, such that each local shape transform can map the SO(3)-equivariant global shape descriptor of the input point cloud to its respective local shape descriptor. In the following, we elaborate on the network architecture of RIST, in particular how we leverage SO(3)-equivariant and invariant representations to facilitate the dynamic formulation of pointwise SO(3)-invariant local shape transforms and the reconstruction of pose-preserved point clouds (Sec. 3.1). Subsequently, we introduce our self-supervisory objective function, which trains RIST to self- and cross-reconstruct the input point clouds in a rotation-equivariant manner (Sec. 3.2), finally enabling the establishment of 3D dense correspondences (Sec. 3.3) via corresponding local shape descriptors. Figure 2 illustrates the outline of the training scheme of RIST." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 576, + 185, + 588 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 576, + 185, + 588 + ], + "spans": [ + { + "bbox": [ + 47, + 576, + 185, + 588 + ], + "type": "text", + "content": "3.1. Network Design of RIST" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 596, + 285, + 609 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 596, + 285, + 609 + ], + "spans": [ + { + "bbox": [ + 47, + 596, + 285, + 609 + ], + "type": "text", + "content": "3.1.1 Preliminary: SO(3)-Equivariant Representation" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "content": "One of the main motivations of RIST is to establish reliable and accurate 3D dense correspondences given arbitrarily rotated shapes, a setting where existing work shows to be brittle. This requires our encoder to formulate the pointwise local shape transforms not only effectively to capture the local shape semantics and geometry, but also robustly against transformations in the SO(3) space. To this end, we integrate SO(3)-equivariant networks into RIST to facilitate" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "spans": [ + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "text", + "content": "robustness to SO(3) transformations of the input. In this work, we choose VNNs [7] to build our SO(3)-equivariant layers for their simplicity and efficacy. In VNNs, a single neuron, which is represented by a scalar-list of values, is lifted to a vector-list feature " + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "inline_equation", + "content": "\\mathbf{V} \\in \\mathbb{R}^{C \\times 3}" + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "text", + "content": ", which is essentially a sequence of 3D vectors. The layers of VNNs handle batches of such vector-list features such that equivariance with respect to rotation " + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "inline_equation", + "content": "R \\in \\mathrm{SO}(3)" + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "text", + "content": " is satisfied i.e. " + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "inline_equation", + "content": "f(\\mathbf{V}R) = f(\\mathbf{V})R^3" + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "text", + "content": ". Notably, we can yield an SO(3)-invariant output by performing a product of an equivariant vector-list feature " + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "inline_equation", + "content": "\\mathbf{V}R \\in \\mathbb{R}^{C \\times 3}" + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "text", + "content": " with the transpose of another consistently equivariant vector-list feature " + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "inline_equation", + "content": "\\mathbf{U}R \\in \\mathbb{R}^{C' \\times 3}" + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "text", + "content": " as follows: " + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "inline_equation", + "content": "(\\mathbf{V}R)(\\mathbf{U}R)^{\\top} = \\mathbf{V}RR^{\\top}\\mathbf{U}^{\\top} = \\mathbf{V}\\mathbf{U}^{\\top}" + }, + { + "bbox": [ + 304, + 361, + 547, + 540 + ], + "type": "text", + "content": ". This serves as a critical functionality when constructing our SO(3)-invariant local shape transform of our encoder (Sec. 3.1.2)." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 555, + 457, + 567 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 555, + 457, + 567 + ], + "spans": [ + { + "bbox": [ + 306, + 555, + 457, + 567 + ], + "type": "text", + "content": "3.1.2 SO(3)-Equivariant Encoder" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 574, + 546, + 623 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 574, + 546, + 623 + ], + "spans": [ + { + "bbox": [ + 304, + 574, + 546, + 623 + ], + "type": "text", + "content": "We design our encoder architecture to take as input a point cloud " + }, + { + "bbox": [ + 304, + 574, + 546, + 623 + ], + "type": "inline_equation", + "content": "\\mathbf{P} \\in \\mathbb{R}^{N \\times 3}" + }, + { + "bbox": [ + 304, + 574, + 546, + 623 + ], + "type": "text", + "content": ", and simultaneously output an SO(3)-equivariant global shape descriptor and formulate pointwise SO(3)-invariant local shape transforms." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 625, + 547, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 625, + 547, + 686 + ], + "spans": [ + { + "bbox": [ + 304, + 625, + 547, + 686 + ], + "type": "text", + "content": "SO(3)-equivariant global shape descriptor. Given a point cloud, we first aim to obtain the SO(3)-equivariant global shape descriptor " + }, + { + "bbox": [ + 304, + 625, + 547, + 686 + ], + "type": "inline_equation", + "content": "\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}" + }, + { + "bbox": [ + 304, + 625, + 547, + 686 + ], + "type": "text", + "content": ", which captures the pose and the global shape characteristics of the input point cloud. We leverage VN-DGCNN [7] as our encoder architecture," + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 306, + 693, + 546, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 546, + 712 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 546, + 712 + ], + "type": "text", + "content": "3We refer the readers to the original paper [7] for further information and detailed formulations of VNNs." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22980" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": "which consists of 4 edge convolutional VN-layers to capture local semantics at a progressively larger receptive field, and a FPN [20] to aggregate the multi-level features. Then, we apply the global average pooling to the aggregated SO(3)-equivariant point-wise features " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "\\mathbf{V}^{\\mathrm{equi}}\\in \\mathbb{R}^{C\\times 3\\times N}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": " to encode SO(3)-equivariant global shape descriptor " + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}" + }, + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": " of the input point cloud. The global shape descriptor can be used subsequently as the input for our SO(3)-invariant point-wise local shape transform, to be mapped to their respective local shape descriptors, as shown in Figure 2." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "spans": [ + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": "SO(3)-invariant local shape transform. Alongside the extraction of SO(3)-equivariant global shape descriptors, we also formulate the SO(3)-invariant local shape transform " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "f_{\\theta_i}:\\mathbb{R}^{C\\times 3}\\mapsto \\mathbb{R}^{C'\\times 3}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": " for each point " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_i\\in \\mathbb{R}^3" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": " of the input point cloud " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{P}\\in \\mathbb{R}^{N\\times 3}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": ". The parameters of each local shape transform " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\theta_{i}\\in \\mathbb{R}^{C^{\\prime}\\times C}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": " are input-dependent - thus, dynamic since they are predicted by our encoder for the " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": "-th point of the point cloud. To predict " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\theta_{i}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": ", we first obtain SO(3)-invariant point-wise features " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{V}^{\\mathrm{in}}\\in \\mathbb{R}^{C^{\\prime}\\times 3\\times N}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": " as described in Sec. 3.1.1. Then, we transform each vectorized SO(3)-invariant point-wise feature " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\operatorname {vec}(\\mathbf{v}_i^{\\mathrm{in}})\\in \\mathbb{R}^{3C'}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": " to the vectorized parameter of the local shape transform " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\operatorname {vec}(\\theta_i)\\in \\mathbb{R}^{C'C}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": " by using a multi-layer perceptron. By reshaping " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\operatorname {vec}(\\theta_i)" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\theta_{i}\\in \\mathbb{R}^{C^{\\prime}\\times C}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": ", we finally obtain the dynamic and SO(3)-invariant local shape transform " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "f_{\\theta_i}" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": " for the point " + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_i" + }, + { + "bbox": [ + 46, + 196, + 289, + 376 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 377, + 289, + 474 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 377, + 289, + 474 + ], + "spans": [ + { + "bbox": [ + 46, + 377, + 289, + 474 + ], + "type": "text", + "content": "The role of these local shape transforms is to map the SO(3)-equivariant global shape descriptor " + }, + { + "bbox": [ + 46, + 377, + 289, + 474 + ], + "type": "inline_equation", + "content": "\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}" + }, + { + "bbox": [ + 46, + 377, + 289, + 474 + ], + "type": "text", + "content": " to their respective local shape descriptors " + }, + { + "bbox": [ + 46, + 377, + 289, + 474 + ], + "type": "inline_equation", + "content": "\\mathbf{v}_i' := f_{\\theta_i}(\\mathbf{Z}) \\in \\mathbb{R}^{C' \\times 3}" + }, + { + "bbox": [ + 46, + 377, + 289, + 474 + ], + "type": "text", + "content": ", which is provided as the input to our decoder for reconstruction. Our self-supervised training scheme encourages the point-wise dynamic local shape transform to encapsulate the local shape information e.g. semantics and geometry, to enhance the reconstruction performance." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 490, + 198, + 502 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 490, + 198, + 502 + ], + "spans": [ + { + "bbox": [ + 47, + 490, + 198, + 502 + ], + "type": "text", + "content": "3.1.3 SO(3)-Equivariant Decoder" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": "Our decoder aims to reconstruct the initial input shapes using the obtained SO(3)-equivariant global shape descriptors " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": " and the SO(3)-invariant local shape transforms " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\{f_{\\theta_i}\\}_{i = 1}^N" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": ". To reconstruct the point clouds aligned to their initial poses, we leverage SO(3)-equivariant layers as the building blocks of our decoder architecture. We first train our decoder to perform self-reconstruction, using the local shape descriptors " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{V}'" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": ", i.e. " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P} \\leftrightarrow \\mathbf{P}' := \\mathrm{Decoder}(\\mathbf{V}') = \\mathrm{Decoder}(\\{f_{\\theta_i}(\\mathbf{Z})\\}_{i = 1}^N)" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": ". We also train our decoder to perform cross-reconstruction, where we use the local shape descriptors obtained using global shape descriptors and local shape transforms from different point clouds. Specifically, assume we are given two point clouds " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1, \\mathbf{P}_2 \\in \\mathbb{R}^{N \\times 3}" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": ", with SO(3)-equivariant global shape descriptors " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}_1, \\mathbf{Z}_2 \\in \\mathbb{R}^{C \\times 3}" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": " and SO(3)-invariant local shape transforms " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\{f_{\\theta_i}^1\\}_{i = 1}^N, \\{f_{\\theta_i}^2\\}_{i = 1}^N" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": ". As shown in Figure 2, we then can perform cross-reconstruction from " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_2" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1" + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 194 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 194 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 194 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1 \\leftrightarrow \\mathbf{P}_{2 \\mapsto 1}' := \\mathrm{Decoder}(\\{f_{\\theta_i}^2(\\mathbf{Z_1})\\}_{i=1}^N)" + }, + { + "bbox": [ + 304, + 72, + 547, + 194 + ], + "type": "text", + "content": ". Intuitively, for the above cross-reconstruction to be carried out successfully, the local shape transforms for points of a true correspondence should hold similar dynamic parameters, mapping global shape descriptors to similar local shape descriptors. By training RIST to cross-reconstruct point clouds, we are supervising local shape transforms to map corresponding points between shapes to similar local shape descriptors, which encode local semantics and geometry that are generalizable across different instances within a category." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 207, + 451, + 220 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 207, + 451, + 220 + ], + "spans": [ + { + "bbox": [ + 305, + 207, + 451, + 220 + ], + "type": "text", + "content": "3.2. Self-Supervised Objective" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 228, + 547, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 228, + 547, + 289 + ], + "spans": [ + { + "bbox": [ + 304, + 228, + 547, + 289 + ], + "type": "text", + "content": "Due to the lack of annotated datasets for dense 3D intershape correspondences, we train RIST in a self-supervised manner by penalizing inaccurate shape reconstructions. First, we supervise RIST for self-reconstruction using the following loss:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 316, + 302, + 545, + 316 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 316, + 302, + 545, + 316 + ], + "spans": [ + { + "bbox": [ + 316, + 302, + 545, + 316 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {S R}} = \\lambda_ {\\mathrm {M S E}} \\operatorname {M S E} \\left(\\mathbf {P}, \\mathbf {P} ^ {\\prime}\\right) + \\lambda_ {\\mathrm {E M D}} \\operatorname {E M D} \\left(\\mathbf {P}, \\mathbf {P} ^ {\\prime}\\right), \\tag {1}", + "image_path": "2f4c77c3dd4f040413e8c0174f821b266432a18fb6aaccd3bbb9eb538ee88352.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "spans": [ + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "text", + "content": "where MSE is the Mean Squared Error, EMD stands for the Earth Mover's Distance, and both " + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "inline_equation", + "content": "\\lambda_{\\mathrm{MSE}}" + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "inline_equation", + "content": "\\lambda_{\\mathrm{EMD}}" + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "text", + "content": " are weight coefficients. In essence, we are trying to minimize the difference between the input and reconstructed point cloud. We also supervise RIST for cross-reconstruction as follows: " + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{CR}} = \\lambda_{\\mathrm{CD}}\\mathrm{CD}(\\mathbf{P}_1,\\mathbf{P}_{2\\mapsto 1}')" + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "text", + "content": ", where CD stands for the Chamfer distance, and " + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "inline_equation", + "content": "\\lambda_{\\mathrm{CD}}" + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "text", + "content": " is a weight coefficient. Finally, our total loss " + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{total}}" + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "text", + "content": " is defined as: " + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{SR}} + \\mathcal{L}_{\\mathrm{CR}}" + }, + { + "bbox": [ + 304, + 330, + 547, + 498 + ], + "type": "text", + "content": ". We omit the CD loss from self-reconstruction, as we can directly use the input point cloud to provide supervision using the MSE loss. We also omit the EMD loss from cross-reconstruction, as EMD tends to overlook the fidelity of detailed structures [36], which is crucial in cross-reconstruction of shapes under intra-class variations." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 513, + 484, + 526 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 513, + 484, + 526 + ], + "spans": [ + { + "bbox": [ + 305, + 513, + 484, + 526 + ], + "type": "text", + "content": "3.3. SO(3)-Invariant Correspondence" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": "In this section, given two randomly rotated point clouds " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_2" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ", we elaborate on how our RIST establishes the 3D dense correspondence from " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_2" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ". As shown in Figure 2, we first encode the SO(3)-equivariant global shape descriptor of " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}_1 \\in \\mathbb{R}^{C \\times 3}" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ", and the SO(3)-invariant local shape transform functions of " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_2" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\{f_{\\theta_i}^2\\}_{i=1}^N" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ". Then, we cross-reconstruct " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": " as follows: " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_{2 \\mapsto 1}' := \\mathrm{Decoder}(\\{f_{\\theta_i}^2(\\mathbf{Z}_1)\\}_{i=1}^N)" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ". Finally, we define the 3D dense correspondence from " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_2" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": " as the nearest point pairs among all possible pairs between " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_{2 \\mapsto 1}'" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ". Since both encoder and decoder are SO(3)-equivariant, the cross-reconstructed point cloud " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_{2 \\mapsto 1}'" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": " is aligned to " + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_1" + }, + { + "bbox": [ + 304, + 534, + 547, + 715 + ], + "type": "text", + "content": ". As a result, our RIST can predict 3D dense correspondences between randomly rotated point clouds, while previous approaches [3, 21] experience a high rate of failure." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "text", + "content": "22981" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 73, + 70, + 523, + 209 + ], + "blocks": [ + { + "bbox": [ + 73, + 70, + 523, + 209 + ], + "lines": [ + { + "bbox": [ + 73, + 70, + 523, + 209 + ], + "spans": [ + { + "bbox": [ + 73, + 70, + 523, + 209 + ], + "type": "table", + "html": "
TrainingMethodAirplaneCapChairGuitarLaptopMotorcycleMugTableAverage
w/o RotationsFoldingNet [38]17.834.722.522.136.212.650.034.628.8
AtlasNetV2 [8]19.731.423.622.736.013.149.735.228.9
DPC [17]22.737.125.631.935.017.551.336.832.2
CPAE [3]21.038.026.022.734.914.751.435.530.5
RIST (ours)52.154.558.374.156.548.675.041.357.6
w/ RotationsFoldingNet [38]22.533.224.031.035.913.549.937.030.9
AtlasNetV2 [8]21.132.725.228.835.514.549.941.031.1
DPC [17]24.638.525.640.234.919.351.837.334.0
CPAE [3]17.036.624.539.437.415.851.936.732.4
RIST (ours)51.257.055.073.560.648.572.244.457.8
", + "image_path": "419fb37df3c3faf145ae1ad1dfbe4c4432cdab0da24945a97a4346d7039a3d4c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 259, + 128, + 272 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 259, + 128, + 272 + ], + "spans": [ + { + "bbox": [ + 47, + 259, + 128, + 272 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 280, + 287, + 399 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 280, + 287, + 399 + ], + "spans": [ + { + "bbox": [ + 46, + 280, + 287, + 399 + ], + "type": "text", + "content": "We present evaluations of RIST on the tasks of 3D part segmentation label transfer and 3D semantic keypoint transfer, following prior work [3, 21]. For both tasks, each method is trained with and without rotation augmentations, and tested on arbitrarily rotated inputs to validate its rotation robustness in predicting semantic correspondences between the rotated inputs. Note that previous approaches [3, 8, 21, 38] used aligned point clouds or slightly rotated point clouds with a subset of SO(3), not the full SO(3), for testing - which is unrealistic in practice, as described in Appendix H." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 401, + 288, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 401, + 288, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 401, + 288, + 593 + ], + "type": "text", + "content": "Datasets. We use the ShapeNetPart [39] and ScanObjectNN [35] datasets to evaluate RIST on the task of 3D part segmentation label transfer, which requires 3D dense semantic correspondence. The ShapeNetPart dataset [39] consists of 16,880 synthetic 3D data from 16 categories. The ScanObjectNN dataset [35] contains real-world scanned data, and provides part label annotations for the chair category. Following the previous work [3], we use the same pre-processed KeypointNet [40] dataset for the 3D semantic keypoint transfer task. Since both KeypointNet and ShapeNetPart are based on the ShapeNet dataset [1], we use the eight overlapping categories between the ShapeNetPart and KeypointNet [40] datasets to evaluate each method on both tasks without fine-tuning the method on each dataset. For all tasks, we follow the experiment setting of the previous work [3]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": "Baseline methods. Throughout the evaluation section, we mainly compare RIST against CPAE [3], the state-of-the-art self-supervised method to establish 3D dense correspondence by exploiting an intermediate UV canonical space. When open-sourced pre-trained models or codes are applicable, we also compare RIST with AtlasNetV2 [8], FoldingNet [38] and DPC [17]. AtlasNetV2 proposes to represent shapes as the deformation and combination of learnable elementary 3D structures, which can be extended to 3D correspondence establishment. FoldingNet introduces" + } + ] + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 331, + 258, + 523, + 337 + ], + "blocks": [ + { + "bbox": [ + 46, + 217, + 547, + 251 + ], + "lines": [ + { + "bbox": [ + 46, + 217, + 547, + 251 + ], + "spans": [ + { + "bbox": [ + 46, + 217, + 547, + 251 + ], + "type": "text", + "content": "Table 1. Average IoU (%) of part label transfer for eight categories in the ShapeNetPart dataset [39]. Ours consistently outperforms previous approaches [3, 8, 17, 38] both with and without rotation augmentations during training, achieving the state-of-the-art IoU. We also provide results of the other classes in Appendix I." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 331, + 258, + 523, + 337 + ], + "lines": [ + { + "bbox": [ + 331, + 258, + 523, + 337 + ], + "spans": [ + { + "bbox": [ + 331, + 258, + 523, + 337 + ], + "type": "table", + "html": "
Methodw/o Rotationsw/ Rotations
FoldingNet [38]23.223.3
AtlasNetV2 [8]23.624.1
DPC [17]23.923.9
CPAE [3]24.423.9
RIST (ours)39.637.9
", + "image_path": "85735000c5d2b24249f949874b7ffc3b375767f41b4b19c35643b94bd41305fd.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_body" + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 344, + 547, + 378 + ], + "lines": [ + { + "bbox": [ + 305, + 344, + 547, + 378 + ], + "spans": [ + { + "bbox": [ + 305, + 344, + 547, + 378 + ], + "type": "text", + "content": "Table 2. Average IoU (\\%) of part label transfer for the chair category in the ScanObjectNN dataset [35]. Ours shows the best IoU both with and without rotation augmentations during training." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 387, + 545, + 471 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 387, + 545, + 471 + ], + "spans": [ + { + "bbox": [ + 304, + 387, + 545, + 471 + ], + "type": "text", + "content": "a folding-based decoder to 'fold' a canonical 2D grid into the 3D object surface, where the canonical 2D grid can be applied to identify cross-shape correspondences. DPC predicts 3D dense correspondence between non-rigidly deformed 3D humans, meaning that it can be a powerful baseline for both 3D part segmentation label transfer and 3D keypoint transfer tasks as well." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "spans": [ + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "content": "Implementation details. We use VN-DGCNN [7] as our SO(3)-equivariant encoder, and VN-based multi-layer perception as our SO(3)-equivariant decoder. For a fair comparison, we set the dimension, " + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "content": ", of SO(3)-equivariant global shape descriptor " + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "inline_equation", + "content": "\\mathbf{Z} \\in \\mathbb{R}^{C \\times 3}" + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "content": " as " + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "inline_equation", + "content": "170 \\ (\\approx 512/3)" + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "content": " since CPAE [3] uses 512-dimensional global shape descriptors. Following the training setup of CPAE [3], we use " + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "inline_equation", + "content": "\\lambda_{\\mathrm{MSE}}" + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "inline_equation", + "content": "\\lambda_{\\mathrm{EMD}}" + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "inline_equation", + "content": "\\lambda_{\\mathrm{CD}}" + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "content": " as 1000, 1, and 10, respectively. RIST is implemented in PyTorch, and is optimized with the Adam [16] optimizer at a constant learning rate of " + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "inline_equation", + "content": "1e^{-3}" + }, + { + "bbox": [ + 304, + 472, + 546, + 593 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 599, + 489, + 612 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 599, + 489, + 612 + ], + "spans": [ + { + "bbox": [ + 305, + 599, + 489, + 612 + ], + "type": "text", + "content": "4.1. Part Segmentation Label Transfer" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 617, + 547, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 665 + ], + "type": "text", + "content": "We compare RIST with the state of the art in 3D part segmentation label transfer on ShapeNetPart [39] and ScanObjectNN [35]. For both datasets, we use the average of instance-wise IoU scores as the evaluation metric." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 665, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 714 + ], + "type": "text", + "content": "ShapeNetPart [39]. The quantitative results are presented in Table 1, where RIST outperforms CPAE [3], DPC [17], AtlasNetV2 [8], and FoldingNet [38] on all classes by a large margin with and without rotation augmentations dur" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22982" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 72, + 69, + 523, + 333 + ], + "blocks": [ + { + "bbox": [ + 72, + 69, + 523, + 333 + ], + "lines": [ + { + "bbox": [ + 72, + 69, + 523, + 333 + ], + "spans": [ + { + "bbox": [ + 72, + 69, + 523, + 333 + ], + "type": "image", + "image_path": "4ee986b5c6538bee1a428ddcd1c50994be351da87421719e93dc99cac977f3c2.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 347, + 547, + 392 + ], + "lines": [ + { + "bbox": [ + 46, + 347, + 547, + 392 + ], + "spans": [ + { + "bbox": [ + 46, + 347, + 547, + 392 + ], + "type": "text", + "content": "Figure 3. Qualitative results of part label transfer on the ShapeNetPart dataset [39]. We visualize the label transfer results via learned correspondences of each method with the ground truth labels of targets. Note that the input shapes were arbitrarily rotated at evaluation, differently for both the source and targets of each row, but have been aligned in the above figure for better visibility of part label transfer results. RIST shows to outperform CPAE [3] consistently, showing a high resemblance to ground truth results." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 407, + 287, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 407, + 287, + 479 + ], + "spans": [ + { + "bbox": [ + 46, + 407, + 287, + 479 + ], + "type": "text", + "content": "ing training. We also provide the qualitative results of the part segmentation label transfer experiments on ShapeNetPart in Figure 3. Attributing to the SO(3)-invariant nature of correspondences established by RIST, we are able to transfer part labels significantly more accurately given randomly rotated shape pairs." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 479, + 288, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 479, + 288, + 598 + ], + "spans": [ + { + "bbox": [ + 46, + 479, + 288, + 598 + ], + "type": "text", + "content": "ScanObjectNN [35]. We evaluate each method trained on synthetic chair data of ShapeNet [1] on the real chair data of ScanObjectNN [35], which is partial and more challenging than ShapeNetPart [39], without fine-tuning. As shown in Table 2, RIST consistently outperforms previous approaches [3, 8, 17, 38] both with and without rotation augmentations during training. The qualitative results presented in Figure 4 show that RIST can predict rotation-robust 3D semantic correspondence between real and partial chair shapes, while CPAE [3] fails." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 605, + 219, + 618 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 605, + 219, + 618 + ], + "spans": [ + { + "bbox": [ + 47, + 605, + 219, + 618 + ], + "type": "text", + "content": "4.2.3D Semantic Keypoint Transfer" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 624, + 287, + 672 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 624, + 287, + 672 + ], + "spans": [ + { + "bbox": [ + 46, + 624, + 287, + 672 + ], + "type": "text", + "content": "Following the previous work [3], we compute the distances from the transferred " + }, + { + "bbox": [ + 46, + 624, + 287, + 672 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 46, + 624, + 287, + 672 + ], + "type": "text", + "content": " keypoints to the ground truth keypoints, and report PCK (Percentage of Correct keypoints) of our transferred keypoints, which is computed by:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 90, + 678, + 287, + 711 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 90, + 678, + 287, + 711 + ], + "spans": [ + { + "bbox": [ + 90, + 678, + 287, + 711 + ], + "type": "interline_equation", + "content": "\\mathrm {P C K} = \\frac {1}{M} \\sum_ {m = 1} ^ {M} \\mathbb {1} \\left[ \\left\\| \\mathbf {k} _ {m} - \\hat {\\mathbf {k}} _ {m} \\right\\| \\leq \\tau \\right], \\tag {2}", + "image_path": "13928c86436a6b3d49869cfc44908f1cc096b0d8b895f206e7ec1a4ef7bade7f.jpg" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 307, + 403, + 545, + 563 + ], + "blocks": [ + { + "bbox": [ + 307, + 403, + 545, + 563 + ], + "lines": [ + { + "bbox": [ + 307, + 403, + 545, + 563 + ], + "spans": [ + { + "bbox": [ + 307, + 403, + 545, + 563 + ], + "type": "image", + "image_path": "c237da1af5b71c1714543729148195284a6ec599dfc63a24a0e9931e0c0c0eaa.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 569, + 547, + 635 + ], + "lines": [ + { + "bbox": [ + 304, + 569, + 547, + 635 + ], + "spans": [ + { + "bbox": [ + 304, + 569, + 547, + 635 + ], + "type": "text", + "content": "Figure 4. Qualitative results of part label transfer on ScanObjectNN [35]. Note that both source and target point clouds were arbitrarily rotated at evaluation, but have been aligned in the figure for better visibility of part label transfer results. The results show that RIST reasonably predicts the semantic correspondences between arbitrarily rotated and partial real point clouds." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{k}_m" + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{k}}_m" + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "content": " are a distance threshold, " + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "content": "-th ground truth keypoint, and " + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "content": "-th transferred keypoint, respectively. The results on the KeypointNet dataset [40] are illustrated in Figure 5 for varying distance thresholds " + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "content": ". It can be seen that RIST consistently outperforms baseline methods with" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22983" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 72, + 174, + 152 + ], + "blocks": [ + { + "bbox": [ + 49, + 72, + 174, + 152 + ], + "lines": [ + { + "bbox": [ + 49, + 72, + 174, + 152 + ], + "spans": [ + { + "bbox": [ + 49, + 72, + 174, + 152 + ], + "type": "image", + "image_path": "1a4608f16826200b6932369e0f2d0964c6ff0c908e89b5cc1ec42cd5ccc237d3.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 173, + 72, + 298, + 152 + ], + "blocks": [ + { + "bbox": [ + 173, + 72, + 298, + 152 + ], + "lines": [ + { + "bbox": [ + 173, + 72, + 298, + 152 + ], + "spans": [ + { + "bbox": [ + 173, + 72, + 298, + 152 + ], + "type": "image", + "image_path": "90eedb8370dda8ae124a88bddab1c89996c4c6042d9cae96c9221bc4beff9a60.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 298, + 72, + 421, + 152 + ], + "blocks": [ + { + "bbox": [ + 298, + 72, + 421, + 152 + ], + "lines": [ + { + "bbox": [ + 298, + 72, + 421, + 152 + ], + "spans": [ + { + "bbox": [ + 298, + 72, + 421, + 152 + ], + "type": "image", + "image_path": "90317cb062f207bf8d15a78e37a352e8a109fbfa9c9e36a7037a1b43ab6de593.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 422, + 72, + 544, + 152 + ], + "blocks": [ + { + "bbox": [ + 422, + 72, + 544, + 152 + ], + "lines": [ + { + "bbox": [ + 422, + 72, + 544, + 152 + ], + "spans": [ + { + "bbox": [ + 422, + 72, + 544, + 152 + ], + "type": "image", + "image_path": "ea3423924f4c04f5f750a206c0add192befa7e9f76f60c90af4eca4618adb7a2.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 48, + 156, + 174, + 237 + ], + "blocks": [ + { + "bbox": [ + 48, + 156, + 174, + 237 + ], + "lines": [ + { + "bbox": [ + 48, + 156, + 174, + 237 + ], + "spans": [ + { + "bbox": [ + 48, + 156, + 174, + 237 + ], + "type": "image", + "image_path": "02a7a8f1c0cbd7dfd5753dd36db1732598ac9e160507e865b03f883cfc2b8b49.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 173, + 156, + 298, + 237 + ], + "blocks": [ + { + "bbox": [ + 173, + 156, + 298, + 237 + ], + "lines": [ + { + "bbox": [ + 173, + 156, + 298, + 237 + ], + "spans": [ + { + "bbox": [ + 173, + 156, + 298, + 237 + ], + "type": "image", + "image_path": "554738b6f0ef160714c62537a663413f80b08131069d20d8900c1ecd806bf095.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 298, + 156, + 421, + 237 + ], + "blocks": [ + { + "bbox": [ + 298, + 156, + 421, + 237 + ], + "lines": [ + { + "bbox": [ + 298, + 156, + 421, + 237 + ], + "spans": [ + { + "bbox": [ + 298, + 156, + 421, + 237 + ], + "type": "image", + "image_path": "558a328480ff168bd7ea3672f4c34d781f6355892348bd8ad200615cfb582d22.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 421, + 156, + 544, + 237 + ], + "blocks": [ + { + "bbox": [ + 421, + 156, + 544, + 237 + ], + "lines": [ + { + "bbox": [ + 421, + 156, + 544, + 237 + ], + "spans": [ + { + "bbox": [ + 421, + 156, + 544, + 237 + ], + "type": "image", + "image_path": "ad40310dc543bcd72f00872ce0963e9074ca6a36b36572131cdafab7c3c5369e.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 48, + 240, + 174, + 321 + ], + "blocks": [ + { + "bbox": [ + 48, + 240, + 174, + 321 + ], + "lines": [ + { + "bbox": [ + 48, + 240, + 174, + 321 + ], + "spans": [ + { + "bbox": [ + 48, + 240, + 174, + 321 + ], + "type": "image", + "image_path": "6328a4059450af8dfb48fca40a75106407ecadeacfb88ad9a4c4ea6277782148.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 365, + 546, + 388 + ], + "lines": [ + { + "bbox": [ + 46, + 365, + 546, + 388 + ], + "spans": [ + { + "bbox": [ + 46, + 365, + 546, + 388 + ], + "type": "text", + "content": "Figure 5. Percentage of Correct Keypoints (PCK) for the 12 categories of the KeypointNet dataset [40] with and without rotation augmentations during training. RIST consistently outperforms previous approaches on all classes and thresholds in both settings." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 173, + 240, + 298, + 322 + ], + "blocks": [ + { + "bbox": [ + 173, + 240, + 298, + 322 + ], + "lines": [ + { + "bbox": [ + 173, + 240, + 298, + 322 + ], + "spans": [ + { + "bbox": [ + 173, + 240, + 298, + 322 + ], + "type": "image", + "image_path": "5471e74130eea9d0498d5feab29d79178a6afb97aafbbd4a41186cbe510ee87a.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 298, + 240, + 421, + 322 + ], + "blocks": [ + { + "bbox": [ + 298, + 240, + 421, + 322 + ], + "lines": [ + { + "bbox": [ + 298, + 240, + 421, + 322 + ], + "spans": [ + { + "bbox": [ + 298, + 240, + 421, + 322 + ], + "type": "image", + "image_path": "046c1e7edf3d796f8865d254196865040fd7a4580494b86e5cf3dc099c4306eb.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 421, + 240, + 544, + 322 + ], + "blocks": [ + { + "bbox": [ + 421, + 240, + 544, + 322 + ], + "lines": [ + { + "bbox": [ + 421, + 240, + 544, + 322 + ], + "spans": [ + { + "bbox": [ + 421, + 240, + 544, + 322 + ], + "type": "image", + "image_path": "af7f0aa42b8055cbf7794ff194b1b450e78c20ee5be4e30f4ef943c289569b53.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 109, + 324, + 485, + 345 + ], + "blocks": [ + { + "bbox": [ + 109, + 324, + 485, + 345 + ], + "lines": [ + { + "bbox": [ + 109, + 324, + 485, + 345 + ], + "spans": [ + { + "bbox": [ + 109, + 324, + 485, + 345 + ], + "type": "image", + "image_path": "d5facbb8dc74061c51c0c544bb8e03b21aff5ab63d7e9bdb5950ce096ee217e3.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 403, + 289, + 571 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 403, + 289, + 571 + ], + "spans": [ + { + "bbox": [ + 46, + 403, + 289, + 571 + ], + "type": "text", + "content": "and without rotation augmentations during training for all classes, by up to " + }, + { + "bbox": [ + 46, + 403, + 289, + 571 + ], + "type": "inline_equation", + "content": "10 \\times" + }, + { + "bbox": [ + 46, + 403, + 289, + 571 + ], + "type": "text", + "content": " on certain classes and thresholds. This substantiates RIST's superior efficacy at establishing dense 3D correspondences between varying shapes. However, for certain classes such as Bathtub or Table, the performance is noticeably low, outperforming baseline methods only by a tight margin. We speculate this to be due to the prevalent rotational symmetry of those classes, making it especially challenging to establish accurate 3D correspondences under arbitrary rotations. The qualitative results of RIST in comparison to baseline methods are presented in Figure 6. It can also be seen that RIST can identify more accurate keypoint correspondences compared to CPAE [3] under arbitrary rotations, confirming the results of Figure 5." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 47, + 582, + 205, + 594 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 582, + 205, + 594 + ], + "spans": [ + { + "bbox": [ + 47, + 582, + 205, + 594 + ], + "type": "text", + "content": "4.3. Ablation Study and Analyses" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 46, + 600, + 287, + 625 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 600, + 287, + 625 + ], + "spans": [ + { + "bbox": [ + 46, + 600, + 287, + 625 + ], + "type": "text", + "content": "We perform an ablation study to justify the design choice of RIST, and evidence the efficacy of each component." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": "Self- and cross-reconstruction. We train RIST in a self-supervised manner via penalizing errors in self- and cross-reconstruction of input point clouds. We conduct an ablation study on RIST's reconstruction, providing comparative results for scenarios with and without its use. The results are illustrated in the first graph of Figure 7. It can be seen that with and without rotation augmentations during training, in" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 403, + 545, + 487 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 545, + 487 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 545, + 487 + ], + "type": "text", + "content": "corporating both self- and cross-reconstruction yields the best results. Removing self-reconstruction results in a much dramatic drop in performance; we conjecture this is because without self-reconstruction, the dynamic local shape transform (Sec. 3.1.2) fails to capture the required locality of its own point cloud in the first place, being unsuitable to establish correspondences." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 498, + 546, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 546, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 546, + 714 + ], + "type": "text", + "content": "Encoder outputs and SO(3)-equivariance. RIST uses VNNs [7] as the SO(3)-equivariant layers to facilitate 3D dense correspondence establishment between arbitrarily rotated point cloud pairs, leveraging local shape transform to map global shape descriptors to local shape descriptors which encode the pointwise semantics and local geometry. We perform an ablation study to demonstrate the efficacy of local shape transforms and SO(3)-equivariant and -invariant representations in RIST on the motorcycle class of the KeypointNet dataset [40]. We start our comparison from the architecture of CPAE [3], given that they also employ an encoder-decoder architecture to self-supervise their network via shape reconstruction. The results are presented in the two rightmost graphs of Figure 7, showing the evaluation results with and without rotation augmentations during training in order. It can be seen that our design choice of using equivariant encoders and decoders shows consistent improvements over using an SO(3)-variant counterpart. Also," + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22984" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 56, + 70, + 539, + 241 + ], + "blocks": [ + { + "bbox": [ + 56, + 70, + 539, + 241 + ], + "lines": [ + { + "bbox": [ + 56, + 70, + 539, + 241 + ], + "spans": [ + { + "bbox": [ + 56, + 70, + 539, + 241 + ], + "type": "image", + "image_path": "d8e9b29f7921f50e2faad0528d2b65a612fdb0df8a05f8c37e27aed98a5b9fd8.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 48, + 298, + 211, + 441 + ], + "blocks": [ + { + "bbox": [ + 48, + 298, + 211, + 441 + ], + "lines": [ + { + "bbox": [ + 48, + 298, + 211, + 441 + ], + "spans": [ + { + "bbox": [ + 48, + 298, + 211, + 441 + ], + "type": "image", + "image_path": "e4717c30df69ec05eec18202f2947c497c9660585a2e1af74a642248e4fec04e.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 452, + 547, + 498 + ], + "lines": [ + { + "bbox": [ + 46, + 452, + 547, + 498 + ], + "spans": [ + { + "bbox": [ + 46, + 452, + 547, + 498 + ], + "type": "text", + "content": "Figure 7. Ablation study on losses (the leftmost) and the components of model architecture (the others); self-reconstruction loss (SR), cross-reconstruction loss (CR), equivariant decoder (ED), local shape transform (LST), and local feature (LF). When excluding the equivariant decoder, local shape transforms, or local features, the default is to use an SO(3)-variant decoder, UV coordinates [3], or global features for encoding, respectively." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 216, + 297, + 376, + 434 + ], + "blocks": [ + { + "bbox": [ + 46, + 257, + 547, + 292 + ], + "lines": [ + { + "bbox": [ + 46, + 257, + 547, + 292 + ], + "spans": [ + { + "bbox": [ + 46, + 257, + 547, + 292 + ], + "type": "text", + "content": "Figure 6. Keypoint transfer results for airplane and motorcycle categories of KeypointNet [40]. Each row contains a shape pair, each with ground-truth keypoints and the keypoint transfer results. Note that the input shapes were arbitrarily rotated at evaluation, but have been aligned in the above figure for better visibility of keypoint transfer results. RIST shows to transfer the keypoints more accurately." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 216, + 297, + 376, + 434 + ], + "lines": [ + { + "bbox": [ + 216, + 297, + 376, + 434 + ], + "spans": [ + { + "bbox": [ + 216, + 297, + 376, + 434 + ], + "type": "image", + "image_path": "4dda6a506ded8115f9f7e42d9863f601064997c1e4cde5d653e8ce1c6e5d6092.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 384, + 297, + 545, + 432 + ], + "blocks": [ + { + "bbox": [ + 384, + 297, + 545, + 432 + ], + "lines": [ + { + "bbox": [ + 384, + 297, + 545, + 432 + ], + "spans": [ + { + "bbox": [ + 384, + 297, + 545, + 432 + ], + "type": "image", + "image_path": "34e976bc2e6186abbbd01417b7278fb48852fcceb61aa730419b94cd03799438.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 512, + 289, + 632 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 512, + 289, + 632 + ], + "spans": [ + { + "bbox": [ + 46, + 512, + 289, + 632 + ], + "type": "text", + "content": "using UV coordinates as proposed in CPAE [3] performs worse compared to our dynamic local shape transform, evidencing the comparatively better efficacy of transforming each point to their local shape descriptors via our dynamic SO(3)-invariant shape transform. While using local features as inputs to the encoder shows varied trends across with and without augmentation settings, using the point-wise local feature as input is a key component that facilitates the learning of point-wise dynamic local shape transform that is essential in establishing the 3D correspondences in RIST." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 645, + 119, + 657 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 645, + 119, + 657 + ], + "spans": [ + { + "bbox": [ + 47, + 645, + 119, + 657 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "content": "We've introduced RIST, a novel self-supervised learner for dense 3D semantic matching across shapes of the same category, even with arbitrary rotations. Its robustness stems from our innovative use of SO(3)-equivariant and -invariant" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 512, + 545, + 609 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 512, + 545, + 609 + ], + "spans": [ + { + "bbox": [ + 304, + 512, + 545, + 609 + ], + "type": "text", + "content": "representations, enabling dynamic local shape transforms that preserve rotation equivariance. These transforms map global descriptors to local ones, facilitating the establishment of dense correspondences. Our method outperforms existing ones on tasks like part label and keypoint transfer, enhancing applicability in computer vision and robotics, e.g., AR/VR and texture mapping. Future research could focus on improving robustness under common corruption." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "spans": [ + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "text", + "content": "Acknowledgement. This work was supported by IITP grants (No.2021-0-02068: AI Innovation Hub " + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "inline_equation", + "content": "(50\\%)" + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "text", + "content": ", No. 2022-0-00290: Visual Intelligence for Space-Time Understanding and Generation " + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "inline_equation", + "content": "(40\\%)" + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "text", + "content": ", No.2019-0-01906: Artificial Intelligence Graduate School Program at POSTECH " + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "inline_equation", + "content": "(5\\%)" + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "text", + "content": ", NO.2021-0-01343, Artificial Intelligence Graduate School Program at Seoul National University " + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "inline_equation", + "content": "(5\\%)" + }, + { + "bbox": [ + 304, + 614, + 546, + 709 + ], + "type": "text", + "content": ") funded by the Korea government (MSIT). Seungwook was supported by the Hyundai-Motor Chung Mong-koo Foundation." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22985" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 713 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Angel X. 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Nevertheless, it is not trivial to capitalize on diffusion models for video super-resolution which necessitates not only the preservation of visual appearance from low-resolution to high-resolution videos, but also the temporal consistency across video frames. In this paper, we propose a novel approach, pursuing Spatial Adaptation and Temporal Coherence (SATeCo), for video super-resolution. SATeCo pivots on learning spatial-temporal guidance from low-resolution videos to calibrate both latent-space high-resolution video denoising and pixel-space video reconstruction. Technically, SATeCo freezes all the parameters of the pre-trained UNet and VAE, and only optimizes two deliberately-designed spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules, in the decoder of UNet and VAE. SFA modulates frame features via adaptively estimating affine parameters for each pixel, guaranteeing pixel-wise guidance for high-resolution frame synthesis. TFA delves into feature interaction within a 3D local window (tubelet) through self-attention, and executes cross-attention between tubelet and its low-resolution counterpart to guide temporal feature alignment. Extensive experiments conducted on the REDS4 and Vid4 datasets demonstrate the effectiveness of our approach.", + "bbox": [ + 75, + 358, + 473, + 720 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 748, + 207, + 763 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In recent years, diffusion models [11, 36, 37, 55] have shown great progress in revolutionizing image generation. In between, a series of image super-resolution works [36, 46, 52] benefit from leveraging knowledge prior embedded in diffusion models to upscale low-resolution (LR) images into high-resolution (HR) ones. Compared to 2D images, videos have one more time dimension, bringing", + "bbox": [ + 75, + 773, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/684b5fb0c070de5fbee23e28f18597e907303bdd7c6b128565cf6466f67cead7.jpg", + "image_caption": [ + "Frame t" + ], + "image_footnote": [], + "bbox": [ + 506, + 334, + 692, + 416 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/f65e91b44669ce145575fecbbcfa56f5190435ac23bdeebdafe256c8e299aa1e.jpg", + "image_caption": [ + "Frame t+1" + ], + "image_footnote": [], + "bbox": [ + 694, + 334, + 880, + 416 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ba41de1b3fe749ca81124984542c297d6a7cad920be2ae648673a8d13317607f.jpg", + "image_caption": [ + "Low Resolution" + ], + "image_footnote": [], + "bbox": [ + 506, + 426, + 692, + 468 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/dcbdfc68fd29b37135cc06710c6f94a8dfd526d9beacca8b61a8f053d372247a.jpg", + "image_caption": [ + "VRT" + ], + "image_footnote": [], + "bbox": [ + 694, + 426, + 880, + 468 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/cfecaae4f758204374e203ae6371da384268a8a6fe739e9c2bee7f33c9514e94.jpg", + "image_caption": [ + "StableSR", + "Figure 1. An illustration of video super-resolution by using different approaches of StableSR [46], VRT [23] and our SATeCo to generate two adjacent frames. The region in the same local position is presented in the zoom-in view." + ], + "image_footnote": [], + "bbox": [ + 506, + 478, + 692, + 518 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/80a7716c2aa1085c9d3a7342bbc941d51d48ad3b70de73329dfc2d8dffcf70bc.jpg", + "image_caption": [ + "SATeCo" + ], + "image_footnote": [], + "bbox": [ + 694, + 478, + 880, + 518 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "more challenges when capitalizing on diffusion models for video super-resolution (VSR). One natural way is to utilize the pre-trained diffusion models for image super-resolution (ISR), e.g., StableSR [46], to magnify each video frame. The representative advances [46, 52] manifest that diffusion models for ISR could synthesize more details than traditional regression models, e.g., VRT [23]. As depicted in Figure 1, the edges of the windows in the building produced by StableSR are much clearer than those generated by VRT. Nevertheless, the inherent stochasticity of diffusion models might jeopardize the spatial fidelity and hallucinate some extra visual content. Moreover, the independent frame-wise super-resolution overlooks the relation across consecutive frames, resulting in the issue of frame inconsistency in the high-resolution videos. For instance, the traffic signs in Figure 1 are totally different between the two adjacent frames generated by StableSR.", + "bbox": [ + 496, + 597, + 892, + 852 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In general, the difficulty of exploring diffusion models for video super-resolution originates from two aspects: 1) how to alleviate the stochasticity in diffusion process to pre", + "bbox": [ + 498, + 854, + 890, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*This work was performed at HiDream.ai.", + "bbox": [ + 94, + 886, + 346, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "9232", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "serve visual appearance? 2) how to guarantee the temporal consistency across frames in the HR videos? We propose to address the two issues through learning spatial-temporal guidance from low-resolution videos to manage diffusion procedure for video super-resolution. To regulate spatial adaptation, we estimate affine parameters on the LR frame features to modulate each pixel in HR frames. As such, the pixel-wise guidance is employed to nicely learn the feature of every pixel in HR frames and better improve spatial fidelity. In an effort to temporally cohere video frames, we strengthen feature interaction across HR frames, and feature calibration between HR frames and LR counterpart via the attention mechanism. Moreover, large receptive field is attained by conducting the self-attention and cross-attention on the features within a 3D local window (tubelet), thereby facilitating temporal feature alignment.", + "bbox": [ + 75, + 90, + 472, + 332 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To materialize our idea, we present a new SATeCo method to carry out Spatial Adaptation and Temporal Coherence for video super-resolution. Technically, SATeCo uses a transformer-based video upscaler to up-sample the input LR video. The VAE encoder then extracts the video features and latent code of LR video, which are further exploited for diffusion calibration. SATeCo deliberately devises spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules, and inserts the two modules into each decoder block of UNet and VAE, for latent-space video denoising and pixel-space video reconstruction. In the regularization of latent-space video denoising, SFA exploits two convolutional layers on the latent code of each up-sampled LR frame, to predict a scale and bias to modulate the pixel-wise feature of HR frame. TFA first executes self-attention on HR video latent code within a tubelet to enhance feature interaction, and further performs cross-attention between the tubelet and its LR counterpart for feature calibration in HR video. The LR video features are exploited in the same way to regulate the HR video feature learning in pixel-space video reconstruction. SATeCo finally refines the decoded HR video by referring to the up-sampled LR video via a neural network to balance synthesized quality and fidelity.", + "bbox": [ + 75, + 333, + 472, + 680 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The main contribution of this paper is the proposal of SATeCo to explore spatial adaptation and temporal coherence in diffusion models for video super-resolution. The solution also leads to the elegant views of how to leverage pixel-wise information from LR videos for visual appearance preservation, and how to achieve frame consistency in HR video generation. Extensive experiments on REDS4 and Vid4 verify the superiority of SATeCo in terms of both spatial quality and temporal consistency.", + "bbox": [ + 75, + 680, + 472, + 816 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 829, + 218, + 845 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Video super-resolution. Modern VSR approaches are mainly based on deep neural networks and can be grouped into two categories, i.e., sliding window-based methods and", + "bbox": [ + 76, + 854, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "recurrent methods. Early sliding window-based VSR techniques [1, 22, 50, 51, 53] rely on 2D or 3D CNNs [19, 20] which incorporate a sequence of LR frames to predict center HR frame. To fully utilize the complementary information across adjacent frames, the deformable convolutions [43, 48] are employed for feature alignment. Inspired by the success of transformer architecture in various computer vision tasks [6, 27-29], self-attention emerges to be integrated into the VSR frameworks [14, 23, 26, 47]. One representative is VRT [23] which plugs the temporal mutual attention block into transformer backbone to facilitate motion estimation, feature alignment and fusion. Nevertheless, the sliding window-based approaches are difficult to capture long-range dependencies which could limit the performance of video super-resolution. In contrast to aggregate information from adjacent frames in a short term, recurrent approaches [2, 3, 15, 17, 18, 24, 38, 39, 54] utilize a hidden state to sequentially propagate information from all previous frames to the current frame, benefiting the frame restoration. For instance, Chan et al. [2] adopt a bidirectional propagation scheme with flow-based feature alignment to maximize information gathering in super resolution. Despite having the great capacity of the recurrent models for temporal information gathering, the local details are still hard to be restored when the LR video encounters significant degradation in a long temporal range.", + "bbox": [ + 496, + 90, + 893, + 484 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Diffusion models for super-resolution. Impressive performances of image synthesis achieved by diffusion models [7, 11, 16, 30, 34, 55] encourage the deployment on image super-resolution. These explorations [9, 10, 13, 21, 31, 42, 49, 57] leverage the knowledge prior embedded in the pre-trained diffusion models to magnify images. For example, StableSR [46] integrates a time-aware encoder into Stable-Diffusion [36] model without altering the pre-trained weights, and achieves promising super-resolution results. To further enhance the reconstruction of image texture details, Yang et al. [52] introduce an attention-based control module to maintain pixel consistency between LR and HR images. Different from the advances which optimize a small part of inserted parameters, several approaches [13, 21, 49] fix all weights in the pre-trained synthesis model and attempt to incorporate constraints into the reverse diffusion process to guide image restoration. Although the effectiveness of knowledge prior has been manifested in various diffusion-based ISR methods, it is still a grand challenge to employ diffusion models for video super-resolution and preserve spatial fidelity and temporal consistency.", + "bbox": [ + 496, + 488, + 893, + 806 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In summary, our work mainly focuses on diffusion models for video super-resolution. The proposal of SATeCo contributes by exploring not only how to preserve spatial fidelity through modulating HR frame features, but also how to calibrate HR video features with LR counterpart for better temporal feature alignment.", + "bbox": [ + 496, + 810, + 893, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "9233", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/3a0bed2ae560a661e058c5700ca6eb93cd913e5720919c36d674beb27706c8fb.jpg", + "image_caption": [ + "Figure 2. An overview of our SATeCo architecture. The input LR video $X_{L}$ is first up-sampled to the target resolution via a transformer-based video upscaler. Then, the up-sampled video $X_{u}$ is fed into the VAE encoder to extract the video features and latent code $Z$ . Next, the Gaussian noise is added into $Z$ according to the diffusion scheduler, and the noisy video latent code is then restored by UNet for quality enhancement. In latent space, a latent encoder extracts the LR latent feature maps $G$ on the LR latent code $Z$ , followed by spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules in each decoder block of UNet for spatial-temporal guidance learning. Given the denoised video latent code $Z_{0}$ , the VAE decoder decodes the video $X_{d}$ based on the guidance learnt by SFA and TFA on LR video features. Finally, the decoded video $X_{d}$ is adjusted by a video refiner via referring to $X_{u}$ for final HR video $X_{H}$ synthesis." + ], + "image_footnote": [], + "bbox": [ + 101, + 95, + 869, + 220 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Our Approach", + "text_level": 1, + "bbox": [ + 76, + 335, + 225, + 353 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we present our newly-minted SATeCo, pursuing Spatial Adaptation and Temporal Coherence in diffusion models for video super-resolution. Figure 2 depicts an overview of the architecture. SATeCo begins with a video upscaler to increase the resolution of the input LR video. Then, the up-sampled video is fed into VAE encoder for video feature extraction and latent code prediction. After that, a spatial feature adaptation (SFA) and a temporal feature alignment (TFA) module are leveraged to learn spatial-temporal guidance on latent code and features of LR video, to calibrate latent-space video denoising and pixel-space video reconstruction. As such, the two modules are plugged into each block of the decoder in UNet and VAE. In procedure of video latent code denoising, SFA estimates the affine parameters on LR video latent code to modulate each pixel of the HR video latent code. TFA first performs self-attention on the HR video latent code within a tubelet, and further enhances latent code by executing cross-attention between the tubelet and its LR counterpart. Similarly, SFA and TFA are conducted in the VAE decoder to guide HR video reconstruction with the LR video features. Finally, SATeCo designs a video refiner to adjust the decoded HR video by referring to the up-sampled video for a good trade-off between synthesized quality and fidelity.", + "bbox": [ + 75, + 363, + 472, + 727 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Video Upscaler", + "text_level": 1, + "bbox": [ + 76, + 739, + 232, + 756 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Most existing VSR approaches [39, 51] first upscale the input LR videos through a resampling operation, and then improve their visual quality. Nevertheless, the widely adopted resampling operations, e.g., Bilinear and Bicubic sampling, might damage the original visual patterns [39] in LR frames, having a negative impact on the subsequent video enhancement. Therefore, we exploit the recipe of reducing frame degradation ahead of the feature learning [4] in neural networks and propose a video upscaler, which gen", + "bbox": [ + 75, + 763, + 468, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "erates more accurate up-sampled videos for the following quality enhancement by diffusion models.", + "bbox": [ + 496, + 338, + 890, + 367 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given the input LR video $X_{L}$ , we utilize a transformer-based video upscaler for video up-scaling as illustrated in Figure 3(a). It consists of two cascaded temporal mutual self-attention (TMSA) blocks [23] to temporally aggregate video features, and a pixel-shuffle layer [40] to increase video spatial resolution via feature reshaping. The upsampled video $X_{u} = \\{x_{u}^{i}\\}_{i=1}^{L}$ with $L$ frames is then fed into the diffusion model for video quality enhancement.", + "bbox": [ + 496, + 368, + 892, + 489 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Spatial Feature Adaptation Module", + "text_level": 1, + "bbox": [ + 498, + 500, + 808, + 515 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The inherent stochasticity [52] of diffusion models might result in the distortion of texture details in image superresolution. A natural way of employing diffusion models for super-resolution is to learn the spatial-level condition via convolution-based [46] or transformer-based [52] structure to guide latent code denoising in UNet. Such kind of mechanism only manages feature regularization in latent space, posting difficulty to learn sufficient inductive bias and provide precise guidance for high-resolution image restoration. The similar issue also exists in video superresolution. To alleviate this, we introduce a spatial feature adaptation (SFA) module which dynamically learns pixelwise guidance from the input LR videos for diffusion calibration. In the meanwhile, the SFA module emphasizes the inductive bias learning in both of the latent-space video denoising (i.e., training of UNet) and pixel-space video reconstruction (i.e., training of VAE).", + "bbox": [ + 496, + 522, + 890, + 779 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Figure 3(c) illustrates our SFA module. Given the upsampled LR video $X_{u}$ , the VAE encoder first encodes $X_{u}$ into the video latent code $Z = \\{z^{i}\\}_{i = 1}^{L}$ . Next, we exploit a convolution-based latent encoder $\\mathcal{E}_z$ to extract the LR latent feature maps $G = \\mathcal{E}_z(Z)$ , which are further utilized to guide the HR feature learning in UNet decoder. Formally, we denote the HR intermediate feature maps in UNet and the LR latent feature maps in latent encoder as", + "bbox": [ + 496, + 780, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "9234", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/ce2469dfa5d28971c257720182ebf2a569a1cfdc395970d0ee770cbb007509de.jpg", + "image_caption": [ + "Figure 3. An illustration of (a) video upscaler, (b) video refiner, (c) spatial feature adaptation and (d) temporal feature alignment module." + ], + "image_footnote": [], + "bbox": [ + 104, + 97, + 279, + 244 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/bed722ea0b1b0bdbc51a6f6b0567e4b1876c24e99d616431d9a76f17015624c4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 292, + 98, + 532, + 244 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/b3e36fa69554affd8566693dc958e8f70a561ad6ecbc13df5cde3990d227029f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 544, + 99, + 866, + 244 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "$F = \\{f^{i}\\}_{i = 1}^{L}$ and $G = \\{g^i\\}_{i = 1}^L$ , respectively. For the $i$ -th frame, we measure a scale ratio $S^i\\in \\mathbb{R}^{H\\times W\\times C}$ and a bias $M^i\\in \\mathbb{R}^{H\\times W\\times C}$ for each pixel of HR intermediate feature map $f^{i}\\in \\mathbb{R}^{H\\times W\\times C}$ based on the LR latent feature map $g^{i}\\in \\mathbb{R}^{H\\times W\\times C}$ via two 2D convolution layers:", + "bbox": [ + 76, + 286, + 468, + 363 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nM ^ {i} = \\operatorname {C o n v 2 D} (g ^ {i}), \\quad S ^ {i} = \\operatorname {C o n v 2 D} (g ^ {i}). \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 130, + 371, + 468, + 388 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Then, the output HR feature map $\\tilde{f}^i$ in UNet is generated by modulating the normalized HR intermediate feature map $f^i$ with $S^i$ and $M^i$ as:", + "bbox": [ + 76, + 397, + 468, + 444 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {f} ^ {i} = S ^ {i} \\odot \\frac {f ^ {i} - \\mu^ {i}}{\\sigma^ {i}} + M ^ {i}, \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 181, + 450, + 468, + 482 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\odot$ denotes point-wise multiplication. $\\mu^i$ and $\\sigma^i$ are the mean and standard deviation values of the feature map $f^i$ . Hence, the affine parameters estimated on the latent feature maps of LR videos calibrate the intermediate feature maps of HR videos in latent code denoising, which adaptively injects the pixel-wise information into the video latent code to preserve the visual appearance. For video feature learning in pixel space, SFA module is inserted into each block of VAE decoder. Similarly, the extracted video features of LR videos are taken as the guidance to estimate the affine parameters in SFA module to adjust HR video feature learning for video reconstruction. We take all the modulated intermediate feature maps $\\tilde{f}^i$ from SFA module as $\\tilde{F} = \\{\\tilde{f}^i\\}_{i=1}^L$ , which is employed for the following temporal feature alignment in the UNet and VAE decoders.", + "bbox": [ + 75, + 491, + 468, + 717 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Temporal Feature Alignment Module", + "text_level": 1, + "bbox": [ + 76, + 726, + 398, + 742 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Frame-wisely conducting ISR models for video super-resolution could amplify the differences of blurry patterns [39] across frames, leading to content inconsistency such as the object shape deformation. The issue originated from solely relying on spatial level super-resolution and lacking temporal coherence modeling across frames. To facilitate visual content alignment in video super-resolution, a temporal feature alignment (TFA) module is devised after each SFA module in UNet and VAE decoder, for the temporal feature interaction and calibration.", + "bbox": [ + 75, + 750, + 468, + 898 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Figure 3(d) depicts the learning procedure of TFA module. Given the input HR intermediate feature maps $\\tilde{F} = \\{\\tilde{f}^i\\}_{i=1}^L$ from the SFA module in UNet decoder, we first partition the feature map $\\tilde{f}^i$ of each frame into $N$ non-overlapping windows with the spatial resolution of $h \\times w$ . $N = \\frac{HW}{hw}$ is the total window number. Then, we link all features within a local window across $L$ frames to form a HR feature tubelet $\\tilde{F}_{tub} \\in \\mathbb{R}^{L \\times h \\times w \\times C}$ . We reshape the dimension of each HR feature tubelet into $hwL \\times C$ and execute the standard self-attention on it:", + "bbox": [ + 498, + 287, + 890, + 436 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nQ, K, V = \\operatorname {C o n v 3 D} (\\tilde {F} _ {t u b}), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 596, + 445, + 890, + 470 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {F} _ {t u b} = \\operatorname {A t t e n t i o n} (Q, K, V),\n$$\n", + "text_format": "latex", + "bbox": [ + 598, + 467, + 792, + 484 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $Q, K, V \\in \\mathbb{R}^{hwL \\times C}$ are the query, key and value matrices, respectively. Each of them is predicted by a 3D convolution layer. The self-attention conducted on the HR feature tubelet enables the feature interaction across different frames, mitigating the temporal feature misalignment in local regions. To further conduct the temporal feature calibration, we leverage the counterpart of HR feature tubelet, i.e., the feature tubelet $G_{tub}$ of the LR latent feature maps, as a reference for feature adjustment. We perform the cross-attention between $\\hat{F}_{tub}$ and $G_{tub}$ to obtain the output feature tubelet $\\bar{F}_{tub}$ :", + "bbox": [ + 496, + 494, + 890, + 661 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nQ ^ {\\prime} = \\operatorname {C o n v 3 D} \\left(\\hat {F} _ {t u b}\\right), \\quad K ^ {\\prime}, V ^ {\\prime} = \\operatorname {C o n v 3 D} \\left(G _ {t u b}\\right), \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 514, + 670, + 890, + 694 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\bar {F} _ {t u b} = \\operatorname {A t t e n t i o n} \\left(Q ^ {\\prime}, K ^ {\\prime}, V ^ {\\prime}\\right),\n$$\n", + "text_format": "latex", + "bbox": [ + 517, + 690, + 725, + 705 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the query $Q^{\\prime}$ is learnt on the HR feature tubelet $\\hat{F}_{tub}$ and the key/value $K^{\\prime} / V^{\\prime}$ is estimated on the LR counterpart via 3D convolution layers, respectively. We collect all the output feature tubelets from the TFA module and reshape them into the original size as $\\bar{F}\\in \\mathbb{R}^{L\\times H\\times W\\times C}$ . The output feature $\\bar{F}$ is then fed into the next block of the decoder in UNet or VAE for video latent denoising or reconstruction.", + "bbox": [ + 496, + 719, + 890, + 824 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this way, the coupled SFA and TFA modules in UNet and VAE decoder not only emphasize the pixel-wise feature adaptation for visual appearance preservation but also strengthen the temporally feature interaction and calibration for temporal coherence modeling.", + "bbox": [ + 496, + 825, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "9235", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "table", + "img_path": "images/9a5e460e7b73a28552299b73a5dd413c194a8776506fb3235f6d0b6951ac7f5c.jpg", + "table_caption": [ + "Table 1. Performance comparisons in terms of pixel-based (PSNR and SSIM) and perception-based (LPIPS, DISTS, NIQE and CLIP-IQA) evaluation metrics on the REDS4 and Vid4 datasets. The width and height of the LR videos are rescaled by 4 times through different VSR approaches. We follow VRT [23] to set the frame number as 6 in each clip for HR video inference." + ], + "table_footnote": [], + "table_body": "
DatasetsMetricsBicubicStableSR [46]TOFlow [51]EDVR-M [48]BasicVSR [2]VRT [23]IconVSR [2]SATeCo
REDS4PSNR↑26.1424.7927.9830.5331.4231.6031.6731.62
SSIM↑0.72920.68970.79900.86990.89090.88880.89480.8932
LPIPS↓0.35190.24120.31040.23120.20230.20770.19390.1735
DISTS↓0.18760.07550.14680.09430.08080.08230.07620.0607
NIQE↓7.2574.1166.2604.5444.1974.2524.1174.104
CLIP-IQA↑0.60450.65790.61760.63820.63530.63790.61620.6622
Vid4PSNR↑23.7822.1825.8927.1027.2427.9327.3927.44
SSIM↑0.63470.59040.76510.81860.82510.84250.82790.8420
LPIPS↓0.39470.36700.33860.28980.28110.27230.27390.2291
DISTS↓0.22010.13850.17760.14680.14420.13720.14060.1015
NIQE↓7.5365.2377.2295.5285.3405.2425.3925.212
CLIP-IQA↑0.68170.76440.73650.73800.74100.74340.74110.7451
", + "bbox": [ + 83, + 136, + 879, + 333 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Video Refiner", + "text_level": 1, + "bbox": [ + 76, + 349, + 220, + 364 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Recent advance [8] reveals that images synthesized by diffusion model conditioning on visual contents might lose some original color information in local regions. To address this problem, StableSR [46] performs a non-parametric post-processor to refine the generation with reference to original input for achieving color preservation. Instead, we propose a trainable video refiner to emphasize the adjustment of decoded HR video from VAE decoder, by leveraging the information from up-sampled LR video.", + "bbox": [ + 75, + 373, + 468, + 508 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Figure 3(b) details the structure of our video refiner. We first concatenate the decoded video $X_{d}$ and the up-sampled LR video $X_{u}$ along channel dimension, and then feed it into a residual block. The refined HR video $X_{H}$ is generated by fusing $X_{u}$ , $X_{d}$ and the output feature mapping of residual block as:", + "bbox": [ + 75, + 508, + 468, + 599 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nX _ {H} = w X _ {u} + (1 - w) X _ {d} + \\operatorname {R e s B l o c k} ([ X _ {u}, X _ {d} ]), \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 606, + 468, + 625 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $w$ is a trade-off parameter. The devised video refiner balances the original visual contents of the up-sampled LR video and the synthesized contents of decoded HR video via feature fusion learning. Accordingly, our design is more powerful in terms of color preservation, and achieves a good trade-off between the synthesized quality and fidelity.", + "bbox": [ + 75, + 628, + 468, + 720 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.5. Training Strategy", + "text_level": 1, + "bbox": [ + 76, + 726, + 250, + 742 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We construct our SATeCo for video super-resolution based on the Stable Diffusion [36] model. There are four training stages to optimize the whole architecture. In the first stage, we train the video upscaler using the Charbonnier loss [5] to optimize the video reconstruction of HR videos. After that, we follow the standard setting in [36] to train UNet for the optimization of the inserted SFA and TFA modules. We fix all parameters of UNet except for the two kinds of modules during training. For the optimization of SFA and TFA modules in VAE decoder, we take the video latent codes of the", + "bbox": [ + 75, + 750, + 470, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "HR videos as the input, and optimize the similarity between the decoded videos and ground-truth HR videos. Finally, we freeze all the parameters in video upscaler, UNet and VAE, and train the video refiner using the pairs of decoded and ground-truth HR videos.", + "bbox": [ + 496, + 349, + 890, + 426 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 498, + 441, + 633, + 459 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Experimental Settings", + "text_level": 1, + "bbox": [ + 498, + 467, + 705, + 484 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We empirically evaluate the effectiveness of our SATeCo on two widely-used datasets: REDS [33] and Vid4 [25]. The REDS dataset consists of 240, 30 and 30 video clips for training, validation and testing. Each video clip contains 100 frames with the resolution of $1,280 \\times 720$ . We employ the standard protocols in [2, 3, 48] and select four video clips from the validation set as the testing data, namely REDS4. The Vid4 dataset also includes four video clips, and there are about 40 frames in each clip with the resolution of $720 \\times 480$ . Following the standard settings [3, 23], we employ all the videos in Vid4 for evaluation and choose the video data in the training set of Vimeo-90K [51] for model optimization. There are 64, 612 training clips and each clip has 7 frames with the resolution of $448 \\times 256$ .", + "bbox": [ + 496, + 491, + 890, + 702 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Implementation Details. We implement our SATeCo on the PyTorch platform by using Diffusers [44] library. The noise scheduler is set as linear scheduler $(\\beta_{1} = 0.00085, \\beta_{T} = 0.0120, \\text{and } T = 1,000)$ . The trade-off parameters $w$ in video refiner is determined as 0.5 by cross validation. We empirically set the window size in TFA as $h = 8$ , $w = 8$ . The frame number $L$ of input clip is 6. The model is trained with AdamW optimizer and the learning rate is $5.0 \\times 10^{-5}$ .", + "bbox": [ + 496, + 703, + 890, + 824 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Evaluation Metrics. We evaluate the VSR models via two kinds of metrics, i.e., pixel-based and perception-based metrics. The pixel-based metrics include PSNR and SSIM which calculate the similarity of every pixel between the generated and ground-truth HR videos. There are also some", + "bbox": [ + 496, + 824, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "9236", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/8e89fa84f260fcb1b7b0253f81692b1cd77e782471946d7ceeea1d127d4c7dfb.jpg", + "image_caption": [ + "Figure 4. Six visual examples of video super-resolution results by different approaches on the REDS4 and Vid4 datasets. The region in the red box is presented in the zoom-in view for comparison." + ], + "image_footnote": [], + "bbox": [ + 117, + 103, + 851, + 477 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "perception-based evaluation metrics for super-resolution. These metrics mainly measure video quality from the viewpoint of human perceptual preference, and we adopt LPIPS [56], DISTS [12], NIQE [32] and CLIP-IQA [45] in this paper. Specifically, LPIPS utilizes VGG [41] model to extract frame features and measures the feature similarity between the synthesized and ground-truth videos. DISTS also computes the feature similarity between video pairs via a variant of VGG model, but the emphasis is on image texture. For NIQE and CLIP-IQA, the scores are directly predicted by the learnt models without using the ground-truth HR videos. NIQE measures the similarity of feature distribution between synthesized frames and a realistic image set [32], while CLIP-IQA computes cosine similarity between generated frames and text prompts (e.g., \"High Resolution\") via CLIP model [35]. In addition, we conduct a user study to verify human preference on different models.", + "bbox": [ + 75, + 521, + 472, + 779 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Comparisons with State-of-the-Art Methods", + "text_level": 1, + "bbox": [ + 76, + 786, + 454, + 803 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We compare our SATeCo with several state-of-the-art techniques, including Bicubic Interpolation, StableSR [46], TOFlow [51], EDVR-M [48], BasicVSR [2], VRT [23] and IconVSR [2], on REDS4 and Vid4 datasets.", + "bbox": [ + 75, + 809, + 468, + 869 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Quantitative Evaluation. Table 1 summarizes the performances of different VSR approaches in terms of the six", + "bbox": [ + 76, + 869, + 470, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "metrics over the two datasets. Overall, SATeCo achieves the best performances across all perception-based metrics (i.e., LPIPS, DISTS, NIQE and CLIP-IQA) on REDS4. These metrics emphasize the quality judgment from human perceptual aspect and the results demonstrate the advantage of exploiting abundant knowledge prior in the pre-trained diffusion models to generate high-quality HR videos with better visual perception. In terms of pixel-based metrics, recent advances [46, 52] manifest that the stochasticity in diffusion models could hurt the preservation of visual appearance in HR videos, resulting in inferior performances to traditional regression models. Our SATeCo, by capitalizing on pixel-wise guidance from LR videos to modulate HR frame feature synthesis, alleviates the downsides and obtains the PSNR of 31.62dB. Notably, such performance is very comparable to that of IconVSR [2], which is the SOTA baseline of regression VSR models. The performance trends on Vid4 are similar with those on REDS4. In particular, SATeCo attains the DISTS of 0.1015, which relatively reduces that of the best competitor VRT [23] by $26.0\\%$ . The results indicate that SATeCo benefits from learning pixel-wise spatial adaption in diffusion to preserve frame-wise image texture for achieving better video fidelity.", + "bbox": [ + 496, + 521, + 893, + 868 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Qualitative Evaluation. Figure 4 visualizes the video super-resolution with six examples from REDS4 and Vid4.", + "bbox": [ + 500, + 869, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "9237", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/ccfdc5641a30ed923d1bb57f6c3fe04827b3bedd11ea9588a7db9761b5634e20.jpg", + "image_caption": [ + "Low Resolution Frame $t$" + ], + "image_footnote": [], + "bbox": [ + 112, + 104, + 272, + 204 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/c5dc7ff17dcb910ccb672f750162c205567edeb39c8c62673d88c208586c98ad.jpg", + "image_caption": [ + "Low Resolution Frame $t + 1$" + ], + "image_footnote": [], + "bbox": [ + 274, + 104, + 434, + 204 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9229339245068d622cf0a751036f7dc99b41aec8c2ec2b6ecf57aeb710743046.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 444, + 92, + 522, + 152 + ], + 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"images/e4a236e993baaa7baf4b04425947f33f6684ffba74a10ee9a58422594cd8d7db.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 611, + 155, + 689, + 215 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/39b729db7ec9905c04ecfe949c9e4348464711994eae0ff6d271e561400900f7.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 92, + 774, + 152 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/611f2207c7321a6c2dce5499d94d8a453bfa1cc7de4e818d5ef330008134de18.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 155, + 774, + 215 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/950dd7be8605d08c21eb0274b282b24d0740c7da7ad8260f79430a2b8a6e6e27.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 779, + 92, + 857, + 152 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9961b0a5b4894c7047380209b6fe0158d13c54ab8a2571745d0483774aad21c6.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 779, + 155, + 857, + 215 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/04f0405f581b043f47f0a062e4fd831af935c1b9a4d2553189ac31120c720042.jpg", + "image_caption": [ + "Low Resolution Frame t" + ], + "image_footnote": [], + "bbox": [ + 112, + 234, + 272, + 334 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/8ca2a8d3a35aa4ec48bd04cd0cd49041c7323f80cf043222185ed93769d2179c.jpg", + "image_caption": [ + "Low Resolution Frame $t + 1$" + ], + "image_footnote": [], + "bbox": [ + 274, + 234, + 434, + 335 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/6fd5a1909db65744a57c98e82f333fdd202b58b95e9ce4bf22a05fe56886e8ac.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 444, + 223, + 522, + 284 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9e63958cdf1622206a5626ac482185309fa3a1c8e61bdb4c48419983ac7c007d.jpg", + "image_caption": [ + "Bicubic" + ], + "image_footnote": [], + "bbox": [ + 444, + 285, + 522, + 345 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/7839cf8edd196eb9c4fb18fb48512c0b17f11c5a22bac031c29387bcd1ebb745.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 527, + 223, + 606, + 284 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/e75eaefaf6aa7e9d342bc3da42548f506c43be65fc3487fb89aa439fbac97023.jpg", + "image_caption": [ + "LDM" + ], + "image_footnote": [], + "bbox": [ + 527, + 285, + 606, + 345 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/523baa5f2f929a7fccfdcbf2c44f900afde4b379295816f06f3246ed4c585ef9.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 611, + 223, + 689, + 284 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/fd3640c2a8f2c79528e350c70112b81a003fd74edeb4228b559c472f01bc26f5.jpg", + "image_caption": [ + "StableSR" + ], + "image_footnote": [], + "bbox": [ + 611, + 285, + 689, + 345 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/998d3ee2a3b74ecc3916df01b7f35af31e008d142ce4e445a671b4399e1cdbb6.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 223, + 774, + 284 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/42c1c8aad7f0bfd152b6e2ad277589124d0494a5b91d1d0d4918a8e7c9a0f577.jpg", + "image_caption": [ + "SATeCo" + ], + "image_footnote": [], + "bbox": [ + 694, + 285, + 774, + 345 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/146eaec14e8f7e859d002766b66b7540b3e206e510bfa0a898f75060b29f0192.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 779, + 223, + 857, + 284 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/e6f6e0e52948277d13e2890157d045a07495055332bc36194df85567b6434efc.jpg", + "image_caption": [ + "GT" + ], + "image_footnote": [], + "bbox": [ + 779, + 285, + 857, + 345 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/3595938b09258414dcba2a1f084ec9b82bda6e9a48b58f9119beefa4f14644bb.jpg", + "image_caption": [ + "Figure 5. Video super-resolution results of two videos in the Vid4 dataset. The region in the same local position across two adjacent frames (i.e., regions highlighted by red and blue boxes) is scaled up to show more details.", + "Figure 6. Human evaluation of user preference ratios between SATeCo and other baselines on REDS4 and Vid4." + ], + "image_footnote": [], + "bbox": [ + 109, + 404, + 434, + 539 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Compared to other baselines, SATeCo can successfully restore more local details (e.g., the sharp edges in the eave and spoke of the 2nd and 3rd case) in frames with high fidelity. Even with large blurriness (e.g., the 4th case), SATeCo still exhibits the strong restoration ability for video super-resolution, which again confirms the effectiveness of leveraging rich knowledge prior of diffusion models and learning spatial adaptation. To further validate the temporal coherence learnt by SATeCo, we visualize two adjacent frames of two synthesized HR videos by using different diffusion-based super-resolution approaches in Figure 5. As observed in the figure, LDM and StableSR synthesize different visual contents across the two frames, e.g., the small windows in the building. In contrast, our SATeCo predicts the HR videos with higher frame consistency and preserves the visual fidelity. That basically validates the merit of performing tubelet-based self-attention within HR videos and cross-attention between HR videos and LR counterparts to achieve better temporal feature interaction and calibration.", + "bbox": [ + 75, + 580, + 468, + 867 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Human Evaluation. Next, we further conduct human study to verify the HR video generation quality by using", + "bbox": [ + 75, + 869, + 468, + 901 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/c6810e74e71c283f85c8812268648dcb159af5d2d13678dfdd3c64b8fef7c0c3.jpg", + "table_caption": [ + "Table 2. Performance comparisons on REDS4 among variants with different integration of SFA and TFA modules." + ], + "table_footnote": [], + "table_body": "
ModelUNetVAEPSNR↑SSIM↑LPIPS↓DISTS↓NIQE↓
SFATFASFATFA
A28.560.79250.21590.07584.404
B✓28.930.80870.20420.06934.349
C✓✓29.450.83980.18920.06204.324
D✓✓✓✓31.620.89320.17350.06074.104
", + "bbox": [ + 500, + 435, + 898, + 542 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "different VSR approaches with respect to the user preference. We invite 100 evaluators on the Amazon MTurk platform, and ask each evaluator to choose the better one from two synthetic HR videos generated by two different methods given the same LR video. Figure 6 depicts the user preference ratios on all eight videos in the REDS4 and Vid4 datasets. SATeCo clearly wins the traditional regression models of IconVSR, BasicVSR and VRT, and the diffusion model of StableSR. The results indicate SATeCo nicely magnifies LR videos with better visual quality and temporal coherence through the spatial feature adaptation and temporal feature alignment design in video diffusion procedure.", + "bbox": [ + 496, + 561, + 890, + 744 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Model Analysis", + "text_level": 1, + "bbox": [ + 500, + 755, + 653, + 771 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Analysis on SFA and TFA modules. We first investigate how the SFA and TFA modules influence the overall performances of video super-resolution. Table 2 lists the performance comparisons among variants with different integration ways of SFA and TFA modules. We start from the basic diffusion model A, which leverages the zero-initialized convolution [55] in UNet/VAE to learn the spatial guidance from LR videos for super-resolution. The model B and C", + "bbox": [ + 496, + 779, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "9238", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/88ec61f3f6b7df5539446fccd7c9ad777825b9a0b124e20303e11daeef8f3acf.jpg", + "table_caption": [ + "Table 3. Ablation studies on the design of video upscaler and video refiner in SATeCo. The performances are reported on REDS4." + ], + "table_footnote": [], + "table_body": "
ModelPSNR↑SSIM↑LPIPS↓DISTS↓NIQE↓
UpscalerPixelShuffle29.770.84260.19790.07204.298
Ours31.620.89320.17350.06074.104
Refinerw = 030.360.85720.15810.03393.457
w = 0.531.620.89320.17350.06074.104
w = 1.028.990.80010.18150.06524.488
", + "bbox": [ + 78, + 125, + 478, + 229 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "gradually upgrade the basic model A through plugging SFA and TFA modules into the UNet, which improves the PSNR from 28.56dB to 29.45dB. Compared to zero-initialized convolution which simply conducts weighted summation of LR frame features and HR ones to guide spatial-level diffusion learning, the combination of SFA and TFA not only enhances the spatial adaptation via feature modulation but also strengthens temporal feature alignment by the tubelet-based attention. As such, the higher PSNR and SSIM which measure the spatial fidelity is attained by the model C. Finally, the model D, i.e., our SATeCo, by further exploiting SFA and TFA in VAE to regulate pixel-space video reconstruction, shows the best performances in PSNR and SSIM. In view of perception-based evaluation metrics, SATeCo also constantly obtains improvements over other variants, indicating the potential benefit from spatial-temporal guidance learning to enhance visual perception in HR videos. Furthermore, Figure 7 showcases video super-resolution in a local region of one example in two adjacent frames. SATeCo reconstructs the HR videos with high-quality visual appearance and promising temporal consistency among adjacent frames, proving the impact of exploring feature adaptation and alignment in diffusion for super-resolution.", + "bbox": [ + 75, + 244, + 472, + 592 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Analysis on Video Upscaler. Then, we study the effectiveness of the video upscaler in the SATeCo. One alternative is to employ the pre-trained Pixel Shuffle layer [40] as the video upscaler. The upper part of Table 3 details the performances of the two approaches on REDS4. Our approach exhibits better performances against PixelShuffle across all evaluation metrics, especially in PSNR and SSIM. Technically, PixelShuffle resamples videos via directly conducting a 2D convolution layer on the input frames. Instead, ours delves into the formulation of frame-wise correlation through temporal mutual self-attention, which is more effective in pixel feature enhancement for video resampling. As such, ours effectively preserves the visual contents in LR videos and facilitates the subsequent video diffusion.", + "bbox": [ + 75, + 595, + 468, + 806 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Analysis on Video Refiner. The video refiner in SATeCo aims for adjusting the decoded HR videos from diffusion model by referring up-sampled original LR videos to alleviate color degradation. The trade-off parameter $w$ in video refiner balances the impact of the visual contents between the decoded videos and the LR videos. To evaluate", + "bbox": [ + 75, + 809, + 470, + 898 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/313aa67c5c46d366ecaae5e3f89267d184ded80e6b084569d3f2276649083f1f.jpg", + "image_caption": [ + "Figure 7. Zoom-in view of two adjacent frames in one video superresolution result synthesized by variants of SATeCo." + ], + "image_footnote": [], + "bbox": [ + 504, + 90, + 890, + 210 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "the influence of the parameter $w$ , we list the VSR performances by varying $w$ in the lower part of Table 3. When $w$ is 0, the performances on perception-based metrics are the best, but there is a slight performance drop on PSNR and SSIM. The performances indicate that the synthesized visual contents by diffusion models are more acceptable for human visual system. In contrast, employing a large value of $w$ (e.g., 1.0) for video refinement considers the information of LR videos more and weakens the contribution of diffusion models, affecting the quality of visual content generation. Therefore, we empirically set the $w$ as 0.5 to seek a good trade-off between the synthesized contents and original visual appearance.", + "bbox": [ + 496, + 257, + 890, + 455 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusions", + "text_level": 1, + "bbox": [ + 500, + 467, + 627, + 483 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We have presented SATeCo that explores spatial adaptation and temporal coherence in diffusion models for video superresolution. In particular, we study the problem of learning spatial-temporal guidance from low-resolution videos to calibrate high-resolution video diffusion procedure. To materialize our idea, SATeCo freezes all the parameters in the pre-trained UNet/VAE, and plugs the spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules in each decoder block to regulate latent-space video denoising and pixel-space video reconstruction. Through learning affine parameters on the guidance of low-resolution videos, SFA modulates the high-resolution features of each pixel to achieve spatial adaptation. TFA performs self-attention within a tubelet to enhance feature interaction and further conducts cross-attention between the tubelet and its low-resolution counterpart to guide temporal feature alignment learning. Experiments conducted on two video datasets, i.e., REDS4 and Vid4, validate the effectiveness of the proposed SATeCo for video super-resolution in terms of both spatial fidelity and temporal consistency.", + "bbox": [ + 496, + 492, + 890, + 794 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments. This work was supported in part by the National Natural Science Foundation of China under Contract 62021001, and in part by the Fundamental Research Funds for the Central Universities under contract WK3490000007. It was also supported by the GPU cluster built by MCC Lab of Information Science and Technology Institution of USTC.", + "bbox": [ + 496, + 795, + 890, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "9239", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Jose Caballero, Christian Ledig, Andrew Aitken, Alejandro Acosta, Johannes Totz, Zehan Wang, and Wenzhe Shi. Realtime Video Super-Resolution with Spatio-Temporal Networks and Motion Compensation. In CVPR, 2017. 2", + "[2] Kelvin CK Chan, Xintao Wang, Ke Yu, Chao Dong, and Chen Change Loy. 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In CVPRW, 2023. 2" + ], + "bbox": [ + 501, + 92, + 890, + 487 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "9241", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Spatial Adaptation and Temporal Coherence in Diffusion Models for Video Super-Resolution/34c7419c-4229-4f4a-ad73-efdadc875a8d_model.json b/2024/Learning Spatial Adaptation and Temporal Coherence in Diffusion Models for Video Super-Resolution/34c7419c-4229-4f4a-ad73-efdadc875a8d_model.json new file mode 100644 index 0000000000000000000000000000000000000000..dd289e5c3fe06db57798a01d7ce7a63063dd97e9 --- /dev/null +++ b/2024/Learning Spatial Adaptation and Temporal Coherence in Diffusion Models for Video Super-Resolution/34c7419c-4229-4f4a-ad73-efdadc875a8d_model.json @@ -0,0 +1,2376 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.109, + 0.13, + 0.862, + 0.176 + ], + "angle": 0, + "content": "Learning Spatial Adaptation and Temporal Coherence in Diffusion Models for Video Super-Resolution*" + }, + { + "type": "text", + "bbox": [ + 0.086, + 0.205, + 0.916, + 0.257 + ], + "angle": 0, + "content": "Zhikai Chen†, Fuchen Long§, Zhaofan Qiu§, Ting Yao§, Wengang Zhou†, Jiebo Luo‡, and Tao Mei§ \n†MoE Key Laboratory of Brain-inspired Intelligent Perception and Cognition, University of Science and Technology of China \n‡University of Rochester, Rochester, NY USA §HiDream.ai Inc." + }, + { + "type": "text", + "bbox": [ + 0.213, + 0.26, + 0.796, + 0.275 + ], + "angle": 0, + "content": "czk654@mail.ustc.edu.cn,{longfuchen, qiuzhaofan,tiyao}@hidream.ai" + }, + { + "type": "text", + "bbox": [ + 0.255, + 0.278, + 0.754, + 0.292 + ], + "angle": 0, + "content": "zhwg@ustc.edu.cn, jluo@cs.ROchester.edu, tmei@hidream.ai" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.327, + 0.313, + 0.343 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.359, + 0.474, + 0.722 + ], + "angle": 0, + "content": "Diffusion models are just at a tipping point for image super-resolution task. Nevertheless, it is not trivial to capitalize on diffusion models for video super-resolution which necessitates not only the preservation of visual appearance from low-resolution to high-resolution videos, but also the temporal consistency across video frames. In this paper, we propose a novel approach, pursuing Spatial Adaptation and Temporal Coherence (SATeCo), for video super-resolution. SATeCo pivots on learning spatial-temporal guidance from low-resolution videos to calibrate both latent-space high-resolution video denoising and pixel-space video reconstruction. Technically, SATeCo freezes all the parameters of the pre-trained UNet and VAE, and only optimizes two deliberately-designed spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules, in the decoder of UNet and VAE. SFA modulates frame features via adaptively estimating affine parameters for each pixel, guaranteeing pixel-wise guidance for high-resolution frame synthesis. TFA delves into feature interaction within a 3D local window (tubelet) through self-attention, and executes cross-attention between tubelet and its low-resolution counterpart to guide temporal feature alignment. Extensive experiments conducted on the REDS4 and Vid4 datasets demonstrate the effectiveness of our approach." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.749, + 0.208, + 0.765 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.774, + 0.47, + 0.88 + ], + "angle": 0, + "content": "In recent years, diffusion models [11, 36, 37, 55] have shown great progress in revolutionizing image generation. In between, a series of image super-resolution works [36, 46, 52] benefit from leveraging knowledge prior embedded in diffusion models to upscale low-resolution (LR) images into high-resolution (HR) ones. Compared to 2D images, videos have one more time dimension, bringing" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.335, + 0.693, + 0.417 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.581, + 0.418, + 0.619, + 0.425 + ], + "angle": 0, + "content": "Frame t" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.335, + 0.882, + 0.417 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.765, + 0.418, + 0.812, + 0.425 + ], + "angle": 0, + "content": "Frame t+1" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.427, + 0.694, + 0.469 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.564, + 0.469, + 0.635, + 0.477 + ], + "angle": 0, + "content": "Low Resolution" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.427, + 0.882, + 0.469 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.779, + 0.469, + 0.799, + 0.477 + ], + "angle": 0, + "content": "VRT" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.479, + 0.694, + 0.52 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.578, + 0.521, + 0.62, + 0.529 + ], + "angle": 0, + "content": "StableSR" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.479, + 0.882, + 0.52 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.771, + 0.521, + 0.807, + 0.529 + ], + "angle": 0, + "content": "SATeCo" + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.532, + 0.892, + 0.587 + ], + "angle": 0, + "content": "Figure 1. An illustration of video super-resolution by using different approaches of StableSR [46], VRT [23] and our SATeCo to generate two adjacent frames. The region in the same local position is presented in the zoom-in view." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.893, + 0.853 + ], + "angle": 0, + "content": "more challenges when capitalizing on diffusion models for video super-resolution (VSR). One natural way is to utilize the pre-trained diffusion models for image super-resolution (ISR), e.g., StableSR [46], to magnify each video frame. The representative advances [46, 52] manifest that diffusion models for ISR could synthesize more details than traditional regression models, e.g., VRT [23]. As depicted in Figure 1, the edges of the windows in the building produced by StableSR are much clearer than those generated by VRT. Nevertheless, the inherent stochasticity of diffusion models might jeopardize the spatial fidelity and hallucinate some extra visual content. Moreover, the independent frame-wise super-resolution overlooks the relation across consecutive frames, resulting in the issue of frame inconsistency in the high-resolution videos. For instance, the traffic signs in Figure 1 are totally different between the two adjacent frames generated by StableSR." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In general, the difficulty of exploring diffusion models for video super-resolution originates from two aspects: 1) how to alleviate the stochasticity in diffusion process to pre" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.347, + 0.9 + ], + "angle": 0, + "content": "*This work was performed at HiDream.ai." + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9232" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.333 + ], + "angle": 0, + "content": "serve visual appearance? 2) how to guarantee the temporal consistency across frames in the HR videos? We propose to address the two issues through learning spatial-temporal guidance from low-resolution videos to manage diffusion procedure for video super-resolution. To regulate spatial adaptation, we estimate affine parameters on the LR frame features to modulate each pixel in HR frames. As such, the pixel-wise guidance is employed to nicely learn the feature of every pixel in HR frames and better improve spatial fidelity. In an effort to temporally cohere video frames, we strengthen feature interaction across HR frames, and feature calibration between HR frames and LR counterpart via the attention mechanism. Moreover, large receptive field is attained by conducting the self-attention and cross-attention on the features within a 3D local window (tubelet), thereby facilitating temporal feature alignment." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.334, + 0.473, + 0.681 + ], + "angle": 0, + "content": "To materialize our idea, we present a new SATeCo method to carry out Spatial Adaptation and Temporal Coherence for video super-resolution. Technically, SATeCo uses a transformer-based video upscaler to up-sample the input LR video. The VAE encoder then extracts the video features and latent code of LR video, which are further exploited for diffusion calibration. SATeCo deliberately devises spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules, and inserts the two modules into each decoder block of UNet and VAE, for latent-space video denoising and pixel-space video reconstruction. In the regularization of latent-space video denoising, SFA exploits two convolutional layers on the latent code of each up-sampled LR frame, to predict a scale and bias to modulate the pixel-wise feature of HR frame. TFA first executes self-attention on HR video latent code within a tubelet to enhance feature interaction, and further performs cross-attention between the tubelet and its LR counterpart for feature calibration in HR video. The LR video features are exploited in the same way to regulate the HR video feature learning in pixel-space video reconstruction. SATeCo finally refines the decoded HR video by referring to the up-sampled LR video via a neural network to balance synthesized quality and fidelity." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.681, + 0.473, + 0.817 + ], + "angle": 0, + "content": "The main contribution of this paper is the proposal of SATeCo to explore spatial adaptation and temporal coherence in diffusion models for video super-resolution. The solution also leads to the elegant views of how to leverage pixel-wise information from LR videos for visual appearance preservation, and how to achieve frame consistency in HR video generation. Extensive experiments on REDS4 and Vid4 verify the superiority of SATeCo in terms of both spatial quality and temporal consistency." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.83, + 0.22, + 0.847 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Video super-resolution. Modern VSR approaches are mainly based on deep neural networks and can be grouped into two categories, i.e., sliding window-based methods and" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.485 + ], + "angle": 0, + "content": "recurrent methods. Early sliding window-based VSR techniques [1, 22, 50, 51, 53] rely on 2D or 3D CNNs [19, 20] which incorporate a sequence of LR frames to predict center HR frame. To fully utilize the complementary information across adjacent frames, the deformable convolutions [43, 48] are employed for feature alignment. Inspired by the success of transformer architecture in various computer vision tasks [6, 27-29], self-attention emerges to be integrated into the VSR frameworks [14, 23, 26, 47]. One representative is VRT [23] which plugs the temporal mutual attention block into transformer backbone to facilitate motion estimation, feature alignment and fusion. Nevertheless, the sliding window-based approaches are difficult to capture long-range dependencies which could limit the performance of video super-resolution. In contrast to aggregate information from adjacent frames in a short term, recurrent approaches [2, 3, 15, 17, 18, 24, 38, 39, 54] utilize a hidden state to sequentially propagate information from all previous frames to the current frame, benefiting the frame restoration. For instance, Chan et al. [2] adopt a bidirectional propagation scheme with flow-based feature alignment to maximize information gathering in super resolution. Despite having the great capacity of the recurrent models for temporal information gathering, the local details are still hard to be restored when the LR video encounters significant degradation in a long temporal range." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.489, + 0.895, + 0.807 + ], + "angle": 0, + "content": "Diffusion models for super-resolution. Impressive performances of image synthesis achieved by diffusion models [7, 11, 16, 30, 34, 55] encourage the deployment on image super-resolution. These explorations [9, 10, 13, 21, 31, 42, 49, 57] leverage the knowledge prior embedded in the pre-trained diffusion models to magnify images. For example, StableSR [46] integrates a time-aware encoder into Stable-Diffusion [36] model without altering the pre-trained weights, and achieves promising super-resolution results. To further enhance the reconstruction of image texture details, Yang et al. [52] introduce an attention-based control module to maintain pixel consistency between LR and HR images. Different from the advances which optimize a small part of inserted parameters, several approaches [13, 21, 49] fix all weights in the pre-trained synthesis model and attempt to incorporate constraints into the reverse diffusion process to guide image restoration. Although the effectiveness of knowledge prior has been manifested in various diffusion-based ISR methods, it is still a grand challenge to employ diffusion models for video super-resolution and preserve spatial fidelity and temporal consistency." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.895, + 0.901 + ], + "angle": 0, + "content": "In summary, our work mainly focuses on diffusion models for video super-resolution. The proposal of SATeCo contributes by exploring not only how to preserve spatial fidelity through modulating HR frame features, but also how to calibrate HR video features with LR counterpart for better temporal feature alignment." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "9233" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.102, + 0.097, + 0.87, + 0.221 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.232, + 0.895, + 0.332 + ], + "angle": 0, + "content": "Figure 2. An overview of our SATeCo architecture. The input LR video \\( X_{L} \\) is first up-sampled to the target resolution via a transformer-based video upscaler. Then, the up-sampled video \\( X_{u} \\) is fed into the VAE encoder to extract the video features and latent code \\( Z \\). Next, the Gaussian noise is added into \\( Z \\) according to the diffusion scheduler, and the noisy video latent code is then restored by UNet for quality enhancement. In latent space, a latent encoder extracts the LR latent feature maps \\( G \\) on the LR latent code \\( Z \\), followed by spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules in each decoder block of UNet for spatial-temporal guidance learning. Given the denoised video latent code \\( Z_{0} \\), the VAE decoder decodes the video \\( X_{d} \\) based on the guidance learnt by SFA and TFA on LR video features. Finally, the decoded video \\( X_{d} \\) is adjusted by a video refiner via referring to \\( X_{u} \\) for final HR video \\( X_{H} \\) synthesis." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.337, + 0.226, + 0.354 + ], + "angle": 0, + "content": "3. Our Approach" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.364, + 0.473, + 0.728 + ], + "angle": 0, + "content": "In this section, we present our newly-minted SATeCo, pursuing Spatial Adaptation and Temporal Coherence in diffusion models for video super-resolution. Figure 2 depicts an overview of the architecture. SATeCo begins with a video upscaler to increase the resolution of the input LR video. Then, the up-sampled video is fed into VAE encoder for video feature extraction and latent code prediction. After that, a spatial feature adaptation (SFA) and a temporal feature alignment (TFA) module are leveraged to learn spatial-temporal guidance on latent code and features of LR video, to calibrate latent-space video denoising and pixel-space video reconstruction. As such, the two modules are plugged into each block of the decoder in UNet and VAE. In procedure of video latent code denoising, SFA estimates the affine parameters on LR video latent code to modulate each pixel of the HR video latent code. TFA first performs self-attention on the HR video latent code within a tubelet, and further enhances latent code by executing cross-attention between the tubelet and its LR counterpart. Similarly, SFA and TFA are conducted in the VAE decoder to guide HR video reconstruction with the LR video features. Finally, SATeCo designs a video refiner to adjust the decoded HR video by referring to the up-sampled video for a good trade-off between synthesized quality and fidelity." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.74, + 0.233, + 0.757 + ], + "angle": 0, + "content": "3.1. Video Upscaler" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Most existing VSR approaches [39, 51] first upscale the input LR videos through a resampling operation, and then improve their visual quality. Nevertheless, the widely adopted resampling operations, e.g., Bilinear and Bicubic sampling, might damage the original visual patterns [39] in LR frames, having a negative impact on the subsequent video enhancement. Therefore, we exploit the recipe of reducing frame degradation ahead of the feature learning [4] in neural networks and propose a video upscaler, which gen" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.339, + 0.892, + 0.368 + ], + "angle": 0, + "content": "erates more accurate up-sampled videos for the following quality enhancement by diffusion models." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.369, + 0.893, + 0.49 + ], + "angle": 0, + "content": "Given the input LR video \\(X_{L}\\), we utilize a transformer-based video upscaler for video up-scaling as illustrated in Figure 3(a). It consists of two cascaded temporal mutual self-attention (TMSA) blocks [23] to temporally aggregate video features, and a pixel-shuffle layer [40] to increase video spatial resolution via feature reshaping. The upsampled video \\(X_{u} = \\{x_{u}^{i}\\}_{i=1}^{L}\\) with \\(L\\) frames is then fed into the diffusion model for video quality enhancement." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.5, + 0.809, + 0.516 + ], + "angle": 0, + "content": "3.2. Spatial Feature Adaptation Module" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.523, + 0.892, + 0.78 + ], + "angle": 0, + "content": "The inherent stochasticity [52] of diffusion models might result in the distortion of texture details in image superresolution. A natural way of employing diffusion models for super-resolution is to learn the spatial-level condition via convolution-based [46] or transformer-based [52] structure to guide latent code denoising in UNet. Such kind of mechanism only manages feature regularization in latent space, posting difficulty to learn sufficient inductive bias and provide precise guidance for high-resolution image restoration. The similar issue also exists in video superresolution. To alleviate this, we introduce a spatial feature adaptation (SFA) module which dynamically learns pixelwise guidance from the input LR videos for diffusion calibration. In the meanwhile, the SFA module emphasizes the inductive bias learning in both of the latent-space video denoising (i.e., training of UNet) and pixel-space video reconstruction (i.e., training of VAE)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.781, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Figure 3(c) illustrates our SFA module. Given the upsampled LR video \\( X_{u} \\), the VAE encoder first encodes \\( X_{u} \\) into the video latent code \\( Z = \\{z^{i}\\}_{i = 1}^{L} \\). Next, we exploit a convolution-based latent encoder \\( \\mathcal{E}_z \\) to extract the LR latent feature maps \\( G = \\mathcal{E}_z(Z) \\), which are further utilized to guide the HR feature learning in UNet decoder. Formally, we denote the HR intermediate feature maps in UNet and the LR latent feature maps in latent encoder as" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9234" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.105, + 0.098, + 0.28, + 0.245 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.293, + 0.099, + 0.534, + 0.246 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.545, + 0.1, + 0.867, + 0.246 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.08, + 0.256, + 0.888, + 0.271 + ], + "angle": 0, + "content": "Figure 3. An illustration of (a) video upscaler, (b) video refiner, (c) spatial feature adaptation and (d) temporal feature alignment module." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.287, + 0.47, + 0.364 + ], + "angle": 0, + "content": "\\(F = \\{f^{i}\\}_{i = 1}^{L}\\) and \\(G = \\{g^i\\}_{i = 1}^L\\) , respectively. For the \\(i\\) -th frame, we measure a scale ratio \\(S^i\\in \\mathbb{R}^{H\\times W\\times C}\\) and a bias \\(M^i\\in \\mathbb{R}^{H\\times W\\times C}\\) for each pixel of HR intermediate feature map \\(f^{i}\\in \\mathbb{R}^{H\\times W\\times C}\\) based on the LR latent feature map \\(g^{i}\\in \\mathbb{R}^{H\\times W\\times C}\\) via two 2D convolution layers:" + }, + { + "type": "equation", + "bbox": [ + 0.131, + 0.372, + 0.469, + 0.39 + ], + "angle": 0, + "content": "\\[\nM ^ {i} = \\operatorname {C o n v 2 D} (g ^ {i}), \\quad S ^ {i} = \\operatorname {C o n v 2 D} (g ^ {i}). \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.398, + 0.469, + 0.445 + ], + "angle": 0, + "content": "Then, the output HR feature map \\(\\tilde{f}^i\\) in UNet is generated by modulating the normalized HR intermediate feature map \\(f^i\\) with \\(S^i\\) and \\(M^i\\) as:" + }, + { + "type": "equation", + "bbox": [ + 0.182, + 0.452, + 0.469, + 0.483 + ], + "angle": 0, + "content": "\\[\n\\tilde {f} ^ {i} = S ^ {i} \\odot \\frac {f ^ {i} - \\mu^ {i}}{\\sigma^ {i}} + M ^ {i}, \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.492, + 0.469, + 0.718 + ], + "angle": 0, + "content": "where \\(\\odot\\) denotes point-wise multiplication. \\(\\mu^i\\) and \\(\\sigma^i\\) are the mean and standard deviation values of the feature map \\(f^i\\). Hence, the affine parameters estimated on the latent feature maps of LR videos calibrate the intermediate feature maps of HR videos in latent code denoising, which adaptively injects the pixel-wise information into the video latent code to preserve the visual appearance. For video feature learning in pixel space, SFA module is inserted into each block of VAE decoder. Similarly, the extracted video features of LR videos are taken as the guidance to estimate the affine parameters in SFA module to adjust HR video feature learning for video reconstruction. We take all the modulated intermediate feature maps \\(\\tilde{f}^i\\) from SFA module as \\(\\tilde{F} = \\{\\tilde{f}^i\\}_{i=1}^L\\), which is employed for the following temporal feature alignment in the UNet and VAE decoders." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.727, + 0.4, + 0.743 + ], + "angle": 0, + "content": "3.3. Temporal Feature Alignment Module" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.469, + 0.9 + ], + "angle": 0, + "content": "Frame-wisely conducting ISR models for video super-resolution could amplify the differences of blurry patterns [39] across frames, leading to content inconsistency such as the object shape deformation. The issue originated from solely relying on spatial level super-resolution and lacking temporal coherence modeling across frames. To facilitate visual content alignment in video super-resolution, a temporal feature alignment (TFA) module is devised after each SFA module in UNet and VAE decoder, for the temporal feature interaction and calibration." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.288, + 0.892, + 0.438 + ], + "angle": 0, + "content": "Figure 3(d) depicts the learning procedure of TFA module. Given the input HR intermediate feature maps \\(\\tilde{F} = \\{\\tilde{f}^i\\}_{i=1}^L\\) from the SFA module in UNet decoder, we first partition the feature map \\(\\tilde{f}^i\\) of each frame into \\(N\\) non-overlapping windows with the spatial resolution of \\(h \\times w\\). \\(N = \\frac{HW}{hw}\\) is the total window number. Then, we link all features within a local window across \\(L\\) frames to form a HR feature tubelet \\(\\tilde{F}_{tub} \\in \\mathbb{R}^{L \\times h \\times w \\times C}\\). We reshape the dimension of each HR feature tubelet into \\(hwL \\times C\\) and execute the standard self-attention on it:" + }, + { + "type": "equation", + "bbox": [ + 0.597, + 0.446, + 0.892, + 0.472 + ], + "angle": 0, + "content": "\\[\nQ, K, V = \\operatorname {C o n v 3 D} (\\tilde {F} _ {t u b}), \\tag {3}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.599, + 0.468, + 0.794, + 0.485 + ], + "angle": 0, + "content": "\\[\n\\hat {F} _ {t u b} = \\operatorname {A t t e n t i o n} (Q, K, V),\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.495, + 0.892, + 0.662 + ], + "angle": 0, + "content": "where \\(Q, K, V \\in \\mathbb{R}^{hwL \\times C}\\) are the query, key and value matrices, respectively. Each of them is predicted by a 3D convolution layer. The self-attention conducted on the HR feature tubelet enables the feature interaction across different frames, mitigating the temporal feature misalignment in local regions. To further conduct the temporal feature calibration, we leverage the counterpart of HR feature tubelet, i.e., the feature tubelet \\(G_{tub}\\) of the LR latent feature maps, as a reference for feature adjustment. We perform the cross-attention between \\(\\hat{F}_{tub}\\) and \\(G_{tub}\\) to obtain the output feature tubelet \\(\\bar{F}_{tub}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.515, + 0.671, + 0.891, + 0.695 + ], + "angle": 0, + "content": "\\[\nQ ^ {\\prime} = \\operatorname {C o n v 3 D} \\left(\\hat {F} _ {t u b}\\right), \\quad K ^ {\\prime}, V ^ {\\prime} = \\operatorname {C o n v 3 D} \\left(G _ {t u b}\\right), \\tag {4}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.518, + 0.691, + 0.726, + 0.707 + ], + "angle": 0, + "content": "\\[\n\\bar {F} _ {t u b} = \\operatorname {A t t e n t i o n} \\left(Q ^ {\\prime}, K ^ {\\prime}, V ^ {\\prime}\\right),\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.892, + 0.825 + ], + "angle": 0, + "content": "where the query \\(Q^{\\prime}\\) is learnt on the HR feature tubelet \\(\\hat{F}_{tub}\\) and the key/value \\(K^{\\prime} / V^{\\prime}\\) is estimated on the LR counterpart via 3D convolution layers, respectively. We collect all the output feature tubelets from the TFA module and reshape them into the original size as \\(\\bar{F}\\in \\mathbb{R}^{L\\times H\\times W\\times C}\\). The output feature \\(\\bar{F}\\) is then fed into the next block of the decoder in UNet or VAE for video latent denoising or reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In this way, the coupled SFA and TFA modules in UNet and VAE decoder not only emphasize the pixel-wise feature adaptation for visual appearance preservation but also strengthen the temporally feature interaction and calibration for temporal coherence modeling." + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9235" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.089, + 0.895, + 0.133 + ], + "angle": 0, + "content": "Table 1. Performance comparisons in terms of pixel-based (PSNR and SSIM) and perception-based (LPIPS, DISTS, NIQE and CLIP-IQA) evaluation metrics on the REDS4 and Vid4 datasets. The width and height of the LR videos are rescaled by 4 times through different VSR approaches. We follow VRT [23] to set the frame number as 6 in each clip for HR video inference." + }, + { + "type": "table", + "bbox": [ + 0.084, + 0.137, + 0.88, + 0.334 + ], + "angle": 0, + "content": "
DatasetsMetricsBicubicStableSR [46]TOFlow [51]EDVR-M [48]BasicVSR [2]VRT [23]IconVSR [2]SATeCo
REDS4PSNR↑26.1424.7927.9830.5331.4231.6031.6731.62
SSIM↑0.72920.68970.79900.86990.89090.88880.89480.8932
LPIPS↓0.35190.24120.31040.23120.20230.20770.19390.1735
DISTS↓0.18760.07550.14680.09430.08080.08230.07620.0607
NIQE↓7.2574.1166.2604.5444.1974.2524.1174.104
CLIP-IQA↑0.60450.65790.61760.63820.63530.63790.61620.6622
Vid4PSNR↑23.7822.1825.8927.1027.2427.9327.3927.44
SSIM↑0.63470.59040.76510.81860.82510.84250.82790.8420
LPIPS↓0.39470.36700.33860.28980.28110.27230.27390.2291
DISTS↓0.22010.13850.17760.14680.14420.13720.14060.1015
NIQE↓7.5365.2377.2295.5285.3405.2425.3925.212
CLIP-IQA↑0.68170.76440.73650.73800.74100.74340.74110.7451
" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.351, + 0.221, + 0.366 + ], + "angle": 0, + "content": "3.4. Video Refiner" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.374, + 0.47, + 0.51 + ], + "angle": 0, + "content": "Recent advance [8] reveals that images synthesized by diffusion model conditioning on visual contents might lose some original color information in local regions. To address this problem, StableSR [46] performs a non-parametric post-processor to refine the generation with reference to original input for achieving color preservation. Instead, we propose a trainable video refiner to emphasize the adjustment of decoded HR video from VAE decoder, by leveraging the information from up-sampled LR video." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.51, + 0.47, + 0.601 + ], + "angle": 0, + "content": "Figure 3(b) details the structure of our video refiner. We first concatenate the decoded video \\( X_{d} \\) and the up-sampled LR video \\( X_{u} \\) along channel dimension, and then feed it into a residual block. The refined HR video \\( X_{H} \\) is generated by fusing \\( X_{u} \\), \\( X_{d} \\) and the output feature mapping of residual block as:" + }, + { + "type": "equation", + "bbox": [ + 0.09, + 0.607, + 0.47, + 0.625 + ], + "angle": 0, + "content": "\\[\nX _ {H} = w X _ {u} + (1 - w) X _ {d} + \\operatorname {R e s B l o c k} ([ X _ {u}, X _ {d} ]), \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.469, + 0.721 + ], + "angle": 0, + "content": "where \\( w \\) is a trade-off parameter. The devised video refiner balances the original visual contents of the up-sampled LR video and the synthesized contents of decoded HR video via feature fusion learning. Accordingly, our design is more powerful in terms of color preservation, and achieves a good trade-off between the synthesized quality and fidelity." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.727, + 0.251, + 0.743 + ], + "angle": 0, + "content": "3.5. Training Strategy" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.901 + ], + "angle": 0, + "content": "We construct our SATeCo for video super-resolution based on the Stable Diffusion [36] model. There are four training stages to optimize the whole architecture. In the first stage, we train the video upscaler using the Charbonnier loss [5] to optimize the video reconstruction of HR videos. After that, we follow the standard setting in [36] to train UNet for the optimization of the inserted SFA and TFA modules. We fix all parameters of UNet except for the two kinds of modules during training. For the optimization of SFA and TFA modules in VAE decoder, we take the video latent codes of the" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.351, + 0.892, + 0.428 + ], + "angle": 0, + "content": "HR videos as the input, and optimize the similarity between the decoded videos and ground-truth HR videos. Finally, we freeze all the parameters in video upscaler, UNet and VAE, and train the video refiner using the pairs of decoded and ground-truth HR videos." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.443, + 0.634, + 0.46 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.468, + 0.707, + 0.485 + ], + "angle": 0, + "content": "4.1. Experimental Settings" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.492, + 0.892, + 0.703 + ], + "angle": 0, + "content": "Datasets. We empirically evaluate the effectiveness of our SATeCo on two widely-used datasets: REDS [33] and Vid4 [25]. The REDS dataset consists of 240, 30 and 30 video clips for training, validation and testing. Each video clip contains 100 frames with the resolution of \\(1,280 \\times 720\\). We employ the standard protocols in [2, 3, 48] and select four video clips from the validation set as the testing data, namely REDS4. The Vid4 dataset also includes four video clips, and there are about 40 frames in each clip with the resolution of \\(720 \\times 480\\). Following the standard settings [3, 23], we employ all the videos in Vid4 for evaluation and choose the video data in the training set of Vimeo-90K [51] for model optimization. There are 64, 612 training clips and each clip has 7 frames with the resolution of \\(448 \\times 256\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.704, + 0.892, + 0.825 + ], + "angle": 0, + "content": "Implementation Details. We implement our SATeCo on the PyTorch platform by using Diffusers [44] library. The noise scheduler is set as linear scheduler \\((\\beta_{1} = 0.00085, \\beta_{T} = 0.0120, \\text{and } T = 1,000)\\). The trade-off parameters \\(w\\) in video refiner is determined as 0.5 by cross validation. We empirically set the window size in TFA as \\(h = 8\\), \\(w = 8\\). The frame number \\(L\\) of input clip is 6. The model is trained with AdamW optimizer and the learning rate is \\(5.0 \\times 10^{-5}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Evaluation Metrics. We evaluate the VSR models via two kinds of metrics, i.e., pixel-based and perception-based metrics. The pixel-based metrics include PSNR and SSIM which calculate the similarity of every pixel between the generated and ground-truth HR videos. There are also some" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9236" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.118, + 0.104, + 0.852, + 0.478 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.485, + 0.893, + 0.514 + ], + "angle": 0, + "content": "Figure 4. Six visual examples of video super-resolution results by different approaches on the REDS4 and Vid4 datasets. The region in the red box is presented in the zoom-in view for comparison." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.522, + 0.473, + 0.78 + ], + "angle": 0, + "content": "perception-based evaluation metrics for super-resolution. These metrics mainly measure video quality from the viewpoint of human perceptual preference, and we adopt LPIPS [56], DISTS [12], NIQE [32] and CLIP-IQA [45] in this paper. Specifically, LPIPS utilizes VGG [41] model to extract frame features and measures the feature similarity between the synthesized and ground-truth videos. DISTS also computes the feature similarity between video pairs via a variant of VGG model, but the emphasis is on image texture. For NIQE and CLIP-IQA, the scores are directly predicted by the learnt models without using the ground-truth HR videos. NIQE measures the similarity of feature distribution between synthesized frames and a realistic image set [32], while CLIP-IQA computes cosine similarity between generated frames and text prompts (e.g., \"High Resolution\") via CLIP model [35]. In addition, we conduct a user study to verify human preference on different models." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.787, + 0.455, + 0.804 + ], + "angle": 0, + "content": "4.2. Comparisons with State-of-the-Art Methods" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.47, + 0.87 + ], + "angle": 0, + "content": "We compare our SATeCo with several state-of-the-art techniques, including Bicubic Interpolation, StableSR [46], TOFlow [51], EDVR-M [48], BasicVSR [2], VRT [23] and IconVSR [2], on REDS4 and Vid4 datasets." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Quantitative Evaluation. Table 1 summarizes the performances of different VSR approaches in terms of the six" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.522, + 0.895, + 0.869 + ], + "angle": 0, + "content": "metrics over the two datasets. Overall, SATeCo achieves the best performances across all perception-based metrics (i.e., LPIPS, DISTS, NIQE and CLIP-IQA) on REDS4. These metrics emphasize the quality judgment from human perceptual aspect and the results demonstrate the advantage of exploiting abundant knowledge prior in the pre-trained diffusion models to generate high-quality HR videos with better visual perception. In terms of pixel-based metrics, recent advances [46, 52] manifest that the stochasticity in diffusion models could hurt the preservation of visual appearance in HR videos, resulting in inferior performances to traditional regression models. Our SATeCo, by capitalizing on pixel-wise guidance from LR videos to modulate HR frame feature synthesis, alleviates the downsides and obtains the PSNR of 31.62dB. Notably, such performance is very comparable to that of IconVSR [2], which is the SOTA baseline of regression VSR models. The performance trends on Vid4 are similar with those on REDS4. In particular, SATeCo attains the DISTS of 0.1015, which relatively reduces that of the best competitor VRT [23] by \\(26.0\\%\\). The results indicate that SATeCo benefits from learning pixel-wise spatial adaption in diffusion to preserve frame-wise image texture for achieving better video fidelity." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Qualitative Evaluation. Figure 4 visualizes the video super-resolution with six examples from REDS4 and Vid4." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9237" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.113, + 0.105, + 0.273, + 0.205 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.133, + 0.207, + 0.254, + 0.216 + ], + "angle": 0, + "content": "Low Resolution Frame \\(t\\)" + }, + { + "type": "image", + "bbox": [ + 0.276, + 0.106, + 0.436, + 0.205 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.29, + 0.207, + 0.423, + 0.216 + ], + "angle": 0, + "content": "Low Resolution Frame \\(t + 1\\)" + }, + { + "type": "image", + "bbox": [ + 0.445, + 0.093, + 0.524, + 0.154 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.446, + 0.156, + 0.524, + 0.217 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.528, + 0.093, + 0.606, + 0.154 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.528, + 0.156, + 0.607, + 0.217 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.612, + 0.093, + 0.69, + 0.154 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.612, + 0.156, + 0.69, + 0.217 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.093, + 0.775, + 0.154 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.156, + 0.775, + 0.217 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.78, + 0.093, + 0.859, + 0.154 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.78, + 0.156, + 0.859, + 0.217 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.113, + 0.235, + 0.273, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.133, + 0.337, + 0.256, + 0.347 + ], + "angle": 0, + "content": "Low Resolution Frame t" + }, + { + "type": "image", + "bbox": [ + 0.276, + 0.235, + 0.436, + 0.336 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.291, + 0.338, + 0.425, + 0.347 + ], + "angle": 0, + "content": "Low Resolution Frame \\(t + 1\\)" + }, + { + "type": "image", + "bbox": [ + 0.445, + 0.224, + 0.524, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.445, + 0.286, + 0.524, + 0.347 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.466, + 0.348, + 0.504, + 0.357 + ], + "angle": 0, + "content": "Bicubic" + }, + { + "type": "image", + "bbox": [ + 0.528, + 0.224, + 0.607, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.528, + 0.286, + 0.607, + 0.347 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.559, + 0.348, + 0.584, + 0.356 + ], + "angle": 0, + "content": "LDM" + }, + { + "type": "image", + "bbox": [ + 0.612, + 0.224, + 0.69, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.612, + 0.286, + 0.69, + 0.347 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.631, + 0.348, + 0.676, + 0.357 + ], + "angle": 0, + "content": "StableSR" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.224, + 0.776, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.286, + 0.776, + 0.347 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.715, + 0.348, + 0.754, + 0.357 + ], + "angle": 0, + "content": "SATeCo" + }, + { + "type": "image", + "bbox": [ + 0.78, + 0.224, + 0.859, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.78, + 0.286, + 0.859, + 0.347 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.813, + 0.348, + 0.828, + 0.356 + ], + "angle": 0, + "content": "GT" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.369, + 0.891, + 0.397 + ], + "angle": 0, + "content": "Figure 5. Video super-resolution results of two videos in the Vid4 dataset. The region in the same local position across two adjacent frames (i.e., regions highlighted by red and blue boxes) is scaled up to show more details." + }, + { + "type": "image", + "bbox": [ + 0.11, + 0.405, + 0.436, + 0.54 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.542, + 0.468, + 0.57 + ], + "angle": 0, + "content": "Figure 6. Human evaluation of user preference ratios between SATeCo and other baselines on REDS4 and Vid4." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.582, + 0.469, + 0.868 + ], + "angle": 0, + "content": "Compared to other baselines, SATeCo can successfully restore more local details (e.g., the sharp edges in the eave and spoke of the 2nd and 3rd case) in frames with high fidelity. Even with large blurriness (e.g., the 4th case), SATeCo still exhibits the strong restoration ability for video super-resolution, which again confirms the effectiveness of leveraging rich knowledge prior of diffusion models and learning spatial adaptation. To further validate the temporal coherence learnt by SATeCo, we visualize two adjacent frames of two synthesized HR videos by using different diffusion-based super-resolution approaches in Figure 5. As observed in the figure, LDM and StableSR synthesize different visual contents across the two frames, e.g., the small windows in the building. In contrast, our SATeCo predicts the HR videos with higher frame consistency and preserves the visual fidelity. That basically validates the merit of performing tubelet-based self-attention within HR videos and cross-attention between HR videos and LR counterparts to achieve better temporal feature interaction and calibration." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.469, + 0.902 + ], + "angle": 0, + "content": "Human Evaluation. Next, we further conduct human study to verify the HR video generation quality by using" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.403, + 0.891, + 0.431 + ], + "angle": 0, + "content": "Table 2. Performance comparisons on REDS4 among variants with different integration of SFA and TFA modules." + }, + { + "type": "table", + "bbox": [ + 0.501, + 0.436, + 0.9, + 0.543 + ], + "angle": 0, + "content": "
ModelUNetVAEPSNR↑SSIM↑LPIPS↓DISTS↓NIQE↓
SFATFASFATFA
A28.560.79250.21590.07584.404
B✓28.930.80870.20420.06934.349
C✓✓29.450.83980.18920.06204.324
D✓✓✓✓31.620.89320.17350.06074.104
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.563, + 0.892, + 0.745 + ], + "angle": 0, + "content": "different VSR approaches with respect to the user preference. We invite 100 evaluators on the Amazon MTurk platform, and ask each evaluator to choose the better one from two synthetic HR videos generated by two different methods given the same LR video. Figure 6 depicts the user preference ratios on all eight videos in the REDS4 and Vid4 datasets. SATeCo clearly wins the traditional regression models of IconVSR, BasicVSR and VRT, and the diffusion model of StableSR. The results indicate SATeCo nicely magnifies LR videos with better visual quality and temporal coherence through the spatial feature adaptation and temporal feature alignment design in video diffusion procedure." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.756, + 0.655, + 0.772 + ], + "angle": 0, + "content": "4.3. Model Analysis" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Analysis on SFA and TFA modules. We first investigate how the SFA and TFA modules influence the overall performances of video super-resolution. Table 2 lists the performance comparisons among variants with different integration ways of SFA and TFA modules. We start from the basic diffusion model A, which leverages the zero-initialized convolution [55] in UNet/VAE to learn the spatial guidance from LR videos for super-resolution. The model B and C" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9238" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.47, + 0.118 + ], + "angle": 0, + "content": "Table 3. Ablation studies on the design of video upscaler and video refiner in SATeCo. The performances are reported on REDS4." + }, + { + "type": "table", + "bbox": [ + 0.079, + 0.125, + 0.479, + 0.23 + ], + "angle": 0, + "content": "
ModelPSNR↑SSIM↑LPIPS↓DISTS↓NIQE↓
UpscalerPixelShuffle29.770.84260.19790.07204.298
Ours31.620.89320.17350.06074.104
Refinerw = 030.360.85720.15810.03393.457
w = 0.531.620.89320.17350.06074.104
w = 1.028.990.80010.18150.06524.488
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.246, + 0.473, + 0.593 + ], + "angle": 0, + "content": "gradually upgrade the basic model A through plugging SFA and TFA modules into the UNet, which improves the PSNR from 28.56dB to 29.45dB. Compared to zero-initialized convolution which simply conducts weighted summation of LR frame features and HR ones to guide spatial-level diffusion learning, the combination of SFA and TFA not only enhances the spatial adaptation via feature modulation but also strengthens temporal feature alignment by the tubelet-based attention. As such, the higher PSNR and SSIM which measure the spatial fidelity is attained by the model C. Finally, the model D, i.e., our SATeCo, by further exploiting SFA and TFA in VAE to regulate pixel-space video reconstruction, shows the best performances in PSNR and SSIM. In view of perception-based evaluation metrics, SATeCo also constantly obtains improvements over other variants, indicating the potential benefit from spatial-temporal guidance learning to enhance visual perception in HR videos. Furthermore, Figure 7 showcases video super-resolution in a local region of one example in two adjacent frames. SATeCo reconstructs the HR videos with high-quality visual appearance and promising temporal consistency among adjacent frames, proving the impact of exploring feature adaptation and alignment in diffusion for super-resolution." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.596, + 0.47, + 0.807 + ], + "angle": 0, + "content": "Analysis on Video Upscaler. Then, we study the effectiveness of the video upscaler in the SATeCo. One alternative is to employ the pre-trained Pixel Shuffle layer [40] as the video upscaler. The upper part of Table 3 details the performances of the two approaches on REDS4. Our approach exhibits better performances against PixelShuffle across all evaluation metrics, especially in PSNR and SSIM. Technically, PixelShuffle resamples videos via directly conducting a 2D convolution layer on the input frames. Instead, ours delves into the formulation of frame-wise correlation through temporal mutual self-attention, which is more effective in pixel feature enhancement for video resampling. As such, ours effectively preserves the visual contents in LR videos and facilitates the subsequent video diffusion." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.471, + 0.9 + ], + "angle": 0, + "content": "Analysis on Video Refiner. The video refiner in SATeCo aims for adjusting the decoded HR videos from diffusion model by referring up-sampled original LR videos to alleviate color degradation. The trade-off parameter \\( w \\) in video refiner balances the impact of the visual contents between the decoded videos and the LR videos. To evaluate" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.091, + 0.891, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.219, + 0.892, + 0.247 + ], + "angle": 0, + "content": "Figure 7. Zoom-in view of two adjacent frames in one video superresolution result synthesized by variants of SATeCo." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.258, + 0.892, + 0.456 + ], + "angle": 0, + "content": "the influence of the parameter \\( w \\), we list the VSR performances by varying \\( w \\) in the lower part of Table 3. When \\( w \\) is 0, the performances on perception-based metrics are the best, but there is a slight performance drop on PSNR and SSIM. The performances indicate that the synthesized visual contents by diffusion models are more acceptable for human visual system. In contrast, employing a large value of \\( w \\) (e.g., 1.0) for video refinement considers the information of LR videos more and weakens the contribution of diffusion models, affecting the quality of visual content generation. Therefore, we empirically set the \\( w \\) as 0.5 to seek a good trade-off between the synthesized contents and original visual appearance." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.468, + 0.628, + 0.484 + ], + "angle": 0, + "content": "5. Conclusions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.493, + 0.892, + 0.795 + ], + "angle": 0, + "content": "We have presented SATeCo that explores spatial adaptation and temporal coherence in diffusion models for video superresolution. In particular, we study the problem of learning spatial-temporal guidance from low-resolution videos to calibrate high-resolution video diffusion procedure. To materialize our idea, SATeCo freezes all the parameters in the pre-trained UNet/VAE, and plugs the spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules in each decoder block to regulate latent-space video denoising and pixel-space video reconstruction. Through learning affine parameters on the guidance of low-resolution videos, SFA modulates the high-resolution features of each pixel to achieve spatial adaptation. TFA performs self-attention within a tubelet to enhance feature interaction and further conducts cross-attention between the tubelet and its low-resolution counterpart to guide temporal feature alignment learning. Experiments conducted on two video datasets, i.e., REDS4 and Vid4, validate the effectiveness of the proposed SATeCo for video super-resolution in terms of both spatial fidelity and temporal consistency." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.892, + 0.9 + ], + "angle": 0, + "content": "Acknowledgments. This work was supported in part by the National Natural Science Foundation of China under Contract 62021001, and in part by the Fundamental Research Funds for the Central Universities under contract WK3490000007. It was also supported by the GPU cluster built by MCC Lab of Information Science and Technology Institution of USTC." + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9239" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.469, + 0.17 + ], + "angle": 0, + "content": "[1] Jose Caballero, Christian Ledig, Andrew Aitken, Alejandro Acosta, Johannes Totz, Zehan Wang, and Wenzhe Shi. Realtime Video Super-Resolution with Spatio-Temporal Networks and Motion Compensation. 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Nevertheless, it is not trivial to capitalize on diffusion models for video super-resolution which necessitates not only the preservation of visual appearance from low-resolution to high-resolution videos, but also the temporal consistency across video frames. In this paper, we propose a novel approach, pursuing Spatial Adaptation and Temporal Coherence (SATeCo), for video super-resolution. SATeCo pivots on learning spatial-temporal guidance from low-resolution videos to calibrate both latent-space high-resolution video denoising and pixel-space video reconstruction. Technically, SATeCo freezes all the parameters of the pre-trained UNet and VAE, and only optimizes two deliberately-designed spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules, in the decoder of UNet and VAE. SFA modulates frame features via adaptively estimating affine parameters for each pixel, guaranteeing pixel-wise guidance for high-resolution frame synthesis. TFA delves into feature interaction within a 3D local window (tubelet) through self-attention, and executes cross-attention between tubelet and its low-resolution counterpart to guide temporal feature alignment. Extensive experiments conducted on the REDS4 and Vid4 datasets demonstrate the effectiveness of our approach. + +# 1. Introduction + +In recent years, diffusion models [11, 36, 37, 55] have shown great progress in revolutionizing image generation. In between, a series of image super-resolution works [36, 46, 52] benefit from leveraging knowledge prior embedded in diffusion models to upscale low-resolution (LR) images into high-resolution (HR) ones. Compared to 2D images, videos have one more time dimension, bringing + +![](images/684b5fb0c070de5fbee23e28f18597e907303bdd7c6b128565cf6466f67cead7.jpg) +Frame t + +![](images/f65e91b44669ce145575fecbbcfa56f5190435ac23bdeebdafe256c8e299aa1e.jpg) +Frame t+1 + +![](images/ba41de1b3fe749ca81124984542c297d6a7cad920be2ae648673a8d13317607f.jpg) +Low Resolution + +![](images/dcbdfc68fd29b37135cc06710c6f94a8dfd526d9beacca8b61a8f053d372247a.jpg) +VRT + +![](images/cfecaae4f758204374e203ae6371da384268a8a6fe739e9c2bee7f33c9514e94.jpg) +StableSR +Figure 1. An illustration of video super-resolution by using different approaches of StableSR [46], VRT [23] and our SATeCo to generate two adjacent frames. The region in the same local position is presented in the zoom-in view. + +![](images/80a7716c2aa1085c9d3a7342bbc941d51d48ad3b70de73329dfc2d8dffcf70bc.jpg) +SATeCo + +more challenges when capitalizing on diffusion models for video super-resolution (VSR). One natural way is to utilize the pre-trained diffusion models for image super-resolution (ISR), e.g., StableSR [46], to magnify each video frame. The representative advances [46, 52] manifest that diffusion models for ISR could synthesize more details than traditional regression models, e.g., VRT [23]. As depicted in Figure 1, the edges of the windows in the building produced by StableSR are much clearer than those generated by VRT. Nevertheless, the inherent stochasticity of diffusion models might jeopardize the spatial fidelity and hallucinate some extra visual content. Moreover, the independent frame-wise super-resolution overlooks the relation across consecutive frames, resulting in the issue of frame inconsistency in the high-resolution videos. For instance, the traffic signs in Figure 1 are totally different between the two adjacent frames generated by StableSR. + +In general, the difficulty of exploring diffusion models for video super-resolution originates from two aspects: 1) how to alleviate the stochasticity in diffusion process to pre + +serve visual appearance? 2) how to guarantee the temporal consistency across frames in the HR videos? We propose to address the two issues through learning spatial-temporal guidance from low-resolution videos to manage diffusion procedure for video super-resolution. To regulate spatial adaptation, we estimate affine parameters on the LR frame features to modulate each pixel in HR frames. As such, the pixel-wise guidance is employed to nicely learn the feature of every pixel in HR frames and better improve spatial fidelity. In an effort to temporally cohere video frames, we strengthen feature interaction across HR frames, and feature calibration between HR frames and LR counterpart via the attention mechanism. Moreover, large receptive field is attained by conducting the self-attention and cross-attention on the features within a 3D local window (tubelet), thereby facilitating temporal feature alignment. + +To materialize our idea, we present a new SATeCo method to carry out Spatial Adaptation and Temporal Coherence for video super-resolution. Technically, SATeCo uses a transformer-based video upscaler to up-sample the input LR video. The VAE encoder then extracts the video features and latent code of LR video, which are further exploited for diffusion calibration. SATeCo deliberately devises spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules, and inserts the two modules into each decoder block of UNet and VAE, for latent-space video denoising and pixel-space video reconstruction. In the regularization of latent-space video denoising, SFA exploits two convolutional layers on the latent code of each up-sampled LR frame, to predict a scale and bias to modulate the pixel-wise feature of HR frame. TFA first executes self-attention on HR video latent code within a tubelet to enhance feature interaction, and further performs cross-attention between the tubelet and its LR counterpart for feature calibration in HR video. The LR video features are exploited in the same way to regulate the HR video feature learning in pixel-space video reconstruction. SATeCo finally refines the decoded HR video by referring to the up-sampled LR video via a neural network to balance synthesized quality and fidelity. + +The main contribution of this paper is the proposal of SATeCo to explore spatial adaptation and temporal coherence in diffusion models for video super-resolution. The solution also leads to the elegant views of how to leverage pixel-wise information from LR videos for visual appearance preservation, and how to achieve frame consistency in HR video generation. Extensive experiments on REDS4 and Vid4 verify the superiority of SATeCo in terms of both spatial quality and temporal consistency. + +# 2. Related Work + +Video super-resolution. Modern VSR approaches are mainly based on deep neural networks and can be grouped into two categories, i.e., sliding window-based methods and + +recurrent methods. Early sliding window-based VSR techniques [1, 22, 50, 51, 53] rely on 2D or 3D CNNs [19, 20] which incorporate a sequence of LR frames to predict center HR frame. To fully utilize the complementary information across adjacent frames, the deformable convolutions [43, 48] are employed for feature alignment. Inspired by the success of transformer architecture in various computer vision tasks [6, 27-29], self-attention emerges to be integrated into the VSR frameworks [14, 23, 26, 47]. One representative is VRT [23] which plugs the temporal mutual attention block into transformer backbone to facilitate motion estimation, feature alignment and fusion. Nevertheless, the sliding window-based approaches are difficult to capture long-range dependencies which could limit the performance of video super-resolution. In contrast to aggregate information from adjacent frames in a short term, recurrent approaches [2, 3, 15, 17, 18, 24, 38, 39, 54] utilize a hidden state to sequentially propagate information from all previous frames to the current frame, benefiting the frame restoration. For instance, Chan et al. [2] adopt a bidirectional propagation scheme with flow-based feature alignment to maximize information gathering in super resolution. Despite having the great capacity of the recurrent models for temporal information gathering, the local details are still hard to be restored when the LR video encounters significant degradation in a long temporal range. + +Diffusion models for super-resolution. Impressive performances of image synthesis achieved by diffusion models [7, 11, 16, 30, 34, 55] encourage the deployment on image super-resolution. These explorations [9, 10, 13, 21, 31, 42, 49, 57] leverage the knowledge prior embedded in the pre-trained diffusion models to magnify images. For example, StableSR [46] integrates a time-aware encoder into Stable-Diffusion [36] model without altering the pre-trained weights, and achieves promising super-resolution results. To further enhance the reconstruction of image texture details, Yang et al. [52] introduce an attention-based control module to maintain pixel consistency between LR and HR images. Different from the advances which optimize a small part of inserted parameters, several approaches [13, 21, 49] fix all weights in the pre-trained synthesis model and attempt to incorporate constraints into the reverse diffusion process to guide image restoration. Although the effectiveness of knowledge prior has been manifested in various diffusion-based ISR methods, it is still a grand challenge to employ diffusion models for video super-resolution and preserve spatial fidelity and temporal consistency. + +In summary, our work mainly focuses on diffusion models for video super-resolution. The proposal of SATeCo contributes by exploring not only how to preserve spatial fidelity through modulating HR frame features, but also how to calibrate HR video features with LR counterpart for better temporal feature alignment. + +![](images/3a0bed2ae560a661e058c5700ca6eb93cd913e5720919c36d674beb27706c8fb.jpg) +Figure 2. An overview of our SATeCo architecture. The input LR video $X_{L}$ is first up-sampled to the target resolution via a transformer-based video upscaler. Then, the up-sampled video $X_{u}$ is fed into the VAE encoder to extract the video features and latent code $Z$ . Next, the Gaussian noise is added into $Z$ according to the diffusion scheduler, and the noisy video latent code is then restored by UNet for quality enhancement. In latent space, a latent encoder extracts the LR latent feature maps $G$ on the LR latent code $Z$ , followed by spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules in each decoder block of UNet for spatial-temporal guidance learning. Given the denoised video latent code $Z_{0}$ , the VAE decoder decodes the video $X_{d}$ based on the guidance learnt by SFA and TFA on LR video features. Finally, the decoded video $X_{d}$ is adjusted by a video refiner via referring to $X_{u}$ for final HR video $X_{H}$ synthesis. + +# 3. Our Approach + +In this section, we present our newly-minted SATeCo, pursuing Spatial Adaptation and Temporal Coherence in diffusion models for video super-resolution. Figure 2 depicts an overview of the architecture. SATeCo begins with a video upscaler to increase the resolution of the input LR video. Then, the up-sampled video is fed into VAE encoder for video feature extraction and latent code prediction. After that, a spatial feature adaptation (SFA) and a temporal feature alignment (TFA) module are leveraged to learn spatial-temporal guidance on latent code and features of LR video, to calibrate latent-space video denoising and pixel-space video reconstruction. As such, the two modules are plugged into each block of the decoder in UNet and VAE. In procedure of video latent code denoising, SFA estimates the affine parameters on LR video latent code to modulate each pixel of the HR video latent code. TFA first performs self-attention on the HR video latent code within a tubelet, and further enhances latent code by executing cross-attention between the tubelet and its LR counterpart. Similarly, SFA and TFA are conducted in the VAE decoder to guide HR video reconstruction with the LR video features. Finally, SATeCo designs a video refiner to adjust the decoded HR video by referring to the up-sampled video for a good trade-off between synthesized quality and fidelity. + +# 3.1. Video Upscaler + +Most existing VSR approaches [39, 51] first upscale the input LR videos through a resampling operation, and then improve their visual quality. Nevertheless, the widely adopted resampling operations, e.g., Bilinear and Bicubic sampling, might damage the original visual patterns [39] in LR frames, having a negative impact on the subsequent video enhancement. Therefore, we exploit the recipe of reducing frame degradation ahead of the feature learning [4] in neural networks and propose a video upscaler, which gen + +erates more accurate up-sampled videos for the following quality enhancement by diffusion models. + +Given the input LR video $X_{L}$ , we utilize a transformer-based video upscaler for video up-scaling as illustrated in Figure 3(a). It consists of two cascaded temporal mutual self-attention (TMSA) blocks [23] to temporally aggregate video features, and a pixel-shuffle layer [40] to increase video spatial resolution via feature reshaping. The upsampled video $X_{u} = \{x_{u}^{i}\}_{i=1}^{L}$ with $L$ frames is then fed into the diffusion model for video quality enhancement. + +# 3.2. Spatial Feature Adaptation Module + +The inherent stochasticity [52] of diffusion models might result in the distortion of texture details in image superresolution. A natural way of employing diffusion models for super-resolution is to learn the spatial-level condition via convolution-based [46] or transformer-based [52] structure to guide latent code denoising in UNet. Such kind of mechanism only manages feature regularization in latent space, posting difficulty to learn sufficient inductive bias and provide precise guidance for high-resolution image restoration. The similar issue also exists in video superresolution. To alleviate this, we introduce a spatial feature adaptation (SFA) module which dynamically learns pixelwise guidance from the input LR videos for diffusion calibration. In the meanwhile, the SFA module emphasizes the inductive bias learning in both of the latent-space video denoising (i.e., training of UNet) and pixel-space video reconstruction (i.e., training of VAE). + +Figure 3(c) illustrates our SFA module. Given the upsampled LR video $X_{u}$ , the VAE encoder first encodes $X_{u}$ into the video latent code $Z = \{z^{i}\}_{i = 1}^{L}$ . Next, we exploit a convolution-based latent encoder $\mathcal{E}_z$ to extract the LR latent feature maps $G = \mathcal{E}_z(Z)$ , which are further utilized to guide the HR feature learning in UNet decoder. Formally, we denote the HR intermediate feature maps in UNet and the LR latent feature maps in latent encoder as + +![](images/ce2469dfa5d28971c257720182ebf2a569a1cfdc395970d0ee770cbb007509de.jpg) +Figure 3. An illustration of (a) video upscaler, (b) video refiner, (c) spatial feature adaptation and (d) temporal feature alignment module. + +![](images/bed722ea0b1b0bdbc51a6f6b0567e4b1876c24e99d616431d9a76f17015624c4.jpg) + +![](images/b3e36fa69554affd8566693dc958e8f70a561ad6ecbc13df5cde3990d227029f.jpg) + +$F = \{f^{i}\}_{i = 1}^{L}$ and $G = \{g^i\}_{i = 1}^L$ , respectively. For the $i$ -th frame, we measure a scale ratio $S^i\in \mathbb{R}^{H\times W\times C}$ and a bias $M^i\in \mathbb{R}^{H\times W\times C}$ for each pixel of HR intermediate feature map $f^{i}\in \mathbb{R}^{H\times W\times C}$ based on the LR latent feature map $g^{i}\in \mathbb{R}^{H\times W\times C}$ via two 2D convolution layers: + +$$ +M ^ {i} = \operatorname {C o n v 2 D} (g ^ {i}), \quad S ^ {i} = \operatorname {C o n v 2 D} (g ^ {i}). \tag {1} +$$ + +Then, the output HR feature map $\tilde{f}^i$ in UNet is generated by modulating the normalized HR intermediate feature map $f^i$ with $S^i$ and $M^i$ as: + +$$ +\tilde {f} ^ {i} = S ^ {i} \odot \frac {f ^ {i} - \mu^ {i}}{\sigma^ {i}} + M ^ {i}, \tag {2} +$$ + +where $\odot$ denotes point-wise multiplication. $\mu^i$ and $\sigma^i$ are the mean and standard deviation values of the feature map $f^i$ . Hence, the affine parameters estimated on the latent feature maps of LR videos calibrate the intermediate feature maps of HR videos in latent code denoising, which adaptively injects the pixel-wise information into the video latent code to preserve the visual appearance. For video feature learning in pixel space, SFA module is inserted into each block of VAE decoder. Similarly, the extracted video features of LR videos are taken as the guidance to estimate the affine parameters in SFA module to adjust HR video feature learning for video reconstruction. We take all the modulated intermediate feature maps $\tilde{f}^i$ from SFA module as $\tilde{F} = \{\tilde{f}^i\}_{i=1}^L$ , which is employed for the following temporal feature alignment in the UNet and VAE decoders. + +# 3.3. Temporal Feature Alignment Module + +Frame-wisely conducting ISR models for video super-resolution could amplify the differences of blurry patterns [39] across frames, leading to content inconsistency such as the object shape deformation. The issue originated from solely relying on spatial level super-resolution and lacking temporal coherence modeling across frames. To facilitate visual content alignment in video super-resolution, a temporal feature alignment (TFA) module is devised after each SFA module in UNet and VAE decoder, for the temporal feature interaction and calibration. + +Figure 3(d) depicts the learning procedure of TFA module. Given the input HR intermediate feature maps $\tilde{F} = \{\tilde{f}^i\}_{i=1}^L$ from the SFA module in UNet decoder, we first partition the feature map $\tilde{f}^i$ of each frame into $N$ non-overlapping windows with the spatial resolution of $h \times w$ . $N = \frac{HW}{hw}$ is the total window number. Then, we link all features within a local window across $L$ frames to form a HR feature tubelet $\tilde{F}_{tub} \in \mathbb{R}^{L \times h \times w \times C}$ . We reshape the dimension of each HR feature tubelet into $hwL \times C$ and execute the standard self-attention on it: + +$$ +Q, K, V = \operatorname {C o n v 3 D} (\tilde {F} _ {t u b}), \tag {3} +$$ + +$$ +\hat {F} _ {t u b} = \operatorname {A t t e n t i o n} (Q, K, V), +$$ + +where $Q, K, V \in \mathbb{R}^{hwL \times C}$ are the query, key and value matrices, respectively. Each of them is predicted by a 3D convolution layer. The self-attention conducted on the HR feature tubelet enables the feature interaction across different frames, mitigating the temporal feature misalignment in local regions. To further conduct the temporal feature calibration, we leverage the counterpart of HR feature tubelet, i.e., the feature tubelet $G_{tub}$ of the LR latent feature maps, as a reference for feature adjustment. We perform the cross-attention between $\hat{F}_{tub}$ and $G_{tub}$ to obtain the output feature tubelet $\bar{F}_{tub}$ : + +$$ +Q ^ {\prime} = \operatorname {C o n v 3 D} \left(\hat {F} _ {t u b}\right), \quad K ^ {\prime}, V ^ {\prime} = \operatorname {C o n v 3 D} \left(G _ {t u b}\right), \tag {4} +$$ + +$$ +\bar {F} _ {t u b} = \operatorname {A t t e n t i o n} \left(Q ^ {\prime}, K ^ {\prime}, V ^ {\prime}\right), +$$ + +where the query $Q^{\prime}$ is learnt on the HR feature tubelet $\hat{F}_{tub}$ and the key/value $K^{\prime} / V^{\prime}$ is estimated on the LR counterpart via 3D convolution layers, respectively. We collect all the output feature tubelets from the TFA module and reshape them into the original size as $\bar{F}\in \mathbb{R}^{L\times H\times W\times C}$ . The output feature $\bar{F}$ is then fed into the next block of the decoder in UNet or VAE for video latent denoising or reconstruction. + +In this way, the coupled SFA and TFA modules in UNet and VAE decoder not only emphasize the pixel-wise feature adaptation for visual appearance preservation but also strengthen the temporally feature interaction and calibration for temporal coherence modeling. + +Table 1. Performance comparisons in terms of pixel-based (PSNR and SSIM) and perception-based (LPIPS, DISTS, NIQE and CLIP-IQA) evaluation metrics on the REDS4 and Vid4 datasets. The width and height of the LR videos are rescaled by 4 times through different VSR approaches. We follow VRT [23] to set the frame number as 6 in each clip for HR video inference. + +
DatasetsMetricsBicubicStableSR [46]TOFlow [51]EDVR-M [48]BasicVSR [2]VRT [23]IconVSR [2]SATeCo
REDS4PSNR↑26.1424.7927.9830.5331.4231.6031.6731.62
SSIM↑0.72920.68970.79900.86990.89090.88880.89480.8932
LPIPS↓0.35190.24120.31040.23120.20230.20770.19390.1735
DISTS↓0.18760.07550.14680.09430.08080.08230.07620.0607
NIQE↓7.2574.1166.2604.5444.1974.2524.1174.104
CLIP-IQA↑0.60450.65790.61760.63820.63530.63790.61620.6622
Vid4PSNR↑23.7822.1825.8927.1027.2427.9327.3927.44
SSIM↑0.63470.59040.76510.81860.82510.84250.82790.8420
LPIPS↓0.39470.36700.33860.28980.28110.27230.27390.2291
DISTS↓0.22010.13850.17760.14680.14420.13720.14060.1015
NIQE↓7.5365.2377.2295.5285.3405.2425.3925.212
CLIP-IQA↑0.68170.76440.73650.73800.74100.74340.74110.7451
+ +# 3.4. Video Refiner + +Recent advance [8] reveals that images synthesized by diffusion model conditioning on visual contents might lose some original color information in local regions. To address this problem, StableSR [46] performs a non-parametric post-processor to refine the generation with reference to original input for achieving color preservation. Instead, we propose a trainable video refiner to emphasize the adjustment of decoded HR video from VAE decoder, by leveraging the information from up-sampled LR video. + +Figure 3(b) details the structure of our video refiner. We first concatenate the decoded video $X_{d}$ and the up-sampled LR video $X_{u}$ along channel dimension, and then feed it into a residual block. The refined HR video $X_{H}$ is generated by fusing $X_{u}$ , $X_{d}$ and the output feature mapping of residual block as: + +$$ +X _ {H} = w X _ {u} + (1 - w) X _ {d} + \operatorname {R e s B l o c k} ([ X _ {u}, X _ {d} ]), \tag {5} +$$ + +where $w$ is a trade-off parameter. The devised video refiner balances the original visual contents of the up-sampled LR video and the synthesized contents of decoded HR video via feature fusion learning. Accordingly, our design is more powerful in terms of color preservation, and achieves a good trade-off between the synthesized quality and fidelity. + +# 3.5. Training Strategy + +We construct our SATeCo for video super-resolution based on the Stable Diffusion [36] model. There are four training stages to optimize the whole architecture. In the first stage, we train the video upscaler using the Charbonnier loss [5] to optimize the video reconstruction of HR videos. After that, we follow the standard setting in [36] to train UNet for the optimization of the inserted SFA and TFA modules. We fix all parameters of UNet except for the two kinds of modules during training. For the optimization of SFA and TFA modules in VAE decoder, we take the video latent codes of the + +HR videos as the input, and optimize the similarity between the decoded videos and ground-truth HR videos. Finally, we freeze all the parameters in video upscaler, UNet and VAE, and train the video refiner using the pairs of decoded and ground-truth HR videos. + +# 4. Experiments + +# 4.1. Experimental Settings + +Datasets. We empirically evaluate the effectiveness of our SATeCo on two widely-used datasets: REDS [33] and Vid4 [25]. The REDS dataset consists of 240, 30 and 30 video clips for training, validation and testing. Each video clip contains 100 frames with the resolution of $1,280 \times 720$ . We employ the standard protocols in [2, 3, 48] and select four video clips from the validation set as the testing data, namely REDS4. The Vid4 dataset also includes four video clips, and there are about 40 frames in each clip with the resolution of $720 \times 480$ . Following the standard settings [3, 23], we employ all the videos in Vid4 for evaluation and choose the video data in the training set of Vimeo-90K [51] for model optimization. There are 64, 612 training clips and each clip has 7 frames with the resolution of $448 \times 256$ . + +Implementation Details. We implement our SATeCo on the PyTorch platform by using Diffusers [44] library. The noise scheduler is set as linear scheduler $(\beta_{1} = 0.00085, \beta_{T} = 0.0120, \text{and } T = 1,000)$ . The trade-off parameters $w$ in video refiner is determined as 0.5 by cross validation. We empirically set the window size in TFA as $h = 8$ , $w = 8$ . The frame number $L$ of input clip is 6. The model is trained with AdamW optimizer and the learning rate is $5.0 \times 10^{-5}$ . + +Evaluation Metrics. We evaluate the VSR models via two kinds of metrics, i.e., pixel-based and perception-based metrics. The pixel-based metrics include PSNR and SSIM which calculate the similarity of every pixel between the generated and ground-truth HR videos. There are also some + +![](images/8e89fa84f260fcb1b7b0253f81692b1cd77e782471946d7ceeea1d127d4c7dfb.jpg) +Figure 4. Six visual examples of video super-resolution results by different approaches on the REDS4 and Vid4 datasets. The region in the red box is presented in the zoom-in view for comparison. + +perception-based evaluation metrics for super-resolution. These metrics mainly measure video quality from the viewpoint of human perceptual preference, and we adopt LPIPS [56], DISTS [12], NIQE [32] and CLIP-IQA [45] in this paper. Specifically, LPIPS utilizes VGG [41] model to extract frame features and measures the feature similarity between the synthesized and ground-truth videos. DISTS also computes the feature similarity between video pairs via a variant of VGG model, but the emphasis is on image texture. For NIQE and CLIP-IQA, the scores are directly predicted by the learnt models without using the ground-truth HR videos. NIQE measures the similarity of feature distribution between synthesized frames and a realistic image set [32], while CLIP-IQA computes cosine similarity between generated frames and text prompts (e.g., "High Resolution") via CLIP model [35]. In addition, we conduct a user study to verify human preference on different models. + +# 4.2. Comparisons with State-of-the-Art Methods + +We compare our SATeCo with several state-of-the-art techniques, including Bicubic Interpolation, StableSR [46], TOFlow [51], EDVR-M [48], BasicVSR [2], VRT [23] and IconVSR [2], on REDS4 and Vid4 datasets. + +Quantitative Evaluation. Table 1 summarizes the performances of different VSR approaches in terms of the six + +metrics over the two datasets. Overall, SATeCo achieves the best performances across all perception-based metrics (i.e., LPIPS, DISTS, NIQE and CLIP-IQA) on REDS4. These metrics emphasize the quality judgment from human perceptual aspect and the results demonstrate the advantage of exploiting abundant knowledge prior in the pre-trained diffusion models to generate high-quality HR videos with better visual perception. In terms of pixel-based metrics, recent advances [46, 52] manifest that the stochasticity in diffusion models could hurt the preservation of visual appearance in HR videos, resulting in inferior performances to traditional regression models. Our SATeCo, by capitalizing on pixel-wise guidance from LR videos to modulate HR frame feature synthesis, alleviates the downsides and obtains the PSNR of 31.62dB. Notably, such performance is very comparable to that of IconVSR [2], which is the SOTA baseline of regression VSR models. The performance trends on Vid4 are similar with those on REDS4. In particular, SATeCo attains the DISTS of 0.1015, which relatively reduces that of the best competitor VRT [23] by $26.0\%$ . The results indicate that SATeCo benefits from learning pixel-wise spatial adaption in diffusion to preserve frame-wise image texture for achieving better video fidelity. + +Qualitative Evaluation. Figure 4 visualizes the video super-resolution with six examples from REDS4 and Vid4. + +![](images/ccfdc5641a30ed923d1bb57f6c3fe04827b3bedd11ea9588a7db9761b5634e20.jpg) +Low Resolution Frame $t$ + +![](images/c5dc7ff17dcb910ccb672f750162c205567edeb39c8c62673d88c208586c98ad.jpg) +Low Resolution Frame $t + 1$ + +![](images/9229339245068d622cf0a751036f7dc99b41aec8c2ec2b6ecf57aeb710743046.jpg) + +![](images/c5beec08493c735c4fed5b1e2852059ce020cfd03675e2d52ca88f9edef649c6.jpg) + +![](images/d97efcc1428741f886d6f1cde3d9fc6ec00581f3fb52cde4e2485b8304590bc4.jpg) + +![](images/daa0715e0eec2c04fb83b1c96e022b7fab31d15aa42433b8f7d8fce6b3bf2c24.jpg) + +![](images/257e13525ced1b74ec4749cde1cb30f830605f994792fd958d6753bd87ac52ae.jpg) + +![](images/e4a236e993baaa7baf4b04425947f33f6684ffba74a10ee9a58422594cd8d7db.jpg) + +![](images/39b729db7ec9905c04ecfe949c9e4348464711994eae0ff6d271e561400900f7.jpg) + +![](images/611f2207c7321a6c2dce5499d94d8a453bfa1cc7de4e818d5ef330008134de18.jpg) + +![](images/950dd7be8605d08c21eb0274b282b24d0740c7da7ad8260f79430a2b8a6e6e27.jpg) + +![](images/9961b0a5b4894c7047380209b6fe0158d13c54ab8a2571745d0483774aad21c6.jpg) + +![](images/04f0405f581b043f47f0a062e4fd831af935c1b9a4d2553189ac31120c720042.jpg) +Low Resolution Frame t + +![](images/8ca2a8d3a35aa4ec48bd04cd0cd49041c7323f80cf043222185ed93769d2179c.jpg) +Low Resolution Frame $t + 1$ + +![](images/6fd5a1909db65744a57c98e82f333fdd202b58b95e9ce4bf22a05fe56886e8ac.jpg) + +![](images/9e63958cdf1622206a5626ac482185309fa3a1c8e61bdb4c48419983ac7c007d.jpg) +Bicubic + +![](images/7839cf8edd196eb9c4fb18fb48512c0b17f11c5a22bac031c29387bcd1ebb745.jpg) + +![](images/e75eaefaf6aa7e9d342bc3da42548f506c43be65fc3487fb89aa439fbac97023.jpg) +LDM + +![](images/523baa5f2f929a7fccfdcbf2c44f900afde4b379295816f06f3246ed4c585ef9.jpg) + +![](images/fd3640c2a8f2c79528e350c70112b81a003fd74edeb4228b559c472f01bc26f5.jpg) +StableSR + +![](images/998d3ee2a3b74ecc3916df01b7f35af31e008d142ce4e445a671b4399e1cdbb6.jpg) + +![](images/42c1c8aad7f0bfd152b6e2ad277589124d0494a5b91d1d0d4918a8e7c9a0f577.jpg) +SATeCo + +![](images/146eaec14e8f7e859d002766b66b7540b3e206e510bfa0a898f75060b29f0192.jpg) + +![](images/e6f6e0e52948277d13e2890157d045a07495055332bc36194df85567b6434efc.jpg) +GT + +![](images/3595938b09258414dcba2a1f084ec9b82bda6e9a48b58f9119beefa4f14644bb.jpg) +Figure 5. Video super-resolution results of two videos in the Vid4 dataset. The region in the same local position across two adjacent frames (i.e., regions highlighted by red and blue boxes) is scaled up to show more details. +Figure 6. Human evaluation of user preference ratios between SATeCo and other baselines on REDS4 and Vid4. + +Compared to other baselines, SATeCo can successfully restore more local details (e.g., the sharp edges in the eave and spoke of the 2nd and 3rd case) in frames with high fidelity. Even with large blurriness (e.g., the 4th case), SATeCo still exhibits the strong restoration ability for video super-resolution, which again confirms the effectiveness of leveraging rich knowledge prior of diffusion models and learning spatial adaptation. To further validate the temporal coherence learnt by SATeCo, we visualize two adjacent frames of two synthesized HR videos by using different diffusion-based super-resolution approaches in Figure 5. As observed in the figure, LDM and StableSR synthesize different visual contents across the two frames, e.g., the small windows in the building. In contrast, our SATeCo predicts the HR videos with higher frame consistency and preserves the visual fidelity. That basically validates the merit of performing tubelet-based self-attention within HR videos and cross-attention between HR videos and LR counterparts to achieve better temporal feature interaction and calibration. + +Human Evaluation. Next, we further conduct human study to verify the HR video generation quality by using + +Table 2. Performance comparisons on REDS4 among variants with different integration of SFA and TFA modules. + +
ModelUNetVAEPSNR↑SSIM↑LPIPS↓DISTS↓NIQE↓
SFATFASFATFA
A28.560.79250.21590.07584.404
B✓28.930.80870.20420.06934.349
C✓✓29.450.83980.18920.06204.324
D✓✓✓✓31.620.89320.17350.06074.104
+ +different VSR approaches with respect to the user preference. We invite 100 evaluators on the Amazon MTurk platform, and ask each evaluator to choose the better one from two synthetic HR videos generated by two different methods given the same LR video. Figure 6 depicts the user preference ratios on all eight videos in the REDS4 and Vid4 datasets. SATeCo clearly wins the traditional regression models of IconVSR, BasicVSR and VRT, and the diffusion model of StableSR. The results indicate SATeCo nicely magnifies LR videos with better visual quality and temporal coherence through the spatial feature adaptation and temporal feature alignment design in video diffusion procedure. + +# 4.3. Model Analysis + +Analysis on SFA and TFA modules. We first investigate how the SFA and TFA modules influence the overall performances of video super-resolution. Table 2 lists the performance comparisons among variants with different integration ways of SFA and TFA modules. We start from the basic diffusion model A, which leverages the zero-initialized convolution [55] in UNet/VAE to learn the spatial guidance from LR videos for super-resolution. The model B and C + +Table 3. Ablation studies on the design of video upscaler and video refiner in SATeCo. The performances are reported on REDS4. + +
ModelPSNR↑SSIM↑LPIPS↓DISTS↓NIQE↓
UpscalerPixelShuffle29.770.84260.19790.07204.298
Ours31.620.89320.17350.06074.104
Refinerw = 030.360.85720.15810.03393.457
w = 0.531.620.89320.17350.06074.104
w = 1.028.990.80010.18150.06524.488
+ +gradually upgrade the basic model A through plugging SFA and TFA modules into the UNet, which improves the PSNR from 28.56dB to 29.45dB. Compared to zero-initialized convolution which simply conducts weighted summation of LR frame features and HR ones to guide spatial-level diffusion learning, the combination of SFA and TFA not only enhances the spatial adaptation via feature modulation but also strengthens temporal feature alignment by the tubelet-based attention. As such, the higher PSNR and SSIM which measure the spatial fidelity is attained by the model C. Finally, the model D, i.e., our SATeCo, by further exploiting SFA and TFA in VAE to regulate pixel-space video reconstruction, shows the best performances in PSNR and SSIM. In view of perception-based evaluation metrics, SATeCo also constantly obtains improvements over other variants, indicating the potential benefit from spatial-temporal guidance learning to enhance visual perception in HR videos. Furthermore, Figure 7 showcases video super-resolution in a local region of one example in two adjacent frames. SATeCo reconstructs the HR videos with high-quality visual appearance and promising temporal consistency among adjacent frames, proving the impact of exploring feature adaptation and alignment in diffusion for super-resolution. + +Analysis on Video Upscaler. Then, we study the effectiveness of the video upscaler in the SATeCo. One alternative is to employ the pre-trained Pixel Shuffle layer [40] as the video upscaler. The upper part of Table 3 details the performances of the two approaches on REDS4. Our approach exhibits better performances against PixelShuffle across all evaluation metrics, especially in PSNR and SSIM. Technically, PixelShuffle resamples videos via directly conducting a 2D convolution layer on the input frames. Instead, ours delves into the formulation of frame-wise correlation through temporal mutual self-attention, which is more effective in pixel feature enhancement for video resampling. As such, ours effectively preserves the visual contents in LR videos and facilitates the subsequent video diffusion. + +Analysis on Video Refiner. The video refiner in SATeCo aims for adjusting the decoded HR videos from diffusion model by referring up-sampled original LR videos to alleviate color degradation. The trade-off parameter $w$ in video refiner balances the impact of the visual contents between the decoded videos and the LR videos. To evaluate + +![](images/313aa67c5c46d366ecaae5e3f89267d184ded80e6b084569d3f2276649083f1f.jpg) +Figure 7. Zoom-in view of two adjacent frames in one video superresolution result synthesized by variants of SATeCo. + +the influence of the parameter $w$ , we list the VSR performances by varying $w$ in the lower part of Table 3. When $w$ is 0, the performances on perception-based metrics are the best, but there is a slight performance drop on PSNR and SSIM. The performances indicate that the synthesized visual contents by diffusion models are more acceptable for human visual system. In contrast, employing a large value of $w$ (e.g., 1.0) for video refinement considers the information of LR videos more and weakens the contribution of diffusion models, affecting the quality of visual content generation. Therefore, we empirically set the $w$ as 0.5 to seek a good trade-off between the synthesized contents and original visual appearance. + +# 5. Conclusions + +We have presented SATeCo that explores spatial adaptation and temporal coherence in diffusion models for video superresolution. In particular, we study the problem of learning spatial-temporal guidance from low-resolution videos to calibrate high-resolution video diffusion procedure. To materialize our idea, SATeCo freezes all the parameters in the pre-trained UNet/VAE, and plugs the spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules in each decoder block to regulate latent-space video denoising and pixel-space video reconstruction. Through learning affine parameters on the guidance of low-resolution videos, SFA modulates the high-resolution features of each pixel to achieve spatial adaptation. TFA performs self-attention within a tubelet to enhance feature interaction and further conducts cross-attention between the tubelet and its low-resolution counterpart to guide temporal feature alignment learning. Experiments conducted on two video datasets, i.e., REDS4 and Vid4, validate the effectiveness of the proposed SATeCo for video super-resolution in terms of both spatial fidelity and temporal consistency. + +Acknowledgments. This work was supported in part by the National Natural Science Foundation of China under Contract 62021001, and in part by the Fundamental Research Funds for the Central Universities under contract WK3490000007. It was also supported by the GPU cluster built by MCC Lab of Information Science and Technology Institution of USTC. + +# References + +[1] Jose Caballero, Christian Ledig, Andrew Aitken, Alejandro Acosta, Johannes Totz, Zehan Wang, and Wenzhe Shi. Realtime Video Super-Resolution with Spatio-Temporal Networks and Motion Compensation. In CVPR, 2017. 2 +[2] Kelvin CK Chan, Xintao Wang, Ke Yu, Chao Dong, and Chen Change Loy. BasicVSR: The Search for Essential Components in Video Super-Resolution and Beyond. In CVPR, 2021. 2, 5, 6 +[3] Kelvin CK Chan, Shangchen Zhou, Xiangyu Xu, and Chen Change Loy. BasicVSR++: Improving Video SuperResolution with Enhanced Propagation and Alignment. In CVPR, 2022. 2, 5 +[4] Kelvin CK Chan, Shangchen Zhou, Xiangyu Xu, and Chen Change Loy. 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Nevertheless, it is not trivial to capitalize on diffusion models for video super-resolution which necessitates not only the preservation of visual appearance from low-resolution to high-resolution videos, but also the temporal consistency across video frames. In this paper, we propose a novel approach, pursuing Spatial Adaptation and Temporal Coherence (SATeCo), for video super-resolution. SATeCo pivots on learning spatial-temporal guidance from low-resolution videos to calibrate both latent-space high-resolution video denoising and pixel-space video reconstruction. Technically, SATeCo freezes all the parameters of the pre-trained UNet and VAE, and only optimizes two deliberately-designed spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules, in the decoder of UNet and VAE. SFA modulates frame features via adaptively estimating affine parameters for each pixel, guaranteeing pixel-wise guidance for high-resolution frame synthesis. 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An illustration of video super-resolution by using different approaches of StableSR [46], VRT [23] and our SATeCo to generate two adjacent frames. The region in the same local position is presented in the zoom-in view." + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "type": "image", + "bbox": [ + 425, + 379, + 539, + 411 + ], + "blocks": [ + { + "bbox": [ + 425, + 379, + 539, + 411 + ], + "lines": [ + { + "bbox": [ + 425, + 379, + 539, + 411 + ], + "spans": [ + { + "bbox": [ + 425, + 379, + 539, + 411 + ], + "type": "image", + "image_path": "80a7716c2aa1085c9d3a7342bbc941d51d48ad3b70de73329dfc2d8dffcf70bc.jpg" + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 471, + 412, + 493, + 418 + ], + "lines": [ + { + "bbox": [ + 471, + 412, + 493, + 418 + ], + "spans": [ + { + "bbox": [ + 471, + 412, + 493, + 418 + ], + "type": "text", + "content": "SATeCo" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "image_caption" + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 473, + 546, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 546, + 675 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 546, + 675 + ], + "type": "text", + "content": "more challenges when capitalizing on diffusion models for video super-resolution (VSR). One natural way is to utilize the pre-trained diffusion models for image super-resolution (ISR), e.g., StableSR [46], to magnify each video frame. The representative advances [46, 52] manifest that diffusion models for ISR could synthesize more details than traditional regression models, e.g., VRT [23]. As depicted in Figure 1, the edges of the windows in the building produced by StableSR are much clearer than those generated by VRT. Nevertheless, the inherent stochasticity of diffusion models might jeopardize the spatial fidelity and hallucinate some extra visual content. Moreover, the independent frame-wise super-resolution overlooks the relation across consecutive frames, resulting in the issue of frame inconsistency in the high-resolution videos. For instance, the traffic signs in Figure 1 are totally different between the two adjacent frames generated by StableSR." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "type": "text", + "content": "In general, the difficulty of exploring diffusion models for video super-resolution originates from two aspects: 1) how to alleviate the stochasticity in diffusion process to pre" + } + ] + } + ], + "index": 24 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 212, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 212, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 212, + 712 + ], + "type": "text", + "content": "*This work was performed at HiDream.ai." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9232" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "type": "text", + "content": "serve visual appearance? 2) how to guarantee the temporal consistency across frames in the HR videos? We propose to address the two issues through learning spatial-temporal guidance from low-resolution videos to manage diffusion procedure for video super-resolution. To regulate spatial adaptation, we estimate affine parameters on the LR frame features to modulate each pixel in HR frames. As such, the pixel-wise guidance is employed to nicely learn the feature of every pixel in HR frames and better improve spatial fidelity. In an effort to temporally cohere video frames, we strengthen feature interaction across HR frames, and feature calibration between HR frames and LR counterpart via the attention mechanism. Moreover, large receptive field is attained by conducting the self-attention and cross-attention on the features within a 3D local window (tubelet), thereby facilitating temporal feature alignment." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 264, + 289, + 539 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 264, + 289, + 539 + ], + "spans": [ + { + "bbox": [ + 46, + 264, + 289, + 539 + ], + "type": "text", + "content": "To materialize our idea, we present a new SATeCo method to carry out Spatial Adaptation and Temporal Coherence for video super-resolution. Technically, SATeCo uses a transformer-based video upscaler to up-sample the input LR video. The VAE encoder then extracts the video features and latent code of LR video, which are further exploited for diffusion calibration. SATeCo deliberately devises spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules, and inserts the two modules into each decoder block of UNet and VAE, for latent-space video denoising and pixel-space video reconstruction. In the regularization of latent-space video denoising, SFA exploits two convolutional layers on the latent code of each up-sampled LR frame, to predict a scale and bias to modulate the pixel-wise feature of HR frame. TFA first executes self-attention on HR video latent code within a tubelet to enhance feature interaction, and further performs cross-attention between the tubelet and its LR counterpart for feature calibration in HR video. The LR video features are exploited in the same way to regulate the HR video feature learning in pixel-space video reconstruction. SATeCo finally refines the decoded HR video by referring to the up-sampled LR video via a neural network to balance synthesized quality and fidelity." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 539, + 289, + 647 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 539, + 289, + 647 + ], + "spans": [ + { + "bbox": [ + 46, + 539, + 289, + 647 + ], + "type": "text", + "content": "The main contribution of this paper is the proposal of SATeCo to explore spatial adaptation and temporal coherence in diffusion models for video super-resolution. The solution also leads to the elegant views of how to leverage pixel-wise information from LR videos for visual appearance preservation, and how to achieve frame consistency in HR video generation. Extensive experiments on REDS4 and Vid4 verify the superiority of SATeCo in terms of both spatial quality and temporal consistency." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 657, + 134, + 670 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 657, + 134, + 670 + ], + "spans": [ + { + "bbox": [ + 47, + 657, + 134, + 670 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "content": "Video super-resolution. Modern VSR approaches are mainly based on deep neural networks and can be grouped into two categories, i.e., sliding window-based methods and" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 384 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 384 + ], + "type": "text", + "content": "recurrent methods. Early sliding window-based VSR techniques [1, 22, 50, 51, 53] rely on 2D or 3D CNNs [19, 20] which incorporate a sequence of LR frames to predict center HR frame. To fully utilize the complementary information across adjacent frames, the deformable convolutions [43, 48] are employed for feature alignment. Inspired by the success of transformer architecture in various computer vision tasks [6, 27-29], self-attention emerges to be integrated into the VSR frameworks [14, 23, 26, 47]. One representative is VRT [23] which plugs the temporal mutual attention block into transformer backbone to facilitate motion estimation, feature alignment and fusion. Nevertheless, the sliding window-based approaches are difficult to capture long-range dependencies which could limit the performance of video super-resolution. In contrast to aggregate information from adjacent frames in a short term, recurrent approaches [2, 3, 15, 17, 18, 24, 38, 39, 54] utilize a hidden state to sequentially propagate information from all previous frames to the current frame, benefiting the frame restoration. For instance, Chan et al. [2] adopt a bidirectional propagation scheme with flow-based feature alignment to maximize information gathering in super resolution. Despite having the great capacity of the recurrent models for temporal information gathering, the local details are still hard to be restored when the LR video encounters significant degradation in a long temporal range." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 387, + 547, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 387, + 547, + 639 + ], + "spans": [ + { + "bbox": [ + 304, + 387, + 547, + 639 + ], + "type": "text", + "content": "Diffusion models for super-resolution. Impressive performances of image synthesis achieved by diffusion models [7, 11, 16, 30, 34, 55] encourage the deployment on image super-resolution. These explorations [9, 10, 13, 21, 31, 42, 49, 57] leverage the knowledge prior embedded in the pre-trained diffusion models to magnify images. For example, StableSR [46] integrates a time-aware encoder into Stable-Diffusion [36] model without altering the pre-trained weights, and achieves promising super-resolution results. To further enhance the reconstruction of image texture details, Yang et al. [52] introduce an attention-based control module to maintain pixel consistency between LR and HR images. Different from the advances which optimize a small part of inserted parameters, several approaches [13, 21, 49] fix all weights in the pre-trained synthesis model and attempt to incorporate constraints into the reverse diffusion process to guide image restoration. Although the effectiveness of knowledge prior has been manifested in various diffusion-based ISR methods, it is still a grand challenge to employ diffusion models for video super-resolution and preserve spatial fidelity and temporal consistency." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 642, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 547, + 713 + ], + "type": "text", + "content": "In summary, our work mainly focuses on diffusion models for video super-resolution. The proposal of SATeCo contributes by exploring not only how to preserve spatial fidelity through modulating HR frame features, but also how to calibrate HR video features with LR counterpart for better temporal feature alignment." + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "9233" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 62, + 76, + 532, + 175 + ], + "blocks": [ + { + "bbox": [ + 62, + 76, + 532, + 175 + ], + "lines": [ + { + "bbox": [ + 62, + 76, + 532, + 175 + ], + "spans": [ + { + "bbox": [ + 62, + 76, + 532, + 175 + ], + "type": "image", + "image_path": "3a0bed2ae560a661e058c5700ca6eb93cd913e5720919c36d674beb27706c8fb.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "lines": [ + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "spans": [ + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": "Figure 2. An overview of our SATeCo architecture. The input LR video " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "X_{L}" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": " is first up-sampled to the target resolution via a transformer-based video upscaler. Then, the up-sampled video " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "X_{u}" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": " is fed into the VAE encoder to extract the video features and latent code " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "Z" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": ". Next, the Gaussian noise is added into " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "Z" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": " according to the diffusion scheduler, and the noisy video latent code is then restored by UNet for quality enhancement. In latent space, a latent encoder extracts the LR latent feature maps " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "G" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": " on the LR latent code " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "Z" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": ", followed by spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules in each decoder block of UNet for spatial-temporal guidance learning. Given the denoised video latent code " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "Z_{0}" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": ", the VAE decoder decodes the video " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "X_{d}" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": " based on the guidance learnt by SFA and TFA on LR video features. Finally, the decoded video " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "X_{d}" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": " is adjusted by a video refiner via referring to " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "X_{u}" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": " for final HR video " + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "inline_equation", + "content": "X_{H}" + }, + { + "bbox": [ + 46, + 183, + 547, + 262 + ], + "type": "text", + "content": " synthesis." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 266, + 138, + 280 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 266, + 138, + 280 + ], + "spans": [ + { + "bbox": [ + 47, + 266, + 138, + 280 + ], + "type": "text", + "content": "3. Our Approach" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 288, + 289, + 576 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 288, + 289, + 576 + ], + "spans": [ + { + "bbox": [ + 46, + 288, + 289, + 576 + ], + "type": "text", + "content": "In this section, we present our newly-minted SATeCo, pursuing Spatial Adaptation and Temporal Coherence in diffusion models for video super-resolution. Figure 2 depicts an overview of the architecture. SATeCo begins with a video upscaler to increase the resolution of the input LR video. Then, the up-sampled video is fed into VAE encoder for video feature extraction and latent code prediction. After that, a spatial feature adaptation (SFA) and a temporal feature alignment (TFA) module are leveraged to learn spatial-temporal guidance on latent code and features of LR video, to calibrate latent-space video denoising and pixel-space video reconstruction. As such, the two modules are plugged into each block of the decoder in UNet and VAE. In procedure of video latent code denoising, SFA estimates the affine parameters on LR video latent code to modulate each pixel of the HR video latent code. TFA first performs self-attention on the HR video latent code within a tubelet, and further enhances latent code by executing cross-attention between the tubelet and its LR counterpart. Similarly, SFA and TFA are conducted in the VAE decoder to guide HR video reconstruction with the LR video features. Finally, SATeCo designs a video refiner to adjust the decoded HR video by referring to the up-sampled video for a good trade-off between synthesized quality and fidelity." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 586, + 142, + 599 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 586, + 142, + 599 + ], + "spans": [ + { + "bbox": [ + 47, + 586, + 142, + 599 + ], + "type": "text", + "content": "3.1. Video Upscaler" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "type": "text", + "content": "Most existing VSR approaches [39, 51] first upscale the input LR videos through a resampling operation, and then improve their visual quality. Nevertheless, the widely adopted resampling operations, e.g., Bilinear and Bicubic sampling, might damage the original visual patterns [39] in LR frames, having a negative impact on the subsequent video enhancement. Therefore, we exploit the recipe of reducing frame degradation ahead of the feature learning [4] in neural networks and propose a video upscaler, which gen" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 268, + 545, + 291 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 268, + 545, + 291 + ], + "spans": [ + { + "bbox": [ + 304, + 268, + 545, + 291 + ], + "type": "text", + "content": "erates more accurate up-sampled videos for the following quality enhancement by diffusion models." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "spans": [ + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "type": "text", + "content": "Given the input LR video " + }, + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "type": "inline_equation", + "content": "X_{L}" + }, + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "type": "text", + "content": ", we utilize a transformer-based video upscaler for video up-scaling as illustrated in Figure 3(a). It consists of two cascaded temporal mutual self-attention (TMSA) blocks [23] to temporally aggregate video features, and a pixel-shuffle layer [40] to increase video spatial resolution via feature reshaping. The upsampled video " + }, + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "type": "inline_equation", + "content": "X_{u} = \\{x_{u}^{i}\\}_{i=1}^{L}" + }, + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "type": "text", + "content": " with " + }, + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 292, + 546, + 388 + ], + "type": "text", + "content": " frames is then fed into the diffusion model for video quality enhancement." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 396, + 495, + 408 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 396, + 495, + 408 + ], + "spans": [ + { + "bbox": [ + 305, + 396, + 495, + 408 + ], + "type": "text", + "content": "3.2. Spatial Feature Adaptation Module" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 414, + 545, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 414, + 545, + 617 + ], + "spans": [ + { + "bbox": [ + 304, + 414, + 545, + 617 + ], + "type": "text", + "content": "The inherent stochasticity [52] of diffusion models might result in the distortion of texture details in image superresolution. A natural way of employing diffusion models for super-resolution is to learn the spatial-level condition via convolution-based [46] or transformer-based [52] structure to guide latent code denoising in UNet. Such kind of mechanism only manages feature regularization in latent space, posting difficulty to learn sufficient inductive bias and provide precise guidance for high-resolution image restoration. The similar issue also exists in video superresolution. To alleviate this, we introduce a spatial feature adaptation (SFA) module which dynamically learns pixelwise guidance from the input LR videos for diffusion calibration. In the meanwhile, the SFA module emphasizes the inductive bias learning in both of the latent-space video denoising (i.e., training of UNet) and pixel-space video reconstruction (i.e., training of VAE)." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": "Figure 3(c) illustrates our SFA module. Given the upsampled LR video " + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "inline_equation", + "content": "X_{u}" + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": ", the VAE encoder first encodes " + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "inline_equation", + "content": "X_{u}" + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": " into the video latent code " + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "inline_equation", + "content": "Z = \\{z^{i}\\}_{i = 1}^{L}" + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": ". Next, we exploit a convolution-based latent encoder " + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{E}_z" + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": " to extract the LR latent feature maps " + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "inline_equation", + "content": "G = \\mathcal{E}_z(Z)" + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": ", which are further utilized to guide the HR feature learning in UNet decoder. Formally, we denote the HR intermediate feature maps in UNet and the LR latent feature maps in latent encoder as" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9234" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 64, + 77, + 171, + 194 + ], + "blocks": [ + { + "bbox": [ + 64, + 77, + 171, + 194 + ], + "lines": [ + { + "bbox": [ + 64, + 77, + 171, + 194 + ], + "spans": [ + { + "bbox": [ + 64, + 77, + 171, + 194 + ], + "type": "image", + "image_path": "ce2469dfa5d28971c257720182ebf2a569a1cfdc395970d0ee770cbb007509de.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 48, + 202, + 543, + 214 + ], + "lines": [ + { + "bbox": [ + 48, + 202, + 543, + 214 + ], + "spans": [ + { + "bbox": [ + 48, + 202, + 543, + 214 + ], + "type": "text", + "content": "Figure 3. An illustration of (a) video upscaler, (b) video refiner, (c) spatial feature adaptation and (d) temporal feature alignment module." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 179, + 78, + 326, + 194 + ], + "blocks": [ + { + "bbox": [ + 179, + 78, + 326, + 194 + ], + "lines": [ + { + "bbox": [ + 179, + 78, + 326, + 194 + ], + "spans": [ + { + "bbox": [ + 179, + 78, + 326, + 194 + ], + "type": "image", + "image_path": "bed722ea0b1b0bdbc51a6f6b0567e4b1876c24e99d616431d9a76f17015624c4.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 333, + 79, + 530, + 194 + ], + "blocks": [ + { + "bbox": [ + 333, + 79, + 530, + 194 + ], + "lines": [ + { + "bbox": [ + 333, + 79, + 530, + 194 + ], + "spans": [ + { + "bbox": [ + 333, + 79, + 530, + 194 + ], + "type": "image", + "image_path": "b3e36fa69554affd8566693dc958e8f70a561ad6ecbc13df5cde3990d227029f.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "spans": [ + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "inline_equation", + "content": "F = \\{f^{i}\\}_{i = 1}^{L}" + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "inline_equation", + "content": "G = \\{g^i\\}_{i = 1}^L" + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "text", + "content": " , respectively. For the " + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "text", + "content": " -th frame, we measure a scale ratio " + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "inline_equation", + "content": "S^i\\in \\mathbb{R}^{H\\times W\\times C}" + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "text", + "content": " and a bias " + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "inline_equation", + "content": "M^i\\in \\mathbb{R}^{H\\times W\\times C}" + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "text", + "content": " for each pixel of HR intermediate feature map " + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "inline_equation", + "content": "f^{i}\\in \\mathbb{R}^{H\\times W\\times C}" + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "text", + "content": " based on the LR latent feature map " + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "inline_equation", + "content": "g^{i}\\in \\mathbb{R}^{H\\times W\\times C}" + }, + { + "bbox": [ + 47, + 227, + 287, + 288 + ], + "type": "text", + "content": " via two 2D convolution layers:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 80, + 294, + 287, + 308 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 80, + 294, + 287, + 308 + ], + "spans": [ + { + "bbox": [ + 80, + 294, + 287, + 308 + ], + "type": "interline_equation", + "content": "M ^ {i} = \\operatorname {C o n v 2 D} (g ^ {i}), \\quad S ^ {i} = \\operatorname {C o n v 2 D} (g ^ {i}). \\tag {1}", + "image_path": "2ca02a9c650fad3fbeb757c05057e3cbd07bca90c3ec85cb50f94c163cee7670.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "spans": [ + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "text", + "content": "Then, the output HR feature map " + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "inline_equation", + "content": "\\tilde{f}^i" + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "text", + "content": " in UNet is generated by modulating the normalized HR intermediate feature map " + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "inline_equation", + "content": "f^i" + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "text", + "content": " with " + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "inline_equation", + "content": "S^i" + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "inline_equation", + "content": "M^i" + }, + { + "bbox": [ + 47, + 315, + 287, + 352 + ], + "type": "text", + "content": " as:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 111, + 357, + 287, + 382 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 111, + 357, + 287, + 382 + ], + "spans": [ + { + "bbox": [ + 111, + 357, + 287, + 382 + ], + "type": "interline_equation", + "content": "\\tilde {f} ^ {i} = S ^ {i} \\odot \\frac {f ^ {i} - \\mu^ {i}}{\\sigma^ {i}} + M ^ {i}, \\tag {2}", + "image_path": "8a13bfa96b50a484c66ad59f3113128ecc662e1d7f8210e2acf3faa6df34bc89.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "spans": [ + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "inline_equation", + "content": "\\odot" + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "text", + "content": " denotes point-wise multiplication. " + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "inline_equation", + "content": "\\mu^i" + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "inline_equation", + "content": "\\sigma^i" + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "text", + "content": " are the mean and standard deviation values of the feature map " + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "inline_equation", + "content": "f^i" + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "text", + "content": ". Hence, the affine parameters estimated on the latent feature maps of LR videos calibrate the intermediate feature maps of HR videos in latent code denoising, which adaptively injects the pixel-wise information into the video latent code to preserve the visual appearance. For video feature learning in pixel space, SFA module is inserted into each block of VAE decoder. Similarly, the extracted video features of LR videos are taken as the guidance to estimate the affine parameters in SFA module to adjust HR video feature learning for video reconstruction. We take all the modulated intermediate feature maps " + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "inline_equation", + "content": "\\tilde{f}^i" + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "text", + "content": " from SFA module as " + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "inline_equation", + "content": "\\tilde{F} = \\{\\tilde{f}^i\\}_{i=1}^L" + }, + { + "bbox": [ + 46, + 389, + 287, + 568 + ], + "type": "text", + "content": ", which is employed for the following temporal feature alignment in the UNet and VAE decoders." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 575, + 244, + 588 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 575, + 244, + 588 + ], + "spans": [ + { + "bbox": [ + 47, + 575, + 244, + 588 + ], + "type": "text", + "content": "3.3. Temporal Feature Alignment Module" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 594, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 287, + 712 + ], + "type": "text", + "content": "Frame-wisely conducting ISR models for video super-resolution could amplify the differences of blurry patterns [39] across frames, leading to content inconsistency such as the object shape deformation. The issue originated from solely relying on spatial level super-resolution and lacking temporal coherence modeling across frames. To facilitate visual content alignment in video super-resolution, a temporal feature alignment (TFA) module is devised after each SFA module in UNet and VAE decoder, for the temporal feature interaction and calibration." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "spans": [ + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": "Figure 3(d) depicts the learning procedure of TFA module. Given the input HR intermediate feature maps " + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\tilde{F} = \\{\\tilde{f}^i\\}_{i=1}^L" + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": " from the SFA module in UNet decoder, we first partition the feature map " + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\tilde{f}^i" + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": " of each frame into " + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": " non-overlapping windows with the spatial resolution of " + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "inline_equation", + "content": "h \\times w" + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "inline_equation", + "content": "N = \\frac{HW}{hw}" + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": " is the total window number. Then, we link all features within a local window across " + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": " frames to form a HR feature tubelet " + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\tilde{F}_{tub} \\in \\mathbb{R}^{L \\times h \\times w \\times C}" + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": ". We reshape the dimension of each HR feature tubelet into " + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "inline_equation", + "content": "hwL \\times C" + }, + { + "bbox": [ + 305, + 228, + 545, + 346 + ], + "type": "text", + "content": " and execute the standard self-attention on it:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 365, + 353, + 545, + 373 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 365, + 353, + 545, + 373 + ], + "spans": [ + { + "bbox": [ + 365, + 353, + 545, + 373 + ], + "type": "interline_equation", + "content": "Q, K, V = \\operatorname {C o n v 3 D} (\\tilde {F} _ {t u b}), \\tag {3}", + "image_path": "e5ff543cac39339b16fa4c7b833811ddeaddcf2db2667bc2d389da1d91b94a7d.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 366, + 370, + 485, + 384 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 366, + 370, + 485, + 384 + ], + "spans": [ + { + "bbox": [ + 366, + 370, + 485, + 384 + ], + "type": "interline_equation", + "content": "\\hat {F} _ {t u b} = \\operatorname {A t t e n t i o n} (Q, K, V),", + "image_path": "281f64e5936881be23c6aaf54b678425483417eabcbd3f32a5e0c61d7ee9bd49.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "spans": [ + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "inline_equation", + "content": "Q, K, V \\in \\mathbb{R}^{hwL \\times C}" + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "text", + "content": " are the query, key and value matrices, respectively. Each of them is predicted by a 3D convolution layer. The self-attention conducted on the HR feature tubelet enables the feature interaction across different frames, mitigating the temporal feature misalignment in local regions. To further conduct the temporal feature calibration, we leverage the counterpart of HR feature tubelet, i.e., the feature tubelet " + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "inline_equation", + "content": "G_{tub}" + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "text", + "content": " of the LR latent feature maps, as a reference for feature adjustment. We perform the cross-attention between " + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "inline_equation", + "content": "\\hat{F}_{tub}" + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "inline_equation", + "content": "G_{tub}" + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "text", + "content": " to obtain the output feature tubelet " + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "inline_equation", + "content": "\\bar{F}_{tub}" + }, + { + "bbox": [ + 304, + 392, + 545, + 524 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 315, + 531, + 545, + 550 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 531, + 545, + 550 + ], + "spans": [ + { + "bbox": [ + 315, + 531, + 545, + 550 + ], + "type": "interline_equation", + "content": "Q ^ {\\prime} = \\operatorname {C o n v 3 D} \\left(\\hat {F} _ {t u b}\\right), \\quad K ^ {\\prime}, V ^ {\\prime} = \\operatorname {C o n v 3 D} \\left(G _ {t u b}\\right), \\tag {4}", + "image_path": "996c3909131470dfac11d4758fa18242ba3e9a5baf39402cf881bd53c8e4cd84.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 317, + 547, + 444, + 559 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 547, + 444, + 559 + ], + "spans": [ + { + "bbox": [ + 317, + 547, + 444, + 559 + ], + "type": "interline_equation", + "content": "\\bar {F} _ {t u b} = \\operatorname {A t t e n t i o n} \\left(Q ^ {\\prime}, K ^ {\\prime}, V ^ {\\prime}\\right),", + "image_path": "d67a9f02e446f810453b4e72c3cb40c53be3969798024b2cafe3ab220e3865c1.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "text", + "content": "where the query " + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "inline_equation", + "content": "Q^{\\prime}" + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "text", + "content": " is learnt on the HR feature tubelet " + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\hat{F}_{tub}" + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "text", + "content": " and the key/value " + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "inline_equation", + "content": "K^{\\prime} / V^{\\prime}" + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "text", + "content": " is estimated on the LR counterpart via 3D convolution layers, respectively. We collect all the output feature tubelets from the TFA module and reshape them into the original size as " + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\bar{F}\\in \\mathbb{R}^{L\\times H\\times W\\times C}" + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "text", + "content": ". The output feature " + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "inline_equation", + "content": "\\bar{F}" + }, + { + "bbox": [ + 304, + 570, + 545, + 653 + ], + "type": "text", + "content": " is then fed into the next block of the decoder in UNet or VAE for video latent denoising or reconstruction." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": "In this way, the coupled SFA and TFA modules in UNet and VAE decoder not only emphasize the pixel-wise feature adaptation for visual appearance preservation but also strengthen the temporally feature interaction and calibration for temporal coherence modeling." + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9235" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 108, + 538, + 264 + ], + "blocks": [ + { + "bbox": [ + 46, + 70, + 547, + 105 + ], + "lines": [ + { + "bbox": [ + 46, + 70, + 547, + 105 + ], + "spans": [ + { + "bbox": [ + 46, + 70, + 547, + 105 + ], + "type": "text", + "content": "Table 1. Performance comparisons in terms of pixel-based (PSNR and SSIM) and perception-based (LPIPS, DISTS, NIQE and CLIP-IQA) evaluation metrics on the REDS4 and Vid4 datasets. The width and height of the LR videos are rescaled by 4 times through different VSR approaches. We follow VRT [23] to set the frame number as 6 in each clip for HR video inference." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 51, + 108, + 538, + 264 + ], + "lines": [ + { + "bbox": [ + 51, + 108, + 538, + 264 + ], + "spans": [ + { + "bbox": [ + 51, + 108, + 538, + 264 + ], + "type": "table", + "html": "
DatasetsMetricsBicubicStableSR [46]TOFlow [51]EDVR-M [48]BasicVSR [2]VRT [23]IconVSR [2]SATeCo
REDS4PSNR↑26.1424.7927.9830.5331.4231.6031.6731.62
SSIM↑0.72920.68970.79900.86990.89090.88880.89480.8932
LPIPS↓0.35190.24120.31040.23120.20230.20770.19390.1735
DISTS↓0.18760.07550.14680.09430.08080.08230.07620.0607
NIQE↓7.2574.1166.2604.5444.1974.2524.1174.104
CLIP-IQA↑0.60450.65790.61760.63820.63530.63790.61620.6622
Vid4PSNR↑23.7822.1825.8927.1027.2427.9327.3927.44
SSIM↑0.63470.59040.76510.81860.82510.84250.82790.8420
LPIPS↓0.39470.36700.33860.28980.28110.27230.27390.2291
DISTS↓0.22010.13850.17760.14680.14420.13720.14060.1015
NIQE↓7.5365.2377.2295.5285.3405.2425.3925.212
CLIP-IQA↑0.68170.76440.73650.73800.74100.74340.74110.7451
", + "image_path": "9a5e460e7b73a28552299b73a5dd413c194a8776506fb3235f6d0b6951ac7f5c.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 277, + 135, + 289 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 277, + 135, + 289 + ], + "spans": [ + { + "bbox": [ + 47, + 277, + 135, + 289 + ], + "type": "text", + "content": "3.4. Video Refiner" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 296, + 287, + 403 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 296, + 287, + 403 + ], + "spans": [ + { + "bbox": [ + 46, + 296, + 287, + 403 + ], + "type": "text", + "content": "Recent advance [8] reveals that images synthesized by diffusion model conditioning on visual contents might lose some original color information in local regions. To address this problem, StableSR [46] performs a non-parametric post-processor to refine the generation with reference to original input for achieving color preservation. Instead, we propose a trainable video refiner to emphasize the adjustment of decoded HR video from VAE decoder, by leveraging the information from up-sampled LR video." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "spans": [ + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "text", + "content": "Figure 3(b) details the structure of our video refiner. We first concatenate the decoded video " + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "inline_equation", + "content": "X_{d}" + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "text", + "content": " and the up-sampled LR video " + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "inline_equation", + "content": "X_{u}" + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "text", + "content": " along channel dimension, and then feed it into a residual block. The refined HR video " + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "inline_equation", + "content": "X_{H}" + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "text", + "content": " is generated by fusing " + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "inline_equation", + "content": "X_{u}" + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "inline_equation", + "content": "X_{d}" + }, + { + "bbox": [ + 46, + 403, + 287, + 475 + ], + "type": "text", + "content": " and the output feature mapping of residual block as:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 55, + 480, + 287, + 495 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 480, + 287, + 495 + ], + "spans": [ + { + "bbox": [ + 55, + 480, + 287, + 495 + ], + "type": "interline_equation", + "content": "X _ {H} = w X _ {u} + (1 - w) X _ {d} + \\operatorname {R e s B l o c k} ([ X _ {u}, X _ {d} ]), \\tag {5}", + "image_path": "93a27350ff1726b323a93373d74c416e446f10cf5078d627a1790d53f6312655.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 498, + 287, + 571 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 287, + 571 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 287, + 571 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 498, + 287, + 571 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 46, + 498, + 287, + 571 + ], + "type": "text", + "content": " is a trade-off parameter. The devised video refiner balances the original visual contents of the up-sampled LR video and the synthesized contents of decoded HR video via feature fusion learning. Accordingly, our design is more powerful in terms of color preservation, and achieves a good trade-off between the synthesized quality and fidelity." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 575, + 153, + 588 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 575, + 153, + 588 + ], + "spans": [ + { + "bbox": [ + 47, + 575, + 153, + 588 + ], + "type": "text", + "content": "3.5. Training Strategy" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 594, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 713 + ], + "type": "text", + "content": "We construct our SATeCo for video super-resolution based on the Stable Diffusion [36] model. There are four training stages to optimize the whole architecture. In the first stage, we train the video upscaler using the Charbonnier loss [5] to optimize the video reconstruction of HR videos. After that, we follow the standard setting in [36] to train UNet for the optimization of the inserted SFA and TFA modules. We fix all parameters of UNet except for the two kinds of modules during training. For the optimization of SFA and TFA modules in VAE decoder, we take the video latent codes of the" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 277, + 545, + 338 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 277, + 545, + 338 + ], + "spans": [ + { + "bbox": [ + 304, + 277, + 545, + 338 + ], + "type": "text", + "content": "HR videos as the input, and optimize the similarity between the decoded videos and ground-truth HR videos. Finally, we freeze all the parameters in video upscaler, UNet and VAE, and train the video refiner using the pairs of decoded and ground-truth HR videos." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 350, + 388, + 364 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 350, + 388, + 364 + ], + "spans": [ + { + "bbox": [ + 305, + 350, + 388, + 364 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 370, + 432, + 384 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 370, + 432, + 384 + ], + "spans": [ + { + "bbox": [ + 305, + 370, + 432, + 384 + ], + "type": "text", + "content": "4.1. Experimental Settings" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "spans": [ + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "type": "text", + "content": "Datasets. We empirically evaluate the effectiveness of our SATeCo on two widely-used datasets: REDS [33] and Vid4 [25]. The REDS dataset consists of 240, 30 and 30 video clips for training, validation and testing. Each video clip contains 100 frames with the resolution of " + }, + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "type": "inline_equation", + "content": "1,280 \\times 720" + }, + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "type": "text", + "content": ". We employ the standard protocols in [2, 3, 48] and select four video clips from the validation set as the testing data, namely REDS4. The Vid4 dataset also includes four video clips, and there are about 40 frames in each clip with the resolution of " + }, + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "type": "inline_equation", + "content": "720 \\times 480" + }, + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "type": "text", + "content": ". Following the standard settings [3, 23], we employ all the videos in Vid4 for evaluation and choose the video data in the training set of Vimeo-90K [51] for model optimization. There are 64, 612 training clips and each clip has 7 frames with the resolution of " + }, + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "type": "inline_equation", + "content": "448 \\times 256" + }, + { + "bbox": [ + 304, + 389, + 545, + 556 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "text", + "content": "Implementation Details. We implement our SATeCo on the PyTorch platform by using Diffusers [44] library. The noise scheduler is set as linear scheduler " + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "inline_equation", + "content": "(\\beta_{1} = 0.00085, \\beta_{T} = 0.0120, \\text{and } T = 1,000)" + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "text", + "content": ". The trade-off parameters " + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "text", + "content": " in video refiner is determined as 0.5 by cross validation. We empirically set the window size in TFA as " + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "inline_equation", + "content": "h = 8" + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "inline_equation", + "content": "w = 8" + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "text", + "content": ". The frame number " + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "text", + "content": " of input clip is 6. The model is trained with AdamW optimizer and the learning rate is " + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "inline_equation", + "content": "5.0 \\times 10^{-5}" + }, + { + "bbox": [ + 304, + 557, + 545, + 653 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "type": "text", + "content": "Evaluation Metrics. We evaluate the VSR models via two kinds of metrics, i.e., pixel-based and perception-based metrics. The pixel-based metrics include PSNR and SSIM which calculate the similarity of every pixel between the generated and ground-truth HR videos. There are also some" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9236" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 72, + 82, + 521, + 378 + ], + "blocks": [ + { + "bbox": [ + 72, + 82, + 521, + 378 + ], + "lines": [ + { + "bbox": [ + 72, + 82, + 521, + 378 + ], + "spans": [ + { + "bbox": [ + 72, + 82, + 521, + 378 + ], + "type": "image", + "image_path": "8e89fa84f260fcb1b7b0253f81692b1cd77e782471946d7ceeea1d127d4c7dfb.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 384, + 546, + 407 + ], + "lines": [ + { + "bbox": [ + 46, + 384, + 546, + 407 + ], + "spans": [ + { + "bbox": [ + 46, + 384, + 546, + 407 + ], + "type": "text", + "content": "Figure 4. Six visual examples of video super-resolution results by different approaches on the REDS4 and Vid4 datasets. The region in the red box is presented in the zoom-in view for comparison." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 413, + 289, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 413, + 289, + 617 + ], + "spans": [ + { + "bbox": [ + 46, + 413, + 289, + 617 + ], + "type": "text", + "content": "perception-based evaluation metrics for super-resolution. These metrics mainly measure video quality from the viewpoint of human perceptual preference, and we adopt LPIPS [56], DISTS [12], NIQE [32] and CLIP-IQA [45] in this paper. Specifically, LPIPS utilizes VGG [41] model to extract frame features and measures the feature similarity between the synthesized and ground-truth videos. DISTS also computes the feature similarity between video pairs via a variant of VGG model, but the emphasis is on image texture. For NIQE and CLIP-IQA, the scores are directly predicted by the learnt models without using the ground-truth HR videos. NIQE measures the similarity of feature distribution between synthesized frames and a realistic image set [32], while CLIP-IQA computes cosine similarity between generated frames and text prompts (e.g., \"High Resolution\") via CLIP model [35]. In addition, we conduct a user study to verify human preference on different models." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 623, + 278, + 636 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 623, + 278, + 636 + ], + "spans": [ + { + "bbox": [ + 47, + 623, + 278, + 636 + ], + "type": "text", + "content": "4.2. Comparisons with State-of-the-Art Methods" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 641, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 287, + 689 + ], + "type": "text", + "content": "We compare our SATeCo with several state-of-the-art techniques, including Bicubic Interpolation, StableSR [46], TOFlow [51], EDVR-M [48], BasicVSR [2], VRT [23] and IconVSR [2], on REDS4 and Vid4 datasets." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 689, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 288, + 715 + ], + "type": "text", + "content": "Quantitative Evaluation. Table 1 summarizes the performances of different VSR approaches in terms of the six" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 413, + 547, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 413, + 547, + 688 + ], + "spans": [ + { + "bbox": [ + 304, + 413, + 547, + 688 + ], + "type": "text", + "content": "metrics over the two datasets. Overall, SATeCo achieves the best performances across all perception-based metrics (i.e., LPIPS, DISTS, NIQE and CLIP-IQA) on REDS4. These metrics emphasize the quality judgment from human perceptual aspect and the results demonstrate the advantage of exploiting abundant knowledge prior in the pre-trained diffusion models to generate high-quality HR videos with better visual perception. In terms of pixel-based metrics, recent advances [46, 52] manifest that the stochasticity in diffusion models could hurt the preservation of visual appearance in HR videos, resulting in inferior performances to traditional regression models. Our SATeCo, by capitalizing on pixel-wise guidance from LR videos to modulate HR frame feature synthesis, alleviates the downsides and obtains the PSNR of 31.62dB. Notably, such performance is very comparable to that of IconVSR [2], which is the SOTA baseline of regression VSR models. The performance trends on Vid4 are similar with those on REDS4. In particular, SATeCo attains the DISTS of 0.1015, which relatively reduces that of the best competitor VRT [23] by " + }, + { + "bbox": [ + 304, + 413, + 547, + 688 + ], + "type": "inline_equation", + "content": "26.0\\%" + }, + { + "bbox": [ + 304, + 413, + 547, + 688 + ], + "type": "text", + "content": ". The results indicate that SATeCo benefits from learning pixel-wise spatial adaption in diffusion to preserve frame-wise image texture for achieving better video fidelity." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 689, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 547, + 715 + ], + "type": "text", + "content": "Qualitative Evaluation. Figure 4 visualizes the video super-resolution with six examples from REDS4 and Vid4." + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "9237" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 69, + 83, + 167, + 162 + ], + "blocks": [ + { + "bbox": [ + 69, + 83, + 167, + 162 + ], + "lines": [ + { + "bbox": [ + 69, + 83, + 167, + 162 + ], + "spans": [ + { + "bbox": [ + 69, + 83, + 167, + 162 + ], + "type": "image", + "image_path": "ccfdc5641a30ed923d1bb57f6c3fe04827b3bedd11ea9588a7db9761b5634e20.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 81, + 163, + 155, + 171 + ], + "lines": [ + { 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Video super-resolution results of two videos in the Vid4 dataset. The region in the same local position across two adjacent frames (i.e., regions highlighted by red and blue boxes) is scaled up to show more details." + } + ] + } + ], + "index": 33, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 67, + 320, + 266, + 427 + ], + "lines": [ + { + "bbox": [ + 67, + 320, + 266, + 427 + ], + "spans": [ + { + "bbox": [ + 67, + 320, + 266, + 427 + ], + "type": "image", + "image_path": "3595938b09258414dcba2a1f084ec9b82bda6e9a48b58f9119beefa4f14644bb.jpg" + } + ] + } + ], + "index": 34, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 429, + 286, + 451 + ], + "lines": [ + { + "bbox": [ + 46, + 429, + 286, + 451 + ], + "spans": [ + { + "bbox": [ + 46, + 429, + 286, + 451 + ], + "type": "text", + "content": "Figure 6. Human evaluation of user preference ratios between SATeCo and other baselines on REDS4 and Vid4." + } + ] + } + ], + "index": 35, + "angle": 0, + "type": "image_caption" + } + ], + "index": 34 + }, + { + "bbox": [ + 46, + 460, + 287, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 460, + 287, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 460, + 287, + 687 + ], + "type": "text", + "content": "Compared to other baselines, SATeCo can successfully restore more local details (e.g., the sharp edges in the eave and spoke of the 2nd and 3rd case) in frames with high fidelity. Even with large blurriness (e.g., the 4th case), SATeCo still exhibits the strong restoration ability for video super-resolution, which again confirms the effectiveness of leveraging rich knowledge prior of diffusion models and learning spatial adaptation. To further validate the temporal coherence learnt by SATeCo, we visualize two adjacent frames of two synthesized HR videos by using different diffusion-based super-resolution approaches in Figure 5. As observed in the figure, LDM and StableSR synthesize different visual contents across the two frames, e.g., the small windows in the building. In contrast, our SATeCo predicts the HR videos with higher frame consistency and preserves the visual fidelity. That basically validates the merit of performing tubelet-based self-attention within HR videos and cross-attention between HR videos and LR counterparts to achieve better temporal feature interaction and calibration." + } + ] + } + ], + "index": 36 + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": "Human Evaluation. Next, we further conduct human study to verify the HR video generation quality by using" + } + ] + } + ], + "index": 37 + }, + { + "type": "table", + "bbox": [ + 306, + 345, + 550, + 430 + ], + "blocks": [ + { + "bbox": [ + 306, + 319, + 545, + 341 + ], + "lines": [ + { + "bbox": [ + 306, + 319, + 545, + 341 + ], + "spans": [ + { + "bbox": [ + 306, + 319, + 545, + 341 + ], + "type": "text", + "content": "Table 2. Performance comparisons on REDS4 among variants with different integration of SFA and TFA modules." + } + ] + } + ], + "index": 38, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 306, + 345, + 550, + 430 + ], + "lines": [ + { + "bbox": [ + 306, + 345, + 550, + 430 + ], + "spans": [ + { + "bbox": [ + 306, + 345, + 550, + 430 + ], + "type": "table", + "html": "
ModelUNetVAEPSNR↑SSIM↑LPIPS↓DISTS↓NIQE↓
SFATFASFATFA
A28.560.79250.21590.07584.404
B✓28.930.80870.20420.06934.349
C✓✓29.450.83980.18920.06204.324
D✓✓✓✓31.620.89320.17350.06074.104
", + "image_path": "c6810e74e71c283f85c8812268648dcb159af5d2d13678dfdd3c64b8fef7c0c3.jpg" + } + ] + } + ], + "index": 39, + "angle": 0, + "type": "table_body" + } + ], + "index": 39 + }, + { + "bbox": [ + 304, + 445, + 545, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 445, + 545, + 590 + ], + "spans": [ + { + "bbox": [ + 304, + 445, + 545, + 590 + ], + "type": "text", + "content": "different VSR approaches with respect to the user preference. We invite 100 evaluators on the Amazon MTurk platform, and ask each evaluator to choose the better one from two synthetic HR videos generated by two different methods given the same LR video. Figure 6 depicts the user preference ratios on all eight videos in the REDS4 and Vid4 datasets. SATeCo clearly wins the traditional regression models of IconVSR, BasicVSR and VRT, and the diffusion model of StableSR. The results indicate SATeCo nicely magnifies LR videos with better visual quality and temporal coherence through the spatial feature adaptation and temporal feature alignment design in video diffusion procedure." + } + ] + } + ], + "index": 40 + }, + { + "bbox": [ + 306, + 598, + 400, + 611 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 598, + 400, + 611 + ], + "spans": [ + { + "bbox": [ + 306, + 598, + 400, + 611 + ], + "type": "text", + "content": "4.3. Model Analysis" + } + ] + } + ], + "index": 41 + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "content": "Analysis on SFA and TFA modules. We first investigate how the SFA and TFA modules influence the overall performances of video super-resolution. Table 2 lists the performance comparisons among variants with different integration ways of SFA and TFA modules. We start from the basic diffusion model A, which leverages the zero-initialized convolution [55] in UNet/VAE to learn the spatial guidance from LR videos for super-resolution. The model B and C" + } + ] + } + ], + "index": 42 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9238" + } + ] + } + ], + "index": 43 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 99, + 293, + 182 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "type": "text", + "content": "Table 3. Ablation studies on the design of video upscaler and video refiner in SATeCo. The performances are reported on REDS4." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 99, + 293, + 182 + ], + "lines": [ + { + "bbox": [ + 48, + 99, + 293, + 182 + ], + "spans": [ + { + "bbox": [ + 48, + 99, + 293, + 182 + ], + "type": "table", + "html": "
ModelPSNR↑SSIM↑LPIPS↓DISTS↓NIQE↓
UpscalerPixelShuffle29.770.84260.19790.07204.298
Ours31.620.89320.17350.06074.104
Refinerw = 030.360.85720.15810.03393.457
w = 0.531.620.89320.17350.06074.104
w = 1.028.990.80010.18150.06524.488
", + "image_path": "88ec61f3f6b7df5539446fccd7c9ad777825b9a0b124e20303e11daeef8f3acf.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 194, + 289, + 469 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 194, + 289, + 469 + ], + "spans": [ + { + "bbox": [ + 46, + 194, + 289, + 469 + ], + "type": "text", + "content": "gradually upgrade the basic model A through plugging SFA and TFA modules into the UNet, which improves the PSNR from 28.56dB to 29.45dB. Compared to zero-initialized convolution which simply conducts weighted summation of LR frame features and HR ones to guide spatial-level diffusion learning, the combination of SFA and TFA not only enhances the spatial adaptation via feature modulation but also strengthens temporal feature alignment by the tubelet-based attention. As such, the higher PSNR and SSIM which measure the spatial fidelity is attained by the model C. Finally, the model D, i.e., our SATeCo, by further exploiting SFA and TFA in VAE to regulate pixel-space video reconstruction, shows the best performances in PSNR and SSIM. In view of perception-based evaluation metrics, SATeCo also constantly obtains improvements over other variants, indicating the potential benefit from spatial-temporal guidance learning to enhance visual perception in HR videos. Furthermore, Figure 7 showcases video super-resolution in a local region of one example in two adjacent frames. SATeCo reconstructs the HR videos with high-quality visual appearance and promising temporal consistency among adjacent frames, proving the impact of exploring feature adaptation and alignment in diffusion for super-resolution." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 472, + 287, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 472, + 287, + 639 + ], + "spans": [ + { + "bbox": [ + 46, + 472, + 287, + 639 + ], + "type": "text", + "content": "Analysis on Video Upscaler. Then, we study the effectiveness of the video upscaler in the SATeCo. One alternative is to employ the pre-trained Pixel Shuffle layer [40] as the video upscaler. The upper part of Table 3 details the performances of the two approaches on REDS4. Our approach exhibits better performances against PixelShuffle across all evaluation metrics, especially in PSNR and SSIM. Technically, PixelShuffle resamples videos via directly conducting a 2D convolution layer on the input frames. Instead, ours delves into the formulation of frame-wise correlation through temporal mutual self-attention, which is more effective in pixel feature enhancement for video resampling. As such, ours effectively preserves the visual contents in LR videos and facilitates the subsequent video diffusion." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 641, + 288, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 288, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 288, + 712 + ], + "type": "text", + "content": "Analysis on Video Refiner. The video refiner in SATeCo aims for adjusting the decoded HR videos from diffusion model by referring up-sampled original LR videos to alleviate color degradation. The trade-off parameter " + }, + { + "bbox": [ + 46, + 641, + 288, + 712 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 46, + 641, + 288, + 712 + ], + "type": "text", + "content": " in video refiner balances the impact of the visual contents between the decoded videos and the LR videos. To evaluate" + } + ] + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 309, + 72, + 545, + 167 + ], + "blocks": [ + { + "bbox": [ + 309, + 72, + 545, + 167 + ], + "lines": [ + { + "bbox": [ + 309, + 72, + 545, + 167 + ], + "spans": [ + { + "bbox": [ + 309, + 72, + 545, + 167 + ], + "type": "image", + "image_path": "313aa67c5c46d366ecaae5e3f89267d184ded80e6b084569d3f2276649083f1f.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 173, + 545, + 195 + ], + "lines": [ + { + "bbox": [ + 305, + 173, + 545, + 195 + ], + "spans": [ + { + "bbox": [ + 305, + 173, + 545, + 195 + ], + "type": "text", + "content": "Figure 7. Zoom-in view of two adjacent frames in one video superresolution result synthesized by variants of SATeCo." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "spans": [ + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "text", + "content": "the influence of the parameter " + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "text", + "content": ", we list the VSR performances by varying " + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "text", + "content": " in the lower part of Table 3. When " + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "text", + "content": " is 0, the performances on perception-based metrics are the best, but there is a slight performance drop on PSNR and SSIM. The performances indicate that the synthesized visual contents by diffusion models are more acceptable for human visual system. In contrast, employing a large value of " + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "text", + "content": " (e.g., 1.0) for video refinement considers the information of LR videos more and weakens the contribution of diffusion models, affecting the quality of visual content generation. Therefore, we empirically set the " + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 304, + 204, + 545, + 361 + ], + "type": "text", + "content": " as 0.5 to seek a good trade-off between the synthesized contents and original visual appearance." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 370, + 384, + 383 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 370, + 384, + 383 + ], + "spans": [ + { + "bbox": [ + 306, + 370, + 384, + 383 + ], + "type": "text", + "content": "5. Conclusions" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 390, + 545, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 390, + 545, + 629 + ], + "spans": [ + { + "bbox": [ + 304, + 390, + 545, + 629 + ], + "type": "text", + "content": "We have presented SATeCo that explores spatial adaptation and temporal coherence in diffusion models for video superresolution. In particular, we study the problem of learning spatial-temporal guidance from low-resolution videos to calibrate high-resolution video diffusion procedure. To materialize our idea, SATeCo freezes all the parameters in the pre-trained UNet/VAE, and plugs the spatial feature adaptation (SFA) and temporal feature alignment (TFA) modules in each decoder block to regulate latent-space video denoising and pixel-space video reconstruction. Through learning affine parameters on the guidance of low-resolution videos, SFA modulates the high-resolution features of each pixel to achieve spatial adaptation. TFA performs self-attention within a tubelet to enhance feature interaction and further conducts cross-attention between the tubelet and its low-resolution counterpart to guide temporal feature alignment learning. Experiments conducted on two video datasets, i.e., REDS4 and Vid4, validate the effectiveness of the proposed SATeCo for video super-resolution in terms of both spatial fidelity and temporal consistency." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 630, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 545, + 712 + ], + "type": "text", + "content": "Acknowledgments. This work was supported in part by the National Natural Science Foundation of China under Contract 62021001, and in part by the Fundamental Research Funds for the Central Universities under contract WK3490000007. It was also supported by the GPU cluster built by MCC Lab of Information Science and Technology Institution of USTC." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9239" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 712 + ], + "type": "list", + "angle": 0, + "index": 18, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "text", + "content": "[1] Jose Caballero, Christian Ledig, Andrew Aitken, Alejandro Acosta, Johannes Totz, Zehan Wang, and Wenzhe Shi. 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In CVPRW, 2023. 2" + } + ] + } + ], + "index": 24 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "text", + "content": "9241" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_content_list.json b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..cfb04ebea5c1d5f8202723e71d074fedb01d5d84 --- /dev/null +++ b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_content_list.json @@ -0,0 +1,1537 @@ +[ + { + "type": "text", + "text": "Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos", + "text_level": 1, + "bbox": [ + 171, + 130, + 799, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Sagnik Majumder $^{1,2}$ Ziad Al-Halah $^{3}$ Kristen Grauman $^{1,2}$ $^{1}$ UT Austin ${}^{2}$ FAIR, Meta ${}^{3}$ University of Utah", + "bbox": [ + 222, + 202, + 746, + 239 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 273, + 313, + 289 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We propose a self-supervised method for learning representations based on spatial audio-visual correspondences in egocentric videos. Our method uses a masked autoencoding framework to synthesize masked binaural audio through the synergy of audio and vision, thereby learning useful spatial relationships between the two modalities. We use our pretrained features to tackle two downstream video tasks requiring spatial understanding in social scenarios: active speaker detection and spatial audio denoising. Through extensive experiments, we show that our features are generic enough to improve over multiple state-of-the-art baselines on both tasks on two challenging egocentric video datasets that offer binaural audio, EgoCom and EasyCom. Project: http://vision.cs.utexas.edu/projects/ego_av_corr.", + "bbox": [ + 75, + 306, + 473, + 532 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 553, + 209, + 569 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Egocentric videos provide a first-person view of how we perceive and interact with our surroundings in daily life, and they are pushing a new frontier in multi-modal learning [9, 25, 31, 62]. A key aspect of ego-video is that it can provide a rich stream of first-person spatial audio alongside visual frames when the audio is captured with multiple microphones [11, 49]. The coupling of such audio and vision provides strong spatial information about the sound sources (e.g. where the sound sources are, if they are in motion or not) in the context of the surrounding physical space (e.g. how big or small the room is, if there is a large wall nearby), as well as the camera wearer's attention in the scene revealed by how they move their head.", + "bbox": [ + 75, + 579, + 470, + 775 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Such spatial cues are especially important for social settings of multiple people talking to each other, where it is valuable to be able to 1) focus on the voice(s) of interest from among various competing sounds and 2) understand where people are directing their speech activity, for better", + "bbox": [ + 75, + 776, + 470, + 853 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e2229996018cf76966a196c5966ebc5fcefa7318d7dfbbee102e277e79b7a11a.jpg", + "image_caption": [ + "Figure 1. Given an egocentric video and binaural audio, we aim to learn spatial correspondences between vision and audio by solving the pretext task of inpainting segments of the binaural audio. The features benefit downstream social tasks where spatial localization is important: active speaker detection and audio denoising." + ], + "image_footnote": [], + "bbox": [ + 500, + 271, + 890, + 449 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "comprehension and communication. In this way, future AR applications in conversational settings could allow a hearing-impaired person to determine who is speaking in order to redirect their attention, or enhance the received audio to make it more intelligible for any listener.", + "bbox": [ + 496, + 549, + 893, + 626 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We argue that this creates the need for human-centric spatially-grounded understanding of audio-visual events. Can we learn representations from video that capture audio-visual events in the context of the persistent physical space of the environment and the human speakers in it? Such representations would be useful for answering questions like \"who is speaking right now?\" and \"what would the voices sound like without the audio noise (distractor sounds)?\" While the former requires inferring the source location for a voice in the scene, the latter requires understanding how the perceived audio is a function of the source locations, the listener, and the surrounding environment.", + "bbox": [ + 496, + 627, + 893, + 808 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Despite the significance of these problems, today's models for audio-visual learning are not human-centric and they lack spatial grounding. On the one hand, current audio-visual representation learning methods exclusively tackle exocentric (third-person) video with monaural audio [2, 23, 24, 29, 34, 50, 52]. That domain sidesteps challenges", + "bbox": [ + 496, + 810, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "1 Throughout we use the term spatial audio to refer to binaural audio, as perceived by two human ears. In contrast, single-channel monaural audio lacks spatial information.", + "bbox": [ + 75, + 862, + 470, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "27058", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "inherent to ego-video arising from the camera wearer's head motion and relatively limited field of view. On the other hand, the limited prior work exploring self-supervised objectives using multi-channel audio and video [18, 22, 45, 70] are also outside of the egocentric and social contexts (e.g., for sounds in empty homes [22], musical instruments [18], or single human speakers [70]), where the need for spatial understanding of multiple sound sources is limited.", + "bbox": [ + 75, + 90, + 470, + 210 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We propose to learn audio-visual representations via spatial correspondence between an egocentric video and its binaural audio, for analyzing social (conversational) settings. In particular, we design a novel pretext task where the goal is to inpaint binaural (two-channel) audio using both video and audio. Given a social egocentric video clip with binaural audio, we mask segments of it and train a model based on masked autoencoding (MAE) [5, 15, 26, 30, 66] to predict the missing segments on the basis of the video and the unmasked segments in the audio. See Figure 1 (top). Additionally, we introduce a novel spatial audio masking strategy that facilitates learning strong audio-visual spatial correspondences while maintaining learning stability when vision alone is insufficient for the binauralization task. Once trained, our model's encoder provides spatial audio-visual features that can be used to address multiple downstream tasks, as we demonstrate using multiple different backbones and social egocentric video datasets.", + "bbox": [ + 75, + 212, + 473, + 482 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In particular, motivated by the AR applications discussed above, we validate our feature learning method on two downstream social egocentric tasks that require strong audio-visual spatial reasoning: 1) active speaker detection: predicting which person in the field of view of an egocentric video is speaking, and 2) spatial audio denoising: separating audio noise (any sounds from non-speakers) from the input audio. See Figure 1 (bottom). We test the generality of our method by evaluating on two social egocentric video datasets, EgoCom [49] and EasyCom [11]—to our knowledge, the only two publicly available video datasets with binaural sound and social settings. On both, our method significantly outperforms multiple state-of-the-art task-specific and audio-visual spatial feature learning models.", + "bbox": [ + 75, + 484, + 470, + 695 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 709, + 218, + 724 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Audio-visual self-supervised pretraining Past work [2, 4, 34, 45, 48, 50–52] extensively studies the synergy of vision and audio for learning representations through self-supervision. They explore using both modalities to construct pretext tasks based on synthesis [51, 52], alignment [2, 4, 22, 34, 50], and masked auto-encoding (MAE) [23, 24, 29], and they focus on semantic downstream tasks like audio-visual event classification and retrieval. However, none of these methods are designed to extract spatial cues from video and multi-channel audio, nor do they analyze the social egocentric setting. On the contrary, we propose self-supervised", + "bbox": [ + 75, + 734, + 470, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "learning of spatial audio-visual features from egocentric video. Further, different from existing MAE-style models [23, 24, 29], we propose a specialized masking strategy that better learns spatial audio-visual cues. Our masking idea promotes the encoding of spatial and semantic information in the learned multimodal representation, thereby improving its effectiveness for transfer learning in downstream tasks that require nuanced reasoning about both what and where aspects, such as active speaker detection and spatial audio-visual denoising. This differs from previous methods [23, 24, 29], which mainly use a learning objective that emphasizes the encoding of semantic cues and tailor to tasks like multimodal event classification or retrieval.", + "bbox": [ + 496, + 90, + 893, + 287 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Audio-visual spatial correspondence learning Learning the spatial alignment between video and audio is important for self-supervision [45, 60, 69, 70], audio generation [7, 18, 40, 44, 46, 56, 73], audio-visual embodied learning [6, 8, 38, 39] and 3D scene mapping [41, 55]. However, these methods are either restricted to exocentric settings [7, 18, 44, 45, 56, 60, 70], or else tackle egocentric settings [8, 38, 40, 41] in simulated 3D environments that lack realism and diversity, both in terms of the audio-visual content of the videos (no people are visible, no objects are moving) and their lack of continuous camera motion from a camerewer's physical movements. In contrast, we learn an audio-visual representation from real-world egocentric video.", + "bbox": [ + 496, + 299, + 895, + 494 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "More closely related to our work are Telling Left from Right (TLR) [70], 2.5D Visual Sounds (2.5D-VS) [18], and audio-visual stereo sound ranking (SSR) [60], all of which learn spatial audio-visual features, albeit for exocentric data only. TLR predicts whether the left and right binaural channels are swapped, and SSR ranks the similarity of video to different stereo audio samples through self-supervision—both of which provide only coarse spatial information about the scene. 2.5D-VS learns to \"lift\" the mono input to binaural audio, which can be underconstrained from the single-channel audio and video alone. We design a novel pretext task using audio-visual inpainting of binaural audio, which is both fine-grained (requiring to capture subtleties about the arrangement of speakers in the environment) and, through our novel masking strategy, exposes better multi-modal constraints that improve learning stability and performance. Our results in Sec. 4 show our model's advantages over all three prior methods [18, 60, 70].", + "bbox": [ + 496, + 496, + 895, + 768 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Active speaker detection Active speaker detection (ASD) entails predicting the active speaker(s) from among all detected faces in a video, and is a special case of generic 2D sound localization [17, 27, 32, 43, 50, 71]. While early ASD methods rely on lip motion and facial gestures [14], recent methods employ ensemble networks [3] or 3D CNNs [33, 61, 65], relation context modules [72], attention [3, 65], or graph neural networks [35, 42]. Multi-", + "bbox": [ + 496, + 780, + 895, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "27059", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/b4dad772f1f7f07250016d258810eef4462406f4e09e04917813a7e9ed4b817b.jpg", + "image_caption": [ + "Figure 2. Our model learns the spatial correspondence between vision and binaural audio by inpainting masked tokens of the audio channels through the use of an audio-visual encoder-decoder model. We combine random token masking (which requires solving a more local binauralization task) with complete audio channel masking (which requires more global cues to synthesize unseen binaural segments). For downstream evaluation, we fuse the features from the audio-visual encoder with the backbones for downstream tasks, and finetune them." + ], + "image_footnote": [], + "bbox": [ + 181, + 87, + 789, + 265 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "channel audio improves ASD [32], but requires privileged information of the speaker's pose for training. Recent work explores using supervised learning to infer not only who is talking, but also to whom a camera-wearer is listening [59]. In contrast, our goal is to learn spatial audio-visual features purely from in-the-wild egocentric video through self-supervision—features generic enough to benefit multiple ASD models, as we show for both TalkNet [65] and SPELL [42].", + "bbox": [ + 75, + 345, + 472, + 481 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Spatial audio denoising Audio denoising, which requires separating a target sound from noise, has traditionally been studied with single-channel (non-spatial) audio, both in the audio-only setting [28, 63, 64, 68] and audio-visual settings [1, 13, 16, 19–21, 50, 53, 54]. Using spatial audio captured with multiple microphones [12, 47, 74] naturally makes the task simpler. Different from the above, we learn task-agnostic audio-visual spatial features. That is, our contribution is the feature learning idea (which benefits both denoising and ASD), rather than a novel denoising approach.", + "bbox": [ + 75, + 492, + 470, + 645 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Learning spatial features from egocentric audio-visual correspondence", + "text_level": 1, + "bbox": [ + 76, + 659, + 468, + 695 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The spatial sound perceived in an egocentric setup is shaped by the environment in which it is emitted and its source location relative to the camera-wearer. Based on this knowledge, we hypothesize that trying to solve the pretext task of audio-visual inpainting of binaural audio—that is, synthesizing missing audio segments by extracting related visual cues about the scene and the source location—can lead to learning useful audio-visual spatial correspondences. To validate our hypothesis, we propose a novel feature-learning task.", + "bbox": [ + 75, + 703, + 468, + 839 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Formally, we consider an egocentric video clip $C = (V, A)$ , where $V$ and $A$ refer to the visual and binaural audio streams, respectively. See Fig. 2 left. The visual clip $V$ comprises $T$ frames, such that $V = \\{V_1, \\ldots, V_T\\}$ .", + "bbox": [ + 76, + 839, + 470, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We generate a set of visual tokens $\\hat{V}$ by splitting $V$ into $P$ non-overlapping tubelets, such that $\\hat{V} = \\{\\hat{V}_1,\\dots ,\\hat{V}_P\\}$ , where $\\hat{V}_k$ denotes the $k^{th}$ tubelet consisting of a contiguous sequence of patches spanning all $T$ frames. We represent the binaural audio $A$ as two Mel-spectrograms [30], $A = \\{A^L,A^R\\}$ , where $A^L$ and $A^R$ are the spectrograms for the left and right channels, respectively. We create a set of audio tokens $\\hat{A}$ by splitting $A$ into $Q$ non-overlapping patches, such that $\\hat{A} = \\{\\hat{A}_1,\\dots ,\\hat{A}_Q\\}$ .", + "bbox": [ + 496, + 344, + 893, + 484 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Next, we mask a portion of the audio tokens in $\\hat{A}$ and obtain complementary subsets of masked and unmasked tokens, $\\hat{A}^M$ and $\\hat{A}^U$ , respectively, where $\\hat{A}^M = \\{\\ddot{A}_1,\\dots ,\\ddot{A}_S\\}$ , $\\hat{A}^U = \\{\\bar{A}_1,\\dots ,\\bar{A}_{Q - S}\\}$ , and $S$ is the number of masked tokens. Given $\\{\\hat{V},\\hat{A}^{M},\\hat{A}^{U}\\}$ , we aim to learn a self-supervised model $\\mathcal{F}$ comprising an encoder $\\mathcal{E}$ and decoder $\\mathcal{D}$ , such that $\\mathcal{F} = \\mathcal{D}\\circ \\mathcal{E}$ and $\\mathcal{F}(\\hat{V},\\hat{A}^U) = \\tilde{A}^M$ , where $\\tilde{A}^M$ is an estimate of the masked audio tokens in $\\hat{A}^M$ . By training on this pretext task, our encoder $\\mathcal{E}$ can learn rich audio-visual spatial correspondences that can be leveraged for multiple downstream tasks that require the synergy of vision and spatial audio, as we show in results.", + "bbox": [ + 496, + 486, + 893, + 672 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In our method (see Fig. 2), $\\mathcal{E}$ (Sec. 3.1) is an audio-visual (AV) spatial correspondence encoder that learns an implicit representation of the spatial relationships between the visual and unmasked binaural audio tokens, while $\\mathcal{D}$ (Sec. 3.2) is an audio-visual decoder for binaural audio inpainting that uses this implicit representation to synthesize the masked audio tokens. We also devise a simple yet novel masking protocol (Sec. 3.3) for our inpainting task, which mixes masking random audio tokens with masking a full audio channel, and helps the model learn stronger audio-visual spatial associations that facilitate the downstream social tasks (Sec. 3.5). We train $\\mathcal{F}$ to minimize the prediction error in the masked audio tokens (Sec. 3.4). Next, we describe our model design, audio masking protocol, training objective and network architecture, and downstream tasks.", + "bbox": [ + 496, + 674, + 895, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "27060", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Audio-visual spatial correspondence encoder", + "text_level": 1, + "bbox": [ + 76, + 90, + 455, + 107 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The audio-visual spatial correspondence encoder $\\mathcal{E}$ (Fig. 2 center) extracts features from the visual and unmasked audio tokens $\\{\\hat{V},\\hat{A}^U\\}$ . It begins by embedding the visual and audio tokens using separate transformer encoders [15] for individually capturing the spatio-temporal features in the two modalities. Next, it uses a shared transformer encoder to jointly encode the audio and visual features, and produces a multi-modal representation suitable for binaural audio inpainting. We describe the individual encoders next.", + "bbox": [ + 75, + 113, + 470, + 250 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Video and audio encoders. We first encode the visual tokens $\\hat{V}$ using a linear layer to generate visual features $v$ , such that $v = \\{v_{1},\\dots,v_{P}\\}$ . We encode the audio tokens $\\hat{A}^{U}$ with another linear layer to produce audio features $a$ , such that $a = \\{a_{1},\\dots,a_{Q - S}\\}$ , where $S$ is the number of masked tokens out of a total of $Q$ audio tokens (cf. Sec. 3). For each visual feature $v_{j}$ , we add a sinusoidal positional embedding $p_j^V$ [67] to it, where $p_j^V$ captures cues about the 3D position of the $j^{\\mathrm{th}}$ tubelet in the visual clip $V$ . For an audio feature $a_{i}$ , we add a sinusoidal positional embedding $p_i^A$ and a learnable channel embedding $c\\in \\{c_L,c_R\\}$ to it to convey information about the 2D location of the $i^{\\mathrm{th}}$ unmasked audio token in the spectrogram and also the audio channel to which it belongs. Next, we feed the transformed visual and audio features to separate transformer encoders, $\\mathcal{E}^V$ and $\\mathcal{E}^A$ , respectively, and obtain visual features $e^V = \\{e_1^V,\\dots,e_P^V\\}$ and audio features $e^A = \\{e_1^A,\\dots,e_{Q - S}^A\\}$ .", + "bbox": [ + 76, + 258, + 472, + 523 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Shared audio-visual encoder. Given the visual features $e^{V}$ and audio features $e^{A}$ , we concatenate them into $e^{AV}$ , such that $e^{AV} = \\{e_1^V, \\dots, e_P^V, e_1^A, \\dots, e_{Q - S}^A\\}$ , and re-add the sinusoidal positional embeddings $p^{V}$ and $p^{A}$ to the features of the respective modalities in $e^{AV}$ . Furthermore, unlike existing audio-visual masked auto-encoders [23, 24, 29], we add the channel embeddings $c$ to the audio features, and learnable modality embeddings $m \\in \\{m_A, m_V\\}$ to all features in $e^{AV}$ to help the model distinguish between the visual and audio modalities. Next, a shared audio-visual transformer $\\mathcal{E}^{AV}$ encoder takes $e^{AV}$ as input and outputs audio-visual features $f^{AV}$ , which implicitly hold spatio-temporal information required for accurate inpainting of audio.", + "bbox": [ + 75, + 532, + 472, + 733 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Audio-visual decoder for binaural audio inpainting", + "text_level": 1, + "bbox": [ + 76, + 741, + 470, + 773 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Our audio-visual decoder $\\mathcal{D}$ (Fig. 2 right) takes $f^{AV}$ as input and attempts to synthesize the masked binaural audio tokens by leveraging spatio-temporal cues in $f^{AV}$ . It first projects $f^{AV}$ to a lower-dimensional feature set $g^{AV}$ . It then appends a learnable embedding for the masked audio tokens to $g^{AV}$ and passes it through a shared audio-visual transformer decoder [26]. Next, it feeds the audio feature outputs of the shared decoder to another transformer decoder", + "bbox": [ + 75, + 777, + 470, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "and uses its outputs to predict an estimate of the masked binaural audio tokens. The decoders are lightweight compared to the encoders, ensuring that the encoders are primarily responsible for driving the inpainting task and producing good audio-visual features for strong downstream performance. We next describe each component of $\\mathcal{D}$ in detail.", + "bbox": [ + 496, + 90, + 893, + 181 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Shared audio-visual decoder. We first create a lower-dimensional projection $g^{AV}$ of the audio-visual encodings $f^{AV}$ by passing it through a linear layer, and append a learnable embedding $\\phi$ corresponding to each of the $S$ masked audio tokens to $g^{AV}$ . Next, we add the positional embeddings $p^V$ and $p^A$ , the audio channel embeddings $c$ , and the modality embeddings $m$ to $g^{AV}$ , and feed it to a shallow transformer decoder $\\mathcal{D}^{AV}$ that outputs an audio-visual feature set $h^{AV}$ . We then take the audio features $h^A$ from $h^{AV}$ and pass them to the audio decoder for further processing.", + "bbox": [ + 496, + 195, + 895, + 348 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Audio decoder. The audio decoder $\\mathcal{D}^A$ re-adds the positional embeddings $p^A$ and channel embeddings $c$ to $g^A$ , and feeds it to a transformer decoder, which outputs audio features $d^A$ .", + "bbox": [ + 496, + 359, + 893, + 421 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Prediction of masked audio tokens. Finally, we take the subset of all audio features $d^{A}$ corresponding to the masked audio tokens $\\hat{A}^{M}$ , upsample them by passing through a linear layer, and reshape them to obtain an estimate $\\tilde{A}^{M}$ of the masked tokens $\\hat{A}^{M}$ , such that $\\tilde{A}^{M} = \\{\\tilde{A}_{1},\\dots,\\tilde{A}_{S}\\}$ .", + "bbox": [ + 496, + 435, + 893, + 513 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Audio masking", + "text_level": 1, + "bbox": [ + 500, + 521, + 653, + 537 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Different from other masked auto-encoding counterparts [23, 24, 29], we design an audio masking protocol that is customized to help our model better extract spatial audio-visual cues during self-supervised pretraining. In particular, we mix the strategy of randomly masking a full audio channel with that of randomly masking audio tokens using a hyperparameter $r$ during training, where $r$ represents the probability with which we randomly drop a full audio channel and $r$ is sampled from a uniform distribution $U(0,1)$ :", + "bbox": [ + 496, + 544, + 893, + 681 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {m a s k} (\\hat {A}) = \\left\\{ \\begin{array}{l l} \\hat {A} ^ {M} = A ^ {L} \\text {o r} \\hat {A} ^ {M} = A ^ {R} & \\text {i f} x \\sim U (0, 1) \\leq r \\\\ \\hat {A} ^ {M} \\subseteq \\{\\hat {A} _ {1}, \\dots , \\hat {A} _ {Q} \\} & \\text {o t h e r w i s e} \\end{array} \\right.\n$$\n", + "text_format": "latex", + "bbox": [ + 501, + 690, + 887, + 724 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "On the one hand, token masking could lead to tokens from the same location in the two audio channels being present among the unmasked tokens, providing additional spatial cues to the model and resulting in a simpler, stabler optimization objective for the inpainting task. In addition, since token masking involves masking a short span in both frequency and time domains, the model can rely more on local audio-visual cues and tolerate the global noise in both the visual and audio streams due to a camera-wearer's motion. On the other hand, channel masking forces the model to solve a more challenging binauralization task solely on the basis of vision,", + "bbox": [ + 496, + 734, + 895, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "27061", + "bbox": [ + 478, + 944, + 517, + 957 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/560fa7a786b2779004fec471ae9573bf9d12887747edff62396c7d09d2b46f31.jpg", + "image_caption": [ + "Figure 3. Masked targets and predictions shown alongside the unmasked inputs for (a) token masking and (b) channel masking. Our predictions accurately capture the global patterns in the target spectrograms, which depend on the scene's spatial properties." + ], + "image_footnote": [], + "bbox": [ + 89, + 87, + 455, + 349 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "which could help it learn even stronger spatial features. This encourages the model to reason about the camera motion at a more global scale (over the entire clip span). Towards achieving high performance on the downstream tasks, we aim to strike a fine balance between these two strategies and combine the benefits of reasoning at both temporal scales.", + "bbox": [ + 75, + 433, + 468, + 525 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Training objective and network architecture", + "text_level": 1, + "bbox": [ + 76, + 532, + 452, + 550 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We train our model to minimize the error in predicting the masked audio tokens. In particular, we compute the mean-squared error $\\mathcal{L}$ averaged over all masked audio tokens:", + "bbox": [ + 75, + 556, + 472, + 602 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\frac {1}{S} \\sum_ {i = 1 \\dots S} | | \\ddot {A} _ {i} - \\tilde {a} _ {i} | | _ {2} ^ {2}. \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 181, + 612, + 470, + 648 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We visualize our predicted audio tokens in Fig. 3 for the cases of token (Fig. 3a) and channel (Fig 3b) masking. Our model is able to accurately predict the masked targets and capture the global patterns in the spectrograms, which are often determined by the spatial audio-visual cues captured from of the scene (visual input not shown in Fig 3 for brevity), thereby further emphasizing our model's ability to learn useful spatial features.", + "bbox": [ + 75, + 657, + 468, + 777 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Our uni-modal encoders, $\\mathcal{E}^A$ and $\\mathcal{E}^V$ , have 8 layers, while the audio-visual encoder $\\mathcal{E}^{AV}$ has 6 layers. All encoders have 12 attention heads and use 768-dimensional hidden embeddings. The audio-visual decoder $\\mathcal{D}^{AV}$ and audio-only decoder $\\mathcal{D}^A$ have 1 and 3 layers, respectively. Both decoders have 6 attention heads and use 384-dimensional hidden embeddings. To pretrain our model, we set the relative frequency of dropping an audio channel in our masking", + "bbox": [ + 75, + 779, + 470, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "protocol for training to $r = 20\\%$ based on disjoint validation data (see Supp.). We train our model for 200 epochs using the AdamW [37] optimizer with a weight decay of $10^{-5}$ , and a learning rate scheduler that reaches a peak learning rate of $2 \\times 10^{-4}$ over 10 warmup epochs, and then decays it through half-cycle cosine annealing [36]. For data augmentation, we perform random flipping of audio channels and video clips along the frame width. For downstream evaluation, we fuse the features from the audio-visual encoder with the backbones for downstream tasks, and finetune them. See Supp. for further details on architecture and training.", + "bbox": [ + 496, + 90, + 893, + 258 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.5. Downstream tasks", + "text_level": 1, + "bbox": [ + 500, + 265, + 678, + 279 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We explore two downstream tasks with our pretrained features: active speaker detection and spatial audio denoising. Active speaker detection (ASD) involves matching an audio clip with an appropriate face track from the corresponding video clip, i.e., answering \"which person is speaking now?\". While current SOTA methods [42, 65] rely on semantic similarities between monaural audio and vision to solve this task, we hypothesize that leveraging spatial audio can additionally reveal the sound source location in the video. In spatial audio denoising, the goal is to separate the target audio from distractors. In particular, we aim to remove the audio from sources extraneous to the conversation—out-of-view sounds from other parts of the scene. We detail the backbone models for each in the next section.", + "bbox": [ + 496, + 287, + 893, + 500 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 511, + 633, + 527 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We validate our learned representations on two downstream tasks and two datasets, and we compare with prior models for spatial audio-visual feature learning [18, 23, 60, 70], as well as various baselines and ablations.", + "bbox": [ + 496, + 532, + 893, + 592 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We train and evaluate our model on two challenging egocentric datasets containing video and binaural audio of people having conversations: 1) EgoCom [49], and 2) EasyCom [11], detailed in Supp. To our knowledge, these are the only two publicly available datasets offering binaural audio with conversations in video, whether exocentric or egocentric. In particular, Ego4D [25] and EPIC [9] do not comprise social scenarios and are not applicable. Whereas EasyCom primarily has participants sitting around a table and talking, EgoCom has videos of participants moving around a room, turning their face and body, standing up, etc. They test our method's robustness in diverse scenarios of varying difficulty.", + "bbox": [ + 496, + 603, + 893, + 800 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Active speaker detection", + "text_level": 1, + "bbox": [ + 500, + 806, + 723, + 823 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We first evaluate on active speaker detection (ASD).", + "bbox": [ + 500, + 830, + 844, + 845 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Backbone models. We consider two SOTA ASD models as the backbones for leveraging our pretrained representations: 1) TalkNet [65], and 2) SPELL [42]. TalkNet encodes", + "bbox": [ + 496, + 854, + 893, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "27062", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "a face track and an audio clip using attention for learning intra- and inter-modal semantic and temporal features. Next, it fuses these features and performs binary classification to predict if the face in the track is active. SPELL extracts audiovisual features for each face in a clip using ResNets [3], and learns long and short-term semantic relations among them using a graph neural network. Finally, it performs binary classification of these features for predicting active speakers.", + "bbox": [ + 75, + 90, + 472, + 212 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Pretrained feature fusion. To fuse our pretrained features with the ASD backbones, we use a transformer decoder that cross-attends to the feature outputs of the shared encoder $\\mathcal{E}^{AV}$ using sinusoidal embedding as queries, with each embedding representing a clip frame index. Next, we append the decoder outputs to the cross-attention outputs in TalkNet, or the audio-visual encoder outputs in SPELL, frame by frame. In essence, while the original audio-visual encoders leverage semantic correlations between vision and audio, our features provide strong complementary spatial cues.", + "bbox": [ + 75, + 228, + 472, + 380 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. For both TalkNet and SPELL, we compare against multiple baselines comprising both the unmodified backbone and improved versions of it, in addition to some naive methods:", + "bbox": [ + 76, + 401, + 468, + 460 + ], + "page_idx": 5 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- All-active: a naive model that predicts that all visible faces are always active", + "- All-inactive: a naive model that predicts that all visible faces are always inactive", + "- Random: a naive model that emits a random ASD confidence score for every visible speaker", + "- Backbone w/o audio: a vision-only version of the backbone with no audio input", + "- Backbone: the originally-proposed backbone that processes only faces and monaural audio", + "- Backbone-binaural: an improved backbone using binaural audio instead of monaural, alongside positional encodings for the faces, indicative of their relative position and depth, for better matching the face to the audio", + "- Backbone-binaural w/ scene: a further improvement over the backbone, where we also provide the scene images (uncropped video frames) to backbone-binaural", + "- Backbone w/ TLR [70]: fuses features from the SOTA Telling Left from Right (TLR) [70], which learns audio-visual spatial correspondences by predicting the spatial alignment between vision and binaural audio", + "- Backbone w/ 2.5D-VS [18]: fuses features from the SOTA audio-visual binauralization model, 2.5D Visual Sounds (2.5D-VS) [18]", + "- Backbone w/ 2.5D-VS [18]++: fuses features from 2.5D-VS with a transformer architecture", + "- Backbone w/ SSR [60]++: fuses features from the SOTA self-supervised audio-visual stereo sound ranking (SSR) [60] model with a transformer architecture" + ], + "bbox": [ + 78, + 462, + 470, + 900 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/cd3aa584d904d351dc2640b134bafe8edabf38295da260b453d1a18f91e5e861.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelTalkNet [65]SPELL [42]
EgoComEasyComEgoComEasyCom
No pretraining
All-active32.930.132.930.1
All-inactive32.930.132.930.1
Random30.828.030.828.0
B w/o audio41.550.160.463.2
B52.845.760.959.0
B-binaural60.059.663.160.3
B-binaural w/ scene60.866.961.261.4
Alternate pretraining methods
B w/ TLR [70]47.959.361.361.7
B w/ 2.5D-VS [18]57.763.761.259.7
B w/ 2.5D-VS [18]++63.468.365.164.5
B w/ SSR [60]++61.270.661.267.4
B w/ AV-MAE [23]61.161.364.465.2
Ours63.971.865.670.2
Ours w/o pretrain62.762.9——
Ours w/ pretrain monaural61.069.463.969.0
", + "bbox": [ + 504, + 88, + 890, + 344 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Mean average precision (\\%) for active speaker detection with TalkNet [65] and SPELL [42] backbones on both datasets. Higher is better. 'B' refers to backbone. Note that SPELL requires storing pretrained features in the graph nodes; therefore it does not allow training from scratch.", + "bbox": [ + 498, + 354, + 893, + 422 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "- Backbone w/ AV-MAE [23]: fuses features from the SOTA modality-inpainting AV-MAE [23] model", + "bbox": [ + 500, + 444, + 890, + 474 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For all alternate feature-learning methods [18, 23, 60, 70], we pretrain them on our datasets and use our feature fusion method. Thus, any advantages in performance of our approach over these SOTA representations will be attributable to our modeling ideas. Importantly, the 2.5D-VS [18]++, SSR [60]++, and AV-MAE [23] features all rely on transformers and have similar model capacity as ours; see Supp. for a detailed analysis on model capacity. We use the standard mean average precision (mAP) metric.", + "bbox": [ + 498, + 474, + 893, + 611 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Results. Table 1 (top) reports our ASD results on both val and test splits. The three naive baselines perform poorly on both EgoCom [49] and EasyCom [11], emphasizing the difficulty of the task. For both TalkNet [65] and SPELL [42], the unchanged backbone model generally performs better than the model without audio, showing that both vision and audio are required. Upgrading from monaural to binaural audio further boosts performance, as the model can now leverage both spatial and semantic information. Additionally using scene features lets the backbone explicitly match the scene area around the inferred source location with the face, and further improves ASD, especially for EgoCom, where the background scene changes more often.", + "bbox": [ + 496, + 627, + 893, + 823 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Among alternate feature learning methods, 2.5D-VS [18]++, SSR [60]++ and AV-MAE [23] consistently outperform TLR [70] and 2.5D-VS [17], and also the basic and enhanced backbones, showing that self-attention and higher model capacity enhance feature quality. Besides, 2.5D-VS", + "bbox": [ + 496, + 824, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "27063", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/aa7401c151b083511f173552cdbb544baac9302bbdefd27b320540a854c62b88.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelSI-SDRi ↑STFT ↓
No pretraining
B w/o vision1.617.36
B1.467.27
B w/ ImageNet features1.486.95
Alternate pretraining methods
B w/ TLR [70]1.417.79
B w/ 2.5D-VS [18]1.677.34
B w/ 2.5D-VS [18]++2.116.60
B w/ SSR [60] ++2.046.70
B w/ AV-MAE [23]2.076.62
Ours2.206.51
B w/o pretrain1.907.25
B w/ pretrain monaural audio2.006.75
", + "bbox": [ + 119, + 88, + 426, + 305 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Audio denoising with U-Net [70] backbone (referred to as 'B' in table) for 0 dB noise (maximum). See Supp. for varying noise levels. All STFT distance measures use base $10^{-3}$ .", + "bbox": [ + 75, + 316, + 468, + 357 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "outperforms TLR, and 2.5D-VS++ and AV-MAE generally outperform SSR++, indicating that objectives that promote reasoning directly at the spectrogram level improve results.", + "bbox": [ + 75, + 375, + 468, + 420 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our model substantially outperforms all baselines—including the SOTA AV representation learning methods—for both backbones (TalkNet and SPELL) on both datasets. This shows that our method learns stronger spatial features that are both backbone- and dataset-agnostic. In contrast, methods developed for exocentric settings with more stationary cameras (such as TLR and 2.5D-VS) rely more on the global visual context and seem to struggle in our setting, where the camera moves frequently and the sound source leaves the field of view. Finally, our improvement over 2.5D-VS++, SSR++ and AV-MAE, which use similar encoders as ours, disentangles the benefits of our masking strategy and model design from those of the model capacity.", + "bbox": [ + 75, + 421, + 468, + 617 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Model analysis. Table 1 (bottom) shows ablations of our method. Upon training for ASD from scratch, we see a sharp drop in performance, showing that our advantage is not solely due to our model design, but also our self-supervised pretraining stage. Performance also declines upon pretraining with monaural audio instead of binaural, showing that our model goes beyond learning semantic features and successfully captures spatial features useful for ASD.", + "bbox": [ + 75, + 627, + 468, + 748 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Spatial audio denoising", + "text_level": 1, + "bbox": [ + 76, + 757, + 290, + 773 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Next we evaluate spatial audio denoising on EgoCom.2 To instantiate this task, we add the binaural audio of a target clip with the downscaled binaural audio from another randomly chosen clip, where the downscaling factor depends on the", + "bbox": [ + 75, + 780, + 468, + 842 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "desired noise level. The goal is to extract the target sound from the mixture. We evaluate three noise levels, expressed using the signal-to-noise (SNR) ratio: 1) $0\\mathrm{dB}$ , 2) $2.5\\mathrm{dB}$ , and 3) $5\\mathrm{dB}$ . The different noise levels test our model's robustness to varying levels of task difficulty—the lower the SNR value, the higher the noise and difficulty.", + "bbox": [ + 504, + 89, + 895, + 180 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Backbone model. We adopt the commonly used U-Net [57] for audio-visual source separation [18, 70] as the backbone, which produces a binaural ratio mask for the target audio (see Supp. for details). We multiply the predicted ratio mask with the mixed magnitude spectrogram to get the predicted magnitude spectrogram, then convert it to a waveform using inverse short-time Fourier transform with the mixed audio phase.", + "bbox": [ + 496, + 196, + 893, + 316 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Pretrained feature fusion. To use our features for denoising, we reshape the visual features and unmasked audio features produced by our audio-visual encoder $\\mathcal{E}^{AV}$ to form multi-channel 2D maps, where the features align with their corresponding tokens vis-a-vis the raster order. Next, we pass the feature maps to separate convolutional layers, concatenate the outputs channel-wise, and use them to replace the visual features at the U-Net [70] bottleneck.", + "bbox": [ + 496, + 332, + 893, + 454 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Baselines. We compare against the following baselines and existing methods:", + "bbox": [ + 498, + 468, + 890, + 497 + ], + "page_idx": 6 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- U-Net w/o vision: an audio-only blind denoising model", + "- U-Net: the original backbone without any alterations", + "- U-Net w/ ImageNet: pretrains the visual encoder on ImageNet [10]", + "- U-Net w/ TLR [70]: fuses features from TLR [70]", + "- U-Net w/ 2.5D-VS [18]: fuses pretrained features from 2.5D-VS [18]", + "- U-Net w/ 2.5D-VS [18]++: fuses features from the transformer-based version of 2.5D-VS", + "- U-Net w/ SSR [60]++: fuses features from the transformer-based version of SSR [60]", + "- U-Net w/ AV-MAE [60]: fuses features from the modality inpainting AV-MAE [23] model" + ], + "bbox": [ + 500, + 500, + 893, + 694 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Evaluation metric. For evaluating our denoising quality, we use standard metrics: 1) STFT distance (the L2 error between the predicted and ground-truth spectrograms) expressed using base $10^{-3}$ and 2) SI-SDRi: the improvement in SI-SDR [58], a scale-invariant estimate of the distortion in the audio, over using the mixed audio as the prediction.", + "bbox": [ + 496, + 714, + 893, + 806 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results. Table 2 (top) shows spatial audio denoising results on the challenging EgoCom dataset with $0\\mathrm{dB}$ , the most difficult noise level. See Supp. for similar results with the other noise levels. The unchanged U-Net backbone lowers the STFT distance compared to the version that lacks vision,", + "bbox": [ + 496, + 824, + 893, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_footnote", + "text": "2For EasyCom, the task setup is ill-posed for all models because mixing audio from a different EasyCom clip as noise leads to spatially overlapping sound sources, since all clips in the dataset are recorded at the same physical location (people sitting around the same table in the same room).", + "bbox": [ + 71, + 849, + 465, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "27064", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/bec3ca3985d84fe6869e1caf35981a218707ad45ab48b712131f1d9c54442ef9.jpg", + "image_caption": [ + "Figure 4. Heat maps showing the image areas our model's AV encoder attends to, placed alongside the images. Brighter yellow means higher attention score. Our model attends to image regions (e.g. faces of speakers, sound-reflecting flat regions like floor and table, etc.) that strongly determine the spatial properties of the audio, including direct sources of sound (marked in red)." + ], + "image_footnote": [], + "bbox": [ + 81, + 88, + 202, + 231 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/3ea40335a68db5a0dfb68890877ffae04894d316118d66dc692446d46fca5c33.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 210, + 88, + 336, + 231 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a77ec49d953a652c870f6e117add878ebe418e9c4637a2d7ec7d47f6c2f8a41f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 343, + 88, + 468, + 231 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "showing that like ASD, vision is crucial for better denoising. Using pretrained features of 2.5D-VS [18] $(++)$ , SSR $[60]++$ or AV-MAE [23] further improves performance, showing that learning spatial audio-visual features aids denoising.", + "bbox": [ + 76, + 342, + 468, + 402 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Our method outperforms all baselines $(p \\leq 0.05)$ across both metrics. While the improvement over the baselines that do not use self-supervised pretraining emphasizes the utility of learning spatial audio-visual relationships through self-supervision, the gain over other pretraining methods underlines the strengths of our self-supervised method design—which are consistently realized for both ASD and denoising. Further, our performance margins are larger for higher noise levels (0 and $2.5\\mathrm{dB}$ ), indicating that our features play a bigger role in the more difficult denoising settings.", + "bbox": [ + 75, + 402, + 473, + 554 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Model analysis. In Table 2 (bottom), we ablate our pretraining method. Similar to ASD, training from scratch on the denoising task hurts performance. This disentangles the impact of our pretext task design from the model architecture and shows that our pretraining stage helps the backbone with learning better audio-visual features, leading to superior denoising quality. Furthermore, pretraining with monaural audio also degrades performance, re-emphasizing that our method is not restricted to learning semantic features—in contrast to prior work [23, 24, 29].", + "bbox": [ + 75, + 565, + 468, + 715 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "See Supp. for analysis of the effect of alternate masking choices, multi-level positional embeddings, task-specific backbones, and our finetuning strategy on performance.", + "bbox": [ + 75, + 715, + 468, + 762 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3. Qualitative analysis", + "text_level": 1, + "bbox": [ + 76, + 770, + 264, + 787 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In Fig. 4, we analyze the visual attention maps of our shared encoder $\\mathcal{E}^{AV}$ . Note that the regions of high attention are not only limited to the direct sound sources (e.g., regions in and around faces of active speakers across examples), but also include large sound-reflecting objects (e.g., the flat surface of the table on the left; the walls on the left and in the middle; the floor on the right, etc.) that determine how sound", + "bbox": [ + 75, + 794, + 470, + 900 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c7b491178e6a561eed8fdfcfc80dae7fafcf330d977ed5fe54c5016971213362.jpg", + "image_caption": [ + "(a) Our model succeeds on ASD even with fast camera motion (left; note image blur), multiple active speakers (right) and partially visible faces (left and right)" + ], + "image_footnote": [], + "bbox": [ + 501, + 88, + 705, + 207 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/95808edb9b9892bc8614815e08a6ca216213b1fba5202616cff6bc6d0f2548ce.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 707, + 88, + 910, + 207 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/efaafdad1430c6a55fbc81f79c13dd63585017084c515b3191e910f3dd47141c.jpg", + "image_caption": [ + "(b) Our model denoises accurately—note the noise patches in mixed audio above points $p_1$ and $p_2$ , which are successfully removed in our prediction." + ], + "image_footnote": [], + "bbox": [ + 501, + 238, + 637, + 325 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f9976d11abc79e9153f5c311848e4955da96af1d9bae7104d6e6a080632cb340.jpg", + "image_caption": [ + "Figure 5. Success cases for ASD (a) and denoising (b)" + ], + "image_footnote": [], + "bbox": [ + 638, + 238, + 772, + 325 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ff92554be065096e6cb96e892b4f7ec4e32cf72ab9de6cbc7c9d5b75bf46bc3b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 774, + 238, + 910, + 325 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "spatializes through early reflections, late reverberations, etc. Interestingly, our model also attends to multiple people if they are speaking at the same time (see left), thereby facilitating the detection of multiple active speakers. See Supp. for additional visualizations showing how, depending on the scene's spatial layout, our model uses one audio channel more than the other to attend to important image locations.", + "bbox": [ + 496, + 382, + 893, + 487 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In Fig. 5, we qualitatively show our model's success cases. On ASD (Fig. 5a), our model can tackle drastic camera movements, multiple active speakers, and partially visible faces. On denoising (Fig. 5b), our model is able to remove interferences from distractor sources, and make predictions that closely match the ground truth in spectrogram structure.", + "bbox": [ + 496, + 488, + 893, + 577 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We also observe some limitations. Our model's performance on ASD declines when there are drastic movements of the camera wearer, or there is a high overlap in speech from different conversation participants. On denoising, our model struggles when the noisy audio is semantically and acoustically similar to the target, or when it cannot extract spatial cues due to occlusions or out-of-view speakers. Refer to our Supp. video for both success and failure cases.", + "bbox": [ + 496, + 579, + 893, + 699 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 713, + 617, + 728 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We introduce a novel self-supervised approach for learning audio-visual representations in social egocentric videos via spatial correspondence between the video and its binaural audio. Through extensive evaluation, we show that our learned features are strong and generic enough to improve over multiple backbone methods on multiple downstream tasks. In future work, we will explore how the learned spatial audio-visual cues may reveal the social attention of speakers. Acknowledgements: UT Austin is supported in part by NSF CCRI and the IFML NSF AI Institute. KG is paid as a research scientist by Meta, and SM is a visiting researcher at Meta.", + "bbox": [ + 496, + 738, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "27065", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Triantafyllos Afouras, Joon Son Chung, and Andrew Zisserman. The conversation: Deep audio-visual speech enhancement. arXiv preprint arXiv:1804.04121, 2018. 3", + "[2] Triantafyllos Afouras, Andrew Owens, Joon Son Chung, and Andrew Zisserman. Self-supervised learning of audio-visual objects from video. In Computer Vision-ECCV 2020: 16th European Conference, Glasgow, UK, August 23–28, 2020, Proceedings, Part XVIII 16, pages 208–224. 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In IEEE TRANSACTIONS ON SIGNAL PROCESSING (2002) SUBMITTED, 2004. 3" + ], + "bbox": [ + 503, + 92, + 893, + 696 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "27068", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_model.json b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_model.json new file mode 100644 index 0000000000000000000000000000000000000000..51456e543fe51374b980f0015cf0de6211070456 --- /dev/null +++ b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_model.json @@ -0,0 +1,2510 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.172, + 0.131, + 0.8, + 0.177 + ], + "angle": 0, + "content": "Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos" + }, + { + "type": "text", + "bbox": [ + 0.223, + 0.203, + 0.748, + 0.24 + ], + "angle": 0, + "content": "Sagnik Majumder\\(^{1,2}\\) Ziad Al-Halah\\(^{3}\\) Kristen Grauman\\(^{1,2}\\) \n\\(^{1}\\)UT Austin \\({}^{2}\\)FAIR, Meta \\({}^{3}\\)University of Utah" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.274, + 0.314, + 0.29 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.307, + 0.474, + 0.534 + ], + "angle": 0, + "content": "We propose a self-supervised method for learning representations based on spatial audio-visual correspondences in egocentric videos. Our method uses a masked autoencoding framework to synthesize masked binaural audio through the synergy of audio and vision, thereby learning useful spatial relationships between the two modalities. We use our pretrained features to tackle two downstream video tasks requiring spatial understanding in social scenarios: active speaker detection and spatial audio denoising. Through extensive experiments, we show that our features are generic enough to improve over multiple state-of-the-art baselines on both tasks on two challenging egocentric video datasets that offer binaural audio, EgoCom and EasyCom. Project: http://vision.cs.utexas.edu/projects/ego_av_corr." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.554, + 0.21, + 0.57 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.58, + 0.471, + 0.776 + ], + "angle": 0, + "content": "Egocentric videos provide a first-person view of how we perceive and interact with our surroundings in daily life, and they are pushing a new frontier in multi-modal learning [9, 25, 31, 62]. A key aspect of ego-video is that it can provide a rich stream of first-person spatial audio alongside visual frames when the audio is captured with multiple microphones [11, 49]. The coupling of such audio and vision provides strong spatial information about the sound sources (e.g. where the sound sources are, if they are in motion or not) in the context of the surrounding physical space (e.g. how big or small the room is, if there is a large wall nearby), as well as the camera wearer's attention in the scene revealed by how they move their head." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.777, + 0.471, + 0.854 + ], + "angle": 0, + "content": "Such spatial cues are especially important for social settings of multiple people talking to each other, where it is valuable to be able to 1) focus on the voice(s) of interest from among various competing sounds and 2) understand where people are directing their speech activity, for better" + }, + { + "type": "image", + "bbox": [ + 0.5, + 0.272, + 0.891, + 0.45 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.46, + 0.894, + 0.53 + ], + "angle": 0, + "content": "Figure 1. Given an egocentric video and binaural audio, we aim to learn spatial correspondences between vision and audio by solving the pretext task of inpainting segments of the binaural audio. The features benefit downstream social tasks where spatial localization is important: active speaker detection and audio denoising." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.55, + 0.895, + 0.627 + ], + "angle": 0, + "content": "comprehension and communication. In this way, future AR applications in conversational settings could allow a hearing-impaired person to determine who is speaking in order to redirect their attention, or enhance the received audio to make it more intelligible for any listener." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.628, + 0.895, + 0.809 + ], + "angle": 0, + "content": "We argue that this creates the need for human-centric spatially-grounded understanding of audio-visual events. Can we learn representations from video that capture audio-visual events in the context of the persistent physical space of the environment and the human speakers in it? Such representations would be useful for answering questions like \"who is speaking right now?\" and \"what would the voices sound like without the audio noise (distractor sounds)?\" While the former requires inferring the source location for a voice in the scene, the latter requires understanding how the perceived audio is a function of the source locations, the listener, and the surrounding environment." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.895, + 0.902 + ], + "angle": 0, + "content": "Despite the significance of these problems, today's models for audio-visual learning are not human-centric and they lack spatial grounding. On the one hand, current audio-visual representation learning methods exclusively tackle exocentric (third-person) video with monaural audio [2, 23, 24, 29, 34, 50, 52]. That domain sidesteps challenges" + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.863, + 0.471, + 0.901 + ], + "angle": 0, + "content": "1 Throughout we use the term spatial audio to refer to binaural audio, as perceived by two human ears. In contrast, single-channel monaural audio lacks spatial information." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27058" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.212 + ], + "angle": 0, + "content": "inherent to ego-video arising from the camera wearer's head motion and relatively limited field of view. On the other hand, the limited prior work exploring self-supervised objectives using multi-channel audio and video [18, 22, 45, 70] are also outside of the egocentric and social contexts (e.g., for sounds in empty homes [22], musical instruments [18], or single human speakers [70]), where the need for spatial understanding of multiple sound sources is limited." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.213, + 0.474, + 0.483 + ], + "angle": 0, + "content": "We propose to learn audio-visual representations via spatial correspondence between an egocentric video and its binaural audio, for analyzing social (conversational) settings. In particular, we design a novel pretext task where the goal is to inpaint binaural (two-channel) audio using both video and audio. Given a social egocentric video clip with binaural audio, we mask segments of it and train a model based on masked autoencoding (MAE) [5, 15, 26, 30, 66] to predict the missing segments on the basis of the video and the unmasked segments in the audio. See Figure 1 (top). Additionally, we introduce a novel spatial audio masking strategy that facilitates learning strong audio-visual spatial correspondences while maintaining learning stability when vision alone is insufficient for the binauralization task. Once trained, our model's encoder provides spatial audio-visual features that can be used to address multiple downstream tasks, as we demonstrate using multiple different backbones and social egocentric video datasets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.485, + 0.472, + 0.696 + ], + "angle": 0, + "content": "In particular, motivated by the AR applications discussed above, we validate our feature learning method on two downstream social egocentric tasks that require strong audio-visual spatial reasoning: 1) active speaker detection: predicting which person in the field of view of an egocentric video is speaking, and 2) spatial audio denoising: separating audio noise (any sounds from non-speakers) from the input audio. See Figure 1 (bottom). We test the generality of our method by evaluating on two social egocentric video datasets, EgoCom [49] and EasyCom [11]—to our knowledge, the only two publicly available video datasets with binaural sound and social settings. On both, our method significantly outperforms multiple state-of-the-art task-specific and audio-visual spatial feature learning models." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.71, + 0.22, + 0.725 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.472, + 0.902 + ], + "angle": 0, + "content": "Audio-visual self-supervised pretraining Past work [2, 4, 34, 45, 48, 50–52] extensively studies the synergy of vision and audio for learning representations through self-supervision. They explore using both modalities to construct pretext tasks based on synthesis [51, 52], alignment [2, 4, 22, 34, 50], and masked auto-encoding (MAE) [23, 24, 29], and they focus on semantic downstream tasks like audio-visual event classification and retrieval. However, none of these methods are designed to extract spatial cues from video and multi-channel audio, nor do they analyze the social egocentric setting. On the contrary, we propose self-supervised" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.288 + ], + "angle": 0, + "content": "learning of spatial audio-visual features from egocentric video. Further, different from existing MAE-style models [23, 24, 29], we propose a specialized masking strategy that better learns spatial audio-visual cues. Our masking idea promotes the encoding of spatial and semantic information in the learned multimodal representation, thereby improving its effectiveness for transfer learning in downstream tasks that require nuanced reasoning about both what and where aspects, such as active speaker detection and spatial audio-visual denoising. This differs from previous methods [23, 24, 29], which mainly use a learning objective that emphasizes the encoding of semantic cues and tailor to tasks like multimodal event classification or retrieval." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.3, + 0.897, + 0.496 + ], + "angle": 0, + "content": "Audio-visual spatial correspondence learning Learning the spatial alignment between video and audio is important for self-supervision [45, 60, 69, 70], audio generation [7, 18, 40, 44, 46, 56, 73], audio-visual embodied learning [6, 8, 38, 39] and 3D scene mapping [41, 55]. However, these methods are either restricted to exocentric settings [7, 18, 44, 45, 56, 60, 70], or else tackle egocentric settings [8, 38, 40, 41] in simulated 3D environments that lack realism and diversity, both in terms of the audio-visual content of the videos (no people are visible, no objects are moving) and their lack of continuous camera motion from a camerewer's physical movements. In contrast, we learn an audio-visual representation from real-world egocentric video." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.497, + 0.897, + 0.769 + ], + "angle": 0, + "content": "More closely related to our work are Telling Left from Right (TLR) [70], 2.5D Visual Sounds (2.5D-VS) [18], and audio-visual stereo sound ranking (SSR) [60], all of which learn spatial audio-visual features, albeit for exocentric data only. TLR predicts whether the left and right binaural channels are swapped, and SSR ranks the similarity of video to different stereo audio samples through self-supervision—both of which provide only coarse spatial information about the scene. 2.5D-VS learns to \"lift\" the mono input to binaural audio, which can be underconstrained from the single-channel audio and video alone. We design a novel pretext task using audio-visual inpainting of binaural audio, which is both fine-grained (requiring to capture subtleties about the arrangement of speakers in the environment) and, through our novel masking strategy, exposes better multi-modal constraints that improve learning stability and performance. Our results in Sec. 4 show our model's advantages over all three prior methods [18, 60, 70]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.781, + 0.897, + 0.902 + ], + "angle": 0, + "content": "Active speaker detection Active speaker detection (ASD) entails predicting the active speaker(s) from among all detected faces in a video, and is a special case of generic 2D sound localization [17, 27, 32, 43, 50, 71]. While early ASD methods rely on lip motion and facial gestures [14], recent methods employ ensemble networks [3] or 3D CNNs [33, 61, 65], relation context modules [72], attention [3, 65], or graph neural networks [35, 42]. Multi-" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27059" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.182, + 0.088, + 0.79, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.277, + 0.895, + 0.334 + ], + "angle": 0, + "content": "Figure 2. Our model learns the spatial correspondence between vision and binaural audio by inpainting masked tokens of the audio channels through the use of an audio-visual encoder-decoder model. We combine random token masking (which requires solving a more local binauralization task) with complete audio channel masking (which requires more global cues to synthesize unseen binaural segments). For downstream evaluation, we fuse the features from the audio-visual encoder with the backbones for downstream tasks, and finetune them." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.346, + 0.473, + 0.482 + ], + "angle": 0, + "content": "channel audio improves ASD [32], but requires privileged information of the speaker's pose for training. Recent work explores using supervised learning to infer not only who is talking, but also to whom a camera-wearer is listening [59]. In contrast, our goal is to learn spatial audio-visual features purely from in-the-wild egocentric video through self-supervision—features generic enough to benefit multiple ASD models, as we show for both TalkNet [65] and SPELL [42]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.493, + 0.472, + 0.646 + ], + "angle": 0, + "content": "Spatial audio denoising Audio denoising, which requires separating a target sound from noise, has traditionally been studied with single-channel (non-spatial) audio, both in the audio-only setting [28, 63, 64, 68] and audio-visual settings [1, 13, 16, 19–21, 50, 53, 54]. Using spatial audio captured with multiple microphones [12, 47, 74] naturally makes the task simpler. Different from the above, we learn task-agnostic audio-visual spatial features. That is, our contribution is the feature learning idea (which benefits both denoising and ASD), rather than a novel denoising approach." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.66, + 0.47, + 0.696 + ], + "angle": 0, + "content": "3. Learning spatial features from egocentric audio-visual correspondence" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.704, + 0.47, + 0.84 + ], + "angle": 0, + "content": "The spatial sound perceived in an egocentric setup is shaped by the environment in which it is emitted and its source location relative to the camera-wearer. Based on this knowledge, we hypothesize that trying to solve the pretext task of audio-visual inpainting of binaural audio—that is, synthesizing missing audio segments by extracting related visual cues about the scene and the source location—can lead to learning useful audio-visual spatial correspondences. To validate our hypothesis, we propose a novel feature-learning task." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.84, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Formally, we consider an egocentric video clip \\( C = (V, A) \\), where \\( V \\) and \\( A \\) refer to the visual and binaural audio streams, respectively. See Fig. 2 left. The visual clip \\( V \\) comprises \\( T \\) frames, such that \\( V = \\{V_1, \\ldots, V_T\\} \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.345, + 0.895, + 0.486 + ], + "angle": 0, + "content": "We generate a set of visual tokens \\(\\hat{V}\\) by splitting \\(V\\) into \\(P\\) non-overlapping tubelets, such that \\(\\hat{V} = \\{\\hat{V}_1,\\dots ,\\hat{V}_P\\}\\), where \\(\\hat{V}_k\\) denotes the \\(k^{th}\\) tubelet consisting of a contiguous sequence of patches spanning all \\(T\\) frames. We represent the binaural audio \\(A\\) as two Mel-spectrograms [30], \\(A = \\{A^L,A^R\\}\\), where \\(A^L\\) and \\(A^R\\) are the spectrograms for the left and right channels, respectively. We create a set of audio tokens \\(\\hat{A}\\) by splitting \\(A\\) into \\(Q\\) non-overlapping patches, such that \\(\\hat{A} = \\{\\hat{A}_1,\\dots ,\\hat{A}_Q\\}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.487, + 0.895, + 0.674 + ], + "angle": 0, + "content": "Next, we mask a portion of the audio tokens in \\(\\hat{A}\\) and obtain complementary subsets of masked and unmasked tokens, \\(\\hat{A}^M\\) and \\(\\hat{A}^U\\), respectively, where \\(\\hat{A}^M = \\{\\ddot{A}_1,\\dots ,\\ddot{A}_S\\}\\), \\(\\hat{A}^U = \\{\\bar{A}_1,\\dots ,\\bar{A}_{Q - S}\\}\\), and \\(S\\) is the number of masked tokens. Given \\(\\{\\hat{V},\\hat{A}^{M},\\hat{A}^{U}\\}\\), we aim to learn a self-supervised model \\(\\mathcal{F}\\) comprising an encoder \\(\\mathcal{E}\\) and decoder \\(\\mathcal{D}\\), such that \\(\\mathcal{F} = \\mathcal{D}\\circ \\mathcal{E}\\) and \\(\\mathcal{F}(\\hat{V},\\hat{A}^U) = \\tilde{A}^M\\), where \\(\\tilde{A}^M\\) is an estimate of the masked audio tokens in \\(\\hat{A}^M\\). By training on this pretext task, our encoder \\(\\mathcal{E}\\) can learn rich audio-visual spatial correspondences that can be leveraged for multiple downstream tasks that require the synergy of vision and spatial audio, as we show in results." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.897, + 0.901 + ], + "angle": 0, + "content": "In our method (see Fig. 2), \\(\\mathcal{E}\\) (Sec. 3.1) is an audio-visual (AV) spatial correspondence encoder that learns an implicit representation of the spatial relationships between the visual and unmasked binaural audio tokens, while \\(\\mathcal{D}\\) (Sec. 3.2) is an audio-visual decoder for binaural audio inpainting that uses this implicit representation to synthesize the masked audio tokens. We also devise a simple yet novel masking protocol (Sec. 3.3) for our inpainting task, which mixes masking random audio tokens with masking a full audio channel, and helps the model learn stronger audio-visual spatial associations that facilitate the downstream social tasks (Sec. 3.5). We train \\(\\mathcal{F}\\) to minimize the prediction error in the masked audio tokens (Sec. 3.4). Next, we describe our model design, audio masking protocol, training objective and network architecture, and downstream tasks." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27060" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.077, + 0.091, + 0.457, + 0.108 + ], + "angle": 0, + "content": "3.1. Audio-visual spatial correspondence encoder" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.114, + 0.471, + 0.251 + ], + "angle": 0, + "content": "The audio-visual spatial correspondence encoder \\(\\mathcal{E}\\) (Fig. 2 center) extracts features from the visual and unmasked audio tokens \\(\\{\\hat{V},\\hat{A}^U\\}\\). It begins by embedding the visual and audio tokens using separate transformer encoders [15] for individually capturing the spatio-temporal features in the two modalities. Next, it uses a shared transformer encoder to jointly encode the audio and visual features, and produces a multi-modal representation suitable for binaural audio inpainting. We describe the individual encoders next." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.259, + 0.473, + 0.524 + ], + "angle": 0, + "content": "Video and audio encoders. We first encode the visual tokens \\(\\hat{V}\\) using a linear layer to generate visual features \\(v\\), such that \\(v = \\{v_{1},\\dots,v_{P}\\}\\). We encode the audio tokens \\(\\hat{A}^{U}\\) with another linear layer to produce audio features \\(a\\), such that \\(a = \\{a_{1},\\dots,a_{Q - S}\\}\\), where \\(S\\) is the number of masked tokens out of a total of \\(Q\\) audio tokens (cf. Sec. 3). For each visual feature \\(v_{j}\\), we add a sinusoidal positional embedding \\(p_j^V\\) [67] to it, where \\(p_j^V\\) captures cues about the 3D position of the \\(j^{\\mathrm{th}}\\) tubelet in the visual clip \\(V\\). For an audio feature \\(a_{i}\\), we add a sinusoidal positional embedding \\(p_i^A\\) and a learnable channel embedding \\(c\\in \\{c_L,c_R\\}\\) to it to convey information about the 2D location of the \\(i^{\\mathrm{th}}\\) unmasked audio token in the spectrogram and also the audio channel to which it belongs. Next, we feed the transformed visual and audio features to separate transformer encoders, \\(\\mathcal{E}^V\\) and \\(\\mathcal{E}^A\\), respectively, and obtain visual features \\(e^V = \\{e_1^V,\\dots,e_P^V\\}\\) and audio features \\(e^A = \\{e_1^A,\\dots,e_{Q - S}^A\\}\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.534, + 0.473, + 0.734 + ], + "angle": 0, + "content": "Shared audio-visual encoder. Given the visual features \\( e^{V} \\) and audio features \\( e^{A} \\), we concatenate them into \\( e^{AV} \\), such that \\( e^{AV} = \\{e_1^V, \\dots, e_P^V, e_1^A, \\dots, e_{Q - S}^A\\} \\), and re-add the sinusoidal positional embeddings \\( p^{V} \\) and \\( p^{A} \\) to the features of the respective modalities in \\( e^{AV} \\). Furthermore, unlike existing audio-visual masked auto-encoders [23, 24, 29], we add the channel embeddings \\( c \\) to the audio features, and learnable modality embeddings \\( m \\in \\{m_A, m_V\\} \\) to all features in \\( e^{AV} \\) to help the model distinguish between the visual and audio modalities. Next, a shared audio-visual transformer \\( \\mathcal{E}^{AV} \\) encoder takes \\( e^{AV} \\) as input and outputs audio-visual features \\( f^{AV} \\), which implicitly hold spatio-temporal information required for accurate inpainting of audio." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.742, + 0.471, + 0.775 + ], + "angle": 0, + "content": "3.2. Audio-visual decoder for binaural audio inpainting" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.779, + 0.472, + 0.903 + ], + "angle": 0, + "content": "Our audio-visual decoder \\(\\mathcal{D}\\) (Fig. 2 right) takes \\(f^{AV}\\) as input and attempts to synthesize the masked binaural audio tokens by leveraging spatio-temporal cues in \\(f^{AV}\\). It first projects \\(f^{AV}\\) to a lower-dimensional feature set \\(g^{AV}\\). It then appends a learnable embedding for the masked audio tokens to \\(g^{AV}\\) and passes it through a shared audio-visual transformer decoder [26]. Next, it feeds the audio feature outputs of the shared decoder to another transformer decoder" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.183 + ], + "angle": 0, + "content": "and uses its outputs to predict an estimate of the masked binaural audio tokens. The decoders are lightweight compared to the encoders, ensuring that the encoders are primarily responsible for driving the inpainting task and producing good audio-visual features for strong downstream performance. We next describe each component of \\(\\mathcal{D}\\) in detail." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.196, + 0.897, + 0.349 + ], + "angle": 0, + "content": "Shared audio-visual decoder. We first create a lower-dimensional projection \\( g^{AV} \\) of the audio-visual encodings \\( f^{AV} \\) by passing it through a linear layer, and append a learnable embedding \\( \\phi \\) corresponding to each of the \\( S \\) masked audio tokens to \\( g^{AV} \\). Next, we add the positional embeddings \\( p^V \\) and \\( p^A \\), the audio channel embeddings \\( c \\), and the modality embeddings \\( m \\) to \\( g^{AV} \\), and feed it to a shallow transformer decoder \\( \\mathcal{D}^{AV} \\) that outputs an audio-visual feature set \\( h^{AV} \\). We then take the audio features \\( h^A \\) from \\( h^{AV} \\) and pass them to the audio decoder for further processing." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.361, + 0.895, + 0.422 + ], + "angle": 0, + "content": "Audio decoder. The audio decoder \\(\\mathcal{D}^A\\) re-adds the positional embeddings \\(p^A\\) and channel embeddings \\(c\\) to \\(g^A\\), and feeds it to a transformer decoder, which outputs audio features \\(d^A\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.436, + 0.895, + 0.515 + ], + "angle": 0, + "content": "Prediction of masked audio tokens. Finally, we take the subset of all audio features \\( d^{A} \\) corresponding to the masked audio tokens \\( \\hat{A}^{M} \\), upsample them by passing through a linear layer, and reshape them to obtain an estimate \\( \\tilde{A}^{M} \\) of the masked tokens \\( \\hat{A}^{M} \\), such that \\( \\tilde{A}^{M} = \\{\\tilde{A}_{1},\\dots,\\tilde{A}_{S}\\} \\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.522, + 0.655, + 0.538 + ], + "angle": 0, + "content": "3.3. Audio masking" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.545, + 0.895, + 0.682 + ], + "angle": 0, + "content": "Different from other masked auto-encoding counterparts [23, 24, 29], we design an audio masking protocol that is customized to help our model better extract spatial audio-visual cues during self-supervised pretraining. In particular, we mix the strategy of randomly masking a full audio channel with that of randomly masking audio tokens using a hyperparameter \\( r \\) during training, where \\( r \\) represents the probability with which we randomly drop a full audio channel and \\( r \\) is sampled from a uniform distribution \\( U(0,1) \\):" + }, + { + "type": "equation", + "bbox": [ + 0.502, + 0.691, + 0.888, + 0.726 + ], + "angle": 0, + "content": "\\[\n\\operatorname {m a s k} (\\hat {A}) = \\left\\{ \\begin{array}{l l} \\hat {A} ^ {M} = A ^ {L} \\text {o r} \\hat {A} ^ {M} = A ^ {R} & \\text {i f} x \\sim U (0, 1) \\leq r \\\\ \\hat {A} ^ {M} \\subseteq \\{\\hat {A} _ {1}, \\dots , \\hat {A} _ {Q} \\} & \\text {o t h e r w i s e} \\end{array} \\right.\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.897, + 0.902 + ], + "angle": 0, + "content": "On the one hand, token masking could lead to tokens from the same location in the two audio channels being present among the unmasked tokens, providing additional spatial cues to the model and resulting in a simpler, stabler optimization objective for the inpainting task. In addition, since token masking involves masking a short span in both frequency and time domains, the model can rely more on local audio-visual cues and tolerate the global noise in both the visual and audio streams due to a camera-wearer's motion. On the other hand, channel masking forces the model to solve a more challenging binauralization task solely on the basis of vision," + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.958 + ], + "angle": 0, + "content": "27061" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.091, + 0.088, + 0.457, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.355, + 0.473, + 0.412 + ], + "angle": 0, + "content": "Figure 3. Masked targets and predictions shown alongside the unmasked inputs for (a) token masking and (b) channel masking. Our predictions accurately capture the global patterns in the target spectrograms, which depend on the scene's spatial properties." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.434, + 0.47, + 0.526 + ], + "angle": 0, + "content": "which could help it learn even stronger spatial features. This encourages the model to reason about the camera motion at a more global scale (over the entire clip span). Towards achieving high performance on the downstream tasks, we aim to strike a fine balance between these two strategies and combine the benefits of reasoning at both temporal scales." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.534, + 0.453, + 0.551 + ], + "angle": 0, + "content": "3.4. Training objective and network architecture" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.557, + 0.473, + 0.603 + ], + "angle": 0, + "content": "We train our model to minimize the error in predicting the masked audio tokens. In particular, we compute the mean-squared error \\(\\mathcal{L}\\) averaged over all masked audio tokens:" + }, + { + "type": "equation", + "bbox": [ + 0.182, + 0.613, + 0.472, + 0.65 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\frac {1}{S} \\sum_ {i = 1 \\dots S} | | \\ddot {A} _ {i} - \\tilde {a} _ {i} | | _ {2} ^ {2}. \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.659, + 0.47, + 0.779 + ], + "angle": 0, + "content": "We visualize our predicted audio tokens in Fig. 3 for the cases of token (Fig. 3a) and channel (Fig 3b) masking. Our model is able to accurately predict the masked targets and capture the global patterns in the spectrograms, which are often determined by the spatial audio-visual cues captured from of the scene (visual input not shown in Fig 3 for brevity), thereby further emphasizing our model's ability to learn useful spatial features." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Our uni-modal encoders, \\(\\mathcal{E}^A\\) and \\(\\mathcal{E}^V\\), have 8 layers, while the audio-visual encoder \\(\\mathcal{E}^{AV}\\) has 6 layers. All encoders have 12 attention heads and use 768-dimensional hidden embeddings. The audio-visual decoder \\(\\mathcal{D}^{AV}\\) and audio-only decoder \\(\\mathcal{D}^A\\) have 1 and 3 layers, respectively. Both decoders have 6 attention heads and use 384-dimensional hidden embeddings. To pretrain our model, we set the relative frequency of dropping an audio channel in our masking" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.259 + ], + "angle": 0, + "content": "protocol for training to \\( r = 20\\% \\) based on disjoint validation data (see Supp.). We train our model for 200 epochs using the AdamW [37] optimizer with a weight decay of \\( 10^{-5} \\), and a learning rate scheduler that reaches a peak learning rate of \\( 2 \\times 10^{-4} \\) over 10 warmup epochs, and then decays it through half-cycle cosine annealing [36]. For data augmentation, we perform random flipping of audio channels and video clips along the frame width. For downstream evaluation, we fuse the features from the audio-visual encoder with the backbones for downstream tasks, and finetune them. See Supp. for further details on architecture and training." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.266, + 0.679, + 0.28 + ], + "angle": 0, + "content": "3.5. Downstream tasks" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.289, + 0.895, + 0.501 + ], + "angle": 0, + "content": "We explore two downstream tasks with our pretrained features: active speaker detection and spatial audio denoising. Active speaker detection (ASD) involves matching an audio clip with an appropriate face track from the corresponding video clip, i.e., answering \"which person is speaking now?\". While current SOTA methods [42, 65] rely on semantic similarities between monaural audio and vision to solve this task, we hypothesize that leveraging spatial audio can additionally reveal the sound source location in the video. In spatial audio denoising, the goal is to separate the target audio from distractors. In particular, we aim to remove the audio from sources extraneous to the conversation—out-of-view sounds from other parts of the scene. We detail the backbone models for each in the next section." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.512, + 0.634, + 0.529 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.533, + 0.894, + 0.593 + ], + "angle": 0, + "content": "We validate our learned representations on two downstream tasks and two datasets, and we compare with prior models for spatial audio-visual feature learning [18, 23, 60, 70], as well as various baselines and ablations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.604, + 0.895, + 0.801 + ], + "angle": 0, + "content": "Datasets. We train and evaluate our model on two challenging egocentric datasets containing video and binaural audio of people having conversations: 1) EgoCom [49], and 2) EasyCom [11], detailed in Supp. To our knowledge, these are the only two publicly available datasets offering binaural audio with conversations in video, whether exocentric or egocentric. In particular, Ego4D [25] and EPIC [9] do not comprise social scenarios and are not applicable. Whereas EasyCom primarily has participants sitting around a table and talking, EgoCom has videos of participants moving around a room, turning their face and body, standing up, etc. They test our method's robustness in diverse scenarios of varying difficulty." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.808, + 0.724, + 0.824 + ], + "angle": 0, + "content": "4.1. Active speaker detection" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.831, + 0.845, + 0.846 + ], + "angle": 0, + "content": "We first evaluate on active speaker detection (ASD)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Backbone models. We consider two SOTA ASD models as the backbones for leveraging our pretrained representations: 1) TalkNet [65], and 2) SPELL [42]. TalkNet encodes" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27062" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.213 + ], + "angle": 0, + "content": "a face track and an audio clip using attention for learning intra- and inter-modal semantic and temporal features. Next, it fuses these features and performs binary classification to predict if the face in the track is active. SPELL extracts audiovisual features for each face in a clip using ResNets [3], and learns long and short-term semantic relations among them using a graph neural network. Finally, it performs binary classification of these features for predicting active speakers." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.229, + 0.473, + 0.381 + ], + "angle": 0, + "content": "Pretrained feature fusion. To fuse our pretrained features with the ASD backbones, we use a transformer decoder that cross-attends to the feature outputs of the shared encoder \\(\\mathcal{E}^{AV}\\) using sinusoidal embedding as queries, with each embedding representing a clip frame index. Next, we append the decoder outputs to the cross-attention outputs in TalkNet, or the audio-visual encoder outputs in SPELL, frame by frame. In essence, while the original audio-visual encoders leverage semantic correlations between vision and audio, our features provide strong complementary spatial cues." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.402, + 0.47, + 0.461 + ], + "angle": 0, + "content": "Baselines. For both TalkNet and SPELL, we compare against multiple baselines comprising both the unmodified backbone and improved versions of it, in addition to some naive methods:" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.463, + 0.469, + 0.493 + ], + "angle": 0, + "content": "- All-active: a naive model that predicts that all visible faces are always active" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.494, + 0.469, + 0.523 + ], + "angle": 0, + "content": "- All-inactive: a naive model that predicts that all visible faces are always inactive" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.524, + 0.47, + 0.553 + ], + "angle": 0, + "content": "- Random: a naive model that emits a random ASD confidence score for every visible speaker" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.554, + 0.47, + 0.584 + ], + "angle": 0, + "content": "- Backbone w/o audio: a vision-only version of the backbone with no audio input" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.585, + 0.47, + 0.613 + ], + "angle": 0, + "content": "- Backbone: the originally-proposed backbone that processes only faces and monaural audio" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.614, + 0.471, + 0.674 + ], + "angle": 0, + "content": "- Backbone-binaural: an improved backbone using binaural audio instead of monaural, alongside positional encodings for the faces, indicative of their relative position and depth, for better matching the face to the audio" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.675, + 0.47, + 0.719 + ], + "angle": 0, + "content": "- Backbone-binaural w/ scene: a further improvement over the backbone, where we also provide the scene images (uncropped video frames) to backbone-binaural" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.72, + 0.471, + 0.78 + ], + "angle": 0, + "content": "- Backbone w/ TLR [70]: fuses features from the SOTA Telling Left from Right (TLR) [70], which learns audio-visual spatial correspondences by predicting the spatial alignment between vision and binaural audio" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.781, + 0.47, + 0.825 + ], + "angle": 0, + "content": "- Backbone w/ 2.5D-VS [18]: fuses features from the SOTA audio-visual binauralization model, 2.5D Visual Sounds (2.5D-VS) [18]" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.826, + 0.471, + 0.855 + ], + "angle": 0, + "content": "- Backbone w/ 2.5D-VS [18]++: fuses features from 2.5D-VS with a transformer architecture" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "- Backbone w/ SSR [60]++: fuses features from the SOTA self-supervised audio-visual stereo sound ranking (SSR) [60] model with a transformer architecture" + }, + { + "type": "list", + "bbox": [ + 0.079, + 0.463, + 0.471, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.089, + 0.891, + 0.345 + ], + "angle": 0, + "content": "
ModelTalkNet [65]SPELL [42]
EgoComEasyComEgoComEasyCom
No pretraining
All-active32.930.132.930.1
All-inactive32.930.132.930.1
Random30.828.030.828.0
B w/o audio41.550.160.463.2
B52.845.760.959.0
B-binaural60.059.663.160.3
B-binaural w/ scene60.866.961.261.4
Alternate pretraining methods
B w/ TLR [70]47.959.361.361.7
B w/ 2.5D-VS [18]57.763.761.259.7
B w/ 2.5D-VS [18]++63.468.365.164.5
B w/ SSR [60]++61.270.661.267.4
B w/ AV-MAE [23]61.161.364.465.2
Ours63.971.865.670.2
Ours w/o pretrain62.762.9——
Ours w/ pretrain monaural61.069.463.969.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.355, + 0.894, + 0.424 + ], + "angle": 0, + "content": "Table 1. Mean average precision (\\%) for active speaker detection with TalkNet [65] and SPELL [42] backbones on both datasets. Higher is better. 'B' refers to backbone. Note that SPELL requires storing pretrained features in the graph nodes; therefore it does not allow training from scratch." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.445, + 0.892, + 0.475 + ], + "angle": 0, + "content": "- Backbone w/ AV-MAE [23]: fuses features from the SOTA modality-inpainting AV-MAE [23] model" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.476, + 0.894, + 0.612 + ], + "angle": 0, + "content": "For all alternate feature-learning methods [18, 23, 60, 70], we pretrain them on our datasets and use our feature fusion method. Thus, any advantages in performance of our approach over these SOTA representations will be attributable to our modeling ideas. Importantly, the 2.5D-VS [18]++, SSR [60]++, and AV-MAE [23] features all rely on transformers and have similar model capacity as ours; see Supp. for a detailed analysis on model capacity. We use the standard mean average precision (mAP) metric." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.628, + 0.894, + 0.824 + ], + "angle": 0, + "content": "Results. Table 1 (top) reports our ASD results on both val and test splits. The three naive baselines perform poorly on both EgoCom [49] and EasyCom [11], emphasizing the difficulty of the task. For both TalkNet [65] and SPELL [42], the unchanged backbone model generally performs better than the model without audio, showing that both vision and audio are required. Upgrading from monaural to binaural audio further boosts performance, as the model can now leverage both spatial and semantic information. Additionally using scene features lets the backbone explicitly match the scene area around the inferred source location with the face, and further improves ASD, especially for EgoCom, where the background scene changes more often." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Among alternate feature learning methods, 2.5D-VS [18]++, SSR [60]++ and AV-MAE [23] consistently outperform TLR [70] and 2.5D-VS [17], and also the basic and enhanced backbones, showing that self-attention and higher model capacity enhance feature quality. Besides, 2.5D-VS" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27063" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.12, + 0.089, + 0.428, + 0.306 + ], + "angle": 0, + "content": "
ModelSI-SDRi ↑STFT ↓
No pretraining
B w/o vision1.617.36
B1.467.27
B w/ ImageNet features1.486.95
Alternate pretraining methods
B w/ TLR [70]1.417.79
B w/ 2.5D-VS [18]1.677.34
B w/ 2.5D-VS [18]++2.116.60
B w/ SSR [60] ++2.046.70
B w/ AV-MAE [23]2.076.62
Ours2.206.51
B w/o pretrain1.907.25
B w/ pretrain monaural audio2.006.75
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.317, + 0.47, + 0.358 + ], + "angle": 0, + "content": "Table 2. Audio denoising with U-Net [70] backbone (referred to as 'B' in table) for 0 dB noise (maximum). See Supp. for varying noise levels. All STFT distance measures use base \\(10^{-3}\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.375, + 0.469, + 0.421 + ], + "angle": 0, + "content": "outperforms TLR, and 2.5D-VS++ and AV-MAE generally outperform SSR++, indicating that objectives that promote reasoning directly at the spectrogram level improve results." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.422, + 0.47, + 0.618 + ], + "angle": 0, + "content": "Our model substantially outperforms all baselines—including the SOTA AV representation learning methods—for both backbones (TalkNet and SPELL) on both datasets. This shows that our method learns stronger spatial features that are both backbone- and dataset-agnostic. In contrast, methods developed for exocentric settings with more stationary cameras (such as TLR and 2.5D-VS) rely more on the global visual context and seem to struggle in our setting, where the camera moves frequently and the sound source leaves the field of view. Finally, our improvement over 2.5D-VS++, SSR++ and AV-MAE, which use similar encoders as ours, disentangles the benefits of our masking strategy and model design from those of the model capacity." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.628, + 0.47, + 0.749 + ], + "angle": 0, + "content": "Model analysis. Table 1 (bottom) shows ablations of our method. Upon training for ASD from scratch, we see a sharp drop in performance, showing that our advantage is not solely due to our model design, but also our self-supervised pretraining stage. Performance also declines upon pretraining with monaural audio instead of binaural, showing that our model goes beyond learning semantic features and successfully captures spatial features useful for ASD." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.758, + 0.292, + 0.774 + ], + "angle": 0, + "content": "4.2. Spatial audio denoising" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.469, + 0.843 + ], + "angle": 0, + "content": "Next we evaluate spatial audio denoising on EgoCom.2 To instantiate this task, we add the binaural audio of a target clip with the downscaled binaural audio from another randomly chosen clip, where the downscaling factor depends on the" + }, + { + "type": "text", + "bbox": [ + 0.506, + 0.09, + 0.897, + 0.181 + ], + "angle": 0, + "content": "desired noise level. The goal is to extract the target sound from the mixture. We evaluate three noise levels, expressed using the signal-to-noise (SNR) ratio: 1) \\(0\\mathrm{dB}\\), 2) \\(2.5\\mathrm{dB}\\), and 3) \\(5\\mathrm{dB}\\). The different noise levels test our model's robustness to varying levels of task difficulty—the lower the SNR value, the higher the noise and difficulty." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.197, + 0.894, + 0.318 + ], + "angle": 0, + "content": "Backbone model. We adopt the commonly used U-Net [57] for audio-visual source separation [18, 70] as the backbone, which produces a binaural ratio mask for the target audio (see Supp. for details). We multiply the predicted ratio mask with the mixed magnitude spectrogram to get the predicted magnitude spectrogram, then convert it to a waveform using inverse short-time Fourier transform with the mixed audio phase." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.333, + 0.894, + 0.455 + ], + "angle": 0, + "content": "Pretrained feature fusion. To use our features for denoising, we reshape the visual features and unmasked audio features produced by our audio-visual encoder \\(\\mathcal{E}^{AV}\\) to form multi-channel 2D maps, where the features align with their corresponding tokens vis-a-vis the raster order. Next, we pass the feature maps to separate convolutional layers, concatenate the outputs channel-wise, and use them to replace the visual features at the U-Net [70] bottleneck." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.469, + 0.892, + 0.498 + ], + "angle": 0, + "content": "Baselines. We compare against the following baselines and existing methods:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.5, + 0.884, + 0.514 + ], + "angle": 0, + "content": "- U-Net w/o vision: an audio-only blind denoising model" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.515, + 0.866, + 0.529 + ], + "angle": 0, + "content": "- U-Net: the original backbone without any alterations" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.53, + 0.894, + 0.559 + ], + "angle": 0, + "content": "- U-Net w/ ImageNet: pretrains the visual encoder on ImageNet [10]" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.56, + 0.852, + 0.575 + ], + "angle": 0, + "content": "- U-Net w/ TLR [70]: fuses features from TLR [70]" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.576, + 0.891, + 0.604 + ], + "angle": 0, + "content": "- U-Net w/ 2.5D-VS [18]: fuses pretrained features from 2.5D-VS [18]" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.605, + 0.891, + 0.634 + ], + "angle": 0, + "content": "- U-Net w/ 2.5D-VS [18]++: fuses features from the transformer-based version of 2.5D-VS" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.635, + 0.891, + 0.665 + ], + "angle": 0, + "content": "- U-Net w/ SSR [60]++: fuses features from the transformer-based version of SSR [60]" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.665, + 0.891, + 0.695 + ], + "angle": 0, + "content": "- U-Net w/ AV-MAE [60]: fuses features from the modality inpainting AV-MAE [23] model" + }, + { + "type": "list", + "bbox": [ + 0.501, + 0.5, + 0.894, + 0.695 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.715, + 0.894, + 0.807 + ], + "angle": 0, + "content": "Evaluation metric. For evaluating our denoising quality, we use standard metrics: 1) STFT distance (the L2 error between the predicted and ground-truth spectrograms) expressed using base \\(10^{-3}\\) and 2) SI-SDRi: the improvement in SI-SDR [58], a scale-invariant estimate of the distortion in the audio, over using the mixed audio as the prediction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Results. Table 2 (top) shows spatial audio denoising results on the challenging EgoCom dataset with \\(0\\mathrm{dB}\\), the most difficult noise level. See Supp. for similar results with the other noise levels. The unchanged U-Net backbone lowers the STFT distance compared to the version that lacks vision," + }, + { + "type": "page_footnote", + "bbox": [ + 0.073, + 0.85, + 0.466, + 0.901 + ], + "angle": 0, + "content": "2For EasyCom, the task setup is ill-posed for all models because mixing audio from a different EasyCom clip as noise leads to spatially overlapping sound sources, since all clips in the dataset are recorded at the same physical location (people sitting around the same table in the same room)." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27064" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.089, + 0.203, + 0.232 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.212, + 0.089, + 0.338, + 0.232 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.344, + 0.089, + 0.47, + 0.232 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.243, + 0.47, + 0.327 + ], + "angle": 0, + "content": "Figure 4. Heat maps showing the image areas our model's AV encoder attends to, placed alongside the images. Brighter yellow means higher attention score. Our model attends to image regions (e.g. faces of speakers, sound-reflecting flat regions like floor and table, etc.) that strongly determine the spatial properties of the audio, including direct sources of sound (marked in red)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.343, + 0.47, + 0.403 + ], + "angle": 0, + "content": "showing that like ASD, vision is crucial for better denoising. Using pretrained features of 2.5D-VS [18] \\((++)\\), SSR \\([60]++\\) or AV-MAE [23] further improves performance, showing that learning spatial audio-visual features aids denoising." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.404, + 0.474, + 0.555 + ], + "angle": 0, + "content": "Our method outperforms all baselines \\((p \\leq 0.05)\\) across both metrics. While the improvement over the baselines that do not use self-supervised pretraining emphasizes the utility of learning spatial audio-visual relationships through self-supervision, the gain over other pretraining methods underlines the strengths of our self-supervised method design—which are consistently realized for both ASD and denoising. Further, our performance margins are larger for higher noise levels (0 and \\(2.5\\mathrm{dB}\\)), indicating that our features play a bigger role in the more difficult denoising settings." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.566, + 0.47, + 0.716 + ], + "angle": 0, + "content": "Model analysis. In Table 2 (bottom), we ablate our pretraining method. Similar to ASD, training from scratch on the denoising task hurts performance. This disentangles the impact of our pretext task design from the model architecture and shows that our pretraining stage helps the backbone with learning better audio-visual features, leading to superior denoising quality. Furthermore, pretraining with monaural audio also degrades performance, re-emphasizing that our method is not restricted to learning semantic features—in contrast to prior work [23, 24, 29]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.717, + 0.469, + 0.763 + ], + "angle": 0, + "content": "See Supp. for analysis of the effect of alternate masking choices, multi-level positional embeddings, task-specific backbones, and our finetuning strategy on performance." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.771, + 0.265, + 0.789 + ], + "angle": 0, + "content": "4.3. Qualitative analysis" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.901 + ], + "angle": 0, + "content": "In Fig. 4, we analyze the visual attention maps of our shared encoder \\(\\mathcal{E}^{AV}\\). Note that the regions of high attention are not only limited to the direct sound sources (e.g., regions in and around faces of active speakers across examples), but also include large sound-reflecting objects (e.g., the flat surface of the table on the left; the walls on the left and in the middle; the floor on the right, etc.) that determine how sound" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.089, + 0.706, + 0.208 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.708, + 0.089, + 0.911, + 0.208 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.21, + 0.91, + 0.235 + ], + "angle": 0, + "content": "(a) Our model succeeds on ASD even with fast camera motion (left; note image blur), multiple active speakers (right) and partially visible faces (left and right)" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.239, + 0.638, + 0.327 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.639, + 0.239, + 0.774, + 0.327 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.775, + 0.239, + 0.911, + 0.327 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.33, + 0.91, + 0.355 + ], + "angle": 0, + "content": "(b) Our model denoises accurately—note the noise patches in mixed audio above points \\( p_1 \\) and \\( p_2 \\), which are successfully removed in our prediction." + }, + { + "type": "image_caption", + "bbox": [ + 0.532, + 0.363, + 0.86, + 0.378 + ], + "angle": 0, + "content": "Figure 5. Success cases for ASD (a) and denoising (b)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.383, + 0.895, + 0.488 + ], + "angle": 0, + "content": "spatializes through early reflections, late reverberations, etc. Interestingly, our model also attends to multiple people if they are speaking at the same time (see left), thereby facilitating the detection of multiple active speakers. See Supp. for additional visualizations showing how, depending on the scene's spatial layout, our model uses one audio channel more than the other to attend to important image locations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.489, + 0.895, + 0.578 + ], + "angle": 0, + "content": "In Fig. 5, we qualitatively show our model's success cases. On ASD (Fig. 5a), our model can tackle drastic camera movements, multiple active speakers, and partially visible faces. On denoising (Fig. 5b), our model is able to remove interferences from distractor sources, and make predictions that closely match the ground truth in spectrogram structure." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.58, + 0.894, + 0.7 + ], + "angle": 0, + "content": "We also observe some limitations. Our model's performance on ASD declines when there are drastic movements of the camera wearer, or there is a high overlap in speech from different conversation participants. On denoising, our model struggles when the noisy audio is semantically and acoustically similar to the target, or when it cannot extract spatial cues due to occlusions or out-of-view speakers. Refer to our Supp. video for both success and failure cases." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.714, + 0.619, + 0.729 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.739, + 0.895, + 0.901 + ], + "angle": 0, + "content": "We introduce a novel self-supervised approach for learning audio-visual representations in social egocentric videos via spatial correspondence between the video and its binaural audio. Through extensive evaluation, we show that our learned features are strong and generic enough to improve over multiple backbone methods on multiple downstream tasks. In future work, we will explore how the learned spatial audio-visual cues may reveal the social attention of speakers. Acknowledgements: UT Austin is supported in part by NSF CCRI and the IFML NSF AI Institute. KG is paid as a research scientist by Meta, and SM is a visiting researcher at Meta." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27065" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.472, + 0.157 + ], + "angle": 0, + "content": "[1] Triantafyllos Afouras, Joon Son Chung, and Andrew Zisserman. The conversation: Deep audio-visual speech enhancement. arXiv preprint arXiv:1804.04121, 2018. 3" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.159, + 0.473, + 0.24 + ], + "angle": 0, + "content": "[2] Triantafyllos Afouras, Andrew Owens, Joon Son Chung, and Andrew Zisserman. Self-supervised learning of audio-visual objects from video. In Computer Vision-ECCV 2020: 16th European Conference, Glasgow, UK, August 23–28, 2020, Proceedings, Part XVIII 16, pages 208–224. 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In IEEE TRANSACTIONS ON SIGNAL PROCESSING (2002) SUBMITTED, 2004. 3" + }, + { + "type": "list", + "bbox": [ + 0.504, + 0.093, + 0.894, + 0.698 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.52, + 0.957 + ], + "angle": 0, + "content": "27068" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_origin.pdf b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..e76e7681e5b987c92c6c9b952fdb51137a367f4b --- /dev/null +++ b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/99328dcb-7d90-4f7e-aee5-421c7b55c1a4_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:0a7489490988a386daf899257890f5db6ea96d34b511dd60db78083e7c7cce78 +size 4152009 diff --git a/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/full.md b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/full.md new file mode 100644 index 0000000000000000000000000000000000000000..b06dcbba6b6a9e765a3b978f4375b3dc48d0e640 --- /dev/null +++ b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/full.md @@ -0,0 +1,315 @@ +# Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos + +Sagnik Majumder $^{1,2}$ Ziad Al-Halah $^{3}$ Kristen Grauman $^{1,2}$ $^{1}$ UT Austin ${}^{2}$ FAIR, Meta ${}^{3}$ University of Utah + +# Abstract + +We propose a self-supervised method for learning representations based on spatial audio-visual correspondences in egocentric videos. Our method uses a masked autoencoding framework to synthesize masked binaural audio through the synergy of audio and vision, thereby learning useful spatial relationships between the two modalities. We use our pretrained features to tackle two downstream video tasks requiring spatial understanding in social scenarios: active speaker detection and spatial audio denoising. Through extensive experiments, we show that our features are generic enough to improve over multiple state-of-the-art baselines on both tasks on two challenging egocentric video datasets that offer binaural audio, EgoCom and EasyCom. Project: http://vision.cs.utexas.edu/projects/ego_av_corr. + +# 1. Introduction + +Egocentric videos provide a first-person view of how we perceive and interact with our surroundings in daily life, and they are pushing a new frontier in multi-modal learning [9, 25, 31, 62]. A key aspect of ego-video is that it can provide a rich stream of first-person spatial audio alongside visual frames when the audio is captured with multiple microphones [11, 49]. The coupling of such audio and vision provides strong spatial information about the sound sources (e.g. where the sound sources are, if they are in motion or not) in the context of the surrounding physical space (e.g. how big or small the room is, if there is a large wall nearby), as well as the camera wearer's attention in the scene revealed by how they move their head. + +Such spatial cues are especially important for social settings of multiple people talking to each other, where it is valuable to be able to 1) focus on the voice(s) of interest from among various competing sounds and 2) understand where people are directing their speech activity, for better + +![](images/e2229996018cf76966a196c5966ebc5fcefa7318d7dfbbee102e277e79b7a11a.jpg) +Figure 1. Given an egocentric video and binaural audio, we aim to learn spatial correspondences between vision and audio by solving the pretext task of inpainting segments of the binaural audio. The features benefit downstream social tasks where spatial localization is important: active speaker detection and audio denoising. + +comprehension and communication. In this way, future AR applications in conversational settings could allow a hearing-impaired person to determine who is speaking in order to redirect their attention, or enhance the received audio to make it more intelligible for any listener. + +We argue that this creates the need for human-centric spatially-grounded understanding of audio-visual events. Can we learn representations from video that capture audio-visual events in the context of the persistent physical space of the environment and the human speakers in it? Such representations would be useful for answering questions like "who is speaking right now?" and "what would the voices sound like without the audio noise (distractor sounds)?" While the former requires inferring the source location for a voice in the scene, the latter requires understanding how the perceived audio is a function of the source locations, the listener, and the surrounding environment. + +Despite the significance of these problems, today's models for audio-visual learning are not human-centric and they lack spatial grounding. On the one hand, current audio-visual representation learning methods exclusively tackle exocentric (third-person) video with monaural audio [2, 23, 24, 29, 34, 50, 52]. That domain sidesteps challenges + +inherent to ego-video arising from the camera wearer's head motion and relatively limited field of view. On the other hand, the limited prior work exploring self-supervised objectives using multi-channel audio and video [18, 22, 45, 70] are also outside of the egocentric and social contexts (e.g., for sounds in empty homes [22], musical instruments [18], or single human speakers [70]), where the need for spatial understanding of multiple sound sources is limited. + +We propose to learn audio-visual representations via spatial correspondence between an egocentric video and its binaural audio, for analyzing social (conversational) settings. In particular, we design a novel pretext task where the goal is to inpaint binaural (two-channel) audio using both video and audio. Given a social egocentric video clip with binaural audio, we mask segments of it and train a model based on masked autoencoding (MAE) [5, 15, 26, 30, 66] to predict the missing segments on the basis of the video and the unmasked segments in the audio. See Figure 1 (top). Additionally, we introduce a novel spatial audio masking strategy that facilitates learning strong audio-visual spatial correspondences while maintaining learning stability when vision alone is insufficient for the binauralization task. Once trained, our model's encoder provides spatial audio-visual features that can be used to address multiple downstream tasks, as we demonstrate using multiple different backbones and social egocentric video datasets. + +In particular, motivated by the AR applications discussed above, we validate our feature learning method on two downstream social egocentric tasks that require strong audio-visual spatial reasoning: 1) active speaker detection: predicting which person in the field of view of an egocentric video is speaking, and 2) spatial audio denoising: separating audio noise (any sounds from non-speakers) from the input audio. See Figure 1 (bottom). We test the generality of our method by evaluating on two social egocentric video datasets, EgoCom [49] and EasyCom [11]—to our knowledge, the only two publicly available video datasets with binaural sound and social settings. On both, our method significantly outperforms multiple state-of-the-art task-specific and audio-visual spatial feature learning models. + +# 2. Related Work + +Audio-visual self-supervised pretraining Past work [2, 4, 34, 45, 48, 50–52] extensively studies the synergy of vision and audio for learning representations through self-supervision. They explore using both modalities to construct pretext tasks based on synthesis [51, 52], alignment [2, 4, 22, 34, 50], and masked auto-encoding (MAE) [23, 24, 29], and they focus on semantic downstream tasks like audio-visual event classification and retrieval. However, none of these methods are designed to extract spatial cues from video and multi-channel audio, nor do they analyze the social egocentric setting. On the contrary, we propose self-supervised + +learning of spatial audio-visual features from egocentric video. Further, different from existing MAE-style models [23, 24, 29], we propose a specialized masking strategy that better learns spatial audio-visual cues. Our masking idea promotes the encoding of spatial and semantic information in the learned multimodal representation, thereby improving its effectiveness for transfer learning in downstream tasks that require nuanced reasoning about both what and where aspects, such as active speaker detection and spatial audio-visual denoising. This differs from previous methods [23, 24, 29], which mainly use a learning objective that emphasizes the encoding of semantic cues and tailor to tasks like multimodal event classification or retrieval. + +Audio-visual spatial correspondence learning Learning the spatial alignment between video and audio is important for self-supervision [45, 60, 69, 70], audio generation [7, 18, 40, 44, 46, 56, 73], audio-visual embodied learning [6, 8, 38, 39] and 3D scene mapping [41, 55]. However, these methods are either restricted to exocentric settings [7, 18, 44, 45, 56, 60, 70], or else tackle egocentric settings [8, 38, 40, 41] in simulated 3D environments that lack realism and diversity, both in terms of the audio-visual content of the videos (no people are visible, no objects are moving) and their lack of continuous camera motion from a camerewer's physical movements. In contrast, we learn an audio-visual representation from real-world egocentric video. + +More closely related to our work are Telling Left from Right (TLR) [70], 2.5D Visual Sounds (2.5D-VS) [18], and audio-visual stereo sound ranking (SSR) [60], all of which learn spatial audio-visual features, albeit for exocentric data only. TLR predicts whether the left and right binaural channels are swapped, and SSR ranks the similarity of video to different stereo audio samples through self-supervision—both of which provide only coarse spatial information about the scene. 2.5D-VS learns to "lift" the mono input to binaural audio, which can be underconstrained from the single-channel audio and video alone. We design a novel pretext task using audio-visual inpainting of binaural audio, which is both fine-grained (requiring to capture subtleties about the arrangement of speakers in the environment) and, through our novel masking strategy, exposes better multi-modal constraints that improve learning stability and performance. Our results in Sec. 4 show our model's advantages over all three prior methods [18, 60, 70]. + +Active speaker detection Active speaker detection (ASD) entails predicting the active speaker(s) from among all detected faces in a video, and is a special case of generic 2D sound localization [17, 27, 32, 43, 50, 71]. While early ASD methods rely on lip motion and facial gestures [14], recent methods employ ensemble networks [3] or 3D CNNs [33, 61, 65], relation context modules [72], attention [3, 65], or graph neural networks [35, 42]. Multi- + +![](images/b4dad772f1f7f07250016d258810eef4462406f4e09e04917813a7e9ed4b817b.jpg) +Figure 2. Our model learns the spatial correspondence between vision and binaural audio by inpainting masked tokens of the audio channels through the use of an audio-visual encoder-decoder model. We combine random token masking (which requires solving a more local binauralization task) with complete audio channel masking (which requires more global cues to synthesize unseen binaural segments). For downstream evaluation, we fuse the features from the audio-visual encoder with the backbones for downstream tasks, and finetune them. + +channel audio improves ASD [32], but requires privileged information of the speaker's pose for training. Recent work explores using supervised learning to infer not only who is talking, but also to whom a camera-wearer is listening [59]. In contrast, our goal is to learn spatial audio-visual features purely from in-the-wild egocentric video through self-supervision—features generic enough to benefit multiple ASD models, as we show for both TalkNet [65] and SPELL [42]. + +Spatial audio denoising Audio denoising, which requires separating a target sound from noise, has traditionally been studied with single-channel (non-spatial) audio, both in the audio-only setting [28, 63, 64, 68] and audio-visual settings [1, 13, 16, 19–21, 50, 53, 54]. Using spatial audio captured with multiple microphones [12, 47, 74] naturally makes the task simpler. Different from the above, we learn task-agnostic audio-visual spatial features. That is, our contribution is the feature learning idea (which benefits both denoising and ASD), rather than a novel denoising approach. + +# 3. Learning spatial features from egocentric audio-visual correspondence + +The spatial sound perceived in an egocentric setup is shaped by the environment in which it is emitted and its source location relative to the camera-wearer. Based on this knowledge, we hypothesize that trying to solve the pretext task of audio-visual inpainting of binaural audio—that is, synthesizing missing audio segments by extracting related visual cues about the scene and the source location—can lead to learning useful audio-visual spatial correspondences. To validate our hypothesis, we propose a novel feature-learning task. + +Formally, we consider an egocentric video clip $C = (V, A)$ , where $V$ and $A$ refer to the visual and binaural audio streams, respectively. See Fig. 2 left. The visual clip $V$ comprises $T$ frames, such that $V = \{V_1, \ldots, V_T\}$ . + +We generate a set of visual tokens $\hat{V}$ by splitting $V$ into $P$ non-overlapping tubelets, such that $\hat{V} = \{\hat{V}_1,\dots ,\hat{V}_P\}$ , where $\hat{V}_k$ denotes the $k^{th}$ tubelet consisting of a contiguous sequence of patches spanning all $T$ frames. We represent the binaural audio $A$ as two Mel-spectrograms [30], $A = \{A^L,A^R\}$ , where $A^L$ and $A^R$ are the spectrograms for the left and right channels, respectively. We create a set of audio tokens $\hat{A}$ by splitting $A$ into $Q$ non-overlapping patches, such that $\hat{A} = \{\hat{A}_1,\dots ,\hat{A}_Q\}$ . + +Next, we mask a portion of the audio tokens in $\hat{A}$ and obtain complementary subsets of masked and unmasked tokens, $\hat{A}^M$ and $\hat{A}^U$ , respectively, where $\hat{A}^M = \{\ddot{A}_1,\dots ,\ddot{A}_S\}$ , $\hat{A}^U = \{\bar{A}_1,\dots ,\bar{A}_{Q - S}\}$ , and $S$ is the number of masked tokens. Given $\{\hat{V},\hat{A}^{M},\hat{A}^{U}\}$ , we aim to learn a self-supervised model $\mathcal{F}$ comprising an encoder $\mathcal{E}$ and decoder $\mathcal{D}$ , such that $\mathcal{F} = \mathcal{D}\circ \mathcal{E}$ and $\mathcal{F}(\hat{V},\hat{A}^U) = \tilde{A}^M$ , where $\tilde{A}^M$ is an estimate of the masked audio tokens in $\hat{A}^M$ . By training on this pretext task, our encoder $\mathcal{E}$ can learn rich audio-visual spatial correspondences that can be leveraged for multiple downstream tasks that require the synergy of vision and spatial audio, as we show in results. + +In our method (see Fig. 2), $\mathcal{E}$ (Sec. 3.1) is an audio-visual (AV) spatial correspondence encoder that learns an implicit representation of the spatial relationships between the visual and unmasked binaural audio tokens, while $\mathcal{D}$ (Sec. 3.2) is an audio-visual decoder for binaural audio inpainting that uses this implicit representation to synthesize the masked audio tokens. We also devise a simple yet novel masking protocol (Sec. 3.3) for our inpainting task, which mixes masking random audio tokens with masking a full audio channel, and helps the model learn stronger audio-visual spatial associations that facilitate the downstream social tasks (Sec. 3.5). We train $\mathcal{F}$ to minimize the prediction error in the masked audio tokens (Sec. 3.4). Next, we describe our model design, audio masking protocol, training objective and network architecture, and downstream tasks. + +# 3.1. Audio-visual spatial correspondence encoder + +The audio-visual spatial correspondence encoder $\mathcal{E}$ (Fig. 2 center) extracts features from the visual and unmasked audio tokens $\{\hat{V},\hat{A}^U\}$ . It begins by embedding the visual and audio tokens using separate transformer encoders [15] for individually capturing the spatio-temporal features in the two modalities. Next, it uses a shared transformer encoder to jointly encode the audio and visual features, and produces a multi-modal representation suitable for binaural audio inpainting. We describe the individual encoders next. + +Video and audio encoders. We first encode the visual tokens $\hat{V}$ using a linear layer to generate visual features $v$ , such that $v = \{v_{1},\dots,v_{P}\}$ . We encode the audio tokens $\hat{A}^{U}$ with another linear layer to produce audio features $a$ , such that $a = \{a_{1},\dots,a_{Q - S}\}$ , where $S$ is the number of masked tokens out of a total of $Q$ audio tokens (cf. Sec. 3). For each visual feature $v_{j}$ , we add a sinusoidal positional embedding $p_j^V$ [67] to it, where $p_j^V$ captures cues about the 3D position of the $j^{\mathrm{th}}$ tubelet in the visual clip $V$ . For an audio feature $a_{i}$ , we add a sinusoidal positional embedding $p_i^A$ and a learnable channel embedding $c\in \{c_L,c_R\}$ to it to convey information about the 2D location of the $i^{\mathrm{th}}$ unmasked audio token in the spectrogram and also the audio channel to which it belongs. Next, we feed the transformed visual and audio features to separate transformer encoders, $\mathcal{E}^V$ and $\mathcal{E}^A$ , respectively, and obtain visual features $e^V = \{e_1^V,\dots,e_P^V\}$ and audio features $e^A = \{e_1^A,\dots,e_{Q - S}^A\}$ . + +Shared audio-visual encoder. Given the visual features $e^{V}$ and audio features $e^{A}$ , we concatenate them into $e^{AV}$ , such that $e^{AV} = \{e_1^V, \dots, e_P^V, e_1^A, \dots, e_{Q - S}^A\}$ , and re-add the sinusoidal positional embeddings $p^{V}$ and $p^{A}$ to the features of the respective modalities in $e^{AV}$ . Furthermore, unlike existing audio-visual masked auto-encoders [23, 24, 29], we add the channel embeddings $c$ to the audio features, and learnable modality embeddings $m \in \{m_A, m_V\}$ to all features in $e^{AV}$ to help the model distinguish between the visual and audio modalities. Next, a shared audio-visual transformer $\mathcal{E}^{AV}$ encoder takes $e^{AV}$ as input and outputs audio-visual features $f^{AV}$ , which implicitly hold spatio-temporal information required for accurate inpainting of audio. + +# 3.2. Audio-visual decoder for binaural audio inpainting + +Our audio-visual decoder $\mathcal{D}$ (Fig. 2 right) takes $f^{AV}$ as input and attempts to synthesize the masked binaural audio tokens by leveraging spatio-temporal cues in $f^{AV}$ . It first projects $f^{AV}$ to a lower-dimensional feature set $g^{AV}$ . It then appends a learnable embedding for the masked audio tokens to $g^{AV}$ and passes it through a shared audio-visual transformer decoder [26]. Next, it feeds the audio feature outputs of the shared decoder to another transformer decoder + +and uses its outputs to predict an estimate of the masked binaural audio tokens. The decoders are lightweight compared to the encoders, ensuring that the encoders are primarily responsible for driving the inpainting task and producing good audio-visual features for strong downstream performance. We next describe each component of $\mathcal{D}$ in detail. + +Shared audio-visual decoder. We first create a lower-dimensional projection $g^{AV}$ of the audio-visual encodings $f^{AV}$ by passing it through a linear layer, and append a learnable embedding $\phi$ corresponding to each of the $S$ masked audio tokens to $g^{AV}$ . Next, we add the positional embeddings $p^V$ and $p^A$ , the audio channel embeddings $c$ , and the modality embeddings $m$ to $g^{AV}$ , and feed it to a shallow transformer decoder $\mathcal{D}^{AV}$ that outputs an audio-visual feature set $h^{AV}$ . We then take the audio features $h^A$ from $h^{AV}$ and pass them to the audio decoder for further processing. + +Audio decoder. The audio decoder $\mathcal{D}^A$ re-adds the positional embeddings $p^A$ and channel embeddings $c$ to $g^A$ , and feeds it to a transformer decoder, which outputs audio features $d^A$ . + +Prediction of masked audio tokens. Finally, we take the subset of all audio features $d^{A}$ corresponding to the masked audio tokens $\hat{A}^{M}$ , upsample them by passing through a linear layer, and reshape them to obtain an estimate $\tilde{A}^{M}$ of the masked tokens $\hat{A}^{M}$ , such that $\tilde{A}^{M} = \{\tilde{A}_{1},\dots,\tilde{A}_{S}\}$ . + +# 3.3. Audio masking + +Different from other masked auto-encoding counterparts [23, 24, 29], we design an audio masking protocol that is customized to help our model better extract spatial audio-visual cues during self-supervised pretraining. In particular, we mix the strategy of randomly masking a full audio channel with that of randomly masking audio tokens using a hyperparameter $r$ during training, where $r$ represents the probability with which we randomly drop a full audio channel and $r$ is sampled from a uniform distribution $U(0,1)$ : + +$$ +\operatorname {m a s k} (\hat {A}) = \left\{ \begin{array}{l l} \hat {A} ^ {M} = A ^ {L} \text {o r} \hat {A} ^ {M} = A ^ {R} & \text {i f} x \sim U (0, 1) \leq r \\ \hat {A} ^ {M} \subseteq \{\hat {A} _ {1}, \dots , \hat {A} _ {Q} \} & \text {o t h e r w i s e} \end{array} \right. +$$ + +On the one hand, token masking could lead to tokens from the same location in the two audio channels being present among the unmasked tokens, providing additional spatial cues to the model and resulting in a simpler, stabler optimization objective for the inpainting task. In addition, since token masking involves masking a short span in both frequency and time domains, the model can rely more on local audio-visual cues and tolerate the global noise in both the visual and audio streams due to a camera-wearer's motion. On the other hand, channel masking forces the model to solve a more challenging binauralization task solely on the basis of vision, + +![](images/560fa7a786b2779004fec471ae9573bf9d12887747edff62396c7d09d2b46f31.jpg) +Figure 3. Masked targets and predictions shown alongside the unmasked inputs for (a) token masking and (b) channel masking. Our predictions accurately capture the global patterns in the target spectrograms, which depend on the scene's spatial properties. + +which could help it learn even stronger spatial features. This encourages the model to reason about the camera motion at a more global scale (over the entire clip span). Towards achieving high performance on the downstream tasks, we aim to strike a fine balance between these two strategies and combine the benefits of reasoning at both temporal scales. + +# 3.4. Training objective and network architecture + +We train our model to minimize the error in predicting the masked audio tokens. In particular, we compute the mean-squared error $\mathcal{L}$ averaged over all masked audio tokens: + +$$ +\mathcal {L} = \frac {1}{S} \sum_ {i = 1 \dots S} | | \ddot {A} _ {i} - \tilde {a} _ {i} | | _ {2} ^ {2}. \tag {1} +$$ + +We visualize our predicted audio tokens in Fig. 3 for the cases of token (Fig. 3a) and channel (Fig 3b) masking. Our model is able to accurately predict the masked targets and capture the global patterns in the spectrograms, which are often determined by the spatial audio-visual cues captured from of the scene (visual input not shown in Fig 3 for brevity), thereby further emphasizing our model's ability to learn useful spatial features. + +Our uni-modal encoders, $\mathcal{E}^A$ and $\mathcal{E}^V$ , have 8 layers, while the audio-visual encoder $\mathcal{E}^{AV}$ has 6 layers. All encoders have 12 attention heads and use 768-dimensional hidden embeddings. The audio-visual decoder $\mathcal{D}^{AV}$ and audio-only decoder $\mathcal{D}^A$ have 1 and 3 layers, respectively. Both decoders have 6 attention heads and use 384-dimensional hidden embeddings. To pretrain our model, we set the relative frequency of dropping an audio channel in our masking + +protocol for training to $r = 20\%$ based on disjoint validation data (see Supp.). We train our model for 200 epochs using the AdamW [37] optimizer with a weight decay of $10^{-5}$ , and a learning rate scheduler that reaches a peak learning rate of $2 \times 10^{-4}$ over 10 warmup epochs, and then decays it through half-cycle cosine annealing [36]. For data augmentation, we perform random flipping of audio channels and video clips along the frame width. For downstream evaluation, we fuse the features from the audio-visual encoder with the backbones for downstream tasks, and finetune them. See Supp. for further details on architecture and training. + +# 3.5. Downstream tasks + +We explore two downstream tasks with our pretrained features: active speaker detection and spatial audio denoising. Active speaker detection (ASD) involves matching an audio clip with an appropriate face track from the corresponding video clip, i.e., answering "which person is speaking now?". While current SOTA methods [42, 65] rely on semantic similarities between monaural audio and vision to solve this task, we hypothesize that leveraging spatial audio can additionally reveal the sound source location in the video. In spatial audio denoising, the goal is to separate the target audio from distractors. In particular, we aim to remove the audio from sources extraneous to the conversation—out-of-view sounds from other parts of the scene. We detail the backbone models for each in the next section. + +# 4. Experiments + +We validate our learned representations on two downstream tasks and two datasets, and we compare with prior models for spatial audio-visual feature learning [18, 23, 60, 70], as well as various baselines and ablations. + +Datasets. We train and evaluate our model on two challenging egocentric datasets containing video and binaural audio of people having conversations: 1) EgoCom [49], and 2) EasyCom [11], detailed in Supp. To our knowledge, these are the only two publicly available datasets offering binaural audio with conversations in video, whether exocentric or egocentric. In particular, Ego4D [25] and EPIC [9] do not comprise social scenarios and are not applicable. Whereas EasyCom primarily has participants sitting around a table and talking, EgoCom has videos of participants moving around a room, turning their face and body, standing up, etc. They test our method's robustness in diverse scenarios of varying difficulty. + +# 4.1. Active speaker detection + +We first evaluate on active speaker detection (ASD). + +Backbone models. We consider two SOTA ASD models as the backbones for leveraging our pretrained representations: 1) TalkNet [65], and 2) SPELL [42]. TalkNet encodes + +a face track and an audio clip using attention for learning intra- and inter-modal semantic and temporal features. Next, it fuses these features and performs binary classification to predict if the face in the track is active. SPELL extracts audiovisual features for each face in a clip using ResNets [3], and learns long and short-term semantic relations among them using a graph neural network. Finally, it performs binary classification of these features for predicting active speakers. + +Pretrained feature fusion. To fuse our pretrained features with the ASD backbones, we use a transformer decoder that cross-attends to the feature outputs of the shared encoder $\mathcal{E}^{AV}$ using sinusoidal embedding as queries, with each embedding representing a clip frame index. Next, we append the decoder outputs to the cross-attention outputs in TalkNet, or the audio-visual encoder outputs in SPELL, frame by frame. In essence, while the original audio-visual encoders leverage semantic correlations between vision and audio, our features provide strong complementary spatial cues. + +Baselines. For both TalkNet and SPELL, we compare against multiple baselines comprising both the unmodified backbone and improved versions of it, in addition to some naive methods: + +- All-active: a naive model that predicts that all visible faces are always active +- All-inactive: a naive model that predicts that all visible faces are always inactive +- Random: a naive model that emits a random ASD confidence score for every visible speaker +- Backbone w/o audio: a vision-only version of the backbone with no audio input +- Backbone: the originally-proposed backbone that processes only faces and monaural audio +- Backbone-binaural: an improved backbone using binaural audio instead of monaural, alongside positional encodings for the faces, indicative of their relative position and depth, for better matching the face to the audio +- Backbone-binaural w/ scene: a further improvement over the backbone, where we also provide the scene images (uncropped video frames) to backbone-binaural +- Backbone w/ TLR [70]: fuses features from the SOTA Telling Left from Right (TLR) [70], which learns audio-visual spatial correspondences by predicting the spatial alignment between vision and binaural audio +- Backbone w/ 2.5D-VS [18]: fuses features from the SOTA audio-visual binauralization model, 2.5D Visual Sounds (2.5D-VS) [18] +- Backbone w/ 2.5D-VS [18]++: fuses features from 2.5D-VS with a transformer architecture +- Backbone w/ SSR [60]++: fuses features from the SOTA self-supervised audio-visual stereo sound ranking (SSR) [60] model with a transformer architecture + +
ModelTalkNet [65]SPELL [42]
EgoComEasyComEgoComEasyCom
No pretraining
All-active32.930.132.930.1
All-inactive32.930.132.930.1
Random30.828.030.828.0
B w/o audio41.550.160.463.2
B52.845.760.959.0
B-binaural60.059.663.160.3
B-binaural w/ scene60.866.961.261.4
Alternate pretraining methods
B w/ TLR [70]47.959.361.361.7
B w/ 2.5D-VS [18]57.763.761.259.7
B w/ 2.5D-VS [18]++63.468.365.164.5
B w/ SSR [60]++61.270.661.267.4
B w/ AV-MAE [23]61.161.364.465.2
Ours63.971.865.670.2
Ours w/o pretrain62.762.9——
Ours w/ pretrain monaural61.069.463.969.0
+ +Table 1. Mean average precision (\%) for active speaker detection with TalkNet [65] and SPELL [42] backbones on both datasets. Higher is better. 'B' refers to backbone. Note that SPELL requires storing pretrained features in the graph nodes; therefore it does not allow training from scratch. + +- Backbone w/ AV-MAE [23]: fuses features from the SOTA modality-inpainting AV-MAE [23] model + +For all alternate feature-learning methods [18, 23, 60, 70], we pretrain them on our datasets and use our feature fusion method. Thus, any advantages in performance of our approach over these SOTA representations will be attributable to our modeling ideas. Importantly, the 2.5D-VS [18]++, SSR [60]++, and AV-MAE [23] features all rely on transformers and have similar model capacity as ours; see Supp. for a detailed analysis on model capacity. We use the standard mean average precision (mAP) metric. + +Results. Table 1 (top) reports our ASD results on both val and test splits. The three naive baselines perform poorly on both EgoCom [49] and EasyCom [11], emphasizing the difficulty of the task. For both TalkNet [65] and SPELL [42], the unchanged backbone model generally performs better than the model without audio, showing that both vision and audio are required. Upgrading from monaural to binaural audio further boosts performance, as the model can now leverage both spatial and semantic information. Additionally using scene features lets the backbone explicitly match the scene area around the inferred source location with the face, and further improves ASD, especially for EgoCom, where the background scene changes more often. + +Among alternate feature learning methods, 2.5D-VS [18]++, SSR [60]++ and AV-MAE [23] consistently outperform TLR [70] and 2.5D-VS [17], and also the basic and enhanced backbones, showing that self-attention and higher model capacity enhance feature quality. Besides, 2.5D-VS + +
ModelSI-SDRi ↑STFT ↓
No pretraining
B w/o vision1.617.36
B1.467.27
B w/ ImageNet features1.486.95
Alternate pretraining methods
B w/ TLR [70]1.417.79
B w/ 2.5D-VS [18]1.677.34
B w/ 2.5D-VS [18]++2.116.60
B w/ SSR [60] ++2.046.70
B w/ AV-MAE [23]2.076.62
Ours2.206.51
B w/o pretrain1.907.25
B w/ pretrain monaural audio2.006.75
+ +Table 2. Audio denoising with U-Net [70] backbone (referred to as 'B' in table) for 0 dB noise (maximum). See Supp. for varying noise levels. All STFT distance measures use base $10^{-3}$ . + +outperforms TLR, and 2.5D-VS++ and AV-MAE generally outperform SSR++, indicating that objectives that promote reasoning directly at the spectrogram level improve results. + +Our model substantially outperforms all baselines—including the SOTA AV representation learning methods—for both backbones (TalkNet and SPELL) on both datasets. This shows that our method learns stronger spatial features that are both backbone- and dataset-agnostic. In contrast, methods developed for exocentric settings with more stationary cameras (such as TLR and 2.5D-VS) rely more on the global visual context and seem to struggle in our setting, where the camera moves frequently and the sound source leaves the field of view. Finally, our improvement over 2.5D-VS++, SSR++ and AV-MAE, which use similar encoders as ours, disentangles the benefits of our masking strategy and model design from those of the model capacity. + +Model analysis. Table 1 (bottom) shows ablations of our method. Upon training for ASD from scratch, we see a sharp drop in performance, showing that our advantage is not solely due to our model design, but also our self-supervised pretraining stage. Performance also declines upon pretraining with monaural audio instead of binaural, showing that our model goes beyond learning semantic features and successfully captures spatial features useful for ASD. + +# 4.2. Spatial audio denoising + +Next we evaluate spatial audio denoising on EgoCom.2 To instantiate this task, we add the binaural audio of a target clip with the downscaled binaural audio from another randomly chosen clip, where the downscaling factor depends on the + +desired noise level. The goal is to extract the target sound from the mixture. We evaluate three noise levels, expressed using the signal-to-noise (SNR) ratio: 1) $0\mathrm{dB}$ , 2) $2.5\mathrm{dB}$ , and 3) $5\mathrm{dB}$ . The different noise levels test our model's robustness to varying levels of task difficulty—the lower the SNR value, the higher the noise and difficulty. + +Backbone model. We adopt the commonly used U-Net [57] for audio-visual source separation [18, 70] as the backbone, which produces a binaural ratio mask for the target audio (see Supp. for details). We multiply the predicted ratio mask with the mixed magnitude spectrogram to get the predicted magnitude spectrogram, then convert it to a waveform using inverse short-time Fourier transform with the mixed audio phase. + +Pretrained feature fusion. To use our features for denoising, we reshape the visual features and unmasked audio features produced by our audio-visual encoder $\mathcal{E}^{AV}$ to form multi-channel 2D maps, where the features align with their corresponding tokens vis-a-vis the raster order. Next, we pass the feature maps to separate convolutional layers, concatenate the outputs channel-wise, and use them to replace the visual features at the U-Net [70] bottleneck. + +Baselines. We compare against the following baselines and existing methods: + +- U-Net w/o vision: an audio-only blind denoising model +- U-Net: the original backbone without any alterations +- U-Net w/ ImageNet: pretrains the visual encoder on ImageNet [10] +- U-Net w/ TLR [70]: fuses features from TLR [70] +- U-Net w/ 2.5D-VS [18]: fuses pretrained features from 2.5D-VS [18] +- U-Net w/ 2.5D-VS [18]++: fuses features from the transformer-based version of 2.5D-VS +- U-Net w/ SSR [60]++: fuses features from the transformer-based version of SSR [60] +- U-Net w/ AV-MAE [60]: fuses features from the modality inpainting AV-MAE [23] model + +Evaluation metric. For evaluating our denoising quality, we use standard metrics: 1) STFT distance (the L2 error between the predicted and ground-truth spectrograms) expressed using base $10^{-3}$ and 2) SI-SDRi: the improvement in SI-SDR [58], a scale-invariant estimate of the distortion in the audio, over using the mixed audio as the prediction. + +Results. Table 2 (top) shows spatial audio denoising results on the challenging EgoCom dataset with $0\mathrm{dB}$ , the most difficult noise level. See Supp. for similar results with the other noise levels. The unchanged U-Net backbone lowers the STFT distance compared to the version that lacks vision, + +![](images/bec3ca3985d84fe6869e1caf35981a218707ad45ab48b712131f1d9c54442ef9.jpg) +Figure 4. Heat maps showing the image areas our model's AV encoder attends to, placed alongside the images. Brighter yellow means higher attention score. Our model attends to image regions (e.g. faces of speakers, sound-reflecting flat regions like floor and table, etc.) that strongly determine the spatial properties of the audio, including direct sources of sound (marked in red). + +![](images/3ea40335a68db5a0dfb68890877ffae04894d316118d66dc692446d46fca5c33.jpg) + +![](images/a77ec49d953a652c870f6e117add878ebe418e9c4637a2d7ec7d47f6c2f8a41f.jpg) + +showing that like ASD, vision is crucial for better denoising. Using pretrained features of 2.5D-VS [18] $(++)$ , SSR $[60]++$ or AV-MAE [23] further improves performance, showing that learning spatial audio-visual features aids denoising. + +Our method outperforms all baselines $(p \leq 0.05)$ across both metrics. While the improvement over the baselines that do not use self-supervised pretraining emphasizes the utility of learning spatial audio-visual relationships through self-supervision, the gain over other pretraining methods underlines the strengths of our self-supervised method design—which are consistently realized for both ASD and denoising. Further, our performance margins are larger for higher noise levels (0 and $2.5\mathrm{dB}$ ), indicating that our features play a bigger role in the more difficult denoising settings. + +Model analysis. In Table 2 (bottom), we ablate our pretraining method. Similar to ASD, training from scratch on the denoising task hurts performance. This disentangles the impact of our pretext task design from the model architecture and shows that our pretraining stage helps the backbone with learning better audio-visual features, leading to superior denoising quality. Furthermore, pretraining with monaural audio also degrades performance, re-emphasizing that our method is not restricted to learning semantic features—in contrast to prior work [23, 24, 29]. + +See Supp. for analysis of the effect of alternate masking choices, multi-level positional embeddings, task-specific backbones, and our finetuning strategy on performance. + +# 4.3. Qualitative analysis + +In Fig. 4, we analyze the visual attention maps of our shared encoder $\mathcal{E}^{AV}$ . Note that the regions of high attention are not only limited to the direct sound sources (e.g., regions in and around faces of active speakers across examples), but also include large sound-reflecting objects (e.g., the flat surface of the table on the left; the walls on the left and in the middle; the floor on the right, etc.) that determine how sound + +![](images/c7b491178e6a561eed8fdfcfc80dae7fafcf330d977ed5fe54c5016971213362.jpg) +(a) Our model succeeds on ASD even with fast camera motion (left; note image blur), multiple active speakers (right) and partially visible faces (left and right) + +![](images/95808edb9b9892bc8614815e08a6ca216213b1fba5202616cff6bc6d0f2548ce.jpg) + +![](images/efaafdad1430c6a55fbc81f79c13dd63585017084c515b3191e910f3dd47141c.jpg) +(b) Our model denoises accurately—note the noise patches in mixed audio above points $p_1$ and $p_2$ , which are successfully removed in our prediction. + +![](images/f9976d11abc79e9153f5c311848e4955da96af1d9bae7104d6e6a080632cb340.jpg) +Figure 5. Success cases for ASD (a) and denoising (b) + +![](images/ff92554be065096e6cb96e892b4f7ec4e32cf72ab9de6cbc7c9d5b75bf46bc3b.jpg) + +spatializes through early reflections, late reverberations, etc. Interestingly, our model also attends to multiple people if they are speaking at the same time (see left), thereby facilitating the detection of multiple active speakers. See Supp. for additional visualizations showing how, depending on the scene's spatial layout, our model uses one audio channel more than the other to attend to important image locations. + +In Fig. 5, we qualitatively show our model's success cases. On ASD (Fig. 5a), our model can tackle drastic camera movements, multiple active speakers, and partially visible faces. On denoising (Fig. 5b), our model is able to remove interferences from distractor sources, and make predictions that closely match the ground truth in spectrogram structure. + +We also observe some limitations. Our model's performance on ASD declines when there are drastic movements of the camera wearer, or there is a high overlap in speech from different conversation participants. On denoising, our model struggles when the noisy audio is semantically and acoustically similar to the target, or when it cannot extract spatial cues due to occlusions or out-of-view speakers. Refer to our Supp. video for both success and failure cases. + +# 5. Conclusion + +We introduce a novel self-supervised approach for learning audio-visual representations in social egocentric videos via spatial correspondence between the video and its binaural audio. Through extensive evaluation, we show that our learned features are strong and generic enough to improve over multiple backbone methods on multiple downstream tasks. In future work, we will explore how the learned spatial audio-visual cues may reveal the social attention of speakers. 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In IEEE TRANSACTIONS ON SIGNAL PROCESSING (2002) SUBMITTED, 2004. 3 \ No newline at end of file diff --git a/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/images.zip b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..42f387a001d9a275569609e21f6540cedd5d0f70 --- /dev/null +++ b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:c6aa1f7f0e6c84a1a2bd59d126085e1523d637e9b38ac492d690369a9df374a7 +size 409133 diff --git a/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/layout.json b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..f1c58c6410033cd6b7eba0d4e06715fa4b7629e7 --- /dev/null +++ b/2024/Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos/layout.json @@ -0,0 +1,10423 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 105, + 103, + 489, + 140 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 105, + 103, + 489, + 140 + ], + "spans": [ + { + "bbox": [ + 105, + 103, + 489, + 140 + ], + "type": "text", + "content": "Learning Spatial Features from Audio-Visual Correspondence in Egocentric Videos" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "spans": [ + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "text", + "content": "Sagnik Majumder" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "inline_equation", + "content": "^{1,2}" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "text", + "content": " Ziad Al-Halah" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "text", + "content": " Kristen Grauman" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "inline_equation", + "content": "^{1,2}" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "text", + "content": "UT Austin " + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "inline_equation", + "content": "{}^{2}" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "text", + "content": "FAIR, Meta " + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "inline_equation", + "content": "{}^{3}" + }, + { + "bbox": [ + 136, + 160, + 457, + 190 + ], + "type": "text", + "content": "University of Utah" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 143, + 217, + 192, + 229 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 217, + 192, + 229 + ], + "spans": [ + { + "bbox": [ + 143, + 217, + 192, + 229 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 243, + 290, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 243, + 290, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 243, + 290, + 422 + ], + "type": "text", + "content": "We propose a self-supervised method for learning representations based on spatial audio-visual correspondences in egocentric videos. Our method uses a masked autoencoding framework to synthesize masked binaural audio through the synergy of audio and vision, thereby learning useful spatial relationships between the two modalities. We use our pretrained features to tackle two downstream video tasks requiring spatial understanding in social scenarios: active speaker detection and spatial audio denoising. Through extensive experiments, we show that our features are generic enough to improve over multiple state-of-the-art baselines on both tasks on two challenging egocentric video datasets that offer binaural audio, EgoCom and EasyCom. Project: http://vision.cs.utexas.edu/projects/ego_av_corr." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 438, + 128, + 451 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 438, + 128, + 451 + ], + "spans": [ + { + "bbox": [ + 47, + 438, + 128, + 451 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 459, + 288, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 459, + 288, + 614 + ], + "spans": [ + { + "bbox": [ + 46, + 459, + 288, + 614 + ], + "type": "text", + "content": "Egocentric videos provide a first-person view of how we perceive and interact with our surroundings in daily life, and they are pushing a new frontier in multi-modal learning [9, 25, 31, 62]. A key aspect of ego-video is that it can provide a rich stream of first-person spatial audio alongside visual frames when the audio is captured with multiple microphones [11, 49]. The coupling of such audio and vision provides strong spatial information about the sound sources (e.g. where the sound sources are, if they are in motion or not) in the context of the surrounding physical space (e.g. how big or small the room is, if there is a large wall nearby), as well as the camera wearer's attention in the scene revealed by how they move their head." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 615, + 288, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 615, + 288, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 615, + 288, + 676 + ], + "type": "text", + "content": "Such spatial cues are especially important for social settings of multiple people talking to each other, where it is valuable to be able to 1) focus on the voice(s) of interest from among various competing sounds and 2) understand where people are directing their speech activity, for better" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 306, + 215, + 545, + 356 + ], + "blocks": [ + { + "bbox": [ + 306, + 215, + 545, + 356 + ], + "lines": [ + { + "bbox": [ + 306, + 215, + 545, + 356 + ], + "spans": [ + { + "bbox": [ + 306, + 215, + 545, + 356 + ], + "type": "image", + "image_path": "e2229996018cf76966a196c5966ebc5fcefa7318d7dfbbee102e277e79b7a11a.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 364, + 547, + 419 + ], + "lines": [ + { + "bbox": [ + 305, + 364, + 547, + 419 + ], + "spans": [ + { + "bbox": [ + 305, + 364, + 547, + 419 + ], + "type": "text", + "content": "Figure 1. Given an egocentric video and binaural audio, we aim to learn spatial correspondences between vision and audio by solving the pretext task of inpainting segments of the binaural audio. The features benefit downstream social tasks where spatial localization is important: active speaker detection and audio denoising." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 435, + 547, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 435, + 547, + 496 + ], + "spans": [ + { + "bbox": [ + 304, + 435, + 547, + 496 + ], + "type": "text", + "content": "comprehension and communication. In this way, future AR applications in conversational settings could allow a hearing-impaired person to determine who is speaking in order to redirect their attention, or enhance the received audio to make it more intelligible for any listener." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 497, + 547, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 497, + 547, + 640 + ], + "spans": [ + { + "bbox": [ + 304, + 497, + 547, + 640 + ], + "type": "text", + "content": "We argue that this creates the need for human-centric spatially-grounded understanding of audio-visual events. Can we learn representations from video that capture audio-visual events in the context of the persistent physical space of the environment and the human speakers in it? Such representations would be useful for answering questions like \"who is speaking right now?\" and \"what would the voices sound like without the audio noise (distractor sounds)?\" While the former requires inferring the source location for a voice in the scene, the latter requires understanding how the perceived audio is a function of the source locations, the listener, and the surrounding environment." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "type": "text", + "content": "Despite the significance of these problems, today's models for audio-visual learning are not human-centric and they lack spatial grounding. On the one hand, current audio-visual representation learning methods exclusively tackle exocentric (third-person) video with monaural audio [2, 23, 24, 29, 34, 50, 52]. That domain sidesteps challenges" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 683, + 288, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 683, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 683, + 288, + 713 + ], + "type": "text", + "content": "1 Throughout we use the term spatial audio to refer to binaural audio, as perceived by two human ears. In contrast, single-channel monaural audio lacks spatial information." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27058" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 167 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 167 + ], + "type": "text", + "content": "inherent to ego-video arising from the camera wearer's head motion and relatively limited field of view. On the other hand, the limited prior work exploring self-supervised objectives using multi-channel audio and video [18, 22, 45, 70] are also outside of the egocentric and social contexts (e.g., for sounds in empty homes [22], musical instruments [18], or single human speakers [70]), where the need for spatial understanding of multiple sound sources is limited." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 168, + 290, + 382 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 168, + 290, + 382 + ], + "spans": [ + { + "bbox": [ + 46, + 168, + 290, + 382 + ], + "type": "text", + "content": "We propose to learn audio-visual representations via spatial correspondence between an egocentric video and its binaural audio, for analyzing social (conversational) settings. In particular, we design a novel pretext task where the goal is to inpaint binaural (two-channel) audio using both video and audio. Given a social egocentric video clip with binaural audio, we mask segments of it and train a model based on masked autoencoding (MAE) [5, 15, 26, 30, 66] to predict the missing segments on the basis of the video and the unmasked segments in the audio. See Figure 1 (top). Additionally, we introduce a novel spatial audio masking strategy that facilitates learning strong audio-visual spatial correspondences while maintaining learning stability when vision alone is insufficient for the binauralization task. Once trained, our model's encoder provides spatial audio-visual features that can be used to address multiple downstream tasks, as we demonstrate using multiple different backbones and social egocentric video datasets." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 384, + 288, + 551 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 384, + 288, + 551 + ], + "spans": [ + { + "bbox": [ + 46, + 384, + 288, + 551 + ], + "type": "text", + "content": "In particular, motivated by the AR applications discussed above, we validate our feature learning method on two downstream social egocentric tasks that require strong audio-visual spatial reasoning: 1) active speaker detection: predicting which person in the field of view of an egocentric video is speaking, and 2) spatial audio denoising: separating audio noise (any sounds from non-speakers) from the input audio. See Figure 1 (bottom). We test the generality of our method by evaluating on two social egocentric video datasets, EgoCom [49] and EasyCom [11]—to our knowledge, the only two publicly available video datasets with binaural sound and social settings. On both, our method significantly outperforms multiple state-of-the-art task-specific and audio-visual spatial feature learning models." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 562, + 134, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 562, + 134, + 574 + ], + "spans": [ + { + "bbox": [ + 47, + 562, + 134, + 574 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "type": "text", + "content": "Audio-visual self-supervised pretraining Past work [2, 4, 34, 45, 48, 50–52] extensively studies the synergy of vision and audio for learning representations through self-supervision. They explore using both modalities to construct pretext tasks based on synthesis [51, 52], alignment [2, 4, 22, 34, 50], and masked auto-encoding (MAE) [23, 24, 29], and they focus on semantic downstream tasks like audio-visual event classification and retrieval. However, none of these methods are designed to extract spatial cues from video and multi-channel audio, nor do they analyze the social egocentric setting. On the contrary, we propose self-supervised" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "text", + "content": "learning of spatial audio-visual features from egocentric video. Further, different from existing MAE-style models [23, 24, 29], we propose a specialized masking strategy that better learns spatial audio-visual cues. Our masking idea promotes the encoding of spatial and semantic information in the learned multimodal representation, thereby improving its effectiveness for transfer learning in downstream tasks that require nuanced reasoning about both what and where aspects, such as active speaker detection and spatial audio-visual denoising. This differs from previous methods [23, 24, 29], which mainly use a learning objective that emphasizes the encoding of semantic cues and tailor to tasks like multimodal event classification or retrieval." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 237, + 548, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 237, + 548, + 392 + ], + "spans": [ + { + "bbox": [ + 304, + 237, + 548, + 392 + ], + "type": "text", + "content": "Audio-visual spatial correspondence learning Learning the spatial alignment between video and audio is important for self-supervision [45, 60, 69, 70], audio generation [7, 18, 40, 44, 46, 56, 73], audio-visual embodied learning [6, 8, 38, 39] and 3D scene mapping [41, 55]. However, these methods are either restricted to exocentric settings [7, 18, 44, 45, 56, 60, 70], or else tackle egocentric settings [8, 38, 40, 41] in simulated 3D environments that lack realism and diversity, both in terms of the audio-visual content of the videos (no people are visible, no objects are moving) and their lack of continuous camera motion from a camerewer's physical movements. In contrast, we learn an audio-visual representation from real-world egocentric video." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 393, + 548, + 609 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 393, + 548, + 609 + ], + "spans": [ + { + "bbox": [ + 304, + 393, + 548, + 609 + ], + "type": "text", + "content": "More closely related to our work are Telling Left from Right (TLR) [70], 2.5D Visual Sounds (2.5D-VS) [18], and audio-visual stereo sound ranking (SSR) [60], all of which learn spatial audio-visual features, albeit for exocentric data only. TLR predicts whether the left and right binaural channels are swapped, and SSR ranks the similarity of video to different stereo audio samples through self-supervision—both of which provide only coarse spatial information about the scene. 2.5D-VS learns to \"lift\" the mono input to binaural audio, which can be underconstrained from the single-channel audio and video alone. We design a novel pretext task using audio-visual inpainting of binaural audio, which is both fine-grained (requiring to capture subtleties about the arrangement of speakers in the environment) and, through our novel masking strategy, exposes better multi-modal constraints that improve learning stability and performance. Our results in Sec. 4 show our model's advantages over all three prior methods [18, 60, 70]." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 618, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 618, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 618, + 548, + 714 + ], + "type": "text", + "content": "Active speaker detection Active speaker detection (ASD) entails predicting the active speaker(s) from among all detected faces in a video, and is a special case of generic 2D sound localization [17, 27, 32, 43, 50, 71]. While early ASD methods rely on lip motion and facial gestures [14], recent methods employ ensemble networks [3] or 3D CNNs [33, 61, 65], relation context modules [72], attention [3, 65], or graph neural networks [35, 42]. Multi-" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27059" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 111, + 69, + 483, + 210 + ], + "blocks": [ + { + "bbox": [ + 111, + 69, + 483, + 210 + ], + "lines": [ + { + "bbox": [ + 111, + 69, + 483, + 210 + ], + "spans": [ + { + "bbox": [ + 111, + 69, + 483, + 210 + ], + "type": "image", + "image_path": "b4dad772f1f7f07250016d258810eef4462406f4e09e04917813a7e9ed4b817b.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 219, + 547, + 264 + ], + "lines": [ + { + "bbox": [ + 46, + 219, + 547, + 264 + ], + "spans": [ + { + "bbox": [ + 46, + 219, + 547, + 264 + ], + "type": "text", + "content": "Figure 2. Our model learns the spatial correspondence between vision and binaural audio by inpainting masked tokens of the audio channels through the use of an audio-visual encoder-decoder model. We combine random token masking (which requires solving a more local binauralization task) with complete audio channel masking (which requires more global cues to synthesize unseen binaural segments). For downstream evaluation, we fuse the features from the audio-visual encoder with the backbones for downstream tasks, and finetune them." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 274, + 289, + 381 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 274, + 289, + 381 + ], + "spans": [ + { + "bbox": [ + 46, + 274, + 289, + 381 + ], + "type": "text", + "content": "channel audio improves ASD [32], but requires privileged information of the speaker's pose for training. Recent work explores using supervised learning to infer not only who is talking, but also to whom a camera-wearer is listening [59]. In contrast, our goal is to learn spatial audio-visual features purely from in-the-wild egocentric video through self-supervision—features generic enough to benefit multiple ASD models, as we show for both TalkNet [65] and SPELL [42]." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 390, + 288, + 511 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 390, + 288, + 511 + ], + "spans": [ + { + "bbox": [ + 46, + 390, + 288, + 511 + ], + "type": "text", + "content": "Spatial audio denoising Audio denoising, which requires separating a target sound from noise, has traditionally been studied with single-channel (non-spatial) audio, both in the audio-only setting [28, 63, 64, 68] and audio-visual settings [1, 13, 16, 19–21, 50, 53, 54]. Using spatial audio captured with multiple microphones [12, 47, 74] naturally makes the task simpler. Different from the above, we learn task-agnostic audio-visual spatial features. That is, our contribution is the feature learning idea (which benefits both denoising and ASD), rather than a novel denoising approach." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 522, + 287, + 551 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 522, + 287, + 551 + ], + "spans": [ + { + "bbox": [ + 47, + 522, + 287, + 551 + ], + "type": "text", + "content": "3. Learning spatial features from egocentric audio-visual correspondence" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 557, + 287, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 557, + 287, + 665 + ], + "spans": [ + { + "bbox": [ + 46, + 557, + 287, + 665 + ], + "type": "text", + "content": "The spatial sound perceived in an egocentric setup is shaped by the environment in which it is emitted and its source location relative to the camera-wearer. Based on this knowledge, we hypothesize that trying to solve the pretext task of audio-visual inpainting of binaural audio—that is, synthesizing missing audio segments by extracting related visual cues about the scene and the source location—can lead to learning useful audio-visual spatial correspondences. To validate our hypothesis, we propose a novel feature-learning task." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "content": "Formally, we consider an egocentric video clip " + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "inline_equation", + "content": "C = (V, A)" + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "inline_equation", + "content": "A" + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "content": " refer to the visual and binaural audio streams, respectively. See Fig. 2 left. The visual clip " + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "content": " comprises " + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "content": " frames, such that " + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "inline_equation", + "content": "V = \\{V_1, \\ldots, V_T\\}" + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "spans": [ + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": "We generate a set of visual tokens " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "\\hat{V}" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " by splitting " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " into " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " non-overlapping tubelets, such that " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "\\hat{V} = \\{\\hat{V}_1,\\dots ,\\hat{V}_P\\}" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "\\hat{V}_k" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " denotes the " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "k^{th}" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " tubelet consisting of a contiguous sequence of patches spanning all " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " frames. We represent the binaural audio " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "A" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " as two Mel-spectrograms [30], " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "A = \\{A^L,A^R\\}" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "A^L" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "A^R" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " are the spectrograms for the left and right channels, respectively. We create a set of audio tokens " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "\\hat{A}" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " by splitting " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "A" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " into " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "Q" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": " non-overlapping patches, such that " + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "inline_equation", + "content": "\\hat{A} = \\{\\hat{A}_1,\\dots ,\\hat{A}_Q\\}" + }, + { + "bbox": [ + 304, + 273, + 547, + 384 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "spans": [ + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": "Next, we mask a portion of the audio tokens in " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\hat{A}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": " and obtain complementary subsets of masked and unmasked tokens, " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\hat{A}^M" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\hat{A}^U" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": ", respectively, where " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\hat{A}^M = \\{\\ddot{A}_1,\\dots ,\\ddot{A}_S\\}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\hat{A}^U = \\{\\bar{A}_1,\\dots ,\\bar{A}_{Q - S}\\}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": " is the number of masked tokens. Given " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\{\\hat{V},\\hat{A}^{M},\\hat{A}^{U}\\}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": ", we aim to learn a self-supervised model " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\mathcal{F}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": " comprising an encoder " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": " and decoder " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": ", such that " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\mathcal{F} = \\mathcal{D}\\circ \\mathcal{E}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\mathcal{F}(\\hat{V},\\hat{A}^U) = \\tilde{A}^M" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\tilde{A}^M" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": " is an estimate of the masked audio tokens in " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\hat{A}^M" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": ". By training on this pretext task, our encoder " + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 304, + 385, + 547, + 533 + ], + "type": "text", + "content": " can learn rich audio-visual spatial correspondences that can be leveraged for multiple downstream tasks that require the synergy of vision and spatial audio, as we show in results." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "type": "text", + "content": "In our method (see Fig. 2), " + }, + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "type": "text", + "content": " (Sec. 3.1) is an audio-visual (AV) spatial correspondence encoder that learns an implicit representation of the spatial relationships between the visual and unmasked binaural audio tokens, while " + }, + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "type": "text", + "content": " (Sec. 3.2) is an audio-visual decoder for binaural audio inpainting that uses this implicit representation to synthesize the masked audio tokens. We also devise a simple yet novel masking protocol (Sec. 3.3) for our inpainting task, which mixes masking random audio tokens with masking a full audio channel, and helps the model learn stronger audio-visual spatial associations that facilitate the downstream social tasks (Sec. 3.5). We train " + }, + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{F}" + }, + { + "bbox": [ + 304, + 534, + 548, + 713 + ], + "type": "text", + "content": " to minimize the prediction error in the masked audio tokens (Sec. 3.4). Next, we describe our model design, audio masking protocol, training objective and network architecture, and downstream tasks." + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27060" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 279, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 279, + 85 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 279, + 85 + ], + "type": "text", + "content": "3.1. Audio-visual spatial correspondence encoder" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 90, + 288, + 198 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 90, + 288, + 198 + ], + "spans": [ + { + "bbox": [ + 46, + 90, + 288, + 198 + ], + "type": "text", + "content": "The audio-visual spatial correspondence encoder " + }, + { + "bbox": [ + 46, + 90, + 288, + 198 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 46, + 90, + 288, + 198 + ], + "type": "text", + "content": " (Fig. 2 center) extracts features from the visual and unmasked audio tokens " + }, + { + "bbox": [ + 46, + 90, + 288, + 198 + ], + "type": "inline_equation", + "content": "\\{\\hat{V},\\hat{A}^U\\}" + }, + { + "bbox": [ + 46, + 90, + 288, + 198 + ], + "type": "text", + "content": ". It begins by embedding the visual and audio tokens using separate transformer encoders [15] for individually capturing the spatio-temporal features in the two modalities. Next, it uses a shared transformer encoder to jointly encode the audio and visual features, and produces a multi-modal representation suitable for binaural audio inpainting. We describe the individual encoders next." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "spans": [ + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": "Video and audio encoders. We first encode the visual tokens " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "\\hat{V}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " using a linear layer to generate visual features " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": ", such that " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "v = \\{v_{1},\\dots,v_{P}\\}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": ". We encode the audio tokens " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "\\hat{A}^{U}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " with another linear layer to produce audio features " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": ", such that " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "a = \\{a_{1},\\dots,a_{Q - S}\\}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " is the number of masked tokens out of a total of " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "Q" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " audio tokens (cf. Sec. 3). For each visual feature " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "v_{j}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": ", we add a sinusoidal positional embedding " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "p_j^V" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " [67] to it, where " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "p_j^V" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " captures cues about the 3D position of the " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "j^{\\mathrm{th}}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " tubelet in the visual clip " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": ". For an audio feature " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "a_{i}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": ", we add a sinusoidal positional embedding " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "p_i^A" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " and a learnable channel embedding " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "c\\in \\{c_L,c_R\\}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " to it to convey information about the 2D location of the " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "i^{\\mathrm{th}}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " unmasked audio token in the spectrogram and also the audio channel to which it belongs. Next, we feed the transformed visual and audio features to separate transformer encoders, " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^V" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^A" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": ", respectively, and obtain visual features " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "e^V = \\{e_1^V,\\dots,e_P^V\\}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": " and audio features " + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "inline_equation", + "content": "e^A = \\{e_1^A,\\dots,e_{Q - S}^A\\}" + }, + { + "bbox": [ + 47, + 205, + 289, + 415 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "spans": [ + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": "Shared audio-visual encoder. Given the visual features " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "e^{V}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": " and audio features " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "e^{A}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": ", we concatenate them into " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "e^{AV}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": ", such that " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "e^{AV} = \\{e_1^V, \\dots, e_P^V, e_1^A, \\dots, e_{Q - S}^A\\}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": ", and re-add the sinusoidal positional embeddings " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "p^{V}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "p^{A}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": " to the features of the respective modalities in " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "e^{AV}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": ". Furthermore, unlike existing audio-visual masked auto-encoders [23, 24, 29], we add the channel embeddings " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": " to the audio features, and learnable modality embeddings " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "m \\in \\{m_A, m_V\\}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": " to all features in " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "e^{AV}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": " to help the model distinguish between the visual and audio modalities. Next, a shared audio-visual transformer " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^{AV}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": " encoder takes " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "e^{AV}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": " as input and outputs audio-visual features " + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "inline_equation", + "content": "f^{AV}" + }, + { + "bbox": [ + 46, + 422, + 289, + 581 + ], + "type": "text", + "content": ", which implicitly hold spatio-temporal information required for accurate inpainting of audio." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 587, + 288, + 613 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 587, + 288, + 613 + ], + "spans": [ + { + "bbox": [ + 47, + 587, + 288, + 613 + ], + "type": "text", + "content": "3.2. Audio-visual decoder for binaural audio inpainting" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "text", + "content": "Our audio-visual decoder " + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "text", + "content": " (Fig. 2 right) takes " + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "inline_equation", + "content": "f^{AV}" + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "text", + "content": " as input and attempts to synthesize the masked binaural audio tokens by leveraging spatio-temporal cues in " + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "inline_equation", + "content": "f^{AV}" + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "text", + "content": ". It first projects " + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "inline_equation", + "content": "f^{AV}" + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "text", + "content": " to a lower-dimensional feature set " + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "inline_equation", + "content": "g^{AV}" + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "text", + "content": ". It then appends a learnable embedding for the masked audio tokens to " + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "inline_equation", + "content": "g^{AV}" + }, + { + "bbox": [ + 46, + 616, + 288, + 715 + ], + "type": "text", + "content": " and passes it through a shared audio-visual transformer decoder [26]. Next, it feeds the audio feature outputs of the shared decoder to another transformer decoder" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 72, + 547, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 144 + ], + "type": "text", + "content": "and uses its outputs to predict an estimate of the masked binaural audio tokens. The decoders are lightweight compared to the encoders, ensuring that the encoders are primarily responsible for driving the inpainting task and producing good audio-visual features for strong downstream performance. We next describe each component of " + }, + { + "bbox": [ + 304, + 72, + 547, + 144 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 304, + 72, + 547, + 144 + ], + "type": "text", + "content": " in detail." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "spans": [ + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": "Shared audio-visual decoder. We first create a lower-dimensional projection " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "g^{AV}" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " of the audio-visual encodings " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "f^{AV}" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " by passing it through a linear layer, and append a learnable embedding " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " corresponding to each of the " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " masked audio tokens to " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "g^{AV}" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": ". Next, we add the positional embeddings " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "p^V" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "p^A" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": ", the audio channel embeddings " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": ", and the modality embeddings " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "g^{AV}" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": ", and feed it to a shallow transformer decoder " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "\\mathcal{D}^{AV}" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " that outputs an audio-visual feature set " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "h^{AV}" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": ". We then take the audio features " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "h^A" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "inline_equation", + "content": "h^{AV}" + }, + { + "bbox": [ + 304, + 155, + 548, + 276 + ], + "type": "text", + "content": " and pass them to the audio decoder for further processing." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "spans": [ + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "text", + "content": "Audio decoder. The audio decoder " + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "inline_equation", + "content": "\\mathcal{D}^A" + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "text", + "content": " re-adds the positional embeddings " + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "inline_equation", + "content": "p^A" + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "text", + "content": " and channel embeddings " + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "inline_equation", + "content": "g^A" + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "text", + "content": ", and feeds it to a transformer decoder, which outputs audio features " + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "inline_equation", + "content": "d^A" + }, + { + "bbox": [ + 304, + 285, + 547, + 334 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "spans": [ + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "text", + "content": "Prediction of masked audio tokens. Finally, we take the subset of all audio features " + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "inline_equation", + "content": "d^{A}" + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "text", + "content": " corresponding to the masked audio tokens " + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "inline_equation", + "content": "\\hat{A}^{M}" + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "text", + "content": ", upsample them by passing through a linear layer, and reshape them to obtain an estimate " + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "inline_equation", + "content": "\\tilde{A}^{M}" + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "text", + "content": " of the masked tokens " + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "inline_equation", + "content": "\\hat{A}^{M}" + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "text", + "content": ", such that " + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "inline_equation", + "content": "\\tilde{A}^{M} = \\{\\tilde{A}_{1},\\dots,\\tilde{A}_{S}\\}" + }, + { + "bbox": [ + 304, + 345, + 547, + 407 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 413, + 400, + 426 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 413, + 400, + 426 + ], + "spans": [ + { + "bbox": [ + 306, + 413, + 400, + 426 + ], + "type": "text", + "content": "3.3. Audio masking" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "spans": [ + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "text", + "content": "Different from other masked auto-encoding counterparts [23, 24, 29], we design an audio masking protocol that is customized to help our model better extract spatial audio-visual cues during self-supervised pretraining. In particular, we mix the strategy of randomly masking a full audio channel with that of randomly masking audio tokens using a hyperparameter " + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "inline_equation", + "content": "r" + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "text", + "content": " during training, where " + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "inline_equation", + "content": "r" + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "text", + "content": " represents the probability with which we randomly drop a full audio channel and " + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "inline_equation", + "content": "r" + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "text", + "content": " is sampled from a uniform distribution " + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "inline_equation", + "content": "U(0,1)" + }, + { + "bbox": [ + 304, + 431, + 547, + 540 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 307, + 547, + 543, + 574 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 307, + 547, + 543, + 574 + ], + "spans": [ + { + "bbox": [ + 307, + 547, + 543, + 574 + ], + "type": "interline_equation", + "content": "\\operatorname {m a s k} (\\hat {A}) = \\left\\{ \\begin{array}{l l} \\hat {A} ^ {M} = A ^ {L} \\text {o r} \\hat {A} ^ {M} = A ^ {R} & \\text {i f} x \\sim U (0, 1) \\leq r \\\\ \\hat {A} ^ {M} \\subseteq \\{\\hat {A} _ {1}, \\dots , \\hat {A} _ {Q} \\} & \\text {o t h e r w i s e} \\end{array} \\right.", + "image_path": "40d45d848d95d90dbbc5faa75a9fcb33305e8ff05af4e6dc1bc2e62343632187.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 582, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 548, + 714 + ], + "type": "text", + "content": "On the one hand, token masking could lead to tokens from the same location in the two audio channels being present among the unmasked tokens, providing additional spatial cues to the model and resulting in a simpler, stabler optimization objective for the inpainting task. In addition, since token masking involves masking a short span in both frequency and time domains, the model can rely more on local audio-visual cues and tolerate the global noise in both the visual and audio streams due to a camera-wearer's motion. On the other hand, channel masking forces the model to solve a more challenging binauralization task solely on the basis of vision," + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "text", + "content": "27061" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 55, + 69, + 279, + 277 + ], + "blocks": [ + { + "bbox": [ + 55, + 69, + 279, + 277 + ], + "lines": [ + { + "bbox": [ + 55, + 69, + 279, + 277 + ], + "spans": [ + { + "bbox": [ + 55, + 69, + 279, + 277 + ], + "type": "image", + "image_path": "560fa7a786b2779004fec471ae9573bf9d12887747edff62396c7d09d2b46f31.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 281, + 289, + 326 + ], + "lines": [ + { + "bbox": [ + 46, + 281, + 289, + 326 + ], + "spans": [ + { + "bbox": [ + 46, + 281, + 289, + 326 + ], + "type": "text", + "content": "Figure 3. Masked targets and predictions shown alongside the unmasked inputs for (a) token masking and (b) channel masking. Our predictions accurately capture the global patterns in the target spectrograms, which depend on the scene's spatial properties." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 343, + 287, + 416 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 343, + 287, + 416 + ], + "spans": [ + { + "bbox": [ + 46, + 343, + 287, + 416 + ], + "type": "text", + "content": "which could help it learn even stronger spatial features. This encourages the model to reason about the camera motion at a more global scale (over the entire clip span). Towards achieving high performance on the downstream tasks, we aim to strike a fine balance between these two strategies and combine the benefits of reasoning at both temporal scales." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 422, + 277, + 436 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 422, + 277, + 436 + ], + "spans": [ + { + "bbox": [ + 47, + 422, + 277, + 436 + ], + "type": "text", + "content": "3.4. Training objective and network architecture" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 441, + 289, + 477 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 441, + 289, + 477 + ], + "spans": [ + { + "bbox": [ + 46, + 441, + 289, + 477 + ], + "type": "text", + "content": "We train our model to minimize the error in predicting the masked audio tokens. In particular, we compute the mean-squared error " + }, + { + "bbox": [ + 46, + 441, + 289, + 477 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 46, + 441, + 289, + 477 + ], + "type": "text", + "content": " averaged over all masked audio tokens:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 111, + 485, + 288, + 514 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 111, + 485, + 288, + 514 + ], + "spans": [ + { + "bbox": [ + 111, + 485, + 288, + 514 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\frac {1}{S} \\sum_ {i = 1 \\dots S} | | \\ddot {A} _ {i} - \\tilde {a} _ {i} | | _ {2} ^ {2}. \\tag {1}", + "image_path": "d1f29df3100abed8a94b488a4ea18806c5d41f3814e067e3894da3cc2ba6ad08.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 521, + 287, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 521, + 287, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 521, + 287, + 616 + ], + "type": "text", + "content": "We visualize our predicted audio tokens in Fig. 3 for the cases of token (Fig. 3a) and channel (Fig 3b) masking. Our model is able to accurately predict the masked targets and capture the global patterns in the spectrograms, which are often determined by the spatial audio-visual cues captured from of the scene (visual input not shown in Fig 3 for brevity), thereby further emphasizing our model's ability to learn useful spatial features." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": "Our uni-modal encoders, " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^A" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^V" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": ", have 8 layers, while the audio-visual encoder " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^{AV}" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": " has 6 layers. All encoders have 12 attention heads and use 768-dimensional hidden embeddings. The audio-visual decoder " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{D}^{AV}" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": " and audio-only decoder " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{D}^A" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": " have 1 and 3 layers, respectively. Both decoders have 6 attention heads and use 384-dimensional hidden embeddings. To pretrain our model, we set the relative frequency of dropping an audio channel in our masking" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "content": "protocol for training to " + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "inline_equation", + "content": "r = 20\\%" + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "content": " based on disjoint validation data (see Supp.). We train our model for 200 epochs using the AdamW [37] optimizer with a weight decay of " + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "inline_equation", + "content": "10^{-5}" + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "content": ", and a learning rate scheduler that reaches a peak learning rate of " + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "inline_equation", + "content": "2 \\times 10^{-4}" + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "content": " over 10 warmup epochs, and then decays it through half-cycle cosine annealing [36]. For data augmentation, we perform random flipping of audio channels and video clips along the frame width. For downstream evaluation, we fuse the features from the audio-visual encoder with the backbones for downstream tasks, and finetune them. See Supp. for further details on architecture and training." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 210, + 415, + 221 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 210, + 415, + 221 + ], + "spans": [ + { + "bbox": [ + 306, + 210, + 415, + 221 + ], + "type": "text", + "content": "3.5. Downstream tasks" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 228, + 547, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 228, + 547, + 396 + ], + "spans": [ + { + "bbox": [ + 304, + 228, + 547, + 396 + ], + "type": "text", + "content": "We explore two downstream tasks with our pretrained features: active speaker detection and spatial audio denoising. Active speaker detection (ASD) involves matching an audio clip with an appropriate face track from the corresponding video clip, i.e., answering \"which person is speaking now?\". While current SOTA methods [42, 65] rely on semantic similarities between monaural audio and vision to solve this task, we hypothesize that leveraging spatial audio can additionally reveal the sound source location in the video. In spatial audio denoising, the goal is to separate the target audio from distractors. In particular, we aim to remove the audio from sources extraneous to the conversation—out-of-view sounds from other parts of the scene. We detail the backbone models for each in the next section." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 405, + 388, + 418 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 405, + 388, + 418 + ], + "spans": [ + { + "bbox": [ + 306, + 405, + 388, + 418 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 422, + 547, + 469 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 422, + 547, + 469 + ], + "spans": [ + { + "bbox": [ + 304, + 422, + 547, + 469 + ], + "type": "text", + "content": "We validate our learned representations on two downstream tasks and two datasets, and we compare with prior models for spatial audio-visual feature learning [18, 23, 60, 70], as well as various baselines and ablations." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 478, + 547, + 634 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 478, + 547, + 634 + ], + "spans": [ + { + "bbox": [ + 304, + 478, + 547, + 634 + ], + "type": "text", + "content": "Datasets. We train and evaluate our model on two challenging egocentric datasets containing video and binaural audio of people having conversations: 1) EgoCom [49], and 2) EasyCom [11], detailed in Supp. To our knowledge, these are the only two publicly available datasets offering binaural audio with conversations in video, whether exocentric or egocentric. In particular, Ego4D [25] and EPIC [9] do not comprise social scenarios and are not applicable. Whereas EasyCom primarily has participants sitting around a table and talking, EgoCom has videos of participants moving around a room, turning their face and body, standing up, etc. They test our method's robustness in diverse scenarios of varying difficulty." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 639, + 443, + 652 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 639, + 443, + 652 + ], + "spans": [ + { + "bbox": [ + 306, + 639, + 443, + 652 + ], + "type": "text", + "content": "4.1. Active speaker detection" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 658, + 517, + 670 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 658, + 517, + 670 + ], + "spans": [ + { + "bbox": [ + 306, + 658, + 517, + 670 + ], + "type": "text", + "content": "We first evaluate on active speaker detection (ASD)." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "type": "text", + "content": "Backbone models. We consider two SOTA ASD models as the backbones for leveraging our pretrained representations: 1) TalkNet [65], and 2) SPELL [42]. TalkNet encodes" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27062" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 168 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 168 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 168 + ], + "type": "text", + "content": "a face track and an audio clip using attention for learning intra- and inter-modal semantic and temporal features. Next, it fuses these features and performs binary classification to predict if the face in the track is active. SPELL extracts audiovisual features for each face in a clip using ResNets [3], and learns long and short-term semantic relations among them using a graph neural network. Finally, it performs binary classification of these features for predicting active speakers." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 181, + 289, + 301 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 181, + 289, + 301 + ], + "spans": [ + { + "bbox": [ + 46, + 181, + 289, + 301 + ], + "type": "text", + "content": "Pretrained feature fusion. To fuse our pretrained features with the ASD backbones, we use a transformer decoder that cross-attends to the feature outputs of the shared encoder " + }, + { + "bbox": [ + 46, + 181, + 289, + 301 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^{AV}" + }, + { + "bbox": [ + 46, + 181, + 289, + 301 + ], + "type": "text", + "content": " using sinusoidal embedding as queries, with each embedding representing a clip frame index. Next, we append the decoder outputs to the cross-attention outputs in TalkNet, or the audio-visual encoder outputs in SPELL, frame by frame. In essence, while the original audio-visual encoders leverage semantic correlations between vision and audio, our features provide strong complementary spatial cues." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 318, + 287, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 318, + 287, + 365 + ], + "spans": [ + { + "bbox": [ + 47, + 318, + 287, + 365 + ], + "type": "text", + "content": "Baselines. For both TalkNet and SPELL, we compare against multiple baselines comprising both the unmodified backbone and improved versions of it, in addition to some naive methods:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 48, + 366, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 48, + 366, + 287, + 390 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 366, + 287, + 390 + ], + "spans": [ + { + "bbox": [ + 48, + 366, + 287, + 390 + ], + "type": "text", + "content": "- All-active: a naive model that predicts that all visible faces are always active" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 48, + 391, + 287, + 414 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 391, + 287, + 414 + ], + "spans": [ + { + "bbox": [ + 48, + 391, + 287, + 414 + ], + "type": "text", + "content": "- All-inactive: a naive model that predicts that all visible faces are always inactive" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 48, + 415, + 287, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 415, + 287, + 437 + ], + "spans": [ + { + "bbox": [ + 48, + 415, + 287, + 437 + ], + "type": "text", + "content": "- Random: a naive model that emits a random ASD confidence score for every visible speaker" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 48, + 438, + 287, + 462 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 438, + 287, + 462 + ], + "spans": [ + { + "bbox": [ + 48, + 438, + 287, + 462 + ], + "type": "text", + "content": "- Backbone w/o audio: a vision-only version of the backbone with no audio input" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 48, + 463, + 287, + 485 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 463, + 287, + 485 + ], + "spans": [ + { + "bbox": [ + 48, + 463, + 287, + 485 + ], + "type": "text", + "content": "- Backbone: the originally-proposed backbone that processes only faces and monaural audio" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 48, + 486, + 288, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 486, + 288, + 533 + ], + "spans": [ + { + "bbox": [ + 48, + 486, + 288, + 533 + ], + "type": "text", + "content": "- Backbone-binaural: an improved backbone using binaural audio instead of monaural, alongside positional encodings for the faces, indicative of their relative position and depth, for better matching the face to the audio" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 48, + 534, + 287, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 534, + 287, + 569 + ], + "spans": [ + { + "bbox": [ + 48, + 534, + 287, + 569 + ], + "type": "text", + "content": "- Backbone-binaural w/ scene: a further improvement over the backbone, where we also provide the scene images (uncropped video frames) to backbone-binaural" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 48, + 570, + 288, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 570, + 288, + 617 + ], + "spans": [ + { + "bbox": [ + 48, + 570, + 288, + 617 + ], + "type": "text", + "content": "- Backbone w/ TLR [70]: fuses features from the SOTA Telling Left from Right (TLR) [70], which learns audio-visual spatial correspondences by predicting the spatial alignment between vision and binaural audio" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 48, + 618, + 287, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 618, + 287, + 653 + ], + "spans": [ + { + "bbox": [ + 48, + 618, + 287, + 653 + ], + "type": "text", + "content": "- Backbone w/ 2.5D-VS [18]: fuses features from the SOTA audio-visual binauralization model, 2.5D Visual Sounds (2.5D-VS) [18]" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 48, + 654, + 288, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 654, + 288, + 677 + ], + "spans": [ + { + "bbox": [ + 48, + 654, + 288, + 677 + ], + "type": "text", + "content": "- Backbone w/ 2.5D-VS [18]++: fuses features from 2.5D-VS with a transformer architecture" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 48, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 48, + 677, + 287, + 713 + ], + "type": "text", + "content": "- Backbone w/ SSR [60]++: fuses features from the SOTA self-supervised audio-visual stereo sound ranking (SSR) [60] model with a transformer architecture" + } + ] + } + ], + "index": 13 + } + ], + "sub_type": "text" + }, + { + "type": "table", + "bbox": [ + 309, + 70, + 545, + 273 + ], + "blocks": [ + { + "bbox": [ + 309, + 70, + 545, + 273 + ], + "lines": [ + { + "bbox": [ + 309, + 70, + 545, + 273 + ], + "spans": [ + { + "bbox": [ + 309, + 70, + 545, + 273 + ], + "type": "table", + "html": "
ModelTalkNet [65]SPELL [42]
EgoComEasyComEgoComEasyCom
No pretraining
All-active32.930.132.930.1
All-inactive32.930.132.930.1
Random30.828.030.828.0
B w/o audio41.550.160.463.2
B52.845.760.959.0
B-binaural60.059.663.160.3
B-binaural w/ scene60.866.961.261.4
Alternate pretraining methods
B w/ TLR [70]47.959.361.361.7
B w/ 2.5D-VS [18]57.763.761.259.7
B w/ 2.5D-VS [18]++63.468.365.164.5
B w/ SSR [60]++61.270.661.267.4
B w/ AV-MAE [23]61.161.364.465.2
Ours63.971.865.670.2
Ours w/o pretrain62.762.9——
Ours w/ pretrain monaural61.069.463.969.0
", + "image_path": "cd3aa584d904d351dc2640b134bafe8edabf38295da260b453d1a18f91e5e861.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "table_body" + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 281, + 547, + 335 + ], + "lines": [ + { + "bbox": [ + 305, + 281, + 547, + 335 + ], + "spans": [ + { + "bbox": [ + 305, + 281, + 547, + 335 + ], + "type": "text", + "content": "Table 1. Mean average precision (\\%) for active speaker detection with TalkNet [65] and SPELL [42] backbones on both datasets. Higher is better. 'B' refers to backbone. Note that SPELL requires storing pretrained features in the graph nodes; therefore it does not allow training from scratch." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 306, + 352, + 545, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 352, + 545, + 376 + ], + "spans": [ + { + "bbox": [ + 306, + 352, + 545, + 376 + ], + "type": "text", + "content": "- Backbone w/ AV-MAE [23]: fuses features from the SOTA modality-inpainting AV-MAE [23] model" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 376, + 547, + 484 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 376, + 547, + 484 + ], + "spans": [ + { + "bbox": [ + 305, + 376, + 547, + 484 + ], + "type": "text", + "content": "For all alternate feature-learning methods [18, 23, 60, 70], we pretrain them on our datasets and use our feature fusion method. Thus, any advantages in performance of our approach over these SOTA representations will be attributable to our modeling ideas. Importantly, the 2.5D-VS [18]++, SSR [60]++, and AV-MAE [23] features all rely on transformers and have similar model capacity as ours; see Supp. for a detailed analysis on model capacity. We use the standard mean average precision (mAP) metric." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 497, + 547, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 497, + 547, + 652 + ], + "spans": [ + { + "bbox": [ + 304, + 497, + 547, + 652 + ], + "type": "text", + "content": "Results. Table 1 (top) reports our ASD results on both val and test splits. The three naive baselines perform poorly on both EgoCom [49] and EasyCom [11], emphasizing the difficulty of the task. For both TalkNet [65] and SPELL [42], the unchanged backbone model generally performs better than the model without audio, showing that both vision and audio are required. Upgrading from monaural to binaural audio further boosts performance, as the model can now leverage both spatial and semantic information. Additionally using scene features lets the backbone explicitly match the scene area around the inferred source location with the face, and further improves ASD, especially for EgoCom, where the background scene changes more often." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "content": "Among alternate feature learning methods, 2.5D-VS [18]++, SSR [60]++ and AV-MAE [23] consistently outperform TLR [70] and 2.5D-VS [17], and also the basic and enhanced backbones, showing that self-attention and higher model capacity enhance feature quality. Besides, 2.5D-VS" + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27063" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 73, + 70, + 261, + 242 + ], + "blocks": [ + { + "bbox": [ + 73, + 70, + 261, + 242 + ], + "lines": [ + { + "bbox": [ + 73, + 70, + 261, + 242 + ], + "spans": [ + { + "bbox": [ + 73, + 70, + 261, + 242 + ], + "type": "table", + "html": "
ModelSI-SDRi ↑STFT ↓
No pretraining
B w/o vision1.617.36
B1.467.27
B w/ ImageNet features1.486.95
Alternate pretraining methods
B w/ TLR [70]1.417.79
B w/ 2.5D-VS [18]1.677.34
B w/ 2.5D-VS [18]++2.116.60
B w/ SSR [60] ++2.046.70
B w/ AV-MAE [23]2.076.62
Ours2.206.51
B w/o pretrain1.907.25
B w/ pretrain monaural audio2.006.75
", + "image_path": "aa7401c151b083511f173552cdbb544baac9302bbdefd27b320540a854c62b88.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 251, + 287, + 283 + ], + "lines": [ + { + "bbox": [ + 46, + 251, + 287, + 283 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 287, + 283 + ], + "type": "text", + "content": "Table 2. Audio denoising with U-Net [70] backbone (referred to as 'B' in table) for 0 dB noise (maximum). See Supp. for varying noise levels. All STFT distance measures use base " + }, + { + "bbox": [ + 46, + 251, + 287, + 283 + ], + "type": "inline_equation", + "content": "10^{-3}" + }, + { + "bbox": [ + 46, + 251, + 287, + 283 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 297, + 287, + 333 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 297, + 287, + 333 + ], + "spans": [ + { + "bbox": [ + 46, + 297, + 287, + 333 + ], + "type": "text", + "content": "outperforms TLR, and 2.5D-VS++ and AV-MAE generally outperform SSR++, indicating that objectives that promote reasoning directly at the spectrogram level improve results." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 334, + 287, + 489 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 334, + 287, + 489 + ], + "spans": [ + { + "bbox": [ + 46, + 334, + 287, + 489 + ], + "type": "text", + "content": "Our model substantially outperforms all baselines—including the SOTA AV representation learning methods—for both backbones (TalkNet and SPELL) on both datasets. This shows that our method learns stronger spatial features that are both backbone- and dataset-agnostic. In contrast, methods developed for exocentric settings with more stationary cameras (such as TLR and 2.5D-VS) rely more on the global visual context and seem to struggle in our setting, where the camera moves frequently and the sound source leaves the field of view. Finally, our improvement over 2.5D-VS++, SSR++ and AV-MAE, which use similar encoders as ours, disentangles the benefits of our masking strategy and model design from those of the model capacity." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 497, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 497, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 497, + 287, + 593 + ], + "type": "text", + "content": "Model analysis. Table 1 (bottom) shows ablations of our method. Upon training for ASD from scratch, we see a sharp drop in performance, showing that our advantage is not solely due to our model design, but also our self-supervised pretraining stage. Performance also declines upon pretraining with monaural audio instead of binaural, showing that our model goes beyond learning semantic features and successfully captures spatial features useful for ASD." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 600, + 178, + 613 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 600, + 178, + 613 + ], + "spans": [ + { + "bbox": [ + 47, + 600, + 178, + 613 + ], + "type": "text", + "content": "4.2. Spatial audio denoising" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 618, + 287, + 667 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 287, + 667 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 287, + 667 + ], + "type": "text", + "content": "Next we evaluate spatial audio denoising on EgoCom.2 To instantiate this task, we add the binaural audio of a target clip with the downscaled binaural audio from another randomly chosen clip, where the downscaling factor depends on the" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "spans": [ + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "type": "text", + "content": "desired noise level. The goal is to extract the target sound from the mixture. We evaluate three noise levels, expressed using the signal-to-noise (SNR) ratio: 1) " + }, + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "type": "inline_equation", + "content": "0\\mathrm{dB}" + }, + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "type": "text", + "content": ", 2) " + }, + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "type": "inline_equation", + "content": "2.5\\mathrm{dB}" + }, + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "type": "text", + "content": ", and 3) " + }, + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "type": "inline_equation", + "content": "5\\mathrm{dB}" + }, + { + "bbox": [ + 309, + 71, + 548, + 143 + ], + "type": "text", + "content": ". The different noise levels test our model's robustness to varying levels of task difficulty—the lower the SNR value, the higher the noise and difficulty." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 156, + 547, + 251 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 156, + 547, + 251 + ], + "spans": [ + { + "bbox": [ + 304, + 156, + 547, + 251 + ], + "type": "text", + "content": "Backbone model. We adopt the commonly used U-Net [57] for audio-visual source separation [18, 70] as the backbone, which produces a binaural ratio mask for the target audio (see Supp. for details). We multiply the predicted ratio mask with the mixed magnitude spectrogram to get the predicted magnitude spectrogram, then convert it to a waveform using inverse short-time Fourier transform with the mixed audio phase." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 263, + 547, + 360 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 263, + 547, + 360 + ], + "spans": [ + { + "bbox": [ + 304, + 263, + 547, + 360 + ], + "type": "text", + "content": "Pretrained feature fusion. To use our features for denoising, we reshape the visual features and unmasked audio features produced by our audio-visual encoder " + }, + { + "bbox": [ + 304, + 263, + 547, + 360 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^{AV}" + }, + { + "bbox": [ + 304, + 263, + 547, + 360 + ], + "type": "text", + "content": " to form multi-channel 2D maps, where the features align with their corresponding tokens vis-a-vis the raster order. Next, we pass the feature maps to separate convolutional layers, concatenate the outputs channel-wise, and use them to replace the visual features at the U-Net [70] bottleneck." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 371, + 545, + 394 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 371, + 545, + 394 + ], + "spans": [ + { + "bbox": [ + 305, + 371, + 545, + 394 + ], + "type": "text", + "content": "Baselines. We compare against the following baselines and existing methods:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 396, + 547, + 550 + ], + "type": "list", + "angle": 0, + "index": 19, + "blocks": [ + { + "bbox": [ + 306, + 396, + 541, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 396, + 541, + 407 + ], + "spans": [ + { + "bbox": [ + 306, + 396, + 541, + 407 + ], + "type": "text", + "content": "- U-Net w/o vision: an audio-only blind denoising model" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 407, + 529, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 407, + 529, + 418 + ], + "spans": [ + { + "bbox": [ + 306, + 407, + 529, + 418 + ], + "type": "text", + "content": "- U-Net: the original backbone without any alterations" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 419, + 547, + 442 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 419, + 547, + 442 + ], + "spans": [ + { + "bbox": [ + 306, + 419, + 547, + 442 + ], + "type": "text", + "content": "- U-Net w/ ImageNet: pretrains the visual encoder on ImageNet [10]" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 443, + 521, + 455 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 443, + 521, + 455 + ], + "spans": [ + { + "bbox": [ + 306, + 443, + 521, + 455 + ], + "type": "text", + "content": "- U-Net w/ TLR [70]: fuses features from TLR [70]" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 456, + 545, + 478 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 456, + 545, + 478 + ], + "spans": [ + { + "bbox": [ + 306, + 456, + 545, + 478 + ], + "type": "text", + "content": "- U-Net w/ 2.5D-VS [18]: fuses pretrained features from 2.5D-VS [18]" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 479, + 545, + 502 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 479, + 545, + 502 + ], + "spans": [ + { + "bbox": [ + 306, + 479, + 545, + 502 + ], + "type": "text", + "content": "- U-Net w/ 2.5D-VS [18]++: fuses features from the transformer-based version of 2.5D-VS" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 502, + 545, + 526 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 502, + 545, + 526 + ], + "spans": [ + { + "bbox": [ + 306, + 502, + 545, + 526 + ], + "type": "text", + "content": "- U-Net w/ SSR [60]++: fuses features from the transformer-based version of SSR [60]" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 526, + 545, + 550 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 526, + 545, + 550 + ], + "spans": [ + { + "bbox": [ + 306, + 526, + 545, + 550 + ], + "type": "text", + "content": "- U-Net w/ AV-MAE [60]: fuses features from the modality inpainting AV-MAE [23] model" + } + ] + } + ], + "index": 18 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 304, + 566, + 547, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 566, + 547, + 639 + ], + "spans": [ + { + "bbox": [ + 304, + 566, + 547, + 639 + ], + "type": "text", + "content": "Evaluation metric. For evaluating our denoising quality, we use standard metrics: 1) STFT distance (the L2 error between the predicted and ground-truth spectrograms) expressed using base " + }, + { + "bbox": [ + 304, + 566, + 547, + 639 + ], + "type": "inline_equation", + "content": "10^{-3}" + }, + { + "bbox": [ + 304, + 566, + 547, + 639 + ], + "type": "text", + "content": " and 2) SI-SDRi: the improvement in SI-SDR [58], a scale-invariant estimate of the distortion in the audio, over using the mixed audio as the prediction." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "content": "Results. Table 2 (top) shows spatial audio denoising results on the challenging EgoCom dataset with " + }, + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "inline_equation", + "content": "0\\mathrm{dB}" + }, + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "content": ", the most difficult noise level. See Supp. for similar results with the other noise levels. The unchanged U-Net backbone lowers the STFT distance compared to the version that lacks vision," + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 44, + 673, + 285, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 44, + 673, + 285, + 713 + ], + "spans": [ + { + "bbox": [ + 44, + 673, + 285, + 713 + ], + "type": "text", + "content": "2For EasyCom, the task setup is ill-posed for all models because mixing audio from a different EasyCom clip as noise leads to spatially overlapping sound sources, since all clips in the dataset are recorded at the same physical location (people sitting around the same table in the same room)." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "27064" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 70, + 124, + 183 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 124, + 183 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 124, + 183 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 124, + 183 + ], + "type": "image", + "image_path": "bec3ca3985d84fe6869e1caf35981a218707ad45ab48b712131f1d9c54442ef9.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 192, + 287, + 258 + ], + "lines": [ + { + "bbox": [ + 47, + 192, + 287, + 258 + ], + "spans": [ + { + "bbox": [ + 47, + 192, + 287, + 258 + ], + "type": "text", + "content": "Figure 4. Heat maps showing the image areas our model's AV encoder attends to, placed alongside the images. Brighter yellow means higher attention score. Our model attends to image regions (e.g. faces of speakers, sound-reflecting flat regions like floor and table, etc.) that strongly determine the spatial properties of the audio, including direct sources of sound (marked in red)." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 129, + 70, + 206, + 183 + ], + "blocks": [ + { + "bbox": [ + 129, + 70, + 206, + 183 + ], + "lines": [ + { + "bbox": [ + 129, + 70, + 206, + 183 + ], + "spans": [ + { + "bbox": [ + 129, + 70, + 206, + 183 + ], + "type": "image", + "image_path": "3ea40335a68db5a0dfb68890877ffae04894d316118d66dc692446d46fca5c33.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 210, + 70, + 287, + 183 + ], + "blocks": [ + { + "bbox": [ + 210, + 70, + 287, + 183 + ], + "lines": [ + { + "bbox": [ + 210, + 70, + 287, + 183 + ], + "spans": [ + { + "bbox": [ + 210, + 70, + 287, + 183 + ], + "type": "image", + "image_path": "a77ec49d953a652c870f6e117add878ebe418e9c4637a2d7ec7d47f6c2f8a41f.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 271, + 287, + 319 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 271, + 287, + 319 + ], + "spans": [ + { + "bbox": [ + 47, + 271, + 287, + 319 + ], + "type": "text", + "content": "showing that like ASD, vision is crucial for better denoising. Using pretrained features of 2.5D-VS [18] " + }, + { + "bbox": [ + 47, + 271, + 287, + 319 + ], + "type": "inline_equation", + "content": "(++)" + }, + { + "bbox": [ + 47, + 271, + 287, + 319 + ], + "type": "text", + "content": ", SSR " + }, + { + "bbox": [ + 47, + 271, + 287, + 319 + ], + "type": "inline_equation", + "content": "[60]++" + }, + { + "bbox": [ + 47, + 271, + 287, + 319 + ], + "type": "text", + "content": " or AV-MAE [23] further improves performance, showing that learning spatial audio-visual features aids denoising." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 319, + 290, + 439 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 319, + 290, + 439 + ], + "spans": [ + { + "bbox": [ + 46, + 319, + 290, + 439 + ], + "type": "text", + "content": "Our method outperforms all baselines " + }, + { + "bbox": [ + 46, + 319, + 290, + 439 + ], + "type": "inline_equation", + "content": "(p \\leq 0.05)" + }, + { + "bbox": [ + 46, + 319, + 290, + 439 + ], + "type": "text", + "content": " across both metrics. While the improvement over the baselines that do not use self-supervised pretraining emphasizes the utility of learning spatial audio-visual relationships through self-supervision, the gain over other pretraining methods underlines the strengths of our self-supervised method design—which are consistently realized for both ASD and denoising. Further, our performance margins are larger for higher noise levels (0 and " + }, + { + "bbox": [ + 46, + 319, + 290, + 439 + ], + "type": "inline_equation", + "content": "2.5\\mathrm{dB}" + }, + { + "bbox": [ + 46, + 319, + 290, + 439 + ], + "type": "text", + "content": "), indicating that our features play a bigger role in the more difficult denoising settings." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 448, + 287, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 448, + 287, + 567 + ], + "spans": [ + { + "bbox": [ + 46, + 448, + 287, + 567 + ], + "type": "text", + "content": "Model analysis. In Table 2 (bottom), we ablate our pretraining method. Similar to ASD, training from scratch on the denoising task hurts performance. This disentangles the impact of our pretext task design from the model architecture and shows that our pretraining stage helps the backbone with learning better audio-visual features, leading to superior denoising quality. Furthermore, pretraining with monaural audio also degrades performance, re-emphasizing that our method is not restricted to learning semantic features—in contrast to prior work [23, 24, 29]." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 567, + 287, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 567, + 287, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 567, + 287, + 604 + ], + "type": "text", + "content": "See Supp. for analysis of the effect of alternate masking choices, multi-level positional embeddings, task-specific backbones, and our finetuning strategy on performance." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 610, + 162, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 610, + 162, + 624 + ], + "spans": [ + { + "bbox": [ + 47, + 610, + 162, + 624 + ], + "type": "text", + "content": "4.3. Qualitative analysis" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "content": "In Fig. 4, we analyze the visual attention maps of our shared encoder " + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{E}^{AV}" + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "content": ". Note that the regions of high attention are not only limited to the direct sound sources (e.g., regions in and around faces of active speakers across examples), but also include large sound-reflecting objects (e.g., the flat surface of the table on the left; the walls on the left and in the middle; the floor on the right, etc.) that determine how sound" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 307, + 70, + 432, + 164 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 432, + 164 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 432, + 164 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 432, + 164 + ], + "type": "image", + "image_path": "c7b491178e6a561eed8fdfcfc80dae7fafcf330d977ed5fe54c5016971213362.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 166, + 556, + 186 + ], + "lines": [ + { + "bbox": [ + 306, + 166, + 556, + 186 + ], + "spans": [ + { + "bbox": [ + 306, + 166, + 556, + 186 + ], + "type": "text", + "content": "(a) Our model succeeds on ASD even with fast camera motion (left; note image blur), multiple active speakers (right) and partially visible faces (left and right)" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 433, + 70, + 557, + 164 + ], + "blocks": [ + { + "bbox": [ + 433, + 70, + 557, + 164 + ], + "lines": [ + { + "bbox": [ + 433, + 70, + 557, + 164 + ], + "spans": [ + { + "bbox": [ + 433, + 70, + 557, + 164 + ], + "type": "image", + "image_path": "95808edb9b9892bc8614815e08a6ca216213b1fba5202616cff6bc6d0f2548ce.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 307, + 189, + 390, + 258 + ], + "blocks": [ + { + "bbox": [ + 307, + 189, + 390, + 258 + ], + "lines": [ + { + "bbox": [ + 307, + 189, + 390, + 258 + ], + "spans": [ + { + "bbox": [ + 307, + 189, + 390, + 258 + ], + "type": "image", + "image_path": "efaafdad1430c6a55fbc81f79c13dd63585017084c515b3191e910f3dd47141c.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 261, + 556, + 281 + ], + "lines": [ + { + "bbox": [ + 306, + 261, + 556, + 281 + ], + "spans": [ + { + "bbox": [ + 306, + 261, + 556, + 281 + ], + "type": "text", + "content": "(b) Our model denoises accurately—note the noise patches in mixed audio above points " + }, + { + "bbox": [ + 306, + 261, + 556, + 281 + ], + "type": "inline_equation", + "content": "p_1" + }, + { + "bbox": [ + 306, + 261, + 556, + 281 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 261, + 556, + 281 + ], + "type": "inline_equation", + "content": "p_2" + }, + { + "bbox": [ + 306, + 261, + 556, + 281 + ], + "type": "text", + "content": ", which are successfully removed in our prediction." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 391, + 189, + 473, + 258 + ], + "blocks": [ + { + "bbox": [ + 391, + 189, + 473, + 258 + ], + "lines": [ + { + "bbox": [ + 391, + 189, + 473, + 258 + ], + "spans": [ + { + "bbox": [ + 391, + 189, + 473, + 258 + ], + "type": "image", + "image_path": "f9976d11abc79e9153f5c311848e4955da96af1d9bae7104d6e6a080632cb340.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 325, + 287, + 526, + 299 + ], + "lines": [ + { + "bbox": [ + 325, + 287, + 526, + 299 + ], + "spans": [ + { + "bbox": [ + 325, + 287, + 526, + 299 + ], + "type": "text", + "content": "Figure 5. Success cases for ASD (a) and denoising (b)" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 474, + 189, + 557, + 258 + ], + "blocks": [ + { + "bbox": [ + 474, + 189, + 557, + 258 + ], + "lines": [ + { + "bbox": [ + 474, + 189, + 557, + 258 + ], + "spans": [ + { + "bbox": [ + 474, + 189, + 557, + 258 + ], + "type": "image", + "image_path": "ff92554be065096e6cb96e892b4f7ec4e32cf72ab9de6cbc7c9d5b75bf46bc3b.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 303, + 547, + 386 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 303, + 547, + 386 + ], + "spans": [ + { + "bbox": [ + 304, + 303, + 547, + 386 + ], + "type": "text", + "content": "spatializes through early reflections, late reverberations, etc. Interestingly, our model also attends to multiple people if they are speaking at the same time (see left), thereby facilitating the detection of multiple active speakers. See Supp. for additional visualizations showing how, depending on the scene's spatial layout, our model uses one audio channel more than the other to attend to important image locations." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 387, + 547, + 457 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 387, + 547, + 457 + ], + "spans": [ + { + "bbox": [ + 304, + 387, + 547, + 457 + ], + "type": "text", + "content": "In Fig. 5, we qualitatively show our model's success cases. On ASD (Fig. 5a), our model can tackle drastic camera movements, multiple active speakers, and partially visible faces. On denoising (Fig. 5b), our model is able to remove interferences from distractor sources, and make predictions that closely match the ground truth in spectrogram structure." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 459, + 547, + 554 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 459, + 547, + 554 + ], + "spans": [ + { + "bbox": [ + 304, + 459, + 547, + 554 + ], + "type": "text", + "content": "We also observe some limitations. Our model's performance on ASD declines when there are drastic movements of the camera wearer, or there is a high overlap in speech from different conversation participants. On denoising, our model struggles when the noisy audio is semantically and acoustically similar to the target, or when it cannot extract spatial cues due to occlusions or out-of-view speakers. Refer to our Supp. video for both success and failure cases." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 565, + 378, + 577 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 565, + 378, + 577 + ], + "spans": [ + { + "bbox": [ + 306, + 565, + 378, + 577 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 585, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 585, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 585, + 547, + 713 + ], + "type": "text", + "content": "We introduce a novel self-supervised approach for learning audio-visual representations in social egocentric videos via spatial correspondence between the video and its binaural audio. Through extensive evaluation, we show that our learned features are strong and generic enough to improve over multiple backbone methods on multiple downstream tasks. In future work, we will explore how the learned spatial audio-visual cues may reveal the social attention of speakers. Acknowledgements: UT Austin is supported in part by NSF CCRI and the IFML NSF AI Institute. KG is paid as a research scientist by Meta, and SM is a visiting researcher at Meta." + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27065" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 289, + 712 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 288, + 124 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 288, + 124 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 288, + 124 + ], + "type": "text", + "content": "[1] Triantafyllos Afouras, Joon Son Chung, and Andrew Zisserman. 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In IEEE TRANSACTIONS ON SIGNAL PROCESSING (2002) SUBMITTED, 2004. 3" + } + ] + } + ], + "index": 23 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "text", + "content": "27068" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Structure-from-Motion with Graph Attention Networks/15e89f9b-21e7-4dd4-a256-0f698de897a3_content_list.json b/2024/Learning Structure-from-Motion with Graph Attention Networks/15e89f9b-21e7-4dd4-a256-0f698de897a3_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..a5c21c04cb0e83d13f0c10467dc97c04c2b24bd0 --- /dev/null +++ b/2024/Learning Structure-from-Motion with Graph Attention Networks/15e89f9b-21e7-4dd4-a256-0f698de897a3_content_list.json @@ -0,0 +1,1556 @@ +[ + { + "type": "text", + "text": "Learning Structure-from-Motion with Graph Attention Networks", + "text_level": 1, + "bbox": [ + 153, + 130, + 818, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Lucas Brynte", + "bbox": [ + 191, + 180, + 303, + 198 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Jose Pedro Iglesias", + "bbox": [ + 339, + 181, + 495, + 198 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Carl Olsson", + "bbox": [ + 535, + 181, + 630, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Fredrik Kahl", + "bbox": [ + 671, + 181, + 774, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Chalmers University of Technology", + "bbox": [ + 343, + 199, + 627, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{brynte, jose.iglesias, caols, fredrik.kahl}@chalmers.se", + "bbox": [ + 250, + 219, + 715, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 268, + 313, + 284 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In this paper we tackle the problem of learning Structurefrom-Motion (SfM) through the use of graph attention networks. SfM is a classic computer vision problem that is solved though iterative minimization of reprojection errors, referred to as Bundle Adjustment (BA), starting from a good initialization. In order to obtain a good enough initialization to BA, conventional methods rely on a sequence of sub-problems (such as pairwise pose estimation, pose averaging or triangulation) which provide an initial solution that can then be refined using BA. In this work we replace these sub-problems by learning a model that takes as input the 2D keypoints detected across multiple views, and outputs the corresponding camera poses and 3D keypoint coordinates. Our model takes advantage of graph neural networks to learn SfM-specific primitives, and we show that it can be used for fast inference of the reconstruction for new and unseen sequences. The experimental results show that the proposed model outperforms competing learning-based methods, and challenges COLMAP while having lower runtime. Our code is available at: https://github.com/lucasbrynte/gasfm/.", + "bbox": [ + 75, + 300, + 473, + 618 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 643, + 209, + 659 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Structure-from-Motion (SfM) is a classic and still relevant problem in computer vision. The goal of SfM is to estimate camera poses and 3D coordinates of keypoints detected across multiple images, and can be formulated as an optimization over $m$ camera matrices $\\{\\mathbf{P}_i\\}$ , $i = 1, \\dots, m$ and $n$ 3D points $\\{\\mathbf{X}_j\\}$ , $j = 1, \\dots, n$ of the form", + "bbox": [ + 75, + 669, + 468, + 762 + ], + "page_idx": 0 + }, + { + "type": "equation", + "text": "\n$$\n\\underset {\\left\\{\\mathbf {P} _ {i} \\right\\}, \\left\\{\\mathbf {X} _ {j} \\right\\}} {\\text {m i n i m i z e}} \\quad \\sum_ {i j} r \\left(\\mathbf {m} _ {i j}, \\mathbf {z} _ {i j}\\right) \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 169, + 768, + 468, + 803 + ], + "page_idx": 0 + }, + { + "type": "equation", + "text": "\n$$\n\\text {s u b j e c t} \\quad \\mathbf {z} _ {i j} = \\mathbf {P} _ {i} \\bar {\\mathbf {X}} _ {j}, \\forall i, j\n$$\n", + "text_format": "latex", + "bbox": [ + 169, + 804, + 377, + 823 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "where $\\mathbf{m}_{ij}$ holds the 2D coordinates of the $j^{\\mathrm{th}}$ keypoint in the $i^{\\mathrm{th}}$ image. The loss in (1) is generally chosen as the reprojection error", + "bbox": [ + 75, + 830, + 468, + 876 + ], + "page_idx": 0 + }, + { + "type": "equation", + "text": "\n$$\nr \\left(\\mathbf {m} _ {i j}, \\mathbf {z} _ {i j}\\right) = \\left| \\left| \\mathbf {m} _ {i j} - \\Pi \\left(\\mathbf {z} _ {i j}\\right) \\right| \\right| ^ {2} \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 156, + 883, + 468, + 902 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "where $\\Pi (\\mathbf{x}) = \\left(\\frac{x_1}{x_3},\\frac{x_2}{x_3}\\right)$ , and the nonlinear least squares problem (1), referred to as Bundle Adjustment (BA) [15], can be solved iteratively using second-order methods like Levenberg-Marquardt [15, 41]. Given the sparsity of the problem, sparse computation methods [27] can be used in order to increase the efficiency of the optimization, allowing BA to be used even for scenes with a large number of views or points. However, it is widely known that BA is highly non-convex and tends to converge to the nearest local minimum when not initialized close to the globally optimal solution. As a consequence, BA is typically the last step of a reconstruction pipeline, preceding global SfM methods such as [9, 10, 20, 25], or incremental SfM methods such as [2, 37, 38] that solve a sequence of subproblems like pairwise pose estimation, pose averaging, triangulation or camera resection [13, 15, 22, 32]. A different approach consists of projective factorization methods [8, 17, 18, 28, 39, 48] which factorize the $2m\\times n$ measurement matrix into two rank four matrices corresponding to the camera matrices and 3D points (in homogeneous coordinates). In particular, works like [17, 18, 48] allow initialization-free SfM given their wide basin of convergence, meaning that their methods can be initialized with random camera poses and still converge with a high rate of success to the desired global minimum. Even though these methods have been improving in terms of accuracy and robustness to missing data, factorization-based methods require the input data to be almost completely free of outliers which unfortunately cannot be guaranteed in most real world sequences or datasets, and hence severely compromises the usability of these methods.", + "bbox": [ + 496, + 268, + 893, + 729 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "A common challenge with all these approaches to solve SfM is their scalability as the number of views and keypoints increase. Incremental SfM tries to tackle this issue by starting with a subset of the views, estimate its reconstruction and incrementally adding more views. Some factorization-based methods can also take advantage of the same sparse computation methods used in BA, which significantly improves their ability to scale with sequence size. While this allows to reconstruct scenes with thousands of views and millions of points, it can still take hours to recover the reconstruction of a single scene.", + "bbox": [ + 496, + 734, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "4808", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "More recently, deep learning methods for 3D reconstruction and SfM have been proposed [7, 29, 31, 35, 44-47]. Given their increased complexity, these models are able to learn complex relations between the input data, outperforming conventional methods and achieving state-of-the-art results in 3D reconstruction and novel view synthesis when the camera pose and calibration are known [7, 29, 46]. Works such as [31, 46, 47] tackle SfM with deep learning models which different degrees of success.", + "bbox": [ + 76, + 90, + 472, + 227 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In DeepSfM [46] the authors propose an end-to-end approach to estimate camera pose and a dense depth map of a target view from multiple source views. Their method estimates a feature map for each of the source views, which are then combined with the feature map of the target view in order to estimate pose and depth cost volumes. These cost volumes are then fed to two heads that estimate the camera pose and depth map of the target view. In PoseDiffusion [44], a probabilistic diffusion framework is proposed to mirror the iterations of bundle adjustment, allowing it to incorporate geometric priors into the problem. The model is trained on object-centric scenes and it is shown that it can generalize to unseen scenes without further training.", + "bbox": [ + 75, + 229, + 472, + 426 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In [31], which is the closest work to ours, the authors have pursued an approach similar to projective factorization, taking as input the 2D keypoints tracked along multiple views. These 2D point tracks are processed by a number of linear permutation-equivariant layers, i.e. layers such that a permutation on the rows and/or columns of the input tensor results in the same permutation on the output. The output of these layers is then fed to camera pose and 3D points coordinate regression heads. The model is learned using reprojection errors as loss combined with a hinge loss term to push points in front of the cameras. By using Adam [26] as optimizer along with gradient normalization, the authors show that their method has improved convergence properties compared to random initializations.", + "bbox": [ + 75, + 429, + 472, + 641 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "A major benefit of learning-based methods is their potential in generalizing to new data after being trained. This can be particularly beneficial to SfM problems since occlusions and missing measurements are common issues that make some scenes particularly challenging to reconstruct. In these cases, the learned model can act as a prior and help constrain the solution based on the data seen during training. However, most of the learning-based methods mentioned for 3D reconstruction or SfM require scene-specific optimization or training, which turns out to be particularly slow for large sequences. PoseDiffusion [44] achieves some degree of generalization to unseen scenes, but it is conditional on the categories and object-centric datasets seen during training. In [31] the authors actually show that their model can be trained on a large collection of scenes and then used for inference on unobserved scenes. However, without fine-tuning on these new scenes (which is time-consuming)", + "bbox": [ + 75, + 643, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "the model's accuracy is significantly reduced.", + "bbox": [ + 498, + 90, + 802, + 106 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this paper we propose a graph attention network for initialization-free Structure-from-Motion that can be trained on multiple scenes and used for fast inference on new, unseen scenes. Similarly to [31], our network takes as input sparse measured image points, matched across multiple viewpoints, which are processed through a sequence of permutation-equivariant graph cross attention layers. The output of the graph cross attention layers is then processed by two regression heads, one for the 3D points and another for the camera poses. By using graph attention layers instead of linear equivariant maps as in [31], our model is able to better learn the implicit geometric primitives of SfM in the input data, leading to more expressiveness and better generalization to unseen sequences. Additionally, by not requiring time-consuming fine-tuning on unseen scenes, our model is able to provide fast inference, which can then be refined directly with BA with good convergence.", + "bbox": [ + 496, + 107, + 893, + 362 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The contributions of the paper can be summarized as:", + "bbox": [ + 517, + 363, + 872, + 378 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose graph attention networks for initialization-free Structure-from-Motion that estimates camera parameters and 3D coordinates of 2D keypoints tracked across multiple views;", + "- The method takes advantage of the graph cross-attention layers, which are equivariant to permutation on the input data regarding order of views and points. We show that these layers can model more complex relations between input data and when combined with data augmentation result in significantly improved performance when compared to baseline methods;", + "- We evaluate the proposed learned method on unobserved scenes and show that it outperforms competing state-of-the-art learning methods at inference in terms of accuracy without the need of scene-specific model fine-tuning;", + "- We show that our method achieves competitive results when compared to state-of-the-art conventional Structure-from-Motion pipelines while having a significantly lower runtime." + ], + "bbox": [ + 500, + 378, + 890, + 664 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Graph Attention Network Preliminaries", + "text_level": 1, + "bbox": [ + 500, + 678, + 861, + 696 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Before introducing our proposed method, we will here briefly outline the graph attention networks that will be utilized - the GATv2 model [4] based on [43].", + "bbox": [ + 496, + 704, + 890, + 750 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The GATv2 model is a type of graph neural network (GNN) that carries out aggregation from neighboring nodes with a dynamic attention-based weighted average. The input to a GATv2 layer is a set of current node features $\\{\\mathbf{h}_i\\in \\mathbb{R}^d\\mid i\\in \\mathcal{V}\\}$ along with a set of directed edges $\\mathcal{E}$ defining the graph connectivity. The layer outputs a new set of node features $\\{\\mathbf{h}_i'\\in \\mathbb{R}^{d'}\\mid i\\in \\mathcal{V}\\}$ , by applying a single shared learned function on every node $h_i$ together with its neighborhood $\\mathcal{N}_i = \\{j\\in \\mathcal{V}\\mid (j,i)\\in \\mathcal{E}\\}$ .", + "bbox": [ + 496, + 750, + 890, + 885 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "First, a scoring function $e:\\mathbb{R}^d\\times \\mathbb{R}^d\\to \\mathbb{R}$ is applied on", + "bbox": [ + 517, + 885, + 890, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "4809", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "all edges, by feeding the respective source and target node features as input to a shared 2-layer Multi-Layer Perceptron (MLP):", + "bbox": [ + 76, + 90, + 468, + 135 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\ne \\left(\\mathbf {h} _ {i}, \\mathbf {h} _ {j}\\right) = \\mathbf {a} ^ {\\top} \\cdot \\text {L e a k y R e L U} \\left(\\mathbf {W} \\left[ \\mathbf {h} _ {i} \\| \\mathbf {h} _ {j} \\right]\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 120, + 143, + 468, + 162 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathbf{a} \\in \\mathbb{R}^{d'}$ and $\\mathbf{W} \\in \\mathbb{R}^{d' \\times 2d}$ are learned parameters, and $\\|\\cdot\\|$ denotes vector concatenation. The attention scores are then normalized across all neighbors:", + "bbox": [ + 76, + 167, + 468, + 215 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\alpha_ {i j} = \\operatorname {s o f t m a x} _ {j} \\left(e \\left(\\mathbf {h} _ {i}, \\mathbf {h} _ {j}\\right)\\right) = \\frac {\\exp \\left(e \\left(\\mathbf {h} _ {i} , \\mathbf {h} _ {j}\\right)\\right)}{\\sum_ {j ^ {\\prime} \\in \\mathcal {N} _ {i}} \\exp \\left(e \\left(\\mathbf {h} _ {i} , \\mathbf {h} _ {j ^ {\\prime}}\\right)\\right)}, \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 78, + 222, + 468, + 268 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "and the layer is completed by carrying out a weighted average of linear projections of all source node features:", + "bbox": [ + 76, + 271, + 468, + 301 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {h} _ {i} ^ {\\prime} = \\sum_ {j \\in \\mathcal {N} _ {i}} \\alpha_ {i j} \\cdot \\mathbf {W h} _ {j}. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 183, + 308, + 468, + 333 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 340, + 166, + 354 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We apply a graph attention network model to perform Structure-from-Motion on a desired scene based on its measured image point correspondences. The model then outputs a reconstruction, represented by all $m$ camera matrices and all $n$ scene points. Structure-from-Motion is in general a large and complex optimization problem, and it is not trivially addressed as a learning problem. Our architecture combines the power and expressivity of the attention mechanism, and exploits its inherent permutation equivariance in a meaningful way, while balancing expressivity with efficiency, resulting in a very limited computational and memory footprint considering the task at hand.", + "bbox": [ + 75, + 364, + 468, + 545 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The input data for a particular scene consists of a sparse set of measured image point correspondences (point tracks). To represent this data, we define a binary observability matrix $\\mathbf{O} \\in \\{0,1\\}^{m \\times n}$ , where $m$ is the number of views and $n$ is the number of scene points, and where $\\mathbf{O}_{ij} = 1$ if and only if scene point $j$ is observed in image $i$ . Furthermore, let $\\mathcal{P} = \\{\\mathbf{m}_{ij} \\in \\mathbb{R}^2 \\mid \\mathbf{O}_{ij} = 1\\}$ be the collection of observed image point tracks, where $\\mathbf{m}_{ij}$ is the (normalized) measured image point for the projection of scene point $j$ in camera $i$ .", + "bbox": [ + 75, + 547, + 468, + 696 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Graph Attention Network Architecture", + "text_level": 1, + "bbox": [ + 76, + 705, + 413, + 720 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we will outline our graph attention network architecture, starting by introducing our feature representation. Then we proceed to define update operations for different feature types, and finally define the entire network architecture based on these operations.", + "bbox": [ + 75, + 729, + 468, + 804 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Feature representation. Throughout the network architecture, we maintain and continuously update a set of features of various types1:", + "bbox": [ + 76, + 821, + 468, + 867 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/36da846ae76d0db4cf0ebb7ef4a5eaa5dca725350024086509a9a9885eaedc7d.jpg", + "image_caption": [ + "Figure 1. Illustration of the different types of features in the network architecture, for $m = 3$ cameras and $n = 6$ scene points. The projection features $\\mathcal{P}$ are represented by a sparse vector-valued matrix, with its sparsity pattern determined by the point track measurements, while view features $\\mathcal{V}$ and scene point features $S$ are represented by dense vector-values column and row vectors. A single vector $\\mathbf{g}$ holds global features." + ], + "image_footnote": [], + "bbox": [ + 535, + 90, + 856, + 218 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Projection features, $\\mathcal{P} = \\{\\mathbf{p}_{ij}\\in \\mathbb{R}^{d_p}\\mid \\mathbf{O}_{ij} = 1\\}$", + "- View features, $\\mathcal{V} = \\{\\mathbf{v}_i\\in \\mathbb{R}^{d_v}\\mid i = 1,2,\\ldots ,m\\}$", + "- Scene point features, $S = \\{ \\mathbf{s}_j \\in \\mathbb{R}^{d_s} \\mid j = 1,2,\\dots,n \\}$ .", + "- Global features, $\\mathbf{g} \\in \\mathbb{R}^{d_g}$ ." + ], + "bbox": [ + 500, + 351, + 882, + 412 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The projection features $\\mathbf{p}_{ij}$ are feature vectors specific to every observed image point. In practice, these are bundled together and organized in a sparse vector-valued matrix, as illustrated by the large top-right matrix in Figure 1. The sparsity pattern of $\\mathcal{P}$ will be fixed throughout the network and is determined by $\\mathbf{O}$ , which however depends on the scene. The view features $\\mathcal{V}$ and scene point features $S$ , on their part, are organized in dense vector-valued column and row vectors, respectively, also illustrated in Figure 1. Finally, the global features $\\mathbf{g}$ , consist of a single globally shared feature vector, and is illustrated in the bottom-left corner of Figure 1.", + "bbox": [ + 496, + 416, + 890, + 595 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In order to define graph operations, we see every feature vector as being associated with a corresponding graph node. At this point, note that a simple approach would be to connect all nodes $\\mathcal{P},\\mathcal{V},\\mathcal{S}$ , and $\\{\\mathbf{g}\\}$ in one unified graph, and directly apply a graph neural network with global weight sharing. Instead, since the nodes are semantically different, we consider these semantics when choosing the level of weight sharing, and even vary the feature dimension depending on the type of node. In practice, we construct different graphs for propagation between different types of nodes.", + "bbox": [ + 496, + 598, + 890, + 748 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Having defined the different feature types, we proceed to define corresponding update operations, which are repeatedly carried out throughout the network. In all pseudo-code, ReLU denotes to the rectified linear unit and LN denotes layer normalization [3]. Linear denotes a learned affine layer and FFN denotes a number of stacked Linear layers interleaved with ReLU activations. Subscripts may occur to emphasize feature dimensions. Note that all of these operations may be applied on multiple nodes at once, with shared parameters. The $+$ notation implies node-wise addition.", + "bbox": [ + 496, + 750, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "1For simplicity, we use a slight abuse of set notation here. If there are feature vector duplicates, they are still considered as separate elements.", + "bbox": [ + 76, + 875, + 468, + 898 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "4810", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Graph Cross-Attention. Procedure 1 is utilized for all feature aggregations throughout the network. It carries out cross-attention [42], attending to and propagating information from one set of input / source nodes $\\mathcal{H}_1$ to another set of output / target nodes $\\widehat{\\mathcal{H}}_2$ . The previous target node features $\\mathcal{H}_2$ , if provided, will act as query features when computing attention scores. In the first few layers these may not be available, and initial zero-features are used instead.", + "bbox": [ + 75, + 90, + 472, + 210 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In our context, the source nodes and target nodes correspond to different feature types, possibly with different feature dimension. As the source and target nodes are disjoint, we may represent the connectivity by a directed bipartite graph. Furthermore, in our context this graph will often consist of a number of disconnected subgraphs. Procedure1 essentially acts as a wrapper around a GATv2 layer [4] (for which we use the PyTorch Geometric [11] implementation), while carrying out input normalization, and feature projections as necessary. We consistently use 4 attention heads for the GATv2 layers.", + "bbox": [ + 75, + 212, + 473, + 378 + ], + "page_idx": 3 + }, + { + "type": "code", + "sub_type": "algorithm", + "code_caption": [ + "Procedure 1 GRAPHCROSSATTENTION" + ], + "code_body": "Input: $\\mathcal{H}_1$ Source node features. \nInput: $\\mathcal{H}_2$ Previous target node features (optional). \nInput: $\\mathcal{E}_{\\mathcal{H}_1\\to \\mathcal{H}_2}$ Set of edges from $\\mathcal{H}_1\\rightarrow \\mathcal{H}_2$ . \nInput: $d_{1}$ Source node feature dimension. \nInput: $d_{2}$ Target node feature dimension. \nOutput: $\\widehat{\\mathcal{H}}_2$ Updated target node features. \n1: $\\widehat{\\mathcal{H}}_1\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{H}_1))$ \n2: if $\\mathcal{H}_2$ provided then \n3: $\\widehat{\\mathcal{H}}_2\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{H}_2))$ \n4: if $d_{1}\\neq d_{2}$ then \n5: $\\widehat{\\mathcal{H}}_2\\gets \\mathrm{Linear}_{d_2\\to d_1}(\\widehat{\\mathcal{H}}_2)$ \n6: else \n7: $\\widehat{\\mathcal{H}}_2\\gets \\mathrm{zero~features}\\vec{0}\\in \\mathbb{R}^{d_1}$ \n8: $\\widehat{\\mathcal{H}}_2\\gets \\mathrm{GATv2Conv}(\\widehat{\\mathcal{H}}_1,\\widehat{\\mathcal{H}}_2,\\mathcal{E}_{\\mathcal{H}_1\\to \\mathcal{H}_2})$ \n9: if $d_{1}\\neq d_{2}$ then \n10: $\\widehat{\\mathcal{H}}_2\\gets \\mathrm{Linear}_{d_1\\to d_2}(\\widehat{\\mathcal{H}}_2)$", + "bbox": [ + 76, + 411, + 359, + 613 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "View & Scene Point Feature Update. View features and scene point features are updated by Procedure 2 and 3, respectively, entirely symmetrical to one another. A directed bipartite graph is constructed by taking $\\mathcal{P}$ as source nodes, and $\\nu$ (or $S$ ) as target nodes, and connecting every projection node with its corresponding view (or scene point) node, corresponding to rows (or columns) of $\\mathcal{P}$ . Graph cross-attention according to Procedure 1 is then carried out on the graph, and used as a residual mapping. This is followed by another residual mapping with a feed-forward network. Illustrations of these update operations are provided in Figures 2 and 3.", + "bbox": [ + 75, + 652, + 472, + 834 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Global Feature Update. The global feature update, outlined in Procedure 4 is carried out in almost the same manner, but now aggregating from all view features $\\nu$ and scene", + "bbox": [ + 75, + 854, + 472, + 902 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/9a285029bdf5110c63f07456ba3031e38b9d90e0ee03f8fdea7b12c1f0b3be35.jpg", + "image_caption": [ + "Figure 2. Illustration of the update of a single view feature. All $\\mathcal{V}$ features are updated based on their previous value and the corresponding rows of $\\mathcal{P}$ ." + ], + "image_footnote": [], + "bbox": [ + 542, + 88, + 851, + 231 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/68f3a593431fd01452381da560b7ce8616cef46fefb01bafd1e7817e27e8957a.jpg", + "image_caption": [ + "Figure 3. Illustration of the update of a single scene point feature. All $S$ features are updated based on their previous value and the corresponding columns of $\\mathcal{P}$ ." + ], + "image_footnote": [], + "bbox": [ + 527, + 295, + 864, + 431 + ], + "page_idx": 3 + }, + { + "type": "code", + "sub_type": "algorithm", + "code_caption": [ + "Procedure 2 UPDATEVIEWFEAT" + ], + "code_body": "Input: $\\mathcal{P}$ O Projection features $^+$ observability matrix. \nInput: $\\nu$ Previous view features (optional). \nInput: $d_p,d_v$ Feature dimensions. \nOutput: $\\widehat{\\nu}$ Updated view features. 1: $\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}}\\gets \\{(\\mathcal{P}_{ij},\\mathcal{V}_i)\\mid \\mathbf{O}_{ij} = 1,i = 1,2,\\ldots ,m\\}$ 2: if $\\nu$ provided then 3: $\\widehat{\\nu}\\gets \\mathcal{V} + \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{V},\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}},d_p,d_v)$ 4: else 5: $\\widehat{\\nu}\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}},d_p,d_v)$ 6: $\\widehat{\\nu}\\gets \\widehat{\\nu} +\\mathrm{FFN}(\\mathrm{ReLU}(\\mathrm{LN}(\\widehat{\\nu})))$", + "bbox": [ + 500, + 518, + 870, + 647 + ], + "page_idx": 3 + }, + { + "type": "code", + "sub_type": "algorithm", + "code_caption": [ + "Procedure 3 UPDATESCENEPOINTFEAT" + ], + "code_body": "Input: $\\mathcal{P}$ , O Projection features $^+$ observability matrix. \nInput: S Previous scene point features (optional). \nInput: $d_p,d_s$ Feature dimensions. \nOutput: $\\widehat{S}$ Updated scene point features. 1: $\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}}\\gets \\{(\\mathcal{P}_{ij},\\mathcal{S}_i)\\mid \\mathbf{O}_{ij} = 1,i = 1,2,\\ldots ,m\\}$ 2: if $\\mathcal{S}$ provided then 3: $\\widehat{S}\\gets \\mathcal{S} + \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{S},\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}},d_p,d_s)$ 4: else 5: $\\widehat{S}\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}},d_p,d_s)$ 6: $\\widehat{S}\\gets \\widehat{S} +\\mathrm{FFN}(\\mathrm{ReLU}(\\mathrm{LN}(\\widehat{S})))$", + "bbox": [ + 500, + 681, + 867, + 810 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "point features $S$ instead of $\\mathcal{P}$ . This is carried out with two independent aggregations, with different learned parameters, and the sum of both aggregations constitute the residual mapping. Figure 4 provides an illustration for the update", + "bbox": [ + 496, + 839, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "4811", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/ed715ae8ff51dda6a4fac7d787d5f44c555c3a1e6d34adf07606546bc735a678.jpg", + "image_caption": [ + "Figure 4. Illustration of the global feature update, where $\\mathbf{g}$ is updated based on its previous value, together with an aggregation of all $\\mathcal{V}$ and $S$ features." + ], + "image_footnote": [], + "bbox": [ + 117, + 88, + 433, + 229 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "operation.", + "bbox": [ + 76, + 308, + 148, + 323 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Procedure 4 UPDATEGLOBALFEAT", + "bbox": [ + 80, + 339, + 323, + 351 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "Input: $\\nu$ View features.", + "Input: $S$ Scene point features.", + "Input: g Previous global features (optional).", + "Input: $d_v, d_s, d_g$ Feature dimensions.", + "Output: $\\widehat{\\mathbf{g}}$ Updated global features.", + "1: $\\mathcal{E}_{\\mathcal{V}\\to \\mathbf{g}}\\gets \\{(\\mathcal{V}_i,\\mathbf{g})\\mid i = 1,2,\\ldots ,m\\}$", + "2: $\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}}\\gets \\left\\{(\\mathcal{S}_j,\\mathbf{g})\\mid j = 1,2,\\ldots ,n\\right\\}$", + "3: if $\\mathbf{g}$ provided then", + "4: $\\widehat{\\mathbf{g}}_v\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{V},\\{\\mathbf{g}\\},\\mathcal{E}_{\\mathcal{V}\\to \\mathbf{g}},d_v,d_g)$", + "5: $\\widehat{\\mathbf{g}}_s\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{S},\\{\\mathbf{g}\\},\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}},d_s,d_g)$", + "6: $\\widehat{\\mathbf{g}}\\gets \\mathbf{g} + \\widehat{\\mathbf{g}}_v + \\widehat{\\mathbf{g}}_s$", + "7: else", + "8: $\\widehat{\\mathbf{g}}_v\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{V}, - ,\\mathcal{E}_{\\mathcal{V}\\to \\mathbf{g}},d_v,d_g)$", + "9: $\\widehat{\\mathbf{g}}_s\\gets +\\mathrm{GRAPHCROSSATTENTION}(\\mathcal{S}, - ,\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}},d_s,d_g)$", + "10: $\\widehat{\\mathbf{g}}\\gets \\widehat{\\mathbf{g}}_v + \\widehat{\\mathbf{g}}_s$", + "11: $\\widehat{\\mathbf{g}}\\gets \\widehat{\\mathbf{g}} +\\mathrm{FFN}(\\mathrm{ReLU}(\\mathrm{LN}(\\widehat{\\mathbf{g}})))$" + ], + "bbox": [ + 78, + 354, + 433, + 549 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Projection Feature Update. The projection features are updated according to Procedure 5. No aggregation is involved during this step. Instead, at every projection node the corresponding $\\nu$ , $S$ and $\\mathbf{g}$ features are all collected along with the current projection features $\\mathcal{P}$ , as illustrated in Figure 5. Each of these sources then undergoes a ReLU activation and normalization with LN, before being concatenated. Note that the initial projection features $\\mathcal{P}_0$ are typically also added to the input, and in this case they are simply concatenated to the previous projection features before the procedure is called. Finally, a residual mapping is applied, by feeding the concatenated features to a shared feed-forward network.", + "bbox": [ + 75, + 592, + 472, + 787 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Entire Network Architecture. Now we have all the pieces to define the complete network architecture, which is outlined in Procedure 6. The structure is straightforward: 1) UPDATEVIEWFEAT and UPDATESCENEPOINTFEAT (Procedures 2 and 3) are called to aggregate projection features. 2) UPDATEGLOBALFEAT (Procedure 4) is called to aggre", + "bbox": [ + 75, + 809, + 472, + 902 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/c2b0f061a2942b8ba7fa558c430767d5fecfb076624389813278412012ff3ffe.jpg", + "image_caption": [ + "Figure 5. Illustration of the update of a single projection feature. All $\\mathcal{P}$ features are updated based on their previous value, as well as initial projection features $\\mathcal{P}_0$ , the global feature $\\mathbf{g}$ , and the corresponding $\\mathcal{V}$ and $S$ features." + ], + "image_footnote": [], + "bbox": [ + 529, + 87, + 864, + 237 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Procedure 5 UPDATEPROJFEAT", + "bbox": [ + 501, + 316, + 720, + 330 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Input: $\\mathcal{P}$ Previous projection features.", + "bbox": [ + 501, + 333, + 715, + 345 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Input: $\\nu$ View features.", + "bbox": [ + 501, + 347, + 640, + 357 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Input: $S$ Scene point features.", + "bbox": [ + 501, + 358, + 673, + 369 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Input: g Global features.", + "bbox": [ + 501, + 369, + 648, + 381 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Input: $d_p^{in}, d_v, d_s, d_g, d_p^{out}$ Feature dimensions.", + "bbox": [ + 501, + 382, + 772, + 396 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Output: $\\hat{\\mathcal{P}}$ Updated projection features.", + "bbox": [ + 501, + 397, + 723, + 409 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "1: $\\widehat{\\mathcal{P}}\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{V}))\\parallel \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{S}))$ $\\| \\operatorname {ReLU}(\\operatorname {LN}(\\mathbf{g}))\\| \\operatorname {ReLU}(\\operatorname {LN}(\\mathcal{P}))$ // View, scene point, and global features are implicitly distributed to their corresponding projection features before feature concatenation.", + "bbox": [ + 506, + 410, + 890, + 468 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "2: $\\widehat{\\mathcal{P}}\\gets \\mathcal{P} + \\mathrm{FFN}_{(d_v + d_s + d_g + d_p^{in})\\to d_p^{out}}(\\widehat{\\mathcal{P}})$", + "bbox": [ + 506, + 469, + 761, + 487 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "gate the resulting features further, to a single global feature vector. 3) UPDATEPROJFEAT (Procedure 5) is called in order to again distribute the aggregated information across the projection features. These steps are repeated $L$ times, where we refer to $L$ as the number of layers. Then, a final call to UPDATEVIEWFEAT and UPDATESCENEPOINTFEAT is carried out, and the resulting view and scene point features are further processed by two corresponding regression heads, consisting of shared 3-layer feed-forward networks (FFN) with hidden neurons of the same dimension as the input ( $d_v$ or $d_s$ ). The scene point head simply outputs the 3 coordinates of every estimated scene point. For Euclidean reconstruction, the view head outputs the 3 coordinates of the location of the camera center, together with a unit-norm quaternion representing its orientation. For projective reconstruction, all 12 camera matrix elements are regressed, followed by a normalization in the same manner as [31]. Except for the regression heads, we use 1-layer FFNs throughout the network, which in general seemed slightly easier to train.", + "bbox": [ + 496, + 518, + 893, + 821 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.2. Loss Function", + "text_level": 1, + "bbox": [ + 500, + 830, + 645, + 845 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The network is trained using the Adam optimizer, and as loss function we use the (non-squared) reprojection error, averaged over all observed image points. To handle negative", + "bbox": [ + 496, + 854, + 893, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "4812", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "code", + "sub_type": "algorithm", + "code_caption": [ + "Procedure 6 GRAPHATTENTIONSFM" + ], + "code_body": "Input: $\\mathcal{M}$ Image point tracks, normalized. \nInput: O Observability matrix. \nInput: $d_p,d_v,d_s,d_g$ Feature dimensions. \nInput: L Number of layers. \nOutput: V Estimated camera parameters. \nOutput: S Estimated scene points. \n1: $\\mathcal{P}_0\\gets \\mathrm{Linear}_{2\\to 2}(\\mathcal{M})$ // Initial projection features: linear embedding of image points. \n2: $\\mathcal{V}\\gets$ UPDATEVIEWFEAT $(\\mathcal{P}_0,\\mathbf{O}, - ,2,d_v)$ \n3: $\\mathcal{S}\\gets$ UPDATESCENEPOINTFEAT $(\\mathcal{P}_0,\\mathbf{O}, - ,2,d_s)$ \n4: $\\mathbf{g}\\gets$ UPDATEGLOBALFEAT $(\\mathcal{V},\\mathcal{S}, - ,d_v,d_s,d_g)$ \n5: for $l = 1,2,\\dots ,L$ do \n6: if $l = 1$ then \n7: $\\mathcal{P}\\gets$ UPDATEPROJFEAT $(\\mathcal{P}_0,\\mathcal{V},\\mathcal{S},\\mathbf{g},2,d_v,d_s,d_g,d_p)$ \n8: else \n9: $\\mathcal{P}\\gets$ UPDATEPROJFEAT $(\\mathcal{P}\\| \\mathcal{P}_0,\\mathcal{V},\\mathcal{S},\\mathbf{g},$ $d_p + 2,d_v,d_s,d_g,d_p)$ \n10: $\\mathcal{V}\\gets$ UPDATEVIEWFEAT $(\\mathcal{P},\\mathbf{O},\\mathcal{V},d_p,d_v)$ \n12: $\\mathcal{S}\\gets$ UPDATESCENEPOINTFEAT $(\\mathcal{P},\\mathbf{O},\\mathcal{S},d_p,d_s)$ \n13: if $l < L$ then \n14: $\\mathbf{g}\\gets$ UPDATEGLOBALFEAT $(\\mathcal{V},\\mathcal{S},\\mathbf{g},d_v,d_s,d_g)$ \n15: $\\{\\mathbf{P}_i\\} \\gets \\mathrm{FFN}(\\mathrm{ReLU}(\\mathcal{V}))$ // Camera regression head \n16: $\\{\\mathbf{X}_j\\} \\gets \\mathrm{FFN}(\\mathrm{ReLU}(\\mathcal{S}))$ // Scene point regression head", + "bbox": [ + 78, + 107, + 468, + 391 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "depths and overcome the singularity at the principal plane, we substitute the reprojection error with minus the depth in the loss function for any projection with depth smaller than a threshold $h = 1e - 4$ . We also apply gradient normalization in the same manner as [31].", + "bbox": [ + 76, + 421, + 468, + 494 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "3.3. Data Augmentation", + "text_level": 1, + "bbox": [ + 76, + 508, + 263, + 523 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For Euclidean reconstruction, where the image points are normalized using the intrinsic camera parameters, and therefore geometrically interpretable, we experiment with augmenting the training scenes with slightly transformed variations. While the scene points remain fixed, each camera is randomly rotated about its center, first by a uniformly sampled angle $\\alpha \\in [-15, 15]$ about the principal axis, followed by a uniformly sampled angle $\\gamma \\in [-20, 20]$ about an axis orthogonal to the principal axis with a random direction. The image points are transformed accordingly.", + "bbox": [ + 75, + 532, + 468, + 683 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "3.4. Artificial Outlier Injection", + "text_level": 1, + "bbox": [ + 76, + 695, + 313, + 710 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We also consider the presence of measurement outliers, by artificially corrupting the data. This is done by: 1) Selecting a subset of the 2D keypoint measurements to be replaced by artificial outliers. 2) For each view, replace all measurements marked to be outliers with random samples from a bivariate normal distribution, which is fit to all remaining (inlier) points. For step 1), we carefully select points for outlier injection such that we avoid getting any scene points visible in $< 2$ views or any views with $< 8$ scene points visible, if regarding only the inlier projections. In the supplementary material, the details are given on how this is achieved. Note that while the network input is corrupted by outlier injec", + "bbox": [ + 75, + 719, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "tion, the uncorrupted data is still used as learning targets for the loss function.", + "bbox": [ + 500, + 90, + 890, + 119 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4. Results", + "text_level": 1, + "bbox": [ + 500, + 136, + 586, + 151 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 500, + 162, + 689, + 178 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We take a particular interest in Euclidean reconstruction, due to the relevance of metric reconstructions for photogrammetry applications. Furthermore, we focus mainly on the task of learning and generalizing from a set of training scenes, due to the great potential in having a fast learned model acquire reconstructions of completely novel scenes. We use the DPESFM method of Moran et al. [31] as a baseline, as they have presented experiments on precisely this. To this end, we also use Olsson's dataset [33] (together with the VGG dataset [12] for additional projective reconstruction experiments in the supplement), and we use the same random partition of 10 test scenes and 3 validation scenes.", + "bbox": [ + 496, + 185, + 890, + 366 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We base our implementation on that of [31], implemented in PyTorch [34], but replace the network architecture with our proposed GRAPHATTENTIONSFM network, implemented using GATv2Conv layers [4] from PyTorch Geometric [11]. The implementation details are in general consistent with [31], for more details see the supplement. The DPESFM results reproduced by us are obtained by running the method of [31] with our code base, with the hyperparameters published on the official GitHub repository of the method [30]. For our model, we use $L = 12$ layers and feature dimensions $d_{p} = 32$ , $d_{v} = 1024$ , $d_{s} = 64$ , $d_{g} = 2048$ , which corresponds to 145M parameters. By using small dimensions for the projection features and scene point features the otherwise high memory consumption is significantly reduced. Hyper-parameters have been chosen based on the performance on the validation data, but without any rigorous hyper-parameter tuning.", + "bbox": [ + 496, + 367, + 892, + 625 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Euclidean Reconstruction of Novel Scenes", + "text_level": 1, + "bbox": [ + 500, + 635, + 856, + 648 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In Table 1, we report the Euclidean reconstruction results of our method, when applied on novel test scenes, and measure the performance by reprojection errors, as well as rotation and translation errors for the estimated camera poses. For calculating the latter, the predicted and ground truth poses are first aligned to a common reference frame, as described in Section C in the supplement. The results of DPESFM as reported in [31] can be seen in parentheses, when available, but we also retrain their model and incorporate further results of the model, not reported in [31], in particular results without bundle adjustment, and additional metrics to reprojection errors. Experiments are carried out both with and without data augmentation with random rotational cameras perturbations, as described in Section 3.3, and the columns are partitioned accordingly. Consistently with [31], Inference refers to the network output followed", + "bbox": [ + 496, + 657, + 892, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "4813", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/b299fb1ecc507bbe1aeeb195be0886ffeef2f0e874c84281e49386e8679c0227.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Without data augmentationWith data augmentationColmap
InferenceInference + BAInferenceInference + BA
OursDPESFMOursDPESFMOursDPESFMOursDPESFM
Reprojection error (px)Alcatraz Courtyard68.4168.501.700.81 (0.82)36.0192.370.810.920.81
Alcatraz Water Tower36.3050.471.051.13 (0.55)87.672831.940.8810.160.55
Drinking Fountain Somewhere in Zurich36.0245.870.550.31 (7.21)219.75234.900.316.730.31
Nijo Castle Gate65.7164.530.730.73 (5.81)61.4168.190.880.890.73
Porta San Donato Bologna74.3294.260.740.74 (1.10)52.1584.460.760.750.75
Round Church Cambridge61.1855.510.390.39 (0.50)29.8059.540.391.490.39
Smolny Cathedral St Petersburg156.16120.850.810.81 (15.15)85.3887.810.810.810.81
Some Cathedral in Barcelona150.01146.1010.4212.71 (21.46)125.68687.830.8916.770.89
Sri Veeramakaliamman Singapore121.02157.392.1916.87 (16.92)83.50166.682.139.300.71
Yueh Hai Ching Temple Singapore37.4652.590.650.65 (1.16)25.6051.350.650.730.65
Average80.6685.611.923.52 (7.07)80.69436.510.854.860.66
Rotation error (deg)Alcatraz Courtyard10.10213.2012.6070.0356.09310.9460.0380.0300.043
Alcatraz Water Tower10.63711.0530.4990.76411.50110.6410.69919.3510.228
Drinking Fountain Somewhere in Zurich15.84616.0140.0030.00115.41515.7040.00122.7590.007
Nijo Castle Gate16.75110.5460.0620.06217.34720.0320.0380.0360.064
Porta San Donato Bologna23.83924.1200.0950.09418.41125.0040.0940.0940.099
Round Church Cambridge18.90614.4730.0290.02610.29518.6850.0291.0860.035
Smolny Cathedral St Petersburg19.38717.9710.0230.02211.66214.3800.0230.0190.029
Some Cathedral in Barcelona27.27030.47110.00920.05027.90829.1190.02047.8920.025
Sri Veeramakaliamman Singapore28.27536.9030.5494.87123.70236.1760.4572.7590.169
Yueh Hai Ching Temple Singapore15.73322.7060.0380.0389.51521.5610.0380.0380.043
Average18.67519.7461.3912.59615.18520.2250.1449.4060.074
Translation error (m)Alcatraz Courtyard4.824.931.090.012.735.740.010.010.01
Alcatraz Water Tower8.667.350.310.447.537.770.419.050.12
Drinking Fountain Somewhere in Zurich4.444.440.000.004.454.460.001.380.00
Nijo Castle Gate5.073.080.010.015.676.950.010.010.01
Porta San Donato Bologna9.5010.720.050.054.8010.480.050.050.05
Round Church Cambridge8.947.190.010.015.289.000.010.560.01
Smolny Cathedral St Petersburg2.702.430.010.012.332.520.010.010.01
Some Cathedral in Barcelona12.6412.693.226.3812.3212.660.0111.930.01
Sri Veeramakaliamman Singapore4.944.900.161.324.934.900.140.770.04
Yueh Hai Ching Temple Singapore4.124.270.010.012.444.280.010.010.01
Average6.586.200.490.825.256.880.072.380.03
", + "bbox": [ + 76, + 87, + 890, + 506 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/73289d5b410e5b30c4303de0d567afe882d8588c07b82357653bb84ed13379a1.jpg", + "table_caption": [ + "Table 1. Results of Euclidean reconstruction of novel test scenes, with and without data augmentation. The results of DPESFM [31] have been acquired by us training the model, along with the results reported by [31] in parentheses, if available. The result of Colmap, as reported by [31], is also added for reference." + ], + "table_footnote": [], + "table_body": "
SceneInfer.BAColmap
Alcatraz Courtyard0.2445.54286
Alcatraz Water Tower0.1331.11130
Drinking Fountain Somewhere In Zurich0.061.9816
Nijo Castle Gate0.093.9721
Porta San Donato Bologna0.1827.02170
Round Church Cambridge0.4356.47229
Smolny Cathedral St Petersburg0.4986.09516
Some Cathedral In Barcelona0.2447.05451
Sri Veeramakaliamman Singapore0.63115.80583
Yueh Hai Ching Temple Singapore0.088.54106
", + "bbox": [ + 84, + 582, + 470, + 718 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Runtime (s) of our method for Euclidean reconstruction on test scenes, in comparison with Colmap (measured by [31]).", + "bbox": [ + 76, + 728, + 468, + 757 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "by a computationally cheap triangulation and Inference $+$ BA refers to the network output followed by bundle adjustment, which is carried out in the same manner as [31], using the Ceres solver [1]. Moran et al. [31] also performed experiments with fine-tuning the network parameters on the test scenes. In contrast, we advocate against this, since this approach is relatively costly, and one might as well acquire", + "bbox": [ + 75, + 794, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "high-quality reconstructions from traditional SfM pipelines such as Colmap, in similar execution time. Nevertheless, the supplementary material includes such experiments, for completeness.", + "bbox": [ + 498, + 585, + 890, + 647 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Without data augmentation, there is no clear difference between the Inference results of both methods. Neither reconstruction is good, and it is not so meaningful to compare minor differences in the metrics under these circumstances. In particular, calculating rotation and translation errors requires aligning the predicted and ground truth camera poses in a common reference frame, as described in Section C in the supplement, and when the predicted configuration of camera poses is not very consistent with the ground truth, determining this alignment itself can be sensitive. In all other scenarios, we outperform DPESFM, and when using both data augmentation and applying bundle adjustment, the solutions we acquire for the novel test scenes are in general very good. In terms of reprojection error and translation error, we match the performance of Colmap for almost every test scene, leading to an average reprojection", + "bbox": [ + 496, + 657, + 892, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "4814", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "error of 0.85 (vs 0.66) px, and an average translation error of 0.07 (vs 0.03) m. In terms of rotation error, the error is actually lower than Colmap's for 8 out of 10 scenes, but the average error is slightly larger: 0.144 (vs 0.074) degrees.", + "bbox": [ + 75, + 90, + 470, + 151 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3. Artificial Outlier Injection", + "text_level": 1, + "bbox": [ + 76, + 162, + 316, + 178 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In Table 3 we present additional results where, on top of data augmentation (see Section 3.3), we also apply artificial outlier injection during training according to Section 3.4.", + "bbox": [ + 75, + 185, + 468, + 229 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We evaluate inference of the model in two settings: 1) Applied on the uncorrupted outlier-free test scenes as is. 2) Applied to the test scenes followed by random injection of $10\\%$ , in the same manner as during training2. One can immediately observe significantly reduced reprojection errors for our model, suggesting that the outlier injection during training has a regularizing effect. Beyond that, this experiment is intended to serve as a teaser for the utility and promise of learning-based methods for SfM. Constant challenges such as the presence of outliers may not be as big of a challenge for learning-based as for conventional methods, and the phenomenon may even be exploited to develop effective training strategies. In fact, for any real-world scenario, it is crucial for learning-based methods applied on image point correspondences to be resilient to outliers, as we do not have the luxury of facing high-quality curated data such as Olsson's [33] in the wild. Note that it should be possible to apply bundle adjustment on the corrupted test data as well, when combined with a robust loss function.", + "bbox": [ + 75, + 231, + 470, + 517 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Similarly as for the data augmentation, we note that DPESFM appears to struggle with the presence of outliers during training, and its performance on the test scenes at inference is not very good. It is very probable that the nonlinear attention layers make our model more powerful and expressive than DPESFM.", + "bbox": [ + 75, + 518, + 468, + 609 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.4. Additional Results", + "text_level": 1, + "bbox": [ + 76, + 619, + 256, + 633 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In the supplementary material we provide additional results on projective reconstruction, as well as single-scene optimization, for completeness. We also include statistics of the number of views and scene points for each scene.", + "bbox": [ + 75, + 642, + 468, + 703 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 76, + 718, + 194, + 734 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "With this paper we have added to the research direction of learned initialization-free Structure-from-Motion by introducing a novel and expressive graph attention network outperforming previous learning-based methods for Euclidean reconstruction of novel scenes. When succeeded by bundle adjustment, we are able to reconstruct novel test scenes to perfection or of very decent precision, at a speedup of about $5 - 10 \\times$ compared to Colmap. Moreover, we illustrate great", + "bbox": [ + 75, + 743, + 468, + 864 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/e4796d1a9b5307bc64ef465411597a51c8735535b2e9cb624ba9574e34e2bc33.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
UncorruptedOutlier-injected
OursDPESFMOursDPESFM
Alcatraz Courtyard47.7485.8152.9994.24
Alcatraz Water Tower35.9672.8437.8983.55
Drinking Fountain \nSomewhere in Zurich52.081012.1446.651453.31
Nijo Castle Gate46.4872.9962.52126.18
Porta San Donato \nBologna53.1288.0265.0894.72
Round Church \nCambridge36.0963.7248.6390.63
Smolny Cathedral St \nPetersburg47.2891.0359.5298.05
Some Cathedral in \nBarcelona109.86397.75123.75462.28
Sri Veeramakali-\namman Singapore63.60169.6370.90146.98
Yueh Hai Ching \nTemple Singapore26.8351.4136.6957.59
Average51.91210.5360.46270.75
", + "bbox": [ + 500, + 87, + 887, + 330 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. Reprojection errors of Euclidean reconstruction of novel test scenes, with model trained with data augmentation as well as artificial outlier injection. The results of DPESFM [31] have been acquired by us training the model.", + "bbox": [ + 498, + 340, + 890, + 396 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "potential in coping with the presence of outliers, and even show artificial outlier injection to provide an effective regularizing training strategy, combined with data augmentation by random rotational camera perturbations.", + "bbox": [ + 496, + 422, + 890, + 483 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "For future work, it could definitely be promising to train on larger datasets, since model generalization is still a challenge. While the proposed model does not require fine-tuning, and thus is much faster to execute than previous work, it still relies on bundle adjustment to acquire a good reconstruction, which constitutes the computational bottleneck. Exploring alternative formulations where the network regresses relative camera poses is also an interesting direction, as the current absolute pose prediction may be a weakness due to the reconstruction ambiguity up to a similarity transformation. Other possible research directions include unrolling the architecture to multiple learned iterations / refinement steps, extensions to non-rigid Structure-from-Motion, and incorporating modern learned image matching pipelines such as [5, 6, 40] in an end-to-end fashion.", + "bbox": [ + 496, + 484, + 892, + 710 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements The work was supported by the Wallenberg AI, Autonomous Systems and Software Program (WASP) funded by the Knut and Alice Wallenberg Foundation, and the Swedish Research Council grants no. 2016-04445, 2018-05375, and 2023-05341. Computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) at Chalmers Centre for Computational Science and Engineering (C3SE) and National Supercomputer Centre (NSC) Berzelius at Linköping University partially funded by the Swedish Research Council through grant no. 2022-06725.", + "bbox": [ + 496, + 728, + 890, + 893 + ], + "page_idx": 7 + }, + { + "type": "page_footnote", + "text": "2Yet, during evaluation, we use all true measurements as ground truth targets when calculating reprojection errors, even in the corrupted case.", + "bbox": [ + 75, + 875, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "4815", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Sameer Agarwal, Keir Mierle, and Others. 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Intell., 29(10):1834-1847, 2007. 1", + "[26] Diederik P. Kingma and Jimmy Ba. Adam: A method for stochastic optimization. In 3rd International Conference on Learning Representations, ICLR 2015, San Diego, CA, USA, May 7-9, 2015, Conference Track Proceedings, 2015. 2", + "[27] Kurt Konolige. Sparse sparse bundle adjustment. In Brit. Mach. Vis. Conf., pages 1-11, 2010. 1", + "[28] Ludovic Magerand and Alessio Del Bue. Practical projective structure from motion (p2sfm). In Int. Conf. Comput. Vis., pages 39-47, 2017. 1, 9", + "[29] Ben Mildenhall, Pratul P. Srinivasan, Matthew Tancik, Jonathan T. Barron, Ravi Ramamoorthi, and Ren Ng. Nerf: Representing scenes as neural radiance fields for view synthesis, 2020. cite arxiv:2003.08934Comment: ECCV 2020 (oral). Project page with videos and code: http://tancik.com/nerf.2", + "[30] Dror Moran, Hodaya Koslowsky, Yoni Kasten, Haggai Maron, Meirav Galun, and Ronen Basri. Deep permutation-equivariant sfm: Github repository. https://github.com/drormoran/Equivariant-SFM/.6", + "[31] Dror Moran, Hodaya Koslowsky, Yoni Kasten, Haggai Maron, Meirav Galun, and Ronen Basri. Deep permutation equivariant structure from motion. In Proceedings of the IEEE/CVF International Conference on Computer Vision" + ], + "bbox": [ + 503, + 92, + 890, + 900 + ], + "page_idx": 8 + }, + { + "type": "page_number", + "text": "4816", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "$(ICCV)$ pages 5976-5986,2021.2,5,6,7,8,1,3,4,9,10, 11,12,13,14,15,16,17,18,19", + "[32] David Nister. An efficient solution to the five-point relative pose problem. IEEE Transactions on Pattern Analysis and Machine Intelligence, 26(6):756-770, 2004. 1", + "[33] Carl Olsson and Olof Enqvist. Stable structure from motion for unordered image collections. In Scand. Conf. Image Analysis, pages 524-535. Springer, 2011. 6, 8", + "[34] Adam Paszke, Sam Gross, Francisco Massa, Adam Lerer, James Bradbury, Gregory Chanan, Trevor Killeen, Zeming Lin, Natalia Gimelshein, Luca Antiga, Alban Desmaison, Andreas Kopf, Edward Yang, Zachary DeVito, Martin Raison, Alykhan Tejani, Sasank Chilamkurthy, Benoit Steiner, Lu Fang, Junjie Bai, and Soumith Chintala. Pytorch: An imperative style, high-performance deep learning library. In Advances in Neural Information Processing Systems 32, pages 8024-8035. Curran Associates, Inc., 2019. 6", + "[35] Pulak Purkait, Tat-Jun Chin, and Ian Reid. Neurora: Neural robust rotation averaging. In Computer Vision – ECCV 2020, pages 137–154, Cham, 2020. Springer International Publishing. 2", + "[36] Johannes L. Schonberger. Colmap code. https://colmap.github.io/.3,6,7,8", + "[37] Johannes Lutz Schonberger and Jan-Michael Frahm. Structure-from-motion revisited. 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NeRF---: Neural radiance fields without known camera parameters. arXiv preprint arXiv:2102.07064, 2021." + ], + "bbox": [ + 78, + 90, + 468, + 898 + ], + "page_idx": 9 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[46] Xingkui Wei, Yinda Zhang, Zhuwen Li, Yanwei Fu, and Xi-angyang Xue. Deepsfm: Structure from motion via deep bundle adjustment. In ECCV, 2020. 2", + "[47] Yi Wei, Shaohui Liu, Yongming Rao, Wang Zhao, Jiwen Lu, and Jie Zhou. Nerfingmvs: Guided optimization of neural radiance fields for indoor multi-view stereo. In ICCV, 2021. 2", + "[48] Christopher Zach and Je Hyeong Hong. pOSE: Pseudo object space error for initialization-free bundle adjustment. In 2018 IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 1876-1885, 2018. 1" + ], + "bbox": [ + 501, + 92, + 890, + 246 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "4817", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning Structure-from-Motion with Graph Attention Networks/15e89f9b-21e7-4dd4-a256-0f698de897a3_model.json b/2024/Learning Structure-from-Motion with Graph Attention Networks/15e89f9b-21e7-4dd4-a256-0f698de897a3_model.json new file mode 100644 index 0000000000000000000000000000000000000000..0814f2e279668acc35320d4632f03e5adaf7385c --- /dev/null +++ b/2024/Learning Structure-from-Motion with Graph Attention Networks/15e89f9b-21e7-4dd4-a256-0f698de897a3_model.json @@ -0,0 +1,2343 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.155, + 0.131, + 0.819, + 0.154 + ], + "angle": 0, + "content": "Learning Structure-from-Motion with Graph Attention Networks" + }, + { + "type": "text", + "bbox": [ + 0.192, + 0.181, + 0.304, + 0.199 + ], + "angle": 0, + "content": "Lucas Brynte" + }, + { + "type": "text", + "bbox": [ + 0.341, + 0.182, + 0.496, + 0.199 + ], + "angle": 0, + "content": "Jose Pedro Iglesias" + }, + { + "type": "text", + "bbox": [ + 0.536, + 0.182, + 0.632, + 0.198 + ], + "angle": 0, + "content": "Carl Olsson" + }, + { + "type": "text", + "bbox": [ + 0.672, + 0.182, + 0.776, + 0.197 + ], + "angle": 0, + "content": "Fredrik Kahl" + }, + { + "type": "text", + "bbox": [ + 0.344, + 0.2, + 0.628, + 0.218 + ], + "angle": 0, + "content": "Chalmers University of Technology" + }, + { + "type": "text", + "bbox": [ + 0.25, + 0.22, + 0.717, + 0.234 + ], + "angle": 0, + "content": "{brynte, jose.iglesias, caols, fredrik.kahl}@chalmers.se" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.301, + 0.474, + 0.619 + ], + "angle": 0, + "content": "In this paper we tackle the problem of learning Structurefrom-Motion (SfM) through the use of graph attention networks. SfM is a classic computer vision problem that is solved though iterative minimization of reprojection errors, referred to as Bundle Adjustment (BA), starting from a good initialization. In order to obtain a good enough initialization to BA, conventional methods rely on a sequence of sub-problems (such as pairwise pose estimation, pose averaging or triangulation) which provide an initial solution that can then be refined using BA. In this work we replace these sub-problems by learning a model that takes as input the 2D keypoints detected across multiple views, and outputs the corresponding camera poses and 3D keypoint coordinates. Our model takes advantage of graph neural networks to learn SfM-specific primitives, and we show that it can be used for fast inference of the reconstruction for new and unseen sequences. The experimental results show that the proposed model outperforms competing learning-based methods, and challenges COLMAP while having lower runtime. Our code is available at: https://github.com/lucasbrynte/gasfm/." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.645, + 0.21, + 0.66 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.67, + 0.47, + 0.763 + ], + "angle": 0, + "content": "Structure-from-Motion (SfM) is a classic and still relevant problem in computer vision. The goal of SfM is to estimate camera poses and 3D coordinates of keypoints detected across multiple images, and can be formulated as an optimization over \\( m \\) camera matrices \\( \\{\\mathbf{P}_i\\} \\), \\( i = 1, \\dots, m \\) and \\( n \\) 3D points \\( \\{\\mathbf{X}_j\\} \\), \\( j = 1, \\dots, n \\) of the form" + }, + { + "type": "equation", + "bbox": [ + 0.17, + 0.77, + 0.47, + 0.804 + ], + "angle": 0, + "content": "\\[\n\\underset {\\left\\{\\mathbf {P} _ {i} \\right\\}, \\left\\{\\mathbf {X} _ {j} \\right\\}} {\\text {m i n i m i z e}} \\quad \\sum_ {i j} r \\left(\\mathbf {m} _ {i j}, \\mathbf {z} _ {i j}\\right) \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.171, + 0.805, + 0.378, + 0.824 + ], + "angle": 0, + "content": "\\[\n\\text {s u b j e c t} \\quad \\mathbf {z} _ {i j} = \\mathbf {P} _ {i} \\bar {\\mathbf {X}} _ {j}, \\forall i, j\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.831, + 0.47, + 0.877 + ], + "angle": 0, + "content": "where \\(\\mathbf{m}_{ij}\\) holds the 2D coordinates of the \\(j^{\\mathrm{th}}\\) keypoint in the \\(i^{\\mathrm{th}}\\) image. The loss in (1) is generally chosen as the reprojection error" + }, + { + "type": "equation", + "bbox": [ + 0.158, + 0.884, + 0.47, + 0.903 + ], + "angle": 0, + "content": "\\[\nr \\left(\\mathbf {m} _ {i j}, \\mathbf {z} _ {i j}\\right) = \\left| \\left| \\mathbf {m} _ {i j} - \\Pi \\left(\\mathbf {z} _ {i j}\\right) \\right| \\right| ^ {2} \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.269, + 0.895, + 0.73 + ], + "angle": 0, + "content": "where \\(\\Pi (\\mathbf{x}) = \\left(\\frac{x_1}{x_3},\\frac{x_2}{x_3}\\right)\\), and the nonlinear least squares problem (1), referred to as Bundle Adjustment (BA) [15], can be solved iteratively using second-order methods like Levenberg-Marquardt [15, 41]. Given the sparsity of the problem, sparse computation methods [27] can be used in order to increase the efficiency of the optimization, allowing BA to be used even for scenes with a large number of views or points. However, it is widely known that BA is highly non-convex and tends to converge to the nearest local minimum when not initialized close to the globally optimal solution. As a consequence, BA is typically the last step of a reconstruction pipeline, preceding global SfM methods such as [9, 10, 20, 25], or incremental SfM methods such as [2, 37, 38] that solve a sequence of subproblems like pairwise pose estimation, pose averaging, triangulation or camera resection [13, 15, 22, 32]. A different approach consists of projective factorization methods [8, 17, 18, 28, 39, 48] which factorize the \\(2m\\times n\\) measurement matrix into two rank four matrices corresponding to the camera matrices and 3D points (in homogeneous coordinates). In particular, works like [17, 18, 48] allow initialization-free SfM given their wide basin of convergence, meaning that their methods can be initialized with random camera poses and still converge with a high rate of success to the desired global minimum. Even though these methods have been improving in terms of accuracy and robustness to missing data, factorization-based methods require the input data to be almost completely free of outliers which unfortunately cannot be guaranteed in most real world sequences or datasets, and hence severely compromises the usability of these methods." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.902 + ], + "angle": 0, + "content": "A common challenge with all these approaches to solve SfM is their scalability as the number of views and keypoints increase. Incremental SfM tries to tackle this issue by starting with a subset of the views, estimate its reconstruction and incrementally adding more views. Some factorization-based methods can also take advantage of the same sparse computation methods used in BA, which significantly improves their ability to scale with sequence size. While this allows to reconstruct scenes with thousands of views and millions of points, it can still take hours to recover the reconstruction of a single scene." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4808" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.228 + ], + "angle": 0, + "content": "More recently, deep learning methods for 3D reconstruction and SfM have been proposed [7, 29, 31, 35, 44-47]. Given their increased complexity, these models are able to learn complex relations between the input data, outperforming conventional methods and achieving state-of-the-art results in 3D reconstruction and novel view synthesis when the camera pose and calibration are known [7, 29, 46]. Works such as [31, 46, 47] tackle SfM with deep learning models which different degrees of success." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.23, + 0.473, + 0.428 + ], + "angle": 0, + "content": "In DeepSfM [46] the authors propose an end-to-end approach to estimate camera pose and a dense depth map of a target view from multiple source views. Their method estimates a feature map for each of the source views, which are then combined with the feature map of the target view in order to estimate pose and depth cost volumes. These cost volumes are then fed to two heads that estimate the camera pose and depth map of the target view. In PoseDiffusion [44], a probabilistic diffusion framework is proposed to mirror the iterations of bundle adjustment, allowing it to incorporate geometric priors into the problem. The model is trained on object-centric scenes and it is shown that it can generalize to unseen scenes without further training." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.43, + 0.473, + 0.642 + ], + "angle": 0, + "content": "In [31], which is the closest work to ours, the authors have pursued an approach similar to projective factorization, taking as input the 2D keypoints tracked along multiple views. These 2D point tracks are processed by a number of linear permutation-equivariant layers, i.e. layers such that a permutation on the rows and/or columns of the input tensor results in the same permutation on the output. The output of these layers is then fed to camera pose and 3D points coordinate regression heads. The model is learned using reprojection errors as loss combined with a hinge loss term to push points in front of the cameras. By using Adam [26] as optimizer along with gradient normalization, the authors show that their method has improved convergence properties compared to random initializations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.645, + 0.473, + 0.903 + ], + "angle": 0, + "content": "A major benefit of learning-based methods is their potential in generalizing to new data after being trained. This can be particularly beneficial to SfM problems since occlusions and missing measurements are common issues that make some scenes particularly challenging to reconstruct. In these cases, the learned model can act as a prior and help constrain the solution based on the data seen during training. However, most of the learning-based methods mentioned for 3D reconstruction or SfM require scene-specific optimization or training, which turns out to be particularly slow for large sequences. PoseDiffusion [44] achieves some degree of generalization to unseen scenes, but it is conditional on the categories and object-centric datasets seen during training. In [31] the authors actually show that their model can be trained on a large collection of scenes and then used for inference on unobserved scenes. However, without fine-tuning on these new scenes (which is time-consuming)" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.803, + 0.107 + ], + "angle": 0, + "content": "the model's accuracy is significantly reduced." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.108, + 0.895, + 0.363 + ], + "angle": 0, + "content": "In this paper we propose a graph attention network for initialization-free Structure-from-Motion that can be trained on multiple scenes and used for fast inference on new, unseen scenes. Similarly to [31], our network takes as input sparse measured image points, matched across multiple viewpoints, which are processed through a sequence of permutation-equivariant graph cross attention layers. The output of the graph cross attention layers is then processed by two regression heads, one for the 3D points and another for the camera poses. By using graph attention layers instead of linear equivariant maps as in [31], our model is able to better learn the implicit geometric primitives of SfM in the input data, leading to more expressiveness and better generalization to unseen sequences. Additionally, by not requiring time-consuming fine-tuning on unseen scenes, our model is able to provide fast inference, which can then be refined directly with BA with good convergence." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.364, + 0.874, + 0.379 + ], + "angle": 0, + "content": "The contributions of the paper can be summarized as:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.38, + 0.892, + 0.438 + ], + "angle": 0, + "content": "- We propose graph attention networks for initialization-free Structure-from-Motion that estimates camera parameters and 3D coordinates of 2D keypoints tracked across multiple views;" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.44, + 0.892, + 0.544 + ], + "angle": 0, + "content": "- The method takes advantage of the graph cross-attention layers, which are equivariant to permutation on the input data regarding order of views and points. We show that these layers can model more complex relations between input data and when combined with data augmentation result in significantly improved performance when compared to baseline methods;" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.545, + 0.892, + 0.605 + ], + "angle": 0, + "content": "- We evaluate the proposed learned method on unobserved scenes and show that it outperforms competing state-of-the-art learning methods at inference in terms of accuracy without the need of scene-specific model fine-tuning;" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.606, + 0.892, + 0.665 + ], + "angle": 0, + "content": "- We show that our method achieves competitive results when compared to state-of-the-art conventional Structure-from-Motion pipelines while having a significantly lower runtime." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.38, + 0.892, + 0.665 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.679, + 0.862, + 0.697 + ], + "angle": 0, + "content": "2. Graph Attention Network Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.892, + 0.75 + ], + "angle": 0, + "content": "Before introducing our proposed method, we will here briefly outline the graph attention networks that will be utilized - the GATv2 model [4] based on [43]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.886 + ], + "angle": 0, + "content": "The GATv2 model is a type of graph neural network (GNN) that carries out aggregation from neighboring nodes with a dynamic attention-based weighted average. The input to a GATv2 layer is a set of current node features \\(\\{\\mathbf{h}_i\\in \\mathbb{R}^d\\mid i\\in \\mathcal{V}\\}\\) along with a set of directed edges \\(\\mathcal{E}\\) defining the graph connectivity. The layer outputs a new set of node features \\(\\{\\mathbf{h}_i'\\in \\mathbb{R}^{d'}\\mid i\\in \\mathcal{V}\\}\\), by applying a single shared learned function on every node \\(h_i\\) together with its neighborhood \\(\\mathcal{N}_i = \\{j\\in \\mathcal{V}\\mid (j,i)\\in \\mathcal{E}\\}\\)." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.886, + 0.892, + 0.902 + ], + "angle": 0, + "content": "First, a scoring function \\(e:\\mathbb{R}^d\\times \\mathbb{R}^d\\to \\mathbb{R}\\) is applied on" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4809" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.136 + ], + "angle": 0, + "content": "all edges, by feeding the respective source and target node features as input to a shared 2-layer Multi-Layer Perceptron (MLP):" + }, + { + "type": "equation", + "bbox": [ + 0.122, + 0.144, + 0.469, + 0.163 + ], + "angle": 0, + "content": "\\[\ne \\left(\\mathbf {h} _ {i}, \\mathbf {h} _ {j}\\right) = \\mathbf {a} ^ {\\top} \\cdot \\text {L e a k y R e L U} \\left(\\mathbf {W} \\left[ \\mathbf {h} _ {i} \\| \\mathbf {h} _ {j} \\right]\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.169, + 0.469, + 0.217 + ], + "angle": 0, + "content": "where \\(\\mathbf{a} \\in \\mathbb{R}^{d'}\\) and \\(\\mathbf{W} \\in \\mathbb{R}^{d' \\times 2d}\\) are learned parameters, and \\(\\|\\cdot\\|\\) denotes vector concatenation. The attention scores are then normalized across all neighbors:" + }, + { + "type": "equation", + "bbox": [ + 0.08, + 0.223, + 0.469, + 0.27 + ], + "angle": 0, + "content": "\\[\n\\alpha_ {i j} = \\operatorname {s o f t m a x} _ {j} \\left(e \\left(\\mathbf {h} _ {i}, \\mathbf {h} _ {j}\\right)\\right) = \\frac {\\exp \\left(e \\left(\\mathbf {h} _ {i} , \\mathbf {h} _ {j}\\right)\\right)}{\\sum_ {j ^ {\\prime} \\in \\mathcal {N} _ {i}} \\exp \\left(e \\left(\\mathbf {h} _ {i} , \\mathbf {h} _ {j ^ {\\prime}}\\right)\\right)}, \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.272, + 0.469, + 0.302 + ], + "angle": 0, + "content": "and the layer is completed by carrying out a weighted average of linear projections of all source node features:" + }, + { + "type": "equation", + "bbox": [ + 0.184, + 0.309, + 0.469, + 0.334 + ], + "angle": 0, + "content": "\\[\n\\mathbf {h} _ {i} ^ {\\prime} = \\sum_ {j \\in \\mathcal {N} _ {i}} \\alpha_ {i j} \\cdot \\mathbf {W h} _ {j}. \\tag {5}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.341, + 0.168, + 0.356 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.366, + 0.469, + 0.546 + ], + "angle": 0, + "content": "We apply a graph attention network model to perform Structure-from-Motion on a desired scene based on its measured image point correspondences. The model then outputs a reconstruction, represented by all \\( m \\) camera matrices and all \\( n \\) scene points. Structure-from-Motion is in general a large and complex optimization problem, and it is not trivially addressed as a learning problem. Our architecture combines the power and expressivity of the attention mechanism, and exploits its inherent permutation equivariance in a meaningful way, while balancing expressivity with efficiency, resulting in a very limited computational and memory footprint considering the task at hand." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.548, + 0.469, + 0.697 + ], + "angle": 0, + "content": "The input data for a particular scene consists of a sparse set of measured image point correspondences (point tracks). To represent this data, we define a binary observability matrix \\(\\mathbf{O} \\in \\{0,1\\}^{m \\times n}\\), where \\(m\\) is the number of views and \\(n\\) is the number of scene points, and where \\(\\mathbf{O}_{ij} = 1\\) if and only if scene point \\(j\\) is observed in image \\(i\\). Furthermore, let \\(\\mathcal{P} = \\{\\mathbf{m}_{ij} \\in \\mathbb{R}^2 \\mid \\mathbf{O}_{ij} = 1\\}\\) be the collection of observed image point tracks, where \\(\\mathbf{m}_{ij}\\) is the (normalized) measured image point for the projection of scene point \\(j\\) in camera \\(i\\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.706, + 0.414, + 0.722 + ], + "angle": 0, + "content": "3.1. Graph Attention Network Architecture" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.73, + 0.469, + 0.805 + ], + "angle": 0, + "content": "In this section, we will outline our graph attention network architecture, starting by introducing our feature representation. Then we proceed to define update operations for different feature types, and finally define the entire network architecture based on these operations." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.823, + 0.469, + 0.868 + ], + "angle": 0, + "content": "Feature representation. Throughout the network architecture, we maintain and continuously update a set of features of various types1:" + }, + { + "type": "image", + "bbox": [ + 0.536, + 0.092, + 0.857, + 0.219 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.228, + 0.892, + 0.325 + ], + "angle": 0, + "content": "Figure 1. Illustration of the different types of features in the network architecture, for \\( m = 3 \\) cameras and \\( n = 6 \\) scene points. The projection features \\( \\mathcal{P} \\) are represented by a sparse vector-valued matrix, with its sparsity pattern determined by the point track measurements, while view features \\( \\mathcal{V} \\) and scene point features \\( S \\) are represented by dense vector-values column and row vectors. A single vector \\( \\mathbf{g} \\) holds global features." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.352, + 0.842, + 0.368 + ], + "angle": 0, + "content": "- Projection features, \\(\\mathcal{P} = \\{\\mathbf{p}_{ij}\\in \\mathbb{R}^{d_p}\\mid \\mathbf{O}_{ij} = 1\\}\\)" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.368, + 0.842, + 0.383 + ], + "angle": 0, + "content": "- View features, \\(\\mathcal{V} = \\{\\mathbf{v}_i\\in \\mathbb{R}^{d_v}\\mid i = 1,2,\\ldots ,m\\}\\)" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.383, + 0.883, + 0.399 + ], + "angle": 0, + "content": "- Scene point features, \\( S = \\{ \\mathbf{s}_j \\in \\mathbb{R}^{d_s} \\mid j = 1,2,\\dots,n \\} \\)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.399, + 0.687, + 0.413 + ], + "angle": 0, + "content": "- Global features, \\(\\mathbf{g} \\in \\mathbb{R}^{d_g}\\)." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.352, + 0.883, + 0.413 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.417, + 0.892, + 0.597 + ], + "angle": 0, + "content": "The projection features \\(\\mathbf{p}_{ij}\\) are feature vectors specific to every observed image point. In practice, these are bundled together and organized in a sparse vector-valued matrix, as illustrated by the large top-right matrix in Figure 1. The sparsity pattern of \\(\\mathcal{P}\\) will be fixed throughout the network and is determined by \\(\\mathbf{O}\\), which however depends on the scene. The view features \\(\\mathcal{V}\\) and scene point features \\(S\\), on their part, are organized in dense vector-valued column and row vectors, respectively, also illustrated in Figure 1. Finally, the global features \\(\\mathbf{g}\\), consist of a single globally shared feature vector, and is illustrated in the bottom-left corner of Figure 1." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.892, + 0.749 + ], + "angle": 0, + "content": "In order to define graph operations, we see every feature vector as being associated with a corresponding graph node. At this point, note that a simple approach would be to connect all nodes \\(\\mathcal{P},\\mathcal{V},\\mathcal{S}\\), and \\(\\{\\mathbf{g}\\}\\) in one unified graph, and directly apply a graph neural network with global weight sharing. Instead, since the nodes are semantically different, we consider these semantics when choosing the level of weight sharing, and even vary the feature dimension depending on the type of node. In practice, we construct different graphs for propagation between different types of nodes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Having defined the different feature types, we proceed to define corresponding update operations, which are repeatedly carried out throughout the network. In all pseudo-code, ReLU denotes to the rectified linear unit and LN denotes layer normalization [3]. Linear denotes a learned affine layer and FFN denotes a number of stacked Linear layers interleaved with ReLU activations. Subscripts may occur to emphasize feature dimensions. Note that all of these operations may be applied on multiple nodes at once, with shared parameters. The \\(+\\) notation implies node-wise addition." + }, + { + "type": "page_footnote", + "bbox": [ + 0.077, + 0.875, + 0.469, + 0.9 + ], + "angle": 0, + "content": "1For simplicity, we use a slight abuse of set notation here. If there are feature vector duplicates, they are still considered as separate elements." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "4810" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.212 + ], + "angle": 0, + "content": "Graph Cross-Attention. Procedure 1 is utilized for all feature aggregations throughout the network. It carries out cross-attention [42], attending to and propagating information from one set of input / source nodes \\(\\mathcal{H}_1\\) to another set of output / target nodes \\(\\widehat{\\mathcal{H}}_2\\). The previous target node features \\(\\mathcal{H}_2\\), if provided, will act as query features when computing attention scores. In the first few layers these may not be available, and initial zero-features are used instead." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.213, + 0.474, + 0.38 + ], + "angle": 0, + "content": "In our context, the source nodes and target nodes correspond to different feature types, possibly with different feature dimension. As the source and target nodes are disjoint, we may represent the connectivity by a directed bipartite graph. Furthermore, in our context this graph will often consist of a number of disconnected subgraphs. Procedure1 essentially acts as a wrapper around a GATv2 layer [4] (for which we use the PyTorch Geometric [11] implementation), while carrying out input normalization, and feature projections as necessary. We consistently use 4 attention heads for the GATv2 layers." + }, + { + "type": "code_caption", + "bbox": [ + 0.08, + 0.395, + 0.351, + 0.408 + ], + "angle": 0, + "content": "Procedure 1 GRAPHCROSSATTENTION" + }, + { + "type": "algorithm", + "bbox": [ + 0.078, + 0.412, + 0.361, + 0.614 + ], + "angle": 0, + "content": "Input: \\(\\mathcal{H}_1\\) Source node features. \nInput: \\(\\mathcal{H}_2\\) Previous target node features (optional). \nInput: \\(\\mathcal{E}_{\\mathcal{H}_1\\to \\mathcal{H}_2}\\) Set of edges from \\(\\mathcal{H}_1\\rightarrow \\mathcal{H}_2\\) . \nInput: \\(d_{1}\\) Source node feature dimension. \nInput: \\(d_{2}\\) Target node feature dimension. \nOutput: \\(\\widehat{\\mathcal{H}}_2\\) Updated target node features. \n1: \\(\\widehat{\\mathcal{H}}_1\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{H}_1))\\) \n2: if \\(\\mathcal{H}_2\\) provided then \n3: \\(\\widehat{\\mathcal{H}}_2\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{H}_2))\\) \n4: if \\(d_{1}\\neq d_{2}\\) then \n5: \\(\\widehat{\\mathcal{H}}_2\\gets \\mathrm{Linear}_{d_2\\to d_1}(\\widehat{\\mathcal{H}}_2)\\) \n6: else \n7: \\(\\widehat{\\mathcal{H}}_2\\gets \\mathrm{zero~features}\\vec{0}\\in \\mathbb{R}^{d_1}\\) \n8: \\(\\widehat{\\mathcal{H}}_2\\gets \\mathrm{GATv2Conv}(\\widehat{\\mathcal{H}}_1,\\widehat{\\mathcal{H}}_2,\\mathcal{E}_{\\mathcal{H}_1\\to \\mathcal{H}_2})\\) \n9: if \\(d_{1}\\neq d_{2}\\) then \n10: \\(\\widehat{\\mathcal{H}}_2\\gets \\mathrm{Linear}_{d_1\\to d_2}(\\widehat{\\mathcal{H}}_2)\\)" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.654, + 0.473, + 0.835 + ], + "angle": 0, + "content": "View & Scene Point Feature Update. View features and scene point features are updated by Procedure 2 and 3, respectively, entirely symmetrical to one another. A directed bipartite graph is constructed by taking \\(\\mathcal{P}\\) as source nodes, and \\(\\nu\\) (or \\(S\\)) as target nodes, and connecting every projection node with its corresponding view (or scene point) node, corresponding to rows (or columns) of \\(\\mathcal{P}\\). Graph cross-attention according to Procedure 1 is then carried out on the graph, and used as a residual mapping. This is followed by another residual mapping with a feed-forward network. Illustrations of these update operations are provided in Figures 2 and 3." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Global Feature Update. The global feature update, outlined in Procedure 4 is carried out in almost the same manner, but now aggregating from all view features \\(\\nu\\) and scene" + }, + { + "type": "image", + "bbox": [ + 0.543, + 0.089, + 0.852, + 0.232 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.239, + 0.895, + 0.283 + ], + "angle": 0, + "content": "Figure 2. Illustration of the update of a single view feature. All \\(\\mathcal{V}\\) features are updated based on their previous value and the corresponding rows of \\(\\mathcal{P}\\)." + }, + { + "type": "image", + "bbox": [ + 0.529, + 0.296, + 0.866, + 0.433 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.445, + 0.894, + 0.489 + ], + "angle": 0, + "content": "Figure 3. Illustration of the update of a single scene point feature. All \\( S \\) features are updated based on their previous value and the corresponding columns of \\( \\mathcal{P} \\)." + }, + { + "type": "code_caption", + "bbox": [ + 0.502, + 0.504, + 0.726, + 0.517 + ], + "angle": 0, + "content": "Procedure 2 UPDATEVIEWFEAT" + }, + { + "type": "algorithm", + "bbox": [ + 0.501, + 0.52, + 0.872, + 0.648 + ], + "angle": 0, + "content": "Input: \\(\\mathcal{P}\\) O Projection features \\(^+\\) observability matrix. \nInput: \\(\\nu\\) Previous view features (optional). \nInput: \\(d_p,d_v\\) Feature dimensions. \nOutput: \\(\\widehat{\\nu}\\) Updated view features. 1: \\(\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}}\\gets \\{(\\mathcal{P}_{ij},\\mathcal{V}_i)\\mid \\mathbf{O}_{ij} = 1,i = 1,2,\\ldots ,m\\}\\) 2: if \\(\\nu\\) provided then 3: \\(\\widehat{\\nu}\\gets \\mathcal{V} + \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{V},\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}},d_p,d_v)\\) 4: else 5: \\(\\widehat{\\nu}\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}},d_p,d_v)\\) 6: \\(\\widehat{\\nu}\\gets \\widehat{\\nu} +\\mathrm{FFN}(\\mathrm{ReLU}(\\mathrm{LN}(\\widehat{\\nu})))\\)" + }, + { + "type": "code_caption", + "bbox": [ + 0.502, + 0.667, + 0.779, + 0.68 + ], + "angle": 0, + "content": "Procedure 3 UPDATESCENEPOINTFEAT" + }, + { + "type": "algorithm", + "bbox": [ + 0.501, + 0.683, + 0.868, + 0.811 + ], + "angle": 0, + "content": "Input: \\(\\mathcal{P}\\) , O Projection features \\(^+\\) observability matrix. \nInput: S Previous scene point features (optional). \nInput: \\(d_p,d_s\\) Feature dimensions. \nOutput: \\(\\widehat{S}\\) Updated scene point features. 1: \\(\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}}\\gets \\{(\\mathcal{P}_{ij},\\mathcal{S}_i)\\mid \\mathbf{O}_{ij} = 1,i = 1,2,\\ldots ,m\\}\\) 2: if \\(\\mathcal{S}\\) provided then 3: \\(\\widehat{S}\\gets \\mathcal{S} + \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{S},\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}},d_p,d_s)\\) 4: else 5: \\(\\widehat{S}\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}},d_p,d_s)\\) 6: \\(\\widehat{S}\\gets \\widehat{S} +\\mathrm{FFN}(\\mathrm{ReLU}(\\mathrm{LN}(\\widehat{S})))\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.903 + ], + "angle": 0, + "content": "point features \\( S \\) instead of \\( \\mathcal{P} \\). This is carried out with two independent aggregations, with different learned parameters, and the sum of both aggregations constitute the residual mapping. Figure 4 provides an illustration for the update" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.514, + 0.957 + ], + "angle": 0, + "content": "4811" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.118, + 0.089, + 0.434, + 0.23 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.238, + 0.473, + 0.281 + ], + "angle": 0, + "content": "Figure 4. Illustration of the global feature update, where \\(\\mathbf{g}\\) is updated based on its previous value, together with an aggregation of all \\(\\mathcal{V}\\) and \\(S\\) features." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.309, + 0.15, + 0.324 + ], + "angle": 0, + "content": "operation." + }, + { + "type": "code_caption", + "bbox": [ + 0.081, + 0.34, + 0.324, + 0.352 + ], + "angle": 0, + "content": "Procedure 4 UPDATEGLOBALFEAT" + }, + { + "type": "text", + "bbox": [ + 0.08, + 0.356, + 0.218, + 0.367 + ], + "angle": 0, + "content": "Input: \\(\\nu\\) View features." + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.369, + 0.252, + 0.38 + ], + "angle": 0, + "content": "Input: \\(S\\) Scene point features." + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.381, + 0.325, + 0.392 + ], + "angle": 0, + "content": "Input: g Previous global features (optional)." + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.393, + 0.293, + 0.404 + ], + "angle": 0, + "content": "Input: \\(d_v, d_s, d_g\\) Feature dimensions." + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.405, + 0.278, + 0.416 + ], + "angle": 0, + "content": "Output: \\(\\widehat{\\mathbf{g}}\\) Updated global features." + }, + { + "type": "text", + "bbox": [ + 0.086, + 0.416, + 0.311, + 0.429 + ], + "angle": 0, + "content": "1: \\(\\mathcal{E}_{\\mathcal{V}\\to \\mathbf{g}}\\gets \\{(\\mathcal{V}_i,\\mathbf{g})\\mid i = 1,2,\\ldots ,m\\}\\)" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.429, + 0.309, + 0.44 + ], + "angle": 0, + "content": "2: \\(\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}}\\gets \\left\\{(\\mathcal{S}_j,\\mathbf{g})\\mid j = 1,2,\\ldots ,n\\right\\}\\)" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.441, + 0.202, + 0.451 + ], + "angle": 0, + "content": "3: if \\(\\mathbf{g}\\) provided then" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.452, + 0.434, + 0.465 + ], + "angle": 0, + "content": "4: \\(\\widehat{\\mathbf{g}}_v\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{V},\\{\\mathbf{g}\\},\\mathcal{E}_{\\mathcal{V}\\to \\mathbf{g}},d_v,d_g)\\)" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.465, + 0.432, + 0.477 + ], + "angle": 0, + "content": "5: \\(\\widehat{\\mathbf{g}}_s\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{S},\\{\\mathbf{g}\\},\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}},d_s,d_g)\\)" + }, + { + "type": "text", + "bbox": [ + 0.086, + 0.477, + 0.225, + 0.488 + ], + "angle": 0, + "content": "6: \\(\\widehat{\\mathbf{g}}\\gets \\mathbf{g} + \\widehat{\\mathbf{g}}_v + \\widehat{\\mathbf{g}}_s\\)" + }, + { + "type": "text", + "bbox": [ + 0.086, + 0.489, + 0.125, + 0.498 + ], + "angle": 0, + "content": "7: else" + }, + { + "type": "text", + "bbox": [ + 0.086, + 0.5, + 0.423, + 0.512 + ], + "angle": 0, + "content": "8: \\(\\widehat{\\mathbf{g}}_v\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{V}, - ,\\mathcal{E}_{\\mathcal{V}\\to \\mathbf{g}},d_v,d_g)\\)" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.512, + 0.431, + 0.524 + ], + "angle": 0, + "content": "9: \\(\\widehat{\\mathbf{g}}_s\\gets +\\mathrm{GRAPHCROSSATTENTION}(\\mathcal{S}, - ,\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}},d_s,d_g)\\)" + }, + { + "type": "text", + "bbox": [ + 0.084, + 0.524, + 0.2, + 0.535 + ], + "angle": 0, + "content": "10: \\(\\widehat{\\mathbf{g}}\\gets \\widehat{\\mathbf{g}}_v + \\widehat{\\mathbf{g}}_s\\)" + }, + { + "type": "text", + "bbox": [ + 0.082, + 0.537, + 0.273, + 0.55 + ], + "angle": 0, + "content": "11: \\(\\widehat{\\mathbf{g}}\\gets \\widehat{\\mathbf{g}} +\\mathrm{FFN}(\\mathrm{ReLU}(\\mathrm{LN}(\\widehat{\\mathbf{g}})))\\)" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.356, + 0.434, + 0.55 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.593, + 0.473, + 0.789 + ], + "angle": 0, + "content": "Projection Feature Update. The projection features are updated according to Procedure 5. No aggregation is involved during this step. Instead, at every projection node the corresponding \\(\\nu\\), \\(S\\) and \\(\\mathbf{g}\\) features are all collected along with the current projection features \\(\\mathcal{P}\\), as illustrated in Figure 5. Each of these sources then undergoes a ReLU activation and normalization with LN, before being concatenated. Note that the initial projection features \\(\\mathcal{P}_0\\) are typically also added to the input, and in this case they are simply concatenated to the previous projection features before the procedure is called. Finally, a residual mapping is applied, by feeding the concatenated features to a shared feed-forward network." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.473, + 0.904 + ], + "angle": 0, + "content": "Entire Network Architecture. Now we have all the pieces to define the complete network architecture, which is outlined in Procedure 6. The structure is straightforward: 1) UPDATEVIEWFEAT and UPDATESCENEPOINTFEAT (Procedures 2 and 3) are called to aggregate projection features. 2) UPDATEGLOBALFEAT (Procedure 4) is called to aggre" + }, + { + "type": "image", + "bbox": [ + 0.53, + 0.088, + 0.865, + 0.238 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.245, + 0.895, + 0.302 + ], + "angle": 0, + "content": "Figure 5. Illustration of the update of a single projection feature. All \\(\\mathcal{P}\\) features are updated based on their previous value, as well as initial projection features \\(\\mathcal{P}_0\\), the global feature \\(\\mathbf{g}\\), and the corresponding \\(\\mathcal{V}\\) and \\(S\\) features." + }, + { + "type": "code_caption", + "bbox": [ + 0.502, + 0.318, + 0.722, + 0.332 + ], + "angle": 0, + "content": "Procedure 5 UPDATEPROJFEAT" + }, + { + "type": "text", + "bbox": [ + 0.503, + 0.334, + 0.716, + 0.347 + ], + "angle": 0, + "content": "Input: \\(\\mathcal{P}\\) Previous projection features." + }, + { + "type": "text", + "bbox": [ + 0.503, + 0.348, + 0.641, + 0.358 + ], + "angle": 0, + "content": "Input: \\(\\nu\\) View features." + }, + { + "type": "text", + "bbox": [ + 0.503, + 0.359, + 0.674, + 0.37 + ], + "angle": 0, + "content": "Input: \\(S\\) Scene point features." + }, + { + "type": "text", + "bbox": [ + 0.503, + 0.371, + 0.649, + 0.382 + ], + "angle": 0, + "content": "Input: g Global features." + }, + { + "type": "text", + "bbox": [ + 0.503, + 0.383, + 0.774, + 0.397 + ], + "angle": 0, + "content": "Input: \\(d_p^{in}, d_v, d_s, d_g, d_p^{out}\\) Feature dimensions." + }, + { + "type": "text", + "bbox": [ + 0.503, + 0.398, + 0.725, + 0.41 + ], + "angle": 0, + "content": "Output: \\(\\hat{\\mathcal{P}}\\) Updated projection features." + }, + { + "type": "text", + "bbox": [ + 0.508, + 0.411, + 0.892, + 0.469 + ], + "angle": 0, + "content": "1: \\(\\widehat{\\mathcal{P}}\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{V}))\\parallel \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{S}))\\) \\(\\| \\operatorname {ReLU}(\\operatorname {LN}(\\mathbf{g}))\\| \\operatorname {ReLU}(\\operatorname {LN}(\\mathcal{P}))\\) // View, scene point, and global features are implicitly distributed to their corresponding projection features before feature concatenation." + }, + { + "type": "text", + "bbox": [ + 0.508, + 0.47, + 0.763, + 0.488 + ], + "angle": 0, + "content": "2: \\(\\widehat{\\mathcal{P}}\\gets \\mathcal{P} + \\mathrm{FFN}_{(d_v + d_s + d_g + d_p^{in})\\to d_p^{out}}(\\widehat{\\mathcal{P}})\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.519, + 0.895, + 0.822 + ], + "angle": 0, + "content": "gate the resulting features further, to a single global feature vector. 3) UPDATEPROJFEAT (Procedure 5) is called in order to again distribute the aggregated information across the projection features. These steps are repeated \\( L \\) times, where we refer to \\( L \\) as the number of layers. Then, a final call to UPDATEVIEWFEAT and UPDATESCENEPOINTFEAT is carried out, and the resulting view and scene point features are further processed by two corresponding regression heads, consisting of shared 3-layer feed-forward networks (FFN) with hidden neurons of the same dimension as the input (\\( d_v \\) or \\( d_s \\)). The scene point head simply outputs the 3 coordinates of every estimated scene point. For Euclidean reconstruction, the view head outputs the 3 coordinates of the location of the camera center, together with a unit-norm quaternion representing its orientation. For projective reconstruction, all 12 camera matrix elements are regressed, followed by a normalization in the same manner as [31]. Except for the regression heads, we use 1-layer FFNs throughout the network, which in general seemed slightly easier to train." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.832, + 0.646, + 0.847 + ], + "angle": 0, + "content": "3.2. Loss Function" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.895, + 0.903 + ], + "angle": 0, + "content": "The network is trained using the Adam optimizer, and as loss function we use the (non-squared) reprojection error, averaged over all observed image points. To handle negative" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4812" + } + ], + [ + { + "type": "code_caption", + "bbox": [ + 0.081, + 0.092, + 0.333, + 0.104 + ], + "angle": 0, + "content": "Procedure 6 GRAPHATTENTIONSFM" + }, + { + "type": "algorithm", + "bbox": [ + 0.08, + 0.108, + 0.47, + 0.392 + ], + "angle": 0, + "content": "Input: \\(\\mathcal{M}\\) Image point tracks, normalized. \nInput: O Observability matrix. \nInput: \\(d_p,d_v,d_s,d_g\\) Feature dimensions. \nInput: L Number of layers. \nOutput: V Estimated camera parameters. \nOutput: S Estimated scene points. \n1: \\(\\mathcal{P}_0\\gets \\mathrm{Linear}_{2\\to 2}(\\mathcal{M})\\) // Initial projection features: linear embedding of image points. \n2: \\(\\mathcal{V}\\gets\\) UPDATEVIEWFEAT \\((\\mathcal{P}_0,\\mathbf{O}, - ,2,d_v)\\) \n3: \\(\\mathcal{S}\\gets\\) UPDATESCENEPOINTFEAT \\((\\mathcal{P}_0,\\mathbf{O}, - ,2,d_s)\\) \n4: \\(\\mathbf{g}\\gets\\) UPDATEGLOBALFEAT \\((\\mathcal{V},\\mathcal{S}, - ,d_v,d_s,d_g)\\) \n5: for \\(l = 1,2,\\dots ,L\\) do \n6: if \\(l = 1\\) then \n7: \\(\\mathcal{P}\\gets\\) UPDATEPROJFEAT \\((\\mathcal{P}_0,\\mathcal{V},\\mathcal{S},\\mathbf{g},2,d_v,d_s,d_g,d_p)\\) \n8: else \n9: \\(\\mathcal{P}\\gets\\) UPDATEPROJFEAT \\((\\mathcal{P}\\| \\mathcal{P}_0,\\mathcal{V},\\mathcal{S},\\mathbf{g},\\) \\(d_p + 2,d_v,d_s,d_g,d_p)\\) \n10: \\(\\mathcal{V}\\gets\\) UPDATEVIEWFEAT \\((\\mathcal{P},\\mathbf{O},\\mathcal{V},d_p,d_v)\\) \n12: \\(\\mathcal{S}\\gets\\) UPDATESCENEPOINTFEAT \\((\\mathcal{P},\\mathbf{O},\\mathcal{S},d_p,d_s)\\) \n13: if \\(l < L\\) then \n14: \\(\\mathbf{g}\\gets\\) UPDATEGLOBALFEAT \\((\\mathcal{V},\\mathcal{S},\\mathbf{g},d_v,d_s,d_g)\\) \n15: \\(\\{\\mathbf{P}_i\\} \\gets \\mathrm{FFN}(\\mathrm{ReLU}(\\mathcal{V}))\\) // Camera regression head \n16: \\(\\{\\mathbf{X}_j\\} \\gets \\mathrm{FFN}(\\mathrm{ReLU}(\\mathcal{S}))\\) // Scene point regression head" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.422, + 0.47, + 0.496 + ], + "angle": 0, + "content": "depths and overcome the singularity at the principal plane, we substitute the reprojection error with minus the depth in the loss function for any projection with depth smaller than a threshold \\( h = 1e - 4 \\). We also apply gradient normalization in the same manner as [31]." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.509, + 0.264, + 0.525 + ], + "angle": 0, + "content": "3.3. Data Augmentation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.533, + 0.469, + 0.684 + ], + "angle": 0, + "content": "For Euclidean reconstruction, where the image points are normalized using the intrinsic camera parameters, and therefore geometrically interpretable, we experiment with augmenting the training scenes with slightly transformed variations. While the scene points remain fixed, each camera is randomly rotated about its center, first by a uniformly sampled angle \\(\\alpha \\in [-15, 15]\\) about the principal axis, followed by a uniformly sampled angle \\(\\gamma \\in [-20, 20]\\) about an axis orthogonal to the principal axis with a random direction. The image points are transformed accordingly." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.696, + 0.315, + 0.712 + ], + "angle": 0, + "content": "3.4. Artificial Outlier Injection" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.47, + 0.901 + ], + "angle": 0, + "content": "We also consider the presence of measurement outliers, by artificially corrupting the data. This is done by: 1) Selecting a subset of the 2D keypoint measurements to be replaced by artificial outliers. 2) For each view, replace all measurements marked to be outliers with random samples from a bivariate normal distribution, which is fit to all remaining (inlier) points. For step 1), we carefully select points for outlier injection such that we avoid getting any scene points visible in \\(< 2\\) views or any views with \\(< 8\\) scene points visible, if regarding only the inlier projections. In the supplementary material, the details are given on how this is achieved. Note that while the network input is corrupted by outlier injec" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.121 + ], + "angle": 0, + "content": "tion, the uncorrupted data is still used as learning targets for the loss function." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.137, + 0.587, + 0.152 + ], + "angle": 0, + "content": "4. Results" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.163, + 0.691, + 0.179 + ], + "angle": 0, + "content": "4.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.186, + 0.892, + 0.367 + ], + "angle": 0, + "content": "We take a particular interest in Euclidean reconstruction, due to the relevance of metric reconstructions for photogrammetry applications. Furthermore, we focus mainly on the task of learning and generalizing from a set of training scenes, due to the great potential in having a fast learned model acquire reconstructions of completely novel scenes. We use the DPESFM method of Moran et al. [31] as a baseline, as they have presented experiments on precisely this. To this end, we also use Olsson's dataset [33] (together with the VGG dataset [12] for additional projective reconstruction experiments in the supplement), and we use the same random partition of 10 test scenes and 3 validation scenes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.368, + 0.893, + 0.626 + ], + "angle": 0, + "content": "We base our implementation on that of [31], implemented in PyTorch [34], but replace the network architecture with our proposed GRAPHATTENTIONSFM network, implemented using GATv2Conv layers [4] from PyTorch Geometric [11]. The implementation details are in general consistent with [31], for more details see the supplement. The DPESFM results reproduced by us are obtained by running the method of [31] with our code base, with the hyperparameters published on the official GitHub repository of the method [30]. For our model, we use \\( L = 12 \\) layers and feature dimensions \\( d_{p} = 32 \\), \\( d_{v} = 1024 \\), \\( d_{s} = 64 \\), \\( d_{g} = 2048 \\), which corresponds to 145M parameters. By using small dimensions for the projection features and scene point features the otherwise high memory consumption is significantly reduced. Hyper-parameters have been chosen based on the performance on the validation data, but without any rigorous hyper-parameter tuning." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.636, + 0.857, + 0.65 + ], + "angle": 0, + "content": "4.2. Euclidean Reconstruction of Novel Scenes" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.893, + 0.901 + ], + "angle": 0, + "content": "In Table 1, we report the Euclidean reconstruction results of our method, when applied on novel test scenes, and measure the performance by reprojection errors, as well as rotation and translation errors for the estimated camera poses. For calculating the latter, the predicted and ground truth poses are first aligned to a common reference frame, as described in Section C in the supplement. The results of DPESFM as reported in [31] can be seen in parentheses, when available, but we also retrain their model and incorporate further results of the model, not reported in [31], in particular results without bundle adjustment, and additional metrics to reprojection errors. Experiments are carried out both with and without data augmentation with random rotational cameras perturbations, as described in Section 3.3, and the columns are partitioned accordingly. Consistently with [31], Inference refers to the network output followed" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4813" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.078, + 0.088, + 0.891, + 0.507 + ], + "angle": 0, + "content": "
Without data augmentationWith data augmentationColmap
InferenceInference + BAInferenceInference + BA
OursDPESFMOursDPESFMOursDPESFMOursDPESFM
Reprojection error (px)Alcatraz Courtyard68.4168.501.700.81 (0.82)36.0192.370.810.920.81
Alcatraz Water Tower36.3050.471.051.13 (0.55)87.672831.940.8810.160.55
Drinking Fountain Somewhere in Zurich36.0245.870.550.31 (7.21)219.75234.900.316.730.31
Nijo Castle Gate65.7164.530.730.73 (5.81)61.4168.190.880.890.73
Porta San Donato Bologna74.3294.260.740.74 (1.10)52.1584.460.760.750.75
Round Church Cambridge61.1855.510.390.39 (0.50)29.8059.540.391.490.39
Smolny Cathedral St Petersburg156.16120.850.810.81 (15.15)85.3887.810.810.810.81
Some Cathedral in Barcelona150.01146.1010.4212.71 (21.46)125.68687.830.8916.770.89
Sri Veeramakaliamman Singapore121.02157.392.1916.87 (16.92)83.50166.682.139.300.71
Yueh Hai Ching Temple Singapore37.4652.590.650.65 (1.16)25.6051.350.650.730.65
Average80.6685.611.923.52 (7.07)80.69436.510.854.860.66
Rotation error (deg)Alcatraz Courtyard10.10213.2012.6070.0356.09310.9460.0380.0300.043
Alcatraz Water Tower10.63711.0530.4990.76411.50110.6410.69919.3510.228
Drinking Fountain Somewhere in Zurich15.84616.0140.0030.00115.41515.7040.00122.7590.007
Nijo Castle Gate16.75110.5460.0620.06217.34720.0320.0380.0360.064
Porta San Donato Bologna23.83924.1200.0950.09418.41125.0040.0940.0940.099
Round Church Cambridge18.90614.4730.0290.02610.29518.6850.0291.0860.035
Smolny Cathedral St Petersburg19.38717.9710.0230.02211.66214.3800.0230.0190.029
Some Cathedral in Barcelona27.27030.47110.00920.05027.90829.1190.02047.8920.025
Sri Veeramakaliamman Singapore28.27536.9030.5494.87123.70236.1760.4572.7590.169
Yueh Hai Ching Temple Singapore15.73322.7060.0380.0389.51521.5610.0380.0380.043
Average18.67519.7461.3912.59615.18520.2250.1449.4060.074
Translation error (m)Alcatraz Courtyard4.824.931.090.012.735.740.010.010.01
Alcatraz Water Tower8.667.350.310.447.537.770.419.050.12
Drinking Fountain Somewhere in Zurich4.444.440.000.004.454.460.001.380.00
Nijo Castle Gate5.073.080.010.015.676.950.010.010.01
Porta San Donato Bologna9.5010.720.050.054.8010.480.050.050.05
Round Church Cambridge8.947.190.010.015.289.000.010.560.01
Smolny Cathedral St Petersburg2.702.430.010.012.332.520.010.010.01
Some Cathedral in Barcelona12.6412.693.226.3812.3212.660.0111.930.01
Sri Veeramakaliamman Singapore4.944.900.161.324.934.900.140.770.04
Yueh Hai Ching Temple Singapore4.124.270.010.012.444.280.010.010.01
Average6.586.200.490.825.256.880.072.380.03
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.518, + 0.893, + 0.561 + ], + "angle": 0, + "content": "Table 1. Results of Euclidean reconstruction of novel test scenes, with and without data augmentation. The results of DPESFM [31] have been acquired by us training the model, along with the results reported by [31] in parentheses, if available. The result of Colmap, as reported by [31], is also added for reference." + }, + { + "type": "table", + "bbox": [ + 0.085, + 0.583, + 0.472, + 0.719 + ], + "angle": 0, + "content": "
SceneInfer.BAColmap
Alcatraz Courtyard0.2445.54286
Alcatraz Water Tower0.1331.11130
Drinking Fountain Somewhere In Zurich0.061.9816
Nijo Castle Gate0.093.9721
Porta San Donato Bologna0.1827.02170
Round Church Cambridge0.4356.47229
Smolny Cathedral St Petersburg0.4986.09516
Some Cathedral In Barcelona0.2447.05451
Sri Veeramakaliamman Singapore0.63115.80583
Yueh Hai Ching Temple Singapore0.088.54106
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.729, + 0.47, + 0.758 + ], + "angle": 0, + "content": "Table 2. Runtime (s) of our method for Euclidean reconstruction on test scenes, in comparison with Colmap (measured by [31])." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.903 + ], + "angle": 0, + "content": "by a computationally cheap triangulation and Inference \\( + \\) BA refers to the network output followed by bundle adjustment, which is carried out in the same manner as [31], using the Ceres solver [1]. Moran et al. [31] also performed experiments with fine-tuning the network parameters on the test scenes. In contrast, we advocate against this, since this approach is relatively costly, and one might as well acquire" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.586, + 0.892, + 0.648 + ], + "angle": 0, + "content": "high-quality reconstructions from traditional SfM pipelines such as Colmap, in similar execution time. Nevertheless, the supplementary material includes such experiments, for completeness." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.893, + 0.903 + ], + "angle": 0, + "content": "Without data augmentation, there is no clear difference between the Inference results of both methods. Neither reconstruction is good, and it is not so meaningful to compare minor differences in the metrics under these circumstances. In particular, calculating rotation and translation errors requires aligning the predicted and ground truth camera poses in a common reference frame, as described in Section C in the supplement, and when the predicted configuration of camera poses is not very consistent with the ground truth, determining this alignment itself can be sensitive. In all other scenarios, we outperform DPESFM, and when using both data augmentation and applying bundle adjustment, the solutions we acquire for the novel test scenes are in general very good. In terms of reprojection error and translation error, we match the performance of Colmap for almost every test scene, leading to an average reprojection" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "4814" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.152 + ], + "angle": 0, + "content": "error of 0.85 (vs 0.66) px, and an average translation error of 0.07 (vs 0.03) m. In terms of rotation error, the error is actually lower than Colmap's for 8 out of 10 scenes, but the average error is slightly larger: 0.144 (vs 0.074) degrees." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.163, + 0.317, + 0.179 + ], + "angle": 0, + "content": "4.3. Artificial Outlier Injection" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.186, + 0.47, + 0.231 + ], + "angle": 0, + "content": "In Table 3 we present additional results where, on top of data augmentation (see Section 3.3), we also apply artificial outlier injection during training according to Section 3.4." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.232, + 0.471, + 0.518 + ], + "angle": 0, + "content": "We evaluate inference of the model in two settings: 1) Applied on the uncorrupted outlier-free test scenes as is. 2) Applied to the test scenes followed by random injection of \\(10\\%\\), in the same manner as during training2. One can immediately observe significantly reduced reprojection errors for our model, suggesting that the outlier injection during training has a regularizing effect. Beyond that, this experiment is intended to serve as a teaser for the utility and promise of learning-based methods for SfM. Constant challenges such as the presence of outliers may not be as big of a challenge for learning-based as for conventional methods, and the phenomenon may even be exploited to develop effective training strategies. In fact, for any real-world scenario, it is crucial for learning-based methods applied on image point correspondences to be resilient to outliers, as we do not have the luxury of facing high-quality curated data such as Olsson's [33] in the wild. Note that it should be possible to apply bundle adjustment on the corrupted test data as well, when combined with a robust loss function." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.519, + 0.47, + 0.61 + ], + "angle": 0, + "content": "Similarly as for the data augmentation, we note that DPESFM appears to struggle with the presence of outliers during training, and its performance on the test scenes at inference is not very good. It is very probable that the nonlinear attention layers make our model more powerful and expressive than DPESFM." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.62, + 0.258, + 0.635 + ], + "angle": 0, + "content": "4.4. Additional Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.643, + 0.47, + 0.704 + ], + "angle": 0, + "content": "In the supplementary material we provide additional results on projective reconstruction, as well as single-scene optimization, for completeness. We also include statistics of the number of views and scene points for each scene." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.719, + 0.196, + 0.735 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.744, + 0.47, + 0.866 + ], + "angle": 0, + "content": "With this paper we have added to the research direction of learned initialization-free Structure-from-Motion by introducing a novel and expressive graph attention network outperforming previous learning-based methods for Euclidean reconstruction of novel scenes. When succeeded by bundle adjustment, we are able to reconstruct novel test scenes to perfection or of very decent precision, at a speedup of about \\(5 - 10 \\times\\) compared to Colmap. Moreover, we illustrate great" + }, + { + "type": "table", + "bbox": [ + 0.501, + 0.088, + 0.888, + 0.332 + ], + "angle": 0, + "content": "
UncorruptedOutlier-injected
OursDPESFMOursDPESFM
Alcatraz Courtyard47.7485.8152.9994.24
Alcatraz Water Tower35.9672.8437.8983.55
Drinking Fountain \nSomewhere in Zurich52.081012.1446.651453.31
Nijo Castle Gate46.4872.9962.52126.18
Porta San Donato \nBologna53.1288.0265.0894.72
Round Church \nCambridge36.0963.7248.6390.63
Smolny Cathedral St \nPetersburg47.2891.0359.5298.05
Some Cathedral in \nBarcelona109.86397.75123.75462.28
Sri Veeramakali-\namman Singapore63.60169.6370.90146.98
Yueh Hai Ching \nTemple Singapore26.8351.4136.6957.59
Average51.91210.5360.46270.75
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.341, + 0.892, + 0.397 + ], + "angle": 0, + "content": "Table 3. Reprojection errors of Euclidean reconstruction of novel test scenes, with model trained with data augmentation as well as artificial outlier injection. The results of DPESFM [31] have been acquired by us training the model." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.424, + 0.892, + 0.484 + ], + "angle": 0, + "content": "potential in coping with the presence of outliers, and even show artificial outlier injection to provide an effective regularizing training strategy, combined with data augmentation by random rotational camera perturbations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.485, + 0.893, + 0.711 + ], + "angle": 0, + "content": "For future work, it could definitely be promising to train on larger datasets, since model generalization is still a challenge. While the proposed model does not require fine-tuning, and thus is much faster to execute than previous work, it still relies on bundle adjustment to acquire a good reconstruction, which constitutes the computational bottleneck. Exploring alternative formulations where the network regresses relative camera poses is also an interesting direction, as the current absolute pose prediction may be a weakness due to the reconstruction ambiguity up to a similarity transformation. Other possible research directions include unrolling the architecture to multiple learned iterations / refinement steps, extensions to non-rigid Structure-from-Motion, and incorporating modern learned image matching pipelines such as [5, 6, 40] in an end-to-end fashion." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.729, + 0.892, + 0.895 + ], + "angle": 0, + "content": "Acknowledgements The work was supported by the Wallenberg AI, Autonomous Systems and Software Program (WASP) funded by the Knut and Alice Wallenberg Foundation, and the Swedish Research Council grants no. 2016-04445, 2018-05375, and 2023-05341. Computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) at Chalmers Centre for Computational Science and Engineering (C3SE) and National Supercomputer Centre (NSC) Berzelius at Linköping University partially funded by the Swedish Research Council through grant no. 2022-06725." + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.875, + 0.47, + 0.901 + ], + "angle": 0, + "content": "2Yet, during evaluation, we use all true measurements as ground truth targets when calculating reprojection errors, even in the corrupted case." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4815" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.468, + 0.143 + ], + "angle": 0, + "content": "[1] Sameer Agarwal, Keir Mierle, and Others. 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SfM is a classic computer vision problem that is solved though iterative minimization of reprojection errors, referred to as Bundle Adjustment (BA), starting from a good initialization. In order to obtain a good enough initialization to BA, conventional methods rely on a sequence of sub-problems (such as pairwise pose estimation, pose averaging or triangulation) which provide an initial solution that can then be refined using BA. In this work we replace these sub-problems by learning a model that takes as input the 2D keypoints detected across multiple views, and outputs the corresponding camera poses and 3D keypoint coordinates. Our model takes advantage of graph neural networks to learn SfM-specific primitives, and we show that it can be used for fast inference of the reconstruction for new and unseen sequences. The experimental results show that the proposed model outperforms competing learning-based methods, and challenges COLMAP while having lower runtime. Our code is available at: https://github.com/lucasbrynte/gasfm/. + +# 1. Introduction + +Structure-from-Motion (SfM) is a classic and still relevant problem in computer vision. The goal of SfM is to estimate camera poses and 3D coordinates of keypoints detected across multiple images, and can be formulated as an optimization over $m$ camera matrices $\{\mathbf{P}_i\}$ , $i = 1, \dots, m$ and $n$ 3D points $\{\mathbf{X}_j\}$ , $j = 1, \dots, n$ of the form + +$$ +\underset {\left\{\mathbf {P} _ {i} \right\}, \left\{\mathbf {X} _ {j} \right\}} {\text {m i n i m i z e}} \quad \sum_ {i j} r \left(\mathbf {m} _ {i j}, \mathbf {z} _ {i j}\right) \tag {1} +$$ + +$$ +\text {s u b j e c t} \quad \mathbf {z} _ {i j} = \mathbf {P} _ {i} \bar {\mathbf {X}} _ {j}, \forall i, j +$$ + +where $\mathbf{m}_{ij}$ holds the 2D coordinates of the $j^{\mathrm{th}}$ keypoint in the $i^{\mathrm{th}}$ image. The loss in (1) is generally chosen as the reprojection error + +$$ +r \left(\mathbf {m} _ {i j}, \mathbf {z} _ {i j}\right) = \left| \left| \mathbf {m} _ {i j} - \Pi \left(\mathbf {z} _ {i j}\right) \right| \right| ^ {2} \tag {2} +$$ + +where $\Pi (\mathbf{x}) = \left(\frac{x_1}{x_3},\frac{x_2}{x_3}\right)$ , and the nonlinear least squares problem (1), referred to as Bundle Adjustment (BA) [15], can be solved iteratively using second-order methods like Levenberg-Marquardt [15, 41]. Given the sparsity of the problem, sparse computation methods [27] can be used in order to increase the efficiency of the optimization, allowing BA to be used even for scenes with a large number of views or points. However, it is widely known that BA is highly non-convex and tends to converge to the nearest local minimum when not initialized close to the globally optimal solution. As a consequence, BA is typically the last step of a reconstruction pipeline, preceding global SfM methods such as [9, 10, 20, 25], or incremental SfM methods such as [2, 37, 38] that solve a sequence of subproblems like pairwise pose estimation, pose averaging, triangulation or camera resection [13, 15, 22, 32]. A different approach consists of projective factorization methods [8, 17, 18, 28, 39, 48] which factorize the $2m\times n$ measurement matrix into two rank four matrices corresponding to the camera matrices and 3D points (in homogeneous coordinates). In particular, works like [17, 18, 48] allow initialization-free SfM given their wide basin of convergence, meaning that their methods can be initialized with random camera poses and still converge with a high rate of success to the desired global minimum. Even though these methods have been improving in terms of accuracy and robustness to missing data, factorization-based methods require the input data to be almost completely free of outliers which unfortunately cannot be guaranteed in most real world sequences or datasets, and hence severely compromises the usability of these methods. + +A common challenge with all these approaches to solve SfM is their scalability as the number of views and keypoints increase. Incremental SfM tries to tackle this issue by starting with a subset of the views, estimate its reconstruction and incrementally adding more views. Some factorization-based methods can also take advantage of the same sparse computation methods used in BA, which significantly improves their ability to scale with sequence size. While this allows to reconstruct scenes with thousands of views and millions of points, it can still take hours to recover the reconstruction of a single scene. + +More recently, deep learning methods for 3D reconstruction and SfM have been proposed [7, 29, 31, 35, 44-47]. Given their increased complexity, these models are able to learn complex relations between the input data, outperforming conventional methods and achieving state-of-the-art results in 3D reconstruction and novel view synthesis when the camera pose and calibration are known [7, 29, 46]. Works such as [31, 46, 47] tackle SfM with deep learning models which different degrees of success. + +In DeepSfM [46] the authors propose an end-to-end approach to estimate camera pose and a dense depth map of a target view from multiple source views. Their method estimates a feature map for each of the source views, which are then combined with the feature map of the target view in order to estimate pose and depth cost volumes. These cost volumes are then fed to two heads that estimate the camera pose and depth map of the target view. In PoseDiffusion [44], a probabilistic diffusion framework is proposed to mirror the iterations of bundle adjustment, allowing it to incorporate geometric priors into the problem. The model is trained on object-centric scenes and it is shown that it can generalize to unseen scenes without further training. + +In [31], which is the closest work to ours, the authors have pursued an approach similar to projective factorization, taking as input the 2D keypoints tracked along multiple views. These 2D point tracks are processed by a number of linear permutation-equivariant layers, i.e. layers such that a permutation on the rows and/or columns of the input tensor results in the same permutation on the output. The output of these layers is then fed to camera pose and 3D points coordinate regression heads. The model is learned using reprojection errors as loss combined with a hinge loss term to push points in front of the cameras. By using Adam [26] as optimizer along with gradient normalization, the authors show that their method has improved convergence properties compared to random initializations. + +A major benefit of learning-based methods is their potential in generalizing to new data after being trained. This can be particularly beneficial to SfM problems since occlusions and missing measurements are common issues that make some scenes particularly challenging to reconstruct. In these cases, the learned model can act as a prior and help constrain the solution based on the data seen during training. However, most of the learning-based methods mentioned for 3D reconstruction or SfM require scene-specific optimization or training, which turns out to be particularly slow for large sequences. PoseDiffusion [44] achieves some degree of generalization to unseen scenes, but it is conditional on the categories and object-centric datasets seen during training. In [31] the authors actually show that their model can be trained on a large collection of scenes and then used for inference on unobserved scenes. However, without fine-tuning on these new scenes (which is time-consuming) + +the model's accuracy is significantly reduced. + +In this paper we propose a graph attention network for initialization-free Structure-from-Motion that can be trained on multiple scenes and used for fast inference on new, unseen scenes. Similarly to [31], our network takes as input sparse measured image points, matched across multiple viewpoints, which are processed through a sequence of permutation-equivariant graph cross attention layers. The output of the graph cross attention layers is then processed by two regression heads, one for the 3D points and another for the camera poses. By using graph attention layers instead of linear equivariant maps as in [31], our model is able to better learn the implicit geometric primitives of SfM in the input data, leading to more expressiveness and better generalization to unseen sequences. Additionally, by not requiring time-consuming fine-tuning on unseen scenes, our model is able to provide fast inference, which can then be refined directly with BA with good convergence. + +The contributions of the paper can be summarized as: + +- We propose graph attention networks for initialization-free Structure-from-Motion that estimates camera parameters and 3D coordinates of 2D keypoints tracked across multiple views; +- The method takes advantage of the graph cross-attention layers, which are equivariant to permutation on the input data regarding order of views and points. We show that these layers can model more complex relations between input data and when combined with data augmentation result in significantly improved performance when compared to baseline methods; +- We evaluate the proposed learned method on unobserved scenes and show that it outperforms competing state-of-the-art learning methods at inference in terms of accuracy without the need of scene-specific model fine-tuning; +- We show that our method achieves competitive results when compared to state-of-the-art conventional Structure-from-Motion pipelines while having a significantly lower runtime. + +# 2. Graph Attention Network Preliminaries + +Before introducing our proposed method, we will here briefly outline the graph attention networks that will be utilized - the GATv2 model [4] based on [43]. + +The GATv2 model is a type of graph neural network (GNN) that carries out aggregation from neighboring nodes with a dynamic attention-based weighted average. The input to a GATv2 layer is a set of current node features $\{\mathbf{h}_i\in \mathbb{R}^d\mid i\in \mathcal{V}\}$ along with a set of directed edges $\mathcal{E}$ defining the graph connectivity. The layer outputs a new set of node features $\{\mathbf{h}_i'\in \mathbb{R}^{d'}\mid i\in \mathcal{V}\}$ , by applying a single shared learned function on every node $h_i$ together with its neighborhood $\mathcal{N}_i = \{j\in \mathcal{V}\mid (j,i)\in \mathcal{E}\}$ . + +First, a scoring function $e:\mathbb{R}^d\times \mathbb{R}^d\to \mathbb{R}$ is applied on + +all edges, by feeding the respective source and target node features as input to a shared 2-layer Multi-Layer Perceptron (MLP): + +$$ +e \left(\mathbf {h} _ {i}, \mathbf {h} _ {j}\right) = \mathbf {a} ^ {\top} \cdot \text {L e a k y R e L U} \left(\mathbf {W} \left[ \mathbf {h} _ {i} \| \mathbf {h} _ {j} \right]\right), \tag {3} +$$ + +where $\mathbf{a} \in \mathbb{R}^{d'}$ and $\mathbf{W} \in \mathbb{R}^{d' \times 2d}$ are learned parameters, and $\|\cdot\|$ denotes vector concatenation. The attention scores are then normalized across all neighbors: + +$$ +\alpha_ {i j} = \operatorname {s o f t m a x} _ {j} \left(e \left(\mathbf {h} _ {i}, \mathbf {h} _ {j}\right)\right) = \frac {\exp \left(e \left(\mathbf {h} _ {i} , \mathbf {h} _ {j}\right)\right)}{\sum_ {j ^ {\prime} \in \mathcal {N} _ {i}} \exp \left(e \left(\mathbf {h} _ {i} , \mathbf {h} _ {j ^ {\prime}}\right)\right)}, \tag {4} +$$ + +and the layer is completed by carrying out a weighted average of linear projections of all source node features: + +$$ +\mathbf {h} _ {i} ^ {\prime} = \sum_ {j \in \mathcal {N} _ {i}} \alpha_ {i j} \cdot \mathbf {W h} _ {j}. \tag {5} +$$ + +# 3. Method + +We apply a graph attention network model to perform Structure-from-Motion on a desired scene based on its measured image point correspondences. The model then outputs a reconstruction, represented by all $m$ camera matrices and all $n$ scene points. Structure-from-Motion is in general a large and complex optimization problem, and it is not trivially addressed as a learning problem. Our architecture combines the power and expressivity of the attention mechanism, and exploits its inherent permutation equivariance in a meaningful way, while balancing expressivity with efficiency, resulting in a very limited computational and memory footprint considering the task at hand. + +The input data for a particular scene consists of a sparse set of measured image point correspondences (point tracks). To represent this data, we define a binary observability matrix $\mathbf{O} \in \{0,1\}^{m \times n}$ , where $m$ is the number of views and $n$ is the number of scene points, and where $\mathbf{O}_{ij} = 1$ if and only if scene point $j$ is observed in image $i$ . Furthermore, let $\mathcal{P} = \{\mathbf{m}_{ij} \in \mathbb{R}^2 \mid \mathbf{O}_{ij} = 1\}$ be the collection of observed image point tracks, where $\mathbf{m}_{ij}$ is the (normalized) measured image point for the projection of scene point $j$ in camera $i$ . + +# 3.1. Graph Attention Network Architecture + +In this section, we will outline our graph attention network architecture, starting by introducing our feature representation. Then we proceed to define update operations for different feature types, and finally define the entire network architecture based on these operations. + +Feature representation. Throughout the network architecture, we maintain and continuously update a set of features of various types1: + +![](images/36da846ae76d0db4cf0ebb7ef4a5eaa5dca725350024086509a9a9885eaedc7d.jpg) +Figure 1. Illustration of the different types of features in the network architecture, for $m = 3$ cameras and $n = 6$ scene points. The projection features $\mathcal{P}$ are represented by a sparse vector-valued matrix, with its sparsity pattern determined by the point track measurements, while view features $\mathcal{V}$ and scene point features $S$ are represented by dense vector-values column and row vectors. A single vector $\mathbf{g}$ holds global features. + +- Projection features, $\mathcal{P} = \{\mathbf{p}_{ij}\in \mathbb{R}^{d_p}\mid \mathbf{O}_{ij} = 1\}$ +- View features, $\mathcal{V} = \{\mathbf{v}_i\in \mathbb{R}^{d_v}\mid i = 1,2,\ldots ,m\}$ +- Scene point features, $S = \{ \mathbf{s}_j \in \mathbb{R}^{d_s} \mid j = 1,2,\dots,n \}$ . +- Global features, $\mathbf{g} \in \mathbb{R}^{d_g}$ . + +The projection features $\mathbf{p}_{ij}$ are feature vectors specific to every observed image point. In practice, these are bundled together and organized in a sparse vector-valued matrix, as illustrated by the large top-right matrix in Figure 1. The sparsity pattern of $\mathcal{P}$ will be fixed throughout the network and is determined by $\mathbf{O}$ , which however depends on the scene. The view features $\mathcal{V}$ and scene point features $S$ , on their part, are organized in dense vector-valued column and row vectors, respectively, also illustrated in Figure 1. Finally, the global features $\mathbf{g}$ , consist of a single globally shared feature vector, and is illustrated in the bottom-left corner of Figure 1. + +In order to define graph operations, we see every feature vector as being associated with a corresponding graph node. At this point, note that a simple approach would be to connect all nodes $\mathcal{P},\mathcal{V},\mathcal{S}$ , and $\{\mathbf{g}\}$ in one unified graph, and directly apply a graph neural network with global weight sharing. Instead, since the nodes are semantically different, we consider these semantics when choosing the level of weight sharing, and even vary the feature dimension depending on the type of node. In practice, we construct different graphs for propagation between different types of nodes. + +Having defined the different feature types, we proceed to define corresponding update operations, which are repeatedly carried out throughout the network. In all pseudo-code, ReLU denotes to the rectified linear unit and LN denotes layer normalization [3]. Linear denotes a learned affine layer and FFN denotes a number of stacked Linear layers interleaved with ReLU activations. Subscripts may occur to emphasize feature dimensions. Note that all of these operations may be applied on multiple nodes at once, with shared parameters. The $+$ notation implies node-wise addition. + +Graph Cross-Attention. Procedure 1 is utilized for all feature aggregations throughout the network. It carries out cross-attention [42], attending to and propagating information from one set of input / source nodes $\mathcal{H}_1$ to another set of output / target nodes $\widehat{\mathcal{H}}_2$ . The previous target node features $\mathcal{H}_2$ , if provided, will act as query features when computing attention scores. In the first few layers these may not be available, and initial zero-features are used instead. + +In our context, the source nodes and target nodes correspond to different feature types, possibly with different feature dimension. As the source and target nodes are disjoint, we may represent the connectivity by a directed bipartite graph. Furthermore, in our context this graph will often consist of a number of disconnected subgraphs. Procedure1 essentially acts as a wrapper around a GATv2 layer [4] (for which we use the PyTorch Geometric [11] implementation), while carrying out input normalization, and feature projections as necessary. We consistently use 4 attention heads for the GATv2 layers. + +Procedure 1 GRAPHCROSSATTENTION +Input: $\mathcal{H}_1$ Source node features. +Input: $\mathcal{H}_2$ Previous target node features (optional). +Input: $\mathcal{E}_{\mathcal{H}_1\to \mathcal{H}_2}$ Set of edges from $\mathcal{H}_1\rightarrow \mathcal{H}_2$ . +Input: $d_{1}$ Source node feature dimension. +Input: $d_{2}$ Target node feature dimension. +Output: $\widehat{\mathcal{H}}_2$ Updated target node features. +1: $\widehat{\mathcal{H}}_1\gets \mathrm{ReLU}(\mathrm{LN}(\mathcal{H}_1))$ +2: if $\mathcal{H}_2$ provided then +3: $\widehat{\mathcal{H}}_2\gets \mathrm{ReLU}(\mathrm{LN}(\mathcal{H}_2))$ +4: if $d_{1}\neq d_{2}$ then +5: $\widehat{\mathcal{H}}_2\gets \mathrm{Linear}_{d_2\to d_1}(\widehat{\mathcal{H}}_2)$ +6: else +7: $\widehat{\mathcal{H}}_2\gets \mathrm{zero~features}\vec{0}\in \mathbb{R}^{d_1}$ +8: $\widehat{\mathcal{H}}_2\gets \mathrm{GATv2Conv}(\widehat{\mathcal{H}}_1,\widehat{\mathcal{H}}_2,\mathcal{E}_{\mathcal{H}_1\to \mathcal{H}_2})$ +9: if $d_{1}\neq d_{2}$ then +10: $\widehat{\mathcal{H}}_2\gets \mathrm{Linear}_{d_1\to d_2}(\widehat{\mathcal{H}}_2)$ + +View & Scene Point Feature Update. View features and scene point features are updated by Procedure 2 and 3, respectively, entirely symmetrical to one another. A directed bipartite graph is constructed by taking $\mathcal{P}$ as source nodes, and $\nu$ (or $S$ ) as target nodes, and connecting every projection node with its corresponding view (or scene point) node, corresponding to rows (or columns) of $\mathcal{P}$ . Graph cross-attention according to Procedure 1 is then carried out on the graph, and used as a residual mapping. This is followed by another residual mapping with a feed-forward network. Illustrations of these update operations are provided in Figures 2 and 3. + +Global Feature Update. The global feature update, outlined in Procedure 4 is carried out in almost the same manner, but now aggregating from all view features $\nu$ and scene + +![](images/9a285029bdf5110c63f07456ba3031e38b9d90e0ee03f8fdea7b12c1f0b3be35.jpg) +Figure 2. Illustration of the update of a single view feature. All $\mathcal{V}$ features are updated based on their previous value and the corresponding rows of $\mathcal{P}$ . + +![](images/68f3a593431fd01452381da560b7ce8616cef46fefb01bafd1e7817e27e8957a.jpg) +Figure 3. Illustration of the update of a single scene point feature. All $S$ features are updated based on their previous value and the corresponding columns of $\mathcal{P}$ . + +Procedure 2 UPDATEVIEWFEAT +Input: $\mathcal{P}$ O Projection features $^+$ observability matrix. +Input: $\nu$ Previous view features (optional). +Input: $d_p,d_v$ Feature dimensions. +Output: $\widehat{\nu}$ Updated view features. 1: $\mathcal{E}_{\mathcal{P}\rightarrow \mathcal{V}}\gets \{(\mathcal{P}_{ij},\mathcal{V}_i)\mid \mathbf{O}_{ij} = 1,i = 1,2,\ldots ,m\}$ 2: if $\nu$ provided then 3: $\widehat{\nu}\gets \mathcal{V} + \mathrm{GRAPHCROSSATTENTION}(\mathcal{P},\mathcal{V},\mathcal{E}_{\mathcal{P}\rightarrow \mathcal{V}},d_p,d_v)$ 4: else 5: $\widehat{\nu}\gets \mathrm{GRAPHCROSSATTENTION}(\mathcal{P},\mathcal{E}_{\mathcal{P}\rightarrow \mathcal{V}},d_p,d_v)$ 6: $\widehat{\nu}\gets \widehat{\nu} +\mathrm{FFN}(\mathrm{ReLU}(\mathrm{LN}(\widehat{\nu})))$ + +Procedure 3 UPDATESCENEPOINTFEAT +Input: $\mathcal{P}$ , O Projection features $^+$ observability matrix. +Input: S Previous scene point features (optional). +Input: $d_p,d_s$ Feature dimensions. +Output: $\widehat{S}$ Updated scene point features. 1: $\mathcal{E}_{\mathcal{P}\to \mathcal{S}}\gets \{(\mathcal{P}_{ij},\mathcal{S}_i)\mid \mathbf{O}_{ij} = 1,i = 1,2,\ldots ,m\}$ 2: if $\mathcal{S}$ provided then 3: $\widehat{S}\gets \mathcal{S} + \mathrm{GRAPHCROSSATTENTION}(\mathcal{P},\mathcal{S},\mathcal{E}_{\mathcal{P}\to \mathcal{S}},d_p,d_s)$ 4: else 5: $\widehat{S}\gets \mathrm{GRAPHCROSSATTENTION}(\mathcal{P},\mathcal{E}_{\mathcal{P}\to \mathcal{S}},d_p,d_s)$ 6: $\widehat{S}\gets \widehat{S} +\mathrm{FFN}(\mathrm{ReLU}(\mathrm{LN}(\widehat{S})))$ + +point features $S$ instead of $\mathcal{P}$ . This is carried out with two independent aggregations, with different learned parameters, and the sum of both aggregations constitute the residual mapping. Figure 4 provides an illustration for the update + +![](images/ed715ae8ff51dda6a4fac7d787d5f44c555c3a1e6d34adf07606546bc735a678.jpg) +Figure 4. Illustration of the global feature update, where $\mathbf{g}$ is updated based on its previous value, together with an aggregation of all $\mathcal{V}$ and $S$ features. + +operation. + +Procedure 4 UPDATEGLOBALFEAT + +Input: $\nu$ View features. +Input: $S$ Scene point features. +Input: g Previous global features (optional). +Input: $d_v, d_s, d_g$ Feature dimensions. +Output: $\widehat{\mathbf{g}}$ Updated global features. +1: $\mathcal{E}_{\mathcal{V}\to \mathbf{g}}\gets \{(\mathcal{V}_i,\mathbf{g})\mid i = 1,2,\ldots ,m\}$ +2: $\mathcal{E}_{\mathcal{S}\to \mathbf{g}}\gets \left\{(\mathcal{S}_j,\mathbf{g})\mid j = 1,2,\ldots ,n\right\}$ +3: if $\mathbf{g}$ provided then +4: $\widehat{\mathbf{g}}_v\gets \mathrm{GRAPHCROSSATTENTION}(\mathcal{V},\{\mathbf{g}\},\mathcal{E}_{\mathcal{V}\to \mathbf{g}},d_v,d_g)$ +5: $\widehat{\mathbf{g}}_s\gets \mathrm{GRAPHCROSSATTENTION}(\mathcal{S},\{\mathbf{g}\},\mathcal{E}_{\mathcal{S}\to \mathbf{g}},d_s,d_g)$ +6: $\widehat{\mathbf{g}}\gets \mathbf{g} + \widehat{\mathbf{g}}_v + \widehat{\mathbf{g}}_s$ +7: else +8: $\widehat{\mathbf{g}}_v\gets \mathrm{GRAPHCROSSATTENTION}(\mathcal{V}, - ,\mathcal{E}_{\mathcal{V}\to \mathbf{g}},d_v,d_g)$ +9: $\widehat{\mathbf{g}}_s\gets +\mathrm{GRAPHCROSSATTENTION}(\mathcal{S}, - ,\mathcal{E}_{\mathcal{S}\to \mathbf{g}},d_s,d_g)$ +10: $\widehat{\mathbf{g}}\gets \widehat{\mathbf{g}}_v + \widehat{\mathbf{g}}_s$ +11: $\widehat{\mathbf{g}}\gets \widehat{\mathbf{g}} +\mathrm{FFN}(\mathrm{ReLU}(\mathrm{LN}(\widehat{\mathbf{g}})))$ + +Projection Feature Update. The projection features are updated according to Procedure 5. No aggregation is involved during this step. Instead, at every projection node the corresponding $\nu$ , $S$ and $\mathbf{g}$ features are all collected along with the current projection features $\mathcal{P}$ , as illustrated in Figure 5. Each of these sources then undergoes a ReLU activation and normalization with LN, before being concatenated. Note that the initial projection features $\mathcal{P}_0$ are typically also added to the input, and in this case they are simply concatenated to the previous projection features before the procedure is called. Finally, a residual mapping is applied, by feeding the concatenated features to a shared feed-forward network. + +Entire Network Architecture. Now we have all the pieces to define the complete network architecture, which is outlined in Procedure 6. The structure is straightforward: 1) UPDATEVIEWFEAT and UPDATESCENEPOINTFEAT (Procedures 2 and 3) are called to aggregate projection features. 2) UPDATEGLOBALFEAT (Procedure 4) is called to aggre + +![](images/c2b0f061a2942b8ba7fa558c430767d5fecfb076624389813278412012ff3ffe.jpg) +Figure 5. Illustration of the update of a single projection feature. All $\mathcal{P}$ features are updated based on their previous value, as well as initial projection features $\mathcal{P}_0$ , the global feature $\mathbf{g}$ , and the corresponding $\mathcal{V}$ and $S$ features. + +Procedure 5 UPDATEPROJFEAT + +Input: $\mathcal{P}$ Previous projection features. + +Input: $\nu$ View features. + +Input: $S$ Scene point features. + +Input: g Global features. + +Input: $d_p^{in}, d_v, d_s, d_g, d_p^{out}$ Feature dimensions. + +Output: $\hat{\mathcal{P}}$ Updated projection features. + +1: $\widehat{\mathcal{P}}\gets \mathrm{ReLU}(\mathrm{LN}(\mathcal{V}))\parallel \mathrm{ReLU}(\mathrm{LN}(\mathcal{S}))$ $\| \operatorname {ReLU}(\operatorname {LN}(\mathbf{g}))\| \operatorname {ReLU}(\operatorname {LN}(\mathcal{P}))$ // View, scene point, and global features are implicitly distributed to their corresponding projection features before feature concatenation. + +2: $\widehat{\mathcal{P}}\gets \mathcal{P} + \mathrm{FFN}_{(d_v + d_s + d_g + d_p^{in})\to d_p^{out}}(\widehat{\mathcal{P}})$ + +gate the resulting features further, to a single global feature vector. 3) UPDATEPROJFEAT (Procedure 5) is called in order to again distribute the aggregated information across the projection features. These steps are repeated $L$ times, where we refer to $L$ as the number of layers. Then, a final call to UPDATEVIEWFEAT and UPDATESCENEPOINTFEAT is carried out, and the resulting view and scene point features are further processed by two corresponding regression heads, consisting of shared 3-layer feed-forward networks (FFN) with hidden neurons of the same dimension as the input ( $d_v$ or $d_s$ ). The scene point head simply outputs the 3 coordinates of every estimated scene point. For Euclidean reconstruction, the view head outputs the 3 coordinates of the location of the camera center, together with a unit-norm quaternion representing its orientation. For projective reconstruction, all 12 camera matrix elements are regressed, followed by a normalization in the same manner as [31]. Except for the regression heads, we use 1-layer FFNs throughout the network, which in general seemed slightly easier to train. + +# 3.2. Loss Function + +The network is trained using the Adam optimizer, and as loss function we use the (non-squared) reprojection error, averaged over all observed image points. To handle negative + +Procedure 6 GRAPHATTENTIONSFM +Input: $\mathcal{M}$ Image point tracks, normalized. +Input: O Observability matrix. +Input: $d_p,d_v,d_s,d_g$ Feature dimensions. +Input: L Number of layers. +Output: V Estimated camera parameters. +Output: S Estimated scene points. +1: $\mathcal{P}_0\gets \mathrm{Linear}_{2\to 2}(\mathcal{M})$ // Initial projection features: linear embedding of image points. +2: $\mathcal{V}\gets$ UPDATEVIEWFEAT $(\mathcal{P}_0,\mathbf{O}, - ,2,d_v)$ +3: $\mathcal{S}\gets$ UPDATESCENEPOINTFEAT $(\mathcal{P}_0,\mathbf{O}, - ,2,d_s)$ +4: $\mathbf{g}\gets$ UPDATEGLOBALFEAT $(\mathcal{V},\mathcal{S}, - ,d_v,d_s,d_g)$ +5: for $l = 1,2,\dots ,L$ do +6: if $l = 1$ then +7: $\mathcal{P}\gets$ UPDATEPROJFEAT $(\mathcal{P}_0,\mathcal{V},\mathcal{S},\mathbf{g},2,d_v,d_s,d_g,d_p)$ +8: else +9: $\mathcal{P}\gets$ UPDATEPROJFEAT $(\mathcal{P}\| \mathcal{P}_0,\mathcal{V},\mathcal{S},\mathbf{g},$ $d_p + 2,d_v,d_s,d_g,d_p)$ +10: $\mathcal{V}\gets$ UPDATEVIEWFEAT $(\mathcal{P},\mathbf{O},\mathcal{V},d_p,d_v)$ +12: $\mathcal{S}\gets$ UPDATESCENEPOINTFEAT $(\mathcal{P},\mathbf{O},\mathcal{S},d_p,d_s)$ +13: if $l < L$ then +14: $\mathbf{g}\gets$ UPDATEGLOBALFEAT $(\mathcal{V},\mathcal{S},\mathbf{g},d_v,d_s,d_g)$ +15: $\{\mathbf{P}_i\} \gets \mathrm{FFN}(\mathrm{ReLU}(\mathcal{V}))$ // Camera regression head +16: $\{\mathbf{X}_j\} \gets \mathrm{FFN}(\mathrm{ReLU}(\mathcal{S}))$ // Scene point regression head + +depths and overcome the singularity at the principal plane, we substitute the reprojection error with minus the depth in the loss function for any projection with depth smaller than a threshold $h = 1e - 4$ . We also apply gradient normalization in the same manner as [31]. + +# 3.3. Data Augmentation + +For Euclidean reconstruction, where the image points are normalized using the intrinsic camera parameters, and therefore geometrically interpretable, we experiment with augmenting the training scenes with slightly transformed variations. While the scene points remain fixed, each camera is randomly rotated about its center, first by a uniformly sampled angle $\alpha \in [-15, 15]$ about the principal axis, followed by a uniformly sampled angle $\gamma \in [-20, 20]$ about an axis orthogonal to the principal axis with a random direction. The image points are transformed accordingly. + +# 3.4. Artificial Outlier Injection + +We also consider the presence of measurement outliers, by artificially corrupting the data. This is done by: 1) Selecting a subset of the 2D keypoint measurements to be replaced by artificial outliers. 2) For each view, replace all measurements marked to be outliers with random samples from a bivariate normal distribution, which is fit to all remaining (inlier) points. For step 1), we carefully select points for outlier injection such that we avoid getting any scene points visible in $< 2$ views or any views with $< 8$ scene points visible, if regarding only the inlier projections. In the supplementary material, the details are given on how this is achieved. Note that while the network input is corrupted by outlier injec + +tion, the uncorrupted data is still used as learning targets for the loss function. + +# 4. Results + +# 4.1. Experimental Setup + +We take a particular interest in Euclidean reconstruction, due to the relevance of metric reconstructions for photogrammetry applications. Furthermore, we focus mainly on the task of learning and generalizing from a set of training scenes, due to the great potential in having a fast learned model acquire reconstructions of completely novel scenes. We use the DPESFM method of Moran et al. [31] as a baseline, as they have presented experiments on precisely this. To this end, we also use Olsson's dataset [33] (together with the VGG dataset [12] for additional projective reconstruction experiments in the supplement), and we use the same random partition of 10 test scenes and 3 validation scenes. + +We base our implementation on that of [31], implemented in PyTorch [34], but replace the network architecture with our proposed GRAPHATTENTIONSFM network, implemented using GATv2Conv layers [4] from PyTorch Geometric [11]. The implementation details are in general consistent with [31], for more details see the supplement. The DPESFM results reproduced by us are obtained by running the method of [31] with our code base, with the hyperparameters published on the official GitHub repository of the method [30]. For our model, we use $L = 12$ layers and feature dimensions $d_{p} = 32$ , $d_{v} = 1024$ , $d_{s} = 64$ , $d_{g} = 2048$ , which corresponds to 145M parameters. By using small dimensions for the projection features and scene point features the otherwise high memory consumption is significantly reduced. Hyper-parameters have been chosen based on the performance on the validation data, but without any rigorous hyper-parameter tuning. + +# 4.2. Euclidean Reconstruction of Novel Scenes + +In Table 1, we report the Euclidean reconstruction results of our method, when applied on novel test scenes, and measure the performance by reprojection errors, as well as rotation and translation errors for the estimated camera poses. For calculating the latter, the predicted and ground truth poses are first aligned to a common reference frame, as described in Section C in the supplement. The results of DPESFM as reported in [31] can be seen in parentheses, when available, but we also retrain their model and incorporate further results of the model, not reported in [31], in particular results without bundle adjustment, and additional metrics to reprojection errors. Experiments are carried out both with and without data augmentation with random rotational cameras perturbations, as described in Section 3.3, and the columns are partitioned accordingly. Consistently with [31], Inference refers to the network output followed + +
Without data augmentationWith data augmentationColmap
InferenceInference + BAInferenceInference + BA
OursDPESFMOursDPESFMOursDPESFMOursDPESFM
Reprojection error (px)Alcatraz Courtyard68.4168.501.700.81 (0.82)36.0192.370.810.920.81
Alcatraz Water Tower36.3050.471.051.13 (0.55)87.672831.940.8810.160.55
Drinking Fountain Somewhere in Zurich36.0245.870.550.31 (7.21)219.75234.900.316.730.31
Nijo Castle Gate65.7164.530.730.73 (5.81)61.4168.190.880.890.73
Porta San Donato Bologna74.3294.260.740.74 (1.10)52.1584.460.760.750.75
Round Church Cambridge61.1855.510.390.39 (0.50)29.8059.540.391.490.39
Smolny Cathedral St Petersburg156.16120.850.810.81 (15.15)85.3887.810.810.810.81
Some Cathedral in Barcelona150.01146.1010.4212.71 (21.46)125.68687.830.8916.770.89
Sri Veeramakaliamman Singapore121.02157.392.1916.87 (16.92)83.50166.682.139.300.71
Yueh Hai Ching Temple Singapore37.4652.590.650.65 (1.16)25.6051.350.650.730.65
Average80.6685.611.923.52 (7.07)80.69436.510.854.860.66
Rotation error (deg)Alcatraz Courtyard10.10213.2012.6070.0356.09310.9460.0380.0300.043
Alcatraz Water Tower10.63711.0530.4990.76411.50110.6410.69919.3510.228
Drinking Fountain Somewhere in Zurich15.84616.0140.0030.00115.41515.7040.00122.7590.007
Nijo Castle Gate16.75110.5460.0620.06217.34720.0320.0380.0360.064
Porta San Donato Bologna23.83924.1200.0950.09418.41125.0040.0940.0940.099
Round Church Cambridge18.90614.4730.0290.02610.29518.6850.0291.0860.035
Smolny Cathedral St Petersburg19.38717.9710.0230.02211.66214.3800.0230.0190.029
Some Cathedral in Barcelona27.27030.47110.00920.05027.90829.1190.02047.8920.025
Sri Veeramakaliamman Singapore28.27536.9030.5494.87123.70236.1760.4572.7590.169
Yueh Hai Ching Temple Singapore15.73322.7060.0380.0389.51521.5610.0380.0380.043
Average18.67519.7461.3912.59615.18520.2250.1449.4060.074
Translation error (m)Alcatraz Courtyard4.824.931.090.012.735.740.010.010.01
Alcatraz Water Tower8.667.350.310.447.537.770.419.050.12
Drinking Fountain Somewhere in Zurich4.444.440.000.004.454.460.001.380.00
Nijo Castle Gate5.073.080.010.015.676.950.010.010.01
Porta San Donato Bologna9.5010.720.050.054.8010.480.050.050.05
Round Church Cambridge8.947.190.010.015.289.000.010.560.01
Smolny Cathedral St Petersburg2.702.430.010.012.332.520.010.010.01
Some Cathedral in Barcelona12.6412.693.226.3812.3212.660.0111.930.01
Sri Veeramakaliamman Singapore4.944.900.161.324.934.900.140.770.04
Yueh Hai Ching Temple Singapore4.124.270.010.012.444.280.010.010.01
Average6.586.200.490.825.256.880.072.380.03
+ +Table 1. Results of Euclidean reconstruction of novel test scenes, with and without data augmentation. The results of DPESFM [31] have been acquired by us training the model, along with the results reported by [31] in parentheses, if available. The result of Colmap, as reported by [31], is also added for reference. + +
SceneInfer.BAColmap
Alcatraz Courtyard0.2445.54286
Alcatraz Water Tower0.1331.11130
Drinking Fountain Somewhere In Zurich0.061.9816
Nijo Castle Gate0.093.9721
Porta San Donato Bologna0.1827.02170
Round Church Cambridge0.4356.47229
Smolny Cathedral St Petersburg0.4986.09516
Some Cathedral In Barcelona0.2447.05451
Sri Veeramakaliamman Singapore0.63115.80583
Yueh Hai Ching Temple Singapore0.088.54106
+ +Table 2. Runtime (s) of our method for Euclidean reconstruction on test scenes, in comparison with Colmap (measured by [31]). + +by a computationally cheap triangulation and Inference $+$ BA refers to the network output followed by bundle adjustment, which is carried out in the same manner as [31], using the Ceres solver [1]. Moran et al. [31] also performed experiments with fine-tuning the network parameters on the test scenes. In contrast, we advocate against this, since this approach is relatively costly, and one might as well acquire + +high-quality reconstructions from traditional SfM pipelines such as Colmap, in similar execution time. Nevertheless, the supplementary material includes such experiments, for completeness. + +Without data augmentation, there is no clear difference between the Inference results of both methods. Neither reconstruction is good, and it is not so meaningful to compare minor differences in the metrics under these circumstances. In particular, calculating rotation and translation errors requires aligning the predicted and ground truth camera poses in a common reference frame, as described in Section C in the supplement, and when the predicted configuration of camera poses is not very consistent with the ground truth, determining this alignment itself can be sensitive. In all other scenarios, we outperform DPESFM, and when using both data augmentation and applying bundle adjustment, the solutions we acquire for the novel test scenes are in general very good. In terms of reprojection error and translation error, we match the performance of Colmap for almost every test scene, leading to an average reprojection + +error of 0.85 (vs 0.66) px, and an average translation error of 0.07 (vs 0.03) m. In terms of rotation error, the error is actually lower than Colmap's for 8 out of 10 scenes, but the average error is slightly larger: 0.144 (vs 0.074) degrees. + +# 4.3. Artificial Outlier Injection + +In Table 3 we present additional results where, on top of data augmentation (see Section 3.3), we also apply artificial outlier injection during training according to Section 3.4. + +We evaluate inference of the model in two settings: 1) Applied on the uncorrupted outlier-free test scenes as is. 2) Applied to the test scenes followed by random injection of $10\%$ , in the same manner as during training2. One can immediately observe significantly reduced reprojection errors for our model, suggesting that the outlier injection during training has a regularizing effect. Beyond that, this experiment is intended to serve as a teaser for the utility and promise of learning-based methods for SfM. Constant challenges such as the presence of outliers may not be as big of a challenge for learning-based as for conventional methods, and the phenomenon may even be exploited to develop effective training strategies. In fact, for any real-world scenario, it is crucial for learning-based methods applied on image point correspondences to be resilient to outliers, as we do not have the luxury of facing high-quality curated data such as Olsson's [33] in the wild. Note that it should be possible to apply bundle adjustment on the corrupted test data as well, when combined with a robust loss function. + +Similarly as for the data augmentation, we note that DPESFM appears to struggle with the presence of outliers during training, and its performance on the test scenes at inference is not very good. It is very probable that the nonlinear attention layers make our model more powerful and expressive than DPESFM. + +# 4.4. Additional Results + +In the supplementary material we provide additional results on projective reconstruction, as well as single-scene optimization, for completeness. We also include statistics of the number of views and scene points for each scene. + +# 5. Conclusion + +With this paper we have added to the research direction of learned initialization-free Structure-from-Motion by introducing a novel and expressive graph attention network outperforming previous learning-based methods for Euclidean reconstruction of novel scenes. When succeeded by bundle adjustment, we are able to reconstruct novel test scenes to perfection or of very decent precision, at a speedup of about $5 - 10 \times$ compared to Colmap. Moreover, we illustrate great + +
UncorruptedOutlier-injected
OursDPESFMOursDPESFM
Alcatraz Courtyard47.7485.8152.9994.24
Alcatraz Water Tower35.9672.8437.8983.55
Drinking Fountain +Somewhere in Zurich52.081012.1446.651453.31
Nijo Castle Gate46.4872.9962.52126.18
Porta San Donato +Bologna53.1288.0265.0894.72
Round Church +Cambridge36.0963.7248.6390.63
Smolny Cathedral St +Petersburg47.2891.0359.5298.05
Some Cathedral in +Barcelona109.86397.75123.75462.28
Sri Veeramakali- +amman Singapore63.60169.6370.90146.98
Yueh Hai Ching +Temple Singapore26.8351.4136.6957.59
Average51.91210.5360.46270.75
+ +Table 3. Reprojection errors of Euclidean reconstruction of novel test scenes, with model trained with data augmentation as well as artificial outlier injection. The results of DPESFM [31] have been acquired by us training the model. + +potential in coping with the presence of outliers, and even show artificial outlier injection to provide an effective regularizing training strategy, combined with data augmentation by random rotational camera perturbations. + +For future work, it could definitely be promising to train on larger datasets, since model generalization is still a challenge. While the proposed model does not require fine-tuning, and thus is much faster to execute than previous work, it still relies on bundle adjustment to acquire a good reconstruction, which constitutes the computational bottleneck. Exploring alternative formulations where the network regresses relative camera poses is also an interesting direction, as the current absolute pose prediction may be a weakness due to the reconstruction ambiguity up to a similarity transformation. Other possible research directions include unrolling the architecture to multiple learned iterations / refinement steps, extensions to non-rigid Structure-from-Motion, and incorporating modern learned image matching pipelines such as [5, 6, 40] in an end-to-end fashion. + +Acknowledgements The work was supported by the Wallenberg AI, Autonomous Systems and Software Program (WASP) funded by the Knut and Alice Wallenberg Foundation, and the Swedish Research Council grants no. 2016-04445, 2018-05375, and 2023-05341. Computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) at Chalmers Centre for Computational Science and Engineering (C3SE) and National Supercomputer Centre (NSC) Berzelius at Linköping University partially funded by the Swedish Research Council through grant no. 2022-06725. + +# References + +[1] Sameer Agarwal, Keir Mierle, and Others. Ceres solver. http://ceres-solver.org/.7 +[2] Sameer Agarwal, Noah Snavely, Ian Simon, Steven M. Seitz, and Richard Szeliski. Building rome in a day. In 2009 IEEE 12th International Conference on Computer Vision, pages 72-79, 2009. 1 +[3] Jimmy Lei Ba, Jamie Ryan Kiros, and Geoffrey E. Hinton. Layer normalization, 2016. 3 +[4] Shaked Brody, Uri Alon, and Eran Yahav. How attentive are graph attention networks? In International Conference on Learning Representations, 2022. 2, 4, 6 +[5] Georg Bokman and Fredrik Kahl. 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The loss in (1) is generally chosen as the reprojection error" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 96, + 700, + 287, + 715 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 96, + 700, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 96, + 700, + 287, + 715 + ], + "type": "interline_equation", + "content": "r \\left(\\mathbf {m} _ {i j}, \\mathbf {z} _ {i j}\\right) = \\left| \\left| \\mathbf {m} _ {i j} - \\Pi \\left(\\mathbf {z} _ {i j}\\right) \\right| \\right| ^ {2} \\tag {2}", + "image_path": "b1f3c9995bf0307b7f38b9ebc8992d54ebc89cee007bd18eaa2dd1172746c35c.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 213, + 547, + 578 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 213, + 547, + 578 + ], + "spans": [ + { + "bbox": [ + 304, + 213, + 547, + 578 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 213, + 547, + 578 + ], + "type": "inline_equation", + "content": "\\Pi (\\mathbf{x}) = \\left(\\frac{x_1}{x_3},\\frac{x_2}{x_3}\\right)" + }, + { + "bbox": [ + 304, + 213, + 547, + 578 + ], + "type": "text", + "content": ", and the nonlinear least squares problem (1), referred to as Bundle Adjustment (BA) [15], can be solved iteratively using second-order methods like Levenberg-Marquardt [15, 41]. Given the sparsity of the problem, sparse computation methods [27] can be used in order to increase the efficiency of the optimization, allowing BA to be used even for scenes with a large number of views or points. However, it is widely known that BA is highly non-convex and tends to converge to the nearest local minimum when not initialized close to the globally optimal solution. As a consequence, BA is typically the last step of a reconstruction pipeline, preceding global SfM methods such as [9, 10, 20, 25], or incremental SfM methods such as [2, 37, 38] that solve a sequence of subproblems like pairwise pose estimation, pose averaging, triangulation or camera resection [13, 15, 22, 32]. A different approach consists of projective factorization methods [8, 17, 18, 28, 39, 48] which factorize the " + }, + { + "bbox": [ + 304, + 213, + 547, + 578 + ], + "type": "inline_equation", + "content": "2m\\times n" + }, + { + "bbox": [ + 304, + 213, + 547, + 578 + ], + "type": "text", + "content": " measurement matrix into two rank four matrices corresponding to the camera matrices and 3D points (in homogeneous coordinates). In particular, works like [17, 18, 48] allow initialization-free SfM given their wide basin of convergence, meaning that their methods can be initialized with random camera poses and still converge with a high rate of success to the desired global minimum. Even though these methods have been improving in terms of accuracy and robustness to missing data, factorization-based methods require the input data to be almost completely free of outliers which unfortunately cannot be guaranteed in most real world sequences or datasets, and hence severely compromises the usability of these methods." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "type": "text", + "content": "A common challenge with all these approaches to solve SfM is their scalability as the number of views and keypoints increase. Incremental SfM tries to tackle this issue by starting with a subset of the views, estimate its reconstruction and incrementally adding more views. Some factorization-based methods can also take advantage of the same sparse computation methods used in BA, which significantly improves their ability to scale with sequence size. While this allows to reconstruct scenes with thousands of views and millions of points, it can still take hours to recover the reconstruction of a single scene." + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4808" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 180 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 180 + ], + "type": "text", + "content": "More recently, deep learning methods for 3D reconstruction and SfM have been proposed [7, 29, 31, 35, 44-47]. Given their increased complexity, these models are able to learn complex relations between the input data, outperforming conventional methods and achieving state-of-the-art results in 3D reconstruction and novel view synthesis when the camera pose and calibration are known [7, 29, 46]. Works such as [31, 46, 47] tackle SfM with deep learning models which different degrees of success." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 182, + 289, + 338 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 182, + 289, + 338 + ], + "spans": [ + { + "bbox": [ + 46, + 182, + 289, + 338 + ], + "type": "text", + "content": "In DeepSfM [46] the authors propose an end-to-end approach to estimate camera pose and a dense depth map of a target view from multiple source views. Their method estimates a feature map for each of the source views, which are then combined with the feature map of the target view in order to estimate pose and depth cost volumes. These cost volumes are then fed to two heads that estimate the camera pose and depth map of the target view. In PoseDiffusion [44], a probabilistic diffusion framework is proposed to mirror the iterations of bundle adjustment, allowing it to incorporate geometric priors into the problem. The model is trained on object-centric scenes and it is shown that it can generalize to unseen scenes without further training." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 340, + 289, + 508 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 340, + 289, + 508 + ], + "spans": [ + { + "bbox": [ + 46, + 340, + 289, + 508 + ], + "type": "text", + "content": "In [31], which is the closest work to ours, the authors have pursued an approach similar to projective factorization, taking as input the 2D keypoints tracked along multiple views. These 2D point tracks are processed by a number of linear permutation-equivariant layers, i.e. layers such that a permutation on the rows and/or columns of the input tensor results in the same permutation on the output. The output of these layers is then fed to camera pose and 3D points coordinate regression heads. The model is learned using reprojection errors as loss combined with a hinge loss term to push points in front of the cameras. By using Adam [26] as optimizer along with gradient normalization, the authors show that their method has improved convergence properties compared to random initializations." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": "A major benefit of learning-based methods is their potential in generalizing to new data after being trained. This can be particularly beneficial to SfM problems since occlusions and missing measurements are common issues that make some scenes particularly challenging to reconstruct. In these cases, the learned model can act as a prior and help constrain the solution based on the data seen during training. However, most of the learning-based methods mentioned for 3D reconstruction or SfM require scene-specific optimization or training, which turns out to be particularly slow for large sequences. PoseDiffusion [44] achieves some degree of generalization to unseen scenes, but it is conditional on the categories and object-centric datasets seen during training. In [31] the authors actually show that their model can be trained on a large collection of scenes and then used for inference on unobserved scenes. However, without fine-tuning on these new scenes (which is time-consuming)" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 305, + 72, + 491, + 84 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 491, + 84 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 491, + 84 + ], + "type": "text", + "content": "the model's accuracy is significantly reduced." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 85, + 547, + 287 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 85, + 547, + 287 + ], + "spans": [ + { + "bbox": [ + 304, + 85, + 547, + 287 + ], + "type": "text", + "content": "In this paper we propose a graph attention network for initialization-free Structure-from-Motion that can be trained on multiple scenes and used for fast inference on new, unseen scenes. Similarly to [31], our network takes as input sparse measured image points, matched across multiple viewpoints, which are processed through a sequence of permutation-equivariant graph cross attention layers. The output of the graph cross attention layers is then processed by two regression heads, one for the 3D points and another for the camera poses. By using graph attention layers instead of linear equivariant maps as in [31], our model is able to better learn the implicit geometric primitives of SfM in the input data, leading to more expressiveness and better generalization to unseen sequences. Additionally, by not requiring time-consuming fine-tuning on unseen scenes, our model is able to provide fast inference, which can then be refined directly with BA with good convergence." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 317, + 288, + 534, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 288, + 534, + 300 + ], + "spans": [ + { + "bbox": [ + 317, + 288, + 534, + 300 + ], + "type": "text", + "content": "The contributions of the paper can be summarized as:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 300, + 545, + 526 + ], + "type": "list", + "angle": 0, + "index": 11, + "blocks": [ + { + "bbox": [ + 306, + 300, + 545, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 300, + 545, + 346 + ], + "spans": [ + { + "bbox": [ + 306, + 300, + 545, + 346 + ], + "type": "text", + "content": "- We propose graph attention networks for initialization-free Structure-from-Motion that estimates camera parameters and 3D coordinates of 2D keypoints tracked across multiple views;" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 348, + 545, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 348, + 545, + 430 + ], + "spans": [ + { + "bbox": [ + 306, + 348, + 545, + 430 + ], + "type": "text", + "content": "- The method takes advantage of the graph cross-attention layers, which are equivariant to permutation on the input data regarding order of views and points. We show that these layers can model more complex relations between input data and when combined with data augmentation result in significantly improved performance when compared to baseline methods;" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 431, + 545, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 431, + 545, + 479 + ], + "spans": [ + { + "bbox": [ + 306, + 431, + 545, + 479 + ], + "type": "text", + "content": "- We evaluate the proposed learned method on unobserved scenes and show that it outperforms competing state-of-the-art learning methods at inference in terms of accuracy without the need of scene-specific model fine-tuning;" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 479, + 545, + 526 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 479, + 545, + 526 + ], + "spans": [ + { + "bbox": [ + 306, + 479, + 545, + 526 + ], + "type": "text", + "content": "- We show that our method achieves competitive results when compared to state-of-the-art conventional Structure-from-Motion pipelines while having a significantly lower runtime." + } + ] + } + ], + "index": 10 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 537, + 527, + 552 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 537, + 527, + 552 + ], + "spans": [ + { + "bbox": [ + 306, + 537, + 527, + 552 + ], + "type": "text", + "content": "2. Graph Attention Network Preliminaries" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 558, + 545, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 545, + 594 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 545, + 594 + ], + "type": "text", + "content": "Before introducing our proposed method, we will here briefly outline the graph attention networks that will be utilized - the GATv2 model [4] based on [43]." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "content": "The GATv2 model is a type of graph neural network (GNN) that carries out aggregation from neighboring nodes with a dynamic attention-based weighted average. The input to a GATv2 layer is a set of current node features " + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{h}_i\\in \\mathbb{R}^d\\mid i\\in \\mathcal{V}\\}" + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "content": " along with a set of directed edges " + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "content": " defining the graph connectivity. The layer outputs a new set of node features " + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{h}_i'\\in \\mathbb{R}^{d'}\\mid i\\in \\mathcal{V}\\}" + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "content": ", by applying a single shared learned function on every node " + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "inline_equation", + "content": "h_i" + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "content": " together with its neighborhood " + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_i = \\{j\\in \\mathcal{V}\\mid (j,i)\\in \\mathcal{E}\\}" + }, + { + "bbox": [ + 304, + 594, + 545, + 701 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "type": "text", + "content": "First, a scoring function " + }, + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "type": "inline_equation", + "content": "e:\\mathbb{R}^d\\times \\mathbb{R}^d\\to \\mathbb{R}" + }, + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "type": "text", + "content": " is applied on" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4809" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 107 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 107 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 107 + ], + "type": "text", + "content": "all edges, by feeding the respective source and target node features as input to a shared 2-layer Multi-Layer Perceptron (MLP):" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 74, + 114, + 287, + 129 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 74, + 114, + 287, + 129 + ], + "spans": [ + { + "bbox": [ + 74, + 114, + 287, + 129 + ], + "type": "interline_equation", + "content": "e \\left(\\mathbf {h} _ {i}, \\mathbf {h} _ {j}\\right) = \\mathbf {a} ^ {\\top} \\cdot \\text {L e a k y R e L U} \\left(\\mathbf {W} \\left[ \\mathbf {h} _ {i} \\| \\mathbf {h} _ {j} \\right]\\right), \\tag {3}", + "image_path": "27655f9ac382726e106e8a2b4d390366e97084c51262244ab9c9a4a17469cfbe.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "spans": [ + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "type": "inline_equation", + "content": "\\mathbf{a} \\in \\mathbb{R}^{d'}" + }, + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "type": "inline_equation", + "content": "\\mathbf{W} \\in \\mathbb{R}^{d' \\times 2d}" + }, + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "type": "text", + "content": " are learned parameters, and " + }, + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "type": "inline_equation", + "content": "\\|\\cdot\\|" + }, + { + "bbox": [ + 47, + 133, + 287, + 171 + ], + "type": "text", + "content": " denotes vector concatenation. The attention scores are then normalized across all neighbors:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 48, + 176, + 287, + 213 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 176, + 287, + 213 + ], + "spans": [ + { + "bbox": [ + 48, + 176, + 287, + 213 + ], + "type": "interline_equation", + "content": "\\alpha_ {i j} = \\operatorname {s o f t m a x} _ {j} \\left(e \\left(\\mathbf {h} _ {i}, \\mathbf {h} _ {j}\\right)\\right) = \\frac {\\exp \\left(e \\left(\\mathbf {h} _ {i} , \\mathbf {h} _ {j}\\right)\\right)}{\\sum_ {j ^ {\\prime} \\in \\mathcal {N} _ {i}} \\exp \\left(e \\left(\\mathbf {h} _ {i} , \\mathbf {h} _ {j ^ {\\prime}}\\right)\\right)}, \\tag {4}", + "image_path": "bc3bc423c3802abd716fa44c98ccf54ce539ba46b28682085d1d5491b3ce8a4d.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 215, + 287, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 215, + 287, + 239 + ], + "spans": [ + { + "bbox": [ + 47, + 215, + 287, + 239 + ], + "type": "text", + "content": "and the layer is completed by carrying out a weighted average of linear projections of all source node features:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 112, + 244, + 287, + 264 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 112, + 244, + 287, + 264 + ], + "spans": [ + { + "bbox": [ + 112, + 244, + 287, + 264 + ], + "type": "interline_equation", + "content": "\\mathbf {h} _ {i} ^ {\\prime} = \\sum_ {j \\in \\mathcal {N} _ {i}} \\alpha_ {i j} \\cdot \\mathbf {W h} _ {j}. \\tag {5}", + "image_path": "8bb25bf07e76e902c2dfad6242d69005c30865d59f4d549fc70dd51333390d14.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 270, + 102, + 281 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 270, + 102, + 281 + ], + "spans": [ + { + "bbox": [ + 47, + 270, + 102, + 281 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 289, + 287, + 432 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 289, + 287, + 432 + ], + "spans": [ + { + "bbox": [ + 46, + 289, + 287, + 432 + ], + "type": "text", + "content": "We apply a graph attention network model to perform Structure-from-Motion on a desired scene based on its measured image point correspondences. The model then outputs a reconstruction, represented by all " + }, + { + "bbox": [ + 46, + 289, + 287, + 432 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 46, + 289, + 287, + 432 + ], + "type": "text", + "content": " camera matrices and all " + }, + { + "bbox": [ + 46, + 289, + 287, + 432 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 289, + 287, + 432 + ], + "type": "text", + "content": " scene points. Structure-from-Motion is in general a large and complex optimization problem, and it is not trivially addressed as a learning problem. Our architecture combines the power and expressivity of the attention mechanism, and exploits its inherent permutation equivariance in a meaningful way, while balancing expressivity with efficiency, resulting in a very limited computational and memory footprint considering the task at hand." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "spans": [ + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": "The input data for a particular scene consists of a sparse set of measured image point correspondences (point tracks). To represent this data, we define a binary observability matrix " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "\\mathbf{O} \\in \\{0,1\\}^{m \\times n}" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": " is the number of views and " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": " is the number of scene points, and where " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_{ij} = 1" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": " if and only if scene point " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": " is observed in image " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": ". Furthermore, let " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "\\mathcal{P} = \\{\\mathbf{m}_{ij} \\in \\mathbb{R}^2 \\mid \\mathbf{O}_{ij} = 1\\}" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": " be the collection of observed image point tracks, where " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "\\mathbf{m}_{ij}" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": " is the (normalized) measured image point for the projection of scene point " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": " in camera " + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 434, + 287, + 552 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 559, + 253, + 571 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 559, + 253, + 571 + ], + "spans": [ + { + "bbox": [ + 47, + 559, + 253, + 571 + ], + "type": "text", + "content": "3.1. Graph Attention Network Architecture" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 578, + 287, + 637 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 578, + 287, + 637 + ], + "spans": [ + { + "bbox": [ + 46, + 578, + 287, + 637 + ], + "type": "text", + "content": "In this section, we will outline our graph attention network architecture, starting by introducing our feature representation. Then we proceed to define update operations for different feature types, and finally define the entire network architecture based on these operations." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 651, + 287, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 651, + 287, + 687 + ], + "spans": [ + { + "bbox": [ + 47, + 651, + 287, + 687 + ], + "type": "text", + "content": "Feature representation. Throughout the network architecture, we maintain and continuously update a set of features of various types1:" + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 328, + 72, + 524, + 173 + ], + "blocks": [ + { + "bbox": [ + 328, + 72, + 524, + 173 + ], + "lines": [ + { + "bbox": [ + 328, + 72, + 524, + 173 + ], + "spans": [ + { + "bbox": [ + 328, + 72, + 524, + 173 + ], + "type": "image", + "image_path": "36da846ae76d0db4cf0ebb7ef4a5eaa5dca725350024086509a9a9885eaedc7d.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "lines": [ + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "spans": [ + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "text", + "content": "Figure 1. Illustration of the different types of features in the network architecture, for " + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "inline_equation", + "content": "m = 3" + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "text", + "content": " cameras and " + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "inline_equation", + "content": "n = 6" + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "text", + "content": " scene points. The projection features " + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "text", + "content": " are represented by a sparse vector-valued matrix, with its sparsity pattern determined by the point track measurements, while view features " + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "text", + "content": " and scene point features " + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "text", + "content": " are represented by dense vector-values column and row vectors. A single vector " + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "inline_equation", + "content": "\\mathbf{g}" + }, + { + "bbox": [ + 304, + 180, + 545, + 257 + ], + "type": "text", + "content": " holds global features." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 278, + 540, + 327 + ], + "type": "list", + "angle": 0, + "index": 18, + "blocks": [ + { + "bbox": [ + 306, + 278, + 515, + 291 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 278, + 515, + 291 + ], + "spans": [ + { + "bbox": [ + 306, + 278, + 515, + 291 + ], + "type": "text", + "content": "- Projection features, " + }, + { + "bbox": [ + 306, + 278, + 515, + 291 + ], + "type": "inline_equation", + "content": "\\mathcal{P} = \\{\\mathbf{p}_{ij}\\in \\mathbb{R}^{d_p}\\mid \\mathbf{O}_{ij} = 1\\}" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 291, + 515, + 303 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 291, + 515, + 303 + ], + "spans": [ + { + "bbox": [ + 306, + 291, + 515, + 303 + ], + "type": "text", + "content": "- View features, " + }, + { + "bbox": [ + 306, + 291, + 515, + 303 + ], + "type": "inline_equation", + "content": "\\mathcal{V} = \\{\\mathbf{v}_i\\in \\mathbb{R}^{d_v}\\mid i = 1,2,\\ldots ,m\\}" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 303, + 540, + 316 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 303, + 540, + 316 + ], + "spans": [ + { + "bbox": [ + 306, + 303, + 540, + 316 + ], + "type": "text", + "content": "- Scene point features, " + }, + { + "bbox": [ + 306, + 303, + 540, + 316 + ], + "type": "inline_equation", + "content": "S = \\{ \\mathbf{s}_j \\in \\mathbb{R}^{d_s} \\mid j = 1,2,\\dots,n \\}" + }, + { + "bbox": [ + 306, + 303, + 540, + 316 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 316, + 420, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 316, + 420, + 327 + ], + "spans": [ + { + "bbox": [ + 306, + 316, + 420, + 327 + ], + "type": "text", + "content": "- Global features, " + }, + { + "bbox": [ + 306, + 316, + 420, + 327 + ], + "type": "inline_equation", + "content": "\\mathbf{g} \\in \\mathbb{R}^{d_g}" + }, + { + "bbox": [ + 306, + 316, + 420, + 327 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 17 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "spans": [ + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "text", + "content": "The projection features " + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{ij}" + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "text", + "content": " are feature vectors specific to every observed image point. In practice, these are bundled together and organized in a sparse vector-valued matrix, as illustrated by the large top-right matrix in Figure 1. The sparsity pattern of " + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "text", + "content": " will be fixed throughout the network and is determined by " + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "inline_equation", + "content": "\\mathbf{O}" + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "text", + "content": ", which however depends on the scene. The view features " + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "text", + "content": " and scene point features " + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "text", + "content": ", on their part, are organized in dense vector-valued column and row vectors, respectively, also illustrated in Figure 1. Finally, the global features " + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "inline_equation", + "content": "\\mathbf{g}" + }, + { + "bbox": [ + 304, + 330, + 545, + 472 + ], + "type": "text", + "content": ", consist of a single globally shared feature vector, and is illustrated in the bottom-left corner of Figure 1." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 474, + 545, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 545, + 593 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 545, + 593 + ], + "type": "text", + "content": "In order to define graph operations, we see every feature vector as being associated with a corresponding graph node. At this point, note that a simple approach would be to connect all nodes " + }, + { + "bbox": [ + 304, + 474, + 545, + 593 + ], + "type": "inline_equation", + "content": "\\mathcal{P},\\mathcal{V},\\mathcal{S}" + }, + { + "bbox": [ + 304, + 474, + 545, + 593 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 474, + 545, + 593 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{g}\\}" + }, + { + "bbox": [ + 304, + 474, + 545, + 593 + ], + "type": "text", + "content": " in one unified graph, and directly apply a graph neural network with global weight sharing. Instead, since the nodes are semantically different, we consider these semantics when choosing the level of weight sharing, and even vary the feature dimension depending on the type of node. In practice, we construct different graphs for propagation between different types of nodes." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": "Having defined the different feature types, we proceed to define corresponding update operations, which are repeatedly carried out throughout the network. In all pseudo-code, ReLU denotes to the rectified linear unit and LN denotes layer normalization [3]. Linear denotes a learned affine layer and FFN denotes a number of stacked Linear layers interleaved with ReLU activations. Subscripts may occur to emphasize feature dimensions. Note that all of these operations may be applied on multiple nodes at once, with shared parameters. The " + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "inline_equation", + "content": "+" + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": " notation implies node-wise addition." + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 47, + 693, + 287, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 287, + 712 + ], + "type": "text", + "content": "1For simplicity, we use a slight abuse of set notation here. If there are feature vector duplicates, they are still considered as separate elements." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4810" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "type": "text", + "content": "Graph Cross-Attention. Procedure 1 is utilized for all feature aggregations throughout the network. It carries out cross-attention [42], attending to and propagating information from one set of input / source nodes " + }, + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "type": "inline_equation", + "content": "\\mathcal{H}_1" + }, + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "type": "text", + "content": " to another set of output / target nodes " + }, + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{H}}_2" + }, + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "type": "text", + "content": ". The previous target node features " + }, + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "type": "inline_equation", + "content": "\\mathcal{H}_2" + }, + { + "bbox": [ + 46, + 72, + 289, + 167 + ], + "type": "text", + "content": ", if provided, will act as query features when computing attention scores. In the first few layers these may not be available, and initial zero-features are used instead." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 168, + 290, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 168, + 290, + 300 + ], + "spans": [ + { + "bbox": [ + 46, + 168, + 290, + 300 + ], + "type": "text", + "content": "In our context, the source nodes and target nodes correspond to different feature types, possibly with different feature dimension. As the source and target nodes are disjoint, we may represent the connectivity by a directed bipartite graph. Furthermore, in our context this graph will often consist of a number of disconnected subgraphs. Procedure1 essentially acts as a wrapper around a GATv2 layer [4] (for which we use the PyTorch Geometric [11] implementation), while carrying out input normalization, and feature projections as necessary. We consistently use 4 attention heads for the GATv2 layers." + } + ] + } + ], + "index": 1 + }, + { + "type": "code", + "bbox": [ + 47, + 326, + 220, + 486 + ], + "blocks": [ + { + "bbox": [ + 48, + 312, + 214, + 323 + ], + "lines": [ + { + "bbox": [ + 48, + 312, + 214, + 323 + ], + "spans": [ + { + "bbox": [ + 48, + 312, + 214, + 323 + ], + "type": "text", + "content": "Procedure 1 GRAPHCROSSATTENTION" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "code_caption" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "lines": [ + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "spans": [ + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": "Input: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\mathcal{H}_1" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " Source node features. \nInput: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\mathcal{H}_2" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " Previous target node features (optional). \nInput: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\mathcal{E}_{\\mathcal{H}_1\\to \\mathcal{H}_2}" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " Set of edges from " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\mathcal{H}_1\\rightarrow \\mathcal{H}_2" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " . \nInput: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "d_{1}" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " Source node feature dimension. \nInput: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "d_{2}" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " Target node feature dimension. \nOutput: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{H}}_2" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " Updated target node features. \n1: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{H}}_1\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{H}_1))" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " \n2: if " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\mathcal{H}_2" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " provided then \n3: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{H}}_2\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{H}_2))" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " \n4: if " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "d_{1}\\neq d_{2}" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " then \n5: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{H}}_2\\gets \\mathrm{Linear}_{d_2\\to d_1}(\\widehat{\\mathcal{H}}_2)" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " \n6: else \n7: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{H}}_2\\gets \\mathrm{zero~features}\\vec{0}\\in \\mathbb{R}^{d_1}" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " \n8: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{H}}_2\\gets \\mathrm{GATv2Conv}(\\widehat{\\mathcal{H}}_1,\\widehat{\\mathcal{H}}_2,\\mathcal{E}_{\\mathcal{H}_1\\to \\mathcal{H}_2})" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " \n9: if " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "d_{1}\\neq d_{2}" + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "text", + "content": " then \n10: " + }, + { + "bbox": [ + 47, + 326, + 220, + 486 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{H}}_2\\gets \\mathrm{Linear}_{d_1\\to d_2}(\\widehat{\\mathcal{H}}_2)" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "code_body" + } + ], + "index": 3, + "sub_type": "algorithm" + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "spans": [ + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "text", + "content": "View & Scene Point Feature Update. View features and scene point features are updated by Procedure 2 and 3, respectively, entirely symmetrical to one another. A directed bipartite graph is constructed by taking " + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "text", + "content": " as source nodes, and " + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "inline_equation", + "content": "\\nu" + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "text", + "content": " (or " + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "text", + "content": ") as target nodes, and connecting every projection node with its corresponding view (or scene point) node, corresponding to rows (or columns) of " + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 517, + 289, + 661 + ], + "type": "text", + "content": ". Graph cross-attention according to Procedure 1 is then carried out on the graph, and used as a residual mapping. This is followed by another residual mapping with a feed-forward network. Illustrations of these update operations are provided in Figures 2 and 3." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 677, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 289, + 715 + ], + "type": "text", + "content": "Global Feature Update. The global feature update, outlined in Procedure 4 is carried out in almost the same manner, but now aggregating from all view features " + }, + { + "bbox": [ + 46, + 677, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\nu" + }, + { + "bbox": [ + 46, + 677, + 289, + 715 + ], + "type": "text", + "content": " and scene" + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 332, + 70, + 521, + 183 + ], + "blocks": [ + { + "bbox": [ + 332, + 70, + 521, + 183 + ], + "lines": [ + { + "bbox": [ + 332, + 70, + 521, + 183 + ], + "spans": [ + { + "bbox": [ + 332, + 70, + 521, + 183 + ], + "type": "image", + "image_path": "9a285029bdf5110c63f07456ba3031e38b9d90e0ee03f8fdea7b12c1f0b3be35.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 189, + 547, + 224 + ], + "lines": [ + { + "bbox": [ + 304, + 189, + 547, + 224 + ], + "spans": [ + { + "bbox": [ + 304, + 189, + 547, + 224 + ], + "type": "text", + "content": "Figure 2. Illustration of the update of a single view feature. All " + }, + { + "bbox": [ + 304, + 189, + 547, + 224 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 304, + 189, + 547, + 224 + ], + "type": "text", + "content": " features are updated based on their previous value and the corresponding rows of " + }, + { + "bbox": [ + 304, + 189, + 547, + 224 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 189, + 547, + 224 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 323, + 234, + 529, + 342 + ], + "blocks": [ + { + "bbox": [ + 323, + 234, + 529, + 342 + ], + "lines": [ + { + "bbox": [ + 323, + 234, + 529, + 342 + ], + "spans": [ + { + "bbox": [ + 323, + 234, + 529, + 342 + ], + "type": "image", + "image_path": "68f3a593431fd01452381da560b7ce8616cef46fefb01bafd1e7817e27e8957a.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 352, + 547, + 387 + ], + "lines": [ + { + "bbox": [ + 304, + 352, + 547, + 387 + ], + "spans": [ + { + "bbox": [ + 304, + 352, + 547, + 387 + ], + "type": "text", + "content": "Figure 3. Illustration of the update of a single scene point feature. All " + }, + { + "bbox": [ + 304, + 352, + 547, + 387 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 352, + 547, + 387 + ], + "type": "text", + "content": " features are updated based on their previous value and the corresponding columns of " + }, + { + "bbox": [ + 304, + 352, + 547, + 387 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 352, + 547, + 387 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "code", + "bbox": [ + 306, + 411, + 533, + 513 + ], + "blocks": [ + { + "bbox": [ + 307, + 399, + 444, + 409 + ], + "lines": [ + { + "bbox": [ + 307, + 399, + 444, + 409 + ], + "spans": [ + { + "bbox": [ + 307, + 399, + 444, + 409 + ], + "type": "text", + "content": "Procedure 2 UPDATEVIEWFEAT" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "code_caption" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "lines": [ + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "spans": [ + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": "Input: " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " O Projection features " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "^+" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " observability matrix. \nInput: " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "\\nu" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " Previous view features (optional). \nInput: " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "d_p,d_v" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " Feature dimensions. \nOutput: " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "\\widehat{\\nu}" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " Updated view features. 1: " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}}\\gets \\{(\\mathcal{P}_{ij},\\mathcal{V}_i)\\mid \\mathbf{O}_{ij} = 1,i = 1,2,\\ldots ,m\\}" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " 2: if " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "\\nu" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " provided then 3: " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "\\widehat{\\nu}\\gets \\mathcal{V} + \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{V},\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}},d_p,d_v)" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " 4: else 5: " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "\\widehat{\\nu}\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{E}_{\\mathcal{P}\\rightarrow \\mathcal{V}},d_p,d_v)" + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "text", + "content": " 6: " + }, + { + "bbox": [ + 306, + 411, + 533, + 513 + ], + "type": "inline_equation", + "content": "\\widehat{\\nu}\\gets \\widehat{\\nu} +\\mathrm{FFN}(\\mathrm{ReLU}(\\mathrm{LN}(\\widehat{\\nu})))" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "code_body" + } + ], + "index": 11, + "sub_type": "algorithm" + }, + { + "type": "code", + "bbox": [ + 306, + 540, + 531, + 642 + ], + "blocks": [ + { + "bbox": [ + 307, + 528, + 476, + 538 + ], + "lines": [ + { + "bbox": [ + 307, + 528, + 476, + 538 + ], + "spans": [ + { + "bbox": [ + 307, + 528, + 476, + 538 + ], + "type": "text", + "content": "Procedure 3 UPDATESCENEPOINTFEAT" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "code_caption" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "lines": [ + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "spans": [ + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": "Input: " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": " , O Projection features " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "^+" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": " observability matrix. \nInput: S Previous scene point features (optional). \nInput: " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "d_p,d_s" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": " Feature dimensions. \nOutput: " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "\\widehat{S}" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": " Updated scene point features. 1: " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}}\\gets \\{(\\mathcal{P}_{ij},\\mathcal{S}_i)\\mid \\mathbf{O}_{ij} = 1,i = 1,2,\\ldots ,m\\}" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": " 2: if " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "\\mathcal{S}" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": " provided then 3: " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "\\widehat{S}\\gets \\mathcal{S} + \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{S},\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}},d_p,d_s)" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": " 4: else 5: " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "\\widehat{S}\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{P},\\mathcal{E}_{\\mathcal{P}\\to \\mathcal{S}},d_p,d_s)" + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "text", + "content": " 6: " + }, + { + "bbox": [ + 306, + 540, + 531, + 642 + ], + "type": "inline_equation", + "content": "\\widehat{S}\\gets \\widehat{S} +\\mathrm{FFN}(\\mathrm{ReLU}(\\mathrm{LN}(\\widehat{S})))" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "code_body" + } + ], + "index": 13, + "sub_type": "algorithm" + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": "point features " + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": " instead of " + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": ". This is carried out with two independent aggregations, with different learned parameters, and the sum of both aggregations constitute the residual mapping. Figure 4 provides an illustration for the update" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "text", + "content": "4811" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 72, + 70, + 265, + 182 + ], + "blocks": [ + { + "bbox": [ + 72, + 70, + 265, + 182 + ], + "lines": [ + { + "bbox": [ + 72, + 70, + 265, + 182 + ], + "spans": [ + { + "bbox": [ + 72, + 70, + 265, + 182 + ], + "type": "image", + "image_path": "ed715ae8ff51dda6a4fac7d787d5f44c555c3a1e6d34adf07606546bc735a678.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "lines": [ + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "spans": [ + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "type": "text", + "content": "Figure 4. Illustration of the global feature update, where " + }, + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "type": "inline_equation", + "content": "\\mathbf{g}" + }, + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "type": "text", + "content": " is updated based on its previous value, together with an aggregation of all " + }, + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 188, + 289, + 222 + ], + "type": "text", + "content": " features." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 244, + 91, + 256 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 244, + 91, + 256 + ], + "spans": [ + { + "bbox": [ + 47, + 244, + 91, + 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" + }, + { + "bbox": [ + 49, + 311, + 179, + 319 + ], + "type": "inline_equation", + "content": "d_v, d_s, d_g" + }, + { + "bbox": [ + 49, + 311, + 179, + 319 + ], + "type": "text", + "content": " Feature dimensions." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 49, + 320, + 170, + 329 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 320, + 170, + 329 + ], + "spans": [ + { + "bbox": [ + 49, + 320, + 170, + 329 + ], + "type": "text", + "content": "Output: " + }, + { + "bbox": [ + 49, + 320, + 170, + 329 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathbf{g}}" + }, + { + "bbox": [ + 49, + 320, + 170, + 329 + ], + "type": "text", + "content": " Updated global features." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 52, + 329, + 190, + 339 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 329, + 190, + 339 + ], + "spans": [ + { + "bbox": [ + 52, + 329, + 190, + 339 + ], + "type": "text", + "content": "1: " + }, + { + "bbox": [ + 52, + 329, + 190, + 339 + ], + "type": "inline_equation", + "content": "\\mathcal{E}_{\\mathcal{V}\\to \\mathbf{g}}\\gets \\{(\\mathcal{V}_i,\\mathbf{g})\\mid i = 1,2,\\ldots ,m\\}" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 52, + 339, + 189, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 339, + 189, + 348 + ], + "spans": [ + { + "bbox": [ + 52, + 339, + 189, + 348 + ], + "type": "text", + "content": "2: " + }, + { + "bbox": [ + 52, + 339, + 189, + 348 + ], + "type": "inline_equation", + "content": "\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}}\\gets \\left\\{(\\mathcal{S}_j,\\mathbf{g})\\mid j = 1,2,\\ldots ,n\\right\\}" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 52, + 349, + 123, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 349, + 123, + 357 + ], + "spans": [ + { + "bbox": [ + 52, + 349, + 123, + 357 + ], + "type": "text", + "content": "3: if " + }, + { + "bbox": [ + 52, + 349, + 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377 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathbf{g}}_s\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{S},\\{\\mathbf{g}\\},\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}},d_s,d_g)" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 52, + 377, + 137, + 386 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 377, + 137, + 386 + ], + "spans": [ + { + "bbox": [ + 52, + 377, + 137, + 386 + ], + "type": "text", + "content": "6: " + }, + { + "bbox": [ + 52, + 377, + 137, + 386 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathbf{g}}\\gets \\mathbf{g} + \\widehat{\\mathbf{g}}_v + \\widehat{\\mathbf{g}}_s" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 52, + 387, + 76, + 394 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 387, + 76, + 394 + ], + "spans": [ + { + "bbox": [ + 52, + 387, + 76, + 394 + ], + "type": "text", + "content": "7: else" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 52, + 396, + 258, + 405 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 396, + 258, + 405 + ], + "spans": [ + { + "bbox": [ + 52, + 396, + 258, + 405 + ], + "type": "text", + "content": "8: " + }, + { + "bbox": [ + 52, + 396, + 258, + 405 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathbf{g}}_v\\gets \\mathrm{GRAPHCROSSATTENTION}(\\mathcal{V}, - ,\\mathcal{E}_{\\mathcal{V}\\to \\mathbf{g}},d_v,d_g)" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 52, + 405, + 263, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 405, + 263, + 415 + ], + "spans": [ + { + "bbox": [ + 52, + 405, + 263, + 415 + ], + "type": "text", + "content": "9: " + }, + { + "bbox": [ + 52, + 405, + 263, + 415 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathbf{g}}_s\\gets +\\mathrm{GRAPHCROSSATTENTION}(\\mathcal{S}, - ,\\mathcal{E}_{\\mathcal{S}\\to \\mathbf{g}},d_s,d_g)" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 51, + 415, + 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The projection features are updated according to Procedure 5. No aggregation is involved during this step. Instead, at every projection node the corresponding " + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "inline_equation", + "content": "\\nu" + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "inline_equation", + "content": "\\mathbf{g}" + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "text", + "content": " features are all collected along with the current projection features " + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "text", + "content": ", as illustrated in Figure 5. Each of these sources then undergoes a ReLU activation and normalization with LN, before being concatenated. Note that the initial projection features " + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "inline_equation", + "content": "\\mathcal{P}_0" + }, + { + "bbox": [ + 46, + 469, + 289, + 624 + ], + "type": "text", + "content": " are typically also added to the input, and in this case they are simply concatenated to the previous projection features before the procedure is called. Finally, a residual mapping is applied, by feeding the concatenated features to a shared feed-forward network." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 46, + 641, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 289, + 715 + ], + "type": "text", + "content": "Entire Network Architecture. Now we have all the pieces to define the complete network architecture, which is outlined in Procedure 6. The structure is straightforward: 1) UPDATEVIEWFEAT and UPDATESCENEPOINTFEAT (Procedures 2 and 3) are called to aggregate projection features. 2) UPDATEGLOBALFEAT (Procedure 4) is called to aggre" + } + ] + } + ], + "index": 22 + }, + { + "type": "image", + "bbox": [ + 324, + 69, + 529, + 188 + ], + "blocks": [ + { + "bbox": [ + 324, + 69, + 529, + 188 + ], + "lines": [ + { + "bbox": [ + 324, + 69, + 529, + 188 + ], + "spans": [ + { + "bbox": [ + 324, + 69, + 529, + 188 + ], + "type": "image", + "image_path": "c2b0f061a2942b8ba7fa558c430767d5fecfb076624389813278412012ff3ffe.jpg" + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "lines": [ + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "spans": [ + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "text", + "content": "Figure 5. Illustration of the update of a single projection feature. All " + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "text", + "content": " features are updated based on their previous value, as well as initial projection features " + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "inline_equation", + "content": "\\mathcal{P}_0" + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "text", + "content": ", the global feature " + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "inline_equation", + "content": "\\mathbf{g}" + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "text", + "content": ", and the corresponding " + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 194, + 547, + 239 + ], + "type": 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315, + 443, + 324 + ], + "type": "text", + "content": "Output: " + }, + { + "bbox": [ + 307, + 315, + 443, + 324 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 307, + 315, + 443, + 324 + ], + "type": "text", + "content": " Updated projection features." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 310, + 325, + 545, + 371 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 325, + 545, + 371 + ], + "spans": [ + { + "bbox": [ + 310, + 325, + 545, + 371 + ], + "type": "text", + "content": "1: " + }, + { + "bbox": [ + 310, + 325, + 545, + 371 + ], + "type": "inline_equation", + "content": "\\widehat{\\mathcal{P}}\\gets \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{V}))\\parallel \\mathrm{ReLU}(\\mathrm{LN}(\\mathcal{S}))" + }, + { + "bbox": [ + 310, + 325, + 545, + 371 + ], + "type": "inline_equation", + "content": "\\| \\operatorname {ReLU}(\\operatorname {LN}(\\mathbf{g}))\\| \\operatorname {ReLU}(\\operatorname 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"text", + "content": "gate the resulting features further, to a single global feature vector. 3) UPDATEPROJFEAT (Procedure 5) is called in order to again distribute the aggregated information across the projection features. These steps are repeated " + }, + { + "bbox": [ + 304, + 411, + 547, + 651 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 411, + 547, + 651 + ], + "type": "text", + "content": " times, where we refer to " + }, + { + "bbox": [ + 304, + 411, + 547, + 651 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 411, + 547, + 651 + ], + "type": "text", + "content": " as the number of layers. Then, a final call to UPDATEVIEWFEAT and UPDATESCENEPOINTFEAT is carried out, and the resulting view and scene point features are further processed by two corresponding regression heads, consisting of shared 3-layer feed-forward networks (FFN) with hidden neurons of the same dimension as the input (" + }, + { + "bbox": [ + 304, + 411, + 547, + 651 + ], + "type": "inline_equation", + "content": "d_v" + }, + { + "bbox": [ + 304, + 411, + 547, + 651 + ], + "type": "text", + "content": " or " + }, + { + "bbox": [ + 304, + 411, + 547, + 651 + ], + "type": "inline_equation", + "content": "d_s" + }, + { + "bbox": [ + 304, + 411, + 547, + 651 + ], + "type": "text", + "content": "). The scene point head simply outputs the 3 coordinates of every estimated scene point. For Euclidean reconstruction, the view head outputs the 3 coordinates of the location of the camera center, together with a unit-norm quaternion representing its orientation. For projective reconstruction, all 12 camera matrix elements are regressed, followed by a normalization in the same manner as [31]. Except for the regression heads, we use 1-layer FFNs throughout the network, which in general seemed slightly easier to train." + } + ] + } + ], + "index": 34 + }, + { + "bbox": [ + 306, + 658, + 395, + 670 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 658, + 395, + 670 + ], + "spans": [ + { + "bbox": [ + 306, + 658, + 395, + 670 + ], + "type": "text", + "content": "3.2. Loss Function" + } + ] + } + ], + "index": 35 + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": "The network is trained using the Adam optimizer, and as loss function we use the (non-squared) reprojection error, averaged over all observed image points. To handle negative" + } + ] + } + ], + "index": 36 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4812" + } + ] + } + ], + "index": 37 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "code", + "bbox": [ + 48, + 85, + 287, + 310 + ], + "blocks": [ + { + "bbox": [ + 49, + 72, + 203, + 82 + ], + "lines": [ + { + "bbox": [ + 49, + 72, + 203, + 82 + ], + "spans": [ + { + "bbox": [ + 49, + 72, + 203, + 82 + ], + "type": "text", + "content": "Procedure 6 GRAPHATTENTIONSFM" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "code_caption" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "lines": [ + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "spans": [ + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": "Input: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathcal{M}" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " Image point tracks, normalized. \nInput: O Observability matrix. \nInput: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "d_p,d_v,d_s,d_g" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " Feature dimensions. \nInput: L Number of layers. \nOutput: V Estimated camera parameters. \nOutput: S Estimated scene points. \n1: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathcal{P}_0\\gets \\mathrm{Linear}_{2\\to 2}(\\mathcal{M})" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " // Initial projection features: linear embedding of image points. \n2: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathcal{V}\\gets" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " UPDATEVIEWFEAT " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "(\\mathcal{P}_0,\\mathbf{O}, - ,2,d_v)" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " \n3: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathcal{S}\\gets" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " UPDATESCENEPOINTFEAT " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "(\\mathcal{P}_0,\\mathbf{O}, - ,2,d_s)" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " \n4: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathbf{g}\\gets" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " UPDATEGLOBALFEAT " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "(\\mathcal{V},\\mathcal{S}, - ,d_v,d_s,d_g)" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " \n5: for " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "l = 1,2,\\dots ,L" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " do \n6: if " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "l = 1" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " then \n7: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathcal{P}\\gets" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " UPDATEPROJFEAT " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "(\\mathcal{P}_0,\\mathcal{V},\\mathcal{S},\\mathbf{g},2,d_v,d_s,d_g,d_p)" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " \n8: else \n9: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathcal{P}\\gets" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " UPDATEPROJFEAT " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "(\\mathcal{P}\\| \\mathcal{P}_0,\\mathcal{V},\\mathcal{S},\\mathbf{g}," + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "d_p + 2,d_v,d_s,d_g,d_p)" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " \n10: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathcal{V}\\gets" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " UPDATEVIEWFEAT " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "(\\mathcal{P},\\mathbf{O},\\mathcal{V},d_p,d_v)" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " \n12: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathcal{S}\\gets" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " UPDATESCENEPOINTFEAT " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "(\\mathcal{P},\\mathbf{O},\\mathcal{S},d_p,d_s)" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " \n13: if " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "l < L" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " then \n14: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\mathbf{g}\\gets" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " UPDATEGLOBALFEAT " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "(\\mathcal{V},\\mathcal{S},\\mathbf{g},d_v,d_s,d_g)" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " \n15: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{P}_i\\} \\gets \\mathrm{FFN}(\\mathrm{ReLU}(\\mathcal{V}))" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " // Camera regression head \n16: " + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{X}_j\\} \\gets \\mathrm{FFN}(\\mathrm{ReLU}(\\mathcal{S}))" + }, + { + "bbox": [ + 48, + 85, + 287, + 310 + ], + "type": "text", + "content": " // Scene point regression head" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "code_body" + } + ], + "index": 1, + "sub_type": "algorithm" + }, + { + "bbox": [ + 47, + 334, + 287, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 334, + 287, + 392 + ], + "spans": [ + { + "bbox": [ + 47, + 334, + 287, + 392 + ], + "type": "text", + "content": "depths and overcome the singularity at the principal plane, we substitute the reprojection error with minus the depth in the loss function for any projection with depth smaller than a threshold " + }, + { + "bbox": [ + 47, + 334, + 287, + 392 + ], + "type": "inline_equation", + "content": "h = 1e - 4" + }, + { + "bbox": [ + 47, + 334, + 287, + 392 + ], + "type": "text", + "content": ". We also apply gradient normalization in the same manner as [31]." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 403, + 161, + 415 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 403, + 161, + 415 + ], + "spans": [ + { + "bbox": [ + 47, + 403, + 161, + 415 + ], + "type": "text", + "content": "3.3. Data Augmentation" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 422, + 287, + 541 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 422, + 287, + 541 + ], + "spans": [ + { + "bbox": [ + 46, + 422, + 287, + 541 + ], + "type": "text", + "content": "For Euclidean reconstruction, where the image points are normalized using the intrinsic camera parameters, and therefore geometrically interpretable, we experiment with augmenting the training scenes with slightly transformed variations. While the scene points remain fixed, each camera is randomly rotated about its center, first by a uniformly sampled angle " + }, + { + "bbox": [ + 46, + 422, + 287, + 541 + ], + "type": "inline_equation", + "content": "\\alpha \\in [-15, 15]" + }, + { + "bbox": [ + 46, + 422, + 287, + 541 + ], + "type": "text", + "content": " about the principal axis, followed by a uniformly sampled angle " + }, + { + "bbox": [ + 46, + 422, + 287, + 541 + ], + "type": "inline_equation", + "content": "\\gamma \\in [-20, 20]" + }, + { + "bbox": [ + 46, + 422, + 287, + 541 + ], + "type": "text", + "content": " about an axis orthogonal to the principal axis with a random direction. The image points are transformed accordingly." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 551, + 192, + 563 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 551, + 192, + 563 + ], + "spans": [ + { + "bbox": [ + 47, + 551, + 192, + 563 + ], + "type": "text", + "content": "3.4. Artificial Outlier Injection" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": "We also consider the presence of measurement outliers, by artificially corrupting the data. This is done by: 1) Selecting a subset of the 2D keypoint measurements to be replaced by artificial outliers. 2) For each view, replace all measurements marked to be outliers with random samples from a bivariate normal distribution, which is fit to all remaining (inlier) points. For step 1), we carefully select points for outlier injection such that we avoid getting any scene points visible in " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "< 2" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": " views or any views with " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "< 8" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": " scene points visible, if regarding only the inlier projections. In the supplementary material, the details are given on how this is achieved. Note that while the network input is corrupted by outlier injec" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 72, + 545, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 95 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 95 + ], + "type": "text", + "content": "tion, the uncorrupted data is still used as learning targets for the loss function." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 108, + 359, + 120 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 108, + 359, + 120 + ], + "spans": [ + { + "bbox": [ + 306, + 108, + 359, + 120 + ], + "type": "text", + "content": "4. Results" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 129, + 422, + 141 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 129, + 422, + 141 + ], + "spans": [ + { + "bbox": [ + 306, + 129, + 422, + 141 + ], + "type": "text", + "content": "4.1. Experimental Setup" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 147, + 545, + 290 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 147, + 545, + 290 + ], + "spans": [ + { + "bbox": [ + 304, + 147, + 545, + 290 + ], + "type": "text", + "content": "We take a particular interest in Euclidean reconstruction, due to the relevance of metric reconstructions for photogrammetry applications. Furthermore, we focus mainly on the task of learning and generalizing from a set of training scenes, due to the great potential in having a fast learned model acquire reconstructions of completely novel scenes. We use the DPESFM method of Moran et al. [31] as a baseline, as they have presented experiments on precisely this. To this end, we also use Olsson's dataset [33] (together with the VGG dataset [12] for additional projective reconstruction experiments in the supplement), and we use the same random partition of 10 test scenes and 3 validation scenes." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "spans": [ + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "text", + "content": "We base our implementation on that of [31], implemented in PyTorch [34], but replace the network architecture with our proposed GRAPHATTENTIONSFM network, implemented using GATv2Conv layers [4] from PyTorch Geometric [11]. The implementation details are in general consistent with [31], for more details see the supplement. The DPESFM results reproduced by us are obtained by running the method of [31] with our code base, with the hyperparameters published on the official GitHub repository of the method [30]. For our model, we use " + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "inline_equation", + "content": "L = 12" + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "text", + "content": " layers and feature dimensions " + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "inline_equation", + "content": "d_{p} = 32" + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "inline_equation", + "content": "d_{v} = 1024" + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "inline_equation", + "content": "d_{s} = 64" + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "inline_equation", + "content": "d_{g} = 2048" + }, + { + "bbox": [ + 304, + 291, + 546, + 495 + ], + "type": "text", + "content": ", which corresponds to 145M parameters. By using small dimensions for the projection features and scene point features the otherwise high memory consumption is significantly reduced. Hyper-parameters have been chosen based on the performance on the validation data, but without any rigorous hyper-parameter tuning." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 503, + 524, + 514 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 503, + 524, + 514 + ], + "spans": [ + { + "bbox": [ + 306, + 503, + 524, + 514 + ], + "type": "text", + "content": "4.2. Euclidean Reconstruction of Novel Scenes" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": "In Table 1, we report the Euclidean reconstruction results of our method, when applied on novel test scenes, and measure the performance by reprojection errors, as well as rotation and translation errors for the estimated camera poses. For calculating the latter, the predicted and ground truth poses are first aligned to a common reference frame, as described in Section C in the supplement. The results of DPESFM as reported in [31] can be seen in parentheses, when available, but we also retrain their model and incorporate further results of the model, not reported in [31], in particular results without bundle adjustment, and additional metrics to reprojection errors. Experiments are carried out both with and without data augmentation with random rotational cameras perturbations, as described in Section 3.3, and the columns are partitioned accordingly. Consistently with [31], Inference refers to the network output followed" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4813" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 47, + 69, + 545, + 401 + ], + "blocks": [ + { + "bbox": [ + 47, + 69, + 545, + 401 + ], + "lines": [ + { + "bbox": [ + 47, + 69, + 545, + 401 + ], + "spans": [ + { + "bbox": [ + 47, + 69, + 545, + 401 + ], + "type": "table", + "html": "
Without data augmentationWith data augmentationColmap
InferenceInference + BAInferenceInference + BA
OursDPESFMOursDPESFMOursDPESFMOursDPESFM
Reprojection error (px)Alcatraz Courtyard68.4168.501.700.81 (0.82)36.0192.370.810.920.81
Alcatraz Water Tower36.3050.471.051.13 (0.55)87.672831.940.8810.160.55
Drinking Fountain Somewhere in Zurich36.0245.870.550.31 (7.21)219.75234.900.316.730.31
Nijo Castle Gate65.7164.530.730.73 (5.81)61.4168.190.880.890.73
Porta San Donato Bologna74.3294.260.740.74 (1.10)52.1584.460.760.750.75
Round Church Cambridge61.1855.510.390.39 (0.50)29.8059.540.391.490.39
Smolny Cathedral St Petersburg156.16120.850.810.81 (15.15)85.3887.810.810.810.81
Some Cathedral in Barcelona150.01146.1010.4212.71 (21.46)125.68687.830.8916.770.89
Sri Veeramakaliamman Singapore121.02157.392.1916.87 (16.92)83.50166.682.139.300.71
Yueh Hai Ching Temple Singapore37.4652.590.650.65 (1.16)25.6051.350.650.730.65
Average80.6685.611.923.52 (7.07)80.69436.510.854.860.66
Rotation error (deg)Alcatraz Courtyard10.10213.2012.6070.0356.09310.9460.0380.0300.043
Alcatraz Water Tower10.63711.0530.4990.76411.50110.6410.69919.3510.228
Drinking Fountain Somewhere in Zurich15.84616.0140.0030.00115.41515.7040.00122.7590.007
Nijo Castle Gate16.75110.5460.0620.06217.34720.0320.0380.0360.064
Porta San Donato Bologna23.83924.1200.0950.09418.41125.0040.0940.0940.099
Round Church Cambridge18.90614.4730.0290.02610.29518.6850.0291.0860.035
Smolny Cathedral St Petersburg19.38717.9710.0230.02211.66214.3800.0230.0190.029
Some Cathedral in Barcelona27.27030.47110.00920.05027.90829.1190.02047.8920.025
Sri Veeramakaliamman Singapore28.27536.9030.5494.87123.70236.1760.4572.7590.169
Yueh Hai Ching Temple Singapore15.73322.7060.0380.0389.51521.5610.0380.0380.043
Average18.67519.7461.3912.59615.18520.2250.1449.4060.074
Translation error (m)Alcatraz Courtyard4.824.931.090.012.735.740.010.010.01
Alcatraz Water Tower8.667.350.310.447.537.770.419.050.12
Drinking Fountain Somewhere in Zurich4.444.440.000.004.454.460.001.380.00
Nijo Castle Gate5.073.080.010.015.676.950.010.010.01
Porta San Donato Bologna9.5010.720.050.054.8010.480.050.050.05
Round Church Cambridge8.947.190.010.015.289.000.010.560.01
Smolny Cathedral St Petersburg2.702.430.010.012.332.520.010.010.01
Some Cathedral in Barcelona12.6412.693.226.3812.3212.660.0111.930.01
Sri Veeramakaliamman Singapore4.944.900.161.324.934.900.140.770.04
Yueh Hai Ching Temple Singapore4.124.270.010.012.444.280.010.010.01
Average6.586.200.490.825.256.880.072.380.03
", + "image_path": "b299fb1ecc507bbe1aeeb195be0886ffeef2f0e874c84281e49386e8679c0227.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 52, + 461, + 288, + 569 + ], + "blocks": [ + { + "bbox": [ + 46, + 410, + 546, + 444 + ], + "lines": [ + { + "bbox": [ + 46, + 410, + 546, + 444 + ], + "spans": [ + { + "bbox": [ + 46, + 410, + 546, + 444 + ], + "type": "text", + "content": "Table 1. Results of Euclidean reconstruction of novel test scenes, with and without data augmentation. The results of DPESFM [31] have been acquired by us training the model, along with the results reported by [31] in parentheses, if available. The result of Colmap, as reported by [31], is also added for reference." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 52, + 461, + 288, + 569 + ], + "lines": [ + { + "bbox": [ + 52, + 461, + 288, + 569 + ], + "spans": [ + { + "bbox": [ + 52, + 461, + 288, + 569 + ], + "type": "table", + "html": "
SceneInfer.BAColmap
Alcatraz Courtyard0.2445.54286
Alcatraz Water Tower0.1331.11130
Drinking Fountain Somewhere In Zurich0.061.9816
Nijo Castle Gate0.093.9721
Porta San Donato Bologna0.1827.02170
Round Church Cambridge0.4356.47229
Smolny Cathedral St Petersburg0.4986.09516
Some Cathedral In Barcelona0.2447.05451
Sri Veeramakaliamman Singapore0.63115.80583
Yueh Hai Ching Temple Singapore0.088.54106
", + "image_path": "73289d5b410e5b30c4303de0d567afe882d8588c07b82357653bb84ed13379a1.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 577, + 287, + 600 + ], + "lines": [ + { + "bbox": [ + 47, + 577, + 287, + 600 + ], + "spans": [ + { + "bbox": [ + 47, + 577, + 287, + 600 + ], + "type": "text", + "content": "Table 2. Runtime (s) of our method for Euclidean reconstruction on test scenes, in comparison with Colmap (measured by [31])." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": "by a computationally cheap triangulation and Inference " + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "inline_equation", + "content": "+" + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": " BA refers to the network output followed by bundle adjustment, which is carried out in the same manner as [31], using the Ceres solver [1]. Moran et al. [31] also performed experiments with fine-tuning the network parameters on the test scenes. In contrast, we advocate against this, since this approach is relatively costly, and one might as well acquire" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 305, + 464, + 545, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 464, + 545, + 513 + ], + "spans": [ + { + "bbox": [ + 305, + 464, + 545, + 513 + ], + "type": "text", + "content": "high-quality reconstructions from traditional SfM pipelines such as Colmap, in similar execution time. Nevertheless, the supplementary material includes such experiments, for completeness." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 521, + 546, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 546, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 546, + 715 + ], + "type": "text", + "content": "Without data augmentation, there is no clear difference between the Inference results of both methods. Neither reconstruction is good, and it is not so meaningful to compare minor differences in the metrics under these circumstances. In particular, calculating rotation and translation errors requires aligning the predicted and ground truth camera poses in a common reference frame, as described in Section C in the supplement, and when the predicted configuration of camera poses is not very consistent with the ground truth, determining this alignment itself can be sensitive. In all other scenarios, we outperform DPESFM, and when using both data augmentation and applying bundle adjustment, the solutions we acquire for the novel test scenes are in general very good. In terms of reprojection error and translation error, we match the performance of Colmap for almost every test scene, leading to an average reprojection" + } + ] + } + ], + "index": 6 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4814" + } + ] + } + ], + "index": 7 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 120 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 120 + ], + "type": "text", + "content": "error of 0.85 (vs 0.66) px, and an average translation error of 0.07 (vs 0.03) m. In terms of rotation error, the error is actually lower than Colmap's for 8 out of 10 scenes, but the average error is slightly larger: 0.144 (vs 0.074) degrees." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 129, + 194, + 141 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 129, + 194, + 141 + ], + "spans": [ + { + "bbox": [ + 47, + 129, + 194, + 141 + ], + "type": "text", + "content": "4.3. Artificial Outlier Injection" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 147, + 287, + 182 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 147, + 287, + 182 + ], + "spans": [ + { + "bbox": [ + 46, + 147, + 287, + 182 + ], + "type": "text", + "content": "In Table 3 we present additional results where, on top of data augmentation (see Section 3.3), we also apply artificial outlier injection during training according to Section 3.4." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 183, + 288, + 410 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 183, + 288, + 410 + ], + "spans": [ + { + "bbox": [ + 46, + 183, + 288, + 410 + ], + "type": "text", + "content": "We evaluate inference of the model in two settings: 1) Applied on the uncorrupted outlier-free test scenes as is. 2) Applied to the test scenes followed by random injection of " + }, + { + "bbox": [ + 46, + 183, + 288, + 410 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 46, + 183, + 288, + 410 + ], + "type": "text", + "content": ", in the same manner as during training2. One can immediately observe significantly reduced reprojection errors for our model, suggesting that the outlier injection during training has a regularizing effect. Beyond that, this experiment is intended to serve as a teaser for the utility and promise of learning-based methods for SfM. Constant challenges such as the presence of outliers may not be as big of a challenge for learning-based as for conventional methods, and the phenomenon may even be exploited to develop effective training strategies. In fact, for any real-world scenario, it is crucial for learning-based methods applied on image point correspondences to be resilient to outliers, as we do not have the luxury of facing high-quality curated data such as Olsson's [33] in the wild. Note that it should be possible to apply bundle adjustment on the corrupted test data as well, when combined with a robust loss function." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 411, + 287, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 411, + 287, + 483 + ], + "spans": [ + { + "bbox": [ + 46, + 411, + 287, + 483 + ], + "type": "text", + "content": "Similarly as for the data augmentation, we note that DPESFM appears to struggle with the presence of outliers during training, and its performance on the test scenes at inference is not very good. It is very probable that the nonlinear attention layers make our model more powerful and expressive than DPESFM." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 491, + 157, + 502 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 491, + 157, + 502 + ], + "spans": [ + { + "bbox": [ + 47, + 491, + 157, + 502 + ], + "type": "text", + "content": "4.4. Additional Results" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 509, + 287, + 557 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 509, + 287, + 557 + ], + "spans": [ + { + "bbox": [ + 46, + 509, + 287, + 557 + ], + "type": "text", + "content": "In the supplementary material we provide additional results on projective reconstruction, as well as single-scene optimization, for completeness. We also include statistics of the number of views and scene points for each scene." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 569, + 119, + 582 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 569, + 119, + 582 + ], + "spans": [ + { + "bbox": [ + 47, + 569, + 119, + 582 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 589, + 287, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 589, + 287, + 685 + ], + "spans": [ + { + "bbox": [ + 46, + 589, + 287, + 685 + ], + "type": "text", + "content": "With this paper we have added to the research direction of learned initialization-free Structure-from-Motion by introducing a novel and expressive graph attention network outperforming previous learning-based methods for Euclidean reconstruction of novel scenes. When succeeded by bundle adjustment, we are able to reconstruct novel test scenes to perfection or of very decent precision, at a speedup of about " + }, + { + "bbox": [ + 46, + 589, + 287, + 685 + ], + "type": "inline_equation", + "content": "5 - 10 \\times" + }, + { + "bbox": [ + 46, + 589, + 287, + 685 + ], + "type": "text", + "content": " compared to Colmap. Moreover, we illustrate great" + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 306, + 69, + 543, + 262 + ], + "blocks": [ + { + "bbox": [ + 306, + 69, + 543, + 262 + ], + "lines": [ + { + "bbox": [ + 306, + 69, + 543, + 262 + ], + "spans": [ + { + "bbox": [ + 306, + 69, + 543, + 262 + ], + "type": "table", + "html": "
UncorruptedOutlier-injected
OursDPESFMOursDPESFM
Alcatraz Courtyard47.7485.8152.9994.24
Alcatraz Water Tower35.9672.8437.8983.55
Drinking Fountain \nSomewhere in Zurich52.081012.1446.651453.31
Nijo Castle Gate46.4872.9962.52126.18
Porta San Donato \nBologna53.1288.0265.0894.72
Round Church \nCambridge36.0963.7248.6390.63
Smolny Cathedral St \nPetersburg47.2891.0359.5298.05
Some Cathedral in \nBarcelona109.86397.75123.75462.28
Sri Veeramakali-\namman Singapore63.60169.6370.90146.98
Yueh Hai Ching \nTemple Singapore26.8351.4136.6957.59
Average51.91210.5360.46270.75
", + "image_path": "e4796d1a9b5307bc64ef465411597a51c8735535b2e9cb624ba9574e34e2bc33.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 270, + 545, + 314 + ], + "lines": [ + { + "bbox": [ + 305, + 270, + 545, + 314 + ], + "spans": [ + { + "bbox": [ + 305, + 270, + 545, + 314 + ], + "type": "text", + "content": "Table 3. Reprojection errors of Euclidean reconstruction of novel test scenes, with model trained with data augmentation as well as artificial outlier injection. The results of DPESFM [31] have been acquired by us training the model." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 335, + 545, + 383 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 335, + 545, + 383 + ], + "spans": [ + { + "bbox": [ + 304, + 335, + 545, + 383 + ], + "type": "text", + "content": "potential in coping with the presence of outliers, and even show artificial outlier injection to provide an effective regularizing training strategy, combined with data augmentation by random rotational camera perturbations." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 384, + 546, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 384, + 546, + 563 + ], + "spans": [ + { + "bbox": [ + 304, + 384, + 546, + 563 + ], + "type": "text", + "content": "For future work, it could definitely be promising to train on larger datasets, since model generalization is still a challenge. While the proposed model does not require fine-tuning, and thus is much faster to execute than previous work, it still relies on bundle adjustment to acquire a good reconstruction, which constitutes the computational bottleneck. Exploring alternative formulations where the network regresses relative camera poses is also an interesting direction, as the current absolute pose prediction may be a weakness due to the reconstruction ambiguity up to a similarity transformation. Other possible research directions include unrolling the architecture to multiple learned iterations / refinement steps, extensions to non-rigid Structure-from-Motion, and incorporating modern learned image matching pipelines such as [5, 6, 40] in an end-to-end fashion." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 577, + 545, + 708 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 577, + 545, + 708 + ], + "spans": [ + { + "bbox": [ + 304, + 577, + 545, + 708 + ], + "type": "text", + "content": "Acknowledgements The work was supported by the Wallenberg AI, Autonomous Systems and Software Program (WASP) funded by the Knut and Alice Wallenberg Foundation, and the Swedish Research Council grants no. 2016-04445, 2018-05375, and 2023-05341. Computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) at Chalmers Centre for Computational Science and Engineering (C3SE) and National Supercomputer Centre (NSC) Berzelius at Linköping University partially funded by the Swedish Research Council through grant no. 2022-06725." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 46, + 693, + 287, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 693, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 693, + 287, + 713 + ], + "type": "text", + "content": "2Yet, during evaluation, we use all true measurements as ground truth targets when calculating reprojection errors, even in the corrupted case." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4815" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 713 + ], + "type": "list", + "angle": 0, + "index": 18, + "blocks": [ + { + "bbox": [ + 53, + 91, + 286, + 113 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 286, + 113 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 286, + 113 + ], + "type": "text", + "content": "[1] Sameer Agarwal, Keir Mierle, and Others. 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In 2018 IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 1876-1885, 2018. 1" + } + ] + } + ], + "index": 18 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "4817" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_content_list.json b/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..dc9f1462ccd9739ce077bb09b99fd62945e452a6 --- /dev/null +++ b/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_content_list.json @@ -0,0 +1,1565 @@ +[ + { + "type": "text", + "text": "Learning Transferable Negative Prompts for Out-of-Distribution Detection", + "text_level": 1, + "bbox": [ + 107, + 130, + 861, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Tianqi Li $^{1}$ , Guansong Pang $^{*2}$ , Xiao Bai $^{*1}$ , Wenjun Miao $^{1}$ , and Jin Zheng $^{1}$", + "bbox": [ + 194, + 176, + 772, + 196 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{1}$ School of Computer Science and Engineering, State Key Laboratory of Complex & Critical Software Environment, Jiangxi Research Institute, Beihang University, China", + "bbox": [ + 83, + 207, + 885, + 243 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ School of Computing and Information Systems, Singapore Management University", + "bbox": [ + 151, + 243, + 815, + 262 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 299, + 312, + 315 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Existing prompt learning methods have shown certain capabilities in Out-of-Distribution (OOD) detection, but the lack of OOD images in the target dataset in their training can lead to mismatches between OOD images and InDistribution (ID) categories, resulting in a high false positive rate. To address this issue, we introduce a novel OOD detection method, named 'NegPrompt', to learn a set of negative prompts, each representing a negative connotation of a given class label, for delineating the boundaries between ID and OOD images. It learns such negative prompts with ID data only, without any reliance on external outlier data. Further, current methods assume the availability of samples of all ID classes, rendering them ineffective in open-vocabulary learning scenarios where the inference stage can contain novel ID classes not present during training. In contrast, our learned negative prompts are transferable to novel class labels. Experiments on various ImageNet benchmarks show that NegPrompt surpasses state-of-the-art prompt-learning-based OOD detection methods and maintains a consistent lead in hard OOD detection in closed- and open-vocabulary classification scenarios. Code is available at https://github.com/mala-lab/negprompt.", + "bbox": [ + 75, + 330, + 473, + 664 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 675, + 209, + 690 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Since the advent of deep learning, numerous image recognition models [5, 9, 29] have relied solely on image features for classification. However, in recent years large pre-trained vision-language models (VLMs), such as CLIP [37], integrated natural language processing into computer vision, enhancing the semantic understanding capabilities of computer vision models. It has been observed that these VLMs excel in image classification, particularly in zero-shot scenarios. This is attributed to their extensive self-supervised pre-training on web-scale image-text data, which has endowed them with robust semantic transfer abilities.", + "bbox": [ + 75, + 700, + 468, + 864 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/a26a53cb8e4acb4e42ce9ab9fc1e8307b384667804981ba7b389b40980f1beb5.jpg", + "image_caption": [ + "Figure 1. Illustration of the key intuition of NegPrompt. For each ID class, NegPrompt trains a small set of learnable prompts that have negative semantics to the learned positive prompt of the given class. As a result, OOD samples exhibit higher similarity to the negative prompts than the positive prompts." + ], + "image_footnote": [], + "bbox": [ + 503, + 297, + 890, + 465 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Despite the strong zero-shot classification capabilities of VLMs, numerous research efforts are put to unleash their potential, e.g., by investigating whether models like CLIP can achieve enhanced performance with training on downstream target datasets. This has led to the development of various techniques to fine-tune CLIP [8, 18], among which prompt learning has sparked widespread interest. Prompt learning (or prompt tuning) [19, 39, 50], a methodology originating from natural language processing, focuses on learning the prompt inputs into a large-scale pre-trained network, rather than learning or fine-tuning the parameters of the network. In CLIP, a common prompt is 'a photo of a [class name]'. The aim of prompt learning, e.g., in approaches like CoOp [54], is to learn a soft/differentiable context vector to replace the fixed text prompt like 'a photo of a', thereby leveraging CLIP's powerful generalization in semantic understanding while also fine-tuning for specific target datasets [53, 54].", + "bbox": [ + 496, + 550, + 893, + 823 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "However, even though prompt learning enhances the target dataset perception capabilities of VLMs, it struggles with Out-Of-Distribution (OOD) detection [10, 26]. Under the OOD detection task, the test set comprises images from both the training classes - in-distribution (ID) data -", + "bbox": [ + 496, + 825, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author: G. Pang (gspang@smu.edu.sg) and X. Bai (baixiao@buaa.edu.cn)", + "bbox": [ + 76, + 875, + 468, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "17584", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "and images from other unknown categories (OOD images). VLM-based classification is typically performed by first replacing the '[class name]' with the class label of each category in a prompt, which is then processed by the text encoder of CLIP to obtain the class embedding and assign the class label that has the highest cosine similarity with the embedding of a test image from the image encoder of CLIP. However in OOD detection tasks, the models do not have access to the class names of OOD images, thereby lacking the knowledge about OOD data.", + "bbox": [ + 75, + 90, + 472, + 241 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "This issue, exacerbated by the models' tendency towards overconfidence that often predicts OOD data as ID images with high confidence [34], undermines their ability to effectively detect OOD images.", + "bbox": [ + 76, + 243, + 468, + 304 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "There have been a number of CLIP-based methods designed specifically for VLM-driven OOD detection methods, but most of them [6, 32, 46] focused on a zero-shot setting where no training data of the target dataset is available. Due to the lack of adaptation to the target dataset, they tend to detect unusual ID images as OOD data. Among them, CLIPN [46], which trains an additional 'no' text encoder to provide prompt embeddings of not having specific classes, is the best detector, but it relies on a large-scale auxiliary dataset to train such a text encoder and it is computationally expensive.", + "bbox": [ + 75, + 306, + 468, + 470 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The most related work is a very recent approach LoCoOp [33] that utilizes the training ID data to tune CLIP to capture local features of the ID classes in the prompt. It shows substantially improved performance compared to zero-shot methods [32], but it may compromise the ID classification accuracy due to an overemphasis on modeling local features. LoCoOp also lacks knowledge about OOD samples, making it difficult to differentiate boundary ID/OOD images.", + "bbox": [ + 75, + 474, + 468, + 609 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this work, we propose a novel CLIP-based OOD detection method, named NegPrompt. Inspired by [25], Negprompt is designed to learn a set of negative prompts, each representing a negative connotation of a given ID class label, to delineate the boundaries between ID and OOD images, as shown in Fig. 1. The negative prompts represent specialized ID-class-dependent concepts, guiding the models to pay attention to the characteristics that are contrary to or disjoint from the ID classes. NegPrompt aims to utilize ID training data and positive prompts (i.e., the text prompt embeddings of ID classes) to learn such negative prompts in a way to which OOD images exhibits higher similarity than ID images.", + "bbox": [ + 75, + 611, + 468, + 808 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Essentially, the learned negative prompts have similar semantics to the text prompts generated from the 'no' text encoder in CLIPN, but NegPrompt presents a fundamentally different approach: it capitalizes on the generalization ability of the CLIP model and learns the negative prompts with training ID data only, eliminating the reliance on external", + "bbox": [ + 75, + 810, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "data and the extensive computation overhead as in CLIPN.", + "bbox": [ + 498, + 90, + 885, + 106 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Furthermore, benefiting from the superior generalization ability of CLIP, our method does not require the exposure to all ID classes during training. In other words, the model learns transferable negative prompts by using only a small subset of the ID classes, after which we can obtain the negative prompts for the other ID classes by simply replacing the '[class name]' in the prompts with the name of those unexposed classes. This allows our model to work in open-vocabulary [7, 31] learning settings, where the models are required to classify images of novel classes that are not seen during training, in addition to a set of training base classes.", + "bbox": [ + 496, + 107, + 890, + 272 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our main contributions can be summarized as follows:", + "bbox": [ + 517, + 273, + 880, + 287 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose a prompt learning-based OOD detection approach NegPrompt, which is able to learn negative semantics relative to specific ID classes, thereby enhancing the VLMs' sensitivity to unknown samples. It is a lightweight method that does not require training extra encoders on external data as in related methods [46].", + "- NegPrompt possesses an open-vocabulary capability due to the transferability of its negative prompts. This means that with training images from just a small subset of ID classes and the class names of all IDs, we can achieve OOD detection on test data with all these ID classes. To the best of our knowledge, there have been no previous fine-tuning methods exploring such a capability.", + "- Extensive experiments on multiple ImageNet-based benchmarks show that NegPrompt consistently outperforms current state-of-the-art methods in both conventional and hard OOD Detection settings." + ], + "bbox": [ + 500, + 291, + 890, + 547 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 559, + 640, + 574 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Pre-trained Vision-Language Models", + "text_level": 1, + "bbox": [ + 500, + 584, + 818, + 599 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Understanding the semantic information of images remains a significant challenge in the field of computer vision. With the advent of Transformer [44] in computer vision tasks [5], CLIP [37] has been introduced as one of the most advanced pre-trained VLMs. Utilizing contrastive learning [21], large-scale models and datasets [38], CLIP employs image-text pairs as the training data for self-supervised learning. This approach has successfully trained the model to align visual and text signals in a latent space. Concurrently, other researchers [1, 24, 49] have also shown the remarkable generalization capabilities of CLIP and similar vision-language models [17] in various downstream tasks [7, 20, 56].", + "bbox": [ + 496, + 601, + 890, + 782 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.2. Prompt Learning", + "text_level": 1, + "bbox": [ + 500, + 792, + 669, + 809 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The concept of prompt learning was initially focused on automating the creation of templates/prompts for extracting knowledge from Bert [4] or GPT [36]. To bypass manual creation, prompt learning advocates the use of supervised learning to automate the prompt development. [39] proposed a gradient-based approach for identifying the", + "bbox": [ + 496, + 810, + 890, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "17585", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "best prompt, establishing the foundation of prompt learning. Later, CoOp [54] integrated prompt learning into computer vision. CoOp learns a segment of the context before it is fed into the text encoder of CLIP, thus tailoring the learned prompt to the specific target dataset. Many other prompt learning methods for different vision tasks [13, 18, 20, 40, 47, 53, 55] are subsequently introduced. However, they are not designed for OOD detection, so they struggle with dealing with the unknown OOD samples during inference.", + "bbox": [ + 75, + 90, + 472, + 242 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.3. Out-of-Distribution Detection", + "text_level": 1, + "bbox": [ + 76, + 250, + 341, + 263 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "OOD detection is committed to identifying images in image classification tasks that belong to categories not present in the training dataset, typically originating from a different distribution. While traditional OOD detection methods often tackle the problem by either exploiting the prediction logits to define OOD scores [10, 12, 15, 26, 27] or focusing on the class-agnostic information in feature space that is not recoverable from logits [41, 45], recent methods [11, 14, 22, 28, 30, 42, 52] introduce extra or synthetic OOD data, employing fine-tuning to elevate their model's sensitivity towards unknown classes.", + "bbox": [ + 75, + 266, + 468, + 431 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "With the introduction of large pre-trained VLMs, OOD detection has embarked on a new trajectory driven by VLMs. MCM [32] aims to integrate the idea of maximum softmax probability [10] into the inference process of CLIP, while ZOC [6] enhances OOD detection in a zero-shot setting by learning an additional image interpreter and guessing the category of images. CLIPN [46] and LoCoOp [33], the most related methods to ours, are based on text prompts. However, CLIPN, during its pretraining phase, trains an additional negative text encoder using a large external dataset to improve its negative semantic prompt, which increases network parameters and deviates from prompt learning that is focused on tuning the target data. LoCoOp, on the other hand, uses prompt learning for matching text and image local features, which can compromise the global perception capability of CLIP and reduce classification accuracy for in-distribution (ID) samples. Also, its model lacks knowledge about OOD samples, which can often lead to high detection errors.", + "bbox": [ + 75, + 431, + 472, + 719 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 731, + 168, + 744 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this paper, we propose an approach named NegPropmt that leverages pre-trained VLMs, specifically CLIP, to learn negative prompts relative to ID classes for the purpose of OOD detection. The negative prompts are learned in the CLIP's text-image-aligned embedding space with the support of training ID data and their positive prompts (i.e., prompt embeddings of ID classes); no external outlier data is required. Due to its general effectiveness, the popular prompt learning method CoOp [54] is used by default to provide the positive prompts for training NegPrompt.", + "bbox": [ + 75, + 750, + 472, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Preliminaries", + "text_level": 1, + "bbox": [ + 500, + 90, + 640, + 104 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Problem Statement. Formally, we assume that we have two datasets, namely ID dataset denoted as $D^{in}$ and OOD dataset denoted as $D^{out}$ . The ID dataset consists of image-label pairs $(x^{in}, y^{in})$ , where $y^{in} \\in Y^{in} = \\{0, 1, 2, 3 \\dots k\\}$ belong to the ID class set. Similarly, the OOD dataset contains image-label pairs $(x^{out}, y^{out})$ , but all $y^{out} \\in Y^{out} = \\{k + 1, k + 2, \\dots\\}$ belong to the OOD class set. It is important to note that these two sets do not intersect, meaning that $Y^{in} \\cap Y^{out} = \\emptyset$ . As we have a test set $X^{test}$ consists of images from ID and OOD, the goal of OOD detection is to train a classifier $\\phi(x)$ that takes an image $x$ as input and returns whether the image belongs to OOD. Unlike existing studies using full-/zero-shot ID training samples, we only use a few samples (16 samples per class) for $D_{train}^{in}$ like [33] does. In the open-vocabulary detection setting, we only use a small part (10%) but not all the classes of $D_{train}^{in}$ . CLIP and CoOp. CLIP [37] is currently one of the most popular image-text models. During the pre-training phase, it uses large-scale image-text pairs for self-supervised contrastive learning, aligning images and texts into the same latent space. The main components of CLIP are an image encoder $Encoder^{image}(I)$ and a text encoder $Encoder^{text}(T)$ , which respectively accept image and text inputs. In zero-shot image classification tasks, assume we have $k$ class labels for classification, such as \"cat\", \"dog\", etc., CLIP first incorporates the class labels into pre-designed hard/unlearnable text prompts, such as \"a photo of a [class name]\", forming a prompt input set of \"a photo of a cat\", \"a photo of a dog\" and so on. These prompts are then individually fed into the text encoder $Encoder^{text}(T)$ to obtain $k$ text features $T^f$ . The testing image is then input into the image encoder to obtain an image feature $I^f$ . The cosine similarity is calculated between the normalized image feature and all text features, formally, $Sim(T^f, I^f) = T^f \\cdot I^f$ , and the text feature $T^f$ with the highest similarity to $I^f$ is considered to be the category to which the image belongs.", + "bbox": [ + 496, + 109, + 893, + 670 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Besides zero-shot classification, many have explored ways to improve CLIP's performance when the target data is accessible. CoOp [54] introduces prompt learning with CLIP by freezing its encoders and using backpropagation to learn dataset-specific soft/learnable prompts. The text prompts are represented as $t_i = \\{\\omega_1^{pos}, \\omega_2^{pos}, \\dots, \\omega_n^{pos}, c_i\\}$ , where $c_i$ is the word embedding of the class name and $\\omega^{pos}s$ are learnable vectors that have positive semantics w.r.t. the class $i$ . The goal is to optimize these $\\omega^{positive}$ s. Specifically, $t_i$ is processed by Encoder $^{text}$ to yield $T_i^{f,pos}$ as a positive prompt embedding of the class $i$ , and then the prediction probability is computed as:", + "bbox": [ + 496, + 670, + 893, + 852 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\np (y = i | x) = \\frac {\\exp \\left(\\operatorname {s i m} \\left(T _ {i} ^ {f , p o s} , I ^ {f}\\right) / \\tau\\right)}{\\sum_ {j = 1} ^ {k} \\exp \\left(\\operatorname {s i m} \\left(T _ {j} ^ {f , p o s} , I ^ {f}\\right) / \\tau\\right)}, \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 537, + 863, + 890, + 905 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "17586", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/93cf385c0b8c948651681b6fcac01869930ef400e17eb5f15c85686ebc874f29.jpg", + "image_caption": [ + "Figure 2. Overview of NegPropmt. Given the CLIP model and positive prompts learned by existing prompt learning methods such as CoOp [54], NegPrompt learns a set of negative prompts relative to different ID class labels via three loss functions that enforce the separation between negative prompts and ID images, and between negative and positive prompts, as well as the diversity of the negative prompts." + ], + "image_footnote": [], + "bbox": [ + 155, + 99, + 815, + 364 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $I^{f} = \\text{Encoder}^{image}(x)$ and $\\tau$ is a temperature parameter. Next, cross-entropy loss is used to maximize similarity between ID class text embeddings and images.", + "bbox": [ + 75, + 426, + 470, + 474 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {p o s i t i v e}} = \\mathbb {E} _ {\\mathbf {x} _ {\\text {i n}} \\sim D _ {\\text {t r a i n}} ^ {\\text {i n}}} [ - \\log (p (y = i | x) ]. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 132, + 483, + 468, + 503 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "This method largely improves CLIP's classification performance by adapting the learnable prompts to the target data. The resulting prompt embeddings of ID classes are used as positive prompts to support the accurate learning of negative prompts in our method below.", + "bbox": [ + 75, + 508, + 468, + 585 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Proposed Approach", + "text_level": 1, + "bbox": [ + 76, + 593, + 266, + 609 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "NegPrompt aims to learn a set of negative prompts, each representing a negative connotation of an ID class. As shown in Fig. 2, it involves generating a series of prompts that resemble the positive prompts obtained through CoOp, but with a negative class semantic, such as \"A photo of not a [class label]\". These negative prompts, combined with class labels, can generate a range of negative text features around the positive prompts, so that OOD images exhibit higher similarity to the negative prompts than ID images.", + "bbox": [ + 75, + 609, + 470, + 746 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2.1 Learning Negative Prompts", + "text_level": 1, + "bbox": [ + 76, + 763, + 323, + 777 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To acquire accurate negative prompts representing negative class semantics, we first utilize CoOp to learn positive prompts $\\omega^{pos}$ s, after which we consider positive prompts to accurately capture the class semantics of samples in the ID dataset. Thereafter, we freeze the positive prompts and focus solely on learning the negative prompts. A negative prompt is denoted as $\\{\\omega_1^{neg},\\omega_2^{neg},\\dots,\\omega_n^{neg}\\}$ , where $n$ represents the number of context vectors we aim to learn. By", + "bbox": [ + 75, + 780, + 470, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "utilizing the frozen CLIP text encoder, we can obtain negative prompt embeddings $T_{l,i}^{f,neg} = \\text{Encoder}^{text}(t_{l,i}^{neg})$ , where $t_{l,i}^{neg} = \\{\\omega_{l,1}^{neg}, \\omega_{l,2}^{neg}, \\dots, \\omega_{l,n}^{neg}, c_i\\}$ is the $l$ -th negative prompt relative the ID class $i$ . Thus, due to the presence of the negative prompts, we turn the prediction probability into the following form:", + "bbox": [ + 496, + 428, + 890, + 521 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\np (y = i \\mid x) = \\frac {\\exp \\left(S _ {i} ^ {f , p o s}\\right)}{\\sum_ {j = 1} ^ {k} \\exp \\left(S _ {j} ^ {f , p o s}\\right) + \\sum_ {l = 1} ^ {p} \\sum_ {j = 1} ^ {k} \\exp \\left(S _ {l , j} ^ {f , n e g}\\right)} \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 496, + 527, + 906, + 583 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $S_{j}^{f,pos} = \\frac{\\text{sim}(T_{j}^{f,pos}, I^{f})}{\\tau}$ , $S_{l,j}^{f,neg} = \\frac{\\text{sim}(T_{l,j}^{f,neg}, I^{f})}{\\tau}$ and $p$ is the number of negative prompts we aim to learn for each ID class. The objective is to learn negative text prompt embeddings that can effectively separate ID and OOD samples around the positive text features. To achieve this, we introduce the following three loss functions:", + "bbox": [ + 496, + 590, + 890, + 703 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Negative-Image Separation Loss. One of our objectives is to have the negative text prompt embeddings serve as the closest text features to OOD images. However, we only have images from the ID dataset; no OOD images are available. To remedy this problem, we take an alternative approach that aims to push the negative text features away from the ID images. In this regard, we draw inspiration from OE [11]. Contrary to the approach in OE, where the probability distribution of outlier images is evenly distributed among all ID labels, we distribute the probability distribution obtained from ID images evenly among all negative prompts. Since the network parameters are frozen, this drives the negative text features to move away from the ID", + "bbox": [ + 496, + 704, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "17587", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "images, resulting in the learning of prompts with a negative connotation. The formulation is as follows:", + "bbox": [ + 76, + 90, + 468, + 119 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {N I S} = \\mathbb {E} _ {x _ {\\text {i n}} \\sim D _ {\\text {t r a i n}} ^ {\\text {i n}}} [ H (\\mathbf {u}; F (x)) ], \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 158, + 133, + 468, + 154 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $F(x)$ is the probability vector computed as $\\text{Softmax}(S^{f,neg})$ , and $\\mathbf{u}$ is a uniform distribution and $H$ is the cross entropy loss.", + "bbox": [ + 76, + 165, + 468, + 210 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Negative-Positive Distance Loss. To avoid learning trivial negative prompts that are distant from both ID and OOD images, we need to control the negative text feature within a certain range between the ID and OOD images. To this end, we devise a constraint, enforcing that the negative text feature does not deviate too far from the positive text feature. Therefore, we introduce the following loss function to guarantee a certain level of similarity between the negative and positive text feature in the latent space:", + "bbox": [ + 75, + 210, + 468, + 347 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {N P D} = - \\frac {1}{k * p} \\sum_ {j = 1} ^ {k} \\sum_ {i = 1} ^ {p} \\operatorname {s i m} \\left(T _ {i, j} ^ {f, n e g}, T _ {j} ^ {f, p o s}\\right). \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 114, + 359, + 468, + 401 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Negative-Negative Distance Loss. Furthermore, to ensure that we are effectively learning diverse, non-overlapping negative prompts, we extend the distances between different negative text features within the same label via the following loss function:", + "bbox": [ + 76, + 414, + 468, + 491 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {N N D} = \\frac {1}{k * p * (p - 1)} \\sum_ {j = 1} ^ {k} \\sum_ {i = 1} ^ {p} \\sum_ {l \\neq i} \\operatorname {s i m} \\left(T _ {i, j} ^ {f, n e g}, T _ {l, j} ^ {f, n e g}\\right). \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 502, + 470, + 556 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Overall, our NegPrompt objective consists of the above three losses. During training, we are able to obtain a diverse set of non-trivial prompts that effectively convey negative meanings relative to the ID class labels by minimizing the following overall loss:", + "bbox": [ + 76, + 559, + 468, + 633 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {N e g a t i v e P r o m p t s}} = \\mathcal {L} _ {N I S} + \\beta * \\mathcal {L} _ {N P D} + \\gamma * \\mathcal {L} _ {N N D}, \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 84, + 648, + 468, + 664 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\beta$ and $\\gamma$ are hyper-parameters to balance the losses.", + "bbox": [ + 76, + 676, + 459, + 691 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.2.2 Open-Vocabulary Capability", + "text_level": 1, + "bbox": [ + 76, + 698, + 331, + 714 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Since the negative prompts we learn do not depend on specific class labels but are instead generic templates representing negative semantics of any given class labels, it is possible to utilize the generalization ability of CLIP to learn a set of transferable negative prompts. Specifically, instead of utilizing all of the ID classes $D_{train}^{in}$ , NegPrompt may only employ its small subset $D_{train}^{in,sub}$ for training the negative prompts $\\omega^{neg}$ , where $D_{train}^{in,sub} = \\{(x,y_{sub}^{in}) \\mid y_{sub}^{in} \\subset y^{in}\\}$ . After obtaining the trained negative prompts, we combine them with the remaining ID class names, i.e., replace $c_i$ in $t_{l,i}^{neg}$ with the unseen ID class names, to obtain the corresponding negative prompts for the novel ID classes that are", + "bbox": [ + 75, + 715, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/0d2da6e40f0e07244aaf4f9d319de4eb134d0e9dbdce0183c1f36f07ff63734e.jpg", + "table_caption": [], + "table_footnote": [ + "Table 1. Three ImageNet-1K splits for hard OOD detection." + ], + "table_body": "
IDOOD
Split-1All dog classesNon-animal classes
Split-2Half of hunting dog classesOther 4-legged animal classes
Split-3Mix of common classesMix of common classes
", + "bbox": [ + 532, + 89, + 859, + 143 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "unseen during training. This approach, which achieves out-of-distribution detection by only exposing with a small portion of ID images, is unprecedented in prior research. We refer this as to be open-vocabulary OOD detection.", + "bbox": [ + 498, + 162, + 890, + 223 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.2.3 Inference", + "text_level": 1, + "bbox": [ + 500, + 244, + 619, + 257 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "During inference, we employ the MCM [32] scoring approach for OOD detection, but with the addition of our negative prompts into the softmax function. Particularly, MCM uses the inverse of the maximum softmax score in Eq. 1 as the OOD score. Our OOD scoring extends MCM and defines it as: $s(x) = \\max(p(y = i|x))$ , where $p(y = i|x)$ is defined in Eq. 3 that also includes the similarities of the test image to the negative prompts, in addition to the similarities to the positive prompts. The rationale behind this is that for ID images, they will be matched to one of the positive text features, leading to a higher $S^{f,pos}$ but lower $S^{f,neg}$ , and thereby a higher maximum softmax score (i.e., a lower OOD score). Conversely, for OOD data, it will be matched to one of the negative text features, resulting in a lower maximum softmax score (i.e., a higher OOD score).", + "bbox": [ + 498, + 261, + 890, + 488 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiment", + "text_level": 1, + "bbox": [ + 500, + 496, + 624, + 512 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Experimental Details", + "text_level": 1, + "bbox": [ + 500, + 521, + 697, + 536 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. For conventional OOD detection, we use a popular benchmark in which ImageNet-1K [3] with 1,000 classes is used as the ID dataset, and the same OOD datasets as in [32] are used, including subsets of Texture [2], iNaturalist [43], Places [51] and SUN [48]. In addressing the more challenging OOD scenarios, we partitioned the ImageNet1k dataset into two segments: one segment of the data serves as the ID, while the other serves as OOD. As shown in Table 1, three different splits are derived, following from [35]. We further create another ImageNet split, Split-4, in which the first 100 classes are used as ID data and the subsequent 900 classes are used as OOD samples. Following CoOp and LoCoOp [33, 54], during our training process, we utilized only few-shot training data for each category. Particularly, we only train the model with 16 images per ID class and without any exposure to OOD images. During testing, we employ the entire ID and OOD test set for evaluation.", + "bbox": [ + 498, + 537, + 890, + 792 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Implementation Details. Following existing studies [46], we use CLIP based on CLIP-B/16 which is pre-trained from OpenCLIP [16]. NegPrompt is trained using 16-shot images of all ID classes under the normal OOD detection setting. For open-vocabulary OOD detection, we train our model using only the images of the first $10\\%$ classes from the ID dataset, withholding $90\\%$ ID classes that only appear", + "bbox": [ + 498, + 795, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "17588", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/4f332383a22872227eb7d7a7f86303642f873e7243ce1315ed60c7e8785cfdc2.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodTextureiNaturalistPlacesSUNAvg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓
Zero-shot methods
MCM [32]†86.1157.7794.6130.9189.7744.6992.5734.5990.7642.74
CLIPN [46]†90.9340.8395.2723.9492.2833.4593.9226.1793.1031.10
CLIP-based posthoc methods
MSP [10]†74.8473.6677.7474.5772.1879.1273.9776.9574.9876.22
MaxLogit [12]†88.6348.7288.0360.8887.4555.5491.1644.8388.8252.49
Energy [27]†88.2250.3987.1864.9887.3357.4091.1746.4288.4854.80
ReAct [41]†88.1349.8886.8765.5787.4256.8591.0446.1788.3754.62
ODIN [26]†87.8551.6794.6530.2285.5455.0687.1754.0488.8047.75
Prompt learning methods
CoOp [54]89.4745.0093.7729.8190.5840.1193.2940.8391.7851.68
LoCoOp [33]†90.1942.2896.8616.0591.9832.8795.0723.4493.5228.66
NegPrompt (Ours)91.6035.2198.736.3293.3427.6095.5522.8994.8123.01
Open-vocabulary OOD detection
CoOp (10%)87.5850.5591.0842.5389.5646.1291.5241.9289.9445.28
LoCoOp (10%)88.2147.3294.4734.9091.6439.8592.5426.3090.1537.09
NegPrompt (Ours) (10%)90.3039.3198.397.4892.6829.7593.7026.9293.7625.86
", + "bbox": [ + 127, + 88, + 844, + 319 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Conventional OOD detection results. We trained using ImageNet1k as the ID and CLIP-B/16 as the CLIP backbone. The boldfaced results indicate the best performance. Results marked with $\\dagger$ are taken from [46] and [33]. 'METHOD' (10%) in open-vocabulary OOD detection is to evaluate the performance of the 'METHOD' when only images from 10% ID classes are accessible during training.", + "bbox": [ + 75, + 320, + 893, + 363 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "together with OOD data during inference. We train a shared positive prompt and two shared negative prompts w.r.t. each training ID class. The hyperparameters $\\beta$ and $\\gamma$ are set to 0.1 and 0.05, respectively (see Appendix A for detail). In the first stage, CoOp is trained for 100 epochs to obtain the positive prompts. In the second stage, the positive prompts are frozen, and our model is trained for 10 epochs to learn the negative prompts. For all experiments, we report the averaged results over three runs with different random seeds.", + "bbox": [ + 75, + 381, + 470, + 517 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Comparison Methods. To substantiate the effectiveness of NegPrompts, we conduct an empirical analysis of three distinct categories of methodologies employed for OOD detection utilizing Vision-language models. These categories encompass zero-shot pretraining approaches, the methods that combine the CLIP image encoder with classical approaches, and the methods grounded in prompt learning. In the context of zero-shot methods, we opted for the two recent methods, MCM [32] and CLIPN [46]. MCM employs the original CLIP, utilizing the maximum softmax probability operation on the similarities for detection, and CLIPN involves an additional training phase during pretraining, specifically training a negative text encoder using large external data. For the second group of methods, we adapt previous logits-based methodologies to the use of the CLIP image encoder, including MSP [10], Energy [27], MaxLogit [12], ReAct [41] and ODIN [26], to serve as the CLIP-adapted methods. For the prompt learning methods, NegPrompt is compared with CoOp [54] and LoCoOp [33].", + "bbox": [ + 75, + 518, + 468, + 806 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation Metrics. Two OOD detection metrics are used. The first metric is the False Positive Rate at a $95\\%$ True Negative Rate (FPR95), which denotes the rate of falsely identified OOD instances when the true negative rate is maintained at $95\\%$ . The second metric is the Area Under the Receiver Operating Characteristic curve (AUROC), rep", + "bbox": [ + 75, + 809, + 468, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "resenting the measure of OOD ranking across various classification thresholds. We also check the classification accuracy of the ID data to evaluate how the OOD detectors affect the ID classification.", + "bbox": [ + 498, + 381, + 893, + 441 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Comparison to State-of-the-art Models", + "text_level": 1, + "bbox": [ + 498, + 455, + 834, + 472 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Conventional OOD Detection. The results of conventional OOD detection are reported in Table 2. It is clear that our proposed NegPrompt achieves consistently superior performance in both individual OOD datasets and the averaged results. When compared with the zero-shot methods, on average, our approach surpasses the best competing method CLIPN by more than $1.5\\%$ in AUC and around $8\\%$ in FPR95, despite the fact that CLIPN requires the use of an additional large external dataset to train an additional negative text encoder. In other words, although NegPrompt is significantly more lightweight than CLIPN in model size, it can substantially and consistently outperform CLIPN in both metrics across all OOD datasets. The adapted post-hoc methods generally do not leverage the CLIP's capabilities well and thus perform less effectively.", + "bbox": [ + 496, + 474, + 890, + 700 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "NegPrompt also substantially surpasses both prompt learning-based methods, reducing the FPR95 by about $28\\%$ (CoOp) and $5\\%$ (LoCoOp). This indicates that the learned negative prompts provide informed knowledge about OOD data, which is lacking in the competing methods, helping largely reduce detection errors.", + "bbox": [ + 496, + 702, + 890, + 792 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Hard OOD Detection. Hard OOD detection presents unique challenges as the OOD samples often exhibit some similar features as the ID samples. The results on the four hard OOD datasets derived from ImageNet-1K are shown in Table 3. Similar empirical observations can be derived. Our method NegPropmt is consistently the best performer in the average performance, showcasing its general effec", + "bbox": [ + 496, + 794, + 890, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "17589", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/cfdc1a9fe5222c472663ca9bb7592755d6a18a1689e0cf4a6a61f9ba4f01bd55.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodSplit-1Split-2Split-3Split-4Avg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓
Zero-shot methods
MCM97.939.1788.1056.4090.3433.0598.724.7393.7725.83
CLIPN99.382.0797.7710.5590.0336.8598.834.6896.5013.53
CLIP-based posthoc methods
MSP77.8563.6068.7383.6379.1070.5582.4065.5277.0270.83
MaxLogit99.870.4998.068.6990.9634.3499.352.6697.0611.55
Energy99.880.4698.188.4090.6535.0299.362.8397.0211.68
ReAct99.340.7297.919.3390.7235.6599.122.9496.7712.16
ODIN98.781.1298.238.1889.9237.2098.7613.2096.4214.92
Prompt learning methods
CoOp98.536.7888.2550.7690.6433.8998.545.1193.9924.14
LoCoOp98.646.2984.6361.0991.3027.7998.8341.4493.3534.15
NegPrompt (Ours)99.850.6298.547.6093.8922.8999.571.6097.968.18
Open-vocabulary OOD detection
CoOp (10%)97.9712.21780.1174.6287.9246.0096.5916.6090.6537.36
LoCoOp (10%)98.009.2387.0252.1880.5159.9382.4148.7286.9942.52
NegPrompt (Ours) (10%)99.661.3696.3019.8991.7526.9298.145.2496.4613.36
", + "bbox": [ + 127, + 88, + 844, + 319 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "tiveness across different dataset splits. The superiority of NegPrompt over the zero-shot and prompt learning-based methods is similar to that in Table 2. Although it is slightly less effective than Energy under the Split-1 setting, it outperforms Energy in all other metrics, achieving maximally over $3\\%$ AUC and $12\\%$ FPR95 improvement among the performance on the other OOD datasets.", + "bbox": [ + 75, + 352, + 468, + 457 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Note that the results in Table 3 are generally more promising than that in Table 2. This is mainly because the OOD detection difficulty in all four ImageNet-1K splits is largely reduced since the number of their ID classes is significantly less than that in the full ImageNet-1K data.", + "bbox": [ + 75, + 458, + 468, + 532 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Open-Vocabulary OOD Detection. The open-vocabulary OOD detection results are reported in both Tables 2 and 3. Impressively, even when training on only $10\\%$ ID classes, our approach can still perform better than the competing methods using the full ID classes, e.g., the average AUC and FPR95 in Table 2. In this open-vocabulary setting, in general, both LoCoOp and CoOp exhibit a much larger performance decline than NegPrompt, especially on the results in Table 3, in which CoOp has over $3\\%$ AUC drop and LoCoOp has over $6\\%$ AUC drop while our method has only about $1.5\\%$ AUC drop. These results demonstrate that the negative prompts in NegPrompt have much better transferability than those in the two competing methods.", + "bbox": [ + 75, + 534, + 470, + 731 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2.1 Classification Accuracy on ID Data", + "text_level": 1, + "bbox": [ + 76, + 748, + 375, + 762 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We also evaluate the classification accuracy on the ID data when using NegPrompt for OOD detection, with CoOp, LoCoOp, MCM and CLIPN as the baselines. The classification accuracy results on the full ImageNet-1K test data are shown in Table 4. When using the full ImageNet-1K training ID class data, our method NegPrompt can maintain the same classification accuracy as CoOp.", + "bbox": [ + 75, + 763, + 468, + 869 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our accuracy is slightly compromised when using only $10\\%$ ID classes in our training. On the other hand, the OOD", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/c8f3311dbb39d81c189dee922f4cbf7c53cb12b0d9ffd3f467cc024bc414dadd.jpg", + "table_caption": [ + "Table 3. Hard OOD detection results. We use the same notations here as those used in Table 2." + ], + "table_footnote": [], + "table_body": "
MethodTop-1 Accuracy
CoOp72.1
\\( \\text{LoCoOp}^\\dagger \\)71.7
CLIPN & MCM67.0
NegPrompt(Ours)(10%)71.9
NegPrompt(Ours)(Full)72.1
", + "bbox": [ + 566, + 349, + 826, + 435 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 4. Top-1 Accuracy. Results with $\\dagger$ are taken from [33].", + "bbox": [ + 511, + 436, + 877, + 450 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a9d9a3a19417481f1d8454e532aba78a1a4b2038ce4bab3bbf7c376843ffc4b3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 501, + 473, + 681, + 611 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/818085285795656b3cff7aa2a252d098ad84771fc51f527a4293072ddb230b1f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 707, + 473, + 888, + 611 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/e905a8a2f8a1f1f1d6a476cd9588aa25d4f9878aa38dd5cf5767ab0f3cc1a6d7.jpg", + "image_caption": [ + "Figure 3. Similarity of ID/OOD and Positive/Negative Prompts." + ], + "image_footnote": [], + "bbox": [ + 501, + 611, + 681, + 720 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/bb0dcc3bb85f8c59e65fe7fdd4edbc736f7ee6a676f7fce9255631a7ea584eb6.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 710, + 611, + 888, + 720 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "detection in LoCoOp compromises the ID classification accuracy, dropped from $72.1\\%$ in CoOp to $71.7\\%$ . This may be attributed to its focus on the localized regions within the background rather than the primary object of interest, resulting in the missing of some discriminative features for ID data classification. CLIPN and MCM, being zero-shot methods, have not been exposed to the target ID data, leading to a much lower accuracy than the other methods.", + "bbox": [ + 496, + 784, + 890, + 905 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "17590", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/a79809da6e5652671d794f1f8573291d85aebd1f37645424629546f465dc7b34.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Ablation StudyTextureiNaturalistPlacesSUNAvg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓ACC ↑
Backbones
ResNet-5079.4472.7390.9744.1084.3561.3788.0450.5585.7057.1968.2
ResNet-10182.9770.8393.9631.386.4151.6688.8147.6188.0450.3570.3
ViT-B-3290.4338.7997.4012.6492.8332.7992.8226.0393.3727.5672.6
# Negative Prompts
190.0440.6798.249.2390.3732.6292.2627.3392.7327.4672.1
Training Process
One-stage80.2572.8777.0295.7482.5395.9481.1395.7280.2390.0762.8
ViT-B-16 & 2 & Two-stage90.3039.3198.397.4892.6829.7593.7026.9293.7625.8672.1
", + "bbox": [ + 114, + 88, + 857, + 232 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 5. Results of our ablation experiments.", + "bbox": [ + 349, + 233, + 617, + 246 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/b9ab64efe1415f22e303b493b00551921694dc74a30285b2fc105d0b45829043.jpg", + "image_caption": [ + "Figure 4. T-SNE visualization of NegPrompt, utilizing a subset of ImageNet - TinyImageNet as the dataset." + ], + "image_footnote": [], + "bbox": [ + 112, + 262, + 434, + 425 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3. Analysis of NegPrompt", + "text_level": 1, + "bbox": [ + 76, + 474, + 290, + 491 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3.1 Why Does NegPrompt Work?", + "text_level": 1, + "bbox": [ + 76, + 497, + 338, + 512 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To better understand the effectiveness of NegPrompt, we summarize the average maximum similarity between ID/OOD images and positive/negative prompts, as shown in Fig. 3. Across all four OOD datasets, ID images have the highest similarity with positive prompts, and OOD images with negative prompts. This suggests positive prompts are closer to ID images and negative prompts to OOD images in latent space, ensuring OOD images receive lower softmax scores (i.e., higher OOD scores) than ID images in Eq. 3.", + "bbox": [ + 75, + 513, + 468, + 648 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Using TinyImageNet [23], a subset of ImageNet, we further visualized the learned negative text features with its test data [6]. Learning three negative prompts per ID class, the results in Fig. 4 demonstrate that positive text features from positive prompts align closely with ID images in latent space. Conversely, the negative text features encoded from negative prompts lie outside of the ID data, with OOD images interspersed among them. This suggests negative text features effectively act as a fence aligning much better to the OOD images than the ID images, well supporting the OOD detection while preserving the ID classification accuracy.", + "bbox": [ + 75, + 650, + 468, + 816 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3.2 Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 827, + 236, + 840 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 5 shows our ablation study results on the backbone, the number of negative prompts, and the training process.", + "bbox": [ + 75, + 840, + 467, + 869 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Backbones. We experiment with diverse CLIP backbones. The results reveal that for CNN-based backbones", + "bbox": [ + 75, + 869, + 468, + 898 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "like ResNet50 and ResNet101, the OOF detection performance is not as proficient as the ViT-based backbones. Regarding ViT-B-32 and ViT-B-16, their performance is found to be uneven. Overall, the performance of OOD detection tends to increase with more advanced backbones.", + "bbox": [ + 496, + 262, + 890, + 337 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "The Number of Negative Prompts. The number of negative prompts also influences the results. It is observed that the OOD detection performance improves when increasing the number of negative prompts from one to two. Therefore, it is suggested to further increase the number of negative prompts for better detection accuracy. However, note that with an increase in the number of negative prompts, the computational cost also rises rapidly. A good balance between computational cost and detection accuracy is needed when determining the number of negative prompts.", + "bbox": [ + 496, + 338, + 892, + 489 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Training Process. The training process is also important. As discussed before, due to the necessity of anchoring the positive prompts, a two-stage training process is used in our model. This process involves training the positive prompts in the first stage and freezing them before proceeding to train the negative prompts in the second stage. When simultaneously training both positive and negative prompts in a unified step, the model's ability to effectively learn positive prompts is significantly undermined, and consequently we obtain unstable negative prompts, leading to the largely decreased OOD detection performance.", + "bbox": [ + 496, + 489, + 890, + 655 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 670, + 617, + 686 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We present NegPrompt, a novel approach for prompt learning-based OOD detection. It utilizes VLMs to learn a small set of negative prompts for conveying negative semantics relative to ID classes. Our empirical results reveal that NegPrompt 1) achieves superior OOD detection performance compared to the SOTA models across various OOD datasets in both conventional and hard OOD detection scenarios, and 2) learns transfer negative prompts that enable excellent open-vocabulary OOD detection performance.", + "bbox": [ + 496, + 696, + 890, + 832 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Acknowledgement", + "text_level": 1, + "bbox": [ + 500, + 847, + 679, + 864 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by the National Natural Science Foundation of China 62276016, 62372029.", + "bbox": [ + 500, + 871, + 890, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "17591", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katherine Millican, Malcolm Reynolds, et al. Flamingo: a visual language model for few-shot learning. Advances in Neural Information Processing Systems, 35:23716-23736, 2022. 2", + "[2] Mircea Cimpoi, Subhransu Maji, Iasonas Kokkinos, Sammy Mohamed, and Andrea Vedaldi. 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Toward generalist anomaly detection via in-context residual learning with few-shot sample prompts. arXiv preprint arXiv:2403.06495, 2024. 2" + ], + "bbox": [ + 78, + 90, + 468, + 316 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "17594", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_model.json b/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_model.json new file mode 100644 index 0000000000000000000000000000000000000000..f5877c01eff4a6613c9dc9934e37ddcd06bd6042 --- /dev/null +++ b/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_model.json @@ -0,0 +1,2180 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.108, + 0.131, + 0.862, + 0.154 + ], + "angle": 0, + "content": "Learning Transferable Negative Prompts for Out-of-Distribution Detection" + }, + { + "type": "text", + "bbox": [ + 0.195, + 0.178, + 0.773, + 0.197 + ], + "angle": 0, + "content": "Tianqi Li\\(^{1}\\), Guansong Pang\\(^{*2}\\), Xiao Bai\\(^{*1}\\), Wenjun Miao\\(^{1}\\), and Jin Zheng\\(^{1}\\)" + }, + { + "type": "text", + "bbox": [ + 0.084, + 0.208, + 0.886, + 0.244 + ], + "angle": 0, + "content": "\\(^{1}\\)School of Computer Science and Engineering, State Key Laboratory of Complex & Critical Software Environment, Jiangxi Research Institute, Beihang University, China" + }, + { + "type": "text", + "bbox": [ + 0.153, + 0.244, + 0.816, + 0.263 + ], + "angle": 0, + "content": "\\(^{2}\\)School of Computing and Information Systems, Singapore Management University" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.3, + 0.313, + 0.316 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.332, + 0.474, + 0.665 + ], + "angle": 0, + "content": "Existing prompt learning methods have shown certain capabilities in Out-of-Distribution (OOD) detection, but the lack of OOD images in the target dataset in their training can lead to mismatches between OOD images and InDistribution (ID) categories, resulting in a high false positive rate. To address this issue, we introduce a novel OOD detection method, named 'NegPrompt', to learn a set of negative prompts, each representing a negative connotation of a given class label, for delineating the boundaries between ID and OOD images. It learns such negative prompts with ID data only, without any reliance on external outlier data. Further, current methods assume the availability of samples of all ID classes, rendering them ineffective in open-vocabulary learning scenarios where the inference stage can contain novel ID classes not present during training. In contrast, our learned negative prompts are transferable to novel class labels. Experiments on various ImageNet benchmarks show that NegPrompt surpasses state-of-the-art prompt-learning-based OOD detection methods and maintains a consistent lead in hard OOD detection in closed- and open-vocabulary classification scenarios. Code is available at https://github.com/mala-lab/negprompt." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.676, + 0.21, + 0.691 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.702, + 0.47, + 0.866 + ], + "angle": 0, + "content": "Since the advent of deep learning, numerous image recognition models [5, 9, 29] have relied solely on image features for classification. However, in recent years large pre-trained vision-language models (VLMs), such as CLIP [37], integrated natural language processing into computer vision, enhancing the semantic understanding capabilities of computer vision models. It has been observed that these VLMs excel in image classification, particularly in zero-shot scenarios. This is attributed to their extensive self-supervised pre-training on web-scale image-text data, which has endowed them with robust semantic transfer abilities." + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.299, + 0.891, + 0.467 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.469, + 0.894, + 0.539 + ], + "angle": 0, + "content": "Figure 1. Illustration of the key intuition of NegPrompt. For each ID class, NegPrompt trains a small set of learnable prompts that have negative semantics to the learned positive prompt of the given class. As a result, OOD samples exhibit higher similarity to the negative prompts than the positive prompts." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.551, + 0.895, + 0.824 + ], + "angle": 0, + "content": "Despite the strong zero-shot classification capabilities of VLMs, numerous research efforts are put to unleash their potential, e.g., by investigating whether models like CLIP can achieve enhanced performance with training on downstream target datasets. This has led to the development of various techniques to fine-tune CLIP [8, 18], among which prompt learning has sparked widespread interest. Prompt learning (or prompt tuning) [19, 39, 50], a methodology originating from natural language processing, focuses on learning the prompt inputs into a large-scale pre-trained network, rather than learning or fine-tuning the parameters of the network. In CLIP, a common prompt is 'a photo of a [class name]'. The aim of prompt learning, e.g., in approaches like CoOp [54], is to learn a soft/differentiable context vector to replace the fixed text prompt like 'a photo of a', thereby leveraging CLIP's powerful generalization in semantic understanding while also fine-tuning for specific target datasets [53, 54]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.895, + 0.901 + ], + "angle": 0, + "content": "However, even though prompt learning enhances the target dataset perception capabilities of VLMs, it struggles with Out-Of-Distribution (OOD) detection [10, 26]. Under the OOD detection task, the test set comprises images from both the training classes - in-distribution (ID) data -" + }, + { + "type": "page_footnote", + "bbox": [ + 0.078, + 0.875, + 0.47, + 0.901 + ], + "angle": 0, + "content": "*Corresponding author: G. Pang (gspang@smu.edu.sg) and X. Bai (baixiao@buaa.edu.cn)" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17584" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.242 + ], + "angle": 0, + "content": "and images from other unknown categories (OOD images). VLM-based classification is typically performed by first replacing the '[class name]' with the class label of each category in a prompt, which is then processed by the text encoder of CLIP to obtain the class embedding and assign the class label that has the highest cosine similarity with the embedding of a test image from the image encoder of CLIP. However in OOD detection tasks, the models do not have access to the class names of OOD images, thereby lacking the knowledge about OOD data." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.244, + 0.47, + 0.305 + ], + "angle": 0, + "content": "This issue, exacerbated by the models' tendency towards overconfidence that often predicts OOD data as ID images with high confidence [34], undermines their ability to effectively detect OOD images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.307, + 0.47, + 0.472 + ], + "angle": 0, + "content": "There have been a number of CLIP-based methods designed specifically for VLM-driven OOD detection methods, but most of them [6, 32, 46] focused on a zero-shot setting where no training data of the target dataset is available. Due to the lack of adaptation to the target dataset, they tend to detect unusual ID images as OOD data. Among them, CLIPN [46], which trains an additional 'no' text encoder to provide prompt embeddings of not having specific classes, is the best detector, but it relies on a large-scale auxiliary dataset to train such a text encoder and it is computationally expensive." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.475, + 0.47, + 0.61 + ], + "angle": 0, + "content": "The most related work is a very recent approach LoCoOp [33] that utilizes the training ID data to tune CLIP to capture local features of the ID classes in the prompt. It shows substantially improved performance compared to zero-shot methods [32], but it may compromise the ID classification accuracy due to an overemphasis on modeling local features. LoCoOp also lacks knowledge about OOD samples, making it difficult to differentiate boundary ID/OOD images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.612, + 0.47, + 0.809 + ], + "angle": 0, + "content": "In this work, we propose a novel CLIP-based OOD detection method, named NegPrompt. Inspired by [25], Negprompt is designed to learn a set of negative prompts, each representing a negative connotation of a given ID class label, to delineate the boundaries between ID and OOD images, as shown in Fig. 1. The negative prompts represent specialized ID-class-dependent concepts, guiding the models to pay attention to the characteristics that are contrary to or disjoint from the ID classes. NegPrompt aims to utilize ID training data and positive prompts (i.e., the text prompt embeddings of ID classes) to learn such negative prompts in a way to which OOD images exhibits higher similarity than ID images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Essentially, the learned negative prompts have similar semantics to the text prompts generated from the 'no' text encoder in CLIPN, but NegPrompt presents a fundamentally different approach: it capitalizes on the generalization ability of the CLIP model and learns the negative prompts with training ID data only, eliminating the reliance on external" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.887, + 0.107 + ], + "angle": 0, + "content": "data and the extensive computation overhead as in CLIPN." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.108, + 0.892, + 0.273 + ], + "angle": 0, + "content": "Furthermore, benefiting from the superior generalization ability of CLIP, our method does not require the exposure to all ID classes during training. In other words, the model learns transferable negative prompts by using only a small subset of the ID classes, after which we can obtain the negative prompts for the other ID classes by simply replacing the '[class name]' in the prompts with the name of those unexposed classes. This allows our model to work in open-vocabulary [7, 31] learning settings, where the models are required to classify images of novel classes that are not seen during training, in addition to a set of training base classes." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.274, + 0.882, + 0.288 + ], + "angle": 0, + "content": "Our main contributions can be summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.292, + 0.892, + 0.382 + ], + "angle": 0, + "content": "- We propose a prompt learning-based OOD detection approach NegPrompt, which is able to learn negative semantics relative to specific ID classes, thereby enhancing the VLMs' sensitivity to unknown samples. It is a lightweight method that does not require training extra encoders on external data as in related methods [46]." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.384, + 0.892, + 0.488 + ], + "angle": 0, + "content": "- NegPrompt possesses an open-vocabulary capability due to the transferability of its negative prompts. This means that with training images from just a small subset of ID classes and the class names of all IDs, we can achieve OOD detection on test data with all these ID classes. To the best of our knowledge, there have been no previous fine-tuning methods exploring such a capability." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.489, + 0.892, + 0.549 + ], + "angle": 0, + "content": "- Extensive experiments on multiple ImageNet-based benchmarks show that NegPrompt consistently outperforms current state-of-the-art methods in both conventional and hard OOD Detection settings." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.292, + 0.892, + 0.549 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.56, + 0.642, + 0.575 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.585, + 0.82, + 0.601 + ], + "angle": 0, + "content": "2.1. Pre-trained Vision-Language Models" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.602, + 0.892, + 0.783 + ], + "angle": 0, + "content": "Understanding the semantic information of images remains a significant challenge in the field of computer vision. With the advent of Transformer [44] in computer vision tasks [5], CLIP [37] has been introduced as one of the most advanced pre-trained VLMs. Utilizing contrastive learning [21], large-scale models and datasets [38], CLIP employs image-text pairs as the training data for self-supervised learning. This approach has successfully trained the model to align visual and text signals in a latent space. Concurrently, other researchers [1, 24, 49] have also shown the remarkable generalization capabilities of CLIP and similar vision-language models [17] in various downstream tasks [7, 20, 56]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.794, + 0.671, + 0.81 + ], + "angle": 0, + "content": "2.2. Prompt Learning" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.892, + 0.902 + ], + "angle": 0, + "content": "The concept of prompt learning was initially focused on automating the creation of templates/prompts for extracting knowledge from Bert [4] or GPT [36]. To bypass manual creation, prompt learning advocates the use of supervised learning to automate the prompt development. [39] proposed a gradient-based approach for identifying the" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17585" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.243 + ], + "angle": 0, + "content": "best prompt, establishing the foundation of prompt learning. Later, CoOp [54] integrated prompt learning into computer vision. CoOp learns a segment of the context before it is fed into the text encoder of CLIP, thus tailoring the learned prompt to the specific target dataset. Many other prompt learning methods for different vision tasks [13, 18, 20, 40, 47, 53, 55] are subsequently introduced. However, they are not designed for OOD detection, so they struggle with dealing with the unknown OOD samples during inference." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.251, + 0.342, + 0.265 + ], + "angle": 0, + "content": "2.3. Out-of-Distribution Detection" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.267, + 0.47, + 0.432 + ], + "angle": 0, + "content": "OOD detection is committed to identifying images in image classification tasks that belong to categories not present in the training dataset, typically originating from a different distribution. While traditional OOD detection methods often tackle the problem by either exploiting the prediction logits to define OOD scores [10, 12, 15, 26, 27] or focusing on the class-agnostic information in feature space that is not recoverable from logits [41, 45], recent methods [11, 14, 22, 28, 30, 42, 52] introduce extra or synthetic OOD data, employing fine-tuning to elevate their model's sensitivity towards unknown classes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.433, + 0.473, + 0.72 + ], + "angle": 0, + "content": "With the introduction of large pre-trained VLMs, OOD detection has embarked on a new trajectory driven by VLMs. MCM [32] aims to integrate the idea of maximum softmax probability [10] into the inference process of CLIP, while ZOC [6] enhances OOD detection in a zero-shot setting by learning an additional image interpreter and guessing the category of images. CLIPN [46] and LoCoOp [33], the most related methods to ours, are based on text prompts. However, CLIPN, during its pretraining phase, trains an additional negative text encoder using a large external dataset to improve its negative semantic prompt, which increases network parameters and deviates from prompt learning that is focused on tuning the target data. LoCoOp, on the other hand, uses prompt learning for matching text and image local features, which can compromise the global perception capability of CLIP and reduce classification accuracy for in-distribution (ID) samples. Also, its model lacks knowledge about OOD samples, which can often lead to high detection errors." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.732, + 0.169, + 0.746 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.473, + 0.903 + ], + "angle": 0, + "content": "In this paper, we propose an approach named NegPropmt that leverages pre-trained VLMs, specifically CLIP, to learn negative prompts relative to ID classes for the purpose of OOD detection. The negative prompts are learned in the CLIP's text-image-aligned embedding space with the support of training ID data and their positive prompts (i.e., prompt embeddings of ID classes); no external outlier data is required. Due to its general effectiveness, the popular prompt learning method CoOp [54] is used by default to provide the positive prompts for training NegPrompt." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.091, + 0.642, + 0.105 + ], + "angle": 0, + "content": "3.1. Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.111, + 0.895, + 0.671 + ], + "angle": 0, + "content": "Problem Statement. Formally, we assume that we have two datasets, namely ID dataset denoted as \\( D^{in} \\) and OOD dataset denoted as \\( D^{out} \\). The ID dataset consists of image-label pairs \\( (x^{in}, y^{in}) \\), where \\( y^{in} \\in Y^{in} = \\{0, 1, 2, 3 \\dots k\\} \\) belong to the ID class set. Similarly, the OOD dataset contains image-label pairs \\( (x^{out}, y^{out}) \\), but all \\( y^{out} \\in Y^{out} = \\{k + 1, k + 2, \\dots\\} \\) belong to the OOD class set. It is important to note that these two sets do not intersect, meaning that \\( Y^{in} \\cap Y^{out} = \\emptyset \\). As we have a test set \\( X^{test} \\) consists of images from ID and OOD, the goal of OOD detection is to train a classifier \\( \\phi(x) \\) that takes an image \\( x \\) as input and returns whether the image belongs to OOD. Unlike existing studies using full-/zero-shot ID training samples, we only use a few samples (16 samples per class) for \\( D_{train}^{in} \\) like [33] does. In the open-vocabulary detection setting, we only use a small part (10%) but not all the classes of \\( D_{train}^{in} \\). CLIP and CoOp. CLIP [37] is currently one of the most popular image-text models. During the pre-training phase, it uses large-scale image-text pairs for self-supervised contrastive learning, aligning images and texts into the same latent space. The main components of CLIP are an image encoder \\( Encoder^{image}(I) \\) and a text encoder \\( Encoder^{text}(T) \\), which respectively accept image and text inputs. In zero-shot image classification tasks, assume we have \\( k \\) class labels for classification, such as \"cat\", \"dog\", etc., CLIP first incorporates the class labels into pre-designed hard/unlearnable text prompts, such as \"a photo of a [class name]\", forming a prompt input set of \"a photo of a cat\", \"a photo of a dog\" and so on. These prompts are then individually fed into the text encoder \\( Encoder^{text}(T) \\) to obtain \\( k \\) text features \\( T^f \\). The testing image is then input into the image encoder to obtain an image feature \\( I^f \\). The cosine similarity is calculated between the normalized image feature and all text features, formally, \\( Sim(T^f, I^f) = T^f \\cdot I^f \\), and the text feature \\( T^f \\) with the highest similarity to \\( I^f \\) is considered to be the category to which the image belongs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.671, + 0.895, + 0.853 + ], + "angle": 0, + "content": "Besides zero-shot classification, many have explored ways to improve CLIP's performance when the target data is accessible. CoOp [54] introduces prompt learning with CLIP by freezing its encoders and using backpropagation to learn dataset-specific soft/learnable prompts. The text prompts are represented as \\( t_i = \\{\\omega_1^{pos}, \\omega_2^{pos}, \\dots, \\omega_n^{pos}, c_i\\} \\), where \\( c_i \\) is the word embedding of the class name and \\( \\omega^{pos}s \\) are learnable vectors that have positive semantics w.r.t. the class \\( i \\). The goal is to optimize these \\( \\omega^{positive} \\)s. Specifically, \\( t_i \\) is processed by Encoder\\( ^{text} \\) to yield \\( T_i^{f,pos} \\) as a positive prompt embedding of the class \\( i \\), and then the prediction probability is computed as:" + }, + { + "type": "equation", + "bbox": [ + 0.538, + 0.864, + 0.892, + 0.906 + ], + "angle": 0, + "content": "\\[\np (y = i | x) = \\frac {\\exp \\left(\\operatorname {s i m} \\left(T _ {i} ^ {f , p o s} , I ^ {f}\\right) / \\tau\\right)}{\\sum_ {j = 1} ^ {k} \\exp \\left(\\operatorname {s i m} \\left(T _ {j} ^ {f , p o s} , I ^ {f}\\right) / \\tau\\right)}, \\tag {1}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "17586" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.156, + 0.1, + 0.816, + 0.365 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.371, + 0.895, + 0.415 + ], + "angle": 0, + "content": "Figure 2. Overview of NegPropmt. Given the CLIP model and positive prompts learned by existing prompt learning methods such as CoOp [54], NegPrompt learns a set of negative prompts relative to different ID class labels via three loss functions that enforce the separation between negative prompts and ID images, and between negative and positive prompts, as well as the diversity of the negative prompts." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.428, + 0.471, + 0.475 + ], + "angle": 0, + "content": "where \\( I^{f} = \\text{Encoder}^{image}(x) \\) and \\( \\tau \\) is a temperature parameter. Next, cross-entropy loss is used to maximize similarity between ID class text embeddings and images." + }, + { + "type": "equation", + "bbox": [ + 0.133, + 0.484, + 0.47, + 0.504 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {p o s i t i v e}} = \\mathbb {E} _ {\\mathbf {x} _ {\\text {i n}} \\sim D _ {\\text {t r a i n}} ^ {\\text {i n}}} [ - \\log (p (y = i | x) ]. \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.51, + 0.47, + 0.587 + ], + "angle": 0, + "content": "This method largely improves CLIP's classification performance by adapting the learnable prompts to the target data. The resulting prompt embeddings of ID classes are used as positive prompts to support the accurate learning of negative prompts in our method below." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.594, + 0.267, + 0.61 + ], + "angle": 0, + "content": "3.2. Proposed Approach" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.61, + 0.471, + 0.747 + ], + "angle": 0, + "content": "NegPrompt aims to learn a set of negative prompts, each representing a negative connotation of an ID class. As shown in Fig. 2, it involves generating a series of prompts that resemble the positive prompts obtained through CoOp, but with a negative class semantic, such as \"A photo of not a [class label]\". These negative prompts, combined with class labels, can generate a range of negative text features around the positive prompts, so that OOD images exhibit higher similarity to the negative prompts than ID images." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.764, + 0.325, + 0.779 + ], + "angle": 0, + "content": "3.2.1 Learning Negative Prompts" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.471, + 0.903 + ], + "angle": 0, + "content": "To acquire accurate negative prompts representing negative class semantics, we first utilize CoOp to learn positive prompts \\(\\omega^{pos}\\)s, after which we consider positive prompts to accurately capture the class semantics of samples in the ID dataset. Thereafter, we freeze the positive prompts and focus solely on learning the negative prompts. A negative prompt is denoted as \\(\\{\\omega_1^{neg},\\omega_2^{neg},\\dots,\\omega_n^{neg}\\}\\), where \\(n\\) represents the number of context vectors we aim to learn. By" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.429, + 0.892, + 0.522 + ], + "angle": 0, + "content": "utilizing the frozen CLIP text encoder, we can obtain negative prompt embeddings \\( T_{l,i}^{f,neg} = \\text{Encoder}^{text}(t_{l,i}^{neg}) \\), where \\( t_{l,i}^{neg} = \\{\\omega_{l,1}^{neg}, \\omega_{l,2}^{neg}, \\dots, \\omega_{l,n}^{neg}, c_i\\} \\) is the \\( l \\)-th negative prompt relative the ID class \\( i \\). Thus, due to the presence of the negative prompts, we turn the prediction probability into the following form:" + }, + { + "type": "equation", + "bbox": [ + 0.498, + 0.528, + 0.908, + 0.584 + ], + "angle": 0, + "content": "\\[\np (y = i \\mid x) = \\frac {\\exp \\left(S _ {i} ^ {f , p o s}\\right)}{\\sum_ {j = 1} ^ {k} \\exp \\left(S _ {j} ^ {f , p o s}\\right) + \\sum_ {l = 1} ^ {p} \\sum_ {j = 1} ^ {k} \\exp \\left(S _ {l , j} ^ {f , n e g}\\right)} \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.592, + 0.892, + 0.704 + ], + "angle": 0, + "content": "where \\( S_{j}^{f,pos} = \\frac{\\text{sim}(T_{j}^{f,pos}, I^{f})}{\\tau} \\), \\( S_{l,j}^{f,neg} = \\frac{\\text{sim}(T_{l,j}^{f,neg}, I^{f})}{\\tau} \\) and \\( p \\) is the number of negative prompts we aim to learn for each ID class. The objective is to learn negative text prompt embeddings that can effectively separate ID and OOD samples around the positive text features. To achieve this, we introduce the following three loss functions:" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Negative-Image Separation Loss. One of our objectives is to have the negative text prompt embeddings serve as the closest text features to OOD images. However, we only have images from the ID dataset; no OOD images are available. To remedy this problem, we take an alternative approach that aims to push the negative text features away from the ID images. In this regard, we draw inspiration from OE [11]. Contrary to the approach in OE, where the probability distribution of outlier images is evenly distributed among all ID labels, we distribute the probability distribution obtained from ID images evenly among all negative prompts. Since the network parameters are frozen, this drives the negative text features to move away from the ID" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17587" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.121 + ], + "angle": 0, + "content": "images, resulting in the learning of prompts with a negative connotation. The formulation is as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.16, + 0.135, + 0.469, + 0.155 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {N I S} = \\mathbb {E} _ {x _ {\\text {i n}} \\sim D _ {\\text {t r a i n}} ^ {\\text {i n}}} [ H (\\mathbf {u}; F (x)) ], \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.166, + 0.469, + 0.211 + ], + "angle": 0, + "content": "where \\( F(x) \\) is the probability vector computed as \\( \\text{Softmax}(S^{f,neg}) \\), and \\( \\mathbf{u} \\) is a uniform distribution and \\( H \\) is the cross entropy loss." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.212, + 0.47, + 0.348 + ], + "angle": 0, + "content": "Negative-Positive Distance Loss. To avoid learning trivial negative prompts that are distant from both ID and OOD images, we need to control the negative text feature within a certain range between the ID and OOD images. To this end, we devise a constraint, enforcing that the negative text feature does not deviate too far from the positive text feature. Therefore, we introduce the following loss function to guarantee a certain level of similarity between the negative and positive text feature in the latent space:" + }, + { + "type": "equation", + "bbox": [ + 0.115, + 0.36, + 0.469, + 0.402 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {N P D} = - \\frac {1}{k * p} \\sum_ {j = 1} ^ {k} \\sum_ {i = 1} ^ {p} \\operatorname {s i m} \\left(T _ {i, j} ^ {f, n e g}, T _ {j} ^ {f, p o s}\\right). \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.415, + 0.469, + 0.492 + ], + "angle": 0, + "content": "Negative-Negative Distance Loss. Furthermore, to ensure that we are effectively learning diverse, non-overlapping negative prompts, we extend the distances between different negative text features within the same label via the following loss function:" + }, + { + "type": "equation", + "bbox": [ + 0.078, + 0.503, + 0.472, + 0.558 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {N N D} = \\frac {1}{k * p * (p - 1)} \\sum_ {j = 1} ^ {k} \\sum_ {i = 1} ^ {p} \\sum_ {l \\neq i} \\operatorname {s i m} \\left(T _ {i, j} ^ {f, n e g}, T _ {l, j} ^ {f, n e g}\\right). \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.56, + 0.469, + 0.635 + ], + "angle": 0, + "content": "Overall, our NegPrompt objective consists of the above three losses. During training, we are able to obtain a diverse set of non-trivial prompts that effectively convey negative meanings relative to the ID class labels by minimizing the following overall loss:" + }, + { + "type": "equation", + "bbox": [ + 0.085, + 0.649, + 0.469, + 0.665 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {N e g a t i v e P r o m p t s}} = \\mathcal {L} _ {N I S} + \\beta * \\mathcal {L} _ {N P D} + \\gamma * \\mathcal {L} _ {N N D}, \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.677, + 0.46, + 0.693 + ], + "angle": 0, + "content": "where \\(\\beta\\) and \\(\\gamma\\) are hyper-parameters to balance the losses." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.699, + 0.333, + 0.715 + ], + "angle": 0, + "content": "3.2.2 Open-Vocabulary Capability" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.717, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Since the negative prompts we learn do not depend on specific class labels but are instead generic templates representing negative semantics of any given class labels, it is possible to utilize the generalization ability of CLIP to learn a set of transferable negative prompts. Specifically, instead of utilizing all of the ID classes \\( D_{train}^{in} \\), NegPrompt may only employ its small subset \\( D_{train}^{in,sub} \\) for training the negative prompts \\( \\omega^{neg} \\), where \\( D_{train}^{in,sub} = \\{(x,y_{sub}^{in}) \\mid y_{sub}^{in} \\subset y^{in}\\} \\). After obtaining the trained negative prompts, we combine them with the remaining ID class names, i.e., replace \\( c_i \\) in \\( t_{l,i}^{neg} \\) with the unseen ID class names, to obtain the corresponding negative prompts for the novel ID classes that are" + }, + { + "type": "table", + "bbox": [ + 0.533, + 0.09, + 0.86, + 0.144 + ], + "angle": 0, + "content": "
IDOOD
Split-1All dog classesNon-animal classes
Split-2Half of hunting dog classesOther 4-legged animal classes
Split-3Mix of common classesMix of common classes
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.518, + 0.144, + 0.872, + 0.157 + ], + "angle": 0, + "content": "Table 1. Three ImageNet-1K splits for hard OOD detection." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.164, + 0.892, + 0.224 + ], + "angle": 0, + "content": "unseen during training. This approach, which achieves out-of-distribution detection by only exposing with a small portion of ID images, is unprecedented in prior research. We refer this as to be open-vocabulary OOD detection." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.245, + 0.62, + 0.258 + ], + "angle": 0, + "content": "3.2.3 Inference" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.262, + 0.892, + 0.489 + ], + "angle": 0, + "content": "During inference, we employ the MCM [32] scoring approach for OOD detection, but with the addition of our negative prompts into the softmax function. Particularly, MCM uses the inverse of the maximum softmax score in Eq. 1 as the OOD score. Our OOD scoring extends MCM and defines it as: \\( s(x) = \\max(p(y = i|x)) \\), where \\( p(y = i|x) \\) is defined in Eq. 3 that also includes the similarities of the test image to the negative prompts, in addition to the similarities to the positive prompts. The rationale behind this is that for ID images, they will be matched to one of the positive text features, leading to a higher \\( S^{f,pos} \\) but lower \\( S^{f,neg} \\), and thereby a higher maximum softmax score (i.e., a lower OOD score). Conversely, for OOD data, it will be matched to one of the negative text features, resulting in a lower maximum softmax score (i.e., a higher OOD score)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.497, + 0.625, + 0.513 + ], + "angle": 0, + "content": "4. Experiment" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.522, + 0.699, + 0.537 + ], + "angle": 0, + "content": "4.1. Experimental Details" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.539, + 0.892, + 0.794 + ], + "angle": 0, + "content": "Datasets. For conventional OOD detection, we use a popular benchmark in which ImageNet-1K [3] with 1,000 classes is used as the ID dataset, and the same OOD datasets as in [32] are used, including subsets of Texture [2], iNaturalist [43], Places [51] and SUN [48]. In addressing the more challenging OOD scenarios, we partitioned the ImageNet1k dataset into two segments: one segment of the data serves as the ID, while the other serves as OOD. As shown in Table 1, three different splits are derived, following from [35]. We further create another ImageNet split, Split-4, in which the first 100 classes are used as ID data and the subsequent 900 classes are used as OOD samples. Following CoOp and LoCoOp [33, 54], during our training process, we utilized only few-shot training data for each category. Particularly, we only train the model with 16 images per ID class and without any exposure to OOD images. During testing, we employ the entire ID and OOD test set for evaluation." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.796, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Implementation Details. Following existing studies [46], we use CLIP based on CLIP-B/16 which is pre-trained from OpenCLIP [16]. NegPrompt is trained using 16-shot images of all ID classes under the normal OOD detection setting. For open-vocabulary OOD detection, we train our model using only the images of the first \\(10\\%\\) classes from the ID dataset, withholding \\(90\\%\\) ID classes that only appear" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17588" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.128, + 0.089, + 0.846, + 0.32 + ], + "angle": 0, + "content": "
MethodTextureiNaturalistPlacesSUNAvg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓
Zero-shot methods
MCM [32]†86.1157.7794.6130.9189.7744.6992.5734.5990.7642.74
CLIPN [46]†90.9340.8395.2723.9492.2833.4593.9226.1793.1031.10
CLIP-based posthoc methods
MSP [10]†74.8473.6677.7474.5772.1879.1273.9776.9574.9876.22
MaxLogit [12]†88.6348.7288.0360.8887.4555.5491.1644.8388.8252.49
Energy [27]†88.2250.3987.1864.9887.3357.4091.1746.4288.4854.80
ReAct [41]†88.1349.8886.8765.5787.4256.8591.0446.1788.3754.62
ODIN [26]†87.8551.6794.6530.2285.5455.0687.1754.0488.8047.75
Prompt learning methods
CoOp [54]89.4745.0093.7729.8190.5840.1193.2940.8391.7851.68
LoCoOp [33]†90.1942.2896.8616.0591.9832.8795.0723.4493.5228.66
NegPrompt (Ours)91.6035.2198.736.3293.3427.6095.5522.8994.8123.01
Open-vocabulary OOD detection
CoOp (10%)87.5850.5591.0842.5389.5646.1291.5241.9289.9445.28
LoCoOp (10%)88.2147.3294.4734.9091.6439.8592.5426.3090.1537.09
NegPrompt (Ours) (10%)90.3039.3198.397.4892.6829.7593.7026.9293.7625.86
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.321, + 0.895, + 0.364 + ], + "angle": 0, + "content": "Table 2. Conventional OOD detection results. We trained using ImageNet1k as the ID and CLIP-B/16 as the CLIP backbone. The boldfaced results indicate the best performance. Results marked with \\(\\dagger\\) are taken from [46] and [33]. 'METHOD' (10%) in open-vocabulary OOD detection is to evaluate the performance of the 'METHOD' when only images from 10% ID classes are accessible during training." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.382, + 0.471, + 0.518 + ], + "angle": 0, + "content": "together with OOD data during inference. We train a shared positive prompt and two shared negative prompts w.r.t. each training ID class. The hyperparameters \\(\\beta\\) and \\(\\gamma\\) are set to 0.1 and 0.05, respectively (see Appendix A for detail). In the first stage, CoOp is trained for 100 epochs to obtain the positive prompts. In the second stage, the positive prompts are frozen, and our model is trained for 10 epochs to learn the negative prompts. For all experiments, we report the averaged results over three runs with different random seeds." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.52, + 0.47, + 0.808 + ], + "angle": 0, + "content": "Comparison Methods. To substantiate the effectiveness of NegPrompts, we conduct an empirical analysis of three distinct categories of methodologies employed for OOD detection utilizing Vision-language models. These categories encompass zero-shot pretraining approaches, the methods that combine the CLIP image encoder with classical approaches, and the methods grounded in prompt learning. In the context of zero-shot methods, we opted for the two recent methods, MCM [32] and CLIPN [46]. MCM employs the original CLIP, utilizing the maximum softmax probability operation on the similarities for detection, and CLIPN involves an additional training phase during pretraining, specifically training a negative text encoder using large external data. For the second group of methods, we adapt previous logits-based methodologies to the use of the CLIP image encoder, including MSP [10], Energy [27], MaxLogit [12], ReAct [41] and ODIN [26], to serve as the CLIP-adapted methods. For the prompt learning methods, NegPrompt is compared with CoOp [54] and LoCoOp [33]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Evaluation Metrics. Two OOD detection metrics are used. The first metric is the False Positive Rate at a \\(95\\%\\) True Negative Rate (FPR95), which denotes the rate of falsely identified OOD instances when the true negative rate is maintained at \\(95\\%\\). The second metric is the Area Under the Receiver Operating Characteristic curve (AUROC), rep" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.382, + 0.895, + 0.442 + ], + "angle": 0, + "content": "resenting the measure of OOD ranking across various classification thresholds. We also check the classification accuracy of the ID data to evaluate how the OOD detectors affect the ID classification." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.457, + 0.836, + 0.473 + ], + "angle": 0, + "content": "4.2. Comparison to State-of-the-art Models" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.475, + 0.892, + 0.701 + ], + "angle": 0, + "content": "Conventional OOD Detection. The results of conventional OOD detection are reported in Table 2. It is clear that our proposed NegPrompt achieves consistently superior performance in both individual OOD datasets and the averaged results. When compared with the zero-shot methods, on average, our approach surpasses the best competing method CLIPN by more than \\(1.5\\%\\) in AUC and around \\(8\\%\\) in FPR95, despite the fact that CLIPN requires the use of an additional large external dataset to train an additional negative text encoder. In other words, although NegPrompt is significantly more lightweight than CLIPN in model size, it can substantially and consistently outperform CLIPN in both metrics across all OOD datasets. The adapted post-hoc methods generally do not leverage the CLIP's capabilities well and thus perform less effectively." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.703, + 0.892, + 0.794 + ], + "angle": 0, + "content": "NegPrompt also substantially surpasses both prompt learning-based methods, reducing the FPR95 by about \\(28\\%\\) (CoOp) and \\(5\\%\\) (LoCoOp). This indicates that the learned negative prompts provide informed knowledge about OOD data, which is lacking in the competing methods, helping largely reduce detection errors." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Hard OOD Detection. Hard OOD detection presents unique challenges as the OOD samples often exhibit some similar features as the ID samples. The results on the four hard OOD datasets derived from ImageNet-1K are shown in Table 3. Similar empirical observations can be derived. Our method NegPropmt is consistently the best performer in the average performance, showcasing its general effec" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "17589" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.128, + 0.089, + 0.845, + 0.32 + ], + "angle": 0, + "content": "
MethodSplit-1Split-2Split-3Split-4Avg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓
Zero-shot methods
MCM97.939.1788.1056.4090.3433.0598.724.7393.7725.83
CLIPN99.382.0797.7710.5590.0336.8598.834.6896.5013.53
CLIP-based posthoc methods
MSP77.8563.6068.7383.6379.1070.5582.4065.5277.0270.83
MaxLogit99.870.4998.068.6990.9634.3499.352.6697.0611.55
Energy99.880.4698.188.4090.6535.0299.362.8397.0211.68
ReAct99.340.7297.919.3390.7235.6599.122.9496.7712.16
ODIN98.781.1298.238.1889.9237.2098.7613.2096.4214.92
Prompt learning methods
CoOp98.536.7888.2550.7690.6433.8998.545.1193.9924.14
LoCoOp98.646.2984.6361.0991.3027.7998.8341.4493.3534.15
NegPrompt (Ours)99.850.6298.547.6093.8922.8999.571.6097.968.18
Open-vocabulary OOD detection
CoOp (10%)97.9712.21780.1174.6287.9246.0096.5916.6090.6537.36
LoCoOp (10%)98.009.2387.0252.1880.5159.9382.4148.7286.9942.52
NegPrompt (Ours) (10%)99.661.3696.3019.8991.7526.9298.145.2496.4613.36
" + }, + { + "type": "table_caption", + "bbox": [ + 0.205, + 0.321, + 0.766, + 0.333 + ], + "angle": 0, + "content": "Table 3. Hard OOD detection results. We use the same notations here as those used in Table 2." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.353, + 0.47, + 0.458 + ], + "angle": 0, + "content": "tiveness across different dataset splits. The superiority of NegPrompt over the zero-shot and prompt learning-based methods is similar to that in Table 2. Although it is slightly less effective than Energy under the Split-1 setting, it outperforms Energy in all other metrics, achieving maximally over \\(3\\%\\) AUC and \\(12\\%\\) FPR95 improvement among the performance on the other OOD datasets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.459, + 0.47, + 0.534 + ], + "angle": 0, + "content": "Note that the results in Table 3 are generally more promising than that in Table 2. This is mainly because the OOD detection difficulty in all four ImageNet-1K splits is largely reduced since the number of their ID classes is significantly less than that in the full ImageNet-1K data." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.535, + 0.471, + 0.732 + ], + "angle": 0, + "content": "Open-Vocabulary OOD Detection. The open-vocabulary OOD detection results are reported in both Tables 2 and 3. Impressively, even when training on only \\(10\\%\\) ID classes, our approach can still perform better than the competing methods using the full ID classes, e.g., the average AUC and FPR95 in Table 2. In this open-vocabulary setting, in general, both LoCoOp and CoOp exhibit a much larger performance decline than NegPrompt, especially on the results in Table 3, in which CoOp has over \\(3\\%\\) AUC drop and LoCoOp has over \\(6\\%\\) AUC drop while our method has only about \\(1.5\\%\\) AUC drop. These results demonstrate that the negative prompts in NegPrompt have much better transferability than those in the two competing methods." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.749, + 0.377, + 0.763 + ], + "angle": 0, + "content": "4.2.1 Classification Accuracy on ID Data" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.469, + 0.87 + ], + "angle": 0, + "content": "We also evaluate the classification accuracy on the ID data when using NegPrompt for OOD detection, with CoOp, LoCoOp, MCM and CLIPN as the baselines. The classification accuracy results on the full ImageNet-1K test data are shown in Table 4. When using the full ImageNet-1K training ID class data, our method NegPrompt can maintain the same classification accuracy as CoOp." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.871, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Our accuracy is slightly compromised when using only \\(10\\%\\) ID classes in our training. On the other hand, the OOD" + }, + { + "type": "table", + "bbox": [ + 0.567, + 0.351, + 0.828, + 0.436 + ], + "angle": 0, + "content": "
MethodTop-1 Accuracy
CoOp72.1
\\( \\text{LoCoOp}^\\dagger \\)71.7
CLIPN & MCM67.0
NegPrompt(Ours)(10%)71.9
NegPrompt(Ours)(Full)72.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.513, + 0.437, + 0.878, + 0.451 + ], + "angle": 0, + "content": "Table 4. Top-1 Accuracy. Results with \\( \\dagger \\) are taken from [33]." + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.474, + 0.682, + 0.612 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.709, + 0.474, + 0.89, + 0.612 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.612, + 0.682, + 0.722 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.711, + 0.612, + 0.889, + 0.722 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.505, + 0.723, + 0.885, + 0.738 + ], + "angle": 0, + "content": "Figure 3. Similarity of ID/OOD and Positive/Negative Prompts." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.785, + 0.892, + 0.906 + ], + "angle": 0, + "content": "detection in LoCoOp compromises the ID classification accuracy, dropped from \\(72.1\\%\\) in CoOp to \\(71.7\\%\\). This may be attributed to its focus on the localized regions within the background rather than the primary object of interest, resulting in the missing of some discriminative features for ID data classification. CLIPN and MCM, being zero-shot methods, have not been exposed to the target ID data, leading to a much lower accuracy than the other methods." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17590" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.116, + 0.089, + 0.858, + 0.233 + ], + "angle": 0, + "content": "
Ablation StudyTextureiNaturalistPlacesSUNAvg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓ACC ↑
Backbones
ResNet-5079.4472.7390.9744.1084.3561.3788.0450.5585.7057.1968.2
ResNet-10182.9770.8393.9631.386.4151.6688.8147.6188.0450.3570.3
ViT-B-3290.4338.7997.4012.6492.8332.7992.8226.0393.3727.5672.6
# Negative Prompts
190.0440.6798.249.2390.3732.6292.2627.3392.7327.4672.1
Training Process
One-stage80.2572.8777.0295.7482.5395.9481.1395.7280.2390.0762.8
ViT-B-16 & 2 & Two-stage90.3039.3198.397.4892.6829.7593.7026.9293.7625.8672.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.35, + 0.234, + 0.618, + 0.247 + ], + "angle": 0, + "content": "Table 5. Results of our ablation experiments." + }, + { + "type": "image", + "bbox": [ + 0.114, + 0.263, + 0.436, + 0.426 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.429, + 0.472, + 0.457 + ], + "angle": 0, + "content": "Figure 4. T-SNE visualization of NegPrompt, utilizing a subset of ImageNet - TinyImageNet as the dataset." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.475, + 0.292, + 0.492 + ], + "angle": 0, + "content": "4.3. Analysis of NegPrompt" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.498, + 0.339, + 0.513 + ], + "angle": 0, + "content": "4.3.1 Why Does NegPrompt Work?" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.515, + 0.469, + 0.65 + ], + "angle": 0, + "content": "To better understand the effectiveness of NegPrompt, we summarize the average maximum similarity between ID/OOD images and positive/negative prompts, as shown in Fig. 3. Across all four OOD datasets, ID images have the highest similarity with positive prompts, and OOD images with negative prompts. This suggests positive prompts are closer to ID images and negative prompts to OOD images in latent space, ensuring OOD images receive lower softmax scores (i.e., higher OOD scores) than ID images in Eq. 3." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.651, + 0.469, + 0.817 + ], + "angle": 0, + "content": "Using TinyImageNet [23], a subset of ImageNet, we further visualized the learned negative text features with its test data [6]. Learning three negative prompts per ID class, the results in Fig. 4 demonstrate that positive text features from positive prompts align closely with ID images in latent space. Conversely, the negative text features encoded from negative prompts lie outside of the ID data, with OOD images interspersed among them. This suggests negative text features effectively act as a fence aligning much better to the OOD images than the ID images, well supporting the OOD detection while preserving the ID classification accuracy." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.828, + 0.238, + 0.841 + ], + "angle": 0, + "content": "4.3.2 Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.841, + 0.468, + 0.871 + ], + "angle": 0, + "content": "Table 5 shows our ablation study results on the backbone, the number of negative prompts, and the training process." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.469, + 0.899 + ], + "angle": 0, + "content": "Backbones. We experiment with diverse CLIP backbones. The results reveal that for CNN-based backbones" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.263, + 0.892, + 0.338 + ], + "angle": 0, + "content": "like ResNet50 and ResNet101, the OOF detection performance is not as proficient as the ViT-based backbones. Regarding ViT-B-32 and ViT-B-16, their performance is found to be uneven. Overall, the performance of OOD detection tends to increase with more advanced backbones." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.339, + 0.893, + 0.49 + ], + "angle": 0, + "content": "The Number of Negative Prompts. The number of negative prompts also influences the results. It is observed that the OOD detection performance improves when increasing the number of negative prompts from one to two. Therefore, it is suggested to further increase the number of negative prompts for better detection accuracy. However, note that with an increase in the number of negative prompts, the computational cost also rises rapidly. A good balance between computational cost and detection accuracy is needed when determining the number of negative prompts." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.491, + 0.892, + 0.656 + ], + "angle": 0, + "content": "Training Process. The training process is also important. As discussed before, due to the necessity of anchoring the positive prompts, a two-stage training process is used in our model. This process involves training the positive prompts in the first stage and freezing them before proceeding to train the negative prompts in the second stage. When simultaneously training both positive and negative prompts in a unified step, the model's ability to effectively learn positive prompts is significantly undermined, and consequently we obtain unstable negative prompts, leading to the largely decreased OOD detection performance." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.671, + 0.619, + 0.687 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.697, + 0.892, + 0.833 + ], + "angle": 0, + "content": "We present NegPrompt, a novel approach for prompt learning-based OOD detection. It utilizes VLMs to learn a small set of negative prompts for conveying negative semantics relative to ID classes. Our empirical results reveal that NegPrompt 1) achieves superior OOD detection performance compared to the SOTA models across various OOD datasets in both conventional and hard OOD detection scenarios, and 2) learns transfer negative prompts that enable excellent open-vocabulary OOD detection performance." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.848, + 0.681, + 0.865 + ], + "angle": 0, + "content": "6. Acknowledgement" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.872, + 0.892, + 0.9 + ], + "angle": 0, + "content": "This work was supported by the National Natural Science Foundation of China 62276016, 62372029." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "17591" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.197 + ], + "angle": 0, + "content": "[1] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katherine Millican, Malcolm Reynolds, et al. Flamingo: a visual language model for few-shot learning. 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Toward generalist anomaly detection via in-context residual learning with few-shot sample prompts. arXiv preprint arXiv:2403.06495, 2024. 2" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.47, + 0.318 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.946, + 0.519, + 0.956 + ], + "angle": 0, + "content": "17594" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_origin.pdf b/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..a3418b00912291a12b558ac30ba867a9803798f5 --- /dev/null +++ b/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/5385f0b8-2f8e-4840-b283-fc050f4ae0b4_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:78cf23a86b0b3719a183da9907be8aea53b0e9409725377b06f6683c4d789fa5 +size 3641178 diff --git a/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/full.md b/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/full.md new file mode 100644 index 0000000000000000000000000000000000000000..0a260e79c9205b749357e2fbe0f28cc500cc0b60 --- /dev/null +++ b/2024/Learning Transferable Negative Prompts for Out-of-Distribution Detection/full.md @@ -0,0 +1,306 @@ +# Learning Transferable Negative Prompts for Out-of-Distribution Detection + +Tianqi Li $^{1}$ , Guansong Pang $^{*2}$ , Xiao Bai $^{*1}$ , Wenjun Miao $^{1}$ , and Jin Zheng $^{1}$ + +$^{1}$ School of Computer Science and Engineering, State Key Laboratory of Complex & Critical Software Environment, Jiangxi Research Institute, Beihang University, China + +$^{2}$ School of Computing and Information Systems, Singapore Management University + +# Abstract + +Existing prompt learning methods have shown certain capabilities in Out-of-Distribution (OOD) detection, but the lack of OOD images in the target dataset in their training can lead to mismatches between OOD images and InDistribution (ID) categories, resulting in a high false positive rate. To address this issue, we introduce a novel OOD detection method, named 'NegPrompt', to learn a set of negative prompts, each representing a negative connotation of a given class label, for delineating the boundaries between ID and OOD images. It learns such negative prompts with ID data only, without any reliance on external outlier data. Further, current methods assume the availability of samples of all ID classes, rendering them ineffective in open-vocabulary learning scenarios where the inference stage can contain novel ID classes not present during training. In contrast, our learned negative prompts are transferable to novel class labels. Experiments on various ImageNet benchmarks show that NegPrompt surpasses state-of-the-art prompt-learning-based OOD detection methods and maintains a consistent lead in hard OOD detection in closed- and open-vocabulary classification scenarios. Code is available at https://github.com/mala-lab/negprompt. + +# 1. Introduction + +Since the advent of deep learning, numerous image recognition models [5, 9, 29] have relied solely on image features for classification. However, in recent years large pre-trained vision-language models (VLMs), such as CLIP [37], integrated natural language processing into computer vision, enhancing the semantic understanding capabilities of computer vision models. It has been observed that these VLMs excel in image classification, particularly in zero-shot scenarios. This is attributed to their extensive self-supervised pre-training on web-scale image-text data, which has endowed them with robust semantic transfer abilities. + +![](images/a26a53cb8e4acb4e42ce9ab9fc1e8307b384667804981ba7b389b40980f1beb5.jpg) +Figure 1. Illustration of the key intuition of NegPrompt. For each ID class, NegPrompt trains a small set of learnable prompts that have negative semantics to the learned positive prompt of the given class. As a result, OOD samples exhibit higher similarity to the negative prompts than the positive prompts. + +Despite the strong zero-shot classification capabilities of VLMs, numerous research efforts are put to unleash their potential, e.g., by investigating whether models like CLIP can achieve enhanced performance with training on downstream target datasets. This has led to the development of various techniques to fine-tune CLIP [8, 18], among which prompt learning has sparked widespread interest. Prompt learning (or prompt tuning) [19, 39, 50], a methodology originating from natural language processing, focuses on learning the prompt inputs into a large-scale pre-trained network, rather than learning or fine-tuning the parameters of the network. In CLIP, a common prompt is 'a photo of a [class name]'. The aim of prompt learning, e.g., in approaches like CoOp [54], is to learn a soft/differentiable context vector to replace the fixed text prompt like 'a photo of a', thereby leveraging CLIP's powerful generalization in semantic understanding while also fine-tuning for specific target datasets [53, 54]. + +However, even though prompt learning enhances the target dataset perception capabilities of VLMs, it struggles with Out-Of-Distribution (OOD) detection [10, 26]. Under the OOD detection task, the test set comprises images from both the training classes - in-distribution (ID) data - + +and images from other unknown categories (OOD images). VLM-based classification is typically performed by first replacing the '[class name]' with the class label of each category in a prompt, which is then processed by the text encoder of CLIP to obtain the class embedding and assign the class label that has the highest cosine similarity with the embedding of a test image from the image encoder of CLIP. However in OOD detection tasks, the models do not have access to the class names of OOD images, thereby lacking the knowledge about OOD data. + +This issue, exacerbated by the models' tendency towards overconfidence that often predicts OOD data as ID images with high confidence [34], undermines their ability to effectively detect OOD images. + +There have been a number of CLIP-based methods designed specifically for VLM-driven OOD detection methods, but most of them [6, 32, 46] focused on a zero-shot setting where no training data of the target dataset is available. Due to the lack of adaptation to the target dataset, they tend to detect unusual ID images as OOD data. Among them, CLIPN [46], which trains an additional 'no' text encoder to provide prompt embeddings of not having specific classes, is the best detector, but it relies on a large-scale auxiliary dataset to train such a text encoder and it is computationally expensive. + +The most related work is a very recent approach LoCoOp [33] that utilizes the training ID data to tune CLIP to capture local features of the ID classes in the prompt. It shows substantially improved performance compared to zero-shot methods [32], but it may compromise the ID classification accuracy due to an overemphasis on modeling local features. LoCoOp also lacks knowledge about OOD samples, making it difficult to differentiate boundary ID/OOD images. + +In this work, we propose a novel CLIP-based OOD detection method, named NegPrompt. Inspired by [25], Negprompt is designed to learn a set of negative prompts, each representing a negative connotation of a given ID class label, to delineate the boundaries between ID and OOD images, as shown in Fig. 1. The negative prompts represent specialized ID-class-dependent concepts, guiding the models to pay attention to the characteristics that are contrary to or disjoint from the ID classes. NegPrompt aims to utilize ID training data and positive prompts (i.e., the text prompt embeddings of ID classes) to learn such negative prompts in a way to which OOD images exhibits higher similarity than ID images. + +Essentially, the learned negative prompts have similar semantics to the text prompts generated from the 'no' text encoder in CLIPN, but NegPrompt presents a fundamentally different approach: it capitalizes on the generalization ability of the CLIP model and learns the negative prompts with training ID data only, eliminating the reliance on external + +data and the extensive computation overhead as in CLIPN. + +Furthermore, benefiting from the superior generalization ability of CLIP, our method does not require the exposure to all ID classes during training. In other words, the model learns transferable negative prompts by using only a small subset of the ID classes, after which we can obtain the negative prompts for the other ID classes by simply replacing the '[class name]' in the prompts with the name of those unexposed classes. This allows our model to work in open-vocabulary [7, 31] learning settings, where the models are required to classify images of novel classes that are not seen during training, in addition to a set of training base classes. + +Our main contributions can be summarized as follows: + +- We propose a prompt learning-based OOD detection approach NegPrompt, which is able to learn negative semantics relative to specific ID classes, thereby enhancing the VLMs' sensitivity to unknown samples. It is a lightweight method that does not require training extra encoders on external data as in related methods [46]. +- NegPrompt possesses an open-vocabulary capability due to the transferability of its negative prompts. This means that with training images from just a small subset of ID classes and the class names of all IDs, we can achieve OOD detection on test data with all these ID classes. To the best of our knowledge, there have been no previous fine-tuning methods exploring such a capability. +- Extensive experiments on multiple ImageNet-based benchmarks show that NegPrompt consistently outperforms current state-of-the-art methods in both conventional and hard OOD Detection settings. + +# 2. Related Work + +# 2.1. Pre-trained Vision-Language Models + +Understanding the semantic information of images remains a significant challenge in the field of computer vision. With the advent of Transformer [44] in computer vision tasks [5], CLIP [37] has been introduced as one of the most advanced pre-trained VLMs. Utilizing contrastive learning [21], large-scale models and datasets [38], CLIP employs image-text pairs as the training data for self-supervised learning. This approach has successfully trained the model to align visual and text signals in a latent space. Concurrently, other researchers [1, 24, 49] have also shown the remarkable generalization capabilities of CLIP and similar vision-language models [17] in various downstream tasks [7, 20, 56]. + +# 2.2. Prompt Learning + +The concept of prompt learning was initially focused on automating the creation of templates/prompts for extracting knowledge from Bert [4] or GPT [36]. To bypass manual creation, prompt learning advocates the use of supervised learning to automate the prompt development. [39] proposed a gradient-based approach for identifying the + +best prompt, establishing the foundation of prompt learning. Later, CoOp [54] integrated prompt learning into computer vision. CoOp learns a segment of the context before it is fed into the text encoder of CLIP, thus tailoring the learned prompt to the specific target dataset. Many other prompt learning methods for different vision tasks [13, 18, 20, 40, 47, 53, 55] are subsequently introduced. However, they are not designed for OOD detection, so they struggle with dealing with the unknown OOD samples during inference. + +# 2.3. Out-of-Distribution Detection + +OOD detection is committed to identifying images in image classification tasks that belong to categories not present in the training dataset, typically originating from a different distribution. While traditional OOD detection methods often tackle the problem by either exploiting the prediction logits to define OOD scores [10, 12, 15, 26, 27] or focusing on the class-agnostic information in feature space that is not recoverable from logits [41, 45], recent methods [11, 14, 22, 28, 30, 42, 52] introduce extra or synthetic OOD data, employing fine-tuning to elevate their model's sensitivity towards unknown classes. + +With the introduction of large pre-trained VLMs, OOD detection has embarked on a new trajectory driven by VLMs. MCM [32] aims to integrate the idea of maximum softmax probability [10] into the inference process of CLIP, while ZOC [6] enhances OOD detection in a zero-shot setting by learning an additional image interpreter and guessing the category of images. CLIPN [46] and LoCoOp [33], the most related methods to ours, are based on text prompts. However, CLIPN, during its pretraining phase, trains an additional negative text encoder using a large external dataset to improve its negative semantic prompt, which increases network parameters and deviates from prompt learning that is focused on tuning the target data. LoCoOp, on the other hand, uses prompt learning for matching text and image local features, which can compromise the global perception capability of CLIP and reduce classification accuracy for in-distribution (ID) samples. Also, its model lacks knowledge about OOD samples, which can often lead to high detection errors. + +# 3. Method + +In this paper, we propose an approach named NegPropmt that leverages pre-trained VLMs, specifically CLIP, to learn negative prompts relative to ID classes for the purpose of OOD detection. The negative prompts are learned in the CLIP's text-image-aligned embedding space with the support of training ID data and their positive prompts (i.e., prompt embeddings of ID classes); no external outlier data is required. Due to its general effectiveness, the popular prompt learning method CoOp [54] is used by default to provide the positive prompts for training NegPrompt. + +# 3.1. Preliminaries + +Problem Statement. Formally, we assume that we have two datasets, namely ID dataset denoted as $D^{in}$ and OOD dataset denoted as $D^{out}$ . The ID dataset consists of image-label pairs $(x^{in}, y^{in})$ , where $y^{in} \in Y^{in} = \{0, 1, 2, 3 \dots k\}$ belong to the ID class set. Similarly, the OOD dataset contains image-label pairs $(x^{out}, y^{out})$ , but all $y^{out} \in Y^{out} = \{k + 1, k + 2, \dots\}$ belong to the OOD class set. It is important to note that these two sets do not intersect, meaning that $Y^{in} \cap Y^{out} = \emptyset$ . As we have a test set $X^{test}$ consists of images from ID and OOD, the goal of OOD detection is to train a classifier $\phi(x)$ that takes an image $x$ as input and returns whether the image belongs to OOD. Unlike existing studies using full-/zero-shot ID training samples, we only use a few samples (16 samples per class) for $D_{train}^{in}$ like [33] does. In the open-vocabulary detection setting, we only use a small part (10%) but not all the classes of $D_{train}^{in}$ . CLIP and CoOp. CLIP [37] is currently one of the most popular image-text models. During the pre-training phase, it uses large-scale image-text pairs for self-supervised contrastive learning, aligning images and texts into the same latent space. The main components of CLIP are an image encoder $Encoder^{image}(I)$ and a text encoder $Encoder^{text}(T)$ , which respectively accept image and text inputs. In zero-shot image classification tasks, assume we have $k$ class labels for classification, such as "cat", "dog", etc., CLIP first incorporates the class labels into pre-designed hard/unlearnable text prompts, such as "a photo of a [class name]", forming a prompt input set of "a photo of a cat", "a photo of a dog" and so on. These prompts are then individually fed into the text encoder $Encoder^{text}(T)$ to obtain $k$ text features $T^f$ . The testing image is then input into the image encoder to obtain an image feature $I^f$ . The cosine similarity is calculated between the normalized image feature and all text features, formally, $Sim(T^f, I^f) = T^f \cdot I^f$ , and the text feature $T^f$ with the highest similarity to $I^f$ is considered to be the category to which the image belongs. + +Besides zero-shot classification, many have explored ways to improve CLIP's performance when the target data is accessible. CoOp [54] introduces prompt learning with CLIP by freezing its encoders and using backpropagation to learn dataset-specific soft/learnable prompts. The text prompts are represented as $t_i = \{\omega_1^{pos}, \omega_2^{pos}, \dots, \omega_n^{pos}, c_i\}$ , where $c_i$ is the word embedding of the class name and $\omega^{pos}s$ are learnable vectors that have positive semantics w.r.t. the class $i$ . The goal is to optimize these $\omega^{positive}$ s. Specifically, $t_i$ is processed by Encoder $^{text}$ to yield $T_i^{f,pos}$ as a positive prompt embedding of the class $i$ , and then the prediction probability is computed as: + +$$ +p (y = i | x) = \frac {\exp \left(\operatorname {s i m} \left(T _ {i} ^ {f , p o s} , I ^ {f}\right) / \tau\right)}{\sum_ {j = 1} ^ {k} \exp \left(\operatorname {s i m} \left(T _ {j} ^ {f , p o s} , I ^ {f}\right) / \tau\right)}, \tag {1} +$$ + +![](images/93cf385c0b8c948651681b6fcac01869930ef400e17eb5f15c85686ebc874f29.jpg) +Figure 2. Overview of NegPropmt. Given the CLIP model and positive prompts learned by existing prompt learning methods such as CoOp [54], NegPrompt learns a set of negative prompts relative to different ID class labels via three loss functions that enforce the separation between negative prompts and ID images, and between negative and positive prompts, as well as the diversity of the negative prompts. + +where $I^{f} = \text{Encoder}^{image}(x)$ and $\tau$ is a temperature parameter. Next, cross-entropy loss is used to maximize similarity between ID class text embeddings and images. + +$$ +\mathcal {L} _ {\text {p o s i t i v e}} = \mathbb {E} _ {\mathbf {x} _ {\text {i n}} \sim D _ {\text {t r a i n}} ^ {\text {i n}}} [ - \log (p (y = i | x) ]. \tag {2} +$$ + +This method largely improves CLIP's classification performance by adapting the learnable prompts to the target data. The resulting prompt embeddings of ID classes are used as positive prompts to support the accurate learning of negative prompts in our method below. + +# 3.2. Proposed Approach + +NegPrompt aims to learn a set of negative prompts, each representing a negative connotation of an ID class. As shown in Fig. 2, it involves generating a series of prompts that resemble the positive prompts obtained through CoOp, but with a negative class semantic, such as "A photo of not a [class label]". These negative prompts, combined with class labels, can generate a range of negative text features around the positive prompts, so that OOD images exhibit higher similarity to the negative prompts than ID images. + +# 3.2.1 Learning Negative Prompts + +To acquire accurate negative prompts representing negative class semantics, we first utilize CoOp to learn positive prompts $\omega^{pos}$ s, after which we consider positive prompts to accurately capture the class semantics of samples in the ID dataset. Thereafter, we freeze the positive prompts and focus solely on learning the negative prompts. A negative prompt is denoted as $\{\omega_1^{neg},\omega_2^{neg},\dots,\omega_n^{neg}\}$ , where $n$ represents the number of context vectors we aim to learn. By + +utilizing the frozen CLIP text encoder, we can obtain negative prompt embeddings $T_{l,i}^{f,neg} = \text{Encoder}^{text}(t_{l,i}^{neg})$ , where $t_{l,i}^{neg} = \{\omega_{l,1}^{neg}, \omega_{l,2}^{neg}, \dots, \omega_{l,n}^{neg}, c_i\}$ is the $l$ -th negative prompt relative the ID class $i$ . Thus, due to the presence of the negative prompts, we turn the prediction probability into the following form: + +$$ +p (y = i \mid x) = \frac {\exp \left(S _ {i} ^ {f , p o s}\right)}{\sum_ {j = 1} ^ {k} \exp \left(S _ {j} ^ {f , p o s}\right) + \sum_ {l = 1} ^ {p} \sum_ {j = 1} ^ {k} \exp \left(S _ {l , j} ^ {f , n e g}\right)} \tag {3} +$$ + +where $S_{j}^{f,pos} = \frac{\text{sim}(T_{j}^{f,pos}, I^{f})}{\tau}$ , $S_{l,j}^{f,neg} = \frac{\text{sim}(T_{l,j}^{f,neg}, I^{f})}{\tau}$ and $p$ is the number of negative prompts we aim to learn for each ID class. The objective is to learn negative text prompt embeddings that can effectively separate ID and OOD samples around the positive text features. To achieve this, we introduce the following three loss functions: + +Negative-Image Separation Loss. One of our objectives is to have the negative text prompt embeddings serve as the closest text features to OOD images. However, we only have images from the ID dataset; no OOD images are available. To remedy this problem, we take an alternative approach that aims to push the negative text features away from the ID images. In this regard, we draw inspiration from OE [11]. Contrary to the approach in OE, where the probability distribution of outlier images is evenly distributed among all ID labels, we distribute the probability distribution obtained from ID images evenly among all negative prompts. Since the network parameters are frozen, this drives the negative text features to move away from the ID + +images, resulting in the learning of prompts with a negative connotation. The formulation is as follows: + +$$ +\mathcal {L} _ {N I S} = \mathbb {E} _ {x _ {\text {i n}} \sim D _ {\text {t r a i n}} ^ {\text {i n}}} [ H (\mathbf {u}; F (x)) ], \tag {4} +$$ + +where $F(x)$ is the probability vector computed as $\text{Softmax}(S^{f,neg})$ , and $\mathbf{u}$ is a uniform distribution and $H$ is the cross entropy loss. + +Negative-Positive Distance Loss. To avoid learning trivial negative prompts that are distant from both ID and OOD images, we need to control the negative text feature within a certain range between the ID and OOD images. To this end, we devise a constraint, enforcing that the negative text feature does not deviate too far from the positive text feature. Therefore, we introduce the following loss function to guarantee a certain level of similarity between the negative and positive text feature in the latent space: + +$$ +\mathcal {L} _ {N P D} = - \frac {1}{k * p} \sum_ {j = 1} ^ {k} \sum_ {i = 1} ^ {p} \operatorname {s i m} \left(T _ {i, j} ^ {f, n e g}, T _ {j} ^ {f, p o s}\right). \tag {5} +$$ + +Negative-Negative Distance Loss. Furthermore, to ensure that we are effectively learning diverse, non-overlapping negative prompts, we extend the distances between different negative text features within the same label via the following loss function: + +$$ +\mathcal {L} _ {N N D} = \frac {1}{k * p * (p - 1)} \sum_ {j = 1} ^ {k} \sum_ {i = 1} ^ {p} \sum_ {l \neq i} \operatorname {s i m} \left(T _ {i, j} ^ {f, n e g}, T _ {l, j} ^ {f, n e g}\right). \tag {6} +$$ + +Overall, our NegPrompt objective consists of the above three losses. During training, we are able to obtain a diverse set of non-trivial prompts that effectively convey negative meanings relative to the ID class labels by minimizing the following overall loss: + +$$ +\mathcal {L} _ {\text {N e g a t i v e P r o m p t s}} = \mathcal {L} _ {N I S} + \beta * \mathcal {L} _ {N P D} + \gamma * \mathcal {L} _ {N N D}, \tag {7} +$$ + +where $\beta$ and $\gamma$ are hyper-parameters to balance the losses. + +# 3.2.2 Open-Vocabulary Capability + +Since the negative prompts we learn do not depend on specific class labels but are instead generic templates representing negative semantics of any given class labels, it is possible to utilize the generalization ability of CLIP to learn a set of transferable negative prompts. Specifically, instead of utilizing all of the ID classes $D_{train}^{in}$ , NegPrompt may only employ its small subset $D_{train}^{in,sub}$ for training the negative prompts $\omega^{neg}$ , where $D_{train}^{in,sub} = \{(x,y_{sub}^{in}) \mid y_{sub}^{in} \subset y^{in}\}$ . After obtaining the trained negative prompts, we combine them with the remaining ID class names, i.e., replace $c_i$ in $t_{l,i}^{neg}$ with the unseen ID class names, to obtain the corresponding negative prompts for the novel ID classes that are + +
IDOOD
Split-1All dog classesNon-animal classes
Split-2Half of hunting dog classesOther 4-legged animal classes
Split-3Mix of common classesMix of common classes
+ +Table 1. Three ImageNet-1K splits for hard OOD detection. + +unseen during training. This approach, which achieves out-of-distribution detection by only exposing with a small portion of ID images, is unprecedented in prior research. We refer this as to be open-vocabulary OOD detection. + +# 3.2.3 Inference + +During inference, we employ the MCM [32] scoring approach for OOD detection, but with the addition of our negative prompts into the softmax function. Particularly, MCM uses the inverse of the maximum softmax score in Eq. 1 as the OOD score. Our OOD scoring extends MCM and defines it as: $s(x) = \max(p(y = i|x))$ , where $p(y = i|x)$ is defined in Eq. 3 that also includes the similarities of the test image to the negative prompts, in addition to the similarities to the positive prompts. The rationale behind this is that for ID images, they will be matched to one of the positive text features, leading to a higher $S^{f,pos}$ but lower $S^{f,neg}$ , and thereby a higher maximum softmax score (i.e., a lower OOD score). Conversely, for OOD data, it will be matched to one of the negative text features, resulting in a lower maximum softmax score (i.e., a higher OOD score). + +# 4. Experiment + +# 4.1. Experimental Details + +Datasets. For conventional OOD detection, we use a popular benchmark in which ImageNet-1K [3] with 1,000 classes is used as the ID dataset, and the same OOD datasets as in [32] are used, including subsets of Texture [2], iNaturalist [43], Places [51] and SUN [48]. In addressing the more challenging OOD scenarios, we partitioned the ImageNet1k dataset into two segments: one segment of the data serves as the ID, while the other serves as OOD. As shown in Table 1, three different splits are derived, following from [35]. We further create another ImageNet split, Split-4, in which the first 100 classes are used as ID data and the subsequent 900 classes are used as OOD samples. Following CoOp and LoCoOp [33, 54], during our training process, we utilized only few-shot training data for each category. Particularly, we only train the model with 16 images per ID class and without any exposure to OOD images. During testing, we employ the entire ID and OOD test set for evaluation. + +Implementation Details. Following existing studies [46], we use CLIP based on CLIP-B/16 which is pre-trained from OpenCLIP [16]. NegPrompt is trained using 16-shot images of all ID classes under the normal OOD detection setting. For open-vocabulary OOD detection, we train our model using only the images of the first $10\%$ classes from the ID dataset, withholding $90\%$ ID classes that only appear + +
MethodTextureiNaturalistPlacesSUNAvg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓
Zero-shot methods
MCM [32]†86.1157.7794.6130.9189.7744.6992.5734.5990.7642.74
CLIPN [46]†90.9340.8395.2723.9492.2833.4593.9226.1793.1031.10
CLIP-based posthoc methods
MSP [10]†74.8473.6677.7474.5772.1879.1273.9776.9574.9876.22
MaxLogit [12]†88.6348.7288.0360.8887.4555.5491.1644.8388.8252.49
Energy [27]†88.2250.3987.1864.9887.3357.4091.1746.4288.4854.80
ReAct [41]†88.1349.8886.8765.5787.4256.8591.0446.1788.3754.62
ODIN [26]†87.8551.6794.6530.2285.5455.0687.1754.0488.8047.75
Prompt learning methods
CoOp [54]89.4745.0093.7729.8190.5840.1193.2940.8391.7851.68
LoCoOp [33]†90.1942.2896.8616.0591.9832.8795.0723.4493.5228.66
NegPrompt (Ours)91.6035.2198.736.3293.3427.6095.5522.8994.8123.01
Open-vocabulary OOD detection
CoOp (10%)87.5850.5591.0842.5389.5646.1291.5241.9289.9445.28
LoCoOp (10%)88.2147.3294.4734.9091.6439.8592.5426.3090.1537.09
NegPrompt (Ours) (10%)90.3039.3198.397.4892.6829.7593.7026.9293.7625.86
+ +Table 2. Conventional OOD detection results. We trained using ImageNet1k as the ID and CLIP-B/16 as the CLIP backbone. The boldfaced results indicate the best performance. Results marked with $\dagger$ are taken from [46] and [33]. 'METHOD' (10%) in open-vocabulary OOD detection is to evaluate the performance of the 'METHOD' when only images from 10% ID classes are accessible during training. + +together with OOD data during inference. We train a shared positive prompt and two shared negative prompts w.r.t. each training ID class. The hyperparameters $\beta$ and $\gamma$ are set to 0.1 and 0.05, respectively (see Appendix A for detail). In the first stage, CoOp is trained for 100 epochs to obtain the positive prompts. In the second stage, the positive prompts are frozen, and our model is trained for 10 epochs to learn the negative prompts. For all experiments, we report the averaged results over three runs with different random seeds. + +Comparison Methods. To substantiate the effectiveness of NegPrompts, we conduct an empirical analysis of three distinct categories of methodologies employed for OOD detection utilizing Vision-language models. These categories encompass zero-shot pretraining approaches, the methods that combine the CLIP image encoder with classical approaches, and the methods grounded in prompt learning. In the context of zero-shot methods, we opted for the two recent methods, MCM [32] and CLIPN [46]. MCM employs the original CLIP, utilizing the maximum softmax probability operation on the similarities for detection, and CLIPN involves an additional training phase during pretraining, specifically training a negative text encoder using large external data. For the second group of methods, we adapt previous logits-based methodologies to the use of the CLIP image encoder, including MSP [10], Energy [27], MaxLogit [12], ReAct [41] and ODIN [26], to serve as the CLIP-adapted methods. For the prompt learning methods, NegPrompt is compared with CoOp [54] and LoCoOp [33]. + +Evaluation Metrics. Two OOD detection metrics are used. The first metric is the False Positive Rate at a $95\%$ True Negative Rate (FPR95), which denotes the rate of falsely identified OOD instances when the true negative rate is maintained at $95\%$ . The second metric is the Area Under the Receiver Operating Characteristic curve (AUROC), rep + +resenting the measure of OOD ranking across various classification thresholds. We also check the classification accuracy of the ID data to evaluate how the OOD detectors affect the ID classification. + +# 4.2. Comparison to State-of-the-art Models + +Conventional OOD Detection. The results of conventional OOD detection are reported in Table 2. It is clear that our proposed NegPrompt achieves consistently superior performance in both individual OOD datasets and the averaged results. When compared with the zero-shot methods, on average, our approach surpasses the best competing method CLIPN by more than $1.5\%$ in AUC and around $8\%$ in FPR95, despite the fact that CLIPN requires the use of an additional large external dataset to train an additional negative text encoder. In other words, although NegPrompt is significantly more lightweight than CLIPN in model size, it can substantially and consistently outperform CLIPN in both metrics across all OOD datasets. The adapted post-hoc methods generally do not leverage the CLIP's capabilities well and thus perform less effectively. + +NegPrompt also substantially surpasses both prompt learning-based methods, reducing the FPR95 by about $28\%$ (CoOp) and $5\%$ (LoCoOp). This indicates that the learned negative prompts provide informed knowledge about OOD data, which is lacking in the competing methods, helping largely reduce detection errors. + +Hard OOD Detection. Hard OOD detection presents unique challenges as the OOD samples often exhibit some similar features as the ID samples. The results on the four hard OOD datasets derived from ImageNet-1K are shown in Table 3. Similar empirical observations can be derived. Our method NegPropmt is consistently the best performer in the average performance, showcasing its general effec + +
MethodSplit-1Split-2Split-3Split-4Avg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓
Zero-shot methods
MCM97.939.1788.1056.4090.3433.0598.724.7393.7725.83
CLIPN99.382.0797.7710.5590.0336.8598.834.6896.5013.53
CLIP-based posthoc methods
MSP77.8563.6068.7383.6379.1070.5582.4065.5277.0270.83
MaxLogit99.870.4998.068.6990.9634.3499.352.6697.0611.55
Energy99.880.4698.188.4090.6535.0299.362.8397.0211.68
ReAct99.340.7297.919.3390.7235.6599.122.9496.7712.16
ODIN98.781.1298.238.1889.9237.2098.7613.2096.4214.92
Prompt learning methods
CoOp98.536.7888.2550.7690.6433.8998.545.1193.9924.14
LoCoOp98.646.2984.6361.0991.3027.7998.8341.4493.3534.15
NegPrompt (Ours)99.850.6298.547.6093.8922.8999.571.6097.968.18
Open-vocabulary OOD detection
CoOp (10%)97.9712.21780.1174.6287.9246.0096.5916.6090.6537.36
LoCoOp (10%)98.009.2387.0252.1880.5159.9382.4148.7286.9942.52
NegPrompt (Ours) (10%)99.661.3696.3019.8991.7526.9298.145.2496.4613.36
+ +tiveness across different dataset splits. The superiority of NegPrompt over the zero-shot and prompt learning-based methods is similar to that in Table 2. Although it is slightly less effective than Energy under the Split-1 setting, it outperforms Energy in all other metrics, achieving maximally over $3\%$ AUC and $12\%$ FPR95 improvement among the performance on the other OOD datasets. + +Note that the results in Table 3 are generally more promising than that in Table 2. This is mainly because the OOD detection difficulty in all four ImageNet-1K splits is largely reduced since the number of their ID classes is significantly less than that in the full ImageNet-1K data. + +Open-Vocabulary OOD Detection. The open-vocabulary OOD detection results are reported in both Tables 2 and 3. Impressively, even when training on only $10\%$ ID classes, our approach can still perform better than the competing methods using the full ID classes, e.g., the average AUC and FPR95 in Table 2. In this open-vocabulary setting, in general, both LoCoOp and CoOp exhibit a much larger performance decline than NegPrompt, especially on the results in Table 3, in which CoOp has over $3\%$ AUC drop and LoCoOp has over $6\%$ AUC drop while our method has only about $1.5\%$ AUC drop. These results demonstrate that the negative prompts in NegPrompt have much better transferability than those in the two competing methods. + +# 4.2.1 Classification Accuracy on ID Data + +We also evaluate the classification accuracy on the ID data when using NegPrompt for OOD detection, with CoOp, LoCoOp, MCM and CLIPN as the baselines. The classification accuracy results on the full ImageNet-1K test data are shown in Table 4. When using the full ImageNet-1K training ID class data, our method NegPrompt can maintain the same classification accuracy as CoOp. + +Our accuracy is slightly compromised when using only $10\%$ ID classes in our training. On the other hand, the OOD + +Table 3. Hard OOD detection results. We use the same notations here as those used in Table 2. + +
MethodTop-1 Accuracy
CoOp72.1
\( \text{LoCoOp}^\dagger \)71.7
CLIPN & MCM67.0
NegPrompt(Ours)(10%)71.9
NegPrompt(Ours)(Full)72.1
+ +Table 4. Top-1 Accuracy. Results with $\dagger$ are taken from [33]. + +![](images/a9d9a3a19417481f1d8454e532aba78a1a4b2038ce4bab3bbf7c376843ffc4b3.jpg) + +![](images/818085285795656b3cff7aa2a252d098ad84771fc51f527a4293072ddb230b1f.jpg) + +![](images/e905a8a2f8a1f1f1d6a476cd9588aa25d4f9878aa38dd5cf5767ab0f3cc1a6d7.jpg) +Figure 3. Similarity of ID/OOD and Positive/Negative Prompts. + +![](images/bb0dcc3bb85f8c59e65fe7fdd4edbc736f7ee6a676f7fce9255631a7ea584eb6.jpg) + +detection in LoCoOp compromises the ID classification accuracy, dropped from $72.1\%$ in CoOp to $71.7\%$ . This may be attributed to its focus on the localized regions within the background rather than the primary object of interest, resulting in the missing of some discriminative features for ID data classification. CLIPN and MCM, being zero-shot methods, have not been exposed to the target ID data, leading to a much lower accuracy than the other methods. + +
Ablation StudyTextureiNaturalistPlacesSUNAvg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓ACC ↑
Backbones
ResNet-5079.4472.7390.9744.1084.3561.3788.0450.5585.7057.1968.2
ResNet-10182.9770.8393.9631.386.4151.6688.8147.6188.0450.3570.3
ViT-B-3290.4338.7997.4012.6492.8332.7992.8226.0393.3727.5672.6
# Negative Prompts
190.0440.6798.249.2390.3732.6292.2627.3392.7327.4672.1
Training Process
One-stage80.2572.8777.0295.7482.5395.9481.1395.7280.2390.0762.8
ViT-B-16 & 2 & Two-stage90.3039.3198.397.4892.6829.7593.7026.9293.7625.8672.1
+ +Table 5. Results of our ablation experiments. + +![](images/b9ab64efe1415f22e303b493b00551921694dc74a30285b2fc105d0b45829043.jpg) +Figure 4. T-SNE visualization of NegPrompt, utilizing a subset of ImageNet - TinyImageNet as the dataset. + +# 4.3. Analysis of NegPrompt + +# 4.3.1 Why Does NegPrompt Work? + +To better understand the effectiveness of NegPrompt, we summarize the average maximum similarity between ID/OOD images and positive/negative prompts, as shown in Fig. 3. Across all four OOD datasets, ID images have the highest similarity with positive prompts, and OOD images with negative prompts. This suggests positive prompts are closer to ID images and negative prompts to OOD images in latent space, ensuring OOD images receive lower softmax scores (i.e., higher OOD scores) than ID images in Eq. 3. + +Using TinyImageNet [23], a subset of ImageNet, we further visualized the learned negative text features with its test data [6]. Learning three negative prompts per ID class, the results in Fig. 4 demonstrate that positive text features from positive prompts align closely with ID images in latent space. Conversely, the negative text features encoded from negative prompts lie outside of the ID data, with OOD images interspersed among them. This suggests negative text features effectively act as a fence aligning much better to the OOD images than the ID images, well supporting the OOD detection while preserving the ID classification accuracy. + +# 4.3.2 Ablation Study + +Table 5 shows our ablation study results on the backbone, the number of negative prompts, and the training process. + +Backbones. We experiment with diverse CLIP backbones. The results reveal that for CNN-based backbones + +like ResNet50 and ResNet101, the OOF detection performance is not as proficient as the ViT-based backbones. Regarding ViT-B-32 and ViT-B-16, their performance is found to be uneven. Overall, the performance of OOD detection tends to increase with more advanced backbones. + +The Number of Negative Prompts. The number of negative prompts also influences the results. It is observed that the OOD detection performance improves when increasing the number of negative prompts from one to two. Therefore, it is suggested to further increase the number of negative prompts for better detection accuracy. However, note that with an increase in the number of negative prompts, the computational cost also rises rapidly. A good balance between computational cost and detection accuracy is needed when determining the number of negative prompts. + +Training Process. The training process is also important. As discussed before, due to the necessity of anchoring the positive prompts, a two-stage training process is used in our model. This process involves training the positive prompts in the first stage and freezing them before proceeding to train the negative prompts in the second stage. When simultaneously training both positive and negative prompts in a unified step, the model's ability to effectively learn positive prompts is significantly undermined, and consequently we obtain unstable negative prompts, leading to the largely decreased OOD detection performance. + +# 5. Conclusion + +We present NegPrompt, a novel approach for prompt learning-based OOD detection. It utilizes VLMs to learn a small set of negative prompts for conveying negative semantics relative to ID classes. Our empirical results reveal that NegPrompt 1) achieves superior OOD detection performance compared to the SOTA models across various OOD datasets in both conventional and hard OOD detection scenarios, and 2) learns transfer negative prompts that enable excellent open-vocabulary OOD detection performance. + +# 6. Acknowledgement + +This work was supported by the National Natural Science Foundation of China 62276016, 62372029. + +# References + +[1] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katherine Millican, Malcolm Reynolds, et al. Flamingo: a visual language model for few-shot learning. Advances in Neural Information Processing Systems, 35:23716-23736, 2022. 2 +[2] Mircea Cimpoi, Subhransu Maji, Iasonas Kokkinos, Sammy Mohamed, and Andrea Vedaldi. Describing textures in the wild. In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 3606-3613, 2014. 5 +[3] Jia Deng, Wei Dong, Richard Socher, Li-Jia Li, Kai Li, and Li Fei-Fei. Imagenet: A large-scale hierarchical image database. In 2009 IEEE conference on computer vision and pattern recognition, pages 248-255. IEEE, 2009. 5 +[4] Jacob Devlin, Ming-Wei Chang, Kenton Lee, and Kristina Toutanova. 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To address this issue, we introduce a novel OOD detection method, named 'NegPrompt', to learn a set of negative prompts, each representing a negative connotation of a given class label, for delineating the boundaries between ID and OOD images. It learns such negative prompts with ID data only, without any reliance on external outlier data. Further, current methods assume the availability of samples of all ID classes, rendering them ineffective in open-vocabulary learning scenarios where the inference stage can contain novel ID classes not present during training. In contrast, our learned negative prompts are transferable to novel class labels. Experiments on various ImageNet benchmarks show that NegPrompt surpasses state-of-the-art prompt-learning-based OOD detection methods and maintains a consistent lead in hard OOD detection in closed- and open-vocabulary classification scenarios. Code is available at https://github.com/mala-lab/negprompt." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 535, + 128, + 547 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 535, + 128, + 547 + ], + "spans": [ + { + "bbox": [ + 47, + 535, + 128, + 547 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 555, + 287, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 555, + 287, + 685 + ], + "spans": [ + { + "bbox": [ + 46, + 555, + 287, + 685 + ], + "type": "text", + "content": "Since the advent of deep learning, numerous image recognition models [5, 9, 29] have relied solely on image features for classification. However, in recent years large pre-trained vision-language models (VLMs), such as CLIP [37], integrated natural language processing into computer vision, enhancing the semantic understanding capabilities of computer vision models. It has been observed that these VLMs excel in image classification, particularly in zero-shot scenarios. This is attributed to their extensive self-supervised pre-training on web-scale image-text data, which has endowed them with robust semantic transfer abilities." + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 308, + 236, + 545, + 369 + ], + "blocks": [ + { + "bbox": [ + 308, + 236, + 545, + 369 + ], + "lines": [ + { + "bbox": [ + 308, + 236, + 545, + 369 + ], + "spans": [ + { + "bbox": [ + 308, + 236, + 545, + 369 + ], + "type": "image", + "image_path": "a26a53cb8e4acb4e42ce9ab9fc1e8307b384667804981ba7b389b40980f1beb5.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 371, + 547, + 426 + ], + "lines": [ + { + "bbox": [ + 305, + 371, + 547, + 426 + ], + "spans": [ + { + "bbox": [ + 305, + 371, + 547, + 426 + ], + "type": "text", + "content": "Figure 1. Illustration of the key intuition of NegPrompt. For each ID class, NegPrompt trains a small set of learnable prompts that have negative semantics to the learned positive prompt of the given class. As a result, OOD samples exhibit higher similarity to the negative prompts than the positive prompts." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 436, + 547, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 436, + 547, + 652 + ], + "spans": [ + { + "bbox": [ + 304, + 436, + 547, + 652 + ], + "type": "text", + "content": "Despite the strong zero-shot classification capabilities of VLMs, numerous research efforts are put to unleash their potential, e.g., by investigating whether models like CLIP can achieve enhanced performance with training on downstream target datasets. This has led to the development of various techniques to fine-tune CLIP [8, 18], among which prompt learning has sparked widespread interest. Prompt learning (or prompt tuning) [19, 39, 50], a methodology originating from natural language processing, focuses on learning the prompt inputs into a large-scale pre-trained network, rather than learning or fine-tuning the parameters of the network. In CLIP, a common prompt is 'a photo of a [class name]'. The aim of prompt learning, e.g., in approaches like CoOp [54], is to learn a soft/differentiable context vector to replace the fixed text prompt like 'a photo of a', thereby leveraging CLIP's powerful generalization in semantic understanding while also fine-tuning for specific target datasets [53, 54]." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": "However, even though prompt learning enhances the target dataset perception capabilities of VLMs, it struggles with Out-Of-Distribution (OOD) detection [10, 26]. Under the OOD detection task, the test set comprises images from both the training classes - in-distribution (ID) data -" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 287, + 713 + ], + "type": "text", + "content": "*Corresponding author: G. Pang (gspang@smu.edu.sg) and X. Bai (baixiao@buaa.edu.cn)" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "17584" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": "and images from other unknown categories (OOD images). VLM-based classification is typically performed by first replacing the '[class name]' with the class label of each category in a prompt, which is then processed by the text encoder of CLIP to obtain the class embedding and assign the class label that has the highest cosine similarity with the embedding of a test image from the image encoder of CLIP. However in OOD detection tasks, the models do not have access to the class names of OOD images, thereby lacking the knowledge about OOD data." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 193, + 287, + 241 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 193, + 287, + 241 + ], + "spans": [ + { + "bbox": [ + 47, + 193, + 287, + 241 + ], + "type": "text", + "content": "This issue, exacerbated by the models' tendency towards overconfidence that often predicts OOD data as ID images with high confidence [34], undermines their ability to effectively detect OOD images." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 243, + 287, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 243, + 287, + 373 + ], + "spans": [ + { + "bbox": [ + 46, + 243, + 287, + 373 + ], + "type": "text", + "content": "There have been a number of CLIP-based methods designed specifically for VLM-driven OOD detection methods, but most of them [6, 32, 46] focused on a zero-shot setting where no training data of the target dataset is available. Due to the lack of adaptation to the target dataset, they tend to detect unusual ID images as OOD data. Among them, CLIPN [46], which trains an additional 'no' text encoder to provide prompt embeddings of not having specific classes, is the best detector, but it relies on a large-scale auxiliary dataset to train such a text encoder and it is computationally expensive." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 376, + 287, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 376, + 287, + 483 + ], + "spans": [ + { + "bbox": [ + 46, + 376, + 287, + 483 + ], + "type": "text", + "content": "The most related work is a very recent approach LoCoOp [33] that utilizes the training ID data to tune CLIP to capture local features of the ID classes in the prompt. It shows substantially improved performance compared to zero-shot methods [32], but it may compromise the ID classification accuracy due to an overemphasis on modeling local features. LoCoOp also lacks knowledge about OOD samples, making it difficult to differentiate boundary ID/OOD images." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 484, + 287, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 484, + 287, + 640 + ], + "spans": [ + { + "bbox": [ + 46, + 484, + 287, + 640 + ], + "type": "text", + "content": "In this work, we propose a novel CLIP-based OOD detection method, named NegPrompt. Inspired by [25], Negprompt is designed to learn a set of negative prompts, each representing a negative connotation of a given ID class label, to delineate the boundaries between ID and OOD images, as shown in Fig. 1. The negative prompts represent specialized ID-class-dependent concepts, guiding the models to pay attention to the characteristics that are contrary to or disjoint from the ID classes. NegPrompt aims to utilize ID training data and positive prompts (i.e., the text prompt embeddings of ID classes) to learn such negative prompts in a way to which OOD images exhibits higher similarity than ID images." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "type": "text", + "content": "Essentially, the learned negative prompts have similar semantics to the text prompts generated from the 'no' text encoder in CLIPN, but NegPrompt presents a fundamentally different approach: it capitalizes on the generalization ability of the CLIP model and learns the negative prompts with training ID data only, eliminating the reliance on external" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 72, + 542, + 84 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 542, + 84 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 542, + 84 + ], + "type": "text", + "content": "data and the extensive computation overhead as in CLIPN." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 85, + 545, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 85, + 545, + 216 + ], + "spans": [ + { + "bbox": [ + 304, + 85, + 545, + 216 + ], + "type": "text", + "content": "Furthermore, benefiting from the superior generalization ability of CLIP, our method does not require the exposure to all ID classes during training. In other words, the model learns transferable negative prompts by using only a small subset of the ID classes, after which we can obtain the negative prompts for the other ID classes by simply replacing the '[class name]' in the prompts with the name of those unexposed classes. This allows our model to work in open-vocabulary [7, 31] learning settings, where the models are required to classify images of novel classes that are not seen during training, in addition to a set of training base classes." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 317, + 217, + 539, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 217, + 539, + 228 + ], + "spans": [ + { + "bbox": [ + 317, + 217, + 539, + 228 + ], + "type": "text", + "content": "Our main contributions can be summarized as follows:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 231, + 545, + 434 + ], + "type": "list", + "angle": 0, + "index": 12, + "blocks": [ + { + "bbox": [ + 306, + 231, + 545, + 302 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 231, + 545, + 302 + ], + "spans": [ + { + "bbox": [ + 306, + 231, + 545, + 302 + ], + "type": "text", + "content": "- We propose a prompt learning-based OOD detection approach NegPrompt, which is able to learn negative semantics relative to specific ID classes, thereby enhancing the VLMs' sensitivity to unknown samples. It is a lightweight method that does not require training extra encoders on external data as in related methods [46]." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 304, + 545, + 386 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 304, + 545, + 386 + ], + "spans": [ + { + "bbox": [ + 306, + 304, + 545, + 386 + ], + "type": "text", + "content": "- NegPrompt possesses an open-vocabulary capability due to the transferability of its negative prompts. This means that with training images from just a small subset of ID classes and the class names of all IDs, we can achieve OOD detection on test data with all these ID classes. To the best of our knowledge, there have been no previous fine-tuning methods exploring such a capability." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 387, + 545, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 387, + 545, + 434 + ], + "spans": [ + { + "bbox": [ + 306, + 387, + 545, + 434 + ], + "type": "text", + "content": "- Extensive experiments on multiple ImageNet-based benchmarks show that NegPrompt consistently outperforms current state-of-the-art methods in both conventional and hard OOD Detection settings." + } + ] + } + ], + "index": 11 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 443, + 392, + 455 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 443, + 392, + 455 + ], + "spans": [ + { + "bbox": [ + 306, + 443, + 392, + 455 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 463, + 501, + 475 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 463, + 501, + 475 + ], + "spans": [ + { + "bbox": [ + 306, + 463, + 501, + 475 + ], + "type": "text", + "content": "2.1. Pre-trained Vision-Language Models" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 476, + 545, + 620 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 476, + 545, + 620 + ], + "spans": [ + { + "bbox": [ + 304, + 476, + 545, + 620 + ], + "type": "text", + "content": "Understanding the semantic information of images remains a significant challenge in the field of computer vision. With the advent of Transformer [44] in computer vision tasks [5], CLIP [37] has been introduced as one of the most advanced pre-trained VLMs. Utilizing contrastive learning [21], large-scale models and datasets [38], CLIP employs image-text pairs as the training data for self-supervised learning. This approach has successfully trained the model to align visual and text signals in a latent space. Concurrently, other researchers [1, 24, 49] have also shown the remarkable generalization capabilities of CLIP and similar vision-language models [17] in various downstream tasks [7, 20, 56]." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 628, + 410, + 641 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 628, + 410, + 641 + ], + "spans": [ + { + "bbox": [ + 306, + 628, + 410, + 641 + ], + "type": "text", + "content": "2.2. Prompt Learning" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 642, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 545, + 714 + ], + "type": "text", + "content": "The concept of prompt learning was initially focused on automating the creation of templates/prompts for extracting knowledge from Bert [4] or GPT [36]. To bypass manual creation, prompt learning advocates the use of supervised learning to automate the prompt development. [39] proposed a gradient-based approach for identifying the" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17585" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "content": "best prompt, establishing the foundation of prompt learning. Later, CoOp [54] integrated prompt learning into computer vision. CoOp learns a segment of the context before it is fed into the text encoder of CLIP, thus tailoring the learned prompt to the specific target dataset. Many other prompt learning methods for different vision tasks [13, 18, 20, 40, 47, 53, 55] are subsequently introduced. However, they are not designed for OOD detection, so they struggle with dealing with the unknown OOD samples during inference." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 198, + 209, + 209 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 198, + 209, + 209 + ], + "spans": [ + { + "bbox": [ + 47, + 198, + 209, + 209 + ], + "type": "text", + "content": "2.3. Out-of-Distribution Detection" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 211, + 287, + 342 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 211, + 287, + 342 + ], + "spans": [ + { + "bbox": [ + 46, + 211, + 287, + 342 + ], + "type": "text", + "content": "OOD detection is committed to identifying images in image classification tasks that belong to categories not present in the training dataset, typically originating from a different distribution. While traditional OOD detection methods often tackle the problem by either exploiting the prediction logits to define OOD scores [10, 12, 15, 26, 27] or focusing on the class-agnostic information in feature space that is not recoverable from logits [41, 45], recent methods [11, 14, 22, 28, 30, 42, 52] introduce extra or synthetic OOD data, employing fine-tuning to elevate their model's sensitivity towards unknown classes." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 342, + 289, + 570 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 342, + 289, + 570 + ], + "spans": [ + { + "bbox": [ + 46, + 342, + 289, + 570 + ], + "type": "text", + "content": "With the introduction of large pre-trained VLMs, OOD detection has embarked on a new trajectory driven by VLMs. MCM [32] aims to integrate the idea of maximum softmax probability [10] into the inference process of CLIP, while ZOC [6] enhances OOD detection in a zero-shot setting by learning an additional image interpreter and guessing the category of images. CLIPN [46] and LoCoOp [33], the most related methods to ours, are based on text prompts. However, CLIPN, during its pretraining phase, trains an additional negative text encoder using a large external dataset to improve its negative semantic prompt, which increases network parameters and deviates from prompt learning that is focused on tuning the target data. LoCoOp, on the other hand, uses prompt learning for matching text and image local features, which can compromise the global perception capability of CLIP and reduce classification accuracy for in-distribution (ID) samples. Also, its model lacks knowledge about OOD samples, which can often lead to high detection errors." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 579, + 103, + 590 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 579, + 103, + 590 + ], + "spans": [ + { + "bbox": [ + 47, + 579, + 103, + 590 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "type": "text", + "content": "In this paper, we propose an approach named NegPropmt that leverages pre-trained VLMs, specifically CLIP, to learn negative prompts relative to ID classes for the purpose of OOD detection. The negative prompts are learned in the CLIP's text-image-aligned embedding space with the support of training ID data and their positive prompts (i.e., prompt embeddings of ID classes); no external outlier data is required. Due to its general effectiveness, the popular prompt learning method CoOp [54] is used by default to provide the positive prompts for training NegPrompt." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 72, + 392, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 392, + 83 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 392, + 83 + ], + "type": "text", + "content": "3.1. Preliminaries" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "spans": [ + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": "Problem Statement. Formally, we assume that we have two datasets, namely ID dataset denoted as " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "D^{in}" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " and OOD dataset denoted as " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "D^{out}" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ". The ID dataset consists of image-label pairs " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "(x^{in}, y^{in})" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "y^{in} \\in Y^{in} = \\{0, 1, 2, 3 \\dots k\\}" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " belong to the ID class set. Similarly, the OOD dataset contains image-label pairs " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "(x^{out}, y^{out})" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ", but all " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "y^{out} \\in Y^{out} = \\{k + 1, k + 2, \\dots\\}" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " belong to the OOD class set. It is important to note that these two sets do not intersect, meaning that " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "Y^{in} \\cap Y^{out} = \\emptyset" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ". As we have a test set " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "X^{test}" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " consists of images from ID and OOD, the goal of OOD detection is to train a classifier " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "\\phi(x)" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " that takes an image " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " as input and returns whether the image belongs to OOD. Unlike existing studies using full-/zero-shot ID training samples, we only use a few samples (16 samples per class) for " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "D_{train}^{in}" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " like [33] does. In the open-vocabulary detection setting, we only use a small part (10%) but not all the classes of " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "D_{train}^{in}" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ". CLIP and CoOp. CLIP [37] is currently one of the most popular image-text models. During the pre-training phase, it uses large-scale image-text pairs for self-supervised contrastive learning, aligning images and texts into the same latent space. The main components of CLIP are an image encoder " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "Encoder^{image}(I)" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " and a text encoder " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "Encoder^{text}(T)" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ", which respectively accept image and text inputs. In zero-shot image classification tasks, assume we have " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " class labels for classification, such as \"cat\", \"dog\", etc., CLIP first incorporates the class labels into pre-designed hard/unlearnable text prompts, such as \"a photo of a [class name]\", forming a prompt input set of \"a photo of a cat\", \"a photo of a dog\" and so on. These prompts are then individually fed into the text encoder " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "Encoder^{text}(T)" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " to obtain " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " text features " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "T^f" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ". The testing image is then input into the image encoder to obtain an image feature " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "I^f" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ". The cosine similarity is calculated between the normalized image feature and all text features, formally, " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "Sim(T^f, I^f) = T^f \\cdot I^f" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": ", and the text feature " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "T^f" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " with the highest similarity to " + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "inline_equation", + "content": "I^f" + }, + { + "bbox": [ + 304, + 87, + 547, + 531 + ], + "type": "text", + "content": " is considered to be the category to which the image belongs." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "spans": [ + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": "Besides zero-shot classification, many have explored ways to improve CLIP's performance when the target data is accessible. CoOp [54] introduces prompt learning with CLIP by freezing its encoders and using backpropagation to learn dataset-specific soft/learnable prompts. The text prompts are represented as " + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "t_i = \\{\\omega_1^{pos}, \\omega_2^{pos}, \\dots, \\omega_n^{pos}, c_i\\}" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "c_i" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": " is the word embedding of the class name and " + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "\\omega^{pos}s" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": " are learnable vectors that have positive semantics w.r.t. the class " + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": ". The goal is to optimize these " + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "\\omega^{positive}" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": "s. Specifically, " + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "t_i" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": " is processed by Encoder" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "^{text}" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": " to yield " + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "T_i^{f,pos}" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": " as a positive prompt embedding of the class " + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 531, + 547, + 675 + ], + "type": "text", + "content": ", and then the prediction probability is computed as:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 329, + 684, + 545, + 717 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 329, + 684, + 545, + 717 + ], + "spans": [ + { + "bbox": [ + 329, + 684, + 545, + 717 + ], + "type": "interline_equation", + "content": "p (y = i | x) = \\frac {\\exp \\left(\\operatorname {s i m} \\left(T _ {i} ^ {f , p o s} , I ^ {f}\\right) / \\tau\\right)}{\\sum_ {j = 1} ^ {k} \\exp \\left(\\operatorname {s i m} \\left(T _ {j} ^ {f , p o s} , I ^ {f}\\right) / \\tau\\right)}, \\tag {1}", + "image_path": "241c17751953ba61b8607ea55568d15a23009b20d2fa7659ba587e12c17f9cc5.jpg" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "17586" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 95, + 79, + 499, + 289 + ], + "blocks": [ + { + "bbox": [ + 95, + 79, + 499, + 289 + ], + "lines": [ + { + "bbox": [ + 95, + 79, + 499, + 289 + ], + "spans": [ + { + "bbox": [ + 95, + 79, + 499, + 289 + ], + "type": "image", + "image_path": "93cf385c0b8c948651681b6fcac01869930ef400e17eb5f15c85686ebc874f29.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 293, + 547, + 328 + ], + "lines": [ + { + "bbox": [ + 46, + 293, + 547, + 328 + ], + "spans": [ + { + "bbox": [ + 46, + 293, + 547, + 328 + ], + "type": "text", + "content": "Figure 2. Overview of NegPropmt. Given the CLIP model and positive prompts learned by existing prompt learning methods such as CoOp [54], NegPrompt learns a set of negative prompts relative to different ID class labels via three loss functions that enforce the separation between negative prompts and ID images, and between negative and positive prompts, as well as the diversity of the negative prompts." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 338, + 288, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 338, + 288, + 376 + ], + "spans": [ + { + "bbox": [ + 46, + 338, + 288, + 376 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 338, + 288, + 376 + ], + "type": "inline_equation", + "content": "I^{f} = \\text{Encoder}^{image}(x)" + }, + { + "bbox": [ + 46, + 338, + 288, + 376 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 338, + 288, + 376 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 46, + 338, + 288, + 376 + ], + "type": "text", + "content": " is a temperature parameter. Next, cross-entropy loss is used to maximize similarity between ID class text embeddings and images." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 81, + 383, + 287, + 399 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 81, + 383, + 287, + 399 + ], + "spans": [ + { + "bbox": [ + 81, + 383, + 287, + 399 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {p o s i t i v e}} = \\mathbb {E} _ {\\mathbf {x} _ {\\text {i n}} \\sim D _ {\\text {t r a i n}} ^ {\\text {i n}}} [ - \\log (p (y = i | x) ]. \\tag {2}", + "image_path": "eb1746fbdedea6a9710fc42b5d33114423d6c63853eaf1a1327a8a7b889086e5.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 403, + 287, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 403, + 287, + 464 + ], + "spans": [ + { + "bbox": [ + 46, + 403, + 287, + 464 + ], + "type": "text", + "content": "This method largely improves CLIP's classification performance by adapting the learnable prompts to the target data. The resulting prompt embeddings of ID classes are used as positive prompts to support the accurate learning of negative prompts in our method below." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 470, + 163, + 483 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 470, + 163, + 483 + ], + "spans": [ + { + "bbox": [ + 47, + 470, + 163, + 483 + ], + "type": "text", + "content": "3.2. Proposed Approach" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 483, + 288, + 591 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 483, + 288, + 591 + ], + "spans": [ + { + "bbox": [ + 46, + 483, + 288, + 591 + ], + "type": "text", + "content": "NegPrompt aims to learn a set of negative prompts, each representing a negative connotation of an ID class. As shown in Fig. 2, it involves generating a series of prompts that resemble the positive prompts obtained through CoOp, but with a negative class semantic, such as \"A photo of not a [class label]\". These negative prompts, combined with class labels, can generate a range of negative text features around the positive prompts, so that OOD images exhibit higher similarity to the negative prompts than ID images." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 605, + 198, + 616 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 605, + 198, + 616 + ], + "spans": [ + { + "bbox": [ + 47, + 605, + 198, + 616 + ], + "type": "text", + "content": "3.2.1 Learning Negative Prompts" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "type": "text", + "content": "To acquire accurate negative prompts representing negative class semantics, we first utilize CoOp to learn positive prompts " + }, + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\omega^{pos}" + }, + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "type": "text", + "content": "s, after which we consider positive prompts to accurately capture the class semantics of samples in the ID dataset. Thereafter, we freeze the positive prompts and focus solely on learning the negative prompts. A negative prompt is denoted as " + }, + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\{\\omega_1^{neg},\\omega_2^{neg},\\dots,\\omega_n^{neg}\\}" + }, + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 618, + 288, + 715 + ], + "type": "text", + "content": " represents the number of context vectors we aim to learn. By" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "spans": [ + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "text", + "content": "utilizing the frozen CLIP text encoder, we can obtain negative prompt embeddings " + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "inline_equation", + "content": "T_{l,i}^{f,neg} = \\text{Encoder}^{text}(t_{l,i}^{neg})" + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "inline_equation", + "content": "t_{l,i}^{neg} = \\{\\omega_{l,1}^{neg}, \\omega_{l,2}^{neg}, \\dots, \\omega_{l,n}^{neg}, c_i\\}" + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "text", + "content": " is the " + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "text", + "content": "-th negative prompt relative the ID class " + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 339, + 545, + 413 + ], + "type": "text", + "content": ". Thus, due to the presence of the negative prompts, we turn the prediction probability into the following form:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 418, + 555, + 462 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 418, + 555, + 462 + ], + "spans": [ + { + "bbox": [ + 304, + 418, + 555, + 462 + ], + "type": "interline_equation", + "content": "p (y = i \\mid x) = \\frac {\\exp \\left(S _ {i} ^ {f , p o s}\\right)}{\\sum_ {j = 1} ^ {k} \\exp \\left(S _ {j} ^ {f , p o s}\\right) + \\sum_ {l = 1} ^ {p} \\sum_ {j = 1} ^ {k} \\exp \\left(S _ {l , j} ^ {f , n e g}\\right)} \\tag {3}", + "image_path": "6c570efafd89e8d62a14d3f3882300dc3564dedd19b46906622557a3a03d59ec.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "spans": [ + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "type": "inline_equation", + "content": "S_{j}^{f,pos} = \\frac{\\text{sim}(T_{j}^{f,pos}, I^{f})}{\\tau}" + }, + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "type": "inline_equation", + "content": "S_{l,j}^{f,neg} = \\frac{\\text{sim}(T_{l,j}^{f,neg}, I^{f})}{\\tau}" + }, + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 468, + 545, + 557 + ], + "type": "text", + "content": " is the number of negative prompts we aim to learn for each ID class. The objective is to learn negative text prompt embeddings that can effectively separate ID and OOD samples around the positive text features. To achieve this, we introduce the following three loss functions:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": "Negative-Image Separation Loss. One of our objectives is to have the negative text prompt embeddings serve as the closest text features to OOD images. However, we only have images from the ID dataset; no OOD images are available. To remedy this problem, we take an alternative approach that aims to push the negative text features away from the ID images. In this regard, we draw inspiration from OE [11]. Contrary to the approach in OE, where the probability distribution of outlier images is evenly distributed among all ID labels, we distribute the probability distribution obtained from ID images evenly among all negative prompts. Since the network parameters are frozen, this drives the negative text features to move away from the ID" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "17587" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "type": "text", + "content": "images, resulting in the learning of prompts with a negative connotation. The formulation is as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 97, + 106, + 287, + 122 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 97, + 106, + 287, + 122 + ], + "spans": [ + { + "bbox": [ + 97, + 106, + 287, + 122 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {N I S} = \\mathbb {E} _ {x _ {\\text {i n}} \\sim D _ {\\text {t r a i n}} ^ {\\text {i n}}} [ H (\\mathbf {u}; F (x)) ], \\tag {4}", + "image_path": "3c663ff87afe7ceea665534edb8bb1d2f3f4f2fb24932d6bda501a6dba439f2a.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "spans": [ + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "inline_equation", + "content": "F(x)" + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "text", + "content": " is the probability vector computed as " + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "inline_equation", + "content": "\\text{Softmax}(S^{f,neg})" + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "inline_equation", + "content": "\\mathbf{u}" + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "text", + "content": " is a uniform distribution and " + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "inline_equation", + "content": "H" + }, + { + "bbox": [ + 47, + 131, + 287, + 167 + ], + "type": "text", + "content": " is the cross entropy loss." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 167, + 287, + 275 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 167, + 287, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 167, + 287, + 275 + ], + "type": "text", + "content": "Negative-Positive Distance Loss. To avoid learning trivial negative prompts that are distant from both ID and OOD images, we need to control the negative text feature within a certain range between the ID and OOD images. To this end, we devise a constraint, enforcing that the negative text feature does not deviate too far from the positive text feature. Therefore, we introduce the following loss function to guarantee a certain level of similarity between the negative and positive text feature in the latent space:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 70, + 285, + 287, + 318 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 70, + 285, + 287, + 318 + ], + "spans": [ + { + "bbox": [ + 70, + 285, + 287, + 318 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {N P D} = - \\frac {1}{k * p} \\sum_ {j = 1} ^ {k} \\sum_ {i = 1} ^ {p} \\operatorname {s i m} \\left(T _ {i, j} ^ {f, n e g}, T _ {j} ^ {f, p o s}\\right). \\tag {5}", + "image_path": "60c08f9e58aa77d019950ae5de9eff27de2f4eb28a072b3627221b77f964bd43.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 328, + 287, + 389 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 328, + 287, + 389 + ], + "spans": [ + { + "bbox": [ + 47, + 328, + 287, + 389 + ], + "type": "text", + "content": "Negative-Negative Distance Loss. Furthermore, to ensure that we are effectively learning diverse, non-overlapping negative prompts, we extend the distances between different negative text features within the same label via the following loss function:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 398, + 288, + 441 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 398, + 288, + 441 + ], + "spans": [ + { + "bbox": [ + 47, + 398, + 288, + 441 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {N N D} = \\frac {1}{k * p * (p - 1)} \\sum_ {j = 1} ^ {k} \\sum_ {i = 1} ^ {p} \\sum_ {l \\neq i} \\operatorname {s i m} \\left(T _ {i, j} ^ {f, n e g}, T _ {l, j} ^ {f, n e g}\\right). \\tag {6}", + "image_path": "49893268498ca7da6063294cd1f14753ccfb6b166ae7e488873cc9bbed6a4036.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 443, + 287, + 502 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 443, + 287, + 502 + ], + "spans": [ + { + "bbox": [ + 47, + 443, + 287, + 502 + ], + "type": "text", + "content": "Overall, our NegPrompt objective consists of the above three losses. During training, we are able to obtain a diverse set of non-trivial prompts that effectively convey negative meanings relative to the ID class labels by minimizing the following overall loss:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 52, + 514, + 287, + 526 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 514, + 287, + 526 + ], + "spans": [ + { + "bbox": [ + 52, + 514, + 287, + 526 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {N e g a t i v e P r o m p t s}} = \\mathcal {L} _ {N I S} + \\beta * \\mathcal {L} _ {N P D} + \\gamma * \\mathcal {L} _ {N N D}, \\tag {7}", + "image_path": "e90fc0e409804715ce17c79ccb5a616d2fb77eaacb77e310fa37eeec19800fdd.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 536, + 281, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 536, + 281, + 548 + ], + "spans": [ + { + "bbox": [ + 47, + 536, + 281, + 548 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 536, + 281, + 548 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 47, + 536, + 281, + 548 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 536, + 281, + 548 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 47, + 536, + 281, + 548 + ], + "type": "text", + "content": " are hyper-parameters to balance the losses." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 553, + 203, + 566 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 553, + 203, + 566 + ], + "spans": [ + { + "bbox": [ + 47, + 553, + 203, + 566 + ], + "type": "text", + "content": "3.2.2 Open-Vocabulary Capability" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": "Since the negative prompts we learn do not depend on specific class labels but are instead generic templates representing negative semantics of any given class labels, it is possible to utilize the generalization ability of CLIP to learn a set of transferable negative prompts. Specifically, instead of utilizing all of the ID classes " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "D_{train}^{in}" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": ", NegPrompt may only employ its small subset " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "D_{train}^{in,sub}" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": " for training the negative prompts " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\omega^{neg}" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "D_{train}^{in,sub} = \\{(x,y_{sub}^{in}) \\mid y_{sub}^{in} \\subset y^{in}\\}" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": ". After obtaining the trained negative prompts, we combine them with the remaining ID class names, i.e., replace " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "c_i" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "inline_equation", + "content": "t_{l,i}^{neg}" + }, + { + "bbox": [ + 46, + 567, + 287, + 713 + ], + "type": "text", + "content": " with the unseen ID class names, to obtain the corresponding negative prompts for the novel ID classes that are" + } + ] + } + ], + "index": 11 + }, + { + "type": "table", + "bbox": [ + 326, + 71, + 526, + 114 + ], + "blocks": [ + { + "bbox": [ + 326, + 71, + 526, + 114 + ], + "lines": [ + { + "bbox": [ + 326, + 71, + 526, + 114 + ], + "spans": [ + { + "bbox": [ + 326, + 71, + 526, + 114 + ], + "type": "table", + "html": "
IDOOD
Split-1All dog classesNon-animal classes
Split-2Half of hunting dog classesOther 4-legged animal classes
Split-3Mix of common classesMix of common classes
", + "image_path": "0d2da6e40f0e07244aaf4f9d319de4eb134d0e9dbdce0183c1f36f07ff63734e.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 317, + 114, + 533, + 124 + ], + "lines": [ + { + "bbox": [ + 317, + 114, + 533, + 124 + ], + "spans": [ + { + "bbox": [ + 317, + 114, + 533, + 124 + ], + "type": "text", + "content": "Table 1. Three ImageNet-1K splits for hard OOD detection." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 129, + 545, + 177 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 129, + 545, + 177 + ], + "spans": [ + { + "bbox": [ + 305, + 129, + 545, + 177 + ], + "type": "text", + "content": "unseen during training. This approach, which achieves out-of-distribution detection by only exposing with a small portion of ID images, is unprecedented in prior research. We refer this as to be open-vocabulary OOD detection." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 194, + 379, + 204 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 194, + 379, + 204 + ], + "spans": [ + { + "bbox": [ + 306, + 194, + 379, + 204 + ], + "type": "text", + "content": "3.2.3 Inference" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "spans": [ + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "text", + "content": "During inference, we employ the MCM [32] scoring approach for OOD detection, but with the addition of our negative prompts into the softmax function. Particularly, MCM uses the inverse of the maximum softmax score in Eq. 1 as the OOD score. Our OOD scoring extends MCM and defines it as: " + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "inline_equation", + "content": "s(x) = \\max(p(y = i|x))" + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "inline_equation", + "content": "p(y = i|x)" + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "text", + "content": " is defined in Eq. 3 that also includes the similarities of the test image to the negative prompts, in addition to the similarities to the positive prompts. The rationale behind this is that for ID images, they will be matched to one of the positive text features, leading to a higher " + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "inline_equation", + "content": "S^{f,pos}" + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "text", + "content": " but lower " + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "inline_equation", + "content": "S^{f,neg}" + }, + { + "bbox": [ + 305, + 207, + 545, + 387 + ], + "type": "text", + "content": ", and thereby a higher maximum softmax score (i.e., a lower OOD score). Conversely, for OOD data, it will be matched to one of the negative text features, resulting in a lower maximum softmax score (i.e., a higher OOD score)." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 393, + 382, + 406 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 393, + 382, + 406 + ], + "spans": [ + { + "bbox": [ + 306, + 393, + 382, + 406 + ], + "type": "text", + "content": "4. Experiment" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 413, + 427, + 425 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 413, + 427, + 425 + ], + "spans": [ + { + "bbox": [ + 306, + 413, + 427, + 425 + ], + "type": "text", + "content": "4.1. Experimental Details" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 305, + 426, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 426, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 305, + 426, + 545, + 628 + ], + "type": "text", + "content": "Datasets. For conventional OOD detection, we use a popular benchmark in which ImageNet-1K [3] with 1,000 classes is used as the ID dataset, and the same OOD datasets as in [32] are used, including subsets of Texture [2], iNaturalist [43], Places [51] and SUN [48]. In addressing the more challenging OOD scenarios, we partitioned the ImageNet1k dataset into two segments: one segment of the data serves as the ID, while the other serves as OOD. As shown in Table 1, three different splits are derived, following from [35]. We further create another ImageNet split, Split-4, in which the first 100 classes are used as ID data and the subsequent 900 classes are used as OOD samples. Following CoOp and LoCoOp [33, 54], during our training process, we utilized only few-shot training data for each category. Particularly, we only train the model with 16 images per ID class and without any exposure to OOD images. During testing, we employ the entire ID and OOD test set for evaluation." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 630, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 630, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 630, + 545, + 713 + ], + "type": "text", + "content": "Implementation Details. Following existing studies [46], we use CLIP based on CLIP-B/16 which is pre-trained from OpenCLIP [16]. NegPrompt is trained using 16-shot images of all ID classes under the normal OOD detection setting. For open-vocabulary OOD detection, we train our model using only the images of the first " + }, + { + "bbox": [ + 305, + 630, + 545, + 713 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 305, + 630, + 545, + 713 + ], + "type": "text", + "content": " classes from the ID dataset, withholding " + }, + { + "bbox": [ + 305, + 630, + 545, + 713 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 305, + 630, + 545, + 713 + ], + "type": "text", + "content": " ID classes that only appear" + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17588" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 78, + 70, + 517, + 253 + ], + "blocks": [ + { + "bbox": [ + 78, + 70, + 517, + 253 + ], + "lines": [ + { + "bbox": [ + 78, + 70, + 517, + 253 + ], + "spans": [ + { + "bbox": [ + 78, + 70, + 517, + 253 + ], + "type": "table", + "html": "
MethodTextureiNaturalistPlacesSUNAvg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓
Zero-shot methods
MCM [32]†86.1157.7794.6130.9189.7744.6992.5734.5990.7642.74
CLIPN [46]†90.9340.8395.2723.9492.2833.4593.9226.1793.1031.10
CLIP-based posthoc methods
MSP [10]†74.8473.6677.7474.5772.1879.1273.9776.9574.9876.22
MaxLogit [12]†88.6348.7288.0360.8887.4555.5491.1644.8388.8252.49
Energy [27]†88.2250.3987.1864.9887.3357.4091.1746.4288.4854.80
ReAct [41]†88.1349.8886.8765.5787.4256.8591.0446.1788.3754.62
ODIN [26]†87.8551.6794.6530.2285.5455.0687.1754.0488.8047.75
Prompt learning methods
CoOp [54]89.4745.0093.7729.8190.5840.1193.2940.8391.7851.68
LoCoOp [33]†90.1942.2896.8616.0591.9832.8795.0723.4493.5228.66
NegPrompt (Ours)91.6035.2198.736.3293.3427.6095.5522.8994.8123.01
Open-vocabulary OOD detection
CoOp (10%)87.5850.5591.0842.5389.5646.1291.5241.9289.9445.28
LoCoOp (10%)88.2147.3294.4734.9091.6439.8592.5426.3090.1537.09
NegPrompt (Ours) (10%)90.3039.3198.397.4892.6829.7593.7026.9293.7625.86
", + "image_path": "4f332383a22872227eb7d7a7f86303642f873e7243ce1315ed60c7e8785cfdc2.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 254, + 547, + 288 + ], + "lines": [ + { + "bbox": [ + 46, + 254, + 547, + 288 + ], + "spans": [ + { + "bbox": [ + 46, + 254, + 547, + 288 + ], + "type": "text", + "content": "Table 2. Conventional OOD detection results. We trained using ImageNet1k as the ID and CLIP-B/16 as the CLIP backbone. The boldfaced results indicate the best performance. Results marked with " + }, + { + "bbox": [ + 46, + 254, + 547, + 288 + ], + "type": "inline_equation", + "content": "\\dagger" + }, + { + "bbox": [ + 46, + 254, + 547, + 288 + ], + "type": "text", + "content": " are taken from [46] and [33]. 'METHOD' (10%) in open-vocabulary OOD detection is to evaluate the performance of the 'METHOD' when only images from 10% ID classes are accessible during training." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 302, + 288, + 410 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 302, + 288, + 410 + ], + "spans": [ + { + "bbox": [ + 46, + 302, + 288, + 410 + ], + "type": "text", + "content": "together with OOD data during inference. We train a shared positive prompt and two shared negative prompts w.r.t. each training ID class. The hyperparameters " + }, + { + "bbox": [ + 46, + 302, + 288, + 410 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 302, + 288, + 410 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 302, + 288, + 410 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 46, + 302, + 288, + 410 + ], + "type": "text", + "content": " are set to 0.1 and 0.05, respectively (see Appendix A for detail). In the first stage, CoOp is trained for 100 epochs to obtain the positive prompts. In the second stage, the positive prompts are frozen, and our model is trained for 10 epochs to learn the negative prompts. For all experiments, we report the averaged results over three runs with different random seeds." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 411, + 287, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 411, + 287, + 639 + ], + "spans": [ + { + "bbox": [ + 46, + 411, + 287, + 639 + ], + "type": "text", + "content": "Comparison Methods. To substantiate the effectiveness of NegPrompts, we conduct an empirical analysis of three distinct categories of methodologies employed for OOD detection utilizing Vision-language models. These categories encompass zero-shot pretraining approaches, the methods that combine the CLIP image encoder with classical approaches, and the methods grounded in prompt learning. In the context of zero-shot methods, we opted for the two recent methods, MCM [32] and CLIPN [46]. MCM employs the original CLIP, utilizing the maximum softmax probability operation on the similarities for detection, and CLIPN involves an additional training phase during pretraining, specifically training a negative text encoder using large external data. For the second group of methods, we adapt previous logits-based methodologies to the use of the CLIP image encoder, including MSP [10], Energy [27], MaxLogit [12], ReAct [41] and ODIN [26], to serve as the CLIP-adapted methods. For the prompt learning methods, NegPrompt is compared with CoOp [54] and LoCoOp [33]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": "Evaluation Metrics. Two OOD detection metrics are used. The first metric is the False Positive Rate at a " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "95\\%" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": " True Negative Rate (FPR95), which denotes the rate of falsely identified OOD instances when the true negative rate is maintained at " + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "inline_equation", + "content": "95\\%" + }, + { + "bbox": [ + 46, + 641, + 287, + 714 + ], + "type": "text", + "content": ". The second metric is the Area Under the Receiver Operating Characteristic curve (AUROC), rep" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 305, + 302, + 547, + 350 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 302, + 547, + 350 + ], + "spans": [ + { + "bbox": [ + 305, + 302, + 547, + 350 + ], + "type": "text", + "content": "resenting the measure of OOD ranking across various classification thresholds. We also check the classification accuracy of the ID data to evaluate how the OOD detectors affect the ID classification." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 361, + 511, + 374 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 361, + 511, + 374 + ], + "spans": [ + { + "bbox": [ + 305, + 361, + 511, + 374 + ], + "type": "text", + "content": "4.2. Comparison to State-of-the-art Models" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 376, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 376, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 376, + 545, + 555 + ], + "type": "text", + "content": "Conventional OOD Detection. The results of conventional OOD detection are reported in Table 2. It is clear that our proposed NegPrompt achieves consistently superior performance in both individual OOD datasets and the averaged results. When compared with the zero-shot methods, on average, our approach surpasses the best competing method CLIPN by more than " + }, + { + "bbox": [ + 304, + 376, + 545, + 555 + ], + "type": "inline_equation", + "content": "1.5\\%" + }, + { + "bbox": [ + 304, + 376, + 545, + 555 + ], + "type": "text", + "content": " in AUC and around " + }, + { + "bbox": [ + 304, + 376, + 545, + 555 + ], + "type": "inline_equation", + "content": "8\\%" + }, + { + "bbox": [ + 304, + 376, + 545, + 555 + ], + "type": "text", + "content": " in FPR95, despite the fact that CLIPN requires the use of an additional large external dataset to train an additional negative text encoder. In other words, although NegPrompt is significantly more lightweight than CLIPN in model size, it can substantially and consistently outperform CLIPN in both metrics across all OOD datasets. The adapted post-hoc methods generally do not leverage the CLIP's capabilities well and thus perform less effectively." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 556, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 556, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 556, + 545, + 628 + ], + "type": "text", + "content": "NegPrompt also substantially surpasses both prompt learning-based methods, reducing the FPR95 by about " + }, + { + "bbox": [ + 304, + 556, + 545, + 628 + ], + "type": "inline_equation", + "content": "28\\%" + }, + { + "bbox": [ + 304, + 556, + 545, + 628 + ], + "type": "text", + "content": " (CoOp) and " + }, + { + "bbox": [ + 304, + 556, + 545, + 628 + ], + "type": "inline_equation", + "content": "5\\%" + }, + { + "bbox": [ + 304, + 556, + 545, + 628 + ], + "type": "text", + "content": " (LoCoOp). This indicates that the learned negative prompts provide informed knowledge about OOD data, which is lacking in the competing methods, helping largely reduce detection errors." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 629, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 715 + ], + "type": "text", + "content": "Hard OOD Detection. Hard OOD detection presents unique challenges as the OOD samples often exhibit some similar features as the ID samples. The results on the four hard OOD datasets derived from ImageNet-1K are shown in Table 3. Similar empirical observations can be derived. Our method NegPropmt is consistently the best performer in the average performance, showcasing its general effec" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "17589" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 78, + 70, + 517, + 253 + ], + "blocks": [ + { + "bbox": [ + 78, + 70, + 517, + 253 + ], + "lines": [ + { + "bbox": [ + 78, + 70, + 517, + 253 + ], + "spans": [ + { + "bbox": [ + 78, + 70, + 517, + 253 + ], + "type": "table", + "html": "
MethodSplit-1Split-2Split-3Split-4Avg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓
Zero-shot methods
MCM97.939.1788.1056.4090.3433.0598.724.7393.7725.83
CLIPN99.382.0797.7710.5590.0336.8598.834.6896.5013.53
CLIP-based posthoc methods
MSP77.8563.6068.7383.6379.1070.5582.4065.5277.0270.83
MaxLogit99.870.4998.068.6990.9634.3499.352.6697.0611.55
Energy99.880.4698.188.4090.6535.0299.362.8397.0211.68
ReAct99.340.7297.919.3390.7235.6599.122.9496.7712.16
ODIN98.781.1298.238.1889.9237.2098.7613.2096.4214.92
Prompt learning methods
CoOp98.536.7888.2550.7690.6433.8998.545.1193.9924.14
LoCoOp98.646.2984.6361.0991.3027.7998.8341.4493.3534.15
NegPrompt (Ours)99.850.6298.547.6093.8922.8999.571.6097.968.18
Open-vocabulary OOD detection
CoOp (10%)97.9712.21780.1174.6287.9246.0096.5916.6090.6537.36
LoCoOp (10%)98.009.2387.0252.1880.5159.9382.4148.7286.9942.52
NegPrompt (Ours) (10%)99.661.3696.3019.8991.7526.9298.145.2496.4613.36
", + "image_path": "cfdc1a9fe5222c472663ca9bb7592755d6a18a1689e0cf4a6a61f9ba4f01bd55.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 279, + 287, + 362 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 279, + 287, + 362 + ], + "spans": [ + { + "bbox": [ + 46, + 279, + 287, + 362 + ], + "type": "text", + "content": "tiveness across different dataset splits. The superiority of NegPrompt over the zero-shot and prompt learning-based methods is similar to that in Table 2. Although it is slightly less effective than Energy under the Split-1 setting, it outperforms Energy in all other metrics, achieving maximally over " + }, + { + "bbox": [ + 46, + 279, + 287, + 362 + ], + "type": "inline_equation", + "content": "3\\%" + }, + { + "bbox": [ + 46, + 279, + 287, + 362 + ], + "type": "text", + "content": " AUC and " + }, + { + "bbox": [ + 46, + 279, + 287, + 362 + ], + "type": "inline_equation", + "content": "12\\%" + }, + { + "bbox": [ + 46, + 279, + 287, + 362 + ], + "type": "text", + "content": " FPR95 improvement among the performance on the other OOD datasets." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 363, + 287, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 363, + 287, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 363, + 287, + 422 + ], + "type": "text", + "content": "Note that the results in Table 3 are generally more promising than that in Table 2. This is mainly because the OOD detection difficulty in all four ImageNet-1K splits is largely reduced since the number of their ID classes is significantly less than that in the full ImageNet-1K data." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "spans": [ + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "text", + "content": "Open-Vocabulary OOD Detection. The open-vocabulary OOD detection results are reported in both Tables 2 and 3. Impressively, even when training on only " + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "text", + "content": " ID classes, our approach can still perform better than the competing methods using the full ID classes, e.g., the average AUC and FPR95 in Table 2. In this open-vocabulary setting, in general, both LoCoOp and CoOp exhibit a much larger performance decline than NegPrompt, especially on the results in Table 3, in which CoOp has over " + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "inline_equation", + "content": "3\\%" + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "text", + "content": " AUC drop and LoCoOp has over " + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "inline_equation", + "content": "6\\%" + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "text", + "content": " AUC drop while our method has only about " + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "inline_equation", + "content": "1.5\\%" + }, + { + "bbox": [ + 46, + 423, + 288, + 579 + ], + "type": "text", + "content": " AUC drop. These results demonstrate that the negative prompts in NegPrompt have much better transferability than those in the two competing methods." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 593, + 230, + 604 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 593, + 230, + 604 + ], + "spans": [ + { + "bbox": [ + 47, + 593, + 230, + 604 + ], + "type": "text", + "content": "4.2.1 Classification Accuracy on ID Data" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": "We also evaluate the classification accuracy on the ID data when using NegPrompt for OOD detection, with CoOp, LoCoOp, MCM and CLIPN as the baselines. The classification accuracy results on the full ImageNet-1K test data are shown in Table 4. When using the full ImageNet-1K training ID class data, our method NegPrompt can maintain the same classification accuracy as CoOp." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "Our accuracy is slightly compromised when using only " + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": " ID classes in our training. On the other hand, the OOD" + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 347, + 277, + 506, + 345 + ], + "blocks": [ + { + "bbox": [ + 125, + 254, + 468, + 263 + ], + "lines": [ + { + "bbox": [ + 125, + 254, + 468, + 263 + ], + "spans": [ + { + "bbox": [ + 125, + 254, + 468, + 263 + ], + "type": "text", + "content": "Table 3. Hard OOD detection results. We use the same notations here as those used in Table 2." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 347, + 277, + 506, + 345 + ], + "lines": [ + { + "bbox": [ + 347, + 277, + 506, + 345 + ], + "spans": [ + { + "bbox": [ + 347, + 277, + 506, + 345 + ], + "type": "table", + "html": "
MethodTop-1 Accuracy
CoOp72.1
\\( \\text{LoCoOp}^\\dagger \\)71.7
CLIPN & MCM67.0
NegPrompt(Ours)(10%)71.9
NegPrompt(Ours)(Full)72.1
", + "image_path": "c8f3311dbb39d81c189dee922f4cbf7c53cb12b0d9ffd3f467cc024bc414dadd.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 313, + 346, + 537, + 357 + ], + "lines": [ + { + "bbox": [ + 313, + 346, + 537, + 357 + ], + "spans": [ + { + "bbox": [ + 313, + 346, + 537, + 357 + ], + "type": "text", + "content": "Table 4. Top-1 Accuracy. Results with " + }, + { + "bbox": [ + 313, + 346, + 537, + 357 + ], + "type": "inline_equation", + "content": "\\dagger" + }, + { + "bbox": [ + 313, + 346, + 537, + 357 + ], + "type": "text", + "content": " are taken from [33]." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 307, + 375, + 417, + 484 + ], + "blocks": [ + { + "bbox": [ + 307, + 375, + 417, + 484 + ], + "lines": [ + { + "bbox": [ + 307, + 375, + 417, + 484 + ], + "spans": [ + { + "bbox": [ + 307, + 375, + 417, + 484 + ], + "type": "image", + "image_path": "a9d9a3a19417481f1d8454e532aba78a1a4b2038ce4bab3bbf7c376843ffc4b3.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 433, + 375, + 544, + 484 + ], + "blocks": [ + { + "bbox": [ + 433, + 375, + 544, + 484 + ], + "lines": [ + { + "bbox": [ + 433, + 375, + 544, + 484 + ], + "spans": [ + { + "bbox": [ + 433, + 375, + 544, + 484 + ], + "type": "image", + "image_path": "818085285795656b3cff7aa2a252d098ad84771fc51f527a4293072ddb230b1f.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 307, + 484, + 417, + 571 + ], + "blocks": [ + { + "bbox": [ + 307, + 484, + 417, + 571 + ], + "lines": [ + { + "bbox": [ + 307, + 484, + 417, + 571 + ], + "spans": [ + { + "bbox": [ + 307, + 484, + 417, + 571 + ], + "type": "image", + "image_path": "e905a8a2f8a1f1f1d6a476cd9588aa25d4f9878aa38dd5cf5767ab0f3cc1a6d7.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 309, + 572, + 541, + 584 + ], + "lines": [ + { + "bbox": [ + 309, + 572, + 541, + 584 + ], + "spans": [ + { + "bbox": [ + 309, + 572, + 541, + 584 + ], + "type": "text", + "content": "Figure 3. Similarity of ID/OOD and Positive/Negative Prompts." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 435, + 484, + 544, + 571 + ], + "blocks": [ + { + "bbox": [ + 435, + 484, + 544, + 571 + ], + "lines": [ + { + "bbox": [ + 435, + 484, + 544, + 571 + ], + "spans": [ + { + "bbox": [ + 435, + 484, + 544, + 571 + ], + "type": "image", + "image_path": "bb0dcc3bb85f8c59e65fe7fdd4edbc736f7ee6a676f7fce9255631a7ea584eb6.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 621, + 545, + 717 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 621, + 545, + 717 + ], + "spans": [ + { + "bbox": [ + 304, + 621, + 545, + 717 + ], + "type": "text", + "content": "detection in LoCoOp compromises the ID classification accuracy, dropped from " + }, + { + "bbox": [ + 304, + 621, + 545, + 717 + ], + "type": "inline_equation", + "content": "72.1\\%" + }, + { + "bbox": [ + 304, + 621, + 545, + 717 + ], + "type": "text", + "content": " in CoOp to " + }, + { + "bbox": [ + 304, + 621, + 545, + 717 + ], + "type": "inline_equation", + "content": "71.7\\%" + }, + { + "bbox": [ + 304, + 621, + 545, + 717 + ], + "type": "text", + "content": ". This may be attributed to its focus on the localized regions within the background rather than the primary object of interest, resulting in the missing of some discriminative features for ID data classification. CLIPN and MCM, being zero-shot methods, have not been exposed to the target ID data, leading to a much lower accuracy than the other methods." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "17590" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 70, + 70, + 525, + 184 + ], + "blocks": [ + { + "bbox": [ + 70, + 70, + 525, + 184 + ], + "lines": [ + { + "bbox": [ + 70, + 70, + 525, + 184 + ], + "spans": [ + { + "bbox": [ + 70, + 70, + 525, + 184 + ], + "type": "table", + "html": "
Ablation StudyTextureiNaturalistPlacesSUNAvg
AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓AUC ↑FPR95 ↓ACC ↑
Backbones
ResNet-5079.4472.7390.9744.1084.3561.3788.0450.5585.7057.1968.2
ResNet-10182.9770.8393.9631.386.4151.6688.8147.6188.0450.3570.3
ViT-B-3290.4338.7997.4012.6492.8332.7992.8226.0393.3727.5672.6
# Negative Prompts
190.0440.6798.249.2390.3732.6292.2627.3392.7327.4672.1
Training Process
One-stage80.2572.8777.0295.7482.5395.9481.1395.7280.2390.0762.8
ViT-B-16 & 2 & Two-stage90.3039.3198.397.4892.6829.7593.7026.9293.7625.8672.1
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Results of our ablation experiments." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 69, + 208, + 266, + 337 + ], + "blocks": [ + { + "bbox": [ + 69, + 208, + 266, + 337 + ], + "lines": [ + { + "bbox": [ + 69, + 208, + 266, + 337 + ], + "spans": [ + { + "bbox": [ + 69, + 208, + 266, + 337 + ], + "type": "image", + "image_path": "b9ab64efe1415f22e303b493b00551921694dc74a30285b2fc105d0b45829043.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 339, + 288, + 361 + ], + "lines": [ + { + "bbox": [ + 47, + 339, + 288, + 361 + ], + "spans": [ + { + "bbox": [ + 47, + 339, + 288, + 361 + ], + "type": "text", + "content": "Figure 4. T-SNE visualization of NegPrompt, utilizing a subset of ImageNet - TinyImageNet as the dataset." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 376, + 178, + 389 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 376, + 178, + 389 + ], + "spans": [ + { + "bbox": [ + 47, + 376, + 178, + 389 + ], + "type": "text", + "content": "4.3. Analysis of NegPrompt" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 394, + 207, + 406 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 394, + 207, + 406 + ], + "spans": [ + { + "bbox": [ + 47, + 394, + 207, + 406 + ], + "type": "text", + "content": "4.3.1 Why Does NegPrompt Work?" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 407, + 287, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 407, + 287, + 514 + ], + "spans": [ + { + "bbox": [ + 46, + 407, + 287, + 514 + ], + "type": "text", + "content": "To better understand the effectiveness of NegPrompt, we summarize the average maximum similarity between ID/OOD images and positive/negative prompts, as shown in Fig. 3. Across all four OOD datasets, ID images have the highest similarity with positive prompts, and OOD images with negative prompts. This suggests positive prompts are closer to ID images and negative prompts to OOD images in latent space, ensuring OOD images receive lower softmax scores (i.e., higher OOD scores) than ID images in Eq. 3." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 515, + 287, + 647 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 515, + 287, + 647 + ], + "spans": [ + { + "bbox": [ + 46, + 515, + 287, + 647 + ], + "type": "text", + "content": "Using TinyImageNet [23], a subset of ImageNet, we further visualized the learned negative text features with its test data [6]. Learning three negative prompts per ID class, the results in Fig. 4 demonstrate that positive text features from positive prompts align closely with ID images in latent space. Conversely, the negative text features encoded from negative prompts lie outside of the ID data, with OOD images interspersed among them. This suggests negative text features effectively act as a fence aligning much better to the OOD images than the ID images, well supporting the OOD detection while preserving the ID classification accuracy." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 655, + 145, + 666 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 655, + 145, + 666 + ], + "spans": [ + { + "bbox": [ + 47, + 655, + 145, + 666 + ], + "type": "text", + "content": "4.3.2 Ablation Study" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 666, + 286, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 666, + 286, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 666, + 286, + 689 + ], + "type": "text", + "content": "Table 5 shows our ablation study results on the backbone, the number of negative prompts, and the training process." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 689, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 712 + ], + "type": "text", + "content": "Backbones. We experiment with diverse CLIP backbones. The results reveal that for CNN-based backbones" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 208, + 545, + 267 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 208, + 545, + 267 + ], + "spans": [ + { + "bbox": [ + 304, + 208, + 545, + 267 + ], + "type": "text", + "content": "like ResNet50 and ResNet101, the OOF detection performance is not as proficient as the ViT-based backbones. Regarding ViT-B-32 and ViT-B-16, their performance is found to be uneven. Overall, the performance of OOD detection tends to increase with more advanced backbones." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 268, + 546, + 388 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 268, + 546, + 388 + ], + "spans": [ + { + "bbox": [ + 304, + 268, + 546, + 388 + ], + "type": "text", + "content": "The Number of Negative Prompts. The number of negative prompts also influences the results. It is observed that the OOD detection performance improves when increasing the number of negative prompts from one to two. Therefore, it is suggested to further increase the number of negative prompts for better detection accuracy. However, note that with an increase in the number of negative prompts, the computational cost also rises rapidly. A good balance between computational cost and detection accuracy is needed when determining the number of negative prompts." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 388, + 545, + 519 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 388, + 545, + 519 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 545, + 519 + ], + "type": "text", + "content": "Training Process. The training process is also important. As discussed before, due to the necessity of anchoring the positive prompts, a two-stage training process is used in our model. This process involves training the positive prompts in the first stage and freezing them before proceeding to train the negative prompts in the second stage. When simultaneously training both positive and negative prompts in a unified step, the model's ability to effectively learn positive prompts is significantly undermined, and consequently we obtain unstable negative prompts, leading to the largely decreased OOD detection performance." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 531, + 378, + 544 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 531, + 378, + 544 + ], + "spans": [ + { + "bbox": [ + 306, + 531, + 378, + 544 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 552, + 545, + 659 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 552, + 545, + 659 + ], + "spans": [ + { + "bbox": [ + 304, + 552, + 545, + 659 + ], + "type": "text", + "content": "We present NegPrompt, a novel approach for prompt learning-based OOD detection. It utilizes VLMs to learn a small set of negative prompts for conveying negative semantics relative to ID classes. Our empirical results reveal that NegPrompt 1) achieves superior OOD detection performance compared to the SOTA models across various OOD datasets in both conventional and hard OOD detection scenarios, and 2) learns transfer negative prompts that enable excellent open-vocabulary OOD detection performance." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 671, + 416, + 685 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 671, + 416, + 685 + ], + "spans": [ + { + "bbox": [ + 306, + 671, + 416, + 685 + ], + "type": "text", + "content": "6. Acknowledgement" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 690, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 690, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 306, + 690, + 545, + 712 + ], + "type": "text", + "content": "This work was supported by the National Natural Science Foundation of China 62276016, 62372029." + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17591" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "text", + "content": "[1] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katherine Millican, Malcolm Reynolds, et al. 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However, how the discrepancy between features is mapped to the label discrepancy is ambient, and its correctness is not guaranteed. To address these problems, we study the mathematical connection between feature and its label, presenting a general and simple framework for label distribution learning. We propose a so-called Triangular Distribution Transform (TDT) to build an injective function between feature and label, guaranteeing that any symmetric feature discrepancy linearly reflects the difference between labels. The proposed TDT can be used as a plug-in in mainstream backbone networks to address different label distribution learning tasks. Experiments on Facial Age Recognition, Illumination Chromaticity Estimation, and Aesthetics assessment show that TDT achieves on-par or better results than the prior arts. Code is available at https://github.com/redcping/TDT.", + "bbox": [ + 76, + 300, + 473, + 589 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 609, + 209, + 626 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Label distribution learning (LDL) utilizes the advantages of distribution to solve the task of quasi-continuous label or inner-correlation between labels [22, 58]. LDL assigns a distribution over label value to an instance, which can be obtained by fitting a Gaussian or Triangle distribution whose peak indicates the label and represents the relative importance of each label describing an instance [58]. Hence, LDL has an impact on many real-world applications, such as facial age estimation [22], head-pose estimation [20, 23], crowd counting [76], zero-shot learning [35], facial beauty prediction [51], hierarchical classification [68], partial multi-label learning [69] and so on.", + "bbox": [ + 75, + 636, + 468, + 816 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "When LDL was first proposed, it mainly used maximum entropy and Kullback-Leibler divergence to learn label distribution [22]. Then, a more efficient optimization method BFGS is proposed to replace the IIS method [19]. The", + "bbox": [ + 75, + 816, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "LDL is also widely combined with other algorithms, such as random forest [57], deep convolution neural network [71], hashing method [77], Bayesian [79], metric learning [80] and so on. Although LDL has wide applications, it encounters some challenges, i.e. the feature space and label (solution) space are inhomogeneous [57]. To be more specific, the feature space generated by the model is nonlinear, while the label information is gradually changing. In addition, the existing label distribution is mainly based on label information to construct the distribution, placing the label information for one instance over the whole label distribution.", + "bbox": [ + 500, + 268, + 892, + 435 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Therefore, this article proposes a Triangular Distribution Transform (TDT) method, aiming to linearly map the transformed feature information to its corresponding label information concisely and efficiently. Inspired by label distribution learning [57], we propose using symmetric triangular distributions to represent this symmetric linear transformation. Specifically, the high-dimensional features obtained by feature extraction networks will reflect the relationship between labels through symmetric triangular distributions. To better achieve this goal, we draw inspiration from the paradigm of comparative learning and supply two sets of images to the feature extraction network each time. One set is the prior knowledge that needs to be compared, and the other set is the training sample. Our method is more suitable for visual tasks with linearly continuous changing label information, such as age, aesthetics, lighting intensity, etc. Our TDT can be used as a plug-in in mainstream backbone networks. Therefore, our method has achieved excellent results on multiple visual tasks, such as facial age estimation, image aesthetics estimation, and illumination estimation.", + "bbox": [ + 496, + 436, + 893, + 737 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The contribution of this article is summarized as follows:", + "bbox": [ + 517, + 738, + 890, + 752 + ], + "page_idx": 0 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We analyze to lay the theoretical foundation for the Triangular Distribution Transform, enabling feature discrepancy to explain label difference.", + "- We show with the proposed symmetry-related loss and commutativity-related loss, TDT can be learnt by mainstream backbone networks.", + "- TDT outperforms other methods on age estimation, aesthetics estimation, and illumination estimation." + ], + "bbox": [ + 517, + 761, + 890, + 898 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author. †These authors contributed equally.", + "bbox": [ + 94, + 886, + 411, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "11019", + "bbox": [ + 478, + 924, + 519, + 936 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/7cef8ab8c4868c5ac129958296e36327551fc0786bc3351f925674c0698821f6.jpg", + "image_caption": [ + "Figure 1. The overall structure of our TDT. Our pipeline (b) diverges from the general pipeline (a) by incorporating a parameter-free TDT (Triangular Distribution Transform), enabling converting the nonlinear feature to the one which vary \"linearly\" as per Eq.4. Consequently, a linear head module alone suffices to establish the mapping between image features and their respective labels, with clear explanation which is missing for a conventional network head. For detailed information on the TDT loss, please refer to Figure.2." + ], + "image_footnote": [], + "bbox": [ + 122, + 95, + 849, + 402 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related works", + "text_level": 1, + "bbox": [ + 76, + 500, + 225, + 515 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Label distribution learning", + "text_level": 1, + "bbox": [ + 76, + 523, + 321, + 540 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The label distribution method learns the relevance between labels to reflect the relative importance of different labels [21, 22, 29, 58], which can also be seen as a special facial age classification method. Label distribution learning methods learn a label distribution that represents the relative importance of each label when describing an instance[21]. The label distribution covers a certain number of labels. Each label has its description degree, representing the degree to which each label describes the instance[62]. The description degrees of all the labels sum up to 1 [62]. Due to the advantages of label distributed learning, it has achieved very excellent performance in tasks such as facial age estimation[22], head-pose estimation [20, 23], crowd counting [76], zero-shot learning[35], facial beauty prediction[51], hierarchical classification[68], and partial multi-label learning [69]. The label distribution learning method is very consistent with the potential law of big data. Nevertheless, acquiring distributional labels for thousands of face images itself is a non-trivial task[58].", + "bbox": [ + 75, + 547, + 472, + 835 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.2. Facial Age estimation", + "text_level": 1, + "bbox": [ + 76, + 845, + 279, + 863 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The regression methods [45], classification methods [53], and ranking methods [7, 9] for age estimation pay more", + "bbox": [ + 75, + 869, + 470, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "attention to putting forward different research methods according to label information. The age regression methods consider labels as continuous numerical values. To handle the heterogeneous data, researchers also proposed hierarchical models [26] and the soft-margin mixture of regression [33]. And age classification regards labels as independent values[53]. It regards each age as a separate category and ignores the similarity of the same person between different ages. While the ranking approaches treat labels as rank-order data and use multiple binary classifiers to determine the age rank in a facial image[7, 9]. Besides, some scholars also focus on the objective optimization function [12, 46]. ML-loss [46] proposed mean-variance loss for robust age estimation via distribution learning. Deng et al. [12] proposed progressive margin loss (PML) for long-tailed age classification. These methods gradually consider that aging is a slow and continuous process, which also means that the processing of label information is significant.", + "bbox": [ + 496, + 500, + 893, + 773 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.3. Aesthetic Assessment", + "text_level": 1, + "bbox": [ + 500, + 785, + 700, + 800 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "An aesthetic assessment task refers to evaluating the visual beauty and artistic value of given image. Early studies rely on handcrafted features [13, 43, 44], which ignore the spatial features and semantics in assessing aesthetics. In data-driven learning-based methods, NIMA[63] uses Earth Mover's Distance to optimize aesthetic distribution predic", + "bbox": [ + 496, + 810, + 893, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "11020", + "bbox": [ + 478, + 924, + 519, + 936 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "tion. A-lamp[42] and $\\mathrm{MP}_{ada}[59]$ both achieve good results with a multi-patch approach. Hierarchical Layout-aware Graph Convolution Network (HGCN)[56] captures layout information. TANet [27] adaptively learns aesthetic prediction rules based on identified themes, using Mean Squared Error as the metric. Transformer [28] assign attention levels to color spaces, enabling segmentation learning. Yi et al. [72] effectively combine feature style and general aesthetic information using AdaIN [34] and self-supervised pre-training for accurate aesthetic assessment.", + "bbox": [ + 75, + 90, + 472, + 242 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.4. Illumination Estimation", + "text_level": 1, + "bbox": [ + 76, + 250, + 299, + 265 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Illumination Estimation is often dubbed as Auto White Balance verbally and aims at measuring the normalized illumination vector given at least one single image. There exists a bunch of traditional methods that are easy to implement but easily fail due to the over-optimistic assumption, for example, White Patch [4], General Gray World [1], Gray Edge [65], Shades-of-Gray [16], LSRS [17], PCA [10] and Grayness Index [49], etc. Relying on labeled data, a bunch of learning-based methods with tunable inner weight e.g. [2, 5, 6, 15, 18, 24, 25, 32, 36, 48, 61] leads the leaderboard by a large gap generally. All aforementioned methods output a single illumination vector in a deterministic way. A few works deal with label distribution learning; Egor et al. [14] proposed an efficient illumination distribution estimation method; FFCC [3] from Barron outputs a unique illumination vector which can be modified as a distribution.", + "bbox": [ + 75, + 272, + 472, + 515 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Proposed Method", + "text_level": 1, + "bbox": [ + 76, + 527, + 250, + 544 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The pipeline of proposed Triangular distribution learning is illustrated in Fig.1. Fig.1(a) depicts the general pipeline for CNN tasks, where non-linear head modules are employed to map non-linear features to labels due to the linear independence of image features. These non-linear head modules can include modules that combine convolution with nonlinear activation functions, Gaussian Mixture Model, and others. In Fig.1(b), we propose a novel pipeline that differs from the general pipeline. We introduce a parameter-free TDT (Triangular Distribution Transform) after the nonlinear image features, allowing for the possibility of transforming linearly independent image features into linearly correlated ones. As a result, we only need to utilize a linear head module, such as a fully connected (FC) module, in combination with the relevant loss function to achieve linear correlation learning among the features. Additionally, we employ a contrastive learning-like approach to guide the predictions of unknown samples based on known samples.", + "bbox": [ + 75, + 551, + 472, + 825 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Triangular Distribution Transform on Latent Feature", + "text_level": 1, + "bbox": [ + 76, + 832, + 470, + 862 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "With some ambiguity, vision regression problems can be classified into linear-label problems and nonlinear-label", + "bbox": [ + 76, + 869, + 470, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ones. The mapping from the original information modality (for example 2D images, text, voice, video etc.) to the corresponding labels is usually non-linear and hard to model in a fixed rule. Take facial age recognition as an example, age label varies linearly while the visual feature of the facial image usually does not work in the same way. The majority of works on distribution learning mainly focus on learning a mapping from visual features to the label in a nonlinear way, such as the deep net, with its interpretability remaining in suspense. In this article, we discuss the relationship between the feature and its label and present a so-called Triangular Distribution Transform (TDT) to rigidly connect the feature and its label, so that the connection is injective.", + "bbox": [ + 496, + 90, + 890, + 286 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Starting with an input $X\\in \\mathbb{R}^{N\\times 3\\times H\\times W}$ ( $N$ is the batch size, $3,H,W$ denotes the channel, height, and width respectively) and its label $Y$ , we extract feature by some net module $g$ (parameterized by $\\Theta$ ) as follows:", + "bbox": [ + 496, + 286, + 890, + 348 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {X} _ {g} = g (\\mathcal {X}, \\Theta) \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 643, + 358, + 890, + 376 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathcal{X}_g\\in \\mathbb{R}^{N\\times C\\times h\\times w}$ is a C-channel feature extracted from some backbone nets (e.g., ResNet18). The mean and standard deviation are calculated along the $h$ and $w$ dimensions, referred to as $\\mu (\\mathcal{X}_g)\\in \\mathbb{R}^{N\\times C\\times 1\\times 1}$ and $\\sigma (\\mathcal{X}_g)\\in$ $\\mathbb{R}^{N\\times C\\times 1\\times 1}$ respectively.", + "bbox": [ + 496, + 385, + 890, + 460 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Based on the Central Limit Theorem, we assume $\\mathcal{X}_g$ follows Gaussian distribution and denote the probability density function (PDF) as $\\phi(\\mathcal{X}_g)$ . Given features for two samples $(\\mathcal{X}_g^1$ and $\\mathcal{X}_g^2$ ), we define their \"feature difference\" based on the Gaussian distribution of $\\mathcal{X}_g^1$ as:", + "bbox": [ + 496, + 462, + 890, + 539 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) = \\phi \\left(\\mathcal {X} _ {g} ^ {1}\\right) - \\phi \\left(\\mathcal {X} _ {g} ^ {2}\\right) \\tag {2} \\\\ \\propto \\mathcal {N} _ {0, 1} (\\frac {\\mathcal {X} _ {g} ^ {1} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})}) - \\mathcal {N} _ {0, 1} (\\frac {\\mathcal {X} _ {g} ^ {2} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})}) \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 501, + 547, + 890, + 606 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The last part of Eq.2 is the normalized feature difference using the standard Gaussian distribution $\\mathcal{N}_{0,1}$ . We give our first assumption:", + "bbox": [ + 496, + 614, + 890, + 660 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Assumption 1: There exists a function transforming $\\mathcal{X}_g$ to $\\mathcal{X}_g'$ , whose change linearly w.r.t. the label.", + "bbox": [ + 496, + 660, + 890, + 690 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To better fit Assumption 1, considering $\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2)$ does not correlate linearly with the label, we approximate the Gaussian distribution in Eq.2 using a symmetric Triangular distribution $\\tau (\\cdot |b)$ following [55], formulated as:", + "bbox": [ + 496, + 690, + 890, + 751 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) \\approx \\Delta_ {\\tau} \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) \\tag {3} \\\\ = \\tau (\\frac {\\mathcal {X} _ {g} ^ {1} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})} | b) - \\tau (\\frac {\\mathcal {X} _ {g} ^ {2} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})} | b), \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 509, + 760, + 890, + 818 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\tau (s | b) = \\left\\{ \\begin{array}{l l} \\frac {1}{b} \\cdot \\left(1 - \\frac {| s |}{b}\\right), & - b \\leq s \\leq b \\\\ 0, & \\text {o t h e r w i s e} \\end{array} \\right. \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 545, + 820, + 890, + 861 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where the scalar $b$ controls the approximation error and is set to $\\sqrt{6}$ ( $b$ is obtained via the method of moments in [55]).", + "bbox": [ + 496, + 869, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "11021", + "bbox": [ + 478, + 925, + 517, + 936 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/f20923bffec47bae74c97127bebeed8465581225dd036282b70a54c53625bf8b.jpg", + "image_caption": [ + "Figure 2. TDT is learned relying on the commutativity-related loss and symmetry-related loss, while the latter plays the primary role. The feature difference, associated with the symmetry-related loss, is used for result prediction. MSE is the mean square error." + ], + "image_footnote": [], + "bbox": [ + 99, + 88, + 356, + 287 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/e469feb9545e454a5030504f9bda8bc692e1da588d25d21fedb6f5085dc2e254.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 357, + 88, + 864, + 287 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In contrast to Eq.2, Eq.4 has the property of linearly describing the corresponding label difference. Then we can search a linear function $f(\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2))$ that transforming the feature difference to the label difference $|Y^{1} - Y^{2}|$ , in a linear, symmetric and commutative way1.", + "bbox": [ + 75, + 356, + 468, + 434 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Optimization towards Triangular Distribution Transform and Vision Tasks", + "text_level": 1, + "bbox": [ + 76, + 444, + 468, + 474 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The learned feature does not follow Triangular distribution unless we optimize the net towards it. Then we state the optimization loss towards TDT and related task-specific loss. The optimization loss of TDT, shown in Fig.2, aims to gradually transform the non-linear correlation among image features into a linear correlation through label-guided learning.", + "bbox": [ + 75, + 483, + 468, + 575 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Loss for Triangular Distribution", + "text_level": 1, + "bbox": [ + 96, + 575, + 326, + 590 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given two sets of nonlinear features $\\mathcal{X}_g^1$ and $\\mathcal{X}_g^2$ extracted from backbone network, we use multiple convolution layers to learn to make a feature that follows symmetric Triangular distribution, formulated as $\\mathcal{X}_s = \\text{Conv}(\\text{Concat}(\\mathcal{X}_g^1, \\mathcal{X}_g^2), \\theta)$ , where the concatenation happens in the batch dimension. We calculate the mean and standard deviation separately for $\\mathcal{X}_s$ , $\\mathcal{X}_g^1$ and $\\mathcal{X}_g^2$ along the spatial dimensions. Via Eq.4, we get $\\Delta(\\mathcal{X}_s, \\mathcal{X}_g^1)$ and $\\Delta(\\mathcal{X}_s, \\mathcal{X}_g^2)$ .", + "bbox": [ + 75, + 590, + 468, + 728 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To guide the net to reach a state that $\\mathcal{X}_g^1$ and $\\mathcal{X}_g^2$ are symmetrical around the \"center\" $\\mathcal{X}_s$ , a symmetry-related loss is introduced:", + "bbox": [ + 75, + 728, + 468, + 772 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nL _ {S} = \\left\\| \\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1}\\right) - \\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right) \\right\\| _ {2}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 151, + 787, + 468, + 806 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the operator $\\| \\cdot \\| _2$ is a L2 loss. Analogously, the", + "bbox": [ + 76, + 818, + 468, + 835 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "commutativity-related loss is designed as:", + "bbox": [ + 500, + 356, + 777, + 372 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nL _ {M} = \\left\\| \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) - \\Delta \\left(\\mathcal {X} _ {g} ^ {2}, \\mathcal {X} _ {g} ^ {1}\\right) \\right\\| _ {2}, \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 383, + 890, + 402 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Then, to facilitate the learning of the linear function $f(\\Delta)$ , we adopt a comparative approach and design a relevant supervised loss:", + "bbox": [ + 498, + 414, + 890, + 460 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} L _ {P} = \\| \\delta (Y) - 2 \\cdot f (\\Delta (\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1}) \\cdot s g n (\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1})) \\| _ {1} \\\\ + \\| \\delta (Y) + 2 \\cdot f \\left(\\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right) \\cdot s g n \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right)\\right) \\| _ {1}, \\tag {7} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 514, + 470, + 890, + 512 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Here, $\\| \\cdot \\|_1$ refers to smooth L1 operator, $\\delta(Y) = Y^2 - Y^1$ , $\\operatorname{sgn}(\\mathcal{X}_s, \\mathcal{X}_g)$ represents the sign of $\\Delta(\\mathcal{X}_s, \\mathcal{X}_g)$ . When $\\mathcal{X}_g$ in the distribution of $\\mathcal{X}_s$ has a cumulative distribution function (CDF) less than 0.5, $\\operatorname{sgn}(\\mathcal{X}_s, \\mathcal{X}_g)$ is considered positive, and vice versa. The first part of Eq.7 represents using samples labeled as $Y^2$ to predict samples labeled as $Y^1$ , and the other term follows the same principle.", + "bbox": [ + 496, + 521, + 890, + 628 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Therefore, the final loss function for learning the triangular distribution can be formulated as follows:", + "bbox": [ + 498, + 628, + 890, + 659 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nL _ {T} = L _ {S} + L _ {M} + L _ {P}, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 614, + 672, + 890, + 689 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Loss for Vision Tasks", + "text_level": 1, + "bbox": [ + 517, + 703, + 671, + 715 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To quickly validate the effectiveness of TDT, we have selected three common visual tasks: facial age recognition, aesthetic assessment, and illumination estimation. Below are the descriptions and loss definitions for these three tasks.", + "bbox": [ + 496, + 717, + 890, + 777 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Facial Age Recognition: Age variation can be considered linear, and we can utilize TDT to draw the relationship between visual feature differences among different images and the corresponding age variation. Therefore, we can directly employ Eq.8 for optimizing age estimation.", + "bbox": [ + 496, + 777, + 890, + 854 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Aesthetic Assessment: The aesthetic assessment variation in scores can be considered linear, similar to the optimization for the age estimation task, we can also choose", + "bbox": [ + 496, + 854, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_footnote", + "text": "$^{1}$ Linearity: given $\\Delta_{\\tau}(\\mathcal{X}_g^1, \\mathcal{X}_g^2) = \\Delta_{\\tau}(\\mathcal{X}_g^2, \\mathcal{X}_g^3)$ , we have $Y^{1} - Y^{2} = Y^{2} - Y^{3}$ .", + "bbox": [ + 75, + 845, + 467, + 872 + ], + "page_idx": 3 + }, + { + "type": "page_footnote", + "text": "Symmetry: $\\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^1 +\\delta \\mathcal{X}_g) = \\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^1 -\\delta \\mathcal{X}_g)$", + "bbox": [ + 76, + 872, + 393, + 887 + ], + "page_idx": 3 + }, + { + "type": "page_footnote", + "text": "Commutativity: $\\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^2) = \\Delta_{\\tau}(\\mathcal{X}_g^2,\\mathcal{X}_g^1)$ .", + "bbox": [ + 78, + 887, + 336, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "11022", + "bbox": [ + 478, + 924, + 519, + 936 + ], + "page_idx": 3 + }, + { + "type": "table", + "img_path": "images/3ebbf05f6fdf59e096a28e96706fc4e9b273077ac75781562762b6cf6cb63d98.jpg", + "table_caption": [ + "Table 1. Experiments setting for three tasks evaluated." + ], + "table_footnote": [], + "table_body": "
TaskBaselineDatasetInput size
Facial Age RecognitionDAA(Resnet18)[8]MegaAge-Asian[75]96 × 96
Aesthetic AssessmentSAAN(Resnet50+VGG19) [72]TAD66K[27]256 × 256
Illumination EstimationFC4(FC, SqueezeNet)[31]Reprocessed Color Checker [18, 60]512 × 512
", + "bbox": [ + 107, + 113, + 859, + 180 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Eq.8 as the overall optimization. In this case, the label corresponds to the aesthetic score.", + "bbox": [ + 75, + 193, + 468, + 222 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Illumination Estimation: In illumination estimation, a key step of automatic white balance, we consider the variation of the illumination to be approximately linear. Additionally, to better capture the differences in illumination angles, we combine Eq.8 and the angle error [31] as the overall optimization function $L_{ill} = L_T + \\frac{180}{\\pi} \\cdot \\arccos(p \\cdot p^*)$ , where the $p$ and $p^*$ represent the normalized estimation and ground truth of illumination color, respectively.", + "bbox": [ + 75, + 223, + 468, + 344 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Algorithm 1 The training process of our method", + "bbox": [ + 78, + 357, + 400, + 373 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1: Input: Sample set $X$ and corresponding labels $Y$", + "2: Output: Loss", + "3: Prior Set Selection: Randomly select $N$ samples $X_{2}$ from the training set with labels $Y_{2}$ .", + "4: for each sample $X_{1}$ in forward pass do", + "5: #Feature fusion and distribution generation", + "6: $\\mathcal{X}_g^1, \\mathcal{X}_g^2 \\gets g(X_1, \\Theta), g(X_2, \\Theta) \\# \\text{Extract features}$", + "7: $N, C, \\bar{h}, w \\gets \\mathcal{X}_g^2$ . shape # $C$ is distribution number", + "8: $\\mathcal{X}_q^1\\gets \\mathcal{X}_q^1.\\text{repeat}(N,1,1,1)$", + "9: $\\mathcal{X}_s\\gets conv(conv(\\mathcal{X}_q^1,\\mathcal{X}_q^2,1),C)$", + "10: # Perform TDT operation on $\\mathcal{X}_q^1$ based on $\\mathcal{X}_s$", + "11: $\\mu (\\mathcal{X}_s),\\sigma (\\mathcal{X}_s)\\gets calc\\_ mean\\_ std(\\mathcal{X}_s)$", + "12: $\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^1)\\gets \\tau (\\frac{\\mathcal{X}_s - \\mu(\\mathcal{X}_s)}{\\sigma(\\mathcal{X}_s)} |b) - \\tau (\\frac{\\mathcal{X}_g^1 - \\mu(\\mathcal{X}_s)}{\\sigma(\\mathcal{X}_s)} |b)$", + "13: #Feature-to-Label Difference Mapping", + "14: $sgn(\\mathcal{X}_s,\\mathcal{X}_g^1)\\gets (-1)^{cdf(\\mathcal{X}_g^1) > 0.5}$", + "15: $\\delta Y_{1}\\gets f(\\tilde{\\Delta} (\\mathcal{X}_{s},\\mathcal{X}_{g}^{1})\\cdot sgn(\\mathcal{X}_{s},\\mathcal{X}_{g}^{1}))$ # via Eq.7", + "16: where $f(\\cdot) = fc(gap(\\cdot))$", + "17: Optimize TDT, including $L_{S}, L_{M}$ , and $L_{P}$", + "18: end for" + ], + "bbox": [ + 84, + 376, + 467, + 670 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. TDT Algorithm Process", + "text_level": 1, + "bbox": [ + 76, + 695, + 295, + 710 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To be more clear, we provide pseudocode 1, in 5 parts.", + "bbox": [ + 75, + 719, + 437, + 734 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Prior Samples Selection: Prior samples are several selected training samples, providing comparison with those samples used for training/testing. Features for the prior samples can be pre-computed and integrated into the model.", + "bbox": [ + 75, + 734, + 468, + 794 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Distribution generation: We obtain $\\mathcal{X}_s$ and form its high-dimensional Normal Distribution using $\\mu(\\mathcal{X}_s)$ and $\\sigma(\\mathcal{X}_s)$ . After standardizing and approximating, we get a zero-symmetric high-dimensional Triangular Distribution to linearly represent feature differences.", + "bbox": [ + 75, + 795, + 468, + 869 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "TDT Operation: It calculates the PDF differences between $\\mathcal{X}_s$ and $\\mathcal{X}_g$ based on the distribution of $\\mathcal{X}_s$ meet", + "bbox": [ + 75, + 869, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "$\\left|\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2)\\right| = 2\\cdot \\left|\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^1)\\right| = 2\\cdot \\left|\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^2)\\right|$ Remarkably, TDT is entirely formulaic, parameter-free, and fit any net outputting feature maps.", + "bbox": [ + 498, + 191, + 890, + 238 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Difference Mapping: Base on distribution of $\\mathcal{X}_s$ , $\\mathcal{X}_s$ generally has a higher PDF than $\\mathcal{X}_g$ , meaning $\\Delta(\\mathcal{X}_s, \\mathcal{X}_g) = \\text{pdf}(\\mathcal{X}_s) - \\text{pdf}(\\mathcal{X}_g) \\geq 0$ . We infer feature difference signs from $\\text{cdf}(\\mathcal{X}_g) > 0.5$ and linearly map them to label difference via global average pooling and a linear layer.", + "bbox": [ + 496, + 239, + 890, + 315 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "**Optimization:** For commutativity loss, we utilize the mean and std of $\\mathcal{X}_g^1$ and $\\mathcal{X}_g^2$ . For symmetry and supervisory losses, those of $\\mathcal{X}_s$ are computed.", + "bbox": [ + 496, + 316, + 890, + 361 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 498, + 378, + 630, + 395 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Notes and Implementation Details", + "text_level": 1, + "bbox": [ + 498, + 402, + 795, + 419 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We perform TDT validation on the baseline in three tasks, whose configuration details are shown in Table 1.", + "bbox": [ + 496, + 428, + 890, + 458 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Train and Test notes: As observed in pseudocode 1, our TDT aims to guide the learning of unknown samples using prior samples, resembling contrastive learning. Therefore, for each task experiment, we randomly select a prior set from the training dataset. During training and testing, each batch comprises both the prior set samples used to obtain $\\mathcal{X}_g^2$ and the unknown samples used to obtain $\\mathcal{X}_g^1$ . Each unknown sample undergoes TDT operations with all prior samples to make predictions, and the average of these predictions is considered as the final prediction. To reduce feature extraction time during testing, we encapsulate all the features from the prior set into the model parameters, resulting in an optimized model with accelerated inference.", + "bbox": [ + 496, + 459, + 890, + 655 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Common Setting: For all experiments, we used the Adam optimizer, where the weight decay and the momentum were set to 0.0005 and 0.9, respectively. The initial learning rate was set to 0.001 and changed according to cosine learning rate decay. We trained our model using PyTorch on a cluster of 8 RTX 3090 GPUs. In an online manner, we augment all images with random horizontal flipping, scaling, rotation, and translation.", + "bbox": [ + 496, + 656, + 890, + 777 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Facial Age Recognition: We utilize the FG-Net [47] dataset, which comprises 1002 facial images from 82 subjects, spanning an age range from 0 to 69. We follow the setup described in the papers [8, 12, 40], employing leave-one-person-out (LOPO) cross-validation. We report the average performance over 82 splits using the Mean Absolute Error (MAE) as the evaluation metric.", + "bbox": [ + 496, + 777, + 890, + 882 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Additionally, we also use the MegaAge-Asian [75]", + "bbox": [ + 519, + 885, + 890, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "11023", + "bbox": [ + 478, + 925, + 517, + 936 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/73c2fc411f4adcbbdb2d752354d3b78849d8ed3b53aad4411cd85df8f0b1e632.jpg", + "table_caption": [ + "Table 2. CA on MegaAge-Asian." + ], + "table_footnote": [], + "table_body": "
MethodsPre-trainedCA(3)CA(5)CA(7)
Posterior [75]IMDB-WIKI62.0880.4390.42
MobileNet [54]IMDB-WIKI44.060.6-
DenseNet [70]IMDB-WIKI51.769.4-
SSR-Net [70]IMDB-WIKI54.974.1-
UVA [38]-60.4779.9590.44
LRN(ResNet10) [39]IMDB-WIKI62.8681.4791.34
LRN(ResNet18) [39]IMDB-WIKI64.4582.9591.98
VGG16(norm) [78]ImageNet, IMDB-WIKI, AFAD65.5883.0189.17
PVP+VGG16 [78]ImageNet, IMDB-WIKI, AFAD72.6587.2493.16
DAA(single channel) [8]-67.9784.0692.40
DAA(multi-channel) [8]-68.2984.8492.47
DAA [8]-68.8284.8992.70
TDT (ours)-69.6085.4293.26
", + "bbox": [ + 84, + 113, + 460, + 250 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/3af716a9b5841160a41eb179c2efbbd061152d8e47b83344f5be02fc384dd87b.jpg", + "table_caption": [ + "Table 3. MAEs on FG-Net dataset." + ], + "table_footnote": [], + "table_body": "
MethodsMAEYear
DEX[52]3.092015
MV[46]2.682018
C3AE[74]2.952019
DRFs[58]3.852021
PML[12]2.162021
DAA [8]2.192023
TDT(ours)2.12-
", + "bbox": [ + 187, + 290, + 354, + 392 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Dataset, consisting of 40,000 age-labeled samples spanning 0 to 70 years and 3,945 images for testing. For this dataset, we choose cumulative accuracy (CA) [75] as the evaluation metric, defined as $CA(n) = \\frac{K_n}{K} \\times 100$ , where $K$ is total number of testing images and $K_n$ is the number whose absolute errors are smaller than $n$ .", + "bbox": [ + 75, + 412, + 467, + 503 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We adopt the official implementation of DAA[8] as the baseline for this task while replacing its DAA mapping with our TDT. The output size of $\\mathcal{X}_q$ is set to $3\\times 3$ .", + "bbox": [ + 75, + 505, + 468, + 549 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In this task, 256 images are randomly picked from the training set serves as the prior set for all experiments.", + "bbox": [ + 75, + 551, + 468, + 580 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Aesthetic Assessment: We use TAD66K (Theme and Aesthetics Dataset with 66K images) Dataset [27], a large-scale aesthetic quality assessment database with 47 themes. Images belonging to each theme are annotated independently, with each image containing a minimum of 1200 valid annotations. The aesthetic score of each image is treated as the label. Following TANet[27], the evaluation metric is the Mean Squared Error (MSE). We adopt the same train-test split setting. For the prior set, we select samples by choosing 2 random samples for each score ranging from 0 to 10 with interval 0.1 for each theme. We employ the official implementation of SAAN[72] as the baseline for this task while removing the final average pooling and BN layers. Additionally, we incorporate extra convolutions to obtain $\\mathcal{X}_g$ with size of $8\\times 8$ .", + "bbox": [ + 75, + 582, + 468, + 809 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Illumination Estimation: We use reprocessed Color Checker [18, 60] dataset, one of the most widely adopted datasets in illumination estimation. Following $\\mathrm{FC^4}$ [31], the evaluation metric is the Recovery Angular Error. To facilitate better comparisons, we use the linear fully connected version of $\\mathrm{FC^4}$ -net as the baseline, instead of the non-linear", + "bbox": [ + 75, + 810, + 468, + 898 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/13d482d354dfabaa7eebe2528e084fe73229e4f203605de741f244fa7ffd7cc8.jpg", + "table_caption": [ + "Table 4. Results on Aesthetic Benchmark TAD66K." + ], + "table_footnote": [], + "table_body": "
methodPub.BasicMSE
RAPID [41]ACMMM2014incorporate heterogeneous0.0200
PAM[50]ICCV2017residual-based, active learning0.0200
ALamp[42]CVPR2017layout-aware, multi-patch0.0190
NIMA [63]TIP2018predict distribution0.0210
MPada [59]ACMM2018attention, multi-patch0.0220
MLSP [30]CVPR2019staged training,multi-level features0.0190
UIAA [73]TIP2019unified probabilistic formulation0.0210
HGCN [56]CVPR2021graph convolution networks0.0200
TANet [27]IJCAI2022attention, adaptive features0.0161
SAAN [72]CVPR2023AdaIN,self-supervised Pretraining0.0185
TDT(ours)-Triangular Distribution0.0172
", + "bbox": [ + 504, + 113, + 890, + 250 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "weight pooling version. With additional convolutional layers, we obtain $\\mathcal{X}_g\\in \\mathbb{R}^{N\\times C\\times 8\\times 8}$ . When comparing with the $\\mathrm{FC^4}$ model, we randomly select 128 samples from the training set as the prior set. However, when comparing with the method proposed by Tang et al. [64] that utilizes the extended external sRGB datasets, we choose same images for scene classification as the prior set, but only 1280 samples.", + "bbox": [ + 496, + 267, + 890, + 373 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Following previous AWB works[18, 31, 60], 3-fold cross-validation is used. Standard metrics (mean, median, tri-mean of all the errors, the mean of the lowest $25\\%$ , and the mean of the highest $25\\%$ of errors, the 95th percentile error) are reported in terms of angular error in degrees.", + "bbox": [ + 496, + 373, + 890, + 450 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Results and Analysis", + "text_level": 1, + "bbox": [ + 500, + 462, + 694, + 478 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Facial Age Estimation", + "text_level": 1, + "bbox": [ + 500, + 486, + 660, + 501 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The quantitative comparison of a list of top-performing methods on the MegaAge-Asian Dataset is shown in Table 2. From the table, we can find that even stocked with pre-training on large-scale datasets, methods like [39, 78] are inferior to ours. Compared with SSR-Net, our improvement is over $8\\%$ . PVP [78] gets higher CA(3) and CA(5) indexes, due to the massive pretraining on ImageNet[11], IMDB-WIKI[53], and AFAD[45]. DAA[8], published in 2023, shares the same setting with our proposed method, while TDT obtains better scores in all CA indexes.", + "bbox": [ + 496, + 502, + 890, + 652 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To better prove the effectiveness of TDT, we also profile TDT on FG-Net [47], reported in Table 3. Using MAE as the metric, TDT leads the board with the smallest MAE, surpassing the same-setting competitor DAA.", + "bbox": [ + 496, + 654, + 890, + 715 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Aesthetic Assessment.", + "text_level": 1, + "bbox": [ + 500, + 717, + 656, + 729 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In Table 4, we list the MSE scores for the selected and close-related aesthetic works. In an overall manner, TDT ranks second with an MSE score of 0.0172. This improvement simply originates from the deployment of the TDT plugin over SAAN [72], whose MSE is 0.0185, again showing the advantage of the label discriminative ability of TDT.", + "bbox": [ + 496, + 732, + 890, + 823 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Illumination Estimation.", + "text_level": 1, + "bbox": [ + 500, + 824, + 676, + 837 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In Table 5, we report the statistics of the predicted angular error for a set of AWB algorithms on the Color Checker Dataset. On metrics like mean, and median values, the TDT based on $\\mathrm{FC^4}$ outperforms other state-of-the-art methods,", + "bbox": [ + 496, + 839, + 890, + 898 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "11024", + "bbox": [ + 478, + 925, + 519, + 936 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/947f0f3dd8e31845b569040e250ac333b31391bfb8da01b8c354eb2f24476b48.jpg", + "table_caption": [ + "Table 5. Results on AWB Dataset Color Checker Dataset." + ], + "table_footnote": [], + "table_body": "
modelsmeanmed.tri.best25%worst 25%95th pct.
FFCC [3]1.800.951.180.274.65-
FC4(Weighted) [31]1.651.181.270.383.784.73
FC4[31]1.841.271.390.464.205.46
AlexNet FC4 [31]1.771.111.290.343.784.29
Multi-Hypothesis [37]2.101.321.530.365.10-
IGTN [67]1.580.92-0.283.70-
MDLCC [66]1.580.951.110.373.77-
TLCC+sRGB [64]1.510.981.070.333.52-
TDT+FC41.641.121.250.413.804.53
TDT+FC4+sRGB1.460.851.050.263.614.61
", + "bbox": [ + 81, + 114, + 467, + 232 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/1bdf1883ecd70ee14456f404915204be19985ecbe0e05454128adea1c9f6646c.jpg", + "table_caption": [ + "Table 6. Loss ablation analysis on MegaAge-Asian. $\\checkmark$ and - indicate whether to add this loss to the final loss." + ], + "table_footnote": [], + "table_body": "
\\( L_S \\)\\( L_M \\)\\( L_P \\)CA(3)CA(5)CA(7)
-✓✓67.7484.3392.51
✓-✓68.4384.6292.60
✓✓✓69.6085.4293.26
", + "bbox": [ + 135, + 285, + 406, + 342 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "such as MDLCC [66] and TLCC [64]. On top of $\\mathrm{FC^4}$ , TDT also boosts the performance by a noticeable gap.", + "bbox": [ + 76, + 358, + 467, + 388 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 401, + 228, + 416 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We conduct an ablation study on the loss choice, the number of distributions and prior samples.", + "bbox": [ + 76, + 425, + 467, + 455 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Loss function", + "text_level": 1, + "bbox": [ + 76, + 455, + 174, + 469 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "It is vital to study the impact of different losses in Eq.8 and the results are presented in Table 6. We observe that removing any loss incurs a decrement in the overall performance. And symmetry loss brings the most improvement.", + "bbox": [ + 76, + 472, + 467, + 532 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We design a toy experiment to further analyze the loss function Eq.7. The age loss $L_{P}$ is a supervisory loss due to the label is needed for computing $L_{P}$ , while the symmetry-related loss $L_{S}$ and the commutativity-related loss $L_{M}$ are unsupervisory losses. Switching off all nonsupervisory loss, as seen in the top two rows of Table 7, we see a clear CA score drop, indicating the advantage brought by the nonsupervisory loss.", + "bbox": [ + 75, + 534, + 467, + 654 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "If we cut off the access to unsupervisory loss for part1 (in other words, for only $75\\%$ data, the unsupersiory loss is calculated), as reported in the bottom half of Table 7, we claim: with increasing unlabeled data, the performance is massively improved, which again verifies the functionality of the symmetry-related and commutativity-related loss.", + "bbox": [ + 75, + 656, + 467, + 744 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Distribution and Prior Number", + "text_level": 1, + "bbox": [ + 76, + 748, + 299, + 761 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Besides the loss selection, the number of distributions is a vital factor. On the same MegaAge-Asian Dataset, we test the number of distributions from the set 32, 64, 128, 256. Table 8 shows that in general, the number of distributions has a minor effect on the final results and when feature is set 128-dimensional the performance is optimal.", + "bbox": [ + 75, + 763, + 467, + 853 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The selected prior samples work like expert voting, hence we exploit the factor of the prior sample number. Table 8 proves that as the number of samples increases, the", + "bbox": [ + 76, + 854, + 467, + 898 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/034f522ea093b53ab2d800f19fa22bb4e1dc56e702c1394911c698b0a2d8ae7c.jpg", + "table_caption": [ + "Table 7. Loss analysis on MegaAge-Asian. The whole dataset is divided into part1 and part2, with a ratio of $25\\%$ and $75\\%$ ." + ], + "table_footnote": [], + "table_body": "
LS,LMLPlabel accessed toCA(3)CA(5)
Noallall68.2684.26
Yesallall69.6085.42
part2part2part260.2378.54
allpart2part266.5983.62
", + "bbox": [ + 535, + 128, + 856, + 196 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/85d1b4d7be876093740dd775537cc0a51239555b596b07597316e9580b9be5e0.jpg", + "table_caption": [ + "Table 8. Experiments on feature distributions and prior samples." + ], + "table_footnote": [], + "table_body": "
typesnumbersCA(3)CA(5)CA(7)
feature distributions25668.7784.8292.70
12869.6085.4293.26
6468.3984.5992.85
3267.8085.0492.90
prior samples25669.6085.4293.26
12868.7384.9492.80
6467.3483.4291.38
", + "bbox": [ + 513, + 234, + 874, + 345 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "credibility of the results improves, yet the enhancement in credibility gradually diminishes.", + "bbox": [ + 498, + 354, + 890, + 385 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Visualization of what TDT learns", + "text_level": 1, + "bbox": [ + 500, + 396, + 790, + 411 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Fig.3 shows that: once the training is completed, we see feature difference approximates a triangular distribution function on varying symmetric age. The same property can be found for the predicted delta age (Inset (b)) in Fig.3). This results from TDT learning. From the inset (c) in Fig.3, we observe that the symmetry loss range is almost the same, meeting the feature symmetry assumption.", + "bbox": [ + 496, + 420, + 890, + 526 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Fig.4 shows some qualitative comparison on illumination estimation task. Starting from raw image, different prior sample gives a close-to-groundtruth predicted white point, averaged to form the final robust white point. For the 3rd row, the prediction slightly shifts away from the groundtruth, which we guess it is due to multi-illumination.", + "bbox": [ + 496, + 527, + 890, + 617 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "As shown in Fig.5, we study the performance of TDT learning the symmetry axis location. For any pair of facial images, for example an age- $a$ image from test set and an age- $b$ image from the prior set, thus the symmetry axis should locate at $(a + b)/2$ . With $(a + b)/2$ fixed, we alter the testing image and prior image, and draw a histogram of the resulted $\\mathcal{X}_s$ , which in fact gather around the symmetry axis. For pairs of $\\{\\text{age-3}, \\text{age-34}\\}$ , the mean of predicted symmetric age is 18.27, close to the symmetric age 18.50.", + "bbox": [ + 496, + 618, + 890, + 753 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 768, + 617, + 784 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "A learning framework based on the Triangular Distribution Transform is proposed in this paper. It connects the nonlinear feature difference and the corresponding label difference in a verified linear, symmetric, and commutativity manner. This transform can be used as a portable plug-in for vision regression tasks, e.g., we verify its application on three vision tasks. On facial age estimation, aesthetic as-", + "bbox": [ + 496, + 794, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "11025", + "bbox": [ + 478, + 925, + 517, + 936 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/763f1716649e444b17554834266237cf060e94b24d273b1a2b607a251ffbca1a.jpg", + "image_caption": [ + "(a)" + ], + "image_footnote": [], + "bbox": [ + 117, + 85, + 361, + 223 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/db24380c13873a11b37f720445fd0193ef423d863ef389b71f82abb93ef19036.jpg", + "image_caption": [ + "(b)", + "Figure 3. Relationship between symmetric age with the feature discrepancy, predicted delta age, and symmetric loss. (a) feature discrepancy; (b) predicted delta age; (c) symmetric loss" + ], + "image_footnote": [], + "bbox": [ + 364, + 85, + 606, + 223 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/66ed7d3c2b68c755b28ef8e884691ad54b9c196914556773693a63aaefa32173.jpg", + "image_caption": [ + "(c)" + ], + "image_footnote": [], + "bbox": [ + 611, + 85, + 851, + 223 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/2fc0fde64c67b87f4a73053255be22cdd0ab774e115c5d3c24743542658147da.jpg", + "image_caption": [ + "RAW" + ], + "image_footnote": [], + "bbox": [ + 117, + 309, + 243, + 406 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/641ef309663944574d78ca46fadc9a9f3ca88d4fbe785250f0570d437f421004.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 117, + 407, + 243, + 503 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5e3765771c4e80a6de8210ac88e3233590e6a183f860cd4aef914c644ee18596.jpg", + "image_caption": [ + "Figure 4. Qualitative comparison of the final color correction result and those from individual prior samples. In the fourth column, the predictions from different priors (their color corrected images are given in right insets) are shown clustered around the ground truth location, with limited variance. In the rightmost column, prior samples are given." + ], + "image_footnote": [], + "bbox": [ + 117, + 506, + 243, + 602 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c79bed9ffbc6acc698c872ea1f57131352a1b376d13eee1f312f41ade264d4c8.jpg", + "image_caption": [ + "GT" + ], + "image_footnote": [], + "bbox": [ + 251, + 309, + 375, + 406 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c6ad170d51d7f767ac544879e812a9be55c3f46028d582bfb3649421be5448db.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 251, + 407, + 375, + 503 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/aca720403067956f417b1aaca6c27695070059b126951726809b2db37d325c6f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 251, + 506, + 375, + 602 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e0d98c8fbbc985f44f0d387e5b789cc26d9649ad1de08acdcd57225258084772.jpg", + "image_caption": [ + "Ours" + ], + "image_footnote": [], + "bbox": [ + 383, + 309, + 508, + 406 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7a59f2832b3e7971862282b8f55a3ba098ee28b3bed85b418fb1ecb96fa2b8df.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 383, + 407, + 508, + 503 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5b5bacbe0845ac1835ee43e3bbf1ea03eade103623580dfd5c9a1546426b1c8c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 383, + 506, + 509, + 602 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c72d75cf5ef5dfee138ca4b7835f345d76710850fd5a514a67f1fedabd7c043c.jpg", + "image_caption": [ + "Distribution" + ], + "image_footnote": [], + "bbox": [ + 514, + 309, + 661, + 406 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/3884f91cc1c881a78a522964ed9bc1ddd3ff82e997e3916e6e99b845e335347e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 514, + 407, + 663, + 503 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c82bddb0a71b67a96af37a82aa1fe3a42f8db2c202b81c54f29ed591a72c7da0.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 514, + 506, + 663, + 603 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/bea5413bec1dab1e153e57527cc1c27bbac7ef17b6682eec7b0164de1ba71eac.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 666, + 309, + 707, + 406 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a9b2bf6a4ded861df868509bf905e8b3de50b3b8f9b2ce81156e73b61a10b0db.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 666, + 407, + 707, + 503 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/57fed6ca185b85b416232f595960172eb5d6a14b1b95cdaca2aca9f7c76c87ce.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 666, + 506, + 707, + 602 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/317d589a363b82002ceaceda2dfe788b164eef1017d6a91e32e71c3a7935d306.jpg", + "image_caption": [ + "Prior" + ], + "image_footnote": [], + "bbox": [ + 725, + 309, + 851, + 406 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e47b4d979f282f8c4ca428d7b6366a41139101373ac2ecd433e4ad9dac13b7f1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 725, + 407, + 851, + 503 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/1c16103f4be42fd497819229a28079b98e47c26c703f9ba622f3d559d67e6bf9.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 725, + 506, + 851, + 602 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e3405a3b0eee49c9d2e9416d6705f354ab5ddb5f13928ff3c9beced33f1eaab8.jpg", + "image_caption": [ + "Figure 5. Study on the symmetry learnt in $\\mathcal{X}_s$ . For any pair of age- $a$ image from test set and age- $b$ image from the prior set, we draw a histogram of the resulted $\\mathcal{X}_s$ , which in fact gather around the symmetry axis $(a + b) / 2$ , w.r.t. the histogram figure." + ], + "image_footnote": [], + "bbox": [ + 98, + 674, + 447, + 818 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "sessment, and illumination estimation, the proposed TDT obtains on-par or even better performance than the prior arts, without much modification on the affiliated backbone. In the future, we will explore the application of TDT in a wider context, for example shape and pose estimation.", + "bbox": [ + 498, + 676, + 890, + 753 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Acknowledgements", + "text_level": 1, + "bbox": [ + 500, + 763, + 687, + 781 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work is supported by the Natural Science Starting Project of SWPU (No.2022QHZ023), the Sichuan Scientific Innovation Fund (No.2022JDRC0009), the Sichuan Provincial Department of Science and Technology Project (No.2022NSFSC0283) and the Key Research and Development Project of Sichuan Provincial Department of Science and Technology (No.2023YFG0129).", + "bbox": [ + 496, + 787, + 890, + 887 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "11026", + "bbox": [ + 478, + 925, + 519, + 936 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Kobus Barnard, Vlad Cardei, and Brian Funt. 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Comput., 13(3):1605-1618, 2022. 1" + ], + "bbox": [ + 78, + 90, + 468, + 503 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "11029", + "bbox": [ + 478, + 926, + 519, + 936 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Triangular Distribution in Visual World/7d1e6df8-db40-4bc4-aab8-58f2635d78ba_model.json b/2024/Learning Triangular Distribution in Visual World/7d1e6df8-db40-4bc4-aab8-58f2635d78ba_model.json new file mode 100644 index 0000000000000000000000000000000000000000..60ec1731e86fbe06450d945fa8e880b97387555d --- /dev/null +++ b/2024/Learning Triangular Distribution in Visual World/7d1e6df8-db40-4bc4-aab8-58f2635d78ba_model.json @@ -0,0 +1,3225 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.234, + 0.131, + 0.738, + 0.154 + ], + "angle": 0, + "content": "Learning Triangular Distribution in Visual World" + }, + { + "type": "text", + "bbox": [ + 0.104, + 0.18, + 0.92, + 0.217 + ], + "angle": 0, + "content": "Ping Chen\\(^{1}\\), Xingpeng Zhang\\(^{4}\\), Chengtao Zhou\\(^{1}\\), Dichao Fan\\(^{1}\\), Peng Tu\\(^{3}\\), Le Zhang\\(^{1}\\), Yanlin Qian\\(^{1,2*}\\), \\(^{1}\\)MicroBT Inc. \\(^{2}\\)Waseda University, IPS. \\(^{3}\\)RuqiMobility Inc." + }, + { + "type": "text", + "bbox": [ + 0.089, + 0.217, + 0.931, + 0.235 + ], + "angle": 0, + "content": "\\(^{4}\\)School of Computer Science and Software Engineering, Southwest Petroleum University, Chengdu, China" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.301, + 0.474, + 0.59 + ], + "angle": 0, + "content": "Convolution neural network is successful in pervasive vision tasks, including label distribution learning, which usually takes the form of learning an injection from the nonlinear visual features to the well-defined labels. However, how the discrepancy between features is mapped to the label discrepancy is ambient, and its correctness is not guaranteed. To address these problems, we study the mathematical connection between feature and its label, presenting a general and simple framework for label distribution learning. We propose a so-called Triangular Distribution Transform (TDT) to build an injective function between feature and label, guaranteeing that any symmetric feature discrepancy linearly reflects the difference between labels. The proposed TDT can be used as a plug-in in mainstream backbone networks to address different label distribution learning tasks. Experiments on Facial Age Recognition, Illumination Chromaticity Estimation, and Aesthetics assessment show that TDT achieves on-par or better results than the prior arts. Code is available at https://github.com/redcping/TDT." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.611, + 0.21, + 0.627 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.637, + 0.47, + 0.818 + ], + "angle": 0, + "content": "Label distribution learning (LDL) utilizes the advantages of distribution to solve the task of quasi-continuous label or inner-correlation between labels [22, 58]. LDL assigns a distribution over label value to an instance, which can be obtained by fitting a Gaussian or Triangle distribution whose peak indicates the label and represents the relative importance of each label describing an instance [58]. Hence, LDL has an impact on many real-world applications, such as facial age estimation [22], head-pose estimation [20, 23], crowd counting [76], zero-shot learning [35], facial beauty prediction [51], hierarchical classification [68], partial multi-label learning [69] and so on." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.818, + 0.47, + 0.879 + ], + "angle": 0, + "content": "When LDL was first proposed, it mainly used maximum entropy and Kullback-Leibler divergence to learn label distribution [22]. Then, a more efficient optimization method BFGS is proposed to replace the IIS method [19]. The" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.27, + 0.893, + 0.436 + ], + "angle": 0, + "content": "LDL is also widely combined with other algorithms, such as random forest [57], deep convolution neural network [71], hashing method [77], Bayesian [79], metric learning [80] and so on. Although LDL has wide applications, it encounters some challenges, i.e. the feature space and label (solution) space are inhomogeneous [57]. To be more specific, the feature space generated by the model is nonlinear, while the label information is gradually changing. In addition, the existing label distribution is mainly based on label information to construct the distribution, placing the label information for one instance over the whole label distribution." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.437, + 0.895, + 0.738 + ], + "angle": 0, + "content": "Therefore, this article proposes a Triangular Distribution Transform (TDT) method, aiming to linearly map the transformed feature information to its corresponding label information concisely and efficiently. Inspired by label distribution learning [57], we propose using symmetric triangular distributions to represent this symmetric linear transformation. Specifically, the high-dimensional features obtained by feature extraction networks will reflect the relationship between labels through symmetric triangular distributions. To better achieve this goal, we draw inspiration from the paradigm of comparative learning and supply two sets of images to the feature extraction network each time. One set is the prior knowledge that needs to be compared, and the other set is the training sample. Our method is more suitable for visual tasks with linearly continuous changing label information, such as age, aesthetics, lighting intensity, etc. Our TDT can be used as a plug-in in mainstream backbone networks. Therefore, our method has achieved excellent results on multiple visual tasks, such as facial age estimation, image aesthetics estimation, and illumination estimation." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.739, + 0.892, + 0.753 + ], + "angle": 0, + "content": "The contribution of this article is summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.762, + 0.892, + 0.807 + ], + "angle": 0, + "content": "- We analyze to lay the theoretical foundation for the Triangular Distribution Transform, enabling feature discrepancy to explain label difference." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.816, + 0.892, + 0.86 + ], + "angle": 0, + "content": "- We show with the proposed symmetry-related loss and commutativity-related loss, TDT can be learnt by mainstream backbone networks." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.871, + 0.892, + 0.9 + ], + "angle": 0, + "content": "- TDT outperforms other methods on age estimation, aesthetics estimation, and illumination estimation." + }, + { + "type": "list", + "bbox": [ + 0.519, + 0.762, + 0.892, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.412, + 0.901 + ], + "angle": 0, + "content": "*Corresponding author. †These authors contributed equally." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.925, + 0.521, + 0.937 + ], + "angle": 0, + "content": "11019" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.123, + 0.096, + 0.85, + 0.403 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.419, + 0.896, + 0.477 + ], + "angle": 0, + "content": "Figure 1. The overall structure of our TDT. Our pipeline (b) diverges from the general pipeline (a) by incorporating a parameter-free TDT (Triangular Distribution Transform), enabling converting the nonlinear feature to the one which vary \"linearly\" as per Eq.4. Consequently, a linear head module alone suffices to establish the mapping between image features and their respective labels, with clear explanation which is missing for a conventional network head. For detailed information on the TDT loss, please refer to Figure.2." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.5, + 0.226, + 0.516 + ], + "angle": 0, + "content": "2. Related works" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.525, + 0.322, + 0.541 + ], + "angle": 0, + "content": "2.1. Label distribution learning" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.549, + 0.473, + 0.837 + ], + "angle": 0, + "content": "The label distribution method learns the relevance between labels to reflect the relative importance of different labels [21, 22, 29, 58], which can also be seen as a special facial age classification method. Label distribution learning methods learn a label distribution that represents the relative importance of each label when describing an instance[21]. The label distribution covers a certain number of labels. Each label has its description degree, representing the degree to which each label describes the instance[62]. The description degrees of all the labels sum up to 1 [62]. Due to the advantages of label distributed learning, it has achieved very excellent performance in tasks such as facial age estimation[22], head-pose estimation [20, 23], crowd counting [76], zero-shot learning[35], facial beauty prediction[51], hierarchical classification[68], and partial multi-label learning [69]. The label distribution learning method is very consistent with the potential law of big data. Nevertheless, acquiring distributional labels for thousands of face images itself is a non-trivial task[58]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.847, + 0.281, + 0.864 + ], + "angle": 0, + "content": "2.2. Facial Age estimation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.471, + 0.903 + ], + "angle": 0, + "content": "The regression methods [45], classification methods [53], and ranking methods [7, 9] for age estimation pay more" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.501, + 0.895, + 0.775 + ], + "angle": 0, + "content": "attention to putting forward different research methods according to label information. The age regression methods consider labels as continuous numerical values. To handle the heterogeneous data, researchers also proposed hierarchical models [26] and the soft-margin mixture of regression [33]. And age classification regards labels as independent values[53]. It regards each age as a separate category and ignores the similarity of the same person between different ages. While the ranking approaches treat labels as rank-order data and use multiple binary classifiers to determine the age rank in a facial image[7, 9]. Besides, some scholars also focus on the objective optimization function [12, 46]. ML-loss [46] proposed mean-variance loss for robust age estimation via distribution learning. Deng et al. [12] proposed progressive margin loss (PML) for long-tailed age classification. These methods gradually consider that aging is a slow and continuous process, which also means that the processing of label information is significant." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.786, + 0.702, + 0.801 + ], + "angle": 0, + "content": "2.3. Aesthetic Assessment" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.895, + 0.903 + ], + "angle": 0, + "content": "An aesthetic assessment task refers to evaluating the visual beauty and artistic value of given image. Early studies rely on handcrafted features [13, 43, 44], which ignore the spatial features and semantics in assessing aesthetics. In data-driven learning-based methods, NIMA[63] uses Earth Mover's Distance to optimize aesthetic distribution predic" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.925, + 0.52, + 0.937 + ], + "angle": 0, + "content": "11020" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.243 + ], + "angle": 0, + "content": "tion. A-lamp[42] and \\(\\mathrm{MP}_{ada}[59]\\) both achieve good results with a multi-patch approach. Hierarchical Layout-aware Graph Convolution Network (HGCN)[56] captures layout information. TANet [27] adaptively learns aesthetic prediction rules based on identified themes, using Mean Squared Error as the metric. Transformer [28] assign attention levels to color spaces, enabling segmentation learning. Yi et al. [72] effectively combine feature style and general aesthetic information using AdaIN [34] and self-supervised pre-training for accurate aesthetic assessment." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.251, + 0.3, + 0.266 + ], + "angle": 0, + "content": "2.4. Illumination Estimation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.273, + 0.473, + 0.516 + ], + "angle": 0, + "content": "Illumination Estimation is often dubbed as Auto White Balance verbally and aims at measuring the normalized illumination vector given at least one single image. There exists a bunch of traditional methods that are easy to implement but easily fail due to the over-optimistic assumption, for example, White Patch [4], General Gray World [1], Gray Edge [65], Shades-of-Gray [16], LSRS [17], PCA [10] and Grayness Index [49], etc. Relying on labeled data, a bunch of learning-based methods with tunable inner weight e.g. [2, 5, 6, 15, 18, 24, 25, 32, 36, 48, 61] leads the leaderboard by a large gap generally. All aforementioned methods output a single illumination vector in a deterministic way. A few works deal with label distribution learning; Egor et al. [14] proposed an efficient illumination distribution estimation method; FFCC [3] from Barron outputs a unique illumination vector which can be modified as a distribution." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.528, + 0.251, + 0.545 + ], + "angle": 0, + "content": "3. Proposed Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.552, + 0.473, + 0.826 + ], + "angle": 0, + "content": "The pipeline of proposed Triangular distribution learning is illustrated in Fig.1. Fig.1(a) depicts the general pipeline for CNN tasks, where non-linear head modules are employed to map non-linear features to labels due to the linear independence of image features. These non-linear head modules can include modules that combine convolution with nonlinear activation functions, Gaussian Mixture Model, and others. In Fig.1(b), we propose a novel pipeline that differs from the general pipeline. We introduce a parameter-free TDT (Triangular Distribution Transform) after the nonlinear image features, allowing for the possibility of transforming linearly independent image features into linearly correlated ones. As a result, we only need to utilize a linear head module, such as a fully connected (FC) module, in combination with the relevant loss function to achieve linear correlation learning among the features. Additionally, we employ a contrastive learning-like approach to guide the predictions of unknown samples based on known samples." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.833, + 0.471, + 0.863 + ], + "angle": 0, + "content": "3.1. Triangular Distribution Transform on Latent Feature" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.471, + 0.902 + ], + "angle": 0, + "content": "With some ambiguity, vision regression problems can be classified into linear-label problems and nonlinear-label" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.287 + ], + "angle": 0, + "content": "ones. The mapping from the original information modality (for example 2D images, text, voice, video etc.) to the corresponding labels is usually non-linear and hard to model in a fixed rule. Take facial age recognition as an example, age label varies linearly while the visual feature of the facial image usually does not work in the same way. The majority of works on distribution learning mainly focus on learning a mapping from visual features to the label in a nonlinear way, such as the deep net, with its interpretability remaining in suspense. In this article, we discuss the relationship between the feature and its label and present a so-called Triangular Distribution Transform (TDT) to rigidly connect the feature and its label, so that the connection is injective." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.287, + 0.892, + 0.349 + ], + "angle": 0, + "content": "Starting with an input \\(X\\in \\mathbb{R}^{N\\times 3\\times H\\times W}\\) (\\(N\\) is the batch size, \\(3,H,W\\) denotes the channel, height, and width respectively) and its label \\(Y\\), we extract feature by some net module \\(g\\) (parameterized by \\(\\Theta\\)) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.645, + 0.359, + 0.892, + 0.377 + ], + "angle": 0, + "content": "\\[\n\\mathcal {X} _ {g} = g (\\mathcal {X}, \\Theta) \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.386, + 0.892, + 0.462 + ], + "angle": 0, + "content": "where \\(\\mathcal{X}_g\\in \\mathbb{R}^{N\\times C\\times h\\times w}\\) is a C-channel feature extracted from some backbone nets (e.g., ResNet18). The mean and standard deviation are calculated along the \\(h\\) and \\(w\\) dimensions, referred to as \\(\\mu (\\mathcal{X}_g)\\in \\mathbb{R}^{N\\times C\\times 1\\times 1}\\) and \\(\\sigma (\\mathcal{X}_g)\\in\\) \\(\\mathbb{R}^{N\\times C\\times 1\\times 1}\\) respectively." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.463, + 0.892, + 0.54 + ], + "angle": 0, + "content": "Based on the Central Limit Theorem, we assume \\(\\mathcal{X}_g\\) follows Gaussian distribution and denote the probability density function (PDF) as \\(\\phi(\\mathcal{X}_g)\\). Given features for two samples \\((\\mathcal{X}_g^1\\) and \\(\\mathcal{X}_g^2\\)), we define their \"feature difference\" based on the Gaussian distribution of \\(\\mathcal{X}_g^1\\) as:" + }, + { + "type": "equation", + "bbox": [ + 0.502, + 0.548, + 0.892, + 0.607 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) = \\phi \\left(\\mathcal {X} _ {g} ^ {1}\\right) - \\phi \\left(\\mathcal {X} _ {g} ^ {2}\\right) \\tag {2} \\\\ \\propto \\mathcal {N} _ {0, 1} (\\frac {\\mathcal {X} _ {g} ^ {1} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})}) - \\mathcal {N} _ {0, 1} (\\frac {\\mathcal {X} _ {g} ^ {2} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})}) \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.616, + 0.892, + 0.661 + ], + "angle": 0, + "content": "The last part of Eq.2 is the normalized feature difference using the standard Gaussian distribution \\(\\mathcal{N}_{0,1}\\). We give our first assumption:" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.661, + 0.892, + 0.691 + ], + "angle": 0, + "content": "Assumption 1: There exists a function transforming \\(\\mathcal{X}_g\\) to \\(\\mathcal{X}_g'\\), whose change linearly w.r.t. the label." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.691, + 0.892, + 0.752 + ], + "angle": 0, + "content": "To better fit Assumption 1, considering \\(\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2)\\) does not correlate linearly with the label, we approximate the Gaussian distribution in Eq.2 using a symmetric Triangular distribution \\(\\tau (\\cdot |b)\\) following [55], formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.51, + 0.761, + 0.892, + 0.819 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) \\approx \\Delta_ {\\tau} \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) \\tag {3} \\\\ = \\tau (\\frac {\\mathcal {X} _ {g} ^ {1} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})} | b) - \\tau (\\frac {\\mathcal {X} _ {g} ^ {2} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})} | b), \\\\ \\end{array}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.547, + 0.821, + 0.892, + 0.862 + ], + "angle": 0, + "content": "\\[\n\\tau (s | b) = \\left\\{ \\begin{array}{l l} \\frac {1}{b} \\cdot \\left(1 - \\frac {| s |}{b}\\right), & - b \\leq s \\leq b \\\\ 0, & \\text {o t h e r w i s e} \\end{array} \\right. \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "where the scalar \\( b \\) controls the approximation error and is set to \\( \\sqrt{6} \\) (\\( b \\) is obtained via the method of moments in [55])." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.926, + 0.518, + 0.938 + ], + "angle": 0, + "content": "11021" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.1, + 0.089, + 0.357, + 0.288 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.359, + 0.089, + 0.866, + 0.289 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.302, + 0.894, + 0.332 + ], + "angle": 0, + "content": "Figure 2. TDT is learned relying on the commutativity-related loss and symmetry-related loss, while the latter plays the primary role. The feature difference, associated with the symmetry-related loss, is used for result prediction. MSE is the mean square error." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.357, + 0.47, + 0.435 + ], + "angle": 0, + "content": "In contrast to Eq.2, Eq.4 has the property of linearly describing the corresponding label difference. Then we can search a linear function \\( f(\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2)) \\) that transforming the feature difference to the label difference \\( |Y^{1} - Y^{2}| \\), in a linear, symmetric and commutative way1." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.445, + 0.47, + 0.476 + ], + "angle": 0, + "content": "3.2. Optimization towards Triangular Distribution Transform and Vision Tasks" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.484, + 0.47, + 0.576 + ], + "angle": 0, + "content": "The learned feature does not follow Triangular distribution unless we optimize the net towards it. Then we state the optimization loss towards TDT and related task-specific loss. The optimization loss of TDT, shown in Fig.2, aims to gradually transform the non-linear correlation among image features into a linear correlation through label-guided learning." + }, + { + "type": "title", + "bbox": [ + 0.097, + 0.577, + 0.328, + 0.591 + ], + "angle": 0, + "content": "Loss for Triangular Distribution" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.591, + 0.47, + 0.729 + ], + "angle": 0, + "content": "Given two sets of nonlinear features \\(\\mathcal{X}_g^1\\) and \\(\\mathcal{X}_g^2\\) extracted from backbone network, we use multiple convolution layers to learn to make a feature that follows symmetric Triangular distribution, formulated as \\(\\mathcal{X}_s = \\text{Conv}(\\text{Concat}(\\mathcal{X}_g^1, \\mathcal{X}_g^2), \\theta)\\), where the concatenation happens in the batch dimension. We calculate the mean and standard deviation separately for \\(\\mathcal{X}_s\\), \\(\\mathcal{X}_g^1\\) and \\(\\mathcal{X}_g^2\\) along the spatial dimensions. Via Eq.4, we get \\(\\Delta(\\mathcal{X}_s, \\mathcal{X}_g^1)\\) and \\(\\Delta(\\mathcal{X}_s, \\mathcal{X}_g^2)\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.729, + 0.47, + 0.773 + ], + "angle": 0, + "content": "To guide the net to reach a state that \\(\\mathcal{X}_g^1\\) and \\(\\mathcal{X}_g^2\\) are symmetrical around the \"center\" \\(\\mathcal{X}_s\\), a symmetry-related loss is introduced:" + }, + { + "type": "equation", + "bbox": [ + 0.152, + 0.788, + 0.47, + 0.808 + ], + "angle": 0, + "content": "\\[\nL _ {S} = \\left\\| \\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1}\\right) - \\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right) \\right\\| _ {2}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.819, + 0.47, + 0.836 + ], + "angle": 0, + "content": "where the operator \\(\\| \\cdot \\| _2\\) is a L2 loss. Analogously, the" + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.846, + 0.468, + 0.873 + ], + "angle": 0, + "content": "\\(^{1}\\)Linearity: given \\(\\Delta_{\\tau}(\\mathcal{X}_g^1, \\mathcal{X}_g^2) = \\Delta_{\\tau}(\\mathcal{X}_g^2, \\mathcal{X}_g^3)\\), we have \\(Y^{1} - Y^{2} = Y^{2} - Y^{3}\\)." + }, + { + "type": "page_footnote", + "bbox": [ + 0.078, + 0.873, + 0.394, + 0.888 + ], + "angle": 0, + "content": "Symmetry: \\(\\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^1 +\\delta \\mathcal{X}_g) = \\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^1 -\\delta \\mathcal{X}_g)\\)" + }, + { + "type": "page_footnote", + "bbox": [ + 0.079, + 0.888, + 0.337, + 0.902 + ], + "angle": 0, + "content": "Commutativity: \\(\\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^2) = \\Delta_{\\tau}(\\mathcal{X}_g^2,\\mathcal{X}_g^1)\\)." + }, + { + "type": "list", + "bbox": [ + 0.076, + 0.846, + 0.468, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.357, + 0.779, + 0.373 + ], + "angle": 0, + "content": "commutativity-related loss is designed as:" + }, + { + "type": "equation", + "bbox": [ + 0.57, + 0.384, + 0.892, + 0.404 + ], + "angle": 0, + "content": "\\[\nL _ {M} = \\left\\| \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) - \\Delta \\left(\\mathcal {X} _ {g} ^ {2}, \\mathcal {X} _ {g} ^ {1}\\right) \\right\\| _ {2}, \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.415, + 0.892, + 0.461 + ], + "angle": 0, + "content": "Then, to facilitate the learning of the linear function \\( f(\\Delta) \\), we adopt a comparative approach and design a relevant supervised loss:" + }, + { + "type": "equation", + "bbox": [ + 0.515, + 0.472, + 0.892, + 0.513 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} L _ {P} = \\| \\delta (Y) - 2 \\cdot f (\\Delta (\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1}) \\cdot s g n (\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1})) \\| _ {1} \\\\ + \\| \\delta (Y) + 2 \\cdot f \\left(\\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right) \\cdot s g n \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right)\\right) \\| _ {1}, \\tag {7} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.522, + 0.892, + 0.629 + ], + "angle": 0, + "content": "Here, \\( \\| \\cdot \\|_1 \\) refers to smooth L1 operator, \\( \\delta(Y) = Y^2 - Y^1 \\), \\( \\operatorname{sgn}(\\mathcal{X}_s, \\mathcal{X}_g) \\) represents the sign of \\( \\Delta(\\mathcal{X}_s, \\mathcal{X}_g) \\). When \\( \\mathcal{X}_g \\) in the distribution of \\( \\mathcal{X}_s \\) has a cumulative distribution function (CDF) less than 0.5, \\( \\operatorname{sgn}(\\mathcal{X}_s, \\mathcal{X}_g) \\) is considered positive, and vice versa. The first part of Eq.7 represents using samples labeled as \\( Y^2 \\) to predict samples labeled as \\( Y^1 \\), and the other term follows the same principle." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.63, + 0.892, + 0.66 + ], + "angle": 0, + "content": "Therefore, the final loss function for learning the triangular distribution can be formulated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.616, + 0.674, + 0.892, + 0.69 + ], + "angle": 0, + "content": "\\[\nL _ {T} = L _ {S} + L _ {M} + L _ {P}, \\tag {8}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.519, + 0.704, + 0.673, + 0.717 + ], + "angle": 0, + "content": "Loss for Vision Tasks" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.718, + 0.892, + 0.779 + ], + "angle": 0, + "content": "To quickly validate the effectiveness of TDT, we have selected three common visual tasks: facial age recognition, aesthetic assessment, and illumination estimation. Below are the descriptions and loss definitions for these three tasks." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.779, + 0.892, + 0.856 + ], + "angle": 0, + "content": "Facial Age Recognition: Age variation can be considered linear, and we can utilize TDT to draw the relationship between visual feature differences among different images and the corresponding age variation. Therefore, we can directly employ Eq.8 for optimizing age estimation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Aesthetic Assessment: The aesthetic assessment variation in scores can be considered linear, similar to the optimization for the age estimation task, we can also choose" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.925, + 0.52, + 0.937 + ], + "angle": 0, + "content": "11022" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.323, + 0.09, + 0.645, + 0.103 + ], + "angle": 0, + "content": "Table 1. Experiments setting for three tasks evaluated." + }, + { + "type": "table", + "bbox": [ + 0.108, + 0.114, + 0.86, + 0.181 + ], + "angle": 0, + "content": "
TaskBaselineDatasetInput size
Facial Age RecognitionDAA(Resnet18)[8]MegaAge-Asian[75]96 × 96
Aesthetic AssessmentSAAN(Resnet50+VGG19) [72]TAD66K[27]256 × 256
Illumination EstimationFC4(FC, SqueezeNet)[31]Reprocessed Color Checker [18, 60]512 × 512
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.194, + 0.47, + 0.223 + ], + "angle": 0, + "content": "Eq.8 as the overall optimization. In this case, the label corresponds to the aesthetic score." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.224, + 0.47, + 0.345 + ], + "angle": 0, + "content": "Illumination Estimation: In illumination estimation, a key step of automatic white balance, we consider the variation of the illumination to be approximately linear. Additionally, to better capture the differences in illumination angles, we combine Eq.8 and the angle error [31] as the overall optimization function \\( L_{ill} = L_T + \\frac{180}{\\pi} \\cdot \\arccos(p \\cdot p^*) \\), where the \\( p \\) and \\( p^* \\) represent the normalized estimation and ground truth of illumination color, respectively." + }, + { + "type": "code_caption", + "bbox": [ + 0.08, + 0.358, + 0.401, + 0.374 + ], + "angle": 0, + "content": "Algorithm 1 The training process of our method" + }, + { + "type": "text", + "bbox": [ + 0.085, + 0.377, + 0.435, + 0.393 + ], + "angle": 0, + "content": "1: Input: Sample set \\( X \\) and corresponding labels \\( Y \\)" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.394, + 0.203, + 0.408 + ], + "angle": 0, + "content": "2: Output: Loss" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.408, + 0.468, + 0.438 + ], + "angle": 0, + "content": "3: Prior Set Selection: Randomly select \\(N\\) samples \\(X_{2}\\) from the training set with labels \\(Y_{2}\\)." + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.439, + 0.366, + 0.453 + ], + "angle": 0, + "content": "4: for each sample \\(X_{1}\\) in forward pass do" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.453, + 0.433, + 0.468 + ], + "angle": 0, + "content": "5: #Feature fusion and distribution generation" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.468, + 0.451, + 0.484 + ], + "angle": 0, + "content": "6: \\(\\mathcal{X}_g^1, \\mathcal{X}_g^2 \\gets g(X_1, \\Theta), g(X_2, \\Theta) \\# \\text{Extract features}\\)" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.484, + 0.461, + 0.5 + ], + "angle": 0, + "content": "7: \\(N, C, \\bar{h}, w \\gets \\mathcal{X}_g^2\\). shape # \\(C\\) is distribution number" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.5, + 0.316, + 0.514 + ], + "angle": 0, + "content": "8: \\(\\mathcal{X}_q^1\\gets \\mathcal{X}_q^1.\\text{repeat}(N,1,1,1)\\)" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.514, + 0.36, + 0.529 + ], + "angle": 0, + "content": "9: \\(\\mathcal{X}_s\\gets conv(conv(\\mathcal{X}_q^1,\\mathcal{X}_q^2,1),C)\\)" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.529, + 0.439, + 0.544 + ], + "angle": 0, + "content": "10: # Perform TDT operation on \\(\\mathcal{X}_q^1\\) based on \\(\\mathcal{X}_s\\)" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.544, + 0.374, + 0.559 + ], + "angle": 0, + "content": "11: \\(\\mu (\\mathcal{X}_s),\\sigma (\\mathcal{X}_s)\\gets calc\\_ mean\\_ std(\\mathcal{X}_s)\\)" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.559, + 0.439, + 0.582 + ], + "angle": 0, + "content": "12: \\(\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^1)\\gets \\tau (\\frac{\\mathcal{X}_s - \\mu(\\mathcal{X}_s)}{\\sigma(\\mathcal{X}_s)} |b) - \\tau (\\frac{\\mathcal{X}_g^1 - \\mu(\\mathcal{X}_s)}{\\sigma(\\mathcal{X}_s)} |b)\\)" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.582, + 0.401, + 0.595 + ], + "angle": 0, + "content": "13: #Feature-to-Label Difference Mapping" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.595, + 0.343, + 0.611 + ], + "angle": 0, + "content": "14: \\(sgn(\\mathcal{X}_s,\\mathcal{X}_g^1)\\gets (-1)^{cdf(\\mathcal{X}_g^1) > 0.5}\\)" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.611, + 0.44, + 0.628 + ], + "angle": 0, + "content": "15: \\(\\delta Y_{1}\\gets f(\\tilde{\\Delta} (\\mathcal{X}_{s},\\mathcal{X}_{g}^{1})\\cdot sgn(\\mathcal{X}_{s},\\mathcal{X}_{g}^{1}))\\) # via Eq.7" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.628, + 0.31, + 0.643 + ], + "angle": 0, + "content": "16: where \\(f(\\cdot) = fc(gap(\\cdot))\\)" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.643, + 0.418, + 0.658 + ], + "angle": 0, + "content": "17: Optimize TDT, including \\(L_{S}, L_{M}\\), and \\(L_{P}\\)" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.659, + 0.16, + 0.671 + ], + "angle": 0, + "content": "18: end for" + }, + { + "type": "list", + "bbox": [ + 0.085, + 0.377, + 0.468, + 0.671 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.696, + 0.297, + 0.712 + ], + "angle": 0, + "content": "3.3. TDT Algorithm Process" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.438, + 0.735 + ], + "angle": 0, + "content": "To be more clear, we provide pseudocode 1, in 5 parts." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.469, + 0.795 + ], + "angle": 0, + "content": "Prior Samples Selection: Prior samples are several selected training samples, providing comparison with those samples used for training/testing. Features for the prior samples can be pre-computed and integrated into the model." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.469, + 0.87 + ], + "angle": 0, + "content": "Distribution generation: We obtain \\(\\mathcal{X}_s\\) and form its high-dimensional Normal Distribution using \\(\\mu(\\mathcal{X}_s)\\) and \\(\\sigma(\\mathcal{X}_s)\\). After standardizing and approximating, we get a zero-symmetric high-dimensional Triangular Distribution to linearly represent feature differences." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.469, + 0.902 + ], + "angle": 0, + "content": "TDT Operation: It calculates the PDF differences between \\(\\mathcal{X}_s\\) and \\(\\mathcal{X}_g\\) based on the distribution of \\(\\mathcal{X}_s\\) meet" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.192, + 0.892, + 0.239 + ], + "angle": 0, + "content": "\\(\\left|\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2)\\right| = 2\\cdot \\left|\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^1)\\right| = 2\\cdot \\left|\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^2)\\right|\\) Remarkably, TDT is entirely formulaic, parameter-free, and fit any net outputting feature maps." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.24, + 0.892, + 0.316 + ], + "angle": 0, + "content": "Difference Mapping: Base on distribution of \\(\\mathcal{X}_s\\), \\(\\mathcal{X}_s\\) generally has a higher PDF than \\(\\mathcal{X}_g\\), meaning \\(\\Delta(\\mathcal{X}_s, \\mathcal{X}_g) = \\text{pdf}(\\mathcal{X}_s) - \\text{pdf}(\\mathcal{X}_g) \\geq 0\\). We infer feature difference signs from \\(\\text{cdf}(\\mathcal{X}_g) > 0.5\\) and linearly map them to label difference via global average pooling and a linear layer." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.317, + 0.892, + 0.362 + ], + "angle": 0, + "content": "**Optimization:** For commutativity loss, we utilize the mean and std of \\(\\mathcal{X}_g^1\\) and \\(\\mathcal{X}_g^2\\). For symmetry and supervisory losses, those of \\(\\mathcal{X}_s\\) are computed." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.379, + 0.632, + 0.396 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.404, + 0.797, + 0.42 + ], + "angle": 0, + "content": "4.1. Notes and Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.429, + 0.891, + 0.459 + ], + "angle": 0, + "content": "We perform TDT validation on the baseline in three tasks, whose configuration details are shown in Table 1." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.46, + 0.892, + 0.656 + ], + "angle": 0, + "content": "Train and Test notes: As observed in pseudocode 1, our TDT aims to guide the learning of unknown samples using prior samples, resembling contrastive learning. Therefore, for each task experiment, we randomly select a prior set from the training dataset. During training and testing, each batch comprises both the prior set samples used to obtain \\(\\mathcal{X}_g^2\\) and the unknown samples used to obtain \\(\\mathcal{X}_g^1\\). Each unknown sample undergoes TDT operations with all prior samples to make predictions, and the average of these predictions is considered as the final prediction. To reduce feature extraction time during testing, we encapsulate all the features from the prior set into the model parameters, resulting in an optimized model with accelerated inference." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.657, + 0.892, + 0.778 + ], + "angle": 0, + "content": "Common Setting: For all experiments, we used the Adam optimizer, where the weight decay and the momentum were set to 0.0005 and 0.9, respectively. The initial learning rate was set to 0.001 and changed according to cosine learning rate decay. We trained our model using PyTorch on a cluster of 8 RTX 3090 GPUs. In an online manner, we augment all images with random horizontal flipping, scaling, rotation, and translation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.779, + 0.892, + 0.883 + ], + "angle": 0, + "content": "Facial Age Recognition: We utilize the FG-Net [47] dataset, which comprises 1002 facial images from 82 subjects, spanning an age range from 0 to 69. We follow the setup described in the papers [8, 12, 40], employing leave-one-person-out (LOPO) cross-validation. We report the average performance over 82 splits using the Mean Absolute Error (MAE) as the evaluation metric." + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.886, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Additionally, we also use the MegaAge-Asian [75]" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.926, + 0.519, + 0.938 + ], + "angle": 0, + "content": "11023" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.174, + 0.09, + 0.373, + 0.104 + ], + "angle": 0, + "content": "Table 2. CA on MegaAge-Asian." + }, + { + "type": "table", + "bbox": [ + 0.086, + 0.114, + 0.462, + 0.251 + ], + "angle": 0, + "content": "
MethodsPre-trainedCA(3)CA(5)CA(7)
Posterior [75]IMDB-WIKI62.0880.4390.42
MobileNet [54]IMDB-WIKI44.060.6-
DenseNet [70]IMDB-WIKI51.769.4-
SSR-Net [70]IMDB-WIKI54.974.1-
UVA [38]-60.4779.9590.44
LRN(ResNet10) [39]IMDB-WIKI62.8681.4791.34
LRN(ResNet18) [39]IMDB-WIKI64.4582.9591.98
VGG16(norm) [78]ImageNet, IMDB-WIKI, AFAD65.5883.0189.17
PVP+VGG16 [78]ImageNet, IMDB-WIKI, AFAD72.6587.2493.16
DAA(single channel) [8]-67.9784.0692.40
DAA(multi-channel) [8]-68.2984.8492.47
DAA [8]-68.8284.8992.70
TDT (ours)-69.6085.4293.26
" + }, + { + "type": "table_caption", + "bbox": [ + 0.169, + 0.267, + 0.378, + 0.28 + ], + "angle": 0, + "content": "Table 3. MAEs on FG-Net dataset." + }, + { + "type": "table", + "bbox": [ + 0.189, + 0.291, + 0.356, + 0.393 + ], + "angle": 0, + "content": "
MethodsMAEYear
DEX[52]3.092015
MV[46]2.682018
C3AE[74]2.952019
DRFs[58]3.852021
PML[12]2.162021
DAA [8]2.192023
TDT(ours)2.12-
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.414, + 0.468, + 0.504 + ], + "angle": 0, + "content": "Dataset, consisting of 40,000 age-labeled samples spanning 0 to 70 years and 3,945 images for testing. For this dataset, we choose cumulative accuracy (CA) [75] as the evaluation metric, defined as \\( CA(n) = \\frac{K_n}{K} \\times 100 \\), where \\( K \\) is total number of testing images and \\( K_n \\) is the number whose absolute errors are smaller than \\( n \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.506, + 0.469, + 0.55 + ], + "angle": 0, + "content": "We adopt the official implementation of DAA[8] as the baseline for this task while replacing its DAA mapping with our TDT. The output size of \\(\\mathcal{X}_q\\) is set to \\(3\\times 3\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.552, + 0.469, + 0.582 + ], + "angle": 0, + "content": "In this task, 256 images are randomly picked from the training set serves as the prior set for all experiments." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.583, + 0.469, + 0.81 + ], + "angle": 0, + "content": "Aesthetic Assessment: We use TAD66K (Theme and Aesthetics Dataset with 66K images) Dataset [27], a large-scale aesthetic quality assessment database with 47 themes. Images belonging to each theme are annotated independently, with each image containing a minimum of 1200 valid annotations. The aesthetic score of each image is treated as the label. Following TANet[27], the evaluation metric is the Mean Squared Error (MSE). We adopt the same train-test split setting. For the prior set, we select samples by choosing 2 random samples for each score ranging from 0 to 10 with interval 0.1 for each theme. We employ the official implementation of SAAN[72] as the baseline for this task while removing the final average pooling and BN layers. Additionally, we incorporate extra convolutions to obtain \\(\\mathcal{X}_g\\) with size of \\(8\\times 8\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.469, + 0.899 + ], + "angle": 0, + "content": "Illumination Estimation: We use reprocessed Color Checker [18, 60] dataset, one of the most widely adopted datasets in illumination estimation. Following \\(\\mathrm{FC^4}\\) [31], the evaluation metric is the Recovery Angular Error. To facilitate better comparisons, we use the linear fully connected version of \\(\\mathrm{FC^4}\\)-net as the baseline, instead of the non-linear" + }, + { + "type": "table_caption", + "bbox": [ + 0.542, + 0.09, + 0.851, + 0.103 + ], + "angle": 0, + "content": "Table 4. Results on Aesthetic Benchmark TAD66K." + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.114, + 0.892, + 0.251 + ], + "angle": 0, + "content": "
methodPub.BasicMSE
RAPID [41]ACMMM2014incorporate heterogeneous0.0200
PAM[50]ICCV2017residual-based, active learning0.0200
ALamp[42]CVPR2017layout-aware, multi-patch0.0190
NIMA [63]TIP2018predict distribution0.0210
MPada [59]ACMM2018attention, multi-patch0.0220
MLSP [30]CVPR2019staged training,multi-level features0.0190
UIAA [73]TIP2019unified probabilistic formulation0.0210
HGCN [56]CVPR2021graph convolution networks0.0200
TANet [27]IJCAI2022attention, adaptive features0.0161
SAAN [72]CVPR2023AdaIN,self-supervised Pretraining0.0185
TDT(ours)-Triangular Distribution0.0172
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.268, + 0.892, + 0.374 + ], + "angle": 0, + "content": "weight pooling version. With additional convolutional layers, we obtain \\(\\mathcal{X}_g\\in \\mathbb{R}^{N\\times C\\times 8\\times 8}\\). When comparing with the \\(\\mathrm{FC^4}\\) model, we randomly select 128 samples from the training set as the prior set. However, when comparing with the method proposed by Tang et al. [64] that utilizes the extended external sRGB datasets, we choose same images for scene classification as the prior set, but only 1280 samples." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.374, + 0.892, + 0.451 + ], + "angle": 0, + "content": "Following previous AWB works[18, 31, 60], 3-fold cross-validation is used. Standard metrics (mean, median, tri-mean of all the errors, the mean of the lowest \\(25\\%\\), and the mean of the highest \\(25\\%\\) of errors, the 95th percentile error) are reported in terms of angular error in degrees." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.463, + 0.695, + 0.479 + ], + "angle": 0, + "content": "4.2. Results and Analysis" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.487, + 0.661, + 0.502 + ], + "angle": 0, + "content": "Facial Age Estimation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.503, + 0.892, + 0.653 + ], + "angle": 0, + "content": "The quantitative comparison of a list of top-performing methods on the MegaAge-Asian Dataset is shown in Table 2. From the table, we can find that even stocked with pre-training on large-scale datasets, methods like [39, 78] are inferior to ours. Compared with SSR-Net, our improvement is over \\(8\\%\\). PVP [78] gets higher CA(3) and CA(5) indexes, due to the massive pretraining on ImageNet[11], IMDB-WIKI[53], and AFAD[45]. DAA[8], published in 2023, shares the same setting with our proposed method, while TDT obtains better scores in all CA indexes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.655, + 0.892, + 0.716 + ], + "angle": 0, + "content": "To better prove the effectiveness of TDT, we also profile TDT on FG-Net [47], reported in Table 3. Using MAE as the metric, TDT leads the board with the smallest MAE, surpassing the same-setting competitor DAA." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.718, + 0.658, + 0.73 + ], + "angle": 0, + "content": "Aesthetic Assessment." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.733, + 0.892, + 0.824 + ], + "angle": 0, + "content": "In Table 4, we list the MSE scores for the selected and close-related aesthetic works. In an overall manner, TDT ranks second with an MSE score of 0.0172. This improvement simply originates from the deployment of the TDT plugin over SAAN [72], whose MSE is 0.0185, again showing the advantage of the label discriminative ability of TDT." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.825, + 0.677, + 0.838 + ], + "angle": 0, + "content": "Illumination Estimation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.9 + ], + "angle": 0, + "content": "In Table 5, we report the statistics of the predicted angular error for a set of AWB algorithms on the Color Checker Dataset. On metrics like mean, and median values, the TDT based on \\(\\mathrm{FC^4}\\) outperforms other state-of-the-art methods," + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.926, + 0.52, + 0.938 + ], + "angle": 0, + "content": "11024" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.102, + 0.09, + 0.444, + 0.103 + ], + "angle": 0, + "content": "Table 5. Results on AWB Dataset Color Checker Dataset." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.115, + 0.468, + 0.233 + ], + "angle": 0, + "content": "
modelsmeanmed.tri.best25%worst 25%95th pct.
FFCC [3]1.800.951.180.274.65-
FC4(Weighted) [31]1.651.181.270.383.784.73
FC4[31]1.841.271.390.464.205.46
AlexNet FC4 [31]1.771.111.290.343.784.29
Multi-Hypothesis [37]2.101.321.530.365.10-
IGTN [67]1.580.92-0.283.70-
MDLCC [66]1.580.951.110.373.77-
TLCC+sRGB [64]1.510.981.070.333.52-
TDT+FC41.641.121.250.413.804.53
TDT+FC4+sRGB1.460.851.050.263.614.61
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.248, + 0.468, + 0.274 + ], + "angle": 0, + "content": "Table 6. Loss ablation analysis on MegaAge-Asian. \\(\\checkmark\\) and - indicate whether to add this loss to the final loss." + }, + { + "type": "table", + "bbox": [ + 0.137, + 0.286, + 0.408, + 0.343 + ], + "angle": 0, + "content": "
\\( L_S \\)\\( L_M \\)\\( L_P \\)CA(3)CA(5)CA(7)
-✓✓67.7484.3392.51
✓-✓68.4384.6292.60
✓✓✓69.6085.4293.26
" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.359, + 0.468, + 0.39 + ], + "angle": 0, + "content": "such as MDLCC [66] and TLCC [64]. On top of \\(\\mathrm{FC^4}\\), TDT also boosts the performance by a noticeable gap." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.402, + 0.229, + 0.417 + ], + "angle": 0, + "content": "4.3. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.426, + 0.468, + 0.456 + ], + "angle": 0, + "content": "We conduct an ablation study on the loss choice, the number of distributions and prior samples." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.457, + 0.176, + 0.47 + ], + "angle": 0, + "content": "Loss function" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.473, + 0.468, + 0.534 + ], + "angle": 0, + "content": "It is vital to study the impact of different losses in Eq.8 and the results are presented in Table 6. We observe that removing any loss incurs a decrement in the overall performance. And symmetry loss brings the most improvement." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.535, + 0.468, + 0.655 + ], + "angle": 0, + "content": "We design a toy experiment to further analyze the loss function Eq.7. The age loss \\( L_{P} \\) is a supervisory loss due to the label is needed for computing \\( L_{P} \\), while the symmetry-related loss \\( L_{S} \\) and the commutativity-related loss \\( L_{M} \\) are unsupervisory losses. Switching off all nonsupervisory loss, as seen in the top two rows of Table 7, we see a clear CA score drop, indicating the advantage brought by the nonsupervisory loss." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.657, + 0.468, + 0.746 + ], + "angle": 0, + "content": "If we cut off the access to unsupervisory loss for part1 (in other words, for only \\(75\\%\\) data, the unsupersiory loss is calculated), as reported in the bottom half of Table 7, we claim: with increasing unlabeled data, the performance is massively improved, which again verifies the functionality of the symmetry-related and commutativity-related loss." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.749, + 0.3, + 0.762 + ], + "angle": 0, + "content": "Distribution and Prior Number" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.764, + 0.468, + 0.854 + ], + "angle": 0, + "content": "Besides the loss selection, the number of distributions is a vital factor. On the same MegaAge-Asian Dataset, we test the number of distributions from the set 32, 64, 128, 256. Table 8 shows that in general, the number of distributions has a minor effect on the final results and when feature is set 128-dimensional the performance is optimal." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.468, + 0.9 + ], + "angle": 0, + "content": "The selected prior samples work like expert voting, hence we exploit the factor of the prior sample number. Table 8 proves that as the number of samples increases, the" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.09, + 0.892, + 0.117 + ], + "angle": 0, + "content": "Table 7. Loss analysis on MegaAge-Asian. The whole dataset is divided into part1 and part2, with a ratio of \\(25\\%\\) and \\(75\\%\\)." + }, + { + "type": "table", + "bbox": [ + 0.536, + 0.129, + 0.857, + 0.197 + ], + "angle": 0, + "content": "
LS,LMLPlabel accessed toCA(3)CA(5)
Noallall68.2684.26
Yesallall69.6085.42
part2part2part260.2378.54
allpart2part266.5983.62
" + }, + { + "type": "table_caption", + "bbox": [ + 0.505, + 0.211, + 0.885, + 0.225 + ], + "angle": 0, + "content": "Table 8. Experiments on feature distributions and prior samples." + }, + { + "type": "table", + "bbox": [ + 0.514, + 0.236, + 0.875, + 0.346 + ], + "angle": 0, + "content": "
typesnumbersCA(3)CA(5)CA(7)
feature distributions25668.7784.8292.70
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" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.356, + 0.892, + 0.386 + ], + "angle": 0, + "content": "credibility of the results improves, yet the enhancement in credibility gradually diminishes." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.397, + 0.791, + 0.412 + ], + "angle": 0, + "content": "4.4. Visualization of what TDT learns" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.421, + 0.892, + 0.527 + ], + "angle": 0, + "content": "Fig.3 shows that: once the training is completed, we see feature difference approximates a triangular distribution function on varying symmetric age. The same property can be found for the predicted delta age (Inset (b)) in Fig.3). This results from TDT learning. From the inset (c) in Fig.3, we observe that the symmetry loss range is almost the same, meeting the feature symmetry assumption." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.528, + 0.892, + 0.618 + ], + "angle": 0, + "content": "Fig.4 shows some qualitative comparison on illumination estimation task. Starting from raw image, different prior sample gives a close-to-groundtruth predicted white point, averaged to form the final robust white point. For the 3rd row, the prediction slightly shifts away from the groundtruth, which we guess it is due to multi-illumination." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.619, + 0.892, + 0.755 + ], + "angle": 0, + "content": "As shown in Fig.5, we study the performance of TDT learning the symmetry axis location. For any pair of facial images, for example an age-\\(a\\) image from test set and an age-\\(b\\) image from the prior set, thus the symmetry axis should locate at \\((a + b)/2\\). With \\((a + b)/2\\) fixed, we alter the testing image and prior image, and draw a histogram of the resulted \\(\\mathcal{X}_s\\), which in fact gather around the symmetry axis. For pairs of \\(\\{\\text{age-3}, \\text{age-34}\\}\\), the mean of predicted symmetric age is 18.27, close to the symmetric age 18.50." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.77, + 0.619, + 0.785 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.901 + ], + "angle": 0, + "content": "A learning framework based on the Triangular Distribution Transform is proposed in this paper. It connects the nonlinear feature difference and the corresponding label difference in a verified linear, symmetric, and commutativity manner. This transform can be used as a portable plug-in for vision regression tasks, e.g., we verify its application on three vision tasks. On facial age estimation, aesthetic as-" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.926, + 0.519, + 0.938 + ], + "angle": 0, + "content": "11025" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.119, + 0.087, + 0.362, + 0.224 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.246, + 0.226, + 0.261, + 0.236 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.365, + 0.087, + 0.607, + 0.224 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.495, + 0.226, + 0.51, + 0.236 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image", + "bbox": [ + 0.612, + 0.087, + 0.852, + 0.224 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.746, + 0.226, + 0.761, + 0.236 + ], + "angle": 0, + "content": "(c)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.252, + 0.892, + 0.281 + ], + "angle": 0, + "content": "Figure 3. Relationship between symmetric age with the feature discrepancy, predicted delta age, and symmetric loss. (a) feature discrepancy; (b) predicted delta age; (c) symmetric loss" + }, + { + "type": "image_caption", + "bbox": [ + 0.163, + 0.294, + 0.201, + 0.308 + ], + "angle": 0, + "content": "RAW" + }, + { + "type": "image", + "bbox": [ + 0.119, + 0.31, + 0.245, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.119, + 0.409, + 0.244, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.119, + 0.507, + 0.244, + 0.603 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.304, + 0.295, + 0.327, + 0.307 + ], + "angle": 0, + "content": "GT" + }, + { + "type": "image", + "bbox": [ + 0.252, + 0.31, + 0.376, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.252, + 0.409, + 0.376, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.252, + 0.507, + 0.377, + 0.603 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.432, + 0.295, + 0.464, + 0.307 + ], + "angle": 0, + "content": "Ours" + }, + { + "type": "image", + "bbox": [ + 0.384, + 0.31, + 0.509, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.384, + 0.409, + 0.509, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.384, + 0.507, + 0.51, + 0.603 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.567, + 0.295, + 0.64, + 0.307 + ], + "angle": 0, + "content": "Distribution" + }, + { + "type": "image", + "bbox": [ + 0.515, + 0.31, + 0.663, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.515, + 0.409, + 0.664, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.515, + 0.507, + 0.664, + 0.604 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.667, + 0.31, + 0.708, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.667, + 0.409, + 0.708, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.667, + 0.507, + 0.708, + 0.603 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.773, + 0.294, + 0.806, + 0.306 + ], + "angle": 0, + "content": "Prior" + }, + { + "type": "image", + "bbox": [ + 0.727, + 0.31, + 0.852, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.727, + 0.409, + 0.852, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.727, + 0.507, + 0.852, + 0.603 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.615, + 0.894, + 0.658 + ], + "angle": 0, + "content": "Figure 4. Qualitative comparison of the final color correction result and those from individual prior samples. In the fourth column, the predictions from different priors (their color corrected images are given in right insets) are shown clustered around the ground truth location, with limited variance. In the rightmost column, prior samples are given." + }, + { + "type": "image", + "bbox": [ + 0.099, + 0.675, + 0.449, + 0.819 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.831, + 0.471, + 0.888 + ], + "angle": 0, + "content": "Figure 5. Study on the symmetry learnt in \\(\\mathcal{X}_s\\). For any pair of age-\\(a\\) image from test set and age-\\(b\\) image from the prior set, we draw a histogram of the resulted \\(\\mathcal{X}_s\\), which in fact gather around the symmetry axis \\((a + b) / 2\\), w.r.t. the histogram figure." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.678, + 0.892, + 0.754 + ], + "angle": 0, + "content": "sessment, and illumination estimation, the proposed TDT obtains on-par or even better performance than the prior arts, without much modification on the affiliated backbone. In the future, we will explore the application of TDT in a wider context, for example shape and pose estimation." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.765, + 0.688, + 0.782 + ], + "angle": 0, + "content": "6. Acknowledgements" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.789, + 0.892, + 0.888 + ], + "angle": 0, + "content": "This work is supported by the Natural Science Starting Project of SWPU (No.2022QHZ023), the Sichuan Scientific Innovation Fund (No.2022JDRC0009), the Sichuan Provincial Department of Science and Technology Project (No.2022NSFSC0283) and the Key Research and Development Project of Sichuan Provincial Department of Science and Technology (No.2023YFG0129)." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.926, + 0.52, + 0.938 + ], + "angle": 0, + "content": "11026" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.468, + 0.17 + ], + "angle": 0, + "content": "[1] Kobus Barnard, Vlad Cardei, and Brian Funt. A comparison of computational color constancy algorithms. i: Methodology and experiments with synthesized data. 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Comput., 13(3):1605-1618, 2022. 1" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.47, + 0.504 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.927, + 0.52, + 0.938 + ], + "angle": 0, + "content": "11029" + } + ] +] \ No newline at end of file diff --git a/2024/Learning Triangular Distribution in Visual World/7d1e6df8-db40-4bc4-aab8-58f2635d78ba_origin.pdf b/2024/Learning Triangular Distribution in Visual World/7d1e6df8-db40-4bc4-aab8-58f2635d78ba_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..62aa63aa23a1d7ebe36420756a45a844d597a6fb --- /dev/null +++ b/2024/Learning Triangular Distribution in Visual World/7d1e6df8-db40-4bc4-aab8-58f2635d78ba_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:6bf5b959f904e50c524c13648bb756942054227627ab5916a885bdce023947b1 +size 7002877 diff --git a/2024/Learning Triangular Distribution in Visual World/full.md b/2024/Learning Triangular Distribution in Visual World/full.md new file mode 100644 index 0000000000000000000000000000000000000000..83ec88e74446d32104ce5828ed6bbe69f457c258 --- /dev/null +++ b/2024/Learning Triangular Distribution in Visual World/full.md @@ -0,0 +1,440 @@ +# Learning Triangular Distribution in Visual World + +Ping Chen $^{1}$ , Xingpeng Zhang $^{4}$ , Chengtao Zhou $^{1}$ , Dichao Fan $^{1}$ , Peng Tu $^{3}$ , Le Zhang $^{1}$ , Yanlin Qian $^{1,2*}$ , $^{1}$ MicroBT Inc. $^{2}$ Waseda University, IPS. $^{3}$ RuqiMobility Inc. + +$^{4}$ School of Computer Science and Software Engineering, Southwest Petroleum University, Chengdu, China + +# Abstract + +Convolution neural network is successful in pervasive vision tasks, including label distribution learning, which usually takes the form of learning an injection from the nonlinear visual features to the well-defined labels. However, how the discrepancy between features is mapped to the label discrepancy is ambient, and its correctness is not guaranteed. To address these problems, we study the mathematical connection between feature and its label, presenting a general and simple framework for label distribution learning. We propose a so-called Triangular Distribution Transform (TDT) to build an injective function between feature and label, guaranteeing that any symmetric feature discrepancy linearly reflects the difference between labels. The proposed TDT can be used as a plug-in in mainstream backbone networks to address different label distribution learning tasks. Experiments on Facial Age Recognition, Illumination Chromaticity Estimation, and Aesthetics assessment show that TDT achieves on-par or better results than the prior arts. Code is available at https://github.com/redcping/TDT. + +# 1. Introduction + +Label distribution learning (LDL) utilizes the advantages of distribution to solve the task of quasi-continuous label or inner-correlation between labels [22, 58]. LDL assigns a distribution over label value to an instance, which can be obtained by fitting a Gaussian or Triangle distribution whose peak indicates the label and represents the relative importance of each label describing an instance [58]. Hence, LDL has an impact on many real-world applications, such as facial age estimation [22], head-pose estimation [20, 23], crowd counting [76], zero-shot learning [35], facial beauty prediction [51], hierarchical classification [68], partial multi-label learning [69] and so on. + +When LDL was first proposed, it mainly used maximum entropy and Kullback-Leibler divergence to learn label distribution [22]. Then, a more efficient optimization method BFGS is proposed to replace the IIS method [19]. The + +LDL is also widely combined with other algorithms, such as random forest [57], deep convolution neural network [71], hashing method [77], Bayesian [79], metric learning [80] and so on. Although LDL has wide applications, it encounters some challenges, i.e. the feature space and label (solution) space are inhomogeneous [57]. To be more specific, the feature space generated by the model is nonlinear, while the label information is gradually changing. In addition, the existing label distribution is mainly based on label information to construct the distribution, placing the label information for one instance over the whole label distribution. + +Therefore, this article proposes a Triangular Distribution Transform (TDT) method, aiming to linearly map the transformed feature information to its corresponding label information concisely and efficiently. Inspired by label distribution learning [57], we propose using symmetric triangular distributions to represent this symmetric linear transformation. Specifically, the high-dimensional features obtained by feature extraction networks will reflect the relationship between labels through symmetric triangular distributions. To better achieve this goal, we draw inspiration from the paradigm of comparative learning and supply two sets of images to the feature extraction network each time. One set is the prior knowledge that needs to be compared, and the other set is the training sample. Our method is more suitable for visual tasks with linearly continuous changing label information, such as age, aesthetics, lighting intensity, etc. Our TDT can be used as a plug-in in mainstream backbone networks. Therefore, our method has achieved excellent results on multiple visual tasks, such as facial age estimation, image aesthetics estimation, and illumination estimation. + +The contribution of this article is summarized as follows: + +- We analyze to lay the theoretical foundation for the Triangular Distribution Transform, enabling feature discrepancy to explain label difference. +- We show with the proposed symmetry-related loss and commutativity-related loss, TDT can be learnt by mainstream backbone networks. +- TDT outperforms other methods on age estimation, aesthetics estimation, and illumination estimation. + +![](images/7cef8ab8c4868c5ac129958296e36327551fc0786bc3351f925674c0698821f6.jpg) +Figure 1. The overall structure of our TDT. Our pipeline (b) diverges from the general pipeline (a) by incorporating a parameter-free TDT (Triangular Distribution Transform), enabling converting the nonlinear feature to the one which vary "linearly" as per Eq.4. Consequently, a linear head module alone suffices to establish the mapping between image features and their respective labels, with clear explanation which is missing for a conventional network head. For detailed information on the TDT loss, please refer to Figure.2. + +# 2. Related works + +# 2.1. Label distribution learning + +The label distribution method learns the relevance between labels to reflect the relative importance of different labels [21, 22, 29, 58], which can also be seen as a special facial age classification method. Label distribution learning methods learn a label distribution that represents the relative importance of each label when describing an instance[21]. The label distribution covers a certain number of labels. Each label has its description degree, representing the degree to which each label describes the instance[62]. The description degrees of all the labels sum up to 1 [62]. Due to the advantages of label distributed learning, it has achieved very excellent performance in tasks such as facial age estimation[22], head-pose estimation [20, 23], crowd counting [76], zero-shot learning[35], facial beauty prediction[51], hierarchical classification[68], and partial multi-label learning [69]. The label distribution learning method is very consistent with the potential law of big data. Nevertheless, acquiring distributional labels for thousands of face images itself is a non-trivial task[58]. + +# 2.2. Facial Age estimation + +The regression methods [45], classification methods [53], and ranking methods [7, 9] for age estimation pay more + +attention to putting forward different research methods according to label information. The age regression methods consider labels as continuous numerical values. To handle the heterogeneous data, researchers also proposed hierarchical models [26] and the soft-margin mixture of regression [33]. And age classification regards labels as independent values[53]. It regards each age as a separate category and ignores the similarity of the same person between different ages. While the ranking approaches treat labels as rank-order data and use multiple binary classifiers to determine the age rank in a facial image[7, 9]. Besides, some scholars also focus on the objective optimization function [12, 46]. ML-loss [46] proposed mean-variance loss for robust age estimation via distribution learning. Deng et al. [12] proposed progressive margin loss (PML) for long-tailed age classification. These methods gradually consider that aging is a slow and continuous process, which also means that the processing of label information is significant. + +# 2.3. Aesthetic Assessment + +An aesthetic assessment task refers to evaluating the visual beauty and artistic value of given image. Early studies rely on handcrafted features [13, 43, 44], which ignore the spatial features and semantics in assessing aesthetics. In data-driven learning-based methods, NIMA[63] uses Earth Mover's Distance to optimize aesthetic distribution predic + +tion. A-lamp[42] and $\mathrm{MP}_{ada}[59]$ both achieve good results with a multi-patch approach. Hierarchical Layout-aware Graph Convolution Network (HGCN)[56] captures layout information. TANet [27] adaptively learns aesthetic prediction rules based on identified themes, using Mean Squared Error as the metric. Transformer [28] assign attention levels to color spaces, enabling segmentation learning. Yi et al. [72] effectively combine feature style and general aesthetic information using AdaIN [34] and self-supervised pre-training for accurate aesthetic assessment. + +# 2.4. Illumination Estimation + +Illumination Estimation is often dubbed as Auto White Balance verbally and aims at measuring the normalized illumination vector given at least one single image. There exists a bunch of traditional methods that are easy to implement but easily fail due to the over-optimistic assumption, for example, White Patch [4], General Gray World [1], Gray Edge [65], Shades-of-Gray [16], LSRS [17], PCA [10] and Grayness Index [49], etc. Relying on labeled data, a bunch of learning-based methods with tunable inner weight e.g. [2, 5, 6, 15, 18, 24, 25, 32, 36, 48, 61] leads the leaderboard by a large gap generally. All aforementioned methods output a single illumination vector in a deterministic way. A few works deal with label distribution learning; Egor et al. [14] proposed an efficient illumination distribution estimation method; FFCC [3] from Barron outputs a unique illumination vector which can be modified as a distribution. + +# 3. Proposed Method + +The pipeline of proposed Triangular distribution learning is illustrated in Fig.1. Fig.1(a) depicts the general pipeline for CNN tasks, where non-linear head modules are employed to map non-linear features to labels due to the linear independence of image features. These non-linear head modules can include modules that combine convolution with nonlinear activation functions, Gaussian Mixture Model, and others. In Fig.1(b), we propose a novel pipeline that differs from the general pipeline. We introduce a parameter-free TDT (Triangular Distribution Transform) after the nonlinear image features, allowing for the possibility of transforming linearly independent image features into linearly correlated ones. As a result, we only need to utilize a linear head module, such as a fully connected (FC) module, in combination with the relevant loss function to achieve linear correlation learning among the features. Additionally, we employ a contrastive learning-like approach to guide the predictions of unknown samples based on known samples. + +# 3.1. Triangular Distribution Transform on Latent Feature + +With some ambiguity, vision regression problems can be classified into linear-label problems and nonlinear-label + +ones. The mapping from the original information modality (for example 2D images, text, voice, video etc.) to the corresponding labels is usually non-linear and hard to model in a fixed rule. Take facial age recognition as an example, age label varies linearly while the visual feature of the facial image usually does not work in the same way. The majority of works on distribution learning mainly focus on learning a mapping from visual features to the label in a nonlinear way, such as the deep net, with its interpretability remaining in suspense. In this article, we discuss the relationship between the feature and its label and present a so-called Triangular Distribution Transform (TDT) to rigidly connect the feature and its label, so that the connection is injective. + +Starting with an input $X\in \mathbb{R}^{N\times 3\times H\times W}$ ( $N$ is the batch size, $3,H,W$ denotes the channel, height, and width respectively) and its label $Y$ , we extract feature by some net module $g$ (parameterized by $\Theta$ ) as follows: + +$$ +\mathcal {X} _ {g} = g (\mathcal {X}, \Theta) \tag {1} +$$ + +where $\mathcal{X}_g\in \mathbb{R}^{N\times C\times h\times w}$ is a C-channel feature extracted from some backbone nets (e.g., ResNet18). The mean and standard deviation are calculated along the $h$ and $w$ dimensions, referred to as $\mu (\mathcal{X}_g)\in \mathbb{R}^{N\times C\times 1\times 1}$ and $\sigma (\mathcal{X}_g)\in$ $\mathbb{R}^{N\times C\times 1\times 1}$ respectively. + +Based on the Central Limit Theorem, we assume $\mathcal{X}_g$ follows Gaussian distribution and denote the probability density function (PDF) as $\phi(\mathcal{X}_g)$ . Given features for two samples $(\mathcal{X}_g^1$ and $\mathcal{X}_g^2$ ), we define their "feature difference" based on the Gaussian distribution of $\mathcal{X}_g^1$ as: + +$$ +\begin{array}{l} \Delta \left(\mathcal {X} _ {g} ^ {1}, \mathcal {X} _ {g} ^ {2}\right) = \phi \left(\mathcal {X} _ {g} ^ {1}\right) - \phi \left(\mathcal {X} _ {g} ^ {2}\right) \tag {2} \\ \propto \mathcal {N} _ {0, 1} (\frac {\mathcal {X} _ {g} ^ {1} - \mu (\mathcal {X} _ {g} ^ {1})}{\sigma (\mathcal {X} _ {g} ^ {1})}) - \mathcal {N} _ {0, 1} (\frac {\mathcal {X} _ {g} ^ {2} - \mu (\mathcal {X} _ {g} ^ {1})}{\sigma (\mathcal {X} _ {g} ^ {1})}) \\ \end{array} +$$ + +The last part of Eq.2 is the normalized feature difference using the standard Gaussian distribution $\mathcal{N}_{0,1}$ . We give our first assumption: + +Assumption 1: There exists a function transforming $\mathcal{X}_g$ to $\mathcal{X}_g'$ , whose change linearly w.r.t. the label. + +To better fit Assumption 1, considering $\Delta (\mathcal{X}_g^1,\mathcal{X}_g^2)$ does not correlate linearly with the label, we approximate the Gaussian distribution in Eq.2 using a symmetric Triangular distribution $\tau (\cdot |b)$ following [55], formulated as: + +$$ +\begin{array}{l} \Delta \left(\mathcal {X} _ {g} ^ {1}, \mathcal {X} _ {g} ^ {2}\right) \approx \Delta_ {\tau} \left(\mathcal {X} _ {g} ^ {1}, \mathcal {X} _ {g} ^ {2}\right) \tag {3} \\ = \tau (\frac {\mathcal {X} _ {g} ^ {1} - \mu (\mathcal {X} _ {g} ^ {1})}{\sigma (\mathcal {X} _ {g} ^ {1})} | b) - \tau (\frac {\mathcal {X} _ {g} ^ {2} - \mu (\mathcal {X} _ {g} ^ {1})}{\sigma (\mathcal {X} _ {g} ^ {1})} | b), \\ \end{array} +$$ + +$$ +\tau (s | b) = \left\{ \begin{array}{l l} \frac {1}{b} \cdot \left(1 - \frac {| s |}{b}\right), & - b \leq s \leq b \\ 0, & \text {o t h e r w i s e} \end{array} \right. \tag {4} +$$ + +where the scalar $b$ controls the approximation error and is set to $\sqrt{6}$ ( $b$ is obtained via the method of moments in [55]). + +![](images/f20923bffec47bae74c97127bebeed8465581225dd036282b70a54c53625bf8b.jpg) +Figure 2. TDT is learned relying on the commutativity-related loss and symmetry-related loss, while the latter plays the primary role. The feature difference, associated with the symmetry-related loss, is used for result prediction. MSE is the mean square error. + +![](images/e469feb9545e454a5030504f9bda8bc692e1da588d25d21fedb6f5085dc2e254.jpg) + +In contrast to Eq.2, Eq.4 has the property of linearly describing the corresponding label difference. Then we can search a linear function $f(\Delta (\mathcal{X}_g^1,\mathcal{X}_g^2))$ that transforming the feature difference to the label difference $|Y^{1} - Y^{2}|$ , in a linear, symmetric and commutative way1. + +# 3.2. Optimization towards Triangular Distribution Transform and Vision Tasks + +The learned feature does not follow Triangular distribution unless we optimize the net towards it. Then we state the optimization loss towards TDT and related task-specific loss. The optimization loss of TDT, shown in Fig.2, aims to gradually transform the non-linear correlation among image features into a linear correlation through label-guided learning. + +# Loss for Triangular Distribution + +Given two sets of nonlinear features $\mathcal{X}_g^1$ and $\mathcal{X}_g^2$ extracted from backbone network, we use multiple convolution layers to learn to make a feature that follows symmetric Triangular distribution, formulated as $\mathcal{X}_s = \text{Conv}(\text{Concat}(\mathcal{X}_g^1, \mathcal{X}_g^2), \theta)$ , where the concatenation happens in the batch dimension. We calculate the mean and standard deviation separately for $\mathcal{X}_s$ , $\mathcal{X}_g^1$ and $\mathcal{X}_g^2$ along the spatial dimensions. Via Eq.4, we get $\Delta(\mathcal{X}_s, \mathcal{X}_g^1)$ and $\Delta(\mathcal{X}_s, \mathcal{X}_g^2)$ . + +To guide the net to reach a state that $\mathcal{X}_g^1$ and $\mathcal{X}_g^2$ are symmetrical around the "center" $\mathcal{X}_s$ , a symmetry-related loss is introduced: + +$$ +L _ {S} = \left\| \Delta \left(\mathcal {X} _ {s}, \mathcal {X} _ {g} ^ {1}\right) - \Delta \left(\mathcal {X} _ {s}, \mathcal {X} _ {g} ^ {2}\right) \right\| _ {2}, \tag {5} +$$ + +where the operator $\| \cdot \| _2$ is a L2 loss. Analogously, the + +commutativity-related loss is designed as: + +$$ +L _ {M} = \left\| \Delta \left(\mathcal {X} _ {g} ^ {1}, \mathcal {X} _ {g} ^ {2}\right) - \Delta \left(\mathcal {X} _ {g} ^ {2}, \mathcal {X} _ {g} ^ {1}\right) \right\| _ {2}, \tag {6} +$$ + +Then, to facilitate the learning of the linear function $f(\Delta)$ , we adopt a comparative approach and design a relevant supervised loss: + +$$ +\begin{array}{l} L _ {P} = \| \delta (Y) - 2 \cdot f (\Delta (\mathcal {X} _ {s}, \mathcal {X} _ {g} ^ {1}) \cdot s g n (\mathcal {X} _ {s}, \mathcal {X} _ {g} ^ {1})) \| _ {1} \\ + \| \delta (Y) + 2 \cdot f \left(\Delta \left(\mathcal {X} _ {s}, \mathcal {X} _ {g} ^ {2}\right) \cdot s g n \left(\mathcal {X} _ {s}, \mathcal {X} _ {g} ^ {2}\right)\right) \| _ {1}, \tag {7} \\ \end{array} +$$ + +Here, $\| \cdot \|_1$ refers to smooth L1 operator, $\delta(Y) = Y^2 - Y^1$ , $\operatorname{sgn}(\mathcal{X}_s, \mathcal{X}_g)$ represents the sign of $\Delta(\mathcal{X}_s, \mathcal{X}_g)$ . When $\mathcal{X}_g$ in the distribution of $\mathcal{X}_s$ has a cumulative distribution function (CDF) less than 0.5, $\operatorname{sgn}(\mathcal{X}_s, \mathcal{X}_g)$ is considered positive, and vice versa. The first part of Eq.7 represents using samples labeled as $Y^2$ to predict samples labeled as $Y^1$ , and the other term follows the same principle. + +Therefore, the final loss function for learning the triangular distribution can be formulated as follows: + +$$ +L _ {T} = L _ {S} + L _ {M} + L _ {P}, \tag {8} +$$ + +# Loss for Vision Tasks + +To quickly validate the effectiveness of TDT, we have selected three common visual tasks: facial age recognition, aesthetic assessment, and illumination estimation. Below are the descriptions and loss definitions for these three tasks. + +Facial Age Recognition: Age variation can be considered linear, and we can utilize TDT to draw the relationship between visual feature differences among different images and the corresponding age variation. Therefore, we can directly employ Eq.8 for optimizing age estimation. + +Aesthetic Assessment: The aesthetic assessment variation in scores can be considered linear, similar to the optimization for the age estimation task, we can also choose + +Table 1. Experiments setting for three tasks evaluated. + +
TaskBaselineDatasetInput size
Facial Age RecognitionDAA(Resnet18)[8]MegaAge-Asian[75]96 × 96
Aesthetic AssessmentSAAN(Resnet50+VGG19) [72]TAD66K[27]256 × 256
Illumination EstimationFC4(FC, SqueezeNet)[31]Reprocessed Color Checker [18, 60]512 × 512
+ +Eq.8 as the overall optimization. In this case, the label corresponds to the aesthetic score. + +Illumination Estimation: In illumination estimation, a key step of automatic white balance, we consider the variation of the illumination to be approximately linear. Additionally, to better capture the differences in illumination angles, we combine Eq.8 and the angle error [31] as the overall optimization function $L_{ill} = L_T + \frac{180}{\pi} \cdot \arccos(p \cdot p^*)$ , where the $p$ and $p^*$ represent the normalized estimation and ground truth of illumination color, respectively. + +Algorithm 1 The training process of our method + +1: Input: Sample set $X$ and corresponding labels $Y$ +2: Output: Loss +3: Prior Set Selection: Randomly select $N$ samples $X_{2}$ from the training set with labels $Y_{2}$ . +4: for each sample $X_{1}$ in forward pass do +5: #Feature fusion and distribution generation +6: $\mathcal{X}_g^1, \mathcal{X}_g^2 \gets g(X_1, \Theta), g(X_2, \Theta) \# \text{Extract features}$ +7: $N, C, \bar{h}, w \gets \mathcal{X}_g^2$ . shape # $C$ is distribution number +8: $\mathcal{X}_q^1\gets \mathcal{X}_q^1.\text{repeat}(N,1,1,1)$ +9: $\mathcal{X}_s\gets conv(conv(\mathcal{X}_q^1,\mathcal{X}_q^2,1),C)$ +10: # Perform TDT operation on $\mathcal{X}_q^1$ based on $\mathcal{X}_s$ +11: $\mu (\mathcal{X}_s),\sigma (\mathcal{X}_s)\gets calc\_ mean\_ std(\mathcal{X}_s)$ +12: $\Delta (\mathcal{X}_s,\mathcal{X}_g^1)\gets \tau (\frac{\mathcal{X}_s - \mu(\mathcal{X}_s)}{\sigma(\mathcal{X}_s)} |b) - \tau (\frac{\mathcal{X}_g^1 - \mu(\mathcal{X}_s)}{\sigma(\mathcal{X}_s)} |b)$ +13: #Feature-to-Label Difference Mapping +14: $sgn(\mathcal{X}_s,\mathcal{X}_g^1)\gets (-1)^{cdf(\mathcal{X}_g^1) > 0.5}$ +15: $\delta Y_{1}\gets f(\tilde{\Delta} (\mathcal{X}_{s},\mathcal{X}_{g}^{1})\cdot sgn(\mathcal{X}_{s},\mathcal{X}_{g}^{1}))$ # via Eq.7 +16: where $f(\cdot) = fc(gap(\cdot))$ +17: Optimize TDT, including $L_{S}, L_{M}$ , and $L_{P}$ +18: end for + +# 3.3. TDT Algorithm Process + +To be more clear, we provide pseudocode 1, in 5 parts. + +Prior Samples Selection: Prior samples are several selected training samples, providing comparison with those samples used for training/testing. Features for the prior samples can be pre-computed and integrated into the model. + +Distribution generation: We obtain $\mathcal{X}_s$ and form its high-dimensional Normal Distribution using $\mu(\mathcal{X}_s)$ and $\sigma(\mathcal{X}_s)$ . After standardizing and approximating, we get a zero-symmetric high-dimensional Triangular Distribution to linearly represent feature differences. + +TDT Operation: It calculates the PDF differences between $\mathcal{X}_s$ and $\mathcal{X}_g$ based on the distribution of $\mathcal{X}_s$ meet + +$\left|\Delta (\mathcal{X}_g^1,\mathcal{X}_g^2)\right| = 2\cdot \left|\Delta (\mathcal{X}_s,\mathcal{X}_g^1)\right| = 2\cdot \left|\Delta (\mathcal{X}_s,\mathcal{X}_g^2)\right|$ Remarkably, TDT is entirely formulaic, parameter-free, and fit any net outputting feature maps. + +Difference Mapping: Base on distribution of $\mathcal{X}_s$ , $\mathcal{X}_s$ generally has a higher PDF than $\mathcal{X}_g$ , meaning $\Delta(\mathcal{X}_s, \mathcal{X}_g) = \text{pdf}(\mathcal{X}_s) - \text{pdf}(\mathcal{X}_g) \geq 0$ . We infer feature difference signs from $\text{cdf}(\mathcal{X}_g) > 0.5$ and linearly map them to label difference via global average pooling and a linear layer. + +**Optimization:** For commutativity loss, we utilize the mean and std of $\mathcal{X}_g^1$ and $\mathcal{X}_g^2$ . For symmetry and supervisory losses, those of $\mathcal{X}_s$ are computed. + +# 4. Experiments + +# 4.1. Notes and Implementation Details + +We perform TDT validation on the baseline in three tasks, whose configuration details are shown in Table 1. + +Train and Test notes: As observed in pseudocode 1, our TDT aims to guide the learning of unknown samples using prior samples, resembling contrastive learning. Therefore, for each task experiment, we randomly select a prior set from the training dataset. During training and testing, each batch comprises both the prior set samples used to obtain $\mathcal{X}_g^2$ and the unknown samples used to obtain $\mathcal{X}_g^1$ . Each unknown sample undergoes TDT operations with all prior samples to make predictions, and the average of these predictions is considered as the final prediction. To reduce feature extraction time during testing, we encapsulate all the features from the prior set into the model parameters, resulting in an optimized model with accelerated inference. + +Common Setting: For all experiments, we used the Adam optimizer, where the weight decay and the momentum were set to 0.0005 and 0.9, respectively. The initial learning rate was set to 0.001 and changed according to cosine learning rate decay. We trained our model using PyTorch on a cluster of 8 RTX 3090 GPUs. In an online manner, we augment all images with random horizontal flipping, scaling, rotation, and translation. + +Facial Age Recognition: We utilize the FG-Net [47] dataset, which comprises 1002 facial images from 82 subjects, spanning an age range from 0 to 69. We follow the setup described in the papers [8, 12, 40], employing leave-one-person-out (LOPO) cross-validation. We report the average performance over 82 splits using the Mean Absolute Error (MAE) as the evaluation metric. + +Additionally, we also use the MegaAge-Asian [75] + +Table 2. CA on MegaAge-Asian. + +
MethodsPre-trainedCA(3)CA(5)CA(7)
Posterior [75]IMDB-WIKI62.0880.4390.42
MobileNet [54]IMDB-WIKI44.060.6-
DenseNet [70]IMDB-WIKI51.769.4-
SSR-Net [70]IMDB-WIKI54.974.1-
UVA [38]-60.4779.9590.44
LRN(ResNet10) [39]IMDB-WIKI62.8681.4791.34
LRN(ResNet18) [39]IMDB-WIKI64.4582.9591.98
VGG16(norm) [78]ImageNet, IMDB-WIKI, AFAD65.5883.0189.17
PVP+VGG16 [78]ImageNet, IMDB-WIKI, AFAD72.6587.2493.16
DAA(single channel) [8]-67.9784.0692.40
DAA(multi-channel) [8]-68.2984.8492.47
DAA [8]-68.8284.8992.70
TDT (ours)-69.6085.4293.26
+ +Table 3. MAEs on FG-Net dataset. + +
MethodsMAEYear
DEX[52]3.092015
MV[46]2.682018
C3AE[74]2.952019
DRFs[58]3.852021
PML[12]2.162021
DAA [8]2.192023
TDT(ours)2.12-
+ +Dataset, consisting of 40,000 age-labeled samples spanning 0 to 70 years and 3,945 images for testing. For this dataset, we choose cumulative accuracy (CA) [75] as the evaluation metric, defined as $CA(n) = \frac{K_n}{K} \times 100$ , where $K$ is total number of testing images and $K_n$ is the number whose absolute errors are smaller than $n$ . + +We adopt the official implementation of DAA[8] as the baseline for this task while replacing its DAA mapping with our TDT. The output size of $\mathcal{X}_q$ is set to $3\times 3$ . + +In this task, 256 images are randomly picked from the training set serves as the prior set for all experiments. + +Aesthetic Assessment: We use TAD66K (Theme and Aesthetics Dataset with 66K images) Dataset [27], a large-scale aesthetic quality assessment database with 47 themes. Images belonging to each theme are annotated independently, with each image containing a minimum of 1200 valid annotations. The aesthetic score of each image is treated as the label. Following TANet[27], the evaluation metric is the Mean Squared Error (MSE). We adopt the same train-test split setting. For the prior set, we select samples by choosing 2 random samples for each score ranging from 0 to 10 with interval 0.1 for each theme. We employ the official implementation of SAAN[72] as the baseline for this task while removing the final average pooling and BN layers. Additionally, we incorporate extra convolutions to obtain $\mathcal{X}_g$ with size of $8\times 8$ . + +Illumination Estimation: We use reprocessed Color Checker [18, 60] dataset, one of the most widely adopted datasets in illumination estimation. Following $\mathrm{FC^4}$ [31], the evaluation metric is the Recovery Angular Error. To facilitate better comparisons, we use the linear fully connected version of $\mathrm{FC^4}$ -net as the baseline, instead of the non-linear + +Table 4. Results on Aesthetic Benchmark TAD66K. + +
methodPub.BasicMSE
RAPID [41]ACMMM2014incorporate heterogeneous0.0200
PAM[50]ICCV2017residual-based, active learning0.0200
ALamp[42]CVPR2017layout-aware, multi-patch0.0190
NIMA [63]TIP2018predict distribution0.0210
MPada [59]ACMM2018attention, multi-patch0.0220
MLSP [30]CVPR2019staged training,multi-level features0.0190
UIAA [73]TIP2019unified probabilistic formulation0.0210
HGCN [56]CVPR2021graph convolution networks0.0200
TANet [27]IJCAI2022attention, adaptive features0.0161
SAAN [72]CVPR2023AdaIN,self-supervised Pretraining0.0185
TDT(ours)-Triangular Distribution0.0172
+ +weight pooling version. With additional convolutional layers, we obtain $\mathcal{X}_g\in \mathbb{R}^{N\times C\times 8\times 8}$ . When comparing with the $\mathrm{FC^4}$ model, we randomly select 128 samples from the training set as the prior set. However, when comparing with the method proposed by Tang et al. [64] that utilizes the extended external sRGB datasets, we choose same images for scene classification as the prior set, but only 1280 samples. + +Following previous AWB works[18, 31, 60], 3-fold cross-validation is used. Standard metrics (mean, median, tri-mean of all the errors, the mean of the lowest $25\%$ , and the mean of the highest $25\%$ of errors, the 95th percentile error) are reported in terms of angular error in degrees. + +# 4.2. Results and Analysis + +# Facial Age Estimation + +The quantitative comparison of a list of top-performing methods on the MegaAge-Asian Dataset is shown in Table 2. From the table, we can find that even stocked with pre-training on large-scale datasets, methods like [39, 78] are inferior to ours. Compared with SSR-Net, our improvement is over $8\%$ . PVP [78] gets higher CA(3) and CA(5) indexes, due to the massive pretraining on ImageNet[11], IMDB-WIKI[53], and AFAD[45]. DAA[8], published in 2023, shares the same setting with our proposed method, while TDT obtains better scores in all CA indexes. + +To better prove the effectiveness of TDT, we also profile TDT on FG-Net [47], reported in Table 3. Using MAE as the metric, TDT leads the board with the smallest MAE, surpassing the same-setting competitor DAA. + +# Aesthetic Assessment. + +In Table 4, we list the MSE scores for the selected and close-related aesthetic works. In an overall manner, TDT ranks second with an MSE score of 0.0172. This improvement simply originates from the deployment of the TDT plugin over SAAN [72], whose MSE is 0.0185, again showing the advantage of the label discriminative ability of TDT. + +# Illumination Estimation. + +In Table 5, we report the statistics of the predicted angular error for a set of AWB algorithms on the Color Checker Dataset. On metrics like mean, and median values, the TDT based on $\mathrm{FC^4}$ outperforms other state-of-the-art methods, + +Table 5. Results on AWB Dataset Color Checker Dataset. + +
modelsmeanmed.tri.best25%worst 25%95th pct.
FFCC [3]1.800.951.180.274.65-
FC4(Weighted) [31]1.651.181.270.383.784.73
FC4[31]1.841.271.390.464.205.46
AlexNet FC4 [31]1.771.111.290.343.784.29
Multi-Hypothesis [37]2.101.321.530.365.10-
IGTN [67]1.580.92-0.283.70-
MDLCC [66]1.580.951.110.373.77-
TLCC+sRGB [64]1.510.981.070.333.52-
TDT+FC41.641.121.250.413.804.53
TDT+FC4+sRGB1.460.851.050.263.614.61
+ +Table 6. Loss ablation analysis on MegaAge-Asian. $\checkmark$ and - indicate whether to add this loss to the final loss. + +
\( L_S \)\( L_M \)\( L_P \)CA(3)CA(5)CA(7)
-✓✓67.7484.3392.51
✓-✓68.4384.6292.60
✓✓✓69.6085.4293.26
+ +such as MDLCC [66] and TLCC [64]. On top of $\mathrm{FC^4}$ , TDT also boosts the performance by a noticeable gap. + +# 4.3. Ablation Study + +We conduct an ablation study on the loss choice, the number of distributions and prior samples. + +# Loss function + +It is vital to study the impact of different losses in Eq.8 and the results are presented in Table 6. We observe that removing any loss incurs a decrement in the overall performance. And symmetry loss brings the most improvement. + +We design a toy experiment to further analyze the loss function Eq.7. The age loss $L_{P}$ is a supervisory loss due to the label is needed for computing $L_{P}$ , while the symmetry-related loss $L_{S}$ and the commutativity-related loss $L_{M}$ are unsupervisory losses. Switching off all nonsupervisory loss, as seen in the top two rows of Table 7, we see a clear CA score drop, indicating the advantage brought by the nonsupervisory loss. + +If we cut off the access to unsupervisory loss for part1 (in other words, for only $75\%$ data, the unsupersiory loss is calculated), as reported in the bottom half of Table 7, we claim: with increasing unlabeled data, the performance is massively improved, which again verifies the functionality of the symmetry-related and commutativity-related loss. + +# Distribution and Prior Number + +Besides the loss selection, the number of distributions is a vital factor. On the same MegaAge-Asian Dataset, we test the number of distributions from the set 32, 64, 128, 256. Table 8 shows that in general, the number of distributions has a minor effect on the final results and when feature is set 128-dimensional the performance is optimal. + +The selected prior samples work like expert voting, hence we exploit the factor of the prior sample number. Table 8 proves that as the number of samples increases, the + +Table 7. Loss analysis on MegaAge-Asian. The whole dataset is divided into part1 and part2, with a ratio of $25\%$ and $75\%$ . + +
LS,LMLPlabel accessed toCA(3)CA(5)
Noallall68.2684.26
Yesallall69.6085.42
part2part2part260.2378.54
allpart2part266.5983.62
+ +Table 8. Experiments on feature distributions and prior samples. + +
typesnumbersCA(3)CA(5)CA(7)
feature distributions25668.7784.8292.70
12869.6085.4293.26
6468.3984.5992.85
3267.8085.0492.90
prior samples25669.6085.4293.26
12868.7384.9492.80
6467.3483.4291.38
+ +credibility of the results improves, yet the enhancement in credibility gradually diminishes. + +# 4.4. Visualization of what TDT learns + +Fig.3 shows that: once the training is completed, we see feature difference approximates a triangular distribution function on varying symmetric age. The same property can be found for the predicted delta age (Inset (b)) in Fig.3). This results from TDT learning. From the inset (c) in Fig.3, we observe that the symmetry loss range is almost the same, meeting the feature symmetry assumption. + +Fig.4 shows some qualitative comparison on illumination estimation task. Starting from raw image, different prior sample gives a close-to-groundtruth predicted white point, averaged to form the final robust white point. For the 3rd row, the prediction slightly shifts away from the groundtruth, which we guess it is due to multi-illumination. + +As shown in Fig.5, we study the performance of TDT learning the symmetry axis location. For any pair of facial images, for example an age- $a$ image from test set and an age- $b$ image from the prior set, thus the symmetry axis should locate at $(a + b)/2$ . With $(a + b)/2$ fixed, we alter the testing image and prior image, and draw a histogram of the resulted $\mathcal{X}_s$ , which in fact gather around the symmetry axis. For pairs of $\{\text{age-3}, \text{age-34}\}$ , the mean of predicted symmetric age is 18.27, close to the symmetric age 18.50. + +# 5. Conclusion + +A learning framework based on the Triangular Distribution Transform is proposed in this paper. It connects the nonlinear feature difference and the corresponding label difference in a verified linear, symmetric, and commutativity manner. This transform can be used as a portable plug-in for vision regression tasks, e.g., we verify its application on three vision tasks. On facial age estimation, aesthetic as- + +![](images/763f1716649e444b17554834266237cf060e94b24d273b1a2b607a251ffbca1a.jpg) +(a) + +![](images/db24380c13873a11b37f720445fd0193ef423d863ef389b71f82abb93ef19036.jpg) +(b) +Figure 3. Relationship between symmetric age with the feature discrepancy, predicted delta age, and symmetric loss. (a) feature discrepancy; (b) predicted delta age; (c) symmetric loss + +![](images/66ed7d3c2b68c755b28ef8e884691ad54b9c196914556773693a63aaefa32173.jpg) +(c) + +![](images/2fc0fde64c67b87f4a73053255be22cdd0ab774e115c5d3c24743542658147da.jpg) +RAW + +![](images/641ef309663944574d78ca46fadc9a9f3ca88d4fbe785250f0570d437f421004.jpg) + +![](images/5e3765771c4e80a6de8210ac88e3233590e6a183f860cd4aef914c644ee18596.jpg) +Figure 4. Qualitative comparison of the final color correction result and those from individual prior samples. In the fourth column, the predictions from different priors (their color corrected images are given in right insets) are shown clustered around the ground truth location, with limited variance. In the rightmost column, prior samples are given. + +![](images/c79bed9ffbc6acc698c872ea1f57131352a1b376d13eee1f312f41ade264d4c8.jpg) +GT + +![](images/c6ad170d51d7f767ac544879e812a9be55c3f46028d582bfb3649421be5448db.jpg) + +![](images/aca720403067956f417b1aaca6c27695070059b126951726809b2db37d325c6f.jpg) + +![](images/e0d98c8fbbc985f44f0d387e5b789cc26d9649ad1de08acdcd57225258084772.jpg) +Ours + +![](images/7a59f2832b3e7971862282b8f55a3ba098ee28b3bed85b418fb1ecb96fa2b8df.jpg) + +![](images/5b5bacbe0845ac1835ee43e3bbf1ea03eade103623580dfd5c9a1546426b1c8c.jpg) + +![](images/c72d75cf5ef5dfee138ca4b7835f345d76710850fd5a514a67f1fedabd7c043c.jpg) +Distribution + +![](images/3884f91cc1c881a78a522964ed9bc1ddd3ff82e997e3916e6e99b845e335347e.jpg) + +![](images/c82bddb0a71b67a96af37a82aa1fe3a42f8db2c202b81c54f29ed591a72c7da0.jpg) + +![](images/bea5413bec1dab1e153e57527cc1c27bbac7ef17b6682eec7b0164de1ba71eac.jpg) + +![](images/a9b2bf6a4ded861df868509bf905e8b3de50b3b8f9b2ce81156e73b61a10b0db.jpg) + +![](images/57fed6ca185b85b416232f595960172eb5d6a14b1b95cdaca2aca9f7c76c87ce.jpg) + +![](images/317d589a363b82002ceaceda2dfe788b164eef1017d6a91e32e71c3a7935d306.jpg) +Prior + +![](images/e47b4d979f282f8c4ca428d7b6366a41139101373ac2ecd433e4ad9dac13b7f1.jpg) + +![](images/1c16103f4be42fd497819229a28079b98e47c26c703f9ba622f3d559d67e6bf9.jpg) + +![](images/e3405a3b0eee49c9d2e9416d6705f354ab5ddb5f13928ff3c9beced33f1eaab8.jpg) +Figure 5. Study on the symmetry learnt in $\mathcal{X}_s$ . For any pair of age- $a$ image from test set and age- $b$ image from the prior set, we draw a histogram of the resulted $\mathcal{X}_s$ , which in fact gather around the symmetry axis $(a + b) / 2$ , w.r.t. the histogram figure. + +sessment, and illumination estimation, the proposed TDT obtains on-par or even better performance than the prior arts, without much modification on the affiliated backbone. In the future, we will explore the application of TDT in a wider context, for example shape and pose estimation. + +# 6. Acknowledgements + +This work is supported by the Natural Science Starting Project of SWPU (No.2022QHZ023), the Sichuan Scientific Innovation Fund (No.2022JDRC0009), the Sichuan Provincial Department of Science and Technology Project (No.2022NSFSC0283) and the Key Research and Development Project of Sichuan Provincial Department of Science and Technology (No.2023YFG0129). + +# References + +[1] Kobus Barnard, Vlad Cardei, and Brian Funt. A comparison of computational color constancy algorithms. i: Methodology and experiments with synthesized data. IEEE TIP, 11 (9):972-984, 2002. 3 +[2] Jonathan T Barron. Convolutional color constancy. In ICCV, pages 379-387, 2015. 3 +[3] Jonathan T. Barron and Yun-Ta Tsai. Fast fourier color constancy. In CVPR, pages 6950-6958, 2017. 3, 7 +[4] David H Brainard and Brian A Wandell. Analysis of the retina theory of color vision. JOSA A, 3(10), 1986. 3 +[5] Ayan Chakrabarti. Color constancy by learning to predict chromaticity from luminance. 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However, how the discrepancy between features is mapped to the label discrepancy is ambient, and its correctness is not guaranteed. To address these problems, we study the mathematical connection between feature and its label, presenting a general and simple framework for label distribution learning. We propose a so-called Triangular Distribution Transform (TDT) to build an injective function between feature and label, guaranteeing that any symmetric feature discrepancy linearly reflects the difference between labels. The proposed TDT can be used as a plug-in in mainstream backbone networks to address different label distribution learning tasks. Experiments on Facial Age Recognition, Illumination Chromaticity Estimation, and Aesthetics assessment show that TDT achieves on-par or better results than the prior arts. Code is available at https://github.com/redcping/TDT." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 483, + 128, + 496 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 483, + 128, + 496 + ], + "spans": [ + { + "bbox": [ + 47, + 483, + 128, + 496 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 504, + 287, + 647 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 504, + 287, + 647 + ], + "spans": [ + { + "bbox": [ + 46, + 504, + 287, + 647 + ], + "type": "text", + "content": "Label distribution learning (LDL) utilizes the advantages of distribution to solve the task of quasi-continuous label or inner-correlation between labels [22, 58]. LDL assigns a distribution over label value to an instance, which can be obtained by fitting a Gaussian or Triangle distribution whose peak indicates the label and represents the relative importance of each label describing an instance [58]. Hence, LDL has an impact on many real-world applications, such as facial age estimation [22], head-pose estimation [20, 23], crowd counting [76], zero-shot learning [35], facial beauty prediction [51], hierarchical classification [68], partial multi-label learning [69] and so on." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "type": "text", + "content": "When LDL was first proposed, it mainly used maximum entropy and Kullback-Leibler divergence to learn label distribution [22]. Then, a more efficient optimization method BFGS is proposed to replace the IIS method [19]. The" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 213, + 546, + 345 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 213, + 546, + 345 + ], + "spans": [ + { + "bbox": [ + 306, + 213, + 546, + 345 + ], + "type": "text", + "content": "LDL is also widely combined with other algorithms, such as random forest [57], deep convolution neural network [71], hashing method [77], Bayesian [79], metric learning [80] and so on. Although LDL has wide applications, it encounters some challenges, i.e. the feature space and label (solution) space are inhomogeneous [57]. To be more specific, the feature space generated by the model is nonlinear, while the label information is gradually changing. In addition, the existing label distribution is mainly based on label information to construct the distribution, placing the label information for one instance over the whole label distribution." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 346, + 547, + 584 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 346, + 547, + 584 + ], + "spans": [ + { + "bbox": [ + 304, + 346, + 547, + 584 + ], + "type": "text", + "content": "Therefore, this article proposes a Triangular Distribution Transform (TDT) method, aiming to linearly map the transformed feature information to its corresponding label information concisely and efficiently. Inspired by label distribution learning [57], we propose using symmetric triangular distributions to represent this symmetric linear transformation. Specifically, the high-dimensional features obtained by feature extraction networks will reflect the relationship between labels through symmetric triangular distributions. To better achieve this goal, we draw inspiration from the paradigm of comparative learning and supply two sets of images to the feature extraction network each time. One set is the prior knowledge that needs to be compared, and the other set is the training sample. Our method is more suitable for visual tasks with linearly continuous changing label information, such as age, aesthetics, lighting intensity, etc. Our TDT can be used as a plug-in in mainstream backbone networks. Therefore, our method has achieved excellent results on multiple visual tasks, such as facial age estimation, image aesthetics estimation, and illumination estimation." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 317, + 585, + 545, + 596 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 585, + 545, + 596 + ], + "spans": [ + { + "bbox": [ + 317, + 585, + 545, + 596 + ], + "type": "text", + "content": "The contribution of this article is summarized as follows:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 317, + 603, + 545, + 712 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 317, + 603, + 545, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 603, + 545, + 639 + ], + "spans": [ + { + "bbox": [ + 317, + 603, + 545, + 639 + ], + "type": "text", + "content": "- We analyze to lay the theoretical foundation for the Triangular Distribution Transform, enabling feature discrepancy to explain label difference." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 317, + 646, + 545, + 681 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 646, + 545, + 681 + ], + "spans": [ + { + "bbox": [ + 317, + 646, + 545, + 681 + ], + "type": "text", + "content": "- We show with the proposed symmetry-related loss and commutativity-related loss, TDT can be learnt by mainstream backbone networks." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 317, + 689, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 689, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 317, + 689, + 545, + 712 + ], + "type": "text", + "content": "- TDT outperforms other methods on age estimation, aesthetics estimation, and illumination estimation." + } + ] + } + ], + "index": 15 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 252, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 252, + 713 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 252, + 713 + ], + "type": "text", + "content": "*Corresponding author. †These authors contributed equally." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "type": "text", + "content": "11019" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 75, + 76, + 520, + 319 + ], + "blocks": [ + { + "bbox": [ + 75, + 76, + 520, + 319 + ], + "lines": [ + { + "bbox": [ + 75, + 76, + 520, + 319 + ], + "spans": [ + { + "bbox": [ + 75, + 76, + 520, + 319 + ], + "type": "image", + "image_path": "7cef8ab8c4868c5ac129958296e36327551fc0786bc3351f925674c0698821f6.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 331, + 548, + 377 + ], + "lines": [ + { + "bbox": [ + 46, + 331, + 548, + 377 + ], + "spans": [ + { + "bbox": [ + 46, + 331, + 548, + 377 + ], + "type": "text", + "content": "Figure 1. The overall structure of our TDT. Our pipeline (b) diverges from the general pipeline (a) by incorporating a parameter-free TDT (Triangular Distribution Transform), enabling converting the nonlinear feature to the one which vary \"linearly\" as per Eq.4. Consequently, a linear head module alone suffices to establish the mapping between image features and their respective labels, with clear explanation which is missing for a conventional network head. For detailed information on the TDT loss, please refer to Figure.2." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 396, + 138, + 408 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 396, + 138, + 408 + ], + "spans": [ + { + "bbox": [ + 47, + 396, + 138, + 408 + ], + "type": "text", + "content": "2. Related works" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 415, + 197, + 428 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 415, + 197, + 428 + ], + "spans": [ + { + "bbox": [ + 47, + 415, + 197, + 428 + ], + "type": "text", + "content": "2.1. Label distribution learning" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 434, + 289, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 434, + 289, + 662 + ], + "spans": [ + { + "bbox": [ + 46, + 434, + 289, + 662 + ], + "type": "text", + "content": "The label distribution method learns the relevance between labels to reflect the relative importance of different labels [21, 22, 29, 58], which can also be seen as a special facial age classification method. Label distribution learning methods learn a label distribution that represents the relative importance of each label when describing an instance[21]. The label distribution covers a certain number of labels. Each label has its description degree, representing the degree to which each label describes the instance[62]. The description degrees of all the labels sum up to 1 [62]. Due to the advantages of label distributed learning, it has achieved very excellent performance in tasks such as facial age estimation[22], head-pose estimation [20, 23], crowd counting [76], zero-shot learning[35], facial beauty prediction[51], hierarchical classification[68], and partial multi-label learning [69]. The label distribution learning method is very consistent with the potential law of big data. Nevertheless, acquiring distributional labels for thousands of face images itself is a non-trivial task[58]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 670, + 171, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 171, + 684 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 171, + 684 + ], + "type": "text", + "content": "2.2. Facial Age estimation" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "content": "The regression methods [45], classification methods [53], and ranking methods [7, 9] for age estimation pay more" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 396, + 547, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 396, + 547, + 613 + ], + "spans": [ + { + "bbox": [ + 304, + 396, + 547, + 613 + ], + "type": "text", + "content": "attention to putting forward different research methods according to label information. The age regression methods consider labels as continuous numerical values. To handle the heterogeneous data, researchers also proposed hierarchical models [26] and the soft-margin mixture of regression [33]. And age classification regards labels as independent values[53]. It regards each age as a separate category and ignores the similarity of the same person between different ages. While the ranking approaches treat labels as rank-order data and use multiple binary classifiers to determine the age rank in a facial image[7, 9]. Besides, some scholars also focus on the objective optimization function [12, 46]. ML-loss [46] proposed mean-variance loss for robust age estimation via distribution learning. Deng et al. [12] proposed progressive margin loss (PML) for long-tailed age classification. These methods gradually consider that aging is a slow and continuous process, which also means that the processing of label information is significant." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 622, + 429, + 634 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 622, + 429, + 634 + ], + "spans": [ + { + "bbox": [ + 306, + 622, + 429, + 634 + ], + "type": "text", + "content": "2.3. Aesthetic Assessment" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "content": "An aesthetic assessment task refers to evaluating the visual beauty and artistic value of given image. Early studies rely on handcrafted features [13, 43, 44], which ignore the spatial features and semantics in assessing aesthetics. In data-driven learning-based methods, NIMA[63] uses Earth Mover's Distance to optimize aesthetic distribution predic" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "type": "text", + "content": "11020" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "content": "tion. A-lamp[42] and " + }, + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "inline_equation", + "content": "\\mathrm{MP}_{ada}[59]" + }, + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "content": " both achieve good results with a multi-patch approach. Hierarchical Layout-aware Graph Convolution Network (HGCN)[56] captures layout information. TANet [27] adaptively learns aesthetic prediction rules based on identified themes, using Mean Squared Error as the metric. Transformer [28] assign attention levels to color spaces, enabling segmentation learning. Yi et al. [72] effectively combine feature style and general aesthetic information using AdaIN [34] and self-supervised pre-training for accurate aesthetic assessment." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 198, + 183, + 210 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 198, + 183, + 210 + ], + "spans": [ + { + "bbox": [ + 47, + 198, + 183, + 210 + ], + "type": "text", + "content": "2.4. Illumination Estimation" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 216, + 289, + 408 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 216, + 289, + 408 + ], + "spans": [ + { + "bbox": [ + 46, + 216, + 289, + 408 + ], + "type": "text", + "content": "Illumination Estimation is often dubbed as Auto White Balance verbally and aims at measuring the normalized illumination vector given at least one single image. There exists a bunch of traditional methods that are easy to implement but easily fail due to the over-optimistic assumption, for example, White Patch [4], General Gray World [1], Gray Edge [65], Shades-of-Gray [16], LSRS [17], PCA [10] and Grayness Index [49], etc. Relying on labeled data, a bunch of learning-based methods with tunable inner weight e.g. [2, 5, 6, 15, 18, 24, 25, 32, 36, 48, 61] leads the leaderboard by a large gap generally. All aforementioned methods output a single illumination vector in a deterministic way. A few works deal with label distribution learning; Egor et al. [14] proposed an efficient illumination distribution estimation method; FFCC [3] from Barron outputs a unique illumination vector which can be modified as a distribution." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 418, + 153, + 431 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 418, + 153, + 431 + ], + "spans": [ + { + "bbox": [ + 47, + 418, + 153, + 431 + ], + "type": "text", + "content": "3. Proposed Method" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 437, + 289, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 289, + 654 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 289, + 654 + ], + "type": "text", + "content": "The pipeline of proposed Triangular distribution learning is illustrated in Fig.1. Fig.1(a) depicts the general pipeline for CNN tasks, where non-linear head modules are employed to map non-linear features to labels due to the linear independence of image features. These non-linear head modules can include modules that combine convolution with nonlinear activation functions, Gaussian Mixture Model, and others. In Fig.1(b), we propose a novel pipeline that differs from the general pipeline. We introduce a parameter-free TDT (Triangular Distribution Transform) after the nonlinear image features, allowing for the possibility of transforming linearly independent image features into linearly correlated ones. As a result, we only need to utilize a linear head module, such as a fully connected (FC) module, in combination with the relevant loss function to achieve linear correlation learning among the features. Additionally, we employ a contrastive learning-like approach to guide the predictions of unknown samples based on known samples." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 659, + 288, + 683 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 659, + 288, + 683 + ], + "spans": [ + { + "bbox": [ + 47, + 659, + 288, + 683 + ], + "type": "text", + "content": "3.1. Triangular Distribution Transform on Latent Feature" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 689, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 288, + 714 + ], + "type": "text", + "content": "With some ambiguity, vision regression problems can be classified into linear-label problems and nonlinear-label" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 227 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 227 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 227 + ], + "type": "text", + "content": "ones. The mapping from the original information modality (for example 2D images, text, voice, video etc.) to the corresponding labels is usually non-linear and hard to model in a fixed rule. Take facial age recognition as an example, age label varies linearly while the visual feature of the facial image usually does not work in the same way. The majority of works on distribution learning mainly focus on learning a mapping from visual features to the label in a nonlinear way, such as the deep net, with its interpretability remaining in suspense. In this article, we discuss the relationship between the feature and its label and present a so-called Triangular Distribution Transform (TDT) to rigidly connect the feature and its label, so that the connection is injective." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "spans": [ + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "text", + "content": "Starting with an input " + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "inline_equation", + "content": "X\\in \\mathbb{R}^{N\\times 3\\times H\\times W}" + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "text", + "content": " is the batch size, " + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "inline_equation", + "content": "3,H,W" + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "text", + "content": " denotes the channel, height, and width respectively) and its label " + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "inline_equation", + "content": "Y" + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "text", + "content": ", we extract feature by some net module " + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "text", + "content": " (parameterized by " + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "inline_equation", + "content": "\\Theta" + }, + { + "bbox": [ + 304, + 227, + 545, + 276 + ], + "type": "text", + "content": ") as follows:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 394, + 284, + 545, + 298 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 394, + 284, + 545, + 298 + ], + "spans": [ + { + "bbox": [ + 394, + 284, + 545, + 298 + ], + "type": "interline_equation", + "content": "\\mathcal {X} _ {g} = g (\\mathcal {X}, \\Theta) \\tag {1}", + "image_path": "ff999d3e6f6de7983a3c3ba2376264ac98684e00267317ad92149efd0e36681a.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "spans": [ + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g\\in \\mathbb{R}^{N\\times C\\times h\\times w}" + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "text", + "content": " is a C-channel feature extracted from some backbone nets (e.g., ResNet18). The mean and standard deviation are calculated along the " + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "text", + "content": " dimensions, referred to as " + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "inline_equation", + "content": "\\mu (\\mathcal{X}_g)\\in \\mathbb{R}^{N\\times C\\times 1\\times 1}" + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "inline_equation", + "content": "\\sigma (\\mathcal{X}_g)\\in" + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{N\\times C\\times 1\\times 1}" + }, + { + "bbox": [ + 304, + 305, + 545, + 365 + ], + "type": "text", + "content": " respectively." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "spans": [ + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "text", + "content": "Based on the Central Limit Theorem, we assume " + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g" + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "text", + "content": " follows Gaussian distribution and denote the probability density function (PDF) as " + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "inline_equation", + "content": "\\phi(\\mathcal{X}_g)" + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "text", + "content": ". Given features for two samples " + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "inline_equation", + "content": "(\\mathcal{X}_g^1" + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^2" + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "text", + "content": "), we define their \"feature difference\" based on the Gaussian distribution of " + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^1" + }, + { + "bbox": [ + 304, + 366, + 545, + 427 + ], + "type": "text", + "content": " as:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 307, + 434, + 545, + 480 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 307, + 434, + 545, + 480 + ], + "spans": [ + { + "bbox": [ + 307, + 434, + 545, + 480 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) = \\phi \\left(\\mathcal {X} _ {g} ^ {1}\\right) - \\phi \\left(\\mathcal {X} _ {g} ^ {2}\\right) \\tag {2} \\\\ \\propto \\mathcal {N} _ {0, 1} (\\frac {\\mathcal {X} _ {g} ^ {1} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})}) - \\mathcal {N} _ {0, 1} (\\frac {\\mathcal {X} _ {g} ^ {2} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})}) \\\\ \\end{array}", + "image_path": "ca229f2a692f7c197b72ed0837197c5be86fed55736967f96c89ea2044b1c952.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 487, + 545, + 523 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 487, + 545, + 523 + ], + "spans": [ + { + "bbox": [ + 304, + 487, + 545, + 523 + ], + "type": "text", + "content": "The last part of Eq.2 is the normalized feature difference using the standard Gaussian distribution " + }, + { + "bbox": [ + 304, + 487, + 545, + 523 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_{0,1}" + }, + { + "bbox": [ + 304, + 487, + 545, + 523 + ], + "type": "text", + "content": ". We give our first assumption:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 523, + 545, + 547 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 523, + 545, + 547 + ], + "spans": [ + { + "bbox": [ + 304, + 523, + 545, + 547 + ], + "type": "text", + "content": "Assumption 1: There exists a function transforming " + }, + { + "bbox": [ + 304, + 523, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g" + }, + { + "bbox": [ + 304, + 523, + 545, + 547 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 523, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g'" + }, + { + "bbox": [ + 304, + 523, + 545, + 547 + ], + "type": "text", + "content": ", whose change linearly w.r.t. the label." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 547, + 545, + 595 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 547, + 545, + 595 + ], + "spans": [ + { + "bbox": [ + 304, + 547, + 545, + 595 + ], + "type": "text", + "content": "To better fit Assumption 1, considering " + }, + { + "bbox": [ + 304, + 547, + 545, + 595 + ], + "type": "inline_equation", + "content": "\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2)" + }, + { + "bbox": [ + 304, + 547, + 545, + 595 + ], + "type": "text", + "content": " does not correlate linearly with the label, we approximate the Gaussian distribution in Eq.2 using a symmetric Triangular distribution " + }, + { + "bbox": [ + 304, + 547, + 545, + 595 + ], + "type": "inline_equation", + "content": "\\tau (\\cdot |b)" + }, + { + "bbox": [ + 304, + 547, + 545, + 595 + ], + "type": "text", + "content": " following [55], formulated as:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 312, + 602, + 545, + 648 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 602, + 545, + 648 + ], + "spans": [ + { + "bbox": [ + 312, + 602, + 545, + 648 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) \\approx \\Delta_ {\\tau} \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) \\tag {3} \\\\ = \\tau (\\frac {\\mathcal {X} _ {g} ^ {1} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})} | b) - \\tau (\\frac {\\mathcal {X} _ {g} ^ {2} - \\mu (\\mathcal {X} _ {g} ^ {1})}{\\sigma (\\mathcal {X} _ {g} ^ {1})} | b), \\\\ \\end{array}", + "image_path": "65b28ce7db17e7b582cf1f73ffa25567c841dd0807dfa78d59a8704e32fd8331.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 334, + 650, + 545, + 682 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 334, + 650, + 545, + 682 + ], + "spans": [ + { + "bbox": [ + 334, + 650, + 545, + 682 + ], + "type": "interline_equation", + "content": "\\tau (s | b) = \\left\\{ \\begin{array}{l l} \\frac {1}{b} \\cdot \\left(1 - \\frac {| s |}{b}\\right), & - b \\leq s \\leq b \\\\ 0, & \\text {o t h e r w i s e} \\end{array} \\right. \\tag {4}", + "image_path": "26fba53fec5e6956dfe8f84e47f913e7488ddae0855df874cfa033df3b6f9e06.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "content": "where the scalar " + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "content": " controls the approximation error and is set to " + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\sqrt{6}" + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "content": " is obtained via the method of moments in [55])." + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "text", + "content": "11021" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 61, + 70, + 218, + 228 + ], + "blocks": [ + { + "bbox": [ + 61, + 70, + 218, + 228 + ], + "lines": [ + { + "bbox": [ + 61, + 70, + 218, + 228 + ], + "spans": [ + { + "bbox": [ + 61, + 70, + 218, + 228 + ], + "type": "image", + "image_path": "f20923bffec47bae74c97127bebeed8465581225dd036282b70a54c53625bf8b.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 239, + 547, + 262 + ], + "lines": [ + { + "bbox": [ + 46, + 239, + 547, + 262 + ], + "spans": [ + { + "bbox": [ + 46, + 239, + 547, + 262 + ], + "type": "text", + "content": "Figure 2. TDT is learned relying on the commutativity-related loss and symmetry-related loss, while the latter plays the primary role. The feature difference, associated with the symmetry-related loss, is used for result prediction. MSE is the mean square error." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 219, + 70, + 529, + 228 + ], + "blocks": [ + { + "bbox": [ + 219, + 70, + 529, + 228 + ], + "lines": [ + { + "bbox": [ + 219, + 70, + 529, + 228 + ], + "spans": [ + { + "bbox": [ + 219, + 70, + 529, + 228 + ], + "type": "image", + "image_path": "e469feb9545e454a5030504f9bda8bc692e1da588d25d21fedb6f5085dc2e254.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 282, + 287, + 344 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 282, + 287, + 344 + ], + "spans": [ + { + "bbox": [ + 46, + 282, + 287, + 344 + ], + "type": "text", + "content": "In contrast to Eq.2, Eq.4 has the property of linearly describing the corresponding label difference. Then we can search a linear function " + }, + { + "bbox": [ + 46, + 282, + 287, + 344 + ], + "type": "inline_equation", + "content": "f(\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2))" + }, + { + "bbox": [ + 46, + 282, + 287, + 344 + ], + "type": "text", + "content": " that transforming the feature difference to the label difference " + }, + { + "bbox": [ + 46, + 282, + 287, + 344 + ], + "type": "inline_equation", + "content": "|Y^{1} - Y^{2}|" + }, + { + "bbox": [ + 46, + 282, + 287, + 344 + ], + "type": "text", + "content": ", in a linear, symmetric and commutative way1." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 352, + 287, + 376 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 352, + 287, + 376 + ], + "spans": [ + { + "bbox": [ + 47, + 352, + 287, + 376 + ], + "type": "text", + "content": "3.2. Optimization towards Triangular Distribution Transform and Vision Tasks" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 383, + 287, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 383, + 287, + 456 + ], + "spans": [ + { + "bbox": [ + 46, + 383, + 287, + 456 + ], + "type": "text", + "content": "The learned feature does not follow Triangular distribution unless we optimize the net towards it. Then we state the optimization loss towards TDT and related task-specific loss. The optimization loss of TDT, shown in Fig.2, aims to gradually transform the non-linear correlation among image features into a linear correlation through label-guided learning." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 59, + 456, + 200, + 468 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 456, + 200, + 468 + ], + "spans": [ + { + "bbox": [ + 59, + 456, + 200, + 468 + ], + "type": "text", + "content": "Loss for Triangular Distribution" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "spans": [ + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": "Given two sets of nonlinear features " + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^1" + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^2" + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": " extracted from backbone network, we use multiple convolution layers to learn to make a feature that follows symmetric Triangular distribution, formulated as " + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s = \\text{Conv}(\\text{Concat}(\\mathcal{X}_g^1, \\mathcal{X}_g^2), \\theta)" + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": ", where the concatenation happens in the batch dimension. We calculate the mean and standard deviation separately for " + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^1" + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^2" + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": " along the spatial dimensions. Via Eq.4, we get " + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "inline_equation", + "content": "\\Delta(\\mathcal{X}_s, \\mathcal{X}_g^1)" + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "inline_equation", + "content": "\\Delta(\\mathcal{X}_s, \\mathcal{X}_g^2)" + }, + { + "bbox": [ + 46, + 468, + 287, + 577 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "spans": [ + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "type": "text", + "content": "To guide the net to reach a state that " + }, + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^1" + }, + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^2" + }, + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "type": "text", + "content": " are symmetrical around the \"center\" " + }, + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 46, + 577, + 287, + 612 + ], + "type": "text", + "content": ", a symmetry-related loss is introduced:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 93, + 624, + 287, + 639 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 93, + 624, + 287, + 639 + ], + "spans": [ + { + "bbox": [ + 93, + 624, + 287, + 639 + ], + "type": "interline_equation", + "content": "L _ {S} = \\left\\| \\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1}\\right) - \\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right) \\right\\| _ {2}, \\tag {5}", + "image_path": "26dd1164bc65b7ce89a330bdaa9695ec3c02f4b1656d4cbba727a861aa24528b.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 648, + 287, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 648, + 287, + 662 + ], + "spans": [ + { + "bbox": [ + 47, + 648, + 287, + 662 + ], + "type": "text", + "content": "where the operator " + }, + { + "bbox": [ + 47, + 648, + 287, + 662 + ], + "type": "inline_equation", + "content": "\\| \\cdot \\| _2" + }, + { + "bbox": [ + 47, + 648, + 287, + 662 + ], + "type": "text", + "content": " is a L2 loss. Analogously, the" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 282, + 476, + 295 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 282, + 476, + 295 + ], + "spans": [ + { + "bbox": [ + 306, + 282, + 476, + 295 + ], + "type": "text", + "content": "commutativity-related loss is designed as:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 348, + 304, + 545, + 319 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 304, + 545, + 319 + ], + "spans": [ + { + "bbox": [ + 348, + 304, + 545, + 319 + ], + "type": "interline_equation", + "content": "L _ {M} = \\left\\| \\Delta \\left(\\mathcal {X} _ {g} ^ {1}, \\mathcal {X} _ {g} ^ {2}\\right) - \\Delta \\left(\\mathcal {X} _ {g} ^ {2}, \\mathcal {X} _ {g} ^ {1}\\right) \\right\\| _ {2}, \\tag {6}", + "image_path": "a1aefe9e59ca8624f3a911bcffed4a4a380263f6d419862a462ef98d0d835735.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 328, + 545, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 328, + 545, + 365 + ], + "spans": [ + { + "bbox": [ + 305, + 328, + 545, + 365 + ], + "type": "text", + "content": "Then, to facilitate the learning of the linear function " + }, + { + "bbox": [ + 305, + 328, + 545, + 365 + ], + "type": "inline_equation", + "content": "f(\\Delta)" + }, + { + "bbox": [ + 305, + 328, + 545, + 365 + ], + "type": "text", + "content": ", we adopt a comparative approach and design a relevant supervised loss:" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 315, + 373, + 545, + 406 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 373, + 545, + 406 + ], + "spans": [ + { + "bbox": [ + 315, + 373, + 545, + 406 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} L _ {P} = \\| \\delta (Y) - 2 \\cdot f (\\Delta (\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1}) \\cdot s g n (\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {1})) \\| _ {1} \\\\ + \\| \\delta (Y) + 2 \\cdot f \\left(\\Delta \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right) \\cdot s g n \\left(\\mathcal {X} _ {s}, \\mathcal {X} _ {g} ^ {2}\\right)\\right) \\| _ {1}, \\tag {7} \\\\ \\end{array}", + "image_path": "d97091c74f9f724ae9d1955524942fe8303094a5f2641bf534f37bf041417089.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": "Here, " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\| \\cdot \\|_1" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": " refers to smooth L1 operator, " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\delta(Y) = Y^2 - Y^1" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\operatorname{sgn}(\\mathcal{X}_s, \\mathcal{X}_g)" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": " represents the sign of " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\Delta(\\mathcal{X}_s, \\mathcal{X}_g)" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": ". When " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": " in the distribution of " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": " has a cumulative distribution function (CDF) less than 0.5, " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\operatorname{sgn}(\\mathcal{X}_s, \\mathcal{X}_g)" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": " is considered positive, and vice versa. The first part of Eq.7 represents using samples labeled as " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "Y^2" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": " to predict samples labeled as " + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "inline_equation", + "content": "Y^1" + }, + { + "bbox": [ + 304, + 413, + 545, + 498 + ], + "type": "text", + "content": ", and the other term follows the same principle." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 498, + 545, + 522 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 498, + 545, + 522 + ], + "spans": [ + { + "bbox": [ + 305, + 498, + 545, + 522 + ], + "type": "text", + "content": "Therefore, the final loss function for learning the triangular distribution can be formulated as follows:" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 376, + 533, + 545, + 546 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 376, + 533, + 545, + 546 + ], + "spans": [ + { + "bbox": [ + 376, + 533, + 545, + 546 + ], + "type": "interline_equation", + "content": "L _ {T} = L _ {S} + L _ {M} + L _ {P}, \\tag {8}", + "image_path": "6867909aa0ff70f49f8c3bea9c7be0d5824fc7639fac096d2ff4734e2f257083.jpg" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 317, + 557, + 411, + 567 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 557, + 411, + 567 + ], + "spans": [ + { + "bbox": [ + 317, + 557, + 411, + 567 + ], + "type": "text", + "content": "Loss for Vision Tasks" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 568, + 545, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 568, + 545, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 568, + 545, + 616 + ], + "type": "text", + "content": "To quickly validate the effectiveness of TDT, we have selected three common visual tasks: facial age recognition, aesthetic assessment, and illumination estimation. Below are the descriptions and loss definitions for these three tasks." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 616, + 545, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 616, + 545, + 677 + ], + "spans": [ + { + "bbox": [ + 304, + 616, + 545, + 677 + ], + "type": "text", + "content": "Facial Age Recognition: Age variation can be considered linear, and we can utilize TDT to draw the relationship between visual feature differences among different images and the corresponding age variation. Therefore, we can directly employ Eq.8 for optimizing age estimation." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "content": "Aesthetic Assessment: The aesthetic assessment variation in scores can be considered linear, similar to the optimization for the age estimation task, we can also choose" + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 46, + 670, + 286, + 691 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 670, + 286, + 691 + ], + "spans": [ + { + "bbox": [ + 46, + 670, + 286, + 691 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 46, + 670, + 286, + 691 + ], + "type": "text", + "content": "Linearity: given " + }, + { + "bbox": [ + 46, + 670, + 286, + 691 + ], + "type": "inline_equation", + "content": "\\Delta_{\\tau}(\\mathcal{X}_g^1, \\mathcal{X}_g^2) = \\Delta_{\\tau}(\\mathcal{X}_g^2, \\mathcal{X}_g^3)" + }, + { + "bbox": [ + 46, + 670, + 286, + 691 + ], + "type": "text", + "content": ", we have " + }, + { + "bbox": [ + 46, + 670, + 286, + 691 + ], + "type": "inline_equation", + "content": "Y^{1} - Y^{2} = Y^{2} - Y^{3}" + }, + { + "bbox": [ + 46, + 670, + 286, + 691 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 691, + 241, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 691, + 241, + 703 + ], + "spans": [ + { + "bbox": [ + 47, + 691, + 241, + 703 + ], + "type": "text", + "content": "Symmetry: " + }, + { + "bbox": [ + 47, + 691, + 241, + 703 + ], + "type": "inline_equation", + "content": "\\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^1 +\\delta \\mathcal{X}_g) = \\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^1 -\\delta \\mathcal{X}_g)" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 48, + 703, + 206, + 714 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 703, + 206, + 714 + ], + "spans": [ + { + "bbox": [ + 48, + 703, + 206, + 714 + ], + "type": "text", + "content": "Commutativity: " + }, + { + "bbox": [ + 48, + 703, + 206, + 714 + ], + "type": "inline_equation", + "content": "\\Delta_{\\tau}(\\mathcal{X}_g^1,\\mathcal{X}_g^2) = \\Delta_{\\tau}(\\mathcal{X}_g^2,\\mathcal{X}_g^1)" + }, + { + "bbox": [ + 48, + 703, + 206, + 714 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "type": "text", + "content": "11022" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 66, + 90, + 526, + 143 + ], + "blocks": [ + { + "bbox": [ + 197, + 71, + 394, + 81 + ], + "lines": [ + { + "bbox": [ + 197, + 71, + 394, + 81 + ], + "spans": [ + { + "bbox": [ + 197, + 71, + 394, + 81 + ], + "type": "text", + "content": "Table 1. Experiments setting for three tasks evaluated." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 66, + 90, + 526, + 143 + ], + "lines": [ + { + "bbox": [ + 66, + 90, + 526, + 143 + ], + "spans": [ + { + "bbox": [ + 66, + 90, + 526, + 143 + ], + "type": "table", + "html": "
TaskBaselineDatasetInput size
Facial Age RecognitionDAA(Resnet18)[8]MegaAge-Asian[75]96 × 96
Aesthetic AssessmentSAAN(Resnet50+VGG19) [72]TAD66K[27]256 × 256
Illumination EstimationFC4(FC, SqueezeNet)[31]Reprocessed Color Checker [18, 60]512 × 512
", + "image_path": "3ebbf05f6fdf59e096a28e96706fc4e9b273077ac75781562762b6cf6cb63d98.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 153, + 287, + 176 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 153, + 287, + 176 + ], + "spans": [ + { + "bbox": [ + 46, + 153, + 287, + 176 + ], + "type": "text", + "content": "Eq.8 as the overall optimization. In this case, the label corresponds to the aesthetic score." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "spans": [ + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "type": "text", + "content": "Illumination Estimation: In illumination estimation, a key step of automatic white balance, we consider the variation of the illumination to be approximately linear. Additionally, to better capture the differences in illumination angles, we combine Eq.8 and the angle error [31] as the overall optimization function " + }, + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "type": "inline_equation", + "content": "L_{ill} = L_T + \\frac{180}{\\pi} \\cdot \\arccos(p \\cdot p^*)" + }, + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "type": "text", + "content": ", where the " + }, + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "type": "inline_equation", + "content": "p^*" + }, + { + "bbox": [ + 46, + 177, + 287, + 273 + ], + "type": "text", + "content": " represent the normalized estimation and ground truth of illumination color, respectively." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 48, + 283, + 245, + 296 + ], + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 283, + 245, + 296 + ], + "spans": [ + { + "bbox": [ + 48, + 283, + 245, + 296 + ], + "type": "text", + "content": "Algorithm 1 The training process of our method" + } + ] + } + ], + "index": 4, + "type": "text" + }, + { + "bbox": [ + 52, + 298, + 286, + 531 + ], + "type": "list", + "angle": 0, + "index": 23, + "blocks": [ + { + "bbox": [ + 52, + 298, + 266, + 311 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 298, + 266, + 311 + ], + "spans": [ + { + "bbox": [ + 52, + 298, + 266, + 311 + ], + "type": "text", + "content": "1: Input: Sample set " + }, + { + "bbox": [ + 52, + 298, + 266, + 311 + ], + "type": "inline_equation", + "content": "X" + }, + { + "bbox": [ + 52, + 298, + 266, + 311 + ], + "type": "text", + "content": " and corresponding labels " + }, + { + "bbox": [ + 52, + 298, + 266, + 311 + ], + "type": "inline_equation", + "content": "Y" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 53, + 312, + 124, + 323 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 312, + 124, + 323 + ], + "spans": [ + { + "bbox": [ + 53, + 312, + 124, + 323 + ], + "type": "text", + "content": "2: Output: Loss" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "spans": [ + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "type": "text", + "content": "3: Prior Set Selection: Randomly select " + }, + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "type": "text", + "content": " samples " + }, + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "type": "inline_equation", + "content": "X_{2}" + }, + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "type": "text", + "content": " from the training set with labels " + }, + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "type": "inline_equation", + "content": "Y_{2}" + }, + { + "bbox": [ + 53, + 323, + 286, + 346 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 53, + 347, + 223, + 358 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 347, + 223, + 358 + ], + "spans": [ + { + "bbox": [ + 53, + 347, + 223, + 358 + ], + "type": "text", + "content": "4: for each sample " + }, + { + "bbox": [ + 53, + 347, + 223, + 358 + ], + "type": "inline_equation", + "content": "X_{1}" + }, + { + "bbox": [ + 53, + 347, + 223, + 358 + ], + "type": "text", + "content": " in forward pass do" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 53, + 358, + 264, + 370 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 358, + 264, + 370 + ], + "spans": [ + { + "bbox": [ + 53, + 358, + 264, + 370 + ], + "type": "text", + "content": "5: #Feature fusion and distribution generation" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 53, + 370, + 276, + 383 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 370, + 276, + 383 + ], + "spans": [ + { + "bbox": [ + 53, + 370, + 276, + 383 + ], + "type": "text", + "content": "6: " + }, + { + "bbox": [ + 53, + 370, + 276, + 383 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^1, \\mathcal{X}_g^2 \\gets g(X_1, \\Theta), g(X_2, \\Theta) \\# \\text{Extract features}" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 53, + 383, + 282, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 383, + 282, + 396 + ], + "spans": [ + { + "bbox": [ + 53, + 383, + 282, + 396 + ], + "type": "text", + "content": "7: " + }, + { + "bbox": [ + 53, + 383, + 282, + 396 + ], + "type": "inline_equation", + "content": "N, C, \\bar{h}, w \\gets \\mathcal{X}_g^2" + }, + { + "bbox": [ + 53, + 383, + 282, + 396 + ], + "type": "text", + "content": ". shape # " + }, + { + "bbox": [ + 53, + 383, + 282, + 396 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 53, + 383, + 282, + 396 + ], + "type": "text", + "content": " is distribution number" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 53, + 396, + 193, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 396, + 193, + 407 + ], + "spans": [ + { + "bbox": [ + 53, + 396, + 193, + 407 + ], + "type": "text", + "content": "8: " + }, + { + "bbox": [ + 53, + 396, + 193, + 407 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_q^1\\gets \\mathcal{X}_q^1.\\text{repeat}(N,1,1,1)" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 53, + 407, + 220, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 407, + 220, + 418 + ], + "spans": [ + { + "bbox": [ + 53, + 407, + 220, + 418 + ], + "type": "text", + "content": "9: " + }, + { + "bbox": [ + 53, + 407, + 220, + 418 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s\\gets conv(conv(\\mathcal{X}_q^1,\\mathcal{X}_q^2,1),C)" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 53, + 418, + 268, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 418, + 268, + 430 + ], + "spans": [ + { + "bbox": [ + 53, + 418, + 268, + 430 + ], + "type": "text", + "content": "10: # Perform TDT operation on " + }, + { + "bbox": [ + 53, + 418, + 268, + 430 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_q^1" + }, + { + "bbox": [ + 53, + 418, + 268, + 430 + ], + "type": "text", + "content": " based on " + }, + { + "bbox": [ + 53, + 418, + 268, + 430 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 53, + 430, + 228, + 442 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 430, + 228, + 442 + ], + "spans": [ + { + "bbox": [ + 53, + 430, + 228, + 442 + ], + "type": "text", + "content": "11: " + }, + { + "bbox": [ + 53, + 430, + 228, + 442 + ], + "type": "inline_equation", + "content": "\\mu (\\mathcal{X}_s),\\sigma (\\mathcal{X}_s)\\gets calc\\_ mean\\_ std(\\mathcal{X}_s)" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 53, + 442, + 268, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 442, + 268, + 460 + ], + "spans": [ + { + "bbox": [ + 53, + 442, + 268, + 460 + ], + "type": "text", + "content": "12: " + }, + { + "bbox": [ + 53, + 442, + 268, + 460 + ], + "type": "inline_equation", + "content": "\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^1)\\gets \\tau (\\frac{\\mathcal{X}_s - \\mu(\\mathcal{X}_s)}{\\sigma(\\mathcal{X}_s)} |b) - \\tau (\\frac{\\mathcal{X}_g^1 - \\mu(\\mathcal{X}_s)}{\\sigma(\\mathcal{X}_s)} |b)" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 53, + 460, + 245, + 471 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 460, + 245, + 471 + ], + "spans": [ + { + "bbox": [ + 53, + 460, + 245, + 471 + ], + "type": "text", + "content": "13: #Feature-to-Label Difference Mapping" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 53, + 471, + 209, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 471, + 209, + 483 + ], + "spans": [ + { + "bbox": [ + 53, + 471, + 209, + 483 + ], + "type": "text", + "content": "14: " + }, + { + "bbox": [ + 53, + 471, + 209, + 483 + ], + "type": "inline_equation", + "content": "sgn(\\mathcal{X}_s,\\mathcal{X}_g^1)\\gets (-1)^{cdf(\\mathcal{X}_g^1) > 0.5}" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 53, + 483, + 269, + 497 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 483, + 269, + 497 + ], + "spans": [ + { + "bbox": [ + 53, + 483, + 269, + 497 + ], + "type": "text", + "content": "15: " + }, + { + "bbox": [ + 53, + 483, + 269, + 497 + ], + "type": "inline_equation", + "content": "\\delta Y_{1}\\gets f(\\tilde{\\Delta} (\\mathcal{X}_{s},\\mathcal{X}_{g}^{1})\\cdot sgn(\\mathcal{X}_{s},\\mathcal{X}_{g}^{1}))" + }, + { + "bbox": [ + 53, + 483, + 269, + 497 + ], + "type": "text", + "content": " # via Eq.7" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 53, + 497, + 189, + 509 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 497, + 189, + 509 + ], + "spans": [ + { + "bbox": [ + 53, + 497, + 189, + 509 + ], + "type": "text", + "content": "16: where " + }, + { + "bbox": [ + 53, + 497, + 189, + 509 + ], + "type": "inline_equation", + "content": "f(\\cdot) = fc(gap(\\cdot))" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 53, + 509, + 255, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 509, + 255, + 521 + ], + "spans": [ + { + "bbox": [ + 53, + 509, + 255, + 521 + ], + "type": "text", + "content": "17: Optimize TDT, including " + }, + { + "bbox": [ + 53, + 509, + 255, + 521 + ], + "type": "inline_equation", + "content": "L_{S}, L_{M}" + }, + { + "bbox": [ + 53, + 509, + 255, + 521 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 53, + 509, + 255, + 521 + ], + "type": "inline_equation", + "content": "L_{P}" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 53, + 521, + 97, + 531 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 521, + 97, + 531 + ], + "spans": [ + { + "bbox": [ + 53, + 521, + 97, + 531 + ], + "type": "text", + "content": "18: end for" + } + ] + } + ], + "index": 22 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 551, + 181, + 563 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 551, + 181, + 563 + ], + "spans": [ + { + "bbox": [ + 47, + 551, + 181, + 563 + ], + "type": "text", + "content": "3.3. TDT Algorithm Process" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 46, + 570, + 268, + 582 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 268, + 582 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 268, + 582 + ], + "type": "text", + "content": "To be more clear, we provide pseudocode 1, in 5 parts." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 46, + 582, + 287, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 287, + 629 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 287, + 629 + ], + "type": "text", + "content": "Prior Samples Selection: Prior samples are several selected training samples, providing comparison with those samples used for training/testing. Features for the prior samples can be pre-computed and integrated into the model." + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "type": "text", + "content": "Distribution generation: We obtain " + }, + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "type": "text", + "content": " and form its high-dimensional Normal Distribution using " + }, + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "type": "inline_equation", + "content": "\\mu(\\mathcal{X}_s)" + }, + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "type": "inline_equation", + "content": "\\sigma(\\mathcal{X}_s)" + }, + { + "bbox": [ + 46, + 630, + 287, + 689 + ], + "type": "text", + "content": ". After standardizing and approximating, we get a zero-symmetric high-dimensional Triangular Distribution to linearly represent feature differences." + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": "TDT Operation: It calculates the PDF differences between " + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g" + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": " based on the distribution of " + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": " meet" + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 305, + 152, + 545, + 189 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 152, + 545, + 189 + ], + "spans": [ + { + "bbox": [ + 305, + 152, + 545, + 189 + ], + "type": "inline_equation", + "content": "\\left|\\Delta (\\mathcal{X}_g^1,\\mathcal{X}_g^2)\\right| = 2\\cdot \\left|\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^1)\\right| = 2\\cdot \\left|\\Delta (\\mathcal{X}_s,\\mathcal{X}_g^2)\\right|" + }, + { + "bbox": [ + 305, + 152, + 545, + 189 + ], + "type": "text", + "content": " Remarkably, TDT is entirely formulaic, parameter-free, and fit any net outputting feature maps." + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "spans": [ + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "text", + "content": "Difference Mapping: Base on distribution of " + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "text", + "content": " generally has a higher PDF than " + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g" + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "text", + "content": ", meaning " + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "inline_equation", + "content": "\\Delta(\\mathcal{X}_s, \\mathcal{X}_g) = \\text{pdf}(\\mathcal{X}_s) - \\text{pdf}(\\mathcal{X}_g) \\geq 0" + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "text", + "content": ". We infer feature difference signs from " + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "inline_equation", + "content": "\\text{cdf}(\\mathcal{X}_g) > 0.5" + }, + { + "bbox": [ + 304, + 190, + 545, + 250 + ], + "type": "text", + "content": " and linearly map them to label difference via global average pooling and a linear layer." + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "spans": [ + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "type": "text", + "content": "**Optimization:** For commutativity loss, we utilize the mean and std of " + }, + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^1" + }, + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^2" + }, + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "type": "text", + "content": ". For symmetry and supervisory losses, those of " + }, + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 304, + 251, + 545, + 286 + ], + "type": "text", + "content": " are computed." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 305, + 300, + 386, + 313 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 300, + 386, + 313 + ], + "spans": [ + { + "bbox": [ + 305, + 300, + 386, + 313 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 32 + }, + { + "bbox": [ + 305, + 319, + 487, + 332 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 319, + 487, + 332 + ], + "spans": [ + { + "bbox": [ + 305, + 319, + 487, + 332 + ], + "type": "text", + "content": "4.1. Notes and Implementation Details" + } + ] + } + ], + "index": 33 + }, + { + "bbox": [ + 304, + 339, + 545, + 363 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 339, + 545, + 363 + ], + "spans": [ + { + "bbox": [ + 304, + 339, + 545, + 363 + ], + "type": "text", + "content": "We perform TDT validation on the baseline in three tasks, whose configuration details are shown in Table 1." + } + ] + } + ], + "index": 34 + }, + { + "bbox": [ + 304, + 364, + 545, + 519 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 364, + 545, + 519 + ], + "spans": [ + { + "bbox": [ + 304, + 364, + 545, + 519 + ], + "type": "text", + "content": "Train and Test notes: As observed in pseudocode 1, our TDT aims to guide the learning of unknown samples using prior samples, resembling contrastive learning. Therefore, for each task experiment, we randomly select a prior set from the training dataset. During training and testing, each batch comprises both the prior set samples used to obtain " + }, + { + "bbox": [ + 304, + 364, + 545, + 519 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^2" + }, + { + "bbox": [ + 304, + 364, + 545, + 519 + ], + "type": "text", + "content": " and the unknown samples used to obtain " + }, + { + "bbox": [ + 304, + 364, + 545, + 519 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g^1" + }, + { + "bbox": [ + 304, + 364, + 545, + 519 + ], + "type": "text", + "content": ". Each unknown sample undergoes TDT operations with all prior samples to make predictions, and the average of these predictions is considered as the final prediction. To reduce feature extraction time during testing, we encapsulate all the features from the prior set into the model parameters, resulting in an optimized model with accelerated inference." + } + ] + } + ], + "index": 35 + }, + { + "bbox": [ + 304, + 520, + 545, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 520, + 545, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 520, + 545, + 616 + ], + "type": "text", + "content": "Common Setting: For all experiments, we used the Adam optimizer, where the weight decay and the momentum were set to 0.0005 and 0.9, respectively. The initial learning rate was set to 0.001 and changed according to cosine learning rate decay. We trained our model using PyTorch on a cluster of 8 RTX 3090 GPUs. In an online manner, we augment all images with random horizontal flipping, scaling, rotation, and translation." + } + ] + } + ], + "index": 36 + }, + { + "bbox": [ + 304, + 616, + 545, + 699 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 616, + 545, + 699 + ], + "spans": [ + { + "bbox": [ + 304, + 616, + 545, + 699 + ], + "type": "text", + "content": "Facial Age Recognition: We utilize the FG-Net [47] dataset, which comprises 1002 facial images from 82 subjects, spanning an age range from 0 to 69. We follow the setup described in the papers [8, 12, 40], employing leave-one-person-out (LOPO) cross-validation. We report the average performance over 82 splits using the Mean Absolute Error (MAE) as the evaluation metric." + } + ] + } + ], + "index": 37 + }, + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "content": "Additionally, we also use the MegaAge-Asian [75]" + } + ] + } + ], + "index": 38 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "text", + "content": "11023" + } + ] + } + ], + "index": 39 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 52, + 90, + 282, + 198 + ], + "blocks": [ + { + "bbox": [ + 106, + 71, + 228, + 82 + ], + "lines": [ + { + "bbox": [ + 106, + 71, + 228, + 82 + ], + "spans": [ + { + "bbox": [ + 106, + 71, + 228, + 82 + ], + "type": "text", + "content": "Table 2. CA on MegaAge-Asian." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 52, + 90, + 282, + 198 + ], + "lines": [ + { + "bbox": [ + 52, + 90, + 282, + 198 + ], + "spans": [ + { + "bbox": [ + 52, + 90, + 282, + 198 + ], + "type": "table", + "html": "
MethodsPre-trainedCA(3)CA(5)CA(7)
Posterior [75]IMDB-WIKI62.0880.4390.42
MobileNet [54]IMDB-WIKI44.060.6-
DenseNet [70]IMDB-WIKI51.769.4-
SSR-Net [70]IMDB-WIKI54.974.1-
UVA [38]-60.4779.9590.44
LRN(ResNet10) [39]IMDB-WIKI62.8681.4791.34
LRN(ResNet18) [39]IMDB-WIKI64.4582.9591.98
VGG16(norm) [78]ImageNet, IMDB-WIKI, AFAD65.5883.0189.17
PVP+VGG16 [78]ImageNet, IMDB-WIKI, AFAD72.6587.2493.16
DAA(single channel) [8]-67.9784.0692.40
DAA(multi-channel) [8]-68.2984.8492.47
DAA [8]-68.8284.8992.70
TDT (ours)-69.6085.4293.26
", + "image_path": "73c2fc411f4adcbbdb2d752354d3b78849d8ed3b53aad4411cd85df8f0b1e632.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 115, + 230, + 217, + 311 + ], + "blocks": [ + { + "bbox": [ + 103, + 211, + 231, + 221 + ], + "lines": [ + { + "bbox": [ + 103, + 211, + 231, + 221 + ], + "spans": [ + { + "bbox": [ + 103, + 211, + 231, + 221 + ], + "type": "text", + "content": "Table 3. MAEs on FG-Net dataset." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 115, + 230, + 217, + 311 + ], + "lines": [ + { + "bbox": [ + 115, + 230, + 217, + 311 + ], + "spans": [ + { + "bbox": [ + 115, + 230, + 217, + 311 + ], + "type": "table", + "html": "
MethodsMAEYear
DEX[52]3.092015
MV[46]2.682018
C3AE[74]2.952019
DRFs[58]3.852021
PML[12]2.162021
DAA [8]2.192023
TDT(ours)2.12-
", + "image_path": "3af716a9b5841160a41eb179c2efbbd061152d8e47b83344f5be02fc384dd87b.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "spans": [ + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "text", + "content": "Dataset, consisting of 40,000 age-labeled samples spanning 0 to 70 years and 3,945 images for testing. For this dataset, we choose cumulative accuracy (CA) [75] as the evaluation metric, defined as " + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "inline_equation", + "content": "CA(n) = \\frac{K_n}{K} \\times 100" + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "text", + "content": " is total number of testing images and " + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "inline_equation", + "content": "K_n" + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "text", + "content": " is the number whose absolute errors are smaller than " + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 327, + 286, + 399 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 400, + 287, + 435 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 400, + 287, + 435 + ], + "spans": [ + { + "bbox": [ + 46, + 400, + 287, + 435 + ], + "type": "text", + "content": "We adopt the official implementation of DAA[8] as the baseline for this task while replacing its DAA mapping with our TDT. The output size of " + }, + { + "bbox": [ + 46, + 400, + 287, + 435 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_q" + }, + { + "bbox": [ + 46, + 400, + 287, + 435 + ], + "type": "text", + "content": " is set to " + }, + { + "bbox": [ + 46, + 400, + 287, + 435 + ], + "type": "inline_equation", + "content": "3\\times 3" + }, + { + "bbox": [ + 46, + 400, + 287, + 435 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 437, + 287, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 287, + 460 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 287, + 460 + ], + "type": "text", + "content": "In this task, 256 images are randomly picked from the training set serves as the prior set for all experiments." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 461, + 287, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 461, + 287, + 641 + ], + "spans": [ + { + "bbox": [ + 46, + 461, + 287, + 641 + ], + "type": "text", + "content": "Aesthetic Assessment: We use TAD66K (Theme and Aesthetics Dataset with 66K images) Dataset [27], a large-scale aesthetic quality assessment database with 47 themes. Images belonging to each theme are annotated independently, with each image containing a minimum of 1200 valid annotations. The aesthetic score of each image is treated as the label. Following TANet[27], the evaluation metric is the Mean Squared Error (MSE). We adopt the same train-test split setting. For the prior set, we select samples by choosing 2 random samples for each score ranging from 0 to 10 with interval 0.1 for each theme. We employ the official implementation of SAAN[72] as the baseline for this task while removing the final average pooling and BN layers. Additionally, we incorporate extra convolutions to obtain " + }, + { + "bbox": [ + 46, + 461, + 287, + 641 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g" + }, + { + "bbox": [ + 46, + 461, + 287, + 641 + ], + "type": "text", + "content": " with size of " + }, + { + "bbox": [ + 46, + 461, + 287, + 641 + ], + "type": "inline_equation", + "content": "8\\times 8" + }, + { + "bbox": [ + 46, + 461, + 287, + 641 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 642, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 287, + 712 + ], + "type": "text", + "content": "Illumination Estimation: We use reprocessed Color Checker [18, 60] dataset, one of the most widely adopted datasets in illumination estimation. Following " + }, + { + "bbox": [ + 46, + 642, + 287, + 712 + ], + "type": "inline_equation", + "content": "\\mathrm{FC^4}" + }, + { + "bbox": [ + 46, + 642, + 287, + 712 + ], + "type": "text", + "content": " [31], the evaluation metric is the Recovery Angular Error. To facilitate better comparisons, we use the linear fully connected version of " + }, + { + "bbox": [ + 46, + 642, + 287, + 712 + ], + "type": "inline_equation", + "content": "\\mathrm{FC^4}" + }, + { + "bbox": [ + 46, + 642, + 287, + 712 + ], + "type": "text", + "content": "-net as the baseline, instead of the non-linear" + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 309, + 90, + 545, + 198 + ], + "blocks": [ + { + "bbox": [ + 331, + 71, + 520, + 81 + ], + "lines": [ + { + "bbox": [ + 331, + 71, + 520, + 81 + ], + "spans": [ + { + "bbox": [ + 331, + 71, + 520, + 81 + ], + "type": "text", + "content": "Table 4. Results on Aesthetic Benchmark TAD66K." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 90, + 545, + 198 + ], + "lines": [ + { + "bbox": [ + 309, + 90, + 545, + 198 + ], + "spans": [ + { + "bbox": [ + 309, + 90, + 545, + 198 + ], + "type": "table", + "html": "
methodPub.BasicMSE
RAPID [41]ACMMM2014incorporate heterogeneous0.0200
PAM[50]ICCV2017residual-based, active learning0.0200
ALamp[42]CVPR2017layout-aware, multi-patch0.0190
NIMA [63]TIP2018predict distribution0.0210
MPada [59]ACMM2018attention, multi-patch0.0220
MLSP [30]CVPR2019staged training,multi-level features0.0190
UIAA [73]TIP2019unified probabilistic formulation0.0210
HGCN [56]CVPR2021graph convolution networks0.0200
TANet [27]IJCAI2022attention, adaptive features0.0161
SAAN [72]CVPR2023AdaIN,self-supervised Pretraining0.0185
TDT(ours)-Triangular Distribution0.0172
", + "image_path": "13d482d354dfabaa7eebe2528e084fe73229e4f203605de741f244fa7ffd7cc8.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 212, + 545, + 296 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 212, + 545, + 296 + ], + "spans": [ + { + "bbox": [ + 304, + 212, + 545, + 296 + ], + "type": "text", + "content": "weight pooling version. With additional convolutional layers, we obtain " + }, + { + "bbox": [ + 304, + 212, + 545, + 296 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_g\\in \\mathbb{R}^{N\\times C\\times 8\\times 8}" + }, + { + "bbox": [ + 304, + 212, + 545, + 296 + ], + "type": "text", + "content": ". When comparing with the " + }, + { + "bbox": [ + 304, + 212, + 545, + 296 + ], + "type": "inline_equation", + "content": "\\mathrm{FC^4}" + }, + { + "bbox": [ + 304, + 212, + 545, + 296 + ], + "type": "text", + "content": " model, we randomly select 128 samples from the training set as the prior set. However, when comparing with the method proposed by Tang et al. [64] that utilizes the extended external sRGB datasets, we choose same images for scene classification as the prior set, but only 1280 samples." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 296, + 545, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 296, + 545, + 357 + ], + "spans": [ + { + "bbox": [ + 304, + 296, + 545, + 357 + ], + "type": "text", + "content": "Following previous AWB works[18, 31, 60], 3-fold cross-validation is used. Standard metrics (mean, median, tri-mean of all the errors, the mean of the lowest " + }, + { + "bbox": [ + 304, + 296, + 545, + 357 + ], + "type": "inline_equation", + "content": "25\\%" + }, + { + "bbox": [ + 304, + 296, + 545, + 357 + ], + "type": "text", + "content": ", and the mean of the highest " + }, + { + "bbox": [ + 304, + 296, + 545, + 357 + ], + "type": "inline_equation", + "content": "25\\%" + }, + { + "bbox": [ + 304, + 296, + 545, + 357 + ], + "type": "text", + "content": " of errors, the 95th percentile error) are reported in terms of angular error in degrees." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 366, + 425, + 379 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 366, + 425, + 379 + ], + "spans": [ + { + "bbox": [ + 306, + 366, + 425, + 379 + ], + "type": "text", + "content": "4.2. Results and Analysis" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 385, + 404, + 397 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 385, + 404, + 397 + ], + "spans": [ + { + "bbox": [ + 306, + 385, + 404, + 397 + ], + "type": "text", + "content": "Facial Age Estimation" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 398, + 545, + 517 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 398, + 545, + 517 + ], + "spans": [ + { + "bbox": [ + 304, + 398, + 545, + 517 + ], + "type": "text", + "content": "The quantitative comparison of a list of top-performing methods on the MegaAge-Asian Dataset is shown in Table 2. From the table, we can find that even stocked with pre-training on large-scale datasets, methods like [39, 78] are inferior to ours. Compared with SSR-Net, our improvement is over " + }, + { + "bbox": [ + 304, + 398, + 545, + 517 + ], + "type": "inline_equation", + "content": "8\\%" + }, + { + "bbox": [ + 304, + 398, + 545, + 517 + ], + "type": "text", + "content": ". PVP [78] gets higher CA(3) and CA(5) indexes, due to the massive pretraining on ImageNet[11], IMDB-WIKI[53], and AFAD[45]. DAA[8], published in 2023, shares the same setting with our proposed method, while TDT obtains better scores in all CA indexes." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 518, + 545, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 518, + 545, + 567 + ], + "spans": [ + { + "bbox": [ + 304, + 518, + 545, + 567 + ], + "type": "text", + "content": "To better prove the effectiveness of TDT, we also profile TDT on FG-Net [47], reported in Table 3. Using MAE as the metric, TDT leads the board with the smallest MAE, surpassing the same-setting competitor DAA." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 568, + 402, + 578 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 568, + 402, + 578 + ], + "spans": [ + { + "bbox": [ + 306, + 568, + 402, + 578 + ], + "type": "text", + "content": "Aesthetic Assessment." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 580, + 545, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 580, + 545, + 652 + ], + "spans": [ + { + "bbox": [ + 304, + 580, + 545, + 652 + ], + "type": "text", + "content": "In Table 4, we list the MSE scores for the selected and close-related aesthetic works. In an overall manner, TDT ranks second with an MSE score of 0.0172. This improvement simply originates from the deployment of the TDT plugin over SAAN [72], whose MSE is 0.0185, again showing the advantage of the label discriminative ability of TDT." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 653, + 414, + 663 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 653, + 414, + 663 + ], + "spans": [ + { + "bbox": [ + 306, + 653, + 414, + 663 + ], + "type": "text", + "content": "Illumination Estimation." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 665, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 712 + ], + "type": "text", + "content": "In Table 5, we report the statistics of the predicted angular error for a set of AWB algorithms on the Color Checker Dataset. On metrics like mean, and median values, the TDT based on " + }, + { + "bbox": [ + 304, + 665, + 545, + 712 + ], + "type": "inline_equation", + "content": "\\mathrm{FC^4}" + }, + { + "bbox": [ + 304, + 665, + 545, + 712 + ], + "type": "text", + "content": " outperforms other state-of-the-art methods," + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "text", + "content": "11024" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 91, + 286, + 184 + ], + "blocks": [ + { + "bbox": [ + 62, + 71, + 271, + 81 + ], + "lines": [ + { + "bbox": [ + 62, + 71, + 271, + 81 + ], + "spans": [ + { + "bbox": [ + 62, + 71, + 271, + 81 + ], + "type": "text", + "content": "Table 5. Results on AWB Dataset Color Checker Dataset." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 91, + 286, + 184 + ], + "lines": [ + { + "bbox": [ + 50, + 91, + 286, + 184 + ], + "spans": [ + { + "bbox": [ + 50, + 91, + 286, + 184 + ], + "type": "table", + "html": "
modelsmeanmed.tri.best25%worst 25%95th pct.
FFCC [3]1.800.951.180.274.65-
FC4(Weighted) [31]1.651.181.270.383.784.73
FC4[31]1.841.271.390.464.205.46
AlexNet FC4 [31]1.771.111.290.343.784.29
Multi-Hypothesis [37]2.101.321.530.365.10-
IGTN [67]1.580.92-0.283.70-
MDLCC [66]1.580.951.110.373.77-
TLCC+sRGB [64]1.510.981.070.333.52-
TDT+FC41.641.121.250.413.804.53
TDT+FC4+sRGB1.460.851.050.263.614.61
", + "image_path": "947f0f3dd8e31845b569040e250ac333b31391bfb8da01b8c354eb2f24476b48.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 83, + 226, + 249, + 271 + ], + "blocks": [ + { + "bbox": [ + 47, + 196, + 286, + 217 + ], + "lines": [ + { + "bbox": [ + 47, + 196, + 286, + 217 + ], + "spans": [ + { + "bbox": [ + 47, + 196, + 286, + 217 + ], + "type": "text", + "content": "Table 6. Loss ablation analysis on MegaAge-Asian. " + }, + { + "bbox": [ + 47, + 196, + 286, + 217 + ], + "type": "inline_equation", + "content": "\\checkmark" + }, + { + "bbox": [ + 47, + 196, + 286, + 217 + ], + "type": "text", + "content": " and - indicate whether to add this loss to the final loss." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 83, + 226, + 249, + 271 + ], + "lines": [ + { + "bbox": [ + 83, + 226, + 249, + 271 + ], + "spans": [ + { + "bbox": [ + 83, + 226, + 249, + 271 + ], + "type": "table", + "html": "
\\( L_S \\)\\( L_M \\)\\( L_P \\)CA(3)CA(5)CA(7)
-✓✓67.7484.3392.51
✓-✓68.4384.6292.60
✓✓✓69.6085.4293.26
", + "image_path": "1bdf1883ecd70ee14456f404915204be19985ecbe0e05454128adea1c9f6646c.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 284, + 286, + 308 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 284, + 286, + 308 + ], + "spans": [ + { + "bbox": [ + 47, + 284, + 286, + 308 + ], + "type": "text", + "content": "such as MDLCC [66] and TLCC [64]. On top of " + }, + { + "bbox": [ + 47, + 284, + 286, + 308 + ], + "type": "inline_equation", + "content": "\\mathrm{FC^4}" + }, + { + "bbox": [ + 47, + 284, + 286, + 308 + ], + "type": "text", + "content": ", TDT also boosts the performance by a noticeable gap." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 318, + 140, + 330 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 318, + 140, + 330 + ], + "spans": [ + { + "bbox": [ + 47, + 318, + 140, + 330 + ], + "type": "text", + "content": "4.3. Ablation Study" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 337, + 286, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 337, + 286, + 361 + ], + "spans": [ + { + "bbox": [ + 47, + 337, + 286, + 361 + ], + "type": "text", + "content": "We conduct an ablation study on the loss choice, the number of distributions and prior samples." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 361, + 107, + 372 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 361, + 107, + 372 + ], + "spans": [ + { + "bbox": [ + 47, + 361, + 107, + 372 + ], + "type": "text", + "content": "Loss function" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 374, + 286, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 374, + 286, + 422 + ], + "spans": [ + { + "bbox": [ + 47, + 374, + 286, + 422 + ], + "type": "text", + "content": "It is vital to study the impact of different losses in Eq.8 and the results are presented in Table 6. We observe that removing any loss incurs a decrement in the overall performance. And symmetry loss brings the most improvement." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "spans": [ + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "text", + "content": "We design a toy experiment to further analyze the loss function Eq.7. The age loss " + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "inline_equation", + "content": "L_{P}" + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "text", + "content": " is a supervisory loss due to the label is needed for computing " + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "inline_equation", + "content": "L_{P}" + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "text", + "content": ", while the symmetry-related loss " + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "inline_equation", + "content": "L_{S}" + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "text", + "content": " and the commutativity-related loss " + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "inline_equation", + "content": "L_{M}" + }, + { + "bbox": [ + 46, + 423, + 286, + 518 + ], + "type": "text", + "content": " are unsupervisory losses. Switching off all nonsupervisory loss, as seen in the top two rows of Table 7, we see a clear CA score drop, indicating the advantage brought by the nonsupervisory loss." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 520, + 286, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 520, + 286, + 590 + ], + "spans": [ + { + "bbox": [ + 46, + 520, + 286, + 590 + ], + "type": "text", + "content": "If we cut off the access to unsupervisory loss for part1 (in other words, for only " + }, + { + "bbox": [ + 46, + 520, + 286, + 590 + ], + "type": "inline_equation", + "content": "75\\%" + }, + { + "bbox": [ + 46, + 520, + 286, + 590 + ], + "type": "text", + "content": " data, the unsupersiory loss is calculated), as reported in the bottom half of Table 7, we claim: with increasing unlabeled data, the performance is massively improved, which again verifies the functionality of the symmetry-related and commutativity-related loss." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 593, + 183, + 603 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 593, + 183, + 603 + ], + "spans": [ + { + "bbox": [ + 47, + 593, + 183, + 603 + ], + "type": "text", + "content": "Distribution and Prior Number" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 605, + 286, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 286, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 286, + 676 + ], + "type": "text", + "content": "Besides the loss selection, the number of distributions is a vital factor. On the same MegaAge-Asian Dataset, we test the number of distributions from the set 32, 64, 128, 256. Table 8 shows that in general, the number of distributions has a minor effect on the final results and when feature is set 128-dimensional the performance is optimal." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 47, + 677, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 286, + 712 + ], + "type": "text", + "content": "The selected prior samples work like expert voting, hence we exploit the factor of the prior sample number. Table 8 proves that as the number of samples increases, the" + } + ] + } + ], + "index": 13 + }, + { + "type": "table", + "bbox": [ + 328, + 102, + 524, + 156 + ], + "blocks": [ + { + "bbox": [ + 306, + 71, + 545, + 92 + ], + "lines": [ + { + "bbox": [ + 306, + 71, + 545, + 92 + ], + "spans": [ + { + "bbox": [ + 306, + 71, + 545, + 92 + ], + "type": "text", + "content": "Table 7. Loss analysis on MegaAge-Asian. The whole dataset is divided into part1 and part2, with a ratio of " + }, + { + "bbox": [ + 306, + 71, + 545, + 92 + ], + "type": "inline_equation", + "content": "25\\%" + }, + { + "bbox": [ + 306, + 71, + 545, + 92 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 71, + 545, + 92 + ], + "type": "inline_equation", + "content": "75\\%" + }, + { + "bbox": [ + 306, + 71, + 545, + 92 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 328, + 102, + 524, + 156 + ], + "lines": [ + { + "bbox": [ + 328, + 102, + 524, + 156 + ], + "spans": [ + { + "bbox": [ + 328, + 102, + 524, + 156 + ], + "type": "table", + "html": "
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", + "image_path": "034f522ea093b53ab2d800f19fa22bb4e1dc56e702c1394911c698b0a2d8ae7c.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "table_body" + } + ], + "index": 15 + }, + { + "type": "table", + "bbox": [ + 314, + 186, + 535, + 274 + ], + "blocks": [ + { + "bbox": [ + 309, + 167, + 541, + 178 + ], + "lines": [ + { + "bbox": [ + 309, + 167, + 541, + 178 + ], + "spans": [ + { + "bbox": [ + 309, + 167, + 541, + 178 + ], + "type": "text", + "content": "Table 8. Experiments on feature distributions and prior samples." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 314, + 186, + 535, + 274 + ], + "lines": [ + { + "bbox": [ + 314, + 186, + 535, + 274 + ], + "spans": [ + { + "bbox": [ + 314, + 186, + 535, + 274 + ], + "type": "table", + "html": "
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", + "image_path": "85d1b4d7be876093740dd775537cc0a51239555b596b07597316e9580b9be5e0.jpg" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "table_body" + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 281, + 545, + 305 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 281, + 545, + 305 + ], + "spans": [ + { + "bbox": [ + 305, + 281, + 545, + 305 + ], + "type": "text", + "content": "credibility of the results improves, yet the enhancement in credibility gradually diminishes." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 314, + 484, + 326 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 314, + 484, + 326 + ], + "spans": [ + { + "bbox": [ + 306, + 314, + 484, + 326 + ], + "type": "text", + "content": "4.4. Visualization of what TDT learns" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 333, + 545, + 417 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 333, + 545, + 417 + ], + "spans": [ + { + "bbox": [ + 304, + 333, + 545, + 417 + ], + "type": "text", + "content": "Fig.3 shows that: once the training is completed, we see feature difference approximates a triangular distribution function on varying symmetric age. The same property can be found for the predicted delta age (Inset (b)) in Fig.3). This results from TDT learning. From the inset (c) in Fig.3, we observe that the symmetry loss range is almost the same, meeting the feature symmetry assumption." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 418, + 545, + 489 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 418, + 545, + 489 + ], + "spans": [ + { + "bbox": [ + 304, + 418, + 545, + 489 + ], + "type": "text", + "content": "Fig.4 shows some qualitative comparison on illumination estimation task. Starting from raw image, different prior sample gives a close-to-groundtruth predicted white point, averaged to form the final robust white point. For the 3rd row, the prediction slightly shifts away from the groundtruth, which we guess it is due to multi-illumination." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "spans": [ + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "text", + "content": "As shown in Fig.5, we study the performance of TDT learning the symmetry axis location. For any pair of facial images, for example an age-" + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "text", + "content": " image from test set and an age-" + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "text", + "content": " image from the prior set, thus the symmetry axis should locate at " + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "inline_equation", + "content": "(a + b)/2" + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "text", + "content": ". With " + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "inline_equation", + "content": "(a + b)/2" + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "text", + "content": " fixed, we alter the testing image and prior image, and draw a histogram of the resulted " + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "text", + "content": ", which in fact gather around the symmetry axis. For pairs of " + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "inline_equation", + "content": "\\{\\text{age-3}, \\text{age-34}\\}" + }, + { + "bbox": [ + 304, + 490, + 545, + 597 + ], + "type": "text", + "content": ", the mean of predicted symmetric age is 18.27, close to the symmetric age 18.50." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 609, + 378, + 621 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 609, + 378, + 621 + ], + "spans": [ + { + "bbox": [ + 306, + 609, + 378, + 621 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 713 + ], + "type": "text", + "content": "A learning framework based on the Triangular Distribution Transform is proposed in this paper. It connects the nonlinear feature difference and the corresponding label difference in a verified linear, symmetric, and commutativity manner. This transform can be used as a portable plug-in for vision regression tasks, e.g., we verify its application on three vision tasks. On facial age estimation, aesthetic as-" + } + ] + } + ], + "index": 24 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "text", + "content": "11025" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 72, + 68, + 221, + 177 + ], + "blocks": [ + { + "bbox": [ + 72, + 68, + 221, + 177 + ], + "lines": [ + { + "bbox": [ + 72, + 68, + 221, + 177 + ], + "spans": [ + { + "bbox": [ + 72, + 68, + 221, + 177 + ], + "type": "image", + "image_path": "763f1716649e444b17554834266237cf060e94b24d273b1a2b607a251ffbca1a.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 150, + 178, + 159, + 186 + ], + "lines": [ + { + "bbox": [ + 150, + 178, + 159, + 186 + ], + "spans": [ + { + "bbox": [ + 150, + 178, + 159, + 186 + ], + "type": "text", + "content": "(a)" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 223, + 68, + 371, + 177 + ], + "blocks": [ + { + "bbox": [ + 223, + 68, + 371, + 177 + ], + "lines": [ + { + "bbox": [ + 223, + 68, + 371, + 177 + ], + "spans": [ + { + "bbox": [ + 223, + 68, + 371, + 177 + ], + "type": "image", + "image_path": "db24380c13873a11b37f720445fd0193ef423d863ef389b71f82abb93ef19036.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 302, + 178, + 312, + 186 + ], + "lines": [ + { + "bbox": [ + 302, + 178, + 312, + 186 + ], + "spans": [ + { + "bbox": [ + 302, + 178, + 312, + 186 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 199, + 545, + 222 + ], + "lines": [ + { + "bbox": [ + 46, + 199, + 545, + 222 + ], + "spans": [ + { + "bbox": [ + 46, + 199, + 545, + 222 + ], + "type": "text", + "content": "Figure 3. 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Qualitative comparison of the final color correction result and those from individual prior samples. In the fourth column, the predictions from different priors (their color corrected images are given in right insets) are shown clustered around the ground truth location, with limited variance. 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For any pair of age-" + }, + { + "bbox": [ + 46, + 658, + 288, + 703 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 46, + 658, + 288, + 703 + ], + "type": "text", + "content": " image from test set and age-" + }, + { + "bbox": [ + 46, + 658, + 288, + 703 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 46, + 658, + 288, + 703 + ], + "type": "text", + "content": " image from the prior set, we draw a histogram of the resulted " + }, + { + "bbox": [ + 46, + 658, + 288, + 703 + ], + "type": "inline_equation", + "content": "\\mathcal{X}_s" + }, + { + "bbox": [ + 46, + 658, + 288, + 703 + ], + "type": "text", + "content": ", which in fact gather around the symmetry axis " + }, + { + "bbox": [ + 46, + 658, + 288, + 703 + ], + "type": "inline_equation", + "content": "(a + b) / 2" + }, + { + "bbox": [ + 46, + 658, + 288, + 703 + ], + "type": "text", + "content": ", w.r.t. the histogram figure." + } + ] + } + ], + "index": 32, + "angle": 0, + "type": "image_caption" + } + ], + "index": 31 + }, + { + "bbox": [ + 305, + 536, + 545, + 597 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 536, + 545, + 597 + ], + "spans": [ + { + "bbox": [ + 305, + 536, + 545, + 597 + ], + "type": "text", + "content": "sessment, and illumination estimation, the proposed TDT obtains on-par or even better performance than the prior arts, without much modification on the affiliated backbone. In the future, we will explore the application of TDT in a wider context, for example shape and pose estimation." + } + ] + } + ], + "index": 33 + }, + { + "bbox": [ + 306, + 605, + 421, + 619 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 605, + 421, + 619 + ], + "spans": [ + { + "bbox": [ + 306, + 605, + 421, + 619 + ], + "type": "text", + "content": "6. Acknowledgements" + } + ] + } + ], + "index": 34 + }, + { + "bbox": [ + 304, + 624, + 545, + 703 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 624, + 545, + 703 + ], + "spans": [ + { + "bbox": [ + 304, + 624, + 545, + 703 + ], + "type": "text", + "content": "This work is supported by the Natural Science Starting Project of SWPU (No.2022QHZ023), the Sichuan Scientific Innovation Fund (No.2022JDRC0009), the Sichuan Provincial Department of Science and Technology Project (No.2022NSFSC0283) and the Key Research and Development Project of Sichuan Provincial Department of Science and Technology (No.2023YFG0129)." + } + ] + } + ], + "index": 35 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "text", + "content": "11026" + } + ] + } + ], + "index": 36 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 286, + 712 + ], + "type": "list", + "angle": 0, + "index": 19, + "blocks": [ + { + "bbox": [ + 53, + 91, + 286, + 134 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 286, + 134 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 286, + 134 + ], + "type": "text", + "content": "[1] Kobus Barnard, Vlad Cardei, and Brian Funt. 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Comput., 13(3):1605-1618, 2022. 1" + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 734, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 734, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 734, + 318, + 742 + ], + "type": "text", + "content": "11029" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Vision from Models Rivals Learning Vision from Data/b7bae39a-3af5-4fdf-bc33-43a030ca35b8_content_list.json b/2024/Learning Vision from Models Rivals Learning Vision from Data/b7bae39a-3af5-4fdf-bc33-43a030ca35b8_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..5a06216d6deb6f2228b0bcc979b64898ee365410 --- /dev/null +++ b/2024/Learning Vision from Models Rivals Learning Vision from Data/b7bae39a-3af5-4fdf-bc33-43a030ca35b8_content_list.json @@ -0,0 +1,1553 @@ +[ + { + "type": "text", + "text": "Learning Vision from Models Rivals Learning Vision from Data", + "text_level": 1, + "bbox": [ + 161, + 130, + 805, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yonglong Tian $^{1,\\dagger}$ Lijie Fan $^{2,\\dagger,*}$ Kaifeng Chen $^{1}$ Dina Katabi $^{2}$ Dilip Krishnan $^{1}$ Phillip Isola $^{2}$", + "bbox": [ + 109, + 179, + 857, + 200 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1Google Research, 2MIT CSAIL, †equal contribution", + "bbox": [ + 264, + 208, + 704, + 227 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "GibthuRe: https://github.com/google-research/syn-rep-learn", + "bbox": [ + 228, + 236, + 743, + 252 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 286, + 313, + 301 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We introduce SynCLR, a novel approach for learning visual representations exclusively from synthetic images and synthetic captions, without any real data. We synthesize a large dataset of image captions using LLMs, then use an off-the-shelf text-to-image model to generate multiple images corresponding to each synthetic caption. We perform visual representation learning on these synthetic images via contrastive learning, treating images sharing the same caption as positive pairs. The resulting representations transfer well to many downstream tasks, competing favorably with other general-purpose visual representation learners such as CLIP and DINO v2 in image classification tasks. Furthermore, in dense prediction tasks such as semantic segmentation, SynCLR outperforms previous self-supervised methods by a significant margin, e.g., improving over MAE and iBOT by 6.2 and 4.3 mIoU on ADE20k for ViT-B/16.", + "bbox": [ + 75, + 318, + 473, + 561 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 590, + 209, + 607 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Representation learning extracts and organizes information from raw, often unlabeled data. The quality, quantity, and diversity of the data determines how good a representation the model can learn. The model becomes a reflection of the collective intelligence that exists in the data. We get what we feed in.", + "bbox": [ + 75, + 617, + 468, + 707 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Unsurprisingly, the current best-performing visual representation learning methods [59, 62] rely on large scale real datasets. However, the collection of real data has its own dilemmas. Collecting large scale uncurated data [71] is relatively cheap and thus quite achievable. However, for self-supervised representation learning, this approach exhibits poor scaling behavior –i.e., adding more uncurated data has little effect at large data scales [33, 80]. Collecting small scale curated data [21] also is achievable, but models trained in this way are limited to relatively narrow tasks. The ideal would be large scale curated datasets of real images, and", + "bbox": [ + 75, + 709, + 470, + 875 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/0055ce920975e0db375007ce202ef860a324e6798f2d7c37d54212d135862e3c.jpg", + "image_caption": [ + "Figure 1. Three paradigms for visual representation learning. Top row: Traditional methods, such as CLIP [62], learn only from real data; Middle row: Recent methods, such as StableRep [81], learn from real text and generated images; Bottom row: Our method, SynCLR, learns from synthetic text and synthetic images, and rival the linear transfer performance of CLIP on ImageNet despite not directly observing any real data." + ], + "image_footnote": [], + "bbox": [ + 506, + 286, + 867, + 522 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "recent work has indeed shown that this can lead to strong performance gains at scale [59], but this path is costly to pursue.", + "bbox": [ + 496, + 655, + 892, + 700 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To alleviate the cost, in this paper we ask if synthetic data, sampled from off-the-shelf generative models, is a viable path toward large scale curated datasets that can train state-of-the-art visual representations.", + "bbox": [ + 496, + 702, + 893, + 762 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We call such a paradigm learning from models, in contrast to directly learning from data. Models have several advantages as a data source for building large scale training sets: via their latent variables, conditioning variables, and hyperparameters, they provide new controls for curating data; we will make use of these controls in the method we propose. Models also can be easier to share and store (because models are more compressed than data), and can produce an unlimited number of data samples (albeit with", + "bbox": [ + 496, + 763, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Work done while interning at Google.", + "bbox": [ + 94, + 886, + 303, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "15887", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "finite diversity). A growing literature has studied these properties and other advantages (and disadvantages) of using generative models as a data source for training downstream models [3, 26, 40, 41, 69, 81]. Some of these methods use a hybrid mode – either mixing real and synthetic datasets [3] or needing a real dataset to generate another synthetic dataset [81]. Other methods try to learn representations from purely synthetic data [69] but lag far behind the best performing models. Instead, we show that learning from models, without training on any real data, can yield representations that match the top-performing representations learnt from real data. For instance, as illustrated in Figure 1, representations learnt by our method are able to transfer as well as OpenAI's CLIP [62] on ImageNet (both methods using ViT-B [24]).", + "bbox": [ + 73, + 90, + 472, + 316 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our approach leverages generative models to re-define the granularity of visual classes. As shown in Figure 2, consider we have four images generated using two prompts: \"a golden retriever; wearing sunglasses and a beach hat, rides a bike\" and \"a cute golden retriever sits in a house made of sushi\". Traditional self-supervised method such as SimCLR [13] will treat each of these images as a different class; embeddings for different images are pushed apart with no explicit consideration of the shared semantics between images. On the other extreme, supervised learning methods (i.e. SupCE) will regard all these images as a single class (e.g., \"golden retriever\"). This ignores nuances in the semantics of the images, such as the fact that the dogs are riding a bike in one pair of images and sitting inside a sushi house in the other pair of images. Instead, our method, SynCLR, treats captions as classes, i.e., each caption describes a visual class (this level of granularity was also explored in StableRep [81]). This allows us to group images by the concepts of \"riding a bike\" and \"sitting in a sushi house\", in addition to grouping by a coarser class label like \"golden retrieval\". This level of granularity is difficult to mine in real data, since collecting multiple images described by a given caption is non-trivial, especially when scaling up the number of captions. However, text-to-image diffusion models are fundamentally built with this ability; simply by conditioning on the same caption and using different noise inputs, a text-to-image diffusion model will produce different images that all match the same caption. In our experiments, we find the caption-level granularity outperforms both SimCLR and supervised training. Another advantage is that this definition of visual classes has good scalability. Unlike ImageNet-1k/21k where a given number of classes is fixed, we can augment existing classes (or data) in an online fashion, and theoretically scale up to as many classes as needed.", + "bbox": [ + 75, + 321, + 472, + 835 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our system consists of three steps. The first step is to synthesize a large corpus of image captions. We design a scalable approach by leveraging the in-context learning capability of large language models (LLMs), where we present", + "bbox": [ + 75, + 839, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/0d6c87813b3f7ca4064843a7584d68a8003cba40aa27e6a81a42b5ea57afa551.jpg", + "image_caption": [ + "Figure 2. Different learning objectives treat classification granularity differently. These images are generated by two prompts \"a golden retriever, wearing sunglasses and a beach hat, rides a bike\" and \"a cute golden retriever sits in a house made of sushi\". SimCLR treats each image as a class, while supervised cross-entropy treats them all as the same \"golden retrieval\" class. The former does not consider shared semantics between images, and the latter is coarse-grained and ignores actions or relationships between subjects/background. Our approach, SynCLR, defines visual classes by sentences." + ], + "image_footnote": [], + "bbox": [ + 501, + 88, + 890, + 324 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "examples of word-to-caption translations. Next, a text-to-image diffusion model is adopted to synthesize multiple images for each synthetic caption. This yields a synthetic dataset of 600M images. Then we train visual representation models by a combination of multi-positive contrastive learning [43] and masked image modeling [98].", + "bbox": [ + 496, + 494, + 893, + 585 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our learned representations transfer well. With SynCLR pre-training, our ViT-B and ViT-L models achieve $80.7\\%$ and $83.0\\%$ top-1 linear probing accuracy on ImageNet-1K, respectively, which is on par with OpenAI's CLIP [62]. On fine-grained classification tasks, SynCLR outperforms CLIP by $3.3\\%$ for ViT-B and $1.5\\%$ for ViT-L, and performs similarly to DINO v2 [59] models, which are distilled from a pre-trained ViT-g model. For semantic segmentation on ADE20k, SynCLR outperforms MAE pre-trained on ImageNet by 6.2 and 4.1 in mIoU for ViT-B and ViT-L under the same setup, showing strong transfer ability for dense prediction tasks similar to DINO v2, which additionally involves a training period on 518x518 resolution images that SynCLR does not have.", + "bbox": [ + 496, + 585, + 895, + 797 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 500, + 814, + 650, + 830 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Self-supervised representation learning approaches in vision develop domain-specific pre-text tasks, such as colorization [94], rotation prediction [31], and solving jigsaw puzzles [56]. Domain-agnostic approaches have been pop", + "bbox": [ + 496, + 839, + 895, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "15888", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "ular, such as contrastive learning [6, 13, 35, 38, 57, 78, 87] and masked image modeling [2, 4, 5, 29, 39, 86, 90, 98]. Contrastive learning promotes invariance [79] for two views of the same image and pushes apart representations for different images [85] (or only invariance [11, 34]); the resulting representations yield strong performance for linear or zero-shot transfer. Masked image modeling reconstructs the pixels [39, 90] or local features [4], often producing excellent fine-tuning transfer performance, especially in dense prediction tasks [39]. The state of the art DINO v2 [59] leverages both approaches, and our approach shares a similar spirit.", + "bbox": [ + 75, + 90, + 472, + 257 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Supervised learning [36, 45, 75] used to be the dominant approach for learning transferable visual representations for various tasks [23, 32, 72]. Recent studies [37, 49] has shown that, the transferability of representations learned in this way is limited, e.g., pre-training has no improvement over random initialization for dense prediction tasks (e.g., object detection) when the fine-tuning is long enough. Such limitation continues when the model has been scaled up to 22B [20]. An alternative paradigm learns visual representations from text supervision [42, 62], e.g., CLIP [62]. This approach is more flexible (i.e., not requiring classes) and provides richer supervision, often learning generalizable representations.", + "bbox": [ + 75, + 265, + 472, + 446 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Generative models as representation learners. A number of papers have explored the representations that are learned by generative models for various recognition tasks [22, 48]. As might be expected intuitively, such models indeed learn especially good representations for dense tasks, such as optical flow estimation [70], semantic segmentation [8, 91], and depth estimation [95]. Another line of work [18, 47] adapt pre-trained diffusion models for zero-shot image recognition via analysis-by-synthesis. These approaches may need to be adapted when the architectures of the generative models change or a new family of generative model emerge. Our approach treats images as universal interfaces with the hope of better generality.", + "bbox": [ + 75, + 454, + 472, + 650 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Learning from synthetic data from generative models. Synthetic data has been explored to train machine learning models in various domains [27, 46, 53, 54, 65, 66, 74, 77, 92]. In computer vision, the utilization of synthetic data for training models is common, ranging from optical flow [52] and autonomous driving [1] to semantic segmentation [15] and human pose estimation [84]. Others [41, 50] have explored synthetic data for representation learning, with the predominant approach of altering the latent variables of deep generative models. Our approach aligns with this research paradigm, but it diverges in its use of text-to-image models, which have also been investigated by other researchers [40, 69, 99]. But they use synthetic data for supervised learning [26, 69]. The closet work is StableRep [81], which also conducts representation learning but still needs a real text dataset.", + "bbox": [ + 75, + 659, + 472, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Approach", + "text_level": 1, + "bbox": [ + 498, + 90, + 609, + 107 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this paper, we study the problem of learning a visual encoder $f$ in the absence of real images or textual data. Our approach hinges on the utilization of three key resources: a language generation model $(g_1)$ , a text-to-image generative model $(g_2)$ , and a curated list of visual concepts $(C)$ . Our exploration include three steps: (1) we employ $g_1$ to synthesize a comprehensive set of image descriptions $T$ , which encompasses the range of visual concepts in $C$ ; (2) for each caption in $T$ , we generate multiple images using $g_2$ , culminating in an extensive synthetic image dataset $X$ ; (3) we train on $X$ to obtain a visual representation encoder $f$ .", + "bbox": [ + 496, + 116, + 893, + 282 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We use Llama-2 7B [83] and Stable Diffusion 1.5 [64] as $g_{1}$ and $g_{2}$ , respectively, because of their fast inference speed. We anticipate that better $g_{1}$ and $g_{2}$ in the future will further enhance the effectiveness of this approach.", + "bbox": [ + 496, + 282, + 893, + 344 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Synthesizing captions", + "text_level": 1, + "bbox": [ + 498, + 357, + 702, + 373 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To harness the capability of powerful text-to-image models for generating a substantial dataset of training images, we initially require a collection of captions that not only precisely depict an image but also exhibit diversity to encompass a broad spectrum of visual concepts.", + "bbox": [ + 496, + 381, + 893, + 455 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We have developed a scalable approach to create such a large collection of captions, leveraging the in-context learning capability of LLMs [9]. Our method involves crafting specific prompt engineering templates that guide the LLM to produce the required captions. We start by gathering the concept list $C$ from some existing datasets, such as ImageNet-21k [21] and Places-365 [96]. For each concept $c \\in C$ , we consider three straightforward templates to generate captions effectively.", + "bbox": [ + 496, + 458, + 893, + 593 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- $c \\rightarrow$ caption. As the most direct and simple approach, we have the Llama-2 model sample a sentence for the concept $c$ .", + "- $c, bg \\rightarrow$ caption. We combine the visual concept $c$ with a background or setting $bg$ . A naive approach would randomly select both $c$ and $bg$ , where $bg$ may correspond to a class name from a places dataset like [96]. However, this method often leads to unlikely combinations in the real world, such as a blue whale in a football field. Our ablation experiments demonstrate that this strategy results in suboptimal performance, likely because the generated captions fall far outside the training distribution of $g_{2}$ . Instead, we employ GPT-4 [58] to generate a list of suitable backgrounds for the chosen concepts. This approach increases the likelihood of generating more plausible combinations, such as a tiger in a forest or a cat in a kitchen, enhancing the overall quality of the results.", + "- $c, \\text{rel} \\rightarrow$ caption. Given a visual concept $c$ , we consider pairing it with a positional relationship word, $\\text{rel}$ . Take for instance, if $c$ signifies $\\text{cat}$ and $\\text{rel}$ translates to in front" + ], + "bbox": [ + 500, + 598, + 893, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "15889", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 2 + }, + { + "type": "table", + "img_path": "images/9c059581603d7f922b72bd316a2a38112c5b7468661aa8b6f2c1dd389a6c4564.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
TemplatesIn context examples
c->captionrevolver ->Multiple antique revolvers lie on a wooden table, gleaming under soft, ambient light. closetet ->The compact closet, brimming with clothes and shoes, exudes a feeling of organization. zebra ->A zebra is gallantly trotting across the vast, sunlit plains of the African savannah, creating a captivating black and white spectacle. bus station ->The bustling bus station thrums with restless energy, as travelers navigate through the crowded space, awaiting their journeys amid the echoes of departing buses.
c,bg->captiontiger, forest ->Two tigers are running together in the forest. lighter, motorhome ->In the cozy, cluttered environment of a well-traveled motorhome, a sleek silver lighter holds dominion on the rustic wooden table. sunset, lake ->Golden sunset hues reflect on a calm lake, silhouetting a lone canoeist against a backdrop of fiery clouds.
c,rel->captionkit fox, in front of ->A group of small, fluffy, golden kit foxes is playfully gathered in front of a lush, green, towering forest backdrop. cabbage, besides ->A vibrant image portrays a lush, green cabbage, glistening with dewdrops, nestled besides a rustic, wooden crate full of freshly harvested vegetables.
", + "bbox": [ + 89, + 88, + 880, + 323 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Table 1. We show examples for the three synthesis templates. Such examples are used as demonstrations for Llama-2 to perform the in-context learning task. We have 176 such examples in total. Most of them are generated by prompting GPT-4 [58], while a handful of others are human generated (in a 10M scale pilot study of synthetic captions, we do not notice significant differences between including or excluding human generated examples.)", + "bbox": [ + 75, + 330, + 893, + 388 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/8a42f1841f22903e4b63eb70e60d711d71f5a05e01cac9bfe87c99dfd12c5267.jpg", + "image_caption": [ + "Figure 3. In-context caption generation using Llama-2 [83]. We randomly sample three in-context examples for each inference run." + ], + "image_footnote": [], + "bbox": [ + 81, + 407, + 467, + 523 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "of, our objective is to prompt the LLM to create captions such as a cute yellow cat is enjoying the fish in front of the sofa. To add variety, we have a selection of 10 different positional relationship words that we randomly choose from.", + "bbox": [ + 89, + 594, + 468, + 670 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For each of the three templates, we have prepared multiple demonstration examples that serve as instructions for the LLM to complete the caption synthesis task. Table 1 shows a couple of examples for each template. In total, we have 106 examples for $c->prompt$ , 50 examples for $c, bg->prompt$ , and 20 examples for $c, rel->prompt$ . Such examples are mostly collected by prompting GPT-4, with a handful from human. In a pilot study, we do not observe difference between including or excluding human generated examples.", + "bbox": [ + 75, + 683, + 470, + 820 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In the stage of generating captions in-context, we select a concept and one of the three templates. Next, we randomly pick three examples from the chosen template and frame the caption generation as a text completion task. This process is illustrated in Figure 3.", + "bbox": [ + 75, + 825, + 470, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Synthesizing Images", + "text_level": 1, + "bbox": [ + 500, + 407, + 692, + 424 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For each text caption, we generate a variety of images by initiating the reverse diffusion process with different random noise. The Classifier-Free Guidance (CFG) scale is a crucial factor in this process. A higher CFG scale enhances the quality of the samples and the alignment between text and image, whereas a lower scale results in more diverse samples and better adherence to the original conditional distribution of images based on the given text. Following the approach used in StableRep [81], we opt for a lower CFG scale, specifically 2.5, and produce 4 images for each caption. Examples of these images can be seen in Figure 4.", + "bbox": [ + 496, + 436, + 893, + 604 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Representation Learning", + "text_level": 1, + "bbox": [ + 500, + 635, + 728, + 652 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Our representation learning method is built upon StableRep [81]. The key component of our approach is the multi-positive contrastive learning loss [43] which works by aligning (in the embedding space) images generated from the same caption. We additionally combine multiple techniques from other self-supervised learning methods, including a patch-level masked image modeling objective. We briefly review StableRep and elaborate on the added modules.", + "bbox": [ + 496, + 666, + 893, + 787 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "StableRep [81] minimizes the cross-entropy loss between a ground-truth assignment distribution and a contrastive assignment distribution. Consider an encoded anchor sample $\\pmb{a}$ and a set of encoded candidates $\\{\\pmb{b}_1, \\pmb{b}_2, \\dots, \\pmb{b}_K\\}$ . The contrastive assignment distribution $\\mathbf{q}$ describes how likely the model predicts $\\pmb{a}$ and each $\\pmb{b}$ to be generated from the same caption, and the ground-truth distribution is the actual match", + "bbox": [ + 496, + 794, + 895, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "15890", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/dc99af57ce94112007c0043dbe70f56a359cc6068754a28f472dc85053281589.jpg", + "image_caption": [ + "A plate of paella, a mixed rice dish with chicken, beans, and seafood" + ], + "image_footnote": [], + "bbox": [ + 99, + 88, + 447, + 157 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/9c549d9d6852c2bed63f35884b2498ecbe23a23b1be85f1137677ab6c2fb8d44.jpg", + "image_caption": [ + "An industrial power plant with its smokestacks belching black smoke." + ], + "image_footnote": [], + "bbox": [ + 99, + 174, + 447, + 243 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/7183cd8ec8c687dba982a5f8c99be5008b3add07a27b232ead4282a53c4e14f9.jpg", + "image_caption": [ + "A fluffy, black and white junco bird perches on a snow-covered fence, overlooking a dark forest.", + "Figure 4. Random examples of synthetic captions and images generated in our SynCLR pipeline. Each caption comes with 4 images." + ], + "image_footnote": [], + "bbox": [ + 99, + 253, + 447, + 321 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "between $\\pmb{a}$ and $\\pmb{b}$ ( $\\pmb{a}$ is allowed to match multiple $\\pmb{b}$ ):", + "bbox": [ + 76, + 404, + 421, + 420 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {q} _ {i} = \\frac {\\exp \\left(\\boldsymbol {a} \\cdot \\boldsymbol {b} _ {i} / \\tau\\right)}{\\sum_ {j = 1} ^ {K} \\exp \\left(\\boldsymbol {a} \\cdot \\boldsymbol {b} _ {j} / \\tau\\right)} \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 181, + 426, + 468, + 465 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {p} _ {i} = \\frac {\\mathbb {1} _ {\\operatorname {m a t c h} \\left(\\boldsymbol {a} , \\boldsymbol {b} _ {i}\\right)}}{\\sum_ {j = 1} ^ {K} \\mathbb {1} _ {\\operatorname {m a t c h} \\left(\\boldsymbol {a} , \\boldsymbol {b} _ {j}\\right)}} \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 200, + 467, + 468, + 503 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\tau \\in \\mathcal{R}_{+}$ is the scalar temperature, $\\pmb{a}$ and all $\\pmb{b}$ have been $\\ell_{2}$ normalized, and the indicator function $\\mathbb{1}_{\\mathrm{match}(\\cdot ,\\cdot)}$ indicates whether two samples are from the same caption. The contrastive loss for $\\pmb{a}$ is given as", + "bbox": [ + 76, + 511, + 468, + 571 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} (\\boldsymbol {a}) = H (\\boldsymbol {p}, \\boldsymbol {q}) = - \\sum_ {i = 1} ^ {K} \\mathbf {p} _ {i} \\log \\mathbf {q} _ {i} \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 153, + 580, + 468, + 622 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "iBOT [98] is a masked image modeling objective, wherein a localized patch is masked, and the model is tasked with predicting the tokenized representation of said masked patch. It adapts the DINO [11] objective from the image level into the patch level. We follow [67] to replace the softmax-centering method with the iterative Sinkhorn-Knopp (SK) algorithm [19]. We run SK for 3 iterations to build the prediction target.", + "bbox": [ + 75, + 628, + 468, + 750 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Exponential Moving Average (EMA) is firstly introduced into self-supervised learning by MoCo [38]. We use EMA to encode crops as $\\mathbf{b}$ and to produce the targets for iBOT loss. We update the EMA model as $\\theta_{ema} \\gets \\lambda \\theta_{ema} + (1 - \\lambda)\\theta$ , following a cosine schedule for $\\lambda$ from 0.994 to 1 during training [34, 59]. We find the EMA module not only increases the final performance, but also improves the training stability for long training schedules.", + "bbox": [ + 75, + 750, + 470, + 869 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Multi-crop strategy is introduced by [10] as a smart way to improve computation efficiency, and is adopted in this paper.", + "bbox": [ + 76, + 869, + 470, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For these local crops, we only employ the contrastive loss, omitting the iBOT loss. Local crops are encoded only by the student network, and matched to global crops from the same caption encoded by the EMA model. Such reuse of global crops saves computation. For each image $x$ , where we generate a single global crop $x^g$ alongside $n$ local crops $x^l$ , the final loss can be expressed as follows:", + "bbox": [ + 496, + 90, + 893, + 196 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} \\left(x ^ {g}\\right) + \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\mathcal {L} \\left(x _ {i} ^ {l}\\right) + \\mathcal {L} ^ {i B O T} \\left(x ^ {g}\\right) \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 573, + 204, + 892, + 243 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Implementation", + "text_level": 1, + "bbox": [ + 500, + 250, + 660, + 266 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Concept list. We concatenate class names from various datasets, including IN-1k [21], IN-21k (we keep the most frequent 13k classes), Aircraft [51], Cars [44], DTD [17], Flowers [55], Pets [60], Sun397 [88], Caltech-101 [30], Food101 [7], and Places-365 [96]. If the concept is a place (i.e. SUN397 and Places) or a texture (i.e. DTD), we only apply the $c \\rightarrow$ caption template. For fine-grained classes such as pets or flowers, we employ GPT-4 to generate a consolidated list of probable backgrounds, rather than producing distinct lists for each specific class. We favor more frequent sampling from IN-1k, Food101, Cars, Aircraft, and Flowers.", + "bbox": [ + 496, + 273, + 893, + 438 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Batches. For each training batch, we sample 2048 captions (except when noted), and use all of the 4 images generated by each caption. We generate 1 global and 4 local crops for each image. As a result, each batch contains 8192 global crops, which is similar with prior work [13, 14, 34, 81].", + "bbox": [ + 496, + 439, + 893, + 515 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Masking. For the iBOT loss, we randomly choose $50\\%$ images inside a batch to mask, and randomly mask $50\\%$ of the tokens in each chosen image. We use 65536 prototypes. While the target from the EMA model is ascertained using the SK algorithm, we apply softmax normalization to the output of the student model.", + "bbox": [ + 496, + 513, + 893, + 604 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Projection heads. We follow the design in MoCo v3 [14] and DINO [11] for the contrastive and iBOT loss heads, respectively, ensuring consistency with established methods. Other hyper-parameters. We set the temperature in the contrastive loss to 0.08. For the temperature used in the iBOT loss, we linearly increase it from 0.04 to 0.07 over 4000 iterations, and keep it as 0.07 afterwards, as in DINO [11]. Additionally, the weight decay parameter is incrementally adjusted from 0.04 to 0.2, adhering to a cosine schedule.", + "bbox": [ + 496, + 604, + 893, + 741 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiment", + "text_level": 1, + "bbox": [ + 500, + 753, + 624, + 770 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We first perform an ablation study to evaluate the efficacy of various designs and modules within our pipeline. Then we proceed to scale up the volume of synthetic data.", + "bbox": [ + 496, + 777, + 892, + 824 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Study different components", + "text_level": 1, + "bbox": [ + 500, + 832, + 750, + 848 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We analyze each component of SynCLR, and ablate their effectiveness in two measurements: (1) linear probing performance on IN-1k; (2) average accuracy of linear transfer on", + "bbox": [ + 496, + 854, + 893, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "15891", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/6620bcbf13362b40399a4909011b5b3d32e0506477099ad68d39c46b1c083af4.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
captionsStableRepSynCLR
INavg.INavg.
cc12m73.081.677.185.3
IN+h+Places75.480.078.783.0
IN+Places+LLM73.776.977.681.8
IN+OurBG+LLM75.378.578.281.9
our final config.75.885.778.888.1
", + "bbox": [ + 119, + 75, + 426, + 195 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/730d4ba3c1e8c9d69bbc3797e867aea64f6723f1b7e333458f3e97612bfa4b06.jpg", + "table_caption": [ + "Table 2. Comparison of different caption synthesis strategies. We report top-1 ImageNet linear evaluation accuracy and the average accuracy over 9 fine-grained datasets. Every item here includes 10M captions and 4 images per caption." + ], + "table_footnote": [], + "table_body": "
CFG234
IN top-172.872.672.6
", + "bbox": [ + 166, + 271, + 377, + 316 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "fine-grained datasets Aircraft [51], Cars [44], DTD [17], Flowers [55], Pets [60], Sun397 [88], Caltech-101 [30], Food-101 [7], and Pascal VOC [25]. For analysis conducted in this subsection, we train ViT-B/16 [24] models for 85000 iterations, and use the c1s token as image representation.", + "bbox": [ + 75, + 366, + 468, + 443 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Synthesize captions. Following [81], we use cc12m [12] real captions as our baseline, which has 10M sentences. To synthesize captions, we design the following variants: (a) $IN + h + \\text{Places}$ randomly combines one IN class plus its hypernyms in WordNet graph, with one place class; (b) $IN + \\text{Places} + \\text{LLM}$ uses the $c, bg \\rightarrow$ caption in-context synthesis template with $c$ from IN and $bg$ from places; (c) $IN + ourBG + \\text{LLM}$ uses the background classes output by GPT-4, instead of Places; (d) ours means our full configuration specified in Section 3.1. For each of the config, we generate 10M captions. If not enough, we do duplication.", + "bbox": [ + 75, + 443, + 470, + 611 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Results are summarized in Table 2, where we train both StableRep and SynCLR to avoid biases favored by a single method. Compared to a real caption dataset cc12m, simply concatenating IN and Places class names improves the ImageNet linear accuracy but reduces the fine-grained classification performance. Interestingly, naively asking Llama to combine IN and Places classes into captions yields the worst performance. Replacing random background from places with GPT generated background improves the accuracy. This shows the importance of synthesizing captions that follow the distribution of real captions, which were used to train the text-to-image model. Finally, our full configuration achieves the best accuracy on both ImageNet and fine-grained classification. Another advantage of our synthesis method is its scalability – scale up to hundreds of millions of captions with little duplication. In contrast, if we concatenate IN classes with Places classes, there are at most 365k unique captions.", + "bbox": [ + 75, + 611, + 470, + 869 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Synthesize images. There are two major parameters in this process: number of images per caption and classifier free", + "bbox": [ + 75, + 869, + 468, + 901 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/d655a86b77928bdc17af1622048f03b4ee1a91009e4c4a83fd0c9865dd47f7f6.jpg", + "table_caption": [ + "Table 3. Classifier-free guidance scale (CFG). Contrastive loss prefers small CFG scale but is not very sensitive to it." + ], + "table_footnote": [], + "table_body": "
methodEMAiBOTMCINavg.ADE20k
StableRep75.885.7-
✓76.786.748.0
✓✓77.687.150.5
✓✓78.687.849.5
SynCLR✓✓✓78.888.150.8
", + "bbox": [ + 522, + 75, + 870, + 172 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/c229974171e682b19749c65f3f03d269bcc016a01b08e1763605d0f90fa4e524.jpg", + "table_caption": [ + "Table 4. Important components for our model. ViT-B/16 models are trained for 85000 iterations. We study the modules that affect the ImageNet linear evaluation, the fine-grained classification (avg.), and ADE20k segmentation." + ], + "table_footnote": [], + "table_body": "
methodINavg.
Supervised CE71.975.0
SimCLR63.667.9
SynCLR75.378.5
", + "bbox": [ + 575, + 247, + 818, + 325 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 5. Comparison of different learning objectives. These objectives assume different levels of classification granularity, as shown in Figure 2. Our modeling, i.e., defining classes as captions, outperforms the other two. To accommodate Supervised CE training, all items here used $IN + OurBG + LLM$ entry in Table 2.", + "bbox": [ + 496, + 335, + 893, + 405 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "guidance scale. For the former, we find generating 4 images is almost able to reproduce StableRep [81]'s performance (10 images) when using cc12m captions (ours $73.0\\%$ v.s. StableRep $73.5\\%$ on ImageNet). Thus we stick to 4. For guidance scale, we briefly find the contrastive loss is not very sensitive to CFG in a pilot study, as shown in Table 3. Thus we stick to 2.5, similar as StableRep [81].", + "bbox": [ + 496, + 417, + 893, + 523 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Model components. We present the improvement of accuracy brought by different modules in Table 4. Compared to the baseline StableRep, adding a teacher EMA model improves the IN linear accuracy by $0.9\\%$ . Further adding iBOT local objective or the multi-crop strategy increases the accuracy by $0.9\\%$ and $1.9\\%$ , respectively. Combining all of them results in our full SynCLR model, which achieves $78.8\\%$ top-1 IN linear accuracy. The fine-grained classification performance follows a similar trend, and reaches $88.1\\%$ . Besides, we test the transfer ability to semantic segmentation on ADE20k. The iBOT objective brings 1.0 more mIoU than multi-crop strategy, demonstrating the effectiveness of masked image modeling for dense prediction tasks.", + "bbox": [ + 496, + 523, + 893, + 719 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Compare to SimCLR and supervised training. We compare the three different representation learning objectives shown in Figure 2, which classify images at different levels of granularity. Since supervised cross-entropy training requires a fixed set of balanced classes (indeed both fixed set and balance are limitations of such method), we use the $IN + ourBG + LLM$ configuration where we have 1000 balanced classes (i.e., each class has 40k images). The supervised training recipe follows [76]. For a fair comparison with SimCLR, we remove all unmatched modules (i.e., EMA, iBOT, and MC) to make sure that the only difference between SimCLR and our SynCLR is the classification gran", + "bbox": [ + 496, + 719, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "15892", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/93725bd73b2a8e4e82558695fb4896873771a709d686802bb23447578541c29f.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
textimg#imgsImageNetAircraftCarsDTDFlowersPetsSUN397Caltech-101Food-101VOC2007Average
StableReprealsyn100MViT-B/1675.759.283.580.197.388.374.394.785.187.983.4
CLIPrealreal400MViT-B/1680.259.586.779.298.193.178.494.792.889.285.7
ViT-L/1483.969.490.982.199.295.181.896.595.289.688.9
OpenCLIPrealreal400MViT-B/1678.961.192.381.998.291.577.995.290.988.086.3
400MViT-L/1482.367.194.083.698.892.581.096.493.488.888.4
2BViT-L/1483.471.795.385.399.094.282.297.594.188.989.8
DINO v2*-real142MViT-B/14\\( 83.9^{\\dagger} \\)79.488.283.399.696.277.396.192.888.289.0
ViT-L/14\\( 85.7^{\\dagger} \\)81.590.184.099.796.678.797.594.388.390.1
SynCLRsynsyn600MViT-B/1680.781.793.879.999.193.676.295.391.689.489.0
ViT-L/1483.085.694.282.199.294.178.496.193.490.390.4
", + "bbox": [ + 112, + 74, + 857, + 281 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ularity defined by the contrastive loss. For all of them, we do pre-training and then linear probing on the target dataset.", + "bbox": [ + 75, + 347, + 470, + 378 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 5 presents the comparison. Our multi-positive objective, which defines images as the same class if they are generated by the same caption, achieves the best performance. It outperforms supervised cross-entropy training and SimCLR by $3.4\\%$ and $11.7\\%$ for top-1 accuracy on ImageNet linear evaluation, and by $3.5\\%$ and $10.6\\%$ on fine-grained classification tasks. Besides, our objective does not require balance between samples from a fixed set of classes, making it easier to scale up.", + "bbox": [ + 75, + 378, + 470, + 513 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Scaling up", + "text_level": 1, + "bbox": [ + 76, + 526, + 194, + 542 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "After we have ablated different components, we scale up our experiments. Specifically, we synthesize a dataset of 150M captions, called SynCaps-150M, from which we generate 600M images. We train both ViT-B/16 and ViT-L/14 (no SwiGLU [73] or LayerScale [82]), and extend the training schedules to 500k steps with a batch size of 8192 captions. We use 224x224 resolution for all pre-training tasks.", + "bbox": [ + 75, + 551, + 468, + 656 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We compare SynCLR with OpenAI's CLIP [62], OpenCLIP [16], and DINO v2 [59], which represent learning from data. We note that ViT-B/14 and ViT-L/14 from DINO v2 are distilled from a ViT-g [93] model, which makes DINO v2 advantageous in our comparison. We also include StableRep [81], which uses the hybrid paradigm.", + "bbox": [ + 73, + 657, + 470, + 748 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ImageNet linear evaluation. For fair comparison,CLS token from the last block is used as representation across all models (whereas in DINO v2, results are from concatenating multiple layers). As shown in Table 6, SynCLR achieves $80.7\\%$ with ViT-B and $83.0\\%$ with ViT-L. This is similar as CLIP, but still lags behind DINO v2 by $3.2\\%$ and $2.7\\%$ , respectively, partially because of the extra distillation in DINO v2. We note SynCLR has already outperformed other self-supervised methods pre-trained directly on ImageNet-1k (e.g., DINO achieves $78.2\\%$ with ViT-B/16 and iBOT", + "bbox": [ + 75, + 750, + 470, + 901 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/2fcb919b1ea59aad5eaa27ec7353c3658657c25346997944144455bcda1e74f4.jpg", + "table_caption": [ + "Table 6. Comparison on ImageNet linear evaluation and fine-grained classifier. SynCLR achieves comparable results with OpenAI's CLIP and DINO v2 models, despite only using synthetic data. *DINO v2 modes are distilled from a ViT-g model, thus advantageous in this comparison. † we rerun only using c1s token instead of concatenating multiple layers presented in the original DINO v2 paper [59]." + ], + "table_footnote": [], + "table_body": "
methodpre-train datadistillViT-BViT-L
StableRephybrid, 100M49.4-
MoCo v3real, IN1K-1M47.349.1
BEiTreal, IN1K-1M+DALLE47.153.3
MAEreal, IN1K-1M48.153.6
iBOTreal, IN1K-1M50.0-
CLIPreal, WIT-400M52.6-
BEiT v2real, WIT-400M, IN1K✓53.156.7
DINO v2real, LVD-142M✓54.4†57.5†
SynCLRsynthetic, 600M54.357.7†
", + "bbox": [ + 503, + 344, + 890, + 507 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 7. ADE20K semantic segmentation (mIoU) using UperNet, with single scale at 512x512 resolution. ${}^{ \\dagger }$ use patch size of ${14}\\mathrm{x}{14}$ , thus adapt to 518x518 resolution.", + "bbox": [ + 498, + 517, + 893, + 559 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "reaches $81.0\\%$ with ViT-L/16).", + "bbox": [ + 500, + 566, + 705, + 580 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Fine-grained classification. On the nine fine-grained datasets we have evaluated in Table 6, SynCLR achieves very similar average accuracy as DINO v2, e.g., $89.0\\%$ vs. $89.0\\%$ for ViT-B, and $90.1\\%$ vs $90.4\\%$ for ViT-L. Both SynCLR and DINO v2 have curated the pre-training data to include the distribution for these datasets (but in different ways and portions), and end up with similar performance. Interestingly, SynCLR outperforms others on Aircraft and Cars, possibly because we favor more frequent sampling towards them. This can be an advantage for synthetic data when we know what downstream tasks to solve. Besides, SynCLR outperforms CLIP and StableRep by $3.3\\%$ and by $5.6\\%$ for ViT-B, respectively.", + "bbox": [ + 496, + 582, + 893, + 777 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Semantic segmentation. To evaluate the pixel-level understanding ability of SynCLR, we fine-tune the pre-trained models on ADE20k [97], following the setup in [5, 39]. UperNet [89] is used as the task layer, and we evaluate with a single-scale, i.e. $512 \\times 512$ . Besides CLIP and DINO v2, we also compare to self-supervised methods pre-trained on ImageNet, as well as BEiT v2 [61], which distills from CLIP. Table 7 shows that our SynCLR outperforms self-supervised", + "bbox": [ + 496, + 779, + 893, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "15893", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1ecdab7690d8f4a818dfb9f95dd53fe7776b7e644e3f37a1b082ce935ce9199b.jpg", + "image_caption": [ + "Figure 5. PCA visualization. Follow DINO v2 [59], we compute a PCA between the image patches from the same set and colorize by their first 3 components. Compared to DINO v2, SynCLR produces more accurate maps for cars (e.g., zoom-in to see the two bars on the roof of the first car, and the three side windows of the third car) and airplanes (e.g., the boundaries), while being slightly worse for dogs (e.g., heads). We use ViT-L/14 for both methods. Images are resized to $336 \\times 448$ resolution, yielding $24 \\times 32$ visualization grids." + ], + "image_footnote": [], + "bbox": [ + 106, + 90, + 349, + 296 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/74a4c6d2efba77a5dd546920a00901c13bd84234012634666c185976f07f49e4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 361, + 90, + 607, + 296 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/70ce50aa55f598f936bb951b4bbfe06e68d455294d9887f86a91e470f6596350.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 620, + 90, + 862, + 296 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "methods trained on IN-1k by a clear marge, e.g., 4.3 higher mIoU than iBOT. Despite not involving a high resolution pretraining period like DINO v2 (e.g., 518x518), SynCLR performs similarly with DINO v2 (0.1 lower for ViT-B possibly because DINO v2 uses a smaller patch size of 14x14, but 0.2 higher for ViT-L). This suggests SynCLR pre-training is suitable for dense prediction tasks.", + "bbox": [ + 75, + 377, + 470, + 482 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ImageNet fine-tuning. We evaluate the fine-tuning transfer ability of SynCLR on ImageNet. Our SynCLR achieves $87.9\\%$ top-1 accuracy with ViT-L, outperforming models trained on ImageNet images or large scale image datasets. Specifically, SynCLR outperforms OpenCLIP ViT-L (87.1% top-1) trained on Laion-2B, which is the dataset Stable Diffusion (the text2image model we used) is trained on. This contrasts with [26, 69], which shows that directly training a classifier on synthetic images yields bad classification accuracy. Our finding suggests synthetic images are good for training representations, which later can be easily adapted to a downstream task with limited amount of real data. Detailed comparisons are provided in Appendix C.", + "bbox": [ + 75, + 483, + 470, + 679 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "PCA visualization. Following the method used in DINO v2 [59], we present visualizations derived from the Principal Component Analysis (PCA) conducted on patch features extracted using our model SynCLR. As depicted in Figure 5, a comparative analysis is conducted between SynCLR and DINO v2, both utilizing the ViT-L/14 architecture. The results demonstrate that SynCLR effectively accentuates the features of cars and planes, while efficiently minimizing background clutter.", + "bbox": [ + 75, + 679, + 468, + 815 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Discussions and Conclusion", + "text_level": 1, + "bbox": [ + 76, + 829, + 333, + 845 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Why learn from generative models? One compelling reason is that a generative model can act like hundreds of datasets simultaneously. Traditionally, researchers have to", + "bbox": [ + 75, + 854, + 472, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "spend separate effort collecting datasets for different image categories, e.g., cars, flowers, cats, dogs, and so on. DINO v2 [59] achieves robust representations by curating and amalgamating numerous such datasets. Such a process introduces complexities such as clustering and search challenges. In contrast, advanced text-to-image generative models like Stable Diffusion [63] or Imagen [68] have the capability to generate many diverse datasets. These models provide the flexibility to produce an infinite number of samples (albeit finite diversity) and control the generation process through textual input. Thus, generative models offer a convenient and effective method for curating training data. In our study, we harness this advantage to synthesize images encompassing a broad spectrum of visual concepts.", + "bbox": [ + 496, + 377, + 893, + 589 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "What can be further improved? Enhanced caption sets can be achieved through various methods, such as enriching the set of in-context examples, optimizing the sampling ratios among different concepts, and utilizing more advanced LLMs. In terms of the learning process, one approach is to distill knowledge from a larger model, and incorporate an additional high-resolution training phase (as discussed in [59]) or an intermediate IN-21k fine-tuning stage (as per [5, 61]). Regarding architectural improvements, the integration of SwiGLU and LayerScale, coupled with superior model initialization strategies (referenced in [28]), can be beneficial. However, due to limited resources and the scope of this paper not being focused on achieving the highest possible metrics, we propose these areas for further exploration in future research endeavors.", + "bbox": [ + 496, + 595, + 893, + 820 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In summary, this paper studies a new paradigm for visual representation learning – learning from generative models. 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Training on thin air: Improve image classification with generated data. arXiv preprint arXiv:2305.15316, 2023. 3" + ], + "bbox": [ + 78, + 90, + 470, + 233 + ], + "page_idx": 11 + }, + { + "type": "page_number", + "text": "15898", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 11 + } +] \ No newline at end of file diff --git a/2024/Learning Vision from Models Rivals Learning Vision from Data/b7bae39a-3af5-4fdf-bc33-43a030ca35b8_model.json b/2024/Learning Vision from Models Rivals Learning Vision from Data/b7bae39a-3af5-4fdf-bc33-43a030ca35b8_model.json new file mode 100644 index 0000000000000000000000000000000000000000..be2e0da348edc38464a4e40c87c4da929f56c9a7 --- /dev/null +++ b/2024/Learning Vision from Models Rivals Learning Vision from Data/b7bae39a-3af5-4fdf-bc33-43a030ca35b8_model.json @@ -0,0 +1,2633 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.044 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.163, + 0.131, + 0.807, + 0.154 + ], + "angle": 0, + "content": "Learning Vision from Models Rivals Learning Vision from Data" + }, + { + "type": "text", + "bbox": [ + 0.111, + 0.18, + 0.859, + 0.201 + ], + "angle": 0, + "content": "Yonglong Tian\\(^{1,\\dagger}\\) Lijie Fan\\(^{2,\\dagger,*}\\) Kaifeng Chen\\(^{1}\\) Dina Katabi\\(^{2}\\) Dilip Krishnan\\(^{1}\\) Phillip Isola\\(^{2}\\)" + }, + { + "type": "text", + "bbox": [ + 0.265, + 0.209, + 0.705, + 0.228 + ], + "angle": 0, + "content": "1Google Research, 2MIT CSAIL, †equal contribution" + }, + { + "type": "text", + "bbox": [ + 0.229, + 0.237, + 0.744, + 0.253 + ], + "angle": 0, + "content": "GibthuRe: https://github.com/google-research/syn-rep-learn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.287, + 0.314, + 0.303 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.319, + 0.474, + 0.562 + ], + "angle": 0, + "content": "We introduce SynCLR, a novel approach for learning visual representations exclusively from synthetic images and synthetic captions, without any real data. We synthesize a large dataset of image captions using LLMs, then use an off-the-shelf text-to-image model to generate multiple images corresponding to each synthetic caption. We perform visual representation learning on these synthetic images via contrastive learning, treating images sharing the same caption as positive pairs. The resulting representations transfer well to many downstream tasks, competing favorably with other general-purpose visual representation learners such as CLIP and DINO v2 in image classification tasks. Furthermore, in dense prediction tasks such as semantic segmentation, SynCLR outperforms previous self-supervised methods by a significant margin, e.g., improving over MAE and iBOT by 6.2 and 4.3 mIoU on ADE20k for ViT-B/16." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.592, + 0.21, + 0.608 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.618, + 0.47, + 0.708 + ], + "angle": 0, + "content": "Representation learning extracts and organizes information from raw, often unlabeled data. The quality, quantity, and diversity of the data determines how good a representation the model can learn. The model becomes a reflection of the collective intelligence that exists in the data. We get what we feed in." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.71, + 0.471, + 0.876 + ], + "angle": 0, + "content": "Unsurprisingly, the current best-performing visual representation learning methods [59, 62] rely on large scale real datasets. However, the collection of real data has its own dilemmas. Collecting large scale uncurated data [71] is relatively cheap and thus quite achievable. However, for self-supervised representation learning, this approach exhibits poor scaling behavior –i.e., adding more uncurated data has little effect at large data scales [33, 80]. Collecting small scale curated data [21] also is achievable, but models trained in this way are limited to relatively narrow tasks. The ideal would be large scale curated datasets of real images, and" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.287, + 0.868, + 0.523 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.534, + 0.895, + 0.633 + ], + "angle": 0, + "content": "Figure 1. Three paradigms for visual representation learning. Top row: Traditional methods, such as CLIP [62], learn only from real data; Middle row: Recent methods, such as StableRep [81], learn from real text and generated images; Bottom row: Our method, SynCLR, learns from synthetic text and synthetic images, and rival the linear transfer performance of CLIP on ImageNet despite not directly observing any real data." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.656, + 0.893, + 0.701 + ], + "angle": 0, + "content": "recent work has indeed shown that this can lead to strong performance gains at scale [59], but this path is costly to pursue." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.703, + 0.894, + 0.763 + ], + "angle": 0, + "content": "To alleviate the cost, in this paper we ask if synthetic data, sampled from off-the-shelf generative models, is a viable path toward large scale curated datasets that can train state-of-the-art visual representations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.895, + 0.903 + ], + "angle": 0, + "content": "We call such a paradigm learning from models, in contrast to directly learning from data. Models have several advantages as a data source for building large scale training sets: via their latent variables, conditioning variables, and hyperparameters, they provide new controls for curating data; we will make use of these controls in the method we propose. Models also can be easier to share and store (because models are more compressed than data), and can produce an unlimited number of data samples (albeit with" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.304, + 0.901 + ], + "angle": 0, + "content": "*Work done while interning at Google." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15887" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.075, + 0.092, + 0.473, + 0.318 + ], + "angle": 0, + "content": "finite diversity). A growing literature has studied these properties and other advantages (and disadvantages) of using generative models as a data source for training downstream models [3, 26, 40, 41, 69, 81]. Some of these methods use a hybrid mode – either mixing real and synthetic datasets [3] or needing a real dataset to generate another synthetic dataset [81]. Other methods try to learn representations from purely synthetic data [69] but lag far behind the best performing models. Instead, we show that learning from models, without training on any real data, can yield representations that match the top-performing representations learnt from real data. For instance, as illustrated in Figure 1, representations learnt by our method are able to transfer as well as OpenAI's CLIP [62] on ImageNet (both methods using ViT-B [24])." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.323, + 0.473, + 0.837 + ], + "angle": 0, + "content": "Our approach leverages generative models to re-define the granularity of visual classes. As shown in Figure 2, consider we have four images generated using two prompts: \"a golden retriever; wearing sunglasses and a beach hat, rides a bike\" and \"a cute golden retriever sits in a house made of sushi\". Traditional self-supervised method such as SimCLR [13] will treat each of these images as a different class; embeddings for different images are pushed apart with no explicit consideration of the shared semantics between images. On the other extreme, supervised learning methods (i.e. SupCE) will regard all these images as a single class (e.g., \"golden retriever\"). This ignores nuances in the semantics of the images, such as the fact that the dogs are riding a bike in one pair of images and sitting inside a sushi house in the other pair of images. Instead, our method, SynCLR, treats captions as classes, i.e., each caption describes a visual class (this level of granularity was also explored in StableRep [81]). This allows us to group images by the concepts of \"riding a bike\" and \"sitting in a sushi house\", in addition to grouping by a coarser class label like \"golden retrieval\". This level of granularity is difficult to mine in real data, since collecting multiple images described by a given caption is non-trivial, especially when scaling up the number of captions. However, text-to-image diffusion models are fundamentally built with this ability; simply by conditioning on the same caption and using different noise inputs, a text-to-image diffusion model will produce different images that all match the same caption. In our experiments, we find the caption-level granularity outperforms both SimCLR and supervised training. Another advantage is that this definition of visual classes has good scalability. Unlike ImageNet-1k/21k where a given number of classes is fixed, we can augment existing classes (or data) in an online fashion, and theoretically scale up to as many classes as needed." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Our system consists of three steps. The first step is to synthesize a large corpus of image captions. We design a scalable approach by leveraging the in-context learning capability of large language models (LLMs), where we present" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.089, + 0.892, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.334, + 0.896, + 0.473 + ], + "angle": 0, + "content": "Figure 2. Different learning objectives treat classification granularity differently. These images are generated by two prompts \"a golden retriever, wearing sunglasses and a beach hat, rides a bike\" and \"a cute golden retriever sits in a house made of sushi\". SimCLR treats each image as a class, while supervised cross-entropy treats them all as the same \"golden retrieval\" class. The former does not consider shared semantics between images, and the latter is coarse-grained and ignores actions or relationships between subjects/background. Our approach, SynCLR, defines visual classes by sentences." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.495, + 0.895, + 0.586 + ], + "angle": 0, + "content": "examples of word-to-caption translations. Next, a text-to-image diffusion model is adopted to synthesize multiple images for each synthetic caption. This yields a synthetic dataset of 600M images. Then we train visual representation models by a combination of multi-positive contrastive learning [43] and masked image modeling [98]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.587, + 0.897, + 0.799 + ], + "angle": 0, + "content": "Our learned representations transfer well. With SynCLR pre-training, our ViT-B and ViT-L models achieve \\(80.7\\%\\) and \\(83.0\\%\\) top-1 linear probing accuracy on ImageNet-1K, respectively, which is on par with OpenAI's CLIP [62]. On fine-grained classification tasks, SynCLR outperforms CLIP by \\(3.3\\%\\) for ViT-B and \\(1.5\\%\\) for ViT-L, and performs similarly to DINO v2 [59] models, which are distilled from a pre-trained ViT-g model. For semantic segmentation on ADE20k, SynCLR outperforms MAE pre-trained on ImageNet by 6.2 and 4.1 in mIoU for ViT-B and ViT-L under the same setup, showing strong transfer ability for dense prediction tasks similar to DINO v2, which additionally involves a training period on 518x518 resolution images that SynCLR does not have." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.815, + 0.651, + 0.831 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Self-supervised representation learning approaches in vision develop domain-specific pre-text tasks, such as colorization [94], rotation prediction [31], and solving jigsaw puzzles [56]. Domain-agnostic approaches have been pop" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "15888" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.258 + ], + "angle": 0, + "content": "ular, such as contrastive learning [6, 13, 35, 38, 57, 78, 87] and masked image modeling [2, 4, 5, 29, 39, 86, 90, 98]. Contrastive learning promotes invariance [79] for two views of the same image and pushes apart representations for different images [85] (or only invariance [11, 34]); the resulting representations yield strong performance for linear or zero-shot transfer. Masked image modeling reconstructs the pixels [39, 90] or local features [4], often producing excellent fine-tuning transfer performance, especially in dense prediction tasks [39]. The state of the art DINO v2 [59] leverages both approaches, and our approach shares a similar spirit." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.266, + 0.473, + 0.448 + ], + "angle": 0, + "content": "Supervised learning [36, 45, 75] used to be the dominant approach for learning transferable visual representations for various tasks [23, 32, 72]. Recent studies [37, 49] has shown that, the transferability of representations learned in this way is limited, e.g., pre-training has no improvement over random initialization for dense prediction tasks (e.g., object detection) when the fine-tuning is long enough. Such limitation continues when the model has been scaled up to 22B [20]. An alternative paradigm learns visual representations from text supervision [42, 62], e.g., CLIP [62]. This approach is more flexible (i.e., not requiring classes) and provides richer supervision, often learning generalizable representations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.455, + 0.473, + 0.651 + ], + "angle": 0, + "content": "Generative models as representation learners. A number of papers have explored the representations that are learned by generative models for various recognition tasks [22, 48]. As might be expected intuitively, such models indeed learn especially good representations for dense tasks, such as optical flow estimation [70], semantic segmentation [8, 91], and depth estimation [95]. Another line of work [18, 47] adapt pre-trained diffusion models for zero-shot image recognition via analysis-by-synthesis. These approaches may need to be adapted when the architectures of the generative models change or a new family of generative model emerge. Our approach treats images as universal interfaces with the hope of better generality." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.66, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Learning from synthetic data from generative models. Synthetic data has been explored to train machine learning models in various domains [27, 46, 53, 54, 65, 66, 74, 77, 92]. In computer vision, the utilization of synthetic data for training models is common, ranging from optical flow [52] and autonomous driving [1] to semantic segmentation [15] and human pose estimation [84]. Others [41, 50] have explored synthetic data for representation learning, with the predominant approach of altering the latent variables of deep generative models. Our approach aligns with this research paradigm, but it diverges in its use of text-to-image models, which have also been investigated by other researchers [40, 69, 99]. But they use synthetic data for supervised learning [26, 69]. The closet work is StableRep [81], which also conducts representation learning but still needs a real text dataset." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.091, + 0.61, + 0.108 + ], + "angle": 0, + "content": "3. Approach" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.117, + 0.895, + 0.283 + ], + "angle": 0, + "content": "In this paper, we study the problem of learning a visual encoder \\( f \\) in the absence of real images or textual data. Our approach hinges on the utilization of three key resources: a language generation model \\( (g_1) \\), a text-to-image generative model \\( (g_2) \\), and a curated list of visual concepts \\( (C) \\). Our exploration include three steps: (1) we employ \\( g_1 \\) to synthesize a comprehensive set of image descriptions \\( T \\), which encompasses the range of visual concepts in \\( C \\); (2) for each caption in \\( T \\), we generate multiple images using \\( g_2 \\), culminating in an extensive synthetic image dataset \\( X \\); (3) we train on \\( X \\) to obtain a visual representation encoder \\( f \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.284, + 0.895, + 0.345 + ], + "angle": 0, + "content": "We use Llama-2 7B [83] and Stable Diffusion 1.5 [64] as \\( g_{1} \\) and \\( g_{2} \\), respectively, because of their fast inference speed. We anticipate that better \\( g_{1} \\) and \\( g_{2} \\) in the future will further enhance the effectiveness of this approach." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.358, + 0.704, + 0.374 + ], + "angle": 0, + "content": "3.1. Synthesizing captions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.382, + 0.895, + 0.457 + ], + "angle": 0, + "content": "To harness the capability of powerful text-to-image models for generating a substantial dataset of training images, we initially require a collection of captions that not only precisely depict an image but also exhibit diversity to encompass a broad spectrum of visual concepts." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.459, + 0.895, + 0.594 + ], + "angle": 0, + "content": "We have developed a scalable approach to create such a large collection of captions, leveraging the in-context learning capability of LLMs [9]. Our method involves crafting specific prompt engineering templates that guide the LLM to produce the required captions. We start by gathering the concept list \\( C \\) from some existing datasets, such as ImageNet-21k [21] and Places-365 [96]. For each concept \\( c \\in C \\), we consider three straightforward templates to generate captions effectively." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.599, + 0.892, + 0.642 + ], + "angle": 0, + "content": "- \\( c \\rightarrow \\) caption. As the most direct and simple approach, we have the Llama-2 model sample a sentence for the concept \\( c \\)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.645, + 0.895, + 0.854 + ], + "angle": 0, + "content": "- \\(c, bg \\rightarrow\\) caption. We combine the visual concept \\(c\\) with a background or setting \\(bg\\). A naive approach would randomly select both \\(c\\) and \\(bg\\), where \\(bg\\) may correspond to a class name from a places dataset like [96]. However, this method often leads to unlikely combinations in the real world, such as a blue whale in a football field. Our ablation experiments demonstrate that this strategy results in suboptimal performance, likely because the generated captions fall far outside the training distribution of \\(g_{2}\\). Instead, we employ GPT-4 [58] to generate a list of suitable backgrounds for the chosen concepts. This approach increases the likelihood of generating more plausible combinations, such as a tiger in a forest or a cat in a kitchen, enhancing the overall quality of the results." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.857, + 0.895, + 0.901 + ], + "angle": 0, + "content": "- \\( c, \\text{rel} \\rightarrow \\) caption. Given a visual concept \\( c \\), we consider pairing it with a positional relationship word, \\( \\text{rel} \\). Take for instance, if \\( c \\) signifies \\( \\text{cat} \\) and \\( \\text{rel} \\) translates to in front" + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.599, + 0.895, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "15889" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.091, + 0.089, + 0.881, + 0.324 + ], + "angle": 0, + "content": "
TemplatesIn context examples
c->captionrevolver ->Multiple antique revolvers lie on a wooden table, gleaming under soft, ambient light. closetet ->The compact closet, brimming with clothes and shoes, exudes a feeling of organization. zebra ->A zebra is gallantly trotting across the vast, sunlit plains of the African savannah, creating a captivating black and white spectacle. bus station ->The bustling bus station thrums with restless energy, as travelers navigate through the crowded space, awaiting their journeys amid the echoes of departing buses.
c,bg->captiontiger, forest ->Two tigers are running together in the forest. lighter, motorhome ->In the cozy, cluttered environment of a well-traveled motorhome, a sleek silver lighter holds dominion on the rustic wooden table. sunset, lake ->Golden sunset hues reflect on a calm lake, silhouetting a lone canoeist against a backdrop of fiery clouds.
c,rel->captionkit fox, in front of ->A group of small, fluffy, golden kit foxes is playfully gathered in front of a lush, green, towering forest backdrop. cabbage, besides ->A vibrant image portrays a lush, green cabbage, glistening with dewdrops, nestled besides a rustic, wooden crate full of freshly harvested vegetables.
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.332, + 0.895, + 0.39 + ], + "angle": 0, + "content": "Table 1. We show examples for the three synthesis templates. Such examples are used as demonstrations for Llama-2 to perform the in-context learning task. We have 176 such examples in total. Most of them are generated by prompting GPT-4 [58], while a handful of others are human generated (in a 10M scale pilot study of synthetic captions, we do not notice significant differences between including or excluding human generated examples.)" + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.408, + 0.468, + 0.525 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.535, + 0.472, + 0.565 + ], + "angle": 0, + "content": "Figure 3. In-context caption generation using Llama-2 [83]. We randomly sample three in-context examples for each inference run." + }, + { + "type": "text", + "bbox": [ + 0.09, + 0.595, + 0.47, + 0.671 + ], + "angle": 0, + "content": "of, our objective is to prompt the LLM to create captions such as a cute yellow cat is enjoying the fish in front of the sofa. To add variety, we have a selection of 10 different positional relationship words that we randomly choose from." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.684, + 0.472, + 0.821 + ], + "angle": 0, + "content": "For each of the three templates, we have prepared multiple demonstration examples that serve as instructions for the LLM to complete the caption synthesis task. Table 1 shows a couple of examples for each template. In total, we have 106 examples for \\( c->prompt \\), 50 examples for \\( c, bg->prompt \\), and 20 examples for \\( c, rel->prompt \\). Such examples are mostly collected by prompting GPT-4, with a handful from human. In a pilot study, we do not observe difference between including or excluding human generated examples." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.826, + 0.471, + 0.903 + ], + "angle": 0, + "content": "In the stage of generating captions in-context, we select a concept and one of the three templates. Next, we randomly pick three examples from the chosen template and frame the caption generation as a text completion task. This process is illustrated in Figure 3." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.408, + 0.694, + 0.425 + ], + "angle": 0, + "content": "3.2. Synthesizing Images" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.438, + 0.895, + 0.606 + ], + "angle": 0, + "content": "For each text caption, we generate a variety of images by initiating the reverse diffusion process with different random noise. The Classifier-Free Guidance (CFG) scale is a crucial factor in this process. A higher CFG scale enhances the quality of the samples and the alignment between text and image, whereas a lower scale results in more diverse samples and better adherence to the original conditional distribution of images based on the given text. Following the approach used in StableRep [81], we opt for a lower CFG scale, specifically 2.5, and produce 4 images for each caption. Examples of these images can be seen in Figure 4." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.636, + 0.729, + 0.654 + ], + "angle": 0, + "content": "3.3. Representation Learning" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.667, + 0.895, + 0.789 + ], + "angle": 0, + "content": "Our representation learning method is built upon StableRep [81]. The key component of our approach is the multi-positive contrastive learning loss [43] which works by aligning (in the embedding space) images generated from the same caption. We additionally combine multiple techniques from other self-supervised learning methods, including a patch-level masked image modeling objective. We briefly review StableRep and elaborate on the added modules." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.897, + 0.903 + ], + "angle": 0, + "content": "StableRep [81] minimizes the cross-entropy loss between a ground-truth assignment distribution and a contrastive assignment distribution. Consider an encoded anchor sample \\(\\pmb{a}\\) and a set of encoded candidates \\(\\{\\pmb{b}_1, \\pmb{b}_2, \\dots, \\pmb{b}_K\\}\\). The contrastive assignment distribution \\(\\mathbf{q}\\) describes how likely the model predicts \\(\\pmb{a}\\) and each \\(\\pmb{b}\\) to be generated from the same caption, and the ground-truth distribution is the actual match" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "15890" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.1, + 0.089, + 0.449, + 0.158 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.102, + 0.157, + 0.405, + 0.166 + ], + "angle": 0, + "content": "A plate of paella, a mixed rice dish with chicken, beans, and seafood" + }, + { + "type": "image", + "bbox": [ + 0.1, + 0.175, + 0.449, + 0.244 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.102, + 0.244, + 0.408, + 0.252 + ], + "angle": 0, + "content": "An industrial power plant with its smokestacks belching black smoke." + }, + { + "type": "image", + "bbox": [ + 0.1, + 0.254, + 0.449, + 0.323 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.102, + 0.323, + 0.414, + 0.34 + ], + "angle": 0, + "content": "A fluffy, black and white junco bird perches on a snow-covered fence, overlooking a dark forest." + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.346, + 0.47, + 0.387 + ], + "angle": 0, + "content": "Figure 4. Random examples of synthetic captions and images generated in our SynCLR pipeline. Each caption comes with 4 images." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.405, + 0.423, + 0.421 + ], + "angle": 0, + "content": "between \\( \\pmb{a} \\) and \\( \\pmb{b} \\) (\\( \\pmb{a} \\) is allowed to match multiple \\( \\pmb{b} \\)):" + }, + { + "type": "equation", + "bbox": [ + 0.182, + 0.428, + 0.47, + 0.467 + ], + "angle": 0, + "content": "\\[\n\\mathbf {q} _ {i} = \\frac {\\exp \\left(\\boldsymbol {a} \\cdot \\boldsymbol {b} _ {i} / \\tau\\right)}{\\sum_ {j = 1} ^ {K} \\exp \\left(\\boldsymbol {a} \\cdot \\boldsymbol {b} _ {j} / \\tau\\right)} \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.202, + 0.468, + 0.47, + 0.505 + ], + "angle": 0, + "content": "\\[\n\\mathbf {p} _ {i} = \\frac {\\mathbb {1} _ {\\operatorname {m a t c h} \\left(\\boldsymbol {a} , \\boldsymbol {b} _ {i}\\right)}}{\\sum_ {j = 1} ^ {K} \\mathbb {1} _ {\\operatorname {m a t c h} \\left(\\boldsymbol {a} , \\boldsymbol {b} _ {j}\\right)}} \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.512, + 0.47, + 0.573 + ], + "angle": 0, + "content": "where \\(\\tau \\in \\mathcal{R}_{+}\\) is the scalar temperature, \\(\\pmb{a}\\) and all \\(\\pmb{b}\\) have been \\(\\ell_{2}\\) normalized, and the indicator function \\(\\mathbb{1}_{\\mathrm{match}(\\cdot ,\\cdot)}\\) indicates whether two samples are from the same caption. The contrastive loss for \\(\\pmb{a}\\) is given as" + }, + { + "type": "equation", + "bbox": [ + 0.154, + 0.581, + 0.47, + 0.623 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} (\\boldsymbol {a}) = H (\\boldsymbol {p}, \\boldsymbol {q}) = - \\sum_ {i = 1} ^ {K} \\mathbf {p} _ {i} \\log \\mathbf {q} _ {i} \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.47, + 0.75 + ], + "angle": 0, + "content": "iBOT [98] is a masked image modeling objective, wherein a localized patch is masked, and the model is tasked with predicting the tokenized representation of said masked patch. It adapts the DINO [11] objective from the image level into the patch level. We follow [67] to replace the softmax-centering method with the iterative Sinkhorn-Knopp (SK) algorithm [19]. We run SK for 3 iterations to build the prediction target." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.871 + ], + "angle": 0, + "content": "Exponential Moving Average (EMA) is firstly introduced into self-supervised learning by MoCo [38]. We use EMA to encode crops as \\( \\mathbf{b} \\) and to produce the targets for iBOT loss. We update the EMA model as \\( \\theta_{ema} \\gets \\lambda \\theta_{ema} + (1 - \\lambda)\\theta \\), following a cosine schedule for \\( \\lambda \\) from 0.994 to 1 during training [34, 59]. We find the EMA module not only increases the final performance, but also improves the training stability for long training schedules." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.472, + 0.902 + ], + "angle": 0, + "content": "Multi-crop strategy is introduced by [10] as a smart way to improve computation efficiency, and is adopted in this paper." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.894, + 0.198 + ], + "angle": 0, + "content": "For these local crops, we only employ the contrastive loss, omitting the iBOT loss. Local crops are encoded only by the student network, and matched to global crops from the same caption encoded by the EMA model. Such reuse of global crops saves computation. For each image \\( x \\), where we generate a single global crop \\( x^g \\) alongside \\( n \\) local crops \\( x^l \\), the final loss can be expressed as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.574, + 0.205, + 0.893, + 0.244 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} \\left(x ^ {g}\\right) + \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\mathcal {L} \\left(x _ {i} ^ {l}\\right) + \\mathcal {L} ^ {i B O T} \\left(x ^ {g}\\right) \\tag {4}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.251, + 0.661, + 0.267 + ], + "angle": 0, + "content": "3.4. Implementation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.274, + 0.895, + 0.439 + ], + "angle": 0, + "content": "Concept list. We concatenate class names from various datasets, including IN-1k [21], IN-21k (we keep the most frequent 13k classes), Aircraft [51], Cars [44], DTD [17], Flowers [55], Pets [60], Sun397 [88], Caltech-101 [30], Food101 [7], and Places-365 [96]. If the concept is a place (i.e. SUN397 and Places) or a texture (i.e. DTD), we only apply the \\( c \\rightarrow \\) caption template. For fine-grained classes such as pets or flowers, we employ GPT-4 to generate a consolidated list of probable backgrounds, rather than producing distinct lists for each specific class. We favor more frequent sampling from IN-1k, Food101, Cars, Aircraft, and Flowers." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.44, + 0.894, + 0.516 + ], + "angle": 0, + "content": "Batches. For each training batch, we sample 2048 captions (except when noted), and use all of the 4 images generated by each caption. We generate 1 global and 4 local crops for each image. As a result, each batch contains 8192 global crops, which is similar with prior work [13, 14, 34, 81]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.515, + 0.894, + 0.605 + ], + "angle": 0, + "content": "Masking. For the iBOT loss, we randomly choose \\(50\\%\\) images inside a batch to mask, and randomly mask \\(50\\%\\) of the tokens in each chosen image. We use 65536 prototypes. While the target from the EMA model is ascertained using the SK algorithm, we apply softmax normalization to the output of the student model." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.606, + 0.894, + 0.742 + ], + "angle": 0, + "content": "Projection heads. We follow the design in MoCo v3 [14] and DINO [11] for the contrastive and iBOT loss heads, respectively, ensuring consistency with established methods. Other hyper-parameters. We set the temperature in the contrastive loss to 0.08. For the temperature used in the iBOT loss, we linearly increase it from 0.04 to 0.07 over 4000 iterations, and keep it as 0.07 afterwards, as in DINO [11]. Additionally, the weight decay parameter is incrementally adjusted from 0.04 to 0.2, adhering to a cosine schedule." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.754, + 0.625, + 0.771 + ], + "angle": 0, + "content": "4. Experiment" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.779, + 0.893, + 0.825 + ], + "angle": 0, + "content": "We first perform an ablation study to evaluate the efficacy of various designs and modules within our pipeline. Then we proceed to scale up the volume of synthetic data." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.833, + 0.75, + 0.849 + ], + "angle": 0, + "content": "4.1. Study different components" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.894, + 0.901 + ], + "angle": 0, + "content": "We analyze each component of SynCLR, and ablate their effectiveness in two measurements: (1) linear probing performance on IN-1k; (2) average accuracy of linear transfer on" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "15891" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.12, + 0.076, + 0.428, + 0.196 + ], + "angle": 0, + "content": "
captionsStableRepSynCLR
INavg.INavg.
cc12m73.081.677.185.3
IN+h+Places75.480.078.783.0
IN+Places+LLM73.776.977.681.8
IN+OurBG+LLM75.378.578.281.9
our final config.75.885.778.888.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.2, + 0.47, + 0.255 + ], + "angle": 0, + "content": "Table 2. Comparison of different caption synthesis strategies. We report top-1 ImageNet linear evaluation accuracy and the average accuracy over 9 fine-grained datasets. Every item here includes 10M captions and 4 images per caption." + }, + { + "type": "table", + "bbox": [ + 0.167, + 0.272, + 0.378, + 0.317 + ], + "angle": 0, + "content": "
CFG234
IN top-172.872.672.6
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.322, + 0.468, + 0.351 + ], + "angle": 0, + "content": "Table 3. Classifier-free guidance scale (CFG). Contrastive loss prefers small CFG scale but is not very sensitive to it." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.367, + 0.47, + 0.444 + ], + "angle": 0, + "content": "fine-grained datasets Aircraft [51], Cars [44], DTD [17], Flowers [55], Pets [60], Sun397 [88], Caltech-101 [30], Food-101 [7], and Pascal VOC [25]. For analysis conducted in this subsection, we train ViT-B/16 [24] models for 85000 iterations, and use the c1s token as image representation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.444, + 0.471, + 0.612 + ], + "angle": 0, + "content": "Synthesize captions. Following [81], we use cc12m [12] real captions as our baseline, which has 10M sentences. To synthesize captions, we design the following variants: (a) \\(IN + h + \\text{Places}\\) randomly combines one IN class plus its hypernyms in WordNet graph, with one place class; (b) \\(IN + \\text{Places} + \\text{LLM}\\) uses the \\(c, bg \\rightarrow\\) caption in-context synthesis template with \\(c\\) from IN and \\(bg\\) from places; (c) \\(IN + ourBG + \\text{LLM}\\) uses the background classes output by GPT-4, instead of Places; (d) ours means our full configuration specified in Section 3.1. For each of the config, we generate 10M captions. If not enough, we do duplication." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.612, + 0.471, + 0.871 + ], + "angle": 0, + "content": "Results are summarized in Table 2, where we train both StableRep and SynCLR to avoid biases favored by a single method. Compared to a real caption dataset cc12m, simply concatenating IN and Places class names improves the ImageNet linear accuracy but reduces the fine-grained classification performance. Interestingly, naively asking Llama to combine IN and Places classes into captions yields the worst performance. Replacing random background from places with GPT generated background improves the accuracy. This shows the importance of synthesizing captions that follow the distribution of real captions, which were used to train the text-to-image model. Finally, our full configuration achieves the best accuracy on both ImageNet and fine-grained classification. Another advantage of our synthesis method is its scalability – scale up to hundreds of millions of captions with little duplication. In contrast, if we concatenate IN classes with Places classes, there are at most 365k unique captions." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.469, + 0.902 + ], + "angle": 0, + "content": "Synthesize images. There are two major parameters in this process: number of images per caption and classifier free" + }, + { + "type": "table", + "bbox": [ + 0.523, + 0.077, + 0.871, + 0.173 + ], + "angle": 0, + "content": "
methodEMAiBOTMCINavg.ADE20k
StableRep75.885.7-
✓76.786.748.0
✓✓77.687.150.5
✓✓78.687.849.5
SynCLR✓✓✓78.888.150.8
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.178, + 0.894, + 0.234 + ], + "angle": 0, + "content": "Table 4. Important components for our model. ViT-B/16 models are trained for 85000 iterations. We study the modules that affect the ImageNet linear evaluation, the fine-grained classification (avg.), and ADE20k segmentation." + }, + { + "type": "table", + "bbox": [ + 0.576, + 0.248, + 0.819, + 0.327 + ], + "angle": 0, + "content": "
methodINavg.
Supervised CE71.975.0
SimCLR63.667.9
SynCLR75.378.5
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.337, + 0.894, + 0.406 + ], + "angle": 0, + "content": "Table 5. Comparison of different learning objectives. These objectives assume different levels of classification granularity, as shown in Figure 2. Our modeling, i.e., defining classes as captions, outperforms the other two. To accommodate Supervised CE training, all items here used \\(IN + OurBG + LLM\\) entry in Table 2." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.418, + 0.894, + 0.524 + ], + "angle": 0, + "content": "guidance scale. For the former, we find generating 4 images is almost able to reproduce StableRep [81]'s performance (10 images) when using cc12m captions (ours \\(73.0\\%\\) v.s. StableRep \\(73.5\\%\\) on ImageNet). Thus we stick to 4. For guidance scale, we briefly find the contrastive loss is not very sensitive to CFG in a pilot study, as shown in Table 3. Thus we stick to 2.5, similar as StableRep [81]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.524, + 0.895, + 0.72 + ], + "angle": 0, + "content": "Model components. We present the improvement of accuracy brought by different modules in Table 4. Compared to the baseline StableRep, adding a teacher EMA model improves the IN linear accuracy by \\(0.9\\%\\). Further adding iBOT local objective or the multi-crop strategy increases the accuracy by \\(0.9\\%\\) and \\(1.9\\%\\), respectively. Combining all of them results in our full SynCLR model, which achieves \\(78.8\\%\\) top-1 IN linear accuracy. The fine-grained classification performance follows a similar trend, and reaches \\(88.1\\%\\). Besides, we test the transfer ability to semantic segmentation on ADE20k. The iBOT objective brings 1.0 more mIoU than multi-crop strategy, demonstrating the effectiveness of masked image modeling for dense prediction tasks." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Compare to SimCLR and supervised training. We compare the three different representation learning objectives shown in Figure 2, which classify images at different levels of granularity. Since supervised cross-entropy training requires a fixed set of balanced classes (indeed both fixed set and balance are limitations of such method), we use the \\(IN + ourBG + LLM\\) configuration where we have 1000 balanced classes (i.e., each class has 40k images). The supervised training recipe follows [76]. For a fair comparison with SimCLR, we remove all unmatched modules (i.e., EMA, iBOT, and MC) to make sure that the only difference between SimCLR and our SynCLR is the classification gran" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15892" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.114, + 0.075, + 0.858, + 0.282 + ], + "angle": 0, + "content": "
textimg#imgsImageNetAircraftCarsDTDFlowersPetsSUN397Caltech-101Food-101VOC2007Average
StableReprealsyn100MViT-B/1675.759.283.580.197.388.374.394.785.187.983.4
CLIPrealreal400MViT-B/1680.259.586.779.298.193.178.494.792.889.285.7
ViT-L/1483.969.490.982.199.295.181.896.595.289.688.9
OpenCLIPrealreal400MViT-B/1678.961.192.381.998.291.577.995.290.988.086.3
400MViT-L/1482.367.194.083.698.892.581.096.493.488.888.4
2BViT-L/1483.471.795.385.399.094.282.297.594.188.989.8
DINO v2*-real142MViT-B/14\\( 83.9^{\\dagger} \\)79.488.283.399.696.277.396.192.888.289.0
ViT-L/14\\( 85.7^{\\dagger} \\)81.590.184.099.796.678.797.594.388.390.1
SynCLRsynsyn600MViT-B/1680.781.793.879.999.193.676.295.391.689.489.0
ViT-L/1483.085.694.282.199.294.178.496.193.490.390.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.292, + 0.892, + 0.335 + ], + "angle": 0, + "content": "Table 6. Comparison on ImageNet linear evaluation and fine-grained classifier. SynCLR achieves comparable results with OpenAI's CLIP and DINO v2 models, despite only using synthetic data. *DINO v2 modes are distilled from a ViT-g model, thus advantageous in this comparison. † we rerun only using c1s token instead of concatenating multiple layers presented in the original DINO v2 paper [59]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.348, + 0.471, + 0.379 + ], + "angle": 0, + "content": "ularity defined by the contrastive loss. For all of them, we do pre-training and then linear probing on the target dataset." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.379, + 0.472, + 0.515 + ], + "angle": 0, + "content": "Table 5 presents the comparison. Our multi-positive objective, which defines images as the same class if they are generated by the same caption, achieves the best performance. It outperforms supervised cross-entropy training and SimCLR by \\(3.4\\%\\) and \\(11.7\\%\\) for top-1 accuracy on ImageNet linear evaluation, and by \\(3.5\\%\\) and \\(10.6\\%\\) on fine-grained classification tasks. Besides, our objective does not require balance between samples from a fixed set of classes, making it easier to scale up." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.527, + 0.196, + 0.544 + ], + "angle": 0, + "content": "4.2. Scaling up" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.552, + 0.47, + 0.657 + ], + "angle": 0, + "content": "After we have ablated different components, we scale up our experiments. Specifically, we synthesize a dataset of 150M captions, called SynCaps-150M, from which we generate 600M images. We train both ViT-B/16 and ViT-L/14 (no SwiGLU [73] or LayerScale [82]), and extend the training schedules to 500k steps with a batch size of 8192 captions. We use 224x224 resolution for all pre-training tasks." + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.659, + 0.471, + 0.749 + ], + "angle": 0, + "content": "We compare SynCLR with OpenAI's CLIP [62], OpenCLIP [16], and DINO v2 [59], which represent learning from data. We note that ViT-B/14 and ViT-L/14 from DINO v2 are distilled from a ViT-g [93] model, which makes DINO v2 advantageous in our comparison. We also include StableRep [81], which uses the hybrid paradigm." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.902 + ], + "angle": 0, + "content": "ImageNet linear evaluation. For fair comparison,CLS token from the last block is used as representation across all models (whereas in DINO v2, results are from concatenating multiple layers). As shown in Table 6, SynCLR achieves \\(80.7\\%\\) with ViT-B and \\(83.0\\%\\) with ViT-L. This is similar as CLIP, but still lags behind DINO v2 by \\(3.2\\%\\) and \\(2.7\\%\\), respectively, partially because of the extra distillation in DINO v2. We note SynCLR has already outperformed other self-supervised methods pre-trained directly on ImageNet-1k (e.g., DINO achieves \\(78.2\\%\\) with ViT-B/16 and iBOT" + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.345, + 0.892, + 0.508 + ], + "angle": 0, + "content": "
methodpre-train datadistillViT-BViT-L
StableRephybrid, 100M49.4-
MoCo v3real, IN1K-1M47.349.1
BEiTreal, IN1K-1M+DALLE47.153.3
MAEreal, IN1K-1M48.153.6
iBOTreal, IN1K-1M50.0-
CLIPreal, WIT-400M52.6-
BEiT v2real, WIT-400M, IN1K✓53.156.7
DINO v2real, LVD-142M✓54.4†57.5†
SynCLRsynthetic, 600M54.357.7†
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.518, + 0.894, + 0.56 + ], + "angle": 0, + "content": "Table 7. ADE20K semantic segmentation (mIoU) using UperNet, with single scale at 512x512 resolution. \\( {}^{ \\dagger } \\) use patch size of \\( {14}\\mathrm{x}{14} \\) , thus adapt to 518x518 resolution." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.567, + 0.707, + 0.582 + ], + "angle": 0, + "content": "reaches \\(81.0\\%\\) with ViT-L/16)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.583, + 0.895, + 0.779 + ], + "angle": 0, + "content": "Fine-grained classification. On the nine fine-grained datasets we have evaluated in Table 6, SynCLR achieves very similar average accuracy as DINO v2, e.g., \\(89.0\\%\\) vs. \\(89.0\\%\\) for ViT-B, and \\(90.1\\%\\) vs \\(90.4\\%\\) for ViT-L. Both SynCLR and DINO v2 have curated the pre-training data to include the distribution for these datasets (but in different ways and portions), and end up with similar performance. Interestingly, SynCLR outperforms others on Aircraft and Cars, possibly because we favor more frequent sampling towards them. This can be an advantage for synthetic data when we know what downstream tasks to solve. Besides, SynCLR outperforms CLIP and StableRep by \\(3.3\\%\\) and by \\(5.6\\%\\) for ViT-B, respectively." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Semantic segmentation. To evaluate the pixel-level understanding ability of SynCLR, we fine-tune the pre-trained models on ADE20k [97], following the setup in [5, 39]. UperNet [89] is used as the task layer, and we evaluate with a single-scale, i.e. \\(512 \\times 512\\). Besides CLIP and DINO v2, we also compare to self-supervised methods pre-trained on ImageNet, as well as BEiT v2 [61], which distills from CLIP. Table 7 shows that our SynCLR outperforms self-supervised" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15893" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.107, + 0.091, + 0.351, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.362, + 0.091, + 0.608, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.621, + 0.092, + 0.864, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.306, + 0.895, + 0.364 + ], + "angle": 0, + "content": "Figure 5. PCA visualization. Follow DINO v2 [59], we compute a PCA between the image patches from the same set and colorize by their first 3 components. Compared to DINO v2, SynCLR produces more accurate maps for cars (e.g., zoom-in to see the two bars on the roof of the first car, and the three side windows of the third car) and airplanes (e.g., the boundaries), while being slightly worse for dogs (e.g., heads). We use ViT-L/14 for both methods. Images are resized to \\(336 \\times 448\\) resolution, yielding \\(24 \\times 32\\) visualization grids." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.378, + 0.471, + 0.483 + ], + "angle": 0, + "content": "methods trained on IN-1k by a clear marge, e.g., 4.3 higher mIoU than iBOT. Despite not involving a high resolution pretraining period like DINO v2 (e.g., 518x518), SynCLR performs similarly with DINO v2 (0.1 lower for ViT-B possibly because DINO v2 uses a smaller patch size of 14x14, but 0.2 higher for ViT-L). This suggests SynCLR pre-training is suitable for dense prediction tasks." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.484, + 0.471, + 0.68 + ], + "angle": 0, + "content": "ImageNet fine-tuning. We evaluate the fine-tuning transfer ability of SynCLR on ImageNet. Our SynCLR achieves \\(87.9\\%\\) top-1 accuracy with ViT-L, outperforming models trained on ImageNet images or large scale image datasets. Specifically, SynCLR outperforms OpenCLIP ViT-L (87.1% top-1) trained on Laion-2B, which is the dataset Stable Diffusion (the text2image model we used) is trained on. This contrasts with [26, 69], which shows that directly training a classifier on synthetic images yields bad classification accuracy. Our finding suggests synthetic images are good for training representations, which later can be easily adapted to a downstream task with limited amount of real data. Detailed comparisons are provided in Appendix C." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.68, + 0.47, + 0.816 + ], + "angle": 0, + "content": "PCA visualization. Following the method used in DINO v2 [59], we present visualizations derived from the Principal Component Analysis (PCA) conducted on patch features extracted using our model SynCLR. As depicted in Figure 5, a comparative analysis is conducted between SynCLR and DINO v2, both utilizing the ViT-L/14 architecture. The results demonstrate that SynCLR effectively accentuates the features of cars and planes, while efficiently minimizing background clutter." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.83, + 0.334, + 0.847 + ], + "angle": 0, + "content": "5. Discussions and Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Why learn from generative models? One compelling reason is that a generative model can act like hundreds of datasets simultaneously. Traditionally, researchers have to" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.378, + 0.895, + 0.59 + ], + "angle": 0, + "content": "spend separate effort collecting datasets for different image categories, e.g., cars, flowers, cats, dogs, and so on. DINO v2 [59] achieves robust representations by curating and amalgamating numerous such datasets. Such a process introduces complexities such as clustering and search challenges. In contrast, advanced text-to-image generative models like Stable Diffusion [63] or Imagen [68] have the capability to generate many diverse datasets. These models provide the flexibility to produce an infinite number of samples (albeit finite diversity) and control the generation process through textual input. Thus, generative models offer a convenient and effective method for curating training data. In our study, we harness this advantage to synthesize images encompassing a broad spectrum of visual concepts." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.597, + 0.895, + 0.821 + ], + "angle": 0, + "content": "What can be further improved? Enhanced caption sets can be achieved through various methods, such as enriching the set of in-context examples, optimizing the sampling ratios among different concepts, and utilizing more advanced LLMs. In terms of the learning process, one approach is to distill knowledge from a larger model, and incorporate an additional high-resolution training phase (as discussed in [59]) or an intermediate IN-21k fine-tuning stage (as per [5, 61]). Regarding architectural improvements, the integration of SwiGLU and LayerScale, coupled with superior model initialization strategies (referenced in [28]), can be beneficial. However, due to limited resources and the scope of this paper not being focused on achieving the highest possible metrics, we propose these areas for further exploration in future research endeavors." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.823, + 0.895, + 0.899 + ], + "angle": 0, + "content": "In summary, this paper studies a new paradigm for visual representation learning – learning from generative models. Without using any real data, SynCLR learns visual representations that are comparable with those achieved by state of the art general-purpose visual representation learners." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15894" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.17 + ], + "angle": 0, + "content": "[1] Hassan Abu Alhajja, Siva Karthik Mustikovela, Lars Mescheder, Andreas Geiger, and Carsten Rother. Augmented reality meets computer vision: Efficient data generation for urban driving scenes. IJCV, 2018. 3" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.172, + 0.472, + 0.227 + ], + "angle": 0, + "content": "[2] Mahmoud Assran, Mathilde Caron, Ishan Misra, Piotr Bojanowski, Florian Bordes, Pascal Vincent, Armand Joulin, Mike Rabbat, and Nicolas Ballas. 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We synthesize a large dataset of image captions using LLMs, then use an off-the-shelf text-to-image model to generate multiple images corresponding to each synthetic caption. We perform visual representation learning on these synthetic images via contrastive learning, treating images sharing the same caption as positive pairs. The resulting representations transfer well to many downstream tasks, competing favorably with other general-purpose visual representation learners such as CLIP and DINO v2 in image classification tasks. Furthermore, in dense prediction tasks such as semantic segmentation, SynCLR outperforms previous self-supervised methods by a significant margin, e.g., improving over MAE and iBOT by 6.2 and 4.3 mIoU on ADE20k for ViT-B/16. + +# 1. Introduction + +Representation learning extracts and organizes information from raw, often unlabeled data. The quality, quantity, and diversity of the data determines how good a representation the model can learn. The model becomes a reflection of the collective intelligence that exists in the data. We get what we feed in. + +Unsurprisingly, the current best-performing visual representation learning methods [59, 62] rely on large scale real datasets. However, the collection of real data has its own dilemmas. Collecting large scale uncurated data [71] is relatively cheap and thus quite achievable. However, for self-supervised representation learning, this approach exhibits poor scaling behavior –i.e., adding more uncurated data has little effect at large data scales [33, 80]. Collecting small scale curated data [21] also is achievable, but models trained in this way are limited to relatively narrow tasks. The ideal would be large scale curated datasets of real images, and + +![](images/0055ce920975e0db375007ce202ef860a324e6798f2d7c37d54212d135862e3c.jpg) +Figure 1. Three paradigms for visual representation learning. Top row: Traditional methods, such as CLIP [62], learn only from real data; Middle row: Recent methods, such as StableRep [81], learn from real text and generated images; Bottom row: Our method, SynCLR, learns from synthetic text and synthetic images, and rival the linear transfer performance of CLIP on ImageNet despite not directly observing any real data. + +recent work has indeed shown that this can lead to strong performance gains at scale [59], but this path is costly to pursue. + +To alleviate the cost, in this paper we ask if synthetic data, sampled from off-the-shelf generative models, is a viable path toward large scale curated datasets that can train state-of-the-art visual representations. + +We call such a paradigm learning from models, in contrast to directly learning from data. Models have several advantages as a data source for building large scale training sets: via their latent variables, conditioning variables, and hyperparameters, they provide new controls for curating data; we will make use of these controls in the method we propose. Models also can be easier to share and store (because models are more compressed than data), and can produce an unlimited number of data samples (albeit with + +finite diversity). A growing literature has studied these properties and other advantages (and disadvantages) of using generative models as a data source for training downstream models [3, 26, 40, 41, 69, 81]. Some of these methods use a hybrid mode – either mixing real and synthetic datasets [3] or needing a real dataset to generate another synthetic dataset [81]. Other methods try to learn representations from purely synthetic data [69] but lag far behind the best performing models. Instead, we show that learning from models, without training on any real data, can yield representations that match the top-performing representations learnt from real data. For instance, as illustrated in Figure 1, representations learnt by our method are able to transfer as well as OpenAI's CLIP [62] on ImageNet (both methods using ViT-B [24]). + +Our approach leverages generative models to re-define the granularity of visual classes. As shown in Figure 2, consider we have four images generated using two prompts: "a golden retriever; wearing sunglasses and a beach hat, rides a bike" and "a cute golden retriever sits in a house made of sushi". Traditional self-supervised method such as SimCLR [13] will treat each of these images as a different class; embeddings for different images are pushed apart with no explicit consideration of the shared semantics between images. On the other extreme, supervised learning methods (i.e. SupCE) will regard all these images as a single class (e.g., "golden retriever"). This ignores nuances in the semantics of the images, such as the fact that the dogs are riding a bike in one pair of images and sitting inside a sushi house in the other pair of images. Instead, our method, SynCLR, treats captions as classes, i.e., each caption describes a visual class (this level of granularity was also explored in StableRep [81]). This allows us to group images by the concepts of "riding a bike" and "sitting in a sushi house", in addition to grouping by a coarser class label like "golden retrieval". This level of granularity is difficult to mine in real data, since collecting multiple images described by a given caption is non-trivial, especially when scaling up the number of captions. However, text-to-image diffusion models are fundamentally built with this ability; simply by conditioning on the same caption and using different noise inputs, a text-to-image diffusion model will produce different images that all match the same caption. In our experiments, we find the caption-level granularity outperforms both SimCLR and supervised training. Another advantage is that this definition of visual classes has good scalability. Unlike ImageNet-1k/21k where a given number of classes is fixed, we can augment existing classes (or data) in an online fashion, and theoretically scale up to as many classes as needed. + +Our system consists of three steps. The first step is to synthesize a large corpus of image captions. We design a scalable approach by leveraging the in-context learning capability of large language models (LLMs), where we present + +![](images/0d6c87813b3f7ca4064843a7584d68a8003cba40aa27e6a81a42b5ea57afa551.jpg) +Figure 2. Different learning objectives treat classification granularity differently. These images are generated by two prompts "a golden retriever, wearing sunglasses and a beach hat, rides a bike" and "a cute golden retriever sits in a house made of sushi". SimCLR treats each image as a class, while supervised cross-entropy treats them all as the same "golden retrieval" class. The former does not consider shared semantics between images, and the latter is coarse-grained and ignores actions or relationships between subjects/background. Our approach, SynCLR, defines visual classes by sentences. + +examples of word-to-caption translations. Next, a text-to-image diffusion model is adopted to synthesize multiple images for each synthetic caption. This yields a synthetic dataset of 600M images. Then we train visual representation models by a combination of multi-positive contrastive learning [43] and masked image modeling [98]. + +Our learned representations transfer well. With SynCLR pre-training, our ViT-B and ViT-L models achieve $80.7\%$ and $83.0\%$ top-1 linear probing accuracy on ImageNet-1K, respectively, which is on par with OpenAI's CLIP [62]. On fine-grained classification tasks, SynCLR outperforms CLIP by $3.3\%$ for ViT-B and $1.5\%$ for ViT-L, and performs similarly to DINO v2 [59] models, which are distilled from a pre-trained ViT-g model. For semantic segmentation on ADE20k, SynCLR outperforms MAE pre-trained on ImageNet by 6.2 and 4.1 in mIoU for ViT-B and ViT-L under the same setup, showing strong transfer ability for dense prediction tasks similar to DINO v2, which additionally involves a training period on 518x518 resolution images that SynCLR does not have. + +# 2. Related Works + +Self-supervised representation learning approaches in vision develop domain-specific pre-text tasks, such as colorization [94], rotation prediction [31], and solving jigsaw puzzles [56]. Domain-agnostic approaches have been pop + +ular, such as contrastive learning [6, 13, 35, 38, 57, 78, 87] and masked image modeling [2, 4, 5, 29, 39, 86, 90, 98]. Contrastive learning promotes invariance [79] for two views of the same image and pushes apart representations for different images [85] (or only invariance [11, 34]); the resulting representations yield strong performance for linear or zero-shot transfer. Masked image modeling reconstructs the pixels [39, 90] or local features [4], often producing excellent fine-tuning transfer performance, especially in dense prediction tasks [39]. The state of the art DINO v2 [59] leverages both approaches, and our approach shares a similar spirit. + +Supervised learning [36, 45, 75] used to be the dominant approach for learning transferable visual representations for various tasks [23, 32, 72]. Recent studies [37, 49] has shown that, the transferability of representations learned in this way is limited, e.g., pre-training has no improvement over random initialization for dense prediction tasks (e.g., object detection) when the fine-tuning is long enough. Such limitation continues when the model has been scaled up to 22B [20]. An alternative paradigm learns visual representations from text supervision [42, 62], e.g., CLIP [62]. This approach is more flexible (i.e., not requiring classes) and provides richer supervision, often learning generalizable representations. + +Generative models as representation learners. A number of papers have explored the representations that are learned by generative models for various recognition tasks [22, 48]. As might be expected intuitively, such models indeed learn especially good representations for dense tasks, such as optical flow estimation [70], semantic segmentation [8, 91], and depth estimation [95]. Another line of work [18, 47] adapt pre-trained diffusion models for zero-shot image recognition via analysis-by-synthesis. These approaches may need to be adapted when the architectures of the generative models change or a new family of generative model emerge. Our approach treats images as universal interfaces with the hope of better generality. + +Learning from synthetic data from generative models. Synthetic data has been explored to train machine learning models in various domains [27, 46, 53, 54, 65, 66, 74, 77, 92]. In computer vision, the utilization of synthetic data for training models is common, ranging from optical flow [52] and autonomous driving [1] to semantic segmentation [15] and human pose estimation [84]. Others [41, 50] have explored synthetic data for representation learning, with the predominant approach of altering the latent variables of deep generative models. Our approach aligns with this research paradigm, but it diverges in its use of text-to-image models, which have also been investigated by other researchers [40, 69, 99]. But they use synthetic data for supervised learning [26, 69]. The closet work is StableRep [81], which also conducts representation learning but still needs a real text dataset. + +# 3. Approach + +In this paper, we study the problem of learning a visual encoder $f$ in the absence of real images or textual data. Our approach hinges on the utilization of three key resources: a language generation model $(g_1)$ , a text-to-image generative model $(g_2)$ , and a curated list of visual concepts $(C)$ . Our exploration include three steps: (1) we employ $g_1$ to synthesize a comprehensive set of image descriptions $T$ , which encompasses the range of visual concepts in $C$ ; (2) for each caption in $T$ , we generate multiple images using $g_2$ , culminating in an extensive synthetic image dataset $X$ ; (3) we train on $X$ to obtain a visual representation encoder $f$ . + +We use Llama-2 7B [83] and Stable Diffusion 1.5 [64] as $g_{1}$ and $g_{2}$ , respectively, because of their fast inference speed. We anticipate that better $g_{1}$ and $g_{2}$ in the future will further enhance the effectiveness of this approach. + +# 3.1. Synthesizing captions + +To harness the capability of powerful text-to-image models for generating a substantial dataset of training images, we initially require a collection of captions that not only precisely depict an image but also exhibit diversity to encompass a broad spectrum of visual concepts. + +We have developed a scalable approach to create such a large collection of captions, leveraging the in-context learning capability of LLMs [9]. Our method involves crafting specific prompt engineering templates that guide the LLM to produce the required captions. We start by gathering the concept list $C$ from some existing datasets, such as ImageNet-21k [21] and Places-365 [96]. For each concept $c \in C$ , we consider three straightforward templates to generate captions effectively. + +- $c \rightarrow$ caption. As the most direct and simple approach, we have the Llama-2 model sample a sentence for the concept $c$ . +- $c, bg \rightarrow$ caption. We combine the visual concept $c$ with a background or setting $bg$ . A naive approach would randomly select both $c$ and $bg$ , where $bg$ may correspond to a class name from a places dataset like [96]. However, this method often leads to unlikely combinations in the real world, such as a blue whale in a football field. Our ablation experiments demonstrate that this strategy results in suboptimal performance, likely because the generated captions fall far outside the training distribution of $g_{2}$ . Instead, we employ GPT-4 [58] to generate a list of suitable backgrounds for the chosen concepts. This approach increases the likelihood of generating more plausible combinations, such as a tiger in a forest or a cat in a kitchen, enhancing the overall quality of the results. +- $c, \text{rel} \rightarrow$ caption. Given a visual concept $c$ , we consider pairing it with a positional relationship word, $\text{rel}$ . Take for instance, if $c$ signifies $\text{cat}$ and $\text{rel}$ translates to in front + +
TemplatesIn context examples
c->captionrevolver ->Multiple antique revolvers lie on a wooden table, gleaming under soft, ambient light. closetet ->The compact closet, brimming with clothes and shoes, exudes a feeling of organization. zebra ->A zebra is gallantly trotting across the vast, sunlit plains of the African savannah, creating a captivating black and white spectacle. bus station ->The bustling bus station thrums with restless energy, as travelers navigate through the crowded space, awaiting their journeys amid the echoes of departing buses.
c,bg->captiontiger, forest ->Two tigers are running together in the forest. lighter, motorhome ->In the cozy, cluttered environment of a well-traveled motorhome, a sleek silver lighter holds dominion on the rustic wooden table. sunset, lake ->Golden sunset hues reflect on a calm lake, silhouetting a lone canoeist against a backdrop of fiery clouds.
c,rel->captionkit fox, in front of ->A group of small, fluffy, golden kit foxes is playfully gathered in front of a lush, green, towering forest backdrop. cabbage, besides ->A vibrant image portrays a lush, green cabbage, glistening with dewdrops, nestled besides a rustic, wooden crate full of freshly harvested vegetables.
+ +Table 1. We show examples for the three synthesis templates. Such examples are used as demonstrations for Llama-2 to perform the in-context learning task. We have 176 such examples in total. Most of them are generated by prompting GPT-4 [58], while a handful of others are human generated (in a 10M scale pilot study of synthetic captions, we do not notice significant differences between including or excluding human generated examples.) + +![](images/8a42f1841f22903e4b63eb70e60d711d71f5a05e01cac9bfe87c99dfd12c5267.jpg) +Figure 3. In-context caption generation using Llama-2 [83]. We randomly sample three in-context examples for each inference run. + +of, our objective is to prompt the LLM to create captions such as a cute yellow cat is enjoying the fish in front of the sofa. To add variety, we have a selection of 10 different positional relationship words that we randomly choose from. + +For each of the three templates, we have prepared multiple demonstration examples that serve as instructions for the LLM to complete the caption synthesis task. Table 1 shows a couple of examples for each template. In total, we have 106 examples for $c->prompt$ , 50 examples for $c, bg->prompt$ , and 20 examples for $c, rel->prompt$ . Such examples are mostly collected by prompting GPT-4, with a handful from human. In a pilot study, we do not observe difference between including or excluding human generated examples. + +In the stage of generating captions in-context, we select a concept and one of the three templates. Next, we randomly pick three examples from the chosen template and frame the caption generation as a text completion task. This process is illustrated in Figure 3. + +# 3.2. Synthesizing Images + +For each text caption, we generate a variety of images by initiating the reverse diffusion process with different random noise. The Classifier-Free Guidance (CFG) scale is a crucial factor in this process. A higher CFG scale enhances the quality of the samples and the alignment between text and image, whereas a lower scale results in more diverse samples and better adherence to the original conditional distribution of images based on the given text. Following the approach used in StableRep [81], we opt for a lower CFG scale, specifically 2.5, and produce 4 images for each caption. Examples of these images can be seen in Figure 4. + +# 3.3. Representation Learning + +Our representation learning method is built upon StableRep [81]. The key component of our approach is the multi-positive contrastive learning loss [43] which works by aligning (in the embedding space) images generated from the same caption. We additionally combine multiple techniques from other self-supervised learning methods, including a patch-level masked image modeling objective. We briefly review StableRep and elaborate on the added modules. + +StableRep [81] minimizes the cross-entropy loss between a ground-truth assignment distribution and a contrastive assignment distribution. Consider an encoded anchor sample $\pmb{a}$ and a set of encoded candidates $\{\pmb{b}_1, \pmb{b}_2, \dots, \pmb{b}_K\}$ . The contrastive assignment distribution $\mathbf{q}$ describes how likely the model predicts $\pmb{a}$ and each $\pmb{b}$ to be generated from the same caption, and the ground-truth distribution is the actual match + +![](images/dc99af57ce94112007c0043dbe70f56a359cc6068754a28f472dc85053281589.jpg) +A plate of paella, a mixed rice dish with chicken, beans, and seafood + +![](images/9c549d9d6852c2bed63f35884b2498ecbe23a23b1be85f1137677ab6c2fb8d44.jpg) +An industrial power plant with its smokestacks belching black smoke. + +![](images/7183cd8ec8c687dba982a5f8c99be5008b3add07a27b232ead4282a53c4e14f9.jpg) +A fluffy, black and white junco bird perches on a snow-covered fence, overlooking a dark forest. +Figure 4. Random examples of synthetic captions and images generated in our SynCLR pipeline. Each caption comes with 4 images. + +between $\pmb{a}$ and $\pmb{b}$ ( $\pmb{a}$ is allowed to match multiple $\pmb{b}$ ): + +$$ +\mathbf {q} _ {i} = \frac {\exp \left(\boldsymbol {a} \cdot \boldsymbol {b} _ {i} / \tau\right)}{\sum_ {j = 1} ^ {K} \exp \left(\boldsymbol {a} \cdot \boldsymbol {b} _ {j} / \tau\right)} \tag {1} +$$ + +$$ +\mathbf {p} _ {i} = \frac {\mathbb {1} _ {\operatorname {m a t c h} \left(\boldsymbol {a} , \boldsymbol {b} _ {i}\right)}}{\sum_ {j = 1} ^ {K} \mathbb {1} _ {\operatorname {m a t c h} \left(\boldsymbol {a} , \boldsymbol {b} _ {j}\right)}} \tag {2} +$$ + +where $\tau \in \mathcal{R}_{+}$ is the scalar temperature, $\pmb{a}$ and all $\pmb{b}$ have been $\ell_{2}$ normalized, and the indicator function $\mathbb{1}_{\mathrm{match}(\cdot ,\cdot)}$ indicates whether two samples are from the same caption. The contrastive loss for $\pmb{a}$ is given as + +$$ +\mathcal {L} (\boldsymbol {a}) = H (\boldsymbol {p}, \boldsymbol {q}) = - \sum_ {i = 1} ^ {K} \mathbf {p} _ {i} \log \mathbf {q} _ {i} \tag {3} +$$ + +iBOT [98] is a masked image modeling objective, wherein a localized patch is masked, and the model is tasked with predicting the tokenized representation of said masked patch. It adapts the DINO [11] objective from the image level into the patch level. We follow [67] to replace the softmax-centering method with the iterative Sinkhorn-Knopp (SK) algorithm [19]. We run SK for 3 iterations to build the prediction target. + +Exponential Moving Average (EMA) is firstly introduced into self-supervised learning by MoCo [38]. We use EMA to encode crops as $\mathbf{b}$ and to produce the targets for iBOT loss. We update the EMA model as $\theta_{ema} \gets \lambda \theta_{ema} + (1 - \lambda)\theta$ , following a cosine schedule for $\lambda$ from 0.994 to 1 during training [34, 59]. We find the EMA module not only increases the final performance, but also improves the training stability for long training schedules. + +Multi-crop strategy is introduced by [10] as a smart way to improve computation efficiency, and is adopted in this paper. + +For these local crops, we only employ the contrastive loss, omitting the iBOT loss. Local crops are encoded only by the student network, and matched to global crops from the same caption encoded by the EMA model. Such reuse of global crops saves computation. For each image $x$ , where we generate a single global crop $x^g$ alongside $n$ local crops $x^l$ , the final loss can be expressed as follows: + +$$ +\mathcal {L} \left(x ^ {g}\right) + \frac {1}{n} \sum_ {i = 1} ^ {n} \mathcal {L} \left(x _ {i} ^ {l}\right) + \mathcal {L} ^ {i B O T} \left(x ^ {g}\right) \tag {4} +$$ + +# 3.4. Implementation + +Concept list. We concatenate class names from various datasets, including IN-1k [21], IN-21k (we keep the most frequent 13k classes), Aircraft [51], Cars [44], DTD [17], Flowers [55], Pets [60], Sun397 [88], Caltech-101 [30], Food101 [7], and Places-365 [96]. If the concept is a place (i.e. SUN397 and Places) or a texture (i.e. DTD), we only apply the $c \rightarrow$ caption template. For fine-grained classes such as pets or flowers, we employ GPT-4 to generate a consolidated list of probable backgrounds, rather than producing distinct lists for each specific class. We favor more frequent sampling from IN-1k, Food101, Cars, Aircraft, and Flowers. + +Batches. For each training batch, we sample 2048 captions (except when noted), and use all of the 4 images generated by each caption. We generate 1 global and 4 local crops for each image. As a result, each batch contains 8192 global crops, which is similar with prior work [13, 14, 34, 81]. + +Masking. For the iBOT loss, we randomly choose $50\%$ images inside a batch to mask, and randomly mask $50\%$ of the tokens in each chosen image. We use 65536 prototypes. While the target from the EMA model is ascertained using the SK algorithm, we apply softmax normalization to the output of the student model. + +Projection heads. We follow the design in MoCo v3 [14] and DINO [11] for the contrastive and iBOT loss heads, respectively, ensuring consistency with established methods. Other hyper-parameters. We set the temperature in the contrastive loss to 0.08. For the temperature used in the iBOT loss, we linearly increase it from 0.04 to 0.07 over 4000 iterations, and keep it as 0.07 afterwards, as in DINO [11]. Additionally, the weight decay parameter is incrementally adjusted from 0.04 to 0.2, adhering to a cosine schedule. + +# 4. Experiment + +We first perform an ablation study to evaluate the efficacy of various designs and modules within our pipeline. Then we proceed to scale up the volume of synthetic data. + +# 4.1. Study different components + +We analyze each component of SynCLR, and ablate their effectiveness in two measurements: (1) linear probing performance on IN-1k; (2) average accuracy of linear transfer on + +
captionsStableRepSynCLR
INavg.INavg.
cc12m73.081.677.185.3
IN+h+Places75.480.078.783.0
IN+Places+LLM73.776.977.681.8
IN+OurBG+LLM75.378.578.281.9
our final config.75.885.778.888.1
+ +Table 2. Comparison of different caption synthesis strategies. We report top-1 ImageNet linear evaluation accuracy and the average accuracy over 9 fine-grained datasets. Every item here includes 10M captions and 4 images per caption. + +
CFG234
IN top-172.872.672.6
+ +fine-grained datasets Aircraft [51], Cars [44], DTD [17], Flowers [55], Pets [60], Sun397 [88], Caltech-101 [30], Food-101 [7], and Pascal VOC [25]. For analysis conducted in this subsection, we train ViT-B/16 [24] models for 85000 iterations, and use the c1s token as image representation. + +Synthesize captions. Following [81], we use cc12m [12] real captions as our baseline, which has 10M sentences. To synthesize captions, we design the following variants: (a) $IN + h + \text{Places}$ randomly combines one IN class plus its hypernyms in WordNet graph, with one place class; (b) $IN + \text{Places} + \text{LLM}$ uses the $c, bg \rightarrow$ caption in-context synthesis template with $c$ from IN and $bg$ from places; (c) $IN + ourBG + \text{LLM}$ uses the background classes output by GPT-4, instead of Places; (d) ours means our full configuration specified in Section 3.1. For each of the config, we generate 10M captions. If not enough, we do duplication. + +Results are summarized in Table 2, where we train both StableRep and SynCLR to avoid biases favored by a single method. Compared to a real caption dataset cc12m, simply concatenating IN and Places class names improves the ImageNet linear accuracy but reduces the fine-grained classification performance. Interestingly, naively asking Llama to combine IN and Places classes into captions yields the worst performance. Replacing random background from places with GPT generated background improves the accuracy. This shows the importance of synthesizing captions that follow the distribution of real captions, which were used to train the text-to-image model. Finally, our full configuration achieves the best accuracy on both ImageNet and fine-grained classification. Another advantage of our synthesis method is its scalability – scale up to hundreds of millions of captions with little duplication. In contrast, if we concatenate IN classes with Places classes, there are at most 365k unique captions. + +Synthesize images. There are two major parameters in this process: number of images per caption and classifier free + +Table 3. Classifier-free guidance scale (CFG). Contrastive loss prefers small CFG scale but is not very sensitive to it. + +
methodEMAiBOTMCINavg.ADE20k
StableRep75.885.7-
✓76.786.748.0
✓✓77.687.150.5
✓✓78.687.849.5
SynCLR✓✓✓78.888.150.8
+ +Table 4. Important components for our model. ViT-B/16 models are trained for 85000 iterations. We study the modules that affect the ImageNet linear evaluation, the fine-grained classification (avg.), and ADE20k segmentation. + +
methodINavg.
Supervised CE71.975.0
SimCLR63.667.9
SynCLR75.378.5
+ +Table 5. Comparison of different learning objectives. These objectives assume different levels of classification granularity, as shown in Figure 2. Our modeling, i.e., defining classes as captions, outperforms the other two. To accommodate Supervised CE training, all items here used $IN + OurBG + LLM$ entry in Table 2. + +guidance scale. For the former, we find generating 4 images is almost able to reproduce StableRep [81]'s performance (10 images) when using cc12m captions (ours $73.0\%$ v.s. StableRep $73.5\%$ on ImageNet). Thus we stick to 4. For guidance scale, we briefly find the contrastive loss is not very sensitive to CFG in a pilot study, as shown in Table 3. Thus we stick to 2.5, similar as StableRep [81]. + +Model components. We present the improvement of accuracy brought by different modules in Table 4. Compared to the baseline StableRep, adding a teacher EMA model improves the IN linear accuracy by $0.9\%$ . Further adding iBOT local objective or the multi-crop strategy increases the accuracy by $0.9\%$ and $1.9\%$ , respectively. Combining all of them results in our full SynCLR model, which achieves $78.8\%$ top-1 IN linear accuracy. The fine-grained classification performance follows a similar trend, and reaches $88.1\%$ . Besides, we test the transfer ability to semantic segmentation on ADE20k. The iBOT objective brings 1.0 more mIoU than multi-crop strategy, demonstrating the effectiveness of masked image modeling for dense prediction tasks. + +Compare to SimCLR and supervised training. We compare the three different representation learning objectives shown in Figure 2, which classify images at different levels of granularity. Since supervised cross-entropy training requires a fixed set of balanced classes (indeed both fixed set and balance are limitations of such method), we use the $IN + ourBG + LLM$ configuration where we have 1000 balanced classes (i.e., each class has 40k images). The supervised training recipe follows [76]. For a fair comparison with SimCLR, we remove all unmatched modules (i.e., EMA, iBOT, and MC) to make sure that the only difference between SimCLR and our SynCLR is the classification gran + +
textimg#imgsImageNetAircraftCarsDTDFlowersPetsSUN397Caltech-101Food-101VOC2007Average
StableReprealsyn100MViT-B/1675.759.283.580.197.388.374.394.785.187.983.4
CLIPrealreal400MViT-B/1680.259.586.779.298.193.178.494.792.889.285.7
ViT-L/1483.969.490.982.199.295.181.896.595.289.688.9
OpenCLIPrealreal400MViT-B/1678.961.192.381.998.291.577.995.290.988.086.3
400MViT-L/1482.367.194.083.698.892.581.096.493.488.888.4
2BViT-L/1483.471.795.385.399.094.282.297.594.188.989.8
DINO v2*-real142MViT-B/14\( 83.9^{\dagger} \)79.488.283.399.696.277.396.192.888.289.0
ViT-L/14\( 85.7^{\dagger} \)81.590.184.099.796.678.797.594.388.390.1
SynCLRsynsyn600MViT-B/1680.781.793.879.999.193.676.295.391.689.489.0
ViT-L/1483.085.694.282.199.294.178.496.193.490.390.4
+ +ularity defined by the contrastive loss. For all of them, we do pre-training and then linear probing on the target dataset. + +Table 5 presents the comparison. Our multi-positive objective, which defines images as the same class if they are generated by the same caption, achieves the best performance. It outperforms supervised cross-entropy training and SimCLR by $3.4\%$ and $11.7\%$ for top-1 accuracy on ImageNet linear evaluation, and by $3.5\%$ and $10.6\%$ on fine-grained classification tasks. Besides, our objective does not require balance between samples from a fixed set of classes, making it easier to scale up. + +# 4.2. Scaling up + +After we have ablated different components, we scale up our experiments. Specifically, we synthesize a dataset of 150M captions, called SynCaps-150M, from which we generate 600M images. We train both ViT-B/16 and ViT-L/14 (no SwiGLU [73] or LayerScale [82]), and extend the training schedules to 500k steps with a batch size of 8192 captions. We use 224x224 resolution for all pre-training tasks. + +We compare SynCLR with OpenAI's CLIP [62], OpenCLIP [16], and DINO v2 [59], which represent learning from data. We note that ViT-B/14 and ViT-L/14 from DINO v2 are distilled from a ViT-g [93] model, which makes DINO v2 advantageous in our comparison. We also include StableRep [81], which uses the hybrid paradigm. + +ImageNet linear evaluation. For fair comparison,CLS token from the last block is used as representation across all models (whereas in DINO v2, results are from concatenating multiple layers). As shown in Table 6, SynCLR achieves $80.7\%$ with ViT-B and $83.0\%$ with ViT-L. This is similar as CLIP, but still lags behind DINO v2 by $3.2\%$ and $2.7\%$ , respectively, partially because of the extra distillation in DINO v2. We note SynCLR has already outperformed other self-supervised methods pre-trained directly on ImageNet-1k (e.g., DINO achieves $78.2\%$ with ViT-B/16 and iBOT + +Table 6. Comparison on ImageNet linear evaluation and fine-grained classifier. SynCLR achieves comparable results with OpenAI's CLIP and DINO v2 models, despite only using synthetic data. *DINO v2 modes are distilled from a ViT-g model, thus advantageous in this comparison. † we rerun only using c1s token instead of concatenating multiple layers presented in the original DINO v2 paper [59]. + +
methodpre-train datadistillViT-BViT-L
StableRephybrid, 100M49.4-
MoCo v3real, IN1K-1M47.349.1
BEiTreal, IN1K-1M+DALLE47.153.3
MAEreal, IN1K-1M48.153.6
iBOTreal, IN1K-1M50.0-
CLIPreal, WIT-400M52.6-
BEiT v2real, WIT-400M, IN1K✓53.156.7
DINO v2real, LVD-142M✓54.4†57.5†
SynCLRsynthetic, 600M54.357.7†
+ +Table 7. ADE20K semantic segmentation (mIoU) using UperNet, with single scale at 512x512 resolution. ${}^{ \dagger }$ use patch size of ${14}\mathrm{x}{14}$ , thus adapt to 518x518 resolution. + +reaches $81.0\%$ with ViT-L/16). + +Fine-grained classification. On the nine fine-grained datasets we have evaluated in Table 6, SynCLR achieves very similar average accuracy as DINO v2, e.g., $89.0\%$ vs. $89.0\%$ for ViT-B, and $90.1\%$ vs $90.4\%$ for ViT-L. Both SynCLR and DINO v2 have curated the pre-training data to include the distribution for these datasets (but in different ways and portions), and end up with similar performance. Interestingly, SynCLR outperforms others on Aircraft and Cars, possibly because we favor more frequent sampling towards them. This can be an advantage for synthetic data when we know what downstream tasks to solve. Besides, SynCLR outperforms CLIP and StableRep by $3.3\%$ and by $5.6\%$ for ViT-B, respectively. + +Semantic segmentation. To evaluate the pixel-level understanding ability of SynCLR, we fine-tune the pre-trained models on ADE20k [97], following the setup in [5, 39]. UperNet [89] is used as the task layer, and we evaluate with a single-scale, i.e. $512 \times 512$ . Besides CLIP and DINO v2, we also compare to self-supervised methods pre-trained on ImageNet, as well as BEiT v2 [61], which distills from CLIP. Table 7 shows that our SynCLR outperforms self-supervised + +![](images/1ecdab7690d8f4a818dfb9f95dd53fe7776b7e644e3f37a1b082ce935ce9199b.jpg) +Figure 5. PCA visualization. Follow DINO v2 [59], we compute a PCA between the image patches from the same set and colorize by their first 3 components. Compared to DINO v2, SynCLR produces more accurate maps for cars (e.g., zoom-in to see the two bars on the roof of the first car, and the three side windows of the third car) and airplanes (e.g., the boundaries), while being slightly worse for dogs (e.g., heads). We use ViT-L/14 for both methods. Images are resized to $336 \times 448$ resolution, yielding $24 \times 32$ visualization grids. + +![](images/74a4c6d2efba77a5dd546920a00901c13bd84234012634666c185976f07f49e4.jpg) + +![](images/70ce50aa55f598f936bb951b4bbfe06e68d455294d9887f86a91e470f6596350.jpg) + +methods trained on IN-1k by a clear marge, e.g., 4.3 higher mIoU than iBOT. Despite not involving a high resolution pretraining period like DINO v2 (e.g., 518x518), SynCLR performs similarly with DINO v2 (0.1 lower for ViT-B possibly because DINO v2 uses a smaller patch size of 14x14, but 0.2 higher for ViT-L). This suggests SynCLR pre-training is suitable for dense prediction tasks. + +ImageNet fine-tuning. We evaluate the fine-tuning transfer ability of SynCLR on ImageNet. Our SynCLR achieves $87.9\%$ top-1 accuracy with ViT-L, outperforming models trained on ImageNet images or large scale image datasets. Specifically, SynCLR outperforms OpenCLIP ViT-L (87.1% top-1) trained on Laion-2B, which is the dataset Stable Diffusion (the text2image model we used) is trained on. This contrasts with [26, 69], which shows that directly training a classifier on synthetic images yields bad classification accuracy. Our finding suggests synthetic images are good for training representations, which later can be easily adapted to a downstream task with limited amount of real data. Detailed comparisons are provided in Appendix C. + +PCA visualization. Following the method used in DINO v2 [59], we present visualizations derived from the Principal Component Analysis (PCA) conducted on patch features extracted using our model SynCLR. As depicted in Figure 5, a comparative analysis is conducted between SynCLR and DINO v2, both utilizing the ViT-L/14 architecture. The results demonstrate that SynCLR effectively accentuates the features of cars and planes, while efficiently minimizing background clutter. + +# 5. Discussions and Conclusion + +Why learn from generative models? One compelling reason is that a generative model can act like hundreds of datasets simultaneously. Traditionally, researchers have to + +spend separate effort collecting datasets for different image categories, e.g., cars, flowers, cats, dogs, and so on. DINO v2 [59] achieves robust representations by curating and amalgamating numerous such datasets. Such a process introduces complexities such as clustering and search challenges. In contrast, advanced text-to-image generative models like Stable Diffusion [63] or Imagen [68] have the capability to generate many diverse datasets. These models provide the flexibility to produce an infinite number of samples (albeit finite diversity) and control the generation process through textual input. Thus, generative models offer a convenient and effective method for curating training data. In our study, we harness this advantage to synthesize images encompassing a broad spectrum of visual concepts. + +What can be further improved? Enhanced caption sets can be achieved through various methods, such as enriching the set of in-context examples, optimizing the sampling ratios among different concepts, and utilizing more advanced LLMs. In terms of the learning process, one approach is to distill knowledge from a larger model, and incorporate an additional high-resolution training phase (as discussed in [59]) or an intermediate IN-21k fine-tuning stage (as per [5, 61]). Regarding architectural improvements, the integration of SwiGLU and LayerScale, coupled with superior model initialization strategies (referenced in [28]), can be beneficial. However, due to limited resources and the scope of this paper not being focused on achieving the highest possible metrics, we propose these areas for further exploration in future research endeavors. + +In summary, this paper studies a new paradigm for visual representation learning – learning from generative models. Without using any real data, SynCLR learns visual representations that are comparable with those achieved by state of the art general-purpose visual representation learners. + +# References + +[1] Hassan Abu Alhajja, Siva Karthik Mustikovela, Lars Mescheder, Andreas Geiger, and Carsten Rother. Augmented reality meets computer vision: Efficient data generation for urban driving scenes. IJCV, 2018. 3 +[2] Mahmoud Assran, Mathilde Caron, Ishan Misra, Piotr Bojanowski, Florian Bordes, Pascal Vincent, Armand Joulin, Mike Rabbat, and Nicolas Ballas. Masked siamese networks for label-efficient learning. 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Training on thin air: Improve image classification with generated data. arXiv preprint arXiv:2305.15316, 2023. 3 \ No newline at end of file diff --git a/2024/Learning Vision from Models Rivals Learning Vision from Data/images.zip b/2024/Learning Vision from Models Rivals Learning Vision from Data/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..7d1125c854fd511af0a6114556eb10b0e4c64f5e --- /dev/null +++ b/2024/Learning Vision from Models Rivals Learning Vision from Data/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:f436302d0f70451b9e0a442959d76f1b6384c5b2b60c09a63393c581f3f5a490 +size 598523 diff --git a/2024/Learning Vision from Models Rivals Learning Vision from Data/layout.json b/2024/Learning Vision from Models Rivals Learning Vision from Data/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..926698fb7917e7d6f647be8ec6ea5d53c9513ac7 --- /dev/null +++ b/2024/Learning Vision from Models Rivals Learning Vision from Data/layout.json @@ -0,0 +1,10160 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 99, + 103, + 493, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 99, + 103, + 493, + 121 + ], + "spans": [ + { + "bbox": [ + 99, + 103, + 493, + 121 + ], + "type": "text", + "content": "Learning Vision from Models Rivals Learning Vision from Data" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "spans": [ + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "text", + "content": "Yonglong Tian" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "inline_equation", + "content": "^{1,\\dagger}" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "text", + "content": " Lijie Fan" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "inline_equation", + "content": "^{2,\\dagger,*}" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "text", + "content": " Kaifeng Chen" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "text", + "content": " Dina Katabi" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "text", + "content": " Dilip Krishnan" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "text", + "content": " Phillip Isola" + }, + { + "bbox": [ + 67, + 142, + 525, + 159 + ], + "type": "inline_equation", + "content": "^{2}" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 162, + 165, + 431, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 162, + 165, + 431, + 180 + ], + "spans": [ + { + "bbox": [ + 162, + 165, + 431, + 180 + ], + "type": "text", + "content": "1Google Research, 2MIT CSAIL, †equal contribution" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 140, + 187, + 455, + 200 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 140, + 187, + 455, + 200 + ], + "spans": [ + { + "bbox": [ + 140, + 187, + 455, + 200 + ], + "type": "text", + "content": "GibthuRe: https://github.com/google-research/syn-rep-learn" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 143, + 227, + 192, + 239 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 227, + 192, + 239 + ], + "spans": [ + { + "bbox": [ + 143, + 227, + 192, + 239 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 252, + 290, + 445 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 252, + 290, + 445 + ], + "spans": [ + { + "bbox": [ + 46, + 252, + 290, + 445 + ], + "type": "text", + "content": "We introduce SynCLR, a novel approach for learning visual representations exclusively from synthetic images and synthetic captions, without any real data. We synthesize a large dataset of image captions using LLMs, then use an off-the-shelf text-to-image model to generate multiple images corresponding to each synthetic caption. We perform visual representation learning on these synthetic images via contrastive learning, treating images sharing the same caption as positive pairs. The resulting representations transfer well to many downstream tasks, competing favorably with other general-purpose visual representation learners such as CLIP and DINO v2 in image classification tasks. Furthermore, in dense prediction tasks such as semantic segmentation, SynCLR outperforms previous self-supervised methods by a significant margin, e.g., improving over MAE and iBOT by 6.2 and 4.3 mIoU on ADE20k for ViT-B/16." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 468, + 128, + 481 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 468, + 128, + 481 + ], + "spans": [ + { + "bbox": [ + 47, + 468, + 128, + 481 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 489, + 287, + 560 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 489, + 287, + 560 + ], + "spans": [ + { + "bbox": [ + 46, + 489, + 287, + 560 + ], + "type": "text", + "content": "Representation learning extracts and organizes information from raw, often unlabeled data. The quality, quantity, and diversity of the data determines how good a representation the model can learn. The model becomes a reflection of the collective intelligence that exists in the data. We get what we feed in." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 562, + 288, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 562, + 288, + 693 + ], + "spans": [ + { + "bbox": [ + 46, + 562, + 288, + 693 + ], + "type": "text", + "content": "Unsurprisingly, the current best-performing visual representation learning methods [59, 62] rely on large scale real datasets. However, the collection of real data has its own dilemmas. Collecting large scale uncurated data [71] is relatively cheap and thus quite achievable. However, for self-supervised representation learning, this approach exhibits poor scaling behavior –i.e., adding more uncurated data has little effect at large data scales [33, 80]. Collecting small scale curated data [21] also is achievable, but models trained in this way are limited to relatively narrow tasks. The ideal would be large scale curated datasets of real images, and" + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 310, + 227, + 531, + 414 + ], + "blocks": [ + { + "bbox": [ + 310, + 227, + 531, + 414 + ], + "lines": [ + { + "bbox": [ + 310, + 227, + 531, + 414 + ], + "spans": [ + { + "bbox": [ + 310, + 227, + 531, + 414 + ], + "type": "image", + "image_path": "0055ce920975e0db375007ce202ef860a324e6798f2d7c37d54212d135862e3c.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 422, + 547, + 501 + ], + "lines": [ + { + "bbox": [ + 305, + 422, + 547, + 501 + ], + "spans": [ + { + "bbox": [ + 305, + 422, + 547, + 501 + ], + "type": "text", + "content": "Figure 1. Three paradigms for visual representation learning. Top row: Traditional methods, such as CLIP [62], learn only from real data; Middle row: Recent methods, such as StableRep [81], learn from real text and generated images; Bottom row: Our method, SynCLR, learns from synthetic text and synthetic images, and rival the linear transfer performance of CLIP on ImageNet despite not directly observing any real data." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 519, + 546, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 519, + 546, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 519, + 546, + 555 + ], + "type": "text", + "content": "recent work has indeed shown that this can lead to strong performance gains at scale [59], but this path is costly to pursue." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 556, + 547, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 556, + 547, + 604 + ], + "spans": [ + { + "bbox": [ + 304, + 556, + 547, + 604 + ], + "type": "text", + "content": "To alleviate the cost, in this paper we ask if synthetic data, sampled from off-the-shelf generative models, is a viable path toward large scale curated datasets that can train state-of-the-art visual representations." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 605, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 547, + 715 + ], + "type": "text", + "content": "We call such a paradigm learning from models, in contrast to directly learning from data. Models have several advantages as a data source for building large scale training sets: via their latent variables, conditioning variables, and hyperparameters, they provide new controls for curating data; we will make use of these controls in the method we propose. Models also can be easier to share and store (because models are more compressed than data), and can produce an unlimited number of data samples (albeit with" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 186, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 186, + 713 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 186, + 713 + ], + "type": "text", + "content": "*Work done while interning at Google." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15887" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 45, + 72, + 289, + 251 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 72, + 289, + 251 + ], + "spans": [ + { + "bbox": [ + 45, + 72, + 289, + 251 + ], + "type": "text", + "content": "finite diversity). A growing literature has studied these properties and other advantages (and disadvantages) of using generative models as a data source for training downstream models [3, 26, 40, 41, 69, 81]. Some of these methods use a hybrid mode – either mixing real and synthetic datasets [3] or needing a real dataset to generate another synthetic dataset [81]. Other methods try to learn representations from purely synthetic data [69] but lag far behind the best performing models. Instead, we show that learning from models, without training on any real data, can yield representations that match the top-performing representations learnt from real data. For instance, as illustrated in Figure 1, representations learnt by our method are able to transfer as well as OpenAI's CLIP [62] on ImageNet (both methods using ViT-B [24])." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 255, + 289, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 255, + 289, + 662 + ], + "spans": [ + { + "bbox": [ + 46, + 255, + 289, + 662 + ], + "type": "text", + "content": "Our approach leverages generative models to re-define the granularity of visual classes. As shown in Figure 2, consider we have four images generated using two prompts: \"a golden retriever; wearing sunglasses and a beach hat, rides a bike\" and \"a cute golden retriever sits in a house made of sushi\". Traditional self-supervised method such as SimCLR [13] will treat each of these images as a different class; embeddings for different images are pushed apart with no explicit consideration of the shared semantics between images. On the other extreme, supervised learning methods (i.e. SupCE) will regard all these images as a single class (e.g., \"golden retriever\"). This ignores nuances in the semantics of the images, such as the fact that the dogs are riding a bike in one pair of images and sitting inside a sushi house in the other pair of images. Instead, our method, SynCLR, treats captions as classes, i.e., each caption describes a visual class (this level of granularity was also explored in StableRep [81]). This allows us to group images by the concepts of \"riding a bike\" and \"sitting in a sushi house\", in addition to grouping by a coarser class label like \"golden retrieval\". This level of granularity is difficult to mine in real data, since collecting multiple images described by a given caption is non-trivial, especially when scaling up the number of captions. However, text-to-image diffusion models are fundamentally built with this ability; simply by conditioning on the same caption and using different noise inputs, a text-to-image diffusion model will produce different images that all match the same caption. In our experiments, we find the caption-level granularity outperforms both SimCLR and supervised training. Another advantage is that this definition of visual classes has good scalability. Unlike ImageNet-1k/21k where a given number of classes is fixed, we can augment existing classes (or data) in an online fashion, and theoretically scale up to as many classes as needed." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 665, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 289, + 715 + ], + "type": "text", + "content": "Our system consists of three steps. The first step is to synthesize a large corpus of image captions. We design a scalable approach by leveraging the in-context learning capability of large language models (LLMs), where we present" + } + ] + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 307, + 70, + 545, + 257 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 545, + 257 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 545, + 257 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 545, + 257 + ], + "type": "image", + "image_path": "0d6c87813b3f7ca4064843a7584d68a8003cba40aa27e6a81a42b5ea57afa551.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 264, + 548, + 374 + ], + "lines": [ + { + "bbox": [ + 304, + 264, + 548, + 374 + ], + "spans": [ + { + "bbox": [ + 304, + 264, + 548, + 374 + ], + "type": "text", + "content": "Figure 2. Different learning objectives treat classification granularity differently. These images are generated by two prompts \"a golden retriever, wearing sunglasses and a beach hat, rides a bike\" and \"a cute golden retriever sits in a house made of sushi\". SimCLR treats each image as a class, while supervised cross-entropy treats them all as the same \"golden retrieval\" class. The former does not consider shared semantics between images, and the latter is coarse-grained and ignores actions or relationships between subjects/background. Our approach, SynCLR, defines visual classes by sentences." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 392, + 547, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 392, + 547, + 464 + ], + "spans": [ + { + "bbox": [ + 304, + 392, + 547, + 464 + ], + "type": "text", + "content": "examples of word-to-caption translations. Next, a text-to-image diffusion model is adopted to synthesize multiple images for each synthetic caption. This yields a synthetic dataset of 600M images. Then we train visual representation models by a combination of multi-positive contrastive learning [43] and masked image modeling [98]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "spans": [ + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "text", + "content": "Our learned representations transfer well. With SynCLR pre-training, our ViT-B and ViT-L models achieve " + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "inline_equation", + "content": "80.7\\%" + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "inline_equation", + "content": "83.0\\%" + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "text", + "content": " top-1 linear probing accuracy on ImageNet-1K, respectively, which is on par with OpenAI's CLIP [62]. On fine-grained classification tasks, SynCLR outperforms CLIP by " + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "inline_equation", + "content": "3.3\\%" + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "text", + "content": " for ViT-B and " + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "inline_equation", + "content": "1.5\\%" + }, + { + "bbox": [ + 304, + 464, + 548, + 632 + ], + "type": "text", + "content": " for ViT-L, and performs similarly to DINO v2 [59] models, which are distilled from a pre-trained ViT-g model. For semantic segmentation on ADE20k, SynCLR outperforms MAE pre-trained on ImageNet by 6.2 and 4.1 in mIoU for ViT-B and ViT-L under the same setup, showing strong transfer ability for dense prediction tasks similar to DINO v2, which additionally involves a training period on 518x518 resolution images that SynCLR does not have." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 645, + 398, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 645, + 398, + 658 + ], + "spans": [ + { + "bbox": [ + 306, + 645, + 398, + 658 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 665, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 548, + 715 + ], + "type": "text", + "content": "Self-supervised representation learning approaches in vision develop domain-specific pre-text tasks, such as colorization [94], rotation prediction [31], and solving jigsaw puzzles [56]. Domain-agnostic approaches have been pop" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "15888" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "content": "ular, such as contrastive learning [6, 13, 35, 38, 57, 78, 87] and masked image modeling [2, 4, 5, 29, 39, 86, 90, 98]. Contrastive learning promotes invariance [79] for two views of the same image and pushes apart representations for different images [85] (or only invariance [11, 34]); the resulting representations yield strong performance for linear or zero-shot transfer. Masked image modeling reconstructs the pixels [39, 90] or local features [4], often producing excellent fine-tuning transfer performance, especially in dense prediction tasks [39]. The state of the art DINO v2 [59] leverages both approaches, and our approach shares a similar spirit." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 210, + 289, + 354 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 210, + 289, + 354 + ], + "spans": [ + { + "bbox": [ + 46, + 210, + 289, + 354 + ], + "type": "text", + "content": "Supervised learning [36, 45, 75] used to be the dominant approach for learning transferable visual representations for various tasks [23, 32, 72]. Recent studies [37, 49] has shown that, the transferability of representations learned in this way is limited, e.g., pre-training has no improvement over random initialization for dense prediction tasks (e.g., object detection) when the fine-tuning is long enough. Such limitation continues when the model has been scaled up to 22B [20]. An alternative paradigm learns visual representations from text supervision [42, 62], e.g., CLIP [62]. This approach is more flexible (i.e., not requiring classes) and provides richer supervision, often learning generalizable representations." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 360, + 289, + 515 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 360, + 289, + 515 + ], + "spans": [ + { + "bbox": [ + 46, + 360, + 289, + 515 + ], + "type": "text", + "content": "Generative models as representation learners. A number of papers have explored the representations that are learned by generative models for various recognition tasks [22, 48]. As might be expected intuitively, such models indeed learn especially good representations for dense tasks, such as optical flow estimation [70], semantic segmentation [8, 91], and depth estimation [95]. Another line of work [18, 47] adapt pre-trained diffusion models for zero-shot image recognition via analysis-by-synthesis. These approaches may need to be adapted when the architectures of the generative models change or a new family of generative model emerge. Our approach treats images as universal interfaces with the hope of better generality." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 522, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 522, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 522, + 289, + 713 + ], + "type": "text", + "content": "Learning from synthetic data from generative models. Synthetic data has been explored to train machine learning models in various domains [27, 46, 53, 54, 65, 66, 74, 77, 92]. In computer vision, the utilization of synthetic data for training models is common, ranging from optical flow [52] and autonomous driving [1] to semantic segmentation [15] and human pose estimation [84]. Others [41, 50] have explored synthetic data for representation learning, with the predominant approach of altering the latent variables of deep generative models. Our approach aligns with this research paradigm, but it diverges in its use of text-to-image models, which have also been investigated by other researchers [40, 69, 99]. But they use synthetic data for supervised learning [26, 69]. The closet work is StableRep [81], which also conducts representation learning but still needs a real text dataset." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 305, + 72, + 373, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 373, + 85 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 373, + 85 + ], + "type": "text", + "content": "3. Approach" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "spans": [ + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": "In this paper, we study the problem of learning a visual encoder " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": " in the absence of real images or textual data. Our approach hinges on the utilization of three key resources: a language generation model " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "(g_1)" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": ", a text-to-image generative model " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "(g_2)" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": ", and a curated list of visual concepts " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "(C)" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": ". Our exploration include three steps: (1) we employ " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "g_1" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": " to synthesize a comprehensive set of image descriptions " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": ", which encompasses the range of visual concepts in " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": "; (2) for each caption in " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": ", we generate multiple images using " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "g_2" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": ", culminating in an extensive synthetic image dataset " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "X" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": "; (3) we train on " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "X" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": " to obtain a visual representation encoder " + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 304, + 92, + 547, + 224 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "spans": [ + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "text", + "content": "We use Llama-2 7B [83] and Stable Diffusion 1.5 [64] as " + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "inline_equation", + "content": "g_{1}" + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "inline_equation", + "content": "g_{2}" + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "text", + "content": ", respectively, because of their fast inference speed. We anticipate that better " + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "inline_equation", + "content": "g_{1}" + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "inline_equation", + "content": "g_{2}" + }, + { + "bbox": [ + 304, + 224, + 547, + 273 + ], + "type": "text", + "content": " in the future will further enhance the effectiveness of this approach." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 283, + 430, + 296 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 283, + 430, + 296 + ], + "spans": [ + { + "bbox": [ + 305, + 283, + 430, + 296 + ], + "type": "text", + "content": "3.1. Synthesizing captions" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 302, + 547, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 302, + 547, + 361 + ], + "spans": [ + { + "bbox": [ + 304, + 302, + 547, + 361 + ], + "type": "text", + "content": "To harness the capability of powerful text-to-image models for generating a substantial dataset of training images, we initially require a collection of captions that not only precisely depict an image but also exhibit diversity to encompass a broad spectrum of visual concepts." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 363, + 547, + 470 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 363, + 547, + 470 + ], + "spans": [ + { + "bbox": [ + 304, + 363, + 547, + 470 + ], + "type": "text", + "content": "We have developed a scalable approach to create such a large collection of captions, leveraging the in-context learning capability of LLMs [9]. Our method involves crafting specific prompt engineering templates that guide the LLM to produce the required captions. We start by gathering the concept list " + }, + { + "bbox": [ + 304, + 363, + 547, + 470 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 363, + 547, + 470 + ], + "type": "text", + "content": " from some existing datasets, such as ImageNet-21k [21] and Places-365 [96]. For each concept " + }, + { + "bbox": [ + 304, + 363, + 547, + 470 + ], + "type": "inline_equation", + "content": "c \\in C" + }, + { + "bbox": [ + 304, + 363, + 547, + 470 + ], + "type": "text", + "content": ", we consider three straightforward templates to generate captions effectively." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 474, + 547, + 713 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 306, + 474, + 545, + 508 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 474, + 545, + 508 + ], + "spans": [ + { + "bbox": [ + 306, + 474, + 545, + 508 + ], + "type": "text", + "content": "- " + }, + { + "bbox": [ + 306, + 474, + 545, + 508 + ], + "type": "inline_equation", + "content": "c \\rightarrow" + }, + { + "bbox": [ + 306, + 474, + 545, + 508 + ], + "type": "text", + "content": " caption. As the most direct and simple approach, we have the Llama-2 model sample a sentence for the concept " + }, + { + "bbox": [ + 306, + 474, + 545, + 508 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 306, + 474, + 545, + 508 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "spans": [ + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "content": "- " + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "inline_equation", + "content": "c, bg \\rightarrow" + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "content": " caption. We combine the visual concept " + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "content": " with a background or setting " + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "inline_equation", + "content": "bg" + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "content": ". A naive approach would randomly select both " + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "inline_equation", + "content": "bg" + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "inline_equation", + "content": "bg" + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "content": " may correspond to a class name from a places dataset like [96]. However, this method often leads to unlikely combinations in the real world, such as a blue whale in a football field. Our ablation experiments demonstrate that this strategy results in suboptimal performance, likely because the generated captions fall far outside the training distribution of " + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "inline_equation", + "content": "g_{2}" + }, + { + "bbox": [ + 306, + 510, + 547, + 676 + ], + "type": "text", + "content": ". Instead, we employ GPT-4 [58] to generate a list of suitable backgrounds for the chosen concepts. This approach increases the likelihood of generating more plausible combinations, such as a tiger in a forest or a cat in a kitchen, enhancing the overall quality of the results." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "text", + "content": "- " + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "inline_equation", + "content": "c, \\text{rel} \\rightarrow" + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "text", + "content": " caption. Given a visual concept " + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "text", + "content": ", we consider pairing it with a positional relationship word, " + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\text{rel}" + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "text", + "content": ". Take for instance, if " + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "text", + "content": " signifies " + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\text{cat}" + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\text{rel}" + }, + { + "bbox": [ + 306, + 678, + 547, + 713 + ], + "type": "text", + "content": " translates to in front" + } + ] + } + ], + "index": 12 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "15889" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 55, + 70, + 539, + 256 + ], + "blocks": [ + { + "bbox": [ + 55, + 70, + 539, + 256 + ], + "lines": [ + { + "bbox": [ + 55, + 70, + 539, + 256 + ], + "spans": [ + { + "bbox": [ + 55, + 70, + 539, + 256 + ], + "type": "table", + "html": "
TemplatesIn context examples
c->captionrevolver ->Multiple antique revolvers lie on a wooden table, gleaming under soft, ambient light. closetet ->The compact closet, brimming with clothes and shoes, exudes a feeling of organization. zebra ->A zebra is gallantly trotting across the vast, sunlit plains of the African savannah, creating a captivating black and white spectacle. bus station ->The bustling bus station thrums with restless energy, as travelers navigate through the crowded space, awaiting their journeys amid the echoes of departing buses.
c,bg->captiontiger, forest ->Two tigers are running together in the forest. lighter, motorhome ->In the cozy, cluttered environment of a well-traveled motorhome, a sleek silver lighter holds dominion on the rustic wooden table. sunset, lake ->Golden sunset hues reflect on a calm lake, silhouetting a lone canoeist against a backdrop of fiery clouds.
c,rel->captionkit fox, in front of ->A group of small, fluffy, golden kit foxes is playfully gathered in front of a lush, green, towering forest backdrop. cabbage, besides ->A vibrant image portrays a lush, green cabbage, glistening with dewdrops, nestled besides a rustic, wooden crate full of freshly harvested vegetables.
", + "image_path": "9c059581603d7f922b72bd316a2a38112c5b7468661aa8b6f2c1dd389a6c4564.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 262, + 547, + 308 + ], + "lines": [ + { + "bbox": [ + 46, + 262, + 547, + 308 + ], + "spans": [ + { + "bbox": [ + 46, + 262, + 547, + 308 + ], + "type": "text", + "content": "Table 1. We show examples for the three synthesis templates. Such examples are used as demonstrations for Llama-2 to perform the in-context learning task. We have 176 such examples in total. Most of them are generated by prompting GPT-4 [58], while a handful of others are human generated (in a 10M scale pilot study of synthetic captions, we do not notice significant differences between including or excluding human generated examples.)" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 50, + 323, + 286, + 415 + ], + "blocks": [ + { + "bbox": [ + 50, + 323, + 286, + 415 + ], + "lines": [ + { + "bbox": [ + 50, + 323, + 286, + 415 + ], + "spans": [ + { + "bbox": [ + 50, + 323, + 286, + 415 + ], + "type": "image", + "image_path": "8a42f1841f22903e4b63eb70e60d711d71f5a05e01cac9bfe87c99dfd12c5267.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 423, + 288, + 447 + ], + "lines": [ + { + "bbox": [ + 47, + 423, + 288, + 447 + ], + "spans": [ + { + "bbox": [ + 47, + 423, + 288, + 447 + ], + "type": "text", + "content": "Figure 3. In-context caption generation using Llama-2 [83]. We randomly sample three in-context examples for each inference run." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 55, + 471, + 287, + 531 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 471, + 287, + 531 + ], + "spans": [ + { + "bbox": [ + 55, + 471, + 287, + 531 + ], + "type": "text", + "content": "of, our objective is to prompt the LLM to create captions such as a cute yellow cat is enjoying the fish in front of the sofa. To add variety, we have a selection of 10 different positional relationship words that we randomly choose from." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "spans": [ + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "type": "text", + "content": "For each of the three templates, we have prepared multiple demonstration examples that serve as instructions for the LLM to complete the caption synthesis task. Table 1 shows a couple of examples for each template. In total, we have 106 examples for " + }, + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "type": "inline_equation", + "content": "c->prompt" + }, + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "type": "text", + "content": ", 50 examples for " + }, + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "type": "inline_equation", + "content": "c, bg->prompt" + }, + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "type": "text", + "content": ", and 20 examples for " + }, + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "type": "inline_equation", + "content": "c, rel->prompt" + }, + { + "bbox": [ + 46, + 541, + 288, + 650 + ], + "type": "text", + "content": ". Such examples are mostly collected by prompting GPT-4, with a handful from human. In a pilot study, we do not observe difference between including or excluding human generated examples." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 654, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 654, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 654, + 288, + 715 + ], + "type": "text", + "content": "In the stage of generating captions in-context, we select a concept and one of the three templates. Next, we randomly pick three examples from the chosen template and frame the caption generation as a text completion task. This process is illustrated in Figure 3." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 323, + 424, + 336 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 323, + 424, + 336 + ], + "spans": [ + { + "bbox": [ + 306, + 323, + 424, + 336 + ], + "type": "text", + "content": "3.2. Synthesizing Images" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 346, + 547, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 346, + 547, + 479 + ], + "spans": [ + { + "bbox": [ + 304, + 346, + 547, + 479 + ], + "type": "text", + "content": "For each text caption, we generate a variety of images by initiating the reverse diffusion process with different random noise. The Classifier-Free Guidance (CFG) scale is a crucial factor in this process. A higher CFG scale enhances the quality of the samples and the alignment between text and image, whereas a lower scale results in more diverse samples and better adherence to the original conditional distribution of images based on the given text. Following the approach used in StableRep [81], we opt for a lower CFG scale, specifically 2.5, and produce 4 images for each caption. Examples of these images can be seen in Figure 4." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 503, + 446, + 517 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 503, + 446, + 517 + ], + "spans": [ + { + "bbox": [ + 306, + 503, + 446, + 517 + ], + "type": "text", + "content": "3.3. Representation Learning" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 528, + 547, + 624 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 528, + 547, + 624 + ], + "spans": [ + { + "bbox": [ + 304, + 528, + 547, + 624 + ], + "type": "text", + "content": "Our representation learning method is built upon StableRep [81]. The key component of our approach is the multi-positive contrastive learning loss [43] which works by aligning (in the embedding space) images generated from the same caption. We additionally combine multiple techniques from other self-supervised learning methods, including a patch-level masked image modeling objective. We briefly review StableRep and elaborate on the added modules." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "text", + "content": "StableRep [81] minimizes the cross-entropy loss between a ground-truth assignment distribution and a contrastive assignment distribution. Consider an encoded anchor sample " + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\pmb{a}" + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "text", + "content": " and a set of encoded candidates " + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\{\\pmb{b}_1, \\pmb{b}_2, \\dots, \\pmb{b}_K\\}" + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "text", + "content": ". The contrastive assignment distribution " + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{q}" + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "text", + "content": " describes how likely the model predicts " + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\pmb{a}" + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "text", + "content": " and each " + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\pmb{b}" + }, + { + "bbox": [ + 304, + 629, + 548, + 715 + ], + "type": "text", + "content": " to be generated from the same caption, and the ground-truth distribution is the actual match" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "15890" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 61, + 70, + 274, + 125 + ], + "blocks": [ + { + "bbox": [ + 61, + 70, + 274, + 125 + ], + "lines": [ + { + "bbox": [ + 61, + 70, + 274, + 125 + ], + "spans": [ + { + "bbox": [ + 61, + 70, + 274, + 125 + ], + "type": "image", + "image_path": "dc99af57ce94112007c0043dbe70f56a359cc6068754a28f472dc85053281589.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 62, + 124, + 247, + 131 + ], + "lines": [ + { + "bbox": [ + 62, + 124, + 247, + 131 + ], + "spans": [ + { + "bbox": [ + 62, + 124, + 247, + 131 + ], + "type": "text", + "content": "A plate of paella, a mixed rice dish with chicken, beans, and seafood" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 61, + 138, + 274, + 193 + ], + "blocks": [ + { + "bbox": [ + 61, + 138, + 274, + 193 + ], + "lines": [ + { + "bbox": [ + 61, + 138, + 274, + 193 + ], + "spans": [ + { + "bbox": [ + 61, + 138, + 274, + 193 + ], + "type": "image", + "image_path": "9c549d9d6852c2bed63f35884b2498ecbe23a23b1be85f1137677ab6c2fb8d44.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 62, + 193, + 249, + 199 + ], + "lines": [ + { + "bbox": [ + 62, + 193, + 249, + 199 + ], + "spans": [ + { + "bbox": [ + 62, + 193, + 249, + 199 + ], + "type": "text", + "content": "An industrial power plant with its smokestacks belching black smoke." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 61, + 201, + 274, + 255 + ], + "blocks": [ + { + "bbox": [ + 61, + 201, + 274, + 255 + ], + "lines": [ + { + "bbox": [ + 61, + 201, + 274, + 255 + ], + "spans": [ + { + "bbox": [ + 61, + 201, + 274, + 255 + ], + "type": "image", + "image_path": "7183cd8ec8c687dba982a5f8c99be5008b3add07a27b232ead4282a53c4e14f9.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 62, + 255, + 253, + 269 + ], + "lines": [ + { + "bbox": [ + 62, + 255, + 253, + 269 + ], + "spans": [ + { + "bbox": [ + 62, + 255, + 253, + 269 + ], + "type": "text", + "content": "A fluffy, black and white junco bird perches on a snow-covered fence, overlooking a dark forest." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 47, + 274, + 287, + 306 + ], + "lines": [ + { + "bbox": [ + 47, + 274, + 287, + 306 + ], + "spans": [ + { + "bbox": [ + 47, + 274, + 287, + 306 + ], + "type": "text", + "content": "Figure 4. Random examples of synthetic captions and images generated in our SynCLR pipeline. Each caption comes with 4 images." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "spans": [ + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "text", + "content": "between " + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "inline_equation", + "content": "\\pmb{a}" + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "inline_equation", + "content": "\\pmb{b}" + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "inline_equation", + "content": "\\pmb{a}" + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "text", + "content": " is allowed to match multiple " + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "inline_equation", + "content": "\\pmb{b}" + }, + { + "bbox": [ + 47, + 320, + 258, + 333 + ], + "type": "text", + "content": "):" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 111, + 338, + 287, + 369 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 111, + 338, + 287, + 369 + ], + "spans": [ + { + "bbox": [ + 111, + 338, + 287, + 369 + ], + "type": "interline_equation", + "content": "\\mathbf {q} _ {i} = \\frac {\\exp \\left(\\boldsymbol {a} \\cdot \\boldsymbol {b} _ {i} / \\tau\\right)}{\\sum_ {j = 1} ^ {K} \\exp \\left(\\boldsymbol {a} \\cdot \\boldsymbol {b} _ {j} / \\tau\\right)} \\tag {1}", + "image_path": "e318576116f5d14fb85e13a74108a882d9d80465b5749327c6e97682058479fb.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 123, + 370, + 287, + 399 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 123, + 370, + 287, + 399 + ], + "spans": [ + { + "bbox": [ + 123, + 370, + 287, + 399 + ], + "type": "interline_equation", + "content": "\\mathbf {p} _ {i} = \\frac {\\mathbb {1} _ {\\operatorname {m a t c h} \\left(\\boldsymbol {a} , \\boldsymbol {b} _ {i}\\right)}}{\\sum_ {j = 1} ^ {K} \\mathbb {1} _ {\\operatorname {m a t c h} \\left(\\boldsymbol {a} , \\boldsymbol {b} _ {j}\\right)}} \\tag {2}", + "image_path": "a71eb6addba44bdb80d42d4afe7efc8b5329d5909e0dce5d2d9895c34e1ddd8f.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "spans": [ + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\tau \\in \\mathcal{R}_{+}" + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "text", + "content": " is the scalar temperature, " + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\pmb{a}" + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "text", + "content": " and all " + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\pmb{b}" + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "text", + "content": " have been " + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\ell_{2}" + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "text", + "content": " normalized, and the indicator function " + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\mathbb{1}_{\\mathrm{match}(\\cdot ,\\cdot)}" + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "text", + "content": " indicates whether two samples are from the same caption. The contrastive loss for " + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\pmb{a}" + }, + { + "bbox": [ + 47, + 405, + 287, + 453 + ], + "type": "text", + "content": " is given as" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 94, + 460, + 287, + 493 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 94, + 460, + 287, + 493 + ], + "spans": [ + { + "bbox": [ + 94, + 460, + 287, + 493 + ], + "type": "interline_equation", + "content": "\\mathcal {L} (\\boldsymbol {a}) = H (\\boldsymbol {p}, \\boldsymbol {q}) = - \\sum_ {i = 1} ^ {K} \\mathbf {p} _ {i} \\log \\mathbf {q} _ {i} \\tag {3}", + "image_path": "0181ec253f36b888af31a77c3fe1d19cf3f590659149fa22ecf99f7b287be17f.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 498, + 287, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 287, + 594 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 287, + 594 + ], + "type": "text", + "content": "iBOT [98] is a masked image modeling objective, wherein a localized patch is masked, and the model is tasked with predicting the tokenized representation of said masked patch. It adapts the DINO [11] objective from the image level into the patch level. We follow [67] to replace the softmax-centering method with the iterative Sinkhorn-Knopp (SK) algorithm [19]. We run SK for 3 iterations to build the prediction target." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "type": "text", + "content": "Exponential Moving Average (EMA) is firstly introduced into self-supervised learning by MoCo [38]. We use EMA to encode crops as " + }, + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "type": "inline_equation", + "content": "\\mathbf{b}" + }, + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "type": "text", + "content": " and to produce the targets for iBOT loss. We update the EMA model as " + }, + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "type": "inline_equation", + "content": "\\theta_{ema} \\gets \\lambda \\theta_{ema} + (1 - \\lambda)\\theta" + }, + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "type": "text", + "content": ", following a cosine schedule for " + }, + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 46, + 594, + 288, + 689 + ], + "type": "text", + "content": " from 0.994 to 1 during training [34, 59]. We find the EMA module not only increases the final performance, but also improves the training stability for long training schedules." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 689, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 288, + 714 + ], + "type": "text", + "content": "Multi-crop strategy is introduced by [10] as a smart way to improve computation efficiency, and is adopted in this paper." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "text", + "content": "For these local crops, we only employ the contrastive loss, omitting the iBOT loss. Local crops are encoded only by the student network, and matched to global crops from the same caption encoded by the EMA model. Such reuse of global crops saves computation. For each image " + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "text", + "content": ", where we generate a single global crop " + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "inline_equation", + "content": "x^g" + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "text", + "content": " alongside " + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "text", + "content": " local crops " + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "inline_equation", + "content": "x^l" + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "text", + "content": ", the final loss can be expressed as follows:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 351, + 162, + 546, + 193 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 351, + 162, + 546, + 193 + ], + "spans": [ + { + "bbox": [ + 351, + 162, + 546, + 193 + ], + "type": "interline_equation", + "content": "\\mathcal {L} \\left(x ^ {g}\\right) + \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\mathcal {L} \\left(x _ {i} ^ {l}\\right) + \\mathcal {L} ^ {i B O T} \\left(x ^ {g}\\right) \\tag {4}", + "image_path": "ad1dc0bd08b9b8948bd50fc510b461562426105341e99ef0d14dbfe88eec2ccf.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 198, + 404, + 211 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 198, + 404, + 211 + ], + "spans": [ + { + "bbox": [ + 306, + 198, + 404, + 211 + ], + "type": "text", + "content": "3.4. Implementation" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 217, + 547, + 347 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 217, + 547, + 347 + ], + "spans": [ + { + "bbox": [ + 304, + 217, + 547, + 347 + ], + "type": "text", + "content": "Concept list. We concatenate class names from various datasets, including IN-1k [21], IN-21k (we keep the most frequent 13k classes), Aircraft [51], Cars [44], DTD [17], Flowers [55], Pets [60], Sun397 [88], Caltech-101 [30], Food101 [7], and Places-365 [96]. If the concept is a place (i.e. SUN397 and Places) or a texture (i.e. DTD), we only apply the " + }, + { + "bbox": [ + 304, + 217, + 547, + 347 + ], + "type": "inline_equation", + "content": "c \\rightarrow" + }, + { + "bbox": [ + 304, + 217, + 547, + 347 + ], + "type": "text", + "content": " caption template. For fine-grained classes such as pets or flowers, we employ GPT-4 to generate a consolidated list of probable backgrounds, rather than producing distinct lists for each specific class. We favor more frequent sampling from IN-1k, Food101, Cars, Aircraft, and Flowers." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 348, + 547, + 408 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 348, + 547, + 408 + ], + "spans": [ + { + "bbox": [ + 304, + 348, + 547, + 408 + ], + "type": "text", + "content": "Batches. For each training batch, we sample 2048 captions (except when noted), and use all of the 4 images generated by each caption. We generate 1 global and 4 local crops for each image. As a result, each batch contains 8192 global crops, which is similar with prior work [13, 14, 34, 81]." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 407, + 547, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 407, + 547, + 479 + ], + "spans": [ + { + "bbox": [ + 304, + 407, + 547, + 479 + ], + "type": "text", + "content": "Masking. For the iBOT loss, we randomly choose " + }, + { + "bbox": [ + 304, + 407, + 547, + 479 + ], + "type": "inline_equation", + "content": "50\\%" + }, + { + "bbox": [ + 304, + 407, + 547, + 479 + ], + "type": "text", + "content": " images inside a batch to mask, and randomly mask " + }, + { + "bbox": [ + 304, + 407, + 547, + 479 + ], + "type": "inline_equation", + "content": "50\\%" + }, + { + "bbox": [ + 304, + 407, + 547, + 479 + ], + "type": "text", + "content": " of the tokens in each chosen image. We use 65536 prototypes. While the target from the EMA model is ascertained using the SK algorithm, we apply softmax normalization to the output of the student model." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 479, + 547, + 587 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 479, + 547, + 587 + ], + "spans": [ + { + "bbox": [ + 304, + 479, + 547, + 587 + ], + "type": "text", + "content": "Projection heads. We follow the design in MoCo v3 [14] and DINO [11] for the contrastive and iBOT loss heads, respectively, ensuring consistency with established methods. Other hyper-parameters. We set the temperature in the contrastive loss to 0.08. For the temperature used in the iBOT loss, we linearly increase it from 0.04 to 0.07 over 4000 iterations, and keep it as 0.07 afterwards, as in DINO [11]. Additionally, the weight decay parameter is incrementally adjusted from 0.04 to 0.2, adhering to a cosine schedule." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 306, + 597, + 382, + 610 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 597, + 382, + 610 + ], + "spans": [ + { + "bbox": [ + 306, + 597, + 382, + 610 + ], + "type": "text", + "content": "4. Experiment" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 616, + 546, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 616, + 546, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 616, + 546, + 653 + ], + "type": "text", + "content": "We first perform an ablation study to evaluate the efficacy of various designs and modules within our pipeline. Then we proceed to scale up the volume of synthetic data." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 306, + 659, + 459, + 672 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 659, + 459, + 672 + ], + "spans": [ + { + "bbox": [ + 306, + 659, + 459, + 672 + ], + "type": "text", + "content": "4.1. Study different components" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 713 + ], + "type": "text", + "content": "We analyze each component of SynCLR, and ablate their effectiveness in two measurements: (1) linear probing performance on IN-1k; (2) average accuracy of linear transfer on" + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15891" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 73, + 60, + 261, + 155 + ], + "blocks": [ + { + "bbox": [ + 73, + 60, + 261, + 155 + ], + "lines": [ + { + "bbox": [ + 73, + 60, + 261, + 155 + ], + "spans": [ + { + "bbox": [ + 73, + 60, + 261, + 155 + ], + "type": "table", + "html": "
captionsStableRepSynCLR
INavg.INavg.
cc12m73.081.677.185.3
IN+h+Places75.480.078.783.0
IN+Places+LLM73.776.977.681.8
IN+OurBG+LLM75.378.578.281.9
our final config.75.885.778.888.1
", + "image_path": "6620bcbf13362b40399a4909011b5b3d32e0506477099ad68d39c46b1c083af4.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 102, + 215, + 231, + 251 + ], + "blocks": [ + { + "bbox": [ + 46, + 158, + 287, + 201 + ], + "lines": [ + { + "bbox": [ + 46, + 158, + 287, + 201 + ], + "spans": [ + { + "bbox": [ + 46, + 158, + 287, + 201 + ], + "type": "text", + "content": "Table 2. Comparison of different caption synthesis strategies. We report top-1 ImageNet linear evaluation accuracy and the average accuracy over 9 fine-grained datasets. Every item here includes 10M captions and 4 images per caption." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 102, + 215, + 231, + 251 + ], + "lines": [ + { + "bbox": [ + 102, + 215, + 231, + 251 + ], + "spans": [ + { + "bbox": [ + 102, + 215, + 231, + 251 + ], + "type": "table", + "html": "
CFG234
IN top-172.872.672.6
", + "image_path": "730d4ba3c1e8c9d69bbc3797e867aea64f6723f1b7e333458f3e97612bfa4b06.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 290, + 287, + 351 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 290, + 287, + 351 + ], + "spans": [ + { + "bbox": [ + 46, + 290, + 287, + 351 + ], + "type": "text", + "content": "fine-grained datasets Aircraft [51], Cars [44], DTD [17], Flowers [55], Pets [60], Sun397 [88], Caltech-101 [30], Food-101 [7], and Pascal VOC [25]. For analysis conducted in this subsection, we train ViT-B/16 [24] models for 85000 iterations, and use the c1s token as image representation." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "spans": [ + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "text", + "content": "Synthesize captions. Following [81], we use cc12m [12] real captions as our baseline, which has 10M sentences. To synthesize captions, we design the following variants: (a) " + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "inline_equation", + "content": "IN + h + \\text{Places}" + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "text", + "content": " randomly combines one IN class plus its hypernyms in WordNet graph, with one place class; (b) " + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "inline_equation", + "content": "IN + \\text{Places} + \\text{LLM}" + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "text", + "content": " uses the " + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "inline_equation", + "content": "c, bg \\rightarrow" + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "text", + "content": " caption in-context synthesis template with " + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "text", + "content": " from IN and " + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "inline_equation", + "content": "bg" + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "text", + "content": " from places; (c) " + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "inline_equation", + "content": "IN + ourBG + \\text{LLM}" + }, + { + "bbox": [ + 46, + 351, + 288, + 484 + ], + "type": "text", + "content": " uses the background classes output by GPT-4, instead of Places; (d) ours means our full configuration specified in Section 3.1. For each of the config, we generate 10M captions. If not enough, we do duplication." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 484, + 288, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 484, + 288, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 484, + 288, + 689 + ], + "type": "text", + "content": "Results are summarized in Table 2, where we train both StableRep and SynCLR to avoid biases favored by a single method. Compared to a real caption dataset cc12m, simply concatenating IN and Places class names improves the ImageNet linear accuracy but reduces the fine-grained classification performance. Interestingly, naively asking Llama to combine IN and Places classes into captions yields the worst performance. Replacing random background from places with GPT generated background improves the accuracy. This shows the importance of synthesizing captions that follow the distribution of real captions, which were used to train the text-to-image model. Finally, our full configuration achieves the best accuracy on both ImageNet and fine-grained classification. Another advantage of our synthesis method is its scalability – scale up to hundreds of millions of captions with little duplication. In contrast, if we concatenate IN classes with Places classes, there are at most 365k unique captions." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": "Synthesize images. There are two major parameters in this process: number of images per caption and classifier free" + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 320, + 60, + 533, + 137 + ], + "blocks": [ + { + "bbox": [ + 46, + 255, + 286, + 277 + ], + "lines": [ + { + "bbox": [ + 46, + 255, + 286, + 277 + ], + "spans": [ + { + "bbox": [ + 46, + 255, + 286, + 277 + ], + "type": "text", + "content": "Table 3. Classifier-free guidance scale (CFG). Contrastive loss prefers small CFG scale but is not very sensitive to it." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 320, + 60, + 533, + 137 + ], + "lines": [ + { + "bbox": [ + 320, + 60, + 533, + 137 + ], + "spans": [ + { + "bbox": [ + 320, + 60, + 533, + 137 + ], + "type": "table", + "html": "
methodEMAiBOTMCINavg.ADE20k
StableRep75.885.7-
✓76.786.748.0
✓✓77.687.150.5
✓✓78.687.849.5
SynCLR✓✓✓78.888.150.8
", + "image_path": "d655a86b77928bdc17af1622048f03b4ee1a91009e4c4a83fd0c9865dd47f7f6.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 352, + 196, + 501, + 258 + ], + "blocks": [ + { + "bbox": [ + 304, + 140, + 547, + 185 + ], + "lines": [ + { + "bbox": [ + 304, + 140, + 547, + 185 + ], + "spans": [ + { + "bbox": [ + 304, + 140, + 547, + 185 + ], + "type": "text", + "content": "Table 4. Important components for our model. ViT-B/16 models are trained for 85000 iterations. We study the modules that affect the ImageNet linear evaluation, the fine-grained classification (avg.), and ADE20k segmentation." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 352, + 196, + 501, + 258 + ], + "lines": [ + { + "bbox": [ + 352, + 196, + 501, + 258 + ], + "spans": [ + { + "bbox": [ + 352, + 196, + 501, + 258 + ], + "type": "table", + "html": "
methodINavg.
Supervised CE71.975.0
SimCLR63.667.9
SynCLR75.378.5
", + "image_path": "c229974171e682b19749c65f3f03d269bcc016a01b08e1763605d0f90fa4e524.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 266, + 547, + 321 + ], + "lines": [ + { + "bbox": [ + 304, + 266, + 547, + 321 + ], + "spans": [ + { + "bbox": [ + 304, + 266, + 547, + 321 + ], + "type": "text", + "content": "Table 5. Comparison of different learning objectives. These objectives assume different levels of classification granularity, as shown in Figure 2. Our modeling, i.e., defining classes as captions, outperforms the other two. To accommodate Supervised CE training, all items here used " + }, + { + "bbox": [ + 304, + 266, + 547, + 321 + ], + "type": "inline_equation", + "content": "IN + OurBG + LLM" + }, + { + "bbox": [ + 304, + 266, + 547, + 321 + ], + "type": "text", + "content": " entry in Table 2." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 331, + 547, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 331, + 547, + 415 + ], + "spans": [ + { + "bbox": [ + 304, + 331, + 547, + 415 + ], + "type": "text", + "content": "guidance scale. For the former, we find generating 4 images is almost able to reproduce StableRep [81]'s performance (10 images) when using cc12m captions (ours " + }, + { + "bbox": [ + 304, + 331, + 547, + 415 + ], + "type": "inline_equation", + "content": "73.0\\%" + }, + { + "bbox": [ + 304, + 331, + 547, + 415 + ], + "type": "text", + "content": " v.s. StableRep " + }, + { + "bbox": [ + 304, + 331, + 547, + 415 + ], + "type": "inline_equation", + "content": "73.5\\%" + }, + { + "bbox": [ + 304, + 331, + 547, + 415 + ], + "type": "text", + "content": " on ImageNet). Thus we stick to 4. For guidance scale, we briefly find the contrastive loss is not very sensitive to CFG in a pilot study, as shown in Table 3. Thus we stick to 2.5, similar as StableRep [81]." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "spans": [ + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "text", + "content": "Model components. We present the improvement of accuracy brought by different modules in Table 4. Compared to the baseline StableRep, adding a teacher EMA model improves the IN linear accuracy by " + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "inline_equation", + "content": "0.9\\%" + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "text", + "content": ". Further adding iBOT local objective or the multi-crop strategy increases the accuracy by " + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "inline_equation", + "content": "0.9\\%" + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "inline_equation", + "content": "1.9\\%" + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "text", + "content": ", respectively. Combining all of them results in our full SynCLR model, which achieves " + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "inline_equation", + "content": "78.8\\%" + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "text", + "content": " top-1 IN linear accuracy. The fine-grained classification performance follows a similar trend, and reaches " + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "inline_equation", + "content": "88.1\\%" + }, + { + "bbox": [ + 304, + 415, + 547, + 570 + ], + "type": "text", + "content": ". Besides, we test the transfer ability to semantic segmentation on ADE20k. The iBOT objective brings 1.0 more mIoU than multi-crop strategy, demonstrating the effectiveness of masked image modeling for dense prediction tasks." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": "Compare to SimCLR and supervised training. We compare the three different representation learning objectives shown in Figure 2, which classify images at different levels of granularity. Since supervised cross-entropy training requires a fixed set of balanced classes (indeed both fixed set and balance are limitations of such method), we use the " + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "inline_equation", + "content": "IN + ourBG + LLM" + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": " configuration where we have 1000 balanced classes (i.e., each class has 40k images). The supervised training recipe follows [76]. For a fair comparison with SimCLR, we remove all unmatched modules (i.e., EMA, iBOT, and MC) to make sure that the only difference between SimCLR and our SynCLR is the classification gran" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15892" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 69, + 59, + 525, + 223 + ], + "blocks": [ + { + "bbox": [ + 69, + 59, + 525, + 223 + ], + "lines": [ + { + "bbox": [ + 69, + 59, + 525, + 223 + ], + "spans": [ + { + "bbox": [ + 69, + 59, + 525, + 223 + ], + "type": "table", + "html": "
textimg#imgsImageNetAircraftCarsDTDFlowersPetsSUN397Caltech-101Food-101VOC2007Average
StableReprealsyn100MViT-B/1675.759.283.580.197.388.374.394.785.187.983.4
CLIPrealreal400MViT-B/1680.259.586.779.298.193.178.494.792.889.285.7
ViT-L/1483.969.490.982.199.295.181.896.595.289.688.9
OpenCLIPrealreal400MViT-B/1678.961.192.381.998.291.577.995.290.988.086.3
400MViT-L/1482.367.194.083.698.892.581.096.493.488.888.4
2BViT-L/1483.471.795.385.399.094.282.297.594.188.989.8
DINO v2*-real142MViT-B/14\\( 83.9^{\\dagger} \\)79.488.283.399.696.277.396.192.888.289.0
ViT-L/14\\( 85.7^{\\dagger} \\)81.590.184.099.796.678.797.594.388.390.1
SynCLRsynsyn600MViT-B/1680.781.793.879.999.193.676.295.391.689.489.0
ViT-L/1483.085.694.282.199.294.178.496.193.490.390.4
", + "image_path": "93725bd73b2a8e4e82558695fb4896873771a709d686802bb23447578541c29f.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 275, + 288, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 275, + 288, + 300 + ], + "spans": [ + { + "bbox": [ + 46, + 275, + 288, + 300 + ], + "type": "text", + "content": "ularity defined by the contrastive loss. For all of them, we do pre-training and then linear probing on the target dataset." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "spans": [ + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "text", + "content": "Table 5 presents the comparison. Our multi-positive objective, which defines images as the same class if they are generated by the same caption, achieves the best performance. It outperforms supervised cross-entropy training and SimCLR by " + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "inline_equation", + "content": "3.4\\%" + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "inline_equation", + "content": "11.7\\%" + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "text", + "content": " for top-1 accuracy on ImageNet linear evaluation, and by " + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "inline_equation", + "content": "3.5\\%" + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "inline_equation", + "content": "10.6\\%" + }, + { + "bbox": [ + 46, + 300, + 288, + 407 + ], + "type": "text", + "content": " on fine-grained classification tasks. Besides, our objective does not require balance between samples from a fixed set of classes, making it easier to scale up." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 417, + 119, + 430 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 417, + 119, + 430 + ], + "spans": [ + { + "bbox": [ + 47, + 417, + 119, + 430 + ], + "type": "text", + "content": "4.2. Scaling up" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 437, + 287, + 520 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 287, + 520 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 287, + 520 + ], + "type": "text", + "content": "After we have ablated different components, we scale up our experiments. Specifically, we synthesize a dataset of 150M captions, called SynCaps-150M, from which we generate 600M images. We train both ViT-B/16 and ViT-L/14 (no SwiGLU [73] or LayerScale [82]), and extend the training schedules to 500k steps with a batch size of 8192 captions. We use 224x224 resolution for all pre-training tasks." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 45, + 521, + 288, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 521, + 288, + 593 + ], + "spans": [ + { + "bbox": [ + 45, + 521, + 288, + 593 + ], + "type": "text", + "content": "We compare SynCLR with OpenAI's CLIP [62], OpenCLIP [16], and DINO v2 [59], which represent learning from data. We note that ViT-B/14 and ViT-L/14 from DINO v2 are distilled from a ViT-g [93] model, which makes DINO v2 advantageous in our comparison. We also include StableRep [81], which uses the hybrid paradigm." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": "ImageNet linear evaluation. For fair comparison,CLS token from the last block is used as representation across all models (whereas in DINO v2, results are from concatenating multiple layers). As shown in Table 6, SynCLR achieves " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "80.7\\%" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " with ViT-B and " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "83.0\\%" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " with ViT-L. This is similar as CLIP, but still lags behind DINO v2 by " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "3.2\\%" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "2.7\\%" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": ", respectively, partially because of the extra distillation in DINO v2. We note SynCLR has already outperformed other self-supervised methods pre-trained directly on ImageNet-1k (e.g., DINO achieves " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "78.2\\%" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " with ViT-B/16 and iBOT" + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 308, + 273, + 545, + 402 + ], + "blocks": [ + { + "bbox": [ + 46, + 231, + 545, + 265 + ], + "lines": [ + { + "bbox": [ + 46, + 231, + 545, + 265 + ], + "spans": [ + { + "bbox": [ + 46, + 231, + 545, + 265 + ], + "type": "text", + "content": "Table 6. Comparison on ImageNet linear evaluation and fine-grained classifier. SynCLR achieves comparable results with OpenAI's CLIP and DINO v2 models, despite only using synthetic data. *DINO v2 modes are distilled from a ViT-g model, thus advantageous in this comparison. † we rerun only using c1s token instead of concatenating multiple layers presented in the original DINO v2 paper [59]." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 308, + 273, + 545, + 402 + ], + "lines": [ + { + "bbox": [ + 308, + 273, + 545, + 402 + ], + "spans": [ + { + "bbox": [ + 308, + 273, + 545, + 402 + ], + "type": "table", + "html": "
methodpre-train datadistillViT-BViT-L
StableRephybrid, 100M49.4-
MoCo v3real, IN1K-1M47.349.1
BEiTreal, IN1K-1M+DALLE47.153.3
MAEreal, IN1K-1M48.153.6
iBOTreal, IN1K-1M50.0-
CLIPreal, WIT-400M52.6-
BEiT v2real, WIT-400M, IN1K✓53.156.7
DINO v2real, LVD-142M✓54.4†57.5†
SynCLRsynthetic, 600M54.357.7†
", + "image_path": "2fcb919b1ea59aad5eaa27ec7353c3658657c25346997944144455bcda1e74f4.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 410, + 547, + 443 + ], + "lines": [ + { + "bbox": [ + 305, + 410, + 547, + 443 + ], + "spans": [ + { + "bbox": [ + 305, + 410, + 547, + 443 + ], + "type": "text", + "content": "Table 7. ADE20K semantic segmentation (mIoU) using UperNet, with single scale at 512x512 resolution. " + }, + { + "bbox": [ + 305, + 410, + 547, + 443 + ], + "type": "inline_equation", + "content": "{}^{ \\dagger }" + }, + { + "bbox": [ + 305, + 410, + 547, + 443 + ], + "type": "text", + "content": " use patch size of " + }, + { + "bbox": [ + 305, + 410, + 547, + 443 + ], + "type": "inline_equation", + "content": "{14}\\mathrm{x}{14}" + }, + { + "bbox": [ + 305, + 410, + 547, + 443 + ], + "type": "text", + "content": " , thus adapt to 518x518 resolution." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 306, + 449, + 432, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 449, + 432, + 460 + ], + "spans": [ + { + "bbox": [ + 306, + 449, + 432, + 460 + ], + "type": "text", + "content": "reaches " + }, + { + "bbox": [ + 306, + 449, + 432, + 460 + ], + "type": "inline_equation", + "content": "81.0\\%" + }, + { + "bbox": [ + 306, + 449, + 432, + 460 + ], + "type": "text", + "content": " with ViT-L/16)." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "text", + "content": "Fine-grained classification. On the nine fine-grained datasets we have evaluated in Table 6, SynCLR achieves very similar average accuracy as DINO v2, e.g., " + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "inline_equation", + "content": "89.0\\%" + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "text", + "content": " vs. " + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "inline_equation", + "content": "89.0\\%" + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "text", + "content": " for ViT-B, and " + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "inline_equation", + "content": "90.1\\%" + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "text", + "content": " vs " + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "inline_equation", + "content": "90.4\\%" + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "text", + "content": " for ViT-L. Both SynCLR and DINO v2 have curated the pre-training data to include the distribution for these datasets (but in different ways and portions), and end up with similar performance. Interestingly, SynCLR outperforms others on Aircraft and Cars, possibly because we favor more frequent sampling towards them. This can be an advantage for synthetic data when we know what downstream tasks to solve. Besides, SynCLR outperforms CLIP and StableRep by " + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "inline_equation", + "content": "3.3\\%" + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "text", + "content": " and by " + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "inline_equation", + "content": "5.6\\%" + }, + { + "bbox": [ + 304, + 461, + 547, + 616 + ], + "type": "text", + "content": " for ViT-B, respectively." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "text", + "content": "Semantic segmentation. To evaluate the pixel-level understanding ability of SynCLR, we fine-tune the pre-trained models on ADE20k [97], following the setup in [5, 39]. UperNet [89] is used as the task layer, and we evaluate with a single-scale, i.e. " + }, + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "text", + "content": ". Besides CLIP and DINO v2, we also compare to self-supervised methods pre-trained on ImageNet, as well as BEiT v2 [61], which distills from CLIP. Table 7 shows that our SynCLR outperforms self-supervised" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15893" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 65, + 72, + 214, + 235 + ], + "blocks": [ + { + "bbox": [ + 65, + 72, + 214, + 235 + ], + "lines": [ + { + "bbox": [ + 65, + 72, + 214, + 235 + ], + "spans": [ + { + "bbox": [ + 65, + 72, + 214, + 235 + ], + "type": "image", + "image_path": "1ecdab7690d8f4a818dfb9f95dd53fe7776b7e644e3f37a1b082ce935ce9199b.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 242, + 547, + 288 + ], + "lines": [ + { + "bbox": [ + 46, + 242, + 547, + 288 + ], + "spans": [ + { + "bbox": [ + 46, + 242, + 547, + 288 + ], + "type": "text", + "content": "Figure 5. PCA visualization. Follow DINO v2 [59], we compute a PCA between the image patches from the same set and colorize by their first 3 components. Compared to DINO v2, SynCLR produces more accurate maps for cars (e.g., zoom-in to see the two bars on the roof of the first car, and the three side windows of the third car) and airplanes (e.g., the boundaries), while being slightly worse for dogs (e.g., heads). We use ViT-L/14 for both methods. Images are resized to " + }, + { + "bbox": [ + 46, + 242, + 547, + 288 + ], + "type": "inline_equation", + "content": "336 \\times 448" + }, + { + "bbox": [ + 46, + 242, + 547, + 288 + ], + "type": "text", + "content": " resolution, yielding " + }, + { + "bbox": [ + 46, + 242, + 547, + 288 + ], + "type": "inline_equation", + "content": "24 \\times 32" + }, + { + "bbox": [ + 46, + 242, + 547, + 288 + ], + "type": "text", + "content": " visualization grids." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 221, + 72, + 372, + 235 + ], + "blocks": [ + { + "bbox": [ + 221, + 72, + 372, + 235 + ], + "lines": [ + { + "bbox": [ + 221, + 72, + 372, + 235 + ], + "spans": [ + { + "bbox": [ + 221, + 72, + 372, + 235 + ], + "type": "image", + "image_path": "74a4c6d2efba77a5dd546920a00901c13bd84234012634666c185976f07f49e4.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 380, + 72, + 528, + 235 + ], + "blocks": [ + { + "bbox": [ + 380, + 72, + 528, + 235 + ], + "lines": [ + { + "bbox": [ + 380, + 72, + 528, + 235 + ], + "spans": [ + { + "bbox": [ + 380, + 72, + 528, + 235 + ], + "type": "image", + "image_path": "70ce50aa55f598f936bb951b4bbfe06e68d455294d9887f86a91e470f6596350.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 299, + 288, + 382 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 299, + 288, + 382 + ], + "spans": [ + { + "bbox": [ + 46, + 299, + 288, + 382 + ], + "type": "text", + "content": "methods trained on IN-1k by a clear marge, e.g., 4.3 higher mIoU than iBOT. Despite not involving a high resolution pretraining period like DINO v2 (e.g., 518x518), SynCLR performs similarly with DINO v2 (0.1 lower for ViT-B possibly because DINO v2 uses a smaller patch size of 14x14, but 0.2 higher for ViT-L). This suggests SynCLR pre-training is suitable for dense prediction tasks." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 383, + 288, + 538 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 383, + 288, + 538 + ], + "spans": [ + { + "bbox": [ + 46, + 383, + 288, + 538 + ], + "type": "text", + "content": "ImageNet fine-tuning. We evaluate the fine-tuning transfer ability of SynCLR on ImageNet. Our SynCLR achieves " + }, + { + "bbox": [ + 46, + 383, + 288, + 538 + ], + "type": "inline_equation", + "content": "87.9\\%" + }, + { + "bbox": [ + 46, + 383, + 288, + 538 + ], + "type": "text", + "content": " top-1 accuracy with ViT-L, outperforming models trained on ImageNet images or large scale image datasets. Specifically, SynCLR outperforms OpenCLIP ViT-L (87.1% top-1) trained on Laion-2B, which is the dataset Stable Diffusion (the text2image model we used) is trained on. This contrasts with [26, 69], which shows that directly training a classifier on synthetic images yields bad classification accuracy. Our finding suggests synthetic images are good for training representations, which later can be easily adapted to a downstream task with limited amount of real data. Detailed comparisons are provided in Appendix C." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 538, + 287, + 646 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 538, + 287, + 646 + ], + "spans": [ + { + "bbox": [ + 46, + 538, + 287, + 646 + ], + "type": "text", + "content": "PCA visualization. Following the method used in DINO v2 [59], we present visualizations derived from the Principal Component Analysis (PCA) conducted on patch features extracted using our model SynCLR. As depicted in Figure 5, a comparative analysis is conducted between SynCLR and DINO v2, both utilizing the ViT-L/14 architecture. The results demonstrate that SynCLR effectively accentuates the features of cars and planes, while efficiently minimizing background clutter." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 657, + 204, + 670 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 657, + 204, + 670 + ], + "spans": [ + { + "bbox": [ + 47, + 657, + 204, + 670 + ], + "type": "text", + "content": "5. Discussions and Conclusion" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 677, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 289, + 713 + ], + "type": "text", + "content": "Why learn from generative models? One compelling reason is that a generative model can act like hundreds of datasets simultaneously. Traditionally, researchers have to" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 299, + 547, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 299, + 547, + 467 + ], + "spans": [ + { + "bbox": [ + 304, + 299, + 547, + 467 + ], + "type": "text", + "content": "spend separate effort collecting datasets for different image categories, e.g., cars, flowers, cats, dogs, and so on. DINO v2 [59] achieves robust representations by curating and amalgamating numerous such datasets. Such a process introduces complexities such as clustering and search challenges. In contrast, advanced text-to-image generative models like Stable Diffusion [63] or Imagen [68] have the capability to generate many diverse datasets. These models provide the flexibility to produce an infinite number of samples (albeit finite diversity) and control the generation process through textual input. Thus, generative models offer a convenient and effective method for curating training data. In our study, we harness this advantage to synthesize images encompassing a broad spectrum of visual concepts." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 472, + 547, + 650 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 472, + 547, + 650 + ], + "spans": [ + { + "bbox": [ + 304, + 472, + 547, + 650 + ], + "type": "text", + "content": "What can be further improved? Enhanced caption sets can be achieved through various methods, such as enriching the set of in-context examples, optimizing the sampling ratios among different concepts, and utilizing more advanced LLMs. In terms of the learning process, one approach is to distill knowledge from a larger model, and incorporate an additional high-resolution training phase (as discussed in [59]) or an intermediate IN-21k fine-tuning stage (as per [5, 61]). Regarding architectural improvements, the integration of SwiGLU and LayerScale, coupled with superior model initialization strategies (referenced in [28]), can be beneficial. However, due to limited resources and the scope of this paper not being focused on achieving the highest possible metrics, we propose these areas for further exploration in future research endeavors." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 651, + 547, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 651, + 547, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 651, + 547, + 712 + ], + "type": "text", + "content": "In summary, this paper studies a new paradigm for visual representation learning – learning from generative models. Without using any real data, SynCLR learns visual representations that are comparable with those achieved by state of the art general-purpose visual representation learners." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15894" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "text", + "content": "[1] Hassan Abu Alhajja, Siva Karthik Mustikovela, Lars Mescheder, Andreas Geiger, and Carsten Rother. 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Training on thin air: Improve image classification with generated data. arXiv preprint arXiv:2305.15316, 2023. 3" + } + ] + } + ], + "index": 2 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "text", + "content": "15898" + } + ] + } + ], + "index": 4 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 11 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning Visual Prompt for Gait Recognition/250e53d0-2beb-4a17-986d-3fa0bac7cb32_content_list.json b/2024/Learning Visual Prompt for Gait Recognition/250e53d0-2beb-4a17-986d-3fa0bac7cb32_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..b6db7626d0e7dea96657f1310a2962455fa3dc8b --- /dev/null +++ b/2024/Learning Visual Prompt for Gait Recognition/250e53d0-2beb-4a17-986d-3fa0bac7cb32_content_list.json @@ -0,0 +1,1505 @@ +[ + { + "type": "text", + "text": "Learning Visual Prompt for Gait Recognition", + "text_level": 1, + "bbox": [ + 254, + 130, + 715, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Kang Ma $^{1}$ , Ying Fu $^{1*}$ , Chunshui Cao $^{2}$ , Saihui Hou $^{2,3}$ , Yongzhen Huang $^{2,3}$ , Dezhi Zheng $^{1*}$ $^{1}$ Beijing Institute of Technology, $^{2}$ WATRIX.AI, $^{3}$ Beijing Normal University", + "bbox": [ + 135, + 179, + 836, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "kangx.ma@gmail.com, fuying@bit.edu.cn, chunshui.cao@watrix.ai, housaihui@bnu.edu.cn, huangyongzhen@bnu.edu.cn, zhengdezhi@bit.edu.cn", + "bbox": [ + 107, + 219, + 849, + 251 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 286, + 313, + 301 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Gait, a prevalent and complex form of human motion, plays a significant role in the field of long-range pedestrian retrieval due to the unique characteristics inherent in individual motion patterns. However, gait recognition in real-world scenarios is challenging due to the limitations of capturing comprehensive cross-viewing and cross-clothing data. Additionally, distractors such as occlusions, directional changes, and lingering movements further complicate the problem. The widespread application of deep learning techniques has led to the development of various potential gait recognition methods. However, these methods utilize convolutional networks to extract shared information across different views and attire conditions. Once trained, the parameters and non-linear function become constrained to fixed patterns, limiting their adaptability to various distractors in real-world scenarios. In this paper, we present a unified gait recognition framework to extract global motion patterns and develop a novel dynamic transformer to generate representative gait features. Specifically, we develop a trainable part-based prompt pool with numerous key-value pairs that can dynamically select prompt templates to incorporate into the gait sequence, thereby providing task-relevant shared knowledge information. Furthermore, we specifically design dynamic attention to extract robust motion patterns and address the length generalization issue. Extensive experiments on four widely recognized gait datasets, i.e., Gait3D, GREW, OUMVLP, and CASIA-B, reveal that the proposed method yields substantial improvements compared to current state-of-the-art approaches.", + "bbox": [ + 76, + 318, + 473, + 758 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 787, + 209, + 803 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Gait, as a distinct and intricate form of movement [4, 43], holds significant implications for long-distance recognition [36, 49, 60] owing to its remarkable uniqueness. However, gait recognition suffers from various complicating factors", + "bbox": [ + 75, + 813, + 468, + 875 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c4148697f59420b32b0268a2061f733ca61e398b69eb27a64c4a934cd2254fc2.jpg", + "image_caption": [ + "Figure 1. Performance comparison of prevailing methods and the proposed method in both real-world and laboratory scenarios." + ], + "image_footnote": [], + "bbox": [ + 506, + 287, + 890, + 579 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "in real-world scenarios. Silhouette data from the same individual can exhibit significant variation depending on viewing angles and clothing conditions [44, 58], resulting in more intra-class variation than inter-class variation. In addition, potential obstructions from crowds and actions of the observed subjects [61, 63], such as turning, lingering, or stopping, may manifest within a single gait sequence. Despite the ability of human visual perception to seamlessly establish correspondences between occlusions, viewpoint changes, and object transformations, it still poses a formidable challenge for the gait recognition network.", + "bbox": [ + 496, + 638, + 893, + 806 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Learning robust motion patterns from multiple variations all at once is not a trivial task. With the widespread application of deep learning, some promising methods [7, 14, 22, 33, 35] have emerged. However, these methods preserve shared information across different viewpoints and attire conditions while discarding task-relevant knowledge", + "bbox": [ + 496, + 810, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding Authors", + "bbox": [ + 94, + 886, + 228, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "593", + "bbox": [ + 485, + 945, + 511, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "relevant to particular conditions. Intuitively, the knowledge is crucial for the gait network to learn valuable invariances. Thus, we aim to reveal it from the following aspects:", + "bbox": [ + 76, + 90, + 468, + 136 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "(i) Prompt Templates. A widely acknowledged assumption [7, 35, 54] regarding gait is that individuals maintain consistent motion patterns regardless of external factors. Central to all of these capabilities is the ability to establish associations despite occlusions, viewpoint changes, and varying object appearances. Indeed, in controlled laboratory settings marked by abundant data and well-managed conditions, stable associations tend to form readily. Conversely, addressing scenarios in the wild, constrained by limited data and influenced by obstructions and crowded environments, significantly increases the complexity of establishing stable associations. Consequently, a simple and effective approach is to provide task-relevant knowledge using a learnable prompt pool, which is expected to adaptively select prompt templates based on sequence attributes to establish stable associations under various disturbances.", + "bbox": [ + 75, + 137, + 470, + 378 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "(ii) Length Generalization. Similar to natural language processing (NLP) tasks [47], gait also faces the problem of length generalization [17, 42, 55]. In particular, the majority of the most promising gait recognition methods involve training by randomly selecting a subset of the sequence and testing by extracting features from the entire sequence. Nevertheless, these methods frequently neglect the challenges presented by the longer sequence. To this end, we implement a dynamic context window mask for gait, enabling the network to focus its attention on the features within the specified window. Furthermore, we propose to establish a correlation between the localized window and the prompt templates, with the aim of emphasizing the significance of distinctive gait features within the sequence.", + "bbox": [ + 75, + 380, + 468, + 592 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Based on the above analysis, we present a comprehensive Visual Prompt Network (VPNet) for gait recognition. VPNet leverages prompt templates to augment the task-relevant information associated with the gait feature. Dynamic attention is employed to establish connections between prompt templates and local window features, enabling the network to capture crucial invariant gait features. As illustrated in Fig. 2, VPNet initially extracts features from the sampled sequence using a backbone network. These features are then compared with a trainable part-based prompt pool, with prompt templates dynamically selected and integrated into the gait sequence. The merged features are further input into the dynamic transformer to enhance the learning of global motion patterns. VPNet exhibits superior performance, especially in realistic scenarios, compared to state-of-the-art (SOTA) methods on publicly available datasets as shown in Fig. 1. A brief overview of our main contributions can be summarized as follows:", + "bbox": [ + 75, + 593, + 468, + 864 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "- We introduce an innovative visual prompt that integrates key-value pairs with gait features, encoding factors such", + "bbox": [ + 76, + 869, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "as viewpoint, attire, occlusion, etc. These prompt templates provide task-related information to the network, facilitating the extraction of representative gait features.", + "bbox": [ + 511, + 90, + 890, + 136 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We design an efficient dynamic transformer with a context window mask structure to correlate prompt templates with local motion patterns, addressing the length generalization problem for gait recognition.", + "- We present a unified framework that yields competitive results on publicly accessible datasets, namely Gait3D [61], GREW [63], OUMVLP [44], and CASIA-B [58]. In addition, a series of rigorous ablation experiments further validate the effectiveness of our approach." + ], + "bbox": [ + 500, + 137, + 890, + 272 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Relate Work", + "text_level": 1, + "bbox": [ + 500, + 284, + 630, + 300 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this section, we present a review of the most relevant studies on gait recognition and prompt engineering.", + "bbox": [ + 500, + 310, + 890, + 340 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Gait Recognition", + "text_level": 1, + "bbox": [ + 500, + 348, + 666, + 364 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Gait recognition approaches can be broadly classified into two categories based on their modeling methodology, i.e., model-based methods and appearance-based methods.", + "bbox": [ + 498, + 372, + 890, + 416 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Model-based method. Model-based approaches [2, 48, 59] aim to capture the inherent biomechanical characteristics of pedestrians. Early approaches [3, 28, 56] focused on distinguishing identities by estimating pedestrian motion parameters. However, such methods were constrained by predefined empirical points and yielded limited recognition accuracy. With the rapid advancement of deep learning, researchers have shifted their focus to extracting training data using pose estimation or Skinned Multi-Person Linear (SMPL) models. Subsequently, a well-designed network [21, 29, 30, 45, 46] is employed to further learn the gait features based on joint-based datasets. Despite substantial advancements, the efficacy of model-based methods remains constrained by the empirical design of predefined points and the estimation of results from low-quality images.", + "bbox": [ + 498, + 417, + 892, + 643 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Appearance-based method. Appearance-based methods aim to learn gait features directly from silhouette data. Previous methods [18, 37, 54] have employed an efficient approach by directly applying weighted averaging to the sequence, i.e., Gait Energy Image (GEI). These methods have achieved significant advancements across various viewpoints and clothing conditions. However, the weighted averaging of video sequence data inevitably leads to the loss of substantial motion details. To this end, current research [22, 23, 26, 32] emphasizes the utilization of video input to learn gait features in order to address this limitation. Some of the 2D convolution-based methods [7, 14] independently extract local spatial features from each frame and subsequently utilize set-based pooling techniques, i.e., MaxPooling and MeanPooling, to directly extract global temporal features from the variable-length sequence. These methods have yielded impressive experimental results, significantly", + "bbox": [ + 498, + 643, + 892, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "594", + "bbox": [ + 485, + 945, + 509, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/4d6b06ac783d6230c2558fcd88e7ae5899e462a6f46d0da2e44423c9e8fead25.jpg", + "image_caption": [ + "Figure 2. Overview of the proposed Visual Prompt Network (VPNet), where \"HP\" denotes the Horizontal Pooling. (a) VPNet incorporates the FTS module into the backbone based on ResNet, focusing on the extraction of global motion patterns without any extra parameters. (b) VPNet utilizes a trainable prompt pool comprising numerous key-value pairs, dynamically selecting prompt templates and integrating them into gait features to provide task-relevant knowledge. (c) Three different loss functions are combined for supervised network training." + ], + "image_footnote": [], + "bbox": [ + 81, + 95, + 885, + 286 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "advancing the field of gait recognition. However, gait represents a coordinated whole-body motion process, and processing the features of each frame individually disregards the preservation of robust local motion patterns, which are essential for accurate gait information. Consequently, some 3D convolution-based methods [6, 12, 33, 35, 36] proposed to local spatio-temporal features from adjacent frame images using a shared 3D convolution kernel, while further modeling the unfixed length sequence to obtain robust global features. The approach presented in this paper falls within the category of appearance-based methods. In contrast to previous methods, we aim to explore further improvements within the deep network structure.", + "bbox": [ + 75, + 382, + 472, + 580 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Prompt Engineering", + "text_level": 1, + "bbox": [ + 76, + 589, + 272, + 606 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Prompt Engineering [5, 9, 40] is a methodology that involves the incorporation of additional information as a condition in the inference process using a model. It has gained considerable popularity [16, 19, 41] in the field of natural language processing (NLP) due to its ability to integrate task-specific cues for each individual task. In recent years, there has been a notable surge in prompt-based research [31, 38, 57, 62] within the field of computer vision. It integrates visual and linguistic tasks, using NLP to reference or define visual concepts. To address inherent disparities in information densities between visual and NLP tasks, researchers have developed methodologies [1, 24, 27] that involve pre-filling model inputs with adaptive parameters. These parameters, functioning as prompts, can be finetuned through gradient-based optimization, thereby facilitating their contribution to visual tasks. Specifically, VPT [27] and VP [1] load a set of trainable prompts into the model inputs while maintaining the architectural integrity of the core network. This strategic implementation consis", + "bbox": [ + 75, + 613, + 472, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "tently yields noteworthy performance improvements across a range of downstream tasks. In contrast, DAM-VP [24] adopts a divide-and-conquer scheme, segregating datasets associated with downstream tasks into smaller, homogeneous subsets. Each subset is endowed with its distinct cue, and subsequently, optimization is carried out independently for each subset. We extend the concept of prompt learning from prior research [52, 53], utilizing it to provide task-related information and extract robust motion patterns.", + "bbox": [ + 496, + 382, + 893, + 518 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Methodology", + "text_level": 1, + "bbox": [ + 498, + 531, + 635, + 549 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we present the overall architecture of the proposed Visual Prompt Network (VPNet) for gait and provide an in-depth explanation of the motivation in Sec. 3.1. We then provide a comprehensive elucidation of the backbone architecture in Sec. 3.2. Finally, we present the specific structure of the dynamic transformer in Sec. 3.3.", + "bbox": [ + 496, + 556, + 893, + 647 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Preliminary and Motivation", + "text_level": 1, + "bbox": [ + 498, + 656, + 751, + 672 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "A vanilla vision gait recognition framework typically comprises two essential components: the backbone $\\mathcal{B}$ and the head $\\mathcal{H}$ . Formally, given a gait silhouette sequence $X \\in \\mathbb{R}^{T \\times H \\times W}$ , where $H$ , $W$ , and $T$ represent the height, width, and number of frames, respectively. Firstly, the gait sequence is fed into the backbone to extract the local motion patterns, followed by its passage through the head to derive the global motion patterns. The extraction of gait features can be briefly represented as", + "bbox": [ + 496, + 679, + 893, + 816 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {F} = \\mathcal {H} (\\mathcal {B} (\\boldsymbol {X})), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 642, + 827, + 890, + 843 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\pmb{F} \\in \\mathbb{R}^{P \\times C}$ denotes the output features, $P$ is the number of horizontal slices, and $C$ is the feature dimension. Most of the existing research [8, 15, 33] places a significant", + "bbox": [ + 496, + 854, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "595", + "bbox": [ + 485, + 945, + 509, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "focus on improving the efficiency of the backbone component for extracting complex spatio-temporal features. Despite their progress, these approaches struggle to address the challenges of gait recognition in real-world scenarios. To this end, as shown in Fig. 2, we intend to introduce a comprehensive framework for gait recognition. In particular, it involves utilizing a common backbone to directly extract global motion patterns, designing a trainable prompt pool $\\mathcal{P}$ that adaptively selects task-relevant templates to concatenate with the original gait features, and employing dynamic attention to learn representative gait features, i.e.,", + "bbox": [ + 75, + 90, + 472, + 257 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {F} = \\mathcal {H} (\\text {c o n c a t} [ \\overbrace {\\mathcal {P} (\\boldsymbol {B} (\\boldsymbol {X}))} ^ {\\text {p r o m p t t e m p l a t e s}}, \\boldsymbol {B} (\\boldsymbol {X}) ]), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 148, + 265, + 468, + 301 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where concat represents the concatenation along the temporal dimension. The prompt templates, functioning as trainable embeddings, essentially encode the gait task. These templates include various aspects such as viewpoint, attire, carrying conditions, occlusion, and so on. They provide instructions to the model, specifying the task it executes.", + "bbox": [ + 75, + 309, + 468, + 398 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Backbone Architecture", + "text_level": 1, + "bbox": [ + 76, + 407, + 290, + 422 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We utilize the bottleneck structure in ResNet [20] to establish the backbone for gait recognition and introduce a plug-and-play gait temporal-shift operation [34, 36], coupled with a 3D convolutional network, as the foundational motion pattern extraction element within the bottleneck. By modifying the depth of the backbone network, we sequentially construct three models with distinct parameters in Sec. 4.1, namely VPNet-T, VPNet-M, and VPNet-L.", + "bbox": [ + 75, + 431, + 468, + 551 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Temporal Shift Bottleneck. 3D convolution is commonly used in gait recognition tasks due to its proficiency in local spatio-temporal aggregation. However, its ability to be used in real-world scenarios with numerous long silhouette sequences may pose certain challenges. Inspired by temporal shift operation [34, 36], as shown in Fig. 2, we design a novel Forward cycle Temporal Shift (FTS) module for the gait recognition network. Considering that forward walking is the predominant daily practice, whereas backward walking is less frequent, we employ a forward cyclic shifting approach along the temporal dimension instead of the zero padding technique used in TSCov [34]. Specifically, the FTS module divides the features $f \\in \\mathbb{R}^{C \\times T \\times H \\times W}$ of each pixel into four segments. It only cyclically shifts the first segment $f_{1} \\in \\mathbb{R}^{\\frac{C}{4} \\times T \\times H \\times W}$ along the temporal dimension. The extraction of motion patterns with a global receptive field can be achieved by incorporating the FTS module before 3D convolution, without the additional parameters.", + "bbox": [ + 75, + 551, + 470, + 824 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Dynamic Transformer", + "text_level": 1, + "bbox": [ + 76, + 832, + 284, + 848 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We present a dynamic transformer as an integral head layer $\\mathcal{H}$ in the network architecture. As shown in Fig. 2, it employs prompt engineering to provide task-specific shared", + "bbox": [ + 76, + 854, + 468, + 901 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/40066a8a0585d0dd869515c99687cf014b366d33acd4f0a9d9b10dd74b6a1faf.jpg", + "image_caption": [ + "Figure 3. The dynamic attention architecture. We utilize both prompt templates and gait sequence as inputs, employing the Context Window Mask to overcome the length generalization problem." + ], + "image_footnote": [], + "bbox": [ + 509, + 93, + 883, + 327 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "knowledge information for gait sequence and introduces a dynamic context window mask to effectively alleviate the problem of length generalization in real-world scenarios.", + "bbox": [ + 496, + 392, + 890, + 436 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Part-based Prompt Pool. Prompt learning has emerged as a methodology in NLP, and its application in gait recognition is motivated by three main considerations. Firstly, the adaptable visual prompt templates facilitate the integration of shared insights concerning the gait sequence. Secondly, the shared knowledge seamlessly incorporates into the gait sequence as a global feature through a flexible plug-and-play process. Finally, specific visual prompts are associated with salient features within the gait sequence. To address this, we introduce a part-based prompt pool with shared parameters, delivering task-specific information. The $j$ -th prompt pool can be defined as", + "bbox": [ + 496, + 436, + 892, + 619 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {P} _ {j} = \\left\\{\\boldsymbol {P} _ {j, 1}, \\boldsymbol {P} _ {j, 2}, \\dots , \\boldsymbol {P} _ {j, N} \\mid \\boldsymbol {P} _ {j, i} = \\left(k _ {j, i}, v _ {j, i}\\right) \\right\\}, \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 630, + 890, + 648 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\{\\mathcal{P}_j|j = 1,\\dots,P\\}$ is the $j$ -th prompt pool, $P$ denotes the number of horizontal slices, $P_{j,i}$ is the $i$ -th prompt token, $N$ denotes the number of trainable tokens in the prompt pool, $k_{j,i}\\in \\mathbb{R}^{C}$ and $v_{j,i}\\in \\mathbb{R}^C$ represent the key and value, respectively. We utilize key-value pairs as prompt tokens, matching the key with the input gait sequence. Following this alignment, the top- $k$ values are selected as prompt templates based on their similarity, and these chosen templates are smoothly integrated with the original sequence along the temporal dimension. Specifically, given a gait sequence feature $\\pmb {S}\\in \\mathbb{R}^{P\\times T\\times C}$ , for the $j$ -th part sequence feature $S_{j}\\in \\mathbb{R}^{T\\times C}$ , we first compute the average feature along the temporal dimension $\\bar{S}_j\\in \\mathbb{R}^C$ and then perform similarity matching with key embeddings in the prompt pool to select the top- $k$ values with the highest similarity. Denote $\\mathcal{R}$ as the function to lookup the top- $k$ keys in the ranked list, the", + "bbox": [ + 496, + 657, + 892, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "596", + "bbox": [ + 485, + 945, + 509, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "selection process for the key can be represented as", + "bbox": [ + 76, + 90, + 413, + 107 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {K} _ {j} = \\mathcal {R} \\left(\\frac {\\bar {S} _ {j} \\otimes k _ {j , i}}{\\| \\bar {S} _ {j} \\| \\otimes \\| k _ {j , i} \\|}\\right), \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 178, + 114, + 468, + 151 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{K}_j$ denotes a list of sets, generating a top- $k$ index that is linked to the query sequence, and $\\otimes$ represents matrix multiplication. The index value is employed to retrieve $k$ values, denoted as $V_j = \\{v_{j,\\kappa}|\\kappa \\in \\mathcal{K}_s\\}$ . Subsequently, we combine the indexed value $V_j$ with the feature $S_j$ , i.e.,", + "bbox": [ + 76, + 159, + 468, + 236 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nS _ {j} ^ {*} = \\operatorname {c o n c a t} \\left[ V _ {j}, S _ {j} \\right], \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 194, + 244, + 468, + 263 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where concat represents the concatenation of prompt templates and gait vectors along the temporal dimension. The resulting gait sequence, denoted as $S_{j}^{*} \\in \\mathbb{R}^{(T + k) \\times C}$ , integrates the prompt information, $(T + k)$ is the length of the gait sequence, and $k$ is empirically set to 6. Similar to the codebook collapse issue faced in VQ-VAE [10, 39], there exists a risk that all index $\\mathcal{K}_{j}$ map to a limited set of prompt templates. To address this, we implement a randomized restart strategy: the key vector in the prompt pool is randomly reset to one of the encoder outputs if its average utilization falls below a predefined threshold $(\\tau = 0.001)$ .", + "bbox": [ + 75, + 273, + 468, + 438 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Dynamic Attention. As shown in Fig. 3, we propose to extract global motion patterns for each body part based on prompt templates using the multi-head attention [11, 47]. Formally, the $j$ -th part sequence feature $S_{j}^{*}$ is mapped as query $\\pmb{Q}$ , key $\\pmb{K}$ and value $\\pmb{V}$ . The mapping process is as", + "bbox": [ + 75, + 439, + 468, + 515 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {Q} = S _ {j} ^ {*} W ^ {Q}, \\boldsymbol {K} = S _ {j} ^ {*} W ^ {K}, \\boldsymbol {V} = S _ {j} ^ {*} W ^ {V}, \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 132, + 537, + 468, + 560 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $W^{Q} \\in \\mathbb{R}^{C \\times h \\cdot C'}$ , $W^{K} \\in \\mathbb{R}^{C \\times h \\cdot C'}$ and $W^{V} \\in \\mathbb{R}^{C \\times h \\cdot C'}$ are learnable parameters, $h$ denotes the number of heads, and $C'$ represents the feature dimension of each head. Then, we employ $Q$ and $K$ to establish similarity relationships between each frame. It is notable that prompt templates can be associated with the features of each frame, thereby giving rise to the establishment of correlations, i.e.,", + "bbox": [ + 75, + 569, + 468, + 681 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {s i m} (\\boldsymbol {Q}, \\boldsymbol {K}) = \\boldsymbol {Q} \\boldsymbol {K} ^ {T}, \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 197, + 705, + 468, + 724 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\operatorname{sim}(Q, K)$ denotes the similarity matrix. Similar to natural language processing, gait recognition also faces the challenge of length generalization [17, 42, 55]. During training, a limited number of frames are randomly selected, but during testing, the longer sequence can distract the attention of the network. To effectively utilize the shared information provided by prompt templates in discerning distinctive global motion patterns within varying length sequences, we introduce a context window mask structure. This design dynamically establishes connections between prompt templates and gait sequence. As depicted in Fig. 3,", + "bbox": [ + 75, + 734, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "the architecture comprises a global branch on the left and a local branch on the right. The global branch allows each feature in the sequence to focus on establishing relationships with prompt templates, while the local branch fosters associations between each feature and other features within a defined local length range. Features outside of these two branches are excluded from the attention process, i.e.,", + "bbox": [ + 496, + 90, + 893, + 198 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {A t t} (\\boldsymbol {Q}, \\boldsymbol {K}, \\boldsymbol {V}) = \\operatorname {s o f t m a x} \\left(\\frac {\\operatorname {s i m} (\\boldsymbol {Q} , \\boldsymbol {K})}{\\sqrt {C ^ {\\prime}}} \\oplus \\mathcal {M}\\right) \\boldsymbol {V}, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 207, + 890, + 241 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\sqrt{C'}$ is the scaling factor, $\\mathcal{M}$ is the dynamic context window mask, and $\\oplus$ denotes element-wise sum operation.", + "bbox": [ + 498, + 251, + 892, + 284 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Learning Details", + "text_level": 1, + "bbox": [ + 500, + 292, + 666, + 308 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this work, we introduce three loss functions during training: triplet loss $\\mathcal{L}_{tp}$ , cross-entropy loss $\\mathcal{L}_{\\text{cet}}$ , and cosine embedding loss $\\mathcal{L}_{\\text{cem}}$ in Fig. 2. The $\\mathcal{L}_{tp}$ and $\\mathcal{L}_{\\text{cet}}$ serve to supervise part-based features individually, while the $\\mathcal{L}_{\\text{cem}}$ is applied to supervise the key embedding $(k_{j,i})$ within the prompt pool. $\\mathcal{L}_{\\text{cem}}$ requires that the selected key embedding be closely related to the query sequence $\\bar{S}_i$ , i.e.,", + "bbox": [ + 496, + 315, + 892, + 421 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {c e m} = \\underset {\\kappa \\in \\mathcal {K} _ {j}} {\\arg \\min } \\sum_ {i = 1} ^ {P} \\frac {- 1}{N _ {c e m}} \\left(\\frac {\\bar {S} _ {i} \\otimes k _ {j , \\kappa}}{\\| \\bar {S} _ {i} \\| \\otimes \\| k _ {j , \\kappa} \\|}\\right), \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 537, + 431, + 890, + 473 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $N_{cem}$ is a positive integer obtained by multiplying the batch size with the number of parts. In each training step, we adhere to the previously described strategy to select $\\kappa_{s}$ . The selected prompt templates are then merged with gait sequence vectors and fed into the dynamic transformer and BNNeck [15] to extract representative gait features. In general, the training process involves the use of a combined loss following the end-to-end method, i.e.,", + "bbox": [ + 496, + 482, + 892, + 603 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {s u m} = \\mathcal {L} _ {t p} + \\alpha \\mathcal {L} _ {c e m} + \\beta \\mathcal {L} _ {c e t}, \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 586, + 616, + 890, + 632 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\alpha$ and $\\beta$ are the hyper-parameters to balance the combined loss, $\\alpha$ is empirically set to 0.01 and $\\beta$ is set to 0.3.", + "bbox": [ + 498, + 642, + 890, + 672 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 686, + 633, + 704 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Datasets and Implementation Details", + "text_level": 1, + "bbox": [ + 500, + 710, + 818, + 727 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The gait datasets are divided into two subsets, i.e., in-the-wild and in-the-lab, distinguished by their respective collection environments in Tab. 1. A standardized preprocessing procedure [7] is uniformly applied to these datasets, and the data sizes used in this paper are all resized to $64 \\times 64$ .", + "bbox": [ + 496, + 734, + 890, + 809 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In-the-wild datasets. In-the-wild datasets introduce numerous unforeseen challenges, such as occlusions, clothing changes, viewpoint variations, and carrying conditions. Pedestrians may also pause or alter their walking patterns. These datasets are essential benchmarks for evaluating gait recognition methods under various external disturbances.", + "bbox": [ + 496, + 810, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "597", + "bbox": [ + 485, + 945, + 509, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/00b154eede76a5000473c8d9168827aec82d81d9c325334278ca30e102010d3a.jpg", + "table_caption": [ + "Table 1. Comparison of the specific values of the adopted datasets and corresponding parameters. Where “#Ide., #Seq., #Cam.” refer to numbers of identities, sequences, and cameras respectively. Additionally, “lr, dr, wd” denote learning rate, decay rate, and weight decay." + ], + "table_footnote": [], + "table_body": "
EnvironmentDatasetsTrainTest# Cam.Batch SizeOptimizerScheduler
# Ide.# Seq.# Ide.# Seq.step sizeepochs
In-the-wildGait3D [61]3,00018,9401,0006,369Diverse(32, 4)SGD lr = 0.12080
GREW [63]20,000102,8876,00024,000Diverse(64, 4)50200
In-the-labOUMVLP [44]5,153144,2845,154144,31214(32, 8)dr = 0.150200
CASIA-B [58]748,140505,50011(8, 16)wd = 0.00051040
", + "bbox": [ + 80, + 128, + 890, + 224 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/b6fb057be70ca0228df6bc2110d5607822e771086d52487d06029d7cc4d206d3.jpg", + "table_caption": [ + "Table 2. The detailed structure of the backbone in VPNet-L, where FTSCov denotes the combined of FTS module and convolution." + ], + "table_footnote": [], + "table_body": "
LayerOutput size
conv13 × 3 × 3, 64, stride(1,1,1)T × H × W
stage1[1 × 1 × 1, 64, (0,0,0)FTSCnv, 64, (1,1,1)1 × 1 × 1, 64, (0,0,0)] × 3T × H × W
stage2[1 × 1 × 1, 128, (0,0,0)FTSCnv, 128, (1,2,2)1 × 1 × 1, 128, (0,0,0)] × 4T × H/2 × W/2
stage3[1 × 1 × 1, 256, (0,0,0)FTSCnv, 256, (1,2,2)1 × 1 × 1, 256, (0,0,0)] × 6T × H/4 × W/4
stage4[1 × 1 × 1, 512, (0,0,0)FTSCnv, 512, (1,1,1)1 × 1 × 1, 512, (0,0,0)] × 3T × H/4 × W/4
", + "bbox": [ + 96, + 273, + 444, + 479 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We evaluate our method on the widely adopted Gait3D [61] and GREW [63] datasets in Tab. 1. To enhance the robustness of our model, we employ three data augmentation techniques: rotation, flipping, and perspective. We conduct training using VPNet-L on both Gait3D and GREW datasets and report rank-1 (\\%) and rank-5 (\\%) accuracy.", + "bbox": [ + 75, + 489, + 468, + 580 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In-the-lab datasets. In-the-lab datasets encompass various controllable conditions, including camera angles, predetermined walking routes, and dress variations. These datasets play a pivotal role in evaluating the ability of the gait network to handle cross-viewing and cross-dressing scenarios. We select the well-established OUMVLP [44] and CASIA-B [58] datasets to evaluate our approach in Tab. 1. Specifically, the OUMVLP provides an abundance of cross-viewing data, while the CASIA-B offers valuable cross-dressing data. Limited datasets, particularly those obtained from laboratory scenarios, may result in overfitting if the network parameters are excessively large. Therefore, we employ VPNet-M for training on OUMVLP and VPNet-T for training on CASIA-B. We present the rank-1 $(\\%)$ accuracy for all perspectives, excluding the identical-view cases.", + "bbox": [ + 73, + 580, + 468, + 808 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation Details. We establish the network parameters based on the dataset scale and complexity, as outlined in Tab. 1. The batch size is represented as $(S, T)$ , indicating that each mini-batch involves $S$ subjects. For each subject, $T$ sequences are sampled, and within each sequence, a random selection of 20 to 40 frames is chosen following", + "bbox": [ + 75, + 810, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/cccc4d4f625281589c9942ba48b6703f9aa6ef0cc74cde0650c39f33fcecdefa.jpg", + "table_caption": [ + "Table 3. The performance comparisons on Gait3D are reported with rank-1 and rank-5 accuracy (\\%)." + ], + "table_footnote": [], + "table_body": "
MethodsPublicationrank-1 (%)rank-5 (%)
GaitSet [7]AAAI 201936.758.3
GaitPart [14]CVPR 202028.247.6
GLN [22]ECCV 202031.452.9
GaitGL [33]ICCV 202129.748.5
CSTL [25]ICCV 202111.719.2
SMPLGait [61]CVPR 202246.364.5
GaitBase [15]CVPR 202365.6-
GaitGCI [13]CVPR 202350.368.5
DANet [35]CVPR 202348.069.7
HSTL [50]ICCV 202361.376.3
DyGait [51]ICCV 202366.380.8
VPNet-L-75.487.1
", + "bbox": [ + 519, + 273, + 870, + 460 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/a005ead5fa5a6e17661c480e766fbb38de1a65366e7df91594c8bb2dc8f07713.jpg", + "table_caption": [ + "Table 4. The performance comparisons on GREW are reported with rank-1 and rank-5 accuracy $(\\%)$ ." + ], + "table_footnote": [], + "table_body": "
MethodsPublicationrank-1 (%)rank-5 (%)
GaitSet[7]AAAI 201946.363.6
GaitPart [14]CVPR 202044.060.7
GaitGL [33]ICCV 202147.363.6
GaitGraph [45]ICIP 20211.33.5
GaitBase [15]CVPR 202360.1-
GaitGCI [13]CVPR 202368.580.8
HSTL [50]ICCV 202362.776.6
DyGait [51]ICCV 202371.483.2
VPNet-L-80.089.4
", + "bbox": [ + 519, + 513, + 864, + 662 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "DANet [35]. The optimization strategy employs Stochastic Gradient Descent (SGD) with an initial learning rate of 0.1, and each epoch consists of 1000 iterations. The learning rate undergoes periodic reduction based on the step size in Tab. 1, with a decay rate of 0.1. The entire model is built by sequentially stacking the temporal shift bottleneck in Sec. 3.2. We construct three models with distinct parameters, namely VPNet-T, VPNet-M, and VPNet-L, by modifying the depth of the backbone network. Specifically, VPNet-T is composed of three stages, each comprising a specific number of layers (1, 1, 1) and channels (64, 128, 256). In contrast, both VPNet-M and VPNet-L consist of four stages with channel configurations (64, 128, 256, 512) in Tab. 2. VPNet-M employs a layer stack of (2, 2, 2, 2), while VPNet-L utilizes a stack of layers (3, 4, 6, 3).", + "bbox": [ + 496, + 672, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "598", + "bbox": [ + 486, + 945, + 511, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/b6e85ec7a5b3859ee4d43c0c126d1f9c9e0818d3ea32b7dc19ade63e652f10cc.jpg", + "table_caption": [ + "Table 5. Rank-1 accuracy (%) on OUMVLP under all view angles, excluding the identical-views cases." + ], + "table_footnote": [], + "table_body": "
MethodProbe ViewMean
0°15°30°45°60°75°90°180°195°210°225°240°255°270°
GaitSet [7]79.587.989.990.288.188.787.881.786.789.089.387.287.886.287.1
GaitPart [14]82.688.990.891.089.789.989.585.288.190.090.189.089.188.288.7
GLN [22]83.890.091.091.290.390.089.485.389.190.590.689.689.388.589.2
GaitGL [33]84.990.291.191.591.190.890.388.588.690.390.489.689.588.889.7
GaitBase [15]--------------90.0
GaitGCI [13]91.292.392.692.793.092.392.192.091.891.992.692.391.491.692.1
DANet [35]87.791.391.691.891.791.491.190.490.390.790.990.590.389.990.7
HSTL [50]91.492.992.793.092.992.592.592.792.392.192.392.291.891.892.4
VPNet-M91.993.092.492.793.292.592.392.992.491.992.192.591.991.992.4
", + "bbox": [ + 81, + 116, + 893, + 286 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/a58d2a576564d05877386ece937647be0a874b2d68a235c3dc48cb570b268ea5.jpg", + "table_caption": [ + "Table 6. The performance comparisons on CASIA-B are reported with rank-1 accuracy $(\\%)$ , excluding the identical-view cases." + ], + "table_footnote": [], + "table_body": "
MethodsPublicationNMBGCLMean
GaitSet[7]AAAI 201995.087.270.484.2
GaitPart[14]CVPR 202096.291.578.788.8
GLN [22]ECCV 202096.994.077.589.5
MT3D [32]MM 202096.793.081.590.4
GaitGL [33]ICCV 202197.494.583.691.8
GaitBase [15]CVPR 202397.694.077.489.8
GaitGCI-T [13]CVPR 202397.995.086.493.1
DANet [35]CVPR 202398.095.989.994.6
HSTL [50]ICCV 202398.195.988.994.3
DyGait [51]ICCV 202398.496.287.894.1
VPNet-T-98.396.390.094.9
", + "bbox": [ + 81, + 340, + 465, + 522 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Results under in-the-wild Scenario", + "text_level": 1, + "bbox": [ + 76, + 536, + 379, + 550 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Gait3D. VPNet-L demonstrates superior performance in terms of rank-1 and rank-5 accuracy in Tab. 3, surpassing state-of-the-art methods. Notably, it exhibits a $9.1\\%$ improvement over DyGait [51], a silhouette-based approach, and a remarkable $29.1\\%$ improvement compared to SMPL-Gait [61], a multimodal method. These experimental results underscore the efficacy of our method in extracting robust features in the presence of diverse external disturbances.", + "bbox": [ + 75, + 561, + 468, + 683 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "GREW. VPNet-L achieves the advanced accuracy of rank-1 and rank-5 as shown in Tab. 4, outperforming GaitGCI [13] by $11.5\\%$ and GaitGraph [45] by $79.7\\%$ . These experimental results demonstrate that our method effectively handles various unexpected external factors in realistic scenes, yielding effective global motion patterns in gait sequences.", + "bbox": [ + 75, + 686, + 468, + 777 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Summary. We specifically design VPNet-L to tackle the intricacies of outdoor scenes, leading to state-of-the-art performance on real-world datasets. (1) Our method introduces a unified backbone architecture designed for the extraction of global motion patterns in real-world scenarios. (2) Prompt templates convey task-related knowledge, and a dynamic transformer is subsequently employed to effectively alleviate the problem of length generalization. (3) Ex", + "bbox": [ + 75, + 780, + 468, + 901 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "experimental results validate the effectiveness of the proposed framework in the wild datasets.", + "bbox": [ + 498, + 304, + 890, + 333 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Results under in-the-lab Scenario", + "text_level": 1, + "bbox": [ + 498, + 344, + 792, + 359 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "OUMVLP. The experimental results of VPNet-M in Tab. 5 exhibit superior performance compared to the majority of methods, underscoring its robustness and effectiveness. Notably, VPNet-M attains average accuracies on par with HSTL [50]. It is noteworthy that the accuracy of VPNet-M is further improved after excluding invalid probe sequences. CASIA-B. The experimental outcomes in Tab. 6 underscore the competitive performance of VPNet-T, surpassing other gait recognition methods. It is worth noting that, excluding the cases of identical views, VPNet-T achieved an average accuracy of over $90\\%$ in cross-viewing and cross-dressing. Summary. We customize VPNet-T and VPNet-M based on data size and complexity, achieving state-of-the-art performance on in-the-lab datasets. (1) Previously, different depth networks have been designed on unified architectures are common, such as ResNet-18 [20] and ResNet-50 [20]. Our proposed VPNet architecture fills a gap in the design of network architectures for gait recognition across diverse datasets. (2) In indoor scenarios, performance has reached its peak due to the utilization of continuously improving methods. Therefore, it is expected that gait recognition will increasingly concentrate on outdoor scenarios in the future.", + "bbox": [ + 496, + 367, + 890, + 700 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 710, + 653, + 726 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effectiveness of core designs. We perform ablation experiments of the proposed module in Gait3D [61] and CASIA-B [58] datasets. (1) The experimental results reveal that the core design module, comprising the FTS module, prompt pool, and dynamic attention module, notably influenced cross-dressing and carrying conditions within the CASIA-B dataset. In contrast, the introduced module exhibits a more pronounced impact on Gait3D. (2) The results show that replacing the dynamic attention with the max+mean maintains competitive accuracy in CASIA-B. However, the results show a significant decrease in Gait3D, highlighting the", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "599", + "bbox": [ + 486, + 945, + 509, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/bd85c0c07d3790cf6be7fa4d2a129c678dddcf0545d20c83977e3e0f75d61d16.jpg", + "table_caption": [ + "Table 7. The ablation study on Gait3D and CASIA-B are reported with rank-1 accuracy(%) excluding the identical-views cases." + ], + "table_footnote": [], + "table_body": "
MethodGait3DCASIA-B
R-1 (%)NM (%)BG (%)CL (%)
VPNet75.498.396.390.0
Analysis of each component in VPNet
- w/o FTS73.298.096.189.2
- w/o prompt72.898.096.089.1
- w/o mask73.098.396.390.0
w max+mean72.198.095.788.5
Analysis of temporal shift bottleneck
2D Conv69.798.095.786.8
3D Conv73.298.096.189.2
2D Conv + FTS74.198.196.288.2
3D Conv + FTS75.498.396.390.0
Analysis of the local length in dynamic attention
l=874.998.096.389.8
l=1675.498.196.489.8
l=3273.298.396.390.0
", + "bbox": [ + 88, + 127, + 459, + 402 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "effectiveness of our module in real-world scenarios.", + "bbox": [ + 76, + 416, + 419, + 430 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Analysis of temporal shift bottleneck. We perform an empirical analysis comparing convolution outcomes within the temporal shift bottleneck in Tab. 7. (1) The network utilizing 2D convolution experienced a noteworthy decline in performance, representing a substantial improvement over using the FTS module in conjunction with 2D convolution. These results indicate that the FTS module plays a role in acquiring global motion patterns. (2) The network utilizing 3D convolution effectively captures local motion patterns, whereas the incorporation of the FTS module into 3D convolution facilitates the extraction of global motion patterns. Analysis of the local length. Different length affects the receptive fields in dynamic attention. (1) The experimental results demonstrate that an optimal range of receptive fields $(l = 16)$ is essential for real data, as an excessively long receptive field $(l = 32)$ may introduce noise. (2) In laboratory scenarios with relatively short sequence lengths, the impact of local receptive fields is minimal. (3) The issue of training and testing inconsistency can be alleviated by incorporating local receptive fields in the real world.", + "bbox": [ + 75, + 431, + 468, + 733 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Visualization of the prompt selection. We quantify the frequency of prompt template selection across various viewpoints and dress conditions on CASIA-B, as detailed in Fig. 4. The visualization results reveal variability in prompt template selection influenced by external factors, illustrating the encoding of task-relevant knowledge. (1) The statistical results show that different dressings and viewpoints have obvious differences in the frequency of prompt template selection. (2) The visualization results reveal variability in prompt template selection influenced by external factors, illustrating the encoding of task-relevant knowledge.", + "bbox": [ + 75, + 734, + 468, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/3704d89421692a06a39f625abf32905a6169f473529097de10548acb6be53565.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 504, + 88, + 694, + 233 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/43c5766c8690ff12d55282dd874e852657f6d820fbb0a853d561a0d7b7168bbf.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 699, + 88, + 890, + 233 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/cca979bd97cbb5cd029a88c8aceb1d22ab168a37de0e15cc5e72a42aa4df3486.jpg", + "image_caption": [ + "Figure 4. Histogram of prompt template selection on CASIA-B, where \"Prompt ID\", \"View ID\", and \"Type ID\" denote the index of prompt, view angle, and dressing, respectively. (a) Comparison of the selection frequency of prompt templates under cross-dressing and carrying conditions. (b)(c)(d) Comparison of prompt template selection frequency across various views and body parts." + ], + "image_footnote": [], + "bbox": [ + 500, + 233, + 692, + 375 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5f9c5c739ab926220d8f36bf673baaa3f31f7ad16cc30da6851ebff4ea7e96bb.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 699, + 233, + 890, + 375 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion and Limitations", + "text_level": 1, + "bbox": [ + 500, + 484, + 756, + 500 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we present a Visual Prompt Network (VPNet) for gait recognition. VPNet employs temporal shift bottleneck as the foundational module of a backbone network to extract global motion patterns and utilizes prompt engineering to adaptively select templates with corresponding prompt information tailored for different gait sequences. To enhance the robustness of global motion patterns, the relationships between these templates and global features of gait sequence are further established using dynamic transformer structures. VPNet demonstrates superior performance in both in-the-wild and in-the-lab scenarios, highlighting its significant potential in real-world applications.", + "bbox": [ + 496, + 508, + 890, + 691 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Limitations. Prompt learning has gained prominence in natural language processing for retraining large-scale pretrained language models, whereas the proposed network does not incorporate pre-training. In future work, we will investigate the applications of prompt engineering for large-scale gait recognition pre-training in real-world scenarios.", + "bbox": [ + 496, + 691, + 890, + 782 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Acknowledgement", + "text_level": 1, + "bbox": [ + 500, + 799, + 679, + 815 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by the National Key R&D Program of China (2022YFC3300700), the National Natural Science Foundation of China (62331006, 62171038, 62088101, 62276031, 62276025, and 62276025), and the Fundamental Research Funds for the Central Universities.", + "bbox": [ + 496, + 824, + 890, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "600", + "bbox": [ + 486, + 945, + 511, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Hyojin Bahng, Ali Jahanian, Swami Sankaranarayanan, and Phillip Isola. Exploring visual prompts for adapting large-scale models. arXiv preprint arXiv:2203.17274, 2022. 3", + "[2] A.F. Bobick and A.Y. Johnson. 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IJCV, 130(9):2337-2348, 2022. 3" + ], + "bbox": [ + 501, + 92, + 890, + 898 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "602", + "bbox": [ + 486, + 945, + 511, + 955 + ], + "page_idx": 9 + }, + { + "type": "ref_text", + "text": "[63] Zheng Zhu, Xianda Guo, Tian Yang, Junjie Huang, Jiankang Deng, Guan Huang, Dalong Du, Jiwen Lu, and Jie Zhou. Gait recognition in the wild: A benchmark. In ICCV, pages 14789-14799, 2021. 1, 2, 6", + "bbox": [ + 78, + 90, + 470, + 147 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "603", + "bbox": [ + 486, + 945, + 509, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning Visual Prompt for Gait Recognition/250e53d0-2beb-4a17-986d-3fa0bac7cb32_model.json b/2024/Learning Visual Prompt for Gait Recognition/250e53d0-2beb-4a17-986d-3fa0bac7cb32_model.json new file mode 100644 index 0000000000000000000000000000000000000000..93550ffcc512eef9424ba55d31f1d5a7e2c8accd --- /dev/null +++ b/2024/Learning Visual Prompt for Gait Recognition/250e53d0-2beb-4a17-986d-3fa0bac7cb32_model.json @@ -0,0 +1,2202 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.255, + 0.131, + 0.717, + 0.154 + ], + "angle": 0, + "content": "Learning Visual Prompt for Gait Recognition" + }, + { + "type": "text", + "bbox": [ + 0.136, + 0.18, + 0.838, + 0.218 + ], + "angle": 0, + "content": "Kang Ma\\(^{1}\\), Ying Fu\\(^{1*}\\), Chunshui Cao\\(^{2}\\), Saihui Hou\\(^{2,3}\\), Yongzhen Huang\\(^{2,3}\\), Dezhi Zheng\\(^{1*}\\) \n\\(^{1}\\)Beijing Institute of Technology, \\(^{2}\\)WATRIX.AI, \\(^{3}\\)Beijing Normal University" + }, + { + "type": "text", + "bbox": [ + 0.108, + 0.22, + 0.85, + 0.252 + ], + "angle": 0, + "content": "kangx.ma@gmail.com, fuying@bit.edu.cn, chunshui.cao@watrix.ai, housaihui@bnu.edu.cn, huangyongzhen@bnu.edu.cn, zhengdezhi@bit.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.287, + 0.314, + 0.303 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.319, + 0.474, + 0.76 + ], + "angle": 0, + "content": "Gait, a prevalent and complex form of human motion, plays a significant role in the field of long-range pedestrian retrieval due to the unique characteristics inherent in individual motion patterns. However, gait recognition in real-world scenarios is challenging due to the limitations of capturing comprehensive cross-viewing and cross-clothing data. Additionally, distractors such as occlusions, directional changes, and lingering movements further complicate the problem. The widespread application of deep learning techniques has led to the development of various potential gait recognition methods. However, these methods utilize convolutional networks to extract shared information across different views and attire conditions. Once trained, the parameters and non-linear function become constrained to fixed patterns, limiting their adaptability to various distractors in real-world scenarios. In this paper, we present a unified gait recognition framework to extract global motion patterns and develop a novel dynamic transformer to generate representative gait features. Specifically, we develop a trainable part-based prompt pool with numerous key-value pairs that can dynamically select prompt templates to incorporate into the gait sequence, thereby providing task-relevant shared knowledge information. Furthermore, we specifically design dynamic attention to extract robust motion patterns and address the length generalization issue. Extensive experiments on four widely recognized gait datasets, i.e., Gait3D, GREW, OUMVLP, and CASIA-B, reveal that the proposed method yields substantial improvements compared to current state-of-the-art approaches." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.789, + 0.21, + 0.804 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.814, + 0.47, + 0.876 + ], + "angle": 0, + "content": "Gait, as a distinct and intricate form of movement [4, 43], holds significant implications for long-distance recognition [36, 49, 60] owing to its remarkable uniqueness. However, gait recognition suffers from various complicating factors" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.288, + 0.891, + 0.58 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.591, + 0.893, + 0.621 + ], + "angle": 0, + "content": "Figure 1. Performance comparison of prevailing methods and the proposed method in both real-world and laboratory scenarios." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.64, + 0.895, + 0.807 + ], + "angle": 0, + "content": "in real-world scenarios. Silhouette data from the same individual can exhibit significant variation depending on viewing angles and clothing conditions [44, 58], resulting in more intra-class variation than inter-class variation. In addition, potential obstructions from crowds and actions of the observed subjects [61, 63], such as turning, lingering, or stopping, may manifest within a single gait sequence. Despite the ability of human visual perception to seamlessly establish correspondences between occlusions, viewpoint changes, and object transformations, it still poses a formidable challenge for the gait recognition network." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.895, + 0.902 + ], + "angle": 0, + "content": "Learning robust motion patterns from multiple variations all at once is not a trivial task. With the widespread application of deep learning, some promising methods [7, 14, 22, 33, 35] have emerged. However, these methods preserve shared information across different viewpoints and attire conditions while discarding task-relevant knowledge" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.23, + 0.9 + ], + "angle": 0, + "content": "*Corresponding Authors" + }, + { + "type": "page_number", + "bbox": [ + 0.486, + 0.946, + 0.512, + 0.957 + ], + "angle": 0, + "content": "593" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.137 + ], + "angle": 0, + "content": "relevant to particular conditions. Intuitively, the knowledge is crucial for the gait network to learn valuable invariances. Thus, we aim to reveal it from the following aspects:" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.138, + 0.471, + 0.379 + ], + "angle": 0, + "content": "(i) Prompt Templates. A widely acknowledged assumption [7, 35, 54] regarding gait is that individuals maintain consistent motion patterns regardless of external factors. Central to all of these capabilities is the ability to establish associations despite occlusions, viewpoint changes, and varying object appearances. Indeed, in controlled laboratory settings marked by abundant data and well-managed conditions, stable associations tend to form readily. Conversely, addressing scenarios in the wild, constrained by limited data and influenced by obstructions and crowded environments, significantly increases the complexity of establishing stable associations. Consequently, a simple and effective approach is to provide task-relevant knowledge using a learnable prompt pool, which is expected to adaptively select prompt templates based on sequence attributes to establish stable associations under various disturbances." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.381, + 0.47, + 0.593 + ], + "angle": 0, + "content": "(ii) Length Generalization. Similar to natural language processing (NLP) tasks [47], gait also faces the problem of length generalization [17, 42, 55]. In particular, the majority of the most promising gait recognition methods involve training by randomly selecting a subset of the sequence and testing by extracting features from the entire sequence. Nevertheless, these methods frequently neglect the challenges presented by the longer sequence. To this end, we implement a dynamic context window mask for gait, enabling the network to focus its attention on the features within the specified window. Furthermore, we propose to establish a correlation between the localized window and the prompt templates, with the aim of emphasizing the significance of distinctive gait features within the sequence." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.594, + 0.47, + 0.866 + ], + "angle": 0, + "content": "Based on the above analysis, we present a comprehensive Visual Prompt Network (VPNet) for gait recognition. VPNet leverages prompt templates to augment the task-relevant information associated with the gait feature. Dynamic attention is employed to establish connections between prompt templates and local window features, enabling the network to capture crucial invariant gait features. As illustrated in Fig. 2, VPNet initially extracts features from the sampled sequence using a backbone network. These features are then compared with a trainable part-based prompt pool, with prompt templates dynamically selected and integrated into the gait sequence. The merged features are further input into the dynamic transformer to enhance the learning of global motion patterns. VPNet exhibits superior performance, especially in realistic scenarios, compared to state-of-the-art (SOTA) methods on publicly available datasets as shown in Fig. 1. A brief overview of our main contributions can be summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.902 + ], + "angle": 0, + "content": "- We introduce an innovative visual prompt that integrates key-value pairs with gait features, encoding factors such" + }, + { + "type": "text", + "bbox": [ + 0.512, + 0.092, + 0.892, + 0.137 + ], + "angle": 0, + "content": "as viewpoint, attire, occlusion, etc. These prompt templates provide task-related information to the network, facilitating the extraction of representative gait features." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.138, + 0.892, + 0.197 + ], + "angle": 0, + "content": "- We design an efficient dynamic transformer with a context window mask structure to correlate prompt templates with local motion patterns, addressing the length generalization problem for gait recognition." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.198, + 0.892, + 0.273 + ], + "angle": 0, + "content": "- We present a unified framework that yields competitive results on publicly accessible datasets, namely Gait3D [61], GREW [63], OUMVLP [44], and CASIA-B [58]. In addition, a series of rigorous ablation experiments further validate the effectiveness of our approach." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.138, + 0.892, + 0.273 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.285, + 0.631, + 0.301 + ], + "angle": 0, + "content": "2. Relate Work" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.311, + 0.892, + 0.342 + ], + "angle": 0, + "content": "In this section, we present a review of the most relevant studies on gait recognition and prompt engineering." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.349, + 0.667, + 0.366 + ], + "angle": 0, + "content": "2.1. Gait Recognition" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.373, + 0.892, + 0.417 + ], + "angle": 0, + "content": "Gait recognition approaches can be broadly classified into two categories based on their modeling methodology, i.e., model-based methods and appearance-based methods." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.418, + 0.893, + 0.644 + ], + "angle": 0, + "content": "Model-based method. Model-based approaches [2, 48, 59] aim to capture the inherent biomechanical characteristics of pedestrians. Early approaches [3, 28, 56] focused on distinguishing identities by estimating pedestrian motion parameters. However, such methods were constrained by predefined empirical points and yielded limited recognition accuracy. With the rapid advancement of deep learning, researchers have shifted their focus to extracting training data using pose estimation or Skinned Multi-Person Linear (SMPL) models. Subsequently, a well-designed network [21, 29, 30, 45, 46] is employed to further learn the gait features based on joint-based datasets. Despite substantial advancements, the efficacy of model-based methods remains constrained by the empirical design of predefined points and the estimation of results from low-quality images." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.645, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Appearance-based method. Appearance-based methods aim to learn gait features directly from silhouette data. Previous methods [18, 37, 54] have employed an efficient approach by directly applying weighted averaging to the sequence, i.e., Gait Energy Image (GEI). These methods have achieved significant advancements across various viewpoints and clothing conditions. However, the weighted averaging of video sequence data inevitably leads to the loss of substantial motion details. To this end, current research [22, 23, 26, 32] emphasizes the utilization of video input to learn gait features in order to address this limitation. Some of the 2D convolution-based methods [7, 14] independently extract local spatial features from each frame and subsequently utilize set-based pooling techniques, i.e., MaxPooling and MeanPooling, to directly extract global temporal features from the variable-length sequence. These methods have yielded impressive experimental results, significantly" + }, + { + "type": "page_number", + "bbox": [ + 0.486, + 0.946, + 0.511, + 0.957 + ], + "angle": 0, + "content": "594" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.096, + 0.887, + 0.287 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.3, + 0.893, + 0.358 + ], + "angle": 0, + "content": "Figure 2. Overview of the proposed Visual Prompt Network (VPNet), where \"HP\" denotes the Horizontal Pooling. (a) VPNet incorporates the FTS module into the backbone based on ResNet, focusing on the extraction of global motion patterns without any extra parameters. (b) VPNet utilizes a trainable prompt pool comprising numerous key-value pairs, dynamically selecting prompt templates and integrating them into gait features to provide task-relevant knowledge. (c) Three different loss functions are combined for supervised network training." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.383, + 0.473, + 0.581 + ], + "angle": 0, + "content": "advancing the field of gait recognition. However, gait represents a coordinated whole-body motion process, and processing the features of each frame individually disregards the preservation of robust local motion patterns, which are essential for accurate gait information. Consequently, some 3D convolution-based methods [6, 12, 33, 35, 36] proposed to local spatio-temporal features from adjacent frame images using a shared 3D convolution kernel, while further modeling the unfixed length sequence to obtain robust global features. The approach presented in this paper falls within the category of appearance-based methods. In contrast to previous methods, we aim to explore further improvements within the deep network structure." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.59, + 0.273, + 0.607 + ], + "angle": 0, + "content": "2.2. Prompt Engineering" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.614, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Prompt Engineering [5, 9, 40] is a methodology that involves the incorporation of additional information as a condition in the inference process using a model. It has gained considerable popularity [16, 19, 41] in the field of natural language processing (NLP) due to its ability to integrate task-specific cues for each individual task. In recent years, there has been a notable surge in prompt-based research [31, 38, 57, 62] within the field of computer vision. It integrates visual and linguistic tasks, using NLP to reference or define visual concepts. To address inherent disparities in information densities between visual and NLP tasks, researchers have developed methodologies [1, 24, 27] that involve pre-filling model inputs with adaptive parameters. These parameters, functioning as prompts, can be finetuned through gradient-based optimization, thereby facilitating their contribution to visual tasks. Specifically, VPT [27] and VP [1] load a set of trainable prompts into the model inputs while maintaining the architectural integrity of the core network. This strategic implementation consis" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.383, + 0.895, + 0.52 + ], + "angle": 0, + "content": "tently yields noteworthy performance improvements across a range of downstream tasks. In contrast, DAM-VP [24] adopts a divide-and-conquer scheme, segregating datasets associated with downstream tasks into smaller, homogeneous subsets. Each subset is endowed with its distinct cue, and subsequently, optimization is carried out independently for each subset. We extend the concept of prompt learning from prior research [52, 53], utilizing it to provide task-related information and extract robust motion patterns." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.532, + 0.637, + 0.55 + ], + "angle": 0, + "content": "3. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.557, + 0.895, + 0.648 + ], + "angle": 0, + "content": "In this section, we present the overall architecture of the proposed Visual Prompt Network (VPNet) for gait and provide an in-depth explanation of the motivation in Sec. 3.1. We then provide a comprehensive elucidation of the backbone architecture in Sec. 3.2. Finally, we present the specific structure of the dynamic transformer in Sec. 3.3." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.657, + 0.753, + 0.673 + ], + "angle": 0, + "content": "3.1. Preliminary and Motivation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.68, + 0.895, + 0.817 + ], + "angle": 0, + "content": "A vanilla vision gait recognition framework typically comprises two essential components: the backbone \\(\\mathcal{B}\\) and the head \\(\\mathcal{H}\\). Formally, given a gait silhouette sequence \\(X \\in \\mathbb{R}^{T \\times H \\times W}\\), where \\(H\\), \\(W\\), and \\(T\\) represent the height, width, and number of frames, respectively. Firstly, the gait sequence is fed into the backbone to extract the local motion patterns, followed by its passage through the head to derive the global motion patterns. The extraction of gait features can be briefly represented as" + }, + { + "type": "equation", + "bbox": [ + 0.643, + 0.828, + 0.891, + 0.844 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {F} = \\mathcal {H} (\\mathcal {B} (\\boldsymbol {X})), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.855, + 0.895, + 0.903 + ], + "angle": 0, + "content": "where \\( \\pmb{F} \\in \\mathbb{R}^{P \\times C} \\) denotes the output features, \\( P \\) is the number of horizontal slices, and \\( C \\) is the feature dimension. Most of the existing research [8, 15, 33] places a significant" + }, + { + "type": "page_number", + "bbox": [ + 0.486, + 0.946, + 0.511, + 0.957 + ], + "angle": 0, + "content": "595" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.258 + ], + "angle": 0, + "content": "focus on improving the efficiency of the backbone component for extracting complex spatio-temporal features. Despite their progress, these approaches struggle to address the challenges of gait recognition in real-world scenarios. To this end, as shown in Fig. 2, we intend to introduce a comprehensive framework for gait recognition. In particular, it involves utilizing a common backbone to directly extract global motion patterns, designing a trainable prompt pool \\(\\mathcal{P}\\) that adaptively selects task-relevant templates to concatenate with the original gait features, and employing dynamic attention to learn representative gait features, i.e.," + }, + { + "type": "equation", + "bbox": [ + 0.149, + 0.266, + 0.47, + 0.302 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {F} = \\mathcal {H} (\\text {c o n c a t} [ \\overbrace {\\mathcal {P} (\\boldsymbol {B} (\\boldsymbol {X}))} ^ {\\text {p r o m p t t e m p l a t e s}}, \\boldsymbol {B} (\\boldsymbol {X}) ]), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.31, + 0.47, + 0.4 + ], + "angle": 0, + "content": "where concat represents the concatenation along the temporal dimension. The prompt templates, functioning as trainable embeddings, essentially encode the gait task. These templates include various aspects such as viewpoint, attire, carrying conditions, occlusion, and so on. They provide instructions to the model, specifying the task it executes." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.408, + 0.292, + 0.423 + ], + "angle": 0, + "content": "3.2. Backbone Architecture" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.432, + 0.47, + 0.552 + ], + "angle": 0, + "content": "We utilize the bottleneck structure in ResNet [20] to establish the backbone for gait recognition and introduce a plug-and-play gait temporal-shift operation [34, 36], coupled with a 3D convolutional network, as the foundational motion pattern extraction element within the bottleneck. By modifying the depth of the backbone network, we sequentially construct three models with distinct parameters in Sec. 4.1, namely VPNet-T, VPNet-M, and VPNet-L." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.553, + 0.471, + 0.825 + ], + "angle": 0, + "content": "Temporal Shift Bottleneck. 3D convolution is commonly used in gait recognition tasks due to its proficiency in local spatio-temporal aggregation. However, its ability to be used in real-world scenarios with numerous long silhouette sequences may pose certain challenges. Inspired by temporal shift operation [34, 36], as shown in Fig. 2, we design a novel Forward cycle Temporal Shift (FTS) module for the gait recognition network. Considering that forward walking is the predominant daily practice, whereas backward walking is less frequent, we employ a forward cyclic shifting approach along the temporal dimension instead of the zero padding technique used in TSCov [34]. Specifically, the FTS module divides the features \\( f \\in \\mathbb{R}^{C \\times T \\times H \\times W} \\) of each pixel into four segments. It only cyclically shifts the first segment \\( f_{1} \\in \\mathbb{R}^{\\frac{C}{4} \\times T \\times H \\times W} \\) along the temporal dimension. The extraction of motion patterns with a global receptive field can be achieved by incorporating the FTS module before 3D convolution, without the additional parameters." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.833, + 0.285, + 0.849 + ], + "angle": 0, + "content": "3.3. Dynamic Transformer" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.469, + 0.902 + ], + "angle": 0, + "content": "We present a dynamic transformer as an integral head layer \\(\\mathcal{H}\\) in the network architecture. As shown in Fig. 2, it employs prompt engineering to provide task-specific shared" + }, + { + "type": "image", + "bbox": [ + 0.511, + 0.094, + 0.885, + 0.328 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.343, + 0.892, + 0.385 + ], + "angle": 0, + "content": "Figure 3. The dynamic attention architecture. We utilize both prompt templates and gait sequence as inputs, employing the Context Window Mask to overcome the length generalization problem." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.393, + 0.892, + 0.437 + ], + "angle": 0, + "content": "knowledge information for gait sequence and introduces a dynamic context window mask to effectively alleviate the problem of length generalization in real-world scenarios." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.438, + 0.893, + 0.62 + ], + "angle": 0, + "content": "Part-based Prompt Pool. Prompt learning has emerged as a methodology in NLP, and its application in gait recognition is motivated by three main considerations. Firstly, the adaptable visual prompt templates facilitate the integration of shared insights concerning the gait sequence. Secondly, the shared knowledge seamlessly incorporates into the gait sequence as a global feature through a flexible plug-and-play process. Finally, specific visual prompts are associated with salient features within the gait sequence. To address this, we introduce a part-based prompt pool with shared parameters, delivering task-specific information. The \\(j\\)-th prompt pool can be defined as" + }, + { + "type": "equation", + "bbox": [ + 0.521, + 0.631, + 0.892, + 0.649 + ], + "angle": 0, + "content": "\\[\n\\mathcal {P} _ {j} = \\left\\{\\boldsymbol {P} _ {j, 1}, \\boldsymbol {P} _ {j, 2}, \\dots , \\boldsymbol {P} _ {j, N} \\mid \\boldsymbol {P} _ {j, i} = \\left(k _ {j, i}, v _ {j, i}\\right) \\right\\}, \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.893, + 0.901 + ], + "angle": 0, + "content": "where \\(\\{\\mathcal{P}_j|j = 1,\\dots,P\\}\\) is the \\(j\\) -th prompt pool, \\(P\\) denotes the number of horizontal slices, \\(P_{j,i}\\) is the \\(i\\) -th prompt token, \\(N\\) denotes the number of trainable tokens in the prompt pool, \\(k_{j,i}\\in \\mathbb{R}^{C}\\) and \\(v_{j,i}\\in \\mathbb{R}^C\\) represent the key and value, respectively. We utilize key-value pairs as prompt tokens, matching the key with the input gait sequence. Following this alignment, the top- \\(k\\) values are selected as prompt templates based on their similarity, and these chosen templates are smoothly integrated with the original sequence along the temporal dimension. Specifically, given a gait sequence feature \\(\\pmb {S}\\in \\mathbb{R}^{P\\times T\\times C}\\) , for the \\(j\\) -th part sequence feature \\(S_{j}\\in \\mathbb{R}^{T\\times C}\\) , we first compute the average feature along the temporal dimension \\(\\bar{S}_j\\in \\mathbb{R}^C\\) and then perform similarity matching with key embeddings in the prompt pool to select the top- \\(k\\) values with the highest similarity. Denote \\(\\mathcal{R}\\) as the function to lookup the top- \\(k\\) keys in the ranked list, the" + }, + { + "type": "page_number", + "bbox": [ + 0.486, + 0.946, + 0.511, + 0.957 + ], + "angle": 0, + "content": "596" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.078, + 0.092, + 0.414, + 0.108 + ], + "angle": 0, + "content": "selection process for the key can be represented as" + }, + { + "type": "equation", + "bbox": [ + 0.179, + 0.116, + 0.47, + 0.152 + ], + "angle": 0, + "content": "\\[\n\\mathcal {K} _ {j} = \\mathcal {R} \\left(\\frac {\\bar {S} _ {j} \\otimes k _ {j , i}}{\\| \\bar {S} _ {j} \\| \\otimes \\| k _ {j , i} \\|}\\right), \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.16, + 0.47, + 0.237 + ], + "angle": 0, + "content": "where \\(\\mathcal{K}_j\\) denotes a list of sets, generating a top-\\(k\\) index that is linked to the query sequence, and \\(\\otimes\\) represents matrix multiplication. The index value is employed to retrieve \\(k\\) values, denoted as \\(V_j = \\{v_{j,\\kappa}|\\kappa \\in \\mathcal{K}_s\\}\\). Subsequently, we combine the indexed value \\(V_j\\) with the feature \\(S_j\\), i.e.," + }, + { + "type": "equation", + "bbox": [ + 0.196, + 0.246, + 0.47, + 0.265 + ], + "angle": 0, + "content": "\\[\nS _ {j} ^ {*} = \\operatorname {c o n c a t} \\left[ V _ {j}, S _ {j} \\right], \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.274, + 0.47, + 0.439 + ], + "angle": 0, + "content": "where concat represents the concatenation of prompt templates and gait vectors along the temporal dimension. The resulting gait sequence, denoted as \\( S_{j}^{*} \\in \\mathbb{R}^{(T + k) \\times C} \\), integrates the prompt information, \\( (T + k) \\) is the length of the gait sequence, and \\( k \\) is empirically set to 6. Similar to the codebook collapse issue faced in VQ-VAE [10, 39], there exists a risk that all index \\( \\mathcal{K}_{j} \\) map to a limited set of prompt templates. To address this, we implement a randomized restart strategy: the key vector in the prompt pool is randomly reset to one of the encoder outputs if its average utilization falls below a predefined threshold \\( (\\tau = 0.001) \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.44, + 0.47, + 0.516 + ], + "angle": 0, + "content": "Dynamic Attention. As shown in Fig. 3, we propose to extract global motion patterns for each body part based on prompt templates using the multi-head attention [11, 47]. Formally, the \\(j\\)-th part sequence feature \\(S_{j}^{*}\\) is mapped as query \\(\\pmb{Q}\\), key \\(\\pmb{K}\\) and value \\(\\pmb{V}\\). The mapping process is as" + }, + { + "type": "equation", + "bbox": [ + 0.133, + 0.539, + 0.47, + 0.561 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {Q} = S _ {j} ^ {*} W ^ {Q}, \\boldsymbol {K} = S _ {j} ^ {*} W ^ {K}, \\boldsymbol {V} = S _ {j} ^ {*} W ^ {V}, \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.57, + 0.47, + 0.682 + ], + "angle": 0, + "content": "where \\( W^{Q} \\in \\mathbb{R}^{C \\times h \\cdot C'} \\), \\( W^{K} \\in \\mathbb{R}^{C \\times h \\cdot C'} \\) and \\( W^{V} \\in \\mathbb{R}^{C \\times h \\cdot C'} \\) are learnable parameters, \\( h \\) denotes the number of heads, and \\( C' \\) represents the feature dimension of each head. Then, we employ \\( Q \\) and \\( K \\) to establish similarity relationships between each frame. It is notable that prompt templates can be associated with the features of each frame, thereby giving rise to the establishment of correlations, i.e.," + }, + { + "type": "equation", + "bbox": [ + 0.198, + 0.706, + 0.47, + 0.725 + ], + "angle": 0, + "content": "\\[\n\\operatorname {s i m} (\\boldsymbol {Q}, \\boldsymbol {K}) = \\boldsymbol {Q} \\boldsymbol {K} ^ {T}, \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.47, + 0.902 + ], + "angle": 0, + "content": "where \\(\\operatorname{sim}(Q, K)\\) denotes the similarity matrix. Similar to natural language processing, gait recognition also faces the challenge of length generalization [17, 42, 55]. During training, a limited number of frames are randomly selected, but during testing, the longer sequence can distract the attention of the network. To effectively utilize the shared information provided by prompt templates in discerning distinctive global motion patterns within varying length sequences, we introduce a context window mask structure. This design dynamically establishes connections between prompt templates and gait sequence. As depicted in Fig. 3," + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.894, + 0.199 + ], + "angle": 0, + "content": "the architecture comprises a global branch on the left and a local branch on the right. The global branch allows each feature in the sequence to focus on establishing relationships with prompt templates, while the local branch fosters associations between each feature and other features within a defined local length range. Features outside of these two branches are excluded from the attention process, i.e.," + }, + { + "type": "equation", + "bbox": [ + 0.52, + 0.208, + 0.892, + 0.242 + ], + "angle": 0, + "content": "\\[\n\\operatorname {A t t} (\\boldsymbol {Q}, \\boldsymbol {K}, \\boldsymbol {V}) = \\operatorname {s o f t m a x} \\left(\\frac {\\operatorname {s i m} (\\boldsymbol {Q} , \\boldsymbol {K})}{\\sqrt {C ^ {\\prime}}} \\oplus \\mathcal {M}\\right) \\boldsymbol {V}, \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.252, + 0.893, + 0.285 + ], + "angle": 0, + "content": "where \\(\\sqrt{C'}\\) is the scaling factor, \\(\\mathcal{M}\\) is the dynamic context window mask, and \\(\\oplus\\) denotes element-wise sum operation." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.293, + 0.667, + 0.309 + ], + "angle": 0, + "content": "3.4. Learning Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.316, + 0.893, + 0.422 + ], + "angle": 0, + "content": "In this work, we introduce three loss functions during training: triplet loss \\(\\mathcal{L}_{tp}\\), cross-entropy loss \\(\\mathcal{L}_{\\text{cet}}\\), and cosine embedding loss \\(\\mathcal{L}_{\\text{cem}}\\) in Fig. 2. The \\(\\mathcal{L}_{tp}\\) and \\(\\mathcal{L}_{\\text{cet}}\\) serve to supervise part-based features individually, while the \\(\\mathcal{L}_{\\text{cem}}\\) is applied to supervise the key embedding \\((k_{j,i})\\) within the prompt pool. \\(\\mathcal{L}_{\\text{cem}}\\) requires that the selected key embedding be closely related to the query sequence \\(\\bar{S}_i\\), i.e.," + }, + { + "type": "equation", + "bbox": [ + 0.538, + 0.433, + 0.892, + 0.474 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {c e m} = \\underset {\\kappa \\in \\mathcal {K} _ {j}} {\\arg \\min } \\sum_ {i = 1} ^ {P} \\frac {- 1}{N _ {c e m}} \\left(\\frac {\\bar {S} _ {i} \\otimes k _ {j , \\kappa}}{\\| \\bar {S} _ {i} \\| \\otimes \\| k _ {j , \\kappa} \\|}\\right), \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.483, + 0.893, + 0.604 + ], + "angle": 0, + "content": "where \\( N_{cem} \\) is a positive integer obtained by multiplying the batch size with the number of parts. In each training step, we adhere to the previously described strategy to select \\( \\kappa_{s} \\). The selected prompt templates are then merged with gait sequence vectors and fed into the dynamic transformer and BNNeck [15] to extract representative gait features. In general, the training process involves the use of a combined loss following the end-to-end method, i.e.," + }, + { + "type": "equation", + "bbox": [ + 0.587, + 0.617, + 0.892, + 0.633 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {s u m} = \\mathcal {L} _ {t p} + \\alpha \\mathcal {L} _ {c e m} + \\beta \\mathcal {L} _ {c e t}, \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.643, + 0.892, + 0.674 + ], + "angle": 0, + "content": "where \\(\\alpha\\) and \\(\\beta\\) are the hyper-parameters to balance the combined loss, \\(\\alpha\\) is empirically set to 0.01 and \\(\\beta\\) is set to 0.3." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.687, + 0.634, + 0.705 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.712, + 0.82, + 0.728 + ], + "angle": 0, + "content": "4.1. Datasets and Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.81 + ], + "angle": 0, + "content": "The gait datasets are divided into two subsets, i.e., in-the-wild and in-the-lab, distinguished by their respective collection environments in Tab. 1. A standardized preprocessing procedure [7] is uniformly applied to these datasets, and the data sizes used in this paper are all resized to \\(64 \\times 64\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In-the-wild datasets. In-the-wild datasets introduce numerous unforeseen challenges, such as occlusions, clothing changes, viewpoint variations, and carrying conditions. Pedestrians may also pause or alter their walking patterns. These datasets are essential benchmarks for evaluating gait recognition methods under various external disturbances." + }, + { + "type": "page_number", + "bbox": [ + 0.486, + 0.946, + 0.511, + 0.957 + ], + "angle": 0, + "content": "597" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.895, + 0.12 + ], + "angle": 0, + "content": "Table 1. Comparison of the specific values of the adopted datasets and corresponding parameters. Where “#Ide., #Seq., #Cam.” refer to numbers of identities, sequences, and cameras respectively. Additionally, “lr, dr, wd” denote learning rate, decay rate, and weight decay." + }, + { + "type": "table", + "bbox": [ + 0.081, + 0.13, + 0.891, + 0.226 + ], + "angle": 0, + "content": "
EnvironmentDatasetsTrainTest# Cam.Batch SizeOptimizerScheduler
# Ide.# Seq.# Ide.# Seq.step sizeepochs
In-the-wildGait3D [61]3,00018,9401,0006,369Diverse(32, 4)SGD lr = 0.12080
GREW [63]20,000102,8876,00024,000Diverse(64, 4)50200
In-the-labOUMVLP [44]5,153144,2845,154144,31214(32, 8)dr = 0.150200
CASIA-B [58]748,140505,50011(8, 16)wd = 0.00051040
" + }, + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.234, + 0.471, + 0.263 + ], + "angle": 0, + "content": "Table 2. The detailed structure of the backbone in VPNet-L, where FTSCov denotes the combined of FTS module and convolution." + }, + { + "type": "table", + "bbox": [ + 0.097, + 0.274, + 0.446, + 0.48 + ], + "angle": 0, + "content": "
LayerOutput size
conv13 × 3 × 3, 64, stride(1,1,1)T × H × W
stage1[1 × 1 × 1, 64, (0,0,0)FTSCnv, 64, (1,1,1)1 × 1 × 1, 64, (0,0,0)] × 3T × H × W
stage2[1 × 1 × 1, 128, (0,0,0)FTSCnv, 128, (1,2,2)1 × 1 × 1, 128, (0,0,0)] × 4T × H/2 × W/2
stage3[1 × 1 × 1, 256, (0,0,0)FTSCnv, 256, (1,2,2)1 × 1 × 1, 256, (0,0,0)] × 6T × H/4 × W/4
stage4[1 × 1 × 1, 512, (0,0,0)FTSCnv, 512, (1,1,1)1 × 1 × 1, 512, (0,0,0)] × 3T × H/4 × W/4
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.49, + 0.47, + 0.581 + ], + "angle": 0, + "content": "We evaluate our method on the widely adopted Gait3D [61] and GREW [63] datasets in Tab. 1. To enhance the robustness of our model, we employ three data augmentation techniques: rotation, flipping, and perspective. We conduct training using VPNet-L on both Gait3D and GREW datasets and report rank-1 (\\%) and rank-5 (\\%) accuracy." + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.582, + 0.47, + 0.809 + ], + "angle": 0, + "content": "In-the-lab datasets. In-the-lab datasets encompass various controllable conditions, including camera angles, predetermined walking routes, and dress variations. These datasets play a pivotal role in evaluating the ability of the gait network to handle cross-viewing and cross-dressing scenarios. We select the well-established OUMVLP [44] and CASIA-B [58] datasets to evaluate our approach in Tab. 1. Specifically, the OUMVLP provides an abundance of cross-viewing data, while the CASIA-B offers valuable cross-dressing data. Limited datasets, particularly those obtained from laboratory scenarios, may result in overfitting if the network parameters are excessively large. Therefore, we employ VPNet-M for training on OUMVLP and VPNet-T for training on CASIA-B. We present the rank-1 \\((\\%)\\) accuracy for all perspectives, excluding the identical-view cases." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Implementation Details. We establish the network parameters based on the dataset scale and complexity, as outlined in Tab. 1. The batch size is represented as \\((S, T)\\), indicating that each mini-batch involves \\(S\\) subjects. For each subject, \\(T\\) sequences are sampled, and within each sequence, a random selection of 20 to 40 frames is chosen following" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.234, + 0.894, + 0.264 + ], + "angle": 0, + "content": "Table 3. The performance comparisons on Gait3D are reported with rank-1 and rank-5 accuracy (\\%)." + }, + { + "type": "table", + "bbox": [ + 0.52, + 0.274, + 0.871, + 0.462 + ], + "angle": 0, + "content": "
MethodsPublicationrank-1 (%)rank-5 (%)
GaitSet [7]AAAI 201936.758.3
GaitPart [14]CVPR 202028.247.6
GLN [22]ECCV 202031.452.9
GaitGL [33]ICCV 202129.748.5
CSTL [25]ICCV 202111.719.2
SMPLGait [61]CVPR 202246.364.5
GaitBase [15]CVPR 202365.6-
GaitGCI [13]CVPR 202350.368.5
DANet [35]CVPR 202348.069.7
HSTL [50]ICCV 202361.376.3
DyGait [51]ICCV 202366.380.8
VPNet-L-75.487.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.474, + 0.893, + 0.503 + ], + "angle": 0, + "content": "Table 4. The performance comparisons on GREW are reported with rank-1 and rank-5 accuracy \\((\\%)\\)." + }, + { + "type": "table", + "bbox": [ + 0.52, + 0.514, + 0.866, + 0.663 + ], + "angle": 0, + "content": "
MethodsPublicationrank-1 (%)rank-5 (%)
GaitSet[7]AAAI 201946.363.6
GaitPart [14]CVPR 202044.060.7
GaitGL [33]ICCV 202147.363.6
GaitGraph [45]ICIP 20211.33.5
GaitBase [15]CVPR 202360.1-
GaitGCI [13]CVPR 202368.580.8
HSTL [50]ICCV 202362.776.6
DyGait [51]ICCV 202371.483.2
VPNet-L-80.089.4
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.674, + 0.895, + 0.903 + ], + "angle": 0, + "content": "DANet [35]. The optimization strategy employs Stochastic Gradient Descent (SGD) with an initial learning rate of 0.1, and each epoch consists of 1000 iterations. The learning rate undergoes periodic reduction based on the step size in Tab. 1, with a decay rate of 0.1. The entire model is built by sequentially stacking the temporal shift bottleneck in Sec. 3.2. We construct three models with distinct parameters, namely VPNet-T, VPNet-M, and VPNet-L, by modifying the depth of the backbone network. Specifically, VPNet-T is composed of three stages, each comprising a specific number of layers (1, 1, 1) and channels (64, 128, 256). In contrast, both VPNet-M and VPNet-L consist of four stages with channel configurations (64, 128, 256, 512) in Tab. 2. VPNet-M employs a layer stack of (2, 2, 2, 2), while VPNet-L utilizes a stack of layers (3, 4, 6, 3)." + }, + { + "type": "page_number", + "bbox": [ + 0.487, + 0.946, + 0.512, + 0.957 + ], + "angle": 0, + "content": "598" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.18, + 0.09, + 0.79, + 0.104 + ], + "angle": 0, + "content": "Table 5. Rank-1 accuracy (%) on OUMVLP under all view angles, excluding the identical-views cases." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.117, + 0.895, + 0.287 + ], + "angle": 0, + "content": "
MethodProbe ViewMean
0°15°30°45°60°75°90°180°195°210°225°240°255°270°
GaitSet [7]79.587.989.990.288.188.787.881.786.789.089.387.287.886.287.1
GaitPart [14]82.688.990.891.089.789.989.585.288.190.090.189.089.188.288.7
GLN [22]83.890.091.091.290.390.089.485.389.190.590.689.689.388.589.2
GaitGL [33]84.990.291.191.591.190.890.388.588.690.390.489.689.588.889.7
GaitBase [15]--------------90.0
GaitGCI [13]91.292.392.692.793.092.392.192.091.891.992.692.391.491.692.1
DANet [35]87.791.391.691.891.791.491.190.490.390.790.990.590.389.990.7
HSTL [50]91.492.992.793.092.992.592.592.792.392.192.392.291.891.892.4
VPNet-M91.993.092.492.793.292.592.392.992.491.992.192.591.991.992.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.303, + 0.47, + 0.331 + ], + "angle": 0, + "content": "Table 6. The performance comparisons on CASIA-B are reported with rank-1 accuracy \\((\\%)\\), excluding the identical-view cases." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.342, + 0.466, + 0.523 + ], + "angle": 0, + "content": "
MethodsPublicationNMBGCLMean
GaitSet[7]AAAI 201995.087.270.484.2
GaitPart[14]CVPR 202096.291.578.788.8
GLN [22]ECCV 202096.994.077.589.5
MT3D [32]MM 202096.793.081.590.4
GaitGL [33]ICCV 202197.494.583.691.8
GaitBase [15]CVPR 202397.694.077.489.8
GaitGCI-T [13]CVPR 202397.995.086.493.1
DANet [35]CVPR 202398.095.989.994.6
HSTL [50]ICCV 202398.195.988.994.3
DyGait [51]ICCV 202398.496.287.894.1
VPNet-T-98.396.390.094.9
" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.537, + 0.38, + 0.551 + ], + "angle": 0, + "content": "4.2. Results under in-the-wild Scenario" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.563, + 0.469, + 0.684 + ], + "angle": 0, + "content": "Gait3D. VPNet-L demonstrates superior performance in terms of rank-1 and rank-5 accuracy in Tab. 3, surpassing state-of-the-art methods. Notably, it exhibits a \\(9.1\\%\\) improvement over DyGait [51], a silhouette-based approach, and a remarkable \\(29.1\\%\\) improvement compared to SMPL-Gait [61], a multimodal method. These experimental results underscore the efficacy of our method in extracting robust features in the presence of diverse external disturbances." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.687, + 0.469, + 0.779 + ], + "angle": 0, + "content": "GREW. VPNet-L achieves the advanced accuracy of rank-1 and rank-5 as shown in Tab. 4, outperforming GaitGCI [13] by \\(11.5\\%\\) and GaitGraph [45] by \\(79.7\\%\\). These experimental results demonstrate that our method effectively handles various unexpected external factors in realistic scenes, yielding effective global motion patterns in gait sequences." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.469, + 0.902 + ], + "angle": 0, + "content": "Summary. We specifically design VPNet-L to tackle the intricacies of outdoor scenes, leading to state-of-the-art performance on real-world datasets. (1) Our method introduces a unified backbone architecture designed for the extraction of global motion patterns in real-world scenarios. (2) Prompt templates convey task-related knowledge, and a dynamic transformer is subsequently employed to effectively alleviate the problem of length generalization. (3) Ex" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.305, + 0.892, + 0.334 + ], + "angle": 0, + "content": "experimental results validate the effectiveness of the proposed framework in the wild datasets." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.345, + 0.794, + 0.36 + ], + "angle": 0, + "content": "4.3. Results under in-the-lab Scenario" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.368, + 0.892, + 0.702 + ], + "angle": 0, + "content": "OUMVLP. The experimental results of VPNet-M in Tab. 5 exhibit superior performance compared to the majority of methods, underscoring its robustness and effectiveness. Notably, VPNet-M attains average accuracies on par with HSTL [50]. It is noteworthy that the accuracy of VPNet-M is further improved after excluding invalid probe sequences. CASIA-B. The experimental outcomes in Tab. 6 underscore the competitive performance of VPNet-T, surpassing other gait recognition methods. It is worth noting that, excluding the cases of identical views, VPNet-T achieved an average accuracy of over \\(90\\%\\) in cross-viewing and cross-dressing. Summary. We customize VPNet-T and VPNet-M based on data size and complexity, achieving state-of-the-art performance on in-the-lab datasets. (1) Previously, different depth networks have been designed on unified architectures are common, such as ResNet-18 [20] and ResNet-50 [20]. Our proposed VPNet architecture fills a gap in the design of network architectures for gait recognition across diverse datasets. (2) In indoor scenarios, performance has reached its peak due to the utilization of continuously improving methods. Therefore, it is expected that gait recognition will increasingly concentrate on outdoor scenarios in the future." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.711, + 0.655, + 0.727 + ], + "angle": 0, + "content": "4.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Effectiveness of core designs. We perform ablation experiments of the proposed module in Gait3D [61] and CASIA-B [58] datasets. (1) The experimental results reveal that the core design module, comprising the FTS module, prompt pool, and dynamic attention module, notably influenced cross-dressing and carrying conditions within the CASIA-B dataset. In contrast, the introduced module exhibits a more pronounced impact on Gait3D. (2) The results show that replacing the dynamic attention with the max+mean maintains competitive accuracy in CASIA-B. However, the results show a significant decrease in Gait3D, highlighting the" + }, + { + "type": "page_number", + "bbox": [ + 0.487, + 0.946, + 0.511, + 0.957 + ], + "angle": 0, + "content": "599" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.47, + 0.118 + ], + "angle": 0, + "content": "Table 7. The ablation study on Gait3D and CASIA-B are reported with rank-1 accuracy(%) excluding the identical-views cases." + }, + { + "type": "table", + "bbox": [ + 0.089, + 0.128, + 0.46, + 0.404 + ], + "angle": 0, + "content": "
MethodGait3DCASIA-B
R-1 (%)NM (%)BG (%)CL (%)
VPNet75.498.396.390.0
Analysis of each component in VPNet
- w/o FTS73.298.096.189.2
- w/o prompt72.898.096.089.1
- w/o mask73.098.396.390.0
w max+mean72.198.095.788.5
Analysis of temporal shift bottleneck
2D Conv69.798.095.786.8
3D Conv73.298.096.189.2
2D Conv + FTS74.198.196.288.2
3D Conv + FTS75.498.396.390.0
Analysis of the local length in dynamic attention
l=874.998.096.389.8
l=1675.498.196.489.8
l=3273.298.396.390.0
" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.417, + 0.42, + 0.431 + ], + "angle": 0, + "content": "effectiveness of our module in real-world scenarios." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.432, + 0.47, + 0.734 + ], + "angle": 0, + "content": "Analysis of temporal shift bottleneck. We perform an empirical analysis comparing convolution outcomes within the temporal shift bottleneck in Tab. 7. (1) The network utilizing 2D convolution experienced a noteworthy decline in performance, representing a substantial improvement over using the FTS module in conjunction with 2D convolution. These results indicate that the FTS module plays a role in acquiring global motion patterns. (2) The network utilizing 3D convolution effectively captures local motion patterns, whereas the incorporation of the FTS module into 3D convolution facilitates the extraction of global motion patterns. Analysis of the local length. Different length affects the receptive fields in dynamic attention. (1) The experimental results demonstrate that an optimal range of receptive fields \\((l = 16)\\) is essential for real data, as an excessively long receptive field \\((l = 32)\\) may introduce noise. (2) In laboratory scenarios with relatively short sequence lengths, the impact of local receptive fields is minimal. (3) The issue of training and testing inconsistency can be alleviated by incorporating local receptive fields in the real world." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Visualization of the prompt selection. We quantify the frequency of prompt template selection across various viewpoints and dress conditions on CASIA-B, as detailed in Fig. 4. The visualization results reveal variability in prompt template selection influenced by external factors, illustrating the encoding of task-relevant knowledge. (1) The statistical results show that different dressings and viewpoints have obvious differences in the frequency of prompt template selection. (2) The visualization results reveal variability in prompt template selection influenced by external factors, illustrating the encoding of task-relevant knowledge." + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.089, + 0.695, + 0.234 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.7, + 0.089, + 0.891, + 0.234 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.501, + 0.234, + 0.693, + 0.375 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.7, + 0.234, + 0.891, + 0.375 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.386, + 0.893, + 0.47 + ], + "angle": 0, + "content": "Figure 4. Histogram of prompt template selection on CASIA-B, where \"Prompt ID\", \"View ID\", and \"Type ID\" denote the index of prompt, view angle, and dressing, respectively. (a) Comparison of the selection frequency of prompt templates under cross-dressing and carrying conditions. (b)(c)(d) Comparison of prompt template selection frequency across various views and body parts." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.485, + 0.757, + 0.5 + ], + "angle": 0, + "content": "5. Conclusion and Limitations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.51, + 0.892, + 0.692 + ], + "angle": 0, + "content": "In this paper, we present a Visual Prompt Network (VPNet) for gait recognition. VPNet employs temporal shift bottleneck as the foundational module of a backbone network to extract global motion patterns and utilizes prompt engineering to adaptively select templates with corresponding prompt information tailored for different gait sequences. To enhance the robustness of global motion patterns, the relationships between these templates and global features of gait sequence are further established using dynamic transformer structures. VPNet demonstrates superior performance in both in-the-wild and in-the-lab scenarios, highlighting its significant potential in real-world applications." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.693, + 0.892, + 0.784 + ], + "angle": 0, + "content": "Limitations. Prompt learning has gained prominence in natural language processing for retraining large-scale pretrained language models, whereas the proposed network does not incorporate pre-training. In future work, we will investigate the applications of prompt engineering for large-scale gait recognition pre-training in real-world scenarios." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.8, + 0.681, + 0.816 + ], + "angle": 0, + "content": "6. Acknowledgement" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.892, + 0.9 + ], + "angle": 0, + "content": "This work was supported by the National Key R&D Program of China (2022YFC3300700), the National Natural Science Foundation of China (62331006, 62171038, 62088101, 62276031, 62276025, and 62276025), and the Fundamental Research Funds for the Central Universities." + }, + { + "type": "page_number", + "bbox": [ + 0.487, + 0.946, + 0.512, + 0.957 + ], + "angle": 0, + "content": "600" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.469, + 0.157 + ], + "angle": 0, + "content": "[1] Hyojin Bahng, Ali Jahanian, Swami Sankaranarayanan, and Phillip Isola. 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However, gait recognition in real-world scenarios is challenging due to the limitations of capturing comprehensive cross-viewing and cross-clothing data. Additionally, distractors such as occlusions, directional changes, and lingering movements further complicate the problem. The widespread application of deep learning techniques has led to the development of various potential gait recognition methods. However, these methods utilize convolutional networks to extract shared information across different views and attire conditions. Once trained, the parameters and non-linear function become constrained to fixed patterns, limiting their adaptability to various distractors in real-world scenarios. In this paper, we present a unified gait recognition framework to extract global motion patterns and develop a novel dynamic transformer to generate representative gait features. Specifically, we develop a trainable part-based prompt pool with numerous key-value pairs that can dynamically select prompt templates to incorporate into the gait sequence, thereby providing task-relevant shared knowledge information. Furthermore, we specifically design dynamic attention to extract robust motion patterns and address the length generalization issue. Extensive experiments on four widely recognized gait datasets, i.e., Gait3D, GREW, OUMVLP, and CASIA-B, reveal that the proposed method yields substantial improvements compared to current state-of-the-art approaches. + +# 1. Introduction + +Gait, as a distinct and intricate form of movement [4, 43], holds significant implications for long-distance recognition [36, 49, 60] owing to its remarkable uniqueness. However, gait recognition suffers from various complicating factors + +![](images/c4148697f59420b32b0268a2061f733ca61e398b69eb27a64c4a934cd2254fc2.jpg) +Figure 1. Performance comparison of prevailing methods and the proposed method in both real-world and laboratory scenarios. + +in real-world scenarios. Silhouette data from the same individual can exhibit significant variation depending on viewing angles and clothing conditions [44, 58], resulting in more intra-class variation than inter-class variation. In addition, potential obstructions from crowds and actions of the observed subjects [61, 63], such as turning, lingering, or stopping, may manifest within a single gait sequence. Despite the ability of human visual perception to seamlessly establish correspondences between occlusions, viewpoint changes, and object transformations, it still poses a formidable challenge for the gait recognition network. + +Learning robust motion patterns from multiple variations all at once is not a trivial task. With the widespread application of deep learning, some promising methods [7, 14, 22, 33, 35] have emerged. However, these methods preserve shared information across different viewpoints and attire conditions while discarding task-relevant knowledge + +relevant to particular conditions. Intuitively, the knowledge is crucial for the gait network to learn valuable invariances. Thus, we aim to reveal it from the following aspects: + +(i) Prompt Templates. A widely acknowledged assumption [7, 35, 54] regarding gait is that individuals maintain consistent motion patterns regardless of external factors. Central to all of these capabilities is the ability to establish associations despite occlusions, viewpoint changes, and varying object appearances. Indeed, in controlled laboratory settings marked by abundant data and well-managed conditions, stable associations tend to form readily. Conversely, addressing scenarios in the wild, constrained by limited data and influenced by obstructions and crowded environments, significantly increases the complexity of establishing stable associations. Consequently, a simple and effective approach is to provide task-relevant knowledge using a learnable prompt pool, which is expected to adaptively select prompt templates based on sequence attributes to establish stable associations under various disturbances. + +(ii) Length Generalization. Similar to natural language processing (NLP) tasks [47], gait also faces the problem of length generalization [17, 42, 55]. In particular, the majority of the most promising gait recognition methods involve training by randomly selecting a subset of the sequence and testing by extracting features from the entire sequence. Nevertheless, these methods frequently neglect the challenges presented by the longer sequence. To this end, we implement a dynamic context window mask for gait, enabling the network to focus its attention on the features within the specified window. Furthermore, we propose to establish a correlation between the localized window and the prompt templates, with the aim of emphasizing the significance of distinctive gait features within the sequence. + +Based on the above analysis, we present a comprehensive Visual Prompt Network (VPNet) for gait recognition. VPNet leverages prompt templates to augment the task-relevant information associated with the gait feature. Dynamic attention is employed to establish connections between prompt templates and local window features, enabling the network to capture crucial invariant gait features. As illustrated in Fig. 2, VPNet initially extracts features from the sampled sequence using a backbone network. These features are then compared with a trainable part-based prompt pool, with prompt templates dynamically selected and integrated into the gait sequence. The merged features are further input into the dynamic transformer to enhance the learning of global motion patterns. VPNet exhibits superior performance, especially in realistic scenarios, compared to state-of-the-art (SOTA) methods on publicly available datasets as shown in Fig. 1. A brief overview of our main contributions can be summarized as follows: + +- We introduce an innovative visual prompt that integrates key-value pairs with gait features, encoding factors such + +as viewpoint, attire, occlusion, etc. These prompt templates provide task-related information to the network, facilitating the extraction of representative gait features. + +- We design an efficient dynamic transformer with a context window mask structure to correlate prompt templates with local motion patterns, addressing the length generalization problem for gait recognition. +- We present a unified framework that yields competitive results on publicly accessible datasets, namely Gait3D [61], GREW [63], OUMVLP [44], and CASIA-B [58]. In addition, a series of rigorous ablation experiments further validate the effectiveness of our approach. + +# 2. Relate Work + +In this section, we present a review of the most relevant studies on gait recognition and prompt engineering. + +# 2.1. Gait Recognition + +Gait recognition approaches can be broadly classified into two categories based on their modeling methodology, i.e., model-based methods and appearance-based methods. + +Model-based method. Model-based approaches [2, 48, 59] aim to capture the inherent biomechanical characteristics of pedestrians. Early approaches [3, 28, 56] focused on distinguishing identities by estimating pedestrian motion parameters. However, such methods were constrained by predefined empirical points and yielded limited recognition accuracy. With the rapid advancement of deep learning, researchers have shifted their focus to extracting training data using pose estimation or Skinned Multi-Person Linear (SMPL) models. Subsequently, a well-designed network [21, 29, 30, 45, 46] is employed to further learn the gait features based on joint-based datasets. Despite substantial advancements, the efficacy of model-based methods remains constrained by the empirical design of predefined points and the estimation of results from low-quality images. + +Appearance-based method. Appearance-based methods aim to learn gait features directly from silhouette data. Previous methods [18, 37, 54] have employed an efficient approach by directly applying weighted averaging to the sequence, i.e., Gait Energy Image (GEI). These methods have achieved significant advancements across various viewpoints and clothing conditions. However, the weighted averaging of video sequence data inevitably leads to the loss of substantial motion details. To this end, current research [22, 23, 26, 32] emphasizes the utilization of video input to learn gait features in order to address this limitation. Some of the 2D convolution-based methods [7, 14] independently extract local spatial features from each frame and subsequently utilize set-based pooling techniques, i.e., MaxPooling and MeanPooling, to directly extract global temporal features from the variable-length sequence. These methods have yielded impressive experimental results, significantly + +![](images/4d6b06ac783d6230c2558fcd88e7ae5899e462a6f46d0da2e44423c9e8fead25.jpg) +Figure 2. Overview of the proposed Visual Prompt Network (VPNet), where "HP" denotes the Horizontal Pooling. (a) VPNet incorporates the FTS module into the backbone based on ResNet, focusing on the extraction of global motion patterns without any extra parameters. (b) VPNet utilizes a trainable prompt pool comprising numerous key-value pairs, dynamically selecting prompt templates and integrating them into gait features to provide task-relevant knowledge. (c) Three different loss functions are combined for supervised network training. + +advancing the field of gait recognition. However, gait represents a coordinated whole-body motion process, and processing the features of each frame individually disregards the preservation of robust local motion patterns, which are essential for accurate gait information. Consequently, some 3D convolution-based methods [6, 12, 33, 35, 36] proposed to local spatio-temporal features from adjacent frame images using a shared 3D convolution kernel, while further modeling the unfixed length sequence to obtain robust global features. The approach presented in this paper falls within the category of appearance-based methods. In contrast to previous methods, we aim to explore further improvements within the deep network structure. + +# 2.2. Prompt Engineering + +Prompt Engineering [5, 9, 40] is a methodology that involves the incorporation of additional information as a condition in the inference process using a model. It has gained considerable popularity [16, 19, 41] in the field of natural language processing (NLP) due to its ability to integrate task-specific cues for each individual task. In recent years, there has been a notable surge in prompt-based research [31, 38, 57, 62] within the field of computer vision. It integrates visual and linguistic tasks, using NLP to reference or define visual concepts. To address inherent disparities in information densities between visual and NLP tasks, researchers have developed methodologies [1, 24, 27] that involve pre-filling model inputs with adaptive parameters. These parameters, functioning as prompts, can be finetuned through gradient-based optimization, thereby facilitating their contribution to visual tasks. Specifically, VPT [27] and VP [1] load a set of trainable prompts into the model inputs while maintaining the architectural integrity of the core network. This strategic implementation consis + +tently yields noteworthy performance improvements across a range of downstream tasks. In contrast, DAM-VP [24] adopts a divide-and-conquer scheme, segregating datasets associated with downstream tasks into smaller, homogeneous subsets. Each subset is endowed with its distinct cue, and subsequently, optimization is carried out independently for each subset. We extend the concept of prompt learning from prior research [52, 53], utilizing it to provide task-related information and extract robust motion patterns. + +# 3. Methodology + +In this section, we present the overall architecture of the proposed Visual Prompt Network (VPNet) for gait and provide an in-depth explanation of the motivation in Sec. 3.1. We then provide a comprehensive elucidation of the backbone architecture in Sec. 3.2. Finally, we present the specific structure of the dynamic transformer in Sec. 3.3. + +# 3.1. Preliminary and Motivation + +A vanilla vision gait recognition framework typically comprises two essential components: the backbone $\mathcal{B}$ and the head $\mathcal{H}$ . Formally, given a gait silhouette sequence $X \in \mathbb{R}^{T \times H \times W}$ , where $H$ , $W$ , and $T$ represent the height, width, and number of frames, respectively. Firstly, the gait sequence is fed into the backbone to extract the local motion patterns, followed by its passage through the head to derive the global motion patterns. The extraction of gait features can be briefly represented as + +$$ +\boldsymbol {F} = \mathcal {H} (\mathcal {B} (\boldsymbol {X})), \tag {1} +$$ + +where $\pmb{F} \in \mathbb{R}^{P \times C}$ denotes the output features, $P$ is the number of horizontal slices, and $C$ is the feature dimension. Most of the existing research [8, 15, 33] places a significant + +focus on improving the efficiency of the backbone component for extracting complex spatio-temporal features. Despite their progress, these approaches struggle to address the challenges of gait recognition in real-world scenarios. To this end, as shown in Fig. 2, we intend to introduce a comprehensive framework for gait recognition. In particular, it involves utilizing a common backbone to directly extract global motion patterns, designing a trainable prompt pool $\mathcal{P}$ that adaptively selects task-relevant templates to concatenate with the original gait features, and employing dynamic attention to learn representative gait features, i.e., + +$$ +\boldsymbol {F} = \mathcal {H} (\text {c o n c a t} [ \overbrace {\mathcal {P} (\boldsymbol {B} (\boldsymbol {X}))} ^ {\text {p r o m p t t e m p l a t e s}}, \boldsymbol {B} (\boldsymbol {X}) ]), \tag {2} +$$ + +where concat represents the concatenation along the temporal dimension. The prompt templates, functioning as trainable embeddings, essentially encode the gait task. These templates include various aspects such as viewpoint, attire, carrying conditions, occlusion, and so on. They provide instructions to the model, specifying the task it executes. + +# 3.2. Backbone Architecture + +We utilize the bottleneck structure in ResNet [20] to establish the backbone for gait recognition and introduce a plug-and-play gait temporal-shift operation [34, 36], coupled with a 3D convolutional network, as the foundational motion pattern extraction element within the bottleneck. By modifying the depth of the backbone network, we sequentially construct three models with distinct parameters in Sec. 4.1, namely VPNet-T, VPNet-M, and VPNet-L. + +Temporal Shift Bottleneck. 3D convolution is commonly used in gait recognition tasks due to its proficiency in local spatio-temporal aggregation. However, its ability to be used in real-world scenarios with numerous long silhouette sequences may pose certain challenges. Inspired by temporal shift operation [34, 36], as shown in Fig. 2, we design a novel Forward cycle Temporal Shift (FTS) module for the gait recognition network. Considering that forward walking is the predominant daily practice, whereas backward walking is less frequent, we employ a forward cyclic shifting approach along the temporal dimension instead of the zero padding technique used in TSCov [34]. Specifically, the FTS module divides the features $f \in \mathbb{R}^{C \times T \times H \times W}$ of each pixel into four segments. It only cyclically shifts the first segment $f_{1} \in \mathbb{R}^{\frac{C}{4} \times T \times H \times W}$ along the temporal dimension. The extraction of motion patterns with a global receptive field can be achieved by incorporating the FTS module before 3D convolution, without the additional parameters. + +# 3.3. Dynamic Transformer + +We present a dynamic transformer as an integral head layer $\mathcal{H}$ in the network architecture. As shown in Fig. 2, it employs prompt engineering to provide task-specific shared + +![](images/40066a8a0585d0dd869515c99687cf014b366d33acd4f0a9d9b10dd74b6a1faf.jpg) +Figure 3. The dynamic attention architecture. We utilize both prompt templates and gait sequence as inputs, employing the Context Window Mask to overcome the length generalization problem. + +knowledge information for gait sequence and introduces a dynamic context window mask to effectively alleviate the problem of length generalization in real-world scenarios. + +Part-based Prompt Pool. Prompt learning has emerged as a methodology in NLP, and its application in gait recognition is motivated by three main considerations. Firstly, the adaptable visual prompt templates facilitate the integration of shared insights concerning the gait sequence. Secondly, the shared knowledge seamlessly incorporates into the gait sequence as a global feature through a flexible plug-and-play process. Finally, specific visual prompts are associated with salient features within the gait sequence. To address this, we introduce a part-based prompt pool with shared parameters, delivering task-specific information. The $j$ -th prompt pool can be defined as + +$$ +\mathcal {P} _ {j} = \left\{\boldsymbol {P} _ {j, 1}, \boldsymbol {P} _ {j, 2}, \dots , \boldsymbol {P} _ {j, N} \mid \boldsymbol {P} _ {j, i} = \left(k _ {j, i}, v _ {j, i}\right) \right\}, \tag {3} +$$ + +where $\{\mathcal{P}_j|j = 1,\dots,P\}$ is the $j$ -th prompt pool, $P$ denotes the number of horizontal slices, $P_{j,i}$ is the $i$ -th prompt token, $N$ denotes the number of trainable tokens in the prompt pool, $k_{j,i}\in \mathbb{R}^{C}$ and $v_{j,i}\in \mathbb{R}^C$ represent the key and value, respectively. We utilize key-value pairs as prompt tokens, matching the key with the input gait sequence. Following this alignment, the top- $k$ values are selected as prompt templates based on their similarity, and these chosen templates are smoothly integrated with the original sequence along the temporal dimension. Specifically, given a gait sequence feature $\pmb {S}\in \mathbb{R}^{P\times T\times C}$ , for the $j$ -th part sequence feature $S_{j}\in \mathbb{R}^{T\times C}$ , we first compute the average feature along the temporal dimension $\bar{S}_j\in \mathbb{R}^C$ and then perform similarity matching with key embeddings in the prompt pool to select the top- $k$ values with the highest similarity. Denote $\mathcal{R}$ as the function to lookup the top- $k$ keys in the ranked list, the + +selection process for the key can be represented as + +$$ +\mathcal {K} _ {j} = \mathcal {R} \left(\frac {\bar {S} _ {j} \otimes k _ {j , i}}{\| \bar {S} _ {j} \| \otimes \| k _ {j , i} \|}\right), \tag {4} +$$ + +where $\mathcal{K}_j$ denotes a list of sets, generating a top- $k$ index that is linked to the query sequence, and $\otimes$ represents matrix multiplication. The index value is employed to retrieve $k$ values, denoted as $V_j = \{v_{j,\kappa}|\kappa \in \mathcal{K}_s\}$ . Subsequently, we combine the indexed value $V_j$ with the feature $S_j$ , i.e., + +$$ +S _ {j} ^ {*} = \operatorname {c o n c a t} \left[ V _ {j}, S _ {j} \right], \tag {5} +$$ + +where concat represents the concatenation of prompt templates and gait vectors along the temporal dimension. The resulting gait sequence, denoted as $S_{j}^{*} \in \mathbb{R}^{(T + k) \times C}$ , integrates the prompt information, $(T + k)$ is the length of the gait sequence, and $k$ is empirically set to 6. Similar to the codebook collapse issue faced in VQ-VAE [10, 39], there exists a risk that all index $\mathcal{K}_{j}$ map to a limited set of prompt templates. To address this, we implement a randomized restart strategy: the key vector in the prompt pool is randomly reset to one of the encoder outputs if its average utilization falls below a predefined threshold $(\tau = 0.001)$ . + +Dynamic Attention. As shown in Fig. 3, we propose to extract global motion patterns for each body part based on prompt templates using the multi-head attention [11, 47]. Formally, the $j$ -th part sequence feature $S_{j}^{*}$ is mapped as query $\pmb{Q}$ , key $\pmb{K}$ and value $\pmb{V}$ . The mapping process is as + +$$ +\boldsymbol {Q} = S _ {j} ^ {*} W ^ {Q}, \boldsymbol {K} = S _ {j} ^ {*} W ^ {K}, \boldsymbol {V} = S _ {j} ^ {*} W ^ {V}, \tag {6} +$$ + +where $W^{Q} \in \mathbb{R}^{C \times h \cdot C'}$ , $W^{K} \in \mathbb{R}^{C \times h \cdot C'}$ and $W^{V} \in \mathbb{R}^{C \times h \cdot C'}$ are learnable parameters, $h$ denotes the number of heads, and $C'$ represents the feature dimension of each head. Then, we employ $Q$ and $K$ to establish similarity relationships between each frame. It is notable that prompt templates can be associated with the features of each frame, thereby giving rise to the establishment of correlations, i.e., + +$$ +\operatorname {s i m} (\boldsymbol {Q}, \boldsymbol {K}) = \boldsymbol {Q} \boldsymbol {K} ^ {T}, \tag {7} +$$ + +where $\operatorname{sim}(Q, K)$ denotes the similarity matrix. Similar to natural language processing, gait recognition also faces the challenge of length generalization [17, 42, 55]. During training, a limited number of frames are randomly selected, but during testing, the longer sequence can distract the attention of the network. To effectively utilize the shared information provided by prompt templates in discerning distinctive global motion patterns within varying length sequences, we introduce a context window mask structure. This design dynamically establishes connections between prompt templates and gait sequence. As depicted in Fig. 3, + +the architecture comprises a global branch on the left and a local branch on the right. The global branch allows each feature in the sequence to focus on establishing relationships with prompt templates, while the local branch fosters associations between each feature and other features within a defined local length range. Features outside of these two branches are excluded from the attention process, i.e., + +$$ +\operatorname {A t t} (\boldsymbol {Q}, \boldsymbol {K}, \boldsymbol {V}) = \operatorname {s o f t m a x} \left(\frac {\operatorname {s i m} (\boldsymbol {Q} , \boldsymbol {K})}{\sqrt {C ^ {\prime}}} \oplus \mathcal {M}\right) \boldsymbol {V}, \tag {8} +$$ + +where $\sqrt{C'}$ is the scaling factor, $\mathcal{M}$ is the dynamic context window mask, and $\oplus$ denotes element-wise sum operation. + +# 3.4. Learning Details + +In this work, we introduce three loss functions during training: triplet loss $\mathcal{L}_{tp}$ , cross-entropy loss $\mathcal{L}_{\text{cet}}$ , and cosine embedding loss $\mathcal{L}_{\text{cem}}$ in Fig. 2. The $\mathcal{L}_{tp}$ and $\mathcal{L}_{\text{cet}}$ serve to supervise part-based features individually, while the $\mathcal{L}_{\text{cem}}$ is applied to supervise the key embedding $(k_{j,i})$ within the prompt pool. $\mathcal{L}_{\text{cem}}$ requires that the selected key embedding be closely related to the query sequence $\bar{S}_i$ , i.e., + +$$ +\mathcal {L} _ {c e m} = \underset {\kappa \in \mathcal {K} _ {j}} {\arg \min } \sum_ {i = 1} ^ {P} \frac {- 1}{N _ {c e m}} \left(\frac {\bar {S} _ {i} \otimes k _ {j , \kappa}}{\| \bar {S} _ {i} \| \otimes \| k _ {j , \kappa} \|}\right), \tag {9} +$$ + +where $N_{cem}$ is a positive integer obtained by multiplying the batch size with the number of parts. In each training step, we adhere to the previously described strategy to select $\kappa_{s}$ . The selected prompt templates are then merged with gait sequence vectors and fed into the dynamic transformer and BNNeck [15] to extract representative gait features. In general, the training process involves the use of a combined loss following the end-to-end method, i.e., + +$$ +\mathcal {L} _ {s u m} = \mathcal {L} _ {t p} + \alpha \mathcal {L} _ {c e m} + \beta \mathcal {L} _ {c e t}, \tag {10} +$$ + +where $\alpha$ and $\beta$ are the hyper-parameters to balance the combined loss, $\alpha$ is empirically set to 0.01 and $\beta$ is set to 0.3. + +# 4. Experiments + +# 4.1. Datasets and Implementation Details + +The gait datasets are divided into two subsets, i.e., in-the-wild and in-the-lab, distinguished by their respective collection environments in Tab. 1. A standardized preprocessing procedure [7] is uniformly applied to these datasets, and the data sizes used in this paper are all resized to $64 \times 64$ . + +In-the-wild datasets. In-the-wild datasets introduce numerous unforeseen challenges, such as occlusions, clothing changes, viewpoint variations, and carrying conditions. Pedestrians may also pause or alter their walking patterns. These datasets are essential benchmarks for evaluating gait recognition methods under various external disturbances. + +Table 1. Comparison of the specific values of the adopted datasets and corresponding parameters. Where “#Ide., #Seq., #Cam.” refer to numbers of identities, sequences, and cameras respectively. Additionally, “lr, dr, wd” denote learning rate, decay rate, and weight decay. + +
EnvironmentDatasetsTrainTest# Cam.Batch SizeOptimizerScheduler
# Ide.# Seq.# Ide.# Seq.step sizeepochs
In-the-wildGait3D [61]3,00018,9401,0006,369Diverse(32, 4)SGD lr = 0.12080
GREW [63]20,000102,8876,00024,000Diverse(64, 4)50200
In-the-labOUMVLP [44]5,153144,2845,154144,31214(32, 8)dr = 0.150200
CASIA-B [58]748,140505,50011(8, 16)wd = 0.00051040
+ +Table 2. The detailed structure of the backbone in VPNet-L, where FTSCov denotes the combined of FTS module and convolution. + +
LayerOutput size
conv13 × 3 × 3, 64, stride(1,1,1)T × H × W
stage1[1 × 1 × 1, 64, (0,0,0)FTSCnv, 64, (1,1,1)1 × 1 × 1, 64, (0,0,0)] × 3T × H × W
stage2[1 × 1 × 1, 128, (0,0,0)FTSCnv, 128, (1,2,2)1 × 1 × 1, 128, (0,0,0)] × 4T × H/2 × W/2
stage3[1 × 1 × 1, 256, (0,0,0)FTSCnv, 256, (1,2,2)1 × 1 × 1, 256, (0,0,0)] × 6T × H/4 × W/4
stage4[1 × 1 × 1, 512, (0,0,0)FTSCnv, 512, (1,1,1)1 × 1 × 1, 512, (0,0,0)] × 3T × H/4 × W/4
+ +We evaluate our method on the widely adopted Gait3D [61] and GREW [63] datasets in Tab. 1. To enhance the robustness of our model, we employ three data augmentation techniques: rotation, flipping, and perspective. We conduct training using VPNet-L on both Gait3D and GREW datasets and report rank-1 (\%) and rank-5 (\%) accuracy. + +In-the-lab datasets. In-the-lab datasets encompass various controllable conditions, including camera angles, predetermined walking routes, and dress variations. These datasets play a pivotal role in evaluating the ability of the gait network to handle cross-viewing and cross-dressing scenarios. We select the well-established OUMVLP [44] and CASIA-B [58] datasets to evaluate our approach in Tab. 1. Specifically, the OUMVLP provides an abundance of cross-viewing data, while the CASIA-B offers valuable cross-dressing data. Limited datasets, particularly those obtained from laboratory scenarios, may result in overfitting if the network parameters are excessively large. Therefore, we employ VPNet-M for training on OUMVLP and VPNet-T for training on CASIA-B. We present the rank-1 $(\%)$ accuracy for all perspectives, excluding the identical-view cases. + +Implementation Details. We establish the network parameters based on the dataset scale and complexity, as outlined in Tab. 1. The batch size is represented as $(S, T)$ , indicating that each mini-batch involves $S$ subjects. For each subject, $T$ sequences are sampled, and within each sequence, a random selection of 20 to 40 frames is chosen following + +Table 3. The performance comparisons on Gait3D are reported with rank-1 and rank-5 accuracy (\%). + +
MethodsPublicationrank-1 (%)rank-5 (%)
GaitSet [7]AAAI 201936.758.3
GaitPart [14]CVPR 202028.247.6
GLN [22]ECCV 202031.452.9
GaitGL [33]ICCV 202129.748.5
CSTL [25]ICCV 202111.719.2
SMPLGait [61]CVPR 202246.364.5
GaitBase [15]CVPR 202365.6-
GaitGCI [13]CVPR 202350.368.5
DANet [35]CVPR 202348.069.7
HSTL [50]ICCV 202361.376.3
DyGait [51]ICCV 202366.380.8
VPNet-L-75.487.1
+ +Table 4. The performance comparisons on GREW are reported with rank-1 and rank-5 accuracy $(\%)$ . + +
MethodsPublicationrank-1 (%)rank-5 (%)
GaitSet[7]AAAI 201946.363.6
GaitPart [14]CVPR 202044.060.7
GaitGL [33]ICCV 202147.363.6
GaitGraph [45]ICIP 20211.33.5
GaitBase [15]CVPR 202360.1-
GaitGCI [13]CVPR 202368.580.8
HSTL [50]ICCV 202362.776.6
DyGait [51]ICCV 202371.483.2
VPNet-L-80.089.4
+ +DANet [35]. The optimization strategy employs Stochastic Gradient Descent (SGD) with an initial learning rate of 0.1, and each epoch consists of 1000 iterations. The learning rate undergoes periodic reduction based on the step size in Tab. 1, with a decay rate of 0.1. The entire model is built by sequentially stacking the temporal shift bottleneck in Sec. 3.2. We construct three models with distinct parameters, namely VPNet-T, VPNet-M, and VPNet-L, by modifying the depth of the backbone network. Specifically, VPNet-T is composed of three stages, each comprising a specific number of layers (1, 1, 1) and channels (64, 128, 256). In contrast, both VPNet-M and VPNet-L consist of four stages with channel configurations (64, 128, 256, 512) in Tab. 2. VPNet-M employs a layer stack of (2, 2, 2, 2), while VPNet-L utilizes a stack of layers (3, 4, 6, 3). + +Table 5. Rank-1 accuracy (%) on OUMVLP under all view angles, excluding the identical-views cases. + +
MethodProbe ViewMean
0°15°30°45°60°75°90°180°195°210°225°240°255°270°
GaitSet [7]79.587.989.990.288.188.787.881.786.789.089.387.287.886.287.1
GaitPart [14]82.688.990.891.089.789.989.585.288.190.090.189.089.188.288.7
GLN [22]83.890.091.091.290.390.089.485.389.190.590.689.689.388.589.2
GaitGL [33]84.990.291.191.591.190.890.388.588.690.390.489.689.588.889.7
GaitBase [15]--------------90.0
GaitGCI [13]91.292.392.692.793.092.392.192.091.891.992.692.391.491.692.1
DANet [35]87.791.391.691.891.791.491.190.490.390.790.990.590.389.990.7
HSTL [50]91.492.992.793.092.992.592.592.792.392.192.392.291.891.892.4
VPNet-M91.993.092.492.793.292.592.392.992.491.992.192.591.991.992.4
+ +Table 6. The performance comparisons on CASIA-B are reported with rank-1 accuracy $(\%)$ , excluding the identical-view cases. + +
MethodsPublicationNMBGCLMean
GaitSet[7]AAAI 201995.087.270.484.2
GaitPart[14]CVPR 202096.291.578.788.8
GLN [22]ECCV 202096.994.077.589.5
MT3D [32]MM 202096.793.081.590.4
GaitGL [33]ICCV 202197.494.583.691.8
GaitBase [15]CVPR 202397.694.077.489.8
GaitGCI-T [13]CVPR 202397.995.086.493.1
DANet [35]CVPR 202398.095.989.994.6
HSTL [50]ICCV 202398.195.988.994.3
DyGait [51]ICCV 202398.496.287.894.1
VPNet-T-98.396.390.094.9
+ +# 4.2. Results under in-the-wild Scenario + +Gait3D. VPNet-L demonstrates superior performance in terms of rank-1 and rank-5 accuracy in Tab. 3, surpassing state-of-the-art methods. Notably, it exhibits a $9.1\%$ improvement over DyGait [51], a silhouette-based approach, and a remarkable $29.1\%$ improvement compared to SMPL-Gait [61], a multimodal method. These experimental results underscore the efficacy of our method in extracting robust features in the presence of diverse external disturbances. + +GREW. VPNet-L achieves the advanced accuracy of rank-1 and rank-5 as shown in Tab. 4, outperforming GaitGCI [13] by $11.5\%$ and GaitGraph [45] by $79.7\%$ . These experimental results demonstrate that our method effectively handles various unexpected external factors in realistic scenes, yielding effective global motion patterns in gait sequences. + +Summary. We specifically design VPNet-L to tackle the intricacies of outdoor scenes, leading to state-of-the-art performance on real-world datasets. (1) Our method introduces a unified backbone architecture designed for the extraction of global motion patterns in real-world scenarios. (2) Prompt templates convey task-related knowledge, and a dynamic transformer is subsequently employed to effectively alleviate the problem of length generalization. (3) Ex + +experimental results validate the effectiveness of the proposed framework in the wild datasets. + +# 4.3. Results under in-the-lab Scenario + +OUMVLP. The experimental results of VPNet-M in Tab. 5 exhibit superior performance compared to the majority of methods, underscoring its robustness and effectiveness. Notably, VPNet-M attains average accuracies on par with HSTL [50]. It is noteworthy that the accuracy of VPNet-M is further improved after excluding invalid probe sequences. CASIA-B. The experimental outcomes in Tab. 6 underscore the competitive performance of VPNet-T, surpassing other gait recognition methods. It is worth noting that, excluding the cases of identical views, VPNet-T achieved an average accuracy of over $90\%$ in cross-viewing and cross-dressing. Summary. We customize VPNet-T and VPNet-M based on data size and complexity, achieving state-of-the-art performance on in-the-lab datasets. (1) Previously, different depth networks have been designed on unified architectures are common, such as ResNet-18 [20] and ResNet-50 [20]. Our proposed VPNet architecture fills a gap in the design of network architectures for gait recognition across diverse datasets. (2) In indoor scenarios, performance has reached its peak due to the utilization of continuously improving methods. Therefore, it is expected that gait recognition will increasingly concentrate on outdoor scenarios in the future. + +# 4.4. Ablation Study + +Effectiveness of core designs. We perform ablation experiments of the proposed module in Gait3D [61] and CASIA-B [58] datasets. (1) The experimental results reveal that the core design module, comprising the FTS module, prompt pool, and dynamic attention module, notably influenced cross-dressing and carrying conditions within the CASIA-B dataset. In contrast, the introduced module exhibits a more pronounced impact on Gait3D. (2) The results show that replacing the dynamic attention with the max+mean maintains competitive accuracy in CASIA-B. However, the results show a significant decrease in Gait3D, highlighting the + +Table 7. The ablation study on Gait3D and CASIA-B are reported with rank-1 accuracy(%) excluding the identical-views cases. + +
MethodGait3DCASIA-B
R-1 (%)NM (%)BG (%)CL (%)
VPNet75.498.396.390.0
Analysis of each component in VPNet
- w/o FTS73.298.096.189.2
- w/o prompt72.898.096.089.1
- w/o mask73.098.396.390.0
w max+mean72.198.095.788.5
Analysis of temporal shift bottleneck
2D Conv69.798.095.786.8
3D Conv73.298.096.189.2
2D Conv + FTS74.198.196.288.2
3D Conv + FTS75.498.396.390.0
Analysis of the local length in dynamic attention
l=874.998.096.389.8
l=1675.498.196.489.8
l=3273.298.396.390.0
+ +effectiveness of our module in real-world scenarios. + +Analysis of temporal shift bottleneck. We perform an empirical analysis comparing convolution outcomes within the temporal shift bottleneck in Tab. 7. (1) The network utilizing 2D convolution experienced a noteworthy decline in performance, representing a substantial improvement over using the FTS module in conjunction with 2D convolution. These results indicate that the FTS module plays a role in acquiring global motion patterns. (2) The network utilizing 3D convolution effectively captures local motion patterns, whereas the incorporation of the FTS module into 3D convolution facilitates the extraction of global motion patterns. Analysis of the local length. Different length affects the receptive fields in dynamic attention. (1) The experimental results demonstrate that an optimal range of receptive fields $(l = 16)$ is essential for real data, as an excessively long receptive field $(l = 32)$ may introduce noise. (2) In laboratory scenarios with relatively short sequence lengths, the impact of local receptive fields is minimal. (3) The issue of training and testing inconsistency can be alleviated by incorporating local receptive fields in the real world. + +Visualization of the prompt selection. We quantify the frequency of prompt template selection across various viewpoints and dress conditions on CASIA-B, as detailed in Fig. 4. The visualization results reveal variability in prompt template selection influenced by external factors, illustrating the encoding of task-relevant knowledge. (1) The statistical results show that different dressings and viewpoints have obvious differences in the frequency of prompt template selection. (2) The visualization results reveal variability in prompt template selection influenced by external factors, illustrating the encoding of task-relevant knowledge. + +![](images/3704d89421692a06a39f625abf32905a6169f473529097de10548acb6be53565.jpg) + +![](images/43c5766c8690ff12d55282dd874e852657f6d820fbb0a853d561a0d7b7168bbf.jpg) + +![](images/cca979bd97cbb5cd029a88c8aceb1d22ab168a37de0e15cc5e72a42aa4df3486.jpg) +Figure 4. Histogram of prompt template selection on CASIA-B, where "Prompt ID", "View ID", and "Type ID" denote the index of prompt, view angle, and dressing, respectively. (a) Comparison of the selection frequency of prompt templates under cross-dressing and carrying conditions. (b)(c)(d) Comparison of prompt template selection frequency across various views and body parts. + +![](images/5f9c5c739ab926220d8f36bf673baaa3f31f7ad16cc30da6851ebff4ea7e96bb.jpg) + +# 5. Conclusion and Limitations + +In this paper, we present a Visual Prompt Network (VPNet) for gait recognition. VPNet employs temporal shift bottleneck as the foundational module of a backbone network to extract global motion patterns and utilizes prompt engineering to adaptively select templates with corresponding prompt information tailored for different gait sequences. To enhance the robustness of global motion patterns, the relationships between these templates and global features of gait sequence are further established using dynamic transformer structures. VPNet demonstrates superior performance in both in-the-wild and in-the-lab scenarios, highlighting its significant potential in real-world applications. + +Limitations. Prompt learning has gained prominence in natural language processing for retraining large-scale pretrained language models, whereas the proposed network does not incorporate pre-training. In future work, we will investigate the applications of prompt engineering for large-scale gait recognition pre-training in real-world scenarios. + +# 6. Acknowledgement + +This work was supported by the National Key R&D Program of China (2022YFC3300700), the National Natural Science Foundation of China (62331006, 62171038, 62088101, 62276031, 62276025, and 62276025), and the Fundamental Research Funds for the Central Universities. + +# References + +[1] Hyojin Bahng, Ali Jahanian, Swami Sankaranarayanan, and Phillip Isola. Exploring visual prompts for adapting large-scale models. arXiv preprint arXiv:2203.17274, 2022. 3 +[2] A.F. Bobick and A.Y. Johnson. Gait recognition using static, activity-specific parameters. In CVPR, pages I-I, 2001. 2 +[3] Robert Bodor, Andrew Drenner, Duc Fehr, Osama Masoud, and Nikolaos Papanikolopoulos. View-independent human motion classification using image-based reconstruction. Image Vision Comput., 27(8):1194-1206, 2009. 2 +[4] Dennis M Bramble and David R Carrier. Running and breathing in mammals. 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However, gait recognition in real-world scenarios is challenging due to the limitations of capturing comprehensive cross-viewing and cross-clothing data. Additionally, distractors such as occlusions, directional changes, and lingering movements further complicate the problem. The widespread application of deep learning techniques has led to the development of various potential gait recognition methods. However, these methods utilize convolutional networks to extract shared information across different views and attire conditions. Once trained, the parameters and non-linear function become constrained to fixed patterns, limiting their adaptability to various distractors in real-world scenarios. In this paper, we present a unified gait recognition framework to extract global motion patterns and develop a novel dynamic transformer to generate representative gait features. Specifically, we develop a trainable part-based prompt pool with numerous key-value pairs that can dynamically select prompt templates to incorporate into the gait sequence, thereby providing task-relevant shared knowledge information. Furthermore, we specifically design dynamic attention to extract robust motion patterns and address the length generalization issue. Extensive experiments on four widely recognized gait datasets, i.e., Gait3D, GREW, OUMVLP, and CASIA-B, reveal that the proposed method yields substantial improvements compared to current state-of-the-art approaches." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 624, + 128, + 636 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 624, + 128, + 636 + ], + "spans": [ + { + "bbox": [ + 47, + 624, + 128, + 636 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 644, + 287, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 644, + 287, + 693 + ], + "spans": [ + { + "bbox": [ + 46, + 644, + 287, + 693 + ], + "type": "text", + "content": "Gait, as a distinct and intricate form of movement [4, 43], holds significant implications for long-distance recognition [36, 49, 60] owing to its remarkable uniqueness. However, gait recognition suffers from various complicating factors" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 310, + 228, + 545, + 459 + ], + "blocks": [ + { + "bbox": [ + 310, + 228, + 545, + 459 + ], + "lines": [ + { + "bbox": [ + 310, + 228, + 545, + 459 + ], + "spans": [ + { + "bbox": [ + 310, + 228, + 545, + 459 + ], + "type": "image", + "image_path": "c4148697f59420b32b0268a2061f733ca61e398b69eb27a64c4a934cd2254fc2.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 468, + 546, + 491 + ], + "lines": [ + { + "bbox": [ + 305, + 468, + 546, + 491 + ], + "spans": [ + { + "bbox": [ + 305, + 468, + 546, + 491 + ], + "type": "text", + "content": "Figure 1. Performance comparison of prevailing methods and the proposed method in both real-world and laboratory scenarios." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 506, + 547, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 506, + 547, + 639 + ], + "spans": [ + { + "bbox": [ + 304, + 506, + 547, + 639 + ], + "type": "text", + "content": "in real-world scenarios. Silhouette data from the same individual can exhibit significant variation depending on viewing angles and clothing conditions [44, 58], resulting in more intra-class variation than inter-class variation. In addition, potential obstructions from crowds and actions of the observed subjects [61, 63], such as turning, lingering, or stopping, may manifest within a single gait sequence. Despite the ability of human visual perception to seamlessly establish correspondences between occlusions, viewpoint changes, and object transformations, it still poses a formidable challenge for the gait recognition network." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "type": "text", + "content": "Learning robust motion patterns from multiple variations all at once is not a trivial task. With the widespread application of deep learning, some promising methods [7, 14, 22, 33, 35] have emerged. However, these methods preserve shared information across different viewpoints and attire conditions while discarding task-relevant knowledge" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 140, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 140, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 140, + 712 + ], + "type": "text", + "content": "*Corresponding Authors" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 297, + 749, + 313, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 297, + 749, + 313, + 757 + ], + "spans": [ + { + "bbox": [ + 297, + 749, + 313, + 757 + ], + "type": "text", + "content": "593" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 108 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 108 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 108 + ], + "type": "text", + "content": "relevant to particular conditions. Intuitively, the knowledge is crucial for the gait network to learn valuable invariances. Thus, we aim to reveal it from the following aspects:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 109, + 288, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 109, + 288, + 300 + ], + "spans": [ + { + "bbox": [ + 46, + 109, + 288, + 300 + ], + "type": "text", + "content": "(i) Prompt Templates. A widely acknowledged assumption [7, 35, 54] regarding gait is that individuals maintain consistent motion patterns regardless of external factors. Central to all of these capabilities is the ability to establish associations despite occlusions, viewpoint changes, and varying object appearances. Indeed, in controlled laboratory settings marked by abundant data and well-managed conditions, stable associations tend to form readily. Conversely, addressing scenarios in the wild, constrained by limited data and influenced by obstructions and crowded environments, significantly increases the complexity of establishing stable associations. Consequently, a simple and effective approach is to provide task-relevant knowledge using a learnable prompt pool, which is expected to adaptively select prompt templates based on sequence attributes to establish stable associations under various disturbances." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 301, + 287, + 469 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 301, + 287, + 469 + ], + "spans": [ + { + "bbox": [ + 46, + 301, + 287, + 469 + ], + "type": "text", + "content": "(ii) Length Generalization. Similar to natural language processing (NLP) tasks [47], gait also faces the problem of length generalization [17, 42, 55]. In particular, the majority of the most promising gait recognition methods involve training by randomly selecting a subset of the sequence and testing by extracting features from the entire sequence. Nevertheless, these methods frequently neglect the challenges presented by the longer sequence. To this end, we implement a dynamic context window mask for gait, enabling the network to focus its attention on the features within the specified window. Furthermore, we propose to establish a correlation between the localized window and the prompt templates, with the aim of emphasizing the significance of distinctive gait features within the sequence." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 470, + 287, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 470, + 287, + 685 + ], + "spans": [ + { + "bbox": [ + 46, + 470, + 287, + 685 + ], + "type": "text", + "content": "Based on the above analysis, we present a comprehensive Visual Prompt Network (VPNet) for gait recognition. VPNet leverages prompt templates to augment the task-relevant information associated with the gait feature. Dynamic attention is employed to establish connections between prompt templates and local window features, enabling the network to capture crucial invariant gait features. As illustrated in Fig. 2, VPNet initially extracts features from the sampled sequence using a backbone network. These features are then compared with a trainable part-based prompt pool, with prompt templates dynamically selected and integrated into the gait sequence. The merged features are further input into the dynamic transformer to enhance the learning of global motion patterns. VPNet exhibits superior performance, especially in realistic scenarios, compared to state-of-the-art (SOTA) methods on publicly available datasets as shown in Fig. 1. A brief overview of our main contributions can be summarized as follows:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": "- We introduce an innovative visual prompt that integrates key-value pairs with gait features, encoding factors such" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 313, + 72, + 545, + 108 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 72, + 545, + 108 + ], + "spans": [ + { + "bbox": [ + 313, + 72, + 545, + 108 + ], + "type": "text", + "content": "as viewpoint, attire, occlusion, etc. These prompt templates provide task-related information to the network, facilitating the extraction of representative gait features." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 109, + 545, + 216 + ], + "type": "list", + "angle": 0, + "index": 8, + "blocks": [ + { + "bbox": [ + 306, + 109, + 545, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 109, + 545, + 156 + ], + "spans": [ + { + "bbox": [ + 306, + 109, + 545, + 156 + ], + "type": "text", + "content": "- We design an efficient dynamic transformer with a context window mask structure to correlate prompt templates with local motion patterns, addressing the length generalization problem for gait recognition." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 156, + 545, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 156, + 545, + 216 + ], + "spans": [ + { + "bbox": [ + 306, + 156, + 545, + 216 + ], + "type": "text", + "content": "- We present a unified framework that yields competitive results on publicly accessible datasets, namely Gait3D [61], GREW [63], OUMVLP [44], and CASIA-B [58]. In addition, a series of rigorous ablation experiments further validate the effectiveness of our approach." + } + ] + } + ], + "index": 7 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 225, + 386, + 238 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 225, + 386, + 238 + ], + "spans": [ + { + "bbox": [ + 306, + 225, + 386, + 238 + ], + "type": "text", + "content": "2. Relate Work" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 246, + 545, + 270 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 246, + 545, + 270 + ], + "spans": [ + { + "bbox": [ + 306, + 246, + 545, + 270 + ], + "type": "text", + "content": "In this section, we present a review of the most relevant studies on gait recognition and prompt engineering." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 276, + 408, + 289 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 276, + 408, + 289 + ], + "spans": [ + { + "bbox": [ + 306, + 276, + 408, + 289 + ], + "type": "text", + "content": "2.1. Gait Recognition" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 295, + 545, + 330 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 295, + 545, + 330 + ], + "spans": [ + { + "bbox": [ + 305, + 295, + 545, + 330 + ], + "type": "text", + "content": "Gait recognition approaches can be broadly classified into two categories based on their modeling methodology, i.e., model-based methods and appearance-based methods." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 331, + 546, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 331, + 546, + 510 + ], + "spans": [ + { + "bbox": [ + 305, + 331, + 546, + 510 + ], + "type": "text", + "content": "Model-based method. Model-based approaches [2, 48, 59] aim to capture the inherent biomechanical characteristics of pedestrians. Early approaches [3, 28, 56] focused on distinguishing identities by estimating pedestrian motion parameters. However, such methods were constrained by predefined empirical points and yielded limited recognition accuracy. With the rapid advancement of deep learning, researchers have shifted their focus to extracting training data using pose estimation or Skinned Multi-Person Linear (SMPL) models. Subsequently, a well-designed network [21, 29, 30, 45, 46] is employed to further learn the gait features based on joint-based datasets. Despite substantial advancements, the efficacy of model-based methods remains constrained by the empirical design of predefined points and the estimation of results from low-quality images." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 510, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 510, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 510, + 546, + 713 + ], + "type": "text", + "content": "Appearance-based method. Appearance-based methods aim to learn gait features directly from silhouette data. Previous methods [18, 37, 54] have employed an efficient approach by directly applying weighted averaging to the sequence, i.e., Gait Energy Image (GEI). These methods have achieved significant advancements across various viewpoints and clothing conditions. However, the weighted averaging of video sequence data inevitably leads to the loss of substantial motion details. To this end, current research [22, 23, 26, 32] emphasizes the utilization of video input to learn gait features in order to address this limitation. Some of the 2D convolution-based methods [7, 14] independently extract local spatial features from each frame and subsequently utilize set-based pooling techniques, i.e., MaxPooling and MeanPooling, to directly extract global temporal features from the variable-length sequence. These methods have yielded impressive experimental results, significantly" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "spans": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "type": "text", + "content": "594" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 76, + 542, + 227 + ], + "blocks": [ + { + "bbox": [ + 50, + 76, + 542, + 227 + ], + "lines": [ + { + "bbox": [ + 50, + 76, + 542, + 227 + ], + "spans": [ + { + "bbox": [ + 50, + 76, + 542, + 227 + ], + "type": "image", + "image_path": "4d6b06ac783d6230c2558fcd88e7ae5899e462a6f46d0da2e44423c9e8fead25.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 237, + 546, + 283 + ], + "lines": [ + { + "bbox": [ + 46, + 237, + 546, + 283 + ], + "spans": [ + { + "bbox": [ + 46, + 237, + 546, + 283 + ], + "type": "text", + "content": "Figure 2. Overview of the proposed Visual Prompt Network (VPNet), where \"HP\" denotes the Horizontal Pooling. (a) VPNet incorporates the FTS module into the backbone based on ResNet, focusing on the extraction of global motion patterns without any extra parameters. (b) VPNet utilizes a trainable prompt pool comprising numerous key-value pairs, dynamically selecting prompt templates and integrating them into gait features to provide task-relevant knowledge. (c) Three different loss functions are combined for supervised network training." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 303, + 289, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 303, + 289, + 460 + ], + "spans": [ + { + "bbox": [ + 46, + 303, + 289, + 460 + ], + "type": "text", + "content": "advancing the field of gait recognition. However, gait represents a coordinated whole-body motion process, and processing the features of each frame individually disregards the preservation of robust local motion patterns, which are essential for accurate gait information. Consequently, some 3D convolution-based methods [6, 12, 33, 35, 36] proposed to local spatio-temporal features from adjacent frame images using a shared 3D convolution kernel, while further modeling the unfixed length sequence to obtain robust global features. The approach presented in this paper falls within the category of appearance-based methods. In contrast to previous methods, we aim to explore further improvements within the deep network structure." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 467, + 167, + 480 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 467, + 167, + 480 + ], + "spans": [ + { + "bbox": [ + 47, + 467, + 167, + 480 + ], + "type": "text", + "content": "2.2. Prompt Engineering" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "text", + "content": "Prompt Engineering [5, 9, 40] is a methodology that involves the incorporation of additional information as a condition in the inference process using a model. It has gained considerable popularity [16, 19, 41] in the field of natural language processing (NLP) due to its ability to integrate task-specific cues for each individual task. In recent years, there has been a notable surge in prompt-based research [31, 38, 57, 62] within the field of computer vision. It integrates visual and linguistic tasks, using NLP to reference or define visual concepts. To address inherent disparities in information densities between visual and NLP tasks, researchers have developed methodologies [1, 24, 27] that involve pre-filling model inputs with adaptive parameters. These parameters, functioning as prompts, can be finetuned through gradient-based optimization, thereby facilitating their contribution to visual tasks. Specifically, VPT [27] and VP [1] load a set of trainable prompts into the model inputs while maintaining the architectural integrity of the core network. This strategic implementation consis" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 303, + 547, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 303, + 547, + 411 + ], + "spans": [ + { + "bbox": [ + 304, + 303, + 547, + 411 + ], + "type": "text", + "content": "tently yields noteworthy performance improvements across a range of downstream tasks. In contrast, DAM-VP [24] adopts a divide-and-conquer scheme, segregating datasets associated with downstream tasks into smaller, homogeneous subsets. Each subset is endowed with its distinct cue, and subsequently, optimization is carried out independently for each subset. We extend the concept of prompt learning from prior research [52, 53], utilizing it to provide task-related information and extract robust motion patterns." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 421, + 389, + 435 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 421, + 389, + 435 + ], + "spans": [ + { + "bbox": [ + 305, + 421, + 389, + 435 + ], + "type": "text", + "content": "3. Methodology" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 441, + 547, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 441, + 547, + 513 + ], + "spans": [ + { + "bbox": [ + 304, + 441, + 547, + 513 + ], + "type": "text", + "content": "In this section, we present the overall architecture of the proposed Visual Prompt Network (VPNet) for gait and provide an in-depth explanation of the motivation in Sec. 3.1. We then provide a comprehensive elucidation of the backbone architecture in Sec. 3.2. Finally, we present the specific structure of the dynamic transformer in Sec. 3.3." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 520, + 460, + 533 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 520, + 460, + 533 + ], + "spans": [ + { + "bbox": [ + 305, + 520, + 460, + 533 + ], + "type": "text", + "content": "3.1. Preliminary and Motivation" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "spans": [ + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "text", + "content": "A vanilla vision gait recognition framework typically comprises two essential components: the backbone " + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "inline_equation", + "content": "\\mathcal{B}" + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "text", + "content": " and the head " + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "inline_equation", + "content": "\\mathcal{H}" + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "text", + "content": ". Formally, given a gait silhouette sequence " + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "inline_equation", + "content": "X \\in \\mathbb{R}^{T \\times H \\times W}" + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "inline_equation", + "content": "H" + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "inline_equation", + "content": "W" + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 538, + 547, + 647 + ], + "type": "text", + "content": " represent the height, width, and number of frames, respectively. Firstly, the gait sequence is fed into the backbone to extract the local motion patterns, followed by its passage through the head to derive the global motion patterns. The extraction of gait features can be briefly represented as" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 393, + 655, + 545, + 668 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 393, + 655, + 545, + 668 + ], + "spans": [ + { + "bbox": [ + 393, + 655, + 545, + 668 + ], + "type": "interline_equation", + "content": "\\boldsymbol {F} = \\mathcal {H} (\\mathcal {B} (\\boldsymbol {X})), \\tag {1}", + "image_path": "58e95006769b7559a298edb28606e04d334b01928d35cda84a87590212e8047a.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\pmb{F} \\in \\mathbb{R}^{P \\times C}" + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": " denotes the output features, " + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": " is the number of horizontal slices, and " + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": " is the feature dimension. Most of the existing research [8, 15, 33] places a significant" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "spans": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "type": "text", + "content": "595" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "content": "focus on improving the efficiency of the backbone component for extracting complex spatio-temporal features. Despite their progress, these approaches struggle to address the challenges of gait recognition in real-world scenarios. To this end, as shown in Fig. 2, we intend to introduce a comprehensive framework for gait recognition. In particular, it involves utilizing a common backbone to directly extract global motion patterns, designing a trainable prompt pool " + }, + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 72, + 289, + 204 + ], + "type": "text", + "content": " that adaptively selects task-relevant templates to concatenate with the original gait features, and employing dynamic attention to learn representative gait features, i.e.," + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 91, + 210, + 287, + 239 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 91, + 210, + 287, + 239 + ], + "spans": [ + { + "bbox": [ + 91, + 210, + 287, + 239 + ], + "type": "interline_equation", + "content": "\\boldsymbol {F} = \\mathcal {H} (\\text {c o n c a t} [ \\overbrace {\\mathcal {P} (\\boldsymbol {B} (\\boldsymbol {X}))} ^ {\\text {p r o m p t t e m p l a t e s}}, \\boldsymbol {B} (\\boldsymbol {X}) ]), \\tag {2}", + "image_path": "6380f86a4d33a1fa997684ad9df3f7aad59a8956f6be2dfc8ff72c338294d21d.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 245, + 287, + 316 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 245, + 287, + 316 + ], + "spans": [ + { + "bbox": [ + 46, + 245, + 287, + 316 + ], + "type": "text", + "content": "where concat represents the concatenation along the temporal dimension. The prompt templates, functioning as trainable embeddings, essentially encode the gait task. These templates include various aspects such as viewpoint, attire, carrying conditions, occlusion, and so on. They provide instructions to the model, specifying the task it executes." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 323, + 178, + 335 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 323, + 178, + 335 + ], + "spans": [ + { + "bbox": [ + 47, + 323, + 178, + 335 + ], + "type": "text", + "content": "3.2. Backbone Architecture" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 342, + 287, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 342, + 287, + 437 + ], + "spans": [ + { + "bbox": [ + 46, + 342, + 287, + 437 + ], + "type": "text", + "content": "We utilize the bottleneck structure in ResNet [20] to establish the backbone for gait recognition and introduce a plug-and-play gait temporal-shift operation [34, 36], coupled with a 3D convolutional network, as the foundational motion pattern extraction element within the bottleneck. By modifying the depth of the backbone network, we sequentially construct three models with distinct parameters in Sec. 4.1, namely VPNet-T, VPNet-M, and VPNet-L." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 437, + 288, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 288, + 653 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 288, + 653 + ], + "type": "text", + "content": "Temporal Shift Bottleneck. 3D convolution is commonly used in gait recognition tasks due to its proficiency in local spatio-temporal aggregation. However, its ability to be used in real-world scenarios with numerous long silhouette sequences may pose certain challenges. Inspired by temporal shift operation [34, 36], as shown in Fig. 2, we design a novel Forward cycle Temporal Shift (FTS) module for the gait recognition network. Considering that forward walking is the predominant daily practice, whereas backward walking is less frequent, we employ a forward cyclic shifting approach along the temporal dimension instead of the zero padding technique used in TSCov [34]. Specifically, the FTS module divides the features " + }, + { + "bbox": [ + 46, + 437, + 288, + 653 + ], + "type": "inline_equation", + "content": "f \\in \\mathbb{R}^{C \\times T \\times H \\times W}" + }, + { + "bbox": [ + 46, + 437, + 288, + 653 + ], + "type": "text", + "content": " of each pixel into four segments. It only cyclically shifts the first segment " + }, + { + "bbox": [ + 46, + 437, + 288, + 653 + ], + "type": "inline_equation", + "content": "f_{1} \\in \\mathbb{R}^{\\frac{C}{4} \\times T \\times H \\times W}" + }, + { + "bbox": [ + 46, + 437, + 288, + 653 + ], + "type": "text", + "content": " along the temporal dimension. The extraction of motion patterns with a global receptive field can be achieved by incorporating the FTS module before 3D convolution, without the additional parameters." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 659, + 174, + 672 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 659, + 174, + 672 + ], + "spans": [ + { + "bbox": [ + 47, + 659, + 174, + 672 + ], + "type": "text", + "content": "3.3. Dynamic Transformer" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": "We present a dynamic transformer as an integral head layer " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{H}" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": " in the network architecture. As shown in Fig. 2, it employs prompt engineering to provide task-specific shared" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 312, + 74, + 541, + 259 + ], + "blocks": [ + { + "bbox": [ + 312, + 74, + 541, + 259 + ], + "lines": [ + { + "bbox": [ + 312, + 74, + 541, + 259 + ], + "spans": [ + { + "bbox": [ + 312, + 74, + 541, + 259 + ], + "type": "image", + "image_path": "40066a8a0585d0dd869515c99687cf014b366d33acd4f0a9d9b10dd74b6a1faf.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 271, + 545, + 304 + ], + "lines": [ + { + "bbox": [ + 304, + 271, + 545, + 304 + ], + "spans": [ + { + "bbox": [ + 304, + 271, + 545, + 304 + ], + "type": "text", + "content": "Figure 3. The dynamic attention architecture. We utilize both prompt templates and gait sequence as inputs, employing the Context Window Mask to overcome the length generalization problem." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 311, + 545, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 311, + 545, + 346 + ], + "spans": [ + { + "bbox": [ + 304, + 311, + 545, + 346 + ], + "type": "text", + "content": "knowledge information for gait sequence and introduces a dynamic context window mask to effectively alleviate the problem of length generalization in real-world scenarios." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 346, + 546, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 346, + 546, + 491 + ], + "spans": [ + { + "bbox": [ + 304, + 346, + 546, + 491 + ], + "type": "text", + "content": "Part-based Prompt Pool. Prompt learning has emerged as a methodology in NLP, and its application in gait recognition is motivated by three main considerations. Firstly, the adaptable visual prompt templates facilitate the integration of shared insights concerning the gait sequence. Secondly, the shared knowledge seamlessly incorporates into the gait sequence as a global feature through a flexible plug-and-play process. Finally, specific visual prompts are associated with salient features within the gait sequence. To address this, we introduce a part-based prompt pool with shared parameters, delivering task-specific information. The " + }, + { + "bbox": [ + 304, + 346, + 546, + 491 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 346, + 546, + 491 + ], + "type": "text", + "content": "-th prompt pool can be defined as" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 318, + 499, + 545, + 514 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 499, + 545, + 514 + ], + "spans": [ + { + "bbox": [ + 318, + 499, + 545, + 514 + ], + "type": "interline_equation", + "content": "\\mathcal {P} _ {j} = \\left\\{\\boldsymbol {P} _ {j, 1}, \\boldsymbol {P} _ {j, 2}, \\dots , \\boldsymbol {P} _ {j, N} \\mid \\boldsymbol {P} _ {j, i} = \\left(k _ {j, i}, v _ {j, i}\\right) \\right\\}, \\tag {3}", + "image_path": "a42a2f669bdb72c5d251d6bf5f85c9ffe74f21f2ba03076eea7fe3035660289f.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{P}_j|j = 1,\\dots,P\\}" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " is the " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " -th prompt pool, " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " denotes the number of horizontal slices, " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "P_{j,i}" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " is the " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " -th prompt token, " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " denotes the number of trainable tokens in the prompt pool, " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "k_{j,i}\\in \\mathbb{R}^{C}" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "v_{j,i}\\in \\mathbb{R}^C" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " represent the key and value, respectively. We utilize key-value pairs as prompt tokens, matching the key with the input gait sequence. Following this alignment, the top- " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " values are selected as prompt templates based on their similarity, and these chosen templates are smoothly integrated with the original sequence along the temporal dimension. Specifically, given a gait sequence feature " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\pmb {S}\\in \\mathbb{R}^{P\\times T\\times C}" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " , for the " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " -th part sequence feature " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "S_{j}\\in \\mathbb{R}^{T\\times C}" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " , we first compute the average feature along the temporal dimension " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\bar{S}_j\\in \\mathbb{R}^C" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " and then perform similarity matching with key embeddings in the prompt pool to select the top- " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " values with the highest similarity. Denote " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{R}" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " as the function to lookup the top- " + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 521, + 546, + 713 + ], + "type": "text", + "content": " keys in the ranked list, the" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "spans": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "type": "text", + "content": "596" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 253, + 85 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 253, + 85 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 253, + 85 + ], + "type": "text", + "content": "selection process for the key can be represented as" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 109, + 91, + 287, + 120 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 109, + 91, + 287, + 120 + ], + "spans": [ + { + "bbox": [ + 109, + 91, + 287, + 120 + ], + "type": "interline_equation", + "content": "\\mathcal {K} _ {j} = \\mathcal {R} \\left(\\frac {\\bar {S} _ {j} \\otimes k _ {j , i}}{\\| \\bar {S} _ {j} \\| \\otimes \\| k _ {j , i} \\|}\\right), \\tag {4}", + "image_path": "b81e4bed38bac1727c962bfdec60e01559de77bda1e54055c4e689099648bc5e.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "spans": [ + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "inline_equation", + "content": "\\mathcal{K}_j" + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "content": " denotes a list of sets, generating a top-" + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "content": " index that is linked to the query sequence, and " + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "inline_equation", + "content": "\\otimes" + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "content": " represents matrix multiplication. The index value is employed to retrieve " + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "content": " values, denoted as " + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "inline_equation", + "content": "V_j = \\{v_{j,\\kappa}|\\kappa \\in \\mathcal{K}_s\\}" + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "content": ". Subsequently, we combine the indexed value " + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "inline_equation", + "content": "V_j" + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "content": " with the feature " + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "inline_equation", + "content": "S_j" + }, + { + "bbox": [ + 47, + 126, + 287, + 187 + ], + "type": "text", + "content": ", i.e.," + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 119, + 194, + 287, + 209 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 119, + 194, + 287, + 209 + ], + "spans": [ + { + "bbox": [ + 119, + 194, + 287, + 209 + ], + "type": "interline_equation", + "content": "S _ {j} ^ {*} = \\operatorname {c o n c a t} \\left[ V _ {j}, S _ {j} \\right], \\tag {5}", + "image_path": "ff86f6a957f3db042ae4923814b03dabf028705f3bdaf0881090dabbe87f835e.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "spans": [ + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "text", + "content": "where concat represents the concatenation of prompt templates and gait vectors along the temporal dimension. The resulting gait sequence, denoted as " + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "inline_equation", + "content": "S_{j}^{*} \\in \\mathbb{R}^{(T + k) \\times C}" + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "text", + "content": ", integrates the prompt information, " + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "inline_equation", + "content": "(T + k)" + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "text", + "content": " is the length of the gait sequence, and " + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "text", + "content": " is empirically set to 6. Similar to the codebook collapse issue faced in VQ-VAE [10, 39], there exists a risk that all index " + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "inline_equation", + "content": "\\mathcal{K}_{j}" + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "text", + "content": " map to a limited set of prompt templates. To address this, we implement a randomized restart strategy: the key vector in the prompt pool is randomly reset to one of the encoder outputs if its average utilization falls below a predefined threshold " + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "inline_equation", + "content": "(\\tau = 0.001)" + }, + { + "bbox": [ + 46, + 217, + 287, + 347 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "spans": [ + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "text", + "content": "Dynamic Attention. As shown in Fig. 3, we propose to extract global motion patterns for each body part based on prompt templates using the multi-head attention [11, 47]. Formally, the " + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "text", + "content": "-th part sequence feature " + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "inline_equation", + "content": "S_{j}^{*}" + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "text", + "content": " is mapped as query " + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "inline_equation", + "content": "\\pmb{Q}" + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "text", + "content": ", key " + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "inline_equation", + "content": "\\pmb{K}" + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "text", + "content": " and value " + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "inline_equation", + "content": "\\pmb{V}" + }, + { + "bbox": [ + 46, + 348, + 287, + 408 + ], + "type": "text", + "content": ". The mapping process is as" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 81, + 426, + 287, + 444 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 81, + 426, + 287, + 444 + ], + "spans": [ + { + "bbox": [ + 81, + 426, + 287, + 444 + ], + "type": "interline_equation", + "content": "\\boldsymbol {Q} = S _ {j} ^ {*} W ^ {Q}, \\boldsymbol {K} = S _ {j} ^ {*} W ^ {K}, \\boldsymbol {V} = S _ {j} ^ {*} W ^ {V}, \\tag {6}", + "image_path": "18c13ba627ef018517947790ea17e22a5e6e1f3f35f4669409a5fa36ccf38ff5.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "spans": [ + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "inline_equation", + "content": "W^{Q} \\in \\mathbb{R}^{C \\times h \\cdot C'}" + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "inline_equation", + "content": "W^{K} \\in \\mathbb{R}^{C \\times h \\cdot C'}" + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "inline_equation", + "content": "W^{V} \\in \\mathbb{R}^{C \\times h \\cdot C'}" + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "content": " are learnable parameters, " + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "content": " denotes the number of heads, and " + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "inline_equation", + "content": "C'" + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "content": " represents the feature dimension of each head. Then, we employ " + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "inline_equation", + "content": "Q" + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 451, + 287, + 540 + ], + "type": "text", + "content": " to establish similarity relationships between each frame. It is notable that prompt templates can be associated with the features of each frame, thereby giving rise to the establishment of correlations, i.e.," + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 121, + 559, + 287, + 574 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 121, + 559, + 287, + 574 + ], + "spans": [ + { + "bbox": [ + 121, + 559, + 287, + 574 + ], + "type": "interline_equation", + "content": "\\operatorname {s i m} (\\boldsymbol {Q}, \\boldsymbol {K}) = \\boldsymbol {Q} \\boldsymbol {K} ^ {T}, \\tag {7}", + "image_path": "e06d69483eecf6ea9ff3f688d32730220c4706bd0094821a79feefc7df99b2f3.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\operatorname{sim}(Q, K)" + }, + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "type": "text", + "content": " denotes the similarity matrix. Similar to natural language processing, gait recognition also faces the challenge of length generalization [17, 42, 55]. During training, a limited number of frames are randomly selected, but during testing, the longer sequence can distract the attention of the network. To effectively utilize the shared information provided by prompt templates in discerning distinctive global motion patterns within varying length sequences, we introduce a context window mask structure. This design dynamically establishes connections between prompt templates and gait sequence. As depicted in Fig. 3," + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 72, + 547, + 157 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 157 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 157 + ], + "type": "text", + "content": "the architecture comprises a global branch on the left and a local branch on the right. The global branch allows each feature in the sequence to focus on establishing relationships with prompt templates, while the local branch fosters associations between each feature and other features within a defined local length range. Features outside of these two branches are excluded from the attention process, i.e.," + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 318, + 164, + 545, + 191 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 164, + 545, + 191 + ], + "spans": [ + { + "bbox": [ + 318, + 164, + 545, + 191 + ], + "type": "interline_equation", + "content": "\\operatorname {A t t} (\\boldsymbol {Q}, \\boldsymbol {K}, \\boldsymbol {V}) = \\operatorname {s o f t m a x} \\left(\\frac {\\operatorname {s i m} (\\boldsymbol {Q} , \\boldsymbol {K})}{\\sqrt {C ^ {\\prime}}} \\oplus \\mathcal {M}\\right) \\boldsymbol {V}, \\tag {8}", + "image_path": "a5a93982a0499d01e9e31f57308d4afa77ceb27baf3a83aa787d452e3aa6d504.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "spans": [ + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "type": "inline_equation", + "content": "\\sqrt{C'}" + }, + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "type": "text", + "content": " is the scaling factor, " + }, + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "type": "inline_equation", + "content": "\\mathcal{M}" + }, + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "type": "text", + "content": " is the dynamic context window mask, and " + }, + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "type": "inline_equation", + "content": "\\oplus" + }, + { + "bbox": [ + 305, + 199, + 546, + 225 + ], + "type": "text", + "content": " denotes element-wise sum operation." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 232, + 408, + 244 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 232, + 408, + 244 + ], + "spans": [ + { + "bbox": [ + 306, + 232, + 408, + 244 + ], + "type": "text", + "content": "3.4. Learning Details" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "spans": [ + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": "In this work, we introduce three loss functions during training: triplet loss " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{tp}" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": ", cross-entropy loss " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\text{cet}}" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": ", and cosine embedding loss " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\text{cem}}" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": " in Fig. 2. The " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{tp}" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\text{cet}}" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": " serve to supervise part-based features individually, while the " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\text{cem}}" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": " is applied to supervise the key embedding " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "(k_{j,i})" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": " within the prompt pool. " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\text{cem}}" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": " requires that the selected key embedding be closely related to the query sequence " + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "inline_equation", + "content": "\\bar{S}_i" + }, + { + "bbox": [ + 304, + 250, + 546, + 334 + ], + "type": "text", + "content": ", i.e.," + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 329, + 342, + 545, + 375 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 329, + 342, + 545, + 375 + ], + "spans": [ + { + "bbox": [ + 329, + 342, + 545, + 375 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {c e m} = \\underset {\\kappa \\in \\mathcal {K} _ {j}} {\\arg \\min } \\sum_ {i = 1} ^ {P} \\frac {- 1}{N _ {c e m}} \\left(\\frac {\\bar {S} _ {i} \\otimes k _ {j , \\kappa}}{\\| \\bar {S} _ {i} \\| \\otimes \\| k _ {j , \\kappa} \\|}\\right), \\tag {9}", + "image_path": "4c9953e6d6682f159e9ec683b10683682fe7cd7d3b51a1ca355c0556224a7aef.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 382, + 546, + 478 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 382, + 546, + 478 + ], + "spans": [ + { + "bbox": [ + 304, + 382, + 546, + 478 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 382, + 546, + 478 + ], + "type": "inline_equation", + "content": "N_{cem}" + }, + { + "bbox": [ + 304, + 382, + 546, + 478 + ], + "type": "text", + "content": " is a positive integer obtained by multiplying the batch size with the number of parts. In each training step, we adhere to the previously described strategy to select " + }, + { + "bbox": [ + 304, + 382, + 546, + 478 + ], + "type": "inline_equation", + "content": "\\kappa_{s}" + }, + { + "bbox": [ + 304, + 382, + 546, + 478 + ], + "type": "text", + "content": ". The selected prompt templates are then merged with gait sequence vectors and fed into the dynamic transformer and BNNeck [15] to extract representative gait features. In general, the training process involves the use of a combined loss following the end-to-end method, i.e.," + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 359, + 488, + 545, + 501 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 359, + 488, + 545, + 501 + ], + "spans": [ + { + "bbox": [ + 359, + 488, + 545, + 501 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {s u m} = \\mathcal {L} _ {t p} + \\alpha \\mathcal {L} _ {c e m} + \\beta \\mathcal {L} _ {c e t}, \\tag {10}", + "image_path": "e79048e672c8c345602c0fe4e8d0db021a80792abb1ed3970c99497dd6587708.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "text", + "content": " are the hyper-parameters to balance the combined loss, " + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "text", + "content": " is empirically set to 0.01 and " + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 305, + 509, + 545, + 533 + ], + "type": "text", + "content": " is set to 0.3." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 544, + 388, + 558 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 544, + 388, + 558 + ], + "spans": [ + { + "bbox": [ + 306, + 544, + 388, + 558 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 563, + 501, + 576 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 563, + 501, + 576 + ], + "spans": [ + { + "bbox": [ + 306, + 563, + 501, + 576 + ], + "type": "text", + "content": "4.1. Datasets and Implementation Details" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 582, + 545, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 641 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 641 + ], + "type": "text", + "content": "The gait datasets are divided into two subsets, i.e., in-the-wild and in-the-lab, distinguished by their respective collection environments in Tab. 1. A standardized preprocessing procedure [7] is uniformly applied to these datasets, and the data sizes used in this paper are all resized to " + }, + { + "bbox": [ + 304, + 582, + 545, + 641 + ], + "type": "inline_equation", + "content": "64 \\times 64" + }, + { + "bbox": [ + 304, + 582, + 545, + 641 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": "In-the-wild datasets. In-the-wild datasets introduce numerous unforeseen challenges, such as occlusions, clothing changes, viewpoint variations, and carrying conditions. Pedestrians may also pause or alter their walking patterns. These datasets are essential benchmarks for evaluating gait recognition methods under various external disturbances." + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "spans": [ + { + "bbox": [ + 297, + 749, + 312, + 757 + ], + "type": "text", + "content": "597" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 49, + 102, + 545, + 178 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 547, + 95 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 547, + 95 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 547, + 95 + ], + "type": "text", + "content": "Table 1. Comparison of the specific values of the adopted datasets and corresponding parameters. Where “#Ide., #Seq., #Cam.” refer to numbers of identities, sequences, and cameras respectively. Additionally, “lr, dr, wd” denote learning rate, decay rate, and weight decay." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 49, + 102, + 545, + 178 + ], + "lines": [ + { + "bbox": [ + 49, + 102, + 545, + 178 + ], + "spans": [ + { + "bbox": [ + 49, + 102, + 545, + 178 + ], + "type": "table", + "html": "
EnvironmentDatasetsTrainTest# Cam.Batch SizeOptimizerScheduler
# Ide.# Seq.# Ide.# Seq.step sizeepochs
In-the-wildGait3D [61]3,00018,9401,0006,369Diverse(32, 4)SGD lr = 0.12080
GREW [63]20,000102,8876,00024,000Diverse(64, 4)50200
In-the-labOUMVLP [44]5,153144,2845,154144,31214(32, 8)dr = 0.150200
CASIA-B [58]748,140505,50011(8, 16)wd = 0.00051040
", + "image_path": "00b154eede76a5000473c8d9168827aec82d81d9c325334278ca30e102010d3a.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 59, + 217, + 272, + 380 + ], + "blocks": [ + { + "bbox": [ + 47, + 185, + 288, + 208 + ], + "lines": [ + { + "bbox": [ + 47, + 185, + 288, + 208 + ], + "spans": [ + { + "bbox": [ + 47, + 185, + 288, + 208 + ], + "type": "text", + "content": "Table 2. The detailed structure of the backbone in VPNet-L, where FTSCov denotes the combined of FTS module and convolution." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 59, + 217, + 272, + 380 + ], + "lines": [ + { + "bbox": [ + 59, + 217, + 272, + 380 + ], + "spans": [ + { + "bbox": [ + 59, + 217, + 272, + 380 + ], + "type": "table", + "html": "
LayerOutput size
conv13 × 3 × 3, 64, stride(1,1,1)T × H × W
stage1[1 × 1 × 1, 64, (0,0,0)FTSCnv, 64, (1,1,1)1 × 1 × 1, 64, (0,0,0)] × 3T × H × W
stage2[1 × 1 × 1, 128, (0,0,0)FTSCnv, 128, (1,2,2)1 × 1 × 1, 128, (0,0,0)] × 4T × H/2 × W/2
stage3[1 × 1 × 1, 256, (0,0,0)FTSCnv, 256, (1,2,2)1 × 1 × 1, 256, (0,0,0)] × 6T × H/4 × W/4
stage4[1 × 1 × 1, 512, (0,0,0)FTSCnv, 512, (1,1,1)1 × 1 × 1, 512, (0,0,0)] × 3T × H/4 × W/4
", + "image_path": "b6fb057be70ca0228df6bc2110d5607822e771086d52487d06029d7cc4d206d3.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 388, + 287, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 388, + 287, + 460 + ], + "spans": [ + { + "bbox": [ + 46, + 388, + 287, + 460 + ], + "type": "text", + "content": "We evaluate our method on the widely adopted Gait3D [61] and GREW [63] datasets in Tab. 1. To enhance the robustness of our model, we employ three data augmentation techniques: rotation, flipping, and perspective. We conduct training using VPNet-L on both Gait3D and GREW datasets and report rank-1 (\\%) and rank-5 (\\%) accuracy." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 45, + 460, + 287, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 460, + 287, + 640 + ], + "spans": [ + { + "bbox": [ + 45, + 460, + 287, + 640 + ], + "type": "text", + "content": "In-the-lab datasets. In-the-lab datasets encompass various controllable conditions, including camera angles, predetermined walking routes, and dress variations. These datasets play a pivotal role in evaluating the ability of the gait network to handle cross-viewing and cross-dressing scenarios. We select the well-established OUMVLP [44] and CASIA-B [58] datasets to evaluate our approach in Tab. 1. Specifically, the OUMVLP provides an abundance of cross-viewing data, while the CASIA-B offers valuable cross-dressing data. Limited datasets, particularly those obtained from laboratory scenarios, may result in overfitting if the network parameters are excessively large. Therefore, we employ VPNet-M for training on OUMVLP and VPNet-T for training on CASIA-B. We present the rank-1 " + }, + { + "bbox": [ + 45, + 460, + 287, + 640 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 45, + 460, + 287, + 640 + ], + "type": "text", + "content": " accuracy for all perspectives, excluding the identical-view cases." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "content": "Implementation Details. We establish the network parameters based on the dataset scale and complexity, as outlined in Tab. 1. The batch size is represented as " + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "inline_equation", + "content": "(S, T)" + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "content": ", indicating that each mini-batch involves " + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "content": " subjects. For each subject, " + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "content": " sequences are sampled, and within each sequence, a random selection of 20 to 40 frames is chosen following" + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 318, + 217, + 533, + 365 + ], + "blocks": [ + { + "bbox": [ + 305, + 185, + 547, + 209 + ], + "lines": [ + { + "bbox": [ + 305, + 185, + 547, + 209 + ], + "spans": [ + { + "bbox": [ + 305, + 185, + 547, + 209 + ], + "type": "text", + "content": "Table 3. The performance comparisons on Gait3D are reported with rank-1 and rank-5 accuracy (\\%)." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 318, + 217, + 533, + 365 + ], + "lines": [ + { + "bbox": [ + 318, + 217, + 533, + 365 + ], + "spans": [ + { + "bbox": [ + 318, + 217, + 533, + 365 + ], + "type": "table", + "html": "
MethodsPublicationrank-1 (%)rank-5 (%)
GaitSet [7]AAAI 201936.758.3
GaitPart [14]CVPR 202028.247.6
GLN [22]ECCV 202031.452.9
GaitGL [33]ICCV 202129.748.5
CSTL [25]ICCV 202111.719.2
SMPLGait [61]CVPR 202246.364.5
GaitBase [15]CVPR 202365.6-
GaitGCI [13]CVPR 202350.368.5
DANet [35]CVPR 202348.069.7
HSTL [50]ICCV 202361.376.3
DyGait [51]ICCV 202366.380.8
VPNet-L-75.487.1
", + "image_path": "cccc4d4f625281589c9942ba48b6703f9aa6ef0cc74cde0650c39f33fcecdefa.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 318, + 407, + 529, + 525 + ], + "blocks": [ + { + "bbox": [ + 306, + 375, + 546, + 398 + ], + "lines": [ + { + "bbox": [ + 306, + 375, + 546, + 398 + ], + "spans": [ + { + "bbox": [ + 306, + 375, + 546, + 398 + ], + "type": "text", + "content": "Table 4. The performance comparisons on GREW are reported with rank-1 and rank-5 accuracy " + }, + { + "bbox": [ + 306, + 375, + 546, + 398 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 306, + 375, + 546, + 398 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 318, + 407, + 529, + 525 + ], + "lines": [ + { + "bbox": [ + 318, + 407, + 529, + 525 + ], + "spans": [ + { + "bbox": [ + 318, + 407, + 529, + 525 + ], + "type": "table", + "html": "
MethodsPublicationrank-1 (%)rank-5 (%)
GaitSet[7]AAAI 201946.363.6
GaitPart [14]CVPR 202044.060.7
GaitGL [33]ICCV 202147.363.6
GaitGraph [45]ICIP 20211.33.5
GaitBase [15]CVPR 202360.1-
GaitGCI [13]CVPR 202368.580.8
HSTL [50]ICCV 202362.776.6
DyGait [51]ICCV 202371.483.2
VPNet-L-80.089.4
", + "image_path": "a005ead5fa5a6e17661c480e766fbb38de1a65366e7df91594c8bb2dc8f07713.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 533, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 547, + 715 + ], + "type": "text", + "content": "DANet [35]. The optimization strategy employs Stochastic Gradient Descent (SGD) with an initial learning rate of 0.1, and each epoch consists of 1000 iterations. The learning rate undergoes periodic reduction based on the step size in Tab. 1, with a decay rate of 0.1. The entire model is built by sequentially stacking the temporal shift bottleneck in Sec. 3.2. We construct three models with distinct parameters, namely VPNet-T, VPNet-M, and VPNet-L, by modifying the depth of the backbone network. Specifically, VPNet-T is composed of three stages, each comprising a specific number of layers (1, 1, 1) and channels (64, 128, 256). In contrast, both VPNet-M and VPNet-L consist of four stages with channel configurations (64, 128, 256, 512) in Tab. 2. VPNet-M employs a layer stack of (2, 2, 2, 2), while VPNet-L utilizes a stack of layers (3, 4, 6, 3)." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 298, + 749, + 313, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 298, + 749, + 313, + 757 + ], + "spans": [ + { + "bbox": [ + 298, + 749, + 313, + 757 + ], + "type": "text", + "content": "598" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 92, + 547, + 227 + ], + "blocks": [ + { + "bbox": [ + 110, + 71, + 483, + 82 + ], + "lines": [ + { + "bbox": [ + 110, + 71, + 483, + 82 + ], + "spans": [ + { + "bbox": [ + 110, + 71, + 483, + 82 + ], + "type": "text", + "content": "Table 5. Rank-1 accuracy (%) on OUMVLP under all view angles, excluding the identical-views cases." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 92, + 547, + 227 + ], + "lines": [ + { + "bbox": [ + 50, + 92, + 547, + 227 + ], + "spans": [ + { + "bbox": [ + 50, + 92, + 547, + 227 + ], + "type": "table", + "html": "
MethodProbe ViewMean
0°15°30°45°60°75°90°180°195°210°225°240°255°270°
GaitSet [7]79.587.989.990.288.188.787.881.786.789.089.387.287.886.287.1
GaitPart [14]82.688.990.891.089.789.989.585.288.190.090.189.089.188.288.7
GLN [22]83.890.091.091.290.390.089.485.389.190.590.689.689.388.589.2
GaitGL [33]84.990.291.191.591.190.890.388.588.690.390.489.689.588.889.7
GaitBase [15]--------------90.0
GaitGCI [13]91.292.392.692.793.092.392.192.091.891.992.692.391.491.692.1
DANet [35]87.791.391.691.891.791.491.190.490.390.790.990.590.389.990.7
HSTL [50]91.492.992.793.092.992.592.592.792.392.192.392.291.891.892.4
VPNet-M91.993.092.492.793.292.592.392.992.491.992.192.591.991.992.4
", + "image_path": "b6e85ec7a5b3859ee4d43c0c126d1f9c9e0818d3ea32b7dc19ade63e652f10cc.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 50, + 270, + 285, + 414 + ], + "blocks": [ + { + "bbox": [ + 47, + 239, + 287, + 262 + ], + "lines": [ + { + "bbox": [ + 47, + 239, + 287, + 262 + ], + "spans": [ + { + "bbox": [ + 47, + 239, + 287, + 262 + ], + "type": "text", + "content": "Table 6. The performance comparisons on CASIA-B are reported with rank-1 accuracy " + }, + { + "bbox": [ + 47, + 239, + 287, + 262 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 47, + 239, + 287, + 262 + ], + "type": "text", + "content": ", excluding the identical-view cases." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 270, + 285, + 414 + ], + "lines": [ + { + "bbox": [ + 50, + 270, + 285, + 414 + ], + "spans": [ + { + "bbox": [ + 50, + 270, + 285, + 414 + ], + "type": "table", + "html": "
MethodsPublicationNMBGCLMean
GaitSet[7]AAAI 201995.087.270.484.2
GaitPart[14]CVPR 202096.291.578.788.8
GLN [22]ECCV 202096.994.077.589.5
MT3D [32]MM 202096.793.081.590.4
GaitGL [33]ICCV 202197.494.583.691.8
GaitBase [15]CVPR 202397.694.077.489.8
GaitGCI-T [13]CVPR 202397.995.086.493.1
DANet [35]CVPR 202398.095.989.994.6
HSTL [50]ICCV 202398.195.988.994.3
DyGait [51]ICCV 202398.496.287.894.1
VPNet-T-98.396.390.094.9
", + "image_path": "a58d2a576564d05877386ece937647be0a874b2d68a235c3dc48cb570b268ea5.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 425, + 232, + 436 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 425, + 232, + 436 + ], + "spans": [ + { + "bbox": [ + 47, + 425, + 232, + 436 + ], + "type": "text", + "content": "4.2. Results under in-the-wild Scenario" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 445, + 287, + 541 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 445, + 287, + 541 + ], + "spans": [ + { + "bbox": [ + 46, + 445, + 287, + 541 + ], + "type": "text", + "content": "Gait3D. VPNet-L demonstrates superior performance in terms of rank-1 and rank-5 accuracy in Tab. 3, surpassing state-of-the-art methods. Notably, it exhibits a " + }, + { + "bbox": [ + 46, + 445, + 287, + 541 + ], + "type": "inline_equation", + "content": "9.1\\%" + }, + { + "bbox": [ + 46, + 445, + 287, + 541 + ], + "type": "text", + "content": " improvement over DyGait [51], a silhouette-based approach, and a remarkable " + }, + { + "bbox": [ + 46, + 445, + 287, + 541 + ], + "type": "inline_equation", + "content": "29.1\\%" + }, + { + "bbox": [ + 46, + 445, + 287, + 541 + ], + "type": "text", + "content": " improvement compared to SMPL-Gait [61], a multimodal method. These experimental results underscore the efficacy of our method in extracting robust features in the presence of diverse external disturbances." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 544, + 287, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 287, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 287, + 616 + ], + "type": "text", + "content": "GREW. VPNet-L achieves the advanced accuracy of rank-1 and rank-5 as shown in Tab. 4, outperforming GaitGCI [13] by " + }, + { + "bbox": [ + 46, + 544, + 287, + 616 + ], + "type": "inline_equation", + "content": "11.5\\%" + }, + { + "bbox": [ + 46, + 544, + 287, + 616 + ], + "type": "text", + "content": " and GaitGraph [45] by " + }, + { + "bbox": [ + 46, + 544, + 287, + 616 + ], + "type": "inline_equation", + "content": "79.7\\%" + }, + { + "bbox": [ + 46, + 544, + 287, + 616 + ], + "type": "text", + "content": ". These experimental results demonstrate that our method effectively handles various unexpected external factors in realistic scenes, yielding effective global motion patterns in gait sequences." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 618, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 287, + 714 + ], + "type": "text", + "content": "Summary. We specifically design VPNet-L to tackle the intricacies of outdoor scenes, leading to state-of-the-art performance on real-world datasets. (1) Our method introduces a unified backbone architecture designed for the extraction of global motion patterns in real-world scenarios. (2) Prompt templates convey task-related knowledge, and a dynamic transformer is subsequently employed to effectively alleviate the problem of length generalization. (3) Ex" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 241, + 545, + 264 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 241, + 545, + 264 + ], + "spans": [ + { + "bbox": [ + 305, + 241, + 545, + 264 + ], + "type": "text", + "content": "experimental results validate the effectiveness of the proposed framework in the wild datasets." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 273, + 485, + 285 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 273, + 485, + 285 + ], + "spans": [ + { + "bbox": [ + 305, + 273, + 485, + 285 + ], + "type": "text", + "content": "4.3. Results under in-the-lab Scenario" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 291, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 291, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 291, + 545, + 555 + ], + "type": "text", + "content": "OUMVLP. The experimental results of VPNet-M in Tab. 5 exhibit superior performance compared to the majority of methods, underscoring its robustness and effectiveness. Notably, VPNet-M attains average accuracies on par with HSTL [50]. It is noteworthy that the accuracy of VPNet-M is further improved after excluding invalid probe sequences. CASIA-B. The experimental outcomes in Tab. 6 underscore the competitive performance of VPNet-T, surpassing other gait recognition methods. It is worth noting that, excluding the cases of identical views, VPNet-T achieved an average accuracy of over " + }, + { + "bbox": [ + 304, + 291, + 545, + 555 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 304, + 291, + 545, + 555 + ], + "type": "text", + "content": " in cross-viewing and cross-dressing. Summary. We customize VPNet-T and VPNet-M based on data size and complexity, achieving state-of-the-art performance on in-the-lab datasets. (1) Previously, different depth networks have been designed on unified architectures are common, such as ResNet-18 [20] and ResNet-50 [20]. Our proposed VPNet architecture fills a gap in the design of network architectures for gait recognition across diverse datasets. (2) In indoor scenarios, performance has reached its peak due to the utilization of continuously improving methods. Therefore, it is expected that gait recognition will increasingly concentrate on outdoor scenarios in the future." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 563, + 400, + 575 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 563, + 400, + 575 + ], + "spans": [ + { + "bbox": [ + 306, + 563, + 400, + 575 + ], + "type": "text", + "content": "4.4. Ablation Study" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "Effectiveness of core designs. We perform ablation experiments of the proposed module in Gait3D [61] and CASIA-B [58] datasets. (1) The experimental results reveal that the core design module, comprising the FTS module, prompt pool, and dynamic attention module, notably influenced cross-dressing and carrying conditions within the CASIA-B dataset. In contrast, the introduced module exhibits a more pronounced impact on Gait3D. (2) The results show that replacing the dynamic attention with the max+mean maintains competitive accuracy in CASIA-B. However, the results show a significant decrease in Gait3D, highlighting the" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 298, + 749, + 312, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 298, + 749, + 312, + 757 + ], + "spans": [ + { + "bbox": [ + 298, + 749, + 312, + 757 + ], + "type": "text", + "content": "599" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 54, + 101, + 281, + 319 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "type": "text", + "content": "Table 7. The ablation study on Gait3D and CASIA-B are reported with rank-1 accuracy(%) excluding the identical-views cases." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 54, + 101, + 281, + 319 + ], + "lines": [ + { + "bbox": [ + 54, + 101, + 281, + 319 + ], + "spans": [ + { + "bbox": [ + 54, + 101, + 281, + 319 + ], + "type": "table", + "html": "
MethodGait3DCASIA-B
R-1 (%)NM (%)BG (%)CL (%)
VPNet75.498.396.390.0
Analysis of each component in VPNet
- w/o FTS73.298.096.189.2
- w/o prompt72.898.096.089.1
- w/o mask73.098.396.390.0
w max+mean72.198.095.788.5
Analysis of temporal shift bottleneck
2D Conv69.798.095.786.8
3D Conv73.298.096.189.2
2D Conv + FTS74.198.196.288.2
3D Conv + FTS75.498.396.390.0
Analysis of the local length in dynamic attention
l=874.998.096.389.8
l=1675.498.196.489.8
l=3273.298.396.390.0
", + "image_path": "bd85c0c07d3790cf6be7fa4d2a129c678dddcf0545d20c83977e3e0f75d61d16.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 330, + 257, + 341 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 330, + 257, + 341 + ], + "spans": [ + { + "bbox": [ + 47, + 330, + 257, + 341 + ], + "type": "text", + "content": "effectiveness of our module in real-world scenarios." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 342, + 287, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 342, + 287, + 581 + ], + "spans": [ + { + "bbox": [ + 46, + 342, + 287, + 581 + ], + "type": "text", + "content": "Analysis of temporal shift bottleneck. We perform an empirical analysis comparing convolution outcomes within the temporal shift bottleneck in Tab. 7. (1) The network utilizing 2D convolution experienced a noteworthy decline in performance, representing a substantial improvement over using the FTS module in conjunction with 2D convolution. These results indicate that the FTS module plays a role in acquiring global motion patterns. (2) The network utilizing 3D convolution effectively captures local motion patterns, whereas the incorporation of the FTS module into 3D convolution facilitates the extraction of global motion patterns. Analysis of the local length. Different length affects the receptive fields in dynamic attention. (1) The experimental results demonstrate that an optimal range of receptive fields " + }, + { + "bbox": [ + 46, + 342, + 287, + 581 + ], + "type": "inline_equation", + "content": "(l = 16)" + }, + { + "bbox": [ + 46, + 342, + 287, + 581 + ], + "type": "text", + "content": " is essential for real data, as an excessively long receptive field " + }, + { + "bbox": [ + 46, + 342, + 287, + 581 + ], + "type": "inline_equation", + "content": "(l = 32)" + }, + { + "bbox": [ + 46, + 342, + 287, + 581 + ], + "type": "text", + "content": " may introduce noise. (2) In laboratory scenarios with relatively short sequence lengths, the impact of local receptive fields is minimal. (3) The issue of training and testing inconsistency can be alleviated by incorporating local receptive fields in the real world." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "type": "text", + "content": "Visualization of the prompt selection. We quantify the frequency of prompt template selection across various viewpoints and dress conditions on CASIA-B, as detailed in Fig. 4. The visualization results reveal variability in prompt template selection influenced by external factors, illustrating the encoding of task-relevant knowledge. (1) The statistical results show that different dressings and viewpoints have obvious differences in the frequency of prompt template selection. (2) The visualization results reveal variability in prompt template selection influenced by external factors, illustrating the encoding of task-relevant knowledge." + } + ] + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 309, + 70, + 425, + 185 + ], + "blocks": [ + { + "bbox": [ + 309, + 70, + 425, + 185 + ], + "lines": [ + { + "bbox": [ + 309, + 70, + 425, + 185 + ], + "spans": [ + { + "bbox": [ + 309, + 70, + 425, + 185 + ], + "type": "image", + "image_path": "3704d89421692a06a39f625abf32905a6169f473529097de10548acb6be53565.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 428, + 70, + 545, + 185 + ], + "blocks": [ + { + "bbox": [ + 428, + 70, + 545, + 185 + ], + "lines": [ + { + "bbox": [ + 428, + 70, + 545, + 185 + ], + "spans": [ + { + "bbox": [ + 428, + 70, + 545, + 185 + ], + "type": "image", + "image_path": "43c5766c8690ff12d55282dd874e852657f6d820fbb0a853d561a0d7b7168bbf.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 306, + 185, + 424, + 297 + ], + "blocks": [ + { + "bbox": [ + 306, + 185, + 424, + 297 + ], + "lines": [ + { + "bbox": [ + 306, + 185, + 424, + 297 + ], + "spans": [ + { + "bbox": [ + 306, + 185, + 424, + 297 + ], + "type": "image", + "image_path": "cca979bd97cbb5cd029a88c8aceb1d22ab168a37de0e15cc5e72a42aa4df3486.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 305, + 546, + 372 + ], + "lines": [ + { + "bbox": [ + 305, + 305, + 546, + 372 + ], + "spans": [ + { + "bbox": [ + 305, + 305, + 546, + 372 + ], + "type": "text", + "content": "Figure 4. Histogram of prompt template selection on CASIA-B, where \"Prompt ID\", \"View ID\", and \"Type ID\" denote the index of prompt, view angle, and dressing, respectively. (a) Comparison of the selection frequency of prompt templates under cross-dressing and carrying conditions. (b)(c)(d) Comparison of prompt template selection frequency across various views and body parts." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 428, + 185, + 545, + 297 + ], + "blocks": [ + { + "bbox": [ + 428, + 185, + 545, + 297 + ], + "lines": [ + { + "bbox": [ + 428, + 185, + 545, + 297 + ], + "spans": [ + { + "bbox": [ + 428, + 185, + 545, + 297 + ], + "type": "image", + "image_path": "5f9c5c739ab926220d8f36bf673baaa3f31f7ad16cc30da6851ebff4ea7e96bb.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 384, + 463, + 396 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 384, + 463, + 396 + ], + "spans": [ + { + "bbox": [ + 306, + 384, + 463, + 396 + ], + "type": "text", + "content": "5. Conclusion and Limitations" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 403, + 545, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 545, + 548 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 545, + 548 + ], + "type": "text", + "content": "In this paper, we present a Visual Prompt Network (VPNet) for gait recognition. VPNet employs temporal shift bottleneck as the foundational module of a backbone network to extract global motion patterns and utilizes prompt engineering to adaptively select templates with corresponding prompt information tailored for different gait sequences. To enhance the robustness of global motion patterns, the relationships between these templates and global features of gait sequence are further established using dynamic transformer structures. VPNet demonstrates superior performance in both in-the-wild and in-the-lab scenarios, highlighting its significant potential in real-world applications." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 548, + 545, + 620 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 548, + 545, + 620 + ], + "spans": [ + { + "bbox": [ + 304, + 548, + 545, + 620 + ], + "type": "text", + "content": "Limitations. Prompt learning has gained prominence in natural language processing for retraining large-scale pretrained language models, whereas the proposed network does not incorporate pre-training. In future work, we will investigate the applications of prompt engineering for large-scale gait recognition pre-training in real-world scenarios." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 633, + 416, + 646 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 633, + 416, + 646 + ], + "spans": [ + { + "bbox": [ + 306, + 633, + 416, + 646 + ], + "type": "text", + "content": "6. Acknowledgement" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 653, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 545, + 712 + ], + "type": "text", + "content": "This work was supported by the National Key R&D Program of China (2022YFC3300700), the National Natural Science Foundation of China (62331006, 62171038, 62088101, 62276031, 62276025, and 62276025), and the Fundamental Research Funds for the Central Universities." + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 298, + 749, + 313, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 298, + 749, + 313, + 757 + ], + "spans": [ + { + "bbox": [ + 298, + 749, + 313, + 757 + ], + "type": "text", + "content": "600" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 714 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "type": "text", + "content": "[1] Hyojin Bahng, Ali Jahanian, Swami Sankaranarayanan, and Phillip Isola. 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In ICCV, pages 14789-14799, 2021. 1, 2, 6" + } + ] + } + ], + "index": 0 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 298, + 749, + 312, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 298, + 749, + 312, + 757 + ], + "spans": [ + { + "bbox": [ + 298, + 749, + 312, + 757 + ], + "type": "text", + "content": "603" + } + ] + } + ], + "index": 1 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_content_list.json b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..7d6c080d10a5e3b92d90065c41dab2e43bd336f0 --- /dev/null +++ b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_content_list.json @@ -0,0 +1,1607 @@ +[ + { + "type": "text", + "text": "Learning by Correction: Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning", + "text_level": 1, + "bbox": [ + 119, + 128, + 849, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Rongjie Li $^{1*}$ Yu Wu $^{1*}$ Xuming He $^{1,2‡}$", + "bbox": [ + 326, + 210, + 648, + 229 + ], + "page_idx": 0 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "$^{1}$ School of Information Science and Technology, ShanghaiTech University", + "$^{2}$ Shanghai Engineering Research Center of Intelligent Vision and Imaging {lirj2, wuyu1, hexm} $@$ shanghaiitech.edu.cn" + ], + "bbox": [ + 189, + 232, + 776, + 294 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 328, + 312, + 344 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Generative vision-language models (VLMs) have shown impressive performance in zero-shot vision-language tasks like image captioning and visual question answering. However, improving their zero-shot reasoning typically requires second-stage instruction tuning, which relies heavily on human-labeled or large language model-generated annotation, incurring high labeling costs. To tackle this challenge, we introduce Image-Conditioned Caption Correction (ICCC), a novel pre-training task designed to enhance VLMs' zero-shot performance without the need for labeled task-aware data. The ICCC task compels VLMs to rectify mismatches between visual and language concepts, thereby enhancing instruction following and text generation conditioned on visual inputs. Leveraging language structure and a lightweight dependency parser, we construct data samples of ICCC task from image-text datasets with low labeling and computation costs. Experimental results on BLIP-2 and InstructBLIP demonstrate significant improvements in zero-shot image-text generation-based VL tasks through ICCC instruction tuning.", + "bbox": [ + 76, + 361, + 473, + 664 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 696, + 209, + 710 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Vision-language models (VLMs) have demonstrated remarkable performance across a wide range of vision-language (VL) tasks, including image captioning [1, 19, 22, 33, 36], visual recognition [15, 29, 44], image-text retrieval [18, 29], and answering visual questions [1, 19, 22, 33, 36]. Generally, existing VLMs are able to conduct two", + "bbox": [ + 75, + 722, + 468, + 814 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/437351355d83a00c39300a719f0cf34efc6b2d48e90e65408067f8c4e063acf7.jpg", + "image_caption": [ + "Figure 1. Illustration of second-stage tuning for zero-shot VL task adaptation comparison. The instruction tuning in recent works needs human label or LLM-generated data; in contrast, our image caption correction tuning is conducted on unlabeled image-text data with an NLP parser." + ], + "image_footnote": [], + "bbox": [ + 506, + 332, + 890, + 720 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "essential tasks: image-text matching (ITM) and image-text generation (ITG). The contrastive-based ITM aims to model the similarity between vision and text through a shared embedding [15, 18, 29]. In contrast, the generative-based ITG has more flexibility in adapting to various VL tasks. More-", + "bbox": [ + 496, + 824, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal Contribution. This work was supported by NSFC 62350610269, the Shanghai Frontiers Science Center of Human-centered Artificial Intelligence, and the MoE Key Lab of Intelligent Perception and Human-Machine Collaboration (ShanghaiTech University). ‡ denotes corresponding author. Code is available: https://github.com/SHTUPLUS/ICCC_CVPR2024", + "bbox": [ + 75, + 827, + 468, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "13428", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "over, several recent VLM frameworks integrate the LLMs for ITG, which extend the powerful text generation across vision and text modality [1, 8, 19, 22], and allow VLMs to perform zero-shot inference on various VL tasks with impressive performance.", + "bbox": [ + 75, + 90, + 470, + 167 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To perform zero-shot inference on VL tasks, the VLMs need to have generalizable text generation capability according to text inputs and concepts from the visual modality. The existing works typically conduct second-stage instruction tuning for pre-trained VLMs with task-oriented data. This improves VLMs for following instructions to generate texts conditioned on visual modality, which ultimately enhances the zero-shot performance on VL-tasks such as InstructBLIP [8] and LLAVA [22], as shown in the upper part of Fig. 1. However, these methods necessitate substantial downstream task data annotation for fine-tuning, which is either human-labeled or generated externally by large language models. This process escalates labor costs throughout the system.", + "bbox": [ + 75, + 169, + 468, + 381 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this study, we introduce a novel pre-training task, Image-Conditioned Caption Correction (ICCC), aimed at enhancing VLMs' performance on zero-shot VL tasks. Our approach leverages the semantic dependency structure of language utilized for second-stage tuning of VLMs, using image-text data without task-specific annotation, as depicted in Fig. 1. By enforcing VLMs to identify and rectify mismatched concepts between visual and language, our method enhances VLMs' capability of generating text from the visual modality. Importantly, the adopted universal semantic dependency [26] ensures comprehensive coverage of various concepts, including objects, their attributes, and interactions between them. Furthermore, we construct the data from unlabeled image-text datasets only with a lightweight dependency parser, which achieves low labeling and computation costs.", + "bbox": [ + 75, + 383, + 468, + 626 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Specifically, our pre-training framework first generates the task of image-conditioned text correction in an automatic manner. To this end, we develop a data construction pipeline with two components: the concept extractor and the correction task constructor. Firstly, the concept extractor identifies various concepts from the text modality. With the off-the-shelf dependency parser, it extracts the set of language units by parsing the semantic dependency structure of text. Subsequently, the correction task constructor generates samples from the unlabeled image-text data according to language structure and concept set. It swaps or replaces language units according to the extracted concept set, thereby creating concept-mismatched image-text pairs. Thanks to the universality of dependency, this approach allows us to create a wide variety of samples covering diverse visual-language concepts. The resulting text correction task requires VLMs to detect and recover the language units of mismatched concepts (words and phrases) according to the", + "bbox": [ + 75, + 628, + 470, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "image. Finally, we use the generated samples together with the original image-text data to fine-tune pre-trained VLMs with language modeling objectives.", + "bbox": [ + 496, + 90, + 890, + 136 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We conduct extensive experiments on two VLMs, BLIP-2 [19] and InstructBLIP [8], and evaluate the zero-shot performance of ITG on the representative tasks: visual question answering and image caption. Our findings reveal that our proposed method yields substantial improvements in zero-shot generalization based on the initial pre-train model without requiring any manually labeled or LLM-generated data. The main contributions of our work are threefold:", + "bbox": [ + 496, + 136, + 890, + 256 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We introduce a novel image-conditioned text correction fine-tuning strategy for VLMs that enhances their generalization of ITG for VL tasks.", + "- We developed an automated data construction pipeline that produces large amounts of samples for fine-tuning, all generated from image-text pairs without the need for human annotations or additional LLMs.", + "- We demonstrated notable improvements in the zero-shot generalization capabilities of VLMs across various VL tasks." + ], + "bbox": [ + 500, + 257, + 890, + 406 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 421, + 640, + 436 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Generative Vision Language Models With advancements in large-scale pretraining, vision-language models (VLMs) have demonstrated notable zero-shot generalization across various tasks. Unlike contrastive VLMs such as CLIP [29] and ALIGN [15], which focus on image-text similarity scores, generative VLMs output text based on image and text inputs for tasks like visual question answering and image captioning.", + "bbox": [ + 496, + 446, + 890, + 568 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In earlier studies, generative VLMs utilized fusion-encoder transformers [4, 20, 32, 41] to simultaneously encode visual and linguistic tokens, and subsequent models [5, 33, 36] integrated visual input information into different architecture language models, giving rise to unified generative VL transformer models. Recently, with advancements in Large Language Models (LLMs) [6, 28, 42, 43], efforts have sought to utilize LLMs' capabilities to project visual input into the language embedding space. BLIP-2 [19] bridges the modality gap using a pre-trained Q-Former. Building upon BLIP-2, MiniGPT-4 [45] and InstructBLIP [8] focus on next-stage instruction tuning to further enhance performance. LLaVA [22] involves GPT-4 [27] in generating instructions and conversations for training. LLaMA-Adapter v2 [11] and LaVIN [24] employ adapters for architecture fine-tuning.", + "bbox": [ + 496, + 568, + 890, + 809 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In our study, akin to LLaVA and Instruct-BLIP, we focus on leveraging the benefits of second-stage fine-tuning of pre-trained VLMs. However, unlike these approaches, we aim to achieve this without down-stream tasks data from human annotation and large models generation. Instead, we introduce a novel correction task, construct from the image", + "bbox": [ + 496, + 810, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "13429", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "text data with light-weight pipeline.", + "bbox": [ + 76, + 90, + 315, + 107 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Language Structure-based Data Augmentation Data augmentation is widely employed in machine learning, with common techniques such as mixup [40], CutMix [39], and RandAugment [7] in computer vision, and backtranslation [35], random word editing [34] in natural language processing. In the field of vision and language (VL), an effective approach often involves synthesizing new data using pre-trained models as augmentation [2]. For instance, BLIP [18] leverages the model's initially trained capabilities to generate additional training data, thereby further enhancing the model's performance.", + "bbox": [ + 75, + 125, + 468, + 289 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Some researchers in visual-linguistic (VL) studies pursue performance enhancements on challenging tasks by crafting difficult negative samples. For instance, NegCLIP [38] employs a language parser to swap elements between sentences, generating hard negative image-text pairs for contrastive fine-tuning. SVLC [9] achieves a similar outcome by substituting elements in sentences. Our approach leverages linguistic structure to improve image-text generation (ITG) tasks. Unlike image-text matching (ITM) tasks, which focus on learning similarity metrics, generative models encounter difficulties with negative samples. To address this, we introduce a correction task for instruction fine-tuning, using structural language information to construct data samples. This enhances the generalization performance of VLMs in zero-shot ITG-based visual language tasks.", + "bbox": [ + 75, + 290, + 470, + 531 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Preliminary", + "text_level": 1, + "bbox": [ + 76, + 544, + 202, + 561 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Image-text Generation of VLMs Image-text generation, a fundamental task of VLMs, involves generating text from both visual and textual inputs. Specifically, VLMs with parameters $\\Theta_{vlm}$ generate output text from images and textual input in an auto-regressive manner. The visual input is projected into language embedding as visual tokens $\\mathbf{Z}$ together with textual input $\\mathbf{w} = [w_1, w_2, \\dots, w_{i-1}]$ and fed into the subsequent LLM to predict the next token $w_i$ of the sequence $\\mathbf{w}$ .", + "bbox": [ + 75, + 569, + 468, + 705 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nw _ {i} = \\mathcal {F} _ {v l m} (\\mathbf {Z}, w _ {1}, w _ {2}, \\dots , w _ {i - 1}; \\boldsymbol {\\Theta} _ {v l m}). \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 138, + 715, + 468, + 732 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Second-stage Tuning for Zero-shot Generation While generative image-text pre-training provides VLMs with aligned vision-language representations, effective instruction-following of image-text generation for diverse zero-shot VL tasks is crucial. Recent works address this issue by leveraging either human-labeled [8] or large language model-generated task-oriented data [22] for instruction tuning. Concretely, in the second stage of tuning, the VLMs are optimized with the same objective of generative image-text pre-training with task-oriented data:", + "bbox": [ + 75, + 750, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\underset {\\Theta_ {v l m}} {\\arg \\max } \\sum_ {i = 1} ^ {K} \\log P \\left(w _ {i} \\mid \\mathbf {Z}, w _ {1}, w _ {2}, \\dots , w _ {i - 1}; \\Theta_ {v l m}\\right). \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 517, + 89, + 890, + 130 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Our Approach", + "text_level": 1, + "bbox": [ + 498, + 148, + 648, + 165 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we introduce our proposed Image Conditional Caption Correction (ICCC) task for second-stage tuning, which constructs data from unlabeled data with low resource consumption. We first provide a Task Definition of ICCC in Sec. 4.1. Then we introduce the data construction pipeline for ICCC, which includes two modules: the Concept Extractor and the Correction Data constructor. The concept extractor parses the text structure and extracts the concept set for the following data construction, discussed in Sec. 4.2. Subsequently, the correction data constructor generates data by augmenting text structure with the extracted concept set, described in Sec.4.3, Finally, Sec. 4.4 outlines our training and inference procedures for incorporating our task into VLM pre-training.", + "bbox": [ + 496, + 172, + 890, + 385 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. Task definition", + "text_level": 1, + "bbox": [ + 498, + 393, + 650, + 407 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As illustrated in Fig. 2, the ICCC task involves identifying and correcting language units of mismatched concepts of caption. To define the ICCC task, we need to define the concept set, how we perturb to produce concept-mismatched samples, and how the perturb operation changes the language structure.", + "bbox": [ + 496, + 415, + 890, + 505 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "For each sentence, concepts are composed of linguistic units representing their semantic meaning. These linguistic units are categorized into five types based on semantics and language granularity: $\\mathcal{E} = \\{\\text{entity phrase}, \\text{predicate phrase}, \\text{attribute phrase}, \\text{noun word}, \\text{verb word}\\}$ . The entity phrase, noun word, attribute phrase represent the object-level semantic, and predicate phrase, verb word represent the composition-level semantic. The phrase and word represent different levels of language granularity.", + "bbox": [ + 496, + 506, + 890, + 643 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "There are two operations for perturbing the language structure: $\\{\\mathrm{replace},\\mathrm{swap}\\}$ . The replace involves substituting a concept with another one of the same type from the image-text pair dataset, while the swap involves swapping the positions of two concepts of the same type within the original caption. More details are introduced in Sec. 4.3. Consequently, replace focuses on modeling the intrinsic meaning of individual concepts, while swap prioritizes the order of compositional concepts within sentences. Overall, the task is to use linguistic unit modifications of image-text pairs, providing universal concepts aligned between vision and language, which improves text generation capabilities across two modalities.", + "bbox": [ + 496, + 643, + 890, + 838 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.2. Concept Extractor", + "text_level": 1, + "bbox": [ + 500, + 847, + 679, + 863 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As mentioned earlier, the data of ICCC is generated by perturbing concepts in $\\mathcal{E}$ according to the structure of sen", + "bbox": [ + 498, + 869, + 890, + 901 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "13430", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/d666cd18de624b971507cfd028f9e790dea96f71bfa05b330f0eebbaf1eac523.jpg", + "image_caption": [ + "Figure 2. Illustration of the overall pipeline of ICCC. The concept extractor parses the sentence to obtain linguistic units of concepts. The task data constructor aims to produce the sample according to the sentence structure with the \"replace\" and \"swap\" operations. Finally, the generated ICCC data is used for image-to-text generative training for VLMs." + ], + "image_footnote": [], + "bbox": [ + 86, + 89, + 880, + 377 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "tences. The concept extractor takes captions as input and parses the dependency to identify linguistic units of concepts, which the following task constructor then uses to generate data samples. The concept extractor module has three processes: (1) universal dependency parsing; (2) linguistic unit selection and grouping; (2) concept collection.", + "bbox": [ + 75, + 434, + 472, + 525 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Universal Dependency Parsing We use the off-the-shelf universal dependency parser implemented by the spaCy [13] software library to extract the dependency structure of the original caption. As shown in Fig. 2, the dependency parser translates the sentence into a universal dependency tree [26]. The node of the dependency tree is the minimal linguistic unit $u_{[pos]}$ , which has Part-of-Speech (POS) tags to indicate its grammatical role. The edge represents the dependency relation between linguistic units $r_{[REL]}$ , which also has the relation type (REL). The dependency structure provides us with an indication of how linguistic units organize to represent the concept of a sentence.", + "bbox": [ + 75, + 545, + 468, + 728 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Linguistic Unit Selection and Grouping We extract the linguistic unit set of concept $U_{\\text{concept}}$ within $\\mathcal{E}$ by grouping and selecting $u_{[pos]}$ . To achieve this, we design a heuristic method by traversing the dependency tree to select the corresponding $u_{[pos]}$ . Firstly, we extract the concept represented by the concept of a word-level linguistic unit according to the POS tag:", + "bbox": [ + 75, + 748, + 468, + 853 + ], + "page_idx": 3 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. $U_{\\text{noun word}}: u_{[\\text{noun}]}$", + "2. $U_{verbword} : u_{[verb]}$" + ], + "bbox": [ + 78, + 856, + 222, + 886 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Based on such word-level concepts $u_{[pos]}$ , we further ex", + "bbox": [ + 78, + 887, + 468, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "tract linguistic units of phrase-level concepts, such as entity phrase, predicate phrase, attribute phrase, by grouping the $u_{[pos]}$ into $U_{concept}$ according to the $r_{[REL]}$ associated with word-level concept units:", + "bbox": [ + 496, + 434, + 892, + 494 + ], + "page_idx": 3 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. $U_{\\text{entity phrase}}$ : $u_{[adj]}$ and $U_{[det]}$ adjacent to $U_{[noun]}$", + "2. $U_{predicate phrase}$ : all $u_{[pos]}$ within two $u_{[noun]}$", + "3. $U_{\\text{attribute phrase}}$ : all $u_{[amod]}$ adjacent to $u_{[noun]}$" + ], + "bbox": [ + 500, + 494, + 836, + 541 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To this end, we extract the linguistic units of each concept type $U_{\\text{concept}}$ from the text according to the dependency structure.", + "bbox": [ + 500, + 542, + 890, + 585 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Concept Collection For each sentence from the image-text dataset, we collect all $U_{\\text{concept}}$ according to their concept type, respectively. We merge the $U_{\\text{noun word}}$ with the $U_{\\text{entity phrase}}$ and the $U_{\\text{verb word}}$ with the $U_{\\text{predicate phrase}}$ into the same concept type, respectively. This global-level concept base stores all the concepts that occurred in the dataset. We filter them by frequency to remove infrequent concepts, which could be extracted from low-quality captions or parsing errors, and the most frequent, which could be a trivial concept or language bias that occurred uniformly.", + "bbox": [ + 496, + 608, + 892, + 760 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.3. Correction Task Data Constructor", + "text_level": 1, + "bbox": [ + 500, + 770, + 800, + 786 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The correction task data constructor uses the extracted concept structure to generate data samples with multi-level concept mismatch captions. The data constructor takes the input text, which has identified concepts of language units and concept-based units, and produces the augmented text with expected corrections.", + "bbox": [ + 496, + 794, + 890, + 883 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Specifically, the data constructor perturbs the initial lin", + "bbox": [ + 517, + 885, + 890, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "13431", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "guistic structure by predefined operations: replace, swap, as shown in Fig. 2. Specifically, the replace randomly selects the concept of the original text and replaces it with an external $U_{\\text{concept}}$ that has the same semantic type but does not occur in the current text from the concept base. For instance, the entity phrase can be replaced by all object-level concepts, such as noun word or entity phrase. The swap operation, instead of replacing concept by concept, swaps the two linguistic unit sets with the same concept type in the text. This perturbation operation provides the order mismatch of the concept. To calibrate those two operations, we randomly select one by Bernoulli distribution with a preset parameter $p_s \\in [0,1]$ to decide which type of operation is used for perturbation. In those cases where a sentence doesn't have two of the same concept-type linguistic units, we simply use the replace operation.", + "bbox": [ + 75, + 90, + 472, + 332 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "After the perturb operation, we map back the tree structure sentence into sequence and construct the caption correction samples, which are composed of the following components: correction instruction prompt, perturbed caption, and correcting description, as shown in Fig. 2. The correction instruction prompt is selected from a template base, and the correcting description includes the mismatch concept and the correct ones.", + "bbox": [ + 75, + 332, + 472, + 454 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.4. Training and Inference", + "text_level": 1, + "bbox": [ + 76, + 460, + 290, + 477 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The data generated by ICCC is utilized in the second-stage tuning process to improve VLMs, as introduced in Sec 3. We combine ICCC data samples with original image-text pairs for training to prevent focusing too much on the specific task and catastrophic forgetting. The proportion of ICCC data samples to original pairs in each training batch is determined by a hyper-parameter $p_c$ . The overall pre-training objective remains unchanged from the initial image-text generation pre-training. This design enables VLMs to grasp the alignment of concepts and facilitate instruction following for various downstream generative VL tasks, enhancing their performance across different tasks. During inference, VLMs conduct standard image-to-text generation for VL tasks, consistent with previous generative VLMs [8, 19].", + "bbox": [ + 75, + 484, + 472, + 710 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 76, + 723, + 209, + 739 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this section, we thoroughly explore the effectiveness of our proposed training task. We detail the experimented models and implementation in Sec. 5.1, conduct primary zero-shot evaluations in Sec. 5.2, present ablation studies in Sec. 5.3, and offer qualitative insights in Sec. 5.4.", + "bbox": [ + 75, + 748, + 468, + 825 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.1. Experiments Configuration", + "text_level": 1, + "bbox": [ + 76, + 832, + 323, + 848 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Models and Training Data In the realm of generative VLMs, we select BLIP-2 [19] and InstructBLIP [8], representing different pre-training data paradigms. BLIP", + "bbox": [ + 76, + 854, + 468, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "2 utilizes image-text pair data without instructions, employing a frozen image encoder and a large language model. It integrates a lightweight querying transformer for mapping visual information into the language embedding space. Instead, InstructBLIP incorporates instruction tuning, enhancing the architecture of pre-trained BLIP-2 with an instruction-aware visual feature extractor. It undergoes complementary training with additional task-specific instruction-tuning data.", + "bbox": [ + 496, + 90, + 890, + 226 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In our model setup, we explore three variants of BLIP-2 to assess the generality of our training method across different LLM architectures. They share the same image encoder (ViT-G/14 from EVA-CLIP [10]) but employ distinct frozen LLMs: OPT [42] with 2.7B and 6.7B parameters, and FlanT5-XL [15] with 3B parameters. For InstructBLIP, we experiment with the Vicuna-7B [43] version. Initializing both models with pre-trained parameters, we freeze the vision encoder and LLM, focusing solely on training their Q-former and fully connected projection network.", + "bbox": [ + 496, + 227, + 890, + 378 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We construct ICCC samples using our proposed method on the COCO Caption [3] and Visual Genome (VG) Caption [16] datasets, totaling approximately 1 million imagedataset pairs. These samples are then utilized for language modeling training and image captioning in a second-stage training paradigm outlined in Sec. 4.4.", + "bbox": [ + 496, + 378, + 890, + 469 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Implementation Details We implement and evaluate our method using the LAVIS library [17], and mainly followed the training setup for the original models. The AdamW [23] optimizer with $\\beta_{1} = 0.9$ , $\\beta_{2} = 0.999$ , and a weight decay of 0.05 was employed. We used a linear warmup of the learning rate over the initial 1,000 steps, increasing from $10^{-8}$ to $10^{-5}$ , followed by a cosine decay with a minimum learning rate of 0. Batch sizes varied across models: 64 for BLIP-2 OPT2.7B and BLIP-2 FlanT5-XL, 28 for BLIP-2 OPT6.7B, and 24 for InstructBLIP. The images are resized to size $224\\times 224$ , and we apply random resized cropping and horizontal flipping augmentations. All training spanned a maximum of 20,000 iterations, with model performance validated every 1,000 iterations. Each training process utilized four Nvidia A40 (40G) GPUs, completed within a day.", + "bbox": [ + 496, + 489, + 890, + 715 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Regarding the hyperparameters, we conducted comparison experiments. We set $(p_c, p_s)$ as (0.3, 0.15), (0.3, 0), (0.01, 0.2), and (0.3, 0.3). for BLIP-2 OPT2.7B, BLIP-2 OPT6.7B, BLIP-2 FlanT5-XL, and InstructBLIP, respectively. Further details will be demonstrated in Sec. 5.3.", + "bbox": [ + 496, + 715, + 890, + 791 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.2. Zero-shot Evaluations", + "text_level": 1, + "bbox": [ + 500, + 801, + 705, + 816 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We present zero-shot evaluation results in Tab. 1 and Tab. 2 for BLIP-2 and InstructBLIP experiments. Our second-stage training strategy ICCC consistently improves zero-shot performance across various tasks and datasets, like visual question answering (VQA) and image captioning (IC),", + "bbox": [ + 496, + 825, + 890, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "13432", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/df765246ac4b24f628f8f4a6f75abede2df05aed7a150f3f953a8e5490480b62.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
BLIP-2GQAOK-VQAVQAv2VSRNoCaps
B@4SC
OPT2.7B33.526.651.948.343.613.8105.7
OPT2.7B w/ ICCC38.929.554.347.846.014.3111.9
OPT6.7B35.530.752.648.541.513.0101.4
OPT6.7B w/ ICCC38.231.758.851.544.113.6106.9
FlanT5-XL44.040.763.163.442.213.3103.1
FlanT5-XL w/ ICCC44.641.064.064.243.913.6106.0
", + "bbox": [ + 215, + 88, + 759, + 250 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/05129492101d75136bf06b6696e67e5ebb89706945e22012949f385d2938c8e3.jpg", + "table_caption": [ + "Table 1. The zero-shot evaluation results on BLIP-2 experiments. For three VQA datasets, we report top-1 accuracy $(\\%)$ on the testdev set of GQA [14], VSR [21], the test set of OK-VQA [25], and the validation set of VQAv2 [12]. For IC, we report metrics of BLUE@4 (B@4), CIDEr (C), and SPICE (S) on the validation set of NoCaps." + ], + "table_footnote": [], + "table_body": "
ModelGQAVSRNoCaps
InstructBLIP48.461.114.2
InstructBLIP w/ ICCC49.863.115.7
", + "bbox": [ + 120, + 323, + 431, + 385 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "demonstrating enhanced zero-shot generalization.", + "bbox": [ + 76, + 444, + 406, + 459 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The experimental results on BLIP-2 (Tab. 1) demonstrate the effectiveness of ICCC on models pre-trained by image-text pairs. Notable findings include:", + "bbox": [ + 75, + 460, + 468, + 505 + ], + "page_idx": 5 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- ICCC yields consistent improvements for BLIP-2 OPT2.7B, BLIP-2 OPT6.7B, and BLIP-2 FlanT5-XL. Specifically, the BLIP-2 OPT2.7B with ICCC shows a significant enhancement in GQA $(+5.4\\%)$ , while the BLIP-2 OPT6.7B improves considerably in VQAv2 $(+6.2\\%)$ . These results emphasize ICCC's ability to refine vision-conditioned language generation, irrespective of LLM sizes and architectures.", + "- In captioning tasks, SPICE metrics highlight improved accuracy at the structured scene level, including VL relations and attributes. Our task design, focusing on learning ITG generalizations for various concept roles, not only enhances object recognition accuracy but also improves understanding of object attributes and relations.", + "- In the InstructBLIP experiment results shown in Tab. 2, we note a consistent improvement in zero-shot evaluation benchmarks, even when the original model heavily relies on instruction tuning. This indicates the effectiveness of our approach across diverse pre-training image-text data, offering a valuable complementary method for augmenting visual-linguistic knowledge.", + "- We emphasize the Visual Spatial Reasoning (VSR) benchmark [21], created to evaluate a model's grasp of spatial relationships for vision-language reasoning. These enhancements stem from the varied concept data samples in our ICCC pre-training, which are able to encompass a" + ], + "bbox": [ + 76, + 508, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/974716e9bf0cb2a19e38737a8c49b7c7f632b205344e502f5ad8bbb26f249456.jpg", + "table_caption": [ + "Table 2. The zero-shot evaluation results on InstructBLIP experiments. We report the SPICE score for NoCaps." + ], + "table_footnote": [], + "table_body": "
Data SourceGQAOK-VQAVQAv2NoCaps
C+VVQAv2w/ ICCCB@4SC
1---33.526.651.943.613.8105.7
2✓--33.026.349.745.613.9108.1
3✓-✓38.929.554.346.014.3111.9
4✓✓-41.338.0-45.212.6106.4
5✓✓✓42.839.1-45.014.0108.2
", + "bbox": [ + 503, + 323, + 890, + 425 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 3. Ablation study on our method upon different second-stage training data types. C+V represents COCO and VG caption data. Since our focus is on zero-shot performance, we omit the results on the VQAv2 validation set after training with the VQAv2 training set.", + "bbox": [ + 498, + 429, + 893, + 500 + ], + "page_idx": 5 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "broad spectrum of vision-language relational concepts.", + "- Additionally, we assess the effectiveness of ICCC on another VLM (LLAVA [22]) and various vision-language reasoning datasets, including ScienceQA-IMG [31], MM-VET [37], and hallucinations [30]. Further experimental results can be found in the supplementary material." + ], + "bbox": [ + 500, + 516, + 890, + 621 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.3. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 643, + 653, + 662 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Effectiveness of Correction Task In Tab. 3, we compare our approach with alternative second-stage training methods, focusing on the BLIP-2 OPT2.7B model. We explore two types of second-stage training: one utilizing only COCO and VG caption datasets (lines 2 and 3), and the other incorporating the VQAv2 training set (lines 4 and 5) to assess the impact of instruction tuning. Our approach exclusively targets caption datasets, maintaining consistent task sample construction parameters.", + "bbox": [ + 496, + 671, + 890, + 808 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Experimental results indicate that our training approach consistently outperforms conventional second-stage methods, regardless of the inclusion of VQA data for instruction-tuning. This underscores the efficacy of our task, emphasizing its superiority over traditional ITG second-stage training strategies.", + "bbox": [ + 496, + 810, + 890, + 901 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "13433", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/2768b48a5f42a614881891aa42f811fc5f2f1c6b1de8e17ac6c71d070334948c.jpg", + "image_caption": [ + "Figure 3. Hyper-parameter searching on $p_c$ and $p_s$ ." + ], + "image_footnote": [], + "bbox": [ + 91, + 95, + 477, + 281 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/3f5069e8f2d49cd4bbcf0031f6ebc5ff17e0b1b366830f7e2256046ee6abaa26.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 491, + 95, + 875, + 280 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Ablation for Task Construction In Tab. 4, we demonstrate the necessity of including different types of concepts to edit for constructing mismatched captions. The experiments were conducted on the BLIP-2 OPT2.7B model, maintaining consistent hyper-parameters. Results indicate that using concepts of different natures for task construction yields complementary effects.", + "bbox": [ + 75, + 316, + 468, + 421 + ], + "page_idx": 6 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- In the first part, we investigate influence of language granularity, focusing on tasks constructed around words and phrases. As shown in lines 3-4 of Tab.4, our findings reveal the significance of phrase-level concepts for the VQA task, while word-level concepts aid in refining the model's understanding of individual words, thereby improving captioning accuracy metrics such as BLUE@4 and CIDEr.", + "- In the subsequent section (lines 5-6), we delve into the roles of various concepts in semantics, exploring the impact of tasks centered on entity-level, relation-level, and attribute-level concepts. Referencing Tab.4, our analysis reveals that focusing solely on learning at the entity level yields strong performance in VQA tasks but may sacrifice accuracy in comprehending relations and attributes, thereby resulting in sub-optimal image captioning performance.", + "- We conducted an ablation study to assess the impact of instructions and language structure (line 7, Tab.4). We retained the instructions of the ICCC task while randomly altering words within the sentences. Surprisingly, the addition of correction instructions and random language masking did not enhance the generalization capability of VLMs on downstream tasks. This highlights the importance of language structure in instruction tuning." + ], + "bbox": [ + 76, + 425, + 470, + 803 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In conclusion, the diversity in concept extraction allows our method to perform well on various zero-shot generation tasks, demonstrating strong generality.", + "bbox": [ + 75, + 805, + 468, + 851 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Hyper-parameter Selection The hyperparameters $p_c$ and $p_s$ are pivotal in adjusting the distribution of task samples", + "bbox": [ + 76, + 869, + 468, + 902 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/5f0f29760b86ba1a0f1279b841a31874832e7c9e3b219a53c6d83f117c4a761f.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
TypeGQAOK-VQAVQAv2NoCaps
B@4SC
1none33.026.349.745.613.9108.1
2all38.929.554.346.014.3111.9
3noun, verb36.430.752.146.014.3114.3
4ent, pred, attr38.327.554.945.214.7111.3
5noun, ent38.529.854.846.514.4112.4
6verb, pred, attr36.029.654.146.914.5114.1
7random33.026.248.644.114.5107.1
", + "bbox": [ + 503, + 313, + 890, + 460 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 4. Ablation study on editing different subsets of concept types for mismatched caption construction.", + "bbox": [ + 498, + 469, + 890, + 497 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "in our approach. We conducted a comprehensive hyperparameter search for each experimental model, analyzing the impact of these parameters on model performance. Fig. 3 illustrate the performance variations of BLIP-2 OPT2.7B after second-stage training under different hyperparameter settings:", + "bbox": [ + 496, + 508, + 890, + 599 + ], + "page_idx": 6 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- In the left of Fig. 3, with $p_s$ fixed at 0.1, we study the influence of different correction task sample proportions by varying $p_c$ at intervals of 0.15.", + "- In the right of Fig. 3, with $p_c$ fixed at 0.3, we explore the impact of different swap operation proportions on mismatched caption sampling by varying $p_s$ at intervals of 0.15." + ], + "bbox": [ + 500, + 604, + 890, + 709 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In our experiments, we present several key findings:", + "bbox": [ + 517, + 714, + 861, + 729 + ], + "page_idx": 6 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- From both figures, it is evident that the impact of hyperparameters $p_{c}$ and $p_{s}$ on model performance follows a consistent trend, initially increasing before decreasing. This phenomenon arises due to the risk of language bias when incorporating excessive correction task samples, particularly those generated through swap operations.", + "- Notably, the saturation point of $p_{s}$ is reached early, suggesting that the model can easily identify and correct mismatched captions created through swap operations. Despite this, proper inclusion of such samples proves beneficial for overall performance enhancement, particularly" + ], + "bbox": [ + 500, + 734, + 890, + 901 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "13434", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/f82f9b60febece513d29d72bcdf8a26f0d0dda29e3480a51517a550448f38ed0.jpg", + "image_caption": [ + "Is the jar made of the same materials as the hook?" + ], + "image_footnote": [], + "bbox": [ + 130, + 94, + 197, + 156 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/fcdf40dfb8c6ad42d6e0aecd8b0824596104000060325fdf7aeadd6bdf1ca5b0.jpg", + "image_caption": [ + "Are there men to the right of the woman that is wearing trousers?" + ], + "image_footnote": [], + "bbox": [ + 207, + 93, + 328, + 156 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/90aa250ebd47a03a6193385c75fcfff6f2e1746324b35edace3cf9b2b4957b45.jpg", + "image_caption": [ + "What kind of furniture is surrounding the table?" + ], + "image_footnote": [], + "bbox": [ + 341, + 94, + 460, + 156 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/6866c2d394b7968efc8a7c2826622d4ef71619e62ea0b23895328e18c87c0718.jpg", + "image_caption": [ + "BLIP-2: Yes." + ], + "image_footnote": [], + "bbox": [ + 132, + 176, + 197, + 238 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/558b893637c02799fd205e0efcad6722930fc9014af681cfd4550901de3b8a78.jpg", + "image_caption": [ + "BLIP-2: Yes." + ], + "image_footnote": [], + "bbox": [ + 207, + 175, + 328, + 238 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/19bd9fb27687ba650b318565c0a1da466554f673fa5a7ccd91c63c6a18ee576f.jpg", + "image_caption": [ + "BLIP-2: Kitchen." + ], + "image_footnote": [], + "bbox": [ + 341, + 175, + 460, + 238 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/cccf7c51c03f65e477ecbc4ac9639e590c3d5f339dfb021cdfa6a17989eace0d.jpg", + "image_caption": [ + "Ours: No." + ], + "image_footnote": [], + "bbox": [ + 132, + 253, + 197, + 316 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/981c70c45bbdc1ee829f7dec59ea26191f2ab38e4b46310f4342e0be34c32636.jpg", + "image_caption": [ + "Ours: No." + ], + "image_footnote": [], + "bbox": [ + 207, + 253, + 328, + 316 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d5948d4b430c4ffa90f0e1a19d64668a23cb49dbcdd4cc938f16918d96557bee.jpg", + "image_caption": [ + "Ours: Chair." + ], + "image_footnote": [], + "bbox": [ + 341, + 253, + 460, + 316 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/bdab1b91fcab60ee607791df9ab7e6548fa8736b8226c682db2fd51e6cd7dbdd.jpg", + "image_caption": [ + "BLIP-2: A red kite flying over a forest." + ], + "image_footnote": [], + "bbox": [ + 114, + 340, + 217, + 393 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a187607ab43895d0258d1e643e348cb04d13b217ea2840c991b94ed1029b6d0b.jpg", + "image_caption": [ + "A group of children in a library." + ], + "image_footnote": [], + "bbox": [ + 227, + 340, + 348, + 393 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/441d84473c706cc90f41209130c72b63fdb532db5ce93b77fce2a3c8247c20bb.jpg", + "image_caption": [ + "A man sitting in front of", + "a wood burning stove.", + "A person looking at a fire", + "in a wood stove.", + "Figure 4. Visualization results include model output examples and attention gradients on images. The first block illustrates three examples from the GQA testdev set, while the second block showcases three examples from the NoCaps validation set. With our training, the model demonstrates improved accuracy in focusing on prompt-relevant image regions. Additionally, it generates captions with more detailed descriptions of scenes and actions." + ], + "image_footnote": [], + "bbox": [ + 357, + 340, + 457, + 393 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "in image captioning tasks.", + "bbox": [ + 89, + 560, + 264, + 574 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "- Furthermore, our investigation reveals that BLIP-2 FlanT5-XL tends to overfit on our task samples, possibly attributed to its encoder-decoder architecture. This results in the Q-former learning an overfitted encoding of soft prompts associated with task text patterns. Nonetheless, even minimal incorporation of correction task samples $(p_c = 0.01)$ effectively serves our training objectives while mitigating the risk of overfitting.", + "bbox": [ + 76, + 575, + 468, + 696 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Qualitative Results", + "text_level": 1, + "bbox": [ + 76, + 708, + 259, + 724 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To provide a more intuitive understanding of the effects of our training, we show some qualitative model output examples in Fig. 4. We demonstrate the differences between the model outputs and intermediate results on the VQA and IC tasks before and after our second-stage training respectively. The heat maps show the gradient of the output logit corresponding to the ground truth token with regard to the image attention, which reflects the potential visual contribution of the model output.", + "bbox": [ + 75, + 732, + 468, + 868 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "According to the outputs for VQA, the results reveal that the proposed correction task training produces inter", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "pretable improvements to VQA responses. Our model demonstrates increased accuracy in locating objects referenced in prompts and exhibits a more precise understanding of compositional concepts, avoiding biases toward prominent objects. For instance, in the first example, our model focuses on the \"hook\", which the original model misses. In the second example, our model correctly considers the composed concept of \"the woman that is wearing trousers\". Lastly, our model interprets the relational concept \"surrounding the table\" and directs attention appropriately toward the relevant region, rather than the table itself. Overall, our findings indicate that this training methodology enhances VLMs' capacity for interpreting corresponding visual concepts expressed through language.", + "bbox": [ + 496, + 90, + 890, + 303 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Examples from our experiments with IC illustrate this improved ability to correct misidentified objects and provide richer, more fine-grained descriptions of object relationships and actions. For instance, our model correctly identifies the wrong \"red kite\" concept in the first case and provides more nuanced details about the scene, such as \"standing around a table\" and \"looking\". We posit that the primary source of improved overall captioning performance lies in the generation of more accurate and comprehensive concepts in captions.", + "bbox": [ + 496, + 311, + 890, + 462 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Conclusively, our study indicates that the proposed training method potentially enhances generative VLMs' capacity for aligning concepts across multiple types and granularities in visual and language modalities. We believe this insight could shed light on the future development of cost-effective, multi-granularity, and structured generative VL pre-trained models.", + "bbox": [ + 496, + 470, + 890, + 575 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 616, + 617, + 631 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we propose the image-conditioned text correction task for enhancing zero-shot text generation with unlabeled data. In this task, VLMs requires to identify and correct the error in accordance with the vision modality via text generation. We propose a scalable and cost-effective data construction framework for generating the image-text pair for this task by utilizing the inherent structure of language. The experimental results indicate that the implementation of our training framework substantially improves the ability of VLMs to generalize across a range of VL tasks involving image-to-text generation.", + "bbox": [ + 496, + 650, + 890, + 816 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Discussion of Limitation Due to the limitation of the computing resource, extending our approach to larger datasets and models remains unexplored. Future work should explore its application to more extensive datasets and diverse large vision-language models.", + "bbox": [ + 496, + 825, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "13435", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 106 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katherine Millican, Malcolm Reynolds, et al. Flamingo: a visual language model for few-shot learning. Advances in Neural Information Processing Systems, 35:23716-23736, 2022. 1, 2", + "[2] Paola Cascante-Bonilla, Khaled Shehada, James Seale Smith, Sivan Doveh, Donghyun Kim, Rameswar Panda, Gul Varol, Aude Oliva, Vicente Ordonez, Rogerio Feris, et al. 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Minigpt-4: Enhancing vision-language understanding with advanced large language models. arXiv preprint arXiv:2304.10592, 2023. 2" + ], + "bbox": [ + 501, + 92, + 890, + 698 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "13437", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_model.json b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_model.json new file mode 100644 index 0000000000000000000000000000000000000000..75d502e4a4f22202db00e6e16e55b8224e3a44cc --- /dev/null +++ b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_model.json @@ -0,0 +1,2431 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.12, + 0.13, + 0.85, + 0.177 + ], + "angle": 0, + "content": "Learning by Correction: Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning" + }, + { + "type": "text", + "bbox": [ + 0.327, + 0.211, + 0.65, + 0.231 + ], + "angle": 0, + "content": "Rongjie Li\\(^{1*}\\) Yu Wu\\(^{1*}\\) Xuming He\\(^{1,2‡}\\)" + }, + { + "type": "text", + "bbox": [ + 0.19, + 0.233, + 0.777, + 0.253 + ], + "angle": 0, + "content": "\\(^{1}\\)School of Information Science and Technology, ShanghaiTech University" + }, + { + "type": "text", + "bbox": [ + 0.192, + 0.255, + 0.777, + 0.295 + ], + "angle": 0, + "content": "\\(^{2}\\)Shanghai Engineering Research Center of Intelligent Vision and Imaging {lirj2, wuyu1, hexm} \\(@\\) shanghaiitech.edu.cn" + }, + { + "type": "list", + "bbox": [ + 0.19, + 0.233, + 0.777, + 0.295 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.329, + 0.313, + 0.345 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.362, + 0.474, + 0.665 + ], + "angle": 0, + "content": "Generative vision-language models (VLMs) have shown impressive performance in zero-shot vision-language tasks like image captioning and visual question answering. However, improving their zero-shot reasoning typically requires second-stage instruction tuning, which relies heavily on human-labeled or large language model-generated annotation, incurring high labeling costs. To tackle this challenge, we introduce Image-Conditioned Caption Correction (ICCC), a novel pre-training task designed to enhance VLMs' zero-shot performance without the need for labeled task-aware data. The ICCC task compels VLMs to rectify mismatches between visual and language concepts, thereby enhancing instruction following and text generation conditioned on visual inputs. Leveraging language structure and a lightweight dependency parser, we construct data samples of ICCC task from image-text datasets with low labeling and computation costs. Experimental results on BLIP-2 and InstructBLIP demonstrate significant improvements in zero-shot image-text generation-based VL tasks through ICCC instruction tuning." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.697, + 0.21, + 0.712 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.723, + 0.47, + 0.815 + ], + "angle": 0, + "content": "Vision-language models (VLMs) have demonstrated remarkable performance across a wide range of vision-language (VL) tasks, including image captioning [1, 19, 22, 33, 36], visual recognition [15, 29, 44], image-text retrieval [18, 29], and answering visual questions [1, 19, 22, 33, 36]. Generally, existing VLMs are able to conduct two" + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.828, + 0.47, + 0.9 + ], + "angle": 0, + "content": "*Equal Contribution. This work was supported by NSFC 62350610269, the Shanghai Frontiers Science Center of Human-centered Artificial Intelligence, and the MoE Key Lab of Intelligent Perception and Human-Machine Collaboration (ShanghaiTech University). ‡ denotes corresponding author. Code is available: https://github.com/SHTUPLUS/ICCC_CVPR2024" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.333, + 0.891, + 0.721 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.741, + 0.894, + 0.811 + ], + "angle": 0, + "content": "Figure 1. Illustration of second-stage tuning for zero-shot VL task adaptation comparison. The instruction tuning in recent works needs human label or LLM-generated data; in contrast, our image caption correction tuning is conducted on unlabeled image-text data with an NLP parser." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.894, + 0.901 + ], + "angle": 0, + "content": "essential tasks: image-text matching (ITM) and image-text generation (ITG). The contrastive-based ITM aims to model the similarity between vision and text through a shared embedding [15, 18, 29]. In contrast, the generative-based ITG has more flexibility in adapting to various VL tasks. More-" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13428" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.168 + ], + "angle": 0, + "content": "over, several recent VLM frameworks integrate the LLMs for ITG, which extend the powerful text generation across vision and text modality [1, 8, 19, 22], and allow VLMs to perform zero-shot inference on various VL tasks with impressive performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.17, + 0.47, + 0.382 + ], + "angle": 0, + "content": "To perform zero-shot inference on VL tasks, the VLMs need to have generalizable text generation capability according to text inputs and concepts from the visual modality. The existing works typically conduct second-stage instruction tuning for pre-trained VLMs with task-oriented data. This improves VLMs for following instructions to generate texts conditioned on visual modality, which ultimately enhances the zero-shot performance on VL-tasks such as InstructBLIP [8] and LLAVA [22], as shown in the upper part of Fig. 1. However, these methods necessitate substantial downstream task data annotation for fine-tuning, which is either human-labeled or generated externally by large language models. This process escalates labor costs throughout the system." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.385, + 0.47, + 0.627 + ], + "angle": 0, + "content": "In this study, we introduce a novel pre-training task, Image-Conditioned Caption Correction (ICCC), aimed at enhancing VLMs' performance on zero-shot VL tasks. Our approach leverages the semantic dependency structure of language utilized for second-stage tuning of VLMs, using image-text data without task-specific annotation, as depicted in Fig. 1. By enforcing VLMs to identify and rectify mismatched concepts between visual and language, our method enhances VLMs' capability of generating text from the visual modality. Importantly, the adopted universal semantic dependency [26] ensures comprehensive coverage of various concepts, including objects, their attributes, and interactions between them. Furthermore, we construct the data from unlabeled image-text datasets only with a lightweight dependency parser, which achieves low labeling and computation costs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Specifically, our pre-training framework first generates the task of image-conditioned text correction in an automatic manner. To this end, we develop a data construction pipeline with two components: the concept extractor and the correction task constructor. Firstly, the concept extractor identifies various concepts from the text modality. With the off-the-shelf dependency parser, it extracts the set of language units by parsing the semantic dependency structure of text. Subsequently, the correction task constructor generates samples from the unlabeled image-text data according to language structure and concept set. It swaps or replaces language units according to the extracted concept set, thereby creating concept-mismatched image-text pairs. Thanks to the universality of dependency, this approach allows us to create a wide variety of samples covering diverse visual-language concepts. The resulting text correction task requires VLMs to detect and recover the language units of mismatched concepts (words and phrases) according to the" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.137 + ], + "angle": 0, + "content": "image. Finally, we use the generated samples together with the original image-text data to fine-tune pre-trained VLMs with language modeling objectives." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.137, + 0.892, + 0.257 + ], + "angle": 0, + "content": "We conduct extensive experiments on two VLMs, BLIP-2 [19] and InstructBLIP [8], and evaluate the zero-shot performance of ITG on the representative tasks: visual question answering and image caption. Our findings reveal that our proposed method yields substantial improvements in zero-shot generalization based on the initial pre-train model without requiring any manually labeled or LLM-generated data. The main contributions of our work are threefold:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.258, + 0.892, + 0.302 + ], + "angle": 0, + "content": "- We introduce a novel image-conditioned text correction fine-tuning strategy for VLMs that enhances their generalization of ITG for VL tasks." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.304, + 0.892, + 0.362 + ], + "angle": 0, + "content": "- We developed an automated data construction pipeline that produces large amounts of samples for fine-tuning, all generated from image-text pairs without the need for human annotations or additional LLMs." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.364, + 0.892, + 0.407 + ], + "angle": 0, + "content": "- We demonstrated notable improvements in the zero-shot generalization capabilities of VLMs across various VL tasks." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.258, + 0.892, + 0.407 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.422, + 0.642, + 0.438 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.448, + 0.892, + 0.569 + ], + "angle": 0, + "content": "Generative Vision Language Models With advancements in large-scale pretraining, vision-language models (VLMs) have demonstrated notable zero-shot generalization across various tasks. Unlike contrastive VLMs such as CLIP [29] and ALIGN [15], which focus on image-text similarity scores, generative VLMs output text based on image and text inputs for tasks like visual question answering and image captioning." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.569, + 0.892, + 0.81 + ], + "angle": 0, + "content": "In earlier studies, generative VLMs utilized fusion-encoder transformers [4, 20, 32, 41] to simultaneously encode visual and linguistic tokens, and subsequent models [5, 33, 36] integrated visual input information into different architecture language models, giving rise to unified generative VL transformer models. Recently, with advancements in Large Language Models (LLMs) [6, 28, 42, 43], efforts have sought to utilize LLMs' capabilities to project visual input into the language embedding space. BLIP-2 [19] bridges the modality gap using a pre-trained Q-Former. Building upon BLIP-2, MiniGPT-4 [45] and InstructBLIP [8] focus on next-stage instruction tuning to further enhance performance. LLaVA [22] involves GPT-4 [27] in generating instructions and conversations for training. LLaMA-Adapter v2 [11] and LaVIN [24] employ adapters for architecture fine-tuning." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In our study, akin to LLaVA and Instruct-BLIP, we focus on leveraging the benefits of second-stage fine-tuning of pre-trained VLMs. However, unlike these approaches, we aim to achieve this without down-stream tasks data from human annotation and large models generation. Instead, we introduce a novel correction task, construct from the image" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13429" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.316, + 0.108 + ], + "angle": 0, + "content": "text data with light-weight pipeline." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.125, + 0.47, + 0.29 + ], + "angle": 0, + "content": "Language Structure-based Data Augmentation Data augmentation is widely employed in machine learning, with common techniques such as mixup [40], CutMix [39], and RandAugment [7] in computer vision, and backtranslation [35], random word editing [34] in natural language processing. In the field of vision and language (VL), an effective approach often involves synthesizing new data using pre-trained models as augmentation [2]. For instance, BLIP [18] leverages the model's initially trained capabilities to generate additional training data, thereby further enhancing the model's performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.291, + 0.471, + 0.532 + ], + "angle": 0, + "content": "Some researchers in visual-linguistic (VL) studies pursue performance enhancements on challenging tasks by crafting difficult negative samples. For instance, NegCLIP [38] employs a language parser to swap elements between sentences, generating hard negative image-text pairs for contrastive fine-tuning. SVLC [9] achieves a similar outcome by substituting elements in sentences. Our approach leverages linguistic structure to improve image-text generation (ITG) tasks. Unlike image-text matching (ITM) tasks, which focus on learning similarity metrics, generative models encounter difficulties with negative samples. To address this, we introduce a correction task for instruction fine-tuning, using structural language information to construct data samples. This enhances the generalization performance of VLMs in zero-shot ITG-based visual language tasks." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.545, + 0.204, + 0.563 + ], + "angle": 0, + "content": "3. Preliminary" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.57, + 0.469, + 0.706 + ], + "angle": 0, + "content": "Image-text Generation of VLMs Image-text generation, a fundamental task of VLMs, involves generating text from both visual and textual inputs. Specifically, VLMs with parameters \\(\\Theta_{vlm}\\) generate output text from images and textual input in an auto-regressive manner. The visual input is projected into language embedding as visual tokens \\(\\mathbf{Z}\\) together with textual input \\(\\mathbf{w} = [w_1, w_2, \\dots, w_{i-1}]\\) and fed into the subsequent LLM to predict the next token \\(w_i\\) of the sequence \\(\\mathbf{w}\\)." + }, + { + "type": "equation", + "bbox": [ + 0.139, + 0.716, + 0.469, + 0.733 + ], + "angle": 0, + "content": "\\[\nw _ {i} = \\mathcal {F} _ {v l m} (\\mathbf {Z}, w _ {1}, w _ {2}, \\dots , w _ {i - 1}; \\boldsymbol {\\Theta} _ {v l m}). \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Second-stage Tuning for Zero-shot Generation While generative image-text pre-training provides VLMs with aligned vision-language representations, effective instruction-following of image-text generation for diverse zero-shot VL tasks is crucial. Recent works address this issue by leveraging either human-labeled [8] or large language model-generated task-oriented data [22] for instruction tuning. Concretely, in the second stage of tuning, the VLMs are optimized with the same objective of generative image-text pre-training with task-oriented data:" + }, + { + "type": "equation", + "bbox": [ + 0.518, + 0.09, + 0.892, + 0.131 + ], + "angle": 0, + "content": "\\[\n\\underset {\\Theta_ {v l m}} {\\arg \\max } \\sum_ {i = 1} ^ {K} \\log P \\left(w _ {i} \\mid \\mathbf {Z}, w _ {1}, w _ {2}, \\dots , w _ {i - 1}; \\Theta_ {v l m}\\right). \\tag {2}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.149, + 0.649, + 0.166 + ], + "angle": 0, + "content": "4. Our Approach" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.174, + 0.892, + 0.386 + ], + "angle": 0, + "content": "In this section, we introduce our proposed Image Conditional Caption Correction (ICCC) task for second-stage tuning, which constructs data from unlabeled data with low resource consumption. We first provide a Task Definition of ICCC in Sec. 4.1. Then we introduce the data construction pipeline for ICCC, which includes two modules: the Concept Extractor and the Correction Data constructor. The concept extractor parses the text structure and extracts the concept set for the following data construction, discussed in Sec. 4.2. Subsequently, the correction data constructor generates data by augmenting text structure with the extracted concept set, described in Sec.4.3, Finally, Sec. 4.4 outlines our training and inference procedures for incorporating our task into VLM pre-training." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.394, + 0.651, + 0.408 + ], + "angle": 0, + "content": "4.1. Task definition" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.416, + 0.892, + 0.506 + ], + "angle": 0, + "content": "As illustrated in Fig. 2, the ICCC task involves identifying and correcting language units of mismatched concepts of caption. To define the ICCC task, we need to define the concept set, how we perturb to produce concept-mismatched samples, and how the perturb operation changes the language structure." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.507, + 0.892, + 0.644 + ], + "angle": 0, + "content": "For each sentence, concepts are composed of linguistic units representing their semantic meaning. These linguistic units are categorized into five types based on semantics and language granularity: \\(\\mathcal{E} = \\{\\text{entity phrase}, \\text{predicate phrase}, \\text{attribute phrase}, \\text{noun word}, \\text{verb word}\\}\\). The entity phrase, noun word, attribute phrase represent the object-level semantic, and predicate phrase, verb word represent the composition-level semantic. The phrase and word represent different levels of language granularity." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.892, + 0.839 + ], + "angle": 0, + "content": "There are two operations for perturbing the language structure: \\(\\{\\mathrm{replace},\\mathrm{swap}\\}\\). The replace involves substituting a concept with another one of the same type from the image-text pair dataset, while the swap involves swapping the positions of two concepts of the same type within the original caption. More details are introduced in Sec. 4.3. Consequently, replace focuses on modeling the intrinsic meaning of individual concepts, while swap prioritizes the order of compositional concepts within sentences. Overall, the task is to use linguistic unit modifications of image-text pairs, providing universal concepts aligned between vision and language, which improves text generation capabilities across two modalities." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.848, + 0.681, + 0.864 + ], + "angle": 0, + "content": "4.2. Concept Extractor" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.892, + 0.902 + ], + "angle": 0, + "content": "As mentioned earlier, the data of ICCC is generated by perturbing concepts in \\(\\mathcal{E}\\) according to the structure of sen" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13430" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.088, + 0.09, + 0.881, + 0.378 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.38, + 0.893, + 0.424 + ], + "angle": 0, + "content": "Figure 2. Illustration of the overall pipeline of ICCC. The concept extractor parses the sentence to obtain linguistic units of concepts. The task data constructor aims to produce the sample according to the sentence structure with the \"replace\" and \"swap\" operations. Finally, the generated ICCC data is used for image-to-text generative training for VLMs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.435, + 0.473, + 0.526 + ], + "angle": 0, + "content": "tences. The concept extractor takes captions as input and parses the dependency to identify linguistic units of concepts, which the following task constructor then uses to generate data samples. The concept extractor module has three processes: (1) universal dependency parsing; (2) linguistic unit selection and grouping; (2) concept collection." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.546, + 0.47, + 0.729 + ], + "angle": 0, + "content": "Universal Dependency Parsing We use the off-the-shelf universal dependency parser implemented by the spaCy [13] software library to extract the dependency structure of the original caption. As shown in Fig. 2, the dependency parser translates the sentence into a universal dependency tree [26]. The node of the dependency tree is the minimal linguistic unit \\( u_{[pos]} \\), which has Part-of-Speech (POS) tags to indicate its grammatical role. The edge represents the dependency relation between linguistic units \\( r_{[REL]} \\), which also has the relation type (REL). The dependency structure provides us with an indication of how linguistic units organize to represent the concept of a sentence." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.749, + 0.47, + 0.854 + ], + "angle": 0, + "content": "Linguistic Unit Selection and Grouping We extract the linguistic unit set of concept \\( U_{\\text{concept}} \\) within \\( \\mathcal{E} \\) by grouping and selecting \\( u_{[pos]} \\). To achieve this, we design a heuristic method by traversing the dependency tree to select the corresponding \\( u_{[pos]} \\). Firstly, we extract the concept represented by the concept of a word-level linguistic unit according to the POS tag:" + }, + { + "type": "text", + "bbox": [ + 0.08, + 0.857, + 0.223, + 0.872 + ], + "angle": 0, + "content": "1. \\(U_{\\text{noun word}}: u_{[\\text{noun}]}\\)" + }, + { + "type": "text", + "bbox": [ + 0.08, + 0.873, + 0.216, + 0.887 + ], + "angle": 0, + "content": "2. \\( U_{verbword} : u_{[verb]} \\)" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.857, + 0.223, + 0.887 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.888, + 0.469, + 0.903 + ], + "angle": 0, + "content": "Based on such word-level concepts \\(u_{[pos]}\\), we further ex" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.435, + 0.893, + 0.495 + ], + "angle": 0, + "content": "tract linguistic units of phrase-level concepts, such as entity phrase, predicate phrase, attribute phrase, by grouping the \\( u_{[pos]} \\) into \\( U_{concept} \\) according to the \\( r_{[REL]} \\) associated with word-level concept units:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.496, + 0.838, + 0.512 + ], + "angle": 0, + "content": "1. \\( U_{\\text{entity phrase}} \\): \\( u_{[adj]} \\) and \\( U_{[det]} \\) adjacent to \\( U_{[noun]} \\)" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.512, + 0.805, + 0.528 + ], + "angle": 0, + "content": "2. \\( U_{predicate phrase} \\): all \\( u_{[pos]} \\) within two \\( u_{[noun]} \\)" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.528, + 0.816, + 0.542 + ], + "angle": 0, + "content": "3. \\( U_{\\text{attribute phrase}} \\): all \\( u_{[amod]} \\) adjacent to \\( u_{[noun]} \\)" + }, + { + "type": "list", + "bbox": [ + 0.501, + 0.496, + 0.838, + 0.542 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.543, + 0.892, + 0.587 + ], + "angle": 0, + "content": "To this end, we extract the linguistic units of each concept type \\( U_{\\text{concept}} \\) from the text according to the dependency structure." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.609, + 0.893, + 0.761 + ], + "angle": 0, + "content": "Concept Collection For each sentence from the image-text dataset, we collect all \\( U_{\\text{concept}} \\) according to their concept type, respectively. We merge the \\( U_{\\text{noun word}} \\) with the \\( U_{\\text{entity phrase}} \\) and the \\( U_{\\text{verb word}} \\) with the \\( U_{\\text{predicate phrase}} \\) into the same concept type, respectively. This global-level concept base stores all the concepts that occurred in the dataset. We filter them by frequency to remove infrequent concepts, which could be extracted from low-quality captions or parsing errors, and the most frequent, which could be a trivial concept or language bias that occurred uniformly." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.771, + 0.802, + 0.787 + ], + "angle": 0, + "content": "4.3. Correction Task Data Constructor" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.884 + ], + "angle": 0, + "content": "The correction task data constructor uses the extracted concept structure to generate data samples with multi-level concept mismatch captions. The data constructor takes the input text, which has identified concepts of language units and concept-based units, and produces the augmented text with expected corrections." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.886, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Specifically, the data constructor perturbs the initial lin" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "13431" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.333 + ], + "angle": 0, + "content": "guistic structure by predefined operations: replace, swap, as shown in Fig. 2. Specifically, the replace randomly selects the concept of the original text and replaces it with an external \\( U_{\\text{concept}} \\) that has the same semantic type but does not occur in the current text from the concept base. For instance, the entity phrase can be replaced by all object-level concepts, such as noun word or entity phrase. The swap operation, instead of replacing concept by concept, swaps the two linguistic unit sets with the same concept type in the text. This perturbation operation provides the order mismatch of the concept. To calibrate those two operations, we randomly select one by Bernoulli distribution with a preset parameter \\( p_s \\in [0,1] \\) to decide which type of operation is used for perturbation. In those cases where a sentence doesn't have two of the same concept-type linguistic units, we simply use the replace operation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.333, + 0.473, + 0.455 + ], + "angle": 0, + "content": "After the perturb operation, we map back the tree structure sentence into sequence and construct the caption correction samples, which are composed of the following components: correction instruction prompt, perturbed caption, and correcting description, as shown in Fig. 2. The correction instruction prompt is selected from a template base, and the correcting description includes the mismatch concept and the correct ones." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.462, + 0.292, + 0.478 + ], + "angle": 0, + "content": "4.4. Training and Inference" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.485, + 0.473, + 0.712 + ], + "angle": 0, + "content": "The data generated by ICCC is utilized in the second-stage tuning process to improve VLMs, as introduced in Sec 3. We combine ICCC data samples with original image-text pairs for training to prevent focusing too much on the specific task and catastrophic forgetting. The proportion of ICCC data samples to original pairs in each training batch is determined by a hyper-parameter \\( p_c \\). The overall pre-training objective remains unchanged from the initial image-text generation pre-training. This design enables VLMs to grasp the alignment of concepts and facilitate instruction following for various downstream generative VL tasks, enhancing their performance across different tasks. During inference, VLMs conduct standard image-to-text generation for VL tasks, consistent with previous generative VLMs [8, 19]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.724, + 0.21, + 0.74 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.749, + 0.47, + 0.826 + ], + "angle": 0, + "content": "In this section, we thoroughly explore the effectiveness of our proposed training task. We detail the experimented models and implementation in Sec. 5.1, conduct primary zero-shot evaluations in Sec. 5.2, present ablation studies in Sec. 5.3, and offer qualitative insights in Sec. 5.4." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.833, + 0.325, + 0.849 + ], + "angle": 0, + "content": "5.1. Experiments Configuration" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Models and Training Data In the realm of generative VLMs, we select BLIP-2 [19] and InstructBLIP [8], representing different pre-training data paradigms. BLIP" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.227 + ], + "angle": 0, + "content": "2 utilizes image-text pair data without instructions, employing a frozen image encoder and a large language model. It integrates a lightweight querying transformer for mapping visual information into the language embedding space. Instead, InstructBLIP incorporates instruction tuning, enhancing the architecture of pre-trained BLIP-2 with an instruction-aware visual feature extractor. It undergoes complementary training with additional task-specific instruction-tuning data." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.228, + 0.892, + 0.379 + ], + "angle": 0, + "content": "In our model setup, we explore three variants of BLIP-2 to assess the generality of our training method across different LLM architectures. They share the same image encoder (ViT-G/14 from EVA-CLIP [10]) but employ distinct frozen LLMs: OPT [42] with 2.7B and 6.7B parameters, and FlanT5-XL [15] with 3B parameters. For InstructBLIP, we experiment with the Vicuna-7B [43] version. Initializing both models with pre-trained parameters, we freeze the vision encoder and LLM, focusing solely on training their Q-former and fully connected projection network." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.379, + 0.892, + 0.47 + ], + "angle": 0, + "content": "We construct ICCC samples using our proposed method on the COCO Caption [3] and Visual Genome (VG) Caption [16] datasets, totaling approximately 1 million imagedataset pairs. These samples are then utilized for language modeling training and image captioning in a second-stage training paradigm outlined in Sec. 4.4." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.49, + 0.892, + 0.716 + ], + "angle": 0, + "content": "Implementation Details We implement and evaluate our method using the LAVIS library [17], and mainly followed the training setup for the original models. The AdamW [23] optimizer with \\(\\beta_{1} = 0.9\\), \\(\\beta_{2} = 0.999\\), and a weight decay of 0.05 was employed. We used a linear warmup of the learning rate over the initial 1,000 steps, increasing from \\(10^{-8}\\) to \\(10^{-5}\\), followed by a cosine decay with a minimum learning rate of 0. Batch sizes varied across models: 64 for BLIP-2 OPT2.7B and BLIP-2 FlanT5-XL, 28 for BLIP-2 OPT6.7B, and 24 for InstructBLIP. The images are resized to size \\(224\\times 224\\), and we apply random resized cropping and horizontal flipping augmentations. All training spanned a maximum of 20,000 iterations, with model performance validated every 1,000 iterations. Each training process utilized four Nvidia A40 (40G) GPUs, completed within a day." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.717, + 0.892, + 0.792 + ], + "angle": 0, + "content": "Regarding the hyperparameters, we conducted comparison experiments. We set \\((p_c, p_s)\\) as (0.3, 0.15), (0.3, 0), (0.01, 0.2), and (0.3, 0.3). for BLIP-2 OPT2.7B, BLIP-2 OPT6.7B, BLIP-2 FlanT5-XL, and InstructBLIP, respectively. Further details will be demonstrated in Sec. 5.3." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.802, + 0.707, + 0.817 + ], + "angle": 0, + "content": "5.2. Zero-shot Evaluations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.903 + ], + "angle": 0, + "content": "We present zero-shot evaluation results in Tab. 1 and Tab. 2 for BLIP-2 and InstructBLIP experiments. Our second-stage training strategy ICCC consistently improves zero-shot performance across various tasks and datasets, like visual question answering (VQA) and image captioning (IC)," + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13432" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.216, + 0.089, + 0.761, + 0.251 + ], + "angle": 0, + "content": "
BLIP-2GQAOK-VQAVQAv2VSRNoCaps
B@4SC
OPT2.7B33.526.651.948.343.613.8105.7
OPT2.7B w/ ICCC38.929.554.347.846.014.3111.9
OPT6.7B35.530.752.648.541.513.0101.4
OPT6.7B w/ ICCC38.231.758.851.544.113.6106.9
FlanT5-XL44.040.763.163.442.213.3103.1
FlanT5-XL w/ ICCC44.641.064.064.243.913.6106.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.261, + 0.895, + 0.306 + ], + "angle": 0, + "content": "Table 1. The zero-shot evaluation results on BLIP-2 experiments. For three VQA datasets, we report top-1 accuracy \\((\\%)\\) on the testdev set of GQA [14], VSR [21], the test set of OK-VQA [25], and the validation set of VQAv2 [12]. For IC, we report metrics of BLUE@4 (B@4), CIDEr (C), and SPICE (S) on the validation set of NoCaps." + }, + { + "type": "table", + "bbox": [ + 0.122, + 0.324, + 0.432, + 0.386 + ], + "angle": 0, + "content": "
ModelGQAVSRNoCaps
InstructBLIP48.461.114.2
InstructBLIP w/ ICCC49.863.115.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.397, + 0.471, + 0.426 + ], + "angle": 0, + "content": "Table 2. The zero-shot evaluation results on InstructBLIP experiments. We report the SPICE score for NoCaps." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.445, + 0.407, + 0.46 + ], + "angle": 0, + "content": "demonstrating enhanced zero-shot generalization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.461, + 0.47, + 0.506 + ], + "angle": 0, + "content": "The experimental results on BLIP-2 (Tab. 1) demonstrate the effectiveness of ICCC on models pre-trained by image-text pairs. Notable findings include:" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.509, + 0.47, + 0.628 + ], + "angle": 0, + "content": "- ICCC yields consistent improvements for BLIP-2 OPT2.7B, BLIP-2 OPT6.7B, and BLIP-2 FlanT5-XL. Specifically, the BLIP-2 OPT2.7B with ICCC shows a significant enhancement in GQA \\((+5.4\\%)\\), while the BLIP-2 OPT6.7B improves considerably in VQAv2 \\((+6.2\\%)\\). These results emphasize ICCC's ability to refine vision-conditioned language generation, irrespective of LLM sizes and architectures." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.629, + 0.47, + 0.719 + ], + "angle": 0, + "content": "- In captioning tasks, SPICE metrics highlight improved accuracy at the structured scene level, including VL relations and attributes. Our task design, focusing on learning ITG generalizations for various concept roles, not only enhances object recognition accuracy but also improves understanding of object attributes and relations." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.72, + 0.47, + 0.825 + ], + "angle": 0, + "content": "- In the InstructBLIP experiment results shown in Tab. 2, we note a consistent improvement in zero-shot evaluation benchmarks, even when the original model heavily relies on instruction tuning. This indicates the effectiveness of our approach across diverse pre-training image-text data, offering a valuable complementary method for augmenting visual-linguistic knowledge." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.825, + 0.471, + 0.902 + ], + "angle": 0, + "content": "- We emphasize the Visual Spatial Reasoning (VSR) benchmark [21], created to evaluate a model's grasp of spatial relationships for vision-language reasoning. These enhancements stem from the varied concept data samples in our ICCC pre-training, which are able to encompass a" + }, + { + "type": "list", + "bbox": [ + 0.077, + 0.509, + 0.471, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.324, + 0.892, + 0.426 + ], + "angle": 0, + "content": "
Data SourceGQAOK-VQAVQAv2NoCaps
C+VVQAv2w/ ICCCB@4SC
1---33.526.651.943.613.8105.7
2✓--33.026.349.745.613.9108.1
3✓-✓38.929.554.346.014.3111.9
4✓✓-41.338.0-45.212.6106.4
5✓✓✓42.839.1-45.014.0108.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.43, + 0.894, + 0.5 + ], + "angle": 0, + "content": "Table 3. Ablation study on our method upon different second-stage training data types. C+V represents COCO and VG caption data. Since our focus is on zero-shot performance, we omit the results on the VQAv2 validation set after training with the VQAv2 training set." + }, + { + "type": "text", + "bbox": [ + 0.513, + 0.517, + 0.875, + 0.532 + ], + "angle": 0, + "content": "broad spectrum of vision-language relational concepts." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.532, + 0.892, + 0.622 + ], + "angle": 0, + "content": "- Additionally, we assess the effectiveness of ICCC on another VLM (LLAVA [22]) and various vision-language reasoning datasets, including ScienceQA-IMG [31], MM-VET [37], and hallucinations [30]. Further experimental results can be found in the supplementary material." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.517, + 0.892, + 0.622 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.645, + 0.655, + 0.663 + ], + "angle": 0, + "content": "5.3. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.672, + 0.892, + 0.809 + ], + "angle": 0, + "content": "Effectiveness of Correction Task In Tab. 3, we compare our approach with alternative second-stage training methods, focusing on the BLIP-2 OPT2.7B model. We explore two types of second-stage training: one utilizing only COCO and VG caption datasets (lines 2 and 3), and the other incorporating the VQAv2 training set (lines 4 and 5) to assess the impact of instruction tuning. Our approach exclusively targets caption datasets, maintaining consistent task sample construction parameters." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Experimental results indicate that our training approach consistently outperforms conventional second-stage methods, regardless of the inclusion of VQA data for instruction-tuning. This underscores the efficacy of our task, emphasizing its superiority over traditional ITG second-stage training strategies." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13433" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.093, + 0.096, + 0.478, + 0.282 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.493, + 0.096, + 0.877, + 0.281 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.323, + 0.294, + 0.645, + 0.308 + ], + "angle": 0, + "content": "Figure 3. Hyper-parameter searching on \\( p_c \\) and \\( p_s \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.317, + 0.47, + 0.422 + ], + "angle": 0, + "content": "Ablation for Task Construction In Tab. 4, we demonstrate the necessity of including different types of concepts to edit for constructing mismatched captions. The experiments were conducted on the BLIP-2 OPT2.7B model, maintaining consistent hyper-parameters. Results indicate that using concepts of different natures for task construction yields complementary effects." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.426, + 0.47, + 0.546 + ], + "angle": 0, + "content": "- In the first part, we investigate influence of language granularity, focusing on tasks constructed around words and phrases. As shown in lines 3-4 of Tab.4, our findings reveal the significance of phrase-level concepts for the VQA task, while word-level concepts aid in refining the model's understanding of individual words, thereby improving captioning accuracy metrics such as BLUE@4 and CIDEr." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.546, + 0.47, + 0.682 + ], + "angle": 0, + "content": "- In the subsequent section (lines 5-6), we delve into the roles of various concepts in semantics, exploring the impact of tasks centered on entity-level, relation-level, and attribute-level concepts. Referencing Tab.4, our analysis reveals that focusing solely on learning at the entity level yields strong performance in VQA tasks but may sacrifice accuracy in comprehending relations and attributes, thereby resulting in sub-optimal image captioning performance." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.682, + 0.471, + 0.804 + ], + "angle": 0, + "content": "- We conducted an ablation study to assess the impact of instructions and language structure (line 7, Tab.4). We retained the instructions of the ICCC task while randomly altering words within the sentences. Surprisingly, the addition of correction instructions and random language masking did not enhance the generalization capability of VLMs on downstream tasks. This highlights the importance of language structure in instruction tuning." + }, + { + "type": "list", + "bbox": [ + 0.077, + 0.426, + 0.471, + 0.804 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.806, + 0.47, + 0.852 + ], + "angle": 0, + "content": "In conclusion, the diversity in concept extraction allows our method to perform well on various zero-shot generation tasks, demonstrating strong generality." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Hyper-parameter Selection The hyperparameters \\( p_c \\) and \\( p_s \\) are pivotal in adjusting the distribution of task samples" + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.314, + 0.892, + 0.462 + ], + "angle": 0, + "content": "
TypeGQAOK-VQAVQAv2NoCaps
B@4SC
1none33.026.349.745.613.9108.1
2all38.929.554.346.014.3111.9
3noun, verb36.430.752.146.014.3114.3
4ent, pred, attr38.327.554.945.214.7111.3
5noun, ent38.529.854.846.514.4112.4
6verb, pred, attr36.029.654.146.914.5114.1
7random33.026.248.644.114.5107.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.47, + 0.892, + 0.498 + ], + "angle": 0, + "content": "Table 4. Ablation study on editing different subsets of concept types for mismatched caption construction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.51, + 0.892, + 0.601 + ], + "angle": 0, + "content": "in our approach. We conducted a comprehensive hyperparameter search for each experimental model, analyzing the impact of these parameters on model performance. Fig. 3 illustrate the performance variations of BLIP-2 OPT2.7B after second-stage training under different hyperparameter settings:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.605, + 0.891, + 0.65 + ], + "angle": 0, + "content": "- In the left of Fig. 3, with \\( p_s \\) fixed at 0.1, we study the influence of different correction task sample proportions by varying \\( p_c \\) at intervals of 0.15." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.651, + 0.892, + 0.71 + ], + "angle": 0, + "content": "- In the right of Fig. 3, with \\( p_c \\) fixed at 0.3, we explore the impact of different swap operation proportions on mismatched caption sampling by varying \\( p_s \\) at intervals of 0.15." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.605, + 0.892, + 0.71 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.715, + 0.862, + 0.731 + ], + "angle": 0, + "content": "In our experiments, we present several key findings:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.735, + 0.892, + 0.826 + ], + "angle": 0, + "content": "- From both figures, it is evident that the impact of hyperparameters \\( p_{c} \\) and \\( p_{s} \\) on model performance follows a consistent trend, initially increasing before decreasing. This phenomenon arises due to the risk of language bias when incorporating excessive correction task samples, particularly those generated through swap operations." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.826, + 0.892, + 0.902 + ], + "angle": 0, + "content": "- Notably, the saturation point of \\( p_{s} \\) is reached early, suggesting that the model can easily identify and correct mismatched captions created through swap operations. Despite this, proper inclusion of such samples proves beneficial for overall performance enhancement, particularly" + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.735, + 0.892, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13434" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.131, + 0.095, + 0.198, + 0.157 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.09, + 0.158, + 0.205, + 0.175 + ], + "angle": 0, + "content": "Is the jar made of the same materials as the hook?" + }, + { + "type": "image", + "bbox": [ + 0.209, + 0.094, + 0.33, + 0.157 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.207, + 0.158, + 0.343, + 0.175 + ], + "angle": 0, + "content": "Are there men to the right of the woman that is wearing trousers?" + }, + { + "type": "image", + "bbox": [ + 0.342, + 0.095, + 0.461, + 0.157 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.347, + 0.158, + 0.451, + 0.175 + ], + "angle": 0, + "content": "What kind of furniture is surrounding the table?" + }, + { + "type": "image", + "bbox": [ + 0.133, + 0.178, + 0.198, + 0.239 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.109, + 0.242, + 0.161, + 0.251 + ], + "angle": 0, + "content": "BLIP-2: Yes." + }, + { + "type": "image", + "bbox": [ + 0.209, + 0.176, + 0.33, + 0.239 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.215, + 0.242, + 0.267, + 0.251 + ], + "angle": 0, + "content": "BLIP-2: Yes." + }, + { + "type": "image", + "bbox": [ + 0.342, + 0.176, + 0.461, + 0.239 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.347, + 0.242, + 0.418, + 0.251 + ], + "angle": 0, + "content": "BLIP-2: Kitchen." + }, + { + "type": "image", + "bbox": [ + 0.133, + 0.254, + 0.198, + 0.317 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.111, + 0.321, + 0.156, + 0.331 + ], + "angle": 0, + "content": "Ours: No." + }, + { + "type": "image", + "bbox": [ + 0.209, + 0.254, + 0.33, + 0.318 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.218, + 0.321, + 0.262, + 0.33 + ], + "angle": 0, + "content": "Ours: No." + }, + { + "type": "image", + "bbox": [ + 0.342, + 0.254, + 0.461, + 0.318 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.35, + 0.321, + 0.402, + 0.33 + ], + "angle": 0, + "content": "Ours: Chair." + }, + { + "type": "image", + "bbox": [ + 0.115, + 0.341, + 0.218, + 0.395 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.084, + 0.401, + 0.228, + 0.41 + ], + "angle": 0, + "content": "BLIP-2: A red kite flying over a forest." + }, + { + "type": "image", + "bbox": [ + 0.228, + 0.341, + 0.349, + 0.395 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.231, + 0.401, + 0.353, + 0.41 + ], + "angle": 0, + "content": "A group of children in a library." + }, + { + "type": "image", + "bbox": [ + 0.359, + 0.342, + 0.459, + 0.395 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.359, + 0.397, + 0.458, + 0.406 + ], + "angle": 0, + "content": "A man sitting in front of" + }, + { + "type": "image_caption", + "bbox": [ + 0.359, + 0.407, + 0.448, + 0.415 + ], + "angle": 0, + "content": "a wood burning stove." + }, + { + "type": "image_caption", + "bbox": [ + 0.359, + 0.416, + 0.459, + 0.424 + ], + "angle": 0, + "content": "A person looking at a fire" + }, + { + "type": "image_caption", + "bbox": [ + 0.359, + 0.424, + 0.424, + 0.432 + ], + "angle": 0, + "content": "in a wood stove." + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.449, + 0.47, + 0.546 + ], + "angle": 0, + "content": "Figure 4. Visualization results include model output examples and attention gradients on images. The first block illustrates three examples from the GQA testdev set, while the second block showcases three examples from the NoCaps validation set. With our training, the model demonstrates improved accuracy in focusing on prompt-relevant image regions. Additionally, it generates captions with more detailed descriptions of scenes and actions." + }, + { + "type": "text", + "bbox": [ + 0.09, + 0.561, + 0.266, + 0.575 + ], + "angle": 0, + "content": "in image captioning tasks." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.576, + 0.47, + 0.697 + ], + "angle": 0, + "content": "- Furthermore, our investigation reveals that BLIP-2 FlanT5-XL tends to overfit on our task samples, possibly attributed to its encoder-decoder architecture. This results in the Q-former learning an overfitted encoding of soft prompts associated with task text patterns. Nonetheless, even minimal incorporation of correction task samples \\((p_c = 0.01)\\) effectively serves our training objectives while mitigating the risk of overfitting." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.709, + 0.26, + 0.725 + ], + "angle": 0, + "content": "5.4. Qualitative Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.733, + 0.469, + 0.869 + ], + "angle": 0, + "content": "To provide a more intuitive understanding of the effects of our training, we show some qualitative model output examples in Fig. 4. We demonstrate the differences between the model outputs and intermediate results on the VQA and IC tasks before and after our second-stage training respectively. The heat maps show the gradient of the output logit corresponding to the ground truth token with regard to the image attention, which reflects the potential visual contribution of the model output." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.469, + 0.901 + ], + "angle": 0, + "content": "According to the outputs for VQA, the results reveal that the proposed correction task training produces inter" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.304 + ], + "angle": 0, + "content": "pretable improvements to VQA responses. Our model demonstrates increased accuracy in locating objects referenced in prompts and exhibits a more precise understanding of compositional concepts, avoiding biases toward prominent objects. For instance, in the first example, our model focuses on the \"hook\", which the original model misses. In the second example, our model correctly considers the composed concept of \"the woman that is wearing trousers\". Lastly, our model interprets the relational concept \"surrounding the table\" and directs attention appropriately toward the relevant region, rather than the table itself. Overall, our findings indicate that this training methodology enhances VLMs' capacity for interpreting corresponding visual concepts expressed through language." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.312, + 0.892, + 0.463 + ], + "angle": 0, + "content": "Examples from our experiments with IC illustrate this improved ability to correct misidentified objects and provide richer, more fine-grained descriptions of object relationships and actions. For instance, our model correctly identifies the wrong \"red kite\" concept in the first case and provides more nuanced details about the scene, such as \"standing around a table\" and \"looking\". We posit that the primary source of improved overall captioning performance lies in the generation of more accurate and comprehensive concepts in captions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.471, + 0.892, + 0.577 + ], + "angle": 0, + "content": "Conclusively, our study indicates that the proposed training method potentially enhances generative VLMs' capacity for aligning concepts across multiple types and granularities in visual and language modalities. We believe this insight could shed light on the future development of cost-effective, multi-granularity, and structured generative VL pre-trained models." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.617, + 0.619, + 0.632 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.651, + 0.892, + 0.817 + ], + "angle": 0, + "content": "In this work, we propose the image-conditioned text correction task for enhancing zero-shot text generation with unlabeled data. In this task, VLMs requires to identify and correct the error in accordance with the vision modality via text generation. We propose a scalable and cost-effective data construction framework for generating the image-text pair for this task by utilizing the inherent structure of language. The experimental results indicate that the implementation of our training framework substantially improves the ability of VLMs to generalize across a range of VL tasks involving image-to-text generation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Discussion of Limitation Due to the limitation of the computing resource, extending our approach to larger datasets and models remains unexplored. Future work should explore its application to more extensive datasets and diverse large vision-language models." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13435" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.176, + 0.107 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.197 + ], + "angle": 0, + "content": "[1] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katherine Millican, Malcolm Reynolds, et al. Flamingo: a visual language model for few-shot learning. 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Minigpt-4: Enhancing vision-language understanding with advanced large language models. arXiv preprint arXiv:2304.10592, 2023. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.699 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13437" + } + ] +] \ No newline at end of file diff --git a/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_origin.pdf b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..135266c148859f1b43a277b83c1be2b985c857c8 --- /dev/null +++ b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/b024fa39-4df3-49c4-9b05-b3492e317bba_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:b20a458e7d166cb04d2057243eb2e53ab6ba2cd1e4087f2572d425f419986bea +size 2110883 diff --git a/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/full.md b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/full.md new file mode 100644 index 0000000000000000000000000000000000000000..00ec56acffca7cf3361e9c1151be7d1d6db7a17c --- /dev/null +++ b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/full.md @@ -0,0 +1,313 @@ +# Learning by Correction: Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning + +Rongjie Li $^{1*}$ Yu Wu $^{1*}$ Xuming He $^{1,2‡}$ + +$^{1}$ School of Information Science and Technology, ShanghaiTech University +$^{2}$ Shanghai Engineering Research Center of Intelligent Vision and Imaging {lirj2, wuyu1, hexm} $@$ shanghaiitech.edu.cn + +# Abstract + +Generative vision-language models (VLMs) have shown impressive performance in zero-shot vision-language tasks like image captioning and visual question answering. However, improving their zero-shot reasoning typically requires second-stage instruction tuning, which relies heavily on human-labeled or large language model-generated annotation, incurring high labeling costs. To tackle this challenge, we introduce Image-Conditioned Caption Correction (ICCC), a novel pre-training task designed to enhance VLMs' zero-shot performance without the need for labeled task-aware data. The ICCC task compels VLMs to rectify mismatches between visual and language concepts, thereby enhancing instruction following and text generation conditioned on visual inputs. Leveraging language structure and a lightweight dependency parser, we construct data samples of ICCC task from image-text datasets with low labeling and computation costs. Experimental results on BLIP-2 and InstructBLIP demonstrate significant improvements in zero-shot image-text generation-based VL tasks through ICCC instruction tuning. + +# 1. Introduction + +Vision-language models (VLMs) have demonstrated remarkable performance across a wide range of vision-language (VL) tasks, including image captioning [1, 19, 22, 33, 36], visual recognition [15, 29, 44], image-text retrieval [18, 29], and answering visual questions [1, 19, 22, 33, 36]. Generally, existing VLMs are able to conduct two + +![](images/437351355d83a00c39300a719f0cf34efc6b2d48e90e65408067f8c4e063acf7.jpg) +Figure 1. Illustration of second-stage tuning for zero-shot VL task adaptation comparison. The instruction tuning in recent works needs human label or LLM-generated data; in contrast, our image caption correction tuning is conducted on unlabeled image-text data with an NLP parser. + +essential tasks: image-text matching (ITM) and image-text generation (ITG). The contrastive-based ITM aims to model the similarity between vision and text through a shared embedding [15, 18, 29]. In contrast, the generative-based ITG has more flexibility in adapting to various VL tasks. More- + +over, several recent VLM frameworks integrate the LLMs for ITG, which extend the powerful text generation across vision and text modality [1, 8, 19, 22], and allow VLMs to perform zero-shot inference on various VL tasks with impressive performance. + +To perform zero-shot inference on VL tasks, the VLMs need to have generalizable text generation capability according to text inputs and concepts from the visual modality. The existing works typically conduct second-stage instruction tuning for pre-trained VLMs with task-oriented data. This improves VLMs for following instructions to generate texts conditioned on visual modality, which ultimately enhances the zero-shot performance on VL-tasks such as InstructBLIP [8] and LLAVA [22], as shown in the upper part of Fig. 1. However, these methods necessitate substantial downstream task data annotation for fine-tuning, which is either human-labeled or generated externally by large language models. This process escalates labor costs throughout the system. + +In this study, we introduce a novel pre-training task, Image-Conditioned Caption Correction (ICCC), aimed at enhancing VLMs' performance on zero-shot VL tasks. Our approach leverages the semantic dependency structure of language utilized for second-stage tuning of VLMs, using image-text data without task-specific annotation, as depicted in Fig. 1. By enforcing VLMs to identify and rectify mismatched concepts between visual and language, our method enhances VLMs' capability of generating text from the visual modality. Importantly, the adopted universal semantic dependency [26] ensures comprehensive coverage of various concepts, including objects, their attributes, and interactions between them. Furthermore, we construct the data from unlabeled image-text datasets only with a lightweight dependency parser, which achieves low labeling and computation costs. + +Specifically, our pre-training framework first generates the task of image-conditioned text correction in an automatic manner. To this end, we develop a data construction pipeline with two components: the concept extractor and the correction task constructor. Firstly, the concept extractor identifies various concepts from the text modality. With the off-the-shelf dependency parser, it extracts the set of language units by parsing the semantic dependency structure of text. Subsequently, the correction task constructor generates samples from the unlabeled image-text data according to language structure and concept set. It swaps or replaces language units according to the extracted concept set, thereby creating concept-mismatched image-text pairs. Thanks to the universality of dependency, this approach allows us to create a wide variety of samples covering diverse visual-language concepts. The resulting text correction task requires VLMs to detect and recover the language units of mismatched concepts (words and phrases) according to the + +image. Finally, we use the generated samples together with the original image-text data to fine-tune pre-trained VLMs with language modeling objectives. + +We conduct extensive experiments on two VLMs, BLIP-2 [19] and InstructBLIP [8], and evaluate the zero-shot performance of ITG on the representative tasks: visual question answering and image caption. Our findings reveal that our proposed method yields substantial improvements in zero-shot generalization based on the initial pre-train model without requiring any manually labeled or LLM-generated data. The main contributions of our work are threefold: + +- We introduce a novel image-conditioned text correction fine-tuning strategy for VLMs that enhances their generalization of ITG for VL tasks. +- We developed an automated data construction pipeline that produces large amounts of samples for fine-tuning, all generated from image-text pairs without the need for human annotations or additional LLMs. +- We demonstrated notable improvements in the zero-shot generalization capabilities of VLMs across various VL tasks. + +# 2. Related Work + +Generative Vision Language Models With advancements in large-scale pretraining, vision-language models (VLMs) have demonstrated notable zero-shot generalization across various tasks. Unlike contrastive VLMs such as CLIP [29] and ALIGN [15], which focus on image-text similarity scores, generative VLMs output text based on image and text inputs for tasks like visual question answering and image captioning. + +In earlier studies, generative VLMs utilized fusion-encoder transformers [4, 20, 32, 41] to simultaneously encode visual and linguistic tokens, and subsequent models [5, 33, 36] integrated visual input information into different architecture language models, giving rise to unified generative VL transformer models. Recently, with advancements in Large Language Models (LLMs) [6, 28, 42, 43], efforts have sought to utilize LLMs' capabilities to project visual input into the language embedding space. BLIP-2 [19] bridges the modality gap using a pre-trained Q-Former. Building upon BLIP-2, MiniGPT-4 [45] and InstructBLIP [8] focus on next-stage instruction tuning to further enhance performance. LLaVA [22] involves GPT-4 [27] in generating instructions and conversations for training. LLaMA-Adapter v2 [11] and LaVIN [24] employ adapters for architecture fine-tuning. + +In our study, akin to LLaVA and Instruct-BLIP, we focus on leveraging the benefits of second-stage fine-tuning of pre-trained VLMs. However, unlike these approaches, we aim to achieve this without down-stream tasks data from human annotation and large models generation. Instead, we introduce a novel correction task, construct from the image + +text data with light-weight pipeline. + +Language Structure-based Data Augmentation Data augmentation is widely employed in machine learning, with common techniques such as mixup [40], CutMix [39], and RandAugment [7] in computer vision, and backtranslation [35], random word editing [34] in natural language processing. In the field of vision and language (VL), an effective approach often involves synthesizing new data using pre-trained models as augmentation [2]. For instance, BLIP [18] leverages the model's initially trained capabilities to generate additional training data, thereby further enhancing the model's performance. + +Some researchers in visual-linguistic (VL) studies pursue performance enhancements on challenging tasks by crafting difficult negative samples. For instance, NegCLIP [38] employs a language parser to swap elements between sentences, generating hard negative image-text pairs for contrastive fine-tuning. SVLC [9] achieves a similar outcome by substituting elements in sentences. Our approach leverages linguistic structure to improve image-text generation (ITG) tasks. Unlike image-text matching (ITM) tasks, which focus on learning similarity metrics, generative models encounter difficulties with negative samples. To address this, we introduce a correction task for instruction fine-tuning, using structural language information to construct data samples. This enhances the generalization performance of VLMs in zero-shot ITG-based visual language tasks. + +# 3. Preliminary + +Image-text Generation of VLMs Image-text generation, a fundamental task of VLMs, involves generating text from both visual and textual inputs. Specifically, VLMs with parameters $\Theta_{vlm}$ generate output text from images and textual input in an auto-regressive manner. The visual input is projected into language embedding as visual tokens $\mathbf{Z}$ together with textual input $\mathbf{w} = [w_1, w_2, \dots, w_{i-1}]$ and fed into the subsequent LLM to predict the next token $w_i$ of the sequence $\mathbf{w}$ . + +$$ +w _ {i} = \mathcal {F} _ {v l m} (\mathbf {Z}, w _ {1}, w _ {2}, \dots , w _ {i - 1}; \boldsymbol {\Theta} _ {v l m}). \tag {1} +$$ + +Second-stage Tuning for Zero-shot Generation While generative image-text pre-training provides VLMs with aligned vision-language representations, effective instruction-following of image-text generation for diverse zero-shot VL tasks is crucial. Recent works address this issue by leveraging either human-labeled [8] or large language model-generated task-oriented data [22] for instruction tuning. Concretely, in the second stage of tuning, the VLMs are optimized with the same objective of generative image-text pre-training with task-oriented data: + +$$ +\underset {\Theta_ {v l m}} {\arg \max } \sum_ {i = 1} ^ {K} \log P \left(w _ {i} \mid \mathbf {Z}, w _ {1}, w _ {2}, \dots , w _ {i - 1}; \Theta_ {v l m}\right). \tag {2} +$$ + +# 4. Our Approach + +In this section, we introduce our proposed Image Conditional Caption Correction (ICCC) task for second-stage tuning, which constructs data from unlabeled data with low resource consumption. We first provide a Task Definition of ICCC in Sec. 4.1. Then we introduce the data construction pipeline for ICCC, which includes two modules: the Concept Extractor and the Correction Data constructor. The concept extractor parses the text structure and extracts the concept set for the following data construction, discussed in Sec. 4.2. Subsequently, the correction data constructor generates data by augmenting text structure with the extracted concept set, described in Sec.4.3, Finally, Sec. 4.4 outlines our training and inference procedures for incorporating our task into VLM pre-training. + +# 4.1. Task definition + +As illustrated in Fig. 2, the ICCC task involves identifying and correcting language units of mismatched concepts of caption. To define the ICCC task, we need to define the concept set, how we perturb to produce concept-mismatched samples, and how the perturb operation changes the language structure. + +For each sentence, concepts are composed of linguistic units representing their semantic meaning. These linguistic units are categorized into five types based on semantics and language granularity: $\mathcal{E} = \{\text{entity phrase}, \text{predicate phrase}, \text{attribute phrase}, \text{noun word}, \text{verb word}\}$ . The entity phrase, noun word, attribute phrase represent the object-level semantic, and predicate phrase, verb word represent the composition-level semantic. The phrase and word represent different levels of language granularity. + +There are two operations for perturbing the language structure: $\{\mathrm{replace},\mathrm{swap}\}$ . The replace involves substituting a concept with another one of the same type from the image-text pair dataset, while the swap involves swapping the positions of two concepts of the same type within the original caption. More details are introduced in Sec. 4.3. Consequently, replace focuses on modeling the intrinsic meaning of individual concepts, while swap prioritizes the order of compositional concepts within sentences. Overall, the task is to use linguistic unit modifications of image-text pairs, providing universal concepts aligned between vision and language, which improves text generation capabilities across two modalities. + +# 4.2. Concept Extractor + +As mentioned earlier, the data of ICCC is generated by perturbing concepts in $\mathcal{E}$ according to the structure of sen + +![](images/d666cd18de624b971507cfd028f9e790dea96f71bfa05b330f0eebbaf1eac523.jpg) +Figure 2. Illustration of the overall pipeline of ICCC. The concept extractor parses the sentence to obtain linguistic units of concepts. The task data constructor aims to produce the sample according to the sentence structure with the "replace" and "swap" operations. Finally, the generated ICCC data is used for image-to-text generative training for VLMs. + +tences. The concept extractor takes captions as input and parses the dependency to identify linguistic units of concepts, which the following task constructor then uses to generate data samples. The concept extractor module has three processes: (1) universal dependency parsing; (2) linguistic unit selection and grouping; (2) concept collection. + +Universal Dependency Parsing We use the off-the-shelf universal dependency parser implemented by the spaCy [13] software library to extract the dependency structure of the original caption. As shown in Fig. 2, the dependency parser translates the sentence into a universal dependency tree [26]. The node of the dependency tree is the minimal linguistic unit $u_{[pos]}$ , which has Part-of-Speech (POS) tags to indicate its grammatical role. The edge represents the dependency relation between linguistic units $r_{[REL]}$ , which also has the relation type (REL). The dependency structure provides us with an indication of how linguistic units organize to represent the concept of a sentence. + +Linguistic Unit Selection and Grouping We extract the linguistic unit set of concept $U_{\text{concept}}$ within $\mathcal{E}$ by grouping and selecting $u_{[pos]}$ . To achieve this, we design a heuristic method by traversing the dependency tree to select the corresponding $u_{[pos]}$ . Firstly, we extract the concept represented by the concept of a word-level linguistic unit according to the POS tag: + +1. $U_{\text{noun word}}: u_{[\text{noun}]}$ +2. $U_{verbword} : u_{[verb]}$ + +Based on such word-level concepts $u_{[pos]}$ , we further ex + +tract linguistic units of phrase-level concepts, such as entity phrase, predicate phrase, attribute phrase, by grouping the $u_{[pos]}$ into $U_{concept}$ according to the $r_{[REL]}$ associated with word-level concept units: + +1. $U_{\text{entity phrase}}$ : $u_{[adj]}$ and $U_{[det]}$ adjacent to $U_{[noun]}$ +2. $U_{predicate phrase}$ : all $u_{[pos]}$ within two $u_{[noun]}$ +3. $U_{\text{attribute phrase}}$ : all $u_{[amod]}$ adjacent to $u_{[noun]}$ + +To this end, we extract the linguistic units of each concept type $U_{\text{concept}}$ from the text according to the dependency structure. + +Concept Collection For each sentence from the image-text dataset, we collect all $U_{\text{concept}}$ according to their concept type, respectively. We merge the $U_{\text{noun word}}$ with the $U_{\text{entity phrase}}$ and the $U_{\text{verb word}}$ with the $U_{\text{predicate phrase}}$ into the same concept type, respectively. This global-level concept base stores all the concepts that occurred in the dataset. We filter them by frequency to remove infrequent concepts, which could be extracted from low-quality captions or parsing errors, and the most frequent, which could be a trivial concept or language bias that occurred uniformly. + +# 4.3. Correction Task Data Constructor + +The correction task data constructor uses the extracted concept structure to generate data samples with multi-level concept mismatch captions. The data constructor takes the input text, which has identified concepts of language units and concept-based units, and produces the augmented text with expected corrections. + +Specifically, the data constructor perturbs the initial lin + +guistic structure by predefined operations: replace, swap, as shown in Fig. 2. Specifically, the replace randomly selects the concept of the original text and replaces it with an external $U_{\text{concept}}$ that has the same semantic type but does not occur in the current text from the concept base. For instance, the entity phrase can be replaced by all object-level concepts, such as noun word or entity phrase. The swap operation, instead of replacing concept by concept, swaps the two linguistic unit sets with the same concept type in the text. This perturbation operation provides the order mismatch of the concept. To calibrate those two operations, we randomly select one by Bernoulli distribution with a preset parameter $p_s \in [0,1]$ to decide which type of operation is used for perturbation. In those cases where a sentence doesn't have two of the same concept-type linguistic units, we simply use the replace operation. + +After the perturb operation, we map back the tree structure sentence into sequence and construct the caption correction samples, which are composed of the following components: correction instruction prompt, perturbed caption, and correcting description, as shown in Fig. 2. The correction instruction prompt is selected from a template base, and the correcting description includes the mismatch concept and the correct ones. + +# 4.4. Training and Inference + +The data generated by ICCC is utilized in the second-stage tuning process to improve VLMs, as introduced in Sec 3. We combine ICCC data samples with original image-text pairs for training to prevent focusing too much on the specific task and catastrophic forgetting. The proportion of ICCC data samples to original pairs in each training batch is determined by a hyper-parameter $p_c$ . The overall pre-training objective remains unchanged from the initial image-text generation pre-training. This design enables VLMs to grasp the alignment of concepts and facilitate instruction following for various downstream generative VL tasks, enhancing their performance across different tasks. During inference, VLMs conduct standard image-to-text generation for VL tasks, consistent with previous generative VLMs [8, 19]. + +# 5. Experiments + +In this section, we thoroughly explore the effectiveness of our proposed training task. We detail the experimented models and implementation in Sec. 5.1, conduct primary zero-shot evaluations in Sec. 5.2, present ablation studies in Sec. 5.3, and offer qualitative insights in Sec. 5.4. + +# 5.1. Experiments Configuration + +Models and Training Data In the realm of generative VLMs, we select BLIP-2 [19] and InstructBLIP [8], representing different pre-training data paradigms. BLIP + +2 utilizes image-text pair data without instructions, employing a frozen image encoder and a large language model. It integrates a lightweight querying transformer for mapping visual information into the language embedding space. Instead, InstructBLIP incorporates instruction tuning, enhancing the architecture of pre-trained BLIP-2 with an instruction-aware visual feature extractor. It undergoes complementary training with additional task-specific instruction-tuning data. + +In our model setup, we explore three variants of BLIP-2 to assess the generality of our training method across different LLM architectures. They share the same image encoder (ViT-G/14 from EVA-CLIP [10]) but employ distinct frozen LLMs: OPT [42] with 2.7B and 6.7B parameters, and FlanT5-XL [15] with 3B parameters. For InstructBLIP, we experiment with the Vicuna-7B [43] version. Initializing both models with pre-trained parameters, we freeze the vision encoder and LLM, focusing solely on training their Q-former and fully connected projection network. + +We construct ICCC samples using our proposed method on the COCO Caption [3] and Visual Genome (VG) Caption [16] datasets, totaling approximately 1 million imagedataset pairs. These samples are then utilized for language modeling training and image captioning in a second-stage training paradigm outlined in Sec. 4.4. + +Implementation Details We implement and evaluate our method using the LAVIS library [17], and mainly followed the training setup for the original models. The AdamW [23] optimizer with $\beta_{1} = 0.9$ , $\beta_{2} = 0.999$ , and a weight decay of 0.05 was employed. We used a linear warmup of the learning rate over the initial 1,000 steps, increasing from $10^{-8}$ to $10^{-5}$ , followed by a cosine decay with a minimum learning rate of 0. Batch sizes varied across models: 64 for BLIP-2 OPT2.7B and BLIP-2 FlanT5-XL, 28 for BLIP-2 OPT6.7B, and 24 for InstructBLIP. The images are resized to size $224\times 224$ , and we apply random resized cropping and horizontal flipping augmentations. All training spanned a maximum of 20,000 iterations, with model performance validated every 1,000 iterations. Each training process utilized four Nvidia A40 (40G) GPUs, completed within a day. + +Regarding the hyperparameters, we conducted comparison experiments. We set $(p_c, p_s)$ as (0.3, 0.15), (0.3, 0), (0.01, 0.2), and (0.3, 0.3). for BLIP-2 OPT2.7B, BLIP-2 OPT6.7B, BLIP-2 FlanT5-XL, and InstructBLIP, respectively. Further details will be demonstrated in Sec. 5.3. + +# 5.2. Zero-shot Evaluations + +We present zero-shot evaluation results in Tab. 1 and Tab. 2 for BLIP-2 and InstructBLIP experiments. Our second-stage training strategy ICCC consistently improves zero-shot performance across various tasks and datasets, like visual question answering (VQA) and image captioning (IC), + +
BLIP-2GQAOK-VQAVQAv2VSRNoCaps
B@4SC
OPT2.7B33.526.651.948.343.613.8105.7
OPT2.7B w/ ICCC38.929.554.347.846.014.3111.9
OPT6.7B35.530.752.648.541.513.0101.4
OPT6.7B w/ ICCC38.231.758.851.544.113.6106.9
FlanT5-XL44.040.763.163.442.213.3103.1
FlanT5-XL w/ ICCC44.641.064.064.243.913.6106.0
+ +Table 1. The zero-shot evaluation results on BLIP-2 experiments. For three VQA datasets, we report top-1 accuracy $(\%)$ on the testdev set of GQA [14], VSR [21], the test set of OK-VQA [25], and the validation set of VQAv2 [12]. For IC, we report metrics of BLUE@4 (B@4), CIDEr (C), and SPICE (S) on the validation set of NoCaps. + +
ModelGQAVSRNoCaps
InstructBLIP48.461.114.2
InstructBLIP w/ ICCC49.863.115.7
+ +demonstrating enhanced zero-shot generalization. + +The experimental results on BLIP-2 (Tab. 1) demonstrate the effectiveness of ICCC on models pre-trained by image-text pairs. Notable findings include: + +- ICCC yields consistent improvements for BLIP-2 OPT2.7B, BLIP-2 OPT6.7B, and BLIP-2 FlanT5-XL. Specifically, the BLIP-2 OPT2.7B with ICCC shows a significant enhancement in GQA $(+5.4\%)$ , while the BLIP-2 OPT6.7B improves considerably in VQAv2 $(+6.2\%)$ . These results emphasize ICCC's ability to refine vision-conditioned language generation, irrespective of LLM sizes and architectures. +- In captioning tasks, SPICE metrics highlight improved accuracy at the structured scene level, including VL relations and attributes. Our task design, focusing on learning ITG generalizations for various concept roles, not only enhances object recognition accuracy but also improves understanding of object attributes and relations. +- In the InstructBLIP experiment results shown in Tab. 2, we note a consistent improvement in zero-shot evaluation benchmarks, even when the original model heavily relies on instruction tuning. This indicates the effectiveness of our approach across diverse pre-training image-text data, offering a valuable complementary method for augmenting visual-linguistic knowledge. +- We emphasize the Visual Spatial Reasoning (VSR) benchmark [21], created to evaluate a model's grasp of spatial relationships for vision-language reasoning. These enhancements stem from the varied concept data samples in our ICCC pre-training, which are able to encompass a + +Table 2. The zero-shot evaluation results on InstructBLIP experiments. We report the SPICE score for NoCaps. + +
Data SourceGQAOK-VQAVQAv2NoCaps
C+VVQAv2w/ ICCCB@4SC
1---33.526.651.943.613.8105.7
2✓--33.026.349.745.613.9108.1
3✓-✓38.929.554.346.014.3111.9
4✓✓-41.338.0-45.212.6106.4
5✓✓✓42.839.1-45.014.0108.2
+ +Table 3. Ablation study on our method upon different second-stage training data types. C+V represents COCO and VG caption data. Since our focus is on zero-shot performance, we omit the results on the VQAv2 validation set after training with the VQAv2 training set. + +broad spectrum of vision-language relational concepts. +- Additionally, we assess the effectiveness of ICCC on another VLM (LLAVA [22]) and various vision-language reasoning datasets, including ScienceQA-IMG [31], MM-VET [37], and hallucinations [30]. Further experimental results can be found in the supplementary material. + +# 5.3. Ablation Study + +Effectiveness of Correction Task In Tab. 3, we compare our approach with alternative second-stage training methods, focusing on the BLIP-2 OPT2.7B model. We explore two types of second-stage training: one utilizing only COCO and VG caption datasets (lines 2 and 3), and the other incorporating the VQAv2 training set (lines 4 and 5) to assess the impact of instruction tuning. Our approach exclusively targets caption datasets, maintaining consistent task sample construction parameters. + +Experimental results indicate that our training approach consistently outperforms conventional second-stage methods, regardless of the inclusion of VQA data for instruction-tuning. This underscores the efficacy of our task, emphasizing its superiority over traditional ITG second-stage training strategies. + +![](images/2768b48a5f42a614881891aa42f811fc5f2f1c6b1de8e17ac6c71d070334948c.jpg) +Figure 3. Hyper-parameter searching on $p_c$ and $p_s$ . + +![](images/3f5069e8f2d49cd4bbcf0031f6ebc5ff17e0b1b366830f7e2256046ee6abaa26.jpg) + +Ablation for Task Construction In Tab. 4, we demonstrate the necessity of including different types of concepts to edit for constructing mismatched captions. The experiments were conducted on the BLIP-2 OPT2.7B model, maintaining consistent hyper-parameters. Results indicate that using concepts of different natures for task construction yields complementary effects. + +- In the first part, we investigate influence of language granularity, focusing on tasks constructed around words and phrases. As shown in lines 3-4 of Tab.4, our findings reveal the significance of phrase-level concepts for the VQA task, while word-level concepts aid in refining the model's understanding of individual words, thereby improving captioning accuracy metrics such as BLUE@4 and CIDEr. +- In the subsequent section (lines 5-6), we delve into the roles of various concepts in semantics, exploring the impact of tasks centered on entity-level, relation-level, and attribute-level concepts. Referencing Tab.4, our analysis reveals that focusing solely on learning at the entity level yields strong performance in VQA tasks but may sacrifice accuracy in comprehending relations and attributes, thereby resulting in sub-optimal image captioning performance. +- We conducted an ablation study to assess the impact of instructions and language structure (line 7, Tab.4). We retained the instructions of the ICCC task while randomly altering words within the sentences. Surprisingly, the addition of correction instructions and random language masking did not enhance the generalization capability of VLMs on downstream tasks. This highlights the importance of language structure in instruction tuning. + +In conclusion, the diversity in concept extraction allows our method to perform well on various zero-shot generation tasks, demonstrating strong generality. + +Hyper-parameter Selection The hyperparameters $p_c$ and $p_s$ are pivotal in adjusting the distribution of task samples + +
TypeGQAOK-VQAVQAv2NoCaps
B@4SC
1none33.026.349.745.613.9108.1
2all38.929.554.346.014.3111.9
3noun, verb36.430.752.146.014.3114.3
4ent, pred, attr38.327.554.945.214.7111.3
5noun, ent38.529.854.846.514.4112.4
6verb, pred, attr36.029.654.146.914.5114.1
7random33.026.248.644.114.5107.1
+ +Table 4. Ablation study on editing different subsets of concept types for mismatched caption construction. + +in our approach. We conducted a comprehensive hyperparameter search for each experimental model, analyzing the impact of these parameters on model performance. Fig. 3 illustrate the performance variations of BLIP-2 OPT2.7B after second-stage training under different hyperparameter settings: + +- In the left of Fig. 3, with $p_s$ fixed at 0.1, we study the influence of different correction task sample proportions by varying $p_c$ at intervals of 0.15. +- In the right of Fig. 3, with $p_c$ fixed at 0.3, we explore the impact of different swap operation proportions on mismatched caption sampling by varying $p_s$ at intervals of 0.15. + +In our experiments, we present several key findings: + +- From both figures, it is evident that the impact of hyperparameters $p_{c}$ and $p_{s}$ on model performance follows a consistent trend, initially increasing before decreasing. This phenomenon arises due to the risk of language bias when incorporating excessive correction task samples, particularly those generated through swap operations. +- Notably, the saturation point of $p_{s}$ is reached early, suggesting that the model can easily identify and correct mismatched captions created through swap operations. Despite this, proper inclusion of such samples proves beneficial for overall performance enhancement, particularly + +![](images/f82f9b60febece513d29d72bcdf8a26f0d0dda29e3480a51517a550448f38ed0.jpg) +Is the jar made of the same materials as the hook? + +![](images/fcdf40dfb8c6ad42d6e0aecd8b0824596104000060325fdf7aeadd6bdf1ca5b0.jpg) +Are there men to the right of the woman that is wearing trousers? + +![](images/90aa250ebd47a03a6193385c75fcfff6f2e1746324b35edace3cf9b2b4957b45.jpg) +What kind of furniture is surrounding the table? + +![](images/6866c2d394b7968efc8a7c2826622d4ef71619e62ea0b23895328e18c87c0718.jpg) +BLIP-2: Yes. + +![](images/558b893637c02799fd205e0efcad6722930fc9014af681cfd4550901de3b8a78.jpg) +BLIP-2: Yes. + +![](images/19bd9fb27687ba650b318565c0a1da466554f673fa5a7ccd91c63c6a18ee576f.jpg) +BLIP-2: Kitchen. + +![](images/cccf7c51c03f65e477ecbc4ac9639e590c3d5f339dfb021cdfa6a17989eace0d.jpg) +Ours: No. + +![](images/981c70c45bbdc1ee829f7dec59ea26191f2ab38e4b46310f4342e0be34c32636.jpg) +Ours: No. + +![](images/d5948d4b430c4ffa90f0e1a19d64668a23cb49dbcdd4cc938f16918d96557bee.jpg) +Ours: Chair. + +![](images/bdab1b91fcab60ee607791df9ab7e6548fa8736b8226c682db2fd51e6cd7dbdd.jpg) +BLIP-2: A red kite flying over a forest. + +![](images/a187607ab43895d0258d1e643e348cb04d13b217ea2840c991b94ed1029b6d0b.jpg) +A group of children in a library. + +![](images/441d84473c706cc90f41209130c72b63fdb532db5ce93b77fce2a3c8247c20bb.jpg) +A man sitting in front of +a wood burning stove. +A person looking at a fire +in a wood stove. +Figure 4. Visualization results include model output examples and attention gradients on images. The first block illustrates three examples from the GQA testdev set, while the second block showcases three examples from the NoCaps validation set. With our training, the model demonstrates improved accuracy in focusing on prompt-relevant image regions. Additionally, it generates captions with more detailed descriptions of scenes and actions. + +in image captioning tasks. + +- Furthermore, our investigation reveals that BLIP-2 FlanT5-XL tends to overfit on our task samples, possibly attributed to its encoder-decoder architecture. This results in the Q-former learning an overfitted encoding of soft prompts associated with task text patterns. Nonetheless, even minimal incorporation of correction task samples $(p_c = 0.01)$ effectively serves our training objectives while mitigating the risk of overfitting. + +# 5.4. Qualitative Results + +To provide a more intuitive understanding of the effects of our training, we show some qualitative model output examples in Fig. 4. We demonstrate the differences between the model outputs and intermediate results on the VQA and IC tasks before and after our second-stage training respectively. The heat maps show the gradient of the output logit corresponding to the ground truth token with regard to the image attention, which reflects the potential visual contribution of the model output. + +According to the outputs for VQA, the results reveal that the proposed correction task training produces inter + +pretable improvements to VQA responses. Our model demonstrates increased accuracy in locating objects referenced in prompts and exhibits a more precise understanding of compositional concepts, avoiding biases toward prominent objects. For instance, in the first example, our model focuses on the "hook", which the original model misses. In the second example, our model correctly considers the composed concept of "the woman that is wearing trousers". Lastly, our model interprets the relational concept "surrounding the table" and directs attention appropriately toward the relevant region, rather than the table itself. Overall, our findings indicate that this training methodology enhances VLMs' capacity for interpreting corresponding visual concepts expressed through language. + +Examples from our experiments with IC illustrate this improved ability to correct misidentified objects and provide richer, more fine-grained descriptions of object relationships and actions. For instance, our model correctly identifies the wrong "red kite" concept in the first case and provides more nuanced details about the scene, such as "standing around a table" and "looking". We posit that the primary source of improved overall captioning performance lies in the generation of more accurate and comprehensive concepts in captions. + +Conclusively, our study indicates that the proposed training method potentially enhances generative VLMs' capacity for aligning concepts across multiple types and granularities in visual and language modalities. We believe this insight could shed light on the future development of cost-effective, multi-granularity, and structured generative VL pre-trained models. + +# 6. Conclusion + +In this work, we propose the image-conditioned text correction task for enhancing zero-shot text generation with unlabeled data. In this task, VLMs requires to identify and correct the error in accordance with the vision modality via text generation. We propose a scalable and cost-effective data construction framework for generating the image-text pair for this task by utilizing the inherent structure of language. 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Advances in neural information processing systems, 33:6256-6268, 2020. 3 +[36] Zhengyuan Yang, Zhe Gan, Jianfeng Wang, Xiaowei Hu, Faisal Ahmed, Zicheng Liu, Yumao Lu, and Lijuan Wang. + +Unitab: Unifying text and box outputs for grounded vision-language modeling. In European Conference on Computer Vision, pages 521-539. Springer, 2022. 1, 2 +[37] Weihao Yu, Zhengyuan Yang, Linjie Li, Jianfeng Wang, Kevin Lin, Zicheng Liu, Xinchao Wang, and Lijuan Wang. Mm-vet: Evaluating large multimodal models for integrated capabilities. arXiv preprint arXiv:2308.02490, 2023. 6 +[38] Mert Yuksekgonul, Federico Bianchi, Pratyusha Kalluri, Dan Jurafsky, and James Zou. When and why vision-language models behave like bags-of-words, and what to do about it? arXiv e-prints, pages arXiv-2210, 2022. 3 +[39] Sangdoo Yun, Dongyoon Han, Seong Joon Oh, Sanghyuk Chun, Junsuk Choe, and Youngjoon Yoo. Cutmix: Regularization strategy to train strong classifiers with localizable features. 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Judging lmm-as-a-judge with mt-bench and chatbot arena, 2023. 2, 5 +[44] Kaiyang Zhou, Jingkang Yang, Chen Change Loy, and Ziwei Liu. Conditional prompt learning for vision-language models. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 16816-16825, 2022. 1 +[45] Deyao Zhu, Jun Chen, Xiaogian Shen, Xiang Li, and Mohamed Elhoseiny. Minigpt-4: Enhancing vision-language understanding with advanced large language models. arXiv preprint arXiv:2304.10592, 2023. 2 \ No newline at end of file diff --git a/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/images.zip b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..ee3c8007e34bb135562db70759a80d1e33ca8af1 --- /dev/null +++ b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:d85fa66c1db55b4be1956d3df0e0f9b926ca066745e796e3f3ee210859c781d6 +size 449199 diff --git a/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/layout.json b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..a28b052479ae67a65ee818e3e6e4b31bf6b1275c --- /dev/null +++ b/2024/Learning by Correction_ Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning/layout.json @@ -0,0 +1,8582 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 73, + 102, + 520, + 140 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 73, + 102, + 520, + 140 + ], + "spans": [ + { + "bbox": [ + 73, + 102, + 520, + 140 + ], + "type": "text", + "content": "Learning by Correction: Efficient Tuning Task for Zero-Shot Generative Vision-Language Reasoning" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 200, + 167, + 397, + 182 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 200, + 167, + 397, + 182 + ], + "spans": [ + { + "bbox": [ + 200, + 167, + 397, + 182 + ], + "type": "text", + "content": "Rongjie Li" + }, + { + "bbox": [ + 200, + 167, + 397, + 182 + ], + "type": "inline_equation", + "content": "^{1*}" + }, + { + "bbox": [ + 200, + 167, + 397, + 182 + ], + "type": "text", + "content": " Yu Wu" + }, + { + "bbox": [ + 200, + 167, + 397, + 182 + ], + "type": "inline_equation", + "content": "^{1*}" + }, + { + "bbox": [ + 200, + 167, + 397, + 182 + ], + "type": "text", + "content": " Xuming He" + }, + { + "bbox": [ + 200, + 167, + 397, + 182 + ], + "type": "inline_equation", + "content": "^{1,2‡}" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 116, + 184, + 475, + 233 + ], + "type": "list", + "angle": 0, + "index": 6, + "blocks": [ + { + "bbox": [ + 116, + 184, + 475, + 200 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 116, + 184, + 475, + 200 + ], + "spans": [ + { + "bbox": [ + 116, + 184, + 475, + 200 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 116, + 184, + 475, + 200 + ], + "type": "text", + "content": "School of Information Science and Technology, ShanghaiTech University" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 117, + 201, + 475, + 233 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 117, + 201, + 475, + 233 + ], + "spans": [ + { + "bbox": [ + 117, + 201, + 475, + 233 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 117, + 201, + 475, + 233 + ], + "type": "text", + "content": "Shanghai Engineering Research Center of Intelligent Vision and Imaging {lirj2, wuyu1, hexm} " + }, + { + "bbox": [ + 117, + 201, + 475, + 233 + ], + "type": "inline_equation", + "content": "@" + }, + { + "bbox": [ + 117, + 201, + 475, + 233 + ], + "type": "text", + "content": " shanghaiitech.edu.cn" + } + ] + } + ], + "index": 5 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 143, + 260, + 191, + 273 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 260, + 191, + 273 + ], + "spans": [ + { + "bbox": [ + 143, + 260, + 191, + 273 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 286, + 290, + 526 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 286, + 290, + 526 + ], + "spans": [ + { + "bbox": [ + 47, + 286, + 290, + 526 + ], + "type": "text", + "content": "Generative vision-language models (VLMs) have shown impressive performance in zero-shot vision-language tasks like image captioning and visual question answering. However, improving their zero-shot reasoning typically requires second-stage instruction tuning, which relies heavily on human-labeled or large language model-generated annotation, incurring high labeling costs. To tackle this challenge, we introduce Image-Conditioned Caption Correction (ICCC), a novel pre-training task designed to enhance VLMs' zero-shot performance without the need for labeled task-aware data. The ICCC task compels VLMs to rectify mismatches between visual and language concepts, thereby enhancing instruction following and text generation conditioned on visual inputs. Leveraging language structure and a lightweight dependency parser, we construct data samples of ICCC task from image-text datasets with low labeling and computation costs. Experimental results on BLIP-2 and InstructBLIP demonstrate significant improvements in zero-shot image-text generation-based VL tasks through ICCC instruction tuning." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 552, + 128, + 563 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 552, + 128, + 563 + ], + "spans": [ + { + "bbox": [ + 47, + 552, + 128, + 563 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 572, + 287, + 645 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 572, + 287, + 645 + ], + "spans": [ + { + "bbox": [ + 46, + 572, + 287, + 645 + ], + "type": "text", + "content": "Vision-language models (VLMs) have demonstrated remarkable performance across a wide range of vision-language (VL) tasks, including image captioning [1, 19, 22, 33, 36], visual recognition [15, 29, 44], image-text retrieval [18, 29], and answering visual questions [1, 19, 22, 33, 36]. Generally, existing VLMs are able to conduct two" + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 310, + 263, + 545, + 571 + ], + "blocks": [ + { + "bbox": [ + 310, + 263, + 545, + 571 + ], + "lines": [ + { + "bbox": [ + 310, + 263, + 545, + 571 + ], + "spans": [ + { + "bbox": [ + 310, + 263, + 545, + 571 + ], + "type": "image", + "image_path": "437351355d83a00c39300a719f0cf34efc6b2d48e90e65408067f8c4e063acf7.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 586, + 547, + 642 + ], + "lines": [ + { + "bbox": [ + 304, + 586, + 547, + 642 + ], + "spans": [ + { + "bbox": [ + 304, + 586, + 547, + 642 + ], + "type": "text", + "content": "Figure 1. Illustration of second-stage tuning for zero-shot VL task adaptation comparison. The instruction tuning in recent works needs human label or LLM-generated data; in contrast, our image caption correction tuning is conducted on unlabeled image-text data with an NLP parser." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "content": "essential tasks: image-text matching (ITM) and image-text generation (ITG). The contrastive-based ITM aims to model the similarity between vision and text through a shared embedding [15, 18, 29]. In contrast, the generative-based ITG has more flexibility in adapting to various VL tasks. More-" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 655, + 287, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 655, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 655, + 287, + 712 + ], + "type": "text", + "content": "*Equal Contribution. This work was supported by NSFC 62350610269, the Shanghai Frontiers Science Center of Human-centered Artificial Intelligence, and the MoE Key Lab of Intelligent Perception and Human-Machine Collaboration (ShanghaiTech University). ‡ denotes corresponding author. Code is available: https://github.com/SHTUPLUS/ICCC_CVPR2024" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13428" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "type": "text", + "content": "over, several recent VLM frameworks integrate the LLMs for ITG, which extend the powerful text generation across vision and text modality [1, 8, 19, 22], and allow VLMs to perform zero-shot inference on various VL tasks with impressive performance." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 134, + 287, + 302 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 134, + 287, + 302 + ], + "spans": [ + { + "bbox": [ + 46, + 134, + 287, + 302 + ], + "type": "text", + "content": "To perform zero-shot inference on VL tasks, the VLMs need to have generalizable text generation capability according to text inputs and concepts from the visual modality. The existing works typically conduct second-stage instruction tuning for pre-trained VLMs with task-oriented data. This improves VLMs for following instructions to generate texts conditioned on visual modality, which ultimately enhances the zero-shot performance on VL-tasks such as InstructBLIP [8] and LLAVA [22], as shown in the upper part of Fig. 1. However, these methods necessitate substantial downstream task data annotation for fine-tuning, which is either human-labeled or generated externally by large language models. This process escalates labor costs throughout the system." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 304, + 287, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 304, + 287, + 496 + ], + "spans": [ + { + "bbox": [ + 46, + 304, + 287, + 496 + ], + "type": "text", + "content": "In this study, we introduce a novel pre-training task, Image-Conditioned Caption Correction (ICCC), aimed at enhancing VLMs' performance on zero-shot VL tasks. Our approach leverages the semantic dependency structure of language utilized for second-stage tuning of VLMs, using image-text data without task-specific annotation, as depicted in Fig. 1. By enforcing VLMs to identify and rectify mismatched concepts between visual and language, our method enhances VLMs' capability of generating text from the visual modality. Importantly, the adopted universal semantic dependency [26] ensures comprehensive coverage of various concepts, including objects, their attributes, and interactions between them. Furthermore, we construct the data from unlabeled image-text datasets only with a lightweight dependency parser, which achieves low labeling and computation costs." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 498, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 288, + 714 + ], + "type": "text", + "content": "Specifically, our pre-training framework first generates the task of image-conditioned text correction in an automatic manner. To this end, we develop a data construction pipeline with two components: the concept extractor and the correction task constructor. Firstly, the concept extractor identifies various concepts from the text modality. With the off-the-shelf dependency parser, it extracts the set of language units by parsing the semantic dependency structure of text. Subsequently, the correction task constructor generates samples from the unlabeled image-text data according to language structure and concept set. It swaps or replaces language units according to the extracted concept set, thereby creating concept-mismatched image-text pairs. Thanks to the universality of dependency, this approach allows us to create a wide variety of samples covering diverse visual-language concepts. The resulting text correction task requires VLMs to detect and recover the language units of mismatched concepts (words and phrases) according to the" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 72, + 545, + 108 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 108 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 108 + ], + "type": "text", + "content": "image. Finally, we use the generated samples together with the original image-text data to fine-tune pre-trained VLMs with language modeling objectives." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 108, + 545, + 203 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 108, + 545, + 203 + ], + "spans": [ + { + "bbox": [ + 304, + 108, + 545, + 203 + ], + "type": "text", + "content": "We conduct extensive experiments on two VLMs, BLIP-2 [19] and InstructBLIP [8], and evaluate the zero-shot performance of ITG on the representative tasks: visual question answering and image caption. Our findings reveal that our proposed method yields substantial improvements in zero-shot generalization based on the initial pre-train model without requiring any manually labeled or LLM-generated data. The main contributions of our work are threefold:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 204, + 545, + 322 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 306, + 204, + 545, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 204, + 545, + 239 + ], + "spans": [ + { + "bbox": [ + 306, + 204, + 545, + 239 + ], + "type": "text", + "content": "- We introduce a novel image-conditioned text correction fine-tuning strategy for VLMs that enhances their generalization of ITG for VL tasks." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 240, + 545, + 286 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 240, + 545, + 286 + ], + "spans": [ + { + "bbox": [ + 306, + 240, + 545, + 286 + ], + "type": "text", + "content": "- We developed an automated data construction pipeline that produces large amounts of samples for fine-tuning, all generated from image-text pairs without the need for human annotations or additional LLMs." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 288, + 545, + 322 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 288, + 545, + 322 + ], + "spans": [ + { + "bbox": [ + 306, + 288, + 545, + 322 + ], + "type": "text", + "content": "- We demonstrated notable improvements in the zero-shot generalization capabilities of VLMs across various VL tasks." + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 334, + 392, + 346 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 334, + 392, + 346 + ], + "spans": [ + { + "bbox": [ + 306, + 334, + 392, + 346 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 354, + 545, + 450 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 354, + 545, + 450 + ], + "spans": [ + { + "bbox": [ + 304, + 354, + 545, + 450 + ], + "type": "text", + "content": "Generative Vision Language Models With advancements in large-scale pretraining, vision-language models (VLMs) have demonstrated notable zero-shot generalization across various tasks. Unlike contrastive VLMs such as CLIP [29] and ALIGN [15], which focus on image-text similarity scores, generative VLMs output text based on image and text inputs for tasks like visual question answering and image captioning." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 450, + 545, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 450, + 545, + 641 + ], + "spans": [ + { + "bbox": [ + 304, + 450, + 545, + 641 + ], + "type": "text", + "content": "In earlier studies, generative VLMs utilized fusion-encoder transformers [4, 20, 32, 41] to simultaneously encode visual and linguistic tokens, and subsequent models [5, 33, 36] integrated visual input information into different architecture language models, giving rise to unified generative VL transformer models. Recently, with advancements in Large Language Models (LLMs) [6, 28, 42, 43], efforts have sought to utilize LLMs' capabilities to project visual input into the language embedding space. BLIP-2 [19] bridges the modality gap using a pre-trained Q-Former. Building upon BLIP-2, MiniGPT-4 [45] and InstructBLIP [8] focus on next-stage instruction tuning to further enhance performance. LLaVA [22] involves GPT-4 [27] in generating instructions and conversations for training. LLaMA-Adapter v2 [11] and LaVIN [24] employ adapters for architecture fine-tuning." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": "In our study, akin to LLaVA and Instruct-BLIP, we focus on leveraging the benefits of second-stage fine-tuning of pre-trained VLMs. However, unlike these approaches, we aim to achieve this without down-stream tasks data from human annotation and large models generation. Instead, we introduce a novel correction task, construct from the image" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13429" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 193, + 85 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 193, + 85 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 193, + 85 + ], + "type": "text", + "content": "text data with light-weight pipeline." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 99, + 287, + 229 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 99, + 287, + 229 + ], + "spans": [ + { + "bbox": [ + 46, + 99, + 287, + 229 + ], + "type": "text", + "content": "Language Structure-based Data Augmentation Data augmentation is widely employed in machine learning, with common techniques such as mixup [40], CutMix [39], and RandAugment [7] in computer vision, and backtranslation [35], random word editing [34] in natural language processing. In the field of vision and language (VL), an effective approach often involves synthesizing new data using pre-trained models as augmentation [2]. For instance, BLIP [18] leverages the model's initially trained capabilities to generate additional training data, thereby further enhancing the model's performance." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 230, + 288, + 421 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 230, + 288, + 421 + ], + "spans": [ + { + "bbox": [ + 46, + 230, + 288, + 421 + ], + "type": "text", + "content": "Some researchers in visual-linguistic (VL) studies pursue performance enhancements on challenging tasks by crafting difficult negative samples. For instance, NegCLIP [38] employs a language parser to swap elements between sentences, generating hard negative image-text pairs for contrastive fine-tuning. SVLC [9] achieves a similar outcome by substituting elements in sentences. Our approach leverages linguistic structure to improve image-text generation (ITG) tasks. Unlike image-text matching (ITM) tasks, which focus on learning similarity metrics, generative models encounter difficulties with negative samples. To address this, we introduce a correction task for instruction fine-tuning, using structural language information to construct data samples. This enhances the generalization performance of VLMs in zero-shot ITG-based visual language tasks." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 431, + 124, + 445 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 431, + 124, + 445 + ], + "spans": [ + { + "bbox": [ + 47, + 431, + 124, + 445 + ], + "type": "text", + "content": "3. Preliminary" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "spans": [ + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "text", + "content": "Image-text Generation of VLMs Image-text generation, a fundamental task of VLMs, involves generating text from both visual and textual inputs. Specifically, VLMs with parameters " + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "inline_equation", + "content": "\\Theta_{vlm}" + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "text", + "content": " generate output text from images and textual input in an auto-regressive manner. The visual input is projected into language embedding as visual tokens " + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "inline_equation", + "content": "\\mathbf{Z}" + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "text", + "content": " together with textual input " + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "inline_equation", + "content": "\\mathbf{w} = [w_1, w_2, \\dots, w_{i-1}]" + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "text", + "content": " and fed into the subsequent LLM to predict the next token " + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "inline_equation", + "content": "w_i" + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "text", + "content": " of the sequence " + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "inline_equation", + "content": "\\mathbf{w}" + }, + { + "bbox": [ + 46, + 451, + 287, + 559 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 85, + 567, + 287, + 580 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 85, + 567, + 287, + 580 + ], + "spans": [ + { + "bbox": [ + 85, + 567, + 287, + 580 + ], + "type": "interline_equation", + "content": "w _ {i} = \\mathcal {F} _ {v l m} (\\mathbf {Z}, w _ {1}, w _ {2}, \\dots , w _ {i - 1}; \\boldsymbol {\\Theta} _ {v l m}). \\tag {1}", + "image_path": "e2e1660de10f902bd1941305228133e0290a6532cc8430a0bb52d7b08515dba8.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "type": "text", + "content": "Second-stage Tuning for Zero-shot Generation While generative image-text pre-training provides VLMs with aligned vision-language representations, effective instruction-following of image-text generation for diverse zero-shot VL tasks is crucial. Recent works address this issue by leveraging either human-labeled [8] or large language model-generated task-oriented data [22] for instruction tuning. Concretely, in the second stage of tuning, the VLMs are optimized with the same objective of generative image-text pre-training with task-oriented data:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 317, + 71, + 545, + 103 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 71, + 545, + 103 + ], + "spans": [ + { + "bbox": [ + 317, + 71, + 545, + 103 + ], + "type": "interline_equation", + "content": "\\underset {\\Theta_ {v l m}} {\\arg \\max } \\sum_ {i = 1} ^ {K} \\log P \\left(w _ {i} \\mid \\mathbf {Z}, w _ {1}, w _ {2}, \\dots , w _ {i - 1}; \\Theta_ {v l m}\\right). \\tag {2}", + "image_path": "e65005f612f832609728e9bc1a8311a4862ef20de5ec6043de51bdb6f63b16ed.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 118, + 397, + 131 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 118, + 397, + 131 + ], + "spans": [ + { + "bbox": [ + 305, + 118, + 397, + 131 + ], + "type": "text", + "content": "4. Our Approach" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 137, + 545, + 305 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 137, + 545, + 305 + ], + "spans": [ + { + "bbox": [ + 304, + 137, + 545, + 305 + ], + "type": "text", + "content": "In this section, we introduce our proposed Image Conditional Caption Correction (ICCC) task for second-stage tuning, which constructs data from unlabeled data with low resource consumption. We first provide a Task Definition of ICCC in Sec. 4.1. Then we introduce the data construction pipeline for ICCC, which includes two modules: the Concept Extractor and the Correction Data constructor. The concept extractor parses the text structure and extracts the concept set for the following data construction, discussed in Sec. 4.2. Subsequently, the correction data constructor generates data by augmenting text structure with the extracted concept set, described in Sec.4.3, Finally, Sec. 4.4 outlines our training and inference procedures for incorporating our task into VLM pre-training." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 312, + 398, + 323 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 312, + 398, + 323 + ], + "spans": [ + { + "bbox": [ + 305, + 312, + 398, + 323 + ], + "type": "text", + "content": "4.1. Task definition" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 329, + 545, + 400 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 329, + 545, + 400 + ], + "spans": [ + { + "bbox": [ + 304, + 329, + 545, + 400 + ], + "type": "text", + "content": "As illustrated in Fig. 2, the ICCC task involves identifying and correcting language units of mismatched concepts of caption. To define the ICCC task, we need to define the concept set, how we perturb to produce concept-mismatched samples, and how the perturb operation changes the language structure." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 401, + 545, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 401, + 545, + 510 + ], + "spans": [ + { + "bbox": [ + 304, + 401, + 545, + 510 + ], + "type": "text", + "content": "For each sentence, concepts are composed of linguistic units representing their semantic meaning. These linguistic units are categorized into five types based on semantics and language granularity: " + }, + { + "bbox": [ + 304, + 401, + 545, + 510 + ], + "type": "inline_equation", + "content": "\\mathcal{E} = \\{\\text{entity phrase}, \\text{predicate phrase}, \\text{attribute phrase}, \\text{noun word}, \\text{verb word}\\}" + }, + { + "bbox": [ + 304, + 401, + 545, + 510 + ], + "type": "text", + "content": ". The entity phrase, noun word, attribute phrase represent the object-level semantic, and predicate phrase, verb word represent the composition-level semantic. The phrase and word represent different levels of language granularity." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 510, + 545, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 545, + 664 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 545, + 664 + ], + "type": "text", + "content": "There are two operations for perturbing the language structure: " + }, + { + "bbox": [ + 304, + 510, + 545, + 664 + ], + "type": "inline_equation", + "content": "\\{\\mathrm{replace},\\mathrm{swap}\\}" + }, + { + "bbox": [ + 304, + 510, + 545, + 664 + ], + "type": "text", + "content": ". The replace involves substituting a concept with another one of the same type from the image-text pair dataset, while the swap involves swapping the positions of two concepts of the same type within the original caption. More details are introduced in Sec. 4.3. Consequently, replace focuses on modeling the intrinsic meaning of individual concepts, while swap prioritizes the order of compositional concepts within sentences. Overall, the task is to use linguistic unit modifications of image-text pairs, providing universal concepts aligned between vision and language, which improves text generation capabilities across two modalities." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 671, + 416, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 671, + 416, + 684 + ], + "spans": [ + { + "bbox": [ + 306, + 671, + 416, + 684 + ], + "type": "text", + "content": "4.2. Concept Extractor" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "text", + "content": "As mentioned earlier, the data of ICCC is generated by perturbing concepts in " + }, + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "text", + "content": " according to the structure of sen" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13430" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 71, + 539, + 299 + ], + "blocks": [ + { + "bbox": [ + 53, + 71, + 539, + 299 + ], + "lines": [ + { + "bbox": [ + 53, + 71, + 539, + 299 + ], + "spans": [ + { + "bbox": [ + 53, + 71, + 539, + 299 + ], + "type": "image", + "image_path": "d666cd18de624b971507cfd028f9e790dea96f71bfa05b330f0eebbaf1eac523.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 300, + 546, + 335 + ], + "lines": [ + { + "bbox": [ + 46, + 300, + 546, + 335 + ], + "spans": [ + { + "bbox": [ + 46, + 300, + 546, + 335 + ], + "type": "text", + "content": "Figure 2. Illustration of the overall pipeline of ICCC. The concept extractor parses the sentence to obtain linguistic units of concepts. The task data constructor aims to produce the sample according to the sentence structure with the \"replace\" and \"swap\" operations. Finally, the generated ICCC data is used for image-to-text generative training for VLMs." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 344, + 289, + 416 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 344, + 289, + 416 + ], + "spans": [ + { + "bbox": [ + 46, + 344, + 289, + 416 + ], + "type": "text", + "content": "tences. The concept extractor takes captions as input and parses the dependency to identify linguistic units of concepts, which the following task constructor then uses to generate data samples. The concept extractor module has three processes: (1) universal dependency parsing; (2) linguistic unit selection and grouping; (2) concept collection." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 432, + 287, + 577 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 432, + 287, + 577 + ], + "spans": [ + { + "bbox": [ + 46, + 432, + 287, + 577 + ], + "type": "text", + "content": "Universal Dependency Parsing We use the off-the-shelf universal dependency parser implemented by the spaCy [13] software library to extract the dependency structure of the original caption. As shown in Fig. 2, the dependency parser translates the sentence into a universal dependency tree [26]. The node of the dependency tree is the minimal linguistic unit " + }, + { + "bbox": [ + 46, + 432, + 287, + 577 + ], + "type": "inline_equation", + "content": "u_{[pos]}" + }, + { + "bbox": [ + 46, + 432, + 287, + 577 + ], + "type": "text", + "content": ", which has Part-of-Speech (POS) tags to indicate its grammatical role. The edge represents the dependency relation between linguistic units " + }, + { + "bbox": [ + 46, + 432, + 287, + 577 + ], + "type": "inline_equation", + "content": "r_{[REL]}" + }, + { + "bbox": [ + 46, + 432, + 287, + 577 + ], + "type": "text", + "content": ", which also has the relation type (REL). The dependency structure provides us with an indication of how linguistic units organize to represent the concept of a sentence." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "text", + "content": "Linguistic Unit Selection and Grouping We extract the linguistic unit set of concept " + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "inline_equation", + "content": "U_{\\text{concept}}" + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "text", + "content": " within " + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "text", + "content": " by grouping and selecting " + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "inline_equation", + "content": "u_{[pos]}" + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "text", + "content": ". To achieve this, we design a heuristic method by traversing the dependency tree to select the corresponding " + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "inline_equation", + "content": "u_{[pos]}" + }, + { + "bbox": [ + 46, + 593, + 287, + 676 + ], + "type": "text", + "content": ". Firstly, we extract the concept represented by the concept of a word-level linguistic unit according to the POS tag:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 48, + 678, + 136, + 702 + ], + "type": "list", + "angle": 0, + "index": 7, + "blocks": [ + { + "bbox": [ + 48, + 678, + 136, + 690 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 678, + 136, + 690 + ], + "spans": [ + { + "bbox": [ + 48, + 678, + 136, + 690 + ], + "type": "text", + "content": "1. " + }, + { + "bbox": [ + 48, + 678, + 136, + 690 + ], + "type": "inline_equation", + "content": "U_{\\text{noun word}}: u_{[\\text{noun}]}" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 48, + 691, + 132, + 702 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 691, + 132, + 702 + ], + "spans": [ + { + "bbox": [ + 48, + 691, + 132, + 702 + ], + "type": "text", + "content": "2. " + }, + { + "bbox": [ + 48, + 691, + 132, + 702 + ], + "type": "inline_equation", + "content": "U_{verbword} : u_{[verb]}" + } + ] + } + ], + "index": 6 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 48, + 703, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 703, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 48, + 703, + 287, + 715 + ], + "type": "text", + "content": "Based on such word-level concepts " + }, + { + "bbox": [ + 48, + 703, + 287, + 715 + ], + "type": "inline_equation", + "content": "u_{[pos]}" + }, + { + "bbox": [ + 48, + 703, + 287, + 715 + ], + "type": "text", + "content": ", we further ex" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "spans": [ + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "type": "text", + "content": "tract linguistic units of phrase-level concepts, such as entity phrase, predicate phrase, attribute phrase, by grouping the " + }, + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "type": "inline_equation", + "content": "u_{[pos]}" + }, + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "type": "text", + "content": " into " + }, + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "type": "inline_equation", + "content": "U_{concept}" + }, + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "type": "text", + "content": " according to the " + }, + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "type": "inline_equation", + "content": "r_{[REL]}" + }, + { + "bbox": [ + 304, + 344, + 546, + 392 + ], + "type": "text", + "content": " associated with word-level concept units:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 392, + 512, + 429 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "spans": [ + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "text", + "content": "1. " + }, + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "inline_equation", + "content": "U_{\\text{entity phrase}}" + }, + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "text", + "content": ": " + }, + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "inline_equation", + "content": "u_{[adj]}" + }, + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "inline_equation", + "content": "U_{[det]}" + }, + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "text", + "content": " adjacent to " + }, + { + "bbox": [ + 306, + 392, + 512, + 405 + ], + "type": "inline_equation", + "content": "U_{[noun]}" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 405, + 492, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 405, + 492, + 418 + ], + "spans": [ + { + "bbox": [ + 306, + 405, + 492, + 418 + ], + "type": "text", + "content": "2. " + }, + { + "bbox": [ + 306, + 405, + 492, + 418 + ], + "type": "inline_equation", + "content": "U_{predicate phrase}" + }, + { + "bbox": [ + 306, + 405, + 492, + 418 + ], + "type": "text", + "content": ": all " + }, + { + "bbox": [ + 306, + 405, + 492, + 418 + ], + "type": "inline_equation", + "content": "u_{[pos]}" + }, + { + "bbox": [ + 306, + 405, + 492, + 418 + ], + "type": "text", + "content": " within two " + }, + { + "bbox": [ + 306, + 405, + 492, + 418 + ], + "type": "inline_equation", + "content": "u_{[noun]}" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 418, + 499, + 429 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 418, + 499, + 429 + ], + "spans": [ + { + "bbox": [ + 306, + 418, + 499, + 429 + ], + "type": "text", + "content": "3. " + }, + { + "bbox": [ + 306, + 418, + 499, + 429 + ], + "type": "inline_equation", + "content": "U_{\\text{attribute phrase}}" + }, + { + "bbox": [ + 306, + 418, + 499, + 429 + ], + "type": "text", + "content": ": all " + }, + { + "bbox": [ + 306, + 418, + 499, + 429 + ], + "type": "inline_equation", + "content": "u_{[amod]}" + }, + { + "bbox": [ + 306, + 418, + 499, + 429 + ], + "type": "text", + "content": " adjacent to " + }, + { + "bbox": [ + 306, + 418, + 499, + 429 + ], + "type": "inline_equation", + "content": "u_{[noun]}" + } + ] + } + ], + "index": 12 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 430, + 545, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 430, + 545, + 464 + ], + "spans": [ + { + "bbox": [ + 306, + 430, + 545, + 464 + ], + "type": "text", + "content": "To this end, we extract the linguistic units of each concept type " + }, + { + "bbox": [ + 306, + 430, + 545, + 464 + ], + "type": "inline_equation", + "content": "U_{\\text{concept}}" + }, + { + "bbox": [ + 306, + 430, + 545, + 464 + ], + "type": "text", + "content": " from the text according to the dependency structure." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "spans": [ + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "text", + "content": "Concept Collection For each sentence from the image-text dataset, we collect all " + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "inline_equation", + "content": "U_{\\text{concept}}" + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "text", + "content": " according to their concept type, respectively. We merge the " + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "inline_equation", + "content": "U_{\\text{noun word}}" + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "text", + "content": " with the " + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "inline_equation", + "content": "U_{\\text{entity phrase}}" + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "text", + "content": " and the " + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "inline_equation", + "content": "U_{\\text{verb word}}" + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "text", + "content": " with the " + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "inline_equation", + "content": "U_{\\text{predicate phrase}}" + }, + { + "bbox": [ + 304, + 482, + 546, + 602 + ], + "type": "text", + "content": " into the same concept type, respectively. This global-level concept base stores all the concepts that occurred in the dataset. We filter them by frequency to remove infrequent concepts, which could be extracted from low-quality captions or parsing errors, and the most frequent, which could be a trivial concept or language bias that occurred uniformly." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 610, + 490, + 623 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 610, + 490, + 623 + ], + "spans": [ + { + "bbox": [ + 306, + 610, + 490, + 623 + ], + "type": "text", + "content": "4.3. Correction Task Data Constructor" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 629, + 545, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 700 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 700 + ], + "type": "text", + "content": "The correction task data constructor uses the extracted concept structure to generate data samples with multi-level concept mismatch captions. The data constructor takes the input text, which has identified concepts of language units and concept-based units, and produces the augmented text with expected corrections." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 317, + 701, + 545, + 714 + ], + "type": "text", + "content": "Specifically, the data constructor perturbs the initial lin" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13431" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "type": "text", + "content": "guistic structure by predefined operations: replace, swap, as shown in Fig. 2. Specifically, the replace randomly selects the concept of the original text and replaces it with an external " + }, + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "type": "inline_equation", + "content": "U_{\\text{concept}}" + }, + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "type": "text", + "content": " that has the same semantic type but does not occur in the current text from the concept base. For instance, the entity phrase can be replaced by all object-level concepts, such as noun word or entity phrase. The swap operation, instead of replacing concept by concept, swaps the two linguistic unit sets with the same concept type in the text. This perturbation operation provides the order mismatch of the concept. To calibrate those two operations, we randomly select one by Bernoulli distribution with a preset parameter " + }, + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "type": "inline_equation", + "content": "p_s \\in [0,1]" + }, + { + "bbox": [ + 46, + 72, + 289, + 263 + ], + "type": "text", + "content": " to decide which type of operation is used for perturbation. In those cases where a sentence doesn't have two of the same concept-type linguistic units, we simply use the replace operation." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 263, + 289, + 360 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 263, + 289, + 360 + ], + "spans": [ + { + "bbox": [ + 46, + 263, + 289, + 360 + ], + "type": "text", + "content": "After the perturb operation, we map back the tree structure sentence into sequence and construct the caption correction samples, which are composed of the following components: correction instruction prompt, perturbed caption, and correcting description, as shown in Fig. 2. The correction instruction prompt is selected from a template base, and the correcting description includes the mismatch concept and the correct ones." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 365, + 178, + 378 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 365, + 178, + 378 + ], + "spans": [ + { + "bbox": [ + 47, + 365, + 178, + 378 + ], + "type": "text", + "content": "4.4. Training and Inference" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 384, + 289, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 384, + 289, + 563 + ], + "spans": [ + { + "bbox": [ + 46, + 384, + 289, + 563 + ], + "type": "text", + "content": "The data generated by ICCC is utilized in the second-stage tuning process to improve VLMs, as introduced in Sec 3. We combine ICCC data samples with original image-text pairs for training to prevent focusing too much on the specific task and catastrophic forgetting. The proportion of ICCC data samples to original pairs in each training batch is determined by a hyper-parameter " + }, + { + "bbox": [ + 46, + 384, + 289, + 563 + ], + "type": "inline_equation", + "content": "p_c" + }, + { + "bbox": [ + 46, + 384, + 289, + 563 + ], + "type": "text", + "content": ". The overall pre-training objective remains unchanged from the initial image-text generation pre-training. This design enables VLMs to grasp the alignment of concepts and facilitate instruction following for various downstream generative VL tasks, enhancing their performance across different tasks. During inference, VLMs conduct standard image-to-text generation for VL tasks, consistent with previous generative VLMs [8, 19]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 573, + 128, + 586 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 573, + 128, + 586 + ], + "spans": [ + { + "bbox": [ + 47, + 573, + 128, + 586 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 593, + 287, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 593, + 287, + 654 + ], + "spans": [ + { + "bbox": [ + 46, + 593, + 287, + 654 + ], + "type": "text", + "content": "In this section, we thoroughly explore the effectiveness of our proposed training task. We detail the experimented models and implementation in Sec. 5.1, conduct primary zero-shot evaluations in Sec. 5.2, present ablation studies in Sec. 5.3, and offer qualitative insights in Sec. 5.4." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 659, + 198, + 672 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 659, + 198, + 672 + ], + "spans": [ + { + "bbox": [ + 47, + 659, + 198, + 672 + ], + "type": "text", + "content": "5.1. Experiments Configuration" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 677, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 715 + ], + "type": "text", + "content": "Models and Training Data In the realm of generative VLMs, we select BLIP-2 [19] and InstructBLIP [8], representing different pre-training data paradigms. BLIP" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 545, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 179 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 179 + ], + "type": "text", + "content": "2 utilizes image-text pair data without instructions, employing a frozen image encoder and a large language model. It integrates a lightweight querying transformer for mapping visual information into the language embedding space. Instead, InstructBLIP incorporates instruction tuning, enhancing the architecture of pre-trained BLIP-2 with an instruction-aware visual feature extractor. It undergoes complementary training with additional task-specific instruction-tuning data." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 180, + 545, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 180, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 304, + 180, + 545, + 300 + ], + "type": "text", + "content": "In our model setup, we explore three variants of BLIP-2 to assess the generality of our training method across different LLM architectures. They share the same image encoder (ViT-G/14 from EVA-CLIP [10]) but employ distinct frozen LLMs: OPT [42] with 2.7B and 6.7B parameters, and FlanT5-XL [15] with 3B parameters. For InstructBLIP, we experiment with the Vicuna-7B [43] version. Initializing both models with pre-trained parameters, we freeze the vision encoder and LLM, focusing solely on training their Q-former and fully connected projection network." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "spans": [ + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "content": "We construct ICCC samples using our proposed method on the COCO Caption [3] and Visual Genome (VG) Caption [16] datasets, totaling approximately 1 million imagedataset pairs. These samples are then utilized for language modeling training and image captioning in a second-stage training paradigm outlined in Sec. 4.4." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "text", + "content": "Implementation Details We implement and evaluate our method using the LAVIS library [17], and mainly followed the training setup for the original models. The AdamW [23] optimizer with " + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "inline_equation", + "content": "\\beta_{1} = 0.9" + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "inline_equation", + "content": "\\beta_{2} = 0.999" + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "text", + "content": ", and a weight decay of 0.05 was employed. We used a linear warmup of the learning rate over the initial 1,000 steps, increasing from " + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "inline_equation", + "content": "10^{-8}" + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "inline_equation", + "content": "10^{-5}" + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "text", + "content": ", followed by a cosine decay with a minimum learning rate of 0. Batch sizes varied across models: 64 for BLIP-2 OPT2.7B and BLIP-2 FlanT5-XL, 28 for BLIP-2 OPT6.7B, and 24 for InstructBLIP. The images are resized to size " + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "inline_equation", + "content": "224\\times 224" + }, + { + "bbox": [ + 304, + 388, + 545, + 567 + ], + "type": "text", + "content": ", and we apply random resized cropping and horizontal flipping augmentations. All training spanned a maximum of 20,000 iterations, with model performance validated every 1,000 iterations. Each training process utilized four Nvidia A40 (40G) GPUs, completed within a day." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 567, + 545, + 627 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 567, + 545, + 627 + ], + "spans": [ + { + "bbox": [ + 304, + 567, + 545, + 627 + ], + "type": "text", + "content": "Regarding the hyperparameters, we conducted comparison experiments. We set " + }, + { + "bbox": [ + 304, + 567, + 545, + 627 + ], + "type": "inline_equation", + "content": "(p_c, p_s)" + }, + { + "bbox": [ + 304, + 567, + 545, + 627 + ], + "type": "text", + "content": " as (0.3, 0.15), (0.3, 0), (0.01, 0.2), and (0.3, 0.3). for BLIP-2 OPT2.7B, BLIP-2 OPT6.7B, BLIP-2 FlanT5-XL, and InstructBLIP, respectively. Further details will be demonstrated in Sec. 5.3." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 635, + 432, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 635, + 432, + 647 + ], + "spans": [ + { + "bbox": [ + 306, + 635, + 432, + 647 + ], + "type": "text", + "content": "5.2. Zero-shot Evaluations" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 654, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 715 + ], + "type": "text", + "content": "We present zero-shot evaluation results in Tab. 1 and Tab. 2 for BLIP-2 and InstructBLIP experiments. Our second-stage training strategy ICCC consistently improves zero-shot performance across various tasks and datasets, like visual question answering (VQA) and image captioning (IC)," + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13432" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 132, + 70, + 465, + 198 + ], + "blocks": [ + { + "bbox": [ + 132, + 70, + 465, + 198 + ], + "lines": [ + { + "bbox": [ + 132, + 70, + 465, + 198 + ], + "spans": [ + { + "bbox": [ + 132, + 70, + 465, + 198 + ], + "type": "table", + "html": "
BLIP-2GQAOK-VQAVQAv2VSRNoCaps
B@4SC
OPT2.7B33.526.651.948.343.613.8105.7
OPT2.7B w/ ICCC38.929.554.347.846.014.3111.9
OPT6.7B35.530.752.648.541.513.0101.4
OPT6.7B w/ ICCC38.231.758.851.544.113.6106.9
FlanT5-XL44.040.763.163.442.213.3103.1
FlanT5-XL w/ ICCC44.641.064.064.243.913.6106.0
", + "image_path": "df765246ac4b24f628f8f4a6f75abede2df05aed7a150f3f953a8e5490480b62.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 74, + 256, + 264, + 305 + ], + "blocks": [ + { + "bbox": [ + 46, + 206, + 547, + 242 + ], + "lines": [ + { + "bbox": [ + 46, + 206, + 547, + 242 + ], + "spans": [ + { + "bbox": [ + 46, + 206, + 547, + 242 + ], + "type": "text", + "content": "Table 1. The zero-shot evaluation results on BLIP-2 experiments. For three VQA datasets, we report top-1 accuracy " + }, + { + "bbox": [ + 46, + 206, + 547, + 242 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 46, + 206, + 547, + 242 + ], + "type": "text", + "content": " on the testdev set of GQA [14], VSR [21], the test set of OK-VQA [25], and the validation set of VQAv2 [12]. For IC, we report metrics of BLUE@4 (B@4), CIDEr (C), and SPICE (S) on the validation set of NoCaps." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 74, + 256, + 264, + 305 + ], + "lines": [ + { + "bbox": [ + 74, + 256, + 264, + 305 + ], + "spans": [ + { + "bbox": [ + 74, + 256, + 264, + 305 + ], + "type": "table", + "html": "
ModelGQAVSRNoCaps
InstructBLIP48.461.114.2
InstructBLIP w/ ICCC49.863.115.7
", + "image_path": "05129492101d75136bf06b6696e67e5ebb89706945e22012949f385d2938c8e3.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 352, + 249, + 364 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 352, + 249, + 364 + ], + "spans": [ + { + "bbox": [ + 47, + 352, + 249, + 364 + ], + "type": "text", + "content": "demonstrating enhanced zero-shot generalization." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 365, + 287, + 400 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 365, + 287, + 400 + ], + "spans": [ + { + "bbox": [ + 46, + 365, + 287, + 400 + ], + "type": "text", + "content": "The experimental results on BLIP-2 (Tab. 1) demonstrate the effectiveness of ICCC on models pre-trained by image-text pairs. Notable findings include:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 403, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 10, + "blocks": [ + { + "bbox": [ + 47, + 403, + 287, + 497 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 403, + 287, + 497 + ], + "spans": [ + { + "bbox": [ + 47, + 403, + 287, + 497 + ], + "type": "text", + "content": "- ICCC yields consistent improvements for BLIP-2 OPT2.7B, BLIP-2 OPT6.7B, and BLIP-2 FlanT5-XL. Specifically, the BLIP-2 OPT2.7B with ICCC shows a significant enhancement in GQA " + }, + { + "bbox": [ + 47, + 403, + 287, + 497 + ], + "type": "inline_equation", + "content": "(+5.4\\%)" + }, + { + "bbox": [ + 47, + 403, + 287, + 497 + ], + "type": "text", + "content": ", while the BLIP-2 OPT6.7B improves considerably in VQAv2 " + }, + { + "bbox": [ + 47, + 403, + 287, + 497 + ], + "type": "inline_equation", + "content": "(+6.2\\%)" + }, + { + "bbox": [ + 47, + 403, + 287, + 497 + ], + "type": "text", + "content": ". These results emphasize ICCC's ability to refine vision-conditioned language generation, irrespective of LLM sizes and architectures." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 498, + 287, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 498, + 287, + 569 + ], + "spans": [ + { + "bbox": [ + 47, + 498, + 287, + 569 + ], + "type": "text", + "content": "- In captioning tasks, SPICE metrics highlight improved accuracy at the structured scene level, including VL relations and attributes. Our task design, focusing on learning ITG generalizations for various concept roles, not only enhances object recognition accuracy but also improves understanding of object attributes and relations." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 570, + 287, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 570, + 287, + 653 + ], + "spans": [ + { + "bbox": [ + 47, + 570, + 287, + 653 + ], + "type": "text", + "content": "- In the InstructBLIP experiment results shown in Tab. 2, we note a consistent improvement in zero-shot evaluation benchmarks, even when the original model heavily relies on instruction tuning. This indicates the effectiveness of our approach across diverse pre-training image-text data, offering a valuable complementary method for augmenting visual-linguistic knowledge." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 653, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 653, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 653, + 288, + 714 + ], + "type": "text", + "content": "- We emphasize the Visual Spatial Reasoning (VSR) benchmark [21], created to evaluate a model's grasp of spatial relationships for vision-language reasoning. These enhancements stem from the varied concept data samples in our ICCC pre-training, which are able to encompass a" + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "text" + }, + { + "type": "table", + "bbox": [ + 308, + 256, + 545, + 337 + ], + "blocks": [ + { + "bbox": [ + 47, + 314, + 288, + 337 + ], + "lines": [ + { + "bbox": [ + 47, + 314, + 288, + 337 + ], + "spans": [ + { + "bbox": [ + 47, + 314, + 288, + 337 + ], + "type": "text", + "content": "Table 2. The zero-shot evaluation results on InstructBLIP experiments. We report the SPICE score for NoCaps." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 308, + 256, + 545, + 337 + ], + "lines": [ + { + "bbox": [ + 308, + 256, + 545, + 337 + ], + "spans": [ + { + "bbox": [ + 308, + 256, + 545, + 337 + ], + "type": "table", + "html": "
Data SourceGQAOK-VQAVQAv2NoCaps
C+VVQAv2w/ ICCCB@4SC
1---33.526.651.943.613.8105.7
2✓--33.026.349.745.613.9108.1
3✓-✓38.929.554.346.014.3111.9
4✓✓-41.338.0-45.212.6106.4
5✓✓✓42.839.1-45.014.0108.2
", + "image_path": "974716e9bf0cb2a19e38737a8c49b7c7f632b205344e502f5ad8bbb26f249456.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 340, + 547, + 396 + ], + "lines": [ + { + "bbox": [ + 305, + 340, + 547, + 396 + ], + "spans": [ + { + "bbox": [ + 305, + 340, + 547, + 396 + ], + "type": "text", + "content": "Table 3. Ablation study on our method upon different second-stage training data types. C+V represents COCO and VG caption data. Since our focus is on zero-shot performance, we omit the results on the VQAv2 validation set after training with the VQAv2 training set." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 306, + 409, + 545, + 492 + ], + "type": "list", + "angle": 0, + "index": 15, + "blocks": [ + { + "bbox": [ + 313, + 409, + 535, + 421 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 409, + 535, + 421 + ], + "spans": [ + { + "bbox": [ + 313, + 409, + 535, + 421 + ], + "type": "text", + "content": "broad spectrum of vision-language relational concepts." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 421, + 545, + 492 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 421, + 545, + 492 + ], + "spans": [ + { + "bbox": [ + 306, + 421, + 545, + 492 + ], + "type": "text", + "content": "- Additionally, we assess the effectiveness of ICCC on another VLM (LLAVA [22]) and various vision-language reasoning datasets, including ScienceQA-IMG [31], MM-VET [37], and hallucinations [30]. Further experimental results can be found in the supplementary material." + } + ] + } + ], + "index": 14 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 510, + 400, + 525 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 510, + 400, + 525 + ], + "spans": [ + { + "bbox": [ + 306, + 510, + 400, + 525 + ], + "type": "text", + "content": "5.3. Ablation Study" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 532, + 545, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 532, + 545, + 640 + ], + "spans": [ + { + "bbox": [ + 304, + 532, + 545, + 640 + ], + "type": "text", + "content": "Effectiveness of Correction Task In Tab. 3, we compare our approach with alternative second-stage training methods, focusing on the BLIP-2 OPT2.7B model. We explore two types of second-stage training: one utilizing only COCO and VG caption datasets (lines 2 and 3), and the other incorporating the VQAv2 training set (lines 4 and 5) to assess the impact of instruction tuning. Our approach exclusively targets caption datasets, maintaining consistent task sample construction parameters." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 642, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 545, + 714 + ], + "type": "text", + "content": "Experimental results indicate that our training approach consistently outperforms conventional second-stage methods, regardless of the inclusion of VQA data for instruction-tuning. This underscores the efficacy of our task, emphasizing its superiority over traditional ITG second-stage training strategies." + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13433" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 56, + 76, + 292, + 223 + ], + "blocks": [ + { + "bbox": [ + 56, + 76, + 292, + 223 + ], + "lines": [ + { + "bbox": [ + 56, + 76, + 292, + 223 + ], + "spans": [ + { + "bbox": [ + 56, + 76, + 292, + 223 + ], + "type": "image", + "image_path": "2768b48a5f42a614881891aa42f811fc5f2f1c6b1de8e17ac6c71d070334948c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 197, + 232, + 394, + 243 + ], + "lines": [ + { + "bbox": [ + 197, + 232, + 394, + 243 + ], + "spans": [ + { + "bbox": [ + 197, + 232, + 394, + 243 + ], + "type": "text", + "content": "Figure 3. Hyper-parameter searching on " + }, + { + "bbox": [ + 197, + 232, + 394, + 243 + ], + "type": "inline_equation", + "content": "p_c" + }, + { + "bbox": [ + 197, + 232, + 394, + 243 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 197, + 232, + 394, + 243 + ], + "type": "inline_equation", + "content": "p_s" + }, + { + "bbox": [ + 197, + 232, + 394, + 243 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 301, + 76, + 536, + 222 + ], + "blocks": [ + { + "bbox": [ + 301, + 76, + 536, + 222 + ], + "lines": [ + { + "bbox": [ + 301, + 76, + 536, + 222 + ], + "spans": [ + { + "bbox": [ + 301, + 76, + 536, + 222 + ], + "type": "image", + "image_path": "3f5069e8f2d49cd4bbcf0031f6ebc5ff17e0b1b366830f7e2256046ee6abaa26.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 251, + 287, + 334 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 251, + 287, + 334 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 287, + 334 + ], + "type": "text", + "content": "Ablation for Task Construction In Tab. 4, we demonstrate the necessity of including different types of concepts to edit for constructing mismatched captions. The experiments were conducted on the BLIP-2 OPT2.7B model, maintaining consistent hyper-parameters. Results indicate that using concepts of different natures for task construction yields complementary effects." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 337, + 288, + 636 + ], + "type": "list", + "angle": 0, + "index": 7, + "blocks": [ + { + "bbox": [ + 47, + 337, + 287, + 432 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 337, + 287, + 432 + ], + "spans": [ + { + "bbox": [ + 47, + 337, + 287, + 432 + ], + "type": "text", + "content": "- In the first part, we investigate influence of language granularity, focusing on tasks constructed around words and phrases. As shown in lines 3-4 of Tab.4, our findings reveal the significance of phrase-level concepts for the VQA task, while word-level concepts aid in refining the model's understanding of individual words, thereby improving captioning accuracy metrics such as BLUE@4 and CIDEr." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "spans": [ + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": "- In the subsequent section (lines 5-6), we delve into the roles of various concepts in semantics, exploring the impact of tasks centered on entity-level, relation-level, and attribute-level concepts. Referencing Tab.4, our analysis reveals that focusing solely on learning at the entity level yields strong performance in VQA tasks but may sacrifice accuracy in comprehending relations and attributes, thereby resulting in sub-optimal image captioning performance." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 540, + 288, + 636 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 540, + 288, + 636 + ], + "spans": [ + { + "bbox": [ + 47, + 540, + 288, + 636 + ], + "type": "text", + "content": "- We conducted an ablation study to assess the impact of instructions and language structure (line 7, Tab.4). We retained the instructions of the ICCC task while randomly altering words within the sentences. Surprisingly, the addition of correction instructions and random language masking did not enhance the generalization capability of VLMs on downstream tasks. This highlights the importance of language structure in instruction tuning." + } + ] + } + ], + "index": 6 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 46, + 638, + 287, + 674 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 638, + 287, + 674 + ], + "spans": [ + { + "bbox": [ + 46, + 638, + 287, + 674 + ], + "type": "text", + "content": "In conclusion, the diversity in concept extraction allows our method to perform well on various zero-shot generation tasks, demonstrating strong generality." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": "Hyper-parameter Selection The hyperparameters " + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "inline_equation", + "content": "p_c" + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "inline_equation", + "content": "p_s" + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": " are pivotal in adjusting the distribution of task samples" + } + ] + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 308, + 248, + 545, + 365 + ], + "blocks": [ + { + "bbox": [ + 308, + 248, + 545, + 365 + ], + "lines": [ + { + "bbox": [ + 308, + 248, + 545, + 365 + ], + "spans": [ + { + "bbox": [ + 308, + 248, + 545, + 365 + ], + "type": "table", + "html": "
TypeGQAOK-VQAVQAv2NoCaps
B@4SC
1none33.026.349.745.613.9108.1
2all38.929.554.346.014.3111.9
3noun, verb36.430.752.146.014.3114.3
4ent, pred, attr38.327.554.945.214.7111.3
5noun, ent38.529.854.846.514.4112.4
6verb, pred, attr36.029.654.146.914.5114.1
7random33.026.248.644.114.5107.1
", + "image_path": "5f0f29760b86ba1a0f1279b841a31874832e7c9e3b219a53c6d83f117c4a761f.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 372, + 545, + 394 + ], + "lines": [ + { + "bbox": [ + 305, + 372, + 545, + 394 + ], + "spans": [ + { + "bbox": [ + 305, + 372, + 545, + 394 + ], + "type": "text", + "content": "Table 4. Ablation study on editing different subsets of concept types for mismatched caption construction." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 403, + 545, + 475 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 545, + 475 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 545, + 475 + ], + "type": "text", + "content": "in our approach. We conducted a comprehensive hyperparameter search for each experimental model, analyzing the impact of these parameters on model performance. Fig. 3 illustrate the performance variations of BLIP-2 OPT2.7B after second-stage training under different hyperparameter settings:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 479, + 545, + 562 + ], + "type": "list", + "angle": 0, + "index": 15, + "blocks": [ + { + "bbox": [ + 306, + 479, + 545, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 479, + 545, + 514 + ], + "spans": [ + { + "bbox": [ + 306, + 479, + 545, + 514 + ], + "type": "text", + "content": "- In the left of Fig. 3, with " + }, + { + "bbox": [ + 306, + 479, + 545, + 514 + ], + "type": "inline_equation", + "content": "p_s" + }, + { + "bbox": [ + 306, + 479, + 545, + 514 + ], + "type": "text", + "content": " fixed at 0.1, we study the influence of different correction task sample proportions by varying " + }, + { + "bbox": [ + 306, + 479, + 545, + 514 + ], + "type": "inline_equation", + "content": "p_c" + }, + { + "bbox": [ + 306, + 479, + 545, + 514 + ], + "type": "text", + "content": " at intervals of 0.15." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 515, + 545, + 562 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 515, + 545, + 562 + ], + "spans": [ + { + "bbox": [ + 306, + 515, + 545, + 562 + ], + "type": "text", + "content": "- In the right of Fig. 3, with " + }, + { + "bbox": [ + 306, + 515, + 545, + 562 + ], + "type": "inline_equation", + "content": "p_c" + }, + { + "bbox": [ + 306, + 515, + 545, + 562 + ], + "type": "text", + "content": " fixed at 0.3, we explore the impact of different swap operation proportions on mismatched caption sampling by varying " + }, + { + "bbox": [ + 306, + 515, + 545, + 562 + ], + "type": "inline_equation", + "content": "p_s" + }, + { + "bbox": [ + 306, + 515, + 545, + 562 + ], + "type": "text", + "content": " at intervals of 0.15." + } + ] + } + ], + "index": 14 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 317, + 566, + 527, + 578 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 566, + 527, + 578 + ], + "spans": [ + { + "bbox": [ + 317, + 566, + 527, + 578 + ], + "type": "text", + "content": "In our experiments, we present several key findings:" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 582, + 545, + 714 + ], + "type": "list", + "angle": 0, + "index": 19, + "blocks": [ + { + "bbox": [ + 306, + 582, + 545, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 582, + 545, + 654 + ], + "spans": [ + { + "bbox": [ + 306, + 582, + 545, + 654 + ], + "type": "text", + "content": "- From both figures, it is evident that the impact of hyperparameters " + }, + { + "bbox": [ + 306, + 582, + 545, + 654 + ], + "type": "inline_equation", + "content": "p_{c}" + }, + { + "bbox": [ + 306, + 582, + 545, + 654 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 582, + 545, + 654 + ], + "type": "inline_equation", + "content": "p_{s}" + }, + { + "bbox": [ + 306, + 582, + 545, + 654 + ], + "type": "text", + "content": " on model performance follows a consistent trend, initially increasing before decreasing. This phenomenon arises due to the risk of language bias when incorporating excessive correction task samples, particularly those generated through swap operations." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 654, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 654, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 306, + 654, + 545, + 714 + ], + "type": "text", + "content": "- Notably, the saturation point of " + }, + { + "bbox": [ + 306, + 654, + 545, + 714 + ], + "type": "inline_equation", + "content": "p_{s}" + }, + { + "bbox": [ + 306, + 654, + 545, + 714 + ], + "type": "text", + "content": " is reached early, suggesting that the model can easily identify and correct mismatched captions created through swap operations. Despite this, proper inclusion of such samples proves beneficial for overall performance enhancement, particularly" + } + ] + } + ], + "index": 18 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13434" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 80, + 75, + 121, + 124 + ], + "blocks": [ + { + "bbox": [ + 80, + 75, + 121, + 124 + ], + "lines": [ + { + "bbox": [ + 80, + 75, + 121, + 124 + ], + "spans": [ + { + "bbox": [ + 80, + 75, + 121, + 124 + ], + "type": "image", + "image_path": "f82f9b60febece513d29d72bcdf8a26f0d0dda29e3480a51517a550448f38ed0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + 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"angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 219, + 329, + 280, + 335 + ], + "lines": [ + { + "bbox": [ + 219, + 329, + 280, + 335 + ], + "spans": [ + { + "bbox": [ + 219, + 329, + 280, + 335 + ], + "type": "text", + "content": "A person looking at a fire" + } + ] + } + ], + "index": 25, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 219, + 335, + 259, + 342 + ], + "lines": [ + { + "bbox": [ + 219, + 335, + 259, + 342 + ], + "spans": [ + { + "bbox": [ + 219, + 335, + 259, + 342 + ], + "type": "text", + "content": "in a wood stove." + } + ] + } + ], + "index": 26, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 355, + 287, + 432 + ], + "lines": [ + { + "bbox": [ + 46, + 355, + 287, + 432 + ], + "spans": [ + { + "bbox": [ + 46, + 355, + 287, + 432 + ], + "type": "text", + "content": "Figure 4. Visualization results include model output examples and attention gradients on images. The first block illustrates three examples from the GQA testdev set, while the second block showcases three examples from the NoCaps validation set. With our training, the model demonstrates improved accuracy in focusing on prompt-relevant image regions. Additionally, it generates captions with more detailed descriptions of scenes and actions." + } + ] + } + ], + "index": 27, + "angle": 0, + "type": "image_caption" + } + ], + "index": 22 + }, + { + "bbox": [ + 55, + 444, + 162, + 455 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 444, + 162, + 455 + ], + "spans": [ + { + "bbox": [ + 55, + 444, + 162, + 455 + ], + "type": "text", + "content": "in image captioning tasks." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 47, + 456, + 287, + 552 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 456, + 287, + 552 + ], + "spans": [ + { + "bbox": [ + 47, + 456, + 287, + 552 + ], + "type": "text", + "content": "- Furthermore, our investigation reveals that BLIP-2 FlanT5-XL tends to overfit on our task samples, possibly attributed to its encoder-decoder architecture. This results in the Q-former learning an overfitted encoding of soft prompts associated with task text patterns. Nonetheless, even minimal incorporation of correction task samples " + }, + { + "bbox": [ + 47, + 456, + 287, + 552 + ], + "type": "inline_equation", + "content": "(p_c = 0.01)" + }, + { + "bbox": [ + 47, + 456, + 287, + 552 + ], + "type": "text", + "content": " effectively serves our training objectives while mitigating the risk of overfitting." + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 47, + 561, + 159, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 561, + 159, + 574 + ], + "spans": [ + { + "bbox": [ + 47, + 561, + 159, + 574 + ], + "type": "text", + "content": "5.4. Qualitative Results" + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 46, + 580, + 287, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 580, + 287, + 688 + ], + "spans": [ + { + "bbox": [ + 46, + 580, + 287, + 688 + ], + "type": "text", + "content": "To provide a more intuitive understanding of the effects of our training, we show some qualitative model output examples in Fig. 4. We demonstrate the differences between the model outputs and intermediate results on the VQA and IC tasks before and after our second-stage training respectively. The heat maps show the gradient of the output logit corresponding to the ground truth token with regard to the image attention, which reflects the potential visual contribution of the model output." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "According to the outputs for VQA, the results reveal that the proposed correction task training produces inter" + } + ] + } + ], + "index": 32 + }, + { + "bbox": [ + 304, + 72, + 545, + 240 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 240 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 240 + ], + "type": "text", + "content": "pretable improvements to VQA responses. Our model demonstrates increased accuracy in locating objects referenced in prompts and exhibits a more precise understanding of compositional concepts, avoiding biases toward prominent objects. For instance, in the first example, our model focuses on the \"hook\", which the original model misses. In the second example, our model correctly considers the composed concept of \"the woman that is wearing trousers\". Lastly, our model interprets the relational concept \"surrounding the table\" and directs attention appropriately toward the relevant region, rather than the table itself. Overall, our findings indicate that this training methodology enhances VLMs' capacity for interpreting corresponding visual concepts expressed through language." + } + ] + } + ], + "index": 33 + }, + { + "bbox": [ + 304, + 247, + 545, + 366 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 247, + 545, + 366 + ], + "spans": [ + { + "bbox": [ + 304, + 247, + 545, + 366 + ], + "type": "text", + "content": "Examples from our experiments with IC illustrate this improved ability to correct misidentified objects and provide richer, more fine-grained descriptions of object relationships and actions. For instance, our model correctly identifies the wrong \"red kite\" concept in the first case and provides more nuanced details about the scene, such as \"standing around a table\" and \"looking\". We posit that the primary source of improved overall captioning performance lies in the generation of more accurate and comprehensive concepts in captions." + } + ] + } + ], + "index": 34 + }, + { + "bbox": [ + 304, + 373, + 545, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 373, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 304, + 373, + 545, + 456 + ], + "type": "text", + "content": "Conclusively, our study indicates that the proposed training method potentially enhances generative VLMs' capacity for aligning concepts across multiple types and granularities in visual and language modalities. We believe this insight could shed light on the future development of cost-effective, multi-granularity, and structured generative VL pre-trained models." + } + ] + } + ], + "index": 35 + }, + { + "bbox": [ + 306, + 488, + 378, + 500 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 488, + 378, + 500 + ], + "spans": [ + { + "bbox": [ + 306, + 488, + 378, + 500 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 36 + }, + { + "bbox": [ + 304, + 515, + 545, + 647 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 515, + 545, + 647 + ], + "spans": [ + { + "bbox": [ + 304, + 515, + 545, + 647 + ], + "type": "text", + "content": "In this work, we propose the image-conditioned text correction task for enhancing zero-shot text generation with unlabeled data. In this task, VLMs requires to identify and correct the error in accordance with the vision modality via text generation. We propose a scalable and cost-effective data construction framework for generating the image-text pair for this task by utilizing the inherent structure of language. The experimental results indicate that the implementation of our training framework substantially improves the ability of VLMs to generalize across a range of VL tasks involving image-to-text generation." + } + ] + } + ], + "index": 37 + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": "Discussion of Limitation Due to the limitation of the computing resource, extending our approach to larger datasets and models remains unexplored. Future work should explore its application to more extensive datasets and diverse large vision-language models." + } + ] + } + ], + "index": 38 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13435" + } + ] + } + ], + "index": 39 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 12, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "text", + "content": "[1] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katherine Millican, Malcolm Reynolds, et al. 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Minigpt-4: Enhancing vision-language understanding with advanced large language models. arXiv preprint arXiv:2304.10592, 2023. 2" + } + ] + } + ], + "index": 24 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13437" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_content_list.json b/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..13ed412dde1e02c55662fc035b161ef20f4f3d06 --- /dev/null +++ b/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_content_list.json @@ -0,0 +1,1496 @@ +[ + { + "type": "text", + "text": "Learning for Transductive Threshold Calibration in Open-World Recognition", + "text_level": 1, + "bbox": [ + 94, + 130, + 875, + 154 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Qin Zhang $^{1}$ , Dongsheng An $^{1}$ , Tianjun Xiao $^{2}$ , Tong He $^{2}$ , Qingming Tang $^{3}$ , Ying Nian Wu $^{1}$ , Joseph Tighe $^{1}$ , Yifan Xing $^{1}$", + "bbox": [ + 107, + 179, + 869, + 215 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "AWS AI Labs", + "bbox": [ + 238, + 218, + 367, + 236 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "2 Amazon Web Services", + "bbox": [ + 406, + 219, + 601, + 234 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "3 Alexa AI", + "bbox": [ + 640, + 219, + 728, + 234 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{qzaamz, andongsh, tianjux, htong, qmtang, wunyin, yifax}@amazon.com, jtighe@cs.unc.edu", + "bbox": [ + 122, + 239, + 836, + 255 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 290, + 313, + 306 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In deep metric learning for visual recognition, the calibration of distance thresholds is crucial for achieving desired model performance in the true positive rates (TPR) or true negative rates (TNR). However, calibrating this threshold presents challenges in open-world scenarios, where the test classes can be entirely disjoint from those encountered during training. We define the problem of finding distance thresholds for a trained embedding model to achieve target performance metrics over unseen open-world test classes as open-world threshold calibration. Existing posthoc threshold calibration methods, reliant on inductive inference and requiring a calibration dataset with a similar distance distribution as the test data, often prove ineffective in open-world scenarios. To address this, we introduce OpenGCN, a Graph Neural Network-based transductive threshold calibration method with enhanced adaptability and robustness. OpenGCN learns to predict pairwise connectivity for the unlabeled test instances embedded in a graph to determine its TPR and TNR at various distance thresholds, allowing for transductive inference of the distance thresholds which also incorporates test-time information. Extensive experiments across open-world visual recognition benchmarks validate OpenGCN's superiority over existing posthoc calibration methods for open-world threshold calibration.", + "bbox": [ + 75, + 323, + 473, + 686 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 720, + 209, + 738 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In deep metric learning (DML) for visual recognition, distance calibration plays a critical role in determining the user-perceived model performance. Unlike confidence calibration in closed-set classification settings which focuses on aligning confidence probabilities with true likelihood of correctness in a fixed label space [27, 33], distance calibration in DML aims to pinpoint an optimal distance threshold to achieve a target true positive rate (TPR) or true negative rate (TNR) for diverse test-time distributions [26]. This calibration is vital because, even with a highly effic", + "bbox": [ + 75, + 750, + 468, + 901 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/0833c74c5f6b823bc13deeb6c08f8e11ec5274da21fae2d17638ab8e420e0acf.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 535, + 290, + 849, + 420 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ea218448e17b1823c2b75facddb837bb7ecb56d876a0fdffa09016dff59ee063.jpg", + "image_caption": [ + "Figure 1. This figure illustrates the open-world threshold calibration problem. In open-world recognition, the embedding model is trained on closed-set classes but tested on distinct open-world classes. When applying the model to open-world classes, it often produces less compact embeddings than those encountered during training, necessitating the calibration of the distance threshold for achieving the desired TPR and TNR trade-off. However, the absence of prior knowledge about open-world test classes and distributions makes it challenging to find the optimal distance threshold, denoted as $d^{\\mathrm{opt}}$ . Best viewed in color." + ], + "image_footnote": [], + "bbox": [ + 517, + 422, + 843, + 523 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "tive embedding model, an inappropriate distance threshold can significantly degrade user experience. The issue becomes more pronounced in open-world recognition, where the embedding model, trained on a closed set of classes (e.g., dog, cat, bird), is tested on an open collection of unseen classes (e.g., wolf, sheep, mouse, ...). These open-world classes may have very different intra-class and interclass representation structures, typically being less compact, compared to the training classes. In such open-world scenarios, where prior knowledge about test-time classes and distributions are absent, calibrating the distance threshold becomes a challenging task, as illustrated in Fig. 1. We term this task of distance calibration in an open-world scenario as open-world threshold calibration.", + "bbox": [ + 496, + 688, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "17097", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Existing posthoc calibration methods, such as [16, 24, 34, 37, 53, 54], typically utilize a fully-labeled calibration dataset that has a similar distribution as the test data [35, 42, 56] to learn general calibration rules for test distributions. However, this approach has a key limitation: it heavily relies on the assumption of identical distributions between test and calibration data for effective calibration. In open-world scenarios, this assumption becomes unreliable, posing significant challenges to threshold calibration, including:", + "bbox": [ + 76, + 90, + 472, + 227 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. The open-world challenge The test data may exclusively contain open-world classes, which exhibit different relationships between distance thresholds and TPR or TNR compared to those encountered during the embedding model training [26]. Meanwhile, test data composition and quality can vary significantly, potentially exhibiting substantial class imbalances and data corruptions.", + "2. Non-stationary data In real-world testing environments, the test distribution can be infinitely varied and highly dynamic, rendering the assumption of similar distribution between calibration and test data obsolete.", + "3. Deployment Scalability Real-world systems require calibration methods that can adapt to diverse user distributions without individual recalibration. Existing methods lack deployment scalability as they frequently require dedicated calibration data and the creation of specific calibration functions for each user. Imagine a scenario with 1,000 user profiles with distinct classes and data distributions – creating and deploying custom calibration datasets and functions for each would be impractical." + ], + "bbox": [ + 76, + 231, + 468, + 534 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Addressing these challenges is crucial for the reliability of DML-based open-world recognition systems. Current posthoc calibration methods are ill-suited for this purpose, as they are inherently inductive and prone to failure when confronted with test data with different distance distributions from the calibration data. To address this, we adopt a fresh perspective on distance threshold calibration, treating it as a transductive inference process, where the calibration method incorporates the information of the unlabeled test samples along with the learned calibration rules to make better threshold estimations. Our proposed method, OpenGCN, employs a Graph Neural Network (GNN), known for its generalization capabilities [3, 5, 9, 10, 49, 51, 52], to jointly predict pairwise connectivity and two instance-wise representation densities for test data, where the predicted pairwise connectivity is used to compute the TPR and TNR of the test data at each distance threshold to enable transductive threshold calibration. OpenGCN is tailored for the task of open-world threshold calibration through a carefully crafted learning process, which accurately estimates the mapping between performance metrics and pairwise distance thresholds in open-world scenarios. In particular, the multi-task learning of connectivities and representation densities facilitates infor", + "bbox": [ + 76, + 537, + 472, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "mation sharing, which helps enhance the model's generalization to open-world scenarios [49, 52]. Additionally, our joint prediction design incorporates two types of density metrics, addressing both intra-class and inter-class connectivity estimations. This approach, as opposed to using a single density metric, is shown to enhance calibration performance, as illustrated in Sec. 4.3. Furthermore, OpenGCN adopts a two-stage training process. It pre-trains on a large closed-world dataset, followed by fine-tuning on a small open-world calibration dataset with disjoint classes to both the closed-world and test data, to adapt the model to be aware of the open-world context. By these design choices, OpenGCN sidesteps the requirement for calibration data to have a similar distance distribution1 as the test data, significantly improving calibration performance in open-world scenarios. To summarize, our contributions are as follows:", + "bbox": [ + 496, + 90, + 893, + 330 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. We are, to the best of our knowledge, the first to formally define the open-world threshold calibration problem.", + "2. We propose Transductive Threshold Calibration (TTC), a new threshold calibration paradigm that diverges from traditional inductive posthoc calibration methods, which does not rely on the assumption of similar distance distributions between the test and calibration data.", + "3. We introduce OpenGCN, a GNN-based TTC method tailored for open-world threshold calibration against diverse test distributions. We build comprehensive evaluation protocols with and without distance distribution shifts to assess OpenGCN's performance. The evaluation result underscores OpenGCN's effectiveness and robustness in real-world testing environments." + ], + "bbox": [ + 500, + 333, + 890, + 544 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Problem Definition and Related Works", + "text_level": 1, + "bbox": [ + 500, + 556, + 849, + 573 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We first introduce some notations and formalize the open-world threshold calibration problem. Let $D_{\\mathrm{labled}}$ be a labeled dataset consisting of two disjoint subsets: $D_{\\mathrm{train}}$ and $D_{\\mathrm{cal}}$ , and let $D_{\\mathrm{test}}$ be an unlabeled dataset. In open-world scenarios, the class sets of $D_{\\mathrm{train}}$ , $D_{\\mathrm{cal}}$ , and $D_{\\mathrm{test}}$ , denoted as $C_{\\mathrm{train}}$ , $C_{\\mathrm{cal}}$ , and $C_{\\mathrm{test}}$ , are disjoint, i.e., $C_{\\mathrm{train}} \\cap C_{\\mathrm{cal}} = C_{\\mathrm{train}} \\cap C_{\\mathrm{test}} = C_{\\mathrm{cal}} \\cap C_{\\mathrm{test}} = \\emptyset$ . The goal of open-world threshold calibration is to find a suitable distance threshold that achieves the target TPR and TNR for $D_{\\mathrm{test}}$ , given an embedding model trained on $D_{\\mathrm{train}}$ . We approach this as a constrained optimization task, with the objective being maximizing the metric of interest. Take optimizing for TNR with a minimum TPR requirement as an example, this problem can be formulated as follows:", + "bbox": [ + 496, + 582, + 893, + 794 + ], + "page_idx": 1 + }, + { + "type": "equation", + "text": "\n$$\n\\underset {d} {\\text {m a x i m i z e}} \\mathrm {T N R} _ {\\text {t e s t}}, \\quad \\text {s u b j e c t t o T P R} _ {\\text {t e s t}} (d) \\geq \\alpha \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 804, + 890, + 827 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "where $d$ is the distance threshold, and $\\alpha$ is the minimum performance requirement for $\\mathrm{TPR}_{\\mathrm{test}}$ . Due to the inherent", + "bbox": [ + 498, + 835, + 893, + 867 + ], + "page_idx": 1 + }, + { + "type": "page_footnote", + "text": "1We use \"distance distribution\" to refer to the distribution of pairwise distances between L2-normalized embeddings from a trained DML model.", + "bbox": [ + 500, + 875, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "17098", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "trade-off between TPR and TNR, the objective in Eq. (1) is equivalent to finding an optimal distance threshold $d^{\\mathrm{opt}}$ for which $\\mathrm{TPR}_{\\mathrm{test}}(d^{\\mathrm{opt}}) = \\alpha$ . To solve this, we express $\\mathrm{TPR}_{\\mathrm{test}}$ and $\\mathrm{TNR}_{\\mathrm{test}}$ at a distance threshold $d$ as follows:", + "bbox": [ + 76, + 90, + 468, + 151 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {T P R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} = y _ {j}} \\cdot 1 _ {d _ {i j} < d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} = y _ {j}} \\tag{2}\n$$\n", + "text_format": "latex", + "bbox": [ + 122, + 161, + 468, + 191 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {T N R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} \\neq y _ {j}} \\cdot 1 _ {d _ {i j} > d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} \\neq y _ {j}} \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 122, + 200, + 468, + 229 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $d_{ij}$ is the L2 distance between the embeddings of samples $i$ and $j$ , and $y_i$ is the label for sample $i$ . The symbol $1_{\\text{condition}}$ represents the indicator function which equals 1 if the condition is met, otherwise 0. With $\\mathrm{TPR}_{\\text{test}}$ and $\\mathrm{TNR}_{\\text{test}}$ calculated at each distance threshold, we can optimize for the optimal distance threshold $d^{\\text{opt}}$ to achieve the target performance metrics, as described in Eq. (1).", + "bbox": [ + 76, + 233, + 468, + 339 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.1. Related Works", + "text_level": 1, + "bbox": [ + 76, + 348, + 227, + 363 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Open-world Recognition [29] aims to learn discriminative representations that align distances between representations with their semantic similarities. This allows for effective generalization to diverse, previously unseen open-world classes during testing, setting it apart from closed-set classification where training and testing classes are the same. Popular recognition losses [6, 12, 36] typically encourage compact intra-class representations, promoting strong affinity within each class while maintaining separation from other classes. However, it is widely observed that these losses tend to produce highly varied intra-class and inter-class representation structures across classes and distributions [32, 39, 55], necessitating threshold calibration to ensure consistent performance across diverse users.", + "bbox": [ + 75, + 372, + 468, + 583 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Posthoc Calibration We focus on posthoc calibration methods which are more relevant to our research. Generally, existing posthoc calibration methods fall into two categories: (i) non-parametric methods like isotonic regression [54] and histogram binning [34, 53]; and (ii) parametric methods such as Platt scaling [37] and temperature scaling [16]. These methods are inductive: they rely on a holdout calibration set with similar distribution as the test data to derive general rules for fine-tuning the decision threshold, aiming to align the performance metrics with a predefined target. While effective in closed-set classification, these methods struggle in scenarios with significant distribution differences between test and calibration data. Diverging from traditional methods, another group of methods such as conformal prediction [4, 15, 40, 43] or Prediction-Powered Inference [1] emphasize confidence coverage guarantees, and has been shown applicable even beyond the setting of exchangeable data [14, 15]. However, these methods inherently assume a closed-set setting, making them unsuitable for open-world scenarios. Currently, open-world posthoc calibration remains largely under-explored.", + "bbox": [ + 75, + 584, + 468, + 900 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/acac3cbc24540cb2dc93d0a80a195f4838a7e382d9612d09e952340800d46a46.jpg", + "image_caption": [ + "Figure 2. This figure distinguishes between (left) inductive and (right) transductive threshold calibration methods in open-world scenarios with disjoint test-time classes. Inductive methods rely on a labeled hold-out dataset with the same distance distribution as the test data to learn general calibration rules. Transductive methods, however, also use the test information for more specific calibration, as indicated by the red arrow. Best viewed in color." + ], + "image_footnote": [], + "bbox": [ + 517, + 87, + 877, + 178 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Transductive Inference Transduction is the reasoning from observed, specific (training) cases to specific (test) cases [45]. Such an approach is desirable as it alleviates the problem of overfitting on limited support set since information from the test data is also used for inference. This is also known as increasing VC-dimension for structural risk minimization in classical statistical learning [19]. Recently, a large body of works investigated transductive inference for few-shot and open-world recognition tasks [8, 18, 28, 38], where significant increases in performances have been reported. Given the relevance of these tasks, it is worthwhile to reconsider existing inductive posthoc calibration methods for distance threshold calibration in open-world scenarios.", + "bbox": [ + 496, + 310, + 892, + 507 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Methodology", + "text_level": 1, + "bbox": [ + 500, + 520, + 635, + 537 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Transductive Threshold Calibration", + "text_level": 1, + "bbox": [ + 500, + 544, + 812, + 559 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Traditional calibration methods are inherently inductive - they rely on a calibration dataset to learn general calibration rules under the assumption of identically distributed data. However, in open-world scenarios, this assumption seldom holds, as the test distribution is unknown and can be infinitely varied and highly dynamic. To improve calibration specificity in the open world, it is natural to adopt a transductive approach, where the TPR and TNR estimations directly involve the test data, rather than relying on a separate calibration dataset that might not accurately represent the test data. As illustrated in Fig. 2, a transductive approach allows the calibration model to \"see\" the unlabeled test data when deciding on the distance threshold, contrasting with the traditional inductive methods which are \"blind\" to the test data. We term this approach as Transductive Threshold Calibration (TTC), and the traditional inductive calibration methods as Inductive Threshold Calibration (ITC).", + "bbox": [ + 496, + 568, + 890, + 824 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To overcome the limitations of ITC methods, we propose OpenGCN, a GNN-based TTC method with enhanced adaptability and robustness for open-world scenarios with diverse concepts and distance distributions. We highlight the key differences between OpenGCN and conventional", + "bbox": [ + 496, + 825, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "17099", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/baf4fc0173ce1b1b2a383e34f646b0f3346a3c4e94d2d9f75aaf5c8bdf3e0fac.jpg", + "image_caption": [ + "(a) Pre-training on Closed-World Examples" + ], + "image_footnote": [], + "bbox": [ + 81, + 87, + 488, + 205 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/dbdd4b7f54fc80102d66a70ab7f8f399b97f6c1e33394574d0a1ae0b5e11c331.jpg", + "image_caption": [ + "(b) Fine-tuning on Open-World Examples", + "Figure 3. OpenGCN training workflow: (a) During pre-training, OpenGCN jointly optimizes pairwise connectivity, and instance-specific neighborhood and average densities. (b) During fine-tuning, the 2-layer MLP is reset for fine-tuning, while the other weights remain frozen. Solid blue and dashed red arrows represent forward and backward propagation, respectively. At test time, we employ the trained OpenGCN model and MLP head to predict the TPR and TNR as functions of each distance threshold specifically for each test distribution. We then follow Eq. (1) and use grid search to find the optimal distance threshold for each test dataset. Best viewed in color." + ], + "image_footnote": [], + "bbox": [ + 501, + 88, + 883, + 205 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "ITC methods. First, OpenGCN, as a transductive method, derives distance thresholds by leveraging information directly from the test data. This empowers it to adapt to the characteristics of the test data, thereby eliminating the requirement for the calibration data to share a similar distribution with the test data. Second, OpenGCN is engineered to integrate useful information from both closed-world and open-world data sources. This is achieved through a two-stage training process, as illustrated in Fig. 3. We first pretrain OpenGCN on a closed-world dataset, which is the same dataset used to train the DML embedding model. Afterwards, we fine-tune it on a smaller calibration dataset. This calibration dataset contains open-world classes that do not overlap with those in the test data or the closed-world pretraining data. This approach allows the model to smoothly transition from a closed-world context to open-world scenarios, effectively utilizing closed-world knowledge to enhance its transductive reasoning capabilities in the dynamic and unknown open world. In the next section, we delve into the details of OpenGCN, elaborating on how it enables effective TTC for open-world scenarios.", + "bbox": [ + 75, + 330, + 472, + 648 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. OpenGCN: Learning for Effective TTC", + "text_level": 1, + "bbox": [ + 76, + 655, + 416, + 672 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "OpenGCN Inference Workflow A straight-forward way to estimate $\\mathrm{TPR}_{\\mathrm{test}}$ and $\\mathrm{TNR}_{\\mathrm{test}}$ , as defined in Eqs. (2) and (3), is to model the true pairwise connectivities with edge connectivity probability [52]. This probability, denoted as $p_{ij}$ , quantifies the likelihood that two samples have the same label. By setting a proper connectivity threshold $\\tau$ , we can approximate $\\mathrm{TPR}_{\\mathrm{test}}$ and $\\mathrm{TNR}_{\\mathrm{test}}$ as follows:", + "bbox": [ + 75, + 678, + 468, + 785 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {T P R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} > \\tau} \\cdot 1 _ {d _ {i j} < d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} > \\tau} \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 120, + 789, + 468, + 819 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {T N R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} \\leq \\tau} \\cdot 1 _ {d _ {i j} > d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} \\leq \\tau} \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 120, + 824, + 468, + 854 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "These formulations offer a TTC solution that centers on precisely predicting pairwise connectivities for open-world test distributions, a problem well-suited for modern", + "bbox": [ + 76, + 854, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "deep learning algorithms. Specifically, as shown in Fig. 3, OpenGCN is designed as a GNN-based method for predicting pairwise connectivities over graph data constructed from the unlabeled test samples. We adopt a GNN architecture, specifically a Graph Attention Network (GAT) [46], due to its demonstrated effectiveness in generalizing to open-world scenarios [3, 5, 9, 10, 49, 51, 52]. Additionally, we use fully connected graphs to ensure that in-graph pairwise distance distribution is representative of the overall pairwise distance distribution. For inference, nodal features extracted by the GAT encoder are concatenated with the original DML embedding features [52] and passed through a 2-layer MLP to predict pairwise connectivities. The connectivity predictions are then used to transductively estimate TPR and TNR at each distance threshold for the test distributions, following the formulations in Eqs. (4) and (5), where the connectivity threshold $\\tau$ is selected by 10-fold cross validation on $D_{\\mathrm{cal}}$ . Due to the typically large size of the test data, for efficient inference, we randomly sample subsets from $D_{\\mathrm{test}}$ to construct fully connected sub-graphs for connectivity inference, repeating this process until the TPR and TNR estimations converge.", + "bbox": [ + 496, + 330, + 890, + 664 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Joint Connectivity and Density Estimations Using representation density prediction as an auxiliary task to enhance connectivity prediction is widely used in clustering tasks [2, 7, 31]. This approach is based on the idea that a cluster typically exists within a contiguous region of high sample density, separated from other clusters. Recent supervised visual clustering works also leverage density as a key modeling parameter to enhance clustering performance by encouraging information sharing between the tasks [49, 50, 52]. Driven by the intrinsic connections between density and connectivity, we adopt a multitask approach, where we simultaneously learn for pairwise edge connectivity and instance-wise representation densities. However, unlike previous works which only consider one density metric, we simultaneously learn two density", + "bbox": [ + 496, + 674, + 892, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "17100", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "metrics: the average density ( $s^{\\mathrm{avg}}$ ), and the neighborhood density ( $s^{\\mathrm{nbr}}$ ). Formally, these two density metrics, defined in [52], can be expressed as follows $^2$ :", + "bbox": [ + 75, + 90, + 468, + 137 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\ns _ {i} ^ {\\text {a v g}} = \\frac {\\sum_ {j \\in \\mathcal {N} _ {i}} a _ {i j} \\cdot 1 _ {y _ {i} = y _ {j}}}{| \\mathcal {N} _ {i} |}, s _ {i} ^ {\\text {n b r}} = \\frac {\\sum_ {j \\in \\mathcal {N} _ {i}} a _ {i j} \\cdot \\left(1 _ {y _ {i} = y _ {j}} - 1 _ {y _ {i} \\neq y _ {j}}\\right)}{| \\mathcal {N} _ {i} |} \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 88, + 143, + 468, + 181 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{N}_i$ denotes the neighbourhood of a sample $i$ , and $a_{ij}$ represents the cosine similarity between the original embedding features of sample $i$ and sample $j$ .", + "bbox": [ + 75, + 190, + 468, + 234 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To illustrate the motivation of utilizing both density metrics instead of just one, we first introduce two metrics adapted from prior works [20, 41], namely the class-specific TPR and TNR scores, denoted as $\\mathrm{TPR}^k$ and $\\mathrm{TNR}^k$ , respectively. Let $f_{i}$ denote the $\\mathrm{L}_2$ -normalized embeddings of an image in a dataset $D$ . For a given class $k$ , its class-specific TPR and TNR scores can be expressed as:", + "bbox": [ + 75, + 236, + 468, + 340 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {T P R} ^ {k} = \\frac {\\left\\| \\sum_ {i \\in D} f _ {i} \\cdot 1 _ {y _ {i} = k} \\right\\|}{\\sum_ {i \\in D} 1 _ {y _ {i} = k}}, \\quad \\mathrm {T N R} ^ {k} = \\frac {\\sum_ {i , j \\in D} \\left(1 - a _ {i j}\\right) \\cdot 1 _ {y _ {j} \\neq y _ {i} = k}}{\\sum_ {i , j \\in D} 1 _ {y _ {j} \\neq y _ {i} = k}} \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 84, + 349, + 468, + 395 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The subsequent theorems formally establish a connection between two density metrics defined in Eq. (6) and the class-specific TPR and TNR scores.", + "bbox": [ + 75, + 404, + 468, + 449 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Theorem 1 (Correspondence between $s^{\\mathrm{avg}}$ and $TPR^{k}$ )", + "text_level": 1, + "bbox": [ + 75, + 459, + 468, + 474 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Let $\\mathcal{N}$ be a cluster with high purity, where the majority class is $k$ . For each sample $i \\in \\mathcal{N}$ , when both $|\\mathcal{N}|$ and $|\\mathcal{N}_i|$ are sufficiently large, $TPR^k$ can be approximated as:", + "bbox": [ + 75, + 474, + 468, + 520 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\lim _ {| \\mathcal {N} _ {i} | \\rightarrow \\infty} T P R ^ {k} = \\left(\\frac {| \\mathcal {N} _ {i} |}{2 | \\mathcal {N} |} \\right. \\cdot \\underbrace {\\left(\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {n b r}} \\right.} _ {\\substack {\\text {avg s} ^ {\\mathrm {n b r}}\\\\2 \\times \\text {avg s} ^ {\\mathrm {a v g}}}} + \\underbrace {\\left(\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} \\mathfrak {a} _ {\\mathrm {i}} ^ {\\mathrm {a v g}}\\right) ^ {1 / 2}} _ {\\substack {\\text {avg a} ^ {\\mathrm {a v g}}}} \\tag{8}\n$$\n", + "text_format": "latex", + "bbox": [ + 96, + 527, + 468, + 592 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathfrak{a}_i^{\\mathrm{avg}} = \\frac{1}{|\\mathcal{N}_i|}\\sum_{j\\in \\mathcal{N}_i}a_{ij}$ , and $\\mathfrak{a}^{\\mathrm{avg}}$ is the mean of average cosine similarity of all vertices in $\\mathcal{N}_i$ .", + "bbox": [ + 75, + 602, + 468, + 635 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Theorem 2 (Correspondence between $s^{\\mathrm{avg}} - s^{\\mathrm{nbr}}$ and $TNR^{k}$ ) Under the same assumptions in Theorem 1, for a given class $k$ , its $TNR^{k}$ can be approximated as:", + "bbox": [ + 75, + 643, + 468, + 691 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\lim _ {| \\mathcal {N} _ {i} | \\rightarrow \\infty} T N R ^ {k} = 1 - \\frac {| \\mathcal {N} |}{| \\mathcal {N} | _ {k ^ {-}}} \\cdot (\\underbrace {\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {a v g}} - \\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {n b r}})} _ {\\text {a v e r a g e (s} ^ {\\mathrm {a v g}} - \\mathrm {s} ^ {\\mathrm {n b r}} \\text {)}}) \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 99, + 698, + 468, + 748 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $|\\mathcal{N}|_{k^{-}}$ denotes the number of negative pairs in $\\mathcal{N}$ where one sample of each negative pair must have label $k$ .", + "bbox": [ + 75, + 755, + 468, + 787 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Based on the theorems, when the neighborhood size is sufficiently large, considering both density metrics effectively encapsulates both class-specific TPR and TNR within", + "bbox": [ + 75, + 797, + 468, + 843 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "this neighbourhood. As open-world threshold calibration aims to balance the TPR and TNR trade-off for unknown test distributions, it is crucial to capture both aspects to improve within-class and cross-class connectivity predictions. Furthermore, the class-specific nature of these metrics grants them the versatility to adapt to varying class compositions. In Sec. 4.3, we provide an ablation study comparing the use of a single density metric versus both densities, where jointly predicting both densities along with connectivity yields better calibration performance. Thus, we introduce predictions of both density metrics, $s^{\\mathrm{avg}}$ and $s^{\\mathrm{nbr}}$ , as auxiliary tasks to enhance the generalization of connectivity prediction. This leads to the following learning objective for training OpenGCN:", + "bbox": [ + 500, + 90, + 890, + 303 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {o v e r a l l}} = \\underbrace {\\mathcal {L} _ {\\text {c o n n}}} _ {\\text {m a i n t a s k}} + \\underbrace {\\lambda \\cdot \\left(\\mathcal {L} _ {s ^ {\\mathrm {n b r}}} + \\mathcal {L} _ {s ^ {\\mathrm {a v g}}}\\right)} _ {\\text {a u x i l i a r y t a s k}} \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 562, + 314, + 890, + 349 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{L}_{\\mathrm{conn}}$ is the balanced cross-entropy loss for pairwise edge connectivity and $\\mathcal{L}_{s^{\\mathrm{nbr}}}$ and $\\mathcal{L}_{s^{\\mathrm{avg}}}$ are the mean squared error losses for $s^{\\mathrm{nbr}}$ and $s^{\\mathrm{avg}}$ , respectively. Specifically, we define $\\mathcal{L}_{\\mathrm{conn}}$ as follows to ensure equal importance for both within-class and cross-class connectivities:", + "bbox": [ + 498, + 361, + 890, + 436 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {c o n n}} = \\frac {\\sum_ {i , j \\in V} 1 _ {y _ {i} = y _ {j}} \\cdot \\log \\left(p _ {i j}\\right)}{\\sum_ {i , j \\in V} 1 _ {y _ {i} = y _ {j}}} + \\frac {\\sum_ {i , j \\in V} 1 _ {y _ {i} \\neq y _ {j}} \\cdot \\log \\left(1 - p _ {i j}\\right)}{\\sum_ {i , j \\in V} 1 _ {y _ {i} \\neq y _ {j}}} \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 514, + 444, + 890, + 506 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Meanwhile, $\\mathcal{L}_{s^{\\mathrm{nbr}}}$ and $\\mathcal{L}_{s^{\\mathrm{avg}}}$ can be expressed as:", + "bbox": [ + 500, + 507, + 823, + 522 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {s ^ {\\text {a v g}}} = \\frac {\\sum_ {i \\in V} \\left(s _ {i} ^ {\\text {a v g}} - \\hat {s} _ {i} ^ {\\text {a v g}}\\right) ^ {2}}{| V |}, \\quad \\mathcal {L} _ {s ^ {\\text {n b r}}} = \\frac {\\sum_ {i \\in V} \\left(s _ {i} ^ {\\text {n b r}} - \\hat {s} _ {i} ^ {\\text {n b r}}\\right) ^ {2}}{| V |} \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 511, + 532, + 890, + 573 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $V$ represents the node vertices in the graph data, and $\\hat{s}_i$ is the estimated density for each sample based on $p_{ij}$ .", + "bbox": [ + 498, + 583, + 890, + 613 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Two-stage Training for Adaptability The DML embedding model, trained on $D_{\\mathrm{train}}$ (closed-set examples), tends to produce more compact embeddings for these examples than those of open-world classes. If OpenGCN is trained solely on $D_{\\mathrm{train}}$ , its ability to generalize to the open-world scenarios will be limited. On the other hand, if OpenGCN is trained solely on $D_{\\mathrm{cal}}$ , its knowledge may be very narrow since the calibration dataset is typically small and lacks diverse concepts. To tackle this, we borrow established experience in domain generalization and adaptation [11, 21, 48], and adopt a two-stage training strategy. First, we pretrain OpenGCN on $D_{\\mathrm{train}}$ , which consists of a large collection of closed-set examples. After this, we reset the 2-layer MLP while keeping the other parameters frozen. Subsequently, we fine-tune the MLP on $D_{\\mathrm{cal}}$ , a small open-world calibration dataset containing disjoint classes to the test data, to adapt the pretrained model to open-world scenarios. In Sec. 4.3, we conduct an ablation study to provide further support for this two-stage training approach. We choose to", + "bbox": [ + 496, + 614, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_footnote", + "text": "2. Although the original definition of $s^{\\mathrm{avg}}$ in [52] requires a neighborhood size that includes all samples belonging to a given class, it can be shown by stochastic convergence of random variables that our definition is a tight approximation for [52] when $|\\mathcal{N}_i|$ is sufficiently large.", + "bbox": [ + 75, + 849, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "17101", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "fine-tune only the MLP based on the practical observations that $D_{\\mathrm{cal}}$ is typically limited in size, and fine-tuning the entire model on such a small dataset may lead to overfitting. It is worth reiterating that this approach does not require additional training data, as the closed-set data is already in place for training the DML embedding model, and the separate open-world calibration dataset is required for conventional inductive posthoc calibration methods as well.", + "bbox": [ + 75, + 90, + 472, + 212 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4. Experiment and Result", + "text_level": 1, + "bbox": [ + 76, + 224, + 295, + 242 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We experiment on public recognition benchmarks including iNaturalist-2018 [44], CUB-200 [47] and Cars-196 [23]. Below, we outline our setup and present the results. Further experiments can be found in the supplementary materials.", + "bbox": [ + 75, + 250, + 468, + 311 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.1. Dataset and Implementation Details", + "text_level": 1, + "bbox": [ + 76, + 318, + 390, + 335 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Datasets To simulate real-world testing environments, we consider three calibration scenarios: SameDist, ShiftDist and DiffDist. The SameDist scenario involves cases where $D_{\\mathrm{cal}}$ and $D_{\\mathrm{test}}$ share similar distance distributions, the ShiftDist scenario accounts for test-time non-semantic distance distribution shifts, and the DiffDist scenario represents out-of-distribution calibration, where $D_{\\mathrm{cal}}$ and $D_{\\mathrm{test}}$ have very different distance distributions. Note that in all three scenarios, we adhere to the open-world setting where $C_{\\mathrm{train}} \\cap C_{\\mathrm{cal}} = C_{\\mathrm{train}} \\cap C_{\\mathrm{test}} = C_{\\mathrm{cal}} \\cap C_{\\mathrm{test}} = \\emptyset$ . Below, we elaborate on the setup for each calibration scenario:", + "bbox": [ + 75, + 340, + 468, + 507 + ], + "page_idx": 5 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- SameDist For iNaturalist, the training and testing classes are distinct, so we directly use the training partition as $D_{\\text{train}}$ . To create $D_{\\text{cal}}$ , we randomly select $10\\%$ of the test classes, leaving the remaining classes for $D_{\\text{test}}$ . For CUB and Cars, where there is overlap between training and testing classes, we divide them into train / cal / test subsets. The train set comprises the first half of the class indices, while the cal / test sets are randomly chosen from the remaining classes with a $1/9$ ratio. As $D_{\\text{cal}}$ and $D_{\\text{test}}$ are randomly split from the same dataset, they are expected to have similar distance distributions.", + "- ShiftDist We consider 13 common image corruption and perturbation types, including noise, blur, weather, and digital distortions, to assess the robustness of the calibration methods under varied adversities. We follow the setups in [17] and apply the changes to $D_{\\mathrm{test}}$ only, while leaving $D_{\\mathrm{cal}}$ and $D_{\\mathrm{train}}$ unchanged.", + "- DiffDist To induce significant distance distribution shifts between $D_{\\mathrm{cal}}$ and $D_{\\mathrm{test}}$ , we employ the following treatments. For iNaturalist, characterized by a long-tailed distribution, we divide its test classes into two sets based on cluster size, each containing approximately the same number of images. For calibration purposes, we use the set with a higher number of images per class (\"head\" set, denoted as $D_{\\mathrm{head}}$ ) as $D_{\\mathrm{cal}}$ and the set with fewer images per class (\"tail\" set, denoted as $D_{\\mathrm{tail}}$ ) as $D_{\\mathrm{test}}$ to simu" + ], + "bbox": [ + 76, + 508, + 468, + 901 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/4deecfce793f06d95e4b7ffe2998245a7b8458d5a4f4e0a275ee9d1e30e835df.jpg", + "table_caption": [ + "Table 1. Detailed statistics of the datasets." + ], + "table_footnote": [], + "table_body": "
SettingDatasetPartition# img# cls# img/cls
SameDistCarsDtrain7,9619881.2
Dcal8661086.6
Dtest7,3568883.6
CUBDtrain5,8029958.6
Dcal5991059.9
Dtest5,3859159.2
iNatDtrain324,4185,69057.0
Dcal12,61324551.5
Dtest123,0472,20755.8
ShiftDistCarsSameDist except for corruption on Dtest
DiffDistiNatDtrainiNat SameDist Dtrain
Dhead70,057200350.3
Dtail66,0362,25229.3
CarsSameDist except for sketchifying Dtest
iNat/CUB (cross dataset)DtrainiNat SameDist Dtrain
DcaliNat SameDist Dcal
DtestEntire CUB dataset
", + "bbox": [ + 514, + 109, + 883, + 323 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "late a calibration for the long tail scenario. In addition, we also explore two out-of-domain calibration scenarios. First, for Cars, we transform $D_{\\mathrm{test}}$ into sketches while leaving $D_{\\mathrm{train}}$ and $D_{\\mathrm{cal}}$ untouched. Second, we consider cross-dataset calibration, where the OpenGCN model is pretrained and fine-tuned on iNaturalist (general natural species images) but evaluated on CUB (bird images).", + "bbox": [ + 509, + 344, + 890, + 450 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation Metrics For a comprehensive evaluation, we consider two approaches to assess calibration performance:", + "bbox": [ + 500, + 450, + 890, + 479 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "- Global Evaluation: Since we define open-world threshold calibration as the accurate prediction of both TPR and TNR at each distance threshold to meet specific TPR or TNR performance requirements of diverse test-time users, it is natural to employ the combined Mean Absolute Errors (MAE) for both TPR and TNR predictions across the entire distance range as our evaluation metric. Formally, this metric can be expressed as:", + "bbox": [ + 500, + 481, + 890, + 601 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {M A E} _ {\\text {c o m b}} = \\frac {1}{2} \\int_ {0} ^ {2} \\left(| \\hat {\\mathrm {T P R}} (\\mathrm {d}) - \\mathrm {T P R} (\\mathrm {d}) | + \\right. \\tag {13}\n$$\n", + "text_format": "latex", + "bbox": [ + 534, + 609, + 890, + 646 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\left. \\left| \\mathrm {T N R} (\\mathrm {d}) - \\mathrm {T N R} (\\mathrm {d}) \\right|\\right) d \\mathrm {d}\n$$\n", + "text_format": "latex", + "bbox": [ + 671, + 648, + 841, + 666 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "- Point-wise Evaluation: We first set a performance target and compute the optimal distance threshold, denoted as $\\hat{d}^{\\mathrm{opt}}$ , based on the TPR or TNR estimations. We then compute the Absolute Error (AE) between the actual performance at $\\hat{d}^{\\mathrm{opt}}$ and the target, denoted as $\\mathrm{AE}_{\\mathrm{TPR}} = |\\mathrm{TPR}(\\hat{d}^{\\mathrm{opt}}) - \\mathrm{TPR}_{\\mathrm{target}}|$ and $\\mathrm{AE}_{\\mathrm{TNR}} = |\\mathrm{TNR}(\\hat{d}^{\\mathrm{opt}}) - \\mathrm{TNR}_{\\mathrm{target}}|$ for TPR and TNR, respectively.", + "bbox": [ + 500, + 674, + 890, + 780 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baseline Methods We consider the most representative inductive posthoc calibration methods including Platt Scaling [37], Histogram Calibration [53], Isotonic Calibration [54] and Beta Calibration [24]. Additionally, we explore pseudolabel-based baselines, including traditional clustering methods such as DBSCAN [13] and the state-of-the-art method in GNN-based clustering, HiLANDER [49]. For clustering-based methods, we follow", + "bbox": [ + 496, + 780, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "17102", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/787723a1aafad3bf02c51ae07566bce024350e50b94d3f0265bb400a52183f97.jpg", + "table_caption": [ + "Table 2. Evaluation in the SameDist scenario using pointwise metrics of $\\mathrm{AE}_{\\mathrm{TPR}}$ (optimize for TPR) and $\\mathrm{AE}_{\\mathrm{TNR}}$ (optimize for TNR). The smaller the metric, the better. For each dataset, the best and second best results are marked in Red and Blue, respectively. Shading in the Table: Gray for posthoc calibration baselines, Cyan for clustering baselines, and Blue for our OpenGCN method. Best viewed in color." + ], + "table_footnote": [], + "table_body": "
MethodOptimize for TPR=80%Optimize for TPR=90%Optimize for TNR=80%Optimize for TNR=90%Rank
CarsCUBInatCarsCUBInatCarsCUBInatCarsCUBInat
Platt scaling [37]1.35%5.10%6.08%0.44%2.63%4.63%2.83%2.02%7.54%2.93%6.49%0.92%6
Beta calibration [24]1.13%5.16%5.51%0.02%2.91%3.26%2.94%1.41%7.57%2.78%6.43%0.93%5
Isotonic regression [54]0.82%5.28%4.53%0.90%2.56%3.54%1.94%1.00%5.78%1.26%4.65%0.65%3
Histogram Calibration [53]0.82%5.28%4.53%0.90%2.56%3.54%1.94%1.00%5.78%1.26%4.65%0.65%4
DBSCAN [13]43.11%18.87%0.45%34.57%9.18%1.85%4.09%13.77%12.90%1.60%9.32%9.32%7
Hi-LANDER [49]3.44%1.36%10.54%2.02%0.93%7.00%0.06%0.38%2.35%0.10%2.20%0.21%2
OpenGCN (ours)0.33%0.74%1.59%0.72%1.41%2.37%0.61%0.09%0.74%0.58%0.72%0.10%1
", + "bbox": [ + 80, + 138, + 893, + 247 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "their original clustering decoding inference workflows to estimate pseudo labels, and use these pseudo labels to compute $\\mathrm{TPR}_{\\mathrm{test}}$ and $\\mathrm{TNR}_{\\mathrm{test}}$ for finding $d^{\\mathrm{opt}}$ .", + "bbox": [ + 75, + 271, + 468, + 316 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Implementation Details In all experiments, we train ResNet-50 models with 128-dimensional embeddings on $D_{\\mathrm{train}}$ using the setups in [6]. The embedding models are then used to extract the embeddings for $D_{\\mathrm{train}}$ , $D_{\\mathrm{cal}}$ and $D_{\\mathrm{test}}$ . For training OpenGCN, as implied in Theorems 1 and 2, the neighborhood size needs to be sufficiently large to encapsulate both intra-class and inter-class representation structures. Thus, we use a batch sizes of 256 for graph construction during training. We use the Adam optimizer [22] with a cosine annealing schedule [30]. For traditional calibration methods, we use the official codebase from [25] to map the ground truth TPR (or TNR) as a function of the distance threshold from $D_{\\mathrm{train}}$ to $D_{\\mathrm{cal}}$ . When doing point-wise evaluation, the optimal distance threshold $d^{\\mathrm{opt}}$ is solved with grid search at a grid size of 0.01. Further details are provided in the supplementary materials.", + "bbox": [ + 75, + 316, + 473, + 561 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Evaluation Results", + "text_level": 1, + "bbox": [ + 76, + 573, + 259, + 589 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "SameDist Calibration We present the global and pointwise evaluation results for the SameDist scenario in Tab. 3 and Tab. 2, respectively. For pointwise evaluation, we evaluate at multiple target values (TPR=80%, 90% and TNR=80%, 90%) to provide a comprehensive assessment. Our results reveal that no single calibration method consistently excels across all distance thresholds and datasets. However, on average, OpenGCN achieves the highest rank. This underscores the importance of TTC in open-world scenarios, where calibration is conducted based on the characteristics of $D_{\\mathrm{test}}$ rather than relying on a calibration dataset that may not accurately represent $D_{\\mathrm{test}}$ . Additionally, the global metrics in Tab. 3 show that, compared to the best baseline method, OpenGCN significantly reduces global error rates by 59.30%, 66.49%, and 59.15% for Cars, CUB, and iNaturalist, respectively. Among the baseline methods, we observe that DBSCAN performs worse than the traditional posthoc calibration methods, while Hi-LANDER outperforms traditional posthoc methods on Cars and CUB but underperforms on iNaturalist. In contrast, OpenGCN con", + "bbox": [ + 75, + 598, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/06bde4a86f89057c4261bf1ced05edf4d6e7dc82b12bb867c1915bd9a44c6577.jpg", + "table_caption": [ + "Table 3. Evaluation in the SameDist scenario using the global error metric of $\\mathrm{MAE}_{\\mathrm{comb}}$ . For each benchmark, the best and second best results are marked in Red and Blue, respectively. We also report the improvement in error reduction of OpenGCN over the best baseline method. Best viewed in color." + ], + "table_footnote": [], + "table_body": "
MethodCarsCUBiNatRank
Platt scaling1.55e-23.59e-21.23e-26
Beta calibration1.53e-23.59e-21.18e-25
Isotonic regression1.38e-23.61e-21.18e-23
Histogram calibration1.38e-23.62e-21.18e-24
DBSCAN1.02e-11.10e-13.65e-27
Hi-LANDER1.29e-21.94e-22.14e-22
OpenGCN (ours)5.25e-36.50e-34.82e-31
Imp. over top baseline ↑59.30%66.49%59.15%69.14% (avg.)
", + "bbox": [ + 504, + 345, + 890, + 455 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "sistently performs well across all three datasets.", + "bbox": [ + 498, + 486, + 815, + 502 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ShiftDist Calibration In Tab. 4, we report the global error metric $\\mathrm{MAE}_{\\mathrm{comb}}$ for each corruption type across various calibration methods. Among the baseline methods, Isotonic Regression and Histogram Calibration appear to be the most effective in the presence of image corruptions. However, it is evident that OpenGCN consistently outperform these baseline methods across all corruption types, achieving an average error reduction of $55.03\\%$ compared to the best baseline method. This robust performance against image corruptions can be attributed to the model's pretraining stage, where it was exposed to closed-set data with similar types of corruptions. Additionally, it is observed that, among the various corruption categories, OpenGCN exhibits the most improvement in the weather category, while showing the least improvement in the blur category.", + "bbox": [ + 496, + 503, + 890, + 733 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "DiffDist Calibration We present the DiffDist calibration results in Tab. 5. As observed, in this scenario characterized by a substantial shift in distance distributions between $D_{\\mathrm{cal}}$ and $D_{\\mathrm{test}}$ , all calibration methods display elevated errors compared to the SameDist scenario. However, OpenGCN demonstrates superior performance compared to the other calibration methods in both out-of-domain settings (sketch and cross-dataset) and the long-tail calibration setting, achieving an average relative reduction in the global error $\\mathrm{MAE}_{\\mathrm{comb}}$ of $43.99\\%$ . In particular, we observe significant improvement in the cross-dataset setting (pretrained", + "bbox": [ + 496, + 734, + 893, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "17103", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/7f8b2ed15375e59e9bf69116212ed084c5cb64d63cca26c500d9d38516559f71.jpg", + "table_caption": [ + "Table 4. Evaluation on the Cars-196 dataset in the ShiftDist scenario across 13 common corruption and perturbation types using combined global error metric of $\\mathrm{MAE}_{\\mathrm{comb}}$ . The best results are marked in Red." + ], + "table_footnote": [], + "table_body": "
MethodNoiseBlurWeatherDigitalRank
GaussShotImpulseDefocusMotionZoomSnowFogBrightContrastElasticPixelJPEG
Platt scaling2.95e-22.99e-23.41e-22.66e-22.62e-25.02e-24.24e-24.37e-22.16e-24.61e-22.16e-22.24e-22.03e-24
Beta calibration2.94e-22.97e-23.41e-22.67e-22.69e-25.06e-24.32e-24.37e-22.18e-24.61e-22.20e-22.23e-22.02e-25
Isotonic regression2.88e-22.85e-23.38e-22.37e-22.31e-24.85e-24.07e-24.34e-21.83e-24.59e-21.85e-22.03e-21.80e-22
Histogram calibration2.88e-22.85e-23.38e-22.37e-22.31e-24.85e-24.07e-24.34e-21.83e-24.59e-21.85e-22.03e-21. 80e-23
DBSCAN4.96e-26.02e-27.79e-29.81e-21.13e-11.22e-11.19e-14.02e-29.27e-24.53e-21.09e-11.04e-18.21e-27
Hi-LANDER7.65e-26.30e-26.59e-23.98e-25.33e-24.48e-25.94e-27.16e-25.09e-29.45e-24.42e-29.48e-26.91e-26
OpenGCN (ours)1.33e-25.87e-31.66e-21.50e-21.71e-23.92e-21.42e-27.32e-36.73e-37.08e-35.34e-31.15e-21.68e-21
Imp. over top baseline ↑53.82%79.40%50.89%36.71%25.97%12.50%65.11%81.79%63.22%84.37%71.14%43.35%6.67%55.03% (avg.)
", + "bbox": [ + 78, + 125, + 890, + 277 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/d9d62b715254e76a62d9686706409d4d385543b0dfb9924b8ed316211fcde865.jpg", + "table_caption": [ + "Table 5. Evaluation in the DiffDist scenario using the global error metric $\\mathrm{MAE}_{\\mathrm{comb}}$ . The best results are highlighted in Red." + ], + "table_footnote": [], + "table_body": "
MethodCars: SketchCUB: Cross-datasetiNat: Longtail
Platt scaling1.08e-11.15e-12.09e-2
Beta calibration1.08e-11.15e-12.12e-2
Isotonic regression1.08e-11.15e-12.11e-2
Histogram Calibration1.08e-11.15e-12.11e-2
DBSCAN5.16e-21.60e-17.21e-2
Hi-LANDER6.67e-21.30e-16.26e-2
OpenGCN (ours)3.54e-21.42e-21.82e-2
Imp. over top baseline ↑31.40%87.65%12.92%
", + "bbox": [ + 81, + 330, + 467, + 428 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/0af1aa6a8093474eb1f5c87d8d8049c0f2824c8d965edaef60dfe8e58b7dcca0.jpg", + "table_caption": [ + "Table 6. Impact of multi-task learning on global error metric $\\mathrm{MAE}_{\\mathrm{comb}}$ on iNaturalist-2018. We use $\\lambda = 10$ for all experiments." + ], + "table_footnote": [], + "table_body": "
Best baselineOpenGCN loss ablations
Lconn+λ·Lsavg+λ·Lsshr+λ·(Lsavg + Lsshr)
MAEcomb1.18e-26.25e-35.37e-35.12e-34.82e-3
", + "bbox": [ + 81, + 477, + 467, + 513 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/e5c6d8761e2e3fd439b3b20eeb127895297389e1675f6f2a2701d23d729ffb66.jpg", + "table_caption": [ + "Table 7. Impact of fine-tuning on open-world calibration dataset on global error metric $\\mathrm{MAE}_{\\mathrm{comb}}$ . PT: pretraining FT: finetuning. Numbers in the bracket show the relative improvement over PT." + ], + "table_footnote": [], + "table_body": "
MethodCarsCUBiNat
OpenGCN (PT)2.90e-22.52e-23.55e-2
OpenGCN (PT+FT)5.25e-3 (81.9%)6.50e-3 (74.2%)4.82e-3 (86.4%)
", + "bbox": [ + 81, + 575, + 467, + 614 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "and finetuned on the iNaturalist-2018 nature species dataset but tested on the CUB birds dataset), where OpenGCN achieves a notable error reduction of $87.65\\%$ .", + "bbox": [ + 76, + 640, + 468, + 685 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3. Ablation Studies", + "text_level": 1, + "bbox": [ + 76, + 695, + 240, + 709 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Importance of Multi-task Learning We assess the impact of multi-task learning on $\\mathrm{MAE}_{\\mathrm{comb}}$ . As shown in Tab. 6, compared to predicting connectivity only, employing a single density metric in conjunction with connectivity prediction helps reduce $\\mathrm{MAE}_{\\mathrm{comb}}$ from $6.25\\mathrm{e} - 3$ to $5.37\\mathrm{e} - 3$ for $s^{\\mathrm{avg}}$ and to $5.12\\mathrm{e} - 3$ for $s^{\\mathrm{nbr}}$ , respectively. However, by utilizing both density metrics, we further decrease this error to $4.82\\mathrm{e} - 3$ . This supports our choice to incorporate both density metrics, allowing us to capture both intra-class compactness and inter-class separation while facilitating information sharing for improved connectivity prediction.", + "bbox": [ + 75, + 719, + 468, + 883 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Importance of Two-stage Training We assess the impact", + "bbox": [ + 76, + 885, + 470, + 901 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "of two-stage training on OpenGCN by comparing $\\mathrm{MAE}_{\\mathrm{comb}}$ before and after fine-tuning on $D_{\\mathrm{cal}}$ across all three benchmarks. The comparison in Tab. 7 reveals significant error reduction of up to $86.4\\%$ after fine-tuning on the open-world calibration dataset. This results supports our choice of two-stage training in adapting the calibration model from the closed-world context to the open-world scenarios.", + "bbox": [ + 496, + 297, + 890, + 405 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusions", + "text_level": 1, + "bbox": [ + 500, + 417, + 627, + 434 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we formally define the open-world threshold calibration problem for DML-based open-world visual recognition systems. To address this problem, we introduce OpenGCN, a GNN-based transductive threshold calibration method designed to enhance adaptability in open-world scenarios. Unlike traditional posthoc calibration methods, OpenGCN does not rely on the common assumption of matching distance distributions between $D_{\\mathrm{cal}}$ and $D_{\\mathrm{test}}$ . Instead, it leverages the information of the unlabeled test instances along with learnt calibration rules to predict pairwise connectivity of the test data, via a GNN, to enable effective transductive threshold calibration in open-world scenarios. Our evaluations demonstrate that OpenGCN outperforms both traditional posthoc calibration methods and pseudolabel-based calibration techniques. When assessed using global error metrics, OpenGCN exhibits significant improvements, achieving average error reductions of $69.14\\%$ , $40.85\\%$ , and $22.58\\%$ for SameDist, ShiftDist, and DiffDist calibration scenarios, respectively, compared to the best baseline method. Overall, our results underscore OpenGCN's robustness across different distance distribution patterns between $D_{\\mathrm{cal}}$ and $D_{\\mathrm{test}}$ , highlighting its practical applicability for threshold calibration in DML-based open-world recognition applications.", + "bbox": [ + 496, + 443, + 890, + 805 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Limitations OpenGCN is computationally less efficient and more susceptible to over-parameterization compared to traditional posthoc calibration methods. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 16489-16498, 2021." + ], + "bbox": [ + 501, + 92, + 890, + 771 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "17106", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_model.json b/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_model.json new file mode 100644 index 0000000000000000000000000000000000000000..7497f0a71477ad89f2b21b30fd15b24c3ac82074 --- /dev/null +++ b/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_model.json @@ -0,0 +1,2211 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.095, + 0.131, + 0.877, + 0.155 + ], + "angle": 0, + "content": "Learning for Transductive Threshold Calibration in Open-World Recognition" + }, + { + "type": "text", + "bbox": [ + 0.108, + 0.18, + 0.87, + 0.217 + ], + "angle": 0, + "content": "Qin Zhang\\(^{1}\\), Dongsheng An\\(^{1}\\), Tianjun Xiao\\(^{2}\\), Tong He\\(^{2}\\), Qingming Tang\\(^{3}\\), Ying Nian Wu\\(^{1}\\), Joseph Tighe\\(^{1}\\), Yifan Xing\\(^{1}\\)" + }, + { + "type": "text", + "bbox": [ + 0.24, + 0.219, + 0.369, + 0.237 + ], + "angle": 0, + "content": "AWS AI Labs" + }, + { + "type": "text", + "bbox": [ + 0.407, + 0.22, + 0.602, + 0.236 + ], + "angle": 0, + "content": "2 Amazon Web Services" + }, + { + "type": "text", + "bbox": [ + 0.641, + 0.22, + 0.73, + 0.236 + ], + "angle": 0, + "content": "3 Alexa AI" + }, + { + "type": "text", + "bbox": [ + 0.123, + 0.241, + 0.838, + 0.256 + ], + "angle": 0, + "content": "{qzaamz, andongsh, tianjux, htong, qmtang, wunyin, yifax}@amazon.com, jtighe@cs.unc.edu" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.291, + 0.314, + 0.307 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.324, + 0.474, + 0.687 + ], + "angle": 0, + "content": "In deep metric learning for visual recognition, the calibration of distance thresholds is crucial for achieving desired model performance in the true positive rates (TPR) or true negative rates (TNR). However, calibrating this threshold presents challenges in open-world scenarios, where the test classes can be entirely disjoint from those encountered during training. We define the problem of finding distance thresholds for a trained embedding model to achieve target performance metrics over unseen open-world test classes as open-world threshold calibration. Existing posthoc threshold calibration methods, reliant on inductive inference and requiring a calibration dataset with a similar distance distribution as the test data, often prove ineffective in open-world scenarios. To address this, we introduce OpenGCN, a Graph Neural Network-based transductive threshold calibration method with enhanced adaptability and robustness. OpenGCN learns to predict pairwise connectivity for the unlabeled test instances embedded in a graph to determine its TPR and TNR at various distance thresholds, allowing for transductive inference of the distance thresholds which also incorporates test-time information. Extensive experiments across open-world visual recognition benchmarks validate OpenGCN's superiority over existing posthoc calibration methods for open-world threshold calibration." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.722, + 0.21, + 0.739 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.47, + 0.902 + ], + "angle": 0, + "content": "In deep metric learning (DML) for visual recognition, distance calibration plays a critical role in determining the user-perceived model performance. Unlike confidence calibration in closed-set classification settings which focuses on aligning confidence probabilities with true likelihood of correctness in a fixed label space [27, 33], distance calibration in DML aims to pinpoint an optimal distance threshold to achieve a target true positive rate (TPR) or true negative rate (TNR) for diverse test-time distributions [26]. This calibration is vital because, even with a highly effic" + }, + { + "type": "image", + "bbox": [ + 0.536, + 0.291, + 0.85, + 0.421 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.519, + 0.424, + 0.844, + 0.524 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.527, + 0.895, + 0.667 + ], + "angle": 0, + "content": "Figure 1. This figure illustrates the open-world threshold calibration problem. In open-world recognition, the embedding model is trained on closed-set classes but tested on distinct open-world classes. When applying the model to open-world classes, it often produces less compact embeddings than those encountered during training, necessitating the calibration of the distance threshold for achieving the desired TPR and TNR trade-off. However, the absence of prior knowledge about open-world test classes and distributions makes it challenging to find the optimal distance threshold, denoted as \\( d^{\\mathrm{opt}} \\). Best viewed in color." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.895, + 0.903 + ], + "angle": 0, + "content": "tive embedding model, an inappropriate distance threshold can significantly degrade user experience. The issue becomes more pronounced in open-world recognition, where the embedding model, trained on a closed set of classes (e.g., dog, cat, bird), is tested on an open collection of unseen classes (e.g., wolf, sheep, mouse, ...). These open-world classes may have very different intra-class and interclass representation structures, typically being less compact, compared to the training classes. In such open-world scenarios, where prior knowledge about test-time classes and distributions are absent, calibrating the distance threshold becomes a challenging task, as illustrated in Fig. 1. We term this task of distance calibration in an open-world scenario as open-world threshold calibration." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17097" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.228 + ], + "angle": 0, + "content": "Existing posthoc calibration methods, such as [16, 24, 34, 37, 53, 54], typically utilize a fully-labeled calibration dataset that has a similar distribution as the test data [35, 42, 56] to learn general calibration rules for test distributions. However, this approach has a key limitation: it heavily relies on the assumption of identical distributions between test and calibration data for effective calibration. In open-world scenarios, this assumption becomes unreliable, posing significant challenges to threshold calibration, including:" + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.232, + 0.47, + 0.338 + ], + "angle": 0, + "content": "1. The open-world challenge The test data may exclusively contain open-world classes, which exhibit different relationships between distance thresholds and TPR or TNR compared to those encountered during the embedding model training [26]. Meanwhile, test data composition and quality can vary significantly, potentially exhibiting substantial class imbalances and data corruptions." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.338, + 0.47, + 0.398 + ], + "angle": 0, + "content": "2. Non-stationary data In real-world testing environments, the test distribution can be infinitely varied and highly dynamic, rendering the assumption of similar distribution between calibration and test data obsolete." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.399, + 0.47, + 0.535 + ], + "angle": 0, + "content": "3. Deployment Scalability Real-world systems require calibration methods that can adapt to diverse user distributions without individual recalibration. Existing methods lack deployment scalability as they frequently require dedicated calibration data and the creation of specific calibration functions for each user. Imagine a scenario with 1,000 user profiles with distinct classes and data distributions – creating and deploying custom calibration datasets and functions for each would be impractical." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.232, + 0.47, + 0.535 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.539, + 0.473, + 0.902 + ], + "angle": 0, + "content": "Addressing these challenges is crucial for the reliability of DML-based open-world recognition systems. Current posthoc calibration methods are ill-suited for this purpose, as they are inherently inductive and prone to failure when confronted with test data with different distance distributions from the calibration data. To address this, we adopt a fresh perspective on distance threshold calibration, treating it as a transductive inference process, where the calibration method incorporates the information of the unlabeled test samples along with the learned calibration rules to make better threshold estimations. Our proposed method, OpenGCN, employs a Graph Neural Network (GNN), known for its generalization capabilities [3, 5, 9, 10, 49, 51, 52], to jointly predict pairwise connectivity and two instance-wise representation densities for test data, where the predicted pairwise connectivity is used to compute the TPR and TNR of the test data at each distance threshold to enable transductive threshold calibration. OpenGCN is tailored for the task of open-world threshold calibration through a carefully crafted learning process, which accurately estimates the mapping between performance metrics and pairwise distance thresholds in open-world scenarios. In particular, the multi-task learning of connectivities and representation densities facilitates infor" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.332 + ], + "angle": 0, + "content": "mation sharing, which helps enhance the model's generalization to open-world scenarios [49, 52]. Additionally, our joint prediction design incorporates two types of density metrics, addressing both intra-class and inter-class connectivity estimations. This approach, as opposed to using a single density metric, is shown to enhance calibration performance, as illustrated in Sec. 4.3. Furthermore, OpenGCN adopts a two-stage training process. It pre-trains on a large closed-world dataset, followed by fine-tuning on a small open-world calibration dataset with disjoint classes to both the closed-world and test data, to adapt the model to be aware of the open-world context. By these design choices, OpenGCN sidesteps the requirement for calibration data to have a similar distance distribution1 as the test data, significantly improving calibration performance in open-world scenarios. To summarize, our contributions are as follows:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.334, + 0.891, + 0.363 + ], + "angle": 0, + "content": "1. We are, to the best of our knowledge, the first to formally define the open-world threshold calibration problem." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.364, + 0.892, + 0.438 + ], + "angle": 0, + "content": "2. We propose Transductive Threshold Calibration (TTC), a new threshold calibration paradigm that diverges from traditional inductive posthoc calibration methods, which does not rely on the assumption of similar distance distributions between the test and calibration data." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.439, + 0.892, + 0.545 + ], + "angle": 0, + "content": "3. We introduce OpenGCN, a GNN-based TTC method tailored for open-world threshold calibration against diverse test distributions. We build comprehensive evaluation protocols with and without distance distribution shifts to assess OpenGCN's performance. The evaluation result underscores OpenGCN's effectiveness and robustness in real-world testing environments." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.334, + 0.892, + 0.545 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.558, + 0.85, + 0.574 + ], + "angle": 0, + "content": "2. Problem Definition and Related Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.583, + 0.895, + 0.795 + ], + "angle": 0, + "content": "We first introduce some notations and formalize the open-world threshold calibration problem. Let \\( D_{\\mathrm{labled}} \\) be a labeled dataset consisting of two disjoint subsets: \\( D_{\\mathrm{train}} \\) and \\( D_{\\mathrm{cal}} \\), and let \\( D_{\\mathrm{test}} \\) be an unlabeled dataset. In open-world scenarios, the class sets of \\( D_{\\mathrm{train}} \\), \\( D_{\\mathrm{cal}} \\), and \\( D_{\\mathrm{test}} \\), denoted as \\( C_{\\mathrm{train}} \\), \\( C_{\\mathrm{cal}} \\), and \\( C_{\\mathrm{test}} \\), are disjoint, i.e., \\( C_{\\mathrm{train}} \\cap C_{\\mathrm{cal}} = C_{\\mathrm{train}} \\cap C_{\\mathrm{test}} = C_{\\mathrm{cal}} \\cap C_{\\mathrm{test}} = \\emptyset \\). The goal of open-world threshold calibration is to find a suitable distance threshold that achieves the target TPR and TNR for \\( D_{\\mathrm{test}} \\), given an embedding model trained on \\( D_{\\mathrm{train}} \\). We approach this as a constrained optimization task, with the objective being maximizing the metric of interest. Take optimizing for TNR with a minimum TPR requirement as an example, this problem can be formulated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.52, + 0.805, + 0.892, + 0.828 + ], + "angle": 0, + "content": "\\[\n\\underset {d} {\\text {m a x i m i z e}} \\mathrm {T N R} _ {\\text {t e s t}}, \\quad \\text {s u b j e c t t o T P R} _ {\\text {t e s t}} (d) \\geq \\alpha \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.837, + 0.894, + 0.868 + ], + "angle": 0, + "content": "where \\(d\\) is the distance threshold, and \\(\\alpha\\) is the minimum performance requirement for \\(\\mathrm{TPR}_{\\mathrm{test}}\\). Due to the inherent" + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.875, + 0.892, + 0.901 + ], + "angle": 0, + "content": "1We use \"distance distribution\" to refer to the distribution of pairwise distances between L2-normalized embeddings from a trained DML model." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17098" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.152 + ], + "angle": 0, + "content": "trade-off between TPR and TNR, the objective in Eq. (1) is equivalent to finding an optimal distance threshold \\( d^{\\mathrm{opt}} \\) for which \\( \\mathrm{TPR}_{\\mathrm{test}}(d^{\\mathrm{opt}}) = \\alpha \\). To solve this, we express \\( \\mathrm{TPR}_{\\mathrm{test}} \\) and \\( \\mathrm{TNR}_{\\mathrm{test}} \\) at a distance threshold \\( d \\) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.124, + 0.162, + 0.47, + 0.192 + ], + "angle": 0, + "content": "\\[\n\\operatorname {T P R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} = y _ {j}} \\cdot 1 _ {d _ {i j} < d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} = y _ {j}} \\tag{2}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.124, + 0.202, + 0.469, + 0.23 + ], + "angle": 0, + "content": "\\[\n\\mathrm {T N R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} \\neq y _ {j}} \\cdot 1 _ {d _ {i j} > d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} \\neq y _ {j}} \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.234, + 0.469, + 0.34 + ], + "angle": 0, + "content": "where \\( d_{ij} \\) is the L2 distance between the embeddings of samples \\( i \\) and \\( j \\), and \\( y_i \\) is the label for sample \\( i \\). The symbol \\( 1_{\\text{condition}} \\) represents the indicator function which equals 1 if the condition is met, otherwise 0. With \\( \\mathrm{TPR}_{\\text{test}} \\) and \\( \\mathrm{TNR}_{\\text{test}} \\) calculated at each distance threshold, we can optimize for the optimal distance threshold \\( d^{\\text{opt}} \\) to achieve the target performance metrics, as described in Eq. (1)." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.349, + 0.228, + 0.364 + ], + "angle": 0, + "content": "2.1. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.373, + 0.469, + 0.584 + ], + "angle": 0, + "content": "Open-world Recognition [29] aims to learn discriminative representations that align distances between representations with their semantic similarities. This allows for effective generalization to diverse, previously unseen open-world classes during testing, setting it apart from closed-set classification where training and testing classes are the same. Popular recognition losses [6, 12, 36] typically encourage compact intra-class representations, promoting strong affinity within each class while maintaining separation from other classes. However, it is widely observed that these losses tend to produce highly varied intra-class and inter-class representation structures across classes and distributions [32, 39, 55], necessitating threshold calibration to ensure consistent performance across diverse users." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.585, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Posthoc Calibration We focus on posthoc calibration methods which are more relevant to our research. Generally, existing posthoc calibration methods fall into two categories: (i) non-parametric methods like isotonic regression [54] and histogram binning [34, 53]; and (ii) parametric methods such as Platt scaling [37] and temperature scaling [16]. These methods are inductive: they rely on a holdout calibration set with similar distribution as the test data to derive general rules for fine-tuning the decision threshold, aiming to align the performance metrics with a predefined target. While effective in closed-set classification, these methods struggle in scenarios with significant distribution differences between test and calibration data. Diverging from traditional methods, another group of methods such as conformal prediction [4, 15, 40, 43] or Prediction-Powered Inference [1] emphasize confidence coverage guarantees, and has been shown applicable even beyond the setting of exchangeable data [14, 15]. However, these methods inherently assume a closed-set setting, making them unsuitable for open-world scenarios. Currently, open-world posthoc calibration remains largely under-explored." + }, + { + "type": "image", + "bbox": [ + 0.518, + 0.088, + 0.878, + 0.179 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.188, + 0.892, + 0.286 + ], + "angle": 0, + "content": "Figure 2. This figure distinguishes between (left) inductive and (right) transductive threshold calibration methods in open-world scenarios with disjoint test-time classes. Inductive methods rely on a labeled hold-out dataset with the same distance distribution as the test data to learn general calibration rules. Transductive methods, however, also use the test information for more specific calibration, as indicated by the red arrow. Best viewed in color." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.311, + 0.893, + 0.508 + ], + "angle": 0, + "content": "Transductive Inference Transduction is the reasoning from observed, specific (training) cases to specific (test) cases [45]. Such an approach is desirable as it alleviates the problem of overfitting on limited support set since information from the test data is also used for inference. This is also known as increasing VC-dimension for structural risk minimization in classical statistical learning [19]. Recently, a large body of works investigated transductive inference for few-shot and open-world recognition tasks [8, 18, 28, 38], where significant increases in performances have been reported. Given the relevance of these tasks, it is worthwhile to reconsider existing inductive posthoc calibration methods for distance threshold calibration in open-world scenarios." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.521, + 0.636, + 0.538 + ], + "angle": 0, + "content": "3. Methodology" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.545, + 0.813, + 0.56 + ], + "angle": 0, + "content": "3.1. Transductive Threshold Calibration" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.569, + 0.892, + 0.825 + ], + "angle": 0, + "content": "Traditional calibration methods are inherently inductive - they rely on a calibration dataset to learn general calibration rules under the assumption of identically distributed data. However, in open-world scenarios, this assumption seldom holds, as the test distribution is unknown and can be infinitely varied and highly dynamic. To improve calibration specificity in the open world, it is natural to adopt a transductive approach, where the TPR and TNR estimations directly involve the test data, rather than relying on a separate calibration dataset that might not accurately represent the test data. As illustrated in Fig. 2, a transductive approach allows the calibration model to \"see\" the unlabeled test data when deciding on the distance threshold, contrasting with the traditional inductive methods which are \"blind\" to the test data. We term this approach as Transductive Threshold Calibration (TTC), and the traditional inductive calibration methods as Inductive Threshold Calibration (ITC)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.901 + ], + "angle": 0, + "content": "To overcome the limitations of ITC methods, we propose OpenGCN, a GNN-based TTC method with enhanced adaptability and robustness for open-world scenarios with diverse concepts and distance distributions. We highlight the key differences between OpenGCN and conventional" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17099" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.088, + 0.49, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.157, + 0.211, + 0.42, + 0.225 + ], + "angle": 0, + "content": "(a) Pre-training on Closed-World Examples" + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.089, + 0.885, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.562, + 0.21, + 0.815, + 0.224 + ], + "angle": 0, + "content": "(b) Fine-tuning on Open-World Examples" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.235, + 0.894, + 0.306 + ], + "angle": 0, + "content": "Figure 3. OpenGCN training workflow: (a) During pre-training, OpenGCN jointly optimizes pairwise connectivity, and instance-specific neighborhood and average densities. (b) During fine-tuning, the 2-layer MLP is reset for fine-tuning, while the other weights remain frozen. Solid blue and dashed red arrows represent forward and backward propagation, respectively. At test time, we employ the trained OpenGCN model and MLP head to predict the TPR and TNR as functions of each distance threshold specifically for each test distribution. We then follow Eq. (1) and use grid search to find the optimal distance threshold for each test dataset. Best viewed in color." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.332, + 0.473, + 0.65 + ], + "angle": 0, + "content": "ITC methods. First, OpenGCN, as a transductive method, derives distance thresholds by leveraging information directly from the test data. This empowers it to adapt to the characteristics of the test data, thereby eliminating the requirement for the calibration data to share a similar distribution with the test data. Second, OpenGCN is engineered to integrate useful information from both closed-world and open-world data sources. This is achieved through a two-stage training process, as illustrated in Fig. 3. We first pretrain OpenGCN on a closed-world dataset, which is the same dataset used to train the DML embedding model. Afterwards, we fine-tune it on a smaller calibration dataset. This calibration dataset contains open-world classes that do not overlap with those in the test data or the closed-world pretraining data. This approach allows the model to smoothly transition from a closed-world context to open-world scenarios, effectively utilizing closed-world knowledge to enhance its transductive reasoning capabilities in the dynamic and unknown open world. In the next section, we delve into the details of OpenGCN, elaborating on how it enables effective TTC for open-world scenarios." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.656, + 0.418, + 0.673 + ], + "angle": 0, + "content": "3.2. OpenGCN: Learning for Effective TTC" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.679, + 0.47, + 0.786 + ], + "angle": 0, + "content": "OpenGCN Inference Workflow A straight-forward way to estimate \\(\\mathrm{TPR}_{\\mathrm{test}}\\) and \\(\\mathrm{TNR}_{\\mathrm{test}}\\), as defined in Eqs. (2) and (3), is to model the true pairwise connectivities with edge connectivity probability [52]. This probability, denoted as \\(p_{ij}\\), quantifies the likelihood that two samples have the same label. By setting a proper connectivity threshold \\(\\tau\\), we can approximate \\(\\mathrm{TPR}_{\\mathrm{test}}\\) and \\(\\mathrm{TNR}_{\\mathrm{test}}\\) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.121, + 0.79, + 0.47, + 0.82 + ], + "angle": 0, + "content": "\\[\n\\mathrm {T P R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} > \\tau} \\cdot 1 _ {d _ {i j} < d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} > \\tau} \\tag {4}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.121, + 0.825, + 0.469, + 0.855 + ], + "angle": 0, + "content": "\\[\n\\mathrm {T N R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} \\leq \\tau} \\cdot 1 _ {d _ {i j} > d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} \\leq \\tau} \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "These formulations offer a TTC solution that centers on precisely predicting pairwise connectivities for open-world test distributions, a problem well-suited for modern" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.332, + 0.892, + 0.665 + ], + "angle": 0, + "content": "deep learning algorithms. Specifically, as shown in Fig. 3, OpenGCN is designed as a GNN-based method for predicting pairwise connectivities over graph data constructed from the unlabeled test samples. We adopt a GNN architecture, specifically a Graph Attention Network (GAT) [46], due to its demonstrated effectiveness in generalizing to open-world scenarios [3, 5, 9, 10, 49, 51, 52]. Additionally, we use fully connected graphs to ensure that in-graph pairwise distance distribution is representative of the overall pairwise distance distribution. For inference, nodal features extracted by the GAT encoder are concatenated with the original DML embedding features [52] and passed through a 2-layer MLP to predict pairwise connectivities. The connectivity predictions are then used to transductively estimate TPR and TNR at each distance threshold for the test distributions, following the formulations in Eqs. (4) and (5), where the connectivity threshold \\(\\tau\\) is selected by 10-fold cross validation on \\(D_{\\mathrm{cal}}\\). Due to the typically large size of the test data, for efficient inference, we randomly sample subsets from \\(D_{\\mathrm{test}}\\) to construct fully connected sub-graphs for connectivity inference, repeating this process until the TPR and TNR estimations converge." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Joint Connectivity and Density Estimations Using representation density prediction as an auxiliary task to enhance connectivity prediction is widely used in clustering tasks [2, 7, 31]. This approach is based on the idea that a cluster typically exists within a contiguous region of high sample density, separated from other clusters. Recent supervised visual clustering works also leverage density as a key modeling parameter to enhance clustering performance by encouraging information sharing between the tasks [49, 50, 52]. Driven by the intrinsic connections between density and connectivity, we adopt a multitask approach, where we simultaneously learn for pairwise edge connectivity and instance-wise representation densities. However, unlike previous works which only consider one density metric, we simultaneously learn two density" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17100" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.138 + ], + "angle": 0, + "content": "metrics: the average density (\\( s^{\\mathrm{avg}} \\)), and the neighborhood density (\\( s^{\\mathrm{nbr}} \\)). Formally, these two density metrics, defined in [52], can be expressed as follows\\(^2\\):" + }, + { + "type": "equation", + "bbox": [ + 0.089, + 0.145, + 0.469, + 0.183 + ], + "angle": 0, + "content": "\\[\ns _ {i} ^ {\\text {a v g}} = \\frac {\\sum_ {j \\in \\mathcal {N} _ {i}} a _ {i j} \\cdot 1 _ {y _ {i} = y _ {j}}}{| \\mathcal {N} _ {i} |}, s _ {i} ^ {\\text {n b r}} = \\frac {\\sum_ {j \\in \\mathcal {N} _ {i}} a _ {i j} \\cdot \\left(1 _ {y _ {i} = y _ {j}} - 1 _ {y _ {i} \\neq y _ {j}}\\right)}{| \\mathcal {N} _ {i} |} \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.191, + 0.469, + 0.236 + ], + "angle": 0, + "content": "where \\(\\mathcal{N}_i\\) denotes the neighbourhood of a sample \\(i\\), and \\(a_{ij}\\) represents the cosine similarity between the original embedding features of sample \\(i\\) and sample \\(j\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.237, + 0.469, + 0.342 + ], + "angle": 0, + "content": "To illustrate the motivation of utilizing both density metrics instead of just one, we first introduce two metrics adapted from prior works [20, 41], namely the class-specific TPR and TNR scores, denoted as \\(\\mathrm{TPR}^k\\) and \\(\\mathrm{TNR}^k\\), respectively. Let \\(f_{i}\\) denote the \\(\\mathrm{L}_2\\)-normalized embeddings of an image in a dataset \\(D\\). For a given class \\(k\\), its class-specific TPR and TNR scores can be expressed as:" + }, + { + "type": "equation", + "bbox": [ + 0.086, + 0.35, + 0.469, + 0.396 + ], + "angle": 0, + "content": "\\[\n\\mathrm {T P R} ^ {k} = \\frac {\\left\\| \\sum_ {i \\in D} f _ {i} \\cdot 1 _ {y _ {i} = k} \\right\\|}{\\sum_ {i \\in D} 1 _ {y _ {i} = k}}, \\quad \\mathrm {T N R} ^ {k} = \\frac {\\sum_ {i , j \\in D} \\left(1 - a _ {i j}\\right) \\cdot 1 _ {y _ {j} \\neq y _ {i} = k}}{\\sum_ {i , j \\in D} 1 _ {y _ {j} \\neq y _ {i} = k}} \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.405, + 0.469, + 0.45 + ], + "angle": 0, + "content": "The subsequent theorems formally establish a connection between two density metrics defined in Eq. (6) and the class-specific TPR and TNR scores." + }, + { + "type": "title", + "bbox": [ + 0.076, + 0.46, + 0.469, + 0.475 + ], + "angle": 0, + "content": "Theorem 1 (Correspondence between \\( s^{\\mathrm{avg}} \\) and \\( TPR^{k} \\))" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.476, + 0.469, + 0.521 + ], + "angle": 0, + "content": "Let \\(\\mathcal{N}\\) be a cluster with high purity, where the majority class is \\(k\\). For each sample \\(i \\in \\mathcal{N}\\), when both \\(|\\mathcal{N}|\\) and \\(|\\mathcal{N}_i|\\) are sufficiently large, \\(TPR^k\\) can be approximated as:" + }, + { + "type": "equation", + "bbox": [ + 0.098, + 0.529, + 0.469, + 0.593 + ], + "angle": 0, + "content": "\\[\n\\lim _ {| \\mathcal {N} _ {i} | \\rightarrow \\infty} T P R ^ {k} = \\left(\\frac {| \\mathcal {N} _ {i} |}{2 | \\mathcal {N} |} \\right. \\cdot \\underbrace {\\left(\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {n b r}} \\right.} _ {\\substack {\\text {avg s} ^ {\\mathrm {n b r}}\\\\2 \\times \\text {avg s} ^ {\\mathrm {a v g}}}} + \\underbrace {\\left(\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} \\mathfrak {a} _ {\\mathrm {i}} ^ {\\mathrm {a v g}}\\right) ^ {1 / 2}} _ {\\substack {\\text {avg a} ^ {\\mathrm {a v g}}}} \\tag{8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.603, + 0.469, + 0.636 + ], + "angle": 0, + "content": "where \\(\\mathfrak{a}_i^{\\mathrm{avg}} = \\frac{1}{|\\mathcal{N}_i|}\\sum_{j\\in \\mathcal{N}_i}a_{ij}\\), and \\(\\mathfrak{a}^{\\mathrm{avg}}\\) is the mean of average cosine similarity of all vertices in \\(\\mathcal{N}_i\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.645, + 0.47, + 0.692 + ], + "angle": 0, + "content": "Theorem 2 (Correspondence between \\( s^{\\mathrm{avg}} - s^{\\mathrm{nbr}} \\) and \\( TNR^{k} \\)) Under the same assumptions in Theorem 1, for a given class \\( k \\), its \\( TNR^{k} \\) can be approximated as:" + }, + { + "type": "equation", + "bbox": [ + 0.1, + 0.699, + 0.469, + 0.749 + ], + "angle": 0, + "content": "\\[\n\\lim _ {| \\mathcal {N} _ {i} | \\rightarrow \\infty} T N R ^ {k} = 1 - \\frac {| \\mathcal {N} |}{| \\mathcal {N} | _ {k ^ {-}}} \\cdot (\\underbrace {\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {a v g}} - \\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {n b r}})} _ {\\text {a v e r a g e (s} ^ {\\mathrm {a v g}} - \\mathrm {s} ^ {\\mathrm {n b r}} \\text {)}}) \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.756, + 0.469, + 0.789 + ], + "angle": 0, + "content": "where \\(|\\mathcal{N}|_{k^{-}}\\) denotes the number of negative pairs in \\(\\mathcal{N}\\) where one sample of each negative pair must have label \\(k\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.798, + 0.469, + 0.844 + ], + "angle": 0, + "content": "Based on the theorems, when the neighborhood size is sufficiently large, considering both density metrics effectively encapsulates both class-specific TPR and TNR within" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.304 + ], + "angle": 0, + "content": "this neighbourhood. As open-world threshold calibration aims to balance the TPR and TNR trade-off for unknown test distributions, it is crucial to capture both aspects to improve within-class and cross-class connectivity predictions. Furthermore, the class-specific nature of these metrics grants them the versatility to adapt to varying class compositions. In Sec. 4.3, we provide an ablation study comparing the use of a single density metric versus both densities, where jointly predicting both densities along with connectivity yields better calibration performance. Thus, we introduce predictions of both density metrics, \\( s^{\\mathrm{avg}} \\) and \\( s^{\\mathrm{nbr}} \\), as auxiliary tasks to enhance the generalization of connectivity prediction. This leads to the following learning objective for training OpenGCN:" + }, + { + "type": "equation", + "bbox": [ + 0.563, + 0.315, + 0.892, + 0.351 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {o v e r a l l}} = \\underbrace {\\mathcal {L} _ {\\text {c o n n}}} _ {\\text {m a i n t a s k}} + \\underbrace {\\lambda \\cdot \\left(\\mathcal {L} _ {s ^ {\\mathrm {n b r}}} + \\mathcal {L} _ {s ^ {\\mathrm {a v g}}}\\right)} _ {\\text {a u x i l i a r y t a s k}} \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.362, + 0.892, + 0.437 + ], + "angle": 0, + "content": "where \\(\\mathcal{L}_{\\mathrm{conn}}\\) is the balanced cross-entropy loss for pairwise edge connectivity and \\(\\mathcal{L}_{s^{\\mathrm{nbr}}}\\) and \\(\\mathcal{L}_{s^{\\mathrm{avg}}}\\) are the mean squared error losses for \\(s^{\\mathrm{nbr}}\\) and \\(s^{\\mathrm{avg}}\\), respectively. Specifically, we define \\(\\mathcal{L}_{\\mathrm{conn}}\\) as follows to ensure equal importance for both within-class and cross-class connectivities:" + }, + { + "type": "equation", + "bbox": [ + 0.515, + 0.445, + 0.891, + 0.507 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {c o n n}} = \\frac {\\sum_ {i , j \\in V} 1 _ {y _ {i} = y _ {j}} \\cdot \\log \\left(p _ {i j}\\right)}{\\sum_ {i , j \\in V} 1 _ {y _ {i} = y _ {j}}} + \\frac {\\sum_ {i , j \\in V} 1 _ {y _ {i} \\neq y _ {j}} \\cdot \\log \\left(1 - p _ {i j}\\right)}{\\sum_ {i , j \\in V} 1 _ {y _ {i} \\neq y _ {j}}} \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.508, + 0.825, + 0.523 + ], + "angle": 0, + "content": "Meanwhile, \\(\\mathcal{L}_{s^{\\mathrm{nbr}}}\\) and \\(\\mathcal{L}_{s^{\\mathrm{avg}}}\\) can be expressed as:" + }, + { + "type": "equation", + "bbox": [ + 0.512, + 0.533, + 0.891, + 0.574 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {s ^ {\\text {a v g}}} = \\frac {\\sum_ {i \\in V} \\left(s _ {i} ^ {\\text {a v g}} - \\hat {s} _ {i} ^ {\\text {a v g}}\\right) ^ {2}}{| V |}, \\quad \\mathcal {L} _ {s ^ {\\text {n b r}}} = \\frac {\\sum_ {i \\in V} \\left(s _ {i} ^ {\\text {n b r}} - \\hat {s} _ {i} ^ {\\text {n b r}}\\right) ^ {2}}{| V |} \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.584, + 0.892, + 0.614 + ], + "angle": 0, + "content": "where \\(V\\) represents the node vertices in the graph data, and \\(\\hat{s}_i\\) is the estimated density for each sample based on \\(p_{ij}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.615, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Two-stage Training for Adaptability The DML embedding model, trained on \\(D_{\\mathrm{train}}\\) (closed-set examples), tends to produce more compact embeddings for these examples than those of open-world classes. If OpenGCN is trained solely on \\(D_{\\mathrm{train}}\\), its ability to generalize to the open-world scenarios will be limited. On the other hand, if OpenGCN is trained solely on \\(D_{\\mathrm{cal}}\\), its knowledge may be very narrow since the calibration dataset is typically small and lacks diverse concepts. To tackle this, we borrow established experience in domain generalization and adaptation [11, 21, 48], and adopt a two-stage training strategy. First, we pretrain OpenGCN on \\(D_{\\mathrm{train}}\\), which consists of a large collection of closed-set examples. After this, we reset the 2-layer MLP while keeping the other parameters frozen. Subsequently, we fine-tune the MLP on \\(D_{\\mathrm{cal}}\\), a small open-world calibration dataset containing disjoint classes to the test data, to adapt the pretrained model to open-world scenarios. In Sec. 4.3, we conduct an ablation study to provide further support for this two-stage training approach. We choose to" + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.85, + 0.469, + 0.902 + ], + "angle": 0, + "content": "2. Although the original definition of \\( s^{\\mathrm{avg}} \\) in [52] requires a neighborhood size that includes all samples belonging to a given class, it can be shown by stochastic convergence of random variables that our definition is a tight approximation for [52] when \\( |\\mathcal{N}_i| \\) is sufficiently large." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "17101" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.213 + ], + "angle": 0, + "content": "fine-tune only the MLP based on the practical observations that \\( D_{\\mathrm{cal}} \\) is typically limited in size, and fine-tuning the entire model on such a small dataset may lead to overfitting. It is worth reiterating that this approach does not require additional training data, as the closed-set data is already in place for training the DML embedding model, and the separate open-world calibration dataset is required for conventional inductive posthoc calibration methods as well." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.225, + 0.296, + 0.243 + ], + "angle": 0, + "content": "4. Experiment and Result" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.25, + 0.47, + 0.312 + ], + "angle": 0, + "content": "We experiment on public recognition benchmarks including iNaturalist-2018 [44], CUB-200 [47] and Cars-196 [23]. Below, we outline our setup and present the results. Further experiments can be found in the supplementary materials." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.319, + 0.391, + 0.336 + ], + "angle": 0, + "content": "4.1. Dataset and Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.342, + 0.47, + 0.508 + ], + "angle": 0, + "content": "Datasets To simulate real-world testing environments, we consider three calibration scenarios: SameDist, ShiftDist and DiffDist. The SameDist scenario involves cases where \\( D_{\\mathrm{cal}} \\) and \\( D_{\\mathrm{test}} \\) share similar distance distributions, the ShiftDist scenario accounts for test-time non-semantic distance distribution shifts, and the DiffDist scenario represents out-of-distribution calibration, where \\( D_{\\mathrm{cal}} \\) and \\( D_{\\mathrm{test}} \\) have very different distance distributions. Note that in all three scenarios, we adhere to the open-world setting where \\( C_{\\mathrm{train}} \\cap C_{\\mathrm{cal}} = C_{\\mathrm{train}} \\cap C_{\\mathrm{test}} = C_{\\mathrm{cal}} \\cap C_{\\mathrm{test}} = \\emptyset \\). Below, we elaborate on the setup for each calibration scenario:" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.509, + 0.47, + 0.674 + ], + "angle": 0, + "content": "- SameDist For iNaturalist, the training and testing classes are distinct, so we directly use the training partition as \\( D_{\\text{train}} \\). To create \\( D_{\\text{cal}} \\), we randomly select \\( 10\\% \\) of the test classes, leaving the remaining classes for \\( D_{\\text{test}} \\). For CUB and Cars, where there is overlap between training and testing classes, we divide them into train / cal / test subsets. The train set comprises the first half of the class indices, while the cal / test sets are randomly chosen from the remaining classes with a \\( 1/9 \\) ratio. As \\( D_{\\text{cal}} \\) and \\( D_{\\text{test}} \\) are randomly split from the same dataset, they are expected to have similar distance distributions." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.675, + 0.47, + 0.765 + ], + "angle": 0, + "content": "- ShiftDist We consider 13 common image corruption and perturbation types, including noise, blur, weather, and digital distortions, to assess the robustness of the calibration methods under varied adversities. We follow the setups in [17] and apply the changes to \\( D_{\\mathrm{test}} \\) only, while leaving \\( D_{\\mathrm{cal}} \\) and \\( D_{\\mathrm{train}} \\) unchanged." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.765, + 0.47, + 0.902 + ], + "angle": 0, + "content": "- DiffDist To induce significant distance distribution shifts between \\( D_{\\mathrm{cal}} \\) and \\( D_{\\mathrm{test}} \\), we employ the following treatments. For iNaturalist, characterized by a long-tailed distribution, we divide its test classes into two sets based on cluster size, each containing approximately the same number of images. For calibration purposes, we use the set with a higher number of images per class (\"head\" set, denoted as \\( D_{\\mathrm{head}} \\)) as \\( D_{\\mathrm{cal}} \\) and the set with fewer images per class (\"tail\" set, denoted as \\( D_{\\mathrm{tail}} \\)) as \\( D_{\\mathrm{test}} \\) to simu" + }, + { + "type": "list", + "bbox": [ + 0.077, + 0.509, + 0.47, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "table_caption", + "bbox": [ + 0.571, + 0.09, + 0.822, + 0.103 + ], + "angle": 0, + "content": "Table 1. Detailed statistics of the datasets." + }, + { + "type": "table", + "bbox": [ + 0.516, + 0.111, + 0.885, + 0.324 + ], + "angle": 0, + "content": "
SettingDatasetPartition# img# cls# img/cls
SameDistCarsDtrain7,9619881.2
Dcal8661086.6
Dtest7,3568883.6
CUBDtrain5,8029958.6
Dcal5991059.9
Dtest5,3859159.2
iNatDtrain324,4185,69057.0
Dcal12,61324551.5
Dtest123,0472,20755.8
ShiftDistCarsSameDist except for corruption on Dtest
DiffDistiNatDtrainiNat SameDist Dtrain
Dhead70,057200350.3
Dtail66,0362,25229.3
CarsSameDist except for sketchifying Dtest
iNat/CUB (cross dataset)DtrainiNat SameDist Dtrain
DcaliNat SameDist Dcal
DtestEntire CUB dataset
" + }, + { + "type": "text", + "bbox": [ + 0.51, + 0.345, + 0.892, + 0.451 + ], + "angle": 0, + "content": "late a calibration for the long tail scenario. In addition, we also explore two out-of-domain calibration scenarios. First, for Cars, we transform \\( D_{\\mathrm{test}} \\) into sketches while leaving \\( D_{\\mathrm{train}} \\) and \\( D_{\\mathrm{cal}} \\) untouched. Second, we consider cross-dataset calibration, where the OpenGCN model is pretrained and fine-tuned on iNaturalist (general natural species images) but evaluated on CUB (bird images)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.452, + 0.892, + 0.481 + ], + "angle": 0, + "content": "Evaluation Metrics For a comprehensive evaluation, we consider two approaches to assess calibration performance:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.482, + 0.892, + 0.602 + ], + "angle": 0, + "content": "- Global Evaluation: Since we define open-world threshold calibration as the accurate prediction of both TPR and TNR at each distance threshold to meet specific TPR or TNR performance requirements of diverse test-time users, it is natural to employ the combined Mean Absolute Errors (MAE) for both TPR and TNR predictions across the entire distance range as our evaluation metric. Formally, this metric can be expressed as:" + }, + { + "type": "equation", + "bbox": [ + 0.535, + 0.611, + 0.891, + 0.647 + ], + "angle": 0, + "content": "\\[\n\\mathrm {M A E} _ {\\text {c o m b}} = \\frac {1}{2} \\int_ {0} ^ {2} \\left(| \\hat {\\mathrm {T P R}} (\\mathrm {d}) - \\mathrm {T P R} (\\mathrm {d}) | + \\right. \\tag {13}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.673, + 0.649, + 0.843, + 0.667 + ], + "angle": 0, + "content": "\\[\n\\left. \\left| \\mathrm {T N R} (\\mathrm {d}) - \\mathrm {T N R} (\\mathrm {d}) \\right|\\right) d \\mathrm {d}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.675, + 0.892, + 0.781 + ], + "angle": 0, + "content": "- Point-wise Evaluation: We first set a performance target and compute the optimal distance threshold, denoted as \\(\\hat{d}^{\\mathrm{opt}}\\), based on the TPR or TNR estimations. We then compute the Absolute Error (AE) between the actual performance at \\(\\hat{d}^{\\mathrm{opt}}\\) and the target, denoted as \\(\\mathrm{AE}_{\\mathrm{TPR}} = |\\mathrm{TPR}(\\hat{d}^{\\mathrm{opt}}) - \\mathrm{TPR}_{\\mathrm{target}}|\\) and \\(\\mathrm{AE}_{\\mathrm{TNR}} = |\\mathrm{TNR}(\\hat{d}^{\\mathrm{opt}}) - \\mathrm{TNR}_{\\mathrm{target}}|\\) for TPR and TNR, respectively." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.781, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Baseline Methods We consider the most representative inductive posthoc calibration methods including Platt Scaling [37], Histogram Calibration [53], Isotonic Calibration [54] and Beta Calibration [24]. Additionally, we explore pseudolabel-based baselines, including traditional clustering methods such as DBSCAN [13] and the state-of-the-art method in GNN-based clustering, HiLANDER [49]. For clustering-based methods, we follow" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17102" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.895, + 0.133 + ], + "angle": 0, + "content": "Table 2. Evaluation in the SameDist scenario using pointwise metrics of \\( \\mathrm{AE}_{\\mathrm{TPR}} \\) (optimize for TPR) and \\( \\mathrm{AE}_{\\mathrm{TNR}} \\) (optimize for TNR). The smaller the metric, the better. For each dataset, the best and second best results are marked in Red and Blue, respectively. Shading in the Table: Gray for posthoc calibration baselines, Cyan for clustering baselines, and Blue for our OpenGCN method. Best viewed in color." + }, + { + "type": "table", + "bbox": [ + 0.081, + 0.139, + 0.894, + 0.248 + ], + "angle": 0, + "content": "
MethodOptimize for TPR=80%Optimize for TPR=90%Optimize for TNR=80%Optimize for TNR=90%Rank
CarsCUBInatCarsCUBInatCarsCUBInatCarsCUBInat
Platt scaling [37]1.35%5.10%6.08%0.44%2.63%4.63%2.83%2.02%7.54%2.93%6.49%0.92%6
Beta calibration [24]1.13%5.16%5.51%0.02%2.91%3.26%2.94%1.41%7.57%2.78%6.43%0.93%5
Isotonic regression [54]0.82%5.28%4.53%0.90%2.56%3.54%1.94%1.00%5.78%1.26%4.65%0.65%3
Histogram Calibration [53]0.82%5.28%4.53%0.90%2.56%3.54%1.94%1.00%5.78%1.26%4.65%0.65%4
DBSCAN [13]43.11%18.87%0.45%34.57%9.18%1.85%4.09%13.77%12.90%1.60%9.32%9.32%7
Hi-LANDER [49]3.44%1.36%10.54%2.02%0.93%7.00%0.06%0.38%2.35%0.10%2.20%0.21%2
OpenGCN (ours)0.33%0.74%1.59%0.72%1.41%2.37%0.61%0.09%0.74%0.58%0.72%0.10%1
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.272, + 0.47, + 0.317 + ], + "angle": 0, + "content": "their original clustering decoding inference workflows to estimate pseudo labels, and use these pseudo labels to compute \\(\\mathrm{TPR}_{\\mathrm{test}}\\) and \\(\\mathrm{TNR}_{\\mathrm{test}}\\) for finding \\(d^{\\mathrm{opt}}\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.318, + 0.474, + 0.562 + ], + "angle": 0, + "content": "Implementation Details In all experiments, we train ResNet-50 models with 128-dimensional embeddings on \\( D_{\\mathrm{train}} \\) using the setups in [6]. The embedding models are then used to extract the embeddings for \\( D_{\\mathrm{train}} \\), \\( D_{\\mathrm{cal}} \\) and \\( D_{\\mathrm{test}} \\). For training OpenGCN, as implied in Theorems 1 and 2, the neighborhood size needs to be sufficiently large to encapsulate both intra-class and inter-class representation structures. Thus, we use a batch sizes of 256 for graph construction during training. We use the Adam optimizer [22] with a cosine annealing schedule [30]. For traditional calibration methods, we use the official codebase from [25] to map the ground truth TPR (or TNR) as a function of the distance threshold from \\( D_{\\mathrm{train}} \\) to \\( D_{\\mathrm{cal}} \\). When doing point-wise evaluation, the optimal distance threshold \\( d^{\\mathrm{opt}} \\) is solved with grid search at a grid size of 0.01. Further details are provided in the supplementary materials." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.574, + 0.26, + 0.59 + ], + "angle": 0, + "content": "4.2. Evaluation Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.599, + 0.471, + 0.903 + ], + "angle": 0, + "content": "SameDist Calibration We present the global and pointwise evaluation results for the SameDist scenario in Tab. 3 and Tab. 2, respectively. For pointwise evaluation, we evaluate at multiple target values (TPR=80%, 90% and TNR=80%, 90%) to provide a comprehensive assessment. Our results reveal that no single calibration method consistently excels across all distance thresholds and datasets. However, on average, OpenGCN achieves the highest rank. This underscores the importance of TTC in open-world scenarios, where calibration is conducted based on the characteristics of \\( D_{\\mathrm{test}} \\) rather than relying on a calibration dataset that may not accurately represent \\( D_{\\mathrm{test}} \\). Additionally, the global metrics in Tab. 3 show that, compared to the best baseline method, OpenGCN significantly reduces global error rates by 59.30%, 66.49%, and 59.15% for Cars, CUB, and iNaturalist, respectively. Among the baseline methods, we observe that DBSCAN performs worse than the traditional posthoc calibration methods, while Hi-LANDER outperforms traditional posthoc methods on Cars and CUB but underperforms on iNaturalist. In contrast, OpenGCN con" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.27, + 0.895, + 0.34 + ], + "angle": 0, + "content": "Table 3. Evaluation in the SameDist scenario using the global error metric of \\(\\mathrm{MAE}_{\\mathrm{comb}}\\). For each benchmark, the best and second best results are marked in Red and Blue, respectively. We also report the improvement in error reduction of OpenGCN over the best baseline method. Best viewed in color." + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.347, + 0.892, + 0.457 + ], + "angle": 0, + "content": "
MethodCarsCUBiNatRank
Platt scaling1.55e-23.59e-21.23e-26
Beta calibration1.53e-23.59e-21.18e-25
Isotonic regression1.38e-23.61e-21.18e-23
Histogram calibration1.38e-23.62e-21.18e-24
DBSCAN1.02e-11.10e-13.65e-27
Hi-LANDER1.29e-21.94e-22.14e-22
OpenGCN (ours)5.25e-36.50e-34.82e-31
Imp. over top baseline ↑59.30%66.49%59.15%69.14% (avg.)
" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.487, + 0.816, + 0.503 + ], + "angle": 0, + "content": "sistently performs well across all three datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.505, + 0.892, + 0.734 + ], + "angle": 0, + "content": "ShiftDist Calibration In Tab. 4, we report the global error metric \\(\\mathrm{MAE}_{\\mathrm{comb}}\\) for each corruption type across various calibration methods. Among the baseline methods, Isotonic Regression and Histogram Calibration appear to be the most effective in the presence of image corruptions. However, it is evident that OpenGCN consistently outperform these baseline methods across all corruption types, achieving an average error reduction of \\(55.03\\%\\) compared to the best baseline method. This robust performance against image corruptions can be attributed to the model's pretraining stage, where it was exposed to closed-set data with similar types of corruptions. Additionally, it is observed that, among the various corruption categories, OpenGCN exhibits the most improvement in the weather category, while showing the least improvement in the blur category." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.903 + ], + "angle": 0, + "content": "DiffDist Calibration We present the DiffDist calibration results in Tab. 5. As observed, in this scenario characterized by a substantial shift in distance distributions between \\( D_{\\mathrm{cal}} \\) and \\( D_{\\mathrm{test}} \\), all calibration methods display elevated errors compared to the SameDist scenario. However, OpenGCN demonstrates superior performance compared to the other calibration methods in both out-of-domain settings (sketch and cross-dataset) and the long-tail calibration setting, achieving an average relative reduction in the global error \\( \\mathrm{MAE}_{\\mathrm{comb}} \\) of \\( 43.99\\% \\). In particular, we observe significant improvement in the cross-dataset setting (pretrained" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "17103" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.895, + 0.119 + ], + "angle": 0, + "content": "Table 4. Evaluation on the Cars-196 dataset in the ShiftDist scenario across 13 common corruption and perturbation types using combined global error metric of \\(\\mathrm{MAE}_{\\mathrm{comb}}\\). The best results are marked in Red." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.125, + 0.892, + 0.278 + ], + "angle": 0, + "content": "
MethodNoiseBlurWeatherDigitalRank
GaussShotImpulseDefocusMotionZoomSnowFogBrightContrastElasticPixelJPEG
Platt scaling2.95e-22.99e-23.41e-22.66e-22.62e-25.02e-24.24e-24.37e-22.16e-24.61e-22.16e-22.24e-22.03e-24
Beta calibration2.94e-22.97e-23.41e-22.67e-22.69e-25.06e-24.32e-24.37e-22.18e-24.61e-22.20e-22.23e-22.02e-25
Isotonic regression2.88e-22.85e-23.38e-22.37e-22.31e-24.85e-24.07e-24.34e-21.83e-24.59e-21.85e-22.03e-21.80e-22
Histogram calibration2.88e-22.85e-23.38e-22.37e-22.31e-24.85e-24.07e-24.34e-21.83e-24.59e-21.85e-22.03e-21. 80e-23
DBSCAN4.96e-26.02e-27.79e-29.81e-21.13e-11.22e-11.19e-14.02e-29.27e-24.53e-21.09e-11.04e-18.21e-27
Hi-LANDER7.65e-26.30e-26.59e-23.98e-25.33e-24.48e-25.94e-27.16e-25.09e-29.45e-24.42e-29.48e-26.91e-26
OpenGCN (ours)1.33e-25.87e-31.66e-21.50e-21.71e-23.92e-21.42e-27.32e-36.73e-37.08e-35.34e-31.15e-21.68e-21
Imp. over top baseline ↑53.82%79.40%50.89%36.71%25.97%12.50%65.11%81.79%63.22%84.37%71.14%43.35%6.67%55.03% (avg.)
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.297, + 0.471, + 0.326 + ], + "angle": 0, + "content": "Table 5. Evaluation in the DiffDist scenario using the global error metric \\(\\mathrm{MAE}_{\\mathrm{comb}}\\). The best results are highlighted in Red." + }, + { + "type": "table", + "bbox": [ + 0.083, + 0.332, + 0.468, + 0.429 + ], + "angle": 0, + "content": "
MethodCars: SketchCUB: Cross-datasetiNat: Longtail
Platt scaling1.08e-11.15e-12.09e-2
Beta calibration1.08e-11.15e-12.12e-2
Isotonic regression1.08e-11.15e-12.11e-2
Histogram Calibration1.08e-11.15e-12.11e-2
DBSCAN5.16e-21.60e-17.21e-2
Hi-LANDER6.67e-21.30e-16.26e-2
OpenGCN (ours)3.54e-21.42e-21.82e-2
Imp. over top baseline ↑31.40%87.65%12.92%
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.442, + 0.47, + 0.471 + ], + "angle": 0, + "content": "Table 6. Impact of multi-task learning on global error metric \\(\\mathrm{MAE}_{\\mathrm{comb}}\\) on iNaturalist-2018. We use \\(\\lambda = 10\\) for all experiments." + }, + { + "type": "table", + "bbox": [ + 0.083, + 0.478, + 0.468, + 0.515 + ], + "angle": 0, + "content": "
Best baselineOpenGCN loss ablations
Lconn+λ·Lsavg+λ·Lsshr+λ·(Lsavg + Lsshr)
MAEcomb1.18e-26.25e-35.37e-35.12e-34.82e-3
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.527, + 0.47, + 0.571 + ], + "angle": 0, + "content": "Table 7. Impact of fine-tuning on open-world calibration dataset on global error metric \\(\\mathrm{MAE}_{\\mathrm{comb}}\\). PT: pretraining FT: finetuning. Numbers in the bracket show the relative improvement over PT." + }, + { + "type": "table", + "bbox": [ + 0.083, + 0.577, + 0.468, + 0.616 + ], + "angle": 0, + "content": "
MethodCarsCUBiNat
OpenGCN (PT)2.90e-22.52e-23.55e-2
OpenGCN (PT+FT)5.25e-3 (81.9%)6.50e-3 (74.2%)4.82e-3 (86.4%)
" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.641, + 0.47, + 0.686 + ], + "angle": 0, + "content": "and finetuned on the iNaturalist-2018 nature species dataset but tested on the CUB birds dataset), where OpenGCN achieves a notable error reduction of \\(87.65\\%\\)." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.696, + 0.241, + 0.71 + ], + "angle": 0, + "content": "4.3. Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.47, + 0.885 + ], + "angle": 0, + "content": "Importance of Multi-task Learning We assess the impact of multi-task learning on \\(\\mathrm{MAE}_{\\mathrm{comb}}\\). As shown in Tab. 6, compared to predicting connectivity only, employing a single density metric in conjunction with connectivity prediction helps reduce \\(\\mathrm{MAE}_{\\mathrm{comb}}\\) from \\(6.25\\mathrm{e} - 3\\) to \\(5.37\\mathrm{e} - 3\\) for \\(s^{\\mathrm{avg}}\\) and to \\(5.12\\mathrm{e} - 3\\) for \\(s^{\\mathrm{nbr}}\\), respectively. However, by utilizing both density metrics, we further decrease this error to \\(4.82\\mathrm{e} - 3\\). This supports our choice to incorporate both density metrics, allowing us to capture both intra-class compactness and inter-class separation while facilitating information sharing for improved connectivity prediction." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.886, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Importance of Two-stage Training We assess the impact" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.299, + 0.892, + 0.406 + ], + "angle": 0, + "content": "of two-stage training on OpenGCN by comparing \\(\\mathrm{MAE}_{\\mathrm{comb}}\\) before and after fine-tuning on \\(D_{\\mathrm{cal}}\\) across all three benchmarks. The comparison in Tab. 7 reveals significant error reduction of up to \\(86.4\\%\\) after fine-tuning on the open-world calibration dataset. This results supports our choice of two-stage training in adapting the calibration model from the closed-world context to the open-world scenarios." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.419, + 0.628, + 0.435 + ], + "angle": 0, + "content": "5. Conclusions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.444, + 0.892, + 0.806 + ], + "angle": 0, + "content": "In this work, we formally define the open-world threshold calibration problem for DML-based open-world visual recognition systems. To address this problem, we introduce OpenGCN, a GNN-based transductive threshold calibration method designed to enhance adaptability in open-world scenarios. Unlike traditional posthoc calibration methods, OpenGCN does not rely on the common assumption of matching distance distributions between \\(D_{\\mathrm{cal}}\\) and \\(D_{\\mathrm{test}}\\). Instead, it leverages the information of the unlabeled test instances along with learnt calibration rules to predict pairwise connectivity of the test data, via a GNN, to enable effective transductive threshold calibration in open-world scenarios. Our evaluations demonstrate that OpenGCN outperforms both traditional posthoc calibration methods and pseudolabel-based calibration techniques. When assessed using global error metrics, OpenGCN exhibits significant improvements, achieving average error reductions of \\(69.14\\%\\), \\(40.85\\%\\), and \\(22.58\\%\\) for SameDist, ShiftDist, and DiffDist calibration scenarios, respectively, compared to the best baseline method. Overall, our results underscore OpenGCN's robustness across different distance distribution patterns between \\(D_{\\mathrm{cal}}\\) and \\(D_{\\mathrm{test}}\\), highlighting its practical applicability for threshold calibration in DML-based open-world recognition applications." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.806, + 0.895, + 0.897 + ], + "angle": 0, + "content": "Limitations OpenGCN is computationally less efficient and more susceptible to over-parameterization compared to traditional posthoc calibration methods. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 16489-16498, 2021." + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.772 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17106" + } + ] +] \ No newline at end of file diff --git a/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_origin.pdf b/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..4ede077683a06beed94c65cf55028ae22c235fb4 --- /dev/null +++ b/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/487c5882-cae9-4d51-9135-8fd112247491_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:0b74af509e274189f3f14fcc7136d4f42606975ffc36eac0c876c3669acef98d +size 3468405 diff --git a/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/full.md b/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/full.md new file mode 100644 index 0000000000000000000000000000000000000000..64564154eb89ec143fbdc1e61a01cf9ef3ae54a6 --- /dev/null +++ b/2024/Learning for Transductive Threshold Calibration in Open-World Recognition/full.md @@ -0,0 +1,319 @@ +# Learning for Transductive Threshold Calibration in Open-World Recognition + +Qin Zhang $^{1}$ , Dongsheng An $^{1}$ , Tianjun Xiao $^{2}$ , Tong He $^{2}$ , Qingming Tang $^{3}$ , Ying Nian Wu $^{1}$ , Joseph Tighe $^{1}$ , Yifan Xing $^{1}$ + +AWS AI Labs + +2 Amazon Web Services + +3 Alexa AI + +{qzaamz, andongsh, tianjux, htong, qmtang, wunyin, yifax}@amazon.com, jtighe@cs.unc.edu + +# Abstract + +In deep metric learning for visual recognition, the calibration of distance thresholds is crucial for achieving desired model performance in the true positive rates (TPR) or true negative rates (TNR). However, calibrating this threshold presents challenges in open-world scenarios, where the test classes can be entirely disjoint from those encountered during training. We define the problem of finding distance thresholds for a trained embedding model to achieve target performance metrics over unseen open-world test classes as open-world threshold calibration. Existing posthoc threshold calibration methods, reliant on inductive inference and requiring a calibration dataset with a similar distance distribution as the test data, often prove ineffective in open-world scenarios. To address this, we introduce OpenGCN, a Graph Neural Network-based transductive threshold calibration method with enhanced adaptability and robustness. OpenGCN learns to predict pairwise connectivity for the unlabeled test instances embedded in a graph to determine its TPR and TNR at various distance thresholds, allowing for transductive inference of the distance thresholds which also incorporates test-time information. Extensive experiments across open-world visual recognition benchmarks validate OpenGCN's superiority over existing posthoc calibration methods for open-world threshold calibration. + +# 1. Introduction + +In deep metric learning (DML) for visual recognition, distance calibration plays a critical role in determining the user-perceived model performance. Unlike confidence calibration in closed-set classification settings which focuses on aligning confidence probabilities with true likelihood of correctness in a fixed label space [27, 33], distance calibration in DML aims to pinpoint an optimal distance threshold to achieve a target true positive rate (TPR) or true negative rate (TNR) for diverse test-time distributions [26]. This calibration is vital because, even with a highly effic + +![](images/0833c74c5f6b823bc13deeb6c08f8e11ec5274da21fae2d17638ab8e420e0acf.jpg) + +![](images/ea218448e17b1823c2b75facddb837bb7ecb56d876a0fdffa09016dff59ee063.jpg) +Figure 1. This figure illustrates the open-world threshold calibration problem. In open-world recognition, the embedding model is trained on closed-set classes but tested on distinct open-world classes. When applying the model to open-world classes, it often produces less compact embeddings than those encountered during training, necessitating the calibration of the distance threshold for achieving the desired TPR and TNR trade-off. However, the absence of prior knowledge about open-world test classes and distributions makes it challenging to find the optimal distance threshold, denoted as $d^{\mathrm{opt}}$ . Best viewed in color. + +tive embedding model, an inappropriate distance threshold can significantly degrade user experience. The issue becomes more pronounced in open-world recognition, where the embedding model, trained on a closed set of classes (e.g., dog, cat, bird), is tested on an open collection of unseen classes (e.g., wolf, sheep, mouse, ...). These open-world classes may have very different intra-class and interclass representation structures, typically being less compact, compared to the training classes. In such open-world scenarios, where prior knowledge about test-time classes and distributions are absent, calibrating the distance threshold becomes a challenging task, as illustrated in Fig. 1. We term this task of distance calibration in an open-world scenario as open-world threshold calibration. + +Existing posthoc calibration methods, such as [16, 24, 34, 37, 53, 54], typically utilize a fully-labeled calibration dataset that has a similar distribution as the test data [35, 42, 56] to learn general calibration rules for test distributions. However, this approach has a key limitation: it heavily relies on the assumption of identical distributions between test and calibration data for effective calibration. In open-world scenarios, this assumption becomes unreliable, posing significant challenges to threshold calibration, including: + +1. The open-world challenge The test data may exclusively contain open-world classes, which exhibit different relationships between distance thresholds and TPR or TNR compared to those encountered during the embedding model training [26]. Meanwhile, test data composition and quality can vary significantly, potentially exhibiting substantial class imbalances and data corruptions. +2. Non-stationary data In real-world testing environments, the test distribution can be infinitely varied and highly dynamic, rendering the assumption of similar distribution between calibration and test data obsolete. +3. Deployment Scalability Real-world systems require calibration methods that can adapt to diverse user distributions without individual recalibration. Existing methods lack deployment scalability as they frequently require dedicated calibration data and the creation of specific calibration functions for each user. Imagine a scenario with 1,000 user profiles with distinct classes and data distributions – creating and deploying custom calibration datasets and functions for each would be impractical. + +Addressing these challenges is crucial for the reliability of DML-based open-world recognition systems. Current posthoc calibration methods are ill-suited for this purpose, as they are inherently inductive and prone to failure when confronted with test data with different distance distributions from the calibration data. To address this, we adopt a fresh perspective on distance threshold calibration, treating it as a transductive inference process, where the calibration method incorporates the information of the unlabeled test samples along with the learned calibration rules to make better threshold estimations. Our proposed method, OpenGCN, employs a Graph Neural Network (GNN), known for its generalization capabilities [3, 5, 9, 10, 49, 51, 52], to jointly predict pairwise connectivity and two instance-wise representation densities for test data, where the predicted pairwise connectivity is used to compute the TPR and TNR of the test data at each distance threshold to enable transductive threshold calibration. OpenGCN is tailored for the task of open-world threshold calibration through a carefully crafted learning process, which accurately estimates the mapping between performance metrics and pairwise distance thresholds in open-world scenarios. In particular, the multi-task learning of connectivities and representation densities facilitates infor + +mation sharing, which helps enhance the model's generalization to open-world scenarios [49, 52]. Additionally, our joint prediction design incorporates two types of density metrics, addressing both intra-class and inter-class connectivity estimations. This approach, as opposed to using a single density metric, is shown to enhance calibration performance, as illustrated in Sec. 4.3. Furthermore, OpenGCN adopts a two-stage training process. It pre-trains on a large closed-world dataset, followed by fine-tuning on a small open-world calibration dataset with disjoint classes to both the closed-world and test data, to adapt the model to be aware of the open-world context. By these design choices, OpenGCN sidesteps the requirement for calibration data to have a similar distance distribution1 as the test data, significantly improving calibration performance in open-world scenarios. To summarize, our contributions are as follows: + +1. We are, to the best of our knowledge, the first to formally define the open-world threshold calibration problem. +2. We propose Transductive Threshold Calibration (TTC), a new threshold calibration paradigm that diverges from traditional inductive posthoc calibration methods, which does not rely on the assumption of similar distance distributions between the test and calibration data. +3. We introduce OpenGCN, a GNN-based TTC method tailored for open-world threshold calibration against diverse test distributions. We build comprehensive evaluation protocols with and without distance distribution shifts to assess OpenGCN's performance. The evaluation result underscores OpenGCN's effectiveness and robustness in real-world testing environments. + +# 2. Problem Definition and Related Works + +We first introduce some notations and formalize the open-world threshold calibration problem. Let $D_{\mathrm{labled}}$ be a labeled dataset consisting of two disjoint subsets: $D_{\mathrm{train}}$ and $D_{\mathrm{cal}}$ , and let $D_{\mathrm{test}}$ be an unlabeled dataset. In open-world scenarios, the class sets of $D_{\mathrm{train}}$ , $D_{\mathrm{cal}}$ , and $D_{\mathrm{test}}$ , denoted as $C_{\mathrm{train}}$ , $C_{\mathrm{cal}}$ , and $C_{\mathrm{test}}$ , are disjoint, i.e., $C_{\mathrm{train}} \cap C_{\mathrm{cal}} = C_{\mathrm{train}} \cap C_{\mathrm{test}} = C_{\mathrm{cal}} \cap C_{\mathrm{test}} = \emptyset$ . The goal of open-world threshold calibration is to find a suitable distance threshold that achieves the target TPR and TNR for $D_{\mathrm{test}}$ , given an embedding model trained on $D_{\mathrm{train}}$ . We approach this as a constrained optimization task, with the objective being maximizing the metric of interest. Take optimizing for TNR with a minimum TPR requirement as an example, this problem can be formulated as follows: + +$$ +\underset {d} {\text {m a x i m i z e}} \mathrm {T N R} _ {\text {t e s t}}, \quad \text {s u b j e c t t o T P R} _ {\text {t e s t}} (d) \geq \alpha \tag {1} +$$ + +where $d$ is the distance threshold, and $\alpha$ is the minimum performance requirement for $\mathrm{TPR}_{\mathrm{test}}$ . Due to the inherent + +trade-off between TPR and TNR, the objective in Eq. (1) is equivalent to finding an optimal distance threshold $d^{\mathrm{opt}}$ for which $\mathrm{TPR}_{\mathrm{test}}(d^{\mathrm{opt}}) = \alpha$ . To solve this, we express $\mathrm{TPR}_{\mathrm{test}}$ and $\mathrm{TNR}_{\mathrm{test}}$ at a distance threshold $d$ as follows: + +$$ +\operatorname {T P R} _ {\text {t e s t}} (d) = \sum_ {i, j \in D _ {\text {t e s t}}} 1 _ {y _ {i} = y _ {j}} \cdot 1 _ {d _ {i j} < d} / \sum_ {i, j \in D _ {\text {t e s t}}} 1 _ {y _ {i} = y _ {j}} \tag{2} +$$ + +$$ +\mathrm {T N R} _ {\text {t e s t}} (d) = \sum_ {i, j \in D _ {\text {t e s t}}} 1 _ {y _ {i} \neq y _ {j}} \cdot 1 _ {d _ {i j} > d} / \sum_ {i, j \in D _ {\text {t e s t}}} 1 _ {y _ {i} \neq y _ {j}} \tag {3} +$$ + +where $d_{ij}$ is the L2 distance between the embeddings of samples $i$ and $j$ , and $y_i$ is the label for sample $i$ . The symbol $1_{\text{condition}}$ represents the indicator function which equals 1 if the condition is met, otherwise 0. With $\mathrm{TPR}_{\text{test}}$ and $\mathrm{TNR}_{\text{test}}$ calculated at each distance threshold, we can optimize for the optimal distance threshold $d^{\text{opt}}$ to achieve the target performance metrics, as described in Eq. (1). + +# 2.1. Related Works + +Open-world Recognition [29] aims to learn discriminative representations that align distances between representations with their semantic similarities. This allows for effective generalization to diverse, previously unseen open-world classes during testing, setting it apart from closed-set classification where training and testing classes are the same. Popular recognition losses [6, 12, 36] typically encourage compact intra-class representations, promoting strong affinity within each class while maintaining separation from other classes. However, it is widely observed that these losses tend to produce highly varied intra-class and inter-class representation structures across classes and distributions [32, 39, 55], necessitating threshold calibration to ensure consistent performance across diverse users. + +Posthoc Calibration We focus on posthoc calibration methods which are more relevant to our research. Generally, existing posthoc calibration methods fall into two categories: (i) non-parametric methods like isotonic regression [54] and histogram binning [34, 53]; and (ii) parametric methods such as Platt scaling [37] and temperature scaling [16]. These methods are inductive: they rely on a holdout calibration set with similar distribution as the test data to derive general rules for fine-tuning the decision threshold, aiming to align the performance metrics with a predefined target. While effective in closed-set classification, these methods struggle in scenarios with significant distribution differences between test and calibration data. Diverging from traditional methods, another group of methods such as conformal prediction [4, 15, 40, 43] or Prediction-Powered Inference [1] emphasize confidence coverage guarantees, and has been shown applicable even beyond the setting of exchangeable data [14, 15]. However, these methods inherently assume a closed-set setting, making them unsuitable for open-world scenarios. Currently, open-world posthoc calibration remains largely under-explored. + +![](images/acac3cbc24540cb2dc93d0a80a195f4838a7e382d9612d09e952340800d46a46.jpg) +Figure 2. This figure distinguishes between (left) inductive and (right) transductive threshold calibration methods in open-world scenarios with disjoint test-time classes. Inductive methods rely on a labeled hold-out dataset with the same distance distribution as the test data to learn general calibration rules. Transductive methods, however, also use the test information for more specific calibration, as indicated by the red arrow. Best viewed in color. + +Transductive Inference Transduction is the reasoning from observed, specific (training) cases to specific (test) cases [45]. Such an approach is desirable as it alleviates the problem of overfitting on limited support set since information from the test data is also used for inference. This is also known as increasing VC-dimension for structural risk minimization in classical statistical learning [19]. Recently, a large body of works investigated transductive inference for few-shot and open-world recognition tasks [8, 18, 28, 38], where significant increases in performances have been reported. Given the relevance of these tasks, it is worthwhile to reconsider existing inductive posthoc calibration methods for distance threshold calibration in open-world scenarios. + +# 3. Methodology + +# 3.1. Transductive Threshold Calibration + +Traditional calibration methods are inherently inductive - they rely on a calibration dataset to learn general calibration rules under the assumption of identically distributed data. However, in open-world scenarios, this assumption seldom holds, as the test distribution is unknown and can be infinitely varied and highly dynamic. To improve calibration specificity in the open world, it is natural to adopt a transductive approach, where the TPR and TNR estimations directly involve the test data, rather than relying on a separate calibration dataset that might not accurately represent the test data. As illustrated in Fig. 2, a transductive approach allows the calibration model to "see" the unlabeled test data when deciding on the distance threshold, contrasting with the traditional inductive methods which are "blind" to the test data. We term this approach as Transductive Threshold Calibration (TTC), and the traditional inductive calibration methods as Inductive Threshold Calibration (ITC). + +To overcome the limitations of ITC methods, we propose OpenGCN, a GNN-based TTC method with enhanced adaptability and robustness for open-world scenarios with diverse concepts and distance distributions. We highlight the key differences between OpenGCN and conventional + +![](images/baf4fc0173ce1b1b2a383e34f646b0f3346a3c4e94d2d9f75aaf5c8bdf3e0fac.jpg) +(a) Pre-training on Closed-World Examples + +![](images/dbdd4b7f54fc80102d66a70ab7f8f399b97f6c1e33394574d0a1ae0b5e11c331.jpg) +(b) Fine-tuning on Open-World Examples +Figure 3. OpenGCN training workflow: (a) During pre-training, OpenGCN jointly optimizes pairwise connectivity, and instance-specific neighborhood and average densities. (b) During fine-tuning, the 2-layer MLP is reset for fine-tuning, while the other weights remain frozen. Solid blue and dashed red arrows represent forward and backward propagation, respectively. At test time, we employ the trained OpenGCN model and MLP head to predict the TPR and TNR as functions of each distance threshold specifically for each test distribution. We then follow Eq. (1) and use grid search to find the optimal distance threshold for each test dataset. Best viewed in color. + +ITC methods. First, OpenGCN, as a transductive method, derives distance thresholds by leveraging information directly from the test data. This empowers it to adapt to the characteristics of the test data, thereby eliminating the requirement for the calibration data to share a similar distribution with the test data. Second, OpenGCN is engineered to integrate useful information from both closed-world and open-world data sources. This is achieved through a two-stage training process, as illustrated in Fig. 3. We first pretrain OpenGCN on a closed-world dataset, which is the same dataset used to train the DML embedding model. Afterwards, we fine-tune it on a smaller calibration dataset. This calibration dataset contains open-world classes that do not overlap with those in the test data or the closed-world pretraining data. This approach allows the model to smoothly transition from a closed-world context to open-world scenarios, effectively utilizing closed-world knowledge to enhance its transductive reasoning capabilities in the dynamic and unknown open world. In the next section, we delve into the details of OpenGCN, elaborating on how it enables effective TTC for open-world scenarios. + +# 3.2. OpenGCN: Learning for Effective TTC + +OpenGCN Inference Workflow A straight-forward way to estimate $\mathrm{TPR}_{\mathrm{test}}$ and $\mathrm{TNR}_{\mathrm{test}}$ , as defined in Eqs. (2) and (3), is to model the true pairwise connectivities with edge connectivity probability [52]. This probability, denoted as $p_{ij}$ , quantifies the likelihood that two samples have the same label. By setting a proper connectivity threshold $\tau$ , we can approximate $\mathrm{TPR}_{\mathrm{test}}$ and $\mathrm{TNR}_{\mathrm{test}}$ as follows: + +$$ +\mathrm {T P R} _ {\text {t e s t}} (d) = \sum_ {i, j \in D _ {\text {t e s t}}} 1 _ {p _ {i j} > \tau} \cdot 1 _ {d _ {i j} < d} / \sum_ {i, j \in D _ {\text {t e s t}}} 1 _ {p _ {i j} > \tau} \tag {4} +$$ + +$$ +\mathrm {T N R} _ {\text {t e s t}} (d) = \sum_ {i, j \in D _ {\text {t e s t}}} 1 _ {p _ {i j} \leq \tau} \cdot 1 _ {d _ {i j} > d} / \sum_ {i, j \in D _ {\text {t e s t}}} 1 _ {p _ {i j} \leq \tau} \tag {5} +$$ + +These formulations offer a TTC solution that centers on precisely predicting pairwise connectivities for open-world test distributions, a problem well-suited for modern + +deep learning algorithms. Specifically, as shown in Fig. 3, OpenGCN is designed as a GNN-based method for predicting pairwise connectivities over graph data constructed from the unlabeled test samples. We adopt a GNN architecture, specifically a Graph Attention Network (GAT) [46], due to its demonstrated effectiveness in generalizing to open-world scenarios [3, 5, 9, 10, 49, 51, 52]. Additionally, we use fully connected graphs to ensure that in-graph pairwise distance distribution is representative of the overall pairwise distance distribution. For inference, nodal features extracted by the GAT encoder are concatenated with the original DML embedding features [52] and passed through a 2-layer MLP to predict pairwise connectivities. The connectivity predictions are then used to transductively estimate TPR and TNR at each distance threshold for the test distributions, following the formulations in Eqs. (4) and (5), where the connectivity threshold $\tau$ is selected by 10-fold cross validation on $D_{\mathrm{cal}}$ . Due to the typically large size of the test data, for efficient inference, we randomly sample subsets from $D_{\mathrm{test}}$ to construct fully connected sub-graphs for connectivity inference, repeating this process until the TPR and TNR estimations converge. + +Joint Connectivity and Density Estimations Using representation density prediction as an auxiliary task to enhance connectivity prediction is widely used in clustering tasks [2, 7, 31]. This approach is based on the idea that a cluster typically exists within a contiguous region of high sample density, separated from other clusters. Recent supervised visual clustering works also leverage density as a key modeling parameter to enhance clustering performance by encouraging information sharing between the tasks [49, 50, 52]. Driven by the intrinsic connections between density and connectivity, we adopt a multitask approach, where we simultaneously learn for pairwise edge connectivity and instance-wise representation densities. However, unlike previous works which only consider one density metric, we simultaneously learn two density + +metrics: the average density ( $s^{\mathrm{avg}}$ ), and the neighborhood density ( $s^{\mathrm{nbr}}$ ). Formally, these two density metrics, defined in [52], can be expressed as follows $^2$ : + +$$ +s _ {i} ^ {\text {a v g}} = \frac {\sum_ {j \in \mathcal {N} _ {i}} a _ {i j} \cdot 1 _ {y _ {i} = y _ {j}}}{| \mathcal {N} _ {i} |}, s _ {i} ^ {\text {n b r}} = \frac {\sum_ {j \in \mathcal {N} _ {i}} a _ {i j} \cdot \left(1 _ {y _ {i} = y _ {j}} - 1 _ {y _ {i} \neq y _ {j}}\right)}{| \mathcal {N} _ {i} |} \tag {6} +$$ + +where $\mathcal{N}_i$ denotes the neighbourhood of a sample $i$ , and $a_{ij}$ represents the cosine similarity between the original embedding features of sample $i$ and sample $j$ . + +To illustrate the motivation of utilizing both density metrics instead of just one, we first introduce two metrics adapted from prior works [20, 41], namely the class-specific TPR and TNR scores, denoted as $\mathrm{TPR}^k$ and $\mathrm{TNR}^k$ , respectively. Let $f_{i}$ denote the $\mathrm{L}_2$ -normalized embeddings of an image in a dataset $D$ . For a given class $k$ , its class-specific TPR and TNR scores can be expressed as: + +$$ +\mathrm {T P R} ^ {k} = \frac {\left\| \sum_ {i \in D} f _ {i} \cdot 1 _ {y _ {i} = k} \right\|}{\sum_ {i \in D} 1 _ {y _ {i} = k}}, \quad \mathrm {T N R} ^ {k} = \frac {\sum_ {i , j \in D} \left(1 - a _ {i j}\right) \cdot 1 _ {y _ {j} \neq y _ {i} = k}}{\sum_ {i , j \in D} 1 _ {y _ {j} \neq y _ {i} = k}} \tag {7} +$$ + +The subsequent theorems formally establish a connection between two density metrics defined in Eq. (6) and the class-specific TPR and TNR scores. + +# Theorem 1 (Correspondence between $s^{\mathrm{avg}}$ and $TPR^{k}$ ) + +Let $\mathcal{N}$ be a cluster with high purity, where the majority class is $k$ . For each sample $i \in \mathcal{N}$ , when both $|\mathcal{N}|$ and $|\mathcal{N}_i|$ are sufficiently large, $TPR^k$ can be approximated as: + +$$ +\lim _ {| \mathcal {N} _ {i} | \rightarrow \infty} T P R ^ {k} = \left(\frac {| \mathcal {N} _ {i} |}{2 | \mathcal {N} |} \right. \cdot \underbrace {\left(\frac {1}{| \mathcal {N} |} \sum_ {i \in \mathcal {N}} s _ {i} ^ {\mathrm {n b r}} \right.} _ {\substack {\text {avg s} ^ {\mathrm {n b r}}\\2 \times \text {avg s} ^ {\mathrm {a v g}}}} + \underbrace {\left(\frac {1}{| \mathcal {N} |} \sum_ {i \in \mathcal {N}} \mathfrak {a} _ {\mathrm {i}} ^ {\mathrm {a v g}}\right) ^ {1 / 2}} _ {\substack {\text {avg a} ^ {\mathrm {a v g}}}} \tag{8} +$$ + +where $\mathfrak{a}_i^{\mathrm{avg}} = \frac{1}{|\mathcal{N}_i|}\sum_{j\in \mathcal{N}_i}a_{ij}$ , and $\mathfrak{a}^{\mathrm{avg}}$ is the mean of average cosine similarity of all vertices in $\mathcal{N}_i$ . + +Theorem 2 (Correspondence between $s^{\mathrm{avg}} - s^{\mathrm{nbr}}$ and $TNR^{k}$ ) Under the same assumptions in Theorem 1, for a given class $k$ , its $TNR^{k}$ can be approximated as: + +$$ +\lim _ {| \mathcal {N} _ {i} | \rightarrow \infty} T N R ^ {k} = 1 - \frac {| \mathcal {N} |}{| \mathcal {N} | _ {k ^ {-}}} \cdot (\underbrace {\frac {1}{| \mathcal {N} |} \sum_ {i \in \mathcal {N}} s _ {i} ^ {\mathrm {a v g}} - \frac {1}{| \mathcal {N} |} \sum_ {i \in \mathcal {N}} s _ {i} ^ {\mathrm {n b r}})} _ {\text {a v e r a g e (s} ^ {\mathrm {a v g}} - \mathrm {s} ^ {\mathrm {n b r}} \text {)}}) \tag {9} +$$ + +where $|\mathcal{N}|_{k^{-}}$ denotes the number of negative pairs in $\mathcal{N}$ where one sample of each negative pair must have label $k$ . + +Based on the theorems, when the neighborhood size is sufficiently large, considering both density metrics effectively encapsulates both class-specific TPR and TNR within + +this neighbourhood. As open-world threshold calibration aims to balance the TPR and TNR trade-off for unknown test distributions, it is crucial to capture both aspects to improve within-class and cross-class connectivity predictions. Furthermore, the class-specific nature of these metrics grants them the versatility to adapt to varying class compositions. In Sec. 4.3, we provide an ablation study comparing the use of a single density metric versus both densities, where jointly predicting both densities along with connectivity yields better calibration performance. Thus, we introduce predictions of both density metrics, $s^{\mathrm{avg}}$ and $s^{\mathrm{nbr}}$ , as auxiliary tasks to enhance the generalization of connectivity prediction. This leads to the following learning objective for training OpenGCN: + +$$ +\mathcal {L} _ {\text {o v e r a l l}} = \underbrace {\mathcal {L} _ {\text {c o n n}}} _ {\text {m a i n t a s k}} + \underbrace {\lambda \cdot \left(\mathcal {L} _ {s ^ {\mathrm {n b r}}} + \mathcal {L} _ {s ^ {\mathrm {a v g}}}\right)} _ {\text {a u x i l i a r y t a s k}} \tag {10} +$$ + +where $\mathcal{L}_{\mathrm{conn}}$ is the balanced cross-entropy loss for pairwise edge connectivity and $\mathcal{L}_{s^{\mathrm{nbr}}}$ and $\mathcal{L}_{s^{\mathrm{avg}}}$ are the mean squared error losses for $s^{\mathrm{nbr}}$ and $s^{\mathrm{avg}}$ , respectively. Specifically, we define $\mathcal{L}_{\mathrm{conn}}$ as follows to ensure equal importance for both within-class and cross-class connectivities: + +$$ +\mathcal {L} _ {\text {c o n n}} = \frac {\sum_ {i , j \in V} 1 _ {y _ {i} = y _ {j}} \cdot \log \left(p _ {i j}\right)}{\sum_ {i , j \in V} 1 _ {y _ {i} = y _ {j}}} + \frac {\sum_ {i , j \in V} 1 _ {y _ {i} \neq y _ {j}} \cdot \log \left(1 - p _ {i j}\right)}{\sum_ {i , j \in V} 1 _ {y _ {i} \neq y _ {j}}} \tag {11} +$$ + +Meanwhile, $\mathcal{L}_{s^{\mathrm{nbr}}}$ and $\mathcal{L}_{s^{\mathrm{avg}}}$ can be expressed as: + +$$ +\mathcal {L} _ {s ^ {\text {a v g}}} = \frac {\sum_ {i \in V} \left(s _ {i} ^ {\text {a v g}} - \hat {s} _ {i} ^ {\text {a v g}}\right) ^ {2}}{| V |}, \quad \mathcal {L} _ {s ^ {\text {n b r}}} = \frac {\sum_ {i \in V} \left(s _ {i} ^ {\text {n b r}} - \hat {s} _ {i} ^ {\text {n b r}}\right) ^ {2}}{| V |} \tag {12} +$$ + +where $V$ represents the node vertices in the graph data, and $\hat{s}_i$ is the estimated density for each sample based on $p_{ij}$ . + +Two-stage Training for Adaptability The DML embedding model, trained on $D_{\mathrm{train}}$ (closed-set examples), tends to produce more compact embeddings for these examples than those of open-world classes. If OpenGCN is trained solely on $D_{\mathrm{train}}$ , its ability to generalize to the open-world scenarios will be limited. On the other hand, if OpenGCN is trained solely on $D_{\mathrm{cal}}$ , its knowledge may be very narrow since the calibration dataset is typically small and lacks diverse concepts. To tackle this, we borrow established experience in domain generalization and adaptation [11, 21, 48], and adopt a two-stage training strategy. First, we pretrain OpenGCN on $D_{\mathrm{train}}$ , which consists of a large collection of closed-set examples. After this, we reset the 2-layer MLP while keeping the other parameters frozen. Subsequently, we fine-tune the MLP on $D_{\mathrm{cal}}$ , a small open-world calibration dataset containing disjoint classes to the test data, to adapt the pretrained model to open-world scenarios. In Sec. 4.3, we conduct an ablation study to provide further support for this two-stage training approach. We choose to + +fine-tune only the MLP based on the practical observations that $D_{\mathrm{cal}}$ is typically limited in size, and fine-tuning the entire model on such a small dataset may lead to overfitting. It is worth reiterating that this approach does not require additional training data, as the closed-set data is already in place for training the DML embedding model, and the separate open-world calibration dataset is required for conventional inductive posthoc calibration methods as well. + +# 4. Experiment and Result + +We experiment on public recognition benchmarks including iNaturalist-2018 [44], CUB-200 [47] and Cars-196 [23]. Below, we outline our setup and present the results. Further experiments can be found in the supplementary materials. + +# 4.1. Dataset and Implementation Details + +Datasets To simulate real-world testing environments, we consider three calibration scenarios: SameDist, ShiftDist and DiffDist. The SameDist scenario involves cases where $D_{\mathrm{cal}}$ and $D_{\mathrm{test}}$ share similar distance distributions, the ShiftDist scenario accounts for test-time non-semantic distance distribution shifts, and the DiffDist scenario represents out-of-distribution calibration, where $D_{\mathrm{cal}}$ and $D_{\mathrm{test}}$ have very different distance distributions. Note that in all three scenarios, we adhere to the open-world setting where $C_{\mathrm{train}} \cap C_{\mathrm{cal}} = C_{\mathrm{train}} \cap C_{\mathrm{test}} = C_{\mathrm{cal}} \cap C_{\mathrm{test}} = \emptyset$ . Below, we elaborate on the setup for each calibration scenario: + +- SameDist For iNaturalist, the training and testing classes are distinct, so we directly use the training partition as $D_{\text{train}}$ . To create $D_{\text{cal}}$ , we randomly select $10\%$ of the test classes, leaving the remaining classes for $D_{\text{test}}$ . For CUB and Cars, where there is overlap between training and testing classes, we divide them into train / cal / test subsets. The train set comprises the first half of the class indices, while the cal / test sets are randomly chosen from the remaining classes with a $1/9$ ratio. As $D_{\text{cal}}$ and $D_{\text{test}}$ are randomly split from the same dataset, they are expected to have similar distance distributions. +- ShiftDist We consider 13 common image corruption and perturbation types, including noise, blur, weather, and digital distortions, to assess the robustness of the calibration methods under varied adversities. We follow the setups in [17] and apply the changes to $D_{\mathrm{test}}$ only, while leaving $D_{\mathrm{cal}}$ and $D_{\mathrm{train}}$ unchanged. +- DiffDist To induce significant distance distribution shifts between $D_{\mathrm{cal}}$ and $D_{\mathrm{test}}$ , we employ the following treatments. For iNaturalist, characterized by a long-tailed distribution, we divide its test classes into two sets based on cluster size, each containing approximately the same number of images. For calibration purposes, we use the set with a higher number of images per class ("head" set, denoted as $D_{\mathrm{head}}$ ) as $D_{\mathrm{cal}}$ and the set with fewer images per class ("tail" set, denoted as $D_{\mathrm{tail}}$ ) as $D_{\mathrm{test}}$ to simu + +Table 1. Detailed statistics of the datasets. + +
SettingDatasetPartition# img# cls# img/cls
SameDistCarsDtrain7,9619881.2
Dcal8661086.6
Dtest7,3568883.6
CUBDtrain5,8029958.6
Dcal5991059.9
Dtest5,3859159.2
iNatDtrain324,4185,69057.0
Dcal12,61324551.5
Dtest123,0472,20755.8
ShiftDistCarsSameDist except for corruption on Dtest
DiffDistiNatDtrainiNat SameDist Dtrain
Dhead70,057200350.3
Dtail66,0362,25229.3
CarsSameDist except for sketchifying Dtest
iNat/CUB (cross dataset)DtrainiNat SameDist Dtrain
DcaliNat SameDist Dcal
DtestEntire CUB dataset
+ +late a calibration for the long tail scenario. In addition, we also explore two out-of-domain calibration scenarios. First, for Cars, we transform $D_{\mathrm{test}}$ into sketches while leaving $D_{\mathrm{train}}$ and $D_{\mathrm{cal}}$ untouched. Second, we consider cross-dataset calibration, where the OpenGCN model is pretrained and fine-tuned on iNaturalist (general natural species images) but evaluated on CUB (bird images). + +Evaluation Metrics For a comprehensive evaluation, we consider two approaches to assess calibration performance: + +- Global Evaluation: Since we define open-world threshold calibration as the accurate prediction of both TPR and TNR at each distance threshold to meet specific TPR or TNR performance requirements of diverse test-time users, it is natural to employ the combined Mean Absolute Errors (MAE) for both TPR and TNR predictions across the entire distance range as our evaluation metric. Formally, this metric can be expressed as: + +$$ +\mathrm {M A E} _ {\text {c o m b}} = \frac {1}{2} \int_ {0} ^ {2} \left(| \hat {\mathrm {T P R}} (\mathrm {d}) - \mathrm {T P R} (\mathrm {d}) | + \right. \tag {13} +$$ + +$$ +\left. \left| \mathrm {T N R} (\mathrm {d}) - \mathrm {T N R} (\mathrm {d}) \right|\right) d \mathrm {d} +$$ + +- Point-wise Evaluation: We first set a performance target and compute the optimal distance threshold, denoted as $\hat{d}^{\mathrm{opt}}$ , based on the TPR or TNR estimations. We then compute the Absolute Error (AE) between the actual performance at $\hat{d}^{\mathrm{opt}}$ and the target, denoted as $\mathrm{AE}_{\mathrm{TPR}} = |\mathrm{TPR}(\hat{d}^{\mathrm{opt}}) - \mathrm{TPR}_{\mathrm{target}}|$ and $\mathrm{AE}_{\mathrm{TNR}} = |\mathrm{TNR}(\hat{d}^{\mathrm{opt}}) - \mathrm{TNR}_{\mathrm{target}}|$ for TPR and TNR, respectively. + +Baseline Methods We consider the most representative inductive posthoc calibration methods including Platt Scaling [37], Histogram Calibration [53], Isotonic Calibration [54] and Beta Calibration [24]. Additionally, we explore pseudolabel-based baselines, including traditional clustering methods such as DBSCAN [13] and the state-of-the-art method in GNN-based clustering, HiLANDER [49]. For clustering-based methods, we follow + +Table 2. Evaluation in the SameDist scenario using pointwise metrics of $\mathrm{AE}_{\mathrm{TPR}}$ (optimize for TPR) and $\mathrm{AE}_{\mathrm{TNR}}$ (optimize for TNR). The smaller the metric, the better. For each dataset, the best and second best results are marked in Red and Blue, respectively. Shading in the Table: Gray for posthoc calibration baselines, Cyan for clustering baselines, and Blue for our OpenGCN method. Best viewed in color. + +
MethodOptimize for TPR=80%Optimize for TPR=90%Optimize for TNR=80%Optimize for TNR=90%Rank
CarsCUBInatCarsCUBInatCarsCUBInatCarsCUBInat
Platt scaling [37]1.35%5.10%6.08%0.44%2.63%4.63%2.83%2.02%7.54%2.93%6.49%0.92%6
Beta calibration [24]1.13%5.16%5.51%0.02%2.91%3.26%2.94%1.41%7.57%2.78%6.43%0.93%5
Isotonic regression [54]0.82%5.28%4.53%0.90%2.56%3.54%1.94%1.00%5.78%1.26%4.65%0.65%3
Histogram Calibration [53]0.82%5.28%4.53%0.90%2.56%3.54%1.94%1.00%5.78%1.26%4.65%0.65%4
DBSCAN [13]43.11%18.87%0.45%34.57%9.18%1.85%4.09%13.77%12.90%1.60%9.32%9.32%7
Hi-LANDER [49]3.44%1.36%10.54%2.02%0.93%7.00%0.06%0.38%2.35%0.10%2.20%0.21%2
OpenGCN (ours)0.33%0.74%1.59%0.72%1.41%2.37%0.61%0.09%0.74%0.58%0.72%0.10%1
+ +their original clustering decoding inference workflows to estimate pseudo labels, and use these pseudo labels to compute $\mathrm{TPR}_{\mathrm{test}}$ and $\mathrm{TNR}_{\mathrm{test}}$ for finding $d^{\mathrm{opt}}$ . + +Implementation Details In all experiments, we train ResNet-50 models with 128-dimensional embeddings on $D_{\mathrm{train}}$ using the setups in [6]. The embedding models are then used to extract the embeddings for $D_{\mathrm{train}}$ , $D_{\mathrm{cal}}$ and $D_{\mathrm{test}}$ . For training OpenGCN, as implied in Theorems 1 and 2, the neighborhood size needs to be sufficiently large to encapsulate both intra-class and inter-class representation structures. Thus, we use a batch sizes of 256 for graph construction during training. We use the Adam optimizer [22] with a cosine annealing schedule [30]. For traditional calibration methods, we use the official codebase from [25] to map the ground truth TPR (or TNR) as a function of the distance threshold from $D_{\mathrm{train}}$ to $D_{\mathrm{cal}}$ . When doing point-wise evaluation, the optimal distance threshold $d^{\mathrm{opt}}$ is solved with grid search at a grid size of 0.01. Further details are provided in the supplementary materials. + +# 4.2. Evaluation Results + +SameDist Calibration We present the global and pointwise evaluation results for the SameDist scenario in Tab. 3 and Tab. 2, respectively. For pointwise evaluation, we evaluate at multiple target values (TPR=80%, 90% and TNR=80%, 90%) to provide a comprehensive assessment. Our results reveal that no single calibration method consistently excels across all distance thresholds and datasets. However, on average, OpenGCN achieves the highest rank. This underscores the importance of TTC in open-world scenarios, where calibration is conducted based on the characteristics of $D_{\mathrm{test}}$ rather than relying on a calibration dataset that may not accurately represent $D_{\mathrm{test}}$ . Additionally, the global metrics in Tab. 3 show that, compared to the best baseline method, OpenGCN significantly reduces global error rates by 59.30%, 66.49%, and 59.15% for Cars, CUB, and iNaturalist, respectively. Among the baseline methods, we observe that DBSCAN performs worse than the traditional posthoc calibration methods, while Hi-LANDER outperforms traditional posthoc methods on Cars and CUB but underperforms on iNaturalist. In contrast, OpenGCN con + +Table 3. Evaluation in the SameDist scenario using the global error metric of $\mathrm{MAE}_{\mathrm{comb}}$ . For each benchmark, the best and second best results are marked in Red and Blue, respectively. We also report the improvement in error reduction of OpenGCN over the best baseline method. Best viewed in color. + +
MethodCarsCUBiNatRank
Platt scaling1.55e-23.59e-21.23e-26
Beta calibration1.53e-23.59e-21.18e-25
Isotonic regression1.38e-23.61e-21.18e-23
Histogram calibration1.38e-23.62e-21.18e-24
DBSCAN1.02e-11.10e-13.65e-27
Hi-LANDER1.29e-21.94e-22.14e-22
OpenGCN (ours)5.25e-36.50e-34.82e-31
Imp. over top baseline ↑59.30%66.49%59.15%69.14% (avg.)
+ +sistently performs well across all three datasets. + +ShiftDist Calibration In Tab. 4, we report the global error metric $\mathrm{MAE}_{\mathrm{comb}}$ for each corruption type across various calibration methods. Among the baseline methods, Isotonic Regression and Histogram Calibration appear to be the most effective in the presence of image corruptions. However, it is evident that OpenGCN consistently outperform these baseline methods across all corruption types, achieving an average error reduction of $55.03\%$ compared to the best baseline method. This robust performance against image corruptions can be attributed to the model's pretraining stage, where it was exposed to closed-set data with similar types of corruptions. Additionally, it is observed that, among the various corruption categories, OpenGCN exhibits the most improvement in the weather category, while showing the least improvement in the blur category. + +DiffDist Calibration We present the DiffDist calibration results in Tab. 5. As observed, in this scenario characterized by a substantial shift in distance distributions between $D_{\mathrm{cal}}$ and $D_{\mathrm{test}}$ , all calibration methods display elevated errors compared to the SameDist scenario. However, OpenGCN demonstrates superior performance compared to the other calibration methods in both out-of-domain settings (sketch and cross-dataset) and the long-tail calibration setting, achieving an average relative reduction in the global error $\mathrm{MAE}_{\mathrm{comb}}$ of $43.99\%$ . In particular, we observe significant improvement in the cross-dataset setting (pretrained + +Table 4. Evaluation on the Cars-196 dataset in the ShiftDist scenario across 13 common corruption and perturbation types using combined global error metric of $\mathrm{MAE}_{\mathrm{comb}}$ . The best results are marked in Red. + +
MethodNoiseBlurWeatherDigitalRank
GaussShotImpulseDefocusMotionZoomSnowFogBrightContrastElasticPixelJPEG
Platt scaling2.95e-22.99e-23.41e-22.66e-22.62e-25.02e-24.24e-24.37e-22.16e-24.61e-22.16e-22.24e-22.03e-24
Beta calibration2.94e-22.97e-23.41e-22.67e-22.69e-25.06e-24.32e-24.37e-22.18e-24.61e-22.20e-22.23e-22.02e-25
Isotonic regression2.88e-22.85e-23.38e-22.37e-22.31e-24.85e-24.07e-24.34e-21.83e-24.59e-21.85e-22.03e-21.80e-22
Histogram calibration2.88e-22.85e-23.38e-22.37e-22.31e-24.85e-24.07e-24.34e-21.83e-24.59e-21.85e-22.03e-21. 80e-23
DBSCAN4.96e-26.02e-27.79e-29.81e-21.13e-11.22e-11.19e-14.02e-29.27e-24.53e-21.09e-11.04e-18.21e-27
Hi-LANDER7.65e-26.30e-26.59e-23.98e-25.33e-24.48e-25.94e-27.16e-25.09e-29.45e-24.42e-29.48e-26.91e-26
OpenGCN (ours)1.33e-25.87e-31.66e-21.50e-21.71e-23.92e-21.42e-27.32e-36.73e-37.08e-35.34e-31.15e-21.68e-21
Imp. over top baseline ↑53.82%79.40%50.89%36.71%25.97%12.50%65.11%81.79%63.22%84.37%71.14%43.35%6.67%55.03% (avg.)
+ +Table 5. Evaluation in the DiffDist scenario using the global error metric $\mathrm{MAE}_{\mathrm{comb}}$ . The best results are highlighted in Red. + +
MethodCars: SketchCUB: Cross-datasetiNat: Longtail
Platt scaling1.08e-11.15e-12.09e-2
Beta calibration1.08e-11.15e-12.12e-2
Isotonic regression1.08e-11.15e-12.11e-2
Histogram Calibration1.08e-11.15e-12.11e-2
DBSCAN5.16e-21.60e-17.21e-2
Hi-LANDER6.67e-21.30e-16.26e-2
OpenGCN (ours)3.54e-21.42e-21.82e-2
Imp. over top baseline ↑31.40%87.65%12.92%
+ +Table 6. Impact of multi-task learning on global error metric $\mathrm{MAE}_{\mathrm{comb}}$ on iNaturalist-2018. We use $\lambda = 10$ for all experiments. + +
Best baselineOpenGCN loss ablations
Lconn+λ·Lsavg+λ·Lsshr+λ·(Lsavg + Lsshr)
MAEcomb1.18e-26.25e-35.37e-35.12e-34.82e-3
+ +Table 7. Impact of fine-tuning on open-world calibration dataset on global error metric $\mathrm{MAE}_{\mathrm{comb}}$ . PT: pretraining FT: finetuning. Numbers in the bracket show the relative improvement over PT. + +
MethodCarsCUBiNat
OpenGCN (PT)2.90e-22.52e-23.55e-2
OpenGCN (PT+FT)5.25e-3 (81.9%)6.50e-3 (74.2%)4.82e-3 (86.4%)
+ +and finetuned on the iNaturalist-2018 nature species dataset but tested on the CUB birds dataset), where OpenGCN achieves a notable error reduction of $87.65\%$ . + +# 4.3. Ablation Studies + +Importance of Multi-task Learning We assess the impact of multi-task learning on $\mathrm{MAE}_{\mathrm{comb}}$ . As shown in Tab. 6, compared to predicting connectivity only, employing a single density metric in conjunction with connectivity prediction helps reduce $\mathrm{MAE}_{\mathrm{comb}}$ from $6.25\mathrm{e} - 3$ to $5.37\mathrm{e} - 3$ for $s^{\mathrm{avg}}$ and to $5.12\mathrm{e} - 3$ for $s^{\mathrm{nbr}}$ , respectively. However, by utilizing both density metrics, we further decrease this error to $4.82\mathrm{e} - 3$ . This supports our choice to incorporate both density metrics, allowing us to capture both intra-class compactness and inter-class separation while facilitating information sharing for improved connectivity prediction. + +Importance of Two-stage Training We assess the impact + +of two-stage training on OpenGCN by comparing $\mathrm{MAE}_{\mathrm{comb}}$ before and after fine-tuning on $D_{\mathrm{cal}}$ across all three benchmarks. The comparison in Tab. 7 reveals significant error reduction of up to $86.4\%$ after fine-tuning on the open-world calibration dataset. This results supports our choice of two-stage training in adapting the calibration model from the closed-world context to the open-world scenarios. + +# 5. Conclusions + +In this work, we formally define the open-world threshold calibration problem for DML-based open-world visual recognition systems. To address this problem, we introduce OpenGCN, a GNN-based transductive threshold calibration method designed to enhance adaptability in open-world scenarios. Unlike traditional posthoc calibration methods, OpenGCN does not rely on the common assumption of matching distance distributions between $D_{\mathrm{cal}}$ and $D_{\mathrm{test}}$ . Instead, it leverages the information of the unlabeled test instances along with learnt calibration rules to predict pairwise connectivity of the test data, via a GNN, to enable effective transductive threshold calibration in open-world scenarios. Our evaluations demonstrate that OpenGCN outperforms both traditional posthoc calibration methods and pseudolabel-based calibration techniques. When assessed using global error metrics, OpenGCN exhibits significant improvements, achieving average error reductions of $69.14\%$ , $40.85\%$ , and $22.58\%$ for SameDist, ShiftDist, and DiffDist calibration scenarios, respectively, compared to the best baseline method. Overall, our results underscore OpenGCN's robustness across different distance distribution patterns between $D_{\mathrm{cal}}$ and $D_{\mathrm{test}}$ , highlighting its practical applicability for threshold calibration in DML-based open-world recognition applications. + +Limitations OpenGCN is computationally less efficient and more susceptible to over-parameterization compared to traditional posthoc calibration methods. Furthermore, OpenGCN is not a calibration-data-free method as it still requires some calibration data in addition to the closed-world data used for training the embedding model. + +# References + +[1] Anastasios N. Angelopoulos, Stephen Bates, Clara Fannjiang, Michael I. Jordan, and Tijana Zrnic. 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However, calibrating this threshold presents challenges in open-world scenarios, where the test classes can be entirely disjoint from those encountered during training. We define the problem of finding distance thresholds for a trained embedding model to achieve target performance metrics over unseen open-world test classes as open-world threshold calibration. Existing posthoc threshold calibration methods, reliant on inductive inference and requiring a calibration dataset with a similar distance distribution as the test data, often prove ineffective in open-world scenarios. To address this, we introduce OpenGCN, a Graph Neural Network-based transductive threshold calibration method with enhanced adaptability and robustness. 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Introduction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 287, + 714 + ], + "type": "text", + "content": "In deep metric learning (DML) for visual recognition, distance calibration plays a critical role in determining the user-perceived model performance. Unlike confidence calibration in closed-set classification settings which focuses on aligning confidence probabilities with true likelihood of correctness in a fixed label space [27, 33], distance calibration in DML aims to pinpoint an optimal distance threshold to achieve a target true positive rate (TPR) or true negative rate (TNR) for diverse test-time distributions [26]. 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This figure illustrates the open-world threshold calibration problem. In open-world recognition, the embedding model is trained on closed-set classes but tested on distinct open-world classes. When applying the model to open-world classes, it often produces less compact embeddings than those encountered during training, necessitating the calibration of the distance threshold for achieving the desired TPR and TNR trade-off. However, the absence of prior knowledge about open-world test classes and distributions makes it challenging to find the optimal distance threshold, denoted as " + }, + { + "bbox": [ + 304, + 417, + 547, + 528 + ], + "type": "inline_equation", + "content": "d^{\\mathrm{opt}}" + }, + { + "bbox": [ + 304, + 417, + 547, + 528 + ], + "type": "text", + "content": ". Best viewed in color." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 545, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 547, + 715 + ], + "type": "text", + "content": "tive embedding model, an inappropriate distance threshold can significantly degrade user experience. The issue becomes more pronounced in open-world recognition, where the embedding model, trained on a closed set of classes (e.g., dog, cat, bird), is tested on an open collection of unseen classes (e.g., wolf, sheep, mouse, ...). These open-world classes may have very different intra-class and interclass representation structures, typically being less compact, compared to the training classes. In such open-world scenarios, where prior knowledge about test-time classes and distributions are absent, calibrating the distance threshold becomes a challenging task, as illustrated in Fig. 1. We term this task of distance calibration in an open-world scenario as open-world threshold calibration." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17097" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 180 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 180 + ], + "type": "text", + "content": "Existing posthoc calibration methods, such as [16, 24, 34, 37, 53, 54], typically utilize a fully-labeled calibration dataset that has a similar distribution as the test data [35, 42, 56] to learn general calibration rules for test distributions. However, this approach has a key limitation: it heavily relies on the assumption of identical distributions between test and calibration data for effective calibration. In open-world scenarios, this assumption becomes unreliable, posing significant challenges to threshold calibration, including:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 183, + 287, + 423 + ], + "type": "list", + "angle": 0, + "index": 4, + "blocks": [ + { + "bbox": [ + 48, + 183, + 287, + 267 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 183, + 287, + 267 + ], + "spans": [ + { + "bbox": [ + 48, + 183, + 287, + 267 + ], + "type": "text", + "content": "1. The open-world challenge The test data may exclusively contain open-world classes, which exhibit different relationships between distance thresholds and TPR or TNR compared to those encountered during the embedding model training [26]. Meanwhile, test data composition and quality can vary significantly, potentially exhibiting substantial class imbalances and data corruptions." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 267, + 287, + 315 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 267, + 287, + 315 + ], + "spans": [ + { + "bbox": [ + 47, + 267, + 287, + 315 + ], + "type": "text", + "content": "2. Non-stationary data In real-world testing environments, the test distribution can be infinitely varied and highly dynamic, rendering the assumption of similar distribution between calibration and test data obsolete." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 316, + 287, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 316, + 287, + 423 + ], + "spans": [ + { + "bbox": [ + 47, + 316, + 287, + 423 + ], + "type": "text", + "content": "3. Deployment Scalability Real-world systems require calibration methods that can adapt to diverse user distributions without individual recalibration. Existing methods lack deployment scalability as they frequently require dedicated calibration data and the creation of specific calibration functions for each user. Imagine a scenario with 1,000 user profiles with distinct classes and data distributions – creating and deploying custom calibration datasets and functions for each would be impractical." + } + ] + } + ], + "index": 3 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 426, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 426, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 426, + 289, + 714 + ], + "type": "text", + "content": "Addressing these challenges is crucial for the reliability of DML-based open-world recognition systems. Current posthoc calibration methods are ill-suited for this purpose, as they are inherently inductive and prone to failure when confronted with test data with different distance distributions from the calibration data. To address this, we adopt a fresh perspective on distance threshold calibration, treating it as a transductive inference process, where the calibration method incorporates the information of the unlabeled test samples along with the learned calibration rules to make better threshold estimations. Our proposed method, OpenGCN, employs a Graph Neural Network (GNN), known for its generalization capabilities [3, 5, 9, 10, 49, 51, 52], to jointly predict pairwise connectivity and two instance-wise representation densities for test data, where the predicted pairwise connectivity is used to compute the TPR and TNR of the test data at each distance threshold to enable transductive threshold calibration. OpenGCN is tailored for the task of open-world threshold calibration through a carefully crafted learning process, which accurately estimates the mapping between performance metrics and pairwise distance thresholds in open-world scenarios. In particular, the multi-task learning of connectivities and representation densities facilitates infor" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 72, + 547, + 262 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 262 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 262 + ], + "type": "text", + "content": "mation sharing, which helps enhance the model's generalization to open-world scenarios [49, 52]. Additionally, our joint prediction design incorporates two types of density metrics, addressing both intra-class and inter-class connectivity estimations. This approach, as opposed to using a single density metric, is shown to enhance calibration performance, as illustrated in Sec. 4.3. Furthermore, OpenGCN adopts a two-stage training process. It pre-trains on a large closed-world dataset, followed by fine-tuning on a small open-world calibration dataset with disjoint classes to both the closed-world and test data, to adapt the model to be aware of the open-world context. By these design choices, OpenGCN sidesteps the requirement for calibration data to have a similar distance distribution1 as the test data, significantly improving calibration performance in open-world scenarios. To summarize, our contributions are as follows:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 264, + 545, + 431 + ], + "type": "list", + "angle": 0, + "index": 10, + "blocks": [ + { + "bbox": [ + 306, + 264, + 545, + 287 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 264, + 545, + 287 + ], + "spans": [ + { + "bbox": [ + 306, + 264, + 545, + 287 + ], + "type": "text", + "content": "1. We are, to the best of our knowledge, the first to formally define the open-world threshold calibration problem." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 288, + 545, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 288, + 545, + 346 + ], + "spans": [ + { + "bbox": [ + 306, + 288, + 545, + 346 + ], + "type": "text", + "content": "2. We propose Transductive Threshold Calibration (TTC), a new threshold calibration paradigm that diverges from traditional inductive posthoc calibration methods, which does not rely on the assumption of similar distance distributions between the test and calibration data." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 347, + 545, + 431 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 347, + 545, + 431 + ], + "spans": [ + { + "bbox": [ + 306, + 347, + 545, + 431 + ], + "type": "text", + "content": "3. We introduce OpenGCN, a GNN-based TTC method tailored for open-world threshold calibration against diverse test distributions. We build comprehensive evaluation protocols with and without distance distribution shifts to assess OpenGCN's performance. The evaluation result underscores OpenGCN's effectiveness and robustness in real-world testing environments." + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 441, + 520, + 454 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 441, + 520, + 454 + ], + "spans": [ + { + "bbox": [ + 306, + 441, + 520, + 454 + ], + "type": "text", + "content": "2. Problem Definition and Related Works" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "spans": [ + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": "We first introduce some notations and formalize the open-world threshold calibration problem. Let " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{labled}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": " be a labeled dataset consisting of two disjoint subsets: " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ", and let " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": " be an unlabeled dataset. In open-world scenarios, the class sets of " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ", denoted as " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "C_{\\mathrm{train}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "C_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "C_{\\mathrm{test}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ", are disjoint, i.e., " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "C_{\\mathrm{train}} \\cap C_{\\mathrm{cal}} = C_{\\mathrm{train}} \\cap C_{\\mathrm{test}} = C_{\\mathrm{cal}} \\cap C_{\\mathrm{test}} = \\emptyset" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ". The goal of open-world threshold calibration is to find a suitable distance threshold that achieves the target TPR and TNR for " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ", given an embedding model trained on " + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 304, + 461, + 547, + 629 + ], + "type": "text", + "content": ". We approach this as a constrained optimization task, with the objective being maximizing the metric of interest. Take optimizing for TNR with a minimum TPR requirement as an example, this problem can be formulated as follows:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 318, + 637, + 545, + 655 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 637, + 545, + 655 + ], + "spans": [ + { + "bbox": [ + 318, + 637, + 545, + 655 + ], + "type": "interline_equation", + "content": "\\underset {d} {\\text {m a x i m i z e}} \\mathrm {T N R} _ {\\text {t e s t}}, \\quad \\text {s u b j e c t t o T P R} _ {\\text {t e s t}} (d) \\geq \\alpha \\tag {1}", + "image_path": "5c62a89069bde75eeb6181ea82f38d4a228ef42b78b460d207fce9e5cc639894.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "spans": [ + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "type": "text", + "content": " is the distance threshold, and " + }, + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "type": "text", + "content": " is the minimum performance requirement for " + }, + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "type": "inline_equation", + "content": "\\mathrm{TPR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 305, + 662, + 547, + 687 + ], + "type": "text", + "content": ". Due to the inherent" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "text", + "content": "1We use \"distance distribution\" to refer to the distribution of pairwise distances between L2-normalized embeddings from a trained DML model." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17098" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": "trade-off between TPR and TNR, the objective in Eq. (1) is equivalent to finding an optimal distance threshold " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "d^{\\mathrm{opt}}" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": " for which " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "\\mathrm{TPR}_{\\mathrm{test}}(d^{\\mathrm{opt}}) = \\alpha" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": ". To solve this, we express " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "\\mathrm{TPR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "\\mathrm{TNR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": " at a distance threshold " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 75, + 128, + 287, + 152 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 75, + 128, + 287, + 152 + ], + "spans": [ + { + "bbox": [ + 75, + 128, + 287, + 152 + ], + "type": "interline_equation", + "content": "\\operatorname {T P R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} = y _ {j}} \\cdot 1 _ {d _ {i j} < d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} = y _ {j}} \\tag{2}", + "image_path": "87c41ba39ad985c56a59115b71840a69e255fec3d71cd78ed4dc77be7eee61cb.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 75, + 159, + 287, + 182 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 75, + 159, + 287, + 182 + ], + "spans": [ + { + "bbox": [ + 75, + 159, + 287, + 182 + ], + "type": "interline_equation", + "content": "\\mathrm {T N R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} \\neq y _ {j}} \\cdot 1 _ {d _ {i j} > d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {y _ {i} \\neq y _ {j}} \\tag {3}", + "image_path": "a28dc47ef774529756e764896d3ee9747ca13347a37885b851d8d81fba092a8d.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "spans": [ + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "d_{ij}" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": " is the L2 distance between the embeddings of samples " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "y_i" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": " is the label for sample " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": ". The symbol " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "1_{\\text{condition}}" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": " represents the indicator function which equals 1 if the condition is met, otherwise 0. With " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "\\mathrm{TPR}_{\\text{test}}" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "\\mathrm{TNR}_{\\text{test}}" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": " calculated at each distance threshold, we can optimize for the optimal distance threshold " + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "inline_equation", + "content": "d^{\\text{opt}}" + }, + { + "bbox": [ + 47, + 185, + 287, + 269 + ], + "type": "text", + "content": " to achieve the target performance metrics, as described in Eq. (1)." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 276, + 139, + 288 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 276, + 139, + 288 + ], + "spans": [ + { + "bbox": [ + 47, + 276, + 139, + 288 + ], + "type": "text", + "content": "2.1. Related Works" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 295, + 287, + 462 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 295, + 287, + 462 + ], + "spans": [ + { + "bbox": [ + 46, + 295, + 287, + 462 + ], + "type": "text", + "content": "Open-world Recognition [29] aims to learn discriminative representations that align distances between representations with their semantic similarities. This allows for effective generalization to diverse, previously unseen open-world classes during testing, setting it apart from closed-set classification where training and testing classes are the same. Popular recognition losses [6, 12, 36] typically encourage compact intra-class representations, promoting strong affinity within each class while maintaining separation from other classes. However, it is widely observed that these losses tend to produce highly varied intra-class and inter-class representation structures across classes and distributions [32, 39, 55], necessitating threshold calibration to ensure consistent performance across diverse users." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 463, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 463, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 463, + 287, + 713 + ], + "type": "text", + "content": "Posthoc Calibration We focus on posthoc calibration methods which are more relevant to our research. Generally, existing posthoc calibration methods fall into two categories: (i) non-parametric methods like isotonic regression [54] and histogram binning [34, 53]; and (ii) parametric methods such as Platt scaling [37] and temperature scaling [16]. These methods are inductive: they rely on a holdout calibration set with similar distribution as the test data to derive general rules for fine-tuning the decision threshold, aiming to align the performance metrics with a predefined target. While effective in closed-set classification, these methods struggle in scenarios with significant distribution differences between test and calibration data. Diverging from traditional methods, another group of methods such as conformal prediction [4, 15, 40, 43] or Prediction-Powered Inference [1] emphasize confidence coverage guarantees, and has been shown applicable even beyond the setting of exchangeable data [14, 15]. However, these methods inherently assume a closed-set setting, making them unsuitable for open-world scenarios. Currently, open-world posthoc calibration remains largely under-explored." + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 317, + 69, + 537, + 141 + ], + "blocks": [ + { + "bbox": [ + 317, + 69, + 537, + 141 + ], + "lines": [ + { + "bbox": [ + 317, + 69, + 537, + 141 + ], + "spans": [ + { + "bbox": [ + 317, + 69, + 537, + 141 + ], + "type": "image", + "image_path": "acac3cbc24540cb2dc93d0a80a195f4838a7e382d9612d09e952340800d46a46.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 148, + 545, + 226 + ], + "lines": [ + { + "bbox": [ + 304, + 148, + 545, + 226 + ], + "spans": [ + { + "bbox": [ + 304, + 148, + 545, + 226 + ], + "type": "text", + "content": "Figure 2. This figure distinguishes between (left) inductive and (right) transductive threshold calibration methods in open-world scenarios with disjoint test-time classes. Inductive methods rely on a labeled hold-out dataset with the same distance distribution as the test data to learn general calibration rules. Transductive methods, however, also use the test information for more specific calibration, as indicated by the red arrow. Best viewed in color." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 246, + 546, + 402 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 246, + 546, + 402 + ], + "spans": [ + { + "bbox": [ + 304, + 246, + 546, + 402 + ], + "type": "text", + "content": "Transductive Inference Transduction is the reasoning from observed, specific (training) cases to specific (test) cases [45]. Such an approach is desirable as it alleviates the problem of overfitting on limited support set since information from the test data is also used for inference. This is also known as increasing VC-dimension for structural risk minimization in classical statistical learning [19]. Recently, a large body of works investigated transductive inference for few-shot and open-world recognition tasks [8, 18, 28, 38], where significant increases in performances have been reported. Given the relevance of these tasks, it is worthwhile to reconsider existing inductive posthoc calibration methods for distance threshold calibration in open-world scenarios." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 412, + 389, + 426 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 412, + 389, + 426 + ], + "spans": [ + { + "bbox": [ + 306, + 412, + 389, + 426 + ], + "type": "text", + "content": "3. Methodology" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 431, + 497, + 443 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 431, + 497, + 443 + ], + "spans": [ + { + "bbox": [ + 306, + 431, + 497, + 443 + ], + "type": "text", + "content": "3.1. Transductive Threshold Calibration" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 450, + 545, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 450, + 545, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 450, + 545, + 653 + ], + "type": "text", + "content": "Traditional calibration methods are inherently inductive - they rely on a calibration dataset to learn general calibration rules under the assumption of identically distributed data. However, in open-world scenarios, this assumption seldom holds, as the test distribution is unknown and can be infinitely varied and highly dynamic. To improve calibration specificity in the open world, it is natural to adopt a transductive approach, where the TPR and TNR estimations directly involve the test data, rather than relying on a separate calibration dataset that might not accurately represent the test data. As illustrated in Fig. 2, a transductive approach allows the calibration model to \"see\" the unlabeled test data when deciding on the distance threshold, contrasting with the traditional inductive methods which are \"blind\" to the test data. We term this approach as Transductive Threshold Calibration (TTC), and the traditional inductive calibration methods as Inductive Threshold Calibration (ITC)." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": "To overcome the limitations of ITC methods, we propose OpenGCN, a GNN-based TTC method with enhanced adaptability and robustness for open-world scenarios with diverse concepts and distance distributions. We highlight the key differences between OpenGCN and conventional" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17099" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 69, + 299, + 163 + ], + "blocks": [ + { + "bbox": [ + 50, + 69, + 299, + 163 + ], + "lines": [ + { + "bbox": [ + 50, + 69, + 299, + 163 + ], + "spans": [ + { + "bbox": [ + 50, + 69, + 299, + 163 + ], + "type": "image", + "image_path": "baf4fc0173ce1b1b2a383e34f646b0f3346a3c4e94d2d9f75aaf5c8bdf3e0fac.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 96, + 167, + 257, + 178 + ], + "lines": [ + { + "bbox": [ + 96, + 167, + 257, + 178 + ], + "spans": [ + { + "bbox": [ + 96, + 167, + 257, + 178 + ], + "type": "text", + "content": "(a) Pre-training on Closed-World Examples" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 307, + 70, + 541, + 163 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 541, + 163 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 541, + 163 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 541, + 163 + ], + "type": "image", + "image_path": "dbdd4b7f54fc80102d66a70ab7f8f399b97f6c1e33394574d0a1ae0b5e11c331.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 343, + 166, + 498, + 177 + ], + "lines": [ + { + "bbox": [ + 343, + 166, + 498, + 177 + ], + "spans": [ + { + "bbox": [ + 343, + 166, + 498, + 177 + ], + "type": "text", + "content": "(b) Fine-tuning on Open-World Examples" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 186, + 547, + 242 + ], + "lines": [ + { + "bbox": [ + 46, + 186, + 547, + 242 + ], + "spans": [ + { + "bbox": [ + 46, + 186, + 547, + 242 + ], + "type": "text", + "content": "Figure 3. OpenGCN training workflow: (a) During pre-training, OpenGCN jointly optimizes pairwise connectivity, and instance-specific neighborhood and average densities. (b) During fine-tuning, the 2-layer MLP is reset for fine-tuning, while the other weights remain frozen. Solid blue and dashed red arrows represent forward and backward propagation, respectively. At test time, we employ the trained OpenGCN model and MLP head to predict the TPR and TNR as functions of each distance threshold specifically for each test distribution. We then follow Eq. (1) and use grid search to find the optimal distance threshold for each test dataset. Best viewed in color." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 262, + 289, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 262, + 289, + 514 + ], + "spans": [ + { + "bbox": [ + 46, + 262, + 289, + 514 + ], + "type": "text", + "content": "ITC methods. First, OpenGCN, as a transductive method, derives distance thresholds by leveraging information directly from the test data. This empowers it to adapt to the characteristics of the test data, thereby eliminating the requirement for the calibration data to share a similar distribution with the test data. Second, OpenGCN is engineered to integrate useful information from both closed-world and open-world data sources. This is achieved through a two-stage training process, as illustrated in Fig. 3. We first pretrain OpenGCN on a closed-world dataset, which is the same dataset used to train the DML embedding model. Afterwards, we fine-tune it on a smaller calibration dataset. This calibration dataset contains open-world classes that do not overlap with those in the test data or the closed-world pretraining data. This approach allows the model to smoothly transition from a closed-world context to open-world scenarios, effectively utilizing closed-world knowledge to enhance its transductive reasoning capabilities in the dynamic and unknown open world. In the next section, we delve into the details of OpenGCN, elaborating on how it enables effective TTC for open-world scenarios." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 519, + 255, + 533 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 519, + 255, + 533 + ], + "spans": [ + { + "bbox": [ + 47, + 519, + 255, + 533 + ], + "type": "text", + "content": "3.2. OpenGCN: Learning for Effective TTC" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "spans": [ + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "text", + "content": "OpenGCN Inference Workflow A straight-forward way to estimate " + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "inline_equation", + "content": "\\mathrm{TPR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "inline_equation", + "content": "\\mathrm{TNR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "text", + "content": ", as defined in Eqs. (2) and (3), is to model the true pairwise connectivities with edge connectivity probability [52]. This probability, denoted as " + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "inline_equation", + "content": "p_{ij}" + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "text", + "content": ", quantifies the likelihood that two samples have the same label. By setting a proper connectivity threshold " + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "text", + "content": ", we can approximate " + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "inline_equation", + "content": "\\mathrm{TPR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "inline_equation", + "content": "\\mathrm{TNR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 537, + 287, + 622 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 74, + 625, + 287, + 649 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 74, + 625, + 287, + 649 + ], + "spans": [ + { + "bbox": [ + 74, + 625, + 287, + 649 + ], + "type": "interline_equation", + "content": "\\mathrm {T P R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} > \\tau} \\cdot 1 _ {d _ {i j} < d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} > \\tau} \\tag {4}", + "image_path": "1d33cf40af18c94476c152521a6fa65ed48a12c1585a22de2af46f4b0ef473ea.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 74, + 653, + 287, + 677 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 74, + 653, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 74, + 653, + 287, + 677 + ], + "type": "interline_equation", + "content": "\\mathrm {T N R} _ {\\text {t e s t}} (d) = \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} \\leq \\tau} \\cdot 1 _ {d _ {i j} > d} / \\sum_ {i, j \\in D _ {\\text {t e s t}}} 1 _ {p _ {i j} \\leq \\tau} \\tag {5}", + "image_path": "a3fa576a43b1fe608addfebab28ed563dfd34fea8332f70346649c5e1fd0aa04.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "content": "These formulations offer a TTC solution that centers on precisely predicting pairwise connectivities for open-world test distributions, a problem well-suited for modern" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "spans": [ + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "type": "text", + "content": "deep learning algorithms. Specifically, as shown in Fig. 3, OpenGCN is designed as a GNN-based method for predicting pairwise connectivities over graph data constructed from the unlabeled test samples. We adopt a GNN architecture, specifically a Graph Attention Network (GAT) [46], due to its demonstrated effectiveness in generalizing to open-world scenarios [3, 5, 9, 10, 49, 51, 52]. Additionally, we use fully connected graphs to ensure that in-graph pairwise distance distribution is representative of the overall pairwise distance distribution. For inference, nodal features extracted by the GAT encoder are concatenated with the original DML embedding features [52] and passed through a 2-layer MLP to predict pairwise connectivities. The connectivity predictions are then used to transductively estimate TPR and TNR at each distance threshold for the test distributions, following the formulations in Eqs. (4) and (5), where the connectivity threshold " + }, + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "type": "text", + "content": " is selected by 10-fold cross validation on " + }, + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "type": "text", + "content": ". Due to the typically large size of the test data, for efficient inference, we randomly sample subsets from " + }, + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 304, + 262, + 545, + 526 + ], + "type": "text", + "content": " to construct fully connected sub-graphs for connectivity inference, repeating this process until the TPR and TNR estimations converge." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 534, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 546, + 713 + ], + "type": "text", + "content": "Joint Connectivity and Density Estimations Using representation density prediction as an auxiliary task to enhance connectivity prediction is widely used in clustering tasks [2, 7, 31]. This approach is based on the idea that a cluster typically exists within a contiguous region of high sample density, separated from other clusters. Recent supervised visual clustering works also leverage density as a key modeling parameter to enhance clustering performance by encouraging information sharing between the tasks [49, 50, 52]. Driven by the intrinsic connections between density and connectivity, we adopt a multitask approach, where we simultaneously learn for pairwise edge connectivity and instance-wise representation densities. However, unlike previous works which only consider one density metric, we simultaneously learn two density" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17100" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "text", + "content": "metrics: the average density (" + }, + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{avg}}" + }, + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "text", + "content": "), and the neighborhood density (" + }, + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{nbr}}" + }, + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "text", + "content": "). Formally, these two density metrics, defined in [52], can be expressed as follows" + }, + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "^2" + }, + { + "bbox": [ + 46, + 72, + 287, + 109 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 54, + 114, + 287, + 144 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 54, + 114, + 287, + 144 + ], + "spans": [ + { + "bbox": [ + 54, + 114, + 287, + 144 + ], + "type": "interline_equation", + "content": "s _ {i} ^ {\\text {a v g}} = \\frac {\\sum_ {j \\in \\mathcal {N} _ {i}} a _ {i j} \\cdot 1 _ {y _ {i} = y _ {j}}}{| \\mathcal {N} _ {i} |}, s _ {i} ^ {\\text {n b r}} = \\frac {\\sum_ {j \\in \\mathcal {N} _ {i}} a _ {i j} \\cdot \\left(1 _ {y _ {i} = y _ {j}} - 1 _ {y _ {i} \\neq y _ {j}}\\right)}{| \\mathcal {N} _ {i} |} \\tag {6}", + "image_path": "1cfdad9c9906ac77c5b7ee2d9589accf243fb3a6926d0e46fc57c418b3bc4381.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "spans": [ + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_i" + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "text", + "content": " denotes the neighbourhood of a sample " + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "inline_equation", + "content": "a_{ij}" + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "text", + "content": " represents the cosine similarity between the original embedding features of sample " + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "text", + "content": " and sample " + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 151, + 287, + 186 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "spans": [ + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "text", + "content": "To illustrate the motivation of utilizing both density metrics instead of just one, we first introduce two metrics adapted from prior works [20, 41], namely the class-specific TPR and TNR scores, denoted as " + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "inline_equation", + "content": "\\mathrm{TPR}^k" + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "inline_equation", + "content": "\\mathrm{TNR}^k" + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "text", + "content": ", respectively. Let " + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "inline_equation", + "content": "f_{i}" + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "text", + "content": " denote the " + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "inline_equation", + "content": "\\mathrm{L}_2" + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "text", + "content": "-normalized embeddings of an image in a dataset " + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "text", + "content": ". For a given class " + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 187, + 287, + 270 + ], + "type": "text", + "content": ", its class-specific TPR and TNR scores can be expressed as:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 52, + 277, + 287, + 313 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 277, + 287, + 313 + ], + "spans": [ + { + "bbox": [ + 52, + 277, + 287, + 313 + ], + "type": "interline_equation", + "content": "\\mathrm {T P R} ^ {k} = \\frac {\\left\\| \\sum_ {i \\in D} f _ {i} \\cdot 1 _ {y _ {i} = k} \\right\\|}{\\sum_ {i \\in D} 1 _ {y _ {i} = k}}, \\quad \\mathrm {T N R} ^ {k} = \\frac {\\sum_ {i , j \\in D} \\left(1 - a _ {i j}\\right) \\cdot 1 _ {y _ {j} \\neq y _ {i} = k}}{\\sum_ {i , j \\in D} 1 _ {y _ {j} \\neq y _ {i} = k}} \\tag {7}", + "image_path": "56e7dbdb74acb11f859f6ee5848e5df47eafb440263e4b6f981727b634e99c5d.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 320, + 287, + 356 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 320, + 287, + 356 + ], + "spans": [ + { + "bbox": [ + 46, + 320, + 287, + 356 + ], + "type": "text", + "content": "The subsequent theorems formally establish a connection between two density metrics defined in Eq. (6) and the class-specific TPR and TNR scores." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 364, + 287, + 376 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 364, + 287, + 376 + ], + "spans": [ + { + "bbox": [ + 46, + 364, + 287, + 376 + ], + "type": "text", + "content": "Theorem 1 (Correspondence between " + }, + { + "bbox": [ + 46, + 364, + 287, + 376 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{avg}}" + }, + { + "bbox": [ + 46, + 364, + 287, + 376 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 364, + 287, + 376 + ], + "type": "inline_equation", + "content": "TPR^{k}" + }, + { + "bbox": [ + 46, + 364, + 287, + 376 + ], + "type": "text", + "content": ")" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "spans": [ + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "text", + "content": "Let " + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "inline_equation", + "content": "\\mathcal{N}" + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "text", + "content": " be a cluster with high purity, where the majority class is " + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "text", + "content": ". For each sample " + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "inline_equation", + "content": "i \\in \\mathcal{N}" + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "text", + "content": ", when both " + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "inline_equation", + "content": "|\\mathcal{N}|" + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "inline_equation", + "content": "|\\mathcal{N}_i|" + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "text", + "content": " are sufficiently large, " + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "inline_equation", + "content": "TPR^k" + }, + { + "bbox": [ + 46, + 376, + 287, + 412 + ], + "type": "text", + "content": " can be approximated as:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 59, + 418, + 287, + 469 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 418, + 287, + 469 + ], + "spans": [ + { + "bbox": [ + 59, + 418, + 287, + 469 + ], + "type": "interline_equation", + "content": "\\lim _ {| \\mathcal {N} _ {i} | \\rightarrow \\infty} T P R ^ {k} = \\left(\\frac {| \\mathcal {N} _ {i} |}{2 | \\mathcal {N} |} \\right. \\cdot \\underbrace {\\left(\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {n b r}} \\right.} _ {\\substack {\\text {avg s} ^ {\\mathrm {n b r}}\\\\2 \\times \\text {avg s} ^ {\\mathrm {a v g}}}} + \\underbrace {\\left(\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} \\mathfrak {a} _ {\\mathrm {i}} ^ {\\mathrm {a v g}}\\right) ^ {1 / 2}} _ {\\substack {\\text {avg a} ^ {\\mathrm {a v g}}}} \\tag{8}", + "image_path": "84b59b519b2f51de91c9f3f848511b20ebb70edb6b989d2b6334047cae72d223.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "spans": [ + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "type": "inline_equation", + "content": "\\mathfrak{a}_i^{\\mathrm{avg}} = \\frac{1}{|\\mathcal{N}_i|}\\sum_{j\\in \\mathcal{N}_i}a_{ij}" + }, + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "type": "inline_equation", + "content": "\\mathfrak{a}^{\\mathrm{avg}}" + }, + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "type": "text", + "content": " is the mean of average cosine similarity of all vertices in " + }, + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_i" + }, + { + "bbox": [ + 46, + 477, + 287, + 503 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "text", + "content": "Theorem 2 (Correspondence between " + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{avg}} - s^{\\mathrm{nbr}}" + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "inline_equation", + "content": "TNR^{k}" + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "text", + "content": ") Under the same assumptions in Theorem 1, for a given class " + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "text", + "content": ", its " + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "inline_equation", + "content": "TNR^{k}" + }, + { + "bbox": [ + 46, + 510, + 287, + 548 + ], + "type": "text", + "content": " can be approximated as:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 61, + 553, + 287, + 593 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 553, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 61, + 553, + 287, + 593 + ], + "type": "interline_equation", + "content": "\\lim _ {| \\mathcal {N} _ {i} | \\rightarrow \\infty} T N R ^ {k} = 1 - \\frac {| \\mathcal {N} |}{| \\mathcal {N} | _ {k ^ {-}}} \\cdot (\\underbrace {\\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {a v g}} - \\frac {1}{| \\mathcal {N} |} \\sum_ {i \\in \\mathcal {N}} s _ {i} ^ {\\mathrm {n b r}})} _ {\\text {a v e r a g e (s} ^ {\\mathrm {a v g}} - \\mathrm {s} ^ {\\mathrm {n b r}} \\text {)}}) \\tag {9}", + "image_path": "0ce5ce4f62369d1840dec5ad969a28c18cd62814b7ac4ea0c39527f221497389.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "spans": [ + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "type": "inline_equation", + "content": "|\\mathcal{N}|_{k^{-}}" + }, + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "type": "text", + "content": " denotes the number of negative pairs in " + }, + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "type": "inline_equation", + "content": "\\mathcal{N}" + }, + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "type": "text", + "content": " where one sample of each negative pair must have label " + }, + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 598, + 287, + 624 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 632, + 287, + 668 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 632, + 287, + 668 + ], + "spans": [ + { + "bbox": [ + 46, + 632, + 287, + 668 + ], + "type": "text", + "content": "Based on the theorems, when the neighborhood size is sufficiently large, considering both density metrics effectively encapsulates both class-specific TPR and TNR within" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 72, + 545, + 240 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 240 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 240 + ], + "type": "text", + "content": "this neighbourhood. As open-world threshold calibration aims to balance the TPR and TNR trade-off for unknown test distributions, it is crucial to capture both aspects to improve within-class and cross-class connectivity predictions. Furthermore, the class-specific nature of these metrics grants them the versatility to adapt to varying class compositions. In Sec. 4.3, we provide an ablation study comparing the use of a single density metric versus both densities, where jointly predicting both densities along with connectivity yields better calibration performance. Thus, we introduce predictions of both density metrics, " + }, + { + "bbox": [ + 306, + 72, + 545, + 240 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{avg}}" + }, + { + "bbox": [ + 306, + 72, + 545, + 240 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 72, + 545, + 240 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{nbr}}" + }, + { + "bbox": [ + 306, + 72, + 545, + 240 + ], + "type": "text", + "content": ", as auxiliary tasks to enhance the generalization of connectivity prediction. This leads to the following learning objective for training OpenGCN:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 344, + 249, + 545, + 277 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 344, + 249, + 545, + 277 + ], + "spans": [ + { + "bbox": [ + 344, + 249, + 545, + 277 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {o v e r a l l}} = \\underbrace {\\mathcal {L} _ {\\text {c o n n}}} _ {\\text {m a i n t a s k}} + \\underbrace {\\lambda \\cdot \\left(\\mathcal {L} _ {s ^ {\\mathrm {n b r}}} + \\mathcal {L} _ {s ^ {\\mathrm {a v g}}}\\right)} _ {\\text {a u x i l i a r y t a s k}} \\tag {10}", + "image_path": "52b7ca182fe333a34926515aa22e16bd4d1e1d74c6fddee988414692b515b7f1.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "spans": [ + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{conn}}" + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "text", + "content": " is the balanced cross-entropy loss for pairwise edge connectivity and " + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{s^{\\mathrm{nbr}}}" + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{s^{\\mathrm{avg}}}" + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "text", + "content": " are the mean squared error losses for " + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{nbr}}" + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{avg}}" + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "text", + "content": ", respectively. Specifically, we define " + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{conn}}" + }, + { + "bbox": [ + 305, + 286, + 545, + 346 + ], + "type": "text", + "content": " as follows to ensure equal importance for both within-class and cross-class connectivities:" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 315, + 352, + 545, + 401 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 352, + 545, + 401 + ], + "spans": [ + { + "bbox": [ + 315, + 352, + 545, + 401 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {c o n n}} = \\frac {\\sum_ {i , j \\in V} 1 _ {y _ {i} = y _ {j}} \\cdot \\log \\left(p _ {i j}\\right)}{\\sum_ {i , j \\in V} 1 _ {y _ {i} = y _ {j}}} + \\frac {\\sum_ {i , j \\in V} 1 _ {y _ {i} \\neq y _ {j}} \\cdot \\log \\left(1 - p _ {i j}\\right)}{\\sum_ {i , j \\in V} 1 _ {y _ {i} \\neq y _ {j}}} \\tag {11}", + "image_path": "a75cbdf8048e3b6cb2f775b7097bd153390b24240c8eeda24705742a53a892b6.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 402, + 504, + 414 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 402, + 504, + 414 + ], + "spans": [ + { + "bbox": [ + 306, + 402, + 504, + 414 + ], + "type": "text", + "content": "Meanwhile, " + }, + { + "bbox": [ + 306, + 402, + 504, + 414 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{s^{\\mathrm{nbr}}}" + }, + { + "bbox": [ + 306, + 402, + 504, + 414 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 402, + 504, + 414 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{s^{\\mathrm{avg}}}" + }, + { + "bbox": [ + 306, + 402, + 504, + 414 + ], + "type": "text", + "content": " can be expressed as:" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 313, + 422, + 545, + 454 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 422, + 545, + 454 + ], + "spans": [ + { + "bbox": [ + 313, + 422, + 545, + 454 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {s ^ {\\text {a v g}}} = \\frac {\\sum_ {i \\in V} \\left(s _ {i} ^ {\\text {a v g}} - \\hat {s} _ {i} ^ {\\text {a v g}}\\right) ^ {2}}{| V |}, \\quad \\mathcal {L} _ {s ^ {\\text {n b r}}} = \\frac {\\sum_ {i \\in V} \\left(s _ {i} ^ {\\text {n b r}} - \\hat {s} _ {i} ^ {\\text {n b r}}\\right) ^ {2}}{| V |} \\tag {12}", + "image_path": "74a45d845e3b64ce5b4fe81ef7c42a8daf7c9a8ff98b4b94060eb7b052abcb97.jpg" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "spans": [ + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "type": "text", + "content": " represents the node vertices in the graph data, and " + }, + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "type": "inline_equation", + "content": "\\hat{s}_i" + }, + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "type": "text", + "content": " is the estimated density for each sample based on " + }, + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "type": "inline_equation", + "content": "p_{ij}" + }, + { + "bbox": [ + 305, + 462, + 545, + 486 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "text", + "content": "Two-stage Training for Adaptability The DML embedding model, trained on " + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "text", + "content": " (closed-set examples), tends to produce more compact embeddings for these examples than those of open-world classes. If OpenGCN is trained solely on " + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "text", + "content": ", its ability to generalize to the open-world scenarios will be limited. On the other hand, if OpenGCN is trained solely on " + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "text", + "content": ", its knowledge may be very narrow since the calibration dataset is typically small and lacks diverse concepts. To tackle this, we borrow established experience in domain generalization and adaptation [11, 21, 48], and adopt a two-stage training strategy. First, we pretrain OpenGCN on " + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "text", + "content": ", which consists of a large collection of closed-set examples. After this, we reset the 2-layer MLP while keeping the other parameters frozen. Subsequently, we fine-tune the MLP on " + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 487, + 545, + 713 + ], + "type": "text", + "content": ", a small open-world calibration dataset containing disjoint classes to the test data, to adapt the pretrained model to open-world scenarios. In Sec. 4.3, we conduct an ablation study to provide further support for this two-stage training approach. We choose to" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 46, + 673, + 287, + 714 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 673, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 673, + 287, + 714 + ], + "type": "text", + "content": "2. Although the original definition of " + }, + { + "bbox": [ + 46, + 673, + 287, + 714 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{avg}}" + }, + { + "bbox": [ + 46, + 673, + 287, + 714 + ], + "type": "text", + "content": " in [52] requires a neighborhood size that includes all samples belonging to a given class, it can be shown by stochastic convergence of random variables that our definition is a tight approximation for [52] when " + }, + { + "bbox": [ + 46, + 673, + 287, + 714 + ], + "type": "inline_equation", + "content": "|\\mathcal{N}_i|" + }, + { + "bbox": [ + 46, + 673, + 287, + 714 + ], + "type": "text", + "content": " is sufficiently large." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17101" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 168 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 168 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 168 + ], + "type": "text", + "content": "fine-tune only the MLP based on the practical observations that " + }, + { + "bbox": [ + 46, + 72, + 289, + 168 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 46, + 72, + 289, + 168 + ], + "type": "text", + "content": " is typically limited in size, and fine-tuning the entire model on such a small dataset may lead to overfitting. It is worth reiterating that this approach does not require additional training data, as the closed-set data is already in place for training the DML embedding model, and the separate open-world calibration dataset is required for conventional inductive posthoc calibration methods as well." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 178, + 181, + 192 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 178, + 181, + 192 + ], + "spans": [ + { + "bbox": [ + 47, + 178, + 181, + 192 + ], + "type": "text", + "content": "4. Experiment and Result" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 198, + 287, + 247 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 198, + 287, + 247 + ], + "spans": [ + { + "bbox": [ + 46, + 198, + 287, + 247 + ], + "type": "text", + "content": "We experiment on public recognition benchmarks including iNaturalist-2018 [44], CUB-200 [47] and Cars-196 [23]. Below, we outline our setup and present the results. Further experiments can be found in the supplementary materials." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 252, + 239, + 266 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 252, + 239, + 266 + ], + "spans": [ + { + "bbox": [ + 47, + 252, + 239, + 266 + ], + "type": "text", + "content": "4.1. Dataset and Implementation Details" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "spans": [ + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "text", + "content": "Datasets To simulate real-world testing environments, we consider three calibration scenarios: SameDist, ShiftDist and DiffDist. The SameDist scenario involves cases where " + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "text", + "content": " share similar distance distributions, the ShiftDist scenario accounts for test-time non-semantic distance distribution shifts, and the DiffDist scenario represents out-of-distribution calibration, where " + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "text", + "content": " have very different distance distributions. Note that in all three scenarios, we adhere to the open-world setting where " + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "inline_equation", + "content": "C_{\\mathrm{train}} \\cap C_{\\mathrm{cal}} = C_{\\mathrm{train}} \\cap C_{\\mathrm{test}} = C_{\\mathrm{cal}} \\cap C_{\\mathrm{test}} = \\emptyset" + }, + { + "bbox": [ + 46, + 270, + 287, + 402 + ], + "type": "text", + "content": ". Below, we elaborate on the setup for each calibration scenario:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 403, + 287, + 714 + ], + "type": "list", + "angle": 0, + "index": 8, + "blocks": [ + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "spans": [ + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "content": "- SameDist For iNaturalist, the training and testing classes are distinct, so we directly use the training partition as " + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "inline_equation", + "content": "D_{\\text{train}}" + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "content": ". To create " + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "inline_equation", + "content": "D_{\\text{cal}}" + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "content": ", we randomly select " + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "content": " of the test classes, leaving the remaining classes for " + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "inline_equation", + "content": "D_{\\text{test}}" + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "content": ". For CUB and Cars, where there is overlap between training and testing classes, we divide them into train / cal / test subsets. The train set comprises the first half of the class indices, while the cal / test sets are randomly chosen from the remaining classes with a " + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "inline_equation", + "content": "1/9" + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "content": " ratio. As " + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "inline_equation", + "content": "D_{\\text{cal}}" + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "inline_equation", + "content": "D_{\\text{test}}" + }, + { + "bbox": [ + 47, + 403, + 287, + 533 + ], + "type": "text", + "content": " are randomly split from the same dataset, they are expected to have similar distance distributions." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "spans": [ + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "type": "text", + "content": "- ShiftDist We consider 13 common image corruption and perturbation types, including noise, blur, weather, and digital distortions, to assess the robustness of the calibration methods under varied adversities. We follow the setups in [17] and apply the changes to " + }, + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "type": "text", + "content": " only, while leaving " + }, + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 47, + 534, + 287, + 605 + ], + "type": "text", + "content": " unchanged." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "text", + "content": "- DiffDist To induce significant distance distribution shifts between " + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "text", + "content": ", we employ the following treatments. For iNaturalist, characterized by a long-tailed distribution, we divide its test classes into two sets based on cluster size, each containing approximately the same number of images. For calibration purposes, we use the set with a higher number of images per class (\"head\" set, denoted as " + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{head}}" + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "text", + "content": ") as " + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "text", + "content": " and the set with fewer images per class (\"tail\" set, denoted as " + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{tail}}" + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "text", + "content": ") as " + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "text", + "content": " to simu" + } + ] + } + ], + "index": 7 + } + ], + "sub_type": "text" + }, + { + "type": "table", + "bbox": [ + 315, + 87, + 541, + 256 + ], + "blocks": [ + { + "bbox": [ + 349, + 71, + 503, + 81 + ], + "lines": [ + { + "bbox": [ + 349, + 71, + 503, + 81 + ], + "spans": [ + { + "bbox": [ + 349, + 71, + 503, + 81 + ], + "type": "text", + "content": "Table 1. Detailed statistics of the datasets." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 315, + 87, + 541, + 256 + ], + "lines": [ + { + "bbox": [ + 315, + 87, + 541, + 256 + ], + "spans": [ + { + "bbox": [ + 315, + 87, + 541, + 256 + ], + "type": "table", + "html": "
SettingDatasetPartition# img# cls# img/cls
SameDistCarsDtrain7,9619881.2
Dcal8661086.6
Dtest7,3568883.6
CUBDtrain5,8029958.6
Dcal5991059.9
Dtest5,3859159.2
iNatDtrain324,4185,69057.0
Dcal12,61324551.5
Dtest123,0472,20755.8
ShiftDistCarsSameDist except for corruption on Dtest
DiffDistiNatDtrainiNat SameDist Dtrain
Dhead70,057200350.3
Dtail66,0362,25229.3
CarsSameDist except for sketchifying Dtest
iNat/CUB (cross dataset)DtrainiNat SameDist Dtrain
DcaliNat SameDist Dcal
DtestEntire CUB dataset
", + "image_path": "4deecfce793f06d95e4b7ffe2998245a7b8458d5a4f4e0a275ee9d1e30e835df.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "spans": [ + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "type": "text", + "content": "late a calibration for the long tail scenario. In addition, we also explore two out-of-domain calibration scenarios. First, for Cars, we transform " + }, + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "type": "text", + "content": " into sketches while leaving " + }, + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 312, + 273, + 545, + 357 + ], + "type": "text", + "content": " untouched. Second, we consider cross-dataset calibration, where the OpenGCN model is pretrained and fine-tuned on iNaturalist (general natural species images) but evaluated on CUB (bird images)." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 357, + 545, + 380 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 357, + 545, + 380 + ], + "spans": [ + { + "bbox": [ + 306, + 357, + 545, + 380 + ], + "type": "text", + "content": "Evaluation Metrics For a comprehensive evaluation, we consider two approaches to assess calibration performance:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 381, + 545, + 476 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 381, + 545, + 476 + ], + "spans": [ + { + "bbox": [ + 306, + 381, + 545, + 476 + ], + "type": "text", + "content": "- Global Evaluation: Since we define open-world threshold calibration as the accurate prediction of both TPR and TNR at each distance threshold to meet specific TPR or TNR performance requirements of diverse test-time users, it is natural to employ the combined Mean Absolute Errors (MAE) for both TPR and TNR predictions across the entire distance range as our evaluation metric. Formally, this metric can be expressed as:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 327, + 483, + 545, + 512 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 327, + 483, + 545, + 512 + ], + "spans": [ + { + "bbox": [ + 327, + 483, + 545, + 512 + ], + "type": "interline_equation", + "content": "\\mathrm {M A E} _ {\\text {c o m b}} = \\frac {1}{2} \\int_ {0} ^ {2} \\left(| \\hat {\\mathrm {T P R}} (\\mathrm {d}) - \\mathrm {T P R} (\\mathrm {d}) | + \\right. \\tag {13}", + "image_path": "a29a277a0569531504b55c209505f97429bb1ca5e0112f685e267e97be76df9e.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 411, + 514, + 515, + 528 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 411, + 514, + 515, + 528 + ], + "spans": [ + { + "bbox": [ + 411, + 514, + 515, + 528 + ], + "type": "interline_equation", + "content": "\\left. \\left| \\mathrm {T N R} (\\mathrm {d}) - \\mathrm {T N R} (\\mathrm {d}) \\right|\\right) d \\mathrm {d}", + "image_path": "e1fe7f04e3fc7ebc99b1d6dc37f5b81d871d03fe7b3ff3e18525572e030e7816.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "spans": [ + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "text", + "content": "- Point-wise Evaluation: We first set a performance target and compute the optimal distance threshold, denoted as " + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "inline_equation", + "content": "\\hat{d}^{\\mathrm{opt}}" + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "text", + "content": ", based on the TPR or TNR estimations. We then compute the Absolute Error (AE) between the actual performance at " + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "inline_equation", + "content": "\\hat{d}^{\\mathrm{opt}}" + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "text", + "content": " and the target, denoted as " + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "inline_equation", + "content": "\\mathrm{AE}_{\\mathrm{TPR}} = |\\mathrm{TPR}(\\hat{d}^{\\mathrm{opt}}) - \\mathrm{TPR}_{\\mathrm{target}}|" + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "inline_equation", + "content": "\\mathrm{AE}_{\\mathrm{TNR}} = |\\mathrm{TNR}(\\hat{d}^{\\mathrm{opt}}) - \\mathrm{TNR}_{\\mathrm{target}}|" + }, + { + "bbox": [ + 306, + 534, + 545, + 618 + ], + "type": "text", + "content": " for TPR and TNR, respectively." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": "Baseline Methods We consider the most representative inductive posthoc calibration methods including Platt Scaling [37], Histogram Calibration [53], Isotonic Calibration [54] and Beta Calibration [24]. Additionally, we explore pseudolabel-based baselines, including traditional clustering methods such as DBSCAN [13] and the state-of-the-art method in GNN-based clustering, HiLANDER [49]. For clustering-based methods, we follow" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "17102" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 49, + 110, + 547, + 196 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 547, + 105 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 547, + 105 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 547, + 105 + ], + "type": "text", + "content": "Table 2. Evaluation in the SameDist scenario using pointwise metrics of " + }, + { + "bbox": [ + 47, + 70, + 547, + 105 + ], + "type": "inline_equation", + "content": "\\mathrm{AE}_{\\mathrm{TPR}}" + }, + { + "bbox": [ + 47, + 70, + 547, + 105 + ], + "type": "text", + "content": " (optimize for TPR) and " + }, + { + "bbox": [ + 47, + 70, + 547, + 105 + ], + "type": "inline_equation", + "content": "\\mathrm{AE}_{\\mathrm{TNR}}" + }, + { + "bbox": [ + 47, + 70, + 547, + 105 + ], + "type": "text", + "content": " (optimize for TNR). The smaller the metric, the better. For each dataset, the best and second best results are marked in Red and Blue, respectively. Shading in the Table: Gray for posthoc calibration baselines, Cyan for clustering baselines, and Blue for our OpenGCN method. Best viewed in color." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 49, + 110, + 547, + 196 + ], + "lines": [ + { + "bbox": [ + 49, + 110, + 547, + 196 + ], + "spans": [ + { + "bbox": [ + 49, + 110, + 547, + 196 + ], + "type": "table", + "html": "
MethodOptimize for TPR=80%Optimize for TPR=90%Optimize for TNR=80%Optimize for TNR=90%Rank
CarsCUBInatCarsCUBInatCarsCUBInatCarsCUBInat
Platt scaling [37]1.35%5.10%6.08%0.44%2.63%4.63%2.83%2.02%7.54%2.93%6.49%0.92%6
Beta calibration [24]1.13%5.16%5.51%0.02%2.91%3.26%2.94%1.41%7.57%2.78%6.43%0.93%5
Isotonic regression [54]0.82%5.28%4.53%0.90%2.56%3.54%1.94%1.00%5.78%1.26%4.65%0.65%3
Histogram Calibration [53]0.82%5.28%4.53%0.90%2.56%3.54%1.94%1.00%5.78%1.26%4.65%0.65%4
DBSCAN [13]43.11%18.87%0.45%34.57%9.18%1.85%4.09%13.77%12.90%1.60%9.32%9.32%7
Hi-LANDER [49]3.44%1.36%10.54%2.02%0.93%7.00%0.06%0.38%2.35%0.10%2.20%0.21%2
OpenGCN (ours)0.33%0.74%1.59%0.72%1.41%2.37%0.61%0.09%0.74%0.58%0.72%0.10%1
", + "image_path": "787723a1aafad3bf02c51ae07566bce024350e50b94d3f0265bb400a52183f97.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "spans": [ + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "type": "text", + "content": "their original clustering decoding inference workflows to estimate pseudo labels, and use these pseudo labels to compute " + }, + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "type": "inline_equation", + "content": "\\mathrm{TPR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "type": "inline_equation", + "content": "\\mathrm{TNR}_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "type": "text", + "content": " for finding " + }, + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "type": "inline_equation", + "content": "d^{\\mathrm{opt}}" + }, + { + "bbox": [ + 46, + 215, + 287, + 251 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "content": "Implementation Details In all experiments, we train ResNet-50 models with 128-dimensional embeddings on " + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "content": " using the setups in [6]. The embedding models are then used to extract the embeddings for " + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "content": ". For training OpenGCN, as implied in Theorems 1 and 2, the neighborhood size needs to be sufficiently large to encapsulate both intra-class and inter-class representation structures. Thus, we use a batch sizes of 256 for graph construction during training. We use the Adam optimizer [22] with a cosine annealing schedule [30]. For traditional calibration methods, we use the official codebase from [25] to map the ground truth TPR (or TNR) as a function of the distance threshold from " + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{train}}" + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "content": ". When doing point-wise evaluation, the optimal distance threshold " + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "inline_equation", + "content": "d^{\\mathrm{opt}}" + }, + { + "bbox": [ + 46, + 251, + 290, + 445 + ], + "type": "text", + "content": " is solved with grid search at a grid size of 0.01. Further details are provided in the supplementary materials." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 454, + 159, + 467 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 454, + 159, + 467 + ], + "spans": [ + { + "bbox": [ + 47, + 454, + 159, + 467 + ], + "type": "text", + "content": "4.2. Evaluation Results" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 474, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 474, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 474, + 288, + 715 + ], + "type": "text", + "content": "SameDist Calibration We present the global and pointwise evaluation results for the SameDist scenario in Tab. 3 and Tab. 2, respectively. For pointwise evaluation, we evaluate at multiple target values (TPR=80%, 90% and TNR=80%, 90%) to provide a comprehensive assessment. Our results reveal that no single calibration method consistently excels across all distance thresholds and datasets. However, on average, OpenGCN achieves the highest rank. This underscores the importance of TTC in open-world scenarios, where calibration is conducted based on the characteristics of " + }, + { + "bbox": [ + 46, + 474, + 288, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 474, + 288, + 715 + ], + "type": "text", + "content": " rather than relying on a calibration dataset that may not accurately represent " + }, + { + "bbox": [ + 46, + 474, + 288, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 46, + 474, + 288, + 715 + ], + "type": "text", + "content": ". Additionally, the global metrics in Tab. 3 show that, compared to the best baseline method, OpenGCN significantly reduces global error rates by 59.30%, 66.49%, and 59.15% for Cars, CUB, and iNaturalist, respectively. Among the baseline methods, we observe that DBSCAN performs worse than the traditional posthoc calibration methods, while Hi-LANDER outperforms traditional posthoc methods on Cars and CUB but underperforms on iNaturalist. In contrast, OpenGCN con" + } + ] + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 309, + 274, + 545, + 361 + ], + "blocks": [ + { + "bbox": [ + 305, + 213, + 547, + 269 + ], + "lines": [ + { + "bbox": [ + 305, + 213, + 547, + 269 + ], + "spans": [ + { + "bbox": [ + 305, + 213, + 547, + 269 + ], + "type": "text", + "content": "Table 3. Evaluation in the SameDist scenario using the global error metric of " + }, + { + "bbox": [ + 305, + 213, + 547, + 269 + ], + "type": "inline_equation", + "content": "\\mathrm{MAE}_{\\mathrm{comb}}" + }, + { + "bbox": [ + 305, + 213, + 547, + 269 + ], + "type": "text", + "content": ". For each benchmark, the best and second best results are marked in Red and Blue, respectively. We also report the improvement in error reduction of OpenGCN over the best baseline method. Best viewed in color." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 274, + 545, + 361 + ], + "lines": [ + { + "bbox": [ + 309, + 274, + 545, + 361 + ], + "spans": [ + { + "bbox": [ + 309, + 274, + 545, + 361 + ], + "type": "table", + "html": "
MethodCarsCUBiNatRank
Platt scaling1.55e-23.59e-21.23e-26
Beta calibration1.53e-23.59e-21.18e-25
Isotonic regression1.38e-23.61e-21.18e-23
Histogram calibration1.38e-23.62e-21.18e-24
DBSCAN1.02e-11.10e-13.65e-27
Hi-LANDER1.29e-21.94e-22.14e-22
OpenGCN (ours)5.25e-36.50e-34.82e-31
Imp. over top baseline ↑59.30%66.49%59.15%69.14% (avg.)
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Among the baseline methods, Isotonic Regression and Histogram Calibration appear to be the most effective in the presence of image corruptions. However, it is evident that OpenGCN consistently outperform these baseline methods across all corruption types, achieving an average error reduction of " + }, + { + "bbox": [ + 304, + 399, + 545, + 581 + ], + "type": "inline_equation", + "content": "55.03\\%" + }, + { + "bbox": [ + 304, + 399, + 545, + 581 + ], + "type": "text", + "content": " compared to the best baseline method. This robust performance against image corruptions can be attributed to the model's pretraining stage, where it was exposed to closed-set data with similar types of corruptions. Additionally, it is observed that, among the various corruption categories, OpenGCN exhibits the most improvement in the weather category, while showing the least improvement in the blur category." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": "DiffDist Calibration We present the DiffDist calibration results in Tab. 5. As observed, in this scenario characterized by a substantial shift in distance distributions between " + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": ", all calibration methods display elevated errors compared to the SameDist scenario. However, OpenGCN demonstrates superior performance compared to the other calibration methods in both out-of-domain settings (sketch and cross-dataset) and the long-tail calibration setting, achieving an average relative reduction in the global error " + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathrm{MAE}_{\\mathrm{comb}}" + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "inline_equation", + "content": "43.99\\%" + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": ". In particular, we observe significant improvement in the cross-dataset setting (pretrained" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "17103" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 99, + 545, + 220 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 547, + 94 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 547, + 94 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 547, + 94 + ], + "type": "text", + "content": "Table 4. Evaluation on the Cars-196 dataset in the ShiftDist scenario across 13 common corruption and perturbation types using combined global error metric of " + }, + { + "bbox": [ + 47, + 70, + 547, + 94 + ], + "type": "inline_equation", + "content": "\\mathrm{MAE}_{\\mathrm{comb}}" + }, + { + "bbox": [ + 47, + 70, + 547, + 94 + ], + "type": "text", + "content": ". The best results are marked in Red." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 99, + 545, + 220 + ], + "lines": [ + { + "bbox": [ + 48, + 99, + 545, + 220 + ], + "spans": [ + { + "bbox": [ + 48, + 99, + 545, + 220 + ], + "type": "table", + "html": "
MethodNoiseBlurWeatherDigitalRank
GaussShotImpulseDefocusMotionZoomSnowFogBrightContrastElasticPixelJPEG
Platt scaling2.95e-22.99e-23.41e-22.66e-22.62e-25.02e-24.24e-24.37e-22.16e-24.61e-22.16e-22.24e-22.03e-24
Beta calibration2.94e-22.97e-23.41e-22.67e-22.69e-25.06e-24.32e-24.37e-22.18e-24.61e-22.20e-22.23e-22.02e-25
Isotonic regression2.88e-22.85e-23.38e-22.37e-22.31e-24.85e-24.07e-24.34e-21.83e-24.59e-21.85e-22.03e-21.80e-22
Histogram calibration2.88e-22.85e-23.38e-22.37e-22.31e-24.85e-24.07e-24.34e-21.83e-24.59e-21.85e-22.03e-21. 80e-23
DBSCAN4.96e-26.02e-27.79e-29.81e-21.13e-11.22e-11.19e-14.02e-29.27e-24.53e-21.09e-11.04e-18.21e-27
Hi-LANDER7.65e-26.30e-26.59e-23.98e-25.33e-24.48e-25.94e-27.16e-25.09e-29.45e-24.42e-29.48e-26.91e-26
OpenGCN (ours)1.33e-25.87e-31.66e-21.50e-21.71e-23.92e-21.42e-27.32e-36.73e-37.08e-35.34e-31.15e-21.68e-21
Imp. over top baseline ↑53.82%79.40%50.89%36.71%25.97%12.50%65.11%81.79%63.22%84.37%71.14%43.35%6.67%55.03% (avg.)
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MethodCars: SketchCUB: Cross-datasetiNat: Longtail
Platt scaling1.08e-11.15e-12.09e-2
Beta calibration1.08e-11.15e-12.12e-2
Isotonic regression1.08e-11.15e-12.11e-2
Histogram Calibration1.08e-11.15e-12.11e-2
DBSCAN5.16e-21.60e-17.21e-2
Hi-LANDER6.67e-21.30e-16.26e-2
OpenGCN (ours)3.54e-21.42e-21.82e-2
Imp. over top baseline ↑31.40%87.65%12.92%
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Best baselineOpenGCN loss ablations
Lconn+λ·Lsavg+λ·Lsshr+λ·(Lsavg + Lsshr)
MAEcomb1.18e-26.25e-35.37e-35.12e-34.82e-3
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MethodCarsCUBiNat
OpenGCN (PT)2.90e-22.52e-23.55e-2
OpenGCN (PT+FT)5.25e-3 (81.9%)6.50e-3 (74.2%)4.82e-3 (86.4%)
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Ablation Studies" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": "Importance of Multi-task Learning We assess the impact of multi-task learning on " + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "inline_equation", + "content": "\\mathrm{MAE}_{\\mathrm{comb}}" + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": ". As shown in Tab. 6, compared to predicting connectivity only, employing a single density metric in conjunction with connectivity prediction helps reduce " + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "inline_equation", + "content": "\\mathrm{MAE}_{\\mathrm{comb}}" + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "inline_equation", + "content": "6.25\\mathrm{e} - 3" + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "inline_equation", + "content": "5.37\\mathrm{e} - 3" + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{avg}}" + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": " and to " + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "inline_equation", + "content": "5.12\\mathrm{e} - 3" + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "inline_equation", + "content": "s^{\\mathrm{nbr}}" + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": ", respectively. However, by utilizing both density metrics, we further decrease this error to " + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "inline_equation", + "content": "4.82\\mathrm{e} - 3" + }, + { + "bbox": [ + 46, + 570, + 287, + 700 + ], + "type": "text", + "content": ". This supports our choice to incorporate both density metrics, allowing us to capture both intra-class compactness and inter-class separation while facilitating information sharing for improved connectivity prediction." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 701, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 701, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 701, + 288, + 714 + ], + "type": "text", + "content": "Importance of Two-stage Training We assess the impact" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "spans": [ + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "type": "text", + "content": "of two-stage training on OpenGCN by comparing " + }, + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "type": "inline_equation", + "content": "\\mathrm{MAE}_{\\mathrm{comb}}" + }, + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "type": "text", + "content": " before and after fine-tuning on " + }, + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "type": "text", + "content": " across all three benchmarks. The comparison in Tab. 7 reveals significant error reduction of up to " + }, + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "type": "inline_equation", + "content": "86.4\\%" + }, + { + "bbox": [ + 304, + 236, + 545, + 321 + ], + "type": "text", + "content": " after fine-tuning on the open-world calibration dataset. This results supports our choice of two-stage training in adapting the calibration model from the closed-world context to the open-world scenarios." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 331, + 384, + 344 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 331, + 384, + 344 + ], + "spans": [ + { + "bbox": [ + 306, + 331, + 384, + 344 + ], + "type": "text", + "content": "5. Conclusions" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "spans": [ + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "content": "In this work, we formally define the open-world threshold calibration problem for DML-based open-world visual recognition systems. To address this problem, we introduce OpenGCN, a GNN-based transductive threshold calibration method designed to enhance adaptability in open-world scenarios. Unlike traditional posthoc calibration methods, OpenGCN does not rely on the common assumption of matching distance distributions between " + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "content": ". Instead, it leverages the information of the unlabeled test instances along with learnt calibration rules to predict pairwise connectivity of the test data, via a GNN, to enable effective transductive threshold calibration in open-world scenarios. Our evaluations demonstrate that OpenGCN outperforms both traditional posthoc calibration methods and pseudolabel-based calibration techniques. When assessed using global error metrics, OpenGCN exhibits significant improvements, achieving average error reductions of " + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "inline_equation", + "content": "69.14\\%" + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "inline_equation", + "content": "40.85\\%" + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "inline_equation", + "content": "22.58\\%" + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "content": " for SameDist, ShiftDist, and DiffDist calibration scenarios, respectively, compared to the best baseline method. Overall, our results underscore OpenGCN's robustness across different distance distribution patterns between " + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{cal}}" + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{test}}" + }, + { + "bbox": [ + 304, + 351, + 545, + 638 + ], + "type": "text", + "content": ", highlighting its practical applicability for threshold calibration in DML-based open-world recognition applications." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 638, + 547, + 710 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 638, + 547, + 710 + ], + "spans": [ + { + "bbox": [ + 304, + 638, + 547, + 710 + ], + "type": "text", + "content": "Limitations OpenGCN is computationally less efficient and more susceptible to over-parameterization compared to traditional posthoc calibration methods. 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However, the more complex interaction-oriented attention, arising from the comprehension of interactions between instances by human observers, remains largely unexplored. This is equally crucial for advancing human-machine interaction and human-centered artificial intelligence. To bridge this gap, we first collect a novel gaze fixation dataset named IG, comprising 530,000 fixation points across 740 diverse interaction categories, capturing visual attention during human observers' cognitive processes of interactions. Subsequently, we introduce the zero-shot interaction-oriented attention prediction task (ZeroIA), which challenges models to predict visual cues for interactions not encountered during training. Thirdly, we present the Interactive Attention model (IA), designed to emulate human observers' cognitive processes to tackle the ZeroIA problem. Extensive experiments demonstrate that the proposed IA outperforms other state-of-the-art approaches in both ZeroIA and fully supervised settings. Lastly, we endeavor to apply interaction-oriented attention to the interaction recognition task itself. Further experimental results demonstrate the promising potential to enhance the performance and interpretability of existing state-of-the-art HOI models by incorporating real human attention data from IG and attention labels generated by IA.", + "bbox": [ + 75, + 340, + 473, + 734 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 762, + 209, + 777 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Human visual attention reveals a wealth of information about internal cognitive states, including bottom-up visual stimulation and top-down goal-directed empirical knowledge [10,47,61]. Predicting visual attention provides a valuable understanding of how humans perceive, comprehend, and interact with the world, especially within the context", + "bbox": [ + 75, + 786, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/b66ca2a13b790cdf91eead34e231be8c2ba2a4546b38f97b77dafe679ed8154c.jpg", + "image_caption": [ + "Instance-centric Attention Prediction", + "person, donut", + "person, banana" + ], + "image_footnote": [], + "bbox": [ + 501, + 325, + 684, + 378 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/06361b28ccd3e4d73d8ce7ceb4406bb9ec880346f6288eac84efd090607c2886.jpg", + "image_caption": [ + "person,horse", + "person, sheep" + ], + "image_footnote": [], + "bbox": [ + 501, + 386, + 684, + 440 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/7f437ab54e846064c37010518f9f2e5f5539fc31f7eebca2d30e69cbce07caca.jpg", + "image_caption": [ + "person, car", + "person, book", + "Figure 1. Previous attention prediction models have traditionally focused on the instance-level, primarily emphasizing foreground humans and objects. In contrast, our proposed interaction-oriented attention aims to capture subtler and more fine-grained visual cues associated with actions, such as body parts (row 1), human-object contact (row 2), and scene context (row 3). This proposition challenges the research community with a more intricate and cognitively demanding task." + ], + "image_footnote": [], + "bbox": [ + 501, + 448, + 684, + 501 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ee8ec1ed5753c32d8b391e519e155e008f2a5c82fd0ebe420e8c845dccddb745.jpg", + "image_caption": [ + "Our Interaction-oriented Attention Prediction", + "" + ], + "image_footnote": [], + "bbox": [ + 694, + 325, + 784, + 378 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e530f97f9cc13562a8b61d58151f93f44fb1aa465b376856888355dbcdda1afc.jpg", + "image_caption": [ + "" + ], + "image_footnote": [], + "bbox": [ + 785, + 325, + 877, + 378 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/7bbd458c47d5d5cb368f379c831a4a3d45f828251b83de0a879672c2afcffb35.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 386, + 787, + 438 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/2e1e79c25c0667a740b0c7871b0c186ff4cf9a1d3570f525d3b58c2372d65f34.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 789, + 386, + 877, + 438 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/10120cd7f00b6a09e8719f861b2f51f0f40b4497ed8e791cc945e03aab31ac01.jpg", + "image_caption": [ + "person,straddle,horse>", + "" + ], + "image_footnote": [], + "bbox": [ + 694, + 448, + 787, + 501 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e3ed46e99ead3d3b76485aba810c83643d350d1f7d020555cc23d9dba1ef4251.jpg", + "image_caption": [ + "", + "" + ], + "image_footnote": [], + "bbox": [ + 795, + 448, + 877, + 501 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "of goal-directed attention [3-5, 39, 46, 50]. This holds profound implications for enhancing human-computer interaction [11, 25, 49], and contributing to fields such as assistance for visual impaired [15, 16], education [1, 51], and autonomous driving [13, 21, 43, 65].", + "bbox": [ + 496, + 670, + 890, + 746 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Goal-oriented attention prediction studies have made some progress recently [8, 12, 24, 37, 42, 55-57], mostly focusing on predicting gaze fixation when searching or recognizing objects with relative explicit and invariant visual cues. However, interactions [27, 38, 68, 69, 71], another fundamental component of visual understanding that encapsulates how humans and objects interact with each other, remain largely unexplored. Interactions pose greater cognitive challenges than objects, due to their diverse and subtle visual cues, as shown in Figure 1. Consequently, predicting", + "bbox": [ + 496, + 750, + 892, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation.", + "bbox": [ + 236, + 1, + 807, + 18 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "Except for this watermark, it is identical to the accepted version;", + "bbox": [ + 325, + 16, + 722, + 30 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 292, + 31, + 754, + 45 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author.", + "bbox": [ + 94, + 887, + 220, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "28390", + "bbox": [ + 478, + 924, + 519, + 936 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "interaction-oriented visual attention proves to be a more demanding task compared to previous efforts. Moreover, the inherent diversity and almost infinite granularity of actions intersect with limited available data, necessitating the adoption of zero-shot learning. We name this problem Zero-shot Interaction-oriented Attention prediction (ZeroIA).", + "bbox": [ + 75, + 90, + 468, + 181 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "On the other hand, in the domain of human-object interaction (HOI) detection [29, 29, 34, 53, 60, 62, 64, 66, 67], current state-of-the-art methods also face limitations in the interaction comprehension phase, even though they demonstrate proficiency in handling the object detection phase. This limitation is rooted in the inherent difficulty of capturing visual cues related to actions.", + "bbox": [ + 75, + 183, + 468, + 289 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To alleviate these problems, we first introduce Interactive-Gaze (IG), a novel dataset of gaze fixations capturing human cognitive process of interactions, filling a crucial gap in interaction-oriented visual attention research. IG contains 530,000 fixation points from 32 human observers, spanning 740 interaction categories, 80 objects, and 132 actions. Human observers are invited to capture key visual cues in various interaction scenes, while their visual attention during the cognitive process is recorded. All interaction scenes are selected from HOI benchmark datasets, HICO-det [2] and VCOCO [14]. This means that IG has the potential to bridge the fields of visual attention and HOI detection and be a catalyst for advancing both research areas simultaneously.", + "bbox": [ + 75, + 292, + 468, + 501 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Secondly, inspired by the cognitive processes of human observers, we further propose a goal-oriented attention prediction approach, termed Interactive Attention (IA). Our approach begins by a set of clever interaction-oriented prompts and adapters to activate and leverage CLIP's powerful knowledge representation capabilities [48], thereby facilitating zero-shot learning. This process involves establishing adaptive knowledge prototypes based on each visual scene, avoiding direct retrieval of fixed knowledge from CLIP, which may exhibit strong noun bias [18,41,45]. Guided by these knowledge, IA first focuses on the perception and understanding of individual instances, i.e., humans and objects. Then, it further understands the interactions unfolding between instances, ultimately completing the generation of interaction-oriented attention. Extensive experiments demonstrate that IA outperforms state-of-the-art approaches in both ZeroIA and fully supervised settings.", + "bbox": [ + 75, + 506, + 467, + 762 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Furthermore, we explore how goal-oriented attention can be fed back to the goal itself, particularly establishing an initial bidirectional pathway connecting goal-oriented attention and action understanding. We introduce a general and effective HOI training strategy. This can supplement most state-of-the-art model loss with additional supervision for interaction-oriented attention. Remarkably, extensive experiments reveal the substantial potential of visual attention for HOI models from two aspects. (1) Aligning a lim", + "bbox": [ + 75, + 763, + 467, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "ited yet valuable genuine human interaction-oriented attention from the proposed IG enhances the performance and interpretability of existing state-of-the-art HOI models. (2) Integrating interaction-oriented attention generated by the proposed IA model further enhances HOI models, surpassing even the performance achieved in the context of human observers' attention. To summarize, the contributions of our work are three-fold:", + "bbox": [ + 496, + 90, + 890, + 210 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Firstly, we address a crucial gap in interaction-oriented attention studies by introducing the ZeroIA problem and IG dataset, marking a pioneering endeavor as the inaugural gaze fixation dataset specifically designed for interaction analysis. Given the composite nature of IG, it has significant potential to facilitate the intersection of multiple domains, such as goal-directed attention and interaction comprehension.", + "- Secondly, we present the IA model, a novel approach crafted to emulate human cognitive processes for predicting high-quality interaction-oriented attention. Extensive experiments demonstrate IA outperforms other state-of-the-art attention prediction methods in both the ZeroIA and fully-supervised settings.", + "- Thirdly, we introduce a general and simple HOI training strategy with attention and demonstrate that both aligning a small yet precious genuine human attention from IG and aligning attention generated by IA can enhance the performance and interpretability of existing state-of-the-art HOI models." + ], + "bbox": [ + 517, + 223, + 890, + 544 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Interactive Gaze (IG) Dataset", + "text_level": 1, + "bbox": [ + 500, + 558, + 769, + 574 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To study human visual attention oriented by HOI, we collect the Interactive Gaze (IG), the first large-scale interaction-centric gaze fixation dataset, as shown in Figure 2. IG comprises 6,299 interaction scenarios across 740 interaction categories, 80 object categories, and 132 action categories. IG captures the visual attention of 32 human observers during the cognition of these interaction scenarios, resulting in 530,000 corresponding fixation points. IG holds substantial potential to bridge the domains of visual attention and action understanding, serving as a catalyst to jointly promote these two areas of study. We use mouse clicks to simulate gaze fixation for visual attention studies [8,24,36,37], and more details about the IG dataset are presented in the supplementary materials.", + "bbox": [ + 496, + 583, + 890, + 794 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Dataset Comparison. Previous gaze fixation datasets have primarily concentrated on instances (e.g., objects, humans, animals, texts) as targets for recognition, search, and free-viewing, as illustrated in Table 1. In contrast, IG stands as the pioneering interaction-centric gaze fixation dataset. Given the inherent diversity, composability, and context dependency of interactions, interaction-oriented attention is", + "bbox": [ + 496, + 795, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "28391", + "bbox": [ + 478, + 924, + 517, + 936 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/8dd5e30534b75da00586680a29a3bb1682ae2fecfc2d424aab9c033bf60ddf45.jpg", + "image_caption": [ + "Figure 2. Our proposed IG is the first interaction-centric gaze fixation dataset, comprising 530K fixation points across 740 interaction categories." + ], + "image_footnote": [], + "bbox": [ + 78, + 88, + 446, + 258 + ], + "page_idx": 2 + }, + { + "type": "table", + "img_path": "images/b68c73c519faed7370cba59dec9b4bd2bdf8b7e6a97273f339131deab34beb70.jpg", + "table_caption": [ + "Table 1. Comparison of fixation datasets. Previous work all focus on instances of objects, humans, animals, texts, etc." + ], + "table_footnote": [], + "table_body": "
DatasetFocusSceneClassFixation
SALICON [24]Object10000-4600K
POET [44]Object627010178K
People900 [7]Human912155K
MCS [58]Object2183216K
PET [9]Animal4135630K
COCO-Search18 [55]Object620218300K
SalECI [23]Object & Text97213257K
Our (IG)Action6299740530K
", + "bbox": [ + 89, + 367, + 452, + 489 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "associated with elevated cognitive challenges and empirical knowledge.", + "bbox": [ + 75, + 518, + 467, + 547 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Data Selection & Subsetting. To bring the visual attention and HOI detection domains closer, we select image samples from HOI benchmark dataset VCOCO [14] and HICO-det [2] as experimental materials. VCOCO consists of 24 action classes and 214 HOI classes, while HICO-det is larger and more challenging, covering 117 action classes and 600 HOI classes. We select 4,475 samples from the V-COCO training set (13 samples per HOI class on average) to train the attention prediction model. Additionally, we use 1,104 samples from the HICO-det test set and 720 samples from the V-COCO test set for testing the attention prediction model under ZeroIA and fully supervised interaction-oriented attention prediction tasks, respectively.", + "bbox": [ + 75, + 549, + 467, + 744 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 760, + 166, + 776 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Problem Definition", + "text_level": 1, + "bbox": [ + 76, + 785, + 259, + 800 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given a sample of HOI pair, the goal of zero-shot interaction-oriented human visual attention prediction (ZeroIA) is to generate an attention heatmap that reflects key visual cues for comprehending the interaction between human and object without any training for this interaction, as shown on the left of Figure 3. A complete HOI sample con", + "bbox": [ + 75, + 809, + 467, + 898 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "sists of five components: an RGB image $x \\in \\mathbb{R}^{H \\times W \\times 3}$ , a bounding box of human $b^H$ , a bounding box of object $b^O$ , an object label $C_O$ , and an interaction label $C_I$ . The output of ZeroIA is expressed as a spatial attention heatmap $m_{IA} \\in \\mathbb{R}^{H \\times W \\times 1}$ .", + "bbox": [ + 496, + 89, + 890, + 165 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Interactive Attention", + "text_level": 1, + "bbox": [ + 500, + 178, + 696, + 191 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Under goal-oriented cognitive tasks, humans tend to use their existing empirical knowledge and memory to model cognitive goals, and then progressively perceive and understand visual scenes with the goal. Inspired by the human cognitive process, we propose the Interactive Attention (IA) to tackle the ZeroIA problem, as shown in Figure 3.", + "bbox": [ + 496, + 202, + 890, + 292 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In IA, we first activate the strong knowledge representation capabilities of CLIP [48] through a clever interaction-oriented prompt block (PB). Secondly, we design two tiny and learnable adapters to model the HOI cognitive task. It generates scene-adaptive knowledge prototypes (KPs) for humans, objects, interactions, and robust visual features. Guided by these knowledge, we progressively perceive and understand the HOI scene. Specifically, we first perceive the human and object through a human-object cognitive block (HOCB), then delve deeper into understanding the interaction that occurs between the human and objects through an interaction cognitive block (ICB), and finally decode the interaction-oriented attention map.", + "bbox": [ + 496, + 294, + 890, + 489 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Interaction-oriented Prompt. Given an HOI sample, the interaction-oriented prompt block (PB) provides the visual-linguistic large model CLIP with clever inputs applicable to the HOI cognitive task to activate CLIP's powerful representation capabilities. Due to the natural composability of HOI, PB considers humans, objects, and interactions separately, i.e., constructing human-centric, object-centric, and interaction-centric prompts and extracting their textual representations, respectively.", + "bbox": [ + 496, + 491, + 890, + 627 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "PB takes \"person\" and object textual label $C_O$ as inputs to CLIP text encoder and extracts the human- and object-centric textual representations, $T_H$ , and $T_O$ . The human and object texts are merged into the interaction-centric prompt, i.e., \"a photo of a person $[C_I]$ $[C_O]$ \" since they are closely related to the interaction. Then, the interaction-centric textual representation $T_I$ is extracted. Correspondingly, CLIP's image encoder is leveraged to extract robust visual features $V = [v_1, \\dots, v_M]$ to take advantage of the semantic alignment between image and linguistics.", + "bbox": [ + 496, + 628, + 890, + 777 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Positional & Visual Adapter. The features extracted from CLIP based on PB are somewhat applicable to the cognitive goal, but this is a fixed holistic representation modeling of the goal, which lacks the ability to adapt to each specific HOI sample, especially to diverse spatial configurations and visual scenes. As a result, we design the tiny positional adapter and visual adapter to provide HOI sample-aware knowledge that enables better modeling of HOI cog", + "bbox": [ + 496, + 779, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "28392", + "bbox": [ + 478, + 925, + 517, + 936 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/cc3714cdd121b4522c9429eca4594470774158e6aeb950ad0c0079b89a2ac438.jpg", + "image_caption": [ + "Figure 3. The overall architecture of our Interactive Attention (IA). Inspired by the HOI cognitive process of human observers, IA is divided into three phases: empirical knowledge representation, cognitive goal modeling, and progressive understanding. First, a set of interaction-oriented prompts activate and leverage the robust knowledge representation capability of CLIP. Secondly, positional and visual adapters are introduced to acquire scene-adaptive human, object, and interaction Knowledge Prototypes (KPs) along with visual features of the HOI scene. Thirdly, guided by these KPs, IA progressively comprehends the scene, starting with an instance-level understanding of humans and objects and deepening insight into their interactions. The decoder generates predicted attention maps, supervised by the real attention maps of human observers using $L_{H2IA}$ ." + ], + "image_footnote": [], + "bbox": [ + 84, + 93, + 890, + 305 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "nitive tasks in each specific sample.", + "bbox": [ + 76, + 440, + 313, + 455 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Positional adapter (PA) provides sample-aware spatial information on textual representations:", + "bbox": [ + 76, + 455, + 468, + 484 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nK _ {H} = M L P \\left(\\left[ \\left(T _ {H}\\right), F o u r i e r \\left(b ^ {H}\\right) \\right]\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 145, + 497, + 468, + 515 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nK _ {O} = M L P \\left(\\left[ \\left(T _ {O}\\right), F o u r i e r \\left(b ^ {O}\\right) \\right]\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 148, + 525, + 468, + 542 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nK _ {I} = M L P \\left(\\left[ \\left(T _ {I}\\right), F o u r i e r \\left(C _ {H}\\right), F o u r i e r \\left(C _ {O}\\right) \\right]\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 88, + 549, + 468, + 566 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $K_{H}$ , $K_{O}$ , and $K_{I}$ represent adaptive knowledge prototypes of human, object, and interaction. Fourier is the Fourier embedding, MLP is a multi-layer perceptron, and [·] is the concatenate operation. Visual adapter (VA) is implemented as two Transformer encoder layers to transform $V$ into refined visual features $V' = [v_1', \\dots, v_M']$ .", + "bbox": [ + 76, + 573, + 468, + 662 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Human-Object Cognitive Block. The HOI scene is further learned under the guidance of knowledge prototypes of human and object ( $K_{H}$ and $K_{O}$ ). The self-attention mechanism with gating is introduced to establish cognitive dependencies between knowledge prototypes and visual features, then the human-object-aware visual feature $V_{HO}$ is obtained:", + "bbox": [ + 75, + 662, + 468, + 767 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nV _ {H O} = V ^ {\\prime} + \\text {G a t e} \\left(\\text {S e l f A t t n} \\left(\\left[ K _ {H}, K _ {O}, V ^ {\\prime} \\right]\\right)\\right), \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 102, + 781, + 468, + 799 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $Gate(\\cdot)$ is a token gating operation that considers visual tokens only, SelfAttn( $\\cdot$ ) denotes a self-attention computation.", + "bbox": [ + 76, + 809, + 468, + 854 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Interaction Cognitive Block. Expanding upon the instance-level cognition, including the human and object, the model further delves into comprehending higher-level", + "bbox": [ + 76, + 854, + 468, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "interactions that occur between the human and object. To achieve this, the cross-attention mechanism with gating is introduced to guide the learning of more subtle interaction cues by interaction knowledge prototype and obtaining the primary HOI-aware visual feature $V_{HOI}$ :", + "bbox": [ + 496, + 440, + 890, + 516 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nV _ {H O I} = V _ {H O} + \\operatorname {G a t e} \\left(\\operatorname {C r o s s A t t n} \\left(V _ {H O}, K _ {I}\\right)\\right), \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 524, + 523, + 890, + 541 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where we denote $CrossAttn(q, kv)$ as a cross-attention operation. After that, the general self-attention operation is conducted on $V_{HOI}$ to obtain the full HOI-aware visual feature $V_{HOI}'$ :", + "bbox": [ + 496, + 547, + 890, + 611 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nV _ {H O I} ^ {\\prime} = V _ {H O I} + \\text {S e l f A t t n} \\left(V _ {H O I}\\right). \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 571, + 617, + 890, + 635 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Interaction-oriented Attention Decoder. The goal of the decoder is to generate interaction-oriented attention heatmap $m_{IA} \\in \\mathbb{R}^{H \\times W \\times 1}$ , we first reshape the full interaction-aware visual feature, $V_{HOI}'$ , from a 2D shape of $\\frac{HW}{p^2} \\times C$ to a standard 3D feature map $\\frac{H}{p} \\times \\frac{W}{p} \\times C$ , $C$ is the feature channel size, $p$ is the image patch size. Then, we adopt tiny 2-layers of $1 \\times 1$ convolution with batch norm and ReLU activation to reduce the feature dimension to $\\frac{H}{p} \\times \\frac{W}{p} \\times 1$ . Last, we adopt a bilinearly upsample operation to achieve the full image size $H \\times W$ .", + "bbox": [ + 496, + 642, + 890, + 792 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Loss Function. We utilize the binary cross-entropy as a loss function for attention alignment, which can be expressed as follows:", + "bbox": [ + 496, + 792, + 890, + 838 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {B C E} (p, y) = - \\frac {1}{N} \\sum_ {i = 1} ^ {N} \\left(y _ {i} \\cdot \\log \\left(p _ {i}\\right) + \\left(1 - y _ {i}\\right) \\cdot \\log \\left(1 - p _ {i}\\right)\\right), \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 500, + 845, + 908, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "28393", + "bbox": [ + 478, + 924, + 517, + 936 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/03f7c68b986320c4fce14dacc9fb46a09d455b8d66af369358e560971aa97932.jpg", + "image_caption": [ + "Figure 4. We incorporate aligned attention into the existing HOI model training pipeline, divided into two strategies: supervising by a limited amount of real attention from human observers and supervising by a large number of attention pseudo-labels generated by our proposed IA." + ], + "image_footnote": [], + "bbox": [ + 78, + 92, + 467, + 299 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {H 2 I A} = \\mathrm {B C E} \\left(m _ {H}, m _ {I A}\\right), \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 179, + 409, + 468, + 426 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $p$ is the predictive probability, $y$ is the target, $N$ is the number of pixels in $m_{IA}$ , $m_H$ is human observer's real attention heatmap.", + "bbox": [ + 76, + 431, + 468, + 478 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Training HOI Models with Interaction-oriented Attention", + "text_level": 1, + "bbox": [ + 76, + 486, + 468, + 516 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Here, we formulate the majority of recent state-of-the-art HOI models in the pipeline of CNN Backbone $\\rightarrow$ Encoder $\\rightarrow$ Decoder $\\rightarrow$ Output Head. We enhance these HOI models by incorporating a supervision of interaction-oriented attention into the training process. This involves two strategies: supervising with a limited amount of real attention samples from human observers and supervising with a large number of pseudo-labeled attention samples from the IA model, as shown in Figure 4.", + "bbox": [ + 75, + 525, + 468, + 660 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For these HOI models, we first introduce a simple attention head to extract and reshape the averaged attention maps $m_{HOI}$ from the last layer of cross-attention computation in the decoder. The attention head is intentionally kept simple for a more direct back propagation of guidance to the representation. Subsequently, the corresponding human observer's attention heatmap $m_{H}$ and IA-generated pseudolabels $m_{IA}$ are scaled down to match the size of $m_{HOI}$ through adaptive 2D max-pooling. Finally, $m_{H}$ and $m_{IA}$ are used to supervise $m_{HOI}$ for two kinds of strategies, respectively.", + "bbox": [ + 75, + 661, + 468, + 825 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For the strategy of supervising by human observers, the attention alignment loss function $L_{H2HOI}$ and the overall HOI model's loss function $L$ can be expressed as", + "bbox": [ + 76, + 827, + 468, + 872 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {H 2 H O I} = \\mathrm {B C E} \\left(m _ {H O I}, m _ {H}\\right), \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 166, + 885, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL = \\lambda_ {1} L _ {\\text {r a w}} + \\lambda_ {2} L _ {H 2 H O I}, \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 599, + 90, + 890, + 106 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $L_{raw}$ represents the loss function of the original HOI model, which varies depending on the specific model, while $\\lambda_1$ and $\\lambda_2$ denote loss scaling factors. Similarly, for the strategy of supervising by IA, $L_{IA2HOI}$ and the overall loss function $L$ can be expressed as", + "bbox": [ + 498, + 113, + 893, + 189 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {I A 2 H O I} = \\mathrm {B C E} \\left(m _ {H O I}, m _ {I A}\\right), \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 584, + 202, + 890, + 218 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL = \\lambda_ {1} L _ {\\text {r a w}} + \\lambda_ {2} L _ {I A 2 H O I}. \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 598, + 229, + 890, + 247 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 260, + 633, + 277 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Implementation Details", + "text_level": 1, + "bbox": [ + 500, + 285, + 718, + 301 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Interactive Attention. We apply 2 versions of CLIP (ViT-B/16 and ViT-L/14) to build the IA models, resulting in IA-B and IA-L, respectively. The output dimension of Fourier embedding is 64. During training, we use AdamW as the optimizer with an initial learning rate of $1 \\times 10^{-4}$ . The IA model is trained for 80 epochs with a learning rate reduction pre-20 epochs by a factor of 10. The momentum and the weight decay are set as 0.9 and $1 \\times 10^{-4}$ . The experiments are conducted on four NVIDIA GeForce RTX 3090 GPUs with a batch size of 16.", + "bbox": [ + 496, + 308, + 890, + 458 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Training HOI Models with Attention Alignment. We apply our attention-guided training strategy on three typical state-of-the-art HOI methods: MUREN [29], representing the one-stage structure, and UPT [60] and STIP [62], representing the two-stage structure. In MUREN, we align the cross-attention map of the last layer in its interaction branch module with our interaction-oriented attention. In UPT, we first add two transformer decoder layers at the end of its interaction head, conducting cross-attention computation with global visual features, and align the cross-attention map of last layer. In STIP, we align the cross-attention map of the last layer in its structure-aware transformer module with our interaction-oriented attention. Due to variations in the raw losses of different methods, particularly for one-stage structure requiring additional supervision of object detection results, corresponding loss scaling factors differ. $\\lambda_{1}$ and $\\lambda_{2}$ are set to 1 and 10 in MUREN. $\\lambda_{1}$ and $\\lambda_{2}$ are set to 1 and 6 in UPT and STIP. Note that the IA model, responsible for generating interaction-oriented attention, is trained without exposure to samples from VCOCO test set and HICO-det test set, preventing any possibility of label leakage.", + "bbox": [ + 496, + 459, + 892, + 777 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Comparison methods & Metrics.", + "text_level": 1, + "bbox": [ + 500, + 786, + 785, + 801 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We evaluate the performance of our IA model on interaction-oriented attention prediction, comparing it with 10 state-of-the-art methods: ITTI [22], GBVS [17], DeepGaze I [30], DeepGaze IIE [35], UMB [70], ConvNext [40], MLNet [6], SSwin Transformer [23], CLIP-ViT-B/16 [48], CLIP-ViT-L/14 [48]. Among these, ITTI and GBVS", + "bbox": [ + 498, + 810, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "28394", + "bbox": [ + 478, + 925, + 519, + 936 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/cdd9078d995b643f808ebdcb580f1e5edbf7f4d4f70db75c5fcc4ab9a24b1ed5.jpg", + "table_caption": [ + "Table 2. Performance comparison on IG dataset. Bold and underline show the best and second-best performances." + ], + "table_footnote": [], + "table_body": "
MethodZerola SettingFully Supervised Setting
CC↑KLdiv↓SIM↑AUC↑CC↑KLdiv↓SIM↑AUC↑
ITTI [22]0.07844.35530.01420.49990.07543.18150.01170.5301
GBVS [17]0.02624.54950.02340.50000.17732.94980.02070.5037
DeepGaze I [30]0.18733.06630.00800.55700.19693.18690.00810.6143
DeepGaze IIE [35]0.20653.02550.00910.58140.17213.23570.00700.6049
UMB [70]0.21213.90040.59370.53260.20114.23380.61470.5319
MLNet [6]0.29373.89870.46460.59720.31953.68040.41530.5743
ConvNext [40]0.25714.87290.61100.54820.27314.51540.57470.5524
SSwin Transformer [23]0.24942.66540.33090.52120.29383.43090.33230.5391
CLIP-base [48]0.14033.61180.00580.35160.15643.87210.00740.3385
CLIP-large [48]0.16813.64980.00640.31830.16903.85470.00660.3356
IA CLIP-base0.40132.71140.72050.59530.48102.21320.75210.6375
IA CLIP-large0.44882.84090.71520.60680.51062.14090.77960.6386
", + "bbox": [ + 78, + 127, + 470, + 261 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "excel in early saliency prediction based on manual features, while the remaining methods are recent learning-based approaches. DeepGaze I and DeepGaze IIE utilize official pre-trained models for predictions, and UMB, ConvNext, MLNet, and SSwin Transformer are all trained with IG datasets. Additionally, we compute the similarity maps of two commonly used raw CLIP versions (CLIP-ViT-B/16 and CLIP-ViT-L/14). These similarity maps compute the similarity distance between image features and text features, serving as the raw CLIP's class attention maps [31].", + "bbox": [ + 75, + 289, + 468, + 439 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We apply 4 metrics to measure performance: KL divergence (KLdiv), correlation coefficient (CC), similarity (SIM), and the area under the receiver operating characteristic curve (AUC). KLdiv, CC, and SIM are distribution-based metrics, while AUC is a localization-based metric. Except KLdiv, where lower values are preferable, higher values are desirable for all other metrics.", + "bbox": [ + 75, + 439, + 468, + 545 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3.Quantitative Comparison.", + "text_level": 1, + "bbox": [ + 76, + 556, + 313, + 571 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2 presents the quantitative comparison results in the ZeroIA and the fully supervised settings. We can observe that both versions of our model IA outperform all 10 baselines in both metrics. In particular, for CC metric, IA w/ CLIP-L outperforms the third-best MLNet by $52.8\\%$ and $59.8\\%$ on the ZeroIA and the fully supervised settings, respectively.", + "bbox": [ + 75, + 579, + 468, + 685 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Moreover, we observe that the manual feature-based ITTI and GBVS approaches fail in the interaction-oriented attention prediction task, which demands higher cognitive capabilities. Additionally, when comparing IA with the similarity map of raw CLIP output, our IA achieves significant improvements across all metrics. For example, IA w/ CLIP-B exceeds raw CLIP-B by $186\\%$ under CC metric of the ZeroIA setting. This suggests that our model effectively activates and utilizes CLIP's knowledge representation capabilities, adapting them to cognitive tasks on interaction.", + "bbox": [ + 75, + 685, + 470, + 838 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.4. Qualitative Analyses.", + "text_level": 1, + "bbox": [ + 76, + 845, + 276, + 863 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "As shown in Figures 5 and 6, the visualizations of interaction-oriented attention prediction under ZeroIA and", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/042029977f1ac7116255833f2cd070eb7cab64e8789949ffe5e1adde26ff88b1.jpg", + "table_caption": [ + "Table 3. Performance comparison of each module in IA." + ], + "table_footnote": [], + "table_body": "
MethodZeroIA SettingFully Supervised Setting
CC↑KLdiv↓SIM↑AUC↑CC↑KLdiv↓SIM↑AUC↑
w/o PA0.36523.21150.67330.58020.39612.46760.68640.6023
w/o VA0.38382.98010.67540.58320.40812.43460.68930.6182
w/o HOCB0.34983.31230.64210.57430.36972.56890.64840.6034
w/o ICB0.32493.65410.58450.56440.34452.85330.60230.5934
IA0.40132.71140.72050.59530.48102.21320.75210.6375
", + "bbox": [ + 513, + 114, + 877, + 194 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "fully supervised settings, respectively. Notably, across both settings, IA exhibits attention distributions that are consistently closer to human observers, outperforming the remaining eight methods.", + "bbox": [ + 496, + 218, + 890, + 277 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Compared with SOTA models. The previous untrained instance-centric models (columns 6-7) only capture coarse-grained salient persons and objects, but not interaction-related cues. Methods trained on IG prove limited in the complex multi-instance \"push\" scenario (Figure 5, row 4) under the ZeroIA setting and also in the \"talk on\" scenario (Figure 6, row 3) with a limited number of training samples.", + "bbox": [ + 496, + 277, + 890, + 383 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Compared with raw CLIP, IA accurately captures key visual cues, particularly for unseen categories such as \"repair\", \"kiss\", \"lick\", \"push\", and \"sign\" in Figure 5. Noteworthy is the comparison with columns 5-6, where the similarity maps generated by raw CLIP lack interpretability, displaying properties such as opposite visualization and noisy activation, as highlighted in recent work [31, 32]. These observations, along with quantitative results in Table 2, underscore the fact that our work effectively activates CLIP's powerful knowledge representation capabilities and improves interpretability.", + "bbox": [ + 496, + 383, + 892, + 551 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.5. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 559, + 653, + 574 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To examine the impact of each module in IA, we conduct an ablation study by removing modules in Table 3. Specifically, we sequentially exclude the positional adapter (PA), visual adapter (VA), human-object cognitive block (HOCB), and interaction cognitive block (ICB). All ablated models are variations of IA w/ CLIP-B. Results indicate consistent performance degradation across both ZeroIA and fully supervised settings upon removal of any module. Notably, the most significant degradation occurs when the ICB is omitted, emphasizing its crucial role in guiding the learning of interaction-oriented attention by injecting the interaction knowledge. Subsequently, the HOCB, enriched with information about the subjects and objects involved in the interaction, the PA, which incorporates spatial configuration, and the VA, receiving refined visual features, contribute to the model's performance in descending order from high to low.", + "bbox": [ + 496, + 580, + 892, + 839 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.6. Effectiveness of Attention Training Strategy", + "text_level": 1, + "bbox": [ + 500, + 847, + 872, + 863 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Aligning human attention enhances HOI model accuracy. We leverage the VCOCO training subset within", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "28395", + "bbox": [ + 478, + 925, + 519, + 936 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/8f846bffa0e105a5480d6e080c260fa7418e92378b6c39851a63860ec62a433f.jpg", + "image_caption": [ + "Figure 5. Qualitative comparison of interaction-oriented attention prediction under the ZeroIA setting." + ], + "image_footnote": [], + "bbox": [ + 147, + 89, + 830, + 303 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5b89d75baa7eff3b891ea064db747e2260031aa942cd902665a268536d05223a.jpg", + "image_caption": [ + "Figure 6. Qualitative comparison of interaction-oriented attention prediction under the fully supervised setting." + ], + "image_footnote": [], + "bbox": [ + 145, + 342, + 828, + 594 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "the proposed IG, comprising 4,475 samples, approximately $32.4\\%$ of the complete VCOCO training set, as the attention ground truth for additional supervision of existing HOI models. As shown in Table 4, MUREN, UPT, and STIP are improved by $0.6\\mathrm{mAP}$ , $0.8\\mathrm{mAP}$ , and $0.4\\mathrm{mAP}$ , respectively, under the Scenario1 setting. Similarly, under the Scenario2 setting, MUREN, UPT, and STIP are enhanced by $0.7\\mathrm{mAP}$ , $1.3\\mathrm{mAP}$ , and $0.4\\mathrm{mAP}$ , respectively. This highlight the significant potential of aligned human attention in enhancing action comprehension, even with limited training data.", + "bbox": [ + 75, + 643, + 472, + 797 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Aligning IA-generated attention enhances HOI model accuracy more significantly. We further enhance the additional supervision of HOI models through large-scale interaction-oriented pseudo-labeling, generated by the proposed IA model on the training sets of VCOCO and HICO-det, respectively. In Table 4, on the VCOCO dataset,", + "bbox": [ + 75, + 809, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "our training strategies consistently obtain performance improvements for MUREN, UPT, and STIP. In particular, thanks to the precise emulation of human attention by our proposed IA model, the results of all HOI models reveal that training by a large number of pseudo-attention labels is superior to using limited genuine human attention. On HICO-det dataset, our training strategy similarly achieves consistent performance gains in Table 5. Particularly, we observe that our training strategy significantly enhances the performance of the rare set, by $6.0\\%$ , $4.0\\%$ , and $2.7\\%$ on MUREN, UPT, and STIP, respectively. Note that the reported experimental results are all obtained by reproducing these models under the same experimental settings.", + "bbox": [ + 496, + 643, + 890, + 843 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Aligning attention makes HOI models more interpretable. We present visualizations of the cross-attention maps of interaction branches in original MUREN and the", + "bbox": [ + 498, + 854, + 893, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "28396", + "bbox": [ + 478, + 925, + 519, + 936 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/6f57e4ab39f327b4b78cd4fd9b3112702a70847b43d6f928e9eae8e3a36da841.jpg", + "table_caption": [ + "Table 4. Comparison of HOI detection performance on VCOCO." + ], + "table_footnote": [], + "table_body": "
MethodBackboneScenario #1Scenario #2
One-stage methods
UnionDet [26]ResNet-50-FPN47.556.2
IP-Net [54]Hourglass-10451.0-
GG-Net [33]Hourglass-10454.7-
HOTR [27]ResNet-5055.264.4
QPIC [52]ResNet-10158.360.7
MUREN [29]ResNet-5066.969.0
MUREN w/ HumanResNet-5067.569.7
MUREN w/ IA-BResNet-5067.770.3
MUREN w/ IA-LResNet-5068.070.4
Two-stage methods
VCL [19]ResNet-5048.3-
SCG [59]ResNet-50-FPN54.2-
UPT [60]ResNet-5059.865.5
STIP [62]ResNet-5066.070.7
UPT w/ HumanResNet-5060.766.4
UPT w/ IA-BResNet-5061.166.8
UPT w/ IA-LResNet-5061.467.0
STIP w/ HumanResNet-5066.471.1
STIP w/ IA-BResNet-5067.071.3
STIP w/ IA-LResNet-5067.271.4
", + "bbox": [ + 114, + 114, + 431, + 347 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/025a32947417929dbcdad04420404a1c31de654a7ce367c360f94b920bfaaa88.jpg", + "table_caption": [ + "Table 5. Comparison of HOI detection performance on HICO-det." + ], + "table_footnote": [], + "table_body": "
MethodBackboneFullRareNon-rare
One-stage methods
UnionDet [26]ResNet-50-FPN17.5811.7219.33
IP-Net [54]Hourglass-10419.5612.7921.58
PPDM [33]Hourglass-10421.7313.7821.40
GG-Net [63]Hourglass-10423.4716.4825.60
HOTR [27]ResNet-5025.1017.3427.42
QPIC [52]ResNet-10129.9023.9231.69
MSTR [28]ResNet-5031.1725.3132.92
MUREN [29]ResNet-5032.0927.3633.50
MUREN w/ IA-BResNet-5032.4528.9033.51
MUREN w/ IA-LResNet-5032.4829.0133.53
Two-stage methods
VCL [19]ResNet-5023.6317.2125.55
ATL [20]ResNet-5023.6717.6425.47
SCG [59]ResNet-50-FPN29.2624.6130.65
UPT [60]ResNet-5031.9326.7033.49
STIP [62]ResNet-5032.2228.1533.43
UPT w/ IA-BResNet-5032.2027.5933.58
UPT w/ IA-LResNet-5032.4727.7633.72
STIP w/ IA-BResNet-5032.3228.4733.59
STIP w/ IA-LResNet-5032.6428.9033.76
", + "bbox": [ + 114, + 383, + 431, + 623 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "MUREN aligned with interaction-oriented attention, respectively, as shown in Figure 7. It is evident that the attention map of original MUREN appears fragmented and struggles to focus on interaction-related visual cues, leading to failures in interaction recognition. Conversely, after aligning with interaction-oriented attention, not only are the erroneous results corrected, but the attention map becomes significantly more interpretable and focuses on key regions.", + "bbox": [ + 75, + 648, + 468, + 770 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 76, + 784, + 194, + 799 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This paper aims to address a critical gap in interaction-oriented attention by introducing the challenging yet meaningful ZeroIA problem. To achieve this, we collect the IG dataset, marking the first large-scale interaction-centric gaze fixation dataset, featuring 530,000 fixation points across 740 diverse interaction categories. Subsequently, we", + "bbox": [ + 75, + 810, + 468, + 902 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5192f6356bd6ebd9da82d9c23c4cc44d7eda18f75341a3a1cd2cdb2e5ef5fe56.jpg", + "image_caption": [ + "Figure 7. The predicted results and corresponding attention visualizations for MUREN and our (MUREN w/ IA-L, MUREN w/ Human). We mark true positive results in green, and false positive results in red. After aligning interaction-oriented attention, the erroneous prediction results are corrected, and the corresponding attention becomes more converged and more interpretable. More in supplementary materials." + ], + "image_footnote": [], + "bbox": [ + 506, + 90, + 859, + 287 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "present the IA model, ingeniously designed to activate and leverage the knowledge representation capabilities of CLIP, emulating the cognitive processes of human observers to generate high-quality interaction-oriented attention. Extensive experiments demonstrate that the proposed IA model outperforms state-of-the-art attention prediction methods in both zero-shot and fully supervised settings. Furthermore, we propose an attention-guided HOI training strategy, leveraging interaction-oriented attention to guide existing HOI models for more effective learning. Quantitative and qualitative results demonstrate that both genuine human attention and IA-generated attention significantly enhance the performance and interpretability of existing HOI models, making them more capable of visual reasoning like human observers. This highlights the significant potential of visual attention in action comprehension.", + "bbox": [ + 496, + 435, + 892, + 678 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Our endeavor represents the pioneering effort to establish a bi-directional connection between visual attention and HOI detection, starting by directing visual attention through the interaction comprehension task and ending by incorporating this attention to repay existing HOI methods. We believe our work can inspire further research on goal-oriented attention and its application in various action-related tasks like classification, VQA, and captioning. Our work also has potential applications in DNNs' interpretability evaluation, human-AI collaboration, and values alignment research.", + "bbox": [ + 496, + 683, + 890, + 834 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements. This work is supported in part by National Natural Science Foundation of China under Grant 62373387, and in part by Natural Science Foundation of Guangdong Province (No. 2023A1515030264).", + "bbox": [ + 498, + 840, + 893, + 901 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "28397", + "bbox": [ + 478, + 925, + 517, + 936 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Souradeep Chakraborty, Zijun Wei, Conor Kelton, Seoyoung Ahn, A. Balasubramanian, G. Zelinsky, and D. Samaras. Predicting visual attention in graphic design documents. IEEE Transactions on Multimedia, 25:4478-4493, 2023. 1", + "[2] Yu-Wei Chao, Yunfan Liu, Xieyang Liu, Huayi Zeng, and Jia Deng. Learning to detect human-object interactions. In WACV, pages 381-389. 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In CVPR, pages 11825-11834, 2021. 1" + ], + "bbox": [ + 78, + 90, + 468, + 614 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "28400", + "bbox": [ + 478, + 926, + 517, + 936 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning from Observer Gaze_ Zero-Shot Attention Prediction Oriented by Human-Object Interaction Recognition/111dd706-825f-4535-846b-ae607fa98e28_model.json b/2024/Learning from Observer Gaze_ Zero-Shot Attention Prediction Oriented by Human-Object Interaction Recognition/111dd706-825f-4535-846b-ae607fa98e28_model.json new file mode 100644 index 0000000000000000000000000000000000000000..5d03534988dc8169d8bb51836b97901a99eb6671 --- /dev/null +++ b/2024/Learning from Observer Gaze_ Zero-Shot Attention Prediction Oriented by Human-Object Interaction Recognition/111dd706-825f-4535-846b-ae607fa98e28_model.json @@ -0,0 +1,2598 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.002, + 0.808, + 0.02 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation." + }, + { + "type": "header", + "bbox": [ + 0.326, + 0.017, + 0.723, + 0.031 + ], + "angle": 0, + "content": "Except for this watermark, it is identical to the accepted version;" + }, + { + "type": "header", + "bbox": [ + 0.294, + 0.032, + 0.755, + 0.046 + ], + "angle": 0, + "content": "the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.105, + 0.13, + 0.867, + 0.177 + ], + "angle": 0, + "content": "Learning from Observer Gaze: Zero-Shot Attention Prediction Oriented by Human-Object Interaction Recognition" + }, + { + "type": "text", + "bbox": [ + 0.339, + 0.204, + 0.639, + 0.221 + ], + "angle": 0, + "content": "Yuchen Zhou, Linkai Liu, Chao Gou*" + }, + { + "type": "text", + "bbox": [ + 0.393, + 0.223, + 0.578, + 0.24 + ], + "angle": 0, + "content": "Sun Yat-sen University" + }, + { + "type": "text", + "bbox": [ + 0.28, + 0.242, + 0.69, + 0.257 + ], + "angle": 0, + "content": "https://yuchen2199.github.io/Interactive-Gaze/" + }, + { + "type": "text", + "bbox": [ + 0.212, + 0.26, + 0.758, + 0.275 + ], + "angle": 0, + "content": "{zhouych37, liulk6}@mail2.sysu.edu.cn, gouchao@mail.sysu.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.31, + 0.314, + 0.326 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.342, + 0.474, + 0.735 + ], + "angle": 0, + "content": "Most existing attention prediction research focuses on salient instances like humans and objects. However, the more complex interaction-oriented attention, arising from the comprehension of interactions between instances by human observers, remains largely unexplored. This is equally crucial for advancing human-machine interaction and human-centered artificial intelligence. To bridge this gap, we first collect a novel gaze fixation dataset named IG, comprising 530,000 fixation points across 740 diverse interaction categories, capturing visual attention during human observers' cognitive processes of interactions. Subsequently, we introduce the zero-shot interaction-oriented attention prediction task (ZeroIA), which challenges models to predict visual cues for interactions not encountered during training. Thirdly, we present the Interactive Attention model (IA), designed to emulate human observers' cognitive processes to tackle the ZeroIA problem. Extensive experiments demonstrate that the proposed IA outperforms other state-of-the-art approaches in both ZeroIA and fully supervised settings. Lastly, we endeavor to apply interaction-oriented attention to the interaction recognition task itself. Further experimental results demonstrate the promising potential to enhance the performance and interpretability of existing state-of-the-art HOI models by incorporating real human attention data from IG and attention labels generated by IA." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.763, + 0.21, + 0.779 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.787, + 0.47, + 0.879 + ], + "angle": 0, + "content": "Human visual attention reveals a wealth of information about internal cognitive states, including bottom-up visual stimulation and top-down goal-directed empirical knowledge [10,47,61]. Predicting visual attention provides a valuable understanding of how humans perceive, comprehend, and interact with the world, especially within the context" + }, + { + "type": "image_caption", + "bbox": [ + 0.515, + 0.313, + 0.667, + 0.324 + ], + "angle": 0, + "content": "Instance-centric Attention Prediction" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.326, + 0.685, + 0.38 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.521, + 0.38, + 0.574, + 0.387 + ], + "angle": 0, + "content": "person, donut" + }, + { + "type": "image_caption", + "bbox": [ + 0.607, + 0.38, + 0.666, + 0.387 + ], + "angle": 0, + "content": "person, banana" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.387, + 0.685, + 0.441 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.521, + 0.441, + 0.573, + 0.448 + ], + "angle": 0, + "content": "person,horse" + }, + { + "type": "image_caption", + "bbox": [ + 0.612, + 0.441, + 0.664, + 0.448 + ], + "angle": 0, + "content": "person, sheep" + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.449, + 0.686, + 0.502 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.525, + 0.503, + 0.568, + 0.51 + ], + "angle": 0, + "content": "person, car" + }, + { + "type": "image_caption", + "bbox": [ + 0.613, + 0.503, + 0.663, + 0.51 + ], + "angle": 0, + "content": "person, book" + }, + { + "type": "image_caption", + "bbox": [ + 0.692, + 0.313, + 0.885, + 0.324 + ], + "angle": 0, + "content": "Our Interaction-oriented Attention Prediction" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.326, + 0.785, + 0.379 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.787, + 0.326, + 0.879, + 0.379 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.697, + 0.38, + 0.782, + 0.387 + ], + "angle": 0, + "content": "" + }, + { + "type": "image_caption", + "bbox": [ + 0.794, + 0.38, + 0.872, + 0.387 + ], + "angle": 0, + "content": "" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.387, + 0.788, + 0.439 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.79, + 0.387, + 0.879, + 0.439 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.697, + 0.441, + 0.787, + 0.448 + ], + "angle": 0, + "content": "person,straddle,horse>" + }, + { + "type": "image_caption", + "bbox": [ + 0.797, + 0.441, + 0.87, + 0.448 + ], + "angle": 0, + "content": "" + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.449, + 0.788, + 0.502 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.797, + 0.449, + 0.879, + 0.502 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.708, + 0.503, + 0.776, + 0.51 + ], + "angle": 0, + "content": "" + }, + { + "type": "image_caption", + "bbox": [ + 0.798, + 0.503, + 0.87, + 0.51 + ], + "angle": 0, + "content": "" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.526, + 0.895, + 0.638 + ], + "angle": 0, + "content": "Figure 1. Previous attention prediction models have traditionally focused on the instance-level, primarily emphasizing foreground humans and objects. In contrast, our proposed interaction-oriented attention aims to capture subtler and more fine-grained visual cues associated with actions, such as body parts (row 1), human-object contact (row 2), and scene context (row 3). This proposition challenges the research community with a more intricate and cognitively demanding task." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.671, + 0.892, + 0.747 + ], + "angle": 0, + "content": "of goal-directed attention [3-5, 39, 46, 50]. This holds profound implications for enhancing human-computer interaction [11, 25, 49], and contributing to fields such as assistance for visual impaired [15, 16], education [1, 51], and autonomous driving [13, 21, 43, 65]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.893, + 0.902 + ], + "angle": 0, + "content": "Goal-oriented attention prediction studies have made some progress recently [8, 12, 24, 37, 42, 55-57], mostly focusing on predicting gaze fixation when searching or recognizing objects with relative explicit and invariant visual cues. However, interactions [27, 38, 68, 69, 71], another fundamental component of visual understanding that encapsulates how humans and objects interact with each other, remain largely unexplored. Interactions pose greater cognitive challenges than objects, due to their diverse and subtle visual cues, as shown in Figure 1. Consequently, predicting" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.888, + 0.222, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.925, + 0.521, + 0.937 + ], + "angle": 0, + "content": "28390" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.182 + ], + "angle": 0, + "content": "interaction-oriented visual attention proves to be a more demanding task compared to previous efforts. Moreover, the inherent diversity and almost infinite granularity of actions intersect with limited available data, necessitating the adoption of zero-shot learning. We name this problem Zero-shot Interaction-oriented Attention prediction (ZeroIA)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.184, + 0.47, + 0.29 + ], + "angle": 0, + "content": "On the other hand, in the domain of human-object interaction (HOI) detection [29, 29, 34, 53, 60, 62, 64, 66, 67], current state-of-the-art methods also face limitations in the interaction comprehension phase, even though they demonstrate proficiency in handling the object detection phase. This limitation is rooted in the inherent difficulty of capturing visual cues related to actions." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.293, + 0.47, + 0.502 + ], + "angle": 0, + "content": "To alleviate these problems, we first introduce Interactive-Gaze (IG), a novel dataset of gaze fixations capturing human cognitive process of interactions, filling a crucial gap in interaction-oriented visual attention research. IG contains 530,000 fixation points from 32 human observers, spanning 740 interaction categories, 80 objects, and 132 actions. Human observers are invited to capture key visual cues in various interaction scenes, while their visual attention during the cognitive process is recorded. All interaction scenes are selected from HOI benchmark datasets, HICO-det [2] and VCOCO [14]. This means that IG has the potential to bridge the fields of visual attention and HOI detection and be a catalyst for advancing both research areas simultaneously." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.507, + 0.468, + 0.763 + ], + "angle": 0, + "content": "Secondly, inspired by the cognitive processes of human observers, we further propose a goal-oriented attention prediction approach, termed Interactive Attention (IA). Our approach begins by a set of clever interaction-oriented prompts and adapters to activate and leverage CLIP's powerful knowledge representation capabilities [48], thereby facilitating zero-shot learning. This process involves establishing adaptive knowledge prototypes based on each visual scene, avoiding direct retrieval of fixed knowledge from CLIP, which may exhibit strong noun bias [18,41,45]. Guided by these knowledge, IA first focuses on the perception and understanding of individual instances, i.e., humans and objects. Then, it further understands the interactions unfolding between instances, ultimately completing the generation of interaction-oriented attention. Extensive experiments demonstrate that IA outperforms state-of-the-art approaches in both ZeroIA and fully supervised settings." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Furthermore, we explore how goal-oriented attention can be fed back to the goal itself, particularly establishing an initial bidirectional pathway connecting goal-oriented attention and action understanding. We introduce a general and effective HOI training strategy. This can supplement most state-of-the-art model loss with additional supervision for interaction-oriented attention. Remarkably, extensive experiments reveal the substantial potential of visual attention for HOI models from two aspects. (1) Aligning a lim" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.212 + ], + "angle": 0, + "content": "ited yet valuable genuine human interaction-oriented attention from the proposed IG enhances the performance and interpretability of existing state-of-the-art HOI models. (2) Integrating interaction-oriented attention generated by the proposed IA model further enhances HOI models, surpassing even the performance achieved in the context of human observers' attention. To summarize, the contributions of our work are three-fold:" + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.224, + 0.892, + 0.345 + ], + "angle": 0, + "content": "- Firstly, we address a crucial gap in interaction-oriented attention studies by introducing the ZeroIA problem and IG dataset, marking a pioneering endeavor as the inaugural gaze fixation dataset specifically designed for interaction analysis. Given the composite nature of IG, it has significant potential to facilitate the intersection of multiple domains, such as goal-directed attention and interaction comprehension." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.355, + 0.892, + 0.446 + ], + "angle": 0, + "content": "- Secondly, we present the IA model, a novel approach crafted to emulate human cognitive processes for predicting high-quality interaction-oriented attention. Extensive experiments demonstrate IA outperforms other state-of-the-art attention prediction methods in both the ZeroIA and fully-supervised settings." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.455, + 0.892, + 0.545 + ], + "angle": 0, + "content": "- Thirdly, we introduce a general and simple HOI training strategy with attention and demonstrate that both aligning a small yet precious genuine human attention from IG and aligning attention generated by IA can enhance the performance and interpretability of existing state-of-the-art HOI models." + }, + { + "type": "list", + "bbox": [ + 0.518, + 0.224, + 0.892, + 0.545 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.559, + 0.771, + 0.575 + ], + "angle": 0, + "content": "2. Interactive Gaze (IG) Dataset" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.584, + 0.892, + 0.795 + ], + "angle": 0, + "content": "To study human visual attention oriented by HOI, we collect the Interactive Gaze (IG), the first large-scale interaction-centric gaze fixation dataset, as shown in Figure 2. IG comprises 6,299 interaction scenarios across 740 interaction categories, 80 object categories, and 132 action categories. IG captures the visual attention of 32 human observers during the cognition of these interaction scenarios, resulting in 530,000 corresponding fixation points. IG holds substantial potential to bridge the domains of visual attention and action understanding, serving as a catalyst to jointly promote these two areas of study. We use mouse clicks to simulate gaze fixation for visual attention studies [8,24,36,37], and more details about the IG dataset are presented in the supplementary materials." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Dataset Comparison. Previous gaze fixation datasets have primarily concentrated on instances (e.g., objects, humans, animals, texts) as targets for recognition, search, and free-viewing, as illustrated in Table 1. In contrast, IG stands as the pioneering interaction-centric gaze fixation dataset. Given the inherent diversity, composability, and context dependency of interactions, interaction-oriented attention is" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.925, + 0.518, + 0.937 + ], + "angle": 0, + "content": "28391" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.08, + 0.089, + 0.447, + 0.26 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.271, + 0.47, + 0.313 + ], + "angle": 0, + "content": "Figure 2. Our proposed IG is the first interaction-centric gaze fixation dataset, comprising 530K fixation points across 740 interaction categories." + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.33, + 0.468, + 0.357 + ], + "angle": 0, + "content": "Table 1. Comparison of fixation datasets. Previous work all focus on instances of objects, humans, animals, texts, etc." + }, + { + "type": "table", + "bbox": [ + 0.091, + 0.368, + 0.453, + 0.491 + ], + "angle": 0, + "content": "
DatasetFocusSceneClassFixation
SALICON [24]Object10000-4600K
POET [44]Object627010178K
People900 [7]Human912155K
MCS [58]Object2183216K
PET [9]Animal4135630K
COCO-Search18 [55]Object620218300K
SalECI [23]Object & Text97213257K
Our (IG)Action6299740530K
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.519, + 0.468, + 0.548 + ], + "angle": 0, + "content": "associated with elevated cognitive challenges and empirical knowledge." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.55, + 0.468, + 0.745 + ], + "angle": 0, + "content": "Data Selection & Subsetting. To bring the visual attention and HOI detection domains closer, we select image samples from HOI benchmark dataset VCOCO [14] and HICO-det [2] as experimental materials. VCOCO consists of 24 action classes and 214 HOI classes, while HICO-det is larger and more challenging, covering 117 action classes and 600 HOI classes. We select 4,475 samples from the V-COCO training set (13 samples per HOI class on average) to train the attention prediction model. Additionally, we use 1,104 samples from the HICO-det test set and 720 samples from the V-COCO test set for testing the attention prediction model under ZeroIA and fully supervised interaction-oriented attention prediction tasks, respectively." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.761, + 0.167, + 0.777 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.786, + 0.26, + 0.801 + ], + "angle": 0, + "content": "3.1. Problem Definition" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.468, + 0.9 + ], + "angle": 0, + "content": "Given a sample of HOI pair, the goal of zero-shot interaction-oriented human visual attention prediction (ZeroIA) is to generate an attention heatmap that reflects key visual cues for comprehending the interaction between human and object without any training for this interaction, as shown on the left of Figure 3. A complete HOI sample con" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.09, + 0.892, + 0.166 + ], + "angle": 0, + "content": "sists of five components: an RGB image \\( x \\in \\mathbb{R}^{H \\times W \\times 3} \\), a bounding box of human \\( b^H \\), a bounding box of object \\( b^O \\), an object label \\( C_O \\), and an interaction label \\( C_I \\). The output of ZeroIA is expressed as a spatial attention heatmap \\( m_{IA} \\in \\mathbb{R}^{H \\times W \\times 1} \\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.179, + 0.697, + 0.193 + ], + "angle": 0, + "content": "3.2. Interactive Attention" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.203, + 0.892, + 0.294 + ], + "angle": 0, + "content": "Under goal-oriented cognitive tasks, humans tend to use their existing empirical knowledge and memory to model cognitive goals, and then progressively perceive and understand visual scenes with the goal. Inspired by the human cognitive process, we propose the Interactive Attention (IA) to tackle the ZeroIA problem, as shown in Figure 3." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.295, + 0.892, + 0.49 + ], + "angle": 0, + "content": "In IA, we first activate the strong knowledge representation capabilities of CLIP [48] through a clever interaction-oriented prompt block (PB). Secondly, we design two tiny and learnable adapters to model the HOI cognitive task. It generates scene-adaptive knowledge prototypes (KPs) for humans, objects, interactions, and robust visual features. Guided by these knowledge, we progressively perceive and understand the HOI scene. Specifically, we first perceive the human and object through a human-object cognitive block (HOCB), then delve deeper into understanding the interaction that occurs between the human and objects through an interaction cognitive block (ICB), and finally decode the interaction-oriented attention map." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.492, + 0.892, + 0.628 + ], + "angle": 0, + "content": "Interaction-oriented Prompt. Given an HOI sample, the interaction-oriented prompt block (PB) provides the visual-linguistic large model CLIP with clever inputs applicable to the HOI cognitive task to activate CLIP's powerful representation capabilities. Due to the natural composability of HOI, PB considers humans, objects, and interactions separately, i.e., constructing human-centric, object-centric, and interaction-centric prompts and extracting their textual representations, respectively." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.892, + 0.779 + ], + "angle": 0, + "content": "PB takes \"person\" and object textual label \\( C_O \\) as inputs to CLIP text encoder and extracts the human- and object-centric textual representations, \\( T_H \\), and \\( T_O \\). The human and object texts are merged into the interaction-centric prompt, i.e., \"a photo of a person \\( [C_I] \\) \\( [C_O] \\)\" since they are closely related to the interaction. Then, the interaction-centric textual representation \\( T_I \\) is extracted. Correspondingly, CLIP's image encoder is leveraged to extract robust visual features \\( V = [v_1, \\dots, v_M] \\) to take advantage of the semantic alignment between image and linguistics." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Positional & Visual Adapter. The features extracted from CLIP based on PB are somewhat applicable to the cognitive goal, but this is a fixed holistic representation modeling of the goal, which lacks the ability to adapt to each specific HOI sample, especially to diverse spatial configurations and visual scenes. As a result, we design the tiny positional adapter and visual adapter to provide HOI sample-aware knowledge that enables better modeling of HOI cog" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.926, + 0.519, + 0.938 + ], + "angle": 0, + "content": "28392" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.086, + 0.094, + 0.891, + 0.306 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.317, + 0.895, + 0.416 + ], + "angle": 0, + "content": "Figure 3. The overall architecture of our Interactive Attention (IA). Inspired by the HOI cognitive process of human observers, IA is divided into three phases: empirical knowledge representation, cognitive goal modeling, and progressive understanding. First, a set of interaction-oriented prompts activate and leverage the robust knowledge representation capability of CLIP. Secondly, positional and visual adapters are introduced to acquire scene-adaptive human, object, and interaction Knowledge Prototypes (KPs) along with visual features of the HOI scene. Thirdly, guided by these KPs, IA progressively comprehends the scene, starting with an instance-level understanding of humans and objects and deepening insight into their interactions. The decoder generates predicted attention maps, supervised by the real attention maps of human observers using \\( L_{H2IA} \\)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.441, + 0.315, + 0.456 + ], + "angle": 0, + "content": "nitive tasks in each specific sample." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.456, + 0.47, + 0.486 + ], + "angle": 0, + "content": "Positional adapter (PA) provides sample-aware spatial information on textual representations:" + }, + { + "type": "equation", + "bbox": [ + 0.146, + 0.498, + 0.47, + 0.516 + ], + "angle": 0, + "content": "\\[\nK _ {H} = M L P \\left(\\left[ \\left(T _ {H}\\right), F o u r i e r \\left(b ^ {H}\\right) \\right]\\right), \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.149, + 0.526, + 0.469, + 0.544 + ], + "angle": 0, + "content": "\\[\nK _ {O} = M L P \\left(\\left[ \\left(T _ {O}\\right), F o u r i e r \\left(b ^ {O}\\right) \\right]\\right), \\tag {2}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.089, + 0.55, + 0.469, + 0.567 + ], + "angle": 0, + "content": "\\[\nK _ {I} = M L P \\left(\\left[ \\left(T _ {I}\\right), F o u r i e r \\left(C _ {H}\\right), F o u r i e r \\left(C _ {O}\\right) \\right]\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.574, + 0.469, + 0.664 + ], + "angle": 0, + "content": "where \\( K_{H} \\), \\( K_{O} \\), and \\( K_{I} \\) represent adaptive knowledge prototypes of human, object, and interaction. Fourier is the Fourier embedding, MLP is a multi-layer perceptron, and [·] is the concatenate operation. Visual adapter (VA) is implemented as two Transformer encoder layers to transform \\( V \\) into refined visual features \\( V' = [v_1', \\dots, v_M'] \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.664, + 0.47, + 0.768 + ], + "angle": 0, + "content": "Human-Object Cognitive Block. The HOI scene is further learned under the guidance of knowledge prototypes of human and object (\\(K_{H}\\) and \\(K_{O}\\)). The self-attention mechanism with gating is introduced to establish cognitive dependencies between knowledge prototypes and visual features, then the human-object-aware visual feature \\(V_{HO}\\) is obtained:" + }, + { + "type": "equation", + "bbox": [ + 0.104, + 0.782, + 0.469, + 0.8 + ], + "angle": 0, + "content": "\\[\nV _ {H O} = V ^ {\\prime} + \\text {G a t e} \\left(\\text {S e l f A t t n} \\left(\\left[ K _ {H}, K _ {O}, V ^ {\\prime} \\right]\\right)\\right), \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.81, + 0.469, + 0.855 + ], + "angle": 0, + "content": "where \\(Gate(\\cdot)\\) is a token gating operation that considers visual tokens only, SelfAttn(\\(\\cdot\\)) denotes a self-attention computation." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Interaction Cognitive Block. Expanding upon the instance-level cognition, including the human and object, the model further delves into comprehending higher-level" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.441, + 0.892, + 0.517 + ], + "angle": 0, + "content": "interactions that occur between the human and object. To achieve this, the cross-attention mechanism with gating is introduced to guide the learning of more subtle interaction cues by interaction knowledge prototype and obtaining the primary HOI-aware visual feature \\( V_{HOI} \\):" + }, + { + "type": "equation", + "bbox": [ + 0.525, + 0.525, + 0.892, + 0.542 + ], + "angle": 0, + "content": "\\[\nV _ {H O I} = V _ {H O} + \\operatorname {G a t e} \\left(\\operatorname {C r o s s A t t n} \\left(V _ {H O}, K _ {I}\\right)\\right), \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.549, + 0.892, + 0.612 + ], + "angle": 0, + "content": "where we denote \\(CrossAttn(q, kv)\\) as a cross-attention operation. After that, the general self-attention operation is conducted on \\(V_{HOI}\\) to obtain the full HOI-aware visual feature \\(V_{HOI}'\\):" + }, + { + "type": "equation", + "bbox": [ + 0.572, + 0.618, + 0.891, + 0.636 + ], + "angle": 0, + "content": "\\[\nV _ {H O I} ^ {\\prime} = V _ {H O I} + \\text {S e l f A t t n} \\left(V _ {H O I}\\right). \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.892, + 0.793 + ], + "angle": 0, + "content": "Interaction-oriented Attention Decoder. The goal of the decoder is to generate interaction-oriented attention heatmap \\(m_{IA} \\in \\mathbb{R}^{H \\times W \\times 1}\\), we first reshape the full interaction-aware visual feature, \\(V_{HOI}'\\), from a 2D shape of \\(\\frac{HW}{p^2} \\times C\\) to a standard 3D feature map \\(\\frac{H}{p} \\times \\frac{W}{p} \\times C\\), \\(C\\) is the feature channel size, \\(p\\) is the image patch size. Then, we adopt tiny 2-layers of \\(1 \\times 1\\) convolution with batch norm and ReLU activation to reduce the feature dimension to \\(\\frac{H}{p} \\times \\frac{W}{p} \\times 1\\). Last, we adopt a bilinearly upsample operation to achieve the full image size \\(H \\times W\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.794, + 0.892, + 0.839 + ], + "angle": 0, + "content": "Loss Function. We utilize the binary cross-entropy as a loss function for attention alignment, which can be expressed as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.5, + 0.847, + 0.909, + 0.901 + ], + "angle": 0, + "content": "\\[\n\\operatorname {B C E} (p, y) = - \\frac {1}{N} \\sum_ {i = 1} ^ {N} \\left(y _ {i} \\cdot \\log \\left(p _ {i}\\right) + \\left(1 - y _ {i}\\right) \\cdot \\log \\left(1 - p _ {i}\\right)\\right), \\tag {7}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.925, + 0.519, + 0.937 + ], + "angle": 0, + "content": "28393" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.08, + 0.093, + 0.468, + 0.3 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.313, + 0.471, + 0.384 + ], + "angle": 0, + "content": "Figure 4. We incorporate aligned attention into the existing HOI model training pipeline, divided into two strategies: supervising by a limited amount of real attention from human observers and supervising by a large number of attention pseudo-labels generated by our proposed IA." + }, + { + "type": "equation", + "bbox": [ + 0.18, + 0.41, + 0.469, + 0.427 + ], + "angle": 0, + "content": "\\[\nL _ {H 2 I A} = \\mathrm {B C E} \\left(m _ {H}, m _ {I A}\\right), \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.433, + 0.47, + 0.479 + ], + "angle": 0, + "content": "where \\( p \\) is the predictive probability, \\( y \\) is the target, \\( N \\) is the number of pixels in \\( m_{IA} \\), \\( m_H \\) is human observer's real attention heatmap." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.487, + 0.469, + 0.517 + ], + "angle": 0, + "content": "3.3. Training HOI Models with Interaction-oriented Attention" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.526, + 0.47, + 0.661 + ], + "angle": 0, + "content": "Here, we formulate the majority of recent state-of-the-art HOI models in the pipeline of CNN Backbone \\(\\rightarrow\\) Encoder \\(\\rightarrow\\) Decoder \\(\\rightarrow\\) Output Head. We enhance these HOI models by incorporating a supervision of interaction-oriented attention into the training process. This involves two strategies: supervising with a limited amount of real attention samples from human observers and supervising with a large number of pseudo-labeled attention samples from the IA model, as shown in Figure 4." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.662, + 0.469, + 0.827 + ], + "angle": 0, + "content": "For these HOI models, we first introduce a simple attention head to extract and reshape the averaged attention maps \\( m_{HOI} \\) from the last layer of cross-attention computation in the decoder. The attention head is intentionally kept simple for a more direct back propagation of guidance to the representation. Subsequently, the corresponding human observer's attention heatmap \\( m_{H} \\) and IA-generated pseudolabels \\( m_{IA} \\) are scaled down to match the size of \\( m_{HOI} \\) through adaptive 2D max-pooling. Finally, \\( m_{H} \\) and \\( m_{IA} \\) are used to supervise \\( m_{HOI} \\) for two kinds of strategies, respectively." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.828, + 0.469, + 0.873 + ], + "angle": 0, + "content": "For the strategy of supervising by human observers, the attention alignment loss function \\( L_{H2HOI} \\) and the overall HOI model's loss function \\( L \\) can be expressed as" + }, + { + "type": "equation", + "bbox": [ + 0.167, + 0.886, + 0.469, + 0.902 + ], + "angle": 0, + "content": "\\[\nL _ {H 2 H O I} = \\mathrm {B C E} \\left(m _ {H O I}, m _ {H}\\right), \\tag {9}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.601, + 0.092, + 0.892, + 0.107 + ], + "angle": 0, + "content": "\\[\nL = \\lambda_ {1} L _ {\\text {r a w}} + \\lambda_ {2} L _ {H 2 H O I}, \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.114, + 0.894, + 0.19 + ], + "angle": 0, + "content": "where \\( L_{raw} \\) represents the loss function of the original HOI model, which varies depending on the specific model, while \\( \\lambda_1 \\) and \\( \\lambda_2 \\) denote loss scaling factors. Similarly, for the strategy of supervising by IA, \\( L_{IA2HOI} \\) and the overall loss function \\( L \\) can be expressed as" + }, + { + "type": "equation", + "bbox": [ + 0.585, + 0.203, + 0.892, + 0.219 + ], + "angle": 0, + "content": "\\[\nL _ {I A 2 H O I} = \\mathrm {B C E} \\left(m _ {H O I}, m _ {I A}\\right), \\tag {11}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.599, + 0.231, + 0.892, + 0.248 + ], + "angle": 0, + "content": "\\[\nL = \\lambda_ {1} L _ {\\text {r a w}} + \\lambda_ {2} L _ {I A 2 H O I}. \\tag {12}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.261, + 0.634, + 0.278 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.286, + 0.719, + 0.302 + ], + "angle": 0, + "content": "4.1. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.309, + 0.892, + 0.459 + ], + "angle": 0, + "content": "Interactive Attention. We apply 2 versions of CLIP (ViT-B/16 and ViT-L/14) to build the IA models, resulting in IA-B and IA-L, respectively. The output dimension of Fourier embedding is 64. During training, we use AdamW as the optimizer with an initial learning rate of \\(1 \\times 10^{-4}\\). The IA model is trained for 80 epochs with a learning rate reduction pre-20 epochs by a factor of 10. The momentum and the weight decay are set as 0.9 and \\(1 \\times 10^{-4}\\). The experiments are conducted on four NVIDIA GeForce RTX 3090 GPUs with a batch size of 16." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.46, + 0.893, + 0.779 + ], + "angle": 0, + "content": "Training HOI Models with Attention Alignment. We apply our attention-guided training strategy on three typical state-of-the-art HOI methods: MUREN [29], representing the one-stage structure, and UPT [60] and STIP [62], representing the two-stage structure. In MUREN, we align the cross-attention map of the last layer in its interaction branch module with our interaction-oriented attention. In UPT, we first add two transformer decoder layers at the end of its interaction head, conducting cross-attention computation with global visual features, and align the cross-attention map of last layer. In STIP, we align the cross-attention map of the last layer in its structure-aware transformer module with our interaction-oriented attention. Due to variations in the raw losses of different methods, particularly for one-stage structure requiring additional supervision of object detection results, corresponding loss scaling factors differ. \\(\\lambda_{1}\\) and \\(\\lambda_{2}\\) are set to 1 and 10 in MUREN. \\(\\lambda_{1}\\) and \\(\\lambda_{2}\\) are set to 1 and 6 in UPT and STIP. Note that the IA model, responsible for generating interaction-oriented attention, is trained without exposure to samples from VCOCO test set and HICO-det test set, preventing any possibility of label leakage." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.787, + 0.787, + 0.803 + ], + "angle": 0, + "content": "4.2. Comparison methods & Metrics." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.811, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We evaluate the performance of our IA model on interaction-oriented attention prediction, comparing it with 10 state-of-the-art methods: ITTI [22], GBVS [17], DeepGaze I [30], DeepGaze IIE [35], UMB [70], ConvNext [40], MLNet [6], SSwin Transformer [23], CLIP-ViT-B/16 [48], CLIP-ViT-L/14 [48]. Among these, ITTI and GBVS" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.926, + 0.521, + 0.938 + ], + "angle": 0, + "content": "28394" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.47, + 0.118 + ], + "angle": 0, + "content": "Table 2. Performance comparison on IG dataset. Bold and underline show the best and second-best performances." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.128, + 0.472, + 0.262 + ], + "angle": 0, + "content": "
MethodZerola SettingFully Supervised Setting
CC↑KLdiv↓SIM↑AUC↑CC↑KLdiv↓SIM↑AUC↑
ITTI [22]0.07844.35530.01420.49990.07543.18150.01170.5301
GBVS [17]0.02624.54950.02340.50000.17732.94980.02070.5037
DeepGaze I [30]0.18733.06630.00800.55700.19693.18690.00810.6143
DeepGaze IIE [35]0.20653.02550.00910.58140.17213.23570.00700.6049
UMB [70]0.21213.90040.59370.53260.20114.23380.61470.5319
MLNet [6]0.29373.89870.46460.59720.31953.68040.41530.5743
ConvNext [40]0.25714.87290.61100.54820.27314.51540.57470.5524
SSwin Transformer [23]0.24942.66540.33090.52120.29383.43090.33230.5391
CLIP-base [48]0.14033.61180.00580.35160.15643.87210.00740.3385
CLIP-large [48]0.16813.64980.00640.31830.16903.85470.00660.3356
IA CLIP-base0.40132.71140.72050.59530.48102.21320.75210.6375
IA CLIP-large0.44882.84090.71520.60680.51062.14090.77960.6386
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.29, + 0.47, + 0.44 + ], + "angle": 0, + "content": "excel in early saliency prediction based on manual features, while the remaining methods are recent learning-based approaches. DeepGaze I and DeepGaze IIE utilize official pre-trained models for predictions, and UMB, ConvNext, MLNet, and SSwin Transformer are all trained with IG datasets. Additionally, we compute the similarity maps of two commonly used raw CLIP versions (CLIP-ViT-B/16 and CLIP-ViT-L/14). These similarity maps compute the similarity distance between image features and text features, serving as the raw CLIP's class attention maps [31]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.44, + 0.47, + 0.546 + ], + "angle": 0, + "content": "We apply 4 metrics to measure performance: KL divergence (KLdiv), correlation coefficient (CC), similarity (SIM), and the area under the receiver operating characteristic curve (AUC). KLdiv, CC, and SIM are distribution-based metrics, while AUC is a localization-based metric. Except KLdiv, where lower values are preferable, higher values are desirable for all other metrics." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.557, + 0.314, + 0.573 + ], + "angle": 0, + "content": "4.3.Quantitative Comparison." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.58, + 0.47, + 0.686 + ], + "angle": 0, + "content": "Table 2 presents the quantitative comparison results in the ZeroIA and the fully supervised settings. We can observe that both versions of our model IA outperform all 10 baselines in both metrics. In particular, for CC metric, IA w/ CLIP-L outperforms the third-best MLNet by \\(52.8\\%\\) and \\(59.8\\%\\) on the ZeroIA and the fully supervised settings, respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.686, + 0.471, + 0.839 + ], + "angle": 0, + "content": "Moreover, we observe that the manual feature-based ITTI and GBVS approaches fail in the interaction-oriented attention prediction task, which demands higher cognitive capabilities. Additionally, when comparing IA with the similarity map of raw CLIP output, our IA achieves significant improvements across all metrics. For example, IA w/ CLIP-B exceeds raw CLIP-B by \\(186\\%\\) under CC metric of the ZeroIA setting. This suggests that our model effectively activates and utilizes CLIP's knowledge representation capabilities, adapting them to cognitive tasks on interaction." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.847, + 0.277, + 0.864 + ], + "angle": 0, + "content": "4.4. Qualitative Analyses." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.901 + ], + "angle": 0, + "content": "As shown in Figures 5 and 6, the visualizations of interaction-oriented attention prediction under ZeroIA and" + }, + { + "type": "table_caption", + "bbox": [ + 0.527, + 0.09, + 0.866, + 0.104 + ], + "angle": 0, + "content": "Table 3. Performance comparison of each module in IA." + }, + { + "type": "table", + "bbox": [ + 0.514, + 0.115, + 0.879, + 0.195 + ], + "angle": 0, + "content": "
MethodZeroIA SettingFully Supervised Setting
CC↑KLdiv↓SIM↑AUC↑CC↑KLdiv↓SIM↑AUC↑
w/o PA0.36523.21150.67330.58020.39612.46760.68640.6023
w/o VA0.38382.98010.67540.58320.40812.43460.68930.6182
w/o HOCB0.34983.31230.64210.57430.36972.56890.64840.6034
w/o ICB0.32493.65410.58450.56440.34452.85330.60230.5934
IA0.40132.71140.72050.59530.48102.21320.75210.6375
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.219, + 0.892, + 0.278 + ], + "angle": 0, + "content": "fully supervised settings, respectively. Notably, across both settings, IA exhibits attention distributions that are consistently closer to human observers, outperforming the remaining eight methods." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.279, + 0.892, + 0.385 + ], + "angle": 0, + "content": "Compared with SOTA models. The previous untrained instance-centric models (columns 6-7) only capture coarse-grained salient persons and objects, but not interaction-related cues. Methods trained on IG prove limited in the complex multi-instance \"push\" scenario (Figure 5, row 4) under the ZeroIA setting and also in the \"talk on\" scenario (Figure 6, row 3) with a limited number of training samples." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.385, + 0.893, + 0.552 + ], + "angle": 0, + "content": "Compared with raw CLIP, IA accurately captures key visual cues, particularly for unseen categories such as \"repair\", \"kiss\", \"lick\", \"push\", and \"sign\" in Figure 5. Noteworthy is the comparison with columns 5-6, where the similarity maps generated by raw CLIP lack interpretability, displaying properties such as opposite visualization and noisy activation, as highlighted in recent work [31, 32]. These observations, along with quantitative results in Table 2, underscore the fact that our work effectively activates CLIP's powerful knowledge representation capabilities and improves interpretability." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.56, + 0.655, + 0.575 + ], + "angle": 0, + "content": "4.5. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.582, + 0.893, + 0.84 + ], + "angle": 0, + "content": "To examine the impact of each module in IA, we conduct an ablation study by removing modules in Table 3. Specifically, we sequentially exclude the positional adapter (PA), visual adapter (VA), human-object cognitive block (HOCB), and interaction cognitive block (ICB). All ablated models are variations of IA w/ CLIP-B. Results indicate consistent performance degradation across both ZeroIA and fully supervised settings upon removal of any module. Notably, the most significant degradation occurs when the ICB is omitted, emphasizing its crucial role in guiding the learning of interaction-oriented attention by injecting the interaction knowledge. Subsequently, the HOCB, enriched with information about the subjects and objects involved in the interaction, the PA, which incorporates spatial configuration, and the VA, receiving refined visual features, contribute to the model's performance in descending order from high to low." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.848, + 0.874, + 0.864 + ], + "angle": 0, + "content": "4.6. Effectiveness of Attention Training Strategy" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Aligning human attention enhances HOI model accuracy. We leverage the VCOCO training subset within" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.926, + 0.521, + 0.938 + ], + "angle": 0, + "content": "28395" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.148, + 0.09, + 0.831, + 0.304 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.182, + 0.313, + 0.786, + 0.328 + ], + "angle": 0, + "content": "Figure 5. Qualitative comparison of interaction-oriented attention prediction under the ZeroIA setting." + }, + { + "type": "image", + "bbox": [ + 0.147, + 0.343, + 0.83, + 0.595 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.156, + 0.604, + 0.812, + 0.619 + ], + "angle": 0, + "content": "Figure 6. Qualitative comparison of interaction-oriented attention prediction under the fully supervised setting." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.645, + 0.473, + 0.798 + ], + "angle": 0, + "content": "the proposed IG, comprising 4,475 samples, approximately \\(32.4\\%\\) of the complete VCOCO training set, as the attention ground truth for additional supervision of existing HOI models. As shown in Table 4, MUREN, UPT, and STIP are improved by \\(0.6\\mathrm{mAP}\\), \\(0.8\\mathrm{mAP}\\), and \\(0.4\\mathrm{mAP}\\), respectively, under the Scenario1 setting. Similarly, under the Scenario2 setting, MUREN, UPT, and STIP are enhanced by \\(0.7\\mathrm{mAP}\\), \\(1.3\\mathrm{mAP}\\), and \\(0.4\\mathrm{mAP}\\), respectively. This highlight the significant potential of aligned human attention in enhancing action comprehension, even with limited training data." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Aligning IA-generated attention enhances HOI model accuracy more significantly. We further enhance the additional supervision of HOI models through large-scale interaction-oriented pseudo-labeling, generated by the proposed IA model on the training sets of VCOCO and HICO-det, respectively. In Table 4, on the VCOCO dataset," + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.645, + 0.892, + 0.844 + ], + "angle": 0, + "content": "our training strategies consistently obtain performance improvements for MUREN, UPT, and STIP. In particular, thanks to the precise emulation of human attention by our proposed IA model, the results of all HOI models reveal that training by a large number of pseudo-attention labels is superior to using limited genuine human attention. On HICO-det dataset, our training strategy similarly achieves consistent performance gains in Table 5. Particularly, we observe that our training strategy significantly enhances the performance of the rare set, by \\(6.0\\%\\), \\(4.0\\%\\), and \\(2.7\\%\\) on MUREN, UPT, and STIP, respectively. Note that the reported experimental results are all obtained by reproducing these models under the same experimental settings." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.856, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Aligning attention makes HOI models more interpretable. We present visualizations of the cross-attention maps of interaction branches in original MUREN and the" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.926, + 0.521, + 0.938 + ], + "angle": 0, + "content": "28396" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.081, + 0.09, + 0.466, + 0.104 + ], + "angle": 0, + "content": "Table 4. Comparison of HOI detection performance on VCOCO." + }, + { + "type": "table", + "bbox": [ + 0.115, + 0.115, + 0.432, + 0.348 + ], + "angle": 0, + "content": "
MethodBackboneScenario #1Scenario #2
One-stage methods
UnionDet [26]ResNet-50-FPN47.556.2
IP-Net [54]Hourglass-10451.0-
GG-Net [33]Hourglass-10454.7-
HOTR [27]ResNet-5055.264.4
QPIC [52]ResNet-10158.360.7
MUREN [29]ResNet-5066.969.0
MUREN w/ HumanResNet-5067.569.7
MUREN w/ IA-BResNet-5067.770.3
MUREN w/ IA-LResNet-5068.070.4
Two-stage methods
VCL [19]ResNet-5048.3-
SCG [59]ResNet-50-FPN54.2-
UPT [60]ResNet-5059.865.5
STIP [62]ResNet-5066.070.7
UPT w/ HumanResNet-5060.766.4
UPT w/ IA-BResNet-5061.166.8
UPT w/ IA-LResNet-5061.467.0
STIP w/ HumanResNet-5066.471.1
STIP w/ IA-BResNet-5067.071.3
STIP w/ IA-LResNet-5067.271.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.36, + 0.468, + 0.374 + ], + "angle": 0, + "content": "Table 5. Comparison of HOI detection performance on HICO-det." + }, + { + "type": "table", + "bbox": [ + 0.115, + 0.385, + 0.432, + 0.624 + ], + "angle": 0, + "content": "
MethodBackboneFullRareNon-rare
One-stage methods
UnionDet [26]ResNet-50-FPN17.5811.7219.33
IP-Net [54]Hourglass-10419.5612.7921.58
PPDM [33]Hourglass-10421.7313.7821.40
GG-Net [63]Hourglass-10423.4716.4825.60
HOTR [27]ResNet-5025.1017.3427.42
QPIC [52]ResNet-10129.9023.9231.69
MSTR [28]ResNet-5031.1725.3132.92
MUREN [29]ResNet-5032.0927.3633.50
MUREN w/ IA-BResNet-5032.4528.9033.51
MUREN w/ IA-LResNet-5032.4829.0133.53
Two-stage methods
VCL [19]ResNet-5023.6317.2125.55
ATL [20]ResNet-5023.6717.6425.47
SCG [59]ResNet-50-FPN29.2624.6130.65
UPT [60]ResNet-5031.9326.7033.49
STIP [62]ResNet-5032.2228.1533.43
UPT w/ IA-BResNet-5032.2027.5933.58
UPT w/ IA-LResNet-5032.4727.7633.72
STIP w/ IA-BResNet-5032.3228.4733.59
STIP w/ IA-LResNet-5032.6428.9033.76
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.65, + 0.47, + 0.771 + ], + "angle": 0, + "content": "MUREN aligned with interaction-oriented attention, respectively, as shown in Figure 7. It is evident that the attention map of original MUREN appears fragmented and struggles to focus on interaction-related visual cues, leading to failures in interaction recognition. Conversely, after aligning with interaction-oriented attention, not only are the erroneous results corrected, but the attention map becomes significantly more interpretable and focuses on key regions." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.785, + 0.196, + 0.8 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.47, + 0.903 + ], + "angle": 0, + "content": "This paper aims to address a critical gap in interaction-oriented attention by introducing the challenging yet meaningful ZeroIA problem. To achieve this, we collect the IG dataset, marking the first large-scale interaction-centric gaze fixation dataset, featuring 530,000 fixation points across 740 diverse interaction categories. Subsequently, we" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.091, + 0.861, + 0.289 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.301, + 0.895, + 0.398 + ], + "angle": 0, + "content": "Figure 7. The predicted results and corresponding attention visualizations for MUREN and our (MUREN w/ IA-L, MUREN w/ Human). We mark true positive results in green, and false positive results in red. After aligning interaction-oriented attention, the erroneous prediction results are corrected, and the corresponding attention becomes more converged and more interpretable. More in supplementary materials." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.436, + 0.893, + 0.679 + ], + "angle": 0, + "content": "present the IA model, ingeniously designed to activate and leverage the knowledge representation capabilities of CLIP, emulating the cognitive processes of human observers to generate high-quality interaction-oriented attention. Extensive experiments demonstrate that the proposed IA model outperforms state-of-the-art attention prediction methods in both zero-shot and fully supervised settings. Furthermore, we propose an attention-guided HOI training strategy, leveraging interaction-oriented attention to guide existing HOI models for more effective learning. Quantitative and qualitative results demonstrate that both genuine human attention and IA-generated attention significantly enhance the performance and interpretability of existing HOI models, making them more capable of visual reasoning like human observers. This highlights the significant potential of visual attention in action comprehension." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.684, + 0.892, + 0.835 + ], + "angle": 0, + "content": "Our endeavor represents the pioneering effort to establish a bi-directional connection between visual attention and HOI detection, starting by directing visual attention through the interaction comprehension task and ending by incorporating this attention to repay existing HOI methods. We believe our work can inspire further research on goal-oriented attention and its application in various action-related tasks like classification, VQA, and captioning. Our work also has potential applications in DNNs' interpretability evaluation, human-AI collaboration, and values alignment research." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.841, + 0.895, + 0.902 + ], + "angle": 0, + "content": "Acknowledgements. This work is supported in part by National Natural Science Foundation of China under Grant 62373387, and in part by Natural Science Foundation of Guangdong Province (No. 2023A1515030264)." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.926, + 0.519, + 0.938 + ], + "angle": 0, + "content": "28397" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.175, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.17 + ], + "angle": 0, + "content": "[1] Souradeep Chakraborty, Zijun Wei, Conor Kelton, Seoyoung Ahn, A. Balasubramanian, G. Zelinsky, and D. Samaras. Predicting visual attention in graphic design documents. IEEE Transactions on Multimedia, 25:4478-4493, 2023. 1" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.171, + 0.47, + 0.213 + ], + "angle": 0, + "content": "[2] Yu-Wei Chao, Yunfan Liu, Xieyang Liu, Huayi Zeng, and Jia Deng. Learning to detect human-object interactions. 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However, the more complex interaction-oriented attention, arising from the comprehension of interactions between instances by human observers, remains largely unexplored. This is equally crucial for advancing human-machine interaction and human-centered artificial intelligence. To bridge this gap, we first collect a novel gaze fixation dataset named IG, comprising 530,000 fixation points across 740 diverse interaction categories, capturing visual attention during human observers' cognitive processes of interactions. Subsequently, we introduce the zero-shot interaction-oriented attention prediction task (ZeroIA), which challenges models to predict visual cues for interactions not encountered during training. Thirdly, we present the Interactive Attention model (IA), designed to emulate human observers' cognitive processes to tackle the ZeroIA problem. Extensive experiments demonstrate that the proposed IA outperforms other state-of-the-art approaches in both ZeroIA and fully supervised settings. Lastly, we endeavor to apply interaction-oriented attention to the interaction recognition task itself. Further experimental results demonstrate the promising potential to enhance the performance and interpretability of existing state-of-the-art HOI models by incorporating real human attention data from IG and attention labels generated by IA. + +# 1. Introduction + +Human visual attention reveals a wealth of information about internal cognitive states, including bottom-up visual stimulation and top-down goal-directed empirical knowledge [10,47,61]. Predicting visual attention provides a valuable understanding of how humans perceive, comprehend, and interact with the world, especially within the context + +![](images/b66ca2a13b790cdf91eead34e231be8c2ba2a4546b38f97b77dafe679ed8154c.jpg) +Instance-centric Attention Prediction +person, donut +person, banana + +![](images/06361b28ccd3e4d73d8ce7ceb4406bb9ec880346f6288eac84efd090607c2886.jpg) +person,horse +person, sheep + +![](images/7f437ab54e846064c37010518f9f2e5f5539fc31f7eebca2d30e69cbce07caca.jpg) +person, car +person, book +Figure 1. Previous attention prediction models have traditionally focused on the instance-level, primarily emphasizing foreground humans and objects. In contrast, our proposed interaction-oriented attention aims to capture subtler and more fine-grained visual cues associated with actions, such as body parts (row 1), human-object contact (row 2), and scene context (row 3). This proposition challenges the research community with a more intricate and cognitively demanding task. + +![](images/ee8ec1ed5753c32d8b391e519e155e008f2a5c82fd0ebe420e8c845dccddb745.jpg) +Our Interaction-oriented Attention Prediction + + +![](images/e530f97f9cc13562a8b61d58151f93f44fb1aa465b376856888355dbcdda1afc.jpg) + + +![](images/7bbd458c47d5d5cb368f379c831a4a3d45f828251b83de0a879672c2afcffb35.jpg) + +![](images/2e1e79c25c0667a740b0c7871b0c186ff4cf9a1d3570f525d3b58c2372d65f34.jpg) + +![](images/10120cd7f00b6a09e8719f861b2f51f0f40b4497ed8e791cc945e03aab31ac01.jpg) +person,straddle,horse> + + +![](images/e3ed46e99ead3d3b76485aba810c83643d350d1f7d020555cc23d9dba1ef4251.jpg) + + + +of goal-directed attention [3-5, 39, 46, 50]. This holds profound implications for enhancing human-computer interaction [11, 25, 49], and contributing to fields such as assistance for visual impaired [15, 16], education [1, 51], and autonomous driving [13, 21, 43, 65]. + +Goal-oriented attention prediction studies have made some progress recently [8, 12, 24, 37, 42, 55-57], mostly focusing on predicting gaze fixation when searching or recognizing objects with relative explicit and invariant visual cues. However, interactions [27, 38, 68, 69, 71], another fundamental component of visual understanding that encapsulates how humans and objects interact with each other, remain largely unexplored. Interactions pose greater cognitive challenges than objects, due to their diverse and subtle visual cues, as shown in Figure 1. Consequently, predicting + +interaction-oriented visual attention proves to be a more demanding task compared to previous efforts. Moreover, the inherent diversity and almost infinite granularity of actions intersect with limited available data, necessitating the adoption of zero-shot learning. We name this problem Zero-shot Interaction-oriented Attention prediction (ZeroIA). + +On the other hand, in the domain of human-object interaction (HOI) detection [29, 29, 34, 53, 60, 62, 64, 66, 67], current state-of-the-art methods also face limitations in the interaction comprehension phase, even though they demonstrate proficiency in handling the object detection phase. This limitation is rooted in the inherent difficulty of capturing visual cues related to actions. + +To alleviate these problems, we first introduce Interactive-Gaze (IG), a novel dataset of gaze fixations capturing human cognitive process of interactions, filling a crucial gap in interaction-oriented visual attention research. IG contains 530,000 fixation points from 32 human observers, spanning 740 interaction categories, 80 objects, and 132 actions. Human observers are invited to capture key visual cues in various interaction scenes, while their visual attention during the cognitive process is recorded. All interaction scenes are selected from HOI benchmark datasets, HICO-det [2] and VCOCO [14]. This means that IG has the potential to bridge the fields of visual attention and HOI detection and be a catalyst for advancing both research areas simultaneously. + +Secondly, inspired by the cognitive processes of human observers, we further propose a goal-oriented attention prediction approach, termed Interactive Attention (IA). Our approach begins by a set of clever interaction-oriented prompts and adapters to activate and leverage CLIP's powerful knowledge representation capabilities [48], thereby facilitating zero-shot learning. This process involves establishing adaptive knowledge prototypes based on each visual scene, avoiding direct retrieval of fixed knowledge from CLIP, which may exhibit strong noun bias [18,41,45]. Guided by these knowledge, IA first focuses on the perception and understanding of individual instances, i.e., humans and objects. Then, it further understands the interactions unfolding between instances, ultimately completing the generation of interaction-oriented attention. Extensive experiments demonstrate that IA outperforms state-of-the-art approaches in both ZeroIA and fully supervised settings. + +Furthermore, we explore how goal-oriented attention can be fed back to the goal itself, particularly establishing an initial bidirectional pathway connecting goal-oriented attention and action understanding. We introduce a general and effective HOI training strategy. This can supplement most state-of-the-art model loss with additional supervision for interaction-oriented attention. Remarkably, extensive experiments reveal the substantial potential of visual attention for HOI models from two aspects. (1) Aligning a lim + +ited yet valuable genuine human interaction-oriented attention from the proposed IG enhances the performance and interpretability of existing state-of-the-art HOI models. (2) Integrating interaction-oriented attention generated by the proposed IA model further enhances HOI models, surpassing even the performance achieved in the context of human observers' attention. To summarize, the contributions of our work are three-fold: + +- Firstly, we address a crucial gap in interaction-oriented attention studies by introducing the ZeroIA problem and IG dataset, marking a pioneering endeavor as the inaugural gaze fixation dataset specifically designed for interaction analysis. Given the composite nature of IG, it has significant potential to facilitate the intersection of multiple domains, such as goal-directed attention and interaction comprehension. +- Secondly, we present the IA model, a novel approach crafted to emulate human cognitive processes for predicting high-quality interaction-oriented attention. Extensive experiments demonstrate IA outperforms other state-of-the-art attention prediction methods in both the ZeroIA and fully-supervised settings. +- Thirdly, we introduce a general and simple HOI training strategy with attention and demonstrate that both aligning a small yet precious genuine human attention from IG and aligning attention generated by IA can enhance the performance and interpretability of existing state-of-the-art HOI models. + +# 2. Interactive Gaze (IG) Dataset + +To study human visual attention oriented by HOI, we collect the Interactive Gaze (IG), the first large-scale interaction-centric gaze fixation dataset, as shown in Figure 2. IG comprises 6,299 interaction scenarios across 740 interaction categories, 80 object categories, and 132 action categories. IG captures the visual attention of 32 human observers during the cognition of these interaction scenarios, resulting in 530,000 corresponding fixation points. IG holds substantial potential to bridge the domains of visual attention and action understanding, serving as a catalyst to jointly promote these two areas of study. We use mouse clicks to simulate gaze fixation for visual attention studies [8,24,36,37], and more details about the IG dataset are presented in the supplementary materials. + +Dataset Comparison. Previous gaze fixation datasets have primarily concentrated on instances (e.g., objects, humans, animals, texts) as targets for recognition, search, and free-viewing, as illustrated in Table 1. In contrast, IG stands as the pioneering interaction-centric gaze fixation dataset. Given the inherent diversity, composability, and context dependency of interactions, interaction-oriented attention is + +![](images/8dd5e30534b75da00586680a29a3bb1682ae2fecfc2d424aab9c033bf60ddf45.jpg) +Figure 2. Our proposed IG is the first interaction-centric gaze fixation dataset, comprising 530K fixation points across 740 interaction categories. + +Table 1. Comparison of fixation datasets. Previous work all focus on instances of objects, humans, animals, texts, etc. + +
DatasetFocusSceneClassFixation
SALICON [24]Object10000-4600K
POET [44]Object627010178K
People900 [7]Human912155K
MCS [58]Object2183216K
PET [9]Animal4135630K
COCO-Search18 [55]Object620218300K
SalECI [23]Object & Text97213257K
Our (IG)Action6299740530K
+ +associated with elevated cognitive challenges and empirical knowledge. + +Data Selection & Subsetting. To bring the visual attention and HOI detection domains closer, we select image samples from HOI benchmark dataset VCOCO [14] and HICO-det [2] as experimental materials. VCOCO consists of 24 action classes and 214 HOI classes, while HICO-det is larger and more challenging, covering 117 action classes and 600 HOI classes. We select 4,475 samples from the V-COCO training set (13 samples per HOI class on average) to train the attention prediction model. Additionally, we use 1,104 samples from the HICO-det test set and 720 samples from the V-COCO test set for testing the attention prediction model under ZeroIA and fully supervised interaction-oriented attention prediction tasks, respectively. + +# 3. Method + +# 3.1. Problem Definition + +Given a sample of HOI pair, the goal of zero-shot interaction-oriented human visual attention prediction (ZeroIA) is to generate an attention heatmap that reflects key visual cues for comprehending the interaction between human and object without any training for this interaction, as shown on the left of Figure 3. A complete HOI sample con + +sists of five components: an RGB image $x \in \mathbb{R}^{H \times W \times 3}$ , a bounding box of human $b^H$ , a bounding box of object $b^O$ , an object label $C_O$ , and an interaction label $C_I$ . The output of ZeroIA is expressed as a spatial attention heatmap $m_{IA} \in \mathbb{R}^{H \times W \times 1}$ . + +# 3.2. Interactive Attention + +Under goal-oriented cognitive tasks, humans tend to use their existing empirical knowledge and memory to model cognitive goals, and then progressively perceive and understand visual scenes with the goal. Inspired by the human cognitive process, we propose the Interactive Attention (IA) to tackle the ZeroIA problem, as shown in Figure 3. + +In IA, we first activate the strong knowledge representation capabilities of CLIP [48] through a clever interaction-oriented prompt block (PB). Secondly, we design two tiny and learnable adapters to model the HOI cognitive task. It generates scene-adaptive knowledge prototypes (KPs) for humans, objects, interactions, and robust visual features. Guided by these knowledge, we progressively perceive and understand the HOI scene. Specifically, we first perceive the human and object through a human-object cognitive block (HOCB), then delve deeper into understanding the interaction that occurs between the human and objects through an interaction cognitive block (ICB), and finally decode the interaction-oriented attention map. + +Interaction-oriented Prompt. Given an HOI sample, the interaction-oriented prompt block (PB) provides the visual-linguistic large model CLIP with clever inputs applicable to the HOI cognitive task to activate CLIP's powerful representation capabilities. Due to the natural composability of HOI, PB considers humans, objects, and interactions separately, i.e., constructing human-centric, object-centric, and interaction-centric prompts and extracting their textual representations, respectively. + +PB takes "person" and object textual label $C_O$ as inputs to CLIP text encoder and extracts the human- and object-centric textual representations, $T_H$ , and $T_O$ . The human and object texts are merged into the interaction-centric prompt, i.e., "a photo of a person $[C_I]$ $[C_O]$ " since they are closely related to the interaction. Then, the interaction-centric textual representation $T_I$ is extracted. Correspondingly, CLIP's image encoder is leveraged to extract robust visual features $V = [v_1, \dots, v_M]$ to take advantage of the semantic alignment between image and linguistics. + +Positional & Visual Adapter. The features extracted from CLIP based on PB are somewhat applicable to the cognitive goal, but this is a fixed holistic representation modeling of the goal, which lacks the ability to adapt to each specific HOI sample, especially to diverse spatial configurations and visual scenes. As a result, we design the tiny positional adapter and visual adapter to provide HOI sample-aware knowledge that enables better modeling of HOI cog + +![](images/cc3714cdd121b4522c9429eca4594470774158e6aeb950ad0c0079b89a2ac438.jpg) +Figure 3. The overall architecture of our Interactive Attention (IA). Inspired by the HOI cognitive process of human observers, IA is divided into three phases: empirical knowledge representation, cognitive goal modeling, and progressive understanding. First, a set of interaction-oriented prompts activate and leverage the robust knowledge representation capability of CLIP. Secondly, positional and visual adapters are introduced to acquire scene-adaptive human, object, and interaction Knowledge Prototypes (KPs) along with visual features of the HOI scene. Thirdly, guided by these KPs, IA progressively comprehends the scene, starting with an instance-level understanding of humans and objects and deepening insight into their interactions. The decoder generates predicted attention maps, supervised by the real attention maps of human observers using $L_{H2IA}$ . + +nitive tasks in each specific sample. + +Positional adapter (PA) provides sample-aware spatial information on textual representations: + +$$ +K _ {H} = M L P \left(\left[ \left(T _ {H}\right), F o u r i e r \left(b ^ {H}\right) \right]\right), \tag {1} +$$ + +$$ +K _ {O} = M L P \left(\left[ \left(T _ {O}\right), F o u r i e r \left(b ^ {O}\right) \right]\right), \tag {2} +$$ + +$$ +K _ {I} = M L P \left(\left[ \left(T _ {I}\right), F o u r i e r \left(C _ {H}\right), F o u r i e r \left(C _ {O}\right) \right]\right), \tag {3} +$$ + +where $K_{H}$ , $K_{O}$ , and $K_{I}$ represent adaptive knowledge prototypes of human, object, and interaction. Fourier is the Fourier embedding, MLP is a multi-layer perceptron, and [·] is the concatenate operation. Visual adapter (VA) is implemented as two Transformer encoder layers to transform $V$ into refined visual features $V' = [v_1', \dots, v_M']$ . + +Human-Object Cognitive Block. The HOI scene is further learned under the guidance of knowledge prototypes of human and object ( $K_{H}$ and $K_{O}$ ). The self-attention mechanism with gating is introduced to establish cognitive dependencies between knowledge prototypes and visual features, then the human-object-aware visual feature $V_{HO}$ is obtained: + +$$ +V _ {H O} = V ^ {\prime} + \text {G a t e} \left(\text {S e l f A t t n} \left(\left[ K _ {H}, K _ {O}, V ^ {\prime} \right]\right)\right), \tag {4} +$$ + +where $Gate(\cdot)$ is a token gating operation that considers visual tokens only, SelfAttn( $\cdot$ ) denotes a self-attention computation. + +Interaction Cognitive Block. Expanding upon the instance-level cognition, including the human and object, the model further delves into comprehending higher-level + +interactions that occur between the human and object. To achieve this, the cross-attention mechanism with gating is introduced to guide the learning of more subtle interaction cues by interaction knowledge prototype and obtaining the primary HOI-aware visual feature $V_{HOI}$ : + +$$ +V _ {H O I} = V _ {H O} + \operatorname {G a t e} \left(\operatorname {C r o s s A t t n} \left(V _ {H O}, K _ {I}\right)\right), \tag {5} +$$ + +where we denote $CrossAttn(q, kv)$ as a cross-attention operation. After that, the general self-attention operation is conducted on $V_{HOI}$ to obtain the full HOI-aware visual feature $V_{HOI}'$ : + +$$ +V _ {H O I} ^ {\prime} = V _ {H O I} + \text {S e l f A t t n} \left(V _ {H O I}\right). \tag {6} +$$ + +Interaction-oriented Attention Decoder. The goal of the decoder is to generate interaction-oriented attention heatmap $m_{IA} \in \mathbb{R}^{H \times W \times 1}$ , we first reshape the full interaction-aware visual feature, $V_{HOI}'$ , from a 2D shape of $\frac{HW}{p^2} \times C$ to a standard 3D feature map $\frac{H}{p} \times \frac{W}{p} \times C$ , $C$ is the feature channel size, $p$ is the image patch size. Then, we adopt tiny 2-layers of $1 \times 1$ convolution with batch norm and ReLU activation to reduce the feature dimension to $\frac{H}{p} \times \frac{W}{p} \times 1$ . Last, we adopt a bilinearly upsample operation to achieve the full image size $H \times W$ . + +Loss Function. We utilize the binary cross-entropy as a loss function for attention alignment, which can be expressed as follows: + +$$ +\operatorname {B C E} (p, y) = - \frac {1}{N} \sum_ {i = 1} ^ {N} \left(y _ {i} \cdot \log \left(p _ {i}\right) + \left(1 - y _ {i}\right) \cdot \log \left(1 - p _ {i}\right)\right), \tag {7} +$$ + +![](images/03f7c68b986320c4fce14dacc9fb46a09d455b8d66af369358e560971aa97932.jpg) +Figure 4. We incorporate aligned attention into the existing HOI model training pipeline, divided into two strategies: supervising by a limited amount of real attention from human observers and supervising by a large number of attention pseudo-labels generated by our proposed IA. + +$$ +L _ {H 2 I A} = \mathrm {B C E} \left(m _ {H}, m _ {I A}\right), \tag {8} +$$ + +where $p$ is the predictive probability, $y$ is the target, $N$ is the number of pixels in $m_{IA}$ , $m_H$ is human observer's real attention heatmap. + +# 3.3. Training HOI Models with Interaction-oriented Attention + +Here, we formulate the majority of recent state-of-the-art HOI models in the pipeline of CNN Backbone $\rightarrow$ Encoder $\rightarrow$ Decoder $\rightarrow$ Output Head. We enhance these HOI models by incorporating a supervision of interaction-oriented attention into the training process. This involves two strategies: supervising with a limited amount of real attention samples from human observers and supervising with a large number of pseudo-labeled attention samples from the IA model, as shown in Figure 4. + +For these HOI models, we first introduce a simple attention head to extract and reshape the averaged attention maps $m_{HOI}$ from the last layer of cross-attention computation in the decoder. The attention head is intentionally kept simple for a more direct back propagation of guidance to the representation. Subsequently, the corresponding human observer's attention heatmap $m_{H}$ and IA-generated pseudolabels $m_{IA}$ are scaled down to match the size of $m_{HOI}$ through adaptive 2D max-pooling. Finally, $m_{H}$ and $m_{IA}$ are used to supervise $m_{HOI}$ for two kinds of strategies, respectively. + +For the strategy of supervising by human observers, the attention alignment loss function $L_{H2HOI}$ and the overall HOI model's loss function $L$ can be expressed as + +$$ +L _ {H 2 H O I} = \mathrm {B C E} \left(m _ {H O I}, m _ {H}\right), \tag {9} +$$ + +$$ +L = \lambda_ {1} L _ {\text {r a w}} + \lambda_ {2} L _ {H 2 H O I}, \tag {10} +$$ + +where $L_{raw}$ represents the loss function of the original HOI model, which varies depending on the specific model, while $\lambda_1$ and $\lambda_2$ denote loss scaling factors. Similarly, for the strategy of supervising by IA, $L_{IA2HOI}$ and the overall loss function $L$ can be expressed as + +$$ +L _ {I A 2 H O I} = \mathrm {B C E} \left(m _ {H O I}, m _ {I A}\right), \tag {11} +$$ + +$$ +L = \lambda_ {1} L _ {\text {r a w}} + \lambda_ {2} L _ {I A 2 H O I}. \tag {12} +$$ + +# 4. Experiments + +# 4.1. Implementation Details + +Interactive Attention. We apply 2 versions of CLIP (ViT-B/16 and ViT-L/14) to build the IA models, resulting in IA-B and IA-L, respectively. The output dimension of Fourier embedding is 64. During training, we use AdamW as the optimizer with an initial learning rate of $1 \times 10^{-4}$ . The IA model is trained for 80 epochs with a learning rate reduction pre-20 epochs by a factor of 10. The momentum and the weight decay are set as 0.9 and $1 \times 10^{-4}$ . The experiments are conducted on four NVIDIA GeForce RTX 3090 GPUs with a batch size of 16. + +Training HOI Models with Attention Alignment. We apply our attention-guided training strategy on three typical state-of-the-art HOI methods: MUREN [29], representing the one-stage structure, and UPT [60] and STIP [62], representing the two-stage structure. In MUREN, we align the cross-attention map of the last layer in its interaction branch module with our interaction-oriented attention. In UPT, we first add two transformer decoder layers at the end of its interaction head, conducting cross-attention computation with global visual features, and align the cross-attention map of last layer. In STIP, we align the cross-attention map of the last layer in its structure-aware transformer module with our interaction-oriented attention. Due to variations in the raw losses of different methods, particularly for one-stage structure requiring additional supervision of object detection results, corresponding loss scaling factors differ. $\lambda_{1}$ and $\lambda_{2}$ are set to 1 and 10 in MUREN. $\lambda_{1}$ and $\lambda_{2}$ are set to 1 and 6 in UPT and STIP. Note that the IA model, responsible for generating interaction-oriented attention, is trained without exposure to samples from VCOCO test set and HICO-det test set, preventing any possibility of label leakage. + +# 4.2. Comparison methods & Metrics. + +We evaluate the performance of our IA model on interaction-oriented attention prediction, comparing it with 10 state-of-the-art methods: ITTI [22], GBVS [17], DeepGaze I [30], DeepGaze IIE [35], UMB [70], ConvNext [40], MLNet [6], SSwin Transformer [23], CLIP-ViT-B/16 [48], CLIP-ViT-L/14 [48]. Among these, ITTI and GBVS + +Table 2. Performance comparison on IG dataset. Bold and underline show the best and second-best performances. + +
MethodZerola SettingFully Supervised Setting
CC↑KLdiv↓SIM↑AUC↑CC↑KLdiv↓SIM↑AUC↑
ITTI [22]0.07844.35530.01420.49990.07543.18150.01170.5301
GBVS [17]0.02624.54950.02340.50000.17732.94980.02070.5037
DeepGaze I [30]0.18733.06630.00800.55700.19693.18690.00810.6143
DeepGaze IIE [35]0.20653.02550.00910.58140.17213.23570.00700.6049
UMB [70]0.21213.90040.59370.53260.20114.23380.61470.5319
MLNet [6]0.29373.89870.46460.59720.31953.68040.41530.5743
ConvNext [40]0.25714.87290.61100.54820.27314.51540.57470.5524
SSwin Transformer [23]0.24942.66540.33090.52120.29383.43090.33230.5391
CLIP-base [48]0.14033.61180.00580.35160.15643.87210.00740.3385
CLIP-large [48]0.16813.64980.00640.31830.16903.85470.00660.3356
IA CLIP-base0.40132.71140.72050.59530.48102.21320.75210.6375
IA CLIP-large0.44882.84090.71520.60680.51062.14090.77960.6386
+ +excel in early saliency prediction based on manual features, while the remaining methods are recent learning-based approaches. DeepGaze I and DeepGaze IIE utilize official pre-trained models for predictions, and UMB, ConvNext, MLNet, and SSwin Transformer are all trained with IG datasets. Additionally, we compute the similarity maps of two commonly used raw CLIP versions (CLIP-ViT-B/16 and CLIP-ViT-L/14). These similarity maps compute the similarity distance between image features and text features, serving as the raw CLIP's class attention maps [31]. + +We apply 4 metrics to measure performance: KL divergence (KLdiv), correlation coefficient (CC), similarity (SIM), and the area under the receiver operating characteristic curve (AUC). KLdiv, CC, and SIM are distribution-based metrics, while AUC is a localization-based metric. Except KLdiv, where lower values are preferable, higher values are desirable for all other metrics. + +# 4.3.Quantitative Comparison. + +Table 2 presents the quantitative comparison results in the ZeroIA and the fully supervised settings. We can observe that both versions of our model IA outperform all 10 baselines in both metrics. In particular, for CC metric, IA w/ CLIP-L outperforms the third-best MLNet by $52.8\%$ and $59.8\%$ on the ZeroIA and the fully supervised settings, respectively. + +Moreover, we observe that the manual feature-based ITTI and GBVS approaches fail in the interaction-oriented attention prediction task, which demands higher cognitive capabilities. Additionally, when comparing IA with the similarity map of raw CLIP output, our IA achieves significant improvements across all metrics. For example, IA w/ CLIP-B exceeds raw CLIP-B by $186\%$ under CC metric of the ZeroIA setting. This suggests that our model effectively activates and utilizes CLIP's knowledge representation capabilities, adapting them to cognitive tasks on interaction. + +# 4.4. Qualitative Analyses. + +As shown in Figures 5 and 6, the visualizations of interaction-oriented attention prediction under ZeroIA and + +Table 3. Performance comparison of each module in IA. + +
MethodZeroIA SettingFully Supervised Setting
CC↑KLdiv↓SIM↑AUC↑CC↑KLdiv↓SIM↑AUC↑
w/o PA0.36523.21150.67330.58020.39612.46760.68640.6023
w/o VA0.38382.98010.67540.58320.40812.43460.68930.6182
w/o HOCB0.34983.31230.64210.57430.36972.56890.64840.6034
w/o ICB0.32493.65410.58450.56440.34452.85330.60230.5934
IA0.40132.71140.72050.59530.48102.21320.75210.6375
+ +fully supervised settings, respectively. Notably, across both settings, IA exhibits attention distributions that are consistently closer to human observers, outperforming the remaining eight methods. + +Compared with SOTA models. The previous untrained instance-centric models (columns 6-7) only capture coarse-grained salient persons and objects, but not interaction-related cues. Methods trained on IG prove limited in the complex multi-instance "push" scenario (Figure 5, row 4) under the ZeroIA setting and also in the "talk on" scenario (Figure 6, row 3) with a limited number of training samples. + +Compared with raw CLIP, IA accurately captures key visual cues, particularly for unseen categories such as "repair", "kiss", "lick", "push", and "sign" in Figure 5. Noteworthy is the comparison with columns 5-6, where the similarity maps generated by raw CLIP lack interpretability, displaying properties such as opposite visualization and noisy activation, as highlighted in recent work [31, 32]. These observations, along with quantitative results in Table 2, underscore the fact that our work effectively activates CLIP's powerful knowledge representation capabilities and improves interpretability. + +# 4.5. Ablation Study + +To examine the impact of each module in IA, we conduct an ablation study by removing modules in Table 3. Specifically, we sequentially exclude the positional adapter (PA), visual adapter (VA), human-object cognitive block (HOCB), and interaction cognitive block (ICB). All ablated models are variations of IA w/ CLIP-B. Results indicate consistent performance degradation across both ZeroIA and fully supervised settings upon removal of any module. Notably, the most significant degradation occurs when the ICB is omitted, emphasizing its crucial role in guiding the learning of interaction-oriented attention by injecting the interaction knowledge. Subsequently, the HOCB, enriched with information about the subjects and objects involved in the interaction, the PA, which incorporates spatial configuration, and the VA, receiving refined visual features, contribute to the model's performance in descending order from high to low. + +# 4.6. Effectiveness of Attention Training Strategy + +Aligning human attention enhances HOI model accuracy. We leverage the VCOCO training subset within + +![](images/8f846bffa0e105a5480d6e080c260fa7418e92378b6c39851a63860ec62a433f.jpg) +Figure 5. Qualitative comparison of interaction-oriented attention prediction under the ZeroIA setting. + +![](images/5b89d75baa7eff3b891ea064db747e2260031aa942cd902665a268536d05223a.jpg) +Figure 6. Qualitative comparison of interaction-oriented attention prediction under the fully supervised setting. + +the proposed IG, comprising 4,475 samples, approximately $32.4\%$ of the complete VCOCO training set, as the attention ground truth for additional supervision of existing HOI models. As shown in Table 4, MUREN, UPT, and STIP are improved by $0.6\mathrm{mAP}$ , $0.8\mathrm{mAP}$ , and $0.4\mathrm{mAP}$ , respectively, under the Scenario1 setting. Similarly, under the Scenario2 setting, MUREN, UPT, and STIP are enhanced by $0.7\mathrm{mAP}$ , $1.3\mathrm{mAP}$ , and $0.4\mathrm{mAP}$ , respectively. This highlight the significant potential of aligned human attention in enhancing action comprehension, even with limited training data. + +Aligning IA-generated attention enhances HOI model accuracy more significantly. We further enhance the additional supervision of HOI models through large-scale interaction-oriented pseudo-labeling, generated by the proposed IA model on the training sets of VCOCO and HICO-det, respectively. In Table 4, on the VCOCO dataset, + +our training strategies consistently obtain performance improvements for MUREN, UPT, and STIP. In particular, thanks to the precise emulation of human attention by our proposed IA model, the results of all HOI models reveal that training by a large number of pseudo-attention labels is superior to using limited genuine human attention. On HICO-det dataset, our training strategy similarly achieves consistent performance gains in Table 5. Particularly, we observe that our training strategy significantly enhances the performance of the rare set, by $6.0\%$ , $4.0\%$ , and $2.7\%$ on MUREN, UPT, and STIP, respectively. Note that the reported experimental results are all obtained by reproducing these models under the same experimental settings. + +Aligning attention makes HOI models more interpretable. We present visualizations of the cross-attention maps of interaction branches in original MUREN and the + +Table 4. Comparison of HOI detection performance on VCOCO. + +
MethodBackboneScenario #1Scenario #2
One-stage methods
UnionDet [26]ResNet-50-FPN47.556.2
IP-Net [54]Hourglass-10451.0-
GG-Net [33]Hourglass-10454.7-
HOTR [27]ResNet-5055.264.4
QPIC [52]ResNet-10158.360.7
MUREN [29]ResNet-5066.969.0
MUREN w/ HumanResNet-5067.569.7
MUREN w/ IA-BResNet-5067.770.3
MUREN w/ IA-LResNet-5068.070.4
Two-stage methods
VCL [19]ResNet-5048.3-
SCG [59]ResNet-50-FPN54.2-
UPT [60]ResNet-5059.865.5
STIP [62]ResNet-5066.070.7
UPT w/ HumanResNet-5060.766.4
UPT w/ IA-BResNet-5061.166.8
UPT w/ IA-LResNet-5061.467.0
STIP w/ HumanResNet-5066.471.1
STIP w/ IA-BResNet-5067.071.3
STIP w/ IA-LResNet-5067.271.4
+ +Table 5. Comparison of HOI detection performance on HICO-det. + +
MethodBackboneFullRareNon-rare
One-stage methods
UnionDet [26]ResNet-50-FPN17.5811.7219.33
IP-Net [54]Hourglass-10419.5612.7921.58
PPDM [33]Hourglass-10421.7313.7821.40
GG-Net [63]Hourglass-10423.4716.4825.60
HOTR [27]ResNet-5025.1017.3427.42
QPIC [52]ResNet-10129.9023.9231.69
MSTR [28]ResNet-5031.1725.3132.92
MUREN [29]ResNet-5032.0927.3633.50
MUREN w/ IA-BResNet-5032.4528.9033.51
MUREN w/ IA-LResNet-5032.4829.0133.53
Two-stage methods
VCL [19]ResNet-5023.6317.2125.55
ATL [20]ResNet-5023.6717.6425.47
SCG [59]ResNet-50-FPN29.2624.6130.65
UPT [60]ResNet-5031.9326.7033.49
STIP [62]ResNet-5032.2228.1533.43
UPT w/ IA-BResNet-5032.2027.5933.58
UPT w/ IA-LResNet-5032.4727.7633.72
STIP w/ IA-BResNet-5032.3228.4733.59
STIP w/ IA-LResNet-5032.6428.9033.76
+ +MUREN aligned with interaction-oriented attention, respectively, as shown in Figure 7. It is evident that the attention map of original MUREN appears fragmented and struggles to focus on interaction-related visual cues, leading to failures in interaction recognition. Conversely, after aligning with interaction-oriented attention, not only are the erroneous results corrected, but the attention map becomes significantly more interpretable and focuses on key regions. + +# 5. Conclusion + +This paper aims to address a critical gap in interaction-oriented attention by introducing the challenging yet meaningful ZeroIA problem. To achieve this, we collect the IG dataset, marking the first large-scale interaction-centric gaze fixation dataset, featuring 530,000 fixation points across 740 diverse interaction categories. Subsequently, we + +![](images/5192f6356bd6ebd9da82d9c23c4cc44d7eda18f75341a3a1cd2cdb2e5ef5fe56.jpg) +Figure 7. The predicted results and corresponding attention visualizations for MUREN and our (MUREN w/ IA-L, MUREN w/ Human). We mark true positive results in green, and false positive results in red. After aligning interaction-oriented attention, the erroneous prediction results are corrected, and the corresponding attention becomes more converged and more interpretable. More in supplementary materials. + +present the IA model, ingeniously designed to activate and leverage the knowledge representation capabilities of CLIP, emulating the cognitive processes of human observers to generate high-quality interaction-oriented attention. Extensive experiments demonstrate that the proposed IA model outperforms state-of-the-art attention prediction methods in both zero-shot and fully supervised settings. Furthermore, we propose an attention-guided HOI training strategy, leveraging interaction-oriented attention to guide existing HOI models for more effective learning. Quantitative and qualitative results demonstrate that both genuine human attention and IA-generated attention significantly enhance the performance and interpretability of existing HOI models, making them more capable of visual reasoning like human observers. This highlights the significant potential of visual attention in action comprehension. + +Our endeavor represents the pioneering effort to establish a bi-directional connection between visual attention and HOI detection, starting by directing visual attention through the interaction comprehension task and ending by incorporating this attention to repay existing HOI methods. We believe our work can inspire further research on goal-oriented attention and its application in various action-related tasks like classification, VQA, and captioning. Our work also has potential applications in DNNs' interpretability evaluation, human-AI collaboration, and values alignment research. + +Acknowledgements. 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However, the more complex interaction-oriented attention, arising from the comprehension of interactions between instances by human observers, remains largely unexplored. This is equally crucial for advancing human-machine interaction and human-centered artificial intelligence. To bridge this gap, we first collect a novel gaze fixation dataset named IG, comprising 530,000 fixation points across 740 diverse interaction categories, capturing visual attention during human observers' cognitive processes of interactions. Subsequently, we introduce the zero-shot interaction-oriented attention prediction task (ZeroIA), which challenges models to predict visual cues for interactions not encountered during training. Thirdly, we present the Interactive Attention model (IA), designed to emulate human observers' cognitive processes to tackle the ZeroIA problem. Extensive experiments demonstrate that the proposed IA outperforms other state-of-the-art approaches in both ZeroIA and fully supervised settings. Lastly, we endeavor to apply interaction-oriented attention to the interaction recognition task itself. Further experimental results demonstrate the promising potential to enhance the performance and interpretability of existing state-of-the-art HOI models by incorporating real human attention data from IG and attention labels generated by IA." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 604, + 128, + 616 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 604, + 128, + 616 + ], + "spans": [ + { + "bbox": [ + 47, + 604, + 128, + 616 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 623, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 623, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 623, + 287, + 696 + ], + "type": "text", + "content": "Human visual attention reveals a wealth of information about internal cognitive states, including bottom-up visual stimulation and top-down goal-directed empirical knowledge [10,47,61]. Predicting visual attention provides a valuable understanding of how humans perceive, comprehend, and interact with the world, especially within the context" + } + ] + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 307, + 258, + 419, + 300 + ], + "blocks": [ + { + "bbox": [ + 315, + 247, + 408, + 256 + ], + "lines": [ + { + "bbox": [ + 315, + 247, + 408, + 256 + ], + "spans": [ + { + "bbox": [ + 315, + 247, + 408, + 256 + ], + "type": "text", + "content": "Instance-centric Attention Prediction" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 307, + 258, + 419, + 300 + ], + "lines": [ + { + "bbox": [ + 307, + 258, + 419, + 300 + ], + "spans": [ + { + "bbox": [ + 307, + 258, + 419, + 300 + ], + "type": "image", + "image_path": "b66ca2a13b790cdf91eead34e231be8c2ba2a4546b38f97b77dafe679ed8154c.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 318, + 300, + 351, + 306 + ], + "lines": [ + { + "bbox": [ + 318, + 300, + 351, + 306 + ], + "spans": [ + { + "bbox": [ + 318, + 300, + 351, + 306 + ], + "type": "text", + "content": "person, donut" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 371, + 300, + 407, + 306 + ], + "lines": [ + { + "bbox": [ + 371, + 300, + 407, + 306 + ], + "spans": [ + { + "bbox": [ + 371, + 300, + 407, + 306 + ], + "type": "text", + "content": "person, banana" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 307, + 306, + 419, + 349 + ], + "blocks": [ + { + "bbox": [ + 307, + 306, + 419, + 349 + ], + "lines": [ + { + "bbox": [ + 307, + 306, + 419, + 349 + ], + "spans": [ + { + "bbox": [ + 307, + 306, + 419, + 349 + ], + "type": "image", + "image_path": "06361b28ccd3e4d73d8ce7ceb4406bb9ec880346f6288eac84efd090607c2886.jpg" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 318, + 349, + 350, + 354 + ], + "lines": [ + { + "bbox": [ + 318, + 349, + 350, + 354 + ], + "spans": [ + { + "bbox": [ + 318, + 349, + 350, + 354 + ], + "type": "text", + "content": "person,horse" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 374, + 349, + 406, + 354 + ], + "lines": [ + { + "bbox": [ + 374, + 349, + 406, + 354 + ], + "spans": [ + { + "bbox": [ + 374, + 349, + 406, + 354 + ], + "type": "text", + "content": "person, sheep" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + } + ], + "index": 17 + }, + { + "type": "image", + "bbox": [ + 307, + 355, + 419, + 397 + ], + "blocks": [ + { + "bbox": [ + 307, + 355, + 419, + 397 + ], + "lines": [ + { + "bbox": [ + 307, + 355, + 419, + 397 + ], + "spans": [ + { + "bbox": [ + 307, + 355, + 419, + 397 + ], + "type": "image", + "image_path": "7f437ab54e846064c37010518f9f2e5f5539fc31f7eebca2d30e69cbce07caca.jpg" + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 321, + 398, + 347, + 403 + ], + "lines": [ + { + "bbox": [ + 321, + 398, + 347, + 403 + ], + "spans": [ + { + "bbox": [ + 321, + 398, + 347, + 403 + ], + "type": "text", + "content": "person, car" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 375, + 398, + 405, + 403 + ], + "lines": [ + { + "bbox": [ + 375, + 398, + 405, + 403 + ], + "spans": [ + { + "bbox": [ + 375, + 398, + 405, + 403 + ], + "type": "text", + "content": "person, book" + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 416, + 547, + 505 + ], + "lines": [ + { + "bbox": [ + 304, + 416, + 547, + 505 + ], + "spans": [ + { + "bbox": [ + 304, + 416, + 547, + 505 + ], + "type": "text", + "content": "Figure 1. Previous attention prediction models have traditionally focused on the instance-level, primarily emphasizing foreground humans and objects. In contrast, our proposed interaction-oriented attention aims to capture subtler and more fine-grained visual cues associated with actions, such as body parts (row 1), human-object contact (row 2), and scene context (row 3). This proposition challenges the research community with a more intricate and cognitively demanding task." + } + ] + } + ], + "index": 36, + "angle": 0, + "type": "image_caption" + } + ], + "index": 20 + }, + { + "type": "image", + "bbox": [ + 425, + 258, + 480, + 300 + ], + "blocks": [ + { + "bbox": [ + 423, + 247, + 541, + 256 + ], + "lines": [ + { + "bbox": [ + 423, + 247, + 541, + 256 + ], + "spans": [ + { + "bbox": [ + 423, + 247, + 541, + 256 + ], + "type": "text", + "content": "Our Interaction-oriented Attention Prediction" + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 425, + 258, + 480, + 300 + ], + "lines": [ + { + "bbox": [ + 425, + 258, + 480, + 300 + ], + "spans": [ + { + "bbox": [ + 425, + 258, + 480, + 300 + ], + "type": "image", + "image_path": "ee8ec1ed5753c32d8b391e519e155e008f2a5c82fd0ebe420e8c845dccddb745.jpg" + } + ] + } + ], + "index": 24, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 426, + 300, + 478, 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545, + 591 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 531, + 545, + 591 + ], + "spans": [ + { + "bbox": [ + 304, + 531, + 545, + 591 + ], + "type": "text", + "content": "of goal-directed attention [3-5, 39, 46, 50]. This holds profound implications for enhancing human-computer interaction [11, 25, 49], and contributing to fields such as assistance for visual impaired [15, 16], education [1, 51], and autonomous driving [13, 21, 43, 65]." + } + ] + } + ], + "index": 37 + }, + { + "bbox": [ + 304, + 594, + 546, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 546, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 546, + 714 + ], + "type": "text", + "content": "Goal-oriented attention prediction studies have made some progress recently [8, 12, 24, 37, 42, 55-57], mostly focusing on predicting gaze fixation when searching or recognizing objects with relative explicit and invariant visual cues. However, interactions [27, 38, 68, 69, 71], another fundamental component of visual understanding that encapsulates how humans and objects interact with each other, remain largely unexplored. Interactions pose greater cognitive challenges than objects, due to their diverse and subtle visual cues, as shown in Figure 1. Consequently, predicting" + } + ] + } + ], + "index": 38 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 1, + 494, + 15 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 1, + 494, + 15 + ], + "spans": [ + { + "bbox": [ + 145, + 1, + 494, + 15 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 199, + 13, + 442, + 24 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 199, + 13, + 442, + 24 + ], + "spans": [ + { + "bbox": [ + 199, + 13, + 442, + 24 + ], + "type": "text", + "content": "Except for this watermark, it is identical to the accepted version;" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 179, + 25, + 462, + 36 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 179, + 25, + 462, + 36 + ], + "spans": [ + { + "bbox": [ + 179, + 25, + 462, + 36 + ], + "type": "text", + "content": "the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "type": "text", + "content": "*Corresponding author." + } + ] + } + ], + "index": 39 + }, + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 732, + 318, + 742 + ], + "type": "text", + "content": "28390" + } + ] + } + ], + "index": 40 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 144 + ], + "type": "text", + "content": "interaction-oriented visual attention proves to be a more demanding task compared to previous efforts. Moreover, the inherent diversity and almost infinite granularity of actions intersect with limited available data, necessitating the adoption of zero-shot learning. We name this problem Zero-shot Interaction-oriented Attention prediction (ZeroIA)." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 145, + 287, + 229 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 145, + 287, + 229 + ], + "spans": [ + { + "bbox": [ + 46, + 145, + 287, + 229 + ], + "type": "text", + "content": "On the other hand, in the domain of human-object interaction (HOI) detection [29, 29, 34, 53, 60, 62, 64, 66, 67], current state-of-the-art methods also face limitations in the interaction comprehension phase, even though they demonstrate proficiency in handling the object detection phase. This limitation is rooted in the inherent difficulty of capturing visual cues related to actions." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 232, + 287, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 232, + 287, + 397 + ], + "spans": [ + { + "bbox": [ + 46, + 232, + 287, + 397 + ], + "type": "text", + "content": "To alleviate these problems, we first introduce Interactive-Gaze (IG), a novel dataset of gaze fixations capturing human cognitive process of interactions, filling a crucial gap in interaction-oriented visual attention research. IG contains 530,000 fixation points from 32 human observers, spanning 740 interaction categories, 80 objects, and 132 actions. Human observers are invited to capture key visual cues in various interaction scenes, while their visual attention during the cognitive process is recorded. All interaction scenes are selected from HOI benchmark datasets, HICO-det [2] and VCOCO [14]. This means that IG has the potential to bridge the fields of visual attention and HOI detection and be a catalyst for advancing both research areas simultaneously." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 401, + 286, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 401, + 286, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 401, + 286, + 604 + ], + "type": "text", + "content": "Secondly, inspired by the cognitive processes of human observers, we further propose a goal-oriented attention prediction approach, termed Interactive Attention (IA). Our approach begins by a set of clever interaction-oriented prompts and adapters to activate and leverage CLIP's powerful knowledge representation capabilities [48], thereby facilitating zero-shot learning. This process involves establishing adaptive knowledge prototypes based on each visual scene, avoiding direct retrieval of fixed knowledge from CLIP, which may exhibit strong noun bias [18,41,45]. Guided by these knowledge, IA first focuses on the perception and understanding of individual instances, i.e., humans and objects. Then, it further understands the interactions unfolding between instances, ultimately completing the generation of interaction-oriented attention. Extensive experiments demonstrate that IA outperforms state-of-the-art approaches in both ZeroIA and fully supervised settings." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 605, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 286, + 713 + ], + "type": "text", + "content": "Furthermore, we explore how goal-oriented attention can be fed back to the goal itself, particularly establishing an initial bidirectional pathway connecting goal-oriented attention and action understanding. We introduce a general and effective HOI training strategy. This can supplement most state-of-the-art model loss with additional supervision for interaction-oriented attention. Remarkably, extensive experiments reveal the substantial potential of visual attention for HOI models from two aspects. (1) Aligning a lim" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 167 + ], + "type": "text", + "content": "ited yet valuable genuine human interaction-oriented attention from the proposed IG enhances the performance and interpretability of existing state-of-the-art HOI models. (2) Integrating interaction-oriented attention generated by the proposed IA model further enhances HOI models, surpassing even the performance achieved in the context of human observers' attention. To summarize, the contributions of our work are three-fold:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 317, + 177, + 545, + 431 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 317, + 177, + 545, + 273 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 177, + 545, + 273 + ], + "spans": [ + { + "bbox": [ + 317, + 177, + 545, + 273 + ], + "type": "text", + "content": "- Firstly, we address a crucial gap in interaction-oriented attention studies by introducing the ZeroIA problem and IG dataset, marking a pioneering endeavor as the inaugural gaze fixation dataset specifically designed for interaction analysis. Given the composite nature of IG, it has significant potential to facilitate the intersection of multiple domains, such as goal-directed attention and interaction comprehension." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 317, + 281, + 545, + 353 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 281, + 545, + 353 + ], + "spans": [ + { + "bbox": [ + 317, + 281, + 545, + 353 + ], + "type": "text", + "content": "- Secondly, we present the IA model, a novel approach crafted to emulate human cognitive processes for predicting high-quality interaction-oriented attention. Extensive experiments demonstrate IA outperforms other state-of-the-art attention prediction methods in both the ZeroIA and fully-supervised settings." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 317, + 360, + 545, + 431 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 360, + 545, + 431 + ], + "spans": [ + { + "bbox": [ + 317, + 360, + 545, + 431 + ], + "type": "text", + "content": "- Thirdly, we introduce a general and simple HOI training strategy with attention and demonstrate that both aligning a small yet precious genuine human attention from IG and aligning attention generated by IA can enhance the performance and interpretability of existing state-of-the-art HOI models." + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 442, + 471, + 455 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 442, + 471, + 455 + ], + "spans": [ + { + "bbox": [ + 306, + 442, + 471, + 455 + ], + "type": "text", + "content": "2. Interactive Gaze (IG) Dataset" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 462, + 545, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 462, + 545, + 629 + ], + "spans": [ + { + "bbox": [ + 304, + 462, + 545, + 629 + ], + "type": "text", + "content": "To study human visual attention oriented by HOI, we collect the Interactive Gaze (IG), the first large-scale interaction-centric gaze fixation dataset, as shown in Figure 2. IG comprises 6,299 interaction scenarios across 740 interaction categories, 80 object categories, and 132 action categories. IG captures the visual attention of 32 human observers during the cognition of these interaction scenarios, resulting in 530,000 corresponding fixation points. IG holds substantial potential to bridge the domains of visual attention and action understanding, serving as a catalyst to jointly promote these two areas of study. We use mouse clicks to simulate gaze fixation for visual attention studies [8,24,36,37], and more details about the IG dataset are presented in the supplementary materials." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "content": "Dataset Comparison. Previous gaze fixation datasets have primarily concentrated on instances (e.g., objects, humans, animals, texts) as targets for recognition, search, and free-viewing, as illustrated in Table 1. In contrast, IG stands as the pioneering interaction-centric gaze fixation dataset. Given the inherent diversity, composability, and context dependency of interactions, interaction-oriented attention is" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 732, + 317, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 732, + 317, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 732, + 317, + 742 + ], + "type": "text", + "content": "28391" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 70, + 273, + 205 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 273, + 205 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 273, + 205 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 273, + 205 + ], + "type": "image", + "image_path": "8dd5e30534b75da00586680a29a3bb1682ae2fecfc2d424aab9c033bf60ddf45.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 214, + 287, + 247 + ], + "lines": [ + { + "bbox": [ + 46, + 214, + 287, + 247 + ], + "spans": [ + { + "bbox": [ + 46, + 214, + 287, + 247 + ], + "type": "text", + "content": "Figure 2. Our proposed IG is the first interaction-centric gaze fixation dataset, comprising 530K fixation points across 740 interaction categories." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 55, + 291, + 277, + 388 + ], + "blocks": [ + { + "bbox": [ + 47, + 261, + 286, + 282 + ], + "lines": [ + { + "bbox": [ + 47, + 261, + 286, + 282 + ], + "spans": [ + { + "bbox": [ + 47, + 261, + 286, + 282 + ], + "type": "text", + "content": "Table 1. Comparison of fixation datasets. Previous work all focus on instances of objects, humans, animals, texts, etc." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 55, + 291, + 277, + 388 + ], + "lines": [ + { + "bbox": [ + 55, + 291, + 277, + 388 + ], + "spans": [ + { + "bbox": [ + 55, + 291, + 277, + 388 + ], + "type": "table", + "html": "
DatasetFocusSceneClassFixation
SALICON [24]Object10000-4600K
POET [44]Object627010178K
People900 [7]Human912155K
MCS [58]Object2183216K
PET [9]Animal4135630K
COCO-Search18 [55]Object620218300K
SalECI [23]Object & Text97213257K
Our (IG)Action6299740530K
", + "image_path": "b68c73c519faed7370cba59dec9b4bd2bdf8b7e6a97273f339131deab34beb70.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 411, + 286, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 411, + 286, + 434 + ], + "spans": [ + { + "bbox": [ + 46, + 411, + 286, + 434 + ], + "type": "text", + "content": "associated with elevated cognitive challenges and empirical knowledge." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 435, + 286, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 435, + 286, + 590 + ], + "spans": [ + { + "bbox": [ + 46, + 435, + 286, + 590 + ], + "type": "text", + "content": "Data Selection & Subsetting. To bring the visual attention and HOI detection domains closer, we select image samples from HOI benchmark dataset VCOCO [14] and HICO-det [2] as experimental materials. VCOCO consists of 24 action classes and 214 HOI classes, while HICO-det is larger and more challenging, covering 117 action classes and 600 HOI classes. We select 4,475 samples from the V-COCO training set (13 samples per HOI class on average) to train the attention prediction model. Additionally, we use 1,104 samples from the HICO-det test set and 720 samples from the V-COCO test set for testing the attention prediction model under ZeroIA and fully supervised interaction-oriented attention prediction tasks, respectively." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 602, + 102, + 615 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 602, + 102, + 615 + ], + "spans": [ + { + "bbox": [ + 47, + 602, + 102, + 615 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 622, + 159, + 634 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 622, + 159, + 634 + ], + "spans": [ + { + "bbox": [ + 47, + 622, + 159, + 634 + ], + "type": "text", + "content": "3.1. Problem Definition" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 641, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 286, + 712 + ], + "type": "text", + "content": "Given a sample of HOI pair, the goal of zero-shot interaction-oriented human visual attention prediction (ZeroIA) is to generate an attention heatmap that reflects key visual cues for comprehending the interaction between human and object without any training for this interaction, as shown on the left of Figure 3. A complete HOI sample con" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "spans": [ + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "text", + "content": "sists of five components: an RGB image " + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "inline_equation", + "content": "x \\in \\mathbb{R}^{H \\times W \\times 3}" + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "text", + "content": ", a bounding box of human " + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "inline_equation", + "content": "b^H" + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "text", + "content": ", a bounding box of object " + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "inline_equation", + "content": "b^O" + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "text", + "content": ", an object label " + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "inline_equation", + "content": "C_O" + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "text", + "content": ", and an interaction label " + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "inline_equation", + "content": "C_I" + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "text", + "content": ". The output of ZeroIA is expressed as a spatial attention heatmap " + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "inline_equation", + "content": "m_{IA} \\in \\mathbb{R}^{H \\times W \\times 1}" + }, + { + "bbox": [ + 304, + 71, + 545, + 131 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 141, + 426, + 152 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 141, + 426, + 152 + ], + "spans": [ + { + "bbox": [ + 306, + 141, + 426, + 152 + ], + "type": "text", + "content": "3.2. Interactive Attention" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 160, + 545, + 232 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 160, + 545, + 232 + ], + "spans": [ + { + "bbox": [ + 304, + 160, + 545, + 232 + ], + "type": "text", + "content": "Under goal-oriented cognitive tasks, humans tend to use their existing empirical knowledge and memory to model cognitive goals, and then progressively perceive and understand visual scenes with the goal. Inspired by the human cognitive process, we propose the Interactive Attention (IA) to tackle the ZeroIA problem, as shown in Figure 3." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 233, + 545, + 388 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 233, + 545, + 388 + ], + "spans": [ + { + "bbox": [ + 304, + 233, + 545, + 388 + ], + "type": "text", + "content": "In IA, we first activate the strong knowledge representation capabilities of CLIP [48] through a clever interaction-oriented prompt block (PB). Secondly, we design two tiny and learnable adapters to model the HOI cognitive task. It generates scene-adaptive knowledge prototypes (KPs) for humans, objects, interactions, and robust visual features. Guided by these knowledge, we progressively perceive and understand the HOI scene. Specifically, we first perceive the human and object through a human-object cognitive block (HOCB), then delve deeper into understanding the interaction that occurs between the human and objects through an interaction cognitive block (ICB), and finally decode the interaction-oriented attention map." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 389, + 545, + 497 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 389, + 545, + 497 + ], + "spans": [ + { + "bbox": [ + 304, + 389, + 545, + 497 + ], + "type": "text", + "content": "Interaction-oriented Prompt. Given an HOI sample, the interaction-oriented prompt block (PB) provides the visual-linguistic large model CLIP with clever inputs applicable to the HOI cognitive task to activate CLIP's powerful representation capabilities. Due to the natural composability of HOI, PB considers humans, objects, and interactions separately, i.e., constructing human-centric, object-centric, and interaction-centric prompts and extracting their textual representations, respectively." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "text", + "content": "PB takes \"person\" and object textual label " + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "inline_equation", + "content": "C_O" + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "text", + "content": " as inputs to CLIP text encoder and extracts the human- and object-centric textual representations, " + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "inline_equation", + "content": "T_H" + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "inline_equation", + "content": "T_O" + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "text", + "content": ". The human and object texts are merged into the interaction-centric prompt, i.e., \"a photo of a person " + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "inline_equation", + "content": "[C_I]" + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "inline_equation", + "content": "[C_O]" + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "text", + "content": "\" since they are closely related to the interaction. Then, the interaction-centric textual representation " + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "inline_equation", + "content": "T_I" + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "text", + "content": " is extracted. Correspondingly, CLIP's image encoder is leveraged to extract robust visual features " + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "inline_equation", + "content": "V = [v_1, \\dots, v_M]" + }, + { + "bbox": [ + 304, + 498, + 545, + 616 + ], + "type": "text", + "content": " to take advantage of the semantic alignment between image and linguistics." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "content": "Positional & Visual Adapter. The features extracted from CLIP based on PB are somewhat applicable to the cognitive goal, but this is a fixed holistic representation modeling of the goal, which lacks the ability to adapt to each specific HOI sample, especially to diverse spatial configurations and visual scenes. As a result, we design the tiny positional adapter and visual adapter to provide HOI sample-aware knowledge that enables better modeling of HOI cog" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "text", + "content": "28392" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 52, + 74, + 545, + 242 + ], + "blocks": [ + { + "bbox": [ + 52, + 74, + 545, + 242 + ], + "lines": [ + { + "bbox": [ + 52, + 74, + 545, + 242 + ], + "spans": [ + { + "bbox": [ + 52, + 74, + 545, + 242 + ], + "type": "image", + "image_path": "cc3714cdd121b4522c9429eca4594470774158e6aeb950ad0c0079b89a2ac438.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 251, + 547, + 329 + ], + "lines": [ + { + "bbox": [ + 46, + 251, + 547, + 329 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 547, + 329 + ], + "type": "text", + "content": "Figure 3. The overall architecture of our Interactive Attention (IA). Inspired by the HOI cognitive process of human observers, IA is divided into three phases: empirical knowledge representation, cognitive goal modeling, and progressive understanding. First, a set of interaction-oriented prompts activate and leverage the robust knowledge representation capability of CLIP. Secondly, positional and visual adapters are introduced to acquire scene-adaptive human, object, and interaction Knowledge Prototypes (KPs) along with visual features of the HOI scene. Thirdly, guided by these KPs, IA progressively comprehends the scene, starting with an instance-level understanding of humans and objects and deepening insight into their interactions. The decoder generates predicted attention maps, supervised by the real attention maps of human observers using " + }, + { + "bbox": [ + 46, + 251, + 547, + 329 + ], + "type": "inline_equation", + "content": "L_{H2IA}" + }, + { + "bbox": [ + 46, + 251, + 547, + 329 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 349, + 192, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 349, + 192, + 361 + ], + "spans": [ + { + "bbox": [ + 47, + 349, + 192, + 361 + ], + "type": "text", + "content": "nitive tasks in each specific sample." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 361, + 287, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 361, + 287, + 384 + ], + "spans": [ + { + "bbox": [ + 47, + 361, + 287, + 384 + ], + "type": "text", + "content": "Positional adapter (PA) provides sample-aware spatial information on textual representations:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 89, + 394, + 287, + 408 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 89, + 394, + 287, + 408 + ], + "spans": [ + { + "bbox": [ + 89, + 394, + 287, + 408 + ], + "type": "interline_equation", + "content": "K _ {H} = M L P \\left(\\left[ \\left(T _ {H}\\right), F o u r i e r \\left(b ^ {H}\\right) \\right]\\right), \\tag {1}", + "image_path": "9c91b198550bdbfcd2262f20b2abbd2e9e491aa1bea036120b6e1041bd0da51b.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 91, + 416, + 287, + 430 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 91, + 416, + 287, + 430 + ], + "spans": [ + { + "bbox": [ + 91, + 416, + 287, + 430 + ], + "type": "interline_equation", + "content": "K _ {O} = M L P \\left(\\left[ \\left(T _ {O}\\right), F o u r i e r \\left(b ^ {O}\\right) \\right]\\right), \\tag {2}", + "image_path": "b64d3e3afd5122115f5ad45db8c234ee37e88ffb5e15e20aec774886075ef83e.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 54, + 435, + 287, + 449 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 54, + 435, + 287, + 449 + ], + "spans": [ + { + "bbox": [ + 54, + 435, + 287, + 449 + ], + "type": "interline_equation", + "content": "K _ {I} = M L P \\left(\\left[ \\left(T _ {I}\\right), F o u r i e r \\left(C _ {H}\\right), F o u r i e r \\left(C _ {O}\\right) \\right]\\right), \\tag {3}", + "image_path": "8ed31cffcecc799342beda686777d3ce97577e5fbdc3eaca57d4ada05e601fa3.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "spans": [ + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "inline_equation", + "content": "K_{H}" + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "inline_equation", + "content": "K_{O}" + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "inline_equation", + "content": "K_{I}" + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "text", + "content": " represent adaptive knowledge prototypes of human, object, and interaction. Fourier is the Fourier embedding, MLP is a multi-layer perceptron, and [·] is the concatenate operation. Visual adapter (VA) is implemented as two Transformer encoder layers to transform " + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "text", + "content": " into refined visual features " + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "inline_equation", + "content": "V' = [v_1', \\dots, v_M']" + }, + { + "bbox": [ + 47, + 454, + 287, + 525 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "spans": [ + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "type": "text", + "content": "Human-Object Cognitive Block. The HOI scene is further learned under the guidance of knowledge prototypes of human and object (" + }, + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "type": "inline_equation", + "content": "K_{H}" + }, + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "type": "inline_equation", + "content": "K_{O}" + }, + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "type": "text", + "content": "). The self-attention mechanism with gating is introduced to establish cognitive dependencies between knowledge prototypes and visual features, then the human-object-aware visual feature " + }, + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "type": "inline_equation", + "content": "V_{HO}" + }, + { + "bbox": [ + 46, + 525, + 287, + 608 + ], + "type": "text", + "content": " is obtained:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 63, + 619, + 287, + 633 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 63, + 619, + 287, + 633 + ], + "spans": [ + { + "bbox": [ + 63, + 619, + 287, + 633 + ], + "type": "interline_equation", + "content": "V _ {H O} = V ^ {\\prime} + \\text {G a t e} \\left(\\text {S e l f A t t n} \\left(\\left[ K _ {H}, K _ {O}, V ^ {\\prime} \\right]\\right)\\right), \\tag {4}", + "image_path": "8bb6ce633011c9c24c4283dc4fa67f1320c922e67f34b7d6b53992e02b8750c3.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 641, + 287, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 641, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 47, + 641, + 287, + 677 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 641, + 287, + 677 + ], + "type": "inline_equation", + "content": "Gate(\\cdot)" + }, + { + "bbox": [ + 47, + 641, + 287, + 677 + ], + "type": "text", + "content": " is a token gating operation that considers visual tokens only, SelfAttn(" + }, + { + "bbox": [ + 47, + 641, + 287, + 677 + ], + "type": "inline_equation", + "content": "\\cdot" + }, + { + "bbox": [ + 47, + 641, + 287, + 677 + ], + "type": "text", + "content": ") denotes a self-attention computation." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": "Interaction Cognitive Block. Expanding upon the instance-level cognition, including the human and object, the model further delves into comprehending higher-level" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 349, + 545, + 409 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 349, + 545, + 409 + ], + "spans": [ + { + "bbox": [ + 304, + 349, + 545, + 409 + ], + "type": "text", + "content": "interactions that occur between the human and object. To achieve this, the cross-attention mechanism with gating is introduced to guide the learning of more subtle interaction cues by interaction knowledge prototype and obtaining the primary HOI-aware visual feature " + }, + { + "bbox": [ + 304, + 349, + 545, + 409 + ], + "type": "inline_equation", + "content": "V_{HOI}" + }, + { + "bbox": [ + 304, + 349, + 545, + 409 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 321, + 415, + 545, + 429 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 321, + 415, + 545, + 429 + ], + "spans": [ + { + "bbox": [ + 321, + 415, + 545, + 429 + ], + "type": "interline_equation", + "content": "V _ {H O I} = V _ {H O} + \\operatorname {G a t e} \\left(\\operatorname {C r o s s A t t n} \\left(V _ {H O}, K _ {I}\\right)\\right), \\tag {5}", + "image_path": "b16ec45532a125bc75ebcfade5f3496add45e81f9c50b2e928d57782a73b0e61.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "spans": [ + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "type": "text", + "content": "where we denote " + }, + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "type": "inline_equation", + "content": "CrossAttn(q, kv)" + }, + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "type": "text", + "content": " as a cross-attention operation. After that, the general self-attention operation is conducted on " + }, + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "type": "inline_equation", + "content": "V_{HOI}" + }, + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "type": "text", + "content": " to obtain the full HOI-aware visual feature " + }, + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "type": "inline_equation", + "content": "V_{HOI}'" + }, + { + "bbox": [ + 304, + 434, + 545, + 484 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 350, + 489, + 545, + 503 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 350, + 489, + 545, + 503 + ], + "spans": [ + { + "bbox": [ + 350, + 489, + 545, + 503 + ], + "type": "interline_equation", + "content": "V _ {H O I} ^ {\\prime} = V _ {H O I} + \\text {S e l f A t t n} \\left(V _ {H O I}\\right). \\tag {6}", + "image_path": "a4c99f08c0dcf634e521a68797d4615a1ff5d13022c4c3add494e16b68983124.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": "Interaction-oriented Attention Decoder. The goal of the decoder is to generate interaction-oriented attention heatmap " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "m_{IA} \\in \\mathbb{R}^{H \\times W \\times 1}" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": ", we first reshape the full interaction-aware visual feature, " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "V_{HOI}'" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": ", from a 2D shape of " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "\\frac{HW}{p^2} \\times C" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": " to a standard 3D feature map " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "\\frac{H}{p} \\times \\frac{W}{p} \\times C" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": " is the feature channel size, " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": " is the image patch size. Then, we adopt tiny 2-layers of " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "1 \\times 1" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": " convolution with batch norm and ReLU activation to reduce the feature dimension to " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "\\frac{H}{p} \\times \\frac{W}{p} \\times 1" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": ". Last, we adopt a bilinearly upsample operation to achieve the full image size " + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "inline_equation", + "content": "H \\times W" + }, + { + "bbox": [ + 304, + 509, + 545, + 628 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 628, + 545, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 628, + 545, + 664 + ], + "spans": [ + { + "bbox": [ + 304, + 628, + 545, + 664 + ], + "type": "text", + "content": "Loss Function. We utilize the binary cross-entropy as a loss function for attention alignment, which can be expressed as follows:" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 670, + 556, + 713 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 670, + 556, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 670, + 556, + 713 + ], + "type": "interline_equation", + "content": "\\operatorname {B C E} (p, y) = - \\frac {1}{N} \\sum_ {i = 1} ^ {N} \\left(y _ {i} \\cdot \\log \\left(p _ {i}\\right) + \\left(1 - y _ {i}\\right) \\cdot \\log \\left(1 - p _ {i}\\right)\\right), \\tag {7}", + "image_path": "e36c446b6ba9046cf76b71eca18b52f04b4167763ad4bf6d5f98666e9ff3855a.jpg" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 732, + 317, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 732, + 317, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 732, + 317, + 742 + ], + "type": "text", + "content": "28393" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 73, + 286, + 237 + ], + "blocks": [ + { + "bbox": [ + 48, + 73, + 286, + 237 + ], + "lines": [ + { + "bbox": [ + 48, + 73, + 286, + 237 + ], + "spans": [ + { + "bbox": [ + 48, + 73, + 286, + 237 + ], + "type": "image", + "image_path": "03f7c68b986320c4fce14dacc9fb46a09d455b8d66af369358e560971aa97932.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 247, + 288, + 304 + ], + "lines": [ + { + "bbox": [ + 46, + 247, + 288, + 304 + ], + "spans": [ + { + "bbox": [ + 46, + 247, + 288, + 304 + ], + "type": "text", + "content": "Figure 4. We incorporate aligned attention into the existing HOI model training pipeline, divided into two strategies: supervising by a limited amount of real attention from human observers and supervising by a large number of attention pseudo-labels generated by our proposed IA." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 110, + 324, + 287, + 338 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 110, + 324, + 287, + 338 + ], + "spans": [ + { + "bbox": [ + 110, + 324, + 287, + 338 + ], + "type": "interline_equation", + "content": "L _ {H 2 I A} = \\mathrm {B C E} \\left(m _ {H}, m _ {I A}\\right), \\tag {8}", + "image_path": "92247236d727d2be66a61a12f09558efcfa3882bb074b51fb24eeeefa03374ba.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "spans": [ + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "text", + "content": " is the predictive probability, " + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "text", + "content": " is the target, " + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "text", + "content": " is the number of pixels in " + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "inline_equation", + "content": "m_{IA}" + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "inline_equation", + "content": "m_H" + }, + { + "bbox": [ + 47, + 342, + 287, + 379 + ], + "type": "text", + "content": " is human observer's real attention heatmap." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 385, + 287, + 409 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 385, + 287, + 409 + ], + "spans": [ + { + "bbox": [ + 47, + 385, + 287, + 409 + ], + "type": "text", + "content": "3.3. Training HOI Models with Interaction-oriented Attention" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "spans": [ + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "type": "text", + "content": "Here, we formulate the majority of recent state-of-the-art HOI models in the pipeline of CNN Backbone " + }, + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "type": "text", + "content": " Encoder " + }, + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "type": "text", + "content": " Decoder " + }, + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 46, + 416, + 287, + 523 + ], + "type": "text", + "content": " Output Head. We enhance these HOI models by incorporating a supervision of interaction-oriented attention into the training process. This involves two strategies: supervising with a limited amount of real attention samples from human observers and supervising with a large number of pseudo-labeled attention samples from the IA model, as shown in Figure 4." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "spans": [ + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "content": "For these HOI models, we first introduce a simple attention head to extract and reshape the averaged attention maps " + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "inline_equation", + "content": "m_{HOI}" + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "content": " from the last layer of cross-attention computation in the decoder. The attention head is intentionally kept simple for a more direct back propagation of guidance to the representation. Subsequently, the corresponding human observer's attention heatmap " + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "inline_equation", + "content": "m_{H}" + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "content": " and IA-generated pseudolabels " + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "inline_equation", + "content": "m_{IA}" + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "content": " are scaled down to match the size of " + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "inline_equation", + "content": "m_{HOI}" + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "content": " through adaptive 2D max-pooling. Finally, " + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "inline_equation", + "content": "m_{H}" + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "inline_equation", + "content": "m_{IA}" + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "content": " are used to supervise " + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "inline_equation", + "content": "m_{HOI}" + }, + { + "bbox": [ + 46, + 524, + 287, + 654 + ], + "type": "text", + "content": " for two kinds of strategies, respectively." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 655, + 287, + 691 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 655, + 287, + 691 + ], + "spans": [ + { + "bbox": [ + 47, + 655, + 287, + 691 + ], + "type": "text", + "content": "For the strategy of supervising by human observers, the attention alignment loss function " + }, + { + "bbox": [ + 47, + 655, + 287, + 691 + ], + "type": "inline_equation", + "content": "L_{H2HOI}" + }, + { + "bbox": [ + 47, + 655, + 287, + 691 + ], + "type": "text", + "content": " and the overall HOI model's loss function " + }, + { + "bbox": [ + 47, + 655, + 287, + 691 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 47, + 655, + 287, + 691 + ], + "type": "text", + "content": " can be expressed as" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 102, + 701, + 287, + 714 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 102, + 701, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 102, + 701, + 287, + 714 + ], + "type": "interline_equation", + "content": "L _ {H 2 H O I} = \\mathrm {B C E} \\left(m _ {H O I}, m _ {H}\\right), \\tag {9}", + "image_path": "db12605ae886957411044345378cf3a0c5efd4a36e80bfdf1f4cb9776e7f029b.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 367, + 72, + 545, + 84 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 367, + 72, + 545, + 84 + ], + "spans": [ + { + "bbox": [ + 367, + 72, + 545, + 84 + ], + "type": "interline_equation", + "content": "L = \\lambda_ {1} L _ {\\text {r a w}} + \\lambda_ {2} L _ {H 2 H O I}, \\tag {10}", + "image_path": "2fb47a5ec8c3a362d25b2c247bca21b63e9d7d4471e259f4132e7c7f5d8e86e3.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "spans": [ + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "inline_equation", + "content": "L_{raw}" + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "text", + "content": " represents the loss function of the original HOI model, which varies depending on the specific model, while " + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "inline_equation", + "content": "\\lambda_1" + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "inline_equation", + "content": "\\lambda_2" + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "text", + "content": " denote loss scaling factors. Similarly, for the strategy of supervising by IA, " + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "inline_equation", + "content": "L_{IA2HOI}" + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "text", + "content": " and the overall loss function " + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 305, + 90, + 547, + 150 + ], + "type": "text", + "content": " can be expressed as" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 358, + 160, + 545, + 173 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 358, + 160, + 545, + 173 + ], + "spans": [ + { + "bbox": [ + 358, + 160, + 545, + 173 + ], + "type": "interline_equation", + "content": "L _ {I A 2 H O I} = \\mathrm {B C E} \\left(m _ {H O I}, m _ {I A}\\right), \\tag {11}", + "image_path": "bc613ac6433638d10a87fbca010ef4c221bd48f2cd078a6edfa322f57aab41f7.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 366, + 182, + 545, + 196 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 366, + 182, + 545, + 196 + ], + "spans": [ + { + "bbox": [ + 366, + 182, + 545, + 196 + ], + "type": "interline_equation", + "content": "L = \\lambda_ {1} L _ {\\text {r a w}} + \\lambda_ {2} L _ {I A 2 H O I}. \\tag {12}", + "image_path": "a032aa9a8af7221972b9685773ef2b6974de8ae631ee4fd541e9ed465344238e.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 206, + 388, + 220 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 206, + 388, + 220 + ], + "spans": [ + { + "bbox": [ + 306, + 206, + 388, + 220 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 226, + 440, + 239 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 226, + 440, + 239 + ], + "spans": [ + { + "bbox": [ + 306, + 226, + 440, + 239 + ], + "type": "text", + "content": "4.1. Implementation Details" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 244, + 545, + 363 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 244, + 545, + 363 + ], + "spans": [ + { + "bbox": [ + 304, + 244, + 545, + 363 + ], + "type": "text", + "content": "Interactive Attention. We apply 2 versions of CLIP (ViT-B/16 and ViT-L/14) to build the IA models, resulting in IA-B and IA-L, respectively. The output dimension of Fourier embedding is 64. During training, we use AdamW as the optimizer with an initial learning rate of " + }, + { + "bbox": [ + 304, + 244, + 545, + 363 + ], + "type": "inline_equation", + "content": "1 \\times 10^{-4}" + }, + { + "bbox": [ + 304, + 244, + 545, + 363 + ], + "type": "text", + "content": ". The IA model is trained for 80 epochs with a learning rate reduction pre-20 epochs by a factor of 10. The momentum and the weight decay are set as 0.9 and " + }, + { + "bbox": [ + 304, + 244, + 545, + 363 + ], + "type": "inline_equation", + "content": "1 \\times 10^{-4}" + }, + { + "bbox": [ + 304, + 244, + 545, + 363 + ], + "type": "text", + "content": ". The experiments are conducted on four NVIDIA GeForce RTX 3090 GPUs with a batch size of 16." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "text", + "content": "Training HOI Models with Attention Alignment. We apply our attention-guided training strategy on three typical state-of-the-art HOI methods: MUREN [29], representing the one-stage structure, and UPT [60] and STIP [62], representing the two-stage structure. In MUREN, we align the cross-attention map of the last layer in its interaction branch module with our interaction-oriented attention. In UPT, we first add two transformer decoder layers at the end of its interaction head, conducting cross-attention computation with global visual features, and align the cross-attention map of last layer. In STIP, we align the cross-attention map of the last layer in its structure-aware transformer module with our interaction-oriented attention. Due to variations in the raw losses of different methods, particularly for one-stage structure requiring additional supervision of object detection results, corresponding loss scaling factors differ. " + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "inline_equation", + "content": "\\lambda_{1}" + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "inline_equation", + "content": "\\lambda_{2}" + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "text", + "content": " are set to 1 and 10 in MUREN. " + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "inline_equation", + "content": "\\lambda_{1}" + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "inline_equation", + "content": "\\lambda_{2}" + }, + { + "bbox": [ + 304, + 364, + 546, + 616 + ], + "type": "text", + "content": " are set to 1 and 6 in UPT and STIP. Note that the IA model, responsible for generating interaction-oriented attention, is trained without exposure to samples from VCOCO test set and HICO-det test set, preventing any possibility of label leakage." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 623, + 481, + 635 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 623, + 481, + 635 + ], + "spans": [ + { + "bbox": [ + 306, + 623, + 481, + 635 + ], + "type": "text", + "content": "4.2. Comparison methods & Metrics." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 642, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 642, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 642, + 545, + 713 + ], + "type": "text", + "content": "We evaluate the performance of our IA model on interaction-oriented attention prediction, comparing it with 10 state-of-the-art methods: ITTI [22], GBVS [17], DeepGaze I [30], DeepGaze IIE [35], UMB [70], ConvNext [40], MLNet [6], SSwin Transformer [23], CLIP-ViT-B/16 [48], CLIP-ViT-L/14 [48]. Among these, ITTI and GBVS" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "text", + "content": "28394" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 101, + 288, + 207 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 287, + 93 + ], + "type": "text", + "content": "Table 2. Performance comparison on IG dataset. Bold and underline show the best and second-best performances." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 101, + 288, + 207 + ], + "lines": [ + { + "bbox": [ + 48, + 101, + 288, + 207 + ], + "spans": [ + { + "bbox": [ + 48, + 101, + 288, + 207 + ], + "type": "table", + "html": "
MethodZerola SettingFully Supervised Setting
CC↑KLdiv↓SIM↑AUC↑CC↑KLdiv↓SIM↑AUC↑
ITTI [22]0.07844.35530.01420.49990.07543.18150.01170.5301
GBVS [17]0.02624.54950.02340.50000.17732.94980.02070.5037
DeepGaze I [30]0.18733.06630.00800.55700.19693.18690.00810.6143
DeepGaze IIE [35]0.20653.02550.00910.58140.17213.23570.00700.6049
UMB [70]0.21213.90040.59370.53260.20114.23380.61470.5319
MLNet [6]0.29373.89870.46460.59720.31953.68040.41530.5743
ConvNext [40]0.25714.87290.61100.54820.27314.51540.57470.5524
SSwin Transformer [23]0.24942.66540.33090.52120.29383.43090.33230.5391
CLIP-base [48]0.14033.61180.00580.35160.15643.87210.00740.3385
CLIP-large [48]0.16813.64980.00640.31830.16903.85470.00660.3356
IA CLIP-base0.40132.71140.72050.59530.48102.21320.75210.6375
IA CLIP-large0.44882.84090.71520.60680.51062.14090.77960.6386
", + "image_path": "cdd9078d995b643f808ebdcb580f1e5edbf7f4d4f70db75c5fcc4ab9a24b1ed5.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 229, + 287, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 229, + 287, + 348 + ], + "spans": [ + { + "bbox": [ + 46, + 229, + 287, + 348 + ], + "type": "text", + "content": "excel in early saliency prediction based on manual features, while the remaining methods are recent learning-based approaches. DeepGaze I and DeepGaze IIE utilize official pre-trained models for predictions, and UMB, ConvNext, MLNet, and SSwin Transformer are all trained with IG datasets. Additionally, we compute the similarity maps of two commonly used raw CLIP versions (CLIP-ViT-B/16 and CLIP-ViT-L/14). These similarity maps compute the similarity distance between image features and text features, serving as the raw CLIP's class attention maps [31]." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 348, + 287, + 432 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 348, + 287, + 432 + ], + "spans": [ + { + "bbox": [ + 46, + 348, + 287, + 432 + ], + "type": "text", + "content": "We apply 4 metrics to measure performance: KL divergence (KLdiv), correlation coefficient (CC), similarity (SIM), and the area under the receiver operating characteristic curve (AUC). KLdiv, CC, and SIM are distribution-based metrics, while AUC is a localization-based metric. Except KLdiv, where lower values are preferable, higher values are desirable for all other metrics." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 441, + 192, + 453 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 441, + 192, + 453 + ], + "spans": [ + { + "bbox": [ + 47, + 441, + 192, + 453 + ], + "type": "text", + "content": "4.3.Quantitative Comparison." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 459, + 287, + 543 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 459, + 287, + 543 + ], + "spans": [ + { + "bbox": [ + 46, + 459, + 287, + 543 + ], + "type": "text", + "content": "Table 2 presents the quantitative comparison results in the ZeroIA and the fully supervised settings. We can observe that both versions of our model IA outperform all 10 baselines in both metrics. In particular, for CC metric, IA w/ CLIP-L outperforms the third-best MLNet by " + }, + { + "bbox": [ + 46, + 459, + 287, + 543 + ], + "type": "inline_equation", + "content": "52.8\\%" + }, + { + "bbox": [ + 46, + 459, + 287, + 543 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 459, + 287, + 543 + ], + "type": "inline_equation", + "content": "59.8\\%" + }, + { + "bbox": [ + 46, + 459, + 287, + 543 + ], + "type": "text", + "content": " on the ZeroIA and the fully supervised settings, respectively." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 543, + 288, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 543, + 288, + 664 + ], + "spans": [ + { + "bbox": [ + 46, + 543, + 288, + 664 + ], + "type": "text", + "content": "Moreover, we observe that the manual feature-based ITTI and GBVS approaches fail in the interaction-oriented attention prediction task, which demands higher cognitive capabilities. Additionally, when comparing IA with the similarity map of raw CLIP output, our IA achieves significant improvements across all metrics. For example, IA w/ CLIP-B exceeds raw CLIP-B by " + }, + { + "bbox": [ + 46, + 543, + 288, + 664 + ], + "type": "inline_equation", + "content": "186\\%" + }, + { + "bbox": [ + 46, + 543, + 288, + 664 + ], + "type": "text", + "content": " under CC metric of the ZeroIA setting. This suggests that our model effectively activates and utilizes CLIP's knowledge representation capabilities, adapting them to cognitive tasks on interaction." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 670, + 169, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 169, + 684 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 169, + 684 + ], + "type": "text", + "content": "4.4. Qualitative Analyses." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "As shown in Figures 5 and 6, the visualizations of interaction-oriented attention prediction under ZeroIA and" + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 314, + 91, + 537, + 154 + ], + "blocks": [ + { + "bbox": [ + 322, + 71, + 529, + 82 + ], + "lines": [ + { + "bbox": [ + 322, + 71, + 529, + 82 + ], + "spans": [ + { + "bbox": [ + 322, + 71, + 529, + 82 + ], + "type": "text", + "content": "Table 3. Performance comparison of each module in IA." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 314, + 91, + 537, + 154 + ], + "lines": [ + { + "bbox": [ + 314, + 91, + 537, + 154 + ], + "spans": [ + { + "bbox": [ + 314, + 91, + 537, + 154 + ], + "type": "table", + "html": "
MethodZeroIA SettingFully Supervised Setting
CC↑KLdiv↓SIM↑AUC↑CC↑KLdiv↓SIM↑AUC↑
w/o PA0.36523.21150.67330.58020.39612.46760.68640.6023
w/o VA0.38382.98010.67540.58320.40812.43460.68930.6182
w/o HOCB0.34983.31230.64210.57430.36972.56890.64840.6034
w/o ICB0.32493.65410.58450.56440.34452.85330.60230.5934
IA0.40132.71140.72050.59530.48102.21320.75210.6375
", + "image_path": "042029977f1ac7116255833f2cd070eb7cab64e8789949ffe5e1adde26ff88b1.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 173, + 545, + 220 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 173, + 545, + 220 + ], + "spans": [ + { + "bbox": [ + 304, + 173, + 545, + 220 + ], + "type": "text", + "content": "fully supervised settings, respectively. Notably, across both settings, IA exhibits attention distributions that are consistently closer to human observers, outperforming the remaining eight methods." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 220, + 545, + 304 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 220, + 545, + 304 + ], + "spans": [ + { + "bbox": [ + 304, + 220, + 545, + 304 + ], + "type": "text", + "content": "Compared with SOTA models. The previous untrained instance-centric models (columns 6-7) only capture coarse-grained salient persons and objects, but not interaction-related cues. Methods trained on IG prove limited in the complex multi-instance \"push\" scenario (Figure 5, row 4) under the ZeroIA setting and also in the \"talk on\" scenario (Figure 6, row 3) with a limited number of training samples." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 304, + 546, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 304, + 546, + 437 + ], + "spans": [ + { + "bbox": [ + 304, + 304, + 546, + 437 + ], + "type": "text", + "content": "Compared with raw CLIP, IA accurately captures key visual cues, particularly for unseen categories such as \"repair\", \"kiss\", \"lick\", \"push\", and \"sign\" in Figure 5. Noteworthy is the comparison with columns 5-6, where the similarity maps generated by raw CLIP lack interpretability, displaying properties such as opposite visualization and noisy activation, as highlighted in recent work [31, 32]. These observations, along with quantitative results in Table 2, underscore the fact that our work effectively activates CLIP's powerful knowledge representation capabilities and improves interpretability." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 443, + 400, + 455 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 443, + 400, + 455 + ], + "spans": [ + { + "bbox": [ + 306, + 443, + 400, + 455 + ], + "type": "text", + "content": "4.5. Ablation Study" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 460, + 546, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 546, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 546, + 665 + ], + "type": "text", + "content": "To examine the impact of each module in IA, we conduct an ablation study by removing modules in Table 3. Specifically, we sequentially exclude the positional adapter (PA), visual adapter (VA), human-object cognitive block (HOCB), and interaction cognitive block (ICB). All ablated models are variations of IA w/ CLIP-B. Results indicate consistent performance degradation across both ZeroIA and fully supervised settings upon removal of any module. Notably, the most significant degradation occurs when the ICB is omitted, emphasizing its crucial role in guiding the learning of interaction-oriented attention by injecting the interaction knowledge. Subsequently, the HOCB, enriched with information about the subjects and objects involved in the interaction, the PA, which incorporates spatial configuration, and the VA, receiving refined visual features, contribute to the model's performance in descending order from high to low." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 671, + 534, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 671, + 534, + 684 + ], + "spans": [ + { + "bbox": [ + 306, + 671, + 534, + 684 + ], + "type": "text", + "content": "4.6. Effectiveness of Attention Training Strategy" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "Aligning human attention enhances HOI model accuracy. We leverage the VCOCO training subset within" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "text", + "content": "28395" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 90, + 71, + 508, + 240 + ], + "blocks": [ + { + "bbox": [ + 90, + 71, + 508, + 240 + ], + "lines": [ + { + "bbox": [ + 90, + 71, + 508, + 240 + ], + "spans": [ + { + "bbox": [ + 90, + 71, + 508, + 240 + ], + "type": "image", + "image_path": "8f846bffa0e105a5480d6e080c260fa7418e92378b6c39851a63860ec62a433f.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 111, + 247, + 481, + 259 + ], + "lines": [ + { + "bbox": [ + 111, + 247, + 481, + 259 + ], + "spans": [ + { + "bbox": [ + 111, + 247, + 481, + 259 + ], + "type": "text", + "content": "Figure 5. Qualitative comparison of interaction-oriented attention prediction under the ZeroIA setting." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 89, + 271, + 507, + 471 + ], + "blocks": [ + { + "bbox": [ + 89, + 271, + 507, + 471 + ], + "lines": [ + { + "bbox": [ + 89, + 271, + 507, + 471 + ], + "spans": [ + { + "bbox": [ + 89, + 271, + 507, + 471 + ], + "type": "image", + "image_path": "5b89d75baa7eff3b891ea064db747e2260031aa942cd902665a268536d05223a.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 95, + 478, + 496, + 490 + ], + "lines": [ + { + "bbox": [ + 95, + 478, + 496, + 490 + ], + "spans": [ + { + "bbox": [ + 95, + 478, + 496, + 490 + ], + "type": "text", + "content": "Figure 6. Qualitative comparison of interaction-oriented attention prediction under the fully supervised setting." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "content": "the proposed IG, comprising 4,475 samples, approximately " + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "inline_equation", + "content": "32.4\\%" + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "content": " of the complete VCOCO training set, as the attention ground truth for additional supervision of existing HOI models. As shown in Table 4, MUREN, UPT, and STIP are improved by " + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "inline_equation", + "content": "0.6\\mathrm{mAP}" + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "inline_equation", + "content": "0.8\\mathrm{mAP}" + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "inline_equation", + "content": "0.4\\mathrm{mAP}" + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "content": ", respectively, under the Scenario1 setting. Similarly, under the Scenario2 setting, MUREN, UPT, and STIP are enhanced by " + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "inline_equation", + "content": "0.7\\mathrm{mAP}" + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "inline_equation", + "content": "1.3\\mathrm{mAP}" + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "inline_equation", + "content": "0.4\\mathrm{mAP}" + }, + { + "bbox": [ + 46, + 510, + 289, + 632 + ], + "type": "text", + "content": ", respectively. This highlight the significant potential of aligned human attention in enhancing action comprehension, even with limited training data." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "text", + "content": "Aligning IA-generated attention enhances HOI model accuracy more significantly. We further enhance the additional supervision of HOI models through large-scale interaction-oriented pseudo-labeling, generated by the proposed IA model on the training sets of VCOCO and HICO-det, respectively. In Table 4, on the VCOCO dataset," + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "type": "text", + "content": "our training strategies consistently obtain performance improvements for MUREN, UPT, and STIP. In particular, thanks to the precise emulation of human attention by our proposed IA model, the results of all HOI models reveal that training by a large number of pseudo-attention labels is superior to using limited genuine human attention. On HICO-det dataset, our training strategy similarly achieves consistent performance gains in Table 5. Particularly, we observe that our training strategy significantly enhances the performance of the rare set, by " + }, + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "type": "inline_equation", + "content": "6.0\\%" + }, + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "type": "inline_equation", + "content": "4.0\\%" + }, + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "type": "inline_equation", + "content": "2.7\\%" + }, + { + "bbox": [ + 304, + 510, + 545, + 668 + ], + "type": "text", + "content": " on MUREN, UPT, and STIP, respectively. Note that the reported experimental results are all obtained by reproducing these models under the same experimental settings." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 677, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 677, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 305, + 677, + 547, + 715 + ], + "type": "text", + "content": "Aligning attention makes HOI models more interpretable. We present visualizations of the cross-attention maps of interaction branches in original MUREN and the" + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 318, + 742 + ], + "type": "text", + "content": "28396" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 70, + 91, + 264, + 275 + ], + "blocks": [ + { + "bbox": [ + 49, + 71, + 285, + 82 + ], + "lines": [ + { + "bbox": [ + 49, + 71, + 285, + 82 + ], + "spans": [ + { + "bbox": [ + 49, + 71, + 285, + 82 + ], + "type": "text", + "content": "Table 4. Comparison of HOI detection performance on VCOCO." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 70, + 91, + 264, + 275 + ], + "lines": [ + { + "bbox": [ + 70, + 91, + 264, + 275 + ], + "spans": [ + { + "bbox": [ + 70, + 91, + 264, + 275 + ], + "type": "table", + "html": "
MethodBackboneScenario #1Scenario #2
One-stage methods
UnionDet [26]ResNet-50-FPN47.556.2
IP-Net [54]Hourglass-10451.0-
GG-Net [33]Hourglass-10454.7-
HOTR [27]ResNet-5055.264.4
QPIC [52]ResNet-10158.360.7
MUREN [29]ResNet-5066.969.0
MUREN w/ HumanResNet-5067.569.7
MUREN w/ IA-BResNet-5067.770.3
MUREN w/ IA-LResNet-5068.070.4
Two-stage methods
VCL [19]ResNet-5048.3-
SCG [59]ResNet-50-FPN54.2-
UPT [60]ResNet-5059.865.5
STIP [62]ResNet-5066.070.7
UPT w/ HumanResNet-5060.766.4
UPT w/ IA-BResNet-5061.166.8
UPT w/ IA-LResNet-5061.467.0
STIP w/ HumanResNet-5066.471.1
STIP w/ IA-BResNet-5067.071.3
STIP w/ IA-LResNet-5067.271.4
", + "image_path": "6f57e4ab39f327b4b78cd4fd9b3112702a70847b43d6f928e9eae8e3a36da841.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 70, + 304, + 264, + 494 + ], + "blocks": [ + { + "bbox": [ + 47, + 285, + 286, + 296 + ], + "lines": [ + { + "bbox": [ + 47, + 285, + 286, + 296 + ], + "spans": [ + { + "bbox": [ + 47, + 285, + 286, + 296 + ], + "type": "text", + "content": "Table 5. Comparison of HOI detection performance on HICO-det." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 70, + 304, + 264, + 494 + ], + "lines": [ + { + "bbox": [ + 70, + 304, + 264, + 494 + ], + "spans": [ + { + "bbox": [ + 70, + 304, + 264, + 494 + ], + "type": "table", + "html": "
MethodBackboneFullRareNon-rare
One-stage methods
UnionDet [26]ResNet-50-FPN17.5811.7219.33
IP-Net [54]Hourglass-10419.5612.7921.58
PPDM [33]Hourglass-10421.7313.7821.40
GG-Net [63]Hourglass-10423.4716.4825.60
HOTR [27]ResNet-5025.1017.3427.42
QPIC [52]ResNet-10129.9023.9231.69
MSTR [28]ResNet-5031.1725.3132.92
MUREN [29]ResNet-5032.0927.3633.50
MUREN w/ IA-BResNet-5032.4528.9033.51
MUREN w/ IA-LResNet-5032.4829.0133.53
Two-stage methods
VCL [19]ResNet-5023.6317.2125.55
ATL [20]ResNet-5023.6717.6425.47
SCG [59]ResNet-50-FPN29.2624.6130.65
UPT [60]ResNet-5031.9326.7033.49
STIP [62]ResNet-5032.2228.1533.43
UPT w/ IA-BResNet-5032.2027.5933.58
UPT w/ IA-LResNet-5032.4727.7633.72
STIP w/ IA-BResNet-5032.3228.4733.59
STIP w/ IA-LResNet-5032.6428.9033.76
", + "image_path": "025a32947417929dbcdad04420404a1c31de654a7ce367c360f94b920bfaaa88.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 514, + 287, + 610 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 514, + 287, + 610 + ], + "spans": [ + { + "bbox": [ + 46, + 514, + 287, + 610 + ], + "type": "text", + "content": "MUREN aligned with interaction-oriented attention, respectively, as shown in Figure 7. It is evident that the attention map of original MUREN appears fragmented and struggles to focus on interaction-related visual cues, leading to failures in interaction recognition. Conversely, after aligning with interaction-oriented attention, not only are the erroneous results corrected, but the attention map becomes significantly more interpretable and focuses on key regions." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 621, + 119, + 633 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 621, + 119, + 633 + ], + "spans": [ + { + "bbox": [ + 47, + 621, + 119, + 633 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 642, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 287, + 715 + ], + "type": "text", + "content": "This paper aims to address a critical gap in interaction-oriented attention by introducing the challenging yet meaningful ZeroIA problem. To achieve this, we collect the IG dataset, marking the first large-scale interaction-centric gaze fixation dataset, featuring 530,000 fixation points across 740 diverse interaction categories. Subsequently, we" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 310, + 72, + 526, + 228 + ], + "blocks": [ + { + "bbox": [ + 310, + 72, + 526, + 228 + ], + "lines": [ + { + "bbox": [ + 310, + 72, + 526, + 228 + ], + "spans": [ + { + "bbox": [ + 310, + 72, + 526, + 228 + ], + "type": "image", + "image_path": "5192f6356bd6ebd9da82d9c23c4cc44d7eda18f75341a3a1cd2cdb2e5ef5fe56.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 238, + 547, + 315 + ], + "lines": [ + { + "bbox": [ + 305, + 238, + 547, + 315 + ], + "spans": [ + { + "bbox": [ + 305, + 238, + 547, + 315 + ], + "type": "text", + "content": "Figure 7. The predicted results and corresponding attention visualizations for MUREN and our (MUREN w/ IA-L, MUREN w/ Human). We mark true positive results in green, and false positive results in red. After aligning interaction-oriented attention, the erroneous prediction results are corrected, and the corresponding attention becomes more converged and more interpretable. More in supplementary materials." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 345, + 546, + 537 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 345, + 546, + 537 + ], + "spans": [ + { + "bbox": [ + 304, + 345, + 546, + 537 + ], + "type": "text", + "content": "present the IA model, ingeniously designed to activate and leverage the knowledge representation capabilities of CLIP, emulating the cognitive processes of human observers to generate high-quality interaction-oriented attention. Extensive experiments demonstrate that the proposed IA model outperforms state-of-the-art attention prediction methods in both zero-shot and fully supervised settings. Furthermore, we propose an attention-guided HOI training strategy, leveraging interaction-oriented attention to guide existing HOI models for more effective learning. Quantitative and qualitative results demonstrate that both genuine human attention and IA-generated attention significantly enhance the performance and interpretability of existing HOI models, making them more capable of visual reasoning like human observers. This highlights the significant potential of visual attention in action comprehension." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "spans": [ + { + "bbox": [ + 304, + 541, + 545, + 661 + ], + "type": "text", + "content": "Our endeavor represents the pioneering effort to establish a bi-directional connection between visual attention and HOI detection, starting by directing visual attention through the interaction comprehension task and ending by incorporating this attention to repay existing HOI methods. We believe our work can inspire further research on goal-oriented attention and its application in various action-related tasks like classification, VQA, and captioning. Our work also has potential applications in DNNs' interpretability evaluation, human-AI collaboration, and values alignment research." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 666, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 666, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 305, + 666, + 547, + 714 + ], + "type": "text", + "content": "Acknowledgements. This work is supported in part by National Natural Science Foundation of China under Grant 62373387, and in part by Natural Science Foundation of Guangdong Province (No. 2023A1515030264)." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 733, + 317, + 742 + ], + "type": "text", + "content": "28397" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 713 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "text", + "content": "[1] Souradeep Chakraborty, Zijun Wei, Conor Kelton, Seoyoung Ahn, A. 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In CVPR, pages 11825-11834, 2021. 1" + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 734, + 317, + 742 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 734, + 317, + 742 + ], + "spans": [ + { + "bbox": [ + 293, + 734, + 317, + 742 + ], + "type": "text", + "content": "28400" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning from One Continuous Video Stream/a8db15d8-1180-483d-9687-c41b3735ca04_content_list.json b/2024/Learning from One Continuous Video Stream/a8db15d8-1180-483d-9687-c41b3735ca04_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..7c1a111f5be185c27bf73aab9b4bbcc0b08c0207 --- /dev/null +++ b/2024/Learning from One Continuous Video Stream/a8db15d8-1180-483d-9687-c41b3735ca04_content_list.json @@ -0,0 +1,1445 @@ +[ + { + "type": "text", + "text": "Learning from One Continuous Video Stream", + "text_level": 1, + "bbox": [ + 253, + 130, + 718, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "João Carreira $^{1\\dagger}$ , Michael King $^{1\\dagger}$ , Viorica Pătrăucean $^{1\\dagger}$ , Dilara Gokay $^{1\\dagger}$ , Cătălin Ionescu $^{1\\dagger}$ , Yi Yang $^{\\dagger}$ , Daniel Zoran $^{\\dagger}$ , Joseph Heyward $^{\\dagger}$ , Carl Doersch $^{\\dagger}$ , Yusuf Aytar $^{\\dagger}$ , Dima Damen $^{\\dagger \\ddagger}$ , Andrew Zisserman $^{\\dagger \\diamond}$", + "bbox": [ + 130, + 179, + 836, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{\\dagger}$ Google DeepMind, $^{\\ddagger}$ University of Bristol, $^{\\diamond}$ University of Oxford Corresponding author: joaoluis@google.com, $^{\\dagger}$ core contributor", + "bbox": [ + 274, + 234, + 691, + 268 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 304, + 313, + 320 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We introduce a framework for online learning from a single continuous video stream – the way people and animals learn, without mini-batches, data augmentation or shuffling. This poses great challenges given the high correlation between consecutive video frames and there is very little prior work on it. Our framework allows us to do a first deep dive into the topic and includes a collection of streams and tasks composed from two existing video datasets, plus methodology for performance evaluation that considers both adaptation and generalization. We employ pixel-to-pixel modelling as a practical and flexible way to switch between pre-training and single-stream evaluation as well as between arbitrary tasks, without ever requiring changes to models and always using the same pixel loss. Equipped with this framework we obtained large single-stream learning gains from pre-training with a novel family of future prediction tasks, found that momentum hurts, and that the pace of weight updates matters. The combination of these insights leads to matching the performance of IID learning with batch size 1, when using the same architecture and without costly replay buffers. An overview of the paper is available online at https://sites.google.com/view/one-stream-video.", + "bbox": [ + 76, + 338, + 473, + 684 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 720, + 209, + 736 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Humans gather knowledge about themselves and the world through a continuous stream of observations, from their early days as infants. Some experiences are seen once in a lifetime while others are daily repeats. With time, familiarity with environments, objects and experiences form a base to our knowledge, and memory maintains the most important experiences from our ever-further past. Learning successfully adapts to the current surroundings so we can make better predictions over time, while leading to generalization to unseen environments. Despite the naturalness", + "bbox": [ + 75, + 750, + 468, + 900 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "of this approach of learning for humans, video understanding approaches have rarely attempted a similar regime.", + "bbox": [ + 498, + 305, + 890, + 338 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/44982ffc8f8671dd0b3c2d63482cff3fce3657ef935af4c194e331224c065d91.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 503, + 352, + 890, + 476 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/2882fc0d6668fe4f405d65e88840838adbb4f78b24c9463bcaf8b5793dfb9e85.jpg", + "image_caption": [ + "Figure 1. Top: We introduce a framework for studying continuous learning in a single video stream. This is a natural yet unstudied problem, different from standard independent and identically distributed (IID) learning in video where batches contain clips from random videos in a random order. Bottom: We propose pixel-to-pixel models to evaluate our approach across prediction tasks (prediction of future frames, depth, segmentation). We measure both adaptation to the video stream – the model here updates its weights (learns) continuously to improve prediction – as well as generalization to out-of-stream clips – the model being adapted on the first stream is now evaluated on a different held-out stream without being allowed to adapt to it. We propose to maximize both adaptation and generalization." + ], + "image_footnote": [], + "bbox": [ + 501, + 482, + 890, + 638 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The most related fields are continual and lifelong learning, but these are still deeply fractured – no single problem formulation or benchmark is widely accepted. They also mostly focus on simplifications of the problem relative to", + "bbox": [ + 498, + 839, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "28751", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/0f1e7eaef77b3f20abcbceac0bffea6665f404e95f12a81925151623471db689.jpg", + "image_caption": [ + "Figure 2. UNet training on ScanNet-stream for the semantic segmentation task. Left: The cosine similarity of consecutive gradients is normally distributed when training on IID data, but shows very strong correlations when training on a continuous video stream. Right: This is reflected in poor training performance. See the appendix for similar figures for Ego4D-stream." + ], + "image_footnote": [], + "bbox": [ + 81, + 88, + 269, + 185 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/93ad7409674deeb8a0bf297f421b506fc354e8d03113f3177ad50f838b4fd1bc.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 272, + 88, + 460, + 186 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "human and animal experience, for example a popular task is learning one ImageNet class at a time and minimizing forgetting of previous classes [38].", + "bbox": [ + 75, + 286, + 468, + 330 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "But what happens if we attempt to learn continuously from a single video stream (Figure 1), meaning batch size 1 and high frame rate (e.g. 25 fps)? We do not see thousands of dogs per second, unlike the standard ImageNet setting, where images of even a same dog breed are quite uncorrelated at several scales – capturing a wide diversity of edges, textures, etc. Standard deep learning approaches lead to smooth optimization there, but it is very different from the setting of learning from a single video stream, where things happen slowly, at much longer timescales, with great correlation or even no change between frames for periods of time; see Figure 2. Do standard deep learning tools work in this setting? This is currently unknown territory, with very few attempts touching it at all [33] – and it is the focus of this paper.", + "bbox": [ + 75, + 332, + 468, + 559 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We are interested in this problem because models should be able to adapt after deployment to their environment, hence receiving a single stream of information. This is needed for embodied intelligence (robotics), but also for any type of digital assistant that we would want to be able to adapt to a specific user's needs.", + "bbox": [ + 75, + 560, + 468, + 650 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "A framework. We lay out a framework for learning from a single video stream, focusing on the entry-level problem of ... learning. Nevermind forgetting, can the models even learn in the first place? We study how successful learning is for different optimization settings, models, pretraining methods and tasks, when done from a single continuous stream. Our methodology follows the following principles:", + "bbox": [ + 75, + 655, + 468, + 760 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We consider future prediction tasks including pixels-to-pixels, pixels-to-segmentation and pixels-to-depth, all in RGB space (i.e. outputs are always 3 dimensional and with the same shape as the input frames). This way we do not need to change any parameter in the model between pretraining and single-stream learning, independently of what tasks are used in each. It enables using a simple L2 loss between pixel values in all cases.", + "- We evaluate performance in two ways - in-stream, and" + ], + "bbox": [ + 76, + 763, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "out-of-stream. In-stream measures performance on the input video stream. For sufficiently difficult prediction tasks this should be enough. However, it conflates representation quality with adaptation to the scene, lighting condition, etc. For example if the lights in a scene are turned off for an hour, a model can learn to always predict black pixels – which is not ideal. To disentangle adaptation and generalization, we also evaluate out-of-stream, on a second stream on which the model does not learn. We propose to maximize both.", + "bbox": [ + 511, + 90, + 890, + 242 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Contributions. With this methodology in place, we identified the following new results:", + "bbox": [ + 500, + 250, + 890, + 280 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- On the optimization front, we observe that momentum, widely used in popular optimizers such as Adam, is unhelpful in highly correlated video streams. Instead methods without momentum such as RMSprop are more robust.", + "- Another result is a trade-off between adaptation and generalization induced by frequency of weight updates - slower leads to better generalization.", + "- We introduce a family of future prediction pretraining tasks, learnt in the standard independent and identically distributed (IID) setting, with large batches, and show that these lead to better single-stream performance compared to existing ImageNet pretraining tasks.", + "- We combine these results into a combo approach that we call Baby Learning (BL), and compare it to a standard deep learning setup (STDL) that uses Adam and ImageNet MAE pretraining. We show that BL on a sequential stream matches STDL on out-of-stream generalization when that same stream is permuted to be IID, while achieving better performance in-stream thanks to adaptation." + ], + "bbox": [ + 500, + 281, + 890, + 595 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related work", + "text_level": 1, + "bbox": [ + 500, + 614, + 635, + 628 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Online learning from a single video stream. One of the few papers dealing with this problem [33] proposed a minimum-redundancy \"replay\" buffer [27] to deal with temporal correlations. Replay buffers are not the sexiest research avenue for continual learning [41] and increase computation proportionally to the size of the buffer used. Additionally, in [33] performance on the video streams itself was never evaluated, only on unrelated image classification tasks. Test-time training is the next closest problem, such as presented in TTTVS [45] (also related [48]). TTVS's motivation is to \"improve inference quality\" by leveraging self-supervised test-time optimization. Our motivation is to propose single-stream learning, which is reflected in much longer streams (24h in this paper, compared to seconds or few minutes). One challenge in single-stream learning is how to fully exploit available hardware parallelism in a batch size 1 setting [6, 23, 24].", + "bbox": [ + 496, + 643, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "28752", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Learning from a single video. Also relevant are experiments training ConvNets [21] or ViTs [8] on a single image [1] or a long video [43]. While outside of the streaming setting – using data shuffling, augmentation and large batches, these papers showed that learning can be quite successful in this setting (especially for the shallower layers), which was quite encouraging.", + "bbox": [ + 75, + 90, + 468, + 196 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Continual learning. The continual learning literature (e.g. EWC [19]) tends to focus on learning a sequence of tasks, the goal being to learn new tasks as fast as possible without forgetting previous ones, such as in class incremental learning (e.g. iCarl [36]) and CLEAR [22]. Most relevant is online continual learning, where models learn from a stream of data, visited once. One challenge is model cheating by exploiting labels in the data [15], or by learning spurious features [46] that have limited generalisation power. Most of the work in this area has been on collections of images, rather than video.", + "bbox": [ + 75, + 200, + 470, + 366 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Representation learning to the rescue. Recent continual learning papers reported that some of the challenges of the problem are partially mitigated by using features pretrained in IID settings [26, 35, 44]. Various pretraining strategies exist: self-distillation (e.g. BYOL [13], BRaVe [37], DINO [4]), contrastive (CLIP [34], VideoMoco [28], VITO [30]), and masked auto-encoding (e.g. VideoMAE [42], TubeViT [31], AudioVisualMAE [11], SiameseMAE [14], [2]). We investigate this aspect in our setup.", + "bbox": [ + 75, + 369, + 470, + 521 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. The Framework", + "text_level": 1, + "bbox": [ + 76, + 536, + 238, + 551 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Overview. The following is repeated throughout a video stream: a (potentially pretrained) model processes $n$ frames (a time step) from an input video stream, and predicts frames for a future time step. Online (in-stream) performance metrics as well as an L2 loss function are then recorded by comparing predicted and target frames. Given the loss, gradients are computed and the model weights are updated by an optimizer. The target frames can come from the input stream itself or from an associated stream (e.g. for datasets having semantic segmentation or depth). In parallel with in-stream evaluation, we periodically assess performance on a held-out stream (composed of clips from the validation set of the dataset), to assess generalization.", + "bbox": [ + 75, + 564, + 468, + 762 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Unified pixel-to-pixel modelling", + "text_level": 1, + "bbox": [ + 76, + 770, + 356, + 787 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We are interested in having a framework where switching between arbitrary tasks requires no changes to models or losses so we can abstract away decoder nd loss function design (large research areas) and focus on the single-stream learning aspect. To achieve this we map all task target outputs to RGB space, so we can have a single pixel-to-pixel model and a single simple L2 pixel loss.", + "bbox": [ + 75, + 794, + 468, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Models. We use 2 different popular backbones for our experiments: a UNet with self-attention in the bottleneck layer [17] and ViT-L [8]. To enable motion understanding, which is important for future prediction, we feed the models $n = 4$ consecutive frames stacked along the channel dimension. We also have the models predict the same number of frames, so 12 channels in total (4 frames times 3 channels, for RGB). For ViT we decode tokens to pixels using a channel to space transformation: each token gets mapped to an appropriate number of channels using a linear transformation, then gets reshaped into a patch (e.g. a 16x16 grid of 4x3 RGB channels). We provide details of the models in the Appendix, but it is worth noting that the UNet is considerably smaller at 8M parameters, compared to the 350M parameters of the ViT model. We always train the UNet from scratch, whereas we explore various pretraining schemes for ViT. To accommodate for the 12 input channels we use, we inflate [5] the first layer of the ViT (replicate the pretrained weights 4 times).", + "bbox": [ + 496, + 90, + 890, + 378 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Memory. We did not explore explicit memory modules such as memory banks, LSTM cells, or long context in this paper, but we do think it should be very relevant going forward. In all cases, the model \"sees\" only a time step of frames and predicts another time step. Note however that the model weights are updated as it goes through the video stream - so both the weights and the optimizer (when stateful) provide some memory effects.", + "bbox": [ + 496, + 381, + 890, + 502 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Replay buffer. We explored replay buffers [27], which keep a large cache of previous examples, then form batches by sampling from it. They have the disadvantage of increasing computational cost significantly over operating with batch size 1 (increases the theoretical computational cost of learning $K$ times, where $K$ is the batch size).", + "bbox": [ + 496, + 503, + 890, + 594 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Video streams and tasks", + "text_level": 1, + "bbox": [ + 500, + 604, + 720, + 619 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We do not know of public datasets having very long video streams, for example days-long and beyond1, so we create two different video streams: Ego4D-stream and ScanNet-stream, by concatenating videos from, respectively, Ego4D and ScanNet. We include Ego4D as it is large and has very long videos, and ScanNet because it has dense semantic segmentation and depth annotations, allowing us to experiment with different tasks.", + "bbox": [ + 496, + 628, + 890, + 750 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Ego4D-stream. We concatenate the raw (un-trimmed) videos from the Ego4D dataset [12] to create a very long video stream. We use $\\sim 90\\%$ of the data to generate a training stream and $\\sim 10\\%$ for the validation stream. The videos in Ego4D were collected using a head or glass mounted camera, capturing activities of daily life. We use this stream for learning and evaluating future prediction in pixel space – no annotations are employed. See Table 1 for more details.", + "bbox": [ + 496, + 753, + 890, + 875 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "1Other than Krishnacam [20], which is only 70 hours long.", + "bbox": [ + 517, + 886, + 830, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "28753", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "table", + "img_path": "images/e0677bb598c0481a7d844a3b1448681ce81967f571ac46fcde0687f5299becef.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Stream name# videos train# frames train# videos val# frames valMax. lengthMedian length
Ego4D-stream21,704294M (3,265h)230231M (348h)1.95h8.8 minutes
ScanNet-stream1,1991.8M (20h)3120.5M (5.7h)5.5 minutes1 minute
", + "bbox": [ + 132, + 88, + 834, + 133 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Table 1. The two streams we consider, formed out of Ego4D and ScanNet, together with properties of their original video clips.", + "bbox": [ + 107, + 137, + 859, + 151 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "ScanNet-stream. We use the videos from ScanNetV2 [7] to define 3 different prediction tasks, of pixels, semantic segmentation labels (40 classes) and depth. The availability of these additional target streams makes it possible for us to measure more explicitly higher-level understanding, which may not be clear from pixel prediction alone. The videos in this dataset were filmed with a camera navigating indoor scenes with one or more rooms. See Table 1 for more details.", + "bbox": [ + 75, + 178, + 470, + 314 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Tasks. Overall we consider the following tasks across the two stream types: Ego4D-stream pixel prediction, ScanNetstream pixel, semantic segmentation and depth prediction. The difficulty of most of these tasks can be controlled using a time displacement parameter $\\Delta$ - how many steps in advance should the models predict. We consider 0, 1, and 4 time steps. A displacement of 0 only makes sense for semantic tasks as otherwise it corresponds to auto-encoding, which is easy. Note that this task is related to the near-future accuracy metric proposed in [15] to measure (forward transfer) adaptation in a more robust way.", + "bbox": [ + 75, + 318, + 468, + 484 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "RGB-fication. There is some hand design involved in mapping tasks into RGB space. For depth and semantic segmentation we use standard color maps typical for those tasks in ScanNet: the Viridis color map and the ScanNet label color map, respectively. We provide details of these mappings in the Appendix. For computing metrics other than the L2 pixel distance, we compute the nearest neighbor label / depth for each pixel color (e.g. a pixel's color may not correspond exactly to one of the semantic segmentation labels, so we assume the predicted class is the label associated with the nearest color on the color map).", + "bbox": [ + 75, + 488, + 470, + 654 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Evaluation", + "text_level": 1, + "bbox": [ + 76, + 665, + 196, + 679 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Learning a video stream task with a continuously updated model can be seen to decompose into: 1) discovering strong features that are general, for example learning that certain configuration of edges correspond to chair legs for semantic segmentation (generalization), which is likely to happen over long timescales. 2) by specializing to the particular scene being seen in the video, e.g. learning that the chair is the only red object in the scene and using redness to label the chair pixels (adaptation), which can happen over short timescales. Adaptation can be quite useful and lead to efficient visual mechanisms, but may not necessarily lead to generalization. Dummy models that only e.g. exploit temporal correlations in the target stream could misleadingly appear to perform very well [15]; see Table 4, Blind model.", + "bbox": [ + 75, + 688, + 470, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We propose to evaluate both aspects by computing a score continuously in-stream, on the video stream task the model is learning from, to measure adaptation. Separately and periodically we compute the same score out-of-stream, on a held-out stream with the optimizer disabled (out-of-stream). We use the training sets of Ego4D and ScanNet to do in-stream evaluation, and the validation sets for out-of-stream evaluation.", + "bbox": [ + 496, + 178, + 890, + 297 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Cumulative scores. Comparing single-stream learning models and approaches can be difficult if done naively. On the training stream, difficulty of the task may vary over time, for example certain parts of a stream may be more unpredictable due to camera motion or other factors, leading to natural oscillations. On the generalization side we care not just about performance at a particular moment in time, but also how fast it ramps up as training on the sequential video stream progresses. With this in mind, we use a global score over the whole stream – we do this by averaging the performance over 10,000 evenly-spaced points interpolated from the steps in both in-stream and out-of-stream settings.", + "bbox": [ + 496, + 303, + 892, + 484 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Task-specific evaluation. We evaluate pixel prediction with average L2 pixelwise distance, the same that we use as loss for training. For semantic segmentation we use mean per-frame IoU and recall [3, 32] and depth using log relative mean square error (logRMSE) [9]. For both segmentation and depth we mask out pixels that were not annotated from the evaluation and loss.", + "bbox": [ + 496, + 489, + 890, + 594 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Generalized Future Prediction", + "text_level": 1, + "bbox": [ + 498, + 612, + 779, + 628 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "One of the most promising directions for continual learning, as identified in prior work, is representation learning. We are particularly interested in pixel-to-pixel approaches keeping consistent with the overall proposed framework where we never change neither the architecture nor the loss. We propose a family of pretraining methods that generalize future video prediction [40], and that follow a same pattern: given one input video clip the model is trained to predict a future clip from the same video (both clips are 4 frames long). We consider three variants, illustrated in Fig. 3:", + "bbox": [ + 496, + 638, + 890, + 790 + ], + "page_idx": 3 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- The easiest one, Guided future prediction, replaces a few patches from the input clip with patches in the same position from the future clip, hence narrowing down the range of possibilities.", + "- The intermediate one, Vanilla future prediction is just the standard task of predicting the future.", + "- Masked future prediction is a variation of Masked Auto" + ], + "bbox": [ + 500, + 794, + 890, + 898 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "28754", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/32fcdc00c3892ea49ccb72bb5bf62860ee2af339ec508c26d8786de621ef0310.jpg", + "image_caption": [ + "Figure 3. Video pretraining tasks we consider, sorted from easiest to hardest, left to right - guided future prediction, vanilla future prediction, and masked future prediction. Each column shows 4 consecutive frames vertically. For each method we show left-to-right: input frames, predictions from the model, target frames. We use a displacement $(\\Delta)$ of 16 frames (0.64s) between input and target clips." + ], + "image_footnote": [], + "bbox": [ + 76, + 85, + 338, + 319 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/2fab7abefcb4a0bbede0d3eaf5442cbf576844f3b14fb1e7ea3d9ebc061bab1b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 348, + 85, + 614, + 319 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/93b0322a49ff99cd2012e3929a7219c2f37cb5e16801459174015676cbec38d2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 630, + 85, + 893, + 319 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Encoding where the model must predict the future clip based on a partial view of the current clip.", + "bbox": [ + 89, + 383, + 470, + 412 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Guided future prediction is related to Siamese MAE [2, 14, 47], but simpler, requiring a single forward pass over one model. Masked future prediction is related to video MAE-type approaches [10, 42] but with a strict separation between disjoint input and output clips, whereas in traditional video MAE there is a single clip that gets uniformly corrupted as part of denoising auto-encoding.", + "bbox": [ + 75, + 416, + 468, + 523 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Hyperparameters. There are two hyperparameters: the fraction of guiding patches / masked patches and the shape of these patches (we use a constant square shape in all experiments). Vanilla future prediction is a special case of the other two in the case where there is no masked nor guiding patches. A general way to increase the difficulty of any of the variants is to increase the displacement $(\\Delta)$ between the input and the target clips.", + "bbox": [ + 75, + 526, + 470, + 647 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. Results", + "text_level": 1, + "bbox": [ + 76, + 660, + 163, + 676 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Our goal is to achieve similar (or better) learning efficiency from a single continuous video stream as we expect from the standard deep learning setting - using sequences of batches of well shuffled examples. Here is a summary of the main results of our experiments on learning from a continuous video stream:", + "bbox": [ + 75, + 686, + 468, + 775 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Momentum, widely used in optimizers such as Adam, hurts performance in single-stream learning.", + "- Less frequent weight updates (e.g. every 2.5 seconds), helps generalization while sacrificing some adaptation.", + "- Pretraining the models on IID data before single-stream learning is quite impactful. While popular ImageNet-based pretraining helps, we found future-prediction based video pretraining to be vastly superior." + ], + "bbox": [ + 76, + 780, + 467, + 901 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/3e0837848d31bdbb58ec2f4f76f51cd177e513e7be88ba3b46aa167a7aa81a0e.jpg", + "image_caption": [ + "Figure 4. A sweep over commonly used optimizers. Those without momentum are shown in blue and aid the models adaptability considerably compared to the more commonly used Adam variants, which are shown in red." + ], + "image_footnote": [], + "bbox": [ + 504, + 385, + 885, + 503 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We ran all in-stream learning for 24 hours of video, and measured out-of-stream performance from regularly saved checkpoints on 3h30 of video. Resolution was always $224 \\times 224$ .", + "bbox": [ + 498, + 578, + 893, + 638 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.1. Optimization", + "text_level": 1, + "bbox": [ + 500, + 648, + 638, + 666 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Starting from the standard optimizer used in nearly all deep learning setups, Adam, we observed that it does not train well with default parameters in the continuous video stream setting compared to the IID setting; see Fig. 2, right. To understand the differences between the two settings, we analyzed the temporal correlation between consecutive gradients. We found that the norm and variance of the gradients do not reveal strong differences. However, their orientation reveals strong correlations between pairs of consecutive gradients in the continuous case; see Fig. 2, left, where we plot the distribution of the cosine similarity between consecutive gradients in the continuous vs IID case.", + "bbox": [ + 496, + 672, + 892, + 853 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To investigate the optimization further we performed a large sweep over commonly used optimizers, shown in Fig. 4. Results are averaged over 8 settings: 2 tasks", + "bbox": [ + 498, + 854, + 893, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "28755", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/213a18fcfefa0ad3b1539219e4cbaeaa539bccc514ef54ab1f9b370c20265c08.jpg", + "image_caption": [ + "Figure 5. Reducing momentum with the AdamW optimizer helps to recover some of the performance of RMSProp." + ], + "image_footnote": [], + "bbox": [ + 81, + 90, + 460, + 256 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "(Ego4D-stream and ScanNet-stream segmentation prediction), 2 models (ViT and UNet) and 2 displacements (1 step and 4 steps). RMS Prop significantly outperformed the more commonly used Adam variants.", + "bbox": [ + 75, + 316, + 467, + 377 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Momentum hurts. To scrutinize the difference between AdamW and RMSProp, we looked at the impact of momentum. We found that lowering the momentum of the AdamW optimizer recovered some of the performance of RMSProp (as shown in Fig. 5). One possible explanation is that momentum exacerbates the problem of correlated consecutive gradients (that differ from the underlying gradient of the loss function over the whole stream) and makes the weights accelerate too much in the wrong direction. We stick with RMSProp for the rest of the paper, as it is more memory efficient due to not using the average of past gradients.", + "bbox": [ + 75, + 382, + 467, + 547 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Infrequent weight updates help generalization, hurt adaptation. We also observed an interesting effect associated to the frequency of weight updates: doing it less frequently tends to benefit generalization at some cost to adaptation (since the model cannot adapt as frequently or as strongly to any particular time step). We found that updating weights every 16 frames (or 0.64s) provided a decent trade-off between adaptation and generalization across models, tasks and datasets as shown in Tab. 2", + "bbox": [ + 75, + 554, + 467, + 688 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Constant learning rate helps adaptation. We tested a range of common learning rate schedules including constant, linear, cosine and exponential decay, \"1cycle\" and cosine decay with restarts. The main finding was that decaying learning rates over the course of training, in particular cosine decay with exponent 2.0, helps generalization but significantly hurts adaptation as shown in Fig. 7. We therefore used a constant learning rate, with a linear warmup period of 1k steps, in our experiments.", + "bbox": [ + 75, + 695, + 467, + 830 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Replay buffer batches can be small. We focus most of our exploration on the case without replay buffers, but did check what happens when we add a replay buffer to our very best setting - which slows the experiment down proportionally", + "bbox": [ + 75, + 839, + 467, + 900 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/f848979d72e5ebfbf0450ab72b44db2edf07a79ba542e12de62220d4b0e1d702.jpg", + "image_caption": [ + "Figure 6. ScanNet-stream segmentation task generalization results on the exact same out-of-stream clip after different number of hours of exposure to a same stream for 4 model runs. The models differ only by the length of the interval between weight updates / number of steps of gradient aggregation (horizontal axis). Models with less frequent updates tend to generalize better (rightmost column), whereas models with more frequent updates tend to have strong priors about which objects are currently in the scene, leading to hallucinations (leftmost 3 columns in this case)." + ], + "image_footnote": [], + "bbox": [ + 521, + 97, + 874, + 252 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/63354c70b32561b07faab4ee015c3e311b8b9f97db7333ec2d79dec09c79226c.jpg", + "image_caption": [ + "Figure 7. In-stream and out-of-stream results for a learning rate schedule using cosine decay with exponent 2.0 vs a constant learning rate (both with a linear warmup phase of 1k steps. The decaying learning rate is able to generalise more quickly but at a significant cost to adaptation." + ], + "image_footnote": [], + "bbox": [ + 501, + 391, + 887, + 484 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "to the batch size employed. Over 11 hours of wall-clock training on the ScanNet-stream segmentation task with prediction displacement of 1 time step, an experiment with a replay buffer containing 10,000 samples (circular writing, random reading) and batch size 4 reached mean IoU only $2\\%$ superior to a model trained without replay buffer. Batch size 16 did not improve over batch size 4 and we did not use replay buffers in any other experiments.", + "bbox": [ + 496, + 580, + 890, + 700 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Pretraining", + "text_level": 1, + "bbox": [ + 500, + 710, + 624, + 726 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For pretraining we did not learn from a single continuous stream, but instead formed big well-shuffled batches of 1024 clips using 8x8 slices of TPU-v5-lite, used AdamW and updated weights every step, for 150k steps. We pretrained on the Kinetics-700-2020 dataset [39], which is composed of 10s clips. We found that initializing with the ImageNet-MAE checkpoint led to much quicker optimization, so used that in all cases. More details can be found in the Appendix.", + "bbox": [ + 496, + 734, + 890, + 869 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We pretrained ViT-L models on the future prediction tasks from sec. 4 and monitored their representation learn", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "28756", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/e3bbe4d1c6fd96d08e484aa0c0ac5909b58e7581d6f8fd4cb69d9d63d971a8e1.jpg", + "table_caption": [ + "n steps per update" + ], + "table_footnote": [], + "table_body": "
Streamdatasetmodel141664
InEgo4D (↓)UNet.036.038.037.039
ViT.035.037.039.047
Segm (↑)UNet.420.292.211.195
ViT.457.395.302.232
Out-ofEgo4D (↓)UNet.095.051.047.042
ViT.076.062.046.044
Segm (↑)UNet.176.179.205.183
ViT.251.272.280.274
", + "bbox": [ + 80, + 102, + 462, + 229 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Results on video streams from two datasets, two models, different numbers of steps per gradient update (horizontal), and evaluated in-stream and out-of-stream, showing the impact of accumulating gradients over multiple steps. Results are averaged over 1 and 4 displacement steps. For Ego4D-stream we report average L2 pixelwise distance (lower is better), for ScanNet-stream Segm we report mean per-frame IoU (higher is better). Bold marks the best result for each model-stream pair.", + "bbox": [ + 75, + 231, + 468, + 342 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1951bd66df1e56a0cc3c094d20df48869584a5ab79203461d875009cd80e7c02.jpg", + "image_caption": [ + "Figure 8. Linear top-1 accuracy in Kinetics during pretraining for different forms of future prediction tasks: Vanilla, Guided, Masked, and different displacements. The longer the displacement the better the accuracy is. Note that this is an online evaluation where the model only sees 4 frames (that for \"Masked\" and \"Guided\" are distorted) hence performance is far below models evaluated on the whole 10s of video (250 frames), often with plenty of test time augmentation, but the relative performance between the various curves is informative." + ], + "image_footnote": [], + "bbox": [ + 80, + 348, + 462, + 436 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ing performance during training by adding a linear head to the model just before the decoder (we use a stack of 4 self-attention layers on top of the ViT-L encoder). For this monitoring, we employed a standard cross-entropy loss between logits and ground truth labels in conjunction with a stop-gradient so the supervision would not influence the backbone weights.", + "bbox": [ + 75, + 582, + 467, + 686 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We experimented with different input-target clip temporal displacements and observed the interesting effect that the longer the displacement the better the classification performance is as shown in Fig. 8, even for masked future prediction, which reduces to the popular Masked Autoencoding [16] when displacement is 0. Our experiments suggest that 0 may be a sub-optimal choice. For the longest displacement the best method for top-1 accuracy emerged as Guided Future Prediction. The top result shown in the plot also used fewer guiding patches, $5\\%$ instead of $10\\%$ - we used this best model for the rest of our evaluations. We show example video predictions for the various models online at https://sites.google.com/view/one-stream-video.", + "bbox": [ + 75, + 688, + 468, + 898 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 3 has results on in/out-of-stream evaluation, showing large benefits over ImageNet classification pretraining and using no pretraining (training from scratch). ImageNet-MAE also does considerably better than classification-based pretraining. The same ViT-L architecture was used in all cases.", + "bbox": [ + 496, + 90, + 890, + 180 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. IID vs Continuous Learning", + "text_level": 1, + "bbox": [ + 498, + 190, + 751, + 207 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We compare our best setup, which we call, for no particularly technical reason, \"Baby Learning\" (BL), to a standard deep learning setup (STDL). STDL uses AdamW with standard parameters (learning rate 1e-4, momentum b1 as 0.9), with weight updates after each batch, the same ViT-L model but with the popular ImageNet MAE checkpoint. We implement the IID setting by sampling a sequence of random time steps (and associated target time steps) from random videos of the same base dataset. Note that while most approaches employ large batches, SGD with mini-batch size 1 is well known to work well [25] and is even said to generalize better than using large batches. We match the number of frames that each method sees – namely for batch size $>1$ , the total number of learning steps is reduced proportionally.", + "bbox": [ + 496, + 213, + 890, + 425 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Dummy baseline. For reference, we also include a dummy blind baseline, proposed in previous online learning works [15], which exploits the temporal correlations in the target stream without seeing the input frames at all: this \"model\" outputs the mean of the previously seen pixels at the same locations for depth and pixel, and the most frequent colors for segmentation, for the previous target. It produces random performance for out-of-stream evaluation where consecutive targets are unrelated2.", + "bbox": [ + 496, + 431, + 890, + 566 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results on all tasks are shown in Table 4. We show visual results of a subset of these tasks in Fig. 9. It is visible that our approach BL matches STDL with batch size 1 out-of-stream while outperforming it in-stream. In fig. 11 in the Appendix we also report results for STDL on a continuous stream, which does not work at all, and for BL on an IID stream which does best – this shows that there are still many more improvements possible for learning from continuous streams.", + "bbox": [ + 496, + 574, + 890, + 709 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 723, + 617, + 738 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We have presented a different perspective on continual learning by defining prediction tasks on a single very long stream of video and by proposing evaluations that measure both adaptation and generalization. We show that there is a permanent tension between the two aspects, but that it is possible to improve both by specializing the optimizer (lowering momentum, increasing the number of gradient", + "bbox": [ + 496, + 750, + 890, + 854 + ], + "page_idx": 6 + }, + { + "type": "page_footnote", + "text": "Another baseline that may be of interest is one that copies the previous input frames instead of target frames – this could do well for both train and eval for pixels, but poorly for segmentation and depth", + "bbox": [ + 500, + 862, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "28757", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/cfae13538cdb93e33d454dd3fe82d31ab15699d79c6be6435a14bded7d2a42d6.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Pretraining CheckpointEgo4D (↓)ScanNet Depth (↓)ScanNet Segm (↑)ScanNet (↓)
None.074 / .1051.969 / 2.163.177 / .188.083 / .083
ViT-L-I1K-CLS.043 / .0481.821 / 2.040.288 / .234.040 / .042
ViT-L-I21K-CLS.042 / .0481.735 / 2.013.244 / .192.039 / .040
ViT-L-I1K-MAE.040 / .0441.806 / 2.045.360 / .320.037 / .038
Guided Future Prediction.036 / .0431.622 / 1.990.390 / .313.032 / .034
", + "bbox": [ + 181, + 88, + 784, + 175 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/434eeaeb60a31837e7295faa927699a6c34eea83750125c914dbe24b125993af.jpg", + "image_caption": [ + "Figure 9. Future prediction results for video streams from Ego4D-stream, ScanNet-stream Segm, and ScanNet-stream Depth." + ], + "image_footnote": [], + "bbox": [ + 138, + 227, + 831, + 402 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/1abdd9cbbb944f5917515ca2242724f44b139c3153d431e54a1c4228514d432e.jpg", + "table_caption": [ + "Table 3. Table comparing performance of models pretrained on ImageNet-1K and 21K using MAE or classification, and models pretrained on our video tasks in Kinetics. The results are averaged over two sets of experiments, with displacements of 1 and 4 time steps and are shown in the format in-stream / out-of-stream." + ], + "table_footnote": [], + "table_body": "
Ego4D (↓)ScanNet (↓)ScanNet Segm (↑)ScanNet Depth (↓)
displacement (Δ)t+1t+4t+1t+4t+1t+4t+1t+4
STDL (IID) bs 16.023/.019.060/.055.014/.013.042/.061.495/.398.382/.2951.798/2.011.838/2.038
STDL (IID) bs 1.019/.018.057/.056.010/.013.051/.060.376/.302.276/.2271.722/2.0121.759/2.034
BL (Cont.) bs 1.018/.021.055/.066.011/.012.055/.061.463/.312.328/.2411.595/2.0381.655/2.097
Blind (dummy).038 / -.086 / -.032/ -.109/ -.547/ -.307/ -1.256 / -1.649 / -
", + "bbox": [ + 104, + 430, + 864, + 518 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4. Future prediction results for video streams from various datasets for two different temporal displacements (horizontal). We show results for the standard deep learning approach (STDL) on IID data with batch size 16 and 1, and for our approach (BL) when using a continuous video stream (Cont.). Two numbers are reported for every cell, corresponding to in-stream / out-of-stream performance. We highlight which of the two batch size 1 approaches performs best for each number. The Blind (dummy) model exploits correlations in the target stream which is available in-stream and used for learning, hence performs very well in-stream, but has random performance in evaluation where the target stream is not available. This shows the necessity to measure both adaptation and generalization performance.", + "bbox": [ + 75, + 529, + 893, + 612 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "aggregation steps between weight updates) and by pretraining the model appropriately. Conversely, we show that just using Adam with default parameters performs poorly on single-stream learning, due to the large correlations in the data. This makes the proposed setting different from popular ImageNet-based continual learning setups where batches are employed, and the data is significantly uncorrelated - for example in class-by-class learning, seeing different web images of dogs will not break Adam the way consecutive frames in a video does.", + "bbox": [ + 75, + 638, + 468, + 789 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We admit that the motivation for the research direction laid out in this paper may not be immediately crystal clear to everyone, particularly in the context of the current research landscape, that focuses on fitting larger and larger models to the whole internet. We are motivated by a possible future where people have their models in physical devices they carry around and train them via natural interac-", + "bbox": [ + 75, + 795, + 470, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "tion – by showing them the world from their perspective – and teach them only the things that they believe the models should be taught, similar to the way we teach children. It is likely that such models, by not having to know everything, can be smaller, more efficient, have fewer internet biases and be more privacy-friendly.", + "bbox": [ + 496, + 638, + 890, + 731 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments. We would like to thank Ross Goroshin and Ali Eslami for reviewing the paper and providing helpful comments, and Razvan Pascanu and Simon Osindero for insightful advice and interesting pointers into the literature and background work.", + "bbox": [ + 496, + 739, + 890, + 821 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 500, + 847, + 596, + 863 + ], + "page_idx": 7 + }, + { + "type": "ref_text", + "text": "[1] Yuki M. Asano, Christian Rupprecht, and Andrea Vedaldi. A critical analysis of self-supervision, or what we can learn", + "bbox": [ + 506, + 872, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "28758", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "from a single image. In International Conference on Learning Representations, 2020. 3", + "[2] Daniel Bear, Kevin T. 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Label-efficient online continual object detection in streaming video, 2023. 2" + ], + "bbox": [ + 78, + 90, + 468, + 218 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "28761", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning from One Continuous Video Stream/a8db15d8-1180-483d-9687-c41b3735ca04_model.json b/2024/Learning from One Continuous Video Stream/a8db15d8-1180-483d-9687-c41b3735ca04_model.json new file mode 100644 index 0000000000000000000000000000000000000000..fce4a44d57c7adc8de16f8479435edb13b3f9d7b --- /dev/null +++ b/2024/Learning from One Continuous Video Stream/a8db15d8-1180-483d-9687-c41b3735ca04_model.json @@ -0,0 +1,2125 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.254, + 0.131, + 0.719, + 0.154 + ], + "angle": 0, + "content": "Learning from One Continuous Video Stream" + }, + { + "type": "text", + "bbox": [ + 0.131, + 0.18, + 0.838, + 0.234 + ], + "angle": 0, + "content": "João Carreira\\(^{1\\dagger}\\), Michael King\\(^{1\\dagger}\\), Viorica Pătrăucean\\(^{1\\dagger}\\), Dilara Gokay\\(^{1\\dagger}\\), Cătălin Ionescu\\(^{1\\dagger}\\), Yi Yang\\(^{\\dagger}\\), Daniel Zoran\\(^{\\dagger}\\), Joseph Heyward\\(^{\\dagger}\\), Carl Doersch\\(^{\\dagger}\\), Yusuf Aytar\\(^{\\dagger}\\), Dima Damen\\(^{\\dagger \\ddagger}\\), Andrew Zisserman\\(^{\\dagger \\diamond}\\)" + }, + { + "type": "text", + "bbox": [ + 0.275, + 0.236, + 0.692, + 0.27 + ], + "angle": 0, + "content": "\\(^{\\dagger}\\)Google DeepMind, \\(^{\\ddagger}\\)University of Bristol, \\(^{\\diamond}\\)University of Oxford Corresponding author: joaoluis@google.com, \\(^{\\dagger}\\)core contributor" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.305, + 0.314, + 0.321 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.339, + 0.474, + 0.685 + ], + "angle": 0, + "content": "We introduce a framework for online learning from a single continuous video stream – the way people and animals learn, without mini-batches, data augmentation or shuffling. This poses great challenges given the high correlation between consecutive video frames and there is very little prior work on it. Our framework allows us to do a first deep dive into the topic and includes a collection of streams and tasks composed from two existing video datasets, plus methodology for performance evaluation that considers both adaptation and generalization. We employ pixel-to-pixel modelling as a practical and flexible way to switch between pre-training and single-stream evaluation as well as between arbitrary tasks, without ever requiring changes to models and always using the same pixel loss. Equipped with this framework we obtained large single-stream learning gains from pre-training with a novel family of future prediction tasks, found that momentum hurts, and that the pace of weight updates matters. The combination of these insights leads to matching the performance of IID learning with batch size 1, when using the same architecture and without costly replay buffers. An overview of the paper is available online at https://sites.google.com/view/one-stream-video." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.722, + 0.21, + 0.737 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Humans gather knowledge about themselves and the world through a continuous stream of observations, from their early days as infants. Some experiences are seen once in a lifetime while others are daily repeats. With time, familiarity with environments, objects and experiences form a base to our knowledge, and memory maintains the most important experiences from our ever-further past. Learning successfully adapts to the current surroundings so we can make better predictions over time, while leading to generalization to unseen environments. Despite the naturalness" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.306, + 0.892, + 0.339 + ], + "angle": 0, + "content": "of this approach of learning for humans, video understanding approaches have rarely attempted a similar regime." + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.353, + 0.891, + 0.477 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.483, + 0.891, + 0.64 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.65, + 0.892, + 0.832 + ], + "angle": 0, + "content": "Figure 1. Top: We introduce a framework for studying continuous learning in a single video stream. This is a natural yet unstudied problem, different from standard independent and identically distributed (IID) learning in video where batches contain clips from random videos in a random order. Bottom: We propose pixel-to-pixel models to evaluate our approach across prediction tasks (prediction of future frames, depth, segmentation). We measure both adaptation to the video stream – the model here updates its weights (learns) continuously to improve prediction – as well as generalization to out-of-stream clips – the model being adapted on the first stream is now evaluated on a different held-out stream without being allowed to adapt to it. We propose to maximize both adaptation and generalization." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.84, + 0.894, + 0.901 + ], + "angle": 0, + "content": "The most related fields are continual and lifelong learning, but these are still deeply fractured – no single problem formulation or benchmark is widely accepted. They also mostly focus on simplifications of the problem relative to" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "28751" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.089, + 0.27, + 0.186 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.274, + 0.089, + 0.462, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.189, + 0.47, + 0.274 + ], + "angle": 0, + "content": "Figure 2. UNet training on ScanNet-stream for the semantic segmentation task. Left: The cosine similarity of consecutive gradients is normally distributed when training on IID data, but shows very strong correlations when training on a continuous video stream. Right: This is reflected in poor training performance. See the appendix for similar figures for Ego4D-stream." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.287, + 0.469, + 0.332 + ], + "angle": 0, + "content": "human and animal experience, for example a popular task is learning one ImageNet class at a time and minimizing forgetting of previous classes [38]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.333, + 0.469, + 0.56 + ], + "angle": 0, + "content": "But what happens if we attempt to learn continuously from a single video stream (Figure 1), meaning batch size 1 and high frame rate (e.g. 25 fps)? We do not see thousands of dogs per second, unlike the standard ImageNet setting, where images of even a same dog breed are quite uncorrelated at several scales – capturing a wide diversity of edges, textures, etc. Standard deep learning approaches lead to smooth optimization there, but it is very different from the setting of learning from a single video stream, where things happen slowly, at much longer timescales, with great correlation or even no change between frames for periods of time; see Figure 2. Do standard deep learning tools work in this setting? This is currently unknown territory, with very few attempts touching it at all [33] – and it is the focus of this paper." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.561, + 0.47, + 0.651 + ], + "angle": 0, + "content": "We are interested in this problem because models should be able to adapt after deployment to their environment, hence receiving a single stream of information. This is needed for embodied intelligence (robotics), but also for any type of digital assistant that we would want to be able to adapt to a specific user's needs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.656, + 0.469, + 0.761 + ], + "angle": 0, + "content": "A framework. We lay out a framework for learning from a single video stream, focusing on the entry-level problem of ... learning. Nevermind forgetting, can the models even learn in the first place? We study how successful learning is for different optimization settings, models, pretraining methods and tasks, when done from a single continuous stream. Our methodology follows the following principles:" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.765, + 0.469, + 0.886 + ], + "angle": 0, + "content": "- We consider future prediction tasks including pixels-to-pixels, pixels-to-segmentation and pixels-to-depth, all in RGB space (i.e. outputs are always 3 dimensional and with the same shape as the input frames). This way we do not need to change any parameter in the model between pretraining and single-stream learning, independently of what tasks are used in each. It enables using a simple L2 loss between pixel values in all cases." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.887, + 0.469, + 0.902 + ], + "angle": 0, + "content": "- We evaluate performance in two ways - in-stream, and" + }, + { + "type": "list", + "bbox": [ + 0.077, + 0.765, + 0.469, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.512, + 0.092, + 0.892, + 0.243 + ], + "angle": 0, + "content": "out-of-stream. In-stream measures performance on the input video stream. For sufficiently difficult prediction tasks this should be enough. However, it conflates representation quality with adaptation to the scene, lighting condition, etc. For example if the lights in a scene are turned off for an hour, a model can learn to always predict black pixels – which is not ideal. To disentangle adaptation and generalization, we also evaluate out-of-stream, on a second stream on which the model does not learn. We propose to maximize both." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.25, + 0.891, + 0.281 + ], + "angle": 0, + "content": "Contributions. With this methodology in place, we identified the following new results:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.282, + 0.891, + 0.354 + ], + "angle": 0, + "content": "- On the optimization front, we observe that momentum, widely used in popular optimizers such as Adam, is unhelpful in highly correlated video streams. Instead methods without momentum such as RMSprop are more robust." + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.357, + 0.891, + 0.401 + ], + "angle": 0, + "content": "- Another result is a trade-off between adaptation and generalization induced by frequency of weight updates - slower leads to better generalization." + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.403, + 0.891, + 0.478 + ], + "angle": 0, + "content": "- We introduce a family of future prediction pretraining tasks, learnt in the standard independent and identically distributed (IID) setting, with large batches, and show that these lead to better single-stream performance compared to existing ImageNet pretraining tasks." + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.479, + 0.891, + 0.597 + ], + "angle": 0, + "content": "- We combine these results into a combo approach that we call Baby Learning (BL), and compare it to a standard deep learning setup (STDL) that uses Adam and ImageNet MAE pretraining. We show that BL on a sequential stream matches STDL on out-of-stream generalization when that same stream is permuted to be IID, while achieving better performance in-stream thanks to adaptation." + }, + { + "type": "list", + "bbox": [ + 0.501, + 0.282, + 0.891, + 0.597 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.615, + 0.637, + 0.63 + ], + "angle": 0, + "content": "2. Related work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Online learning from a single video stream. One of the few papers dealing with this problem [33] proposed a minimum-redundancy \"replay\" buffer [27] to deal with temporal correlations. Replay buffers are not the sexiest research avenue for continual learning [41] and increase computation proportionally to the size of the buffer used. Additionally, in [33] performance on the video streams itself was never evaluated, only on unrelated image classification tasks. Test-time training is the next closest problem, such as presented in TTTVS [45] (also related [48]). TTVS's motivation is to \"improve inference quality\" by leveraging self-supervised test-time optimization. Our motivation is to propose single-stream learning, which is reflected in much longer streams (24h in this paper, compared to seconds or few minutes). One challenge in single-stream learning is how to fully exploit available hardware parallelism in a batch size 1 setting [6, 23, 24]." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28752" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.198 + ], + "angle": 0, + "content": "Learning from a single video. Also relevant are experiments training ConvNets [21] or ViTs [8] on a single image [1] or a long video [43]. While outside of the streaming setting – using data shuffling, augmentation and large batches, these papers showed that learning can be quite successful in this setting (especially for the shallower layers), which was quite encouraging." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.201, + 0.471, + 0.367 + ], + "angle": 0, + "content": "Continual learning. The continual learning literature (e.g. EWC [19]) tends to focus on learning a sequence of tasks, the goal being to learn new tasks as fast as possible without forgetting previous ones, such as in class incremental learning (e.g. iCarl [36]) and CLEAR [22]. Most relevant is online continual learning, where models learn from a stream of data, visited once. One challenge is model cheating by exploiting labels in the data [15], or by learning spurious features [46] that have limited generalisation power. Most of the work in this area has been on collections of images, rather than video." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.371, + 0.471, + 0.522 + ], + "angle": 0, + "content": "Representation learning to the rescue. Recent continual learning papers reported that some of the challenges of the problem are partially mitigated by using features pretrained in IID settings [26, 35, 44]. Various pretraining strategies exist: self-distillation (e.g. BYOL [13], BRaVe [37], DINO [4]), contrastive (CLIP [34], VideoMoco [28], VITO [30]), and masked auto-encoding (e.g. VideoMAE [42], TubeViT [31], AudioVisualMAE [11], SiameseMAE [14], [2]). We investigate this aspect in our setup." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.537, + 0.24, + 0.552 + ], + "angle": 0, + "content": "3. The Framework" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.565, + 0.47, + 0.763 + ], + "angle": 0, + "content": "Overview. The following is repeated throughout a video stream: a (potentially pretrained) model processes \\( n \\) frames (a time step) from an input video stream, and predicts frames for a future time step. Online (in-stream) performance metrics as well as an L2 loss function are then recorded by comparing predicted and target frames. Given the loss, gradients are computed and the model weights are updated by an optimizer. The target frames can come from the input stream itself or from an associated stream (e.g. for datasets having semantic segmentation or depth). In parallel with in-stream evaluation, we periodically assess performance on a held-out stream (composed of clips from the validation set of the dataset), to assess generalization." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.771, + 0.357, + 0.789 + ], + "angle": 0, + "content": "3.1. Unified pixel-to-pixel modelling" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.47, + 0.903 + ], + "angle": 0, + "content": "We are interested in having a framework where switching between arbitrary tasks requires no changes to models or losses so we can abstract away decoder nd loss function design (large research areas) and focus on the single-stream learning aspect. To achieve this we map all task target outputs to RGB space, so we can have a single pixel-to-pixel model and a single simple L2 pixel loss." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.379 + ], + "angle": 0, + "content": "Models. We use 2 different popular backbones for our experiments: a UNet with self-attention in the bottleneck layer [17] and ViT-L [8]. To enable motion understanding, which is important for future prediction, we feed the models \\( n = 4 \\) consecutive frames stacked along the channel dimension. We also have the models predict the same number of frames, so 12 channels in total (4 frames times 3 channels, for RGB). For ViT we decode tokens to pixels using a channel to space transformation: each token gets mapped to an appropriate number of channels using a linear transformation, then gets reshaped into a patch (e.g. a 16x16 grid of 4x3 RGB channels). We provide details of the models in the Appendix, but it is worth noting that the UNet is considerably smaller at 8M parameters, compared to the 350M parameters of the ViT model. We always train the UNet from scratch, whereas we explore various pretraining schemes for ViT. To accommodate for the 12 input channels we use, we inflate [5] the first layer of the ViT (replicate the pretrained weights 4 times)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.382, + 0.892, + 0.503 + ], + "angle": 0, + "content": "Memory. We did not explore explicit memory modules such as memory banks, LSTM cells, or long context in this paper, but we do think it should be very relevant going forward. In all cases, the model \"sees\" only a time step of frames and predicts another time step. Note however that the model weights are updated as it goes through the video stream - so both the weights and the optimizer (when stateful) provide some memory effects." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.504, + 0.892, + 0.595 + ], + "angle": 0, + "content": "Replay buffer. We explored replay buffers [27], which keep a large cache of previous examples, then form batches by sampling from it. They have the disadvantage of increasing computational cost significantly over operating with batch size 1 (increases the theoretical computational cost of learning \\( K \\) times, where \\( K \\) is the batch size)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.606, + 0.722, + 0.621 + ], + "angle": 0, + "content": "3.2. Video streams and tasks" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.63, + 0.892, + 0.75 + ], + "angle": 0, + "content": "We do not know of public datasets having very long video streams, for example days-long and beyond1, so we create two different video streams: Ego4D-stream and ScanNet-stream, by concatenating videos from, respectively, Ego4D and ScanNet. We include Ego4D as it is large and has very long videos, and ScanNet because it has dense semantic segmentation and depth annotations, allowing us to experiment with different tasks." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.755, + 0.892, + 0.876 + ], + "angle": 0, + "content": "Ego4D-stream. We concatenate the raw (un-trimmed) videos from the Ego4D dataset [12] to create a very long video stream. We use \\(\\sim 90\\%\\) of the data to generate a training stream and \\(\\sim 10\\%\\) for the validation stream. The videos in Ego4D were collected using a head or glass mounted camera, capturing activities of daily life. We use this stream for learning and evaluating future prediction in pixel space – no annotations are employed. See Table 1 for more details." + }, + { + "type": "page_footnote", + "bbox": [ + 0.518, + 0.887, + 0.831, + 0.901 + ], + "angle": 0, + "content": "1Other than Krishnacam [20], which is only 70 hours long." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28753" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.133, + 0.089, + 0.835, + 0.134 + ], + "angle": 0, + "content": "
Stream name# videos train# frames train# videos val# frames valMax. lengthMedian length
Ego4D-stream21,704294M (3,265h)230231M (348h)1.95h8.8 minutes
ScanNet-stream1,1991.8M (20h)3120.5M (5.7h)5.5 minutes1 minute
" + }, + { + "type": "table_caption", + "bbox": [ + 0.108, + 0.138, + 0.86, + 0.152 + ], + "angle": 0, + "content": "Table 1. The two streams we consider, formed out of Ego4D and ScanNet, together with properties of their original video clips." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.179, + 0.471, + 0.315 + ], + "angle": 0, + "content": "ScanNet-stream. We use the videos from ScanNetV2 [7] to define 3 different prediction tasks, of pixels, semantic segmentation labels (40 classes) and depth. The availability of these additional target streams makes it possible for us to measure more explicitly higher-level understanding, which may not be clear from pixel prediction alone. The videos in this dataset were filmed with a camera navigating indoor scenes with one or more rooms. See Table 1 for more details." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.319, + 0.47, + 0.485 + ], + "angle": 0, + "content": "Tasks. Overall we consider the following tasks across the two stream types: Ego4D-stream pixel prediction, ScanNetstream pixel, semantic segmentation and depth prediction. The difficulty of most of these tasks can be controlled using a time displacement parameter \\(\\Delta\\) - how many steps in advance should the models predict. We consider 0, 1, and 4 time steps. A displacement of 0 only makes sense for semantic tasks as otherwise it corresponds to auto-encoding, which is easy. Note that this task is related to the near-future accuracy metric proposed in [15] to measure (forward transfer) adaptation in a more robust way." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.489, + 0.471, + 0.655 + ], + "angle": 0, + "content": "RGB-fication. There is some hand design involved in mapping tasks into RGB space. For depth and semantic segmentation we use standard color maps typical for those tasks in ScanNet: the Viridis color map and the ScanNet label color map, respectively. We provide details of these mappings in the Appendix. For computing metrics other than the L2 pixel distance, we compute the nearest neighbor label / depth for each pixel color (e.g. a pixel's color may not correspond exactly to one of the semantic segmentation labels, so we assume the predicted class is the label associated with the nearest color on the color map)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.666, + 0.197, + 0.68 + ], + "angle": 0, + "content": "3.3. Evaluation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Learning a video stream task with a continuously updated model can be seen to decompose into: 1) discovering strong features that are general, for example learning that certain configuration of edges correspond to chair legs for semantic segmentation (generalization), which is likely to happen over long timescales. 2) by specializing to the particular scene being seen in the video, e.g. learning that the chair is the only red object in the scene and using redness to label the chair pixels (adaptation), which can happen over short timescales. Adaptation can be quite useful and lead to efficient visual mechanisms, but may not necessarily lead to generalization. Dummy models that only e.g. exploit temporal correlations in the target stream could misleadingly appear to perform very well [15]; see Table 4, Blind model." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.179, + 0.892, + 0.299 + ], + "angle": 0, + "content": "We propose to evaluate both aspects by computing a score continuously in-stream, on the video stream task the model is learning from, to measure adaptation. Separately and periodically we compute the same score out-of-stream, on a held-out stream with the optimizer disabled (out-of-stream). We use the training sets of Ego4D and ScanNet to do in-stream evaluation, and the validation sets for out-of-stream evaluation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.304, + 0.893, + 0.486 + ], + "angle": 0, + "content": "Cumulative scores. Comparing single-stream learning models and approaches can be difficult if done naively. On the training stream, difficulty of the task may vary over time, for example certain parts of a stream may be more unpredictable due to camera motion or other factors, leading to natural oscillations. On the generalization side we care not just about performance at a particular moment in time, but also how fast it ramps up as training on the sequential video stream progresses. With this in mind, we use a global score over the whole stream – we do this by averaging the performance over 10,000 evenly-spaced points interpolated from the steps in both in-stream and out-of-stream settings." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.49, + 0.892, + 0.595 + ], + "angle": 0, + "content": "Task-specific evaluation. We evaluate pixel prediction with average L2 pixelwise distance, the same that we use as loss for training. For semantic segmentation we use mean per-frame IoU and recall [3, 32] and depth using log relative mean square error (logRMSE) [9]. For both segmentation and depth we mask out pixels that were not annotated from the evaluation and loss." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.613, + 0.78, + 0.629 + ], + "angle": 0, + "content": "4. Generalized Future Prediction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.639, + 0.892, + 0.791 + ], + "angle": 0, + "content": "One of the most promising directions for continual learning, as identified in prior work, is representation learning. We are particularly interested in pixel-to-pixel approaches keeping consistent with the overall proposed framework where we never change neither the architecture nor the loss. We propose a family of pretraining methods that generalize future video prediction [40], and that follow a same pattern: given one input video clip the model is trained to predict a future clip from the same video (both clips are 4 frames long). We consider three variants, illustrated in Fig. 3:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.795, + 0.892, + 0.854 + ], + "angle": 0, + "content": "- The easiest one, Guided future prediction, replaces a few patches from the input clip with patches in the same position from the future clip, hence narrowing down the range of possibilities." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.856, + 0.891, + 0.885 + ], + "angle": 0, + "content": "- The intermediate one, Vanilla future prediction is just the standard task of predicting the future." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.886, + 0.891, + 0.9 + ], + "angle": 0, + "content": "- Masked future prediction is a variation of Masked Auto" + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.795, + 0.892, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28754" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.086, + 0.339, + 0.32 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.349, + 0.087, + 0.615, + 0.32 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.631, + 0.087, + 0.895, + 0.32 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.326, + 0.895, + 0.37 + ], + "angle": 0, + "content": "Figure 3. Video pretraining tasks we consider, sorted from easiest to hardest, left to right - guided future prediction, vanilla future prediction, and masked future prediction. Each column shows 4 consecutive frames vertically. For each method we show left-to-right: input frames, predictions from the model, target frames. We use a displacement \\((\\Delta)\\) of 16 frames (0.64s) between input and target clips." + }, + { + "type": "text", + "bbox": [ + 0.09, + 0.385, + 0.471, + 0.414 + ], + "angle": 0, + "content": "Encoding where the model must predict the future clip based on a partial view of the current clip." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.417, + 0.47, + 0.524 + ], + "angle": 0, + "content": "Guided future prediction is related to Siamese MAE [2, 14, 47], but simpler, requiring a single forward pass over one model. Masked future prediction is related to video MAE-type approaches [10, 42] but with a strict separation between disjoint input and output clips, whereas in traditional video MAE there is a single clip that gets uniformly corrupted as part of denoising auto-encoding." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.527, + 0.471, + 0.648 + ], + "angle": 0, + "content": "Hyperparameters. There are two hyperparameters: the fraction of guiding patches / masked patches and the shape of these patches (we use a constant square shape in all experiments). Vanilla future prediction is a special case of the other two in the case where there is no masked nor guiding patches. A general way to increase the difficulty of any of the variants is to increase the displacement \\((\\Delta)\\) between the input and the target clips." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.661, + 0.165, + 0.677 + ], + "angle": 0, + "content": "5. Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.687, + 0.47, + 0.776 + ], + "angle": 0, + "content": "Our goal is to achieve similar (or better) learning efficiency from a single continuous video stream as we expect from the standard deep learning setting - using sequences of batches of well shuffled examples. Here is a summary of the main results of our experiments on learning from a continuous video stream:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.781, + 0.468, + 0.81 + ], + "angle": 0, + "content": "- Momentum, widely used in optimizers such as Adam, hurts performance in single-stream learning." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.811, + 0.468, + 0.841 + ], + "angle": 0, + "content": "- Less frequent weight updates (e.g. every 2.5 seconds), helps generalization while sacrificing some adaptation." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.841, + 0.468, + 0.902 + ], + "angle": 0, + "content": "- Pretraining the models on IID data before single-stream learning is quite impactful. While popular ImageNet-based pretraining helps, we found future-prediction based video pretraining to be vastly superior." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.781, + 0.468, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.506, + 0.386, + 0.887, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.506, + 0.893, + 0.562 + ], + "angle": 0, + "content": "Figure 4. A sweep over commonly used optimizers. Those without momentum are shown in blue and aid the models adaptability considerably compared to the more commonly used Adam variants, which are shown in red." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.579, + 0.894, + 0.639 + ], + "angle": 0, + "content": "We ran all in-stream learning for 24 hours of video, and measured out-of-stream performance from regularly saved checkpoints on 3h30 of video. Resolution was always \\(224 \\times 224\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.65, + 0.64, + 0.667 + ], + "angle": 0, + "content": "5.1. Optimization" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.674, + 0.893, + 0.854 + ], + "angle": 0, + "content": "Starting from the standard optimizer used in nearly all deep learning setups, Adam, we observed that it does not train well with default parameters in the continuous video stream setting compared to the IID setting; see Fig. 2, right. To understand the differences between the two settings, we analyzed the temporal correlation between consecutive gradients. We found that the norm and variance of the gradients do not reveal strong differences. However, their orientation reveals strong correlations between pairs of consecutive gradients in the continuous case; see Fig. 2, left, where we plot the distribution of the cosine similarity between consecutive gradients in the continuous vs IID case." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.856, + 0.894, + 0.902 + ], + "angle": 0, + "content": "To investigate the optimization further we performed a large sweep over commonly used optimizers, shown in Fig. 4. Results are averaged over 8 settings: 2 tasks" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "28755" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.092, + 0.462, + 0.257 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.259, + 0.47, + 0.288 + ], + "angle": 0, + "content": "Figure 5. Reducing momentum with the AdamW optimizer helps to recover some of the performance of RMSProp." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.317, + 0.468, + 0.378 + ], + "angle": 0, + "content": "(Ego4D-stream and ScanNet-stream segmentation prediction), 2 models (ViT and UNet) and 2 displacements (1 step and 4 steps). RMS Prop significantly outperformed the more commonly used Adam variants." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.383, + 0.468, + 0.549 + ], + "angle": 0, + "content": "Momentum hurts. To scrutinize the difference between AdamW and RMSProp, we looked at the impact of momentum. We found that lowering the momentum of the AdamW optimizer recovered some of the performance of RMSProp (as shown in Fig. 5). One possible explanation is that momentum exacerbates the problem of correlated consecutive gradients (that differ from the underlying gradient of the loss function over the whole stream) and makes the weights accelerate too much in the wrong direction. We stick with RMSProp for the rest of the paper, as it is more memory efficient due to not using the average of past gradients." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.555, + 0.468, + 0.689 + ], + "angle": 0, + "content": "Infrequent weight updates help generalization, hurt adaptation. We also observed an interesting effect associated to the frequency of weight updates: doing it less frequently tends to benefit generalization at some cost to adaptation (since the model cannot adapt as frequently or as strongly to any particular time step). We found that updating weights every 16 frames (or 0.64s) provided a decent trade-off between adaptation and generalization across models, tasks and datasets as shown in Tab. 2" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.696, + 0.468, + 0.831 + ], + "angle": 0, + "content": "Constant learning rate helps adaptation. We tested a range of common learning rate schedules including constant, linear, cosine and exponential decay, \"1cycle\" and cosine decay with restarts. The main finding was that decaying learning rates over the course of training, in particular cosine decay with exponent 2.0, helps generalization but significantly hurts adaptation as shown in Fig. 7. We therefore used a constant learning rate, with a linear warmup period of 1k steps, in our experiments." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Replay buffer batches can be small. We focus most of our exploration on the case without replay buffers, but did check what happens when we add a replay buffer to our very best setting - which slows the experiment down proportionally" + }, + { + "type": "image", + "bbox": [ + 0.522, + 0.098, + 0.875, + 0.253 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.262, + 0.892, + 0.387 + ], + "angle": 0, + "content": "Figure 6. ScanNet-stream segmentation task generalization results on the exact same out-of-stream clip after different number of hours of exposure to a same stream for 4 model runs. The models differ only by the length of the interval between weight updates / number of steps of gradient aggregation (horizontal axis). Models with less frequent updates tend to generalize better (rightmost column), whereas models with more frequent updates tend to have strong priors about which objects are currently in the scene, leading to hallucinations (leftmost 3 columns in this case)." + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.392, + 0.888, + 0.485 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.491, + 0.892, + 0.561 + ], + "angle": 0, + "content": "Figure 7. In-stream and out-of-stream results for a learning rate schedule using cosine decay with exponent 2.0 vs a constant learning rate (both with a linear warmup phase of 1k steps. The decaying learning rate is able to generalise more quickly but at a significant cost to adaptation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.581, + 0.892, + 0.701 + ], + "angle": 0, + "content": "to the batch size employed. Over 11 hours of wall-clock training on the ScanNet-stream segmentation task with prediction displacement of 1 time step, an experiment with a replay buffer containing 10,000 samples (circular writing, random reading) and batch size 4 reached mean IoU only \\(2\\%\\) superior to a model trained without replay buffer. Batch size 16 did not improve over batch size 4 and we did not use replay buffers in any other experiments." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.711, + 0.625, + 0.727 + ], + "angle": 0, + "content": "5.2. Pretraining" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.87 + ], + "angle": 0, + "content": "For pretraining we did not learn from a single continuous stream, but instead formed big well-shuffled batches of 1024 clips using 8x8 slices of TPU-v5-lite, used AdamW and updated weights every step, for 150k steps. We pretrained on the Kinetics-700-2020 dataset [39], which is composed of 10s clips. We found that initializing with the ImageNet-MAE checkpoint led to much quicker optimization, so used that in all cases. More details can be found in the Appendix." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We pretrained ViT-L models on the future prediction tasks from sec. 4 and monitored their representation learn" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28756" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.318, + 0.091, + 0.426, + 0.103 + ], + "angle": 0, + "content": "n steps per update" + }, + { + "type": "table", + "bbox": [ + 0.081, + 0.103, + 0.464, + 0.23 + ], + "angle": 0, + "content": "
Streamdatasetmodel141664
InEgo4D (↓)UNet.036.038.037.039
ViT.035.037.039.047
Segm (↑)UNet.420.292.211.195
ViT.457.395.302.232
Out-ofEgo4D (↓)UNet.095.051.047.042
ViT.076.062.046.044
Segm (↑)UNet.176.179.205.183
ViT.251.272.280.274
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.232, + 0.469, + 0.343 + ], + "angle": 0, + "content": "Table 2. Results on video streams from two datasets, two models, different numbers of steps per gradient update (horizontal), and evaluated in-stream and out-of-stream, showing the impact of accumulating gradients over multiple steps. Results are averaged over 1 and 4 displacement steps. For Ego4D-stream we report average L2 pixelwise distance (lower is better), for ScanNet-stream Segm we report mean per-frame IoU (higher is better). Bold marks the best result for each model-stream pair." + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.349, + 0.464, + 0.438 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.444, + 0.469, + 0.567 + ], + "angle": 0, + "content": "Figure 8. Linear top-1 accuracy in Kinetics during pretraining for different forms of future prediction tasks: Vanilla, Guided, Masked, and different displacements. The longer the displacement the better the accuracy is. Note that this is an online evaluation where the model only sees 4 frames (that for \"Masked\" and \"Guided\" are distorted) hence performance is far below models evaluated on the whole 10s of video (250 frames), often with plenty of test time augmentation, but the relative performance between the various curves is informative." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.583, + 0.468, + 0.688 + ], + "angle": 0, + "content": "ing performance during training by adding a linear head to the model just before the decoder (we use a stack of 4 self-attention layers on top of the ViT-L encoder). For this monitoring, we employed a standard cross-entropy loss between logits and ground truth labels in conjunction with a stop-gradient so the supervision would not influence the backbone weights." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.469, + 0.9 + ], + "angle": 0, + "content": "We experimented with different input-target clip temporal displacements and observed the interesting effect that the longer the displacement the better the classification performance is as shown in Fig. 8, even for masked future prediction, which reduces to the popular Masked Autoencoding [16] when displacement is 0. Our experiments suggest that 0 may be a sub-optimal choice. For the longest displacement the best method for top-1 accuracy emerged as Guided Future Prediction. The top result shown in the plot also used fewer guiding patches, \\(5\\%\\) instead of \\(10\\%\\) - we used this best model for the rest of our evaluations. We show example video predictions for the various models online at https://sites.google.com/view/one-stream-video." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.181 + ], + "angle": 0, + "content": "Table 3 has results on in/out-of-stream evaluation, showing large benefits over ImageNet classification pretraining and using no pretraining (training from scratch). ImageNet-MAE also does considerably better than classification-based pretraining. The same ViT-L architecture was used in all cases." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.191, + 0.753, + 0.208 + ], + "angle": 0, + "content": "5.3. IID vs Continuous Learning" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.214, + 0.892, + 0.426 + ], + "angle": 0, + "content": "We compare our best setup, which we call, for no particularly technical reason, \"Baby Learning\" (BL), to a standard deep learning setup (STDL). STDL uses AdamW with standard parameters (learning rate 1e-4, momentum b1 as 0.9), with weight updates after each batch, the same ViT-L model but with the popular ImageNet MAE checkpoint. We implement the IID setting by sampling a sequence of random time steps (and associated target time steps) from random videos of the same base dataset. Note that while most approaches employ large batches, SGD with mini-batch size 1 is well known to work well [25] and is even said to generalize better than using large batches. We match the number of frames that each method sees – namely for batch size \\(>1\\), the total number of learning steps is reduced proportionally." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.433, + 0.892, + 0.568 + ], + "angle": 0, + "content": "Dummy baseline. For reference, we also include a dummy blind baseline, proposed in previous online learning works [15], which exploits the temporal correlations in the target stream without seeing the input frames at all: this \"model\" outputs the mean of the previously seen pixels at the same locations for depth and pixel, and the most frequent colors for segmentation, for the previous target. It produces random performance for out-of-stream evaluation where consecutive targets are unrelated2." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.575, + 0.892, + 0.71 + ], + "angle": 0, + "content": "Results on all tasks are shown in Table 4. We show visual results of a subset of these tasks in Fig. 9. It is visible that our approach BL matches STDL with batch size 1 out-of-stream while outperforming it in-stream. In fig. 11 in the Appendix we also report results for STDL on a continuous stream, which does not work at all, and for BL on an IID stream which does best – this shows that there are still many more improvements possible for learning from continuous streams." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.724, + 0.618, + 0.739 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.855 + ], + "angle": 0, + "content": "We have presented a different perspective on continual learning by defining prediction tasks on a single very long stream of video and by proposing evaluations that measure both adaptation and generalization. We show that there is a permanent tension between the two aspects, but that it is possible to improve both by specializing the optimizer (lowering momentum, increasing the number of gradient" + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.863, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Another baseline that may be of interest is one that copies the previous input frames instead of target frames – this could do well for both train and eval for pixels, but poorly for segmentation and depth" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "28757" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.182, + 0.089, + 0.785, + 0.176 + ], + "angle": 0, + "content": "
Pretraining CheckpointEgo4D (↓)ScanNet Depth (↓)ScanNet Segm (↑)ScanNet (↓)
None.074 / .1051.969 / 2.163.177 / .188.083 / .083
ViT-L-I1K-CLS.043 / .0481.821 / 2.040.288 / .234.040 / .042
ViT-L-I21K-CLS.042 / .0481.735 / 2.013.244 / .192.039 / .040
ViT-L-I1K-MAE.040 / .0441.806 / 2.045.360 / .320.037 / .038
Guided Future Prediction.036 / .0431.622 / 1.990.390 / .313.032 / .034
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.178, + 0.893, + 0.218 + ], + "angle": 0, + "content": "Table 3. Table comparing performance of models pretrained on ImageNet-1K and 21K using MAE or classification, and models pretrained on our video tasks in Kinetics. The results are averaged over two sets of experiments, with displacements of 1 and 4 time steps and are shown in the format in-stream / out-of-stream." + }, + { + "type": "image", + "bbox": [ + 0.139, + 0.228, + 0.832, + 0.404 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.114, + 0.407, + 0.855, + 0.421 + ], + "angle": 0, + "content": "Figure 9. Future prediction results for video streams from Ego4D-stream, ScanNet-stream Segm, and ScanNet-stream Depth." + }, + { + "type": "table", + "bbox": [ + 0.106, + 0.431, + 0.865, + 0.52 + ], + "angle": 0, + "content": "
Ego4D (↓)ScanNet (↓)ScanNet Segm (↑)ScanNet Depth (↓)
displacement (Δ)t+1t+4t+1t+4t+1t+4t+1t+4
STDL (IID) bs 16.023/.019.060/.055.014/.013.042/.061.495/.398.382/.2951.798/2.011.838/2.038
STDL (IID) bs 1.019/.018.057/.056.010/.013.051/.060.376/.302.276/.2271.722/2.0121.759/2.034
BL (Cont.) bs 1.018/.021.055/.066.011/.012.055/.061.463/.312.328/.2411.595/2.0381.655/2.097
Blind (dummy).038 / -.086 / -.032/ -.109/ -.547/ -.307/ -1.256 / -1.649 / -
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.53, + 0.894, + 0.613 + ], + "angle": 0, + "content": "Table 4. Future prediction results for video streams from various datasets for two different temporal displacements (horizontal). We show results for the standard deep learning approach (STDL) on IID data with batch size 16 and 1, and for our approach (BL) when using a continuous video stream (Cont.). Two numbers are reported for every cell, corresponding to in-stream / out-of-stream performance. We highlight which of the two batch size 1 approaches performs best for each number. The Blind (dummy) model exploits correlations in the target stream which is available in-stream and used for learning, hence performs very well in-stream, but has random performance in evaluation where the target stream is not available. This shows the necessity to measure both adaptation and generalization performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.64, + 0.47, + 0.79 + ], + "angle": 0, + "content": "aggregation steps between weight updates) and by pretraining the model appropriately. Conversely, we show that just using Adam with default parameters performs poorly on single-stream learning, due to the large correlations in the data. This makes the proposed setting different from popular ImageNet-based continual learning setups where batches are employed, and the data is significantly uncorrelated - for example in class-by-class learning, seeing different web images of dogs will not break Adam the way consecutive frames in a video does." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.471, + 0.901 + ], + "angle": 0, + "content": "We admit that the motivation for the research direction laid out in this paper may not be immediately crystal clear to everyone, particularly in the context of the current research landscape, that focuses on fitting larger and larger models to the whole internet. We are motivated by a possible future where people have their models in physical devices they carry around and train them via natural interac-" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.64, + 0.892, + 0.732 + ], + "angle": 0, + "content": "tion – by showing them the world from their perspective – and teach them only the things that they believe the models should be taught, similar to the way we teach children. It is likely that such models, by not having to know everything, can be smaller, more efficient, have fewer internet biases and be more privacy-friendly." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.74, + 0.892, + 0.823 + ], + "angle": 0, + "content": "Acknowledgments. We would like to thank Ross Goroshin and Ali Eslami for reviewing the paper and providing helpful comments, and Razvan Pascanu and Simon Osindero for insightful advice and interesting pointers into the literature and background work." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.848, + 0.597, + 0.864 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.507, + 0.873, + 0.892, + 0.901 + ], + "angle": 0, + "content": "[1] Yuki M. Asano, Christian Rupprecht, and Andrea Vedaldi. A critical analysis of self-supervision, or what we can learn" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28758" + } + ], + [ + { + "type": "ref_text", + "bbox": [ + 0.109, + 0.093, + 0.468, + 0.12 + ], + "angle": 0, + "content": "from a single image. 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This poses great challenges given the high correlation between consecutive video frames and there is very little prior work on it. Our framework allows us to do a first deep dive into the topic and includes a collection of streams and tasks composed from two existing video datasets, plus methodology for performance evaluation that considers both adaptation and generalization. We employ pixel-to-pixel modelling as a practical and flexible way to switch between pre-training and single-stream evaluation as well as between arbitrary tasks, without ever requiring changes to models and always using the same pixel loss. Equipped with this framework we obtained large single-stream learning gains from pre-training with a novel family of future prediction tasks, found that momentum hurts, and that the pace of weight updates matters. The combination of these insights leads to matching the performance of IID learning with batch size 1, when using the same architecture and without costly replay buffers. An overview of the paper is available online at https://sites.google.com/view/one-stream-video. + +# 1. Introduction + +Humans gather knowledge about themselves and the world through a continuous stream of observations, from their early days as infants. Some experiences are seen once in a lifetime while others are daily repeats. With time, familiarity with environments, objects and experiences form a base to our knowledge, and memory maintains the most important experiences from our ever-further past. Learning successfully adapts to the current surroundings so we can make better predictions over time, while leading to generalization to unseen environments. Despite the naturalness + +of this approach of learning for humans, video understanding approaches have rarely attempted a similar regime. + +![](images/44982ffc8f8671dd0b3c2d63482cff3fce3657ef935af4c194e331224c065d91.jpg) + +![](images/2882fc0d6668fe4f405d65e88840838adbb4f78b24c9463bcaf8b5793dfb9e85.jpg) +Figure 1. Top: We introduce a framework for studying continuous learning in a single video stream. This is a natural yet unstudied problem, different from standard independent and identically distributed (IID) learning in video where batches contain clips from random videos in a random order. Bottom: We propose pixel-to-pixel models to evaluate our approach across prediction tasks (prediction of future frames, depth, segmentation). We measure both adaptation to the video stream – the model here updates its weights (learns) continuously to improve prediction – as well as generalization to out-of-stream clips – the model being adapted on the first stream is now evaluated on a different held-out stream without being allowed to adapt to it. We propose to maximize both adaptation and generalization. + +The most related fields are continual and lifelong learning, but these are still deeply fractured – no single problem formulation or benchmark is widely accepted. They also mostly focus on simplifications of the problem relative to + +![](images/0f1e7eaef77b3f20abcbceac0bffea6665f404e95f12a81925151623471db689.jpg) +Figure 2. UNet training on ScanNet-stream for the semantic segmentation task. Left: The cosine similarity of consecutive gradients is normally distributed when training on IID data, but shows very strong correlations when training on a continuous video stream. Right: This is reflected in poor training performance. See the appendix for similar figures for Ego4D-stream. + +![](images/93ad7409674deeb8a0bf297f421b506fc354e8d03113f3177ad50f838b4fd1bc.jpg) + +human and animal experience, for example a popular task is learning one ImageNet class at a time and minimizing forgetting of previous classes [38]. + +But what happens if we attempt to learn continuously from a single video stream (Figure 1), meaning batch size 1 and high frame rate (e.g. 25 fps)? We do not see thousands of dogs per second, unlike the standard ImageNet setting, where images of even a same dog breed are quite uncorrelated at several scales – capturing a wide diversity of edges, textures, etc. Standard deep learning approaches lead to smooth optimization there, but it is very different from the setting of learning from a single video stream, where things happen slowly, at much longer timescales, with great correlation or even no change between frames for periods of time; see Figure 2. Do standard deep learning tools work in this setting? This is currently unknown territory, with very few attempts touching it at all [33] – and it is the focus of this paper. + +We are interested in this problem because models should be able to adapt after deployment to their environment, hence receiving a single stream of information. This is needed for embodied intelligence (robotics), but also for any type of digital assistant that we would want to be able to adapt to a specific user's needs. + +A framework. We lay out a framework for learning from a single video stream, focusing on the entry-level problem of ... learning. Nevermind forgetting, can the models even learn in the first place? We study how successful learning is for different optimization settings, models, pretraining methods and tasks, when done from a single continuous stream. Our methodology follows the following principles: + +- We consider future prediction tasks including pixels-to-pixels, pixels-to-segmentation and pixels-to-depth, all in RGB space (i.e. outputs are always 3 dimensional and with the same shape as the input frames). This way we do not need to change any parameter in the model between pretraining and single-stream learning, independently of what tasks are used in each. It enables using a simple L2 loss between pixel values in all cases. +- We evaluate performance in two ways - in-stream, and + +out-of-stream. In-stream measures performance on the input video stream. For sufficiently difficult prediction tasks this should be enough. However, it conflates representation quality with adaptation to the scene, lighting condition, etc. For example if the lights in a scene are turned off for an hour, a model can learn to always predict black pixels – which is not ideal. To disentangle adaptation and generalization, we also evaluate out-of-stream, on a second stream on which the model does not learn. We propose to maximize both. + +Contributions. With this methodology in place, we identified the following new results: + +- On the optimization front, we observe that momentum, widely used in popular optimizers such as Adam, is unhelpful in highly correlated video streams. Instead methods without momentum such as RMSprop are more robust. +- Another result is a trade-off between adaptation and generalization induced by frequency of weight updates - slower leads to better generalization. +- We introduce a family of future prediction pretraining tasks, learnt in the standard independent and identically distributed (IID) setting, with large batches, and show that these lead to better single-stream performance compared to existing ImageNet pretraining tasks. +- We combine these results into a combo approach that we call Baby Learning (BL), and compare it to a standard deep learning setup (STDL) that uses Adam and ImageNet MAE pretraining. We show that BL on a sequential stream matches STDL on out-of-stream generalization when that same stream is permuted to be IID, while achieving better performance in-stream thanks to adaptation. + +# 2. Related work + +Online learning from a single video stream. One of the few papers dealing with this problem [33] proposed a minimum-redundancy "replay" buffer [27] to deal with temporal correlations. Replay buffers are not the sexiest research avenue for continual learning [41] and increase computation proportionally to the size of the buffer used. Additionally, in [33] performance on the video streams itself was never evaluated, only on unrelated image classification tasks. Test-time training is the next closest problem, such as presented in TTTVS [45] (also related [48]). TTVS's motivation is to "improve inference quality" by leveraging self-supervised test-time optimization. Our motivation is to propose single-stream learning, which is reflected in much longer streams (24h in this paper, compared to seconds or few minutes). One challenge in single-stream learning is how to fully exploit available hardware parallelism in a batch size 1 setting [6, 23, 24]. + +Learning from a single video. Also relevant are experiments training ConvNets [21] or ViTs [8] on a single image [1] or a long video [43]. While outside of the streaming setting – using data shuffling, augmentation and large batches, these papers showed that learning can be quite successful in this setting (especially for the shallower layers), which was quite encouraging. + +Continual learning. The continual learning literature (e.g. EWC [19]) tends to focus on learning a sequence of tasks, the goal being to learn new tasks as fast as possible without forgetting previous ones, such as in class incremental learning (e.g. iCarl [36]) and CLEAR [22]. Most relevant is online continual learning, where models learn from a stream of data, visited once. One challenge is model cheating by exploiting labels in the data [15], or by learning spurious features [46] that have limited generalisation power. Most of the work in this area has been on collections of images, rather than video. + +Representation learning to the rescue. Recent continual learning papers reported that some of the challenges of the problem are partially mitigated by using features pretrained in IID settings [26, 35, 44]. Various pretraining strategies exist: self-distillation (e.g. BYOL [13], BRaVe [37], DINO [4]), contrastive (CLIP [34], VideoMoco [28], VITO [30]), and masked auto-encoding (e.g. VideoMAE [42], TubeViT [31], AudioVisualMAE [11], SiameseMAE [14], [2]). We investigate this aspect in our setup. + +# 3. The Framework + +Overview. The following is repeated throughout a video stream: a (potentially pretrained) model processes $n$ frames (a time step) from an input video stream, and predicts frames for a future time step. Online (in-stream) performance metrics as well as an L2 loss function are then recorded by comparing predicted and target frames. Given the loss, gradients are computed and the model weights are updated by an optimizer. The target frames can come from the input stream itself or from an associated stream (e.g. for datasets having semantic segmentation or depth). In parallel with in-stream evaluation, we periodically assess performance on a held-out stream (composed of clips from the validation set of the dataset), to assess generalization. + +# 3.1. Unified pixel-to-pixel modelling + +We are interested in having a framework where switching between arbitrary tasks requires no changes to models or losses so we can abstract away decoder nd loss function design (large research areas) and focus on the single-stream learning aspect. To achieve this we map all task target outputs to RGB space, so we can have a single pixel-to-pixel model and a single simple L2 pixel loss. + +Models. We use 2 different popular backbones for our experiments: a UNet with self-attention in the bottleneck layer [17] and ViT-L [8]. To enable motion understanding, which is important for future prediction, we feed the models $n = 4$ consecutive frames stacked along the channel dimension. We also have the models predict the same number of frames, so 12 channels in total (4 frames times 3 channels, for RGB). For ViT we decode tokens to pixels using a channel to space transformation: each token gets mapped to an appropriate number of channels using a linear transformation, then gets reshaped into a patch (e.g. a 16x16 grid of 4x3 RGB channels). We provide details of the models in the Appendix, but it is worth noting that the UNet is considerably smaller at 8M parameters, compared to the 350M parameters of the ViT model. We always train the UNet from scratch, whereas we explore various pretraining schemes for ViT. To accommodate for the 12 input channels we use, we inflate [5] the first layer of the ViT (replicate the pretrained weights 4 times). + +Memory. We did not explore explicit memory modules such as memory banks, LSTM cells, or long context in this paper, but we do think it should be very relevant going forward. In all cases, the model "sees" only a time step of frames and predicts another time step. Note however that the model weights are updated as it goes through the video stream - so both the weights and the optimizer (when stateful) provide some memory effects. + +Replay buffer. We explored replay buffers [27], which keep a large cache of previous examples, then form batches by sampling from it. They have the disadvantage of increasing computational cost significantly over operating with batch size 1 (increases the theoretical computational cost of learning $K$ times, where $K$ is the batch size). + +# 3.2. Video streams and tasks + +We do not know of public datasets having very long video streams, for example days-long and beyond1, so we create two different video streams: Ego4D-stream and ScanNet-stream, by concatenating videos from, respectively, Ego4D and ScanNet. We include Ego4D as it is large and has very long videos, and ScanNet because it has dense semantic segmentation and depth annotations, allowing us to experiment with different tasks. + +Ego4D-stream. We concatenate the raw (un-trimmed) videos from the Ego4D dataset [12] to create a very long video stream. We use $\sim 90\%$ of the data to generate a training stream and $\sim 10\%$ for the validation stream. The videos in Ego4D were collected using a head or glass mounted camera, capturing activities of daily life. We use this stream for learning and evaluating future prediction in pixel space – no annotations are employed. See Table 1 for more details. + +
Stream name# videos train# frames train# videos val# frames valMax. lengthMedian length
Ego4D-stream21,704294M (3,265h)230231M (348h)1.95h8.8 minutes
ScanNet-stream1,1991.8M (20h)3120.5M (5.7h)5.5 minutes1 minute
+ +Table 1. The two streams we consider, formed out of Ego4D and ScanNet, together with properties of their original video clips. + +ScanNet-stream. We use the videos from ScanNetV2 [7] to define 3 different prediction tasks, of pixels, semantic segmentation labels (40 classes) and depth. The availability of these additional target streams makes it possible for us to measure more explicitly higher-level understanding, which may not be clear from pixel prediction alone. The videos in this dataset were filmed with a camera navigating indoor scenes with one or more rooms. See Table 1 for more details. + +Tasks. Overall we consider the following tasks across the two stream types: Ego4D-stream pixel prediction, ScanNetstream pixel, semantic segmentation and depth prediction. The difficulty of most of these tasks can be controlled using a time displacement parameter $\Delta$ - how many steps in advance should the models predict. We consider 0, 1, and 4 time steps. A displacement of 0 only makes sense for semantic tasks as otherwise it corresponds to auto-encoding, which is easy. Note that this task is related to the near-future accuracy metric proposed in [15] to measure (forward transfer) adaptation in a more robust way. + +RGB-fication. There is some hand design involved in mapping tasks into RGB space. For depth and semantic segmentation we use standard color maps typical for those tasks in ScanNet: the Viridis color map and the ScanNet label color map, respectively. We provide details of these mappings in the Appendix. For computing metrics other than the L2 pixel distance, we compute the nearest neighbor label / depth for each pixel color (e.g. a pixel's color may not correspond exactly to one of the semantic segmentation labels, so we assume the predicted class is the label associated with the nearest color on the color map). + +# 3.3. Evaluation + +Learning a video stream task with a continuously updated model can be seen to decompose into: 1) discovering strong features that are general, for example learning that certain configuration of edges correspond to chair legs for semantic segmentation (generalization), which is likely to happen over long timescales. 2) by specializing to the particular scene being seen in the video, e.g. learning that the chair is the only red object in the scene and using redness to label the chair pixels (adaptation), which can happen over short timescales. Adaptation can be quite useful and lead to efficient visual mechanisms, but may not necessarily lead to generalization. Dummy models that only e.g. exploit temporal correlations in the target stream could misleadingly appear to perform very well [15]; see Table 4, Blind model. + +We propose to evaluate both aspects by computing a score continuously in-stream, on the video stream task the model is learning from, to measure adaptation. Separately and periodically we compute the same score out-of-stream, on a held-out stream with the optimizer disabled (out-of-stream). We use the training sets of Ego4D and ScanNet to do in-stream evaluation, and the validation sets for out-of-stream evaluation. + +Cumulative scores. Comparing single-stream learning models and approaches can be difficult if done naively. On the training stream, difficulty of the task may vary over time, for example certain parts of a stream may be more unpredictable due to camera motion or other factors, leading to natural oscillations. On the generalization side we care not just about performance at a particular moment in time, but also how fast it ramps up as training on the sequential video stream progresses. With this in mind, we use a global score over the whole stream – we do this by averaging the performance over 10,000 evenly-spaced points interpolated from the steps in both in-stream and out-of-stream settings. + +Task-specific evaluation. We evaluate pixel prediction with average L2 pixelwise distance, the same that we use as loss for training. For semantic segmentation we use mean per-frame IoU and recall [3, 32] and depth using log relative mean square error (logRMSE) [9]. For both segmentation and depth we mask out pixels that were not annotated from the evaluation and loss. + +# 4. Generalized Future Prediction + +One of the most promising directions for continual learning, as identified in prior work, is representation learning. We are particularly interested in pixel-to-pixel approaches keeping consistent with the overall proposed framework where we never change neither the architecture nor the loss. We propose a family of pretraining methods that generalize future video prediction [40], and that follow a same pattern: given one input video clip the model is trained to predict a future clip from the same video (both clips are 4 frames long). We consider three variants, illustrated in Fig. 3: + +- The easiest one, Guided future prediction, replaces a few patches from the input clip with patches in the same position from the future clip, hence narrowing down the range of possibilities. +- The intermediate one, Vanilla future prediction is just the standard task of predicting the future. +- Masked future prediction is a variation of Masked Auto + +![](images/32fcdc00c3892ea49ccb72bb5bf62860ee2af339ec508c26d8786de621ef0310.jpg) +Figure 3. Video pretraining tasks we consider, sorted from easiest to hardest, left to right - guided future prediction, vanilla future prediction, and masked future prediction. Each column shows 4 consecutive frames vertically. For each method we show left-to-right: input frames, predictions from the model, target frames. We use a displacement $(\Delta)$ of 16 frames (0.64s) between input and target clips. + +![](images/2fab7abefcb4a0bbede0d3eaf5442cbf576844f3b14fb1e7ea3d9ebc061bab1b.jpg) + +![](images/93b0322a49ff99cd2012e3929a7219c2f37cb5e16801459174015676cbec38d2.jpg) + +Encoding where the model must predict the future clip based on a partial view of the current clip. + +Guided future prediction is related to Siamese MAE [2, 14, 47], but simpler, requiring a single forward pass over one model. Masked future prediction is related to video MAE-type approaches [10, 42] but with a strict separation between disjoint input and output clips, whereas in traditional video MAE there is a single clip that gets uniformly corrupted as part of denoising auto-encoding. + +Hyperparameters. There are two hyperparameters: the fraction of guiding patches / masked patches and the shape of these patches (we use a constant square shape in all experiments). Vanilla future prediction is a special case of the other two in the case where there is no masked nor guiding patches. A general way to increase the difficulty of any of the variants is to increase the displacement $(\Delta)$ between the input and the target clips. + +# 5. Results + +Our goal is to achieve similar (or better) learning efficiency from a single continuous video stream as we expect from the standard deep learning setting - using sequences of batches of well shuffled examples. Here is a summary of the main results of our experiments on learning from a continuous video stream: + +- Momentum, widely used in optimizers such as Adam, hurts performance in single-stream learning. +- Less frequent weight updates (e.g. every 2.5 seconds), helps generalization while sacrificing some adaptation. +- Pretraining the models on IID data before single-stream learning is quite impactful. While popular ImageNet-based pretraining helps, we found future-prediction based video pretraining to be vastly superior. + +![](images/3e0837848d31bdbb58ec2f4f76f51cd177e513e7be88ba3b46aa167a7aa81a0e.jpg) +Figure 4. A sweep over commonly used optimizers. Those without momentum are shown in blue and aid the models adaptability considerably compared to the more commonly used Adam variants, which are shown in red. + +We ran all in-stream learning for 24 hours of video, and measured out-of-stream performance from regularly saved checkpoints on 3h30 of video. Resolution was always $224 \times 224$ . + +# 5.1. Optimization + +Starting from the standard optimizer used in nearly all deep learning setups, Adam, we observed that it does not train well with default parameters in the continuous video stream setting compared to the IID setting; see Fig. 2, right. To understand the differences between the two settings, we analyzed the temporal correlation between consecutive gradients. We found that the norm and variance of the gradients do not reveal strong differences. However, their orientation reveals strong correlations between pairs of consecutive gradients in the continuous case; see Fig. 2, left, where we plot the distribution of the cosine similarity between consecutive gradients in the continuous vs IID case. + +To investigate the optimization further we performed a large sweep over commonly used optimizers, shown in Fig. 4. Results are averaged over 8 settings: 2 tasks + +![](images/213a18fcfefa0ad3b1539219e4cbaeaa539bccc514ef54ab1f9b370c20265c08.jpg) +Figure 5. Reducing momentum with the AdamW optimizer helps to recover some of the performance of RMSProp. + +(Ego4D-stream and ScanNet-stream segmentation prediction), 2 models (ViT and UNet) and 2 displacements (1 step and 4 steps). RMS Prop significantly outperformed the more commonly used Adam variants. + +Momentum hurts. To scrutinize the difference between AdamW and RMSProp, we looked at the impact of momentum. We found that lowering the momentum of the AdamW optimizer recovered some of the performance of RMSProp (as shown in Fig. 5). One possible explanation is that momentum exacerbates the problem of correlated consecutive gradients (that differ from the underlying gradient of the loss function over the whole stream) and makes the weights accelerate too much in the wrong direction. We stick with RMSProp for the rest of the paper, as it is more memory efficient due to not using the average of past gradients. + +Infrequent weight updates help generalization, hurt adaptation. We also observed an interesting effect associated to the frequency of weight updates: doing it less frequently tends to benefit generalization at some cost to adaptation (since the model cannot adapt as frequently or as strongly to any particular time step). We found that updating weights every 16 frames (or 0.64s) provided a decent trade-off between adaptation and generalization across models, tasks and datasets as shown in Tab. 2 + +Constant learning rate helps adaptation. We tested a range of common learning rate schedules including constant, linear, cosine and exponential decay, "1cycle" and cosine decay with restarts. The main finding was that decaying learning rates over the course of training, in particular cosine decay with exponent 2.0, helps generalization but significantly hurts adaptation as shown in Fig. 7. We therefore used a constant learning rate, with a linear warmup period of 1k steps, in our experiments. + +Replay buffer batches can be small. We focus most of our exploration on the case without replay buffers, but did check what happens when we add a replay buffer to our very best setting - which slows the experiment down proportionally + +![](images/f848979d72e5ebfbf0450ab72b44db2edf07a79ba542e12de62220d4b0e1d702.jpg) +Figure 6. ScanNet-stream segmentation task generalization results on the exact same out-of-stream clip after different number of hours of exposure to a same stream for 4 model runs. The models differ only by the length of the interval between weight updates / number of steps of gradient aggregation (horizontal axis). Models with less frequent updates tend to generalize better (rightmost column), whereas models with more frequent updates tend to have strong priors about which objects are currently in the scene, leading to hallucinations (leftmost 3 columns in this case). + +![](images/63354c70b32561b07faab4ee015c3e311b8b9f97db7333ec2d79dec09c79226c.jpg) +Figure 7. In-stream and out-of-stream results for a learning rate schedule using cosine decay with exponent 2.0 vs a constant learning rate (both with a linear warmup phase of 1k steps. The decaying learning rate is able to generalise more quickly but at a significant cost to adaptation. + +to the batch size employed. Over 11 hours of wall-clock training on the ScanNet-stream segmentation task with prediction displacement of 1 time step, an experiment with a replay buffer containing 10,000 samples (circular writing, random reading) and batch size 4 reached mean IoU only $2\%$ superior to a model trained without replay buffer. Batch size 16 did not improve over batch size 4 and we did not use replay buffers in any other experiments. + +# 5.2. Pretraining + +For pretraining we did not learn from a single continuous stream, but instead formed big well-shuffled batches of 1024 clips using 8x8 slices of TPU-v5-lite, used AdamW and updated weights every step, for 150k steps. We pretrained on the Kinetics-700-2020 dataset [39], which is composed of 10s clips. We found that initializing with the ImageNet-MAE checkpoint led to much quicker optimization, so used that in all cases. More details can be found in the Appendix. + +We pretrained ViT-L models on the future prediction tasks from sec. 4 and monitored their representation learn + +n steps per update + +
Streamdatasetmodel141664
InEgo4D (↓)UNet.036.038.037.039
ViT.035.037.039.047
Segm (↑)UNet.420.292.211.195
ViT.457.395.302.232
Out-ofEgo4D (↓)UNet.095.051.047.042
ViT.076.062.046.044
Segm (↑)UNet.176.179.205.183
ViT.251.272.280.274
+ +Table 2. Results on video streams from two datasets, two models, different numbers of steps per gradient update (horizontal), and evaluated in-stream and out-of-stream, showing the impact of accumulating gradients over multiple steps. Results are averaged over 1 and 4 displacement steps. For Ego4D-stream we report average L2 pixelwise distance (lower is better), for ScanNet-stream Segm we report mean per-frame IoU (higher is better). Bold marks the best result for each model-stream pair. + +![](images/1951bd66df1e56a0cc3c094d20df48869584a5ab79203461d875009cd80e7c02.jpg) +Figure 8. Linear top-1 accuracy in Kinetics during pretraining for different forms of future prediction tasks: Vanilla, Guided, Masked, and different displacements. The longer the displacement the better the accuracy is. Note that this is an online evaluation where the model only sees 4 frames (that for "Masked" and "Guided" are distorted) hence performance is far below models evaluated on the whole 10s of video (250 frames), often with plenty of test time augmentation, but the relative performance between the various curves is informative. + +ing performance during training by adding a linear head to the model just before the decoder (we use a stack of 4 self-attention layers on top of the ViT-L encoder). For this monitoring, we employed a standard cross-entropy loss between logits and ground truth labels in conjunction with a stop-gradient so the supervision would not influence the backbone weights. + +We experimented with different input-target clip temporal displacements and observed the interesting effect that the longer the displacement the better the classification performance is as shown in Fig. 8, even for masked future prediction, which reduces to the popular Masked Autoencoding [16] when displacement is 0. Our experiments suggest that 0 may be a sub-optimal choice. For the longest displacement the best method for top-1 accuracy emerged as Guided Future Prediction. The top result shown in the plot also used fewer guiding patches, $5\%$ instead of $10\%$ - we used this best model for the rest of our evaluations. We show example video predictions for the various models online at https://sites.google.com/view/one-stream-video. + +Table 3 has results on in/out-of-stream evaluation, showing large benefits over ImageNet classification pretraining and using no pretraining (training from scratch). ImageNet-MAE also does considerably better than classification-based pretraining. The same ViT-L architecture was used in all cases. + +# 5.3. IID vs Continuous Learning + +We compare our best setup, which we call, for no particularly technical reason, "Baby Learning" (BL), to a standard deep learning setup (STDL). STDL uses AdamW with standard parameters (learning rate 1e-4, momentum b1 as 0.9), with weight updates after each batch, the same ViT-L model but with the popular ImageNet MAE checkpoint. We implement the IID setting by sampling a sequence of random time steps (and associated target time steps) from random videos of the same base dataset. Note that while most approaches employ large batches, SGD with mini-batch size 1 is well known to work well [25] and is even said to generalize better than using large batches. We match the number of frames that each method sees – namely for batch size $>1$ , the total number of learning steps is reduced proportionally. + +Dummy baseline. For reference, we also include a dummy blind baseline, proposed in previous online learning works [15], which exploits the temporal correlations in the target stream without seeing the input frames at all: this "model" outputs the mean of the previously seen pixels at the same locations for depth and pixel, and the most frequent colors for segmentation, for the previous target. It produces random performance for out-of-stream evaluation where consecutive targets are unrelated2. + +Results on all tasks are shown in Table 4. We show visual results of a subset of these tasks in Fig. 9. It is visible that our approach BL matches STDL with batch size 1 out-of-stream while outperforming it in-stream. In fig. 11 in the Appendix we also report results for STDL on a continuous stream, which does not work at all, and for BL on an IID stream which does best – this shows that there are still many more improvements possible for learning from continuous streams. + +# 6. Conclusion + +We have presented a different perspective on continual learning by defining prediction tasks on a single very long stream of video and by proposing evaluations that measure both adaptation and generalization. We show that there is a permanent tension between the two aspects, but that it is possible to improve both by specializing the optimizer (lowering momentum, increasing the number of gradient + +
Pretraining CheckpointEgo4D (↓)ScanNet Depth (↓)ScanNet Segm (↑)ScanNet (↓)
None.074 / .1051.969 / 2.163.177 / .188.083 / .083
ViT-L-I1K-CLS.043 / .0481.821 / 2.040.288 / .234.040 / .042
ViT-L-I21K-CLS.042 / .0481.735 / 2.013.244 / .192.039 / .040
ViT-L-I1K-MAE.040 / .0441.806 / 2.045.360 / .320.037 / .038
Guided Future Prediction.036 / .0431.622 / 1.990.390 / .313.032 / .034
+ +![](images/434eeaeb60a31837e7295faa927699a6c34eea83750125c914dbe24b125993af.jpg) +Figure 9. Future prediction results for video streams from Ego4D-stream, ScanNet-stream Segm, and ScanNet-stream Depth. + +Table 3. Table comparing performance of models pretrained on ImageNet-1K and 21K using MAE or classification, and models pretrained on our video tasks in Kinetics. The results are averaged over two sets of experiments, with displacements of 1 and 4 time steps and are shown in the format in-stream / out-of-stream. + +
Ego4D (↓)ScanNet (↓)ScanNet Segm (↑)ScanNet Depth (↓)
displacement (Δ)t+1t+4t+1t+4t+1t+4t+1t+4
STDL (IID) bs 16.023/.019.060/.055.014/.013.042/.061.495/.398.382/.2951.798/2.011.838/2.038
STDL (IID) bs 1.019/.018.057/.056.010/.013.051/.060.376/.302.276/.2271.722/2.0121.759/2.034
BL (Cont.) bs 1.018/.021.055/.066.011/.012.055/.061.463/.312.328/.2411.595/2.0381.655/2.097
Blind (dummy).038 / -.086 / -.032/ -.109/ -.547/ -.307/ -1.256 / -1.649 / -
+ +Table 4. Future prediction results for video streams from various datasets for two different temporal displacements (horizontal). We show results for the standard deep learning approach (STDL) on IID data with batch size 16 and 1, and for our approach (BL) when using a continuous video stream (Cont.). Two numbers are reported for every cell, corresponding to in-stream / out-of-stream performance. We highlight which of the two batch size 1 approaches performs best for each number. The Blind (dummy) model exploits correlations in the target stream which is available in-stream and used for learning, hence performs very well in-stream, but has random performance in evaluation where the target stream is not available. This shows the necessity to measure both adaptation and generalization performance. + +aggregation steps between weight updates) and by pretraining the model appropriately. Conversely, we show that just using Adam with default parameters performs poorly on single-stream learning, due to the large correlations in the data. This makes the proposed setting different from popular ImageNet-based continual learning setups where batches are employed, and the data is significantly uncorrelated - for example in class-by-class learning, seeing different web images of dogs will not break Adam the way consecutive frames in a video does. + +We admit that the motivation for the research direction laid out in this paper may not be immediately crystal clear to everyone, particularly in the context of the current research landscape, that focuses on fitting larger and larger models to the whole internet. We are motivated by a possible future where people have their models in physical devices they carry around and train them via natural interac- + +tion – by showing them the world from their perspective – and teach them only the things that they believe the models should be taught, similar to the way we teach children. It is likely that such models, by not having to know everything, can be smaller, more efficient, have fewer internet biases and be more privacy-friendly. + +Acknowledgments. We would like to thank Ross Goroshin and Ali Eslami for reviewing the paper and providing helpful comments, and Razvan Pascanu and Simon Osindero for insightful advice and interesting pointers into the literature and background work. + +# References + +[1] Yuki M. Asano, Christian Rupprecht, and Andrea Vedaldi. A critical analysis of self-supervision, or what we can learn + +from a single image. In International Conference on Learning Representations, 2020. 3 +[2] Daniel Bear, Kevin T. 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"text", + "content": "core contributor" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 241, + 192, + 254 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 241, + 192, + 254 + ], + "spans": [ + { + "bbox": [ + 143, + 241, + 192, + 254 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 268, + 290, + 542 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 268, + 290, + 542 + ], + "spans": [ + { + "bbox": [ + 47, + 268, + 290, + 542 + ], + "type": "text", + "content": "We introduce a framework for online learning from a single continuous video stream – the way people and animals learn, without mini-batches, data augmentation or shuffling. This poses great challenges given the high correlation between consecutive video frames and there is very little prior work on it. Our framework allows us to do a first deep dive into the topic and includes a collection of streams and tasks composed from two existing video datasets, plus methodology for performance evaluation that considers both adaptation and generalization. We employ pixel-to-pixel modelling as a practical and flexible way to switch between pre-training and single-stream evaluation as well as between arbitrary tasks, without ever requiring changes to models and always using the same pixel loss. Equipped with this framework we obtained large single-stream learning gains from pre-training with a novel family of future prediction tasks, found that momentum hurts, and that the pace of weight updates matters. The combination of these insights leads to matching the performance of IID learning with batch size 1, when using the same architecture and without costly replay buffers. An overview of the paper is available online at https://sites.google.com/view/one-stream-video." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 571, + 128, + 583 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 571, + 128, + 583 + ], + "spans": [ + { + "bbox": [ + 47, + 571, + 128, + 583 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 287, + 713 + ], + "type": "text", + "content": "Humans gather knowledge about themselves and the world through a continuous stream of observations, from their early days as infants. Some experiences are seen once in a lifetime while others are daily repeats. With time, familiarity with environments, objects and experiences form a base to our knowledge, and memory maintains the most important experiences from our ever-further past. Learning successfully adapts to the current surroundings so we can make better predictions over time, while leading to generalization to unseen environments. Despite the naturalness" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 242, + 545, + 268 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 242, + 545, + 268 + ], + "spans": [ + { + "bbox": [ + 305, + 242, + 545, + 268 + ], + "type": "text", + "content": "of this approach of learning for humans, video understanding approaches have rarely attempted a similar regime." + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 308, + 279, + 545, + 377 + ], + "blocks": [ + { + "bbox": [ + 308, + 279, + 545, + 377 + ], + "lines": [ + { + "bbox": [ + 308, + 279, + 545, + 377 + ], + "spans": [ + { + "bbox": [ + 308, + 279, + 545, + 377 + ], + "type": "image", + "image_path": "44982ffc8f8671dd0b3c2d63482cff3fce3657ef935af4c194e331224c065d91.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 307, + 382, + 545, + 506 + ], + "blocks": [ + { + "bbox": [ + 307, + 382, + 545, + 506 + ], + "lines": [ + { + "bbox": [ + 307, + 382, + 545, + 506 + ], + "spans": [ + { + "bbox": [ + 307, + 382, + 545, + 506 + ], + "type": "image", + "image_path": "2882fc0d6668fe4f405d65e88840838adbb4f78b24c9463bcaf8b5793dfb9e85.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 514, + 545, + 658 + ], + "lines": [ + { + "bbox": [ + 304, + 514, + 545, + 658 + ], + "spans": [ + { + "bbox": [ + 304, + 514, + 545, + 658 + ], + "type": "text", + "content": "Figure 1. Top: We introduce a framework for studying continuous learning in a single video stream. This is a natural yet unstudied problem, different from standard independent and identically distributed (IID) learning in video where batches contain clips from random videos in a random order. Bottom: We propose pixel-to-pixel models to evaluate our approach across prediction tasks (prediction of future frames, depth, segmentation). We measure both adaptation to the video stream – the model here updates its weights (learns) continuously to improve prediction – as well as generalization to out-of-stream clips – the model being adapted on the first stream is now evaluated on a different held-out stream without being allowed to adapt to it. We propose to maximize both adaptation and generalization." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 665, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 665, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 665, + 547, + 713 + ], + "type": "text", + "content": "The most related fields are continual and lifelong learning, but these are still deeply fractured – no single problem formulation or benchmark is widely accepted. They also mostly focus on simplifications of the problem relative to" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28751" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 70, + 165, + 147 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 165, + 147 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 165, + 147 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 165, + 147 + ], + "type": "image", + "image_path": "0f1e7eaef77b3f20abcbceac0bffea6665f404e95f12a81925151623471db689.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 149, + 287, + 217 + ], + "lines": [ + { + "bbox": [ + 46, + 149, + 287, + 217 + ], + "spans": [ + { + "bbox": [ + 46, + 149, + 287, + 217 + ], + "type": "text", + "content": "Figure 2. UNet training on ScanNet-stream for the semantic segmentation task. Left: The cosine similarity of consecutive gradients is normally distributed when training on IID data, but shows very strong correlations when training on a continuous video stream. Right: This is reflected in poor training performance. See the appendix for similar figures for Ego4D-stream." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 167, + 70, + 282, + 148 + ], + "blocks": [ + { + "bbox": [ + 167, + 70, + 282, + 148 + ], + "lines": [ + { + "bbox": [ + 167, + 70, + 282, + 148 + ], + "spans": [ + { + "bbox": [ + 167, + 70, + 282, + 148 + ], + "type": "image", + "image_path": "93ad7409674deeb8a0bf297f421b506fc354e8d03113f3177ad50f838b4fd1bc.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 227, + 287, + 262 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 227, + 287, + 262 + ], + "spans": [ + { + "bbox": [ + 46, + 227, + 287, + 262 + ], + "type": "text", + "content": "human and animal experience, for example a popular task is learning one ImageNet class at a time and minimizing forgetting of previous classes [38]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 263, + 287, + 443 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 263, + 287, + 443 + ], + "spans": [ + { + "bbox": [ + 46, + 263, + 287, + 443 + ], + "type": "text", + "content": "But what happens if we attempt to learn continuously from a single video stream (Figure 1), meaning batch size 1 and high frame rate (e.g. 25 fps)? We do not see thousands of dogs per second, unlike the standard ImageNet setting, where images of even a same dog breed are quite uncorrelated at several scales – capturing a wide diversity of edges, textures, etc. Standard deep learning approaches lead to smooth optimization there, but it is very different from the setting of learning from a single video stream, where things happen slowly, at much longer timescales, with great correlation or even no change between frames for periods of time; see Figure 2. Do standard deep learning tools work in this setting? This is currently unknown territory, with very few attempts touching it at all [33] – and it is the focus of this paper." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 444, + 287, + 515 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 444, + 287, + 515 + ], + "spans": [ + { + "bbox": [ + 46, + 444, + 287, + 515 + ], + "type": "text", + "content": "We are interested in this problem because models should be able to adapt after deployment to their environment, hence receiving a single stream of information. This is needed for embodied intelligence (robotics), but also for any type of digital assistant that we would want to be able to adapt to a specific user's needs." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 519, + 287, + 602 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 519, + 287, + 602 + ], + "spans": [ + { + "bbox": [ + 46, + 519, + 287, + 602 + ], + "type": "text", + "content": "A framework. We lay out a framework for learning from a single video stream, focusing on the entry-level problem of ... learning. Nevermind forgetting, can the models even learn in the first place? We study how successful learning is for different optimization settings, models, pretraining methods and tasks, when done from a single continuous stream. Our methodology follows the following principles:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 605, + 287, + 714 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 47, + 605, + 287, + 701 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 605, + 287, + 701 + ], + "spans": [ + { + "bbox": [ + 47, + 605, + 287, + 701 + ], + "type": "text", + "content": "- We consider future prediction tasks including pixels-to-pixels, pixels-to-segmentation and pixels-to-depth, all in RGB space (i.e. outputs are always 3 dimensional and with the same shape as the input frames). This way we do not need to change any parameter in the model between pretraining and single-stream learning, independently of what tasks are used in each. It enables using a simple L2 loss between pixel values in all cases." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 702, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 702, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 702, + 287, + 714 + ], + "type": "text", + "content": "- We evaluate performance in two ways - in-stream, and" + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 313, + 72, + 545, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 72, + 545, + 192 + ], + "spans": [ + { + "bbox": [ + 313, + 72, + 545, + 192 + ], + "type": "text", + "content": "out-of-stream. In-stream measures performance on the input video stream. For sufficiently difficult prediction tasks this should be enough. However, it conflates representation quality with adaptation to the scene, lighting condition, etc. For example if the lights in a scene are turned off for an hour, a model can learn to always predict black pixels – which is not ideal. To disentangle adaptation and generalization, we also evaluate out-of-stream, on a second stream on which the model does not learn. We propose to maximize both." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 198, + 545, + 222 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 198, + 545, + 222 + ], + "spans": [ + { + "bbox": [ + 306, + 198, + 545, + 222 + ], + "type": "text", + "content": "Contributions. With this methodology in place, we identified the following new results:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 223, + 545, + 472 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 306, + 223, + 545, + 280 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 223, + 545, + 280 + ], + "spans": [ + { + "bbox": [ + 306, + 223, + 545, + 280 + ], + "type": "text", + "content": "- On the optimization front, we observe that momentum, widely used in popular optimizers such as Adam, is unhelpful in highly correlated video streams. Instead methods without momentum such as RMSprop are more robust." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 282, + 545, + 317 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 282, + 545, + 317 + ], + "spans": [ + { + "bbox": [ + 306, + 282, + 545, + 317 + ], + "type": "text", + "content": "- Another result is a trade-off between adaptation and generalization induced by frequency of weight updates - slower leads to better generalization." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 319, + 545, + 378 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 319, + 545, + 378 + ], + "spans": [ + { + "bbox": [ + 306, + 319, + 545, + 378 + ], + "type": "text", + "content": "- We introduce a family of future prediction pretraining tasks, learnt in the standard independent and identically distributed (IID) setting, with large batches, and show that these lead to better single-stream performance compared to existing ImageNet pretraining tasks." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 379, + 545, + 472 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 379, + 545, + 472 + ], + "spans": [ + { + "bbox": [ + 306, + 379, + 545, + 472 + ], + "type": "text", + "content": "- We combine these results into a combo approach that we call Baby Learning (BL), and compare it to a standard deep learning setup (STDL) that uses Adam and ImageNet MAE pretraining. We show that BL on a sequential stream matches STDL on out-of-stream generalization when that same stream is permuted to be IID, while achieving better performance in-stream thanks to adaptation." + } + ] + } + ], + "index": 15 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 487, + 389, + 498 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 487, + 389, + 498 + ], + "spans": [ + { + "bbox": [ + 306, + 487, + 389, + 498 + ], + "type": "text", + "content": "2. Related work" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 510, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 545, + 713 + ], + "type": "text", + "content": "Online learning from a single video stream. One of the few papers dealing with this problem [33] proposed a minimum-redundancy \"replay\" buffer [27] to deal with temporal correlations. Replay buffers are not the sexiest research avenue for continual learning [41] and increase computation proportionally to the size of the buffer used. Additionally, in [33] performance on the video streams itself was never evaluated, only on unrelated image classification tasks. Test-time training is the next closest problem, such as presented in TTTVS [45] (also related [48]). TTVS's motivation is to \"improve inference quality\" by leveraging self-supervised test-time optimization. Our motivation is to propose single-stream learning, which is reflected in much longer streams (24h in this paper, compared to seconds or few minutes). One challenge in single-stream learning is how to fully exploit available hardware parallelism in a batch size 1 setting [6, 23, 24]." + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28752" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 156 + ], + "type": "text", + "content": "Learning from a single video. Also relevant are experiments training ConvNets [21] or ViTs [8] on a single image [1] or a long video [43]. While outside of the streaming setting – using data shuffling, augmentation and large batches, these papers showed that learning can be quite successful in this setting (especially for the shallower layers), which was quite encouraging." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 159, + 288, + 290 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 159, + 288, + 290 + ], + "spans": [ + { + "bbox": [ + 46, + 159, + 288, + 290 + ], + "type": "text", + "content": "Continual learning. The continual learning literature (e.g. EWC [19]) tends to focus on learning a sequence of tasks, the goal being to learn new tasks as fast as possible without forgetting previous ones, such as in class incremental learning (e.g. iCarl [36]) and CLEAR [22]. Most relevant is online continual learning, where models learn from a stream of data, visited once. One challenge is model cheating by exploiting labels in the data [15], or by learning spurious features [46] that have limited generalisation power. Most of the work in this area has been on collections of images, rather than video." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 293, + 288, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 293, + 288, + 413 + ], + "spans": [ + { + "bbox": [ + 46, + 293, + 288, + 413 + ], + "type": "text", + "content": "Representation learning to the rescue. Recent continual learning papers reported that some of the challenges of the problem are partially mitigated by using features pretrained in IID settings [26, 35, 44]. Various pretraining strategies exist: self-distillation (e.g. BYOL [13], BRaVe [37], DINO [4]), contrastive (CLIP [34], VideoMoco [28], VITO [30]), and masked auto-encoding (e.g. VideoMAE [42], TubeViT [31], AudioVisualMAE [11], SiameseMAE [14], [2]). We investigate this aspect in our setup." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 425, + 146, + 437 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 425, + 146, + 437 + ], + "spans": [ + { + "bbox": [ + 47, + 425, + 146, + 437 + ], + "type": "text", + "content": "3. The Framework" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 447, + 287, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 447, + 287, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 447, + 287, + 604 + ], + "type": "text", + "content": "Overview. The following is repeated throughout a video stream: a (potentially pretrained) model processes " + }, + { + "bbox": [ + 46, + 447, + 287, + 604 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 447, + 287, + 604 + ], + "type": "text", + "content": " frames (a time step) from an input video stream, and predicts frames for a future time step. Online (in-stream) performance metrics as well as an L2 loss function are then recorded by comparing predicted and target frames. Given the loss, gradients are computed and the model weights are updated by an optimizer. The target frames can come from the input stream itself or from an associated stream (e.g. for datasets having semantic segmentation or depth). In parallel with in-stream evaluation, we periodically assess performance on a held-out stream (composed of clips from the validation set of the dataset), to assess generalization." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 610, + 218, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 610, + 218, + 624 + ], + "spans": [ + { + "bbox": [ + 47, + 610, + 218, + 624 + ], + "type": "text", + "content": "3.1. Unified pixel-to-pixel modelling" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": "We are interested in having a framework where switching between arbitrary tasks requires no changes to models or losses so we can abstract away decoder nd loss function design (large research areas) and focus on the single-stream learning aspect. To achieve this we map all task target outputs to RGB space, so we can have a single pixel-to-pixel model and a single simple L2 pixel loss." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 300 + ], + "type": "text", + "content": "Models. We use 2 different popular backbones for our experiments: a UNet with self-attention in the bottleneck layer [17] and ViT-L [8]. To enable motion understanding, which is important for future prediction, we feed the models " + }, + { + "bbox": [ + 304, + 72, + 545, + 300 + ], + "type": "inline_equation", + "content": "n = 4" + }, + { + "bbox": [ + 304, + 72, + 545, + 300 + ], + "type": "text", + "content": " consecutive frames stacked along the channel dimension. We also have the models predict the same number of frames, so 12 channels in total (4 frames times 3 channels, for RGB). For ViT we decode tokens to pixels using a channel to space transformation: each token gets mapped to an appropriate number of channels using a linear transformation, then gets reshaped into a patch (e.g. a 16x16 grid of 4x3 RGB channels). We provide details of the models in the Appendix, but it is worth noting that the UNet is considerably smaller at 8M parameters, compared to the 350M parameters of the ViT model. We always train the UNet from scratch, whereas we explore various pretraining schemes for ViT. To accommodate for the 12 input channels we use, we inflate [5] the first layer of the ViT (replicate the pretrained weights 4 times)." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 302, + 545, + 398 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 302, + 545, + 398 + ], + "spans": [ + { + "bbox": [ + 304, + 302, + 545, + 398 + ], + "type": "text", + "content": "Memory. We did not explore explicit memory modules such as memory banks, LSTM cells, or long context in this paper, but we do think it should be very relevant going forward. In all cases, the model \"sees\" only a time step of frames and predicts another time step. Note however that the model weights are updated as it goes through the video stream - so both the weights and the optimizer (when stateful) provide some memory effects." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 399, + 545, + 471 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 399, + 545, + 471 + ], + "spans": [ + { + "bbox": [ + 304, + 399, + 545, + 471 + ], + "type": "text", + "content": "Replay buffer. We explored replay buffers [27], which keep a large cache of previous examples, then form batches by sampling from it. They have the disadvantage of increasing computational cost significantly over operating with batch size 1 (increases the theoretical computational cost of learning " + }, + { + "bbox": [ + 304, + 399, + 545, + 471 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 399, + 545, + 471 + ], + "type": "text", + "content": " times, where " + }, + { + "bbox": [ + 304, + 399, + 545, + 471 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 399, + 545, + 471 + ], + "type": "text", + "content": " is the batch size)." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 479, + 441, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 479, + 441, + 491 + ], + "spans": [ + { + "bbox": [ + 306, + 479, + 441, + 491 + ], + "type": "text", + "content": "3.2. Video streams and tasks" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 498, + 545, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 545, + 594 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 545, + 594 + ], + "type": "text", + "content": "We do not know of public datasets having very long video streams, for example days-long and beyond1, so we create two different video streams: Ego4D-stream and ScanNet-stream, by concatenating videos from, respectively, Ego4D and ScanNet. We include Ego4D as it is large and has very long videos, and ScanNet because it has dense semantic segmentation and depth annotations, allowing us to experiment with different tasks." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 597, + 545, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 597, + 545, + 693 + ], + "spans": [ + { + "bbox": [ + 304, + 597, + 545, + 693 + ], + "type": "text", + "content": "Ego4D-stream. We concatenate the raw (un-trimmed) videos from the Ego4D dataset [12] to create a very long video stream. We use " + }, + { + "bbox": [ + 304, + 597, + 545, + 693 + ], + "type": "inline_equation", + "content": "\\sim 90\\%" + }, + { + "bbox": [ + 304, + 597, + 545, + 693 + ], + "type": "text", + "content": " of the data to generate a training stream and " + }, + { + "bbox": [ + 304, + 597, + 545, + 693 + ], + "type": "inline_equation", + "content": "\\sim 10\\%" + }, + { + "bbox": [ + 304, + 597, + 545, + 693 + ], + "type": "text", + "content": " for the validation stream. The videos in Ego4D were collected using a head or glass mounted camera, capturing activities of daily life. We use this stream for learning and evaluating future prediction in pixel space – no annotations are employed. See Table 1 for more details." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 317, + 702, + 508, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 702, + 508, + 713 + ], + "spans": [ + { + "bbox": [ + 317, + 702, + 508, + 713 + ], + "type": "text", + "content": "1Other than Krishnacam [20], which is only 70 hours long." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28753" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 81, + 70, + 511, + 106 + ], + "blocks": [ + { + "bbox": [ + 81, + 70, + 511, + 106 + ], + "lines": [ + { + "bbox": [ + 81, + 70, + 511, + 106 + ], + "spans": [ + { + "bbox": [ + 81, + 70, + 511, + 106 + ], + "type": "table", + "html": "
Stream name# videos train# frames train# videos val# frames valMax. lengthMedian length
Ego4D-stream21,704294M (3,265h)230231M (348h)1.95h8.8 minutes
ScanNet-stream1,1991.8M (20h)3120.5M (5.7h)5.5 minutes1 minute
", + "image_path": "e0677bb598c0481a7d844a3b1448681ce81967f571ac46fcde0687f5299becef.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 66, + 109, + 526, + 120 + ], + "lines": [ + { + "bbox": [ + 66, + 109, + 526, + 120 + ], + "spans": [ + { + "bbox": [ + 66, + 109, + 526, + 120 + ], + "type": "text", + "content": "Table 1. The two streams we consider, formed out of Ego4D and ScanNet, together with properties of their original video clips." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 141, + 288, + 249 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 141, + 288, + 249 + ], + "spans": [ + { + "bbox": [ + 46, + 141, + 288, + 249 + ], + "type": "text", + "content": "ScanNet-stream. We use the videos from ScanNetV2 [7] to define 3 different prediction tasks, of pixels, semantic segmentation labels (40 classes) and depth. The availability of these additional target streams makes it possible for us to measure more explicitly higher-level understanding, which may not be clear from pixel prediction alone. The videos in this dataset were filmed with a camera navigating indoor scenes with one or more rooms. See Table 1 for more details." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 252, + 287, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 252, + 287, + 384 + ], + "spans": [ + { + "bbox": [ + 46, + 252, + 287, + 384 + ], + "type": "text", + "content": "Tasks. Overall we consider the following tasks across the two stream types: Ego4D-stream pixel prediction, ScanNetstream pixel, semantic segmentation and depth prediction. The difficulty of most of these tasks can be controlled using a time displacement parameter " + }, + { + "bbox": [ + 46, + 252, + 287, + 384 + ], + "type": "inline_equation", + "content": "\\Delta" + }, + { + "bbox": [ + 46, + 252, + 287, + 384 + ], + "type": "text", + "content": " - how many steps in advance should the models predict. We consider 0, 1, and 4 time steps. A displacement of 0 only makes sense for semantic tasks as otherwise it corresponds to auto-encoding, which is easy. Note that this task is related to the near-future accuracy metric proposed in [15] to measure (forward transfer) adaptation in a more robust way." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 387, + 288, + 518 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 387, + 288, + 518 + ], + "spans": [ + { + "bbox": [ + 46, + 387, + 288, + 518 + ], + "type": "text", + "content": "RGB-fication. There is some hand design involved in mapping tasks into RGB space. For depth and semantic segmentation we use standard color maps typical for those tasks in ScanNet: the Viridis color map and the ScanNet label color map, respectively. We provide details of these mappings in the Appendix. For computing metrics other than the L2 pixel distance, we compute the nearest neighbor label / depth for each pixel color (e.g. a pixel's color may not correspond exactly to one of the semantic segmentation labels, so we assume the predicted class is the label associated with the nearest color on the color map)." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 527, + 120, + 538 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 527, + 120, + 538 + ], + "spans": [ + { + "bbox": [ + 47, + 527, + 120, + 538 + ], + "type": "text", + "content": "3.3. Evaluation" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "content": "Learning a video stream task with a continuously updated model can be seen to decompose into: 1) discovering strong features that are general, for example learning that certain configuration of edges correspond to chair legs for semantic segmentation (generalization), which is likely to happen over long timescales. 2) by specializing to the particular scene being seen in the video, e.g. learning that the chair is the only red object in the scene and using redness to label the chair pixels (adaptation), which can happen over short timescales. Adaptation can be quite useful and lead to efficient visual mechanisms, but may not necessarily lead to generalization. Dummy models that only e.g. exploit temporal correlations in the target stream could misleadingly appear to perform very well [15]; see Table 4, Blind model." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 141, + 545, + 236 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 141, + 545, + 236 + ], + "spans": [ + { + "bbox": [ + 304, + 141, + 545, + 236 + ], + "type": "text", + "content": "We propose to evaluate both aspects by computing a score continuously in-stream, on the video stream task the model is learning from, to measure adaptation. Separately and periodically we compute the same score out-of-stream, on a held-out stream with the optimizer disabled (out-of-stream). We use the training sets of Ego4D and ScanNet to do in-stream evaluation, and the validation sets for out-of-stream evaluation." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 240, + 546, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 240, + 546, + 384 + ], + "spans": [ + { + "bbox": [ + 304, + 240, + 546, + 384 + ], + "type": "text", + "content": "Cumulative scores. Comparing single-stream learning models and approaches can be difficult if done naively. On the training stream, difficulty of the task may vary over time, for example certain parts of a stream may be more unpredictable due to camera motion or other factors, leading to natural oscillations. On the generalization side we care not just about performance at a particular moment in time, but also how fast it ramps up as training on the sequential video stream progresses. With this in mind, we use a global score over the whole stream – we do this by averaging the performance over 10,000 evenly-spaced points interpolated from the steps in both in-stream and out-of-stream settings." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 388, + 545, + 471 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 388, + 545, + 471 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 545, + 471 + ], + "type": "text", + "content": "Task-specific evaluation. We evaluate pixel prediction with average L2 pixelwise distance, the same that we use as loss for training. For semantic segmentation we use mean per-frame IoU and recall [3, 32] and depth using log relative mean square error (logRMSE) [9]. For both segmentation and depth we mask out pixels that were not annotated from the evaluation and loss." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 485, + 477, + 498 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 485, + 477, + 498 + ], + "spans": [ + { + "bbox": [ + 305, + 485, + 477, + 498 + ], + "type": "text", + "content": "4. Generalized Future Prediction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 506, + 545, + 626 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 506, + 545, + 626 + ], + "spans": [ + { + "bbox": [ + 304, + 506, + 545, + 626 + ], + "type": "text", + "content": "One of the most promising directions for continual learning, as identified in prior work, is representation learning. We are particularly interested in pixel-to-pixel approaches keeping consistent with the overall proposed framework where we never change neither the architecture nor the loss. We propose a family of pretraining methods that generalize future video prediction [40], and that follow a same pattern: given one input video clip the model is trained to predict a future clip from the same video (both clips are 4 frames long). We consider three variants, illustrated in Fig. 3:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 629, + 545, + 712 + ], + "type": "list", + "angle": 0, + "index": 15, + "blocks": [ + { + "bbox": [ + 306, + 629, + 545, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 629, + 545, + 676 + ], + "spans": [ + { + "bbox": [ + 306, + 629, + 545, + 676 + ], + "type": "text", + "content": "- The easiest one, Guided future prediction, replaces a few patches from the input clip with patches in the same position from the future clip, hence narrowing down the range of possibilities." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 677, + 545, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 677, + 545, + 700 + ], + "spans": [ + { + "bbox": [ + 306, + 677, + 545, + 700 + ], + "type": "text", + "content": "- The intermediate one, Vanilla future prediction is just the standard task of predicting the future." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 701, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 701, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 306, + 701, + 545, + 712 + ], + "type": "text", + "content": "- Masked future prediction is a variation of Masked Auto" + } + ] + } + ], + "index": 14 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28754" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 68, + 207, + 253 + ], + "blocks": [ + { + "bbox": [ + 47, + 68, + 207, + 253 + ], + "lines": [ + { + "bbox": [ + 47, + 68, + 207, + 253 + ], + "spans": [ + { + "bbox": [ + 47, + 68, + 207, + 253 + ], + "type": "image", + "image_path": "32fcdc00c3892ea49ccb72bb5bf62860ee2af339ec508c26d8786de621ef0310.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 258, + 547, + 293 + ], + "lines": [ + { + "bbox": [ + 46, + 258, + 547, + 293 + ], + "spans": [ + { + "bbox": [ + 46, + 258, + 547, + 293 + ], + "type": "text", + "content": "Figure 3. Video pretraining tasks we consider, sorted from easiest to hardest, left to right - guided future prediction, vanilla future prediction, and masked future prediction. Each column shows 4 consecutive frames vertically. For each method we show left-to-right: input frames, predictions from the model, target frames. We use a displacement " + }, + { + "bbox": [ + 46, + 258, + 547, + 293 + ], + "type": "inline_equation", + "content": "(\\Delta)" + }, + { + "bbox": [ + 46, + 258, + 547, + 293 + ], + "type": "text", + "content": " of 16 frames (0.64s) between input and target clips." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 213, + 68, + 376, + 253 + ], + "blocks": [ + { + "bbox": [ + 213, + 68, + 376, + 253 + ], + "lines": [ + { + "bbox": [ + 213, + 68, + 376, + 253 + ], + "spans": [ + { + "bbox": [ + 213, + 68, + 376, + 253 + ], + "type": "image", + "image_path": "2fab7abefcb4a0bbede0d3eaf5442cbf576844f3b14fb1e7ea3d9ebc061bab1b.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 386, + 68, + 547, + 253 + ], + "blocks": [ + { + "bbox": [ + 386, + 68, + 547, + 253 + ], + "lines": [ + { + "bbox": [ + 386, + 68, + 547, + 253 + ], + "spans": [ + { + "bbox": [ + 386, + 68, + 547, + 253 + ], + "type": "image", + "image_path": "93b0322a49ff99cd2012e3929a7219c2f37cb5e16801459174015676cbec38d2.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 55, + 304, + 288, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 304, + 288, + 327 + ], + "spans": [ + { + "bbox": [ + 55, + 304, + 288, + 327 + ], + "type": "text", + "content": "Encoding where the model must predict the future clip based on a partial view of the current clip." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 330, + 287, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 330, + 287, + 415 + ], + "spans": [ + { + "bbox": [ + 46, + 330, + 287, + 415 + ], + "type": "text", + "content": "Guided future prediction is related to Siamese MAE [2, 14, 47], but simpler, requiring a single forward pass over one model. Masked future prediction is related to video MAE-type approaches [10, 42] but with a strict separation between disjoint input and output clips, whereas in traditional video MAE there is a single clip that gets uniformly corrupted as part of denoising auto-encoding." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 417, + 288, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 417, + 288, + 513 + ], + "spans": [ + { + "bbox": [ + 46, + 417, + 288, + 513 + ], + "type": "text", + "content": "Hyperparameters. There are two hyperparameters: the fraction of guiding patches / masked patches and the shape of these patches (we use a constant square shape in all experiments). Vanilla future prediction is a special case of the other two in the case where there is no masked nor guiding patches. A general way to increase the difficulty of any of the variants is to increase the displacement " + }, + { + "bbox": [ + 46, + 417, + 288, + 513 + ], + "type": "inline_equation", + "content": "(\\Delta)" + }, + { + "bbox": [ + 46, + 417, + 288, + 513 + ], + "type": "text", + "content": " between the input and the target clips." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 523, + 100, + 536 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 523, + 100, + 536 + ], + "spans": [ + { + "bbox": [ + 47, + 523, + 100, + 536 + ], + "type": "text", + "content": "5. Results" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 544, + 287, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 287, + 614 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 287, + 614 + ], + "type": "text", + "content": "Our goal is to achieve similar (or better) learning efficiency from a single continuous video stream as we expect from the standard deep learning setting - using sequences of batches of well shuffled examples. Here is a summary of the main results of our experiments on learning from a continuous video stream:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 618, + 286, + 714 + ], + "type": "list", + "angle": 0, + "index": 12, + "blocks": [ + { + "bbox": [ + 47, + 618, + 286, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 618, + 286, + 641 + ], + "spans": [ + { + "bbox": [ + 47, + 618, + 286, + 641 + ], + "type": "text", + "content": "- Momentum, widely used in optimizers such as Adam, hurts performance in single-stream learning." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 642, + 286, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 642, + 286, + 666 + ], + "spans": [ + { + "bbox": [ + 47, + 642, + 286, + 666 + ], + "type": "text", + "content": "- Less frequent weight updates (e.g. every 2.5 seconds), helps generalization while sacrificing some adaptation." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 666, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 666, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 666, + 286, + 714 + ], + "type": "text", + "content": "- Pretraining the models on IID data before single-stream learning is quite impactful. While popular ImageNet-based pretraining helps, we found future-prediction based video pretraining to be vastly superior." + } + ] + } + ], + "index": 11 + } + ], + "sub_type": "text" + }, + { + "type": "image", + "bbox": [ + 309, + 305, + 542, + 399 + ], + "blocks": [ + { + "bbox": [ + 309, + 305, + 542, + 399 + ], + "lines": [ + { + "bbox": [ + 309, + 305, + 542, + 399 + ], + "spans": [ + { + "bbox": [ + 309, + 305, + 542, + 399 + ], + "type": "image", + "image_path": "3e0837848d31bdbb58ec2f4f76f51cd177e513e7be88ba3b46aa167a7aa81a0e.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 400, + 546, + 445 + ], + "lines": [ + { + "bbox": [ + 305, + 400, + 546, + 445 + ], + "spans": [ + { + "bbox": [ + 305, + 400, + 546, + 445 + ], + "type": "text", + "content": "Figure 4. A sweep over commonly used optimizers. Those without momentum are shown in blue and aid the models adaptability considerably compared to the more commonly used Adam variants, which are shown in red." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 458, + 547, + 506 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 458, + 547, + 506 + ], + "spans": [ + { + "bbox": [ + 305, + 458, + 547, + 506 + ], + "type": "text", + "content": "We ran all in-stream learning for 24 hours of video, and measured out-of-stream performance from regularly saved checkpoints on 3h30 of video. Resolution was always " + }, + { + "bbox": [ + 305, + 458, + 547, + 506 + ], + "type": "inline_equation", + "content": "224 \\times 224" + }, + { + "bbox": [ + 305, + 458, + 547, + 506 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 514, + 391, + 528 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 514, + 391, + 528 + ], + "spans": [ + { + "bbox": [ + 306, + 514, + 391, + 528 + ], + "type": "text", + "content": "5.1. Optimization" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 533, + 546, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 546, + 676 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 546, + 676 + ], + "type": "text", + "content": "Starting from the standard optimizer used in nearly all deep learning setups, Adam, we observed that it does not train well with default parameters in the continuous video stream setting compared to the IID setting; see Fig. 2, right. To understand the differences between the two settings, we analyzed the temporal correlation between consecutive gradients. We found that the norm and variance of the gradients do not reveal strong differences. However, their orientation reveals strong correlations between pairs of consecutive gradients in the continuous case; see Fig. 2, left, where we plot the distribution of the cosine similarity between consecutive gradients in the continuous vs IID case." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 677, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 677, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 305, + 677, + 547, + 714 + ], + "type": "text", + "content": "To investigate the optimization further we performed a large sweep over commonly used optimizers, shown in Fig. 4. Results are averaged over 8 settings: 2 tasks" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "28755" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 72, + 282, + 203 + ], + "blocks": [ + { + "bbox": [ + 50, + 72, + 282, + 203 + ], + "lines": [ + { + "bbox": [ + 50, + 72, + 282, + 203 + ], + "spans": [ + { + "bbox": [ + 50, + 72, + 282, + 203 + ], + "type": "image", + "image_path": "213a18fcfefa0ad3b1539219e4cbaeaa539bccc514ef54ab1f9b370c20265c08.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 205, + 287, + 228 + ], + "lines": [ + { + "bbox": [ + 46, + 205, + 287, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 205, + 287, + 228 + ], + "type": "text", + "content": "Figure 5. Reducing momentum with the AdamW optimizer helps to recover some of the performance of RMSProp." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 251, + 286, + 299 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 251, + 286, + 299 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 286, + 299 + ], + "type": "text", + "content": "(Ego4D-stream and ScanNet-stream segmentation prediction), 2 models (ViT and UNet) and 2 displacements (1 step and 4 steps). RMS Prop significantly outperformed the more commonly used Adam variants." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 303, + 286, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 303, + 286, + 434 + ], + "spans": [ + { + "bbox": [ + 46, + 303, + 286, + 434 + ], + "type": "text", + "content": "Momentum hurts. To scrutinize the difference between AdamW and RMSProp, we looked at the impact of momentum. We found that lowering the momentum of the AdamW optimizer recovered some of the performance of RMSProp (as shown in Fig. 5). One possible explanation is that momentum exacerbates the problem of correlated consecutive gradients (that differ from the underlying gradient of the loss function over the whole stream) and makes the weights accelerate too much in the wrong direction. We stick with RMSProp for the rest of the paper, as it is more memory efficient due to not using the average of past gradients." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 439, + 286, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 439, + 286, + 545 + ], + "spans": [ + { + "bbox": [ + 46, + 439, + 286, + 545 + ], + "type": "text", + "content": "Infrequent weight updates help generalization, hurt adaptation. We also observed an interesting effect associated to the frequency of weight updates: doing it less frequently tends to benefit generalization at some cost to adaptation (since the model cannot adapt as frequently or as strongly to any particular time step). We found that updating weights every 16 frames (or 0.64s) provided a decent trade-off between adaptation and generalization across models, tasks and datasets as shown in Tab. 2" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 551, + 286, + 658 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 551, + 286, + 658 + ], + "spans": [ + { + "bbox": [ + 46, + 551, + 286, + 658 + ], + "type": "text", + "content": "Constant learning rate helps adaptation. We tested a range of common learning rate schedules including constant, linear, cosine and exponential decay, \"1cycle\" and cosine decay with restarts. The main finding was that decaying learning rates over the course of training, in particular cosine decay with exponent 2.0, helps generalization but significantly hurts adaptation as shown in Fig. 7. We therefore used a constant learning rate, with a linear warmup period of 1k steps, in our experiments." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "content": "Replay buffer batches can be small. We focus most of our exploration on the case without replay buffers, but did check what happens when we add a replay buffer to our very best setting - which slows the experiment down proportionally" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 319, + 77, + 535, + 200 + ], + "blocks": [ + { + "bbox": [ + 319, + 77, + 535, + 200 + ], + "lines": [ + { + "bbox": [ + 319, + 77, + 535, + 200 + ], + "spans": [ + { + "bbox": [ + 319, + 77, + 535, + 200 + ], + "type": "image", + "image_path": "f848979d72e5ebfbf0450ab72b44db2edf07a79ba542e12de62220d4b0e1d702.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 207, + 545, + 306 + ], + "lines": [ + { + "bbox": [ + 304, + 207, + 545, + 306 + ], + "spans": [ + { + "bbox": [ + 304, + 207, + 545, + 306 + ], + "type": "text", + "content": "Figure 6. ScanNet-stream segmentation task generalization results on the exact same out-of-stream clip after different number of hours of exposure to a same stream for 4 model runs. The models differ only by the length of the interval between weight updates / number of steps of gradient aggregation (horizontal axis). Models with less frequent updates tend to generalize better (rightmost column), whereas models with more frequent updates tend to have strong priors about which objects are currently in the scene, leading to hallucinations (leftmost 3 columns in this case)." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 307, + 310, + 543, + 384 + ], + "blocks": [ + { + "bbox": [ + 307, + 310, + 543, + 384 + ], + "lines": [ + { + "bbox": [ + 307, + 310, + 543, + 384 + ], + "spans": [ + { + "bbox": [ + 307, + 310, + 543, + 384 + ], + "type": "image", + "image_path": "63354c70b32561b07faab4ee015c3e311b8b9f97db7333ec2d79dec09c79226c.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 388, + 545, + 444 + ], + "lines": [ + { + "bbox": [ + 304, + 388, + 545, + 444 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 545, + 444 + ], + "type": "text", + "content": "Figure 7. In-stream and out-of-stream results for a learning rate schedule using cosine decay with exponent 2.0 vs a constant learning rate (both with a linear warmup phase of 1k steps. The decaying learning rate is able to generalise more quickly but at a significant cost to adaptation." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 460, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 545, + 555 + ], + "type": "text", + "content": "to the batch size employed. Over 11 hours of wall-clock training on the ScanNet-stream segmentation task with prediction displacement of 1 time step, an experiment with a replay buffer containing 10,000 samples (circular writing, random reading) and batch size 4 reached mean IoU only " + }, + { + "bbox": [ + 304, + 460, + 545, + 555 + ], + "type": "inline_equation", + "content": "2\\%" + }, + { + "bbox": [ + 304, + 460, + 545, + 555 + ], + "type": "text", + "content": " superior to a model trained without replay buffer. Batch size 16 did not improve over batch size 4 and we did not use replay buffers in any other experiments." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 563, + 382, + 575 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 563, + 382, + 575 + ], + "spans": [ + { + "bbox": [ + 306, + 563, + 382, + 575 + ], + "type": "text", + "content": "5.2. Pretraining" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 582, + 545, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 689 + ], + "type": "text", + "content": "For pretraining we did not learn from a single continuous stream, but instead formed big well-shuffled batches of 1024 clips using 8x8 slices of TPU-v5-lite, used AdamW and updated weights every step, for 150k steps. We pretrained on the Kinetics-700-2020 dataset [39], which is composed of 10s clips. We found that initializing with the ImageNet-MAE checkpoint led to much quicker optimization, so used that in all cases. More details can be found in the Appendix." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "We pretrained ViT-L models on the future prediction tasks from sec. 4 and monitored their representation learn" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28756" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 49, + 81, + 283, + 182 + ], + "blocks": [ + { + "bbox": [ + 194, + 72, + 260, + 81 + ], + "lines": [ + { + "bbox": [ + 194, + 72, + 260, + 81 + ], + "spans": [ + { + "bbox": [ + 194, + 72, + 260, + 81 + ], + "type": "text", + "content": "n steps per update" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 49, + 81, + 283, + 182 + ], + "lines": [ + { + "bbox": [ + 49, + 81, + 283, + 182 + ], + "spans": [ + { + "bbox": [ + 49, + 81, + 283, + 182 + ], + "type": "table", + "html": "
Streamdatasetmodel141664
InEgo4D (↓)UNet.036.038.037.039
ViT.035.037.039.047
Segm (↑)UNet.420.292.211.195
ViT.457.395.302.232
Out-ofEgo4D (↓)UNet.095.051.047.042
ViT.076.062.046.044
Segm (↑)UNet.176.179.205.183
ViT.251.272.280.274
", + "image_path": "e3bbe4d1c6fd96d08e484aa0c0ac5909b58e7581d6f8fd4cb69d9d63d971a8e1.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 183, + 287, + 271 + ], + "lines": [ + { + "bbox": [ + 46, + 183, + 287, + 271 + ], + "spans": [ + { + "bbox": [ + 46, + 183, + 287, + 271 + ], + "type": "text", + "content": "Table 2. Results on video streams from two datasets, two models, different numbers of steps per gradient update (horizontal), and evaluated in-stream and out-of-stream, showing the impact of accumulating gradients over multiple steps. Results are averaged over 1 and 4 displacement steps. For Ego4D-stream we report average L2 pixelwise distance (lower is better), for ScanNet-stream Segm we report mean per-frame IoU (higher is better). Bold marks the best result for each model-stream pair." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 49, + 276, + 283, + 346 + ], + "blocks": [ + { + "bbox": [ + 49, + 276, + 283, + 346 + ], + "lines": [ + { + "bbox": [ + 49, + 276, + 283, + 346 + ], + "spans": [ + { + "bbox": [ + 49, + 276, + 283, + 346 + ], + "type": "image", + "image_path": "1951bd66df1e56a0cc3c094d20df48869584a5ab79203461d875009cd80e7c02.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 351, + 287, + 449 + ], + "lines": [ + { + "bbox": [ + 46, + 351, + 287, + 449 + ], + "spans": [ + { + "bbox": [ + 46, + 351, + 287, + 449 + ], + "type": "text", + "content": "Figure 8. Linear top-1 accuracy in Kinetics during pretraining for different forms of future prediction tasks: Vanilla, Guided, Masked, and different displacements. The longer the displacement the better the accuracy is. Note that this is an online evaluation where the model only sees 4 frames (that for \"Masked\" and \"Guided\" are distorted) hence performance is far below models evaluated on the whole 10s of video (250 frames), often with plenty of test time augmentation, but the relative performance between the various curves is informative." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 461, + 286, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 461, + 286, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 461, + 286, + 544 + ], + "type": "text", + "content": "ing performance during training by adding a linear head to the model just before the decoder (we use a stack of 4 self-attention layers on top of the ViT-L encoder). For this monitoring, we employed a standard cross-entropy loss between logits and ground truth labels in conjunction with a stop-gradient so the supervision would not influence the backbone weights." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 545, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 287, + 712 + ], + "type": "text", + "content": "We experimented with different input-target clip temporal displacements and observed the interesting effect that the longer the displacement the better the classification performance is as shown in Fig. 8, even for masked future prediction, which reduces to the popular Masked Autoencoding [16] when displacement is 0. Our experiments suggest that 0 may be a sub-optimal choice. For the longest displacement the best method for top-1 accuracy emerged as Guided Future Prediction. The top result shown in the plot also used fewer guiding patches, " + }, + { + "bbox": [ + 46, + 545, + 287, + 712 + ], + "type": "inline_equation", + "content": "5\\%" + }, + { + "bbox": [ + 46, + 545, + 287, + 712 + ], + "type": "text", + "content": " instead of " + }, + { + "bbox": [ + 46, + 545, + 287, + 712 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 46, + 545, + 287, + 712 + ], + "type": "text", + "content": " - we used this best model for the rest of our evaluations. We show example video predictions for the various models online at https://sites.google.com/view/one-stream-video." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 143 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 143 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 143 + ], + "type": "text", + "content": "Table 3 has results on in/out-of-stream evaluation, showing large benefits over ImageNet classification pretraining and using no pretraining (training from scratch). ImageNet-MAE also does considerably better than classification-based pretraining. The same ViT-L architecture was used in all cases." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 151, + 460, + 164 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 151, + 460, + 164 + ], + "spans": [ + { + "bbox": [ + 305, + 151, + 460, + 164 + ], + "type": "text", + "content": "5.3. IID vs Continuous Learning" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 169, + 545, + 337 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 169, + 545, + 337 + ], + "spans": [ + { + "bbox": [ + 304, + 169, + 545, + 337 + ], + "type": "text", + "content": "We compare our best setup, which we call, for no particularly technical reason, \"Baby Learning\" (BL), to a standard deep learning setup (STDL). STDL uses AdamW with standard parameters (learning rate 1e-4, momentum b1 as 0.9), with weight updates after each batch, the same ViT-L model but with the popular ImageNet MAE checkpoint. We implement the IID setting by sampling a sequence of random time steps (and associated target time steps) from random videos of the same base dataset. Note that while most approaches employ large batches, SGD with mini-batch size 1 is well known to work well [25] and is even said to generalize better than using large batches. We match the number of frames that each method sees – namely for batch size " + }, + { + "bbox": [ + 304, + 169, + 545, + 337 + ], + "type": "inline_equation", + "content": ">1" + }, + { + "bbox": [ + 304, + 169, + 545, + 337 + ], + "type": "text", + "content": ", the total number of learning steps is reduced proportionally." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 342, + 545, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 342, + 545, + 449 + ], + "spans": [ + { + "bbox": [ + 304, + 342, + 545, + 449 + ], + "type": "text", + "content": "Dummy baseline. For reference, we also include a dummy blind baseline, proposed in previous online learning works [15], which exploits the temporal correlations in the target stream without seeing the input frames at all: this \"model\" outputs the mean of the previously seen pixels at the same locations for depth and pixel, and the most frequent colors for segmentation, for the previous target. It produces random performance for out-of-stream evaluation where consecutive targets are unrelated2." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 455, + 545, + 562 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 455, + 545, + 562 + ], + "spans": [ + { + "bbox": [ + 304, + 455, + 545, + 562 + ], + "type": "text", + "content": "Results on all tasks are shown in Table 4. We show visual results of a subset of these tasks in Fig. 9. It is visible that our approach BL matches STDL with batch size 1 out-of-stream while outperforming it in-stream. In fig. 11 in the Appendix we also report results for STDL on a continuous stream, which does not work at all, and for BL on an IID stream which does best – this shows that there are still many more improvements possible for learning from continuous streams." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 573, + 378, + 585 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 573, + 378, + 585 + ], + "spans": [ + { + "bbox": [ + 306, + 573, + 378, + 585 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 594, + 545, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 677 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 677 + ], + "type": "text", + "content": "We have presented a different perspective on continual learning by defining prediction tasks on a single very long stream of video and by proposing evaluations that measure both adaptation and generalization. We show that there is a permanent tension between the two aspects, but that it is possible to improve both by specializing the optimizer (lowering momentum, increasing the number of gradient" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 306, + 683, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 683, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 683, + 545, + 713 + ], + "type": "text", + "content": "Another baseline that may be of interest is one that copies the previous input frames instead of target frames – this could do well for both train and eval for pixels, but poorly for segmentation and depth" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28757" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 111, + 70, + 480, + 139 + ], + "blocks": [ + { + "bbox": [ + 111, + 70, + 480, + 139 + ], + "lines": [ + { + "bbox": [ + 111, + 70, + 480, + 139 + ], + "spans": [ + { + "bbox": [ + 111, + 70, + 480, + 139 + ], + "type": "table", + "html": "
Pretraining CheckpointEgo4D (↓)ScanNet Depth (↓)ScanNet Segm (↑)ScanNet (↓)
None.074 / .1051.969 / 2.163.177 / .188.083 / .083
ViT-L-I1K-CLS.043 / .0481.821 / 2.040.288 / .234.040 / .042
ViT-L-I21K-CLS.042 / .0481.735 / 2.013.244 / .192.039 / .040
ViT-L-I1K-MAE.040 / .0441.806 / 2.045.360 / .320.037 / .038
Guided Future Prediction.036 / .0431.622 / 1.990.390 / .313.032 / .034
", + "image_path": "cfae13538cdb93e33d454dd3fe82d31ab15699d79c6be6435a14bded7d2a42d6.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 85, + 180, + 509, + 319 + ], + "blocks": [ + { + "bbox": [ + 85, + 180, + 509, + 319 + ], + "lines": [ + { + "bbox": [ + 85, + 180, + 509, + 319 + ], + "spans": [ + { + "bbox": [ + 85, + 180, + 509, + 319 + ], + "type": "image", + "image_path": "434eeaeb60a31837e7295faa927699a6c34eea83750125c914dbe24b125993af.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 69, + 322, + 523, + 333 + ], + "lines": [ + { + "bbox": [ + 69, + 322, + 523, + 333 + ], + "spans": [ + { + "bbox": [ + 69, + 322, + 523, + 333 + ], + "type": "text", + "content": "Figure 9. Future prediction results for video streams from Ego4D-stream, ScanNet-stream Segm, and ScanNet-stream Depth." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 64, + 341, + 529, + 411 + ], + "blocks": [ + { + "bbox": [ + 46, + 140, + 546, + 172 + ], + "lines": [ + { + "bbox": [ + 46, + 140, + 546, + 172 + ], + "spans": [ + { + "bbox": [ + 46, + 140, + 546, + 172 + ], + "type": "text", + "content": "Table 3. Table comparing performance of models pretrained on ImageNet-1K and 21K using MAE or classification, and models pretrained on our video tasks in Kinetics. The results are averaged over two sets of experiments, with displacements of 1 and 4 time steps and are shown in the format in-stream / out-of-stream." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 64, + 341, + 529, + 411 + ], + "lines": [ + { + "bbox": [ + 64, + 341, + 529, + 411 + ], + "spans": [ + { + "bbox": [ + 64, + 341, + 529, + 411 + ], + "type": "table", + "html": "
Ego4D (↓)ScanNet (↓)ScanNet Segm (↑)ScanNet Depth (↓)
displacement (Δ)t+1t+4t+1t+4t+1t+4t+1t+4
STDL (IID) bs 16.023/.019.060/.055.014/.013.042/.061.495/.398.382/.2951.798/2.011.838/2.038
STDL (IID) bs 1.019/.018.057/.056.010/.013.051/.060.376/.302.276/.2271.722/2.0121.759/2.034
BL (Cont.) bs 1.018/.021.055/.066.011/.012.055/.061.463/.312.328/.2411.595/2.0381.655/2.097
Blind (dummy).038 / -.086 / -.032/ -.109/ -.547/ -.307/ -1.256 / -1.649 / -
", + "image_path": "1abdd9cbbb944f5917515ca2242724f44b139c3153d431e54a1c4228514d432e.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 419, + 547, + 485 + ], + "lines": [ + { + "bbox": [ + 46, + 419, + 547, + 485 + ], + "spans": [ + { + "bbox": [ + 46, + 419, + 547, + 485 + ], + "type": "text", + "content": "Table 4. Future prediction results for video streams from various datasets for two different temporal displacements (horizontal). We show results for the standard deep learning approach (STDL) on IID data with batch size 16 and 1, and for our approach (BL) when using a continuous video stream (Cont.). Two numbers are reported for every cell, corresponding to in-stream / out-of-stream performance. We highlight which of the two batch size 1 approaches performs best for each number. The Blind (dummy) model exploits correlations in the target stream which is available in-stream and used for learning, hence performs very well in-stream, but has random performance in evaluation where the target stream is not available. This shows the necessity to measure both adaptation and generalization performance." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 506, + 287, + 625 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 506, + 287, + 625 + ], + "spans": [ + { + "bbox": [ + 46, + 506, + 287, + 625 + ], + "type": "text", + "content": "aggregation steps between weight updates) and by pretraining the model appropriately. Conversely, we show that just using Adam with default parameters performs poorly on single-stream learning, due to the large correlations in the data. This makes the proposed setting different from popular ImageNet-based continual learning setups where batches are employed, and the data is significantly uncorrelated - for example in class-by-class learning, seeing different web images of dogs will not break Adam the way consecutive frames in a video does." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 630, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 288, + 713 + ], + "type": "text", + "content": "We admit that the motivation for the research direction laid out in this paper may not be immediately crystal clear to everyone, particularly in the context of the current research landscape, that focuses on fitting larger and larger models to the whole internet. We are motivated by a possible future where people have their models in physical devices they carry around and train them via natural interac-" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 506, + 545, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 506, + 545, + 579 + ], + "spans": [ + { + "bbox": [ + 304, + 506, + 545, + 579 + ], + "type": "text", + "content": "tion – by showing them the world from their perspective – and teach them only the things that they believe the models should be taught, similar to the way we teach children. It is likely that such models, by not having to know everything, can be smaller, more efficient, have fewer internet biases and be more privacy-friendly." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 586, + 545, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 586, + 545, + 651 + ], + "spans": [ + { + "bbox": [ + 304, + 586, + 545, + 651 + ], + "type": "text", + "content": "Acknowledgments. 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Label-efficient online continual object detection in streaming video, 2023. 2" + } + ] + } + ], + "index": 1 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "28761" + } + ] + } + ], + "index": 3 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_content_list.json b/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..73cb9028cdb2a09bb7847270dbd393e07d569e61 --- /dev/null +++ b/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_content_list.json @@ -0,0 +1,1610 @@ +[ + { + "type": "text", + "text": "Learning from Synthetic Human Group Activities", + "text_level": 1, + "bbox": [ + 233, + 130, + 736, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Che-Jui Chang†\nRutgers University\nchejui.chang@rutgers.edu", + "bbox": [ + 153, + 179, + 367, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Parth Goel \nRutgers University \ngoel.parth210@gmail.com", + "bbox": [ + 158, + 241, + 367, + 292 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Samuel S. Sohn \nRutgers University \nsamuel.sohn@rutgers.edu", + "bbox": [ + 140, + 301, + 346, + 354 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Danrui Li\nRutgers University\ndanrui.li@rutgers.edu", + "bbox": [ + 411, + 181, + 602, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Honglu Zhou NEC Laboratories hozhou@nec-labs.com", + "bbox": [ + 390, + 241, + 607, + 292 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Sejong Yoon \nThe College of New Jersey \nyoons@tcnj.edu", + "bbox": [ + 390, + 301, + 607, + 354 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Mubbasir Kapadia Roblox", + "bbox": [ + 410, + 362, + 560, + 395 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "mkapadia@roblox.com", + "bbox": [ + 395, + 401, + 568, + 414 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Deep Patel NEC Laboratories dpatel@nec-labs.com", + "bbox": [ + 630, + 181, + 818, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Seonghyeon Moon† \nRutgers University \nsm206@cs.rutgers.edu", + "bbox": [ + 630, + 241, + 826, + 292 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Vladimir Pavlovic \nRutgers University \nvladimir@rutgers.edu", + "bbox": [ + 651, + 301, + 828, + 354 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 425, + 313, + 440 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The study of complex human interactions and group activities has become a focal point in human-centric computer vision. However, progress in related tasks is often hindered by the challenges of obtaining large-scale labeled datasets from real-world scenarios. To address the limitation, we introduce $M^3$ Act, a synthetic data generator for multi-view multi-group multi-person human atomic actions and group activities. Powered by Unity Engine, $M^3$ Act features multiple semantic groups, highly diverse and photorealistic images, and a comprehensive set of annotations, which facilitates the learning of human-centered tasks across single-person, multi-person, and multi-group conditions. We demonstrate the advantages of $M^3$ Act across three core experiments. The results suggest our synthetic dataset can significantly improve the performance of several downstream methods and replace real-world datasets to reduce cost. Notably, $M^3$ Act improves the state-of-the-art MOTRv2 on DanceTrack dataset, leading to a hop on the leaderboard from $10^{th}$ to $2^{nd}$ place. Moreover, $M^3$ Act opens new research for controllable 3D group activity generation. We define multiple metrics and propose a competitive baseline for the novel task. Our code and data are available at our project page: http://cjerry1243.github.io/M3Act.", + "bbox": [ + 73, + 448, + 472, + 795 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 806, + 209, + 823 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Understanding collective human activities and social groups carries significant implications across diverse domains, as it contributes to bolstering public safety within", + "bbox": [ + 76, + 827, + 468, + 875 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "surveillance systems, ensuring safe navigation for autonomous robots and vehicles amidst human crowds, and enriching social awareness in human-robot interactions [8, 9, 11, 12, 21, 37, 49, 51]. However, the advancement in related tasks is often impeded by the challenges of obtaining large-scale human group activity datasets in real-world scenarios with fine-grained multifaceted annotations.", + "bbox": [ + 500, + 426, + 890, + 531 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Generating synthetic data is an emerging alternative to collecting real-world data due to its capability of producing large-scale datasets with perfect annotations. Nonetheless, most synthetic datasets [4, 20, 40, 48, 53] are primarily designed to facilitate human pose and shape estimation. They can only provide data with independently-animated persons, which is unsuitable for tasks in single-group and multi-group conditions [51]. To address the limitation, we propose $\\mathbf{M}^3\\mathrm{Act}$ , a synthetic data generator, with multi-view multi-group multi-person human actions and group activities. As presented in Tab. 1, $\\mathbf{M}^3\\mathrm{Act}$ stands out by offering comprehensive annotations including both 2D and 3D annotations as well as fine-grained person-level and group-level labels, thereby making it an ideal synthetic dataset generator to support tasks such as human activity recognition and multi-person tracking across all listed real-world datasets.", + "bbox": [ + 496, + 534, + 892, + 790 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Illustrated in Fig. 1, our synthetic data generator features multiple semantic groups, highly diverse and photorealistic images, and a rich set of annotations. It encompasses 25 photometric 3D scenes, 104 HDRIs (High Dynamic Range Images), 5 lighting volumes, 2200 human models, 384 animations (categorized into 14 atomic action classes), and 6 group activities. For our experiments, We generated two", + "bbox": [ + 496, + 794, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "$\\dagger$ Work done during internship at Roblox", + "bbox": [ + 101, + 886, + 316, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "21922", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/2f8377696cb398b2c1f7fec555d61c93582c533c3194499984a418d2151fe716.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 88, + 424, + 258 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/84d512435123117bdc456921bc13f0b3c34566216912e94769387946fd6d6d81.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 426, + 90, + 665, + 256 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/f11abe269237809af3b823ff8a55751f3dc318ddca74607a1ab071ba037a8416.jpg", + "image_caption": [ + "Figure 1. M3Act is a large-scale synthetic data generator designed to support multi-person and multi-group research topics. M3Act features multiple semantic groups and produces highly diverse and photorealistic videos with a rich set of annotations suitable for human-centered tasks including multi-person tracking, group activity recognition, and controllable human group activity generation." + ], + "image_footnote": [], + "bbox": [ + 80, + 263, + 145, + 323 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/4e932e519e03ba716df92952248a80b82f85e9c9969179b324f4ab8dd5ae498b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 148, + 263, + 210, + 321 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/9fcdd490d07ff67b1b5a52aec5cdcc2b929798a6375ea7067276d31df88d9db8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 212, + 265, + 277, + 321 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/213abc73eeb26a12d70f20d298dc6fdb6dfe7c454de2408fc4fe74d4877b11f6.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 279, + 265, + 344, + 321 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/c5525486514f6ca5c7bedce1118cb0d43686e6a9a8cacf60f7977222855e9baf.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 346, + 265, + 410, + 321 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/fdcbdcdc5b5cd8c6ece675ce29e79a1f3f34b9840c5606aa74aca9e895aee4c2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 411, + 263, + 475, + 321 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/053698ccada6bfad1715fbc380c249a6c7aeb27cd8737da032148499ecae0e60.jpg", + "image_caption": [ + "Diverse Scenes and Lighting Conditions" + ], + "image_footnote": [], + "bbox": [ + 483, + 263, + 661, + 323 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/af06b99de4a1c3643ba561c6cb17b790d175e1798fcdc51dc51464b491c84418.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 684, + 89, + 890, + 169 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/01f83d2ef78bbf8da7bda3ca822b987a9b0296d99ea580a0c1abaf837787d9b9.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 683, + 174, + 883, + 253 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/478c37587e8f0dacd8a3c4c4de36d02fa278d0966d7230670ee2be42c2776baa.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 684, + 257, + 888, + 337 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "datasets, M $^3$ ActRGB and M $^3$ Act3D. M $^3$ ActRGB contains both single-group and multi-group data with a total of 6M frames of RGB images and 48M bounding boxes, rendered in 20 FPS. M $^3$ Act3D is a 3D-only and single-group dataset, which contains 3D motions of all persons within a group. It has large group sizes (max 27 people) and an average of 6.7 persons per group. In total, M $^3$ Act3D contains a duration of 87.6 hours of group activities, captured in 30 FPS.", + "bbox": [ + 75, + 398, + 468, + 520 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We first demonstrate the merit of $\\mathsf{M}^3\\mathsf{Act}$ via synthetic data pre-training and mixed training on multi-person tracking and group activity recognition. For multi-person tracking, training with our synthetic data yields significant performance gain on several downstream methods [23, 52, 56, 57]. We also demonstrate notable improvements in the state-of-the-art MOTRv2 method [57] and observe that our synthetic data can substitute for $62.5\\%$ more real-world data, without compromising performance. In terms of group activity recognition, results indicate that pre-training with $\\mathsf{M}^3\\mathsf{ActRGB}$ greatly improves both person-level and group-level accuracy for Composer [58] and ActorTransformer [25] methods. Based on our generated data, we then introduce a novel task, controllable 3D group activity generation, which aims to synthesize a group of 3D human motions, given control signals such as activity labels and group sizes. We systematically approach the new task by introducing both learning-based and heuristics-based metrics, along with a competitive baseline to generate meaningful human activities.", + "bbox": [ + 75, + 521, + 470, + 821 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "This paper makes the following contributions:", + "bbox": [ + 76, + 824, + 382, + 838 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "- We propose a novel synthetic data generator, $\\mathsf{M}^3\\mathsf{Act}$ , and provide two large-scale synthetic datasets with highly diverse human activities, photorealistic multi-view videos, and comprehensive annotations.", + "bbox": [ + 76, + 839, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We demonstrate that $\\mathsf{M}^3\\mathsf{Act}$ can significantly improve benchmark performances for multi-person tracking and group activity recognition and replace a large portion of real-world training data to reduce cost.", + "- $\\mathrm{M}^{3}\\mathrm{Act}$ promotes new research initiatives for controllable 3D group activity generation, suggesting that synthetic data can not only support existing tasks but also create datasets for novel research." + ], + "bbox": [ + 500, + 398, + 892, + 518 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 500, + 530, + 648, + 545 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Human Centered Synthetic Datasets. The use of synthetic datasets for human-centered tasks has become increasingly prominent due to their diversity, scalability, and perfect annotations, with proven merits connected to various fields in machine learning, including domain adaptation [34, 46], heterogeneous multitask learning [54], and sim2real [24] or task2sim [39] transfer. Most previous synthetic datasets are constructed to support human pose estimation. For example, SURREAL [48] contains renderings of human motions from 145 avatars composited to a background image. Subsequent works [2, 20, 40] managed to improve the image quality by leveraging realistic 3D scenes, high-quality renderings, and HDRI images. Recently, synthetic datasets have been proposed to tackle human shape and mesh estimation. SynBody [53] constructs layered human assets to increase character diversity. BEDLAM [4] adds physically simulated hair and clothes to achieve state-of-the-art performances on shape and mesh estimation. Nonetheless, data with collective human motions and group activities cannot be obtained from them. Our work, $\\mathsf{M}^3\\mathsf{Act}$ , is constructed with animated human groups tailored to multi-person and multi-group research.", + "bbox": [ + 496, + 551, + 890, + 883 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Real Multi-Person Datasets. Real-world datasets [15, 17,", + "bbox": [ + 500, + 885, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "21923", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "table", + "img_path": "images/e01c388623b2ed026af9bcebacb35dc9a24b0a4d9645a5b9ef526044046c8225.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DatasetImage TypeAvatar Num.VideoMulti-ViewMulti-PersonMulti-Group2D3DAnnotations Atomic Atn.Group Act.
SURREAL, 2017 [48]Composite145✓✓✓
AGORA, 2021 [40]HDRI350✓✓✓
HSPACE, 2021 [2]3D Scene1600✓✓✓✓✓
GTA-Humans, 2021 [6]3D Scene600✓✓✓✓
PSP-HDRI+, 2022 [20]HDRI28✓✓✓
SynBody, 2023 [53]3D Scene10k✓✓✓✓✓
BEDLAM, 2023 [4]3D Scene271✓✓✓✓
M3Act (Ours)Photometric 3D + HDRI2200✓✓✓✓✓✓✓✓
CAD, 2011 [15]Real-✓✓✓✓✓✓
Volleyball Dataset, 2016 [29]Real-✓✓✓✓✓✓
NTU-RGBD 120, 2019 [33]Real-✓✓✓✓✓✓
HiEve, 2020 [32]Real-✓✓✓✓✓
PoseTrack, 2021 [18]Real-✓✓✓✓
MOT, 2020 [17]Real-✓✓✓✓
DanceTrack, 2022 [45]Real-✓✓✓
JRDB, 2023 [21, 37, 49]Real-✓✓✓✓✓✓
", + "bbox": [ + 76, + 87, + 893, + 311 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Table 1. A comparison of synthetic datasets as well as commonly-used real datasets for activity understanding and person tracking. We refer to JRDB as a union set of JRDB, JRDB-Act, and JRDB-Pose datasets. Note that it offers 3D bounding boxes, but not poses.", + "bbox": [ + 75, + 314, + 892, + 344 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "18, 29, 32, 33, 37, 45] with multiple persons are usually collected for tasks such as group activity understanding, multiperson tracking, and human trajectory prediction. Recognizing and parsing collective human activities [25, 58] rely primarily on multiple modalities (RGB, bounding box, pose) and hierarchical action and activity labels. These fine-grained labels are provided by datasets like CAD [15] and Volleyball Dataset [29]. On the other hand, datasets for person tracking, such as HiEve [32], MOT [17, 38], and DanceTrack [45], require not only 2D annotations (e.g., bounding box) for individual frames, but also the association of the objects between them. Specifically, DanceTrack provides multiple persons in a group with the same clothing, making it difficult for the association of the individuals. MOT datasets target tracking for human crowds and contain mostly outdoor scenes from a bird-eye view. Recently, JRDB [21, 37, 49] with rich annotations is released. The images are captured by a social robot, navigating around daily scenes. It provides fine-grained annotations that support various tasks, including person detection, pose estimation, tracking, collective activity detection, and understanding. M³Act not only offers the same modalities and annotations for supporting the aforementioned tasks, but it also provides full 3D annotations, making it suitable for a wide range of applications beyond the 2D domain.", + "bbox": [ + 75, + 354, + 472, + 733 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. $\\mathbf{M}^3\\mathbf{A}\\mathbf{c}\\mathbf{t}$", + "text_level": 1, + "bbox": [ + 76, + 742, + 156, + 758 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "$\\mathsf{M}^3\\mathsf{Act}$ is a multi-view multi-group multi-person human atomic action and group activity data generator built with Unity Engine and the Perception [5] library. Inspired by PeopleSansPeople [19] that populates randomly posed human avatars in a scene and renders static images, $\\mathsf{M}^3\\mathsf{Act}$ not only offers the same functionalities for human poses but also extends it to the spatio-temporal domain. It generates RGB videos for dynamic human motions and produces a rich set of annotations simultaneously, including (a) 2D", + "bbox": [ + 75, + 763, + 472, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "and 3D joints/meshes, (b) 2D and 3D bounding boxes for individual persons, (c) atomic action and group activity categories, (d) tracking information such as individual and group IDs, (e) segmentation, depth, and normal images, and (f) scene description.", + "bbox": [ + 496, + 354, + 893, + 431 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Data Generation", + "text_level": 1, + "bbox": [ + 498, + 440, + 666, + 455 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The process of our data generation is illustrated in Fig. 2. First, the generation process is configured by the simulation scenario that manages multiple independent simulations of human activities. Then for each simulation, a 3D scene with background objects, lights, and cameras is set up, and groups of human characters are instantiated to be animated. Lastly, the multi-view RGB image frames are rendered and the annotations are exported at the end of the simulation.", + "bbox": [ + 496, + 459, + 893, + 580 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Scene Instantiation. We represent the environment through 25 photometric 3D scenes and 104 panoramic HDRIs. Each scene is initiated with randomized lighting and camera configuration. To attain a balance between realistic environmental illumination and pronounced shadow detail, our lighting schema integrates HDRI Sky lighting with a directional light. This directional light is subject to random variations in its direction, color temperature, and intensity. Regarding camera placement, we always point cameras towards the center of avatar groups and introduce variability by randomizing both the field of view and the camera's distance to these groups.", + "bbox": [ + 496, + 580, + 893, + 762 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Human Models and Motion Assets. M³Act leverages 2000 human models generated by Synthetic Humans [42], ranging across all ages (1 ~ 100), genders, ethnicities (such as Caucasian, Asian, Latin American, African, Middle Eastern), diverse body shapes, hair, and clothing. We also incorporated 200 widely-used human characters from RenderPeople [1]. For the human motions, we collected 384 animation clips from AMASS [36], categorized into 14 atomic action classes. We created a universal animation controller", + "bbox": [ + 496, + 763, + 895, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "21924", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/b7ad24563c921b062901e128d44792afbb317fa30af82ffd6505d64c1eebf9f4.jpg", + "image_caption": [ + "Figure 2. The data generation process of $\\mathsf{M}^3\\mathsf{Act}$ . It consists of multiple data simulations with scene instantiation, group activity authoring, and a data capture module. A high degree of randomization is involved in all aspects of the process to ensure diverse data." + ], + "image_footnote": [], + "bbox": [ + 83, + 88, + 869, + 266 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "that blends styles, including arm space and stride size, to create diverse motions from the collected clips.", + "bbox": [ + 75, + 316, + 470, + 347 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Modular Group Activities. Each group activity is structured as a parameterized module, allowing for the customization of numerous variables. These variables include the number of individuals in the group and the specific atomic actions permitted within the group activity. This modularization ensures easy duplication, repositioning, and reuse of the group activities, enabling simulations of multiple groups at the same time. To procedurally animate a group of humans within a modular group, we establish the positions and orientations of the selected characters while choosing the appropriate animation clip for each character through the activity script. It's important to note that, despite drawing characters from the same set of avatars, the configurations and animations of these characters can vary significantly from one group to another. For example, animating a queueing activity may require all characters to be aligned in a straight line, while those in a walking group may form various shapes. The atomic actions that a person can perform also depend on the specific group activity. We carefully consider all these factors when authoring activities and provide a summary in the Sup. Mat.", + "bbox": [ + 75, + 351, + 470, + 669 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Domain Randomization. $\\mathbf{M}^{3}\\mathrm{Act}$ provides domain randomization for almost all aspects of the data generation process to ensure the simulation data is highly diverse. These aspects include the number of groups in a scene, the number of persons in each group, the positions of groups, the alignment of persons in a group, the positions of individuals, the textures for the instantiated characters, and the selection of scenes, lighting conditions, camera positions, characters, group activities, atomic actions, and animation clips. Despite the fact that animating group activities inherently limits the degree of freedom in the placement of characters, by altering the shapes in which characters align (e.g., either in a cluster, a straight line, or a curve), $\\mathbf{M}^{3}\\mathrm{Act}$ nonetheless generates diverse activities and achieves sufficient randomization for downstream model generalization. More details re", + "bbox": [ + 75, + 674, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "garding the randomization variables and their distributions are provided in Sup. Mat.", + "bbox": [ + 498, + 316, + 890, + 345 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Rendering and Annotations. $\\mathbf{M}^{3}\\mathrm{Act}$ utilizes the Unity high-definition render pipeline for the creation of photorealistic RGB images and leverages the Perception library for capturing annotations. On average, data is generated at a rate of 4.2 FPS using one NVIDIA RTX 3070 Ti graphics card, with a resolution of $1920\\times 1080$ , and all annotations are enabled. Similar to PeopleSansPeople, the 2D skeleton follows COCO [31] format, with additional labelers for exporting 3D joints, meshes, group IDs, and activity classes. After the data generation, the 3D joints and meshes are fitted with SMPL parameters [35, 41].", + "bbox": [ + 496, + 347, + 892, + 513 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Dataset Statistics", + "text_level": 1, + "bbox": [ + 500, + 520, + 668, + 534 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "$\\mathrm{M}^{3}\\mathrm{Act}$ comprises 25 photometric 3D scenes, 104 HDRIs, 5 lighting volumes, 2200 human models, 384 animations (categorized into 14 atomic action classes), and 6 group activities. Using the generator, we first generated our synthetic dataset, $\\mathrm{M}^{3}\\mathrm{ActRGB}$ . It contains 6K simulations of every single-group activity and 9K simulations of multi-group configuration, with 4 camera views. Each simulation produces a 5-second video clip, captured in 20 FPS and FHD resolution. In total, $\\mathrm{M}^{3}\\mathrm{ActRGB}$ contains 6M RGB images and 48M bounding boxes. The average track length is 4.65 seconds.", + "bbox": [ + 496, + 537, + 890, + 700 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Additionally, we generated $\\mathrm{M}^3\\mathrm{Act3D}$ , a large-scale 3D-only dataset. It consists of more than $65\\mathrm{K}$ simulations of single-group activity. Each contains 150 frames of multiperson collective interactions in 30 FPS, resulting in a total duration of 87.6 hours. As shown in Tab. 2, both the group size and the interaction complexity are significantly higher than those in previous multi-person motion datasets. Specifically, when compared with GTA-Combat [44], $\\mathrm{M}^3\\mathrm{Act3D}$ contains more persons in a group, has more group activities, and provides a variable number of persons in a group. To the best of our knowledge, $\\mathrm{M}^3\\mathrm{Act3D}$ is the first large-scale 3D dataset for human group activities with large group sizes as well as per-frame individual action labels. See Sup. Mat.", + "bbox": [ + 496, + 704, + 892, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "21925", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "table", + "img_path": "images/a669e3cd7266e444f0c2ce261d07eaf9111612d85baee8c4d960ccff26c98b75.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DatasetFPS# of Acty.# of Persons# of Actn.Duration
AvgMax
SBU [55]1582.02-7.6 mins
Duet Dance [30]2552.02-2.3 hrs
CHI3D [22]5082.02-2.7 hrs
NTU RGBD 120 [33]30262.02-15.0 hrs
GTA-Combat [44]1513.25-39.0 hrs
M3Act3D3066.727887.6 hrs
", + "bbox": [ + 78, + 89, + 470, + 200 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "for detailed statistics of both datasets.", + "bbox": [ + 76, + 260, + 326, + 273 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 285, + 209, + 301 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We showcase the practical utilities of $\\mathsf{M}^3\\mathsf{Act}$ through three core experiments: Multi-Person Tracking (MPT), Group Activity Recognition (GAR), and controllable Group Activity Generation (GAG). The experiments are carefully designed to cover the following three perspectives:", + "bbox": [ + 75, + 304, + 468, + 380 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Multi-modality: Our experiments cover various modalities contained within our dataset, including RGB videos, 2D keypoints, and 3D joints. We leverage the rich annotations including bounding boxes, tracklets, group activities, and person action labels.", + "- Performance: We conduct the ablation study by altering the amount and the type of synthetic data used for training to see its effect on the model performance.", + "- Novel task: We introduce a novel generative task (GAG), showing that synthetic data can not only support existing CV tasks but also create datasets for new research." + ], + "bbox": [ + 76, + 383, + 468, + 550 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Multi-Person Tracking", + "text_level": 1, + "bbox": [ + 76, + 563, + 289, + 579 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The objective of MPT is to predict the trajectories of all persons from a dynamic video stream. Typically, person tracking involves two separate processes, person detection and association. While the tracking task is approached in some prior works with the tracking-by-detection method [3, 7, 50], we consider end-to-end approaches [23, 52, 56, 57] to evaluate the use of synthetic data on the performance of MPT as a whole, in lieu of an improved performance caused only by refined detection.", + "bbox": [ + 75, + 580, + 468, + 715 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Real-world Dataset: DanceTrack [45] (DT) is a challenging MPT dataset characterized by dynamic movements with human subjects in uniform appearances. It has a total of 100 videos with over 105K frames.", + "bbox": [ + 75, + 718, + 468, + 777 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Synthetic Dataset. Given the motion categories in the real-world dataset, we select a subset of $\\mathbf{M}^3$ ActRGB with groups of people dancing, walking, and running. We use 1000 video clips with a single \"dance\" group as well as 1500 videos with a \"walk\" group and a \"run\" group simulated at the same time (denoted as WalkRun). We alter the use of the synthetic group activities (Dance, WalkRun, and Dance+WalkRun) in our experiments.", + "bbox": [ + 75, + 779, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/bbe30ec9114c8069426fe01b3305b2bbd39593a17188a9cf7a5de8b593de0acf.jpg", + "table_caption": [ + "Table 2. A comparison of datasets for 3D multi-person human activities. $\\mathbb{M}^3\\mathbb{A}\\mathbb{ct}\\mathbb{3}\\mathbb{D}$ is the largest dataset with labels for atomic actions and more persons in a group." + ], + "table_footnote": [], + "table_body": "
Training DataHOTA↑DetA↑AssA↑IDF1↑MOTA↑
DT®69.883.058.971.689.3
DT68.8 (10)82.557.470.390.8
DT + Syn (D)59.075.546.159.082.6
DT + Syn (WR)70.183.159.472.592.0
DT + Syn (WR+D)71.9 (2)83.662.074.792.6
DT + Syn† (WR+D)72.283.462.675.592.7
DT (MOTRv2*)73.483.764.476.092.1
DT + BEDLAM [4]55.968.744.553.879.1
DT + GTA-Humans [6]54.166.844.252.178.8
", + "bbox": [ + 501, + 88, + 890, + 224 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/409e16e2d31a2c16d761a1746e0b8742177d27918adfc000a508c79e0b7bf48f.jpg", + "table_caption": [ + "Table 3. MPT results on DanceTrack with MOTRv2. \"D\" means synthetic dance group. \"WR\" means walk and run groups. \"WR+D\" refers to \"D\" and \"WR\" combined. The symbol $\\text{串}$ represents the author-provided checkpoint. The symbol $\\dagger$ marks the same model with additional association at inference. Numbers in parentheses represent the rank in the DanceTrack leaderboard." + ], + "table_footnote": [], + "table_body": "
ModelSyn. DataHOTADetAAssAIDF1MOTA
MOTR [56]✓54.273.540.251.579.7
60.076.448.156.083.8
MeMOTR [23]✓68.580.558.471.289.9
71.181.862.374.192.2
CO-MOT [52]✓69.482.158.971.991.2
72.583.663.375.992.8
MOTRv2 [57]✓68.882.557.470.390.8
71.983.662.074.792.6
MOTRv2* [57]✓73.483.764.476.092.1
74.684.164.976.493.1
", + "bbox": [ + 504, + 325, + 887, + 484 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Table 4. MPT results on DanceTrack using different methods trained with our synthetic data.", + "bbox": [ + 498, + 489, + 890, + 518 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Results. We mix together both synthetic and real data during training and present the results in Tab. 3. First, adding our synthetic data yields significant improvement in all 5 tracking metrics as well as a hop in ranking on HOTA from $10^{th}$ to $2^{nd}$ place. The model trained with our synthetic data plus the extra association, marked as $\\mathrm{DT} + \\mathrm{Syn}^{\\dagger}$ (WR+D), achieves similar performance to MOTRv2*, the same model that is trained with additional validation data with an ensemble of 4 models [57]. This suggests that the synthetic data used in our experiment is equivalent to at least $62.5\\%$ more real data. Second, Compared with other synthetic data sources, such as BEDLAM and GTA-Humans, M³Act demonstrates superior performance, indicating its better suitability for multi-person dynamic conditions. Third, we observe that the type of synthetic groups affects the model performance on real data. Adding the \"WalkRun\" groups to the training data is more effective than adding the \"Dance\" group. This is because while the DanceTrack dataset contains dynamic dance movements, the real challenge lies in detection and tracking when the subjects switch positions. By design, the positions of the characters in our dance group are well-staged and the movements are nearly synchronous. (See Sup. Mat. for the design.) Contrarily, having a walk and a run group together", + "bbox": [ + 496, + 537, + 890, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "21926", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/517ad54b79d6ae0224d11c9a7c85bb5c0f0c794de1c7de4fbbecddbc97790e37.jpg", + "table_caption": [], + "table_footnote": [ + "Table 5. Results of 2D keypoint-based group activity and person action recognition on CAD2 dataset. The best results are shown in parentheses. The results suggest that pre-training with our synthetic data largely increases the accuracy for both group activity and person actions. Note that group accuracy saturates at $93.4\\%$ and $86.2\\%$ forComposer and Actor Transformer respectively." + ], + "table_body": "
ModelPretrained \nSyn. DataGroup ActivityPerson Action
Top 1 Acc (%) ↑Top 1 Acc (%) ↑
Composer \n[58]N/A84.87±2.3(88.20)81.31±2.4(83.13)
10%86.12±1.8(87.87)84.16±1.8(86.03)
25%87.65±1.2(89.01)86.36±1.3(86.81)
50%89.39±0.4(90.14)86.68±1.5(87.99)
100%89.74±1.0(91.51)88.74±1.7(89.05)
Gains+4.87 (+3.31)+7.43 (+5.92)
Actor \nTransformer \n[25]N/A78.08±1.0(79.47)76.22±2.2(78.07)
10%77.59±2.4(81.00)76.01±3.2(79.76)
25%81.36±2.1(83.19)78.86±2.4(80.05)
50%82.72±1.3(84.56)79.95±1.6(81.47)
100%83.67±1.2(84.88)81.65±1.2(82.22)
Gains+5.59 (+5.41)+5.43 (+4.15)
", + "bbox": [ + 78, + 89, + 475, + 296 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "in a scene leads to frequent position switches relative to the camera view and thus improves the model performance. Lastly, Tab. 4 presents the tracking results using different methods. Results indicate that our synthetic data is effective across various models.", + "bbox": [ + 75, + 401, + 468, + 476 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Group Activity Recognition", + "text_level": 1, + "bbox": [ + 76, + 487, + 326, + 503 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The goal of GAR is to determine the class of the group activity performed by the dominant group as well as the action class of each person. We consider Composer [58] and Actor Transformer [25] as the benchmark models. The former is a multi-scale transformer-based model and accepts only 2D keypoints as input. The latter can take combinations of multiple input modalities.", + "bbox": [ + 75, + 505, + 468, + 609 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Real-world Dataset: CAD2 [15] and Volleyball Dataset [29]. CAD2 is an extended version of the Collective Activity Dataset [14] that records human group activities and is widely used for GAR benchmarks [51]. Volleyball Dataset (VD) is an action recognition dataset. It has 55 videos with 9 player action labels and 8 team activity labels.", + "bbox": [ + 75, + 611, + 468, + 702 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Synthetic Dataset. We use a subset of all single-group data from M³ActRGB. It contains a total of 10K videos and over 600K frames. It contains all group activity and individual action classes that CAD2 provides and further includes 7 more action types.", + "bbox": [ + 75, + 703, + 468, + 779 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Results. We experimentally study how the size of our pretraining synthetic dataset and the capacity of a GAR model affect generalization from the synthetic to real domains. We first train the models on different amounts of synthetic data. Then we fine-tune them on CAD2 and report the top 1 accuracy of both group activity and person action recognition on the test set of CAD2. Tab. 5 presents the results using only 2D keypoints as input. We see a common trend for", + "bbox": [ + 75, + 780, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/11b5bcef8ffc1f8f649c5220323ec3e10e6447534a3ff5ad499332cc34a29220.jpg", + "table_caption": [], + "table_footnote": [ + "Table 6. The group activity recognition accuracy on CAD2 and Volleyball Dataset using different input modalities." + ], + "table_body": "
Model2D RGB FlowCAD2 Syn+CAD2VD Syn+VD
Composer✓88.291.594.695.1
Actor Transformer✓79.584.992.393.7
✓78.280.791.492.5
✓✓81.085.293.594.3
✓81.385.094.495.0
✓79.581.993.094.1
", + "bbox": [ + 501, + 89, + 903, + 186 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "both GAR models that the recognition accuracy increases as more synthetic data is used for pre-training. With $100\\%$ of synthetic data, the accuracy of Composer increases, with an average of $4.87\\%$ at the group level and $7.43\\%$ at the person level, whereas Actor Transformer sees a $5.59\\%$ increase at group level and $5.43\\%$ increase at person level. Moreover, Tab. 6 shows the group recognition accuracy using different input modalities on CAD2 and VD. The performance gains in the experiment indicate that our synthetic data can effectively benefit the downstream GAR task across different methods, input modalities, and datasets.", + "bbox": [ + 496, + 237, + 893, + 402 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Controllable 3D Group Activity Generation", + "text_level": 1, + "bbox": [ + 498, + 411, + 870, + 426 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "While the procedural generation of our group activities in $\\mathbf{M}^{3}\\mathrm{Act}$ yields realistic and diverse human activities, the implementation requires considerable effort and involves the design and application of specific heuristics. Learning a generative model for human group activities, instead, encodes the heuristics to the architecture inherently and encompasses the capabilities of probabilistically generating diverse activities, with control over the entire group of human motions from various signals. To this end, we introduce controllable 3D group activity generation (GAG).", + "bbox": [ + 496, + 429, + 890, + 580 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Definition. Let $G_{t}^{p} = \\{m_{i}^{n}\\}_{i = 1\\sim t,n = 1\\sim p}$ be a group of human motions with $t$ frames and $p$ persons. The individual pose is denoted as $m_i^n\\in R^{j\\times d}$ , where $j$ is the number of joints in the skeleton and $d$ is the joint dimension. The goal of GAG is to synthesize a group of 3D human motions $G_{t}^{p}$ from Gaussian noise, given an activity label and an arbitrary group size as input conditions. It requires a model capable of learning the temporal and spatial motion dependencies among persons within the same group and generating human motions with any group size simultaneously. GAG is related to dyadic motion generation [10, 16] and partner-conditioned reaction generation [43], but involves the motion interactions of more than two persons.", + "bbox": [ + 496, + 580, + 892, + 777 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. Although previous works [16, 43, 44] can generate motions for multiple persons, they are limited to dyadic scenarios or groups with a fixed number of persons. Therefore, we present two baselines. The first one is the vanilla motion diffusion model, MDM [47]. It was proposed for probabilistic single-person motion generation from an input condition. We adopt their action-to-motion architecture for conditional synthesis and train the model on $\\mathbf{M}^3\\mathrm{Act3D}$", + "bbox": [ + 496, + 779, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "21927", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e7d4e10d8f71f892c9781b70078de8e19b2fdf28148afa651eb2715ae04051ab.jpg", + "image_caption": [ + "Figure 3. The qualitative comparison of two group activities from ground truth (GT), MDM, and MDM+IFormer. The distribution of the persons from MDM+IFormer is closer to GT." + ], + "image_footnote": [], + "bbox": [ + 83, + 88, + 433, + 281 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "for generating an individual person's motion from an input group activity class label. In order to generate a group of human motions from a given group size, we repeat the single-person inference several times. In other words, the individual motions are generated independently by MDM. Our second baseline, $\\mathbf{MDM} + \\mathbf{IFormer}$ is extended from MDM and includes an additional interaction transformer (IFormer) that works along the dimension of the persons. The interaction transformer encourages the model to learn the interperson motion dependencies. At inference, MDM+IFormer is capable of producing coordinated group activities in one forward pass, due to its modeling of human interactions.", + "bbox": [ + 75, + 345, + 468, + 526 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Implementation. We utilize a common skeleton for all individual persons with 25 joints. We process the data so each motion is represented as both the 6D joint rotations [59] and the root positions. The final representation of a collective group activity with multiple persons is a tensor with shape (#persons $\\times$ #frames $\\times$ 26 $\\times$ 6). For a fair comparison, both baseline models were trained on an NVIDIA RTX 3090 graphics card with $90\\%$ data from M³Act3D for 320K iterations and then tested on the other $10\\%$ .", + "bbox": [ + 75, + 527, + 468, + 662 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3.1 Evaluation", + "text_level": 1, + "bbox": [ + 76, + 669, + 207, + 681 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Metrics. Due to the probabilistic nature of the task, we consider the following learning-based metrics, recognition accuracy, Frechet Inception Distance (FID), diversity, and multimodality, defined in [26]. These metrics, however, were originally designed for single-person motion generation. To evaluate the generated group activities, we report them at both group and person levels because they account for the fidelity and variations for the groups and the individuals. We train a multi-scale group activity recognition model using theComposer [58] architecture for the metrics. See Sup. Mat. for detailed explanations of how to construct the learning-based metrics, including the recognition model as well as the latent representations at both levels.", + "bbox": [ + 75, + 686, + 467, + 883 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In addition to the learning-based metrics, we tailor four", + "bbox": [ + 96, + 885, + 467, + 898 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "position-based metrics, collision frequency, repulsive interaction force, contact repulsive force, and total repulsive force, to the evaluation of human groups. The latter three are based on the social force model [27, 28], which explains crowd behaviors using socio-psychological and physical forces. Here we describe the four metrics:", + "bbox": [ + 496, + 90, + 890, + 180 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Collision frequency indicates how often a collision (or an invalid interaction) would occur within a group. The collision count is calculated based on a distance threshold between any two persons in a group. It is then normalized by the total number of interactions to obtain the frequency. In other words, if $N$ persons are in a group, the normalization denominator is $N \\cdot (N - 1) / 2$ .", + "bbox": [ + 496, + 181, + 890, + 287 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Repulsive interaction force describes the psychological tendency of two persons to stay away from each other. As the distance between two persons decreases, the repulsive force increases exponentially.", + "bbox": [ + 496, + 287, + 890, + 348 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Contact repulsive force represents the compression body force when two persons collide with each other. The contact force is nonzero only when two persons collide. A larger contact force means the interaction is less likely to occur.", + "bbox": [ + 496, + 349, + 890, + 409 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Total repulsive force is the accumulation of interaction and contact forces.", + "bbox": [ + 496, + 410, + 890, + 438 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "All four position-based metrics are calculated using the Euclidean distances of the persons' positions, with the shoulder width as the collision threshold. The social forces are calculated by averaging the magnitude of each individual's force accumulated through all its interactions with other persons. A well-performing model should generate group activities with low collision frequency and similar social force values to the ground truth. For the evaluation, we generated 500 samples for each group activity using the two well-trained baseline models. Each generated sequence contains 60 frames. We use the test split as the ground truth and randomly extract the group activity of the same length for evaluation. To ensure the distributions of group sizes are similar to the ground truth, we calculate the minimum and maximum group sizes from the training split and uniformly sample a group size from that range to generate group activities. Please refer to Sup. Mat. for more details regarding the baseline architectures, metrics formulas, and evaluation.", + "bbox": [ + 496, + 439, + 890, + 710 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3.2 Results", + "text_level": 1, + "bbox": [ + 500, + 717, + 604, + 729 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "MDM+IFormer is capable of generating group activities with well-aligned character positions. As shown in Fig. 3, MDM generates human groups that are poorly positioned. For example, the persons in a walking group do not walk in the same direction and the persons are poorly placed in a queueing group. This is because MDM generates the group activities by inferring the individual motions independently. The placement of the individuals simply follows the probabilistic distribution of all persons' positions in the dataset. On the other hand, MDM+IFormer successfully learns the probabilistic distribution for the entire group due to its in", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "21928", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/b80256e1f716ae407588e6ece19232161ac070714cb3b58085fa64c4d1c753a0.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Group LevelPerson Level
Acc ↑FID ↓Diversity →Multimodality →FID ↓Diversity →Multimodality →
GT99.9370.001 ± 0.00017.752 ± 0.0253.491 ± 0.0120.001 ± 0.00014.506 ± 0.0137.546 ± 0.010
MDM97.3673.909 ± 0.01917.683 ± 0.0374.155 ± 0.0194.434 ± 0.01014.158 ± 0.0357.588 ± 0.013
MDM+IFormer98.1003.242 ± 0.01617.855 ± 0.0404.198 ± 0.0213.066 ± 0.00714.827 ± 0.0316.945 ± 0.011
", + "bbox": [ + 81, + 88, + 890, + 162 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/1b5c7d64f50eaf4a15f9ad92d5dc5854a150cf1c6803c211103361a328dfd0a1.jpg", + "table_caption": [ + "Table 7. The results of the generated group activities with the learning-based metrics at both levels. An up arrow means the result is better when the metric score is higher. A right arrow means the metric score should be close to ground truth (GT)." + ], + "table_footnote": [], + "table_body": "
Collision Freq. ↓Interaction Force →Contact Force →Total Force →
GT0.03765.7946.55112.33
MDM3.6437,121.503,822.4710,903.57
MDM+IFormer1.1571,796.251,373.403167.80
", + "bbox": [ + 81, + 204, + 465, + 275 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 8. Results of the generated human activities with position-based metrics. The collision frequency is calculated on a 60-frame group activity and normalized by the total number of interactions in a group.", + "bbox": [ + 76, + 279, + 468, + 335 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "teraction transformer. The persons are better aligned in a group and they have coordinated motions.", + "bbox": [ + 75, + 349, + 468, + 378 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Both baselines are capable of generating diverse activities that match the input condition, but MDM+IFformer obtains better FID scores. Tab. 7 shows the results for the learning-based metrics. When compared with ground truth, both baselines obtain similar scores on recognition accuracy, diversity, and multimodality at both levels. The results indicate that both models successfully learn to generate distinguishable individual motions and group activities. The generated motions are also as diverse as the ground truth. The observations align with the results on action-to-motion generation in MDM [47]. MDM+IFformer receives a lower FID score than MDM, suggesting that MDM+IFformer generates group activities with higher quality.", + "bbox": [ + 75, + 380, + 468, + 575 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "The interaction transformer in MDM+IFormer greatly lowers the collision frequency within the generated group activities. As shown in Tab. 8, the collision frequency of the group activities generated by MDM+IFormer is much lower than the vanilla MDM. It suggests that the interaction transformer better learns the inter-person dependencies and generates more valid person interactions. In fact, we observe that the group activities generated by the vanilla MDM sometimes contain overlapping person positions. The high collision frequency of the MDM baseline also affects the repulsive forces, which makes social forces within the group activities of MDM implausible.", + "bbox": [ + 75, + 575, + 468, + 757 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Discussion and Conclusion", + "text_level": 1, + "bbox": [ + 76, + 760, + 326, + 776 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We show the merit of $\\mathsf{M}^3\\mathsf{Act}$ by conducting three core experiments with multiple modalities and enhanced performances, as well as introducing a novel generative task. In both MPT and GAR experiments, we observe positive correlations between the volume of synthetic data used for training and model performance, indicating an improved model generalizability to unseen test cases with more synthetic data. Moreover, our comparison between $\\mathrm{DT + Syn}^{\\dagger}$", + "bbox": [ + 75, + 779, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "and MOTRv2* reveals that synthetic data can replace certain real-world data from the target domain without sacrificing performance [13]. Essentially, our synthetic data reduces the need for extensive real data during training, thereby effectively lowering the costs associated with data collection and annotation. This discovery represents a promising step towards achieving few-shot and potentially zero-shot sim2real transfer. In our 3D Group Activity Generation experiment, we observe that MDM+IFormer, despite being a baseline for the novel task, learns to embed the heuristics for person interactions and produces well-aligned groups given the controls. It's important to highlight that the generative approach, though currently underperforms the procedural method (GT), demonstrates the unique potential of controlling the group motions directly from various signals, including activity class, group size, trajectory, density, speed, and text inputs. With the anticipation of more data availability and increased model capacity for generative models in the future, we expect the generative method to eventually prevail, leading to broader applications for social interactions and human collective activities.", + "bbox": [ + 496, + 207, + 890, + 523 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "While the complexity of group behaviors in our dataset may be constrained by the heuristics used for activity authoring, $\\mathsf{M}^{3}\\mathsf{A}\\mathsf{ct}$ offers notable flexibility for incorporating new group dynamics tailored to any specific downstream tasks. These new groups could be derived from expert-guided heuristics, rules generated by large language models, or outputs from our 3D GAG model. Furthermore, we recognize the existing domain gaps between synthetic and real-world data. With more assets included in our data generator in future iterations, we can enhance model generalizability and alleviate the disparities.", + "bbox": [ + 496, + 525, + 890, + 691 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Acknowledgement", + "text_level": 1, + "bbox": [ + 500, + 699, + 679, + 715 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "The research was supported in part by NSF awards: IIS-1703883, IIS-1955404, IIS-1955365, RETTL-2119265, and EAGER-2122119. This work was also partially supported by the Center for Smart Streetscapes, an NSF Engineering Research Center, under cooperative agreement EEC-2133516. This material is based upon work supported by the U.S. Department of Homeland Security1 under Grant Award Number 22STESE00001 01 01.", + "bbox": [ + 496, + 718, + 890, + 838 + ], + "page_idx": 7 + }, + { + "type": "page_footnote", + "text": "$^{1}$ Disclaimer. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security.", + "bbox": [ + 496, + 849, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "21929", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Renderpeople. https://renderpeople.com/, 2023. 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Human motion diffusion model. arXiv preprint arXiv:2209.14916, 2022. 6, 8" + ], + "bbox": [ + 501, + 92, + 890, + 898 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "21931", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 9 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[48] Gul Varol, Javier Romero, Xavier Martin, Naureen Mahmood, Michael J Black, Ivan Laptev, and Cordelia Schmid. Learning from synthetic humans. In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 109-117, 2017. 1, 2, 3", + "[49] Edward Vendrow, Duy Tho Le, Jianfei Cai, and Hamid Rezatofighi. Jrdb-pose: A large-scale dataset for multiperson pose estimation and tracking. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 4811–4820, 2023. 1, 3", + "[50] Nicolai Wojke, Alex Bewley, and Dietrich Paulus. Simple online and realtime tracking with a deep association metric. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 5745-5753, 2019. 7" + ], + "bbox": [ + 78, + 90, + 470, + 898 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "21932", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_model.json b/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_model.json new file mode 100644 index 0000000000000000000000000000000000000000..e71edb6ab0ee205a1504a4d3a2885927fd9443f5 --- /dev/null +++ b/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_model.json @@ -0,0 +1,2301 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.234, + 0.131, + 0.738, + 0.154 + ], + "angle": 0, + "content": "Learning from Synthetic Human Group Activities" + }, + { + "type": "text", + "bbox": [ + 0.154, + 0.18, + 0.368, + 0.234 + ], + "angle": 0, + "content": "Che-Jui Chang†\nRutgers University\nchejui.chang@rutgers.edu" + }, + { + "type": "text", + "bbox": [ + 0.16, + 0.242, + 0.368, + 0.294 + ], + "angle": 0, + "content": "Parth Goel \nRutgers University \ngoel.parth210@gmail.com" + }, + { + "type": "text", + "bbox": [ + 0.141, + 0.303, + 0.347, + 0.355 + ], + "angle": 0, + "content": "Samuel S. Sohn \nRutgers University \nsamuel.sohn@rutgers.edu" + }, + { + "type": "text", + "bbox": [ + 0.413, + 0.182, + 0.603, + 0.234 + ], + "angle": 0, + "content": "Danrui Li\nRutgers University\ndanrui.li@rutgers.edu" + }, + { + "type": "text", + "bbox": [ + 0.391, + 0.242, + 0.608, + 0.294 + ], + "angle": 0, + "content": "Honglu Zhou NEC Laboratories hozhou@nec-labs.com" + }, + { + "type": "text", + "bbox": [ + 0.391, + 0.303, + 0.608, + 0.355 + ], + "angle": 0, + "content": "Sejong Yoon \nThe College of New Jersey \nyoons@tcnj.edu" + }, + { + "type": "text", + "bbox": [ + 0.411, + 0.363, + 0.562, + 0.396 + ], + "angle": 0, + "content": "Mubbasir Kapadia Roblox" + }, + { + "type": "text", + "bbox": [ + 0.397, + 0.402, + 0.569, + 0.415 + ], + "angle": 0, + "content": "mkapadia@roblox.com" + }, + { + "type": "text", + "bbox": [ + 0.632, + 0.182, + 0.82, + 0.234 + ], + "angle": 0, + "content": "Deep Patel NEC Laboratories dpatel@nec-labs.com" + }, + { + "type": "text", + "bbox": [ + 0.632, + 0.242, + 0.828, + 0.294 + ], + "angle": 0, + "content": "Seonghyeon Moon† \nRutgers University \nsm206@cs.rutgers.edu" + }, + { + "type": "text", + "bbox": [ + 0.652, + 0.303, + 0.83, + 0.355 + ], + "angle": 0, + "content": "Vladimir Pavlovic \nRutgers University \nvladimir@rutgers.edu" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.426, + 0.314, + 0.441 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.449, + 0.473, + 0.796 + ], + "angle": 0, + "content": "The study of complex human interactions and group activities has become a focal point in human-centric computer vision. However, progress in related tasks is often hindered by the challenges of obtaining large-scale labeled datasets from real-world scenarios. To address the limitation, we introduce \\( M^3 \\) Act, a synthetic data generator for multi-view multi-group multi-person human atomic actions and group activities. Powered by Unity Engine, \\( M^3 \\) Act features multiple semantic groups, highly diverse and photorealistic images, and a comprehensive set of annotations, which facilitates the learning of human-centered tasks across single-person, multi-person, and multi-group conditions. We demonstrate the advantages of \\( M^3 \\) Act across three core experiments. The results suggest our synthetic dataset can significantly improve the performance of several downstream methods and replace real-world datasets to reduce cost. Notably, \\( M^3 \\) Act improves the state-of-the-art MOTRv2 on DanceTrack dataset, leading to a hop on the leaderboard from \\( 10^{th} \\) to \\( 2^{nd} \\) place. Moreover, \\( M^3 \\) Act opens new research for controllable 3D group activity generation. We define multiple metrics and propose a competitive baseline for the novel task. Our code and data are available at our project page: http://cjerry1243.github.io/M3Act." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.808, + 0.21, + 0.824 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.828, + 0.47, + 0.875 + ], + "angle": 0, + "content": "Understanding collective human activities and social groups carries significant implications across diverse domains, as it contributes to bolstering public safety within" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.427, + 0.892, + 0.532 + ], + "angle": 0, + "content": "surveillance systems, ensuring safe navigation for autonomous robots and vehicles amidst human crowds, and enriching social awareness in human-robot interactions [8, 9, 11, 12, 21, 37, 49, 51]. However, the advancement in related tasks is often impeded by the challenges of obtaining large-scale human group activity datasets in real-world scenarios with fine-grained multifaceted annotations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.535, + 0.893, + 0.791 + ], + "angle": 0, + "content": "Generating synthetic data is an emerging alternative to collecting real-world data due to its capability of producing large-scale datasets with perfect annotations. Nonetheless, most synthetic datasets [4, 20, 40, 48, 53] are primarily designed to facilitate human pose and shape estimation. They can only provide data with independently-animated persons, which is unsuitable for tasks in single-group and multi-group conditions [51]. To address the limitation, we propose \\(\\mathbf{M}^3\\mathrm{Act}\\), a synthetic data generator, with multi-view multi-group multi-person human actions and group activities. As presented in Tab. 1, \\(\\mathbf{M}^3\\mathrm{Act}\\) stands out by offering comprehensive annotations including both 2D and 3D annotations as well as fine-grained person-level and group-level labels, thereby making it an ideal synthetic dataset generator to support tasks such as human activity recognition and multi-person tracking across all listed real-world datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Illustrated in Fig. 1, our synthetic data generator features multiple semantic groups, highly diverse and photorealistic images, and a rich set of annotations. It encompasses 25 photometric 3D scenes, 104 HDRIs (High Dynamic Range Images), 5 lighting volumes, 2200 human models, 384 animations (categorized into 14 atomic action classes), and 6 group activities. For our experiments, We generated two" + }, + { + "type": "page_footnote", + "bbox": [ + 0.102, + 0.887, + 0.318, + 0.901 + ], + "angle": 0, + "content": "\\(\\dagger\\)Work done during internship at Roblox" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "21922" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.425, + 0.26 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.427, + 0.091, + 0.666, + 0.257 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.264, + 0.147, + 0.324 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.149, + 0.265, + 0.212, + 0.323 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.214, + 0.266, + 0.278, + 0.323 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.28, + 0.266, + 0.345, + 0.323 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.347, + 0.266, + 0.411, + 0.323 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.412, + 0.265, + 0.476, + 0.323 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.484, + 0.264, + 0.662, + 0.324 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.487, + 0.326, + 0.66, + 0.337 + ], + "angle": 0, + "content": "Diverse Scenes and Lighting Conditions" + }, + { + "type": "image", + "bbox": [ + 0.685, + 0.09, + 0.891, + 0.17 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.684, + 0.175, + 0.884, + 0.255 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.685, + 0.258, + 0.89, + 0.338 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.346, + 0.893, + 0.39 + ], + "angle": 0, + "content": "Figure 1. M3Act is a large-scale synthetic data generator designed to support multi-person and multi-group research topics. M3Act features multiple semantic groups and produces highly diverse and photorealistic videos with a rich set of annotations suitable for human-centered tasks including multi-person tracking, group activity recognition, and controllable human group activity generation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.399, + 0.47, + 0.521 + ], + "angle": 0, + "content": "datasets, M\\(^3\\)ActRGB and M\\(^3\\)Act3D. M\\(^3\\)ActRGB contains both single-group and multi-group data with a total of 6M frames of RGB images and 48M bounding boxes, rendered in 20 FPS. M\\(^3\\)Act3D is a 3D-only and single-group dataset, which contains 3D motions of all persons within a group. It has large group sizes (max 27 people) and an average of 6.7 persons per group. In total, M\\(^3\\)Act3D contains a duration of 87.6 hours of group activities, captured in 30 FPS." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.522, + 0.471, + 0.822 + ], + "angle": 0, + "content": "We first demonstrate the merit of \\(\\mathsf{M}^3\\mathsf{Act}\\) via synthetic data pre-training and mixed training on multi-person tracking and group activity recognition. For multi-person tracking, training with our synthetic data yields significant performance gain on several downstream methods [23, 52, 56, 57]. We also demonstrate notable improvements in the state-of-the-art MOTRv2 method [57] and observe that our synthetic data can substitute for \\(62.5\\%\\) more real-world data, without compromising performance. In terms of group activity recognition, results indicate that pre-training with \\(\\mathsf{M}^3\\mathsf{ActRGB}\\) greatly improves both person-level and group-level accuracy for Composer [58] and ActorTransformer [25] methods. Based on our generated data, we then introduce a novel task, controllable 3D group activity generation, which aims to synthesize a group of 3D human motions, given control signals such as activity labels and group sizes. We systematically approach the new task by introducing both learning-based and heuristics-based metrics, along with a competitive baseline to generate meaningful human activities." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.825, + 0.383, + 0.839 + ], + "angle": 0, + "content": "This paper makes the following contributions:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.84, + 0.47, + 0.901 + ], + "angle": 0, + "content": "- We propose a novel synthetic data generator, \\(\\mathsf{M}^3\\mathsf{Act}\\), and provide two large-scale synthetic datasets with highly diverse human activities, photorealistic multi-view videos, and comprehensive annotations." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.4, + 0.893, + 0.46 + ], + "angle": 0, + "content": "- We demonstrate that \\(\\mathsf{M}^3\\mathsf{Act}\\) can significantly improve benchmark performances for multi-person tracking and group activity recognition and replace a large portion of real-world training data to reduce cost." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.46, + 0.892, + 0.52 + ], + "angle": 0, + "content": "- \\(\\mathrm{M}^{3}\\mathrm{Act}\\) promotes new research initiatives for controllable 3D group activity generation, suggesting that synthetic data can not only support existing tasks but also create datasets for novel research." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.4, + 0.893, + 0.52 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.531, + 0.65, + 0.546 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.552, + 0.892, + 0.884 + ], + "angle": 0, + "content": "Human Centered Synthetic Datasets. The use of synthetic datasets for human-centered tasks has become increasingly prominent due to their diversity, scalability, and perfect annotations, with proven merits connected to various fields in machine learning, including domain adaptation [34, 46], heterogeneous multitask learning [54], and sim2real [24] or task2sim [39] transfer. Most previous synthetic datasets are constructed to support human pose estimation. For example, SURREAL [48] contains renderings of human motions from 145 avatars composited to a background image. Subsequent works [2, 20, 40] managed to improve the image quality by leveraging realistic 3D scenes, high-quality renderings, and HDRI images. Recently, synthetic datasets have been proposed to tackle human shape and mesh estimation. SynBody [53] constructs layered human assets to increase character diversity. BEDLAM [4] adds physically simulated hair and clothes to achieve state-of-the-art performances on shape and mesh estimation. Nonetheless, data with collective human motions and group activities cannot be obtained from them. Our work, \\(\\mathsf{M}^3\\mathsf{Act}\\), is constructed with animated human groups tailored to multi-person and multi-group research." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.886, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Real Multi-Person Datasets. Real-world datasets [15, 17," + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "21923" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.078, + 0.088, + 0.895, + 0.312 + ], + "angle": 0, + "content": "
DatasetImage TypeAvatar Num.VideoMulti-ViewMulti-PersonMulti-Group2D3DAnnotations Atomic Atn.Group Act.
SURREAL, 2017 [48]Composite145✓✓✓
AGORA, 2021 [40]HDRI350✓✓✓
HSPACE, 2021 [2]3D Scene1600✓✓✓✓✓
GTA-Humans, 2021 [6]3D Scene600✓✓✓✓
PSP-HDRI+, 2022 [20]HDRI28✓✓✓
SynBody, 2023 [53]3D Scene10k✓✓✓✓✓
BEDLAM, 2023 [4]3D Scene271✓✓✓✓
M3Act (Ours)Photometric 3D + HDRI2200✓✓✓✓✓✓✓✓
CAD, 2011 [15]Real-✓✓✓✓✓✓
Volleyball Dataset, 2016 [29]Real-✓✓✓✓✓✓
NTU-RGBD 120, 2019 [33]Real-✓✓✓✓✓✓
HiEve, 2020 [32]Real-✓✓✓✓✓
PoseTrack, 2021 [18]Real-✓✓✓✓
MOT, 2020 [17]Real-✓✓✓✓
DanceTrack, 2022 [45]Real-✓✓✓
JRDB, 2023 [21, 37, 49]Real-✓✓✓✓✓✓
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.315, + 0.893, + 0.345 + ], + "angle": 0, + "content": "Table 1. A comparison of synthetic datasets as well as commonly-used real datasets for activity understanding and person tracking. We refer to JRDB as a union set of JRDB, JRDB-Act, and JRDB-Pose datasets. Note that it offers 3D bounding boxes, but not poses." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.355, + 0.473, + 0.734 + ], + "angle": 0, + "content": "18, 29, 32, 33, 37, 45] with multiple persons are usually collected for tasks such as group activity understanding, multiperson tracking, and human trajectory prediction. Recognizing and parsing collective human activities [25, 58] rely primarily on multiple modalities (RGB, bounding box, pose) and hierarchical action and activity labels. These fine-grained labels are provided by datasets like CAD [15] and Volleyball Dataset [29]. On the other hand, datasets for person tracking, such as HiEve [32], MOT [17, 38], and DanceTrack [45], require not only 2D annotations (e.g., bounding box) for individual frames, but also the association of the objects between them. Specifically, DanceTrack provides multiple persons in a group with the same clothing, making it difficult for the association of the individuals. MOT datasets target tracking for human crowds and contain mostly outdoor scenes from a bird-eye view. Recently, JRDB [21, 37, 49] with rich annotations is released. The images are captured by a social robot, navigating around daily scenes. It provides fine-grained annotations that support various tasks, including person detection, pose estimation, tracking, collective activity detection, and understanding. M³Act not only offers the same modalities and annotations for supporting the aforementioned tasks, but it also provides full 3D annotations, making it suitable for a wide range of applications beyond the 2D domain." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.743, + 0.158, + 0.759 + ], + "angle": 0, + "content": "3. \\(\\mathbf{M}^3\\mathbf{A}\\mathbf{c}\\mathbf{t}\\)" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.473, + 0.904 + ], + "angle": 0, + "content": "\\(\\mathsf{M}^3\\mathsf{Act}\\) is a multi-view multi-group multi-person human atomic action and group activity data generator built with Unity Engine and the Perception [5] library. Inspired by PeopleSansPeople [19] that populates randomly posed human avatars in a scene and renders static images, \\(\\mathsf{M}^3\\mathsf{Act}\\) not only offers the same functionalities for human poses but also extends it to the spatio-temporal domain. It generates RGB videos for dynamic human motions and produces a rich set of annotations simultaneously, including (a) 2D" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.355, + 0.895, + 0.432 + ], + "angle": 0, + "content": "and 3D joints/meshes, (b) 2D and 3D bounding boxes for individual persons, (c) atomic action and group activity categories, (d) tracking information such as individual and group IDs, (e) segmentation, depth, and normal images, and (f) scene description." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.441, + 0.667, + 0.456 + ], + "angle": 0, + "content": "3.1. Data Generation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.46, + 0.895, + 0.581 + ], + "angle": 0, + "content": "The process of our data generation is illustrated in Fig. 2. First, the generation process is configured by the simulation scenario that manages multiple independent simulations of human activities. Then for each simulation, a 3D scene with background objects, lights, and cameras is set up, and groups of human characters are instantiated to be animated. Lastly, the multi-view RGB image frames are rendered and the annotations are exported at the end of the simulation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.582, + 0.895, + 0.763 + ], + "angle": 0, + "content": "Scene Instantiation. We represent the environment through 25 photometric 3D scenes and 104 panoramic HDRIs. Each scene is initiated with randomized lighting and camera configuration. To attain a balance between realistic environmental illumination and pronounced shadow detail, our lighting schema integrates HDRI Sky lighting with a directional light. This directional light is subject to random variations in its direction, color temperature, and intensity. Regarding camera placement, we always point cameras towards the center of avatar groups and introduce variability by randomizing both the field of view and the camera's distance to these groups." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Human Models and Motion Assets. M³Act leverages 2000 human models generated by Synthetic Humans [42], ranging across all ages (1 ~ 100), genders, ethnicities (such as Caucasian, Asian, Latin American, African, Middle Eastern), diverse body shapes, hair, and clothing. We also incorporated 200 widely-used human characters from RenderPeople [1]. For the human motions, we collected 384 animation clips from AMASS [36], categorized into 14 atomic action classes. We created a universal animation controller" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "21924" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.089, + 0.87, + 0.267 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.277, + 0.893, + 0.307 + ], + "angle": 0, + "content": "Figure 2. The data generation process of \\(\\mathsf{M}^3\\mathsf{Act}\\). It consists of multiple data simulations with scene instantiation, group activity authoring, and a data capture module. A high degree of randomization is involved in all aspects of the process to ensure diverse data." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.317, + 0.471, + 0.348 + ], + "angle": 0, + "content": "that blends styles, including arm space and stride size, to create diverse motions from the collected clips." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.352, + 0.471, + 0.67 + ], + "angle": 0, + "content": "Modular Group Activities. Each group activity is structured as a parameterized module, allowing for the customization of numerous variables. These variables include the number of individuals in the group and the specific atomic actions permitted within the group activity. This modularization ensures easy duplication, repositioning, and reuse of the group activities, enabling simulations of multiple groups at the same time. To procedurally animate a group of humans within a modular group, we establish the positions and orientations of the selected characters while choosing the appropriate animation clip for each character through the activity script. It's important to note that, despite drawing characters from the same set of avatars, the configurations and animations of these characters can vary significantly from one group to another. For example, animating a queueing activity may require all characters to be aligned in a straight line, while those in a walking group may form various shapes. The atomic actions that a person can perform also depend on the specific group activity. We carefully consider all these factors when authoring activities and provide a summary in the Sup. Mat." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.675, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Domain Randomization. \\(\\mathbf{M}^{3}\\mathrm{Act}\\) provides domain randomization for almost all aspects of the data generation process to ensure the simulation data is highly diverse. These aspects include the number of groups in a scene, the number of persons in each group, the positions of groups, the alignment of persons in a group, the positions of individuals, the textures for the instantiated characters, and the selection of scenes, lighting conditions, camera positions, characters, group activities, atomic actions, and animation clips. Despite the fact that animating group activities inherently limits the degree of freedom in the placement of characters, by altering the shapes in which characters align (e.g., either in a cluster, a straight line, or a curve), \\(\\mathbf{M}^{3}\\mathrm{Act}\\) nonetheless generates diverse activities and achieves sufficient randomization for downstream model generalization. More details re" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.317, + 0.892, + 0.346 + ], + "angle": 0, + "content": "garding the randomization variables and their distributions are provided in Sup. Mat." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.348, + 0.893, + 0.514 + ], + "angle": 0, + "content": "Rendering and Annotations. \\(\\mathbf{M}^{3}\\mathrm{Act}\\) utilizes the Unity high-definition render pipeline for the creation of photorealistic RGB images and leverages the Perception library for capturing annotations. On average, data is generated at a rate of 4.2 FPS using one NVIDIA RTX 3070 Ti graphics card, with a resolution of \\(1920\\times 1080\\), and all annotations are enabled. Similar to PeopleSansPeople, the 2D skeleton follows COCO [31] format, with additional labelers for exporting 3D joints, meshes, group IDs, and activity classes. After the data generation, the 3D joints and meshes are fitted with SMPL parameters [35, 41]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.521, + 0.669, + 0.535 + ], + "angle": 0, + "content": "3.2. Dataset Statistics" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.538, + 0.892, + 0.702 + ], + "angle": 0, + "content": "\\(\\mathrm{M}^{3}\\mathrm{Act}\\) comprises 25 photometric 3D scenes, 104 HDRIs, 5 lighting volumes, 2200 human models, 384 animations (categorized into 14 atomic action classes), and 6 group activities. Using the generator, we first generated our synthetic dataset, \\(\\mathrm{M}^{3}\\mathrm{ActRGB}\\). It contains 6K simulations of every single-group activity and 9K simulations of multi-group configuration, with 4 camera views. Each simulation produces a 5-second video clip, captured in 20 FPS and FHD resolution. In total, \\(\\mathrm{M}^{3}\\mathrm{ActRGB}\\) contains 6M RGB images and 48M bounding boxes. The average track length is 4.65 seconds." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Additionally, we generated \\(\\mathrm{M}^3\\mathrm{Act3D}\\), a large-scale 3D-only dataset. It consists of more than \\(65\\mathrm{K}\\) simulations of single-group activity. Each contains 150 frames of multiperson collective interactions in 30 FPS, resulting in a total duration of 87.6 hours. As shown in Tab. 2, both the group size and the interaction complexity are significantly higher than those in previous multi-person motion datasets. Specifically, when compared with GTA-Combat [44], \\(\\mathrm{M}^3\\mathrm{Act3D}\\) contains more persons in a group, has more group activities, and provides a variable number of persons in a group. To the best of our knowledge, \\(\\mathrm{M}^3\\mathrm{Act3D}\\) is the first large-scale 3D dataset for human group activities with large group sizes as well as per-frame individual action labels. See Sup. Mat." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "21925" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.08, + 0.09, + 0.472, + 0.201 + ], + "angle": 0, + "content": "
DatasetFPS# of Acty.# of Persons# of Actn.Duration
AvgMax
SBU [55]1582.02-7.6 mins
Duet Dance [30]2552.02-2.3 hrs
CHI3D [22]5082.02-2.7 hrs
NTU RGBD 120 [33]30262.02-15.0 hrs
GTA-Combat [44]1513.25-39.0 hrs
M3Act3D3066.727887.6 hrs
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.206, + 0.47, + 0.248 + ], + "angle": 0, + "content": "Table 2. A comparison of datasets for 3D multi-person human activities. \\(\\mathbb{M}^3\\mathbb{A}\\mathbb{ct}\\mathbb{3}\\mathbb{D}\\) is the largest dataset with labels for atomic actions and more persons in a group." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.261, + 0.327, + 0.275 + ], + "angle": 0, + "content": "for detailed statistics of both datasets." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.286, + 0.21, + 0.303 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.305, + 0.469, + 0.381 + ], + "angle": 0, + "content": "We showcase the practical utilities of \\(\\mathsf{M}^3\\mathsf{Act}\\) through three core experiments: Multi-Person Tracking (MPT), Group Activity Recognition (GAR), and controllable Group Activity Generation (GAG). The experiments are carefully designed to cover the following three perspectives:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.385, + 0.469, + 0.46 + ], + "angle": 0, + "content": "- Multi-modality: Our experiments cover various modalities contained within our dataset, including RGB videos, 2D keypoints, and 3D joints. We leverage the rich annotations including bounding boxes, tracklets, group activities, and person action labels." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.461, + 0.469, + 0.506 + ], + "angle": 0, + "content": "- Performance: We conduct the ablation study by altering the amount and the type of synthetic data used for training to see its effect on the model performance." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.507, + 0.469, + 0.551 + ], + "angle": 0, + "content": "- Novel task: We introduce a novel generative task (GAG), showing that synthetic data can not only support existing CV tasks but also create datasets for new research." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.385, + 0.469, + 0.551 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.564, + 0.29, + 0.58 + ], + "angle": 0, + "content": "4.1. Multi-Person Tracking" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.582, + 0.469, + 0.717 + ], + "angle": 0, + "content": "The objective of MPT is to predict the trajectories of all persons from a dynamic video stream. Typically, person tracking involves two separate processes, person detection and association. While the tracking task is approached in some prior works with the tracking-by-detection method [3, 7, 50], we consider end-to-end approaches [23, 52, 56, 57] to evaluate the use of synthetic data on the performance of MPT as a whole, in lieu of an improved performance caused only by refined detection." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.719, + 0.469, + 0.778 + ], + "angle": 0, + "content": "Real-world Dataset: DanceTrack [45] (DT) is a challenging MPT dataset characterized by dynamic movements with human subjects in uniform appearances. It has a total of 100 videos with over 105K frames." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Synthetic Dataset. Given the motion categories in the real-world dataset, we select a subset of \\(\\mathbf{M}^3\\) ActRGB with groups of people dancing, walking, and running. We use 1000 video clips with a single \"dance\" group as well as 1500 videos with a \"walk\" group and a \"run\" group simulated at the same time (denoted as WalkRun). We alter the use of the synthetic group activities (Dance, WalkRun, and Dance+WalkRun) in our experiments." + }, + { + "type": "table", + "bbox": [ + 0.503, + 0.089, + 0.892, + 0.226 + ], + "angle": 0, + "content": "
Training DataHOTA↑DetA↑AssA↑IDF1↑MOTA↑
DT®69.883.058.971.689.3
DT68.8 (10)82.557.470.390.8
DT + Syn (D)59.075.546.159.082.6
DT + Syn (WR)70.183.159.472.592.0
DT + Syn (WR+D)71.9 (2)83.662.074.792.6
DT + Syn† (WR+D)72.283.462.675.592.7
DT (MOTRv2*)73.483.764.476.092.1
DT + BEDLAM [4]55.968.744.553.879.1
DT + GTA-Humans [6]54.166.844.252.178.8
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.23, + 0.892, + 0.314 + ], + "angle": 0, + "content": "Table 3. MPT results on DanceTrack with MOTRv2. \"D\" means synthetic dance group. \"WR\" means walk and run groups. \"WR+D\" refers to \"D\" and \"WR\" combined. The symbol \\(\\text{串}\\) represents the author-provided checkpoint. The symbol \\(\\dagger\\) marks the same model with additional association at inference. Numbers in parentheses represent the rank in the DanceTrack leaderboard." + }, + { + "type": "table", + "bbox": [ + 0.506, + 0.327, + 0.888, + 0.486 + ], + "angle": 0, + "content": "
ModelSyn. DataHOTADetAAssAIDF1MOTA
MOTR [56]✓54.273.540.251.579.7
60.076.448.156.083.8
MeMOTR [23]✓68.580.558.471.289.9
71.181.862.374.192.2
CO-MOT [52]✓69.482.158.971.991.2
72.583.663.375.992.8
MOTRv2 [57]✓68.882.557.470.390.8
71.983.662.074.792.6
MOTRv2* [57]✓73.483.764.476.092.1
74.684.164.976.493.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.49, + 0.892, + 0.519 + ], + "angle": 0, + "content": "Table 4. MPT results on DanceTrack using different methods trained with our synthetic data." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.539, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Results. We mix together both synthetic and real data during training and present the results in Tab. 3. First, adding our synthetic data yields significant improvement in all 5 tracking metrics as well as a hop in ranking on HOTA from \\(10^{th}\\) to \\(2^{nd}\\) place. The model trained with our synthetic data plus the extra association, marked as \\(\\mathrm{DT} + \\mathrm{Syn}^{\\dagger}\\) (WR+D), achieves similar performance to MOTRv2*, the same model that is trained with additional validation data with an ensemble of 4 models [57]. This suggests that the synthetic data used in our experiment is equivalent to at least \\(62.5\\%\\) more real data. Second, Compared with other synthetic data sources, such as BEDLAM and GTA-Humans, M³Act demonstrates superior performance, indicating its better suitability for multi-person dynamic conditions. Third, we observe that the type of synthetic groups affects the model performance on real data. Adding the \"WalkRun\" groups to the training data is more effective than adding the \"Dance\" group. This is because while the DanceTrack dataset contains dynamic dance movements, the real challenge lies in detection and tracking when the subjects switch positions. By design, the positions of the characters in our dance group are well-staged and the movements are nearly synchronous. (See Sup. Mat. for the design.) Contrarily, having a walk and a run group together" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "21926" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.08, + 0.09, + 0.477, + 0.297 + ], + "angle": 0, + "content": "
ModelPretrained \nSyn. DataGroup ActivityPerson Action
Top 1 Acc (%) ↑Top 1 Acc (%) ↑
Composer \n[58]N/A84.87±2.3(88.20)81.31±2.4(83.13)
10%86.12±1.8(87.87)84.16±1.8(86.03)
25%87.65±1.2(89.01)86.36±1.3(86.81)
50%89.39±0.4(90.14)86.68±1.5(87.99)
100%89.74±1.0(91.51)88.74±1.7(89.05)
Gains+4.87 (+3.31)+7.43 (+5.92)
Actor \nTransformer \n[25]N/A78.08±1.0(79.47)76.22±2.2(78.07)
10%77.59±2.4(81.00)76.01±3.2(79.76)
25%81.36±2.1(83.19)78.86±2.4(80.05)
50%82.72±1.3(84.56)79.95±1.6(81.47)
100%83.67±1.2(84.88)81.65±1.2(82.22)
Gains+5.59 (+5.41)+5.43 (+4.15)
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.076, + 0.302, + 0.47, + 0.386 + ], + "angle": 0, + "content": "Table 5. Results of 2D keypoint-based group activity and person action recognition on CAD2 dataset. The best results are shown in parentheses. The results suggest that pre-training with our synthetic data largely increases the accuracy for both group activity and person actions. Note that group accuracy saturates at \\(93.4\\%\\) and \\(86.2\\%\\) forComposer and Actor Transformer respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.402, + 0.47, + 0.477 + ], + "angle": 0, + "content": "in a scene leads to frequent position switches relative to the camera view and thus improves the model performance. Lastly, Tab. 4 presents the tracking results using different methods. Results indicate that our synthetic data is effective across various models." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.488, + 0.327, + 0.504 + ], + "angle": 0, + "content": "4.2. Group Activity Recognition" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.506, + 0.47, + 0.611 + ], + "angle": 0, + "content": "The goal of GAR is to determine the class of the group activity performed by the dominant group as well as the action class of each person. We consider Composer [58] and Actor Transformer [25] as the benchmark models. The former is a multi-scale transformer-based model and accepts only 2D keypoints as input. The latter can take combinations of multiple input modalities." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.612, + 0.47, + 0.703 + ], + "angle": 0, + "content": "Real-world Dataset: CAD2 [15] and Volleyball Dataset [29]. CAD2 is an extended version of the Collective Activity Dataset [14] that records human group activities and is widely used for GAR benchmarks [51]. Volleyball Dataset (VD) is an action recognition dataset. It has 55 videos with 9 player action labels and 8 team activity labels." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.704, + 0.47, + 0.78 + ], + "angle": 0, + "content": "Synthetic Dataset. We use a subset of all single-group data from M³ActRGB. It contains a total of 10K videos and over 600K frames. It contains all group activity and individual action classes that CAD2 provides and further includes 7 more action types." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Results. We experimentally study how the size of our pretraining synthetic dataset and the capacity of a GAR model affect generalization from the synthetic to real domains. We first train the models on different amounts of synthetic data. Then we fine-tune them on CAD2 and report the top 1 accuracy of both group activity and person action recognition on the test set of CAD2. Tab. 5 presents the results using only 2D keypoints as input. We see a common trend for" + }, + { + "type": "table", + "bbox": [ + 0.502, + 0.09, + 0.905, + 0.188 + ], + "angle": 0, + "content": "
Model2D RGB FlowCAD2 Syn+CAD2VD Syn+VD
Composer✓88.291.594.695.1
Actor Transformer✓79.584.992.393.7
✓78.280.791.492.5
✓✓81.085.293.594.3
✓81.385.094.495.0
✓79.581.993.094.1
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.499, + 0.193, + 0.892, + 0.221 + ], + "angle": 0, + "content": "Table 6. The group activity recognition accuracy on CAD2 and Volleyball Dataset using different input modalities." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.238, + 0.895, + 0.404 + ], + "angle": 0, + "content": "both GAR models that the recognition accuracy increases as more synthetic data is used for pre-training. With \\(100\\%\\) of synthetic data, the accuracy of Composer increases, with an average of \\(4.87\\%\\) at the group level and \\(7.43\\%\\) at the person level, whereas Actor Transformer sees a \\(5.59\\%\\) increase at group level and \\(5.43\\%\\) increase at person level. Moreover, Tab. 6 shows the group recognition accuracy using different input modalities on CAD2 and VD. The performance gains in the experiment indicate that our synthetic data can effectively benefit the downstream GAR task across different methods, input modalities, and datasets." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.412, + 0.871, + 0.428 + ], + "angle": 0, + "content": "4.3. Controllable 3D Group Activity Generation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.43, + 0.892, + 0.581 + ], + "angle": 0, + "content": "While the procedural generation of our group activities in \\(\\mathbf{M}^{3}\\mathrm{Act}\\) yields realistic and diverse human activities, the implementation requires considerable effort and involves the design and application of specific heuristics. Learning a generative model for human group activities, instead, encodes the heuristics to the architecture inherently and encompasses the capabilities of probabilistically generating diverse activities, with control over the entire group of human motions from various signals. To this end, we introduce controllable 3D group activity generation (GAG)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.582, + 0.893, + 0.779 + ], + "angle": 0, + "content": "Definition. Let \\( G_{t}^{p} = \\{m_{i}^{n}\\}_{i = 1\\sim t,n = 1\\sim p} \\) be a group of human motions with \\( t \\) frames and \\( p \\) persons. The individual pose is denoted as \\( m_i^n\\in R^{j\\times d} \\), where \\( j \\) is the number of joints in the skeleton and \\( d \\) is the joint dimension. The goal of GAG is to synthesize a group of 3D human motions \\( G_{t}^{p} \\) from Gaussian noise, given an activity label and an arbitrary group size as input conditions. It requires a model capable of learning the temporal and spatial motion dependencies among persons within the same group and generating human motions with any group size simultaneously. GAG is related to dyadic motion generation [10, 16] and partner-conditioned reaction generation [43], but involves the motion interactions of more than two persons." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Baselines. Although previous works [16, 43, 44] can generate motions for multiple persons, they are limited to dyadic scenarios or groups with a fixed number of persons. Therefore, we present two baselines. The first one is the vanilla motion diffusion model, MDM [47]. It was proposed for probabilistic single-person motion generation from an input condition. We adopt their action-to-motion architecture for conditional synthesis and train the model on \\(\\mathbf{M}^3\\mathrm{Act3D}\\)" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "21927" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.089, + 0.434, + 0.282 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.288, + 0.47, + 0.331 + ], + "angle": 0, + "content": "Figure 3. The qualitative comparison of two group activities from ground truth (GT), MDM, and MDM+IFormer. The distribution of the persons from MDM+IFormer is closer to GT." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.346, + 0.47, + 0.527 + ], + "angle": 0, + "content": "for generating an individual person's motion from an input group activity class label. In order to generate a group of human motions from a given group size, we repeat the single-person inference several times. In other words, the individual motions are generated independently by MDM. Our second baseline, \\( \\mathbf{MDM} + \\mathbf{IFormer} \\) is extended from MDM and includes an additional interaction transformer (IFormer) that works along the dimension of the persons. The interaction transformer encourages the model to learn the interperson motion dependencies. At inference, MDM+IFormer is capable of producing coordinated group activities in one forward pass, due to its modeling of human interactions." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.529, + 0.47, + 0.664 + ], + "angle": 0, + "content": "Implementation. We utilize a common skeleton for all individual persons with 25 joints. We process the data so each motion is represented as both the 6D joint rotations [59] and the root positions. The final representation of a collective group activity with multiple persons is a tensor with shape (#persons \\(\\times\\) #frames \\(\\times\\) 26 \\(\\times\\) 6). For a fair comparison, both baseline models were trained on an NVIDIA RTX 3090 graphics card with \\(90\\%\\) data from M³Act3D for 320K iterations and then tested on the other \\(10\\%\\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.67, + 0.208, + 0.683 + ], + "angle": 0, + "content": "4.3.1 Evaluation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.688, + 0.468, + 0.884 + ], + "angle": 0, + "content": "Metrics. Due to the probabilistic nature of the task, we consider the following learning-based metrics, recognition accuracy, Frechet Inception Distance (FID), diversity, and multimodality, defined in [26]. These metrics, however, were originally designed for single-person motion generation. To evaluate the generated group activities, we report them at both group and person levels because they account for the fidelity and variations for the groups and the individuals. We train a multi-scale group activity recognition model using theComposer [58] architecture for the metrics. See Sup. Mat. for detailed explanations of how to construct the learning-based metrics, including the recognition model as well as the latent representations at both levels." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.886, + 0.468, + 0.9 + ], + "angle": 0, + "content": "In addition to the learning-based metrics, we tailor four" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.181 + ], + "angle": 0, + "content": "position-based metrics, collision frequency, repulsive interaction force, contact repulsive force, and total repulsive force, to the evaluation of human groups. The latter three are based on the social force model [27, 28], which explains crowd behaviors using socio-psychological and physical forces. Here we describe the four metrics:" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.183, + 0.892, + 0.288 + ], + "angle": 0, + "content": "Collision frequency indicates how often a collision (or an invalid interaction) would occur within a group. The collision count is calculated based on a distance threshold between any two persons in a group. It is then normalized by the total number of interactions to obtain the frequency. In other words, if \\( N \\) persons are in a group, the normalization denominator is \\( N \\cdot (N - 1) / 2 \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.289, + 0.892, + 0.349 + ], + "angle": 0, + "content": "Repulsive interaction force describes the psychological tendency of two persons to stay away from each other. As the distance between two persons decreases, the repulsive force increases exponentially." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.35, + 0.892, + 0.41 + ], + "angle": 0, + "content": "Contact repulsive force represents the compression body force when two persons collide with each other. The contact force is nonzero only when two persons collide. A larger contact force means the interaction is less likely to occur." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.411, + 0.892, + 0.439 + ], + "angle": 0, + "content": "Total repulsive force is the accumulation of interaction and contact forces." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.44, + 0.892, + 0.711 + ], + "angle": 0, + "content": "All four position-based metrics are calculated using the Euclidean distances of the persons' positions, with the shoulder width as the collision threshold. The social forces are calculated by averaging the magnitude of each individual's force accumulated through all its interactions with other persons. A well-performing model should generate group activities with low collision frequency and similar social force values to the ground truth. For the evaluation, we generated 500 samples for each group activity using the two well-trained baseline models. Each generated sequence contains 60 frames. We use the test split as the ground truth and randomly extract the group activity of the same length for evaluation. To ensure the distributions of group sizes are similar to the ground truth, we calculate the minimum and maximum group sizes from the training split and uniformly sample a group size from that range to generate group activities. Please refer to Sup. Mat. for more details regarding the baseline architectures, metrics formulas, and evaluation." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.718, + 0.605, + 0.731 + ], + "angle": 0, + "content": "4.3.2 Results" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "MDM+IFormer is capable of generating group activities with well-aligned character positions. As shown in Fig. 3, MDM generates human groups that are poorly positioned. For example, the persons in a walking group do not walk in the same direction and the persons are poorly placed in a queueing group. This is because MDM generates the group activities by inferring the individual motions independently. The placement of the individuals simply follows the probabilistic distribution of all persons' positions in the dataset. On the other hand, MDM+IFormer successfully learns the probabilistic distribution for the entire group due to its in" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "21928" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.082, + 0.089, + 0.891, + 0.164 + ], + "angle": 0, + "content": "
Group LevelPerson Level
Acc ↑FID ↓Diversity →Multimodality →FID ↓Diversity →Multimodality →
GT99.9370.001 ± 0.00017.752 ± 0.0253.491 ± 0.0120.001 ± 0.00014.506 ± 0.0137.546 ± 0.010
MDM97.3673.909 ± 0.01917.683 ± 0.0374.155 ± 0.0194.434 ± 0.01014.158 ± 0.0357.588 ± 0.013
MDM+IFormer98.1003.242 ± 0.01617.855 ± 0.0404.198 ± 0.0213.066 ± 0.00714.827 ± 0.0316.945 ± 0.011
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.168, + 0.893, + 0.197 + ], + "angle": 0, + "content": "Table 7. The results of the generated group activities with the learning-based metrics at both levels. An up arrow means the result is better when the metric score is higher. A right arrow means the metric score should be close to ground truth (GT)." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.205, + 0.466, + 0.276 + ], + "angle": 0, + "content": "
Collision Freq. ↓Interaction Force →Contact Force →Total Force →
GT0.03765.7946.55112.33
MDM3.6437,121.503,822.4710,903.57
MDM+IFormer1.1571,796.251,373.403167.80
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.28, + 0.469, + 0.336 + ], + "angle": 0, + "content": "Table 8. Results of the generated human activities with position-based metrics. The collision frequency is calculated on a 60-frame group activity and normalized by the total number of interactions in a group." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.35, + 0.469, + 0.379 + ], + "angle": 0, + "content": "teraction transformer. The persons are better aligned in a group and they have coordinated motions." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.381, + 0.469, + 0.576 + ], + "angle": 0, + "content": "Both baselines are capable of generating diverse activities that match the input condition, but MDM+IFformer obtains better FID scores. Tab. 7 shows the results for the learning-based metrics. When compared with ground truth, both baselines obtain similar scores on recognition accuracy, diversity, and multimodality at both levels. The results indicate that both models successfully learn to generate distinguishable individual motions and group activities. The generated motions are also as diverse as the ground truth. The observations align with the results on action-to-motion generation in MDM [47]. MDM+IFformer receives a lower FID score than MDM, suggesting that MDM+IFformer generates group activities with higher quality." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.577, + 0.469, + 0.758 + ], + "angle": 0, + "content": "The interaction transformer in MDM+IFormer greatly lowers the collision frequency within the generated group activities. As shown in Tab. 8, the collision frequency of the group activities generated by MDM+IFormer is much lower than the vanilla MDM. It suggests that the interaction transformer better learns the inter-person dependencies and generates more valid person interactions. In fact, we observe that the group activities generated by the vanilla MDM sometimes contain overlapping person positions. The high collision frequency of the MDM baseline also affects the repulsive forces, which makes social forces within the group activities of MDM implausible." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.761, + 0.327, + 0.777 + ], + "angle": 0, + "content": "5. Discussion and Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.469, + 0.901 + ], + "angle": 0, + "content": "We show the merit of \\(\\mathsf{M}^3\\mathsf{Act}\\) by conducting three core experiments with multiple modalities and enhanced performances, as well as introducing a novel generative task. In both MPT and GAR experiments, we observe positive correlations between the volume of synthetic data used for training and model performance, indicating an improved model generalizability to unseen test cases with more synthetic data. Moreover, our comparison between \\(\\mathrm{DT + Syn}^{\\dagger}\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.208, + 0.892, + 0.524 + ], + "angle": 0, + "content": "and MOTRv2* reveals that synthetic data can replace certain real-world data from the target domain without sacrificing performance [13]. Essentially, our synthetic data reduces the need for extensive real data during training, thereby effectively lowering the costs associated with data collection and annotation. This discovery represents a promising step towards achieving few-shot and potentially zero-shot sim2real transfer. In our 3D Group Activity Generation experiment, we observe that MDM+IFormer, despite being a baseline for the novel task, learns to embed the heuristics for person interactions and produces well-aligned groups given the controls. It's important to highlight that the generative approach, though currently underperforms the procedural method (GT), demonstrates the unique potential of controlling the group motions directly from various signals, including activity class, group size, trajectory, density, speed, and text inputs. With the anticipation of more data availability and increased model capacity for generative models in the future, we expect the generative method to eventually prevail, leading to broader applications for social interactions and human collective activities." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.526, + 0.892, + 0.692 + ], + "angle": 0, + "content": "While the complexity of group behaviors in our dataset may be constrained by the heuristics used for activity authoring, \\(\\mathsf{M}^{3}\\mathsf{A}\\mathsf{ct}\\) offers notable flexibility for incorporating new group dynamics tailored to any specific downstream tasks. These new groups could be derived from expert-guided heuristics, rules generated by large language models, or outputs from our 3D GAG model. Furthermore, we recognize the existing domain gaps between synthetic and real-world data. With more assets included in our data generator in future iterations, we can enhance model generalizability and alleviate the disparities." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.7, + 0.681, + 0.716 + ], + "angle": 0, + "content": "6. Acknowledgement" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.719, + 0.892, + 0.839 + ], + "angle": 0, + "content": "The research was supported in part by NSF awards: IIS-1703883, IIS-1955404, IIS-1955365, RETTL-2119265, and EAGER-2122119. This work was also partially supported by the Center for Smart Streetscapes, an NSF Engineering Research Center, under cooperative agreement EEC-2133516. This material is based upon work supported by the U.S. Department of Homeland Security1 under Grant Award Number 22STESE00001 01 01." + }, + { + "type": "page_footnote", + "bbox": [ + 0.498, + 0.851, + 0.892, + 0.901 + ], + "angle": 0, + "content": "\\(^{1}\\)Disclaimer. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "21929" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.468, + 0.142 + ], + "angle": 0, + "content": "[1] Renderpeople. https://renderpeople.com/, 2023. 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On the continuity of rotation representations in neural networks. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 5745-5753, 2019. 7" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.472, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.52, + 0.957 + ], + "angle": 0, + "content": "21932" + } + ] +] \ No newline at end of file diff --git a/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_origin.pdf b/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..fd5abe95a47f374b1ee321d962844137f936ffaf --- /dev/null +++ b/2024/Learning from Synthetic Human Group Activities/804774d4-d5b8-4f49-9724-9eca71443605_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:b507a9ad0458fa72f0e57d4da1d14f982c63c8895d003a740a62cad1d24f8672 +size 4781187 diff --git a/2024/Learning from Synthetic Human Group Activities/full.md b/2024/Learning from Synthetic Human Group Activities/full.md new file mode 100644 index 0000000000000000000000000000000000000000..be50cf629671d250f63960d31d3f4b323d93c4a8 --- /dev/null +++ b/2024/Learning from Synthetic Human Group Activities/full.md @@ -0,0 +1,323 @@ +# Learning from Synthetic Human Group Activities + +Che-Jui Chang† +Rutgers University +chejui.chang@rutgers.edu + +Parth Goel +Rutgers University +goel.parth210@gmail.com + +Samuel S. Sohn +Rutgers University +samuel.sohn@rutgers.edu + +Danrui Li +Rutgers University +danrui.li@rutgers.edu + +Honglu Zhou NEC Laboratories hozhou@nec-labs.com + +Sejong Yoon +The College of New Jersey +yoons@tcnj.edu + +Mubbasir Kapadia Roblox + +mkapadia@roblox.com + +Deep Patel NEC Laboratories dpatel@nec-labs.com + +Seonghyeon Moon† +Rutgers University +sm206@cs.rutgers.edu + +Vladimir Pavlovic +Rutgers University +vladimir@rutgers.edu + +# Abstract + +The study of complex human interactions and group activities has become a focal point in human-centric computer vision. However, progress in related tasks is often hindered by the challenges of obtaining large-scale labeled datasets from real-world scenarios. To address the limitation, we introduce $M^3$ Act, a synthetic data generator for multi-view multi-group multi-person human atomic actions and group activities. Powered by Unity Engine, $M^3$ Act features multiple semantic groups, highly diverse and photorealistic images, and a comprehensive set of annotations, which facilitates the learning of human-centered tasks across single-person, multi-person, and multi-group conditions. We demonstrate the advantages of $M^3$ Act across three core experiments. The results suggest our synthetic dataset can significantly improve the performance of several downstream methods and replace real-world datasets to reduce cost. Notably, $M^3$ Act improves the state-of-the-art MOTRv2 on DanceTrack dataset, leading to a hop on the leaderboard from $10^{th}$ to $2^{nd}$ place. Moreover, $M^3$ Act opens new research for controllable 3D group activity generation. We define multiple metrics and propose a competitive baseline for the novel task. Our code and data are available at our project page: http://cjerry1243.github.io/M3Act. + +# 1. Introduction + +Understanding collective human activities and social groups carries significant implications across diverse domains, as it contributes to bolstering public safety within + +surveillance systems, ensuring safe navigation for autonomous robots and vehicles amidst human crowds, and enriching social awareness in human-robot interactions [8, 9, 11, 12, 21, 37, 49, 51]. However, the advancement in related tasks is often impeded by the challenges of obtaining large-scale human group activity datasets in real-world scenarios with fine-grained multifaceted annotations. + +Generating synthetic data is an emerging alternative to collecting real-world data due to its capability of producing large-scale datasets with perfect annotations. Nonetheless, most synthetic datasets [4, 20, 40, 48, 53] are primarily designed to facilitate human pose and shape estimation. They can only provide data with independently-animated persons, which is unsuitable for tasks in single-group and multi-group conditions [51]. To address the limitation, we propose $\mathbf{M}^3\mathrm{Act}$ , a synthetic data generator, with multi-view multi-group multi-person human actions and group activities. As presented in Tab. 1, $\mathbf{M}^3\mathrm{Act}$ stands out by offering comprehensive annotations including both 2D and 3D annotations as well as fine-grained person-level and group-level labels, thereby making it an ideal synthetic dataset generator to support tasks such as human activity recognition and multi-person tracking across all listed real-world datasets. + +Illustrated in Fig. 1, our synthetic data generator features multiple semantic groups, highly diverse and photorealistic images, and a rich set of annotations. It encompasses 25 photometric 3D scenes, 104 HDRIs (High Dynamic Range Images), 5 lighting volumes, 2200 human models, 384 animations (categorized into 14 atomic action classes), and 6 group activities. For our experiments, We generated two + +![](images/2f8377696cb398b2c1f7fec555d61c93582c533c3194499984a418d2151fe716.jpg) + +![](images/84d512435123117bdc456921bc13f0b3c34566216912e94769387946fd6d6d81.jpg) + +![](images/f11abe269237809af3b823ff8a55751f3dc318ddca74607a1ab071ba037a8416.jpg) +Figure 1. M3Act is a large-scale synthetic data generator designed to support multi-person and multi-group research topics. M3Act features multiple semantic groups and produces highly diverse and photorealistic videos with a rich set of annotations suitable for human-centered tasks including multi-person tracking, group activity recognition, and controllable human group activity generation. + +![](images/4e932e519e03ba716df92952248a80b82f85e9c9969179b324f4ab8dd5ae498b.jpg) + +![](images/9fcdd490d07ff67b1b5a52aec5cdcc2b929798a6375ea7067276d31df88d9db8.jpg) + +![](images/213abc73eeb26a12d70f20d298dc6fdb6dfe7c454de2408fc4fe74d4877b11f6.jpg) + +![](images/c5525486514f6ca5c7bedce1118cb0d43686e6a9a8cacf60f7977222855e9baf.jpg) + +![](images/fdcbdcdc5b5cd8c6ece675ce29e79a1f3f34b9840c5606aa74aca9e895aee4c2.jpg) + +![](images/053698ccada6bfad1715fbc380c249a6c7aeb27cd8737da032148499ecae0e60.jpg) +Diverse Scenes and Lighting Conditions + +![](images/af06b99de4a1c3643ba561c6cb17b790d175e1798fcdc51dc51464b491c84418.jpg) + +![](images/01f83d2ef78bbf8da7bda3ca822b987a9b0296d99ea580a0c1abaf837787d9b9.jpg) + +![](images/478c37587e8f0dacd8a3c4c4de36d02fa278d0966d7230670ee2be42c2776baa.jpg) + +datasets, M $^3$ ActRGB and M $^3$ Act3D. M $^3$ ActRGB contains both single-group and multi-group data with a total of 6M frames of RGB images and 48M bounding boxes, rendered in 20 FPS. M $^3$ Act3D is a 3D-only and single-group dataset, which contains 3D motions of all persons within a group. It has large group sizes (max 27 people) and an average of 6.7 persons per group. In total, M $^3$ Act3D contains a duration of 87.6 hours of group activities, captured in 30 FPS. + +We first demonstrate the merit of $\mathsf{M}^3\mathsf{Act}$ via synthetic data pre-training and mixed training on multi-person tracking and group activity recognition. For multi-person tracking, training with our synthetic data yields significant performance gain on several downstream methods [23, 52, 56, 57]. We also demonstrate notable improvements in the state-of-the-art MOTRv2 method [57] and observe that our synthetic data can substitute for $62.5\%$ more real-world data, without compromising performance. In terms of group activity recognition, results indicate that pre-training with $\mathsf{M}^3\mathsf{ActRGB}$ greatly improves both person-level and group-level accuracy for Composer [58] and ActorTransformer [25] methods. Based on our generated data, we then introduce a novel task, controllable 3D group activity generation, which aims to synthesize a group of 3D human motions, given control signals such as activity labels and group sizes. We systematically approach the new task by introducing both learning-based and heuristics-based metrics, along with a competitive baseline to generate meaningful human activities. + +This paper makes the following contributions: + +- We propose a novel synthetic data generator, $\mathsf{M}^3\mathsf{Act}$ , and provide two large-scale synthetic datasets with highly diverse human activities, photorealistic multi-view videos, and comprehensive annotations. + +- We demonstrate that $\mathsf{M}^3\mathsf{Act}$ can significantly improve benchmark performances for multi-person tracking and group activity recognition and replace a large portion of real-world training data to reduce cost. +- $\mathrm{M}^{3}\mathrm{Act}$ promotes new research initiatives for controllable 3D group activity generation, suggesting that synthetic data can not only support existing tasks but also create datasets for novel research. + +# 2. Related Works + +Human Centered Synthetic Datasets. The use of synthetic datasets for human-centered tasks has become increasingly prominent due to their diversity, scalability, and perfect annotations, with proven merits connected to various fields in machine learning, including domain adaptation [34, 46], heterogeneous multitask learning [54], and sim2real [24] or task2sim [39] transfer. Most previous synthetic datasets are constructed to support human pose estimation. For example, SURREAL [48] contains renderings of human motions from 145 avatars composited to a background image. Subsequent works [2, 20, 40] managed to improve the image quality by leveraging realistic 3D scenes, high-quality renderings, and HDRI images. Recently, synthetic datasets have been proposed to tackle human shape and mesh estimation. SynBody [53] constructs layered human assets to increase character diversity. BEDLAM [4] adds physically simulated hair and clothes to achieve state-of-the-art performances on shape and mesh estimation. Nonetheless, data with collective human motions and group activities cannot be obtained from them. Our work, $\mathsf{M}^3\mathsf{Act}$ , is constructed with animated human groups tailored to multi-person and multi-group research. + +Real Multi-Person Datasets. Real-world datasets [15, 17, + +
DatasetImage TypeAvatar Num.VideoMulti-ViewMulti-PersonMulti-Group2D3DAnnotations Atomic Atn.Group Act.
SURREAL, 2017 [48]Composite145✓✓✓
AGORA, 2021 [40]HDRI350✓✓✓
HSPACE, 2021 [2]3D Scene1600✓✓✓✓✓
GTA-Humans, 2021 [6]3D Scene600✓✓✓✓
PSP-HDRI+, 2022 [20]HDRI28✓✓✓
SynBody, 2023 [53]3D Scene10k✓✓✓✓✓
BEDLAM, 2023 [4]3D Scene271✓✓✓✓
M3Act (Ours)Photometric 3D + HDRI2200✓✓✓✓✓✓✓✓
CAD, 2011 [15]Real-✓✓✓✓✓✓
Volleyball Dataset, 2016 [29]Real-✓✓✓✓✓✓
NTU-RGBD 120, 2019 [33]Real-✓✓✓✓✓✓
HiEve, 2020 [32]Real-✓✓✓✓✓
PoseTrack, 2021 [18]Real-✓✓✓✓
MOT, 2020 [17]Real-✓✓✓✓
DanceTrack, 2022 [45]Real-✓✓✓
JRDB, 2023 [21, 37, 49]Real-✓✓✓✓✓✓
+ +Table 1. A comparison of synthetic datasets as well as commonly-used real datasets for activity understanding and person tracking. We refer to JRDB as a union set of JRDB, JRDB-Act, and JRDB-Pose datasets. Note that it offers 3D bounding boxes, but not poses. + +18, 29, 32, 33, 37, 45] with multiple persons are usually collected for tasks such as group activity understanding, multiperson tracking, and human trajectory prediction. Recognizing and parsing collective human activities [25, 58] rely primarily on multiple modalities (RGB, bounding box, pose) and hierarchical action and activity labels. These fine-grained labels are provided by datasets like CAD [15] and Volleyball Dataset [29]. On the other hand, datasets for person tracking, such as HiEve [32], MOT [17, 38], and DanceTrack [45], require not only 2D annotations (e.g., bounding box) for individual frames, but also the association of the objects between them. Specifically, DanceTrack provides multiple persons in a group with the same clothing, making it difficult for the association of the individuals. MOT datasets target tracking for human crowds and contain mostly outdoor scenes from a bird-eye view. Recently, JRDB [21, 37, 49] with rich annotations is released. The images are captured by a social robot, navigating around daily scenes. It provides fine-grained annotations that support various tasks, including person detection, pose estimation, tracking, collective activity detection, and understanding. M³Act not only offers the same modalities and annotations for supporting the aforementioned tasks, but it also provides full 3D annotations, making it suitable for a wide range of applications beyond the 2D domain. + +# 3. $\mathbf{M}^3\mathbf{A}\mathbf{c}\mathbf{t}$ + +$\mathsf{M}^3\mathsf{Act}$ is a multi-view multi-group multi-person human atomic action and group activity data generator built with Unity Engine and the Perception [5] library. Inspired by PeopleSansPeople [19] that populates randomly posed human avatars in a scene and renders static images, $\mathsf{M}^3\mathsf{Act}$ not only offers the same functionalities for human poses but also extends it to the spatio-temporal domain. It generates RGB videos for dynamic human motions and produces a rich set of annotations simultaneously, including (a) 2D + +and 3D joints/meshes, (b) 2D and 3D bounding boxes for individual persons, (c) atomic action and group activity categories, (d) tracking information such as individual and group IDs, (e) segmentation, depth, and normal images, and (f) scene description. + +# 3.1. Data Generation + +The process of our data generation is illustrated in Fig. 2. First, the generation process is configured by the simulation scenario that manages multiple independent simulations of human activities. Then for each simulation, a 3D scene with background objects, lights, and cameras is set up, and groups of human characters are instantiated to be animated. Lastly, the multi-view RGB image frames are rendered and the annotations are exported at the end of the simulation. + +Scene Instantiation. We represent the environment through 25 photometric 3D scenes and 104 panoramic HDRIs. Each scene is initiated with randomized lighting and camera configuration. To attain a balance between realistic environmental illumination and pronounced shadow detail, our lighting schema integrates HDRI Sky lighting with a directional light. This directional light is subject to random variations in its direction, color temperature, and intensity. Regarding camera placement, we always point cameras towards the center of avatar groups and introduce variability by randomizing both the field of view and the camera's distance to these groups. + +Human Models and Motion Assets. M³Act leverages 2000 human models generated by Synthetic Humans [42], ranging across all ages (1 ~ 100), genders, ethnicities (such as Caucasian, Asian, Latin American, African, Middle Eastern), diverse body shapes, hair, and clothing. We also incorporated 200 widely-used human characters from RenderPeople [1]. For the human motions, we collected 384 animation clips from AMASS [36], categorized into 14 atomic action classes. We created a universal animation controller + +![](images/b7ad24563c921b062901e128d44792afbb317fa30af82ffd6505d64c1eebf9f4.jpg) +Figure 2. The data generation process of $\mathsf{M}^3\mathsf{Act}$ . It consists of multiple data simulations with scene instantiation, group activity authoring, and a data capture module. A high degree of randomization is involved in all aspects of the process to ensure diverse data. + +that blends styles, including arm space and stride size, to create diverse motions from the collected clips. + +Modular Group Activities. Each group activity is structured as a parameterized module, allowing for the customization of numerous variables. These variables include the number of individuals in the group and the specific atomic actions permitted within the group activity. This modularization ensures easy duplication, repositioning, and reuse of the group activities, enabling simulations of multiple groups at the same time. To procedurally animate a group of humans within a modular group, we establish the positions and orientations of the selected characters while choosing the appropriate animation clip for each character through the activity script. It's important to note that, despite drawing characters from the same set of avatars, the configurations and animations of these characters can vary significantly from one group to another. For example, animating a queueing activity may require all characters to be aligned in a straight line, while those in a walking group may form various shapes. The atomic actions that a person can perform also depend on the specific group activity. We carefully consider all these factors when authoring activities and provide a summary in the Sup. Mat. + +Domain Randomization. $\mathbf{M}^{3}\mathrm{Act}$ provides domain randomization for almost all aspects of the data generation process to ensure the simulation data is highly diverse. These aspects include the number of groups in a scene, the number of persons in each group, the positions of groups, the alignment of persons in a group, the positions of individuals, the textures for the instantiated characters, and the selection of scenes, lighting conditions, camera positions, characters, group activities, atomic actions, and animation clips. Despite the fact that animating group activities inherently limits the degree of freedom in the placement of characters, by altering the shapes in which characters align (e.g., either in a cluster, a straight line, or a curve), $\mathbf{M}^{3}\mathrm{Act}$ nonetheless generates diverse activities and achieves sufficient randomization for downstream model generalization. More details re + +garding the randomization variables and their distributions are provided in Sup. Mat. + +Rendering and Annotations. $\mathbf{M}^{3}\mathrm{Act}$ utilizes the Unity high-definition render pipeline for the creation of photorealistic RGB images and leverages the Perception library for capturing annotations. On average, data is generated at a rate of 4.2 FPS using one NVIDIA RTX 3070 Ti graphics card, with a resolution of $1920\times 1080$ , and all annotations are enabled. Similar to PeopleSansPeople, the 2D skeleton follows COCO [31] format, with additional labelers for exporting 3D joints, meshes, group IDs, and activity classes. After the data generation, the 3D joints and meshes are fitted with SMPL parameters [35, 41]. + +# 3.2. Dataset Statistics + +$\mathrm{M}^{3}\mathrm{Act}$ comprises 25 photometric 3D scenes, 104 HDRIs, 5 lighting volumes, 2200 human models, 384 animations (categorized into 14 atomic action classes), and 6 group activities. Using the generator, we first generated our synthetic dataset, $\mathrm{M}^{3}\mathrm{ActRGB}$ . It contains 6K simulations of every single-group activity and 9K simulations of multi-group configuration, with 4 camera views. Each simulation produces a 5-second video clip, captured in 20 FPS and FHD resolution. In total, $\mathrm{M}^{3}\mathrm{ActRGB}$ contains 6M RGB images and 48M bounding boxes. The average track length is 4.65 seconds. + +Additionally, we generated $\mathrm{M}^3\mathrm{Act3D}$ , a large-scale 3D-only dataset. It consists of more than $65\mathrm{K}$ simulations of single-group activity. Each contains 150 frames of multiperson collective interactions in 30 FPS, resulting in a total duration of 87.6 hours. As shown in Tab. 2, both the group size and the interaction complexity are significantly higher than those in previous multi-person motion datasets. Specifically, when compared with GTA-Combat [44], $\mathrm{M}^3\mathrm{Act3D}$ contains more persons in a group, has more group activities, and provides a variable number of persons in a group. To the best of our knowledge, $\mathrm{M}^3\mathrm{Act3D}$ is the first large-scale 3D dataset for human group activities with large group sizes as well as per-frame individual action labels. See Sup. Mat. + +
DatasetFPS# of Acty.# of Persons# of Actn.Duration
AvgMax
SBU [55]1582.02-7.6 mins
Duet Dance [30]2552.02-2.3 hrs
CHI3D [22]5082.02-2.7 hrs
NTU RGBD 120 [33]30262.02-15.0 hrs
GTA-Combat [44]1513.25-39.0 hrs
M3Act3D3066.727887.6 hrs
+ +for detailed statistics of both datasets. + +# 4. Experiments + +We showcase the practical utilities of $\mathsf{M}^3\mathsf{Act}$ through three core experiments: Multi-Person Tracking (MPT), Group Activity Recognition (GAR), and controllable Group Activity Generation (GAG). The experiments are carefully designed to cover the following three perspectives: + +- Multi-modality: Our experiments cover various modalities contained within our dataset, including RGB videos, 2D keypoints, and 3D joints. We leverage the rich annotations including bounding boxes, tracklets, group activities, and person action labels. +- Performance: We conduct the ablation study by altering the amount and the type of synthetic data used for training to see its effect on the model performance. +- Novel task: We introduce a novel generative task (GAG), showing that synthetic data can not only support existing CV tasks but also create datasets for new research. + +# 4.1. Multi-Person Tracking + +The objective of MPT is to predict the trajectories of all persons from a dynamic video stream. Typically, person tracking involves two separate processes, person detection and association. While the tracking task is approached in some prior works with the tracking-by-detection method [3, 7, 50], we consider end-to-end approaches [23, 52, 56, 57] to evaluate the use of synthetic data on the performance of MPT as a whole, in lieu of an improved performance caused only by refined detection. + +Real-world Dataset: DanceTrack [45] (DT) is a challenging MPT dataset characterized by dynamic movements with human subjects in uniform appearances. It has a total of 100 videos with over 105K frames. + +Synthetic Dataset. Given the motion categories in the real-world dataset, we select a subset of $\mathbf{M}^3$ ActRGB with groups of people dancing, walking, and running. We use 1000 video clips with a single "dance" group as well as 1500 videos with a "walk" group and a "run" group simulated at the same time (denoted as WalkRun). We alter the use of the synthetic group activities (Dance, WalkRun, and Dance+WalkRun) in our experiments. + +Table 2. A comparison of datasets for 3D multi-person human activities. $\mathbb{M}^3\mathbb{A}\mathbb{ct}\mathbb{3}\mathbb{D}$ is the largest dataset with labels for atomic actions and more persons in a group. + +
Training DataHOTA↑DetA↑AssA↑IDF1↑MOTA↑
DT®69.883.058.971.689.3
DT68.8 (10)82.557.470.390.8
DT + Syn (D)59.075.546.159.082.6
DT + Syn (WR)70.183.159.472.592.0
DT + Syn (WR+D)71.9 (2)83.662.074.792.6
DT + Syn† (WR+D)72.283.462.675.592.7
DT (MOTRv2*)73.483.764.476.092.1
DT + BEDLAM [4]55.968.744.553.879.1
DT + GTA-Humans [6]54.166.844.252.178.8
+ +Table 3. MPT results on DanceTrack with MOTRv2. "D" means synthetic dance group. "WR" means walk and run groups. "WR+D" refers to "D" and "WR" combined. The symbol $\text{串}$ represents the author-provided checkpoint. The symbol $\dagger$ marks the same model with additional association at inference. Numbers in parentheses represent the rank in the DanceTrack leaderboard. + +
ModelSyn. DataHOTADetAAssAIDF1MOTA
MOTR [56]✓54.273.540.251.579.7
60.076.448.156.083.8
MeMOTR [23]✓68.580.558.471.289.9
71.181.862.374.192.2
CO-MOT [52]✓69.482.158.971.991.2
72.583.663.375.992.8
MOTRv2 [57]✓68.882.557.470.390.8
71.983.662.074.792.6
MOTRv2* [57]✓73.483.764.476.092.1
74.684.164.976.493.1
+ +Table 4. MPT results on DanceTrack using different methods trained with our synthetic data. + +Results. We mix together both synthetic and real data during training and present the results in Tab. 3. First, adding our synthetic data yields significant improvement in all 5 tracking metrics as well as a hop in ranking on HOTA from $10^{th}$ to $2^{nd}$ place. The model trained with our synthetic data plus the extra association, marked as $\mathrm{DT} + \mathrm{Syn}^{\dagger}$ (WR+D), achieves similar performance to MOTRv2*, the same model that is trained with additional validation data with an ensemble of 4 models [57]. This suggests that the synthetic data used in our experiment is equivalent to at least $62.5\%$ more real data. Second, Compared with other synthetic data sources, such as BEDLAM and GTA-Humans, M³Act demonstrates superior performance, indicating its better suitability for multi-person dynamic conditions. Third, we observe that the type of synthetic groups affects the model performance on real data. Adding the "WalkRun" groups to the training data is more effective than adding the "Dance" group. This is because while the DanceTrack dataset contains dynamic dance movements, the real challenge lies in detection and tracking when the subjects switch positions. By design, the positions of the characters in our dance group are well-staged and the movements are nearly synchronous. (See Sup. Mat. for the design.) Contrarily, having a walk and a run group together + +
ModelPretrained +Syn. DataGroup ActivityPerson Action
Top 1 Acc (%) ↑Top 1 Acc (%) ↑
Composer +[58]N/A84.87±2.3(88.20)81.31±2.4(83.13)
10%86.12±1.8(87.87)84.16±1.8(86.03)
25%87.65±1.2(89.01)86.36±1.3(86.81)
50%89.39±0.4(90.14)86.68±1.5(87.99)
100%89.74±1.0(91.51)88.74±1.7(89.05)
Gains+4.87 (+3.31)+7.43 (+5.92)
Actor +Transformer +[25]N/A78.08±1.0(79.47)76.22±2.2(78.07)
10%77.59±2.4(81.00)76.01±3.2(79.76)
25%81.36±2.1(83.19)78.86±2.4(80.05)
50%82.72±1.3(84.56)79.95±1.6(81.47)
100%83.67±1.2(84.88)81.65±1.2(82.22)
Gains+5.59 (+5.41)+5.43 (+4.15)
+ +Table 5. Results of 2D keypoint-based group activity and person action recognition on CAD2 dataset. The best results are shown in parentheses. The results suggest that pre-training with our synthetic data largely increases the accuracy for both group activity and person actions. Note that group accuracy saturates at $93.4\%$ and $86.2\%$ forComposer and Actor Transformer respectively. + +in a scene leads to frequent position switches relative to the camera view and thus improves the model performance. Lastly, Tab. 4 presents the tracking results using different methods. Results indicate that our synthetic data is effective across various models. + +# 4.2. Group Activity Recognition + +The goal of GAR is to determine the class of the group activity performed by the dominant group as well as the action class of each person. We consider Composer [58] and Actor Transformer [25] as the benchmark models. The former is a multi-scale transformer-based model and accepts only 2D keypoints as input. The latter can take combinations of multiple input modalities. + +Real-world Dataset: CAD2 [15] and Volleyball Dataset [29]. CAD2 is an extended version of the Collective Activity Dataset [14] that records human group activities and is widely used for GAR benchmarks [51]. Volleyball Dataset (VD) is an action recognition dataset. It has 55 videos with 9 player action labels and 8 team activity labels. + +Synthetic Dataset. We use a subset of all single-group data from M³ActRGB. It contains a total of 10K videos and over 600K frames. It contains all group activity and individual action classes that CAD2 provides and further includes 7 more action types. + +Results. We experimentally study how the size of our pretraining synthetic dataset and the capacity of a GAR model affect generalization from the synthetic to real domains. We first train the models on different amounts of synthetic data. Then we fine-tune them on CAD2 and report the top 1 accuracy of both group activity and person action recognition on the test set of CAD2. Tab. 5 presents the results using only 2D keypoints as input. We see a common trend for + +
Model2D RGB FlowCAD2 Syn+CAD2VD Syn+VD
Composer✓88.291.594.695.1
Actor Transformer✓79.584.992.393.7
✓78.280.791.492.5
✓✓81.085.293.594.3
✓81.385.094.495.0
✓79.581.993.094.1
+ +Table 6. The group activity recognition accuracy on CAD2 and Volleyball Dataset using different input modalities. + +both GAR models that the recognition accuracy increases as more synthetic data is used for pre-training. With $100\%$ of synthetic data, the accuracy of Composer increases, with an average of $4.87\%$ at the group level and $7.43\%$ at the person level, whereas Actor Transformer sees a $5.59\%$ increase at group level and $5.43\%$ increase at person level. Moreover, Tab. 6 shows the group recognition accuracy using different input modalities on CAD2 and VD. The performance gains in the experiment indicate that our synthetic data can effectively benefit the downstream GAR task across different methods, input modalities, and datasets. + +# 4.3. Controllable 3D Group Activity Generation + +While the procedural generation of our group activities in $\mathbf{M}^{3}\mathrm{Act}$ yields realistic and diverse human activities, the implementation requires considerable effort and involves the design and application of specific heuristics. Learning a generative model for human group activities, instead, encodes the heuristics to the architecture inherently and encompasses the capabilities of probabilistically generating diverse activities, with control over the entire group of human motions from various signals. To this end, we introduce controllable 3D group activity generation (GAG). + +Definition. Let $G_{t}^{p} = \{m_{i}^{n}\}_{i = 1\sim t,n = 1\sim p}$ be a group of human motions with $t$ frames and $p$ persons. The individual pose is denoted as $m_i^n\in R^{j\times d}$ , where $j$ is the number of joints in the skeleton and $d$ is the joint dimension. The goal of GAG is to synthesize a group of 3D human motions $G_{t}^{p}$ from Gaussian noise, given an activity label and an arbitrary group size as input conditions. It requires a model capable of learning the temporal and spatial motion dependencies among persons within the same group and generating human motions with any group size simultaneously. GAG is related to dyadic motion generation [10, 16] and partner-conditioned reaction generation [43], but involves the motion interactions of more than two persons. + +Baselines. Although previous works [16, 43, 44] can generate motions for multiple persons, they are limited to dyadic scenarios or groups with a fixed number of persons. Therefore, we present two baselines. The first one is the vanilla motion diffusion model, MDM [47]. It was proposed for probabilistic single-person motion generation from an input condition. We adopt their action-to-motion architecture for conditional synthesis and train the model on $\mathbf{M}^3\mathrm{Act3D}$ + +![](images/e7d4e10d8f71f892c9781b70078de8e19b2fdf28148afa651eb2715ae04051ab.jpg) +Figure 3. The qualitative comparison of two group activities from ground truth (GT), MDM, and MDM+IFormer. The distribution of the persons from MDM+IFormer is closer to GT. + +for generating an individual person's motion from an input group activity class label. In order to generate a group of human motions from a given group size, we repeat the single-person inference several times. In other words, the individual motions are generated independently by MDM. Our second baseline, $\mathbf{MDM} + \mathbf{IFormer}$ is extended from MDM and includes an additional interaction transformer (IFormer) that works along the dimension of the persons. The interaction transformer encourages the model to learn the interperson motion dependencies. At inference, MDM+IFormer is capable of producing coordinated group activities in one forward pass, due to its modeling of human interactions. + +Implementation. We utilize a common skeleton for all individual persons with 25 joints. We process the data so each motion is represented as both the 6D joint rotations [59] and the root positions. The final representation of a collective group activity with multiple persons is a tensor with shape (#persons $\times$ #frames $\times$ 26 $\times$ 6). For a fair comparison, both baseline models were trained on an NVIDIA RTX 3090 graphics card with $90\%$ data from M³Act3D for 320K iterations and then tested on the other $10\%$ . + +# 4.3.1 Evaluation + +Metrics. Due to the probabilistic nature of the task, we consider the following learning-based metrics, recognition accuracy, Frechet Inception Distance (FID), diversity, and multimodality, defined in [26]. These metrics, however, were originally designed for single-person motion generation. To evaluate the generated group activities, we report them at both group and person levels because they account for the fidelity and variations for the groups and the individuals. We train a multi-scale group activity recognition model using theComposer [58] architecture for the metrics. See Sup. Mat. for detailed explanations of how to construct the learning-based metrics, including the recognition model as well as the latent representations at both levels. + +In addition to the learning-based metrics, we tailor four + +position-based metrics, collision frequency, repulsive interaction force, contact repulsive force, and total repulsive force, to the evaluation of human groups. The latter three are based on the social force model [27, 28], which explains crowd behaviors using socio-psychological and physical forces. Here we describe the four metrics: + +Collision frequency indicates how often a collision (or an invalid interaction) would occur within a group. The collision count is calculated based on a distance threshold between any two persons in a group. It is then normalized by the total number of interactions to obtain the frequency. In other words, if $N$ persons are in a group, the normalization denominator is $N \cdot (N - 1) / 2$ . + +Repulsive interaction force describes the psychological tendency of two persons to stay away from each other. As the distance between two persons decreases, the repulsive force increases exponentially. + +Contact repulsive force represents the compression body force when two persons collide with each other. The contact force is nonzero only when two persons collide. A larger contact force means the interaction is less likely to occur. + +Total repulsive force is the accumulation of interaction and contact forces. + +All four position-based metrics are calculated using the Euclidean distances of the persons' positions, with the shoulder width as the collision threshold. The social forces are calculated by averaging the magnitude of each individual's force accumulated through all its interactions with other persons. A well-performing model should generate group activities with low collision frequency and similar social force values to the ground truth. For the evaluation, we generated 500 samples for each group activity using the two well-trained baseline models. Each generated sequence contains 60 frames. We use the test split as the ground truth and randomly extract the group activity of the same length for evaluation. To ensure the distributions of group sizes are similar to the ground truth, we calculate the minimum and maximum group sizes from the training split and uniformly sample a group size from that range to generate group activities. Please refer to Sup. Mat. for more details regarding the baseline architectures, metrics formulas, and evaluation. + +# 4.3.2 Results + +MDM+IFormer is capable of generating group activities with well-aligned character positions. As shown in Fig. 3, MDM generates human groups that are poorly positioned. For example, the persons in a walking group do not walk in the same direction and the persons are poorly placed in a queueing group. This is because MDM generates the group activities by inferring the individual motions independently. The placement of the individuals simply follows the probabilistic distribution of all persons' positions in the dataset. On the other hand, MDM+IFormer successfully learns the probabilistic distribution for the entire group due to its in + +
Group LevelPerson Level
Acc ↑FID ↓Diversity →Multimodality →FID ↓Diversity →Multimodality →
GT99.9370.001 ± 0.00017.752 ± 0.0253.491 ± 0.0120.001 ± 0.00014.506 ± 0.0137.546 ± 0.010
MDM97.3673.909 ± 0.01917.683 ± 0.0374.155 ± 0.0194.434 ± 0.01014.158 ± 0.0357.588 ± 0.013
MDM+IFormer98.1003.242 ± 0.01617.855 ± 0.0404.198 ± 0.0213.066 ± 0.00714.827 ± 0.0316.945 ± 0.011
+ +Table 7. The results of the generated group activities with the learning-based metrics at both levels. An up arrow means the result is better when the metric score is higher. A right arrow means the metric score should be close to ground truth (GT). + +
Collision Freq. ↓Interaction Force →Contact Force →Total Force →
GT0.03765.7946.55112.33
MDM3.6437,121.503,822.4710,903.57
MDM+IFormer1.1571,796.251,373.403167.80
+ +Table 8. Results of the generated human activities with position-based metrics. The collision frequency is calculated on a 60-frame group activity and normalized by the total number of interactions in a group. + +teraction transformer. The persons are better aligned in a group and they have coordinated motions. + +Both baselines are capable of generating diverse activities that match the input condition, but MDM+IFformer obtains better FID scores. Tab. 7 shows the results for the learning-based metrics. When compared with ground truth, both baselines obtain similar scores on recognition accuracy, diversity, and multimodality at both levels. The results indicate that both models successfully learn to generate distinguishable individual motions and group activities. The generated motions are also as diverse as the ground truth. The observations align with the results on action-to-motion generation in MDM [47]. MDM+IFformer receives a lower FID score than MDM, suggesting that MDM+IFformer generates group activities with higher quality. + +The interaction transformer in MDM+IFormer greatly lowers the collision frequency within the generated group activities. As shown in Tab. 8, the collision frequency of the group activities generated by MDM+IFormer is much lower than the vanilla MDM. It suggests that the interaction transformer better learns the inter-person dependencies and generates more valid person interactions. In fact, we observe that the group activities generated by the vanilla MDM sometimes contain overlapping person positions. The high collision frequency of the MDM baseline also affects the repulsive forces, which makes social forces within the group activities of MDM implausible. + +# 5. Discussion and Conclusion + +We show the merit of $\mathsf{M}^3\mathsf{Act}$ by conducting three core experiments with multiple modalities and enhanced performances, as well as introducing a novel generative task. In both MPT and GAR experiments, we observe positive correlations between the volume of synthetic data used for training and model performance, indicating an improved model generalizability to unseen test cases with more synthetic data. Moreover, our comparison between $\mathrm{DT + Syn}^{\dagger}$ + +and MOTRv2* reveals that synthetic data can replace certain real-world data from the target domain without sacrificing performance [13]. Essentially, our synthetic data reduces the need for extensive real data during training, thereby effectively lowering the costs associated with data collection and annotation. This discovery represents a promising step towards achieving few-shot and potentially zero-shot sim2real transfer. In our 3D Group Activity Generation experiment, we observe that MDM+IFormer, despite being a baseline for the novel task, learns to embed the heuristics for person interactions and produces well-aligned groups given the controls. It's important to highlight that the generative approach, though currently underperforms the procedural method (GT), demonstrates the unique potential of controlling the group motions directly from various signals, including activity class, group size, trajectory, density, speed, and text inputs. With the anticipation of more data availability and increased model capacity for generative models in the future, we expect the generative method to eventually prevail, leading to broader applications for social interactions and human collective activities. + +While the complexity of group behaviors in our dataset may be constrained by the heuristics used for activity authoring, $\mathsf{M}^{3}\mathsf{A}\mathsf{ct}$ offers notable flexibility for incorporating new group dynamics tailored to any specific downstream tasks. These new groups could be derived from expert-guided heuristics, rules generated by large language models, or outputs from our 3D GAG model. Furthermore, we recognize the existing domain gaps between synthetic and real-world data. With more assets included in our data generator in future iterations, we can enhance model generalizability and alleviate the disparities. + +# 6. Acknowledgement + +The research was supported in part by NSF awards: IIS-1703883, IIS-1955404, IIS-1955365, RETTL-2119265, and EAGER-2122119. This work was also partially supported by the Center for Smart Streetscapes, an NSF Engineering Research Center, under cooperative agreement EEC-2133516. This material is based upon work supported by the U.S. Department of Homeland Security1 under Grant Award Number 22STESE00001 01 01. + +# References + +[1] Renderpeople. https://renderpeople.com/, 2023. Accessed: 2023-02-10. 3 +[2] Eduard Gabriel Bazavan, Andrei Zanfir, Mihai Zanfir, William T Freeman, Rahul Sukthankar, and Cristian Sminchisescu. Hspace: Synthetic parametric humans animated in complex environments. arXiv preprint arXiv:2112.12867, 2021. 2, 3 +[3] Alex Bewley, Zongyuan Ge, Lionel Ott, Fabio Ramos, and Ben Upcroft. Simple online and realtime tracking. In 2016 IEEE international conference on image processing (ICIP), pages 3464-3468. 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However, progress in related tasks is often hindered by the challenges of obtaining large-scale labeled datasets from real-world scenarios. To address the limitation, we introduce " + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "inline_equation", + "content": "M^3" + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "text", + "content": " Act, a synthetic data generator for multi-view multi-group multi-person human atomic actions and group activities. Powered by Unity Engine, " + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "inline_equation", + "content": "M^3" + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "text", + "content": " Act features multiple semantic groups, highly diverse and photorealistic images, and a comprehensive set of annotations, which facilitates the learning of human-centered tasks across single-person, multi-person, and multi-group conditions. We demonstrate the advantages of " + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "inline_equation", + "content": "M^3" + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "text", + "content": " Act across three core experiments. The results suggest our synthetic dataset can significantly improve the performance of several downstream methods and replace real-world datasets to reduce cost. Notably, " + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "inline_equation", + "content": "M^3" + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "text", + "content": " Act improves the state-of-the-art MOTRv2 on DanceTrack dataset, leading to a hop on the leaderboard from " + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "inline_equation", + "content": "10^{th}" + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "inline_equation", + "content": "2^{nd}" + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "text", + "content": " place. Moreover, " + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "inline_equation", + "content": "M^3" + }, + { + "bbox": [ + 45, + 355, + 289, + 630 + ], + "type": "text", + "content": " Act opens new research for controllable 3D group activity generation. We define multiple metrics and propose a competitive baseline for the novel task. Our code and data are available at our project page: http://cjerry1243.github.io/M3Act." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 47, + 639, + 128, + 652 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 639, + 128, + 652 + ], + "spans": [ + { + "bbox": [ + 47, + 639, + 128, + 652 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 47, + 655, + 287, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 655, + 287, + 693 + ], + "spans": [ + { + "bbox": [ + 47, + 655, + 287, + 693 + ], + "type": "text", + "content": "Understanding collective human activities and social groups carries significant implications across diverse domains, as it contributes to bolstering public safety within" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 338, + 545, + 421 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 338, + 545, + 421 + ], + "spans": [ + { + "bbox": [ + 306, + 338, + 545, + 421 + ], + "type": "text", + "content": "surveillance systems, ensuring safe navigation for autonomous robots and vehicles amidst human crowds, and enriching social awareness in human-robot interactions [8, 9, 11, 12, 21, 37, 49, 51]. However, the advancement in related tasks is often impeded by the challenges of obtaining large-scale human group activity datasets in real-world scenarios with fine-grained multifaceted annotations." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 423, + 546, + 626 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 423, + 546, + 626 + ], + "spans": [ + { + "bbox": [ + 304, + 423, + 546, + 626 + ], + "type": "text", + "content": "Generating synthetic data is an emerging alternative to collecting real-world data due to its capability of producing large-scale datasets with perfect annotations. Nonetheless, most synthetic datasets [4, 20, 40, 48, 53] are primarily designed to facilitate human pose and shape estimation. They can only provide data with independently-animated persons, which is unsuitable for tasks in single-group and multi-group conditions [51]. To address the limitation, we propose " + }, + { + "bbox": [ + 304, + 423, + 546, + 626 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^3\\mathrm{Act}" + }, + { + "bbox": [ + 304, + 423, + 546, + 626 + ], + "type": "text", + "content": ", a synthetic data generator, with multi-view multi-group multi-person human actions and group activities. As presented in Tab. 1, " + }, + { + "bbox": [ + 304, + 423, + 546, + 626 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^3\\mathrm{Act}" + }, + { + "bbox": [ + 304, + 423, + 546, + 626 + ], + "type": "text", + "content": " stands out by offering comprehensive annotations including both 2D and 3D annotations as well as fine-grained person-level and group-level labels, thereby making it an ideal synthetic dataset generator to support tasks such as human activity recognition and multi-person tracking across all listed real-world datasets." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": "Illustrated in Fig. 1, our synthetic data generator features multiple semantic groups, highly diverse and photorealistic images, and a rich set of annotations. It encompasses 25 photometric 3D scenes, 104 HDRIs (High Dynamic Range Images), 5 lighting volumes, 2200 human models, 384 animations (categorized into 14 atomic action classes), and 6 group activities. For our experiments, We generated two" + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 62, + 702, + 194, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 62, + 702, + 194, + 713 + ], + "spans": [ + { + "bbox": [ + 62, + 702, + 194, + 713 + ], + "type": "inline_equation", + "content": "\\dagger" + }, + { + "bbox": [ + 62, + 702, + 194, + 713 + ], + "type": "text", + "content": "Work done during internship at Roblox" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "21922" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 70, + 260, + 205 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 260, + 205 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 260, + 205 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 260, + 205 + ], + "type": "image", + "image_path": "2f8377696cb398b2c1f7fec555d61c93582c533c3194499984a418d2151fe716.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 261, + 72, + 407, + 203 + ], + "blocks": [ + { + "bbox": [ + 261, + 72, + 407, + 203 + ], + "lines": [ + { + "bbox": [ + 261, + 72, + 407, + 203 + ], + "spans": [ + { + "bbox": [ + 261, + 72, + 407, + 203 + ], + "type": "image", + "image_path": "84d512435123117bdc456921bc13f0b3c34566216912e94769387946fd6d6d81.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 49, + 209, + 89, + 256 + ], + "blocks": [ + { + "bbox": [ + 49, + 209, + 89, + 256 + ], + "lines": [ + { + "bbox": [ + 49, + 209, + 89, + 256 + ], + "spans": [ + { + "bbox": [ + 49, + 209, + 89, + 256 + ], + "type": "image", + "image_path": "f11abe269237809af3b823ff8a55751f3dc318ddca74607a1ab071ba037a8416.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 274, + 546, + 308 + ], + "lines": [ + { + "bbox": [ + 46, + 274, + 546, + 308 + ], + "spans": [ + { + "bbox": [ + 46, + 274, + 546, + 308 + ], + "type": "text", + "content": "Figure 1. 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In total, M" + }, + { + "bbox": [ + 46, + 316, + 287, + 412 + ], + "type": "inline_equation", + "content": "^3" + }, + { + "bbox": [ + 46, + 316, + 287, + 412 + ], + "type": "text", + "content": "Act3D contains a duration of 87.6 hours of group activities, captured in 30 FPS." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "spans": [ + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "type": "text", + "content": "We first demonstrate the merit of " + }, + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "type": "text", + "content": " via synthetic data pre-training and mixed training on multi-person tracking and group activity recognition. For multi-person tracking, training with our synthetic data yields significant performance gain on several downstream methods [23, 52, 56, 57]. We also demonstrate notable improvements in the state-of-the-art MOTRv2 method [57] and observe that our synthetic data can substitute for " + }, + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "type": "inline_equation", + "content": "62.5\\%" + }, + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "type": "text", + "content": " more real-world data, without compromising performance. In terms of group activity recognition, results indicate that pre-training with " + }, + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{ActRGB}" + }, + { + "bbox": [ + 46, + 413, + 288, + 651 + ], + "type": "text", + "content": " greatly improves both person-level and group-level accuracy for Composer [58] and ActorTransformer [25] methods. Based on our generated data, we then introduce a novel task, controllable 3D group activity generation, which aims to synthesize a group of 3D human motions, given control signals such as activity labels and group sizes. We systematically approach the new task by introducing both learning-based and heuristics-based metrics, along with a competitive baseline to generate meaningful human activities." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 47, + 653, + 234, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 653, + 234, + 664 + ], + "spans": [ + { + "bbox": [ + 47, + 653, + 234, + 664 + ], + "type": "text", + "content": "This paper makes the following contributions:" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 47, + 665, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 665, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 665, + 287, + 713 + ], + "type": "text", + "content": "- We propose a novel synthetic data generator, " + }, + { + "bbox": [ + 47, + 665, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 47, + 665, + 287, + 713 + ], + "type": "text", + "content": ", and provide two large-scale synthetic datasets with highly diverse human activities, photorealistic multi-view videos, and comprehensive annotations." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 316, + 546, + 411 + ], + "type": "list", + "angle": 0, + "index": 20, + "blocks": [ + { + "bbox": [ + 306, + 316, + 546, + 364 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 316, + 546, + 364 + ], + "spans": [ + { + "bbox": [ + 306, + 316, + 546, + 364 + ], + "type": "text", + "content": "- We demonstrate that " + }, + { + "bbox": [ + 306, + 316, + 546, + 364 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 306, + 316, + 546, + 364 + ], + "type": "text", + "content": " can significantly improve benchmark performances for multi-person tracking and group activity recognition and replace a large portion of real-world training data to reduce cost." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 364, + 545, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 364, + 545, + 411 + ], + "spans": [ + { + "bbox": [ + 306, + 364, + 545, + 411 + ], + "type": "text", + "content": "- " + }, + { + "bbox": [ + 306, + 364, + 545, + 411 + ], + "type": "inline_equation", + "content": "\\mathrm{M}^{3}\\mathrm{Act}" + }, + { + "bbox": [ + 306, + 364, + 545, + 411 + ], + "type": "text", + "content": " promotes new research initiatives for controllable 3D group activity generation, suggesting that synthetic data can not only support existing tasks but also create datasets for novel research." + } + ] + } + ], + "index": 19 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 420, + 397, + 432 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 420, + 397, + 432 + ], + "spans": [ + { + "bbox": [ + 306, + 420, + 397, + 432 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 437, + 545, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 437, + 545, + 700 + ], + "spans": [ + { + "bbox": [ + 304, + 437, + 545, + 700 + ], + "type": "text", + "content": "Human Centered Synthetic Datasets. The use of synthetic datasets for human-centered tasks has become increasingly prominent due to their diversity, scalability, and perfect annotations, with proven merits connected to various fields in machine learning, including domain adaptation [34, 46], heterogeneous multitask learning [54], and sim2real [24] or task2sim [39] transfer. Most previous synthetic datasets are constructed to support human pose estimation. For example, SURREAL [48] contains renderings of human motions from 145 avatars composited to a background image. Subsequent works [2, 20, 40] managed to improve the image quality by leveraging realistic 3D scenes, high-quality renderings, and HDRI images. Recently, synthetic datasets have been proposed to tackle human shape and mesh estimation. SynBody [53] constructs layered human assets to increase character diversity. BEDLAM [4] adds physically simulated hair and clothes to achieve state-of-the-art performances on shape and mesh estimation. Nonetheless, data with collective human motions and group activities cannot be obtained from them. Our work, " + }, + { + "bbox": [ + 304, + 437, + 545, + 700 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 304, + 437, + 545, + 700 + ], + "type": "text", + "content": ", is constructed with animated human groups tailored to multi-person and multi-group research." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 701, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 701, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 701, + 545, + 713 + ], + "type": "text", + "content": "Real Multi-Person Datasets. Real-world datasets [15, 17," + } + ] + } + ], + "index": 23 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "21923" + } + ] + } + ], + "index": 24 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 47, + 69, + 547, + 247 + ], + "blocks": [ + { + "bbox": [ + 47, + 69, + 547, + 247 + ], + "lines": [ + { + "bbox": [ + 47, + 69, + 547, + 247 + ], + "spans": [ + { + "bbox": [ + 47, + 69, + 547, + 247 + ], + "type": "table", + "html": "
DatasetImage TypeAvatar Num.VideoMulti-ViewMulti-PersonMulti-Group2D3DAnnotations Atomic Atn.Group Act.
SURREAL, 2017 [48]Composite145✓✓✓
AGORA, 2021 [40]HDRI350✓✓✓
HSPACE, 2021 [2]3D Scene1600✓✓✓✓✓
GTA-Humans, 2021 [6]3D Scene600✓✓✓✓
PSP-HDRI+, 2022 [20]HDRI28✓✓✓
SynBody, 2023 [53]3D Scene10k✓✓✓✓✓
BEDLAM, 2023 [4]3D Scene271✓✓✓✓
M3Act (Ours)Photometric 3D + HDRI2200✓✓✓✓✓✓✓✓
CAD, 2011 [15]Real-✓✓✓✓✓✓
Volleyball Dataset, 2016 [29]Real-✓✓✓✓✓✓
NTU-RGBD 120, 2019 [33]Real-✓✓✓✓✓✓
HiEve, 2020 [32]Real-✓✓✓✓✓
PoseTrack, 2021 [18]Real-✓✓✓✓
MOT, 2020 [17]Real-✓✓✓✓
DanceTrack, 2022 [45]Real-✓✓✓
JRDB, 2023 [21, 37, 49]Real-✓✓✓✓✓✓
", + "image_path": "e01c388623b2ed026af9bcebacb35dc9a24b0a4d9645a5b9ef526044046c8225.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 249, + 546, + 273 + ], + "lines": [ + { + "bbox": [ + 46, + 249, + 546, + 273 + ], + "spans": [ + { + "bbox": [ + 46, + 249, + 546, + 273 + ], + "type": "text", + "content": "Table 1. A comparison of synthetic datasets as well as commonly-used real datasets for activity understanding and person tracking. We refer to JRDB as a union set of JRDB, JRDB-Act, and JRDB-Pose datasets. Note that it offers 3D bounding boxes, but not poses." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 281, + 289, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 281, + 289, + 581 + ], + "spans": [ + { + "bbox": [ + 46, + 281, + 289, + 581 + ], + "type": "text", + "content": "18, 29, 32, 33, 37, 45] with multiple persons are usually collected for tasks such as group activity understanding, multiperson tracking, and human trajectory prediction. Recognizing and parsing collective human activities [25, 58] rely primarily on multiple modalities (RGB, bounding box, pose) and hierarchical action and activity labels. These fine-grained labels are provided by datasets like CAD [15] and Volleyball Dataset [29]. On the other hand, datasets for person tracking, such as HiEve [32], MOT [17, 38], and DanceTrack [45], require not only 2D annotations (e.g., bounding box) for individual frames, but also the association of the objects between them. Specifically, DanceTrack provides multiple persons in a group with the same clothing, making it difficult for the association of the individuals. MOT datasets target tracking for human crowds and contain mostly outdoor scenes from a bird-eye view. Recently, JRDB [21, 37, 49] with rich annotations is released. The images are captured by a social robot, navigating around daily scenes. It provides fine-grained annotations that support various tasks, including person detection, pose estimation, tracking, collective activity detection, and understanding. M³Act not only offers the same modalities and annotations for supporting the aforementioned tasks, but it also provides full 3D annotations, making it suitable for a wide range of applications beyond the 2D domain." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 588, + 96, + 601 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 588, + 96, + 601 + ], + "spans": [ + { + "bbox": [ + 47, + 588, + 96, + 601 + ], + "type": "text", + "content": "3. " + }, + { + "bbox": [ + 47, + 588, + 96, + 601 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^3\\mathbf{A}\\mathbf{c}\\mathbf{t}" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "content": " is a multi-view multi-group multi-person human atomic action and group activity data generator built with Unity Engine and the Perception [5] library. Inspired by PeopleSansPeople [19] that populates randomly posed human avatars in a scene and renders static images, " + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "content": " not only offers the same functionalities for human poses but also extends it to the spatio-temporal domain. It generates RGB videos for dynamic human motions and produces a rich set of annotations simultaneously, including (a) 2D" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 281, + 547, + 342 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 281, + 547, + 342 + ], + "spans": [ + { + "bbox": [ + 304, + 281, + 547, + 342 + ], + "type": "text", + "content": "and 3D joints/meshes, (b) 2D and 3D bounding boxes for individual persons, (c) atomic action and group activity categories, (d) tracking information such as individual and group IDs, (e) segmentation, depth, and normal images, and (f) scene description." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 349, + 408, + 361 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 349, + 408, + 361 + ], + "spans": [ + { + "bbox": [ + 305, + 349, + 408, + 361 + ], + "type": "text", + "content": "3.1. Data Generation" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 364, + 547, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 364, + 547, + 460 + ], + "spans": [ + { + "bbox": [ + 304, + 364, + 547, + 460 + ], + "type": "text", + "content": "The process of our data generation is illustrated in Fig. 2. First, the generation process is configured by the simulation scenario that manages multiple independent simulations of human activities. Then for each simulation, a 3D scene with background objects, lights, and cameras is set up, and groups of human characters are instantiated to be animated. Lastly, the multi-view RGB image frames are rendered and the annotations are exported at the end of the simulation." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 460, + 547, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 547, + 604 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 547, + 604 + ], + "type": "text", + "content": "Scene Instantiation. We represent the environment through 25 photometric 3D scenes and 104 panoramic HDRIs. Each scene is initiated with randomized lighting and camera configuration. To attain a balance between realistic environmental illumination and pronounced shadow detail, our lighting schema integrates HDRI Sky lighting with a directional light. This directional light is subject to random variations in its direction, color temperature, and intensity. Regarding camera placement, we always point cameras towards the center of avatar groups and introduce variability by randomizing both the field of view and the camera's distance to these groups." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 605, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 548, + 715 + ], + "type": "text", + "content": "Human Models and Motion Assets. M³Act leverages 2000 human models generated by Synthetic Humans [42], ranging across all ages (1 ~ 100), genders, ethnicities (such as Caucasian, Asian, Latin American, African, Middle Eastern), diverse body shapes, hair, and clothing. We also incorporated 200 widely-used human characters from RenderPeople [1]. For the human motions, we collected 384 animation clips from AMASS [36], categorized into 14 atomic action classes. We created a universal animation controller" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "21924" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 70, + 532, + 211 + ], + "blocks": [ + { + "bbox": [ + 51, + 70, + 532, + 211 + ], + "lines": [ + { + "bbox": [ + 51, + 70, + 532, + 211 + ], + "spans": [ + { + "bbox": [ + 51, + 70, + 532, + 211 + ], + "type": "image", + "image_path": "b7ad24563c921b062901e128d44792afbb317fa30af82ffd6505d64c1eebf9f4.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 219, + 546, + 243 + ], + "lines": [ + { + "bbox": [ + 46, + 219, + 546, + 243 + ], + "spans": [ + { + "bbox": [ + 46, + 219, + 546, + 243 + ], + "type": "text", + "content": "Figure 2. The data generation process of " + }, + { + "bbox": [ + 46, + 219, + 546, + 243 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 46, + 219, + 546, + 243 + ], + "type": "text", + "content": ". It consists of multiple data simulations with scene instantiation, group activity authoring, and a data capture module. A high degree of randomization is involved in all aspects of the process to ensure diverse data." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 251, + 288, + 275 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 251, + 288, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 288, + 275 + ], + "type": "text", + "content": "that blends styles, including arm space and stride size, to create diverse motions from the collected clips." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 278, + 288, + 530 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 278, + 288, + 530 + ], + "spans": [ + { + "bbox": [ + 46, + 278, + 288, + 530 + ], + "type": "text", + "content": "Modular Group Activities. Each group activity is structured as a parameterized module, allowing for the customization of numerous variables. These variables include the number of individuals in the group and the specific atomic actions permitted within the group activity. This modularization ensures easy duplication, repositioning, and reuse of the group activities, enabling simulations of multiple groups at the same time. To procedurally animate a group of humans within a modular group, we establish the positions and orientations of the selected characters while choosing the appropriate animation clip for each character through the activity script. It's important to note that, despite drawing characters from the same set of avatars, the configurations and animations of these characters can vary significantly from one group to another. For example, animating a queueing activity may require all characters to be aligned in a straight line, while those in a walking group may form various shapes. The atomic actions that a person can perform also depend on the specific group activity. We carefully consider all these factors when authoring activities and provide a summary in the Sup. Mat." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 534, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 534, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 534, + 287, + 713 + ], + "type": "text", + "content": "Domain Randomization. " + }, + { + "bbox": [ + 46, + 534, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^{3}\\mathrm{Act}" + }, + { + "bbox": [ + 46, + 534, + 287, + 713 + ], + "type": "text", + "content": " provides domain randomization for almost all aspects of the data generation process to ensure the simulation data is highly diverse. These aspects include the number of groups in a scene, the number of persons in each group, the positions of groups, the alignment of persons in a group, the positions of individuals, the textures for the instantiated characters, and the selection of scenes, lighting conditions, camera positions, characters, group activities, atomic actions, and animation clips. Despite the fact that animating group activities inherently limits the degree of freedom in the placement of characters, by altering the shapes in which characters align (e.g., either in a cluster, a straight line, or a curve), " + }, + { + "bbox": [ + 46, + 534, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^{3}\\mathrm{Act}" + }, + { + "bbox": [ + 46, + 534, + 287, + 713 + ], + "type": "text", + "content": " nonetheless generates diverse activities and achieves sufficient randomization for downstream model generalization. More details re" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 305, + 251, + 545, + 274 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 251, + 545, + 274 + ], + "spans": [ + { + "bbox": [ + 305, + 251, + 545, + 274 + ], + "type": "text", + "content": "garding the randomization variables and their distributions are provided in Sup. Mat." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 275, + 546, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 275, + 546, + 407 + ], + "spans": [ + { + "bbox": [ + 304, + 275, + 546, + 407 + ], + "type": "text", + "content": "Rendering and Annotations. " + }, + { + "bbox": [ + 304, + 275, + 546, + 407 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^{3}\\mathrm{Act}" + }, + { + "bbox": [ + 304, + 275, + 546, + 407 + ], + "type": "text", + "content": " utilizes the Unity high-definition render pipeline for the creation of photorealistic RGB images and leverages the Perception library for capturing annotations. On average, data is generated at a rate of 4.2 FPS using one NVIDIA RTX 3070 Ti graphics card, with a resolution of " + }, + { + "bbox": [ + 304, + 275, + 546, + 407 + ], + "type": "inline_equation", + "content": "1920\\times 1080" + }, + { + "bbox": [ + 304, + 275, + 546, + 407 + ], + "type": "text", + "content": ", and all annotations are enabled. Similar to PeopleSansPeople, the 2D skeleton follows COCO [31] format, with additional labelers for exporting 3D joints, meshes, group IDs, and activity classes. After the data generation, the 3D joints and meshes are fitted with SMPL parameters [35, 41]." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 412, + 409, + 423 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 412, + 409, + 423 + ], + "spans": [ + { + "bbox": [ + 306, + 412, + 409, + 423 + ], + "type": "text", + "content": "3.2. Dataset Statistics" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 426, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 545, + 555 + ], + "type": "inline_equation", + "content": "\\mathrm{M}^{3}\\mathrm{Act}" + }, + { + "bbox": [ + 304, + 426, + 545, + 555 + ], + "type": "text", + "content": " comprises 25 photometric 3D scenes, 104 HDRIs, 5 lighting volumes, 2200 human models, 384 animations (categorized into 14 atomic action classes), and 6 group activities. Using the generator, we first generated our synthetic dataset, " + }, + { + "bbox": [ + 304, + 426, + 545, + 555 + ], + "type": "inline_equation", + "content": "\\mathrm{M}^{3}\\mathrm{ActRGB}" + }, + { + "bbox": [ + 304, + 426, + 545, + 555 + ], + "type": "text", + "content": ". It contains 6K simulations of every single-group activity and 9K simulations of multi-group configuration, with 4 camera views. Each simulation produces a 5-second video clip, captured in 20 FPS and FHD resolution. In total, " + }, + { + "bbox": [ + 304, + 426, + 545, + 555 + ], + "type": "inline_equation", + "content": "\\mathrm{M}^{3}\\mathrm{ActRGB}" + }, + { + "bbox": [ + 304, + 426, + 545, + 555 + ], + "type": "text", + "content": " contains 6M RGB images and 48M bounding boxes. The average track length is 4.65 seconds." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": "Additionally, we generated " + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{M}^3\\mathrm{Act3D}" + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": ", a large-scale 3D-only dataset. It consists of more than " + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "inline_equation", + "content": "65\\mathrm{K}" + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": " simulations of single-group activity. Each contains 150 frames of multiperson collective interactions in 30 FPS, resulting in a total duration of 87.6 hours. As shown in Tab. 2, both the group size and the interaction complexity are significantly higher than those in previous multi-person motion datasets. Specifically, when compared with GTA-Combat [44], " + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{M}^3\\mathrm{Act3D}" + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": " contains more persons in a group, has more group activities, and provides a variable number of persons in a group. To the best of our knowledge, " + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{M}^3\\mathrm{Act3D}" + }, + { + "bbox": [ + 304, + 558, + 546, + 713 + ], + "type": "text", + "content": " is the first large-scale 3D dataset for human group activities with large group sizes as well as per-frame individual action labels. See Sup. Mat." + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "21925" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 71, + 288, + 159 + ], + "blocks": [ + { + "bbox": [ + 48, + 71, + 288, + 159 + ], + "lines": [ + { + "bbox": [ + 48, + 71, + 288, + 159 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 288, + 159 + ], + "type": "table", + "html": "
DatasetFPS# of Acty.# of Persons# of Actn.Duration
AvgMax
SBU [55]1582.02-7.6 mins
Duet Dance [30]2552.02-2.3 hrs
CHI3D [22]5082.02-2.7 hrs
NTU RGBD 120 [33]30262.02-15.0 hrs
GTA-Combat [44]1513.25-39.0 hrs
M3Act3D3066.727887.6 hrs
", + "image_path": "a669e3cd7266e444f0c2ce261d07eaf9111612d85baee8c4d960ccff26c98b75.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 206, + 200, + 217 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 206, + 200, + 217 + ], + "spans": [ + { + "bbox": [ + 47, + 206, + 200, + 217 + ], + "type": "text", + "content": "for detailed statistics of both datasets." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 226, + 128, + 239 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 226, + 128, + 239 + ], + "spans": [ + { + "bbox": [ + 47, + 226, + 128, + 239 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "spans": [ + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": "We showcase the practical utilities of " + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 46, + 241, + 287, + 301 + ], + "type": "text", + "content": " through three core experiments: Multi-Person Tracking (MPT), Group Activity Recognition (GAR), and controllable Group Activity Generation (GAG). The experiments are carefully designed to cover the following three perspectives:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 304, + 287, + 436 + ], + "type": "list", + "angle": 0, + "index": 8, + "blocks": [ + { + "bbox": [ + 47, + 304, + 287, + 364 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 304, + 287, + 364 + ], + "spans": [ + { + "bbox": [ + 47, + 304, + 287, + 364 + ], + "type": "text", + "content": "- Multi-modality: Our experiments cover various modalities contained within our dataset, including RGB videos, 2D keypoints, and 3D joints. We leverage the rich annotations including bounding boxes, tracklets, group activities, and person action labels." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 365, + 287, + 400 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 365, + 287, + 400 + ], + "spans": [ + { + "bbox": [ + 47, + 365, + 287, + 400 + ], + "type": "text", + "content": "- Performance: We conduct the ablation study by altering the amount and the type of synthetic data used for training to see its effect on the model performance." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 401, + 287, + 436 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 401, + 287, + 436 + ], + "spans": [ + { + "bbox": [ + 47, + 401, + 287, + 436 + ], + "type": "text", + "content": "- Novel task: We introduce a novel generative task (GAG), showing that synthetic data can not only support existing CV tasks but also create datasets for new research." + } + ] + } + ], + "index": 7 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 446, + 177, + 459 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 446, + 177, + 459 + ], + "spans": [ + { + "bbox": [ + 47, + 446, + 177, + 459 + ], + "type": "text", + "content": "4.1. Multi-Person Tracking" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 460, + 287, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 460, + 287, + 567 + ], + "spans": [ + { + "bbox": [ + 46, + 460, + 287, + 567 + ], + "type": "text", + "content": "The objective of MPT is to predict the trajectories of all persons from a dynamic video stream. Typically, person tracking involves two separate processes, person detection and association. While the tracking task is approached in some prior works with the tracking-by-detection method [3, 7, 50], we consider end-to-end approaches [23, 52, 56, 57] to evaluate the use of synthetic data on the performance of MPT as a whole, in lieu of an improved performance caused only by refined detection." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 569, + 287, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 569, + 287, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 569, + 287, + 616 + ], + "type": "text", + "content": "Real-world Dataset: DanceTrack [45] (DT) is a challenging MPT dataset characterized by dynamic movements with human subjects in uniform appearances. It has a total of 100 videos with over 105K frames." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "content": "Synthetic Dataset. Given the motion categories in the real-world dataset, we select a subset of " + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^3" + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "content": " ActRGB with groups of people dancing, walking, and running. We use 1000 video clips with a single \"dance\" group as well as 1500 videos with a \"walk\" group and a \"run\" group simulated at the same time (denoted as WalkRun). We alter the use of the synthetic group activities (Dance, WalkRun, and Dance+WalkRun) in our experiments." + } + ] + } + ], + "index": 12 + }, + { + "type": "table", + "bbox": [ + 307, + 70, + 545, + 178 + ], + "blocks": [ + { + "bbox": [ + 46, + 163, + 287, + 196 + ], + "lines": [ + { + "bbox": [ + 46, + 163, + 287, + 196 + ], + "spans": [ + { + "bbox": [ + 46, + 163, + 287, + 196 + ], + "type": "text", + "content": "Table 2. A comparison of datasets for 3D multi-person human activities. " + }, + { + "bbox": [ + 46, + 163, + 287, + 196 + ], + "type": "inline_equation", + "content": "\\mathbb{M}^3\\mathbb{A}\\mathbb{ct}\\mathbb{3}\\mathbb{D}" + }, + { + "bbox": [ + 46, + 163, + 287, + 196 + ], + "type": "text", + "content": " is the largest dataset with labels for atomic actions and more persons in a group." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 307, + 70, + 545, + 178 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 545, + 178 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 545, + 178 + ], + "type": "table", + "html": "
Training DataHOTA↑DetA↑AssA↑IDF1↑MOTA↑
DT®69.883.058.971.689.3
DT68.8 (10)82.557.470.390.8
DT + Syn (D)59.075.546.159.082.6
DT + Syn (WR)70.183.159.472.592.0
DT + Syn (WR+D)71.9 (2)83.662.074.792.6
DT + Syn† (WR+D)72.283.462.675.592.7
DT (MOTRv2*)73.483.764.476.092.1
DT + BEDLAM [4]55.968.744.553.879.1
DT + GTA-Humans [6]54.166.844.252.178.8
", + "image_path": "bbe30ec9114c8069426fe01b3305b2bbd39593a17188a9cf7a5de8b593de0acf.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "table_body" + } + ], + "index": 13 + }, + { + "type": "table", + "bbox": [ + 309, + 258, + 543, + 384 + ], + "blocks": [ + { + "bbox": [ + 305, + 182, + 545, + 248 + ], + "lines": [ + { + "bbox": [ + 305, + 182, + 545, + 248 + ], + "spans": [ + { + "bbox": [ + 305, + 182, + 545, + 248 + ], + "type": "text", + "content": "Table 3. MPT results on DanceTrack with MOTRv2. \"D\" means synthetic dance group. \"WR\" means walk and run groups. \"WR+D\" refers to \"D\" and \"WR\" combined. The symbol " + }, + { + "bbox": [ + 305, + 182, + 545, + 248 + ], + "type": "inline_equation", + "content": "\\text{串}" + }, + { + "bbox": [ + 305, + 182, + 545, + 248 + ], + "type": "text", + "content": " represents the author-provided checkpoint. The symbol " + }, + { + "bbox": [ + 305, + 182, + 545, + 248 + ], + "type": "inline_equation", + "content": "\\dagger" + }, + { + "bbox": [ + 305, + 182, + 545, + 248 + ], + "type": "text", + "content": " marks the same model with additional association at inference. Numbers in parentheses represent the rank in the DanceTrack leaderboard." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 258, + 543, + 384 + ], + "lines": [ + { + "bbox": [ + 309, + 258, + 543, + 384 + ], + "spans": [ + { + "bbox": [ + 309, + 258, + 543, + 384 + ], + "type": "table", + "html": "
ModelSyn. DataHOTADetAAssAIDF1MOTA
MOTR [56]✓54.273.540.251.579.7
60.076.448.156.083.8
MeMOTR [23]✓68.580.558.471.289.9
71.181.862.374.192.2
CO-MOT [52]✓69.482.158.971.991.2
72.583.663.375.992.8
MOTRv2 [57]✓68.882.557.470.390.8
71.983.662.074.792.6
MOTRv2* [57]✓73.483.764.476.092.1
74.684.164.976.493.1
", + "image_path": "409e16e2d31a2c16d761a1746e0b8742177d27918adfc000a508c79e0b7bf48f.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "table_body" + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 388, + 545, + 411 + ], + "lines": [ + { + "bbox": [ + 305, + 388, + 545, + 411 + ], + "spans": [ + { + "bbox": [ + 305, + 388, + 545, + 411 + ], + "type": "text", + "content": "Table 4. MPT results on DanceTrack using different methods trained with our synthetic data." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "text", + "content": "Results. We mix together both synthetic and real data during training and present the results in Tab. 3. First, adding our synthetic data yields significant improvement in all 5 tracking metrics as well as a hop in ranking on HOTA from " + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "inline_equation", + "content": "10^{th}" + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "inline_equation", + "content": "2^{nd}" + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "text", + "content": " place. The model trained with our synthetic data plus the extra association, marked as " + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\mathrm{DT} + \\mathrm{Syn}^{\\dagger}" + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "text", + "content": " (WR+D), achieves similar performance to MOTRv2*, the same model that is trained with additional validation data with an ensemble of 4 models [57]. This suggests that the synthetic data used in our experiment is equivalent to at least " + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "inline_equation", + "content": "62.5\\%" + }, + { + "bbox": [ + 304, + 426, + 545, + 715 + ], + "type": "text", + "content": " more real data. Second, Compared with other synthetic data sources, such as BEDLAM and GTA-Humans, M³Act demonstrates superior performance, indicating its better suitability for multi-person dynamic conditions. Third, we observe that the type of synthetic groups affects the model performance on real data. Adding the \"WalkRun\" groups to the training data is more effective than adding the \"Dance\" group. This is because while the DanceTrack dataset contains dynamic dance movements, the real challenge lies in detection and tracking when the subjects switch positions. By design, the positions of the characters in our dance group are well-staged and the movements are nearly synchronous. (See Sup. Mat. for the design.) Contrarily, having a walk and a run group together" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "21926" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 71, + 291, + 235 + ], + "blocks": [ + { + "bbox": [ + 48, + 71, + 291, + 235 + ], + "lines": [ + { + "bbox": [ + 48, + 71, + 291, + 235 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 291, + 235 + ], + "type": "table", + "html": "
ModelPretrained \nSyn. DataGroup ActivityPerson Action
Top 1 Acc (%) ↑Top 1 Acc (%) ↑
Composer \n[58]N/A84.87±2.3(88.20)81.31±2.4(83.13)
10%86.12±1.8(87.87)84.16±1.8(86.03)
25%87.65±1.2(89.01)86.36±1.3(86.81)
50%89.39±0.4(90.14)86.68±1.5(87.99)
100%89.74±1.0(91.51)88.74±1.7(89.05)
Gains+4.87 (+3.31)+7.43 (+5.92)
Actor \nTransformer \n[25]N/A78.08±1.0(79.47)76.22±2.2(78.07)
10%77.59±2.4(81.00)76.01±3.2(79.76)
25%81.36±2.1(83.19)78.86±2.4(80.05)
50%82.72±1.3(84.56)79.95±1.6(81.47)
100%83.67±1.2(84.88)81.65±1.2(82.22)
Gains+5.59 (+5.41)+5.43 (+4.15)
", + "image_path": "517ad54b79d6ae0224d11c9a7c85bb5c0f0c794de1c7de4fbbecddbc97790e37.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 46, + 239, + 287, + 305 + ], + "lines": [ + { + "bbox": [ + 46, + 239, + 287, + 305 + ], + "spans": [ + { + "bbox": [ + 46, + 239, + 287, + 305 + ], + "type": "text", + "content": "Table 5. Results of 2D keypoint-based group activity and person action recognition on CAD2 dataset. The best results are shown in parentheses. The results suggest that pre-training with our synthetic data largely increases the accuracy for both group activity and person actions. Note that group accuracy saturates at " + }, + { + "bbox": [ + 46, + 239, + 287, + 305 + ], + "type": "inline_equation", + "content": "93.4\\%" + }, + { + "bbox": [ + 46, + 239, + 287, + 305 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 239, + 287, + 305 + ], + "type": "inline_equation", + "content": "86.2\\%" + }, + { + "bbox": [ + 46, + 239, + 287, + 305 + ], + "type": "text", + "content": " forComposer and Actor Transformer respectively." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 318, + 287, + 377 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 318, + 287, + 377 + ], + "spans": [ + { + "bbox": [ + 46, + 318, + 287, + 377 + ], + "type": "text", + "content": "in a scene leads to frequent position switches relative to the camera view and thus improves the model performance. Lastly, Tab. 4 presents the tracking results using different methods. Results indicate that our synthetic data is effective across various models." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 386, + 200, + 399 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 386, + 200, + 399 + ], + "spans": [ + { + "bbox": [ + 47, + 386, + 200, + 399 + ], + "type": "text", + "content": "4.2. Group Activity Recognition" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 400, + 287, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 400, + 287, + 483 + ], + "spans": [ + { + "bbox": [ + 46, + 400, + 287, + 483 + ], + "type": "text", + "content": "The goal of GAR is to determine the class of the group activity performed by the dominant group as well as the action class of each person. We consider Composer [58] and Actor Transformer [25] as the benchmark models. The former is a multi-scale transformer-based model and accepts only 2D keypoints as input. The latter can take combinations of multiple input modalities." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 484, + 287, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 484, + 287, + 556 + ], + "spans": [ + { + "bbox": [ + 46, + 484, + 287, + 556 + ], + "type": "text", + "content": "Real-world Dataset: CAD2 [15] and Volleyball Dataset [29]. CAD2 is an extended version of the Collective Activity Dataset [14] that records human group activities and is widely used for GAR benchmarks [51]. Volleyball Dataset (VD) is an action recognition dataset. It has 55 videos with 9 player action labels and 8 team activity labels." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 557, + 287, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 557, + 287, + 617 + ], + "spans": [ + { + "bbox": [ + 46, + 557, + 287, + 617 + ], + "type": "text", + "content": "Synthetic Dataset. We use a subset of all single-group data from M³ActRGB. It contains a total of 10K videos and over 600K frames. It contains all group activity and individual action classes that CAD2 provides and further includes 7 more action types." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": "Results. We experimentally study how the size of our pretraining synthetic dataset and the capacity of a GAR model affect generalization from the synthetic to real domains. We first train the models on different amounts of synthetic data. Then we fine-tune them on CAD2 and report the top 1 accuracy of both group activity and person action recognition on the test set of CAD2. Tab. 5 presents the results using only 2D keypoints as input. We see a common trend for" + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 307, + 71, + 553, + 148 + ], + "blocks": [ + { + "bbox": [ + 307, + 71, + 553, + 148 + ], + "lines": [ + { + "bbox": [ + 307, + 71, + 553, + 148 + ], + "spans": [ + { + "bbox": [ + 307, + 71, + 553, + 148 + ], + "type": "table", + "html": "
Model2D RGB FlowCAD2 Syn+CAD2VD Syn+VD
Composer✓88.291.594.695.1
Actor Transformer✓79.584.992.393.7
✓78.280.791.492.5
✓✓81.085.293.594.3
✓81.385.094.495.0
✓79.581.993.094.1
", + "image_path": "11b5bcef8ffc1f8f649c5220323ec3e10e6447534a3ff5ad499332cc34a29220.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 305, + 152, + 545, + 175 + ], + "lines": [ + { + "bbox": [ + 305, + 152, + 545, + 175 + ], + "spans": [ + { + "bbox": [ + 305, + 152, + 545, + 175 + ], + "type": "text", + "content": "Table 6. The group activity recognition accuracy on CAD2 and Volleyball Dataset using different input modalities." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "spans": [ + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "text", + "content": "both GAR models that the recognition accuracy increases as more synthetic data is used for pre-training. With " + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "inline_equation", + "content": "100\\%" + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "text", + "content": " of synthetic data, the accuracy of Composer increases, with an average of " + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "inline_equation", + "content": "4.87\\%" + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "text", + "content": " at the group level and " + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "inline_equation", + "content": "7.43\\%" + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "text", + "content": " at the person level, whereas Actor Transformer sees a " + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "inline_equation", + "content": "5.59\\%" + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "text", + "content": " increase at group level and " + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "inline_equation", + "content": "5.43\\%" + }, + { + "bbox": [ + 304, + 188, + 547, + 319 + ], + "type": "text", + "content": " increase at person level. Moreover, Tab. 6 shows the group recognition accuracy using different input modalities on CAD2 and VD. The performance gains in the experiment indicate that our synthetic data can effectively benefit the downstream GAR task across different methods, input modalities, and datasets." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 326, + 533, + 338 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 326, + 533, + 338 + ], + "spans": [ + { + "bbox": [ + 305, + 326, + 533, + 338 + ], + "type": "text", + "content": "4.3. Controllable 3D Group Activity Generation" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 340, + 545, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 340, + 545, + 460 + ], + "spans": [ + { + "bbox": [ + 304, + 340, + 545, + 460 + ], + "type": "text", + "content": "While the procedural generation of our group activities in " + }, + { + "bbox": [ + 304, + 340, + 545, + 460 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^{3}\\mathrm{Act}" + }, + { + "bbox": [ + 304, + 340, + 545, + 460 + ], + "type": "text", + "content": " yields realistic and diverse human activities, the implementation requires considerable effort and involves the design and application of specific heuristics. Learning a generative model for human group activities, instead, encodes the heuristics to the architecture inherently and encompasses the capabilities of probabilistically generating diverse activities, with control over the entire group of human motions from various signals. To this end, we introduce controllable 3D group activity generation (GAG)." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "content": "Definition. Let " + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "inline_equation", + "content": "G_{t}^{p} = \\{m_{i}^{n}\\}_{i = 1\\sim t,n = 1\\sim p}" + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "content": " be a group of human motions with " + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "content": " frames and " + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "content": " persons. The individual pose is denoted as " + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "inline_equation", + "content": "m_i^n\\in R^{j\\times d}" + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "content": " is the number of joints in the skeleton and " + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "content": " is the joint dimension. The goal of GAG is to synthesize a group of 3D human motions " + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "inline_equation", + "content": "G_{t}^{p}" + }, + { + "bbox": [ + 304, + 460, + 546, + 616 + ], + "type": "text", + "content": " from Gaussian noise, given an activity label and an arbitrary group size as input conditions. It requires a model capable of learning the temporal and spatial motion dependencies among persons within the same group and generating human motions with any group size simultaneously. GAG is related to dyadic motion generation [10, 16] and partner-conditioned reaction generation [43], but involves the motion interactions of more than two persons." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "text", + "content": "Baselines. Although previous works [16, 43, 44] can generate motions for multiple persons, they are limited to dyadic scenarios or groups with a fixed number of persons. Therefore, we present two baselines. The first one is the vanilla motion diffusion model, MDM [47]. It was proposed for probabilistic single-person motion generation from an input condition. We adopt their action-to-motion architecture for conditional synthesis and train the model on " + }, + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{M}^3\\mathrm{Act3D}" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "21927" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 70, + 265, + 223 + ], + "blocks": [ + { + "bbox": [ + 51, + 70, + 265, + 223 + ], + "lines": [ + { + "bbox": [ + 51, + 70, + 265, + 223 + ], + "spans": [ + { + "bbox": [ + 51, + 70, + 265, + 223 + ], + "type": "image", + "image_path": "e7d4e10d8f71f892c9781b70078de8e19b2fdf28148afa651eb2715ae04051ab.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 228, + 287, + 262 + ], + "lines": [ + { + "bbox": [ + 46, + 228, + 287, + 262 + ], + "spans": [ + { + "bbox": [ + 46, + 228, + 287, + 262 + ], + "type": "text", + "content": "Figure 3. The qualitative comparison of two group activities from ground truth (GT), MDM, and MDM+IFormer. The distribution of the persons from MDM+IFormer is closer to GT." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 274, + 287, + 417 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 274, + 287, + 417 + ], + "spans": [ + { + "bbox": [ + 46, + 274, + 287, + 417 + ], + "type": "text", + "content": "for generating an individual person's motion from an input group activity class label. In order to generate a group of human motions from a given group size, we repeat the single-person inference several times. In other words, the individual motions are generated independently by MDM. Our second baseline, " + }, + { + "bbox": [ + 46, + 274, + 287, + 417 + ], + "type": "inline_equation", + "content": "\\mathbf{MDM} + \\mathbf{IFormer}" + }, + { + "bbox": [ + 46, + 274, + 287, + 417 + ], + "type": "text", + "content": " is extended from MDM and includes an additional interaction transformer (IFormer) that works along the dimension of the persons. The interaction transformer encourages the model to learn the interperson motion dependencies. At inference, MDM+IFormer is capable of producing coordinated group activities in one forward pass, due to its modeling of human interactions." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "spans": [ + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "text", + "content": "Implementation. We utilize a common skeleton for all individual persons with 25 joints. We process the data so each motion is represented as both the 6D joint rotations [59] and the root positions. The final representation of a collective group activity with multiple persons is a tensor with shape (#persons " + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "inline_equation", + "content": "\\times" + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "text", + "content": " #frames " + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "inline_equation", + "content": "\\times" + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "text", + "content": " 26 " + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "inline_equation", + "content": "\\times" + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "text", + "content": " 6). For a fair comparison, both baseline models were trained on an NVIDIA RTX 3090 graphics card with " + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "text", + "content": " data from M³Act3D for 320K iterations and then tested on the other " + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 46, + 418, + 287, + 525 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 530, + 127, + 540 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 530, + 127, + 540 + ], + "spans": [ + { + "bbox": [ + 47, + 530, + 127, + 540 + ], + "type": "text", + "content": "4.3.1 Evaluation" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 544, + 286, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 286, + 700 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 286, + 700 + ], + "type": "text", + "content": "Metrics. Due to the probabilistic nature of the task, we consider the following learning-based metrics, recognition accuracy, Frechet Inception Distance (FID), diversity, and multimodality, defined in [26]. These metrics, however, were originally designed for single-person motion generation. To evaluate the generated group activities, we report them at both group and person levels because they account for the fidelity and variations for the groups and the individuals. We train a multi-scale group activity recognition model using theComposer [58] architecture for the metrics. See Sup. Mat. for detailed explanations of how to construct the learning-based metrics, including the recognition model as well as the latent representations at both levels." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 59, + 701, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 701, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 701, + 286, + 712 + ], + "type": "text", + "content": "In addition to the learning-based metrics, we tailor four" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 143 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 143 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 143 + ], + "type": "text", + "content": "position-based metrics, collision frequency, repulsive interaction force, contact repulsive force, and total repulsive force, to the evaluation of human groups. The latter three are based on the social force model [27, 28], which explains crowd behaviors using socio-psychological and physical forces. Here we describe the four metrics:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 144, + 545, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 144, + 545, + 228 + ], + "spans": [ + { + "bbox": [ + 304, + 144, + 545, + 228 + ], + "type": "text", + "content": "Collision frequency indicates how often a collision (or an invalid interaction) would occur within a group. The collision count is calculated based on a distance threshold between any two persons in a group. It is then normalized by the total number of interactions to obtain the frequency. In other words, if " + }, + { + "bbox": [ + 304, + 144, + 545, + 228 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 144, + 545, + 228 + ], + "type": "text", + "content": " persons are in a group, the normalization denominator is " + }, + { + "bbox": [ + 304, + 144, + 545, + 228 + ], + "type": "inline_equation", + "content": "N \\cdot (N - 1) / 2" + }, + { + "bbox": [ + 304, + 144, + 545, + 228 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 228, + 545, + 276 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 228, + 545, + 276 + ], + "spans": [ + { + "bbox": [ + 304, + 228, + 545, + 276 + ], + "type": "text", + "content": "Repulsive interaction force describes the psychological tendency of two persons to stay away from each other. As the distance between two persons decreases, the repulsive force increases exponentially." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "spans": [ + { + "bbox": [ + 304, + 277, + 545, + 324 + ], + "type": "text", + "content": "Contact repulsive force represents the compression body force when two persons collide with each other. The contact force is nonzero only when two persons collide. A larger contact force means the interaction is less likely to occur." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 325, + 545, + 347 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 325, + 545, + 347 + ], + "spans": [ + { + "bbox": [ + 304, + 325, + 545, + 347 + ], + "type": "text", + "content": "Total repulsive force is the accumulation of interaction and contact forces." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 348, + 545, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 348, + 545, + 563 + ], + "spans": [ + { + "bbox": [ + 304, + 348, + 545, + 563 + ], + "type": "text", + "content": "All four position-based metrics are calculated using the Euclidean distances of the persons' positions, with the shoulder width as the collision threshold. The social forces are calculated by averaging the magnitude of each individual's force accumulated through all its interactions with other persons. A well-performing model should generate group activities with low collision frequency and similar social force values to the ground truth. For the evaluation, we generated 500 samples for each group activity using the two well-trained baseline models. Each generated sequence contains 60 frames. We use the test split as the ground truth and randomly extract the group activity of the same length for evaluation. To ensure the distributions of group sizes are similar to the ground truth, we calculate the minimum and maximum group sizes from the training split and uniformly sample a group size from that range to generate group activities. Please refer to Sup. Mat. for more details regarding the baseline architectures, metrics formulas, and evaluation." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 568, + 370, + 578 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 568, + 370, + 578 + ], + "spans": [ + { + "bbox": [ + 306, + 568, + 370, + 578 + ], + "type": "text", + "content": "4.3.2 Results" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "MDM+IFormer is capable of generating group activities with well-aligned character positions. As shown in Fig. 3, MDM generates human groups that are poorly positioned. For example, the persons in a walking group do not walk in the same direction and the persons are poorly placed in a queueing group. This is because MDM generates the group activities by inferring the individual motions independently. The placement of the individuals simply follows the probabilistic distribution of all persons' positions in the dataset. On the other hand, MDM+IFormer successfully learns the probabilistic distribution for the entire group due to its in" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "21928" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 70, + 545, + 129 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 545, + 129 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 545, + 129 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 545, + 129 + ], + "type": "table", + "html": "
Group LevelPerson Level
Acc ↑FID ↓Diversity →Multimodality →FID ↓Diversity →Multimodality →
GT99.9370.001 ± 0.00017.752 ± 0.0253.491 ± 0.0120.001 ± 0.00014.506 ± 0.0137.546 ± 0.010
MDM97.3673.909 ± 0.01917.683 ± 0.0374.155 ± 0.0194.434 ± 0.01014.158 ± 0.0357.588 ± 0.013
MDM+IFormer98.1003.242 ± 0.01617.855 ± 0.0404.198 ± 0.0213.066 ± 0.00714.827 ± 0.0316.945 ± 0.011
", + "image_path": "b80256e1f716ae407588e6ece19232161ac070714cb3b58085fa64c4d1c753a0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 50, + 162, + 285, + 218 + ], + "blocks": [ + { + "bbox": [ + 47, + 133, + 546, + 156 + ], + "lines": [ + { + "bbox": [ + 47, + 133, + 546, + 156 + ], + "spans": [ + { + "bbox": [ + 47, + 133, + 546, + 156 + ], + "type": "text", + "content": "Table 7. The results of the generated group activities with the learning-based metrics at both levels. An up arrow means the result is better when the metric score is higher. A right arrow means the metric score should be close to ground truth (GT)." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 162, + 285, + 218 + ], + "lines": [ + { + "bbox": [ + 50, + 162, + 285, + 218 + ], + "spans": [ + { + "bbox": [ + 50, + 162, + 285, + 218 + ], + "type": "table", + "html": "
Collision Freq. ↓Interaction Force →Contact Force →Total Force →
GT0.03765.7946.55112.33
MDM3.6437,121.503,822.4710,903.57
MDM+IFormer1.1571,796.251,373.403167.80
", + "image_path": "1b5c7d64f50eaf4a15f9ad92d5dc5854a150cf1c6803c211103361a328dfd0a1.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 221, + 287, + 266 + ], + "lines": [ + { + "bbox": [ + 47, + 221, + 287, + 266 + ], + "spans": [ + { + "bbox": [ + 47, + 221, + 287, + 266 + ], + "type": "text", + "content": "Table 8. Results of the generated human activities with position-based metrics. The collision frequency is calculated on a 60-frame group activity and normalized by the total number of interactions in a group." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 277, + 287, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 277, + 287, + 300 + ], + "spans": [ + { + "bbox": [ + 46, + 277, + 287, + 300 + ], + "type": "text", + "content": "teraction transformer. The persons are better aligned in a group and they have coordinated motions." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 301, + 287, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 301, + 287, + 456 + ], + "spans": [ + { + "bbox": [ + 46, + 301, + 287, + 456 + ], + "type": "text", + "content": "Both baselines are capable of generating diverse activities that match the input condition, but MDM+IFformer obtains better FID scores. Tab. 7 shows the results for the learning-based metrics. When compared with ground truth, both baselines obtain similar scores on recognition accuracy, diversity, and multimodality at both levels. The results indicate that both models successfully learn to generate distinguishable individual motions and group activities. The generated motions are also as diverse as the ground truth. The observations align with the results on action-to-motion generation in MDM [47]. MDM+IFformer receives a lower FID score than MDM, suggesting that MDM+IFformer generates group activities with higher quality." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 456, + 287, + 600 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 456, + 287, + 600 + ], + "spans": [ + { + "bbox": [ + 46, + 456, + 287, + 600 + ], + "type": "text", + "content": "The interaction transformer in MDM+IFormer greatly lowers the collision frequency within the generated group activities. As shown in Tab. 8, the collision frequency of the group activities generated by MDM+IFormer is much lower than the vanilla MDM. It suggests that the interaction transformer better learns the inter-person dependencies and generates more valid person interactions. In fact, we observe that the group activities generated by the vanilla MDM sometimes contain overlapping person positions. The high collision frequency of the MDM baseline also affects the repulsive forces, which makes social forces within the group activities of MDM implausible." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 602, + 200, + 615 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 602, + 200, + 615 + ], + "spans": [ + { + "bbox": [ + 47, + 602, + 200, + 615 + ], + "type": "text", + "content": "5. Discussion and Conclusion" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "content": "We show the merit of " + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^3\\mathsf{Act}" + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "text", + "content": " by conducting three core experiments with multiple modalities and enhanced performances, as well as introducing a novel generative task. In both MPT and GAR experiments, we observe positive correlations between the volume of synthetic data used for training and model performance, indicating an improved model generalizability to unseen test cases with more synthetic data. Moreover, our comparison between " + }, + { + "bbox": [ + 46, + 617, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{DT + Syn}^{\\dagger}" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 164, + 545, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 164, + 545, + 415 + ], + "spans": [ + { + "bbox": [ + 304, + 164, + 545, + 415 + ], + "type": "text", + "content": "and MOTRv2* reveals that synthetic data can replace certain real-world data from the target domain without sacrificing performance [13]. Essentially, our synthetic data reduces the need for extensive real data during training, thereby effectively lowering the costs associated with data collection and annotation. This discovery represents a promising step towards achieving few-shot and potentially zero-shot sim2real transfer. In our 3D Group Activity Generation experiment, we observe that MDM+IFormer, despite being a baseline for the novel task, learns to embed the heuristics for person interactions and produces well-aligned groups given the controls. It's important to highlight that the generative approach, though currently underperforms the procedural method (GT), demonstrates the unique potential of controlling the group motions directly from various signals, including activity class, group size, trajectory, density, speed, and text inputs. With the anticipation of more data availability and increased model capacity for generative models in the future, we expect the generative method to eventually prevail, leading to broader applications for social interactions and human collective activities." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 416, + 545, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 416, + 545, + 548 + ], + "spans": [ + { + "bbox": [ + 304, + 416, + 545, + 548 + ], + "type": "text", + "content": "While the complexity of group behaviors in our dataset may be constrained by the heuristics used for activity authoring, " + }, + { + "bbox": [ + 304, + 416, + 545, + 548 + ], + "type": "inline_equation", + "content": "\\mathsf{M}^{3}\\mathsf{A}\\mathsf{ct}" + }, + { + "bbox": [ + 304, + 416, + 545, + 548 + ], + "type": "text", + "content": " offers notable flexibility for incorporating new group dynamics tailored to any specific downstream tasks. These new groups could be derived from expert-guided heuristics, rules generated by large language models, or outputs from our 3D GAG model. Furthermore, we recognize the existing domain gaps between synthetic and real-world data. With more assets included in our data generator in future iterations, we can enhance model generalizability and alleviate the disparities." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 554, + 416, + 567 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 554, + 416, + 567 + ], + "spans": [ + { + "bbox": [ + 306, + 554, + 416, + 567 + ], + "type": "text", + "content": "6. Acknowledgement" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 569, + 545, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 569, + 545, + 664 + ], + "spans": [ + { + "bbox": [ + 304, + 569, + 545, + 664 + ], + "type": "text", + "content": "The research was supported in part by NSF awards: IIS-1703883, IIS-1955404, IIS-1955365, RETTL-2119265, and EAGER-2122119. This work was also partially supported by the Center for Smart Streetscapes, an NSF Engineering Research Center, under cooperative agreement EEC-2133516. This material is based upon work supported by the U.S. Department of Homeland Security1 under Grant Award Number 22STESE00001 01 01." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 304, + 673, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 673, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 673, + 545, + 713 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 304, + 673, + 545, + 713 + ], + "type": "text", + "content": "Disclaimer. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "21929" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 713 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 286, + 112 + ], + "type": "text", + "content": "[1] Renderpeople. https://renderpeople.com/, 2023. 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Learning Diverse 3D Animals from the Internet. Our method, 3D-Fauna, learns a pan-category deformable 3D model of more than 100 different animal species using only 2D Internet images as training data. At test time, the model can turn a single image of an quadruped instance into an articulated, textured 3D mesh in a feed-forward manner, ready for animation and rendering." + ], + "image_footnote": [], + "bbox": [ + 81, + 268, + 888, + 415 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 479, + 313, + 494 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Learning 3D models of all animals in nature requires massively scaling up existing solutions. With this ultimate goal in mind, we develop 3D-Fauna, an approach that learns a pan-category deformable 3D animal model for more than 100 animal species jointly. One crucial bottleneck of modeling animals is the limited availability of training data, which we overcome by learning our model from 2D Internet images. We show that prior approaches, which are category-specific, fail to generalize to rare species with limited training images. We address this challenge by introducing the Semantic Bank of Skinned Models (SBSM), which automatically discovers a small set of base animal shapes by combining geometric inductive priors with semantic knowledge implicitly captured by an off-the-shelf self-supervised feature extractor. To train such a model, we also contribute a new large-scale dataset of diverse animal species. At inference time, given a single image of any quadruped animal, our model reconstructs an articulated 3D mesh in a feed-forward manner in seconds.", + "bbox": [ + 75, + 510, + 473, + 797 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 811, + 209, + 827 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Computer vision models can nowadays reconstruct humans in monocular images and videos robustly and accurately, re", + "bbox": [ + 75, + 837, + 468, + 867 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "covering their 3D shape, articulated pose, and even appearance [3, 11, 12, 14, 21, 34]. However, humans are but a tiny fraction of the animals that exist in nature, and 3D models remain essentially blind to the vast majority of biodiversity.", + "bbox": [ + 500, + 479, + 890, + 542 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "While in principle the same approaches that work for humans could work for many other animal species, in practice scaling it to each of the 2.1 million different animal species on Earth is nearly hopeless. In fact, building a human model such as SMPL [34] and a corresponding pose predictor [3, 14] requires collecting 3D scans of many people in laboratory [21], crafting a corresponding articulated deformable model semi-automatically, and collecting extensive manual labels to train corresponding pose regressors. Of all animals, only humans are currently of sufficient importance in applications to justify the costs.", + "bbox": [ + 496, + 544, + 892, + 712 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "A technically harder but much more practical approach is to learn animal models automatically from images and videos readily available on the Internet. Several authors have demonstrated that at least rough models can be learned from such uncontrolled image collections [22, 60, 70]. Even so, many limitations remain, starting from the fact that these methods can only reconstruct one or a few specific animal exemplars [70], or at most a single class of animals at a given time [22, 60]. The latter restriction is particularly glaring, as it defeats the purpose of using the Internet as a vast data source for modeling biodiversity.", + "bbox": [ + 496, + 715, + 893, + 882 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We introduce 3D-Fauna, a method that learns a pan", + "bbox": [ + 519, + 885, + 890, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal contribution", + "bbox": [ + 94, + 875, + 202, + 886 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "Equal advising", + "bbox": [ + 96, + 887, + 183, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "9752", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "category deformable model for a large number ( $>100$ ) of different quadruped animal species, such as dogs, antelopes, and hedgehogs, as shown in Fig. 1. For the approach to be as automated and thus as scalable as possible, we assume that only Internet images of the animals are provided as training data and only consider as prerequisites a pre-trained 2D object segmentation model and off-the-shelf unsupervised visual features. 3D-Fauna is designed as a feed-forward network that deforms and poses the deformable model to reconstruct any animal given a single image as input. The ability to perform monocular reconstruction is necessary for training on (single-view) Internet images, and is also useful in many real-world applications.", + "bbox": [ + 75, + 90, + 472, + 287 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Crucial to 3D-Fauna is to learn a single joint model of all animals in one go. Despite posing a challenge, modeling many animals jointly is essential for reconstructing rarer species, for which we often have only a small number of images to train on. This allows us to exploit the structural similarity of different animals that results from evolution, and maximize statistical efficiency. Here, we focus our attention on animals that share a given body plan, in particular, quadrupeds, and share the structure of the underlying skeletal model, which would otherwise be difficult to pin down.", + "bbox": [ + 75, + 289, + 472, + 441 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Learning such a model from only unlabeled single-view images requires several technical innovations. The most important is to develop a 3D representation that is sufficiently expressive to model the diverse shape variations of the animals, and at the same time tight enough to be learned from single-view images without overfitting individual views. Prior work partly achieved this goal by using skinned models, which consider small shape variations around a base template followed by articulation [60]. We found that this approach does not provide sufficient inductive biases to learn diverse animal species from Internet images alone. Hence, we introduce the Semantic Bank of Skinned Models (SBSM), which uses off-the-shelf unsupervised features, such as DINO [5, 39], to hypothesize how different animals may relate semantically, and automatically learns a low-dimensional base shape bank.", + "bbox": [ + 75, + 443, + 472, + 685 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Lastly, Internet images, which are not captured with the purpose of 3D reconstruction in mind, are characterized by a strong photographer bias, skewing the viewpoint distribution to mostly frontal, which significantly hinders the stability of 3D shape learning. To mitigate this issue, 3D-Fauna further encourages the predicted shapes to look realistic from all viewpoints, by introducing an efficient mask discriminator that enforces the silhouettes rendered from a random viewpoint to stay within the distribution of the silhouettes of the real images.", + "bbox": [ + 75, + 686, + 472, + 838 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Combining these ideas, 3D-Fauna is an end-to-end framework that learns a pan-category model of 3D quadruped animals from online image collections. To train 3D-Fauna, we collected a large-scale animal dataset of over", + "bbox": [ + 76, + 839, + 470, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "100 quadruped species, dubbed the Fauna Dataset, as part of the contribution. After training, the model can turn a single test image of any quadruped instance into a fully articulated 3D mesh in a feed-forward fashion, ready for animation and rendering. Extensive quantitative and qualitative comparisons demonstrate significant improvements over existing methods. Code and data will be released.", + "bbox": [ + 496, + 90, + 893, + 198 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 215, + 640, + 231 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Optimization-Based 3D Reconstruction of Animals. Due to the lack of explicit 3D data for the vast majority of animals, reconstruction has mostly relied on pre-defined shape models or multi-view images. Initially, efforts focus on fitting a parametric 3D shape model obtained from 3D scans, e.g., SMAL [74], to animal images using annotated 2D keypoints and segmentation masks, which is further extended to multi-view images [75]. Other works aim to optimize the 3D shape [6, 55, 65–67, 70–72] directly from image or video collections of a smaller scale using various forms of supervision in addition to masks, such as keypoints [6, 55], self-supervised semantic correspondences [70–72], optical flow [64–67], surface normals [67], category-specific template shapes [6, 55].", + "bbox": [ + 496, + 241, + 893, + 455 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Learning 3D from Internet Images and Videos. Recently, authors have attempted to learn 3D priors from Internet images and videos at a larger scale [1, 13, 20, 22, 28, 29, 52, 57-60, 73], mostly focusing on a single category at a time. Reconstructing animals presents additional challenges due to their highly deformable nature, which often necessitates stronger supervisory signals for training, similar to the ones used in optimization-based methods. Some methods have, in particular, learned to model articulated animals, such as horses, from single-view image collections without any 3D supervision, adopting a hierarchical shape model that factorizes a category-specific prior shape from instance-specific shape deformation and articulation [20, 59, 60]. However, these models are trained in a category-specific manner and fail to generalize to less common animal species as shown in Sec. 5.3.", + "bbox": [ + 496, + 460, + 893, + 702 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Attempts to model diverse animal species again resort to pre-defined shape models, e.g., SMAL. Ruegg et al. [42, 43] model multiple dog breeds and regularize the learning process by encouraging intra-breed similarities using a triplet loss, which requires breed labels for training, in addition to keypoint annotations and template shape models. In contrast, our approach reconstructs a significantly broader set of animals and is trained in a category-agnostic fashion, without relying on existing 3D shape models or keypoints. Another related work [19] aims to learn a category-agnostic 3D shape regressor by exploiting pre-trained CLIP features and an off-the-shelf normal estimator, but does not model deformation and produces coarse shapes. Concurrent work", + "bbox": [ + 496, + 704, + 895, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "9753", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/5126da6a4c7222951b5a68079b11182256052dd89578f8895d3f39f45798f34e.jpg", + "image_caption": [ + "Figure 2. Training Pipeline. 3D-Fauna is trained using only single-view images from the Internet. Given each input image, it first extracts a feature vector $\\phi$ using a pre-trained unsupervised image encoder [5]. This is then used to query a learned memory bank to produce a base shape and a DINO feature field in the canonical pose. The model also predicts the albedo, instance-specific deformation, articulated pose and lighting, and is trained via image reconstruction losses on RGB, DINO feature map and mask, as well as a mask discriminator loss." + ], + "image_footnote": [], + "bbox": [ + 83, + 89, + 890, + 311 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "SAOR [2] also trains one model to reconstruct diverse animal categories, but obtains less realistic results and tends to suffer from strong photographer bias.", + "bbox": [ + 75, + 388, + 468, + 434 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Another line of research attempts to distill 3D reconstructions from 2D generative models trained on large-scale datasets of Internet images, which can be GAN-based [7, 8, 15, 38] or more recently, diffusion-based models [9, 18, 35, 47] using Score Distillation Sampling [40] and its variants. This idea has been extended to learn image-conditional multi-view generator networks [25, 30-33, 41, 45, 48, 49, 56, 63, 68]. However, most of these methods optimize one single shape at a time, whereas our model learns a pan-category deformable model that can reconstruct any animal instance in a feed-forward fashion.", + "bbox": [ + 75, + 434, + 470, + 599 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Animal Datasets. Learning 3D models often requires high-quality images without blur or occlusion. Existing high-quality datasets were only collected for a small number of categories [46, 54, 59, 66], and more diverse datasets [37, 61, 62, 69] often contain many noisy images unsuitable for training off the shelf. To train our pan-category model for a wide range of quadruped animal species, we aggregate these existing datasets after substantial filtering, and additionally source more images from the Internet to create a large-scale object-centric image dataset spanning over 100 quadruped species, as detailed in Sec. 4.", + "bbox": [ + 75, + 606, + 468, + 773 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 784, + 168, + 799 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Our goal is to learn a deformable model of a large variety of different animals using only Internet images for supervision. Formally, we learn a function $f: I \\mapsto O$ that maps any image $I \\in \\mathbb{R}^{3 \\times H \\times W}$ of an animal to a corresponding 3D reconstruction $O$ , capturing the animal's shape, deformation and appearance.", + "bbox": [ + 75, + 809, + 468, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3D reconstruction is greatly facilitated by using multiview data [17], but this is not available at scale, or at all, for most animals. Instead, we wish to reconstruct animals from weak single-view supervision obtained from the Internet. Compared to prior works [60, 70-72], which focused on reconstructing a single animal type at a time, here we target a large number of animal species at once, which is significantly more difficult. We show in the next section how solving this problem requires carefully exploiting the semantic similarities and geometric correspondences between different animals to regularize their 3D geometry.", + "bbox": [ + 496, + 388, + 892, + 555 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Semantic Bank of Skinned Models", + "text_level": 1, + "bbox": [ + 498, + 566, + 800, + 580 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given an image $I$ , consider the problem of estimating the 3D shape $(V,F)$ of the animal contained in it, where $V \\in \\mathbb{R}^{K \\times 3}$ is a list of vertices of a 3D mesh with face connectivity given by triplets $F \\subset \\{1, \\dots, K\\}^3$ . While recovering a 3D shape from a single image is ill-posed, as we train the model $f$ on a large dataset, we can ultimately observe animals from a variety of viewpoints. However, different images show different animals with different 3D shapes. Non-Rigid Structure-from-Motion [4, 50, 51] shows that reconstruction is still possible, but only if one makes the space of possible 3D shapes sufficiently tight to remove the reconstruction ambiguity. At the same time, the space must be sufficiently expressive to capture all animals.", + "bbox": [ + 496, + 590, + 892, + 787 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Skinned Models (SM). Following SMPL [34], many works [20, 59, 60, 67] have adopted a Skinned Model (SM) to model the shape of deformable objects when learning from single-view image collections or videos. An SM starts from a base shape $V_{\\mathrm{base}}$ of the object (e.g., human or animal) at 'rest', applies as a small deformation $V_{\\mathrm{ins}} = f_{\\mathrm{ins}}(V_{\\mathrm{base}}, \\phi)$ to capture instance-specific details, and then applies a larger", + "bbox": [ + 496, + 794, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "9754", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/ed6ffaf1a90507c82d1af6116314d266fec7d04a00bdaacfe3fb31f35792bee8.jpg", + "image_caption": [ + "Figure 3. Queries from the Semantic Base Shape Bank. Without requiring any category labels, the Semantic Bank (Sec 3.1) automatically learns diverse base shapes for various animals and preserves the semantic similarities across different instances." + ], + "image_footnote": [], + "bbox": [ + 117, + 85, + 433, + 296 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "deformation via a skinning function $V = f_{\\mathrm{pose}}(V_{\\mathrm{ins}}, \\phi)$ , controlled by the articulation of the underlying skeleton. We assume that deformations are predicted by neural networks that receive as input image features $\\phi = f_{\\phi}(I)$ extracted from a powerful self-supervised image encoder.", + "bbox": [ + 75, + 372, + 467, + 446 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In our case, a single SM is insufficient to capture the very large shape variations between different animals, which include horses, dogs, antelopes, hedgehogs, etc. Naively attempting to capture this diversity using the network $f_{\\mathrm{ins}}$ means that the resulting deformations cannot be small any longer, which throws off the tightness of the model.", + "bbox": [ + 75, + 449, + 467, + 540 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Semantic Bank of Skinned Models. In order to increase the expressiveness of the model while still avoiding overfitting individual images, we propose to exploit the fact that different animals often have similar 3D shapes as a result of evolution. We can thus reduce the shape variation to a small number of shape bases $V_{\\mathrm{base}}$ , and interpolate between them.", + "bbox": [ + 75, + 546, + 467, + 637 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To do so, we introduce a Semantic Bank of Skinned Models that automatically discovers a set of latent shape bases and learns to project each image into a linear combination of these bases. Key to this method is to use pre-trained unsupervised image features [5, 39] to automatically and implicitly identify similar animals. This is realized by means of a small memory bank with $K$ learned key-value pairs $\\{(\\phi_k^{\\mathrm{key}},\\phi_k^{\\mathrm{val}})\\}_{k = 1}^{K}$ . Specifically, given an image embedding $\\phi$ , we query the memory bank to obtain a latent shape embedding $\\tilde{\\phi}$ as a linear combination of the value tokens $\\{\\phi_k^{\\mathrm{val}}\\}$ via a mechanism similar to attention [53]:", + "bbox": [ + 75, + 637, + 467, + 804 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {\\phi} = \\sum_ {k = 1} ^ {K} w _ {k} \\phi_ {k} ^ {\\text {v a l}}, \\text {w h e r e} w _ {k} = \\frac {\\operatorname {c o s s i m} \\left(\\phi , \\phi_ {k} ^ {\\text {k e y}}\\right)}{\\sum_ {j = 1} ^ {K} \\operatorname {c o s s i m} \\left(\\phi , \\phi_ {j} ^ {\\text {k e y}}\\right)}, \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 815, + 467, + 869 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "and cossim denotes cosine similarity between two feature vectors. This embedding $\\tilde{\\phi}$ is then used as a condition to the", + "bbox": [ + 76, + 869, + 467, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "base shape predictor $(V_{\\mathrm{base}},F) = f_{\\mathrm{s}}(\\tilde{\\phi})$ , which produces semantically-adaptive base shapes without relying on any category labels or being bound to a hard categorization.", + "bbox": [ + 498, + 89, + 890, + 136 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In practice, the image features $\\phi$ are obtained from a well-trained feature extractor like DINO-ViT [5, 39]. Defining the weights based on the cosine similarities between the image features $\\phi$ and a small number of bases $\\{\\phi_k^{\\mathrm{key}}\\}$ captures the semantic similarities across different animal instances. For instance, as illustrated in Fig. 3, the cosine similarity between the image features of a zebra and a horse is 0.42, whereas the similarity between a zebra and an arctic fox is only 0.06. Ablations in Fig. 6 further verify the importance of this Semantic Bank, without which the model easily overfits each training image and fails to reconstruct plausible 3D shapes.", + "bbox": [ + 496, + 137, + 890, + 318 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Implementation Details. The base shape is predicted using a hybrid SDF-mesh representation [44, 60] parameterized by a coordinate MLP, with a conditioning vector $\\tilde{\\phi}$ injected via layer weight modulation [23, 24]. Since extracting meshes from SDFs using DMTet [44] is memory and compute intensive, in practice, we only compute it once for each iteration, by assuming the batched images contain the same animal species, and simply averaging out the embeddings $\\tilde{\\phi}$ . The instance-specific deformation is predicted using another coordinate MLP that outputs the displacement $\\Delta V_{\\mathrm{ins},i} = f_{\\Delta V}(V_{\\mathrm{base},i},\\phi)$ for each vertex $V_{\\mathrm{base},i}$ of the base mesh conditioned on the image feature $\\phi$ , resulting in the deformed shape $V_{\\mathrm{ins}} = \\Delta V_{\\mathrm{ins}} + V_{\\mathrm{base}}$ . We enforce a bilateral symmetry on both the base shape and the instance deformation by mirroring the query locations for the MLPs. Given the instance mesh $V_{\\mathrm{ins}}$ , we initialize a quadrupedal skeleton using a simple heuristic [60], and predict the rigid pose $\\xi_1 \\in SE(3)$ and bone rotations $\\xi_b \\in SO(3), b = 2,\\dots,B$ using a pose network. These posing parameters are then applied to the instance mesh via a linear blend skinning equation [34]. Refer to the sup. mat. for more details.", + "bbox": [ + 496, + 324, + 892, + 641 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Appearance. Assuming a Lambertian illumination model, we model the appearance of the object using an albedo field $a(\\pmb{x}) = f_{\\mathrm{a}}(\\pmb{x}, \\phi) \\in [0,1]^3$ and a dominant directional light. The final shaded color of each pixel is computed as $\\hat{I}(\\pmb{u}) = (k_a + k_d \\cdot \\max\\{0, \\langle \\pmb{l}, \\pmb{n} \\rangle\\}) \\cdot a(\\pmb{x})$ , where $\\pmb{n}$ is the normal direction of the posed mesh at pixel $\\pmb{u}$ , and $k_a, k_d \\in [0,1]$ and $\\pmb{l} \\in \\mathbb{S}^2$ are respectively the ambient intensity, diffuse intensity and dominant light direction predicted by the lighting network ( $k_a, k_d, l = f_1(\\phi)$ ).", + "bbox": [ + 496, + 648, + 890, + 785 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Learning Formulation", + "text_level": 1, + "bbox": [ + 500, + 794, + 707, + 810 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The entire pipeline is trained in an unsupervised fashion, using only self-supervised image features [5, 39] and object masks obtained from off-the-shelf segmenters [26, 27].", + "bbox": [ + 496, + 816, + 890, + 864 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Reconstruction Losses. Given the final predicted posed shape $V$ and appearance of the object, we use a differen", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "9755", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "tiable renderer $\\mathcal{R}$ to obtain an RGB image $\\hat{I}$ as well as a mask image $\\hat{M}$ , which are compared to the input image $I$ and the pseudo-ground-truth object mask $M$ :", + "bbox": [ + 76, + 90, + 472, + 137 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {m}} = \\left\\| \\hat {M} - M \\right\\| _ {2} ^ {2} + \\lambda_ {\\mathrm {d t}} \\left\\| \\hat {M} \\odot \\mathrm {d t} (M) \\right\\| _ {1}, \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 132, + 143, + 468, + 162 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {i m}} = \\| \\tilde {M} \\odot (\\hat {I} - I) \\| _ {1}, \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 132, + 165, + 468, + 184 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathrm{dt}(\\cdot)$ is distance transform for more effective gradients [22, 58], $\\odot$ denotes the Hadamard product, $\\lambda_{\\mathrm{dt}}$ specifies the balancing weight, and $\\hat{M} = \\hat{M}\\odot M$ is the intersection of the predicted and ground-truth masks.", + "bbox": [ + 76, + 191, + 468, + 253 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Correspondences from Self-Supervised Features. Self-supervised feature extractors are notoriously good at establishing semantic correspondences between objects, which can be distilled to facilitate 3D reconstruction [60]. To do so, we extract a patch-based feature map $\\Phi \\in \\mathbb{R}^{D\\times H\\times W}$ from each training image. These raw feature maps can be noisy and may preserve image-specific information irrelevant to other images. To distill more effective semantic correspondences across different images, we perform a Principal Component Analysis (PCA) across all feature maps [60], reducing the dimension to $D^{\\prime} = 16$ . We then task the model to also learn a feature field in the canonical frame $\\psi (\\pmb {x},\\tilde{\\phi})\\in \\mathbb{R}^{D^{\\prime}}$ that is rendered into a feature image $\\hat{\\Phi}$ given predicted posed shape using the same renderer $\\mathcal{R}$ . Training then encourages the rendered feature images $\\hat{\\Phi}$ to match the pre-extracted PCA features $\\Phi^{\\prime}$ : $\\mathcal{L}_{\\mathrm{feat}} = \\| \\tilde{M}\\odot (\\hat{\\Phi} -\\Phi^{\\prime})\\|_{2}^{2}$ . Note that although the space of the PCA features $\\Phi^{\\prime}$ is shared across different animal instances, the feature field $\\psi$ still receives the latent embedding $\\tilde{\\phi}$ as a condition. This is because different animals vary in shape, resulting in different feature fields.", + "bbox": [ + 76, + 258, + 472, + 577 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Mask Discriminator. In practice, despite exploiting these semantic correspondences, we still find that the viewpoint prediction may easily collapse to only frontal viewpoints, due to the heavy photographer bias in Internet photos. This can lead to overly elongated shapes as shown in Fig. 6, and further deteriorates the viewpoint predictions. To mitigate this, we further encourage the shape to look realistic from arbitrary viewpoints. Specifically, we introduce a mask discriminator $D$ that encourages the mask images $\\hat{M}_{\\mathrm{rv}}$ rendered from a random viewpoint to stay within the distribution of the ground-truth masks $\\mathcal{M}$ . The discriminator also receives the base embedding $\\tilde{\\phi}$ (with gradients detached) as a condition to make this adversarial guidance tailored to specific types of animals and thus more effective. Formally, this is achieved via an adversarial loss [15]:", + "bbox": [ + 76, + 583, + 472, + 811 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {\\mathrm {a d v}} = \\mathbb {E} _ {M \\sim \\mathcal {M}} [ \\log D (M; \\tilde {\\phi}) ] \\\\ + \\mathbb {E} _ {\\hat {M} _ {\\mathrm {r v}} \\sim \\mathcal {M} _ {\\mathrm {r v}}} [ \\log (1 - D (\\hat {M} _ {\\mathrm {r v}}; \\tilde {\\phi})) ]. \\tag {4} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 91, + 820, + 468, + 864 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Note that we do not use a discriminator on the rendered RGB images, as the predicted texture is often much less re", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "alistic when compared to real images, which gives the discriminator a trivial task. Moreover, the distribution of mask images is less susceptible to viewpoint bias than RGB images, and hence we can simply sample random viewpoints uniformly, without requiring a precise viewpoint distribution of the training images.", + "bbox": [ + 496, + 90, + 890, + 181 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Overall Loss. We further enforce the Eikonal constraint $\\mathcal{R}_{\\mathrm{Eik}}$ on the SDF network as well as the viewpoint hypothesis loss $\\mathcal{L}_{\\mathrm{hyp}}$ and the magnitude regularizers $\\mathcal{R}_{\\mathrm{def}}$ on vertex deformations and $\\mathcal{R}_{\\mathrm{art}}$ on articulation parameters $\\xi$ . See the supplementary materials for details.", + "bbox": [ + 496, + 186, + 890, + 263 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The final training objective $\\mathcal{L}$ is thus", + "bbox": [ + 519, + 263, + 764, + 277 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {\\text {r e c}} + \\lambda_ {\\text {h y p}} \\mathcal {L} _ {\\text {h y p}} + \\lambda_ {\\text {a d v}} \\mathcal {L} _ {\\text {a d v}} + \\mathcal {R}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 287, + 890, + 305 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{L}_{\\mathrm{rec}} = \\lambda_{\\mathrm{m}}\\mathcal{L}_{\\mathrm{m}} + \\lambda_{\\mathrm{im}}\\mathcal{L}_{\\mathrm{im}} + \\lambda_{\\mathrm{feat}}\\mathcal{L}_{\\mathrm{feat}}$ summarizes the three reconstruction losses, $\\mathcal{R} = \\lambda_{\\mathrm{Eik}}\\mathcal{R}_{\\mathrm{Eik}} + \\lambda_{\\mathrm{art}}\\mathcal{R}_{\\mathrm{art}} + \\lambda_{\\mathrm{def}}\\mathcal{R}_{\\mathrm{def}}$ summarizes the regularizers, and $\\lambda$ 's balance the contribution of each term.", + "bbox": [ + 496, + 313, + 890, + 372 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Training Schedule. We design a robust training schedule that comprises three stages. First, we train the base shapes and the viewpoint network without articulation or deformation. This significantly improves the stability of the training and allows the model to roughly register the rigid pose of all instances and learn the coarse base shapes.", + "bbox": [ + 496, + 378, + 890, + 469 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "As the viewpoint prediction stabilizes after 20k iterations, in the second stage, we instantiate the bones and enable the articulation, allowing the shapes to gradually grow legs and fit the articulated pose in each image. Meanwhile, we also turn on the mask discriminator to prevent viewpoint collapse and shape elongation. In the final stage, we optimize the instance shape deformation field to allow the model to capture the fine-grained geometric details of individual instances, with the discriminator disabled, as it may corrupt the shape if overused.", + "bbox": [ + 496, + 470, + 890, + 621 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Dataset Collection", + "text_level": 1, + "bbox": [ + 498, + 633, + 678, + 648 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In order to train this pan-category model for all types of quadruped animals, we create a new animal image dataset, dubbed the Fauna Dataset, spanning 128 quadruped species from dogs, antelopes to minks and platypuses, with a total of 78,168 images. We first aggregate the training sets of existing animal image datasets, including Animals-with-Attributes [61], APT-36K [69], Animal3D [62] and DOVE [59]. Many of these images are blurry or contain heavy occlusions, which will impact the stability of the training. We thus filter the images using automatic scripts first, followed by manual inspection. This results in 8,378 images covering approximately 70 animal species. To further increase the size as well as the diversity of the dataset, we additionally collect 69,790 images from the Internet, including 63,115 video frames and 2,358 images for 7 common animals (bear, cow, elephant, giraffe, horse, sheep, ze", + "bbox": [ + 496, + 659, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "9756", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "bra) as well as 4,317 images for another 51 less common species. We use off-the-shelf segmentation models [26, 27] to detect and segment the instances in the images. Out of the 121 few-shot categories, we hold out 5 as novel categories unused at training. For validation, we randomly select 5 images in each of the rest 116 few-shot categories, and 2,462 images for the 7 common species. To reduce the viewpoint bias in the few-shot categories, we manually identify a few (1-10) backward-facing instances in the training set and duplicate them to match the size of the rest.", + "bbox": [ + 75, + 90, + 472, + 243 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 76, + 256, + 209, + 273 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Technical Details", + "text_level": 1, + "bbox": [ + 76, + 281, + 243, + 296 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We base our architecture on MagicPony [60], adding the new SBSM and mask discriminator. For the Semantic Bank, we use $K = 60$ key-value pairs. The dimension of keys is 384 (same as DINO-ViT) and the dimension of values is 128. As the texture network tends to struggle to predict detailed appearance in one go, partially due to limited capacity, for all the visualizations, we follow [60] and fine-tune (only) the texture network for 50 iterations, which takes $< 10$ seconds. Refer to the sup. mat. for further details.", + "bbox": [ + 75, + 304, + 470, + 441 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Qualitative Results", + "text_level": 1, + "bbox": [ + 76, + 450, + 261, + 465 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "After training, 3D-Fauna takes in a single test image of any quadruped animal and produces an articulated and textured 3D mesh in a feed-forward manner, as visualized in Fig. 4. The model can reconstruct very different animals, such as antelopes, armadillos, and fishers, without requiring any category labels. All the input images in Fig. 4 have not been seen during training. In particular, the model also performs well on held-out categories, e.g. the wolf in the third row.", + "bbox": [ + 75, + 474, + 468, + 595 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.3. Comparisons with Prior Work", + "text_level": 1, + "bbox": [ + 76, + 604, + 346, + 619 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. To the best of our knowledge, ours is the first deformable model designed to handle $100+$ quadruped species, learned purely from 2D Internet data. We carry out quantitative and qualitative comparisons to methods that are at least in principle applicable to this setting. The baseline is MagicPony [60], which however is category-specific (they first train on horses, and fine-tune on giraffes, cows and zebras). We also compare with two popular deformable models that can work in the wild, namely UMR [29] and A-CSM [28]. However, they require weakly-supervised part segmentations and shape templates, respectively. Other works, such as LASSIE [70] and its follow-ups [71, 72], optimize a deformable model on a small set of about 20 images covering a single animal category at a time. More recently, image-to-3D methods based on distilling 2D diffusion models and/or large 3D datasets [31] have also demonstrated plausible 3D reconstructions of animals from a single image. In contrast, our model predicts an articulated mesh", + "bbox": [ + 75, + 628, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/8fdb793e103154aab3bc130c2aa018e09ac9469503f24d11fd54be44714e3fa0.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
PASCALAPT-36KAnimal3D
KT-PCK@0.1PCK@0.1PCK@0.1PCK@0.1
UMR [29]0.284---
A-CSM [28]0.3290.6870.6490.822
MagicPony [60]0.429-0.7560.867
Ours0.5390.7820.8410.901
", + "bbox": [ + 506, + 88, + 883, + 200 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Quantitative Comparisons on PASCAL VOC [10], APT-36K [69] and Animal3D [62]. When compared to baselines including the competitive MagicPony [60], our method demonstrates significantly improved performance on all datasets.", + "bbox": [ + 498, + 210, + 890, + 267 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "from a single image within seconds. Although it is difficult to establish a fair numerical comparison given these different settings, in Sec. 5.3, we provide a side-by-side qualitative comparison against baselines [31, 70, 71]. We use the publicly released code [31, 60, 70, 71] and report numbers [28, 29] included in MagicPony [60].", + "bbox": [ + 496, + 282, + 890, + 375 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Quantitative Comparisons. We conduct quantitative evaluation across three different datasets, APT-36K [69], Animal3D [62], and PASCAL VOC [10], which contain images of various animals with 2D keypoint annotations. Following MagicPony [60], we first evaluate on horses in PASCAL VOC [10] using the widely used Keypoint Transfer metric [22, 28, 29]. We use the same protocol as in A-CSM [28] and randomly sample $20\\mathrm{k}$ source-target image pairs. For each source image, we project the visible vertices of the predicted mesh onto the image and map each annotated 2D keypoint to its nearest vertex. We then project that vertex to the target image and check if it lies within a small distance (10% of image size) to the corresponding keypoint in the target image. We summarize the results using the Percentage of Correct Keypoints (KT-PCK@0.1) in Tab. 1.", + "bbox": [ + 496, + 380, + 892, + 606 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In Tab. 1, we follow CMR [22] to evaluate the three datasets on more species, optimizing a linear mapping from mesh vertices to desired keypoints for each category, and reporting PCK@0.1 between the predicted and annotated 2D keypoints. Our model demonstrates significant improvement over existing methods on all datasets. A performance breakdown for each category is provided in the sup. mat.", + "bbox": [ + 496, + 607, + 890, + 713 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Qualitative Comparisons. Figure 5 compares 3D-Fauna qualitatively to several recent works [31, 60, 70, 71]. To establish a fair comparison with MagicPony [60], for categories demonstrated in their paper (e.g. horse), we simply run inference using the released model. For each of the other categories, we use their public code to train a per-category model on our dataset from scratch (which contains less than 100 images for some rare categories). For LASSIE [70] and Hi-LASSIE [71], which optimize over a small set of images, we train their models on the test image together with additional 29 images randomly selected from the training set of that category. Hi-LASSIE [71] is further", + "bbox": [ + 496, + 719, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "9757", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/ebd128df2b235bd0d792ed3127c134e2cb156c99f56b99f343fee058fd0ab0f0.jpg", + "image_caption": [ + "Figure 4. Single Image 3D Reconstruction. Given a single image of any quadruped animal at test time, our model reconstructs an articulated and textured 3D mesh in a feed-forward manner without requiring category labels, which can be readily animated." + ], + "image_footnote": [], + "bbox": [ + 84, + 92, + 890, + 887 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "9758", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/dc079035b559e84447a2efa09b105ea341fcc84443c57014e05b870268d99b70.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 88, + 140, + 141 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/2cc8ecc9467a10e24ff5f017319df159568bb1908c8a2af76184faf7690c9074.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 143, + 140, + 188 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/6478139f613d6c8c6eea8ef370e50e868f491d0a8e99b51c47487e50d01d912a.jpg", + "image_caption": [ + "Input Image" + ], + "image_footnote": [], + "bbox": [ + 81, + 190, + 140, + 237 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/85dea26990b343a77431e954eaac01132f26924883b08ac3b2ab19550e6a05cc.jpg", + "image_caption": [ + "Figure 5. Qualitative Comparisons against MagicPony [60], LASSIE [70], Hi-LASSIE [71] and Zero-1-to-3 [31]. Compared to all baselines, our method predicts more stable poses and higher-fidelity reconstructions. Note that our method is learning-based and predicts 3D meshes in a feed-forward fashion (as opposed to [70, 71] that optimize on test images), which is orders of magnitude faster." + ], + "image_footnote": [], + "bbox": [ + 151, + 88, + 289, + 250 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/cb354bbaedb4e99fe13dc5806843344a89c1181343f88a20afbf344aa7eaa0df.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 308, + 88, + 450, + 250 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c9657a753f4cfdd11315712bf18a9876f637a4f956e586ce4d09acd70a8f7cef.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 452, + 88, + 591, + 250 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/b451aa3d7bffd0eb8a30f352790e3fe9eec9fcd00727e88d154e15318304076d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 602, + 88, + 736, + 250 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ecfa8944b0431e6fba68e66d33649cf0dea26c5197555448a0c9cbd559ed7b73.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 748, + 88, + 879, + 250 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/714643e383b4a6ca624f0205c9f3ff81bef4c22caa082d795c1fe1310022dd53.jpg", + "image_caption": [ + "Figure 6. Ablation Studies. Both the Semantic Bank and the mask discriminator improve the results as discussed in Sec. 5.4." + ], + "image_footnote": [], + "bbox": [ + 76, + 309, + 303, + 545 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/3a9f29df8a99bba87e61b6e001a87a4103df08084aa06445b1144539885a4942.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 308, + 309, + 460, + 545 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "fine-tuned on the test image after training. To compare with Zero-1-to-3 [31], we use the implementation in threestudio [16] to first distill a NeRF [36] using Score Distillation Sampling [40] given the masked test image, and then extract a 3D mesh for fair comparison. Note that our model predicts 3D meshes within seconds, whereas the optimization takes at least 10–20 mins for the other methods [31, 70, 71].", + "bbox": [ + 75, + 594, + 468, + 699 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "As shown in Fig. 5, MagicPony is sensitive to the size of the training set. When trained on rare categories with fewer (< 100) images, such as the puma in Fig. 5, it fails to learn meaningful shapes and produces severe artifacts. Despite optimizing on the test images, LASSIE and Hi-LASSIE produce coarser reconstructions, partially due to the part-based representation that struggles in capturing the detailed geometry and articulation, as well as unstable viewpoint prediction. Zero-1-to-3, on the other hand, often fails to correctly reconstruct the legs, and does not explicitly model the articulated pose. On the contrary, our method predicts accurate viewpoint and reconstructs fine-grained articulated shapes for all different animals, with only one single model.", + "bbox": [ + 75, + 704, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 313, + 653, + 330 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In Fig. 6, we present ablation results on three key design choices in our pipeline: SBSM, category-agnostic training, and mask discriminator. If we remove the SBSM and directly condition the base shape network on each individual image embedding $\\phi$ , the model tends to overfit each training views without learning meaningful canonical 3D shapes and pose. Alternatively, we can simply condition the base shape on an explicit (learned) category-specific embedding and train the model in a category-conditioned manner. This also leads to sub-optimal reconstructions, in particular on rare categories with few training images. Lastly, training without the mask discriminator results in biased viewpoint prediction (towards frontal) and produces elongated shapes.", + "bbox": [ + 496, + 342, + 893, + 540 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusions", + "text_level": 1, + "bbox": [ + 500, + 570, + 627, + 585 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We have presented 3D-Fauna, a deformable model for 100 animal categories learned using only Internet images. 3D-Fauna can reconstruct any quadruped image by instantiating in seconds a posed version of the deformable model to match the input image. Despite capable of modeling diverse animals, the current model is still limited to quadruped species that share a same skeletal structure. Furthermore, the training images still need to be lightly curated. Nevertheless, 3D-Fauna still presents a significant leap compared to prior works and moves us closer to models that will be able to understand and reconstruct all animals in nature.", + "bbox": [ + 496, + 601, + 893, + 767 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments. We thank Cristobal Eyzaguirre, Kyle Sargent, and Yunhao Ge for their insightful discussions and Chen Geng for proofreading. The work is in part supported by the Stanford Institute for Human-Centered AI (HAI), NSF RI #2211258, #2338203, ONR MURI N00014-22-1-2740, ONR YIP N00014-24-1-2117, the Samsung Global Research Outreach (GRO) program, Amazon, Google, and EPSRC VisualAI EP/T028572/1.", + "bbox": [ + 496, + 779, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "9759", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Kalyan Vasudev Alwala, Abhinav Gupta, and Shubham Tulsiani. Pre-train, self-train, distill: A simple recipe for supersizing 3d reconstruction. In CVPR, 2022. 2", + "[2] Mehmet Aygün and Oisin Mac Aodha. Saor: Single-view articulated object reconstruction. 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In CVPR, 2018. 2" + ], + "bbox": [ + 78, + 90, + 468, + 743 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "9762", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning the 3D Fauna of the Web/dd8fb285-42f8-4fbe-a149-b011c10a95c3_model.json b/2024/Learning the 3D Fauna of the Web/dd8fb285-42f8-4fbe-a149-b011c10a95c3_model.json new file mode 100644 index 0000000000000000000000000000000000000000..6caab9afe3885fdabd4aaed19042840ae322a399 --- /dev/null +++ b/2024/Learning the 3D Fauna of the Web/dd8fb285-42f8-4fbe-a149-b011c10a95c3_model.json @@ -0,0 +1,2224 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.309, + 0.131, + 0.66, + 0.152 + ], + "angle": 0, + "content": "Learning the 3D Fauna of the Web" + }, + { + "type": "text", + "bbox": [ + 0.09, + 0.179, + 0.868, + 0.263 + ], + "angle": 0, + "content": "Zizhang Li\\(^{1*}\\) Dor Litvak\\(^{1,2*}\\) Ruining Li\\(^{3}\\) Yunzhi Zhang\\(^{1}\\) Tomas Jakab\\(^{3}\\) Christian Rupprecht\\(^{3}\\) Shangzhe Wu\\(^{1\\dagger}\\) Andrea Vedaldi\\(^{3\\dagger}\\) Jiajun Wu\\(^{1\\dagger}\\) \n\\(^{1}\\)Stanford University \\(^{2}\\)UT Austin \\(^{3}\\)University of Oxford kyleleey.github.io/3DFauna/" + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.27, + 0.889, + 0.416 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.423, + 0.893, + 0.466 + ], + "angle": 0, + "content": "Figure 1. Learning Diverse 3D Animals from the Internet. Our method, 3D-Fauna, learns a pan-category deformable 3D model of more than 100 different animal species using only 2D Internet images as training data. At test time, the model can turn a single image of an quadruped instance into an articulated, textured 3D mesh in a feed-forward manner, ready for animation and rendering." + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.48, + 0.314, + 0.496 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.511, + 0.474, + 0.799 + ], + "angle": 0, + "content": "Learning 3D models of all animals in nature requires massively scaling up existing solutions. With this ultimate goal in mind, we develop 3D-Fauna, an approach that learns a pan-category deformable 3D animal model for more than 100 animal species jointly. One crucial bottleneck of modeling animals is the limited availability of training data, which we overcome by learning our model from 2D Internet images. We show that prior approaches, which are category-specific, fail to generalize to rare species with limited training images. We address this challenge by introducing the Semantic Bank of Skinned Models (SBSM), which automatically discovers a small set of base animal shapes by combining geometric inductive priors with semantic knowledge implicitly captured by an off-the-shelf self-supervised feature extractor. To train such a model, we also contribute a new large-scale dataset of diverse animal species. At inference time, given a single image of any quadruped animal, our model reconstructs an articulated 3D mesh in a feed-forward manner in seconds." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.812, + 0.21, + 0.828 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.838, + 0.47, + 0.868 + ], + "angle": 0, + "content": "Computer vision models can nowadays reconstruct humans in monocular images and videos robustly and accurately, re" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.481, + 0.892, + 0.543 + ], + "angle": 0, + "content": "covering their 3D shape, articulated pose, and even appearance [3, 11, 12, 14, 21, 34]. However, humans are but a tiny fraction of the animals that exist in nature, and 3D models remain essentially blind to the vast majority of biodiversity." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.545, + 0.893, + 0.713 + ], + "angle": 0, + "content": "While in principle the same approaches that work for humans could work for many other animal species, in practice scaling it to each of the 2.1 million different animal species on Earth is nearly hopeless. In fact, building a human model such as SMPL [34] and a corresponding pose predictor [3, 14] requires collecting 3D scans of many people in laboratory [21], crafting a corresponding articulated deformable model semi-automatically, and collecting extensive manual labels to train corresponding pose regressors. Of all animals, only humans are currently of sufficient importance in applications to justify the costs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.716, + 0.895, + 0.883 + ], + "angle": 0, + "content": "A technically harder but much more practical approach is to learn animal models automatically from images and videos readily available on the Internet. Several authors have demonstrated that at least rough models can be learned from such uncontrolled image collections [22, 60, 70]. Even so, many limitations remain, starting from the fact that these methods can only reconstruct one or a few specific animal exemplars [70], or at most a single class of animals at a given time [22, 60]. The latter restriction is particularly glaring, as it defeats the purpose of using the Internet as a vast data source for modeling biodiversity." + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.886, + 0.892, + 0.902 + ], + "angle": 0, + "content": "We introduce 3D-Fauna, a method that learns a pan" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.875, + 0.203, + 0.887 + ], + "angle": 0, + "content": "*Equal contribution" + }, + { + "type": "page_footnote", + "bbox": [ + 0.097, + 0.888, + 0.184, + 0.901 + ], + "angle": 0, + "content": "Equal advising" + }, + { + "type": "list", + "bbox": [ + 0.096, + 0.875, + 0.203, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9752" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.288 + ], + "angle": 0, + "content": "category deformable model for a large number (\\(>100\\)) of different quadruped animal species, such as dogs, antelopes, and hedgehogs, as shown in Fig. 1. For the approach to be as automated and thus as scalable as possible, we assume that only Internet images of the animals are provided as training data and only consider as prerequisites a pre-trained 2D object segmentation model and off-the-shelf unsupervised visual features. 3D-Fauna is designed as a feed-forward network that deforms and poses the deformable model to reconstruct any animal given a single image as input. The ability to perform monocular reconstruction is necessary for training on (single-view) Internet images, and is also useful in many real-world applications." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.29, + 0.473, + 0.442 + ], + "angle": 0, + "content": "Crucial to 3D-Fauna is to learn a single joint model of all animals in one go. Despite posing a challenge, modeling many animals jointly is essential for reconstructing rarer species, for which we often have only a small number of images to train on. This allows us to exploit the structural similarity of different animals that results from evolution, and maximize statistical efficiency. Here, we focus our attention on animals that share a given body plan, in particular, quadrupeds, and share the structure of the underlying skeletal model, which would otherwise be difficult to pin down." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.444, + 0.473, + 0.686 + ], + "angle": 0, + "content": "Learning such a model from only unlabeled single-view images requires several technical innovations. The most important is to develop a 3D representation that is sufficiently expressive to model the diverse shape variations of the animals, and at the same time tight enough to be learned from single-view images without overfitting individual views. Prior work partly achieved this goal by using skinned models, which consider small shape variations around a base template followed by articulation [60]. We found that this approach does not provide sufficient inductive biases to learn diverse animal species from Internet images alone. Hence, we introduce the Semantic Bank of Skinned Models (SBSM), which uses off-the-shelf unsupervised features, such as DINO [5, 39], to hypothesize how different animals may relate semantically, and automatically learns a low-dimensional base shape bank." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.687, + 0.473, + 0.839 + ], + "angle": 0, + "content": "Lastly, Internet images, which are not captured with the purpose of 3D reconstruction in mind, are characterized by a strong photographer bias, skewing the viewpoint distribution to mostly frontal, which significantly hinders the stability of 3D shape learning. To mitigate this issue, 3D-Fauna further encourages the predicted shapes to look realistic from all viewpoints, by introducing an efficient mask discriminator that enforces the silhouettes rendered from a random viewpoint to stay within the distribution of the silhouettes of the real images." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.84, + 0.472, + 0.903 + ], + "angle": 0, + "content": "Combining these ideas, 3D-Fauna is an end-to-end framework that learns a pan-category model of 3D quadruped animals from online image collections. To train 3D-Fauna, we collected a large-scale animal dataset of over" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.199 + ], + "angle": 0, + "content": "100 quadruped species, dubbed the Fauna Dataset, as part of the contribution. After training, the model can turn a single test image of any quadruped instance into a fully articulated 3D mesh in a feed-forward fashion, ready for animation and rendering. Extensive quantitative and qualitative comparisons demonstrate significant improvements over existing methods. Code and data will be released." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.216, + 0.642, + 0.232 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.242, + 0.895, + 0.456 + ], + "angle": 0, + "content": "Optimization-Based 3D Reconstruction of Animals. Due to the lack of explicit 3D data for the vast majority of animals, reconstruction has mostly relied on pre-defined shape models or multi-view images. Initially, efforts focus on fitting a parametric 3D shape model obtained from 3D scans, e.g., SMAL [74], to animal images using annotated 2D keypoints and segmentation masks, which is further extended to multi-view images [75]. Other works aim to optimize the 3D shape [6, 55, 65–67, 70–72] directly from image or video collections of a smaller scale using various forms of supervision in addition to masks, such as keypoints [6, 55], self-supervised semantic correspondences [70–72], optical flow [64–67], surface normals [67], category-specific template shapes [6, 55]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.462, + 0.895, + 0.703 + ], + "angle": 0, + "content": "Learning 3D from Internet Images and Videos. Recently, authors have attempted to learn 3D priors from Internet images and videos at a larger scale [1, 13, 20, 22, 28, 29, 52, 57-60, 73], mostly focusing on a single category at a time. Reconstructing animals presents additional challenges due to their highly deformable nature, which often necessitates stronger supervisory signals for training, similar to the ones used in optimization-based methods. Some methods have, in particular, learned to model articulated animals, such as horses, from single-view image collections without any 3D supervision, adopting a hierarchical shape model that factorizes a category-specific prior shape from instance-specific shape deformation and articulation [20, 59, 60]. However, these models are trained in a category-specific manner and fail to generalize to less common animal species as shown in Sec. 5.3." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Attempts to model diverse animal species again resort to pre-defined shape models, e.g., SMAL. Ruegg et al. [42, 43] model multiple dog breeds and regularize the learning process by encouraging intra-breed similarities using a triplet loss, which requires breed labels for training, in addition to keypoint annotations and template shape models. In contrast, our approach reconstructs a significantly broader set of animals and is trained in a category-agnostic fashion, without relying on existing 3D shape models or keypoints. Another related work [19] aims to learn a category-agnostic 3D shape regressor by exploiting pre-trained CLIP features and an off-the-shelf normal estimator, but does not model deformation and produces coarse shapes. Concurrent work" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9753" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.09, + 0.891, + 0.312 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.316, + 0.893, + 0.375 + ], + "angle": 0, + "content": "Figure 2. Training Pipeline. 3D-Fauna is trained using only single-view images from the Internet. Given each input image, it first extracts a feature vector \\(\\phi\\) using a pre-trained unsupervised image encoder [5]. This is then used to query a learned memory bank to produce a base shape and a DINO feature field in the canonical pose. The model also predicts the albedo, instance-specific deformation, articulated pose and lighting, and is trained via image reconstruction losses on RGB, DINO feature map and mask, as well as a mask discriminator loss." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.39, + 0.47, + 0.435 + ], + "angle": 0, + "content": "SAOR [2] also trains one model to reconstruct diverse animal categories, but obtains less realistic results and tends to suffer from strong photographer bias." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.435, + 0.471, + 0.601 + ], + "angle": 0, + "content": "Another line of research attempts to distill 3D reconstructions from 2D generative models trained on large-scale datasets of Internet images, which can be GAN-based [7, 8, 15, 38] or more recently, diffusion-based models [9, 18, 35, 47] using Score Distillation Sampling [40] and its variants. This idea has been extended to learn image-conditional multi-view generator networks [25, 30-33, 41, 45, 48, 49, 56, 63, 68]. However, most of these methods optimize one single shape at a time, whereas our model learns a pan-category deformable model that can reconstruct any animal instance in a feed-forward fashion." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.607, + 0.47, + 0.775 + ], + "angle": 0, + "content": "Animal Datasets. Learning 3D models often requires high-quality images without blur or occlusion. Existing high-quality datasets were only collected for a small number of categories [46, 54, 59, 66], and more diverse datasets [37, 61, 62, 69] often contain many noisy images unsuitable for training off the shelf. To train our pan-category model for a wide range of quadruped animal species, we aggregate these existing datasets after substantial filtering, and additionally source more images from the Internet to create a large-scale object-centric image dataset spanning over 100 quadruped species, as detailed in Sec. 4." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.785, + 0.169, + 0.8 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.469, + 0.903 + ], + "angle": 0, + "content": "Our goal is to learn a deformable model of a large variety of different animals using only Internet images for supervision. Formally, we learn a function \\( f: I \\mapsto O \\) that maps any image \\( I \\in \\mathbb{R}^{3 \\times H \\times W} \\) of an animal to a corresponding 3D reconstruction \\( O \\), capturing the animal's shape, deformation and appearance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.39, + 0.893, + 0.556 + ], + "angle": 0, + "content": "3D reconstruction is greatly facilitated by using multiview data [17], but this is not available at scale, or at all, for most animals. Instead, we wish to reconstruct animals from weak single-view supervision obtained from the Internet. Compared to prior works [60, 70-72], which focused on reconstructing a single animal type at a time, here we target a large number of animal species at once, which is significantly more difficult. We show in the next section how solving this problem requires carefully exploiting the semantic similarities and geometric correspondences between different animals to regularize their 3D geometry." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.567, + 0.802, + 0.582 + ], + "angle": 0, + "content": "3.1. Semantic Bank of Skinned Models" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.592, + 0.893, + 0.789 + ], + "angle": 0, + "content": "Given an image \\(I\\), consider the problem of estimating the 3D shape \\((V,F)\\) of the animal contained in it, where \\(V \\in \\mathbb{R}^{K \\times 3}\\) is a list of vertices of a 3D mesh with face connectivity given by triplets \\(F \\subset \\{1, \\dots, K\\}^3\\). While recovering a 3D shape from a single image is ill-posed, as we train the model \\(f\\) on a large dataset, we can ultimately observe animals from a variety of viewpoints. However, different images show different animals with different 3D shapes. Non-Rigid Structure-from-Motion [4, 50, 51] shows that reconstruction is still possible, but only if one makes the space of possible 3D shapes sufficiently tight to remove the reconstruction ambiguity. At the same time, the space must be sufficiently expressive to capture all animals." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.894, + 0.903 + ], + "angle": 0, + "content": "Skinned Models (SM). Following SMPL [34], many works [20, 59, 60, 67] have adopted a Skinned Model (SM) to model the shape of deformable objects when learning from single-view image collections or videos. An SM starts from a base shape \\( V_{\\mathrm{base}} \\) of the object (e.g., human or animal) at 'rest', applies as a small deformation \\( V_{\\mathrm{ins}} = f_{\\mathrm{ins}}(V_{\\mathrm{base}}, \\phi) \\) to capture instance-specific details, and then applies a larger" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "9754" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.118, + 0.087, + 0.434, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.299, + 0.47, + 0.356 + ], + "angle": 0, + "content": "Figure 3. Queries from the Semantic Base Shape Bank. Without requiring any category labels, the Semantic Bank (Sec 3.1) automatically learns diverse base shapes for various animals and preserves the semantic similarities across different instances." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.373, + 0.468, + 0.448 + ], + "angle": 0, + "content": "deformation via a skinning function \\( V = f_{\\mathrm{pose}}(V_{\\mathrm{ins}}, \\phi) \\), controlled by the articulation of the underlying skeleton. We assume that deformations are predicted by neural networks that receive as input image features \\( \\phi = f_{\\phi}(I) \\) extracted from a powerful self-supervised image encoder." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.45, + 0.468, + 0.541 + ], + "angle": 0, + "content": "In our case, a single SM is insufficient to capture the very large shape variations between different animals, which include horses, dogs, antelopes, hedgehogs, etc. Naively attempting to capture this diversity using the network \\( f_{\\mathrm{ins}} \\) means that the resulting deformations cannot be small any longer, which throws off the tightness of the model." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.547, + 0.468, + 0.638 + ], + "angle": 0, + "content": "Semantic Bank of Skinned Models. In order to increase the expressiveness of the model while still avoiding overfitting individual images, we propose to exploit the fact that different animals often have similar 3D shapes as a result of evolution. We can thus reduce the shape variation to a small number of shape bases \\( V_{\\mathrm{base}} \\), and interpolate between them." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.638, + 0.468, + 0.805 + ], + "angle": 0, + "content": "To do so, we introduce a Semantic Bank of Skinned Models that automatically discovers a set of latent shape bases and learns to project each image into a linear combination of these bases. Key to this method is to use pre-trained unsupervised image features [5, 39] to automatically and implicitly identify similar animals. This is realized by means of a small memory bank with \\( K \\) learned key-value pairs \\( \\{(\\phi_k^{\\mathrm{key}},\\phi_k^{\\mathrm{val}})\\}_{k = 1}^{K} \\). Specifically, given an image embedding \\( \\phi \\), we query the memory bank to obtain a latent shape embedding \\( \\tilde{\\phi} \\) as a linear combination of the value tokens \\( \\{\\phi_k^{\\mathrm{val}}\\} \\) via a mechanism similar to attention [53]:" + }, + { + "type": "equation", + "bbox": [ + 0.091, + 0.816, + 0.468, + 0.87 + ], + "angle": 0, + "content": "\\[\n\\tilde {\\phi} = \\sum_ {k = 1} ^ {K} w _ {k} \\phi_ {k} ^ {\\text {v a l}}, \\text {w h e r e} w _ {k} = \\frac {\\operatorname {c o s s i m} \\left(\\phi , \\phi_ {k} ^ {\\text {k e y}}\\right)}{\\sum_ {j = 1} ^ {K} \\operatorname {c o s s i m} \\left(\\phi , \\phi_ {j} ^ {\\text {k e y}}\\right)}, \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.468, + 0.901 + ], + "angle": 0, + "content": "and cossim denotes cosine similarity between two feature vectors. This embedding \\(\\tilde{\\phi}\\) is then used as a condition to the" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.09, + 0.891, + 0.137 + ], + "angle": 0, + "content": "base shape predictor \\((V_{\\mathrm{base}},F) = f_{\\mathrm{s}}(\\tilde{\\phi})\\) , which produces semantically-adaptive base shapes without relying on any category labels or being bound to a hard categorization." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.138, + 0.892, + 0.319 + ], + "angle": 0, + "content": "In practice, the image features \\(\\phi\\) are obtained from a well-trained feature extractor like DINO-ViT [5, 39]. Defining the weights based on the cosine similarities between the image features \\(\\phi\\) and a small number of bases \\(\\{\\phi_k^{\\mathrm{key}}\\}\\) captures the semantic similarities across different animal instances. For instance, as illustrated in Fig. 3, the cosine similarity between the image features of a zebra and a horse is 0.42, whereas the similarity between a zebra and an arctic fox is only 0.06. Ablations in Fig. 6 further verify the importance of this Semantic Bank, without which the model easily overfits each training image and fails to reconstruct plausible 3D shapes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.325, + 0.893, + 0.642 + ], + "angle": 0, + "content": "Implementation Details. The base shape is predicted using a hybrid SDF-mesh representation [44, 60] parameterized by a coordinate MLP, with a conditioning vector \\(\\tilde{\\phi}\\) injected via layer weight modulation [23, 24]. Since extracting meshes from SDFs using DMTet [44] is memory and compute intensive, in practice, we only compute it once for each iteration, by assuming the batched images contain the same animal species, and simply averaging out the embeddings \\(\\tilde{\\phi}\\). The instance-specific deformation is predicted using another coordinate MLP that outputs the displacement \\(\\Delta V_{\\mathrm{ins},i} = f_{\\Delta V}(V_{\\mathrm{base},i},\\phi)\\) for each vertex \\(V_{\\mathrm{base},i}\\) of the base mesh conditioned on the image feature \\(\\phi\\), resulting in the deformed shape \\(V_{\\mathrm{ins}} = \\Delta V_{\\mathrm{ins}} + V_{\\mathrm{base}}\\). We enforce a bilateral symmetry on both the base shape and the instance deformation by mirroring the query locations for the MLPs. Given the instance mesh \\(V_{\\mathrm{ins}}\\), we initialize a quadrupedal skeleton using a simple heuristic [60], and predict the rigid pose \\(\\xi_1 \\in SE(3)\\) and bone rotations \\(\\xi_b \\in SO(3), b = 2,\\dots,B\\) using a pose network. These posing parameters are then applied to the instance mesh via a linear blend skinning equation [34]. Refer to the sup. mat. for more details." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.649, + 0.892, + 0.786 + ], + "angle": 0, + "content": "Appearance. Assuming a Lambertian illumination model, we model the appearance of the object using an albedo field \\(a(\\pmb{x}) = f_{\\mathrm{a}}(\\pmb{x}, \\phi) \\in [0,1]^3\\) and a dominant directional light. The final shaded color of each pixel is computed as \\(\\hat{I}(\\pmb{u}) = (k_a + k_d \\cdot \\max\\{0, \\langle \\pmb{l}, \\pmb{n} \\rangle\\}) \\cdot a(\\pmb{x})\\), where \\(\\pmb{n}\\) is the normal direction of the posed mesh at pixel \\(\\pmb{u}\\), and \\(k_a, k_d \\in [0,1]\\) and \\(\\pmb{l} \\in \\mathbb{S}^2\\) are respectively the ambient intensity, diffuse intensity and dominant light direction predicted by the lighting network (\\(k_a, k_d, l = f_1(\\phi)\\))." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.795, + 0.708, + 0.811 + ], + "angle": 0, + "content": "3.2. Learning Formulation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.818, + 0.891, + 0.865 + ], + "angle": 0, + "content": "The entire pipeline is trained in an unsupervised fashion, using only self-supervised image features [5, 39] and object masks obtained from off-the-shelf segmenters [26, 27]." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.891, + 0.901 + ], + "angle": 0, + "content": "Reconstruction Losses. Given the final predicted posed shape \\(V\\) and appearance of the object, we use a differen" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9755" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.091, + 0.473, + 0.138 + ], + "angle": 0, + "content": "tiable renderer \\(\\mathcal{R}\\) to obtain an RGB image \\(\\hat{I}\\) as well as a mask image \\(\\hat{M}\\), which are compared to the input image \\(I\\) and the pseudo-ground-truth object mask \\(M\\):" + }, + { + "type": "equation", + "bbox": [ + 0.133, + 0.145, + 0.47, + 0.163 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {m}} = \\left\\| \\hat {M} - M \\right\\| _ {2} ^ {2} + \\lambda_ {\\mathrm {d t}} \\left\\| \\hat {M} \\odot \\mathrm {d t} (M) \\right\\| _ {1}, \\tag {2}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.133, + 0.166, + 0.469, + 0.185 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {i m}} = \\| \\tilde {M} \\odot (\\hat {I} - I) \\| _ {1}, \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.193, + 0.47, + 0.255 + ], + "angle": 0, + "content": "where \\(\\mathrm{dt}(\\cdot)\\) is distance transform for more effective gradients [22, 58], \\(\\odot\\) denotes the Hadamard product, \\(\\lambda_{\\mathrm{dt}}\\) specifies the balancing weight, and \\(\\hat{M} = \\hat{M}\\odot M\\) is the intersection of the predicted and ground-truth masks." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.26, + 0.473, + 0.578 + ], + "angle": 0, + "content": "Correspondences from Self-Supervised Features. Self-supervised feature extractors are notoriously good at establishing semantic correspondences between objects, which can be distilled to facilitate 3D reconstruction [60]. To do so, we extract a patch-based feature map \\(\\Phi \\in \\mathbb{R}^{D\\times H\\times W}\\) from each training image. These raw feature maps can be noisy and may preserve image-specific information irrelevant to other images. To distill more effective semantic correspondences across different images, we perform a Principal Component Analysis (PCA) across all feature maps [60], reducing the dimension to \\(D^{\\prime} = 16\\). We then task the model to also learn a feature field in the canonical frame \\(\\psi (\\pmb {x},\\tilde{\\phi})\\in \\mathbb{R}^{D^{\\prime}}\\) that is rendered into a feature image \\(\\hat{\\Phi}\\) given predicted posed shape using the same renderer \\(\\mathcal{R}\\). Training then encourages the rendered feature images \\(\\hat{\\Phi}\\) to match the pre-extracted PCA features \\(\\Phi^{\\prime}\\): \\(\\mathcal{L}_{\\mathrm{feat}} = \\| \\tilde{M}\\odot (\\hat{\\Phi} -\\Phi^{\\prime})\\|_{2}^{2}\\). Note that although the space of the PCA features \\(\\Phi^{\\prime}\\) is shared across different animal instances, the feature field \\(\\psi\\) still receives the latent embedding \\(\\tilde{\\phi}\\) as a condition. This is because different animals vary in shape, resulting in different feature fields." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.584, + 0.473, + 0.812 + ], + "angle": 0, + "content": "Mask Discriminator. In practice, despite exploiting these semantic correspondences, we still find that the viewpoint prediction may easily collapse to only frontal viewpoints, due to the heavy photographer bias in Internet photos. This can lead to overly elongated shapes as shown in Fig. 6, and further deteriorates the viewpoint predictions. To mitigate this, we further encourage the shape to look realistic from arbitrary viewpoints. Specifically, we introduce a mask discriminator \\( D \\) that encourages the mask images \\( \\hat{M}_{\\mathrm{rv}} \\) rendered from a random viewpoint to stay within the distribution of the ground-truth masks \\( \\mathcal{M} \\). The discriminator also receives the base embedding \\( \\tilde{\\phi} \\) (with gradients detached) as a condition to make this adversarial guidance tailored to specific types of animals and thus more effective. Formally, this is achieved via an adversarial loss [15]:" + }, + { + "type": "equation", + "bbox": [ + 0.093, + 0.821, + 0.469, + 0.865 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {\\mathrm {a d v}} = \\mathbb {E} _ {M \\sim \\mathcal {M}} [ \\log D (M; \\tilde {\\phi}) ] \\\\ + \\mathbb {E} _ {\\hat {M} _ {\\mathrm {r v}} \\sim \\mathcal {M} _ {\\mathrm {r v}}} [ \\log (1 - D (\\hat {M} _ {\\mathrm {r v}}; \\tilde {\\phi})) ]. \\tag {4} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.871, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Note that we do not use a discriminator on the rendered RGB images, as the predicted texture is often much less re" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.183 + ], + "angle": 0, + "content": "alistic when compared to real images, which gives the discriminator a trivial task. Moreover, the distribution of mask images is less susceptible to viewpoint bias than RGB images, and hence we can simply sample random viewpoints uniformly, without requiring a precise viewpoint distribution of the training images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.188, + 0.892, + 0.264 + ], + "angle": 0, + "content": "Overall Loss. We further enforce the Eikonal constraint \\(\\mathcal{R}_{\\mathrm{Eik}}\\) on the SDF network as well as the viewpoint hypothesis loss \\(\\mathcal{L}_{\\mathrm{hyp}}\\) and the magnitude regularizers \\(\\mathcal{R}_{\\mathrm{def}}\\) on vertex deformations and \\(\\mathcal{R}_{\\mathrm{art}}\\) on articulation parameters \\(\\xi\\). See the supplementary materials for details." + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.265, + 0.766, + 0.279 + ], + "angle": 0, + "content": "The final training objective \\(\\mathcal{L}\\) is thus" + }, + { + "type": "equation", + "bbox": [ + 0.569, + 0.289, + 0.892, + 0.306 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {\\text {r e c}} + \\lambda_ {\\text {h y p}} \\mathcal {L} _ {\\text {h y p}} + \\lambda_ {\\text {a d v}} \\mathcal {L} _ {\\text {a d v}} + \\mathcal {R}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.314, + 0.892, + 0.373 + ], + "angle": 0, + "content": "where \\(\\mathcal{L}_{\\mathrm{rec}} = \\lambda_{\\mathrm{m}}\\mathcal{L}_{\\mathrm{m}} + \\lambda_{\\mathrm{im}}\\mathcal{L}_{\\mathrm{im}} + \\lambda_{\\mathrm{feat}}\\mathcal{L}_{\\mathrm{feat}}\\) summarizes the three reconstruction losses, \\(\\mathcal{R} = \\lambda_{\\mathrm{Eik}}\\mathcal{R}_{\\mathrm{Eik}} + \\lambda_{\\mathrm{art}}\\mathcal{R}_{\\mathrm{art}} + \\lambda_{\\mathrm{def}}\\mathcal{R}_{\\mathrm{def}}\\) summarizes the regularizers, and \\(\\lambda\\) 's balance the contribution of each term." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.38, + 0.892, + 0.47 + ], + "angle": 0, + "content": "Training Schedule. We design a robust training schedule that comprises three stages. First, we train the base shapes and the viewpoint network without articulation or deformation. This significantly improves the stability of the training and allows the model to roughly register the rigid pose of all instances and learn the coarse base shapes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.471, + 0.892, + 0.622 + ], + "angle": 0, + "content": "As the viewpoint prediction stabilizes after 20k iterations, in the second stage, we instantiate the bones and enable the articulation, allowing the shapes to gradually grow legs and fit the articulated pose in each image. Meanwhile, we also turn on the mask discriminator to prevent viewpoint collapse and shape elongation. In the final stage, we optimize the instance shape deformation field to allow the model to capture the fine-grained geometric details of individual instances, with the discriminator disabled, as it may corrupt the shape if overused." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.634, + 0.679, + 0.65 + ], + "angle": 0, + "content": "4. Dataset Collection" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.66, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In order to train this pan-category model for all types of quadruped animals, we create a new animal image dataset, dubbed the Fauna Dataset, spanning 128 quadruped species from dogs, antelopes to minks and platypuses, with a total of 78,168 images. We first aggregate the training sets of existing animal image datasets, including Animals-with-Attributes [61], APT-36K [69], Animal3D [62] and DOVE [59]. Many of these images are blurry or contain heavy occlusions, which will impact the stability of the training. We thus filter the images using automatic scripts first, followed by manual inspection. This results in 8,378 images covering approximately 70 animal species. To further increase the size as well as the diversity of the dataset, we additionally collect 69,790 images from the Internet, including 63,115 video frames and 2,358 images for 7 common animals (bear, cow, elephant, giraffe, horse, sheep, ze" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9756" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.244 + ], + "angle": 0, + "content": "bra) as well as 4,317 images for another 51 less common species. We use off-the-shelf segmentation models [26, 27] to detect and segment the instances in the images. Out of the 121 few-shot categories, we hold out 5 as novel categories unused at training. For validation, we randomly select 5 images in each of the rest 116 few-shot categories, and 2,462 images for the 7 common species. To reduce the viewpoint bias in the few-shot categories, we manually identify a few (1-10) backward-facing instances in the training set and duplicate them to match the size of the rest." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.257, + 0.21, + 0.274 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.282, + 0.245, + 0.297 + ], + "angle": 0, + "content": "5.1. Technical Details" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.305, + 0.471, + 0.442 + ], + "angle": 0, + "content": "We base our architecture on MagicPony [60], adding the new SBSM and mask discriminator. For the Semantic Bank, we use \\( K = 60 \\) key-value pairs. The dimension of keys is 384 (same as DINO-ViT) and the dimension of values is 128. As the texture network tends to struggle to predict detailed appearance in one go, partially due to limited capacity, for all the visualizations, we follow [60] and fine-tune (only) the texture network for 50 iterations, which takes \\( < 10 \\) seconds. Refer to the sup. mat. for further details." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.451, + 0.262, + 0.467 + ], + "angle": 0, + "content": "5.2. Qualitative Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.475, + 0.47, + 0.596 + ], + "angle": 0, + "content": "After training, 3D-Fauna takes in a single test image of any quadruped animal and produces an articulated and textured 3D mesh in a feed-forward manner, as visualized in Fig. 4. The model can reconstruct very different animals, such as antelopes, armadillos, and fishers, without requiring any category labels. All the input images in Fig. 4 have not been seen during training. In particular, the model also performs well on held-out categories, e.g. the wolf in the third row." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.606, + 0.348, + 0.621 + ], + "angle": 0, + "content": "5.3. Comparisons with Prior Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Baselines. To the best of our knowledge, ours is the first deformable model designed to handle \\(100+\\) quadruped species, learned purely from 2D Internet data. We carry out quantitative and qualitative comparisons to methods that are at least in principle applicable to this setting. The baseline is MagicPony [60], which however is category-specific (they first train on horses, and fine-tune on giraffes, cows and zebras). We also compare with two popular deformable models that can work in the wild, namely UMR [29] and A-CSM [28]. However, they require weakly-supervised part segmentations and shape templates, respectively. Other works, such as LASSIE [70] and its follow-ups [71, 72], optimize a deformable model on a small set of about 20 images covering a single animal category at a time. More recently, image-to-3D methods based on distilling 2D diffusion models and/or large 3D datasets [31] have also demonstrated plausible 3D reconstructions of animals from a single image. In contrast, our model predicts an articulated mesh" + }, + { + "type": "table", + "bbox": [ + 0.508, + 0.089, + 0.885, + 0.201 + ], + "angle": 0, + "content": "
PASCALAPT-36KAnimal3D
KT-PCK@0.1PCK@0.1PCK@0.1PCK@0.1
UMR [29]0.284---
A-CSM [28]0.3290.6870.6490.822
MagicPony [60]0.429-0.7560.867
Ours0.5390.7820.8410.901
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.211, + 0.892, + 0.268 + ], + "angle": 0, + "content": "Table 1. Quantitative Comparisons on PASCAL VOC [10], APT-36K [69] and Animal3D [62]. When compared to baselines including the competitive MagicPony [60], our method demonstrates significantly improved performance on all datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.284, + 0.892, + 0.376 + ], + "angle": 0, + "content": "from a single image within seconds. Although it is difficult to establish a fair numerical comparison given these different settings, in Sec. 5.3, we provide a side-by-side qualitative comparison against baselines [31, 70, 71]. We use the publicly released code [31, 60, 70, 71] and report numbers [28, 29] included in MagicPony [60]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.381, + 0.893, + 0.607 + ], + "angle": 0, + "content": "Quantitative Comparisons. We conduct quantitative evaluation across three different datasets, APT-36K [69], Animal3D [62], and PASCAL VOC [10], which contain images of various animals with 2D keypoint annotations. Following MagicPony [60], we first evaluate on horses in PASCAL VOC [10] using the widely used Keypoint Transfer metric [22, 28, 29]. We use the same protocol as in A-CSM [28] and randomly sample \\(20\\mathrm{k}\\) source-target image pairs. For each source image, we project the visible vertices of the predicted mesh onto the image and map each annotated 2D keypoint to its nearest vertex. We then project that vertex to the target image and check if it lies within a small distance (10% of image size) to the corresponding keypoint in the target image. We summarize the results using the Percentage of Correct Keypoints (KT-PCK@0.1) in Tab. 1." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.608, + 0.892, + 0.714 + ], + "angle": 0, + "content": "In Tab. 1, we follow CMR [22] to evaluate the three datasets on more species, optimizing a linear mapping from mesh vertices to desired keypoints for each category, and reporting PCK@0.1 between the predicted and annotated 2D keypoints. Our model demonstrates significant improvement over existing methods on all datasets. A performance breakdown for each category is provided in the sup. mat." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Qualitative Comparisons. Figure 5 compares 3D-Fauna qualitatively to several recent works [31, 60, 70, 71]. To establish a fair comparison with MagicPony [60], for categories demonstrated in their paper (e.g. horse), we simply run inference using the released model. For each of the other categories, we use their public code to train a per-category model on our dataset from scratch (which contains less than 100 images for some rare categories). For LASSIE [70] and Hi-LASSIE [71], which optimize over a small set of images, we train their models on the test image together with additional 29 images randomly selected from the training set of that category. Hi-LASSIE [71] is further" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9757" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.086, + 0.093, + 0.891, + 0.888 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.898, + 0.893, + 0.927 + ], + "angle": 0, + "content": "Figure 4. Single Image 3D Reconstruction. Given a single image of any quadruped animal at test time, our model reconstructs an articulated and textured 3D mesh in a feed-forward manner without requiring category labels, which can be readily animated." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.515, + 0.957 + ], + "angle": 0, + "content": "9758" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.142, + 0.142 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.145, + 0.142, + 0.189 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.191, + 0.142, + 0.238 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.08, + 0.24, + 0.144, + 0.25 + ], + "angle": 0, + "content": "Input Image" + }, + { + "type": "image", + "bbox": [ + 0.153, + 0.089, + 0.29, + 0.251 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.309, + 0.089, + 0.451, + 0.251 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.453, + 0.089, + 0.592, + 0.251 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.604, + 0.089, + 0.737, + 0.251 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.749, + 0.089, + 0.88, + 0.251 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.255, + 0.894, + 0.297 + ], + "angle": 0, + "content": "Figure 5. Qualitative Comparisons against MagicPony [60], LASSIE [70], Hi-LASSIE [71] and Zero-1-to-3 [31]. Compared to all baselines, our method predicts more stable poses and higher-fidelity reconstructions. Note that our method is learning-based and predicts 3D meshes in a feed-forward fashion (as opposed to [70, 71] that optimize on test images), which is orders of magnitude faster." + }, + { + "type": "image", + "bbox": [ + 0.078, + 0.31, + 0.305, + 0.546 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.31, + 0.31, + 0.462, + 0.546 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.549, + 0.47, + 0.577 + ], + "angle": 0, + "content": "Figure 6. Ablation Studies. Both the Semantic Bank and the mask discriminator improve the results as discussed in Sec. 5.4." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.595, + 0.47, + 0.7 + ], + "angle": 0, + "content": "fine-tuned on the test image after training. To compare with Zero-1-to-3 [31], we use the implementation in threestudio [16] to first distill a NeRF [36] using Score Distillation Sampling [40] given the masked test image, and then extract a 3D mesh for fair comparison. Note that our model predicts 3D meshes within seconds, whereas the optimization takes at least 10–20 mins for the other methods [31, 70, 71]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.705, + 0.471, + 0.903 + ], + "angle": 0, + "content": "As shown in Fig. 5, MagicPony is sensitive to the size of the training set. When trained on rare categories with fewer (< 100) images, such as the puma in Fig. 5, it fails to learn meaningful shapes and produces severe artifacts. Despite optimizing on the test images, LASSIE and Hi-LASSIE produce coarser reconstructions, partially due to the part-based representation that struggles in capturing the detailed geometry and articulation, as well as unstable viewpoint prediction. Zero-1-to-3, on the other hand, often fails to correctly reconstruct the legs, and does not explicitly model the articulated pose. On the contrary, our method predicts accurate viewpoint and reconstructs fine-grained articulated shapes for all different animals, with only one single model." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.314, + 0.654, + 0.331 + ], + "angle": 0, + "content": "5.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.343, + 0.895, + 0.541 + ], + "angle": 0, + "content": "In Fig. 6, we present ablation results on three key design choices in our pipeline: SBSM, category-agnostic training, and mask discriminator. If we remove the SBSM and directly condition the base shape network on each individual image embedding \\(\\phi\\), the model tends to overfit each training views without learning meaningful canonical 3D shapes and pose. Alternatively, we can simply condition the base shape on an explicit (learned) category-specific embedding and train the model in a category-conditioned manner. This also leads to sub-optimal reconstructions, in particular on rare categories with few training images. Lastly, training without the mask discriminator results in biased viewpoint prediction (towards frontal) and produces elongated shapes." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.571, + 0.628, + 0.587 + ], + "angle": 0, + "content": "6. Conclusions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.602, + 0.894, + 0.768 + ], + "angle": 0, + "content": "We have presented 3D-Fauna, a deformable model for 100 animal categories learned using only Internet images. 3D-Fauna can reconstruct any quadruped image by instantiating in seconds a posed version of the deformable model to match the input image. Despite capable of modeling diverse animals, the current model is still limited to quadruped species that share a same skeletal structure. Furthermore, the training images still need to be lightly curated. Nevertheless, 3D-Fauna still presents a significant leap compared to prior works and moves us closer to models that will be able to understand and reconstruct all animals in nature." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Acknowledgments. We thank Cristobal Eyzaguirre, Kyle Sargent, and Yunhao Ge for their insightful discussions and Chen Geng for proofreading. The work is in part supported by the Stanford Institute for Human-Centered AI (HAI), NSF RI #2211258, #2338203, ONR MURI N00014-22-1-2740, ONR YIP N00014-24-1-2117, the Samsung Global Research Outreach (GRO) program, Amazon, Google, and EPSRC VisualAI EP/T028572/1." + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "9759" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.157 + ], + "angle": 0, + "content": "[1] Kalyan Vasudev Alwala, Abhinav Gupta, and Shubham Tulsiani. Pre-train, self-train, distill: A simple recipe for supersizing 3d reconstruction. In CVPR, 2022. 2" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.159, + 0.47, + 0.186 + ], + "angle": 0, + "content": "[2] Mehmet Aygün and Oisin Mac Aodha. Saor: Single-view articulated object reconstruction. 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In CVPR, 2018. 2" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.47, + 0.744 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "9762" + } + ] +] \ No newline at end of file diff --git a/2024/Learning the 3D Fauna of the Web/dd8fb285-42f8-4fbe-a149-b011c10a95c3_origin.pdf b/2024/Learning the 3D Fauna of the Web/dd8fb285-42f8-4fbe-a149-b011c10a95c3_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..2f350f229e8e95ea0ab74ab1faf54371f8acc476 --- /dev/null +++ b/2024/Learning the 3D Fauna of the Web/dd8fb285-42f8-4fbe-a149-b011c10a95c3_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:56c512768292912610a8b993e16c3d862d9d4b097fd300bf3bfbf37253a55a20 +size 4332224 diff --git a/2024/Learning the 3D Fauna of the Web/full.md b/2024/Learning the 3D Fauna of the Web/full.md new file mode 100644 index 0000000000000000000000000000000000000000..8370349b45dd4af46e361c17fe087895debb8035 --- /dev/null +++ b/2024/Learning the 3D Fauna of the Web/full.md @@ -0,0 +1,288 @@ +# Learning the 3D Fauna of the Web + +Zizhang Li $^{1*}$ Dor Litvak $^{1,2*}$ Ruining Li $^{3}$ Yunzhi Zhang $^{1}$ Tomas Jakab $^{3}$ Christian Rupprecht $^{3}$ Shangzhe Wu $^{1\dagger}$ Andrea Vedaldi $^{3\dagger}$ Jiajun Wu $^{1\dagger}$ $^{1}$ Stanford University $^{2}$ UT Austin $^{3}$ University of Oxford kyleleey.github.io/3DFauna/ + +![](images/457c271b6b5797e3a41a710b320b6d74a78afc41469c18b25b1cf57c7b3fc298.jpg) +Figure 1. Learning Diverse 3D Animals from the Internet. Our method, 3D-Fauna, learns a pan-category deformable 3D model of more than 100 different animal species using only 2D Internet images as training data. At test time, the model can turn a single image of an quadruped instance into an articulated, textured 3D mesh in a feed-forward manner, ready for animation and rendering. + +# Abstract + +Learning 3D models of all animals in nature requires massively scaling up existing solutions. With this ultimate goal in mind, we develop 3D-Fauna, an approach that learns a pan-category deformable 3D animal model for more than 100 animal species jointly. One crucial bottleneck of modeling animals is the limited availability of training data, which we overcome by learning our model from 2D Internet images. We show that prior approaches, which are category-specific, fail to generalize to rare species with limited training images. We address this challenge by introducing the Semantic Bank of Skinned Models (SBSM), which automatically discovers a small set of base animal shapes by combining geometric inductive priors with semantic knowledge implicitly captured by an off-the-shelf self-supervised feature extractor. To train such a model, we also contribute a new large-scale dataset of diverse animal species. At inference time, given a single image of any quadruped animal, our model reconstructs an articulated 3D mesh in a feed-forward manner in seconds. + +# 1. Introduction + +Computer vision models can nowadays reconstruct humans in monocular images and videos robustly and accurately, re + +covering their 3D shape, articulated pose, and even appearance [3, 11, 12, 14, 21, 34]. However, humans are but a tiny fraction of the animals that exist in nature, and 3D models remain essentially blind to the vast majority of biodiversity. + +While in principle the same approaches that work for humans could work for many other animal species, in practice scaling it to each of the 2.1 million different animal species on Earth is nearly hopeless. In fact, building a human model such as SMPL [34] and a corresponding pose predictor [3, 14] requires collecting 3D scans of many people in laboratory [21], crafting a corresponding articulated deformable model semi-automatically, and collecting extensive manual labels to train corresponding pose regressors. Of all animals, only humans are currently of sufficient importance in applications to justify the costs. + +A technically harder but much more practical approach is to learn animal models automatically from images and videos readily available on the Internet. Several authors have demonstrated that at least rough models can be learned from such uncontrolled image collections [22, 60, 70]. Even so, many limitations remain, starting from the fact that these methods can only reconstruct one or a few specific animal exemplars [70], or at most a single class of animals at a given time [22, 60]. The latter restriction is particularly glaring, as it defeats the purpose of using the Internet as a vast data source for modeling biodiversity. + +We introduce 3D-Fauna, a method that learns a pan + +category deformable model for a large number ( $>100$ ) of different quadruped animal species, such as dogs, antelopes, and hedgehogs, as shown in Fig. 1. For the approach to be as automated and thus as scalable as possible, we assume that only Internet images of the animals are provided as training data and only consider as prerequisites a pre-trained 2D object segmentation model and off-the-shelf unsupervised visual features. 3D-Fauna is designed as a feed-forward network that deforms and poses the deformable model to reconstruct any animal given a single image as input. The ability to perform monocular reconstruction is necessary for training on (single-view) Internet images, and is also useful in many real-world applications. + +Crucial to 3D-Fauna is to learn a single joint model of all animals in one go. Despite posing a challenge, modeling many animals jointly is essential for reconstructing rarer species, for which we often have only a small number of images to train on. This allows us to exploit the structural similarity of different animals that results from evolution, and maximize statistical efficiency. Here, we focus our attention on animals that share a given body plan, in particular, quadrupeds, and share the structure of the underlying skeletal model, which would otherwise be difficult to pin down. + +Learning such a model from only unlabeled single-view images requires several technical innovations. The most important is to develop a 3D representation that is sufficiently expressive to model the diverse shape variations of the animals, and at the same time tight enough to be learned from single-view images without overfitting individual views. Prior work partly achieved this goal by using skinned models, which consider small shape variations around a base template followed by articulation [60]. We found that this approach does not provide sufficient inductive biases to learn diverse animal species from Internet images alone. Hence, we introduce the Semantic Bank of Skinned Models (SBSM), which uses off-the-shelf unsupervised features, such as DINO [5, 39], to hypothesize how different animals may relate semantically, and automatically learns a low-dimensional base shape bank. + +Lastly, Internet images, which are not captured with the purpose of 3D reconstruction in mind, are characterized by a strong photographer bias, skewing the viewpoint distribution to mostly frontal, which significantly hinders the stability of 3D shape learning. To mitigate this issue, 3D-Fauna further encourages the predicted shapes to look realistic from all viewpoints, by introducing an efficient mask discriminator that enforces the silhouettes rendered from a random viewpoint to stay within the distribution of the silhouettes of the real images. + +Combining these ideas, 3D-Fauna is an end-to-end framework that learns a pan-category model of 3D quadruped animals from online image collections. To train 3D-Fauna, we collected a large-scale animal dataset of over + +100 quadruped species, dubbed the Fauna Dataset, as part of the contribution. After training, the model can turn a single test image of any quadruped instance into a fully articulated 3D mesh in a feed-forward fashion, ready for animation and rendering. Extensive quantitative and qualitative comparisons demonstrate significant improvements over existing methods. Code and data will be released. + +# 2. Related Work + +Optimization-Based 3D Reconstruction of Animals. Due to the lack of explicit 3D data for the vast majority of animals, reconstruction has mostly relied on pre-defined shape models or multi-view images. Initially, efforts focus on fitting a parametric 3D shape model obtained from 3D scans, e.g., SMAL [74], to animal images using annotated 2D keypoints and segmentation masks, which is further extended to multi-view images [75]. Other works aim to optimize the 3D shape [6, 55, 65–67, 70–72] directly from image or video collections of a smaller scale using various forms of supervision in addition to masks, such as keypoints [6, 55], self-supervised semantic correspondences [70–72], optical flow [64–67], surface normals [67], category-specific template shapes [6, 55]. + +Learning 3D from Internet Images and Videos. Recently, authors have attempted to learn 3D priors from Internet images and videos at a larger scale [1, 13, 20, 22, 28, 29, 52, 57-60, 73], mostly focusing on a single category at a time. Reconstructing animals presents additional challenges due to their highly deformable nature, which often necessitates stronger supervisory signals for training, similar to the ones used in optimization-based methods. Some methods have, in particular, learned to model articulated animals, such as horses, from single-view image collections without any 3D supervision, adopting a hierarchical shape model that factorizes a category-specific prior shape from instance-specific shape deformation and articulation [20, 59, 60]. However, these models are trained in a category-specific manner and fail to generalize to less common animal species as shown in Sec. 5.3. + +Attempts to model diverse animal species again resort to pre-defined shape models, e.g., SMAL. Ruegg et al. [42, 43] model multiple dog breeds and regularize the learning process by encouraging intra-breed similarities using a triplet loss, which requires breed labels for training, in addition to keypoint annotations and template shape models. In contrast, our approach reconstructs a significantly broader set of animals and is trained in a category-agnostic fashion, without relying on existing 3D shape models or keypoints. Another related work [19] aims to learn a category-agnostic 3D shape regressor by exploiting pre-trained CLIP features and an off-the-shelf normal estimator, but does not model deformation and produces coarse shapes. Concurrent work + +![](images/5126da6a4c7222951b5a68079b11182256052dd89578f8895d3f39f45798f34e.jpg) +Figure 2. Training Pipeline. 3D-Fauna is trained using only single-view images from the Internet. Given each input image, it first extracts a feature vector $\phi$ using a pre-trained unsupervised image encoder [5]. This is then used to query a learned memory bank to produce a base shape and a DINO feature field in the canonical pose. The model also predicts the albedo, instance-specific deformation, articulated pose and lighting, and is trained via image reconstruction losses on RGB, DINO feature map and mask, as well as a mask discriminator loss. + +SAOR [2] also trains one model to reconstruct diverse animal categories, but obtains less realistic results and tends to suffer from strong photographer bias. + +Another line of research attempts to distill 3D reconstructions from 2D generative models trained on large-scale datasets of Internet images, which can be GAN-based [7, 8, 15, 38] or more recently, diffusion-based models [9, 18, 35, 47] using Score Distillation Sampling [40] and its variants. This idea has been extended to learn image-conditional multi-view generator networks [25, 30-33, 41, 45, 48, 49, 56, 63, 68]. However, most of these methods optimize one single shape at a time, whereas our model learns a pan-category deformable model that can reconstruct any animal instance in a feed-forward fashion. + +Animal Datasets. Learning 3D models often requires high-quality images without blur or occlusion. Existing high-quality datasets were only collected for a small number of categories [46, 54, 59, 66], and more diverse datasets [37, 61, 62, 69] often contain many noisy images unsuitable for training off the shelf. To train our pan-category model for a wide range of quadruped animal species, we aggregate these existing datasets after substantial filtering, and additionally source more images from the Internet to create a large-scale object-centric image dataset spanning over 100 quadruped species, as detailed in Sec. 4. + +# 3. Method + +Our goal is to learn a deformable model of a large variety of different animals using only Internet images for supervision. Formally, we learn a function $f: I \mapsto O$ that maps any image $I \in \mathbb{R}^{3 \times H \times W}$ of an animal to a corresponding 3D reconstruction $O$ , capturing the animal's shape, deformation and appearance. + +3D reconstruction is greatly facilitated by using multiview data [17], but this is not available at scale, or at all, for most animals. Instead, we wish to reconstruct animals from weak single-view supervision obtained from the Internet. Compared to prior works [60, 70-72], which focused on reconstructing a single animal type at a time, here we target a large number of animal species at once, which is significantly more difficult. We show in the next section how solving this problem requires carefully exploiting the semantic similarities and geometric correspondences between different animals to regularize their 3D geometry. + +# 3.1. Semantic Bank of Skinned Models + +Given an image $I$ , consider the problem of estimating the 3D shape $(V,F)$ of the animal contained in it, where $V \in \mathbb{R}^{K \times 3}$ is a list of vertices of a 3D mesh with face connectivity given by triplets $F \subset \{1, \dots, K\}^3$ . While recovering a 3D shape from a single image is ill-posed, as we train the model $f$ on a large dataset, we can ultimately observe animals from a variety of viewpoints. However, different images show different animals with different 3D shapes. Non-Rigid Structure-from-Motion [4, 50, 51] shows that reconstruction is still possible, but only if one makes the space of possible 3D shapes sufficiently tight to remove the reconstruction ambiguity. At the same time, the space must be sufficiently expressive to capture all animals. + +Skinned Models (SM). Following SMPL [34], many works [20, 59, 60, 67] have adopted a Skinned Model (SM) to model the shape of deformable objects when learning from single-view image collections or videos. An SM starts from a base shape $V_{\mathrm{base}}$ of the object (e.g., human or animal) at 'rest', applies as a small deformation $V_{\mathrm{ins}} = f_{\mathrm{ins}}(V_{\mathrm{base}}, \phi)$ to capture instance-specific details, and then applies a larger + +![](images/ed6ffaf1a90507c82d1af6116314d266fec7d04a00bdaacfe3fb31f35792bee8.jpg) +Figure 3. Queries from the Semantic Base Shape Bank. Without requiring any category labels, the Semantic Bank (Sec 3.1) automatically learns diverse base shapes for various animals and preserves the semantic similarities across different instances. + +deformation via a skinning function $V = f_{\mathrm{pose}}(V_{\mathrm{ins}}, \phi)$ , controlled by the articulation of the underlying skeleton. We assume that deformations are predicted by neural networks that receive as input image features $\phi = f_{\phi}(I)$ extracted from a powerful self-supervised image encoder. + +In our case, a single SM is insufficient to capture the very large shape variations between different animals, which include horses, dogs, antelopes, hedgehogs, etc. Naively attempting to capture this diversity using the network $f_{\mathrm{ins}}$ means that the resulting deformations cannot be small any longer, which throws off the tightness of the model. + +Semantic Bank of Skinned Models. In order to increase the expressiveness of the model while still avoiding overfitting individual images, we propose to exploit the fact that different animals often have similar 3D shapes as a result of evolution. We can thus reduce the shape variation to a small number of shape bases $V_{\mathrm{base}}$ , and interpolate between them. + +To do so, we introduce a Semantic Bank of Skinned Models that automatically discovers a set of latent shape bases and learns to project each image into a linear combination of these bases. Key to this method is to use pre-trained unsupervised image features [5, 39] to automatically and implicitly identify similar animals. This is realized by means of a small memory bank with $K$ learned key-value pairs $\{(\phi_k^{\mathrm{key}},\phi_k^{\mathrm{val}})\}_{k = 1}^{K}$ . Specifically, given an image embedding $\phi$ , we query the memory bank to obtain a latent shape embedding $\tilde{\phi}$ as a linear combination of the value tokens $\{\phi_k^{\mathrm{val}}\}$ via a mechanism similar to attention [53]: + +$$ +\tilde {\phi} = \sum_ {k = 1} ^ {K} w _ {k} \phi_ {k} ^ {\text {v a l}}, \text {w h e r e} w _ {k} = \frac {\operatorname {c o s s i m} \left(\phi , \phi_ {k} ^ {\text {k e y}}\right)}{\sum_ {j = 1} ^ {K} \operatorname {c o s s i m} \left(\phi , \phi_ {j} ^ {\text {k e y}}\right)}, \tag {1} +$$ + +and cossim denotes cosine similarity between two feature vectors. This embedding $\tilde{\phi}$ is then used as a condition to the + +base shape predictor $(V_{\mathrm{base}},F) = f_{\mathrm{s}}(\tilde{\phi})$ , which produces semantically-adaptive base shapes without relying on any category labels or being bound to a hard categorization. + +In practice, the image features $\phi$ are obtained from a well-trained feature extractor like DINO-ViT [5, 39]. Defining the weights based on the cosine similarities between the image features $\phi$ and a small number of bases $\{\phi_k^{\mathrm{key}}\}$ captures the semantic similarities across different animal instances. For instance, as illustrated in Fig. 3, the cosine similarity between the image features of a zebra and a horse is 0.42, whereas the similarity between a zebra and an arctic fox is only 0.06. Ablations in Fig. 6 further verify the importance of this Semantic Bank, without which the model easily overfits each training image and fails to reconstruct plausible 3D shapes. + +Implementation Details. The base shape is predicted using a hybrid SDF-mesh representation [44, 60] parameterized by a coordinate MLP, with a conditioning vector $\tilde{\phi}$ injected via layer weight modulation [23, 24]. Since extracting meshes from SDFs using DMTet [44] is memory and compute intensive, in practice, we only compute it once for each iteration, by assuming the batched images contain the same animal species, and simply averaging out the embeddings $\tilde{\phi}$ . The instance-specific deformation is predicted using another coordinate MLP that outputs the displacement $\Delta V_{\mathrm{ins},i} = f_{\Delta V}(V_{\mathrm{base},i},\phi)$ for each vertex $V_{\mathrm{base},i}$ of the base mesh conditioned on the image feature $\phi$ , resulting in the deformed shape $V_{\mathrm{ins}} = \Delta V_{\mathrm{ins}} + V_{\mathrm{base}}$ . We enforce a bilateral symmetry on both the base shape and the instance deformation by mirroring the query locations for the MLPs. Given the instance mesh $V_{\mathrm{ins}}$ , we initialize a quadrupedal skeleton using a simple heuristic [60], and predict the rigid pose $\xi_1 \in SE(3)$ and bone rotations $\xi_b \in SO(3), b = 2,\dots,B$ using a pose network. These posing parameters are then applied to the instance mesh via a linear blend skinning equation [34]. Refer to the sup. mat. for more details. + +Appearance. Assuming a Lambertian illumination model, we model the appearance of the object using an albedo field $a(\pmb{x}) = f_{\mathrm{a}}(\pmb{x}, \phi) \in [0,1]^3$ and a dominant directional light. The final shaded color of each pixel is computed as $\hat{I}(\pmb{u}) = (k_a + k_d \cdot \max\{0, \langle \pmb{l}, \pmb{n} \rangle\}) \cdot a(\pmb{x})$ , where $\pmb{n}$ is the normal direction of the posed mesh at pixel $\pmb{u}$ , and $k_a, k_d \in [0,1]$ and $\pmb{l} \in \mathbb{S}^2$ are respectively the ambient intensity, diffuse intensity and dominant light direction predicted by the lighting network ( $k_a, k_d, l = f_1(\phi)$ ). + +# 3.2. Learning Formulation + +The entire pipeline is trained in an unsupervised fashion, using only self-supervised image features [5, 39] and object masks obtained from off-the-shelf segmenters [26, 27]. + +Reconstruction Losses. Given the final predicted posed shape $V$ and appearance of the object, we use a differen + +tiable renderer $\mathcal{R}$ to obtain an RGB image $\hat{I}$ as well as a mask image $\hat{M}$ , which are compared to the input image $I$ and the pseudo-ground-truth object mask $M$ : + +$$ +\mathcal {L} _ {\mathrm {m}} = \left\| \hat {M} - M \right\| _ {2} ^ {2} + \lambda_ {\mathrm {d t}} \left\| \hat {M} \odot \mathrm {d t} (M) \right\| _ {1}, \tag {2} +$$ + +$$ +\mathcal {L} _ {\mathrm {i m}} = \| \tilde {M} \odot (\hat {I} - I) \| _ {1}, \tag {3} +$$ + +where $\mathrm{dt}(\cdot)$ is distance transform for more effective gradients [22, 58], $\odot$ denotes the Hadamard product, $\lambda_{\mathrm{dt}}$ specifies the balancing weight, and $\hat{M} = \hat{M}\odot M$ is the intersection of the predicted and ground-truth masks. + +Correspondences from Self-Supervised Features. Self-supervised feature extractors are notoriously good at establishing semantic correspondences between objects, which can be distilled to facilitate 3D reconstruction [60]. To do so, we extract a patch-based feature map $\Phi \in \mathbb{R}^{D\times H\times W}$ from each training image. These raw feature maps can be noisy and may preserve image-specific information irrelevant to other images. To distill more effective semantic correspondences across different images, we perform a Principal Component Analysis (PCA) across all feature maps [60], reducing the dimension to $D^{\prime} = 16$ . We then task the model to also learn a feature field in the canonical frame $\psi (\pmb {x},\tilde{\phi})\in \mathbb{R}^{D^{\prime}}$ that is rendered into a feature image $\hat{\Phi}$ given predicted posed shape using the same renderer $\mathcal{R}$ . Training then encourages the rendered feature images $\hat{\Phi}$ to match the pre-extracted PCA features $\Phi^{\prime}$ : $\mathcal{L}_{\mathrm{feat}} = \| \tilde{M}\odot (\hat{\Phi} -\Phi^{\prime})\|_{2}^{2}$ . Note that although the space of the PCA features $\Phi^{\prime}$ is shared across different animal instances, the feature field $\psi$ still receives the latent embedding $\tilde{\phi}$ as a condition. This is because different animals vary in shape, resulting in different feature fields. + +Mask Discriminator. In practice, despite exploiting these semantic correspondences, we still find that the viewpoint prediction may easily collapse to only frontal viewpoints, due to the heavy photographer bias in Internet photos. This can lead to overly elongated shapes as shown in Fig. 6, and further deteriorates the viewpoint predictions. To mitigate this, we further encourage the shape to look realistic from arbitrary viewpoints. Specifically, we introduce a mask discriminator $D$ that encourages the mask images $\hat{M}_{\mathrm{rv}}$ rendered from a random viewpoint to stay within the distribution of the ground-truth masks $\mathcal{M}$ . The discriminator also receives the base embedding $\tilde{\phi}$ (with gradients detached) as a condition to make this adversarial guidance tailored to specific types of animals and thus more effective. Formally, this is achieved via an adversarial loss [15]: + +$$ +\begin{array}{l} \mathcal {L} _ {\mathrm {a d v}} = \mathbb {E} _ {M \sim \mathcal {M}} [ \log D (M; \tilde {\phi}) ] \\ + \mathbb {E} _ {\hat {M} _ {\mathrm {r v}} \sim \mathcal {M} _ {\mathrm {r v}}} [ \log (1 - D (\hat {M} _ {\mathrm {r v}}; \tilde {\phi})) ]. \tag {4} \\ \end{array} +$$ + +Note that we do not use a discriminator on the rendered RGB images, as the predicted texture is often much less re + +alistic when compared to real images, which gives the discriminator a trivial task. Moreover, the distribution of mask images is less susceptible to viewpoint bias than RGB images, and hence we can simply sample random viewpoints uniformly, without requiring a precise viewpoint distribution of the training images. + +Overall Loss. We further enforce the Eikonal constraint $\mathcal{R}_{\mathrm{Eik}}$ on the SDF network as well as the viewpoint hypothesis loss $\mathcal{L}_{\mathrm{hyp}}$ and the magnitude regularizers $\mathcal{R}_{\mathrm{def}}$ on vertex deformations and $\mathcal{R}_{\mathrm{art}}$ on articulation parameters $\xi$ . See the supplementary materials for details. + +The final training objective $\mathcal{L}$ is thus + +$$ +\mathcal {L} = \mathcal {L} _ {\text {r e c}} + \lambda_ {\text {h y p}} \mathcal {L} _ {\text {h y p}} + \lambda_ {\text {a d v}} \mathcal {L} _ {\text {a d v}} + \mathcal {R}, \tag {5} +$$ + +where $\mathcal{L}_{\mathrm{rec}} = \lambda_{\mathrm{m}}\mathcal{L}_{\mathrm{m}} + \lambda_{\mathrm{im}}\mathcal{L}_{\mathrm{im}} + \lambda_{\mathrm{feat}}\mathcal{L}_{\mathrm{feat}}$ summarizes the three reconstruction losses, $\mathcal{R} = \lambda_{\mathrm{Eik}}\mathcal{R}_{\mathrm{Eik}} + \lambda_{\mathrm{art}}\mathcal{R}_{\mathrm{art}} + \lambda_{\mathrm{def}}\mathcal{R}_{\mathrm{def}}$ summarizes the regularizers, and $\lambda$ 's balance the contribution of each term. + +Training Schedule. We design a robust training schedule that comprises three stages. First, we train the base shapes and the viewpoint network without articulation or deformation. This significantly improves the stability of the training and allows the model to roughly register the rigid pose of all instances and learn the coarse base shapes. + +As the viewpoint prediction stabilizes after 20k iterations, in the second stage, we instantiate the bones and enable the articulation, allowing the shapes to gradually grow legs and fit the articulated pose in each image. Meanwhile, we also turn on the mask discriminator to prevent viewpoint collapse and shape elongation. In the final stage, we optimize the instance shape deformation field to allow the model to capture the fine-grained geometric details of individual instances, with the discriminator disabled, as it may corrupt the shape if overused. + +# 4. Dataset Collection + +In order to train this pan-category model for all types of quadruped animals, we create a new animal image dataset, dubbed the Fauna Dataset, spanning 128 quadruped species from dogs, antelopes to minks and platypuses, with a total of 78,168 images. We first aggregate the training sets of existing animal image datasets, including Animals-with-Attributes [61], APT-36K [69], Animal3D [62] and DOVE [59]. Many of these images are blurry or contain heavy occlusions, which will impact the stability of the training. We thus filter the images using automatic scripts first, followed by manual inspection. This results in 8,378 images covering approximately 70 animal species. To further increase the size as well as the diversity of the dataset, we additionally collect 69,790 images from the Internet, including 63,115 video frames and 2,358 images for 7 common animals (bear, cow, elephant, giraffe, horse, sheep, ze + +bra) as well as 4,317 images for another 51 less common species. We use off-the-shelf segmentation models [26, 27] to detect and segment the instances in the images. Out of the 121 few-shot categories, we hold out 5 as novel categories unused at training. For validation, we randomly select 5 images in each of the rest 116 few-shot categories, and 2,462 images for the 7 common species. To reduce the viewpoint bias in the few-shot categories, we manually identify a few (1-10) backward-facing instances in the training set and duplicate them to match the size of the rest. + +# 5. Experiments + +# 5.1. Technical Details + +We base our architecture on MagicPony [60], adding the new SBSM and mask discriminator. For the Semantic Bank, we use $K = 60$ key-value pairs. The dimension of keys is 384 (same as DINO-ViT) and the dimension of values is 128. As the texture network tends to struggle to predict detailed appearance in one go, partially due to limited capacity, for all the visualizations, we follow [60] and fine-tune (only) the texture network for 50 iterations, which takes $< 10$ seconds. Refer to the sup. mat. for further details. + +# 5.2. Qualitative Results + +After training, 3D-Fauna takes in a single test image of any quadruped animal and produces an articulated and textured 3D mesh in a feed-forward manner, as visualized in Fig. 4. The model can reconstruct very different animals, such as antelopes, armadillos, and fishers, without requiring any category labels. All the input images in Fig. 4 have not been seen during training. In particular, the model also performs well on held-out categories, e.g. the wolf in the third row. + +# 5.3. Comparisons with Prior Work + +Baselines. To the best of our knowledge, ours is the first deformable model designed to handle $100+$ quadruped species, learned purely from 2D Internet data. We carry out quantitative and qualitative comparisons to methods that are at least in principle applicable to this setting. The baseline is MagicPony [60], which however is category-specific (they first train on horses, and fine-tune on giraffes, cows and zebras). We also compare with two popular deformable models that can work in the wild, namely UMR [29] and A-CSM [28]. However, they require weakly-supervised part segmentations and shape templates, respectively. Other works, such as LASSIE [70] and its follow-ups [71, 72], optimize a deformable model on a small set of about 20 images covering a single animal category at a time. More recently, image-to-3D methods based on distilling 2D diffusion models and/or large 3D datasets [31] have also demonstrated plausible 3D reconstructions of animals from a single image. In contrast, our model predicts an articulated mesh + +
PASCALAPT-36KAnimal3D
KT-PCK@0.1PCK@0.1PCK@0.1PCK@0.1
UMR [29]0.284---
A-CSM [28]0.3290.6870.6490.822
MagicPony [60]0.429-0.7560.867
Ours0.5390.7820.8410.901
+ +Table 1. Quantitative Comparisons on PASCAL VOC [10], APT-36K [69] and Animal3D [62]. When compared to baselines including the competitive MagicPony [60], our method demonstrates significantly improved performance on all datasets. + +from a single image within seconds. Although it is difficult to establish a fair numerical comparison given these different settings, in Sec. 5.3, we provide a side-by-side qualitative comparison against baselines [31, 70, 71]. We use the publicly released code [31, 60, 70, 71] and report numbers [28, 29] included in MagicPony [60]. + +Quantitative Comparisons. We conduct quantitative evaluation across three different datasets, APT-36K [69], Animal3D [62], and PASCAL VOC [10], which contain images of various animals with 2D keypoint annotations. Following MagicPony [60], we first evaluate on horses in PASCAL VOC [10] using the widely used Keypoint Transfer metric [22, 28, 29]. We use the same protocol as in A-CSM [28] and randomly sample $20\mathrm{k}$ source-target image pairs. For each source image, we project the visible vertices of the predicted mesh onto the image and map each annotated 2D keypoint to its nearest vertex. We then project that vertex to the target image and check if it lies within a small distance (10% of image size) to the corresponding keypoint in the target image. We summarize the results using the Percentage of Correct Keypoints (KT-PCK@0.1) in Tab. 1. + +In Tab. 1, we follow CMR [22] to evaluate the three datasets on more species, optimizing a linear mapping from mesh vertices to desired keypoints for each category, and reporting PCK@0.1 between the predicted and annotated 2D keypoints. Our model demonstrates significant improvement over existing methods on all datasets. A performance breakdown for each category is provided in the sup. mat. + +Qualitative Comparisons. Figure 5 compares 3D-Fauna qualitatively to several recent works [31, 60, 70, 71]. To establish a fair comparison with MagicPony [60], for categories demonstrated in their paper (e.g. horse), we simply run inference using the released model. For each of the other categories, we use their public code to train a per-category model on our dataset from scratch (which contains less than 100 images for some rare categories). For LASSIE [70] and Hi-LASSIE [71], which optimize over a small set of images, we train their models on the test image together with additional 29 images randomly selected from the training set of that category. Hi-LASSIE [71] is further + +![](images/ebd128df2b235bd0d792ed3127c134e2cb156c99f56b99f343fee058fd0ab0f0.jpg) +Figure 4. Single Image 3D Reconstruction. Given a single image of any quadruped animal at test time, our model reconstructs an articulated and textured 3D mesh in a feed-forward manner without requiring category labels, which can be readily animated. + +![](images/dc079035b559e84447a2efa09b105ea341fcc84443c57014e05b870268d99b70.jpg) + +![](images/2cc8ecc9467a10e24ff5f017319df159568bb1908c8a2af76184faf7690c9074.jpg) + +![](images/6478139f613d6c8c6eea8ef370e50e868f491d0a8e99b51c47487e50d01d912a.jpg) +Input Image + +![](images/85dea26990b343a77431e954eaac01132f26924883b08ac3b2ab19550e6a05cc.jpg) +Figure 5. Qualitative Comparisons against MagicPony [60], LASSIE [70], Hi-LASSIE [71] and Zero-1-to-3 [31]. Compared to all baselines, our method predicts more stable poses and higher-fidelity reconstructions. Note that our method is learning-based and predicts 3D meshes in a feed-forward fashion (as opposed to [70, 71] that optimize on test images), which is orders of magnitude faster. + +![](images/cb354bbaedb4e99fe13dc5806843344a89c1181343f88a20afbf344aa7eaa0df.jpg) + +![](images/c9657a753f4cfdd11315712bf18a9876f637a4f956e586ce4d09acd70a8f7cef.jpg) + +![](images/b451aa3d7bffd0eb8a30f352790e3fe9eec9fcd00727e88d154e15318304076d.jpg) + +![](images/ecfa8944b0431e6fba68e66d33649cf0dea26c5197555448a0c9cbd559ed7b73.jpg) + +![](images/714643e383b4a6ca624f0205c9f3ff81bef4c22caa082d795c1fe1310022dd53.jpg) +Figure 6. Ablation Studies. Both the Semantic Bank and the mask discriminator improve the results as discussed in Sec. 5.4. + +![](images/3a9f29df8a99bba87e61b6e001a87a4103df08084aa06445b1144539885a4942.jpg) + +fine-tuned on the test image after training. To compare with Zero-1-to-3 [31], we use the implementation in threestudio [16] to first distill a NeRF [36] using Score Distillation Sampling [40] given the masked test image, and then extract a 3D mesh for fair comparison. Note that our model predicts 3D meshes within seconds, whereas the optimization takes at least 10–20 mins for the other methods [31, 70, 71]. + +As shown in Fig. 5, MagicPony is sensitive to the size of the training set. When trained on rare categories with fewer (< 100) images, such as the puma in Fig. 5, it fails to learn meaningful shapes and produces severe artifacts. Despite optimizing on the test images, LASSIE and Hi-LASSIE produce coarser reconstructions, partially due to the part-based representation that struggles in capturing the detailed geometry and articulation, as well as unstable viewpoint prediction. Zero-1-to-3, on the other hand, often fails to correctly reconstruct the legs, and does not explicitly model the articulated pose. On the contrary, our method predicts accurate viewpoint and reconstructs fine-grained articulated shapes for all different animals, with only one single model. + +# 5.4. Ablation Study + +In Fig. 6, we present ablation results on three key design choices in our pipeline: SBSM, category-agnostic training, and mask discriminator. If we remove the SBSM and directly condition the base shape network on each individual image embedding $\phi$ , the model tends to overfit each training views without learning meaningful canonical 3D shapes and pose. Alternatively, we can simply condition the base shape on an explicit (learned) category-specific embedding and train the model in a category-conditioned manner. This also leads to sub-optimal reconstructions, in particular on rare categories with few training images. Lastly, training without the mask discriminator results in biased viewpoint prediction (towards frontal) and produces elongated shapes. + +# 6. Conclusions + +We have presented 3D-Fauna, a deformable model for 100 animal categories learned using only Internet images. 3D-Fauna can reconstruct any quadruped image by instantiating in seconds a posed version of the deformable model to match the input image. Despite capable of modeling diverse animals, the current model is still limited to quadruped species that share a same skeletal structure. Furthermore, the training images still need to be lightly curated. Nevertheless, 3D-Fauna still presents a significant leap compared to prior works and moves us closer to models that will be able to understand and reconstruct all animals in nature. + +Acknowledgments. We thank Cristobal Eyzaguirre, Kyle Sargent, and Yunhao Ge for their insightful discussions and Chen Geng for proofreading. 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ViSER: Video-specific surface embeddings for articulated 3d shape reconstruction. In NeurIPS, 2021. 2 +[66] Gengshan Yang, Minh Vo, Neverova Natalia, Deva Ramanan, Vedaldi Andrea, and Joo Hanbyul. BANMo: Building animatable 3d neural models from many casual videos. In CVPR, 2022. 3 +[67] Gengshan Yang, Chaoyang Wang, N. Dinesh Reddy, and Deva Ramanan. Reconstructing animatable categories from videos. In CVPR, 2023. 2, 3 +[68] Jiayu Yang, Ziang Cheng, Yunfei Duan, Pan Ji, and Hongdong Li. Consistnet: Enforcing 3d consistency for multiview images diffusion. arXiv preprint arXiv:2310.10343, 2023. 3 +[69] Yuxiang Yang, Junjie Yang, Yufei Xu, Jing Zhang, Long Lan, and Dacheng Tao. Apt-36k: A large-scale benchmark for animal pose estimation and tracking. NeurIPS, 2022. 3, 5, 6 +[70] Chun-Han Yao, Wei-Chih Hung, Yuanzhen Li, Michael Rubinstein, Ming-Hsuan Yang, and Varun Jampani. Lassie: Learning articulated shapes from sparse image ensemble via 3d part discovery. NeurIPS, 2022. 1, 2, 3, 6, 8 +[71] Chun-Han Yao, Wei-Chih Hung, Yuanzhen Li, Michael Rubinstein, Ming-Hsuan Yang, and Varun Jampani. Hi-lassie: High-fidelity articulated shape and skeleton discovery from sparse image ensemble. In CVPR, 2023. 6, 8 +[72] Chun-Han Yao, Amit Raj, Wei-Chih Hung, Yuanzhen Li, Michael Rubinstein, Ming-Hsuan Yang, and Varun Jampani. Artic3d: Learning robust articulated 3d shapes from noisy web image collections. NeurIPS, 2023. 2, 3, 6 +[73] Yufei Ye, Shubham Tulsiani, and Abhinav Gupta. Shelf-supervised mesh prediction in the wild. In CVPR, 2021. 2 +[74] Silvia Zuffi, Angjoo Kanazawa, David W Jacobs, and Michael J Black. 3d menagerie: Modeling the 3d shape and pose of animals. In CVPR, 2017. 2 +[75] Silvia Zuffi, Angjoo Kanazawa, and Michael J Black. Lions and tigers and bears: Capturing non-rigid, 3d, articulated shape from images. 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Learning Diverse 3D Animals from the Internet. Our method, 3D-Fauna, learns a pan-category deformable 3D model of more than 100 different animal species using only 2D Internet images as training data. At test time, the model can turn a single image of an quadruped instance into an articulated, textured 3D mesh in a feed-forward manner, ready for animation and rendering." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 380, + 192, + 392 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 380, + 192, + 392 + ], + "spans": [ + { + "bbox": [ + 143, + 380, + 192, + 392 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 404, + 290, + 632 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 404, + 290, + 632 + ], + "spans": [ + { + "bbox": [ + 46, + 404, + 290, + 632 + ], + "type": "text", + "content": "Learning 3D models of all animals in nature requires massively scaling up existing solutions. With this ultimate goal in mind, we develop 3D-Fauna, an approach that learns a pan-category deformable 3D animal model for more than 100 animal species jointly. One crucial bottleneck of modeling animals is the limited availability of training data, which we overcome by learning our model from 2D Internet images. We show that prior approaches, which are category-specific, fail to generalize to rare species with limited training images. We address this challenge by introducing the Semantic Bank of Skinned Models (SBSM), which automatically discovers a small set of base animal shapes by combining geometric inductive priors with semantic knowledge implicitly captured by an off-the-shelf self-supervised feature extractor. To train such a model, we also contribute a new large-scale dataset of diverse animal species. At inference time, given a single image of any quadruped animal, our model reconstructs an articulated 3D mesh in a feed-forward manner in seconds." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 643, + 128, + 655 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 643, + 128, + 655 + ], + "spans": [ + { + "bbox": [ + 47, + 643, + 128, + 655 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 663, + 287, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 663, + 287, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 663, + 287, + 687 + ], + "type": "text", + "content": "Computer vision models can nowadays reconstruct humans in monocular images and videos robustly and accurately, re" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 380, + 545, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 380, + 545, + 430 + ], + "spans": [ + { + "bbox": [ + 306, + 380, + 545, + 430 + ], + "type": "text", + "content": "covering their 3D shape, articulated pose, and even appearance [3, 11, 12, 14, 21, 34]. However, humans are but a tiny fraction of the animals that exist in nature, and 3D models remain essentially blind to the vast majority of biodiversity." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 431, + 546, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 431, + 546, + 564 + ], + "spans": [ + { + "bbox": [ + 304, + 431, + 546, + 564 + ], + "type": "text", + "content": "While in principle the same approaches that work for humans could work for many other animal species, in practice scaling it to each of the 2.1 million different animal species on Earth is nearly hopeless. In fact, building a human model such as SMPL [34] and a corresponding pose predictor [3, 14] requires collecting 3D scans of many people in laboratory [21], crafting a corresponding articulated deformable model semi-automatically, and collecting extensive manual labels to train corresponding pose regressors. Of all animals, only humans are currently of sufficient importance in applications to justify the costs." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 567, + 547, + 699 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 567, + 547, + 699 + ], + "spans": [ + { + "bbox": [ + 304, + 567, + 547, + 699 + ], + "type": "text", + "content": "A technically harder but much more practical approach is to learn animal models automatically from images and videos readily available on the Internet. Several authors have demonstrated that at least rough models can be learned from such uncontrolled image collections [22, 60, 70]. Even so, many limitations remain, starting from the fact that these methods can only reconstruct one or a few specific animal exemplars [70], or at most a single class of animals at a given time [22, 60]. The latter restriction is particularly glaring, as it defeats the purpose of using the Internet as a vast data source for modeling biodiversity." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "content": "We introduce 3D-Fauna, a method that learns a pan" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 693, + 124, + 702 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 693, + 124, + 702 + ], + "spans": [ + { + "bbox": [ + 58, + 693, + 124, + 702 + ], + "type": "text", + "content": "*Equal contribution" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 59, + 703, + 112, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 112, + 713 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 112, + 713 + ], + "type": "text", + "content": "Equal advising" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9752" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": "category deformable model for a large number (" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": ">100" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": ") of different quadruped animal species, such as dogs, antelopes, and hedgehogs, as shown in Fig. 1. For the approach to be as automated and thus as scalable as possible, we assume that only Internet images of the animals are provided as training data and only consider as prerequisites a pre-trained 2D object segmentation model and off-the-shelf unsupervised visual features. 3D-Fauna is designed as a feed-forward network that deforms and poses the deformable model to reconstruct any animal given a single image as input. The ability to perform monocular reconstruction is necessary for training on (single-view) Internet images, and is also useful in many real-world applications." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 229, + 289, + 350 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 229, + 289, + 350 + ], + "spans": [ + { + "bbox": [ + 46, + 229, + 289, + 350 + ], + "type": "text", + "content": "Crucial to 3D-Fauna is to learn a single joint model of all animals in one go. Despite posing a challenge, modeling many animals jointly is essential for reconstructing rarer species, for which we often have only a small number of images to train on. This allows us to exploit the structural similarity of different animals that results from evolution, and maximize statistical efficiency. Here, we focus our attention on animals that share a given body plan, in particular, quadrupeds, and share the structure of the underlying skeletal model, which would otherwise be difficult to pin down." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 351, + 289, + 543 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 351, + 289, + 543 + ], + "spans": [ + { + "bbox": [ + 46, + 351, + 289, + 543 + ], + "type": "text", + "content": "Learning such a model from only unlabeled single-view images requires several technical innovations. The most important is to develop a 3D representation that is sufficiently expressive to model the diverse shape variations of the animals, and at the same time tight enough to be learned from single-view images without overfitting individual views. Prior work partly achieved this goal by using skinned models, which consider small shape variations around a base template followed by articulation [60]. We found that this approach does not provide sufficient inductive biases to learn diverse animal species from Internet images alone. Hence, we introduce the Semantic Bank of Skinned Models (SBSM), which uses off-the-shelf unsupervised features, such as DINO [5, 39], to hypothesize how different animals may relate semantically, and automatically learns a low-dimensional base shape bank." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 544, + 289, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 289, + 664 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 289, + 664 + ], + "type": "text", + "content": "Lastly, Internet images, which are not captured with the purpose of 3D reconstruction in mind, are characterized by a strong photographer bias, skewing the viewpoint distribution to mostly frontal, which significantly hinders the stability of 3D shape learning. To mitigate this issue, 3D-Fauna further encourages the predicted shapes to look realistic from all viewpoints, by introducing an efficient mask discriminator that enforces the silhouettes rendered from a random viewpoint to stay within the distribution of the silhouettes of the real images." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 665, + 288, + 715 + ], + "type": "text", + "content": "Combining these ideas, 3D-Fauna is an end-to-end framework that learns a pan-category model of 3D quadruped animals from online image collections. To train 3D-Fauna, we collected a large-scale animal dataset of over" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 157 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 157 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 157 + ], + "type": "text", + "content": "100 quadruped species, dubbed the Fauna Dataset, as part of the contribution. After training, the model can turn a single test image of any quadruped instance into a fully articulated 3D mesh in a feed-forward fashion, ready for animation and rendering. Extensive quantitative and qualitative comparisons demonstrate significant improvements over existing methods. Code and data will be released." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 171, + 392, + 183 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 171, + 392, + 183 + ], + "spans": [ + { + "bbox": [ + 306, + 171, + 392, + 183 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 191, + 547, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 191, + 547, + 361 + ], + "spans": [ + { + "bbox": [ + 304, + 191, + 547, + 361 + ], + "type": "text", + "content": "Optimization-Based 3D Reconstruction of Animals. Due to the lack of explicit 3D data for the vast majority of animals, reconstruction has mostly relied on pre-defined shape models or multi-view images. Initially, efforts focus on fitting a parametric 3D shape model obtained from 3D scans, e.g., SMAL [74], to animal images using annotated 2D keypoints and segmentation masks, which is further extended to multi-view images [75]. Other works aim to optimize the 3D shape [6, 55, 65–67, 70–72] directly from image or video collections of a smaller scale using various forms of supervision in addition to masks, such as keypoints [6, 55], self-supervised semantic correspondences [70–72], optical flow [64–67], surface normals [67], category-specific template shapes [6, 55]." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 365, + 547, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 365, + 547, + 556 + ], + "spans": [ + { + "bbox": [ + 304, + 365, + 547, + 556 + ], + "type": "text", + "content": "Learning 3D from Internet Images and Videos. Recently, authors have attempted to learn 3D priors from Internet images and videos at a larger scale [1, 13, 20, 22, 28, 29, 52, 57-60, 73], mostly focusing on a single category at a time. Reconstructing animals presents additional challenges due to their highly deformable nature, which often necessitates stronger supervisory signals for training, similar to the ones used in optimization-based methods. Some methods have, in particular, learned to model articulated animals, such as horses, from single-view image collections without any 3D supervision, adopting a hierarchical shape model that factorizes a category-specific prior shape from instance-specific shape deformation and articulation [20, 59, 60]. However, these models are trained in a category-specific manner and fail to generalize to less common animal species as shown in Sec. 5.3." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 558, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 548, + 715 + ], + "type": "text", + "content": "Attempts to model diverse animal species again resort to pre-defined shape models, e.g., SMAL. Ruegg et al. [42, 43] model multiple dog breeds and regularize the learning process by encouraging intra-breed similarities using a triplet loss, which requires breed labels for training, in addition to keypoint annotations and template shape models. In contrast, our approach reconstructs a significantly broader set of animals and is trained in a category-agnostic fashion, without relying on existing 3D shape models or keypoints. Another related work [19] aims to learn a category-agnostic 3D shape regressor by exploiting pre-trained CLIP features and an off-the-shelf normal estimator, but does not model deformation and produces coarse shapes. Concurrent work" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9753" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 71, + 545, + 247 + ], + "blocks": [ + { + "bbox": [ + 51, + 71, + 545, + 247 + ], + "lines": [ + { + "bbox": [ + 51, + 71, + 545, + 247 + ], + "spans": [ + { + "bbox": [ + 51, + 71, + 545, + 247 + ], + "type": "image", + "image_path": "5126da6a4c7222951b5a68079b11182256052dd89578f8895d3f39f45798f34e.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 250, + 546, + 297 + ], + "lines": [ + { + "bbox": [ + 46, + 250, + 546, + 297 + ], + "spans": [ + { + "bbox": [ + 46, + 250, + 546, + 297 + ], + "type": "text", + "content": "Figure 2. Training Pipeline. 3D-Fauna is trained using only single-view images from the Internet. Given each input image, it first extracts a feature vector " + }, + { + "bbox": [ + 46, + 250, + 546, + 297 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 250, + 546, + 297 + ], + "type": "text", + "content": " using a pre-trained unsupervised image encoder [5]. This is then used to query a learned memory bank to produce a base shape and a DINO feature field in the canonical pose. The model also predicts the albedo, instance-specific deformation, articulated pose and lighting, and is trained via image reconstruction losses on RGB, DINO feature map and mask, as well as a mask discriminator loss." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 308, + 287, + 344 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 308, + 287, + 344 + ], + "spans": [ + { + "bbox": [ + 46, + 308, + 287, + 344 + ], + "type": "text", + "content": "SAOR [2] also trains one model to reconstruct diverse animal categories, but obtains less realistic results and tends to suffer from strong photographer bias." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 344, + 288, + 475 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 344, + 288, + 475 + ], + "spans": [ + { + "bbox": [ + 46, + 344, + 288, + 475 + ], + "type": "text", + "content": "Another line of research attempts to distill 3D reconstructions from 2D generative models trained on large-scale datasets of Internet images, which can be GAN-based [7, 8, 15, 38] or more recently, diffusion-based models [9, 18, 35, 47] using Score Distillation Sampling [40] and its variants. This idea has been extended to learn image-conditional multi-view generator networks [25, 30-33, 41, 45, 48, 49, 56, 63, 68]. However, most of these methods optimize one single shape at a time, whereas our model learns a pan-category deformable model that can reconstruct any animal instance in a feed-forward fashion." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 480, + 287, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 480, + 287, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 480, + 287, + 613 + ], + "type": "text", + "content": "Animal Datasets. Learning 3D models often requires high-quality images without blur or occlusion. Existing high-quality datasets were only collected for a small number of categories [46, 54, 59, 66], and more diverse datasets [37, 61, 62, 69] often contain many noisy images unsuitable for training off the shelf. To train our pan-category model for a wide range of quadruped animal species, we aggregate these existing datasets after substantial filtering, and additionally source more images from the Internet to create a large-scale object-centric image dataset spanning over 100 quadruped species, as detailed in Sec. 4." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 621, + 103, + 633 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 621, + 103, + 633 + ], + "spans": [ + { + "bbox": [ + 47, + 621, + 103, + 633 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "type": "text", + "content": "Our goal is to learn a deformable model of a large variety of different animals using only Internet images for supervision. Formally, we learn a function " + }, + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "type": "inline_equation", + "content": "f: I \\mapsto O" + }, + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "type": "text", + "content": " that maps any image " + }, + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "type": "inline_equation", + "content": "I \\in \\mathbb{R}^{3 \\times H \\times W}" + }, + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "type": "text", + "content": " of an animal to a corresponding 3D reconstruction " + }, + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "type": "inline_equation", + "content": "O" + }, + { + "bbox": [ + 46, + 641, + 287, + 715 + ], + "type": "text", + "content": ", capturing the animal's shape, deformation and appearance." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 308, + 546, + 440 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 308, + 546, + 440 + ], + "spans": [ + { + "bbox": [ + 304, + 308, + 546, + 440 + ], + "type": "text", + "content": "3D reconstruction is greatly facilitated by using multiview data [17], but this is not available at scale, or at all, for most animals. Instead, we wish to reconstruct animals from weak single-view supervision obtained from the Internet. Compared to prior works [60, 70-72], which focused on reconstructing a single animal type at a time, here we target a large number of animal species at once, which is significantly more difficult. We show in the next section how solving this problem requires carefully exploiting the semantic similarities and geometric correspondences between different animals to regularize their 3D geometry." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 449, + 490, + 460 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 449, + 490, + 460 + ], + "spans": [ + { + "bbox": [ + 305, + 449, + 490, + 460 + ], + "type": "text", + "content": "3.1. Semantic Bank of Skinned Models" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "spans": [ + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "text", + "content": "Given an image " + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "text", + "content": ", consider the problem of estimating the 3D shape " + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "inline_equation", + "content": "(V,F)" + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "text", + "content": " of the animal contained in it, where " + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "inline_equation", + "content": "V \\in \\mathbb{R}^{K \\times 3}" + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "text", + "content": " is a list of vertices of a 3D mesh with face connectivity given by triplets " + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "inline_equation", + "content": "F \\subset \\{1, \\dots, K\\}^3" + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "text", + "content": ". While recovering a 3D shape from a single image is ill-posed, as we train the model " + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 304, + 468, + 546, + 624 + ], + "type": "text", + "content": " on a large dataset, we can ultimately observe animals from a variety of viewpoints. However, different images show different animals with different 3D shapes. Non-Rigid Structure-from-Motion [4, 50, 51] shows that reconstruction is still possible, but only if one makes the space of possible 3D shapes sufficiently tight to remove the reconstruction ambiguity. At the same time, the space must be sufficiently expressive to capture all animals." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": "Skinned Models (SM). Following SMPL [34], many works [20, 59, 60, 67] have adopted a Skinned Model (SM) to model the shape of deformable objects when learning from single-view image collections or videos. An SM starts from a base shape " + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "inline_equation", + "content": "V_{\\mathrm{base}}" + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": " of the object (e.g., human or animal) at 'rest', applies as a small deformation " + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "inline_equation", + "content": "V_{\\mathrm{ins}} = f_{\\mathrm{ins}}(V_{\\mathrm{base}}, \\phi)" + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": " to capture instance-specific details, and then applies a larger" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9754" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 72, + 68, + 265, + 235 + ], + "blocks": [ + { + "bbox": [ + 72, + 68, + 265, + 235 + ], + "lines": [ + { + "bbox": [ + 72, + 68, + 265, + 235 + ], + "spans": [ + { + "bbox": [ + 72, + 68, + 265, + 235 + ], + "type": "image", + "image_path": "ed6ffaf1a90507c82d1af6116314d266fec7d04a00bdaacfe3fb31f35792bee8.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 236, + 287, + 281 + ], + "lines": [ + { + "bbox": [ + 46, + 236, + 287, + 281 + ], + "spans": [ + { + "bbox": [ + 46, + 236, + 287, + 281 + ], + "type": "text", + "content": "Figure 3. Queries from the Semantic Base Shape Bank. Without requiring any category labels, the Semantic Bank (Sec 3.1) automatically learns diverse base shapes for various animals and preserves the semantic similarities across different instances." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 295, + 286, + 354 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 295, + 286, + 354 + ], + "spans": [ + { + "bbox": [ + 46, + 295, + 286, + 354 + ], + "type": "text", + "content": "deformation via a skinning function " + }, + { + "bbox": [ + 46, + 295, + 286, + 354 + ], + "type": "inline_equation", + "content": "V = f_{\\mathrm{pose}}(V_{\\mathrm{ins}}, \\phi)" + }, + { + "bbox": [ + 46, + 295, + 286, + 354 + ], + "type": "text", + "content": ", controlled by the articulation of the underlying skeleton. We assume that deformations are predicted by neural networks that receive as input image features " + }, + { + "bbox": [ + 46, + 295, + 286, + 354 + ], + "type": "inline_equation", + "content": "\\phi = f_{\\phi}(I)" + }, + { + "bbox": [ + 46, + 295, + 286, + 354 + ], + "type": "text", + "content": " extracted from a powerful self-supervised image encoder." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 356, + 286, + 428 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 356, + 286, + 428 + ], + "spans": [ + { + "bbox": [ + 46, + 356, + 286, + 428 + ], + "type": "text", + "content": "In our case, a single SM is insufficient to capture the very large shape variations between different animals, which include horses, dogs, antelopes, hedgehogs, etc. Naively attempting to capture this diversity using the network " + }, + { + "bbox": [ + 46, + 356, + 286, + 428 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{ins}}" + }, + { + "bbox": [ + 46, + 356, + 286, + 428 + ], + "type": "text", + "content": " means that the resulting deformations cannot be small any longer, which throws off the tightness of the model." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 433, + 286, + 505 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 433, + 286, + 505 + ], + "spans": [ + { + "bbox": [ + 46, + 433, + 286, + 505 + ], + "type": "text", + "content": "Semantic Bank of Skinned Models. In order to increase the expressiveness of the model while still avoiding overfitting individual images, we propose to exploit the fact that different animals often have similar 3D shapes as a result of evolution. We can thus reduce the shape variation to a small number of shape bases " + }, + { + "bbox": [ + 46, + 433, + 286, + 505 + ], + "type": "inline_equation", + "content": "V_{\\mathrm{base}}" + }, + { + "bbox": [ + 46, + 433, + 286, + 505 + ], + "type": "text", + "content": ", and interpolate between them." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "spans": [ + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "text", + "content": "To do so, we introduce a Semantic Bank of Skinned Models that automatically discovers a set of latent shape bases and learns to project each image into a linear combination of these bases. Key to this method is to use pre-trained unsupervised image features [5, 39] to automatically and implicitly identify similar animals. This is realized by means of a small memory bank with " + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "text", + "content": " learned key-value pairs " + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "inline_equation", + "content": "\\{(\\phi_k^{\\mathrm{key}},\\phi_k^{\\mathrm{val}})\\}_{k = 1}^{K}" + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "text", + "content": ". Specifically, given an image embedding " + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "text", + "content": ", we query the memory bank to obtain a latent shape embedding " + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "inline_equation", + "content": "\\tilde{\\phi}" + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "text", + "content": " as a linear combination of the value tokens " + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "inline_equation", + "content": "\\{\\phi_k^{\\mathrm{val}}\\}" + }, + { + "bbox": [ + 46, + 505, + 286, + 637 + ], + "type": "text", + "content": " via a mechanism similar to attention [53]:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 55, + 646, + 286, + 689 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 646, + 286, + 689 + ], + "spans": [ + { + "bbox": [ + 55, + 646, + 286, + 689 + ], + "type": "interline_equation", + "content": "\\tilde {\\phi} = \\sum_ {k = 1} ^ {K} w _ {k} \\phi_ {k} ^ {\\text {v a l}}, \\text {w h e r e} w _ {k} = \\frac {\\operatorname {c o s s i m} \\left(\\phi , \\phi_ {k} ^ {\\text {k e y}}\\right)}{\\sum_ {j = 1} ^ {K} \\operatorname {c o s s i m} \\left(\\phi , \\phi_ {j} ^ {\\text {k e y}}\\right)}, \\tag {1}", + "image_path": "3725af4174eea94bffb8117f7adf88760fe047009e3d1521c8cc1fe985307b36.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "type": "text", + "content": "and cossim denotes cosine similarity between two feature vectors. This embedding " + }, + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\tilde{\\phi}" + }, + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "type": "text", + "content": " is then used as a condition to the" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 71, + 545, + 108 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 71, + 545, + 108 + ], + "spans": [ + { + "bbox": [ + 305, + 71, + 545, + 108 + ], + "type": "text", + "content": "base shape predictor " + }, + { + "bbox": [ + 305, + 71, + 545, + 108 + ], + "type": "inline_equation", + "content": "(V_{\\mathrm{base}},F) = f_{\\mathrm{s}}(\\tilde{\\phi})" + }, + { + "bbox": [ + 305, + 71, + 545, + 108 + ], + "type": "text", + "content": " , which produces semantically-adaptive base shapes without relying on any category labels or being bound to a hard categorization." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "spans": [ + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "type": "text", + "content": "In practice, the image features " + }, + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "type": "text", + "content": " are obtained from a well-trained feature extractor like DINO-ViT [5, 39]. Defining the weights based on the cosine similarities between the image features " + }, + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "type": "text", + "content": " and a small number of bases " + }, + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "type": "inline_equation", + "content": "\\{\\phi_k^{\\mathrm{key}}\\}" + }, + { + "bbox": [ + 304, + 109, + 545, + 252 + ], + "type": "text", + "content": " captures the semantic similarities across different animal instances. For instance, as illustrated in Fig. 3, the cosine similarity between the image features of a zebra and a horse is 0.42, whereas the similarity between a zebra and an arctic fox is only 0.06. Ablations in Fig. 6 further verify the importance of this Semantic Bank, without which the model easily overfits each training image and fails to reconstruct plausible 3D shapes." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "spans": [ + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": "Implementation Details. The base shape is predicted using a hybrid SDF-mesh representation [44, 60] parameterized by a coordinate MLP, with a conditioning vector " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "\\tilde{\\phi}" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": " injected via layer weight modulation [23, 24]. Since extracting meshes from SDFs using DMTet [44] is memory and compute intensive, in practice, we only compute it once for each iteration, by assuming the batched images contain the same animal species, and simply averaging out the embeddings " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "\\tilde{\\phi}" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": ". The instance-specific deformation is predicted using another coordinate MLP that outputs the displacement " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "\\Delta V_{\\mathrm{ins},i} = f_{\\Delta V}(V_{\\mathrm{base},i},\\phi)" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": " for each vertex " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "V_{\\mathrm{base},i}" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": " of the base mesh conditioned on the image feature " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": ", resulting in the deformed shape " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "V_{\\mathrm{ins}} = \\Delta V_{\\mathrm{ins}} + V_{\\mathrm{base}}" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": ". We enforce a bilateral symmetry on both the base shape and the instance deformation by mirroring the query locations for the MLPs. Given the instance mesh " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "V_{\\mathrm{ins}}" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": ", we initialize a quadrupedal skeleton using a simple heuristic [60], and predict the rigid pose " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "\\xi_1 \\in SE(3)" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": " and bone rotations " + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "inline_equation", + "content": "\\xi_b \\in SO(3), b = 2,\\dots,B" + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": " using a pose network. These posing parameters are then applied to the instance mesh via a linear blend skinning equation [34]. Refer to the sup. mat. for more details." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "spans": [ + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "content": "Appearance. Assuming a Lambertian illumination model, we model the appearance of the object using an albedo field " + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "inline_equation", + "content": "a(\\pmb{x}) = f_{\\mathrm{a}}(\\pmb{x}, \\phi) \\in [0,1]^3" + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "content": " and a dominant directional light. The final shaded color of each pixel is computed as " + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "inline_equation", + "content": "\\hat{I}(\\pmb{u}) = (k_a + k_d \\cdot \\max\\{0, \\langle \\pmb{l}, \\pmb{n} \\rangle\\}) \\cdot a(\\pmb{x})" + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "inline_equation", + "content": "\\pmb{n}" + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "content": " is the normal direction of the posed mesh at pixel " + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "inline_equation", + "content": "\\pmb{u}" + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "inline_equation", + "content": "k_a, k_d \\in [0,1]" + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "inline_equation", + "content": "\\pmb{l} \\in \\mathbb{S}^2" + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "content": " are respectively the ambient intensity, diffuse intensity and dominant light direction predicted by the lighting network (" + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "inline_equation", + "content": "k_a, k_d, l = f_1(\\phi)" + }, + { + "bbox": [ + 304, + 514, + 545, + 622 + ], + "type": "text", + "content": ")." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 629, + 433, + 642 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 629, + 433, + 642 + ], + "spans": [ + { + "bbox": [ + 306, + 629, + 433, + 642 + ], + "type": "text", + "content": "3.2. Learning Formulation" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 647, + 545, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 647, + 545, + 685 + ], + "spans": [ + { + "bbox": [ + 304, + 647, + 545, + 685 + ], + "type": "text", + "content": "The entire pipeline is trained in an unsupervised fashion, using only self-supervised image features [5, 39] and object masks obtained from off-the-shelf segmenters [26, 27]." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "Reconstruction Losses. Given the final predicted posed shape " + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": " and appearance of the object, we use a differen" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9755" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "text", + "content": "tiable renderer " + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "inline_equation", + "content": "\\mathcal{R}" + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "text", + "content": " to obtain an RGB image " + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "inline_equation", + "content": "\\hat{I}" + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "text", + "content": " as well as a mask image " + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "inline_equation", + "content": "\\hat{M}" + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "text", + "content": ", which are compared to the input image " + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "text", + "content": " and the pseudo-ground-truth object mask " + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 47, + 72, + 289, + 109 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 81, + 114, + 287, + 129 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 81, + 114, + 287, + 129 + ], + "spans": [ + { + "bbox": [ + 81, + 114, + 287, + 129 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {m}} = \\left\\| \\hat {M} - M \\right\\| _ {2} ^ {2} + \\lambda_ {\\mathrm {d t}} \\left\\| \\hat {M} \\odot \\mathrm {d t} (M) \\right\\| _ {1}, \\tag {2}", + "image_path": "9e3b1ca26705ad1fd83f366e3173e33eb8c3e2c82baad88e2b9c950beb3945b6.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 81, + 131, + 287, + 146 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 81, + 131, + 287, + 146 + ], + "spans": [ + { + "bbox": [ + 81, + 131, + 287, + 146 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {i m}} = \\| \\tilde {M} \\odot (\\hat {I} - I) \\| _ {1}, \\tag {3}", + "image_path": "2444cd91df1fc861aea51c446de44efdce2c1d9f4b0cbcc66e751102587be7a8.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "spans": [ + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "inline_equation", + "content": "\\mathrm{dt}(\\cdot)" + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "text", + "content": " is distance transform for more effective gradients [22, 58], " + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "inline_equation", + "content": "\\odot" + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "text", + "content": " denotes the Hadamard product, " + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "inline_equation", + "content": "\\lambda_{\\mathrm{dt}}" + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "text", + "content": " specifies the balancing weight, and " + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "inline_equation", + "content": "\\hat{M} = \\hat{M}\\odot M" + }, + { + "bbox": [ + 47, + 152, + 287, + 201 + ], + "type": "text", + "content": " is the intersection of the predicted and ground-truth masks." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "spans": [ + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": "Correspondences from Self-Supervised Features. Self-supervised feature extractors are notoriously good at establishing semantic correspondences between objects, which can be distilled to facilitate 3D reconstruction [60]. To do so, we extract a patch-based feature map " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\Phi \\in \\mathbb{R}^{D\\times H\\times W}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": " from each training image. These raw feature maps can be noisy and may preserve image-specific information irrelevant to other images. To distill more effective semantic correspondences across different images, we perform a Principal Component Analysis (PCA) across all feature maps [60], reducing the dimension to " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "D^{\\prime} = 16" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": ". We then task the model to also learn a feature field in the canonical frame " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\psi (\\pmb {x},\\tilde{\\phi})\\in \\mathbb{R}^{D^{\\prime}}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": " that is rendered into a feature image " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\hat{\\Phi}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": " given predicted posed shape using the same renderer " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\mathcal{R}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": ". Training then encourages the rendered feature images " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\hat{\\Phi}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": " to match the pre-extracted PCA features " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\Phi^{\\prime}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": ": " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{feat}} = \\| \\tilde{M}\\odot (\\hat{\\Phi} -\\Phi^{\\prime})\\|_{2}^{2}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": ". Note that although the space of the PCA features " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\Phi^{\\prime}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": " is shared across different animal instances, the feature field " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\psi" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": " still receives the latent embedding " + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\tilde{\\phi}" + }, + { + "bbox": [ + 47, + 205, + 289, + 457 + ], + "type": "text", + "content": " as a condition. This is because different animals vary in shape, resulting in different feature fields." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "spans": [ + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "text", + "content": "Mask Discriminator. In practice, despite exploiting these semantic correspondences, we still find that the viewpoint prediction may easily collapse to only frontal viewpoints, due to the heavy photographer bias in Internet photos. This can lead to overly elongated shapes as shown in Fig. 6, and further deteriorates the viewpoint predictions. To mitigate this, we further encourage the shape to look realistic from arbitrary viewpoints. Specifically, we introduce a mask discriminator " + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "text", + "content": " that encourages the mask images " + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "inline_equation", + "content": "\\hat{M}_{\\mathrm{rv}}" + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "text", + "content": " rendered from a random viewpoint to stay within the distribution of the ground-truth masks " + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "inline_equation", + "content": "\\mathcal{M}" + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "text", + "content": ". The discriminator also receives the base embedding " + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "inline_equation", + "content": "\\tilde{\\phi}" + }, + { + "bbox": [ + 47, + 462, + 289, + 643 + ], + "type": "text", + "content": " (with gradients detached) as a condition to make this adversarial guidance tailored to specific types of animals and thus more effective. Formally, this is achieved via an adversarial loss [15]:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 56, + 650, + 287, + 685 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 56, + 650, + 287, + 685 + ], + "spans": [ + { + "bbox": [ + 56, + 650, + 287, + 685 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {\\mathrm {a d v}} = \\mathbb {E} _ {M \\sim \\mathcal {M}} [ \\log D (M; \\tilde {\\phi}) ] \\\\ + \\mathbb {E} _ {\\hat {M} _ {\\mathrm {r v}} \\sim \\mathcal {M} _ {\\mathrm {r v}}} [ \\log (1 - D (\\hat {M} _ {\\mathrm {r v}}; \\tilde {\\phi})) ]. \\tag {4} \\\\ \\end{array}", + "image_path": "687e3acf986939af2a89edbbcede6873294441da54eb1b4229157395aa882e70.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "Note that we do not use a discriminator on the rendered RGB images, as the predicted texture is often much less re" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": "alistic when compared to real images, which gives the discriminator a trivial task. Moreover, the distribution of mask images is less susceptible to viewpoint bias than RGB images, and hence we can simply sample random viewpoints uniformly, without requiring a precise viewpoint distribution of the training images." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "spans": [ + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "text", + "content": "Overall Loss. We further enforce the Eikonal constraint " + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "inline_equation", + "content": "\\mathcal{R}_{\\mathrm{Eik}}" + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "text", + "content": " on the SDF network as well as the viewpoint hypothesis loss " + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{hyp}}" + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "text", + "content": " and the magnitude regularizers " + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "inline_equation", + "content": "\\mathcal{R}_{\\mathrm{def}}" + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "text", + "content": " on vertex deformations and " + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "inline_equation", + "content": "\\mathcal{R}_{\\mathrm{art}}" + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "text", + "content": " on articulation parameters " + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "inline_equation", + "content": "\\xi" + }, + { + "bbox": [ + 304, + 148, + 545, + 209 + ], + "type": "text", + "content": ". See the supplementary materials for details." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 318, + 209, + 468, + 220 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 209, + 468, + 220 + ], + "spans": [ + { + "bbox": [ + 318, + 209, + 468, + 220 + ], + "type": "text", + "content": "The final training objective " + }, + { + "bbox": [ + 318, + 209, + 468, + 220 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 318, + 209, + 468, + 220 + ], + "type": "text", + "content": " is thus" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 348, + 228, + 545, + 242 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 228, + 545, + 242 + ], + "spans": [ + { + "bbox": [ + 348, + 228, + 545, + 242 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {\\text {r e c}} + \\lambda_ {\\text {h y p}} \\mathcal {L} _ {\\text {h y p}} + \\lambda_ {\\text {a d v}} \\mathcal {L} _ {\\text {a d v}} + \\mathcal {R}, \\tag {5}", + "image_path": "455ba836ed46e8b5c9486c678cfd7d804254c71fb8588f3260757836dc57d36d.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "spans": [ + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{rec}} = \\lambda_{\\mathrm{m}}\\mathcal{L}_{\\mathrm{m}} + \\lambda_{\\mathrm{im}}\\mathcal{L}_{\\mathrm{im}} + \\lambda_{\\mathrm{feat}}\\mathcal{L}_{\\mathrm{feat}}" + }, + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "type": "text", + "content": " summarizes the three reconstruction losses, " + }, + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "type": "inline_equation", + "content": "\\mathcal{R} = \\lambda_{\\mathrm{Eik}}\\mathcal{R}_{\\mathrm{Eik}} + \\lambda_{\\mathrm{art}}\\mathcal{R}_{\\mathrm{art}} + \\lambda_{\\mathrm{def}}\\mathcal{R}_{\\mathrm{def}}" + }, + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "type": "text", + "content": " summarizes the regularizers, and " + }, + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 304, + 248, + 545, + 295 + ], + "type": "text", + "content": " 's balance the contribution of each term." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "spans": [ + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "content": "Training Schedule. We design a robust training schedule that comprises three stages. First, we train the base shapes and the viewpoint network without articulation or deformation. This significantly improves the stability of the training and allows the model to roughly register the rigid pose of all instances and learn the coarse base shapes." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 373, + 545, + 492 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 373, + 545, + 492 + ], + "spans": [ + { + "bbox": [ + 304, + 373, + 545, + 492 + ], + "type": "text", + "content": "As the viewpoint prediction stabilizes after 20k iterations, in the second stage, we instantiate the bones and enable the articulation, allowing the shapes to gradually grow legs and fit the articulated pose in each image. Meanwhile, we also turn on the mask discriminator to prevent viewpoint collapse and shape elongation. In the final stage, we optimize the instance shape deformation field to allow the model to capture the fine-grained geometric details of individual instances, with the discriminator disabled, as it may corrupt the shape if overused." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 502, + 415, + 514 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 502, + 415, + 514 + ], + "spans": [ + { + "bbox": [ + 305, + 502, + 415, + 514 + ], + "type": "text", + "content": "4. Dataset Collection" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 522, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 522, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 522, + 545, + 713 + ], + "type": "text", + "content": "In order to train this pan-category model for all types of quadruped animals, we create a new animal image dataset, dubbed the Fauna Dataset, spanning 128 quadruped species from dogs, antelopes to minks and platypuses, with a total of 78,168 images. We first aggregate the training sets of existing animal image datasets, including Animals-with-Attributes [61], APT-36K [69], Animal3D [62] and DOVE [59]. Many of these images are blurry or contain heavy occlusions, which will impact the stability of the training. We thus filter the images using automatic scripts first, followed by manual inspection. This results in 8,378 images covering approximately 70 animal species. To further increase the size as well as the diversity of the dataset, we additionally collect 69,790 images from the Internet, including 63,115 video frames and 2,358 images for 7 common animals (bear, cow, elephant, giraffe, horse, sheep, ze" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9756" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 193 + ], + "type": "text", + "content": "bra) as well as 4,317 images for another 51 less common species. We use off-the-shelf segmentation models [26, 27] to detect and segment the instances in the images. Out of the 121 few-shot categories, we hold out 5 as novel categories unused at training. For validation, we randomly select 5 images in each of the rest 116 few-shot categories, and 2,462 images for the 7 common species. To reduce the viewpoint bias in the few-shot categories, we manually identify a few (1-10) backward-facing instances in the training set and duplicate them to match the size of the rest." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 203, + 128, + 217 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 203, + 128, + 217 + ], + "spans": [ + { + "bbox": [ + 47, + 203, + 128, + 217 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 223, + 149, + 235 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 223, + 149, + 235 + ], + "spans": [ + { + "bbox": [ + 47, + 223, + 149, + 235 + ], + "type": "text", + "content": "5.1. Technical Details" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 241, + 288, + 350 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 241, + 288, + 350 + ], + "spans": [ + { + "bbox": [ + 46, + 241, + 288, + 350 + ], + "type": "text", + "content": "We base our architecture on MagicPony [60], adding the new SBSM and mask discriminator. For the Semantic Bank, we use " + }, + { + "bbox": [ + 46, + 241, + 288, + 350 + ], + "type": "inline_equation", + "content": "K = 60" + }, + { + "bbox": [ + 46, + 241, + 288, + 350 + ], + "type": "text", + "content": " key-value pairs. The dimension of keys is 384 (same as DINO-ViT) and the dimension of values is 128. As the texture network tends to struggle to predict detailed appearance in one go, partially due to limited capacity, for all the visualizations, we follow [60] and fine-tune (only) the texture network for 50 iterations, which takes " + }, + { + "bbox": [ + 46, + 241, + 288, + 350 + ], + "type": "inline_equation", + "content": "< 10" + }, + { + "bbox": [ + 46, + 241, + 288, + 350 + ], + "type": "text", + "content": " seconds. Refer to the sup. mat. for further details." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 357, + 160, + 369 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 357, + 160, + 369 + ], + "spans": [ + { + "bbox": [ + 47, + 357, + 160, + 369 + ], + "type": "text", + "content": "5.2. Qualitative Results" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 376, + 287, + 472 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 376, + 287, + 472 + ], + "spans": [ + { + "bbox": [ + 46, + 376, + 287, + 472 + ], + "type": "text", + "content": "After training, 3D-Fauna takes in a single test image of any quadruped animal and produces an articulated and textured 3D mesh in a feed-forward manner, as visualized in Fig. 4. The model can reconstruct very different animals, such as antelopes, armadillos, and fishers, without requiring any category labels. All the input images in Fig. 4 have not been seen during training. In particular, the model also performs well on held-out categories, e.g. the wolf in the third row." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 479, + 212, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 479, + 212, + 491 + ], + "spans": [ + { + "bbox": [ + 47, + 479, + 212, + 491 + ], + "type": "text", + "content": "5.3. Comparisons with Prior Work" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 498, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 288, + 714 + ], + "type": "text", + "content": "Baselines. To the best of our knowledge, ours is the first deformable model designed to handle " + }, + { + "bbox": [ + 46, + 498, + 288, + 714 + ], + "type": "inline_equation", + "content": "100+" + }, + { + "bbox": [ + 46, + 498, + 288, + 714 + ], + "type": "text", + "content": " quadruped species, learned purely from 2D Internet data. We carry out quantitative and qualitative comparisons to methods that are at least in principle applicable to this setting. The baseline is MagicPony [60], which however is category-specific (they first train on horses, and fine-tune on giraffes, cows and zebras). We also compare with two popular deformable models that can work in the wild, namely UMR [29] and A-CSM [28]. However, they require weakly-supervised part segmentations and shape templates, respectively. Other works, such as LASSIE [70] and its follow-ups [71, 72], optimize a deformable model on a small set of about 20 images covering a single animal category at a time. More recently, image-to-3D methods based on distilling 2D diffusion models and/or large 3D datasets [31] have also demonstrated plausible 3D reconstructions of animals from a single image. In contrast, our model predicts an articulated mesh" + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 310, + 70, + 541, + 159 + ], + "blocks": [ + { + "bbox": [ + 310, + 70, + 541, + 159 + ], + "lines": [ + { + "bbox": [ + 310, + 70, + 541, + 159 + ], + "spans": [ + { + "bbox": [ + 310, + 70, + 541, + 159 + ], + "type": "table", + "html": "
PASCALAPT-36KAnimal3D
KT-PCK@0.1PCK@0.1PCK@0.1PCK@0.1
UMR [29]0.284---
A-CSM [28]0.3290.6870.6490.822
MagicPony [60]0.429-0.7560.867
Ours0.5390.7820.8410.901
", + "image_path": "8fdb793e103154aab3bc130c2aa018e09ac9469503f24d11fd54be44714e3fa0.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 167, + 545, + 212 + ], + "lines": [ + { + "bbox": [ + 305, + 167, + 545, + 212 + ], + "spans": [ + { + "bbox": [ + 305, + 167, + 545, + 212 + ], + "type": "text", + "content": "Table 1. Quantitative Comparisons on PASCAL VOC [10], APT-36K [69] and Animal3D [62]. When compared to baselines including the competitive MagicPony [60], our method demonstrates significantly improved performance on all datasets." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 224, + 545, + 297 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 224, + 545, + 297 + ], + "spans": [ + { + "bbox": [ + 304, + 224, + 545, + 297 + ], + "type": "text", + "content": "from a single image within seconds. Although it is difficult to establish a fair numerical comparison given these different settings, in Sec. 5.3, we provide a side-by-side qualitative comparison against baselines [31, 70, 71]. We use the publicly released code [31, 60, 70, 71] and report numbers [28, 29] included in MagicPony [60]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 301, + 546, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 301, + 546, + 480 + ], + "spans": [ + { + "bbox": [ + 304, + 301, + 546, + 480 + ], + "type": "text", + "content": "Quantitative Comparisons. We conduct quantitative evaluation across three different datasets, APT-36K [69], Animal3D [62], and PASCAL VOC [10], which contain images of various animals with 2D keypoint annotations. Following MagicPony [60], we first evaluate on horses in PASCAL VOC [10] using the widely used Keypoint Transfer metric [22, 28, 29]. We use the same protocol as in A-CSM [28] and randomly sample " + }, + { + "bbox": [ + 304, + 301, + 546, + 480 + ], + "type": "inline_equation", + "content": "20\\mathrm{k}" + }, + { + "bbox": [ + 304, + 301, + 546, + 480 + ], + "type": "text", + "content": " source-target image pairs. For each source image, we project the visible vertices of the predicted mesh onto the image and map each annotated 2D keypoint to its nearest vertex. We then project that vertex to the target image and check if it lies within a small distance (10% of image size) to the corresponding keypoint in the target image. We summarize the results using the Percentage of Correct Keypoints (KT-PCK@0.1) in Tab. 1." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 481, + 545, + 565 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 481, + 545, + 565 + ], + "spans": [ + { + "bbox": [ + 304, + 481, + 545, + 565 + ], + "type": "text", + "content": "In Tab. 1, we follow CMR [22] to evaluate the three datasets on more species, optimizing a linear mapping from mesh vertices to desired keypoints for each category, and reporting PCK@0.1 between the predicted and annotated 2D keypoints. Our model demonstrates significant improvement over existing methods on all datasets. A performance breakdown for each category is provided in the sup. mat." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": "Qualitative Comparisons. Figure 5 compares 3D-Fauna qualitatively to several recent works [31, 60, 70, 71]. To establish a fair comparison with MagicPony [60], for categories demonstrated in their paper (e.g. horse), we simply run inference using the released model. For each of the other categories, we use their public code to train a per-category model on our dataset from scratch (which contains less than 100 images for some rare categories). For LASSIE [70] and Hi-LASSIE [71], which optimize over a small set of images, we train their models on the test image together with additional 29 images randomly selected from the training set of that category. Hi-LASSIE [71] is further" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9757" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 52, + 73, + 545, + 703 + ], + "blocks": [ + { + "bbox": [ + 52, + 73, + 545, + 703 + ], + "lines": [ + { + "bbox": [ + 52, + 73, + 545, + 703 + ], + "spans": [ + { + "bbox": [ + 52, + 73, + 545, + 703 + ], + "type": "image", + "image_path": "ebd128df2b235bd0d792ed3127c134e2cb156c99f56b99f343fee058fd0ab0f0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 711, + 546, + 734 + ], + "lines": [ + { + "bbox": [ + 46, + 711, + 546, + 734 + ], + "spans": [ + { + "bbox": [ + 46, + 711, + 546, + 734 + ], + "type": "text", + "content": "Figure 4. Single Image 3D Reconstruction. Given a single image of any quadruped animal at test time, our model reconstructs an articulated and textured 3D mesh in a feed-forward manner without requiring category labels, which can be readily animated." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "9758" + } + ] + } + ], + "index": 2 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 70, + 86, + 112 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 86, + 112 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 86, + 112 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 86, + 112 + ], + "type": "image", + "image_path": "dc079035b559e84447a2efa09b105ea341fcc84443c57014e05b870268d99b70.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 49, + 114, + 86, + 149 + ], + "blocks": [ + { + "bbox": [ + 49, + 114, + 86, + 149 + ], + "lines": [ + { + "bbox": [ + 49, + 114, + 86, + 149 + ], + "spans": [ + { + "bbox": [ + 49, + 114, + 86, + 149 + ], + "type": "image", + "image_path": "2cc8ecc9467a10e24ff5f017319df159568bb1908c8a2af76184faf7690c9074.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 50, + 151, + 86, + 188 + ], + "blocks": [ + { + "bbox": [ + 50, + 151, + 86, + 188 + ], + "lines": [ + { + "bbox": [ + 50, + 151, + 86, + 188 + ], + "spans": [ + { + "bbox": [ + 50, + 151, + 86, + 188 + ], + "type": "image", + "image_path": "6478139f613d6c8c6eea8ef370e50e868f491d0a8e99b51c47487e50d01d912a.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 48, + 190, + 88, + 198 + ], + "lines": [ + { + "bbox": [ + 48, + 190, + 88, + 198 + ], + "spans": [ + { + "bbox": [ + 48, + 190, + 88, + 198 + ], + "type": "text", + "content": "Input Image" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 93, + 70, + 177, + 198 + ], + "blocks": [ + { + "bbox": [ + 93, + 70, + 177, + 198 + ], + "lines": [ + { + "bbox": [ + 93, + 70, + 177, + 198 + ], + "spans": [ + { + "bbox": [ + 93, + 70, + 177, + 198 + ], + "type": "image", + "image_path": "85dea26990b343a77431e954eaac01132f26924883b08ac3b2ab19550e6a05cc.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 201, + 547, + 235 + ], + "lines": [ + { + "bbox": [ + 46, + 201, + 547, + 235 + ], + "spans": [ + { + "bbox": [ + 46, + 201, + 547, + 235 + ], + "type": "text", + "content": "Figure 5. Qualitative Comparisons against MagicPony [60], LASSIE [70], Hi-LASSIE [71] and Zero-1-to-3 [31]. Compared to all baselines, our method predicts more stable poses and higher-fidelity reconstructions. Note that our method is learning-based and predicts 3D meshes in a feed-forward fashion (as opposed to [70, 71] that optimize on test images), which is orders of magnitude faster." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 189, + 70, + 276, + 198 + ], + "blocks": [ + { + "bbox": [ + 189, + 70, + 276, + 198 + ], + "lines": [ + { + "bbox": [ + 189, + 70, + 276, + 198 + ], + "spans": [ + { + "bbox": [ + 189, + 70, + 276, + 198 + ], + "type": "image", + "image_path": "cb354bbaedb4e99fe13dc5806843344a89c1181343f88a20afbf344aa7eaa0df.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 277, + 70, + 362, + 198 + ], + "blocks": [ + { + "bbox": [ + 277, + 70, + 362, + 198 + ], + "lines": [ + { + "bbox": [ + 277, + 70, + 362, + 198 + ], + "spans": [ + { + "bbox": [ + 277, + 70, + 362, + 198 + ], + "type": "image", + "image_path": "c9657a753f4cfdd11315712bf18a9876f637a4f956e586ce4d09acd70a8f7cef.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 369, + 70, + 451, + 198 + ], + "blocks": [ + { + "bbox": [ + 369, + 70, + 451, + 198 + ], + "lines": [ + { + "bbox": [ + 369, + 70, + 451, + 198 + ], + "spans": [ + { + "bbox": [ + 369, + 70, + 451, + 198 + ], + "type": "image", + "image_path": "b451aa3d7bffd0eb8a30f352790e3fe9eec9fcd00727e88d154e15318304076d.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 458, + 70, + 538, + 198 + ], + "blocks": [ + { + "bbox": [ + 458, + 70, + 538, + 198 + ], + "lines": [ + { + "bbox": [ + 458, + 70, + 538, + 198 + ], + "spans": [ + { + "bbox": [ + 458, + 70, + 538, + 198 + ], + "type": "image", + "image_path": "ecfa8944b0431e6fba68e66d33649cf0dea26c5197555448a0c9cbd559ed7b73.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 47, + 245, + 186, + 432 + ], + "blocks": [ + { + "bbox": [ + 47, + 245, + 186, + 432 + ], + "lines": [ + { + "bbox": [ + 47, + 245, + 186, + 432 + ], + "spans": [ + { + "bbox": [ + 47, + 245, + 186, + 432 + ], + "type": "image", + "image_path": "714643e383b4a6ca624f0205c9f3ff81bef4c22caa082d795c1fe1310022dd53.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 434, + 287, + 456 + ], + "lines": [ + { + "bbox": [ + 46, + 434, + 287, + 456 + ], + "spans": [ + { + "bbox": [ + 46, + 434, + 287, + 456 + ], + "type": "text", + "content": "Figure 6. Ablation Studies. Both the Semantic Bank and the mask discriminator improve the results as discussed in Sec. 5.4." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 189, + 245, + 282, + 432 + ], + "blocks": [ + { + "bbox": [ + 189, + 245, + 282, + 432 + ], + "lines": [ + { + "bbox": [ + 189, + 245, + 282, + 432 + ], + "spans": [ + { + "bbox": [ + 189, + 245, + 282, + 432 + ], + "type": "image", + "image_path": "3a9f29df8a99bba87e61b6e001a87a4103df08084aa06445b1144539885a4942.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 471, + 287, + 554 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 471, + 287, + 554 + ], + "spans": [ + { + "bbox": [ + 46, + 471, + 287, + 554 + ], + "type": "text", + "content": "fine-tuned on the test image after training. To compare with Zero-1-to-3 [31], we use the implementation in threestudio [16] to first distill a NeRF [36] using Score Distillation Sampling [40] given the masked test image, and then extract a 3D mesh for fair comparison. Note that our model predicts 3D meshes within seconds, whereas the optimization takes at least 10–20 mins for the other methods [31, 70, 71]." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 558, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 558, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 558, + 288, + 715 + ], + "type": "text", + "content": "As shown in Fig. 5, MagicPony is sensitive to the size of the training set. When trained on rare categories with fewer (< 100) images, such as the puma in Fig. 5, it fails to learn meaningful shapes and produces severe artifacts. Despite optimizing on the test images, LASSIE and Hi-LASSIE produce coarser reconstructions, partially due to the part-based representation that struggles in capturing the detailed geometry and articulation, as well as unstable viewpoint prediction. Zero-1-to-3, on the other hand, often fails to correctly reconstruct the legs, and does not explicitly model the articulated pose. On the contrary, our method predicts accurate viewpoint and reconstructs fine-grained articulated shapes for all different animals, with only one single model." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 248, + 400, + 262 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 248, + 400, + 262 + ], + "spans": [ + { + "bbox": [ + 306, + 248, + 400, + 262 + ], + "type": "text", + "content": "5.4. Ablation Study" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 271, + 547, + 428 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 271, + 547, + 428 + ], + "spans": [ + { + "bbox": [ + 304, + 271, + 547, + 428 + ], + "type": "text", + "content": "In Fig. 6, we present ablation results on three key design choices in our pipeline: SBSM, category-agnostic training, and mask discriminator. If we remove the SBSM and directly condition the base shape network on each individual image embedding " + }, + { + "bbox": [ + 304, + 271, + 547, + 428 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 304, + 271, + 547, + 428 + ], + "type": "text", + "content": ", the model tends to overfit each training views without learning meaningful canonical 3D shapes and pose. Alternatively, we can simply condition the base shape on an explicit (learned) category-specific embedding and train the model in a category-conditioned manner. This also leads to sub-optimal reconstructions, in particular on rare categories with few training images. Lastly, training without the mask discriminator results in biased viewpoint prediction (towards frontal) and produces elongated shapes." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 452, + 384, + 464 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 452, + 384, + 464 + ], + "spans": [ + { + "bbox": [ + 306, + 452, + 384, + 464 + ], + "type": "text", + "content": "6. Conclusions" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 476, + 547, + 608 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 476, + 547, + 608 + ], + "spans": [ + { + "bbox": [ + 304, + 476, + 547, + 608 + ], + "type": "text", + "content": "We have presented 3D-Fauna, a deformable model for 100 animal categories learned using only Internet images. 3D-Fauna can reconstruct any quadruped image by instantiating in seconds a posed version of the deformable model to match the input image. Despite capable of modeling diverse animals, the current model is still limited to quadruped species that share a same skeletal structure. Furthermore, the training images still need to be lightly curated. Nevertheless, 3D-Fauna still presents a significant leap compared to prior works and moves us closer to models that will be able to understand and reconstruct all animals in nature." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 713 + ], + "type": "text", + "content": "Acknowledgments. We thank Cristobal Eyzaguirre, Kyle Sargent, and Yunhao Ge for their insightful discussions and Chen Geng for proofreading. The work is in part supported by the Stanford Institute for Human-Centered AI (HAI), NSF RI #2211258, #2338203, ONR MURI N00014-22-1-2740, ONR YIP N00014-24-1-2117, the Samsung Global Research Outreach (GRO) program, Amazon, Google, and EPSRC VisualAI EP/T028572/1." + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "9759" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "type": "text", + "content": "[1] Kalyan Vasudev Alwala, Abhinav Gupta, and Shubham Tulsiani. 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Automatic camera exposure control via deep reinforcement learning. Our proposed method, named DRL-AE, trains an agent to control camera exposure parameters (i.e., exposure time and gain) to acquire well-exposed images with rapid convergence and real-time processing (1ms on a CPU device). The trained agent instantly converges within five frames under dramatic lighting change scenario (a) and affects the performance of various vision applications (b), compared to the camera built-in AE controller [14, 18]." + ], + "image_footnote": [], + "bbox": [ + 94, + 455, + 867, + 584 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 676, + 313, + 694 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Adjusting camera exposure in arbitrary lighting conditions is the first step to ensure the functionality of computer vision applications. Poorly adjusted camera exposure often leads to critical failure and performance degradation. Traditional camera exposure control methods require multiple convergence steps and time-consuming processes, making them unsuitable for dynamic lighting conditions. In this paper, we propose a new camera exposure control framework that rapidly controls camera exposure while performing real-time processing by exploiting deep reinforcement learning. The proposed framework consists", + "bbox": [ + 75, + 709, + 470, + 876 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "of four contributions: 1) a simplified training ground to simulate real-world's diverse and dynamic lighting changes, 2) flickering and image attribute-aware reward design, along with lightweight state design for real-time processing, 3) a static-to-dynamic lighting curriculum to gradually improve the agent's exposure-adjusting capability, and 4) domain randomization techniques to alleviate the limitation of the training ground and achieve seamless generalization in the wild. As a result, our proposed method rapidly reaches a desired exposure level within five steps with real-time processing (1ms). Also, the acquired images are well-exposed and show superiority in various computer vision tasks, such as feature extraction and object detection.", + "bbox": [ + 496, + 679, + 893, + 876 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Both authors contributed equally to this work.", + "bbox": [ + 99, + 887, + 351, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "2975", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 78, + 89, + 207, + 104 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Camera exposure control is the task of adjusting exposure level by controlling exposure time, gain, and aperture to achieve a desired level of brightness and image quality for a given scene. Poorly adjusted exposure parameters result in over-exposed, under-exposed, blurry, or noisy images, which can cause performance degradation in image-based applications and, in the worst cases, even life-threatening accidents. Therefore, finding proper camera exposure is the first primary step to ensure the functionality of computer vision applications, such as object detection [5, 16], semantic segmentation [9, 17], depth estimation [10, 26], and visual odometry [1, 13].", + "bbox": [ + 76, + 114, + 467, + 296 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "There are several essential requirements in camera exposure control. The rapid convergence must be guaranteed to maintain an appropriate exposure level under dynamic light-changing scenarios. Also, the exposure control loop is one of the lowest loops in the camera system. Therefore, lightweight algorithm design must be considered for on-board level operation. Finally, the quality of a converged image should not be sacrificed to meet the requirements.", + "bbox": [ + 76, + 296, + 467, + 416 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Further, the number of simultaneously controlled parameters is also important because it affects the converge time and final quality of the converged image. One-by-one control methods [14, 18, 20] control exposure parameters in a one-by-one manner to achieve a desired exposure level, rather than joint controlling exposure parameters. However, the converged parameters are often not optimal, such as [long exposure time, low gain] and [short exposure time, high gain] pairs. As a result, the values result in undesirable image artifacts, such as motion blur due to long exposure time or severe noise due to high gain.", + "bbox": [ + 76, + 417, + 467, + 582 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Joint exposure parameter control [7, 8, 21, 23, 24] often needs multiple searching steps in a wide range of searching space to find an optimal combination. As a result, they cause a flickering effect and slow convergence speed. Also, the recent methods require high-level computational complexity due to its optimization algorithm [7, 8], image assessment metric [7, 8, 20, 21], and GPU inference [23].", + "bbox": [ + 76, + 583, + 467, + 688 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this paper, we propose a new joint exposure parameter control method that exploits reinforcement learning to achieve instant convergence and real-time processing. The proposed framework consists of four contributions:", + "bbox": [ + 76, + 689, + 467, + 748 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- A simplified training ground to simulate real-world's diverse and dynamic lighting changes.", + "- Flickering and image attribute-aware reward design, along with lightweight and intuitive state design for real-time processing.", + "- A static-to-dynamic lighting curriculum learning to gradually improve agent's exposure adjusting capability.", + "- Domain randomization techniques to alleviate the limitation of the training ground and achieve seamless generalization in the wild without additional training." + ], + "bbox": [ + 76, + 750, + 467, + 898 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The proposed method is thoroughly validated in three different environments: light-controlled darkroom, exposure control dataset [21], and real-world environments. We demonstrate that our proposed method rapidly adjusts camera exposure within five steps with real-time processing of $1 \\, ms$ . Also, the images acquired from our method are well-exposed and show superiority in numerous computer vision tasks, such as feature extraction and object detection.", + "bbox": [ + 496, + 90, + 890, + 212 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 227, + 640, + 242 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Optimization-based Exposure Control", + "text_level": 1, + "bbox": [ + 500, + 252, + 828, + 268 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "One branch to control camera exposure parameters is exploiting white-box and black-box optimizations to find optimal parameters for the desired exposure level. Camera built-in Auto-Exposure (AE) control methods [14, 18] adjust exposure parameters (i.e., exposure time and gain) based on differentiable optimization by using the equation between Exposure Value (EV) and exposure parameters [15]. They control exposure parameters one-by-one to achieve predefined image brightness. These built-in AE methods provide real-time processing ability but result in non-optimum solutions (e.g., long exposure time and low gain) and limited scalability. The former limitation causes motion blur and severe image noise due to long exposure time and high gain. The latter limitation indicates the methods cannot be extendable to maximize other image attributes, such as image gradient or entropy.", + "bbox": [ + 496, + 276, + 890, + 518 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Recent AE algorithms are designed to maximize desirable image attributes for computer vision applications, such as image gradient [20, 22, 25], entropy [7, 8], noise level [21], and optical flow [4]. However, these algorithms mainly focused on image metrics for better quality, not the control method. Therefore, they adopt heuristic control algorithm [20] or black-box optimization methods, such as Bayesian optimization [7, 8] and Nelder-Mead optimization [21]. These black-box optimizations and attribute assessment metrics often require multiple explorations that cause a flickering effect, multiple steps to converge, or heavy computation time. Differing from the previous method, the proposed method provides rapid convergence, real-time processing, and potential scalability by exploiting Deep Reinforcement Learning (DRL).", + "bbox": [ + 496, + 518, + 890, + 744 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.2. Data-driven Exposure Control", + "text_level": 1, + "bbox": [ + 500, + 756, + 769, + 771 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Another emerging branch of AE is utilizing a neural network to predict appropriate exposure parameters. Tomasi et al. [23] proposed an exposure parameter estimation network that predicts optimal exposure time and gain for each given image. The neural network, consisting of a few convolution and linear layers, is trained with Ground Truth (GT) exposure parameters in a supervised manner. However, the GT label generation needs a time-consuming and compli-", + "bbox": [ + 496, + 780, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "2976", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/f8318031ddbd548d9f50ecf54fa60f831d41934fef2a5df7901ad123c9ba520a.jpg", + "image_caption": [ + "Figure 2. Training framework overview. Our DRL agent is trained with the SAC algorithm in the light-controlled dark room environment. For each episode, a lighting condition is assigned by the current curriculum level. The lighting condition can be fixed at random brightness or dynamically changed within each episode, depending on the level. Given the lighting condition, the agent takes a vectorized intensity history for a randomly selected RoI patch as a state. Afterward, the agent estimates exposure time and gain differences that maximize a reward function. With this framework, the trained agent successfully generalized into a real environment without additional training." + ], + "image_footnote": [], + "bbox": [ + 98, + 88, + 872, + 364 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ated process that collects multiple images with varying exposure parameters for every scene. Also, a heavy computation caused by the use of convolution layers is another drawback. Differing from the method, our method trains a neural network by maximizing a reward function without relying on specific GT data or generation processes.", + "bbox": [ + 75, + 454, + 472, + 547 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. DRL for Automatic Exposure Control", + "text_level": 1, + "bbox": [ + 76, + 556, + 419, + 574 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Applying DRL to Automatic Exposure (AE) control task while achieving rapid convergence speed and real-time processing presents several challenges. Our proposed method provides effective solutions for the following questions.", + "bbox": [ + 75, + 582, + 468, + 643 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. Environment: what is the most effective form of training environment to learn camera exposure control?", + "2. Reward: what aspects does the agent need to maximize?", + "3. State: where is the bottleneck for real-time processing?", + "4. Generalization: how to achieve seamless generalization in the wild lighting condition?" + ], + "bbox": [ + 76, + 643, + 468, + 733 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Training Environment", + "text_level": 1, + "bbox": [ + 76, + 741, + 287, + 758 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "DRL requires a large number of samples and interaction with the environment to train the agent. Also, the environment needs to provide a diverse and wide range of problems for the agent to solve. The optimal form of exposure control is to instantly adjust exposure parameters for a variety of lighting conditions, from static lighting conditions to dramatic lighting changes. To this end, the training environment for camera exposure control must provide diverse lighting change scenarios to the agent.", + "bbox": [ + 75, + 763, + 470, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Numerous options exist, such as a simulation, a real-world environment with natural sunlight, and a controlled real-world environment. The simulation can provide various images and lighting conditions but has the limitations of an imperfect exposure parameter implementation and a sim-to-real domain gap. On the other hand, the real-world environment with natural sunlight has no domain gap, but the lighting conditions change very slowly. Therefore, we construct a controlled real-world environment in a darkroom with controllable LEDs to adjust lighting conditions.", + "bbox": [ + 496, + 454, + 893, + 604 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The constructed light-controlled darkroom is shown in Fig. 2. The environment has one machine vision camera, a random target object, a light controller, and an LED bar. The environment provides a random lighting scenario from dark to bright light conditions, and the agent adjusts exposure parameters to capture a high-quality image of the target object in the suggested scenario. The detailed sensor specification can be found in the supplementary material.", + "bbox": [ + 496, + 607, + 893, + 729 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. State, Action, and Reward Design", + "text_level": 1, + "bbox": [ + 500, + 742, + 795, + 758 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2.1 State Design: Vectorized Intensity History", + "text_level": 1, + "bbox": [ + 500, + 767, + 846, + 782 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The widely adopted state design in related fields is utilizing a feature map from a pre-trained network [22, 23]. However, we found the CNN feature is not effective in the exposure control task due to its disadvantages: 1) unclear relation between CNN feature and exposure level, 2) generalization problem of CNN feature, and 3) heavy computation for on-board devices due to multiple convolution layers.", + "bbox": [ + 496, + 794, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "2977", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Therefore, instead of using the CNN feature or other complicated features as a state, we utilize vectorized image intensity as a straightforward and lightweight state representation for the exposure control task. As shown in Fig. 2, we first vectorize image intensity map from a Region-of-Interest (RoI) patch of gray-scale image $\\mathbb{R}^{H_{RoI} \\times W_{RoI}}$ to the intensity vector $\\mathbb{R}^S$ . The RoI patch can be an entire image area or specific regions decided by a domain randomization process. After that, we stack consecutive frame's intensity vectors to embed previous state history, as follows:", + "bbox": [ + 76, + 90, + 472, + 243 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nv _ {t} = f \\left(I _ {t} ^ {R o I}\\right), \\quad v _ {t} \\in \\mathbb {R} ^ {S},\n$$\n", + "text_format": "latex", + "bbox": [ + 166, + 252, + 344, + 270 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ns _ {t} = \\operatorname {c o n c a t} \\left(v _ {t - n}, \\dots , v _ {t - 1}, v _ {t}\\right),\n$$\n", + "text_format": "latex", + "bbox": [ + 169, + 273, + 379, + 290 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $I_{t}$ is a normalized image at time step $t$ , $f(\\cdot)$ is an averaging process through the x-axis of a gray-scale image, defined as $\\frac{1}{H_{RoI}}\\sum_{x}\\mathrm{gray}(I_t^{RoI})$ , $v_{t}$ represents the vectorized intensity that has a dimension of $S$ , and $s_t$ is a state vector. To ensure a fixed and reasonable state length, we resize the given RoI patch to have $S = 128$ and stack previous states with $n = 3$ . The proposed state design is effective, straightforward, and computationally efficient compared to the CNN feature, as described in Sec. 4.1.", + "bbox": [ + 76, + 301, + 472, + 438 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2.2 Action Design: Relative and Continuous Action", + "text_level": 1, + "bbox": [ + 76, + 455, + 460, + 472 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Obviously, we have two controllable parameters, exposure time and gain, to adjust camera exposure. However, there are numerous options for its action design, such as 1) discrete vs. continuous action space, and 2) absolute vs. relative action range. A discrete action space discretizes the action range into a few action values. It has the advantage that the training process is simplified, but there is an approximation gap to the optimal values. The absolute and relative action range is about the change of camera parameters. In the absolute action range, an action value is directly matched to the specific value of camera parameters. On the other hand, in the relative action range, an action value indicates the amount of change in camera parameters.", + "bbox": [ + 75, + 479, + 468, + 676 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Among the options, we select continuous-relative action space. This is because our goal is rapid convergence with minimum exploration step, but discrete action space needs multiple steps and often does not converge, depending on its quantization level. Also, we empirically found that the absolute action range often induces a flickering effect and unstable convergence, as described in Sec. 4.1.", + "bbox": [ + 75, + 676, + 470, + 782 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2.3 Reward Design: Flickering and Image Attribute", + "text_level": 1, + "bbox": [ + 76, + 801, + 467, + 816 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The desirable behavior of exposure control is maximizing image attributes, such as sharp edge, moderate brightness, and low-level noise, and maintaining image attributes during exposure parameter transition. Therefore, we designed the reward function from three perspectives: 1) a moderate", + "bbox": [ + 76, + 825, + 468, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "brightness level to provide clear visibility and edge information, 2) a smoothed exposure transition to ensure stable convergence and prevent flickering, and 3) a low-level noise to provide clear image and avoid too-high gain value. The designed reward functions are as follows:", + "bbox": [ + 496, + 90, + 890, + 167 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {R} _ {m e a n} = \\frac {1}{P} \\sum_ {x y} \\left| I _ {t} ^ {R o I} - M \\right| ^ {p _ {m}}, \\\\ \\mathcal {R} _ {f l k} = \\frac {1}{P} \\sum_ {x y} | | I _ {t} ^ {R o I} - I _ {t - 1} ^ {R o I} | |, \\\\ \\mathcal {R} _ {n o i s e} = \\frac {1}{P} \\sum_ {x y} s o b e l (I _ {t} ^ {R o I}), \\\\ \\mathcal {R} _ {t o t a l} = w _ {m} \\mathcal {R} _ {m e a n} + w _ {f} \\mathcal {R} _ {f l k} + w _ {n} \\mathcal {R} _ {n o i s e}, \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 539, + 171, + 849, + 253 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $P$ is the number of pixels, $M = 0.5$ indicates mid-tone brightness, $p_m = 0.5$ is a parameter for non-linearity and sobel is a gradient operator. Also, we set $w_{m} = 1.5$ , $w_{f} = -1.0$ , $w_{n} = -0.1$ in practice. The proposed reward design might be a primitive and basic form for camera exposure control, however, it can be easily extendable by incorporating modern image assessment metrics [4, 8, 21].", + "bbox": [ + 496, + 258, + 890, + 366 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Static-to-dynamic Lighting Curriculum", + "text_level": 1, + "bbox": [ + 500, + 372, + 839, + 388 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In the wild, the agent must be able to control exposure parameters for a variety of lighting change scenarios. However, training every scenario simultaneously results in an unstable training process and poor generalization. Therefore, we propose static-to-dynamic curriculum strategy that starts with a simple control task and gradually experiences dynamic and dramatic lighting change scenarios. In the end, the trained models possess a comprehensive exposure control capability for diverse lighting conditions.", + "bbox": [ + 496, + 395, + 890, + 531 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We divide the difficulty of lighting conditions into three levels: easy, normal, and hard. The easy level has static lighting conditions with moderate brightness. The normal level also has a fixed brightness but with a darker or brighter than easy level. Lastly, in the hard level, the LED brightness dynamically changes from dark to bright or the opposite way during each scenario. The probability of each level is gradually updated according to the proceeded training episode $t_e$ . The probability set $[p_e, p_n, p_h]$ starts from $[1, 0, 0]$ , through $[0, 1, 0]$ , and ends with $[p_e^f, p_n^f, p_h^f] = [0.1, 0.4, 0.5]$ . In summary, the probability for each difficulty level is updated as follows:", + "bbox": [ + 496, + 531, + 892, + 714 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} p _ {e} = \\left\\{ \\begin{array}{l l} 1, & t _ {e} < T _ {e} \\\\ \\frac {(t _ {e} - T _ {e})}{(T _ {n} - T _ {e})}, & T _ {e} \\leq t _ {e} < T _ {n} \\\\ p _ {e} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ p _ {n} = \\left\\{ \\begin{array}{l l} 0, & t _ {e} < T _ {e} \\\\ 1 - \\frac {\\left(t _ {e} - T _ {e}\\right)}{\\left(T _ {n} - T _ {e}\\right)}, & T _ {e} \\leq t _ {e} < T _ {n} \\\\ p _ {n} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ p _ {h} = \\left\\{ \\begin{array}{l l} 0, & t _ {e} < T _ {n} \\\\ p _ {h} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 566, + 720, + 820, + 881 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We use $T_{e} = 25,000, T_{n} = 45,000$ in practice.", + "bbox": [ + 500, + 885, + 815, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "2978", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.4. Spatial Domain Randomization", + "text_level": 1, + "bbox": [ + 76, + 90, + 354, + 106 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In the wild, the agent encounters various surrounding environments and object contexts, such as office, road, tunnel, and mountain. Although the light-controlled darkroom can provide various lighting scenarios, it is difficult to contain diverse environments and contexts because it only has a few target objects with a fixed background. Therefore, without proper randomization techniques, the agent may overfit to perform exposure control for only a few target objects, resulting in generalization failure in the wild.", + "bbox": [ + 75, + 113, + 467, + 248 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The main idea is to provide as much diverse image structure and context information as possible by augmenting the image from the darkroom environment. Specifically, we spatially augment the images with random flipping, cropping, rotating, and resizing but do not change color and brightness information. Each augmentation and its parameter is randomly selected at the beginning of each training episode and fixed during the episode. With the proposed domain randomization technique, the trained agent can be generalized in the real world without any fine-tuning.", + "bbox": [ + 75, + 250, + 467, + 401 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.5. Policy Optimization", + "text_level": 1, + "bbox": [ + 76, + 409, + 264, + 425 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "As our action space is continuous, we use the SAC [3] algorithm. We excluded on-policy algorithms like PPO [19] because they are widely known to be less sample efficient than the off-policy algorithms like SAC, TD3, and DDPG. We tested TD3 [2] and DDPG [11] as well, but SAC showed the best result.", + "bbox": [ + 75, + 431, + 467, + 521 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "SAC algorithm is a kind of actor-critic algorithm, which has critic $Q(\\theta)$ and actor $\\pi(\\phi)$ . The objective functions to update the critic are as follows:", + "bbox": [ + 75, + 523, + 467, + 568 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} J _ {Q} (\\theta) = \\mathbb {E} _ {(s _ {t}, a _ {t}) \\sim \\mathcal {D}} \\left[ \\frac {1}{2} \\left(Q _ {\\theta} (s _ {t}, a _ {t}) - \\hat {Q} (s _ {t}, a _ {t})\\right) ^ {2} \\right], \\\\ \\hat {Q} (s _ {t}, a _ {t}) = r (s _ {t}, a _ {t}) + \\gamma \\mathbb {E} _ {s _ {t + 1} \\sim p} [ V _ {\\bar {\\theta}} (s _ {t + 1}) ], \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 98, + 578, + 447, + 633 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{D}$ is a replay buffer, $r(s_{t},a_{t})$ is a reward function and $\\gamma$ is a discount factor. The objective functions for updating the actor is as follows:", + "bbox": [ + 76, + 642, + 467, + 686 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nJ _ {\\pi} (\\phi) = \\mathbb {E} _ {s _ {t} \\sim \\mathcal {D}} \\left[ \\mathbb {E} _ {a _ {t} \\sim \\pi_ {\\phi}} \\left[ \\alpha \\log \\left(\\pi_ {\\phi} \\left(a _ {t} \\mid s _ {t}\\right)\\right) - Q _ {\\theta} \\left(s _ {t}, a _ {t}\\right) \\right] \\right],\n$$\n", + "text_format": "latex", + "bbox": [ + 83, + 698, + 460, + 715 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "with $\\alpha$ defined as a temperature parameter.", + "bbox": [ + 76, + 726, + 359, + 741 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 753, + 207, + 771 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this section, we validate our proposed method in three different environments: light-controlled darkroom, exposure control dataset [21], and real-world environments. Throughout the experiments, we provide the validation result of DRL design components, ablation study of reward and training strategy, convergent step comparison, comparison with built-in AE for object detection and feature extraction, and computational time analysis.", + "bbox": [ + 75, + 779, + 467, + 900 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/39d33b9b3f1271ed2a93f513a31f1aa9746dc33ee0cf89fc129a10737575ade8.jpg", + "table_caption": [ + "Table 1. Self-evaluation of DRL-AE framework in the light-controlled darkroom. DR and CL indicate domain randomization and curriculum learning.\"-\" indicates the agent doesn't converge. The best performance in each block is highlighted in bold." + ], + "table_footnote": [], + "table_body": "
Framework ComponentMethodsReward per FrameFrames to Converge
RL AlgorithmDDPG [11]1.11-
TD3 [2]1.03-
SAC [3]1.615
StateCNN0.85-
Vector1.615
ActionAbsolute0.65-
Relative1.615
RewardRflk Rnoise
1.41-
✓1.4416
1.359
✓1.615
Training StrategyDR CL
✓--
1.6415
✓1.615
", + "bbox": [ + 516, + 151, + 877, + 441 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Self-evaluation in Light-controlled Darkroom", + "text_level": 1, + "bbox": [ + 498, + 452, + 883, + 468 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We first validate our DRL design components and their variants in the light-controlled darkroom. We utilize reward per frame and the averaged number of frames to converge as evaluation metrics to measure image quality and convergence speed, respectively. Here, when the difference between current and previous images is less than a certain threshold, we regard it as the convergence. The testing scenarios include various lighting conditions, such as fixed lighting, progressive light changes, and dynamic light changes. The results are shown in Tab. 1.", + "bbox": [ + 496, + 476, + 890, + 626 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We found SAC method [3] shows the best result among the off-policy RL methods. Other algorithms can reach up to 1.0 reward per frame, but they usually do not converge well by showing oscillation. For the state design, the CNN feature is not desirable for the exposure control task due to its intensity-agnostic property. Also, absolute action space seems to make the overall learning process difficult because it needs to estimate the optimum values directly.", + "bbox": [ + 496, + 628, + 890, + 748 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The reward function and the training strategies play an important role in the stable and rapid convergence process and image attribute preservation. $R_{noise}$ suppress high noise level and regularize gain parameter control, leading to better convergence. Also, $R_{flk}$ makes the agent preserve the image attribute during the exposure transition. CL makes the agent encompass the comprehensive exposure control capability for the test set's various lighting conditions. Additionally, DR allows the agent to quickly converge for arbitrary context by increasing generalization ability.", + "bbox": [ + 496, + 750, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "2979", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/d5039d6ae910a2957238f8af729c9a9a0b5a8734ec34586e0af3538aec8c7702.jpg", + "image_caption": [ + "Shin et al. [21]" + ], + "image_footnote": [], + "bbox": [ + 94, + 103, + 452, + 160 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/0f5695d9315063e2774271edd0dce5cd14c882c553f5d426fc7f7e6fe2832b95.jpg", + "image_caption": [ + "DRL-AE (Ours)", + "(a) Acquired image comparison for each convergent step" + ], + "image_footnote": [], + "bbox": [ + 94, + 176, + 452, + 233 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/9fc31a1cc91ae10b2fa46efeb85dbd0aa11cc1980f81ebd00baa660a576bd456.jpg", + "image_caption": [ + "(b) Convergence trajectory of exposure parameter optimization", + "Figure 3. Convergent step comparison in exposure control dataset [21]. Within three frames, our method already reaches a well-exposed image (a) with minimum exploration (b). On the other hand, Shin et al. [21] search local areas with multiple steps (about 30 frames) to converge." + ], + "image_footnote": [], + "bbox": [ + 107, + 263, + 428, + 455 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Convergent Step Comparison", + "text_level": 1, + "bbox": [ + 76, + 587, + 339, + 603 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Exposure Control Dataset [21]. The dataset provides multiple images with many different pairs of exposure and gain values, which are captured from the real world. The dataset consists of several locations, including indoor and outdoor places, with a wide range of exposure and gain values. Outdoor images can have the exposure time from $100\\mu s$ to $7450\\mu s$ , at intervals of $150\\mu s$ , and the gain from $0dB$ to $20dB$ with $2dB$ interval. Similarly, indoor images have exposure time from $4ms$ to $67ms$ with $3ms$ intervals and gain from $0dB$ to $24dB$ with $2dB$ intervals.", + "bbox": [ + 75, + 612, + 468, + 762 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We evaluate our method with Shin et al. [21]. The final converged points are slightly different because of the difference between the proposed reward function and the assessment metric of [21]. Both algorithms converge to a comparable point, as shown in Fig. 3. It only takes three frames to converge with our method. However, the Nelder-Mead optimization method in [21] takes at least 30 timesteps to converge completely. Therefore, it is hard to use it in real scenarios, although they may find a more optimal point.", + "bbox": [ + 75, + 763, + 468, + 902 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/43e58cb5ddf1a3e483dacd314dd0f431cc2f24fbecad67bf2089cd8098058935.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 506, + 89, + 885, + 255 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/14de94ebf73fb889d4e0c765fbbc0bb64f89712a06a4bf85723037dad2df2504.jpg", + "image_caption": [ + "Figure 4. Real-world generalization. We compare our method with the camera's built-in exposure control algorithm in real-world scenarios. Camera lenses are occluded at the initial and suddenly removed in the first frame. Our agent converges to a well-exposed image within 3-5 frames. Yet, the built-in AE algorithm is still in the middle of adjusting the exposure parameters and is far from the well-exposed image, especially in the indoor case. Note that our agent is only trained in the light-controlled darkroom, and this is the zero-shot inference result in the wild." + ], + "image_footnote": [], + "bbox": [ + 508, + 258, + 885, + 417 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Real-world Indoor and Outdoor Environment. We evaluate our method with the camera's built-in AE control algorithm in real-world scenarios. The purposes of this experiment are twofold: 1) comparing convergence speed with the built-in AE algorithm, and 2) testing zero-shot generalization performance in the wild.", + "bbox": [ + 498, + 582, + 890, + 672 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Before starting, we cover the camera lens with enough time to converge in the dark, then quickly remove it to test the convergence speed for a sudden lighting change. Fig. 4 shows the captured initial five images during each optimization. Our method converges to a well-exposed image within 3-5 frames in both indoor and outdoor scenes. However, the built-in AE algorithm takes much longer to converge: 30 frames for indoors and 10 frames for outdoors.", + "bbox": [ + 496, + 674, + 890, + 792 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Also, we found that our agent shows satisfactory zero-shot generalization performance, even though it is only trained in the light-controlled darkroom with limited object context. We believe our state design (i.e., vectorized intensity history) and spatial domain randomization bring this result by removing the potential domain gap issue of the CNN feature and augmenting object context as much as possible.", + "bbox": [ + 496, + 795, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "2980", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/0351b891afbbdfed425340e3b1815e0091d58038f1bd1abf66697b674c0e1d25.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 89, + 133, + 272, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/341ebebcd0a5a070670b981b5417b9ac14c9313aee7e8afcd32ddd9cd7a01d78.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 274, + 133, + 455, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/8d89454f9d597f893d9b98158a5ab823458f458b9efa0c863a4388ac4b40434e.jpg", + "image_caption": [ + "(a) Feature extraction from DRL-AE (Ours)", + "(b) Feature extraction from built-in AE", + "Figure 5. SIFT [12] feature extraction result. Captured images from the proposed algorithm and built-in AE are processed to detect SIFT features. The images were simultaneously captured in real-time from two separate cameras equipped on a driving vehicle. Our method can provide plenty of SIFT features over the image plane. On average, our method detects $38\\%$ more features across a total of 5355 images." + ], + "image_footnote": [], + "bbox": [ + 89, + 227, + 272, + 349 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/2a4d866910489dbde33e8fd54436fbfd902159e10e18aa07748932fc81c06371.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 274, + 232, + 455, + 349 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Real-time Driving Env: Feature Extraction", + "text_level": 1, + "bbox": [ + 76, + 511, + 441, + 526 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In this experiment, two cameras are attached to the top of a moving car, and images are captured simultaneously. One camera is used for our algorithm, and the other camera is for the built-in AE algorithm. We tested the algorithms on real-world driving scenarios, including campus and urban roads. Our algorithm runs on a laptop equipped with an i7-7700HQ@2.80GHz CPU unit. Given an image, the agent predicts exposure time and gain commands in real-time. The estimated actions are transmitted to the attached camera. After driving sequences acquisition, we extract SIFT [12] features from each captured image. Please note that the images of DRL-AE and built-in AE have slightly different views due to the difference in the installed position.", + "bbox": [ + 75, + 536, + 468, + 733 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Fig. 5 shows the comparison of feature extraction results. From the total of 5355 image pairs, our method produces 1,306 SIFT features on average with a 1,157 median value. On the other hand, the built-in AE method only results in 946 features on average, with a 711 median value. Therefore, $38\\%$ more features are detected on average, and the difference is up to $62\\%$ for the median value. The number of detected features and feature repeatability during exposure transition are critical for Visual Odometry (VO) and SLAM tasks. So, we believe our method can be valuable for VO, SLAM, and visual tracking tasks as well.", + "bbox": [ + 75, + 734, + 467, + 901 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/fa211dca3f56f081652e3863f94ca812a9de9ab9c9071d83832a8a7722115af3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 511, + 87, + 696, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/24676ee0f2330ed54566b5820e4e2df59cd0ff9bbacae38f35bf861de3939f9b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 87, + 880, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d282607fb99966c63c4e0c0c34ce7b56586408e73d952e61c4ddcfd679962b7b.jpg", + "image_caption": [ + "(a) Object detection from DRL-AE (Ours)", + "(b) Object detection from built-in AE", + "Figure 6. Object detection result. Captured images from the proposed algorithm and built-in AE are processed to detect target objects. The experiment used the same image sequence as the SIFT experiment. We utilize Yolo-v5 [6] for car and pedestrian detection. On average, our method detects $5\\%$ more objects compared to the built-in AE algorithm." + ], + "image_footnote": [], + "bbox": [ + 511, + 227, + 696, + 349 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/739336b179837e798bd27cc4e39ec50a773effab84b1f3692a7dc09f415ff865.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 227, + 880, + 349 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Real-time Driving Env: Object Detection", + "text_level": 1, + "bbox": [ + 500, + 494, + 846, + 510 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Similar to the feature extraction experiment, the captured images are processed with YOLO-v5 [6]. The images are taken from campus and urban road scenes, so we only take into account cars and pedestrians. Fig. 6 shows the comparison of object detection results from DRL-AE and built-in AE methods. Recent detection models, including YOLO-v5, adopt modern augmentation methods to make the model robust the image brightness changes. Therefore, YOLO-v5 tends to detect objects well in even poorly exposed images. However, our algorithm detects $5\\%$ more objects in terms of the total number of detected objects. Furthermore, the objects in our image are detected much earlier than the built-in AE method. This is highly critical for autonomous vehicles that are driving at high speed. Earlier detected objects can prevent human injury and potential accidents.", + "bbox": [ + 496, + 518, + 890, + 744 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.5. Real-world Env: RoI-aware Exposure Control", + "text_level": 1, + "bbox": [ + 500, + 756, + 888, + 772 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our DRL-AE framework can also take arbitrary input sizes because the framework resizes the image before the vectorized intensity processing. Also, our domain randomization strategy produces a random size of the Region of Interest (RoI) patch by using crop, flip, resize, and rotation in the training stage. Therefore, our agent is able to control camera exposure for a specific RoI or entire image. Fig. 7 shows the RoI-aware exposure control results.", + "bbox": [ + 496, + 779, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "header", + "text": "Features: 876", + "bbox": [ + 96, + 93, + 178, + 104 + ], + "page_idx": 6 + }, + { + "type": "header", + "text": "Features: 1377", + "bbox": [ + 279, + 93, + 367, + 103 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "2981", + "bbox": [ + 482, + 945, + 513, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d0021f5f127f7a4b95b580161517c7a1deee34b79e99d756cf02892bfab80b09.jpg", + "image_caption": [ + "Figure 7. RoI-aware camera exposure control. Our agent is able to control camera exposure for a specific RoI or entire image. Given a RoI box, the agent adjusts the camera parameters to maximize the image attribute for a specific RoI area. It allows the camera to capture the detailed context for the regions of interest." + ], + "image_footnote": [], + "bbox": [ + 86, + 88, + 467, + 289 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "The agent adjusts the camera parameters to maximize the image attribute for a specific RoI area. It allows the camera to capture the detailed context for the regions of interest. We expect that DRL-AE can be combined with object detection, object tracking, and human gaze and attention. As a result, the combination can lead to adaptive exposure control schemes, such as attention-aware or detection-aware exposure control.", + "bbox": [ + 75, + 412, + 468, + 534 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.6. Computation Time Analysis", + "text_level": 1, + "bbox": [ + 76, + 546, + 328, + 561 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Our agent has a simple Multi-Layer Perceptron (MLP) architecture with two hidden layers of 256 units. Also, our method does not require complex matrix computation like convolutions. Therefore, our agent can be run on a CPU device in real-time. We measure the inference time of the agent on the Ryzen 5950x CPU. Tab. 2 shows the computation time results, compared with shin et al. [21]. The network's inference time takes $1ms$ regardless of image resolution because the input image is resized to a fixed resolution. Also, even including other operations, such as image resizing and RoI cropping, it takes a maximum $6ms$ , which is still in the real-time range. Therefore, it can run at 170- $1000\\mathrm{Hz}$ on a CPU device.", + "bbox": [ + 75, + 571, + 468, + 767 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion & Future Work", + "text_level": 1, + "bbox": [ + 76, + 782, + 331, + 799 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Conclusion. In this paper, we proposed a novel joint exposure parameter control framework that exploits Deep Reinforcement Learning (DRL) to achieve instant exposure convergence and real-time processing. The proposed framework, named DRL-AE, effectively solves the challenges when applying DRL to the exposure control task, such as", + "bbox": [ + 75, + 810, + 468, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 2. Processing time analysis. Our algorithm does not use any complex metric or computation; the agent consists of two MLP layers with 256 hidden units, and the vectorized intensity history does not need complex operations. Therefore, our agent can be run on a CPU device in real-time. Here, we measure the processing time on the Ryzen 5950x CPU.", + "bbox": [ + 498, + 88, + 890, + 172 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/b8f7a50417b824f761021001563ad5f9f933174a3329766ab2deba236b8cab4e.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodImage SizeProcessing Time (ms)
Shin et al. [21]1600 x 1200108.7
800 x 60018.2
Ours1600 x 12001.0
800 x 6001.0
", + "bbox": [ + 519, + 196, + 874, + 289 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "1) training environment to provide diverse lighting change scenarios, 2) flickering and image attribute-aware reward design, 3) lightweight state design by using vectorized intensity history, and 4) domain generalization via spatial domain randomization strategy.", + "bbox": [ + 498, + 319, + 890, + 395 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "The proposed method is thoroughly validated in three different environments: light-controlled dark room, exposure control dataset [21], and real-world environments. We demonstrate that our proposed method instantly adjusts camera exposure within five steps with real-time processing of $1 \\, ms$ on a CPU device. Also, our method shows satisfactory generalization performance in the wild. The images acquired from our method are well-exposed and show superiority in numerous computer vision tasks, such as feature extraction and object detection1. To the best of our knowledge, our approach is the first solution that applies DRL to control camera exposure. We hope our paper encourages active research of advanced camera exposure control algorithms to achieve robust visual perception ability.", + "bbox": [ + 496, + 396, + 892, + 607 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Future Work. This paper shows that DRL can be used in the field of camera exposure control. There are lots of open research topics, such as motion-aware AE control, advanced reward function, aperture control, hardware generalization over various cameras, and further domain generalization in the real world. In the future, we plan to extend the current darkroom environment to generate object or camera motion, allowing the agent to consider motion blur for exposure parameter control. Controlling camera aperture by using a mechanical aperture control module is another research direction.", + "bbox": [ + 496, + 608, + 893, + 773 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgment", + "text_level": 1, + "bbox": [ + 500, + 790, + 651, + 806 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This research was supported by a grant (P0026022) from R&D Program funded by Ministry of Trade, Industry and Energy of Korean government.", + "bbox": [ + 500, + 816, + 890, + 862 + ], + "page_idx": 7 + }, + { + "type": "page_footnote", + "text": "Further visualization and video demos are available at https:// sites.google.com/view/drl-ae.", + "bbox": [ + 500, + 875, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "2982", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Christian Forster, Matia Pizzoli, and Davide Scaramuzza. 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Orb-slam2: An opensource slam system for monocular, stereo, and rgb-d cameras. 33(5):1255-1262, 2017. 2" + ], + "bbox": [ + 78, + 114, + 470, + 900 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[14] Masaru Muramatsu. Photometry device for a camera, 1997. US Patent 5,592,256. 1, 2", + "[15] Sidney F Ray, Wally Axford, and Geoffrey G Attridge. The Manual of Photography: Photographic and Digital Imaging. Elsevier Science & Technology, 2000. 2", + "[16] Joseph Redmon and Ali Farhadi. Yolo9000: Better, faster, stronger. In CVPR, pages 6517-6525. IEEE, 2017. 2", + "[17] Olaf Ronneberger, Philipp Fischer, and Thomas Brox. U-net: Convolutional networks for biomedical image segmentation. In Medical Image Computing and Computer-Assisted Intervention-MICCAI 2015: 18th International Conference, Munich, Germany, October 5-9, 2015, Proceedings, Part III 18, pages 234-241. Springer, 2015. 2", + "[18] Nitin Sampat, Shyam Venkataraman, Thomas Yeh, and Robert L Kremens. System implications of implementing auto-exposure on consumer digital cameras. In Sensors, Cameras, and Applications for Digital Photography, pages 100-108. International Society for Optics and Photonics, 1999. 1, 2", + "[19] John Schulman, Filip Wolski, Prafulla Dhariwal, Alec Radford, and Oleg Klimov. Proximal policy optimization algorithms. arXiv preprint arXiv:1707.06347, 2017. 5", + "[20] Inwook Shim, Tae-Hyun Oh, Joon-Young Lee, Jinwook Choi, Dong-Geol Choi, and In So Kweon. Gradient-based camera exposure control for outdoor mobile platforms. IEEE Transactions on Circuits and Systems for Video Technology, 29(6):1569–1583, 2018. 2", + "[21] Ukcheol Shin, Jinsun Park, Gyumin Shim, Francois Rameau, and In So Kweon. Camera exposure control for robust robot vision with noise-aware image quality assessment. 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In 2017 IEEE international conference on robotics and automation (ICRA), pages 3894-3901. IEEE, 2017. 2", + "[26] Chaoqiang Zhao, Qiyu Sun, Chongzhen Zhang, Yang Tang, and Feng Qian. Monocular depth estimation based on deep learning: An overview. Science China Technological Sciences, 63(9):1612-1627, 2020. 2" + ], + "bbox": [ + 501, + 92, + 893, + 881 + ], + "page_idx": 8 + }, + { + "type": "page_number", + "text": "2983", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 8 + } +] \ No newline at end of file diff --git a/2024/Learning to Control Camera Exposure via Reinforcement Learning/e1678f2e-e73f-4113-9734-14288276a0a8_model.json b/2024/Learning to Control Camera Exposure via Reinforcement Learning/e1678f2e-e73f-4113-9734-14288276a0a8_model.json new file mode 100644 index 0000000000000000000000000000000000000000..c885685feaa101d20ea6f092bdedeb8cb0152462 --- /dev/null +++ b/2024/Learning to Control Camera Exposure via Reinforcement Learning/e1678f2e-e73f-4113-9734-14288276a0a8_model.json @@ -0,0 +1,2011 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.145, + 0.131, + 0.828, + 0.154 + ], + "angle": 0, + "content": "Learning to Control Camera Exposure via Reinforcement Learning" + }, + { + "type": "text", + "bbox": [ + 0.175, + 0.182, + 0.314, + 0.216 + ], + "angle": 0, + "content": "Kyunghyun Lee* LG AI Research" + }, + { + "type": "text", + "bbox": [ + 0.123, + 0.22, + 0.364, + 0.234 + ], + "angle": 0, + "content": "kyunghyun.lee@lgresearch.ai" + }, + { + "type": "text", + "bbox": [ + 0.435, + 0.182, + 0.558, + 0.216 + ], + "angle": 0, + "content": "Ukcheol Shin* CMU" + }, + { + "type": "text", + "bbox": [ + 0.406, + 0.22, + 0.587, + 0.234 + ], + "angle": 0, + "content": "ushin@andrew.cmu.edu" + }, + { + "type": "text", + "bbox": [ + 0.672, + 0.182, + 0.803, + 0.216 + ], + "angle": 0, + "content": "Byeong-Uk Lee \nKRAFTON" + }, + { + "type": "text", + "bbox": [ + 0.627, + 0.22, + 0.842, + 0.234 + ], + "angle": 0, + "content": "byeonguk.lee@krafton.com" + }, + { + "type": "image_caption", + "bbox": [ + 0.321, + 0.258, + 0.692, + 0.27 + ], + "angle": 0, + "content": "Deep Reinforcement Learning based Automatic Exposure Control (ours)" + }, + { + "type": "image", + "bbox": [ + 0.099, + 0.27, + 0.871, + 0.442 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.318, + 0.444, + 0.65, + 0.457 + ], + "angle": 0, + "content": "(a) Automatic exposure control for sudden lighting changes" + }, + { + "type": "image", + "bbox": [ + 0.096, + 0.457, + 0.868, + 0.585 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.075, + 0.598, + 0.894, + 0.655 + ], + "angle": 0, + "content": "Figure 1. Automatic camera exposure control via deep reinforcement learning. Our proposed method, named DRL-AE, trains an agent to control camera exposure parameters (i.e., exposure time and gain) to acquire well-exposed images with rapid convergence and real-time processing (1ms on a CPU device). The trained agent instantly converges within five frames under dramatic lighting change scenario (a) and affects the performance of various vision applications (b), compared to the camera built-in AE controller [14, 18]." + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.678, + 0.314, + 0.695 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.71, + 0.471, + 0.877 + ], + "angle": 0, + "content": "Adjusting camera exposure in arbitrary lighting conditions is the first step to ensure the functionality of computer vision applications. Poorly adjusted camera exposure often leads to critical failure and performance degradation. Traditional camera exposure control methods require multiple convergence steps and time-consuming processes, making them unsuitable for dynamic lighting conditions. In this paper, we propose a new camera exposure control framework that rapidly controls camera exposure while performing real-time processing by exploiting deep reinforcement learning. The proposed framework consists" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.68, + 0.895, + 0.877 + ], + "angle": 0, + "content": "of four contributions: 1) a simplified training ground to simulate real-world's diverse and dynamic lighting changes, 2) flickering and image attribute-aware reward design, along with lightweight state design for real-time processing, 3) a static-to-dynamic lighting curriculum to gradually improve the agent's exposure-adjusting capability, and 4) domain randomization techniques to alleviate the limitation of the training ground and achieve seamless generalization in the wild. As a result, our proposed method rapidly reaches a desired exposure level within five steps with real-time processing (1ms). Also, the acquired images are well-exposed and show superiority in various computer vision tasks, such as feature extraction and object detection." + }, + { + "type": "page_footnote", + "bbox": [ + 0.101, + 0.888, + 0.352, + 0.901 + ], + "angle": 0, + "content": "*Both authors contributed equally to this work." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2975" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.208, + 0.106 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.115, + 0.468, + 0.297 + ], + "angle": 0, + "content": "Camera exposure control is the task of adjusting exposure level by controlling exposure time, gain, and aperture to achieve a desired level of brightness and image quality for a given scene. Poorly adjusted exposure parameters result in over-exposed, under-exposed, blurry, or noisy images, which can cause performance degradation in image-based applications and, in the worst cases, even life-threatening accidents. Therefore, finding proper camera exposure is the first primary step to ensure the functionality of computer vision applications, such as object detection [5, 16], semantic segmentation [9, 17], depth estimation [10, 26], and visual odometry [1, 13]." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.297, + 0.468, + 0.417 + ], + "angle": 0, + "content": "There are several essential requirements in camera exposure control. The rapid convergence must be guaranteed to maintain an appropriate exposure level under dynamic light-changing scenarios. Also, the exposure control loop is one of the lowest loops in the camera system. Therefore, lightweight algorithm design must be considered for on-board level operation. Finally, the quality of a converged image should not be sacrificed to meet the requirements." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.418, + 0.468, + 0.583 + ], + "angle": 0, + "content": "Further, the number of simultaneously controlled parameters is also important because it affects the converge time and final quality of the converged image. One-by-one control methods [14, 18, 20] control exposure parameters in a one-by-one manner to achieve a desired exposure level, rather than joint controlling exposure parameters. However, the converged parameters are often not optimal, such as [long exposure time, low gain] and [short exposure time, high gain] pairs. As a result, the values result in undesirable image artifacts, such as motion blur due to long exposure time or severe noise due to high gain." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.584, + 0.468, + 0.689 + ], + "angle": 0, + "content": "Joint exposure parameter control [7, 8, 21, 23, 24] often needs multiple searching steps in a wide range of searching space to find an optimal combination. As a result, they cause a flickering effect and slow convergence speed. Also, the recent methods require high-level computational complexity due to its optimization algorithm [7, 8], image assessment metric [7, 8, 20, 21], and GPU inference [23]." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.69, + 0.468, + 0.749 + ], + "angle": 0, + "content": "In this paper, we propose a new joint exposure parameter control method that exploits reinforcement learning to achieve instant convergence and real-time processing. The proposed framework consists of four contributions:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.75, + 0.468, + 0.779 + ], + "angle": 0, + "content": "- A simplified training ground to simulate real-world's diverse and dynamic lighting changes." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.781, + 0.468, + 0.825 + ], + "angle": 0, + "content": "- Flickering and image attribute-aware reward design, along with lightweight and intuitive state design for real-time processing." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.826, + 0.468, + 0.855 + ], + "angle": 0, + "content": "- A static-to-dynamic lighting curriculum learning to gradually improve agent's exposure adjusting capability." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.856, + 0.468, + 0.9 + ], + "angle": 0, + "content": "- Domain randomization techniques to alleviate the limitation of the training ground and achieve seamless generalization in the wild without additional training." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.75, + 0.468, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.213 + ], + "angle": 0, + "content": "The proposed method is thoroughly validated in three different environments: light-controlled darkroom, exposure control dataset [21], and real-world environments. We demonstrate that our proposed method rapidly adjusts camera exposure within five steps with real-time processing of \\( 1 \\, ms \\). Also, the images acquired from our method are well-exposed and show superiority in numerous computer vision tasks, such as feature extraction and object detection." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.228, + 0.642, + 0.243 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.253, + 0.829, + 0.269 + ], + "angle": 0, + "content": "2.1. Optimization-based Exposure Control" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.277, + 0.892, + 0.519 + ], + "angle": 0, + "content": "One branch to control camera exposure parameters is exploiting white-box and black-box optimizations to find optimal parameters for the desired exposure level. Camera built-in Auto-Exposure (AE) control methods [14, 18] adjust exposure parameters (i.e., exposure time and gain) based on differentiable optimization by using the equation between Exposure Value (EV) and exposure parameters [15]. They control exposure parameters one-by-one to achieve predefined image brightness. These built-in AE methods provide real-time processing ability but result in non-optimum solutions (e.g., long exposure time and low gain) and limited scalability. The former limitation causes motion blur and severe image noise due to long exposure time and high gain. The latter limitation indicates the methods cannot be extendable to maximize other image attributes, such as image gradient or entropy." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.52, + 0.892, + 0.746 + ], + "angle": 0, + "content": "Recent AE algorithms are designed to maximize desirable image attributes for computer vision applications, such as image gradient [20, 22, 25], entropy [7, 8], noise level [21], and optical flow [4]. However, these algorithms mainly focused on image metrics for better quality, not the control method. Therefore, they adopt heuristic control algorithm [20] or black-box optimization methods, such as Bayesian optimization [7, 8] and Nelder-Mead optimization [21]. These black-box optimizations and attribute assessment metrics often require multiple explorations that cause a flickering effect, multiple steps to converge, or heavy computation time. Differing from the previous method, the proposed method provides rapid convergence, real-time processing, and potential scalability by exploiting Deep Reinforcement Learning (DRL)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.757, + 0.771, + 0.772 + ], + "angle": 0, + "content": "2.2. Data-driven Exposure Control" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.781, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Another emerging branch of AE is utilizing a neural network to predict appropriate exposure parameters. Tomasi et al. [23] proposed an exposure parameter estimation network that predicts optimal exposure time and gain for each given image. The neural network, consisting of a few convolution and linear layers, is trained with Ground Truth (GT) exposure parameters in a supervised manner. However, the GT label generation needs a time-consuming and compli-" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2976" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.099, + 0.089, + 0.873, + 0.366 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.373, + 0.896, + 0.445 + ], + "angle": 0, + "content": "Figure 2. Training framework overview. Our DRL agent is trained with the SAC algorithm in the light-controlled dark room environment. For each episode, a lighting condition is assigned by the current curriculum level. The lighting condition can be fixed at random brightness or dynamically changed within each episode, depending on the level. Given the lighting condition, the agent takes a vectorized intensity history for a randomly selected RoI patch as a state. Afterward, the agent estimates exposure time and gain differences that maximize a reward function. With this framework, the trained agent successfully generalized into a real environment without additional training." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.455, + 0.473, + 0.548 + ], + "angle": 0, + "content": "ated process that collects multiple images with varying exposure parameters for every scene. Also, a heavy computation caused by the use of convolution layers is another drawback. Differing from the method, our method trains a neural network by maximizing a reward function without relying on specific GT data or generation processes." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.558, + 0.421, + 0.575 + ], + "angle": 0, + "content": "3. DRL for Automatic Exposure Control" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.583, + 0.47, + 0.644 + ], + "angle": 0, + "content": "Applying DRL to Automatic Exposure (AE) control task while achieving rapid convergence speed and real-time processing presents several challenges. Our proposed method provides effective solutions for the following questions." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.644, + 0.47, + 0.673 + ], + "angle": 0, + "content": "1. Environment: what is the most effective form of training environment to learn camera exposure control?" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.673, + 0.469, + 0.688 + ], + "angle": 0, + "content": "2. Reward: what aspects does the agent need to maximize?" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.689, + 0.462, + 0.703 + ], + "angle": 0, + "content": "3. State: where is the bottleneck for real-time processing?" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.704, + 0.469, + 0.734 + ], + "angle": 0, + "content": "4. Generalization: how to achieve seamless generalization in the wild lighting condition?" + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.644, + 0.47, + 0.734 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.742, + 0.288, + 0.759 + ], + "angle": 0, + "content": "3.1. Training Environment" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.471, + 0.903 + ], + "angle": 0, + "content": "DRL requires a large number of samples and interaction with the environment to train the agent. Also, the environment needs to provide a diverse and wide range of problems for the agent to solve. The optimal form of exposure control is to instantly adjust exposure parameters for a variety of lighting conditions, from static lighting conditions to dramatic lighting changes. To this end, the training environment for camera exposure control must provide diverse lighting change scenarios to the agent." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.455, + 0.895, + 0.606 + ], + "angle": 0, + "content": "Numerous options exist, such as a simulation, a real-world environment with natural sunlight, and a controlled real-world environment. The simulation can provide various images and lighting conditions but has the limitations of an imperfect exposure parameter implementation and a sim-to-real domain gap. On the other hand, the real-world environment with natural sunlight has no domain gap, but the lighting conditions change very slowly. Therefore, we construct a controlled real-world environment in a darkroom with controllable LEDs to adjust lighting conditions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.608, + 0.895, + 0.73 + ], + "angle": 0, + "content": "The constructed light-controlled darkroom is shown in Fig. 2. The environment has one machine vision camera, a random target object, a light controller, and an LED bar. The environment provides a random lighting scenario from dark to bright light conditions, and the agent adjusts exposure parameters to capture a high-quality image of the target object in the suggested scenario. The detailed sensor specification can be found in the supplementary material." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.743, + 0.796, + 0.76 + ], + "angle": 0, + "content": "3.2. State, Action, and Reward Design" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.768, + 0.847, + 0.784 + ], + "angle": 0, + "content": "3.2.1 State Design: Vectorized Intensity History" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.894, + 0.903 + ], + "angle": 0, + "content": "The widely adopted state design in related fields is utilizing a feature map from a pre-trained network [22, 23]. However, we found the CNN feature is not effective in the exposure control task due to its disadvantages: 1) unclear relation between CNN feature and exposure level, 2) generalization problem of CNN feature, and 3) heavy computation for on-board devices due to multiple convolution layers." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2977" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.244 + ], + "angle": 0, + "content": "Therefore, instead of using the CNN feature or other complicated features as a state, we utilize vectorized image intensity as a straightforward and lightweight state representation for the exposure control task. As shown in Fig. 2, we first vectorize image intensity map from a Region-of-Interest (RoI) patch of gray-scale image \\(\\mathbb{R}^{H_{RoI} \\times W_{RoI}}\\) to the intensity vector \\(\\mathbb{R}^S\\). The RoI patch can be an entire image area or specific regions decided by a domain randomization process. After that, we stack consecutive frame's intensity vectors to embed previous state history, as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.167, + 0.253, + 0.346, + 0.271 + ], + "angle": 0, + "content": "\\[\nv _ {t} = f \\left(I _ {t} ^ {R o I}\\right), \\quad v _ {t} \\in \\mathbb {R} ^ {S},\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.17, + 0.274, + 0.38, + 0.291 + ], + "angle": 0, + "content": "\\[\ns _ {t} = \\operatorname {c o n c a t} \\left(v _ {t - n}, \\dots , v _ {t - 1}, v _ {t}\\right),\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.302, + 0.473, + 0.439 + ], + "angle": 0, + "content": "where \\(I_{t}\\) is a normalized image at time step \\(t\\), \\(f(\\cdot)\\) is an averaging process through the x-axis of a gray-scale image, defined as \\(\\frac{1}{H_{RoI}}\\sum_{x}\\mathrm{gray}(I_t^{RoI})\\), \\(v_{t}\\) represents the vectorized intensity that has a dimension of \\(S\\), and \\(s_t\\) is a state vector. To ensure a fixed and reasonable state length, we resize the given RoI patch to have \\(S = 128\\) and stack previous states with \\(n = 3\\). The proposed state design is effective, straightforward, and computationally efficient compared to the CNN feature, as described in Sec. 4.1." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.457, + 0.462, + 0.473 + ], + "angle": 0, + "content": "3.2.2 Action Design: Relative and Continuous Action" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.481, + 0.47, + 0.677 + ], + "angle": 0, + "content": "Obviously, we have two controllable parameters, exposure time and gain, to adjust camera exposure. However, there are numerous options for its action design, such as 1) discrete vs. continuous action space, and 2) absolute vs. relative action range. A discrete action space discretizes the action range into a few action values. It has the advantage that the training process is simplified, but there is an approximation gap to the optimal values. The absolute and relative action range is about the change of camera parameters. In the absolute action range, an action value is directly matched to the specific value of camera parameters. On the other hand, in the relative action range, an action value indicates the amount of change in camera parameters." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.678, + 0.471, + 0.784 + ], + "angle": 0, + "content": "Among the options, we select continuous-relative action space. This is because our goal is rapid convergence with minimum exploration step, but discrete action space needs multiple steps and often does not converge, depending on its quantization level. Also, we empirically found that the absolute action range often induces a flickering effect and unstable convergence, as described in Sec. 4.1." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.802, + 0.468, + 0.818 + ], + "angle": 0, + "content": "3.2.3 Reward Design: Flickering and Image Attribute" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.826, + 0.47, + 0.902 + ], + "angle": 0, + "content": "The desirable behavior of exposure control is maximizing image attributes, such as sharp edge, moderate brightness, and low-level noise, and maintaining image attributes during exposure parameter transition. Therefore, we designed the reward function from three perspectives: 1) a moderate" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.168 + ], + "angle": 0, + "content": "brightness level to provide clear visibility and edge information, 2) a smoothed exposure transition to ensure stable convergence and prevent flickering, and 3) a low-level noise to provide clear image and avoid too-high gain value. The designed reward functions are as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.54, + 0.172, + 0.851, + 0.255 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {R} _ {m e a n} = \\frac {1}{P} \\sum_ {x y} \\left| I _ {t} ^ {R o I} - M \\right| ^ {p _ {m}}, \\\\ \\mathcal {R} _ {f l k} = \\frac {1}{P} \\sum_ {x y} | | I _ {t} ^ {R o I} - I _ {t - 1} ^ {R o I} | |, \\\\ \\mathcal {R} _ {n o i s e} = \\frac {1}{P} \\sum_ {x y} s o b e l (I _ {t} ^ {R o I}), \\\\ \\mathcal {R} _ {t o t a l} = w _ {m} \\mathcal {R} _ {m e a n} + w _ {f} \\mathcal {R} _ {f l k} + w _ {n} \\mathcal {R} _ {n o i s e}, \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.259, + 0.892, + 0.367 + ], + "angle": 0, + "content": "where \\(P\\) is the number of pixels, \\(M = 0.5\\) indicates mid-tone brightness, \\(p_m = 0.5\\) is a parameter for non-linearity and sobel is a gradient operator. Also, we set \\(w_{m} = 1.5\\), \\(w_{f} = -1.0\\), \\(w_{n} = -0.1\\) in practice. The proposed reward design might be a primitive and basic form for camera exposure control, however, it can be easily extendable by incorporating modern image assessment metrics [4, 8, 21]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.373, + 0.84, + 0.389 + ], + "angle": 0, + "content": "3.3. Static-to-dynamic Lighting Curriculum" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.396, + 0.892, + 0.532 + ], + "angle": 0, + "content": "In the wild, the agent must be able to control exposure parameters for a variety of lighting change scenarios. However, training every scenario simultaneously results in an unstable training process and poor generalization. Therefore, we propose static-to-dynamic curriculum strategy that starts with a simple control task and gradually experiences dynamic and dramatic lighting change scenarios. In the end, the trained models possess a comprehensive exposure control capability for diverse lighting conditions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.532, + 0.893, + 0.715 + ], + "angle": 0, + "content": "We divide the difficulty of lighting conditions into three levels: easy, normal, and hard. The easy level has static lighting conditions with moderate brightness. The normal level also has a fixed brightness but with a darker or brighter than easy level. Lastly, in the hard level, the LED brightness dynamically changes from dark to bright or the opposite way during each scenario. The probability of each level is gradually updated according to the proceeded training episode \\( t_e \\). The probability set \\( [p_e, p_n, p_h] \\) starts from \\( [1, 0, 0] \\), through \\( [0, 1, 0] \\), and ends with \\( [p_e^f, p_n^f, p_h^f] = [0.1, 0.4, 0.5] \\). In summary, the probability for each difficulty level is updated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.568, + 0.721, + 0.821, + 0.882 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} p _ {e} = \\left\\{ \\begin{array}{l l} 1, & t _ {e} < T _ {e} \\\\ \\frac {(t _ {e} - T _ {e})}{(T _ {n} - T _ {e})}, & T _ {e} \\leq t _ {e} < T _ {n} \\\\ p _ {e} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ p _ {n} = \\left\\{ \\begin{array}{l l} 0, & t _ {e} < T _ {e} \\\\ 1 - \\frac {\\left(t _ {e} - T _ {e}\\right)}{\\left(T _ {n} - T _ {e}\\right)}, & T _ {e} \\leq t _ {e} < T _ {n} \\\\ p _ {n} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ p _ {h} = \\left\\{ \\begin{array}{l l} 0, & t _ {e} < T _ {n} \\\\ p _ {h} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.886, + 0.816, + 0.902 + ], + "angle": 0, + "content": "We use \\( T_{e} = 25,000, T_{n} = 45,000 \\) in practice." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2978" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.078, + 0.091, + 0.355, + 0.107 + ], + "angle": 0, + "content": "3.4. Spatial Domain Randomization" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.114, + 0.468, + 0.249 + ], + "angle": 0, + "content": "In the wild, the agent encounters various surrounding environments and object contexts, such as office, road, tunnel, and mountain. Although the light-controlled darkroom can provide various lighting scenarios, it is difficult to contain diverse environments and contexts because it only has a few target objects with a fixed background. Therefore, without proper randomization techniques, the agent may overfit to perform exposure control for only a few target objects, resulting in generalization failure in the wild." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.25, + 0.468, + 0.402 + ], + "angle": 0, + "content": "The main idea is to provide as much diverse image structure and context information as possible by augmenting the image from the darkroom environment. Specifically, we spatially augment the images with random flipping, cropping, rotating, and resizing but do not change color and brightness information. Each augmentation and its parameter is randomly selected at the beginning of each training episode and fixed during the episode. With the proposed domain randomization technique, the trained agent can be generalized in the real world without any fine-tuning." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.41, + 0.266, + 0.426 + ], + "angle": 0, + "content": "3.5. Policy Optimization" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.433, + 0.468, + 0.522 + ], + "angle": 0, + "content": "As our action space is continuous, we use the SAC [3] algorithm. We excluded on-policy algorithms like PPO [19] because they are widely known to be less sample efficient than the off-policy algorithms like SAC, TD3, and DDPG. We tested TD3 [2] and DDPG [11] as well, but SAC showed the best result." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.524, + 0.468, + 0.569 + ], + "angle": 0, + "content": "SAC algorithm is a kind of actor-critic algorithm, which has critic \\( Q(\\theta) \\) and actor \\( \\pi(\\phi) \\). The objective functions to update the critic are as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.099, + 0.579, + 0.449, + 0.634 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} J _ {Q} (\\theta) = \\mathbb {E} _ {(s _ {t}, a _ {t}) \\sim \\mathcal {D}} \\left[ \\frac {1}{2} \\left(Q _ {\\theta} (s _ {t}, a _ {t}) - \\hat {Q} (s _ {t}, a _ {t})\\right) ^ {2} \\right], \\\\ \\hat {Q} (s _ {t}, a _ {t}) = r (s _ {t}, a _ {t}) + \\gamma \\mathbb {E} _ {s _ {t + 1} \\sim p} [ V _ {\\bar {\\theta}} (s _ {t + 1}) ], \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.643, + 0.468, + 0.687 + ], + "angle": 0, + "content": "where \\(\\mathcal{D}\\) is a replay buffer, \\(r(s_{t},a_{t})\\) is a reward function and \\(\\gamma\\) is a discount factor. The objective functions for updating the actor is as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.084, + 0.699, + 0.462, + 0.717 + ], + "angle": 0, + "content": "\\[\nJ _ {\\pi} (\\phi) = \\mathbb {E} _ {s _ {t} \\sim \\mathcal {D}} \\left[ \\mathbb {E} _ {a _ {t} \\sim \\pi_ {\\phi}} \\left[ \\alpha \\log \\left(\\pi_ {\\phi} \\left(a _ {t} \\mid s _ {t}\\right)\\right) - Q _ {\\theta} \\left(s _ {t}, a _ {t}\\right) \\right] \\right],\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.727, + 0.361, + 0.742 + ], + "angle": 0, + "content": "with \\(\\alpha\\) defined as a temperature parameter." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.755, + 0.209, + 0.772 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.468, + 0.901 + ], + "angle": 0, + "content": "In this section, we validate our proposed method in three different environments: light-controlled darkroom, exposure control dataset [21], and real-world environments. Throughout the experiments, we provide the validation result of DRL design components, ablation study of reward and training strategy, convergent step comparison, comparison with built-in AE for object detection and feature extraction, and computational time analysis." + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.089, + 0.892, + 0.146 + ], + "angle": 0, + "content": "Table 1. Self-evaluation of DRL-AE framework in the light-controlled darkroom. DR and CL indicate domain randomization and curriculum learning.\"-\" indicates the agent doesn't converge. The best performance in each block is highlighted in bold." + }, + { + "type": "table", + "bbox": [ + 0.517, + 0.152, + 0.878, + 0.442 + ], + "angle": 0, + "content": "
Framework ComponentMethodsReward per FrameFrames to Converge
RL AlgorithmDDPG [11]1.11-
TD3 [2]1.03-
SAC [3]1.615
StateCNN0.85-
Vector1.615
ActionAbsolute0.65-
Relative1.615
RewardRflk Rnoise
1.41-
✓1.4416
1.359
✓1.615
Training StrategyDR CL
✓--
1.6415
✓1.615
" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.453, + 0.884, + 0.469 + ], + "angle": 0, + "content": "4.1. Self-evaluation in Light-controlled Darkroom" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.477, + 0.892, + 0.627 + ], + "angle": 0, + "content": "We first validate our DRL design components and their variants in the light-controlled darkroom. We utilize reward per frame and the averaged number of frames to converge as evaluation metrics to measure image quality and convergence speed, respectively. Here, when the difference between current and previous images is less than a certain threshold, we regard it as the convergence. The testing scenarios include various lighting conditions, such as fixed lighting, progressive light changes, and dynamic light changes. The results are shown in Tab. 1." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.892, + 0.749 + ], + "angle": 0, + "content": "We found SAC method [3] shows the best result among the off-policy RL methods. Other algorithms can reach up to 1.0 reward per frame, but they usually do not converge well by showing oscillation. For the state design, the CNN feature is not desirable for the exposure control task due to its intensity-agnostic property. Also, absolute action space seems to make the overall learning process difficult because it needs to estimate the optimum values directly." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.901 + ], + "angle": 0, + "content": "The reward function and the training strategies play an important role in the stable and rapid convergence process and image attribute preservation. \\( R_{noise} \\) suppress high noise level and regularize gain parameter control, leading to better convergence. Also, \\( R_{flk} \\) makes the agent preserve the image attribute during the exposure transition. CL makes the agent encompass the comprehensive exposure control capability for the test set's various lighting conditions. Additionally, DR allows the agent to quickly converge for arbitrary context by increasing generalization ability." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2979" + } + ], + [ + { + "type": "image_caption", + "bbox": [ + 0.234, + 0.092, + 0.314, + 0.103 + ], + "angle": 0, + "content": "Shin et al. [21]" + }, + { + "type": "image", + "bbox": [ + 0.095, + 0.104, + 0.454, + 0.161 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.23, + 0.166, + 0.318, + 0.177 + ], + "angle": 0, + "content": "DRL-AE (Ours)" + }, + { + "type": "image", + "bbox": [ + 0.095, + 0.178, + 0.454, + 0.234 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.125, + 0.239, + 0.424, + 0.251 + ], + "angle": 0, + "content": "(a) Acquired image comparison for each convergent step" + }, + { + "type": "image", + "bbox": [ + 0.108, + 0.264, + 0.429, + 0.456 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.108, + 0.461, + 0.44, + 0.473 + ], + "angle": 0, + "content": "(b) Convergence trajectory of exposure parameter optimization" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.489, + 0.47, + 0.56 + ], + "angle": 0, + "content": "Figure 3. Convergent step comparison in exposure control dataset [21]. Within three frames, our method already reaches a well-exposed image (a) with minimum exploration (b). On the other hand, Shin et al. [21] search local areas with multiple steps (about 30 frames) to converge." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.588, + 0.34, + 0.604 + ], + "angle": 0, + "content": "4.2. Convergent Step Comparison" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.613, + 0.47, + 0.763 + ], + "angle": 0, + "content": "Exposure Control Dataset [21]. The dataset provides multiple images with many different pairs of exposure and gain values, which are captured from the real world. The dataset consists of several locations, including indoor and outdoor places, with a wide range of exposure and gain values. Outdoor images can have the exposure time from \\(100\\mu s\\) to \\(7450\\mu s\\), at intervals of \\(150\\mu s\\), and the gain from \\(0dB\\) to \\(20dB\\) with \\(2dB\\) interval. Similarly, indoor images have exposure time from \\(4ms\\) to \\(67ms\\) with \\(3ms\\) intervals and gain from \\(0dB\\) to \\(24dB\\) with \\(2dB\\) intervals." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.469, + 0.903 + ], + "angle": 0, + "content": "We evaluate our method with Shin et al. [21]. The final converged points are slightly different because of the difference between the proposed reward function and the assessment metric of [21]. Both algorithms converge to a comparable point, as shown in Fig. 3. It only takes three frames to converge with our method. However, the Nelder-Mead optimization method in [21] takes at least 30 timesteps to converge completely. Therefore, it is hard to use it in real scenarios, although they may find a more optimal point." + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.09, + 0.887, + 0.256 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.509, + 0.259, + 0.887, + 0.419 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.44, + 0.892, + 0.565 + ], + "angle": 0, + "content": "Figure 4. Real-world generalization. We compare our method with the camera's built-in exposure control algorithm in real-world scenarios. Camera lenses are occluded at the initial and suddenly removed in the first frame. Our agent converges to a well-exposed image within 3-5 frames. Yet, the built-in AE algorithm is still in the middle of adjusting the exposure parameters and is far from the well-exposed image, especially in the indoor case. Note that our agent is only trained in the light-controlled darkroom, and this is the zero-shot inference result in the wild." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.583, + 0.892, + 0.674 + ], + "angle": 0, + "content": "Real-world Indoor and Outdoor Environment. We evaluate our method with the camera's built-in AE control algorithm in real-world scenarios. The purposes of this experiment are twofold: 1) comparing convergence speed with the built-in AE algorithm, and 2) testing zero-shot generalization performance in the wild." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.892, + 0.794 + ], + "angle": 0, + "content": "Before starting, we cover the camera lens with enough time to converge in the dark, then quickly remove it to test the convergence speed for a sudden lighting change. Fig. 4 shows the captured initial five images during each optimization. Our method converges to a well-exposed image within 3-5 frames in both indoor and outdoor scenes. However, the built-in AE algorithm takes much longer to converge: 30 frames for indoors and 10 frames for outdoors." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Also, we found that our agent shows satisfactory zero-shot generalization performance, even though it is only trained in the light-controlled darkroom with limited object context. We believe our state design (i.e., vectorized intensity history) and spatial domain randomization bring this result by removing the potential domain gap issue of the CNN feature and augmenting object context as much as possible." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2980" + } + ], + [ + { + "type": "header", + "bbox": [ + 0.097, + 0.094, + 0.179, + 0.105 + ], + "angle": 0, + "content": "Features: 876" + }, + { + "type": "header", + "bbox": [ + 0.281, + 0.094, + 0.368, + 0.104 + ], + "angle": 0, + "content": "Features: 1377" + }, + { + "type": "image", + "bbox": [ + 0.09, + 0.135, + 0.273, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.275, + 0.134, + 0.457, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.158, + 0.217, + 0.39, + 0.228 + ], + "angle": 0, + "content": "(a) Feature extraction from DRL-AE (Ours)" + }, + { + "type": "image", + "bbox": [ + 0.091, + 0.228, + 0.273, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.275, + 0.233, + 0.457, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.171, + 0.355, + 0.377, + 0.367 + ], + "angle": 0, + "content": "(b) Feature extraction from built-in AE" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.384, + 0.47, + 0.482 + ], + "angle": 0, + "content": "Figure 5. SIFT [12] feature extraction result. Captured images from the proposed algorithm and built-in AE are processed to detect SIFT features. The images were simultaneously captured in real-time from two separate cameras equipped on a driving vehicle. Our method can provide plenty of SIFT features over the image plane. On average, our method detects \\(38\\%\\) more features across a total of 5355 images." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.512, + 0.442, + 0.527 + ], + "angle": 0, + "content": "4.3. Real-time Driving Env: Feature Extraction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.537, + 0.47, + 0.734 + ], + "angle": 0, + "content": "In this experiment, two cameras are attached to the top of a moving car, and images are captured simultaneously. One camera is used for our algorithm, and the other camera is for the built-in AE algorithm. We tested the algorithms on real-world driving scenarios, including campus and urban roads. Our algorithm runs on a laptop equipped with an i7-7700HQ@2.80GHz CPU unit. Given an image, the agent predicts exposure time and gain commands in real-time. The estimated actions are transmitted to the attached camera. After driving sequences acquisition, we extract SIFT [12] features from each captured image. Please note that the images of DRL-AE and built-in AE have slightly different views due to the difference in the installed position." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.468, + 0.902 + ], + "angle": 0, + "content": "Fig. 5 shows the comparison of feature extraction results. From the total of 5355 image pairs, our method produces 1,306 SIFT features on average with a 1,157 median value. On the other hand, the built-in AE method only results in 946 features on average, with a 711 median value. Therefore, \\(38\\%\\) more features are detected on average, and the difference is up to \\(62\\%\\) for the median value. The number of detected features and feature repeatability during exposure transition are critical for Visual Odometry (VO) and SLAM tasks. So, we believe our method can be valuable for VO, SLAM, and visual tracking tasks as well." + }, + { + "type": "image", + "bbox": [ + 0.513, + 0.088, + 0.697, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.699, + 0.088, + 0.882, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.586, + 0.216, + 0.808, + 0.228 + ], + "angle": 0, + "content": "(a) Object detection from DRL-AE (Ours)" + }, + { + "type": "image", + "bbox": [ + 0.513, + 0.228, + 0.697, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.698, + 0.228, + 0.881, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.597, + 0.355, + 0.796, + 0.367 + ], + "angle": 0, + "content": "(b) Object detection from built-in AE" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.385, + 0.892, + 0.468 + ], + "angle": 0, + "content": "Figure 6. Object detection result. Captured images from the proposed algorithm and built-in AE are processed to detect target objects. The experiment used the same image sequence as the SIFT experiment. We utilize Yolo-v5 [6] for car and pedestrian detection. On average, our method detects \\(5\\%\\) more objects compared to the built-in AE algorithm." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.495, + 0.848, + 0.511 + ], + "angle": 0, + "content": "4.4. Real-time Driving Env: Object Detection" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.519, + 0.892, + 0.746 + ], + "angle": 0, + "content": "Similar to the feature extraction experiment, the captured images are processed with YOLO-v5 [6]. The images are taken from campus and urban road scenes, so we only take into account cars and pedestrians. Fig. 6 shows the comparison of object detection results from DRL-AE and built-in AE methods. Recent detection models, including YOLO-v5, adopt modern augmentation methods to make the model robust the image brightness changes. Therefore, YOLO-v5 tends to detect objects well in even poorly exposed images. However, our algorithm detects \\(5\\%\\) more objects in terms of the total number of detected objects. Furthermore, the objects in our image are detected much earlier than the built-in AE method. This is highly critical for autonomous vehicles that are driving at high speed. Earlier detected objects can prevent human injury and potential accidents." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.757, + 0.889, + 0.773 + ], + "angle": 0, + "content": "4.5. Real-world Env: RoI-aware Exposure Control" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Our DRL-AE framework can also take arbitrary input sizes because the framework resizes the image before the vectorized intensity processing. Also, our domain randomization strategy produces a random size of the Region of Interest (RoI) patch by using crop, flip, resize, and rotation in the training stage. Therefore, our agent is able to control camera exposure for a specific RoI or entire image. Fig. 7 shows the RoI-aware exposure control results." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.514, + 0.957 + ], + "angle": 0, + "content": "2981" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.088, + 0.089, + 0.468, + 0.29 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.316, + 0.472, + 0.386 + ], + "angle": 0, + "content": "Figure 7. RoI-aware camera exposure control. Our agent is able to control camera exposure for a specific RoI or entire image. Given a RoI box, the agent adjusts the camera parameters to maximize the image attribute for a specific RoI area. It allows the camera to capture the detailed context for the regions of interest." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.414, + 0.47, + 0.535 + ], + "angle": 0, + "content": "The agent adjusts the camera parameters to maximize the image attribute for a specific RoI area. It allows the camera to capture the detailed context for the regions of interest. We expect that DRL-AE can be combined with object detection, object tracking, and human gaze and attention. As a result, the combination can lead to adaptive exposure control schemes, such as attention-aware or detection-aware exposure control." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.547, + 0.33, + 0.563 + ], + "angle": 0, + "content": "4.6. Computation Time Analysis" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.572, + 0.47, + 0.768 + ], + "angle": 0, + "content": "Our agent has a simple Multi-Layer Perceptron (MLP) architecture with two hidden layers of 256 units. Also, our method does not require complex matrix computation like convolutions. Therefore, our agent can be run on a CPU device in real-time. We measure the inference time of the agent on the Ryzen 5950x CPU. Tab. 2 shows the computation time results, compared with shin et al. [21]. The network's inference time takes \\(1ms\\) regardless of image resolution because the input image is resized to a fixed resolution. Also, even including other operations, such as image resizing and RoI cropping, it takes a maximum \\(6ms\\), which is still in the real-time range. Therefore, it can run at 170- \\(1000\\mathrm{Hz}\\) on a CPU device." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.784, + 0.332, + 0.8 + ], + "angle": 0, + "content": "5. Conclusion & Future Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Conclusion. In this paper, we proposed a novel joint exposure parameter control framework that exploits Deep Reinforcement Learning (DRL) to achieve instant exposure convergence and real-time processing. The proposed framework, named DRL-AE, effectively solves the challenges when applying DRL to the exposure control task, such as" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.089, + 0.892, + 0.173 + ], + "angle": 0, + "content": "Table 2. Processing time analysis. Our algorithm does not use any complex metric or computation; the agent consists of two MLP layers with 256 hidden units, and the vectorized intensity history does not need complex operations. Therefore, our agent can be run on a CPU device in real-time. Here, we measure the processing time on the Ryzen 5950x CPU." + }, + { + "type": "table", + "bbox": [ + 0.521, + 0.197, + 0.875, + 0.29 + ], + "angle": 0, + "content": "
MethodImage SizeProcessing Time (ms)
Shin et al. [21]1600 x 1200108.7
800 x 60018.2
Ours1600 x 12001.0
800 x 6001.0
" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.32, + 0.892, + 0.396 + ], + "angle": 0, + "content": "1) training environment to provide diverse lighting change scenarios, 2) flickering and image attribute-aware reward design, 3) lightweight state design by using vectorized intensity history, and 4) domain generalization via spatial domain randomization strategy." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.397, + 0.893, + 0.608 + ], + "angle": 0, + "content": "The proposed method is thoroughly validated in three different environments: light-controlled dark room, exposure control dataset [21], and real-world environments. We demonstrate that our proposed method instantly adjusts camera exposure within five steps with real-time processing of \\( 1 \\, ms \\) on a CPU device. Also, our method shows satisfactory generalization performance in the wild. The images acquired from our method are well-exposed and show superiority in numerous computer vision tasks, such as feature extraction and object detection1. To the best of our knowledge, our approach is the first solution that applies DRL to control camera exposure. We hope our paper encourages active research of advanced camera exposure control algorithms to achieve robust visual perception ability." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.609, + 0.894, + 0.775 + ], + "angle": 0, + "content": "Future Work. This paper shows that DRL can be used in the field of camera exposure control. There are lots of open research topics, such as motion-aware AE control, advanced reward function, aperture control, hardware generalization over various cameras, and further domain generalization in the real world. In the future, we plan to extend the current darkroom environment to generate object or camera motion, allowing the agent to consider motion blur for exposure parameter control. Controlling camera aperture by using a mechanical aperture control module is another research direction." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.791, + 0.652, + 0.808 + ], + "angle": 0, + "content": "Acknowledgment" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.817, + 0.892, + 0.863 + ], + "angle": 0, + "content": "This research was supported by a grant (P0026022) from R&D Program funded by Ministry of Trade, Industry and Energy of Korean government." + }, + { + "type": "page_footnote", + "bbox": [ + 0.501, + 0.875, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Further visualization and video demos are available at https:// sites.google.com/view/drl-ae." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2982" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.171 + ], + "angle": 0, + "content": "[1] Christian Forster, Matia Pizzoli, and Davide Scaramuzza. 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Science China Technological Sciences, 63(9):1612-1627, 2020. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.894, + 0.882 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "2983" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Control Camera Exposure via Reinforcement Learning/e1678f2e-e73f-4113-9734-14288276a0a8_origin.pdf b/2024/Learning to Control Camera Exposure via Reinforcement Learning/e1678f2e-e73f-4113-9734-14288276a0a8_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..26cfa63d18a95d7fc5e3601f837223b772ccf71b --- /dev/null +++ b/2024/Learning to Control Camera Exposure via Reinforcement Learning/e1678f2e-e73f-4113-9734-14288276a0a8_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:7c71fab85dd63336bade275e1461a5abbe23c9e6d51c55d533cbbc2524d6b019 +size 8068943 diff --git a/2024/Learning to Control Camera Exposure via Reinforcement Learning/full.md b/2024/Learning to Control Camera Exposure via Reinforcement Learning/full.md new file mode 100644 index 0000000000000000000000000000000000000000..b7586a3e2852724375009b9fc9c403b2b9d1276c --- /dev/null +++ b/2024/Learning to Control Camera Exposure via Reinforcement Learning/full.md @@ -0,0 +1,289 @@ +# Learning to Control Camera Exposure via Reinforcement Learning + +Kyunghyun Lee* LG AI Research + +kyunghyun.lee@lgresearch.ai + +Ukcheol Shin* CMU + +ushin@andrew.cmu.edu + +Byeong-Uk Lee +KRAFTON + +byeonguk.lee@krafton.com + +![](images/74544727623b75c780eedda3df1cd9ce8ea53aa0675408ce57a994ec0c751a72.jpg) +Deep Reinforcement Learning based Automatic Exposure Control (ours) + +![](images/566f832571d22f41281f9a51fcc290c6a874ae0487dba4609b8362d7463c8479.jpg) +(a) Automatic exposure control for sudden lighting changes +Figure 1. Automatic camera exposure control via deep reinforcement learning. Our proposed method, named DRL-AE, trains an agent to control camera exposure parameters (i.e., exposure time and gain) to acquire well-exposed images with rapid convergence and real-time processing (1ms on a CPU device). The trained agent instantly converges within five frames under dramatic lighting change scenario (a) and affects the performance of various vision applications (b), compared to the camera built-in AE controller [14, 18]. + +# Abstract + +Adjusting camera exposure in arbitrary lighting conditions is the first step to ensure the functionality of computer vision applications. Poorly adjusted camera exposure often leads to critical failure and performance degradation. Traditional camera exposure control methods require multiple convergence steps and time-consuming processes, making them unsuitable for dynamic lighting conditions. In this paper, we propose a new camera exposure control framework that rapidly controls camera exposure while performing real-time processing by exploiting deep reinforcement learning. The proposed framework consists + +of four contributions: 1) a simplified training ground to simulate real-world's diverse and dynamic lighting changes, 2) flickering and image attribute-aware reward design, along with lightweight state design for real-time processing, 3) a static-to-dynamic lighting curriculum to gradually improve the agent's exposure-adjusting capability, and 4) domain randomization techniques to alleviate the limitation of the training ground and achieve seamless generalization in the wild. As a result, our proposed method rapidly reaches a desired exposure level within five steps with real-time processing (1ms). Also, the acquired images are well-exposed and show superiority in various computer vision tasks, such as feature extraction and object detection. + +# 1. Introduction + +Camera exposure control is the task of adjusting exposure level by controlling exposure time, gain, and aperture to achieve a desired level of brightness and image quality for a given scene. Poorly adjusted exposure parameters result in over-exposed, under-exposed, blurry, or noisy images, which can cause performance degradation in image-based applications and, in the worst cases, even life-threatening accidents. Therefore, finding proper camera exposure is the first primary step to ensure the functionality of computer vision applications, such as object detection [5, 16], semantic segmentation [9, 17], depth estimation [10, 26], and visual odometry [1, 13]. + +There are several essential requirements in camera exposure control. The rapid convergence must be guaranteed to maintain an appropriate exposure level under dynamic light-changing scenarios. Also, the exposure control loop is one of the lowest loops in the camera system. Therefore, lightweight algorithm design must be considered for on-board level operation. Finally, the quality of a converged image should not be sacrificed to meet the requirements. + +Further, the number of simultaneously controlled parameters is also important because it affects the converge time and final quality of the converged image. One-by-one control methods [14, 18, 20] control exposure parameters in a one-by-one manner to achieve a desired exposure level, rather than joint controlling exposure parameters. However, the converged parameters are often not optimal, such as [long exposure time, low gain] and [short exposure time, high gain] pairs. As a result, the values result in undesirable image artifacts, such as motion blur due to long exposure time or severe noise due to high gain. + +Joint exposure parameter control [7, 8, 21, 23, 24] often needs multiple searching steps in a wide range of searching space to find an optimal combination. As a result, they cause a flickering effect and slow convergence speed. Also, the recent methods require high-level computational complexity due to its optimization algorithm [7, 8], image assessment metric [7, 8, 20, 21], and GPU inference [23]. + +In this paper, we propose a new joint exposure parameter control method that exploits reinforcement learning to achieve instant convergence and real-time processing. The proposed framework consists of four contributions: + +- A simplified training ground to simulate real-world's diverse and dynamic lighting changes. +- Flickering and image attribute-aware reward design, along with lightweight and intuitive state design for real-time processing. +- A static-to-dynamic lighting curriculum learning to gradually improve agent's exposure adjusting capability. +- Domain randomization techniques to alleviate the limitation of the training ground and achieve seamless generalization in the wild without additional training. + +The proposed method is thoroughly validated in three different environments: light-controlled darkroom, exposure control dataset [21], and real-world environments. We demonstrate that our proposed method rapidly adjusts camera exposure within five steps with real-time processing of $1 \, ms$ . Also, the images acquired from our method are well-exposed and show superiority in numerous computer vision tasks, such as feature extraction and object detection. + +# 2. Related Work + +# 2.1. Optimization-based Exposure Control + +One branch to control camera exposure parameters is exploiting white-box and black-box optimizations to find optimal parameters for the desired exposure level. Camera built-in Auto-Exposure (AE) control methods [14, 18] adjust exposure parameters (i.e., exposure time and gain) based on differentiable optimization by using the equation between Exposure Value (EV) and exposure parameters [15]. They control exposure parameters one-by-one to achieve predefined image brightness. These built-in AE methods provide real-time processing ability but result in non-optimum solutions (e.g., long exposure time and low gain) and limited scalability. The former limitation causes motion blur and severe image noise due to long exposure time and high gain. The latter limitation indicates the methods cannot be extendable to maximize other image attributes, such as image gradient or entropy. + +Recent AE algorithms are designed to maximize desirable image attributes for computer vision applications, such as image gradient [20, 22, 25], entropy [7, 8], noise level [21], and optical flow [4]. However, these algorithms mainly focused on image metrics for better quality, not the control method. Therefore, they adopt heuristic control algorithm [20] or black-box optimization methods, such as Bayesian optimization [7, 8] and Nelder-Mead optimization [21]. These black-box optimizations and attribute assessment metrics often require multiple explorations that cause a flickering effect, multiple steps to converge, or heavy computation time. Differing from the previous method, the proposed method provides rapid convergence, real-time processing, and potential scalability by exploiting Deep Reinforcement Learning (DRL). + +# 2.2. Data-driven Exposure Control + +Another emerging branch of AE is utilizing a neural network to predict appropriate exposure parameters. Tomasi et al. [23] proposed an exposure parameter estimation network that predicts optimal exposure time and gain for each given image. The neural network, consisting of a few convolution and linear layers, is trained with Ground Truth (GT) exposure parameters in a supervised manner. However, the GT label generation needs a time-consuming and compli- + +![](images/f8318031ddbd548d9f50ecf54fa60f831d41934fef2a5df7901ad123c9ba520a.jpg) +Figure 2. Training framework overview. Our DRL agent is trained with the SAC algorithm in the light-controlled dark room environment. For each episode, a lighting condition is assigned by the current curriculum level. The lighting condition can be fixed at random brightness or dynamically changed within each episode, depending on the level. Given the lighting condition, the agent takes a vectorized intensity history for a randomly selected RoI patch as a state. Afterward, the agent estimates exposure time and gain differences that maximize a reward function. With this framework, the trained agent successfully generalized into a real environment without additional training. + +ated process that collects multiple images with varying exposure parameters for every scene. Also, a heavy computation caused by the use of convolution layers is another drawback. Differing from the method, our method trains a neural network by maximizing a reward function without relying on specific GT data or generation processes. + +# 3. DRL for Automatic Exposure Control + +Applying DRL to Automatic Exposure (AE) control task while achieving rapid convergence speed and real-time processing presents several challenges. Our proposed method provides effective solutions for the following questions. + +1. Environment: what is the most effective form of training environment to learn camera exposure control? +2. Reward: what aspects does the agent need to maximize? +3. State: where is the bottleneck for real-time processing? +4. Generalization: how to achieve seamless generalization in the wild lighting condition? + +# 3.1. Training Environment + +DRL requires a large number of samples and interaction with the environment to train the agent. Also, the environment needs to provide a diverse and wide range of problems for the agent to solve. The optimal form of exposure control is to instantly adjust exposure parameters for a variety of lighting conditions, from static lighting conditions to dramatic lighting changes. To this end, the training environment for camera exposure control must provide diverse lighting change scenarios to the agent. + +Numerous options exist, such as a simulation, a real-world environment with natural sunlight, and a controlled real-world environment. The simulation can provide various images and lighting conditions but has the limitations of an imperfect exposure parameter implementation and a sim-to-real domain gap. On the other hand, the real-world environment with natural sunlight has no domain gap, but the lighting conditions change very slowly. Therefore, we construct a controlled real-world environment in a darkroom with controllable LEDs to adjust lighting conditions. + +The constructed light-controlled darkroom is shown in Fig. 2. The environment has one machine vision camera, a random target object, a light controller, and an LED bar. The environment provides a random lighting scenario from dark to bright light conditions, and the agent adjusts exposure parameters to capture a high-quality image of the target object in the suggested scenario. The detailed sensor specification can be found in the supplementary material. + +# 3.2. State, Action, and Reward Design + +# 3.2.1 State Design: Vectorized Intensity History + +The widely adopted state design in related fields is utilizing a feature map from a pre-trained network [22, 23]. However, we found the CNN feature is not effective in the exposure control task due to its disadvantages: 1) unclear relation between CNN feature and exposure level, 2) generalization problem of CNN feature, and 3) heavy computation for on-board devices due to multiple convolution layers. + +Therefore, instead of using the CNN feature or other complicated features as a state, we utilize vectorized image intensity as a straightforward and lightweight state representation for the exposure control task. As shown in Fig. 2, we first vectorize image intensity map from a Region-of-Interest (RoI) patch of gray-scale image $\mathbb{R}^{H_{RoI} \times W_{RoI}}$ to the intensity vector $\mathbb{R}^S$ . The RoI patch can be an entire image area or specific regions decided by a domain randomization process. After that, we stack consecutive frame's intensity vectors to embed previous state history, as follows: + +$$ +v _ {t} = f \left(I _ {t} ^ {R o I}\right), \quad v _ {t} \in \mathbb {R} ^ {S}, +$$ + +$$ +s _ {t} = \operatorname {c o n c a t} \left(v _ {t - n}, \dots , v _ {t - 1}, v _ {t}\right), +$$ + +where $I_{t}$ is a normalized image at time step $t$ , $f(\cdot)$ is an averaging process through the x-axis of a gray-scale image, defined as $\frac{1}{H_{RoI}}\sum_{x}\mathrm{gray}(I_t^{RoI})$ , $v_{t}$ represents the vectorized intensity that has a dimension of $S$ , and $s_t$ is a state vector. To ensure a fixed and reasonable state length, we resize the given RoI patch to have $S = 128$ and stack previous states with $n = 3$ . The proposed state design is effective, straightforward, and computationally efficient compared to the CNN feature, as described in Sec. 4.1. + +# 3.2.2 Action Design: Relative and Continuous Action + +Obviously, we have two controllable parameters, exposure time and gain, to adjust camera exposure. However, there are numerous options for its action design, such as 1) discrete vs. continuous action space, and 2) absolute vs. relative action range. A discrete action space discretizes the action range into a few action values. It has the advantage that the training process is simplified, but there is an approximation gap to the optimal values. The absolute and relative action range is about the change of camera parameters. In the absolute action range, an action value is directly matched to the specific value of camera parameters. On the other hand, in the relative action range, an action value indicates the amount of change in camera parameters. + +Among the options, we select continuous-relative action space. This is because our goal is rapid convergence with minimum exploration step, but discrete action space needs multiple steps and often does not converge, depending on its quantization level. Also, we empirically found that the absolute action range often induces a flickering effect and unstable convergence, as described in Sec. 4.1. + +# 3.2.3 Reward Design: Flickering and Image Attribute + +The desirable behavior of exposure control is maximizing image attributes, such as sharp edge, moderate brightness, and low-level noise, and maintaining image attributes during exposure parameter transition. Therefore, we designed the reward function from three perspectives: 1) a moderate + +brightness level to provide clear visibility and edge information, 2) a smoothed exposure transition to ensure stable convergence and prevent flickering, and 3) a low-level noise to provide clear image and avoid too-high gain value. The designed reward functions are as follows: + +$$ +\begin{array}{l} \mathcal {R} _ {m e a n} = \frac {1}{P} \sum_ {x y} \left| I _ {t} ^ {R o I} - M \right| ^ {p _ {m}}, \\ \mathcal {R} _ {f l k} = \frac {1}{P} \sum_ {x y} | | I _ {t} ^ {R o I} - I _ {t - 1} ^ {R o I} | |, \\ \mathcal {R} _ {n o i s e} = \frac {1}{P} \sum_ {x y} s o b e l (I _ {t} ^ {R o I}), \\ \mathcal {R} _ {t o t a l} = w _ {m} \mathcal {R} _ {m e a n} + w _ {f} \mathcal {R} _ {f l k} + w _ {n} \mathcal {R} _ {n o i s e}, \\ \end{array} +$$ + +where $P$ is the number of pixels, $M = 0.5$ indicates mid-tone brightness, $p_m = 0.5$ is a parameter for non-linearity and sobel is a gradient operator. Also, we set $w_{m} = 1.5$ , $w_{f} = -1.0$ , $w_{n} = -0.1$ in practice. The proposed reward design might be a primitive and basic form for camera exposure control, however, it can be easily extendable by incorporating modern image assessment metrics [4, 8, 21]. + +# 3.3. Static-to-dynamic Lighting Curriculum + +In the wild, the agent must be able to control exposure parameters for a variety of lighting change scenarios. However, training every scenario simultaneously results in an unstable training process and poor generalization. Therefore, we propose static-to-dynamic curriculum strategy that starts with a simple control task and gradually experiences dynamic and dramatic lighting change scenarios. In the end, the trained models possess a comprehensive exposure control capability for diverse lighting conditions. + +We divide the difficulty of lighting conditions into three levels: easy, normal, and hard. The easy level has static lighting conditions with moderate brightness. The normal level also has a fixed brightness but with a darker or brighter than easy level. Lastly, in the hard level, the LED brightness dynamically changes from dark to bright or the opposite way during each scenario. The probability of each level is gradually updated according to the proceeded training episode $t_e$ . The probability set $[p_e, p_n, p_h]$ starts from $[1, 0, 0]$ , through $[0, 1, 0]$ , and ends with $[p_e^f, p_n^f, p_h^f] = [0.1, 0.4, 0.5]$ . In summary, the probability for each difficulty level is updated as follows: + +$$ +\begin{array}{l} p _ {e} = \left\{ \begin{array}{l l} 1, & t _ {e} < T _ {e} \\ \frac {(t _ {e} - T _ {e})}{(T _ {n} - T _ {e})}, & T _ {e} \leq t _ {e} < T _ {n} \\ p _ {e} ^ {f}, & T _ {n} \leq t _ {e} \end{array} \right. \\ p _ {n} = \left\{ \begin{array}{l l} 0, & t _ {e} < T _ {e} \\ 1 - \frac {\left(t _ {e} - T _ {e}\right)}{\left(T _ {n} - T _ {e}\right)}, & T _ {e} \leq t _ {e} < T _ {n} \\ p _ {n} ^ {f}, & T _ {n} \leq t _ {e} \end{array} \right. \\ p _ {h} = \left\{ \begin{array}{l l} 0, & t _ {e} < T _ {n} \\ p _ {h} ^ {f}, & T _ {n} \leq t _ {e} \end{array} \right. \\ \end{array} +$$ + +We use $T_{e} = 25,000, T_{n} = 45,000$ in practice. + +# 3.4. Spatial Domain Randomization + +In the wild, the agent encounters various surrounding environments and object contexts, such as office, road, tunnel, and mountain. Although the light-controlled darkroom can provide various lighting scenarios, it is difficult to contain diverse environments and contexts because it only has a few target objects with a fixed background. Therefore, without proper randomization techniques, the agent may overfit to perform exposure control for only a few target objects, resulting in generalization failure in the wild. + +The main idea is to provide as much diverse image structure and context information as possible by augmenting the image from the darkroom environment. Specifically, we spatially augment the images with random flipping, cropping, rotating, and resizing but do not change color and brightness information. Each augmentation and its parameter is randomly selected at the beginning of each training episode and fixed during the episode. With the proposed domain randomization technique, the trained agent can be generalized in the real world without any fine-tuning. + +# 3.5. Policy Optimization + +As our action space is continuous, we use the SAC [3] algorithm. We excluded on-policy algorithms like PPO [19] because they are widely known to be less sample efficient than the off-policy algorithms like SAC, TD3, and DDPG. We tested TD3 [2] and DDPG [11] as well, but SAC showed the best result. + +SAC algorithm is a kind of actor-critic algorithm, which has critic $Q(\theta)$ and actor $\pi(\phi)$ . The objective functions to update the critic are as follows: + +$$ +\begin{array}{l} J _ {Q} (\theta) = \mathbb {E} _ {(s _ {t}, a _ {t}) \sim \mathcal {D}} \left[ \frac {1}{2} \left(Q _ {\theta} (s _ {t}, a _ {t}) - \hat {Q} (s _ {t}, a _ {t})\right) ^ {2} \right], \\ \hat {Q} (s _ {t}, a _ {t}) = r (s _ {t}, a _ {t}) + \gamma \mathbb {E} _ {s _ {t + 1} \sim p} [ V _ {\bar {\theta}} (s _ {t + 1}) ], \\ \end{array} +$$ + +where $\mathcal{D}$ is a replay buffer, $r(s_{t},a_{t})$ is a reward function and $\gamma$ is a discount factor. The objective functions for updating the actor is as follows: + +$$ +J _ {\pi} (\phi) = \mathbb {E} _ {s _ {t} \sim \mathcal {D}} \left[ \mathbb {E} _ {a _ {t} \sim \pi_ {\phi}} \left[ \alpha \log \left(\pi_ {\phi} \left(a _ {t} \mid s _ {t}\right)\right) - Q _ {\theta} \left(s _ {t}, a _ {t}\right) \right] \right], +$$ + +with $\alpha$ defined as a temperature parameter. + +# 4. Experiments + +In this section, we validate our proposed method in three different environments: light-controlled darkroom, exposure control dataset [21], and real-world environments. Throughout the experiments, we provide the validation result of DRL design components, ablation study of reward and training strategy, convergent step comparison, comparison with built-in AE for object detection and feature extraction, and computational time analysis. + +Table 1. Self-evaluation of DRL-AE framework in the light-controlled darkroom. DR and CL indicate domain randomization and curriculum learning."-" indicates the agent doesn't converge. The best performance in each block is highlighted in bold. + +
Framework ComponentMethodsReward per FrameFrames to Converge
RL AlgorithmDDPG [11]1.11-
TD3 [2]1.03-
SAC [3]1.615
StateCNN0.85-
Vector1.615
ActionAbsolute0.65-
Relative1.615
RewardRflk Rnoise
1.41-
✓1.4416
1.359
✓1.615
Training StrategyDR CL
✓--
1.6415
✓1.615
+ +# 4.1. Self-evaluation in Light-controlled Darkroom + +We first validate our DRL design components and their variants in the light-controlled darkroom. We utilize reward per frame and the averaged number of frames to converge as evaluation metrics to measure image quality and convergence speed, respectively. Here, when the difference between current and previous images is less than a certain threshold, we regard it as the convergence. The testing scenarios include various lighting conditions, such as fixed lighting, progressive light changes, and dynamic light changes. The results are shown in Tab. 1. + +We found SAC method [3] shows the best result among the off-policy RL methods. Other algorithms can reach up to 1.0 reward per frame, but they usually do not converge well by showing oscillation. For the state design, the CNN feature is not desirable for the exposure control task due to its intensity-agnostic property. Also, absolute action space seems to make the overall learning process difficult because it needs to estimate the optimum values directly. + +The reward function and the training strategies play an important role in the stable and rapid convergence process and image attribute preservation. $R_{noise}$ suppress high noise level and regularize gain parameter control, leading to better convergence. Also, $R_{flk}$ makes the agent preserve the image attribute during the exposure transition. CL makes the agent encompass the comprehensive exposure control capability for the test set's various lighting conditions. Additionally, DR allows the agent to quickly converge for arbitrary context by increasing generalization ability. + +![](images/d5039d6ae910a2957238f8af729c9a9a0b5a8734ec34586e0af3538aec8c7702.jpg) +Shin et al. [21] + +![](images/0f5695d9315063e2774271edd0dce5cd14c882c553f5d426fc7f7e6fe2832b95.jpg) +DRL-AE (Ours) +(a) Acquired image comparison for each convergent step + +![](images/9fc31a1cc91ae10b2fa46efeb85dbd0aa11cc1980f81ebd00baa660a576bd456.jpg) +(b) Convergence trajectory of exposure parameter optimization +Figure 3. Convergent step comparison in exposure control dataset [21]. Within three frames, our method already reaches a well-exposed image (a) with minimum exploration (b). On the other hand, Shin et al. [21] search local areas with multiple steps (about 30 frames) to converge. + +# 4.2. Convergent Step Comparison + +Exposure Control Dataset [21]. The dataset provides multiple images with many different pairs of exposure and gain values, which are captured from the real world. The dataset consists of several locations, including indoor and outdoor places, with a wide range of exposure and gain values. Outdoor images can have the exposure time from $100\mu s$ to $7450\mu s$ , at intervals of $150\mu s$ , and the gain from $0dB$ to $20dB$ with $2dB$ interval. Similarly, indoor images have exposure time from $4ms$ to $67ms$ with $3ms$ intervals and gain from $0dB$ to $24dB$ with $2dB$ intervals. + +We evaluate our method with Shin et al. [21]. The final converged points are slightly different because of the difference between the proposed reward function and the assessment metric of [21]. Both algorithms converge to a comparable point, as shown in Fig. 3. It only takes three frames to converge with our method. However, the Nelder-Mead optimization method in [21] takes at least 30 timesteps to converge completely. Therefore, it is hard to use it in real scenarios, although they may find a more optimal point. + +![](images/43e58cb5ddf1a3e483dacd314dd0f431cc2f24fbecad67bf2089cd8098058935.jpg) + +![](images/14de94ebf73fb889d4e0c765fbbc0bb64f89712a06a4bf85723037dad2df2504.jpg) +Figure 4. Real-world generalization. We compare our method with the camera's built-in exposure control algorithm in real-world scenarios. Camera lenses are occluded at the initial and suddenly removed in the first frame. Our agent converges to a well-exposed image within 3-5 frames. Yet, the built-in AE algorithm is still in the middle of adjusting the exposure parameters and is far from the well-exposed image, especially in the indoor case. Note that our agent is only trained in the light-controlled darkroom, and this is the zero-shot inference result in the wild. + +Real-world Indoor and Outdoor Environment. We evaluate our method with the camera's built-in AE control algorithm in real-world scenarios. The purposes of this experiment are twofold: 1) comparing convergence speed with the built-in AE algorithm, and 2) testing zero-shot generalization performance in the wild. + +Before starting, we cover the camera lens with enough time to converge in the dark, then quickly remove it to test the convergence speed for a sudden lighting change. Fig. 4 shows the captured initial five images during each optimization. Our method converges to a well-exposed image within 3-5 frames in both indoor and outdoor scenes. However, the built-in AE algorithm takes much longer to converge: 30 frames for indoors and 10 frames for outdoors. + +Also, we found that our agent shows satisfactory zero-shot generalization performance, even though it is only trained in the light-controlled darkroom with limited object context. We believe our state design (i.e., vectorized intensity history) and spatial domain randomization bring this result by removing the potential domain gap issue of the CNN feature and augmenting object context as much as possible. + +![](images/0351b891afbbdfed425340e3b1815e0091d58038f1bd1abf66697b674c0e1d25.jpg) + +![](images/341ebebcd0a5a070670b981b5417b9ac14c9313aee7e8afcd32ddd9cd7a01d78.jpg) + +![](images/8d89454f9d597f893d9b98158a5ab823458f458b9efa0c863a4388ac4b40434e.jpg) +(a) Feature extraction from DRL-AE (Ours) +(b) Feature extraction from built-in AE +Figure 5. SIFT [12] feature extraction result. Captured images from the proposed algorithm and built-in AE are processed to detect SIFT features. The images were simultaneously captured in real-time from two separate cameras equipped on a driving vehicle. Our method can provide plenty of SIFT features over the image plane. On average, our method detects $38\%$ more features across a total of 5355 images. + +![](images/2a4d866910489dbde33e8fd54436fbfd902159e10e18aa07748932fc81c06371.jpg) + +# 4.3. Real-time Driving Env: Feature Extraction + +In this experiment, two cameras are attached to the top of a moving car, and images are captured simultaneously. One camera is used for our algorithm, and the other camera is for the built-in AE algorithm. We tested the algorithms on real-world driving scenarios, including campus and urban roads. Our algorithm runs on a laptop equipped with an i7-7700HQ@2.80GHz CPU unit. Given an image, the agent predicts exposure time and gain commands in real-time. The estimated actions are transmitted to the attached camera. After driving sequences acquisition, we extract SIFT [12] features from each captured image. Please note that the images of DRL-AE and built-in AE have slightly different views due to the difference in the installed position. + +Fig. 5 shows the comparison of feature extraction results. From the total of 5355 image pairs, our method produces 1,306 SIFT features on average with a 1,157 median value. On the other hand, the built-in AE method only results in 946 features on average, with a 711 median value. Therefore, $38\%$ more features are detected on average, and the difference is up to $62\%$ for the median value. The number of detected features and feature repeatability during exposure transition are critical for Visual Odometry (VO) and SLAM tasks. So, we believe our method can be valuable for VO, SLAM, and visual tracking tasks as well. + +![](images/fa211dca3f56f081652e3863f94ca812a9de9ab9c9071d83832a8a7722115af3.jpg) + +![](images/24676ee0f2330ed54566b5820e4e2df59cd0ff9bbacae38f35bf861de3939f9b.jpg) + +![](images/d282607fb99966c63c4e0c0c34ce7b56586408e73d952e61c4ddcfd679962b7b.jpg) +(a) Object detection from DRL-AE (Ours) +(b) Object detection from built-in AE +Figure 6. Object detection result. Captured images from the proposed algorithm and built-in AE are processed to detect target objects. The experiment used the same image sequence as the SIFT experiment. We utilize Yolo-v5 [6] for car and pedestrian detection. On average, our method detects $5\%$ more objects compared to the built-in AE algorithm. + +![](images/739336b179837e798bd27cc4e39ec50a773effab84b1f3692a7dc09f415ff865.jpg) + +# 4.4. Real-time Driving Env: Object Detection + +Similar to the feature extraction experiment, the captured images are processed with YOLO-v5 [6]. The images are taken from campus and urban road scenes, so we only take into account cars and pedestrians. Fig. 6 shows the comparison of object detection results from DRL-AE and built-in AE methods. Recent detection models, including YOLO-v5, adopt modern augmentation methods to make the model robust the image brightness changes. Therefore, YOLO-v5 tends to detect objects well in even poorly exposed images. However, our algorithm detects $5\%$ more objects in terms of the total number of detected objects. Furthermore, the objects in our image are detected much earlier than the built-in AE method. This is highly critical for autonomous vehicles that are driving at high speed. Earlier detected objects can prevent human injury and potential accidents. + +# 4.5. Real-world Env: RoI-aware Exposure Control + +Our DRL-AE framework can also take arbitrary input sizes because the framework resizes the image before the vectorized intensity processing. Also, our domain randomization strategy produces a random size of the Region of Interest (RoI) patch by using crop, flip, resize, and rotation in the training stage. Therefore, our agent is able to control camera exposure for a specific RoI or entire image. Fig. 7 shows the RoI-aware exposure control results. + +![](images/d0021f5f127f7a4b95b580161517c7a1deee34b79e99d756cf02892bfab80b09.jpg) +Figure 7. RoI-aware camera exposure control. Our agent is able to control camera exposure for a specific RoI or entire image. Given a RoI box, the agent adjusts the camera parameters to maximize the image attribute for a specific RoI area. It allows the camera to capture the detailed context for the regions of interest. + +The agent adjusts the camera parameters to maximize the image attribute for a specific RoI area. It allows the camera to capture the detailed context for the regions of interest. We expect that DRL-AE can be combined with object detection, object tracking, and human gaze and attention. As a result, the combination can lead to adaptive exposure control schemes, such as attention-aware or detection-aware exposure control. + +# 4.6. Computation Time Analysis + +Our agent has a simple Multi-Layer Perceptron (MLP) architecture with two hidden layers of 256 units. Also, our method does not require complex matrix computation like convolutions. Therefore, our agent can be run on a CPU device in real-time. We measure the inference time of the agent on the Ryzen 5950x CPU. Tab. 2 shows the computation time results, compared with shin et al. [21]. The network's inference time takes $1ms$ regardless of image resolution because the input image is resized to a fixed resolution. Also, even including other operations, such as image resizing and RoI cropping, it takes a maximum $6ms$ , which is still in the real-time range. Therefore, it can run at 170- $1000\mathrm{Hz}$ on a CPU device. + +# 5. Conclusion & Future Work + +Conclusion. In this paper, we proposed a novel joint exposure parameter control framework that exploits Deep Reinforcement Learning (DRL) to achieve instant exposure convergence and real-time processing. The proposed framework, named DRL-AE, effectively solves the challenges when applying DRL to the exposure control task, such as + +Table 2. Processing time analysis. Our algorithm does not use any complex metric or computation; the agent consists of two MLP layers with 256 hidden units, and the vectorized intensity history does not need complex operations. Therefore, our agent can be run on a CPU device in real-time. Here, we measure the processing time on the Ryzen 5950x CPU. + +
MethodImage SizeProcessing Time (ms)
Shin et al. [21]1600 x 1200108.7
800 x 60018.2
Ours1600 x 12001.0
800 x 6001.0
+ +1) training environment to provide diverse lighting change scenarios, 2) flickering and image attribute-aware reward design, 3) lightweight state design by using vectorized intensity history, and 4) domain generalization via spatial domain randomization strategy. + +The proposed method is thoroughly validated in three different environments: light-controlled dark room, exposure control dataset [21], and real-world environments. We demonstrate that our proposed method instantly adjusts camera exposure within five steps with real-time processing of $1 \, ms$ on a CPU device. Also, our method shows satisfactory generalization performance in the wild. The images acquired from our method are well-exposed and show superiority in numerous computer vision tasks, such as feature extraction and object detection1. To the best of our knowledge, our approach is the first solution that applies DRL to control camera exposure. We hope our paper encourages active research of advanced camera exposure control algorithms to achieve robust visual perception ability. + +Future Work. This paper shows that DRL can be used in the field of camera exposure control. There are lots of open research topics, such as motion-aware AE control, advanced reward function, aperture control, hardware generalization over various cameras, and further domain generalization in the real world. In the future, we plan to extend the current darkroom environment to generate object or camera motion, allowing the agent to consider motion blur for exposure parameter control. Controlling camera aperture by using a mechanical aperture control module is another research direction. + +# Acknowledgment + +This research was supported by a grant (P0026022) from R&D Program funded by Ministry of Trade, Industry and Energy of Korean government. + +# References + +[1] Christian Forster, Matia Pizzoli, and Davide Scaramuzza. 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Also, the acquired images are well-exposed and show superiority in various computer vision tasks, such as feature extraction and object detection." + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 61, + 703, + 215, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 703, + 215, + 713 + ], + "spans": [ + { + "bbox": [ + 61, + 703, + 215, + 713 + ], + "type": "text", + "content": "*Both authors contributed equally to this work." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2975" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 127, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 127, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 127, + 83 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 91, + 286, + 235 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 91, + 286, + 235 + ], + "spans": [ + { + "bbox": [ + 47, + 91, + 286, + 235 + ], + "type": "text", + "content": "Camera exposure control is the task of adjusting exposure level by controlling exposure time, gain, and aperture to achieve a desired level of brightness and image quality for a given scene. Poorly adjusted exposure parameters result in over-exposed, under-exposed, blurry, or noisy images, which can cause performance degradation in image-based applications and, in the worst cases, even life-threatening accidents. Therefore, finding proper camera exposure is the first primary step to ensure the functionality of computer vision applications, such as object detection [5, 16], semantic segmentation [9, 17], depth estimation [10, 26], and visual odometry [1, 13]." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 235, + 286, + 330 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 235, + 286, + 330 + ], + "spans": [ + { + "bbox": [ + 47, + 235, + 286, + 330 + ], + "type": "text", + "content": "There are several essential requirements in camera exposure control. The rapid convergence must be guaranteed to maintain an appropriate exposure level under dynamic light-changing scenarios. Also, the exposure control loop is one of the lowest loops in the camera system. Therefore, lightweight algorithm design must be considered for on-board level operation. Finally, the quality of a converged image should not be sacrificed to meet the requirements." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 331, + 286, + 461 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 331, + 286, + 461 + ], + "spans": [ + { + "bbox": [ + 47, + 331, + 286, + 461 + ], + "type": "text", + "content": "Further, the number of simultaneously controlled parameters is also important because it affects the converge time and final quality of the converged image. One-by-one control methods [14, 18, 20] control exposure parameters in a one-by-one manner to achieve a desired exposure level, rather than joint controlling exposure parameters. However, the converged parameters are often not optimal, such as [long exposure time, low gain] and [short exposure time, high gain] pairs. As a result, the values result in undesirable image artifacts, such as motion blur due to long exposure time or severe noise due to high gain." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 462, + 286, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 462, + 286, + 545 + ], + "spans": [ + { + "bbox": [ + 47, + 462, + 286, + 545 + ], + "type": "text", + "content": "Joint exposure parameter control [7, 8, 21, 23, 24] often needs multiple searching steps in a wide range of searching space to find an optimal combination. As a result, they cause a flickering effect and slow convergence speed. Also, the recent methods require high-level computational complexity due to its optimization algorithm [7, 8], image assessment metric [7, 8, 20, 21], and GPU inference [23]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 546, + 286, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 546, + 286, + 593 + ], + "spans": [ + { + "bbox": [ + 47, + 546, + 286, + 593 + ], + "type": "text", + "content": "In this paper, we propose a new joint exposure parameter control method that exploits reinforcement learning to achieve instant convergence and real-time processing. The proposed framework consists of four contributions:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 594, + 286, + 712 + ], + "type": "list", + "angle": 0, + "index": 10, + "blocks": [ + { + "bbox": [ + 47, + 594, + 286, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 594, + 286, + 616 + ], + "spans": [ + { + "bbox": [ + 47, + 594, + 286, + 616 + ], + "type": "text", + "content": "- A simplified training ground to simulate real-world's diverse and dynamic lighting changes." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 618, + 286, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 618, + 286, + 653 + ], + "spans": [ + { + "bbox": [ + 47, + 618, + 286, + 653 + ], + "type": "text", + "content": "- Flickering and image attribute-aware reward design, along with lightweight and intuitive state design for real-time processing." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 654, + 286, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 654, + 286, + 677 + ], + "spans": [ + { + "bbox": [ + 47, + 654, + 286, + 677 + ], + "type": "text", + "content": "- A static-to-dynamic lighting curriculum learning to gradually improve agent's exposure adjusting capability." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 677, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 286, + 712 + ], + "type": "text", + "content": "- Domain randomization techniques to alleviate the limitation of the training ground and achieve seamless generalization in the wild without additional training." + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 304, + 72, + 545, + 168 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 168 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 168 + ], + "type": "text", + "content": "The proposed method is thoroughly validated in three different environments: light-controlled darkroom, exposure control dataset [21], and real-world environments. We demonstrate that our proposed method rapidly adjusts camera exposure within five steps with real-time processing of " + }, + { + "bbox": [ + 304, + 72, + 545, + 168 + ], + "type": "inline_equation", + "content": "1 \\, ms" + }, + { + "bbox": [ + 304, + 72, + 545, + 168 + ], + "type": "text", + "content": ". Also, the images acquired from our method are well-exposed and show superiority in numerous computer vision tasks, such as feature extraction and object detection." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 180, + 392, + 192 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 180, + 392, + 192 + ], + "spans": [ + { + "bbox": [ + 306, + 180, + 392, + 192 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 200, + 507, + 213 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 200, + 507, + 213 + ], + "spans": [ + { + "bbox": [ + 306, + 200, + 507, + 213 + ], + "type": "text", + "content": "2.1. Optimization-based Exposure Control" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 219, + 545, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 219, + 545, + 411 + ], + "spans": [ + { + "bbox": [ + 304, + 219, + 545, + 411 + ], + "type": "text", + "content": "One branch to control camera exposure parameters is exploiting white-box and black-box optimizations to find optimal parameters for the desired exposure level. Camera built-in Auto-Exposure (AE) control methods [14, 18] adjust exposure parameters (i.e., exposure time and gain) based on differentiable optimization by using the equation between Exposure Value (EV) and exposure parameters [15]. They control exposure parameters one-by-one to achieve predefined image brightness. These built-in AE methods provide real-time processing ability but result in non-optimum solutions (e.g., long exposure time and low gain) and limited scalability. The former limitation causes motion blur and severe image noise due to long exposure time and high gain. The latter limitation indicates the methods cannot be extendable to maximize other image attributes, such as image gradient or entropy." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 411, + 545, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 411, + 545, + 590 + ], + "spans": [ + { + "bbox": [ + 304, + 411, + 545, + 590 + ], + "type": "text", + "content": "Recent AE algorithms are designed to maximize desirable image attributes for computer vision applications, such as image gradient [20, 22, 25], entropy [7, 8], noise level [21], and optical flow [4]. However, these algorithms mainly focused on image metrics for better quality, not the control method. Therefore, they adopt heuristic control algorithm [20] or black-box optimization methods, such as Bayesian optimization [7, 8] and Nelder-Mead optimization [21]. These black-box optimizations and attribute assessment metrics often require multiple explorations that cause a flickering effect, multiple steps to converge, or heavy computation time. Differing from the previous method, the proposed method provides rapid convergence, real-time processing, and potential scalability by exploiting Deep Reinforcement Learning (DRL)." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 599, + 471, + 611 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 599, + 471, + 611 + ], + "spans": [ + { + "bbox": [ + 306, + 599, + 471, + 611 + ], + "type": "text", + "content": "2.2. Data-driven Exposure Control" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": "Another emerging branch of AE is utilizing a neural network to predict appropriate exposure parameters. Tomasi et al. [23] proposed an exposure parameter estimation network that predicts optimal exposure time and gain for each given image. The neural network, consisting of a few convolution and linear layers, is trained with Ground Truth (GT) exposure parameters in a supervised manner. However, the GT label generation needs a time-consuming and compli-" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2976" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 60, + 70, + 534, + 289 + ], + "blocks": [ + { + "bbox": [ + 60, + 70, + 534, + 289 + ], + "lines": [ + { + "bbox": [ + 60, + 70, + 534, + 289 + ], + "spans": [ + { + "bbox": [ + 60, + 70, + 534, + 289 + ], + "type": "image", + "image_path": "f8318031ddbd548d9f50ecf54fa60f831d41934fef2a5df7901ad123c9ba520a.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 295, + 548, + 352 + ], + "lines": [ + { + "bbox": [ + 46, + 295, + 548, + 352 + ], + "spans": [ + { + "bbox": [ + 46, + 295, + 548, + 352 + ], + "type": "text", + "content": "Figure 2. Training framework overview. Our DRL agent is trained with the SAC algorithm in the light-controlled dark room environment. For each episode, a lighting condition is assigned by the current curriculum level. The lighting condition can be fixed at random brightness or dynamically changed within each episode, depending on the level. Given the lighting condition, the agent takes a vectorized intensity history for a randomly selected RoI patch as a state. Afterward, the agent estimates exposure time and gain differences that maximize a reward function. With this framework, the trained agent successfully generalized into a real environment without additional training." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 360, + 289, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 360, + 289, + 434 + ], + "spans": [ + { + "bbox": [ + 46, + 360, + 289, + 434 + ], + "type": "text", + "content": "ated process that collects multiple images with varying exposure parameters for every scene. Also, a heavy computation caused by the use of convolution layers is another drawback. Differing from the method, our method trains a neural network by maximizing a reward function without relying on specific GT data or generation processes." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 441, + 257, + 455 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 441, + 257, + 455 + ], + "spans": [ + { + "bbox": [ + 47, + 441, + 257, + 455 + ], + "type": "text", + "content": "3. DRL for Automatic Exposure Control" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 461, + 287, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 461, + 287, + 510 + ], + "spans": [ + { + "bbox": [ + 46, + 461, + 287, + 510 + ], + "type": "text", + "content": "Applying DRL to Automatic Exposure (AE) control task while achieving rapid convergence speed and real-time processing presents several challenges. Our proposed method provides effective solutions for the following questions." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 510, + 287, + 581 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 47, + 510, + 287, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 510, + 287, + 533 + ], + "spans": [ + { + "bbox": [ + 47, + 510, + 287, + 533 + ], + "type": "text", + "content": "1. Environment: what is the most effective form of training environment to learn camera exposure control?" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 533, + 287, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 533, + 287, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 533, + 287, + 544 + ], + "type": "text", + "content": "2. Reward: what aspects does the agent need to maximize?" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 545, + 282, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 545, + 282, + 556 + ], + "spans": [ + { + "bbox": [ + 47, + 545, + 282, + 556 + ], + "type": "text", + "content": "3. State: where is the bottleneck for real-time processing?" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 557, + 287, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 557, + 287, + 581 + ], + "spans": [ + { + "bbox": [ + 47, + 557, + 287, + 581 + ], + "type": "text", + "content": "4. Generalization: how to achieve seamless generalization in the wild lighting condition?" + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 587, + 176, + 601 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 587, + 176, + 601 + ], + "spans": [ + { + "bbox": [ + 47, + 587, + 176, + 601 + ], + "type": "text", + "content": "3.1. Training Environment" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": "DRL requires a large number of samples and interaction with the environment to train the agent. Also, the environment needs to provide a diverse and wide range of problems for the agent to solve. The optimal form of exposure control is to instantly adjust exposure parameters for a variety of lighting conditions, from static lighting conditions to dramatic lighting changes. To this end, the training environment for camera exposure control must provide diverse lighting change scenarios to the agent." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 360, + 547, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 360, + 547, + 479 + ], + "spans": [ + { + "bbox": [ + 304, + 360, + 547, + 479 + ], + "type": "text", + "content": "Numerous options exist, such as a simulation, a real-world environment with natural sunlight, and a controlled real-world environment. The simulation can provide various images and lighting conditions but has the limitations of an imperfect exposure parameter implementation and a sim-to-real domain gap. On the other hand, the real-world environment with natural sunlight has no domain gap, but the lighting conditions change very slowly. Therefore, we construct a controlled real-world environment in a darkroom with controllable LEDs to adjust lighting conditions." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 481, + 547, + 578 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 481, + 547, + 578 + ], + "spans": [ + { + "bbox": [ + 304, + 481, + 547, + 578 + ], + "type": "text", + "content": "The constructed light-controlled darkroom is shown in Fig. 2. The environment has one machine vision camera, a random target object, a light controller, and an LED bar. The environment provides a random lighting scenario from dark to bright light conditions, and the agent adjusts exposure parameters to capture a high-quality image of the target object in the suggested scenario. The detailed sensor specification can be found in the supplementary material." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 588, + 487, + 601 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 588, + 487, + 601 + ], + "spans": [ + { + "bbox": [ + 306, + 588, + 487, + 601 + ], + "type": "text", + "content": "3.2. State, Action, and Reward Design" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 608, + 518, + 620 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 608, + 518, + 620 + ], + "spans": [ + { + "bbox": [ + 306, + 608, + 518, + 620 + ], + "type": "text", + "content": "3.2.1 State Design: Vectorized Intensity History" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": "The widely adopted state design in related fields is utilizing a feature map from a pre-trained network [22, 23]. However, we found the CNN feature is not effective in the exposure control task due to its disadvantages: 1) unclear relation between CNN feature and exposure level, 2) generalization problem of CNN feature, and 3) heavy computation for on-board devices due to multiple convolution layers." + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2977" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 193 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 193 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 193 + ], + "type": "text", + "content": "Therefore, instead of using the CNN feature or other complicated features as a state, we utilize vectorized image intensity as a straightforward and lightweight state representation for the exposure control task. As shown in Fig. 2, we first vectorize image intensity map from a Region-of-Interest (RoI) patch of gray-scale image " + }, + { + "bbox": [ + 47, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{H_{RoI} \\times W_{RoI}}" + }, + { + "bbox": [ + 47, + 72, + 289, + 193 + ], + "type": "text", + "content": " to the intensity vector " + }, + { + "bbox": [ + 47, + 72, + 289, + 193 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^S" + }, + { + "bbox": [ + 47, + 72, + 289, + 193 + ], + "type": "text", + "content": ". The RoI patch can be an entire image area or specific regions decided by a domain randomization process. After that, we stack consecutive frame's intensity vectors to embed previous state history, as follows:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 102, + 200, + 211, + 214 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 102, + 200, + 211, + 214 + ], + "spans": [ + { + "bbox": [ + 102, + 200, + 211, + 214 + ], + "type": "interline_equation", + "content": "v _ {t} = f \\left(I _ {t} ^ {R o I}\\right), \\quad v _ {t} \\in \\mathbb {R} ^ {S},", + "image_path": "5d193c491090d302a416df764e65374a0a0f63a3675d0028cf0926dd6f82c84f.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 104, + 217, + 232, + 230 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 104, + 217, + 232, + 230 + ], + "spans": [ + { + "bbox": [ + 104, + 217, + 232, + 230 + ], + "type": "interline_equation", + "content": "s _ {t} = \\operatorname {c o n c a t} \\left(v _ {t - n}, \\dots , v _ {t - 1}, v _ {t}\\right),", + "image_path": "39280ef4a3e640892eb456e9df7a3bb593a54ba0608cc29f330cc8c411741b7a.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "spans": [ + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "I_{t}" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": " is a normalized image at time step " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "f(\\cdot)" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": " is an averaging process through the x-axis of a gray-scale image, defined as " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "\\frac{1}{H_{RoI}}\\sum_{x}\\mathrm{gray}(I_t^{RoI})" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "v_{t}" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": " represents the vectorized intensity that has a dimension of " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "s_t" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": " is a state vector. To ensure a fixed and reasonable state length, we resize the given RoI patch to have " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "S = 128" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": " and stack previous states with " + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "inline_equation", + "content": "n = 3" + }, + { + "bbox": [ + 47, + 239, + 289, + 347 + ], + "type": "text", + "content": ". The proposed state design is effective, straightforward, and computationally efficient compared to the CNN feature, as described in Sec. 4.1." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 361, + 282, + 374 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 361, + 282, + 374 + ], + "spans": [ + { + "bbox": [ + 47, + 361, + 282, + 374 + ], + "type": "text", + "content": "3.2.2 Action Design: Relative and Continuous Action" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 380, + 287, + 536 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 380, + 287, + 536 + ], + "spans": [ + { + "bbox": [ + 46, + 380, + 287, + 536 + ], + "type": "text", + "content": "Obviously, we have two controllable parameters, exposure time and gain, to adjust camera exposure. However, there are numerous options for its action design, such as 1) discrete vs. continuous action space, and 2) absolute vs. relative action range. A discrete action space discretizes the action range into a few action values. It has the advantage that the training process is simplified, but there is an approximation gap to the optimal values. The absolute and relative action range is about the change of camera parameters. In the absolute action range, an action value is directly matched to the specific value of camera parameters. On the other hand, in the relative action range, an action value indicates the amount of change in camera parameters." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 536, + 288, + 620 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 536, + 288, + 620 + ], + "spans": [ + { + "bbox": [ + 46, + 536, + 288, + 620 + ], + "type": "text", + "content": "Among the options, we select continuous-relative action space. This is because our goal is rapid convergence with minimum exploration step, but discrete action space needs multiple steps and often does not converge, depending on its quantization level. Also, we empirically found that the absolute action range often induces a flickering effect and unstable convergence, as described in Sec. 4.1." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 635, + 286, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 635, + 286, + 647 + ], + "spans": [ + { + "bbox": [ + 47, + 635, + 286, + 647 + ], + "type": "text", + "content": "3.2.3 Reward Design: Flickering and Image Attribute" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 654, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 654, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 654, + 287, + 714 + ], + "type": "text", + "content": "The desirable behavior of exposure control is maximizing image attributes, such as sharp edge, moderate brightness, and low-level noise, and maintaining image attributes during exposure parameter transition. Therefore, we designed the reward function from three perspectives: 1) a moderate" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": "brightness level to provide clear visibility and edge information, 2) a smoothed exposure transition to ensure stable convergence and prevent flickering, and 3) a low-level noise to provide clear image and avoid too-high gain value. The designed reward functions are as follows:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 330, + 136, + 520, + 201 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 330, + 136, + 520, + 201 + ], + "spans": [ + { + "bbox": [ + 330, + 136, + 520, + 201 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {R} _ {m e a n} = \\frac {1}{P} \\sum_ {x y} \\left| I _ {t} ^ {R o I} - M \\right| ^ {p _ {m}}, \\\\ \\mathcal {R} _ {f l k} = \\frac {1}{P} \\sum_ {x y} | | I _ {t} ^ {R o I} - I _ {t - 1} ^ {R o I} | |, \\\\ \\mathcal {R} _ {n o i s e} = \\frac {1}{P} \\sum_ {x y} s o b e l (I _ {t} ^ {R o I}), \\\\ \\mathcal {R} _ {t o t a l} = w _ {m} \\mathcal {R} _ {m e a n} + w _ {f} \\mathcal {R} _ {f l k} + w _ {n} \\mathcal {R} _ {n o i s e}, \\\\ \\end{array}", + "image_path": "6a9713dc1a7e9f7f76c85f48b3e733beda8ae43d4ee55938536f804f16ee0eea.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "spans": [ + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "text", + "content": " is the number of pixels, " + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "inline_equation", + "content": "M = 0.5" + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "text", + "content": " indicates mid-tone brightness, " + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "inline_equation", + "content": "p_m = 0.5" + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "text", + "content": " is a parameter for non-linearity and sobel is a gradient operator. Also, we set " + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "inline_equation", + "content": "w_{m} = 1.5" + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "inline_equation", + "content": "w_{f} = -1.0" + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "inline_equation", + "content": "w_{n} = -0.1" + }, + { + "bbox": [ + 304, + 205, + 545, + 290 + ], + "type": "text", + "content": " in practice. The proposed reward design might be a primitive and basic form for camera exposure control, however, it can be easily extendable by incorporating modern image assessment metrics [4, 8, 21]." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 295, + 514, + 308 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 295, + 514, + 308 + ], + "spans": [ + { + "bbox": [ + 306, + 295, + 514, + 308 + ], + "type": "text", + "content": "3.3. Static-to-dynamic Lighting Curriculum" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 313, + 545, + 421 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 313, + 545, + 421 + ], + "spans": [ + { + "bbox": [ + 304, + 313, + 545, + 421 + ], + "type": "text", + "content": "In the wild, the agent must be able to control exposure parameters for a variety of lighting change scenarios. However, training every scenario simultaneously results in an unstable training process and poor generalization. Therefore, we propose static-to-dynamic curriculum strategy that starts with a simple control task and gradually experiences dynamic and dramatic lighting change scenarios. In the end, the trained models possess a comprehensive exposure control capability for diverse lighting conditions." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "spans": [ + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "text", + "content": "We divide the difficulty of lighting conditions into three levels: easy, normal, and hard. The easy level has static lighting conditions with moderate brightness. The normal level also has a fixed brightness but with a darker or brighter than easy level. Lastly, in the hard level, the LED brightness dynamically changes from dark to bright or the opposite way during each scenario. The probability of each level is gradually updated according to the proceeded training episode " + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "inline_equation", + "content": "t_e" + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "text", + "content": ". The probability set " + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "inline_equation", + "content": "[p_e, p_n, p_h]" + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "text", + "content": " starts from " + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "inline_equation", + "content": "[1, 0, 0]" + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "text", + "content": ", through " + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "inline_equation", + "content": "[0, 1, 0]" + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "text", + "content": ", and ends with " + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "inline_equation", + "content": "[p_e^f, p_n^f, p_h^f] = [0.1, 0.4, 0.5]" + }, + { + "bbox": [ + 304, + 421, + 546, + 566 + ], + "type": "text", + "content": ". In summary, the probability for each difficulty level is updated as follows:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 347, + 571, + 502, + 698 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 347, + 571, + 502, + 698 + ], + "spans": [ + { + "bbox": [ + 347, + 571, + 502, + 698 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} p _ {e} = \\left\\{ \\begin{array}{l l} 1, & t _ {e} < T _ {e} \\\\ \\frac {(t _ {e} - T _ {e})}{(T _ {n} - T _ {e})}, & T _ {e} \\leq t _ {e} < T _ {n} \\\\ p _ {e} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ p _ {n} = \\left\\{ \\begin{array}{l l} 0, & t _ {e} < T _ {e} \\\\ 1 - \\frac {\\left(t _ {e} - T _ {e}\\right)}{\\left(T _ {n} - T _ {e}\\right)}, & T _ {e} \\leq t _ {e} < T _ {n} \\\\ p _ {n} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ p _ {h} = \\left\\{ \\begin{array}{l l} 0, & t _ {e} < T _ {n} \\\\ p _ {h} ^ {f}, & T _ {n} \\leq t _ {e} \\end{array} \\right. \\\\ \\end{array}", + "image_path": "ed536f4e1731714d74456d6c93665438ab46c21251288432ffc0d66adea83cf9.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 701, + 499, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 701, + 499, + 714 + ], + "spans": [ + { + "bbox": [ + 306, + 701, + 499, + 714 + ], + "type": "text", + "content": "We use " + }, + { + "bbox": [ + 306, + 701, + 499, + 714 + ], + "type": "inline_equation", + "content": "T_{e} = 25,000, T_{n} = 45,000" + }, + { + "bbox": [ + 306, + 701, + 499, + 714 + ], + "type": "text", + "content": " in practice." + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2978" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 217, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 217, + 84 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 217, + 84 + ], + "type": "text", + "content": "3.4. Spatial Domain Randomization" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 90, + 286, + 197 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 90, + 286, + 197 + ], + "spans": [ + { + "bbox": [ + 46, + 90, + 286, + 197 + ], + "type": "text", + "content": "In the wild, the agent encounters various surrounding environments and object contexts, such as office, road, tunnel, and mountain. Although the light-controlled darkroom can provide various lighting scenarios, it is difficult to contain diverse environments and contexts because it only has a few target objects with a fixed background. Therefore, without proper randomization techniques, the agent may overfit to perform exposure control for only a few target objects, resulting in generalization failure in the wild." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 198, + 286, + 318 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 198, + 286, + 318 + ], + "spans": [ + { + "bbox": [ + 46, + 198, + 286, + 318 + ], + "type": "text", + "content": "The main idea is to provide as much diverse image structure and context information as possible by augmenting the image from the darkroom environment. Specifically, we spatially augment the images with random flipping, cropping, rotating, and resizing but do not change color and brightness information. Each augmentation and its parameter is randomly selected at the beginning of each training episode and fixed during the episode. With the proposed domain randomization technique, the trained agent can be generalized in the real world without any fine-tuning." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 324, + 162, + 337 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 324, + 162, + 337 + ], + "spans": [ + { + "bbox": [ + 47, + 324, + 162, + 337 + ], + "type": "text", + "content": "3.5. Policy Optimization" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 342, + 286, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 342, + 286, + 413 + ], + "spans": [ + { + "bbox": [ + 46, + 342, + 286, + 413 + ], + "type": "text", + "content": "As our action space is continuous, we use the SAC [3] algorithm. We excluded on-policy algorithms like PPO [19] because they are widely known to be less sample efficient than the off-policy algorithms like SAC, TD3, and DDPG. We tested TD3 [2] and DDPG [11] as well, but SAC showed the best result." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 415, + 286, + 450 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 415, + 286, + 450 + ], + "spans": [ + { + "bbox": [ + 46, + 415, + 286, + 450 + ], + "type": "text", + "content": "SAC algorithm is a kind of actor-critic algorithm, which has critic " + }, + { + "bbox": [ + 46, + 415, + 286, + 450 + ], + "type": "inline_equation", + "content": "Q(\\theta)" + }, + { + "bbox": [ + 46, + 415, + 286, + 450 + ], + "type": "text", + "content": " and actor " + }, + { + "bbox": [ + 46, + 415, + 286, + 450 + ], + "type": "inline_equation", + "content": "\\pi(\\phi)" + }, + { + "bbox": [ + 46, + 415, + 286, + 450 + ], + "type": "text", + "content": ". The objective functions to update the critic are as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 60, + 458, + 274, + 502 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 60, + 458, + 274, + 502 + ], + "spans": [ + { + "bbox": [ + 60, + 458, + 274, + 502 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} J _ {Q} (\\theta) = \\mathbb {E} _ {(s _ {t}, a _ {t}) \\sim \\mathcal {D}} \\left[ \\frac {1}{2} \\left(Q _ {\\theta} (s _ {t}, a _ {t}) - \\hat {Q} (s _ {t}, a _ {t})\\right) ^ {2} \\right], \\\\ \\hat {Q} (s _ {t}, a _ {t}) = r (s _ {t}, a _ {t}) + \\gamma \\mathbb {E} _ {s _ {t + 1} \\sim p} [ V _ {\\bar {\\theta}} (s _ {t + 1}) ], \\\\ \\end{array}", + "image_path": "5af8828d0846715f2197846eb3bca54ca5f3a655664d7b7f4661edbf10d98095.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "text", + "content": " is a replay buffer, " + }, + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "inline_equation", + "content": "r(s_{t},a_{t})" + }, + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "text", + "content": " is a reward function and " + }, + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "text", + "content": " is a discount factor. The objective functions for updating the actor is as follows:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 51, + 553, + 282, + 567 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 51, + 553, + 282, + 567 + ], + "spans": [ + { + "bbox": [ + 51, + 553, + 282, + 567 + ], + "type": "interline_equation", + "content": "J _ {\\pi} (\\phi) = \\mathbb {E} _ {s _ {t} \\sim \\mathcal {D}} \\left[ \\mathbb {E} _ {a _ {t} \\sim \\pi_ {\\phi}} \\left[ \\alpha \\log \\left(\\pi_ {\\phi} \\left(a _ {t} \\mid s _ {t}\\right)\\right) - Q _ {\\theta} \\left(s _ {t}, a _ {t}\\right) \\right] \\right],", + "image_path": "9481e8b749206222c7db96ffd92fd893857a825194b7abfbf702b941975a9e58.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 575, + 220, + 587 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 575, + 220, + 587 + ], + "spans": [ + { + "bbox": [ + 47, + 575, + 220, + 587 + ], + "type": "text", + "content": "with " + }, + { + "bbox": [ + 47, + 575, + 220, + 587 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 47, + 575, + 220, + 587 + ], + "type": "text", + "content": " defined as a temperature parameter." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 597, + 127, + 611 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 597, + 127, + 611 + ], + "spans": [ + { + "bbox": [ + 47, + 597, + 127, + 611 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 617, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 286, + 713 + ], + "type": "text", + "content": "In this section, we validate our proposed method in three different environments: light-controlled darkroom, exposure control dataset [21], and real-world environments. Throughout the experiments, we provide the validation result of DRL design components, ablation study of reward and training strategy, convergent step comparison, comparison with built-in AE for object detection and feature extraction, and computational time analysis." + } + ] + } + ], + "index": 11 + }, + { + "type": "table", + "bbox": [ + 316, + 120, + 537, + 350 + ], + "blocks": [ + { + "bbox": [ + 305, + 70, + 545, + 115 + ], + "lines": [ + { + "bbox": [ + 305, + 70, + 545, + 115 + ], + "spans": [ + { + "bbox": [ + 305, + 70, + 545, + 115 + ], + "type": "text", + "content": "Table 1. Self-evaluation of DRL-AE framework in the light-controlled darkroom. DR and CL indicate domain randomization and curriculum learning.\"-\" indicates the agent doesn't converge. The best performance in each block is highlighted in bold." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 316, + 120, + 537, + 350 + ], + "lines": [ + { + "bbox": [ + 316, + 120, + 537, + 350 + ], + "spans": [ + { + "bbox": [ + 316, + 120, + 537, + 350 + ], + "type": "table", + "html": "
Framework ComponentMethodsReward per FrameFrames to Converge
RL AlgorithmDDPG [11]1.11-
TD3 [2]1.03-
SAC [3]1.615
StateCNN0.85-
Vector1.615
ActionAbsolute0.65-
Relative1.615
RewardRflk Rnoise
1.41-
✓1.4416
1.359
✓1.615
Training StrategyDR CL
✓--
1.6415
✓1.615
", + "image_path": "39d33b9b3f1271ed2a93f513a31f1aa9746dc33ee0cf89fc129a10737575ade8.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "table_body" + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 358, + 541, + 371 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 358, + 541, + 371 + ], + "spans": [ + { + "bbox": [ + 305, + 358, + 541, + 371 + ], + "type": "text", + "content": "4.1. Self-evaluation in Light-controlled Darkroom" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 377, + 545, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 377, + 545, + 496 + ], + "spans": [ + { + "bbox": [ + 304, + 377, + 545, + 496 + ], + "type": "text", + "content": "We first validate our DRL design components and their variants in the light-controlled darkroom. We utilize reward per frame and the averaged number of frames to converge as evaluation metrics to measure image quality and convergence speed, respectively. Here, when the difference between current and previous images is less than a certain threshold, we regard it as the convergence. The testing scenarios include various lighting conditions, such as fixed lighting, progressive light changes, and dynamic light changes. The results are shown in Tab. 1." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 498, + 545, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 545, + 593 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 545, + 593 + ], + "type": "text", + "content": "We found SAC method [3] shows the best result among the off-policy RL methods. Other algorithms can reach up to 1.0 reward per frame, but they usually do not converge well by showing oscillation. For the state design, the CNN feature is not desirable for the exposure control task due to its intensity-agnostic property. Also, absolute action space seems to make the overall learning process difficult because it needs to estimate the optimum values directly." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": "The reward function and the training strategies play an important role in the stable and rapid convergence process and image attribute preservation. " + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "inline_equation", + "content": "R_{noise}" + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": " suppress high noise level and regularize gain parameter control, leading to better convergence. Also, " + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "inline_equation", + "content": "R_{flk}" + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": " makes the agent preserve the image attribute during the exposure transition. CL makes the agent encompass the comprehensive exposure control capability for the test set's various lighting conditions. Additionally, DR allows the agent to quickly converge for arbitrary context by increasing generalization ability." + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2979" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 58, + 82, + 277, + 127 + ], + "blocks": [ + { + "bbox": [ + 143, + 72, + 192, + 81 + ], + "lines": [ + { + "bbox": [ + 143, + 72, + 192, + 81 + ], + "spans": [ + { + "bbox": [ + 143, + 72, + 192, + 81 + ], + "type": "text", + "content": "Shin et al. [21]" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 58, + 82, + 277, + 127 + ], + "lines": [ + { + "bbox": [ + 58, + 82, + 277, + 127 + ], + "spans": [ + { + "bbox": [ + 58, + 82, + 277, + 127 + ], + "type": "image", + "image_path": "d5039d6ae910a2957238f8af729c9a9a0b5a8734ec34586e0af3538aec8c7702.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 58, + 140, + 277, + 185 + ], + "blocks": [ + { + "bbox": [ + 140, + 131, + 194, + 140 + ], + "lines": [ + { + "bbox": [ + 140, + 131, + 194, + 140 + ], + "spans": [ + { + "bbox": [ + 140, + 131, + 194, + 140 + ], + "type": "text", + "content": "DRL-AE (Ours)" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 58, + 140, + 277, + 185 + ], + "lines": [ + { + "bbox": [ + 58, + 140, + 277, + 185 + ], + "spans": [ + { + "bbox": [ + 58, + 140, + 277, + 185 + ], + "type": "image", + "image_path": "0f5695d9315063e2774271edd0dce5cd14c882c553f5d426fc7f7e6fe2832b95.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 76, + 189, + 259, + 198 + ], + "lines": [ + { + "bbox": [ + 76, + 189, + 259, + 198 + ], + "spans": [ + { + "bbox": [ + 76, + 189, + 259, + 198 + ], + "type": "text", + "content": "(a) Acquired image comparison for each convergent step" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 66, + 209, + 262, + 361 + ], + "blocks": [ + { + "bbox": [ + 66, + 209, + 262, + 361 + ], + "lines": [ + { + "bbox": [ + 66, + 209, + 262, + 361 + ], + "spans": [ + { + "bbox": [ + 66, + 209, + 262, + 361 + ], + "type": "image", + "image_path": "9fc31a1cc91ae10b2fa46efeb85dbd0aa11cc1980f81ebd00baa660a576bd456.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 66, + 365, + 269, + 374 + ], + "lines": [ + { + "bbox": [ + 66, + 365, + 269, + 374 + ], + "spans": [ + { + "bbox": [ + 66, + 365, + 269, + 374 + ], + "type": "text", + "content": "(b) Convergence trajectory of exposure parameter optimization" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 387, + 287, + 443 + ], + "lines": [ + { + "bbox": [ + 46, + 387, + 287, + 443 + ], + "spans": [ + { + "bbox": [ + 46, + 387, + 287, + 443 + ], + "type": "text", + "content": "Figure 3. Convergent step comparison in exposure control dataset [21]. Within three frames, our method already reaches a well-exposed image (a) with minimum exploration (b). On the other hand, Shin et al. [21] search local areas with multiple steps (about 30 frames) to converge." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 465, + 208, + 478 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 465, + 208, + 478 + ], + "spans": [ + { + "bbox": [ + 47, + 465, + 208, + 478 + ], + "type": "text", + "content": "4.2. Convergent Step Comparison" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": "Exposure Control Dataset [21]. The dataset provides multiple images with many different pairs of exposure and gain values, which are captured from the real world. The dataset consists of several locations, including indoor and outdoor places, with a wide range of exposure and gain values. Outdoor images can have the exposure time from " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "100\\mu s" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "7450\\mu s" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": ", at intervals of " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "150\\mu s" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": ", and the gain from " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "0dB" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "20dB" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " with " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "2dB" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " interval. Similarly, indoor images have exposure time from " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "4ms" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "67ms" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " with " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "3ms" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " intervals and gain from " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "0dB" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "24dB" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " with " + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "inline_equation", + "content": "2dB" + }, + { + "bbox": [ + 46, + 485, + 287, + 604 + ], + "type": "text", + "content": " intervals." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "type": "text", + "content": "We evaluate our method with Shin et al. [21]. The final converged points are slightly different because of the difference between the proposed reward function and the assessment metric of [21]. Both algorithms converge to a comparable point, as shown in Fig. 3. It only takes three frames to converge with our method. However, the Nelder-Mead optimization method in [21] takes at least 30 timesteps to converge completely. Therefore, it is hard to use it in real scenarios, although they may find a more optimal point." + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 310, + 71, + 542, + 202 + ], + "blocks": [ + { + "bbox": [ + 310, + 71, + 542, + 202 + ], + "lines": [ + { + "bbox": [ + 310, + 71, + 542, + 202 + ], + "spans": [ + { + "bbox": [ + 310, + 71, + 542, + 202 + ], + "type": "image", + "image_path": "43e58cb5ddf1a3e483dacd314dd0f431cc2f24fbecad67bf2089cd8098058935.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 311, + 205, + 542, + 331 + ], + "blocks": [ + { + "bbox": [ + 311, + 205, + 542, + 331 + ], + "lines": [ + { + "bbox": [ + 311, + 205, + 542, + 331 + ], + "spans": [ + { + "bbox": [ + 311, + 205, + 542, + 331 + ], + "type": "image", + "image_path": "14de94ebf73fb889d4e0c765fbbc0bb64f89712a06a4bf85723037dad2df2504.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 348, + 545, + 447 + ], + "lines": [ + { + "bbox": [ + 305, + 348, + 545, + 447 + ], + "spans": [ + { + "bbox": [ + 305, + 348, + 545, + 447 + ], + "type": "text", + "content": "Figure 4. Real-world generalization. We compare our method with the camera's built-in exposure control algorithm in real-world scenarios. Camera lenses are occluded at the initial and suddenly removed in the first frame. Our agent converges to a well-exposed image within 3-5 frames. Yet, the built-in AE algorithm is still in the middle of adjusting the exposure parameters and is far from the well-exposed image, especially in the indoor case. Note that our agent is only trained in the light-controlled darkroom, and this is the zero-shot inference result in the wild." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 461, + 545, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 461, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 305, + 461, + 545, + 533 + ], + "type": "text", + "content": "Real-world Indoor and Outdoor Environment. We evaluate our method with the camera's built-in AE control algorithm in real-world scenarios. The purposes of this experiment are twofold: 1) comparing convergence speed with the built-in AE algorithm, and 2) testing zero-shot generalization performance in the wild." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 534, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 545, + 628 + ], + "type": "text", + "content": "Before starting, we cover the camera lens with enough time to converge in the dark, then quickly remove it to test the convergence speed for a sudden lighting change. Fig. 4 shows the captured initial five images during each optimization. Our method converges to a well-exposed image within 3-5 frames in both indoor and outdoor scenes. However, the built-in AE algorithm takes much longer to converge: 30 frames for indoors and 10 frames for outdoors." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "content": "Also, we found that our agent shows satisfactory zero-shot generalization performance, even though it is only trained in the light-controlled darkroom with limited object context. We believe our state design (i.e., vectorized intensity history) and spatial domain randomization bring this result by removing the potential domain gap issue of the CNN feature and augmenting object context as much as possible." + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2980" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 55, + 106, + 167, + 167 + ], + "blocks": [ + { + "bbox": [ + 55, + 106, + 167, + 167 + ], + "lines": [ + { + "bbox": [ + 55, + 106, + 167, + 167 + ], + "spans": [ + { + "bbox": [ + 55, + 106, + 167, + 167 + ], + "type": "image", + "image_path": "0351b891afbbdfed425340e3b1815e0091d58038f1bd1abf66697b674c0e1d25.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 168, + 106, + 279, + 167 + ], + "blocks": [ + { + "bbox": [ + 168, + 106, + 279, + 167 + ], + "lines": [ + { + "bbox": [ + 168, + 106, + 279, + 167 + ], + "spans": [ + { + "bbox": [ + 168, + 106, + 279, + 167 + ], + "type": "image", + "image_path": "341ebebcd0a5a070670b981b5417b9ac14c9313aee7e8afcd32ddd9cd7a01d78.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 55, + 180, + 167, + 277 + ], + "blocks": [ + { + "bbox": [ + 96, + 171, + 238, + 180 + ], + "lines": [ + { + "bbox": [ + 96, + 171, + 238, + 180 + ], + "spans": [ + { + "bbox": [ + 96, + 171, + 238, + 180 + ], + "type": "text", + "content": "(a) Feature extraction from DRL-AE (Ours)" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 55, + 180, + 167, + 277 + ], + "lines": [ + { + "bbox": [ + 55, + 180, + 167, + 277 + ], + "spans": [ + { + "bbox": [ + 55, + 180, + 167, + 277 + ], + "type": "image", + "image_path": "8d89454f9d597f893d9b98158a5ab823458f458b9efa0c863a4388ac4b40434e.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 104, + 281, + 230, + 290 + ], + "lines": [ + { + "bbox": [ + 104, + 281, + 230, + 290 + ], + "spans": [ + { + "bbox": [ + 104, + 281, + 230, + 290 + ], + "type": "text", + "content": "(b) Feature extraction from built-in AE" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 304, + 287, + 381 + ], + "lines": [ + { + "bbox": [ + 46, + 304, + 287, + 381 + ], + "spans": [ + { + "bbox": [ + 46, + 304, + 287, + 381 + ], + "type": "text", + "content": "Figure 5. SIFT [12] feature extraction result. Captured images from the proposed algorithm and built-in AE are processed to detect SIFT features. The images were simultaneously captured in real-time from two separate cameras equipped on a driving vehicle. Our method can provide plenty of SIFT features over the image plane. On average, our method detects " + }, + { + "bbox": [ + 46, + 304, + 287, + 381 + ], + "type": "inline_equation", + "content": "38\\%" + }, + { + "bbox": [ + 46, + 304, + 287, + 381 + ], + "type": "text", + "content": " more features across a total of 5355 images." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 168, + 184, + 279, + 277 + ], + "blocks": [ + { + "bbox": [ + 168, + 184, + 279, + 277 + ], + "lines": [ + { + "bbox": [ + 168, + 184, + 279, + 277 + ], + "spans": [ + { + "bbox": [ + 168, + 184, + 279, + 277 + ], + "type": "image", + "image_path": "2a4d866910489dbde33e8fd54436fbfd902159e10e18aa07748932fc81c06371.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 405, + 270, + 417 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 405, + 270, + 417 + ], + "spans": [ + { + "bbox": [ + 47, + 405, + 270, + 417 + ], + "type": "text", + "content": "4.3. Real-time Driving Env: Feature Extraction" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 425, + 287, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 425, + 287, + 581 + ], + "spans": [ + { + "bbox": [ + 46, + 425, + 287, + 581 + ], + "type": "text", + "content": "In this experiment, two cameras are attached to the top of a moving car, and images are captured simultaneously. One camera is used for our algorithm, and the other camera is for the built-in AE algorithm. We tested the algorithms on real-world driving scenarios, including campus and urban roads. Our algorithm runs on a laptop equipped with an i7-7700HQ@2.80GHz CPU unit. Given an image, the agent predicts exposure time and gain commands in real-time. The estimated actions are transmitted to the attached camera. After driving sequences acquisition, we extract SIFT [12] features from each captured image. Please note that the images of DRL-AE and built-in AE have slightly different views due to the difference in the installed position." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": "Fig. 5 shows the comparison of feature extraction results. From the total of 5355 image pairs, our method produces 1,306 SIFT features on average with a 1,157 median value. On the other hand, the built-in AE method only results in 946 features on average, with a 711 median value. Therefore, " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "38\\%" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " more features are detected on average, and the difference is up to " + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "inline_equation", + "content": "62\\%" + }, + { + "bbox": [ + 46, + 582, + 286, + 714 + ], + "type": "text", + "content": " for the median value. The number of detected features and feature repeatability during exposure transition are critical for Visual Odometry (VO) and SLAM tasks. So, we believe our method can be valuable for VO, SLAM, and visual tracking tasks as well." + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 313, + 69, + 426, + 167 + ], + "blocks": [ + { + "bbox": [ + 313, + 69, + 426, + 167 + ], + "lines": [ + { + "bbox": [ + 313, + 69, + 426, + 167 + ], + "spans": [ + { + "bbox": [ + 313, + 69, + 426, + 167 + ], + "type": "image", + "image_path": "fa211dca3f56f081652e3863f94ca812a9de9ab9c9071d83832a8a7722115af3.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 427, + 69, + 539, + 167 + ], + "blocks": [ + { + "bbox": [ + 427, + 69, + 539, + 167 + ], + "lines": [ + { + "bbox": [ + 427, + 69, + 539, + 167 + ], + "spans": [ + { + "bbox": [ + 427, + 69, + 539, + 167 + ], + "type": "image", + "image_path": "24676ee0f2330ed54566b5820e4e2df59cd0ff9bbacae38f35bf861de3939f9b.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 313, + 180, + 426, + 277 + ], + "blocks": [ + { + "bbox": [ + 358, + 171, + 494, + 180 + ], + "lines": [ + { + "bbox": [ + 358, + 171, + 494, + 180 + ], + "spans": [ + { + "bbox": [ + 358, + 171, + 494, + 180 + ], + "type": "text", + "content": "(a) Object detection from DRL-AE (Ours)" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 313, + 180, + 426, + 277 + ], + "lines": [ + { + "bbox": [ + 313, + 180, + 426, + 277 + ], + "spans": [ + { + "bbox": [ + 313, + 180, + 426, + 277 + ], + "type": "image", + "image_path": "d282607fb99966c63c4e0c0c34ce7b56586408e73d952e61c4ddcfd679962b7b.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 365, + 281, + 487, + 290 + ], + "lines": [ + { + "bbox": [ + 365, + 281, + 487, + 290 + ], + "spans": [ + { + "bbox": [ + 365, + 281, + 487, + 290 + ], + "type": "text", + "content": "(b) Object detection from built-in AE" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 305, + 304, + 545, + 370 + ], + "lines": [ + { + "bbox": [ + 305, + 304, + 545, + 370 + ], + "spans": [ + { + "bbox": [ + 305, + 304, + 545, + 370 + ], + "type": "text", + "content": "Figure 6. Object detection result. Captured images from the proposed algorithm and built-in AE are processed to detect target objects. The experiment used the same image sequence as the SIFT experiment. We utilize Yolo-v5 [6] for car and pedestrian detection. On average, our method detects " + }, + { + "bbox": [ + 305, + 304, + 545, + 370 + ], + "type": "inline_equation", + "content": "5\\%" + }, + { + "bbox": [ + 305, + 304, + 545, + 370 + ], + "type": "text", + "content": " more objects compared to the built-in AE algorithm." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "type": "image", + "bbox": [ + 427, + 180, + 539, + 277 + ], + "blocks": [ + { + "bbox": [ + 427, + 180, + 539, + 277 + ], + "lines": [ + { + "bbox": [ + 427, + 180, + 539, + 277 + ], + "spans": [ + { + "bbox": [ + 427, + 180, + 539, + 277 + ], + "type": "image", + "image_path": "739336b179837e798bd27cc4e39ec50a773effab84b1f3692a7dc09f415ff865.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 392, + 518, + 404 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 392, + 518, + 404 + ], + "spans": [ + { + "bbox": [ + 306, + 392, + 518, + 404 + ], + "type": "text", + "content": "4.4. Real-time Driving Env: Object Detection" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 411, + 545, + 590 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 411, + 545, + 590 + ], + "spans": [ + { + "bbox": [ + 304, + 411, + 545, + 590 + ], + "type": "text", + "content": "Similar to the feature extraction experiment, the captured images are processed with YOLO-v5 [6]. The images are taken from campus and urban road scenes, so we only take into account cars and pedestrians. Fig. 6 shows the comparison of object detection results from DRL-AE and built-in AE methods. Recent detection models, including YOLO-v5, adopt modern augmentation methods to make the model robust the image brightness changes. Therefore, YOLO-v5 tends to detect objects well in even poorly exposed images. However, our algorithm detects " + }, + { + "bbox": [ + 304, + 411, + 545, + 590 + ], + "type": "inline_equation", + "content": "5\\%" + }, + { + "bbox": [ + 304, + 411, + 545, + 590 + ], + "type": "text", + "content": " more objects in terms of the total number of detected objects. Furthermore, the objects in our image are detected much earlier than the built-in AE method. This is highly critical for autonomous vehicles that are driving at high speed. Earlier detected objects can prevent human injury and potential accidents." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 599, + 544, + 612 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 599, + 544, + 612 + ], + "spans": [ + { + "bbox": [ + 306, + 599, + 544, + 612 + ], + "type": "text", + "content": "4.5. Real-world Env: RoI-aware Exposure Control" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "content": "Our DRL-AE framework can also take arbitrary input sizes because the framework resizes the image before the vectorized intensity processing. Also, our domain randomization strategy produces a random size of the Region of Interest (RoI) patch by using crop, flip, resize, and rotation in the training stage. Therefore, our agent is able to control camera exposure for a specific RoI or entire image. Fig. 7 shows the RoI-aware exposure control results." + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 59, + 74, + 109, + 83 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 74, + 109, + 83 + ], + "spans": [ + { + "bbox": [ + 59, + 74, + 109, + 83 + ], + "type": "text", + "content": "Features: 876" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 171, + 74, + 225, + 82 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 171, + 74, + 225, + 82 + ], + "spans": [ + { + "bbox": [ + 171, + 74, + 225, + 82 + ], + "type": "text", + "content": "Features: 1377" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 295, + 749, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 314, + 757 + ], + "type": "text", + "content": "2981" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 70, + 286, + 229 + ], + "blocks": [ + { + "bbox": [ + 53, + 70, + 286, + 229 + ], + "lines": [ + { + "bbox": [ + 53, + 70, + 286, + 229 + ], + "spans": [ + { + "bbox": [ + 53, + 70, + 286, + 229 + ], + "type": "image", + "image_path": "d0021f5f127f7a4b95b580161517c7a1deee34b79e99d756cf02892bfab80b09.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 250, + 288, + 305 + ], + "lines": [ + { + "bbox": [ + 46, + 250, + 288, + 305 + ], + "spans": [ + { + "bbox": [ + 46, + 250, + 288, + 305 + ], + "type": "text", + "content": "Figure 7. RoI-aware camera exposure control. Our agent is able to control camera exposure for a specific RoI or entire image. Given a RoI box, the agent adjusts the camera parameters to maximize the image attribute for a specific RoI area. It allows the camera to capture the detailed context for the regions of interest." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 327, + 287, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 327, + 287, + 423 + ], + "spans": [ + { + "bbox": [ + 46, + 327, + 287, + 423 + ], + "type": "text", + "content": "The agent adjusts the camera parameters to maximize the image attribute for a specific RoI area. It allows the camera to capture the detailed context for the regions of interest. We expect that DRL-AE can be combined with object detection, object tracking, and human gaze and attention. As a result, the combination can lead to adaptive exposure control schemes, such as attention-aware or detection-aware exposure control." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 433, + 201, + 445 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 433, + 201, + 445 + ], + "spans": [ + { + "bbox": [ + 47, + 433, + 201, + 445 + ], + "type": "text", + "content": "4.6. Computation Time Analysis" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "spans": [ + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "type": "text", + "content": "Our agent has a simple Multi-Layer Perceptron (MLP) architecture with two hidden layers of 256 units. Also, our method does not require complex matrix computation like convolutions. Therefore, our agent can be run on a CPU device in real-time. We measure the inference time of the agent on the Ryzen 5950x CPU. Tab. 2 shows the computation time results, compared with shin et al. [21]. The network's inference time takes " + }, + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "type": "inline_equation", + "content": "1ms" + }, + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "type": "text", + "content": " regardless of image resolution because the input image is resized to a fixed resolution. Also, even including other operations, such as image resizing and RoI cropping, it takes a maximum " + }, + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "type": "inline_equation", + "content": "6ms" + }, + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "type": "text", + "content": ", which is still in the real-time range. Therefore, it can run at 170- " + }, + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "type": "inline_equation", + "content": "1000\\mathrm{Hz}" + }, + { + "bbox": [ + 46, + 453, + 287, + 608 + ], + "type": "text", + "content": " on a CPU device." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 620, + 203, + 633 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 620, + 203, + 633 + ], + "spans": [ + { + "bbox": [ + 47, + 620, + 203, + 633 + ], + "type": "text", + "content": "5. Conclusion & Future Work" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 642, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 287, + 715 + ], + "type": "text", + "content": "Conclusion. In this paper, we proposed a novel joint exposure parameter control framework that exploits Deep Reinforcement Learning (DRL) to achieve instant exposure convergence and real-time processing. The proposed framework, named DRL-AE, effectively solves the challenges when applying DRL to the exposure control task, such as" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 70, + 545, + 137 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 70, + 545, + 137 + ], + "spans": [ + { + "bbox": [ + 305, + 70, + 545, + 137 + ], + "type": "text", + "content": "Table 2. Processing time analysis. Our algorithm does not use any complex metric or computation; the agent consists of two MLP layers with 256 hidden units, and the vectorized intensity history does not need complex operations. Therefore, our agent can be run on a CPU device in real-time. Here, we measure the processing time on the Ryzen 5950x CPU." + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 318, + 156, + 535, + 229 + ], + "blocks": [ + { + "bbox": [ + 318, + 156, + 535, + 229 + ], + "lines": [ + { + "bbox": [ + 318, + 156, + 535, + 229 + ], + "spans": [ + { + "bbox": [ + 318, + 156, + 535, + 229 + ], + "type": "table", + "html": "
MethodImage SizeProcessing Time (ms)
Shin et al. [21]1600 x 1200108.7
800 x 60018.2
Ours1600 x 12001.0
800 x 6001.0
", + "image_path": "b8f7a50417b824f761021001563ad5f9f933174a3329766ab2deba236b8cab4e.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 253, + 545, + 313 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 253, + 545, + 313 + ], + "spans": [ + { + "bbox": [ + 305, + 253, + 545, + 313 + ], + "type": "text", + "content": "1) training environment to provide diverse lighting change scenarios, 2) flickering and image attribute-aware reward design, 3) lightweight state design by using vectorized intensity history, and 4) domain generalization via spatial domain randomization strategy." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 314, + 546, + 481 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 314, + 546, + 481 + ], + "spans": [ + { + "bbox": [ + 304, + 314, + 546, + 481 + ], + "type": "text", + "content": "The proposed method is thoroughly validated in three different environments: light-controlled dark room, exposure control dataset [21], and real-world environments. We demonstrate that our proposed method instantly adjusts camera exposure within five steps with real-time processing of " + }, + { + "bbox": [ + 304, + 314, + 546, + 481 + ], + "type": "inline_equation", + "content": "1 \\, ms" + }, + { + "bbox": [ + 304, + 314, + 546, + 481 + ], + "type": "text", + "content": " on a CPU device. Also, our method shows satisfactory generalization performance in the wild. The images acquired from our method are well-exposed and show superiority in numerous computer vision tasks, such as feature extraction and object detection1. To the best of our knowledge, our approach is the first solution that applies DRL to control camera exposure. We hope our paper encourages active research of advanced camera exposure control algorithms to achieve robust visual perception ability." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 482, + 547, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 482, + 547, + 613 + ], + "spans": [ + { + "bbox": [ + 304, + 482, + 547, + 613 + ], + "type": "text", + "content": "Future Work. This paper shows that DRL can be used in the field of camera exposure control. There are lots of open research topics, such as motion-aware AE control, advanced reward function, aperture control, hardware generalization over various cameras, and further domain generalization in the real world. In the future, we plan to extend the current darkroom environment to generate object or camera motion, allowing the agent to consider motion blur for exposure parameter control. Controlling camera aperture by using a mechanical aperture control module is another research direction." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 626, + 399, + 639 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 626, + 399, + 639 + ], + "spans": [ + { + "bbox": [ + 306, + 626, + 399, + 639 + ], + "type": "text", + "content": "Acknowledgment" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 647, + 545, + 683 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 647, + 545, + 683 + ], + "spans": [ + { + "bbox": [ + 306, + 647, + 545, + 683 + ], + "type": "text", + "content": "This research was supported by a grant (P0026022) from R&D Program funded by Ministry of Trade, Industry and Energy of Korean government." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 545, + 713 + ], + "type": "text", + "content": "Further visualization and video demos are available at https:// sites.google.com/view/drl-ae." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2982" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "type": "text", + "content": "[1] Christian Forster, Matia Pizzoli, and Davide Scaramuzza. 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Science China Technological Sciences, 63(9):1612-1627, 2020. 2" + } + ] + } + ], + "index": 27 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "2983" + } + ] + } + ], + "index": 29 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 8 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_content_list.json b/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..2b899bed6f0f7372d7451a1b6852db1c685ac2ac --- /dev/null +++ b/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_content_list.json @@ -0,0 +1,1732 @@ +[ + { + "type": "text", + "text": "Learning to Count without Annotations", + "text_level": 1, + "bbox": [ + 284, + 131, + 687, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Lukas Knobel \nUniversity of Amsterdam \nlukasknbl@gmail.com", + "bbox": [ + 150, + 181, + 352, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Tengda Han* \nUniversity of Oxford \nhtd@robots.ox.ac.uk", + "bbox": [ + 398, + 181, + 570, + 232 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yuki M. Asano* \nUniversity of Amsterdam \ny.m.asano@uva.nl", + "bbox": [ + 614, + 181, + 818, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 286, + 313, + 301 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "While recent supervised methods for reference-based object counting continue to improve the performance on benchmark datasets, they have to rely on small datasets due to the cost associated with manually annotating dozens of objects in images. We propose UnCounTR, a model that can learn this task without requiring any manual annotations. To this end, we construct \"Self-Collages\", images with various pasted objects as training samples, that provide a rich learning signal covering arbitrary object types and counts. Our method builds on existing unsupervised representations and segmentation techniques to successfully demonstrate for the first time the ability of reference-based counting without manual supervision. Our experiments show that our method not only outperforms simple baselines and generic models such as FasterRCNN and DETR, but also matches the performance of supervised counting models in some domains.", + "bbox": [ + 75, + 318, + 473, + 575 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 607, + 209, + 622 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Cognitive neuroscientists speculate that visual counting, especially for a small number of objects, is a pre-attentive and parallel process [12, 55], which can help humans and animals make prompt decisions [43]. Accumulating evidence shows that infants and certain species of animals can differentiate between small numbers of items [11, 12, 41] and as young as 18-month-old infants have been shown to develop counting abilities [53]. These findings indicate that the ability of visual counting may emerge very early or even be inborn in humans and animals.", + "bbox": [ + 75, + 633, + 468, + 784 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "On the non-biological side, recent developments in computer vision have been tremendous. The state-of-the-art computer vision models can classify thousands of image classes [19, 27], detect various objects [66], or segment almost anything from an image [26]. Partially inspired by", + "bbox": [ + 75, + 785, + 470, + 863 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/bfa030c0eccdf66e1d640eb3a6794a05e7263c907c58b26e23e5d4ec47311a33.jpg", + "image_caption": [ + "Figure 1. CountTR vs. our proposed UnCountTRv2. Our counting model, UnCountTRv2, is trained without any labels and manual counting annotations. It generalizes well from its up to 19 pseudo-counts encountered during training to the significantly higher numbers in the FSC-147 test set. This demonstrates that learning to count is possible without annotations." + ], + "image_footnote": [], + "bbox": [ + 509, + 285, + 696, + 428 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/940db8dc4caef36e2b22ead1ba008778982f1c3b5eade06e516ce488f2947357.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 696, + 285, + 883, + 428 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "how babies learn to see the world [54], some of the recent well-performing models are trained with self-supervised learning methods, whereby a learning signal for neural networks is constructed without the need for manual annotations [15, 20]. The pretrained visual representations from such methods have demonstrated superior performances on various downstream visual tasks, like image classification and object detection [7, 20, 21]. Moreover, self-supervised learning signals have been shown to be sufficient for successfully learning image groupings [57, 59] and even object and semantic segmentations without any annotations [7, 62]. Motivated by these, we ask in this paper whether visual counting might also be solvable without relying on human annotations.", + "bbox": [ + 496, + 537, + 892, + 748 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The current state-of-the-art visual counting methods, e.g. CounTR [31], typically adapt pretrained visual representations to the counting task by using a considerable size of human annotations. However, we conjecture that the existing visual representations are already strong enough to perform counting, even without any manual annotations.", + "bbox": [ + 496, + 750, + 893, + 840 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In this paper, we design a straightforward self-supervised training scheme to teach the model 'how to count', by pasting a number of objects on a background image, to make a Self-Collage. Our experiments show that when construct", + "bbox": [ + 496, + 840, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal senior contribution. \n1Code: https://github.com/lukasknobel/SelfCollages", + "bbox": [ + 94, + 875, + 372, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "22924", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ing the Self-Collages carefully, this training method is effective enough to leverage the pretrained visual representation on the counting task, even approaching other methods that require manually annotated counting data. For the visual representation, we use the self-supervised pretrained DINO features [7], which have been shown to be useful and generalisable for a variety of visual tasks like segmenting objects [34, 67]. Note that the DINO model is also trained without manual annotations, thus our entire pipeline does not require annotated datasets.", + "bbox": [ + 75, + 90, + 472, + 241 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To summarise, this paper focuses on the objective of training a reference-based counting model without any manual annotation. The following contributions are made: (i) We propose a simple yet effective data generation method to construct 'Self-Collages', which pastes objects onto an image and gets supervision signals for free. (ii) We leverage self-supervised pretrained visual features from DINO and develop UnCounTR, a transformer-based model architecture for counting. (iii) The experiments show that our method trained without manual annotations not only outperforms baselines and generic models like FasterRCNN and DETR, but also matches the performance of supervised counting models.", + "bbox": [ + 75, + 242, + 472, + 439 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related work", + "text_level": 1, + "bbox": [ + 76, + 452, + 215, + 467 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Counting with object classes. The class-specific counting methods are trained to count instances of a single class of interest, such as cars [23, 36] or people [28, 28, 32, 47, 48]. These methods require retraining to apply them to new object classes [36]. In addition, some works rely on class-specific assumptions such as the proportionality of features and counts [24], or the distribution [48] or shapes [56] of objects, which cannot be easily adapted.", + "bbox": [ + 75, + 477, + 468, + 598 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "By contrast, class-agnostic approaches are not designed with a specific object class in mind. Early work by Zhang et al. [63] proposes the salient object subitizing task, where the model is trained to count by classification of $\\{0,1,2,3,4+\\}$ salient objects regardless of their classes. Other reference-less methods like Hobley and Prisacariu [22] frame counting as a repetition-recognition task and aim to automatically identify the objects to be counted. An alternative approach of class-agnostic counting requires a prior of the object type to be counted in the form of reference images, also called 'exemplars', each containing a single instance of the desired class [14, 29, 33, 45, 50, 60, 61].", + "bbox": [ + 75, + 599, + 468, + 779 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Counting with different methods. Categorised by the approach taken to obtain the final count, counting methods can be divided into classification, detection and regression-based methods.", + "bbox": [ + 75, + 779, + 468, + 839 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Classification-based approaches predict a discrete count for a given image [63]. The classes either correspond to single numbers or potentially open-ended intervals. Thus, predictions are limited to the pre-defined counts and a gen", + "bbox": [ + 75, + 839, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "eralisation to new ranges is by design not possible.", + "bbox": [ + 498, + 90, + 834, + 106 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "An alternative is detection-based methods [23]. By predicting bounding boxes for the counted instances and deriving a global count based on their number, these methods are unlike classification-based approaches not constrained to predefined count classes. While the bounding boxes can facilitate further analysis by explicitly showing the counted instances, the performance of detection-based approaches deteriorates in high-density settings [22].", + "bbox": [ + 496, + 106, + 890, + 227 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Lastly, regression-based methods predict a single number and can be further divided into scalar and density-based approaches. Scalar methods directly map an input image to a single scalar count corresponding to the number of objects in the input [22]. Density-based methods on the contrary predict a density map for a given image and obtain the final count by integrating over it [9, 14, 32, 33, 48, 49]. Similar to detection-based approaches, these methods allow locating the counted instances which correspond to the local maxima of the density map but have the added benefit of performing well in high-density applications with overlapping objects [33]. The recent work CounTR [31] is a class-agnostic, density-based method which is trained to count both with and without exemplars using a transformer decoder structure with learnable special tokens.", + "bbox": [ + 496, + 227, + 892, + 452 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Self-supervised learning. Self-supervised learning (SSL) has shown its effectiveness in many computer vision tasks. Essentially, SSL derives the supervision signal from the data itself rather than manual annotations. The supervision signal can be found from various \"proxy tasks\" like colorization [64], spatial ordering or inpainting [15, 21, 37, 42], temporal ordering [18, 35], contrasting similar instances [10, 20, 39], clustering [3, 6], and from multiple modalities [1, 44]. Another line of SSL methods is knowledge distillation, where one smaller student model is trained to predict the output of the other larger teacher model [4, 8, 25]. BYOL [17] design two identical models but train one model to predict the moving average of the other as the supervision signal. Notably, DINO [7] is trained in a similar way but using Vision Transformers (ViTs) as the visual model [16], and obtains strong visual features. Simply thresholding the attention maps and using the resulting masks yields high-quality image segmentations. Follow-up works [34, 51, 67] demonstrate the semantic segmentation quality can be further improved by applying some lightweight training or post-processing of DINO features. For counting in SSL, Noroozi et al. [38] use feature \"counting\" as a proxy task to learn representations. In this work, we focus on counting itself and explore approaches to teach the model to count without manual supervision.", + "bbox": [ + 496, + 453, + 892, + 830 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 500, + 844, + 591, + 859 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We tackle the task of counting objects given some exemplar crops within an image. With an image dataset $\\mathcal{D} =$", + "bbox": [ + 498, + 869, + 890, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "22925", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/1e3a6a85d43cec1bc0ec5d0d4ccdcd4af76afacd3d56630cd78a8ca60f737f42.jpg", + "image_caption": [ + "Figure 2. Method overview. Our method leverages the strong coherence of deep clusters to provide pseudo-labelled images which are used to construct a self-supervised counting task. The composer utilises self-supervised segmentations for pasting a set of objects onto a background image and UnCounTR is trained to count these when provided with unsupervised exemplars." + ], + "image_footnote": [], + "bbox": [ + 81, + 92, + 883, + 292 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "$\\{(I_1, S_1, \\mathbf{y}_1), \\ldots, (I_i, S_i, \\mathbf{y}_i)\\}$ , where $I_i \\in \\mathbb{R}^{H \\times W \\times 3}$ denotes image $i$ , $S_i = \\{E_i^1, \\ldots, E_i^E\\}$ represent the $E$ visual exemplars of shape $E_i^e \\in \\mathbb{R}^{H' \\times W' \\times 3}$ , and $\\mathbf{y}_i \\in \\mathbb{R}^{H \\times W}$ is the ground-truth density map, the counting task can be written as:", + "bbox": [ + 76, + 357, + 468, + 434 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\mathbf {y}} _ {i} = f _ {\\Theta} \\left(\\boldsymbol {I} _ {i}, \\mathcal {S} _ {i}\\right) \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 217, + 435, + 468, + 450 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Here, the predicted density map $\\hat{\\mathbf{y}}_i$ indicates the objects to be counted, as specified by the exemplars $S_{i}$ , such that $\\sum_{kl} \\hat{\\mathbf{y}}_{i_{kl}}$ yields the overall count for the image $I_{i}$ . We are interested in training a neural network $f$ parameterised by $\\Theta$ to learn how to count based on the exemplars $S_{i}$ . For the supervised counting methods [31, 33], the network parameters $\\Theta$ can be trained with the 'prediction, ground-truth') pairs: $(\\hat{\\mathbf{y}}_i, \\mathbf{y}_i)$ . However, for self-supervised counting, the learning signal $\\mathbf{y}_i$ is not obtained from manual annotations, but instead from the data itself.", + "bbox": [ + 75, + 458, + 468, + 608 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we introduce two essential parts of our method: we start by presenting our data generation method for counting in Section 3.1, that is the construction of the tuple $(I_i, S_i, \\mathbf{y}_i)$ ; then, we explain the UnCounTR model, i.e. $f_\\Theta$ in Equation (1), in Section 3.2. An overview of our method is provided in Figure 2.", + "bbox": [ + 75, + 609, + 468, + 700 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Constructing Self-Collages", + "text_level": 1, + "bbox": [ + 76, + 710, + 318, + 727 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "A key component of self-supervised training is the construction of a supervision signal without any manual annotations. In this paper, we generate training samples by pasting different images on top of a background. This is a well-known technique [2, 65], which next to its conceptual simplicity provides great flexibility regarding the number and type of pasted images. While other works combine annotated training images to enrich the training set [22, 31], we use this idea to construct the whole training set including unsupervised proxy labels, yielding self-supervised collages, or Self-Collages for short. Their generation pro", + "bbox": [ + 75, + 734, + 470, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "cess is described by a composer module $g$ , which forms a distribution $g(\\mathcal{O}, \\mathcal{B}) = p(\\tilde{\\boldsymbol{I}}, S, \\mathbf{y} \\mid \\mathcal{O}, \\mathcal{B})$ of constructed images $\\tilde{\\boldsymbol{I}} \\in \\mathbb{R}^{H \\times W \\times 3}$ along with unsupervised exemplars $\\mathcal{S}$ and labels $\\mathbf{y}$ . The process is based on two sets of unlabelled images $\\mathcal{O}$ and $\\mathcal{B}$ for object and background images. $\\mathcal{S} = \\{\\pmb{E}\\}^E$ , $\\pmb{E} \\in \\mathbb{R}^{H' \\times W' \\times 3}$ is a set of $E \\in \\mathbb{N}$ exemplars and $\\mathbf{y} \\in \\mathbb{R}^{H \\times W}$ corresponds to the density map of $\\tilde{\\boldsymbol{I}}$ .", + "bbox": [ + 496, + 358, + 890, + 464 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The composer module $g$ first randomly selects the number of distinct object categories $n_c \\sim U[t_{\\min}, t_{\\max}]$ the first of which is taken as the target cluster. $t_{\\min}$ and $t_{\\max}$ control the minimum and maximum number of categories in a Self-Collage. To reduce the risk of overfitting to construction artefacts, we always construct images with $n_{\\max}$ objects and change the associated number of target objects $\\sum_{ij} \\mathbf{y}_{ij}$ solely by altering the number of objects in the target cluster. This way, the number of pasted objects and, therefore, the number of artefacts is independent of the target count. The number of target objects $n_0 = n \\sim U[n_{\\min}, n_{\\max} - n_c + 1]$ has an upper-bound lower than $n_{\\max}$ to guarantee that there is at least one object of each of the $n_c$ types. For all other clusters, the number of objects is drawn from a uniform distribution of points on the $n_c - 1$ dimensional polytope with $L1$ -size of $n_{\\max} - n$ ensuring that the total number of objects equals $n_{\\max}$ . Further details, including the pseudocode for the composer module, are shown in the Appendix.", + "bbox": [ + 496, + 465, + 892, + 736 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Unsupervised categories. We obtain unsupervised object categories by first extracting feature representations for all samples in $\\mathcal{O}$ using a pretrained DINO ViT-B/16 backbone [7] $d$ and subsequently running k-means with $K$ clusters:", + "bbox": [ + 496, + 737, + 890, + 811 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nc (\\boldsymbol {I}) = \\mathrm {k} - \\operatorname {m e a n s} _ {K} \\left[ \\left(d (\\mathcal {O})\\right) ^ {\\mathrm {C L S}} \\right] (\\boldsymbol {I}), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 584, + 814, + 890, + 832 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $c(I)$ is the unsupervised category for image $\\pmb{I}$ constructed using the final CLS-embedding of $d$ . For each of the $n_c$ clusters, a random, unique cluster $c_{i}$ , $i\\in [0,n_c - 1]$ is chosen from all $K$ clusters where $c_{0}$ is the target cluster.", + "bbox": [ + 496, + 839, + 893, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "22926", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Image selection. Next, random sets of images $\\mathcal{I}_i\\subset \\mathcal{O}$ are picked from their unsupervised categories $c_{i}$ , such that $|\\mathcal{I}_i| = n_i$ and $c(I) = c_i\\forall I\\in \\mathcal{I}_i$ . We denote the union of these sets as $\\mathcal{I} = \\bigcup_{i = 0}^{n_c - 1}\\mathcal{I}_i$ . In addition, we sample one image $I_{\\mathrm{b}}$ from another dataset $\\mathcal{B}$ , which is assumed to not contain salient objects to serve as the background image.", + "bbox": [ + 76, + 90, + 472, + 183 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.1.1 Construction strategy", + "text_level": 1, + "bbox": [ + 76, + 200, + 282, + 217 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Here we detail the Self-Collage construction. First, the background image $I_{\\mathrm{b}}$ is reshaped to the final dimensions $H \\times W$ and used as a canvas on which the modified images $\\mathcal{I}$ are pasted. To mimic natural images that typically contain similarly sized objects, we first randomly pick a mean object size $d_{\\mathrm{mean}} \\sim U[d_{\\mathrm{min}}, d_{\\mathrm{max}}]$ . Subsequently, the target size of the pasted objects is drawn independently for each $I \\in \\mathcal{I}, I \\in \\mathbb{R}^{d_{\\mathrm{h}} \\times d_{\\mathrm{w}} \\times 3}$ from a uniform distribution $d_{\\mathrm{paste}} \\sim U[(1 - \\sigma) \\cdot d_{\\mathrm{mean}}, (1 + \\sigma) \\cdot d_{\\mathrm{mean}}]$ where $\\sigma \\in (0,1)$ controls the diversity of objects sizes in an image. After resizing $I$ to $I_{\\mathrm{r}} \\in \\mathbb{R}^{d_{\\mathrm{paste}} \\times d_{\\mathrm{paste}} \\times 3}$ , the image is pasted to a random location on $I_{\\mathrm{b}}$ . This location is either a position where previously no object has been pasted, or any location in the constructed image, potentially leading to overlapping images. By default, we will use the latter.", + "bbox": [ + 75, + 224, + 468, + 450 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Segmented pasting. Since pasting the whole image $I_{\\mathrm{r}}$ might violate the assumption of having a single object and results in artefacts by also pasting the background of $I_{\\mathrm{r}}$ , we introduce an alternative using self-supervised segmentations. This method, which we will use by default, uses an unsupervised segmentation method [51] to obtain a noisy foreground segmentation $\\mathbf{s} \\in [0, 1]^{d_{\\mathrm{h}} \\times d_{\\mathrm{w}}}$ for $I$ . Instead of pasting the whole image, the segmentation $\\mathbf{s}$ is used to only copy its foreground. Additionally, having access to $\\mathbf{s}$ , this method can directly control the size of the pasted objects rather than the pasted images. To do that, we first extract the object in $I$ by computing the Hadamard product $I_{\\mathrm{object}} = \\operatorname{cut}(I \\circ \\mathbf{s})$ where the operation \"cut\" removes rows and columns that are completely masked out. In the next step, $I_{\\mathrm{object}} \\in \\mathbb{R}^{h_{\\mathrm{object}} \\times w_{\\mathrm{object}} \\times 3}$ is resized so that its maximum dimension equals $d_{\\mathrm{paste}}$ before pasting it onto $I_{\\mathrm{b}}$ .", + "bbox": [ + 75, + 450, + 468, + 691 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Exemplar selection. To construct the exemplars used for training, we exploit the information about how the sample was constructed using $g$ : The set of $E$ exemplars $S$ is simply obtained by filtering for pasted objects that belong to the target cluster $c_{0}$ and subsequently sampling $E$ randomly. Then, for each of them, a crop of $\\tilde{I}$ is taken as exemplar after resizing its spatial dimensions to $H' \\times W'$ .", + "bbox": [ + 75, + 693, + 467, + 797 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.1.2 Density map construction", + "text_level": 1, + "bbox": [ + 76, + 816, + 308, + 830 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To train our counting model, we construct an unsupervised density map $\\mathbf{y}$ for each training image $\\tilde{\\pmb{I}}$ . It needs to have the following two properties: i) it must sum up to the overall count of objects that we are counting and ii) it must have", + "bbox": [ + 75, + 839, + 467, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "high values at object locations. To this end, we create $\\mathbf{y}$ as a simple density map of Gaussian blobs as done in supervised density-based counting methods [14, 31]. For this, we use the bounding box for each pasted target image $I\\in \\mathcal{I}_0$ and place Gaussian density at the centre and normalise it to one.", + "bbox": [ + 496, + 90, + 890, + 167 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. UnCounTR", + "text_level": 1, + "bbox": [ + 500, + 176, + 625, + 191 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Model architecture. UnCounTR's architecture is inspired by CounTR [31]. To map an input image $\\pmb{I}$ and its exemplars $S$ to a density map $\\hat{\\mathbf{y}}$ , the model consists of four modules: image encoder $\\Phi$ , exemplar encoder $\\Psi$ , feature interaction module $f_{\\mathrm{fim}}$ , and decoder $f_{\\mathrm{dec}}$ . An overview of this architecture can be seen in Figure 2. The image encoder $\\Phi$ encodes an image $\\pmb{I}$ into a feature map $\\mathbf{x} = \\Phi(\\pmb{I}) \\in \\mathbb{R}^{h \\times w \\times d}$ where $h, w, d$ denote the height, width, and channel depth. Similarly, each exemplar $E \\in S$ is projected to a single feature vector $\\mathbf{z} \\in \\mathbb{R}^d$ by taking a weighted average of the grid features. Instead of training a CNN for an exemplar encoder as CounTR does, we choose $\\Psi = \\Phi$ to be the frozen DINO visual encoder weights. Reusing these weights, the exemplar and image features are in the same feature space. The feature interaction module (FIM) $f_{\\mathrm{fim}}$ enriches the feature map $\\mathbf{x}$ with information from the encoded exemplars $\\mathbf{z}_j$ , $j \\in \\{1, \\dots, E\\}$ with a transformer decoder structure. Finally, the decoder $f_{\\mathrm{dec}}$ takes the resulting patch-level feature map of the FIM as input and upsamples it with 4 convolutional blocks, ending up with a density map of the same resolution as the input image. Please refer to the Appendix for the full architectural details.", + "bbox": [ + 496, + 200, + 890, + 531 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "UnCounTR supervision. UnCounTR is trained using the Mean Squared Error between model prediction and pseudo labels. Given a Self-Collage $\\tilde{I}$ , exemplars $S$ , and density map $\\mathbf{y}$ , the loss $\\mathcal{L}$ for an individual sample is computed using the following equation where $f_{\\Theta}(\\tilde{I}, S)_{ij}$ is UnCounTR's spatially-dense output at location $(i, j)$ :", + "bbox": [ + 496, + 532, + 890, + 625 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\frac {1}{H \\cdot W} \\sum_ {i j} \\left(\\mathbf {y} _ {i j} - f _ {\\Theta} (\\tilde {\\boldsymbol {I}}, \\mathcal {S}) _ {i j}\\right) ^ {2} \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 573, + 635, + 890, + 672 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 686, + 632, + 702 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Implementation Details", + "text_level": 1, + "bbox": [ + 500, + 710, + 715, + 726 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Datasets. To construct Self-Collages, we use ImageNet1k [13] and SUN397 [58]. ImageNet-1k contains 1.2M mostly object-centric images spanning 1000 object categories. SUN397 contains 109K images for 397 scene categories like 'cliff' or 'corridor'. Note that the object or scene category information is never used in our method. We assume that images from ImageNet-1k contain a single salient object and images from SUN397 contain no salient objects to serve as sets $\\mathcal{O}$ and $\\mathcal{B}$ . Based on this, $g$ randomly selects images from SUN397 as background images and picks objects from ImageNet-1k. Although Imagenet", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "22927", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "1k and SUN397 contain on average 3 and 17 objects respectively [30], these assumptions are still reasonable for our data construction. Additional ablations show that even explicitly violating the assumption of having no salient objects in $\\mathcal{B}$ by using $\\mathcal{O} = \\mathcal{B}$ only have a small effect on performance, indicating the robustness of our method against violations (see Appendix). An example of a Self-Collage with 5 objects can be seen in Figure 2. Examples of both datasets and a more detailed discussion of these assumptions are included in the Appendix.", + "bbox": [ + 75, + 90, + 472, + 242 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To evaluate the counting ability, we use the standard FSC-147 dataset [45], which contains 6135 images covering 147 object categories, with counts ranging from 7 to 3731 and an average count of 56 objects per image. For each image, the dataset provides at least three randomly chosen object instances with annotated bounding boxes as exemplars. To analyse the counting ability in detailed count ranges, we partition the FSC-147 test set into three parts of roughly 400 images each, resulting in FSC-147{low,medium,high} subsets, each covering object counts from 8-16, 17-40 and 41-3701 respectively. Unless otherwise stated, we evaluate using 3 exemplars.", + "bbox": [ + 75, + 244, + 472, + 425 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Additionally, we also use the CARPK [23] and the Multi-Salient-Object (MSO) dataset [63] for evaluation. CARPK consists of 459 images of parking lots. Each image contains between 2 and 188 cars, with an average of 103. MSO contains 1224 images covering 5 categories: $\\{0,1,2,3,4+\\}$ salient objects with bounding box annotations. This dataset is largely imbalanced as 338 images contain zero salient objects and 20 images contain at least 4. For evaluation, we removed all samples with 0 counts, split the $4+$ category into exact counts, and chose only one annotated object as exemplar.", + "bbox": [ + 75, + 428, + 472, + 594 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Construction details. We configure the composer module to construct training samples using objects of $K = 10,000$ different clusters. To always have objects of a target and a non-target cluster in each image, we set $t_{\\mathrm{min}} = t_{\\mathrm{max}} = 2$ . Since the minimum number of target objects in an image limits the maximum number of exemplars available during training, we set $n_{\\mathrm{min}} = 3$ , the maximum is $n_{\\mathrm{max}} = 20$ . Finally, we choose $d_{\\mathrm{min}} = 15$ , $d_{\\mathrm{max}} = 70$ , and $\\sigma = 0.3$ to obtain diverse training images with objects of different sizes as confirmed by visual inspection of the generated Self-Collages (see the Appendix).", + "bbox": [ + 75, + 595, + 472, + 763 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Training and inference details. During training, the images are cropped and resized to $224 \\times 224$ pixels. The exemplars are resized to $64 \\times 64$ pixels. For each batch, we randomly draw the number of exemplars $E$ to be between 1 and 3. We follow previous work [31] by scaling the loss, in our case by a factor of 3,000, and randomly dropping $20\\%$ of the non-object pixels in the density map to decrease the imbalance of object and non-object pixels. By default, we use an AdamW optimizer and a cosine-decay learning rate", + "bbox": [ + 75, + 763, + 472, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "schedule with linear warmup and a maximum learning rate of $5 \\times 10^{-4}$ . We use a batch size of 128 images. Each model is trained on an Nvidia A100 GPU for 50 epochs of 10,000 Self-Collages each, which takes about 4 hours. At inference, we use a sliding window approach similar to Liu et al. [31], see the Appendix for details. For evaluation metrics, we report Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE) following previous work [14, 31]. We also report Kendall's $\\tau$ coefficient, which is a rank correlation coefficient between the sorted ground-truth counts and the predicted counts.", + "bbox": [ + 496, + 90, + 893, + 257 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Baselines. To verify the effectiveness of our method, we introduce a series of baselines to compare with. (1) Average baseline: the prediction is always the average count of the FSC-147 training set, which is 49.96 objects. (2) Connected components baseline: for this, we use the final-layer attention values from the CLS-token of a pretrained DINO ViT-B/8 model. To derive a final count, we first threshold the attention map of each head to keep $p_{\\mathrm{att}}$ percent of the attention mask. Subsequently, we consider each patch to where at least $n_{\\mathrm{head}}$ attention heads attend to belong to an object. The number of connected components in the resulting feature map which cover more than $p_{\\mathrm{size}}$ percent of the feature map is taken as prediction. To this end, we perform a grid search with almost 800 configurations of different value combinations for the three thresholds $p_{\\mathrm{att}}, n_{\\mathrm{head}}$ , and $p_{\\mathrm{size}}$ on the FSC-147 training set and select the best configuration based on the MAE. The specific values tested can be found in the Appendix. (3) FasterRCNN baseline: we run the strong image detection toolbox FasterRCNN [46] with a score threshold of 0.5 on the image, which predicts a number of object bounding boxes. Then the object count is obtained by parsing the detection results by taking the total number of detected bounding boxes. Just like the connected components baseline, this model is applied to images resized to $384 \\times 384$ pixels. (4) DETR baseline: similar to FasterRCNN, we evaluate the detection model DETR [5] on the counting task. Here, we resize the images to $800 \\times 800$ pixels to better match DETR's evaluation protocol.", + "bbox": [ + 496, + 258, + 893, + 681 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Comparison against baselines", + "text_level": 1, + "bbox": [ + 498, + 695, + 766, + 710 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In Table 1, we compare against multiple baselines on the three splits of FSC-147. As the connected components cannot leverage the additional information of the few-shot samples provided, we try to make the comparison as fair as possible, by testing almost 800 threshold parameters on the FSC-147 training set. While this yields a strong baseline, we find that our method of learning with Self-Collages more than halves the MAE on the low split, despite using a similar visual backbone. Next, we compare against the FasterRCNN and DETR object detectors which, unlike UnCounTR, are trained in a supervised fashion. Even though DETR outperforms UnCounTR in terms of RMSE on FSC", + "bbox": [ + 496, + 719, + 893, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "22928", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/3a2962f6a45ef66a113ce2ca5c06b880d2099b95af29d9014c4ea8fbe124ed82.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodFSC-147 lowFSC-147 mediumFSC-147 high
MAE↓RMSE↓τ↑MAE↓RMSE↓τ↑MAE↓RMSE↓τ↑
Average37.7137.79-22.7423.69-68.88213.08-
Conn. Comp.14.7118.590.1414.1917.900.1669.77210.540.17
FasterRCNN7.068.46-0.0319.8722.25-0.04109.12230.35-0.06
DETR6.928.200.0719.3321.56-0.08109.34162.88-0.07
UnCounTR (ours)5.6010.130.279.4812.730.3467.17189.760.26
σ(5 runs)±0.48±0.84±0.02±0.19±0.33±0.02±1.03±1.38±0.01
", + "bbox": [ + 161, + 80, + 803, + 208 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/7b923d8bd6e9807bfb4fe109791ef91816385259c62e28619d29affdd944d441.jpg", + "table_caption": [ + "Table 1. Comparison to baselines. Evaluation on different FSC-147 test subsets. \"Conn. Comp.\" refers to connected components." + ], + "table_footnote": [], + "table_body": "
Frozen ΦFrozen ΨFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
XX37.64126.917.9913.37
✓X36.94130.229.1014.69
✓✓35.77130.345.6010.13
", + "bbox": [ + 89, + 227, + 436, + 311 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/39d23acf56e75e0f7cc4a3c6d7ed241d3ed3368cdc5fc5e0a5ff7fdc42df9f66.jpg", + "table_caption": [ + "(a) Keeping both image encoder $\\Phi$ and exemplar encoder $\\Psi$ frozen works best." + ], + "table_footnote": [], + "table_body": "
FSC-147FSC-147 low
nmaxMAE↓RMSE↓MAE↓RMSE↓
5030.17115.426.6513.60
2035.77130.345.6010.13
", + "bbox": [ + 135, + 338, + 390, + 406 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/ac6621be764465a03d5afc7ac5b663decd912e8ce11fa7a2c4393f48051fb87f.jpg", + "table_caption": [ + "(c) The number of pasted objects correlates with performance." + ], + "table_footnote": [], + "table_body": "
Segm.Overlap.FSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
✓✘36.47128.978.8414.54
✘✓37.46136.036.3311.55
✓✓35.77130.345.6010.13
", + "bbox": [ + 532, + 228, + 856, + 310 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/43097ebae022121daeba346eda5444284a248845f86edfe6866b6dc226264b1f.jpg", + "table_caption": [ + "(b) Using both segmented objects and allowing for overlapping objects works well." + ], + "table_footnote": [], + "table_body": "
#ExemplarsFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
0 - 336.28131.446.2310.33
1 - 335.77130.345.6010.13
", + "bbox": [ + 547, + 338, + 843, + 405 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Ablations. We ablate various components of our model architecture and Self-Collage construction method. Default settings are highlighted in grey.", + "bbox": [ + 75, + 426, + 892, + 455 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/446373c2e66a404e82330fc9d028a346b77e62ef151726a1cc256deafdab529b.jpg", + "table_caption": [ + "(d) Training our method strictly in the 1-3 exemplar setting works best." + ], + "table_footnote": [], + "table_body": "
ArchitecturePretrainingFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
ViT-B/8Leopard [67]36.04126.755.7210.67
ViT-B/8DINO [7]38.16132.096.109.79
ViT-B/16DINO [7]35.77130.345.6010.13
", + "bbox": [ + 86, + 462, + 455, + 542 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "147 low and high, we find that our method still outperforms all baselines on 7 out of 9 measures. This is despite the additional advantages such as access to the FSC-147 training distribution for these baselines. The gap between most baselines and UnCounTR is the smallest on the high split, suggesting limits to its generalisation which we will explore further in the Appendix. There, we also provide a qualitative analysis of some failure cases of FasterRCNN.", + "bbox": [ + 75, + 603, + 468, + 724 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 738, + 230, + 753 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We analyse the various components of our method in Tables 2a to 2d.", + "bbox": [ + 75, + 762, + 468, + 792 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Keeping backbone frozen works best. In Table 2a, we evaluate the effect of unfreezing the last two backbone blocks shared by $\\Phi$ and $\\Psi$ . In addition, we test training a CNN-based encoder $\\Psi$ from scratch similar to Liu et al. [31]. We find that keeping both frozen, i.e. $\\Phi = \\Psi =$ const. works best, as it discourages the visual features to adapt to potential artefacts in our Self-Collages.", + "bbox": [ + 75, + 794, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/9dba39523a9f1e2d3f3665d05d38783f2615c0201252276a095e903d7c63be04.jpg", + "table_caption": [ + "Table 3. Combining Self-Collages with different backbones. We can apply our method to any recent state-of-the-art pretrained network and achieve strong performances." + ], + "table_footnote": [], + "table_body": "
MethodsValTest
MAE↓RMSE↓MAE↓RMSE↓
CounTR [31]13.1349.8311.9591.23
LOCA [14]10.2432.5610.7956.97
UnCounTR (ours)36.93106.6135.77130.34
σ(5 runs)±0.49±1.46±0.60±0.94
", + "bbox": [ + 527, + 455, + 859, + 555 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 4. Comparison to supervised models. We evaluate on the val and test split of FSC-147.", + "bbox": [ + 498, + 558, + 890, + 585 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Benefit of self-supervised exemplars. In Table 2d we evaluate the effect of including the zero-shot counting task (i.e. counting all salient objects) as done in other works [14, 31]. However, we find that including this task even with only a $25\\%$ chance leads to a lower performance. This is likely due to the zero-shot task overfitting our Self-Collages and finding short-cuts, such as pasting artefacts, as we relax the constraint introduced in Section 3.1.1 and vary the number of pasted objects to match the desired target. We therefore train our model with 1-3 exemplars and show how we can still conduct semantic zero-shot counting in Section 4.7.", + "bbox": [ + 496, + 597, + 890, + 777 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Maximum number of pasted objects. Next, we evaluate the effect of varying $n_{\\mathrm{max}}$ , the maximum number of objects pasted, as shown in Table 2c. Pasting up to 50 objects yields overall better performance on the full FSC-147 test dataset which contains on average 66 objects. While this shows that the construction of Self-Collages can be successfully scaled to higher counts, we find that pasting with 20 objects already achieves good performance with shortened", + "bbox": [ + 496, + 779, + 892, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "22929", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/0e6df28a2f9ad3f2efe380dd3f2e54f295b22b63842450b61b192c11c3e392d1.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodFSC-147 low (8-16 objects)FSC-147 medium (17-40 objects)FSC-147 high (41-3701 objects)
MAE↓RMSE↓Δτ↑MAE↓RMSE↓Δτ↑MAE↓
CounTR6.5848.110.424.4810.020.6020.50
UnCounTR (ours)5.6010.13-37.90.279.4812.73+2.70.3467.17
σ(5 runs)±0.48±0.84±0.02±0.19±0.33±0.02±1.03
", + "bbox": [ + 112, + 84, + 854, + 170 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/77ddc51f7803293020d3eb256eea48bad03062bf10532cd4050c63cf0fbc274d.jpg", + "table_caption": [ + "Table 5. Comparison to CounTR. Evaluation results on the FSC-147 low and medium test subsets." + ], + "table_footnote": [], + "table_body": "
MethodMSO
MAE↓RMSE↓τ↑
Conn. Comp. Baseline10.6712.880.12
CounTR2.348.120.36
UnCounTR (ours)1.072.320.45
σ(5 runs)±0.06±0.25±0.01
", + "bbox": [ + 117, + 189, + 426, + 291 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/e8fa6bcc1ec9511ac305ede15d6a63b8c50feae1bcce96d44b293d7e4a278439.jpg", + "table_caption": [ + "Table 6. Evaluation on the MSO [63] dataset." + ], + "table_footnote": [], + "table_body": "
MethodCARPK
MAE↓RMSE↓τ↑
Conn. Comp. Baseline49.6254.500.56
CounTR19.6229.700.57
UnCounTR (ours)30.3535.670.54
σ(5 runs)±2.26±2.36±0.06
", + "bbox": [ + 540, + 190, + 848, + 290 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "construction times and so use this setting.", + "bbox": [ + 76, + 316, + 352, + 330 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Segmented pasting works best. From Table 2b, We find that the best construction strategy involves pasting the self-supervised segmentations, regardless of their overlap with other objects. We simply store the segmentations and combine these to create diverse Self-Collages at training time.", + "bbox": [ + 75, + 330, + 468, + 407 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Compatible with various pretrained backbones. In Table 3, we show the effect of using different frozen weights for the visual encoder. Across ViT-B models with varying patch sizes and pretrainings, from Leopart's [67] spatially dense to the original DINO's [7] image-level pretraining, we find similar performances across our evaluations. This shows that our method is compatible with various architectures and pretrainings and will likely benefit from the continued progress in self-supervised representation learning which is supported by our findings based on DINOv2 [40] presented in the Appendix. We do not find any benefit in going from patch size 16 to 8 (similar to Simeoni et al. [52]) so we use the faster DINO ViT-B/16 model for the rest of the paper.", + "bbox": [ + 75, + 409, + 468, + 619 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Benchmark comparison", + "text_level": 1, + "bbox": [ + 76, + 633, + 295, + 648 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Next, we compare with previous methods on three datasets: FSC-147 [45], MSO [63], and CARPK [23]. Table 4 shows the results on the validation and test split of the FSC-147 dataset. In contrast to our approach, which investigates the feasibility of learning to count without any reliance on supervised data, these methods heavily depend on manual annotations. Hence, the comparison is certainly not fair: (1) our method does not use manually annotated counting data, also has never seen any FSC-147 training images, (2) our training samples based on Self-Collages only cover 3-19 target objects, whereas the full test set of FSC-147 has 66 objects on average. Evaluating our method on the full set of FSC-147 is actually evaluating the transferring ability as discussed in more detail in the Appendix.", + "bbox": [ + 75, + 657, + 468, + 868 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We choose CounTR [31] for further analysis because of its similar architecture to UnCounTR. To fairly com", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 7. Evaluation on the CARPK [23] dataset.", + "text_level": 1, + "bbox": [ + 540, + 292, + 843, + 306 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "pare with this method, we trisect the FSC-147 test set as described in Section 4.1. Table 5 shows the evaluation results on the three partitions. It is remarkable that our method outperforms supervised CounTR on the low partition, especially on the RMSE metric (10.13 vs 48.11). Also, our method is not far from CounTR's performance on the medium partition (e.g. RMSE 12.7 vs 10.02), showing a reasonable transferring ability since the model is trained with up to 19 object counts only.", + "bbox": [ + 496, + 314, + 890, + 450 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Additionally, Table 6 compares our method with the connected components baseline and CounTR on a subset of MSO as described in Section 4.1. The results show our self-supervised method outperforms the supervised CounTR model by a large margin on the lower counts tasks. In Table 7, the performance on the CARPK dataset is shown. We use the same CounTR model finetuned on the FSC-147 dataset as before to compare the generalisation across datasets. While the MAE of CounTR almost doubles compared to the results on the FSC-147 test set, UnCounTR's performance is more stable, improving by $15\\%$ .", + "bbox": [ + 496, + 450, + 892, + 617 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.5. Qualitative results and limitations", + "text_level": 1, + "bbox": [ + 500, + 628, + 795, + 643 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Figure 3 shows a few qualitative results to demonstrate our method's effectiveness and its limitations. The model is able to correctly predict the number of objects for clearly separated and slightly overlapping instances (e.g. Subfigures a and c). The model also successfully identifies the object type of interest, e.g. in Subfigure b the density map correctly highlights the strawberries rather than blueberries. One limitation of our model is images where the number of objects is ambiguous. For example, in Subfigure d, the prediction missed a few burgers which are possibly the ones partially shown on the edge. However, it is also difficult for humans to decide which of those objects should be counted.", + "bbox": [ + 496, + 652, + 890, + 834 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.6. Improving upon UnCounTR", + "text_level": 1, + "bbox": [ + 500, + 845, + 754, + 861 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Having established UnCounTR and compared it to several methods, we now explore three ways to further improve its", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "22930", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/0fc2311f82cc9c35f6b8ce842fa59a43651a321a271b366b97aeadf9eb548a06.jpg", + "image_caption": [ + "(a) $\\mathrm{GT} = 8$ Pred=8" + ], + "image_footnote": [], + "bbox": [ + 151, + 89, + 336, + 181 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/3cf88baac8c245893c5c3a5b74bafa7950e5ea605ab0e1d3f781c8480b9d2f03.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 341, + 95, + 519, + 181 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/bc300a1cc50bcb6c069294ecebe12eab862c1c48122a7cf5c5340fb325fde529.jpg", + "image_caption": [ + "(b) $\\mathrm{GT} = 16$ ; Pred=17" + ], + "image_footnote": [], + "bbox": [ + 534, + 89, + 671, + 181 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/1907177f78fbc26edc4b3b1724c088c5f672dbd2386e59042cc67fe847ee46ba.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 674, + 90, + 813, + 181 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/6729ce66ae58217bd01efc3de68628f5e4a587279cad9a282d4f6687f9714d4a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 163, + 199, + 339, + 296 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/21a1dc4d5a3adbfddc951755cdb97d00a21a9c77247d0f7dad54a40f0ae2c941.jpg", + "image_caption": [ + "(c) $\\mathrm{GT} = 8$ Pred $= 8$" + ], + "image_footnote": [], + "bbox": [ + 341, + 200, + 517, + 297 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/465997b39c2b8e60f682c24659a8879fa8b69eccbb3be8185496068039ac71b4.jpg", + "image_caption": [ + "(d) $\\mathrm{GT} = 13$ Pred $= 10$" + ], + "image_footnote": [], + "bbox": [ + 534, + 200, + 661, + 297 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/0d93ed17afdc8e8e9e7fe8a3484c96a6066842020707c26d181cf1c2f98edae7.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 663, + 200, + 794, + 297 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f209cd149f2c0e78a040880972dbda880c115361c5205c27c8645a70f70e1e92.jpg", + "image_caption": [ + "Input image (a)" + ], + "image_footnote": [], + "bbox": [ + 88, + 395, + 222, + 483 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/88fd2c81ff8c1720e216715cb2c6ee38b8a240c3fcbd0e95b4853aa74d3e8bc3.jpg", + "image_caption": [ + "exemplar 1" + ], + "image_footnote": [], + "bbox": [ + 230, + 386, + 276, + 421 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7b314733bb03cc998e65f1c75b3142223b8d33f31502b2dccdb953a4c9e5552a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 287, + 363, + 421, + 421 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/6550d54e1e025f1f4f71231394c398df14a4e9778487abd48e0a6c44c8107301.jpg", + "image_caption": [ + "exemplar 2" + ], + "image_footnote": [], + "bbox": [ + 230, + 428, + 277, + 463 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/570325f26bc8b96ca92d03c965a6b7f97205c357efcbf8efa621c2a9d51a43b4.jpg", + "image_caption": [ + "Figure 4. Self-supervised semantic counting. In this setting, the model proposes the exemplars by itself and then performs reference-based counting." + ], + "image_footnote": [], + "bbox": [ + 287, + 428, + 419, + 488 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ce59fe8f2027c7f7ebd89bbecb56b3b7d9ff176afb0d84cdadfcacf823111654.jpg", + "image_caption": [ + "Input image (b)" + ], + "image_footnote": [], + "bbox": [ + 450, + 397, + 633, + 483 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/1ee10c4006f0308cf4ae4578ad2ab981f5284a0a9b562bd43330772a936a98c5.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 638, + 375, + 692, + 420 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c6d645ce7f0b6ef492b39abed2c55ab7b17b581b51a9dbf3fb7f18d78a165e32.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 640, + 430, + 692, + 474 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/61c003a5409ab3410ce4b846971eff438dd7d14358c2836447ec924345ec40ae.jpg", + "image_caption": [ + "Figure 3. Qualitative examples of UnCounTR's predictions. We show predictions on four images from the FSC-147 test set, the green boxes represent the exemplars. Our predicted count is the sum of the density map rounded to the nearest integer." + ], + "image_footnote": [], + "bbox": [ + 705, + 368, + 874, + 420 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/094c0fefa8abf97b0577b196a90582769bfd33233fc5ace9610a063440f90ccd.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 705, + 430, + 875, + 483 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "performance: (1) Integrating the DINOV2 [40] backbone improves the MAE particularly on the FSC-147 low set by $27\\%$ (2) Using cluster similarity to create more challenging Self-Collages reduces the MAE on FSC-147 to 31.06 (3) Refining high-count predictions further improves performance yielding the final UnCounTRv2 model. It achieves an MAE of 28.67 on FSC-147 and 3.88 on FSC-147 low. For a comprehensive discussion, please refer to the Appendix. See Figure 1 for a visual comparison with CounTR.", + "bbox": [ + 75, + 546, + 468, + 681 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.7. Self-supervised semantic counting", + "text_level": 1, + "bbox": [ + 76, + 694, + 375, + 710 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this last section, we explore the potential of UnCounTR for more advanced counting tasks. In particular, we test whether our model can not only unsupervisedly count different kinds of objects in an image, but also determine the categories by itself, a scenario we refer to as semantic counting. To this end, we use a simple pipeline that picks an area surrounding the maximum in the input image's CLS-attention map as the first input and refines it to obtain an exemplar. Next, UnCounTR predicts the number of objects in the image based on the self-constructed exemplar. Finally, the locations that have been detected using this procedure are removed from the initial attention map and if", + "bbox": [ + 75, + 719, + 470, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "the remaining attention values are high enough, the process is repeated to count objects of another type. We provide the details of this method in the Appendix. In Figure 4, we demonstrate results on two difficult real images.", + "bbox": [ + 498, + 546, + 890, + 607 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 625, + 617, + 638 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we have introduced UnCounTR, showcasing, for the first time, the capability of reference-based counting without relying on human supervision. To this end, our method constructs Self-Collages, a simple unsupervised way of generating proxy learning signals from unlabeled data. Our results demonstrate that by utilising an off-the-shelf unsupervisedly pretrained visual encoder, we can learn counting models that can even outperform strong baselines such as DETR and achieve similar performances to dedicated counting models such as CounTR on CARPK, MSO, and various splits of FSC-147. Finally, we have shown that our model can unsupervisedly identify multiple exemplars in an image and count them, something no supervised model can yet do. This work opens a wide space for extending unsupervised visual understanding beyond simple image-level representations to more complex tasks previously out of reach, such as scene graphs or unsupervised semantic instance segmentations.", + "bbox": [ + 496, + 648, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "22931", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 119, + 173, + 136 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Jean-Baptiste Alayrac, Adria Recasens, Rosalia Schneider, Relja Arandjelović, Jason Ramapuram, Jeffrey De Fauw, Lucas Smaira, Sander Dieleman, and Andrew Zisserman. Self-supervised multimodal versatile networks. NeurIPS, 33:25-37, 2020. 2", + "[2] Relja Arandjelović and Andrew Zisserman. 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In CVPR, pages 14502-14511, 2022. 2, 6, 7" + ], + "bbox": [ + 78, + 90, + 468, + 415 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "22934", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_model.json b/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_model.json new file mode 100644 index 0000000000000000000000000000000000000000..b5c4781e8866ba45c73671414f388cb0f68303a5 --- /dev/null +++ b/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_model.json @@ -0,0 +1,2499 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.285, + 0.132, + 0.688, + 0.153 + ], + "angle": 0, + "content": "Learning to Count without Annotations" + }, + { + "type": "text", + "bbox": [ + 0.151, + 0.182, + 0.354, + 0.234 + ], + "angle": 0, + "content": "Lukas Knobel \nUniversity of Amsterdam \nlukasknbl@gmail.com" + }, + { + "type": "text", + "bbox": [ + 0.399, + 0.182, + 0.571, + 0.233 + ], + "angle": 0, + "content": "Tengda Han* \nUniversity of Oxford \nhtd@robots.ox.ac.uk" + }, + { + "type": "text", + "bbox": [ + 0.616, + 0.182, + 0.82, + 0.234 + ], + "angle": 0, + "content": "Yuki M. Asano* \nUniversity of Amsterdam \ny.m.asano@uva.nl" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.287, + 0.314, + 0.303 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.319, + 0.474, + 0.576 + ], + "angle": 0, + "content": "While recent supervised methods for reference-based object counting continue to improve the performance on benchmark datasets, they have to rely on small datasets due to the cost associated with manually annotating dozens of objects in images. We propose UnCounTR, a model that can learn this task without requiring any manual annotations. To this end, we construct \"Self-Collages\", images with various pasted objects as training samples, that provide a rich learning signal covering arbitrary object types and counts. Our method builds on existing unsupervised representations and segmentation techniques to successfully demonstrate for the first time the ability of reference-based counting without manual supervision. Our experiments show that our method not only outperforms simple baselines and generic models such as FasterRCNN and DETR, but also matches the performance of supervised counting models in some domains." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.608, + 0.21, + 0.623 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.634, + 0.47, + 0.785 + ], + "angle": 0, + "content": "Cognitive neuroscientists speculate that visual counting, especially for a small number of objects, is a pre-attentive and parallel process [12, 55], which can help humans and animals make prompt decisions [43]. Accumulating evidence shows that infants and certain species of animals can differentiate between small numbers of items [11, 12, 41] and as young as 18-month-old infants have been shown to develop counting abilities [53]. These findings indicate that the ability of visual counting may emerge very early or even be inborn in humans and animals." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.786, + 0.471, + 0.864 + ], + "angle": 0, + "content": "On the non-biological side, recent developments in computer vision have been tremendous. The state-of-the-art computer vision models can classify thousands of image classes [19, 27], detect various objects [66], or segment almost anything from an image [26]. Partially inspired by" + }, + { + "type": "image", + "bbox": [ + 0.51, + 0.286, + 0.697, + 0.429 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.697, + 0.286, + 0.884, + 0.429 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.441, + 0.895, + 0.526 + ], + "angle": 0, + "content": "Figure 1. CountTR vs. our proposed UnCountTRv2. Our counting model, UnCountTRv2, is trained without any labels and manual counting annotations. It generalizes well from its up to 19 pseudo-counts encountered during training to the significantly higher numbers in the FSC-147 test set. This demonstrates that learning to count is possible without annotations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.538, + 0.893, + 0.749 + ], + "angle": 0, + "content": "how babies learn to see the world [54], some of the recent well-performing models are trained with self-supervised learning methods, whereby a learning signal for neural networks is constructed without the need for manual annotations [15, 20]. The pretrained visual representations from such methods have demonstrated superior performances on various downstream visual tasks, like image classification and object detection [7, 20, 21]. Moreover, self-supervised learning signals have been shown to be sufficient for successfully learning image groupings [57, 59] and even object and semantic segmentations without any annotations [7, 62]. Motivated by these, we ask in this paper whether visual counting might also be solvable without relying on human annotations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.894, + 0.841 + ], + "angle": 0, + "content": "The current state-of-the-art visual counting methods, e.g. CounTR [31], typically adapt pretrained visual representations to the counting task by using a considerable size of human annotations. However, we conjecture that the existing visual representations are already strong enough to perform counting, even without any manual annotations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.841, + 0.894, + 0.901 + ], + "angle": 0, + "content": "In this paper, we design a straightforward self-supervised training scheme to teach the model 'how to count', by pasting a number of objects on a background image, to make a Self-Collage. Our experiments show that when construct" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.875, + 0.373, + 0.901 + ], + "angle": 0, + "content": "*Equal senior contribution. \n1Code: https://github.com/lukasknobel/SelfCollages" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22924" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.242 + ], + "angle": 0, + "content": "ing the Self-Collages carefully, this training method is effective enough to leverage the pretrained visual representation on the counting task, even approaching other methods that require manually annotated counting data. For the visual representation, we use the self-supervised pretrained DINO features [7], which have been shown to be useful and generalisable for a variety of visual tasks like segmenting objects [34, 67]. Note that the DINO model is also trained without manual annotations, thus our entire pipeline does not require annotated datasets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.243, + 0.473, + 0.44 + ], + "angle": 0, + "content": "To summarise, this paper focuses on the objective of training a reference-based counting model without any manual annotation. The following contributions are made: (i) We propose a simple yet effective data generation method to construct 'Self-Collages', which pastes objects onto an image and gets supervision signals for free. (ii) We leverage self-supervised pretrained visual features from DINO and develop UnCounTR, a transformer-based model architecture for counting. (iii) The experiments show that our method trained without manual annotations not only outperforms baselines and generic models like FasterRCNN and DETR, but also matches the performance of supervised counting models." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.453, + 0.216, + 0.468 + ], + "angle": 0, + "content": "2. Related work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.478, + 0.47, + 0.599 + ], + "angle": 0, + "content": "Counting with object classes. The class-specific counting methods are trained to count instances of a single class of interest, such as cars [23, 36] or people [28, 28, 32, 47, 48]. These methods require retraining to apply them to new object classes [36]. In addition, some works rely on class-specific assumptions such as the proportionality of features and counts [24], or the distribution [48] or shapes [56] of objects, which cannot be easily adapted." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.6, + 0.47, + 0.78 + ], + "angle": 0, + "content": "By contrast, class-agnostic approaches are not designed with a specific object class in mind. Early work by Zhang et al. [63] proposes the salient object subitizing task, where the model is trained to count by classification of \\(\\{0,1,2,3,4+\\}\\) salient objects regardless of their classes. Other reference-less methods like Hobley and Prisacariu [22] frame counting as a repetition-recognition task and aim to automatically identify the objects to be counted. An alternative approach of class-agnostic counting requires a prior of the object type to be counted in the form of reference images, also called 'exemplars', each containing a single instance of the desired class [14, 29, 33, 45, 50, 60, 61]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.47, + 0.84 + ], + "angle": 0, + "content": "Counting with different methods. Categorised by the approach taken to obtain the final count, counting methods can be divided into classification, detection and regression-based methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Classification-based approaches predict a discrete count for a given image [63]. The classes either correspond to single numbers or potentially open-ended intervals. Thus, predictions are limited to the pre-defined counts and a gen" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.836, + 0.107 + ], + "angle": 0, + "content": "eralisation to new ranges is by design not possible." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.107, + 0.892, + 0.228 + ], + "angle": 0, + "content": "An alternative is detection-based methods [23]. By predicting bounding boxes for the counted instances and deriving a global count based on their number, these methods are unlike classification-based approaches not constrained to predefined count classes. While the bounding boxes can facilitate further analysis by explicitly showing the counted instances, the performance of detection-based approaches deteriorates in high-density settings [22]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.228, + 0.893, + 0.453 + ], + "angle": 0, + "content": "Lastly, regression-based methods predict a single number and can be further divided into scalar and density-based approaches. Scalar methods directly map an input image to a single scalar count corresponding to the number of objects in the input [22]. Density-based methods on the contrary predict a density map for a given image and obtain the final count by integrating over it [9, 14, 32, 33, 48, 49]. Similar to detection-based approaches, these methods allow locating the counted instances which correspond to the local maxima of the density map but have the added benefit of performing well in high-density applications with overlapping objects [33]. The recent work CounTR [31] is a class-agnostic, density-based method which is trained to count both with and without exemplars using a transformer decoder structure with learnable special tokens." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.454, + 0.893, + 0.832 + ], + "angle": 0, + "content": "Self-supervised learning. Self-supervised learning (SSL) has shown its effectiveness in many computer vision tasks. Essentially, SSL derives the supervision signal from the data itself rather than manual annotations. The supervision signal can be found from various \"proxy tasks\" like colorization [64], spatial ordering or inpainting [15, 21, 37, 42], temporal ordering [18, 35], contrasting similar instances [10, 20, 39], clustering [3, 6], and from multiple modalities [1, 44]. Another line of SSL methods is knowledge distillation, where one smaller student model is trained to predict the output of the other larger teacher model [4, 8, 25]. BYOL [17] design two identical models but train one model to predict the moving average of the other as the supervision signal. Notably, DINO [7] is trained in a similar way but using Vision Transformers (ViTs) as the visual model [16], and obtains strong visual features. Simply thresholding the attention maps and using the resulting masks yields high-quality image segmentations. Follow-up works [34, 51, 67] demonstrate the semantic segmentation quality can be further improved by applying some lightweight training or post-processing of DINO features. For counting in SSL, Noroozi et al. [38] use feature \"counting\" as a proxy task to learn representations. In this work, we focus on counting itself and explore approaches to teach the model to count without manual supervision." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.845, + 0.592, + 0.86 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.892, + 0.902 + ], + "angle": 0, + "content": "We tackle the task of counting objects given some exemplar crops within an image. With an image dataset \\(\\mathcal{D} =\\)" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22925" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.093, + 0.885, + 0.293 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.305, + 0.895, + 0.348 + ], + "angle": 0, + "content": "Figure 2. Method overview. Our method leverages the strong coherence of deep clusters to provide pseudo-labelled images which are used to construct a self-supervised counting task. The composer utilises self-supervised segmentations for pasting a set of objects onto a background image and UnCounTR is trained to count these when provided with unsupervised exemplars." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.358, + 0.47, + 0.435 + ], + "angle": 0, + "content": "\\(\\{(I_1, S_1, \\mathbf{y}_1), \\ldots, (I_i, S_i, \\mathbf{y}_i)\\}\\), where \\(I_i \\in \\mathbb{R}^{H \\times W \\times 3}\\) denotes image \\(i\\), \\(S_i = \\{E_i^1, \\ldots, E_i^E\\}\\) represent the \\(E\\) visual exemplars of shape \\(E_i^e \\in \\mathbb{R}^{H' \\times W' \\times 3}\\), and \\(\\mathbf{y}_i \\in \\mathbb{R}^{H \\times W}\\) is the ground-truth density map, the counting task can be written as:" + }, + { + "type": "equation", + "bbox": [ + 0.218, + 0.436, + 0.47, + 0.452 + ], + "angle": 0, + "content": "\\[\n\\hat {\\mathbf {y}} _ {i} = f _ {\\Theta} \\left(\\boldsymbol {I} _ {i}, \\mathcal {S} _ {i}\\right) \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.459, + 0.47, + 0.609 + ], + "angle": 0, + "content": "Here, the predicted density map \\(\\hat{\\mathbf{y}}_i\\) indicates the objects to be counted, as specified by the exemplars \\(S_{i}\\), such that \\(\\sum_{kl} \\hat{\\mathbf{y}}_{i_{kl}}\\) yields the overall count for the image \\(I_{i}\\). We are interested in training a neural network \\(f\\) parameterised by \\(\\Theta\\) to learn how to count based on the exemplars \\(S_{i}\\). For the supervised counting methods [31, 33], the network parameters \\(\\Theta\\) can be trained with the 'prediction, ground-truth') pairs: \\((\\hat{\\mathbf{y}}_i, \\mathbf{y}_i)\\). However, for self-supervised counting, the learning signal \\(\\mathbf{y}_i\\) is not obtained from manual annotations, but instead from the data itself." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.61, + 0.47, + 0.702 + ], + "angle": 0, + "content": "In this section, we introduce two essential parts of our method: we start by presenting our data generation method for counting in Section 3.1, that is the construction of the tuple \\((I_i, S_i, \\mathbf{y}_i)\\); then, we explain the UnCounTR model, i.e. \\(f_\\Theta\\) in Equation (1), in Section 3.2. An overview of our method is provided in Figure 2." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.711, + 0.32, + 0.728 + ], + "angle": 0, + "content": "3.1. Constructing Self-Collages" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.471, + 0.903 + ], + "angle": 0, + "content": "A key component of self-supervised training is the construction of a supervision signal without any manual annotations. In this paper, we generate training samples by pasting different images on top of a background. This is a well-known technique [2, 65], which next to its conceptual simplicity provides great flexibility regarding the number and type of pasted images. While other works combine annotated training images to enrich the training set [22, 31], we use this idea to construct the whole training set including unsupervised proxy labels, yielding self-supervised collages, or Self-Collages for short. Their generation pro" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.359, + 0.892, + 0.465 + ], + "angle": 0, + "content": "cess is described by a composer module \\(g\\), which forms a distribution \\(g(\\mathcal{O}, \\mathcal{B}) = p(\\tilde{\\boldsymbol{I}}, S, \\mathbf{y} \\mid \\mathcal{O}, \\mathcal{B})\\) of constructed images \\(\\tilde{\\boldsymbol{I}} \\in \\mathbb{R}^{H \\times W \\times 3}\\) along with unsupervised exemplars \\(\\mathcal{S}\\) and labels \\(\\mathbf{y}\\). The process is based on two sets of unlabelled images \\(\\mathcal{O}\\) and \\(\\mathcal{B}\\) for object and background images. \\(\\mathcal{S} = \\{\\pmb{E}\\}^E\\), \\(\\pmb{E} \\in \\mathbb{R}^{H' \\times W' \\times 3}\\) is a set of \\(E \\in \\mathbb{N}\\) exemplars and \\(\\mathbf{y} \\in \\mathbb{R}^{H \\times W}\\) corresponds to the density map of \\(\\tilde{\\boldsymbol{I}}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.466, + 0.893, + 0.737 + ], + "angle": 0, + "content": "The composer module \\( g \\) first randomly selects the number of distinct object categories \\( n_c \\sim U[t_{\\min}, t_{\\max}] \\) the first of which is taken as the target cluster. \\( t_{\\min} \\) and \\( t_{\\max} \\) control the minimum and maximum number of categories in a Self-Collage. To reduce the risk of overfitting to construction artefacts, we always construct images with \\( n_{\\max} \\) objects and change the associated number of target objects \\( \\sum_{ij} \\mathbf{y}_{ij} \\) solely by altering the number of objects in the target cluster. This way, the number of pasted objects and, therefore, the number of artefacts is independent of the target count. The number of target objects \\( n_0 = n \\sim U[n_{\\min}, n_{\\max} - n_c + 1] \\) has an upper-bound lower than \\( n_{\\max} \\) to guarantee that there is at least one object of each of the \\( n_c \\) types. For all other clusters, the number of objects is drawn from a uniform distribution of points on the \\( n_c - 1 \\) dimensional polytope with \\( L1 \\)-size of \\( n_{\\max} - n \\) ensuring that the total number of objects equals \\( n_{\\max} \\). Further details, including the pseudocode for the composer module, are shown in the Appendix." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.738, + 0.892, + 0.812 + ], + "angle": 0, + "content": "Unsupervised categories. We obtain unsupervised object categories by first extracting feature representations for all samples in \\(\\mathcal{O}\\) using a pretrained DINO ViT-B/16 backbone [7] \\(d\\) and subsequently running k-means with \\(K\\) clusters:" + }, + { + "type": "equation", + "bbox": [ + 0.585, + 0.815, + 0.892, + 0.833 + ], + "angle": 0, + "content": "\\[\nc (\\boldsymbol {I}) = \\mathrm {k} - \\operatorname {m e a n s} _ {K} \\left[ \\left(d (\\mathcal {O})\\right) ^ {\\mathrm {C L S}} \\right] (\\boldsymbol {I}), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.894, + 0.901 + ], + "angle": 0, + "content": "where \\(c(I)\\) is the unsupervised category for image \\(\\pmb{I}\\) constructed using the final CLS-embedding of \\(d\\). For each of the \\(n_c\\) clusters, a random, unique cluster \\(c_{i}\\), \\(i\\in [0,n_c - 1]\\) is chosen from all \\(K\\) clusters where \\(c_{0}\\) is the target cluster." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22926" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.184 + ], + "angle": 0, + "content": "Image selection. Next, random sets of images \\(\\mathcal{I}_i\\subset \\mathcal{O}\\) are picked from their unsupervised categories \\(c_{i}\\), such that \\(|\\mathcal{I}_i| = n_i\\) and \\(c(I) = c_i\\forall I\\in \\mathcal{I}_i\\). We denote the union of these sets as \\(\\mathcal{I} = \\bigcup_{i = 0}^{n_c - 1}\\mathcal{I}_i\\). In addition, we sample one image \\(I_{\\mathrm{b}}\\) from another dataset \\(\\mathcal{B}\\), which is assumed to not contain salient objects to serve as the background image." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.202, + 0.283, + 0.218 + ], + "angle": 0, + "content": "3.1.1 Construction strategy" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.225, + 0.47, + 0.451 + ], + "angle": 0, + "content": "Here we detail the Self-Collage construction. First, the background image \\( I_{\\mathrm{b}} \\) is reshaped to the final dimensions \\( H \\times W \\) and used as a canvas on which the modified images \\( \\mathcal{I} \\) are pasted. To mimic natural images that typically contain similarly sized objects, we first randomly pick a mean object size \\( d_{\\mathrm{mean}} \\sim U[d_{\\mathrm{min}}, d_{\\mathrm{max}}] \\). Subsequently, the target size of the pasted objects is drawn independently for each \\( I \\in \\mathcal{I}, I \\in \\mathbb{R}^{d_{\\mathrm{h}} \\times d_{\\mathrm{w}} \\times 3} \\) from a uniform distribution \\( d_{\\mathrm{paste}} \\sim U[(1 - \\sigma) \\cdot d_{\\mathrm{mean}}, (1 + \\sigma) \\cdot d_{\\mathrm{mean}}] \\) where \\( \\sigma \\in (0,1) \\) controls the diversity of objects sizes in an image. After resizing \\( I \\) to \\( I_{\\mathrm{r}} \\in \\mathbb{R}^{d_{\\mathrm{paste}} \\times d_{\\mathrm{paste}} \\times 3} \\), the image is pasted to a random location on \\( I_{\\mathrm{b}} \\). This location is either a position where previously no object has been pasted, or any location in the constructed image, potentially leading to overlapping images. By default, we will use the latter." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.452, + 0.47, + 0.693 + ], + "angle": 0, + "content": "Segmented pasting. Since pasting the whole image \\( I_{\\mathrm{r}} \\) might violate the assumption of having a single object and results in artefacts by also pasting the background of \\( I_{\\mathrm{r}} \\), we introduce an alternative using self-supervised segmentations. This method, which we will use by default, uses an unsupervised segmentation method [51] to obtain a noisy foreground segmentation \\( \\mathbf{s} \\in [0, 1]^{d_{\\mathrm{h}} \\times d_{\\mathrm{w}}} \\) for \\( I \\). Instead of pasting the whole image, the segmentation \\( \\mathbf{s} \\) is used to only copy its foreground. Additionally, having access to \\( \\mathbf{s} \\), this method can directly control the size of the pasted objects rather than the pasted images. To do that, we first extract the object in \\( I \\) by computing the Hadamard product \\( I_{\\mathrm{object}} = \\operatorname{cut}(I \\circ \\mathbf{s}) \\) where the operation \"cut\" removes rows and columns that are completely masked out. In the next step, \\( I_{\\mathrm{object}} \\in \\mathbb{R}^{h_{\\mathrm{object}} \\times w_{\\mathrm{object}} \\times 3} \\) is resized so that its maximum dimension equals \\( d_{\\mathrm{paste}} \\) before pasting it onto \\( I_{\\mathrm{b}} \\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.694, + 0.468, + 0.799 + ], + "angle": 0, + "content": "Exemplar selection. To construct the exemplars used for training, we exploit the information about how the sample was constructed using \\( g \\): The set of \\( E \\) exemplars \\( S \\) is simply obtained by filtering for pasted objects that belong to the target cluster \\( c_{0} \\) and subsequently sampling \\( E \\) randomly. Then, for each of them, a crop of \\( \\tilde{I} \\) is taken as exemplar after resizing its spatial dimensions to \\( H' \\times W' \\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.817, + 0.31, + 0.832 + ], + "angle": 0, + "content": "3.1.2 Density map construction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.468, + 0.901 + ], + "angle": 0, + "content": "To train our counting model, we construct an unsupervised density map \\(\\mathbf{y}\\) for each training image \\(\\tilde{\\pmb{I}}\\). It needs to have the following two properties: i) it must sum up to the overall count of objects that we are counting and ii) it must have" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.168 + ], + "angle": 0, + "content": "high values at object locations. To this end, we create \\(\\mathbf{y}\\) as a simple density map of Gaussian blobs as done in supervised density-based counting methods [14, 31]. For this, we use the bounding box for each pasted target image \\(I\\in \\mathcal{I}_0\\) and place Gaussian density at the centre and normalise it to one." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.178, + 0.627, + 0.192 + ], + "angle": 0, + "content": "3.2. UnCounTR" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.201, + 0.892, + 0.532 + ], + "angle": 0, + "content": "Model architecture. UnCounTR's architecture is inspired by CounTR [31]. To map an input image \\( \\pmb{I} \\) and its exemplars \\( S \\) to a density map \\( \\hat{\\mathbf{y}} \\), the model consists of four modules: image encoder \\( \\Phi \\), exemplar encoder \\( \\Psi \\), feature interaction module \\( f_{\\mathrm{fim}} \\), and decoder \\( f_{\\mathrm{dec}} \\). An overview of this architecture can be seen in Figure 2. The image encoder \\( \\Phi \\) encodes an image \\( \\pmb{I} \\) into a feature map \\( \\mathbf{x} = \\Phi(\\pmb{I}) \\in \\mathbb{R}^{h \\times w \\times d} \\) where \\( h, w, d \\) denote the height, width, and channel depth. Similarly, each exemplar \\( E \\in S \\) is projected to a single feature vector \\( \\mathbf{z} \\in \\mathbb{R}^d \\) by taking a weighted average of the grid features. Instead of training a CNN for an exemplar encoder as CounTR does, we choose \\( \\Psi = \\Phi \\) to be the frozen DINO visual encoder weights. Reusing these weights, the exemplar and image features are in the same feature space. The feature interaction module (FIM) \\( f_{\\mathrm{fim}} \\) enriches the feature map \\( \\mathbf{x} \\) with information from the encoded exemplars \\( \\mathbf{z}_j \\), \\( j \\in \\{1, \\dots, E\\} \\) with a transformer decoder structure. Finally, the decoder \\( f_{\\mathrm{dec}} \\) takes the resulting patch-level feature map of the FIM as input and upsamples it with 4 convolutional blocks, ending up with a density map of the same resolution as the input image. Please refer to the Appendix for the full architectural details." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.534, + 0.892, + 0.626 + ], + "angle": 0, + "content": "UnCounTR supervision. UnCounTR is trained using the Mean Squared Error between model prediction and pseudo labels. Given a Self-Collage \\(\\tilde{I}\\), exemplars \\(S\\), and density map \\(\\mathbf{y}\\), the loss \\(\\mathcal{L}\\) for an individual sample is computed using the following equation where \\(f_{\\Theta}(\\tilde{I}, S)_{ij}\\) is UnCounTR's spatially-dense output at location \\((i, j)\\):" + }, + { + "type": "equation", + "bbox": [ + 0.574, + 0.636, + 0.892, + 0.673 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\frac {1}{H \\cdot W} \\sum_ {i j} \\left(\\mathbf {y} _ {i j} - f _ {\\Theta} (\\tilde {\\boldsymbol {I}}, \\mathcal {S}) _ {i j}\\right) ^ {2} \\tag {3}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.687, + 0.633, + 0.703 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.711, + 0.717, + 0.727 + ], + "angle": 0, + "content": "4.1. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Datasets. To construct Self-Collages, we use ImageNet1k [13] and SUN397 [58]. ImageNet-1k contains 1.2M mostly object-centric images spanning 1000 object categories. SUN397 contains 109K images for 397 scene categories like 'cliff' or 'corridor'. Note that the object or scene category information is never used in our method. We assume that images from ImageNet-1k contain a single salient object and images from SUN397 contain no salient objects to serve as sets \\(\\mathcal{O}\\) and \\(\\mathcal{B}\\). Based on this, \\(g\\) randomly selects images from SUN397 as background images and picks objects from ImageNet-1k. Although Imagenet" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "22927" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.243 + ], + "angle": 0, + "content": "1k and SUN397 contain on average 3 and 17 objects respectively [30], these assumptions are still reasonable for our data construction. Additional ablations show that even explicitly violating the assumption of having no salient objects in \\(\\mathcal{B}\\) by using \\(\\mathcal{O} = \\mathcal{B}\\) only have a small effect on performance, indicating the robustness of our method against violations (see Appendix). An example of a Self-Collage with 5 objects can be seen in Figure 2. Examples of both datasets and a more detailed discussion of these assumptions are included in the Appendix." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.245, + 0.473, + 0.426 + ], + "angle": 0, + "content": "To evaluate the counting ability, we use the standard FSC-147 dataset [45], which contains 6135 images covering 147 object categories, with counts ranging from 7 to 3731 and an average count of 56 objects per image. For each image, the dataset provides at least three randomly chosen object instances with annotated bounding boxes as exemplars. To analyse the counting ability in detailed count ranges, we partition the FSC-147 test set into three parts of roughly 400 images each, resulting in FSC-147{low,medium,high} subsets, each covering object counts from 8-16, 17-40 and 41-3701 respectively. Unless otherwise stated, we evaluate using 3 exemplars." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.429, + 0.473, + 0.595 + ], + "angle": 0, + "content": "Additionally, we also use the CARPK [23] and the Multi-Salient-Object (MSO) dataset [63] for evaluation. CARPK consists of 459 images of parking lots. Each image contains between 2 and 188 cars, with an average of 103. MSO contains 1224 images covering 5 categories: \\(\\{0,1,2,3,4+\\}\\) salient objects with bounding box annotations. This dataset is largely imbalanced as 338 images contain zero salient objects and 20 images contain at least 4. For evaluation, we removed all samples with 0 counts, split the \\(4+\\) category into exact counts, and chose only one annotated object as exemplar." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.597, + 0.473, + 0.764 + ], + "angle": 0, + "content": "Construction details. We configure the composer module to construct training samples using objects of \\( K = 10,000 \\) different clusters. To always have objects of a target and a non-target cluster in each image, we set \\( t_{\\mathrm{min}} = t_{\\mathrm{max}} = 2 \\). Since the minimum number of target objects in an image limits the maximum number of exemplars available during training, we set \\( n_{\\mathrm{min}} = 3 \\), the maximum is \\( n_{\\mathrm{max}} = 20 \\). Finally, we choose \\( d_{\\mathrm{min}} = 15 \\), \\( d_{\\mathrm{max}} = 70 \\), and \\( \\sigma = 0.3 \\) to obtain diverse training images with objects of different sizes as confirmed by visual inspection of the generated Self-Collages (see the Appendix)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Training and inference details. During training, the images are cropped and resized to \\(224 \\times 224\\) pixels. The exemplars are resized to \\(64 \\times 64\\) pixels. For each batch, we randomly draw the number of exemplars \\(E\\) to be between 1 and 3. We follow previous work [31] by scaling the loss, in our case by a factor of 3,000, and randomly dropping \\(20\\%\\) of the non-object pixels in the density map to decrease the imbalance of object and non-object pixels. By default, we use an AdamW optimizer and a cosine-decay learning rate" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.258 + ], + "angle": 0, + "content": "schedule with linear warmup and a maximum learning rate of \\(5 \\times 10^{-4}\\). We use a batch size of 128 images. Each model is trained on an Nvidia A100 GPU for 50 epochs of 10,000 Self-Collages each, which takes about 4 hours. At inference, we use a sliding window approach similar to Liu et al. [31], see the Appendix for details. For evaluation metrics, we report Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE) following previous work [14, 31]. We also report Kendall's \\(\\tau\\) coefficient, which is a rank correlation coefficient between the sorted ground-truth counts and the predicted counts." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.259, + 0.895, + 0.683 + ], + "angle": 0, + "content": "Baselines. To verify the effectiveness of our method, we introduce a series of baselines to compare with. (1) Average baseline: the prediction is always the average count of the FSC-147 training set, which is 49.96 objects. (2) Connected components baseline: for this, we use the final-layer attention values from the CLS-token of a pretrained DINO ViT-B/8 model. To derive a final count, we first threshold the attention map of each head to keep \\( p_{\\mathrm{att}} \\) percent of the attention mask. Subsequently, we consider each patch to where at least \\( n_{\\mathrm{head}} \\) attention heads attend to belong to an object. The number of connected components in the resulting feature map which cover more than \\( p_{\\mathrm{size}} \\) percent of the feature map is taken as prediction. To this end, we perform a grid search with almost 800 configurations of different value combinations for the three thresholds \\( p_{\\mathrm{att}}, n_{\\mathrm{head}} \\), and \\( p_{\\mathrm{size}} \\) on the FSC-147 training set and select the best configuration based on the MAE. The specific values tested can be found in the Appendix. (3) FasterRCNN baseline: we run the strong image detection toolbox FasterRCNN [46] with a score threshold of 0.5 on the image, which predicts a number of object bounding boxes. Then the object count is obtained by parsing the detection results by taking the total number of detected bounding boxes. Just like the connected components baseline, this model is applied to images resized to \\( 384 \\times 384 \\) pixels. (4) DETR baseline: similar to FasterRCNN, we evaluate the detection model DETR [5] on the counting task. Here, we resize the images to \\( 800 \\times 800 \\) pixels to better match DETR's evaluation protocol." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.696, + 0.767, + 0.712 + ], + "angle": 0, + "content": "4.2. Comparison against baselines" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.903 + ], + "angle": 0, + "content": "In Table 1, we compare against multiple baselines on the three splits of FSC-147. As the connected components cannot leverage the additional information of the few-shot samples provided, we try to make the comparison as fair as possible, by testing almost 800 threshold parameters on the FSC-147 training set. While this yields a strong baseline, we find that our method of learning with Self-Collages more than halves the MAE on the low split, despite using a similar visual backbone. Next, we compare against the FasterRCNN and DETR object detectors which, unlike UnCounTR, are trained in a supervised fashion. Even though DETR outperforms UnCounTR in terms of RMSE on FSC" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22928" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.162, + 0.082, + 0.805, + 0.209 + ], + "angle": 0, + "content": "
MethodFSC-147 lowFSC-147 mediumFSC-147 high
MAE↓RMSE↓τ↑MAE↓RMSE↓τ↑MAE↓RMSE↓τ↑
Average37.7137.79-22.7423.69-68.88213.08-
Conn. Comp.14.7118.590.1414.1917.900.1669.77210.540.17
FasterRCNN7.068.46-0.0319.8722.25-0.04109.12230.35-0.06
DETR6.928.200.0719.3321.56-0.08109.34162.88-0.07
UnCounTR (ours)5.6010.130.279.4812.730.3467.17189.760.26
σ(5 runs)±0.48±0.84±0.02±0.19±0.33±0.02±1.03±1.38±0.01
" + }, + { + "type": "table_caption", + "bbox": [ + 0.097, + 0.212, + 0.871, + 0.226 + ], + "angle": 0, + "content": "Table 1. Comparison to baselines. Evaluation on different FSC-147 test subsets. \"Conn. Comp.\" refers to connected components." + }, + { + "type": "table", + "bbox": [ + 0.09, + 0.228, + 0.437, + 0.312 + ], + "angle": 0, + "content": "
Frozen ΦFrozen ΨFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
XX37.64126.917.9913.37
✓X36.94130.229.1014.69
✓✓35.77130.345.6010.13
" + }, + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.314, + 0.446, + 0.337 + ], + "angle": 0, + "content": "(a) Keeping both image encoder \\(\\Phi\\) and exemplar encoder \\(\\Psi\\) frozen works best." + }, + { + "type": "table", + "bbox": [ + 0.137, + 0.339, + 0.391, + 0.407 + ], + "angle": 0, + "content": "
FSC-147FSC-147 low
nmaxMAE↓RMSE↓MAE↓RMSE↓
5030.17115.426.6513.60
2035.77130.345.6010.13
" + }, + { + "type": "table_caption", + "bbox": [ + 0.097, + 0.408, + 0.427, + 0.421 + ], + "angle": 0, + "content": "(c) The number of pasted objects correlates with performance." + }, + { + "type": "table", + "bbox": [ + 0.534, + 0.229, + 0.857, + 0.311 + ], + "angle": 0, + "content": "
Segm.Overlap.FSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
✓✘36.47128.978.8414.54
✘✓37.46136.036.3311.55
✓✓35.77130.345.6010.13
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.314, + 0.892, + 0.337 + ], + "angle": 0, + "content": "(b) Using both segmented objects and allowing for overlapping objects works well." + }, + { + "type": "table", + "bbox": [ + 0.548, + 0.339, + 0.844, + 0.406 + ], + "angle": 0, + "content": "
#ExemplarsFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
0 - 336.28131.446.2310.33
1 - 335.77130.345.6010.13
" + }, + { + "type": "table_caption", + "bbox": [ + 0.508, + 0.408, + 0.882, + 0.421 + ], + "angle": 0, + "content": "(d) Training our method strictly in the 1-3 exemplar setting works best." + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.427, + 0.893, + 0.457 + ], + "angle": 0, + "content": "Table 2. Ablations. We ablate various components of our model architecture and Self-Collage construction method. Default settings are highlighted in grey." + }, + { + "type": "table", + "bbox": [ + 0.088, + 0.463, + 0.457, + 0.543 + ], + "angle": 0, + "content": "
ArchitecturePretrainingFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
ViT-B/8Leopard [67]36.04126.755.7210.67
ViT-B/8DINO [7]38.16132.096.109.79
ViT-B/16DINO [7]35.77130.345.6010.13
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.547, + 0.468, + 0.589 + ], + "angle": 0, + "content": "Table 3. Combining Self-Collages with different backbones. We can apply our method to any recent state-of-the-art pretrained network and achieve strong performances." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.604, + 0.469, + 0.725 + ], + "angle": 0, + "content": "147 low and high, we find that our method still outperforms all baselines on 7 out of 9 measures. This is despite the additional advantages such as access to the FSC-147 training distribution for these baselines. The gap between most baselines and UnCounTR is the smallest on the high split, suggesting limits to its generalisation which we will explore further in the Appendix. There, we also provide a qualitative analysis of some failure cases of FasterRCNN." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.739, + 0.231, + 0.755 + ], + "angle": 0, + "content": "4.3. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.763, + 0.469, + 0.793 + ], + "angle": 0, + "content": "We analyse the various components of our method in Tables 2a to 2d." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Keeping backbone frozen works best. In Table 2a, we evaluate the effect of unfreezing the last two backbone blocks shared by \\(\\Phi\\) and \\(\\Psi\\). In addition, we test training a CNN-based encoder \\(\\Psi\\) from scratch similar to Liu et al. [31]. We find that keeping both frozen, i.e. \\(\\Phi = \\Psi =\\) const. works best, as it discourages the visual features to adapt to potential artefacts in our Self-Collages." + }, + { + "type": "table", + "bbox": [ + 0.529, + 0.456, + 0.86, + 0.556 + ], + "angle": 0, + "content": "
MethodsValTest
MAE↓RMSE↓MAE↓RMSE↓
CounTR [31]13.1349.8311.9591.23
LOCA [14]10.2432.5610.7956.97
UnCounTR (ours)36.93106.6135.77130.34
σ(5 runs)±0.49±1.46±0.60±0.94
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.559, + 0.892, + 0.587 + ], + "angle": 0, + "content": "Table 4. Comparison to supervised models. We evaluate on the val and test split of FSC-147." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.892, + 0.778 + ], + "angle": 0, + "content": "Benefit of self-supervised exemplars. In Table 2d we evaluate the effect of including the zero-shot counting task (i.e. counting all salient objects) as done in other works [14, 31]. However, we find that including this task even with only a \\(25\\%\\) chance leads to a lower performance. This is likely due to the zero-shot task overfitting our Self-Collages and finding short-cuts, such as pasting artefacts, as we relax the constraint introduced in Section 3.1.1 and vary the number of pasted objects to match the desired target. We therefore train our model with 1-3 exemplars and show how we can still conduct semantic zero-shot counting in Section 4.7." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Maximum number of pasted objects. Next, we evaluate the effect of varying \\( n_{\\mathrm{max}} \\), the maximum number of objects pasted, as shown in Table 2c. Pasting up to 50 objects yields overall better performance on the full FSC-147 test dataset which contains on average 66 objects. While this shows that the construction of Self-Collages can be successfully scaled to higher counts, we find that pasting with 20 objects already achieves good performance with shortened" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22929" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.114, + 0.085, + 0.855, + 0.171 + ], + "angle": 0, + "content": "
MethodFSC-147 low (8-16 objects)FSC-147 medium (17-40 objects)FSC-147 high (41-3701 objects)
MAE↓RMSE↓Δτ↑MAE↓RMSE↓Δτ↑MAE↓
CounTR6.5848.110.424.4810.020.6020.50
UnCounTR (ours)5.6010.13-37.90.279.4812.73+2.70.3467.17
σ(5 runs)±0.48±0.84±0.02±0.19±0.33±0.02±1.03
" + }, + { + "type": "table_caption", + "bbox": [ + 0.189, + 0.175, + 0.778, + 0.187 + ], + "angle": 0, + "content": "Table 5. Comparison to CounTR. Evaluation results on the FSC-147 low and medium test subsets." + }, + { + "type": "table", + "bbox": [ + 0.119, + 0.19, + 0.427, + 0.292 + ], + "angle": 0, + "content": "
MethodMSO
MAE↓RMSE↓τ↑
Conn. Comp. Baseline10.6712.880.12
CounTR2.348.120.36
UnCounTR (ours)1.072.320.45
σ(5 runs)±0.06±0.25±0.01
" + }, + { + "type": "table_caption", + "bbox": [ + 0.129, + 0.294, + 0.412, + 0.307 + ], + "angle": 0, + "content": "Table 6. Evaluation on the MSO [63] dataset." + }, + { + "type": "table", + "bbox": [ + 0.541, + 0.191, + 0.849, + 0.291 + ], + "angle": 0, + "content": "
MethodCARPK
MAE↓RMSE↓τ↑
Conn. Comp. Baseline49.6254.500.56
CounTR19.6229.700.57
UnCounTR (ours)30.3535.670.54
σ(5 runs)±2.26±2.36±0.06
" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.317, + 0.353, + 0.331 + ], + "angle": 0, + "content": "construction times and so use this setting." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.332, + 0.469, + 0.408 + ], + "angle": 0, + "content": "Segmented pasting works best. From Table 2b, We find that the best construction strategy involves pasting the self-supervised segmentations, regardless of their overlap with other objects. We simply store the segmentations and combine these to create diverse Self-Collages at training time." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.41, + 0.469, + 0.621 + ], + "angle": 0, + "content": "Compatible with various pretrained backbones. In Table 3, we show the effect of using different frozen weights for the visual encoder. Across ViT-B models with varying patch sizes and pretrainings, from Leopart's [67] spatially dense to the original DINO's [7] image-level pretraining, we find similar performances across our evaluations. This shows that our method is compatible with various architectures and pretrainings and will likely benefit from the continued progress in self-supervised representation learning which is supported by our findings based on DINOv2 [40] presented in the Appendix. We do not find any benefit in going from patch size 16 to 8 (similar to Simeoni et al. [52]) so we use the faster DINO ViT-B/16 model for the rest of the paper." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.634, + 0.296, + 0.649 + ], + "angle": 0, + "content": "4.4. Benchmark comparison" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.658, + 0.469, + 0.869 + ], + "angle": 0, + "content": "Next, we compare with previous methods on three datasets: FSC-147 [45], MSO [63], and CARPK [23]. Table 4 shows the results on the validation and test split of the FSC-147 dataset. In contrast to our approach, which investigates the feasibility of learning to count without any reliance on supervised data, these methods heavily depend on manual annotations. Hence, the comparison is certainly not fair: (1) our method does not use manually annotated counting data, also has never seen any FSC-147 training images, (2) our training samples based on Self-Collages only cover 3-19 target objects, whereas the full test set of FSC-147 has 66 objects on average. Evaluating our method on the full set of FSC-147 is actually evaluating the transferring ability as discussed in more detail in the Appendix." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.469, + 0.901 + ], + "angle": 0, + "content": "We choose CounTR [31] for further analysis because of its similar architecture to UnCounTR. To fairly com" + }, + { + "type": "title", + "bbox": [ + 0.542, + 0.294, + 0.844, + 0.307 + ], + "angle": 0, + "content": "Table 7. Evaluation on the CARPK [23] dataset." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.315, + 0.892, + 0.451 + ], + "angle": 0, + "content": "pare with this method, we trisect the FSC-147 test set as described in Section 4.1. Table 5 shows the evaluation results on the three partitions. It is remarkable that our method outperforms supervised CounTR on the low partition, especially on the RMSE metric (10.13 vs 48.11). Also, our method is not far from CounTR's performance on the medium partition (e.g. RMSE 12.7 vs 10.02), showing a reasonable transferring ability since the model is trained with up to 19 object counts only." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.452, + 0.893, + 0.618 + ], + "angle": 0, + "content": "Additionally, Table 6 compares our method with the connected components baseline and CounTR on a subset of MSO as described in Section 4.1. The results show our self-supervised method outperforms the supervised CounTR model by a large margin on the lower counts tasks. In Table 7, the performance on the CARPK dataset is shown. We use the same CounTR model finetuned on the FSC-147 dataset as before to compare the generalisation across datasets. While the MAE of CounTR almost doubles compared to the results on the FSC-147 test set, UnCounTR's performance is more stable, improving by \\(15\\%\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.63, + 0.796, + 0.645 + ], + "angle": 0, + "content": "4.5. Qualitative results and limitations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.654, + 0.892, + 0.835 + ], + "angle": 0, + "content": "Figure 3 shows a few qualitative results to demonstrate our method's effectiveness and its limitations. The model is able to correctly predict the number of objects for clearly separated and slightly overlapping instances (e.g. Subfigures a and c). The model also successfully identifies the object type of interest, e.g. in Subfigure b the density map correctly highlights the strawberries rather than blueberries. One limitation of our model is images where the number of objects is ambiguous. For example, in Subfigure d, the prediction missed a few burgers which are possibly the ones partially shown on the edge. However, it is also difficult for humans to decide which of those objects should be counted." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.847, + 0.756, + 0.862 + ], + "angle": 0, + "content": "4.6. Improving upon UnCounTR" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Having established UnCounTR and compared it to several methods, we now explore three ways to further improve its" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.518, + 0.957 + ], + "angle": 0, + "content": "22930" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.153, + 0.09, + 0.337, + 0.182 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.256, + 0.182, + 0.365, + 0.194 + ], + "angle": 0, + "content": "(a) \\(\\mathrm{GT} = 8\\) Pred=8" + }, + { + "type": "image", + "bbox": [ + 0.342, + 0.096, + 0.521, + 0.183 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.535, + 0.09, + 0.673, + 0.182 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.599, + 0.182, + 0.724, + 0.195 + ], + "angle": 0, + "content": "(b) \\( \\mathrm{GT} = 16 \\); Pred=17" + }, + { + "type": "image", + "bbox": [ + 0.676, + 0.091, + 0.814, + 0.183 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.164, + 0.2, + 0.34, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.287, + 0.298, + 0.395, + 0.31 + ], + "angle": 0, + "content": "(c) \\(\\mathrm{GT} = 8\\) Pred \\(= 8\\)" + }, + { + "type": "image", + "bbox": [ + 0.343, + 0.202, + 0.518, + 0.298 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.535, + 0.201, + 0.663, + 0.298 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.665, + 0.201, + 0.795, + 0.298 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.6, + 0.298, + 0.725, + 0.31 + ], + "angle": 0, + "content": "(d) \\(\\mathrm{GT} = 13\\) Pred \\(= 10\\)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.317, + 0.893, + 0.345 + ], + "angle": 0, + "content": "Figure 3. Qualitative examples of UnCounTR's predictions. We show predictions on four images from the FSC-147 test set, the green boxes represent the exemplars. Our predicted count is the sum of the density map rounded to the nearest integer." + }, + { + "type": "image_caption", + "bbox": [ + 0.088, + 0.366, + 0.197, + 0.383 + ], + "angle": 0, + "content": "Input image (a)" + }, + { + "type": "image", + "bbox": [ + 0.089, + 0.396, + 0.223, + 0.484 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.23, + 0.377, + 0.282, + 0.387 + ], + "angle": 0, + "content": "exemplar 1" + }, + { + "type": "image", + "bbox": [ + 0.231, + 0.387, + 0.277, + 0.422 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.289, + 0.364, + 0.422, + 0.422 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.232, + 0.429, + 0.278, + 0.464 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.231, + 0.465, + 0.283, + 0.474 + ], + "angle": 0, + "content": "exemplar 2" + }, + { + "type": "image", + "bbox": [ + 0.288, + 0.429, + 0.421, + 0.489 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.453, + 0.368, + 0.562, + 0.383 + ], + "angle": 0, + "content": "Input image (b)" + }, + { + "type": "image", + "bbox": [ + 0.451, + 0.398, + 0.635, + 0.484 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.64, + 0.376, + 0.693, + 0.421 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.642, + 0.431, + 0.694, + 0.475 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.706, + 0.369, + 0.875, + 0.421 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.707, + 0.431, + 0.877, + 0.484 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.499, + 0.89, + 0.527 + ], + "angle": 0, + "content": "Figure 4. Self-supervised semantic counting. In this setting, the model proposes the exemplars by itself and then performs reference-based counting." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.547, + 0.47, + 0.683 + ], + "angle": 0, + "content": "performance: (1) Integrating the DINOV2 [40] backbone improves the MAE particularly on the FSC-147 low set by \\(27\\%\\) (2) Using cluster similarity to create more challenging Self-Collages reduces the MAE on FSC-147 to 31.06 (3) Refining high-count predictions further improves performance yielding the final UnCounTRv2 model. It achieves an MAE of 28.67 on FSC-147 and 3.88 on FSC-147 low. For a comprehensive discussion, please refer to the Appendix. See Figure 1 for a visual comparison with CounTR." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.695, + 0.376, + 0.712 + ], + "angle": 0, + "content": "4.7. Self-supervised semantic counting" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.471, + 0.901 + ], + "angle": 0, + "content": "In this last section, we explore the potential of UnCounTR for more advanced counting tasks. In particular, we test whether our model can not only unsupervisedly count different kinds of objects in an image, but also determine the categories by itself, a scenario we refer to as semantic counting. To this end, we use a simple pipeline that picks an area surrounding the maximum in the input image's CLS-attention map as the first input and refines it to obtain an exemplar. Next, UnCounTR predicts the number of objects in the image based on the self-constructed exemplar. Finally, the locations that have been detected using this procedure are removed from the initial attention map and if" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.547, + 0.892, + 0.608 + ], + "angle": 0, + "content": "the remaining attention values are high enough, the process is repeated to count objects of another type. We provide the details of this method in the Appendix. In Figure 4, we demonstrate results on two difficult real images." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.625, + 0.619, + 0.64 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.65, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In this work, we have introduced UnCounTR, showcasing, for the first time, the capability of reference-based counting without relying on human supervision. To this end, our method constructs Self-Collages, a simple unsupervised way of generating proxy learning signals from unlabeled data. Our results demonstrate that by utilising an off-the-shelf unsupervisedly pretrained visual encoder, we can learn counting models that can even outperform strong baselines such as DETR and achieve similar performances to dedicated counting models such as CounTR on CARPK, MSO, and various splits of FSC-147. Finally, we have shown that our model can unsupervisedly identify multiple exemplars in an image and count them, something no supervised model can yet do. 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In CVPR, pages 14502-14511, 2022. 2, 6, 7" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.47, + 0.416 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22934" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_origin.pdf b/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..4ec4ed58131d69247ad586cbe5cecd369c4716c6 --- /dev/null +++ b/2024/Learning to Count without Annotations/d11673d4-2f49-4551-9017-c5ac90ac3421_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:ca9e8cbc7796fb73897d85f08986658e8f1b1032f29a28d546e18c097bde58dc +size 2304432 diff --git a/2024/Learning to Count without Annotations/full.md b/2024/Learning to Count without Annotations/full.md new file mode 100644 index 0000000000000000000000000000000000000000..b097f2d52cd411484f74d9ccbf557a01f3943ab1 --- /dev/null +++ b/2024/Learning to Count without Annotations/full.md @@ -0,0 +1,349 @@ +# Learning to Count without Annotations + +Lukas Knobel +University of Amsterdam +lukasknbl@gmail.com + +Tengda Han* +University of Oxford +htd@robots.ox.ac.uk + +Yuki M. Asano* +University of Amsterdam +y.m.asano@uva.nl + +# Abstract + +While recent supervised methods for reference-based object counting continue to improve the performance on benchmark datasets, they have to rely on small datasets due to the cost associated with manually annotating dozens of objects in images. We propose UnCounTR, a model that can learn this task without requiring any manual annotations. To this end, we construct "Self-Collages", images with various pasted objects as training samples, that provide a rich learning signal covering arbitrary object types and counts. Our method builds on existing unsupervised representations and segmentation techniques to successfully demonstrate for the first time the ability of reference-based counting without manual supervision. Our experiments show that our method not only outperforms simple baselines and generic models such as FasterRCNN and DETR, but also matches the performance of supervised counting models in some domains. + +# 1. Introduction + +Cognitive neuroscientists speculate that visual counting, especially for a small number of objects, is a pre-attentive and parallel process [12, 55], which can help humans and animals make prompt decisions [43]. Accumulating evidence shows that infants and certain species of animals can differentiate between small numbers of items [11, 12, 41] and as young as 18-month-old infants have been shown to develop counting abilities [53]. These findings indicate that the ability of visual counting may emerge very early or even be inborn in humans and animals. + +On the non-biological side, recent developments in computer vision have been tremendous. The state-of-the-art computer vision models can classify thousands of image classes [19, 27], detect various objects [66], or segment almost anything from an image [26]. Partially inspired by + +![](images/bfa030c0eccdf66e1d640eb3a6794a05e7263c907c58b26e23e5d4ec47311a33.jpg) +Figure 1. CountTR vs. our proposed UnCountTRv2. Our counting model, UnCountTRv2, is trained without any labels and manual counting annotations. It generalizes well from its up to 19 pseudo-counts encountered during training to the significantly higher numbers in the FSC-147 test set. This demonstrates that learning to count is possible without annotations. + +![](images/940db8dc4caef36e2b22ead1ba008778982f1c3b5eade06e516ce488f2947357.jpg) + +how babies learn to see the world [54], some of the recent well-performing models are trained with self-supervised learning methods, whereby a learning signal for neural networks is constructed without the need for manual annotations [15, 20]. The pretrained visual representations from such methods have demonstrated superior performances on various downstream visual tasks, like image classification and object detection [7, 20, 21]. Moreover, self-supervised learning signals have been shown to be sufficient for successfully learning image groupings [57, 59] and even object and semantic segmentations without any annotations [7, 62]. Motivated by these, we ask in this paper whether visual counting might also be solvable without relying on human annotations. + +The current state-of-the-art visual counting methods, e.g. CounTR [31], typically adapt pretrained visual representations to the counting task by using a considerable size of human annotations. However, we conjecture that the existing visual representations are already strong enough to perform counting, even without any manual annotations. + +In this paper, we design a straightforward self-supervised training scheme to teach the model 'how to count', by pasting a number of objects on a background image, to make a Self-Collage. Our experiments show that when construct + +ing the Self-Collages carefully, this training method is effective enough to leverage the pretrained visual representation on the counting task, even approaching other methods that require manually annotated counting data. For the visual representation, we use the self-supervised pretrained DINO features [7], which have been shown to be useful and generalisable for a variety of visual tasks like segmenting objects [34, 67]. Note that the DINO model is also trained without manual annotations, thus our entire pipeline does not require annotated datasets. + +To summarise, this paper focuses on the objective of training a reference-based counting model without any manual annotation. The following contributions are made: (i) We propose a simple yet effective data generation method to construct 'Self-Collages', which pastes objects onto an image and gets supervision signals for free. (ii) We leverage self-supervised pretrained visual features from DINO and develop UnCounTR, a transformer-based model architecture for counting. (iii) The experiments show that our method trained without manual annotations not only outperforms baselines and generic models like FasterRCNN and DETR, but also matches the performance of supervised counting models. + +# 2. Related work + +Counting with object classes. The class-specific counting methods are trained to count instances of a single class of interest, such as cars [23, 36] or people [28, 28, 32, 47, 48]. These methods require retraining to apply them to new object classes [36]. In addition, some works rely on class-specific assumptions such as the proportionality of features and counts [24], or the distribution [48] or shapes [56] of objects, which cannot be easily adapted. + +By contrast, class-agnostic approaches are not designed with a specific object class in mind. Early work by Zhang et al. [63] proposes the salient object subitizing task, where the model is trained to count by classification of $\{0,1,2,3,4+\}$ salient objects regardless of their classes. Other reference-less methods like Hobley and Prisacariu [22] frame counting as a repetition-recognition task and aim to automatically identify the objects to be counted. An alternative approach of class-agnostic counting requires a prior of the object type to be counted in the form of reference images, also called 'exemplars', each containing a single instance of the desired class [14, 29, 33, 45, 50, 60, 61]. + +Counting with different methods. Categorised by the approach taken to obtain the final count, counting methods can be divided into classification, detection and regression-based methods. + +Classification-based approaches predict a discrete count for a given image [63]. The classes either correspond to single numbers or potentially open-ended intervals. Thus, predictions are limited to the pre-defined counts and a gen + +eralisation to new ranges is by design not possible. + +An alternative is detection-based methods [23]. By predicting bounding boxes for the counted instances and deriving a global count based on their number, these methods are unlike classification-based approaches not constrained to predefined count classes. While the bounding boxes can facilitate further analysis by explicitly showing the counted instances, the performance of detection-based approaches deteriorates in high-density settings [22]. + +Lastly, regression-based methods predict a single number and can be further divided into scalar and density-based approaches. Scalar methods directly map an input image to a single scalar count corresponding to the number of objects in the input [22]. Density-based methods on the contrary predict a density map for a given image and obtain the final count by integrating over it [9, 14, 32, 33, 48, 49]. Similar to detection-based approaches, these methods allow locating the counted instances which correspond to the local maxima of the density map but have the added benefit of performing well in high-density applications with overlapping objects [33]. The recent work CounTR [31] is a class-agnostic, density-based method which is trained to count both with and without exemplars using a transformer decoder structure with learnable special tokens. + +Self-supervised learning. Self-supervised learning (SSL) has shown its effectiveness in many computer vision tasks. Essentially, SSL derives the supervision signal from the data itself rather than manual annotations. The supervision signal can be found from various "proxy tasks" like colorization [64], spatial ordering or inpainting [15, 21, 37, 42], temporal ordering [18, 35], contrasting similar instances [10, 20, 39], clustering [3, 6], and from multiple modalities [1, 44]. Another line of SSL methods is knowledge distillation, where one smaller student model is trained to predict the output of the other larger teacher model [4, 8, 25]. BYOL [17] design two identical models but train one model to predict the moving average of the other as the supervision signal. Notably, DINO [7] is trained in a similar way but using Vision Transformers (ViTs) as the visual model [16], and obtains strong visual features. Simply thresholding the attention maps and using the resulting masks yields high-quality image segmentations. Follow-up works [34, 51, 67] demonstrate the semantic segmentation quality can be further improved by applying some lightweight training or post-processing of DINO features. For counting in SSL, Noroozi et al. [38] use feature "counting" as a proxy task to learn representations. In this work, we focus on counting itself and explore approaches to teach the model to count without manual supervision. + +# 3. Method + +We tackle the task of counting objects given some exemplar crops within an image. With an image dataset $\mathcal{D} =$ + +![](images/1e3a6a85d43cec1bc0ec5d0d4ccdcd4af76afacd3d56630cd78a8ca60f737f42.jpg) +Figure 2. Method overview. Our method leverages the strong coherence of deep clusters to provide pseudo-labelled images which are used to construct a self-supervised counting task. The composer utilises self-supervised segmentations for pasting a set of objects onto a background image and UnCounTR is trained to count these when provided with unsupervised exemplars. + +$\{(I_1, S_1, \mathbf{y}_1), \ldots, (I_i, S_i, \mathbf{y}_i)\}$ , where $I_i \in \mathbb{R}^{H \times W \times 3}$ denotes image $i$ , $S_i = \{E_i^1, \ldots, E_i^E\}$ represent the $E$ visual exemplars of shape $E_i^e \in \mathbb{R}^{H' \times W' \times 3}$ , and $\mathbf{y}_i \in \mathbb{R}^{H \times W}$ is the ground-truth density map, the counting task can be written as: + +$$ +\hat {\mathbf {y}} _ {i} = f _ {\Theta} \left(\boldsymbol {I} _ {i}, \mathcal {S} _ {i}\right) \tag {1} +$$ + +Here, the predicted density map $\hat{\mathbf{y}}_i$ indicates the objects to be counted, as specified by the exemplars $S_{i}$ , such that $\sum_{kl} \hat{\mathbf{y}}_{i_{kl}}$ yields the overall count for the image $I_{i}$ . We are interested in training a neural network $f$ parameterised by $\Theta$ to learn how to count based on the exemplars $S_{i}$ . For the supervised counting methods [31, 33], the network parameters $\Theta$ can be trained with the 'prediction, ground-truth') pairs: $(\hat{\mathbf{y}}_i, \mathbf{y}_i)$ . However, for self-supervised counting, the learning signal $\mathbf{y}_i$ is not obtained from manual annotations, but instead from the data itself. + +In this section, we introduce two essential parts of our method: we start by presenting our data generation method for counting in Section 3.1, that is the construction of the tuple $(I_i, S_i, \mathbf{y}_i)$ ; then, we explain the UnCounTR model, i.e. $f_\Theta$ in Equation (1), in Section 3.2. An overview of our method is provided in Figure 2. + +# 3.1. Constructing Self-Collages + +A key component of self-supervised training is the construction of a supervision signal without any manual annotations. In this paper, we generate training samples by pasting different images on top of a background. This is a well-known technique [2, 65], which next to its conceptual simplicity provides great flexibility regarding the number and type of pasted images. While other works combine annotated training images to enrich the training set [22, 31], we use this idea to construct the whole training set including unsupervised proxy labels, yielding self-supervised collages, or Self-Collages for short. Their generation pro + +cess is described by a composer module $g$ , which forms a distribution $g(\mathcal{O}, \mathcal{B}) = p(\tilde{\boldsymbol{I}}, S, \mathbf{y} \mid \mathcal{O}, \mathcal{B})$ of constructed images $\tilde{\boldsymbol{I}} \in \mathbb{R}^{H \times W \times 3}$ along with unsupervised exemplars $\mathcal{S}$ and labels $\mathbf{y}$ . The process is based on two sets of unlabelled images $\mathcal{O}$ and $\mathcal{B}$ for object and background images. $\mathcal{S} = \{\pmb{E}\}^E$ , $\pmb{E} \in \mathbb{R}^{H' \times W' \times 3}$ is a set of $E \in \mathbb{N}$ exemplars and $\mathbf{y} \in \mathbb{R}^{H \times W}$ corresponds to the density map of $\tilde{\boldsymbol{I}}$ . + +The composer module $g$ first randomly selects the number of distinct object categories $n_c \sim U[t_{\min}, t_{\max}]$ the first of which is taken as the target cluster. $t_{\min}$ and $t_{\max}$ control the minimum and maximum number of categories in a Self-Collage. To reduce the risk of overfitting to construction artefacts, we always construct images with $n_{\max}$ objects and change the associated number of target objects $\sum_{ij} \mathbf{y}_{ij}$ solely by altering the number of objects in the target cluster. This way, the number of pasted objects and, therefore, the number of artefacts is independent of the target count. The number of target objects $n_0 = n \sim U[n_{\min}, n_{\max} - n_c + 1]$ has an upper-bound lower than $n_{\max}$ to guarantee that there is at least one object of each of the $n_c$ types. For all other clusters, the number of objects is drawn from a uniform distribution of points on the $n_c - 1$ dimensional polytope with $L1$ -size of $n_{\max} - n$ ensuring that the total number of objects equals $n_{\max}$ . Further details, including the pseudocode for the composer module, are shown in the Appendix. + +Unsupervised categories. We obtain unsupervised object categories by first extracting feature representations for all samples in $\mathcal{O}$ using a pretrained DINO ViT-B/16 backbone [7] $d$ and subsequently running k-means with $K$ clusters: + +$$ +c (\boldsymbol {I}) = \mathrm {k} - \operatorname {m e a n s} _ {K} \left[ \left(d (\mathcal {O})\right) ^ {\mathrm {C L S}} \right] (\boldsymbol {I}), \tag {2} +$$ + +where $c(I)$ is the unsupervised category for image $\pmb{I}$ constructed using the final CLS-embedding of $d$ . For each of the $n_c$ clusters, a random, unique cluster $c_{i}$ , $i\in [0,n_c - 1]$ is chosen from all $K$ clusters where $c_{0}$ is the target cluster. + +Image selection. Next, random sets of images $\mathcal{I}_i\subset \mathcal{O}$ are picked from their unsupervised categories $c_{i}$ , such that $|\mathcal{I}_i| = n_i$ and $c(I) = c_i\forall I\in \mathcal{I}_i$ . We denote the union of these sets as $\mathcal{I} = \bigcup_{i = 0}^{n_c - 1}\mathcal{I}_i$ . In addition, we sample one image $I_{\mathrm{b}}$ from another dataset $\mathcal{B}$ , which is assumed to not contain salient objects to serve as the background image. + +# 3.1.1 Construction strategy + +Here we detail the Self-Collage construction. First, the background image $I_{\mathrm{b}}$ is reshaped to the final dimensions $H \times W$ and used as a canvas on which the modified images $\mathcal{I}$ are pasted. To mimic natural images that typically contain similarly sized objects, we first randomly pick a mean object size $d_{\mathrm{mean}} \sim U[d_{\mathrm{min}}, d_{\mathrm{max}}]$ . Subsequently, the target size of the pasted objects is drawn independently for each $I \in \mathcal{I}, I \in \mathbb{R}^{d_{\mathrm{h}} \times d_{\mathrm{w}} \times 3}$ from a uniform distribution $d_{\mathrm{paste}} \sim U[(1 - \sigma) \cdot d_{\mathrm{mean}}, (1 + \sigma) \cdot d_{\mathrm{mean}}]$ where $\sigma \in (0,1)$ controls the diversity of objects sizes in an image. After resizing $I$ to $I_{\mathrm{r}} \in \mathbb{R}^{d_{\mathrm{paste}} \times d_{\mathrm{paste}} \times 3}$ , the image is pasted to a random location on $I_{\mathrm{b}}$ . This location is either a position where previously no object has been pasted, or any location in the constructed image, potentially leading to overlapping images. By default, we will use the latter. + +Segmented pasting. Since pasting the whole image $I_{\mathrm{r}}$ might violate the assumption of having a single object and results in artefacts by also pasting the background of $I_{\mathrm{r}}$ , we introduce an alternative using self-supervised segmentations. This method, which we will use by default, uses an unsupervised segmentation method [51] to obtain a noisy foreground segmentation $\mathbf{s} \in [0, 1]^{d_{\mathrm{h}} \times d_{\mathrm{w}}}$ for $I$ . Instead of pasting the whole image, the segmentation $\mathbf{s}$ is used to only copy its foreground. Additionally, having access to $\mathbf{s}$ , this method can directly control the size of the pasted objects rather than the pasted images. To do that, we first extract the object in $I$ by computing the Hadamard product $I_{\mathrm{object}} = \operatorname{cut}(I \circ \mathbf{s})$ where the operation "cut" removes rows and columns that are completely masked out. In the next step, $I_{\mathrm{object}} \in \mathbb{R}^{h_{\mathrm{object}} \times w_{\mathrm{object}} \times 3}$ is resized so that its maximum dimension equals $d_{\mathrm{paste}}$ before pasting it onto $I_{\mathrm{b}}$ . + +Exemplar selection. To construct the exemplars used for training, we exploit the information about how the sample was constructed using $g$ : The set of $E$ exemplars $S$ is simply obtained by filtering for pasted objects that belong to the target cluster $c_{0}$ and subsequently sampling $E$ randomly. Then, for each of them, a crop of $\tilde{I}$ is taken as exemplar after resizing its spatial dimensions to $H' \times W'$ . + +# 3.1.2 Density map construction + +To train our counting model, we construct an unsupervised density map $\mathbf{y}$ for each training image $\tilde{\pmb{I}}$ . It needs to have the following two properties: i) it must sum up to the overall count of objects that we are counting and ii) it must have + +high values at object locations. To this end, we create $\mathbf{y}$ as a simple density map of Gaussian blobs as done in supervised density-based counting methods [14, 31]. For this, we use the bounding box for each pasted target image $I\in \mathcal{I}_0$ and place Gaussian density at the centre and normalise it to one. + +# 3.2. UnCounTR + +Model architecture. UnCounTR's architecture is inspired by CounTR [31]. To map an input image $\pmb{I}$ and its exemplars $S$ to a density map $\hat{\mathbf{y}}$ , the model consists of four modules: image encoder $\Phi$ , exemplar encoder $\Psi$ , feature interaction module $f_{\mathrm{fim}}$ , and decoder $f_{\mathrm{dec}}$ . An overview of this architecture can be seen in Figure 2. The image encoder $\Phi$ encodes an image $\pmb{I}$ into a feature map $\mathbf{x} = \Phi(\pmb{I}) \in \mathbb{R}^{h \times w \times d}$ where $h, w, d$ denote the height, width, and channel depth. Similarly, each exemplar $E \in S$ is projected to a single feature vector $\mathbf{z} \in \mathbb{R}^d$ by taking a weighted average of the grid features. Instead of training a CNN for an exemplar encoder as CounTR does, we choose $\Psi = \Phi$ to be the frozen DINO visual encoder weights. Reusing these weights, the exemplar and image features are in the same feature space. The feature interaction module (FIM) $f_{\mathrm{fim}}$ enriches the feature map $\mathbf{x}$ with information from the encoded exemplars $\mathbf{z}_j$ , $j \in \{1, \dots, E\}$ with a transformer decoder structure. Finally, the decoder $f_{\mathrm{dec}}$ takes the resulting patch-level feature map of the FIM as input and upsamples it with 4 convolutional blocks, ending up with a density map of the same resolution as the input image. Please refer to the Appendix for the full architectural details. + +UnCounTR supervision. UnCounTR is trained using the Mean Squared Error between model prediction and pseudo labels. Given a Self-Collage $\tilde{I}$ , exemplars $S$ , and density map $\mathbf{y}$ , the loss $\mathcal{L}$ for an individual sample is computed using the following equation where $f_{\Theta}(\tilde{I}, S)_{ij}$ is UnCounTR's spatially-dense output at location $(i, j)$ : + +$$ +\mathcal {L} = \frac {1}{H \cdot W} \sum_ {i j} \left(\mathbf {y} _ {i j} - f _ {\Theta} (\tilde {\boldsymbol {I}}, \mathcal {S}) _ {i j}\right) ^ {2} \tag {3} +$$ + +# 4. Experiments + +# 4.1. Implementation Details + +Datasets. To construct Self-Collages, we use ImageNet1k [13] and SUN397 [58]. ImageNet-1k contains 1.2M mostly object-centric images spanning 1000 object categories. SUN397 contains 109K images for 397 scene categories like 'cliff' or 'corridor'. Note that the object or scene category information is never used in our method. We assume that images from ImageNet-1k contain a single salient object and images from SUN397 contain no salient objects to serve as sets $\mathcal{O}$ and $\mathcal{B}$ . Based on this, $g$ randomly selects images from SUN397 as background images and picks objects from ImageNet-1k. Although Imagenet + +1k and SUN397 contain on average 3 and 17 objects respectively [30], these assumptions are still reasonable for our data construction. Additional ablations show that even explicitly violating the assumption of having no salient objects in $\mathcal{B}$ by using $\mathcal{O} = \mathcal{B}$ only have a small effect on performance, indicating the robustness of our method against violations (see Appendix). An example of a Self-Collage with 5 objects can be seen in Figure 2. Examples of both datasets and a more detailed discussion of these assumptions are included in the Appendix. + +To evaluate the counting ability, we use the standard FSC-147 dataset [45], which contains 6135 images covering 147 object categories, with counts ranging from 7 to 3731 and an average count of 56 objects per image. For each image, the dataset provides at least three randomly chosen object instances with annotated bounding boxes as exemplars. To analyse the counting ability in detailed count ranges, we partition the FSC-147 test set into three parts of roughly 400 images each, resulting in FSC-147{low,medium,high} subsets, each covering object counts from 8-16, 17-40 and 41-3701 respectively. Unless otherwise stated, we evaluate using 3 exemplars. + +Additionally, we also use the CARPK [23] and the Multi-Salient-Object (MSO) dataset [63] for evaluation. CARPK consists of 459 images of parking lots. Each image contains between 2 and 188 cars, with an average of 103. MSO contains 1224 images covering 5 categories: $\{0,1,2,3,4+\}$ salient objects with bounding box annotations. This dataset is largely imbalanced as 338 images contain zero salient objects and 20 images contain at least 4. For evaluation, we removed all samples with 0 counts, split the $4+$ category into exact counts, and chose only one annotated object as exemplar. + +Construction details. We configure the composer module to construct training samples using objects of $K = 10,000$ different clusters. To always have objects of a target and a non-target cluster in each image, we set $t_{\mathrm{min}} = t_{\mathrm{max}} = 2$ . Since the minimum number of target objects in an image limits the maximum number of exemplars available during training, we set $n_{\mathrm{min}} = 3$ , the maximum is $n_{\mathrm{max}} = 20$ . Finally, we choose $d_{\mathrm{min}} = 15$ , $d_{\mathrm{max}} = 70$ , and $\sigma = 0.3$ to obtain diverse training images with objects of different sizes as confirmed by visual inspection of the generated Self-Collages (see the Appendix). + +Training and inference details. During training, the images are cropped and resized to $224 \times 224$ pixels. The exemplars are resized to $64 \times 64$ pixels. For each batch, we randomly draw the number of exemplars $E$ to be between 1 and 3. We follow previous work [31] by scaling the loss, in our case by a factor of 3,000, and randomly dropping $20\%$ of the non-object pixels in the density map to decrease the imbalance of object and non-object pixels. By default, we use an AdamW optimizer and a cosine-decay learning rate + +schedule with linear warmup and a maximum learning rate of $5 \times 10^{-4}$ . We use a batch size of 128 images. Each model is trained on an Nvidia A100 GPU for 50 epochs of 10,000 Self-Collages each, which takes about 4 hours. At inference, we use a sliding window approach similar to Liu et al. [31], see the Appendix for details. For evaluation metrics, we report Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE) following previous work [14, 31]. We also report Kendall's $\tau$ coefficient, which is a rank correlation coefficient between the sorted ground-truth counts and the predicted counts. + +Baselines. To verify the effectiveness of our method, we introduce a series of baselines to compare with. (1) Average baseline: the prediction is always the average count of the FSC-147 training set, which is 49.96 objects. (2) Connected components baseline: for this, we use the final-layer attention values from the CLS-token of a pretrained DINO ViT-B/8 model. To derive a final count, we first threshold the attention map of each head to keep $p_{\mathrm{att}}$ percent of the attention mask. Subsequently, we consider each patch to where at least $n_{\mathrm{head}}$ attention heads attend to belong to an object. The number of connected components in the resulting feature map which cover more than $p_{\mathrm{size}}$ percent of the feature map is taken as prediction. To this end, we perform a grid search with almost 800 configurations of different value combinations for the three thresholds $p_{\mathrm{att}}, n_{\mathrm{head}}$ , and $p_{\mathrm{size}}$ on the FSC-147 training set and select the best configuration based on the MAE. The specific values tested can be found in the Appendix. (3) FasterRCNN baseline: we run the strong image detection toolbox FasterRCNN [46] with a score threshold of 0.5 on the image, which predicts a number of object bounding boxes. Then the object count is obtained by parsing the detection results by taking the total number of detected bounding boxes. Just like the connected components baseline, this model is applied to images resized to $384 \times 384$ pixels. (4) DETR baseline: similar to FasterRCNN, we evaluate the detection model DETR [5] on the counting task. Here, we resize the images to $800 \times 800$ pixels to better match DETR's evaluation protocol. + +# 4.2. Comparison against baselines + +In Table 1, we compare against multiple baselines on the three splits of FSC-147. As the connected components cannot leverage the additional information of the few-shot samples provided, we try to make the comparison as fair as possible, by testing almost 800 threshold parameters on the FSC-147 training set. While this yields a strong baseline, we find that our method of learning with Self-Collages more than halves the MAE on the low split, despite using a similar visual backbone. Next, we compare against the FasterRCNN and DETR object detectors which, unlike UnCounTR, are trained in a supervised fashion. Even though DETR outperforms UnCounTR in terms of RMSE on FSC + +
MethodFSC-147 lowFSC-147 mediumFSC-147 high
MAE↓RMSE↓τ↑MAE↓RMSE↓τ↑MAE↓RMSE↓τ↑
Average37.7137.79-22.7423.69-68.88213.08-
Conn. Comp.14.7118.590.1414.1917.900.1669.77210.540.17
FasterRCNN7.068.46-0.0319.8722.25-0.04109.12230.35-0.06
DETR6.928.200.0719.3321.56-0.08109.34162.88-0.07
UnCounTR (ours)5.6010.130.279.4812.730.3467.17189.760.26
σ(5 runs)±0.48±0.84±0.02±0.19±0.33±0.02±1.03±1.38±0.01
+ +Table 1. Comparison to baselines. Evaluation on different FSC-147 test subsets. "Conn. Comp." refers to connected components. + +
Frozen ΦFrozen ΨFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
XX37.64126.917.9913.37
✓X36.94130.229.1014.69
✓✓35.77130.345.6010.13
+ +(a) Keeping both image encoder $\Phi$ and exemplar encoder $\Psi$ frozen works best. + +
FSC-147FSC-147 low
nmaxMAE↓RMSE↓MAE↓RMSE↓
5030.17115.426.6513.60
2035.77130.345.6010.13
+ +(c) The number of pasted objects correlates with performance. + +
Segm.Overlap.FSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
✓✘36.47128.978.8414.54
✘✓37.46136.036.3311.55
✓✓35.77130.345.6010.13
+ +(b) Using both segmented objects and allowing for overlapping objects works well. + +
#ExemplarsFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
0 - 336.28131.446.2310.33
1 - 335.77130.345.6010.13
+ +Table 2. Ablations. We ablate various components of our model architecture and Self-Collage construction method. Default settings are highlighted in grey. + +(d) Training our method strictly in the 1-3 exemplar setting works best. + +
ArchitecturePretrainingFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
ViT-B/8Leopard [67]36.04126.755.7210.67
ViT-B/8DINO [7]38.16132.096.109.79
ViT-B/16DINO [7]35.77130.345.6010.13
+ +147 low and high, we find that our method still outperforms all baselines on 7 out of 9 measures. This is despite the additional advantages such as access to the FSC-147 training distribution for these baselines. The gap between most baselines and UnCounTR is the smallest on the high split, suggesting limits to its generalisation which we will explore further in the Appendix. There, we also provide a qualitative analysis of some failure cases of FasterRCNN. + +# 4.3. Ablation Study + +We analyse the various components of our method in Tables 2a to 2d. + +Keeping backbone frozen works best. In Table 2a, we evaluate the effect of unfreezing the last two backbone blocks shared by $\Phi$ and $\Psi$ . In addition, we test training a CNN-based encoder $\Psi$ from scratch similar to Liu et al. [31]. We find that keeping both frozen, i.e. $\Phi = \Psi =$ const. works best, as it discourages the visual features to adapt to potential artefacts in our Self-Collages. + +Table 3. Combining Self-Collages with different backbones. We can apply our method to any recent state-of-the-art pretrained network and achieve strong performances. + +
MethodsValTest
MAE↓RMSE↓MAE↓RMSE↓
CounTR [31]13.1349.8311.9591.23
LOCA [14]10.2432.5610.7956.97
UnCounTR (ours)36.93106.6135.77130.34
σ(5 runs)±0.49±1.46±0.60±0.94
+ +Table 4. Comparison to supervised models. We evaluate on the val and test split of FSC-147. + +Benefit of self-supervised exemplars. In Table 2d we evaluate the effect of including the zero-shot counting task (i.e. counting all salient objects) as done in other works [14, 31]. However, we find that including this task even with only a $25\%$ chance leads to a lower performance. This is likely due to the zero-shot task overfitting our Self-Collages and finding short-cuts, such as pasting artefacts, as we relax the constraint introduced in Section 3.1.1 and vary the number of pasted objects to match the desired target. We therefore train our model with 1-3 exemplars and show how we can still conduct semantic zero-shot counting in Section 4.7. + +Maximum number of pasted objects. Next, we evaluate the effect of varying $n_{\mathrm{max}}$ , the maximum number of objects pasted, as shown in Table 2c. Pasting up to 50 objects yields overall better performance on the full FSC-147 test dataset which contains on average 66 objects. While this shows that the construction of Self-Collages can be successfully scaled to higher counts, we find that pasting with 20 objects already achieves good performance with shortened + +
MethodFSC-147 low (8-16 objects)FSC-147 medium (17-40 objects)FSC-147 high (41-3701 objects)
MAE↓RMSE↓Δτ↑MAE↓RMSE↓Δτ↑MAE↓
CounTR6.5848.110.424.4810.020.6020.50
UnCounTR (ours)5.6010.13-37.90.279.4812.73+2.70.3467.17
σ(5 runs)±0.48±0.84±0.02±0.19±0.33±0.02±1.03
+ +Table 5. Comparison to CounTR. Evaluation results on the FSC-147 low and medium test subsets. + +
MethodMSO
MAE↓RMSE↓τ↑
Conn. Comp. Baseline10.6712.880.12
CounTR2.348.120.36
UnCounTR (ours)1.072.320.45
σ(5 runs)±0.06±0.25±0.01
+ +Table 6. Evaluation on the MSO [63] dataset. + +
MethodCARPK
MAE↓RMSE↓τ↑
Conn. Comp. Baseline49.6254.500.56
CounTR19.6229.700.57
UnCounTR (ours)30.3535.670.54
σ(5 runs)±2.26±2.36±0.06
+ +construction times and so use this setting. + +Segmented pasting works best. From Table 2b, We find that the best construction strategy involves pasting the self-supervised segmentations, regardless of their overlap with other objects. We simply store the segmentations and combine these to create diverse Self-Collages at training time. + +Compatible with various pretrained backbones. In Table 3, we show the effect of using different frozen weights for the visual encoder. Across ViT-B models with varying patch sizes and pretrainings, from Leopart's [67] spatially dense to the original DINO's [7] image-level pretraining, we find similar performances across our evaluations. This shows that our method is compatible with various architectures and pretrainings and will likely benefit from the continued progress in self-supervised representation learning which is supported by our findings based on DINOv2 [40] presented in the Appendix. We do not find any benefit in going from patch size 16 to 8 (similar to Simeoni et al. [52]) so we use the faster DINO ViT-B/16 model for the rest of the paper. + +# 4.4. Benchmark comparison + +Next, we compare with previous methods on three datasets: FSC-147 [45], MSO [63], and CARPK [23]. Table 4 shows the results on the validation and test split of the FSC-147 dataset. In contrast to our approach, which investigates the feasibility of learning to count without any reliance on supervised data, these methods heavily depend on manual annotations. Hence, the comparison is certainly not fair: (1) our method does not use manually annotated counting data, also has never seen any FSC-147 training images, (2) our training samples based on Self-Collages only cover 3-19 target objects, whereas the full test set of FSC-147 has 66 objects on average. Evaluating our method on the full set of FSC-147 is actually evaluating the transferring ability as discussed in more detail in the Appendix. + +We choose CounTR [31] for further analysis because of its similar architecture to UnCounTR. To fairly com + +# Table 7. Evaluation on the CARPK [23] dataset. + +pare with this method, we trisect the FSC-147 test set as described in Section 4.1. Table 5 shows the evaluation results on the three partitions. It is remarkable that our method outperforms supervised CounTR on the low partition, especially on the RMSE metric (10.13 vs 48.11). Also, our method is not far from CounTR's performance on the medium partition (e.g. RMSE 12.7 vs 10.02), showing a reasonable transferring ability since the model is trained with up to 19 object counts only. + +Additionally, Table 6 compares our method with the connected components baseline and CounTR on a subset of MSO as described in Section 4.1. The results show our self-supervised method outperforms the supervised CounTR model by a large margin on the lower counts tasks. In Table 7, the performance on the CARPK dataset is shown. We use the same CounTR model finetuned on the FSC-147 dataset as before to compare the generalisation across datasets. While the MAE of CounTR almost doubles compared to the results on the FSC-147 test set, UnCounTR's performance is more stable, improving by $15\%$ . + +# 4.5. Qualitative results and limitations + +Figure 3 shows a few qualitative results to demonstrate our method's effectiveness and its limitations. The model is able to correctly predict the number of objects for clearly separated and slightly overlapping instances (e.g. Subfigures a and c). The model also successfully identifies the object type of interest, e.g. in Subfigure b the density map correctly highlights the strawberries rather than blueberries. One limitation of our model is images where the number of objects is ambiguous. For example, in Subfigure d, the prediction missed a few burgers which are possibly the ones partially shown on the edge. However, it is also difficult for humans to decide which of those objects should be counted. + +# 4.6. Improving upon UnCounTR + +Having established UnCounTR and compared it to several methods, we now explore three ways to further improve its + +![](images/0fc2311f82cc9c35f6b8ce842fa59a43651a321a271b366b97aeadf9eb548a06.jpg) +(a) $\mathrm{GT} = 8$ Pred=8 + +![](images/3cf88baac8c245893c5c3a5b74bafa7950e5ea605ab0e1d3f781c8480b9d2f03.jpg) + +![](images/bc300a1cc50bcb6c069294ecebe12eab862c1c48122a7cf5c5340fb325fde529.jpg) +(b) $\mathrm{GT} = 16$ ; Pred=17 + +![](images/1907177f78fbc26edc4b3b1724c088c5f672dbd2386e59042cc67fe847ee46ba.jpg) + +![](images/6729ce66ae58217bd01efc3de68628f5e4a587279cad9a282d4f6687f9714d4a.jpg) + +![](images/21a1dc4d5a3adbfddc951755cdb97d00a21a9c77247d0f7dad54a40f0ae2c941.jpg) +(c) $\mathrm{GT} = 8$ Pred $= 8$ + +![](images/465997b39c2b8e60f682c24659a8879fa8b69eccbb3be8185496068039ac71b4.jpg) +(d) $\mathrm{GT} = 13$ Pred $= 10$ + +![](images/0d93ed17afdc8e8e9e7fe8a3484c96a6066842020707c26d181cf1c2f98edae7.jpg) + +![](images/f209cd149f2c0e78a040880972dbda880c115361c5205c27c8645a70f70e1e92.jpg) +Input image (a) + +![](images/88fd2c81ff8c1720e216715cb2c6ee38b8a240c3fcbd0e95b4853aa74d3e8bc3.jpg) +exemplar 1 + +![](images/7b314733bb03cc998e65f1c75b3142223b8d33f31502b2dccdb953a4c9e5552a.jpg) + +![](images/6550d54e1e025f1f4f71231394c398df14a4e9778487abd48e0a6c44c8107301.jpg) +exemplar 2 + +![](images/570325f26bc8b96ca92d03c965a6b7f97205c357efcbf8efa621c2a9d51a43b4.jpg) +Figure 4. Self-supervised semantic counting. In this setting, the model proposes the exemplars by itself and then performs reference-based counting. + +![](images/ce59fe8f2027c7f7ebd89bbecb56b3b7d9ff176afb0d84cdadfcacf823111654.jpg) +Input image (b) + +![](images/1ee10c4006f0308cf4ae4578ad2ab981f5284a0a9b562bd43330772a936a98c5.jpg) + +![](images/c6d645ce7f0b6ef492b39abed2c55ab7b17b581b51a9dbf3fb7f18d78a165e32.jpg) + +![](images/61c003a5409ab3410ce4b846971eff438dd7d14358c2836447ec924345ec40ae.jpg) +Figure 3. Qualitative examples of UnCounTR's predictions. We show predictions on four images from the FSC-147 test set, the green boxes represent the exemplars. Our predicted count is the sum of the density map rounded to the nearest integer. + +![](images/094c0fefa8abf97b0577b196a90582769bfd33233fc5ace9610a063440f90ccd.jpg) + +performance: (1) Integrating the DINOV2 [40] backbone improves the MAE particularly on the FSC-147 low set by $27\%$ (2) Using cluster similarity to create more challenging Self-Collages reduces the MAE on FSC-147 to 31.06 (3) Refining high-count predictions further improves performance yielding the final UnCounTRv2 model. It achieves an MAE of 28.67 on FSC-147 and 3.88 on FSC-147 low. For a comprehensive discussion, please refer to the Appendix. See Figure 1 for a visual comparison with CounTR. + +# 4.7. Self-supervised semantic counting + +In this last section, we explore the potential of UnCounTR for more advanced counting tasks. In particular, we test whether our model can not only unsupervisedly count different kinds of objects in an image, but also determine the categories by itself, a scenario we refer to as semantic counting. To this end, we use a simple pipeline that picks an area surrounding the maximum in the input image's CLS-attention map as the first input and refines it to obtain an exemplar. Next, UnCounTR predicts the number of objects in the image based on the self-constructed exemplar. Finally, the locations that have been detected using this procedure are removed from the initial attention map and if + +the remaining attention values are high enough, the process is repeated to count objects of another type. We provide the details of this method in the Appendix. In Figure 4, we demonstrate results on two difficult real images. + +# 5. Conclusion + +In this work, we have introduced UnCounTR, showcasing, for the first time, the capability of reference-based counting without relying on human supervision. To this end, our method constructs Self-Collages, a simple unsupervised way of generating proxy learning signals from unlabeled data. Our results demonstrate that by utilising an off-the-shelf unsupervisedly pretrained visual encoder, we can learn counting models that can even outperform strong baselines such as DETR and achieve similar performances to dedicated counting models such as CounTR on CARPK, MSO, and various splits of FSC-147. Finally, we have shown that our model can unsupervisedly identify multiple exemplars in an image and count them, something no supervised model can yet do. 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In CVPR, pages 14502-14511, 2022. 2, 6, 7 \ No newline at end of file diff --git a/2024/Learning to Count without Annotations/images.zip b/2024/Learning to Count without Annotations/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..8f8b51fcb86067033b91a9a4b70b6a925560f48a --- /dev/null +++ b/2024/Learning to Count without Annotations/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:acf2a07da59ce9c8bb5bc1dba9f5ca882a9d6971c7c53169ba301c1d4d4e74ea +size 474170 diff --git a/2024/Learning to Count without Annotations/layout.json b/2024/Learning to Count without Annotations/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..411fe0c45dd1b1401a62d78fbacb1f6209657e30 --- /dev/null +++ b/2024/Learning to Count without Annotations/layout.json @@ -0,0 +1,11082 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 174, + 104, + 421, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 174, + 104, + 421, + 121 + ], + "spans": [ + { + "bbox": [ + 174, + 104, + 421, + 121 + ], + "type": "text", + "content": "Learning to Count without Annotations" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 92, + 144, + 216, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 92, + 144, + 216, + 185 + ], + "spans": [ + { + "bbox": [ + 92, + 144, + 216, + 185 + ], + "type": "text", + "content": "Lukas Knobel \nUniversity of Amsterdam \nlukasknbl@gmail.com" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 244, + 144, + 349, + 184 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 244, + 144, + 349, + 184 + ], + "spans": [ + { + "bbox": [ + 244, + 144, + 349, + 184 + ], + "type": "text", + "content": "Tengda Han* \nUniversity of Oxford \nhtd@robots.ox.ac.uk" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 376, + 144, + 501, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 376, + 144, + 501, + 185 + ], + "spans": [ + { + "bbox": [ + 376, + 144, + 501, + 185 + ], + "type": "text", + "content": "Yuki M. Asano* \nUniversity of Amsterdam \ny.m.asano@uva.nl" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 143, + 227, + 192, + 239 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 227, + 192, + 239 + ], + "spans": [ + { + "bbox": [ + 143, + 227, + 192, + 239 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 252, + 290, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 252, + 290, + 456 + ], + "spans": [ + { + "bbox": [ + 46, + 252, + 290, + 456 + ], + "type": "text", + "content": "While recent supervised methods for reference-based object counting continue to improve the performance on benchmark datasets, they have to rely on small datasets due to the cost associated with manually annotating dozens of objects in images. We propose UnCounTR, a model that can learn this task without requiring any manual annotations. To this end, we construct \"Self-Collages\", images with various pasted objects as training samples, that provide a rich learning signal covering arbitrary object types and counts. Our method builds on existing unsupervised representations and segmentation techniques to successfully demonstrate for the first time the ability of reference-based counting without manual supervision. Our experiments show that our method not only outperforms simple baselines and generic models such as FasterRCNN and DETR, but also matches the performance of supervised counting models in some domains." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 481, + 128, + 493 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 481, + 128, + 493 + ], + "spans": [ + { + "bbox": [ + 47, + 481, + 128, + 493 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 502, + 287, + 621 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 502, + 287, + 621 + ], + "spans": [ + { + "bbox": [ + 46, + 502, + 287, + 621 + ], + "type": "text", + "content": "Cognitive neuroscientists speculate that visual counting, especially for a small number of objects, is a pre-attentive and parallel process [12, 55], which can help humans and animals make prompt decisions [43]. Accumulating evidence shows that infants and certain species of animals can differentiate between small numbers of items [11, 12, 41] and as young as 18-month-old infants have been shown to develop counting abilities [53]. These findings indicate that the ability of visual counting may emerge very early or even be inborn in humans and animals." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 622, + 288, + 684 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 622, + 288, + 684 + ], + "spans": [ + { + "bbox": [ + 46, + 622, + 288, + 684 + ], + "type": "text", + "content": "On the non-biological side, recent developments in computer vision have been tremendous. The state-of-the-art computer vision models can classify thousands of image classes [19, 27], detect various objects [66], or segment almost anything from an image [26]. Partially inspired by" + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 312, + 226, + 426, + 339 + ], + "blocks": [ + { + "bbox": [ + 312, + 226, + 426, + 339 + ], + "lines": [ + { + "bbox": [ + 312, + 226, + 426, + 339 + ], + "spans": [ + { + "bbox": [ + 312, + 226, + 426, + 339 + ], + "type": "image", + "image_path": "bfa030c0eccdf66e1d640eb3a6794a05e7263c907c58b26e23e5d4ec47311a33.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 349, + 547, + 416 + ], + "lines": [ + { + "bbox": [ + 304, + 349, + 547, + 416 + ], + "spans": [ + { + "bbox": [ + 304, + 349, + 547, + 416 + ], + "type": "text", + "content": "Figure 1. CountTR vs. our proposed UnCountTRv2. Our counting model, UnCountTRv2, is trained without any labels and manual counting annotations. It generalizes well from its up to 19 pseudo-counts encountered during training to the significantly higher numbers in the FSC-147 test set. This demonstrates that learning to count is possible without annotations." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 426, + 226, + 541, + 339 + ], + "blocks": [ + { + "bbox": [ + 426, + 226, + 541, + 339 + ], + "lines": [ + { + "bbox": [ + 426, + 226, + 541, + 339 + ], + "spans": [ + { + "bbox": [ + 426, + 226, + 541, + 339 + ], + "type": "image", + "image_path": "940db8dc4caef36e2b22ead1ba008778982f1c3b5eade06e516ce488f2947357.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 426, + 546, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 546, + 593 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 546, + 593 + ], + "type": "text", + "content": "how babies learn to see the world [54], some of the recent well-performing models are trained with self-supervised learning methods, whereby a learning signal for neural networks is constructed without the need for manual annotations [15, 20]. The pretrained visual representations from such methods have demonstrated superior performances on various downstream visual tasks, like image classification and object detection [7, 20, 21]. Moreover, self-supervised learning signals have been shown to be sufficient for successfully learning image groupings [57, 59] and even object and semantic segmentations without any annotations [7, 62]. Motivated by these, we ask in this paper whether visual counting might also be solvable without relying on human annotations." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 594, + 547, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 547, + 666 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 547, + 666 + ], + "type": "text", + "content": "The current state-of-the-art visual counting methods, e.g. CounTR [31], typically adapt pretrained visual representations to the counting task by using a considerable size of human annotations. However, we conjecture that the existing visual representations are already strong enough to perform counting, even without any manual annotations." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "type": "text", + "content": "In this paper, we design a straightforward self-supervised training scheme to teach the model 'how to count', by pasting a number of objects on a background image, to make a Self-Collage. Our experiments show that when construct" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 693, + 228, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 693, + 228, + 713 + ], + "spans": [ + { + "bbox": [ + 58, + 693, + 228, + 713 + ], + "type": "text", + "content": "*Equal senior contribution. \n1Code: https://github.com/lukasknobel/SelfCollages" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22924" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": "ing the Self-Collages carefully, this training method is effective enough to leverage the pretrained visual representation on the counting task, even approaching other methods that require manually annotated counting data. For the visual representation, we use the self-supervised pretrained DINO features [7], which have been shown to be useful and generalisable for a variety of visual tasks like segmenting objects [34, 67]. Note that the DINO model is also trained without manual annotations, thus our entire pipeline does not require annotated datasets." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 192, + 289, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 192, + 289, + 348 + ], + "spans": [ + { + "bbox": [ + 46, + 192, + 289, + 348 + ], + "type": "text", + "content": "To summarise, this paper focuses on the objective of training a reference-based counting model without any manual annotation. The following contributions are made: (i) We propose a simple yet effective data generation method to construct 'Self-Collages', which pastes objects onto an image and gets supervision signals for free. (ii) We leverage self-supervised pretrained visual features from DINO and develop UnCounTR, a transformer-based model architecture for counting. (iii) The experiments show that our method trained without manual annotations not only outperforms baselines and generic models like FasterRCNN and DETR, but also matches the performance of supervised counting models." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 358, + 132, + 370 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 358, + 132, + 370 + ], + "spans": [ + { + "bbox": [ + 47, + 358, + 132, + 370 + ], + "type": "text", + "content": "2. Related work" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 378, + 287, + 474 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 378, + 287, + 474 + ], + "spans": [ + { + "bbox": [ + 46, + 378, + 287, + 474 + ], + "type": "text", + "content": "Counting with object classes. The class-specific counting methods are trained to count instances of a single class of interest, such as cars [23, 36] or people [28, 28, 32, 47, 48]. These methods require retraining to apply them to new object classes [36]. In addition, some works rely on class-specific assumptions such as the proportionality of features and counts [24], or the distribution [48] or shapes [56] of objects, which cannot be easily adapted." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 475, + 287, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 475, + 287, + 617 + ], + "spans": [ + { + "bbox": [ + 46, + 475, + 287, + 617 + ], + "type": "text", + "content": "By contrast, class-agnostic approaches are not designed with a specific object class in mind. Early work by Zhang et al. [63] proposes the salient object subitizing task, where the model is trained to count by classification of " + }, + { + "bbox": [ + 46, + 475, + 287, + 617 + ], + "type": "inline_equation", + "content": "\\{0,1,2,3,4+\\}" + }, + { + "bbox": [ + 46, + 475, + 287, + 617 + ], + "type": "text", + "content": " salient objects regardless of their classes. Other reference-less methods like Hobley and Prisacariu [22] frame counting as a repetition-recognition task and aim to automatically identify the objects to be counted. An alternative approach of class-agnostic counting requires a prior of the object type to be counted in the form of reference images, also called 'exemplars', each containing a single instance of the desired class [14, 29, 33, 45, 50, 60, 61]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 617, + 287, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 287, + 665 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 287, + 665 + ], + "type": "text", + "content": "Counting with different methods. Categorised by the approach taken to obtain the final count, counting methods can be divided into classification, detection and regression-based methods." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "content": "Classification-based approaches predict a discrete count for a given image [63]. The classes either correspond to single numbers or potentially open-ended intervals. Thus, predictions are limited to the pre-defined counts and a gen" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 72, + 511, + 84 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 511, + 84 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 511, + 84 + ], + "type": "text", + "content": "eralisation to new ranges is by design not possible." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 84, + 545, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 84, + 545, + 180 + ], + "spans": [ + { + "bbox": [ + 304, + 84, + 545, + 180 + ], + "type": "text", + "content": "An alternative is detection-based methods [23]. By predicting bounding boxes for the counted instances and deriving a global count based on their number, these methods are unlike classification-based approaches not constrained to predefined count classes. While the bounding boxes can facilitate further analysis by explicitly showing the counted instances, the performance of detection-based approaches deteriorates in high-density settings [22]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 180, + 546, + 358 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 180, + 546, + 358 + ], + "spans": [ + { + "bbox": [ + 304, + 180, + 546, + 358 + ], + "type": "text", + "content": "Lastly, regression-based methods predict a single number and can be further divided into scalar and density-based approaches. Scalar methods directly map an input image to a single scalar count corresponding to the number of objects in the input [22]. Density-based methods on the contrary predict a density map for a given image and obtain the final count by integrating over it [9, 14, 32, 33, 48, 49]. Similar to detection-based approaches, these methods allow locating the counted instances which correspond to the local maxima of the density map but have the added benefit of performing well in high-density applications with overlapping objects [33]. The recent work CounTR [31] is a class-agnostic, density-based method which is trained to count both with and without exemplars using a transformer decoder structure with learnable special tokens." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 359, + 546, + 658 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 359, + 546, + 658 + ], + "spans": [ + { + "bbox": [ + 304, + 359, + 546, + 658 + ], + "type": "text", + "content": "Self-supervised learning. Self-supervised learning (SSL) has shown its effectiveness in many computer vision tasks. Essentially, SSL derives the supervision signal from the data itself rather than manual annotations. The supervision signal can be found from various \"proxy tasks\" like colorization [64], spatial ordering or inpainting [15, 21, 37, 42], temporal ordering [18, 35], contrasting similar instances [10, 20, 39], clustering [3, 6], and from multiple modalities [1, 44]. Another line of SSL methods is knowledge distillation, where one smaller student model is trained to predict the output of the other larger teacher model [4, 8, 25]. BYOL [17] design two identical models but train one model to predict the moving average of the other as the supervision signal. Notably, DINO [7] is trained in a similar way but using Vision Transformers (ViTs) as the visual model [16], and obtains strong visual features. Simply thresholding the attention maps and using the resulting masks yields high-quality image segmentations. Follow-up works [34, 51, 67] demonstrate the semantic segmentation quality can be further improved by applying some lightweight training or post-processing of DINO features. For counting in SSL, Noroozi et al. [38] use feature \"counting\" as a proxy task to learn representations. In this work, we focus on counting itself and explore approaches to teach the model to count without manual supervision." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 669, + 362, + 681 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 669, + 362, + 681 + ], + "spans": [ + { + "bbox": [ + 306, + 669, + 362, + 681 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "text", + "content": "We tackle the task of counting objects given some exemplar crops within an image. With an image dataset " + }, + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{D} =" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22925" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 73, + 541, + 232 + ], + "blocks": [ + { + "bbox": [ + 50, + 73, + 541, + 232 + ], + "lines": [ + { + "bbox": [ + 50, + 73, + 541, + 232 + ], + "spans": [ + { + "bbox": [ + 50, + 73, + 541, + 232 + ], + "type": "image", + "image_path": "1e3a6a85d43cec1bc0ec5d0d4ccdcd4af76afacd3d56630cd78a8ca60f737f42.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 241, + 547, + 275 + ], + "lines": [ + { + "bbox": [ + 46, + 241, + 547, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 241, + 547, + 275 + ], + "type": "text", + "content": "Figure 2. Method overview. Our method leverages the strong coherence of deep clusters to provide pseudo-labelled images which are used to construct a self-supervised counting task. The composer utilises self-supervised segmentations for pasting a set of objects onto a background image and UnCounTR is trained to count these when provided with unsupervised exemplars." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "spans": [ + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "inline_equation", + "content": "\\{(I_1, S_1, \\mathbf{y}_1), \\ldots, (I_i, S_i, \\mathbf{y}_i)\\}" + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "inline_equation", + "content": "I_i \\in \\mathbb{R}^{H \\times W \\times 3}" + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "text", + "content": " denotes image " + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "inline_equation", + "content": "S_i = \\{E_i^1, \\ldots, E_i^E\\}" + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "text", + "content": " represent the " + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "text", + "content": " visual exemplars of shape " + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "inline_equation", + "content": "E_i^e \\in \\mathbb{R}^{H' \\times W' \\times 3}" + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "inline_equation", + "content": "\\mathbf{y}_i \\in \\mathbb{R}^{H \\times W}" + }, + { + "bbox": [ + 47, + 283, + 287, + 344 + ], + "type": "text", + "content": " is the ground-truth density map, the counting task can be written as:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 133, + 345, + 287, + 357 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 133, + 345, + 287, + 357 + ], + "spans": [ + { + "bbox": [ + 133, + 345, + 287, + 357 + ], + "type": "interline_equation", + "content": "\\hat {\\mathbf {y}} _ {i} = f _ {\\Theta} \\left(\\boldsymbol {I} _ {i}, \\mathcal {S} _ {i}\\right) \\tag {1}", + "image_path": "6d0120f596b11f29719c9fcbc3e5f22b35c31b41a7f23f462a25cc98d5bbe696.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "spans": [ + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": "Here, the predicted density map " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{y}}_i" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": " indicates the objects to be counted, as specified by the exemplars " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "S_{i}" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": ", such that " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "\\sum_{kl} \\hat{\\mathbf{y}}_{i_{kl}}" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": " yields the overall count for the image " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "I_{i}" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": ". We are interested in training a neural network " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": " parameterised by " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "\\Theta" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": " to learn how to count based on the exemplars " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "S_{i}" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": ". For the supervised counting methods [31, 33], the network parameters " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "\\Theta" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": " can be trained with the 'prediction, ground-truth') pairs: " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "(\\hat{\\mathbf{y}}_i, \\mathbf{y}_i)" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": ". However, for self-supervised counting, the learning signal " + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "inline_equation", + "content": "\\mathbf{y}_i" + }, + { + "bbox": [ + 46, + 363, + 287, + 482 + ], + "type": "text", + "content": " is not obtained from manual annotations, but instead from the data itself." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 483, + 287, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 483, + 287, + 555 + ], + "spans": [ + { + "bbox": [ + 46, + 483, + 287, + 555 + ], + "type": "text", + "content": "In this section, we introduce two essential parts of our method: we start by presenting our data generation method for counting in Section 3.1, that is the construction of the tuple " + }, + { + "bbox": [ + 46, + 483, + 287, + 555 + ], + "type": "inline_equation", + "content": "(I_i, S_i, \\mathbf{y}_i)" + }, + { + "bbox": [ + 46, + 483, + 287, + 555 + ], + "type": "text", + "content": "; then, we explain the UnCounTR model, i.e. " + }, + { + "bbox": [ + 46, + 483, + 287, + 555 + ], + "type": "inline_equation", + "content": "f_\\Theta" + }, + { + "bbox": [ + 46, + 483, + 287, + 555 + ], + "type": "text", + "content": " in Equation (1), in Section 3.2. An overview of our method is provided in Figure 2." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 563, + 195, + 576 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 563, + 195, + 576 + ], + "spans": [ + { + "bbox": [ + 47, + 563, + 195, + 576 + ], + "type": "text", + "content": "3.1. Constructing Self-Collages" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "type": "text", + "content": "A key component of self-supervised training is the construction of a supervision signal without any manual annotations. In this paper, we generate training samples by pasting different images on top of a background. This is a well-known technique [2, 65], which next to its conceptual simplicity provides great flexibility regarding the number and type of pasted images. While other works combine annotated training images to enrich the training set [22, 31], we use this idea to construct the whole training set including unsupervised proxy labels, yielding self-supervised collages, or Self-Collages for short. Their generation pro" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "spans": [ + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": "cess is described by a composer module " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": ", which forms a distribution " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "g(\\mathcal{O}, \\mathcal{B}) = p(\\tilde{\\boldsymbol{I}}, S, \\mathbf{y} \\mid \\mathcal{O}, \\mathcal{B})" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": " of constructed images " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\tilde{\\boldsymbol{I}} \\in \\mathbb{R}^{H \\times W \\times 3}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": " along with unsupervised exemplars " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\mathcal{S}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": " and labels " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": ". The process is based on two sets of unlabelled images " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\mathcal{O}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\mathcal{B}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": " for object and background images. " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\mathcal{S} = \\{\\pmb{E}\\}^E" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\pmb{E} \\in \\mathbb{R}^{H' \\times W' \\times 3}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": " is a set of " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "E \\in \\mathbb{N}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": " exemplars and " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\mathbf{y} \\in \\mathbb{R}^{H \\times W}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": " corresponds to the density map of " + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "inline_equation", + "content": "\\tilde{\\boldsymbol{I}}" + }, + { + "bbox": [ + 304, + 284, + 545, + 368 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "spans": [ + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": "The composer module " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " first randomly selects the number of distinct object categories " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "n_c \\sim U[t_{\\min}, t_{\\max}]" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " the first of which is taken as the target cluster. " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "t_{\\min}" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "t_{\\max}" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " control the minimum and maximum number of categories in a Self-Collage. To reduce the risk of overfitting to construction artefacts, we always construct images with " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "n_{\\max}" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " objects and change the associated number of target objects " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "\\sum_{ij} \\mathbf{y}_{ij}" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " solely by altering the number of objects in the target cluster. This way, the number of pasted objects and, therefore, the number of artefacts is independent of the target count. The number of target objects " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "n_0 = n \\sim U[n_{\\min}, n_{\\max} - n_c + 1]" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " has an upper-bound lower than " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "n_{\\max}" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " to guarantee that there is at least one object of each of the " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "n_c" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " types. For all other clusters, the number of objects is drawn from a uniform distribution of points on the " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "n_c - 1" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " dimensional polytope with " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "L1" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": "-size of " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "n_{\\max} - n" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": " ensuring that the total number of objects equals " + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "inline_equation", + "content": "n_{\\max}" + }, + { + "bbox": [ + 304, + 369, + 546, + 583 + ], + "type": "text", + "content": ". Further details, including the pseudocode for the composer module, are shown in the Appendix." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "spans": [ + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "type": "text", + "content": "Unsupervised categories. We obtain unsupervised object categories by first extracting feature representations for all samples in " + }, + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "type": "inline_equation", + "content": "\\mathcal{O}" + }, + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "type": "text", + "content": " using a pretrained DINO ViT-B/16 backbone [7] " + }, + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "type": "text", + "content": " and subsequently running k-means with " + }, + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 584, + 545, + 643 + ], + "type": "text", + "content": " clusters:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 358, + 645, + 545, + 659 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 358, + 645, + 545, + 659 + ], + "spans": [ + { + "bbox": [ + 358, + 645, + 545, + 659 + ], + "type": "interline_equation", + "content": "c (\\boldsymbol {I}) = \\mathrm {k} - \\operatorname {m e a n s} _ {K} \\left[ \\left(d (\\mathcal {O})\\right) ^ {\\mathrm {C L S}} \\right] (\\boldsymbol {I}), \\tag {2}", + "image_path": "12f1ae1fea514dc0be03eb644a94025b47a563d6bdad05b70d8b6770735df75c.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "inline_equation", + "content": "c(I)" + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": " is the unsupervised category for image " + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{I}" + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": " constructed using the final CLS-embedding of " + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": ". For each of the " + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "inline_equation", + "content": "n_c" + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": " clusters, a random, unique cluster " + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "inline_equation", + "content": "c_{i}" + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "inline_equation", + "content": "i\\in [0,n_c - 1]" + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": " is chosen from all " + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": " clusters where " + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "inline_equation", + "content": "c_{0}" + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": " is the target cluster." + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22926" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "content": "Image selection. Next, random sets of images " + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_i\\subset \\mathcal{O}" + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "content": " are picked from their unsupervised categories " + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "inline_equation", + "content": "c_{i}" + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "content": ", such that " + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "inline_equation", + "content": "|\\mathcal{I}_i| = n_i" + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "inline_equation", + "content": "c(I) = c_i\\forall I\\in \\mathcal{I}_i" + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "content": ". We denote the union of these sets as " + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "inline_equation", + "content": "\\mathcal{I} = \\bigcup_{i = 0}^{n_c - 1}\\mathcal{I}_i" + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "content": ". In addition, we sample one image " + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{b}}" + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "content": " from another dataset " + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "inline_equation", + "content": "\\mathcal{B}" + }, + { + "bbox": [ + 47, + 72, + 289, + 145 + ], + "type": "text", + "content": ", which is assumed to not contain salient objects to serve as the background image." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 159, + 173, + 172 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 159, + 173, + 172 + ], + "spans": [ + { + "bbox": [ + 47, + 159, + 173, + 172 + ], + "type": "text", + "content": "3.1.1 Construction strategy" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "spans": [ + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": "Here we detail the Self-Collage construction. First, the background image " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{b}}" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": " is reshaped to the final dimensions " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "H \\times W" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": " and used as a canvas on which the modified images " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "\\mathcal{I}" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": " are pasted. To mimic natural images that typically contain similarly sized objects, we first randomly pick a mean object size " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "d_{\\mathrm{mean}} \\sim U[d_{\\mathrm{min}}, d_{\\mathrm{max}}]" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": ". Subsequently, the target size of the pasted objects is drawn independently for each " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "I \\in \\mathcal{I}, I \\in \\mathbb{R}^{d_{\\mathrm{h}} \\times d_{\\mathrm{w}} \\times 3}" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": " from a uniform distribution " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "d_{\\mathrm{paste}} \\sim U[(1 - \\sigma) \\cdot d_{\\mathrm{mean}}, (1 + \\sigma) \\cdot d_{\\mathrm{mean}}]" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "\\sigma \\in (0,1)" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": " controls the diversity of objects sizes in an image. After resizing " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{r}} \\in \\mathbb{R}^{d_{\\mathrm{paste}} \\times d_{\\mathrm{paste}} \\times 3}" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": ", the image is pasted to a random location on " + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{b}}" + }, + { + "bbox": [ + 46, + 178, + 287, + 357 + ], + "type": "text", + "content": ". This location is either a position where previously no object has been pasted, or any location in the constructed image, potentially leading to overlapping images. By default, we will use the latter." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "spans": [ + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": "Segmented pasting. Since pasting the whole image " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{r}}" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": " might violate the assumption of having a single object and results in artefacts by also pasting the background of " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{r}}" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": ", we introduce an alternative using self-supervised segmentations. This method, which we will use by default, uses an unsupervised segmentation method [51] to obtain a noisy foreground segmentation " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "\\mathbf{s} \\in [0, 1]^{d_{\\mathrm{h}} \\times d_{\\mathrm{w}}}" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": ". Instead of pasting the whole image, the segmentation " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "\\mathbf{s}" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": " is used to only copy its foreground. Additionally, having access to " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "\\mathbf{s}" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": ", this method can directly control the size of the pasted objects rather than the pasted images. To do that, we first extract the object in " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": " by computing the Hadamard product " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{object}} = \\operatorname{cut}(I \\circ \\mathbf{s})" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": " where the operation \"cut\" removes rows and columns that are completely masked out. In the next step, " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{object}} \\in \\mathbb{R}^{h_{\\mathrm{object}} \\times w_{\\mathrm{object}} \\times 3}" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": " is resized so that its maximum dimension equals " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "d_{\\mathrm{paste}}" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": " before pasting it onto " + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "inline_equation", + "content": "I_{\\mathrm{b}}" + }, + { + "bbox": [ + 46, + 357, + 287, + 548 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "spans": [ + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "content": "Exemplar selection. To construct the exemplars used for training, we exploit the information about how the sample was constructed using " + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "content": ": The set of " + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "content": " exemplars " + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "content": " is simply obtained by filtering for pasted objects that belong to the target cluster " + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "inline_equation", + "content": "c_{0}" + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "content": " and subsequently sampling " + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "content": " randomly. Then, for each of them, a crop of " + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "inline_equation", + "content": "\\tilde{I}" + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "content": " is taken as exemplar after resizing its spatial dimensions to " + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "inline_equation", + "content": "H' \\times W'" + }, + { + "bbox": [ + 46, + 549, + 286, + 632 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 647, + 189, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 647, + 189, + 658 + ], + "spans": [ + { + "bbox": [ + 47, + 647, + 189, + 658 + ], + "type": "text", + "content": "3.1.2 Density map construction" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "content": "To train our counting model, we construct an unsupervised density map " + }, + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "content": " for each training image " + }, + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\tilde{\\pmb{I}}" + }, + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "content": ". It needs to have the following two properties: i) it must sum up to the overall count of objects that we are counting and ii) it must have" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": "high values at object locations. To this end, we create " + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": " as a simple density map of Gaussian blobs as done in supervised density-based counting methods [14, 31]. For this, we use the bounding box for each pasted target image " + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "inline_equation", + "content": "I\\in \\mathcal{I}_0" + }, + { + "bbox": [ + 304, + 72, + 545, + 133 + ], + "type": "text", + "content": " and place Gaussian density at the centre and normalise it to one." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 140, + 383, + 152 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 140, + 383, + 152 + ], + "spans": [ + { + "bbox": [ + 306, + 140, + 383, + 152 + ], + "type": "text", + "content": "3.2. UnCounTR" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "spans": [ + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": "Model architecture. UnCounTR's architecture is inspired by CounTR [31]. To map an input image " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\pmb{I}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " and its exemplars " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " to a density map " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{y}}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": ", the model consists of four modules: image encoder " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\Phi" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": ", exemplar encoder " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\Psi" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": ", feature interaction module " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{fim}}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": ", and decoder " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{dec}}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": ". An overview of this architecture can be seen in Figure 2. The image encoder " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\Phi" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " encodes an image " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\pmb{I}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " into a feature map " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\mathbf{x} = \\Phi(\\pmb{I}) \\in \\mathbb{R}^{h \\times w \\times d}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "h, w, d" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " denote the height, width, and channel depth. Similarly, each exemplar " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "E \\in S" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " is projected to a single feature vector " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\mathbf{z} \\in \\mathbb{R}^d" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " by taking a weighted average of the grid features. Instead of training a CNN for an exemplar encoder as CounTR does, we choose " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\Psi = \\Phi" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " to be the frozen DINO visual encoder weights. Reusing these weights, the exemplar and image features are in the same feature space. The feature interaction module (FIM) " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{fim}}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " enriches the feature map " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " with information from the encoded exemplars " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "\\mathbf{z}_j" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "j \\in \\{1, \\dots, E\\}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " with a transformer decoder structure. Finally, the decoder " + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{dec}}" + }, + { + "bbox": [ + 304, + 159, + 545, + 421 + ], + "type": "text", + "content": " takes the resulting patch-level feature map of the FIM as input and upsamples it with 4 convolutional blocks, ending up with a density map of the same resolution as the input image. Please refer to the Appendix for the full architectural details." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "spans": [ + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "text", + "content": "UnCounTR supervision. UnCounTR is trained using the Mean Squared Error between model prediction and pseudo labels. Given a Self-Collage " + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "inline_equation", + "content": "\\tilde{I}" + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "text", + "content": ", exemplars " + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "text", + "content": ", and density map " + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "text", + "content": ", the loss " + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "text", + "content": " for an individual sample is computed using the following equation where " + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "inline_equation", + "content": "f_{\\Theta}(\\tilde{I}, S)_{ij}" + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "text", + "content": " is UnCounTR's spatially-dense output at location " + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "inline_equation", + "content": "(i, j)" + }, + { + "bbox": [ + 304, + 422, + 545, + 495 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 351, + 503, + 545, + 533 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 351, + 503, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 351, + 503, + 545, + 533 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\frac {1}{H \\cdot W} \\sum_ {i j} \\left(\\mathbf {y} _ {i j} - f _ {\\Theta} (\\tilde {\\boldsymbol {I}}, \\mathcal {S}) _ {i j}\\right) ^ {2} \\tag {3}", + "image_path": "998339ca13de93def66f86b943abca71f3ee4b6ab4b99074902a4afa3ab585d8.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 544, + 387, + 556 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 544, + 387, + 556 + ], + "spans": [ + { + "bbox": [ + 306, + 544, + 387, + 556 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 563, + 438, + 575 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 563, + 438, + 575 + ], + "spans": [ + { + "bbox": [ + 306, + 563, + 438, + 575 + ], + "type": "text", + "content": "4.1. Implementation Details" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "Datasets. To construct Self-Collages, we use ImageNet1k [13] and SUN397 [58]. ImageNet-1k contains 1.2M mostly object-centric images spanning 1000 object categories. SUN397 contains 109K images for 397 scene categories like 'cliff' or 'corridor'. Note that the object or scene category information is never used in our method. We assume that images from ImageNet-1k contain a single salient object and images from SUN397 contain no salient objects to serve as sets " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{O}" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{B}" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": ". Based on this, " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " randomly selects images from SUN397 as background images and picks objects from ImageNet-1k. Although Imagenet" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22927" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "content": "1k and SUN397 contain on average 3 and 17 objects respectively [30], these assumptions are still reasonable for our data construction. Additional ablations show that even explicitly violating the assumption of having no salient objects in " + }, + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "inline_equation", + "content": "\\mathcal{B}" + }, + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "content": " by using " + }, + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "inline_equation", + "content": "\\mathcal{O} = \\mathcal{B}" + }, + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "content": " only have a small effect on performance, indicating the robustness of our method against violations (see Appendix). An example of a Self-Collage with 5 objects can be seen in Figure 2. Examples of both datasets and a more detailed discussion of these assumptions are included in the Appendix." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 194, + 289, + 337 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 194, + 289, + 337 + ], + "spans": [ + { + "bbox": [ + 46, + 194, + 289, + 337 + ], + "type": "text", + "content": "To evaluate the counting ability, we use the standard FSC-147 dataset [45], which contains 6135 images covering 147 object categories, with counts ranging from 7 to 3731 and an average count of 56 objects per image. For each image, the dataset provides at least three randomly chosen object instances with annotated bounding boxes as exemplars. To analyse the counting ability in detailed count ranges, we partition the FSC-147 test set into three parts of roughly 400 images each, resulting in FSC-147{low,medium,high} subsets, each covering object counts from 8-16, 17-40 and 41-3701 respectively. Unless otherwise stated, we evaluate using 3 exemplars." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 339, + 289, + 471 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 339, + 289, + 471 + ], + "spans": [ + { + "bbox": [ + 46, + 339, + 289, + 471 + ], + "type": "text", + "content": "Additionally, we also use the CARPK [23] and the Multi-Salient-Object (MSO) dataset [63] for evaluation. CARPK consists of 459 images of parking lots. Each image contains between 2 and 188 cars, with an average of 103. MSO contains 1224 images covering 5 categories: " + }, + { + "bbox": [ + 46, + 339, + 289, + 471 + ], + "type": "inline_equation", + "content": "\\{0,1,2,3,4+\\}" + }, + { + "bbox": [ + 46, + 339, + 289, + 471 + ], + "type": "text", + "content": " salient objects with bounding box annotations. This dataset is largely imbalanced as 338 images contain zero salient objects and 20 images contain at least 4. For evaluation, we removed all samples with 0 counts, split the " + }, + { + "bbox": [ + 46, + 339, + 289, + 471 + ], + "type": "inline_equation", + "content": "4+" + }, + { + "bbox": [ + 46, + 339, + 289, + 471 + ], + "type": "text", + "content": " category into exact counts, and chose only one annotated object as exemplar." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "content": "Construction details. We configure the composer module to construct training samples using objects of " + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "inline_equation", + "content": "K = 10,000" + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "content": " different clusters. To always have objects of a target and a non-target cluster in each image, we set " + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "inline_equation", + "content": "t_{\\mathrm{min}} = t_{\\mathrm{max}} = 2" + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "content": ". Since the minimum number of target objects in an image limits the maximum number of exemplars available during training, we set " + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "inline_equation", + "content": "n_{\\mathrm{min}} = 3" + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "content": ", the maximum is " + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "inline_equation", + "content": "n_{\\mathrm{max}} = 20" + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "content": ". Finally, we choose " + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "inline_equation", + "content": "d_{\\mathrm{min}} = 15" + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "inline_equation", + "content": "d_{\\mathrm{max}} = 70" + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "inline_equation", + "content": "\\sigma = 0.3" + }, + { + "bbox": [ + 46, + 472, + 289, + 605 + ], + "type": "text", + "content": " to obtain diverse training images with objects of different sizes as confirmed by visual inspection of the generated Self-Collages (see the Appendix)." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "content": "Training and inference details. During training, the images are cropped and resized to " + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "inline_equation", + "content": "224 \\times 224" + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "content": " pixels. The exemplars are resized to " + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "inline_equation", + "content": "64 \\times 64" + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "content": " pixels. For each batch, we randomly draw the number of exemplars " + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "content": " to be between 1 and 3. We follow previous work [31] by scaling the loss, in our case by a factor of 3,000, and randomly dropping " + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "content": " of the non-object pixels in the density map to decrease the imbalance of object and non-object pixels. By default, we use an AdamW optimizer and a cosine-decay learning rate" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "text", + "content": "schedule with linear warmup and a maximum learning rate of " + }, + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "inline_equation", + "content": "5 \\times 10^{-4}" + }, + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "text", + "content": ". We use a batch size of 128 images. Each model is trained on an Nvidia A100 GPU for 50 epochs of 10,000 Self-Collages each, which takes about 4 hours. At inference, we use a sliding window approach similar to Liu et al. [31], see the Appendix for details. For evaluation metrics, we report Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE) following previous work [14, 31]. We also report Kendall's " + }, + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "text", + "content": " coefficient, which is a rank correlation coefficient between the sorted ground-truth counts and the predicted counts." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "spans": [ + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "content": "Baselines. To verify the effectiveness of our method, we introduce a series of baselines to compare with. (1) Average baseline: the prediction is always the average count of the FSC-147 training set, which is 49.96 objects. (2) Connected components baseline: for this, we use the final-layer attention values from the CLS-token of a pretrained DINO ViT-B/8 model. To derive a final count, we first threshold the attention map of each head to keep " + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "inline_equation", + "content": "p_{\\mathrm{att}}" + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "content": " percent of the attention mask. Subsequently, we consider each patch to where at least " + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "inline_equation", + "content": "n_{\\mathrm{head}}" + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "content": " attention heads attend to belong to an object. The number of connected components in the resulting feature map which cover more than " + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "inline_equation", + "content": "p_{\\mathrm{size}}" + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "content": " percent of the feature map is taken as prediction. To this end, we perform a grid search with almost 800 configurations of different value combinations for the three thresholds " + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "inline_equation", + "content": "p_{\\mathrm{att}}, n_{\\mathrm{head}}" + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "inline_equation", + "content": "p_{\\mathrm{size}}" + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "content": " on the FSC-147 training set and select the best configuration based on the MAE. The specific values tested can be found in the Appendix. (3) FasterRCNN baseline: we run the strong image detection toolbox FasterRCNN [46] with a score threshold of 0.5 on the image, which predicts a number of object bounding boxes. Then the object count is obtained by parsing the detection results by taking the total number of detected bounding boxes. Just like the connected components baseline, this model is applied to images resized to " + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "inline_equation", + "content": "384 \\times 384" + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "content": " pixels. (4) DETR baseline: similar to FasterRCNN, we evaluate the detection model DETR [5] on the counting task. Here, we resize the images to " + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "inline_equation", + "content": "800 \\times 800" + }, + { + "bbox": [ + 304, + 205, + 547, + 540 + ], + "type": "text", + "content": " pixels to better match DETR's evaluation protocol." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 551, + 469, + 563 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 551, + 469, + 563 + ], + "spans": [ + { + "bbox": [ + 305, + 551, + 469, + 563 + ], + "type": "text", + "content": "4.2. Comparison against baselines" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": "In Table 1, we compare against multiple baselines on the three splits of FSC-147. As the connected components cannot leverage the additional information of the few-shot samples provided, we try to make the comparison as fair as possible, by testing almost 800 threshold parameters on the FSC-147 training set. While this yields a strong baseline, we find that our method of learning with Self-Collages more than halves the MAE on the low split, despite using a similar visual backbone. Next, we compare against the FasterRCNN and DETR object detectors which, unlike UnCounTR, are trained in a supervised fashion. Even though DETR outperforms UnCounTR in terms of RMSE on FSC" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22928" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 99, + 64, + 492, + 165 + ], + "blocks": [ + { + "bbox": [ + 99, + 64, + 492, + 165 + ], + "lines": [ + { + "bbox": [ + 99, + 64, + 492, + 165 + ], + "spans": [ + { + "bbox": [ + 99, + 64, + 492, + 165 + ], + "type": "table", + "html": "
MethodFSC-147 lowFSC-147 mediumFSC-147 high
MAE↓RMSE↓τ↑MAE↓RMSE↓τ↑MAE↓RMSE↓τ↑
Average37.7137.79-22.7423.69-68.88213.08-
Conn. Comp.14.7118.590.1414.1917.900.1669.77210.540.17
FasterRCNN7.068.46-0.0319.8722.25-0.04109.12230.35-0.06
DETR6.928.200.0719.3321.56-0.08109.34162.88-0.07
UnCounTR (ours)5.6010.130.279.4812.730.3467.17189.760.26
σ(5 runs)±0.48±0.84±0.02±0.19±0.33±0.02±1.03±1.38±0.01
", + "image_path": "3a2962f6a45ef66a113ce2ca5c06b880d2099b95af29d9014c4ea8fbe124ed82.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 55, + 180, + 267, + 247 + ], + "blocks": [ + { + "bbox": [ + 59, + 167, + 533, + 178 + ], + "lines": [ + { + "bbox": [ + 59, + 167, + 533, + 178 + ], + "spans": [ + { + "bbox": [ + 59, + 167, + 533, + 178 + ], + "type": "text", + "content": "Table 1. Comparison to baselines. Evaluation on different FSC-147 test subsets. \"Conn. Comp.\" refers to connected components." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 55, + 180, + 267, + 247 + ], + "lines": [ + { + "bbox": [ + 55, + 180, + 267, + 247 + ], + "spans": [ + { + "bbox": [ + 55, + 180, + 267, + 247 + ], + "type": "table", + "html": "
Frozen ΦFrozen ΨFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
XX37.64126.917.9913.37
✓X36.94130.229.1014.69
✓✓35.77130.345.6010.13
", + "image_path": "7b923d8bd6e9807bfb4fe109791ef91816385259c62e28619d29affdd944d441.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 83, + 268, + 239, + 322 + ], + "blocks": [ + { + "bbox": [ + 47, + 248, + 272, + 266 + ], + "lines": [ + { + "bbox": [ + 47, + 248, + 272, + 266 + ], + "spans": [ + { + "bbox": [ + 47, + 248, + 272, + 266 + ], + "type": "text", + "content": "(a) Keeping both image encoder " + }, + { + "bbox": [ + 47, + 248, + 272, + 266 + ], + "type": "inline_equation", + "content": "\\Phi" + }, + { + "bbox": [ + 47, + 248, + 272, + 266 + ], + "type": "text", + "content": " and exemplar encoder " + }, + { + "bbox": [ + 47, + 248, + 272, + 266 + ], + "type": "inline_equation", + "content": "\\Psi" + }, + { + "bbox": [ + 47, + 248, + 272, + 266 + ], + "type": "text", + "content": " frozen works best." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 83, + 268, + 239, + 322 + ], + "lines": [ + { + "bbox": [ + 83, + 268, + 239, + 322 + ], + "spans": [ + { + "bbox": [ + 83, + 268, + 239, + 322 + ], + "type": "table", + "html": "
FSC-147FSC-147 low
nmaxMAE↓RMSE↓MAE↓RMSE↓
5030.17115.426.6513.60
2035.77130.345.6010.13
", + "image_path": "39d23acf56e75e0f7cc4a3c6d7ed241d3ed3368cdc5fc5e0a5ff7fdc42df9f66.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + } + ], + "index": 4 + }, + { + "type": "table", + "bbox": [ + 326, + 181, + 524, + 246 + ], + "blocks": [ + { + "bbox": [ + 59, + 323, + 261, + 333 + ], + "lines": [ + { + "bbox": [ + 59, + 323, + 261, + 333 + ], + "spans": [ + { + "bbox": [ + 59, + 323, + 261, + 333 + ], + "type": "text", + "content": "(c) The number of pasted objects correlates with performance." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 326, + 181, + 524, + 246 + ], + "lines": [ + { + "bbox": [ + 326, + 181, + 524, + 246 + ], + "spans": [ + { + "bbox": [ + 326, + 181, + 524, + 246 + ], + "type": "table", + "html": "
Segm.Overlap.FSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
✓✘36.47128.978.8414.54
✘✓37.46136.036.3311.55
✓✓35.77130.345.6010.13
", + "image_path": "ac6621be764465a03d5afc7ac5b663decd912e8ce11fa7a2c4393f48051fb87f.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_body" + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 335, + 268, + 516, + 321 + ], + "blocks": [ + { + "bbox": [ + 304, + 248, + 545, + 266 + ], + "lines": [ + { + "bbox": [ + 304, + 248, + 545, + 266 + ], + "spans": [ + { + "bbox": [ + 304, + 248, + 545, + 266 + ], + "type": "text", + "content": "(b) Using both segmented objects and allowing for overlapping objects works well." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 335, + 268, + 516, + 321 + ], + "lines": [ + { + "bbox": [ + 335, + 268, + 516, + 321 + ], + "spans": [ + { + "bbox": [ + 335, + 268, + 516, + 321 + ], + "type": "table", + "html": "
#ExemplarsFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
0 - 336.28131.446.2310.33
1 - 335.77130.345.6010.13
", + "image_path": "43097ebae022121daeba346eda5444284a248845f86edfe6866b6dc226264b1f.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 338, + 546, + 361 + ], + "lines": [ + { + "bbox": [ + 46, + 338, + 546, + 361 + ], + "spans": [ + { + "bbox": [ + 46, + 338, + 546, + 361 + ], + "type": "text", + "content": "Table 2. Ablations. We ablate various components of our model architecture and Self-Collage construction method. Default settings are highlighted in grey." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "text" + }, + { + "type": "table", + "bbox": [ + 53, + 366, + 279, + 430 + ], + "blocks": [ + { + "bbox": [ + 310, + 323, + 539, + 333 + ], + "lines": [ + { + "bbox": [ + 310, + 323, + 539, + 333 + ], + "spans": [ + { + "bbox": [ + 310, + 323, + 539, + 333 + ], + "type": "text", + "content": "(d) Training our method strictly in the 1-3 exemplar setting works best." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 53, + 366, + 279, + 430 + ], + "lines": [ + { + "bbox": [ + 53, + 366, + 279, + 430 + ], + "spans": [ + { + "bbox": [ + 53, + 366, + 279, + 430 + ], + "type": "table", + "html": "
ArchitecturePretrainingFSC-147FSC-147 low
MAE↓RMSE↓MAE↓RMSE↓
ViT-B/8Leopard [67]36.04126.755.7210.67
ViT-B/8DINO [7]38.16132.096.109.79
ViT-B/16DINO [7]35.77130.345.6010.13
", + "image_path": "446373c2e66a404e82330fc9d028a346b77e62ef151726a1cc256deafdab529b.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 478, + 287, + 574 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 478, + 287, + 574 + ], + "spans": [ + { + "bbox": [ + 46, + 478, + 287, + 574 + ], + "type": "text", + "content": "147 low and high, we find that our method still outperforms all baselines on 7 out of 9 measures. This is despite the additional advantages such as access to the FSC-147 training distribution for these baselines. The gap between most baselines and UnCounTR is the smallest on the high split, suggesting limits to its generalisation which we will explore further in the Appendix. There, we also provide a qualitative analysis of some failure cases of FasterRCNN." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 585, + 141, + 597 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 585, + 141, + 597 + ], + "spans": [ + { + "bbox": [ + 47, + 585, + 141, + 597 + ], + "type": "text", + "content": "4.3. Ablation Study" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 604, + 287, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 604, + 287, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 604, + 287, + 628 + ], + "type": "text", + "content": "We analyse the various components of our method in Tables 2a to 2d." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "text", + "content": "Keeping backbone frozen works best. In Table 2a, we evaluate the effect of unfreezing the last two backbone blocks shared by " + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\Phi" + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\Psi" + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "text", + "content": ". In addition, we test training a CNN-based encoder " + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\Psi" + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "text", + "content": " from scratch similar to Liu et al. [31]. We find that keeping both frozen, i.e. " + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\Phi = \\Psi =" + }, + { + "bbox": [ + 46, + 629, + 287, + 713 + ], + "type": "text", + "content": " const. works best, as it discourages the visual features to adapt to potential artefacts in our Self-Collages." + } + ] + } + ], + "index": 16 + }, + { + "type": "table", + "bbox": [ + 323, + 361, + 526, + 440 + ], + "blocks": [ + { + "bbox": [ + 46, + 433, + 286, + 466 + ], + "lines": [ + { + "bbox": [ + 46, + 433, + 286, + 466 + ], + "spans": [ + { + "bbox": [ + 46, + 433, + 286, + 466 + ], + "type": "text", + "content": "Table 3. Combining Self-Collages with different backbones. We can apply our method to any recent state-of-the-art pretrained network and achieve strong performances." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 323, + 361, + 526, + 440 + ], + "lines": [ + { + "bbox": [ + 323, + 361, + 526, + 440 + ], + "spans": [ + { + "bbox": [ + 323, + 361, + 526, + 440 + ], + "type": "table", + "html": "
MethodsValTest
MAE↓RMSE↓MAE↓RMSE↓
CounTR [31]13.1349.8311.9591.23
LOCA [14]10.2432.5610.7956.97
UnCounTR (ours)36.93106.6135.77130.34
σ(5 runs)±0.49±1.46±0.60±0.94
", + "image_path": "9dba39523a9f1e2d3f3665d05d38783f2615c0201252276a095e903d7c63be04.jpg" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "table_body" + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 442, + 545, + 464 + ], + "lines": [ + { + "bbox": [ + 305, + 442, + 545, + 464 + ], + "spans": [ + { + "bbox": [ + 305, + 442, + 545, + 464 + ], + "type": "text", + "content": "Table 4. Comparison to supervised models. We evaluate on the val and test split of FSC-147." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 473, + 545, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 545, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 545, + 616 + ], + "type": "text", + "content": "Benefit of self-supervised exemplars. In Table 2d we evaluate the effect of including the zero-shot counting task (i.e. counting all salient objects) as done in other works [14, 31]. However, we find that including this task even with only a " + }, + { + "bbox": [ + 304, + 473, + 545, + 616 + ], + "type": "inline_equation", + "content": "25\\%" + }, + { + "bbox": [ + 304, + 473, + 545, + 616 + ], + "type": "text", + "content": " chance leads to a lower performance. This is likely due to the zero-shot task overfitting our Self-Collages and finding short-cuts, such as pasting artefacts, as we relax the constraint introduced in Section 3.1.1 and vary the number of pasted objects to match the desired target. We therefore train our model with 1-3 exemplars and show how we can still conduct semantic zero-shot counting in Section 4.7." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "text", + "content": "Maximum number of pasted objects. Next, we evaluate the effect of varying " + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "inline_equation", + "content": "n_{\\mathrm{max}}" + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "text", + "content": ", the maximum number of objects pasted, as shown in Table 2c. Pasting up to 50 objects yields overall better performance on the full FSC-147 test dataset which contains on average 66 objects. While this shows that the construction of Self-Collages can be successfully scaled to higher counts, we find that pasting with 20 objects already achieves good performance with shortened" + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22929" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 69, + 67, + 523, + 135 + ], + "blocks": [ + { + "bbox": [ + 69, + 67, + 523, + 135 + ], + "lines": [ + { + "bbox": [ + 69, + 67, + 523, + 135 + ], + "spans": [ + { + "bbox": [ + 69, + 67, + 523, + 135 + ], + "type": "table", + "html": "
MethodFSC-147 low (8-16 objects)FSC-147 medium (17-40 objects)FSC-147 high (41-3701 objects)
MAE↓RMSE↓Δτ↑MAE↓RMSE↓Δτ↑MAE↓
CounTR6.5848.110.424.4810.020.6020.50
UnCounTR (ours)5.6010.13-37.90.279.4812.73+2.70.3467.17
σ(5 runs)±0.48±0.84±0.02±0.19±0.33±0.02±1.03
", + "image_path": "0e6df28a2f9ad3f2efe380dd3f2e54f295b22b63842450b61b192c11c3e392d1.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 72, + 150, + 261, + 231 + ], + "blocks": [ + { + "bbox": [ + 115, + 138, + 476, + 148 + ], + "lines": [ + { + "bbox": [ + 115, + 138, + 476, + 148 + ], + "spans": [ + { + "bbox": [ + 115, + 138, + 476, + 148 + ], + "type": "text", + "content": "Table 5. Comparison to CounTR. Evaluation results on the FSC-147 low and medium test subsets." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 72, + 150, + 261, + 231 + ], + "lines": [ + { + "bbox": [ + 72, + 150, + 261, + 231 + ], + "spans": [ + { + "bbox": [ + 72, + 150, + 261, + 231 + ], + "type": "table", + "html": "
MethodMSO
MAE↓RMSE↓τ↑
Conn. Comp. Baseline10.6712.880.12
CounTR2.348.120.36
UnCounTR (ours)1.072.320.45
σ(5 runs)±0.06±0.25±0.01
", + "image_path": "77ddc51f7803293020d3eb256eea48bad03062bf10532cd4050c63cf0fbc274d.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 331, + 151, + 519, + 230 + ], + "blocks": [ + { + "bbox": [ + 78, + 232, + 252, + 243 + ], + "lines": [ + { + "bbox": [ + 78, + 232, + 252, + 243 + ], + "spans": [ + { + "bbox": [ + 78, + 232, + 252, + 243 + ], + "type": "text", + "content": "Table 6. Evaluation on the MSO [63] dataset." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 331, + 151, + 519, + 230 + ], + "lines": [ + { + "bbox": [ + 331, + 151, + 519, + 230 + ], + "spans": [ + { + "bbox": [ + 331, + 151, + 519, + 230 + ], + "type": "table", + "html": "
MethodCARPK
MAE↓RMSE↓τ↑
Conn. Comp. Baseline49.6254.500.56
CounTR19.6229.700.57
UnCounTR (ours)30.3535.670.54
σ(5 runs)±2.26±2.36±0.06
", + "image_path": "e8fa6bcc1ec9511ac305ede15d6a63b8c50feae1bcce96d44b293d7e4a278439.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 251, + 216, + 262 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 251, + 216, + 262 + ], + "spans": [ + { + "bbox": [ + 47, + 251, + 216, + 262 + ], + "type": "text", + "content": "construction times and so use this setting." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 262, + 287, + 323 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 262, + 287, + 323 + ], + "spans": [ + { + "bbox": [ + 46, + 262, + 287, + 323 + ], + "type": "text", + "content": "Segmented pasting works best. From Table 2b, We find that the best construction strategy involves pasting the self-supervised segmentations, regardless of their overlap with other objects. We simply store the segmentations and combine these to create diverse Self-Collages at training time." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 324, + 287, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 324, + 287, + 491 + ], + "spans": [ + { + "bbox": [ + 46, + 324, + 287, + 491 + ], + "type": "text", + "content": "Compatible with various pretrained backbones. In Table 3, we show the effect of using different frozen weights for the visual encoder. Across ViT-B models with varying patch sizes and pretrainings, from Leopart's [67] spatially dense to the original DINO's [7] image-level pretraining, we find similar performances across our evaluations. This shows that our method is compatible with various architectures and pretrainings and will likely benefit from the continued progress in self-supervised representation learning which is supported by our findings based on DINOv2 [40] presented in the Appendix. We do not find any benefit in going from patch size 16 to 8 (similar to Simeoni et al. [52]) so we use the faster DINO ViT-B/16 model for the rest of the paper." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 502, + 181, + 514 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 502, + 181, + 514 + ], + "spans": [ + { + "bbox": [ + 47, + 502, + 181, + 514 + ], + "type": "text", + "content": "4.4. Benchmark comparison" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 521, + 287, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 521, + 287, + 688 + ], + "spans": [ + { + "bbox": [ + 46, + 521, + 287, + 688 + ], + "type": "text", + "content": "Next, we compare with previous methods on three datasets: FSC-147 [45], MSO [63], and CARPK [23]. Table 4 shows the results on the validation and test split of the FSC-147 dataset. In contrast to our approach, which investigates the feasibility of learning to count without any reliance on supervised data, these methods heavily depend on manual annotations. Hence, the comparison is certainly not fair: (1) our method does not use manually annotated counting data, also has never seen any FSC-147 training images, (2) our training samples based on Self-Collages only cover 3-19 target objects, whereas the full test set of FSC-147 has 66 objects on average. Evaluating our method on the full set of FSC-147 is actually evaluating the transferring ability as discussed in more detail in the Appendix." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "We choose CounTR [31] for further analysis because of its similar architecture to UnCounTR. To fairly com" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 331, + 232, + 516, + 243 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 331, + 232, + 516, + 243 + ], + "spans": [ + { + "bbox": [ + 331, + 232, + 516, + 243 + ], + "type": "text", + "content": "Table 7. Evaluation on the CARPK [23] dataset." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 249, + 545, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 249, + 545, + 357 + ], + "spans": [ + { + "bbox": [ + 304, + 249, + 545, + 357 + ], + "type": "text", + "content": "pare with this method, we trisect the FSC-147 test set as described in Section 4.1. Table 5 shows the evaluation results on the three partitions. It is remarkable that our method outperforms supervised CounTR on the low partition, especially on the RMSE metric (10.13 vs 48.11). Also, our method is not far from CounTR's performance on the medium partition (e.g. RMSE 12.7 vs 10.02), showing a reasonable transferring ability since the model is trained with up to 19 object counts only." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 357, + 546, + 489 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 357, + 546, + 489 + ], + "spans": [ + { + "bbox": [ + 304, + 357, + 546, + 489 + ], + "type": "text", + "content": "Additionally, Table 6 compares our method with the connected components baseline and CounTR on a subset of MSO as described in Section 4.1. The results show our self-supervised method outperforms the supervised CounTR model by a large margin on the lower counts tasks. In Table 7, the performance on the CARPK dataset is shown. We use the same CounTR model finetuned on the FSC-147 dataset as before to compare the generalisation across datasets. While the MAE of CounTR almost doubles compared to the results on the FSC-147 test set, UnCounTR's performance is more stable, improving by " + }, + { + "bbox": [ + 304, + 357, + 546, + 489 + ], + "type": "inline_equation", + "content": "15\\%" + }, + { + "bbox": [ + 304, + 357, + 546, + 489 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 498, + 487, + 510 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 498, + 487, + 510 + ], + "spans": [ + { + "bbox": [ + 306, + 498, + 487, + 510 + ], + "type": "text", + "content": "4.5. Qualitative results and limitations" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 517, + 545, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 517, + 545, + 661 + ], + "spans": [ + { + "bbox": [ + 304, + 517, + 545, + 661 + ], + "type": "text", + "content": "Figure 3 shows a few qualitative results to demonstrate our method's effectiveness and its limitations. The model is able to correctly predict the number of objects for clearly separated and slightly overlapping instances (e.g. Subfigures a and c). The model also successfully identifies the object type of interest, e.g. in Subfigure b the density map correctly highlights the strawberries rather than blueberries. One limitation of our model is images where the number of objects is ambiguous. For example, in Subfigure d, the prediction missed a few burgers which are possibly the ones partially shown on the edge. However, it is also difficult for humans to decide which of those objects should be counted." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 670, + 462, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 670, + 462, + 682 + ], + "spans": [ + { + "bbox": [ + 306, + 670, + 462, + 682 + ], + "type": "text", + "content": "4.6. 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"Figure 4. Self-supervised semantic counting. 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Qualitative examples of UnCounTR's predictions. We show predictions on four images from the FSC-147 test set, the green boxes represent the exemplars. Our predicted count is the sum of the density map rounded to the nearest integer." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 432, + 292, + 535, + 333 + ], + "lines": [ + { + "bbox": [ + 432, + 292, + 535, + 333 + ], + "spans": [ + { + "bbox": [ + 432, + 292, + 535, + 333 + ], + "type": "image", + "image_path": "61c003a5409ab3410ce4b846971eff438dd7d14358c2836447ec924345ec40ae.jpg" + } + ] + } + ], + "index": 25, + "angle": 0, + "type": "image_body" + } + ], + "index": 25 + }, + { + "type": "image", + "bbox": [ + 432, + 341, + 536, + 383 + ], + "blocks": [ + { + "bbox": [ + 432, + 341, + 536, + 383 + ], + "lines": [ + { + "bbox": [ + 432, + 341, + 536, + 383 + ], + "spans": [ + { + "bbox": [ + 432, + 341, + 536, + 383 + ], + "type": "image", + "image_path": "094c0fefa8abf97b0577b196a90582769bfd33233fc5ace9610a063440f90ccd.jpg" + } + ] + } + ], + "index": 26, + "angle": 0, + "type": "image_body" + } + ], + "index": 26 + }, + { + "bbox": [ + 46, + 433, + 287, + 540 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 433, + 287, + 540 + ], + "spans": [ + { + "bbox": [ + 46, + 433, + 287, + 540 + ], + "type": "text", + "content": "performance: (1) Integrating the DINOV2 [40] backbone improves the MAE particularly on the FSC-147 low set by " + }, + { + "bbox": [ + 46, + 433, + 287, + 540 + ], + "type": "inline_equation", + "content": "27\\%" + }, + { + "bbox": [ + 46, + 433, + 287, + 540 + ], + "type": "text", + "content": " (2) Using cluster similarity to create more challenging Self-Collages reduces the MAE on FSC-147 to 31.06 (3) Refining high-count predictions further improves performance yielding the final UnCounTRv2 model. It achieves an MAE of 28.67 on FSC-147 and 3.88 on FSC-147 low. For a comprehensive discussion, please refer to the Appendix. See Figure 1 for a visual comparison with CounTR." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 47, + 550, + 230, + 563 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 550, + 230, + 563 + ], + "spans": [ + { + "bbox": [ + 47, + 550, + 230, + 563 + ], + "type": "text", + "content": "4.7. Self-supervised semantic counting" + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 46, + 570, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 288, + 713 + ], + "type": "text", + "content": "In this last section, we explore the potential of UnCounTR for more advanced counting tasks. In particular, we test whether our model can not only unsupervisedly count different kinds of objects in an image, but also determine the categories by itself, a scenario we refer to as semantic counting. To this end, we use a simple pipeline that picks an area surrounding the maximum in the input image's CLS-attention map as the first input and refines it to obtain an exemplar. Next, UnCounTR predicts the number of objects in the image based on the self-constructed exemplar. Finally, the locations that have been detected using this procedure are removed from the initial attention map and if" + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 305, + 433, + 545, + 481 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 433, + 545, + 481 + ], + "spans": [ + { + "bbox": [ + 305, + 433, + 545, + 481 + ], + "type": "text", + "content": "the remaining attention values are high enough, the process is repeated to count objects of another type. We provide the details of this method in the Appendix. In Figure 4, we demonstrate results on two difficult real images." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 306, + 495, + 378, + 506 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 495, + 378, + 506 + ], + "spans": [ + { + "bbox": [ + 306, + 495, + 378, + 506 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 32 + }, + { + "bbox": [ + 304, + 514, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 514, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 514, + 545, + 713 + ], + "type": "text", + "content": "In this work, we have introduced UnCounTR, showcasing, for the first time, the capability of reference-based counting without relying on human supervision. To this end, our method constructs Self-Collages, a simple unsupervised way of generating proxy learning signals from unlabeled data. Our results demonstrate that by utilising an off-the-shelf unsupervisedly pretrained visual encoder, we can learn counting models that can even outperform strong baselines such as DETR and achieve similar performances to dedicated counting models such as CounTR on CARPK, MSO, and various splits of FSC-147. Finally, we have shown that our model can unsupervisedly identify multiple exemplars in an image and count them, something no supervised model can yet do. 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Ryoo² Tsung-Yu Lin1", + "bbox": [ + 330, + 198, + 632, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{1}$ Meta $^{2}$ Stony Brook University", + "bbox": [ + 346, + 223, + 616, + 241 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{kranasinghe, mryoo}@cs.stonybrook.edu, {satyanshukla, opoursaed, tsungyulin}@meta.com", + "bbox": [ + 99, + 244, + 864, + 260 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 282, + 312, + 297 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Integration of Large Language Models (LLMs) into visual domain tasks, resulting in visual-LLMs (V-LLMs), has enabled exceptional performance in vision-language tasks, particularly for visual question answering (VQA). However, existing V-LLMs (e.g. BLIP-2, LLaVA) demonstrate weak spatial reasoning and localization awareness. Despite generating highly descriptive and elaborate textual answers, these models fail at simple tasks like distinguishing a left vs right location. In this work, we explore how image-space coordinate based instruction fine-tuning objectives could inject spatial awareness into V-LLMs. We discover optimal coordinate representations, data-efficient instruction fine-tuning objectives, and pseudo-data generation strategies that lead to improved spatial awareness in V-LLMs. Additionally, our resulting model improves VQA across image and video domains, reduces undesired hallucination, and generates better contextual object descriptions. Experiments across 5 vision-language tasks involving 14 different datasets establish the clear performance improvements achieved by our proposed framework.", + "bbox": [ + 75, + 311, + 473, + 613 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 630, + 207, + 645 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Holistic visual understanding requires learning beyond simply content of an image to encompass awareness on spatial locations of objects and their relations [41]. In the context of visual question answering (VQA), such spatial awareness allows better reasoning involving structural and contextual information contained within an image [8].", + "bbox": [ + 75, + 655, + 468, + 747 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Since the introduction of powerful large-language models (LLMs) such as GPT-3 [5], Chat-GPT [44], Vicuna [11], and LLaMA [55, 56] that are capable of human style conversation, their visual counterparts such as BLIP-2 [33], LLaVA [38] have enabled novel tasks within the vision modality. However, despite their [33, 38] highly generic visual understanding, these models exhibit poor language-based spatial reasoning [8]. In fact, they fail at simple tasks such as distinguishing whether an object lies to the left or right of another object (see Tab. 4).", + "bbox": [ + 75, + 750, + 470, + 901 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/220434e2d7b3dce9eb28b3d773ce89703207a01a2e63d1f032250d7bd78dd8c2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 519, + 282, + 687, + 454 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Query: Describe [x1,y1,x2,y2] location in image.", + "bbox": [ + 694, + 289, + 859, + 311 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Ours: A blue plaid blanket behind a teddy bear.", + "bbox": [ + 694, + 318, + 839, + 340 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Query: Which side of the potted plant is the stove?", + "bbox": [ + 702, + 359, + 852, + 382 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "LLaVa: The stove is on the left side of potted plant.", + "bbox": [ + 702, + 390, + 859, + 412 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Ours: The stove is on the right side of potted plant.", + "bbox": [ + 702, + 422, + 852, + 445 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/831c277cee537b96e010839838bb2f33703db97f6af9885cce63fb83ddf493ab.jpg", + "image_caption": [ + "Figure 1. We illustrate one unique ability of our model: contextual region description (top). Note the contextual information used in describing the selected region in each image. Explicitly teaching localization to Visual-LLMs also improves spatial awareness in VQA settings (bottom). Color boxes only for illustration purposes." + ], + "image_footnote": [], + "bbox": [ + 519, + 453, + 870, + 612 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In the case of contrastive language image models (such as CLIP [46], ALIGN [26]), recent works explore how injecting explicit spatial awareness [39, 43, 48, 74] can enable more holistic visual understanding. In fact, [48] shows how such improved spatial awareness benefits model robustness in adversarial domains. This raises the question of how generative language image models, particularly those connecting LLMs to visual encoders [33, 38] can benefit from such spatial awareness specific training. We refer to models of this category that generate textual outputs given joint image-text inputs (e.g. [33, 38]) as visual-LLMs (V-LLMs).", + "bbox": [ + 496, + 700, + 892, + 867 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In this work, we explore location specific instruction fine-tuning objectives that explicitly enforce V-LLMs to", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "12977", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "meaningfully process and generate textual image-space coordinates. We hypothesize that such training would lead to improved spatial awareness in these V-LLMs, therein improving performance on VQA tasks. To this end, we propose three instruction fine-tuning objectives that unify location representation with natural language. We also explore optimal representation forms for image-space locations and how pseudo-data generation can be leveraged for efficient scaling of our framework. We name our resulting model as LocVLM.", + "bbox": [ + 75, + 90, + 472, + 241 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "While the idea of adapting V-LLMs to perform localization related tasks (e.g. detection, segmentation) using V-LLMs has been explored in multiple recent works [30, 45, 58, 66, 68, 73, 75], these approaches depend on task specific architectural modifications or treat localization inputs / outputs differently from natural language. In contrast, our LocVLM focuses on a unified framework treating location and language as a single modality of inputs with the goal of complementing performance in each task. We intuit that processing location represented in textual form would enforce the LLM to select appropriate image regions as opposed to relying on region level features provided by the architecture. At the same time, textual form location outputs promote spatial awareness at language level in a human interpretable manner, in contrast to using secondary heads or specialized tokens for location prediction. Concurrent work in [8] also explores textual location representation with a generic V-LLM architecture similar to our work. Our proposed LocVLM differs with focus on optimal location representation forms, data-efficient pseudo-labelling, and video domain operation.", + "bbox": [ + 75, + 246, + 472, + 564 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our proposed framework exhibits improved spatial awareness in VQA style conversation demonstrated through experimentation on 14 datasets across 5 vision-language tasks: Spatial Reasoning, Image VQA, Video VQA, Object Hallucination, and Region Description. We summarize our key contributions as follows:", + "bbox": [ + 75, + 568, + 470, + 657 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Inject textual spatial coordinate awareness into V-LLMs", + "- Propose three novel localization based instruction finetuning objectives for V-LLMs", + "- Discover optimal coordinate representation forms", + "- Pseudo-Data generation for improved region description and scaling to video domain" + ], + "bbox": [ + 78, + 662, + 468, + 753 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 768, + 218, + 784 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Localization in Contrastive Vision Language Models: Foundation vision language models (VLMs) such as CLIP [46] resulted in extensive exploration into language-tied localization in images both under dense (pixel / bounding-box) supervision [16-18, 21, 27, 31, 32, 35, 69, 70] and weak supervision [14, 39, 43, 48, 60, 61, 65, 74, 76]. Recovering explicit localization information within model rep", + "bbox": [ + 75, + 794, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "table", + "img_path": "images/327ac50a8a9f0c400f3023d2108154adc590c1be126b3826b790bafc5b5ba5b3.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodKosmos [45]Ferret [66]Shikra [8]Ours
Unified Arch.XX✓✓
Purely TextualXX✓✓
Pseudo DataXXX✓
Video DomainXXX✓
", + "bbox": [ + 506, + 88, + 883, + 170 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Table 1. Related Work Comparison: A unified architecture, purely textual inputs, pseudo data for scalable learning, and video domain operation distinguishes our work from these prior methods.", + "bbox": [ + 498, + 174, + 893, + 217 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "resentations has enabled more robust operation for certain tasks [48]. While our work differs from this contrastive setting given our use of LLM based generative predictions, we similarly explore how explicit location information within the language modality can improve V-LLMs.", + "bbox": [ + 496, + 237, + 893, + 313 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Visual Large Language Models (V-LLMs): The advent of powerful large language models (LLMs) such as GPT-3 [5], Chat-GPT [44], and PaLM [13], as well as their open-source counterparts BLOOM [52], Vicuna [11], and LLaMA [55, 56], has resulted in direct use of these LLMs for computer vision tasks [22, 53]. Alternate lines of work explore how LLMs can be connected to existing visual foundation models [2, 3, 33, 38, 42, 47], in particular to CLIP visual backbones [46]. While earlier models explored large-scale (millions to billions of samples) image-text training [2, 3], later models [33, 38, 42] scale down on data dependency. LLaVA [38] in particular scales down on pre-training data to under 1 million image-text pairs, and use instruction fine-tuning [59] to enable human-style conversation with visual awareness. This is extended to video domain in [42, 49]. A shortcoming of these models is their lack of spatial awareness or location understanding in image space [8, 12, 20]. Spatial reasoning limitations in generative VLMs are studied in [12, 20]. Similar failures in captioning (and VQA) models are explored in [28]. A solution in [24] proposes code-generation based reasoning. Our work tackles these same limitations but follows an alternate direction of spatial-aware instruction fine-tuning. Another line of recent works [30, 45, 58, 66, 68, 73, 75] tackle this by introducing architectural modifications to explicitly extract region level features that are injected to the LLM as special tokens. While introducing extra tokens and layers, this also separates the localization task from language. In contrast, we use a generic architectures with purely textual location information (i.e. image space coordinates as text). Concurrent work in [8] explores this same idea, but we differ in 3 ways with, a) focus on optimal coordinate representation forms, b) data-efficient pseudo-labelling strategies, and c) video domain operation (see also Tab. 1).", + "bbox": [ + 496, + 319, + 892, + 834 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Location Representations: Selecting regions within an image has a rich history in computer vision [40, 57] with greater focus on location outputs since the popularity of object detection [6, 9, 10, 19, 50, 54, 58]. Early anchor-based", + "bbox": [ + 496, + 839, + 893, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "12978", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "methods regress locations from anchor centers [19, 50], followed by direct location regression from object-level features [6, 54]. Recent works explore generative location predictions with diffusion processes [9] and sequence-generation [10, 58]. Ours resembles the latter given our use of an LLM, next token prediction objective, and sequential generation of textual location representations. However, [10, 58] utilize 1000 specialized location tokens (introduced to the LLM vocabulary) corresponding to 1000 bins uniformly spread across image space. While we explore similar binning strategies, in contrast we introduce no additional tokens, focus on purely textual representation of locations, and explore multiple textual location representation forms.", + "bbox": [ + 75, + 90, + 472, + 287 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 297, + 168, + 314 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Current V-LLMs [33, 38] exhibit weak understanding of spatial locations within images [8]. We explore and benchmark such shortcomings, and propose three novel instruction fine-tuning objectives aimed at overcoming these drawbacks of existing V-LLMs. We build these objectives based on spatial-coordinate based prompting and demonstrate how LLMs can directly both process and generate meaningful numerical coordinates in image-space after suitable training. In the rest of this section we describe our architecture and training framework, followed by coordinate processing & generation, instruction fine-tuning objectives, pseudo-data generation, and video domain operation.", + "bbox": [ + 75, + 323, + 468, + 505 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Architecture and Training", + "text_level": 1, + "bbox": [ + 76, + 512, + 316, + 527 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The focus of our work is to explore how spatial localization related training can improve a generic V-LLM such as LLaVA [38]. Therein, our architecture and training framework is inspired from [38]. We use a visual encoder, adapter layer, and LLM stacked sequentially (illustrated in Fig. 2), and follow a multi-stage training strategy similar to [38].", + "bbox": [ + 75, + 535, + 468, + 626 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Consider an image $X \\in \\mathbb{R}^{H, W, C}$ where $H, W, C (= 3)$ denote height, width, channels of image and a textual prompt $T$ composed of natural language (asking a question about the image). We define two variants of our model, LocVLM-B and LocVLM-L for better comparison with prior work. We first describe LocVLM-B that processes images with $H = W = 224$ . Our visual encoder, ViTL/14 from CLIP [46], processes the image $X$ to produce a set of 256 visual tokens in $\\mathbb{R}^{1024}$ , which are in turn projected to $\\mathbb{R}^{4096}$ by an adapter layer (implemented as a linear layer). The LLaMA [55] text tokenizer processes the textual prompt $T$ to produce textual tokens in $\\mathbb{R}^{4096}$ . The joint set of visual and textual tokens (of dimension $\\mathbb{R}^{4096}$ ) are processed by a LLaMA [55] LLM to produce the final set of textual tokens which are in turn untokenized to convert to natural language. The final natural language output is expected to be a suitable response to the input textual prompt, $T$ . In variant LocVLM-L, we use images sized", + "bbox": [ + 75, + 627, + 470, + 901 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/150a99aba89437f0a65a9356ecfbebc7567c3a463cfd9d2afc33ae576d288ffe.jpg", + "image_caption": [ + "Figure 2. Architecture: We present the overall model architecture of our framework which is inspired from LLaVa [38]." + ], + "image_footnote": [], + "bbox": [ + 522, + 98, + 869, + 330 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "$H = W = 336$ resulting in 576 visual token, an adapter layer implemented as an MLP, and the LLM from LLaMA-2 [56]. All other design choices remain unchanged.", + "bbox": [ + 498, + 385, + 890, + 431 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We also highlight the BPE tokenization that is employed in our setup. This learned tokenization scheme may split a single word into sub-parts (that alone can appear meaningless to humans) and handles numerical text (including decimal point) as individual tokens (e.g. 12.34 would be split into 5 separate tokens).", + "bbox": [ + 496, + 435, + 890, + 526 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In terms of training, we follow a two-stage strategy. Inspired by LLaVA [38], we adopt an initial pre-training stage that only updates weights of the intermediate adapter layer to align the visual encoder outputs with LLM inputs. Next, we jointly instruction fine-tune the adapter layer and LLaMA LLM with our proposed objectives and template-based localization datasets (see Sec. 4.1). Video domain operation introduces an additional phase (see Sec. 3.5).", + "bbox": [ + 496, + 530, + 890, + 652 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Coordinate Processing and Generation", + "text_level": 1, + "bbox": [ + 500, + 662, + 833, + 678 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Humans contain the ability to reason about images using image-space coordinates. This is in contrast to existing V-LLMs that can describe the contents of an image elegantly, but lack spatial awareness regarding image contents. We hypothesize that injecting LLMs with additional spatial awareness, through coordinate based reasoning could improve their generic reasoning ability as well. To this end, we introduce our first goal of directly using textual coordinate based image locations in both natural language prompts and LLM generated outputs. For textual coordinates, we explore three different representation forms:", + "bbox": [ + 496, + 686, + 890, + 851 + ], + "page_idx": 2 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. Normalized Floating Point Values", + "2. Integer Valued Binning (across image dimensions)", + "3. Deviation from Image-Grid based Anchors" + ], + "bbox": [ + 527, + 854, + 880, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "12979", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "table", + "img_path": "images/16e925f376b10bcc20dfbe35b5e8c054395c7187227ed8e7c7cf4bca3805cbcf.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
CRGQA (Acc)RD (METEOR)A-QA (Acc)
NFP46.119.637.1
IVB47.320.737.4
DIGA47.020.837.3
", + "bbox": [ + 84, + 89, + 457, + 157 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For image locations, we explore point based (e.g. center coordinates [cx, cy] of object) and bounding box based (e.g. top-left and bottom-right extreme coordinates of object region [x1, y1, x2, y2]) forms. We next discuss the three representations for coordinates used for either location.", + "bbox": [ + 75, + 229, + 467, + 305 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Normalized Floating Point Values calculates absolute image coordinates and normalizes with image dimensions to a $(0,1)$ range. We use a 4 decimal point representation for these floating point values. While this representation is simple and generic, given the nature of BPE tokenization, each individual coordinate will be represented by up to 6 tokens.", + "bbox": [ + 75, + 309, + 467, + 398 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Integer Valued Binning discretizes the absolute image coordinates to one of $n_b$ ( $= 224, 336$ for variant B & L respectively) bins spread uniformly across the two image dimensions. Based on the binning parameter, $n_b$ , each coordinate will be represented some number of tokens, in our case up to 3 (less than the floating point variant).", + "bbox": [ + 75, + 402, + 467, + 494 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Deviation from Image-Grid based Anchors is motivated from prior object detection works that estimate an initial anchor followed by deviation from that anchor center to estimate bounding box coordinates. We follow a similar setup, where one of $n_a$ anchors is predicted by the model, followed by deviation of coordinate from that anchor center. Our intuition is that, given the sequential next-token prediction setup of LLMs, such a two-stage strategy would lead to faster learning and more accurate coordinates.", + "bbox": [ + 75, + 497, + 467, + 633 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We refer to Appendix A for further details on each variant. In Tab. 2, we ablate each representation format on three different tasks (see Sec. 4.7 for more details) of image VQA (GQA), region description (RD), and video VQA (A-QA). Our experiments indicate optimal performance for integer valued binning (IVB). In all following experimentation, we fix our coordinate representation to IVB.", + "bbox": [ + 75, + 636, + 467, + 742 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Instruction Fine-Tuning Objectives", + "text_level": 1, + "bbox": [ + 76, + 753, + 382, + 768 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given suitable coordinate representations, we now have a mechanism to directly prompt LLMs with image locations in textual form. Our second goal is to build training objectives using these image coordinates that directly inject spatial awareness into V-LLMs. We propose three instruction fine-tuning objectives for this purpose.", + "bbox": [ + 75, + 776, + 467, + 867 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Let us first revisit the visual instruction fine-tuning methodology in [38]. Building off the COCO dataset,", + "bbox": [ + 76, + 869, + 467, + 901 + ], + "page_idx": 3 + }, + { + "type": "table", + "img_path": "images/0d7b52de128e0acb49d99c6abaadd0ffb221029192487db0ee46e61bbf9463a7.jpg", + "table_caption": [ + "Table 2. Ablation on Coordinate Representation (CR) methods: we compare each of the three proposed CR variants, namely normalized floating point values (NFP), integer valued binning (IVB), and deviation from image-grid based anchors (DIGA)." + ], + "table_footnote": [], + "table_body": "
ObjectivePromptTarget
LocPredWhere is obj1?It's at (x1,y1,x2,y2).
NegPredWhere is obj2?There's no obj2.
RevLocDescribe (cx,cy)Detailed description
", + "bbox": [ + 516, + 89, + 872, + 157 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Table 3. We summarize our three distinct instruction fine-tuning objectives. Refer to appendix (Appendix B) for exact natural language prompts and targets used for training. For illustration, we use both point and bounding-box based image locations here.", + "bbox": [ + 498, + 160, + 890, + 215 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "they construct a VQA dataset containing conversation style question-answer pairs relevant to each COCO image. Question-answer pairs are generated using an LLM that is fed with the ground-truth bounding-box annotations for each image. Inspired by this setup, we build a similar spatial-VQA dataset using images and annotations of the COCO dataset, but instead of LLM prompting, we utilize hand-crafted templates and pseudo-captions (discussed in Sec. 3.4) to generate conversations.", + "bbox": [ + 496, + 232, + 890, + 368 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We propose three types of question-answer pairs that relate to our three instruction fine-tuning objectives: Location Prediction (LocPred), Negative Prediction (NegPred), and Reverse-Location Prediction (RevLoc). See Tab. 3 for examples. Considering the LLM based final text generation in our architecture, we utilize next-token prediction loss to achieve each objective during our training.", + "bbox": [ + 496, + 371, + 890, + 478 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Location Prediction: Given an object category, we query the model to generate a point or bounding box localizing that object in the image. The object category and bounding box are derived from the COCO train set annotations. To avoid object mismatches (i.e. multiple object of same category), we first filter images containing only a single object of a given class.", + "bbox": [ + 496, + 481, + 890, + 587 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Negative Prediction: Using the same prompt templates as in LocPred above, we query the model to generate a point or bounding box localizing a specified object in the image. However, in this case we select an object category not present in the image and accordingly provide a target text of \"no such object in image\". For each image, we utilize COCO bounding-box annotations to discover objects (belonging to COCO classes) that are not present in that image.", + "bbox": [ + 496, + 590, + 890, + 712 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Reverse-Location Prediction: We perform the reverse of LocPred here. Given a point or bounding box in image space, we query the model to describe the object in that location. The bounding box and object category are derived from the COCO train set annotations.", + "bbox": [ + 496, + 715, + 890, + 790 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "While introducing three novel train objectives aimed at injecting location information, we highlight that our proposed framework relies on training data (i.e. human annotations) identical to those used by LLaVA [38]. We do not use any additional ground-truth annotations for training. Next we explore how we could augment the generality of our framework while limiting to this same annotated data.", + "bbox": [ + 496, + 795, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "12980", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.4. Pseudo-Data Generation", + "text_level": 1, + "bbox": [ + 76, + 90, + 302, + 104 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We introduced three train objectives, each utilizing template based conversations as prompts and targets. However, our reliance on categories of COCO dataset limits the object vocabulary seen during training. Therein, we propose a pre-trained V-LLM based pseudo-data generation strategy. In fact, we utilize our model after stage one training as the V-LLM leading to a form of self-training based learning. Given the abundance of only image-level annotated datasets (i.e. no bounding box ground-truth), we also explore how an object-detector generated pseudo-bounding boxes could augment our framework.", + "bbox": [ + 75, + 113, + 468, + 280 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Self-Training: Given an image and bounding box annotations from the COCO train set, we prompt the V-LLM to caption each distinct object in the image. In order to prevent ambiguous object queries, we filter images to select only those containing at most one instance of a single category. We additionally prompt the V-LLM to describe the object using relational information (i.e. relative to other objects in image). This process provides us a dataset with object level bounding boxes and descriptive captions that are not limited to the COCO object categories (dataset details in Appendix C). In turn, we use this data generated by the V-LLM (our stage one model) to further improve performance of our framework. We modify each of our three train objectives (in Sec. 3.3) to utilize these image-specific pseudocaptions instead of the generic dataset level category labels.", + "bbox": [ + 75, + 282, + 470, + 511 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Weak Supervision: We explore how datasets containing no object level annotation (e.g. video classification / VQA datasets) could be leveraged to adapt our framework into domains beyond images. Therein, we utilize an off-the-shelf panoptic segmentation framework from SEEM [77] to generate pseudo-bounding boxes for selected object categories within any image as well as exhaustive pixel level labels (enabling negative class identification). We leverage this setup to extend our introduced train objectives to the video domain as well.", + "bbox": [ + 75, + 513, + 468, + 664 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.5. Video Domain Operation", + "text_level": 1, + "bbox": [ + 76, + 676, + 305, + 691 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Inspired by the simple modifications to LLaVA [38] in [42] enabling video domain operation, we follow a similar strategy of modifying our LocVLM-B architecture to process videos while introducing no additional components. The visual backbone process multiple video frames individually (as images) and resulting tokens are averaged across spatial $(S)$ and temporal $(T)$ axes to obtain $S + T$ tokens. These are processed by the adapter layer and LLM to generate the textual outputs. Further details on our video architecture are discussed in Appendix D.", + "bbox": [ + 75, + 699, + 467, + 851 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In addition to our two training phases discussed in Sec. 3.1, we introduce a third video instruction fine-tuning stage using a dataset we derive from ActivityNet [23]. Fol", + "bbox": [ + 75, + 854, + 467, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "lowing [42], only the adapter layer is fine-tuned leaving all other parameters frozen. This resulting model is referred to as LocVLM-Vid-B.", + "bbox": [ + 496, + 90, + 890, + 135 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We next introduce video variants of our three instruction fine-tuning objectives focused on static objects in videos. We utilize our proposed pseudo-labeling strategy to generate necessary video annotations and train both the adapter layer and LLM to obtain a second video model tagged LocVLM-Vid-B+. Further details on our video fine-tuning objectives are presented in Appendix D.", + "bbox": [ + 496, + 148, + 890, + 255 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 279, + 632, + 295 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this section, we present experimental results to highlight existing weaknesses of SOTA V-LLMs and how our proposed framework addresses these issues. We also evaluate on standard VQA benchmarks across domains to showcase the better reasoning abilities of our model and highlight novel abilities of our framework.", + "bbox": [ + 496, + 304, + 890, + 393 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 500, + 414, + 689, + 430 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets: We utilize the COCO dataset [37] and our model (post stage one training) to construct a localization related VQA dataset as outlined in Sections 3.3 and 3.4. We name this dataset Localize-Instruct-200K. In detail, this contains LocPred and RevLoc question-answer pairs that use pseudo-captions instead of COCO categories as well as NegPred. We define a second video dataset, Localize-ActivityNet, containing question-answer pairs constructed from Activity-Net pseudo-bounding boxes following Section 3.5. Our models are primarily trained on our Localize-Instruct-200K dataset. Our stage one training uses CC3M dataset [7]. Additionally, our Localize-ActivityNet dataset and ActivityNet dataset [23] are used for video domain training.", + "bbox": [ + 496, + 436, + 890, + 648 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Training: We train our models on 8xA100 GPUs (each 80GB) following a two-phase training schedule. Our first phase trains on CC3M [7] following the setup in [38]. The second phase uses our Localize-Instruct-200K dataset and trains for 10 epochs with a batch size of 64, ADAM-W optimizer with initial learning rate $2e - 5$ , 0.3 warm-up ratio, and cosine-decay learning rate schedule. Both the training phases we conduct use standard next-token-prediction loss used in LLM training.", + "bbox": [ + 496, + 661, + 890, + 797 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Evaluation: During evaluation, following standard protocol [38], we iteratively generate next tokens, given visual and textual inputs. The LLM output is a distribution across the entire token vocabulary. The next token is selected through multinomial sampling of this output using a softmax temperature term of 0.2 during normalization.", + "bbox": [ + 496, + 809, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "12981", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Spatial Reasoning: A Toy Experiment", + "text_level": 1, + "bbox": [ + 76, + 90, + 405, + 107 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We investigate spatial reasoning abilities of two SOTA V-LLMs, LLaVA [38] and BLIP-2 [33], using a simple toy experiment. We create an evaluation dataset from COCO annotations containing images with distinct category object triplets (only one instance occurrence of each object category), where each object is entirely to the left or right half of the image and two objects are on opposite sides. The ground-truth bounding box annotation are utilized to automate this dataset creation procedure. This evaluation set, referred as COCO-Spatial-27K, contains 26,716 image-question pairs (see Appendix C for details). We introduce two evaluation settings, direct VQA and in-context learning (ICL) VQA to understand spatial reasoning abilities of these models. In direct VQA, given an image we query the model whether an object lies above or below another object. In ICL VQA, before a similar final query, we provide two example question-answer pairs (involving the other two objects in the image) in the same format as our query. Refer to Appendix E for further details on task. We perform the same for objects in top vs bottom halves of images.", + "bbox": [ + 75, + 112, + 472, + 416 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "These results are presented in Table 4. Our results indicate near random performance for existing V-LLMs. For the case of LLaVA, we perform keyword (left and right) frequency analysis on its instruction tuning dataset (LLaVA-Instruct-80K dataset) to verify the presence of terms left and right in its training corpus. These keywords are present in $0.37\\%$ and $1.13\\%$ of its conversations respectively (see Appendix F for more) indicating presence of these concepts in the image-text training corpus. In contrast to these methods, our proposed framework notably improves performance over both BLIP-2 [33] and the LLaVA baseline [38].", + "bbox": [ + 75, + 422, + 472, + 590 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Image VQA", + "text_level": 1, + "bbox": [ + 76, + 606, + 205, + 622 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Image VQA involves correctly answering natural language questions regarding content within an image. We evaluate our model for Image VQA on two standard datasets, GQA and VQAv2. The GQA dataset focuses on questions requiring compositional reasoning, particularly involving surrounding information of objects within an image. We evaluate on its test-dev split containing 12,578 image-question pairs. The VQAv2 dataset contains open-ended questions about each image that require an understanding of vision, language and commonsense knowledge to answer. We use its validation split containing 214,354 image-question pairs for our evaluation. For each dataset, we follow standard V-LLM evaluation protocol following [33, 42] and report top-1 accuracy metric. Our results in Tab. 5 indicate clear improvements for LocVLM over our baseline and prior work, establishing the usefulness of our proposed framework. The closest to our work, Shikra [8] achieves performance competitive to our LocVLM-B, but", + "bbox": [ + 75, + 628, + 472, + 902 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/8521af775df9c7268f3cb0befce80e1334e9000dfa43ff092beaa3f55750be61.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodICLAllLeftRightAllAboveBelow
BLIP-2 [33]✗45.586.14.7449.250.448.6
LLava [38]✗55.184.536.558.957.859.3
Ours✗69.579.759.265.464.265.9
BLIP-2 [33]✓14.717.811.615.816.515.2
LLaVa [38]✓55.184.736.458.257.758.5
Ours✓76.590.461.574.173.574.4
", + "bbox": [ + 506, + 89, + 885, + 193 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/98ba69b03741bbb8c6c1e236b60f81d6246cfcd597b690a4a545e426fe33f735.jpg", + "table_caption": [ + "Table 4. Spatial Reasoning: We report accuracy $(\\%)$ on a spatial localization dataset derived from COCO annotations to highlight weak spatial awareness of existing V-LLMs. We query these models to answer whether one object is to the left or right / above or below of another object. The SOTA V-LLMs evaluated exhibit close to random performance. Our proposed setup outperforms existing methods. Ours refers to LocVLM-B variant." + ], + "table_footnote": [], + "table_body": "
MethodLLMVSZero-ShotGQAVQA-VVQA-T
SR [4]--X62.172.9-
Shikra [8]7B224X-75.377.4
LLaVA-v1.57B336X62.078.178.4
LocVLM-L7B336X63.578.278.6
LLaVA-v17B224✓44.749.849.3
LocVLM-B7B224✓47.350.350.8
Viper-GPT175B-✓48.1--
BLIP-211B-✓44.754.353.9
LLaVA-v1.57B336✓48.755.755.3
LocVLM-L7B336✓50.255.956.2
", + "bbox": [ + 506, + 301, + 885, + 455 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 5. Image VQA Results: We report accuracy $(\\%)$ on the test-dev split of GQA dataset (GQA) and the validation / test splits of VQAv2 dataset (VQA-V / VQA-T). Our proposed LocVLM improves over prior works achieving state-of-the-art performance.", + "bbox": [ + 496, + 455, + 890, + 511 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "unlike ours they use VQA datasets (containing similar domain question-answer pairs) during training.", + "bbox": [ + 496, + 527, + 890, + 560 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.4. Video VQA", + "text_level": 1, + "bbox": [ + 500, + 570, + 624, + 585 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Our model is also applicable to video tasks following our video domain adaptation described in Sec. 3.5. We simply adopt the additional video instruction fine-tuning phase from [42] on the ActivityNet dataset after our initial two phases of training to obtain LocVLM-Vid-B. This third phase involves fine-tuning only the adapter layer of our model. We also explore video variants of our IFT objectives that train both adapter layer and LLM. The resulting model is termed LocVLM-Vid-B+.", + "bbox": [ + 496, + 594, + 890, + 729 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Video VQA focuses on correctly answering questions regarding a given video that require spatio-temporal awareness to answer. We evaluate our video-adapted model on the task of zero-shot video VQA on four benchmark datasets, ActivityNet-QA, MSRVTT-QA, MSVD-QA, and TGIF-QA. We evaluate on the validation splits of these four datasets. ActivityNet-QA videos cover a wide range of complex human activities relevant to daily living with its question-answer pairs focusing on long-term spatiotemporal reasoning. MSRVTT-QA builds off the MSRVTT dataset that contains web videos covering a comprehensive", + "bbox": [ + 496, + 734, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "12982", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/32bf64ac081a7193f6b9ac9e822395b0f48c45c02f9798578f1df6bb719670aa.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodZero-ShotActivityNet-QAMSRVTT-QAMSVD-QATGIF-QA
JustAsk [63]✘38.941.847.5-
FrozenBiLM [64]✘43.247.054.8-
VideoCoCa [62]✘56.146.356.9-
Flamingo [2]✓-17.435.6-
BLIP-2 [33]✓-17.434.4-
InstructBLIP [15]✓-25.644.3-
FrozenBiLM [64]✓24.716.832.241.0
Video Chat [34]✓26.545.056.334.4
LLaMA Adapter [72]✓34.243.854.9-
Video LLaMA [71]✓12.429.651.6-
Video-ChatGPT [42]✓35.249.364.951.4
LocVLM-Vid-B✓37.451.266.151.8
", + "bbox": [ + 138, + 88, + 828, + 296 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "range of categories and diverse visual content. MSVD-QA is a similar dataset building off the MSVD dataset. TGIFQA contains question-answer pairs from an dataset constructed of animated GIFs. For each dataset, we report the accuracy metric following evaluation protocol in [42]. Our results on these four datasets reported in Tab. 6 demonstrate state-of-the-art performance of our proposed LocVLM-Vid-B, with consistent improvements over the baseline from [42]. Here we use the LocVLM-Vid-B variant for fairer comparison with the baseline from [42]. We attribute the performance gains exhibited by our model to its stronger spatial awareness (see Sec. 4.2). Particularly in the case of video understanding, awareness of content at spatial level of each frame is significant to understand object motions and interactions [1, 51]. We also report more results involving additional model variants in Tab. 7.", + "bbox": [ + 75, + 343, + 472, + 585 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.5. Object Hallucination", + "text_level": 1, + "bbox": [ + 76, + 604, + 274, + 622 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Current state-of-the-art V-LLMs suffer from object hallucination, generating image descriptions inconsistent with the image content [36]. For example, a V-LLM would respond to \"Where is the cat in this image?\" with \"The cat is on the table\" when in reality there is no cat in the image. We evaluate the extent of hallucination in V-LLMs using three datasets we introduce (details in Appendix C) and the POPE dataset [36]. Our three datasets, Hal-COCO, Hal-ADE, and Hal-Act build off COCO, ADE-20K, and ActivityNet datasets respectively. The first two involve images and the latter videeos. These datasets contain \"Is there obj in image / video?\" type questions per sample, for two objects present and not present in the image / video. Hal-ADE object categories contain no overlap with COCO classes allowing evaluation on novel object categories unseen during our instruction fine-tuning. Results reported in Tab. 8 show clear improvements of LocVLM-B over baselines. We also evaluate LocVLM-B on the POPE benchmark [36] that builds", + "bbox": [ + 75, + 628, + 472, + 900 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/82526f80754f3538a8fd04dcee6de9d99d40ad2dbdb4c227980f33d7b4960af3.jpg", + "table_caption": [ + "Table 6. Video VQA Results: Our proposed LocVLM-Vid-B improves over Video-ChatGPT [42] and achieves state-of-the-art results (Top-1 Accuracy %) across four different video VQA benchmarks. Note the zero-shot setting of all these evaluations." + ], + "table_footnote": [], + "table_body": "
MethodVLTFramesAcc (%)
LLaVa (v1) [38]×128.7
LLaVa (v1.5) [38]×131.5
LocVLM-B×129.2
LocVLM-L×132.1
Video-ChatGPT [42]✓10035.2
LocVLM-Vid-B✓10037.4
LocVLM-Vid-B+✓838.2
", + "bbox": [ + 517, + 340, + 870, + 472 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/b66e2ffec55f68704e7093a1bb0cbe02e423af548651c15095d139e10c93ee28.jpg", + "table_caption": [ + "Table 7. Video VQA: We report more results (Top-1 Accuracy) for ActivityNet-QA dataset including multiple baseline and LocVLM variants. Our proposed models exhibit top performance. VLT denotes video level training. More details in Appendix D." + ], + "table_footnote": [], + "table_body": "
MethodHal-COCOHal-ADEHal-Act
Shikra [8]86.258.7-
LLaVa [38]61.953.8-
LocVLM-B88.375.2-
Video-ChatGPT [42]--50.6
LocVLM-Vid-B--68.7
LocVLM-Vid-B+--72.4
", + "bbox": [ + 504, + 531, + 890, + 645 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 8. Hallucination Evaluation: We report top-1 accuracy (\\%) for object presence type questions and showcase reduced object hallucination in our proposed framework.", + "bbox": [ + 498, + 646, + 890, + 688 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "off the COCO dataset object annotations and report results in Tab. 9. Our LocVLM showcases similar performance improvements on this dataset.", + "bbox": [ + 498, + 702, + 890, + 748 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.6. Region Description", + "text_level": 1, + "bbox": [ + 500, + 756, + 684, + 772 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "A unique characteristic of our model (in contrast to V-LLMs like LLaVA [38] & BLIP-2 [33]) is its ability to reason with prompts involving coordinate based image space locations without any input modifications. Given a point or bounding box location, we prompt our model to generate an output describing that location. We refer to this unique ability of our model as region description (RD). We evaluate this RD capability of our model by generating object", + "bbox": [ + 496, + 779, + 890, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "12983", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/b7d4000461d29ec5691a45198819b5ef0246b032e6a16558d5735d57f5cc19db.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DatasetsMetricsBLIP-2ShikraLLaVAOurs
RandomAccuracy (↑)88.686.950.487.9
Precision (↑)84.194.450.283.6
Recall (↑)95.179.399.193.9
F1 Score (↑)89.386.266.688.5
Yes56.643.398.856.2
PopularAccuracy (↑)82.884.049.986.0
Precision (↑)76.387.649.979.7
Recall (↑)95.179.299.393.9
F1 Score (↑)84.783.266.486.3
Yes62.445.299.458.9
AdversarialAccuracy (↑)72.183.149.778.8
Precision (↑)65.185.649.976.6
Recall (↑)95.179.699.193.7
F1 Score (↑)77.382.566.384.3
Yes73.046.599.461.7
", + "bbox": [ + 83, + 88, + 464, + 319 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/180a692b19fe900149b5fff504f24207b1ceca10cca5b887136af2eb6d0eaa7b.jpg", + "table_caption": [ + "Table 9. More object hallucination: Results on POPE evaluation benchmark [36] indicate strong performance of our model." + ], + "table_footnote": [], + "table_body": "
MethodZSRefCOCORefCOCO+RefCOCOg
ValTest
SLR [67]✘---15.4
SLR + Rerank [67]✘---15.9
Kosmos-2 [45]✘8.678.8214.314.1
Shikra [8]✘10.411.119.719.5
LLaVa [38]✘8.438.7313.513.5
LocVLM-B✘14.615.226.026.2
Kosmos-2 [45]✓6.348.2512.412.2
LLava [38]✓4.237.2610.610.3
LocVLM-B✓11.011.120.620.7
", + "bbox": [ + 81, + 368, + 468, + 527 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "level descriptions focused on contextual information (e.g. surrounding of that object in the image). Following evaluation protocol in [45] for region description, we extend their evaluation to three standard referring localization datasets from RefCOCO [29] and report these results in Tab. 10. We select the METEOR score as the evaluation metric to account for variations in word choice in generated answers which may be acceptable in various cases (e.g. different sentence structure leading to alternate word ordering). Our results indicate clear improvements over the LLaVA baseline [38] as well as prior state-of-the-art. We attribute these improvements to our pseudo-data based training.", + "bbox": [ + 75, + 590, + 467, + 772 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.7. Ablations", + "text_level": 1, + "bbox": [ + 76, + 786, + 187, + 801 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Next we conduct ablative studies on separate components of our proposed setup: IFT objectives, location type, and pseudo-data. We follow the same training strategy as described in Sec. 4.1 and present these results in Tab. 11. LocVLM-B is used for all these experiments. The significance of each IFT objective is verified in Tab. 11 (top) with", + "bbox": [ + 75, + 809, + 467, + 900 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/103df4034479e10762a4a43668d369482fea96f8e47733387e1780074ffd3923.jpg", + "table_caption": [ + "Table 10. Region Description: We report METEOR scores for RD task [45]. Test-B split is used for RefCOCO & RefCOCO+ datasets. Our method outperforms all prior work." + ], + "table_footnote": [], + "table_body": "
LocPredNegPredRevLocGQARDA-QA
XXX44.710.335.2
✓XX45.212.235.8
✓✓X46.912.537.2
✓✓✓47.320.737.4
Location TypePDGQARDA-QA
Point✓47.320.637.4
Bounding Box✓47.320.737.4
Bounding BoxX46.511.637.1
", + "bbox": [ + 519, + 89, + 872, + 241 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/6f99c3ec03998962ac1b885cea89288fb062cdbc827ffab3d661c56420ab30a5.jpg", + "table_caption": [ + "Table 11. Ablations: We report top-1 accuracy (\\%) on GQA and ActivityNet-QA (A-QA) datasets and METEOR scores for RD task on RefCOCOg test split. (top) We ablate proposed instruction fine-tuning objectives to verify usefulness of each objective. (bottom) We first ablate point based and bounding box based location forms to showcase minimal difference across them. We next ablate use of object description pseudo-data (PD). We highlight the improvements due to pseudo-data, especially on the RD task." + ], + "table_footnote": [], + "table_body": "
LocPredNegPredRevLocA-QA
XXX37.4
✓XX37.6
✓✓X38.2
✓✓✓38.2
", + "bbox": [ + 550, + 376, + 841, + 455 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 12. Video Ablation: We report top-1 accuracy $(\\%)$ on ActivityNet-QA (A-QA) dataset. Results indicate the generality of proposed IFT objectives for video domain training as well.", + "bbox": [ + 498, + 457, + 890, + 500 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "consistent performance improvements across tasks. The generality of our approach to differing location type (i.e. points vs bounding boxes) and usefulness of pseudo-data is visible in Tab. 11 (bottom). In particular, we highlight the notable performance improvement for RD task gained from using pseudo-data. We also conduct ablations for our video domain training setup and report these results in Tab. 12. The LocVLM-Vid-B+ variant is used in these experiments. Our results showcase the usefulness of proposed IFT objectives for video domain learning as well.", + "bbox": [ + 496, + 529, + 890, + 680 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 709, + 617, + 724 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We introduce a simple framework that equips visual-LLMs (V-LLMs) with greater spatial understanding, termed LocVLM. We leverage the idea of encoding image coordinates within language to propose three instruction finetuning (IFT) objectives. This training process endows V-LLMs with the ability to reason about spatial composition of images using image space coordinates within text. A data efficient training pipeline utilizing pseudo-data allows our approach to achieve state-of-the-art results in Image VQA, Video VQA, and Region Description while improving spatial awareness and reducing object hallucination.", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "12984", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 80, + 90, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Jake K. Aggarwal and Michael S. Ryoo. Human activity analysis. ACM Computing Surveys (CSUR), 43:1-43, 2011. 7", + "[2] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katie Millican, Malcolm Reynolds, et al. 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Segment everything everywhere all at once. 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Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.112, + 0.131, + 0.857, + 0.152 + ], + "angle": 0, + "content": "Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs" + }, + { + "type": "text", + "bbox": [ + 0.202, + 0.18, + 0.765, + 0.199 + ], + "angle": 0, + "content": "Kanchana Ranasinghe1,2 Satya Narayan Shukla1 Amid Poursaeed1" + }, + { + "type": "text", + "bbox": [ + 0.331, + 0.199, + 0.633, + 0.218 + ], + "angle": 0, + "content": "Michael S. Ryoo² Tsung-Yu Lin1" + }, + { + "type": "text", + "bbox": [ + 0.348, + 0.224, + 0.617, + 0.242 + ], + "angle": 0, + "content": "\\(^{1}\\)Meta \\(^{2}\\)Stony Brook University" + }, + { + "type": "text", + "bbox": [ + 0.1, + 0.246, + 0.865, + 0.261 + ], + "angle": 0, + "content": "{kranasinghe, mryoo}@cs.stonybrook.edu, {satyanshukla, opoursaed, tsungyulin}@meta.com" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.283, + 0.313, + 0.299 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.312, + 0.474, + 0.614 + ], + "angle": 0, + "content": "Integration of Large Language Models (LLMs) into visual domain tasks, resulting in visual-LLMs (V-LLMs), has enabled exceptional performance in vision-language tasks, particularly for visual question answering (VQA). However, existing V-LLMs (e.g. BLIP-2, LLaVA) demonstrate weak spatial reasoning and localization awareness. Despite generating highly descriptive and elaborate textual answers, these models fail at simple tasks like distinguishing a left vs right location. In this work, we explore how image-space coordinate based instruction fine-tuning objectives could inject spatial awareness into V-LLMs. We discover optimal coordinate representations, data-efficient instruction fine-tuning objectives, and pseudo-data generation strategies that lead to improved spatial awareness in V-LLMs. Additionally, our resulting model improves VQA across image and video domains, reduces undesired hallucination, and generates better contextual object descriptions. Experiments across 5 vision-language tasks involving 14 different datasets establish the clear performance improvements achieved by our proposed framework." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.631, + 0.208, + 0.646 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.656, + 0.47, + 0.748 + ], + "angle": 0, + "content": "Holistic visual understanding requires learning beyond simply content of an image to encompass awareness on spatial locations of objects and their relations [41]. In the context of visual question answering (VQA), such spatial awareness allows better reasoning involving structural and contextual information contained within an image [8]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Since the introduction of powerful large-language models (LLMs) such as GPT-3 [5], Chat-GPT [44], Vicuna [11], and LLaMA [55, 56] that are capable of human style conversation, their visual counterparts such as BLIP-2 [33], LLaVA [38] have enabled novel tasks within the vision modality. However, despite their [33, 38] highly generic visual understanding, these models exhibit poor language-based spatial reasoning [8]. In fact, they fail at simple tasks such as distinguishing whether an object lies to the left or right of another object (see Tab. 4)." + }, + { + "type": "image", + "bbox": [ + 0.521, + 0.283, + 0.688, + 0.455 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.696, + 0.29, + 0.86, + 0.312 + ], + "angle": 0, + "content": "Query: Describe [x1,y1,x2,y2] location in image." + }, + { + "type": "text", + "bbox": [ + 0.696, + 0.319, + 0.841, + 0.341 + ], + "angle": 0, + "content": "Ours: A blue plaid blanket behind a teddy bear." + }, + { + "type": "text", + "bbox": [ + 0.704, + 0.36, + 0.854, + 0.383 + ], + "angle": 0, + "content": "Query: Which side of the potted plant is the stove?" + }, + { + "type": "text", + "bbox": [ + 0.704, + 0.391, + 0.861, + 0.414 + ], + "angle": 0, + "content": "LLaVa: The stove is on the left side of potted plant." + }, + { + "type": "text", + "bbox": [ + 0.704, + 0.423, + 0.853, + 0.446 + ], + "angle": 0, + "content": "Ours: The stove is on the right side of potted plant." + }, + { + "type": "image", + "bbox": [ + 0.52, + 0.454, + 0.871, + 0.613 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.617, + 0.892, + 0.687 + ], + "angle": 0, + "content": "Figure 1. We illustrate one unique ability of our model: contextual region description (top). Note the contextual information used in describing the selected region in each image. Explicitly teaching localization to Visual-LLMs also improves spatial awareness in VQA settings (bottom). Color boxes only for illustration purposes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.701, + 0.893, + 0.868 + ], + "angle": 0, + "content": "In the case of contrastive language image models (such as CLIP [46], ALIGN [26]), recent works explore how injecting explicit spatial awareness [39, 43, 48, 74] can enable more holistic visual understanding. In fact, [48] shows how such improved spatial awareness benefits model robustness in adversarial domains. This raises the question of how generative language image models, particularly those connecting LLMs to visual encoders [33, 38] can benefit from such spatial awareness specific training. We refer to models of this category that generate textual outputs given joint image-text inputs (e.g. [33, 38]) as visual-LLMs (V-LLMs)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In this work, we explore location specific instruction fine-tuning objectives that explicitly enforce V-LLMs to" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "12977" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.242 + ], + "angle": 0, + "content": "meaningfully process and generate textual image-space coordinates. We hypothesize that such training would lead to improved spatial awareness in these V-LLMs, therein improving performance on VQA tasks. To this end, we propose three instruction fine-tuning objectives that unify location representation with natural language. We also explore optimal representation forms for image-space locations and how pseudo-data generation can be leveraged for efficient scaling of our framework. We name our resulting model as LocVLM." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.247, + 0.473, + 0.565 + ], + "angle": 0, + "content": "While the idea of adapting V-LLMs to perform localization related tasks (e.g. detection, segmentation) using V-LLMs has been explored in multiple recent works [30, 45, 58, 66, 68, 73, 75], these approaches depend on task specific architectural modifications or treat localization inputs / outputs differently from natural language. In contrast, our LocVLM focuses on a unified framework treating location and language as a single modality of inputs with the goal of complementing performance in each task. We intuit that processing location represented in textual form would enforce the LLM to select appropriate image regions as opposed to relying on region level features provided by the architecture. At the same time, textual form location outputs promote spatial awareness at language level in a human interpretable manner, in contrast to using secondary heads or specialized tokens for location prediction. Concurrent work in [8] also explores textual location representation with a generic V-LLM architecture similar to our work. Our proposed LocVLM differs with focus on optimal location representation forms, data-efficient pseudo-labelling, and video domain operation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.569, + 0.472, + 0.659 + ], + "angle": 0, + "content": "Our proposed framework exhibits improved spatial awareness in VQA style conversation demonstrated through experimentation on 14 datasets across 5 vision-language tasks: Spatial Reasoning, Image VQA, Video VQA, Object Hallucination, and Region Description. We summarize our key contributions as follows:" + }, + { + "type": "text", + "bbox": [ + 0.08, + 0.664, + 0.465, + 0.677 + ], + "angle": 0, + "content": "- Inject textual spatial coordinate awareness into V-LLMs" + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.679, + 0.469, + 0.708 + ], + "angle": 0, + "content": "- Propose three novel localization based instruction finetuning objectives for V-LLMs" + }, + { + "type": "text", + "bbox": [ + 0.081, + 0.71, + 0.423, + 0.723 + ], + "angle": 0, + "content": "- Discover optimal coordinate representation forms" + }, + { + "type": "text", + "bbox": [ + 0.08, + 0.724, + 0.469, + 0.754 + ], + "angle": 0, + "content": "- Pseudo-Data generation for improved region description and scaling to video domain" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.664, + 0.469, + 0.754 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.77, + 0.22, + 0.785 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Localization in Contrastive Vision Language Models: Foundation vision language models (VLMs) such as CLIP [46] resulted in extensive exploration into language-tied localization in images both under dense (pixel / bounding-box) supervision [16-18, 21, 27, 31, 32, 35, 69, 70] and weak supervision [14, 39, 43, 48, 60, 61, 65, 74, 76]. Recovering explicit localization information within model rep" + }, + { + "type": "table", + "bbox": [ + 0.508, + 0.089, + 0.885, + 0.171 + ], + "angle": 0, + "content": "
MethodKosmos [45]Ferret [66]Shikra [8]Ours
Unified Arch.XX✓✓
Purely TextualXX✓✓
Pseudo DataXXX✓
Video DomainXXX✓
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.175, + 0.894, + 0.218 + ], + "angle": 0, + "content": "Table 1. Related Work Comparison: A unified architecture, purely textual inputs, pseudo data for scalable learning, and video domain operation distinguishes our work from these prior methods." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.238, + 0.894, + 0.314 + ], + "angle": 0, + "content": "resentations has enabled more robust operation for certain tasks [48]. While our work differs from this contrastive setting given our use of LLM based generative predictions, we similarly explore how explicit location information within the language modality can improve V-LLMs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.32, + 0.893, + 0.835 + ], + "angle": 0, + "content": "Visual Large Language Models (V-LLMs): The advent of powerful large language models (LLMs) such as GPT-3 [5], Chat-GPT [44], and PaLM [13], as well as their open-source counterparts BLOOM [52], Vicuna [11], and LLaMA [55, 56], has resulted in direct use of these LLMs for computer vision tasks [22, 53]. Alternate lines of work explore how LLMs can be connected to existing visual foundation models [2, 3, 33, 38, 42, 47], in particular to CLIP visual backbones [46]. While earlier models explored large-scale (millions to billions of samples) image-text training [2, 3], later models [33, 38, 42] scale down on data dependency. LLaVA [38] in particular scales down on pre-training data to under 1 million image-text pairs, and use instruction fine-tuning [59] to enable human-style conversation with visual awareness. This is extended to video domain in [42, 49]. A shortcoming of these models is their lack of spatial awareness or location understanding in image space [8, 12, 20]. Spatial reasoning limitations in generative VLMs are studied in [12, 20]. Similar failures in captioning (and VQA) models are explored in [28]. A solution in [24] proposes code-generation based reasoning. Our work tackles these same limitations but follows an alternate direction of spatial-aware instruction fine-tuning. Another line of recent works [30, 45, 58, 66, 68, 73, 75] tackle this by introducing architectural modifications to explicitly extract region level features that are injected to the LLM as special tokens. While introducing extra tokens and layers, this also separates the localization task from language. In contrast, we use a generic architectures with purely textual location information (i.e. image space coordinates as text). Concurrent work in [8] explores this same idea, but we differ in 3 ways with, a) focus on optimal coordinate representation forms, b) data-efficient pseudo-labelling strategies, and c) video domain operation (see also Tab. 1)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.894, + 0.903 + ], + "angle": 0, + "content": "Location Representations: Selecting regions within an image has a rich history in computer vision [40, 57] with greater focus on location outputs since the popularity of object detection [6, 9, 10, 19, 50, 54, 58]. Early anchor-based" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "12978" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.289 + ], + "angle": 0, + "content": "methods regress locations from anchor centers [19, 50], followed by direct location regression from object-level features [6, 54]. Recent works explore generative location predictions with diffusion processes [9] and sequence-generation [10, 58]. Ours resembles the latter given our use of an LLM, next token prediction objective, and sequential generation of textual location representations. However, [10, 58] utilize 1000 specialized location tokens (introduced to the LLM vocabulary) corresponding to 1000 bins uniformly spread across image space. While we explore similar binning strategies, in contrast we introduce no additional tokens, focus on purely textual representation of locations, and explore multiple textual location representation forms." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.299, + 0.169, + 0.315 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.324, + 0.47, + 0.506 + ], + "angle": 0, + "content": "Current V-LLMs [33, 38] exhibit weak understanding of spatial locations within images [8]. We explore and benchmark such shortcomings, and propose three novel instruction fine-tuning objectives aimed at overcoming these drawbacks of existing V-LLMs. We build these objectives based on spatial-coordinate based prompting and demonstrate how LLMs can directly both process and generate meaningful numerical coordinates in image-space after suitable training. In the rest of this section we describe our architecture and training framework, followed by coordinate processing & generation, instruction fine-tuning objectives, pseudo-data generation, and video domain operation." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.513, + 0.317, + 0.529 + ], + "angle": 0, + "content": "3.1. Architecture and Training" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.536, + 0.47, + 0.627 + ], + "angle": 0, + "content": "The focus of our work is to explore how spatial localization related training can improve a generic V-LLM such as LLaVA [38]. Therein, our architecture and training framework is inspired from [38]. We use a visual encoder, adapter layer, and LLM stacked sequentially (illustrated in Fig. 2), and follow a multi-stage training strategy similar to [38]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.628, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Consider an image \\(X \\in \\mathbb{R}^{H, W, C}\\) where \\(H, W, C (= 3)\\) denote height, width, channels of image and a textual prompt \\(T\\) composed of natural language (asking a question about the image). We define two variants of our model, LocVLM-B and LocVLM-L for better comparison with prior work. We first describe LocVLM-B that processes images with \\(H = W = 224\\). Our visual encoder, ViTL/14 from CLIP [46], processes the image \\(X\\) to produce a set of 256 visual tokens in \\(\\mathbb{R}^{1024}\\), which are in turn projected to \\(\\mathbb{R}^{4096}\\) by an adapter layer (implemented as a linear layer). The LLaMA [55] text tokenizer processes the textual prompt \\(T\\) to produce textual tokens in \\(\\mathbb{R}^{4096}\\). The joint set of visual and textual tokens (of dimension \\(\\mathbb{R}^{4096}\\)) are processed by a LLaMA [55] LLM to produce the final set of textual tokens which are in turn untokenized to convert to natural language. The final natural language output is expected to be a suitable response to the input textual prompt, \\(T\\). In variant LocVLM-L, we use images sized" + }, + { + "type": "image", + "bbox": [ + 0.523, + 0.099, + 0.87, + 0.332 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.342, + 0.892, + 0.371 + ], + "angle": 0, + "content": "Figure 2. Architecture: We present the overall model architecture of our framework which is inspired from LLaVa [38]." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.386, + 0.892, + 0.432 + ], + "angle": 0, + "content": "\\(H = W = 336\\) resulting in 576 visual token, an adapter layer implemented as an MLP, and the LLM from LLaMA-2 [56]. All other design choices remain unchanged." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.436, + 0.892, + 0.527 + ], + "angle": 0, + "content": "We also highlight the BPE tokenization that is employed in our setup. This learned tokenization scheme may split a single word into sub-parts (that alone can appear meaningless to humans) and handles numerical text (including decimal point) as individual tokens (e.g. 12.34 would be split into 5 separate tokens)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.531, + 0.892, + 0.653 + ], + "angle": 0, + "content": "In terms of training, we follow a two-stage strategy. Inspired by LLaVA [38], we adopt an initial pre-training stage that only updates weights of the intermediate adapter layer to align the visual encoder outputs with LLM inputs. Next, we jointly instruction fine-tune the adapter layer and LLaMA LLM with our proposed objectives and template-based localization datasets (see Sec. 4.1). Video domain operation introduces an additional phase (see Sec. 3.5)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.663, + 0.834, + 0.679 + ], + "angle": 0, + "content": "3.2. Coordinate Processing and Generation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.687, + 0.892, + 0.852 + ], + "angle": 0, + "content": "Humans contain the ability to reason about images using image-space coordinates. This is in contrast to existing V-LLMs that can describe the contents of an image elegantly, but lack spatial awareness regarding image contents. We hypothesize that injecting LLMs with additional spatial awareness, through coordinate based reasoning could improve their generic reasoning ability as well. To this end, we introduce our first goal of directly using textual coordinate based image locations in both natural language prompts and LLM generated outputs. For textual coordinates, we explore three different representation forms:" + }, + { + "type": "text", + "bbox": [ + 0.529, + 0.856, + 0.776, + 0.871 + ], + "angle": 0, + "content": "1. Normalized Floating Point Values" + }, + { + "type": "text", + "bbox": [ + 0.529, + 0.871, + 0.882, + 0.886 + ], + "angle": 0, + "content": "2. Integer Valued Binning (across image dimensions)" + }, + { + "type": "text", + "bbox": [ + 0.529, + 0.886, + 0.835, + 0.901 + ], + "angle": 0, + "content": "3. Deviation from Image-Grid based Anchors" + }, + { + "type": "list", + "bbox": [ + 0.529, + 0.856, + 0.882, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "12979" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.086, + 0.09, + 0.458, + 0.158 + ], + "angle": 0, + "content": "
CRGQA (Acc)RD (METEOR)A-QA (Acc)
NFP46.119.637.1
IVB47.320.737.4
DIGA47.020.837.3
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.159, + 0.468, + 0.214 + ], + "angle": 0, + "content": "Table 2. Ablation on Coordinate Representation (CR) methods: we compare each of the three proposed CR variants, namely normalized floating point values (NFP), integer valued binning (IVB), and deviation from image-grid based anchors (DIGA)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.231, + 0.468, + 0.306 + ], + "angle": 0, + "content": "For image locations, we explore point based (e.g. center coordinates [cx, cy] of object) and bounding box based (e.g. top-left and bottom-right extreme coordinates of object region [x1, y1, x2, y2]) forms. We next discuss the three representations for coordinates used for either location." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.31, + 0.468, + 0.4 + ], + "angle": 0, + "content": "Normalized Floating Point Values calculates absolute image coordinates and normalizes with image dimensions to a \\((0,1)\\) range. We use a 4 decimal point representation for these floating point values. While this representation is simple and generic, given the nature of BPE tokenization, each individual coordinate will be represented by up to 6 tokens." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.403, + 0.468, + 0.495 + ], + "angle": 0, + "content": "Integer Valued Binning discretizes the absolute image coordinates to one of \\( n_b \\) (\\( = 224, 336 \\) for variant B & L respectively) bins spread uniformly across the two image dimensions. Based on the binning parameter, \\( n_b \\), each coordinate will be represented some number of tokens, in our case up to 3 (less than the floating point variant)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.498, + 0.468, + 0.634 + ], + "angle": 0, + "content": "Deviation from Image-Grid based Anchors is motivated from prior object detection works that estimate an initial anchor followed by deviation from that anchor center to estimate bounding box coordinates. We follow a similar setup, where one of \\( n_a \\) anchors is predicted by the model, followed by deviation of coordinate from that anchor center. Our intuition is that, given the sequential next-token prediction setup of LLMs, such a two-stage strategy would lead to faster learning and more accurate coordinates." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.637, + 0.468, + 0.743 + ], + "angle": 0, + "content": "We refer to Appendix A for further details on each variant. In Tab. 2, we ablate each representation format on three different tasks (see Sec. 4.7 for more details) of image VQA (GQA), region description (RD), and video VQA (A-QA). Our experiments indicate optimal performance for integer valued binning (IVB). In all following experimentation, we fix our coordinate representation to IVB." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.754, + 0.383, + 0.77 + ], + "angle": 0, + "content": "3.3. Instruction Fine-Tuning Objectives" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.777, + 0.468, + 0.868 + ], + "angle": 0, + "content": "Given suitable coordinate representations, we now have a mechanism to directly prompt LLMs with image locations in textual form. Our second goal is to build training objectives using these image coordinates that directly inject spatial awareness into V-LLMs. We propose three instruction fine-tuning objectives for this purpose." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.468, + 0.902 + ], + "angle": 0, + "content": "Let us first revisit the visual instruction fine-tuning methodology in [38]. Building off the COCO dataset," + }, + { + "type": "table", + "bbox": [ + 0.517, + 0.09, + 0.873, + 0.159 + ], + "angle": 0, + "content": "
ObjectivePromptTarget
LocPredWhere is obj1?It's at (x1,y1,x2,y2).
NegPredWhere is obj2?There's no obj2.
RevLocDescribe (cx,cy)Detailed description
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.161, + 0.892, + 0.216 + ], + "angle": 0, + "content": "Table 3. We summarize our three distinct instruction fine-tuning objectives. Refer to appendix (Appendix B) for exact natural language prompts and targets used for training. For illustration, we use both point and bounding-box based image locations here." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.233, + 0.892, + 0.369 + ], + "angle": 0, + "content": "they construct a VQA dataset containing conversation style question-answer pairs relevant to each COCO image. Question-answer pairs are generated using an LLM that is fed with the ground-truth bounding-box annotations for each image. Inspired by this setup, we build a similar spatial-VQA dataset using images and annotations of the COCO dataset, but instead of LLM prompting, we utilize hand-crafted templates and pseudo-captions (discussed in Sec. 3.4) to generate conversations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.372, + 0.892, + 0.479 + ], + "angle": 0, + "content": "We propose three types of question-answer pairs that relate to our three instruction fine-tuning objectives: Location Prediction (LocPred), Negative Prediction (NegPred), and Reverse-Location Prediction (RevLoc). See Tab. 3 for examples. Considering the LLM based final text generation in our architecture, we utilize next-token prediction loss to achieve each objective during our training." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.482, + 0.892, + 0.588 + ], + "angle": 0, + "content": "Location Prediction: Given an object category, we query the model to generate a point or bounding box localizing that object in the image. The object category and bounding box are derived from the COCO train set annotations. To avoid object mismatches (i.e. multiple object of same category), we first filter images containing only a single object of a given class." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.592, + 0.892, + 0.713 + ], + "angle": 0, + "content": "Negative Prediction: Using the same prompt templates as in LocPred above, we query the model to generate a point or bounding box localizing a specified object in the image. However, in this case we select an object category not present in the image and accordingly provide a target text of \"no such object in image\". For each image, we utilize COCO bounding-box annotations to discover objects (belonging to COCO classes) that are not present in that image." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.716, + 0.892, + 0.791 + ], + "angle": 0, + "content": "Reverse-Location Prediction: We perform the reverse of LocPred here. Given a point or bounding box in image space, we query the model to describe the object in that location. The bounding box and object category are derived from the COCO train set annotations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.892, + 0.901 + ], + "angle": 0, + "content": "While introducing three novel train objectives aimed at injecting location information, we highlight that our proposed framework relies on training data (i.e. human annotations) identical to those used by LLaVA [38]. We do not use any additional ground-truth annotations for training. Next we explore how we could augment the generality of our framework while limiting to this same annotated data." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "12980" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.078, + 0.091, + 0.303, + 0.106 + ], + "angle": 0, + "content": "3.4. Pseudo-Data Generation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.114, + 0.47, + 0.281 + ], + "angle": 0, + "content": "We introduced three train objectives, each utilizing template based conversations as prompts and targets. However, our reliance on categories of COCO dataset limits the object vocabulary seen during training. Therein, we propose a pre-trained V-LLM based pseudo-data generation strategy. In fact, we utilize our model after stage one training as the V-LLM leading to a form of self-training based learning. Given the abundance of only image-level annotated datasets (i.e. no bounding box ground-truth), we also explore how an object-detector generated pseudo-bounding boxes could augment our framework." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.284, + 0.471, + 0.512 + ], + "angle": 0, + "content": "Self-Training: Given an image and bounding box annotations from the COCO train set, we prompt the V-LLM to caption each distinct object in the image. In order to prevent ambiguous object queries, we filter images to select only those containing at most one instance of a single category. We additionally prompt the V-LLM to describe the object using relational information (i.e. relative to other objects in image). This process provides us a dataset with object level bounding boxes and descriptive captions that are not limited to the COCO object categories (dataset details in Appendix C). In turn, we use this data generated by the V-LLM (our stage one model) to further improve performance of our framework. We modify each of our three train objectives (in Sec. 3.3) to utilize these image-specific pseudocaptions instead of the generic dataset level category labels." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.515, + 0.47, + 0.665 + ], + "angle": 0, + "content": "Weak Supervision: We explore how datasets containing no object level annotation (e.g. video classification / VQA datasets) could be leveraged to adapt our framework into domains beyond images. Therein, we utilize an off-the-shelf panoptic segmentation framework from SEEM [77] to generate pseudo-bounding boxes for selected object categories within any image as well as exhaustive pixel level labels (enabling negative class identification). We leverage this setup to extend our introduced train objectives to the video domain as well." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.677, + 0.307, + 0.693 + ], + "angle": 0, + "content": "3.5. Video Domain Operation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.7, + 0.468, + 0.852 + ], + "angle": 0, + "content": "Inspired by the simple modifications to LLaVA [38] in [42] enabling video domain operation, we follow a similar strategy of modifying our LocVLM-B architecture to process videos while introducing no additional components. The visual backbone process multiple video frames individually (as images) and resulting tokens are averaged across spatial \\((S)\\) and temporal \\((T)\\) axes to obtain \\(S + T\\) tokens. These are processed by the adapter layer and LLM to generate the textual outputs. Further details on our video architecture are discussed in Appendix D." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.468, + 0.901 + ], + "angle": 0, + "content": "In addition to our two training phases discussed in Sec. 3.1, we introduce a third video instruction fine-tuning stage using a dataset we derive from ActivityNet [23]. Fol" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.136 + ], + "angle": 0, + "content": "lowing [42], only the adapter layer is fine-tuned leaving all other parameters frozen. This resulting model is referred to as LocVLM-Vid-B." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.15, + 0.892, + 0.256 + ], + "angle": 0, + "content": "We next introduce video variants of our three instruction fine-tuning objectives focused on static objects in videos. We utilize our proposed pseudo-labeling strategy to generate necessary video annotations and train both the adapter layer and LLM to obtain a second video model tagged LocVLM-Vid-B+. Further details on our video fine-tuning objectives are presented in Appendix D." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.28, + 0.633, + 0.296 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.305, + 0.892, + 0.395 + ], + "angle": 0, + "content": "In this section, we present experimental results to highlight existing weaknesses of SOTA V-LLMs and how our proposed framework addresses these issues. We also evaluate on standard VQA benchmarks across domains to showcase the better reasoning abilities of our model and highlight novel abilities of our framework." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.415, + 0.691, + 0.431 + ], + "angle": 0, + "content": "4.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.438, + 0.892, + 0.65 + ], + "angle": 0, + "content": "Datasets: We utilize the COCO dataset [37] and our model (post stage one training) to construct a localization related VQA dataset as outlined in Sections 3.3 and 3.4. We name this dataset Localize-Instruct-200K. In detail, this contains LocPred and RevLoc question-answer pairs that use pseudo-captions instead of COCO categories as well as NegPred. We define a second video dataset, Localize-ActivityNet, containing question-answer pairs constructed from Activity-Net pseudo-bounding boxes following Section 3.5. Our models are primarily trained on our Localize-Instruct-200K dataset. Our stage one training uses CC3M dataset [7]. Additionally, our Localize-ActivityNet dataset and ActivityNet dataset [23] are used for video domain training." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.662, + 0.892, + 0.798 + ], + "angle": 0, + "content": "Training: We train our models on 8xA100 GPUs (each 80GB) following a two-phase training schedule. Our first phase trains on CC3M [7] following the setup in [38]. The second phase uses our Localize-Instruct-200K dataset and trains for 10 epochs with a batch size of 64, ADAM-W optimizer with initial learning rate \\(2e - 5\\), 0.3 warm-up ratio, and cosine-decay learning rate schedule. Both the training phases we conduct use standard next-token-prediction loss used in LLM training." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.81, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Evaluation: During evaluation, following standard protocol [38], we iteratively generate next tokens, given visual and textual inputs. The LLM output is a distribution across the entire token vocabulary. The next token is selected through multinomial sampling of this output using a softmax temperature term of 0.2 during normalization." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.946, + 0.518, + 0.957 + ], + "angle": 0, + "content": "12981" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.077, + 0.091, + 0.406, + 0.108 + ], + "angle": 0, + "content": "4.2. Spatial Reasoning: A Toy Experiment" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.113, + 0.473, + 0.417 + ], + "angle": 0, + "content": "We investigate spatial reasoning abilities of two SOTA V-LLMs, LLaVA [38] and BLIP-2 [33], using a simple toy experiment. We create an evaluation dataset from COCO annotations containing images with distinct category object triplets (only one instance occurrence of each object category), where each object is entirely to the left or right half of the image and two objects are on opposite sides. The ground-truth bounding box annotation are utilized to automate this dataset creation procedure. This evaluation set, referred as COCO-Spatial-27K, contains 26,716 image-question pairs (see Appendix C for details). We introduce two evaluation settings, direct VQA and in-context learning (ICL) VQA to understand spatial reasoning abilities of these models. In direct VQA, given an image we query the model whether an object lies above or below another object. In ICL VQA, before a similar final query, we provide two example question-answer pairs (involving the other two objects in the image) in the same format as our query. Refer to Appendix E for further details on task. We perform the same for objects in top vs bottom halves of images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.424, + 0.473, + 0.592 + ], + "angle": 0, + "content": "These results are presented in Table 4. Our results indicate near random performance for existing V-LLMs. For the case of LLaVA, we perform keyword (left and right) frequency analysis on its instruction tuning dataset (LLaVA-Instruct-80K dataset) to verify the presence of terms left and right in its training corpus. These keywords are present in \\(0.37\\%\\) and \\(1.13\\%\\) of its conversations respectively (see Appendix F for more) indicating presence of these concepts in the image-text training corpus. In contrast to these methods, our proposed framework notably improves performance over both BLIP-2 [33] and the LLaVA baseline [38]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.607, + 0.206, + 0.623 + ], + "angle": 0, + "content": "4.3. Image VQA" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Image VQA involves correctly answering natural language questions regarding content within an image. We evaluate our model for Image VQA on two standard datasets, GQA and VQAv2. The GQA dataset focuses on questions requiring compositional reasoning, particularly involving surrounding information of objects within an image. We evaluate on its test-dev split containing 12,578 image-question pairs. The VQAv2 dataset contains open-ended questions about each image that require an understanding of vision, language and commonsense knowledge to answer. We use its validation split containing 214,354 image-question pairs for our evaluation. For each dataset, we follow standard V-LLM evaluation protocol following [33, 42] and report top-1 accuracy metric. Our results in Tab. 5 indicate clear improvements for LocVLM over our baseline and prior work, establishing the usefulness of our proposed framework. The closest to our work, Shikra [8] achieves performance competitive to our LocVLM-B, but" + }, + { + "type": "table", + "bbox": [ + 0.508, + 0.09, + 0.887, + 0.194 + ], + "angle": 0, + "content": "
MethodICLAllLeftRightAllAboveBelow
BLIP-2 [33]✗45.586.14.7449.250.448.6
LLava [38]✗55.184.536.558.957.859.3
Ours✗69.579.759.265.464.265.9
BLIP-2 [33]✓14.717.811.615.816.515.2
LLaVa [38]✓55.184.736.458.257.758.5
Ours✓76.590.461.574.173.574.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.199, + 0.892, + 0.298 + ], + "angle": 0, + "content": "Table 4. Spatial Reasoning: We report accuracy \\((\\%)\\) on a spatial localization dataset derived from COCO annotations to highlight weak spatial awareness of existing V-LLMs. We query these models to answer whether one object is to the left or right / above or below of another object. The SOTA V-LLMs evaluated exhibit close to random performance. Our proposed setup outperforms existing methods. Ours refers to LocVLM-B variant." + }, + { + "type": "table", + "bbox": [ + 0.507, + 0.302, + 0.887, + 0.456 + ], + "angle": 0, + "content": "
MethodLLMVSZero-ShotGQAVQA-VVQA-T
SR [4]--X62.172.9-
Shikra [8]7B224X-75.377.4
LLaVA-v1.57B336X62.078.178.4
LocVLM-L7B336X63.578.278.6
LLaVA-v17B224✓44.749.849.3
LocVLM-B7B224✓47.350.350.8
Viper-GPT175B-✓48.1--
BLIP-211B-✓44.754.353.9
LLaVA-v1.57B336✓48.755.755.3
LocVLM-L7B336✓50.255.956.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.457, + 0.892, + 0.512 + ], + "angle": 0, + "content": "Table 5. Image VQA Results: We report accuracy \\((\\%)\\) on the test-dev split of GQA dataset (GQA) and the validation / test splits of VQAv2 dataset (VQA-V / VQA-T). Our proposed LocVLM improves over prior works achieving state-of-the-art performance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.529, + 0.892, + 0.561 + ], + "angle": 0, + "content": "unlike ours they use VQA datasets (containing similar domain question-answer pairs) during training." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.571, + 0.625, + 0.587 + ], + "angle": 0, + "content": "4.4. Video VQA" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.595, + 0.892, + 0.73 + ], + "angle": 0, + "content": "Our model is also applicable to video tasks following our video domain adaptation described in Sec. 3.5. We simply adopt the additional video instruction fine-tuning phase from [42] on the ActivityNet dataset after our initial two phases of training to obtain LocVLM-Vid-B. This third phase involves fine-tuning only the adapter layer of our model. We also explore video variants of our IFT objectives that train both adapter layer and LLM. The resulting model is termed LocVLM-Vid-B+." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Video VQA focuses on correctly answering questions regarding a given video that require spatio-temporal awareness to answer. We evaluate our video-adapted model on the task of zero-shot video VQA on four benchmark datasets, ActivityNet-QA, MSRVTT-QA, MSVD-QA, and TGIF-QA. We evaluate on the validation splits of these four datasets. ActivityNet-QA videos cover a wide range of complex human activities relevant to daily living with its question-answer pairs focusing on long-term spatiotemporal reasoning. MSRVTT-QA builds off the MSRVTT dataset that contains web videos covering a comprehensive" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "12982" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.139, + 0.089, + 0.83, + 0.297 + ], + "angle": 0, + "content": "
MethodZero-ShotActivityNet-QAMSRVTT-QAMSVD-QATGIF-QA
JustAsk [63]✘38.941.847.5-
FrozenBiLM [64]✘43.247.054.8-
VideoCoCa [62]✘56.146.356.9-
Flamingo [2]✓-17.435.6-
BLIP-2 [33]✓-17.434.4-
InstructBLIP [15]✓-25.644.3-
FrozenBiLM [64]✓24.716.832.241.0
Video Chat [34]✓26.545.056.334.4
LLaMA Adapter [72]✓34.243.854.9-
Video LLaMA [71]✓12.429.651.6-
Video-ChatGPT [42]✓35.249.364.951.4
LocVLM-Vid-B✓37.451.266.151.8
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.301, + 0.892, + 0.329 + ], + "angle": 0, + "content": "Table 6. Video VQA Results: Our proposed LocVLM-Vid-B improves over Video-ChatGPT [42] and achieves state-of-the-art results (Top-1 Accuracy %) across four different video VQA benchmarks. Note the zero-shot setting of all these evaluations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.344, + 0.473, + 0.587 + ], + "angle": 0, + "content": "range of categories and diverse visual content. MSVD-QA is a similar dataset building off the MSVD dataset. TGIFQA contains question-answer pairs from an dataset constructed of animated GIFs. For each dataset, we report the accuracy metric following evaluation protocol in [42]. Our results on these four datasets reported in Tab. 6 demonstrate state-of-the-art performance of our proposed LocVLM-Vid-B, with consistent improvements over the baseline from [42]. Here we use the LocVLM-Vid-B variant for fairer comparison with the baseline from [42]. We attribute the performance gains exhibited by our model to its stronger spatial awareness (see Sec. 4.2). Particularly in the case of video understanding, awareness of content at spatial level of each frame is significant to understand object motions and interactions [1, 51]. We also report more results involving additional model variants in Tab. 7." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.606, + 0.276, + 0.623 + ], + "angle": 0, + "content": "4.5. Object Hallucination" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Current state-of-the-art V-LLMs suffer from object hallucination, generating image descriptions inconsistent with the image content [36]. For example, a V-LLM would respond to \"Where is the cat in this image?\" with \"The cat is on the table\" when in reality there is no cat in the image. We evaluate the extent of hallucination in V-LLMs using three datasets we introduce (details in Appendix C) and the POPE dataset [36]. Our three datasets, Hal-COCO, Hal-ADE, and Hal-Act build off COCO, ADE-20K, and ActivityNet datasets respectively. The first two involve images and the latter videeos. These datasets contain \"Is there obj in image / video?\" type questions per sample, for two objects present and not present in the image / video. Hal-ADE object categories contain no overlap with COCO classes allowing evaluation on novel object categories unseen during our instruction fine-tuning. Results reported in Tab. 8 show clear improvements of LocVLM-B over baselines. We also evaluate LocVLM-B on the POPE benchmark [36] that builds" + }, + { + "type": "table", + "bbox": [ + 0.518, + 0.342, + 0.872, + 0.473 + ], + "angle": 0, + "content": "
MethodVLTFramesAcc (%)
LLaVa (v1) [38]×128.7
LLaVa (v1.5) [38]×131.5
LocVLM-B×129.2
LocVLM-L×132.1
Video-ChatGPT [42]✓10035.2
LocVLM-Vid-B✓10037.4
LocVLM-Vid-B+✓838.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.475, + 0.892, + 0.53 + ], + "angle": 0, + "content": "Table 7. Video VQA: We report more results (Top-1 Accuracy) for ActivityNet-QA dataset including multiple baseline and LocVLM variants. Our proposed models exhibit top performance. VLT denotes video level training. More details in Appendix D." + }, + { + "type": "table", + "bbox": [ + 0.506, + 0.532, + 0.892, + 0.646 + ], + "angle": 0, + "content": "
MethodHal-COCOHal-ADEHal-Act
Shikra [8]86.258.7-
LLaVa [38]61.953.8-
LocVLM-B88.375.2-
Video-ChatGPT [42]--50.6
LocVLM-Vid-B--68.7
LocVLM-Vid-B+--72.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.647, + 0.892, + 0.689 + ], + "angle": 0, + "content": "Table 8. Hallucination Evaluation: We report top-1 accuracy (\\%) for object presence type questions and showcase reduced object hallucination in our proposed framework." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.703, + 0.892, + 0.749 + ], + "angle": 0, + "content": "off the COCO dataset object annotations and report results in Tab. 9. Our LocVLM showcases similar performance improvements on this dataset." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.757, + 0.685, + 0.773 + ], + "angle": 0, + "content": "4.6. Region Description" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.903 + ], + "angle": 0, + "content": "A unique characteristic of our model (in contrast to V-LLMs like LLaVA [38] & BLIP-2 [33]) is its ability to reason with prompts involving coordinate based image space locations without any input modifications. Given a point or bounding box location, we prompt our model to generate an output describing that location. We refer to this unique ability of our model as region description (RD). We evaluate this RD capability of our model by generating object" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "12983" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.084, + 0.089, + 0.465, + 0.32 + ], + "angle": 0, + "content": "
DatasetsMetricsBLIP-2ShikraLLaVAOurs
RandomAccuracy (↑)88.686.950.487.9
Precision (↑)84.194.450.283.6
Recall (↑)95.179.399.193.9
F1 Score (↑)89.386.266.688.5
Yes56.643.398.856.2
PopularAccuracy (↑)82.884.049.986.0
Precision (↑)76.387.649.979.7
Recall (↑)95.179.299.393.9
F1 Score (↑)84.783.266.486.3
Yes62.445.299.458.9
AdversarialAccuracy (↑)72.183.149.778.8
Precision (↑)65.185.649.976.6
Recall (↑)95.179.699.193.7
F1 Score (↑)77.382.566.384.3
Yes73.046.599.461.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.322, + 0.468, + 0.352 + ], + "angle": 0, + "content": "Table 9. More object hallucination: Results on POPE evaluation benchmark [36] indicate strong performance of our model." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.369, + 0.47, + 0.529 + ], + "angle": 0, + "content": "
MethodZSRefCOCORefCOCO+RefCOCOg
ValTest
SLR [67]✘---15.4
SLR + Rerank [67]✘---15.9
Kosmos-2 [45]✘8.678.8214.314.1
Shikra [8]✘10.411.119.719.5
LLaVa [38]✘8.438.7313.513.5
LocVLM-B✘14.615.226.026.2
Kosmos-2 [45]✓6.348.2512.412.2
LLava [38]✓4.237.2610.610.3
LocVLM-B✓11.011.120.620.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.531, + 0.468, + 0.573 + ], + "angle": 0, + "content": "Table 10. Region Description: We report METEOR scores for RD task [45]. Test-B split is used for RefCOCO & RefCOCO+ datasets. Our method outperforms all prior work." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.592, + 0.468, + 0.773 + ], + "angle": 0, + "content": "level descriptions focused on contextual information (e.g. surrounding of that object in the image). Following evaluation protocol in [45] for region description, we extend their evaluation to three standard referring localization datasets from RefCOCO [29] and report these results in Tab. 10. We select the METEOR score as the evaluation metric to account for variations in word choice in generated answers which may be acceptable in various cases (e.g. different sentence structure leading to alternate word ordering). Our results indicate clear improvements over the LLaVA baseline [38] as well as prior state-of-the-art. We attribute these improvements to our pseudo-data based training." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.787, + 0.188, + 0.802 + ], + "angle": 0, + "content": "4.7. Ablations" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Next we conduct ablative studies on separate components of our proposed setup: IFT objectives, location type, and pseudo-data. We follow the same training strategy as described in Sec. 4.1 and present these results in Tab. 11. LocVLM-B is used for all these experiments. The significance of each IFT objective is verified in Tab. 11 (top) with" + }, + { + "type": "table", + "bbox": [ + 0.521, + 0.09, + 0.873, + 0.242 + ], + "angle": 0, + "content": "
LocPredNegPredRevLocGQARDA-QA
XXX44.710.335.2
✓XX45.212.235.8
✓✓X46.912.537.2
✓✓✓47.320.737.4
Location TypePDGQARDA-QA
Point✓47.320.637.4
Bounding Box✓47.320.737.4
Bounding BoxX46.511.637.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.244, + 0.892, + 0.355 + ], + "angle": 0, + "content": "Table 11. Ablations: We report top-1 accuracy (\\%) on GQA and ActivityNet-QA (A-QA) datasets and METEOR scores for RD task on RefCOCOg test split. (top) We ablate proposed instruction fine-tuning objectives to verify usefulness of each objective. (bottom) We first ablate point based and bounding box based location forms to showcase minimal difference across them. We next ablate use of object description pseudo-data (PD). We highlight the improvements due to pseudo-data, especially on the RD task." + }, + { + "type": "table", + "bbox": [ + 0.551, + 0.377, + 0.842, + 0.457 + ], + "angle": 0, + "content": "
LocPredNegPredRevLocA-QA
XXX37.4
✓XX37.6
✓✓X38.2
✓✓✓38.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.458, + 0.892, + 0.501 + ], + "angle": 0, + "content": "Table 12. Video Ablation: We report top-1 accuracy \\((\\%)\\) on ActivityNet-QA (A-QA) dataset. Results indicate the generality of proposed IFT objectives for video domain training as well." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.53, + 0.892, + 0.681 + ], + "angle": 0, + "content": "consistent performance improvements across tasks. The generality of our approach to differing location type (i.e. points vs bounding boxes) and usefulness of pseudo-data is visible in Tab. 11 (bottom). In particular, we highlight the notable performance improvement for RD task gained from using pseudo-data. We also conduct ablations for our video domain training setup and report these results in Tab. 12. The LocVLM-Vid-B+ variant is used in these experiments. Our results showcase the usefulness of proposed IFT objectives for video domain learning as well." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.71, + 0.619, + 0.725 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We introduce a simple framework that equips visual-LLMs (V-LLMs) with greater spatial understanding, termed LocVLM. We leverage the idea of encoding image coordinates within language to propose three instruction finetuning (IFT) objectives. This training process endows V-LLMs with the ability to reason about spatial composition of images using image space coordinates within text. A data efficient training pipeline utilizing pseudo-data allows our approach to achieve state-of-the-art results in Image VQA, Video VQA, and Region Description while improving spatial awareness and reducing object hallucination." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "12984" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.081, + 0.091, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.111, + 0.468, + 0.152 + ], + "angle": 0, + "content": "[1] Jake K. Aggarwal and Michael S. Ryoo. Human activity analysis. ACM Computing Surveys (CSUR), 43:1-43, 2011. 7" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.154, + 0.468, + 0.223 + ], + "angle": 0, + "content": "[2] Jean-Baptiste Alayrac, Jeff Donahue, Pauline Luc, Antoine Miech, Iain Barr, Yana Hasson, Karel Lenc, Arthur Mensch, Katie Millican, Malcolm Reynolds, et al. 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In NeurIPS, 2023. 5, 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.403 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "12987" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/7cd84fbe-5225-4590-b9bf-3163d999924f_origin.pdf b/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/7cd84fbe-5225-4590-b9bf-3163d999924f_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..81b145c5d77527a74950041775911fe62182bd6d --- /dev/null +++ b/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/7cd84fbe-5225-4590-b9bf-3163d999924f_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:d301428d00017e648e5d3a2bb860d77d228803c5ebf7a8d1068fabd1ee8ff670 +size 774812 diff --git a/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/full.md b/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/full.md new file mode 100644 index 0000000000000000000000000000000000000000..3ad7b4cb3e7bb5d49469fa3456e7bc8660194ef4 --- /dev/null +++ b/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/full.md @@ -0,0 +1,322 @@ +# Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs + +Kanchana Ranasinghe1,2 Satya Narayan Shukla1 Amid Poursaeed1 + +Michael S. Ryoo² Tsung-Yu Lin1 + +$^{1}$ Meta $^{2}$ Stony Brook University + +{kranasinghe, mryoo}@cs.stonybrook.edu, {satyanshukla, opoursaed, tsungyulin}@meta.com + +# Abstract + +Integration of Large Language Models (LLMs) into visual domain tasks, resulting in visual-LLMs (V-LLMs), has enabled exceptional performance in vision-language tasks, particularly for visual question answering (VQA). However, existing V-LLMs (e.g. BLIP-2, LLaVA) demonstrate weak spatial reasoning and localization awareness. Despite generating highly descriptive and elaborate textual answers, these models fail at simple tasks like distinguishing a left vs right location. In this work, we explore how image-space coordinate based instruction fine-tuning objectives could inject spatial awareness into V-LLMs. We discover optimal coordinate representations, data-efficient instruction fine-tuning objectives, and pseudo-data generation strategies that lead to improved spatial awareness in V-LLMs. Additionally, our resulting model improves VQA across image and video domains, reduces undesired hallucination, and generates better contextual object descriptions. Experiments across 5 vision-language tasks involving 14 different datasets establish the clear performance improvements achieved by our proposed framework. + +# 1. Introduction + +Holistic visual understanding requires learning beyond simply content of an image to encompass awareness on spatial locations of objects and their relations [41]. In the context of visual question answering (VQA), such spatial awareness allows better reasoning involving structural and contextual information contained within an image [8]. + +Since the introduction of powerful large-language models (LLMs) such as GPT-3 [5], Chat-GPT [44], Vicuna [11], and LLaMA [55, 56] that are capable of human style conversation, their visual counterparts such as BLIP-2 [33], LLaVA [38] have enabled novel tasks within the vision modality. However, despite their [33, 38] highly generic visual understanding, these models exhibit poor language-based spatial reasoning [8]. In fact, they fail at simple tasks such as distinguishing whether an object lies to the left or right of another object (see Tab. 4). + +![](images/220434e2d7b3dce9eb28b3d773ce89703207a01a2e63d1f032250d7bd78dd8c2.jpg) + +Query: Describe [x1,y1,x2,y2] location in image. + +Ours: A blue plaid blanket behind a teddy bear. + +Query: Which side of the potted plant is the stove? + +LLaVa: The stove is on the left side of potted plant. + +Ours: The stove is on the right side of potted plant. + +![](images/831c277cee537b96e010839838bb2f33703db97f6af9885cce63fb83ddf493ab.jpg) +Figure 1. We illustrate one unique ability of our model: contextual region description (top). Note the contextual information used in describing the selected region in each image. Explicitly teaching localization to Visual-LLMs also improves spatial awareness in VQA settings (bottom). Color boxes only for illustration purposes. + +In the case of contrastive language image models (such as CLIP [46], ALIGN [26]), recent works explore how injecting explicit spatial awareness [39, 43, 48, 74] can enable more holistic visual understanding. In fact, [48] shows how such improved spatial awareness benefits model robustness in adversarial domains. This raises the question of how generative language image models, particularly those connecting LLMs to visual encoders [33, 38] can benefit from such spatial awareness specific training. We refer to models of this category that generate textual outputs given joint image-text inputs (e.g. [33, 38]) as visual-LLMs (V-LLMs). + +In this work, we explore location specific instruction fine-tuning objectives that explicitly enforce V-LLMs to + +meaningfully process and generate textual image-space coordinates. We hypothesize that such training would lead to improved spatial awareness in these V-LLMs, therein improving performance on VQA tasks. To this end, we propose three instruction fine-tuning objectives that unify location representation with natural language. We also explore optimal representation forms for image-space locations and how pseudo-data generation can be leveraged for efficient scaling of our framework. We name our resulting model as LocVLM. + +While the idea of adapting V-LLMs to perform localization related tasks (e.g. detection, segmentation) using V-LLMs has been explored in multiple recent works [30, 45, 58, 66, 68, 73, 75], these approaches depend on task specific architectural modifications or treat localization inputs / outputs differently from natural language. In contrast, our LocVLM focuses on a unified framework treating location and language as a single modality of inputs with the goal of complementing performance in each task. We intuit that processing location represented in textual form would enforce the LLM to select appropriate image regions as opposed to relying on region level features provided by the architecture. At the same time, textual form location outputs promote spatial awareness at language level in a human interpretable manner, in contrast to using secondary heads or specialized tokens for location prediction. Concurrent work in [8] also explores textual location representation with a generic V-LLM architecture similar to our work. Our proposed LocVLM differs with focus on optimal location representation forms, data-efficient pseudo-labelling, and video domain operation. + +Our proposed framework exhibits improved spatial awareness in VQA style conversation demonstrated through experimentation on 14 datasets across 5 vision-language tasks: Spatial Reasoning, Image VQA, Video VQA, Object Hallucination, and Region Description. We summarize our key contributions as follows: + +- Inject textual spatial coordinate awareness into V-LLMs +- Propose three novel localization based instruction finetuning objectives for V-LLMs +- Discover optimal coordinate representation forms +- Pseudo-Data generation for improved region description and scaling to video domain + +# 2. Related Work + +Localization in Contrastive Vision Language Models: Foundation vision language models (VLMs) such as CLIP [46] resulted in extensive exploration into language-tied localization in images both under dense (pixel / bounding-box) supervision [16-18, 21, 27, 31, 32, 35, 69, 70] and weak supervision [14, 39, 43, 48, 60, 61, 65, 74, 76]. Recovering explicit localization information within model rep + +
MethodKosmos [45]Ferret [66]Shikra [8]Ours
Unified Arch.XX✓✓
Purely TextualXX✓✓
Pseudo DataXXX✓
Video DomainXXX✓
+ +Table 1. Related Work Comparison: A unified architecture, purely textual inputs, pseudo data for scalable learning, and video domain operation distinguishes our work from these prior methods. + +resentations has enabled more robust operation for certain tasks [48]. While our work differs from this contrastive setting given our use of LLM based generative predictions, we similarly explore how explicit location information within the language modality can improve V-LLMs. + +Visual Large Language Models (V-LLMs): The advent of powerful large language models (LLMs) such as GPT-3 [5], Chat-GPT [44], and PaLM [13], as well as their open-source counterparts BLOOM [52], Vicuna [11], and LLaMA [55, 56], has resulted in direct use of these LLMs for computer vision tasks [22, 53]. Alternate lines of work explore how LLMs can be connected to existing visual foundation models [2, 3, 33, 38, 42, 47], in particular to CLIP visual backbones [46]. While earlier models explored large-scale (millions to billions of samples) image-text training [2, 3], later models [33, 38, 42] scale down on data dependency. LLaVA [38] in particular scales down on pre-training data to under 1 million image-text pairs, and use instruction fine-tuning [59] to enable human-style conversation with visual awareness. This is extended to video domain in [42, 49]. A shortcoming of these models is their lack of spatial awareness or location understanding in image space [8, 12, 20]. Spatial reasoning limitations in generative VLMs are studied in [12, 20]. Similar failures in captioning (and VQA) models are explored in [28]. A solution in [24] proposes code-generation based reasoning. Our work tackles these same limitations but follows an alternate direction of spatial-aware instruction fine-tuning. Another line of recent works [30, 45, 58, 66, 68, 73, 75] tackle this by introducing architectural modifications to explicitly extract region level features that are injected to the LLM as special tokens. While introducing extra tokens and layers, this also separates the localization task from language. In contrast, we use a generic architectures with purely textual location information (i.e. image space coordinates as text). Concurrent work in [8] explores this same idea, but we differ in 3 ways with, a) focus on optimal coordinate representation forms, b) data-efficient pseudo-labelling strategies, and c) video domain operation (see also Tab. 1). + +Location Representations: Selecting regions within an image has a rich history in computer vision [40, 57] with greater focus on location outputs since the popularity of object detection [6, 9, 10, 19, 50, 54, 58]. Early anchor-based + +methods regress locations from anchor centers [19, 50], followed by direct location regression from object-level features [6, 54]. Recent works explore generative location predictions with diffusion processes [9] and sequence-generation [10, 58]. Ours resembles the latter given our use of an LLM, next token prediction objective, and sequential generation of textual location representations. However, [10, 58] utilize 1000 specialized location tokens (introduced to the LLM vocabulary) corresponding to 1000 bins uniformly spread across image space. While we explore similar binning strategies, in contrast we introduce no additional tokens, focus on purely textual representation of locations, and explore multiple textual location representation forms. + +# 3. Method + +Current V-LLMs [33, 38] exhibit weak understanding of spatial locations within images [8]. We explore and benchmark such shortcomings, and propose three novel instruction fine-tuning objectives aimed at overcoming these drawbacks of existing V-LLMs. We build these objectives based on spatial-coordinate based prompting and demonstrate how LLMs can directly both process and generate meaningful numerical coordinates in image-space after suitable training. In the rest of this section we describe our architecture and training framework, followed by coordinate processing & generation, instruction fine-tuning objectives, pseudo-data generation, and video domain operation. + +# 3.1. Architecture and Training + +The focus of our work is to explore how spatial localization related training can improve a generic V-LLM such as LLaVA [38]. Therein, our architecture and training framework is inspired from [38]. We use a visual encoder, adapter layer, and LLM stacked sequentially (illustrated in Fig. 2), and follow a multi-stage training strategy similar to [38]. + +Consider an image $X \in \mathbb{R}^{H, W, C}$ where $H, W, C (= 3)$ denote height, width, channels of image and a textual prompt $T$ composed of natural language (asking a question about the image). We define two variants of our model, LocVLM-B and LocVLM-L for better comparison with prior work. We first describe LocVLM-B that processes images with $H = W = 224$ . Our visual encoder, ViTL/14 from CLIP [46], processes the image $X$ to produce a set of 256 visual tokens in $\mathbb{R}^{1024}$ , which are in turn projected to $\mathbb{R}^{4096}$ by an adapter layer (implemented as a linear layer). The LLaMA [55] text tokenizer processes the textual prompt $T$ to produce textual tokens in $\mathbb{R}^{4096}$ . The joint set of visual and textual tokens (of dimension $\mathbb{R}^{4096}$ ) are processed by a LLaMA [55] LLM to produce the final set of textual tokens which are in turn untokenized to convert to natural language. The final natural language output is expected to be a suitable response to the input textual prompt, $T$ . In variant LocVLM-L, we use images sized + +![](images/150a99aba89437f0a65a9356ecfbebc7567c3a463cfd9d2afc33ae576d288ffe.jpg) +Figure 2. Architecture: We present the overall model architecture of our framework which is inspired from LLaVa [38]. + +$H = W = 336$ resulting in 576 visual token, an adapter layer implemented as an MLP, and the LLM from LLaMA-2 [56]. All other design choices remain unchanged. + +We also highlight the BPE tokenization that is employed in our setup. This learned tokenization scheme may split a single word into sub-parts (that alone can appear meaningless to humans) and handles numerical text (including decimal point) as individual tokens (e.g. 12.34 would be split into 5 separate tokens). + +In terms of training, we follow a two-stage strategy. Inspired by LLaVA [38], we adopt an initial pre-training stage that only updates weights of the intermediate adapter layer to align the visual encoder outputs with LLM inputs. Next, we jointly instruction fine-tune the adapter layer and LLaMA LLM with our proposed objectives and template-based localization datasets (see Sec. 4.1). Video domain operation introduces an additional phase (see Sec. 3.5). + +# 3.2. Coordinate Processing and Generation + +Humans contain the ability to reason about images using image-space coordinates. This is in contrast to existing V-LLMs that can describe the contents of an image elegantly, but lack spatial awareness regarding image contents. We hypothesize that injecting LLMs with additional spatial awareness, through coordinate based reasoning could improve their generic reasoning ability as well. To this end, we introduce our first goal of directly using textual coordinate based image locations in both natural language prompts and LLM generated outputs. For textual coordinates, we explore three different representation forms: + +1. Normalized Floating Point Values +2. Integer Valued Binning (across image dimensions) +3. Deviation from Image-Grid based Anchors + +
CRGQA (Acc)RD (METEOR)A-QA (Acc)
NFP46.119.637.1
IVB47.320.737.4
DIGA47.020.837.3
+ +For image locations, we explore point based (e.g. center coordinates [cx, cy] of object) and bounding box based (e.g. top-left and bottom-right extreme coordinates of object region [x1, y1, x2, y2]) forms. We next discuss the three representations for coordinates used for either location. + +Normalized Floating Point Values calculates absolute image coordinates and normalizes with image dimensions to a $(0,1)$ range. We use a 4 decimal point representation for these floating point values. While this representation is simple and generic, given the nature of BPE tokenization, each individual coordinate will be represented by up to 6 tokens. + +Integer Valued Binning discretizes the absolute image coordinates to one of $n_b$ ( $= 224, 336$ for variant B & L respectively) bins spread uniformly across the two image dimensions. Based on the binning parameter, $n_b$ , each coordinate will be represented some number of tokens, in our case up to 3 (less than the floating point variant). + +Deviation from Image-Grid based Anchors is motivated from prior object detection works that estimate an initial anchor followed by deviation from that anchor center to estimate bounding box coordinates. We follow a similar setup, where one of $n_a$ anchors is predicted by the model, followed by deviation of coordinate from that anchor center. Our intuition is that, given the sequential next-token prediction setup of LLMs, such a two-stage strategy would lead to faster learning and more accurate coordinates. + +We refer to Appendix A for further details on each variant. In Tab. 2, we ablate each representation format on three different tasks (see Sec. 4.7 for more details) of image VQA (GQA), region description (RD), and video VQA (A-QA). Our experiments indicate optimal performance for integer valued binning (IVB). In all following experimentation, we fix our coordinate representation to IVB. + +# 3.3. Instruction Fine-Tuning Objectives + +Given suitable coordinate representations, we now have a mechanism to directly prompt LLMs with image locations in textual form. Our second goal is to build training objectives using these image coordinates that directly inject spatial awareness into V-LLMs. We propose three instruction fine-tuning objectives for this purpose. + +Let us first revisit the visual instruction fine-tuning methodology in [38]. Building off the COCO dataset, + +Table 2. Ablation on Coordinate Representation (CR) methods: we compare each of the three proposed CR variants, namely normalized floating point values (NFP), integer valued binning (IVB), and deviation from image-grid based anchors (DIGA). + +
ObjectivePromptTarget
LocPredWhere is obj1?It's at (x1,y1,x2,y2).
NegPredWhere is obj2?There's no obj2.
RevLocDescribe (cx,cy)Detailed description
+ +Table 3. We summarize our three distinct instruction fine-tuning objectives. Refer to appendix (Appendix B) for exact natural language prompts and targets used for training. For illustration, we use both point and bounding-box based image locations here. + +they construct a VQA dataset containing conversation style question-answer pairs relevant to each COCO image. Question-answer pairs are generated using an LLM that is fed with the ground-truth bounding-box annotations for each image. Inspired by this setup, we build a similar spatial-VQA dataset using images and annotations of the COCO dataset, but instead of LLM prompting, we utilize hand-crafted templates and pseudo-captions (discussed in Sec. 3.4) to generate conversations. + +We propose three types of question-answer pairs that relate to our three instruction fine-tuning objectives: Location Prediction (LocPred), Negative Prediction (NegPred), and Reverse-Location Prediction (RevLoc). See Tab. 3 for examples. Considering the LLM based final text generation in our architecture, we utilize next-token prediction loss to achieve each objective during our training. + +Location Prediction: Given an object category, we query the model to generate a point or bounding box localizing that object in the image. The object category and bounding box are derived from the COCO train set annotations. To avoid object mismatches (i.e. multiple object of same category), we first filter images containing only a single object of a given class. + +Negative Prediction: Using the same prompt templates as in LocPred above, we query the model to generate a point or bounding box localizing a specified object in the image. However, in this case we select an object category not present in the image and accordingly provide a target text of "no such object in image". For each image, we utilize COCO bounding-box annotations to discover objects (belonging to COCO classes) that are not present in that image. + +Reverse-Location Prediction: We perform the reverse of LocPred here. Given a point or bounding box in image space, we query the model to describe the object in that location. The bounding box and object category are derived from the COCO train set annotations. + +While introducing three novel train objectives aimed at injecting location information, we highlight that our proposed framework relies on training data (i.e. human annotations) identical to those used by LLaVA [38]. We do not use any additional ground-truth annotations for training. Next we explore how we could augment the generality of our framework while limiting to this same annotated data. + +# 3.4. Pseudo-Data Generation + +We introduced three train objectives, each utilizing template based conversations as prompts and targets. However, our reliance on categories of COCO dataset limits the object vocabulary seen during training. Therein, we propose a pre-trained V-LLM based pseudo-data generation strategy. In fact, we utilize our model after stage one training as the V-LLM leading to a form of self-training based learning. Given the abundance of only image-level annotated datasets (i.e. no bounding box ground-truth), we also explore how an object-detector generated pseudo-bounding boxes could augment our framework. + +Self-Training: Given an image and bounding box annotations from the COCO train set, we prompt the V-LLM to caption each distinct object in the image. In order to prevent ambiguous object queries, we filter images to select only those containing at most one instance of a single category. We additionally prompt the V-LLM to describe the object using relational information (i.e. relative to other objects in image). This process provides us a dataset with object level bounding boxes and descriptive captions that are not limited to the COCO object categories (dataset details in Appendix C). In turn, we use this data generated by the V-LLM (our stage one model) to further improve performance of our framework. We modify each of our three train objectives (in Sec. 3.3) to utilize these image-specific pseudocaptions instead of the generic dataset level category labels. + +Weak Supervision: We explore how datasets containing no object level annotation (e.g. video classification / VQA datasets) could be leveraged to adapt our framework into domains beyond images. Therein, we utilize an off-the-shelf panoptic segmentation framework from SEEM [77] to generate pseudo-bounding boxes for selected object categories within any image as well as exhaustive pixel level labels (enabling negative class identification). We leverage this setup to extend our introduced train objectives to the video domain as well. + +# 3.5. Video Domain Operation + +Inspired by the simple modifications to LLaVA [38] in [42] enabling video domain operation, we follow a similar strategy of modifying our LocVLM-B architecture to process videos while introducing no additional components. The visual backbone process multiple video frames individually (as images) and resulting tokens are averaged across spatial $(S)$ and temporal $(T)$ axes to obtain $S + T$ tokens. These are processed by the adapter layer and LLM to generate the textual outputs. Further details on our video architecture are discussed in Appendix D. + +In addition to our two training phases discussed in Sec. 3.1, we introduce a third video instruction fine-tuning stage using a dataset we derive from ActivityNet [23]. Fol + +lowing [42], only the adapter layer is fine-tuned leaving all other parameters frozen. This resulting model is referred to as LocVLM-Vid-B. + +We next introduce video variants of our three instruction fine-tuning objectives focused on static objects in videos. We utilize our proposed pseudo-labeling strategy to generate necessary video annotations and train both the adapter layer and LLM to obtain a second video model tagged LocVLM-Vid-B+. Further details on our video fine-tuning objectives are presented in Appendix D. + +# 4. Experiments + +In this section, we present experimental results to highlight existing weaknesses of SOTA V-LLMs and how our proposed framework addresses these issues. We also evaluate on standard VQA benchmarks across domains to showcase the better reasoning abilities of our model and highlight novel abilities of our framework. + +# 4.1. Experimental Setup + +Datasets: We utilize the COCO dataset [37] and our model (post stage one training) to construct a localization related VQA dataset as outlined in Sections 3.3 and 3.4. We name this dataset Localize-Instruct-200K. In detail, this contains LocPred and RevLoc question-answer pairs that use pseudo-captions instead of COCO categories as well as NegPred. We define a second video dataset, Localize-ActivityNet, containing question-answer pairs constructed from Activity-Net pseudo-bounding boxes following Section 3.5. Our models are primarily trained on our Localize-Instruct-200K dataset. Our stage one training uses CC3M dataset [7]. Additionally, our Localize-ActivityNet dataset and ActivityNet dataset [23] are used for video domain training. + +Training: We train our models on 8xA100 GPUs (each 80GB) following a two-phase training schedule. Our first phase trains on CC3M [7] following the setup in [38]. The second phase uses our Localize-Instruct-200K dataset and trains for 10 epochs with a batch size of 64, ADAM-W optimizer with initial learning rate $2e - 5$ , 0.3 warm-up ratio, and cosine-decay learning rate schedule. Both the training phases we conduct use standard next-token-prediction loss used in LLM training. + +Evaluation: During evaluation, following standard protocol [38], we iteratively generate next tokens, given visual and textual inputs. The LLM output is a distribution across the entire token vocabulary. The next token is selected through multinomial sampling of this output using a softmax temperature term of 0.2 during normalization. + +# 4.2. Spatial Reasoning: A Toy Experiment + +We investigate spatial reasoning abilities of two SOTA V-LLMs, LLaVA [38] and BLIP-2 [33], using a simple toy experiment. We create an evaluation dataset from COCO annotations containing images with distinct category object triplets (only one instance occurrence of each object category), where each object is entirely to the left or right half of the image and two objects are on opposite sides. The ground-truth bounding box annotation are utilized to automate this dataset creation procedure. This evaluation set, referred as COCO-Spatial-27K, contains 26,716 image-question pairs (see Appendix C for details). We introduce two evaluation settings, direct VQA and in-context learning (ICL) VQA to understand spatial reasoning abilities of these models. In direct VQA, given an image we query the model whether an object lies above or below another object. In ICL VQA, before a similar final query, we provide two example question-answer pairs (involving the other two objects in the image) in the same format as our query. Refer to Appendix E for further details on task. We perform the same for objects in top vs bottom halves of images. + +These results are presented in Table 4. Our results indicate near random performance for existing V-LLMs. For the case of LLaVA, we perform keyword (left and right) frequency analysis on its instruction tuning dataset (LLaVA-Instruct-80K dataset) to verify the presence of terms left and right in its training corpus. These keywords are present in $0.37\%$ and $1.13\%$ of its conversations respectively (see Appendix F for more) indicating presence of these concepts in the image-text training corpus. In contrast to these methods, our proposed framework notably improves performance over both BLIP-2 [33] and the LLaVA baseline [38]. + +# 4.3. Image VQA + +Image VQA involves correctly answering natural language questions regarding content within an image. We evaluate our model for Image VQA on two standard datasets, GQA and VQAv2. The GQA dataset focuses on questions requiring compositional reasoning, particularly involving surrounding information of objects within an image. We evaluate on its test-dev split containing 12,578 image-question pairs. The VQAv2 dataset contains open-ended questions about each image that require an understanding of vision, language and commonsense knowledge to answer. We use its validation split containing 214,354 image-question pairs for our evaluation. For each dataset, we follow standard V-LLM evaluation protocol following [33, 42] and report top-1 accuracy metric. Our results in Tab. 5 indicate clear improvements for LocVLM over our baseline and prior work, establishing the usefulness of our proposed framework. The closest to our work, Shikra [8] achieves performance competitive to our LocVLM-B, but + +
MethodICLAllLeftRightAllAboveBelow
BLIP-2 [33]✗45.586.14.7449.250.448.6
LLava [38]✗55.184.536.558.957.859.3
Ours✗69.579.759.265.464.265.9
BLIP-2 [33]✓14.717.811.615.816.515.2
LLaVa [38]✓55.184.736.458.257.758.5
Ours✓76.590.461.574.173.574.4
+ +Table 4. Spatial Reasoning: We report accuracy $(\%)$ on a spatial localization dataset derived from COCO annotations to highlight weak spatial awareness of existing V-LLMs. We query these models to answer whether one object is to the left or right / above or below of another object. The SOTA V-LLMs evaluated exhibit close to random performance. Our proposed setup outperforms existing methods. Ours refers to LocVLM-B variant. + +
MethodLLMVSZero-ShotGQAVQA-VVQA-T
SR [4]--X62.172.9-
Shikra [8]7B224X-75.377.4
LLaVA-v1.57B336X62.078.178.4
LocVLM-L7B336X63.578.278.6
LLaVA-v17B224✓44.749.849.3
LocVLM-B7B224✓47.350.350.8
Viper-GPT175B-✓48.1--
BLIP-211B-✓44.754.353.9
LLaVA-v1.57B336✓48.755.755.3
LocVLM-L7B336✓50.255.956.2
+ +Table 5. Image VQA Results: We report accuracy $(\%)$ on the test-dev split of GQA dataset (GQA) and the validation / test splits of VQAv2 dataset (VQA-V / VQA-T). Our proposed LocVLM improves over prior works achieving state-of-the-art performance. + +unlike ours they use VQA datasets (containing similar domain question-answer pairs) during training. + +# 4.4. Video VQA + +Our model is also applicable to video tasks following our video domain adaptation described in Sec. 3.5. We simply adopt the additional video instruction fine-tuning phase from [42] on the ActivityNet dataset after our initial two phases of training to obtain LocVLM-Vid-B. This third phase involves fine-tuning only the adapter layer of our model. We also explore video variants of our IFT objectives that train both adapter layer and LLM. The resulting model is termed LocVLM-Vid-B+. + +Video VQA focuses on correctly answering questions regarding a given video that require spatio-temporal awareness to answer. We evaluate our video-adapted model on the task of zero-shot video VQA on four benchmark datasets, ActivityNet-QA, MSRVTT-QA, MSVD-QA, and TGIF-QA. We evaluate on the validation splits of these four datasets. ActivityNet-QA videos cover a wide range of complex human activities relevant to daily living with its question-answer pairs focusing on long-term spatiotemporal reasoning. MSRVTT-QA builds off the MSRVTT dataset that contains web videos covering a comprehensive + +
MethodZero-ShotActivityNet-QAMSRVTT-QAMSVD-QATGIF-QA
JustAsk [63]✘38.941.847.5-
FrozenBiLM [64]✘43.247.054.8-
VideoCoCa [62]✘56.146.356.9-
Flamingo [2]✓-17.435.6-
BLIP-2 [33]✓-17.434.4-
InstructBLIP [15]✓-25.644.3-
FrozenBiLM [64]✓24.716.832.241.0
Video Chat [34]✓26.545.056.334.4
LLaMA Adapter [72]✓34.243.854.9-
Video LLaMA [71]✓12.429.651.6-
Video-ChatGPT [42]✓35.249.364.951.4
LocVLM-Vid-B✓37.451.266.151.8
+ +range of categories and diverse visual content. MSVD-QA is a similar dataset building off the MSVD dataset. TGIFQA contains question-answer pairs from an dataset constructed of animated GIFs. For each dataset, we report the accuracy metric following evaluation protocol in [42]. Our results on these four datasets reported in Tab. 6 demonstrate state-of-the-art performance of our proposed LocVLM-Vid-B, with consistent improvements over the baseline from [42]. Here we use the LocVLM-Vid-B variant for fairer comparison with the baseline from [42]. We attribute the performance gains exhibited by our model to its stronger spatial awareness (see Sec. 4.2). Particularly in the case of video understanding, awareness of content at spatial level of each frame is significant to understand object motions and interactions [1, 51]. We also report more results involving additional model variants in Tab. 7. + +# 4.5. Object Hallucination + +Current state-of-the-art V-LLMs suffer from object hallucination, generating image descriptions inconsistent with the image content [36]. For example, a V-LLM would respond to "Where is the cat in this image?" with "The cat is on the table" when in reality there is no cat in the image. We evaluate the extent of hallucination in V-LLMs using three datasets we introduce (details in Appendix C) and the POPE dataset [36]. Our three datasets, Hal-COCO, Hal-ADE, and Hal-Act build off COCO, ADE-20K, and ActivityNet datasets respectively. The first two involve images and the latter videeos. These datasets contain "Is there obj in image / video?" type questions per sample, for two objects present and not present in the image / video. Hal-ADE object categories contain no overlap with COCO classes allowing evaluation on novel object categories unseen during our instruction fine-tuning. Results reported in Tab. 8 show clear improvements of LocVLM-B over baselines. We also evaluate LocVLM-B on the POPE benchmark [36] that builds + +Table 6. Video VQA Results: Our proposed LocVLM-Vid-B improves over Video-ChatGPT [42] and achieves state-of-the-art results (Top-1 Accuracy %) across four different video VQA benchmarks. Note the zero-shot setting of all these evaluations. + +
MethodVLTFramesAcc (%)
LLaVa (v1) [38]×128.7
LLaVa (v1.5) [38]×131.5
LocVLM-B×129.2
LocVLM-L×132.1
Video-ChatGPT [42]✓10035.2
LocVLM-Vid-B✓10037.4
LocVLM-Vid-B+✓838.2
+ +Table 7. Video VQA: We report more results (Top-1 Accuracy) for ActivityNet-QA dataset including multiple baseline and LocVLM variants. Our proposed models exhibit top performance. VLT denotes video level training. More details in Appendix D. + +
MethodHal-COCOHal-ADEHal-Act
Shikra [8]86.258.7-
LLaVa [38]61.953.8-
LocVLM-B88.375.2-
Video-ChatGPT [42]--50.6
LocVLM-Vid-B--68.7
LocVLM-Vid-B+--72.4
+ +Table 8. Hallucination Evaluation: We report top-1 accuracy (\%) for object presence type questions and showcase reduced object hallucination in our proposed framework. + +off the COCO dataset object annotations and report results in Tab. 9. Our LocVLM showcases similar performance improvements on this dataset. + +# 4.6. Region Description + +A unique characteristic of our model (in contrast to V-LLMs like LLaVA [38] & BLIP-2 [33]) is its ability to reason with prompts involving coordinate based image space locations without any input modifications. Given a point or bounding box location, we prompt our model to generate an output describing that location. We refer to this unique ability of our model as region description (RD). We evaluate this RD capability of our model by generating object + +
DatasetsMetricsBLIP-2ShikraLLaVAOurs
RandomAccuracy (↑)88.686.950.487.9
Precision (↑)84.194.450.283.6
Recall (↑)95.179.399.193.9
F1 Score (↑)89.386.266.688.5
Yes56.643.398.856.2
PopularAccuracy (↑)82.884.049.986.0
Precision (↑)76.387.649.979.7
Recall (↑)95.179.299.393.9
F1 Score (↑)84.783.266.486.3
Yes62.445.299.458.9
AdversarialAccuracy (↑)72.183.149.778.8
Precision (↑)65.185.649.976.6
Recall (↑)95.179.699.193.7
F1 Score (↑)77.382.566.384.3
Yes73.046.599.461.7
+ +Table 9. More object hallucination: Results on POPE evaluation benchmark [36] indicate strong performance of our model. + +
MethodZSRefCOCORefCOCO+RefCOCOg
ValTest
SLR [67]✘---15.4
SLR + Rerank [67]✘---15.9
Kosmos-2 [45]✘8.678.8214.314.1
Shikra [8]✘10.411.119.719.5
LLaVa [38]✘8.438.7313.513.5
LocVLM-B✘14.615.226.026.2
Kosmos-2 [45]✓6.348.2512.412.2
LLava [38]✓4.237.2610.610.3
LocVLM-B✓11.011.120.620.7
+ +level descriptions focused on contextual information (e.g. surrounding of that object in the image). Following evaluation protocol in [45] for region description, we extend their evaluation to three standard referring localization datasets from RefCOCO [29] and report these results in Tab. 10. We select the METEOR score as the evaluation metric to account for variations in word choice in generated answers which may be acceptable in various cases (e.g. different sentence structure leading to alternate word ordering). Our results indicate clear improvements over the LLaVA baseline [38] as well as prior state-of-the-art. We attribute these improvements to our pseudo-data based training. + +# 4.7. Ablations + +Next we conduct ablative studies on separate components of our proposed setup: IFT objectives, location type, and pseudo-data. We follow the same training strategy as described in Sec. 4.1 and present these results in Tab. 11. LocVLM-B is used for all these experiments. The significance of each IFT objective is verified in Tab. 11 (top) with + +Table 10. Region Description: We report METEOR scores for RD task [45]. Test-B split is used for RefCOCO & RefCOCO+ datasets. Our method outperforms all prior work. + +
LocPredNegPredRevLocGQARDA-QA
XXX44.710.335.2
✓XX45.212.235.8
✓✓X46.912.537.2
✓✓✓47.320.737.4
Location TypePDGQARDA-QA
Point✓47.320.637.4
Bounding Box✓47.320.737.4
Bounding BoxX46.511.637.1
+ +Table 11. Ablations: We report top-1 accuracy (\%) on GQA and ActivityNet-QA (A-QA) datasets and METEOR scores for RD task on RefCOCOg test split. (top) We ablate proposed instruction fine-tuning objectives to verify usefulness of each objective. (bottom) We first ablate point based and bounding box based location forms to showcase minimal difference across them. We next ablate use of object description pseudo-data (PD). We highlight the improvements due to pseudo-data, especially on the RD task. + +
LocPredNegPredRevLocA-QA
XXX37.4
✓XX37.6
✓✓X38.2
✓✓✓38.2
+ +Table 12. Video Ablation: We report top-1 accuracy $(\%)$ on ActivityNet-QA (A-QA) dataset. Results indicate the generality of proposed IFT objectives for video domain training as well. + +consistent performance improvements across tasks. The generality of our approach to differing location type (i.e. points vs bounding boxes) and usefulness of pseudo-data is visible in Tab. 11 (bottom). In particular, we highlight the notable performance improvement for RD task gained from using pseudo-data. We also conduct ablations for our video domain training setup and report these results in Tab. 12. The LocVLM-Vid-B+ variant is used in these experiments. Our results showcase the usefulness of proposed IFT objectives for video domain learning as well. + +# 5. Conclusion + +We introduce a simple framework that equips visual-LLMs (V-LLMs) with greater spatial understanding, termed LocVLM. 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In NeurIPS, 2023. 5, 2 \ No newline at end of file diff --git a/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/images.zip b/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..a39fb479c1108d9c76187a924b1f973c5d53e888 --- /dev/null +++ b/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:2c3fd6bcc3e52ba5b1c06aae8e7af1da745ea2a571ba0340151fba1d328862e3 +size 416701 diff --git a/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/layout.json b/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..eafab6b7b488a291beda6fcbb2d13d0bf2f1194f --- /dev/null +++ b/2024/Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs/layout.json @@ -0,0 +1,8053 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 68, + 103, + 524, + 120 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 68, + 103, + 524, + 120 + ], + "spans": [ + { + "bbox": [ + 68, + 103, + 524, + 120 + ], + "type": "text", + "content": "Learning to Localize Objects Improves Spatial Reasoning in Visual-LLMs" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 123, + 142, + 468, + 157 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 123, + 142, + 468, + 157 + ], + "spans": [ + { + "bbox": [ + 123, + 142, + 468, + 157 + ], + "type": "text", + "content": "Kanchana Ranasinghe1,2 Satya Narayan Shukla1 Amid Poursaeed1" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 202, + 157, + 387, + 172 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 202, + 157, + 387, + 172 + ], + "spans": [ + { + "bbox": [ + 202, + 157, + 387, + 172 + ], + "type": "text", + "content": "Michael S. 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However, existing V-LLMs (e.g. BLIP-2, LLaVA) demonstrate weak spatial reasoning and localization awareness. Despite generating highly descriptive and elaborate textual answers, these models fail at simple tasks like distinguishing a left vs right location. In this work, we explore how image-space coordinate based instruction fine-tuning objectives could inject spatial awareness into V-LLMs. We discover optimal coordinate representations, data-efficient instruction fine-tuning objectives, and pseudo-data generation strategies that lead to improved spatial awareness in V-LLMs. Additionally, our resulting model improves VQA across image and video domains, reduces undesired hallucination, and generates better contextual object descriptions. Experiments across 5 vision-language tasks involving 14 different datasets establish the clear performance improvements achieved by our proposed framework." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 499, + 127, + 511 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 499, + 127, + 511 + ], + "spans": [ + { + "bbox": [ + 47, + 499, + 127, + 511 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 519, + 287, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 519, + 287, + 592 + ], + "spans": [ + { + "bbox": [ + 46, + 519, + 287, + 592 + ], + "type": "text", + "content": "Holistic visual understanding requires learning beyond simply content of an image to encompass awareness on spatial locations of objects and their relations [41]. In the context of visual question answering (VQA), such spatial awareness allows better reasoning involving structural and contextual information contained within an image [8]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": "Since the introduction of powerful large-language models (LLMs) such as GPT-3 [5], Chat-GPT [44], Vicuna [11], and LLaMA [55, 56] that are capable of human style conversation, their visual counterparts such as BLIP-2 [33], LLaVA [38] have enabled novel tasks within the vision modality. However, despite their [33, 38] highly generic visual understanding, these models exhibit poor language-based spatial reasoning [8]. In fact, they fail at simple tasks such as distinguishing whether an object lies to the left or right of another object (see Tab. 4)." + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 318, + 224, + 421, + 360 + ], + "blocks": [ + { + "bbox": [ + 318, + 224, + 421, + 360 + ], + "lines": [ + { + "bbox": [ + 318, + 224, + 421, + 360 + ], + "spans": [ + { + "bbox": [ + 318, + 224, + 421, + 360 + ], + "type": "image", + "image_path": "220434e2d7b3dce9eb28b3d773ce89703207a01a2e63d1f032250d7bd78dd8c2.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "bbox": [ + 425, + 229, + 526, + 247 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 425, + 229, + 526, + 247 + ], + "spans": [ + { + "bbox": [ + 425, + 229, + 526, + 247 + ], + "type": "text", + "content": "Query: Describe [x1,y1,x2,y2] location in image." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 425, + 252, + 514, + 270 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 425, + 252, + 514, + 270 + ], + "spans": [ + { + "bbox": [ + 425, + 252, + 514, + 270 + ], + "type": "text", + "content": "Ours: A blue plaid blanket behind a teddy bear." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 430, + 285, + 522, + 303 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 430, + 285, + 522, + 303 + ], + "spans": [ + { + "bbox": [ + 430, + 285, + 522, + 303 + ], + "type": "text", + "content": "Query: Which side of the potted plant is the stove?" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 430, + 309, + 526, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 430, + 309, + 526, + 327 + ], + "spans": [ + { + "bbox": [ + 430, + 309, + 526, + 327 + ], + "type": "text", + "content": "LLaVa: The stove is on the left side of potted plant." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 430, + 335, + 522, + 353 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 430, + 335, + 522, + 353 + ], + "spans": [ + { + "bbox": [ + 430, + 335, + 522, + 353 + ], + "type": "text", + "content": "Ours: The stove is on the right side of potted plant." + } + ] + } + ], + "index": 17 + }, + { + "type": "image", + "bbox": [ + 318, + 359, + 533, + 485 + ], + "blocks": [ + { + "bbox": [ + 318, + 359, + 533, + 485 + ], + "lines": [ + { + "bbox": [ + 318, + 359, + 533, + 485 + ], + "spans": [ + { + "bbox": [ + 318, + 359, + 533, + 485 + ], + "type": "image", + "image_path": "831c277cee537b96e010839838bb2f33703db97f6af9885cce63fb83ddf493ab.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 488, + 545, + 544 + ], + "lines": [ + { + "bbox": [ + 305, + 488, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 305, + 488, + 545, + 544 + ], + "type": "text", + "content": "Figure 1. We illustrate one unique ability of our model: contextual region description (top). Note the contextual information used in describing the selected region in each image. Explicitly teaching localization to Visual-LLMs also improves spatial awareness in VQA settings (bottom). Color boxes only for illustration purposes." + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 555, + 546, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 555, + 546, + 687 + ], + "spans": [ + { + "bbox": [ + 304, + 555, + 546, + 687 + ], + "type": "text", + "content": "In the case of contrastive language image models (such as CLIP [46], ALIGN [26]), recent works explore how injecting explicit spatial awareness [39, 43, 48, 74] can enable more holistic visual understanding. In fact, [48] shows how such improved spatial awareness benefits model robustness in adversarial domains. This raises the question of how generative language image models, particularly those connecting LLMs to visual encoders [33, 38] can benefit from such spatial awareness specific training. We refer to models of this category that generate textual outputs given joint image-text inputs (e.g. [33, 38]) as visual-LLMs (V-LLMs)." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "In this work, we explore location specific instruction fine-tuning objectives that explicitly enforce V-LLMs to" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "12977" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 191 + ], + "type": "text", + "content": "meaningfully process and generate textual image-space coordinates. We hypothesize that such training would lead to improved spatial awareness in these V-LLMs, therein improving performance on VQA tasks. To this end, we propose three instruction fine-tuning objectives that unify location representation with natural language. We also explore optimal representation forms for image-space locations and how pseudo-data generation can be leveraged for efficient scaling of our framework. We name our resulting model as LocVLM." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 195, + 289, + 447 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 195, + 289, + 447 + ], + "spans": [ + { + "bbox": [ + 46, + 195, + 289, + 447 + ], + "type": "text", + "content": "While the idea of adapting V-LLMs to perform localization related tasks (e.g. detection, segmentation) using V-LLMs has been explored in multiple recent works [30, 45, 58, 66, 68, 73, 75], these approaches depend on task specific architectural modifications or treat localization inputs / outputs differently from natural language. In contrast, our LocVLM focuses on a unified framework treating location and language as a single modality of inputs with the goal of complementing performance in each task. We intuit that processing location represented in textual form would enforce the LLM to select appropriate image regions as opposed to relying on region level features provided by the architecture. At the same time, textual form location outputs promote spatial awareness at language level in a human interpretable manner, in contrast to using secondary heads or specialized tokens for location prediction. Concurrent work in [8] also explores textual location representation with a generic V-LLM architecture similar to our work. Our proposed LocVLM differs with focus on optimal location representation forms, data-efficient pseudo-labelling, and video domain operation." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 450, + 288, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 450, + 288, + 521 + ], + "spans": [ + { + "bbox": [ + 46, + 450, + 288, + 521 + ], + "type": "text", + "content": "Our proposed framework exhibits improved spatial awareness in VQA style conversation demonstrated through experimentation on 14 datasets across 5 vision-language tasks: Spatial Reasoning, Image VQA, Video VQA, Object Hallucination, and Region Description. We summarize our key contributions as follows:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 48, + 525, + 287, + 597 + ], + "type": "list", + "angle": 0, + "index": 7, + "blocks": [ + { + "bbox": [ + 48, + 525, + 284, + 536 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 525, + 284, + 536 + ], + "spans": [ + { + "bbox": [ + 48, + 525, + 284, + 536 + ], + "type": "text", + "content": "- Inject textual spatial coordinate awareness into V-LLMs" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 49, + 537, + 287, + 560 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 537, + 287, + 560 + ], + "spans": [ + { + "bbox": [ + 49, + 537, + 287, + 560 + ], + "type": "text", + "content": "- Propose three novel localization based instruction finetuning objectives for V-LLMs" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 49, + 562, + 258, + 572 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 562, + 258, + 572 + ], + "spans": [ + { + "bbox": [ + 49, + 562, + 258, + 572 + ], + "type": "text", + "content": "- Discover optimal coordinate representation forms" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 48, + 573, + 287, + 597 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 573, + 287, + 597 + ], + "spans": [ + { + "bbox": [ + 48, + 573, + 287, + 597 + ], + "type": "text", + "content": "- Pseudo-Data generation for improved region description and scaling to video domain" + } + ] + } + ], + "index": 6 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 609, + 134, + 621 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 609, + 134, + 621 + ], + "spans": [ + { + "bbox": [ + 47, + 609, + 134, + 621 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 629, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 287, + 714 + ], + "type": "text", + "content": "Localization in Contrastive Vision Language Models: Foundation vision language models (VLMs) such as CLIP [46] resulted in extensive exploration into language-tied localization in images both under dense (pixel / bounding-box) supervision [16-18, 21, 27, 31, 32, 35, 69, 70] and weak supervision [14, 39, 43, 48, 60, 61, 65, 74, 76]. Recovering explicit localization information within model rep" + } + ] + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 310, + 70, + 541, + 135 + ], + "blocks": [ + { + "bbox": [ + 310, + 70, + 541, + 135 + ], + "lines": [ + { + "bbox": [ + 310, + 70, + 541, + 135 + ], + "spans": [ + { + "bbox": [ + 310, + 70, + 541, + 135 + ], + "type": "table", + "html": "
MethodKosmos [45]Ferret [66]Shikra [8]Ours
Unified Arch.XX✓✓
Purely TextualXX✓✓
Pseudo DataXXX✓
Video DomainXXX✓
", + "image_path": "327ac50a8a9f0c400f3023d2108154adc590c1be126b3826b790bafc5b5ba5b3.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 138, + 547, + 172 + ], + "lines": [ + { + "bbox": [ + 305, + 138, + 547, + 172 + ], + "spans": [ + { + "bbox": [ + 305, + 138, + 547, + 172 + ], + "type": "text", + "content": "Table 1. Related Work Comparison: A unified architecture, purely textual inputs, pseudo data for scalable learning, and video domain operation distinguishes our work from these prior methods." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 188, + 547, + 248 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 188, + 547, + 248 + ], + "spans": [ + { + "bbox": [ + 304, + 188, + 547, + 248 + ], + "type": "text", + "content": "resentations has enabled more robust operation for certain tasks [48]. While our work differs from this contrastive setting given our use of LLM based generative predictions, we similarly explore how explicit location information within the language modality can improve V-LLMs." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 253, + 546, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 253, + 546, + 661 + ], + "spans": [ + { + "bbox": [ + 304, + 253, + 546, + 661 + ], + "type": "text", + "content": "Visual Large Language Models (V-LLMs): The advent of powerful large language models (LLMs) such as GPT-3 [5], Chat-GPT [44], and PaLM [13], as well as their open-source counterparts BLOOM [52], Vicuna [11], and LLaMA [55, 56], has resulted in direct use of these LLMs for computer vision tasks [22, 53]. Alternate lines of work explore how LLMs can be connected to existing visual foundation models [2, 3, 33, 38, 42, 47], in particular to CLIP visual backbones [46]. While earlier models explored large-scale (millions to billions of samples) image-text training [2, 3], later models [33, 38, 42] scale down on data dependency. LLaVA [38] in particular scales down on pre-training data to under 1 million image-text pairs, and use instruction fine-tuning [59] to enable human-style conversation with visual awareness. This is extended to video domain in [42, 49]. A shortcoming of these models is their lack of spatial awareness or location understanding in image space [8, 12, 20]. Spatial reasoning limitations in generative VLMs are studied in [12, 20]. Similar failures in captioning (and VQA) models are explored in [28]. A solution in [24] proposes code-generation based reasoning. Our work tackles these same limitations but follows an alternate direction of spatial-aware instruction fine-tuning. Another line of recent works [30, 45, 58, 66, 68, 73, 75] tackle this by introducing architectural modifications to explicitly extract region level features that are injected to the LLM as special tokens. While introducing extra tokens and layers, this also separates the localization task from language. In contrast, we use a generic architectures with purely textual location information (i.e. image space coordinates as text). Concurrent work in [8] explores this same idea, but we differ in 3 ways with, a) focus on optimal coordinate representation forms, b) data-efficient pseudo-labelling strategies, and c) video domain operation (see also Tab. 1)." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": "Location Representations: Selecting regions within an image has a rich history in computer vision [40, 57] with greater focus on location outputs since the popularity of object detection [6, 9, 10, 19, 50, 54, 58]. Early anchor-based" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "12978" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": "methods regress locations from anchor centers [19, 50], followed by direct location regression from object-level features [6, 54]. Recent works explore generative location predictions with diffusion processes [9] and sequence-generation [10, 58]. Ours resembles the latter given our use of an LLM, next token prediction objective, and sequential generation of textual location representations. However, [10, 58] utilize 1000 specialized location tokens (introduced to the LLM vocabulary) corresponding to 1000 bins uniformly spread across image space. While we explore similar binning strategies, in contrast we introduce no additional tokens, focus on purely textual representation of locations, and explore multiple textual location representation forms." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 236, + 103, + 249 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 236, + 103, + 249 + ], + "spans": [ + { + "bbox": [ + 47, + 236, + 103, + 249 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 256, + 287, + 400 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 256, + 287, + 400 + ], + "spans": [ + { + "bbox": [ + 46, + 256, + 287, + 400 + ], + "type": "text", + "content": "Current V-LLMs [33, 38] exhibit weak understanding of spatial locations within images [8]. We explore and benchmark such shortcomings, and propose three novel instruction fine-tuning objectives aimed at overcoming these drawbacks of existing V-LLMs. We build these objectives based on spatial-coordinate based prompting and demonstrate how LLMs can directly both process and generate meaningful numerical coordinates in image-space after suitable training. In the rest of this section we describe our architecture and training framework, followed by coordinate processing & generation, instruction fine-tuning objectives, pseudo-data generation, and video domain operation." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 406, + 194, + 418 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 406, + 194, + 418 + ], + "spans": [ + { + "bbox": [ + 47, + 406, + 194, + 418 + ], + "type": "text", + "content": "3.1. Architecture and Training" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 424, + 287, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 424, + 287, + 496 + ], + "spans": [ + { + "bbox": [ + 46, + 424, + 287, + 496 + ], + "type": "text", + "content": "The focus of our work is to explore how spatial localization related training can improve a generic V-LLM such as LLaVA [38]. Therein, our architecture and training framework is inspired from [38]. We use a visual encoder, adapter layer, and LLM stacked sequentially (illustrated in Fig. 2), and follow a multi-stage training strategy similar to [38]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": "Consider an image " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "X \\in \\mathbb{R}^{H, W, C}" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "H, W, C (= 3)" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": " denote height, width, channels of image and a textual prompt " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": " composed of natural language (asking a question about the image). We define two variants of our model, LocVLM-B and LocVLM-L for better comparison with prior work. We first describe LocVLM-B that processes images with " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "H = W = 224" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": ". Our visual encoder, ViTL/14 from CLIP [46], processes the image " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "X" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": " to produce a set of 256 visual tokens in " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{1024}" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": ", which are in turn projected to " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{4096}" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": " by an adapter layer (implemented as a linear layer). The LLaMA [55] text tokenizer processes the textual prompt " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": " to produce textual tokens in " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{4096}" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": ". The joint set of visual and textual tokens (of dimension " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{4096}" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": ") are processed by a LLaMA [55] LLM to produce the final set of textual tokens which are in turn untokenized to convert to natural language. The final natural language output is expected to be a suitable response to the input textual prompt, " + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 497, + 288, + 714 + ], + "type": "text", + "content": ". In variant LocVLM-L, we use images sized" + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 320, + 78, + 532, + 262 + ], + "blocks": [ + { + "bbox": [ + 320, + 78, + 532, + 262 + ], + "lines": [ + { + "bbox": [ + 320, + 78, + 532, + 262 + ], + "spans": [ + { + "bbox": [ + 320, + 78, + 532, + 262 + ], + "type": "image", + "image_path": "150a99aba89437f0a65a9356ecfbebc7567c3a463cfd9d2afc33ae576d288ffe.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 270, + 545, + 293 + ], + "lines": [ + { + "bbox": [ + 305, + 270, + 545, + 293 + ], + "spans": [ + { + "bbox": [ + 305, + 270, + 545, + 293 + ], + "type": "text", + "content": "Figure 2. Architecture: We present the overall model architecture of our framework which is inspired from LLaVa [38]." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 305, + 545, + 342 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 305, + 545, + 342 + ], + "spans": [ + { + "bbox": [ + 305, + 305, + 545, + 342 + ], + "type": "inline_equation", + "content": "H = W = 336" + }, + { + "bbox": [ + 305, + 305, + 545, + 342 + ], + "type": "text", + "content": " resulting in 576 visual token, an adapter layer implemented as an MLP, and the LLM from LLaMA-2 [56]. All other design choices remain unchanged." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 345, + 545, + 417 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 345, + 545, + 417 + ], + "spans": [ + { + "bbox": [ + 304, + 345, + 545, + 417 + ], + "type": "text", + "content": "We also highlight the BPE tokenization that is employed in our setup. This learned tokenization scheme may split a single word into sub-parts (that alone can appear meaningless to humans) and handles numerical text (including decimal point) as individual tokens (e.g. 12.34 would be split into 5 separate tokens)." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 420, + 545, + 517 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 420, + 545, + 517 + ], + "spans": [ + { + "bbox": [ + 304, + 420, + 545, + 517 + ], + "type": "text", + "content": "In terms of training, we follow a two-stage strategy. Inspired by LLaVA [38], we adopt an initial pre-training stage that only updates weights of the intermediate adapter layer to align the visual encoder outputs with LLM inputs. Next, we jointly instruction fine-tune the adapter layer and LLaMA LLM with our proposed objectives and template-based localization datasets (see Sec. 4.1). Video domain operation introduces an additional phase (see Sec. 3.5)." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 525, + 510, + 537 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 525, + 510, + 537 + ], + "spans": [ + { + "bbox": [ + 306, + 525, + 510, + 537 + ], + "type": "text", + "content": "3.2. Coordinate Processing and Generation" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 544, + 545, + 674 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 544, + 545, + 674 + ], + "spans": [ + { + "bbox": [ + 304, + 544, + 545, + 674 + ], + "type": "text", + "content": "Humans contain the ability to reason about images using image-space coordinates. This is in contrast to existing V-LLMs that can describe the contents of an image elegantly, but lack spatial awareness regarding image contents. We hypothesize that injecting LLMs with additional spatial awareness, through coordinate based reasoning could improve their generic reasoning ability as well. To this end, we introduce our first goal of directly using textual coordinate based image locations in both natural language prompts and LLM generated outputs. For textual coordinates, we explore three different representation forms:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 323, + 677, + 539, + 713 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 323, + 677, + 474, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 323, + 677, + 474, + 689 + ], + "spans": [ + { + "bbox": [ + 323, + 677, + 474, + 689 + ], + "type": "text", + "content": "1. Normalized Floating Point Values" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 323, + 689, + 539, + 701 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 323, + 689, + 539, + 701 + ], + "spans": [ + { + "bbox": [ + 323, + 689, + 539, + 701 + ], + "type": "text", + "content": "2. Integer Valued Binning (across image dimensions)" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 323, + 701, + 511, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 323, + 701, + 511, + 713 + ], + "spans": [ + { + "bbox": [ + 323, + 701, + 511, + 713 + ], + "type": "text", + "content": "3. Deviation from Image-Grid based Anchors" + } + ] + } + ], + "index": 15 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "12979" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 52, + 71, + 280, + 125 + ], + "blocks": [ + { + "bbox": [ + 52, + 71, + 280, + 125 + ], + "lines": [ + { + "bbox": [ + 52, + 71, + 280, + 125 + ], + "spans": [ + { + "bbox": [ + 52, + 71, + 280, + 125 + ], + "type": "table", + "html": "
CRGQA (Acc)RD (METEOR)A-QA (Acc)
NFP46.119.637.1
IVB47.320.737.4
DIGA47.020.837.3
", + "image_path": "16e925f376b10bcc20dfbe35b5e8c054395c7187227ed8e7c7cf4bca3805cbcf.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 182, + 286, + 242 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 182, + 286, + 242 + ], + "spans": [ + { + "bbox": [ + 46, + 182, + 286, + 242 + ], + "type": "text", + "content": "For image locations, we explore point based (e.g. center coordinates [cx, cy] of object) and bounding box based (e.g. top-left and bottom-right extreme coordinates of object region [x1, y1, x2, y2]) forms. We next discuss the three representations for coordinates used for either location." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 245, + 286, + 316 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 245, + 286, + 316 + ], + "spans": [ + { + "bbox": [ + 46, + 245, + 286, + 316 + ], + "type": "text", + "content": "Normalized Floating Point Values calculates absolute image coordinates and normalizes with image dimensions to a " + }, + { + "bbox": [ + 46, + 245, + 286, + 316 + ], + "type": "inline_equation", + "content": "(0,1)" + }, + { + "bbox": [ + 46, + 245, + 286, + 316 + ], + "type": "text", + "content": " range. We use a 4 decimal point representation for these floating point values. While this representation is simple and generic, given the nature of BPE tokenization, each individual coordinate will be represented by up to 6 tokens." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "spans": [ + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "type": "text", + "content": "Integer Valued Binning discretizes the absolute image coordinates to one of " + }, + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "type": "inline_equation", + "content": "n_b" + }, + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "type": "inline_equation", + "content": "= 224, 336" + }, + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "type": "text", + "content": " for variant B & L respectively) bins spread uniformly across the two image dimensions. Based on the binning parameter, " + }, + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "type": "inline_equation", + "content": "n_b" + }, + { + "bbox": [ + 46, + 319, + 286, + 392 + ], + "type": "text", + "content": ", each coordinate will be represented some number of tokens, in our case up to 3 (less than the floating point variant)." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 394, + 286, + 502 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 394, + 286, + 502 + ], + "spans": [ + { + "bbox": [ + 46, + 394, + 286, + 502 + ], + "type": "text", + "content": "Deviation from Image-Grid based Anchors is motivated from prior object detection works that estimate an initial anchor followed by deviation from that anchor center to estimate bounding box coordinates. We follow a similar setup, where one of " + }, + { + "bbox": [ + 46, + 394, + 286, + 502 + ], + "type": "inline_equation", + "content": "n_a" + }, + { + "bbox": [ + 46, + 394, + 286, + 502 + ], + "type": "text", + "content": " anchors is predicted by the model, followed by deviation of coordinate from that anchor center. Our intuition is that, given the sequential next-token prediction setup of LLMs, such a two-stage strategy would lead to faster learning and more accurate coordinates." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 504, + 286, + 588 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 504, + 286, + 588 + ], + "spans": [ + { + "bbox": [ + 46, + 504, + 286, + 588 + ], + "type": "text", + "content": "We refer to Appendix A for further details on each variant. In Tab. 2, we ablate each representation format on three different tasks (see Sec. 4.7 for more details) of image VQA (GQA), region description (RD), and video VQA (A-QA). Our experiments indicate optimal performance for integer valued binning (IVB). In all following experimentation, we fix our coordinate representation to IVB." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 597, + 234, + 609 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 597, + 234, + 609 + ], + "spans": [ + { + "bbox": [ + 47, + 597, + 234, + 609 + ], + "type": "text", + "content": "3.3. Instruction Fine-Tuning Objectives" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 615, + 286, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 615, + 286, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 615, + 286, + 687 + ], + "type": "text", + "content": "Given suitable coordinate representations, we now have a mechanism to directly prompt LLMs with image locations in textual form. Our second goal is to build training objectives using these image coordinates that directly inject spatial awareness into V-LLMs. We propose three instruction fine-tuning objectives for this purpose." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 689, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 286, + 714 + ], + "type": "text", + "content": "Let us first revisit the visual instruction fine-tuning methodology in [38]. Building off the COCO dataset," + } + ] + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 316, + 71, + 534, + 125 + ], + "blocks": [ + { + "bbox": [ + 47, + 125, + 286, + 169 + ], + "lines": [ + { + "bbox": [ + 47, + 125, + 286, + 169 + ], + "spans": [ + { + "bbox": [ + 47, + 125, + 286, + 169 + ], + "type": "text", + "content": "Table 2. Ablation on Coordinate Representation (CR) methods: we compare each of the three proposed CR variants, namely normalized floating point values (NFP), integer valued binning (IVB), and deviation from image-grid based anchors (DIGA)." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 316, + 71, + 534, + 125 + ], + "lines": [ + { + "bbox": [ + 316, + 71, + 534, + 125 + ], + "spans": [ + { + "bbox": [ + 316, + 71, + 534, + 125 + ], + "type": "table", + "html": "
ObjectivePromptTarget
LocPredWhere is obj1?It's at (x1,y1,x2,y2).
NegPredWhere is obj2?There's no obj2.
RevLocDescribe (cx,cy)Detailed description
", + "image_path": "0d7b52de128e0acb49d99c6abaadd0ffb221029192487db0ee46e61bbf9463a7.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 127, + 545, + 171 + ], + "lines": [ + { + "bbox": [ + 305, + 127, + 545, + 171 + ], + "spans": [ + { + "bbox": [ + 305, + 127, + 545, + 171 + ], + "type": "text", + "content": "Table 3. We summarize our three distinct instruction fine-tuning objectives. Refer to appendix (Appendix B) for exact natural language prompts and targets used for training. For illustration, we use both point and bounding-box based image locations here." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 184, + 545, + 292 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 184, + 545, + 292 + ], + "spans": [ + { + "bbox": [ + 304, + 184, + 545, + 292 + ], + "type": "text", + "content": "they construct a VQA dataset containing conversation style question-answer pairs relevant to each COCO image. Question-answer pairs are generated using an LLM that is fed with the ground-truth bounding-box annotations for each image. Inspired by this setup, we build a similar spatial-VQA dataset using images and annotations of the COCO dataset, but instead of LLM prompting, we utilize hand-crafted templates and pseudo-captions (discussed in Sec. 3.4) to generate conversations." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 294, + 545, + 379 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 294, + 545, + 379 + ], + "spans": [ + { + "bbox": [ + 304, + 294, + 545, + 379 + ], + "type": "text", + "content": "We propose three types of question-answer pairs that relate to our three instruction fine-tuning objectives: Location Prediction (LocPred), Negative Prediction (NegPred), and Reverse-Location Prediction (RevLoc). See Tab. 3 for examples. Considering the LLM based final text generation in our architecture, we utilize next-token prediction loss to achieve each objective during our training." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 381, + 545, + 465 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 381, + 545, + 465 + ], + "spans": [ + { + "bbox": [ + 304, + 381, + 545, + 465 + ], + "type": "text", + "content": "Location Prediction: Given an object category, we query the model to generate a point or bounding box localizing that object in the image. The object category and bounding box are derived from the COCO train set annotations. To avoid object mismatches (i.e. multiple object of same category), we first filter images containing only a single object of a given class." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 468, + 545, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 468, + 545, + 564 + ], + "spans": [ + { + "bbox": [ + 304, + 468, + 545, + 564 + ], + "type": "text", + "content": "Negative Prediction: Using the same prompt templates as in LocPred above, we query the model to generate a point or bounding box localizing a specified object in the image. However, in this case we select an object category not present in the image and accordingly provide a target text of \"no such object in image\". For each image, we utilize COCO bounding-box annotations to discover objects (belonging to COCO classes) that are not present in that image." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 567, + 545, + 626 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 567, + 545, + 626 + ], + "spans": [ + { + "bbox": [ + 304, + 567, + 545, + 626 + ], + "type": "text", + "content": "Reverse-Location Prediction: We perform the reverse of LocPred here. Given a point or bounding box in image space, we query the model to describe the object in that location. The bounding box and object category are derived from the COCO train set annotations." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 545, + 713 + ], + "type": "text", + "content": "While introducing three novel train objectives aimed at injecting location information, we highlight that our proposed framework relies on training data (i.e. human annotations) identical to those used by LLaVA [38]. We do not use any additional ground-truth annotations for training. Next we explore how we could augment the generality of our framework while limiting to this same annotated data." + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "12980" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 185, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 185, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 185, + 83 + ], + "type": "text", + "content": "3.4. Pseudo-Data Generation" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 90, + 287, + 222 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 90, + 287, + 222 + ], + "spans": [ + { + "bbox": [ + 46, + 90, + 287, + 222 + ], + "type": "text", + "content": "We introduced three train objectives, each utilizing template based conversations as prompts and targets. However, our reliance on categories of COCO dataset limits the object vocabulary seen during training. Therein, we propose a pre-trained V-LLM based pseudo-data generation strategy. In fact, we utilize our model after stage one training as the V-LLM leading to a form of self-training based learning. Given the abundance of only image-level annotated datasets (i.e. no bounding box ground-truth), we also explore how an object-detector generated pseudo-bounding boxes could augment our framework." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 224, + 288, + 405 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 224, + 288, + 405 + ], + "spans": [ + { + "bbox": [ + 46, + 224, + 288, + 405 + ], + "type": "text", + "content": "Self-Training: Given an image and bounding box annotations from the COCO train set, we prompt the V-LLM to caption each distinct object in the image. In order to prevent ambiguous object queries, we filter images to select only those containing at most one instance of a single category. We additionally prompt the V-LLM to describe the object using relational information (i.e. relative to other objects in image). This process provides us a dataset with object level bounding boxes and descriptive captions that are not limited to the COCO object categories (dataset details in Appendix C). In turn, we use this data generated by the V-LLM (our stage one model) to further improve performance of our framework. We modify each of our three train objectives (in Sec. 3.3) to utilize these image-specific pseudocaptions instead of the generic dataset level category labels." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 407, + 287, + 526 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 407, + 287, + 526 + ], + "spans": [ + { + "bbox": [ + 46, + 407, + 287, + 526 + ], + "type": "text", + "content": "Weak Supervision: We explore how datasets containing no object level annotation (e.g. video classification / VQA datasets) could be leveraged to adapt our framework into domains beyond images. Therein, we utilize an off-the-shelf panoptic segmentation framework from SEEM [77] to generate pseudo-bounding boxes for selected object categories within any image as well as exhaustive pixel level labels (enabling negative class identification). We leverage this setup to extend our introduced train objectives to the video domain as well." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 536, + 187, + 548 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 536, + 187, + 548 + ], + "spans": [ + { + "bbox": [ + 47, + 536, + 187, + 548 + ], + "type": "text", + "content": "3.5. Video Domain Operation" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "spans": [ + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "type": "text", + "content": "Inspired by the simple modifications to LLaVA [38] in [42] enabling video domain operation, we follow a similar strategy of modifying our LocVLM-B architecture to process videos while introducing no additional components. The visual backbone process multiple video frames individually (as images) and resulting tokens are averaged across spatial " + }, + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "type": "inline_equation", + "content": "(S)" + }, + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "type": "text", + "content": " and temporal " + }, + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "type": "inline_equation", + "content": "(T)" + }, + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "type": "text", + "content": " axes to obtain " + }, + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "type": "inline_equation", + "content": "S + T" + }, + { + "bbox": [ + 46, + 554, + 286, + 674 + ], + "type": "text", + "content": " tokens. These are processed by the adapter layer and LLM to generate the textual outputs. Further details on our video architecture are discussed in Appendix D." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 677, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 286, + 713 + ], + "type": "text", + "content": "In addition to our two training phases discussed in Sec. 3.1, we introduce a third video instruction fine-tuning stage using a dataset we derive from ActivityNet [23]. Fol" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 107 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 107 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 107 + ], + "type": "text", + "content": "lowing [42], only the adapter layer is fine-tuned leaving all other parameters frozen. This resulting model is referred to as LocVLM-Vid-B." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 118, + 545, + 202 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 118, + 545, + 202 + ], + "spans": [ + { + "bbox": [ + 304, + 118, + 545, + 202 + ], + "type": "text", + "content": "We next introduce video variants of our three instruction fine-tuning objectives focused on static objects in videos. We utilize our proposed pseudo-labeling strategy to generate necessary video annotations and train both the adapter layer and LLM to obtain a second video model tagged LocVLM-Vid-B+. Further details on our video fine-tuning objectives are presented in Appendix D." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 221, + 387, + 234 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 221, + 387, + 234 + ], + "spans": [ + { + "bbox": [ + 306, + 221, + 387, + 234 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 241, + 545, + 312 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 241, + 545, + 312 + ], + "spans": [ + { + "bbox": [ + 304, + 241, + 545, + 312 + ], + "type": "text", + "content": "In this section, we present experimental results to highlight existing weaknesses of SOTA V-LLMs and how our proposed framework addresses these issues. We also evaluate on standard VQA benchmarks across domains to showcase the better reasoning abilities of our model and highlight novel abilities of our framework." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 328, + 422, + 341 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 328, + 422, + 341 + ], + "spans": [ + { + "bbox": [ + 306, + 328, + 422, + 341 + ], + "type": "text", + "content": "4.1. Experimental Setup" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 346, + 545, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 346, + 545, + 514 + ], + "spans": [ + { + "bbox": [ + 304, + 346, + 545, + 514 + ], + "type": "text", + "content": "Datasets: We utilize the COCO dataset [37] and our model (post stage one training) to construct a localization related VQA dataset as outlined in Sections 3.3 and 3.4. We name this dataset Localize-Instruct-200K. In detail, this contains LocPred and RevLoc question-answer pairs that use pseudo-captions instead of COCO categories as well as NegPred. We define a second video dataset, Localize-ActivityNet, containing question-answer pairs constructed from Activity-Net pseudo-bounding boxes following Section 3.5. Our models are primarily trained on our Localize-Instruct-200K dataset. Our stage one training uses CC3M dataset [7]. Additionally, our Localize-ActivityNet dataset and ActivityNet dataset [23] are used for video domain training." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 524, + 545, + 632 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 524, + 545, + 632 + ], + "spans": [ + { + "bbox": [ + 304, + 524, + 545, + 632 + ], + "type": "text", + "content": "Training: We train our models on 8xA100 GPUs (each 80GB) following a two-phase training schedule. Our first phase trains on CC3M [7] following the setup in [38]. The second phase uses our Localize-Instruct-200K dataset and trains for 10 epochs with a batch size of 64, ADAM-W optimizer with initial learning rate " + }, + { + "bbox": [ + 304, + 524, + 545, + 632 + ], + "type": "inline_equation", + "content": "2e - 5" + }, + { + "bbox": [ + 304, + 524, + 545, + 632 + ], + "type": "text", + "content": ", 0.3 warm-up ratio, and cosine-decay learning rate schedule. Both the training phases we conduct use standard next-token-prediction loss used in LLM training." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": "Evaluation: During evaluation, following standard protocol [38], we iteratively generate next tokens, given visual and textual inputs. The LLM output is a distribution across the entire token vocabulary. The next token is selected through multinomial sampling of this output using a softmax temperature term of 0.2 during normalization." + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "text", + "content": "12981" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 248, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 248, + 85 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 248, + 85 + ], + "type": "text", + "content": "4.2. Spatial Reasoning: A Toy Experiment" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 89, + 289, + 330 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 89, + 289, + 330 + ], + "spans": [ + { + "bbox": [ + 46, + 89, + 289, + 330 + ], + "type": "text", + "content": "We investigate spatial reasoning abilities of two SOTA V-LLMs, LLaVA [38] and BLIP-2 [33], using a simple toy experiment. We create an evaluation dataset from COCO annotations containing images with distinct category object triplets (only one instance occurrence of each object category), where each object is entirely to the left or right half of the image and two objects are on opposite sides. The ground-truth bounding box annotation are utilized to automate this dataset creation procedure. This evaluation set, referred as COCO-Spatial-27K, contains 26,716 image-question pairs (see Appendix C for details). We introduce two evaluation settings, direct VQA and in-context learning (ICL) VQA to understand spatial reasoning abilities of these models. In direct VQA, given an image we query the model whether an object lies above or below another object. In ICL VQA, before a similar final query, we provide two example question-answer pairs (involving the other two objects in the image) in the same format as our query. Refer to Appendix E for further details on task. We perform the same for objects in top vs bottom halves of images." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 335, + 289, + 468 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 335, + 289, + 468 + ], + "spans": [ + { + "bbox": [ + 46, + 335, + 289, + 468 + ], + "type": "text", + "content": "These results are presented in Table 4. Our results indicate near random performance for existing V-LLMs. For the case of LLaVA, we perform keyword (left and right) frequency analysis on its instruction tuning dataset (LLaVA-Instruct-80K dataset) to verify the presence of terms left and right in its training corpus. These keywords are present in " + }, + { + "bbox": [ + 46, + 335, + 289, + 468 + ], + "type": "inline_equation", + "content": "0.37\\%" + }, + { + "bbox": [ + 46, + 335, + 289, + 468 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 335, + 289, + 468 + ], + "type": "inline_equation", + "content": "1.13\\%" + }, + { + "bbox": [ + 46, + 335, + 289, + 468 + ], + "type": "text", + "content": " of its conversations respectively (see Appendix F for more) indicating presence of these concepts in the image-text training corpus. In contrast to these methods, our proposed framework notably improves performance over both BLIP-2 [33] and the LLaVA baseline [38]." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 480, + 126, + 493 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 480, + 126, + 493 + ], + "spans": [ + { + "bbox": [ + 47, + 480, + 126, + 493 + ], + "type": "text", + "content": "4.3. Image VQA" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 498, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 289, + 715 + ], + "type": "text", + "content": "Image VQA involves correctly answering natural language questions regarding content within an image. We evaluate our model for Image VQA on two standard datasets, GQA and VQAv2. The GQA dataset focuses on questions requiring compositional reasoning, particularly involving surrounding information of objects within an image. We evaluate on its test-dev split containing 12,578 image-question pairs. The VQAv2 dataset contains open-ended questions about each image that require an understanding of vision, language and commonsense knowledge to answer. We use its validation split containing 214,354 image-question pairs for our evaluation. For each dataset, we follow standard V-LLM evaluation protocol following [33, 42] and report top-1 accuracy metric. Our results in Tab. 5 indicate clear improvements for LocVLM over our baseline and prior work, establishing the usefulness of our proposed framework. The closest to our work, Shikra [8] achieves performance competitive to our LocVLM-B, but" + } + ] + } + ], + "index": 4 + }, + { + "type": "table", + "bbox": [ + 310, + 71, + 542, + 153 + ], + "blocks": [ + { + "bbox": [ + 310, + 71, + 542, + 153 + ], + "lines": [ + { + "bbox": [ + 310, + 71, + 542, + 153 + ], + "spans": [ + { + "bbox": [ + 310, + 71, + 542, + 153 + ], + "type": "table", + "html": "
MethodICLAllLeftRightAllAboveBelow
BLIP-2 [33]✗45.586.14.7449.250.448.6
LLava [38]✗55.184.536.558.957.859.3
Ours✗69.579.759.265.464.265.9
BLIP-2 [33]✓14.717.811.615.816.515.2
LLaVa [38]✓55.184.736.458.257.758.5
Ours✓76.590.461.574.173.574.4
", + "image_path": "8521af775df9c7268f3cb0befce80e1334e9000dfa43ff092beaa3f55750be61.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_body" + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 310, + 239, + 542, + 361 + ], + "blocks": [ + { + "bbox": [ + 304, + 157, + 545, + 236 + ], + "lines": [ + { + "bbox": [ + 304, + 157, + 545, + 236 + ], + "spans": [ + { + "bbox": [ + 304, + 157, + 545, + 236 + ], + "type": "text", + "content": "Table 4. Spatial Reasoning: We report accuracy " + }, + { + "bbox": [ + 304, + 157, + 545, + 236 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 304, + 157, + 545, + 236 + ], + "type": "text", + "content": " on a spatial localization dataset derived from COCO annotations to highlight weak spatial awareness of existing V-LLMs. We query these models to answer whether one object is to the left or right / above or below of another object. The SOTA V-LLMs evaluated exhibit close to random performance. Our proposed setup outperforms existing methods. Ours refers to LocVLM-B variant." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 310, + 239, + 542, + 361 + ], + "lines": [ + { + "bbox": [ + 310, + 239, + 542, + 361 + ], + "spans": [ + { + "bbox": [ + 310, + 239, + 542, + 361 + ], + "type": "table", + "html": "
MethodLLMVSZero-ShotGQAVQA-VVQA-T
SR [4]--X62.172.9-
Shikra [8]7B224X-75.377.4
LLaVA-v1.57B336X62.078.178.4
LocVLM-L7B336X63.578.278.6
LLaVA-v17B224✓44.749.849.3
LocVLM-B7B224✓47.350.350.8
Viper-GPT175B-✓48.1--
BLIP-211B-✓44.754.353.9
LLaVA-v1.57B336✓48.755.755.3
LocVLM-L7B336✓50.255.956.2
", + "image_path": "98ba69b03741bbb8c6c1e236b60f81d6246cfcd597b690a4a545e426fe33f735.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 361, + 545, + 405 + ], + "lines": [ + { + "bbox": [ + 304, + 361, + 545, + 405 + ], + "spans": [ + { + "bbox": [ + 304, + 361, + 545, + 405 + ], + "type": "text", + "content": "Table 5. Image VQA Results: We report accuracy " + }, + { + "bbox": [ + 304, + 361, + 545, + 405 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 304, + 361, + 545, + 405 + ], + "type": "text", + "content": " on the test-dev split of GQA dataset (GQA) and the validation / test splits of VQAv2 dataset (VQA-V / VQA-T). Our proposed LocVLM improves over prior works achieving state-of-the-art performance." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 418, + 545, + 444 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 418, + 545, + 444 + ], + "spans": [ + { + "bbox": [ + 304, + 418, + 545, + 444 + ], + "type": "text", + "content": "unlike ours they use VQA datasets (containing similar domain question-answer pairs) during training." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 452, + 382, + 464 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 452, + 382, + 464 + ], + "spans": [ + { + "bbox": [ + 306, + 452, + 382, + 464 + ], + "type": "text", + "content": "4.4. Video VQA" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 471, + 545, + 578 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 471, + 545, + 578 + ], + "spans": [ + { + "bbox": [ + 304, + 471, + 545, + 578 + ], + "type": "text", + "content": "Our model is also applicable to video tasks following our video domain adaptation described in Sec. 3.5. We simply adopt the additional video instruction fine-tuning phase from [42] on the ActivityNet dataset after our initial two phases of training to obtain LocVLM-Vid-B. This third phase involves fine-tuning only the adapter layer of our model. We also explore video variants of our IFT objectives that train both adapter layer and LLM. The resulting model is termed LocVLM-Vid-B+." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": "Video VQA focuses on correctly answering questions regarding a given video that require spatio-temporal awareness to answer. We evaluate our video-adapted model on the task of zero-shot video VQA on four benchmark datasets, ActivityNet-QA, MSRVTT-QA, MSVD-QA, and TGIF-QA. We evaluate on the validation splits of these four datasets. ActivityNet-QA videos cover a wide range of complex human activities relevant to daily living with its question-answer pairs focusing on long-term spatiotemporal reasoning. MSRVTT-QA builds off the MSRVTT dataset that contains web videos covering a comprehensive" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "12982" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 85, + 70, + 507, + 235 + ], + "blocks": [ + { + "bbox": [ + 85, + 70, + 507, + 235 + ], + "lines": [ + { + "bbox": [ + 85, + 70, + 507, + 235 + ], + "spans": [ + { + "bbox": [ + 85, + 70, + 507, + 235 + ], + "type": "table", + "html": "
MethodZero-ShotActivityNet-QAMSRVTT-QAMSVD-QATGIF-QA
JustAsk [63]✘38.941.847.5-
FrozenBiLM [64]✘43.247.054.8-
VideoCoCa [62]✘56.146.356.9-
Flamingo [2]✓-17.435.6-
BLIP-2 [33]✓-17.434.4-
InstructBLIP [15]✓-25.644.3-
FrozenBiLM [64]✓24.716.832.241.0
Video Chat [34]✓26.545.056.334.4
LLaMA Adapter [72]✓34.243.854.9-
Video LLaMA [71]✓12.429.651.6-
Video-ChatGPT [42]✓35.249.364.951.4
LocVLM-Vid-B✓37.451.266.151.8
", + "image_path": "32bf64ac081a7193f6b9ac9e822395b0f48c45c02f9798578f1df6bb719670aa.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 272, + 289, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 272, + 289, + 464 + ], + "spans": [ + { + "bbox": [ + 46, + 272, + 289, + 464 + ], + "type": "text", + "content": "range of categories and diverse visual content. MSVD-QA is a similar dataset building off the MSVD dataset. TGIFQA contains question-answer pairs from an dataset constructed of animated GIFs. For each dataset, we report the accuracy metric following evaluation protocol in [42]. Our results on these four datasets reported in Tab. 6 demonstrate state-of-the-art performance of our proposed LocVLM-Vid-B, with consistent improvements over the baseline from [42]. Here we use the LocVLM-Vid-B variant for fairer comparison with the baseline from [42]. We attribute the performance gains exhibited by our model to its stronger spatial awareness (see Sec. 4.2). Particularly in the case of video understanding, awareness of content at spatial level of each frame is significant to understand object motions and interactions [1, 51]. We also report more results involving additional model variants in Tab. 7." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 479, + 168, + 493 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 479, + 168, + 493 + ], + "spans": [ + { + "bbox": [ + 47, + 479, + 168, + 493 + ], + "type": "text", + "content": "4.5. Object Hallucination" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 498, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 289, + 713 + ], + "type": "text", + "content": "Current state-of-the-art V-LLMs suffer from object hallucination, generating image descriptions inconsistent with the image content [36]. For example, a V-LLM would respond to \"Where is the cat in this image?\" with \"The cat is on the table\" when in reality there is no cat in the image. We evaluate the extent of hallucination in V-LLMs using three datasets we introduce (details in Appendix C) and the POPE dataset [36]. Our three datasets, Hal-COCO, Hal-ADE, and Hal-Act build off COCO, ADE-20K, and ActivityNet datasets respectively. The first two involve images and the latter videeos. These datasets contain \"Is there obj in image / video?\" type questions per sample, for two objects present and not present in the image / video. Hal-ADE object categories contain no overlap with COCO classes allowing evaluation on novel object categories unseen during our instruction fine-tuning. Results reported in Tab. 8 show clear improvements of LocVLM-B over baselines. We also evaluate LocVLM-B on the POPE benchmark [36] that builds" + } + ] + } + ], + "index": 4 + }, + { + "type": "table", + "bbox": [ + 317, + 270, + 533, + 374 + ], + "blocks": [ + { + "bbox": [ + 46, + 238, + 545, + 260 + ], + "lines": [ + { + "bbox": [ + 46, + 238, + 545, + 260 + ], + "spans": [ + { + "bbox": [ + 46, + 238, + 545, + 260 + ], + "type": "text", + "content": "Table 6. Video VQA Results: Our proposed LocVLM-Vid-B improves over Video-ChatGPT [42] and achieves state-of-the-art results (Top-1 Accuracy %) across four different video VQA benchmarks. Note the zero-shot setting of all these evaluations." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 317, + 270, + 533, + 374 + ], + "lines": [ + { + "bbox": [ + 317, + 270, + 533, + 374 + ], + "spans": [ + { + "bbox": [ + 317, + 270, + 533, + 374 + ], + "type": "table", + "html": "
MethodVLTFramesAcc (%)
LLaVa (v1) [38]×128.7
LLaVa (v1.5) [38]×131.5
LocVLM-B×129.2
LocVLM-L×132.1
Video-ChatGPT [42]✓10035.2
LocVLM-Vid-B✓10037.4
LocVLM-Vid-B+✓838.2
", + "image_path": "82526f80754f3538a8fd04dcee6de9d99d40ad2dbdb4c227980f33d7b4960af3.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_body" + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 309, + 421, + 545, + 511 + ], + "blocks": [ + { + "bbox": [ + 306, + 376, + 545, + 419 + ], + "lines": [ + { + "bbox": [ + 306, + 376, + 545, + 419 + ], + "spans": [ + { + "bbox": [ + 306, + 376, + 545, + 419 + ], + "type": "text", + "content": "Table 7. Video VQA: We report more results (Top-1 Accuracy) for ActivityNet-QA dataset including multiple baseline and LocVLM variants. Our proposed models exhibit top performance. VLT denotes video level training. More details in Appendix D." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 421, + 545, + 511 + ], + "lines": [ + { + "bbox": [ + 309, + 421, + 545, + 511 + ], + "spans": [ + { + "bbox": [ + 309, + 421, + 545, + 511 + ], + "type": "table", + "html": "
MethodHal-COCOHal-ADEHal-Act
Shikra [8]86.258.7-
LLaVa [38]61.953.8-
LocVLM-B88.375.2-
Video-ChatGPT [42]--50.6
LocVLM-Vid-B--68.7
LocVLM-Vid-B+--72.4
", + "image_path": "b66e2ffec55f68704e7093a1bb0cbe02e423af548651c15095d139e10c93ee28.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 512, + 545, + 545 + ], + "lines": [ + { + "bbox": [ + 305, + 512, + 545, + 545 + ], + "spans": [ + { + "bbox": [ + 305, + 512, + 545, + 545 + ], + "type": "text", + "content": "Table 8. Hallucination Evaluation: We report top-1 accuracy (\\%) for object presence type questions and showcase reduced object hallucination in our proposed framework." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 305, + 556, + 545, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 556, + 545, + 593 + ], + "spans": [ + { + "bbox": [ + 305, + 556, + 545, + 593 + ], + "type": "text", + "content": "off the COCO dataset object annotations and report results in Tab. 9. Our LocVLM showcases similar performance improvements on this dataset." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 599, + 419, + 612 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 599, + 419, + 612 + ], + "spans": [ + { + "bbox": [ + 306, + 599, + 419, + 612 + ], + "type": "text", + "content": "4.6. Region Description" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "content": "A unique characteristic of our model (in contrast to V-LLMs like LLaVA [38] & BLIP-2 [33]) is its ability to reason with prompts involving coordinate based image space locations without any input modifications. Given a point or bounding box location, we prompt our model to generate an output describing that location. We refer to this unique ability of our model as region description (RD). We evaluate this RD capability of our model by generating object" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "12983" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 70, + 284, + 253 + ], + "blocks": [ + { + "bbox": [ + 51, + 70, + 284, + 253 + ], + "lines": [ + { + "bbox": [ + 51, + 70, + 284, + 253 + ], + "spans": [ + { + "bbox": [ + 51, + 70, + 284, + 253 + ], + "type": "table", + "html": "
DatasetsMetricsBLIP-2ShikraLLaVAOurs
RandomAccuracy (↑)88.686.950.487.9
Precision (↑)84.194.450.283.6
Recall (↑)95.179.399.193.9
F1 Score (↑)89.386.266.688.5
Yes56.643.398.856.2
PopularAccuracy (↑)82.884.049.986.0
Precision (↑)76.387.649.979.7
Recall (↑)95.179.299.393.9
F1 Score (↑)84.783.266.486.3
Yes62.445.299.458.9
AdversarialAccuracy (↑)72.183.149.778.8
Precision (↑)65.185.649.976.6
Recall (↑)95.179.699.193.7
F1 Score (↑)77.382.566.384.3
Yes73.046.599.461.7
", + "image_path": "b7d4000461d29ec5691a45198819b5ef0246b032e6a16558d5735d57f5cc19db.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 50, + 292, + 287, + 418 + ], + "blocks": [ + { + "bbox": [ + 47, + 255, + 286, + 278 + ], + "lines": [ + { + "bbox": [ + 47, + 255, + 286, + 278 + ], + "spans": [ + { + "bbox": [ + 47, + 255, + 286, + 278 + ], + "type": "text", + "content": "Table 9. More object hallucination: Results on POPE evaluation benchmark [36] indicate strong performance of our model." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 292, + 287, + 418 + ], + "lines": [ + { + "bbox": [ + 50, + 292, + 287, + 418 + ], + "spans": [ + { + "bbox": [ + 50, + 292, + 287, + 418 + ], + "type": "table", + "html": "
MethodZSRefCOCORefCOCO+RefCOCOg
ValTest
SLR [67]✘---15.4
SLR + Rerank [67]✘---15.9
Kosmos-2 [45]✘8.678.8214.314.1
Shikra [8]✘10.411.119.719.5
LLaVa [38]✘8.438.7313.513.5
LocVLM-B✘14.615.226.026.2
Kosmos-2 [45]✓6.348.2512.412.2
LLava [38]✓4.237.2610.610.3
LocVLM-B✓11.011.120.620.7
", + "image_path": "180a692b19fe900149b5fff504f24207b1ceca10cca5b887136af2eb6d0eaa7b.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 468, + 286, + 612 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 468, + 286, + 612 + ], + "spans": [ + { + "bbox": [ + 46, + 468, + 286, + 612 + ], + "type": "text", + "content": "level descriptions focused on contextual information (e.g. surrounding of that object in the image). Following evaluation protocol in [45] for region description, we extend their evaluation to three standard referring localization datasets from RefCOCO [29] and report these results in Tab. 10. We select the METEOR score as the evaluation metric to account for variations in word choice in generated answers which may be acceptable in various cases (e.g. different sentence structure leading to alternate word ordering). Our results indicate clear improvements over the LLaVA baseline [38] as well as prior state-of-the-art. We attribute these improvements to our pseudo-data based training." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 623, + 115, + 635 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 623, + 115, + 635 + ], + "spans": [ + { + "bbox": [ + 47, + 623, + 115, + 635 + ], + "type": "text", + "content": "4.7. Ablations" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "content": "Next we conduct ablative studies on separate components of our proposed setup: IFT objectives, location type, and pseudo-data. We follow the same training strategy as described in Sec. 4.1 and present these results in Tab. 11. LocVLM-B is used for all these experiments. The significance of each IFT objective is verified in Tab. 11 (top) with" + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 318, + 71, + 534, + 191 + ], + "blocks": [ + { + "bbox": [ + 47, + 420, + 286, + 453 + ], + "lines": [ + { + "bbox": [ + 47, + 420, + 286, + 453 + ], + "spans": [ + { + "bbox": [ + 47, + 420, + 286, + 453 + ], + "type": "text", + "content": "Table 10. Region Description: We report METEOR scores for RD task [45]. Test-B split is used for RefCOCO & RefCOCO+ datasets. Our method outperforms all prior work." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 318, + 71, + 534, + 191 + ], + "lines": [ + { + "bbox": [ + 318, + 71, + 534, + 191 + ], + "spans": [ + { + "bbox": [ + 318, + 71, + 534, + 191 + ], + "type": "table", + "html": "
LocPredNegPredRevLocGQARDA-QA
XXX44.710.335.2
✓XX45.212.235.8
✓✓X46.912.537.2
✓✓✓47.320.737.4
Location TypePDGQARDA-QA
Point✓47.320.637.4
Bounding Box✓47.320.737.4
Bounding BoxX46.511.637.1
", + "image_path": "103df4034479e10762a4a43668d369482fea96f8e47733387e1780074ffd3923.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 337, + 298, + 515, + 361 + ], + "blocks": [ + { + "bbox": [ + 305, + 193, + 545, + 281 + ], + "lines": [ + { + "bbox": [ + 305, + 193, + 545, + 281 + ], + "spans": [ + { + "bbox": [ + 305, + 193, + 545, + 281 + ], + "type": "text", + "content": "Table 11. Ablations: We report top-1 accuracy (\\%) on GQA and ActivityNet-QA (A-QA) datasets and METEOR scores for RD task on RefCOCOg test split. (top) We ablate proposed instruction fine-tuning objectives to verify usefulness of each objective. (bottom) We first ablate point based and bounding box based location forms to showcase minimal difference across them. We next ablate use of object description pseudo-data (PD). We highlight the improvements due to pseudo-data, especially on the RD task." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 337, + 298, + 515, + 361 + ], + "lines": [ + { + "bbox": [ + 337, + 298, + 515, + 361 + ], + "spans": [ + { + "bbox": [ + 337, + 298, + 515, + 361 + ], + "type": "table", + "html": "
LocPredNegPredRevLocA-QA
XXX37.4
✓XX37.6
✓✓X38.2
✓✓✓38.2
", + "image_path": "6f99c3ec03998962ac1b885cea89288fb062cdbc827ffab3d661c56420ab30a5.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 362, + 545, + 396 + ], + "lines": [ + { + "bbox": [ + 305, + 362, + 545, + 396 + ], + "spans": [ + { + "bbox": [ + 305, + 362, + 545, + 396 + ], + "type": "text", + "content": "Table 12. Video Ablation: We report top-1 accuracy " + }, + { + "bbox": [ + 305, + 362, + 545, + 396 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 305, + 362, + 545, + 396 + ], + "type": "text", + "content": " on ActivityNet-QA (A-QA) dataset. Results indicate the generality of proposed IFT objectives for video domain training as well." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 419, + 545, + 539 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 419, + 545, + 539 + ], + "spans": [ + { + "bbox": [ + 304, + 419, + 545, + 539 + ], + "type": "text", + "content": "consistent performance improvements across tasks. The generality of our approach to differing location type (i.e. points vs bounding boxes) and usefulness of pseudo-data is visible in Tab. 11 (bottom). In particular, we highlight the notable performance improvement for RD task gained from using pseudo-data. We also conduct ablations for our video domain training setup and report these results in Tab. 12. The LocVLM-Vid-B+ variant is used in these experiments. Our results showcase the usefulness of proposed IFT objectives for video domain learning as well." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 562, + 378, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 562, + 378, + 574 + ], + "spans": [ + { + "bbox": [ + 306, + 562, + 378, + 574 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "We introduce a simple framework that equips visual-LLMs (V-LLMs) with greater spatial understanding, termed LocVLM. We leverage the idea of encoding image coordinates within language to propose three instruction finetuning (IFT) objectives. This training process endows V-LLMs with the ability to reason about spatial composition of images using image space coordinates within text. A data efficient training pipeline utilizing pseudo-data allows our approach to achieve state-of-the-art results in Image VQA, Video VQA, and Region Description while improving spatial awareness and reducing object hallucination." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "12984" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 49, + 72, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 49, + 72, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 49, + 72, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 87, + 286, + 713 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 87, + 286, + 120 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 87, + 286, + 120 + ], + "spans": [ + { + "bbox": [ + 53, + 87, + 286, + 120 + ], + "type": "text", + "content": "[1] Jake K. 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The more recent Embodied AI literature, on the other hand, focuses on modular or end-to-end agents trained in simulators like Habitat or AI-Thor, where the emphasis is put on photorealistic rendering and scene diversity, but high-fidelity robot motion is assigned a less privileged role. The resulting sim2real gap significantly impacts transfer of the trained models to real robotic platforms. In this work we explore end-to-end training of agents in simulation in settings which minimize the sim2real gap both, in sensing and in actuation. Our agent directly predicts (discretized) velocity commands, which are maintained through closed-loop control in the real robot. The behavior of the real robot (including the underlying low-level controller) is identified and simulated in a modified Habitat simulator. Noise models for odometry and localization further contribute in lowering the sim2real gap. We evaluate on real navigation scenarios, explore different localization and point goal calculation methods and report significant gains in performance and robustness compared to prior work.", + "bbox": [ + 76, + 301, + 473, + 662 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 693, + 209, + 709 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Point goal navigation of terrestrial robots in indoor buildings has traditionally been addressed in the robotics community with mapping and planning [6, 30, 50], which led to solutions capable of operating on robots in real environments. The field of computer vision and embodied AI has addressed this problem through large-scale machine learning in simulated 3D environments from reward with RL [24, 34] or with imitation learning [14]. Learning from large-scale data allows the agent to pick up more complex regularities, to process more subtle cues and therefore (in principle) to be more robust, to exploit data regularities to infer hidden and occluded information, and generally to learn more powerful", + "bbox": [ + 75, + 719, + 470, + 901 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/bf0f7190eaad5d2558171f5350c0ffe43cd6985cc71538a77fafd17496fdcf35.jpg", + "image_caption": [ + "Figure 1. Efficient navigation with policies end-to-end trained in 3D photorealistic simulators requires closing the sim2real gap in sensing and actuation. Efficiency demands that the robot continues to move during decision taking (as opposed to stopping for each sensing operation), and this requires a realistic motion model in simulation allowing the agent to internally anticipate its future state. This requirement is exacerbated by the delay between sensing $①$ and actuation $②$ caused by the computational complexity of high-capacity deep networks (visual encoders, policy). To model realistic motion while training in simulation, we create a $2^{nd}$ order dynamical model running with higher frequency, which models the robot and its low-level closed-loop controller. We identify the model from real data and add it to the Habitat [44] Simulator." + ], + "image_footnote": [], + "bbox": [ + 503, + 267, + 890, + 474 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "decision rules. In this context, the specific task of point goal navigation (navigation to coordinates) is now sometimes considered \"solved\" in the literature [38], incorrectly, as we argue. While the machine learning and computer vision community turns its attention towards the exciting goal of integrating language models into navigation [15, 23], we think that further improvements are required to make trained agents perform reliably in real environments with sufficient speed.", + "bbox": [ + 496, + 699, + 893, + 835 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Experiments and evaluations of trained models in real environments and the impact of the sim2real gap do exist in the Embodied AI literature [11, 20, 43], but they are rare and were performed in restricted environments. Known models", + "bbox": [ + 498, + 839, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version:", + "bbox": [ + 236, + 1, + 807, + 23 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 292, + 30, + 753, + 45 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "17837", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "are trained in 3D simulators like Habitat [44] or AI-Thor [26], which are realistic in their perception aspects, but lack the accurate motion models of physical agents which the robotics community uses for articulated robots, for instance, where forward and inverse kinetics are often modeled and identified. This results in a large sim2real gap in motion characteristics, which is either ignored or addressed by discrete motion commands. The latter strategy teleports the agent in simulation for each discrete action and executes these actions on the physical robot by low-level control on positions instead of velocities, stopping the robot between agent decisions and leading to extremely inefficient navigation and overly long episodes [43].", + "bbox": [ + 75, + 90, + 472, + 287 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this work we go beyond current models for terrestrial navigation by realistically modeling both actuation and sensing of real agents in simulation, and we successfully transfer trained models to a real robotic platform. On the actuation side, we take agent decisions as discretized linear and angular velocities and predict them asynchronously while the agent is in motion. The resulting delay between sensing and actuation (see Figure 1) requires the agent to anticipate motion, which it learns in simulation from a realistic motion model. To this end, we create a second-order dynamical model, which approximates the physical properties of the real robot together with its closed-loop low-level controller. We identify this model from real robot rollouts and expert actions. The model is integrated into the Habitat simulator as an intermediate solution between the standard instantaneous motion model and a full-blown computationally-expensive physics simulation based on forces, masses, frictions etc.", + "bbox": [ + 75, + 287, + 472, + 542 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "On the sensing side, we combine visual and Lidar observations with different ways of communicating the navigation (point) goal to the agent, and different estimates of robot pose relative to a reference frame, combining two different types of localization: first, dead reckoning from wheel encoders, and secondly, external localization based on Monte Carlo methods from Lidar input. We perform extensive experiments and ablations on a real navigation platform and quantify the impact of the motion model, action spaces, sensing capabilities and the way we provide goal coordinates on navigation performance, showing that end-to-end trained agents can robustly navigate from visual input when their motion has been correctly modelled in simulation.", + "bbox": [ + 75, + 544, + 472, + 741 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 753, + 218, + 768 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Visual navigation — navigation has been classically solved in robotics using mapping and planning [7, 31, 32], which requires solutions for mapping and localization [6, 28, 50], for planning [27, 46] and for low-level control [19, 42]. These methods depend on accurate sensor models, filtering, dynamical models and optimization. End-to-end trained models directly map input to actions and are typically trained with RL [24, 35] or imitation learning [14]. They learn repre", + "bbox": [ + 75, + 779, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "sentations such as flat recurrent states, occupancy maps [9], semantic maps [8], latent metric maps [4, 21, 37], topological maps [3, 10, 47], self-attention [12, 16, 18, 41], implicit representations [33] or maximizing navigability directly with a blind agent optimizing a collected representation [5]. Our proposed method is end-to-end trained and features recurrent memory, but benefits from an additional motion model in simulation.", + "bbox": [ + 496, + 90, + 893, + 210 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Sim2real transfer — The sim2real gap can compromise strong performance achieved in simulation when agents are tested in the real-world [22, 29], as perception and control policies often do not generalize well to real robots due to inaccuracies in modelling, simplifications and biases. To close the gap, domain randomization methods [39, 49] treat the discrepancy between the domains as variability in the simulation parameters. Alternatively, domain adaptation methods learn an invariant mapping for matching distributions between the simulator and the robot environment. Examples include transfer of visuo-motor policies by adversarial learning [55], adapting dynamics in RL [17], lowering fidelity simulation [52] and adapting object recognition to new domains [56]. Bi-directional adaptation is proposed in [51]; Recently, Chattopadhyay et al. [11] benchmarked the robustness of embodied agents to visual and dynamics corruptions. Kadian et al. [25] investigated sim2real predictability of Habitat-Sim [44] for PointGoal navigation and proposed a new metric to quantify it, called Sim-vs-Real Correlation Coefficient (SRCC). The PointGoal task on real robots is also evaluated in [43]. To reach competitive performance without modelling any sim2real transfer, the agent is pre-trained on a wide variety of environments and then fine-tuned on a simulated version of the target environment.", + "bbox": [ + 496, + 223, + 895, + 585 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Motion models — are usually kept very simple when training visual navigation policies. Several works use a discrete high-level action space in simulation [8, 9, 20] and rely on dedicated controllers to translate these discrete actions into robot controls when transferring to the real world. Alternative approaches predict continuous actions [13, 54] or waypoints [2, 48], that again are subsequently mapped to robot controls when executing the policies in real. Somewhat closer to our approach, Yokoyama et al. [53] adopt a discretized linear and angular velocity space, and introduce a new metric, SCT, that uses a simplified \"unicycle-cart\" dynamical model to estimate the \"optimal\" episode completion time computed by rapidly exploring random trees (RRT). However the unicycle model is only used for evaluation and it is not deployed for training nor testing: as in previous works, the commands are mapped to robot controls using handcrafted heuristics. In contrast to previous approaches, we include the dynamical model of the robot in the training loop to learn complex dependencies between the navigation policy and the robot physical properties.", + "bbox": [ + 496, + 598, + 895, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "17838", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/81e1ba774bd35f70e54ac80f63c84c548dd3222fbdbcb5bab27939e388c50395.jpg", + "image_caption": [ + "Figure 2. The agent uses a recurrent policy with a static point goal $g_{0}$ as input, i.e. the goal is constant and given wrt. to the initial reference frame. During training, the estimation of the dynamic point goal $\\hat{g}_{t}$ is supervised from privileged information." + ], + "image_footnote": [], + "bbox": [ + 78, + 87, + 472, + 241 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. End-to-end training with realistic sensing", + "text_level": 1, + "bbox": [ + 76, + 324, + 447, + 342 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We propose a method for training agents which (in principle) could address a variety of visual navigation problems, and without loss of generality, focusing on sim2real transfer and efficiency, we formalize the problem as a PointGoal task: an agent receives sensor observations at each time step $t$ and must take actions $\\mathbf{a}_t$ to reach a goal position given as polar coordinates. The method is not restricted to any specific observations, in our experiments the agent receives RGB images $\\mathbf{I}_t \\in \\mathbb{R}^{3 \\times H \\times W}$ and a Lidar-like vector of ranges $\\mathbf{S}_t \\in \\mathbb{R}^K$ , where $K$ is the number of laser rays.", + "bbox": [ + 75, + 351, + 468, + 501 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The proposed agent is fully trained and therefore does not require to localize itself on a map for analytical path planning. However, even in this very permissive setting the application itself requires to communicate the goal to the agent in some form of coordinate system, which requires localization at least initially with respect to the goal (in ImageGoal settings this would be replaced by the goal image). We can classically differentiate between three different forms:", + "bbox": [ + 75, + 503, + 468, + 625 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Absolute PointGoal — the goal vector $\\mathbf{g}^a = [\\mathbf{g}_x^a, \\mathbf{g}_y^a]^T$ is given in a pre-defined agent-independent absolute reference frame. This requires access to a global localization system.", + "bbox": [ + 84, + 626, + 470, + 686 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Dynamic PointGoal — the goal vector $\\mathbf{g}_t$ is provided with respect to the current agent pose and therefore updated at each time instant $t$ . This requires an external localization system providing estimates which are then transformed into the egocentric reference frame.", + "bbox": [ + 86, + 686, + 470, + 762 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Static PointGoal — the goal vector is provided with respect to the starting position at $t = 0$ of the robot, and not updated with agent motion $(= \\mathbf{g}_0)$ . This requires the agent to learn this update itself, and therefore some form of internal localization or integration of odometry information.", + "bbox": [ + 86, + 763, + 472, + 839 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We target the Static PointGoal case, which does not require localization beyond the initial relative vector. However, we also argue that some form of localization and/or odometry information is useful, which will assist the dynamics infor", + "bbox": [ + 75, + 839, + 470, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "mation inferred from (visual) sensor readings. Furthermore, during training it will allow the agent to learn a useful latent representation in its hidden state and an associated dynamics in this latent space. We therefore provide the agent with two different localization components:", + "bbox": [ + 496, + 90, + 893, + 167 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "$\\hat{\\mathbf{p}}_t^a$ — an estimate of agent pose with respect to the initial agent position, asynchronously delivered and with low frequency, around 0.5-1 fps. At test, this signal is delivered by external localization, in our case from a Lidar-based AMCL module (see Section 5).", + "bbox": [ + 508, + 169, + 893, + 243 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "$\\hat{\\mathbf{p}}_t^r$ — an estimate coming from onboard odometry, which we integrate over time to provide an estimate situated in the same reference frame as $\\hat{\\mathbf{p}}_t^a$ , i.e. with respect to the initial agent position.", + "bbox": [ + 508, + 244, + 893, + 305 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The characteristics of the two localization signals are different: while $\\hat{\\mathbf{p}}_t^r$ corresponds to a dead reckoning process and is subject to drift, its relative noise is lower. The signal $\\hat{\\mathbf{p}}_t^a$ is not subject to drift but suffers from larger errors in certain regions, due to registration errors or absence of structure.", + "bbox": [ + 496, + 306, + 893, + 382 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The agent policy is recurrent, based on a hidden memory vector $\\mathbf{h}_t$ updated over time from input of all sensor readings $\\mathbf{I}_t, \\mathbf{S}_t, \\mathbf{p}_t^r, \\hat{\\mathbf{p}}_t^a$ , the goal $\\mathbf{g}_0$ and the previous action $\\mathbf{a}_{t-1}$ ,", + "bbox": [ + 496, + 383, + 892, + 430 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {h} _ {t} = d \\left(\\mathbf {h} _ {t - 1}, v \\left(\\mathbf {I} _ {t}\\right), u \\left(\\mathbf {S} _ {t}\\right), \\mathbf {g} _ {0}, \\hat {\\mathbf {p}} _ {t} ^ {r}, \\hat {\\mathbf {p}} _ {t} ^ {a}, e \\left(\\mathbf {a} _ {t - 1}\\right)\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 535, + 431, + 892, + 449 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {a} _ {t} = \\pi (\\mathbf {h} _ {t}), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 537, + 450, + 890, + 468 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\mathbf {g}} _ {t} = l \\left(\\mathbf {h} _ {t}\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 537, + 470, + 890, + 487 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $d$ is a GRU with hidden state $\\mathbf{h}_t$ , $v$ is a visual encoder of the image $\\mathbf{I}_t$ (in our case, a ResNet-18); $u$ is a 1D-CNN encoding the scan $\\mathbf{S}_t$ ; $e$ is a set of action embedding vectors; $\\pi$ is a linear policy. Other inputs go through dedicated MLPs, not named to lighten notations. To help the agent deal with the noisy relative and absolute pose estimates, we put an inductive bias for localization on $\\mathbf{h}_t$ through an auxiliary head $l$ predicting the dynamic goal compass $\\hat{\\mathbf{g}}_t$ , supervised during training from the simulated agent's ground truth pose, as shown in Figure 2. In the following paragraphs we describe the two localization systems and the noise models we use to simulate them during training in simulation. Section 4 then introduces the dynamical model used during training.", + "bbox": [ + 496, + 489, + 893, + 686 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Integrated relative localization - the pose estimate $\\hat{\\mathbf{p}}_t^r$ can be obtained with any commercially available odometry system. In our experiments we integrate readings from wheel encoders. During simulation and training, $\\hat{\\mathbf{p}}_t^r$ is estimated by sampling planar noise $[\\epsilon_x,\\epsilon_\\theta ]^\\intercal$ from a multivariate Gaussian distribution $\\mathcal{N}(\\left[ \\begin{array}{cc}0.01\\\\ 0 \\end{array} \\right],\\left[ \\begin{array}{cc}10^{-4} & 10^{-4}\\\\ 10^{-4} & 10^{-3} \\end{array} \\right])$ which gets added to the step-wise motion of the agent, leading to the accumulation of drift over time.", + "bbox": [ + 496, + 688, + 893, + 821 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Absolute localization - the pose estimate $\\hat{\\mathbf{p}}_t^a$ is obtained with the standard ROS 2 package for Adaptive Monte Carlo Localization (AMCL) [50], a KLD-sampling approach requiring a pre-computed, static map based on particle filtering. During simulation and training, $\\hat{\\mathbf{p}}_t^r$ is es", + "bbox": [ + 496, + 825, + 893, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "17839", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/5c67e1c12db97c5c52a0418878fdd2140a9d22e22884288fc0cd62ca28730736.jpg", + "image_caption": [ + "Figure 3. Training visual navigation with realistic motion models: we train an end-to-end agent in simulation (top) subject to two different simulation loops: a slower loop at $3\\mathrm{Hz}$ (indexed by $t$ ) renders visual observations and takes agent decisions, while a faster loop at $30\\mathrm{Hz}$ (indexed by $\\tau$ ) simulates physics. Physics is approximated with a $2^{nd}$ order model identified from real robot rollouts (bottom) and includes the robot physics as well as the behavior of the closed-loop control of the differential drive (neither onboard control algorithm nor control frequency need to be known). Operations in the intervals are pipelined, e.g. sensing occurs at each time step, as does agent forward pass etc. The agent architecture is detailed in Figure 2." + ], + "image_footnote": [], + "bbox": [ + 80, + 87, + 893, + 424 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "timated by sampling planar noise from another Gaussian $\\mathcal{N}(0, \\mathrm{Diag}[0.03, 0.03, 0.05])$ , but this time it gets directly added to the ground truth pose of the robot, thus modeling imprecise localization (eg. due to Lidar registration failures) without drift accumulation. In addition, we model the potential unreliability of such absolute pose estimates by only providing a new observation to the agent every few steps, at an irregular period governed by a uniform distribution $\\mathcal{U}(8, 12)$ . This potentially allows to plug-in low-frequency visual localization.", + "bbox": [ + 75, + 526, + 472, + 676 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. A dynamical model of realistic robot motion", + "text_level": 1, + "bbox": [ + 76, + 693, + 470, + 709 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "One of our main motivations is to be able to use a trained model to navigate efficiently, i.e. fast and reliably. Stopping the robot between predicted actions is therefore not an option, and we train the model to predict linear and angular velocity commands in parallel to its physical motion, as illustrated in Figure 1. This requires the agent to anticipate motion to predict an action $\\mathbf{a}_t$ relative to the next (yet unobserved) state at $t$ , exacerbated by the delay between sensing at time $t$ and actuation at $t + 1$ , during which computation through the high-capacity visual encoder and policy happens. This motion depends on the physical characteristics of the robot, as shown in Figure 3 (bottom): the linear and angular veloc", + "bbox": [ + 75, + 719, + 472, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "ity commands predicted by the neural policy $\\pi$ are translated into \"set values\" for left and right motor speeds of the differential drive system with a deterministic function and used as targets by the closed loop control algorithm, typically a PID (Proportional Integral Derivative Controller), attempting to reach and maintain the predicted speed between agent decisions. The behavior depends on the control algorithm but also on the physical properties of the robot, like its mass and resulting inertia, power and torque curves of the motors, friction etc. We decrease the actuation sim2real gap as as much as possible by integrating a model of realistic robot behavior into the Habitat [44] platform, shown in the top part of Figure 3. We approximate the robot's motion behavior by modeling the combined behavior of both the robot and the control algorithm implemented on the real platform as an asymmetric second-order dynamic system. The parameters of this low-level loop are estimated from recordings of the real robot platform with a system identification algorithm.", + "bbox": [ + 496, + 526, + 893, + 797 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Classically, a sequential decision process can be modeled as a POMDP $\\langle \\mathcal{X},\\mathcal{U},T,\\mathcal{O},O,R\\rangle$ . In pure 2D navigation settings with a fixed goal in a single static scene, the environment maintains a (hidden) state $\\mathbf{x}_t\\in \\mathcal{X}$ consisting in the pose of the agent, i.e. position and orientation, $\\mathbf{x}_t = [x_t,y_t,\\theta_t]$ . In most settings in the literature", + "bbox": [ + 496, + 810, + 895, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "17840", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/e0c937955b88f2606debdb8455db3b1f2f481b876fe4306210aaa8b2b70faff7.jpg", + "image_caption": [ + "Figure 5. Robustness: Top: The ROS2 baseline fails when obstacles are thin at the height of the single Lidar ray. The robot doesn't see the stool, collides, drags it away. The red circles $\\bigcirc$ show the position of the moved stool. Bottom: our agent is surprisingly robust and allows navigation very close to fine structures." + ], + "image_footnote": [], + "bbox": [ + 78, + 88, + 472, + 237 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "based on 3D photo-realistic simulators like Habitat [44], the state update in simulation ignores physical properties of the robot (mass/inertia, friction, accelerations, etc.), as it is implemented through \"teleportation\" of the robot to a new pose. In that case, the environment transition decomposes into a discrete state update $x_{t + 1} = T(x_t,u_t)$ and an observation $o_{t + 1} = O(x_{t + 1})$ . The discrete action space $\\mathcal{U}_{\\mathrm{motion}} = \\{\\mathrm{FORWARD~25cm},\\mathrm{TURN\\_LEFT~10^{\\circ}},\\mathrm{TURN\\_RIGHT~10^{\\circ}} \\text{ and } \\mathrm{STOP}\\}$ frequently chosen in the navigation literature results in a halting and jerky robot motion.", + "bbox": [ + 75, + 332, + 472, + 484 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Adding realism — To be able to smooth robot trajectories, we need to model accelerations. We extend the agent state as:", + "bbox": [ + 76, + 484, + 472, + 527 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {x} _ {t} = \\left[ x _ {t}, y _ {t}, \\theta_ {t}, v _ {t}, w _ {t}, \\dot {v} _ {t}, \\dot {w} _ {t} \\right], \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 169, + 530, + 468, + 546 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $x_{t}, y_{t}, \\theta_{t}$ are the absolute position and orientation of the robot in the plane of the scene (in m, m and rad); $v_{t}, w_{t}$ are the linear (forward) and angular velocities of the robot (in m/s and rad/s); $\\dot{v}_{t}; \\dot{w}_{t}$ are the linear and angular accelerations of the robot (in m/s² and rad/s²).", + "bbox": [ + 75, + 551, + 468, + 628 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The proposed agent predicts a pair $\\langle v_t^*, w_t^* \\rangle$ of velocity commands, chosen from a discrete action space $\\mathcal{U}_{\\mathrm{vel}}$ resulting from the cartesian product of linear and angular spaces $\\{0, 0.3, 0.6, 1\\} \\times \\{-3, -2, -1, 0, \\dots, 3\\}$ , as shown in Figure 4. To simplify notations, we will use $\\mathbf{u}_t = \\langle v_t^*, w_t^* \\rangle \\in \\mathcal{U}$ .", + "bbox": [ + 76, + 628, + 295, + 779 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "One possibility to model realistic robot behavior is to design a full dynamical model of the robot in the form of a set of differential equations, identify its parameters, discretize it, and simulate it in Habitat, together with running an exact copy of the conti", + "bbox": [ + 75, + 780, + 295, + 901 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/4378f2e4826d500bb54dd4d73b95d66bd45465e9460184b61153d8535d14eb9f.jpg", + "image_caption": [ + "Figure 4. The action space: 28 actions, 4 choices of linear velocities $\\in [0,1]$ m/s, 7 choices for angular vel. $\\in [-3,3]$ rad/s. Arrows show the effect on pose of action held for $\\frac{2}{3}\\mathrm{sec}$ ." + ], + "image_footnote": [], + "bbox": [ + 323, + 637, + 460, + 762 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/18349075bd8fa37460b6927a666f85f48ba4fd51ee385b78cf85ef346440fb5e.jpg", + "image_caption": [ + "Figure 6. Dynamic obstacles: our agent stops and circumvents people, achieved through a highly negative collision reward term." + ], + "image_footnote": [], + "bbox": [ + 501, + 88, + 890, + 164 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "physical robot with exactly the same parameters and control frequency, which is a stringent constraint. Instead, we opted for a more flexible solution and we approximate the combined behavior of the physical robot and its control algorithm by a second order dynamical model [36]. We decompose interactions with the simulator into two different loops running at different frequencies:", + "bbox": [ + 496, + 226, + 893, + 332 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Visual observations, simulator state updates and agent decisions (Equations (1) to (3)) are produced in a slower loop, indexed by letter $t$ in the subsequent notation, and run at $f^{*} = 3\\mathrm{Hz}$ in our experiments.", + "- Between two subsequent steps of the slower loop, a faster loop models physical motion of the robot, without rendering observations. At the end of this loop, the simulator state is updated, and a visual observation is returned. Steps in this faster loop are indexed by a second index $\\tau$ in the subsequent notation, $\\mathbf{x}_{t,\\tau}$ ." + ], + "bbox": [ + 503, + 339, + 893, + 494 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In-between two environment steps $t - 1$ and $t$ , we simulate dynamics at frequency $f^{\\phi} = 30 > f^{*}$ . The number of physical sub-time steps per environment time step is therefore", + "bbox": [ + 496, + 501, + 893, + 547 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "$K^{\\phi} = \\left|\\frac{f^{\\phi}}{f^{*}}\\right| = 10$ their duration is $\\Delta^{\\phi} = \\frac{1}{f^{\\phi}} = 33\\mathrm{ms}$ . The physical loop running between two environment steps can be formalized as the following set of state update equations,", + "bbox": [ + 500, + 547, + 890, + 598 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {o} _ {t} = O (\\mathbf {x} _ {t - 1}).\n$$\n", + "text_format": "latex", + "bbox": [ + 532, + 601, + 635, + 617 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Observation", + "bbox": [ + 818, + 601, + 908, + 614 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {x} _ {t - 1, 0} = \\mathbf {x} _ {t - 1}\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 619, + 604, + 631 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Init", + "bbox": [ + 820, + 617, + 849, + 628 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\dot {v} _ {t, \\tau + 1} = \\dot {v} _ {t, \\tau} + \\Delta^ {\\phi} \\left(f _ {t, \\tau} ^ {v} ^ {2} \\delta_ {t, \\tau} ^ {v} - 2 \\zeta_ {t, \\tau} ^ {v} f _ {t, \\tau} ^ {v} \\dot {v} _ {t, \\tau}\\right)\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 632, + 810, + 648 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Upd.acc.", + "bbox": [ + 820, + 632, + 888, + 646 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\dot {w} _ {t, \\tau + 1} = \\dot {w} _ {t, \\tau} + \\Delta^ {\\phi} \\left(f _ {t, \\tau} ^ {w} ^ {2} \\delta_ {t, \\tau} ^ {w} - 2 \\zeta_ {t, \\tau} ^ {w} f _ {t, \\tau} ^ {w} \\dot {w} _ {t, \\tau}\\right)\n$$\n", + "text_format": "latex", + "bbox": [ + 504, + 648, + 818, + 665 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nv _ {t, \\tau + 1} = v _ {t, \\tau} + \\Delta^ {\\phi} v _ {t, \\tau + 1}\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 665, + 679, + 679 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nw _ {t, \\tau + 1} = w _ {t, \\tau} + \\Delta^ {\\phi} w _ {t, \\tau + 1}\n$$\n", + "text_format": "latex", + "bbox": [ + 504, + 679, + 687, + 695 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\theta_ {t, \\tau + 1} = \\theta_ {t, \\tau} + \\Delta^ {\\phi} w _ {t, \\tau + 1}\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 695, + 684, + 709 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nx _ {t, \\tau + 1} = x _ {t, \\tau} + \\Delta^ {\\phi} v _ {t, \\tau + 1} \\cos \\theta_ {t, \\tau + 1}\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 710, + 750, + 724 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\ny _ {t, \\tau + 1} = y _ {t, \\tau} + \\Delta^ {\\phi} v _ {t, \\tau + 1} \\sin \\theta_ {t, \\tau + 1}\n$$\n", + "text_format": "latex", + "bbox": [ + 506, + 726, + 746, + 741 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {x} _ {t} = \\mathbf {x} _ {t - 1, K}\n$$\n", + "text_format": "latex", + "bbox": [ + 532, + 742, + 620, + 755 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Upd. vel.", + "bbox": [ + 820, + 665, + 885, + 679 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Upd. pose", + "bbox": [ + 820, + 695, + 893, + 710 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Final state", + "bbox": [ + 820, + 739, + 895, + 753 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "(5)", + "bbox": [ + 870, + 755, + 890, + 768 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In these equations, $f$ are natural frequencies and damping coefficients of asymmetric $2^{\\mathrm{nd}}$ order dynamic models for linear and angular motion. At each step $\\tau$ , they are chosen from identified values given command errors as follows:", + "bbox": [ + 500, + 770, + 890, + 829 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\delta_ {t, \\tau} ^ {v} = v _ {t} ^ {*} - v _ {t, \\tau}\n$$\n", + "text_format": "latex", + "bbox": [ + 547, + 833, + 656, + 848 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\langle f _ {t, \\tau} ^ {v}, \\zeta_ {t, \\tau} ^ {v} \\rangle = \\left\\{ \\begin{array}{l l} \\langle f ^ {v \\uparrow}, \\zeta^ {v \\uparrow} \\rangle & \\text {i f} \\delta_ {t, \\tau} ^ {v} \\cdot v _ {t, \\tau} > 0 (\\text {a c c e l e r a t i o n}) \\\\ \\langle f ^ {v \\downarrow}, \\zeta^ {v \\downarrow} \\rangle & \\text {o t h e r w i s e (d e c e l e r a t i o n)} \\end{array} \\right. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 503, + 848, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "17841", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "and similarly for angular model parameters $\\langle f^w,\\zeta^w\\rangle$ . Velocity and acceleration are also clipped to identified maximum values.", + "bbox": [ + 75, + 90, + 470, + 133 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "System identification - the model has 8 parameters, $f^{v\\uparrow}, \\zeta^{v\\uparrow}, f^{v\\downarrow}, \\zeta^{v\\downarrow}, f^{w\\uparrow}, \\zeta^{w\\uparrow}, f^{w\\downarrow}, \\zeta^{w\\downarrow}$ , which we identify from trajectories of a real robot controlled with precomputed trajectories exploring the command space, see the supplementary material for more details.", + "bbox": [ + 75, + 136, + 470, + 210 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Training - the model is trained with RL, in particular PPO [45], and with a reward inspired by [11], $r_t = \\mathrm{R} \\cdot \\mathbb{I}_{\\mathrm{success}} - \\Delta_t^{\\mathrm{Geo}} - \\lambda - \\mathrm{C} \\cdot \\mathbb{I}_{\\mathrm{collision}}$ , where $R = 2.5$ , $\\Delta_t^{\\mathrm{Geo}}$ is the gain in geodesic distance to the goal, a slack cost $\\lambda = 0.01$ encourages efficiency, and a cost $C = 0.1$ penalizes each collision without ending the episode.", + "bbox": [ + 75, + 212, + 470, + 301 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Recovery behavior — similar to what is done in classical analytical planning, we added a rudimentary recovery behavior on top of the trained agent: if the agent is notified of an obstacle and does not move for five seconds, it will move backward at $0.2\\mathrm{m / s}$ for two seconds.", + "bbox": [ + 75, + 301, + 470, + 378 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experimental Results", + "text_level": 1, + "bbox": [ + 76, + 392, + 282, + 409 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Experimental setup — we trained the agent in the Habitat simulator [44] on the 800 scenes of the HM3D Dataset [40] for 200M env. steps. Real robot experiments have been performed on a Naver Rookie robot, which came equipped with various sensors. We added an additional front facing RGB camera and capture images with a resolution of $1280 \\times 720$ resized to $256 \\times 144$ . In our experiments, the Lidar scan S is not taken from an onboard Lidar, but simulated from the 4 RealSense depth cameras which are installed close to the floor and oriented in 4 different directions. We use multiple scan lines of the cameras and fuse them into a single ray, details are given in the supplementary material. We did, however, add a single plane Lidar to the robot (which did not come equipped with one) and used it for localization only (see section 3). All processing has been done onboard, thanks to a Nvidia Jetson AGX Orin we added, with an integrated Nvidia Ampere GPU. It handles pre-processing of visual observations and network forward pass in around 70ms. The exact network architecture of the policy is given in the supplementary material.", + "bbox": [ + 75, + 416, + 470, + 718 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation — evaluating sim2real transfer is inherently difficult, as it would optimally require to evaluate all agent variants and ablations on a real physical robot and on a high number of episodes. We opted for a three-way strategy, all tables are color-coded with numbers corresponding to one of the three following settings: (i) “Real” experiments evaluate the agent trained in simulation on the real Naver Rookie robot. It is the only form of evaluation which correctly estimates navigation performance in a real world scenario, but for practical reasons we limit it to a restricted number of 20 episodes in a large office environment shown in Fig. 7. (ii) “Simulation (+dyn. model)” is a setting in simul", + "bbox": [ + 75, + 719, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "tion (Habitat), which allows large-scale evaluation on a large number of unseen environments and episodes, the HM3D validation set. Most importantly, during evaluation the simulator uses the identified dynamical model and therefore realistic motion, even for baselines which do not have access to one during training. Similar to the \"Real\" setting, this allows to evaluate the impact of not modeling realistic motion during training. (iii) \"Simulation (train domain)\" evaluates in simulation with the same action space an agent variant uses during training, i.e. there is no sim2real gap at all. This setting evaluates the difficulty of the simulated task, which might be a severe approximation of the task in real conditions. High performance in this setting is not necessarily indicative of high performance in a real environment.", + "bbox": [ + 496, + 90, + 893, + 301 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We evaluate on two different sets of episodes: $\\mathrm{HM3D / 2.5k}$ consists of 2500 episodes in the HM3D validation scenes, used in simulation only. $\\mathrm{Office / 20}$ consists of 20 episodes in the targeted office building, Figure 7. They are used for evaluation in both, real world and simulation.", + "bbox": [ + 496, + 301, + 893, + 377 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Metrics — Navigation performance is evaluated by success rate (SR), i.e., fraction of episodes terminated within a distance of $< 0.2\\mathrm{m}$ to the goal by the agent calling the $\\langle v = 0, w = 0 \\rangle$ action enough time to cancel its velocity, and SPL [1], i.e., SR weighted by the optimality of the path, $SPL = \\frac{1}{N} \\sum_{i=1}^{N} \\mathbb{I}_{\\text{success}} \\frac{\\ell_i^*}{\\max(\\ell_i, \\ell_i^*)}$ , where $\\ell_i$ is the agent path length and $\\ell_i^*$ the GT path length.", + "bbox": [ + 496, + 378, + 893, + 487 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "SPL is limited in its ability to properly evaluate agents with complex dynamics. Success Weighted by Completion Time (SCT) [53] explicitly takes the agent's dynamics model into consideration, and aims to accurately capture how well the agent has approximated the fastest navigation behavior. It is defined as $SCT = \\frac{1}{N}\\sum_{i=1}^{N}S_i\\frac{t_i^*}{\\max(c_i,t_i^*)}$ , where $c_i$ is the agent's completion time in episode $i$ , and $t_i^*$ is the shortest possible amount of time it takes to reach the goal point from the start point while circumventing obstacles based on the agent's dynamics. To simplify implementation, we use a lower bound on $t^*$ taking into account linear dynamics along straight shortest path segments.", + "bbox": [ + 496, + 487, + 893, + 672 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Checkpoints have been chosen as follows: performance in Real is given with checkpoints selected as the ones providing max SR in simulation. Performance in Simulation is given on the last checkpoint.", + "bbox": [ + 496, + 672, + 893, + 734 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Results", + "text_level": 1, + "bbox": [ + 500, + 741, + 591, + 755 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Agent behavior — the agent is surprisingly robust and does not collide with the infrastructure even though it can quite closely approach it navigating around it, even if the obstacles are thin and light. Examples are given in Figure 5 (top), but they are best viewed through the video in the supplementary material. This is in stark contrast to the ROS 2 based planner, which uses a 2D Map constructed with the onboard Lidar: thin and light structures do not show up on the map or a filtered, often because the larger part of the obstacle is not", + "bbox": [ + 496, + 763, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "17842", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/576d37a8d17b2a2327770febd8dfd9b504e4aa2b2f3e31db029efaa6290618fb.jpg", + "image_caption": [ + "Figure 7. The 20 trajectories of $\\overline{\\text{Office}} /20$ are distributed over 5 plots and superimposed on the map, color coded. If an episode fails, the remaining distance is shown as a straight black line from the last position to the goal. The agent is variant $\\beta$ of Table 4." + ], + "image_footnote": [], + "bbox": [ + 81, + 90, + 241, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1559dd0aa066ae130a088e5ce90708ea05401af405487d4509ed1b9fbe8a07b5.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 243, + 90, + 403, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/6e5cf29dc92332f0be11a8a45c9c6e803f84cf5360061d68b779e9a786e8f335.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 406, + 90, + 565, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ed863396bcef1a50ca406273c3609dacc4aeeede2ac42f201837813f1cf8d64d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 566, + 90, + 725, + 210 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/de493894d62a242c6903eab86ce917f53bc0158e95a626940296ab91ac4c6b3a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 728, + 90, + 888, + 210 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/03074a32ad421d8f21292fb9c6537d826708ec496f726418634b26db920610d5.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Method & action space+dyn (train)Ref.Sim (+dyn.) (HM3D/2.5k)Sim (+dyn.) (Office/20)Real (Office/20)
SR(%)SPL(%)SCT(%)SR(%)SPL(%)SCT(%)SR(%)SPL(%)SCT(%)
(a)Position, disc(4)×[43]58.248.216.835.030.313.215.011.82.4
(b)Velocity, disc(28)×[53]0.80.10.10.00.00.020.08.72.6
(c)Velocity, disc(28)✓(Ours)97.482.251.0100.078.859.940.028.910.1
", + "bbox": [ + 83, + 255, + 883, + 330 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/32913a18fbd837f42ffecc9885331e5dbc93b9e32dc71b5675b8c268d254d15a.jpg", + "table_caption": [ + "Table 1. Impact of training with a realistic dynamical model: we compare end-to-end trained models using position commands (a) as in [43] and, discretized velocity commands without a dynamical model (considering constant velocity) as in [53], and our proposed method (c). The references [43, 53] are cited for their action space and motion handling, but they have different agent architectures." + ], + "table_footnote": [], + "table_body": "
MethodSim(train)HM3D/2.5kSim(+dyn)HM3D/2.5k
SR%SPL%SCT%SR%SPL%SCT%
(a) Pos, disc(4)92.781.730.358.248.216.8
(b) Vel, disc(28)98.074.258.90.80.10.1
(c) Vel, disc(28)97.482.251.097.482.251.0
", + "bbox": [ + 78, + 402, + 465, + 477 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Difficulty of tasks given action spaces and motion models: we evaluate the baseline model variants in the same simulated environment in which they have been trained. High performance does not necessarily transfer to real. Letters are variants in Table 1.", + "bbox": [ + 75, + 488, + 470, + 544 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "in the height of the single Lidar ray. Collisions are frequent, examples are given in Figure 5 (bottom). The agent is also capable of avoiding dynamic obstacles like people in spite of not having seen them in simulation (cf. Figure 6), which we conjecture is due to a high collision avoidance weight in the reward.", + "bbox": [ + 75, + 566, + 468, + 657 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Sim2real gap and memory — one interesting finding we would like to share is that the raw base agent sometimes tends to get discouraged from initially being blocked in a situation, for instance if the passage through a door is not optimal and requires correction. The initial variants of the agent seemed to abandon relatively quickly and started searching for a different trajectory, circumventing the passage way obstacle altogether. We conjecture that this stems from the fact that such blockings are rarely seen in simulation and the agent is trained to \"write off\" this area quickly, storing in its recurrent memory that this path is blocked. All our real experiments are therefore performed with a version, which resets its recurrent state $\\mathbf{h}_i$ (eq. (1)) every 10 seconds, leading to less frequent abandoning. Future work will address this problem more directly, for instance by simulating blocking situations during training.", + "bbox": [ + 75, + 659, + 470, + 901 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Influence of motion model — Table 1 compares results of different agents trained with different action spaces and with or without realistic motion during simulation. We can see that the impact of training the agent with the correct motion model in simulation is tremendous. The agent in line (b) uses the same action space, but no dynamical model is used in simulation, which means that changes in velocity are instantaneous and velocities are constant between decisions. The behavior is unexploitable, the agent is disoriented and keeps crashing into its environment. Line (a) corresponds to a position controlled agent with action space {FORWARD $25\\mathrm{cm}$ , TURN_LEFT $10^{\\circ}$ , TURN_RIGHT $10^{\\circ}$ , STOP}. After training, it is adapted to motion commands by calculating the corresponding velocity commands given the decision frequency of $3\\mathrm{Hz}$ . It has somewhat acceptable (but low) performance in simulation, although it does not dispose of a motion model during training. This fact that rotating and linear motion are separated and cannot occur in the same time simplifies the problem and leads to some success in simulation, but this behavior does not transfer well to the real robot. The agent with the identified motion model achieves near perfect SR in simulation, which shows that the model can learn to anticipate motion and (internal latent) future state prediction correctly. When transferred to the real robot, performance is the best among all agents, but still leaves room much room for improvement.", + "bbox": [ + 496, + 406, + 893, + 799 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Difficulty of the tasks — Table 2 compares the same three agents also in simulation when validated with the same setting they have been trained on (action space, motion model or absence of). While this comparison is not at all indicative of the performance of these agents on a real robot, it provides evidence of the difficulty of the task in simulation.", + "bbox": [ + 496, + 809, + 893, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "17843", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/602fc77a627fa025f49a6dee3511f49268a921ab2e121b1d39468821dddfd749.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Point Goal\\( \\hat{\\mathbf{p}}_t^r \\)\\( \\hat{\\mathbf{p}}_t^a \\)Sim (+dyn)(Office/20)Real (Office/20)
SR%SPL%SCT%SR%SPL%SCT%
g_tXX40.034.527.435.023.65.2
g_0✓✓70.051.936.950.037.511.4
g_0+ superv.✓✓100.078.859.940.028.910.1
g_0+ superv.✓X70.051.936.925.016.73.0
", + "bbox": [ + 83, + 88, + 460, + 176 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/27a926568b169818aca419093f784f9e86d90516e698e1ce1d8638f18e13cc54.jpg", + "table_caption": [ + "Table 3. Localization and PointGoal calculation: we compare the impact of the presence of external localization to the agent, and the point goal sources: dynamical point goal (through external localization) with static point goal w/ and w/o supervision. All agents are variant (c) from Table 1." + ], + "table_footnote": [], + "table_body": "
MethodReal (Office/20)Real (Office/20-alt)
SR%SPL %SCT%SR%SPL %SCT%
(α) ROS 2 (fused)80.069.526.290.070.527.0
(β) Ours (finetuned)55.040.411.260.042.09.7
", + "bbox": [ + 78, + 268, + 468, + 330 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4. Comparisons — we compare with the ROS 2 NavStack, which has access to the 2D occupancy map beforehand, localizes itself with the single ray Lidar scan and AMCL (Monte Carlo localization), uses the fused laserscan for obstacle avoidance, followed by shortest path planning. Metrics do no measure collisions, which are much higher for the ROS 2 planner. To be comparable, our method is finetuned with RL on the Matterport scan of the same building. We also add an experiment on the same office building with a different furniture arrangement, Office/20-alt.", + "bbox": [ + 75, + 340, + 472, + 467 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Surprisingly, the performances are very close: the additional burden the motion model puts on the learning problem itself can be handled very well by the agent.", + "bbox": [ + 75, + 491, + 468, + 536 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Goal vector calculation — As explained in Section 3, our base agent receives the static point goal $\\mathbf{g}_0$ , i.e. a vector with respect to the initial reference frame at time $t = 0$ , which is not updated. Table 3 compares this agent with two other variants. A version where supervision is removed during training, which surprisingly shows good performance. We conjecture that the additional supervision learns integration of odometry which might not transfer well enough from simulation, indicating insufficient noise modeling in simulation. This will be addressed in future work. In another variant the dynamic point goal $\\mathbf{g}_t$ is provided at each time step in the agent's egocentric frame. It is calculated from an external localization source, noisy in simulation. Letting the agent itself take care of the point goal integration seems to be the better solution.", + "bbox": [ + 75, + 537, + 470, + 762 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Comparison with a map based planner — Table 4 compares the method with a ROS 2 based planner, which uses a 2D occupancy map constructed beforehand (not on the fly). To be comparable, we finetuned our agent on a Matterport scan of the same building. While the ROS 2 based planner is still more efficient in terms of SR and time (SCT), it requires many experiments to finetune its parameters. For example, low values for the inflation radius will produce many collisions with tables. But when this parameter is too", + "bbox": [ + 75, + 763, + 472, + 902 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9c98e17ea4bc51f9a7f73339497fd58f44e7a5c2995c2f82a419afa12efcd0e4.jpg", + "image_caption": [ + "Figure 8. Dynamical sim2real gap: we compared recorded trajectories to simulated rollouts obtained with the same actions." + ], + "image_footnote": [], + "bbox": [ + 509, + 93, + 692, + 252 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d60cce66845737654b7fb4ca50a2a02f1e7f3a7358ca9b84e2f93cf6dff4f580.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 93, + 883, + 172 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/dd77c7ae2b01c9d753e73a590a320cd4e0f0b5860584a136e9ef8769274837d4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 174, + 883, + 252 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "high, the planner cannot find any path through doors and corridors.", + "bbox": [ + 498, + 314, + 890, + 344 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Rearrangement — we test the impact of rearranging furniture significantly in the Office environment (see the supp.mat. for pictures) and show the effect in Table 4, block Office/20-alt. The differences are negligible.", + "bbox": [ + 498, + 345, + 893, + 405 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Dynamical sim2real gap — Figure 8 compares real robot trajectories obtained by the agent on a small map of $4m \\times 4m$ with rollouts of the motion model in simulation with the same actions, indicating very small drift.", + "bbox": [ + 498, + 406, + 893, + 465 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/41b7dddf5ed26b360950746e09747db2466b290158e7814e7360df2dd6154e81.jpg", + "image_caption": [ + "Figure 9. Distribution of actions, Office/20, Sim, Real." + ], + "image_footnote": [], + "bbox": [ + 501, + 467, + 736, + 623 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Actions taken — Figure 9 shows histograms of the actions taken by the action in simulation and in real on Office/20. There is a clear preference for certain combinations of linear and angular velocity. Distributions in sim and real mostly match, except for a tendency to", + "bbox": [ + 743, + 468, + 893, + 662 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "turn in-place in real, which could be explained by obstacle mis-detections due to scan range noise.", + "bbox": [ + 498, + 662, + 890, + 694 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 708, + 619, + 724 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We have presented an end-to-end trained method for swift and precise navigation which can robustly avoid even thin and finely structured obstacles. This is achieved with training in simulation only by adding a realistic motion model identified from recorded trajectories from a real robot. The method has been extensively evaluated in simulation as well as on a real robotic platform, where we assessed the impact of the motion model, the action space, and the way how a point goal is calculated and provided to the agent. The method is robust, future work will focus on closed-loop adaptation of dynamics and sensor noise estimation.", + "bbox": [ + 496, + 734, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "17844", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Peter Anderson, Angel X. Chang, Devendra Singh Chaplot, Alexey Dosovitskiy, Saurabh Gupta, Vladlen Koltun, Jana Kosecka, Jitendra Malik, Roozbeh Mottaghi, Manolis Savva, and Amir Roshan Zamir. 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Adapting object detectors via selective cross-domain alignment. In CVPR, 2019. 2" + ], + "bbox": [ + 501, + 92, + 893, + 702 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "17846", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning to Navigate Efficiently and Precisely in Real Environments/620f678d-eca2-450f-9ffd-9c056c561f0d_model.json b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/620f678d-eca2-450f-9ffd-9c056c561f0d_model.json new file mode 100644 index 0000000000000000000000000000000000000000..c720ab360ef0f8a5ef577afa1c7842aa871650e5 --- /dev/null +++ b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/620f678d-eca2-450f-9ffd-9c056c561f0d_model.json @@ -0,0 +1,2310 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.002, + 0.808, + 0.025 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version:" + }, + { + "type": "header", + "bbox": [ + 0.294, + 0.031, + 0.754, + 0.046 + ], + "angle": 0, + "content": "the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.153, + 0.131, + 0.819, + 0.154 + ], + "angle": 0, + "content": "Learning to navigate efficiently and precisely in real environments" + }, + { + "type": "text", + "bbox": [ + 0.083, + 0.181, + 0.89, + 0.217 + ], + "angle": 0, + "content": "Guillaume Bono, Hervé Poirier, Leonid Antsfeld, Gianluca Monaci, Boris Chidlovskii, Christian Wolf Naver LABS Europe, Meylan, France" + }, + { + "type": "text", + "bbox": [ + 0.326, + 0.219, + 0.644, + 0.234 + ], + "angle": 0, + "content": "{firstname}. {lastname} @naverlabs.com" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.302, + 0.474, + 0.664 + ], + "angle": 0, + "content": "In the context of autonomous navigation of terrestrial robots, the creation of realistic models for agent dynamics and sensing is a widespread habit in the robotics literature and in commercial applications, where they are used for model based control and/or for localization and mapping. The more recent Embodied AI literature, on the other hand, focuses on modular or end-to-end agents trained in simulators like Habitat or AI-Thor, where the emphasis is put on photorealistic rendering and scene diversity, but high-fidelity robot motion is assigned a less privileged role. The resulting sim2real gap significantly impacts transfer of the trained models to real robotic platforms. In this work we explore end-to-end training of agents in simulation in settings which minimize the sim2real gap both, in sensing and in actuation. Our agent directly predicts (discretized) velocity commands, which are maintained through closed-loop control in the real robot. The behavior of the real robot (including the underlying low-level controller) is identified and simulated in a modified Habitat simulator. Noise models for odometry and localization further contribute in lowering the sim2real gap. We evaluate on real navigation scenarios, explore different localization and point goal calculation methods and report significant gains in performance and robustness compared to prior work." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.694, + 0.21, + 0.71 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.472, + 0.902 + ], + "angle": 0, + "content": "Point goal navigation of terrestrial robots in indoor buildings has traditionally been addressed in the robotics community with mapping and planning [6, 30, 50], which led to solutions capable of operating on robots in real environments. The field of computer vision and embodied AI has addressed this problem through large-scale machine learning in simulated 3D environments from reward with RL [24, 34] or with imitation learning [14]. Learning from large-scale data allows the agent to pick up more complex regularities, to process more subtle cues and therefore (in principle) to be more robust, to exploit data regularities to infer hidden and occluded information, and generally to learn more powerful" + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.268, + 0.891, + 0.476 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.485, + 0.895, + 0.665 + ], + "angle": 0, + "content": "Figure 1. Efficient navigation with policies end-to-end trained in 3D photorealistic simulators requires closing the sim2real gap in sensing and actuation. Efficiency demands that the robot continues to move during decision taking (as opposed to stopping for each sensing operation), and this requires a realistic motion model in simulation allowing the agent to internally anticipate its future state. This requirement is exacerbated by the delay between sensing \\(①\\) and actuation \\(②\\) caused by the computational complexity of high-capacity deep networks (visual encoders, policy). To model realistic motion while training in simulation, we create a \\(2^{nd}\\) order dynamical model running with higher frequency, which models the robot and its low-level closed-loop controller. We identify the model from real data and add it to the Habitat [44] Simulator." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.7, + 0.895, + 0.837 + ], + "angle": 0, + "content": "decision rules. In this context, the specific task of point goal navigation (navigation to coordinates) is now sometimes considered \"solved\" in the literature [38], incorrectly, as we argue. While the machine learning and computer vision community turns its attention towards the exciting goal of integrating language models into navigation [15, 23], we think that further improvements are required to make trained agents perform reliably in real environments with sufficient speed." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.84, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Experiments and evaluations of trained models in real environments and the impact of the sim2real gap do exist in the Embodied AI literature [11, 20, 43], but they are rare and were performed in restricted environments. Known models" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17837" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.288 + ], + "angle": 0, + "content": "are trained in 3D simulators like Habitat [44] or AI-Thor [26], which are realistic in their perception aspects, but lack the accurate motion models of physical agents which the robotics community uses for articulated robots, for instance, where forward and inverse kinetics are often modeled and identified. This results in a large sim2real gap in motion characteristics, which is either ignored or addressed by discrete motion commands. The latter strategy teleports the agent in simulation for each discrete action and executes these actions on the physical robot by low-level control on positions instead of velocities, stopping the robot between agent decisions and leading to extremely inefficient navigation and overly long episodes [43]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.288, + 0.473, + 0.544 + ], + "angle": 0, + "content": "In this work we go beyond current models for terrestrial navigation by realistically modeling both actuation and sensing of real agents in simulation, and we successfully transfer trained models to a real robotic platform. On the actuation side, we take agent decisions as discretized linear and angular velocities and predict them asynchronously while the agent is in motion. The resulting delay between sensing and actuation (see Figure 1) requires the agent to anticipate motion, which it learns in simulation from a realistic motion model. To this end, we create a second-order dynamical model, which approximates the physical properties of the real robot together with its closed-loop low-level controller. We identify this model from real robot rollouts and expert actions. The model is integrated into the Habitat simulator as an intermediate solution between the standard instantaneous motion model and a full-blown computationally-expensive physics simulation based on forces, masses, frictions etc." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.545, + 0.473, + 0.742 + ], + "angle": 0, + "content": "On the sensing side, we combine visual and Lidar observations with different ways of communicating the navigation (point) goal to the agent, and different estimates of robot pose relative to a reference frame, combining two different types of localization: first, dead reckoning from wheel encoders, and secondly, external localization based on Monte Carlo methods from Lidar input. We perform extensive experiments and ablations on a real navigation platform and quantify the impact of the motion model, action spaces, sensing capabilities and the way we provide goal coordinates on navigation performance, showing that end-to-end trained agents can robustly navigate from visual input when their motion has been correctly modelled in simulation." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.755, + 0.22, + 0.77 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Visual navigation — navigation has been classically solved in robotics using mapping and planning [7, 31, 32], which requires solutions for mapping and localization [6, 28, 50], for planning [27, 46] and for low-level control [19, 42]. These methods depend on accurate sensor models, filtering, dynamical models and optimization. End-to-end trained models directly map input to actions and are typically trained with RL [24, 35] or imitation learning [14]. They learn repre" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.212 + ], + "angle": 0, + "content": "sentations such as flat recurrent states, occupancy maps [9], semantic maps [8], latent metric maps [4, 21, 37], topological maps [3, 10, 47], self-attention [12, 16, 18, 41], implicit representations [33] or maximizing navigability directly with a blind agent optimizing a collected representation [5]. Our proposed method is end-to-end trained and features recurrent memory, but benefits from an additional motion model in simulation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.224, + 0.897, + 0.587 + ], + "angle": 0, + "content": "Sim2real transfer — The sim2real gap can compromise strong performance achieved in simulation when agents are tested in the real-world [22, 29], as perception and control policies often do not generalize well to real robots due to inaccuracies in modelling, simplifications and biases. To close the gap, domain randomization methods [39, 49] treat the discrepancy between the domains as variability in the simulation parameters. Alternatively, domain adaptation methods learn an invariant mapping for matching distributions between the simulator and the robot environment. Examples include transfer of visuo-motor policies by adversarial learning [55], adapting dynamics in RL [17], lowering fidelity simulation [52] and adapting object recognition to new domains [56]. Bi-directional adaptation is proposed in [51]; Recently, Chattopadhyay et al. [11] benchmarked the robustness of embodied agents to visual and dynamics corruptions. Kadian et al. [25] investigated sim2real predictability of Habitat-Sim [44] for PointGoal navigation and proposed a new metric to quantify it, called Sim-vs-Real Correlation Coefficient (SRCC). The PointGoal task on real robots is also evaluated in [43]. To reach competitive performance without modelling any sim2real transfer, the agent is pre-trained on a wide variety of environments and then fine-tuned on a simulated version of the target environment." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Motion models — are usually kept very simple when training visual navigation policies. Several works use a discrete high-level action space in simulation [8, 9, 20] and rely on dedicated controllers to translate these discrete actions into robot controls when transferring to the real world. Alternative approaches predict continuous actions [13, 54] or waypoints [2, 48], that again are subsequently mapped to robot controls when executing the policies in real. Somewhat closer to our approach, Yokoyama et al. [53] adopt a discretized linear and angular velocity space, and introduce a new metric, SCT, that uses a simplified \"unicycle-cart\" dynamical model to estimate the \"optimal\" episode completion time computed by rapidly exploring random trees (RRT). However the unicycle model is only used for evaluation and it is not deployed for training nor testing: as in previous works, the commands are mapped to robot controls using handcrafted heuristics. In contrast to previous approaches, we include the dynamical model of the robot in the training loop to learn complex dependencies between the navigation policy and the robot physical properties." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17838" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.08, + 0.088, + 0.473, + 0.242 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.251, + 0.47, + 0.308 + ], + "angle": 0, + "content": "Figure 2. The agent uses a recurrent policy with a static point goal \\( g_{0} \\) as input, i.e. the goal is constant and given wrt. to the initial reference frame. During training, the estimation of the dynamic point goal \\( \\hat{g}_{t} \\) is supervised from privileged information." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.325, + 0.449, + 0.343 + ], + "angle": 0, + "content": "3. End-to-end training with realistic sensing" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.352, + 0.47, + 0.502 + ], + "angle": 0, + "content": "We propose a method for training agents which (in principle) could address a variety of visual navigation problems, and without loss of generality, focusing on sim2real transfer and efficiency, we formalize the problem as a PointGoal task: an agent receives sensor observations at each time step \\( t \\) and must take actions \\( \\mathbf{a}_t \\) to reach a goal position given as polar coordinates. The method is not restricted to any specific observations, in our experiments the agent receives RGB images \\( \\mathbf{I}_t \\in \\mathbb{R}^{3 \\times H \\times W} \\) and a Lidar-like vector of ranges \\( \\mathbf{S}_t \\in \\mathbb{R}^K \\), where \\( K \\) is the number of laser rays." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.505, + 0.47, + 0.625 + ], + "angle": 0, + "content": "The proposed agent is fully trained and therefore does not require to localize itself on a map for analytical path planning. However, even in this very permissive setting the application itself requires to communicate the goal to the agent in some form of coordinate system, which requires localization at least initially with respect to the goal (in ImageGoal settings this would be replaced by the goal image). We can classically differentiate between three different forms:" + }, + { + "type": "text", + "bbox": [ + 0.086, + 0.627, + 0.472, + 0.687 + ], + "angle": 0, + "content": "Absolute PointGoal — the goal vector \\(\\mathbf{g}^a = [\\mathbf{g}_x^a, \\mathbf{g}_y^a]^T\\) is given in a pre-defined agent-independent absolute reference frame. This requires access to a global localization system." + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.688, + 0.472, + 0.763 + ], + "angle": 0, + "content": "Dynamic PointGoal — the goal vector \\(\\mathbf{g}_t\\) is provided with respect to the current agent pose and therefore updated at each time instant \\(t\\). This requires an external localization system providing estimates which are then transformed into the egocentric reference frame." + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.764, + 0.473, + 0.84 + ], + "angle": 0, + "content": "Static PointGoal — the goal vector is provided with respect to the starting position at \\( t = 0 \\) of the robot, and not updated with agent motion \\( (= \\mathbf{g}_0) \\). This requires the agent to learn this update itself, and therefore some form of internal localization or integration of odometry information." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.472, + 0.901 + ], + "angle": 0, + "content": "We target the Static PointGoal case, which does not require localization beyond the initial relative vector. However, we also argue that some form of localization and/or odometry information is useful, which will assist the dynamics infor" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.894, + 0.168 + ], + "angle": 0, + "content": "mation inferred from (visual) sensor readings. Furthermore, during training it will allow the agent to learn a useful latent representation in its hidden state and an associated dynamics in this latent space. We therefore provide the agent with two different localization components:" + }, + { + "type": "text", + "bbox": [ + 0.509, + 0.17, + 0.894, + 0.244 + ], + "angle": 0, + "content": "\\(\\hat{\\mathbf{p}}_t^a\\) — an estimate of agent pose with respect to the initial agent position, asynchronously delivered and with low frequency, around 0.5-1 fps. At test, this signal is delivered by external localization, in our case from a Lidar-based AMCL module (see Section 5)." + }, + { + "type": "text", + "bbox": [ + 0.509, + 0.245, + 0.894, + 0.306 + ], + "angle": 0, + "content": "\\(\\hat{\\mathbf{p}}_t^r\\) — an estimate coming from onboard odometry, which we integrate over time to provide an estimate situated in the same reference frame as \\(\\hat{\\mathbf{p}}_t^a\\), i.e. with respect to the initial agent position." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.307, + 0.894, + 0.383 + ], + "angle": 0, + "content": "The characteristics of the two localization signals are different: while \\(\\hat{\\mathbf{p}}_t^r\\) corresponds to a dead reckoning process and is subject to drift, its relative noise is lower. The signal \\(\\hat{\\mathbf{p}}_t^a\\) is not subject to drift but suffers from larger errors in certain regions, due to registration errors or absence of structure." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.385, + 0.893, + 0.431 + ], + "angle": 0, + "content": "The agent policy is recurrent, based on a hidden memory vector \\(\\mathbf{h}_t\\) updated over time from input of all sensor readings \\(\\mathbf{I}_t, \\mathbf{S}_t, \\mathbf{p}_t^r, \\hat{\\mathbf{p}}_t^a\\), the goal \\(\\mathbf{g}_0\\) and the previous action \\(\\mathbf{a}_{t-1}\\)," + }, + { + "type": "equation", + "bbox": [ + 0.537, + 0.433, + 0.893, + 0.45 + ], + "angle": 0, + "content": "\\[\n\\mathbf {h} _ {t} = d \\left(\\mathbf {h} _ {t - 1}, v \\left(\\mathbf {I} _ {t}\\right), u \\left(\\mathbf {S} _ {t}\\right), \\mathbf {g} _ {0}, \\hat {\\mathbf {p}} _ {t} ^ {r}, \\hat {\\mathbf {p}} _ {t} ^ {a}, e \\left(\\mathbf {a} _ {t - 1}\\right)\\right), \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.539, + 0.452, + 0.892, + 0.469 + ], + "angle": 0, + "content": "\\[\n\\mathbf {a} _ {t} = \\pi (\\mathbf {h} _ {t}), \\tag {2}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.539, + 0.471, + 0.892, + 0.488 + ], + "angle": 0, + "content": "\\[\n\\hat {\\mathbf {g}} _ {t} = l \\left(\\mathbf {h} _ {t}\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.49, + 0.894, + 0.687 + ], + "angle": 0, + "content": "where \\(d\\) is a GRU with hidden state \\(\\mathbf{h}_t\\), \\(v\\) is a visual encoder of the image \\(\\mathbf{I}_t\\) (in our case, a ResNet-18); \\(u\\) is a 1D-CNN encoding the scan \\(\\mathbf{S}_t\\); \\(e\\) is a set of action embedding vectors; \\(\\pi\\) is a linear policy. Other inputs go through dedicated MLPs, not named to lighten notations. To help the agent deal with the noisy relative and absolute pose estimates, we put an inductive bias for localization on \\(\\mathbf{h}_t\\) through an auxiliary head \\(l\\) predicting the dynamic goal compass \\(\\hat{\\mathbf{g}}_t\\), supervised during training from the simulated agent's ground truth pose, as shown in Figure 2. In the following paragraphs we describe the two localization systems and the noise models we use to simulate them during training in simulation. Section 4 then introduces the dynamical model used during training." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.894, + 0.823 + ], + "angle": 0, + "content": "Integrated relative localization - the pose estimate \\(\\hat{\\mathbf{p}}_t^r\\) can be obtained with any commercially available odometry system. In our experiments we integrate readings from wheel encoders. During simulation and training, \\(\\hat{\\mathbf{p}}_t^r\\) is estimated by sampling planar noise \\([\\epsilon_x,\\epsilon_\\theta ]^\\intercal\\) from a multivariate Gaussian distribution \\(\\mathcal{N}(\\left[ \\begin{array}{cc}0.01\\\\ 0 \\end{array} \\right],\\left[ \\begin{array}{cc}10^{-4} & 10^{-4}\\\\ 10^{-4} & 10^{-3} \\end{array} \\right])\\) which gets added to the step-wise motion of the agent, leading to the accumulation of drift over time." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Absolute localization - the pose estimate \\(\\hat{\\mathbf{p}}_t^a\\) is obtained with the standard ROS 2 package for Adaptive Monte Carlo Localization (AMCL) [50], a KLD-sampling approach requiring a pre-computed, static map based on particle filtering. During simulation and training, \\(\\hat{\\mathbf{p}}_t^r\\) is es" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17839" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.088, + 0.895, + 0.425 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.434, + 0.896, + 0.517 + ], + "angle": 0, + "content": "Figure 3. Training visual navigation with realistic motion models: we train an end-to-end agent in simulation (top) subject to two different simulation loops: a slower loop at \\(3\\mathrm{Hz}\\) (indexed by \\(t\\)) renders visual observations and takes agent decisions, while a faster loop at \\(30\\mathrm{Hz}\\) (indexed by \\(\\tau\\)) simulates physics. Physics is approximated with a \\(2^{nd}\\) order model identified from real robot rollouts (bottom) and includes the robot physics as well as the behavior of the closed-loop control of the differential drive (neither onboard control algorithm nor control frequency need to be known). Operations in the intervals are pipelined, e.g. sensing occurs at each time step, as does agent forward pass etc. The agent architecture is detailed in Figure 2." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.527, + 0.473, + 0.678 + ], + "angle": 0, + "content": "timated by sampling planar noise from another Gaussian \\(\\mathcal{N}(0, \\mathrm{Diag}[0.03, 0.03, 0.05])\\), but this time it gets directly added to the ground truth pose of the robot, thus modeling imprecise localization (eg. due to Lidar registration failures) without drift accumulation. In addition, we model the potential unreliability of such absolute pose estimates by only providing a new observation to the agent every few steps, at an irregular period governed by a uniform distribution \\(\\mathcal{U}(8, 12)\\). This potentially allows to plug-in low-frequency visual localization." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.694, + 0.471, + 0.71 + ], + "angle": 0, + "content": "4. A dynamical model of realistic robot motion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.473, + 0.902 + ], + "angle": 0, + "content": "One of our main motivations is to be able to use a trained model to navigate efficiently, i.e. fast and reliably. Stopping the robot between predicted actions is therefore not an option, and we train the model to predict linear and angular velocity commands in parallel to its physical motion, as illustrated in Figure 1. This requires the agent to anticipate motion to predict an action \\(\\mathbf{a}_t\\) relative to the next (yet unobserved) state at \\(t\\), exacerbated by the delay between sensing at time \\(t\\) and actuation at \\(t + 1\\), during which computation through the high-capacity visual encoder and policy happens. This motion depends on the physical characteristics of the robot, as shown in Figure 3 (bottom): the linear and angular veloc" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.527, + 0.895, + 0.799 + ], + "angle": 0, + "content": "ity commands predicted by the neural policy \\(\\pi\\) are translated into \"set values\" for left and right motor speeds of the differential drive system with a deterministic function and used as targets by the closed loop control algorithm, typically a PID (Proportional Integral Derivative Controller), attempting to reach and maintain the predicted speed between agent decisions. The behavior depends on the control algorithm but also on the physical properties of the robot, like its mass and resulting inertia, power and torque curves of the motors, friction etc. We decrease the actuation sim2real gap as as much as possible by integrating a model of realistic robot behavior into the Habitat [44] platform, shown in the top part of Figure 3. We approximate the robot's motion behavior by modeling the combined behavior of both the robot and the control algorithm implemented on the real platform as an asymmetric second-order dynamic system. The parameters of this low-level loop are estimated from recordings of the real robot platform with a system identification algorithm." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Classically, a sequential decision process can be modeled as a POMDP \\(\\langle \\mathcal{X},\\mathcal{U},T,\\mathcal{O},O,R\\rangle\\). In pure 2D navigation settings with a fixed goal in a single static scene, the environment maintains a (hidden) state \\(\\mathbf{x}_t\\in \\mathcal{X}\\) consisting in the pose of the agent, i.e. position and orientation, \\(\\mathbf{x}_t = [x_t,y_t,\\theta_t]\\). In most settings in the literature" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17840" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.08, + 0.089, + 0.473, + 0.238 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.248, + 0.473, + 0.318 + ], + "angle": 0, + "content": "Figure 5. Robustness: Top: The ROS2 baseline fails when obstacles are thin at the height of the single Lidar ray. The robot doesn't see the stool, collides, drags it away. The red circles \\(\\bigcirc\\) show the position of the moved stool. Bottom: our agent is surprisingly robust and allows navigation very close to fine structures." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.333, + 0.473, + 0.485 + ], + "angle": 0, + "content": "based on 3D photo-realistic simulators like Habitat [44], the state update in simulation ignores physical properties of the robot (mass/inertia, friction, accelerations, etc.), as it is implemented through \"teleportation\" of the robot to a new pose. In that case, the environment transition decomposes into a discrete state update \\( x_{t + 1} = T(x_t,u_t) \\) and an observation \\( o_{t + 1} = O(x_{t + 1}) \\). The discrete action space \\( \\mathcal{U}_{\\mathrm{motion}} = \\{\\mathrm{FORWARD~25cm},\\mathrm{TURN\\_LEFT~10^{\\circ}},\\mathrm{TURN\\_RIGHT~10^{\\circ}} \\text{ and } \\mathrm{STOP}\\} \\) frequently chosen in the navigation literature results in a halting and jerky robot motion." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.485, + 0.473, + 0.528 + ], + "angle": 0, + "content": "Adding realism — To be able to smooth robot trajectories, we need to model accelerations. We extend the agent state as:" + }, + { + "type": "equation", + "bbox": [ + 0.17, + 0.531, + 0.47, + 0.547 + ], + "angle": 0, + "content": "\\[\n\\mathbf {x} _ {t} = \\left[ x _ {t}, y _ {t}, \\theta_ {t}, v _ {t}, w _ {t}, \\dot {v} _ {t}, \\dot {w} _ {t} \\right], \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.553, + 0.47, + 0.629 + ], + "angle": 0, + "content": "where \\( x_{t}, y_{t}, \\theta_{t} \\) are the absolute position and orientation of the robot in the plane of the scene (in m, m and rad); \\( v_{t}, w_{t} \\) are the linear (forward) and angular velocities of the robot (in m/s and rad/s); \\( \\dot{v}_{t}; \\dot{w}_{t} \\) are the linear and angular accelerations of the robot (in m/s² and rad/s²)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.63, + 0.296, + 0.78 + ], + "angle": 0, + "content": "The proposed agent predicts a pair \\(\\langle v_t^*, w_t^* \\rangle\\) of velocity commands, chosen from a discrete action space \\(\\mathcal{U}_{\\mathrm{vel}}\\) resulting from the cartesian product of linear and angular spaces \\(\\{0, 0.3, 0.6, 1\\} \\times \\{-3, -2, -1, 0, \\dots, 3\\}\\), as shown in Figure 4. To simplify notations, we will use \\(\\mathbf{u}_t = \\langle v_t^*, w_t^* \\rangle \\in \\mathcal{U}\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.296, + 0.902 + ], + "angle": 0, + "content": "One possibility to model realistic robot behavior is to design a full dynamical model of the robot in the form of a set of differential equations, identify its parameters, discretize it, and simulate it in Habitat, together with running an exact copy of the conti" + }, + { + "type": "image", + "bbox": [ + 0.324, + 0.638, + 0.462, + 0.763 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.301, + 0.781, + 0.47, + 0.879 + ], + "angle": 0, + "content": "Figure 4. The action space: 28 actions, 4 choices of linear velocities \\(\\in [0,1]\\) m/s, 7 choices for angular vel. \\(\\in [-3,3]\\) rad/s. Arrows show the effect on pose of action held for \\(\\frac{2}{3}\\mathrm{sec}\\)." + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.089, + 0.892, + 0.165 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.175, + 0.892, + 0.204 + ], + "angle": 0, + "content": "Figure 6. Dynamic obstacles: our agent stops and circumvents people, achieved through a highly negative collision reward term." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.227, + 0.895, + 0.333 + ], + "angle": 0, + "content": "physical robot with exactly the same parameters and control frequency, which is a stringent constraint. Instead, we opted for a more flexible solution and we approximate the combined behavior of the physical robot and its control algorithm by a second order dynamical model [36]. We decompose interactions with the simulator into two different loops running at different frequencies:" + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.34, + 0.892, + 0.401 + ], + "angle": 0, + "content": "- Visual observations, simulator state updates and agent decisions (Equations (1) to (3)) are produced in a slower loop, indexed by letter \\( t \\) in the subsequent notation, and run at \\( f^{*} = 3\\mathrm{Hz} \\) in our experiments." + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.404, + 0.894, + 0.495 + ], + "angle": 0, + "content": "- Between two subsequent steps of the slower loop, a faster loop models physical motion of the robot, without rendering observations. At the end of this loop, the simulator state is updated, and a visual observation is returned. Steps in this faster loop are indexed by a second index \\(\\tau\\) in the subsequent notation, \\(\\mathbf{x}_{t,\\tau}\\)." + }, + { + "type": "list", + "bbox": [ + 0.504, + 0.34, + 0.894, + 0.495 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.502, + 0.894, + 0.548 + ], + "angle": 0, + "content": "In-between two environment steps \\( t - 1 \\) and \\( t \\), we simulate dynamics at frequency \\( f^{\\phi} = 30 > f^{*} \\). The number of physical sub-time steps per environment time step is therefore" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.548, + 0.892, + 0.599 + ], + "angle": 0, + "content": "\\(K^{\\phi} = \\left|\\frac{f^{\\phi}}{f^{*}}\\right| = 10\\) their duration is \\(\\Delta^{\\phi} = \\frac{1}{f^{\\phi}} = 33\\mathrm{ms}\\). The physical loop running between two environment steps can be formalized as the following set of state update equations," + }, + { + "type": "equation", + "bbox": [ + 0.533, + 0.602, + 0.637, + 0.618 + ], + "angle": 0, + "content": "\\[\n\\mathbf {o} _ {t} = O (\\mathbf {x} _ {t - 1}).\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.82, + 0.602, + 0.91, + 0.615 + ], + "angle": 0, + "content": "Observation" + }, + { + "type": "equation", + "bbox": [ + 0.507, + 0.62, + 0.605, + 0.632 + ], + "angle": 0, + "content": "\\[\n\\mathbf {x} _ {t - 1, 0} = \\mathbf {x} _ {t - 1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.821, + 0.618, + 0.85, + 0.63 + ], + "angle": 0, + "content": "Init" + }, + { + "type": "equation", + "bbox": [ + 0.508, + 0.633, + 0.812, + 0.649 + ], + "angle": 0, + "content": "\\[\n\\dot {v} _ {t, \\tau + 1} = \\dot {v} _ {t, \\tau} + \\Delta^ {\\phi} \\left(f _ {t, \\tau} ^ {v} ^ {2} \\delta_ {t, \\tau} ^ {v} - 2 \\zeta_ {t, \\tau} ^ {v} f _ {t, \\tau} ^ {v} \\dot {v} _ {t, \\tau}\\right)\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.821, + 0.633, + 0.89, + 0.647 + ], + "angle": 0, + "content": "Upd.acc." + }, + { + "type": "equation", + "bbox": [ + 0.505, + 0.649, + 0.819, + 0.666 + ], + "angle": 0, + "content": "\\[\n\\dot {w} _ {t, \\tau + 1} = \\dot {w} _ {t, \\tau} + \\Delta^ {\\phi} \\left(f _ {t, \\tau} ^ {w} ^ {2} \\delta_ {t, \\tau} ^ {w} - 2 \\zeta_ {t, \\tau} ^ {w} f _ {t, \\tau} ^ {w} \\dot {w} _ {t, \\tau}\\right)\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.508, + 0.666, + 0.681, + 0.68 + ], + "angle": 0, + "content": "\\[\nv _ {t, \\tau + 1} = v _ {t, \\tau} + \\Delta^ {\\phi} v _ {t, \\tau + 1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.505, + 0.68, + 0.689, + 0.696 + ], + "angle": 0, + "content": "\\[\nw _ {t, \\tau + 1} = w _ {t, \\tau} + \\Delta^ {\\phi} w _ {t, \\tau + 1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.508, + 0.696, + 0.685, + 0.71 + ], + "angle": 0, + "content": "\\[\n\\theta_ {t, \\tau + 1} = \\theta_ {t, \\tau} + \\Delta^ {\\phi} w _ {t, \\tau + 1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.508, + 0.711, + 0.751, + 0.726 + ], + "angle": 0, + "content": "\\[\nx _ {t, \\tau + 1} = x _ {t, \\tau} + \\Delta^ {\\phi} v _ {t, \\tau + 1} \\cos \\theta_ {t, \\tau + 1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.508, + 0.727, + 0.748, + 0.742 + ], + "angle": 0, + "content": "\\[\ny _ {t, \\tau + 1} = y _ {t, \\tau} + \\Delta^ {\\phi} v _ {t, \\tau + 1} \\sin \\theta_ {t, \\tau + 1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.534, + 0.743, + 0.622, + 0.756 + ], + "angle": 0, + "content": "\\[\n\\mathbf {x} _ {t} = \\mathbf {x} _ {t - 1, K}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.821, + 0.666, + 0.887, + 0.68 + ], + "angle": 0, + "content": "Upd. vel." + }, + { + "type": "text", + "bbox": [ + 0.821, + 0.696, + 0.894, + 0.711 + ], + "angle": 0, + "content": "Upd. pose" + }, + { + "type": "text", + "bbox": [ + 0.821, + 0.741, + 0.897, + 0.754 + ], + "angle": 0, + "content": "Final state" + }, + { + "type": "text", + "bbox": [ + 0.871, + 0.756, + 0.892, + 0.77 + ], + "angle": 0, + "content": "(5)" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.771, + 0.892, + 0.83 + ], + "angle": 0, + "content": "In these equations, \\( f \\) are natural frequencies and damping coefficients of asymmetric \\( 2^{\\mathrm{nd}} \\) order dynamic models for linear and angular motion. At each step \\( \\tau \\), they are chosen from identified values given command errors as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.548, + 0.834, + 0.658, + 0.849 + ], + "angle": 0, + "content": "\\[\n\\delta_ {t, \\tau} ^ {v} = v _ {t} ^ {*} - v _ {t, \\tau}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.504, + 0.849, + 0.892, + 0.901 + ], + "angle": 0, + "content": "\\[\n\\langle f _ {t, \\tau} ^ {v}, \\zeta_ {t, \\tau} ^ {v} \\rangle = \\left\\{ \\begin{array}{l l} \\langle f ^ {v \\uparrow}, \\zeta^ {v \\uparrow} \\rangle & \\text {i f} \\delta_ {t, \\tau} ^ {v} \\cdot v _ {t, \\tau} > 0 (\\text {a c c e l e r a t i o n}) \\\\ \\langle f ^ {v \\downarrow}, \\zeta^ {v \\downarrow} \\rangle & \\text {o t h e r w i s e (d e c e l e r a t i o n)} \\end{array} \\right. \\tag {6}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "17841" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.091, + 0.471, + 0.135 + ], + "angle": 0, + "content": "and similarly for angular model parameters \\(\\langle f^w,\\zeta^w\\rangle\\). Velocity and acceleration are also clipped to identified maximum values." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.137, + 0.472, + 0.212 + ], + "angle": 0, + "content": "System identification - the model has 8 parameters, \\( f^{v\\uparrow}, \\zeta^{v\\uparrow}, f^{v\\downarrow}, \\zeta^{v\\downarrow}, f^{w\\uparrow}, \\zeta^{w\\uparrow}, f^{w\\downarrow}, \\zeta^{w\\downarrow} \\), which we identify from trajectories of a real robot controlled with precomputed trajectories exploring the command space, see the supplementary material for more details." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.213, + 0.472, + 0.303 + ], + "angle": 0, + "content": "Training - the model is trained with RL, in particular PPO [45], and with a reward inspired by [11], \\( r_t = \\mathrm{R} \\cdot \\mathbb{I}_{\\mathrm{success}} - \\Delta_t^{\\mathrm{Geo}} - \\lambda - \\mathrm{C} \\cdot \\mathbb{I}_{\\mathrm{collision}} \\), where \\( R = 2.5 \\), \\( \\Delta_t^{\\mathrm{Geo}} \\) is the gain in geodesic distance to the goal, a slack cost \\( \\lambda = 0.01 \\) encourages efficiency, and a cost \\( C = 0.1 \\) penalizes each collision without ending the episode." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.303, + 0.472, + 0.379 + ], + "angle": 0, + "content": "Recovery behavior — similar to what is done in classical analytical planning, we added a rudimentary recovery behavior on top of the trained agent: if the agent is notified of an obstacle and does not move for five seconds, it will move backward at \\(0.2\\mathrm{m / s}\\) for two seconds." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.393, + 0.283, + 0.41 + ], + "angle": 0, + "content": "5. Experimental Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.417, + 0.472, + 0.719 + ], + "angle": 0, + "content": "Experimental setup — we trained the agent in the Habitat simulator [44] on the 800 scenes of the HM3D Dataset [40] for 200M env. steps. Real robot experiments have been performed on a Naver Rookie robot, which came equipped with various sensors. We added an additional front facing RGB camera and capture images with a resolution of \\(1280 \\times 720\\) resized to \\(256 \\times 144\\). In our experiments, the Lidar scan S is not taken from an onboard Lidar, but simulated from the 4 RealSense depth cameras which are installed close to the floor and oriented in 4 different directions. We use multiple scan lines of the cameras and fuse them into a single ray, details are given in the supplementary material. We did, however, add a single plane Lidar to the robot (which did not come equipped with one) and used it for localization only (see section 3). All processing has been done onboard, thanks to a Nvidia Jetson AGX Orin we added, with an integrated Nvidia Ampere GPU. It handles pre-processing of visual observations and network forward pass in around 70ms. The exact network architecture of the policy is given in the supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.472, + 0.902 + ], + "angle": 0, + "content": "Evaluation — evaluating sim2real transfer is inherently difficult, as it would optimally require to evaluate all agent variants and ablations on a real physical robot and on a high number of episodes. We opted for a three-way strategy, all tables are color-coded with numbers corresponding to one of the three following settings: (i) “Real” experiments evaluate the agent trained in simulation on the real Naver Rookie robot. It is the only form of evaluation which correctly estimates navigation performance in a real world scenario, but for practical reasons we limit it to a restricted number of 20 episodes in a large office environment shown in Fig. 7. (ii) “Simulation (+dyn. model)” is a setting in simul" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.303 + ], + "angle": 0, + "content": "tion (Habitat), which allows large-scale evaluation on a large number of unseen environments and episodes, the HM3D validation set. Most importantly, during evaluation the simulator uses the identified dynamical model and therefore realistic motion, even for baselines which do not have access to one during training. Similar to the \"Real\" setting, this allows to evaluate the impact of not modeling realistic motion during training. (iii) \"Simulation (train domain)\" evaluates in simulation with the same action space an agent variant uses during training, i.e. there is no sim2real gap at all. This setting evaluates the difficulty of the simulated task, which might be a severe approximation of the task in real conditions. High performance in this setting is not necessarily indicative of high performance in a real environment." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.303, + 0.895, + 0.378 + ], + "angle": 0, + "content": "We evaluate on two different sets of episodes: \\(\\mathrm{HM3D / 2.5k}\\) consists of 2500 episodes in the HM3D validation scenes, used in simulation only. \\(\\mathrm{Office / 20}\\) consists of 20 episodes in the targeted office building, Figure 7. They are used for evaluation in both, real world and simulation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.379, + 0.895, + 0.488 + ], + "angle": 0, + "content": "Metrics — Navigation performance is evaluated by success rate (SR), i.e., fraction of episodes terminated within a distance of \\(< 0.2\\mathrm{m}\\) to the goal by the agent calling the \\(\\langle v = 0, w = 0 \\rangle\\) action enough time to cancel its velocity, and SPL [1], i.e., SR weighted by the optimality of the path, \\(SPL = \\frac{1}{N} \\sum_{i=1}^{N} \\mathbb{I}_{\\text{success}} \\frac{\\ell_i^*}{\\max(\\ell_i, \\ell_i^*)}\\), where \\(\\ell_i\\) is the agent path length and \\(\\ell_i^*\\) the GT path length." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.488, + 0.895, + 0.674 + ], + "angle": 0, + "content": "SPL is limited in its ability to properly evaluate agents with complex dynamics. Success Weighted by Completion Time (SCT) [53] explicitly takes the agent's dynamics model into consideration, and aims to accurately capture how well the agent has approximated the fastest navigation behavior. It is defined as \\( SCT = \\frac{1}{N}\\sum_{i=1}^{N}S_i\\frac{t_i^*}{\\max(c_i,t_i^*)} \\), where \\( c_i \\) is the agent's completion time in episode \\( i \\), and \\( t_i^* \\) is the shortest possible amount of time it takes to reach the goal point from the start point while circumventing obstacles based on the agent's dynamics. To simplify implementation, we use a lower bound on \\( t^* \\) taking into account linear dynamics along straight shortest path segments." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.673, + 0.895, + 0.735 + ], + "angle": 0, + "content": "Checkpoints have been chosen as follows: performance in Real is given with checkpoints selected as the ones providing max SR in simulation. Performance in Simulation is given on the last checkpoint." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.742, + 0.593, + 0.756 + ], + "angle": 0, + "content": "5.1. Results" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Agent behavior — the agent is surprisingly robust and does not collide with the infrastructure even though it can quite closely approach it navigating around it, even if the obstacles are thin and light. Examples are given in Figure 5 (top), but they are best viewed through the video in the supplementary material. This is in stark contrast to the ROS 2 based planner, which uses a 2D Map constructed with the onboard Lidar: thin and light structures do not show up on the map or a filtered, often because the larger part of the obstacle is not" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17842" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.091, + 0.242, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.245, + 0.091, + 0.404, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.408, + 0.091, + 0.566, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.568, + 0.091, + 0.727, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.73, + 0.091, + 0.89, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.225, + 0.893, + 0.253 + ], + "angle": 0, + "content": "Figure 7. The 20 trajectories of \\(\\overline{\\text{Office}} /20\\) are distributed over 5 plots and superimposed on the map, color coded. If an episode fails, the remaining distance is shown as a straight black line from the last position to the goal. The agent is variant \\(\\beta\\) of Table 4." + }, + { + "type": "table", + "bbox": [ + 0.084, + 0.256, + 0.885, + 0.332 + ], + "angle": 0, + "content": "
Method & action space+dyn (train)Ref.Sim (+dyn.) (HM3D/2.5k)Sim (+dyn.) (Office/20)Real (Office/20)
SR(%)SPL(%)SCT(%)SR(%)SPL(%)SCT(%)SR(%)SPL(%)SCT(%)
(a)Position, disc(4)×[43]58.248.216.835.030.313.215.011.82.4
(b)Velocity, disc(28)×[53]0.80.10.10.00.00.020.08.72.6
(c)Velocity, disc(28)✓(Ours)97.482.251.0100.078.859.940.028.910.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.342, + 0.897, + 0.385 + ], + "angle": 0, + "content": "Table 1. Impact of training with a realistic dynamical model: we compare end-to-end trained models using position commands (a) as in [43] and, discretized velocity commands without a dynamical model (considering constant velocity) as in [53], and our proposed method (c). The references [43, 53] are cited for their action space and motion handling, but they have different agent architectures." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.404, + 0.466, + 0.478 + ], + "angle": 0, + "content": "
MethodSim(train)HM3D/2.5kSim(+dyn)HM3D/2.5k
SR%SPL%SCT%SR%SPL%SCT%
(a) Pos, disc(4)92.781.730.358.248.216.8
(b) Vel, disc(28)98.074.258.90.80.10.1
(c) Vel, disc(28)97.482.251.097.482.251.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.489, + 0.472, + 0.545 + ], + "angle": 0, + "content": "Table 2. Difficulty of tasks given action spaces and motion models: we evaluate the baseline model variants in the same simulated environment in which they have been trained. High performance does not necessarily transfer to real. Letters are variants in Table 1." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.568, + 0.47, + 0.658 + ], + "angle": 0, + "content": "in the height of the single Lidar ray. Collisions are frequent, examples are given in Figure 5 (bottom). The agent is also capable of avoiding dynamic obstacles like people in spite of not having seen them in simulation (cf. Figure 6), which we conjecture is due to a high collision avoidance weight in the reward." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.66, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Sim2real gap and memory — one interesting finding we would like to share is that the raw base agent sometimes tends to get discouraged from initially being blocked in a situation, for instance if the passage through a door is not optimal and requires correction. The initial variants of the agent seemed to abandon relatively quickly and started searching for a different trajectory, circumventing the passage way obstacle altogether. We conjecture that this stems from the fact that such blockings are rarely seen in simulation and the agent is trained to \"write off\" this area quickly, storing in its recurrent memory that this path is blocked. All our real experiments are therefore performed with a version, which resets its recurrent state \\(\\mathbf{h}_i\\) (eq. (1)) every 10 seconds, leading to less frequent abandoning. Future work will address this problem more directly, for instance by simulating blocking situations during training." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.407, + 0.895, + 0.8 + ], + "angle": 0, + "content": "Influence of motion model — Table 1 compares results of different agents trained with different action spaces and with or without realistic motion during simulation. We can see that the impact of training the agent with the correct motion model in simulation is tremendous. The agent in line (b) uses the same action space, but no dynamical model is used in simulation, which means that changes in velocity are instantaneous and velocities are constant between decisions. The behavior is unexploitable, the agent is disoriented and keeps crashing into its environment. Line (a) corresponds to a position controlled agent with action space {FORWARD \\(25\\mathrm{cm}\\), TURN_LEFT \\(10^{\\circ}\\), TURN_RIGHT \\(10^{\\circ}\\), STOP}. After training, it is adapted to motion commands by calculating the corresponding velocity commands given the decision frequency of \\(3\\mathrm{Hz}\\). It has somewhat acceptable (but low) performance in simulation, although it does not dispose of a motion model during training. This fact that rotating and linear motion are separated and cannot occur in the same time simplifies the problem and leads to some success in simulation, but this behavior does not transfer well to the real robot. The agent with the identified motion model achieves near perfect SR in simulation, which shows that the model can learn to anticipate motion and (internal latent) future state prediction correctly. When transferred to the real robot, performance is the best among all agents, but still leaves room much room for improvement." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.81, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Difficulty of the tasks — Table 2 compares the same three agents also in simulation when validated with the same setting they have been trained on (action space, motion model or absence of). While this comparison is not at all indicative of the performance of these agents on a real robot, it provides evidence of the difficulty of the task in simulation." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17843" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.084, + 0.089, + 0.462, + 0.178 + ], + "angle": 0, + "content": "
Point Goal\\( \\hat{\\mathbf{p}}_t^r \\)\\( \\hat{\\mathbf{p}}_t^a \\)Sim (+dyn)(Office/20)Real (Office/20)
SR%SPL%SCT%SR%SPL%SCT%
g_tXX40.034.527.435.023.65.2
g_0✓✓70.051.936.950.037.511.4
g_0+ superv.✓✓100.078.859.940.028.910.1
g_0+ superv.✓X70.051.936.925.016.73.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.187, + 0.471, + 0.258 + ], + "angle": 0, + "content": "Table 3. Localization and PointGoal calculation: we compare the impact of the presence of external localization to the agent, and the point goal sources: dynamical point goal (through external localization) with static point goal w/ and w/o supervision. All agents are variant (c) from Table 1." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.269, + 0.469, + 0.331 + ], + "angle": 0, + "content": "
MethodReal (Office/20)Real (Office/20-alt)
SR%SPL %SCT%SR%SPL %SCT%
(α) ROS 2 (fused)80.069.526.290.070.527.0
(β) Ours (finetuned)55.040.411.260.042.09.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.342, + 0.473, + 0.468 + ], + "angle": 0, + "content": "Table 4. Comparisons — we compare with the ROS 2 NavStack, which has access to the 2D occupancy map beforehand, localizes itself with the single ray Lidar scan and AMCL (Monte Carlo localization), uses the fused laserscan for obstacle avoidance, followed by shortest path planning. Metrics do no measure collisions, which are much higher for the ROS 2 planner. To be comparable, our method is finetuned with RL on the Matterport scan of the same building. We also add an experiment on the same office building with a different furniture arrangement, Office/20-alt." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.492, + 0.47, + 0.537 + ], + "angle": 0, + "content": "Surprisingly, the performances are very close: the additional burden the motion model puts on the learning problem itself can be handled very well by the agent." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.538, + 0.472, + 0.763 + ], + "angle": 0, + "content": "Goal vector calculation — As explained in Section 3, our base agent receives the static point goal \\(\\mathbf{g}_0\\), i.e. a vector with respect to the initial reference frame at time \\(t = 0\\), which is not updated. Table 3 compares this agent with two other variants. A version where supervision is removed during training, which surprisingly shows good performance. We conjecture that the additional supervision learns integration of odometry which might not transfer well enough from simulation, indicating insufficient noise modeling in simulation. This will be addressed in future work. In another variant the dynamic point goal \\(\\mathbf{g}_t\\) is provided at each time step in the agent's egocentric frame. It is calculated from an external localization source, noisy in simulation. Letting the agent itself take care of the point goal integration seems to be the better solution." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Comparison with a map based planner — Table 4 compares the method with a ROS 2 based planner, which uses a 2D occupancy map constructed beforehand (not on the fly). To be comparable, we finetuned our agent on a Matterport scan of the same building. While the ROS 2 based planner is still more efficient in terms of SR and time (SCT), it requires many experiments to finetune its parameters. For example, low values for the inflation radius will produce many collisions with tables. But when this parameter is too" + }, + { + "type": "image", + "bbox": [ + 0.51, + 0.094, + 0.693, + 0.253 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.094, + 0.885, + 0.173 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.175, + 0.885, + 0.253 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.27, + 0.895, + 0.298 + ], + "angle": 0, + "content": "Figure 8. Dynamical sim2real gap: we compared recorded trajectories to simulated rollouts obtained with the same actions." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.315, + 0.892, + 0.345 + ], + "angle": 0, + "content": "high, the planner cannot find any path through doors and corridors." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.346, + 0.894, + 0.406 + ], + "angle": 0, + "content": "Rearrangement — we test the impact of rearranging furniture significantly in the Office environment (see the supp.mat. for pictures) and show the effect in Table 4, block Office/20-alt. The differences are negligible." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.407, + 0.894, + 0.467 + ], + "angle": 0, + "content": "Dynamical sim2real gap — Figure 8 compares real robot trajectories obtained by the agent on a small map of \\(4m \\times 4m\\) with rollouts of the motion model in simulation with the same actions, indicating very small drift." + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.468, + 0.738, + 0.624 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.635, + 0.738, + 0.663 + ], + "angle": 0, + "content": "Figure 9. Distribution of actions, Office/20, Sim, Real." + }, + { + "type": "text", + "bbox": [ + 0.744, + 0.469, + 0.895, + 0.663 + ], + "angle": 0, + "content": "Actions taken — Figure 9 shows histograms of the actions taken by the action in simulation and in real on Office/20. There is a clear preference for certain combinations of linear and angular velocity. Distributions in sim and real mostly match, except for a tendency to" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.664, + 0.892, + 0.695 + ], + "angle": 0, + "content": "turn in-place in real, which could be explained by obstacle mis-detections due to scan range noise." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.709, + 0.62, + 0.725 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.901 + ], + "angle": 0, + "content": "We have presented an end-to-end trained method for swift and precise navigation which can robustly avoid even thin and finely structured obstacles. This is achieved with training in simulation only by adding a realistic motion model identified from recorded trajectories from a real robot. The method has been extensively evaluated in simulation as well as on a real robotic platform, where we assessed the impact of the motion model, the action space, and the way how a point goal is calculated and provided to the agent. The method is robust, future work will focus on closed-loop adaptation of dynamics and sensor noise estimation." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17844" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.473, + 0.184 + ], + "angle": 0, + "content": "[1] Peter Anderson, Angel X. Chang, Devendra Singh Chaplot, Alexey Dosovitskiy, Saurabh Gupta, Vladlen Koltun, Jana Kosecka, Jitendra Malik, Roozbeh Mottaghi, Manolis Savva, and Amir Roshan Zamir. 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In CVPR, 2019. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.894, + 0.703 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17846" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Navigate Efficiently and Precisely in Real Environments/620f678d-eca2-450f-9ffd-9c056c561f0d_origin.pdf b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/620f678d-eca2-450f-9ffd-9c056c561f0d_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..a17b02cd7df1fbfe979af1160186d5cb0e9e0a82 --- /dev/null +++ b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/620f678d-eca2-450f-9ffd-9c056c561f0d_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:90712eb2f36e56fd3512e703c9c77732556edd4d30a9bec9acec2f979307dd9c +size 3951027 diff --git a/2024/Learning to Navigate Efficiently and Precisely in Real Environments/full.md b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/full.md new file mode 100644 index 0000000000000000000000000000000000000000..b7457fbfa8ee145ba5bd8aa6f1a311f5819e113f --- /dev/null +++ b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/full.md @@ -0,0 +1,347 @@ +# Learning to navigate efficiently and precisely in real environments + +Guillaume Bono, Hervé Poirier, Leonid Antsfeld, Gianluca Monaci, Boris Chidlovskii, Christian Wolf Naver LABS Europe, Meylan, France + +{firstname}. {lastname} @naverlabs.com + +# Abstract + +In the context of autonomous navigation of terrestrial robots, the creation of realistic models for agent dynamics and sensing is a widespread habit in the robotics literature and in commercial applications, where they are used for model based control and/or for localization and mapping. The more recent Embodied AI literature, on the other hand, focuses on modular or end-to-end agents trained in simulators like Habitat or AI-Thor, where the emphasis is put on photorealistic rendering and scene diversity, but high-fidelity robot motion is assigned a less privileged role. The resulting sim2real gap significantly impacts transfer of the trained models to real robotic platforms. In this work we explore end-to-end training of agents in simulation in settings which minimize the sim2real gap both, in sensing and in actuation. Our agent directly predicts (discretized) velocity commands, which are maintained through closed-loop control in the real robot. The behavior of the real robot (including the underlying low-level controller) is identified and simulated in a modified Habitat simulator. Noise models for odometry and localization further contribute in lowering the sim2real gap. We evaluate on real navigation scenarios, explore different localization and point goal calculation methods and report significant gains in performance and robustness compared to prior work. + +# 1. Introduction + +Point goal navigation of terrestrial robots in indoor buildings has traditionally been addressed in the robotics community with mapping and planning [6, 30, 50], which led to solutions capable of operating on robots in real environments. The field of computer vision and embodied AI has addressed this problem through large-scale machine learning in simulated 3D environments from reward with RL [24, 34] or with imitation learning [14]. Learning from large-scale data allows the agent to pick up more complex regularities, to process more subtle cues and therefore (in principle) to be more robust, to exploit data regularities to infer hidden and occluded information, and generally to learn more powerful + +![](images/bf0f7190eaad5d2558171f5350c0ffe43cd6985cc71538a77fafd17496fdcf35.jpg) +Figure 1. Efficient navigation with policies end-to-end trained in 3D photorealistic simulators requires closing the sim2real gap in sensing and actuation. Efficiency demands that the robot continues to move during decision taking (as opposed to stopping for each sensing operation), and this requires a realistic motion model in simulation allowing the agent to internally anticipate its future state. This requirement is exacerbated by the delay between sensing $①$ and actuation $②$ caused by the computational complexity of high-capacity deep networks (visual encoders, policy). To model realistic motion while training in simulation, we create a $2^{nd}$ order dynamical model running with higher frequency, which models the robot and its low-level closed-loop controller. We identify the model from real data and add it to the Habitat [44] Simulator. + +decision rules. In this context, the specific task of point goal navigation (navigation to coordinates) is now sometimes considered "solved" in the literature [38], incorrectly, as we argue. While the machine learning and computer vision community turns its attention towards the exciting goal of integrating language models into navigation [15, 23], we think that further improvements are required to make trained agents perform reliably in real environments with sufficient speed. + +Experiments and evaluations of trained models in real environments and the impact of the sim2real gap do exist in the Embodied AI literature [11, 20, 43], but they are rare and were performed in restricted environments. Known models + +are trained in 3D simulators like Habitat [44] or AI-Thor [26], which are realistic in their perception aspects, but lack the accurate motion models of physical agents which the robotics community uses for articulated robots, for instance, where forward and inverse kinetics are often modeled and identified. This results in a large sim2real gap in motion characteristics, which is either ignored or addressed by discrete motion commands. The latter strategy teleports the agent in simulation for each discrete action and executes these actions on the physical robot by low-level control on positions instead of velocities, stopping the robot between agent decisions and leading to extremely inefficient navigation and overly long episodes [43]. + +In this work we go beyond current models for terrestrial navigation by realistically modeling both actuation and sensing of real agents in simulation, and we successfully transfer trained models to a real robotic platform. On the actuation side, we take agent decisions as discretized linear and angular velocities and predict them asynchronously while the agent is in motion. The resulting delay between sensing and actuation (see Figure 1) requires the agent to anticipate motion, which it learns in simulation from a realistic motion model. To this end, we create a second-order dynamical model, which approximates the physical properties of the real robot together with its closed-loop low-level controller. We identify this model from real robot rollouts and expert actions. The model is integrated into the Habitat simulator as an intermediate solution between the standard instantaneous motion model and a full-blown computationally-expensive physics simulation based on forces, masses, frictions etc. + +On the sensing side, we combine visual and Lidar observations with different ways of communicating the navigation (point) goal to the agent, and different estimates of robot pose relative to a reference frame, combining two different types of localization: first, dead reckoning from wheel encoders, and secondly, external localization based on Monte Carlo methods from Lidar input. We perform extensive experiments and ablations on a real navigation platform and quantify the impact of the motion model, action spaces, sensing capabilities and the way we provide goal coordinates on navigation performance, showing that end-to-end trained agents can robustly navigate from visual input when their motion has been correctly modelled in simulation. + +# 2. Related Work + +Visual navigation — navigation has been classically solved in robotics using mapping and planning [7, 31, 32], which requires solutions for mapping and localization [6, 28, 50], for planning [27, 46] and for low-level control [19, 42]. These methods depend on accurate sensor models, filtering, dynamical models and optimization. End-to-end trained models directly map input to actions and are typically trained with RL [24, 35] or imitation learning [14]. They learn repre + +sentations such as flat recurrent states, occupancy maps [9], semantic maps [8], latent metric maps [4, 21, 37], topological maps [3, 10, 47], self-attention [12, 16, 18, 41], implicit representations [33] or maximizing navigability directly with a blind agent optimizing a collected representation [5]. Our proposed method is end-to-end trained and features recurrent memory, but benefits from an additional motion model in simulation. + +Sim2real transfer — The sim2real gap can compromise strong performance achieved in simulation when agents are tested in the real-world [22, 29], as perception and control policies often do not generalize well to real robots due to inaccuracies in modelling, simplifications and biases. To close the gap, domain randomization methods [39, 49] treat the discrepancy between the domains as variability in the simulation parameters. Alternatively, domain adaptation methods learn an invariant mapping for matching distributions between the simulator and the robot environment. Examples include transfer of visuo-motor policies by adversarial learning [55], adapting dynamics in RL [17], lowering fidelity simulation [52] and adapting object recognition to new domains [56]. Bi-directional adaptation is proposed in [51]; Recently, Chattopadhyay et al. [11] benchmarked the robustness of embodied agents to visual and dynamics corruptions. Kadian et al. [25] investigated sim2real predictability of Habitat-Sim [44] for PointGoal navigation and proposed a new metric to quantify it, called Sim-vs-Real Correlation Coefficient (SRCC). The PointGoal task on real robots is also evaluated in [43]. To reach competitive performance without modelling any sim2real transfer, the agent is pre-trained on a wide variety of environments and then fine-tuned on a simulated version of the target environment. + +Motion models — are usually kept very simple when training visual navigation policies. Several works use a discrete high-level action space in simulation [8, 9, 20] and rely on dedicated controllers to translate these discrete actions into robot controls when transferring to the real world. Alternative approaches predict continuous actions [13, 54] or waypoints [2, 48], that again are subsequently mapped to robot controls when executing the policies in real. Somewhat closer to our approach, Yokoyama et al. [53] adopt a discretized linear and angular velocity space, and introduce a new metric, SCT, that uses a simplified "unicycle-cart" dynamical model to estimate the "optimal" episode completion time computed by rapidly exploring random trees (RRT). However the unicycle model is only used for evaluation and it is not deployed for training nor testing: as in previous works, the commands are mapped to robot controls using handcrafted heuristics. In contrast to previous approaches, we include the dynamical model of the robot in the training loop to learn complex dependencies between the navigation policy and the robot physical properties. + +![](images/81e1ba774bd35f70e54ac80f63c84c548dd3222fbdbcb5bab27939e388c50395.jpg) +Figure 2. The agent uses a recurrent policy with a static point goal $g_{0}$ as input, i.e. the goal is constant and given wrt. to the initial reference frame. During training, the estimation of the dynamic point goal $\hat{g}_{t}$ is supervised from privileged information. + +# 3. End-to-end training with realistic sensing + +We propose a method for training agents which (in principle) could address a variety of visual navigation problems, and without loss of generality, focusing on sim2real transfer and efficiency, we formalize the problem as a PointGoal task: an agent receives sensor observations at each time step $t$ and must take actions $\mathbf{a}_t$ to reach a goal position given as polar coordinates. The method is not restricted to any specific observations, in our experiments the agent receives RGB images $\mathbf{I}_t \in \mathbb{R}^{3 \times H \times W}$ and a Lidar-like vector of ranges $\mathbf{S}_t \in \mathbb{R}^K$ , where $K$ is the number of laser rays. + +The proposed agent is fully trained and therefore does not require to localize itself on a map for analytical path planning. However, even in this very permissive setting the application itself requires to communicate the goal to the agent in some form of coordinate system, which requires localization at least initially with respect to the goal (in ImageGoal settings this would be replaced by the goal image). We can classically differentiate between three different forms: + +Absolute PointGoal — the goal vector $\mathbf{g}^a = [\mathbf{g}_x^a, \mathbf{g}_y^a]^T$ is given in a pre-defined agent-independent absolute reference frame. This requires access to a global localization system. + +Dynamic PointGoal — the goal vector $\mathbf{g}_t$ is provided with respect to the current agent pose and therefore updated at each time instant $t$ . This requires an external localization system providing estimates which are then transformed into the egocentric reference frame. + +Static PointGoal — the goal vector is provided with respect to the starting position at $t = 0$ of the robot, and not updated with agent motion $(= \mathbf{g}_0)$ . This requires the agent to learn this update itself, and therefore some form of internal localization or integration of odometry information. + +We target the Static PointGoal case, which does not require localization beyond the initial relative vector. However, we also argue that some form of localization and/or odometry information is useful, which will assist the dynamics infor + +mation inferred from (visual) sensor readings. Furthermore, during training it will allow the agent to learn a useful latent representation in its hidden state and an associated dynamics in this latent space. We therefore provide the agent with two different localization components: + +$\hat{\mathbf{p}}_t^a$ — an estimate of agent pose with respect to the initial agent position, asynchronously delivered and with low frequency, around 0.5-1 fps. At test, this signal is delivered by external localization, in our case from a Lidar-based AMCL module (see Section 5). + +$\hat{\mathbf{p}}_t^r$ — an estimate coming from onboard odometry, which we integrate over time to provide an estimate situated in the same reference frame as $\hat{\mathbf{p}}_t^a$ , i.e. with respect to the initial agent position. + +The characteristics of the two localization signals are different: while $\hat{\mathbf{p}}_t^r$ corresponds to a dead reckoning process and is subject to drift, its relative noise is lower. The signal $\hat{\mathbf{p}}_t^a$ is not subject to drift but suffers from larger errors in certain regions, due to registration errors or absence of structure. + +The agent policy is recurrent, based on a hidden memory vector $\mathbf{h}_t$ updated over time from input of all sensor readings $\mathbf{I}_t, \mathbf{S}_t, \mathbf{p}_t^r, \hat{\mathbf{p}}_t^a$ , the goal $\mathbf{g}_0$ and the previous action $\mathbf{a}_{t-1}$ , + +$$ +\mathbf {h} _ {t} = d \left(\mathbf {h} _ {t - 1}, v \left(\mathbf {I} _ {t}\right), u \left(\mathbf {S} _ {t}\right), \mathbf {g} _ {0}, \hat {\mathbf {p}} _ {t} ^ {r}, \hat {\mathbf {p}} _ {t} ^ {a}, e \left(\mathbf {a} _ {t - 1}\right)\right), \tag {1} +$$ + +$$ +\mathbf {a} _ {t} = \pi (\mathbf {h} _ {t}), \tag {2} +$$ + +$$ +\hat {\mathbf {g}} _ {t} = l \left(\mathbf {h} _ {t}\right), \tag {3} +$$ + +where $d$ is a GRU with hidden state $\mathbf{h}_t$ , $v$ is a visual encoder of the image $\mathbf{I}_t$ (in our case, a ResNet-18); $u$ is a 1D-CNN encoding the scan $\mathbf{S}_t$ ; $e$ is a set of action embedding vectors; $\pi$ is a linear policy. Other inputs go through dedicated MLPs, not named to lighten notations. To help the agent deal with the noisy relative and absolute pose estimates, we put an inductive bias for localization on $\mathbf{h}_t$ through an auxiliary head $l$ predicting the dynamic goal compass $\hat{\mathbf{g}}_t$ , supervised during training from the simulated agent's ground truth pose, as shown in Figure 2. In the following paragraphs we describe the two localization systems and the noise models we use to simulate them during training in simulation. Section 4 then introduces the dynamical model used during training. + +Integrated relative localization - the pose estimate $\hat{\mathbf{p}}_t^r$ can be obtained with any commercially available odometry system. In our experiments we integrate readings from wheel encoders. During simulation and training, $\hat{\mathbf{p}}_t^r$ is estimated by sampling planar noise $[\epsilon_x,\epsilon_\theta ]^\intercal$ from a multivariate Gaussian distribution $\mathcal{N}(\left[ \begin{array}{cc}0.01\\ 0 \end{array} \right],\left[ \begin{array}{cc}10^{-4} & 10^{-4}\\ 10^{-4} & 10^{-3} \end{array} \right])$ which gets added to the step-wise motion of the agent, leading to the accumulation of drift over time. + +Absolute localization - the pose estimate $\hat{\mathbf{p}}_t^a$ is obtained with the standard ROS 2 package for Adaptive Monte Carlo Localization (AMCL) [50], a KLD-sampling approach requiring a pre-computed, static map based on particle filtering. During simulation and training, $\hat{\mathbf{p}}_t^r$ is es + +![](images/5c67e1c12db97c5c52a0418878fdd2140a9d22e22884288fc0cd62ca28730736.jpg) +Figure 3. Training visual navigation with realistic motion models: we train an end-to-end agent in simulation (top) subject to two different simulation loops: a slower loop at $3\mathrm{Hz}$ (indexed by $t$ ) renders visual observations and takes agent decisions, while a faster loop at $30\mathrm{Hz}$ (indexed by $\tau$ ) simulates physics. Physics is approximated with a $2^{nd}$ order model identified from real robot rollouts (bottom) and includes the robot physics as well as the behavior of the closed-loop control of the differential drive (neither onboard control algorithm nor control frequency need to be known). Operations in the intervals are pipelined, e.g. sensing occurs at each time step, as does agent forward pass etc. The agent architecture is detailed in Figure 2. + +timated by sampling planar noise from another Gaussian $\mathcal{N}(0, \mathrm{Diag}[0.03, 0.03, 0.05])$ , but this time it gets directly added to the ground truth pose of the robot, thus modeling imprecise localization (eg. due to Lidar registration failures) without drift accumulation. In addition, we model the potential unreliability of such absolute pose estimates by only providing a new observation to the agent every few steps, at an irregular period governed by a uniform distribution $\mathcal{U}(8, 12)$ . This potentially allows to plug-in low-frequency visual localization. + +# 4. A dynamical model of realistic robot motion + +One of our main motivations is to be able to use a trained model to navigate efficiently, i.e. fast and reliably. Stopping the robot between predicted actions is therefore not an option, and we train the model to predict linear and angular velocity commands in parallel to its physical motion, as illustrated in Figure 1. This requires the agent to anticipate motion to predict an action $\mathbf{a}_t$ relative to the next (yet unobserved) state at $t$ , exacerbated by the delay between sensing at time $t$ and actuation at $t + 1$ , during which computation through the high-capacity visual encoder and policy happens. This motion depends on the physical characteristics of the robot, as shown in Figure 3 (bottom): the linear and angular veloc + +ity commands predicted by the neural policy $\pi$ are translated into "set values" for left and right motor speeds of the differential drive system with a deterministic function and used as targets by the closed loop control algorithm, typically a PID (Proportional Integral Derivative Controller), attempting to reach and maintain the predicted speed between agent decisions. The behavior depends on the control algorithm but also on the physical properties of the robot, like its mass and resulting inertia, power and torque curves of the motors, friction etc. We decrease the actuation sim2real gap as as much as possible by integrating a model of realistic robot behavior into the Habitat [44] platform, shown in the top part of Figure 3. We approximate the robot's motion behavior by modeling the combined behavior of both the robot and the control algorithm implemented on the real platform as an asymmetric second-order dynamic system. The parameters of this low-level loop are estimated from recordings of the real robot platform with a system identification algorithm. + +Classically, a sequential decision process can be modeled as a POMDP $\langle \mathcal{X},\mathcal{U},T,\mathcal{O},O,R\rangle$ . In pure 2D navigation settings with a fixed goal in a single static scene, the environment maintains a (hidden) state $\mathbf{x}_t\in \mathcal{X}$ consisting in the pose of the agent, i.e. position and orientation, $\mathbf{x}_t = [x_t,y_t,\theta_t]$ . In most settings in the literature + +![](images/e0c937955b88f2606debdb8455db3b1f2f481b876fe4306210aaa8b2b70faff7.jpg) +Figure 5. Robustness: Top: The ROS2 baseline fails when obstacles are thin at the height of the single Lidar ray. The robot doesn't see the stool, collides, drags it away. The red circles $\bigcirc$ show the position of the moved stool. Bottom: our agent is surprisingly robust and allows navigation very close to fine structures. + +based on 3D photo-realistic simulators like Habitat [44], the state update in simulation ignores physical properties of the robot (mass/inertia, friction, accelerations, etc.), as it is implemented through "teleportation" of the robot to a new pose. In that case, the environment transition decomposes into a discrete state update $x_{t + 1} = T(x_t,u_t)$ and an observation $o_{t + 1} = O(x_{t + 1})$ . The discrete action space $\mathcal{U}_{\mathrm{motion}} = \{\mathrm{FORWARD~25cm},\mathrm{TURN\_LEFT~10^{\circ}},\mathrm{TURN\_RIGHT~10^{\circ}} \text{ and } \mathrm{STOP}\}$ frequently chosen in the navigation literature results in a halting and jerky robot motion. + +Adding realism — To be able to smooth robot trajectories, we need to model accelerations. We extend the agent state as: + +$$ +\mathbf {x} _ {t} = \left[ x _ {t}, y _ {t}, \theta_ {t}, v _ {t}, w _ {t}, \dot {v} _ {t}, \dot {w} _ {t} \right], \tag {4} +$$ + +where $x_{t}, y_{t}, \theta_{t}$ are the absolute position and orientation of the robot in the plane of the scene (in m, m and rad); $v_{t}, w_{t}$ are the linear (forward) and angular velocities of the robot (in m/s and rad/s); $\dot{v}_{t}; \dot{w}_{t}$ are the linear and angular accelerations of the robot (in m/s² and rad/s²). + +The proposed agent predicts a pair $\langle v_t^*, w_t^* \rangle$ of velocity commands, chosen from a discrete action space $\mathcal{U}_{\mathrm{vel}}$ resulting from the cartesian product of linear and angular spaces $\{0, 0.3, 0.6, 1\} \times \{-3, -2, -1, 0, \dots, 3\}$ , as shown in Figure 4. To simplify notations, we will use $\mathbf{u}_t = \langle v_t^*, w_t^* \rangle \in \mathcal{U}$ . + +One possibility to model realistic robot behavior is to design a full dynamical model of the robot in the form of a set of differential equations, identify its parameters, discretize it, and simulate it in Habitat, together with running an exact copy of the conti + +![](images/4378f2e4826d500bb54dd4d73b95d66bd45465e9460184b61153d8535d14eb9f.jpg) +Figure 4. The action space: 28 actions, 4 choices of linear velocities $\in [0,1]$ m/s, 7 choices for angular vel. $\in [-3,3]$ rad/s. Arrows show the effect on pose of action held for $\frac{2}{3}\mathrm{sec}$ . + +![](images/18349075bd8fa37460b6927a666f85f48ba4fd51ee385b78cf85ef346440fb5e.jpg) +Figure 6. Dynamic obstacles: our agent stops and circumvents people, achieved through a highly negative collision reward term. + +physical robot with exactly the same parameters and control frequency, which is a stringent constraint. Instead, we opted for a more flexible solution and we approximate the combined behavior of the physical robot and its control algorithm by a second order dynamical model [36]. We decompose interactions with the simulator into two different loops running at different frequencies: + +- Visual observations, simulator state updates and agent decisions (Equations (1) to (3)) are produced in a slower loop, indexed by letter $t$ in the subsequent notation, and run at $f^{*} = 3\mathrm{Hz}$ in our experiments. +- Between two subsequent steps of the slower loop, a faster loop models physical motion of the robot, without rendering observations. At the end of this loop, the simulator state is updated, and a visual observation is returned. Steps in this faster loop are indexed by a second index $\tau$ in the subsequent notation, $\mathbf{x}_{t,\tau}$ . + +In-between two environment steps $t - 1$ and $t$ , we simulate dynamics at frequency $f^{\phi} = 30 > f^{*}$ . The number of physical sub-time steps per environment time step is therefore + +$K^{\phi} = \left|\frac{f^{\phi}}{f^{*}}\right| = 10$ their duration is $\Delta^{\phi} = \frac{1}{f^{\phi}} = 33\mathrm{ms}$ . The physical loop running between two environment steps can be formalized as the following set of state update equations, + +$$ +\mathbf {o} _ {t} = O (\mathbf {x} _ {t - 1}). +$$ + +Observation + +$$ +\mathbf {x} _ {t - 1, 0} = \mathbf {x} _ {t - 1} +$$ + +Init + +$$ +\dot {v} _ {t, \tau + 1} = \dot {v} _ {t, \tau} + \Delta^ {\phi} \left(f _ {t, \tau} ^ {v} ^ {2} \delta_ {t, \tau} ^ {v} - 2 \zeta_ {t, \tau} ^ {v} f _ {t, \tau} ^ {v} \dot {v} _ {t, \tau}\right) +$$ + +Upd.acc. + +$$ +\dot {w} _ {t, \tau + 1} = \dot {w} _ {t, \tau} + \Delta^ {\phi} \left(f _ {t, \tau} ^ {w} ^ {2} \delta_ {t, \tau} ^ {w} - 2 \zeta_ {t, \tau} ^ {w} f _ {t, \tau} ^ {w} \dot {w} _ {t, \tau}\right) +$$ + +$$ +v _ {t, \tau + 1} = v _ {t, \tau} + \Delta^ {\phi} v _ {t, \tau + 1} +$$ + +$$ +w _ {t, \tau + 1} = w _ {t, \tau} + \Delta^ {\phi} w _ {t, \tau + 1} +$$ + +$$ +\theta_ {t, \tau + 1} = \theta_ {t, \tau} + \Delta^ {\phi} w _ {t, \tau + 1} +$$ + +$$ +x _ {t, \tau + 1} = x _ {t, \tau} + \Delta^ {\phi} v _ {t, \tau + 1} \cos \theta_ {t, \tau + 1} +$$ + +$$ +y _ {t, \tau + 1} = y _ {t, \tau} + \Delta^ {\phi} v _ {t, \tau + 1} \sin \theta_ {t, \tau + 1} +$$ + +$$ +\mathbf {x} _ {t} = \mathbf {x} _ {t - 1, K} +$$ + +Upd. vel. + +Upd. pose + +Final state + +(5) + +In these equations, $f$ are natural frequencies and damping coefficients of asymmetric $2^{\mathrm{nd}}$ order dynamic models for linear and angular motion. At each step $\tau$ , they are chosen from identified values given command errors as follows: + +$$ +\delta_ {t, \tau} ^ {v} = v _ {t} ^ {*} - v _ {t, \tau} +$$ + +$$ +\langle f _ {t, \tau} ^ {v}, \zeta_ {t, \tau} ^ {v} \rangle = \left\{ \begin{array}{l l} \langle f ^ {v \uparrow}, \zeta^ {v \uparrow} \rangle & \text {i f} \delta_ {t, \tau} ^ {v} \cdot v _ {t, \tau} > 0 (\text {a c c e l e r a t i o n}) \\ \langle f ^ {v \downarrow}, \zeta^ {v \downarrow} \rangle & \text {o t h e r w i s e (d e c e l e r a t i o n)} \end{array} \right. \tag {6} +$$ + +and similarly for angular model parameters $\langle f^w,\zeta^w\rangle$ . Velocity and acceleration are also clipped to identified maximum values. + +System identification - the model has 8 parameters, $f^{v\uparrow}, \zeta^{v\uparrow}, f^{v\downarrow}, \zeta^{v\downarrow}, f^{w\uparrow}, \zeta^{w\uparrow}, f^{w\downarrow}, \zeta^{w\downarrow}$ , which we identify from trajectories of a real robot controlled with precomputed trajectories exploring the command space, see the supplementary material for more details. + +Training - the model is trained with RL, in particular PPO [45], and with a reward inspired by [11], $r_t = \mathrm{R} \cdot \mathbb{I}_{\mathrm{success}} - \Delta_t^{\mathrm{Geo}} - \lambda - \mathrm{C} \cdot \mathbb{I}_{\mathrm{collision}}$ , where $R = 2.5$ , $\Delta_t^{\mathrm{Geo}}$ is the gain in geodesic distance to the goal, a slack cost $\lambda = 0.01$ encourages efficiency, and a cost $C = 0.1$ penalizes each collision without ending the episode. + +Recovery behavior — similar to what is done in classical analytical planning, we added a rudimentary recovery behavior on top of the trained agent: if the agent is notified of an obstacle and does not move for five seconds, it will move backward at $0.2\mathrm{m / s}$ for two seconds. + +# 5. Experimental Results + +Experimental setup — we trained the agent in the Habitat simulator [44] on the 800 scenes of the HM3D Dataset [40] for 200M env. steps. Real robot experiments have been performed on a Naver Rookie robot, which came equipped with various sensors. We added an additional front facing RGB camera and capture images with a resolution of $1280 \times 720$ resized to $256 \times 144$ . In our experiments, the Lidar scan S is not taken from an onboard Lidar, but simulated from the 4 RealSense depth cameras which are installed close to the floor and oriented in 4 different directions. We use multiple scan lines of the cameras and fuse them into a single ray, details are given in the supplementary material. We did, however, add a single plane Lidar to the robot (which did not come equipped with one) and used it for localization only (see section 3). All processing has been done onboard, thanks to a Nvidia Jetson AGX Orin we added, with an integrated Nvidia Ampere GPU. It handles pre-processing of visual observations and network forward pass in around 70ms. The exact network architecture of the policy is given in the supplementary material. + +Evaluation — evaluating sim2real transfer is inherently difficult, as it would optimally require to evaluate all agent variants and ablations on a real physical robot and on a high number of episodes. We opted for a three-way strategy, all tables are color-coded with numbers corresponding to one of the three following settings: (i) “Real” experiments evaluate the agent trained in simulation on the real Naver Rookie robot. It is the only form of evaluation which correctly estimates navigation performance in a real world scenario, but for practical reasons we limit it to a restricted number of 20 episodes in a large office environment shown in Fig. 7. (ii) “Simulation (+dyn. model)” is a setting in simul + +tion (Habitat), which allows large-scale evaluation on a large number of unseen environments and episodes, the HM3D validation set. Most importantly, during evaluation the simulator uses the identified dynamical model and therefore realistic motion, even for baselines which do not have access to one during training. Similar to the "Real" setting, this allows to evaluate the impact of not modeling realistic motion during training. (iii) "Simulation (train domain)" evaluates in simulation with the same action space an agent variant uses during training, i.e. there is no sim2real gap at all. This setting evaluates the difficulty of the simulated task, which might be a severe approximation of the task in real conditions. High performance in this setting is not necessarily indicative of high performance in a real environment. + +We evaluate on two different sets of episodes: $\mathrm{HM3D / 2.5k}$ consists of 2500 episodes in the HM3D validation scenes, used in simulation only. $\mathrm{Office / 20}$ consists of 20 episodes in the targeted office building, Figure 7. They are used for evaluation in both, real world and simulation. + +Metrics — Navigation performance is evaluated by success rate (SR), i.e., fraction of episodes terminated within a distance of $< 0.2\mathrm{m}$ to the goal by the agent calling the $\langle v = 0, w = 0 \rangle$ action enough time to cancel its velocity, and SPL [1], i.e., SR weighted by the optimality of the path, $SPL = \frac{1}{N} \sum_{i=1}^{N} \mathbb{I}_{\text{success}} \frac{\ell_i^*}{\max(\ell_i, \ell_i^*)}$ , where $\ell_i$ is the agent path length and $\ell_i^*$ the GT path length. + +SPL is limited in its ability to properly evaluate agents with complex dynamics. Success Weighted by Completion Time (SCT) [53] explicitly takes the agent's dynamics model into consideration, and aims to accurately capture how well the agent has approximated the fastest navigation behavior. It is defined as $SCT = \frac{1}{N}\sum_{i=1}^{N}S_i\frac{t_i^*}{\max(c_i,t_i^*)}$ , where $c_i$ is the agent's completion time in episode $i$ , and $t_i^*$ is the shortest possible amount of time it takes to reach the goal point from the start point while circumventing obstacles based on the agent's dynamics. To simplify implementation, we use a lower bound on $t^*$ taking into account linear dynamics along straight shortest path segments. + +Checkpoints have been chosen as follows: performance in Real is given with checkpoints selected as the ones providing max SR in simulation. Performance in Simulation is given on the last checkpoint. + +# 5.1. Results + +Agent behavior — the agent is surprisingly robust and does not collide with the infrastructure even though it can quite closely approach it navigating around it, even if the obstacles are thin and light. Examples are given in Figure 5 (top), but they are best viewed through the video in the supplementary material. This is in stark contrast to the ROS 2 based planner, which uses a 2D Map constructed with the onboard Lidar: thin and light structures do not show up on the map or a filtered, often because the larger part of the obstacle is not + +![](images/576d37a8d17b2a2327770febd8dfd9b504e4aa2b2f3e31db029efaa6290618fb.jpg) +Figure 7. The 20 trajectories of $\overline{\text{Office}} /20$ are distributed over 5 plots and superimposed on the map, color coded. If an episode fails, the remaining distance is shown as a straight black line from the last position to the goal. The agent is variant $\beta$ of Table 4. + +![](images/1559dd0aa066ae130a088e5ce90708ea05401af405487d4509ed1b9fbe8a07b5.jpg) + +![](images/6e5cf29dc92332f0be11a8a45c9c6e803f84cf5360061d68b779e9a786e8f335.jpg) + +![](images/ed863396bcef1a50ca406273c3609dacc4aeeede2ac42f201837813f1cf8d64d.jpg) + +![](images/de493894d62a242c6903eab86ce917f53bc0158e95a626940296ab91ac4c6b3a.jpg) + +
Method & action space+dyn (train)Ref.Sim (+dyn.) (HM3D/2.5k)Sim (+dyn.) (Office/20)Real (Office/20)
SR(%)SPL(%)SCT(%)SR(%)SPL(%)SCT(%)SR(%)SPL(%)SCT(%)
(a)Position, disc(4)×[43]58.248.216.835.030.313.215.011.82.4
(b)Velocity, disc(28)×[53]0.80.10.10.00.00.020.08.72.6
(c)Velocity, disc(28)✓(Ours)97.482.251.0100.078.859.940.028.910.1
+ +Table 1. Impact of training with a realistic dynamical model: we compare end-to-end trained models using position commands (a) as in [43] and, discretized velocity commands without a dynamical model (considering constant velocity) as in [53], and our proposed method (c). The references [43, 53] are cited for their action space and motion handling, but they have different agent architectures. + +
MethodSim(train)HM3D/2.5kSim(+dyn)HM3D/2.5k
SR%SPL%SCT%SR%SPL%SCT%
(a) Pos, disc(4)92.781.730.358.248.216.8
(b) Vel, disc(28)98.074.258.90.80.10.1
(c) Vel, disc(28)97.482.251.097.482.251.0
+ +Table 2. Difficulty of tasks given action spaces and motion models: we evaluate the baseline model variants in the same simulated environment in which they have been trained. High performance does not necessarily transfer to real. Letters are variants in Table 1. + +in the height of the single Lidar ray. Collisions are frequent, examples are given in Figure 5 (bottom). The agent is also capable of avoiding dynamic obstacles like people in spite of not having seen them in simulation (cf. Figure 6), which we conjecture is due to a high collision avoidance weight in the reward. + +Sim2real gap and memory — one interesting finding we would like to share is that the raw base agent sometimes tends to get discouraged from initially being blocked in a situation, for instance if the passage through a door is not optimal and requires correction. The initial variants of the agent seemed to abandon relatively quickly and started searching for a different trajectory, circumventing the passage way obstacle altogether. We conjecture that this stems from the fact that such blockings are rarely seen in simulation and the agent is trained to "write off" this area quickly, storing in its recurrent memory that this path is blocked. All our real experiments are therefore performed with a version, which resets its recurrent state $\mathbf{h}_i$ (eq. (1)) every 10 seconds, leading to less frequent abandoning. Future work will address this problem more directly, for instance by simulating blocking situations during training. + +Influence of motion model — Table 1 compares results of different agents trained with different action spaces and with or without realistic motion during simulation. We can see that the impact of training the agent with the correct motion model in simulation is tremendous. The agent in line (b) uses the same action space, but no dynamical model is used in simulation, which means that changes in velocity are instantaneous and velocities are constant between decisions. The behavior is unexploitable, the agent is disoriented and keeps crashing into its environment. Line (a) corresponds to a position controlled agent with action space {FORWARD $25\mathrm{cm}$ , TURN_LEFT $10^{\circ}$ , TURN_RIGHT $10^{\circ}$ , STOP}. After training, it is adapted to motion commands by calculating the corresponding velocity commands given the decision frequency of $3\mathrm{Hz}$ . It has somewhat acceptable (but low) performance in simulation, although it does not dispose of a motion model during training. This fact that rotating and linear motion are separated and cannot occur in the same time simplifies the problem and leads to some success in simulation, but this behavior does not transfer well to the real robot. The agent with the identified motion model achieves near perfect SR in simulation, which shows that the model can learn to anticipate motion and (internal latent) future state prediction correctly. When transferred to the real robot, performance is the best among all agents, but still leaves room much room for improvement. + +Difficulty of the tasks — Table 2 compares the same three agents also in simulation when validated with the same setting they have been trained on (action space, motion model or absence of). While this comparison is not at all indicative of the performance of these agents on a real robot, it provides evidence of the difficulty of the task in simulation. + +
Point Goal\( \hat{\mathbf{p}}_t^r \)\( \hat{\mathbf{p}}_t^a \)Sim (+dyn)(Office/20)Real (Office/20)
SR%SPL%SCT%SR%SPL%SCT%
g_tXX40.034.527.435.023.65.2
g_0✓✓70.051.936.950.037.511.4
g_0+ superv.✓✓100.078.859.940.028.910.1
g_0+ superv.✓X70.051.936.925.016.73.0
+ +Table 3. Localization and PointGoal calculation: we compare the impact of the presence of external localization to the agent, and the point goal sources: dynamical point goal (through external localization) with static point goal w/ and w/o supervision. All agents are variant (c) from Table 1. + +
MethodReal (Office/20)Real (Office/20-alt)
SR%SPL %SCT%SR%SPL %SCT%
(α) ROS 2 (fused)80.069.526.290.070.527.0
(β) Ours (finetuned)55.040.411.260.042.09.7
+ +Table 4. Comparisons — we compare with the ROS 2 NavStack, which has access to the 2D occupancy map beforehand, localizes itself with the single ray Lidar scan and AMCL (Monte Carlo localization), uses the fused laserscan for obstacle avoidance, followed by shortest path planning. Metrics do no measure collisions, which are much higher for the ROS 2 planner. To be comparable, our method is finetuned with RL on the Matterport scan of the same building. We also add an experiment on the same office building with a different furniture arrangement, Office/20-alt. + +Surprisingly, the performances are very close: the additional burden the motion model puts on the learning problem itself can be handled very well by the agent. + +Goal vector calculation — As explained in Section 3, our base agent receives the static point goal $\mathbf{g}_0$ , i.e. a vector with respect to the initial reference frame at time $t = 0$ , which is not updated. Table 3 compares this agent with two other variants. A version where supervision is removed during training, which surprisingly shows good performance. We conjecture that the additional supervision learns integration of odometry which might not transfer well enough from simulation, indicating insufficient noise modeling in simulation. This will be addressed in future work. In another variant the dynamic point goal $\mathbf{g}_t$ is provided at each time step in the agent's egocentric frame. It is calculated from an external localization source, noisy in simulation. Letting the agent itself take care of the point goal integration seems to be the better solution. + +Comparison with a map based planner — Table 4 compares the method with a ROS 2 based planner, which uses a 2D occupancy map constructed beforehand (not on the fly). To be comparable, we finetuned our agent on a Matterport scan of the same building. While the ROS 2 based planner is still more efficient in terms of SR and time (SCT), it requires many experiments to finetune its parameters. For example, low values for the inflation radius will produce many collisions with tables. But when this parameter is too + +![](images/9c98e17ea4bc51f9a7f73339497fd58f44e7a5c2995c2f82a419afa12efcd0e4.jpg) +Figure 8. Dynamical sim2real gap: we compared recorded trajectories to simulated rollouts obtained with the same actions. + +![](images/d60cce66845737654b7fb4ca50a2a02f1e7f3a7358ca9b84e2f93cf6dff4f580.jpg) + +![](images/dd77c7ae2b01c9d753e73a590a320cd4e0f0b5860584a136e9ef8769274837d4.jpg) + +high, the planner cannot find any path through doors and corridors. + +Rearrangement — we test the impact of rearranging furniture significantly in the Office environment (see the supp.mat. for pictures) and show the effect in Table 4, block Office/20-alt. The differences are negligible. + +Dynamical sim2real gap — Figure 8 compares real robot trajectories obtained by the agent on a small map of $4m \times 4m$ with rollouts of the motion model in simulation with the same actions, indicating very small drift. + +![](images/41b7dddf5ed26b360950746e09747db2466b290158e7814e7360df2dd6154e81.jpg) +Figure 9. Distribution of actions, Office/20, Sim, Real. + +Actions taken — Figure 9 shows histograms of the actions taken by the action in simulation and in real on Office/20. There is a clear preference for certain combinations of linear and angular velocity. Distributions in sim and real mostly match, except for a tendency to + +turn in-place in real, which could be explained by obstacle mis-detections due to scan range noise. + +# 6. Conclusion + +We have presented an end-to-end trained method for swift and precise navigation which can robustly avoid even thin and finely structured obstacles. 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In CVPR, 2019. 2 \ No newline at end of file diff --git a/2024/Learning to Navigate Efficiently and Precisely in Real Environments/images.zip b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..0a2018d5ef448c7446f76b262fdb1047ed4707ce --- /dev/null +++ b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:4d88964c4d6b4b16284cf28d694b9df087346b54b6d8b6e0b46b3be1be924d81 +size 598742 diff --git a/2024/Learning to Navigate Efficiently and Precisely in Real Environments/layout.json b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..2c2cb6a5f3073f7c285d32e3edda3dda1798edad --- /dev/null +++ b/2024/Learning to Navigate Efficiently and Precisely in Real Environments/layout.json @@ -0,0 +1,9403 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 93, + 103, + 501, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 93, + 103, + 501, + 121 + ], + "spans": [ + { + "bbox": [ + 93, + 103, + 501, + 121 + ], + "type": "text", + "content": "Learning to navigate efficiently and precisely in real environments" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 50, + 143, + 544, + 171 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 50, + 143, + 544, + 171 + ], + "spans": [ + { + "bbox": [ + 50, + 143, + 544, + 171 + ], + "type": "text", + "content": "Guillaume Bono, Hervé Poirier, Leonid Antsfeld, Gianluca Monaci, Boris Chidlovskii, Christian Wolf Naver LABS Europe, Meylan, France" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 199, + 173, + 394, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 199, + 173, + 394, + 185 + ], + "spans": [ + { + "bbox": [ + 199, + 173, + 394, + 185 + ], + "type": "text", + "content": "{firstname}. {lastname} @naverlabs.com" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "spans": [ + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 239, + 290, + 525 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 239, + 290, + 525 + ], + "spans": [ + { + "bbox": [ + 47, + 239, + 290, + 525 + ], + "type": "text", + "content": "In the context of autonomous navigation of terrestrial robots, the creation of realistic models for agent dynamics and sensing is a widespread habit in the robotics literature and in commercial applications, where they are used for model based control and/or for localization and mapping. The more recent Embodied AI literature, on the other hand, focuses on modular or end-to-end agents trained in simulators like Habitat or AI-Thor, where the emphasis is put on photorealistic rendering and scene diversity, but high-fidelity robot motion is assigned a less privileged role. The resulting sim2real gap significantly impacts transfer of the trained models to real robotic platforms. In this work we explore end-to-end training of agents in simulation in settings which minimize the sim2real gap both, in sensing and in actuation. Our agent directly predicts (discretized) velocity commands, which are maintained through closed-loop control in the real robot. The behavior of the real robot (including the underlying low-level controller) is identified and simulated in a modified Habitat simulator. Noise models for odometry and localization further contribute in lowering the sim2real gap. We evaluate on real navigation scenarios, explore different localization and point goal calculation methods and report significant gains in performance and robustness compared to prior work." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 549, + 128, + 562 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 549, + 128, + 562 + ], + "spans": [ + { + "bbox": [ + 47, + 549, + 128, + 562 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 570, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 288, + 714 + ], + "type": "text", + "content": "Point goal navigation of terrestrial robots in indoor buildings has traditionally been addressed in the robotics community with mapping and planning [6, 30, 50], which led to solutions capable of operating on robots in real environments. The field of computer vision and embodied AI has addressed this problem through large-scale machine learning in simulated 3D environments from reward with RL [24, 34] or with imitation learning [14]. Learning from large-scale data allows the agent to pick up more complex regularities, to process more subtle cues and therefore (in principle) to be more robust, to exploit data regularities to infer hidden and occluded information, and generally to learn more powerful" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 308, + 212, + 545, + 376 + ], + "blocks": [ + { + "bbox": [ + 308, + 212, + 545, + 376 + ], + "lines": [ + { + "bbox": [ + 308, + 212, + 545, + 376 + ], + "spans": [ + { + "bbox": [ + 308, + 212, + 545, + 376 + ], + "type": "image", + "image_path": "bf0f7190eaad5d2558171f5350c0ffe43cd6985cc71538a77fafd17496fdcf35.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "lines": [ + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "spans": [ + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "type": "text", + "content": "Figure 1. Efficient navigation with policies end-to-end trained in 3D photorealistic simulators requires closing the sim2real gap in sensing and actuation. Efficiency demands that the robot continues to move during decision taking (as opposed to stopping for each sensing operation), and this requires a realistic motion model in simulation allowing the agent to internally anticipate its future state. This requirement is exacerbated by the delay between sensing " + }, + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "type": "inline_equation", + "content": "①" + }, + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "type": "text", + "content": " and actuation " + }, + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "type": "inline_equation", + "content": "②" + }, + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "type": "text", + "content": " caused by the computational complexity of high-capacity deep networks (visual encoders, policy). To model realistic motion while training in simulation, we create a " + }, + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "type": "inline_equation", + "content": "2^{nd}" + }, + { + "bbox": [ + 305, + 384, + 547, + 526 + ], + "type": "text", + "content": " order dynamical model running with higher frequency, which models the robot and its low-level closed-loop controller. We identify the model from real data and add it to the Habitat [44] Simulator." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 554, + 547, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 554, + 547, + 662 + ], + "spans": [ + { + "bbox": [ + 304, + 554, + 547, + 662 + ], + "type": "text", + "content": "decision rules. In this context, the specific task of point goal navigation (navigation to coordinates) is now sometimes considered \"solved\" in the literature [38], incorrectly, as we argue. While the machine learning and computer vision community turns its attention towards the exciting goal of integrating language models into navigation [15, 23], we think that further improvements are required to make trained agents perform reliably in real environments with sufficient speed." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 665, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 665, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 665, + 547, + 713 + ], + "type": "text", + "content": "Experiments and evaluations of trained models in real environments and the impact of the sim2real gap do exist in the Embodied AI literature [11, 20, 43], but they are rare and were performed in restricted environments. Known models" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 1, + 494, + 19 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 1, + 494, + 19 + ], + "spans": [ + { + "bbox": [ + 145, + 1, + 494, + 19 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version:" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 179, + 24, + 461, + 36 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 179, + 24, + 461, + 36 + ], + "spans": [ + { + "bbox": [ + 179, + 24, + 461, + 36 + ], + "type": "text", + "content": "the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17837" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": "are trained in 3D simulators like Habitat [44] or AI-Thor [26], which are realistic in their perception aspects, but lack the accurate motion models of physical agents which the robotics community uses for articulated robots, for instance, where forward and inverse kinetics are often modeled and identified. This results in a large sim2real gap in motion characteristics, which is either ignored or addressed by discrete motion commands. The latter strategy teleports the agent in simulation for each discrete action and executes these actions on the physical robot by low-level control on positions instead of velocities, stopping the robot between agent decisions and leading to extremely inefficient navigation and overly long episodes [43]." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 228, + 289, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 228, + 289, + 430 + ], + "spans": [ + { + "bbox": [ + 46, + 228, + 289, + 430 + ], + "type": "text", + "content": "In this work we go beyond current models for terrestrial navigation by realistically modeling both actuation and sensing of real agents in simulation, and we successfully transfer trained models to a real robotic platform. On the actuation side, we take agent decisions as discretized linear and angular velocities and predict them asynchronously while the agent is in motion. The resulting delay between sensing and actuation (see Figure 1) requires the agent to anticipate motion, which it learns in simulation from a realistic motion model. To this end, we create a second-order dynamical model, which approximates the physical properties of the real robot together with its closed-loop low-level controller. We identify this model from real robot rollouts and expert actions. The model is integrated into the Habitat simulator as an intermediate solution between the standard instantaneous motion model and a full-blown computationally-expensive physics simulation based on forces, masses, frictions etc." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 431, + 289, + 587 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 431, + 289, + 587 + ], + "spans": [ + { + "bbox": [ + 46, + 431, + 289, + 587 + ], + "type": "text", + "content": "On the sensing side, we combine visual and Lidar observations with different ways of communicating the navigation (point) goal to the agent, and different estimates of robot pose relative to a reference frame, combining two different types of localization: first, dead reckoning from wheel encoders, and secondly, external localization based on Monte Carlo methods from Lidar input. We perform extensive experiments and ablations on a real navigation platform and quantify the impact of the motion model, action spaces, sensing capabilities and the way we provide goal coordinates on navigation performance, showing that end-to-end trained agents can robustly navigate from visual input when their motion has been correctly modelled in simulation." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 597, + 134, + 609 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 597, + 134, + 609 + ], + "spans": [ + { + "bbox": [ + 47, + 597, + 134, + 609 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "content": "Visual navigation — navigation has been classically solved in robotics using mapping and planning [7, 31, 32], which requires solutions for mapping and localization [6, 28, 50], for planning [27, 46] and for low-level control [19, 42]. These methods depend on accurate sensor models, filtering, dynamical models and optimization. End-to-end trained models directly map input to actions and are typically trained with RL [24, 35] or imitation learning [14]. They learn repre" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 167 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 167 + ], + "type": "text", + "content": "sentations such as flat recurrent states, occupancy maps [9], semantic maps [8], latent metric maps [4, 21, 37], topological maps [3, 10, 47], self-attention [12, 16, 18, 41], implicit representations [33] or maximizing navigability directly with a blind agent optimizing a collected representation [5]. Our proposed method is end-to-end trained and features recurrent memory, but benefits from an additional motion model in simulation." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 177, + 548, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 177, + 548, + 464 + ], + "spans": [ + { + "bbox": [ + 304, + 177, + 548, + 464 + ], + "type": "text", + "content": "Sim2real transfer — The sim2real gap can compromise strong performance achieved in simulation when agents are tested in the real-world [22, 29], as perception and control policies often do not generalize well to real robots due to inaccuracies in modelling, simplifications and biases. To close the gap, domain randomization methods [39, 49] treat the discrepancy between the domains as variability in the simulation parameters. Alternatively, domain adaptation methods learn an invariant mapping for matching distributions between the simulator and the robot environment. Examples include transfer of visuo-motor policies by adversarial learning [55], adapting dynamics in RL [17], lowering fidelity simulation [52] and adapting object recognition to new domains [56]. Bi-directional adaptation is proposed in [51]; Recently, Chattopadhyay et al. [11] benchmarked the robustness of embodied agents to visual and dynamics corruptions. Kadian et al. [25] investigated sim2real predictability of Habitat-Sim [44] for PointGoal navigation and proposed a new metric to quantify it, called Sim-vs-Real Correlation Coefficient (SRCC). The PointGoal task on real robots is also evaluated in [43]. To reach competitive performance without modelling any sim2real transfer, the agent is pre-trained on a wide variety of environments and then fine-tuned on a simulated version of the target environment." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 474, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 548, + 715 + ], + "type": "text", + "content": "Motion models — are usually kept very simple when training visual navigation policies. Several works use a discrete high-level action space in simulation [8, 9, 20] and rely on dedicated controllers to translate these discrete actions into robot controls when transferring to the real world. Alternative approaches predict continuous actions [13, 54] or waypoints [2, 48], that again are subsequently mapped to robot controls when executing the policies in real. Somewhat closer to our approach, Yokoyama et al. [53] adopt a discretized linear and angular velocity space, and introduce a new metric, SCT, that uses a simplified \"unicycle-cart\" dynamical model to estimate the \"optimal\" episode completion time computed by rapidly exploring random trees (RRT). However the unicycle model is only used for evaluation and it is not deployed for training nor testing: as in previous works, the commands are mapped to robot controls using handcrafted heuristics. In contrast to previous approaches, we include the dynamical model of the robot in the training loop to learn complex dependencies between the navigation policy and the robot physical properties." + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "17838" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 69, + 289, + 191 + ], + "blocks": [ + { + "bbox": [ + 48, + 69, + 289, + 191 + ], + "lines": [ + { + "bbox": [ + 48, + 69, + 289, + 191 + ], + "spans": [ + { + "bbox": [ + 48, + 69, + 289, + 191 + ], + "type": "image", + "image_path": "81e1ba774bd35f70e54ac80f63c84c548dd3222fbdbcb5bab27939e388c50395.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 198, + 287, + 243 + ], + "lines": [ + { + "bbox": [ + 46, + 198, + 287, + 243 + ], + "spans": [ + { + "bbox": [ + 46, + 198, + 287, + 243 + ], + "type": "text", + "content": "Figure 2. The agent uses a recurrent policy with a static point goal " + }, + { + "bbox": [ + 46, + 198, + 287, + 243 + ], + "type": "inline_equation", + "content": "g_{0}" + }, + { + "bbox": [ + 46, + 198, + 287, + 243 + ], + "type": "text", + "content": " as input, i.e. the goal is constant and given wrt. to the initial reference frame. During training, the estimation of the dynamic point goal " + }, + { + "bbox": [ + 46, + 198, + 287, + 243 + ], + "type": "inline_equation", + "content": "\\hat{g}_{t}" + }, + { + "bbox": [ + 46, + 198, + 287, + 243 + ], + "type": "text", + "content": " is supervised from privileged information." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 257, + 274, + 271 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 257, + 274, + 271 + ], + "spans": [ + { + "bbox": [ + 47, + 257, + 274, + 271 + ], + "type": "text", + "content": "3. End-to-end training with realistic sensing" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "spans": [ + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "text", + "content": "We propose a method for training agents which (in principle) could address a variety of visual navigation problems, and without loss of generality, focusing on sim2real transfer and efficiency, we formalize the problem as a PointGoal task: an agent receives sensor observations at each time step " + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "text", + "content": " and must take actions " + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "inline_equation", + "content": "\\mathbf{a}_t" + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "text", + "content": " to reach a goal position given as polar coordinates. The method is not restricted to any specific observations, in our experiments the agent receives RGB images " + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_t \\in \\mathbb{R}^{3 \\times H \\times W}" + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "text", + "content": " and a Lidar-like vector of ranges " + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_t \\in \\mathbb{R}^K" + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 278, + 287, + 397 + ], + "type": "text", + "content": " is the number of laser rays." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 399, + 287, + 495 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 399, + 287, + 495 + ], + "spans": [ + { + "bbox": [ + 46, + 399, + 287, + 495 + ], + "type": "text", + "content": "The proposed agent is fully trained and therefore does not require to localize itself on a map for analytical path planning. However, even in this very permissive setting the application itself requires to communicate the goal to the agent in some form of coordinate system, which requires localization at least initially with respect to the goal (in ImageGoal settings this would be replaced by the goal image). We can classically differentiate between three different forms:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 52, + 496, + 288, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 496, + 288, + 544 + ], + "spans": [ + { + "bbox": [ + 52, + 496, + 288, + 544 + ], + "type": "text", + "content": "Absolute PointGoal — the goal vector " + }, + { + "bbox": [ + 52, + 496, + 288, + 544 + ], + "type": "inline_equation", + "content": "\\mathbf{g}^a = [\\mathbf{g}_x^a, \\mathbf{g}_y^a]^T" + }, + { + "bbox": [ + 52, + 496, + 288, + 544 + ], + "type": "text", + "content": " is given in a pre-defined agent-independent absolute reference frame. This requires access to a global localization system." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 53, + 544, + 288, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 544, + 288, + 604 + ], + "spans": [ + { + "bbox": [ + 53, + 544, + 288, + 604 + ], + "type": "text", + "content": "Dynamic PointGoal — the goal vector " + }, + { + "bbox": [ + 53, + 544, + 288, + 604 + ], + "type": "inline_equation", + "content": "\\mathbf{g}_t" + }, + { + "bbox": [ + 53, + 544, + 288, + 604 + ], + "type": "text", + "content": " is provided with respect to the current agent pose and therefore updated at each time instant " + }, + { + "bbox": [ + 53, + 544, + 288, + 604 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 53, + 544, + 288, + 604 + ], + "type": "text", + "content": ". This requires an external localization system providing estimates which are then transformed into the egocentric reference frame." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 53, + 605, + 289, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 605, + 289, + 665 + ], + "spans": [ + { + "bbox": [ + 53, + 605, + 289, + 665 + ], + "type": "text", + "content": "Static PointGoal — the goal vector is provided with respect to the starting position at " + }, + { + "bbox": [ + 53, + 605, + 289, + 665 + ], + "type": "inline_equation", + "content": "t = 0" + }, + { + "bbox": [ + 53, + 605, + 289, + 665 + ], + "type": "text", + "content": " of the robot, and not updated with agent motion " + }, + { + "bbox": [ + 53, + 605, + 289, + 665 + ], + "type": "inline_equation", + "content": "(= \\mathbf{g}_0)" + }, + { + "bbox": [ + 53, + 605, + 289, + 665 + ], + "type": "text", + "content": ". This requires the agent to learn this update itself, and therefore some form of internal localization or integration of odometry information." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 665, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 713 + ], + "type": "text", + "content": "We target the Static PointGoal case, which does not require localization beyond the initial relative vector. However, we also argue that some form of localization and/or odometry information is useful, which will assist the dynamics infor" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 133 + ], + "type": "text", + "content": "mation inferred from (visual) sensor readings. Furthermore, during training it will allow the agent to learn a useful latent representation in its hidden state and an associated dynamics in this latent space. We therefore provide the agent with two different localization components:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 311, + 134, + 547, + 193 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 311, + 134, + 547, + 193 + ], + "spans": [ + { + "bbox": [ + 311, + 134, + 547, + 193 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^a" + }, + { + "bbox": [ + 311, + 134, + 547, + 193 + ], + "type": "text", + "content": " — an estimate of agent pose with respect to the initial agent position, asynchronously delivered and with low frequency, around 0.5-1 fps. At test, this signal is delivered by external localization, in our case from a Lidar-based AMCL module (see Section 5)." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 311, + 194, + 547, + 242 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 311, + 194, + 547, + 242 + ], + "spans": [ + { + "bbox": [ + 311, + 194, + 547, + 242 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^r" + }, + { + "bbox": [ + 311, + 194, + 547, + 242 + ], + "type": "text", + "content": " — an estimate coming from onboard odometry, which we integrate over time to provide an estimate situated in the same reference frame as " + }, + { + "bbox": [ + 311, + 194, + 547, + 242 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^a" + }, + { + "bbox": [ + 311, + 194, + 547, + 242 + ], + "type": "text", + "content": ", i.e. with respect to the initial agent position." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 243, + 547, + 303 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 243, + 547, + 303 + ], + "spans": [ + { + "bbox": [ + 304, + 243, + 547, + 303 + ], + "type": "text", + "content": "The characteristics of the two localization signals are different: while " + }, + { + "bbox": [ + 304, + 243, + 547, + 303 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^r" + }, + { + "bbox": [ + 304, + 243, + 547, + 303 + ], + "type": "text", + "content": " corresponds to a dead reckoning process and is subject to drift, its relative noise is lower. The signal " + }, + { + "bbox": [ + 304, + 243, + 547, + 303 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^a" + }, + { + "bbox": [ + 304, + 243, + 547, + 303 + ], + "type": "text", + "content": " is not subject to drift but suffers from larger errors in certain regions, due to registration errors or absence of structure." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "spans": [ + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "text", + "content": "The agent policy is recurrent, based on a hidden memory vector " + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "inline_equation", + "content": "\\mathbf{h}_t" + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "text", + "content": " updated over time from input of all sensor readings " + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_t, \\mathbf{S}_t, \\mathbf{p}_t^r, \\hat{\\mathbf{p}}_t^a" + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "text", + "content": ", the goal " + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "inline_equation", + "content": "\\mathbf{g}_0" + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "text", + "content": " and the previous action " + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "inline_equation", + "content": "\\mathbf{a}_{t-1}" + }, + { + "bbox": [ + 304, + 304, + 546, + 341 + ], + "type": "text", + "content": "," + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 328, + 342, + 546, + 356 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 328, + 342, + 546, + 356 + ], + "spans": [ + { + "bbox": [ + 328, + 342, + 546, + 356 + ], + "type": "interline_equation", + "content": "\\mathbf {h} _ {t} = d \\left(\\mathbf {h} _ {t - 1}, v \\left(\\mathbf {I} _ {t}\\right), u \\left(\\mathbf {S} _ {t}\\right), \\mathbf {g} _ {0}, \\hat {\\mathbf {p}} _ {t} ^ {r}, \\hat {\\mathbf {p}} _ {t} ^ {a}, e \\left(\\mathbf {a} _ {t - 1}\\right)\\right), \\tag {1}", + "image_path": "a19e34392bf53cd2bfef5658eee154ae6fae7e260a9267b9508e8b5883a5ea91.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 329, + 357, + 545, + 371 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 329, + 357, + 545, + 371 + ], + "spans": [ + { + "bbox": [ + 329, + 357, + 545, + 371 + ], + "type": "interline_equation", + "content": "\\mathbf {a} _ {t} = \\pi (\\mathbf {h} _ {t}), \\tag {2}", + "image_path": "6005003a722d964922e3e1137beb955646d5c82372e7b2c760463bc3a653204c.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 329, + 373, + 545, + 386 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 329, + 373, + 545, + 386 + ], + "spans": [ + { + "bbox": [ + 329, + 373, + 545, + 386 + ], + "type": "interline_equation", + "content": "\\hat {\\mathbf {g}} _ {t} = l \\left(\\mathbf {h} _ {t}\\right), \\tag {3}", + "image_path": "6f3e8bde9280059768c352c5d5b441cd97a286c4641aaa9c59eb354feaff5d22.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": " is a GRU with hidden state " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "\\mathbf{h}_t" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": " is a visual encoder of the image " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_t" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": " (in our case, a ResNet-18); " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "u" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": " is a 1D-CNN encoding the scan " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_t" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": "; " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "e" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": " is a set of action embedding vectors; " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "\\pi" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": " is a linear policy. Other inputs go through dedicated MLPs, not named to lighten notations. To help the agent deal with the noisy relative and absolute pose estimates, we put an inductive bias for localization on " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "\\mathbf{h}_t" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": " through an auxiliary head " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": " predicting the dynamic goal compass " + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{g}}_t" + }, + { + "bbox": [ + 304, + 388, + 547, + 544 + ], + "type": "text", + "content": ", supervised during training from the simulated agent's ground truth pose, as shown in Figure 2. In the following paragraphs we describe the two localization systems and the noise models we use to simulate them during training in simulation. Section 4 then introduces the dynamical model used during training." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "text", + "content": "Integrated relative localization - the pose estimate " + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^r" + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "text", + "content": " can be obtained with any commercially available odometry system. In our experiments we integrate readings from wheel encoders. During simulation and training, " + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^r" + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "text", + "content": " is estimated by sampling planar noise " + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "inline_equation", + "content": "[\\epsilon_x,\\epsilon_\\theta ]^\\intercal" + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "text", + "content": " from a multivariate Gaussian distribution " + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "inline_equation", + "content": "\\mathcal{N}(\\left[ \\begin{array}{cc}0.01\\\\ 0 \\end{array} \\right],\\left[ \\begin{array}{cc}10^{-4} & 10^{-4}\\\\ 10^{-4} & 10^{-3} \\end{array} \\right])" + }, + { + "bbox": [ + 304, + 545, + 547, + 651 + ], + "type": "text", + "content": " which gets added to the step-wise motion of the agent, leading to the accumulation of drift over time." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": "Absolute localization - the pose estimate " + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^a" + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": " is obtained with the standard ROS 2 package for Adaptive Monte Carlo Localization (AMCL) [50], a KLD-sampling approach requiring a pre-computed, static map based on particle filtering. During simulation and training, " + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{p}}_t^r" + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": " is es" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17839" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 69, + 547, + 336 + ], + "blocks": [ + { + "bbox": [ + 49, + 69, + 547, + 336 + ], + "lines": [ + { + "bbox": [ + 49, + 69, + 547, + 336 + ], + "spans": [ + { + "bbox": [ + 49, + 69, + 547, + 336 + ], + "type": "image", + "image_path": "5c67e1c12db97c5c52a0418878fdd2140a9d22e22884288fc0cd62ca28730736.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "lines": [ + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "spans": [ + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "text", + "content": "Figure 3. Training visual navigation with realistic motion models: we train an end-to-end agent in simulation (top) subject to two different simulation loops: a slower loop at " + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "inline_equation", + "content": "3\\mathrm{Hz}" + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "text", + "content": " (indexed by " + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "text", + "content": ") renders visual observations and takes agent decisions, while a faster loop at " + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "inline_equation", + "content": "30\\mathrm{Hz}" + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "text", + "content": " (indexed by " + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "text", + "content": ") simulates physics. Physics is approximated with a " + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "inline_equation", + "content": "2^{nd}" + }, + { + "bbox": [ + 46, + 343, + 548, + 409 + ], + "type": "text", + "content": " order model identified from real robot rollouts (bottom) and includes the robot physics as well as the behavior of the closed-loop control of the differential drive (neither onboard control algorithm nor control frequency need to be known). Operations in the intervals are pipelined, e.g. sensing occurs at each time step, as does agent forward pass etc. The agent architecture is detailed in Figure 2." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 417, + 289, + 536 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 417, + 289, + 536 + ], + "spans": [ + { + "bbox": [ + 46, + 417, + 289, + 536 + ], + "type": "text", + "content": "timated by sampling planar noise from another Gaussian " + }, + { + "bbox": [ + 46, + 417, + 289, + 536 + ], + "type": "inline_equation", + "content": "\\mathcal{N}(0, \\mathrm{Diag}[0.03, 0.03, 0.05])" + }, + { + "bbox": [ + 46, + 417, + 289, + 536 + ], + "type": "text", + "content": ", but this time it gets directly added to the ground truth pose of the robot, thus modeling imprecise localization (eg. due to Lidar registration failures) without drift accumulation. In addition, we model the potential unreliability of such absolute pose estimates by only providing a new observation to the agent every few steps, at an irregular period governed by a uniform distribution " + }, + { + "bbox": [ + 46, + 417, + 289, + 536 + ], + "type": "inline_equation", + "content": "\\mathcal{U}(8, 12)" + }, + { + "bbox": [ + 46, + 417, + 289, + 536 + ], + "type": "text", + "content": ". This potentially allows to plug-in low-frequency visual localization." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 549, + 288, + 562 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 549, + 288, + 562 + ], + "spans": [ + { + "bbox": [ + 47, + 549, + 288, + 562 + ], + "type": "text", + "content": "4. A dynamical model of realistic robot motion" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "text", + "content": "One of our main motivations is to be able to use a trained model to navigate efficiently, i.e. fast and reliably. Stopping the robot between predicted actions is therefore not an option, and we train the model to predict linear and angular velocity commands in parallel to its physical motion, as illustrated in Figure 1. This requires the agent to anticipate motion to predict an action " + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{a}_t" + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "text", + "content": " relative to the next (yet unobserved) state at " + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "text", + "content": ", exacerbated by the delay between sensing at time " + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "text", + "content": " and actuation at " + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "t + 1" + }, + { + "bbox": [ + 46, + 570, + 289, + 714 + ], + "type": "text", + "content": ", during which computation through the high-capacity visual encoder and policy happens. This motion depends on the physical characteristics of the robot, as shown in Figure 3 (bottom): the linear and angular veloc" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 417, + 547, + 632 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 417, + 547, + 632 + ], + "spans": [ + { + "bbox": [ + 304, + 417, + 547, + 632 + ], + "type": "text", + "content": "ity commands predicted by the neural policy " + }, + { + "bbox": [ + 304, + 417, + 547, + 632 + ], + "type": "inline_equation", + "content": "\\pi" + }, + { + "bbox": [ + 304, + 417, + 547, + 632 + ], + "type": "text", + "content": " are translated into \"set values\" for left and right motor speeds of the differential drive system with a deterministic function and used as targets by the closed loop control algorithm, typically a PID (Proportional Integral Derivative Controller), attempting to reach and maintain the predicted speed between agent decisions. The behavior depends on the control algorithm but also on the physical properties of the robot, like its mass and resulting inertia, power and torque curves of the motors, friction etc. We decrease the actuation sim2real gap as as much as possible by integrating a model of realistic robot behavior into the Habitat [44] platform, shown in the top part of Figure 3. We approximate the robot's motion behavior by modeling the combined behavior of both the robot and the control algorithm implemented on the real platform as an asymmetric second-order dynamic system. The parameters of this low-level loop are estimated from recordings of the real robot platform with a system identification algorithm." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "type": "text", + "content": "Classically, a sequential decision process can be modeled as a POMDP " + }, + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\langle \\mathcal{X},\\mathcal{U},T,\\mathcal{O},O,R\\rangle" + }, + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "type": "text", + "content": ". In pure 2D navigation settings with a fixed goal in a single static scene, the environment maintains a (hidden) state " + }, + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_t\\in \\mathcal{X}" + }, + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "type": "text", + "content": " consisting in the pose of the agent, i.e. position and orientation, " + }, + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_t = [x_t,y_t,\\theta_t]" + }, + { + "bbox": [ + 304, + 642, + 548, + 715 + ], + "type": "text", + "content": ". In most settings in the literature" + } + ] + } + ], + "index": 6 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "17840" + } + ] + } + ], + "index": 7 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 70, + 289, + 188 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 289, + 188 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 289, + 188 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 289, + 188 + ], + "type": "image", + "image_path": "e0c937955b88f2606debdb8455db3b1f2f481b876fe4306210aaa8b2b70faff7.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 196, + 289, + 251 + ], + "lines": [ + { + "bbox": [ + 46, + 196, + 289, + 251 + ], + "spans": [ + { + "bbox": [ + 46, + 196, + 289, + 251 + ], + "type": "text", + "content": "Figure 5. Robustness: Top: The ROS2 baseline fails when obstacles are thin at the height of the single Lidar ray. The robot doesn't see the stool, collides, drags it away. The red circles " + }, + { + "bbox": [ + 46, + 196, + 289, + 251 + ], + "type": "inline_equation", + "content": "\\bigcirc" + }, + { + "bbox": [ + 46, + 196, + 289, + 251 + ], + "type": "text", + "content": " show the position of the moved stool. Bottom: our agent is surprisingly robust and allows navigation very close to fine structures." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "spans": [ + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "type": "text", + "content": "based on 3D photo-realistic simulators like Habitat [44], the state update in simulation ignores physical properties of the robot (mass/inertia, friction, accelerations, etc.), as it is implemented through \"teleportation\" of the robot to a new pose. In that case, the environment transition decomposes into a discrete state update " + }, + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "type": "inline_equation", + "content": "x_{t + 1} = T(x_t,u_t)" + }, + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "type": "text", + "content": " and an observation " + }, + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "type": "inline_equation", + "content": "o_{t + 1} = O(x_{t + 1})" + }, + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "type": "text", + "content": ". The discrete action space " + }, + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "type": "inline_equation", + "content": "\\mathcal{U}_{\\mathrm{motion}} = \\{\\mathrm{FORWARD~25cm},\\mathrm{TURN\\_LEFT~10^{\\circ}},\\mathrm{TURN\\_RIGHT~10^{\\circ}} \\text{ and } \\mathrm{STOP}\\}" + }, + { + "bbox": [ + 46, + 263, + 289, + 384 + ], + "type": "text", + "content": " frequently chosen in the navigation literature results in a halting and jerky robot motion." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 384, + 289, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 384, + 289, + 418 + ], + "spans": [ + { + "bbox": [ + 47, + 384, + 289, + 418 + ], + "type": "text", + "content": "Adding realism — To be able to smooth robot trajectories, we need to model accelerations. We extend the agent state as:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 104, + 420, + 287, + 433 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 104, + 420, + 287, + 433 + ], + "spans": [ + { + "bbox": [ + 104, + 420, + 287, + 433 + ], + "type": "interline_equation", + "content": "\\mathbf {x} _ {t} = \\left[ x _ {t}, y _ {t}, \\theta_ {t}, v _ {t}, w _ {t}, \\dot {v} _ {t}, \\dot {w} _ {t} \\right], \\tag {4}", + "image_path": "568ed9c004ffa2759989fbe184a05051f93aed11e97087afb3b943265a3adbe8.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "type": "inline_equation", + "content": "x_{t}, y_{t}, \\theta_{t}" + }, + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "type": "text", + "content": " are the absolute position and orientation of the robot in the plane of the scene (in m, m and rad); " + }, + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "type": "inline_equation", + "content": "v_{t}, w_{t}" + }, + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "type": "text", + "content": " are the linear (forward) and angular velocities of the robot (in m/s and rad/s); " + }, + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "type": "inline_equation", + "content": "\\dot{v}_{t}; \\dot{w}_{t}" + }, + { + "bbox": [ + 46, + 437, + 287, + 498 + ], + "type": "text", + "content": " are the linear and angular accelerations of the robot (in m/s² and rad/s²)." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "spans": [ + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "text", + "content": "The proposed agent predicts a pair " + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "inline_equation", + "content": "\\langle v_t^*, w_t^* \\rangle" + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "text", + "content": " of velocity commands, chosen from a discrete action space " + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "inline_equation", + "content": "\\mathcal{U}_{\\mathrm{vel}}" + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "text", + "content": " resulting from the cartesian product of linear and angular spaces " + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "inline_equation", + "content": "\\{0, 0.3, 0.6, 1\\} \\times \\{-3, -2, -1, 0, \\dots, 3\\}" + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "text", + "content": ", as shown in Figure 4. To simplify notations, we will use " + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "inline_equation", + "content": "\\mathbf{u}_t = \\langle v_t^*, w_t^* \\rangle \\in \\mathcal{U}" + }, + { + "bbox": [ + 47, + 498, + 181, + 617 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 618, + 181, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 181, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 181, + 714 + ], + "type": "text", + "content": "One possibility to model realistic robot behavior is to design a full dynamical model of the robot in the form of a set of differential equations, identify its parameters, discretize it, and simulate it in Habitat, together with running an exact copy of the conti" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 198, + 505, + 282, + 604 + ], + "blocks": [ + { + "bbox": [ + 198, + 505, + 282, + 604 + ], + "lines": [ + { + "bbox": [ + 198, + 505, + 282, + 604 + ], + "spans": [ + { + "bbox": [ + 198, + 505, + 282, + 604 + ], + "type": "image", + "image_path": "4378f2e4826d500bb54dd4d73b95d66bd45465e9460184b61153d8535d14eb9f.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "lines": [ + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "type": "text", + "content": "Figure 4. The action space: 28 actions, 4 choices of linear velocities " + }, + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "type": "inline_equation", + "content": "\\in [0,1]" + }, + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "type": "text", + "content": " m/s, 7 choices for angular vel. " + }, + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "type": "inline_equation", + "content": "\\in [-3,3]" + }, + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "type": "text", + "content": " rad/s. Arrows show the effect on pose of action held for " + }, + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "type": "inline_equation", + "content": "\\frac{2}{3}\\mathrm{sec}" + }, + { + "bbox": [ + 184, + 618, + 287, + 696 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 307, + 70, + 545, + 130 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 545, + 130 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 545, + 130 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 545, + 130 + ], + "type": "image", + "image_path": "18349075bd8fa37460b6927a666f85f48ba4fd51ee385b78cf85ef346440fb5e.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 138, + 545, + 161 + ], + "lines": [ + { + "bbox": [ + 306, + 138, + 545, + 161 + ], + "spans": [ + { + "bbox": [ + 306, + 138, + 545, + 161 + ], + "type": "text", + "content": "Figure 6. Dynamic obstacles: our agent stops and circumvents people, achieved through a highly negative collision reward term." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 179, + 547, + 263 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 179, + 547, + 263 + ], + "spans": [ + { + "bbox": [ + 304, + 179, + 547, + 263 + ], + "type": "text", + "content": "physical robot with exactly the same parameters and control frequency, which is a stringent constraint. Instead, we opted for a more flexible solution and we approximate the combined behavior of the physical robot and its control algorithm by a second order dynamical model [36]. We decompose interactions with the simulator into two different loops running at different frequencies:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 308, + 269, + 547, + 392 + ], + "type": "list", + "angle": 0, + "index": 15, + "blocks": [ + { + "bbox": [ + 308, + 269, + 545, + 317 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 269, + 545, + 317 + ], + "spans": [ + { + "bbox": [ + 308, + 269, + 545, + 317 + ], + "type": "text", + "content": "- Visual observations, simulator state updates and agent decisions (Equations (1) to (3)) are produced in a slower loop, indexed by letter " + }, + { + "bbox": [ + 308, + 269, + 545, + 317 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 308, + 269, + 545, + 317 + ], + "type": "text", + "content": " in the subsequent notation, and run at " + }, + { + "bbox": [ + 308, + 269, + 545, + 317 + ], + "type": "inline_equation", + "content": "f^{*} = 3\\mathrm{Hz}" + }, + { + "bbox": [ + 308, + 269, + 545, + 317 + ], + "type": "text", + "content": " in our experiments." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 308, + 319, + 547, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 319, + 547, + 392 + ], + "spans": [ + { + "bbox": [ + 308, + 319, + 547, + 392 + ], + "type": "text", + "content": "- Between two subsequent steps of the slower loop, a faster loop models physical motion of the robot, without rendering observations. At the end of this loop, the simulator state is updated, and a visual observation is returned. Steps in this faster loop are indexed by a second index " + }, + { + "bbox": [ + 308, + 319, + 547, + 392 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 308, + 319, + 547, + 392 + ], + "type": "text", + "content": " in the subsequent notation, " + }, + { + "bbox": [ + 308, + 319, + 547, + 392 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_{t,\\tau}" + }, + { + "bbox": [ + 308, + 319, + 547, + 392 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "spans": [ + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "type": "text", + "content": "In-between two environment steps " + }, + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "type": "inline_equation", + "content": "t - 1" + }, + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "type": "text", + "content": ", we simulate dynamics at frequency " + }, + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "type": "inline_equation", + "content": "f^{\\phi} = 30 > f^{*}" + }, + { + "bbox": [ + 304, + 397, + 547, + 434 + ], + "type": "text", + "content": ". The number of physical sub-time steps per environment time step is therefore" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 434, + 545, + 474 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 434, + 545, + 474 + ], + "spans": [ + { + "bbox": [ + 306, + 434, + 545, + 474 + ], + "type": "inline_equation", + "content": "K^{\\phi} = \\left|\\frac{f^{\\phi}}{f^{*}}\\right| = 10" + }, + { + "bbox": [ + 306, + 434, + 545, + 474 + ], + "type": "text", + "content": " their duration is " + }, + { + "bbox": [ + 306, + 434, + 545, + 474 + ], + "type": "inline_equation", + "content": "\\Delta^{\\phi} = \\frac{1}{f^{\\phi}} = 33\\mathrm{ms}" + }, + { + "bbox": [ + 306, + 434, + 545, + 474 + ], + "type": "text", + "content": ". The physical loop running between two environment steps can be formalized as the following set of state update equations," + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 326, + 476, + 389, + 489 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 326, + 476, + 389, + 489 + ], + "spans": [ + { + "bbox": [ + 326, + 476, + 389, + 489 + ], + "type": "interline_equation", + "content": "\\mathbf {o} _ {t} = O (\\mathbf {x} _ {t - 1}).", + "image_path": "37a5346ba84850eb8389a1c90188067ef67e9e011d5acc6872ad83276f168274.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 501, + 476, + 556, + 487 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 501, + 476, + 556, + 487 + ], + "spans": [ + { + "bbox": [ + 501, + 476, + 556, + 487 + ], + "type": "text", + "content": "Observation" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 310, + 491, + 370, + 500 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 491, + 370, + 500 + ], + "spans": [ + { + "bbox": [ + 310, + 491, + 370, + 500 + ], + "type": "interline_equation", + "content": "\\mathbf {x} _ {t - 1, 0} = \\mathbf {x} _ {t - 1}", + "image_path": "ad84c3bad4842fc66a39ac06359a6f47c83680decb4bdc22b4a6f4fde24d3fb7.jpg" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 502, + 489, + 520, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 502, + 489, + 520, + 498 + ], + "spans": [ + { + "bbox": [ + 502, + 489, + 520, + 498 + ], + "type": "text", + "content": "Init" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 310, + 501, + 496, + 514 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 501, + 496, + 514 + ], + "spans": [ + { + "bbox": [ + 310, + 501, + 496, + 514 + ], + "type": "interline_equation", + "content": "\\dot {v} _ {t, \\tau + 1} = \\dot {v} _ {t, \\tau} + \\Delta^ {\\phi} \\left(f _ {t, \\tau} ^ {v} ^ {2} \\delta_ {t, \\tau} ^ {v} - 2 \\zeta_ {t, \\tau} ^ {v} f _ {t, \\tau} ^ {v} \\dot {v} _ {t, \\tau}\\right)", + "image_path": "0206ff4ab0181caac968ac07e45c5db863472a877a772b0e3e98daf0cc86a4bf.jpg" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 502, + 501, + 544, + 512 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 502, + 501, + 544, + 512 + ], + "spans": [ + { + "bbox": [ + 502, + 501, + 544, + 512 + ], + "type": "text", + "content": "Upd.acc." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 309, + 514, + 501, + 527 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 514, + 501, + 527 + ], + "spans": [ + { + "bbox": [ + 309, + 514, + 501, + 527 + ], + "type": "interline_equation", + "content": "\\dot {w} _ {t, \\tau + 1} = \\dot {w} _ {t, \\tau} + \\Delta^ {\\phi} \\left(f _ {t, \\tau} ^ {w} ^ {2} \\delta_ {t, \\tau} ^ {w} - 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Velocity and acceleration are also clipped to identified maximum values." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 108, + 288, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 108, + 288, + 167 + ], + "spans": [ + { + "bbox": [ + 46, + 108, + 288, + 167 + ], + "type": "text", + "content": "System identification - the model has 8 parameters, " + }, + { + "bbox": [ + 46, + 108, + 288, + 167 + ], + "type": "inline_equation", + "content": "f^{v\\uparrow}, \\zeta^{v\\uparrow}, f^{v\\downarrow}, \\zeta^{v\\downarrow}, f^{w\\uparrow}, \\zeta^{w\\uparrow}, f^{w\\downarrow}, \\zeta^{w\\downarrow}" + }, + { + "bbox": [ + 46, + 108, + 288, + 167 + ], + "type": "text", + "content": ", which we identify from trajectories of a real robot controlled with precomputed trajectories exploring the command space, see the supplementary material for more details." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "spans": [ + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "text", + "content": "Training - the model is trained with RL, in particular PPO [45], and with a reward inspired by [11], " + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "inline_equation", + "content": "r_t = \\mathrm{R} \\cdot \\mathbb{I}_{\\mathrm{success}} - \\Delta_t^{\\mathrm{Geo}} - \\lambda - \\mathrm{C} \\cdot \\mathbb{I}_{\\mathrm{collision}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "inline_equation", + "content": "R = 2.5" + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "inline_equation", + "content": "\\Delta_t^{\\mathrm{Geo}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "text", + "content": " is the gain in geodesic distance to the goal, a slack cost " + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "inline_equation", + "content": "\\lambda = 0.01" + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "text", + "content": " encourages efficiency, and a cost " + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "inline_equation", + "content": "C = 0.1" + }, + { + "bbox": [ + 46, + 168, + 288, + 239 + ], + "type": "text", + "content": " penalizes each collision without ending the episode." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 239, + 288, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 239, + 288, + 300 + ], + "spans": [ + { + "bbox": [ + 46, + 239, + 288, + 300 + ], + "type": "text", + "content": "Recovery behavior — similar to what is done in classical analytical planning, we added a rudimentary recovery behavior on top of the trained agent: if the agent is notified of an obstacle and does not move for five seconds, it will move backward at " + }, + { + "bbox": [ + 46, + 239, + 288, + 300 + ], + "type": "inline_equation", + "content": "0.2\\mathrm{m / s}" + }, + { + "bbox": [ + 46, + 239, + 288, + 300 + ], + "type": "text", + "content": " for two seconds." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 311, + 173, + 324 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 311, + 173, + 324 + ], + "spans": [ + { + "bbox": [ + 47, + 311, + 173, + 324 + ], + "type": "text", + "content": "5. Experimental Results" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 330, + 288, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 330, + 288, + 569 + ], + "spans": [ + { + "bbox": [ + 46, + 330, + 288, + 569 + ], + "type": "text", + "content": "Experimental setup — we trained the agent in the Habitat simulator [44] on the 800 scenes of the HM3D Dataset [40] for 200M env. steps. Real robot experiments have been performed on a Naver Rookie robot, which came equipped with various sensors. We added an additional front facing RGB camera and capture images with a resolution of " + }, + { + "bbox": [ + 46, + 330, + 288, + 569 + ], + "type": "inline_equation", + "content": "1280 \\times 720" + }, + { + "bbox": [ + 46, + 330, + 288, + 569 + ], + "type": "text", + "content": " resized to " + }, + { + "bbox": [ + 46, + 330, + 288, + 569 + ], + "type": "inline_equation", + "content": "256 \\times 144" + }, + { + "bbox": [ + 46, + 330, + 288, + 569 + ], + "type": "text", + "content": ". In our experiments, the Lidar scan S is not taken from an onboard Lidar, but simulated from the 4 RealSense depth cameras which are installed close to the floor and oriented in 4 different directions. We use multiple scan lines of the cameras and fuse them into a single ray, details are given in the supplementary material. We did, however, add a single plane Lidar to the robot (which did not come equipped with one) and used it for localization only (see section 3). All processing has been done onboard, thanks to a Nvidia Jetson AGX Orin we added, with an integrated Nvidia Ampere GPU. It handles pre-processing of visual observations and network forward pass in around 70ms. The exact network architecture of the policy is given in the supplementary material." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 570, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 288, + 714 + ], + "type": "text", + "content": "Evaluation — evaluating sim2real transfer is inherently difficult, as it would optimally require to evaluate all agent variants and ablations on a real physical robot and on a high number of episodes. We opted for a three-way strategy, all tables are color-coded with numbers corresponding to one of the three following settings: (i) “Real” experiments evaluate the agent trained in simulation on the real Naver Rookie robot. It is the only form of evaluation which correctly estimates navigation performance in a real world scenario, but for practical reasons we limit it to a restricted number of 20 episodes in a large office environment shown in Fig. 7. (ii) “Simulation (+dyn. model)” is a setting in simul" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "content": "tion (Habitat), which allows large-scale evaluation on a large number of unseen environments and episodes, the HM3D validation set. Most importantly, during evaluation the simulator uses the identified dynamical model and therefore realistic motion, even for baselines which do not have access to one during training. Similar to the \"Real\" setting, this allows to evaluate the impact of not modeling realistic motion during training. (iii) \"Simulation (train domain)\" evaluates in simulation with the same action space an agent variant uses during training, i.e. there is no sim2real gap at all. This setting evaluates the difficulty of the simulated task, which might be a severe approximation of the task in real conditions. High performance in this setting is not necessarily indicative of high performance in a real environment." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 239, + 547, + 299 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 239, + 547, + 299 + ], + "spans": [ + { + "bbox": [ + 304, + 239, + 547, + 299 + ], + "type": "text", + "content": "We evaluate on two different sets of episodes: " + }, + { + "bbox": [ + 304, + 239, + 547, + 299 + ], + "type": "inline_equation", + "content": "\\mathrm{HM3D / 2.5k}" + }, + { + "bbox": [ + 304, + 239, + 547, + 299 + ], + "type": "text", + "content": " consists of 2500 episodes in the HM3D validation scenes, used in simulation only. " + }, + { + "bbox": [ + 304, + 239, + 547, + 299 + ], + "type": "inline_equation", + "content": "\\mathrm{Office / 20}" + }, + { + "bbox": [ + 304, + 239, + 547, + 299 + ], + "type": "text", + "content": " consists of 20 episodes in the targeted office building, Figure 7. They are used for evaluation in both, real world and simulation." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "spans": [ + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "text", + "content": "Metrics — Navigation performance is evaluated by success rate (SR), i.e., fraction of episodes terminated within a distance of " + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "inline_equation", + "content": "< 0.2\\mathrm{m}" + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "text", + "content": " to the goal by the agent calling the " + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "inline_equation", + "content": "\\langle v = 0, w = 0 \\rangle" + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "text", + "content": " action enough time to cancel its velocity, and SPL [1], i.e., SR weighted by the optimality of the path, " + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "inline_equation", + "content": "SPL = \\frac{1}{N} \\sum_{i=1}^{N} \\mathbb{I}_{\\text{success}} \\frac{\\ell_i^*}{\\max(\\ell_i, \\ell_i^*)}" + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "inline_equation", + "content": "\\ell_i" + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "text", + "content": " is the agent path length and " + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "inline_equation", + "content": "\\ell_i^*" + }, + { + "bbox": [ + 304, + 300, + 547, + 386 + ], + "type": "text", + "content": " the GT path length." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "spans": [ + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "text", + "content": "SPL is limited in its ability to properly evaluate agents with complex dynamics. Success Weighted by Completion Time (SCT) [53] explicitly takes the agent's dynamics model into consideration, and aims to accurately capture how well the agent has approximated the fastest navigation behavior. It is defined as " + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "inline_equation", + "content": "SCT = \\frac{1}{N}\\sum_{i=1}^{N}S_i\\frac{t_i^*}{\\max(c_i,t_i^*)}" + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "inline_equation", + "content": "c_i" + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "text", + "content": " is the agent's completion time in episode " + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "inline_equation", + "content": "t_i^*" + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "text", + "content": " is the shortest possible amount of time it takes to reach the goal point from the start point while circumventing obstacles based on the agent's dynamics. To simplify implementation, we use a lower bound on " + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "inline_equation", + "content": "t^*" + }, + { + "bbox": [ + 304, + 386, + 547, + 533 + ], + "type": "text", + "content": " taking into account linear dynamics along straight shortest path segments." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 533, + 547, + 582 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 547, + 582 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 547, + 582 + ], + "type": "text", + "content": "Checkpoints have been chosen as follows: performance in Real is given with checkpoints selected as the ones providing max SR in simulation. Performance in Simulation is given on the last checkpoint." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 587, + 362, + 598 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 587, + 362, + 598 + ], + "spans": [ + { + "bbox": [ + 306, + 587, + 362, + 598 + ], + "type": "text", + "content": "5.1. Results" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 605, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 547, + 715 + ], + "type": "text", + "content": "Agent behavior — the agent is surprisingly robust and does not collide with the infrastructure even though it can quite closely approach it navigating around it, even if the obstacles are thin and light. Examples are given in Figure 5 (top), but they are best viewed through the video in the supplementary material. This is in stark contrast to the ROS 2 based planner, which uses a 2D Map constructed with the onboard Lidar: thin and light structures do not show up on the map or a filtered, often because the larger part of the obstacle is not" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17842" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 72, + 148, + 167 + ], + "blocks": [ + { + "bbox": [ + 50, + 72, + 148, + 167 + ], + "lines": [ + { + "bbox": [ + 50, + 72, + 148, + 167 + ], + "spans": [ + { + "bbox": [ + 50, + 72, + 148, + 167 + ], + "type": "image", + "image_path": "576d37a8d17b2a2327770febd8dfd9b504e4aa2b2f3e31db029efaa6290618fb.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 178, + 546, + 200 + ], + "lines": [ + { + "bbox": [ + 46, + 178, + 546, + 200 + ], + "spans": [ + { + "bbox": [ + 46, + 178, + 546, + 200 + ], + "type": "text", + "content": "Figure 7. The 20 trajectories of " + }, + { + "bbox": [ + 46, + 178, + 546, + 200 + ], + "type": "inline_equation", + "content": "\\overline{\\text{Office}} /20" + }, + { + "bbox": [ + 46, + 178, + 546, + 200 + ], + "type": "text", + "content": " are distributed over 5 plots and superimposed on the map, color coded. If an episode fails, the remaining distance is shown as a straight black line from the last position to the goal. 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Method & action space+dyn (train)Ref.Sim (+dyn.) (HM3D/2.5k)Sim (+dyn.) (Office/20)Real (Office/20)
SR(%)SPL(%)SCT(%)SR(%)SPL(%)SCT(%)SR(%)SPL(%)SCT(%)
(a)Position, disc(4)×[43]58.248.216.835.030.313.215.011.82.4
(b)Velocity, disc(28)×[53]0.80.10.10.00.00.020.08.72.6
(c)Velocity, disc(28)✓(Ours)97.482.251.0100.078.859.940.028.910.1
", + "image_path": "03074a32ad421d8f21292fb9c6537d826708ec496f726418634b26db920610d5.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_body" + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 48, + 319, + 285, + 378 + ], + "blocks": [ + { + "bbox": [ + 46, + 270, + 548, + 304 + ], + "lines": [ + { + "bbox": [ + 46, + 270, + 548, + 304 + ], + "spans": [ + { + "bbox": [ + 46, + 270, + 548, + 304 + ], + "type": "text", + "content": "Table 1. Impact of training with a realistic dynamical model: we compare end-to-end trained models using position commands (a) as in [43] and, discretized velocity commands without a dynamical model (considering constant velocity) as in [53], and our proposed method (c). The references [43, 53] are cited for their action space and motion handling, but they have different agent architectures." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 319, + 285, + 378 + ], + "lines": [ + { + "bbox": [ + 48, + 319, + 285, + 378 + ], + "spans": [ + { + "bbox": [ + 48, + 319, + 285, + 378 + ], + "type": "table", + "html": "
MethodSim(train)HM3D/2.5kSim(+dyn)HM3D/2.5k
SR%SPL%SCT%SR%SPL%SCT%
(a) Pos, disc(4)92.781.730.358.248.216.8
(b) Vel, disc(28)98.074.258.90.80.10.1
(c) Vel, disc(28)97.482.251.097.482.251.0
", + "image_path": "32913a18fbd837f42ffecc9885331e5dbc93b9e32dc71b5675b8c268d254d15a.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 387, + 288, + 431 + ], + "lines": [ + { + "bbox": [ + 46, + 387, + 288, + 431 + ], + "spans": [ + { + "bbox": [ + 46, + 387, + 288, + 431 + ], + "type": "text", + "content": "Table 2. Difficulty of tasks given action spaces and motion models: we evaluate the baseline model variants in the same simulated environment in which they have been trained. High performance does not necessarily transfer to real. Letters are variants in Table 1." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 449, + 287, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 449, + 287, + 521 + ], + "spans": [ + { + "bbox": [ + 46, + 449, + 287, + 521 + ], + "type": "text", + "content": "in the height of the single Lidar ray. Collisions are frequent, examples are given in Figure 5 (bottom). The agent is also capable of avoiding dynamic obstacles like people in spite of not having seen them in simulation (cf. Figure 6), which we conjecture is due to a high collision avoidance weight in the reward." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 522, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 522, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 522, + 288, + 714 + ], + "type": "text", + "content": "Sim2real gap and memory — one interesting finding we would like to share is that the raw base agent sometimes tends to get discouraged from initially being blocked in a situation, for instance if the passage through a door is not optimal and requires correction. The initial variants of the agent seemed to abandon relatively quickly and started searching for a different trajectory, circumventing the passage way obstacle altogether. We conjecture that this stems from the fact that such blockings are rarely seen in simulation and the agent is trained to \"write off\" this area quickly, storing in its recurrent memory that this path is blocked. All our real experiments are therefore performed with a version, which resets its recurrent state " + }, + { + "bbox": [ + 46, + 522, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{h}_i" + }, + { + "bbox": [ + 46, + 522, + 288, + 714 + ], + "type": "text", + "content": " (eq. (1)) every 10 seconds, leading to less frequent abandoning. Future work will address this problem more directly, for instance by simulating blocking situations during training." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "spans": [ + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "text", + "content": "Influence of motion model — Table 1 compares results of different agents trained with different action spaces and with or without realistic motion during simulation. We can see that the impact of training the agent with the correct motion model in simulation is tremendous. The agent in line (b) uses the same action space, but no dynamical model is used in simulation, which means that changes in velocity are instantaneous and velocities are constant between decisions. The behavior is unexploitable, the agent is disoriented and keeps crashing into its environment. Line (a) corresponds to a position controlled agent with action space {FORWARD " + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "inline_equation", + "content": "25\\mathrm{cm}" + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "text", + "content": ", TURN_LEFT " + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "inline_equation", + "content": "10^{\\circ}" + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "text", + "content": ", TURN_RIGHT " + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "inline_equation", + "content": "10^{\\circ}" + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "text", + "content": ", STOP}. After training, it is adapted to motion commands by calculating the corresponding velocity commands given the decision frequency of " + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "inline_equation", + "content": "3\\mathrm{Hz}" + }, + { + "bbox": [ + 304, + 322, + 547, + 633 + ], + "type": "text", + "content": ". It has somewhat acceptable (but low) performance in simulation, although it does not dispose of a motion model during training. This fact that rotating and linear motion are separated and cannot occur in the same time simplifies the problem and leads to some success in simulation, but this behavior does not transfer well to the real robot. The agent with the identified motion model achieves near perfect SR in simulation, which shows that the model can learn to anticipate motion and (internal latent) future state prediction correctly. When transferred to the real robot, performance is the best among all agents, but still leaves room much room for improvement." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 641, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 641, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 641, + 547, + 713 + ], + "type": "text", + "content": "Difficulty of the tasks — Table 2 compares the same three agents also in simulation when validated with the same setting they have been trained on (action space, motion model or absence of). While this comparison is not at all indicative of the performance of these agents on a real robot, it provides evidence of the difficulty of the task in simulation." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17843" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 70, + 282, + 140 + ], + "blocks": [ + { + "bbox": [ + 51, + 70, + 282, + 140 + ], + "lines": [ + { + "bbox": [ + 51, + 70, + 282, + 140 + ], + "spans": [ + { + "bbox": [ + 51, + 70, + 282, + 140 + ], + "type": "table", + "html": "
Point Goal\\( \\hat{\\mathbf{p}}_t^r \\)\\( \\hat{\\mathbf{p}}_t^a \\)Sim (+dyn)(Office/20)Real (Office/20)
SR%SPL%SCT%SR%SPL%SCT%
g_tXX40.034.527.435.023.65.2
g_0✓✓70.051.936.950.037.511.4
g_0+ superv.✓✓100.078.859.940.028.910.1
g_0+ superv.✓X70.051.936.925.016.73.0
", + "image_path": "602fc77a627fa025f49a6dee3511f49268a921ab2e121b1d39468821dddfd749.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 48, + 213, + 287, + 262 + ], + "blocks": [ + { + "bbox": [ + 46, + 148, + 288, + 204 + ], + "lines": [ + { + "bbox": [ + 46, + 148, + 288, + 204 + ], + "spans": [ + { + "bbox": [ + 46, + 148, + 288, + 204 + ], + "type": "text", + "content": "Table 3. Localization and PointGoal calculation: we compare the impact of the presence of external localization to the agent, and the point goal sources: dynamical point goal (through external localization) with static point goal w/ and w/o supervision. All agents are variant (c) from Table 1." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 48, + 213, + 287, + 262 + ], + "lines": [ + { + "bbox": [ + 48, + 213, + 287, + 262 + ], + "spans": [ + { + "bbox": [ + 48, + 213, + 287, + 262 + ], + "type": "table", + "html": "
MethodReal (Office/20)Real (Office/20-alt)
SR%SPL %SCT%SR%SPL %SCT%
(α) ROS 2 (fused)80.069.526.290.070.527.0
(β) Ours (finetuned)55.040.411.260.042.09.7
", + "image_path": "27a926568b169818aca419093f784f9e86d90516e698e1ce1d8638f18e13cc54.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 270, + 289, + 370 + ], + "lines": [ + { + "bbox": [ + 46, + 270, + 289, + 370 + ], + "spans": [ + { + "bbox": [ + 46, + 270, + 289, + 370 + ], + "type": "text", + "content": "Table 4. Comparisons — we compare with the ROS 2 NavStack, which has access to the 2D occupancy map beforehand, localizes itself with the single ray Lidar scan and AMCL (Monte Carlo localization), uses the fused laserscan for obstacle avoidance, followed by shortest path planning. Metrics do no measure collisions, which are much higher for the ROS 2 planner. To be comparable, our method is finetuned with RL on the Matterport scan of the same building. We also add an experiment on the same office building with a different furniture arrangement, Office/20-alt." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 389, + 287, + 425 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 389, + 287, + 425 + ], + "spans": [ + { + "bbox": [ + 46, + 389, + 287, + 425 + ], + "type": "text", + "content": "Surprisingly, the performances are very close: the additional burden the motion model puts on the learning problem itself can be handled very well by the agent." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "type": "text", + "content": "Goal vector calculation — As explained in Section 3, our base agent receives the static point goal " + }, + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "type": "inline_equation", + "content": "\\mathbf{g}_0" + }, + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "type": "text", + "content": ", i.e. a vector with respect to the initial reference frame at time " + }, + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "type": "inline_equation", + "content": "t = 0" + }, + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "type": "text", + "content": ", which is not updated. Table 3 compares this agent with two other variants. A version where supervision is removed during training, which surprisingly shows good performance. We conjecture that the additional supervision learns integration of odometry which might not transfer well enough from simulation, indicating insufficient noise modeling in simulation. This will be addressed in future work. In another variant the dynamic point goal " + }, + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "type": "inline_equation", + "content": "\\mathbf{g}_t" + }, + { + "bbox": [ + 46, + 426, + 288, + 604 + ], + "type": "text", + "content": " is provided at each time step in the agent's egocentric frame. It is calculated from an external localization source, noisy in simulation. Letting the agent itself take care of the point goal integration seems to be the better solution." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 289, + 715 + ], + "type": "text", + "content": "Comparison with a map based planner — Table 4 compares the method with a ROS 2 based planner, which uses a 2D occupancy map constructed beforehand (not on the fly). To be comparable, we finetuned our agent on a Matterport scan of the same building. While the ROS 2 based planner is still more efficient in terms of SR and time (SCT), it requires many experiments to finetune its parameters. For example, low values for the inflation radius will produce many collisions with tables. But when this parameter is too" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 312, + 74, + 424, + 200 + ], + "blocks": [ + { + "bbox": [ + 312, + 74, + 424, + 200 + ], + "lines": [ + { + "bbox": [ + 312, + 74, + 424, + 200 + ], + "spans": [ + { + "bbox": [ + 312, + 74, + 424, + 200 + ], + "type": "image", + "image_path": "9c98e17ea4bc51f9a7f73339497fd58f44e7a5c2995c2f82a419afa12efcd0e4.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 213, + 547, + 236 + ], + "lines": [ + { + "bbox": [ + 305, + 213, + 547, + 236 + ], + "spans": [ + { + "bbox": [ + 305, + 213, + 547, + 236 + ], + "type": "text", + "content": "Figure 8. Dynamical sim2real gap: we compared recorded trajectories to simulated rollouts obtained with the same actions." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 425, + 74, + 541, + 137 + ], + "blocks": [ + { + "bbox": [ + 425, + 74, + 541, + 137 + ], + "lines": [ + { + "bbox": [ + 425, + 74, + 541, + 137 + ], + "spans": [ + { + "bbox": [ + 425, + 74, + 541, + 137 + ], + "type": "image", + "image_path": "d60cce66845737654b7fb4ca50a2a02f1e7f3a7358ca9b84e2f93cf6dff4f580.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 425, + 138, + 541, + 200 + ], + "blocks": [ + { + "bbox": [ + 425, + 138, + 541, + 200 + ], + "lines": [ + { + "bbox": [ + 425, + 138, + 541, + 200 + ], + "spans": [ + { + "bbox": [ + 425, + 138, + 541, + 200 + ], + "type": "image", + "image_path": "dd77c7ae2b01c9d753e73a590a320cd4e0f0b5860584a136e9ef8769274837d4.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 249, + 545, + 273 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 249, + 545, + 273 + ], + "spans": [ + { + "bbox": [ + 305, + 249, + 545, + 273 + ], + "type": "text", + "content": "high, the planner cannot find any path through doors and corridors." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 274, + 547, + 321 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 274, + 547, + 321 + ], + "spans": [ + { + "bbox": [ + 305, + 274, + 547, + 321 + ], + "type": "text", + "content": "Rearrangement — we test the impact of rearranging furniture significantly in the Office environment (see the supp.mat. for pictures) and show the effect in Table 4, block Office/20-alt. The differences are negligible." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 322, + 547, + 369 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 322, + 547, + 369 + ], + "spans": [ + { + "bbox": [ + 305, + 322, + 547, + 369 + ], + "type": "text", + "content": "Dynamical sim2real gap — Figure 8 compares real robot trajectories obtained by the agent on a small map of " + }, + { + "bbox": [ + 305, + 322, + 547, + 369 + ], + "type": "inline_equation", + "content": "4m \\times 4m" + }, + { + "bbox": [ + 305, + 322, + 547, + 369 + ], + "type": "text", + "content": " with rollouts of the motion model in simulation with the same actions, indicating very small drift." + } + ] + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 307, + 370, + 451, + 494 + ], + "blocks": [ + { + "bbox": [ + 307, + 370, + 451, + 494 + ], + "lines": [ + { + "bbox": [ + 307, + 370, + 451, + 494 + ], + "spans": [ + { + "bbox": [ + 307, + 370, + 451, + 494 + ], + "type": "image", + "image_path": "41b7dddf5ed26b360950746e09747db2466b290158e7814e7360df2dd6154e81.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 502, + 451, + 525 + ], + "lines": [ + { + "bbox": [ + 306, + 502, + 451, + 525 + ], + "spans": [ + { + "bbox": [ + 306, + 502, + 451, + 525 + ], + "type": "text", + "content": "Figure 9. Distribution of actions, Office/20, Sim, Real." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 455, + 371, + 547, + 525 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 455, + 371, + 547, + 525 + ], + "spans": [ + { + "bbox": [ + 455, + 371, + 547, + 525 + ], + "type": "text", + "content": "Actions taken — Figure 9 shows histograms of the actions taken by the action in simulation and in real on Office/20. There is a clear preference for certain combinations of linear and angular velocity. Distributions in sim and real mostly match, except for a tendency to" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 525, + 545, + 550 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 525, + 545, + 550 + ], + "spans": [ + { + "bbox": [ + 305, + 525, + 545, + 550 + ], + "type": "text", + "content": "turn in-place in real, which could be explained by obstacle mis-detections due to scan range noise." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 561, + 379, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 561, + 379, + 574 + ], + "spans": [ + { + "bbox": [ + 306, + 561, + 379, + 574 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "type": "text", + "content": "We have presented an end-to-end trained method for swift and precise navigation which can robustly avoid even thin and finely structured obstacles. This is achieved with training in simulation only by adding a realistic motion model identified from recorded trajectories from a real robot. The method has been extensively evaluated in simulation as well as on a real robotic platform, where we assessed the impact of the motion model, the action space, and the way how a point goal is calculated and provided to the agent. The method is robust, future work will focus on closed-loop adaptation of dynamics and sensor noise estimation." + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "17844" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 289, + 712 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 289, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 289, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 289, + 145 + ], + "type": "text", + "content": "[1] Peter Anderson, Angel X. 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Our proposed self-supervised representation learning method carefully addresses different action orderings, redundant actions, and background frames to generate improved video representations compared to previous methods. Our model generalizes temporal cycle-consistency learning to allow for more flexibility in determining cycle-consistent neighbors. More specifically, to handle repeated actions, we propose a multi-neighbor cycle consistency and a multi-cycle-back regression loss by finding multiple soft nearest neighbors using a Gaussian Mixture Model. To handle background and redundant frames, we introduce a context-dependent drop function in our framework, discouraging the alignment of droppable frames. On the other hand, to learn from videos of multiple activities jointly, we propose a multi-head crosstalk network, allowing us to embed a video and estimate progress without knowing its activity label. Experiments on multiple datasets show that our method outperforms the state-of-the-art for video alignment and progress prediction.", + "bbox": [ + 75, + 318, + 473, + 636 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 685, + 207, + 700 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Understanding progress is central to a human's learning experience. We constantly modify and enhance our actions and behaviors based on our progress in different daily tasks [31]. Progress understanding is also fundamental for machines whose goal is to guide (e.g., assistive technologies) and seamlessly interact (e.g., robots) with humans [6, 35]. Imagine wearing augmented reality (AR) assistant glasses when assembling a complex machine, performing a medical procedure, or cooking a new hour-long recipe. Depending on the amount of progress made in the", + "bbox": [ + 75, + 710, + 468, + 863 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/4bbba8cf86942d1abfdf2269970f12c19990f20d4ac52bcc6512b1b0ba5d457d.jpg", + "image_caption": [ + "Figure 1. We develop a framework for self-supervised in-the-wild video alignment and online activity progress prediction." + ], + "image_footnote": [], + "bbox": [ + 500, + 284, + 880, + 377 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "current step, the AR needs to show information about the current or next step(s). Additionally, progress is an important signal for computer vision tasks to run on AR task assistants, such as action segmentation and anticipation (depending on little/full progress in a step, subsequent frames will belong to the same/next step) [50] and anomaly/errordetection (a decrease in progress indicates an error) [34].", + "bbox": [ + 496, + 431, + 892, + 537 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Learning to predict progress, however, is challenging [8]. Progress can not be precisely calculated solely on the amount of time spent in an action (an expert often makes more progress than a novice within the same time window) and can be influenced by factors other than the user such as the environment (imagine cooking a recipe in a well-organized vs a cluttered kitchen). To estimate progress, we can break down an action into smaller phases and track where the user is within these phases (e.g., putting a coffee filter into a dripper involves taking a filter from its bag, folding it in half, folding it again into a quarter circle, creating a cone and inserting it into the dripper). Therefore, one approach for progress estimation is to label video clips of an action with its different phases and train a supervised phase classification model [3]. However, the ambiguity of defining a dictionary of fine-grained phases in advance and the high cost of annotating video frames with many action phases makes supervised learning impractical.", + "bbox": [ + 496, + 537, + 893, + 809 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Self-supervised video alignment is an appealing alternative for progress prediction. It finds frame representations and associations between frames of different videos (ideally, aligning the same phases across videos), without requiring fine-grained human labeling. There has been a large body of recent literature addressing video alignment", + "bbox": [ + 496, + 810, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "$^{1}$ Code is publicly available at https://github.com/gerardDonahue/GTCC_CVPR2024.", + "bbox": [ + 76, + 875, + 467, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "18667", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "using different approaches, such as temporal cycle consistency (TCC) [12], dynamic time warping [11, 16, 17] and optimal transport [39]. However, after aligning videos and learning the embedding space, progress prediction has been simply treated as fitting a linear regression model to the embeddings by assuming a linear progress model [12, 17, 39].", + "bbox": [ + 75, + 90, + 470, + 183 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Limitations. Existing self-supervised methods have limitations for video alignment as well as progress prediction. First, when it comes to video alignment, the majority of existing works assume the same ordering of phases (monotonic), which is often violated in real videos (e.g., you can put a filter in a dripper and then put the dripper on the mug or vice versa). Additionally, some videos may have additional steps or background, which should not be aligned. Therefore, the recent approach in [39] (coined VAVA) addressed sequence alignment by considering background and redundant frames as well as non-monotonic ordering by imposing a temporal prior and an optimal prior on an optimal transport formulation, an intra-video contrastive term and an inter-video contrastive term. However, balancing multiple losses and handling repeated actions in the self-supervised setting is challenging and enforcing a temporal prior is unfit for in-the-wild alignment. Moreover, existing alignment techniques train distinct models for each action, resulting in substantial memory and computational overhead. This approach also complicates inference since activity/task identification is necessary, posing challenges particularly at the onset of activity/task execution.", + "bbox": [ + 75, + 204, + 472, + 537 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Paper Contributions. In this paper, we develop a framework for self-supervised video alignment and online progress prediction that addresses the limitations of existing works, see Figure 1. We propose a generalization of TCC [12] to model background and redundant frames, as well as repetitive actions when performing alignment. More specifically, to handle repeated actions, we propose a multi-neighbor cycle consistency and a multi-cycle-back regression loss by finding multiple soft nearest neighbors using a Gaussian Mixture Model (GMM) instead of a single neighbor as in TCC. To handle background and redundant frames, we introduce a context-dependent drop function, discouraging the alignment of droppable frames.", + "bbox": [ + 75, + 559, + 470, + 755 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "On the other hand, to effectively align videos of multiple activities jointly and to better leverage their shared information while handling their distinctions, we propose a multi-head crosstask network, where each head automatically learns to focus on relevant components of video pairs. Thus, we can embed a video and estimate progress without knowing its activity label. Through extensive experiments on multiple datasets, we show the effectiveness of our framework for video alignment and progress estimation.", + "bbox": [ + 75, + 763, + 470, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 500, + 89, + 650, + 106 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Self-Supervised Video Representation Learning. Given the high annotation cost for video-based action learning and the need for copious amounts of data when training deep networks, many researchers have turned to self-supervised methods for embedding video frames [9, 28, 38, 42, 45, 60, 72]. Self-supervision has largely been popularized as a result of higher quality image embedding techniques trained on large-scale image datasets such as [10, 27, 37]. With better datasets, pre-trained image encoders, such as [18, 53-55], allow for more meaningful features that can enhance the performance of self-supervised representation learning methods. Many downstream tasks benefit from self-supervised video representation learning, such as action recognition [26, 71], temporal action segmentation [23, 33, 63, 65], step localization [14, 71], video retrieval [68], text-to-video retrieval [41], and audio-visual representation learning [25].", + "bbox": [ + 496, + 114, + 893, + 375 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Video Alignment is the task of temporally synchronizing videos, such that similar frames or segments in separate videos can be mapped to each other. Traditional methods such as Dynamic Time Warping (DTW) [7, 11, 13, 16, 17, 47], or Canonical Correlation Analysis (CCA) [1, 21, 26, 48] have been used to align video frames. Many methods have adopted the use of Soft-DTW [7, 11, 16, 17, 40], where the gradient is well-defined and back-propagation is feasible. LAV [17] is a self-supervised video alignment method, which uses Soft-DTW in conjunction with temporal intra-video contrastive loss terms. Other contrastive approaches include [5, 39, 42, 49, 60, 66]. Drop-DTW [11] extends DTW by adding a \"trash bucket\" to the cost matrix for dynamic programming for background frame classification. Similarly, VAVA [39] added an additional bucket to the optimal transport formulation to align in-the-wild videos. VAVA also incorporated a bi-modal Gaussian prior on the optimal transport matrix, which allowed for the model to consider the temporality and optimality of the alignment. VAVA was shown to outperform previous methods for unconstrained procedural video datasets. Other methods capable of background detection but not video alignment include [4, 43, 51, 61, 62].", + "bbox": [ + 496, + 378, + 893, + 728 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Cycle-consistency has been a pivotal technique in sequence alignment, involving the mapping of elements from one sequence to another, followed by an inverse mapping back to the original sequence. Beyond its application in video alignment, cycle-consistency finds utility in diverse domains, including 3D shape matching [22], depth estimation [15], co-segmentation [57, 58], and transitivity in deep learning [15, 69, 70]. Cycle-consistency was first introduced for self-supervised video alignment in TCC [12] and showed good performance in aligning synchronizable videos, such as the Penn Action dataset [67] or the Pour", + "bbox": [ + 496, + 734, + 895, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "18668", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/3ddc03ec78a02f309031b55b0e8b14c400d226a0bf7cb24f5560f2f669e641a0.jpg", + "image_caption": [ + "Figure 2. Cycle-consistency Visualization. Here, two videos are embedded by the alignment encoder, $\\phi$ . With a green checkmark, a frame pair is shown to be cycle-consistent. With a red X-mark, a frame pair is shown to be not cycle-consistent." + ], + "image_footnote": [], + "bbox": [ + 78, + 85, + 464, + 170 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ing dataset [32]. Our method extends cycle-consistency to unconstrained videos, as observed in many datasets such as COIN [56] and EgoProceL [2].", + "bbox": [ + 75, + 246, + 468, + 292 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Activity Progress Prediction is the task of predicting temporal progress in videos. While [3, 44] have studied a supervised approach for action progress prediction, they require temporal annotations of every action clip based on its phases, which is hard to define given the fine-grained nature of phases and cost to gather. Action completion [19, 20, 59, 68] is also related to progress, however it is only focused on classifying full progress achievement rather than predicting the progress at every time instant. In this work, we learn to predict progress at every frame in a self-supervised framework. Our proposed progress estimation technique also has applications in goal-based reinforcement learning, providing dense reward for learning [29, 64].", + "bbox": [ + 75, + 297, + 470, + 494 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Problem Setting and Review", + "text_level": 1, + "bbox": [ + 76, + 508, + 339, + 525 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we discuss the problem of video alignment and review temporal cycle consistency (TCC) [12], which we build upon and generalize.", + "bbox": [ + 75, + 532, + 468, + 579 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Video Alignment", + "text_level": 1, + "bbox": [ + 76, + 588, + 243, + 603 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given two video sequences $S = (s_1, \\ldots, s_N)$ and $T = (t_1, \\ldots, t_M)$ with $N$ and $M$ frames, respectively, we denote their embeddings by $U = (u_1, \\ldots, u_N)$ and $V = (v_1, \\ldots, v_M)$ . We use an encoder neural network $\\phi$ to compute these embeddings, as depicted in Fig. 2. The goal of video alignment is to train the encoder, $\\phi$ , such that if the two frames $s_i$ and $t_j$ represent the same action, the distance between their embeddings, $u_i \\in \\mathbb{R}^D$ and $v_j \\in \\mathbb{R}^D$ , will be small, otherwise, the distance will be large.", + "bbox": [ + 75, + 609, + 468, + 748 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Temporal Cycle Consistency (TCC)", + "text_level": 1, + "bbox": [ + 76, + 756, + 385, + 772 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "TCC [12] finds a symmetric nearest neighbor embedding space by maximizing the number of cycle-consistent embeddings between two sequences. More specifically, consider a frame $\\boldsymbol{u}_i \\in U$ , and let its Euclidean nearest neighbor from $V$ be denoted by $\\boldsymbol{v}_j = \\operatorname{argmin}_{\\boldsymbol{v} \\in V} \\| \\boldsymbol{u}_i - \\boldsymbol{v} \\|$ . Similarly, for a frame $\\boldsymbol{v}_j \\in V$ , denote its Euclidean nearest neighbor in $U$ by $\\boldsymbol{u}_k = \\operatorname{argmin}_{\\boldsymbol{u} \\in U} \\| \\boldsymbol{u} - \\boldsymbol{v}_j \\|$ . The frame $\\boldsymbol{u}_i$ is cycle-consistent if and only if $i = k$ , see Fig. 2. TCC", + "bbox": [ + 75, + 779, + 470, + 901 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/55b88eb4aa7512424e7eb4a15facd1517b021114ead01010df4caac5c159b78b.jpg", + "image_caption": [ + "(a) TCC" + ], + "image_footnote": [], + "bbox": [ + 506, + 87, + 694, + 169 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/724a60cc507f126190e85c9047e37baf96cf4f9d0c4706637d4cfc131ca96e9a.jpg", + "image_caption": [ + "(b) GTCC", + "Figure 3. TCC Failure for Repeated Actions. Common action segments of the sequences are shown using varying colors. $\\alpha$ is depicted based on the initial frame, $u_{i}$ , from the yellow action segment. TCC (3a) only allows a single $\\tilde{v}$ between both peaks in $\\alpha$ . GTCC (3b) allows for two distinct neighbors, $\\tilde{v}_{1}$ and $\\tilde{v}_{2}$ , which accurately represents repeated actions." + ], + "image_footnote": [], + "bbox": [ + 697, + 85, + 885, + 169 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "trains an encoder to embed frames such that the number of cycle-consistent frame embeddings is maximized across pairs of videos, hence, a symmetric nearest neighbor embedding space. Since argmin is non-differentiable, TCC adopts the softmax operation. Let $\\Delta^M$ denote the probability simplex in $M$ dimensions.2 TCC begins by computing a soft nearest neighbor (SNN) of $\\pmb{u}_i$ , denoted by $\\tilde{\\pmb{v}}$ ,", + "bbox": [ + 496, + 270, + 892, + 377 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {\\boldsymbol {v}} = \\sum_ {j = 1} ^ {M} \\alpha_ {j} \\boldsymbol {v} _ {j}, \\quad \\text {w h e r e ,} \\quad \\alpha_ {j} = \\frac {e ^ {- \\| \\boldsymbol {u} _ {i} - \\boldsymbol {v} _ {j} \\| ^ {2} / \\tau}}{\\sum_ {k = 1} ^ {M} e ^ {- \\| \\boldsymbol {u} _ {i} - \\boldsymbol {v} _ {k} \\| ^ {2} / \\tau}}. \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 509, + 387, + 890, + 429 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Here $\\alpha = [\\alpha_{1},\\ldots ,\\alpha_{M}]\\in \\Delta^{M}$ is the outgoing normalized similarity (forward distribution) between $\\pmb{u}_i$ and embeddings in $V$ , and $\\tau$ is the softmax temperature. TCC then uses the SNN, $\\tilde{\\pmb{v}}$ , to compute $\\beta = [\\beta_{1},\\dots,\\beta_{N}]\\in \\Delta^{N}$ , which is the incoming normalized similarity (backward distribution) between $\\tilde{\\pmb{v}}$ and frame embeddings in $U$ ,", + "bbox": [ + 496, + 441, + 893, + 532 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\beta_ {l} = \\frac {e ^ {- \\| \\boldsymbol {u} _ {l} - \\tilde {\\boldsymbol {v}} \\| ^ {2} / \\tau}}{\\sum_ {j = 1} ^ {N} e ^ {- \\| \\boldsymbol {u} _ {j} - \\tilde {\\boldsymbol {v}} \\| ^ {2} / \\tau}}. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 604, + 542, + 890, + 584 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Cycle-consistency requires that $\\beta$ must have the highest probability mass at index $i$ and very small mass at indices farther from $i$ . Thus, TCC imposes a Gaussian distribution prior $\\mathcal{N}(\\mu_{\\beta},\\sigma_{\\beta}^{2})$ on entries of $\\beta$ with mean $\\mu_{\\beta} = \\sum_{l = 1}^{N}\\beta_{l}\\cdot l$ and variance $\\sigma_{\\beta}^{2} = \\sum_{l = 1}^{N}\\beta_{l}\\cdot (l - \\mu_{\\beta})^{2}$ . Requiring that the distribution mean be close to $i$ with a small variance leads to minimizing a cycle-back regression loss, defined as", + "bbox": [ + 496, + 593, + 893, + 703 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {c b r}} = \\frac {(i - \\mu_ {\\beta}) ^ {2}}{\\sigma_ {\\beta} ^ {2}} + \\lambda \\log (\\sigma_ {\\beta}), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 589, + 712, + 890, + 751 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\lambda$ is the regularization weight. This leads to a differentiable loss that can be optimized using backpropagation.", + "bbox": [ + 496, + 760, + 890, + 791 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Generalized Temporal Cycle Consistency (GTCC)", + "text_level": 1, + "bbox": [ + 496, + 804, + 890, + 838 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "One of the advantages of TCC [12] compared to DTW-based methods [11, 17] is that it does not assume/enforce", + "bbox": [ + 496, + 847, + 890, + 878 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "${}^{2}\\mathbf{\\alpha } \\in {\\Delta }^{M}$ means that vector entries are nonnegative and sum to one.", + "bbox": [ + 514, + 886, + 883, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "18669", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/966ed83a18e8b2ab8e3f38678d3afc2dc19b4e71a72eeb96697ef505ff5ee8bc.jpg", + "image_caption": [ + "Figure 4. GTCC. We encode two videos into $\\mathbf{U}$ and $\\mathbf{V}$ and calculate the forward distribution, $\\alpha$ . We use the output of the GMM optimization procedure and obtain $K$ SNNs from $K$ discrete Gaussians. We then compute $\\beta^{(k)}$ for each SNN. We also estimate the drop probability of each frame $\\mathrm{P}_{\\mathrm{drop}}(\\pmb{u}_i|\\mathbf{V})$ using a conditional network. Finally, we compute the final loss by weighting each cycle-back regression loss with weight from mixture densities, $\\psi$ , and modulate with the drop probabilities." + ], + "image_footnote": [], + "bbox": [ + 78, + 90, + 893, + 188 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "monotonic ordering of actions across videos. On the other hand, it has two major drawbacks when it comes to aligning in-the-wild videos.", + "bbox": [ + 75, + 267, + 468, + 311 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "First, TCC cannot handle background and additional actions, because it enforces cycle-consistency for every frame embedding. However, background actions (e.g., 'answering phone' when making coffee) or additional actions (e.g., the optional step of 'cleaning coffee filter') in one video but not in another should not be aligned.", + "bbox": [ + 75, + 313, + 468, + 404 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Second, the TCC model assumes that each action only appears once in a video, therefore, cannot model action repetitions (e.g., repeating the actions of 'give breath' and 'give chest compression' when performing CPR). This is because computing the SNN in TCC is done with a unimodal Gaussian assumption on the similarity distributions, which is violated when an action is repeated in a video and leads to computing bad SNNs, see Fig. 3. We propose generalized temporal cycle consistency (GTCC), which addresses these limitations and aligns videos in the wild.", + "bbox": [ + 75, + 405, + 468, + 555 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Multi-Cycle Consistency via Mixture SNNs", + "text_level": 1, + "bbox": [ + 76, + 566, + 442, + 583 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We propose multi-neighbor cycle consistency and a multicycle-back regression loss to handle repeated actions, see Fig. 4. For $\\pmb{u}_i \\in U$ belonging to an action $a$ , a single SNN $\\tilde{\\pmb{v}}$ obtained using (1) is restrictive when action $a$ is repeated in the sequence $V$ . In such a case, as 3 shows, $\\pmb{u}_i$ will have multiple good nearest neighbors, yet the SNN $\\tilde{\\pmb{v}}$ captures an average representation of them leading to a suboptimal solution. Therefore, we generalize TCC to allow for multiple SNNs and to assign an importance score to each SNN. This allows our model to find a set of SNNs based on a given $\\pmb{u}_i$ , and to automatically gain awareness of their relative importance for promoting multiple-neighbor cycle-consistency.", + "bbox": [ + 75, + 590, + 468, + 772 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For $\\pmb{u}_i \\in U$ , we first obtain the outgoing distribution $\\alpha = [\\alpha_1, \\dots, \\alpha_M]$ , where $\\alpha_j$ 's are computed using (1). We then approximate $\\alpha$ with a discretized Gaussian Mixture Model (GMM) to capture different distribution modes corresponding to the same action. More specifically, we model", + "bbox": [ + 75, + 773, + 468, + 849 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\alpha_ {j} \\approx p _ {j} = \\sum_ {k = 1} ^ {K} \\psi_ {k} p _ {j} ^ {(k)}, \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 192, + 861, + 468, + 904 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $p_j^{(k)}$ is the outgoing probability of index $j$ in video $\\mathbf{V}$ for the $k$ -th discretized Gaussian distribution $\\mathcal{N}(\\mu_{\\alpha,k}, \\sigma_{\\alpha,k}^2)$ and $\\psi_k$ denotes the weight of the mixture component $k$ . Here, $K$ is a hyperparameter defining the total number of mixture components. We typically set $K = 10$ in our experiments and as we show the results do not change much for different values of $K$ as long as it is not very small. We find the parameters of the GMM, which are $\\{\\mu_k, \\sigma_k^2, \\psi_k\\}_{k=1}^K$ , by minimizing the KL divergence [52] between the two distributions $[\\alpha_1, \\ldots, \\alpha_M]$ and $[p_1, \\ldots, p_M]$ . After finding the parameters of the GMM, we then compute one SNN for each mixture component,", + "bbox": [ + 496, + 266, + 893, + 450 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {\\boldsymbol {v}} ^ {(k)} = \\sum_ {j = 1} ^ {M} p _ {j} ^ {(k)} \\cdot \\boldsymbol {v} _ {j}, \\quad \\forall k \\in \\{1, \\dots , K \\}. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 558, + 455, + 890, + 500 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "With these $K$ SNNs of $\\pmb{u}_i\\in \\pmb{U}$ , we then compute the incoming similarity distribution $\\beta^{(k)}$ for each SNN, $\\tilde{\\pmb{v}}^{(k)}$ . TCC assumes that throughout the sequence $\\pmb{U}$ , $\\beta$ should only have a sharp peak at index $i$ . For in-the-wild videos, this presents a challenge when $\\pmb{u}_i$ belongs to a repeated or non-contiguous action segment, where there would be more than one valid peak in the incoming distribution. To address this, we only enforce a local sharp peak around $i$ for a discrete temporal window, $w$ , where any index outside the $i$ -centered window has zero probability (see supplementary materials for more details). For each $\\beta^{(k)}$ , we compute the mean and variance over the indices of $\\pmb{U}$", + "bbox": [ + 496, + 503, + 893, + 684 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mu_ {\\beta , k} = \\sum_ {l = 1} ^ {N} \\beta_ {l} ^ {(k)} \\cdot l, \\quad \\sigma_ {\\beta , k} ^ {2} = \\sum_ {l = 1} ^ {N} \\beta_ {l} ^ {(k)} \\cdot (l - \\mu_ {\\beta , k}) ^ {2}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 511, + 689, + 890, + 732 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Finally, we compute one cycle-back regression loss for each mixture component as", + "bbox": [ + 496, + 736, + 890, + 766 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {c b r}} ^ {(k)} = \\frac {\\left(i - \\mu_ {\\beta , k}\\right) ^ {2}}{\\sigma_ {\\beta , k} ^ {2}} + \\lambda \\cdot \\log (\\sigma_ {\\beta , k}). \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 571, + 771, + 890, + 809 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given that $\\psi_{k}$ is the relative importance of the $k$ -th discrete Gaussian distribution, we build a multi-cycle back regression loss as", + "bbox": [ + 496, + 814, + 890, + 857 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {m u l t i - c b r}} = \\sum_ {k = 1} ^ {K} \\psi_ {k} \\cdot \\mathcal {L} _ {\\text {c b r}} ^ {(k)}. \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 609, + 862, + 890, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "18670", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/feac05244c55a31fc7347e273b2a78881fef57f2a90c4ab89735abd38d6be432.jpg", + "image_caption": [ + "Figure 5. Multi-head Crosstalk Network (MCN). Input frames, $S$ , are given to the base network to obtain base features, $U^b$ , which are subsequently given to $L$ head networks that output intermediate video encodings, $\\{U_l^h\\}_{l=1}^L$ . We obtain the final video encoding $U$ using attention over the outputs of the $L$ heads." + ], + "image_footnote": [], + "bbox": [ + 93, + 88, + 452, + 219 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Droppable Frame Detection", + "text_level": 1, + "bbox": [ + 76, + 318, + 328, + 335 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Another major limitation of TCC is that it cannot handle background and additional actions since it enforces cycle-consistency for all embeddings. GTCC addresses this issue by detecting frames in $U$ to be dropped based on the frames in $V$ and subsequently enforcing (i) multi-cycle consistency for alignable embeddings and (ii) bad alignment for droppable embeddings. Information (context) from video $V$ is necessary when dropping frames in video $U$ because the model can not know to drop frames corresponding to an additional action unless that action is not present in $V$ .", + "bbox": [ + 75, + 340, + 468, + 492 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "More specifically, we learn a drop-context function, $c: \\mathbb{R}^D \\to \\mathbb{R}^{D+1}$ , characterized by a feedforward neural network, using all the embeddings $v_j \\in V$ as", + "bbox": [ + 76, + 493, + 468, + 539 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {c} (\\boldsymbol {V}) = \\frac {1}{M} \\sum_ {j = 1} ^ {M} \\boldsymbol {c} \\left(\\boldsymbol {v} _ {j}\\right) \\in \\mathbb {R} ^ {D + 1}. \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 163, + 546, + 468, + 588 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "GTCC uses the information in $\\mathbf{V}$ to condition the drop detection in $\\mathbf{U}$ . More specifically, for each $\\pmb{u}_i\\in U$ , we use a logistic regression model to compute the probability of dropping $\\pmb{u}_i$ given $\\mathbf{V}$ as", + "bbox": [ + 75, + 594, + 468, + 655 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {P} _ {\\text {d r o p}} \\left(\\boldsymbol {u} _ {i} \\mid \\boldsymbol {V}\\right) = \\sigma \\left(\\left[ \\boldsymbol {u} _ {i} ^ {\\top} \\quad 1 \\right] \\boldsymbol {c} (\\boldsymbol {V})\\right), \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 151, + 659, + 468, + 680 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\sigma$ is the sigmoid function. We use the drop probability to build our final loss function, which we discuss next.", + "bbox": [ + 75, + 685, + 468, + 715 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3. Learning GTCC", + "text_level": 1, + "bbox": [ + 76, + 722, + 241, + 738 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To learn the parameters of the embedding network $\\phi$ and the drop-context model, we propose a loss so that alignable frames are encouraged to have good cycle-consistency and droppable frames are encouraged to have bad alignment. This dichotomy isolates the cycle-consistency property only to frames that are deemed 'alignable', and ensures frames deemed 'droppable' have no good nearest neighbors. We propose to minimize", + "bbox": [ + 75, + 744, + 468, + 866 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\left(1 - \\mathrm {P} _ {\\text {d r o p}} (\\boldsymbol {u} _ {i} | \\boldsymbol {V})\\right) \\cdot \\mathcal {L} _ {\\text {m u l t i - c b r}} + \\frac {\\mathrm {P} _ {\\text {d r o p}} (\\boldsymbol {u} _ {i} | \\boldsymbol {V})}{\\mathcal {L} _ {\\text {m u l t i - c b r}}}, \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 871, + 468, + 906 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where we minimize the multi-cycle-back regression loss for alignable frames for which $\\mathrm{P}_{\\mathrm{drop}}(\\pmb {u}_i|\\pmb {V})$ is close to 0, and maximize the multi-cycle-back regression loss for drop-. pable frames for which $\\mathrm{P}_{\\mathrm{drop}}(\\pmb {u}_i|\\pmb {V})$ is close to 1. Notice one can also use $-\\mathcal{L}_{\\mathrm{multi - cbr}}$ instead of $1 / \\mathcal{L}_{\\mathrm{multi - cbr}}$ in (11), however, the latter worked better in our experiments.", + "bbox": [ + 496, + 90, + 890, + 181 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.4. Online Progress Estimation", + "text_level": 1, + "bbox": [ + 498, + 191, + 746, + 207 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "At inference time, given an online sequence up to frame $\\pmb{u}_i$ , we want to estimate the progress, denoted by $\\hat{\\pi}(\\pmb{u}_i) \\in [0,1]$ . We do so, by using the cumulative inter-frame geodesic distance on the frame features,", + "bbox": [ + 496, + 214, + 890, + 273 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\pi} \\left(\\boldsymbol {u} _ {i}\\right) = \\frac {\\sum_ {t = 1} ^ {i - 1} \\left\\| \\boldsymbol {u} _ {t + 1} - \\boldsymbol {u} _ {t} \\right\\|}{\\hat {G}}, \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 593, + 284, + 890, + 319 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\hat{G}$ is ideally the total geodesic distance for the complete sequence (including past and future observations). Given that we do not have access to the future frames, we estimate $\\hat{G}$ by averaging the total geodesic distances for all aligned training videos of the given task.", + "bbox": [ + 496, + 330, + 890, + 407 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. GTCC Embedding Network", + "text_level": 1, + "bbox": [ + 498, + 421, + 761, + 438 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Our goal is to train an embedding model that can leverage the shared information across related actions or tasks (e.g., making otime and making scrambled eggs) for better feature learning and alignment of each task individually, while not requiring to know the action or task label of the video at inference time. Existing works, which train a separate model for each action/task, have neither of these capabilities. Therefore, we propose a new architecture, which we refer to as Multi-head Crosstalk Network (MCN), shown in Fig. 5. MCN consists of a base network, multiple head networks, and an attention network. MCN base network is intended to output general useful features (across actions/tasks) to be used by multiple $(L)$ head networks. Ideally, each head network specializes in aligning related phases of an action or steps of a task. The attention network takes all features from the head networks at each time instant and selects the relevant head and its features. See the supplemental material for more details.", + "bbox": [ + 496, + 446, + 890, + 718 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "6. Experiments", + "text_level": 1, + "bbox": [ + 500, + 732, + 633, + 750 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "6.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 500, + 756, + 689, + 773 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We use four datasets for evaluations, two monotonic and two in-the-wild datasets. Similar to previous works [12, 17, 39], we report results on Pouring [32] and Penn Action [67] datasets, which are monotonic. Pouring contains videos of humans pouring liquid into a cup (e.g., orange juice poured into a blue cup), and Penn Action contains videos of humans completing athletic maneuvers (e.g., a woman serving a tennis ball). We also use COIN [56]", + "bbox": [ + 496, + 779, + 890, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "18671", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "and EgoProceL [2], which are in-the-wild datasets, consisting of background frames, action repetitions, and different sequences of actions. EgoProceL is an egocentric dataset comprised of a collection of several datasets, including CMU-MMAC [30], EGTEA Gaze+ [36], MECCANO [46], and EPIC-tent [24].", + "bbox": [ + 75, + 90, + 467, + 181 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For Pouring, Penn Action, and COIN, we use $75\\%$ of videos for training and $25\\%$ for testing, while for EgoProceL we use $70\\%$ for training and $30\\%$ for testing since there are fewer videos per task. We also study two settings for evaluation. (i) Similar to prior works, we train a model separately for videos of each activity (single-task setting), whereas following other works we use an embedding network that corresponds to the base network in Fig. 5. (ii) We train a single model on videos of all activities jointly (multi-task setting). In Tab. 4, we test the multi-task setting using only the base network vs the full MCN architecture.", + "bbox": [ + 75, + 181, + 467, + 348 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation Metrics. We use multiple metrics to evaluate the performance of different methods for alignment and progress prediction. For evaluating alignment, we use the existing metrics Phase Classification (PC) [12], Enclosed Area Error (EAE) [13] and Kendall's Tau (KT) [12]. PC measures how well the encoder can put frames belonging to the same action class together, thus a higher value is better. Similar to previous works, we use PC, where an SVM classifier is trained on $10\\%$ , $50\\%$ , and $100\\%$ of the ground-truth action labels. While PC measures how well different actions are separated from each other, it does not measure the quality of alignment within each action. Thus, we use Enclosed Area Error (EAE) that measures the alignment error within and across actions by comparing the nearest neighbors between two videos with their ground-truth alignment. When computing EAE for in-the-wild video pairs, we only include alignable frames in the computation. In cases where a frame has multiple valid neighbors, we calculate the smallest EAE among the set of neighbors. EAE is an error metric, therefore lower values indicate better alignment. See [13] for more details about EAE.", + "bbox": [ + 75, + 356, + 467, + 672 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "KT is a statistical measure that indicates how well-aligned two sequences are temporally. Given that KT is only suitable for monotonic sequences, we also propose a modified Kendall's Tau for in-the-wild datasets, which we call Kendall's Tau in the Wild (KTW). More specifically, we only evaluate KT on alignable frames and consider all variations of valid alignment for concordancy. This increases forgiveness when finding concordant pairs, because there may be many concordant neighbors for a frame in a redundant action segment. Therefore, KTW highlights the presence of disconcordant pairs.", + "bbox": [ + 75, + 672, + 467, + 839 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To evaluate progress estimation, we use PHase Progression (PHP) [12] and introduce Online Progress Error (OPE). PHP trains a linear regressor over frame features to predict ground-truth progress values and computes the av", + "bbox": [ + 75, + 839, + 467, + 900 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/1ddd7c5cce0bdd4c0830da9e8c53991266c361186b6fd48f0f9dc41cc6348ff3.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DatasetModelPC↑EAE↓KT↑PHP↑OPE↓
0.10.51.0
PouringSAL85.787.888.0—73.374.5—
TCN89.290.490.4—86.780.6—
TCC89.291.491.814.085.280.338.9
LAV91.692.892.89.085.680.531.4
VAVA91.791.892.529.687.683.637.8
GTCC71.289.293.57.988.185.822.5
Penn ActionSAL74.978.380.0—63.459.4—
TCN82.083.784.0—73.367.6—
TCC81.383.484.518.273.567.335.5
LAV83.684.084.320.580.566.125.5
VAVA83.984.084.523.280.570.980.5
GTCC78.381.281.316.788.370.814.5
", + "bbox": [ + 509, + 89, + 882, + 234 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/3f447bf0dcb6c4900d802f622246e37fb72d3af7168554e92194520e8ef6b5af.jpg", + "table_caption": [ + "Table 1. Alignment and progress evaluations on monotonic datasets." + ], + "table_footnote": [], + "table_body": "
DatasetModelPC ↑EAE ↓KTW ↑OPE ↓
0.10.51.0
EgoProceLTCC66.067.468.321.513.934.0
LAV67.268.268.820.812.736.2
VAVA65.365.966.323.213.135.5
GTCC75.078.980.613.314.013.6
COINTCC35.939.640.728.018.828.7
LAV36.838.939.826.723.222.7
VAVA43.846.247.332.022.227.6
GTCC46.853.256.318.929.021.4
", + "bbox": [ + 509, + 267, + 882, + 388 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Alignment and progress evaluations on in-the-wild datasets.", + "bbox": [ + 509, + 392, + 879, + 405 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "erage $R$ -squared measure over all videos. PHP assumes monotonicity in action sequences and, therefore, is only evaluated on the monotonic datasets. On the other hand, our online progress estimation in (12) applies to monotonic and in-the-wild datasets. Following [3], at each frame $\\pmb{u}_i$ we define a ground-truth progress value $\\pi (\\pmb{u}_i)\\in [0,1]$ assuming that (i) each action segment contributes equally to the overall progress, and (ii) progress linearly increases throughout the duration of each action segment. We assume that silent frames do not contribute to progress, hence progress values remain constant during silent segments, see 6. We define OPE as the mean absolute difference between predicted progress and ground-truth online progress (lower is better).", + "bbox": [ + 496, + 426, + 890, + 623 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. For the single-task setting, we compare our GTCC against SAL [42], TCN [49], TCC [12], LAV [17] and VAVA [39]. Among them, only VAVA is specifically designed for handling in-the-wild videos. For the multi-task setting, we compare GTCC with LAV and VAVA, which are state-of-the-art.", + "bbox": [ + 496, + 633, + 890, + 722 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "On the Penn Action, Pouring, and COIN datasets, for the single-task setting, we report the PC, PHP, and KT as previously reported in the most recent work [39]. Given that previous methods did not report EAE, KTW, and OPE, we re-implement all baselines on all datasets to report the performance based on these metrics. Similarly, we reproduce all numbers for the MCN multi-task (Table 4) and the EgoProceL experiments (Tables 2, 3, 4, 5, 6).", + "bbox": [ + 496, + 724, + 890, + 844 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation Details For the single-task setting, following all previous baselines, we use ResNet-50 [18] for the architecture of the encoder network. Please see [12] for more", + "bbox": [ + 496, + 854, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "18672", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/b5d52a41a1cbda695f37148db223cbecde1801e791f8abac74d3a1d5f0ef983d.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DatasetModelPrecisionRecallF1Accuracy
EgoProceLVAVA66.098.477.064.3
GTCC67.597.978.268.9
COINVAVA41.778.853.544.7
GTCC51.988.265.362.0
", + "bbox": [ + 98, + 88, + 446, + 167 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/4d955577ce21554bdd211b6bddd50aec655fc08e8ae561dce5b38d25aa72f247.jpg", + "table_caption": [ + "Table 3. Evaluation of handling background actions (i.e., drop) of VAVA vs GTCC for the in-the-wild datasets." + ], + "table_footnote": [], + "table_body": "
DatasetMethodArch.PC↑EAE↓KT↑KTW↑PHP↑OPE↓
CMU-MMACLAVResNet65.222.2—6.8—18.2
MCN69.813.4—12.1—16.1
VAVAResNet62.524.0—5.1—20.7
MCN63.719.7—11.4—17.9
GTCCResNet70.426.8—9.0—25.2
MCN67.814.9—21.8—14.0
EGTEALAVResNet82.519.7—2.8—17.9
MCN82.111.4—38.7—22.4
VAVAResNet83.219.6—2.7—19.6
MCN82.310.7—38.1—19.7
GTCCResNet83.617.2—3.3—19.5
MCN82.510.2—47.6—16.0
Penn ActionLAVResNet78.720.568.4—62.527.7
MCN85.35.794.3—69.08.6
VAVAResNet80.326.276.2—64.837.9
MCN85.45.994.4—72.614.3
GTCCResNet73.924.760.7—69.732.9
MCN86.75.694.9—85.59.4
", + "bbox": [ + 84, + 208, + 460, + 436 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 4. Alignment and progress evaluation for the multi-task setting when training on ResNet-50 vs our proposed MCN architecture.", + "bbox": [ + 76, + 441, + 468, + 467 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "details regarding the encoder architecture. For the multi-task setting, we compare the ResNet-50 embedding network with our multi-head crosstalk network (MCN), shown in Fig. 5, where the base network is ResNet-50 and all head and attention networks are 4-layer fully-connected feedforward network. For GTCC, we also simultaneously train a 4-layer feedforward neural network for the drop-context function, $\\mathbf{c}$ , in Sec. 4.2. We use $K = 15$ for in-the-wild datasets and $K = 5$ for monotonic datasets. For multi-task experiments using MCN, we set the number of attention heads to be the number of tasks in the dataset.", + "bbox": [ + 75, + 489, + 468, + 655 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "6.2. Experimental Results", + "text_level": 1, + "bbox": [ + 76, + 666, + 279, + 681 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Single-Task Setting Results. Table 1 and 2 show the alignment and progress estimation evaluation of different methods for monotonic and in-the-wild datasets, respectively. Notice that for the monotonic datasets in Table 1, GTCC achieves significantly better EAE (for alignment) and OPE (for progress) on both datasets, e.g., improving the OPE from $25.5\\%$ to $14.5\\%$ and EAE from $18.2\\%$ to $16.7\\%$ on Penn Action. Similarly, our method achieves higher KT values, especially on Penn Action, where it outperforms other methods by at least $7.8\\%$ . However, GTCC mostly does not improve the PC values of the baselines. This is because PC does not directly represent precise alignment but instead measures the effectiveness of clustering action segments.", + "bbox": [ + 75, + 688, + 468, + 883 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "On the other hand, as the results in Table 2 show,", + "bbox": [ + 96, + 886, + 468, + 898 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/0f152b3b25950650128d033047c5c997db9ba2fd25c0c69eefe44a9f2750ec58.jpg", + "image_caption": [ + "(a) GTCC" + ], + "image_footnote": [], + "bbox": [ + 509, + 92, + 689, + 190 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/c1ecabf61b822a1d11e6b0069c1fb8f4ec0e99710fa9f79653c8d92854fe7431.jpg", + "image_caption": [ + "(b) VAVA" + ], + "image_footnote": [], + "bbox": [ + 700, + 92, + 880, + 191 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/6b062240a71ce69234edf228dd5720343c00b1b5257138913d338910e8ccada4.jpg", + "image_caption": [ + "(c) LAV" + ], + "image_footnote": [], + "bbox": [ + 506, + 208, + 687, + 306 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/0527513895fbb74ff83d2ac3c0ef02f074e64b1550ce08cfe6f687ef5f06f420.jpg", + "image_caption": [ + "(d) TCC", + "Figure 6. Online progress estimation for GTCC (6a), VAVA (6b), LAV (6c) and TCC (6d) for a video from the task \"making brownies\" in the EgoProceL dataset." + ], + "image_footnote": [], + "bbox": [ + 699, + 208, + 879, + 306 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "GTCC significantly outperforms all baselines for all metrics. Specifically, GTCC improves the EAE by at least $7.5\\%$ on both EgoProceL and COIN and reduces OPE from $34.0\\%$ to $13.6\\%$ on EgoProceL and from $22.7\\%$ to $21.4\\%$ on COIN. Similarly, our method significantly improves the PC and KTW over the state-of-the-art. This is thanks to the fact that GTCC is specifically designed to handle inthe-wild videos that contain action repetitions, background activities, and action ordering variations.", + "bbox": [ + 496, + 383, + 890, + 518 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Drop Performance. Table 3 compares the effectiveness of VAVA and GTCC for handling background activities on in-the-wild datasets for the single-task setting. We measure the precision, recall, F1 score, and accuracy of dropping background frames during pairwise alignment. Notice that on both datasets, GTCC has a higher F1 score and accuracy. Notably, GTCC achieves $62.0\\%$ accuracy on COIN compared to $44.7\\%$ by VAVA and obtains $68.9\\%$ accuracy on EgoProceL compared to $64.3\\%$ by VAVA. This shows the effectiveness of our context-based drop and alignment, which jointly learns alignable and droppable frames with a soft probabilistic approach.", + "bbox": [ + 496, + 527, + 892, + 710 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Multi-Task Setting Results. In Table 4, we show the alignment and progress evaluations of LAV, VAVA, and GTCC for the multi-task setting, where we use all videos in each dataset to learn a single embedding network. We compare using ResNet-50 with using our proposed MCN architecture. Since GTCC outperformed TCC on progress and alignment metrics in the previous experiments, we do not report the results for TCC. As the results demonstrate, using ResNet for embedding in the multi-task setting leads to generally low performances for all methods. For example, on CMU-MMAC, KTW is less than $9\\%$ and EAE is more than $22\\%$ for all methods (similarly on EGTEA). On the other", + "bbox": [ + 496, + 719, + 892, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "18673", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/82ce6af0a632d6a59a1e01c07765bddc783a7e2f7aa8fb3752d58e6f56f59e0c.jpg", + "image_caption": [ + "Figure 7. Task Progression. Frames from a video of the \"pizza\" task in EgoProceL. On top is the ground-truth progress $(\\pi_{\\mathrm{gt}})$ , in green is the geodesic progress from GTCC $(\\pi_{\\mathrm{geo}})$ , and in red is the trivial progress $(\\pi_{\\mathrm{triv}})$ obtained by dividing test video time-steps by mean total video length from the train set." + ], + "image_footnote": [], + "bbox": [ + 86, + 87, + 197, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/b8862a86b9975cd36c5bd0ec9c0130ff690b2c8411453257ee8c3017e2b69e94.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 202, + 88, + 313, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ad6dffdc4953f16821ca84750b789d2240af0456cf264271ec10d05a0de6bf32.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 316, + 88, + 424, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/2ced7ee80cba1d0a3c09817338d956f38b2a85a5524f84896446e54d30a0d5f6.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 426, + 88, + 537, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e1d95b2f7fc2436c40628549a6a7d65c30518eefdeb8500ff504a81c44ed2686.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 537, + 88, + 648, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/05b42fd80a3f1e129e2ad7fdc602729d2a920cc87b01a8fe70dd599d33915d55.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 651, + 88, + 761, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/2b283c4257536ea191704f5c986fed8d2621806dc8d4928df98b015e76889663.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 764, + 88, + 874, + 186 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/ec61253cf805f8dd30d9a51e6cf14b8bf1a874e928829bb4e98dc7984e66ee42.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
EAE ↓OPE ↓PC(1.0) ↑
K151015151015151015
EgoP19.419.218.719.420.420.020.320.973.974.875.574.3
COIN23.221.422.218.925.523.122.021.450.149.648.946.8
Pour11.611.111.711.59.712.310.910.287.184.984.986.3
Penn26.716.016.116.115.216.717.816.780.078.278.2278.9
", + "bbox": [ + 81, + 229, + 465, + 321 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "hand, $\\frac{6}{9}$ PC metrics, $\\frac{9}{9}$ EAE metrics, $\\frac{3}{3}$ KT metrics, $\\frac{6}{6}$ KTW metrics, $\\frac{3}{3}$ PHP metrics, and $\\frac{7}{9}$ OPE metrics show improvement with the MCN architecture. Table 4 shows that when using MCN, the EAE, KT, KTW, and PHP metrics outperform $100\\%$ of the time, while PC and OPE outperform $67\\%$ and $78\\%$ of the time. This is because our architecture learns to specialize multiple heads for related actions using attention, while ResNet trains a single shared base model for all actions including the ones that are considerably different (e.g., serving tennis and jumping jack).", + "bbox": [ + 75, + 366, + 468, + 518 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "GMM Tuning and Ablations. Table 5 shows the effect of the number of mixture components, $K$ , in the GMM on alignment and progress performance for GTCC. Notice that performance does not vary much under different values of $K$ , showing the robustness of our approach. It is important to note that, as expected, $K = 1$ performs better comparatively on monotonic datasets than in-the-wild datasets.", + "bbox": [ + 75, + 527, + 468, + 633 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 6 ablates the number of MCN heads (6a), and the drop term in GTCC (6b). We gather from 6a that alignment performance improves when the number of MCN heads scales alongside the number of tasks in the dataset (5 for both EGTEA Gaze+ and CMU-MMAC, which have 5 tasks). Finally, we see in 6b that the removal of the drop term leads to degraded performance, further showing the importance of the drop term in GTCC.", + "bbox": [ + 75, + 633, + 468, + 755 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Qualitative Results. In Fig. 6, we show the comparison of different methods for online progress estimation on a test video from the task \"making brownies\" from the EgoProceL dataset. For each method, we show the ground-truth progress vs progress estimated via (12), $\\hat{\\pi}$ , using the learned embeddings. Notice that GTCC's estimation of the progress fits the ground-truth nicely, while other methods have a large gap. This is because GTCC can effectively drop frames that correspond to background, while obtaining an", + "bbox": [ + 75, + 763, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/97736f94ff9e710fc7697054266d8388d69e00783422f5678cdc93611323c111.jpg", + "image_caption": [ + "Figure 8. In-the-wild Frame Retrieval from COIN dataset." + ], + "image_footnote": [], + "bbox": [ + 506, + 239, + 885, + 368 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/f5eff221ad7b7ac900a6cc868598ca698852441bd899081aca1a4f2b9ad56dee.jpg", + "table_caption": [ + "Table 5. Effect of the number of GMM components, $K$ ,on GTCC." + ], + "table_footnote": [ + "(a) Number of MCN heads." + ], + "table_body": "
PC(1.0)↑EAE↓
# Heads15201520
CMU66.767.864.729.514.929.0
EGTEA82.382.582.015.510.219.3
", + "bbox": [ + 503, + 404, + 697, + 459 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/53182b1e909cf78bd3813777fb65f2eed2bd4b92e7ccd76aacb0723b67797adc.jpg", + "table_caption": [], + "table_footnote": [ + "(b) With $(\\checkmark)$ , without $(\\times)$ dropout" + ], + "table_body": "
PC(1.0)↑EAE↓
Drop✓×✓×
Ego80.665.213.324.3
COIN56.346.618.927.9
", + "bbox": [ + 710, + 404, + 885, + 458 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 6. Ablation studies on (a) Number of MCN heads, (b) Drop.", + "bbox": [ + 517, + 474, + 872, + 487 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "embedding space where different actions are well-aligned. In Fig. 7, we show the ground-truth, trivial estimate via frame-counting, and $\\hat{\\pi}$ by GTCC from a EgoProceL video. Notice GTCC can effectively predict the progress online and better than the trivial estimate from frame-counting. In Fig. 8, we show results for in-the-wild frame retrieval for GTCC on the COIN dataset. This figure showcases the ability of GTCC to align frames with high visual similarity.", + "bbox": [ + 496, + 508, + 890, + 628 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "7. Conclusions", + "text_level": 1, + "bbox": [ + 500, + 643, + 625, + 659 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We studied a self-supervised approach, based on a proposed generalized temporal cycle consistency (GTCC) method, for video alignment and progress prediction, coupled with a novel attention-based architecture for multi-task learning. Our extensive experiments show that GTCC outperforms the state of the art, especially for in-the-wild videos. Additionally, we highlight the efficacy of our MCN architecture for enhancing multi-task learning. The fusion of GTCC and MCN emerges as a competitive and versatile framework.", + "bbox": [ + 496, + 670, + 890, + 806 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements", + "text_level": 1, + "bbox": [ + 500, + 821, + 666, + 838 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work is sponsored by DARPA PTG (HR00112220001), NSF (IIS-2115110), ARO (W911NF2110276). 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Computer Vision and Image Understanding, 227:103597, 2023. 2" + ], + "bbox": [ + 501, + 90, + 890, + 176 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "18677", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning to Predict Activity Progress by Self-Supervised Video Alignment/6059053b-0714-4369-b348-437b5de261d0_model.json b/2024/Learning to Predict Activity Progress by Self-Supervised Video Alignment/6059053b-0714-4369-b348-437b5de261d0_model.json new file mode 100644 index 0000000000000000000000000000000000000000..53ed765f6bfbf75c4a75a1000603d65077b6d3e4 --- /dev/null +++ b/2024/Learning to Predict Activity Progress by Self-Supervised Video Alignment/6059053b-0714-4369-b348-437b5de261d0_model.json @@ -0,0 +1,2664 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.112, + 0.131, + 0.859, + 0.154 + ], + "angle": 0, + "content": "Learning to Predict Activity Progress by Self-Supervised Video Alignment" + }, + { + "type": "text", + "bbox": [ + 0.235, + 0.182, + 0.425, + 0.233 + ], + "angle": 0, + "content": "Gerard Donahue Northeastern University Boston, MA, USA" + }, + { + "type": "text", + "bbox": [ + 0.214, + 0.238, + 0.446, + 0.251 + ], + "angle": 0, + "content": "donahue.g@northeastern.edu" + }, + { + "type": "text", + "bbox": [ + 0.533, + 0.182, + 0.725, + 0.233 + ], + "angle": 0, + "content": "Ehsan Elhamifar Northeastern University Boston, MA, USA" + }, + { + "type": "text", + "bbox": [ + 0.502, + 0.238, + 0.752, + 0.251 + ], + "angle": 0, + "content": "e.elhamifar@northeastern.edu" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.287, + 0.314, + 0.303 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.319, + 0.474, + 0.637 + ], + "angle": 0, + "content": "In this paper, we tackle the problem of self-supervised video alignment and activity progress prediction using in-the-wild videos. Our proposed self-supervised representation learning method carefully addresses different action orderings, redundant actions, and background frames to generate improved video representations compared to previous methods. Our model generalizes temporal cycle-consistency learning to allow for more flexibility in determining cycle-consistent neighbors. More specifically, to handle repeated actions, we propose a multi-neighbor cycle consistency and a multi-cycle-back regression loss by finding multiple soft nearest neighbors using a Gaussian Mixture Model. To handle background and redundant frames, we introduce a context-dependent drop function in our framework, discouraging the alignment of droppable frames. On the other hand, to learn from videos of multiple activities jointly, we propose a multi-head crosstalk network, allowing us to embed a video and estimate progress without knowing its activity label. Experiments on multiple datasets show that our method outperforms the state-of-the-art for video alignment and progress prediction." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.686, + 0.208, + 0.701 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.712, + 0.47, + 0.864 + ], + "angle": 0, + "content": "Understanding progress is central to a human's learning experience. We constantly modify and enhance our actions and behaviors based on our progress in different daily tasks [31]. Progress understanding is also fundamental for machines whose goal is to guide (e.g., assistive technologies) and seamlessly interact (e.g., robots) with humans [6, 35]. Imagine wearing augmented reality (AR) assistant glasses when assembling a complex machine, performing a medical procedure, or cooking a new hour-long recipe. Depending on the amount of progress made in the" + }, + { + "type": "image", + "bbox": [ + 0.5, + 0.285, + 0.882, + 0.378 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.381, + 0.892, + 0.407 + ], + "angle": 0, + "content": "Figure 1. We develop a framework for self-supervised in-the-wild video alignment and online activity progress prediction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.433, + 0.893, + 0.538 + ], + "angle": 0, + "content": "current step, the AR needs to show information about the current or next step(s). Additionally, progress is an important signal for computer vision tasks to run on AR task assistants, such as action segmentation and anticipation (depending on little/full progress in a step, subsequent frames will belong to the same/next step) [50] and anomaly/errordetection (a decrease in progress indicates an error) [34]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.539, + 0.895, + 0.81 + ], + "angle": 0, + "content": "Learning to predict progress, however, is challenging [8]. Progress can not be precisely calculated solely on the amount of time spent in an action (an expert often makes more progress than a novice within the same time window) and can be influenced by factors other than the user such as the environment (imagine cooking a recipe in a well-organized vs a cluttered kitchen). To estimate progress, we can break down an action into smaller phases and track where the user is within these phases (e.g., putting a coffee filter into a dripper involves taking a filter from its bag, folding it in half, folding it again into a quarter circle, creating a cone and inserting it into the dripper). Therefore, one approach for progress estimation is to label video clips of an action with its different phases and train a supervised phase classification model [3]. However, the ambiguity of defining a dictionary of fine-grained phases in advance and the high cost of annotating video frames with many action phases makes supervised learning impractical." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.895, + 0.902 + ], + "angle": 0, + "content": "Self-supervised video alignment is an appealing alternative for progress prediction. It finds frame representations and associations between frames of different videos (ideally, aligning the same phases across videos), without requiring fine-grained human labeling. There has been a large body of recent literature addressing video alignment" + }, + { + "type": "page_footnote", + "bbox": [ + 0.078, + 0.875, + 0.468, + 0.901 + ], + "angle": 0, + "content": "\\(^{1}\\)Code is publicly available at https://github.com/gerardDonahue/GTCC_CVPR2024." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18667" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.184 + ], + "angle": 0, + "content": "using different approaches, such as temporal cycle consistency (TCC) [12], dynamic time warping [11, 16, 17] and optimal transport [39]. However, after aligning videos and learning the embedding space, progress prediction has been simply treated as fitting a linear regression model to the embeddings by assuming a linear progress model [12, 17, 39]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.205, + 0.473, + 0.538 + ], + "angle": 0, + "content": "Limitations. Existing self-supervised methods have limitations for video alignment as well as progress prediction. First, when it comes to video alignment, the majority of existing works assume the same ordering of phases (monotonic), which is often violated in real videos (e.g., you can put a filter in a dripper and then put the dripper on the mug or vice versa). Additionally, some videos may have additional steps or background, which should not be aligned. Therefore, the recent approach in [39] (coined VAVA) addressed sequence alignment by considering background and redundant frames as well as non-monotonic ordering by imposing a temporal prior and an optimal prior on an optimal transport formulation, an intra-video contrastive term and an inter-video contrastive term. However, balancing multiple losses and handling repeated actions in the self-supervised setting is challenging and enforcing a temporal prior is unfit for in-the-wild alignment. Moreover, existing alignment techniques train distinct models for each action, resulting in substantial memory and computational overhead. This approach also complicates inference since activity/task identification is necessary, posing challenges particularly at the onset of activity/task execution." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.56, + 0.472, + 0.756 + ], + "angle": 0, + "content": "Paper Contributions. In this paper, we develop a framework for self-supervised video alignment and online progress prediction that addresses the limitations of existing works, see Figure 1. We propose a generalization of TCC [12] to model background and redundant frames, as well as repetitive actions when performing alignment. More specifically, to handle repeated actions, we propose a multi-neighbor cycle consistency and a multi-cycle-back regression loss by finding multiple soft nearest neighbors using a Gaussian Mixture Model (GMM) instead of a single neighbor as in TCC. To handle background and redundant frames, we introduce a context-dependent drop function, discouraging the alignment of droppable frames." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.472, + 0.903 + ], + "angle": 0, + "content": "On the other hand, to effectively align videos of multiple activities jointly and to better leverage their shared information while handling their distinctions, we propose a multi-head crosstask network, where each head automatically learns to focus on relevant components of video pairs. Thus, we can embed a video and estimate progress without knowing its activity label. Through extensive experiments on multiple datasets, we show the effectiveness of our framework for video alignment and progress estimation." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.09, + 0.651, + 0.107 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.115, + 0.895, + 0.375 + ], + "angle": 0, + "content": "Self-Supervised Video Representation Learning. Given the high annotation cost for video-based action learning and the need for copious amounts of data when training deep networks, many researchers have turned to self-supervised methods for embedding video frames [9, 28, 38, 42, 45, 60, 72]. Self-supervision has largely been popularized as a result of higher quality image embedding techniques trained on large-scale image datasets such as [10, 27, 37]. With better datasets, pre-trained image encoders, such as [18, 53-55], allow for more meaningful features that can enhance the performance of self-supervised representation learning methods. Many downstream tasks benefit from self-supervised video representation learning, such as action recognition [26, 71], temporal action segmentation [23, 33, 63, 65], step localization [14, 71], video retrieval [68], text-to-video retrieval [41], and audio-visual representation learning [25]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.38, + 0.895, + 0.729 + ], + "angle": 0, + "content": "Video Alignment is the task of temporally synchronizing videos, such that similar frames or segments in separate videos can be mapped to each other. Traditional methods such as Dynamic Time Warping (DTW) [7, 11, 13, 16, 17, 47], or Canonical Correlation Analysis (CCA) [1, 21, 26, 48] have been used to align video frames. Many methods have adopted the use of Soft-DTW [7, 11, 16, 17, 40], where the gradient is well-defined and back-propagation is feasible. LAV [17] is a self-supervised video alignment method, which uses Soft-DTW in conjunction with temporal intra-video contrastive loss terms. Other contrastive approaches include [5, 39, 42, 49, 60, 66]. Drop-DTW [11] extends DTW by adding a \"trash bucket\" to the cost matrix for dynamic programming for background frame classification. Similarly, VAVA [39] added an additional bucket to the optimal transport formulation to align in-the-wild videos. VAVA also incorporated a bi-modal Gaussian prior on the optimal transport matrix, which allowed for the model to consider the temporality and optimality of the alignment. VAVA was shown to outperform previous methods for unconstrained procedural video datasets. Other methods capable of background detection but not video alignment include [4, 43, 51, 61, 62]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Cycle-consistency has been a pivotal technique in sequence alignment, involving the mapping of elements from one sequence to another, followed by an inverse mapping back to the original sequence. Beyond its application in video alignment, cycle-consistency finds utility in diverse domains, including 3D shape matching [22], depth estimation [15], co-segmentation [57, 58], and transitivity in deep learning [15, 69, 70]. Cycle-consistency was first introduced for self-supervised video alignment in TCC [12] and showed good performance in aligning synchronizable videos, such as the Penn Action dataset [67] or the Pour" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "18668" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.08, + 0.087, + 0.465, + 0.171 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.175, + 0.47, + 0.224 + ], + "angle": 0, + "content": "Figure 2. Cycle-consistency Visualization. Here, two videos are embedded by the alignment encoder, \\(\\phi\\). With a green checkmark, a frame pair is shown to be cycle-consistent. With a red X-mark, a frame pair is shown to be not cycle-consistent." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.247, + 0.47, + 0.293 + ], + "angle": 0, + "content": "ing dataset [32]. Our method extends cycle-consistency to unconstrained videos, as observed in many datasets such as COIN [56] and EgoProceL [2]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.299, + 0.471, + 0.496 + ], + "angle": 0, + "content": "Activity Progress Prediction is the task of predicting temporal progress in videos. While [3, 44] have studied a supervised approach for action progress prediction, they require temporal annotations of every action clip based on its phases, which is hard to define given the fine-grained nature of phases and cost to gather. Action completion [19, 20, 59, 68] is also related to progress, however it is only focused on classifying full progress achievement rather than predicting the progress at every time instant. In this work, we learn to predict progress at every frame in a self-supervised framework. Our proposed progress estimation technique also has applications in goal-based reinforcement learning, providing dense reward for learning [29, 64]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.509, + 0.34, + 0.526 + ], + "angle": 0, + "content": "3. Problem Setting and Review" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.534, + 0.47, + 0.58 + ], + "angle": 0, + "content": "In this section, we discuss the problem of video alignment and review temporal cycle consistency (TCC) [12], which we build upon and generalize." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.589, + 0.245, + 0.604 + ], + "angle": 0, + "content": "3.1. Video Alignment" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.611, + 0.47, + 0.749 + ], + "angle": 0, + "content": "Given two video sequences \\( S = (s_1, \\ldots, s_N) \\) and \\( T = (t_1, \\ldots, t_M) \\) with \\( N \\) and \\( M \\) frames, respectively, we denote their embeddings by \\( U = (u_1, \\ldots, u_N) \\) and \\( V = (v_1, \\ldots, v_M) \\). We use an encoder neural network \\( \\phi \\) to compute these embeddings, as depicted in Fig. 2. The goal of video alignment is to train the encoder, \\( \\phi \\), such that if the two frames \\( s_i \\) and \\( t_j \\) represent the same action, the distance between their embeddings, \\( u_i \\in \\mathbb{R}^D \\) and \\( v_j \\in \\mathbb{R}^D \\), will be small, otherwise, the distance will be large." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.757, + 0.387, + 0.773 + ], + "angle": 0, + "content": "3.2. Temporal Cycle Consistency (TCC)" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.471, + 0.902 + ], + "angle": 0, + "content": "TCC [12] finds a symmetric nearest neighbor embedding space by maximizing the number of cycle-consistent embeddings between two sequences. More specifically, consider a frame \\( \\boldsymbol{u}_i \\in U \\), and let its Euclidean nearest neighbor from \\( V \\) be denoted by \\( \\boldsymbol{v}_j = \\operatorname{argmin}_{\\boldsymbol{v} \\in V} \\| \\boldsymbol{u}_i - \\boldsymbol{v} \\| \\). Similarly, for a frame \\( \\boldsymbol{v}_j \\in V \\), denote its Euclidean nearest neighbor in \\( U \\) by \\( \\boldsymbol{u}_k = \\operatorname{argmin}_{\\boldsymbol{u} \\in U} \\| \\boldsymbol{u} - \\boldsymbol{v}_j \\| \\). The frame \\( \\boldsymbol{u}_i \\) is cycle-consistent if and only if \\( i = k \\), see Fig. 2. TCC" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.088, + 0.696, + 0.17 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.58, + 0.171, + 0.621, + 0.181 + ], + "angle": 0, + "content": "(a) TCC" + }, + { + "type": "image", + "bbox": [ + 0.699, + 0.087, + 0.887, + 0.17 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.765, + 0.171, + 0.815, + 0.181 + ], + "angle": 0, + "content": "(b) GTCC" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.187, + 0.894, + 0.248 + ], + "angle": 0, + "content": "Figure 3. TCC Failure for Repeated Actions. Common action segments of the sequences are shown using varying colors. \\(\\alpha\\) is depicted based on the initial frame, \\(u_{i}\\), from the yellow action segment. TCC (3a) only allows a single \\(\\tilde{v}\\) between both peaks in \\(\\alpha\\). GTCC (3b) allows for two distinct neighbors, \\(\\tilde{v}_{1}\\) and \\(\\tilde{v}_{2}\\), which accurately represents repeated actions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.271, + 0.893, + 0.378 + ], + "angle": 0, + "content": "trains an encoder to embed frames such that the number of cycle-consistent frame embeddings is maximized across pairs of videos, hence, a symmetric nearest neighbor embedding space. Since argmin is non-differentiable, TCC adopts the softmax operation. Let \\(\\Delta^M\\) denote the probability simplex in \\(M\\) dimensions.2 TCC begins by computing a soft nearest neighbor (SNN) of \\(\\pmb{u}_i\\), denoted by \\(\\tilde{\\pmb{v}}\\)," + }, + { + "type": "equation", + "bbox": [ + 0.51, + 0.388, + 0.892, + 0.43 + ], + "angle": 0, + "content": "\\[\n\\tilde {\\boldsymbol {v}} = \\sum_ {j = 1} ^ {M} \\alpha_ {j} \\boldsymbol {v} _ {j}, \\quad \\text {w h e r e ,} \\quad \\alpha_ {j} = \\frac {e ^ {- \\| \\boldsymbol {u} _ {i} - \\boldsymbol {v} _ {j} \\| ^ {2} / \\tau}}{\\sum_ {k = 1} ^ {M} e ^ {- \\| \\boldsymbol {u} _ {i} - \\boldsymbol {v} _ {k} \\| ^ {2} / \\tau}}. \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.442, + 0.894, + 0.533 + ], + "angle": 0, + "content": "Here \\(\\alpha = [\\alpha_{1},\\ldots ,\\alpha_{M}]\\in \\Delta^{M}\\) is the outgoing normalized similarity (forward distribution) between \\(\\pmb{u}_i\\) and embeddings in \\(V\\), and \\(\\tau\\) is the softmax temperature. TCC then uses the SNN, \\(\\tilde{\\pmb{v}}\\), to compute \\(\\beta = [\\beta_{1},\\dots,\\beta_{N}]\\in \\Delta^{N}\\), which is the incoming normalized similarity (backward distribution) between \\(\\tilde{\\pmb{v}}\\) and frame embeddings in \\(U\\)," + }, + { + "type": "equation", + "bbox": [ + 0.606, + 0.543, + 0.892, + 0.585 + ], + "angle": 0, + "content": "\\[\n\\beta_ {l} = \\frac {e ^ {- \\| \\boldsymbol {u} _ {l} - \\tilde {\\boldsymbol {v}} \\| ^ {2} / \\tau}}{\\sum_ {j = 1} ^ {N} e ^ {- \\| \\boldsymbol {u} _ {j} - \\tilde {\\boldsymbol {v}} \\| ^ {2} / \\tau}}. \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.594, + 0.894, + 0.704 + ], + "angle": 0, + "content": "Cycle-consistency requires that \\(\\beta\\) must have the highest probability mass at index \\(i\\) and very small mass at indices farther from \\(i\\). Thus, TCC imposes a Gaussian distribution prior \\(\\mathcal{N}(\\mu_{\\beta},\\sigma_{\\beta}^{2})\\) on entries of \\(\\beta\\) with mean \\(\\mu_{\\beta} = \\sum_{l = 1}^{N}\\beta_{l}\\cdot l\\) and variance \\(\\sigma_{\\beta}^{2} = \\sum_{l = 1}^{N}\\beta_{l}\\cdot (l - \\mu_{\\beta})^{2}\\). Requiring that the distribution mean be close to \\(i\\) with a small variance leads to minimizing a cycle-back regression loss, defined as" + }, + { + "type": "equation", + "bbox": [ + 0.591, + 0.713, + 0.892, + 0.752 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {c b r}} = \\frac {(i - \\mu_ {\\beta}) ^ {2}}{\\sigma_ {\\beta} ^ {2}} + \\lambda \\log (\\sigma_ {\\beta}), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.761, + 0.892, + 0.792 + ], + "angle": 0, + "content": "where \\(\\lambda\\) is the regularization weight. This leads to a differentiable loss that can be optimized using backpropagation." + }, + { + "type": "title", + "bbox": [ + 0.498, + 0.805, + 0.892, + 0.839 + ], + "angle": 0, + "content": "4. Generalized Temporal Cycle Consistency (GTCC)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.848, + 0.892, + 0.879 + ], + "angle": 0, + "content": "One of the advantages of TCC [12] compared to DTW-based methods [11, 17] is that it does not assume/enforce" + }, + { + "type": "page_footnote", + "bbox": [ + 0.516, + 0.887, + 0.885, + 0.901 + ], + "angle": 0, + "content": "\\( {}^{2}\\mathbf{\\alpha } \\in {\\Delta }^{M} \\) means that vector entries are nonnegative and sum to one." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18669" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.079, + 0.092, + 0.895, + 0.189 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.196, + 0.895, + 0.247 + ], + "angle": 0, + "content": "Figure 4. GTCC. We encode two videos into \\( \\mathbf{U} \\) and \\( \\mathbf{V} \\) and calculate the forward distribution, \\( \\alpha \\). We use the output of the GMM optimization procedure and obtain \\( K \\) SNNs from \\( K \\) discrete Gaussians. We then compute \\( \\beta^{(k)} \\) for each SNN. We also estimate the drop probability of each frame \\( \\mathrm{P}_{\\mathrm{drop}}(\\pmb{u}_i|\\mathbf{V}) \\) using a conditional network. Finally, we compute the final loss by weighting each cycle-back regression loss with weight from mixture densities, \\( \\psi \\), and modulate with the drop probabilities." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.268, + 0.47, + 0.312 + ], + "angle": 0, + "content": "monotonic ordering of actions across videos. On the other hand, it has two major drawbacks when it comes to aligning in-the-wild videos." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.314, + 0.47, + 0.405 + ], + "angle": 0, + "content": "First, TCC cannot handle background and additional actions, because it enforces cycle-consistency for every frame embedding. However, background actions (e.g., 'answering phone' when making coffee) or additional actions (e.g., the optional step of 'cleaning coffee filter') in one video but not in another should not be aligned." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.406, + 0.47, + 0.556 + ], + "angle": 0, + "content": "Second, the TCC model assumes that each action only appears once in a video, therefore, cannot model action repetitions (e.g., repeating the actions of 'give breath' and 'give chest compression' when performing CPR). This is because computing the SNN in TCC is done with a unimodal Gaussian assumption on the similarity distributions, which is violated when an action is repeated in a video and leads to computing bad SNNs, see Fig. 3. We propose generalized temporal cycle consistency (GTCC), which addresses these limitations and aligns videos in the wild." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.568, + 0.444, + 0.584 + ], + "angle": 0, + "content": "4.1. Multi-Cycle Consistency via Mixture SNNs" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.592, + 0.47, + 0.773 + ], + "angle": 0, + "content": "We propose multi-neighbor cycle consistency and a multicycle-back regression loss to handle repeated actions, see Fig. 4. For \\( \\pmb{u}_i \\in U \\) belonging to an action \\( a \\), a single SNN \\( \\tilde{\\pmb{v}} \\) obtained using (1) is restrictive when action \\( a \\) is repeated in the sequence \\( V \\). In such a case, as 3 shows, \\( \\pmb{u}_i \\) will have multiple good nearest neighbors, yet the SNN \\( \\tilde{\\pmb{v}} \\) captures an average representation of them leading to a suboptimal solution. Therefore, we generalize TCC to allow for multiple SNNs and to assign an importance score to each SNN. This allows our model to find a set of SNNs based on a given \\( \\pmb{u}_i \\), and to automatically gain awareness of their relative importance for promoting multiple-neighbor cycle-consistency." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.774, + 0.47, + 0.85 + ], + "angle": 0, + "content": "For \\( \\pmb{u}_i \\in U \\), we first obtain the outgoing distribution \\( \\alpha = [\\alpha_1, \\dots, \\alpha_M] \\), where \\( \\alpha_j \\)'s are computed using (1). We then approximate \\( \\alpha \\) with a discretized Gaussian Mixture Model (GMM) to capture different distribution modes corresponding to the same action. More specifically, we model" + }, + { + "type": "equation", + "bbox": [ + 0.194, + 0.862, + 0.47, + 0.905 + ], + "angle": 0, + "content": "\\[\n\\alpha_ {j} \\approx p _ {j} = \\sum_ {k = 1} ^ {K} \\psi_ {k} p _ {j} ^ {(k)}, \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.267, + 0.895, + 0.452 + ], + "angle": 0, + "content": "where \\(p_j^{(k)}\\) is the outgoing probability of index \\(j\\) in video \\(\\mathbf{V}\\) for the \\(k\\)-th discretized Gaussian distribution \\(\\mathcal{N}(\\mu_{\\alpha,k}, \\sigma_{\\alpha,k}^2)\\) and \\(\\psi_k\\) denotes the weight of the mixture component \\(k\\). Here, \\(K\\) is a hyperparameter defining the total number of mixture components. We typically set \\(K = 10\\) in our experiments and as we show the results do not change much for different values of \\(K\\) as long as it is not very small. We find the parameters of the GMM, which are \\(\\{\\mu_k, \\sigma_k^2, \\psi_k\\}_{k=1}^K\\), by minimizing the KL divergence [52] between the two distributions \\([\\alpha_1, \\ldots, \\alpha_M]\\) and \\([p_1, \\ldots, p_M]\\). After finding the parameters of the GMM, we then compute one SNN for each mixture component," + }, + { + "type": "equation", + "bbox": [ + 0.559, + 0.456, + 0.892, + 0.5 + ], + "angle": 0, + "content": "\\[\n\\tilde {\\boldsymbol {v}} ^ {(k)} = \\sum_ {j = 1} ^ {M} p _ {j} ^ {(k)} \\cdot \\boldsymbol {v} _ {j}, \\quad \\forall k \\in \\{1, \\dots , K \\}. \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.505, + 0.895, + 0.685 + ], + "angle": 0, + "content": "With these \\(K\\) SNNs of \\(\\pmb{u}_i\\in \\pmb{U}\\), we then compute the incoming similarity distribution \\(\\beta^{(k)}\\) for each SNN, \\(\\tilde{\\pmb{v}}^{(k)}\\). TCC assumes that throughout the sequence \\(\\pmb{U}\\), \\(\\beta\\) should only have a sharp peak at index \\(i\\). For in-the-wild videos, this presents a challenge when \\(\\pmb{u}_i\\) belongs to a repeated or non-contiguous action segment, where there would be more than one valid peak in the incoming distribution. To address this, we only enforce a local sharp peak around \\(i\\) for a discrete temporal window, \\(w\\), where any index outside the \\(i\\)-centered window has zero probability (see supplementary materials for more details). For each \\(\\beta^{(k)}\\), we compute the mean and variance over the indices of \\(\\pmb{U}\\)" + }, + { + "type": "equation", + "bbox": [ + 0.513, + 0.69, + 0.892, + 0.733 + ], + "angle": 0, + "content": "\\[\n\\mu_ {\\beta , k} = \\sum_ {l = 1} ^ {N} \\beta_ {l} ^ {(k)} \\cdot l, \\quad \\sigma_ {\\beta , k} ^ {2} = \\sum_ {l = 1} ^ {N} \\beta_ {l} ^ {(k)} \\cdot (l - \\mu_ {\\beta , k}) ^ {2}. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.737, + 0.892, + 0.767 + ], + "angle": 0, + "content": "Finally, we compute one cycle-back regression loss for each mixture component as" + }, + { + "type": "equation", + "bbox": [ + 0.572, + 0.772, + 0.892, + 0.81 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {c b r}} ^ {(k)} = \\frac {\\left(i - \\mu_ {\\beta , k}\\right) ^ {2}}{\\sigma_ {\\beta , k} ^ {2}} + \\lambda \\cdot \\log (\\sigma_ {\\beta , k}). \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.815, + 0.892, + 0.858 + ], + "angle": 0, + "content": "Given that \\(\\psi_{k}\\) is the relative importance of the \\(k\\)-th discrete Gaussian distribution, we build a multi-cycle back regression loss as" + }, + { + "type": "equation", + "bbox": [ + 0.61, + 0.863, + 0.892, + 0.904 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {m u l t i - c b r}} = \\sum_ {k = 1} ^ {K} \\psi_ {k} \\cdot \\mathcal {L} _ {\\text {c b r}} ^ {(k)}. \\tag {8}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18670" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.094, + 0.089, + 0.454, + 0.22 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.227, + 0.471, + 0.289 + ], + "angle": 0, + "content": "Figure 5. Multi-head Crosstalk Network (MCN). Input frames, \\( S \\), are given to the base network to obtain base features, \\( U^b \\), which are subsequently given to \\( L \\) head networks that output intermediate video encodings, \\( \\{U_l^h\\}_{l=1}^L \\). We obtain the final video encoding \\( U \\) using attention over the outputs of the \\( L \\) heads." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.319, + 0.33, + 0.336 + ], + "angle": 0, + "content": "4.2. Droppable Frame Detection" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.342, + 0.47, + 0.493 + ], + "angle": 0, + "content": "Another major limitation of TCC is that it cannot handle background and additional actions since it enforces cycle-consistency for all embeddings. GTCC addresses this issue by detecting frames in \\( U \\) to be dropped based on the frames in \\( V \\) and subsequently enforcing (i) multi-cycle consistency for alignable embeddings and (ii) bad alignment for droppable embeddings. Information (context) from video \\( V \\) is necessary when dropping frames in video \\( U \\) because the model can not know to drop frames corresponding to an additional action unless that action is not present in \\( V \\)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.494, + 0.47, + 0.54 + ], + "angle": 0, + "content": "More specifically, we learn a drop-context function, \\( c: \\mathbb{R}^D \\to \\mathbb{R}^{D+1} \\), characterized by a feedforward neural network, using all the embeddings \\( v_j \\in V \\) as" + }, + { + "type": "equation", + "bbox": [ + 0.165, + 0.547, + 0.47, + 0.589 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {c} (\\boldsymbol {V}) = \\frac {1}{M} \\sum_ {j = 1} ^ {M} \\boldsymbol {c} \\left(\\boldsymbol {v} _ {j}\\right) \\in \\mathbb {R} ^ {D + 1}. \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.595, + 0.47, + 0.656 + ], + "angle": 0, + "content": "GTCC uses the information in \\(\\mathbf{V}\\) to condition the drop detection in \\(\\mathbf{U}\\). More specifically, for each \\(\\pmb{u}_i\\in U\\), we use a logistic regression model to compute the probability of dropping \\(\\pmb{u}_i\\) given \\(\\mathbf{V}\\) as" + }, + { + "type": "equation", + "bbox": [ + 0.153, + 0.66, + 0.469, + 0.681 + ], + "angle": 0, + "content": "\\[\n\\mathrm {P} _ {\\text {d r o p}} \\left(\\boldsymbol {u} _ {i} \\mid \\boldsymbol {V}\\right) = \\sigma \\left(\\left[ \\boldsymbol {u} _ {i} ^ {\\top} \\quad 1 \\right] \\boldsymbol {c} (\\boldsymbol {V})\\right), \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.686, + 0.469, + 0.716 + ], + "angle": 0, + "content": "where \\(\\sigma\\) is the sigmoid function. We use the drop probability to build our final loss function, which we discuss next." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.723, + 0.243, + 0.739 + ], + "angle": 0, + "content": "4.3. Learning GTCC" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.746, + 0.469, + 0.867 + ], + "angle": 0, + "content": "To learn the parameters of the embedding network \\(\\phi\\) and the drop-context model, we propose a loss so that alignable frames are encouraged to have good cycle-consistency and droppable frames are encouraged to have bad alignment. This dichotomy isolates the cycle-consistency property only to frames that are deemed 'alignable', and ensures frames deemed 'droppable' have no good nearest neighbors. We propose to minimize" + }, + { + "type": "equation", + "bbox": [ + 0.091, + 0.872, + 0.47, + 0.907 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\left(1 - \\mathrm {P} _ {\\text {d r o p}} (\\boldsymbol {u} _ {i} | \\boldsymbol {V})\\right) \\cdot \\mathcal {L} _ {\\text {m u l t i - c b r}} + \\frac {\\mathrm {P} _ {\\text {d r o p}} (\\boldsymbol {u} _ {i} | \\boldsymbol {V})}{\\mathcal {L} _ {\\text {m u l t i - c b r}}}, \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.183 + ], + "angle": 0, + "content": "where we minimize the multi-cycle-back regression loss for alignable frames for which \\(\\mathrm{P}_{\\mathrm{drop}}(\\pmb {u}_i|\\pmb {V})\\) is close to 0, and maximize the multi-cycle-back regression loss for drop-. pable frames for which \\(\\mathrm{P}_{\\mathrm{drop}}(\\pmb {u}_i|\\pmb {V})\\) is close to 1. Notice one can also use \\(-\\mathcal{L}_{\\mathrm{multi - cbr}}\\) instead of \\(1 / \\mathcal{L}_{\\mathrm{multi - cbr}}\\) in (11), however, the latter worked better in our experiments." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.192, + 0.748, + 0.208 + ], + "angle": 0, + "content": "4.4. Online Progress Estimation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.215, + 0.892, + 0.275 + ], + "angle": 0, + "content": "At inference time, given an online sequence up to frame \\(\\pmb{u}_i\\), we want to estimate the progress, denoted by \\(\\hat{\\pi}(\\pmb{u}_i) \\in [0,1]\\). We do so, by using the cumulative inter-frame geodesic distance on the frame features," + }, + { + "type": "equation", + "bbox": [ + 0.594, + 0.285, + 0.892, + 0.32 + ], + "angle": 0, + "content": "\\[\n\\hat {\\pi} \\left(\\boldsymbol {u} _ {i}\\right) = \\frac {\\sum_ {t = 1} ^ {i - 1} \\left\\| \\boldsymbol {u} _ {t + 1} - \\boldsymbol {u} _ {t} \\right\\|}{\\hat {G}}, \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.332, + 0.892, + 0.409 + ], + "angle": 0, + "content": "where \\(\\hat{G}\\) is ideally the total geodesic distance for the complete sequence (including past and future observations). Given that we do not have access to the future frames, we estimate \\(\\hat{G}\\) by averaging the total geodesic distances for all aligned training videos of the given task." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.422, + 0.762, + 0.439 + ], + "angle": 0, + "content": "5. GTCC Embedding Network" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.447, + 0.892, + 0.719 + ], + "angle": 0, + "content": "Our goal is to train an embedding model that can leverage the shared information across related actions or tasks (e.g., making otime and making scrambled eggs) for better feature learning and alignment of each task individually, while not requiring to know the action or task label of the video at inference time. Existing works, which train a separate model for each action/task, have neither of these capabilities. Therefore, we propose a new architecture, which we refer to as Multi-head Crosstalk Network (MCN), shown in Fig. 5. MCN consists of a base network, multiple head networks, and an attention network. MCN base network is intended to output general useful features (across actions/tasks) to be used by multiple \\((L)\\) head networks. Ideally, each head network specializes in aligning related phases of an action or steps of a task. The attention network takes all features from the head networks at each time instant and selects the relevant head and its features. See the supplemental material for more details." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.733, + 0.634, + 0.75 + ], + "angle": 0, + "content": "6. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.757, + 0.691, + 0.774 + ], + "angle": 0, + "content": "6.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Datasets. We use four datasets for evaluations, two monotonic and two in-the-wild datasets. Similar to previous works [12, 17, 39], we report results on Pouring [32] and Penn Action [67] datasets, which are monotonic. Pouring contains videos of humans pouring liquid into a cup (e.g., orange juice poured into a blue cup), and Penn Action contains videos of humans completing athletic maneuvers (e.g., a woman serving a tennis ball). We also use COIN [56]" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "18671" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.468, + 0.182 + ], + "angle": 0, + "content": "and EgoProceL [2], which are in-the-wild datasets, consisting of background frames, action repetitions, and different sequences of actions. EgoProceL is an egocentric dataset comprised of a collection of several datasets, including CMU-MMAC [30], EGTEA Gaze+ [36], MECCANO [46], and EPIC-tent [24]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.183, + 0.468, + 0.349 + ], + "angle": 0, + "content": "For Pouring, Penn Action, and COIN, we use \\(75\\%\\) of videos for training and \\(25\\%\\) for testing, while for EgoProceL we use \\(70\\%\\) for training and \\(30\\%\\) for testing since there are fewer videos per task. We also study two settings for evaluation. (i) Similar to prior works, we train a model separately for videos of each activity (single-task setting), whereas following other works we use an embedding network that corresponds to the base network in Fig. 5. (ii) We train a single model on videos of all activities jointly (multi-task setting). In Tab. 4, we test the multi-task setting using only the base network vs the full MCN architecture." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.357, + 0.468, + 0.673 + ], + "angle": 0, + "content": "Evaluation Metrics. We use multiple metrics to evaluate the performance of different methods for alignment and progress prediction. For evaluating alignment, we use the existing metrics Phase Classification (PC) [12], Enclosed Area Error (EAE) [13] and Kendall's Tau (KT) [12]. PC measures how well the encoder can put frames belonging to the same action class together, thus a higher value is better. Similar to previous works, we use PC, where an SVM classifier is trained on \\(10\\%\\), \\(50\\%\\), and \\(100\\%\\) of the ground-truth action labels. While PC measures how well different actions are separated from each other, it does not measure the quality of alignment within each action. Thus, we use Enclosed Area Error (EAE) that measures the alignment error within and across actions by comparing the nearest neighbors between two videos with their ground-truth alignment. When computing EAE for in-the-wild video pairs, we only include alignable frames in the computation. In cases where a frame has multiple valid neighbors, we calculate the smallest EAE among the set of neighbors. EAE is an error metric, therefore lower values indicate better alignment. See [13] for more details about EAE." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.674, + 0.468, + 0.84 + ], + "angle": 0, + "content": "KT is a statistical measure that indicates how well-aligned two sequences are temporally. Given that KT is only suitable for monotonic sequences, we also propose a modified Kendall's Tau for in-the-wild datasets, which we call Kendall's Tau in the Wild (KTW). More specifically, we only evaluate KT on alignable frames and consider all variations of valid alignment for concordancy. This increases forgiveness when finding concordant pairs, because there may be many concordant neighbors for a frame in a redundant action segment. Therefore, KTW highlights the presence of disconcordant pairs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.468, + 0.901 + ], + "angle": 0, + "content": "To evaluate progress estimation, we use PHase Progression (PHP) [12] and introduce Online Progress Error (OPE). PHP trains a linear regressor over frame features to predict ground-truth progress values and computes the av" + }, + { + "type": "table", + "bbox": [ + 0.51, + 0.09, + 0.883, + 0.235 + ], + "angle": 0, + "content": "
DatasetModelPC↑EAE↓KT↑PHP↑OPE↓
0.10.51.0
PouringSAL85.787.888.0—73.374.5—
TCN89.290.490.4—86.780.6—
TCC89.291.491.814.085.280.338.9
LAV91.692.892.89.085.680.531.4
VAVA91.791.892.529.687.683.637.8
GTCC71.289.293.57.988.185.822.5
Penn ActionSAL74.978.380.0—63.459.4—
TCN82.083.784.0—73.367.6—
TCC81.383.484.518.273.567.335.5
LAV83.684.084.320.580.566.125.5
VAVA83.984.084.523.280.570.980.5
GTCC78.381.281.316.788.370.814.5
" + }, + { + "type": "table_caption", + "bbox": [ + 0.511, + 0.239, + 0.88, + 0.253 + ], + "angle": 0, + "content": "Table 1. Alignment and progress evaluations on monotonic datasets." + }, + { + "type": "table", + "bbox": [ + 0.51, + 0.268, + 0.883, + 0.389 + ], + "angle": 0, + "content": "
DatasetModelPC ↑EAE ↓KTW ↑OPE ↓
0.10.51.0
EgoProceLTCC66.067.468.321.513.934.0
LAV67.268.268.820.812.736.2
VAVA65.365.966.323.213.135.5
GTCC75.078.980.613.314.013.6
COINTCC35.939.640.728.018.828.7
LAV36.838.939.826.723.222.7
VAVA43.846.247.332.022.227.6
GTCC46.853.256.318.929.021.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.51, + 0.393, + 0.88, + 0.406 + ], + "angle": 0, + "content": "Table 2. Alignment and progress evaluations on in-the-wild datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.428, + 0.892, + 0.624 + ], + "angle": 0, + "content": "erage \\(R\\)-squared measure over all videos. PHP assumes monotonicity in action sequences and, therefore, is only evaluated on the monotonic datasets. On the other hand, our online progress estimation in (12) applies to monotonic and in-the-wild datasets. Following [3], at each frame \\(\\pmb{u}_i\\) we define a ground-truth progress value \\(\\pi (\\pmb{u}_i)\\in [0,1]\\) assuming that (i) each action segment contributes equally to the overall progress, and (ii) progress linearly increases throughout the duration of each action segment. We assume that silent frames do not contribute to progress, hence progress values remain constant during silent segments, see 6. We define OPE as the mean absolute difference between predicted progress and ground-truth online progress (lower is better)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.634, + 0.892, + 0.723 + ], + "angle": 0, + "content": "Baselines. For the single-task setting, we compare our GTCC against SAL [42], TCN [49], TCC [12], LAV [17] and VAVA [39]. Among them, only VAVA is specifically designed for handling in-the-wild videos. For the multi-task setting, we compare GTCC with LAV and VAVA, which are state-of-the-art." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.725, + 0.892, + 0.845 + ], + "angle": 0, + "content": "On the Penn Action, Pouring, and COIN datasets, for the single-task setting, we report the PC, PHP, and KT as previously reported in the most recent work [39]. Given that previous methods did not report EAE, KTW, and OPE, we re-implement all baselines on all datasets to report the performance based on these metrics. Similarly, we reproduce all numbers for the MCN multi-task (Table 4) and the EgoProceL experiments (Tables 2, 3, 4, 5, 6)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Implementation Details For the single-task setting, following all previous baselines, we use ResNet-50 [18] for the architecture of the encoder network. Please see [12] for more" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.956 + ], + "angle": 0, + "content": "18672" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.099, + 0.089, + 0.447, + 0.169 + ], + "angle": 0, + "content": "
DatasetModelPrecisionRecallF1Accuracy
EgoProceLVAVA66.098.477.064.3
GTCC67.597.978.268.9
COINVAVA41.778.853.544.7
GTCC51.988.265.362.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.173, + 0.47, + 0.197 + ], + "angle": 0, + "content": "Table 3. Evaluation of handling background actions (i.e., drop) of VAVA vs GTCC for the in-the-wild datasets." + }, + { + "type": "table", + "bbox": [ + 0.086, + 0.209, + 0.462, + 0.438 + ], + "angle": 0, + "content": "
DatasetMethodArch.PC↑EAE↓KT↑KTW↑PHP↑OPE↓
CMU-MMACLAVResNet65.222.2—6.8—18.2
MCN69.813.4—12.1—16.1
VAVAResNet62.524.0—5.1—20.7
MCN63.719.7—11.4—17.9
GTCCResNet70.426.8—9.0—25.2
MCN67.814.9—21.8—14.0
EGTEALAVResNet82.519.7—2.8—17.9
MCN82.111.4—38.7—22.4
VAVAResNet83.219.6—2.7—19.6
MCN82.310.7—38.1—19.7
GTCCResNet83.617.2—3.3—19.5
MCN82.510.2—47.6—16.0
Penn ActionLAVResNet78.720.568.4—62.527.7
MCN85.35.794.3—69.08.6
VAVAResNet80.326.276.2—64.837.9
MCN85.45.994.4—72.614.3
GTCCResNet73.924.760.7—69.732.9
MCN86.75.694.9—85.59.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.443, + 0.47, + 0.468 + ], + "angle": 0, + "content": "Table 4. Alignment and progress evaluation for the multi-task setting when training on ResNet-50 vs our proposed MCN architecture." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.491, + 0.47, + 0.656 + ], + "angle": 0, + "content": "details regarding the encoder architecture. For the multi-task setting, we compare the ResNet-50 embedding network with our multi-head crosstalk network (MCN), shown in Fig. 5, where the base network is ResNet-50 and all head and attention networks are 4-layer fully-connected feedforward network. For GTCC, we also simultaneously train a 4-layer feedforward neural network for the drop-context function, \\( \\mathbf{c} \\), in Sec. 4.2. We use \\( K = 15 \\) for in-the-wild datasets and \\( K = 5 \\) for monotonic datasets. For multi-task experiments using MCN, we set the number of attention heads to be the number of tasks in the dataset." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.667, + 0.28, + 0.683 + ], + "angle": 0, + "content": "6.2. Experimental Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.47, + 0.885 + ], + "angle": 0, + "content": "Single-Task Setting Results. Table 1 and 2 show the alignment and progress estimation evaluation of different methods for monotonic and in-the-wild datasets, respectively. Notice that for the monotonic datasets in Table 1, GTCC achieves significantly better EAE (for alignment) and OPE (for progress) on both datasets, e.g., improving the OPE from \\(25.5\\%\\) to \\(14.5\\%\\) and EAE from \\(18.2\\%\\) to \\(16.7\\%\\) on Penn Action. Similarly, our method achieves higher KT values, especially on Penn Action, where it outperforms other methods by at least \\(7.8\\%\\). However, GTCC mostly does not improve the PC values of the baselines. This is because PC does not directly represent precise alignment but instead measures the effectiveness of clustering action segments." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.887, + 0.469, + 0.9 + ], + "angle": 0, + "content": "On the other hand, as the results in Table 2 show," + }, + { + "type": "image", + "bbox": [ + 0.51, + 0.093, + 0.691, + 0.191 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.577, + 0.195, + 0.625, + 0.204 + ], + "angle": 0, + "content": "(a) GTCC" + }, + { + "type": "image", + "bbox": [ + 0.702, + 0.093, + 0.882, + 0.192 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.769, + 0.195, + 0.816, + 0.204 + ], + "angle": 0, + "content": "(b) VAVA" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.209, + 0.689, + 0.308 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.579, + 0.311, + 0.619, + 0.321 + ], + "angle": 0, + "content": "(c) LAV" + }, + { + "type": "image", + "bbox": [ + 0.7, + 0.209, + 0.88, + 0.308 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.77, + 0.311, + 0.811, + 0.321 + ], + "angle": 0, + "content": "(d) TCC" + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.324, + 0.892, + 0.361 + ], + "angle": 0, + "content": "Figure 6. Online progress estimation for GTCC (6a), VAVA (6b), LAV (6c) and TCC (6d) for a video from the task \"making brownies\" in the EgoProceL dataset." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.384, + 0.892, + 0.52 + ], + "angle": 0, + "content": "GTCC significantly outperforms all baselines for all metrics. Specifically, GTCC improves the EAE by at least \\(7.5\\%\\) on both EgoProceL and COIN and reduces OPE from \\(34.0\\%\\) to \\(13.6\\%\\) on EgoProceL and from \\(22.7\\%\\) to \\(21.4\\%\\) on COIN. Similarly, our method significantly improves the PC and KTW over the state-of-the-art. This is thanks to the fact that GTCC is specifically designed to handle inthe-wild videos that contain action repetitions, background activities, and action ordering variations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.529, + 0.893, + 0.711 + ], + "angle": 0, + "content": "Drop Performance. Table 3 compares the effectiveness of VAVA and GTCC for handling background activities on in-the-wild datasets for the single-task setting. We measure the precision, recall, F1 score, and accuracy of dropping background frames during pairwise alignment. Notice that on both datasets, GTCC has a higher F1 score and accuracy. Notably, GTCC achieves \\(62.0\\%\\) accuracy on COIN compared to \\(44.7\\%\\) by VAVA and obtains \\(68.9\\%\\) accuracy on EgoProceL compared to \\(64.3\\%\\) by VAVA. This shows the effectiveness of our context-based drop and alignment, which jointly learns alignable and droppable frames with a soft probabilistic approach." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Multi-Task Setting Results. In Table 4, we show the alignment and progress evaluations of LAV, VAVA, and GTCC for the multi-task setting, where we use all videos in each dataset to learn a single embedding network. We compare using ResNet-50 with using our proposed MCN architecture. Since GTCC outperformed TCC on progress and alignment metrics in the previous experiments, we do not report the results for TCC. As the results demonstrate, using ResNet for embedding in the multi-task setting leads to generally low performances for all methods. For example, on CMU-MMAC, KTW is less than \\(9\\%\\) and EAE is more than \\(22\\%\\) for all methods (similarly on EGTEA). On the other" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18673" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.088, + 0.088, + 0.199, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.203, + 0.089, + 0.314, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.317, + 0.089, + 0.426, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.427, + 0.089, + 0.538, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.539, + 0.089, + 0.65, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.652, + 0.089, + 0.762, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.765, + 0.089, + 0.875, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.196, + 0.892, + 0.222 + ], + "angle": 0, + "content": "Figure 7. Task Progression. Frames from a video of the \"pizza\" task in EgoProceL. On top is the ground-truth progress \\((\\pi_{\\mathrm{gt}})\\), in green is the geodesic progress from GTCC \\((\\pi_{\\mathrm{geo}})\\), and in red is the trivial progress \\((\\pi_{\\mathrm{triv}})\\) obtained by dividing test video time-steps by mean total video length from the train set." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.231, + 0.466, + 0.322 + ], + "angle": 0, + "content": "
EAE ↓OPE ↓PC(1.0) ↑
K151015151015151015
EgoP19.419.218.719.420.420.020.320.973.974.875.574.3
COIN23.221.422.218.925.523.122.021.450.149.648.946.8
Pour11.611.111.711.59.712.310.910.287.184.984.986.3
Penn26.716.016.116.115.216.717.816.780.078.278.2278.9
" + }, + { + "type": "table_caption", + "bbox": [ + 0.093, + 0.328, + 0.453, + 0.34 + ], + "angle": 0, + "content": "Table 5. Effect of the number of GMM components, \\( K \\) ,on GTCC." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.367, + 0.47, + 0.52 + ], + "angle": 0, + "content": "hand, \\(\\frac{6}{9}\\) PC metrics, \\(\\frac{9}{9}\\) EAE metrics, \\(\\frac{3}{3}\\) KT metrics, \\(\\frac{6}{6}\\) KTW metrics, \\(\\frac{3}{3}\\) PHP metrics, and \\(\\frac{7}{9}\\) OPE metrics show improvement with the MCN architecture. Table 4 shows that when using MCN, the EAE, KT, KTW, and PHP metrics outperform \\(100\\%\\) of the time, while PC and OPE outperform \\(67\\%\\) and \\(78\\%\\) of the time. This is because our architecture learns to specialize multiple heads for related actions using attention, while ResNet trains a single shared base model for all actions including the ones that are considerably different (e.g., serving tennis and jumping jack)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.529, + 0.47, + 0.634 + ], + "angle": 0, + "content": "GMM Tuning and Ablations. Table 5 shows the effect of the number of mixture components, \\( K \\), in the GMM on alignment and progress performance for GTCC. Notice that performance does not vary much under different values of \\( K \\), showing the robustness of our approach. It is important to note that, as expected, \\( K = 1 \\) performs better comparatively on monotonic datasets than in-the-wild datasets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.635, + 0.469, + 0.756 + ], + "angle": 0, + "content": "Table 6 ablates the number of MCN heads (6a), and the drop term in GTCC (6b). We gather from 6a that alignment performance improves when the number of MCN heads scales alongside the number of tasks in the dataset (5 for both EGTEA Gaze+ and CMU-MMAC, which have 5 tasks). Finally, we see in 6b that the removal of the drop term leads to degraded performance, further showing the importance of the drop term in GTCC." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Qualitative Results. In Fig. 6, we show the comparison of different methods for online progress estimation on a test video from the task \"making brownies\" from the EgoProceL dataset. For each method, we show the ground-truth progress vs progress estimated via (12), \\(\\hat{\\pi}\\), using the learned embeddings. Notice that GTCC's estimation of the progress fits the ground-truth nicely, while other methods have a large gap. This is because GTCC can effectively drop frames that correspond to background, while obtaining an" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.24, + 0.886, + 0.369 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.534, + 0.377, + 0.858, + 0.39 + ], + "angle": 0, + "content": "Figure 8. In-the-wild Frame Retrieval from COIN dataset." + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.405, + 0.698, + 0.46 + ], + "angle": 0, + "content": "
PC(1.0)↑EAE↓
# Heads15201520
CMU66.767.864.729.514.929.0
EGTEA82.382.582.015.510.219.3
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.536, + 0.461, + 0.665, + 0.47 + ], + "angle": 0, + "content": "(a) Number of MCN heads." + }, + { + "type": "table", + "bbox": [ + 0.712, + 0.405, + 0.886, + 0.459 + ], + "angle": 0, + "content": "
PC(1.0)↑EAE↓
Drop✓×✓×
Ego80.665.213.324.3
COIN56.346.618.927.9
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.719, + 0.461, + 0.88, + 0.471 + ], + "angle": 0, + "content": "(b) With \\((\\checkmark)\\), without \\((\\times)\\) dropout" + }, + { + "type": "table_caption", + "bbox": [ + 0.518, + 0.476, + 0.873, + 0.488 + ], + "angle": 0, + "content": "Table 6. Ablation studies on (a) Number of MCN heads, (b) Drop." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.509, + 0.892, + 0.63 + ], + "angle": 0, + "content": "embedding space where different actions are well-aligned. In Fig. 7, we show the ground-truth, trivial estimate via frame-counting, and \\(\\hat{\\pi}\\) by GTCC from a EgoProceL video. Notice GTCC can effectively predict the progress online and better than the trivial estimate from frame-counting. In Fig. 8, we show results for in-the-wild frame retrieval for GTCC on the COIN dataset. This figure showcases the ability of GTCC to align frames with high visual similarity." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.645, + 0.627, + 0.66 + ], + "angle": 0, + "content": "7. Conclusions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.671, + 0.892, + 0.807 + ], + "angle": 0, + "content": "We studied a self-supervised approach, based on a proposed generalized temporal cycle consistency (GTCC) method, for video alignment and progress prediction, coupled with a novel attention-based architecture for multi-task learning. Our extensive experiments show that GTCC outperforms the state of the art, especially for in-the-wild videos. Additionally, we highlight the efficacy of our MCN architecture for enhancing multi-task learning. The fusion of GTCC and MCN emerges as a competitive and versatile framework." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.822, + 0.667, + 0.839 + ], + "angle": 0, + "content": "Acknowledgements" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.841, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This work is sponsored by DARPA PTG (HR00112220001), NSF (IIS-2115110), ARO (W911NF2110276). Content does not necessarily reflect the position/policy of the Government." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "18674" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.176, + 0.107 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.183 + ], + "angle": 0, + "content": "[1] Galen Andrew, Raman Arora, Jeff Bilmes, and Karen Livescu. Deep canonical correlation analysis. 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Our proposed self-supervised representation learning method carefully addresses different action orderings, redundant actions, and background frames to generate improved video representations compared to previous methods. Our model generalizes temporal cycle-consistency learning to allow for more flexibility in determining cycle-consistent neighbors. More specifically, to handle repeated actions, we propose a multi-neighbor cycle consistency and a multi-cycle-back regression loss by finding multiple soft nearest neighbors using a Gaussian Mixture Model. To handle background and redundant frames, we introduce a context-dependent drop function in our framework, discouraging the alignment of droppable frames. On the other hand, to learn from videos of multiple activities jointly, we propose a multi-head crosstalk network, allowing us to embed a video and estimate progress without knowing its activity label. Experiments on multiple datasets show that our method outperforms the state-of-the-art for video alignment and progress prediction. + +# 1. Introduction + +Understanding progress is central to a human's learning experience. We constantly modify and enhance our actions and behaviors based on our progress in different daily tasks [31]. Progress understanding is also fundamental for machines whose goal is to guide (e.g., assistive technologies) and seamlessly interact (e.g., robots) with humans [6, 35]. Imagine wearing augmented reality (AR) assistant glasses when assembling a complex machine, performing a medical procedure, or cooking a new hour-long recipe. Depending on the amount of progress made in the + +![](images/4bbba8cf86942d1abfdf2269970f12c19990f20d4ac52bcc6512b1b0ba5d457d.jpg) +Figure 1. We develop a framework for self-supervised in-the-wild video alignment and online activity progress prediction. + +current step, the AR needs to show information about the current or next step(s). Additionally, progress is an important signal for computer vision tasks to run on AR task assistants, such as action segmentation and anticipation (depending on little/full progress in a step, subsequent frames will belong to the same/next step) [50] and anomaly/errordetection (a decrease in progress indicates an error) [34]. + +Learning to predict progress, however, is challenging [8]. Progress can not be precisely calculated solely on the amount of time spent in an action (an expert often makes more progress than a novice within the same time window) and can be influenced by factors other than the user such as the environment (imagine cooking a recipe in a well-organized vs a cluttered kitchen). To estimate progress, we can break down an action into smaller phases and track where the user is within these phases (e.g., putting a coffee filter into a dripper involves taking a filter from its bag, folding it in half, folding it again into a quarter circle, creating a cone and inserting it into the dripper). Therefore, one approach for progress estimation is to label video clips of an action with its different phases and train a supervised phase classification model [3]. However, the ambiguity of defining a dictionary of fine-grained phases in advance and the high cost of annotating video frames with many action phases makes supervised learning impractical. + +Self-supervised video alignment is an appealing alternative for progress prediction. It finds frame representations and associations between frames of different videos (ideally, aligning the same phases across videos), without requiring fine-grained human labeling. There has been a large body of recent literature addressing video alignment + +using different approaches, such as temporal cycle consistency (TCC) [12], dynamic time warping [11, 16, 17] and optimal transport [39]. However, after aligning videos and learning the embedding space, progress prediction has been simply treated as fitting a linear regression model to the embeddings by assuming a linear progress model [12, 17, 39]. + +Limitations. Existing self-supervised methods have limitations for video alignment as well as progress prediction. First, when it comes to video alignment, the majority of existing works assume the same ordering of phases (monotonic), which is often violated in real videos (e.g., you can put a filter in a dripper and then put the dripper on the mug or vice versa). Additionally, some videos may have additional steps or background, which should not be aligned. Therefore, the recent approach in [39] (coined VAVA) addressed sequence alignment by considering background and redundant frames as well as non-monotonic ordering by imposing a temporal prior and an optimal prior on an optimal transport formulation, an intra-video contrastive term and an inter-video contrastive term. However, balancing multiple losses and handling repeated actions in the self-supervised setting is challenging and enforcing a temporal prior is unfit for in-the-wild alignment. Moreover, existing alignment techniques train distinct models for each action, resulting in substantial memory and computational overhead. This approach also complicates inference since activity/task identification is necessary, posing challenges particularly at the onset of activity/task execution. + +Paper Contributions. In this paper, we develop a framework for self-supervised video alignment and online progress prediction that addresses the limitations of existing works, see Figure 1. We propose a generalization of TCC [12] to model background and redundant frames, as well as repetitive actions when performing alignment. More specifically, to handle repeated actions, we propose a multi-neighbor cycle consistency and a multi-cycle-back regression loss by finding multiple soft nearest neighbors using a Gaussian Mixture Model (GMM) instead of a single neighbor as in TCC. To handle background and redundant frames, we introduce a context-dependent drop function, discouraging the alignment of droppable frames. + +On the other hand, to effectively align videos of multiple activities jointly and to better leverage their shared information while handling their distinctions, we propose a multi-head crosstask network, where each head automatically learns to focus on relevant components of video pairs. Thus, we can embed a video and estimate progress without knowing its activity label. Through extensive experiments on multiple datasets, we show the effectiveness of our framework for video alignment and progress estimation. + +# 2. Related Works + +Self-Supervised Video Representation Learning. Given the high annotation cost for video-based action learning and the need for copious amounts of data when training deep networks, many researchers have turned to self-supervised methods for embedding video frames [9, 28, 38, 42, 45, 60, 72]. Self-supervision has largely been popularized as a result of higher quality image embedding techniques trained on large-scale image datasets such as [10, 27, 37]. With better datasets, pre-trained image encoders, such as [18, 53-55], allow for more meaningful features that can enhance the performance of self-supervised representation learning methods. Many downstream tasks benefit from self-supervised video representation learning, such as action recognition [26, 71], temporal action segmentation [23, 33, 63, 65], step localization [14, 71], video retrieval [68], text-to-video retrieval [41], and audio-visual representation learning [25]. + +Video Alignment is the task of temporally synchronizing videos, such that similar frames or segments in separate videos can be mapped to each other. Traditional methods such as Dynamic Time Warping (DTW) [7, 11, 13, 16, 17, 47], or Canonical Correlation Analysis (CCA) [1, 21, 26, 48] have been used to align video frames. Many methods have adopted the use of Soft-DTW [7, 11, 16, 17, 40], where the gradient is well-defined and back-propagation is feasible. LAV [17] is a self-supervised video alignment method, which uses Soft-DTW in conjunction with temporal intra-video contrastive loss terms. Other contrastive approaches include [5, 39, 42, 49, 60, 66]. Drop-DTW [11] extends DTW by adding a "trash bucket" to the cost matrix for dynamic programming for background frame classification. Similarly, VAVA [39] added an additional bucket to the optimal transport formulation to align in-the-wild videos. VAVA also incorporated a bi-modal Gaussian prior on the optimal transport matrix, which allowed for the model to consider the temporality and optimality of the alignment. VAVA was shown to outperform previous methods for unconstrained procedural video datasets. Other methods capable of background detection but not video alignment include [4, 43, 51, 61, 62]. + +Cycle-consistency has been a pivotal technique in sequence alignment, involving the mapping of elements from one sequence to another, followed by an inverse mapping back to the original sequence. Beyond its application in video alignment, cycle-consistency finds utility in diverse domains, including 3D shape matching [22], depth estimation [15], co-segmentation [57, 58], and transitivity in deep learning [15, 69, 70]. Cycle-consistency was first introduced for self-supervised video alignment in TCC [12] and showed good performance in aligning synchronizable videos, such as the Penn Action dataset [67] or the Pour + +![](images/3ddc03ec78a02f309031b55b0e8b14c400d226a0bf7cb24f5560f2f669e641a0.jpg) +Figure 2. Cycle-consistency Visualization. Here, two videos are embedded by the alignment encoder, $\phi$ . With a green checkmark, a frame pair is shown to be cycle-consistent. With a red X-mark, a frame pair is shown to be not cycle-consistent. + +ing dataset [32]. Our method extends cycle-consistency to unconstrained videos, as observed in many datasets such as COIN [56] and EgoProceL [2]. + +Activity Progress Prediction is the task of predicting temporal progress in videos. While [3, 44] have studied a supervised approach for action progress prediction, they require temporal annotations of every action clip based on its phases, which is hard to define given the fine-grained nature of phases and cost to gather. Action completion [19, 20, 59, 68] is also related to progress, however it is only focused on classifying full progress achievement rather than predicting the progress at every time instant. In this work, we learn to predict progress at every frame in a self-supervised framework. Our proposed progress estimation technique also has applications in goal-based reinforcement learning, providing dense reward for learning [29, 64]. + +# 3. Problem Setting and Review + +In this section, we discuss the problem of video alignment and review temporal cycle consistency (TCC) [12], which we build upon and generalize. + +# 3.1. Video Alignment + +Given two video sequences $S = (s_1, \ldots, s_N)$ and $T = (t_1, \ldots, t_M)$ with $N$ and $M$ frames, respectively, we denote their embeddings by $U = (u_1, \ldots, u_N)$ and $V = (v_1, \ldots, v_M)$ . We use an encoder neural network $\phi$ to compute these embeddings, as depicted in Fig. 2. The goal of video alignment is to train the encoder, $\phi$ , such that if the two frames $s_i$ and $t_j$ represent the same action, the distance between their embeddings, $u_i \in \mathbb{R}^D$ and $v_j \in \mathbb{R}^D$ , will be small, otherwise, the distance will be large. + +# 3.2. Temporal Cycle Consistency (TCC) + +TCC [12] finds a symmetric nearest neighbor embedding space by maximizing the number of cycle-consistent embeddings between two sequences. More specifically, consider a frame $\boldsymbol{u}_i \in U$ , and let its Euclidean nearest neighbor from $V$ be denoted by $\boldsymbol{v}_j = \operatorname{argmin}_{\boldsymbol{v} \in V} \| \boldsymbol{u}_i - \boldsymbol{v} \|$ . Similarly, for a frame $\boldsymbol{v}_j \in V$ , denote its Euclidean nearest neighbor in $U$ by $\boldsymbol{u}_k = \operatorname{argmin}_{\boldsymbol{u} \in U} \| \boldsymbol{u} - \boldsymbol{v}_j \|$ . The frame $\boldsymbol{u}_i$ is cycle-consistent if and only if $i = k$ , see Fig. 2. TCC + +![](images/55b88eb4aa7512424e7eb4a15facd1517b021114ead01010df4caac5c159b78b.jpg) +(a) TCC + +![](images/724a60cc507f126190e85c9047e37baf96cf4f9d0c4706637d4cfc131ca96e9a.jpg) +(b) GTCC +Figure 3. TCC Failure for Repeated Actions. Common action segments of the sequences are shown using varying colors. $\alpha$ is depicted based on the initial frame, $u_{i}$ , from the yellow action segment. TCC (3a) only allows a single $\tilde{v}$ between both peaks in $\alpha$ . GTCC (3b) allows for two distinct neighbors, $\tilde{v}_{1}$ and $\tilde{v}_{2}$ , which accurately represents repeated actions. + +trains an encoder to embed frames such that the number of cycle-consistent frame embeddings is maximized across pairs of videos, hence, a symmetric nearest neighbor embedding space. Since argmin is non-differentiable, TCC adopts the softmax operation. Let $\Delta^M$ denote the probability simplex in $M$ dimensions.2 TCC begins by computing a soft nearest neighbor (SNN) of $\pmb{u}_i$ , denoted by $\tilde{\pmb{v}}$ , + +$$ +\tilde {\boldsymbol {v}} = \sum_ {j = 1} ^ {M} \alpha_ {j} \boldsymbol {v} _ {j}, \quad \text {w h e r e ,} \quad \alpha_ {j} = \frac {e ^ {- \| \boldsymbol {u} _ {i} - \boldsymbol {v} _ {j} \| ^ {2} / \tau}}{\sum_ {k = 1} ^ {M} e ^ {- \| \boldsymbol {u} _ {i} - \boldsymbol {v} _ {k} \| ^ {2} / \tau}}. \tag {1} +$$ + +Here $\alpha = [\alpha_{1},\ldots ,\alpha_{M}]\in \Delta^{M}$ is the outgoing normalized similarity (forward distribution) between $\pmb{u}_i$ and embeddings in $V$ , and $\tau$ is the softmax temperature. TCC then uses the SNN, $\tilde{\pmb{v}}$ , to compute $\beta = [\beta_{1},\dots,\beta_{N}]\in \Delta^{N}$ , which is the incoming normalized similarity (backward distribution) between $\tilde{\pmb{v}}$ and frame embeddings in $U$ , + +$$ +\beta_ {l} = \frac {e ^ {- \| \boldsymbol {u} _ {l} - \tilde {\boldsymbol {v}} \| ^ {2} / \tau}}{\sum_ {j = 1} ^ {N} e ^ {- \| \boldsymbol {u} _ {j} - \tilde {\boldsymbol {v}} \| ^ {2} / \tau}}. \tag {2} +$$ + +Cycle-consistency requires that $\beta$ must have the highest probability mass at index $i$ and very small mass at indices farther from $i$ . Thus, TCC imposes a Gaussian distribution prior $\mathcal{N}(\mu_{\beta},\sigma_{\beta}^{2})$ on entries of $\beta$ with mean $\mu_{\beta} = \sum_{l = 1}^{N}\beta_{l}\cdot l$ and variance $\sigma_{\beta}^{2} = \sum_{l = 1}^{N}\beta_{l}\cdot (l - \mu_{\beta})^{2}$ . Requiring that the distribution mean be close to $i$ with a small variance leads to minimizing a cycle-back regression loss, defined as + +$$ +\mathcal {L} _ {\mathrm {c b r}} = \frac {(i - \mu_ {\beta}) ^ {2}}{\sigma_ {\beta} ^ {2}} + \lambda \log (\sigma_ {\beta}), \tag {3} +$$ + +where $\lambda$ is the regularization weight. This leads to a differentiable loss that can be optimized using backpropagation. + +# 4. Generalized Temporal Cycle Consistency (GTCC) + +One of the advantages of TCC [12] compared to DTW-based methods [11, 17] is that it does not assume/enforce + +![](images/966ed83a18e8b2ab8e3f38678d3afc2dc19b4e71a72eeb96697ef505ff5ee8bc.jpg) +Figure 4. GTCC. We encode two videos into $\mathbf{U}$ and $\mathbf{V}$ and calculate the forward distribution, $\alpha$ . We use the output of the GMM optimization procedure and obtain $K$ SNNs from $K$ discrete Gaussians. We then compute $\beta^{(k)}$ for each SNN. We also estimate the drop probability of each frame $\mathrm{P}_{\mathrm{drop}}(\pmb{u}_i|\mathbf{V})$ using a conditional network. Finally, we compute the final loss by weighting each cycle-back regression loss with weight from mixture densities, $\psi$ , and modulate with the drop probabilities. + +monotonic ordering of actions across videos. On the other hand, it has two major drawbacks when it comes to aligning in-the-wild videos. + +First, TCC cannot handle background and additional actions, because it enforces cycle-consistency for every frame embedding. However, background actions (e.g., 'answering phone' when making coffee) or additional actions (e.g., the optional step of 'cleaning coffee filter') in one video but not in another should not be aligned. + +Second, the TCC model assumes that each action only appears once in a video, therefore, cannot model action repetitions (e.g., repeating the actions of 'give breath' and 'give chest compression' when performing CPR). This is because computing the SNN in TCC is done with a unimodal Gaussian assumption on the similarity distributions, which is violated when an action is repeated in a video and leads to computing bad SNNs, see Fig. 3. We propose generalized temporal cycle consistency (GTCC), which addresses these limitations and aligns videos in the wild. + +# 4.1. Multi-Cycle Consistency via Mixture SNNs + +We propose multi-neighbor cycle consistency and a multicycle-back regression loss to handle repeated actions, see Fig. 4. For $\pmb{u}_i \in U$ belonging to an action $a$ , a single SNN $\tilde{\pmb{v}}$ obtained using (1) is restrictive when action $a$ is repeated in the sequence $V$ . In such a case, as 3 shows, $\pmb{u}_i$ will have multiple good nearest neighbors, yet the SNN $\tilde{\pmb{v}}$ captures an average representation of them leading to a suboptimal solution. Therefore, we generalize TCC to allow for multiple SNNs and to assign an importance score to each SNN. This allows our model to find a set of SNNs based on a given $\pmb{u}_i$ , and to automatically gain awareness of their relative importance for promoting multiple-neighbor cycle-consistency. + +For $\pmb{u}_i \in U$ , we first obtain the outgoing distribution $\alpha = [\alpha_1, \dots, \alpha_M]$ , where $\alpha_j$ 's are computed using (1). We then approximate $\alpha$ with a discretized Gaussian Mixture Model (GMM) to capture different distribution modes corresponding to the same action. More specifically, we model + +$$ +\alpha_ {j} \approx p _ {j} = \sum_ {k = 1} ^ {K} \psi_ {k} p _ {j} ^ {(k)}, \tag {4} +$$ + +where $p_j^{(k)}$ is the outgoing probability of index $j$ in video $\mathbf{V}$ for the $k$ -th discretized Gaussian distribution $\mathcal{N}(\mu_{\alpha,k}, \sigma_{\alpha,k}^2)$ and $\psi_k$ denotes the weight of the mixture component $k$ . Here, $K$ is a hyperparameter defining the total number of mixture components. We typically set $K = 10$ in our experiments and as we show the results do not change much for different values of $K$ as long as it is not very small. We find the parameters of the GMM, which are $\{\mu_k, \sigma_k^2, \psi_k\}_{k=1}^K$ , by minimizing the KL divergence [52] between the two distributions $[\alpha_1, \ldots, \alpha_M]$ and $[p_1, \ldots, p_M]$ . After finding the parameters of the GMM, we then compute one SNN for each mixture component, + +$$ +\tilde {\boldsymbol {v}} ^ {(k)} = \sum_ {j = 1} ^ {M} p _ {j} ^ {(k)} \cdot \boldsymbol {v} _ {j}, \quad \forall k \in \{1, \dots , K \}. \tag {5} +$$ + +With these $K$ SNNs of $\pmb{u}_i\in \pmb{U}$ , we then compute the incoming similarity distribution $\beta^{(k)}$ for each SNN, $\tilde{\pmb{v}}^{(k)}$ . TCC assumes that throughout the sequence $\pmb{U}$ , $\beta$ should only have a sharp peak at index $i$ . For in-the-wild videos, this presents a challenge when $\pmb{u}_i$ belongs to a repeated or non-contiguous action segment, where there would be more than one valid peak in the incoming distribution. To address this, we only enforce a local sharp peak around $i$ for a discrete temporal window, $w$ , where any index outside the $i$ -centered window has zero probability (see supplementary materials for more details). For each $\beta^{(k)}$ , we compute the mean and variance over the indices of $\pmb{U}$ + +$$ +\mu_ {\beta , k} = \sum_ {l = 1} ^ {N} \beta_ {l} ^ {(k)} \cdot l, \quad \sigma_ {\beta , k} ^ {2} = \sum_ {l = 1} ^ {N} \beta_ {l} ^ {(k)} \cdot (l - \mu_ {\beta , k}) ^ {2}. \tag {6} +$$ + +Finally, we compute one cycle-back regression loss for each mixture component as + +$$ +\mathcal {L} _ {\mathrm {c b r}} ^ {(k)} = \frac {\left(i - \mu_ {\beta , k}\right) ^ {2}}{\sigma_ {\beta , k} ^ {2}} + \lambda \cdot \log (\sigma_ {\beta , k}). \tag {7} +$$ + +Given that $\psi_{k}$ is the relative importance of the $k$ -th discrete Gaussian distribution, we build a multi-cycle back regression loss as + +$$ +\mathcal {L} _ {\text {m u l t i - c b r}} = \sum_ {k = 1} ^ {K} \psi_ {k} \cdot \mathcal {L} _ {\text {c b r}} ^ {(k)}. \tag {8} +$$ + +![](images/feac05244c55a31fc7347e273b2a78881fef57f2a90c4ab89735abd38d6be432.jpg) +Figure 5. Multi-head Crosstalk Network (MCN). Input frames, $S$ , are given to the base network to obtain base features, $U^b$ , which are subsequently given to $L$ head networks that output intermediate video encodings, $\{U_l^h\}_{l=1}^L$ . We obtain the final video encoding $U$ using attention over the outputs of the $L$ heads. + +# 4.2. Droppable Frame Detection + +Another major limitation of TCC is that it cannot handle background and additional actions since it enforces cycle-consistency for all embeddings. GTCC addresses this issue by detecting frames in $U$ to be dropped based on the frames in $V$ and subsequently enforcing (i) multi-cycle consistency for alignable embeddings and (ii) bad alignment for droppable embeddings. Information (context) from video $V$ is necessary when dropping frames in video $U$ because the model can not know to drop frames corresponding to an additional action unless that action is not present in $V$ . + +More specifically, we learn a drop-context function, $c: \mathbb{R}^D \to \mathbb{R}^{D+1}$ , characterized by a feedforward neural network, using all the embeddings $v_j \in V$ as + +$$ +\boldsymbol {c} (\boldsymbol {V}) = \frac {1}{M} \sum_ {j = 1} ^ {M} \boldsymbol {c} \left(\boldsymbol {v} _ {j}\right) \in \mathbb {R} ^ {D + 1}. \tag {9} +$$ + +GTCC uses the information in $\mathbf{V}$ to condition the drop detection in $\mathbf{U}$ . More specifically, for each $\pmb{u}_i\in U$ , we use a logistic regression model to compute the probability of dropping $\pmb{u}_i$ given $\mathbf{V}$ as + +$$ +\mathrm {P} _ {\text {d r o p}} \left(\boldsymbol {u} _ {i} \mid \boldsymbol {V}\right) = \sigma \left(\left[ \boldsymbol {u} _ {i} ^ {\top} \quad 1 \right] \boldsymbol {c} (\boldsymbol {V})\right), \tag {10} +$$ + +where $\sigma$ is the sigmoid function. We use the drop probability to build our final loss function, which we discuss next. + +# 4.3. Learning GTCC + +To learn the parameters of the embedding network $\phi$ and the drop-context model, we propose a loss so that alignable frames are encouraged to have good cycle-consistency and droppable frames are encouraged to have bad alignment. This dichotomy isolates the cycle-consistency property only to frames that are deemed 'alignable', and ensures frames deemed 'droppable' have no good nearest neighbors. We propose to minimize + +$$ +\mathcal {L} = \left(1 - \mathrm {P} _ {\text {d r o p}} (\boldsymbol {u} _ {i} | \boldsymbol {V})\right) \cdot \mathcal {L} _ {\text {m u l t i - c b r}} + \frac {\mathrm {P} _ {\text {d r o p}} (\boldsymbol {u} _ {i} | \boldsymbol {V})}{\mathcal {L} _ {\text {m u l t i - c b r}}}, \tag {11} +$$ + +where we minimize the multi-cycle-back regression loss for alignable frames for which $\mathrm{P}_{\mathrm{drop}}(\pmb {u}_i|\pmb {V})$ is close to 0, and maximize the multi-cycle-back regression loss for drop-. pable frames for which $\mathrm{P}_{\mathrm{drop}}(\pmb {u}_i|\pmb {V})$ is close to 1. Notice one can also use $-\mathcal{L}_{\mathrm{multi - cbr}}$ instead of $1 / \mathcal{L}_{\mathrm{multi - cbr}}$ in (11), however, the latter worked better in our experiments. + +# 4.4. Online Progress Estimation + +At inference time, given an online sequence up to frame $\pmb{u}_i$ , we want to estimate the progress, denoted by $\hat{\pi}(\pmb{u}_i) \in [0,1]$ . We do so, by using the cumulative inter-frame geodesic distance on the frame features, + +$$ +\hat {\pi} \left(\boldsymbol {u} _ {i}\right) = \frac {\sum_ {t = 1} ^ {i - 1} \left\| \boldsymbol {u} _ {t + 1} - \boldsymbol {u} _ {t} \right\|}{\hat {G}}, \tag {12} +$$ + +where $\hat{G}$ is ideally the total geodesic distance for the complete sequence (including past and future observations). Given that we do not have access to the future frames, we estimate $\hat{G}$ by averaging the total geodesic distances for all aligned training videos of the given task. + +# 5. GTCC Embedding Network + +Our goal is to train an embedding model that can leverage the shared information across related actions or tasks (e.g., making otime and making scrambled eggs) for better feature learning and alignment of each task individually, while not requiring to know the action or task label of the video at inference time. Existing works, which train a separate model for each action/task, have neither of these capabilities. Therefore, we propose a new architecture, which we refer to as Multi-head Crosstalk Network (MCN), shown in Fig. 5. MCN consists of a base network, multiple head networks, and an attention network. MCN base network is intended to output general useful features (across actions/tasks) to be used by multiple $(L)$ head networks. Ideally, each head network specializes in aligning related phases of an action or steps of a task. The attention network takes all features from the head networks at each time instant and selects the relevant head and its features. See the supplemental material for more details. + +# 6. Experiments + +# 6.1. Experimental Setup + +Datasets. We use four datasets for evaluations, two monotonic and two in-the-wild datasets. Similar to previous works [12, 17, 39], we report results on Pouring [32] and Penn Action [67] datasets, which are monotonic. Pouring contains videos of humans pouring liquid into a cup (e.g., orange juice poured into a blue cup), and Penn Action contains videos of humans completing athletic maneuvers (e.g., a woman serving a tennis ball). We also use COIN [56] + +and EgoProceL [2], which are in-the-wild datasets, consisting of background frames, action repetitions, and different sequences of actions. EgoProceL is an egocentric dataset comprised of a collection of several datasets, including CMU-MMAC [30], EGTEA Gaze+ [36], MECCANO [46], and EPIC-tent [24]. + +For Pouring, Penn Action, and COIN, we use $75\%$ of videos for training and $25\%$ for testing, while for EgoProceL we use $70\%$ for training and $30\%$ for testing since there are fewer videos per task. We also study two settings for evaluation. (i) Similar to prior works, we train a model separately for videos of each activity (single-task setting), whereas following other works we use an embedding network that corresponds to the base network in Fig. 5. (ii) We train a single model on videos of all activities jointly (multi-task setting). In Tab. 4, we test the multi-task setting using only the base network vs the full MCN architecture. + +Evaluation Metrics. We use multiple metrics to evaluate the performance of different methods for alignment and progress prediction. For evaluating alignment, we use the existing metrics Phase Classification (PC) [12], Enclosed Area Error (EAE) [13] and Kendall's Tau (KT) [12]. PC measures how well the encoder can put frames belonging to the same action class together, thus a higher value is better. Similar to previous works, we use PC, where an SVM classifier is trained on $10\%$ , $50\%$ , and $100\%$ of the ground-truth action labels. While PC measures how well different actions are separated from each other, it does not measure the quality of alignment within each action. Thus, we use Enclosed Area Error (EAE) that measures the alignment error within and across actions by comparing the nearest neighbors between two videos with their ground-truth alignment. When computing EAE for in-the-wild video pairs, we only include alignable frames in the computation. In cases where a frame has multiple valid neighbors, we calculate the smallest EAE among the set of neighbors. EAE is an error metric, therefore lower values indicate better alignment. See [13] for more details about EAE. + +KT is a statistical measure that indicates how well-aligned two sequences are temporally. Given that KT is only suitable for monotonic sequences, we also propose a modified Kendall's Tau for in-the-wild datasets, which we call Kendall's Tau in the Wild (KTW). More specifically, we only evaluate KT on alignable frames and consider all variations of valid alignment for concordancy. This increases forgiveness when finding concordant pairs, because there may be many concordant neighbors for a frame in a redundant action segment. Therefore, KTW highlights the presence of disconcordant pairs. + +To evaluate progress estimation, we use PHase Progression (PHP) [12] and introduce Online Progress Error (OPE). PHP trains a linear regressor over frame features to predict ground-truth progress values and computes the av + +
DatasetModelPC↑EAE↓KT↑PHP↑OPE↓
0.10.51.0
PouringSAL85.787.888.0—73.374.5—
TCN89.290.490.4—86.780.6—
TCC89.291.491.814.085.280.338.9
LAV91.692.892.89.085.680.531.4
VAVA91.791.892.529.687.683.637.8
GTCC71.289.293.57.988.185.822.5
Penn ActionSAL74.978.380.0—63.459.4—
TCN82.083.784.0—73.367.6—
TCC81.383.484.518.273.567.335.5
LAV83.684.084.320.580.566.125.5
VAVA83.984.084.523.280.570.980.5
GTCC78.381.281.316.788.370.814.5
+ +Table 1. Alignment and progress evaluations on monotonic datasets. + +
DatasetModelPC ↑EAE ↓KTW ↑OPE ↓
0.10.51.0
EgoProceLTCC66.067.468.321.513.934.0
LAV67.268.268.820.812.736.2
VAVA65.365.966.323.213.135.5
GTCC75.078.980.613.314.013.6
COINTCC35.939.640.728.018.828.7
LAV36.838.939.826.723.222.7
VAVA43.846.247.332.022.227.6
GTCC46.853.256.318.929.021.4
+ +Table 2. Alignment and progress evaluations on in-the-wild datasets. + +erage $R$ -squared measure over all videos. PHP assumes monotonicity in action sequences and, therefore, is only evaluated on the monotonic datasets. On the other hand, our online progress estimation in (12) applies to monotonic and in-the-wild datasets. Following [3], at each frame $\pmb{u}_i$ we define a ground-truth progress value $\pi (\pmb{u}_i)\in [0,1]$ assuming that (i) each action segment contributes equally to the overall progress, and (ii) progress linearly increases throughout the duration of each action segment. We assume that silent frames do not contribute to progress, hence progress values remain constant during silent segments, see 6. We define OPE as the mean absolute difference between predicted progress and ground-truth online progress (lower is better). + +Baselines. For the single-task setting, we compare our GTCC against SAL [42], TCN [49], TCC [12], LAV [17] and VAVA [39]. Among them, only VAVA is specifically designed for handling in-the-wild videos. For the multi-task setting, we compare GTCC with LAV and VAVA, which are state-of-the-art. + +On the Penn Action, Pouring, and COIN datasets, for the single-task setting, we report the PC, PHP, and KT as previously reported in the most recent work [39]. Given that previous methods did not report EAE, KTW, and OPE, we re-implement all baselines on all datasets to report the performance based on these metrics. Similarly, we reproduce all numbers for the MCN multi-task (Table 4) and the EgoProceL experiments (Tables 2, 3, 4, 5, 6). + +Implementation Details For the single-task setting, following all previous baselines, we use ResNet-50 [18] for the architecture of the encoder network. Please see [12] for more + +
DatasetModelPrecisionRecallF1Accuracy
EgoProceLVAVA66.098.477.064.3
GTCC67.597.978.268.9
COINVAVA41.778.853.544.7
GTCC51.988.265.362.0
+ +Table 3. Evaluation of handling background actions (i.e., drop) of VAVA vs GTCC for the in-the-wild datasets. + +
DatasetMethodArch.PC↑EAE↓KT↑KTW↑PHP↑OPE↓
CMU-MMACLAVResNet65.222.2—6.8—18.2
MCN69.813.4—12.1—16.1
VAVAResNet62.524.0—5.1—20.7
MCN63.719.7—11.4—17.9
GTCCResNet70.426.8—9.0—25.2
MCN67.814.9—21.8—14.0
EGTEALAVResNet82.519.7—2.8—17.9
MCN82.111.4—38.7—22.4
VAVAResNet83.219.6—2.7—19.6
MCN82.310.7—38.1—19.7
GTCCResNet83.617.2—3.3—19.5
MCN82.510.2—47.6—16.0
Penn ActionLAVResNet78.720.568.4—62.527.7
MCN85.35.794.3—69.08.6
VAVAResNet80.326.276.2—64.837.9
MCN85.45.994.4—72.614.3
GTCCResNet73.924.760.7—69.732.9
MCN86.75.694.9—85.59.4
+ +Table 4. Alignment and progress evaluation for the multi-task setting when training on ResNet-50 vs our proposed MCN architecture. + +details regarding the encoder architecture. For the multi-task setting, we compare the ResNet-50 embedding network with our multi-head crosstalk network (MCN), shown in Fig. 5, where the base network is ResNet-50 and all head and attention networks are 4-layer fully-connected feedforward network. For GTCC, we also simultaneously train a 4-layer feedforward neural network for the drop-context function, $\mathbf{c}$ , in Sec. 4.2. We use $K = 15$ for in-the-wild datasets and $K = 5$ for monotonic datasets. For multi-task experiments using MCN, we set the number of attention heads to be the number of tasks in the dataset. + +# 6.2. Experimental Results + +Single-Task Setting Results. Table 1 and 2 show the alignment and progress estimation evaluation of different methods for monotonic and in-the-wild datasets, respectively. Notice that for the monotonic datasets in Table 1, GTCC achieves significantly better EAE (for alignment) and OPE (for progress) on both datasets, e.g., improving the OPE from $25.5\%$ to $14.5\%$ and EAE from $18.2\%$ to $16.7\%$ on Penn Action. Similarly, our method achieves higher KT values, especially on Penn Action, where it outperforms other methods by at least $7.8\%$ . However, GTCC mostly does not improve the PC values of the baselines. This is because PC does not directly represent precise alignment but instead measures the effectiveness of clustering action segments. + +On the other hand, as the results in Table 2 show, + +![](images/0f152b3b25950650128d033047c5c997db9ba2fd25c0c69eefe44a9f2750ec58.jpg) +(a) GTCC + +![](images/c1ecabf61b822a1d11e6b0069c1fb8f4ec0e99710fa9f79653c8d92854fe7431.jpg) +(b) VAVA + +![](images/6b062240a71ce69234edf228dd5720343c00b1b5257138913d338910e8ccada4.jpg) +(c) LAV + +![](images/0527513895fbb74ff83d2ac3c0ef02f074e64b1550ce08cfe6f687ef5f06f420.jpg) +(d) TCC +Figure 6. Online progress estimation for GTCC (6a), VAVA (6b), LAV (6c) and TCC (6d) for a video from the task "making brownies" in the EgoProceL dataset. + +GTCC significantly outperforms all baselines for all metrics. Specifically, GTCC improves the EAE by at least $7.5\%$ on both EgoProceL and COIN and reduces OPE from $34.0\%$ to $13.6\%$ on EgoProceL and from $22.7\%$ to $21.4\%$ on COIN. Similarly, our method significantly improves the PC and KTW over the state-of-the-art. This is thanks to the fact that GTCC is specifically designed to handle inthe-wild videos that contain action repetitions, background activities, and action ordering variations. + +Drop Performance. Table 3 compares the effectiveness of VAVA and GTCC for handling background activities on in-the-wild datasets for the single-task setting. We measure the precision, recall, F1 score, and accuracy of dropping background frames during pairwise alignment. Notice that on both datasets, GTCC has a higher F1 score and accuracy. Notably, GTCC achieves $62.0\%$ accuracy on COIN compared to $44.7\%$ by VAVA and obtains $68.9\%$ accuracy on EgoProceL compared to $64.3\%$ by VAVA. This shows the effectiveness of our context-based drop and alignment, which jointly learns alignable and droppable frames with a soft probabilistic approach. + +Multi-Task Setting Results. In Table 4, we show the alignment and progress evaluations of LAV, VAVA, and GTCC for the multi-task setting, where we use all videos in each dataset to learn a single embedding network. We compare using ResNet-50 with using our proposed MCN architecture. Since GTCC outperformed TCC on progress and alignment metrics in the previous experiments, we do not report the results for TCC. As the results demonstrate, using ResNet for embedding in the multi-task setting leads to generally low performances for all methods. For example, on CMU-MMAC, KTW is less than $9\%$ and EAE is more than $22\%$ for all methods (similarly on EGTEA). On the other + +![](images/82ce6af0a632d6a59a1e01c07765bddc783a7e2f7aa8fb3752d58e6f56f59e0c.jpg) +Figure 7. Task Progression. Frames from a video of the "pizza" task in EgoProceL. On top is the ground-truth progress $(\pi_{\mathrm{gt}})$ , in green is the geodesic progress from GTCC $(\pi_{\mathrm{geo}})$ , and in red is the trivial progress $(\pi_{\mathrm{triv}})$ obtained by dividing test video time-steps by mean total video length from the train set. + +![](images/b8862a86b9975cd36c5bd0ec9c0130ff690b2c8411453257ee8c3017e2b69e94.jpg) + +![](images/ad6dffdc4953f16821ca84750b789d2240af0456cf264271ec10d05a0de6bf32.jpg) + +![](images/2ced7ee80cba1d0a3c09817338d956f38b2a85a5524f84896446e54d30a0d5f6.jpg) + +![](images/e1d95b2f7fc2436c40628549a6a7d65c30518eefdeb8500ff504a81c44ed2686.jpg) + +![](images/05b42fd80a3f1e129e2ad7fdc602729d2a920cc87b01a8fe70dd599d33915d55.jpg) + +![](images/2b283c4257536ea191704f5c986fed8d2621806dc8d4928df98b015e76889663.jpg) + +
EAE ↓OPE ↓PC(1.0) ↑
K151015151015151015
EgoP19.419.218.719.420.420.020.320.973.974.875.574.3
COIN23.221.422.218.925.523.122.021.450.149.648.946.8
Pour11.611.111.711.59.712.310.910.287.184.984.986.3
Penn26.716.016.116.115.216.717.816.780.078.278.2278.9
+ +hand, $\frac{6}{9}$ PC metrics, $\frac{9}{9}$ EAE metrics, $\frac{3}{3}$ KT metrics, $\frac{6}{6}$ KTW metrics, $\frac{3}{3}$ PHP metrics, and $\frac{7}{9}$ OPE metrics show improvement with the MCN architecture. Table 4 shows that when using MCN, the EAE, KT, KTW, and PHP metrics outperform $100\%$ of the time, while PC and OPE outperform $67\%$ and $78\%$ of the time. This is because our architecture learns to specialize multiple heads for related actions using attention, while ResNet trains a single shared base model for all actions including the ones that are considerably different (e.g., serving tennis and jumping jack). + +GMM Tuning and Ablations. Table 5 shows the effect of the number of mixture components, $K$ , in the GMM on alignment and progress performance for GTCC. Notice that performance does not vary much under different values of $K$ , showing the robustness of our approach. It is important to note that, as expected, $K = 1$ performs better comparatively on monotonic datasets than in-the-wild datasets. + +Table 6 ablates the number of MCN heads (6a), and the drop term in GTCC (6b). We gather from 6a that alignment performance improves when the number of MCN heads scales alongside the number of tasks in the dataset (5 for both EGTEA Gaze+ and CMU-MMAC, which have 5 tasks). Finally, we see in 6b that the removal of the drop term leads to degraded performance, further showing the importance of the drop term in GTCC. + +Qualitative Results. In Fig. 6, we show the comparison of different methods for online progress estimation on a test video from the task "making brownies" from the EgoProceL dataset. For each method, we show the ground-truth progress vs progress estimated via (12), $\hat{\pi}$ , using the learned embeddings. Notice that GTCC's estimation of the progress fits the ground-truth nicely, while other methods have a large gap. This is because GTCC can effectively drop frames that correspond to background, while obtaining an + +![](images/97736f94ff9e710fc7697054266d8388d69e00783422f5678cdc93611323c111.jpg) +Figure 8. In-the-wild Frame Retrieval from COIN dataset. + +Table 5. Effect of the number of GMM components, $K$ ,on GTCC. + +
PC(1.0)↑EAE↓
# Heads15201520
CMU66.767.864.729.514.929.0
EGTEA82.382.582.015.510.219.3
+ +(a) Number of MCN heads. + +
PC(1.0)↑EAE↓
Drop✓×✓×
Ego80.665.213.324.3
COIN56.346.618.927.9
+ +(b) With $(\checkmark)$ , without $(\times)$ dropout + +Table 6. Ablation studies on (a) Number of MCN heads, (b) Drop. + +embedding space where different actions are well-aligned. In Fig. 7, we show the ground-truth, trivial estimate via frame-counting, and $\hat{\pi}$ by GTCC from a EgoProceL video. Notice GTCC can effectively predict the progress online and better than the trivial estimate from frame-counting. In Fig. 8, we show results for in-the-wild frame retrieval for GTCC on the COIN dataset. This figure showcases the ability of GTCC to align frames with high visual similarity. + +# 7. Conclusions + +We studied a self-supervised approach, based on a proposed generalized temporal cycle consistency (GTCC) method, for video alignment and progress prediction, coupled with a novel attention-based architecture for multi-task learning. Our extensive experiments show that GTCC outperforms the state of the art, especially for in-the-wild videos. Additionally, we highlight the efficacy of our MCN architecture for enhancing multi-task learning. The fusion of GTCC and MCN emerges as a competitive and versatile framework. + +# Acknowledgements + +This work is sponsored by DARPA PTG (HR00112220001), NSF (IIS-2115110), ARO (W911NF2110276). Content does not necessarily reflect the position/policy of the Government. + +# References + +[1] Galen Andrew, Raman Arora, Jeff Bilmes, and Karen Livescu. Deep canonical correlation analysis. In Proceedings of the 30th International Conference on Machine Learning, pages 1247-1255, Atlanta, Georgia, USA, 2013. PMLR. 2 +[2] Siddhant Bansal, Chetan Arora, and C.V. Jawahar. My view is the best view: Procedure learning from egocentric videos. In European Conference on Computer Vision (ECCV), 2022. 3, 6 +[3] Federico Becattini, Tiberio Uricchio, Lamberto Ballan, Lorenzo Seidenari, and A. Bimbo. Am i done? predicting action progress in videos. 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Learning representational invariances for data-efficient action recognition. 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Our proposed self-supervised representation learning method carefully addresses different action orderings, redundant actions, and background frames to generate improved video representations compared to previous methods. Our model generalizes temporal cycle-consistency learning to allow for more flexibility in determining cycle-consistent neighbors. More specifically, to handle repeated actions, we propose a multi-neighbor cycle consistency and a multi-cycle-back regression loss by finding multiple soft nearest neighbors using a Gaussian Mixture Model. To handle background and redundant frames, we introduce a context-dependent drop function in our framework, discouraging the alignment of droppable frames. On the other hand, to learn from videos of multiple activities jointly, we propose a multi-head crosstalk network, allowing us to embed a video and estimate progress without knowing its activity label. Experiments on multiple datasets show that our method outperforms the state-of-the-art for video alignment and progress prediction." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 543, + 127, + 555 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 543, + 127, + 555 + ], + "spans": [ + { + "bbox": [ + 47, + 543, + 127, + 555 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 563, + 287, + 684 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 563, + 287, + 684 + ], + "spans": [ + { + "bbox": [ + 46, + 563, + 287, + 684 + ], + "type": "text", + "content": "Understanding progress is central to a human's learning experience. We constantly modify and enhance our actions and behaviors based on our progress in different daily tasks [31]. Progress understanding is also fundamental for machines whose goal is to guide (e.g., assistive technologies) and seamlessly interact (e.g., robots) with humans [6, 35]. Imagine wearing augmented reality (AR) assistant glasses when assembling a complex machine, performing a medical procedure, or cooking a new hour-long recipe. Depending on the amount of progress made in the" + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 306, + 225, + 539, + 299 + ], + "blocks": [ + { + "bbox": [ + 306, + 225, + 539, + 299 + ], + "lines": [ + { + "bbox": [ + 306, + 225, + 539, + 299 + ], + "spans": [ + { + "bbox": [ + 306, + 225, + 539, + 299 + ], + "type": "image", + "image_path": "4bbba8cf86942d1abfdf2269970f12c19990f20d4ac52bcc6512b1b0ba5d457d.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 301, + 545, + 322 + ], + "lines": [ + { + "bbox": [ + 306, + 301, + 545, + 322 + ], + "spans": [ + { + "bbox": [ + 306, + 301, + 545, + 322 + ], + "type": "text", + "content": "Figure 1. We develop a framework for self-supervised in-the-wild video alignment and online activity progress prediction." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 342, + 546, + 426 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 342, + 546, + 426 + ], + "spans": [ + { + "bbox": [ + 304, + 342, + 546, + 426 + ], + "type": "text", + "content": "current step, the AR needs to show information about the current or next step(s). Additionally, progress is an important signal for computer vision tasks to run on AR task assistants, such as action segmentation and anticipation (depending on little/full progress in a step, subsequent frames will belong to the same/next step) [50] and anomaly/errordetection (a decrease in progress indicates an error) [34]." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 426, + 547, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 547, + 641 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 547, + 641 + ], + "type": "text", + "content": "Learning to predict progress, however, is challenging [8]. Progress can not be precisely calculated solely on the amount of time spent in an action (an expert often makes more progress than a novice within the same time window) and can be influenced by factors other than the user such as the environment (imagine cooking a recipe in a well-organized vs a cluttered kitchen). To estimate progress, we can break down an action into smaller phases and track where the user is within these phases (e.g., putting a coffee filter into a dripper involves taking a filter from its bag, folding it in half, folding it again into a quarter circle, creating a cone and inserting it into the dripper). Therefore, one approach for progress estimation is to label video clips of an action with its different phases and train a supervised phase classification model [3]. However, the ambiguity of defining a dictionary of fine-grained phases in advance and the high cost of annotating video frames with many action phases makes supervised learning impractical." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 547, + 714 + ], + "type": "text", + "content": "Self-supervised video alignment is an appealing alternative for progress prediction. It finds frame representations and associations between frames of different videos (ideally, aligning the same phases across videos), without requiring fine-grained human labeling. There has been a large body of recent literature addressing video alignment" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 693, + 286, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 286, + 713 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 47, + 693, + 286, + 713 + ], + "type": "text", + "content": "Code is publicly available at https://github.com/gerardDonahue/GTCC_CVPR2024." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18667" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 145 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 145 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 145 + ], + "type": "text", + "content": "using different approaches, such as temporal cycle consistency (TCC) [12], dynamic time warping [11, 16, 17] and optimal transport [39]. However, after aligning videos and learning the embedding space, progress prediction has been simply treated as fitting a linear regression model to the embeddings by assuming a linear progress model [12, 17, 39]." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 162, + 289, + 426 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 162, + 289, + 426 + ], + "spans": [ + { + "bbox": [ + 46, + 162, + 289, + 426 + ], + "type": "text", + "content": "Limitations. Existing self-supervised methods have limitations for video alignment as well as progress prediction. First, when it comes to video alignment, the majority of existing works assume the same ordering of phases (monotonic), which is often violated in real videos (e.g., you can put a filter in a dripper and then put the dripper on the mug or vice versa). Additionally, some videos may have additional steps or background, which should not be aligned. Therefore, the recent approach in [39] (coined VAVA) addressed sequence alignment by considering background and redundant frames as well as non-monotonic ordering by imposing a temporal prior and an optimal prior on an optimal transport formulation, an intra-video contrastive term and an inter-video contrastive term. However, balancing multiple losses and handling repeated actions in the self-supervised setting is challenging and enforcing a temporal prior is unfit for in-the-wild alignment. Moreover, existing alignment techniques train distinct models for each action, resulting in substantial memory and computational overhead. This approach also complicates inference since activity/task identification is necessary, posing challenges particularly at the onset of activity/task execution." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 443, + 288, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 443, + 288, + 598 + ], + "spans": [ + { + "bbox": [ + 46, + 443, + 288, + 598 + ], + "type": "text", + "content": "Paper Contributions. In this paper, we develop a framework for self-supervised video alignment and online progress prediction that addresses the limitations of existing works, see Figure 1. We propose a generalization of TCC [12] to model background and redundant frames, as well as repetitive actions when performing alignment. More specifically, to handle repeated actions, we propose a multi-neighbor cycle consistency and a multi-cycle-back regression loss by finding multiple soft nearest neighbors using a Gaussian Mixture Model (GMM) instead of a single neighbor as in TCC. To handle background and redundant frames, we introduce a context-dependent drop function, discouraging the alignment of droppable frames." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": "On the other hand, to effectively align videos of multiple activities jointly and to better leverage their shared information while handling their distinctions, we propose a multi-head crosstask network, where each head automatically learns to focus on relevant components of video pairs. Thus, we can embed a video and estimate progress without knowing its activity label. Through extensive experiments on multiple datasets, we show the effectiveness of our framework for video alignment and progress estimation." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 306, + 71, + 398, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 71, + 398, + 84 + ], + "spans": [ + { + "bbox": [ + 306, + 71, + 398, + 84 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 91, + 547, + 297 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 547, + 297 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 547, + 297 + ], + "type": "text", + "content": "Self-Supervised Video Representation Learning. Given the high annotation cost for video-based action learning and the need for copious amounts of data when training deep networks, many researchers have turned to self-supervised methods for embedding video frames [9, 28, 38, 42, 45, 60, 72]. Self-supervision has largely been popularized as a result of higher quality image embedding techniques trained on large-scale image datasets such as [10, 27, 37]. With better datasets, pre-trained image encoders, such as [18, 53-55], allow for more meaningful features that can enhance the performance of self-supervised representation learning methods. Many downstream tasks benefit from self-supervised video representation learning, such as action recognition [26, 71], temporal action segmentation [23, 33, 63, 65], step localization [14, 71], video retrieval [68], text-to-video retrieval [41], and audio-visual representation learning [25]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 300, + 547, + 577 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 300, + 547, + 577 + ], + "spans": [ + { + "bbox": [ + 304, + 300, + 547, + 577 + ], + "type": "text", + "content": "Video Alignment is the task of temporally synchronizing videos, such that similar frames or segments in separate videos can be mapped to each other. Traditional methods such as Dynamic Time Warping (DTW) [7, 11, 13, 16, 17, 47], or Canonical Correlation Analysis (CCA) [1, 21, 26, 48] have been used to align video frames. Many methods have adopted the use of Soft-DTW [7, 11, 16, 17, 40], where the gradient is well-defined and back-propagation is feasible. LAV [17] is a self-supervised video alignment method, which uses Soft-DTW in conjunction with temporal intra-video contrastive loss terms. Other contrastive approaches include [5, 39, 42, 49, 60, 66]. Drop-DTW [11] extends DTW by adding a \"trash bucket\" to the cost matrix for dynamic programming for background frame classification. Similarly, VAVA [39] added an additional bucket to the optimal transport formulation to align in-the-wild videos. VAVA also incorporated a bi-modal Gaussian prior on the optimal transport matrix, which allowed for the model to consider the temporality and optimality of the alignment. VAVA was shown to outperform previous methods for unconstrained procedural video datasets. Other methods capable of background detection but not video alignment include [4, 43, 51, 61, 62]." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 582, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 548, + 715 + ], + "type": "text", + "content": "Cycle-consistency has been a pivotal technique in sequence alignment, involving the mapping of elements from one sequence to another, followed by an inverse mapping back to the original sequence. Beyond its application in video alignment, cycle-consistency finds utility in diverse domains, including 3D shape matching [22], depth estimation [15], co-segmentation [57, 58], and transitivity in deep learning [15, 69, 70]. Cycle-consistency was first introduced for self-supervised video alignment in TCC [12] and showed good performance in aligning synchronizable videos, such as the Penn Action dataset [67] or the Pour" + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "18668" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 68, + 284, + 135 + ], + "blocks": [ + { + "bbox": [ + 48, + 68, + 284, + 135 + ], + "lines": [ + { + "bbox": [ + 48, + 68, + 284, + 135 + ], + "spans": [ + { + "bbox": [ + 48, + 68, + 284, + 135 + ], + "type": "image", + "image_path": "3ddc03ec78a02f309031b55b0e8b14c400d226a0bf7cb24f5560f2f669e641a0.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 138, + 287, + 177 + ], + "lines": [ + { + "bbox": [ + 46, + 138, + 287, + 177 + ], + "spans": [ + { + "bbox": [ + 46, + 138, + 287, + 177 + ], + "type": "text", + "content": "Figure 2. Cycle-consistency Visualization. Here, two videos are embedded by the alignment encoder, " + }, + { + "bbox": [ + 46, + 138, + 287, + 177 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 138, + 287, + 177 + ], + "type": "text", + "content": ". With a green checkmark, a frame pair is shown to be cycle-consistent. With a red X-mark, a frame pair is shown to be not cycle-consistent." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 195, + 287, + 232 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 195, + 287, + 232 + ], + "spans": [ + { + "bbox": [ + 46, + 195, + 287, + 232 + ], + "type": "text", + "content": "ing dataset [32]. Our method extends cycle-consistency to unconstrained videos, as observed in many datasets such as COIN [56] and EgoProceL [2]." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 236, + 288, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 236, + 288, + 392 + ], + "spans": [ + { + "bbox": [ + 46, + 236, + 288, + 392 + ], + "type": "text", + "content": "Activity Progress Prediction is the task of predicting temporal progress in videos. While [3, 44] have studied a supervised approach for action progress prediction, they require temporal annotations of every action clip based on its phases, which is hard to define given the fine-grained nature of phases and cost to gather. Action completion [19, 20, 59, 68] is also related to progress, however it is only focused on classifying full progress achievement rather than predicting the progress at every time instant. In this work, we learn to predict progress at every frame in a self-supervised framework. Our proposed progress estimation technique also has applications in goal-based reinforcement learning, providing dense reward for learning [29, 64]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 403, + 208, + 416 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 403, + 208, + 416 + ], + "spans": [ + { + "bbox": [ + 47, + 403, + 208, + 416 + ], + "type": "text", + "content": "3. Problem Setting and Review" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 422, + 287, + 459 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 422, + 287, + 459 + ], + "spans": [ + { + "bbox": [ + 46, + 422, + 287, + 459 + ], + "type": "text", + "content": "In this section, we discuss the problem of video alignment and review temporal cycle consistency (TCC) [12], which we build upon and generalize." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 466, + 149, + 478 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 466, + 149, + 478 + ], + "spans": [ + { + "bbox": [ + 47, + 466, + 149, + 478 + ], + "type": "text", + "content": "3.1. Video Alignment" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": "Given two video sequences " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "S = (s_1, \\ldots, s_N)" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "T = (t_1, \\ldots, t_M)" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " with " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " frames, respectively, we denote their embeddings by " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "U = (u_1, \\ldots, u_N)" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "V = (v_1, \\ldots, v_M)" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": ". We use an encoder neural network " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " to compute these embeddings, as depicted in Fig. 2. The goal of video alignment is to train the encoder, " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": ", such that if the two frames " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "s_i" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "t_j" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " represent the same action, the distance between their embeddings, " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "u_i \\in \\mathbb{R}^D" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "inline_equation", + "content": "v_j \\in \\mathbb{R}^D" + }, + { + "bbox": [ + 46, + 483, + 287, + 593 + ], + "type": "text", + "content": ", will be small, otherwise, the distance will be large." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 599, + 236, + 612 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 599, + 236, + 612 + ], + "spans": [ + { + "bbox": [ + 47, + 599, + 236, + 612 + ], + "type": "text", + "content": "3.2. Temporal Cycle Consistency (TCC)" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": "TCC [12] finds a symmetric nearest neighbor embedding space by maximizing the number of cycle-consistent embeddings between two sequences. More specifically, consider a frame " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\boldsymbol{u}_i \\in U" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": ", and let its Euclidean nearest neighbor from " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": " be denoted by " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\boldsymbol{v}_j = \\operatorname{argmin}_{\\boldsymbol{v} \\in V} \\| \\boldsymbol{u}_i - \\boldsymbol{v} \\|" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": ". Similarly, for a frame " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\boldsymbol{v}_j \\in V" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": ", denote its Euclidean nearest neighbor in " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "U" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": " by " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\boldsymbol{u}_k = \\operatorname{argmin}_{\\boldsymbol{u} \\in U} \\| \\boldsymbol{u} - \\boldsymbol{v}_j \\|" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": ". The frame " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\boldsymbol{u}_i" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": " is cycle-consistent if and only if " + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "i = k" + }, + { + "bbox": [ + 46, + 617, + 288, + 714 + ], + "type": "text", + "content": ", see Fig. 2. TCC" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 310, + 69, + 425, + 134 + ], + "blocks": [ + { + "bbox": [ + 310, + 69, + 425, + 134 + ], + "lines": [ + { + "bbox": [ + 310, + 69, + 425, + 134 + ], + "spans": [ + { + "bbox": [ + 310, + 69, + 425, + 134 + ], + "type": "image", + "image_path": "55b88eb4aa7512424e7eb4a15facd1517b021114ead01010df4caac5c159b78b.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 354, + 135, + 380, + 143 + ], + "lines": [ + { + "bbox": [ + 354, + 135, + 380, + 143 + ], + "spans": [ + { + "bbox": [ + 354, + 135, + 380, + 143 + ], + "type": "text", + "content": "(a) TCC" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 427, + 68, + 542, + 134 + ], + "blocks": [ + { + "bbox": [ + 427, + 68, + 542, + 134 + ], + "lines": [ + { + "bbox": [ + 427, + 68, + 542, + 134 + ], + "spans": [ + { + "bbox": [ + 427, + 68, + 542, + 134 + ], + "type": "image", + "image_path": "724a60cc507f126190e85c9047e37baf96cf4f9d0c4706637d4cfc131ca96e9a.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 468, + 135, + 498, + 143 + ], + "lines": [ + { + "bbox": [ + 468, + 135, + 498, + 143 + ], + "spans": [ + { + "bbox": [ + 468, + 135, + 498, + 143 + ], + "type": "text", + "content": "(b) GTCC" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "lines": [ + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "spans": [ + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "text", + "content": "Figure 3. TCC Failure for Repeated Actions. Common action segments of the sequences are shown using varying colors. " + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "text", + "content": " is depicted based on the initial frame, " + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "inline_equation", + "content": "u_{i}" + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "text", + "content": ", from the yellow action segment. TCC (3a) only allows a single " + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "inline_equation", + "content": "\\tilde{v}" + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "text", + "content": " between both peaks in " + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "text", + "content": ". GTCC (3b) allows for two distinct neighbors, " + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "inline_equation", + "content": "\\tilde{v}_{1}" + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "inline_equation", + "content": "\\tilde{v}_{2}" + }, + { + "bbox": [ + 304, + 148, + 547, + 196 + ], + "type": "text", + "content": ", which accurately represents repeated actions." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "spans": [ + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "text", + "content": "trains an encoder to embed frames such that the number of cycle-consistent frame embeddings is maximized across pairs of videos, hence, a symmetric nearest neighbor embedding space. Since argmin is non-differentiable, TCC adopts the softmax operation. Let " + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "inline_equation", + "content": "\\Delta^M" + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "text", + "content": " denote the probability simplex in " + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "text", + "content": " dimensions.2 TCC begins by computing a soft nearest neighbor (SNN) of " + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i" + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "text", + "content": ", denoted by " + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "inline_equation", + "content": "\\tilde{\\pmb{v}}" + }, + { + "bbox": [ + 304, + 214, + 546, + 299 + ], + "type": "text", + "content": "," + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 312, + 307, + 545, + 340 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 307, + 545, + 340 + ], + "spans": [ + { + "bbox": [ + 312, + 307, + 545, + 340 + ], + "type": "interline_equation", + "content": "\\tilde {\\boldsymbol {v}} = \\sum_ {j = 1} ^ {M} \\alpha_ {j} \\boldsymbol {v} _ {j}, \\quad \\text {w h e r e ,} \\quad \\alpha_ {j} = \\frac {e ^ {- \\| \\boldsymbol {u} _ {i} - \\boldsymbol {v} _ {j} \\| ^ {2} / \\tau}}{\\sum_ {k = 1} ^ {M} e ^ {- \\| \\boldsymbol {u} _ {i} - \\boldsymbol {v} _ {k} \\| ^ {2} / \\tau}}. \\tag {1}", + "image_path": "4880add3a09aff62e17a54ad56a44c5be9c91bb2146b2d555e675b6e16c49b80.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "spans": [ + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": "Here " + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "inline_equation", + "content": "\\alpha = [\\alpha_{1},\\ldots ,\\alpha_{M}]\\in \\Delta^{M}" + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": " is the outgoing normalized similarity (forward distribution) between " + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i" + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": " and embeddings in " + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": " is the softmax temperature. TCC then uses the SNN, " + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "inline_equation", + "content": "\\tilde{\\pmb{v}}" + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": ", to compute " + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "inline_equation", + "content": "\\beta = [\\beta_{1},\\dots,\\beta_{N}]\\in \\Delta^{N}" + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": ", which is the incoming normalized similarity (backward distribution) between " + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "inline_equation", + "content": "\\tilde{\\pmb{v}}" + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": " and frame embeddings in " + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "inline_equation", + "content": "U" + }, + { + "bbox": [ + 304, + 350, + 547, + 422 + ], + "type": "text", + "content": "," + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 370, + 430, + 545, + 463 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 370, + 430, + 545, + 463 + ], + "spans": [ + { + "bbox": [ + 370, + 430, + 545, + 463 + ], + "type": "interline_equation", + "content": "\\beta_ {l} = \\frac {e ^ {- \\| \\boldsymbol {u} _ {l} - \\tilde {\\boldsymbol {v}} \\| ^ {2} / \\tau}}{\\sum_ {j = 1} ^ {N} e ^ {- \\| \\boldsymbol {u} _ {j} - \\tilde {\\boldsymbol {v}} \\| ^ {2} / \\tau}}. \\tag {2}", + "image_path": "8df47a29680e33e819ef4cc597adc3fe14e98d10d5c418398d845b5444ad287d.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "spans": [ + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": "Cycle-consistency requires that " + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": " must have the highest probability mass at index " + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": " and very small mass at indices farther from " + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": ". Thus, TCC imposes a Gaussian distribution prior " + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "inline_equation", + "content": "\\mathcal{N}(\\mu_{\\beta},\\sigma_{\\beta}^{2})" + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": " on entries of " + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": " with mean " + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "inline_equation", + "content": "\\mu_{\\beta} = \\sum_{l = 1}^{N}\\beta_{l}\\cdot l" + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": " and variance " + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "inline_equation", + "content": "\\sigma_{\\beta}^{2} = \\sum_{l = 1}^{N}\\beta_{l}\\cdot (l - \\mu_{\\beta})^{2}" + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": ". Requiring that the distribution mean be close to " + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 470, + 547, + 557 + ], + "type": "text", + "content": " with a small variance leads to minimizing a cycle-back regression loss, defined as" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 361, + 564, + 545, + 595 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 361, + 564, + 545, + 595 + ], + "spans": [ + { + "bbox": [ + 361, + 564, + 545, + 595 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {c b r}} = \\frac {(i - \\mu_ {\\beta}) ^ {2}}{\\sigma_ {\\beta} ^ {2}} + \\lambda \\log (\\sigma_ {\\beta}), \\tag {3}", + "image_path": "de5fd09eb54ccbb4c8b800790dcb25ba5f54aa786222bcedda3d4adf1af4c5ba.jpg" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 602, + 545, + 627 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 602, + 545, + 627 + ], + "spans": [ + { + "bbox": [ + 304, + 602, + 545, + 627 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 602, + 545, + 627 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 304, + 602, + 545, + 627 + ], + "type": "text", + "content": " is the regularization weight. This leads to a differentiable loss that can be optimized using backpropagation." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 637, + 545, + 664 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 637, + 545, + 664 + ], + "spans": [ + { + "bbox": [ + 304, + 637, + 545, + 664 + ], + "type": "text", + "content": "4. Generalized Temporal Cycle Consistency (GTCC)" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 671, + 545, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 671, + 545, + 696 + ], + "spans": [ + { + "bbox": [ + 304, + 671, + 545, + 696 + ], + "type": "text", + "content": "One of the advantages of TCC [12] compared to DTW-based methods [11, 17] is that it does not assume/enforce" + } + ] + } + ], + "index": 23 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 315, + 702, + 541, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 702, + 541, + 713 + ], + "spans": [ + { + "bbox": [ + 315, + 702, + 541, + 713 + ], + "type": "inline_equation", + "content": "{}^{2}\\mathbf{\\alpha } \\in {\\Delta }^{M}" + }, + { + "bbox": [ + 315, + 702, + 541, + 713 + ], + "type": "text", + "content": " means that vector entries are nonnegative and sum to one." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18669" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 72, + 547, + 149 + ], + "blocks": [ + { + "bbox": [ + 48, + 72, + 547, + 149 + ], + "lines": [ + { + "bbox": [ + 48, + 72, + 547, + 149 + ], + "spans": [ + { + "bbox": [ + 48, + 72, + 547, + 149 + ], + "type": "image", + "image_path": "966ed83a18e8b2ab8e3f38678d3afc2dc19b4e71a72eeb96697ef505ff5ee8bc.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "lines": [ + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "spans": [ + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": "Figure 4. GTCC. We encode two videos into " + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "inline_equation", + "content": "\\mathbf{U}" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "inline_equation", + "content": "\\mathbf{V}" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": " and calculate the forward distribution, " + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": ". We use the output of the GMM optimization procedure and obtain " + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": " SNNs from " + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": " discrete Gaussians. We then compute " + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "inline_equation", + "content": "\\beta^{(k)}" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": " for each SNN. We also estimate the drop probability of each frame " + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "inline_equation", + "content": "\\mathrm{P}_{\\mathrm{drop}}(\\pmb{u}_i|\\mathbf{V})" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": " using a conditional network. Finally, we compute the final loss by weighting each cycle-back regression loss with weight from mixture densities, " + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "inline_equation", + "content": "\\psi" + }, + { + "bbox": [ + 46, + 155, + 547, + 195 + ], + "type": "text", + "content": ", and modulate with the drop probabilities." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 212, + 287, + 247 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 212, + 287, + 247 + ], + "spans": [ + { + "bbox": [ + 46, + 212, + 287, + 247 + ], + "type": "text", + "content": "monotonic ordering of actions across videos. On the other hand, it has two major drawbacks when it comes to aligning in-the-wild videos." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 248, + 287, + 320 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 248, + 287, + 320 + ], + "spans": [ + { + "bbox": [ + 46, + 248, + 287, + 320 + ], + "type": "text", + "content": "First, TCC cannot handle background and additional actions, because it enforces cycle-consistency for every frame embedding. However, background actions (e.g., 'answering phone' when making coffee) or additional actions (e.g., the optional step of 'cleaning coffee filter') in one video but not in another should not be aligned." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 321, + 287, + 440 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 321, + 287, + 440 + ], + "spans": [ + { + "bbox": [ + 46, + 321, + 287, + 440 + ], + "type": "text", + "content": "Second, the TCC model assumes that each action only appears once in a video, therefore, cannot model action repetitions (e.g., repeating the actions of 'give breath' and 'give chest compression' when performing CPR). This is because computing the SNN in TCC is done with a unimodal Gaussian assumption on the similarity distributions, which is violated when an action is repeated in a video and leads to computing bad SNNs, see Fig. 3. We propose generalized temporal cycle consistency (GTCC), which addresses these limitations and aligns videos in the wild." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 449, + 271, + 462 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 449, + 271, + 462 + ], + "spans": [ + { + "bbox": [ + 47, + 449, + 271, + 462 + ], + "type": "text", + "content": "4.1. Multi-Cycle Consistency via Mixture SNNs" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "spans": [ + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": "We propose multi-neighbor cycle consistency and a multicycle-back regression loss to handle repeated actions, see Fig. 4. For " + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i \\in U" + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": " belonging to an action " + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": ", a single SNN " + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "inline_equation", + "content": "\\tilde{\\pmb{v}}" + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": " obtained using (1) is restrictive when action " + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": " is repeated in the sequence " + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": ". In such a case, as 3 shows, " + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i" + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": " will have multiple good nearest neighbors, yet the SNN " + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "inline_equation", + "content": "\\tilde{\\pmb{v}}" + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": " captures an average representation of them leading to a suboptimal solution. Therefore, we generalize TCC to allow for multiple SNNs and to assign an importance score to each SNN. This allows our model to find a set of SNNs based on a given " + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i" + }, + { + "bbox": [ + 46, + 468, + 287, + 612 + ], + "type": "text", + "content": ", and to automatically gain awareness of their relative importance for promoting multiple-neighbor cycle-consistency." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "spans": [ + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "text", + "content": "For " + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i \\in U" + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "text", + "content": ", we first obtain the outgoing distribution " + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "inline_equation", + "content": "\\alpha = [\\alpha_1, \\dots, \\alpha_M]" + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "inline_equation", + "content": "\\alpha_j" + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "text", + "content": "'s are computed using (1). We then approximate " + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 46, + 613, + 287, + 673 + ], + "type": "text", + "content": " with a discretized Gaussian Mixture Model (GMM) to capture different distribution modes corresponding to the same action. More specifically, we model" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 118, + 682, + 287, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 118, + 682, + 287, + 716 + ], + "spans": [ + { + "bbox": [ + 118, + 682, + 287, + 716 + ], + "type": "interline_equation", + "content": "\\alpha_ {j} \\approx p _ {j} = \\sum_ {k = 1} ^ {K} \\psi_ {k} p _ {j} ^ {(k)}, \\tag {4}", + "image_path": "33b8676f7bff0ec131f33663c779a7fdd40ce216e93655f035b8d3891cd45dc9.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "spans": [ + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "p_j^{(k)}" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " is the outgoing probability of index " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " in video " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "\\mathbf{V}" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " for the " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": "-th discretized Gaussian distribution " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "\\mathcal{N}(\\mu_{\\alpha,k}, \\sigma_{\\alpha,k}^2)" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "\\psi_k" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " denotes the weight of the mixture component " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": ". Here, " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " is a hyperparameter defining the total number of mixture components. We typically set " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "K = 10" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " in our experiments and as we show the results do not change much for different values of " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " as long as it is not very small. We find the parameters of the GMM, which are " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "\\{\\mu_k, \\sigma_k^2, \\psi_k\\}_{k=1}^K" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": ", by minimizing the KL divergence [52] between the two distributions " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "[\\alpha_1, \\ldots, \\alpha_M]" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "inline_equation", + "content": "[p_1, \\ldots, p_M]" + }, + { + "bbox": [ + 304, + 211, + 547, + 357 + ], + "type": "text", + "content": ". After finding the parameters of the GMM, we then compute one SNN for each mixture component," + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 342, + 361, + 545, + 396 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 342, + 361, + 545, + 396 + ], + "spans": [ + { + "bbox": [ + 342, + 361, + 545, + 396 + ], + "type": "interline_equation", + "content": "\\tilde {\\boldsymbol {v}} ^ {(k)} = \\sum_ {j = 1} ^ {M} p _ {j} ^ {(k)} \\cdot \\boldsymbol {v} _ {j}, \\quad \\forall k \\in \\{1, \\dots , K \\}. \\tag {5}", + "image_path": "5910ef1c93a585c6c626fb4248f728b70fd4fd5abb2580057c332b19e60d8b30.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "spans": [ + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": "With these " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": " SNNs of " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i\\in \\pmb{U}" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": ", we then compute the incoming similarity distribution " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "\\beta^{(k)}" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": " for each SNN, " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "\\tilde{\\pmb{v}}^{(k)}" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": ". TCC assumes that throughout the sequence " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "\\pmb{U}" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": " should only have a sharp peak at index " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": ". For in-the-wild videos, this presents a challenge when " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": " belongs to a repeated or non-contiguous action segment, where there would be more than one valid peak in the incoming distribution. To address this, we only enforce a local sharp peak around " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": " for a discrete temporal window, " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": ", where any index outside the " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": "-centered window has zero probability (see supplementary materials for more details). For each " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "\\beta^{(k)}" + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "text", + "content": ", we compute the mean and variance over the indices of " + }, + { + "bbox": [ + 304, + 399, + 547, + 542 + ], + "type": "inline_equation", + "content": "\\pmb{U}" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 313, + 546, + 545, + 580 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 546, + 545, + 580 + ], + "spans": [ + { + "bbox": [ + 313, + 546, + 545, + 580 + ], + "type": "interline_equation", + "content": "\\mu_ {\\beta , k} = \\sum_ {l = 1} ^ {N} \\beta_ {l} ^ {(k)} \\cdot l, \\quad \\sigma_ {\\beta , k} ^ {2} = \\sum_ {l = 1} ^ {N} \\beta_ {l} ^ {(k)} \\cdot (l - \\mu_ {\\beta , k}) ^ {2}. \\tag {6}", + "image_path": "f030e1ac0a9d5d64c3acdd32f6aecb0fe2936487bfa853ea9ad65317e56eaa89.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 583, + 545, + 607 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 583, + 545, + 607 + ], + "spans": [ + { + "bbox": [ + 304, + 583, + 545, + 607 + ], + "type": "text", + "content": "Finally, we compute one cycle-back regression loss for each mixture component as" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 350, + 611, + 545, + 641 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 350, + 611, + 545, + 641 + ], + "spans": [ + { + "bbox": [ + 350, + 611, + 545, + 641 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {c b r}} ^ {(k)} = \\frac {\\left(i - \\mu_ {\\beta , k}\\right) ^ {2}}{\\sigma_ {\\beta , k} ^ {2}} + \\lambda \\cdot \\log (\\sigma_ {\\beta , k}). \\tag {7}", + "image_path": "1b9647892b4c04e6a79b1cc66a28ac601ee5e4949923b1df67de9990d00058c8.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 645, + 545, + 679 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 645, + 545, + 679 + ], + "spans": [ + { + "bbox": [ + 304, + 645, + 545, + 679 + ], + "type": "text", + "content": "Given that " + }, + { + "bbox": [ + 304, + 645, + 545, + 679 + ], + "type": "inline_equation", + "content": "\\psi_{k}" + }, + { + "bbox": [ + 304, + 645, + 545, + 679 + ], + "type": "text", + "content": " is the relative importance of the " + }, + { + "bbox": [ + 304, + 645, + 545, + 679 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 645, + 545, + 679 + ], + "type": "text", + "content": "-th discrete Gaussian distribution, we build a multi-cycle back regression loss as" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 373, + 683, + 545, + 715 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 373, + 683, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 373, + 683, + 545, + 715 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {m u l t i - c b r}} = \\sum_ {k = 1} ^ {K} \\psi_ {k} \\cdot \\mathcal {L} _ {\\text {c b r}} ^ {(k)}. \\tag {8}", + "image_path": "cc9fc8fdaa97bb150abc6850fc80a33615a1086787547cedbdd086d7be9583fd.jpg" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18670" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 57, + 70, + 277, + 174 + ], + "blocks": [ + { + "bbox": [ + 57, + 70, + 277, + 174 + ], + "lines": [ + { + "bbox": [ + 57, + 70, + 277, + 174 + ], + "spans": [ + { + "bbox": [ + 57, + 70, + 277, + 174 + ], + "type": "image", + "image_path": "feac05244c55a31fc7347e273b2a78881fef57f2a90c4ab89735abd38d6be432.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "lines": [ + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "text", + "content": "Figure 5. Multi-head Crosstalk Network (MCN). Input frames, " + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "text", + "content": ", are given to the base network to obtain base features, " + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "inline_equation", + "content": "U^b" + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "text", + "content": ", which are subsequently given to " + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "text", + "content": " head networks that output intermediate video encodings, " + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "inline_equation", + "content": "\\{U_l^h\\}_{l=1}^L" + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "text", + "content": ". We obtain the final video encoding " + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "inline_equation", + "content": "U" + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "text", + "content": " using attention over the outputs of the " + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 46, + 179, + 288, + 228 + ], + "type": "text", + "content": " heads." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 252, + 201, + 266 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 252, + 201, + 266 + ], + "spans": [ + { + "bbox": [ + 47, + 252, + 201, + 266 + ], + "type": "text", + "content": "4.2. Droppable Frame Detection" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "spans": [ + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "text", + "content": "Another major limitation of TCC is that it cannot handle background and additional actions since it enforces cycle-consistency for all embeddings. GTCC addresses this issue by detecting frames in " + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "inline_equation", + "content": "U" + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "text", + "content": " to be dropped based on the frames in " + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "text", + "content": " and subsequently enforcing (i) multi-cycle consistency for alignable embeddings and (ii) bad alignment for droppable embeddings. Information (context) from video " + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "text", + "content": " is necessary when dropping frames in video " + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "inline_equation", + "content": "U" + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "text", + "content": " because the model can not know to drop frames corresponding to an additional action unless that action is not present in " + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 46, + 270, + 287, + 390 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 391, + 287, + 427 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 391, + 287, + 427 + ], + "spans": [ + { + "bbox": [ + 47, + 391, + 287, + 427 + ], + "type": "text", + "content": "More specifically, we learn a drop-context function, " + }, + { + "bbox": [ + 47, + 391, + 287, + 427 + ], + "type": "inline_equation", + "content": "c: \\mathbb{R}^D \\to \\mathbb{R}^{D+1}" + }, + { + "bbox": [ + 47, + 391, + 287, + 427 + ], + "type": "text", + "content": ", characterized by a feedforward neural network, using all the embeddings " + }, + { + "bbox": [ + 47, + 391, + 287, + 427 + ], + "type": "inline_equation", + "content": "v_j \\in V" + }, + { + "bbox": [ + 47, + 391, + 287, + 427 + ], + "type": "text", + "content": " as" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 100, + 433, + 287, + 466 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 100, + 433, + 287, + 466 + ], + "spans": [ + { + "bbox": [ + 100, + 433, + 287, + 466 + ], + "type": "interline_equation", + "content": "\\boldsymbol {c} (\\boldsymbol {V}) = \\frac {1}{M} \\sum_ {j = 1} ^ {M} \\boldsymbol {c} \\left(\\boldsymbol {v} _ {j}\\right) \\in \\mathbb {R} ^ {D + 1}. \\tag {9}", + "image_path": "7071f621ab9aa886934072c5ebaf61b6a8e6077106a34a81ad62de3df1b1b341.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "spans": [ + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "text", + "content": "GTCC uses the information in " + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\mathbf{V}" + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "text", + "content": " to condition the drop detection in " + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\mathbf{U}" + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "text", + "content": ". More specifically, for each " + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i\\in U" + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "text", + "content": ", we use a logistic regression model to compute the probability of dropping " + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i" + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "text", + "content": " given " + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\mathbf{V}" + }, + { + "bbox": [ + 46, + 471, + 287, + 519 + ], + "type": "text", + "content": " as" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 93, + 522, + 287, + 539 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 93, + 522, + 287, + 539 + ], + "spans": [ + { + "bbox": [ + 93, + 522, + 287, + 539 + ], + "type": "interline_equation", + "content": "\\mathrm {P} _ {\\text {d r o p}} \\left(\\boldsymbol {u} _ {i} \\mid \\boldsymbol {V}\\right) = \\sigma \\left(\\left[ \\boldsymbol {u} _ {i} ^ {\\top} \\quad 1 \\right] \\boldsymbol {c} (\\boldsymbol {V})\\right), \\tag {10}", + "image_path": "f655c45427f9f4932debbf6a53f92c32614fe8181d56cfceea28a333ff3e79d7.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 543, + 287, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 543, + 287, + 567 + ], + "spans": [ + { + "bbox": [ + 46, + 543, + 287, + 567 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 543, + 287, + 567 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 46, + 543, + 287, + 567 + ], + "type": "text", + "content": " is the sigmoid function. We use the drop probability to build our final loss function, which we discuss next." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 572, + 148, + 585 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 572, + 148, + 585 + ], + "spans": [ + { + "bbox": [ + 47, + 572, + 148, + 585 + ], + "type": "text", + "content": "4.3. Learning GTCC" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 590, + 287, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 590, + 287, + 686 + ], + "spans": [ + { + "bbox": [ + 46, + 590, + 287, + 686 + ], + "type": "text", + "content": "To learn the parameters of the embedding network " + }, + { + "bbox": [ + 46, + 590, + 287, + 686 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 590, + 287, + 686 + ], + "type": "text", + "content": " and the drop-context model, we propose a loss so that alignable frames are encouraged to have good cycle-consistency and droppable frames are encouraged to have bad alignment. This dichotomy isolates the cycle-consistency property only to frames that are deemed 'alignable', and ensures frames deemed 'droppable' have no good nearest neighbors. We propose to minimize" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 55, + 690, + 287, + 718 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 690, + 287, + 718 + ], + "spans": [ + { + "bbox": [ + 55, + 690, + 287, + 718 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\left(1 - \\mathrm {P} _ {\\text {d r o p}} (\\boldsymbol {u} _ {i} | \\boldsymbol {V})\\right) \\cdot \\mathcal {L} _ {\\text {m u l t i - c b r}} + \\frac {\\mathrm {P} _ {\\text {d r o p}} (\\boldsymbol {u} _ {i} | \\boldsymbol {V})}{\\mathcal {L} _ {\\text {m u l t i - c b r}}}, \\tag {11}", + "image_path": "dfeea32ee5eeb6332dc02856f842167b3928b7586f9030902be8ee24e57f23e0.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": "where we minimize the multi-cycle-back regression loss for alignable frames for which " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "\\mathrm{P}_{\\mathrm{drop}}(\\pmb {u}_i|\\pmb {V})" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " is close to 0, and maximize the multi-cycle-back regression loss for drop-. pable frames for which " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "\\mathrm{P}_{\\mathrm{drop}}(\\pmb {u}_i|\\pmb {V})" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " is close to 1. Notice one can also use " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "-\\mathcal{L}_{\\mathrm{multi - cbr}}" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " instead of " + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "inline_equation", + "content": "1 / \\mathcal{L}_{\\mathrm{multi - cbr}}" + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": " in (11), however, the latter worked better in our experiments." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 152, + 457, + 164 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 152, + 457, + 164 + ], + "spans": [ + { + "bbox": [ + 305, + 152, + 457, + 164 + ], + "type": "text", + "content": "4.4. Online Progress Estimation" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 170, + 545, + 217 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 170, + 545, + 217 + ], + "spans": [ + { + "bbox": [ + 304, + 170, + 545, + 217 + ], + "type": "text", + "content": "At inference time, given an online sequence up to frame " + }, + { + "bbox": [ + 304, + 170, + 545, + 217 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i" + }, + { + "bbox": [ + 304, + 170, + 545, + 217 + ], + "type": "text", + "content": ", we want to estimate the progress, denoted by " + }, + { + "bbox": [ + 304, + 170, + 545, + 217 + ], + "type": "inline_equation", + "content": "\\hat{\\pi}(\\pmb{u}_i) \\in [0,1]" + }, + { + "bbox": [ + 304, + 170, + 545, + 217 + ], + "type": "text", + "content": ". We do so, by using the cumulative inter-frame geodesic distance on the frame features," + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 363, + 225, + 545, + 253 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 363, + 225, + 545, + 253 + ], + "spans": [ + { + "bbox": [ + 363, + 225, + 545, + 253 + ], + "type": "interline_equation", + "content": "\\hat {\\pi} \\left(\\boldsymbol {u} _ {i}\\right) = \\frac {\\sum_ {t = 1} ^ {i - 1} \\left\\| \\boldsymbol {u} _ {t + 1} - \\boldsymbol {u} _ {t} \\right\\|}{\\hat {G}}, \\tag {12}", + "image_path": "b82b5b3bc60ef5ce45da3f5a627343c4d431321f2d797409559842921e2e6b3a.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 262, + 545, + 323 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 262, + 545, + 323 + ], + "spans": [ + { + "bbox": [ + 304, + 262, + 545, + 323 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 262, + 545, + 323 + ], + "type": "inline_equation", + "content": "\\hat{G}" + }, + { + "bbox": [ + 304, + 262, + 545, + 323 + ], + "type": "text", + "content": " is ideally the total geodesic distance for the complete sequence (including past and future observations). Given that we do not have access to the future frames, we estimate " + }, + { + "bbox": [ + 304, + 262, + 545, + 323 + ], + "type": "inline_equation", + "content": "\\hat{G}" + }, + { + "bbox": [ + 304, + 262, + 545, + 323 + ], + "type": "text", + "content": " by averaging the total geodesic distances for all aligned training videos of the given task." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 334, + 466, + 347 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 334, + 466, + 347 + ], + "spans": [ + { + "bbox": [ + 305, + 334, + 466, + 347 + ], + "type": "text", + "content": "5. GTCC Embedding Network" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 354, + 545, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 354, + 545, + 569 + ], + "spans": [ + { + "bbox": [ + 304, + 354, + 545, + 569 + ], + "type": "text", + "content": "Our goal is to train an embedding model that can leverage the shared information across related actions or tasks (e.g., making otime and making scrambled eggs) for better feature learning and alignment of each task individually, while not requiring to know the action or task label of the video at inference time. Existing works, which train a separate model for each action/task, have neither of these capabilities. Therefore, we propose a new architecture, which we refer to as Multi-head Crosstalk Network (MCN), shown in Fig. 5. MCN consists of a base network, multiple head networks, and an attention network. MCN base network is intended to output general useful features (across actions/tasks) to be used by multiple " + }, + { + "bbox": [ + 304, + 354, + 545, + 569 + ], + "type": "inline_equation", + "content": "(L)" + }, + { + "bbox": [ + 304, + 354, + 545, + 569 + ], + "type": "text", + "content": " head networks. Ideally, each head network specializes in aligning related phases of an action or steps of a task. The attention network takes all features from the head networks at each time instant and selects the relevant head and its features. See the supplemental material for more details." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 580, + 388, + 594 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 580, + 388, + 594 + ], + "spans": [ + { + "bbox": [ + 306, + 580, + 388, + 594 + ], + "type": "text", + "content": "6. Experiments" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 599, + 422, + 613 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 599, + 422, + 613 + ], + "spans": [ + { + "bbox": [ + 306, + 599, + 422, + 613 + ], + "type": "text", + "content": "6.1. Experimental Setup" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 617, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 714 + ], + "type": "text", + "content": "Datasets. We use four datasets for evaluations, two monotonic and two in-the-wild datasets. Similar to previous works [12, 17, 39], we report results on Pouring [32] and Penn Action [67] datasets, which are monotonic. Pouring contains videos of humans pouring liquid into a cup (e.g., orange juice poured into a blue cup), and Penn Action contains videos of humans completing athletic maneuvers (e.g., a woman serving a tennis ball). We also use COIN [56]" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18671" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 286, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 286, + 144 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 286, + 144 + ], + "type": "text", + "content": "and EgoProceL [2], which are in-the-wild datasets, consisting of background frames, action repetitions, and different sequences of actions. EgoProceL is an egocentric dataset comprised of a collection of several datasets, including CMU-MMAC [30], EGTEA Gaze+ [36], MECCANO [46], and EPIC-tent [24]." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "spans": [ + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "text", + "content": "For Pouring, Penn Action, and COIN, we use " + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "inline_equation", + "content": "75\\%" + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "text", + "content": " of videos for training and " + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "inline_equation", + "content": "25\\%" + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "text", + "content": " for testing, while for EgoProceL we use " + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "inline_equation", + "content": "70\\%" + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "text", + "content": " for training and " + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "inline_equation", + "content": "30\\%" + }, + { + "bbox": [ + 46, + 144, + 286, + 276 + ], + "type": "text", + "content": " for testing since there are fewer videos per task. We also study two settings for evaluation. (i) Similar to prior works, we train a model separately for videos of each activity (single-task setting), whereas following other works we use an embedding network that corresponds to the base network in Fig. 5. (ii) We train a single model on videos of all activities jointly (multi-task setting). In Tab. 4, we test the multi-task setting using only the base network vs the full MCN architecture." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "spans": [ + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "type": "text", + "content": "Evaluation Metrics. We use multiple metrics to evaluate the performance of different methods for alignment and progress prediction. For evaluating alignment, we use the existing metrics Phase Classification (PC) [12], Enclosed Area Error (EAE) [13] and Kendall's Tau (KT) [12]. PC measures how well the encoder can put frames belonging to the same action class together, thus a higher value is better. Similar to previous works, we use PC, where an SVM classifier is trained on " + }, + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "type": "inline_equation", + "content": "50\\%" + }, + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "type": "inline_equation", + "content": "100\\%" + }, + { + "bbox": [ + 46, + 282, + 286, + 533 + ], + "type": "text", + "content": " of the ground-truth action labels. While PC measures how well different actions are separated from each other, it does not measure the quality of alignment within each action. Thus, we use Enclosed Area Error (EAE) that measures the alignment error within and across actions by comparing the nearest neighbors between two videos with their ground-truth alignment. When computing EAE for in-the-wild video pairs, we only include alignable frames in the computation. In cases where a frame has multiple valid neighbors, we calculate the smallest EAE among the set of neighbors. EAE is an error metric, therefore lower values indicate better alignment. See [13] for more details about EAE." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 533, + 286, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 533, + 286, + 665 + ], + "spans": [ + { + "bbox": [ + 46, + 533, + 286, + 665 + ], + "type": "text", + "content": "KT is a statistical measure that indicates how well-aligned two sequences are temporally. Given that KT is only suitable for monotonic sequences, we also propose a modified Kendall's Tau for in-the-wild datasets, which we call Kendall's Tau in the Wild (KTW). More specifically, we only evaluate KT on alignable frames and consider all variations of valid alignment for concordancy. This increases forgiveness when finding concordant pairs, because there may be many concordant neighbors for a frame in a redundant action segment. Therefore, KTW highlights the presence of disconcordant pairs." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "content": "To evaluate progress estimation, we use PHase Progression (PHP) [12] and introduce Online Progress Error (OPE). PHP trains a linear regressor over frame features to predict ground-truth progress values and computes the av" + } + ] + } + ], + "index": 4 + }, + { + "type": "table", + "bbox": [ + 312, + 71, + 540, + 186 + ], + "blocks": [ + { + "bbox": [ + 312, + 71, + 540, + 186 + ], + "lines": [ + { + "bbox": [ + 312, + 71, + 540, + 186 + ], + "spans": [ + { + "bbox": [ + 312, + 71, + 540, + 186 + ], + "type": "table", + "html": "
DatasetModelPC↑EAE↓KT↑PHP↑OPE↓
0.10.51.0
PouringSAL85.787.888.0—73.374.5—
TCN89.290.490.4—86.780.6—
TCC89.291.491.814.085.280.338.9
LAV91.692.892.89.085.680.531.4
VAVA91.791.892.529.687.683.637.8
GTCC71.289.293.57.988.185.822.5
Penn ActionSAL74.978.380.0—63.459.4—
TCN82.083.784.0—73.367.6—
TCC81.383.484.518.273.567.335.5
LAV83.684.084.320.580.566.125.5
VAVA83.984.084.523.280.570.980.5
GTCC78.381.281.316.788.370.814.5
", + "image_path": "1ddd7c5cce0bdd4c0830da9e8c53991266c361186b6fd48f0f9dc41cc6348ff3.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_body" + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 312, + 212, + 540, + 308 + ], + "blocks": [ + { + "bbox": [ + 312, + 189, + 538, + 200 + ], + "lines": [ + { + "bbox": [ + 312, + 189, + 538, + 200 + ], + "spans": [ + { + "bbox": [ + 312, + 189, + 538, + 200 + ], + "type": "text", + "content": "Table 1. Alignment and progress evaluations on monotonic datasets." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 312, + 212, + 540, + 308 + ], + "lines": [ + { + "bbox": [ + 312, + 212, + 540, + 308 + ], + "spans": [ + { + "bbox": [ + 312, + 212, + 540, + 308 + ], + "type": "table", + "html": "
DatasetModelPC ↑EAE ↓KTW ↑OPE ↓
0.10.51.0
EgoProceLTCC66.067.468.321.513.934.0
LAV67.268.268.820.812.736.2
VAVA65.365.966.323.213.135.5
GTCC75.078.980.613.314.013.6
COINTCC35.939.640.728.018.828.7
LAV36.838.939.826.723.222.7
VAVA43.846.247.332.022.227.6
GTCC46.853.256.318.929.021.4
", + "image_path": "3f447bf0dcb6c4900d802f622246e37fb72d3af7168554e92194520e8ef6b5af.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 312, + 311, + 538, + 321 + ], + "lines": [ + { + "bbox": [ + 312, + 311, + 538, + 321 + ], + "spans": [ + { + "bbox": [ + 312, + 311, + 538, + 321 + ], + "type": "text", + "content": "Table 2. Alignment and progress evaluations on in-the-wild datasets." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "spans": [ + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "type": "text", + "content": "erage " + }, + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "type": "inline_equation", + "content": "R" + }, + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "type": "text", + "content": "-squared measure over all videos. PHP assumes monotonicity in action sequences and, therefore, is only evaluated on the monotonic datasets. On the other hand, our online progress estimation in (12) applies to monotonic and in-the-wild datasets. Following [3], at each frame " + }, + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "type": "inline_equation", + "content": "\\pmb{u}_i" + }, + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "type": "text", + "content": " we define a ground-truth progress value " + }, + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "type": "inline_equation", + "content": "\\pi (\\pmb{u}_i)\\in [0,1]" + }, + { + "bbox": [ + 304, + 338, + 545, + 494 + ], + "type": "text", + "content": " assuming that (i) each action segment contributes equally to the overall progress, and (ii) progress linearly increases throughout the duration of each action segment. We assume that silent frames do not contribute to progress, hence progress values remain constant during silent segments, see 6. We define OPE as the mean absolute difference between predicted progress and ground-truth online progress (lower is better)." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 502, + 545, + 572 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 502, + 545, + 572 + ], + "spans": [ + { + "bbox": [ + 304, + 502, + 545, + 572 + ], + "type": "text", + "content": "Baselines. For the single-task setting, we compare our GTCC against SAL [42], TCN [49], TCC [12], LAV [17] and VAVA [39]. Among them, only VAVA is specifically designed for handling in-the-wild videos. For the multi-task setting, we compare GTCC with LAV and VAVA, which are state-of-the-art." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 574, + 545, + 669 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 574, + 545, + 669 + ], + "spans": [ + { + "bbox": [ + 304, + 574, + 545, + 669 + ], + "type": "text", + "content": "On the Penn Action, Pouring, and COIN datasets, for the single-task setting, we report the PC, PHP, and KT as previously reported in the most recent work [39]. Given that previous methods did not report EAE, KTW, and OPE, we re-implement all baselines on all datasets to report the performance based on these metrics. Similarly, we reproduce all numbers for the MCN multi-task (Table 4) and the EgoProceL experiments (Tables 2, 3, 4, 5, 6)." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "content": "Implementation Details For the single-task setting, following all previous baselines, we use ResNet-50 [18] for the architecture of the encoder network. Please see [12] for more" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18672" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 60, + 70, + 273, + 133 + ], + "blocks": [ + { + "bbox": [ + 60, + 70, + 273, + 133 + ], + "lines": [ + { + "bbox": [ + 60, + 70, + 273, + 133 + ], + "spans": [ + { + "bbox": [ + 60, + 70, + 273, + 133 + ], + "type": "table", + "html": "
DatasetModelPrecisionRecallF1Accuracy
EgoProceLVAVA66.098.477.064.3
GTCC67.597.978.268.9
COINVAVA41.778.853.544.7
GTCC51.988.265.362.0
", + "image_path": "b5d52a41a1cbda695f37148db223cbecde1801e791f8abac74d3a1d5f0ef983d.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 52, + 165, + 282, + 346 + ], + "blocks": [ + { + "bbox": [ + 47, + 137, + 287, + 156 + ], + "lines": [ + { + "bbox": [ + 47, + 137, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 47, + 137, + 287, + 156 + ], + "type": "text", + "content": "Table 3. Evaluation of handling background actions (i.e., drop) of VAVA vs GTCC for the in-the-wild datasets." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 52, + 165, + 282, + 346 + ], + "lines": [ + { + "bbox": [ + 52, + 165, + 282, + 346 + ], + "spans": [ + { + "bbox": [ + 52, + 165, + 282, + 346 + ], + "type": "table", + "html": "
DatasetMethodArch.PC↑EAE↓KT↑KTW↑PHP↑OPE↓
CMU-MMACLAVResNet65.222.2—6.8—18.2
MCN69.813.4—12.1—16.1
VAVAResNet62.524.0—5.1—20.7
MCN63.719.7—11.4—17.9
GTCCResNet70.426.8—9.0—25.2
MCN67.814.9—21.8—14.0
EGTEALAVResNet82.519.7—2.8—17.9
MCN82.111.4—38.7—22.4
VAVAResNet83.219.6—2.7—19.6
MCN82.310.7—38.1—19.7
GTCCResNet83.617.2—3.3—19.5
MCN82.510.2—47.6—16.0
Penn ActionLAVResNet78.720.568.4—62.527.7
MCN85.35.794.3—69.08.6
VAVAResNet80.326.276.2—64.837.9
MCN85.45.994.4—72.614.3
GTCCResNet73.924.760.7—69.732.9
MCN86.75.694.9—85.59.4
", + "image_path": "4d955577ce21554bdd211b6bddd50aec655fc08e8ae561dce5b38d25aa72f247.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 350, + 287, + 370 + ], + "lines": [ + { + "bbox": [ + 47, + 350, + 287, + 370 + ], + "spans": [ + { + "bbox": [ + 47, + 350, + 287, + 370 + ], + "type": "text", + "content": "Table 4. Alignment and progress evaluation for the multi-task setting when training on ResNet-50 vs our proposed MCN architecture." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "spans": [ + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "type": "text", + "content": "details regarding the encoder architecture. For the multi-task setting, we compare the ResNet-50 embedding network with our multi-head crosstalk network (MCN), shown in Fig. 5, where the base network is ResNet-50 and all head and attention networks are 4-layer fully-connected feedforward network. For GTCC, we also simultaneously train a 4-layer feedforward neural network for the drop-context function, " + }, + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\mathbf{c}" + }, + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "type": "text", + "content": ", in Sec. 4.2. We use " + }, + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "type": "inline_equation", + "content": "K = 15" + }, + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "type": "text", + "content": " for in-the-wild datasets and " + }, + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "type": "inline_equation", + "content": "K = 5" + }, + { + "bbox": [ + 46, + 388, + 287, + 519 + ], + "type": "text", + "content": " for monotonic datasets. For multi-task experiments using MCN, we set the number of attention heads to be the number of tasks in the dataset." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 528, + 171, + 540 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 528, + 171, + 540 + ], + "spans": [ + { + "bbox": [ + 47, + 528, + 171, + 540 + ], + "type": "text", + "content": "6.2. Experimental Results" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "text", + "content": "Single-Task Setting Results. Table 1 and 2 show the alignment and progress estimation evaluation of different methods for monotonic and in-the-wild datasets, respectively. Notice that for the monotonic datasets in Table 1, GTCC achieves significantly better EAE (for alignment) and OPE (for progress) on both datasets, e.g., improving the OPE from " + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "inline_equation", + "content": "25.5\\%" + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "inline_equation", + "content": "14.5\\%" + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "text", + "content": " and EAE from " + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "inline_equation", + "content": "18.2\\%" + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "inline_equation", + "content": "16.7\\%" + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "text", + "content": " on Penn Action. Similarly, our method achieves higher KT values, especially on Penn Action, where it outperforms other methods by at least " + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "inline_equation", + "content": "7.8\\%" + }, + { + "bbox": [ + 46, + 545, + 287, + 700 + ], + "type": "text", + "content": ". However, GTCC mostly does not improve the PC values of the baselines. This is because PC does not directly represent precise alignment but instead measures the effectiveness of clustering action segments." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 59, + 702, + 287, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 702, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 702, + 287, + 712 + ], + "type": "text", + "content": "On the other hand, as the results in Table 2 show," + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 312, + 73, + 422, + 151 + ], + "blocks": [ + { + "bbox": [ + 312, + 73, + 422, + 151 + ], + "lines": [ + { + "bbox": [ + 312, + 73, + 422, + 151 + ], + "spans": [ + { + "bbox": [ + 312, + 73, + 422, + 151 + ], + "type": "image", + "image_path": "0f152b3b25950650128d033047c5c997db9ba2fd25c0c69eefe44a9f2750ec58.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 353, + 154, + 382, + 161 + ], + "lines": [ + { + "bbox": [ + 353, + 154, + 382, + 161 + ], + "spans": [ + { + "bbox": [ + 353, + 154, + 382, + 161 + ], + "type": "text", + "content": "(a) GTCC" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 429, + 73, + 539, + 152 + ], + "blocks": [ + { + "bbox": [ + 429, + 73, + 539, + 152 + ], + "lines": [ + { + "bbox": [ + 429, + 73, + 539, + 152 + ], + "spans": [ + { + "bbox": [ + 429, + 73, + 539, + 152 + ], + "type": "image", + "image_path": "c1ecabf61b822a1d11e6b0069c1fb8f4ec0e99710fa9f79653c8d92854fe7431.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 470, + 154, + 499, + 161 + ], + "lines": [ + { + "bbox": [ + 470, + 154, + 499, + 161 + ], + "spans": [ + { + "bbox": [ + 470, + 154, + 499, + 161 + ], + "type": "text", + "content": "(b) VAVA" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 310, + 165, + 421, + 243 + ], + "blocks": [ + { + "bbox": [ + 310, + 165, + 421, + 243 + ], + "lines": [ + { + "bbox": [ + 310, + 165, + 421, + 243 + ], + "spans": [ + { + "bbox": [ + 310, + 165, + 421, + 243 + ], + "type": "image", + "image_path": "6b062240a71ce69234edf228dd5720343c00b1b5257138913d338910e8ccada4.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 354, + 246, + 378, + 254 + ], + "lines": [ + { + "bbox": [ + 354, + 246, + 378, + 254 + ], + "spans": [ + { + "bbox": [ + 354, + 246, + 378, + 254 + ], + "type": "text", + "content": "(c) LAV" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 428, + 165, + 538, + 243 + ], + "blocks": [ + { + "bbox": [ + 428, + 165, + 538, + 243 + ], + "lines": [ + { + "bbox": [ + 428, + 165, + 538, + 243 + ], + "spans": [ + { + "bbox": [ + 428, + 165, + 538, + 243 + ], + "type": "image", + "image_path": "0527513895fbb74ff83d2ac3c0ef02f074e64b1550ce08cfe6f687ef5f06f420.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 471, + 246, + 496, + 254 + ], + "lines": [ + { + "bbox": [ + 471, + 246, + 496, + 254 + ], + "spans": [ + { + "bbox": [ + 471, + 246, + 496, + 254 + ], + "type": "text", + "content": "(d) TCC" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 306, + 256, + 545, + 285 + ], + "lines": [ + { + "bbox": [ + 306, + 256, + 545, + 285 + ], + "spans": [ + { + "bbox": [ + 306, + 256, + 545, + 285 + ], + "type": "text", + "content": "Figure 6. Online progress estimation for GTCC (6a), VAVA (6b), LAV (6c) and TCC (6d) for a video from the task \"making brownies\" in the EgoProceL dataset." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "spans": [ + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "text", + "content": "GTCC significantly outperforms all baselines for all metrics. Specifically, GTCC improves the EAE by at least " + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "inline_equation", + "content": "7.5\\%" + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "text", + "content": " on both EgoProceL and COIN and reduces OPE from " + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "inline_equation", + "content": "34.0\\%" + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "inline_equation", + "content": "13.6\\%" + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "text", + "content": " on EgoProceL and from " + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "inline_equation", + "content": "22.7\\%" + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "inline_equation", + "content": "21.4\\%" + }, + { + "bbox": [ + 304, + 304, + 545, + 411 + ], + "type": "text", + "content": " on COIN. Similarly, our method significantly improves the PC and KTW over the state-of-the-art. This is thanks to the fact that GTCC is specifically designed to handle inthe-wild videos that contain action repetitions, background activities, and action ordering variations." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "spans": [ + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "text", + "content": "Drop Performance. Table 3 compares the effectiveness of VAVA and GTCC for handling background activities on in-the-wild datasets for the single-task setting. We measure the precision, recall, F1 score, and accuracy of dropping background frames during pairwise alignment. Notice that on both datasets, GTCC has a higher F1 score and accuracy. Notably, GTCC achieves " + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "inline_equation", + "content": "62.0\\%" + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "text", + "content": " accuracy on COIN compared to " + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "inline_equation", + "content": "44.7\\%" + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "text", + "content": " by VAVA and obtains " + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "inline_equation", + "content": "68.9\\%" + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "text", + "content": " accuracy on EgoProceL compared to " + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "inline_equation", + "content": "64.3\\%" + }, + { + "bbox": [ + 304, + 418, + 546, + 563 + ], + "type": "text", + "content": " by VAVA. This shows the effectiveness of our context-based drop and alignment, which jointly learns alignable and droppable frames with a soft probabilistic approach." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 570, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 546, + 713 + ], + "type": "text", + "content": "Multi-Task Setting Results. In Table 4, we show the alignment and progress evaluations of LAV, VAVA, and GTCC for the multi-task setting, where we use all videos in each dataset to learn a single embedding network. We compare using ResNet-50 with using our proposed MCN architecture. Since GTCC outperformed TCC on progress and alignment metrics in the previous experiments, we do not report the results for TCC. As the results demonstrate, using ResNet for embedding in the multi-task setting leads to generally low performances for all methods. 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EAE ↓OPE ↓PC(1.0) ↑
K151015151015151015
EgoP19.419.218.719.420.420.020.320.973.974.875.574.3
COIN23.221.422.218.925.523.122.021.450.149.648.946.8
Pour11.611.111.711.59.712.310.910.287.184.984.986.3
Penn26.716.016.116.115.216.717.816.780.078.278.2278.9
", + "image_path": "ec61253cf805f8dd30d9a51e6cf14b8bf1a874e928829bb4e98dc7984e66ee42.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "spans": [ + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": "hand, " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\frac{6}{9}" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " PC metrics, " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\frac{9}{9}" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " EAE metrics, " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\frac{3}{3}" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " KT metrics, " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\frac{6}{6}" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " KTW metrics, " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\frac{3}{3}" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " PHP metrics, and " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\frac{7}{9}" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " OPE metrics show improvement with the MCN architecture. Table 4 shows that when using MCN, the EAE, KT, KTW, and PHP metrics outperform " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "100\\%" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " of the time, while PC and OPE outperform " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "67\\%" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "inline_equation", + "content": "78\\%" + }, + { + "bbox": [ + 46, + 290, + 287, + 411 + ], + "type": "text", + "content": " of the time. This is because our architecture learns to specialize multiple heads for related actions using attention, while ResNet trains a single shared base model for all actions including the ones that are considerably different (e.g., serving tennis and jumping jack)." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "spans": [ + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "type": "text", + "content": "GMM Tuning and Ablations. Table 5 shows the effect of the number of mixture components, " + }, + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "type": "text", + "content": ", in the GMM on alignment and progress performance for GTCC. Notice that performance does not vary much under different values of " + }, + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "type": "text", + "content": ", showing the robustness of our approach. It is important to note that, as expected, " + }, + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "type": "inline_equation", + "content": "K = 1" + }, + { + "bbox": [ + 46, + 418, + 287, + 502 + ], + "type": "text", + "content": " performs better comparatively on monotonic datasets than in-the-wild datasets." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 502, + 287, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 502, + 287, + 598 + ], + "spans": [ + { + "bbox": [ + 46, + 502, + 287, + 598 + ], + "type": "text", + "content": "Table 6 ablates the number of MCN heads (6a), and the drop term in GTCC (6b). We gather from 6a that alignment performance improves when the number of MCN heads scales alongside the number of tasks in the dataset (5 for both EGTEA Gaze+ and CMU-MMAC, which have 5 tasks). Finally, we see in 6b that the removal of the drop term leads to degraded performance, further showing the importance of the drop term in GTCC." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "content": "Qualitative Results. In Fig. 6, we show the comparison of different methods for online progress estimation on a test video from the task \"making brownies\" from the EgoProceL dataset. For each method, we show the ground-truth progress vs progress estimated via (12), " + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\hat{\\pi}" + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "content": ", using the learned embeddings. Notice that GTCC's estimation of the progress fits the ground-truth nicely, while other methods have a large gap. This is because GTCC can effectively drop frames that correspond to background, while obtaining an" + } + ] + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 310, + 190, + 542, + 292 + ], + "blocks": [ + { + "bbox": [ + 310, + 190, + 542, + 292 + ], + "lines": [ + { + "bbox": [ + 310, + 190, + 542, + 292 + ], + "spans": [ + { + "bbox": [ + 310, + 190, + 542, + 292 + ], + "type": "image", + "image_path": "97736f94ff9e710fc7697054266d8388d69e00783422f5678cdc93611323c111.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 326, + 298, + 525, + 308 + ], + "lines": [ + { + "bbox": [ + 326, + 298, + 525, + 308 + ], + "spans": [ + { + "bbox": [ + 326, + 298, + 525, + 308 + ], + "type": "text", + "content": "Figure 8. In-the-wild Frame Retrieval from COIN dataset." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "type": "table", + "bbox": [ + 308, + 320, + 427, + 364 + ], + "blocks": [ + { + "bbox": [ + 56, + 259, + 277, + 269 + ], + "lines": [ + { + "bbox": [ + 56, + 259, + 277, + 269 + ], + "spans": [ + { + "bbox": [ + 56, + 259, + 277, + 269 + ], + "type": "text", + "content": "Table 5. Effect of the number of GMM components, " + }, + { + "bbox": [ + 56, + 259, + 277, + 269 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 56, + 259, + 277, + 269 + ], + "type": "text", + "content": " ,on GTCC." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 308, + 320, + 427, + 364 + ], + "lines": [ + { + "bbox": [ + 308, + 320, + 427, + 364 + ], + "spans": [ + { + "bbox": [ + 308, + 320, + 427, + 364 + ], + "type": "table", + "html": "
PC(1.0)↑EAE↓
# Heads15201520
CMU66.767.864.729.514.929.0
EGTEA82.382.582.015.510.219.3
", + "image_path": "f5eff221ad7b7ac900a6cc868598ca698852441bd899081aca1a4f2b9ad56dee.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 328, + 365, + 406, + 372 + ], + "lines": [ + { + "bbox": [ + 328, + 365, + 406, + 372 + ], + "spans": [ + { + "bbox": [ + 328, + 365, + 406, + 372 + ], + "type": "text", + "content": "(a) Number of MCN heads." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 16 + }, + { + "type": "table", + "bbox": [ + 435, + 320, + 542, + 363 + ], + "blocks": [ + { + "bbox": [ + 435, + 320, + 542, + 363 + ], + "lines": [ + { + "bbox": [ + 435, + 320, + 542, + 363 + ], + "spans": [ + { + "bbox": [ + 435, + 320, + 542, + 363 + ], + "type": "table", + "html": "
PC(1.0)↑EAE↓
Drop✓×✓×
Ego80.665.213.324.3
COIN56.346.618.927.9
", + "image_path": "53182b1e909cf78bd3813777fb65f2eed2bd4b92e7ccd76aacb0723b67797adc.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 440, + 365, + 538, + 373 + ], + "lines": [ + { + "bbox": [ + 440, + 365, + 538, + 373 + ], + "spans": [ + { + "bbox": [ + 440, + 365, + 538, + 373 + ], + "type": "text", + "content": "(b) With " + }, + { + "bbox": [ + 440, + 365, + 538, + 373 + ], + "type": "inline_equation", + "content": "(\\checkmark)" + }, + { + "bbox": [ + 440, + 365, + 538, + 373 + ], + "type": "text", + "content": ", without " + }, + { + "bbox": [ + 440, + 365, + 538, + 373 + ], + "type": "inline_equation", + "content": "(\\times)" + }, + { + "bbox": [ + 440, + 365, + 538, + 373 + ], + "type": "text", + "content": " dropout" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 18 + }, + { + "bbox": [ + 317, + 376, + 534, + 386 + ], + "lines": [ + { + "bbox": [ + 317, + 376, + 534, + 386 + ], + "spans": [ + { + "bbox": [ + 317, + 376, + 534, + 386 + ], + "type": "text", + "content": "Table 6. Ablation studies on (a) Number of MCN heads, (b) Drop." + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 403, + 545, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 545, + 498 + ], + "type": "text", + "content": "embedding space where different actions are well-aligned. In Fig. 7, we show the ground-truth, trivial estimate via frame-counting, and " + }, + { + "bbox": [ + 304, + 403, + 545, + 498 + ], + "type": "inline_equation", + "content": "\\hat{\\pi}" + }, + { + "bbox": [ + 304, + 403, + 545, + 498 + ], + "type": "text", + "content": " by GTCC from a EgoProceL video. Notice GTCC can effectively predict the progress online and better than the trivial estimate from frame-counting. In Fig. 8, we show results for in-the-wild frame retrieval for GTCC on the COIN dataset. This figure showcases the ability of GTCC to align frames with high visual similarity." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 306, + 510, + 383, + 522 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 510, + 383, + 522 + ], + "spans": [ + { + "bbox": [ + 306, + 510, + 383, + 522 + ], + "type": "text", + "content": "7. Conclusions" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 531, + 545, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 531, + 545, + 639 + ], + "spans": [ + { + "bbox": [ + 304, + 531, + 545, + 639 + ], + "type": "text", + "content": "We studied a self-supervised approach, based on a proposed generalized temporal cycle consistency (GTCC) method, for video alignment and progress prediction, coupled with a novel attention-based architecture for multi-task learning. Our extensive experiments show that GTCC outperforms the state of the art, especially for in-the-wild videos. Additionally, we highlight the efficacy of our MCN architecture for enhancing multi-task learning. The fusion of GTCC and MCN emerges as a competitive and versatile framework." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 306, + 651, + 408, + 664 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 651, + 408, + 664 + ], + "spans": [ + { + "bbox": [ + 306, + 651, + 408, + 664 + ], + "type": "text", + "content": "Acknowledgements" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 666, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 666, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 666, + 545, + 713 + ], + "type": "text", + "content": "This work is sponsored by DARPA PTG (HR00112220001), NSF (IIS-2115110), ARO (W911NF2110276). Content does not necessarily reflect the position/policy of the Government." + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "18674" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 15, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 144 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 144 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 144 + ], + "type": "text", + "content": "[1] Galen Andrew, Raman Arora, Jeff Bilmes, and Karen Livescu. 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While many prior studies have focused on improving image matching performance to facilitate reliable dense keypoint matching between images, existing methods often heavily rely on predefined feature points on a reconstructed 3D model. Consequently, they tend to overlook unobserved keypoints during the matching process. Therefore, dense keypoint matches are not fully exploited, leading to a notable reduction in accuracy, particularly in noisy scenes. To tackle this issue, we propose a novel localization method that extracts reliable semi-dense 2D-3D matching points based on dense keypoint matches. This approach involves regressing semi-dense 2D keypoints into 3D scene coordinates using a point inference network. The network utilizes both geometric and visual cues to effectively infer 3D coordinates for unobserved keypoints from the observed ones. The abundance of matching information significantly enhances the accuracy of camera pose estimation, even in scenarios involving noisy or sparse 3D models. Comprehensive evaluations demonstrate that the proposed method outperforms other methods in challenging scenes and achieves competitive results in large-scale visual localization benchmarks. The code will be available at https://github.com/TruongKhang/DeViLoc.", + "bbox": [ + 75, + 316, + 472, + 710 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 739, + 207, + 753 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Visual localization is the process of determining the 6 degrees of freedom (DoF) camera pose for a given query image within a known scene. This fundamental task in computer vision is critical for applications such as robot navigation [33] and virtual or augmented reality [35, 37]. Most leading studies primarily employ a structure-based approach [8, 41, 43, 47, 68], consistently exhibiting high localization performance across diverse challenging conditions [31, 42, 54, 58].", + "bbox": [ + 75, + 763, + 468, + 902 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Traditionally, structure-based methods heavily rely on feature matching (FM) [11, 46, 51, 55, 64]. These methods establish sparse correspondences between 3D points and 2D pixel-level keypoints in images, followed by estimating camera poses using RANSAC-based Perspective-n-Point (PnP). The recent advancements in FM-based methods [41, 42, 53] have shown outstanding performance across various benchmarks, particularly in large-scale scenes. However, despite these achievements, FM-based methods encounter substantial challenges in practical scenarios, including dealing with complex lighting conditions, seasonal variations, and changes in perspectives.", + "bbox": [ + 496, + 287, + 893, + 469 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Addressing these challenges necessitates a more robust and informative feature-matching approach incorporating detailed 3D points. Current methods, including those achieving semi-dense 2D-2D correspondences through detector-free image matching [15, 24, 53], are limited by relying solely on matched sparse features. This limitation persists when considering semi-dense matches, which only account for keypoints observed in a 3D model, neglecting valuable information from unobserved keypoints. Furthermore, FM-based methods demand a detailed 3D point cloud map for accurate localization. Continuously refining 3D feature points for new image inputs is time-intensive, and in some scenarios, localization must be performed with a noisy or sparse 3D point cloud. Overreliance on predetermined 2D and 3D points in the database can lead to a degradation in pose accuracy, especially in noisy cases with texture-less surfaces or repetitive patterns.", + "bbox": [ + 496, + 473, + 893, + 731 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Recent studies introduce scene coordinate regression (SCR) methods [6, 8, 30, 56], aiming to achieve dense 2D-3D correspondences. Unlike FM-based approaches, SCR methods use an implicit representation of scenes as a learnable function, predicting the dense 3D scene coordinates of a query image. SCR methods excel in compact and stable settings, eliminating the need for storing 3D models; however, they face challenges in dynamic environments and adapting to new viewpoints, limiting their applicability in large-scale scenes. Therefore, there is a need for an alternative method capable of finding dense and accurate 2D-3D", + "bbox": [ + 496, + 734, + 895, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "19468", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ecbb80fe0889602cec40e2a1383294443e2962927f52b6888384b4cd14a53505.jpg", + "image_caption": [ + "Figure 1. The comparison of the 2D-3D correspondence finding process in our method (DeViLoc) and an existing method (HLoc [41]). HLoc heavily relies on a robust 3D point cloud but discards many detected 2D keypoints (depicted in green) during the 2D-3D matching process. In contrast, our method efficiently handles a noisy point cloud through the point inference process of PIN. PIN transforms the entire set of 2D-2D matches into 2D-3D matches. Our method then produces numerous accurate 2D-3D matches across multiple views using a confidence-based aggregation module. These abundant matches significantly enhance localization performance, particularly in scenarios characterized by noisy or sparse 3D point clouds." + ], + "image_footnote": [], + "bbox": [ + 99, + 88, + 872, + 250 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "correspondences for visual localization.", + "bbox": [ + 76, + 373, + 341, + 387 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Therefore, this study proposes a novel FM-based method, semi-Dense Visual Localization (DeViLoc), aiming to predict dense 2D-3D correspondences for robust and accurate localization. In contrast to existing FM-based methods relying solely on pre-existing 3D points, our method directly converts semi-dense 2D-2D matches into 2D-3D matches. This abundant 2D-3D match information significantly enhances the precision of camera pose estimation, even when dealing with noisy or sparse 3D models.", + "bbox": [ + 75, + 392, + 470, + 527 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "This method comprises two main components: 1) the Point Inference Network (PIN) and 2) the Confidence-based Point Aggregation (CPA) module. PIN plays a crucial role in our method by converting semi-dense 2D-2D matches into 2D-3D matches. It achieves this by directly regressing all 2D keypoints, both observed and unobserved, into 3D scene coordinates. The process involves encoding scene geometry from observed points into latent vectors and propagating 3D information to unobserved positions through attention layers. Next, the CPA module aggregates 2D-3D matches from multiple query-reference pairs, identifying consistent and highly confident 3D points corresponding to the same 2D keypoints in multiple matching views. This step effectively removes outliers from dense matches, and the filtered 2D-3D matches expedite RANSAC-based pose estimation. Ultimately, DeViLoc significantly increases the number of accurate 2D-3D matches for localization.", + "bbox": [ + 75, + 532, + 468, + 789 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Fig. 1 illustrates the 2D-3D matching process of our method and an existing one (HLoc+LoFTR [41, 53]). The existing method, despite having a dense and precise 3D model, rejects many important points during 2D-3D estimation. In contrast, our method confidently transforms 2D-2D matches into 2D-3D matches, generating numerous matches even in the presence of noisy 3D input and night-", + "bbox": [ + 75, + 794, + 470, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "time conditions. Consequently, the method yields robust and accurate localization results based on dense matching information, especially in challenging conditions like nighttime scenarios, adverse weather, and seasonal changes.", + "bbox": [ + 498, + 372, + 890, + 433 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "This paper makes the following contributions:", + "bbox": [ + 517, + 434, + 823, + 449 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose a novel visual localization method that leverages rich matching information by directly converting semi-dense 2D-2D matches into 2D-3D matches. This method significantly improves the accuracy of camera pose estimation, particularly in scenarios with noisy or sparse 3D models.", + "- We introduce a network architecture, Point Inference Network (PIN), designed to directly regress 2D keypoints into 3D points. This network effectively exploits geometric and visual connections between unobserved and observed keypoints, ensuring accurate estimation of 3D information along with associated uncertainties.", + "- We conducted a comprehensive evaluation of our method across diverse datasets. The results indicate that our proposed approach outperforms other state-of-the-art methods in challenging scenes and achieves competitive performance in large-scale visual localization benchmarks. The source code is publicly available." + ], + "bbox": [ + 500, + 450, + 890, + 722 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 500, + 738, + 650, + 753 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Visual localization, which involves estimating camera poses from visual inputs, has been a subject of study for decades [8, 28, 31, 39, 49, 54]. Early approaches [1, 49, 59] primarily relied on an image retrieval strategy to directly estimate camera poses from the most similar images in database. This approach is intuitive and efficient, but its performance is significantly influenced by the density of images in the database. To overcome this limitation, an alternative approach learns a neural network to directly predict absolute", + "bbox": [ + 496, + 763, + 890, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "19469", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "camera poses from the input images [26, 27, 61].", + "bbox": [ + 76, + 90, + 401, + 104 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Many studies [8, 9, 11, 25, 41, 47, 51, 54, 55, 68] have shifted their focus towards structure-based approach due to its stability and scalability in diverse scenes. The structure-based methods estimate camera pose by establishing a set of 2D-3D correspondences between image pixels and 3D coordinates of the scene. Leveraging this precise correspondence set, a camera pose can be accurately computed using a PnP solver [22, 29, 40] within a RANSAC paradigm [3, 4, 21]. The structure-based methods can be broadly categorized into two main groups: feature matching (FM) and scene coordinate regression (SCR).", + "bbox": [ + 75, + 107, + 468, + 272 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Feature Matching. FM-based methods [11, 31, 41, 46, 51] initially reconstruct a 3D model of the environment from database images using Structure-from-Motion (SfM) [50, 63]. Each 3D point in the model is associated with one or several feature descriptors for localization. When a localization request for a query image is made, these methods detect a set of 2D keypoints along with their descriptors and proceed to match them with the 3D points. Several works generate the 2D-3D matches by examining all points in the 3D model [31, 44]; however, they face difficulty when dealing with large scenes.", + "bbox": [ + 75, + 275, + 468, + 441 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To address this challenge, recent studies [41, 57, 64] have introduced a coarse-to-fine strategy. They initially identify a set of reference images in a database through image retrieval. They then establish 2D-3D matches based on 2D-2D matches between the query and reference images. Subsequent works have focused on enhancing the performance of image matching by incorporating transformers [15, 24, 42, 53] or semantic information [65]. These approaches produce robust and accurate 2D-2D matches, contributing to the robust construction of 3D model and the accurate generation of 2D-3D matches during the localization step. Consequently, FM-based methods have achieved state-of-the-art performance.", + "bbox": [ + 75, + 443, + 468, + 638 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "However, these methods exhibit inflexibility due to heavily relying on high-fidelity point cloud reconstruction. This time-consuming step is not suitable for online applications such as SLAM or robot navigation, where the 3D point cloud is constructed on-the-fly from a sequence of images. In this situation, the point cloud might be noisy or incomplete, thus degrading localization performance. Furthermore, existing FM-based methods only utilize observed 3D points in the database to generate 2D-3D matches, discarding numerous unrelated 2D-2D matches. This process might compromise the performance in the presence of noisy 3D inputs. On the other hand, our proposed framework aims to adapt to various kinds of 3D inputs and predict semidense 2D-3D correspondences.", + "bbox": [ + 75, + 642, + 468, + 852 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Scene Coordinate Regression. In contrast to the explicit utilization of 3D models seen in FM-based methods, SCR [6, 8, 9, 13, 14, 52, 60] employs an implicit repre", + "bbox": [ + 76, + 854, + 468, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "sensation of scenes in a form of a machine learning model. This model predicts dense 3D scene coordinates for an input query image. While SCR-based methods offer a concise representation of scenes, they encounter challenges when adapting to large-scale scenes, novel scenes, or challenging conditions. Several approaches have been proposed to address these challenges by predicting a scene part-by-part [7, 30] or employing a coarse-to-fine prediction [56, 66]. However, these methods still exhibit lower performance compared to FM-based methods.", + "bbox": [ + 496, + 90, + 890, + 241 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Drawing inspiration from SCR, our method aims to predict 3D coordinates for all keypoints in the query image, identified using a detector-free image-matching model. However, in contrast to the dense prediction in SCR, our semi-dense approach reduces the possibility of incorrect 3D prediction by focusing only on regions of interest between the query and reference images. Consequently, our method achieves more accurate performance than SCR-based methods in outdoor scenes.", + "bbox": [ + 496, + 242, + 890, + 376 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3D Scene Representation. FM-based methods [24, 41, 42, 53] have proven to be effective, but they come with a drawback of requiring substantial storage capacity to store both the 3D coordinates and the associated visual features [41, 42]. Consequently, recent studies [10, 12, 16, 38, 67, 70] have shifted their focus toward discovering more space-efficient representations of the scene. For example, NeuMap [57] proposed encoding a 3D point cloud into a set of latent codes and then regressing 3D coordinates based on these codes. While these methods successfully reduce storage demands, they discard crucial scene information, thereby limiting their performance. In contrast, this study focuses on improving performance when dealing with challenging point cloud inputs.", + "bbox": [ + 496, + 378, + 890, + 589 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Proposed Method", + "text_level": 1, + "bbox": [ + 500, + 602, + 671, + 619 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We follow the coarse-to-fine localization paradigm [41] that first retrieves a set of reference images via image retrieval, and then estimates a camera pose by finding 2D-3D correspondences between image pixels and 3D coordinates of the scene. The proposed method aims to address the task of 2D-3D prediction, while applying image retrieval and a PnP pose solver, similar to [41].", + "bbox": [ + 496, + 627, + 890, + 733 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Overview", + "text_level": 1, + "bbox": [ + 500, + 741, + 609, + 756 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given a query image $I^q$ and a set of reference images $\\{I^{r,1}\\dots I^{r,N_v}\\}$ retrieved from a database, our method establishes a set of 2D-3D correspondences $M = \\{(k_i,p_i)\\}$ , where $k_{i}$ is a 2D keypoint in the query image and $p_i$ represents the corresponding 3D coordinate. Fig. 2 describes the overall architecture of the proposed method, DeViLoc. For each pair of query $I^q$ and reference $I^r$ , DeViLoc first extracts local 2D-2D feature correspondences $\\{(k_i^q,k_i^r)\\}$ using an image-matching network. Here, we employed a", + "bbox": [ + 496, + 763, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "19470", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/6a826f3a788b52a10ba94fd02185c8227e6e25ad85b6ca96465dd17b38be4be1.jpg", + "image_caption": [ + "Figure 2. Overview of DeViLoc. First, a feature matcher is employed to detect 2D-2D matches for each pair of query-reference images. Subsequently, the PIN module infers a set of 3D coordinates for all detected 2D keypoints based on the observed data in the reference image. Finally, the CPA module integrates all 2D-3D matches obtained across all query-reference pairs." + ], + "image_footnote": [], + "bbox": [ + 98, + 95, + 877, + 250 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "detector-free image-matching model [24] to produce semidense correspondences.", + "bbox": [ + 75, + 330, + 468, + 362 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The Point Inference Network (PIN) then converts detected 2D keypoints of the reference image into 3D points (Section 3.2). It takes reference image $I^r$ with known camera parameters, along with a sparse set of observed 3D points as inputs, and predicts a set of 3D scene coordinates, $\\{p_i\\}$ , corresponding to all keypoints $\\{k_i^r\\}$ . Based on predicted 3D points $\\{p_i\\}$ and 2D-2D matches $\\{(k_i^q,k_i^r)\\}$ , we could produce dense 2D-3D matches, $\\{(k_i^q,p_i)\\}$ , for the query image. The basic concept of PIN is inspired by depth completion [62, 69], where a dense depth map is reconstructed from a sparse set of observed depth measurements and an input image. However, unlike depth completion, PIN aims to infer a discrete set of depth points, leading to reduced computational costs. Due to this discrete depth prediction, PIN utilizes attention [19] and MLP layers without the need for complex CNNs, as commonly found in conventional depth completion methods.", + "bbox": [ + 75, + 363, + 468, + 619 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Next, the Confidence-based Point Aggregation (CPA) module integrates all 2D-3D matches from multiple query-reference image pairs (Section 3.3). CPA integrates 2D-3D matches with small distances of keypoints into a representative match. It effectively removes outliers by considering the confidence information of each match during the integration process.", + "bbox": [ + 75, + 619, + 468, + 727 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Point Inference Network", + "text_level": 1, + "bbox": [ + 76, + 739, + 302, + 753 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For reference image $I^r$ , let $O^r = \\{o_i^r\\}$ be the set of 3D points observed from the constructed 3D model. PIN predicts 3D points $P^r = \\{p_i^r\\}$ corresponding to detected 2D keypoints $K^r = \\{k_i^r\\}$ as:", + "bbox": [ + 75, + 763, + 468, + 825 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nP ^ {r} = \\operatorname {P I N} \\left(K ^ {r}, O ^ {r}, F ^ {r}\\right) \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 189, + 839, + 468, + 856 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $K^r \\in \\mathbb{R}^{N_{points}^r \\times 2}$ , $O^r \\in \\mathbb{R}^{N_{points}^o \\times 3}$ , and $F^r$ is a feature map extracted from image $I^r$ using convolutional", + "bbox": [ + 76, + 868, + 468, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "networks $(F^r\\in \\mathbb{R}^{h\\times w\\times c})$ . We directly utilized the output features of the image-matching network [24] as $F^r$", + "bbox": [ + 498, + 330, + 890, + 361 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The method begins with a preprocessing step where keypoints $K^r$ and observed 3D points $O^r$ are transformed into the same camera-coordinate system using the known camera parameters. Subsequently, we decompose the observed 3D points into observed keypoints $K^o \\in \\mathbb{R}^{N_{points}^o \\times 2}$ and depth values $D^o \\in \\mathbb{R}^{N_{points}^o \\times 1}$ . The PIN network then aims to estimate depths $D^r$ for reference keypoints $K^r$ , utilizing observed keypoints $K^o$ , observed depths $D^o$ , and the feature map $F^r$ . The network architecture of PIN is illustrated in Fig. 3, comprising two fundamental steps to leverage both spatial information and visual similarity for depth estimation: geometric guidance and visual guidance.", + "bbox": [ + 496, + 362, + 892, + 542 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To implement geometric guidance, we initially employ two MLP-based encoders to learn embeddings for all 2D keypoint coordinates $\\{K^r, K^o\\}$ , as well as for the observed depths, $D^o$ . Additionally, we encode scene geometry from the observed depths by utilizing a self-attention layer.", + "bbox": [ + 496, + 542, + 890, + 619 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nD _ {e m b} ^ {o} = \\operatorname {D e p t h E n c} \\left(D ^ {o}\\right) \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 599, + 631, + 890, + 647 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left[ K _ {e m b} ^ {r}, K _ {e m b} ^ {o} \\right] = \\text {K e y p o i n t E n c} \\left(\\left[ K ^ {r}, K ^ {o} \\right]\\right) \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 545, + 648, + 890, + 667 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The relative position between the observed and unobserved keypoints serves as a primary geometric cue for propagating depth information from observed to unobserved positions. Therefore, we represent the observed positions with latent codes, $P_{lc}^{o}$ , combined from keypoint embeddings $K_{emb}^{o}$ and depth features $D_{emb}^{o}$ . These latent codes are then passed into a cross-attention layer to generate latent codes $P_{lc}^{r}$ related to reference keypoints $K_{emb}^{r}$ :", + "bbox": [ + 496, + 678, + 890, + 801 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nP _ {l c} ^ {r} = \\operatorname {C r s A t t} \\left(K _ {e m b} ^ {r}, P _ {l c} ^ {o}\\right) \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 602, + 811, + 890, + 828 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In Eq. 4, $K_{emb}^{r}$ is the query, and $P_{lc}^{o}$ represents the key and value for the cross-attention function, CrsAtt().", + "bbox": [ + 496, + 839, + 890, + 869 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The geometric guidance mentioned above may lack robustness in estimating accurate depths due to the sparsity of", + "bbox": [ + 496, + 869, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "19471", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/38ecfd41301bebc41510f2bd95cfc264915ab39c41de6aacf3700115ce489d9e.jpg", + "image_caption": [ + "Figure 3. Point Inference Network (PIN). The network begins by learning embeddings for all keypoints $(K_{emb}^{o}, K_{emb}^{r})$ and observed depths $(D_{emb}^{o})$ . Subsequently, attention layers are employed for both geometric and visual guidance. Finally, the learned latent codes $(P_{lc}^{r})$ are utilized to perform regression for the 3D points along with confidence values." + ], + "image_footnote": [], + "bbox": [ + 148, + 85, + 823, + 251 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "observed data points. Therefore, we also incorporate visual features for more detailed guidance. Considering the feature map $F^r$ in Eq. 1, we utilize a bilinear grid sampling to extract sets of visual features $V^r$ and $V^o$ for both $K^r$ and $K^o$ . These visual features are appended to the latent codes, $P_{lc}^r$ and $P_{lc}^o$ . Subsequently, we employ multiple self/cross-attention layers to facilitate visual guidance:", + "bbox": [ + 76, + 328, + 472, + 434 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nP _ {l c} ^ {r} = \\operatorname {C o n c a t} \\left(P _ {l c} ^ {r}, V ^ {r}\\right), P _ {l c} ^ {o} = \\operatorname {C o n c a t} \\left(P _ {l c} ^ {o}, V ^ {o}\\right) \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 444, + 468, + 462 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nP _ {l c} ^ {o} = \\operatorname {S e l f A t t} \\left(P _ {l c} ^ {o}\\right), P _ {f i n a l} ^ {r} = \\operatorname {C r s A t t} \\left(P _ {l c} ^ {r}, P _ {l c} ^ {o}\\right) \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 91, + 463, + 468, + 482 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "After learning the final latent features, $P_{final}^{r}$ , corresponding to reference keypoints $K^{r}$ , we use two MLP-based networks to predict the depths and confidence:", + "bbox": [ + 76, + 491, + 468, + 536 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nD ^ {r} = \\mathbb {M L P} \\big (P _ {f i n a l} ^ {r} \\big), \\quad C ^ {r} = \\mathbb {M L P} \\big ([ P _ {f i n a l} ^ {r}, D ^ {r} ] \\big) \\quad (7 \\mathrm {a}, \\mathrm {b})\n$$\n", + "text_format": "latex", + "bbox": [ + 93, + 546, + 468, + 566 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Finally, the 3D scene coordinates for the reference keypoints are estimated as follows:", + "bbox": [ + 76, + 574, + 468, + 604 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nP ^ {r} = \\left(T ^ {- 1}\\right) _ {c a m \\rightarrow s c e n e} \\left(D ^ {r} [ \\hat {K} ^ {r}, 1 ] ^ {T}\\right) \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 147, + 613, + 468, + 633 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $T^{-1}$ transforms the 3D points from camera-coordinate to scene-coordinate system. The confidences $C^r$ represent the uncertainty associated with the predicted 3D coordinates, $P^r$ .", + "bbox": [ + 75, + 641, + 468, + 702 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Confidence-based Point Aggregation", + "text_level": 1, + "bbox": [ + 76, + 710, + 393, + 728 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "PIN produced the 2D-3D correspondences, $(K^q,P) = \\{(k_i^q,p_i)\\}$ , along with their associated confidence values $C^r = \\{c_i\\}$ for every query-reference pair $(I^q,I^r)$ . Subsequently, we aggregated the 2D-3D matches $\\{(k_i^q,p_i)^n\\}_{n = 1\\dots N_v}^{i = 1\\dots N_m}$ across $N_{v}$ sets of matches, with $N_{m}$ being the number of matches per set. The goal of CPA is to eliminate outliers from the aggregated matches and determine the final matches that exhibit high confidence and consistency. To accomplish this, we started by discarding matches with low confidence through a threshold $\\tau$ . Next, we grouped adjacent matches using a keypoint quantization", + "bbox": [ + 76, + 734, + 472, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "step. If the coordinates of two keypoints are closer than $s$ pixels, these keypoints are assigned to the same group. This process is represented by a function $Q_{s}$ , where $s$ denotes the quantization size ( $s \\in \\{2, 4\\}$ in our experiments). Once matches within the same group were identified, we merged them using a confidence-based averaging operation.", + "bbox": [ + 496, + 328, + 890, + 419 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Let $k_{j}$ be a quantized keypoint, the formulas for the aggregated 3D point $p_{j}^{agg}$ and the corresponding confidence $c_{j}^{agg}$ can be written as follows:", + "bbox": [ + 498, + 419, + 890, + 467 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\np _ {j} ^ {\\text {a g g}} = \\frac {\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n} p _ {i} ^ {n}}{\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n}} \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 573, + 477, + 890, + 516 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nc _ {j} ^ {a g g} = \\frac {\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n}}{N _ {k _ {j}}} \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 576, + 517, + 890, + 554 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Here, $\\mathbf{1}(Q_s(k_i^n) = k_j)$ is a binary indicator, and $N_{k_j} = \\sum_{i,n}\\mathbf{1}(Q_s(k_i^n) = k_j)$ represents the number of keypoints quantized into $k_{j}$ .", + "bbox": [ + 498, + 564, + 893, + 612 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Loss Functions", + "text_level": 1, + "bbox": [ + 500, + 619, + 653, + 636 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In summary, the proposed approach generates a set of 2D-3D matches, denoted as $M = \\{(k_j, p_j^{agg}, c_j^{agg})\\}$ , for query image $I^q$ . Utilizing ground-truth camera matrices $(C^q, T^q)$ and available depth information $D^q = \\{d_j^q\\}$ , we define two functions, incorporating point-matching loss and confidence loss, to train the proposed network.", + "bbox": [ + 496, + 643, + 890, + 734 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Point-matching loss. We computed the ground-truth 3D coordinates $\\{p_j^{qt}\\}$ for the keypoints $\\{k_{j}\\}$ using the depths $\\{d_j^q\\}$ and camera matrices $(C^q,T^q)$ . Then, we employed the $L1$ function to calculate the loss between the ground-truth 3D points and predicted 3D points:", + "bbox": [ + 498, + 734, + 890, + 811 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {\\text {p o i n t}} ^ {q} = \\frac {1}{| M |} \\sum_ {j} \\left\\| p _ {j} ^ {\\text {a g g}} - p _ {j} ^ {\\text {g t}} \\right\\| \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 586, + 820, + 890, + 859 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Confidence loss. To train the confidence, we projected the 3D points $\\{p_j^{agg}\\}$ onto the image plane and assigned a", + "bbox": [ + 498, + 869, + 893, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "19472", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/eb58dada45f429d626205cdb70caa81516cf4cb4df3baa9333bb2586951aafcc.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Methods7scenes (indoor)Cambridge landmarks (outdoor)
ChessFireHeadsOfficePumpkinKitchenStairsCourtKing'sHospitalShopSt. Mary's
DHSCNet [30]2/0.72/0.91/0.93/0.84/1.04/1.23/0.828/0.218/0.319/0.36/0.39/0.3
DSAC++ [6]2/0.52/0.91/0.83/0.74/1.14/1.19/2.640/0.218/0.320/0.36/0.313/0.4
DSAC* [8]2/1.102/1.241/1.823/1.154/1.344/1.683/1.1649/0.315/0.321/0.45/0.313/0.4
SANet [66]3/0.883/1.082/1.483/1.005/1.324/1.4016/4.59328/1.9532/0.5432/0.5310/0.4716/0.57
DSM [56]2/0.682/0.801/0.803/0.784/1.113/1.114/1.1643/0.1919/0.3523/0.386/0.3011/0.34
SAS [47]3/0.872/1.011/0.824/1.157/1.695/1.724/1.0124/0.1313/0.2220/0.364/0.218/0.25
InLoc [55]3/1.053/1.072/1.163/1.055/1.554/1.319/2.47-----
PixLoc [43]2/0.802/0.731/0.823/0.824/1.213/1.205/1.3030/0.1414/0.2416/0.325/0.2310/0.34
HLoc[SP+SG]2/0.842/0.931/0.743/0.925/1.274/1.405/1.4716/0.1112/0.2015/0.304/0.207/0.21
HLoc[LoFTR]3/0.932/0.871/0.734/1.025/1.245/1.486/1.4719/0.1116/0.2616/0.294/0.219/0.26
SDNeuMap [57]2/0.813/1.112/1.173/0.984/1.114/1.334/1.126/0.1014/0.1919/0.366/0.2517/0.53
DeViLoc (Ours)2/0.782/0.741/0.653/0.824/1.023/1.194/1.1218/0.1112/0.2113/0.284/0.187/0.23
", + "bbox": [ + 99, + 88, + 870, + 252 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Evaluation on 7scenes and Cambridge landmarks. The metrics are the median translation (cm) and rotation (o) errors. The SCR-based methods highlighted in red were trained per scene. The best and second-best results are marked in bold and cyan. DeViLoc outperforms the other methods in overall, despite being trained only on MegaDepth.", + "bbox": [ + 75, + 262, + 892, + 306 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "label to each point based on pixel error. If the error between the projected 2D point and the query keypoint $k_{j}$ is less than $\\theta$ pixels $(\\theta = 8$ in our experiments), the corresponding confidence $c_{j}^{agg}$ is labeled as $l_{j} = 1$ , and vice versa. Consequently, the confidence loss, denoted as $L_{conf}^{q}$ , is established through the binary cross-entropy function:", + "bbox": [ + 75, + 330, + 468, + 422 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nL _ {\\text {c o n f}} ^ {q} = \\frac {1}{| M |} \\sum_ {j} \\left(l _ {j} \\log c _ {j} ^ {\\text {a g g}} + \\left(1 - l _ {j}\\right) \\log \\left(1 - c _ {j} ^ {\\text {a g g}}\\right)\\right) \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 84, + 429, + 468, + 465 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The final loss results from the combination of these two loss terms:", + "bbox": [ + 75, + 472, + 468, + 500 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nL ^ {q} = L _ {\\text {p o i n t}} ^ {q} + \\lambda * L _ {\\text {c o n f}} ^ {q} \\tag {13}\n$$\n", + "text_format": "latex", + "bbox": [ + 187, + 502, + 468, + 520 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Here, $\\lambda$ was set to 0.25 in our experiments.", + "bbox": [ + 76, + 523, + 362, + 537 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 550, + 209, + 566 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.1. Implementation Details", + "text_level": 1, + "bbox": [ + 76, + 575, + 294, + 590 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We conducted experiments on various datasets, including 7scenes [52], Cambridge [27], Aachen Day-Night [45, 48], RobotCar Seasons [36, 48], and Extended CMU Seasons [2, 58].", + "bbox": [ + 76, + 598, + 468, + 657 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Detailed pipeline. To demonstrate the adaptability of the proposed method to noisy and sparse 3D inputs, we utilized 3D point clouds generated through SIFT-based SfM in COLMAP [34, 50]. These 3D point clouds are consistently available across all datasets. We employed DenseVLad [59], NetVLad [1], or CosPlace [5] to retrieve the top-k reference images. Subsequently, the proposed framework was applied to predict 2D-3D matches from these inputs. During the prediction, we utilized the efficient feature-matching model, TopicFM [24], to generate semi-dense 2D-2D matches. Finally, the camera pose was computed from the 2D-3D matches using PnP functions in COLMAP.", + "bbox": [ + 75, + 659, + 468, + 838 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Training. Our network was trained on MegaDepth [32], comprising outdoor scenes from various locations. The trained model was directly used for evaluation across all datasets, eliminating the need for finetuning or retraining.", + "bbox": [ + 75, + 839, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Evaluation on Cambridge and 7scenes", + "text_level": 1, + "bbox": [ + 500, + 330, + 828, + 345 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We conducted a comparative analysis of our method (DeViLoc) against various state-of-the-art structure-based methods. Based on the characteristics outlined in the related works (Section 2), we primarily organized these methods into three categories: dense (D), sparse (S), and semi-dense (SD) methods. In this classification, SCR-based methods like HSCNet [30], SANet [66], DSAC* [8], DSAC++ [6], and DSM [56] were placed in the dense group (D) due to their strategy of making dense 2D-3D predictions. Conversely, methods such as Active Search [47], InLoc [55], and HLoc[SP+SG] [18, 41, 42] executed a sparse matching process between 2D keypoints and the 3D point cloud, classifying them in the sparse group (S). Despite PixLoc [43] not directly detecting 2D keypoints in the query image, its effective utilization of 3D points from a sparse point cloud to find corresponding 2D positions in the query image led us to categorize PixLoc in group S as well. In contrast to both groups (D and S), our method predicts 3D coordinates for all detected keypoints without any point rejection. To the best of our knowledge, NeuMap [57] is the most similar work to ours. Therefore, we assigned DeViLoc and NeuMap to the semi-dense group (SD).", + "bbox": [ + 496, + 354, + 890, + 686 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We compared the estimated camera poses of all methods to the ground-truth poses, calculating translation (in cm) and rotation (in degrees) errors [27] and presenting the median errors for each scene in Table 1. The results highlight the effectiveness of dense methods, following the SCR approach, in indoor scenes. This success is attributed to their scene-specific training (e.g., HSCNet, DSAC++, DSAC*) or training on extensive indoor datasets (e.g., DSM, trained on ScanNet [17]). However, these dense methods face challenges in generalizing to outdoor scenes in Cambridge. In contrast, despite being trained on outdoor scenes, our method demonstrates superior performance compared to the dense methods on the 7scenes dataset. The method secures first-place rankings in three scenes (Fire, Heads, Pumpkin)", + "bbox": [ + 496, + 688, + 892, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "19473", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/97e5a75e8c434fafe254bfdc65d8b71187f6ea4671c36fa8d85d1fbeedd03dfa.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodsAachen Day-NightRobotCar-SeasonsExtended CMU-Seasons
DayNightDay-allNight-allUrbanSuburbanPark
DESAC [7]42.6 / 59.6 / 75.56.1 / 10.2 / 18.4-----
SAS [47]85.3 / 92.2 / 97.939.8 / 49.0 / 64.350.9 / 80.2 / 96.66.9 / 15.6 / 31.781.0 / 87.3 / 92.462.6 / 70.9 / 81.045.5 / 51.6 / 62.0
D2Net [20]84.8 / 92.6 / 97.584.7 / 90.8 / 96.954.5 / 80.0 / 95.320.4 / 40.1 / 55.094.0 / 97.7 / 99.193.0 / 95.7 / 98.389.2 / 93.2 / 95.0
S2DNet [23]84.5 / 90.3 / 95.374.5 / 82.7 / 94.953.9 / 80.6 / 95.814.5 / 40.2 / 69.7---
HLoc[SP] [18, 41]80.5 / 87.4 / 94.268.4 / 77.6 / 88.853.1 / 79.1 / 95.57.2 / 17.4 / 34.489.5 / 94.2 / 97.976.5 / 82.7 / 92.757.4 / 64.4 / 80.4
PixLoc [43]64.3 / 69.3 / 77.451.0 / 55.1 / 67.352.7 / 77.5 / 93.912.0 / 20.7 / 45.488.3 / 90.4 / 93.779.6 / 81.1 / 85.261.0 / 62.5 / 69.4
HLoc[SP+SG]89.6 / 95.4 / 98.886.7 / 93.9 / 100.56.9 / 81.7 / 98.133.3 / 65.9 / 88.895.5 / 98.6 / 99.390.9 / 94.2 / 97.185.7 / 89.0 / 91.6
LBR [64]88.3 / 95.6 / 98.884.7 / 93.9 / 100.56.7 / 81.7 / 98.224.9 / 62.3 / 86.1---
HLoc+PixLoc84.7 / 94.2 / 98.881.6 / 93.9 / 100.56.9 / 82.0 / 98.134.9 / 67.7 / 89.596.9 / 98.9 / 99.393.3 / 95.4 / 97.187.0 / 89.5 / 91.6
HLoc[TopicFM][24]88.8 / 94.7 / 97.986.7 / 92.9 / 100.-----
SDNeuMap [57]80.8 / 90.9 / 95.648.0 / 67.3 / 87.8-----
DeViLoc (Ours)87.4 / 94.8 / 98.287.8 / 93.9 / 100.56.9 / 81.8 / 98.031.3 / 68.9 / 92.495.7 / 98.4 / 99.297.1 / 98.3 / 99.492.1 / 95.1 / 96.3
", + "bbox": [ + 83, + 88, + 885, + 244 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Evaluated results on the long-term benchmark [48] using the recall metrics at thresholds of $\\{(25cm,2^{\\circ}),(50cm,5^{\\circ}),(5m,10^{\\circ})\\}$ . We compare with various complex baselines that integrate robust FM models into HLoc [41] or use PixLoc to refine HLoc's poses. Our method achieves state-of-the-art performance, especially in the highly challenging localization in the CMU dataset (marked in bold red).", + "bbox": [ + 75, + 255, + 890, + 297 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "and second-place ranking in one scene (Kitchen). It also outperforms dense methods on the Cambridge dataset.", + "bbox": [ + 75, + 324, + 467, + 354 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In comparison to methods in group S, DeViLoc consistently delivers superior performance. Among these, HLoc[SP+SG] is the only method achieving competitive results with our approach on the Cambridge dataset. Notably, HLoc employs a complex pipeline involving retriangulating SIFT-based point clouds using robust local features and matches detected by SuperPoint (SP) [18] and SuperGlue (SG) [42]. In contrast, our method directly employs the noisy SIFT-based inputs and generally outperforms HLoc on both the 7scenes and Cambridge datasets.", + "bbox": [ + 75, + 354, + 467, + 505 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Evaluation on large-scale challenging scenes", + "text_level": 1, + "bbox": [ + 76, + 513, + 450, + 530 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We compared DeViLoc with several contemporary image-matching methods including D2Net [20], SP+SG [18, 42], and TopicFM [24], which are frequently incorporated into the HLoc pipeline as robust feature matchers. When using these methods, HLoc requires the extraction of new local features and matches from the database to recalculate the 3D point clouds. Furthermore, we also compared DeViLoc to other methods such as PixLoc [43], ESAC [7], and NeuMap [57], which are not based on the HLoc pipeline. Table 2 presents the results of all these methods.", + "bbox": [ + 75, + 537, + 467, + 686 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Aachen. DeViLoc performed comparably with recent FM-based baselines. Additionally, when compared to HLoc[TopicFM], which utilized the same feature matcher, our method exhibited an overall superior performance, demonstrating the effectiveness of the proposed pipeline.", + "bbox": [ + 75, + 688, + 467, + 763 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "RobotCar. As illustrated in Table 2, our method surpassed other methods and demonstrated competitive performance compared to HLoc[SP+SG] for the day-time queries. Particularly noteworthy is that DeViLoc significantly outperformed HLoc[SP+SG] for the night-time queries. It is important to highlight that both SP and SG were trained using multiple datasets, while DeViLoc was exclusively trained on MegaDepth [32].", + "bbox": [ + 75, + 763, + 467, + 883 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "CMU. Our method significantly outperformed the state", + "bbox": [ + 96, + 885, + 467, + 900 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "of-the-art pipeline HLoc[SP+SG] with a large margin. Compared to the complex pipeline HLoc+PixLoc, which uses PixLoc to refine the estimated poses of HLoc[SP+SG], DeViLoc improved accuracy by up to $5.1\\%$ on the scene \"Park\". This demonstrates the effectiveness and stability of our approach in difficult localization conditions.", + "bbox": [ + 496, + 324, + 890, + 414 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Ablation Study", + "text_level": 1, + "bbox": [ + 498, + 424, + 651, + 439 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Evaluating the performance with noisy and sparse inputs. To assess how effectively DeViLoc handles noisy and sparse inputs, we conducted an experiment using the Aachen Day-Night dataset. Our pipeline utilized 3D point cloud inputs generated by different image-matching models, including SIFT, SP+SG, and LoFTR. As illustrated in Fig. 4, the 3D point cloud generated by SIFT exhibits significantly more noise and sparsity compared to those produced by the SP+SG and LoFTR models. The results for each input model are presented in Table 3. We observe that the precise and dense 3D inputs from SP+SG or LoFTR only slightly improve performance. This highlights the adaptability of our approach in handling various types of 3D inputs, proving effective even in the presence of noisy and sparse data.", + "bbox": [ + 496, + 446, + 890, + 672 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Visualization of semi-dense matching. Fig. 5 illustrates the detected 2D keypoints and the corresponding 3D points produced by DeViLoc. We visualized multiple pairs of query and reference views. Despite a higher number of detected keypoints compared to the observed keypoints (especially in reference view 1), our method is capable of effectively estimating 3D points along with their uncertainties. Notably, points in the sky or near-edge regions of the scene tend to exhibit lower confidence. Ultimately, our method yields a significant number of 2D-3D matches after the point aggregation step, substantially improving performance, particularly in challenging scenes.", + "bbox": [ + 496, + 674, + 890, + 854 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effectiveness of proposed modules. We implemented three models to measure the contributions of the proposed modules, PIN (Section 3.2) and CPA (Section 3.3):", + "bbox": [ + 496, + 854, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "19474", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/2dede17d9a3d1d132679d07ceb9a766b2eb920440a187b03752b199b067f3355.jpg", + "image_caption": [ + "Figure 4. Comparison between point clouds built from traditional FM (SIFT [34]), sparse FM (SP+SG [18, 42]), and detector-free FM (LoFTR [53]). DeViLoc can handle well the noisy SIFT-based input to achieve competitive performance compared to the precise (SP+SG) or dense (LoFTR) inputs (shown in Table 3)." + ], + "image_footnote": [], + "bbox": [ + 98, + 89, + 450, + 239 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/77d95751b14e6ba955138e00970ac1e3d1c990e8f88e522514bd0f43f4b086ec.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelsDayNight
(0.25m,2°) / (0.5m,5°) / (5.0m,10°)
DeViLoc[half-SIFT]87.5 / 94.1 / 97.986.7 / 92.9 / 100.
DeViLoc[SIFT]87.4 / 94.8 / 98.287.8 / 93.9 / 100.
DeViLoc[SP+SG]87.3 / 95.3 / 98.388.8 / 92.9 / 100.
DeViLoc[LoFTR]87.9 / 94.7 / 98.288.8 / 92.9 / 100.
", + "bbox": [ + 111, + 333, + 436, + 405 + ], + "page_idx": 7 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Model-A: This model executes the standard 2D-3D matching process without utilizing the PIN and CPA modules, akin to existing pipelines like HLoc [41].", + "- Model-B: This model only integrates the PIN module, generating semi-dense matches. All these matches are directly fed into the PnP solver for pose estimation.", + "- Model-C: This model combines both PIN and CPA, including the entire process of the proposed method." + ], + "bbox": [ + 76, + 469, + 468, + 589 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4 presents the results of pose estimation using AUC with thresholds of $\\{2^o,5^o,10^o\\}$ [42]. The findings indicate that the proposed modules (Model-B and Model-C) significantly enhance performance as compared to the baseline (Model-A). Notably, these modules do not impose a substantial runtime burden, requiring only about $100ms$ to generate a more extensive set of 2D-3D matches, ultimately enhancing overall performance.", + "bbox": [ + 75, + 590, + 468, + 710 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Impact of the top-k reference images. Table 4 shows that employing more reference images can enhance performance. However, this improvement comes at the expense of significantly increased runtime and the number of matches.", + "bbox": [ + 75, + 710, + 468, + 770 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Using different feature matcher. We evaluated the performance by substituting the detector-free TopicFM [24] with the detector-based $\\mathrm{SP + SG}$ . The AUC metrics did not decrease significantly, as indicated in Table 4.", + "bbox": [ + 75, + 771, + 468, + 832 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusions and Limitations", + "text_level": 1, + "bbox": [ + 76, + 844, + 341, + 861 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This study introduces a robust structure-based framework for visual localization that minimizes reliance on the pre", + "bbox": [ + 75, + 869, + 468, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d34d82ae6cbea590b2084e9873fcbf65e12def87a8e3117338aa3970c29e93ab.jpg", + "image_caption": [ + "Figure 5. Illustration of 2D-3D correspondences estimated by DeViLoc for several pairs of images. The observed 2D keypoints are marked in black, while the reference keypoints are represented in orange (low confidence) or green (high confidence)." + ], + "image_footnote": [], + "bbox": [ + 519, + 89, + 870, + 252 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/a0389c18a5fa291423d71394e808bf1639d15e0170f80ca97eba9e9082d15acf.jpg", + "table_caption": [ + "Table 3. Ablation study of DeViLoc on Aachen Day-Night when using different point cloud inputs." + ], + "table_footnote": [], + "table_body": "
ModelAUC (2o/5o/10o)Time (s)#P ×106#M
A[SIFT] (A ⇌ HLoc)72.4 / 85.5 / 91.10.4911.642
A[SP+SG]72.8 / 86.4 / 92.20.5311.654
A[LoFTR]74.7 / 87.7 / 93.20.5111.6297
B (A+PIN)78.8 / 90.0 / 94.70.5615.94743
C (A+PIN+CPA) ⇌ DeViLoc79.6 / 90.5 / 94.90.5715.94246
C (TopicFM→SP+SG)78.2 / 89.9 / 94.71.0217.6993
DeViLoc (top-5)81.0 / 91.4 / 95.50.9015.97668
DeViLoc (top-10)82.6 / 92.2 / 96.01.9215.913970
", + "bbox": [ + 503, + 339, + 888, + 457 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4. Effectiveness of the proposed PIN and CPA (top), impact of the feature matcher (middle), and ablation of the top-k image retrieval (bottom) on MegaDepth [32]. The top-3 retrieval is used by default. Except for Model-A, the others were tested with SIFT inputs. $\\mathbf{P}$ is the model parameters and $\\mathbf{M}$ is the 2D-3D matches.", + "bbox": [ + 498, + 467, + 890, + 537 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "cise reconstruction of 3D point clouds. Our approach exhibits stable performance even when confronted with sparse and noisy 3D inputs. To achieve this, we present two novel modules: the Point Inference Network and the Confidence-based Point Aggregation. Consequently, the method generates numerous 2D-3D correspondences, leading to significant enhancements in challenging conditions, including textureless scenes, large-scale environments, and variations in weather and seasons. However, the computational efficiency of our proposed method has limitations. The runtime experiences a slowdown as the number of matching pairs between query and reference images increases. Addressing this limitation will be a focus of our future work.", + "bbox": [ + 496, + 569, + 890, + 765 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Acknowledgments", + "text_level": 1, + "bbox": [ + 500, + 789, + 678, + 806 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by the Ministry of Trade, Industry and Energy (MOTIE, Korea) under Grant 20007058, and by the National Research Foundation of Korea (NRF) funded by the Korean Government (MSIT) under Grant RS-2023-00208052.", + "bbox": [ + 498, + 816, + 890, + 886 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "19475", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. Netvlad: Cnn architecture for weakly supervised place recognition. 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Springer, 2022. 3" + ], + "bbox": [ + 503, + 92, + 890, + 712 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "19478", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/3fb41c79-8021-41c2-9eec-bd21aa2928ff_model.json b/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/3fb41c79-8021-41c2-9eec-bd21aa2928ff_model.json new file mode 100644 index 0000000000000000000000000000000000000000..1ebcb805bdca6e095186af20b3bb159e9b02f4e3 --- /dev/null +++ b/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/3fb41c79-8021-41c2-9eec-bd21aa2928ff_model.json @@ -0,0 +1,2455 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.114, + 0.131, + 0.856, + 0.152 + ], + "angle": 0, + "content": "Learning to Produce Semi-dense Correspondences for Visual Localization" + }, + { + "type": "text", + "bbox": [ + 0.264, + 0.18, + 0.714, + 0.2 + ], + "angle": 0, + "content": "Khang Truong Giang\\(^{1}\\) Soohwan Song\\(^{2*}\\) Sungho Jo\\(^{1*}\\)" + }, + { + "type": "text", + "bbox": [ + 0.245, + 0.199, + 0.725, + 0.217 + ], + "angle": 0, + "content": "1 School of Computing, KAIST, Daejeon, Republic of Korea" + }, + { + "type": "text", + "bbox": [ + 0.182, + 0.217, + 0.787, + 0.235 + ], + "angle": 0, + "content": "\\(^{2}\\) College of AI Convergence, Dongguk University, Seoul, Republic of Korea" + }, + { + "type": "text", + "bbox": [ + 0.412, + 0.238, + 0.553, + 0.251 + ], + "angle": 0, + "content": "\\*corresponding authors" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.287, + 0.312, + 0.303 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.318, + 0.473, + 0.712 + ], + "angle": 0, + "content": "This study addresses the challenge of performing visual localization in demanding conditions such as nighttime scenarios, adverse weather, and seasonal changes. While many prior studies have focused on improving image matching performance to facilitate reliable dense keypoint matching between images, existing methods often heavily rely on predefined feature points on a reconstructed 3D model. Consequently, they tend to overlook unobserved keypoints during the matching process. Therefore, dense keypoint matches are not fully exploited, leading to a notable reduction in accuracy, particularly in noisy scenes. To tackle this issue, we propose a novel localization method that extracts reliable semi-dense 2D-3D matching points based on dense keypoint matches. This approach involves regressing semi-dense 2D keypoints into 3D scene coordinates using a point inference network. The network utilizes both geometric and visual cues to effectively infer 3D coordinates for unobserved keypoints from the observed ones. The abundance of matching information significantly enhances the accuracy of camera pose estimation, even in scenarios involving noisy or sparse 3D models. Comprehensive evaluations demonstrate that the proposed method outperforms other methods in challenging scenes and achieves competitive results in large-scale visual localization benchmarks. The code will be available at https://github.com/TruongKhang/DeViLoc." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.74, + 0.208, + 0.755 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Visual localization is the process of determining the 6 degrees of freedom (DoF) camera pose for a given query image within a known scene. This fundamental task in computer vision is critical for applications such as robot navigation [33] and virtual or augmented reality [35, 37]. Most leading studies primarily employ a structure-based approach [8, 41, 43, 47, 68], consistently exhibiting high localization performance across diverse challenging conditions [31, 42, 54, 58]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.288, + 0.895, + 0.47 + ], + "angle": 0, + "content": "Traditionally, structure-based methods heavily rely on feature matching (FM) [11, 46, 51, 55, 64]. These methods establish sparse correspondences between 3D points and 2D pixel-level keypoints in images, followed by estimating camera poses using RANSAC-based Perspective-n-Point (PnP). The recent advancements in FM-based methods [41, 42, 53] have shown outstanding performance across various benchmarks, particularly in large-scale scenes. However, despite these achievements, FM-based methods encounter substantial challenges in practical scenarios, including dealing with complex lighting conditions, seasonal variations, and changes in perspectives." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.474, + 0.895, + 0.732 + ], + "angle": 0, + "content": "Addressing these challenges necessitates a more robust and informative feature-matching approach incorporating detailed 3D points. Current methods, including those achieving semi-dense 2D-2D correspondences through detector-free image matching [15, 24, 53], are limited by relying solely on matched sparse features. This limitation persists when considering semi-dense matches, which only account for keypoints observed in a 3D model, neglecting valuable information from unobserved keypoints. Furthermore, FM-based methods demand a detailed 3D point cloud map for accurate localization. Continuously refining 3D feature points for new image inputs is time-intensive, and in some scenarios, localization must be performed with a noisy or sparse 3D point cloud. Overreliance on predetermined 2D and 3D points in the database can lead to a degradation in pose accuracy, especially in noisy cases with texture-less surfaces or repetitive patterns." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.897, + 0.902 + ], + "angle": 0, + "content": "Recent studies introduce scene coordinate regression (SCR) methods [6, 8, 30, 56], aiming to achieve dense 2D-3D correspondences. Unlike FM-based approaches, SCR methods use an implicit representation of scenes as a learnable function, predicting the dense 3D scene coordinates of a query image. SCR methods excel in compact and stable settings, eliminating the need for storing 3D models; however, they face challenges in dynamic environments and adapting to new viewpoints, limiting their applicability in large-scale scenes. Therefore, there is a need for an alternative method capable of finding dense and accurate 2D-3D" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19468" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.1, + 0.089, + 0.873, + 0.251 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.263, + 0.896, + 0.348 + ], + "angle": 0, + "content": "Figure 1. The comparison of the 2D-3D correspondence finding process in our method (DeViLoc) and an existing method (HLoc [41]). HLoc heavily relies on a robust 3D point cloud but discards many detected 2D keypoints (depicted in green) during the 2D-3D matching process. In contrast, our method efficiently handles a noisy point cloud through the point inference process of PIN. PIN transforms the entire set of 2D-2D matches into 2D-3D matches. Our method then produces numerous accurate 2D-3D matches across multiple views using a confidence-based aggregation module. These abundant matches significantly enhance localization performance, particularly in scenarios characterized by noisy or sparse 3D point clouds." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.374, + 0.343, + 0.388 + ], + "angle": 0, + "content": "correspondences for visual localization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.393, + 0.471, + 0.529 + ], + "angle": 0, + "content": "Therefore, this study proposes a novel FM-based method, semi-Dense Visual Localization (DeViLoc), aiming to predict dense 2D-3D correspondences for robust and accurate localization. In contrast to existing FM-based methods relying solely on pre-existing 3D points, our method directly converts semi-dense 2D-2D matches into 2D-3D matches. This abundant 2D-3D match information significantly enhances the precision of camera pose estimation, even when dealing with noisy or sparse 3D models." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.534, + 0.47, + 0.79 + ], + "angle": 0, + "content": "This method comprises two main components: 1) the Point Inference Network (PIN) and 2) the Confidence-based Point Aggregation (CPA) module. PIN plays a crucial role in our method by converting semi-dense 2D-2D matches into 2D-3D matches. It achieves this by directly regressing all 2D keypoints, both observed and unobserved, into 3D scene coordinates. The process involves encoding scene geometry from observed points into latent vectors and propagating 3D information to unobserved positions through attention layers. Next, the CPA module aggregates 2D-3D matches from multiple query-reference pairs, identifying consistent and highly confident 3D points corresponding to the same 2D keypoints in multiple matching views. This step effectively removes outliers from dense matches, and the filtered 2D-3D matches expedite RANSAC-based pose estimation. Ultimately, DeViLoc significantly increases the number of accurate 2D-3D matches for localization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Fig. 1 illustrates the 2D-3D matching process of our method and an existing one (HLoc+LoFTR [41, 53]). The existing method, despite having a dense and precise 3D model, rejects many important points during 2D-3D estimation. In contrast, our method confidently transforms 2D-2D matches into 2D-3D matches, generating numerous matches even in the presence of noisy 3D input and night-" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.373, + 0.892, + 0.434 + ], + "angle": 0, + "content": "time conditions. Consequently, the method yields robust and accurate localization results based on dense matching information, especially in challenging conditions like nighttime scenarios, adverse weather, and seasonal changes." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.435, + 0.825, + 0.45 + ], + "angle": 0, + "content": "This paper makes the following contributions:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.451, + 0.892, + 0.54 + ], + "angle": 0, + "content": "- We propose a novel visual localization method that leverages rich matching information by directly converting semi-dense 2D-2D matches into 2D-3D matches. This method significantly improves the accuracy of camera pose estimation, particularly in scenarios with noisy or sparse 3D models." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.542, + 0.892, + 0.631 + ], + "angle": 0, + "content": "- We introduce a network architecture, Point Inference Network (PIN), designed to directly regress 2D keypoints into 3D points. This network effectively exploits geometric and visual connections between unobserved and observed keypoints, ensuring accurate estimation of 3D information along with associated uncertainties." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.632, + 0.892, + 0.723 + ], + "angle": 0, + "content": "- We conducted a comprehensive evaluation of our method across diverse datasets. The results indicate that our proposed approach outperforms other state-of-the-art methods in challenging scenes and achieves competitive performance in large-scale visual localization benchmarks. The source code is publicly available." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.451, + 0.892, + 0.723 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.739, + 0.651, + 0.755 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Visual localization, which involves estimating camera poses from visual inputs, has been a subject of study for decades [8, 28, 31, 39, 49, 54]. Early approaches [1, 49, 59] primarily relied on an image retrieval strategy to directly estimate camera poses from the most similar images in database. This approach is intuitive and efficient, but its performance is significantly influenced by the density of images in the database. To overcome this limitation, an alternative approach learns a neural network to directly predict absolute" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "19469" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.402, + 0.106 + ], + "angle": 0, + "content": "camera poses from the input images [26, 27, 61]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.108, + 0.47, + 0.273 + ], + "angle": 0, + "content": "Many studies [8, 9, 11, 25, 41, 47, 51, 54, 55, 68] have shifted their focus towards structure-based approach due to its stability and scalability in diverse scenes. The structure-based methods estimate camera pose by establishing a set of 2D-3D correspondences between image pixels and 3D coordinates of the scene. Leveraging this precise correspondence set, a camera pose can be accurately computed using a PnP solver [22, 29, 40] within a RANSAC paradigm [3, 4, 21]. The structure-based methods can be broadly categorized into two main groups: feature matching (FM) and scene coordinate regression (SCR)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.276, + 0.47, + 0.442 + ], + "angle": 0, + "content": "Feature Matching. FM-based methods [11, 31, 41, 46, 51] initially reconstruct a 3D model of the environment from database images using Structure-from-Motion (SfM) [50, 63]. Each 3D point in the model is associated with one or several feature descriptors for localization. When a localization request for a query image is made, these methods detect a set of 2D keypoints along with their descriptors and proceed to match them with the 3D points. Several works generate the 2D-3D matches by examining all points in the 3D model [31, 44]; however, they face difficulty when dealing with large scenes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.444, + 0.47, + 0.64 + ], + "angle": 0, + "content": "To address this challenge, recent studies [41, 57, 64] have introduced a coarse-to-fine strategy. They initially identify a set of reference images in a database through image retrieval. They then establish 2D-3D matches based on 2D-2D matches between the query and reference images. Subsequent works have focused on enhancing the performance of image matching by incorporating transformers [15, 24, 42, 53] or semantic information [65]. These approaches produce robust and accurate 2D-2D matches, contributing to the robust construction of 3D model and the accurate generation of 2D-3D matches during the localization step. Consequently, FM-based methods have achieved state-of-the-art performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.643, + 0.47, + 0.853 + ], + "angle": 0, + "content": "However, these methods exhibit inflexibility due to heavily relying on high-fidelity point cloud reconstruction. This time-consuming step is not suitable for online applications such as SLAM or robot navigation, where the 3D point cloud is constructed on-the-fly from a sequence of images. In this situation, the point cloud might be noisy or incomplete, thus degrading localization performance. Furthermore, existing FM-based methods only utilize observed 3D points in the database to generate 2D-3D matches, discarding numerous unrelated 2D-2D matches. This process might compromise the performance in the presence of noisy 3D inputs. On the other hand, our proposed framework aims to adapt to various kinds of 3D inputs and predict semidense 2D-3D correspondences." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Scene Coordinate Regression. In contrast to the explicit utilization of 3D models seen in FM-based methods, SCR [6, 8, 9, 13, 14, 52, 60] employs an implicit repre" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.242 + ], + "angle": 0, + "content": "sensation of scenes in a form of a machine learning model. This model predicts dense 3D scene coordinates for an input query image. While SCR-based methods offer a concise representation of scenes, they encounter challenges when adapting to large-scale scenes, novel scenes, or challenging conditions. Several approaches have been proposed to address these challenges by predicting a scene part-by-part [7, 30] or employing a coarse-to-fine prediction [56, 66]. However, these methods still exhibit lower performance compared to FM-based methods." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.243, + 0.892, + 0.377 + ], + "angle": 0, + "content": "Drawing inspiration from SCR, our method aims to predict 3D coordinates for all keypoints in the query image, identified using a detector-free image-matching model. However, in contrast to the dense prediction in SCR, our semi-dense approach reduces the possibility of incorrect 3D prediction by focusing only on regions of interest between the query and reference images. Consequently, our method achieves more accurate performance than SCR-based methods in outdoor scenes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.379, + 0.892, + 0.59 + ], + "angle": 0, + "content": "3D Scene Representation. FM-based methods [24, 41, 42, 53] have proven to be effective, but they come with a drawback of requiring substantial storage capacity to store both the 3D coordinates and the associated visual features [41, 42]. Consequently, recent studies [10, 12, 16, 38, 67, 70] have shifted their focus toward discovering more space-efficient representations of the scene. For example, NeuMap [57] proposed encoding a 3D point cloud into a set of latent codes and then regressing 3D coordinates based on these codes. While these methods successfully reduce storage demands, they discard crucial scene information, thereby limiting their performance. In contrast, this study focuses on improving performance when dealing with challenging point cloud inputs." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.603, + 0.673, + 0.62 + ], + "angle": 0, + "content": "3. Proposed Method" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.628, + 0.892, + 0.734 + ], + "angle": 0, + "content": "We follow the coarse-to-fine localization paradigm [41] that first retrieves a set of reference images via image retrieval, and then estimates a camera pose by finding 2D-3D correspondences between image pixels and 3D coordinates of the scene. The proposed method aims to address the task of 2D-3D prediction, while applying image retrieval and a PnP pose solver, similar to [41]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.742, + 0.611, + 0.757 + ], + "angle": 0, + "content": "3.1. Overview" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Given a query image \\(I^q\\) and a set of reference images \\(\\{I^{r,1}\\dots I^{r,N_v}\\}\\) retrieved from a database, our method establishes a set of 2D-3D correspondences \\(M = \\{(k_i,p_i)\\}\\), where \\(k_{i}\\) is a 2D keypoint in the query image and \\(p_i\\) represents the corresponding 3D coordinate. Fig. 2 describes the overall architecture of the proposed method, DeViLoc. For each pair of query \\(I^q\\) and reference \\(I^r\\), DeViLoc first extracts local 2D-2D feature correspondences \\(\\{(k_i^q,k_i^r)\\}\\) using an image-matching network. Here, we employed a" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19470" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.099, + 0.096, + 0.878, + 0.25 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.263, + 0.895, + 0.308 + ], + "angle": 0, + "content": "Figure 2. Overview of DeViLoc. First, a feature matcher is employed to detect 2D-2D matches for each pair of query-reference images. Subsequently, the PIN module infers a set of 3D coordinates for all detected 2D keypoints based on the observed data in the reference image. Finally, the CPA module integrates all 2D-3D matches obtained across all query-reference pairs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.332, + 0.47, + 0.363 + ], + "angle": 0, + "content": "detector-free image-matching model [24] to produce semidense correspondences." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.364, + 0.47, + 0.62 + ], + "angle": 0, + "content": "The Point Inference Network (PIN) then converts detected 2D keypoints of the reference image into 3D points (Section 3.2). It takes reference image \\(I^r\\) with known camera parameters, along with a sparse set of observed 3D points as inputs, and predicts a set of 3D scene coordinates, \\(\\{p_i\\}\\), corresponding to all keypoints \\(\\{k_i^r\\}\\). Based on predicted 3D points \\(\\{p_i\\}\\) and 2D-2D matches \\(\\{(k_i^q,k_i^r)\\}\\), we could produce dense 2D-3D matches, \\(\\{(k_i^q,p_i)\\}\\), for the query image. The basic concept of PIN is inspired by depth completion [62, 69], where a dense depth map is reconstructed from a sparse set of observed depth measurements and an input image. However, unlike depth completion, PIN aims to infer a discrete set of depth points, leading to reduced computational costs. Due to this discrete depth prediction, PIN utilizes attention [19] and MLP layers without the need for complex CNNs, as commonly found in conventional depth completion methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.621, + 0.47, + 0.728 + ], + "angle": 0, + "content": "Next, the Confidence-based Point Aggregation (CPA) module integrates all 2D-3D matches from multiple query-reference image pairs (Section 3.3). CPA integrates 2D-3D matches with small distances of keypoints into a representative match. It effectively removes outliers by considering the confidence information of each match during the integration process." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.74, + 0.303, + 0.755 + ], + "angle": 0, + "content": "3.2. Point Inference Network" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.469, + 0.827 + ], + "angle": 0, + "content": "For reference image \\(I^r\\), let \\(O^r = \\{o_i^r\\}\\) be the set of 3D points observed from the constructed 3D model. PIN predicts 3D points \\(P^r = \\{p_i^r\\}\\) corresponding to detected 2D keypoints \\(K^r = \\{k_i^r\\}\\) as:" + }, + { + "type": "equation", + "bbox": [ + 0.191, + 0.84, + 0.469, + 0.857 + ], + "angle": 0, + "content": "\\[\nP ^ {r} = \\operatorname {P I N} \\left(K ^ {r}, O ^ {r}, F ^ {r}\\right) \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.869, + 0.47, + 0.902 + ], + "angle": 0, + "content": "where \\(K^r \\in \\mathbb{R}^{N_{points}^r \\times 2}\\), \\(O^r \\in \\mathbb{R}^{N_{points}^o \\times 3}\\), and \\(F^r\\) is a feature map extracted from image \\(I^r\\) using convolutional" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.331, + 0.892, + 0.362 + ], + "angle": 0, + "content": "networks \\((F^r\\in \\mathbb{R}^{h\\times w\\times c})\\) . We directly utilized the output features of the image-matching network [24] as \\(F^r\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.363, + 0.893, + 0.544 + ], + "angle": 0, + "content": "The method begins with a preprocessing step where keypoints \\( K^r \\) and observed 3D points \\( O^r \\) are transformed into the same camera-coordinate system using the known camera parameters. Subsequently, we decompose the observed 3D points into observed keypoints \\( K^o \\in \\mathbb{R}^{N_{points}^o \\times 2} \\) and depth values \\( D^o \\in \\mathbb{R}^{N_{points}^o \\times 1} \\). The PIN network then aims to estimate depths \\( D^r \\) for reference keypoints \\( K^r \\), utilizing observed keypoints \\( K^o \\), observed depths \\( D^o \\), and the feature map \\( F^r \\). The network architecture of PIN is illustrated in Fig. 3, comprising two fundamental steps to leverage both spatial information and visual similarity for depth estimation: geometric guidance and visual guidance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.544, + 0.892, + 0.62 + ], + "angle": 0, + "content": "To implement geometric guidance, we initially employ two MLP-based encoders to learn embeddings for all 2D keypoint coordinates \\(\\{K^r, K^o\\}\\), as well as for the observed depths, \\(D^o\\). Additionally, we encode scene geometry from the observed depths by utilizing a self-attention layer." + }, + { + "type": "equation", + "bbox": [ + 0.6, + 0.632, + 0.891, + 0.648 + ], + "angle": 0, + "content": "\\[\nD _ {e m b} ^ {o} = \\operatorname {D e p t h E n c} \\left(D ^ {o}\\right) \\tag {2}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.547, + 0.65, + 0.891, + 0.668 + ], + "angle": 0, + "content": "\\[\n\\left[ K _ {e m b} ^ {r}, K _ {e m b} ^ {o} \\right] = \\text {K e y p o i n t E n c} \\left(\\left[ K ^ {r}, K ^ {o} \\right]\\right) \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.679, + 0.892, + 0.802 + ], + "angle": 0, + "content": "The relative position between the observed and unobserved keypoints serves as a primary geometric cue for propagating depth information from observed to unobserved positions. Therefore, we represent the observed positions with latent codes, \\( P_{lc}^{o} \\), combined from keypoint embeddings \\( K_{emb}^{o} \\) and depth features \\( D_{emb}^{o} \\). These latent codes are then passed into a cross-attention layer to generate latent codes \\( P_{lc}^{r} \\) related to reference keypoints \\( K_{emb}^{r} \\):" + }, + { + "type": "equation", + "bbox": [ + 0.603, + 0.812, + 0.891, + 0.829 + ], + "angle": 0, + "content": "\\[\nP _ {l c} ^ {r} = \\operatorname {C r s A t t} \\left(K _ {e m b} ^ {r}, P _ {l c} ^ {o}\\right) \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.891, + 0.871 + ], + "angle": 0, + "content": "In Eq. 4, \\( K_{emb}^{r} \\) is the query, and \\( P_{lc}^{o} \\) represents the key and value for the cross-attention function, CrsAtt()." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "The geometric guidance mentioned above may lack robustness in estimating accurate depths due to the sparsity of" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "19471" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.15, + 0.087, + 0.825, + 0.252 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.26, + 0.895, + 0.306 + ], + "angle": 0, + "content": "Figure 3. Point Inference Network (PIN). The network begins by learning embeddings for all keypoints \\((K_{emb}^{o}, K_{emb}^{r})\\) and observed depths \\((D_{emb}^{o})\\). Subsequently, attention layers are employed for both geometric and visual guidance. Finally, the learned latent codes \\((P_{lc}^{r})\\) are utilized to perform regression for the 3D points along with confidence values." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.329, + 0.473, + 0.435 + ], + "angle": 0, + "content": "observed data points. Therefore, we also incorporate visual features for more detailed guidance. Considering the feature map \\( F^r \\) in Eq. 1, we utilize a bilinear grid sampling to extract sets of visual features \\( V^r \\) and \\( V^o \\) for both \\( K^r \\) and \\( K^o \\). These visual features are appended to the latent codes, \\( P_{lc}^r \\) and \\( P_{lc}^o \\). Subsequently, we employ multiple self/cross-attention layers to facilitate visual guidance:" + }, + { + "type": "equation", + "bbox": [ + 0.091, + 0.445, + 0.47, + 0.463 + ], + "angle": 0, + "content": "\\[\nP _ {l c} ^ {r} = \\operatorname {C o n c a t} \\left(P _ {l c} ^ {r}, V ^ {r}\\right), P _ {l c} ^ {o} = \\operatorname {C o n c a t} \\left(P _ {l c} ^ {o}, V ^ {o}\\right) \\tag {5}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.093, + 0.464, + 0.469, + 0.483 + ], + "angle": 0, + "content": "\\[\nP _ {l c} ^ {o} = \\operatorname {S e l f A t t} \\left(P _ {l c} ^ {o}\\right), P _ {f i n a l} ^ {r} = \\operatorname {C r s A t t} \\left(P _ {l c} ^ {r}, P _ {l c} ^ {o}\\right) \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.492, + 0.47, + 0.537 + ], + "angle": 0, + "content": "After learning the final latent features, \\( P_{final}^{r} \\), corresponding to reference keypoints \\( K^{r} \\), we use two MLP-based networks to predict the depths and confidence:" + }, + { + "type": "equation", + "bbox": [ + 0.094, + 0.547, + 0.47, + 0.567 + ], + "angle": 0, + "content": "\\[\nD ^ {r} = \\mathbb {M L P} \\big (P _ {f i n a l} ^ {r} \\big), \\quad C ^ {r} = \\mathbb {M L P} \\big ([ P _ {f i n a l} ^ {r}, D ^ {r} ] \\big) \\quad (7 \\mathrm {a}, \\mathrm {b})\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.575, + 0.469, + 0.606 + ], + "angle": 0, + "content": "Finally, the 3D scene coordinates for the reference keypoints are estimated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.148, + 0.614, + 0.47, + 0.634 + ], + "angle": 0, + "content": "\\[\nP ^ {r} = \\left(T ^ {- 1}\\right) _ {c a m \\rightarrow s c e n e} \\left(D ^ {r} [ \\hat {K} ^ {r}, 1 ] ^ {T}\\right) \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.642, + 0.47, + 0.703 + ], + "angle": 0, + "content": "where \\( T^{-1} \\) transforms the 3D points from camera-coordinate to scene-coordinate system. The confidences \\( C^r \\) represent the uncertainty associated with the predicted 3D coordinates, \\( P^r \\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.712, + 0.394, + 0.729 + ], + "angle": 0, + "content": "3.3. Confidence-based Point Aggregation" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.735, + 0.473, + 0.903 + ], + "angle": 0, + "content": "PIN produced the 2D-3D correspondences, \\((K^q,P) = \\{(k_i^q,p_i)\\}\\), along with their associated confidence values \\(C^r = \\{c_i\\}\\) for every query-reference pair \\((I^q,I^r)\\). Subsequently, we aggregated the 2D-3D matches \\(\\{(k_i^q,p_i)^n\\}_{n = 1\\dots N_v}^{i = 1\\dots N_m}\\) across \\(N_{v}\\) sets of matches, with \\(N_{m}\\) being the number of matches per set. The goal of CPA is to eliminate outliers from the aggregated matches and determine the final matches that exhibit high confidence and consistency. To accomplish this, we started by discarding matches with low confidence through a threshold \\(\\tau\\). Next, we grouped adjacent matches using a keypoint quantization" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.329, + 0.892, + 0.42 + ], + "angle": 0, + "content": "step. If the coordinates of two keypoints are closer than \\( s \\) pixels, these keypoints are assigned to the same group. This process is represented by a function \\( Q_{s} \\), where \\( s \\) denotes the quantization size (\\( s \\in \\{2, 4\\} \\) in our experiments). Once matches within the same group were identified, we merged them using a confidence-based averaging operation." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.42, + 0.892, + 0.468 + ], + "angle": 0, + "content": "Let \\( k_{j} \\) be a quantized keypoint, the formulas for the aggregated 3D point \\( p_{j}^{agg} \\) and the corresponding confidence \\( c_{j}^{agg} \\) can be written as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.575, + 0.478, + 0.891, + 0.517 + ], + "angle": 0, + "content": "\\[\np _ {j} ^ {\\text {a g g}} = \\frac {\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n} p _ {i} ^ {n}}{\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n}} \\tag {9}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.577, + 0.518, + 0.892, + 0.555 + ], + "angle": 0, + "content": "\\[\nc _ {j} ^ {a g g} = \\frac {\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n}}{N _ {k _ {j}}} \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.565, + 0.894, + 0.613 + ], + "angle": 0, + "content": "Here, \\(\\mathbf{1}(Q_s(k_i^n) = k_j)\\) is a binary indicator, and \\(N_{k_j} = \\sum_{i,n}\\mathbf{1}(Q_s(k_i^n) = k_j)\\) represents the number of keypoints quantized into \\(k_{j}\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.621, + 0.654, + 0.637 + ], + "angle": 0, + "content": "3.4. Loss Functions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.645, + 0.892, + 0.735 + ], + "angle": 0, + "content": "In summary, the proposed approach generates a set of 2D-3D matches, denoted as \\( M = \\{(k_j, p_j^{agg}, c_j^{agg})\\} \\), for query image \\( I^q \\). Utilizing ground-truth camera matrices \\( (C^q, T^q) \\) and available depth information \\( D^q = \\{d_j^q\\} \\), we define two functions, incorporating point-matching loss and confidence loss, to train the proposed network." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.735, + 0.892, + 0.812 + ], + "angle": 0, + "content": "Point-matching loss. We computed the ground-truth 3D coordinates \\(\\{p_j^{qt}\\}\\) for the keypoints \\(\\{k_{j}\\}\\) using the depths \\(\\{d_j^q\\}\\) and camera matrices \\((C^q,T^q)\\). Then, we employed the \\(L1\\) function to calculate the loss between the ground-truth 3D points and predicted 3D points:" + }, + { + "type": "equation", + "bbox": [ + 0.587, + 0.821, + 0.892, + 0.86 + ], + "angle": 0, + "content": "\\[\nL _ {\\text {p o i n t}} ^ {q} = \\frac {1}{| M |} \\sum_ {j} \\left\\| p _ {j} ^ {\\text {a g g}} - p _ {j} ^ {\\text {g t}} \\right\\| \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.894, + 0.904 + ], + "angle": 0, + "content": "Confidence loss. To train the confidence, we projected the 3D points \\(\\{p_j^{agg}\\}\\) onto the image plane and assigned a" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "19472" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.1, + 0.089, + 0.872, + 0.253 + ], + "angle": 0, + "content": "
Methods7scenes (indoor)Cambridge landmarks (outdoor)
ChessFireHeadsOfficePumpkinKitchenStairsCourtKing'sHospitalShopSt. Mary's
DHSCNet [30]2/0.72/0.91/0.93/0.84/1.04/1.23/0.828/0.218/0.319/0.36/0.39/0.3
DSAC++ [6]2/0.52/0.91/0.83/0.74/1.14/1.19/2.640/0.218/0.320/0.36/0.313/0.4
DSAC* [8]2/1.102/1.241/1.823/1.154/1.344/1.683/1.1649/0.315/0.321/0.45/0.313/0.4
SANet [66]3/0.883/1.082/1.483/1.005/1.324/1.4016/4.59328/1.9532/0.5432/0.5310/0.4716/0.57
DSM [56]2/0.682/0.801/0.803/0.784/1.113/1.114/1.1643/0.1919/0.3523/0.386/0.3011/0.34
SAS [47]3/0.872/1.011/0.824/1.157/1.695/1.724/1.0124/0.1313/0.2220/0.364/0.218/0.25
InLoc [55]3/1.053/1.072/1.163/1.055/1.554/1.319/2.47-----
PixLoc [43]2/0.802/0.731/0.823/0.824/1.213/1.205/1.3030/0.1414/0.2416/0.325/0.2310/0.34
HLoc[SP+SG]2/0.842/0.931/0.743/0.925/1.274/1.405/1.4716/0.1112/0.2015/0.304/0.207/0.21
HLoc[LoFTR]3/0.932/0.871/0.734/1.025/1.245/1.486/1.4719/0.1116/0.2616/0.294/0.219/0.26
SDNeuMap [57]2/0.813/1.112/1.173/0.984/1.114/1.334/1.126/0.1014/0.1919/0.366/0.2517/0.53
DeViLoc (Ours)2/0.782/0.741/0.653/0.824/1.023/1.194/1.1218/0.1112/0.2113/0.284/0.187/0.23
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.263, + 0.893, + 0.307 + ], + "angle": 0, + "content": "Table 1. Evaluation on 7scenes and Cambridge landmarks. The metrics are the median translation (cm) and rotation (o) errors. The SCR-based methods highlighted in red were trained per scene. The best and second-best results are marked in bold and cyan. DeViLoc outperforms the other methods in overall, despite being trained only on MegaDepth." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.332, + 0.47, + 0.424 + ], + "angle": 0, + "content": "label to each point based on pixel error. If the error between the projected 2D point and the query keypoint \\( k_{j} \\) is less than \\( \\theta \\) pixels \\( (\\theta = 8 \\) in our experiments), the corresponding confidence \\( c_{j}^{agg} \\) is labeled as \\( l_{j} = 1 \\), and vice versa. Consequently, the confidence loss, denoted as \\( L_{conf}^{q} \\), is established through the binary cross-entropy function:" + }, + { + "type": "equation", + "bbox": [ + 0.085, + 0.43, + 0.469, + 0.466 + ], + "angle": 0, + "content": "\\[\nL _ {\\text {c o n f}} ^ {q} = \\frac {1}{| M |} \\sum_ {j} \\left(l _ {j} \\log c _ {j} ^ {\\text {a g g}} + \\left(1 - l _ {j}\\right) \\log \\left(1 - c _ {j} ^ {\\text {a g g}}\\right)\\right) \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.473, + 0.469, + 0.5 + ], + "angle": 0, + "content": "The final loss results from the combination of these two loss terms:" + }, + { + "type": "equation", + "bbox": [ + 0.188, + 0.503, + 0.469, + 0.521 + ], + "angle": 0, + "content": "\\[\nL ^ {q} = L _ {\\text {p o i n t}} ^ {q} + \\lambda * L _ {\\text {c o n f}} ^ {q} \\tag {13}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.524, + 0.363, + 0.539 + ], + "angle": 0, + "content": "Here, \\(\\lambda\\) was set to 0.25 in our experiments." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.551, + 0.21, + 0.568 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.576, + 0.295, + 0.592 + ], + "angle": 0, + "content": "4.1. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.599, + 0.469, + 0.659 + ], + "angle": 0, + "content": "We conducted experiments on various datasets, including 7scenes [52], Cambridge [27], Aachen Day-Night [45, 48], RobotCar Seasons [36, 48], and Extended CMU Seasons [2, 58]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.66, + 0.469, + 0.839 + ], + "angle": 0, + "content": "Detailed pipeline. To demonstrate the adaptability of the proposed method to noisy and sparse 3D inputs, we utilized 3D point clouds generated through SIFT-based SfM in COLMAP [34, 50]. These 3D point clouds are consistently available across all datasets. We employed DenseVLad [59], NetVLad [1], or CosPlace [5] to retrieve the top-k reference images. Subsequently, the proposed framework was applied to predict 2D-3D matches from these inputs. During the prediction, we utilized the efficient feature-matching model, TopicFM [24], to generate semi-dense 2D-2D matches. Finally, the camera pose was computed from the 2D-3D matches using PnP functions in COLMAP." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Training. Our network was trained on MegaDepth [32], comprising outdoor scenes from various locations. The trained model was directly used for evaluation across all datasets, eliminating the need for finetuning or retraining." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.331, + 0.83, + 0.347 + ], + "angle": 0, + "content": "4.2. Evaluation on Cambridge and 7scenes" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.356, + 0.892, + 0.688 + ], + "angle": 0, + "content": "We conducted a comparative analysis of our method (DeViLoc) against various state-of-the-art structure-based methods. Based on the characteristics outlined in the related works (Section 2), we primarily organized these methods into three categories: dense (D), sparse (S), and semi-dense (SD) methods. In this classification, SCR-based methods like HSCNet [30], SANet [66], DSAC* [8], DSAC++ [6], and DSM [56] were placed in the dense group (D) due to their strategy of making dense 2D-3D predictions. Conversely, methods such as Active Search [47], InLoc [55], and HLoc[SP+SG] [18, 41, 42] executed a sparse matching process between 2D keypoints and the 3D point cloud, classifying them in the sparse group (S). Despite PixLoc [43] not directly detecting 2D keypoints in the query image, its effective utilization of 3D points from a sparse point cloud to find corresponding 2D positions in the query image led us to categorize PixLoc in group S as well. In contrast to both groups (D and S), our method predicts 3D coordinates for all detected keypoints without any point rejection. To the best of our knowledge, NeuMap [57] is the most similar work to ours. Therefore, we assigned DeViLoc and NeuMap to the semi-dense group (SD)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.893, + 0.901 + ], + "angle": 0, + "content": "We compared the estimated camera poses of all methods to the ground-truth poses, calculating translation (in cm) and rotation (in degrees) errors [27] and presenting the median errors for each scene in Table 1. The results highlight the effectiveness of dense methods, following the SCR approach, in indoor scenes. This success is attributed to their scene-specific training (e.g., HSCNet, DSAC++, DSAC*) or training on extensive indoor datasets (e.g., DSM, trained on ScanNet [17]). However, these dense methods face challenges in generalizing to outdoor scenes in Cambridge. In contrast, despite being trained on outdoor scenes, our method demonstrates superior performance compared to the dense methods on the 7scenes dataset. The method secures first-place rankings in three scenes (Fire, Heads, Pumpkin)" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19473" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.084, + 0.089, + 0.887, + 0.246 + ], + "angle": 0, + "content": "
MethodsAachen Day-NightRobotCar-SeasonsExtended CMU-Seasons
DayNightDay-allNight-allUrbanSuburbanPark
DESAC [7]42.6 / 59.6 / 75.56.1 / 10.2 / 18.4-----
SAS [47]85.3 / 92.2 / 97.939.8 / 49.0 / 64.350.9 / 80.2 / 96.66.9 / 15.6 / 31.781.0 / 87.3 / 92.462.6 / 70.9 / 81.045.5 / 51.6 / 62.0
D2Net [20]84.8 / 92.6 / 97.584.7 / 90.8 / 96.954.5 / 80.0 / 95.320.4 / 40.1 / 55.094.0 / 97.7 / 99.193.0 / 95.7 / 98.389.2 / 93.2 / 95.0
S2DNet [23]84.5 / 90.3 / 95.374.5 / 82.7 / 94.953.9 / 80.6 / 95.814.5 / 40.2 / 69.7---
HLoc[SP] [18, 41]80.5 / 87.4 / 94.268.4 / 77.6 / 88.853.1 / 79.1 / 95.57.2 / 17.4 / 34.489.5 / 94.2 / 97.976.5 / 82.7 / 92.757.4 / 64.4 / 80.4
PixLoc [43]64.3 / 69.3 / 77.451.0 / 55.1 / 67.352.7 / 77.5 / 93.912.0 / 20.7 / 45.488.3 / 90.4 / 93.779.6 / 81.1 / 85.261.0 / 62.5 / 69.4
HLoc[SP+SG]89.6 / 95.4 / 98.886.7 / 93.9 / 100.56.9 / 81.7 / 98.133.3 / 65.9 / 88.895.5 / 98.6 / 99.390.9 / 94.2 / 97.185.7 / 89.0 / 91.6
LBR [64]88.3 / 95.6 / 98.884.7 / 93.9 / 100.56.7 / 81.7 / 98.224.9 / 62.3 / 86.1---
HLoc+PixLoc84.7 / 94.2 / 98.881.6 / 93.9 / 100.56.9 / 82.0 / 98.134.9 / 67.7 / 89.596.9 / 98.9 / 99.393.3 / 95.4 / 97.187.0 / 89.5 / 91.6
HLoc[TopicFM][24]88.8 / 94.7 / 97.986.7 / 92.9 / 100.-----
SDNeuMap [57]80.8 / 90.9 / 95.648.0 / 67.3 / 87.8-----
DeViLoc (Ours)87.4 / 94.8 / 98.287.8 / 93.9 / 100.56.9 / 81.8 / 98.031.3 / 68.9 / 92.495.7 / 98.4 / 99.297.1 / 98.3 / 99.492.1 / 95.1 / 96.3
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.256, + 0.892, + 0.298 + ], + "angle": 0, + "content": "Table 2. Evaluated results on the long-term benchmark [48] using the recall metrics at thresholds of \\(\\{(25cm,2^{\\circ}),(50cm,5^{\\circ}),(5m,10^{\\circ})\\}\\). We compare with various complex baselines that integrate robust FM models into HLoc [41] or use PixLoc to refine HLoc's poses. Our method achieves state-of-the-art performance, especially in the highly challenging localization in the CMU dataset (marked in bold red)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.325, + 0.468, + 0.355 + ], + "angle": 0, + "content": "and second-place ranking in one scene (Kitchen). It also outperforms dense methods on the Cambridge dataset." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.356, + 0.468, + 0.506 + ], + "angle": 0, + "content": "In comparison to methods in group S, DeViLoc consistently delivers superior performance. Among these, HLoc[SP+SG] is the only method achieving competitive results with our approach on the Cambridge dataset. Notably, HLoc employs a complex pipeline involving retriangulating SIFT-based point clouds using robust local features and matches detected by SuperPoint (SP) [18] and SuperGlue (SG) [42]. In contrast, our method directly employs the noisy SIFT-based inputs and generally outperforms HLoc on both the 7scenes and Cambridge datasets." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.515, + 0.452, + 0.531 + ], + "angle": 0, + "content": "4.3. Evaluation on large-scale challenging scenes" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.539, + 0.468, + 0.688 + ], + "angle": 0, + "content": "We compared DeViLoc with several contemporary image-matching methods including D2Net [20], SP+SG [18, 42], and TopicFM [24], which are frequently incorporated into the HLoc pipeline as robust feature matchers. When using these methods, HLoc requires the extraction of new local features and matches from the database to recalculate the 3D point clouds. Furthermore, we also compared DeViLoc to other methods such as PixLoc [43], ESAC [7], and NeuMap [57], which are not based on the HLoc pipeline. Table 2 presents the results of all these methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.468, + 0.764 + ], + "angle": 0, + "content": "Aachen. DeViLoc performed comparably with recent FM-based baselines. Additionally, when compared to HLoc[TopicFM], which utilized the same feature matcher, our method exhibited an overall superior performance, demonstrating the effectiveness of the proposed pipeline." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.468, + 0.885 + ], + "angle": 0, + "content": "RobotCar. As illustrated in Table 2, our method surpassed other methods and demonstrated competitive performance compared to HLoc[SP+SG] for the day-time queries. Particularly noteworthy is that DeViLoc significantly outperformed HLoc[SP+SG] for the night-time queries. It is important to highlight that both SP and SG were trained using multiple datasets, while DeViLoc was exclusively trained on MegaDepth [32]." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.886, + 0.468, + 0.901 + ], + "angle": 0, + "content": "CMU. Our method significantly outperformed the state" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.325, + 0.892, + 0.415 + ], + "angle": 0, + "content": "of-the-art pipeline HLoc[SP+SG] with a large margin. Compared to the complex pipeline HLoc+PixLoc, which uses PixLoc to refine the estimated poses of HLoc[SP+SG], DeViLoc improved accuracy by up to \\(5.1\\%\\) on the scene \"Park\". This demonstrates the effectiveness and stability of our approach in difficult localization conditions." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.425, + 0.653, + 0.44 + ], + "angle": 0, + "content": "4.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.448, + 0.892, + 0.674 + ], + "angle": 0, + "content": "Evaluating the performance with noisy and sparse inputs. To assess how effectively DeViLoc handles noisy and sparse inputs, we conducted an experiment using the Aachen Day-Night dataset. Our pipeline utilized 3D point cloud inputs generated by different image-matching models, including SIFT, SP+SG, and LoFTR. As illustrated in Fig. 4, the 3D point cloud generated by SIFT exhibits significantly more noise and sparsity compared to those produced by the SP+SG and LoFTR models. The results for each input model are presented in Table 3. We observe that the precise and dense 3D inputs from SP+SG or LoFTR only slightly improve performance. This highlights the adaptability of our approach in handling various types of 3D inputs, proving effective even in the presence of noisy and sparse data." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.892, + 0.855 + ], + "angle": 0, + "content": "Visualization of semi-dense matching. Fig. 5 illustrates the detected 2D keypoints and the corresponding 3D points produced by DeViLoc. We visualized multiple pairs of query and reference views. Despite a higher number of detected keypoints compared to the observed keypoints (especially in reference view 1), our method is capable of effectively estimating 3D points along with their uncertainties. Notably, points in the sky or near-edge regions of the scene tend to exhibit lower confidence. Ultimately, our method yields a significant number of 2D-3D matches after the point aggregation step, substantially improving performance, particularly in challenging scenes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Effectiveness of proposed modules. We implemented three models to measure the contributions of the proposed modules, PIN (Section 3.2) and CPA (Section 3.3):" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.956 + ], + "angle": 0, + "content": "19474" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.099, + 0.09, + 0.452, + 0.241 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.251, + 0.473, + 0.322 + ], + "angle": 0, + "content": "Figure 4. Comparison between point clouds built from traditional FM (SIFT [34]), sparse FM (SP+SG [18, 42]), and detector-free FM (LoFTR [53]). DeViLoc can handle well the noisy SIFT-based input to achieve competitive performance compared to the precise (SP+SG) or dense (LoFTR) inputs (shown in Table 3)." + }, + { + "type": "table", + "bbox": [ + 0.112, + 0.334, + 0.437, + 0.406 + ], + "angle": 0, + "content": "
ModelsDayNight
(0.25m,2°) / (0.5m,5°) / (5.0m,10°)
DeViLoc[half-SIFT]87.5 / 94.1 / 97.986.7 / 92.9 / 100.
DeViLoc[SIFT]87.4 / 94.8 / 98.287.8 / 93.9 / 100.
DeViLoc[SP+SG]87.3 / 95.3 / 98.388.8 / 92.9 / 100.
DeViLoc[LoFTR]87.9 / 94.7 / 98.288.8 / 92.9 / 100.
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.416, + 0.47, + 0.446 + ], + "angle": 0, + "content": "Table 3. Ablation study of DeViLoc on Aachen Day-Night when using different point cloud inputs." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.47, + 0.469, + 0.514 + ], + "angle": 0, + "content": "- Model-A: This model executes the standard 2D-3D matching process without utilizing the PIN and CPA modules, akin to existing pipelines like HLoc [41]." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.516, + 0.469, + 0.56 + ], + "angle": 0, + "content": "- Model-B: This model only integrates the PIN module, generating semi-dense matches. All these matches are directly fed into the PnP solver for pose estimation." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.561, + 0.469, + 0.59 + ], + "angle": 0, + "content": "- Model-C: This model combines both PIN and CPA, including the entire process of the proposed method." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.47, + 0.469, + 0.59 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.591, + 0.469, + 0.711 + ], + "angle": 0, + "content": "Table 4 presents the results of pose estimation using AUC with thresholds of \\(\\{2^o,5^o,10^o\\}\\) [42]. The findings indicate that the proposed modules (Model-B and Model-C) significantly enhance performance as compared to the baseline (Model-A). Notably, these modules do not impose a substantial runtime burden, requiring only about \\(100ms\\) to generate a more extensive set of 2D-3D matches, ultimately enhancing overall performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.712, + 0.469, + 0.771 + ], + "angle": 0, + "content": "Impact of the top-k reference images. Table 4 shows that employing more reference images can enhance performance. However, this improvement comes at the expense of significantly increased runtime and the number of matches." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.772, + 0.469, + 0.833 + ], + "angle": 0, + "content": "Using different feature matcher. We evaluated the performance by substituting the detector-free TopicFM [24] with the detector-based \\(\\mathrm{SP + SG}\\). The AUC metrics did not decrease significantly, as indicated in Table 4." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.845, + 0.342, + 0.862 + ], + "angle": 0, + "content": "5. Conclusions and Limitations" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.469, + 0.902 + ], + "angle": 0, + "content": "This study introduces a robust structure-based framework for visual localization that minimizes reliance on the pre" + }, + { + "type": "image", + "bbox": [ + 0.521, + 0.09, + 0.872, + 0.253 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.265, + 0.892, + 0.321 + ], + "angle": 0, + "content": "Figure 5. Illustration of 2D-3D correspondences estimated by DeViLoc for several pairs of images. The observed 2D keypoints are marked in black, while the reference keypoints are represented in orange (low confidence) or green (high confidence)." + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.34, + 0.89, + 0.458 + ], + "angle": 0, + "content": "
ModelAUC (2o/5o/10o)Time (s)#P ×106#M
A[SIFT] (A ⇌ HLoc)72.4 / 85.5 / 91.10.4911.642
A[SP+SG]72.8 / 86.4 / 92.20.5311.654
A[LoFTR]74.7 / 87.7 / 93.20.5111.6297
B (A+PIN)78.8 / 90.0 / 94.70.5615.94743
C (A+PIN+CPA) ⇌ DeViLoc79.6 / 90.5 / 94.90.5715.94246
C (TopicFM→SP+SG)78.2 / 89.9 / 94.71.0217.6993
DeViLoc (top-5)81.0 / 91.4 / 95.50.9015.97668
DeViLoc (top-10)82.6 / 92.2 / 96.01.9215.913970
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.468, + 0.892, + 0.538 + ], + "angle": 0, + "content": "Table 4. Effectiveness of the proposed PIN and CPA (top), impact of the feature matcher (middle), and ablation of the top-k image retrieval (bottom) on MegaDepth [32]. The top-3 retrieval is used by default. Except for Model-A, the others were tested with SIFT inputs. \\(\\mathbf{P}\\) is the model parameters and \\(\\mathbf{M}\\) is the 2D-3D matches." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.57, + 0.892, + 0.766 + ], + "angle": 0, + "content": "cise reconstruction of 3D point clouds. Our approach exhibits stable performance even when confronted with sparse and noisy 3D inputs. To achieve this, we present two novel modules: the Point Inference Network and the Confidence-based Point Aggregation. Consequently, the method generates numerous 2D-3D correspondences, leading to significant enhancements in challenging conditions, including textureless scenes, large-scale environments, and variations in weather and seasons. However, the computational efficiency of our proposed method has limitations. The runtime experiences a slowdown as the number of matching pairs between query and reference images increases. Addressing this limitation will be a focus of our future work." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.79, + 0.679, + 0.807 + ], + "angle": 0, + "content": "6. Acknowledgments" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.817, + 0.892, + 0.887 + ], + "angle": 0, + "content": "This work was supported by the Ministry of Trade, Industry and Energy (MOTIE, Korea) under Grant 20007058, and by the National Research Foundation of Korea (NRF) funded by the Korean Government (MSIT) under Grant RS-2023-00208052." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19475" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. Netvlad: Cnn architecture for weakly supervised place recognition. 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Springer, 2022. 3" + }, + { + "type": "list", + "bbox": [ + 0.504, + 0.093, + 0.892, + 0.713 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "19478" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/3fb41c79-8021-41c2-9eec-bd21aa2928ff_origin.pdf b/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/3fb41c79-8021-41c2-9eec-bd21aa2928ff_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..298597f17308d7c32a2cc14aa0a4c153c2542cb7 --- /dev/null +++ b/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/3fb41c79-8021-41c2-9eec-bd21aa2928ff_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:ddb3b023de0b5fbcf84d994f4c001548049e622f11f678124a197867d0f24dd8 +size 6064818 diff --git a/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/full.md b/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/full.md new file mode 100644 index 0000000000000000000000000000000000000000..3c83a089c1026a3e8311569ed2834ff2fb9dc0ba --- /dev/null +++ b/2024/Learning to Produce Semi-dense Correspondences for Visual Localization/full.md @@ -0,0 +1,349 @@ +# Learning to Produce Semi-dense Correspondences for Visual Localization + +Khang Truong Giang $^{1}$ Soohwan Song $^{2*}$ Sungho Jo $^{1*}$ + +1 School of Computing, KAIST, Daejeon, Republic of Korea + +$^{2}$ College of AI Convergence, Dongguk University, Seoul, Republic of Korea + +\*corresponding authors + +# Abstract + +This study addresses the challenge of performing visual localization in demanding conditions such as nighttime scenarios, adverse weather, and seasonal changes. While many prior studies have focused on improving image matching performance to facilitate reliable dense keypoint matching between images, existing methods often heavily rely on predefined feature points on a reconstructed 3D model. Consequently, they tend to overlook unobserved keypoints during the matching process. Therefore, dense keypoint matches are not fully exploited, leading to a notable reduction in accuracy, particularly in noisy scenes. To tackle this issue, we propose a novel localization method that extracts reliable semi-dense 2D-3D matching points based on dense keypoint matches. This approach involves regressing semi-dense 2D keypoints into 3D scene coordinates using a point inference network. The network utilizes both geometric and visual cues to effectively infer 3D coordinates for unobserved keypoints from the observed ones. The abundance of matching information significantly enhances the accuracy of camera pose estimation, even in scenarios involving noisy or sparse 3D models. Comprehensive evaluations demonstrate that the proposed method outperforms other methods in challenging scenes and achieves competitive results in large-scale visual localization benchmarks. The code will be available at https://github.com/TruongKhang/DeViLoc. + +# 1. Introduction + +Visual localization is the process of determining the 6 degrees of freedom (DoF) camera pose for a given query image within a known scene. This fundamental task in computer vision is critical for applications such as robot navigation [33] and virtual or augmented reality [35, 37]. Most leading studies primarily employ a structure-based approach [8, 41, 43, 47, 68], consistently exhibiting high localization performance across diverse challenging conditions [31, 42, 54, 58]. + +Traditionally, structure-based methods heavily rely on feature matching (FM) [11, 46, 51, 55, 64]. These methods establish sparse correspondences between 3D points and 2D pixel-level keypoints in images, followed by estimating camera poses using RANSAC-based Perspective-n-Point (PnP). The recent advancements in FM-based methods [41, 42, 53] have shown outstanding performance across various benchmarks, particularly in large-scale scenes. However, despite these achievements, FM-based methods encounter substantial challenges in practical scenarios, including dealing with complex lighting conditions, seasonal variations, and changes in perspectives. + +Addressing these challenges necessitates a more robust and informative feature-matching approach incorporating detailed 3D points. Current methods, including those achieving semi-dense 2D-2D correspondences through detector-free image matching [15, 24, 53], are limited by relying solely on matched sparse features. This limitation persists when considering semi-dense matches, which only account for keypoints observed in a 3D model, neglecting valuable information from unobserved keypoints. Furthermore, FM-based methods demand a detailed 3D point cloud map for accurate localization. Continuously refining 3D feature points for new image inputs is time-intensive, and in some scenarios, localization must be performed with a noisy or sparse 3D point cloud. Overreliance on predetermined 2D and 3D points in the database can lead to a degradation in pose accuracy, especially in noisy cases with texture-less surfaces or repetitive patterns. + +Recent studies introduce scene coordinate regression (SCR) methods [6, 8, 30, 56], aiming to achieve dense 2D-3D correspondences. Unlike FM-based approaches, SCR methods use an implicit representation of scenes as a learnable function, predicting the dense 3D scene coordinates of a query image. SCR methods excel in compact and stable settings, eliminating the need for storing 3D models; however, they face challenges in dynamic environments and adapting to new viewpoints, limiting their applicability in large-scale scenes. Therefore, there is a need for an alternative method capable of finding dense and accurate 2D-3D + +![](images/ecbb80fe0889602cec40e2a1383294443e2962927f52b6888384b4cd14a53505.jpg) +Figure 1. The comparison of the 2D-3D correspondence finding process in our method (DeViLoc) and an existing method (HLoc [41]). HLoc heavily relies on a robust 3D point cloud but discards many detected 2D keypoints (depicted in green) during the 2D-3D matching process. In contrast, our method efficiently handles a noisy point cloud through the point inference process of PIN. PIN transforms the entire set of 2D-2D matches into 2D-3D matches. Our method then produces numerous accurate 2D-3D matches across multiple views using a confidence-based aggregation module. These abundant matches significantly enhance localization performance, particularly in scenarios characterized by noisy or sparse 3D point clouds. + +correspondences for visual localization. + +Therefore, this study proposes a novel FM-based method, semi-Dense Visual Localization (DeViLoc), aiming to predict dense 2D-3D correspondences for robust and accurate localization. In contrast to existing FM-based methods relying solely on pre-existing 3D points, our method directly converts semi-dense 2D-2D matches into 2D-3D matches. This abundant 2D-3D match information significantly enhances the precision of camera pose estimation, even when dealing with noisy or sparse 3D models. + +This method comprises two main components: 1) the Point Inference Network (PIN) and 2) the Confidence-based Point Aggregation (CPA) module. PIN plays a crucial role in our method by converting semi-dense 2D-2D matches into 2D-3D matches. It achieves this by directly regressing all 2D keypoints, both observed and unobserved, into 3D scene coordinates. The process involves encoding scene geometry from observed points into latent vectors and propagating 3D information to unobserved positions through attention layers. Next, the CPA module aggregates 2D-3D matches from multiple query-reference pairs, identifying consistent and highly confident 3D points corresponding to the same 2D keypoints in multiple matching views. This step effectively removes outliers from dense matches, and the filtered 2D-3D matches expedite RANSAC-based pose estimation. Ultimately, DeViLoc significantly increases the number of accurate 2D-3D matches for localization. + +Fig. 1 illustrates the 2D-3D matching process of our method and an existing one (HLoc+LoFTR [41, 53]). The existing method, despite having a dense and precise 3D model, rejects many important points during 2D-3D estimation. In contrast, our method confidently transforms 2D-2D matches into 2D-3D matches, generating numerous matches even in the presence of noisy 3D input and night- + +time conditions. Consequently, the method yields robust and accurate localization results based on dense matching information, especially in challenging conditions like nighttime scenarios, adverse weather, and seasonal changes. + +This paper makes the following contributions: + +- We propose a novel visual localization method that leverages rich matching information by directly converting semi-dense 2D-2D matches into 2D-3D matches. This method significantly improves the accuracy of camera pose estimation, particularly in scenarios with noisy or sparse 3D models. +- We introduce a network architecture, Point Inference Network (PIN), designed to directly regress 2D keypoints into 3D points. This network effectively exploits geometric and visual connections between unobserved and observed keypoints, ensuring accurate estimation of 3D information along with associated uncertainties. +- We conducted a comprehensive evaluation of our method across diverse datasets. The results indicate that our proposed approach outperforms other state-of-the-art methods in challenging scenes and achieves competitive performance in large-scale visual localization benchmarks. The source code is publicly available. + +# 2. Related Works + +Visual localization, which involves estimating camera poses from visual inputs, has been a subject of study for decades [8, 28, 31, 39, 49, 54]. Early approaches [1, 49, 59] primarily relied on an image retrieval strategy to directly estimate camera poses from the most similar images in database. This approach is intuitive and efficient, but its performance is significantly influenced by the density of images in the database. To overcome this limitation, an alternative approach learns a neural network to directly predict absolute + +camera poses from the input images [26, 27, 61]. + +Many studies [8, 9, 11, 25, 41, 47, 51, 54, 55, 68] have shifted their focus towards structure-based approach due to its stability and scalability in diverse scenes. The structure-based methods estimate camera pose by establishing a set of 2D-3D correspondences between image pixels and 3D coordinates of the scene. Leveraging this precise correspondence set, a camera pose can be accurately computed using a PnP solver [22, 29, 40] within a RANSAC paradigm [3, 4, 21]. The structure-based methods can be broadly categorized into two main groups: feature matching (FM) and scene coordinate regression (SCR). + +Feature Matching. FM-based methods [11, 31, 41, 46, 51] initially reconstruct a 3D model of the environment from database images using Structure-from-Motion (SfM) [50, 63]. Each 3D point in the model is associated with one or several feature descriptors for localization. When a localization request for a query image is made, these methods detect a set of 2D keypoints along with their descriptors and proceed to match them with the 3D points. Several works generate the 2D-3D matches by examining all points in the 3D model [31, 44]; however, they face difficulty when dealing with large scenes. + +To address this challenge, recent studies [41, 57, 64] have introduced a coarse-to-fine strategy. They initially identify a set of reference images in a database through image retrieval. They then establish 2D-3D matches based on 2D-2D matches between the query and reference images. Subsequent works have focused on enhancing the performance of image matching by incorporating transformers [15, 24, 42, 53] or semantic information [65]. These approaches produce robust and accurate 2D-2D matches, contributing to the robust construction of 3D model and the accurate generation of 2D-3D matches during the localization step. Consequently, FM-based methods have achieved state-of-the-art performance. + +However, these methods exhibit inflexibility due to heavily relying on high-fidelity point cloud reconstruction. This time-consuming step is not suitable for online applications such as SLAM or robot navigation, where the 3D point cloud is constructed on-the-fly from a sequence of images. In this situation, the point cloud might be noisy or incomplete, thus degrading localization performance. Furthermore, existing FM-based methods only utilize observed 3D points in the database to generate 2D-3D matches, discarding numerous unrelated 2D-2D matches. This process might compromise the performance in the presence of noisy 3D inputs. On the other hand, our proposed framework aims to adapt to various kinds of 3D inputs and predict semidense 2D-3D correspondences. + +Scene Coordinate Regression. In contrast to the explicit utilization of 3D models seen in FM-based methods, SCR [6, 8, 9, 13, 14, 52, 60] employs an implicit repre + +sensation of scenes in a form of a machine learning model. This model predicts dense 3D scene coordinates for an input query image. While SCR-based methods offer a concise representation of scenes, they encounter challenges when adapting to large-scale scenes, novel scenes, or challenging conditions. Several approaches have been proposed to address these challenges by predicting a scene part-by-part [7, 30] or employing a coarse-to-fine prediction [56, 66]. However, these methods still exhibit lower performance compared to FM-based methods. + +Drawing inspiration from SCR, our method aims to predict 3D coordinates for all keypoints in the query image, identified using a detector-free image-matching model. However, in contrast to the dense prediction in SCR, our semi-dense approach reduces the possibility of incorrect 3D prediction by focusing only on regions of interest between the query and reference images. Consequently, our method achieves more accurate performance than SCR-based methods in outdoor scenes. + +3D Scene Representation. FM-based methods [24, 41, 42, 53] have proven to be effective, but they come with a drawback of requiring substantial storage capacity to store both the 3D coordinates and the associated visual features [41, 42]. Consequently, recent studies [10, 12, 16, 38, 67, 70] have shifted their focus toward discovering more space-efficient representations of the scene. For example, NeuMap [57] proposed encoding a 3D point cloud into a set of latent codes and then regressing 3D coordinates based on these codes. While these methods successfully reduce storage demands, they discard crucial scene information, thereby limiting their performance. In contrast, this study focuses on improving performance when dealing with challenging point cloud inputs. + +# 3. Proposed Method + +We follow the coarse-to-fine localization paradigm [41] that first retrieves a set of reference images via image retrieval, and then estimates a camera pose by finding 2D-3D correspondences between image pixels and 3D coordinates of the scene. The proposed method aims to address the task of 2D-3D prediction, while applying image retrieval and a PnP pose solver, similar to [41]. + +# 3.1. Overview + +Given a query image $I^q$ and a set of reference images $\{I^{r,1}\dots I^{r,N_v}\}$ retrieved from a database, our method establishes a set of 2D-3D correspondences $M = \{(k_i,p_i)\}$ , where $k_{i}$ is a 2D keypoint in the query image and $p_i$ represents the corresponding 3D coordinate. Fig. 2 describes the overall architecture of the proposed method, DeViLoc. For each pair of query $I^q$ and reference $I^r$ , DeViLoc first extracts local 2D-2D feature correspondences $\{(k_i^q,k_i^r)\}$ using an image-matching network. Here, we employed a + +![](images/6a826f3a788b52a10ba94fd02185c8227e6e25ad85b6ca96465dd17b38be4be1.jpg) +Figure 2. Overview of DeViLoc. First, a feature matcher is employed to detect 2D-2D matches for each pair of query-reference images. Subsequently, the PIN module infers a set of 3D coordinates for all detected 2D keypoints based on the observed data in the reference image. Finally, the CPA module integrates all 2D-3D matches obtained across all query-reference pairs. + +detector-free image-matching model [24] to produce semidense correspondences. + +The Point Inference Network (PIN) then converts detected 2D keypoints of the reference image into 3D points (Section 3.2). It takes reference image $I^r$ with known camera parameters, along with a sparse set of observed 3D points as inputs, and predicts a set of 3D scene coordinates, $\{p_i\}$ , corresponding to all keypoints $\{k_i^r\}$ . Based on predicted 3D points $\{p_i\}$ and 2D-2D matches $\{(k_i^q,k_i^r)\}$ , we could produce dense 2D-3D matches, $\{(k_i^q,p_i)\}$ , for the query image. The basic concept of PIN is inspired by depth completion [62, 69], where a dense depth map is reconstructed from a sparse set of observed depth measurements and an input image. However, unlike depth completion, PIN aims to infer a discrete set of depth points, leading to reduced computational costs. Due to this discrete depth prediction, PIN utilizes attention [19] and MLP layers without the need for complex CNNs, as commonly found in conventional depth completion methods. + +Next, the Confidence-based Point Aggregation (CPA) module integrates all 2D-3D matches from multiple query-reference image pairs (Section 3.3). CPA integrates 2D-3D matches with small distances of keypoints into a representative match. It effectively removes outliers by considering the confidence information of each match during the integration process. + +# 3.2. Point Inference Network + +For reference image $I^r$ , let $O^r = \{o_i^r\}$ be the set of 3D points observed from the constructed 3D model. PIN predicts 3D points $P^r = \{p_i^r\}$ corresponding to detected 2D keypoints $K^r = \{k_i^r\}$ as: + +$$ +P ^ {r} = \operatorname {P I N} \left(K ^ {r}, O ^ {r}, F ^ {r}\right) \tag {1} +$$ + +where $K^r \in \mathbb{R}^{N_{points}^r \times 2}$ , $O^r \in \mathbb{R}^{N_{points}^o \times 3}$ , and $F^r$ is a feature map extracted from image $I^r$ using convolutional + +networks $(F^r\in \mathbb{R}^{h\times w\times c})$ . We directly utilized the output features of the image-matching network [24] as $F^r$ + +The method begins with a preprocessing step where keypoints $K^r$ and observed 3D points $O^r$ are transformed into the same camera-coordinate system using the known camera parameters. Subsequently, we decompose the observed 3D points into observed keypoints $K^o \in \mathbb{R}^{N_{points}^o \times 2}$ and depth values $D^o \in \mathbb{R}^{N_{points}^o \times 1}$ . The PIN network then aims to estimate depths $D^r$ for reference keypoints $K^r$ , utilizing observed keypoints $K^o$ , observed depths $D^o$ , and the feature map $F^r$ . The network architecture of PIN is illustrated in Fig. 3, comprising two fundamental steps to leverage both spatial information and visual similarity for depth estimation: geometric guidance and visual guidance. + +To implement geometric guidance, we initially employ two MLP-based encoders to learn embeddings for all 2D keypoint coordinates $\{K^r, K^o\}$ , as well as for the observed depths, $D^o$ . Additionally, we encode scene geometry from the observed depths by utilizing a self-attention layer. + +$$ +D _ {e m b} ^ {o} = \operatorname {D e p t h E n c} \left(D ^ {o}\right) \tag {2} +$$ + +$$ +\left[ K _ {e m b} ^ {r}, K _ {e m b} ^ {o} \right] = \text {K e y p o i n t E n c} \left(\left[ K ^ {r}, K ^ {o} \right]\right) \tag {3} +$$ + +The relative position between the observed and unobserved keypoints serves as a primary geometric cue for propagating depth information from observed to unobserved positions. Therefore, we represent the observed positions with latent codes, $P_{lc}^{o}$ , combined from keypoint embeddings $K_{emb}^{o}$ and depth features $D_{emb}^{o}$ . These latent codes are then passed into a cross-attention layer to generate latent codes $P_{lc}^{r}$ related to reference keypoints $K_{emb}^{r}$ : + +$$ +P _ {l c} ^ {r} = \operatorname {C r s A t t} \left(K _ {e m b} ^ {r}, P _ {l c} ^ {o}\right) \tag {4} +$$ + +In Eq. 4, $K_{emb}^{r}$ is the query, and $P_{lc}^{o}$ represents the key and value for the cross-attention function, CrsAtt(). + +The geometric guidance mentioned above may lack robustness in estimating accurate depths due to the sparsity of + +![](images/38ecfd41301bebc41510f2bd95cfc264915ab39c41de6aacf3700115ce489d9e.jpg) +Figure 3. Point Inference Network (PIN). The network begins by learning embeddings for all keypoints $(K_{emb}^{o}, K_{emb}^{r})$ and observed depths $(D_{emb}^{o})$ . Subsequently, attention layers are employed for both geometric and visual guidance. Finally, the learned latent codes $(P_{lc}^{r})$ are utilized to perform regression for the 3D points along with confidence values. + +observed data points. Therefore, we also incorporate visual features for more detailed guidance. Considering the feature map $F^r$ in Eq. 1, we utilize a bilinear grid sampling to extract sets of visual features $V^r$ and $V^o$ for both $K^r$ and $K^o$ . These visual features are appended to the latent codes, $P_{lc}^r$ and $P_{lc}^o$ . Subsequently, we employ multiple self/cross-attention layers to facilitate visual guidance: + +$$ +P _ {l c} ^ {r} = \operatorname {C o n c a t} \left(P _ {l c} ^ {r}, V ^ {r}\right), P _ {l c} ^ {o} = \operatorname {C o n c a t} \left(P _ {l c} ^ {o}, V ^ {o}\right) \tag {5} +$$ + +$$ +P _ {l c} ^ {o} = \operatorname {S e l f A t t} \left(P _ {l c} ^ {o}\right), P _ {f i n a l} ^ {r} = \operatorname {C r s A t t} \left(P _ {l c} ^ {r}, P _ {l c} ^ {o}\right) \tag {6} +$$ + +After learning the final latent features, $P_{final}^{r}$ , corresponding to reference keypoints $K^{r}$ , we use two MLP-based networks to predict the depths and confidence: + +$$ +D ^ {r} = \mathbb {M L P} \big (P _ {f i n a l} ^ {r} \big), \quad C ^ {r} = \mathbb {M L P} \big ([ P _ {f i n a l} ^ {r}, D ^ {r} ] \big) \quad (7 \mathrm {a}, \mathrm {b}) +$$ + +Finally, the 3D scene coordinates for the reference keypoints are estimated as follows: + +$$ +P ^ {r} = \left(T ^ {- 1}\right) _ {c a m \rightarrow s c e n e} \left(D ^ {r} [ \hat {K} ^ {r}, 1 ] ^ {T}\right) \tag {8} +$$ + +where $T^{-1}$ transforms the 3D points from camera-coordinate to scene-coordinate system. The confidences $C^r$ represent the uncertainty associated with the predicted 3D coordinates, $P^r$ . + +# 3.3. Confidence-based Point Aggregation + +PIN produced the 2D-3D correspondences, $(K^q,P) = \{(k_i^q,p_i)\}$ , along with their associated confidence values $C^r = \{c_i\}$ for every query-reference pair $(I^q,I^r)$ . Subsequently, we aggregated the 2D-3D matches $\{(k_i^q,p_i)^n\}_{n = 1\dots N_v}^{i = 1\dots N_m}$ across $N_{v}$ sets of matches, with $N_{m}$ being the number of matches per set. The goal of CPA is to eliminate outliers from the aggregated matches and determine the final matches that exhibit high confidence and consistency. To accomplish this, we started by discarding matches with low confidence through a threshold $\tau$ . Next, we grouped adjacent matches using a keypoint quantization + +step. If the coordinates of two keypoints are closer than $s$ pixels, these keypoints are assigned to the same group. This process is represented by a function $Q_{s}$ , where $s$ denotes the quantization size ( $s \in \{2, 4\}$ in our experiments). Once matches within the same group were identified, we merged them using a confidence-based averaging operation. + +Let $k_{j}$ be a quantized keypoint, the formulas for the aggregated 3D point $p_{j}^{agg}$ and the corresponding confidence $c_{j}^{agg}$ can be written as follows: + +$$ +p _ {j} ^ {\text {a g g}} = \frac {\sum_ {i , n} \mathbf {1} \left(Q _ {s} \left(k _ {i} ^ {n}\right) = k _ {j}\right) c _ {i} ^ {n} p _ {i} ^ {n}}{\sum_ {i , n} \mathbf {1} \left(Q _ {s} \left(k _ {i} ^ {n}\right) = k _ {j}\right) c _ {i} ^ {n}} \tag {9} +$$ + +$$ +c _ {j} ^ {a g g} = \frac {\sum_ {i , n} \mathbf {1} \left(Q _ {s} \left(k _ {i} ^ {n}\right) = k _ {j}\right) c _ {i} ^ {n}}{N _ {k _ {j}}} \tag {10} +$$ + +Here, $\mathbf{1}(Q_s(k_i^n) = k_j)$ is a binary indicator, and $N_{k_j} = \sum_{i,n}\mathbf{1}(Q_s(k_i^n) = k_j)$ represents the number of keypoints quantized into $k_{j}$ . + +# 3.4. Loss Functions + +In summary, the proposed approach generates a set of 2D-3D matches, denoted as $M = \{(k_j, p_j^{agg}, c_j^{agg})\}$ , for query image $I^q$ . Utilizing ground-truth camera matrices $(C^q, T^q)$ and available depth information $D^q = \{d_j^q\}$ , we define two functions, incorporating point-matching loss and confidence loss, to train the proposed network. + +Point-matching loss. We computed the ground-truth 3D coordinates $\{p_j^{qt}\}$ for the keypoints $\{k_{j}\}$ using the depths $\{d_j^q\}$ and camera matrices $(C^q,T^q)$ . Then, we employed the $L1$ function to calculate the loss between the ground-truth 3D points and predicted 3D points: + +$$ +L _ {\text {p o i n t}} ^ {q} = \frac {1}{| M |} \sum_ {j} \left\| p _ {j} ^ {\text {a g g}} - p _ {j} ^ {\text {g t}} \right\| \tag {11} +$$ + +Confidence loss. To train the confidence, we projected the 3D points $\{p_j^{agg}\}$ onto the image plane and assigned a + +
Methods7scenes (indoor)Cambridge landmarks (outdoor)
ChessFireHeadsOfficePumpkinKitchenStairsCourtKing'sHospitalShopSt. Mary's
DHSCNet [30]2/0.72/0.91/0.93/0.84/1.04/1.23/0.828/0.218/0.319/0.36/0.39/0.3
DSAC++ [6]2/0.52/0.91/0.83/0.74/1.14/1.19/2.640/0.218/0.320/0.36/0.313/0.4
DSAC* [8]2/1.102/1.241/1.823/1.154/1.344/1.683/1.1649/0.315/0.321/0.45/0.313/0.4
SANet [66]3/0.883/1.082/1.483/1.005/1.324/1.4016/4.59328/1.9532/0.5432/0.5310/0.4716/0.57
DSM [56]2/0.682/0.801/0.803/0.784/1.113/1.114/1.1643/0.1919/0.3523/0.386/0.3011/0.34
SAS [47]3/0.872/1.011/0.824/1.157/1.695/1.724/1.0124/0.1313/0.2220/0.364/0.218/0.25
InLoc [55]3/1.053/1.072/1.163/1.055/1.554/1.319/2.47-----
PixLoc [43]2/0.802/0.731/0.823/0.824/1.213/1.205/1.3030/0.1414/0.2416/0.325/0.2310/0.34
HLoc[SP+SG]2/0.842/0.931/0.743/0.925/1.274/1.405/1.4716/0.1112/0.2015/0.304/0.207/0.21
HLoc[LoFTR]3/0.932/0.871/0.734/1.025/1.245/1.486/1.4719/0.1116/0.2616/0.294/0.219/0.26
SDNeuMap [57]2/0.813/1.112/1.173/0.984/1.114/1.334/1.126/0.1014/0.1919/0.366/0.2517/0.53
DeViLoc (Ours)2/0.782/0.741/0.653/0.824/1.023/1.194/1.1218/0.1112/0.2113/0.284/0.187/0.23
+ +Table 1. Evaluation on 7scenes and Cambridge landmarks. The metrics are the median translation (cm) and rotation (o) errors. The SCR-based methods highlighted in red were trained per scene. The best and second-best results are marked in bold and cyan. DeViLoc outperforms the other methods in overall, despite being trained only on MegaDepth. + +label to each point based on pixel error. If the error between the projected 2D point and the query keypoint $k_{j}$ is less than $\theta$ pixels $(\theta = 8$ in our experiments), the corresponding confidence $c_{j}^{agg}$ is labeled as $l_{j} = 1$ , and vice versa. Consequently, the confidence loss, denoted as $L_{conf}^{q}$ , is established through the binary cross-entropy function: + +$$ +L _ {\text {c o n f}} ^ {q} = \frac {1}{| M |} \sum_ {j} \left(l _ {j} \log c _ {j} ^ {\text {a g g}} + \left(1 - l _ {j}\right) \log \left(1 - c _ {j} ^ {\text {a g g}}\right)\right) \tag {12} +$$ + +The final loss results from the combination of these two loss terms: + +$$ +L ^ {q} = L _ {\text {p o i n t}} ^ {q} + \lambda * L _ {\text {c o n f}} ^ {q} \tag {13} +$$ + +Here, $\lambda$ was set to 0.25 in our experiments. + +# 4. Experiments + +# 4.1. Implementation Details + +We conducted experiments on various datasets, including 7scenes [52], Cambridge [27], Aachen Day-Night [45, 48], RobotCar Seasons [36, 48], and Extended CMU Seasons [2, 58]. + +Detailed pipeline. To demonstrate the adaptability of the proposed method to noisy and sparse 3D inputs, we utilized 3D point clouds generated through SIFT-based SfM in COLMAP [34, 50]. These 3D point clouds are consistently available across all datasets. We employed DenseVLad [59], NetVLad [1], or CosPlace [5] to retrieve the top-k reference images. Subsequently, the proposed framework was applied to predict 2D-3D matches from these inputs. During the prediction, we utilized the efficient feature-matching model, TopicFM [24], to generate semi-dense 2D-2D matches. Finally, the camera pose was computed from the 2D-3D matches using PnP functions in COLMAP. + +Training. Our network was trained on MegaDepth [32], comprising outdoor scenes from various locations. The trained model was directly used for evaluation across all datasets, eliminating the need for finetuning or retraining. + +# 4.2. Evaluation on Cambridge and 7scenes + +We conducted a comparative analysis of our method (DeViLoc) against various state-of-the-art structure-based methods. Based on the characteristics outlined in the related works (Section 2), we primarily organized these methods into three categories: dense (D), sparse (S), and semi-dense (SD) methods. In this classification, SCR-based methods like HSCNet [30], SANet [66], DSAC* [8], DSAC++ [6], and DSM [56] were placed in the dense group (D) due to their strategy of making dense 2D-3D predictions. Conversely, methods such as Active Search [47], InLoc [55], and HLoc[SP+SG] [18, 41, 42] executed a sparse matching process between 2D keypoints and the 3D point cloud, classifying them in the sparse group (S). Despite PixLoc [43] not directly detecting 2D keypoints in the query image, its effective utilization of 3D points from a sparse point cloud to find corresponding 2D positions in the query image led us to categorize PixLoc in group S as well. In contrast to both groups (D and S), our method predicts 3D coordinates for all detected keypoints without any point rejection. To the best of our knowledge, NeuMap [57] is the most similar work to ours. Therefore, we assigned DeViLoc and NeuMap to the semi-dense group (SD). + +We compared the estimated camera poses of all methods to the ground-truth poses, calculating translation (in cm) and rotation (in degrees) errors [27] and presenting the median errors for each scene in Table 1. The results highlight the effectiveness of dense methods, following the SCR approach, in indoor scenes. This success is attributed to their scene-specific training (e.g., HSCNet, DSAC++, DSAC*) or training on extensive indoor datasets (e.g., DSM, trained on ScanNet [17]). However, these dense methods face challenges in generalizing to outdoor scenes in Cambridge. In contrast, despite being trained on outdoor scenes, our method demonstrates superior performance compared to the dense methods on the 7scenes dataset. The method secures first-place rankings in three scenes (Fire, Heads, Pumpkin) + +
MethodsAachen Day-NightRobotCar-SeasonsExtended CMU-Seasons
DayNightDay-allNight-allUrbanSuburbanPark
DESAC [7]42.6 / 59.6 / 75.56.1 / 10.2 / 18.4-----
SAS [47]85.3 / 92.2 / 97.939.8 / 49.0 / 64.350.9 / 80.2 / 96.66.9 / 15.6 / 31.781.0 / 87.3 / 92.462.6 / 70.9 / 81.045.5 / 51.6 / 62.0
D2Net [20]84.8 / 92.6 / 97.584.7 / 90.8 / 96.954.5 / 80.0 / 95.320.4 / 40.1 / 55.094.0 / 97.7 / 99.193.0 / 95.7 / 98.389.2 / 93.2 / 95.0
S2DNet [23]84.5 / 90.3 / 95.374.5 / 82.7 / 94.953.9 / 80.6 / 95.814.5 / 40.2 / 69.7---
HLoc[SP] [18, 41]80.5 / 87.4 / 94.268.4 / 77.6 / 88.853.1 / 79.1 / 95.57.2 / 17.4 / 34.489.5 / 94.2 / 97.976.5 / 82.7 / 92.757.4 / 64.4 / 80.4
PixLoc [43]64.3 / 69.3 / 77.451.0 / 55.1 / 67.352.7 / 77.5 / 93.912.0 / 20.7 / 45.488.3 / 90.4 / 93.779.6 / 81.1 / 85.261.0 / 62.5 / 69.4
HLoc[SP+SG]89.6 / 95.4 / 98.886.7 / 93.9 / 100.56.9 / 81.7 / 98.133.3 / 65.9 / 88.895.5 / 98.6 / 99.390.9 / 94.2 / 97.185.7 / 89.0 / 91.6
LBR [64]88.3 / 95.6 / 98.884.7 / 93.9 / 100.56.7 / 81.7 / 98.224.9 / 62.3 / 86.1---
HLoc+PixLoc84.7 / 94.2 / 98.881.6 / 93.9 / 100.56.9 / 82.0 / 98.134.9 / 67.7 / 89.596.9 / 98.9 / 99.393.3 / 95.4 / 97.187.0 / 89.5 / 91.6
HLoc[TopicFM][24]88.8 / 94.7 / 97.986.7 / 92.9 / 100.-----
SDNeuMap [57]80.8 / 90.9 / 95.648.0 / 67.3 / 87.8-----
DeViLoc (Ours)87.4 / 94.8 / 98.287.8 / 93.9 / 100.56.9 / 81.8 / 98.031.3 / 68.9 / 92.495.7 / 98.4 / 99.297.1 / 98.3 / 99.492.1 / 95.1 / 96.3
+ +Table 2. Evaluated results on the long-term benchmark [48] using the recall metrics at thresholds of $\{(25cm,2^{\circ}),(50cm,5^{\circ}),(5m,10^{\circ})\}$ . We compare with various complex baselines that integrate robust FM models into HLoc [41] or use PixLoc to refine HLoc's poses. Our method achieves state-of-the-art performance, especially in the highly challenging localization in the CMU dataset (marked in bold red). + +and second-place ranking in one scene (Kitchen). It also outperforms dense methods on the Cambridge dataset. + +In comparison to methods in group S, DeViLoc consistently delivers superior performance. Among these, HLoc[SP+SG] is the only method achieving competitive results with our approach on the Cambridge dataset. Notably, HLoc employs a complex pipeline involving retriangulating SIFT-based point clouds using robust local features and matches detected by SuperPoint (SP) [18] and SuperGlue (SG) [42]. In contrast, our method directly employs the noisy SIFT-based inputs and generally outperforms HLoc on both the 7scenes and Cambridge datasets. + +# 4.3. Evaluation on large-scale challenging scenes + +We compared DeViLoc with several contemporary image-matching methods including D2Net [20], SP+SG [18, 42], and TopicFM [24], which are frequently incorporated into the HLoc pipeline as robust feature matchers. When using these methods, HLoc requires the extraction of new local features and matches from the database to recalculate the 3D point clouds. Furthermore, we also compared DeViLoc to other methods such as PixLoc [43], ESAC [7], and NeuMap [57], which are not based on the HLoc pipeline. Table 2 presents the results of all these methods. + +Aachen. DeViLoc performed comparably with recent FM-based baselines. Additionally, when compared to HLoc[TopicFM], which utilized the same feature matcher, our method exhibited an overall superior performance, demonstrating the effectiveness of the proposed pipeline. + +RobotCar. As illustrated in Table 2, our method surpassed other methods and demonstrated competitive performance compared to HLoc[SP+SG] for the day-time queries. Particularly noteworthy is that DeViLoc significantly outperformed HLoc[SP+SG] for the night-time queries. It is important to highlight that both SP and SG were trained using multiple datasets, while DeViLoc was exclusively trained on MegaDepth [32]. + +CMU. Our method significantly outperformed the state + +of-the-art pipeline HLoc[SP+SG] with a large margin. Compared to the complex pipeline HLoc+PixLoc, which uses PixLoc to refine the estimated poses of HLoc[SP+SG], DeViLoc improved accuracy by up to $5.1\%$ on the scene "Park". This demonstrates the effectiveness and stability of our approach in difficult localization conditions. + +# 4.4. Ablation Study + +Evaluating the performance with noisy and sparse inputs. To assess how effectively DeViLoc handles noisy and sparse inputs, we conducted an experiment using the Aachen Day-Night dataset. Our pipeline utilized 3D point cloud inputs generated by different image-matching models, including SIFT, SP+SG, and LoFTR. As illustrated in Fig. 4, the 3D point cloud generated by SIFT exhibits significantly more noise and sparsity compared to those produced by the SP+SG and LoFTR models. The results for each input model are presented in Table 3. We observe that the precise and dense 3D inputs from SP+SG or LoFTR only slightly improve performance. This highlights the adaptability of our approach in handling various types of 3D inputs, proving effective even in the presence of noisy and sparse data. + +Visualization of semi-dense matching. Fig. 5 illustrates the detected 2D keypoints and the corresponding 3D points produced by DeViLoc. We visualized multiple pairs of query and reference views. Despite a higher number of detected keypoints compared to the observed keypoints (especially in reference view 1), our method is capable of effectively estimating 3D points along with their uncertainties. Notably, points in the sky or near-edge regions of the scene tend to exhibit lower confidence. Ultimately, our method yields a significant number of 2D-3D matches after the point aggregation step, substantially improving performance, particularly in challenging scenes. + +Effectiveness of proposed modules. We implemented three models to measure the contributions of the proposed modules, PIN (Section 3.2) and CPA (Section 3.3): + +![](images/2dede17d9a3d1d132679d07ceb9a766b2eb920440a187b03752b199b067f3355.jpg) +Figure 4. Comparison between point clouds built from traditional FM (SIFT [34]), sparse FM (SP+SG [18, 42]), and detector-free FM (LoFTR [53]). DeViLoc can handle well the noisy SIFT-based input to achieve competitive performance compared to the precise (SP+SG) or dense (LoFTR) inputs (shown in Table 3). + +
ModelsDayNight
(0.25m,2°) / (0.5m,5°) / (5.0m,10°)
DeViLoc[half-SIFT]87.5 / 94.1 / 97.986.7 / 92.9 / 100.
DeViLoc[SIFT]87.4 / 94.8 / 98.287.8 / 93.9 / 100.
DeViLoc[SP+SG]87.3 / 95.3 / 98.388.8 / 92.9 / 100.
DeViLoc[LoFTR]87.9 / 94.7 / 98.288.8 / 92.9 / 100.
+ +- Model-A: This model executes the standard 2D-3D matching process without utilizing the PIN and CPA modules, akin to existing pipelines like HLoc [41]. +- Model-B: This model only integrates the PIN module, generating semi-dense matches. All these matches are directly fed into the PnP solver for pose estimation. +- Model-C: This model combines both PIN and CPA, including the entire process of the proposed method. + +Table 4 presents the results of pose estimation using AUC with thresholds of $\{2^o,5^o,10^o\}$ [42]. The findings indicate that the proposed modules (Model-B and Model-C) significantly enhance performance as compared to the baseline (Model-A). Notably, these modules do not impose a substantial runtime burden, requiring only about $100ms$ to generate a more extensive set of 2D-3D matches, ultimately enhancing overall performance. + +Impact of the top-k reference images. Table 4 shows that employing more reference images can enhance performance. However, this improvement comes at the expense of significantly increased runtime and the number of matches. + +Using different feature matcher. We evaluated the performance by substituting the detector-free TopicFM [24] with the detector-based $\mathrm{SP + SG}$ . The AUC metrics did not decrease significantly, as indicated in Table 4. + +# 5. Conclusions and Limitations + +This study introduces a robust structure-based framework for visual localization that minimizes reliance on the pre + +![](images/d34d82ae6cbea590b2084e9873fcbf65e12def87a8e3117338aa3970c29e93ab.jpg) +Figure 5. Illustration of 2D-3D correspondences estimated by DeViLoc for several pairs of images. The observed 2D keypoints are marked in black, while the reference keypoints are represented in orange (low confidence) or green (high confidence). + +Table 3. Ablation study of DeViLoc on Aachen Day-Night when using different point cloud inputs. + +
ModelAUC (2o/5o/10o)Time (s)#P ×106#M
A[SIFT] (A ⇌ HLoc)72.4 / 85.5 / 91.10.4911.642
A[SP+SG]72.8 / 86.4 / 92.20.5311.654
A[LoFTR]74.7 / 87.7 / 93.20.5111.6297
B (A+PIN)78.8 / 90.0 / 94.70.5615.94743
C (A+PIN+CPA) ⇌ DeViLoc79.6 / 90.5 / 94.90.5715.94246
C (TopicFM→SP+SG)78.2 / 89.9 / 94.71.0217.6993
DeViLoc (top-5)81.0 / 91.4 / 95.50.9015.97668
DeViLoc (top-10)82.6 / 92.2 / 96.01.9215.913970
+ +Table 4. Effectiveness of the proposed PIN and CPA (top), impact of the feature matcher (middle), and ablation of the top-k image retrieval (bottom) on MegaDepth [32]. The top-3 retrieval is used by default. Except for Model-A, the others were tested with SIFT inputs. $\mathbf{P}$ is the model parameters and $\mathbf{M}$ is the 2D-3D matches. + +cise reconstruction of 3D point clouds. Our approach exhibits stable performance even when confronted with sparse and noisy 3D inputs. To achieve this, we present two novel modules: the Point Inference Network and the Confidence-based Point Aggregation. Consequently, the method generates numerous 2D-3D correspondences, leading to significant enhancements in challenging conditions, including textureless scenes, large-scale environments, and variations in weather and seasons. However, the computational efficiency of our proposed method has limitations. 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Learning to navigate the energy landscape. 2016 Fourth International Conference on 3D Vision (3DV), pages 323-332, 2016. 3 +[61] Florian Walch, Caner Hazirbas, Laura Leal-Taixe, Torsten Sattler, Sebastian Hilsenbeck, and Daniel Cremers. Image-based localization using lstms for structured feature correla + +tion. In Proceedings of the IEEE international conference on computer vision, pages 627-637, 2017. 3 +[62] Yufei Wang, Bo Li, Ge Zhang, Qi Liu, Tao Gao, and Yuchao Dai. Lrru: Long-short range recurrent updating networks for depth completion. In Proceedings of the IEEE/CVF International Conference on Computer Vision, pages 9422-9432, 2023. 4 +[63] Changchang Wu. Towards linear-time incremental structure from motion. In 2013 International Conference on 3D Vision-3DV 2013, pages 127–134. IEEE, 2013. 3 +[64] Fei Xue, Ignas Budvytis, Daniel Olmeda Reino, and Roberto Cipolla. Efficient large-scale localization by global instance recognition. 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While many prior studies have focused on improving image matching performance to facilitate reliable dense keypoint matching between images, existing methods often heavily rely on predefined feature points on a reconstructed 3D model. Consequently, they tend to overlook unobserved keypoints during the matching process. Therefore, dense keypoint matches are not fully exploited, leading to a notable reduction in accuracy, particularly in noisy scenes. To tackle this issue, we propose a novel localization method that extracts reliable semi-dense 2D-3D matching points based on dense keypoint matches. This approach involves regressing semi-dense 2D keypoints into 3D scene coordinates using a point inference network. The network utilizes both geometric and visual cues to effectively infer 3D coordinates for unobserved keypoints from the observed ones. The abundance of matching information significantly enhances the accuracy of camera pose estimation, even in scenarios involving noisy or sparse 3D models. Comprehensive evaluations demonstrate that the proposed method outperforms other methods in challenging scenes and achieves competitive results in large-scale visual localization benchmarks. The code will be available at https://github.com/TruongKhang/DeViLoc." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 586, + 127, + 597 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 586, + 127, + 597 + ], + "spans": [ + { + "bbox": [ + 47, + 586, + 127, + 597 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 715 + ], + "type": "text", + "content": "Visual localization is the process of determining the 6 degrees of freedom (DoF) camera pose for a given query image within a known scene. This fundamental task in computer vision is critical for applications such as robot navigation [33] and virtual or augmented reality [35, 37]. Most leading studies primarily employ a structure-based approach [8, 41, 43, 47, 68], consistently exhibiting high localization performance across diverse challenging conditions [31, 42, 54, 58]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 228, + 547, + 372 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 228, + 547, + 372 + ], + "spans": [ + { + "bbox": [ + 304, + 228, + 547, + 372 + ], + "type": "text", + "content": "Traditionally, structure-based methods heavily rely on feature matching (FM) [11, 46, 51, 55, 64]. These methods establish sparse correspondences between 3D points and 2D pixel-level keypoints in images, followed by estimating camera poses using RANSAC-based Perspective-n-Point (PnP). The recent advancements in FM-based methods [41, 42, 53] have shown outstanding performance across various benchmarks, particularly in large-scale scenes. However, despite these achievements, FM-based methods encounter substantial challenges in practical scenarios, including dealing with complex lighting conditions, seasonal variations, and changes in perspectives." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 375, + 547, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 375, + 547, + 579 + ], + "spans": [ + { + "bbox": [ + 304, + 375, + 547, + 579 + ], + "type": "text", + "content": "Addressing these challenges necessitates a more robust and informative feature-matching approach incorporating detailed 3D points. Current methods, including those achieving semi-dense 2D-2D correspondences through detector-free image matching [15, 24, 53], are limited by relying solely on matched sparse features. This limitation persists when considering semi-dense matches, which only account for keypoints observed in a 3D model, neglecting valuable information from unobserved keypoints. Furthermore, FM-based methods demand a detailed 3D point cloud map for accurate localization. Continuously refining 3D feature points for new image inputs is time-intensive, and in some scenarios, localization must be performed with a noisy or sparse 3D point cloud. Overreliance on predetermined 2D and 3D points in the database can lead to a degradation in pose accuracy, especially in noisy cases with texture-less surfaces or repetitive patterns." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 582, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 548, + 714 + ], + "type": "text", + "content": "Recent studies introduce scene coordinate regression (SCR) methods [6, 8, 30, 56], aiming to achieve dense 2D-3D correspondences. Unlike FM-based approaches, SCR methods use an implicit representation of scenes as a learnable function, predicting the dense 3D scene coordinates of a query image. SCR methods excel in compact and stable settings, eliminating the need for storing 3D models; however, they face challenges in dynamic environments and adapting to new viewpoints, limiting their applicability in large-scale scenes. Therefore, there is a need for an alternative method capable of finding dense and accurate 2D-3D" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19468" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 61, + 70, + 534, + 198 + ], + "blocks": [ + { + "bbox": [ + 61, + 70, + 534, + 198 + ], + "lines": [ + { + "bbox": [ + 61, + 70, + 534, + 198 + ], + "spans": [ + { + "bbox": [ + 61, + 70, + 534, + 198 + ], + "type": "image", + "image_path": "ecbb80fe0889602cec40e2a1383294443e2962927f52b6888384b4cd14a53505.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 208, + 548, + 275 + ], + "lines": [ + { + "bbox": [ + 46, + 208, + 548, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 208, + 548, + 275 + ], + "type": "text", + "content": "Figure 1. The comparison of the 2D-3D correspondence finding process in our method (DeViLoc) and an existing method (HLoc [41]). HLoc heavily relies on a robust 3D point cloud but discards many detected 2D keypoints (depicted in green) during the 2D-3D matching process. In contrast, our method efficiently handles a noisy point cloud through the point inference process of PIN. PIN transforms the entire set of 2D-2D matches into 2D-3D matches. Our method then produces numerous accurate 2D-3D matches across multiple views using a confidence-based aggregation module. These abundant matches significantly enhance localization performance, particularly in scenarios characterized by noisy or sparse 3D point clouds." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 296, + 209, + 307 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 296, + 209, + 307 + ], + "spans": [ + { + "bbox": [ + 47, + 296, + 209, + 307 + ], + "type": "text", + "content": "correspondences for visual localization." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 311, + 288, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 311, + 288, + 418 + ], + "spans": [ + { + "bbox": [ + 46, + 311, + 288, + 418 + ], + "type": "text", + "content": "Therefore, this study proposes a novel FM-based method, semi-Dense Visual Localization (DeViLoc), aiming to predict dense 2D-3D correspondences for robust and accurate localization. In contrast to existing FM-based methods relying solely on pre-existing 3D points, our method directly converts semi-dense 2D-2D matches into 2D-3D matches. This abundant 2D-3D match information significantly enhances the precision of camera pose estimation, even when dealing with noisy or sparse 3D models." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 422, + 287, + 625 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 422, + 287, + 625 + ], + "spans": [ + { + "bbox": [ + 46, + 422, + 287, + 625 + ], + "type": "text", + "content": "This method comprises two main components: 1) the Point Inference Network (PIN) and 2) the Confidence-based Point Aggregation (CPA) module. PIN plays a crucial role in our method by converting semi-dense 2D-2D matches into 2D-3D matches. It achieves this by directly regressing all 2D keypoints, both observed and unobserved, into 3D scene coordinates. The process involves encoding scene geometry from observed points into latent vectors and propagating 3D information to unobserved positions through attention layers. Next, the CPA module aggregates 2D-3D matches from multiple query-reference pairs, identifying consistent and highly confident 3D points corresponding to the same 2D keypoints in multiple matching views. This step effectively removes outliers from dense matches, and the filtered 2D-3D matches expedite RANSAC-based pose estimation. Ultimately, DeViLoc significantly increases the number of accurate 2D-3D matches for localization." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": "Fig. 1 illustrates the 2D-3D matching process of our method and an existing one (HLoc+LoFTR [41, 53]). The existing method, despite having a dense and precise 3D model, rejects many important points during 2D-3D estimation. In contrast, our method confidently transforms 2D-2D matches into 2D-3D matches, generating numerous matches even in the presence of noisy 3D input and night-" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 295, + 545, + 343 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 295, + 545, + 343 + ], + "spans": [ + { + "bbox": [ + 305, + 295, + 545, + 343 + ], + "type": "text", + "content": "time conditions. Consequently, the method yields robust and accurate localization results based on dense matching information, especially in challenging conditions like nighttime scenarios, adverse weather, and seasonal changes." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 317, + 344, + 504, + 356 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 344, + 504, + 356 + ], + "spans": [ + { + "bbox": [ + 317, + 344, + 504, + 356 + ], + "type": "text", + "content": "This paper makes the following contributions:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 357, + 545, + 572 + ], + "type": "list", + "angle": 0, + "index": 11, + "blocks": [ + { + "bbox": [ + 306, + 357, + 545, + 427 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 357, + 545, + 427 + ], + "spans": [ + { + "bbox": [ + 306, + 357, + 545, + 427 + ], + "type": "text", + "content": "- We propose a novel visual localization method that leverages rich matching information by directly converting semi-dense 2D-2D matches into 2D-3D matches. This method significantly improves the accuracy of camera pose estimation, particularly in scenarios with noisy or sparse 3D models." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 429, + 545, + 499 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 429, + 545, + 499 + ], + "spans": [ + { + "bbox": [ + 306, + 429, + 545, + 499 + ], + "type": "text", + "content": "- We introduce a network architecture, Point Inference Network (PIN), designed to directly regress 2D keypoints into 3D points. This network effectively exploits geometric and visual connections between unobserved and observed keypoints, ensuring accurate estimation of 3D information along with associated uncertainties." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 500, + 545, + 572 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 500, + 545, + 572 + ], + "spans": [ + { + "bbox": [ + 306, + 500, + 545, + 572 + ], + "type": "text", + "content": "- We conducted a comprehensive evaluation of our method across diverse datasets. The results indicate that our proposed approach outperforms other state-of-the-art methods in challenging scenes and achieves competitive performance in large-scale visual localization benchmarks. The source code is publicly available." + } + ] + } + ], + "index": 10 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 585, + 398, + 597 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 585, + 398, + 597 + ], + "spans": [ + { + "bbox": [ + 306, + 585, + 398, + 597 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 605, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 715 + ], + "type": "text", + "content": "Visual localization, which involves estimating camera poses from visual inputs, has been a subject of study for decades [8, 28, 31, 39, 49, 54]. Early approaches [1, 49, 59] primarily relied on an image retrieval strategy to directly estimate camera poses from the most similar images in database. This approach is intuitive and efficient, but its performance is significantly influenced by the density of images in the database. To overcome this limitation, an alternative approach learns a neural network to directly predict absolute" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "19469" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 246, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 246, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 246, + 83 + ], + "type": "text", + "content": "camera poses from the input images [26, 27, 61]." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 85, + 287, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 85, + 287, + 216 + ], + "spans": [ + { + "bbox": [ + 46, + 85, + 287, + 216 + ], + "type": "text", + "content": "Many studies [8, 9, 11, 25, 41, 47, 51, 54, 55, 68] have shifted their focus towards structure-based approach due to its stability and scalability in diverse scenes. The structure-based methods estimate camera pose by establishing a set of 2D-3D correspondences between image pixels and 3D coordinates of the scene. Leveraging this precise correspondence set, a camera pose can be accurately computed using a PnP solver [22, 29, 40] within a RANSAC paradigm [3, 4, 21]. The structure-based methods can be broadly categorized into two main groups: feature matching (FM) and scene coordinate regression (SCR)." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 218, + 287, + 350 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 218, + 287, + 350 + ], + "spans": [ + { + "bbox": [ + 46, + 218, + 287, + 350 + ], + "type": "text", + "content": "Feature Matching. FM-based methods [11, 31, 41, 46, 51] initially reconstruct a 3D model of the environment from database images using Structure-from-Motion (SfM) [50, 63]. Each 3D point in the model is associated with one or several feature descriptors for localization. When a localization request for a query image is made, these methods detect a set of 2D keypoints along with their descriptors and proceed to match them with the 3D points. Several works generate the 2D-3D matches by examining all points in the 3D model [31, 44]; however, they face difficulty when dealing with large scenes." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 351, + 287, + 506 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 351, + 287, + 506 + ], + "spans": [ + { + "bbox": [ + 46, + 351, + 287, + 506 + ], + "type": "text", + "content": "To address this challenge, recent studies [41, 57, 64] have introduced a coarse-to-fine strategy. They initially identify a set of reference images in a database through image retrieval. They then establish 2D-3D matches based on 2D-2D matches between the query and reference images. Subsequent works have focused on enhancing the performance of image matching by incorporating transformers [15, 24, 42, 53] or semantic information [65]. These approaches produce robust and accurate 2D-2D matches, contributing to the robust construction of 3D model and the accurate generation of 2D-3D matches during the localization step. Consequently, FM-based methods have achieved state-of-the-art performance." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 509, + 287, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 509, + 287, + 675 + ], + "spans": [ + { + "bbox": [ + 46, + 509, + 287, + 675 + ], + "type": "text", + "content": "However, these methods exhibit inflexibility due to heavily relying on high-fidelity point cloud reconstruction. This time-consuming step is not suitable for online applications such as SLAM or robot navigation, where the 3D point cloud is constructed on-the-fly from a sequence of images. In this situation, the point cloud might be noisy or incomplete, thus degrading localization performance. Furthermore, existing FM-based methods only utilize observed 3D points in the database to generate 2D-3D matches, discarding numerous unrelated 2D-2D matches. This process might compromise the performance in the presence of noisy 3D inputs. On the other hand, our proposed framework aims to adapt to various kinds of 3D inputs and predict semidense 2D-3D correspondences." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 713 + ], + "type": "text", + "content": "Scene Coordinate Regression. In contrast to the explicit utilization of 3D models seen in FM-based methods, SCR [6, 8, 9, 13, 14, 52, 60] employs an implicit repre" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "type": "text", + "content": "sensation of scenes in a form of a machine learning model. This model predicts dense 3D scene coordinates for an input query image. While SCR-based methods offer a concise representation of scenes, they encounter challenges when adapting to large-scale scenes, novel scenes, or challenging conditions. Several approaches have been proposed to address these challenges by predicting a scene part-by-part [7, 30] or employing a coarse-to-fine prediction [56, 66]. However, these methods still exhibit lower performance compared to FM-based methods." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 192, + 545, + 298 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 192, + 545, + 298 + ], + "spans": [ + { + "bbox": [ + 304, + 192, + 545, + 298 + ], + "type": "text", + "content": "Drawing inspiration from SCR, our method aims to predict 3D coordinates for all keypoints in the query image, identified using a detector-free image-matching model. However, in contrast to the dense prediction in SCR, our semi-dense approach reduces the possibility of incorrect 3D prediction by focusing only on regions of interest between the query and reference images. Consequently, our method achieves more accurate performance than SCR-based methods in outdoor scenes." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 300, + 545, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 300, + 545, + 467 + ], + "spans": [ + { + "bbox": [ + 304, + 300, + 545, + 467 + ], + "type": "text", + "content": "3D Scene Representation. FM-based methods [24, 41, 42, 53] have proven to be effective, but they come with a drawback of requiring substantial storage capacity to store both the 3D coordinates and the associated visual features [41, 42]. Consequently, recent studies [10, 12, 16, 38, 67, 70] have shifted their focus toward discovering more space-efficient representations of the scene. For example, NeuMap [57] proposed encoding a 3D point cloud into a set of latent codes and then regressing 3D coordinates based on these codes. While these methods successfully reduce storage demands, they discard crucial scene information, thereby limiting their performance. In contrast, this study focuses on improving performance when dealing with challenging point cloud inputs." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 477, + 411, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 477, + 411, + 491 + ], + "spans": [ + { + "bbox": [ + 306, + 477, + 411, + 491 + ], + "type": "text", + "content": "3. Proposed Method" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 497, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 497, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 497, + 545, + 581 + ], + "type": "text", + "content": "We follow the coarse-to-fine localization paradigm [41] that first retrieves a set of reference images via image retrieval, and then estimates a camera pose by finding 2D-3D correspondences between image pixels and 3D coordinates of the scene. The proposed method aims to address the task of 2D-3D prediction, while applying image retrieval and a PnP pose solver, similar to [41]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 587, + 373, + 599 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 587, + 373, + 599 + ], + "spans": [ + { + "bbox": [ + 306, + 587, + 373, + 599 + ], + "type": "text", + "content": "3.1. Overview" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": "Given a query image " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "I^q" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": " and a set of reference images " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\{I^{r,1}\\dots I^{r,N_v}\\}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": " retrieved from a database, our method establishes a set of 2D-3D correspondences " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "M = \\{(k_i,p_i)\\}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "k_{i}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": " is a 2D keypoint in the query image and " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "p_i" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": " represents the corresponding 3D coordinate. Fig. 2 describes the overall architecture of the proposed method, DeViLoc. For each pair of query " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "I^q" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": " and reference " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "I^r" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": ", DeViLoc first extracts local 2D-2D feature correspondences " + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\{(k_i^q,k_i^r)\\}" + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": " using an image-matching network. Here, we employed a" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19470" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 60, + 76, + 537, + 198 + ], + "blocks": [ + { + "bbox": [ + 60, + 76, + 537, + 198 + ], + "lines": [ + { + "bbox": [ + 60, + 76, + 537, + 198 + ], + "spans": [ + { + "bbox": [ + 60, + 76, + 537, + 198 + ], + "type": "image", + "image_path": "6a826f3a788b52a10ba94fd02185c8227e6e25ad85b6ca96465dd17b38be4be1.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 208, + 547, + 243 + ], + "lines": [ + { + "bbox": [ + 46, + 208, + 547, + 243 + ], + "spans": [ + { + "bbox": [ + 46, + 208, + 547, + 243 + ], + "type": "text", + "content": "Figure 2. Overview of DeViLoc. First, a feature matcher is employed to detect 2D-2D matches for each pair of query-reference images. Subsequently, the PIN module infers a set of 3D coordinates for all detected 2D keypoints based on the observed data in the reference image. Finally, the CPA module integrates all 2D-3D matches obtained across all query-reference pairs." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 262, + 287, + 287 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 262, + 287, + 287 + ], + "spans": [ + { + "bbox": [ + 46, + 262, + 287, + 287 + ], + "type": "text", + "content": "detector-free image-matching model [24] to produce semidense correspondences." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "spans": [ + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "text", + "content": "The Point Inference Network (PIN) then converts detected 2D keypoints of the reference image into 3D points (Section 3.2). It takes reference image " + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "inline_equation", + "content": "I^r" + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "text", + "content": " with known camera parameters, along with a sparse set of observed 3D points as inputs, and predicts a set of 3D scene coordinates, " + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "inline_equation", + "content": "\\{p_i\\}" + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "text", + "content": ", corresponding to all keypoints " + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "inline_equation", + "content": "\\{k_i^r\\}" + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "text", + "content": ". Based on predicted 3D points " + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "inline_equation", + "content": "\\{p_i\\}" + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "text", + "content": " and 2D-2D matches " + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "inline_equation", + "content": "\\{(k_i^q,k_i^r)\\}" + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "text", + "content": ", we could produce dense 2D-3D matches, " + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "inline_equation", + "content": "\\{(k_i^q,p_i)\\}" + }, + { + "bbox": [ + 46, + 288, + 287, + 491 + ], + "type": "text", + "content": ", for the query image. The basic concept of PIN is inspired by depth completion [62, 69], where a dense depth map is reconstructed from a sparse set of observed depth measurements and an input image. However, unlike depth completion, PIN aims to infer a discrete set of depth points, leading to reduced computational costs. Due to this discrete depth prediction, PIN utilizes attention [19] and MLP layers without the need for complex CNNs, as commonly found in conventional depth completion methods." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 491, + 287, + 576 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 491, + 287, + 576 + ], + "spans": [ + { + "bbox": [ + 46, + 491, + 287, + 576 + ], + "type": "text", + "content": "Next, the Confidence-based Point Aggregation (CPA) module integrates all 2D-3D matches from multiple query-reference image pairs (Section 3.3). CPA integrates 2D-3D matches with small distances of keypoints into a representative match. It effectively removes outliers by considering the confidence information of each match during the integration process." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 586, + 185, + 597 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 586, + 185, + 597 + ], + "spans": [ + { + "bbox": [ + 47, + 586, + 185, + 597 + ], + "type": "text", + "content": "3.2. Point Inference Network" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "text", + "content": "For reference image " + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "inline_equation", + "content": "I^r" + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "text", + "content": ", let " + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "inline_equation", + "content": "O^r = \\{o_i^r\\}" + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "text", + "content": " be the set of 3D points observed from the constructed 3D model. PIN predicts 3D points " + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "inline_equation", + "content": "P^r = \\{p_i^r\\}" + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "text", + "content": " corresponding to detected 2D keypoints " + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "inline_equation", + "content": "K^r = \\{k_i^r\\}" + }, + { + "bbox": [ + 46, + 605, + 287, + 654 + ], + "type": "text", + "content": " as:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 116, + 665, + 287, + 678 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 116, + 665, + 287, + 678 + ], + "spans": [ + { + "bbox": [ + 116, + 665, + 287, + 678 + ], + "type": "interline_equation", + "content": "P ^ {r} = \\operatorname {P I N} \\left(K ^ {r}, O ^ {r}, F ^ {r}\\right) \\tag {1}", + "image_path": "8fed8876d75ca4a0d08ea688fb2eb75ebeecce64e8e0c37a83d5ef4a4f74be85.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "inline_equation", + "content": "K^r \\in \\mathbb{R}^{N_{points}^r \\times 2}" + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "inline_equation", + "content": "O^r \\in \\mathbb{R}^{N_{points}^o \\times 3}" + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "inline_equation", + "content": "F^r" + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "text", + "content": " is a feature map extracted from image " + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "inline_equation", + "content": "I^r" + }, + { + "bbox": [ + 47, + 688, + 287, + 714 + ], + "type": "text", + "content": " using convolutional" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 262, + 545, + 286 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 262, + 545, + 286 + ], + "spans": [ + { + "bbox": [ + 305, + 262, + 545, + 286 + ], + "type": "text", + "content": "networks " + }, + { + "bbox": [ + 305, + 262, + 545, + 286 + ], + "type": "inline_equation", + "content": "(F^r\\in \\mathbb{R}^{h\\times w\\times c})" + }, + { + "bbox": [ + 305, + 262, + 545, + 286 + ], + "type": "text", + "content": " . We directly utilized the output features of the image-matching network [24] as " + }, + { + "bbox": [ + 305, + 262, + 545, + 286 + ], + "type": "inline_equation", + "content": "F^r" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "spans": [ + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": "The method begins with a preprocessing step where keypoints " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "K^r" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": " and observed 3D points " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "O^r" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": " are transformed into the same camera-coordinate system using the known camera parameters. Subsequently, we decompose the observed 3D points into observed keypoints " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "K^o \\in \\mathbb{R}^{N_{points}^o \\times 2}" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": " and depth values " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "D^o \\in \\mathbb{R}^{N_{points}^o \\times 1}" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": ". The PIN network then aims to estimate depths " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "D^r" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": " for reference keypoints " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "K^r" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": ", utilizing observed keypoints " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "K^o" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": ", observed depths " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "D^o" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": ", and the feature map " + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "inline_equation", + "content": "F^r" + }, + { + "bbox": [ + 304, + 287, + 546, + 430 + ], + "type": "text", + "content": ". The network architecture of PIN is illustrated in Fig. 3, comprising two fundamental steps to leverage both spatial information and visual similarity for depth estimation: geometric guidance and visual guidance." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 430, + 545, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 430, + 545, + 491 + ], + "spans": [ + { + "bbox": [ + 304, + 430, + 545, + 491 + ], + "type": "text", + "content": "To implement geometric guidance, we initially employ two MLP-based encoders to learn embeddings for all 2D keypoint coordinates " + }, + { + "bbox": [ + 304, + 430, + 545, + 491 + ], + "type": "inline_equation", + "content": "\\{K^r, K^o\\}" + }, + { + "bbox": [ + 304, + 430, + 545, + 491 + ], + "type": "text", + "content": ", as well as for the observed depths, " + }, + { + "bbox": [ + 304, + 430, + 545, + 491 + ], + "type": "inline_equation", + "content": "D^o" + }, + { + "bbox": [ + 304, + 430, + 545, + 491 + ], + "type": "text", + "content": ". Additionally, we encode scene geometry from the observed depths by utilizing a self-attention layer." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 367, + 500, + 545, + 513 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 367, + 500, + 545, + 513 + ], + "spans": [ + { + "bbox": [ + 367, + 500, + 545, + 513 + ], + "type": "interline_equation", + "content": "D _ {e m b} ^ {o} = \\operatorname {D e p t h E n c} \\left(D ^ {o}\\right) \\tag {2}", + "image_path": "f014ca53cb83b97477264eae96c30165df1f4fd7ee08d98abcce8e4c68f317b5.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 334, + 514, + 545, + 529 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 334, + 514, + 545, + 529 + ], + "spans": [ + { + "bbox": [ + 334, + 514, + 545, + 529 + ], + "type": "interline_equation", + "content": "\\left[ K _ {e m b} ^ {r}, K _ {e m b} ^ {o} \\right] = \\text {K e y p o i n t E n c} \\left(\\left[ K ^ {r}, K ^ {o} \\right]\\right) \\tag {3}", + "image_path": "77661b0a93a01264a629163f65ec13a979143df5da25b17ab63d72cf8ca6c85d.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "spans": [ + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "text", + "content": "The relative position between the observed and unobserved keypoints serves as a primary geometric cue for propagating depth information from observed to unobserved positions. Therefore, we represent the observed positions with latent codes, " + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "inline_equation", + "content": "P_{lc}^{o}" + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "text", + "content": ", combined from keypoint embeddings " + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "inline_equation", + "content": "K_{emb}^{o}" + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "text", + "content": " and depth features " + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "inline_equation", + "content": "D_{emb}^{o}" + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "text", + "content": ". These latent codes are then passed into a cross-attention layer to generate latent codes " + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "inline_equation", + "content": "P_{lc}^{r}" + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "text", + "content": " related to reference keypoints " + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "inline_equation", + "content": "K_{emb}^{r}" + }, + { + "bbox": [ + 304, + 537, + 545, + 635 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 369, + 643, + 545, + 656 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 369, + 643, + 545, + 656 + ], + "spans": [ + { + "bbox": [ + 369, + 643, + 545, + 656 + ], + "type": "interline_equation", + "content": "P _ {l c} ^ {r} = \\operatorname {C r s A t t} \\left(K _ {e m b} ^ {r}, P _ {l c} ^ {o}\\right) \\tag {4}", + "image_path": "0c6a6c78a7543b291d34639dc3c8f1c10cc2e46a612350221d9aae14045dc2e6.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 665, + 545, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 689 + ], + "type": "text", + "content": "In Eq. 4, " + }, + { + "bbox": [ + 304, + 665, + 545, + 689 + ], + "type": "inline_equation", + "content": "K_{emb}^{r}" + }, + { + "bbox": [ + 304, + 665, + 545, + 689 + ], + "type": "text", + "content": " is the query, and " + }, + { + "bbox": [ + 304, + 665, + 545, + 689 + ], + "type": "inline_equation", + "content": "P_{lc}^{o}" + }, + { + "bbox": [ + 304, + 665, + 545, + 689 + ], + "type": "text", + "content": " represents the key and value for the cross-attention function, CrsAtt()." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "content": "The geometric guidance mentioned above may lack robustness in estimating accurate depths due to the sparsity of" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19471" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 91, + 68, + 504, + 199 + ], + "blocks": [ + { + "bbox": [ + 91, + 68, + 504, + 199 + ], + "lines": [ + { + "bbox": [ + 91, + 68, + 504, + 199 + ], + "spans": [ + { + "bbox": [ + 91, + 68, + 504, + 199 + ], + "type": "image", + "image_path": "38ecfd41301bebc41510f2bd95cfc264915ab39c41de6aacf3700115ce489d9e.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "lines": [ + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "spans": [ + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "type": "text", + "content": "Figure 3. Point Inference Network (PIN). The network begins by learning embeddings for all keypoints " + }, + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "type": "inline_equation", + "content": "(K_{emb}^{o}, K_{emb}^{r})" + }, + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "type": "text", + "content": " and observed depths " + }, + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "type": "inline_equation", + "content": "(D_{emb}^{o})" + }, + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "type": "text", + "content": ". Subsequently, attention layers are employed for both geometric and visual guidance. Finally, the learned latent codes " + }, + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "type": "inline_equation", + "content": "(P_{lc}^{r})" + }, + { + "bbox": [ + 46, + 205, + 547, + 242 + ], + "type": "text", + "content": " are utilized to perform regression for the 3D points along with confidence values." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "spans": [ + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "content": "observed data points. Therefore, we also incorporate visual features for more detailed guidance. Considering the feature map " + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "inline_equation", + "content": "F^r" + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "content": " in Eq. 1, we utilize a bilinear grid sampling to extract sets of visual features " + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "inline_equation", + "content": "V^r" + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "inline_equation", + "content": "V^o" + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "content": " for both " + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "inline_equation", + "content": "K^r" + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "inline_equation", + "content": "K^o" + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "content": ". These visual features are appended to the latent codes, " + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "inline_equation", + "content": "P_{lc}^r" + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "inline_equation", + "content": "P_{lc}^o" + }, + { + "bbox": [ + 47, + 260, + 289, + 344 + ], + "type": "text", + "content": ". Subsequently, we employ multiple self/cross-attention layers to facilitate visual guidance:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 55, + 352, + 287, + 366 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 352, + 287, + 366 + ], + "spans": [ + { + "bbox": [ + 55, + 352, + 287, + 366 + ], + "type": "interline_equation", + "content": "P _ {l c} ^ {r} = \\operatorname {C o n c a t} \\left(P _ {l c} ^ {r}, V ^ {r}\\right), P _ {l c} ^ {o} = \\operatorname {C o n c a t} \\left(P _ {l c} ^ {o}, V ^ {o}\\right) \\tag {5}", + "image_path": "b17e560015c84dcea898bae5f37fdeb2b89f2a2fe86e365ca3152eb1b74b4fd9.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 56, + 367, + 287, + 382 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 56, + 367, + 287, + 382 + ], + "spans": [ + { + "bbox": [ + 56, + 367, + 287, + 382 + ], + "type": "interline_equation", + "content": "P _ {l c} ^ {o} = \\operatorname {S e l f A t t} \\left(P _ {l c} ^ {o}\\right), P _ {f i n a l} ^ {r} = \\operatorname {C r s A t t} \\left(P _ {l c} ^ {r}, P _ {l c} ^ {o}\\right) \\tag {6}", + "image_path": "129f8d995c4fd74b86fbb6cf4dc95c65c94f5aa1d49d5b1115927cb63959cd22.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 389, + 287, + 425 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 389, + 287, + 425 + ], + "spans": [ + { + "bbox": [ + 47, + 389, + 287, + 425 + ], + "type": "text", + "content": "After learning the final latent features, " + }, + { + "bbox": [ + 47, + 389, + 287, + 425 + ], + "type": "inline_equation", + "content": "P_{final}^{r}" + }, + { + "bbox": [ + 47, + 389, + 287, + 425 + ], + "type": "text", + "content": ", corresponding to reference keypoints " + }, + { + "bbox": [ + 47, + 389, + 287, + 425 + ], + "type": "inline_equation", + "content": "K^{r}" + }, + { + "bbox": [ + 47, + 389, + 287, + 425 + ], + "type": "text", + "content": ", we use two MLP-based networks to predict the depths and confidence:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 57, + 433, + 287, + 449 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 433, + 287, + 449 + ], + "spans": [ + { + "bbox": [ + 57, + 433, + 287, + 449 + ], + "type": "interline_equation", + "content": "D ^ {r} = \\mathbb {M L P} \\big (P _ {f i n a l} ^ {r} \\big), \\quad C ^ {r} = \\mathbb {M L P} \\big ([ P _ {f i n a l} ^ {r}, D ^ {r} ] \\big) \\quad (7 \\mathrm {a}, \\mathrm {b})", + "image_path": "457fa55780096261a3f2c4cea68a7fdcb25958449db684dabe112e4bf3f014a4.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 455, + 287, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 455, + 287, + 479 + ], + "spans": [ + { + "bbox": [ + 47, + 455, + 287, + 479 + ], + "type": "text", + "content": "Finally, the 3D scene coordinates for the reference keypoints are estimated as follows:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 90, + 486, + 287, + 502 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 90, + 486, + 287, + 502 + ], + "spans": [ + { + "bbox": [ + 90, + 486, + 287, + 502 + ], + "type": "interline_equation", + "content": "P ^ {r} = \\left(T ^ {- 1}\\right) _ {c a m \\rightarrow s c e n e} \\left(D ^ {r} [ \\hat {K} ^ {r}, 1 ] ^ {T}\\right) \\tag {8}", + "image_path": "a4b1f3fced31259aa789def79d0425d59bce0ab55d4098b98a6bffca48a9cb81.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "spans": [ + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "type": "inline_equation", + "content": "T^{-1}" + }, + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "type": "text", + "content": " transforms the 3D points from camera-coordinate to scene-coordinate system. The confidences " + }, + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "type": "inline_equation", + "content": "C^r" + }, + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "type": "text", + "content": " represent the uncertainty associated with the predicted 3D coordinates, " + }, + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "type": "inline_equation", + "content": "P^r" + }, + { + "bbox": [ + 46, + 508, + 287, + 556 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 563, + 241, + 577 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 563, + 241, + 577 + ], + "spans": [ + { + "bbox": [ + 47, + 563, + 241, + 577 + ], + "type": "text", + "content": "3.3. Confidence-based Point Aggregation" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "content": "PIN produced the 2D-3D correspondences, " + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "(K^q,P) = \\{(k_i^q,p_i)\\}" + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "content": ", along with their associated confidence values " + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "C^r = \\{c_i\\}" + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "content": " for every query-reference pair " + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "(I^q,I^r)" + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "content": ". Subsequently, we aggregated the 2D-3D matches " + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\{(k_i^q,p_i)^n\\}_{n = 1\\dots N_v}^{i = 1\\dots N_m}" + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "content": " across " + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "N_{v}" + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "content": " sets of matches, with " + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "N_{m}" + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "content": " being the number of matches per set. The goal of CPA is to eliminate outliers from the aggregated matches and determine the final matches that exhibit high confidence and consistency. To accomplish this, we started by discarding matches with low confidence through a threshold " + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 47, + 582, + 289, + 715 + ], + "type": "text", + "content": ". Next, we grouped adjacent matches using a keypoint quantization" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "spans": [ + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "text", + "content": "step. If the coordinates of two keypoints are closer than " + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "text", + "content": " pixels, these keypoints are assigned to the same group. This process is represented by a function " + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "inline_equation", + "content": "Q_{s}" + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "text", + "content": " denotes the quantization size (" + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "inline_equation", + "content": "s \\in \\{2, 4\\}" + }, + { + "bbox": [ + 304, + 260, + 545, + 332 + ], + "type": "text", + "content": " in our experiments). Once matches within the same group were identified, we merged them using a confidence-based averaging operation." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "spans": [ + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "type": "text", + "content": "Let " + }, + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "type": "inline_equation", + "content": "k_{j}" + }, + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "type": "text", + "content": " be a quantized keypoint, the formulas for the aggregated 3D point " + }, + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "type": "inline_equation", + "content": "p_{j}^{agg}" + }, + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "type": "text", + "content": " and the corresponding confidence " + }, + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "type": "inline_equation", + "content": "c_{j}^{agg}" + }, + { + "bbox": [ + 305, + 332, + 545, + 370 + ], + "type": "text", + "content": " can be written as follows:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 351, + 378, + 545, + 409 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 351, + 378, + 545, + 409 + ], + "spans": [ + { + "bbox": [ + 351, + 378, + 545, + 409 + ], + "type": "interline_equation", + "content": "p _ {j} ^ {\\text {a g g}} = \\frac {\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n} p _ {i} ^ {n}}{\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n}} \\tag {9}", + "image_path": "571b3dab6bf398a6aec2dad3eca8e1bfb09818b1688642a9014c0c9fec75e9ae.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 353, + 410, + 545, + 439 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 353, + 410, + 545, + 439 + ], + "spans": [ + { + "bbox": [ + 353, + 410, + 545, + 439 + ], + "type": "interline_equation", + "content": "c _ {j} ^ {a g g} = \\frac {\\sum_ {i , n} \\mathbf {1} \\left(Q _ {s} \\left(k _ {i} ^ {n}\\right) = k _ {j}\\right) c _ {i} ^ {n}}{N _ {k _ {j}}} \\tag {10}", + "image_path": "7d97517862451412a4deeb852f48594b9aa9726e4c6687daf492e9f985c9ae79.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "spans": [ + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "type": "text", + "content": "Here, " + }, + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "type": "inline_equation", + "content": "\\mathbf{1}(Q_s(k_i^n) = k_j)" + }, + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "type": "text", + "content": " is a binary indicator, and " + }, + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "type": "inline_equation", + "content": "N_{k_j} = \\sum_{i,n}\\mathbf{1}(Q_s(k_i^n) = k_j)" + }, + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "type": "text", + "content": " represents the number of keypoints quantized into " + }, + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "type": "inline_equation", + "content": "k_{j}" + }, + { + "bbox": [ + 305, + 447, + 547, + 485 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 491, + 400, + 504 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 491, + 400, + 504 + ], + "spans": [ + { + "bbox": [ + 306, + 491, + 400, + 504 + ], + "type": "text", + "content": "3.4. Loss Functions" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "text", + "content": "In summary, the proposed approach generates a set of 2D-3D matches, denoted as " + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "inline_equation", + "content": "M = \\{(k_j, p_j^{agg}, c_j^{agg})\\}" + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "text", + "content": ", for query image " + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "inline_equation", + "content": "I^q" + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "text", + "content": ". Utilizing ground-truth camera matrices " + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "inline_equation", + "content": "(C^q, T^q)" + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "text", + "content": " and available depth information " + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "inline_equation", + "content": "D^q = \\{d_j^q\\}" + }, + { + "bbox": [ + 304, + 510, + 545, + 582 + ], + "type": "text", + "content": ", we define two functions, incorporating point-matching loss and confidence loss, to train the proposed network." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "spans": [ + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "text", + "content": "Point-matching loss. We computed the ground-truth 3D coordinates " + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "inline_equation", + "content": "\\{p_j^{qt}\\}" + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "text", + "content": " for the keypoints " + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "inline_equation", + "content": "\\{k_{j}\\}" + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "text", + "content": " using the depths " + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "inline_equation", + "content": "\\{d_j^q\\}" + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "text", + "content": " and camera matrices " + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "inline_equation", + "content": "(C^q,T^q)" + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "text", + "content": ". Then, we employed the " + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "inline_equation", + "content": "L1" + }, + { + "bbox": [ + 305, + 582, + 545, + 643 + ], + "type": "text", + "content": " function to calculate the loss between the ground-truth 3D points and predicted 3D points:" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 359, + 650, + 545, + 681 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 359, + 650, + 545, + 681 + ], + "spans": [ + { + "bbox": [ + 359, + 650, + 545, + 681 + ], + "type": "interline_equation", + "content": "L _ {\\text {p o i n t}} ^ {q} = \\frac {1}{| M |} \\sum_ {j} \\left\\| p _ {j} ^ {\\text {a g g}} - p _ {j} ^ {\\text {g t}} \\right\\| \\tag {11}", + "image_path": "161b493ea98d98e238abcf89d4e58eabc59950b3f947066d83edd45b57b89289.jpg" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 305, + 689, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 547, + 715 + ], + "type": "text", + "content": "Confidence loss. To train the confidence, we projected the 3D points " + }, + { + "bbox": [ + 305, + 689, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\{p_j^{agg}\\}" + }, + { + "bbox": [ + 305, + 689, + 547, + 715 + ], + "type": "text", + "content": " onto the image plane and assigned a" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "19472" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 61, + 70, + 533, + 200 + ], + "blocks": [ + { + "bbox": [ + 61, + 70, + 533, + 200 + ], + "lines": [ + { + "bbox": [ + 61, + 70, + 533, + 200 + ], + "spans": [ + { + "bbox": [ + 61, + 70, + 533, + 200 + ], + "type": "table", + "html": "
Methods7scenes (indoor)Cambridge landmarks (outdoor)
ChessFireHeadsOfficePumpkinKitchenStairsCourtKing'sHospitalShopSt. Mary's
DHSCNet [30]2/0.72/0.91/0.93/0.84/1.04/1.23/0.828/0.218/0.319/0.36/0.39/0.3
DSAC++ [6]2/0.52/0.91/0.83/0.74/1.14/1.19/2.640/0.218/0.320/0.36/0.313/0.4
DSAC* [8]2/1.102/1.241/1.823/1.154/1.344/1.683/1.1649/0.315/0.321/0.45/0.313/0.4
SANet [66]3/0.883/1.082/1.483/1.005/1.324/1.4016/4.59328/1.9532/0.5432/0.5310/0.4716/0.57
DSM [56]2/0.682/0.801/0.803/0.784/1.113/1.114/1.1643/0.1919/0.3523/0.386/0.3011/0.34
SAS [47]3/0.872/1.011/0.824/1.157/1.695/1.724/1.0124/0.1313/0.2220/0.364/0.218/0.25
InLoc [55]3/1.053/1.072/1.163/1.055/1.554/1.319/2.47-----
PixLoc [43]2/0.802/0.731/0.823/0.824/1.213/1.205/1.3030/0.1414/0.2416/0.325/0.2310/0.34
HLoc[SP+SG]2/0.842/0.931/0.743/0.925/1.274/1.405/1.4716/0.1112/0.2015/0.304/0.207/0.21
HLoc[LoFTR]3/0.932/0.871/0.734/1.025/1.245/1.486/1.4719/0.1116/0.2616/0.294/0.219/0.26
SDNeuMap [57]2/0.813/1.112/1.173/0.984/1.114/1.334/1.126/0.1014/0.1919/0.366/0.2517/0.53
DeViLoc (Ours)2/0.782/0.741/0.653/0.824/1.023/1.194/1.1218/0.1112/0.2113/0.284/0.187/0.23
", + "image_path": "eb58dada45f429d626205cdb70caa81516cf4cb4df3baa9333bb2586951aafcc.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 208, + 546, + 243 + ], + "lines": [ + { + "bbox": [ + 46, + 208, + 546, + 243 + ], + "spans": [ + { + "bbox": [ + 46, + 208, + 546, + 243 + ], + "type": "text", + "content": "Table 1. Evaluation on 7scenes and Cambridge landmarks. The metrics are the median translation (cm) and rotation (o) errors. The SCR-based methods highlighted in red were trained per scene. The best and second-best results are marked in bold and cyan. DeViLoc outperforms the other methods in overall, despite being trained only on MegaDepth." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "spans": [ + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "text", + "content": "label to each point based on pixel error. If the error between the projected 2D point and the query keypoint " + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "inline_equation", + "content": "k_{j}" + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "text", + "content": " is less than " + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "text", + "content": " pixels " + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "inline_equation", + "content": "(\\theta = 8" + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "text", + "content": " in our experiments), the corresponding confidence " + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "inline_equation", + "content": "c_{j}^{agg}" + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "text", + "content": " is labeled as " + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "inline_equation", + "content": "l_{j} = 1" + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "text", + "content": ", and vice versa. Consequently, the confidence loss, denoted as " + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "inline_equation", + "content": "L_{conf}^{q}" + }, + { + "bbox": [ + 46, + 262, + 287, + 335 + ], + "type": "text", + "content": ", is established through the binary cross-entropy function:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 52, + 340, + 287, + 369 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 340, + 287, + 369 + ], + "spans": [ + { + "bbox": [ + 52, + 340, + 287, + 369 + ], + "type": "interline_equation", + "content": "L _ {\\text {c o n f}} ^ {q} = \\frac {1}{| M |} \\sum_ {j} \\left(l _ {j} \\log c _ {j} ^ {\\text {a g g}} + \\left(1 - l _ {j}\\right) \\log \\left(1 - c _ {j} ^ {\\text {a g g}}\\right)\\right) \\tag {12}", + "image_path": "8b9c6f73a444f94a066bc9bcd78a45f9fc77705b15b18bd581f75544e9a7cc17.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 374, + 287, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 374, + 287, + 396 + ], + "spans": [ + { + "bbox": [ + 46, + 374, + 287, + 396 + ], + "type": "text", + "content": "The final loss results from the combination of these two loss terms:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 115, + 398, + 287, + 412 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 115, + 398, + 287, + 412 + ], + "spans": [ + { + "bbox": [ + 115, + 398, + 287, + 412 + ], + "type": "interline_equation", + "content": "L ^ {q} = L _ {\\text {p o i n t}} ^ {q} + \\lambda * L _ {\\text {c o n f}} ^ {q} \\tag {13}", + "image_path": "249ea829dbf8d54aba33c3e51298a7907eefe78b900803f17b998a492a4a56d7.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 415, + 222, + 426 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 415, + 222, + 426 + ], + "spans": [ + { + "bbox": [ + 47, + 415, + 222, + 426 + ], + "type": "text", + "content": "Here, " + }, + { + "bbox": [ + 47, + 415, + 222, + 426 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 47, + 415, + 222, + 426 + ], + "type": "text", + "content": " was set to 0.25 in our experiments." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 436, + 128, + 449 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 436, + 128, + 449 + ], + "spans": [ + { + "bbox": [ + 47, + 436, + 128, + 449 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 456, + 180, + 468 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 456, + 180, + 468 + ], + "spans": [ + { + "bbox": [ + 47, + 456, + 180, + 468 + ], + "type": "text", + "content": "4.1. Implementation Details" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 474, + 287, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 474, + 287, + 521 + ], + "spans": [ + { + "bbox": [ + 47, + 474, + 287, + 521 + ], + "type": "text", + "content": "We conducted experiments on various datasets, including 7scenes [52], Cambridge [27], Aachen Day-Night [45, 48], RobotCar Seasons [36, 48], and Extended CMU Seasons [2, 58]." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 522, + 287, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 522, + 287, + 664 + ], + "spans": [ + { + "bbox": [ + 46, + 522, + 287, + 664 + ], + "type": "text", + "content": "Detailed pipeline. To demonstrate the adaptability of the proposed method to noisy and sparse 3D inputs, we utilized 3D point clouds generated through SIFT-based SfM in COLMAP [34, 50]. These 3D point clouds are consistently available across all datasets. We employed DenseVLad [59], NetVLad [1], or CosPlace [5] to retrieve the top-k reference images. Subsequently, the proposed framework was applied to predict 2D-3D matches from these inputs. During the prediction, we utilized the efficient feature-matching model, TopicFM [24], to generate semi-dense 2D-2D matches. Finally, the camera pose was computed from the 2D-3D matches using PnP functions in COLMAP." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 713 + ], + "type": "text", + "content": "Training. Our network was trained on MegaDepth [32], comprising outdoor scenes from various locations. The trained model was directly used for evaluation across all datasets, eliminating the need for finetuning or retraining." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 262, + 507, + 274 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 262, + 507, + 274 + ], + "spans": [ + { + "bbox": [ + 306, + 262, + 507, + 274 + ], + "type": "text", + "content": "4.2. Evaluation on Cambridge and 7scenes" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 281, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 281, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 281, + 545, + 544 + ], + "type": "text", + "content": "We conducted a comparative analysis of our method (DeViLoc) against various state-of-the-art structure-based methods. Based on the characteristics outlined in the related works (Section 2), we primarily organized these methods into three categories: dense (D), sparse (S), and semi-dense (SD) methods. In this classification, SCR-based methods like HSCNet [30], SANet [66], DSAC* [8], DSAC++ [6], and DSM [56] were placed in the dense group (D) due to their strategy of making dense 2D-3D predictions. Conversely, methods such as Active Search [47], InLoc [55], and HLoc[SP+SG] [18, 41, 42] executed a sparse matching process between 2D keypoints and the 3D point cloud, classifying them in the sparse group (S). Despite PixLoc [43] not directly detecting 2D keypoints in the query image, its effective utilization of 3D points from a sparse point cloud to find corresponding 2D positions in the query image led us to categorize PixLoc in group S as well. In contrast to both groups (D and S), our method predicts 3D coordinates for all detected keypoints without any point rejection. To the best of our knowledge, NeuMap [57] is the most similar work to ours. Therefore, we assigned DeViLoc and NeuMap to the semi-dense group (SD)." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 545, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 546, + 713 + ], + "type": "text", + "content": "We compared the estimated camera poses of all methods to the ground-truth poses, calculating translation (in cm) and rotation (in degrees) errors [27] and presenting the median errors for each scene in Table 1. The results highlight the effectiveness of dense methods, following the SCR approach, in indoor scenes. This success is attributed to their scene-specific training (e.g., HSCNet, DSAC++, DSAC*) or training on extensive indoor datasets (e.g., DSM, trained on ScanNet [17]). However, these dense methods face challenges in generalizing to outdoor scenes in Cambridge. In contrast, despite being trained on outdoor scenes, our method demonstrates superior performance compared to the dense methods on the 7scenes dataset. The method secures first-place rankings in three scenes (Fire, Heads, Pumpkin)" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19473" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 51, + 70, + 542, + 194 + ], + "blocks": [ + { + "bbox": [ + 51, + 70, + 542, + 194 + ], + "lines": [ + { + "bbox": [ + 51, + 70, + 542, + 194 + ], + "spans": [ + { + "bbox": [ + 51, + 70, + 542, + 194 + ], + "type": "table", + "html": "
MethodsAachen Day-NightRobotCar-SeasonsExtended CMU-Seasons
DayNightDay-allNight-allUrbanSuburbanPark
DESAC [7]42.6 / 59.6 / 75.56.1 / 10.2 / 18.4-----
SAS [47]85.3 / 92.2 / 97.939.8 / 49.0 / 64.350.9 / 80.2 / 96.66.9 / 15.6 / 31.781.0 / 87.3 / 92.462.6 / 70.9 / 81.045.5 / 51.6 / 62.0
D2Net [20]84.8 / 92.6 / 97.584.7 / 90.8 / 96.954.5 / 80.0 / 95.320.4 / 40.1 / 55.094.0 / 97.7 / 99.193.0 / 95.7 / 98.389.2 / 93.2 / 95.0
S2DNet [23]84.5 / 90.3 / 95.374.5 / 82.7 / 94.953.9 / 80.6 / 95.814.5 / 40.2 / 69.7---
HLoc[SP] [18, 41]80.5 / 87.4 / 94.268.4 / 77.6 / 88.853.1 / 79.1 / 95.57.2 / 17.4 / 34.489.5 / 94.2 / 97.976.5 / 82.7 / 92.757.4 / 64.4 / 80.4
PixLoc [43]64.3 / 69.3 / 77.451.0 / 55.1 / 67.352.7 / 77.5 / 93.912.0 / 20.7 / 45.488.3 / 90.4 / 93.779.6 / 81.1 / 85.261.0 / 62.5 / 69.4
HLoc[SP+SG]89.6 / 95.4 / 98.886.7 / 93.9 / 100.56.9 / 81.7 / 98.133.3 / 65.9 / 88.895.5 / 98.6 / 99.390.9 / 94.2 / 97.185.7 / 89.0 / 91.6
LBR [64]88.3 / 95.6 / 98.884.7 / 93.9 / 100.56.7 / 81.7 / 98.224.9 / 62.3 / 86.1---
HLoc+PixLoc84.7 / 94.2 / 98.881.6 / 93.9 / 100.56.9 / 82.0 / 98.134.9 / 67.7 / 89.596.9 / 98.9 / 99.393.3 / 95.4 / 97.187.0 / 89.5 / 91.6
HLoc[TopicFM][24]88.8 / 94.7 / 97.986.7 / 92.9 / 100.-----
SDNeuMap [57]80.8 / 90.9 / 95.648.0 / 67.3 / 87.8-----
DeViLoc (Ours)87.4 / 94.8 / 98.287.8 / 93.9 / 100.56.9 / 81.8 / 98.031.3 / 68.9 / 92.495.7 / 98.4 / 99.297.1 / 98.3 / 99.492.1 / 95.1 / 96.3
", + "image_path": "97e5a75e8c434fafe254bfdc65d8b71187f6ea4671c36fa8d85d1fbeedd03dfa.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 202, + 545, + 236 + ], + "lines": [ + { + "bbox": [ + 46, + 202, + 545, + 236 + ], + "spans": [ + { + "bbox": [ + 46, + 202, + 545, + 236 + ], + "type": "text", + "content": "Table 2. Evaluated results on the long-term benchmark [48] using the recall metrics at thresholds of " + }, + { + "bbox": [ + 46, + 202, + 545, + 236 + ], + "type": "inline_equation", + "content": "\\{(25cm,2^{\\circ}),(50cm,5^{\\circ}),(5m,10^{\\circ})\\}" + }, + { + "bbox": [ + 46, + 202, + 545, + 236 + ], + "type": "text", + "content": ". We compare with various complex baselines that integrate robust FM models into HLoc [41] or use PixLoc to refine HLoc's poses. Our method achieves state-of-the-art performance, especially in the highly challenging localization in the CMU dataset (marked in bold red)." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 257, + 286, + 281 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 257, + 286, + 281 + ], + "spans": [ + { + "bbox": [ + 46, + 257, + 286, + 281 + ], + "type": "text", + "content": "and second-place ranking in one scene (Kitchen). It also outperforms dense methods on the Cambridge dataset." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 281, + 286, + 400 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 281, + 286, + 400 + ], + "spans": [ + { + "bbox": [ + 46, + 281, + 286, + 400 + ], + "type": "text", + "content": "In comparison to methods in group S, DeViLoc consistently delivers superior performance. Among these, HLoc[SP+SG] is the only method achieving competitive results with our approach on the Cambridge dataset. Notably, HLoc employs a complex pipeline involving retriangulating SIFT-based point clouds using robust local features and matches detected by SuperPoint (SP) [18] and SuperGlue (SG) [42]. In contrast, our method directly employs the noisy SIFT-based inputs and generally outperforms HLoc on both the 7scenes and Cambridge datasets." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 407, + 276, + 420 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 407, + 276, + 420 + ], + "spans": [ + { + "bbox": [ + 47, + 407, + 276, + 420 + ], + "type": "text", + "content": "4.3. Evaluation on large-scale challenging scenes" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 426, + 286, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 426, + 286, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 426, + 286, + 544 + ], + "type": "text", + "content": "We compared DeViLoc with several contemporary image-matching methods including D2Net [20], SP+SG [18, 42], and TopicFM [24], which are frequently incorporated into the HLoc pipeline as robust feature matchers. When using these methods, HLoc requires the extraction of new local features and matches from the database to recalculate the 3D point clouds. Furthermore, we also compared DeViLoc to other methods such as PixLoc [43], ESAC [7], and NeuMap [57], which are not based on the HLoc pipeline. Table 2 presents the results of all these methods." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 545, + 286, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 286, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 286, + 605 + ], + "type": "text", + "content": "Aachen. DeViLoc performed comparably with recent FM-based baselines. Additionally, when compared to HLoc[TopicFM], which utilized the same feature matcher, our method exhibited an overall superior performance, demonstrating the effectiveness of the proposed pipeline." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 605, + 286, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 286, + 700 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 286, + 700 + ], + "type": "text", + "content": "RobotCar. As illustrated in Table 2, our method surpassed other methods and demonstrated competitive performance compared to HLoc[SP+SG] for the day-time queries. Particularly noteworthy is that DeViLoc significantly outperformed HLoc[SP+SG] for the night-time queries. It is important to highlight that both SP and SG were trained using multiple datasets, while DeViLoc was exclusively trained on MegaDepth [32]." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 59, + 701, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 701, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 59, + 701, + 286, + 713 + ], + "type": "text", + "content": "CMU. Our method significantly outperformed the state" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 257, + 545, + 328 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 257, + 545, + 328 + ], + "spans": [ + { + "bbox": [ + 304, + 257, + 545, + 328 + ], + "type": "text", + "content": "of-the-art pipeline HLoc[SP+SG] with a large margin. Compared to the complex pipeline HLoc+PixLoc, which uses PixLoc to refine the estimated poses of HLoc[SP+SG], DeViLoc improved accuracy by up to " + }, + { + "bbox": [ + 304, + 257, + 545, + 328 + ], + "type": "inline_equation", + "content": "5.1\\%" + }, + { + "bbox": [ + 304, + 257, + 545, + 328 + ], + "type": "text", + "content": " on the scene \"Park\". This demonstrates the effectiveness and stability of our approach in difficult localization conditions." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 336, + 399, + 348 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 336, + 399, + 348 + ], + "spans": [ + { + "bbox": [ + 305, + 336, + 399, + 348 + ], + "type": "text", + "content": "4.4. Ablation Study" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 354, + 545, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 354, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 304, + 354, + 545, + 533 + ], + "type": "text", + "content": "Evaluating the performance with noisy and sparse inputs. To assess how effectively DeViLoc handles noisy and sparse inputs, we conducted an experiment using the Aachen Day-Night dataset. Our pipeline utilized 3D point cloud inputs generated by different image-matching models, including SIFT, SP+SG, and LoFTR. As illustrated in Fig. 4, the 3D point cloud generated by SIFT exhibits significantly more noise and sparsity compared to those produced by the SP+SG and LoFTR models. The results for each input model are presented in Table 3. We observe that the precise and dense 3D inputs from SP+SG or LoFTR only slightly improve performance. This highlights the adaptability of our approach in handling various types of 3D inputs, proving effective even in the presence of noisy and sparse data." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 534, + 545, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 545, + 677 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 545, + 677 + ], + "type": "text", + "content": "Visualization of semi-dense matching. Fig. 5 illustrates the detected 2D keypoints and the corresponding 3D points produced by DeViLoc. We visualized multiple pairs of query and reference views. Despite a higher number of detected keypoints compared to the observed keypoints (especially in reference view 1), our method is capable of effectively estimating 3D points along with their uncertainties. Notably, points in the sky or near-edge regions of the scene tend to exhibit lower confidence. Ultimately, our method yields a significant number of 2D-3D matches after the point aggregation step, substantially improving performance, particularly in challenging scenes." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "content": "Effectiveness of proposed modules. We implemented three models to measure the contributions of the proposed modules, PIN (Section 3.2) and CPA (Section 3.3):" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19474" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 60, + 71, + 276, + 190 + ], + "blocks": [ + { + "bbox": [ + 60, + 71, + 276, + 190 + ], + "lines": [ + { + "bbox": [ + 60, + 71, + 276, + 190 + ], + "spans": [ + { + "bbox": [ + 60, + 71, + 276, + 190 + ], + "type": "image", + "image_path": "2dede17d9a3d1d132679d07ceb9a766b2eb920440a187b03752b199b067f3355.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 198, + 289, + 255 + ], + "lines": [ + { + "bbox": [ + 46, + 198, + 289, + 255 + ], + "spans": [ + { + "bbox": [ + 46, + 198, + 289, + 255 + ], + "type": "text", + "content": "Figure 4. Comparison between point clouds built from traditional FM (SIFT [34]), sparse FM (SP+SG [18, 42]), and detector-free FM (LoFTR [53]). DeViLoc can handle well the noisy SIFT-based input to achieve competitive performance compared to the precise (SP+SG) or dense (LoFTR) inputs (shown in Table 3)." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 68, + 264, + 267, + 321 + ], + "blocks": [ + { + "bbox": [ + 68, + 264, + 267, + 321 + ], + "lines": [ + { + "bbox": [ + 68, + 264, + 267, + 321 + ], + "spans": [ + { + "bbox": [ + 68, + 264, + 267, + 321 + ], + "type": "table", + "html": "
ModelsDayNight
(0.25m,2°) / (0.5m,5°) / (5.0m,10°)
DeViLoc[half-SIFT]87.5 / 94.1 / 97.986.7 / 92.9 / 100.
DeViLoc[SIFT]87.4 / 94.8 / 98.287.8 / 93.9 / 100.
DeViLoc[SP+SG]87.3 / 95.3 / 98.388.8 / 92.9 / 100.
DeViLoc[LoFTR]87.9 / 94.7 / 98.288.8 / 92.9 / 100.
", + "image_path": "77d95751b14e6ba955138e00970ac1e3d1c990e8f88e522514bd0f43f4b086ec.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 372, + 287, + 467 + ], + "type": "list", + "angle": 0, + "index": 7, + "blocks": [ + { + "bbox": [ + 47, + 372, + 287, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 372, + 287, + 407 + ], + "spans": [ + { + "bbox": [ + 47, + 372, + 287, + 407 + ], + "type": "text", + "content": "- Model-A: This model executes the standard 2D-3D matching process without utilizing the PIN and CPA modules, akin to existing pipelines like HLoc [41]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 408, + 287, + 443 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 408, + 287, + 443 + ], + "spans": [ + { + "bbox": [ + 47, + 408, + 287, + 443 + ], + "type": "text", + "content": "- Model-B: This model only integrates the PIN module, generating semi-dense matches. All these matches are directly fed into the PnP solver for pose estimation." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 444, + 287, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 444, + 287, + 467 + ], + "spans": [ + { + "bbox": [ + 47, + 444, + 287, + 467 + ], + "type": "text", + "content": "- Model-C: This model combines both PIN and CPA, including the entire process of the proposed method." + } + ] + } + ], + "index": 6 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 46, + 468, + 287, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 468, + 287, + 563 + ], + "spans": [ + { + "bbox": [ + 46, + 468, + 287, + 563 + ], + "type": "text", + "content": "Table 4 presents the results of pose estimation using AUC with thresholds of " + }, + { + "bbox": [ + 46, + 468, + 287, + 563 + ], + "type": "inline_equation", + "content": "\\{2^o,5^o,10^o\\}" + }, + { + "bbox": [ + 46, + 468, + 287, + 563 + ], + "type": "text", + "content": " [42]. The findings indicate that the proposed modules (Model-B and Model-C) significantly enhance performance as compared to the baseline (Model-A). Notably, these modules do not impose a substantial runtime burden, requiring only about " + }, + { + "bbox": [ + 46, + 468, + 287, + 563 + ], + "type": "inline_equation", + "content": "100ms" + }, + { + "bbox": [ + 46, + 468, + 287, + 563 + ], + "type": "text", + "content": " to generate a more extensive set of 2D-3D matches, ultimately enhancing overall performance." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 563, + 287, + 610 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 563, + 287, + 610 + ], + "spans": [ + { + "bbox": [ + 46, + 563, + 287, + 610 + ], + "type": "text", + "content": "Impact of the top-k reference images. Table 4 shows that employing more reference images can enhance performance. However, this improvement comes at the expense of significantly increased runtime and the number of matches." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 611, + 287, + 659 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 611, + 287, + 659 + ], + "spans": [ + { + "bbox": [ + 46, + 611, + 287, + 659 + ], + "type": "text", + "content": "Using different feature matcher. We evaluated the performance by substituting the detector-free TopicFM [24] with the detector-based " + }, + { + "bbox": [ + 46, + 611, + 287, + 659 + ], + "type": "inline_equation", + "content": "\\mathrm{SP + SG}" + }, + { + "bbox": [ + 46, + 611, + 287, + 659 + ], + "type": "text", + "content": ". The AUC metrics did not decrease significantly, as indicated in Table 4." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 669, + 209, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 669, + 209, + 682 + ], + "spans": [ + { + "bbox": [ + 47, + 669, + 209, + 682 + ], + "type": "text", + "content": "5. Conclusions and Limitations" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": "This study introduces a robust structure-based framework for visual localization that minimizes reliance on the pre" + } + ] + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 318, + 71, + 533, + 200 + ], + "blocks": [ + { + "bbox": [ + 318, + 71, + 533, + 200 + ], + "lines": [ + { + "bbox": [ + 318, + 71, + 533, + 200 + ], + "spans": [ + { + "bbox": [ + 318, + 71, + 533, + 200 + ], + "type": "image", + "image_path": "d34d82ae6cbea590b2084e9873fcbf65e12def87a8e3117338aa3970c29e93ab.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 209, + 545, + 254 + ], + "lines": [ + { + "bbox": [ + 305, + 209, + 545, + 254 + ], + "spans": [ + { + "bbox": [ + 305, + 209, + 545, + 254 + ], + "type": "text", + "content": "Figure 5. Illustration of 2D-3D correspondences estimated by DeViLoc for several pairs of images. The observed 2D keypoints are marked in black, while the reference keypoints are represented in orange (low confidence) or green (high confidence)." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "table", + "bbox": [ + 308, + 269, + 544, + 362 + ], + "blocks": [ + { + "bbox": [ + 46, + 329, + 287, + 353 + ], + "lines": [ + { + "bbox": [ + 46, + 329, + 287, + 353 + ], + "spans": [ + { + "bbox": [ + 46, + 329, + 287, + 353 + ], + "type": "text", + "content": "Table 3. Ablation study of DeViLoc on Aachen Day-Night when using different point cloud inputs." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 308, + 269, + 544, + 362 + ], + "lines": [ + { + "bbox": [ + 308, + 269, + 544, + 362 + ], + "spans": [ + { + "bbox": [ + 308, + 269, + 544, + 362 + ], + "type": "table", + "html": "
ModelAUC (2o/5o/10o)Time (s)#P ×106#M
A[SIFT] (A ⇌ HLoc)72.4 / 85.5 / 91.10.4911.642
A[SP+SG]72.8 / 86.4 / 92.20.5311.654
A[LoFTR]74.7 / 87.7 / 93.20.5111.6297
B (A+PIN)78.8 / 90.0 / 94.70.5615.94743
C (A+PIN+CPA) ⇌ DeViLoc79.6 / 90.5 / 94.90.5715.94246
C (TopicFM→SP+SG)78.2 / 89.9 / 94.71.0217.6993
DeViLoc (top-5)81.0 / 91.4 / 95.50.9015.97668
DeViLoc (top-10)82.6 / 92.2 / 96.01.9215.913970
", + "image_path": "a0389c18a5fa291423d71394e808bf1639d15e0170f80ca97eba9e9082d15acf.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "table_body" + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 370, + 545, + 426 + ], + "lines": [ + { + "bbox": [ + 305, + 370, + 545, + 426 + ], + "spans": [ + { + "bbox": [ + 305, + 370, + 545, + 426 + ], + "type": "text", + "content": "Table 4. Effectiveness of the proposed PIN and CPA (top), impact of the feature matcher (middle), and ablation of the top-k image retrieval (bottom) on MegaDepth [32]. The top-3 retrieval is used by default. Except for Model-A, the others were tested with SIFT inputs. " + }, + { + "bbox": [ + 305, + 370, + 545, + 426 + ], + "type": "inline_equation", + "content": "\\mathbf{P}" + }, + { + "bbox": [ + 305, + 370, + 545, + 426 + ], + "type": "text", + "content": " is the model parameters and " + }, + { + "bbox": [ + 305, + 370, + 545, + 426 + ], + "type": "inline_equation", + "content": "\\mathbf{M}" + }, + { + "bbox": [ + 305, + 370, + 545, + 426 + ], + "type": "text", + "content": " is the 2D-3D matches." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 451, + 545, + 606 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 451, + 545, + 606 + ], + "spans": [ + { + "bbox": [ + 304, + 451, + 545, + 606 + ], + "type": "text", + "content": "cise reconstruction of 3D point clouds. Our approach exhibits stable performance even when confronted with sparse and noisy 3D inputs. To achieve this, we present two novel modules: the Point Inference Network and the Confidence-based Point Aggregation. Consequently, the method generates numerous 2D-3D correspondences, leading to significant enhancements in challenging conditions, including textureless scenes, large-scale environments, and variations in weather and seasons. However, the computational efficiency of our proposed method has limitations. The runtime experiences a slowdown as the number of matching pairs between query and reference images increases. Addressing this limitation will be a focus of our future work." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 625, + 415, + 639 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 625, + 415, + 639 + ], + "spans": [ + { + "bbox": [ + 306, + 625, + 415, + 639 + ], + "type": "text", + "content": "6. 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Springer, 2022. 3" + } + ] + } + ], + "index": 22 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "19478" + } + ] + } + ], + "index": 24 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_content_list.json b/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..9109b6b351c7871f862e4d6ea93a3207e435b5d8 --- /dev/null +++ b/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_content_list.json @@ -0,0 +1,1894 @@ +[ + { + "type": "text", + "text": "Learning to Rank Patches for Unbiased Image Redundancy Reduction", + "text_level": 1, + "bbox": [ + 129, + 130, + 839, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yang Luo $^{1}$ , Zhineng Chen $^{1*}$ , Peng Zhou $^{2}$ , Zuxuan Wu $^{1}$ , Xieping Gao $^{3}$ , Yu-Gang Jiang $^{1}$", + "bbox": [ + 122, + 188, + 859, + 208 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{1}$ School of Computer Science, Shanghai Collaborative Innovation Center of Intelligent Visual Computing, Fudan University $^{2}$ University of Maryland, College Park", + "bbox": [ + 89, + 210, + 900, + 242 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "3College of Information Science and Engineering, Hunan Normal University", + "bbox": [ + 243, + 243, + 750, + 260 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "yangluo21@m.fudan.edu.cn, {zhinchen, zxwu, ygj}@fudan.edu.cn,", + "bbox": [ + 225, + 263, + 759, + 277 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "pengzhou@terpmail.umd.edu, xpgao@hunnu.edu.cn", + "bbox": [ + 292, + 282, + 691, + 295 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 330, + 312, + 345 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Images suffer from heavy spatial redundancy because pixels in neighboring regions are spatially correlated. Existing approaches strive to overcome this limitation by reducing less meaningful image regions. However, current leading methods rely on supervisory signals. They may compel models to preserve content that aligns with labeled categories and discard content belonging to unlabeled categories. This categorical inductive bias makes these methods less effective in real-world scenarios. To address this issue, we propose a self-supervised framework for image redundancy reduction called Learning to Rank Patches (LTRP). We observe that image reconstruction of masked image modeling models is sensitive to the removal of visible patches when the masking ratio is high (e.g., $90\\%$ ). Building upon it, we implement LTRP via two steps: inferring the semantic density score of each patch by quantifying variation between reconstructions with and without this patch, and learning to rank the patches with the pseudo score. The entire process is self-supervised, thus getting out of the dilemma of categorical inductive bias. We design extensive experiments on different datasets and tasks. The results demonstrate that LTRP outperforms both supervised and other self-supervised methods due to the fair assessment of image content. Code is available at https://github.com/irsLu/Ltrp.", + "bbox": [ + 75, + 363, + 473, + 741 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 772, + 207, + 787 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Image redundancy reduction refers to discarding the less informative regions of an image while preserving its essential semantics. It is a fundamental task in computer vision as compact image representation is an attractive property in various applications, especially in the era of vision Trans-", + "bbox": [ + 75, + 797, + 468, + 875 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/cc7f177cbb2b172dd9736a89a11ff8e3a91bf0306cd667382d82864819d9f72c.jpg", + "image_caption": [ + "Raw" + ], + "image_footnote": [], + "bbox": [ + 504, + 330, + 578, + 388 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/aa830ec1c56bec54179acb8c5ccf433a09bba38a91d7e82e433ff21109e3c228.jpg", + "image_caption": [ + "Supervised methods" + ], + "image_footnote": [], + "bbox": [ + 581, + 330, + 656, + 388 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e115dc84a354da98de4443a6af9c1c7103270624446ad6774e329256ddf3ff72.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 658, + 330, + 733, + 388 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ff7688372f68bfd1c414960af8719abc78e085992e25ae87dbcd1626ea7b2815.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 735, + 330, + 810, + 388 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/d216f63f11f16abe1bbb5f0cc6aebcef180821d92bd2cd286010920a646bd184.jpg", + "image_caption": [ + "LTRP" + ], + "image_footnote": [], + "bbox": [ + 813, + 330, + 888, + 388 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e9a7464254b3f7bf2e6e513a0a421e29bc76b92f55bcda8f19c504610ba86073.jpg", + "image_caption": [ + "Raw" + ], + "image_footnote": [], + "bbox": [ + 504, + 421, + 580, + 478 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/9319321b15675a10f5ef52378b614c24fcc309a643a5011fedbf1bd16cf76eed.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 583, + 421, + 656, + 477 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/bef06b8d9668daa8e3b6e2d0266c14cb9f2165a87cd3b3c128a059733239e1c8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 684, + 406, + 705, + 421 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/a73ad731af3a49398f2e9e5aa2dd112cc773a7958dec0b81c43907566b493eab.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 741, + 407, + 763, + 421 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/5015b864785f7e029350ef9e0b954c07f9a26dfc355c109e2b3a24a9df721326.jpg", + "image_caption": [ + "GT", + "Reconstructions" + ], + "image_footnote": [], + "bbox": [ + 660, + 421, + 733, + 478 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/73d729ebff224e214e5013aec90d550c1d7b781833fd54227a4c00c4bc3c7e01.jpg", + "image_caption": [ + "Informative patches" + ], + "image_footnote": [], + "bbox": [ + 738, + 422, + 810, + 478 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/1fd5930e074c18e7e730abf4426bdaacf8d5e5aa36dcaf03f508d8b1422b4740.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 815, + 422, + 888, + 478 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/4f48b668b0e1beb5a465f84a1da0b550c14d059c163ef40ef10d989280e13bc6.jpg", + "image_caption": [ + "Visible patches Removed patch", + "Figure 1. Redundancy reduction (upper): given an image, LTRP selects informative patches regardless of whether they are from the categories already learned. While for supervised methods (from left to right: GFNet [41], Grad-CAM [38] using ViT, EViT [24]) the preserved patches are mostly located on the learned category. Patch removing (bottom): an image and its reconstructions using MAE [20] with different sets of visible patches, columns 3-5 denote that the red patch is removed from the visible set. They generate reconstructions with different levels of semantic shift, e.g., without the dog tail, eyes, etc." + ], + "image_footnote": [], + "bbox": [ + 640, + 498, + 661, + 511 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "former (ViT) [14, 29]. The computational complexity of ViT grows quadratically with the number of image patches, making patch-level image redundancy reduction gaining increasing attention.", + "bbox": [ + 496, + 699, + 890, + 760 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Current leading methods [12, 31, 41, 48] generally require supervised learning to endow the model with the capability to recognize informative image patches. Specifically, the model is simultaneously trained to estimate the patch's informativeness and classify the image to the right category. Thus, the learning process tends to select image patches that are less likely to degrade the classification accuracy, leading to categorical inductive bias. The bias may cause the model to remove image patches containing mean", + "bbox": [ + 496, + 763, + 890, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author: Zhineng Chen", + "bbox": [ + 94, + 886, + 300, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "22831", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ingful semantics that do not belong to the learned category. As shown in the upper of Fig. 1, supervised methods trained based on ImageNet-1K tend to select informative patches located on train, a category learned. While considering patches on unseen categories like traffic light as redundant and removing them. Note that such categorical inductive bias is unavoidable for models trained based on famous image datasets [13, 17, 25], which typically annotate one or a few categories for each image. On the other hand, activation mapping of popular unsupervised pre-training methods [6, 32] also reveal the informativeness of image patches to some extent. Nevertheless, they are less effective as the pretraining is not targeted for redundancy reduction.", + "bbox": [ + 75, + 90, + 472, + 287 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Recently, masked autoencoder (MAE) [20] has gained increasing attention due to its great representative learning capability. Given an image with a portion of patches randomly masked, MAE learns the feature representation by reconstructing the masked patches. It can generate a reconstruction with meaningful semantics by using a small subset (e.g., $25\\%$ ) of visible patches. We observe that when the masking ratio is high (e.g., $90\\%$ ), further removing a visible patch may cause an obvious semantic shift in the reconstructed image. As shown in the bottom of Fig. 1, if the only visible patch on the dog's tail is masked, the reconstruction will not have the tail. Conversely, masking a patch on the dog's body does not induce perceptible semantic alteration. The result suggests that the informativeness of patches can be revealed from such an unsupervised perspective.", + "bbox": [ + 75, + 289, + 472, + 517 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Motivated by this observation, we propose learning to rank patches (LTRP), a self-supervised framework to fairly reduce image redundancy. It firstly leverages a pre-trained MAE to generate a pseudo score for each visible patch by quantifying the semantic difference between reconstructions with and without that patch. A larger pseudo score indicates that the patch has a greater impact on the quality of the reconstructed image and is thus more valuable. Therefore, LTRP utilizes another ranking model to learn to rank the visible patches according to the pseudo scores, which successfully learns this scoring property. After pretraining, by ranking the patches descendingly according to their scores and keeping the top ones, LTRP can remain valuable patches for the subsequent downstream tasks like classification. As shown in the top right image of Fig. 1, patches containing meaningful semantics are unbiasedly preserved under the same keep ratio.", + "bbox": [ + 75, + 518, + 472, + 777 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We conduct extensive experiments to validate the unbiasedness of LTRP in image redundancy reduction. For image classification at different keep ratios, LTRP not only achieves competitive accuracy compared to current leading methods in single-label classification, but also outperforms them by a clear margin in multi-label classification. When inspecting categories not included in ImageNet-1K, patches remained by LTRP are also more consistent with object de", + "bbox": [ + 75, + 779, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "tection and semantic segmentation labels, getting superior performance in all the evaluated metrics. Moreover, if a small ranking model is employed, we observe that an approximate linear speedup with the keep ratio is coincidentally obtained for image classification, which constitutes a promising solution for efficient ViT. Contributions of this paper are summarized as follows:", + "bbox": [ + 496, + 90, + 893, + 196 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose to treat the image redundancy reduction as a self-supervised patch-level ranking problem. It eliminates the reliance on supervisory signals, expanding the means to reduce image redundancy.", + "- We develop LTRP. It quantifies the variation between MAE-reconstructed images to create pseudo labels, then learns to rank these patches. It offers an elegant way to avoid categorical inductive bias.", + "- Extensive quantitative and qualitative evaluations demonstrate that LTRP can fairly and effectively score the learned and unseen categories, and provide highly competitive solutions for efficient ViT." + ], + "bbox": [ + 500, + 200, + 893, + 380 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 398, + 640, + 414 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Image Redundancy Reduction", + "text_level": 1, + "bbox": [ + 500, + 422, + 769, + 439 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "While sharing similarities with tasks like salient object detection [16, 21] and image compression [33], image redundancy reduction has been studied mainly in the era of deep learning. Some CNN-based methods explored this task for inference efficiency [12, 41, 48]. Meanwhile, ViT models have been implicitly endowed with the redundancy reduction capability. Based on how this capability is built, we can broadly categorize existing studies into three classes.", + "bbox": [ + 496, + 446, + 893, + 568 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Class activation mapping (CAM): Starting from a label, CAM [38, 50] was proposed to provide visual explanations for CNNs by combining feature maps from the penultimate layer using learned or gradient-based weights. CAM achieved success in various visual tasks, such as weakly-supervised object detection [11] and semantic segmentation [1, 18], which regards the activation as initial pseudo object labels. CAM can also be applied to ViT. However, it relies on supervisory signals to build the localization ability, thus suffering from the categorical inductive bias.", + "bbox": [ + 496, + 568, + 893, + 718 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Self-supervised activation mapping: Recent studies in self-supervised learning (SSL) shows that the capability to perceive fine-grained objects can be obtained from contrastive learning-based pre-training. For example, object locations can be roughly inferred by using MoCo [9] to train a CNN and visualizing activation mapping of the last convolutional layer [32]. A similar capability is also observed from the heads of DINO [6]. Object localization is a natural property learned from SSL. However, as redundancy reduction is not the central goal for SSL, preserving image patches according to the generated activation mapping generally leads to worse performance in downstream tasks.", + "bbox": [ + 496, + 719, + 893, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "22832", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/27b023579174f525a77584ff2856ba5034867ca0592d8de86b3f5ffac7f80797.jpg", + "image_caption": [ + "Figure 2. LTRP training (left): given an image, LTRP randomly selects a set of visible patches using a high masking ratio (e.g. $90\\%$ ). A pre-trained MAE (parameter frozen) is applied to get its reconstruction, i.e., the anchor image. Then, the visible patches (red) are removed one by one with replacement, each time generating a new reconstruction and its semantic density score w.r.t the anchor image. The scores are treated as pseudo labels to train the ranking model using learning to rank. Once trained, the ranking model is preserved and the MAE is discarded. LTRP inference (right): Top-k patches are selected using the trained ranking model and fed into downstream tasks." + ], + "image_footnote": [], + "bbox": [ + 76, + 88, + 895, + 330 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Token reduction: Since the computational complexity of ViT is quadratically linear to the number of tokens [14], reducing tokens, which can be viewed as a special form of image patches by using token-to-patch mapping, is an effective method for efficient ViT. Current studies can be classified into two categories. First, token pruning that discards redundant tokens. It involves retraining a network to dynamically filter tokens [34], using the policy gradient to select patches [31], reducing the number of tokens as inference proceeds [49], etc. Second, token merging that combines similar tokens. It involves leveraging attention scores between the class token and other tokens to gradually merge tokens [24], merging tokens between two subsets with equal size by using similarity of their key vectors from the self-attention layer [2] and others [35, 46]. Typically, the research focus of these methods is on efficient ViT. Unbiased redundancy reduction is rarely considered.", + "bbox": [ + 75, + 435, + 472, + 691 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Learning to Rank", + "text_level": 1, + "bbox": [ + 76, + 709, + 250, + 724 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Learning to rank (LTR) [26] is a technique widely employed in information retrieval tasks such as search [8] and recommendation [22]. LTR primarily involves three types according to the utilization of document labels: the point-wise method [7, 23], which uses the rank of an individual document as label and formulates the learning as either classification or regression problem; the pair-wise method [3, 4], which utilizes the relative order of two documents as label for learning; and the list-wise method [5, 44], which considers the order relationship among all or a part of documents associated with a given query. Some studies [27, 47] have", + "bbox": [ + 75, + 734, + 472, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "made meaningful attempts by leveraging learning to rank in computer vision tasks. To our knowledge, it has not been used for image redundancy reduction before.", + "bbox": [ + 496, + 435, + 892, + 479 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "LTRP is an application of LTR to image redundancy reduction. The query is the randomly masked image. Each document is associated with a visible patch, and whose pseudo score is the document label. Different from most existing solutions where the label is obtained from manual annotation or human-machine interaction, our label is obtained from an elegantly designed pre-task, thus enabling a novel self-supervised solution as described below.", + "bbox": [ + 496, + 479, + 893, + 602 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 500, + 614, + 591, + 630 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "An overview of our learning to rank patches (LTRP) is depicted in Fig. 2. Its core elements can be summarized using two words: infer and rank. Given a pre-trained MAE model and an image with a portion of patches randomly masked, LTRP first infers the semantic density score for each visible patch by quantifying variation between the reconstructions with and without that patch. By repeating this process patch-by-patch, we obtain a series of scores. Then, LTRP ranks these patches by treating their scores as pseudo labels using learning-to-rank algorithms. When the training converges, we use the ranking model to select informative patches and only consider them in downstream tasks.", + "bbox": [ + 496, + 640, + 893, + 821 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Preliminary", + "text_level": 1, + "bbox": [ + 500, + 830, + 629, + 847 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "MAE [20] learns a robust image representation by first masking a portion of image patches and then recovering the original image, namely the mask-then-prediction task.", + "bbox": [ + 496, + 854, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "22833", + "bbox": [ + 478, + 944, + 517, + 957 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Specifically, MAE divides an image $I$ into visible and masked patch sets according to a predefined masking ratio, where the visible set $\\mathbf{P}_v = [\\mathbf{p}_1,\\mathbf{p}_2,\\dots ,\\mathbf{p}_n]$ has $n$ patches. Then, the pre-training target can be written as:", + "bbox": [ + 76, + 90, + 468, + 151 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\underset {\\theta} {m i n} H \\left(\\mathcal {T} \\left(I _ {m}\\right), I _ {m} ^ {R}\\right), I _ {m} ^ {R} = \\mathcal {M} _ {\\theta} \\left(\\mathbf {P} _ {v}\\right) \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 150, + 164, + 468, + 186 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $I_{m}$ , $I_{m}^{R}$ and $\\mathcal{M}_{\\theta}$ denote the masked image, the reconstructed image and MAE parameterized by $\\theta$ , respectively, $\\mathcal{T}$ denotes a certain transformation (optional, e.g., HOG [42], normalized pixel values of each masked patch [20], etc.), and $H$ is a distance measurement function.", + "bbox": [ + 76, + 191, + 468, + 268 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Patch Informativeness Inference", + "text_level": 1, + "bbox": [ + 76, + 276, + 361, + 290 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To infer the patch informativeness, we adopt a higher masking ratio of $90\\%$ rather than $50\\%$ or $75\\%$ used in previous MAE studies [20, 45]. The reason is twofold. First, it enables reconstructions exhibiting perceptible change even when only one visible patch is further removed. Second, it decreases the likelihood of semantically similar patches being visible simultaneously, which may confuse the model regarding their informativeness.", + "bbox": [ + 75, + 297, + 468, + 417 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Then, we use a pre-trained, parameter-frozen MAE to perform the reconstruction. For an image, the visible set $\\mathbf{P}_v$ is stochastically selected and its reconstruction $I_m^R$ , or saying, the anchor image, is obtained, we iteratively remove a visible patch $\\mathbf{p}_i \\in \\mathbf{P}_v$ to obtain $\\mathbf{P}_v^i = \\mathbf{P}_v \\backslash \\mathbf{p}_i$ . It can be simply achieved by using masked attention [40]. By reconstructing again, we get $I_m^{R_i}$ , the image reconstruction without the $i$ -th visible patch. A similarity-based function $\\mathcal{F}$ runs over the pair $< I_m^R, I_m^{R_i}>$ , and the quantitative similarity $y_i$ is calculated by:", + "bbox": [ + 75, + 419, + 468, + 570 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ny _ {i} = \\mathcal {F} \\left(I _ {m} ^ {R}, I _ {m} ^ {R _ {i}}\\right), I _ {m} ^ {R _ {i}} = \\mathcal {M} _ {\\theta} \\left(\\mathbf {P} _ {v} ^ {i}\\right) \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 156, + 577, + 468, + 595 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We term the inferred result as the semantic density score, as it quantizes the semantic variant between the two reconstructions. We simply use the $\\ell_1$ distance to measure the variant in this paper. By polling all the visible patches one-by-one, we get a pseudo score vector $\\mathbf{y} = [y_{1},y_{2},\\dots,y_{n}]$ . Note that the scores are obtained in a self-supervised manner, and Eq. (2) can be regarded as the pre-task to reveal the patch informativeness. In the implementation, the score inference can be parallelized for training acceleration.", + "bbox": [ + 75, + 602, + 468, + 738 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/784f3d05bfc960f5d16523359ee519d83a46f5e69b14a22d2ed5be5c01d5ceec.jpg", + "image_caption": [ + "Figure 3. Normalized score maps generated by our ranking model." + ], + "image_footnote": [], + "bbox": [ + 78, + 750, + 468, + 800 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Learning to Rank", + "text_level": 1, + "bbox": [ + 76, + 847, + 250, + 862 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "With pseudo score $\\mathbf{y}$ calculated from Eq. (2), we use learning-to-rank algorithms to train an independent ranking", + "bbox": [ + 76, + 869, + 468, + 901 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/4a999c08b22e2ce14d1d3220d9df87793564058a86d07688e9b1dea2cc9a038c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 514, + 89, + 895, + 157 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/f58c70da7335490aba639f8a0f9aaba2a5e09265bcabae5b003860101ed83a82.jpg", + "image_caption": [ + "(a) ImageNet-1K" + ], + "image_footnote": [], + "bbox": [ + 513, + 157, + 895, + 228 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/5df1d1f581f6aae0d249ba98fca7e86618bd156aa2525d4c55b8cf5be746b7da.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 511, + 244, + 893, + 314 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/6e27cc947b493cff1a109acd267345f2327f89388668f072fcdebac9bd8fdb92.jpg", + "image_caption": [ + "(b) MS-COCO", + "Figure 4. Classification results on single-label dataset (upper, ImageNet-1K) and multi-label dataset (bottom, MS-COCO) at different krs. All methods differ only in the patch selection step. Supervised and self-supervised methods are depicted using different colors. LTRP is annotated spots." + ], + "image_footnote": [], + "bbox": [ + 511, + 313, + 893, + 382 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "model to rank the patches. Formally, each image-partition instance $\\mathbf{x} = < I, \\mathbf{P}_v, \\mathbf{y}>$ can be viewed as a training sample for the ranking model, which accepts $\\mathbf{x}$ as the input and outputs a vector $\\mathbf{s} = [s_1, s_2, \\dots, s_n]$ containing predicted scores for the patches. Our LTRP utilizes a list-wise loss, ListMLE [44], to train the model as follows.", + "bbox": [ + 498, + 506, + 890, + 597 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nL = - \\log P _ {s} (\\pi), P _ {s} (\\pi) = \\prod_ {i = 1} ^ {n} \\frac {\\exp \\left(s _ {\\pi (i)}\\right)}{\\sum_ {k = i} ^ {n} \\exp \\left(s _ {\\pi (k)}\\right)} \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 521, + 608, + 890, + 647 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\pi$ denotes the descending permutation according to $\\mathbf{y}$ , and $\\pi(k)$ is the patch ranked at the $k$ -th position in $\\pi$ . The ranking model will optimize towards sorting patches in line with their semantic density scores. Compared with the other two kinds of ranking loss, i.e., point-wise and pairwise losses, the list-wise loss more completely considers the overall relationships among patches. In the implementation, we apply a sparse design to the ranking model, which solely inputs the visible patches instead of the full set. We will verify this design and architecture choice of the ranking model in ablation studies.", + "bbox": [ + 496, + 657, + 890, + 823 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Note that each training instance only contains a small portion of visible patches and scores. However, when going through a sufficient number of instances, the ranking model sees all patch locations of an image and learns to judge relative ranks among patches. In other words, the", + "bbox": [ + 496, + 825, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "22834", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "ranking model knows how to score all the image patches regarding their informativeness. Consequently, we can solely use the ranking model for image redundancy reduction, as shown in the right part of Fig. 2.", + "bbox": [ + 76, + 90, + 468, + 151 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Patch Selection", + "text_level": 1, + "bbox": [ + 76, + 162, + 230, + 176 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "With the ranking model, a straightforward way for redundancy reduction is to select the top-k patches. Our observation suggests that the top patches favor object boundaries rather than homogeneous regions (e.g., dog's body in Fig. 1), as shown in Fig. 3. We attribute it to that changes in object boundaries more easily cause semantic shifts in the reconstructed image. However, a small proportion of patches from homogeneous regions are also essential for visual tasks [28]. Thus, we introduce DPC-KNN [15] to capture the representative homogeneous patches. Specifically, to select $k$ informative patches including $h$ ( $h < k$ ) ones from homogeneous regions, we first select ( $k - h$ ) patches as described above. Then, we use DPC-KNN to cluster all patches into $k$ groups and select the largest $h$ ones, given that larger groups are more likely to associate with homogeneous regions. For each selected group, we extract one patch that satisfies the following two conditions, i.e., not selected previously and closest to the cluster center in the remaining patches. The two sets of patches constitute the output of our LTRP. We will ablate $h$ in experiments.", + "bbox": [ + 76, + 185, + 472, + 488 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 503, + 209, + 520 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Datasets and Experimental Setting", + "text_level": 1, + "bbox": [ + 76, + 527, + 380, + 545 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets and evaluation metrics. We pre-train our LTRP on ImageNet-1K training set, and then assess it on two scenarios as follows. The first is image-level evaluation. We conduct image classification on ImageNet-1K, a single-label classification dataset, and on MS-COCO [25], a multi-label classification dataset. The classification model is trained only with the patches remained by different methods. Top-1 accuracy and mAP are employed as the evaluation metrics, respectively. The second is patch-level evaluation. It is conducted both on MS-COCO and PASCAL VOC [17] with their object detection labels, MS-COCO and ADE20K [51] with their semantic segmentation labels. In practice, we treat all the labeled bounding boxes or masks as foreground and evaluate their consistency with the retained patches by using IoU, F1-score, recall, and precision. Following EViT [24], IA-RED² [31], etc., we evaluate these methods at different keep ratios (krs). That is, the top-scored $kr\\%$ patches are preserved. Meanwhile, all the ablation experiments are conducted on ImageNet-100, a subset of ImageNet-1K, given hardware resource constraints.", + "bbox": [ + 76, + 551, + 472, + 854 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Model architectures. In LTRP training, we use MAE with ViT-B and choose ViT or CNN (e.g., ResNet50) as our ranking model. In image classification, we utilize ViT-B", + "bbox": [ + 76, + 854, + 470, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "on ImageNet-1K and MS-COCO, ViT-S on ImageNet-100 as the backbone for model training. They are both initialized from the MAE encoder [20]. Moreover, we add ML-Decoder [37] behind the classification backbone and use Asymmetric loss [36] for multi-label classification. No additional model is required for the patch-level evaluation, as the performance is obtained by comparing the preserved image patches with groundtruth. All experiments are conducted on a server with 8 NVIDIA GTX 3090 GPUs and Intel(R) Xeon(R) Gold 6226R CPU.", + "bbox": [ + 496, + 90, + 890, + 241 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Comparing methods. We compare LTRP with off-the-shelf models from the three classes mentioned previously (see Sec. 2.1). For CAM, we choose Grad-Cam [38] with ViT. For self-supervised methods, we choose MoCo [9] with ResNet50 and DINO [6]. For token reduction, we choose EViT [24], IA-RED² [31], DynamicViT [34], AdaViT [30], DGE [39] and ToMe [2]. For fair assessment, these methods are all trained (supervised) or pre-trained (unsupervised) on ImageNet-1K.", + "bbox": [ + 496, + 242, + 893, + 378 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Performance Evaluation", + "text_level": 1, + "bbox": [ + 498, + 391, + 723, + 405 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Image-level evaluation. Figure 4a shows the results of different methods at krs 0.7 and 0.5 on single-label classification. The unsupervised and supervised methods are depicted by different colors. LTRP performs better than the self-supervised ones, and slightly worse or on par with state-of-the-art supervised methods. Note that LTRP achieves this without utilizing any supervisory signals.", + "bbox": [ + 496, + 415, + 890, + 521 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We then test LTRP on MS-COCO to validate the performance on multi-label classification. As shown in Fig. 4b, LTRP achieves mAP of $82.8\\%$ and $81.8\\%$ at krs 0.75 and 0.5, respectively. It outperforms the previous best unsupervised methods by $1.1\\%$ and $1.4\\%$ , and the state-of-the-art supervised methods by $0.7\\%$ at both krs. Note that these values correspond to clear accuracy gaps, as the performance differences between existing methods are small. Since different methods only differ in the patches selected, these improvements clearly indicate that LTRP enables a fairer and more meaningful redundancy reduction.", + "bbox": [ + 496, + 522, + 890, + 688 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Patch-level evaluation. To further validate whether the patches are unbiasedly retained, we focus on the categories not included in ImageNet-1K, i.e., the unseen categories, for which all the methods have not been explicitly told to learn. We first evaluate the methods based on the object detection labels. The performance of different methods on PASCAL VOC and MS-COCO is shown in the first two rows in Fig. 5. Encouragingly, LTRP surpasses all the competitors in all the evaluated metrics at different krs. The significant improvement in precision highlights that patches selected by LTRP are more accurately located in bounding boxes of unseen categories. With the decrease of krs, the precision of many supervised methods goes up slowly or even goes down. It means that these methods tend to not re", + "bbox": [ + 496, + 689, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "22835", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/855366435cf33482b20712a82b4ea872bd8931c06bb3967d137f77cd3f8907a7.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 76, + 88, + 267, + 191 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/92d4b77bacf6055da56ba783a62eb4a1a7792dece09f65744ee7fd1021cf2a44.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 266, + 90, + 433, + 191 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/2620ba49e9b019898bde0c189fabf89424a47991fd0488bfdbc984e5eff1b4cc.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 433, + 90, + 598, + 191 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/0435d5689d68a11fa6a4909e1181d96079fc2dc12e4ee86468f7e9ff4befb44b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 598, + 90, + 766, + 191 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/6359b3a76b2e4dc3208816c89f047785b5f4b1a48ca850cd02d1afa1aef644dd.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 767, + 90, + 890, + 191 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/a79a21e54b4c90ddf07b93cb0925c0e0393f0a0b437fdc138b86613966bd00a1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 76, + 191, + 267, + 292 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/dc8c3d2bc4cabe11ed8ddcd2ac2848e7132a6fc295d306e6afa663aed767e03c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 267, + 191, + 433, + 292 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/c7a5d3a598b1427454d01c9593ca5182473a1eb3a2c0156492a97469b2d10f2f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 433, + 191, + 598, + 292 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/f5ddddacfba783912fd92e74fc8d1e707c1f4c42f7926c7f679d99287a3ce0ba.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 599, + 191, + 766, + 292 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/7e33fa4360c519970acbaabae2dc9351be8cf41dba32c2c1f393cd041a94ef06.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 766, + 191, + 890, + 292 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/c1e1116ace9fd00d5da7f944b6f3ef30adb00875e42b26760f92586d1e54d75d.jpg", + "image_caption": [ + "Figure 5. Experimental results on object detection and semantic segmentation datasets. For each dataset, we exclude the categories overlapped with ImageNet-1K (learned) and only compute the metrics on the remaining (unseen) categories, which all the methods have not been explicitly told to learn. The results illustrate the merit of LTRP in unbiased image redundancy reduction." + ], + "image_footnote": [], + "bbox": [ + 76, + 292, + 267, + 393 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/def713ee8d0d51ffec6dd3eb00dd25977a0b3a594948d75d81039c35c6e30066.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 266, + 292, + 433, + 393 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/6853659c7988379ade631d4bfb2b215b54d4874f4bf9668fdef17d24e9f773bf.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 433, + 292, + 598, + 393 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/0ad60c5c962ea57f7ffa6fafb6bddcc9b149b45e44081f3ff13d975ad432e402.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 599, + 292, + 766, + 393 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/6e62819db20a6ad2b5122bfd2eb175c5b2b703c8449c54825da06ef6c7e89cec.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 766, + 292, + 890, + 393 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "gard patches from unseen categories as the most important ones, while our LTRP still goes up quickly and successfully avoids this bias. The result implies that LTRP can be well generalized to datasets with quite different categories.", + "bbox": [ + 75, + 473, + 468, + 532 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We then evaluate the methods based on the semantic segmentation labels. The third row in Fig. 5 shows the results on MS-COCO. LTRP also consistently gives the best results and exhibits a noticeable improvement compared to DynamicViT, the second-best method. We observe that the performance gap becomes larger as the kr decreases. It again demonstrates that LTRP preserves semantics corresponding to the unseen categories well.", + "bbox": [ + 75, + 534, + 468, + 654 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Ablations", + "text_level": 1, + "bbox": [ + 76, + 665, + 187, + 679 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In Tab. 1, we provide detailed ablation experiments and introduce some empirical observations as follows.", + "bbox": [ + 75, + 688, + 468, + 718 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Reconstruction model. Tab. 1a presents LTRP with different MAE as the image reconstruction model. The optimal model is surprisingly the lightweight model MAE-B. Utilizing MAE-B to generate pseudo label boosts the accuracy by $0.2\\%$ compared to larger MAE-L (21 M v.s. 81 M in #params). Moreover, MAE-L with GAN [19] loss can get even better reconstruction, but performs worse at kr 0.5. We observe that reconstructions of large models or utilizing GAN loss have finer low-level semantics such as texture details. It tends to pull these patches that excel in recovering low-level semantics ahead in the ranking, consequently reducing the proportion of patches with high-level semantics.", + "bbox": [ + 75, + 719, + 468, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "This phenomenon causes the accuracy drop.", + "bbox": [ + 500, + 473, + 792, + 488 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Masking ratio. Tab. 1b shows the influence of the ratio of removed patches. The accuracy of an excessively high masking ratio (0.95) drops by $0.1\\%$ compared with baseline. And a lower masking ratio (0.7) does not perform better than the masking ratio of 0.8. We note that extremely high and low masking ratios both result in the issue of plateau in the pseudo score sequence, namely some patches have similar pseudo scores and occupy a continuous position in the ranking sequence. This causes the ranking model to be confused about the right order of these patches. Considering the efficiency issue, LTRP selects a masking ratio of 0.9.", + "bbox": [ + 496, + 489, + 892, + 655 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Ranking model. We investigate the architecture, sparse design and similarity metric of ranking model in Tabs. 1c, 1d and 1h, respectively. We find out that our ranking model is model-agnostic, and even smaller models like ViT-T or ResNet50 can achieve performance similar to the baseline (ViT-S). However, to align with the comparing methods, we select ViT-S. The sparse design excludes the sort-irrelevant patches from the ranking model, it improves accuracy by $0.2\\%$ to $0.3\\%$ across different krs. Moreover, by skipping these patches, we significantly reduce computational costs.", + "bbox": [ + 496, + 657, + 892, + 808 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Clustering. Tab. 1e presents our investigation of clustering. Interestingly, selecting all patches (with clustering ratio 1) through clustering at the pixel level is not extremely bad compared with our baseline (82.7% v.s. 83.7%). A small subset (e.g., 20%) of patches from homogeneous regions gets an improved LTRP.", + "bbox": [ + 496, + 810, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "22836", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/256f76fa4c813e06ec0c93fc2c3073efdc881d80f2fb91ad55b68e9426e78d61.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
modelkr=0.75kr=0.5
MAE-B84.483.3
MAE-L84.283.2
MAE-L-GAN84.283.0
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ratiospeedupkr=0.75kr=0.5
0.956.4x84.383.2
0.93.1x84.483.3
0.81.5x84.883.6
0.71.0x84.683.4
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metricskr=0.75kr=0.5
l184.483.3
PSNR83.882.5
SSIM83.679.9
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modelparamskr=0.75kr=0.5
Mobile-Former[10]3.2M84.383.1
ViT-T5.5M84.583.4
ViT-S22M84.483.3
ResNet5024M84.583.4
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ratiokr=0.75kr=0.5
084.483.3
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183.682.7
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losskr=0.75kr=0.5
Regression84.183.0
RankNet82.979.5
ListNet84.182.5
ListMLE84.483.3
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phasespeedupkr=0.75kr=0.5inputkr=0.75kr=0.5
encoder184.483.7visible patches84.783.5
decoder1.3x84.483.3all patches84.483.3
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casekr=0.75kr=0.5
pixel (w/o norm)84.483.3
pixel (w norm)81.575.7
", + "bbox": [ + 620, + 325, + 888, + 377 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "(g) Removal phase. Removing visible patches be- (h) Sparse design. Inputting only visible patches(i) Reconstruction target. LTRP favors MIM fore the decoder well balances accuracy and speed. into the ranking model yields better results. models based on raw pixels.", + "bbox": [ + 76, + 381, + 888, + 406 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 1. LTRP ablation experiments on ImageNet-100. We report accuracy (%) results for krs 0.75 and 0.5, respectively. The selected configurations are marked in gray.", + "bbox": [ + 75, + 417, + 892, + 448 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Ranking loss. Tab. 1f studies the choice of ranking loss. Interestingly, the point-wise approach also has decent performance in our LTRP. Compared to ListMLE, its accuracy drops by only $0.3\\%$ at both krs. Point-wise methods train $\\langle$ query, document $\\rangle$ pair independently, ignoring the relationship among documents. In contrast, our ranking model considers all documents (patches), i.e., $\\langle$ query, documents $\\rangle$ , enabling the acquisition of holistic knowledge. For pair-wise methods, the accuracy drops obviously at krs of 0.75 and 0.5 (82.9 v.s. 84.4 and 79.5 v.s. 83.3, respectively). Overall, ListMLE performs the best and is also the most appropriate method for utilizing our pseudo-labels.", + "bbox": [ + 75, + 474, + 468, + 655 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Removal phase. In Tab. 1g, although the results of removing visible patches before the lightweight decoder show a decrease in performance compared to the approach of removing before the encoder (a reduction of $0.4\\%$ at kr 0.5), we can achieve a noteworthy $1.3\\mathrm{x}$ speedup in terms of FLOPs (7.07G vs. 5.38G). So we employ the former.", + "bbox": [ + 75, + 657, + 468, + 747 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Reconstruction target. Pre-patch normalization is a trick that normalizes a patch using the mean and standard deviation of its pixels. In Tab. 1i, we observe that utilizing pre-trained MAE based on pre-patch normalization for generating pseudo-labels performs exceedingly poorly, which is $7.6\\%$ worse than using unnormalized pixels. We suspect this drop partially because LTRP requires quantifying the global semantic changes between two images. Conversely, pre-patch normalization appears to reducing global coherence, as it focuses on enhancing the contrast locally [20].", + "bbox": [ + 75, + 750, + 470, + 901 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/03f366993b1132d7447c5e268635e2c2013fdc8b0da1e5fa7ef755e7ee2369dd.jpg", + "image_caption": [ + "Figure 6. Normalized score maps generated by LTRP on validation set of ImageNet-1K (top) and MS-COCO (bottom). Only the top-scored 64 patches are displayed." + ], + "image_footnote": [], + "bbox": [ + 501, + 472, + 890, + 628 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. LTRP for Efficient ViT", + "text_level": 1, + "bbox": [ + 500, + 708, + 712, + 723 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "LTRP allows the classification model to be trained only on a subset of image patches. We verify whether this LTRP-based classification would be more efficient for ViT.", + "bbox": [ + 498, + 733, + 890, + 777 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We elucidate this issue from both inference and training perspectives. For inference, time for both patch ranking and classification should be counted. As shown in Tab. 1d, even ViT-T has commendable performance. So we choose small ranking model and large classification model as LTRP-based solutions. Table 2 enumerates several combinations on ImageNet-1K at kr 0.75. Using ViT-T as the ranking model shows $1.19 \\times$ , $1.36 \\times$ , or $1.33 \\times$ acceleration on GPU", + "bbox": [ + 496, + 779, + 892, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "22837", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/79f79e8cc97588074933b30b3e448213102ffbd383282e9721255cc448379244.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
cls.rankingparamsFLOPs ↓inference speed↑top-1 acc.
modelmodel(M)(G)GPUim/sCPUim/s
ViT-B-8617.61095.14.383.3†)
ViT-S108(+25.6%)13.1(-25.6%)1034.9(-5.5%)4.1(-4.7%)83.2(-0.1%)
ViT-T91.5(+6.4%)13.1(-25.6%)1302.2(+18.9%)5.1(+18.6%)83.1(-0.2%)
ViT-L-30761.62357.71.385.8†)
ViT-S329(+7.2%)46.0(-25.3%)445.6(+24.6%)1.5(+15.4%)85.7(-0.1%)
ViT-T312.5(+1.8%)45.9(-25.5%)485.5(+35.8%)1.7(+23.1%)85.6(-0.2%)
ViT-H-632167.4140.00.586.6†)
ViT-S654(+3.5%)124.8(-25.4%)181.0(+29.3%)0.6(+20.0%)86.3(-0.3%)
ViT-T637.5(+0.9%)124.7(-25.5%)185.8(+32.7%)0.6(+20.0%)86.1(-0.5%)
", + "bbox": [ + 80, + 88, + 477, + 202 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 2. Experiments on efficient ViT on ImageNet-1K at kr 0.75. Different combinations of the ranking and classification (cls.) models show different balances between FLOPs (or inference speed) and accuracy. \" -\" means do not incorporate the ranking model and select all patches. $\\dagger$ means run by us. When using ViT-T as the ranking model, LTRP accelerates the inference ranging from 18.9% to 32.7% with accuracy sacrifice of 0.1%-0.5%.", + "bbox": [ + 75, + 212, + 468, + 311 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "over the scheme that directly uses ViT-B, ViT-L or ViT-H as the classification model, respectively (ViT-H uses a $16^{*}16$ patch grid while ViT-B and ViT-L use $14^{*}14$ ). Meanwhile, the accuracy drops only range from $0.2\\%$ to $0.5\\%$ . The results imply that LTRP-based ones are more appropriate choices in scenarios requiring both efficiency and accuracy. With the popularity of large visual and multi-modal models, large ViT models are more frequently utilized and we believe that these solutions would receive more attention. While for training, LTRP-based solutions include running the ranking model once for patch selection and training the classification model $N$ epochs. The cost raised by the ranking model would be negligible as $N$ increases. Meanwhile, training the classification model would also be accelerated by nearly $1 / kr^2 \\times$ as fewer patches are involved.", + "bbox": [ + 75, + 337, + 468, + 564 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In sum, compared with the vanilla classification, LTRP-based solutions not only accelerate training but also can improve the inference speed up to over $30\\%$ on GPU with a possible neglectable accuracy degradation.", + "bbox": [ + 75, + 564, + 468, + 625 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.5. Visualization", + "text_level": 1, + "bbox": [ + 76, + 635, + 212, + 648 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Figure 6 displays the informativeness-aware capability of LTRP on ImageNet-1k and MS-COCO. LTRP well identifies patches located in meaningful object regions in ImageNet-1K images. Meanwhile, it also shows superior unbiasedness in selecting multiple objects from MS-COCO images. We also visualize a process of hierarchical patch selection in Fig. 7. With the decrease of retained patches, less important patches are gradually removed. LTRP is consistent in favour of patches located on semantic objects. This removal process is mostly in line with human perception. The results again demonstrate the effectiveness of LTRP.", + "bbox": [ + 75, + 657, + 468, + 823 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To explore why LTRP performs better than popular self-supervised methods, we plot the average attention distance of each head of DINO and our LTRP ranking model (both are ViT-S) in Fig. 8. A more scattered distance distribution is observed for LTRP especially in the last few layers. As", + "bbox": [ + 75, + 824, + 468, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f97448d905d1b63f82adb7939fda10769c77e97931f60fdcff73d4b6152177f6.jpg", + "image_caption": [ + "Figure 7. Hierarchical redundancy reduction process of LTRP on MS-COCO validation set. Keep ratios are shown in the top left of each image. Patches with green boxes are the retained ones." + ], + "image_footnote": [], + "bbox": [ + 501, + 88, + 890, + 200 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/355021130e366950b6c77bf725886ac0af15a566d61db9306b99c4ccc2869dc6.jpg", + "image_caption": [ + "(a) DINO" + ], + "image_footnote": [], + "bbox": [ + 503, + 266, + 702, + 382 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d8c4cd701bd5a4cbfe8c954cbf8a1d3ad460a470cd8255c1133d986a7083f6e6.jpg", + "image_caption": [ + "(b) LTRP", + "Figure 8. Average attention distances organized according to layer and head for DINO and our LTRP ranking model." + ], + "image_footnote": [], + "bbox": [ + 704, + 267, + 901, + 382 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "stated in [43], such a distribution suggests that more diverse representation learning is achieved, which explains in part the superiority of LTRP.", + "bbox": [ + 498, + 463, + 890, + 508 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 522, + 617, + 537 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We have introduced LTRP, the first self-supervised method for image redundancy reduction. By leveraging the characteristic of self-supervised learning to create patch-level pseudo labels, and then learning to rank patches, LTRP elegantly eliminates the issue of categorical inductive bias commonly observed in leading supervised methods. Extensive experiments on different datasets and tasks basically validate our proposal. LTRP achieves competitive accuracy in single-label classification and obviously better accuracy in multi-label classification. Meanwhile, the retained patches align more closely with object detection and semantic segmentation labels, especially for categories not explicitly learned by supervised methods. In addition, incorporating LTRP into image classification can lead to a notable speedup in inference with neglectable accuracy degradation if applied appropriately. These results convincingly indicate the effectiveness of LTRP and its unbiased patch selection. We hope that LTRP will provide valuable insights into image redundancy reduction and related visual tasks.", + "bbox": [ + 496, + 547, + 890, + 834 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement This work was supported by National Science and Technology Major Project (No. 2021ZD0112805) and in part by National Natural Science Foundation of China (No. 62372170, 62172103).", + "bbox": [ + 498, + 834, + 890, + 895 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "22838", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 106 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Jiwoon Ahn and Suha Kwak. Learning pixel-level semantic affinity with image-level supervision for weakly supervised semantic segmentation. 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In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 633-641, 2017. 5" + ], + "bbox": [ + 503, + 92, + 890, + 893 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "22840", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_model.json b/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_model.json new file mode 100644 index 0000000000000000000000000000000000000000..ce25f133c9a6d898c9f58eab6c42b88368508dae --- /dev/null +++ b/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_model.json @@ -0,0 +1,2541 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.13, + 0.131, + 0.84, + 0.154 + ], + "angle": 0, + "content": "Learning to Rank Patches for Unbiased Image Redundancy Reduction" + }, + { + "type": "text", + "bbox": [ + 0.123, + 0.189, + 0.86, + 0.209 + ], + "angle": 0, + "content": "Yang Luo\\(^{1}\\), Zhineng Chen\\(^{1*}\\), Peng Zhou\\(^{2}\\), Zuxuan Wu\\(^{1}\\), Xieping Gao\\(^{3}\\), Yu-Gang Jiang\\(^{1}\\)" + }, + { + "type": "text", + "bbox": [ + 0.09, + 0.211, + 0.901, + 0.243 + ], + "angle": 0, + "content": "\\(^{1}\\)School of Computer Science, Shanghai Collaborative Innovation Center of Intelligent Visual Computing, Fudan University \\(^{2}\\)University of Maryland, College Park" + }, + { + "type": "text", + "bbox": [ + 0.245, + 0.244, + 0.75, + 0.261 + ], + "angle": 0, + "content": "3College of Information Science and Engineering, Hunan Normal University" + }, + { + "type": "text", + "bbox": [ + 0.227, + 0.264, + 0.76, + 0.279 + ], + "angle": 0, + "content": "yangluo21@m.fudan.edu.cn, {zhinchen, zxwu, ygj}@fudan.edu.cn," + }, + { + "type": "text", + "bbox": [ + 0.293, + 0.283, + 0.692, + 0.296 + ], + "angle": 0, + "content": "pengzhou@terpmail.umd.edu, xpgao@hunnu.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.331, + 0.313, + 0.347 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.364, + 0.474, + 0.742 + ], + "angle": 0, + "content": "Images suffer from heavy spatial redundancy because pixels in neighboring regions are spatially correlated. Existing approaches strive to overcome this limitation by reducing less meaningful image regions. However, current leading methods rely on supervisory signals. They may compel models to preserve content that aligns with labeled categories and discard content belonging to unlabeled categories. This categorical inductive bias makes these methods less effective in real-world scenarios. To address this issue, we propose a self-supervised framework for image redundancy reduction called Learning to Rank Patches (LTRP). We observe that image reconstruction of masked image modeling models is sensitive to the removal of visible patches when the masking ratio is high (e.g., \\(90\\%\\)). Building upon it, we implement LTRP via two steps: inferring the semantic density score of each patch by quantifying variation between reconstructions with and without this patch, and learning to rank the patches with the pseudo score. The entire process is self-supervised, thus getting out of the dilemma of categorical inductive bias. We design extensive experiments on different datasets and tasks. The results demonstrate that LTRP outperforms both supervised and other self-supervised methods due to the fair assessment of image content. Code is available at https://github.com/irsLu/Ltrp." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.773, + 0.208, + 0.789 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.799, + 0.47, + 0.875 + ], + "angle": 0, + "content": "Image redundancy reduction refers to discarding the less informative regions of an image while preserving its essential semantics. It is a fundamental task in computer vision as compact image representation is an attractive property in various applications, especially in the era of vision Trans-" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.331, + 0.58, + 0.389 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.526, + 0.391, + 0.558, + 0.403 + ], + "angle": 0, + "content": "Raw" + }, + { + "type": "image", + "bbox": [ + 0.582, + 0.332, + 0.657, + 0.389 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.636, + 0.391, + 0.766, + 0.403 + ], + "angle": 0, + "content": "Supervised methods" + }, + { + "type": "image", + "bbox": [ + 0.66, + 0.332, + 0.734, + 0.389 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.736, + 0.332, + 0.812, + 0.389 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.815, + 0.332, + 0.89, + 0.389 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.836, + 0.391, + 0.877, + 0.402 + ], + "angle": 0, + "content": "LTRP" + }, + { + "type": "image", + "bbox": [ + 0.506, + 0.422, + 0.581, + 0.479 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.526, + 0.482, + 0.558, + 0.493 + ], + "angle": 0, + "content": "Raw" + }, + { + "type": "image", + "bbox": [ + 0.584, + 0.422, + 0.657, + 0.478 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.685, + 0.407, + 0.706, + 0.422 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.715, + 0.408, + 0.734, + 0.422 + ], + "angle": 0, + "content": "GT" + }, + { + "type": "image", + "bbox": [ + 0.743, + 0.408, + 0.764, + 0.422 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.769, + 0.408, + 0.889, + 0.422 + ], + "angle": 0, + "content": "Informative patches" + }, + { + "type": "image", + "bbox": [ + 0.661, + 0.422, + 0.735, + 0.479 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.685, + 0.482, + 0.789, + 0.493 + ], + "angle": 0, + "content": "Reconstructions" + }, + { + "type": "image", + "bbox": [ + 0.739, + 0.423, + 0.812, + 0.479 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.816, + 0.423, + 0.89, + 0.479 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.642, + 0.499, + 0.662, + 0.512 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.665, + 0.499, + 0.89, + 0.514 + ], + "angle": 0, + "content": "Visible patches Removed patch" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.526, + 0.892, + 0.665 + ], + "angle": 0, + "content": "Figure 1. Redundancy reduction (upper): given an image, LTRP selects informative patches regardless of whether they are from the categories already learned. While for supervised methods (from left to right: GFNet [41], Grad-CAM [38] using ViT, EViT [24]) the preserved patches are mostly located on the learned category. Patch removing (bottom): an image and its reconstructions using MAE [20] with different sets of visible patches, columns 3-5 denote that the red patch is removed from the visible set. They generate reconstructions with different levels of semantic shift, e.g., without the dog tail, eyes, etc." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.7, + 0.892, + 0.761 + ], + "angle": 0, + "content": "former (ViT) [14, 29]. The computational complexity of ViT grows quadratically with the number of image patches, making patch-level image redundancy reduction gaining increasing attention." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Current leading methods [12, 31, 41, 48] generally require supervised learning to endow the model with the capability to recognize informative image patches. Specifically, the model is simultaneously trained to estimate the patch's informativeness and classify the image to the right category. Thus, the learning process tends to select image patches that are less likely to degrade the classification accuracy, leading to categorical inductive bias. The bias may cause the model to remove image patches containing mean" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.302, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author: Zhineng Chen" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "22831" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.288 + ], + "angle": 0, + "content": "ingful semantics that do not belong to the learned category. As shown in the upper of Fig. 1, supervised methods trained based on ImageNet-1K tend to select informative patches located on train, a category learned. While considering patches on unseen categories like traffic light as redundant and removing them. Note that such categorical inductive bias is unavoidable for models trained based on famous image datasets [13, 17, 25], which typically annotate one or a few categories for each image. On the other hand, activation mapping of popular unsupervised pre-training methods [6, 32] also reveal the informativeness of image patches to some extent. Nevertheless, they are less effective as the pretraining is not targeted for redundancy reduction." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.29, + 0.473, + 0.518 + ], + "angle": 0, + "content": "Recently, masked autoencoder (MAE) [20] has gained increasing attention due to its great representative learning capability. Given an image with a portion of patches randomly masked, MAE learns the feature representation by reconstructing the masked patches. It can generate a reconstruction with meaningful semantics by using a small subset (e.g., \\(25\\%\\)) of visible patches. We observe that when the masking ratio is high (e.g., \\(90\\%\\)), further removing a visible patch may cause an obvious semantic shift in the reconstructed image. As shown in the bottom of Fig. 1, if the only visible patch on the dog's tail is masked, the reconstruction will not have the tail. Conversely, masking a patch on the dog's body does not induce perceptible semantic alteration. The result suggests that the informativeness of patches can be revealed from such an unsupervised perspective." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.52, + 0.473, + 0.779 + ], + "angle": 0, + "content": "Motivated by this observation, we propose learning to rank patches (LTRP), a self-supervised framework to fairly reduce image redundancy. It firstly leverages a pre-trained MAE to generate a pseudo score for each visible patch by quantifying the semantic difference between reconstructions with and without that patch. A larger pseudo score indicates that the patch has a greater impact on the quality of the reconstructed image and is thus more valuable. Therefore, LTRP utilizes another ranking model to learn to rank the visible patches according to the pseudo scores, which successfully learns this scoring property. After pretraining, by ranking the patches descendingly according to their scores and keeping the top ones, LTRP can remain valuable patches for the subsequent downstream tasks like classification. As shown in the top right image of Fig. 1, patches containing meaningful semantics are unbiasedly preserved under the same keep ratio." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.473, + 0.903 + ], + "angle": 0, + "content": "We conduct extensive experiments to validate the unbiasedness of LTRP in image redundancy reduction. For image classification at different keep ratios, LTRP not only achieves competitive accuracy compared to current leading methods in single-label classification, but also outperforms them by a clear margin in multi-label classification. When inspecting categories not included in ImageNet-1K, patches remained by LTRP are also more consistent with object de" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.198 + ], + "angle": 0, + "content": "tection and semantic segmentation labels, getting superior performance in all the evaluated metrics. Moreover, if a small ranking model is employed, we observe that an approximate linear speedup with the keep ratio is coincidentally obtained for image classification, which constitutes a promising solution for efficient ViT. Contributions of this paper are summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.201, + 0.894, + 0.261 + ], + "angle": 0, + "content": "- We propose to treat the image redundancy reduction as a self-supervised patch-level ranking problem. It eliminates the reliance on supervisory signals, expanding the means to reduce image redundancy." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.261, + 0.895, + 0.32 + ], + "angle": 0, + "content": "- We develop LTRP. It quantifies the variation between MAE-reconstructed images to create pseudo labels, then learns to rank these patches. It offers an elegant way to avoid categorical inductive bias." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.322, + 0.895, + 0.381 + ], + "angle": 0, + "content": "- Extensive quantitative and qualitative evaluations demonstrate that LTRP can fairly and effectively score the learned and unseen categories, and provide highly competitive solutions for efficient ViT." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.201, + 0.895, + 0.381 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.399, + 0.642, + 0.415 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.424, + 0.771, + 0.44 + ], + "angle": 0, + "content": "2.1. Image Redundancy Reduction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.448, + 0.895, + 0.569 + ], + "angle": 0, + "content": "While sharing similarities with tasks like salient object detection [16, 21] and image compression [33], image redundancy reduction has been studied mainly in the era of deep learning. Some CNN-based methods explored this task for inference efficiency [12, 41, 48]. Meanwhile, ViT models have been implicitly endowed with the redundancy reduction capability. Based on how this capability is built, we can broadly categorize existing studies into three classes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.569, + 0.895, + 0.719 + ], + "angle": 0, + "content": "Class activation mapping (CAM): Starting from a label, CAM [38, 50] was proposed to provide visual explanations for CNNs by combining feature maps from the penultimate layer using learned or gradient-based weights. CAM achieved success in various visual tasks, such as weakly-supervised object detection [11] and semantic segmentation [1, 18], which regards the activation as initial pseudo object labels. CAM can also be applied to ViT. However, it relies on supervisory signals to build the localization ability, thus suffering from the categorical inductive bias." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Self-supervised activation mapping: Recent studies in self-supervised learning (SSL) shows that the capability to perceive fine-grained objects can be obtained from contrastive learning-based pre-training. For example, object locations can be roughly inferred by using MoCo [9] to train a CNN and visualizing activation mapping of the last convolutional layer [32]. A similar capability is also observed from the heads of DINO [6]. Object localization is a natural property learned from SSL. However, as redundancy reduction is not the central goal for SSL, preserving image patches according to the generated activation mapping generally leads to worse performance in downstream tasks." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "22832" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.089, + 0.896, + 0.332 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.339, + 0.897, + 0.41 + ], + "angle": 0, + "content": "Figure 2. LTRP training (left): given an image, LTRP randomly selects a set of visible patches using a high masking ratio (e.g. \\(90\\%\\)). A pre-trained MAE (parameter frozen) is applied to get its reconstruction, i.e., the anchor image. Then, the visible patches (red) are removed one by one with replacement, each time generating a new reconstruction and its semantic density score w.r.t the anchor image. The scores are treated as pseudo labels to train the ranking model using learning to rank. Once trained, the ranking model is preserved and the MAE is discarded. LTRP inference (right): Top-k patches are selected using the trained ranking model and fed into downstream tasks." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.436, + 0.473, + 0.693 + ], + "angle": 0, + "content": "Token reduction: Since the computational complexity of ViT is quadratically linear to the number of tokens [14], reducing tokens, which can be viewed as a special form of image patches by using token-to-patch mapping, is an effective method for efficient ViT. Current studies can be classified into two categories. First, token pruning that discards redundant tokens. It involves retraining a network to dynamically filter tokens [34], using the policy gradient to select patches [31], reducing the number of tokens as inference proceeds [49], etc. Second, token merging that combines similar tokens. It involves leveraging attention scores between the class token and other tokens to gradually merge tokens [24], merging tokens between two subsets with equal size by using similarity of their key vectors from the self-attention layer [2] and others [35, 46]. Typically, the research focus of these methods is on efficient ViT. Unbiased redundancy reduction is rarely considered." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.71, + 0.251, + 0.725 + ], + "angle": 0, + "content": "2.2. Learning to Rank" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Learning to rank (LTR) [26] is a technique widely employed in information retrieval tasks such as search [8] and recommendation [22]. LTR primarily involves three types according to the utilization of document labels: the point-wise method [7, 23], which uses the rank of an individual document as label and formulates the learning as either classification or regression problem; the pair-wise method [3, 4], which utilizes the relative order of two documents as label for learning; and the list-wise method [5, 44], which considers the order relationship among all or a part of documents associated with a given query. Some studies [27, 47] have" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.436, + 0.893, + 0.481 + ], + "angle": 0, + "content": "made meaningful attempts by leveraging learning to rank in computer vision tasks. To our knowledge, it has not been used for image redundancy reduction before." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.481, + 0.895, + 0.603 + ], + "angle": 0, + "content": "LTRP is an application of LTR to image redundancy reduction. The query is the randomly masked image. Each document is associated with a visible patch, and whose pseudo score is the document label. Different from most existing solutions where the label is obtained from manual annotation or human-machine interaction, our label is obtained from an elegantly designed pre-task, thus enabling a novel self-supervised solution as described below." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.616, + 0.593, + 0.631 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.641, + 0.895, + 0.823 + ], + "angle": 0, + "content": "An overview of our learning to rank patches (LTRP) is depicted in Fig. 2. Its core elements can be summarized using two words: infer and rank. Given a pre-trained MAE model and an image with a portion of patches randomly masked, LTRP first infers the semantic density score for each visible patch by quantifying variation between the reconstructions with and without that patch. By repeating this process patch-by-patch, we obtain a series of scores. Then, LTRP ranks these patches by treating their scores as pseudo labels using learning-to-rank algorithms. When the training converges, we use the ranking model to select informative patches and only consider them in downstream tasks." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.832, + 0.63, + 0.848 + ], + "angle": 0, + "content": "3.1. Preliminary" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.895, + 0.903 + ], + "angle": 0, + "content": "MAE [20] learns a robust image representation by first masking a portion of image patches and then recovering the original image, namely the mask-then-prediction task." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.958 + ], + "angle": 0, + "content": "22833" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.091, + 0.47, + 0.152 + ], + "angle": 0, + "content": "Specifically, MAE divides an image \\(I\\) into visible and masked patch sets according to a predefined masking ratio, where the visible set \\(\\mathbf{P}_v = [\\mathbf{p}_1,\\mathbf{p}_2,\\dots ,\\mathbf{p}_n]\\) has \\(n\\) patches. Then, the pre-training target can be written as:" + }, + { + "type": "equation", + "bbox": [ + 0.151, + 0.165, + 0.469, + 0.188 + ], + "angle": 0, + "content": "\\[\n\\underset {\\theta} {m i n} H \\left(\\mathcal {T} \\left(I _ {m}\\right), I _ {m} ^ {R}\\right), I _ {m} ^ {R} = \\mathcal {M} _ {\\theta} \\left(\\mathbf {P} _ {v}\\right) \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.192, + 0.469, + 0.269 + ], + "angle": 0, + "content": "where \\(I_{m}\\), \\(I_{m}^{R}\\) and \\(\\mathcal{M}_{\\theta}\\) denote the masked image, the reconstructed image and MAE parameterized by \\(\\theta\\), respectively, \\(\\mathcal{T}\\) denotes a certain transformation (optional, e.g., HOG [42], normalized pixel values of each masked patch [20], etc.), and \\(H\\) is a distance measurement function." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.277, + 0.362, + 0.291 + ], + "angle": 0, + "content": "3.2. Patch Informativeness Inference" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.299, + 0.469, + 0.419 + ], + "angle": 0, + "content": "To infer the patch informativeness, we adopt a higher masking ratio of \\(90\\%\\) rather than \\(50\\%\\) or \\(75\\%\\) used in previous MAE studies [20, 45]. The reason is twofold. First, it enables reconstructions exhibiting perceptible change even when only one visible patch is further removed. Second, it decreases the likelihood of semantically similar patches being visible simultaneously, which may confuse the model regarding their informativeness." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.42, + 0.469, + 0.571 + ], + "angle": 0, + "content": "Then, we use a pre-trained, parameter-frozen MAE to perform the reconstruction. For an image, the visible set \\(\\mathbf{P}_v\\) is stochastically selected and its reconstruction \\(I_m^R\\), or saying, the anchor image, is obtained, we iteratively remove a visible patch \\(\\mathbf{p}_i \\in \\mathbf{P}_v\\) to obtain \\(\\mathbf{P}_v^i = \\mathbf{P}_v \\backslash \\mathbf{p}_i\\). It can be simply achieved by using masked attention [40]. By reconstructing again, we get \\(I_m^{R_i}\\), the image reconstruction without the \\(i\\)-th visible patch. A similarity-based function \\(\\mathcal{F}\\) runs over the pair \\(< I_m^R, I_m^{R_i}>\\), and the quantitative similarity \\(y_i\\) is calculated by:" + }, + { + "type": "equation", + "bbox": [ + 0.157, + 0.578, + 0.469, + 0.597 + ], + "angle": 0, + "content": "\\[\ny _ {i} = \\mathcal {F} \\left(I _ {m} ^ {R}, I _ {m} ^ {R _ {i}}\\right), I _ {m} ^ {R _ {i}} = \\mathcal {M} _ {\\theta} \\left(\\mathbf {P} _ {v} ^ {i}\\right) \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.603, + 0.469, + 0.739 + ], + "angle": 0, + "content": "We term the inferred result as the semantic density score, as it quantizes the semantic variant between the two reconstructions. We simply use the \\(\\ell_1\\) distance to measure the variant in this paper. By polling all the visible patches one-by-one, we get a pseudo score vector \\(\\mathbf{y} = [y_{1},y_{2},\\dots,y_{n}]\\). Note that the scores are obtained in a self-supervised manner, and Eq. (2) can be regarded as the pre-task to reveal the patch informativeness. In the implementation, the score inference can be parallelized for training acceleration." + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.75, + 0.469, + 0.801 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.811, + 0.468, + 0.825 + ], + "angle": 0, + "content": "Figure 3. Normalized score maps generated by our ranking model." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.848, + 0.25, + 0.863 + ], + "angle": 0, + "content": "3.3. Learning to Rank" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.469, + 0.902 + ], + "angle": 0, + "content": "With pseudo score \\( \\mathbf{y} \\) calculated from Eq. (2), we use learning-to-rank algorithms to train an independent ranking" + }, + { + "type": "image", + "bbox": [ + 0.515, + 0.09, + 0.896, + 0.159 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.514, + 0.159, + 0.896, + 0.229 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.656, + 0.232, + 0.746, + 0.243 + ], + "angle": 0, + "content": "(a) ImageNet-1K" + }, + { + "type": "image", + "bbox": [ + 0.512, + 0.246, + 0.894, + 0.315 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.512, + 0.314, + 0.894, + 0.383 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.664, + 0.387, + 0.743, + 0.397 + ], + "angle": 0, + "content": "(b) MS-COCO" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.41, + 0.892, + 0.48 + ], + "angle": 0, + "content": "Figure 4. Classification results on single-label dataset (upper, ImageNet-1K) and multi-label dataset (bottom, MS-COCO) at different krs. All methods differ only in the patch selection step. Supervised and self-supervised methods are depicted using different colors. LTRP is annotated spots." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.507, + 0.892, + 0.598 + ], + "angle": 0, + "content": "model to rank the patches. Formally, each image-partition instance \\(\\mathbf{x} = < I, \\mathbf{P}_v, \\mathbf{y}>\\) can be viewed as a training sample for the ranking model, which accepts \\(\\mathbf{x}\\) as the input and outputs a vector \\(\\mathbf{s} = [s_1, s_2, \\dots, s_n]\\) containing predicted scores for the patches. Our LTRP utilizes a list-wise loss, ListMLE [44], to train the model as follows." + }, + { + "type": "equation", + "bbox": [ + 0.522, + 0.609, + 0.892, + 0.648 + ], + "angle": 0, + "content": "\\[\nL = - \\log P _ {s} (\\pi), P _ {s} (\\pi) = \\prod_ {i = 1} ^ {n} \\frac {\\exp \\left(s _ {\\pi (i)}\\right)}{\\sum_ {k = i} ^ {n} \\exp \\left(s _ {\\pi (k)}\\right)} \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.892, + 0.824 + ], + "angle": 0, + "content": "where \\(\\pi\\) denotes the descending permutation according to \\(\\mathbf{y}\\), and \\(\\pi(k)\\) is the patch ranked at the \\(k\\)-th position in \\(\\pi\\). The ranking model will optimize towards sorting patches in line with their semantic density scores. Compared with the other two kinds of ranking loss, i.e., point-wise and pairwise losses, the list-wise loss more completely considers the overall relationships among patches. In the implementation, we apply a sparse design to the ranking model, which solely inputs the visible patches instead of the full set. We will verify this design and architecture choice of the ranking model in ablation studies." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Note that each training instance only contains a small portion of visible patches and scores. However, when going through a sufficient number of instances, the ranking model sees all patch locations of an image and learns to judge relative ranks among patches. In other words, the" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "22834" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.152 + ], + "angle": 0, + "content": "ranking model knows how to score all the image patches regarding their informativeness. Consequently, we can solely use the ranking model for image redundancy reduction, as shown in the right part of Fig. 2." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.163, + 0.231, + 0.178 + ], + "angle": 0, + "content": "3.4. Patch Selection" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.186, + 0.473, + 0.489 + ], + "angle": 0, + "content": "With the ranking model, a straightforward way for redundancy reduction is to select the top-k patches. Our observation suggests that the top patches favor object boundaries rather than homogeneous regions (e.g., dog's body in Fig. 1), as shown in Fig. 3. We attribute it to that changes in object boundaries more easily cause semantic shifts in the reconstructed image. However, a small proportion of patches from homogeneous regions are also essential for visual tasks [28]. Thus, we introduce DPC-KNN [15] to capture the representative homogeneous patches. Specifically, to select \\( k \\) informative patches including \\( h \\) (\\( h < k \\)) ones from homogeneous regions, we first select (\\( k - h \\)) patches as described above. Then, we use DPC-KNN to cluster all patches into \\( k \\) groups and select the largest \\( h \\) ones, given that larger groups are more likely to associate with homogeneous regions. For each selected group, we extract one patch that satisfies the following two conditions, i.e., not selected previously and closest to the cluster center in the remaining patches. The two sets of patches constitute the output of our LTRP. We will ablate \\( h \\) in experiments." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.505, + 0.21, + 0.521 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.529, + 0.381, + 0.546 + ], + "angle": 0, + "content": "4.1. Datasets and Experimental Setting" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.553, + 0.473, + 0.855 + ], + "angle": 0, + "content": "Datasets and evaluation metrics. We pre-train our LTRP on ImageNet-1K training set, and then assess it on two scenarios as follows. The first is image-level evaluation. We conduct image classification on ImageNet-1K, a single-label classification dataset, and on MS-COCO [25], a multi-label classification dataset. The classification model is trained only with the patches remained by different methods. Top-1 accuracy and mAP are employed as the evaluation metrics, respectively. The second is patch-level evaluation. It is conducted both on MS-COCO and PASCAL VOC [17] with their object detection labels, MS-COCO and ADE20K [51] with their semantic segmentation labels. In practice, we treat all the labeled bounding boxes or masks as foreground and evaluate their consistency with the retained patches by using IoU, F1-score, recall, and precision. Following EViT [24], IA-RED² [31], etc., we evaluate these methods at different keep ratios (krs). That is, the top-scored \\( kr\\% \\) patches are preserved. Meanwhile, all the ablation experiments are conducted on ImageNet-100, a subset of ImageNet-1K, given hardware resource constraints." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.472, + 0.901 + ], + "angle": 0, + "content": "Model architectures. In LTRP training, we use MAE with ViT-B and choose ViT or CNN (e.g., ResNet50) as our ranking model. In image classification, we utilize ViT-B" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.242 + ], + "angle": 0, + "content": "on ImageNet-1K and MS-COCO, ViT-S on ImageNet-100 as the backbone for model training. They are both initialized from the MAE encoder [20]. Moreover, we add ML-Decoder [37] behind the classification backbone and use Asymmetric loss [36] for multi-label classification. No additional model is required for the patch-level evaluation, as the performance is obtained by comparing the preserved image patches with groundtruth. All experiments are conducted on a server with 8 NVIDIA GTX 3090 GPUs and Intel(R) Xeon(R) Gold 6226R CPU." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.243, + 0.895, + 0.38 + ], + "angle": 0, + "content": "Comparing methods. We compare LTRP with off-the-shelf models from the three classes mentioned previously (see Sec. 2.1). For CAM, we choose Grad-Cam [38] with ViT. For self-supervised methods, we choose MoCo [9] with ResNet50 and DINO [6]. For token reduction, we choose EViT [24], IA-RED² [31], DynamicViT [34], AdaViT [30], DGE [39] and ToMe [2]. For fair assessment, these methods are all trained (supervised) or pre-trained (unsupervised) on ImageNet-1K." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.392, + 0.724, + 0.406 + ], + "angle": 0, + "content": "4.2. Performance Evaluation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.416, + 0.892, + 0.522 + ], + "angle": 0, + "content": "Image-level evaluation. Figure 4a shows the results of different methods at krs 0.7 and 0.5 on single-label classification. The unsupervised and supervised methods are depicted by different colors. LTRP performs better than the self-supervised ones, and slightly worse or on par with state-of-the-art supervised methods. Note that LTRP achieves this without utilizing any supervisory signals." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.523, + 0.892, + 0.689 + ], + "angle": 0, + "content": "We then test LTRP on MS-COCO to validate the performance on multi-label classification. As shown in Fig. 4b, LTRP achieves mAP of \\(82.8\\%\\) and \\(81.8\\%\\) at krs 0.75 and 0.5, respectively. It outperforms the previous best unsupervised methods by \\(1.1\\%\\) and \\(1.4\\%\\), and the state-of-the-art supervised methods by \\(0.7\\%\\) at both krs. Note that these values correspond to clear accuracy gaps, as the performance differences between existing methods are small. Since different methods only differ in the patches selected, these improvements clearly indicate that LTRP enables a fairer and more meaningful redundancy reduction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.69, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Patch-level evaluation. To further validate whether the patches are unbiasedly retained, we focus on the categories not included in ImageNet-1K, i.e., the unseen categories, for which all the methods have not been explicitly told to learn. We first evaluate the methods based on the object detection labels. The performance of different methods on PASCAL VOC and MS-COCO is shown in the first two rows in Fig. 5. Encouragingly, LTRP surpasses all the competitors in all the evaluated metrics at different krs. The significant improvement in precision highlights that patches selected by LTRP are more accurately located in bounding boxes of unseen categories. With the decrease of krs, the precision of many supervised methods goes up slowly or even goes down. It means that these methods tend to not re" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22835" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.089, + 0.268, + 0.192 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.267, + 0.091, + 0.434, + 0.192 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.434, + 0.092, + 0.599, + 0.192 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.599, + 0.092, + 0.767, + 0.192 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.768, + 0.092, + 0.891, + 0.192 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.078, + 0.192, + 0.268, + 0.293 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.268, + 0.192, + 0.434, + 0.293 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.434, + 0.192, + 0.599, + 0.293 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.6, + 0.192, + 0.767, + 0.293 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.767, + 0.192, + 0.891, + 0.293 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.078, + 0.293, + 0.268, + 0.395 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.267, + 0.293, + 0.434, + 0.394 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.434, + 0.293, + 0.599, + 0.394 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.6, + 0.293, + 0.767, + 0.394 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.767, + 0.293, + 0.891, + 0.394 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.075, + 0.405, + 0.893, + 0.448 + ], + "angle": 0, + "content": "Figure 5. Experimental results on object detection and semantic segmentation datasets. For each dataset, we exclude the categories overlapped with ImageNet-1K (learned) and only compute the metrics on the remaining (unseen) categories, which all the methods have not been explicitly told to learn. The results illustrate the merit of LTRP in unbiased image redundancy reduction." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.474, + 0.47, + 0.534 + ], + "angle": 0, + "content": "gard patches from unseen categories as the most important ones, while our LTRP still goes up quickly and successfully avoids this bias. The result implies that LTRP can be well generalized to datasets with quite different categories." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.535, + 0.47, + 0.655 + ], + "angle": 0, + "content": "We then evaluate the methods based on the semantic segmentation labels. The third row in Fig. 5 shows the results on MS-COCO. LTRP also consistently gives the best results and exhibits a noticeable improvement compared to DynamicViT, the second-best method. We observe that the performance gap becomes larger as the kr decreases. It again demonstrates that LTRP preserves semantics corresponding to the unseen categories well." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.666, + 0.188, + 0.68 + ], + "angle": 0, + "content": "4.3. Ablations" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.469, + 0.719 + ], + "angle": 0, + "content": "In Tab. 1, we provide detailed ablation experiments and introduce some empirical observations as follows." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Reconstruction model. Tab. 1a presents LTRP with different MAE as the image reconstruction model. The optimal model is surprisingly the lightweight model MAE-B. Utilizing MAE-B to generate pseudo label boosts the accuracy by \\(0.2\\%\\) compared to larger MAE-L (21 M v.s. 81 M in #params). Moreover, MAE-L with GAN [19] loss can get even better reconstruction, but performs worse at kr 0.5. We observe that reconstructions of large models or utilizing GAN loss have finer low-level semantics such as texture details. It tends to pull these patches that excel in recovering low-level semantics ahead in the ranking, consequently reducing the proportion of patches with high-level semantics." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.474, + 0.793, + 0.489 + ], + "angle": 0, + "content": "This phenomenon causes the accuracy drop." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.49, + 0.893, + 0.656 + ], + "angle": 0, + "content": "Masking ratio. Tab. 1b shows the influence of the ratio of removed patches. The accuracy of an excessively high masking ratio (0.95) drops by \\(0.1\\%\\) compared with baseline. And a lower masking ratio (0.7) does not perform better than the masking ratio of 0.8. We note that extremely high and low masking ratios both result in the issue of plateau in the pseudo score sequence, namely some patches have similar pseudo scores and occupy a continuous position in the ranking sequence. This causes the ranking model to be confused about the right order of these patches. Considering the efficiency issue, LTRP selects a masking ratio of 0.9." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.658, + 0.893, + 0.809 + ], + "angle": 0, + "content": "Ranking model. We investigate the architecture, sparse design and similarity metric of ranking model in Tabs. 1c, 1d and 1h, respectively. We find out that our ranking model is model-agnostic, and even smaller models like ViT-T or ResNet50 can achieve performance similar to the baseline (ViT-S). However, to align with the comparing methods, we select ViT-S. The sparse design excludes the sort-irrelevant patches from the ranking model, it improves accuracy by \\(0.2\\%\\) to \\(0.3\\%\\) across different krs. Moreover, by skipping these patches, we significantly reduce computational costs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Clustering. Tab. 1e presents our investigation of clustering. Interestingly, selecting all patches (with clustering ratio 1) through clustering at the pixel level is not extremely bad compared with our baseline (82.7% v.s. 83.7%). A small subset (e.g., 20%) of patches from homogeneous regions gets an improved LTRP." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "22836" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.082, + 0.089, + 0.329, + 0.158 + ], + "angle": 0, + "content": "
modelkr=0.75kr=0.5
MAE-B84.483.3
MAE-L84.283.2
MAE-L-GAN84.283.0
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ratiospeedupkr=0.75kr=0.5
0.956.4x84.383.2
0.93.1x84.483.3
0.81.5x84.883.6
0.71.0x84.683.4
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metricskr=0.75kr=0.5
l184.483.3
PSNR83.882.5
SSIM83.679.9
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.175, + 0.892, + 0.199 + ], + "angle": 0, + "content": "(a) Reconstruction model. Lightweight MAE per- (b) Masking ratio. A ratio of 0.9 gets a better (c) Distance Metric. The \\(\\ell_1\\) distance is more sim-. forms better. trade-off between speedup and accuracy. ple and effective." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.2, + 0.379, + 0.297 + ], + "angle": 0, + "content": "
modelparamskr=0.75kr=0.5
Mobile-Former[10]3.2M84.383.1
ViT-T5.5M84.583.4
ViT-S22M84.483.3
ResNet5024M84.583.4
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ratiokr=0.75kr=0.5
084.483.3
0.184.783.4
0.284.683.7
0.384.683.6
183.682.7
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losskr=0.75kr=0.5
Regression84.183.0
RankNet82.979.5
ListNet84.182.5
ListMLE84.483.3
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.301, + 0.892, + 0.326 + ], + "angle": 0, + "content": "(d) Ranking Model. All models exhibit similar ac- (e) Clustering ratio. A few patches with homoge- (f) Ranking loss. List-wise methods perform better accuracy. For a fair comparison, we employ ViT-S. Neous regions can improve classification accuracy. than point-wise and pair-wise ranking losses." + }, + { + "type": "table", + "bbox": [ + 0.081, + 0.327, + 0.614, + 0.379 + ], + "angle": 0, + "content": "
phasespeedupkr=0.75kr=0.5inputkr=0.75kr=0.5
encoder184.483.7visible patches84.783.5
decoder1.3x84.483.3all patches84.483.3
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casekr=0.75kr=0.5
pixel (w/o norm)84.483.3
pixel (w norm)81.575.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.382, + 0.89, + 0.407 + ], + "angle": 0, + "content": "(g) Removal phase. Removing visible patches be- (h) Sparse design. Inputting only visible patches(i) Reconstruction target. LTRP favors MIM fore the decoder well balances accuracy and speed. into the ranking model yields better results. models based on raw pixels." + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.418, + 0.893, + 0.449 + ], + "angle": 0, + "content": "Table 1. LTRP ablation experiments on ImageNet-100. We report accuracy (%) results for krs 0.75 and 0.5, respectively. The selected configurations are marked in gray." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.475, + 0.469, + 0.656 + ], + "angle": 0, + "content": "Ranking loss. Tab. 1f studies the choice of ranking loss. Interestingly, the point-wise approach also has decent performance in our LTRP. Compared to ListMLE, its accuracy drops by only \\(0.3\\%\\) at both krs. Point-wise methods train \\(\\langle\\) query, document \\(\\rangle\\) pair independently, ignoring the relationship among documents. In contrast, our ranking model considers all documents (patches), i.e., \\(\\langle\\) query, documents \\(\\rangle\\), enabling the acquisition of holistic knowledge. For pair-wise methods, the accuracy drops obviously at krs of 0.75 and 0.5 (82.9 v.s. 84.4 and 79.5 v.s. 83.3, respectively). Overall, ListMLE performs the best and is also the most appropriate method for utilizing our pseudo-labels." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.658, + 0.47, + 0.748 + ], + "angle": 0, + "content": "Removal phase. In Tab. 1g, although the results of removing visible patches before the lightweight decoder show a decrease in performance compared to the approach of removing before the encoder (a reduction of \\(0.4\\%\\) at kr 0.5), we can achieve a noteworthy \\(1.3\\mathrm{x}\\) speedup in terms of FLOPs (7.07G vs. 5.38G). So we employ the former." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Reconstruction target. Pre-patch normalization is a trick that normalizes a patch using the mean and standard deviation of its pixels. In Tab. 1i, we observe that utilizing pre-trained MAE based on pre-patch normalization for generating pseudo-labels performs exceedingly poorly, which is \\(7.6\\%\\) worse than using unnormalized pixels. We suspect this drop partially because LTRP requires quantifying the global semantic changes between two images. Conversely, pre-patch normalization appears to reducing global coherence, as it focuses on enhancing the contrast locally [20]." + }, + { + "type": "image", + "bbox": [ + 0.502, + 0.473, + 0.891, + 0.629 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.639, + 0.892, + 0.682 + ], + "angle": 0, + "content": "Figure 6. Normalized score maps generated by LTRP on validation set of ImageNet-1K (top) and MS-COCO (bottom). Only the top-scored 64 patches are displayed." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.709, + 0.714, + 0.724 + ], + "angle": 0, + "content": "4.4. LTRP for Efficient ViT" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.734, + 0.892, + 0.779 + ], + "angle": 0, + "content": "LTRP allows the classification model to be trained only on a subset of image patches. We verify whether this LTRP-based classification would be more efficient for ViT." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.893, + 0.901 + ], + "angle": 0, + "content": "We elucidate this issue from both inference and training perspectives. For inference, time for both patch ranking and classification should be counted. As shown in Tab. 1d, even ViT-T has commendable performance. So we choose small ranking model and large classification model as LTRP-based solutions. Table 2 enumerates several combinations on ImageNet-1K at kr 0.75. Using ViT-T as the ranking model shows \\(1.19 \\times\\), \\(1.36 \\times\\), or \\(1.33 \\times\\) acceleration on GPU" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22837" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.081, + 0.089, + 0.478, + 0.203 + ], + "angle": 0, + "content": "
cls.rankingparamsFLOPs ↓inference speed↑top-1 acc.
modelmodel(M)(G)GPUim/sCPUim/s
ViT-B-8617.61095.14.383.3†)
ViT-S108(+25.6%)13.1(-25.6%)1034.9(-5.5%)4.1(-4.7%)83.2(-0.1%)
ViT-T91.5(+6.4%)13.1(-25.6%)1302.2(+18.9%)5.1(+18.6%)83.1(-0.2%)
ViT-L-30761.62357.71.385.8†)
ViT-S329(+7.2%)46.0(-25.3%)445.6(+24.6%)1.5(+15.4%)85.7(-0.1%)
ViT-T312.5(+1.8%)45.9(-25.5%)485.5(+35.8%)1.7(+23.1%)85.6(-0.2%)
ViT-H-632167.4140.00.586.6†)
ViT-S654(+3.5%)124.8(-25.4%)181.0(+29.3%)0.6(+20.0%)86.3(-0.3%)
ViT-T637.5(+0.9%)124.7(-25.5%)185.8(+32.7%)0.6(+20.0%)86.1(-0.5%)
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.213, + 0.47, + 0.312 + ], + "angle": 0, + "content": "Table 2. Experiments on efficient ViT on ImageNet-1K at kr 0.75. Different combinations of the ranking and classification (cls.) models show different balances between FLOPs (or inference speed) and accuracy. \" -\" means do not incorporate the ranking model and select all patches. \\( \\dagger \\) means run by us. When using ViT-T as the ranking model, LTRP accelerates the inference ranging from 18.9% to 32.7% with accuracy sacrifice of 0.1%-0.5%." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.338, + 0.47, + 0.565 + ], + "angle": 0, + "content": "over the scheme that directly uses ViT-B, ViT-L or ViT-H as the classification model, respectively (ViT-H uses a \\(16^{*}16\\) patch grid while ViT-B and ViT-L use \\(14^{*}14\\)). Meanwhile, the accuracy drops only range from \\(0.2\\%\\) to \\(0.5\\%\\). The results imply that LTRP-based ones are more appropriate choices in scenarios requiring both efficiency and accuracy. With the popularity of large visual and multi-modal models, large ViT models are more frequently utilized and we believe that these solutions would receive more attention. While for training, LTRP-based solutions include running the ranking model once for patch selection and training the classification model \\(N\\) epochs. The cost raised by the ranking model would be negligible as \\(N\\) increases. Meanwhile, training the classification model would also be accelerated by nearly \\(1 / kr^2 \\times\\) as fewer patches are involved." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.565, + 0.47, + 0.626 + ], + "angle": 0, + "content": "In sum, compared with the vanilla classification, LTRP-based solutions not only accelerate training but also can improve the inference speed up to over \\(30\\%\\) on GPU with a possible neglectable accuracy degradation." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.636, + 0.214, + 0.65 + ], + "angle": 0, + "content": "4.5. Visualization" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.659, + 0.47, + 0.824 + ], + "angle": 0, + "content": "Figure 6 displays the informativeness-aware capability of LTRP on ImageNet-1k and MS-COCO. LTRP well identifies patches located in meaningful object regions in ImageNet-1K images. Meanwhile, it also shows superior unbiasedness in selecting multiple objects from MS-COCO images. We also visualize a process of hierarchical patch selection in Fig. 7. With the decrease of retained patches, less important patches are gradually removed. LTRP is consistent in favour of patches located on semantic objects. This removal process is mostly in line with human perception. The results again demonstrate the effectiveness of LTRP." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.47, + 0.902 + ], + "angle": 0, + "content": "To explore why LTRP performs better than popular self-supervised methods, we plot the average attention distance of each head of DINO and our LTRP ranking model (both are ViT-S) in Fig. 8. A more scattered distance distribution is observed for LTRP especially in the last few layers. As" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.089, + 0.892, + 0.201 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.212, + 0.894, + 0.254 + ], + "angle": 0, + "content": "Figure 7. Hierarchical redundancy reduction process of LTRP on MS-COCO validation set. Keep ratios are shown in the top left of each image. Patches with green boxes are the retained ones." + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.267, + 0.703, + 0.383 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.576, + 0.385, + 0.629, + 0.397 + ], + "angle": 0, + "content": "(a) DINO" + }, + { + "type": "image", + "bbox": [ + 0.705, + 0.268, + 0.902, + 0.383 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.776, + 0.385, + 0.828, + 0.397 + ], + "angle": 0, + "content": "(b) LTRP" + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.41, + 0.892, + 0.437 + ], + "angle": 0, + "content": "Figure 8. Average attention distances organized according to layer and head for DINO and our LTRP ranking model." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.464, + 0.892, + 0.51 + ], + "angle": 0, + "content": "stated in [43], such a distribution suggests that more diverse representation learning is achieved, which explains in part the superiority of LTRP." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.523, + 0.619, + 0.538 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.548, + 0.892, + 0.835 + ], + "angle": 0, + "content": "We have introduced LTRP, the first self-supervised method for image redundancy reduction. By leveraging the characteristic of self-supervised learning to create patch-level pseudo labels, and then learning to rank patches, LTRP elegantly eliminates the issue of categorical inductive bias commonly observed in leading supervised methods. Extensive experiments on different datasets and tasks basically validate our proposal. LTRP achieves competitive accuracy in single-label classification and obviously better accuracy in multi-label classification. Meanwhile, the retained patches align more closely with object detection and semantic segmentation labels, especially for categories not explicitly learned by supervised methods. In addition, incorporating LTRP into image classification can lead to a notable speedup in inference with neglectable accuracy degradation if applied appropriately. These results convincingly indicate the effectiveness of LTRP and its unbiased patch selection. We hope that LTRP will provide valuable insights into image redundancy reduction and related visual tasks." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.835, + 0.892, + 0.896 + ], + "angle": 0, + "content": "Acknowledgement This work was supported by National Science and Technology Major Project (No. 2021ZD0112805) and in part by National Natural Science Foundation of China (No. 62372170, 62172103)." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "22838" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.176, + 0.107 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Jiwoon Ahn and Suha Kwak. Learning pixel-level semantic affinity with image-level supervision for weakly supervised semantic segmentation. 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In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 633-641, 2017. 5" + }, + { + "type": "list", + "bbox": [ + 0.504, + 0.093, + 0.892, + 0.895 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.52, + 0.957 + ], + "angle": 0, + "content": "22840" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_origin.pdf b/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..b02118c14fe5effb6edd169b579bafa29d840834 --- /dev/null +++ b/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/77fab6af-6f9d-408d-9dae-8e7bad3bdc39_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:9f4ca0e6d036a36589faa86283b9e0b8fb598fe699d7a2850c4fa1a31a286fed +size 9423111 diff --git a/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/full.md b/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/full.md new file mode 100644 index 0000000000000000000000000000000000000000..c7b01d035e551d387561f79b1068300e64022b5a --- /dev/null +++ b/2024/Learning to Rank Patches for Unbiased Image Redundancy Reduction/full.md @@ -0,0 +1,356 @@ +# Learning to Rank Patches for Unbiased Image Redundancy Reduction + +Yang Luo $^{1}$ , Zhineng Chen $^{1*}$ , Peng Zhou $^{2}$ , Zuxuan Wu $^{1}$ , Xieping Gao $^{3}$ , Yu-Gang Jiang $^{1}$ + +$^{1}$ School of Computer Science, Shanghai Collaborative Innovation Center of Intelligent Visual Computing, Fudan University $^{2}$ University of Maryland, College Park + +3College of Information Science and Engineering, Hunan Normal University + +yangluo21@m.fudan.edu.cn, {zhinchen, zxwu, ygj}@fudan.edu.cn, + +pengzhou@terpmail.umd.edu, xpgao@hunnu.edu.cn + +# Abstract + +Images suffer from heavy spatial redundancy because pixels in neighboring regions are spatially correlated. Existing approaches strive to overcome this limitation by reducing less meaningful image regions. However, current leading methods rely on supervisory signals. They may compel models to preserve content that aligns with labeled categories and discard content belonging to unlabeled categories. This categorical inductive bias makes these methods less effective in real-world scenarios. To address this issue, we propose a self-supervised framework for image redundancy reduction called Learning to Rank Patches (LTRP). We observe that image reconstruction of masked image modeling models is sensitive to the removal of visible patches when the masking ratio is high (e.g., $90\%$ ). Building upon it, we implement LTRP via two steps: inferring the semantic density score of each patch by quantifying variation between reconstructions with and without this patch, and learning to rank the patches with the pseudo score. The entire process is self-supervised, thus getting out of the dilemma of categorical inductive bias. We design extensive experiments on different datasets and tasks. The results demonstrate that LTRP outperforms both supervised and other self-supervised methods due to the fair assessment of image content. Code is available at https://github.com/irsLu/Ltrp. + +# 1. Introduction + +Image redundancy reduction refers to discarding the less informative regions of an image while preserving its essential semantics. It is a fundamental task in computer vision as compact image representation is an attractive property in various applications, especially in the era of vision Trans- + +![](images/cc7f177cbb2b172dd9736a89a11ff8e3a91bf0306cd667382d82864819d9f72c.jpg) +Raw + +![](images/aa830ec1c56bec54179acb8c5ccf433a09bba38a91d7e82e433ff21109e3c228.jpg) +Supervised methods + +![](images/e115dc84a354da98de4443a6af9c1c7103270624446ad6774e329256ddf3ff72.jpg) + +![](images/ff7688372f68bfd1c414960af8719abc78e085992e25ae87dbcd1626ea7b2815.jpg) + +![](images/d216f63f11f16abe1bbb5f0cc6aebcef180821d92bd2cd286010920a646bd184.jpg) +LTRP + +![](images/e9a7464254b3f7bf2e6e513a0a421e29bc76b92f55bcda8f19c504610ba86073.jpg) +Raw + +![](images/9319321b15675a10f5ef52378b614c24fcc309a643a5011fedbf1bd16cf76eed.jpg) + +![](images/bef06b8d9668daa8e3b6e2d0266c14cb9f2165a87cd3b3c128a059733239e1c8.jpg) + +![](images/a73ad731af3a49398f2e9e5aa2dd112cc773a7958dec0b81c43907566b493eab.jpg) + +![](images/5015b864785f7e029350ef9e0b954c07f9a26dfc355c109e2b3a24a9df721326.jpg) +GT +Reconstructions + +![](images/73d729ebff224e214e5013aec90d550c1d7b781833fd54227a4c00c4bc3c7e01.jpg) +Informative patches + +![](images/1fd5930e074c18e7e730abf4426bdaacf8d5e5aa36dcaf03f508d8b1422b4740.jpg) + +![](images/4f48b668b0e1beb5a465f84a1da0b550c14d059c163ef40ef10d989280e13bc6.jpg) +Visible patches Removed patch +Figure 1. Redundancy reduction (upper): given an image, LTRP selects informative patches regardless of whether they are from the categories already learned. While for supervised methods (from left to right: GFNet [41], Grad-CAM [38] using ViT, EViT [24]) the preserved patches are mostly located on the learned category. Patch removing (bottom): an image and its reconstructions using MAE [20] with different sets of visible patches, columns 3-5 denote that the red patch is removed from the visible set. They generate reconstructions with different levels of semantic shift, e.g., without the dog tail, eyes, etc. + +former (ViT) [14, 29]. The computational complexity of ViT grows quadratically with the number of image patches, making patch-level image redundancy reduction gaining increasing attention. + +Current leading methods [12, 31, 41, 48] generally require supervised learning to endow the model with the capability to recognize informative image patches. Specifically, the model is simultaneously trained to estimate the patch's informativeness and classify the image to the right category. Thus, the learning process tends to select image patches that are less likely to degrade the classification accuracy, leading to categorical inductive bias. The bias may cause the model to remove image patches containing mean + +ingful semantics that do not belong to the learned category. As shown in the upper of Fig. 1, supervised methods trained based on ImageNet-1K tend to select informative patches located on train, a category learned. While considering patches on unseen categories like traffic light as redundant and removing them. Note that such categorical inductive bias is unavoidable for models trained based on famous image datasets [13, 17, 25], which typically annotate one or a few categories for each image. On the other hand, activation mapping of popular unsupervised pre-training methods [6, 32] also reveal the informativeness of image patches to some extent. Nevertheless, they are less effective as the pretraining is not targeted for redundancy reduction. + +Recently, masked autoencoder (MAE) [20] has gained increasing attention due to its great representative learning capability. Given an image with a portion of patches randomly masked, MAE learns the feature representation by reconstructing the masked patches. It can generate a reconstruction with meaningful semantics by using a small subset (e.g., $25\%$ ) of visible patches. We observe that when the masking ratio is high (e.g., $90\%$ ), further removing a visible patch may cause an obvious semantic shift in the reconstructed image. As shown in the bottom of Fig. 1, if the only visible patch on the dog's tail is masked, the reconstruction will not have the tail. Conversely, masking a patch on the dog's body does not induce perceptible semantic alteration. The result suggests that the informativeness of patches can be revealed from such an unsupervised perspective. + +Motivated by this observation, we propose learning to rank patches (LTRP), a self-supervised framework to fairly reduce image redundancy. It firstly leverages a pre-trained MAE to generate a pseudo score for each visible patch by quantifying the semantic difference between reconstructions with and without that patch. A larger pseudo score indicates that the patch has a greater impact on the quality of the reconstructed image and is thus more valuable. Therefore, LTRP utilizes another ranking model to learn to rank the visible patches according to the pseudo scores, which successfully learns this scoring property. After pretraining, by ranking the patches descendingly according to their scores and keeping the top ones, LTRP can remain valuable patches for the subsequent downstream tasks like classification. As shown in the top right image of Fig. 1, patches containing meaningful semantics are unbiasedly preserved under the same keep ratio. + +We conduct extensive experiments to validate the unbiasedness of LTRP in image redundancy reduction. For image classification at different keep ratios, LTRP not only achieves competitive accuracy compared to current leading methods in single-label classification, but also outperforms them by a clear margin in multi-label classification. When inspecting categories not included in ImageNet-1K, patches remained by LTRP are also more consistent with object de + +tection and semantic segmentation labels, getting superior performance in all the evaluated metrics. Moreover, if a small ranking model is employed, we observe that an approximate linear speedup with the keep ratio is coincidentally obtained for image classification, which constitutes a promising solution for efficient ViT. Contributions of this paper are summarized as follows: + +- We propose to treat the image redundancy reduction as a self-supervised patch-level ranking problem. It eliminates the reliance on supervisory signals, expanding the means to reduce image redundancy. +- We develop LTRP. It quantifies the variation between MAE-reconstructed images to create pseudo labels, then learns to rank these patches. It offers an elegant way to avoid categorical inductive bias. +- Extensive quantitative and qualitative evaluations demonstrate that LTRP can fairly and effectively score the learned and unseen categories, and provide highly competitive solutions for efficient ViT. + +# 2. Related Work + +# 2.1. Image Redundancy Reduction + +While sharing similarities with tasks like salient object detection [16, 21] and image compression [33], image redundancy reduction has been studied mainly in the era of deep learning. Some CNN-based methods explored this task for inference efficiency [12, 41, 48]. Meanwhile, ViT models have been implicitly endowed with the redundancy reduction capability. Based on how this capability is built, we can broadly categorize existing studies into three classes. + +Class activation mapping (CAM): Starting from a label, CAM [38, 50] was proposed to provide visual explanations for CNNs by combining feature maps from the penultimate layer using learned or gradient-based weights. CAM achieved success in various visual tasks, such as weakly-supervised object detection [11] and semantic segmentation [1, 18], which regards the activation as initial pseudo object labels. CAM can also be applied to ViT. However, it relies on supervisory signals to build the localization ability, thus suffering from the categorical inductive bias. + +Self-supervised activation mapping: Recent studies in self-supervised learning (SSL) shows that the capability to perceive fine-grained objects can be obtained from contrastive learning-based pre-training. For example, object locations can be roughly inferred by using MoCo [9] to train a CNN and visualizing activation mapping of the last convolutional layer [32]. A similar capability is also observed from the heads of DINO [6]. Object localization is a natural property learned from SSL. However, as redundancy reduction is not the central goal for SSL, preserving image patches according to the generated activation mapping generally leads to worse performance in downstream tasks. + +![](images/27b023579174f525a77584ff2856ba5034867ca0592d8de86b3f5ffac7f80797.jpg) +Figure 2. LTRP training (left): given an image, LTRP randomly selects a set of visible patches using a high masking ratio (e.g. $90\%$ ). A pre-trained MAE (parameter frozen) is applied to get its reconstruction, i.e., the anchor image. Then, the visible patches (red) are removed one by one with replacement, each time generating a new reconstruction and its semantic density score w.r.t the anchor image. The scores are treated as pseudo labels to train the ranking model using learning to rank. Once trained, the ranking model is preserved and the MAE is discarded. LTRP inference (right): Top-k patches are selected using the trained ranking model and fed into downstream tasks. + +Token reduction: Since the computational complexity of ViT is quadratically linear to the number of tokens [14], reducing tokens, which can be viewed as a special form of image patches by using token-to-patch mapping, is an effective method for efficient ViT. Current studies can be classified into two categories. First, token pruning that discards redundant tokens. It involves retraining a network to dynamically filter tokens [34], using the policy gradient to select patches [31], reducing the number of tokens as inference proceeds [49], etc. Second, token merging that combines similar tokens. It involves leveraging attention scores between the class token and other tokens to gradually merge tokens [24], merging tokens between two subsets with equal size by using similarity of their key vectors from the self-attention layer [2] and others [35, 46]. Typically, the research focus of these methods is on efficient ViT. Unbiased redundancy reduction is rarely considered. + +# 2.2. Learning to Rank + +Learning to rank (LTR) [26] is a technique widely employed in information retrieval tasks such as search [8] and recommendation [22]. LTR primarily involves three types according to the utilization of document labels: the point-wise method [7, 23], which uses the rank of an individual document as label and formulates the learning as either classification or regression problem; the pair-wise method [3, 4], which utilizes the relative order of two documents as label for learning; and the list-wise method [5, 44], which considers the order relationship among all or a part of documents associated with a given query. Some studies [27, 47] have + +made meaningful attempts by leveraging learning to rank in computer vision tasks. To our knowledge, it has not been used for image redundancy reduction before. + +LTRP is an application of LTR to image redundancy reduction. The query is the randomly masked image. Each document is associated with a visible patch, and whose pseudo score is the document label. Different from most existing solutions where the label is obtained from manual annotation or human-machine interaction, our label is obtained from an elegantly designed pre-task, thus enabling a novel self-supervised solution as described below. + +# 3. Method + +An overview of our learning to rank patches (LTRP) is depicted in Fig. 2. Its core elements can be summarized using two words: infer and rank. Given a pre-trained MAE model and an image with a portion of patches randomly masked, LTRP first infers the semantic density score for each visible patch by quantifying variation between the reconstructions with and without that patch. By repeating this process patch-by-patch, we obtain a series of scores. Then, LTRP ranks these patches by treating their scores as pseudo labels using learning-to-rank algorithms. When the training converges, we use the ranking model to select informative patches and only consider them in downstream tasks. + +# 3.1. Preliminary + +MAE [20] learns a robust image representation by first masking a portion of image patches and then recovering the original image, namely the mask-then-prediction task. + +Specifically, MAE divides an image $I$ into visible and masked patch sets according to a predefined masking ratio, where the visible set $\mathbf{P}_v = [\mathbf{p}_1,\mathbf{p}_2,\dots ,\mathbf{p}_n]$ has $n$ patches. Then, the pre-training target can be written as: + +$$ +\underset {\theta} {m i n} H \left(\mathcal {T} \left(I _ {m}\right), I _ {m} ^ {R}\right), I _ {m} ^ {R} = \mathcal {M} _ {\theta} \left(\mathbf {P} _ {v}\right) \tag {1} +$$ + +where $I_{m}$ , $I_{m}^{R}$ and $\mathcal{M}_{\theta}$ denote the masked image, the reconstructed image and MAE parameterized by $\theta$ , respectively, $\mathcal{T}$ denotes a certain transformation (optional, e.g., HOG [42], normalized pixel values of each masked patch [20], etc.), and $H$ is a distance measurement function. + +# 3.2. Patch Informativeness Inference + +To infer the patch informativeness, we adopt a higher masking ratio of $90\%$ rather than $50\%$ or $75\%$ used in previous MAE studies [20, 45]. The reason is twofold. First, it enables reconstructions exhibiting perceptible change even when only one visible patch is further removed. Second, it decreases the likelihood of semantically similar patches being visible simultaneously, which may confuse the model regarding their informativeness. + +Then, we use a pre-trained, parameter-frozen MAE to perform the reconstruction. For an image, the visible set $\mathbf{P}_v$ is stochastically selected and its reconstruction $I_m^R$ , or saying, the anchor image, is obtained, we iteratively remove a visible patch $\mathbf{p}_i \in \mathbf{P}_v$ to obtain $\mathbf{P}_v^i = \mathbf{P}_v \backslash \mathbf{p}_i$ . It can be simply achieved by using masked attention [40]. By reconstructing again, we get $I_m^{R_i}$ , the image reconstruction without the $i$ -th visible patch. A similarity-based function $\mathcal{F}$ runs over the pair $< I_m^R, I_m^{R_i}>$ , and the quantitative similarity $y_i$ is calculated by: + +$$ +y _ {i} = \mathcal {F} \left(I _ {m} ^ {R}, I _ {m} ^ {R _ {i}}\right), I _ {m} ^ {R _ {i}} = \mathcal {M} _ {\theta} \left(\mathbf {P} _ {v} ^ {i}\right) \tag {2} +$$ + +We term the inferred result as the semantic density score, as it quantizes the semantic variant between the two reconstructions. We simply use the $\ell_1$ distance to measure the variant in this paper. By polling all the visible patches one-by-one, we get a pseudo score vector $\mathbf{y} = [y_{1},y_{2},\dots,y_{n}]$ . Note that the scores are obtained in a self-supervised manner, and Eq. (2) can be regarded as the pre-task to reveal the patch informativeness. In the implementation, the score inference can be parallelized for training acceleration. + +![](images/784f3d05bfc960f5d16523359ee519d83a46f5e69b14a22d2ed5be5c01d5ceec.jpg) +Figure 3. Normalized score maps generated by our ranking model. + +# 3.3. Learning to Rank + +With pseudo score $\mathbf{y}$ calculated from Eq. (2), we use learning-to-rank algorithms to train an independent ranking + +![](images/4a999c08b22e2ce14d1d3220d9df87793564058a86d07688e9b1dea2cc9a038c.jpg) + +![](images/f58c70da7335490aba639f8a0f9aaba2a5e09265bcabae5b003860101ed83a82.jpg) +(a) ImageNet-1K + +![](images/5df1d1f581f6aae0d249ba98fca7e86618bd156aa2525d4c55b8cf5be746b7da.jpg) + +![](images/6e27cc947b493cff1a109acd267345f2327f89388668f072fcdebac9bd8fdb92.jpg) +(b) MS-COCO +Figure 4. Classification results on single-label dataset (upper, ImageNet-1K) and multi-label dataset (bottom, MS-COCO) at different krs. All methods differ only in the patch selection step. Supervised and self-supervised methods are depicted using different colors. LTRP is annotated spots. + +model to rank the patches. Formally, each image-partition instance $\mathbf{x} = < I, \mathbf{P}_v, \mathbf{y}>$ can be viewed as a training sample for the ranking model, which accepts $\mathbf{x}$ as the input and outputs a vector $\mathbf{s} = [s_1, s_2, \dots, s_n]$ containing predicted scores for the patches. Our LTRP utilizes a list-wise loss, ListMLE [44], to train the model as follows. + +$$ +L = - \log P _ {s} (\pi), P _ {s} (\pi) = \prod_ {i = 1} ^ {n} \frac {\exp \left(s _ {\pi (i)}\right)}{\sum_ {k = i} ^ {n} \exp \left(s _ {\pi (k)}\right)} \tag {3} +$$ + +where $\pi$ denotes the descending permutation according to $\mathbf{y}$ , and $\pi(k)$ is the patch ranked at the $k$ -th position in $\pi$ . The ranking model will optimize towards sorting patches in line with their semantic density scores. Compared with the other two kinds of ranking loss, i.e., point-wise and pairwise losses, the list-wise loss more completely considers the overall relationships among patches. In the implementation, we apply a sparse design to the ranking model, which solely inputs the visible patches instead of the full set. We will verify this design and architecture choice of the ranking model in ablation studies. + +Note that each training instance only contains a small portion of visible patches and scores. However, when going through a sufficient number of instances, the ranking model sees all patch locations of an image and learns to judge relative ranks among patches. In other words, the + +ranking model knows how to score all the image patches regarding their informativeness. Consequently, we can solely use the ranking model for image redundancy reduction, as shown in the right part of Fig. 2. + +# 3.4. Patch Selection + +With the ranking model, a straightforward way for redundancy reduction is to select the top-k patches. Our observation suggests that the top patches favor object boundaries rather than homogeneous regions (e.g., dog's body in Fig. 1), as shown in Fig. 3. We attribute it to that changes in object boundaries more easily cause semantic shifts in the reconstructed image. However, a small proportion of patches from homogeneous regions are also essential for visual tasks [28]. Thus, we introduce DPC-KNN [15] to capture the representative homogeneous patches. Specifically, to select $k$ informative patches including $h$ ( $h < k$ ) ones from homogeneous regions, we first select ( $k - h$ ) patches as described above. Then, we use DPC-KNN to cluster all patches into $k$ groups and select the largest $h$ ones, given that larger groups are more likely to associate with homogeneous regions. For each selected group, we extract one patch that satisfies the following two conditions, i.e., not selected previously and closest to the cluster center in the remaining patches. The two sets of patches constitute the output of our LTRP. We will ablate $h$ in experiments. + +# 4. Experiments + +# 4.1. Datasets and Experimental Setting + +Datasets and evaluation metrics. We pre-train our LTRP on ImageNet-1K training set, and then assess it on two scenarios as follows. The first is image-level evaluation. We conduct image classification on ImageNet-1K, a single-label classification dataset, and on MS-COCO [25], a multi-label classification dataset. The classification model is trained only with the patches remained by different methods. Top-1 accuracy and mAP are employed as the evaluation metrics, respectively. The second is patch-level evaluation. It is conducted both on MS-COCO and PASCAL VOC [17] with their object detection labels, MS-COCO and ADE20K [51] with their semantic segmentation labels. In practice, we treat all the labeled bounding boxes or masks as foreground and evaluate their consistency with the retained patches by using IoU, F1-score, recall, and precision. Following EViT [24], IA-RED² [31], etc., we evaluate these methods at different keep ratios (krs). That is, the top-scored $kr\%$ patches are preserved. Meanwhile, all the ablation experiments are conducted on ImageNet-100, a subset of ImageNet-1K, given hardware resource constraints. + +Model architectures. In LTRP training, we use MAE with ViT-B and choose ViT or CNN (e.g., ResNet50) as our ranking model. In image classification, we utilize ViT-B + +on ImageNet-1K and MS-COCO, ViT-S on ImageNet-100 as the backbone for model training. They are both initialized from the MAE encoder [20]. Moreover, we add ML-Decoder [37] behind the classification backbone and use Asymmetric loss [36] for multi-label classification. No additional model is required for the patch-level evaluation, as the performance is obtained by comparing the preserved image patches with groundtruth. All experiments are conducted on a server with 8 NVIDIA GTX 3090 GPUs and Intel(R) Xeon(R) Gold 6226R CPU. + +Comparing methods. We compare LTRP with off-the-shelf models from the three classes mentioned previously (see Sec. 2.1). For CAM, we choose Grad-Cam [38] with ViT. For self-supervised methods, we choose MoCo [9] with ResNet50 and DINO [6]. For token reduction, we choose EViT [24], IA-RED² [31], DynamicViT [34], AdaViT [30], DGE [39] and ToMe [2]. For fair assessment, these methods are all trained (supervised) or pre-trained (unsupervised) on ImageNet-1K. + +# 4.2. Performance Evaluation + +Image-level evaluation. Figure 4a shows the results of different methods at krs 0.7 and 0.5 on single-label classification. The unsupervised and supervised methods are depicted by different colors. LTRP performs better than the self-supervised ones, and slightly worse or on par with state-of-the-art supervised methods. Note that LTRP achieves this without utilizing any supervisory signals. + +We then test LTRP on MS-COCO to validate the performance on multi-label classification. As shown in Fig. 4b, LTRP achieves mAP of $82.8\%$ and $81.8\%$ at krs 0.75 and 0.5, respectively. It outperforms the previous best unsupervised methods by $1.1\%$ and $1.4\%$ , and the state-of-the-art supervised methods by $0.7\%$ at both krs. Note that these values correspond to clear accuracy gaps, as the performance differences between existing methods are small. Since different methods only differ in the patches selected, these improvements clearly indicate that LTRP enables a fairer and more meaningful redundancy reduction. + +Patch-level evaluation. To further validate whether the patches are unbiasedly retained, we focus on the categories not included in ImageNet-1K, i.e., the unseen categories, for which all the methods have not been explicitly told to learn. We first evaluate the methods based on the object detection labels. The performance of different methods on PASCAL VOC and MS-COCO is shown in the first two rows in Fig. 5. Encouragingly, LTRP surpasses all the competitors in all the evaluated metrics at different krs. The significant improvement in precision highlights that patches selected by LTRP are more accurately located in bounding boxes of unseen categories. With the decrease of krs, the precision of many supervised methods goes up slowly or even goes down. It means that these methods tend to not re + +![](images/855366435cf33482b20712a82b4ea872bd8931c06bb3967d137f77cd3f8907a7.jpg) + +![](images/92d4b77bacf6055da56ba783a62eb4a1a7792dece09f65744ee7fd1021cf2a44.jpg) + +![](images/2620ba49e9b019898bde0c189fabf89424a47991fd0488bfdbc984e5eff1b4cc.jpg) + +![](images/0435d5689d68a11fa6a4909e1181d96079fc2dc12e4ee86468f7e9ff4befb44b.jpg) + +![](images/6359b3a76b2e4dc3208816c89f047785b5f4b1a48ca850cd02d1afa1aef644dd.jpg) + +![](images/a79a21e54b4c90ddf07b93cb0925c0e0393f0a0b437fdc138b86613966bd00a1.jpg) + +![](images/dc8c3d2bc4cabe11ed8ddcd2ac2848e7132a6fc295d306e6afa663aed767e03c.jpg) + +![](images/c7a5d3a598b1427454d01c9593ca5182473a1eb3a2c0156492a97469b2d10f2f.jpg) + +![](images/f5ddddacfba783912fd92e74fc8d1e707c1f4c42f7926c7f679d99287a3ce0ba.jpg) + +![](images/7e33fa4360c519970acbaabae2dc9351be8cf41dba32c2c1f393cd041a94ef06.jpg) + +![](images/c1e1116ace9fd00d5da7f944b6f3ef30adb00875e42b26760f92586d1e54d75d.jpg) +Figure 5. Experimental results on object detection and semantic segmentation datasets. For each dataset, we exclude the categories overlapped with ImageNet-1K (learned) and only compute the metrics on the remaining (unseen) categories, which all the methods have not been explicitly told to learn. The results illustrate the merit of LTRP in unbiased image redundancy reduction. + +![](images/def713ee8d0d51ffec6dd3eb00dd25977a0b3a594948d75d81039c35c6e30066.jpg) + +![](images/6853659c7988379ade631d4bfb2b215b54d4874f4bf9668fdef17d24e9f773bf.jpg) + +![](images/0ad60c5c962ea57f7ffa6fafb6bddcc9b149b45e44081f3ff13d975ad432e402.jpg) + +![](images/6e62819db20a6ad2b5122bfd2eb175c5b2b703c8449c54825da06ef6c7e89cec.jpg) + +gard patches from unseen categories as the most important ones, while our LTRP still goes up quickly and successfully avoids this bias. The result implies that LTRP can be well generalized to datasets with quite different categories. + +We then evaluate the methods based on the semantic segmentation labels. The third row in Fig. 5 shows the results on MS-COCO. LTRP also consistently gives the best results and exhibits a noticeable improvement compared to DynamicViT, the second-best method. We observe that the performance gap becomes larger as the kr decreases. It again demonstrates that LTRP preserves semantics corresponding to the unseen categories well. + +# 4.3. Ablations + +In Tab. 1, we provide detailed ablation experiments and introduce some empirical observations as follows. + +Reconstruction model. Tab. 1a presents LTRP with different MAE as the image reconstruction model. The optimal model is surprisingly the lightweight model MAE-B. Utilizing MAE-B to generate pseudo label boosts the accuracy by $0.2\%$ compared to larger MAE-L (21 M v.s. 81 M in #params). Moreover, MAE-L with GAN [19] loss can get even better reconstruction, but performs worse at kr 0.5. We observe that reconstructions of large models or utilizing GAN loss have finer low-level semantics such as texture details. It tends to pull these patches that excel in recovering low-level semantics ahead in the ranking, consequently reducing the proportion of patches with high-level semantics. + +This phenomenon causes the accuracy drop. + +Masking ratio. Tab. 1b shows the influence of the ratio of removed patches. The accuracy of an excessively high masking ratio (0.95) drops by $0.1\%$ compared with baseline. And a lower masking ratio (0.7) does not perform better than the masking ratio of 0.8. We note that extremely high and low masking ratios both result in the issue of plateau in the pseudo score sequence, namely some patches have similar pseudo scores and occupy a continuous position in the ranking sequence. This causes the ranking model to be confused about the right order of these patches. Considering the efficiency issue, LTRP selects a masking ratio of 0.9. + +Ranking model. We investigate the architecture, sparse design and similarity metric of ranking model in Tabs. 1c, 1d and 1h, respectively. We find out that our ranking model is model-agnostic, and even smaller models like ViT-T or ResNet50 can achieve performance similar to the baseline (ViT-S). However, to align with the comparing methods, we select ViT-S. The sparse design excludes the sort-irrelevant patches from the ranking model, it improves accuracy by $0.2\%$ to $0.3\%$ across different krs. Moreover, by skipping these patches, we significantly reduce computational costs. + +Clustering. Tab. 1e presents our investigation of clustering. Interestingly, selecting all patches (with clustering ratio 1) through clustering at the pixel level is not extremely bad compared with our baseline (82.7% v.s. 83.7%). A small subset (e.g., 20%) of patches from homogeneous regions gets an improved LTRP. + +
modelkr=0.75kr=0.5
MAE-B84.483.3
MAE-L84.283.2
MAE-L-GAN84.283.0
+ +
ratiospeedupkr=0.75kr=0.5
0.956.4x84.383.2
0.93.1x84.483.3
0.81.5x84.883.6
0.71.0x84.683.4
+ +
metricskr=0.75kr=0.5
l184.483.3
PSNR83.882.5
SSIM83.679.9
+ +(a) Reconstruction model. Lightweight MAE per- (b) Masking ratio. A ratio of 0.9 gets a better (c) Distance Metric. The $\ell_1$ distance is more sim-. forms better. trade-off between speedup and accuracy. ple and effective. + +
modelparamskr=0.75kr=0.5
Mobile-Former[10]3.2M84.383.1
ViT-T5.5M84.583.4
ViT-S22M84.483.3
ResNet5024M84.583.4
+ +
ratiokr=0.75kr=0.5
084.483.3
0.184.783.4
0.284.683.7
0.384.683.6
183.682.7
+ +
losskr=0.75kr=0.5
Regression84.183.0
RankNet82.979.5
ListNet84.182.5
ListMLE84.483.3
+ +(d) Ranking Model. All models exhibit similar ac- (e) Clustering ratio. A few patches with homoge- (f) Ranking loss. List-wise methods perform better accuracy. For a fair comparison, we employ ViT-S. Neous regions can improve classification accuracy. than point-wise and pair-wise ranking losses. + +
phasespeedupkr=0.75kr=0.5inputkr=0.75kr=0.5
encoder184.483.7visible patches84.783.5
decoder1.3x84.483.3all patches84.483.3
+ +
casekr=0.75kr=0.5
pixel (w/o norm)84.483.3
pixel (w norm)81.575.7
+ +(g) Removal phase. Removing visible patches be- (h) Sparse design. Inputting only visible patches(i) Reconstruction target. LTRP favors MIM fore the decoder well balances accuracy and speed. into the ranking model yields better results. models based on raw pixels. + +Table 1. LTRP ablation experiments on ImageNet-100. We report accuracy (%) results for krs 0.75 and 0.5, respectively. The selected configurations are marked in gray. + +Ranking loss. Tab. 1f studies the choice of ranking loss. Interestingly, the point-wise approach also has decent performance in our LTRP. Compared to ListMLE, its accuracy drops by only $0.3\%$ at both krs. Point-wise methods train $\langle$ query, document $\rangle$ pair independently, ignoring the relationship among documents. In contrast, our ranking model considers all documents (patches), i.e., $\langle$ query, documents $\rangle$ , enabling the acquisition of holistic knowledge. For pair-wise methods, the accuracy drops obviously at krs of 0.75 and 0.5 (82.9 v.s. 84.4 and 79.5 v.s. 83.3, respectively). Overall, ListMLE performs the best and is also the most appropriate method for utilizing our pseudo-labels. + +Removal phase. In Tab. 1g, although the results of removing visible patches before the lightweight decoder show a decrease in performance compared to the approach of removing before the encoder (a reduction of $0.4\%$ at kr 0.5), we can achieve a noteworthy $1.3\mathrm{x}$ speedup in terms of FLOPs (7.07G vs. 5.38G). So we employ the former. + +Reconstruction target. Pre-patch normalization is a trick that normalizes a patch using the mean and standard deviation of its pixels. In Tab. 1i, we observe that utilizing pre-trained MAE based on pre-patch normalization for generating pseudo-labels performs exceedingly poorly, which is $7.6\%$ worse than using unnormalized pixels. We suspect this drop partially because LTRP requires quantifying the global semantic changes between two images. Conversely, pre-patch normalization appears to reducing global coherence, as it focuses on enhancing the contrast locally [20]. + +![](images/03f366993b1132d7447c5e268635e2c2013fdc8b0da1e5fa7ef755e7ee2369dd.jpg) +Figure 6. Normalized score maps generated by LTRP on validation set of ImageNet-1K (top) and MS-COCO (bottom). Only the top-scored 64 patches are displayed. + +# 4.4. LTRP for Efficient ViT + +LTRP allows the classification model to be trained only on a subset of image patches. We verify whether this LTRP-based classification would be more efficient for ViT. + +We elucidate this issue from both inference and training perspectives. For inference, time for both patch ranking and classification should be counted. As shown in Tab. 1d, even ViT-T has commendable performance. So we choose small ranking model and large classification model as LTRP-based solutions. Table 2 enumerates several combinations on ImageNet-1K at kr 0.75. Using ViT-T as the ranking model shows $1.19 \times$ , $1.36 \times$ , or $1.33 \times$ acceleration on GPU + +
cls.rankingparamsFLOPs ↓inference speed↑top-1 acc.
modelmodel(M)(G)GPUim/sCPUim/s
ViT-B-8617.61095.14.383.3†)
ViT-S108(+25.6%)13.1(-25.6%)1034.9(-5.5%)4.1(-4.7%)83.2(-0.1%)
ViT-T91.5(+6.4%)13.1(-25.6%)1302.2(+18.9%)5.1(+18.6%)83.1(-0.2%)
ViT-L-30761.62357.71.385.8†)
ViT-S329(+7.2%)46.0(-25.3%)445.6(+24.6%)1.5(+15.4%)85.7(-0.1%)
ViT-T312.5(+1.8%)45.9(-25.5%)485.5(+35.8%)1.7(+23.1%)85.6(-0.2%)
ViT-H-632167.4140.00.586.6†)
ViT-S654(+3.5%)124.8(-25.4%)181.0(+29.3%)0.6(+20.0%)86.3(-0.3%)
ViT-T637.5(+0.9%)124.7(-25.5%)185.8(+32.7%)0.6(+20.0%)86.1(-0.5%)
+ +Table 2. Experiments on efficient ViT on ImageNet-1K at kr 0.75. Different combinations of the ranking and classification (cls.) models show different balances between FLOPs (or inference speed) and accuracy. " -" means do not incorporate the ranking model and select all patches. $\dagger$ means run by us. When using ViT-T as the ranking model, LTRP accelerates the inference ranging from 18.9% to 32.7% with accuracy sacrifice of 0.1%-0.5%. + +over the scheme that directly uses ViT-B, ViT-L or ViT-H as the classification model, respectively (ViT-H uses a $16^{*}16$ patch grid while ViT-B and ViT-L use $14^{*}14$ ). Meanwhile, the accuracy drops only range from $0.2\%$ to $0.5\%$ . The results imply that LTRP-based ones are more appropriate choices in scenarios requiring both efficiency and accuracy. With the popularity of large visual and multi-modal models, large ViT models are more frequently utilized and we believe that these solutions would receive more attention. While for training, LTRP-based solutions include running the ranking model once for patch selection and training the classification model $N$ epochs. The cost raised by the ranking model would be negligible as $N$ increases. Meanwhile, training the classification model would also be accelerated by nearly $1 / kr^2 \times$ as fewer patches are involved. + +In sum, compared with the vanilla classification, LTRP-based solutions not only accelerate training but also can improve the inference speed up to over $30\%$ on GPU with a possible neglectable accuracy degradation. + +# 4.5. Visualization + +Figure 6 displays the informativeness-aware capability of LTRP on ImageNet-1k and MS-COCO. LTRP well identifies patches located in meaningful object regions in ImageNet-1K images. Meanwhile, it also shows superior unbiasedness in selecting multiple objects from MS-COCO images. We also visualize a process of hierarchical patch selection in Fig. 7. With the decrease of retained patches, less important patches are gradually removed. LTRP is consistent in favour of patches located on semantic objects. This removal process is mostly in line with human perception. The results again demonstrate the effectiveness of LTRP. + +To explore why LTRP performs better than popular self-supervised methods, we plot the average attention distance of each head of DINO and our LTRP ranking model (both are ViT-S) in Fig. 8. A more scattered distance distribution is observed for LTRP especially in the last few layers. As + +![](images/f97448d905d1b63f82adb7939fda10769c77e97931f60fdcff73d4b6152177f6.jpg) +Figure 7. Hierarchical redundancy reduction process of LTRP on MS-COCO validation set. Keep ratios are shown in the top left of each image. Patches with green boxes are the retained ones. + +![](images/355021130e366950b6c77bf725886ac0af15a566d61db9306b99c4ccc2869dc6.jpg) +(a) DINO + +![](images/d8c4cd701bd5a4cbfe8c954cbf8a1d3ad460a470cd8255c1133d986a7083f6e6.jpg) +(b) LTRP +Figure 8. Average attention distances organized according to layer and head for DINO and our LTRP ranking model. + +stated in [43], such a distribution suggests that more diverse representation learning is achieved, which explains in part the superiority of LTRP. + +# 5. Conclusion + +We have introduced LTRP, the first self-supervised method for image redundancy reduction. By leveraging the characteristic of self-supervised learning to create patch-level pseudo labels, and then learning to rank patches, LTRP elegantly eliminates the issue of categorical inductive bias commonly observed in leading supervised methods. Extensive experiments on different datasets and tasks basically validate our proposal. LTRP achieves competitive accuracy in single-label classification and obviously better accuracy in multi-label classification. Meanwhile, the retained patches align more closely with object detection and semantic segmentation labels, especially for categories not explicitly learned by supervised methods. In addition, incorporating LTRP into image classification can lead to a notable speedup in inference with neglectable accuracy degradation if applied appropriately. These results convincingly indicate the effectiveness of LTRP and its unbiased patch selection. We hope that LTRP will provide valuable insights into image redundancy reduction and related visual tasks. + +Acknowledgement This work was supported by National Science and Technology Major Project (No. 2021ZD0112805) and in part by National Natural Science Foundation of China (No. 62372170, 62172103). + +# References + +[1] Jiwoon Ahn and Suha Kwak. 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Redundancy reduction (upper): given an image, LTRP selects informative patches regardless of whether they are from the categories already learned. While for supervised methods (from left to right: GFNet [41], Grad-CAM [38] using ViT, EViT [24]) the preserved patches are mostly located on the learned category. Patch removing (bottom): an image and its reconstructions using MAE [20] with different sets of visible patches, columns 3-5 denote that the red patch is removed from the visible set. They generate reconstructions with different levels of semantic shift, e.g., without the dog tail, eyes, etc." + } + ] + } + ], + "index": 33, + "angle": 0, + "type": "image_caption" + } + ], + "index": 31 + }, + { + "bbox": [ + 304, + 554, + 545, + 602 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 554, + 545, + 602 + ], + "spans": [ + { + "bbox": [ + 304, + 554, + 545, + 602 + ], + "type": "text", + "content": "former (ViT) [14, 29]. The computational complexity of ViT grows quadratically with the number of image patches, making patch-level image redundancy reduction gaining increasing attention." + } + ] + } + ], + "index": 34 + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": "Current leading methods [12, 31, 41, 48] generally require supervised learning to endow the model with the capability to recognize informative image patches. Specifically, the model is simultaneously trained to estimate the patch's informativeness and classify the image to the right category. Thus, the learning process tends to select image patches that are less likely to degrade the classification accuracy, leading to categorical inductive bias. The bias may cause the model to remove image patches containing mean" + } + ] + } + ], + "index": 35 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 184, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 184, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 184, + 712 + ], + "type": "text", + "content": "*Corresponding author: Zhineng Chen" + } + ] + } + ], + "index": 36 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22831" + } + ] + } + ], + "index": 37 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": "ingful semantics that do not belong to the learned category. As shown in the upper of Fig. 1, supervised methods trained based on ImageNet-1K tend to select informative patches located on train, a category learned. While considering patches on unseen categories like traffic light as redundant and removing them. Note that such categorical inductive bias is unavoidable for models trained based on famous image datasets [13, 17, 25], which typically annotate one or a few categories for each image. On the other hand, activation mapping of popular unsupervised pre-training methods [6, 32] also reveal the informativeness of image patches to some extent. Nevertheless, they are less effective as the pretraining is not targeted for redundancy reduction." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 229, + 289, + 410 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 229, + 289, + 410 + ], + "spans": [ + { + "bbox": [ + 46, + 229, + 289, + 410 + ], + "type": "text", + "content": "Recently, masked autoencoder (MAE) [20] has gained increasing attention due to its great representative learning capability. Given an image with a portion of patches randomly masked, MAE learns the feature representation by reconstructing the masked patches. It can generate a reconstruction with meaningful semantics by using a small subset (e.g., " + }, + { + "bbox": [ + 46, + 229, + 289, + 410 + ], + "type": "inline_equation", + "content": "25\\%" + }, + { + "bbox": [ + 46, + 229, + 289, + 410 + ], + "type": "text", + "content": ") of visible patches. We observe that when the masking ratio is high (e.g., " + }, + { + "bbox": [ + 46, + 229, + 289, + 410 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 46, + 229, + 289, + 410 + ], + "type": "text", + "content": "), further removing a visible patch may cause an obvious semantic shift in the reconstructed image. As shown in the bottom of Fig. 1, if the only visible patch on the dog's tail is masked, the reconstruction will not have the tail. Conversely, masking a patch on the dog's body does not induce perceptible semantic alteration. The result suggests that the informativeness of patches can be revealed from such an unsupervised perspective." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 411, + 289, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 411, + 289, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 411, + 289, + 616 + ], + "type": "text", + "content": "Motivated by this observation, we propose learning to rank patches (LTRP), a self-supervised framework to fairly reduce image redundancy. It firstly leverages a pre-trained MAE to generate a pseudo score for each visible patch by quantifying the semantic difference between reconstructions with and without that patch. A larger pseudo score indicates that the patch has a greater impact on the quality of the reconstructed image and is thus more valuable. Therefore, LTRP utilizes another ranking model to learn to rank the visible patches according to the pseudo scores, which successfully learns this scoring property. After pretraining, by ranking the patches descendingly according to their scores and keeping the top ones, LTRP can remain valuable patches for the subsequent downstream tasks like classification. As shown in the top right image of Fig. 1, patches containing meaningful semantics are unbiasedly preserved under the same keep ratio." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "content": "We conduct extensive experiments to validate the unbiasedness of LTRP in image redundancy reduction. For image classification at different keep ratios, LTRP not only achieves competitive accuracy compared to current leading methods in single-label classification, but also outperforms them by a clear margin in multi-label classification. When inspecting categories not included in ImageNet-1K, patches remained by LTRP are also more consistent with object de" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 156 + ], + "type": "text", + "content": "tection and semantic segmentation labels, getting superior performance in all the evaluated metrics. Moreover, if a small ranking model is employed, we observe that an approximate linear speedup with the keep ratio is coincidentally obtained for image classification, which constitutes a promising solution for efficient ViT. Contributions of this paper are summarized as follows:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 159, + 547, + 301 + ], + "type": "list", + "angle": 0, + "index": 8, + "blocks": [ + { + "bbox": [ + 306, + 159, + 547, + 206 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 159, + 547, + 206 + ], + "spans": [ + { + "bbox": [ + 306, + 159, + 547, + 206 + ], + "type": "text", + "content": "- We propose to treat the image redundancy reduction as a self-supervised patch-level ranking problem. It eliminates the reliance on supervisory signals, expanding the means to reduce image redundancy." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 206, + 547, + 253 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 206, + 547, + 253 + ], + "spans": [ + { + "bbox": [ + 306, + 206, + 547, + 253 + ], + "type": "text", + "content": "- We develop LTRP. It quantifies the variation between MAE-reconstructed images to create pseudo labels, then learns to rank these patches. It offers an elegant way to avoid categorical inductive bias." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 255, + 547, + 301 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 255, + 547, + 301 + ], + "spans": [ + { + "bbox": [ + 306, + 255, + 547, + 301 + ], + "type": "text", + "content": "- Extensive quantitative and qualitative evaluations demonstrate that LTRP can fairly and effectively score the learned and unseen categories, and provide highly competitive solutions for efficient ViT." + } + ] + } + ], + "index": 7 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 316, + 392, + 328 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 316, + 392, + 328 + ], + "spans": [ + { + "bbox": [ + 306, + 316, + 392, + 328 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 335, + 471, + 348 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 335, + 471, + 348 + ], + "spans": [ + { + "bbox": [ + 306, + 335, + 471, + 348 + ], + "type": "text", + "content": "2.1. Image Redundancy Reduction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 354, + 547, + 450 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 354, + 547, + 450 + ], + "spans": [ + { + "bbox": [ + 304, + 354, + 547, + 450 + ], + "type": "text", + "content": "While sharing similarities with tasks like salient object detection [16, 21] and image compression [33], image redundancy reduction has been studied mainly in the era of deep learning. Some CNN-based methods explored this task for inference efficiency [12, 41, 48]. Meanwhile, ViT models have been implicitly endowed with the redundancy reduction capability. Based on how this capability is built, we can broadly categorize existing studies into three classes." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 450, + 547, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 450, + 547, + 569 + ], + "spans": [ + { + "bbox": [ + 304, + 450, + 547, + 569 + ], + "type": "text", + "content": "Class activation mapping (CAM): Starting from a label, CAM [38, 50] was proposed to provide visual explanations for CNNs by combining feature maps from the penultimate layer using learned or gradient-based weights. CAM achieved success in various visual tasks, such as weakly-supervised object detection [11] and semantic segmentation [1, 18], which regards the activation as initial pseudo object labels. CAM can also be applied to ViT. However, it relies on supervisory signals to build the localization ability, thus suffering from the categorical inductive bias." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": "Self-supervised activation mapping: Recent studies in self-supervised learning (SSL) shows that the capability to perceive fine-grained objects can be obtained from contrastive learning-based pre-training. For example, object locations can be roughly inferred by using MoCo [9] to train a CNN and visualizing activation mapping of the last convolutional layer [32]. A similar capability is also observed from the heads of DINO [6]. Object localization is a natural property learned from SSL. However, as redundancy reduction is not the central goal for SSL, preserving image patches according to the generated activation mapping generally leads to worse performance in downstream tasks." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "22832" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 70, + 548, + 262 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 548, + 262 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 548, + 262 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 548, + 262 + ], + "type": "image", + "image_path": "27b023579174f525a77584ff2856ba5034867ca0592d8de86b3f5ffac7f80797.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 268, + 548, + 324 + ], + "lines": [ + { + "bbox": [ + 46, + 268, + 548, + 324 + ], + "spans": [ + { + "bbox": [ + 46, + 268, + 548, + 324 + ], + "type": "text", + "content": "Figure 2. LTRP training (left): given an image, LTRP randomly selects a set of visible patches using a high masking ratio (e.g. " + }, + { + "bbox": [ + 46, + 268, + 548, + 324 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 46, + 268, + 548, + 324 + ], + "type": "text", + "content": "). A pre-trained MAE (parameter frozen) is applied to get its reconstruction, i.e., the anchor image. Then, the visible patches (red) are removed one by one with replacement, each time generating a new reconstruction and its semantic density score w.r.t the anchor image. The scores are treated as pseudo labels to train the ranking model using learning to rank. Once trained, the ranking model is preserved and the MAE is discarded. LTRP inference (right): Top-k patches are selected using the trained ranking model and fed into downstream tasks." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 345, + 289, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 345, + 289, + 548 + ], + "spans": [ + { + "bbox": [ + 46, + 345, + 289, + 548 + ], + "type": "text", + "content": "Token reduction: Since the computational complexity of ViT is quadratically linear to the number of tokens [14], reducing tokens, which can be viewed as a special form of image patches by using token-to-patch mapping, is an effective method for efficient ViT. Current studies can be classified into two categories. First, token pruning that discards redundant tokens. It involves retraining a network to dynamically filter tokens [34], using the policy gradient to select patches [31], reducing the number of tokens as inference proceeds [49], etc. Second, token merging that combines similar tokens. It involves leveraging attention scores between the class token and other tokens to gradually merge tokens [24], merging tokens between two subsets with equal size by using similarity of their key vectors from the self-attention layer [2] and others [35, 46]. Typically, the research focus of these methods is on efficient ViT. Unbiased redundancy reduction is rarely considered." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 562, + 153, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 562, + 153, + 574 + ], + "spans": [ + { + "bbox": [ + 47, + 562, + 153, + 574 + ], + "type": "text", + "content": "2.2. Learning to Rank" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "content": "Learning to rank (LTR) [26] is a technique widely employed in information retrieval tasks such as search [8] and recommendation [22]. LTR primarily involves three types according to the utilization of document labels: the point-wise method [7, 23], which uses the rank of an individual document as label and formulates the learning as either classification or regression problem; the pair-wise method [3, 4], which utilizes the relative order of two documents as label for learning; and the list-wise method [5, 44], which considers the order relationship among all or a part of documents associated with a given query. Some studies [27, 47] have" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 345, + 546, + 380 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 345, + 546, + 380 + ], + "spans": [ + { + "bbox": [ + 304, + 345, + 546, + 380 + ], + "type": "text", + "content": "made meaningful attempts by leveraging learning to rank in computer vision tasks. To our knowledge, it has not been used for image redundancy reduction before." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 380, + 547, + 477 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 380, + 547, + 477 + ], + "spans": [ + { + "bbox": [ + 304, + 380, + 547, + 477 + ], + "type": "text", + "content": "LTRP is an application of LTR to image redundancy reduction. The query is the randomly masked image. Each document is associated with a visible patch, and whose pseudo score is the document label. Different from most existing solutions where the label is obtained from manual annotation or human-machine interaction, our label is obtained from an elegantly designed pre-task, thus enabling a novel self-supervised solution as described below." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 487, + 362, + 499 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 487, + 362, + 499 + ], + "spans": [ + { + "bbox": [ + 306, + 487, + 362, + 499 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 507, + 547, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 507, + 547, + 651 + ], + "spans": [ + { + "bbox": [ + 304, + 507, + 547, + 651 + ], + "type": "text", + "content": "An overview of our learning to rank patches (LTRP) is depicted in Fig. 2. Its core elements can be summarized using two words: infer and rank. Given a pre-trained MAE model and an image with a portion of patches randomly masked, LTRP first infers the semantic density score for each visible patch by quantifying variation between the reconstructions with and without that patch. By repeating this process patch-by-patch, we obtain a series of scores. Then, LTRP ranks these patches by treating their scores as pseudo labels using learning-to-rank algorithms. When the training converges, we use the ranking model to select informative patches and only consider them in downstream tasks." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 658, + 385, + 671 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 658, + 385, + 671 + ], + "spans": [ + { + "bbox": [ + 306, + 658, + 385, + 671 + ], + "type": "text", + "content": "3.1. Preliminary" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": "MAE [20] learns a robust image representation by first masking a portion of image patches and then recovering the original image, namely the mask-then-prediction task." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "text", + "content": "22833" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": "Specifically, MAE divides an image " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": " into visible and masked patch sets according to a predefined masking ratio, where the visible set " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_v = [\\mathbf{p}_1,\\mathbf{p}_2,\\dots ,\\mathbf{p}_n]" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": " has " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": " patches. Then, the pre-training target can be written as:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 92, + 130, + 287, + 148 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 92, + 130, + 287, + 148 + ], + "spans": [ + { + "bbox": [ + 92, + 130, + 287, + 148 + ], + "type": "interline_equation", + "content": "\\underset {\\theta} {m i n} H \\left(\\mathcal {T} \\left(I _ {m}\\right), I _ {m} ^ {R}\\right), I _ {m} ^ {R} = \\mathcal {M} _ {\\theta} \\left(\\mathbf {P} _ {v}\\right) \\tag {1}", + "image_path": "57c8ab6f74f681567c122c259cb8b45fd4ad236405c1d95defecdd915d2b682a.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "spans": [ + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "inline_equation", + "content": "I_{m}" + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "inline_equation", + "content": "I_{m}^{R}" + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "inline_equation", + "content": "\\mathcal{M}_{\\theta}" + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "text", + "content": " denote the masked image, the reconstructed image and MAE parameterized by " + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "text", + "content": ", respectively, " + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "text", + "content": " denotes a certain transformation (optional, e.g., HOG [42], normalized pixel values of each masked patch [20], etc.), and " + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "inline_equation", + "content": "H" + }, + { + "bbox": [ + 47, + 152, + 287, + 213 + ], + "type": "text", + "content": " is a distance measurement function." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 219, + 221, + 230 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 219, + 221, + 230 + ], + "spans": [ + { + "bbox": [ + 47, + 219, + 221, + 230 + ], + "type": "text", + "content": "3.2. Patch Informativeness Inference" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "spans": [ + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "type": "text", + "content": "To infer the patch informativeness, we adopt a higher masking ratio of " + }, + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "type": "text", + "content": " rather than " + }, + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "type": "inline_equation", + "content": "50\\%" + }, + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "type": "text", + "content": " or " + }, + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "type": "inline_equation", + "content": "75\\%" + }, + { + "bbox": [ + 46, + 236, + 287, + 331 + ], + "type": "text", + "content": " used in previous MAE studies [20, 45]. The reason is twofold. First, it enables reconstructions exhibiting perceptible change even when only one visible patch is further removed. Second, it decreases the likelihood of semantically similar patches being visible simultaneously, which may confuse the model regarding their informativeness." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "spans": [ + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": "Then, we use a pre-trained, parameter-frozen MAE to perform the reconstruction. For an image, the visible set " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_v" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": " is stochastically selected and its reconstruction " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "I_m^R" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": ", or saying, the anchor image, is obtained, we iteratively remove a visible patch " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_i \\in \\mathbf{P}_v" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": " to obtain " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "\\mathbf{P}_v^i = \\mathbf{P}_v \\backslash \\mathbf{p}_i" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": ". It can be simply achieved by using masked attention [40]. By reconstructing again, we get " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "I_m^{R_i}" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": ", the image reconstruction without the " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": "-th visible patch. A similarity-based function " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "\\mathcal{F}" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": " runs over the pair " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "< I_m^R, I_m^{R_i}>" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": ", and the quantitative similarity " + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "inline_equation", + "content": "y_i" + }, + { + "bbox": [ + 46, + 332, + 287, + 452 + ], + "type": "text", + "content": " is calculated by:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 96, + 457, + 287, + 472 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 96, + 457, + 287, + 472 + ], + "spans": [ + { + "bbox": [ + 96, + 457, + 287, + 472 + ], + "type": "interline_equation", + "content": "y _ {i} = \\mathcal {F} \\left(I _ {m} ^ {R}, I _ {m} ^ {R _ {i}}\\right), I _ {m} ^ {R _ {i}} = \\mathcal {M} _ {\\theta} \\left(\\mathbf {P} _ {v} ^ {i}\\right) \\tag {2}", + "image_path": "6bb4233c85844c8c1f513a806fda556e9b163241af8bd61036b83d9ad7e725a1.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 477, + 287, + 585 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 477, + 287, + 585 + ], + "spans": [ + { + "bbox": [ + 46, + 477, + 287, + 585 + ], + "type": "text", + "content": "We term the inferred result as the semantic density score, as it quantizes the semantic variant between the two reconstructions. We simply use the " + }, + { + "bbox": [ + 46, + 477, + 287, + 585 + ], + "type": "inline_equation", + "content": "\\ell_1" + }, + { + "bbox": [ + 46, + 477, + 287, + 585 + ], + "type": "text", + "content": " distance to measure the variant in this paper. By polling all the visible patches one-by-one, we get a pseudo score vector " + }, + { + "bbox": [ + 46, + 477, + 287, + 585 + ], + "type": "inline_equation", + "content": "\\mathbf{y} = [y_{1},y_{2},\\dots,y_{n}]" + }, + { + "bbox": [ + 46, + 477, + 287, + 585 + ], + "type": "text", + "content": ". Note that the scores are obtained in a self-supervised manner, and Eq. (2) can be regarded as the pre-task to reveal the patch informativeness. In the implementation, the score inference can be parallelized for training acceleration." + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 48, + 594, + 287, + 634 + ], + "blocks": [ + { + "bbox": [ + 48, + 594, + 287, + 634 + ], + "lines": [ + { + "bbox": [ + 48, + 594, + 287, + 634 + ], + "spans": [ + { + "bbox": [ + 48, + 594, + 287, + 634 + ], + "type": "image", + "image_path": "784f3d05bfc960f5d16523359ee519d83a46f5e69b14a22d2ed5be5c01d5ceec.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 642, + 286, + 653 + ], + "lines": [ + { + "bbox": [ + 47, + 642, + 286, + 653 + ], + "spans": [ + { + "bbox": [ + 47, + 642, + 286, + 653 + ], + "type": "text", + "content": "Figure 3. Normalized score maps generated by our ranking model." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 671, + 153, + 683 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 671, + 153, + 683 + ], + "spans": [ + { + "bbox": [ + 47, + 671, + 153, + 683 + ], + "type": "text", + "content": "3.3. Learning to Rank" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": "With pseudo score " + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": " calculated from Eq. (2), we use learning-to-rank algorithms to train an independent ranking" + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 315, + 71, + 548, + 125 + ], + "blocks": [ + { + "bbox": [ + 315, + 71, + 548, + 125 + ], + "lines": [ + { + "bbox": [ + 315, + 71, + 548, + 125 + ], + "spans": [ + { + "bbox": [ + 315, + 71, + 548, + 125 + ], + "type": "image", + "image_path": "4a999c08b22e2ce14d1d3220d9df87793564058a86d07688e9b1dea2cc9a038c.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 314, + 125, + 548, + 181 + ], + "blocks": [ + { + "bbox": [ + 314, + 125, + 548, + 181 + ], + "lines": [ + { + "bbox": [ + 314, + 125, + 548, + 181 + ], + "spans": [ + { + "bbox": [ + 314, + 125, + 548, + 181 + ], + "type": "image", + "image_path": "f58c70da7335490aba639f8a0f9aaba2a5e09265bcabae5b003860101ed83a82.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 401, + 183, + 456, + 192 + ], + "lines": [ + { + "bbox": [ + 401, + 183, + 456, + 192 + ], + "spans": [ + { + "bbox": [ + 401, + 183, + 456, + 192 + ], + "type": "text", + "content": "(a) ImageNet-1K" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 313, + 194, + 547, + 249 + ], + "blocks": [ + { + "bbox": [ + 313, + 194, + 547, + 249 + ], + "lines": [ + { + "bbox": [ + 313, + 194, + 547, + 249 + ], + "spans": [ + { + "bbox": [ + 313, + 194, + 547, + 249 + ], + "type": "image", + "image_path": "5df1d1f581f6aae0d249ba98fca7e86618bd156aa2525d4c55b8cf5be746b7da.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + } + ], + "index": 15 + }, + { + "type": "image", + "bbox": [ + 313, + 248, + 547, + 303 + ], + "blocks": [ + { + "bbox": [ + 313, + 248, + 547, + 303 + ], + "lines": [ + { + "bbox": [ + 313, + 248, + 547, + 303 + ], + "spans": [ + { + "bbox": [ + 313, + 248, + 547, + 303 + ], + "type": "image", + "image_path": "6e27cc947b493cff1a109acd267345f2327f89388668f072fcdebac9bd8fdb92.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 406, + 306, + 454, + 314 + ], + "lines": [ + { + "bbox": [ + 406, + 306, + 454, + 314 + ], + "spans": [ + { + "bbox": [ + 406, + 306, + 454, + 314 + ], + "type": "text", + "content": "(b) MS-COCO" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 305, + 324, + 545, + 380 + ], + "lines": [ + { + "bbox": [ + 305, + 324, + 545, + 380 + ], + "spans": [ + { + "bbox": [ + 305, + 324, + 545, + 380 + ], + "type": "text", + "content": "Figure 4. Classification results on single-label dataset (upper, ImageNet-1K) and multi-label dataset (bottom, MS-COCO) at different krs. All methods differ only in the patch selection step. Supervised and self-supervised methods are depicted using different colors. LTRP is annotated spots." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_caption" + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "spans": [ + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "type": "text", + "content": "model to rank the patches. Formally, each image-partition instance " + }, + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "type": "inline_equation", + "content": "\\mathbf{x} = < I, \\mathbf{P}_v, \\mathbf{y}>" + }, + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "type": "text", + "content": " can be viewed as a training sample for the ranking model, which accepts " + }, + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "type": "text", + "content": " as the input and outputs a vector " + }, + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "type": "inline_equation", + "content": "\\mathbf{s} = [s_1, s_2, \\dots, s_n]" + }, + { + "bbox": [ + 305, + 401, + 545, + 473 + ], + "type": "text", + "content": " containing predicted scores for the patches. Our LTRP utilizes a list-wise loss, ListMLE [44], to train the model as follows." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 319, + 482, + 545, + 513 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 319, + 482, + 545, + 513 + ], + "spans": [ + { + "bbox": [ + 319, + 482, + 545, + 513 + ], + "type": "interline_equation", + "content": "L = - \\log P _ {s} (\\pi), P _ {s} (\\pi) = \\prod_ {i = 1} ^ {n} \\frac {\\exp \\left(s _ {\\pi (i)}\\right)}{\\sum_ {k = i} ^ {n} \\exp \\left(s _ {\\pi (k)}\\right)} \\tag {3}", + "image_path": "3175d52d8aac91b58a3423e87163c28408615909a81ee160c569df371304f860.jpg" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "inline_equation", + "content": "\\pi" + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "text", + "content": " denotes the descending permutation according to " + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "inline_equation", + "content": "\\mathbf{y}" + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "inline_equation", + "content": "\\pi(k)" + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "text", + "content": " is the patch ranked at the " + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "text", + "content": "-th position in " + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "inline_equation", + "content": "\\pi" + }, + { + "bbox": [ + 304, + 521, + 545, + 652 + ], + "type": "text", + "content": ". The ranking model will optimize towards sorting patches in line with their semantic density scores. Compared with the other two kinds of ranking loss, i.e., point-wise and pairwise losses, the list-wise loss more completely considers the overall relationships among patches. In the implementation, we apply a sparse design to the ranking model, which solely inputs the visible patches instead of the full set. We will verify this design and architecture choice of the ranking model in ablation studies." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": "Note that each training instance only contains a small portion of visible patches and scores. However, when going through a sufficient number of instances, the ranking model sees all patch locations of an image and learns to judge relative ranks among patches. In other words, the" + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22834" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": "ranking model knows how to score all the image patches regarding their informativeness. Consequently, we can solely use the ranking model for image redundancy reduction, as shown in the right part of Fig. 2." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 129, + 141, + 140 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 129, + 141, + 140 + ], + "spans": [ + { + "bbox": [ + 47, + 129, + 141, + 140 + ], + "type": "text", + "content": "3.4. Patch Selection" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "spans": [ + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "content": "With the ranking model, a straightforward way for redundancy reduction is to select the top-k patches. Our observation suggests that the top patches favor object boundaries rather than homogeneous regions (e.g., dog's body in Fig. 1), as shown in Fig. 3. We attribute it to that changes in object boundaries more easily cause semantic shifts in the reconstructed image. However, a small proportion of patches from homogeneous regions are also essential for visual tasks [28]. Thus, we introduce DPC-KNN [15] to capture the representative homogeneous patches. Specifically, to select " + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "content": " informative patches including " + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "inline_equation", + "content": "h < k" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "content": ") ones from homogeneous regions, we first select (" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "inline_equation", + "content": "k - h" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "content": ") patches as described above. Then, we use DPC-KNN to cluster all patches into " + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "content": " groups and select the largest " + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "content": " ones, given that larger groups are more likely to associate with homogeneous regions. For each selected group, we extract one patch that satisfies the following two conditions, i.e., not selected previously and closest to the cluster center in the remaining patches. The two sets of patches constitute the output of our LTRP. We will ablate " + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 47, + 147, + 289, + 387 + ], + "type": "text", + "content": " in experiments." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 399, + 128, + 412 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 399, + 128, + 412 + ], + "spans": [ + { + "bbox": [ + 47, + 399, + 128, + 412 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 418, + 233, + 432 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 418, + 233, + 432 + ], + "spans": [ + { + "bbox": [ + 47, + 418, + 233, + 432 + ], + "type": "text", + "content": "4.1. Datasets and Experimental Setting" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 437, + 289, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 437, + 289, + 677 + ], + "spans": [ + { + "bbox": [ + 47, + 437, + 289, + 677 + ], + "type": "text", + "content": "Datasets and evaluation metrics. We pre-train our LTRP on ImageNet-1K training set, and then assess it on two scenarios as follows. The first is image-level evaluation. We conduct image classification on ImageNet-1K, a single-label classification dataset, and on MS-COCO [25], a multi-label classification dataset. The classification model is trained only with the patches remained by different methods. Top-1 accuracy and mAP are employed as the evaluation metrics, respectively. The second is patch-level evaluation. It is conducted both on MS-COCO and PASCAL VOC [17] with their object detection labels, MS-COCO and ADE20K [51] with their semantic segmentation labels. In practice, we treat all the labeled bounding boxes or masks as foreground and evaluate their consistency with the retained patches by using IoU, F1-score, recall, and precision. Following EViT [24], IA-RED² [31], etc., we evaluate these methods at different keep ratios (krs). That is, the top-scored " + }, + { + "bbox": [ + 47, + 437, + 289, + 677 + ], + "type": "inline_equation", + "content": "kr\\%" + }, + { + "bbox": [ + 47, + 437, + 289, + 677 + ], + "type": "text", + "content": " patches are preserved. Meanwhile, all the ablation experiments are conducted on ImageNet-100, a subset of ImageNet-1K, given hardware resource constraints." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 288, + 713 + ], + "type": "text", + "content": "Model architectures. In LTRP training, we use MAE with ViT-B and choose ViT or CNN (e.g., ResNet50) as our ranking model. In image classification, we utilize ViT-B" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "type": "text", + "content": "on ImageNet-1K and MS-COCO, ViT-S on ImageNet-100 as the backbone for model training. They are both initialized from the MAE encoder [20]. Moreover, we add ML-Decoder [37] behind the classification backbone and use Asymmetric loss [36] for multi-label classification. No additional model is required for the patch-level evaluation, as the performance is obtained by comparing the preserved image patches with groundtruth. All experiments are conducted on a server with 8 NVIDIA GTX 3090 GPUs and Intel(R) Xeon(R) Gold 6226R CPU." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 192, + 547, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 192, + 547, + 300 + ], + "spans": [ + { + "bbox": [ + 304, + 192, + 547, + 300 + ], + "type": "text", + "content": "Comparing methods. We compare LTRP with off-the-shelf models from the three classes mentioned previously (see Sec. 2.1). For CAM, we choose Grad-Cam [38] with ViT. For self-supervised methods, we choose MoCo [9] with ResNet50 and DINO [6]. For token reduction, we choose EViT [24], IA-RED² [31], DynamicViT [34], AdaViT [30], DGE [39] and ToMe [2]. For fair assessment, these methods are all trained (supervised) or pre-trained (unsupervised) on ImageNet-1K." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 310, + 443, + 321 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 310, + 443, + 321 + ], + "spans": [ + { + "bbox": [ + 305, + 310, + 443, + 321 + ], + "type": "text", + "content": "4.2. Performance Evaluation" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 329, + 545, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 329, + 545, + 413 + ], + "spans": [ + { + "bbox": [ + 304, + 329, + 545, + 413 + ], + "type": "text", + "content": "Image-level evaluation. Figure 4a shows the results of different methods at krs 0.7 and 0.5 on single-label classification. The unsupervised and supervised methods are depicted by different colors. LTRP performs better than the self-supervised ones, and slightly worse or on par with state-of-the-art supervised methods. Note that LTRP achieves this without utilizing any supervisory signals." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "spans": [ + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "text", + "content": "We then test LTRP on MS-COCO to validate the performance on multi-label classification. As shown in Fig. 4b, LTRP achieves mAP of " + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "inline_equation", + "content": "82.8\\%" + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "inline_equation", + "content": "81.8\\%" + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "text", + "content": " at krs 0.75 and 0.5, respectively. It outperforms the previous best unsupervised methods by " + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "inline_equation", + "content": "1.1\\%" + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "inline_equation", + "content": "1.4\\%" + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "text", + "content": ", and the state-of-the-art supervised methods by " + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "inline_equation", + "content": "0.7\\%" + }, + { + "bbox": [ + 304, + 414, + 545, + 545 + ], + "type": "text", + "content": " at both krs. Note that these values correspond to clear accuracy gaps, as the performance differences between existing methods are small. Since different methods only differ in the patches selected, these improvements clearly indicate that LTRP enables a fairer and more meaningful redundancy reduction." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 546, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 546, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 546, + 545, + 713 + ], + "type": "text", + "content": "Patch-level evaluation. To further validate whether the patches are unbiasedly retained, we focus on the categories not included in ImageNet-1K, i.e., the unseen categories, for which all the methods have not been explicitly told to learn. We first evaluate the methods based on the object detection labels. The performance of different methods on PASCAL VOC and MS-COCO is shown in the first two rows in Fig. 5. Encouragingly, LTRP surpasses all the competitors in all the evaluated metrics at different krs. The significant improvement in precision highlights that patches selected by LTRP are more accurately located in bounding boxes of unseen categories. With the decrease of krs, the precision of many supervised methods goes up slowly or even goes down. 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Experimental results on object detection and semantic segmentation datasets. For each dataset, we exclude the categories overlapped with ImageNet-1K (learned) and only compute the metrics on the remaining (unseen) categories, which all the methods have not been explicitly told to learn. The results illustrate the merit of LTRP in unbiased image redundancy reduction." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 163, + 232, + 265, + 312 + ], + "blocks": [ + { + "bbox": [ + 163, + 232, + 265, + 312 + ], + "lines": [ + { + "bbox": [ + 163, + 232, + 265, + 312 + ], + "spans": [ + { + "bbox": [ + 163, + 232, + 265, + 312 + ], + "type": "image", + "image_path": "def713ee8d0d51ffec6dd3eb00dd25977a0b3a594948d75d81039c35c6e30066.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 265, + 232, + 366, + 312 + ], + "blocks": [ + { + "bbox": [ + 265, + 232, + 366, + 312 + ], + "lines": [ + { + "bbox": [ + 265, + 232, + 366, + 312 + ], + "spans": [ + { + "bbox": [ + 265, + 232, + 366, + 312 + ], + "type": "image", + "image_path": "6853659c7988379ade631d4bfb2b215b54d4874f4bf9668fdef17d24e9f773bf.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 367, + 232, + 469, + 312 + ], + "blocks": [ + { + "bbox": [ + 367, + 232, + 469, + 312 + ], + "lines": [ + { + "bbox": [ + 367, + 232, + 469, + 312 + ], + "spans": [ + { + "bbox": [ + 367, + 232, + 469, + 312 + ], + "type": "image", + "image_path": "0ad60c5c962ea57f7ffa6fafb6bddcc9b149b45e44081f3ff13d975ad432e402.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 469, + 232, + 545, + 312 + ], + "blocks": [ + { + "bbox": [ + 469, + 232, + 545, + 312 + ], + "lines": [ + { + "bbox": [ + 469, + 232, + 545, + 312 + ], + "spans": [ + { + "bbox": [ + 469, + 232, + 545, + 312 + ], + "type": "image", + "image_path": "6e62819db20a6ad2b5122bfd2eb175c5b2b703c8449c54825da06ef6c7e89cec.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 375, + 287, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 375, + 287, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 375, + 287, + 422 + ], + "type": "text", + "content": "gard patches from unseen categories as the most important ones, while our LTRP still goes up quickly and successfully avoids this bias. The result implies that LTRP can be well generalized to datasets with quite different categories." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 46, + 423, + 287, + 518 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 423, + 287, + 518 + ], + "spans": [ + { + "bbox": [ + 46, + 423, + 287, + 518 + ], + "type": "text", + "content": "We then evaluate the methods based on the semantic segmentation labels. The third row in Fig. 5 shows the results on MS-COCO. LTRP also consistently gives the best results and exhibits a noticeable improvement compared to DynamicViT, the second-best method. We observe that the performance gap becomes larger as the kr decreases. It again demonstrates that LTRP preserves semantics corresponding to the unseen categories well." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 47, + 527, + 115, + 538 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 527, + 115, + 538 + ], + "spans": [ + { + "bbox": [ + 47, + 527, + 115, + 538 + ], + "type": "text", + "content": "4.3. Ablations" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 287, + 569 + ], + "type": "text", + "content": "In Tab. 1, we provide detailed ablation experiments and introduce some empirical observations as follows." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "text", + "content": "Reconstruction model. Tab. 1a presents LTRP with different MAE as the image reconstruction model. The optimal model is surprisingly the lightweight model MAE-B. Utilizing MAE-B to generate pseudo label boosts the accuracy by " + }, + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "inline_equation", + "content": "0.2\\%" + }, + { + "bbox": [ + 46, + 570, + 287, + 714 + ], + "type": "text", + "content": " compared to larger MAE-L (21 M v.s. 81 M in #params). Moreover, MAE-L with GAN [19] loss can get even better reconstruction, but performs worse at kr 0.5. We observe that reconstructions of large models or utilizing GAN loss have finer low-level semantics such as texture details. It tends to pull these patches that excel in recovering low-level semantics ahead in the ranking, consequently reducing the proportion of patches with high-level semantics." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 375, + 485, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 375, + 485, + 387 + ], + "spans": [ + { + "bbox": [ + 306, + 375, + 485, + 387 + ], + "type": "text", + "content": "This phenomenon causes the accuracy drop." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 388, + 546, + 519 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 388, + 546, + 519 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 546, + 519 + ], + "type": "text", + "content": "Masking ratio. Tab. 1b shows the influence of the ratio of removed patches. The accuracy of an excessively high masking ratio (0.95) drops by " + }, + { + "bbox": [ + 304, + 388, + 546, + 519 + ], + "type": "inline_equation", + "content": "0.1\\%" + }, + { + "bbox": [ + 304, + 388, + 546, + 519 + ], + "type": "text", + "content": " compared with baseline. And a lower masking ratio (0.7) does not perform better than the masking ratio of 0.8. We note that extremely high and low masking ratios both result in the issue of plateau in the pseudo score sequence, namely some patches have similar pseudo scores and occupy a continuous position in the ranking sequence. This causes the ranking model to be confused about the right order of these patches. Considering the efficiency issue, LTRP selects a masking ratio of 0.9." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 521, + 546, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 546, + 640 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 546, + 640 + ], + "type": "text", + "content": "Ranking model. We investigate the architecture, sparse design and similarity metric of ranking model in Tabs. 1c, 1d and 1h, respectively. We find out that our ranking model is model-agnostic, and even smaller models like ViT-T or ResNet50 can achieve performance similar to the baseline (ViT-S). However, to align with the comparing methods, we select ViT-S. The sparse design excludes the sort-irrelevant patches from the ranking model, it improves accuracy by " + }, + { + "bbox": [ + 304, + 521, + 546, + 640 + ], + "type": "inline_equation", + "content": "0.2\\%" + }, + { + "bbox": [ + 304, + 521, + 546, + 640 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 521, + 546, + 640 + ], + "type": "inline_equation", + "content": "0.3\\%" + }, + { + "bbox": [ + 304, + 521, + 546, + 640 + ], + "type": "text", + "content": " across different krs. Moreover, by skipping these patches, we significantly reduce computational costs." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 642, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 547, + 713 + ], + "type": "text", + "content": "Clustering. Tab. 1e presents our investigation of clustering. Interestingly, selecting all patches (with clustering ratio 1) through clustering at the pixel level is not extremely bad compared with our baseline (82.7% v.s. 83.7%). A small subset (e.g., 20%) of patches from homogeneous regions gets an improved LTRP." + } + ] + } + ], + "index": 24 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "22836" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 70, + 201, + 125 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 201, + 125 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 201, + 125 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 201, + 125 + ], + "type": "table", + "html": "
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ratiospeedupkr=0.75kr=0.5
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l184.483.3
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modelparamskr=0.75kr=0.5
Mobile-Former[10]3.2M84.383.1
ViT-T5.5M84.583.4
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Regression84.183.0
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phasespeedupkr=0.75kr=0.5inputkr=0.75kr=0.5
encoder184.483.7visible patches84.783.5
decoder1.3x84.483.3all patches84.483.3
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pixel (w/o norm)84.483.3
pixel (w norm)81.575.7
", + "image_path": "23dbfadf51fe772e5811d4001a35777fdcd61795754243bed26a848dfc306c77.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 302, + 544, + 322 + ], + "lines": [ + { + "bbox": [ + 47, + 302, + 544, + 322 + ], + "spans": [ + { + "bbox": [ + 47, + 302, + 544, + 322 + ], + "type": "text", + "content": "(g) Removal phase. Removing visible patches be- (h) Sparse design. Inputting only visible patches(i) Reconstruction target. LTRP favors MIM fore the decoder well balances accuracy and speed. into the ranking model yields better results. models based on raw pixels." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 331, + 546, + 355 + ], + "lines": [ + { + "bbox": [ + 46, + 331, + 546, + 355 + ], + "spans": [ + { + "bbox": [ + 46, + 331, + 546, + 355 + ], + "type": "text", + "content": "Table 1. LTRP ablation experiments on ImageNet-100. We report accuracy (%) results for krs 0.75 and 0.5, respectively. The selected configurations are marked in gray." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "spans": [ + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "text", + "content": "Ranking loss. Tab. 1f studies the choice of ranking loss. Interestingly, the point-wise approach also has decent performance in our LTRP. Compared to ListMLE, its accuracy drops by only " + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "inline_equation", + "content": "0.3\\%" + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "text", + "content": " at both krs. Point-wise methods train " + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\langle" + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "text", + "content": " query, document " + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\rangle" + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "text", + "content": " pair independently, ignoring the relationship among documents. In contrast, our ranking model considers all documents (patches), i.e., " + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\langle" + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "text", + "content": " query, documents " + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "inline_equation", + "content": "\\rangle" + }, + { + "bbox": [ + 46, + 376, + 287, + 519 + ], + "type": "text", + "content": ", enabling the acquisition of holistic knowledge. For pair-wise methods, the accuracy drops obviously at krs of 0.75 and 0.5 (82.9 v.s. 84.4 and 79.5 v.s. 83.3, respectively). Overall, ListMLE performs the best and is also the most appropriate method for utilizing our pseudo-labels." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 521, + 287, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 521, + 287, + 592 + ], + "spans": [ + { + "bbox": [ + 46, + 521, + 287, + 592 + ], + "type": "text", + "content": "Removal phase. In Tab. 1g, although the results of removing visible patches before the lightweight decoder show a decrease in performance compared to the approach of removing before the encoder (a reduction of " + }, + { + "bbox": [ + 46, + 521, + 287, + 592 + ], + "type": "inline_equation", + "content": "0.4\\%" + }, + { + "bbox": [ + 46, + 521, + 287, + 592 + ], + "type": "text", + "content": " at kr 0.5), we can achieve a noteworthy " + }, + { + "bbox": [ + 46, + 521, + 287, + 592 + ], + "type": "inline_equation", + "content": "1.3\\mathrm{x}" + }, + { + "bbox": [ + 46, + 521, + 287, + 592 + ], + "type": "text", + "content": " speedup in terms of FLOPs (7.07G vs. 5.38G). So we employ the former." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": "Reconstruction target. Pre-patch normalization is a trick that normalizes a patch using the mean and standard deviation of its pixels. In Tab. 1i, we observe that utilizing pre-trained MAE based on pre-patch normalization for generating pseudo-labels performs exceedingly poorly, which is " + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "inline_equation", + "content": "7.6\\%" + }, + { + "bbox": [ + 46, + 594, + 288, + 714 + ], + "type": "text", + "content": " worse than using unnormalized pixels. We suspect this drop partially because LTRP requires quantifying the global semantic changes between two images. Conversely, pre-patch normalization appears to reducing global coherence, as it focuses on enhancing the contrast locally [20]." + } + ] + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 307, + 374, + 545, + 498 + ], + "blocks": [ + { + "bbox": [ + 307, + 374, + 545, + 498 + ], + "lines": [ + { + "bbox": [ + 307, + 374, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 307, + 374, + 545, + 498 + ], + "type": "image", + "image_path": "03f366993b1132d7447c5e268635e2c2013fdc8b0da1e5fa7ef755e7ee2369dd.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 506, + 545, + 540 + ], + "lines": [ + { + "bbox": [ + 305, + 506, + 545, + 540 + ], + "spans": [ + { + "bbox": [ + 305, + 506, + 545, + 540 + ], + "type": "text", + "content": "Figure 6. Normalized score maps generated by LTRP on validation set of ImageNet-1K (top) and MS-COCO (bottom). Only the top-scored 64 patches are displayed." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 561, + 436, + 573 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 561, + 436, + 573 + ], + "spans": [ + { + "bbox": [ + 306, + 561, + 436, + 573 + ], + "type": "text", + "content": "4.4. LTRP for Efficient ViT" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 581, + 545, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 581, + 545, + 616 + ], + "spans": [ + { + "bbox": [ + 305, + 581, + 545, + 616 + ], + "type": "text", + "content": "LTRP allows the classification model to be trained only on a subset of image patches. We verify whether this LTRP-based classification would be more efficient for ViT." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "text", + "content": "We elucidate this issue from both inference and training perspectives. For inference, time for both patch ranking and classification should be counted. As shown in Tab. 1d, even ViT-T has commendable performance. So we choose small ranking model and large classification model as LTRP-based solutions. Table 2 enumerates several combinations on ImageNet-1K at kr 0.75. Using ViT-T as the ranking model shows " + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "inline_equation", + "content": "1.19 \\times" + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "inline_equation", + "content": "1.36 \\times" + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "text", + "content": ", or " + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "inline_equation", + "content": "1.33 \\times" + }, + { + "bbox": [ + 304, + 617, + 546, + 713 + ], + "type": "text", + "content": " acceleration on GPU" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22837" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 49, + 70, + 292, + 160 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 292, + 160 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 292, + 160 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 292, + 160 + ], + "type": "table", + "html": "
cls.rankingparamsFLOPs ↓inference speed↑top-1 acc.
modelmodel(M)(G)GPUim/sCPUim/s
ViT-B-8617.61095.14.383.3†)
ViT-S108(+25.6%)13.1(-25.6%)1034.9(-5.5%)4.1(-4.7%)83.2(-0.1%)
ViT-T91.5(+6.4%)13.1(-25.6%)1302.2(+18.9%)5.1(+18.6%)83.1(-0.2%)
ViT-L-30761.62357.71.385.8†)
ViT-S329(+7.2%)46.0(-25.3%)445.6(+24.6%)1.5(+15.4%)85.7(-0.1%)
ViT-T312.5(+1.8%)45.9(-25.5%)485.5(+35.8%)1.7(+23.1%)85.6(-0.2%)
ViT-H-632167.4140.00.586.6†)
ViT-S654(+3.5%)124.8(-25.4%)181.0(+29.3%)0.6(+20.0%)86.3(-0.3%)
ViT-T637.5(+0.9%)124.7(-25.5%)185.8(+32.7%)0.6(+20.0%)86.1(-0.5%)
", + "image_path": "79f79e8cc97588074933b30b3e448213102ffbd383282e9721255cc448379244.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 168, + 287, + 247 + ], + "lines": [ + { + "bbox": [ + 46, + 168, + 287, + 247 + ], + "spans": [ + { + "bbox": [ + 46, + 168, + 287, + 247 + ], + "type": "text", + "content": "Table 2. Experiments on efficient ViT on ImageNet-1K at kr 0.75. Different combinations of the ranking and classification (cls.) models show different balances between FLOPs (or inference speed) and accuracy. \" -\" means do not incorporate the ranking model and select all patches. " + }, + { + "bbox": [ + 46, + 168, + 287, + 247 + ], + "type": "inline_equation", + "content": "\\dagger" + }, + { + "bbox": [ + 46, + 168, + 287, + 247 + ], + "type": "text", + "content": " means run by us. When using ViT-T as the ranking model, LTRP accelerates the inference ranging from 18.9% to 32.7% with accuracy sacrifice of 0.1%-0.5%." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "spans": [ + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "content": "over the scheme that directly uses ViT-B, ViT-L or ViT-H as the classification model, respectively (ViT-H uses a " + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "inline_equation", + "content": "16^{*}16" + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "content": " patch grid while ViT-B and ViT-L use " + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "inline_equation", + "content": "14^{*}14" + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "content": "). Meanwhile, the accuracy drops only range from " + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "inline_equation", + "content": "0.2\\%" + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "inline_equation", + "content": "0.5\\%" + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "content": ". The results imply that LTRP-based ones are more appropriate choices in scenarios requiring both efficiency and accuracy. With the popularity of large visual and multi-modal models, large ViT models are more frequently utilized and we believe that these solutions would receive more attention. While for training, LTRP-based solutions include running the ranking model once for patch selection and training the classification model " + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "content": " epochs. The cost raised by the ranking model would be negligible as " + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "content": " increases. Meanwhile, training the classification model would also be accelerated by nearly " + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "inline_equation", + "content": "1 / kr^2 \\times" + }, + { + "bbox": [ + 46, + 267, + 287, + 447 + ], + "type": "text", + "content": " as fewer patches are involved." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 447, + 287, + 495 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 447, + 287, + 495 + ], + "spans": [ + { + "bbox": [ + 46, + 447, + 287, + 495 + ], + "type": "text", + "content": "In sum, compared with the vanilla classification, LTRP-based solutions not only accelerate training but also can improve the inference speed up to over " + }, + { + "bbox": [ + 46, + 447, + 287, + 495 + ], + "type": "inline_equation", + "content": "30\\%" + }, + { + "bbox": [ + 46, + 447, + 287, + 495 + ], + "type": "text", + "content": " on GPU with a possible neglectable accuracy degradation." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 503, + 130, + 514 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 503, + 130, + 514 + ], + "spans": [ + { + "bbox": [ + 47, + 503, + 130, + 514 + ], + "type": "text", + "content": "4.5. Visualization" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 521, + 287, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 521, + 287, + 652 + ], + "spans": [ + { + "bbox": [ + 46, + 521, + 287, + 652 + ], + "type": "text", + "content": "Figure 6 displays the informativeness-aware capability of LTRP on ImageNet-1k and MS-COCO. LTRP well identifies patches located in meaningful object regions in ImageNet-1K images. Meanwhile, it also shows superior unbiasedness in selecting multiple objects from MS-COCO images. We also visualize a process of hierarchical patch selection in Fig. 7. With the decrease of retained patches, less important patches are gradually removed. LTRP is consistent in favour of patches located on semantic objects. This removal process is mostly in line with human perception. The results again demonstrate the effectiveness of LTRP." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 653, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 287, + 714 + ], + "type": "text", + "content": "To explore why LTRP performs better than popular self-supervised methods, we plot the average attention distance of each head of DINO and our LTRP ranking model (both are ViT-S) in Fig. 8. A more scattered distance distribution is observed for LTRP especially in the last few layers. As" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 307, + 70, + 545, + 159 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 545, + 159 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 545, + 159 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 545, + 159 + ], + "type": "image", + "image_path": "f97448d905d1b63f82adb7939fda10769c77e97931f60fdcff73d4b6152177f6.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 167, + 547, + 201 + ], + "lines": [ + { + "bbox": [ + 305, + 167, + 547, + 201 + ], + "spans": [ + { + "bbox": [ + 305, + 167, + 547, + 201 + ], + "type": "text", + "content": "Figure 7. Hierarchical redundancy reduction process of LTRP on MS-COCO validation set. Keep ratios are shown in the top left of each image. Patches with green boxes are the retained ones." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 308, + 211, + 430, + 303 + ], + "blocks": [ + { + "bbox": [ + 308, + 211, + 430, + 303 + ], + "lines": [ + { + "bbox": [ + 308, + 211, + 430, + 303 + ], + "spans": [ + { + "bbox": [ + 308, + 211, + 430, + 303 + ], + "type": "image", + "image_path": "355021130e366950b6c77bf725886ac0af15a566d61db9306b99c4ccc2869dc6.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 352, + 304, + 384, + 314 + ], + "lines": [ + { + "bbox": [ + 352, + 304, + 384, + 314 + ], + "spans": [ + { + "bbox": [ + 352, + 304, + 384, + 314 + ], + "type": "text", + "content": "(a) DINO" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 431, + 212, + 552, + 303 + ], + "blocks": [ + { + "bbox": [ + 431, + 212, + 552, + 303 + ], + "lines": [ + { + "bbox": [ + 431, + 212, + 552, + 303 + ], + "spans": [ + { + "bbox": [ + 431, + 212, + 552, + 303 + ], + "type": "image", + "image_path": "d8c4cd701bd5a4cbfe8c954cbf8a1d3ad460a470cd8255c1133d986a7083f6e6.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 474, + 304, + 506, + 314 + ], + "lines": [ + { + "bbox": [ + 474, + 304, + 506, + 314 + ], + "spans": [ + { + "bbox": [ + 474, + 304, + 506, + 314 + ], + "type": "text", + "content": "(b) LTRP" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 306, + 324, + 545, + 346 + ], + "lines": [ + { + "bbox": [ + 306, + 324, + 545, + 346 + ], + "spans": [ + { + "bbox": [ + 306, + 324, + 545, + 346 + ], + "type": "text", + "content": "Figure 8. Average attention distances organized according to layer and head for DINO and our LTRP ranking model." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 367, + 545, + 403 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 367, + 545, + 403 + ], + "spans": [ + { + "bbox": [ + 305, + 367, + 545, + 403 + ], + "type": "text", + "content": "stated in [43], such a distribution suggests that more diverse representation learning is achieved, which explains in part the superiority of LTRP." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 414, + 378, + 426 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 414, + 378, + 426 + ], + "spans": [ + { + "bbox": [ + 306, + 414, + 378, + 426 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 434, + 545, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 434, + 545, + 661 + ], + "spans": [ + { + "bbox": [ + 304, + 434, + 545, + 661 + ], + "type": "text", + "content": "We have introduced LTRP, the first self-supervised method for image redundancy reduction. By leveraging the characteristic of self-supervised learning to create patch-level pseudo labels, and then learning to rank patches, LTRP elegantly eliminates the issue of categorical inductive bias commonly observed in leading supervised methods. Extensive experiments on different datasets and tasks basically validate our proposal. LTRP achieves competitive accuracy in single-label classification and obviously better accuracy in multi-label classification. Meanwhile, the retained patches align more closely with object detection and semantic segmentation labels, especially for categories not explicitly learned by supervised methods. In addition, incorporating LTRP into image classification can lead to a notable speedup in inference with neglectable accuracy degradation if applied appropriately. These results convincingly indicate the effectiveness of LTRP and its unbiased patch selection. We hope that LTRP will provide valuable insights into image redundancy reduction and related visual tasks." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 661, + 545, + 709 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 661, + 545, + 709 + ], + "spans": [ + { + "bbox": [ + 305, + 661, + 545, + 709 + ], + "type": "text", + "content": "Acknowledgement This work was supported by National Science and Technology Major Project (No. 2021ZD0112805) and in part by National Natural Science Foundation of China (No. 62372170, 62172103)." + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "22838" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 91, + 288, + 715 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Jiwoon Ahn and Suha Kwak. 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However, in real-world scenarios, massive multimodal data are harvested from the Internet, which inevitably contains Partially Mismatched Pairs (PMPs). Undoubtedly, such semantical irrelevant data will remarkably harm the cross-modal retrieval performance. Previous efforts tend to mitigate this problem by estimating a soft correspondence to down-weight the contribution of PMPs. In this paper, we aim to address this challenge from a new perspective: the potential semantic similarity among unpaired samples makes it possible to excavate useful knowledge from mismatched pairs. To achieve this, we propose L2RM, a general framework based on Optimal Transport (OT) that learns to rematch mismatched pairs. In detail, L2RM aims to generate refined alignments by seeking a minimal-cost transport plan across different modalities. To formalize the rematching idea in OT, first, we propose a self-supervised cost function that automatically learns from explicit similarity-cost mapping relation. Second, we present to model a partial OT problem while restricting the transport among false positives to further boost refined alignments. Extensive experiments on three benchmarks demonstrate our L2RM significantly improves the robustness against PMPs for existing models. The code is available at https://github.com/hhc1997/L2RM.", + "bbox": [ + 75, + 318, + 473, + 710 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 741, + 209, + 757 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The pursuit of general intelligence has advanced the progress of multimodal learning, which aims to understand and integrate multiple sensory modalities like humans. Cross-modal retrieval is one of the most important", + "bbox": [ + 75, + 767, + 468, + 828 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/55074c0a0a7a8ba12a566525e996a168355222c66f22673d63b929d660d42c31.jpg", + "image_caption": [ + "Figure 1. A toy example to illustrate our idea. The potential semantic similarity among unpaired samples makes it possible to excavate useful knowledge from mismatched pairs. Our L2RM aims to rematch PMPs by generating a refined alignment that brings relevant cross-modal samples (green links) together while repelling irrelevant ones (red links) away from each other. We also show some real-world rematched cases for our L2RM in Fig. 5." + ], + "image_footnote": [], + "bbox": [ + 504, + 286, + 614, + 440 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ac434f70813a086843aba5986b2f069c2d72915be35a01928f6f0e1485c47cad.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 627, + 290, + 746, + 439 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/d91763d8d1cff34bdf79fa2ba4e62e0b25264462c4fa99a229c9eb5f6f69351a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 759, + 286, + 888, + 440 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "techniques in multimodal learning due to its flexibility in bridging different modalities [15, 20, 22, 25, 37, 42], which has powered various real-world applications.", + "bbox": [ + 496, + 575, + 892, + 621 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Despite the remarkable performance of previous methods, much of their success can be attributed to the voracious appetite for well-matched cross-modal pairs. In practice, collecting such ideal data [24] is notoriously labor-intensive and even impossible. Alternatively, several mainstream cross-modal datasets utilize the co-occurred information to crawl data from the Internet, especially for visual-text samples [11]. Although such a data collection way is free from expensive annotations, it will inevitably introduce partially mismatched pairs. For example, the standard image-caption dataset, Conceptual Captions [36], is estimated to contain about $3\\%$ to $20\\%$ mismatched pairs. Such semantically irrelevant data will be wrongly treated as the matched pairs for training, which undoubtedly impairs the performance of cross-modal retrieval models. Thus, endowing cross-modal learning with robustness against PMPs is crucial to suit real-world retrieval scenarios.", + "bbox": [ + 496, + 625, + 893, + 880 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To alleviate the PMP problem, existing works [19,23,45]", + "bbox": [ + 519, + 885, + 890, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*This work was completed during his internship at SGIT AI Lab.", + "bbox": [ + 94, + 838, + 439, + 851 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "†Corresponding author. This work was supported by the National Key Research and Development Program of China (2022YFB3102600), and National Nature Science Foundation of China (62272374, 62192781, 62202367, 62250009, and 62137002).", + "bbox": [ + 76, + 851, + 468, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "26679", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "typically resort to recasting the estimated soft correspondence into a soft margin to adjust the distance in triplet ranking loss. However, the underuse of mismatched pairs, only limited to down-weighting their contribution, has led to sub-optimal retrieval performance. Hence, it is necessary to address the PMP issue in a data-efficient manner.", + "bbox": [ + 75, + 90, + 468, + 180 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "A question naturally arises: Could cross-modal retrieval models even learn useful knowledge from mismatched pairs? To answer this question, this paper presents L2RM, a general framework that learns to rematch mismatched pairs for robust cross-modal retrieval. As illustrated in Fig. 1, our key idea is to excavate the potential matching relationship among mismatched cross-modal samples. Specifically, we first identify possibly mismatched pairs from training data by modeling the per-sample loss distribution. Then, we formalize the rematching idea as an OT problem to generate a new set of refined alignments for mismatched pairs in every minibatch. Notably, the cost function plays a paramount role when applying OT, which is typically designed as feature-driven distance [5, 10, 18]. However, the over-dependence on representations has led to a cycle of self-reinforcing errors—the existence of PMPs can generate corrupted representations—in turn, preventing the effective transport plan. To handle this problem, we propose a self-supervised learning solution to automatically learn the cost function from explicit similarity-cost mapping relation, which is unexplored in previous OT literature. Moreover, instead of exactly rematching all mismatched samples, we suggest modeling a partial OT problem while restricting the transport among false positives to boost the refined alignment. In practice, we show that our optimization objective could be solved by the Sinkhorn algorithm [9], which only incurs cheap computational overheads.", + "bbox": [ + 75, + 181, + 472, + 589 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our main contributions are summarized as follows: (1) We propose a general OT-based framework to address the widely-existed PMP problem in cross-modal retrieval. The key to our method is learning to rematch mismatched pairs, which goes beyond previous efforts from the data-efficient view. (2) To address the error accumulation faced by the vanilla cost function, we propose a novel self-supervised learner that automatically learns the transport cost from explicit similarity-cost mapping relation. (3) To further boost the refined alignment, we present to model a partial OT problem and restrict the transport among false positives. (4) Extensive experiments on several benchmarks demonstrate our L2RM endows existing cross-modal retrieval methods with strong robustness against PMPs.", + "bbox": [ + 75, + 589, + 470, + 801 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 814, + 218, + 830 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Cross-Modal Retrieval. Approaches for cross-modal retrieval aim to retrieve relevant items across different modalities for the query data. Current dominant methods project different modalities into a shared embedding space to mea", + "bbox": [ + 75, + 839, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "sure the similarity of cross-modal pairs, which generally follow two research lines: 1) Global Alignment focuses on learning the correspondence between whole cross-modal data. Existing studies usually propose a two-stream network to learn comparable global features [13, 30, 47]. 2) Local Alignment. It seeks to align the fine-grained regions for more precise cross-modal matching. For example, [26] employ the cross-attention mechanism to fully excavate the semantic region-word alignments. [43, 44] explore the intramodal relation to facilitate inter-modal alignments.", + "bbox": [ + 496, + 90, + 890, + 241 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Although these prior arts have achieved promising results, their success mainly relies on well-matched data, which is extremely expensive and even impossible to collect. To satisfy a more practical retrieval that is robust against the PMPs, [23, 33, 45] divide the mismatched pairs from training data and estimate a soft correspondence to downweight their training contribution. Recently, [21] resorts to complementary contrastive learning that only utilizes the negative information to avoid overfitting. However, these methods neglect the usage of either the negative information [23, 33, 45] or the positive one [21]. To fully leverage the training data, this paper proposes an OT-based method to rematch those partially mismatched pairs.", + "bbox": [ + 496, + 242, + 892, + 439 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Optimal Transport. OT is used to seek a minimal-cost transport plan from one probability measure to another. The original OT model is a linear program that incurs expensive computational cost. [9] proposes the entropy-regularized OT to provide a computationally cheaper solver. Recently, OT has gained increasing attention from different fields in machine learning, including unsupervised learning [4, 29], semi-supervised learning [39], object detection [1, 17], domain adaptation [14, 35], and long-tailed recognition [32, 40]. To the best of our knowledge, we are the first to perform the PMP problem from an OT perspective.", + "bbox": [ + 496, + 455, + 892, + 623 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. Preliminaries", + "text_level": 1, + "bbox": [ + 500, + 633, + 638, + 650 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3.1. Background on OT", + "text_level": 1, + "bbox": [ + 500, + 659, + 684, + 674 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "OT provides a mechanism to infer the correspondence between two measures. We briefly introduce the OT theory to help us better view the PMP problem from an OT perspective. Consider $\\mathbf{X} = \\{x_{i}\\}_{i = 1}^{m}$ and $\\mathbf{Y} = \\{y_{j}\\}_{j = 1}^{n}$ as two discrete variables, and we denote their probability measures as $\\pmb {p} = \\sum_{i = 1}^{m}p_{i}\\delta (x_{i})$ and $\\pmb {q} = \\sum_{j = 1}^{n}q_{j}\\delta (y_{j})$ where $\\delta$ is the Dirac function, $p_i$ and $q_{j}$ are the probability mass belonging to the probability simplex. When a meaningful cost function $c(\\cdot)$ is defined, we can get the cost matrix $C\\in \\mathbb{R}^{m\\times n}$ between $\\mathbf{X}$ and $\\mathbf{Y}$ , where $C_{ij} = c(x_i,y_j)$ . Based on these, the OT distance can be expressed as:", + "bbox": [ + 496, + 681, + 890, + 849 + ], + "page_idx": 1 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {O T} (\\boldsymbol {p}, \\boldsymbol {q}) \\triangleq \\min _ {\\boldsymbol {\\pi} \\in \\Pi (\\boldsymbol {p}, \\boldsymbol {q})} \\left\\langle \\boldsymbol {\\pi}, \\boldsymbol {C} \\right\\rangle_ {F} \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 596, + 857, + 890, + 886 + ], + "page_idx": 1 + }, + { + "type": "equation", + "text": "\n$$\n\\text {s . t .} \\Pi (\\boldsymbol {p}, \\boldsymbol {q}) = \\left\\{\\boldsymbol {\\pi} \\in \\mathbb {R} _ {+} ^ {m \\times n} | \\boldsymbol {\\pi} \\mathbb {1} _ {n} = \\boldsymbol {p}, \\boldsymbol {\\pi} ^ {\\top} \\mathbb {1} _ {m} = \\boldsymbol {q} \\right\\},\n$$\n", + "text_format": "latex", + "bbox": [ + 517, + 886, + 864, + 904 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "26680", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "where $\\langle \\cdot, \\cdot \\rangle_F$ is the Frobenius dot-product and $\\mathbb{1}_d$ denotes a $d$ -dimensional all-one vector. $\\pi$ is called the optimal transport plan that transport $\\pmb{p}$ towards $\\pmb{q}$ at the smallest cost.", + "bbox": [ + 76, + 90, + 468, + 137 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Problem Definition", + "text_level": 1, + "bbox": [ + 76, + 147, + 261, + 162 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Without losing generality, we take the visual-text retrieval as an example to present the PMP problem in cross-modal retrieval. Consider a training dataset $\\mathbb{D} = \\{(V_i,T_i,m_i)\\}_{i=1}^N$ consisting of $N$ samples, where $(V_i,T_i)$ is the visual-text pair and $m_i \\in \\{1,0\\}$ indicates whether the bimodal data is semantically matched or not. The key to cross-modal retrieval lies in measuring the similarity across distinct modalities. To achieve this, existing methods usually project the visual and textual modalities into a comparable feature space via the corresponding modal-specific networks $f_v$ and $f_t$ , respectively. Then the similarity of a given visual-text pair is measured through $S_{ij} = g(f_v(V_i), f_t(T_j))$ , where $g$ is a nonparametric or parametric mapping function. For convenience, we denote $g(f_v(V_i), f_t(T_j))$ as $g(V_i, T_j)$ in the following.", + "bbox": [ + 76, + 171, + 468, + 398 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Ideally, the positive (matched) pairs should have higher similarity while the negative (mismatched) pairs should have lower ones, which can be achieved by minimizing the triplet loss [13] or InfoNCE loss [31]. Consider a batch of $N_{b}$ pairs $\\{(V_{i},T_{i})\\}_{i = 1}^{N_{b}}$ , the triplet loss is defined as:", + "bbox": [ + 76, + 398, + 470, + 474 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) = [ \\alpha - g \\left(V _ {i}, T _ {i}\\right) + g \\left(V _ {i}, \\hat {T} _ {h}\\right) ] _ {+} \\tag {2} \\\\ + \\left[ \\alpha - g \\left(V _ {i}, T _ {i}\\right) + g \\left(\\hat {V} _ {h}, T _ {i}\\right) \\right] _ {+}, \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 122, + 488, + 468, + 526 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\alpha$ is a margin and $[x]_{+} = \\max (x,0)$ . $\\hat{V}_h$ and $\\hat{T}_h$ are the most similar negatives in the given batch corresponding to $(V_i,T_i)$ . Eq.(2) aims to enforce the negative pairs to be distant from the positives by a certain margin value.", + "bbox": [ + 76, + 541, + 468, + 602 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Alternatively, InfoNCE loss is extended to cross-modal scenario [21,34] that encourages the similarity gap between positives and negatives as large as possible. Formally, the matching probability of $j$ -th textual sample w.r.t. the $i$ -th visual query is defined as $p_{ij}^{2t} = \\frac{\\exp(g(V_i,T_j) / \\tau)}{\\sum_{j' = 1}^{N_b}\\exp(g(V_i,T_{j'}) / \\tau)}$ , where $\\tau$ is a temperature parameter. As InfoNCE loss is symmetric, the matching probability $p_{ij}^{t2v}$ is defined similarly. For notation convenience, we denote $\\pmb{p}_i^{2t} = [p_{i1}^{2t},\\dots ,p_{iN_b}^{2t}]^\\top$ and $\\pmb{p}_i^{t2v} = [p_{i1}^{t2v},\\dots ,p_{iN_b}^{t2v}]^\\top$ as the probability vectors. To align cross-modal samples, the corresponding one-hot vector $\\pmb{y}_i = [y_{i1},\\dots ,y_{iN_b}]^\\top$ is used as supervision, where $y_{ij}$ equal to 1 if $i = j$ while other elements are 0. Thus, the cross-modal InfoNCE loss is given by:", + "bbox": [ + 76, + 603, + 468, + 811 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} ^ {\\text {I n f o N C E}} \\left(V _ {i}, T _ {i}\\right) = \\mathcal {H} \\left(\\boldsymbol {y} _ {i}, \\boldsymbol {p} _ {i} ^ {v 2 t}\\right) + \\mathcal {H} \\left(\\boldsymbol {y} _ {i}, \\boldsymbol {p} _ {i} ^ {t 2 v}\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 120, + 823, + 468, + 842 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathcal{H}$ is the batched cross-entropy function.", + "bbox": [ + 76, + 854, + 387, + 869 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The success of both Eq.(2) and Eq.(3) relies on the well-matched pairs. However, in practice, the multimedia", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "datasets are usually web-collected, and thus inevitably contains an unknown portion of irrelevant pairs but are wrongly treated as matched ( $m_i = 1$ ). Our goal is to combat such PMPs to facilitate robust cross-modal retrieval.", + "bbox": [ + 498, + 90, + 890, + 150 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Methodology", + "text_level": 1, + "bbox": [ + 500, + 164, + 633, + 181 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To tackle the PMP problem, the mainstream pipeline first uses the memorization effect [3] of DNNs, i.e., DNNs learn simpler patterns before memorizing the difficult ones, to partition the dataset into a matched subset $\\mathbb{D}_m$ , and a mismatched subset $\\mathbb{D}_{\\widetilde{m}} = \\mathbb{D} / \\mathbb{D}_m$ . After that, $\\mathbb{D}_m$ can be used for standard cross-modal training. To mitigate the impact of PMPs, recent advances [19, 23, 45] introduce a soft margin into Eq.(2) to down-weight the samples from $\\mathbb{D}_{\\widetilde{m}}$ . However, due to the underuse of mismatched pairs, the achieved performance by them is argued to be sub-optimal. In this work, we aim to fully leverage PMPs by trying to excavate the potential semantic similarity among mismatched pairs. In the following, we present the details of our method.", + "bbox": [ + 498, + 189, + 890, + 386 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. Identifying Mismatched Pairs", + "text_level": 1, + "bbox": [ + 500, + 395, + 764, + 411 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Following the mainstream learning style, we first identify possibly mismatched pairs from all training data. The memorization effect of DNNs indicates that mismatched samples tend to have relatively higher loss during the early stage of training. Based on this, we use the difference in loss distribution between the matched and mismatched pairs to divide the training set. Empirically, we observe that the distribution of triplet loss is more distinguishable. Thus, given the retrieval model $(f_v, f_t, g)$ , we compute the per-sample loss through Eq.(2):", + "bbox": [ + 498, + 417, + 890, + 569 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\ell_ {\\left(f _ {v}, f _ {t}, g\\right)} = \\left\\{\\ell_ {i} \\right\\} _ {i = 1} ^ {N} = \\left\\{\\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) \\right\\} _ {i = 1} ^ {N}. \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 553, + 578, + 890, + 597 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Then, we fit a two-component beta mixture model [2,19,45] to $\\ell_{(f_v,f_t,g)}$ using the Expectation-Maximization algorithm. For $i$ -th pair, its probability $w_{i}$ being mismatched is the posterior probability $p(b|\\ell_i)$ , where $b$ is the beta component with a higher mean. By setting a threshold on $\\{w_{i}\\}_{i = 1}^{N}$ , we can divide the training data into the matched subset $\\mathbb{D}_m$ and mismatched subset $\\mathbb{D}_{\\widetilde{m}}$ (we set the threshold to 0.5 in all experiments for brevity).", + "bbox": [ + 498, + 606, + 890, + 727 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "For initial convergence of the algorithm, we warm up the model for a few epochs by training on all data with Eq.(2) or Eq.(3). However, for extreme mismatching rates, the model would quickly overfit to mismatched pairs and produce unreliable loss. To address this issue, we mitigate the overconfidence of the model by adding a reverse cross entropy [41] term to the InfoNCE loss during warm-up, i.e.,", + "bbox": [ + 498, + 727, + 890, + 833 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} ^ {\\mathrm {R C E}} \\left(V _ {i}, T _ {i}\\right) = \\mathcal {H} \\left(\\boldsymbol {p} _ {i} ^ {v 2 t}, \\boldsymbol {y} _ {i}\\right) + \\mathcal {H} \\left(\\boldsymbol {p} _ {i} ^ {t 2 v}, \\boldsymbol {y} _ {i}\\right). \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 553, + 842, + 890, + 861 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In the presence of PMPs, $y_{i}$ may provide the wrong matching relation. Instead, the estimated probability could reflect", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "26681", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/90f9e79f5dde2eb384dc91fad136b9f01a72f9429a3aef295e0d7760d83c19f9.jpg", + "image_caption": [ + "Figure 2. Overview of the learnable cost function with self-supervised learning. The up part illustrates the reconstructed pairs that only $(V_4, T_1)$ , $(V_2, T_3)$ , and $(V_{N_b}, T_{N_b})$ are the reserved matching ones. Then, the matching matrix is viewed as supervision to guide the cost function from the explicit similarity-cost mapping relation through an OT loss (the down part)." + ], + "image_footnote": [], + "bbox": [ + 76, + 88, + 893, + 291 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "the truer distribution to a certain extent. Note that we bound the one-hot label into $[\\epsilon, 1 - \\epsilon]$ for computational feasibility. $(\\epsilon = 10^{-7}$ in our experiments).", + "bbox": [ + 75, + 367, + 470, + 412 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.2. Rematching Mismatched Pairs", + "text_level": 1, + "bbox": [ + 76, + 421, + 349, + 436 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We formalize the rematching idea as an OT problem, generating refined alignments by seeking a minimal-cost transport plan. We will first introduce the novel learnable cost function to suit the PMP scenario, then we show how to boost the refined alignment by a relaxed OT model.", + "bbox": [ + 75, + 444, + 468, + 521 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Cost Function with Self-Supervised Learning. Cost function plays a crucial role when learning the transport plan for OT. In general, $C_{ij}$ is set to a distance measure, e.g., $L_{2}$ -distance [18] or cosine distance [10] to measure the expense of transporting a visual sample $i$ to a textual sample $j$ . However, the existence of PMPs imposes formidable obstacles for these feature-driven distance measures. On the one hand, training with PMPs can wrongly bring irrelevant data together, which undoubtedly prevents effective representation learning. Even worse, different modalities will be embedded into separate regions of the shared space due to the inherent modality gap [27]. On the other hand, the refined alignments produced by those corrupted features would be used to guide subsequent training, leading to the cycle of self-reinforcing errors [8].", + "bbox": [ + 75, + 537, + 468, + 763 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To address the aforementioned limitations, we propose a novel self-supervised learning approach to automatically learn the cost function. Intuitively, for a given image and caption, the transport cost can be modeled as a function of similarity that higher similarity enjoys a lower cost. Thus, we formulate the cost function as a single-layer feedforward network with parameters $\\Theta_c$ , i.e., $f_c(\\cdot;\\Theta_c)$ , which takes the similarity matrix of the batched visual-text samples as input and attempts to learn the corresponding cost", + "bbox": [ + 75, + 765, + 470, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "matrix. To achieve this, we reconstruct the visual-text pairs to guide the cost function from explicit similarity-cost mapping relation. Specifically, for the matched pairs sampled from $\\mathbb{D}_m$ , we randomly reserve a part of the matching images and substitute the images from $\\mathbb{D}_{\\widetilde{m}}$ for the remaining ones. With the reserved indexes, we could automatically obtain a matching matrix that indicates the ideal matching probability for each reconstructed pair. For the example illustrated in Fig. 2, $(V_4,T_1)$ , $(V_{2},T_{3})$ , and $(V_{N_b},T_{N_b})$ are the reserved matching pairs with a matching probability of 1, while the others could be considered as mismatched ones with a matching probability of 0. For convenience, let $\\mathbb{D}'$ be the reconstructed data, and $(V,T) \\in \\mathbb{D}'$ be matrices that contain a batch of images and captions. To relate the similarity-cost mapping with the matching matrix, we optimize the cost function by the following OT loss:", + "bbox": [ + 496, + 367, + 893, + 609 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {O T}} \\left(\\boldsymbol {\\pi} ^ {\\sup }, \\boldsymbol {V}, \\boldsymbol {T}\\right) = \\left\\langle \\boldsymbol {\\pi} ^ {\\sup }, f _ {c} \\left(g (\\boldsymbol {V}, \\boldsymbol {T}); \\Theta_ {c}\\right) \\right\\rangle_ {F}, \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 524, + 616, + 890, + 633 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\pi^{\\mathrm{sup}}$ is the matching matrix, and $g(\\mathbf{V},\\mathbf{T})$ denotes the similarity matrix for the batched visual-text pairs.", + "bbox": [ + 496, + 641, + 890, + 671 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Eq.(6) seeks an effective cost function from a reverse perspective of OT, which views the ideal transport plan as the supervision to minimize the transport cost.", + "bbox": [ + 496, + 671, + 890, + 717 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Boosting Refined Alignments with Relaxed OT. Given the defined cost function, we could generate the refined alignments for mismatched pairs following the OT objective described in Eq.(1). However, Eq.(1) requires the two distributions to have the same total mass and that all the mass of $p$ should be transported to exactly match the mass of $q$ . In practice, due to the limited batch size, one caption may be irrelevant to all images in the batch and vice versa. To this end, we adopt the partial OT model [6, 16] to relax such strict all-to-all mass constraints, which seeks a minimal cost of only transporting $0 \\leqslant \\rho \\leqslant \\min(\\|p\\|_1, \\|q\\|_1)$", + "bbox": [ + 496, + 734, + 890, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "26682", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/6e5f6943323c0b5bd47309d6e844360e89d779947cb8bfb5d0bb7db2dd8c00da.jpg", + "image_caption": [ + "Figure 3. Illustration of the proposed rematching loss. For the mismatched pairs, we formalize a partial OT problem with positive pairs masked to generate the refined alignment in each batch. The refined alignment provides a more reliable matching relation to supervise the mismatched pairs. Then, we compute the symmetric KL-divergence to optimize the retrieval model $(f_v, f_t, g)$ ." + ], + "image_footnote": [], + "bbox": [ + 76, + 88, + 893, + 222 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "unit mass between the visual and textual distribution, i.e.,", + "bbox": [ + 76, + 286, + 468, + 301 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\min _ {\\boldsymbol {\\pi} \\in \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q})} \\left\\langle \\boldsymbol {\\pi}, \\boldsymbol {C} \\right\\rangle_ {F}, \\text {s . t .} \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q}) = \\left\\{\\boldsymbol {\\pi} \\in \\mathbb {R} _ {+} ^ {m \\times n} | \\boldsymbol {\\pi} \\mathbb {1} _ {n} \\leqslant \\boldsymbol {p}, \\right.\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 324, + 468, + 349 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {\\pi} ^ {\\top} \\mathbb {1} _ {m} \\leqslant \\boldsymbol {q}, \\mathbb {1} _ {m} ^ {\\top} \\pi \\mathbb {1} _ {n} = \\rho \\}. \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 200, + 351, + 468, + 369 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Furthermore, the false positives contained in the mismatched pairs introduce an implicit constraint to our transport plan $\\pi$ that the transport mass between the same element in two distributions should be limited. To this end, we propose to impose a mask operation on the transport plan that restricts the transport to only concentrate among the unpaired pairs. Specifically, the mask matrix $M\\in \\mathbb{R}^{m\\times n}$ is defined as:", + "bbox": [ + 75, + 378, + 468, + 498 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nM _ {i j} \\triangleq \\left\\{ \\begin{array}{l l} 0, & \\text {i f} i = j, \\\\ 1, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 189, + 503, + 468, + 545 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Then the masked transport plan is defined as the Hadamard product $\\tilde{\\pi} = M\\odot \\pi$ and be optimized through Eq.(7).", + "bbox": [ + 75, + 551, + 468, + 582 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3. The Training Objective", + "text_level": 1, + "bbox": [ + 76, + 589, + 292, + 606 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Given the mismatched pairs $\\{(V_i, T_i)\\}_{i=1}^{N_b}$ sampled from $\\mathbb{D}_{\\widetilde{m}}$ , if we don't have any prior knowledge, we could consider the visual and textual samples following the uniform distributions, i.e., $\\pmb{p} = \\sum_{i=1}^{N_b} \\frac{1}{N_b} \\delta(V_i)$ and $\\pmb{q} = \\sum_{i=1}^{N_b} \\frac{1}{N_b} \\delta(T_i)$ , respectively. To guarantee the efficiency of our algorithm, we adopt an online strategy to update $\\Theta_c$ and calculate $\\widetilde{\\pi}$ through a single optimization loop:", + "bbox": [ + 76, + 611, + 468, + 724 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\min _ {\\tilde {\\boldsymbol {\\pi}} \\in \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q})} \\mathbb {E} _ {(\\boldsymbol {V}, \\boldsymbol {T}) \\in \\mathbb {D} _ {\\tilde {m}}} \\left\\langle \\tilde {\\boldsymbol {\\pi}}, f _ {c} \\left(g \\left(\\boldsymbol {V}, \\boldsymbol {T}\\right); \\Theta_ {c} ^ {*}\\right) \\right\\rangle_ {F} - \\lambda H (\\tilde {\\boldsymbol {\\pi}}), \\\\ \\text {s . t .} \\Theta_ {c} ^ {*} = \\underset {\\Theta_ {c}} {\\arg \\min } \\mathbb {E} _ {(\\boldsymbol {V}, \\boldsymbol {T}, \\boldsymbol {\\pi} ^ {\\sup }) \\in \\mathbb {D} ^ {\\prime}} \\mathcal {L} _ {O T} (\\boldsymbol {\\pi} ^ {\\sup }, \\boldsymbol {V}, \\boldsymbol {T}) \\tag {9} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 78, + 742, + 468, + 809 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\lambda > 0$ is a regularization parameter for the entropic constraint $H(\\tilde{\\pi}) = -\\sum_{ij} \\tilde{\\pi}_{ij} \\log \\tilde{\\pi}_{ij}$ . Note that Eq.(9) introduces an entropy regularization item to the OT model, which enables the transport plan to be solved by the computationally cheaper Sinkhorn-Knopp algorithm [9]. The detailed solution is presented in Appendix A.", + "bbox": [ + 75, + 810, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The optimal transport plan from Eq.(9) represents a refined alignment that provides a more reliable matching relation for those mismatched visual-text samples. As our refined alignment is generated dynamically, we adopt the KL-divergence to compute the rematching loss instead of the cross entropy. Besides, a reverse term is added to symmetrize the KL-divergence, which makes the training more stable. Formally, let $\\tilde{\\pi}_i^{v2t}$ and $\\tilde{\\pi}_i^{t2v}$ be the row-wise and column-wise normalized refined alignment for the $i$ -th sample, respectively. Then, the rematching loss (see Fig. 3) is defined as:", + "bbox": [ + 496, + 286, + 893, + 450 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} ^ {\\mathrm {r e}} \\left(V _ {i}, T _ {i}\\right) = \\frac {1}{2} \\left[ D _ {K L} \\left(\\tilde {\\boldsymbol {\\pi}} _ {i} ^ {v 2 t} \\parallel \\boldsymbol {p} _ {i} ^ {v 2 t}\\right) + D _ {K L} \\left(\\boldsymbol {p} _ {i} ^ {v 2 t} \\parallel \\tilde {\\boldsymbol {\\pi}} _ {i} ^ {v 2 t}\\right) \\right] \\\\ + \\frac {1}{2} \\left[ D _ {K L} \\left(\\tilde {\\boldsymbol {\\pi}} _ {i} ^ {t 2 v} \\| \\boldsymbol {p} _ {i} ^ {t 2 v}\\right) + D _ {K L} \\left(\\boldsymbol {p} _ {i} ^ {t 2 v} \\| \\tilde {\\boldsymbol {\\pi}} _ {i} ^ {t 2 v}\\right) \\right]. \\tag {10} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 500, + 455, + 893, + 526 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For the pairs that are divided as matched, we use the triplet ranking loss to directly control the distance gap. Thus, our final objective function is defined as:", + "bbox": [ + 496, + 527, + 893, + 571 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} ^ {\\text {F i n a l}} = \\sum_ {(V _ {i}, T _ {i}) \\in \\mathbb {D} _ {m}} \\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) + \\sum_ {(V _ {i}, T _ {i}) \\in \\mathbb {D} _ {\\tilde {m}}} \\mathcal {L} ^ {\\text {r e}} \\left(V _ {i}, T _ {i}\\right). \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 579, + 890, + 614 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The detailed training pseudo-code is shown in Appendix B.", + "bbox": [ + 500, + 621, + 890, + 636 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. Experiment", + "text_level": 1, + "bbox": [ + 500, + 648, + 624, + 665 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this section, we experimentally analyze the effectiveness of L2RM in robust cross-modal retrieval.", + "bbox": [ + 500, + 672, + 890, + 702 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.1. Setup", + "text_level": 1, + "bbox": [ + 500, + 710, + 581, + 727 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We apply our method to three image-text retrieval datasets varying in scale and scope. Specifically, Flickr30K [46] consists of 31,000 images with five corresponding text annotations for each image from the Flickr website. Following [23], we split 1,000 images for validation, 1,000 images for testing, and the rest for training. MS-COCO [28] is a large-scale cross-modal dataset, which collects 123,287 images with five sentences each. Following [23], we use 5,000 images for validation, 5,000 images for testing, and the rest for training. Conceptual Captions [36] is a web-crawled large-scale dataset containing", + "bbox": [ + 496, + 734, + 893, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "26683", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/cb52478f98ecb0149f1025d7b0713cbfb24d614a61884fd6dbb06e5947d153cf.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MRateMethodFlickr30KMS-COCO
Image-to-TextText-to-ImagerSumImage-to-TextText-to-ImagerSum
R@1R@5R@10R@1R@5R@10R@1R@5R@10R@1R@5R@10
0.2IMRAM59.185.491.944.571.479.4431.769.993.697.455.984.489.6490.8
NCR73.593.296.656.982.488.5491.176.695.698.260.888.895.0515.0
BiCro74.794.396.856.681.488.2492.076.695.498.261.388.894.8515.1
DECL-SGR74.592.997.153.679.586.8484.475.695.198.359.988.394.7511.9
DECL-SGRAF77.593.897.056.181.888.5494.777.595.998.461.789.395.4518.2
RCL-SGR74.291.896.955.681.287.5487.277.095.598.161.388.894.8515.5
RCL-SGRAF75.994.597.357.982.688.6496.878.996.098.462.889.995.4521.4
L2RM-SAF73.794.397.756.881.888.1492.477.996.098.362.189.294.9518.4
L2RM-SGR76.593.797.355.581.588.0492.578.495.798.362.189.194.9518.5
L2RM-SGRAF77.995.297.859.883.689.5503.880.296.398.564.290.195.4524.7
0.4IMRAM44.973.282.631.656.365.6354.251.882.490.938.470.378.9412.7
NCR68.189.694.851.478.484.8467.174.794.698.059.688.194.7509.7
BiCro70.792.095.551.977.785.4473.275.295.398.160.087.894.3510.7
DECL-SGR69.090.294.850.776.384.1465.173.694.697.957.886.993.9504.7
DECL-SGRAF72.792.395.453.479.486.4479.675.695.598.359.588.394.8512.0
RCL-SGR71.391.195.351.478.085.2472.373.994.997.959.087.493.9507.0
RCL-SGRAF72.792.796.154.880.087.1483.477.095.598.361.288.594.8515.3
L2RM-SAF72.192.196.152.778.885.9477.774.494.798.359.287.994.4508.9
L2RM-SGR73.192.496.352.379.486.3479.875.294.898.159.487.894.1509.4
L2RM-SGRAF75.893.296.956.381.087.3490.577.595.898.462.089.194.9517.7
0.6IMRAM16.438.250.97.519.225.3157.518.251.668.017.943.654.6253.9
NCR13.937.750.511.030.141.4184.60.10.30.40.10.51.02.4
BiCro64.187.192.747.274.082.3447.473.293.997.657.586.393.4501.9
DECL-SGR64.585.892.644.071.680.6439.169.793.497.554.585.292.6492.9
DECL-SGRAF65.288.494.046.874.082.2450.673.094.297.957.086.693.8502.5
RCL-SGR62.386.392.945.171.380.2438.171.493.297.155.484.792.3494.1
RCL-SGRAF67.789.193.648.074.983.3456.674.094.397.557.686.493.5503.3
L2RM-SAF66.188.893.847.874.282.2452.971.293.497.556.585.993.0497.5
L2RM-SGR65.187.893.647.073.581.5448.572.793.997.556.986.293.3500.5
L2RM-SGRAF70.090.895.451.376.483.7467.675.494.797.959.287.493.8508.4
0.8IMRAM3.19.75.20.30.91.921.11.35.08.30.20.61.316.7
NCR1.56.29.90.31.02.121.00.10.30.40.10.51.02.4
BiCro2.39.217.22.610.216.858.362.288.694.647.479.288.5460.5
DECL-SGR44.472.682.033.959.569.0361.460.088.794.545.978.888.3456.2
DECL-SGRAF53.478.886.937.663.873.9394.464.890.596.049.781.790.3473.0
RCL-SGR47.170.579.430.356.166.3349.763.289.395.247.678.788.0462.0
RCL-SGRAF51.775.884.434.561.270.7378.367.490.896.050.681.090.1475.9
L2RM-SAF50.877.985.535.662.672.7385.164.790.895.850.080.989.4471.6
L2RM-SGR50.577.283.934.261.171.6378.565.290.396.149.881.088.2470.6
L2RM-SGRAF55.780.887.839.465.474.9404.069.091.996.452.682.490.3482.6
", + "bbox": [ + 91, + 87, + 890, + 628 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Image-text retrieval performance under different mismatching rates (MRate) on Flickr30K and MS-COCO.", + "bbox": [ + 140, + 638, + 823, + 654 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "3.3M one-to-one images and captions. Following [23], we use the subset, i.e., CC152K to conduct experiments, which has 150,000 images for training, 1,000 images for validation, and 1,000 images for testing.", + "bbox": [ + 75, + 672, + 468, + 736 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation Details. As a general method, L2RM could be directly applied to almost all cross-modal retrieval methods to improve their robustness. Following [21, 33], we apply L2RM to SGR, SAF, and SGRAF for a comprehensive comparison. We evaluate the retrieval performance with the Recall@K (R@K) metric. Following [23], we save the best performance checkpoint on the validation set w.r.t. the sum of the evaluation scores and report its results on the testing set. We follow the same training setting as [23], our specific parameters setting can be found in Appendix C.1.", + "bbox": [ + 75, + 750, + 470, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. We compare L2RM with eight state-of-the-art cross-modal retrieval methods, including four general methods (i.e., IMRAM [7], SGR, SAF, and SGRAF [12]) and four robust learning methods against the PMPs (i.e., NCR [23], DECL [33], BiCro [45], and RCL [21]). Note that the original BiCro combines four models, i.e., two co-trained SGR, and two co-trained SAF. For a fair comparison, we report the results of 2 co-trained SGR for BiCro like [23].", + "bbox": [ + 496, + 672, + 890, + 796 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Main Results", + "text_level": 1, + "bbox": [ + 500, + 813, + 637, + 829 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In this section, we conduct comparison experiments with different mismatching rates on three datasets to evaluate the performance of our L2RM. As Flickr30K and MS-COCO are well-established datasets, we carry out experiments by", + "bbox": [ + 496, + 839, + 890, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "26684", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "generating the synthesized false positive pairs, i.e., the mismatching rate (MRate) increases from 0.2 to 0.8 in intervals of 0.2. Following [21, 33], we randomly select a specific percentage of images and randomly permute all their corresponding captions, which is more challenging and practical than the setting in [23, 45]. For the web-collected dataset CC152K, which naturally contains about $3\\% \\sim 20\\%$ unknown mismatched pairs [36]. Thus we directly conduct experiments on it to evaluate the performance with real PMPs.", + "bbox": [ + 75, + 90, + 472, + 227 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results on Synthesized PMPs. Tab. 1 shows the experimental results on Flickr30K and MS-COCO. Note that for MS-COCO, the results are computed by averaging over 5 folds of 1K test images like [21, 33]. Due to space limitation, we omit the results of some general methods (SGR, SAF, and SGRAF), and the comparison on original datasets (0 MRate), which could be found in Appendix C.2. From the results, we can find that L2RM achieves the best results on all metrics than the other state-of-the-art methods, which shows the superior robustness of L2RM against PMPs. Moreover, when the mismatching rate is high, e.g., 0.6 and 0.8, the improvement of L2RM is more evident, proving that excavating mismatched pairs could effectively facilitate robust cross-modal retrieval.", + "bbox": [ + 75, + 248, + 472, + 459 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results on Real-World PMPs. We validate our method on the real-world dataset CC152K, which contains an unknown portion of mismatched pairs. As shown in Tab. 2, our method considerably outperforms the best baseline in terms of sum in retrieval by $9.8\\%$ . Notably, our L2RM-SGR surpasses all SGR variants by a clear margin, achieving as much as a $16.9\\%$ (rSum) absolute improvement over the best variant. It is because the real-world rematched pairs are more likely to involve only local alignments, e.g., Fig. 5(e)-Fig. 5(f), while the SGR model itself is adept at capturing the relationship between local alignments.", + "bbox": [ + 75, + 479, + 470, + 647 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/d8667f3c7c787f6e9afb8799b615e2a6b15b02e61c92d51edd3b88810cde6a9b.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodImage-to-TextText-to-ImagerSum
R@1R@5R@10R@1R@5R@10
IMRAM27.852.460.929.251.561.2283.0
SAF32.559.570.032.560.768.7323.9
SGR14.535.548.913.736.147.9196.6
NCR39.564.573.540.364.673.2355.6
BiCro39.764.672.639.265.074.1355.2
DECL-SAF36.663.073.338.563.273.5348.1
DECL-SGR36.263.673.237.163.673.7347.4
DECL-SGRAF39.066.175.540.766.376.7364.3
RCL-SAF37.563.071.437.862.472.4344.5
RCL-SGR38.363.070.439.263.272.3346.4
RCL-SGRAF41.766.073.641.666.475.1364.4
L2RM-SAF37.362.771.738.865.774.8351.0
L2RM-SGR39.566.276.041.865.974.9364.3
L2RM-SGRAF43.067.575.742.868.077.2374.2
", + "bbox": [ + 78, + 660, + 470, + 873 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 90, + 653, + 107 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Impact of Each Component. To study the influence of specific components in our method, we carry out the ablation study on the Flickr30K with 0.6 MRate. Specifically, we ablate the contributions of three key components of L2RM, i.e., partial OT, positives masked, and the learnable cost function (we use the cosine distance to measure the cost instead). Besides, we compare L2RM with different formulas of rematching loss: KL-divergence and InfoNCE. From Tab. 3, we observe the following conclusions: 1) The full L2RM could achieve the best overall performance, showing that all three components are important to improve the robustness against PMPs. 2) Using the learnable cost function substantially outperforms the variant with the cosine distance cost (e.g., +11.9 in terms of the rSum), which signifies the simple feature-driven cost is sub-optimal to the PMP situation. 3) Formulating different rematching loss could also achieve decent results, which verifies the ability of L2RM to provide effective matching relations.", + "bbox": [ + 496, + 112, + 893, + 385 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/be938b279f30c87190469202588ea6d0f8bb7b8ed5a8444a58c189462a9f242c.jpg", + "table_caption": [ + "Table 2. Image-text retrieval performance on CC152K." + ], + "table_footnote": [], + "table_body": "
AblationImage-to-TextText-to-Image
R@1R@5R@10R@1R@5R@10
L2RM65.187.893.647.073.581.5
L2RM w KL-divergence64.787.693.246.774.081.5
L2RM w InfoNCE Loss64.987.593.546.072.980.9
L2RM w/o Partial OT62.286.491.544.768.672.6
L2RM w/o Positives Masked64.987.692.746.473.281.1
L2RM w/o Cost Function61.385.691.444.972.481.0
", + "bbox": [ + 511, + 397, + 893, + 500 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 3. Ablation studies on Flickr30K with 0.6 MRate.", + "bbox": [ + 527, + 511, + 861, + 523 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Parameter Analysis. We now investigate the effect of the parameter $\\rho$ by plotting the recall scores with incremental $\\rho$ on Flickr30K. The figure shows that the overall performance tends to decrease as $\\rho$ increases. We further analyze how untransported pairs benefit the model training in Appendix C.3. Experimentally, we find that the refined alignments for untransported pairs can be equivalent to the label smoothing strategy [38].", + "bbox": [ + 496, + 537, + 890, + 657 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/baa7dc4ae6e29bfd3f2c8659c63a9e87d57d7579e069a5c4ec279c043bdc0525.jpg", + "image_caption": [ + "(a) Image to Text" + ], + "image_footnote": [], + "bbox": [ + 506, + 670, + 696, + 781 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a14098b1fbbcc991579b15d55b699c20c7f36f014395474a47fb3be546cb918a.jpg", + "image_caption": [ + "(b) Text to Image", + "Figure 4. Parameter analysis of L2RM-SGR in terms of recall scores on the testing set of Flickr30K under 0.2 MRate." + ], + "image_footnote": [], + "bbox": [ + 694, + 670, + 883, + 781 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Discussions on Warm-up Methods. We use different warm-up methods, i.e., triplet loss [13] and InfoNCE loss [31] for our L2RM-SGR. The experiments are conducted on the Flickr30K with 0.8 MRate and the CC152K with real", + "bbox": [ + 496, + 839, + 893, + 898 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "26685", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/63271031ab4ee06fc364b2dd7cd929e5067b476f8ead3963e750fb133aee4990.jpg", + "image_caption": [ + "Given: view bar out on the lounge chairs" + ], + "image_footnote": [], + "bbox": [ + 81, + 90, + 212, + 169 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/859227471a931c939cbd9d313b205bef614d6e9e5d48a7c8e795e802fc89b751.jpg", + "image_caption": [ + "Rematched: the facade can be lit up at night using different coloured led lights (0.988)", + "Given: the gift of the present", + "Rematched: a man on a bicycle (0.996)", + "(b)", + "Rematched: suspension bridge over a city (0.963)" + ], + "image_footnote": [], + "bbox": [ + 223, + 90, + 315, + 179 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d1e6671c51c30a43d64de328f0969afccd66d2f189c42a10be234fb04dc8f0de.jpg", + "image_caption": [ + "(a)", + "Given: a survey has revealed that a third would be less likely to travel if it was no longer a member", + "(c)", + "Rematched: most popular sports in the world - hockey (0.965)" + ], + "image_footnote": [], + "bbox": [ + 326, + 90, + 457, + 169 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/fa716680cd2d0f75af90be62c18f5fd84d5508e0934c3ae8819b8cca967569b7.jpg", + "image_caption": [ + "Given: video: fans sing composition after mic issue", + "(d)" + ], + "image_footnote": [], + "bbox": [ + 468, + 90, + 601, + 167 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/41cc0394427109d593aa2e154534e04879e085fc5dd07604209d5e8ffc16cab4.jpg", + "image_caption": [ + "Given: day on the place unknown", + "Rematched: a couple of men stand on a small hill (0.938)", + "(e)" + ], + "image_footnote": [], + "bbox": [ + 614, + 90, + 743, + 167 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/83f32a9602eda87e3a948f62d2c4ecbc1d374f8f40d962f20309e3125905ca05.jpg", + "image_caption": [ + "Given: a general view of atmosphere outside the diesel and launch party", + "Rematched: a motorcycle winds their way through country (0.626)", + "(f)" + ], + "image_footnote": [], + "bbox": [ + 756, + 90, + 887, + 167 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/88727890fb6081b9367905779781b13895d7f9fed443ac0d849c0ab4d6bd44b5.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodFlickr30KCC152K
Image-to-TextText-to-ImageImage-to-TextText-to-Image
R@1R@5R@10R@1R@5R@10R@1R@5R@10R@1R@5R@10
Triplet0.10.71.30.10.71.138.264.271.439.564.271.9
InfoNCE45.971.480.329.252.761.139.366.875.040.865.274.2
", + "bbox": [ + 84, + 291, + 468, + 351 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4. Comparison with different warm-up methods on Flickr30K with 0.8 MRate and CC152K.", + "bbox": [ + 75, + 362, + 468, + 388 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "PMPs. As shown in Tab. 4, one could see that the triplet loss cannot achieve satisfactory performance under the extreme mismatching rate. Compared with the results of the L2RM-SGR in Tab. 1, one could find that it is necessary to limit the overconfidence of the model during the warm-up process. The results on CC152K show that our method is robust to the choice of warm-up methods under a relatively low mismatching rate.", + "bbox": [ + 75, + 410, + 468, + 530 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Visualization and Analysis", + "text_level": 1, + "bbox": [ + 76, + 540, + 316, + 556 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Distribution of Transport Cost. To intuitively show the effectiveness of the learnable cost function, we illustrate the transport cost for matched and mismatched training pairs on Flickr30K with 0.8 MRate. From Fig. 6, one could see that our cost function first learns to assign higher transport costs to those mismatched pairs. Although the costs of matched pairs are distributed over a large range in the early stage, they gradually become smaller and tend toward 0 as training proceeds. In conclusion, our cost function could successfully learn to distinguish matched and mismatched data, which lays the foundation for the further OT model.", + "bbox": [ + 75, + 564, + 468, + 729 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Visualizing Rematched Image-Text Pairs. To visually illustrate the rematching ability of our L2RM, we conduct the case study on CC152K to show real-world rematched examples. Specifically, the first two rows of Fig. 5 show the image and its original mismatched caption, respectively. The third row shows the rematched caption provided by our method, and we also show the refined alignment scores in brackets. In particular, we could find that some real-world visual-text pairs are completely uncorrelated (e.g., Fig. 5(a)-Fig. 5(b)) or contain only a few local similarities (e.g., Fig. 5(c)-Fig. 5(e)). Thanks to our L2RM, the", + "bbox": [ + 75, + 734, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9e64827d05f2da7d9937006a34379cdb6d2ab8bb54e27df658a38ed946c6fd38.jpg", + "image_caption": [ + "Figure 5. The ability of our L2RM to rematch the mismatched visual-text samples. The figure shows some representative rematched pairs for L2RM-SGR on the training set of CC152K dataset. We highlight the matched words in green and the mismatched words in red.", + "(a) Epoch 5", + "Figure 6. Transport cost distribution for matched and mismatched pairs at different training phases of our L2RM. The experiments are conducted on Flickr30K with 0.8 MRate." + ], + "image_footnote": [], + "bbox": [ + 504, + 292, + 694, + 398 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e238b617e4c7dbfe0a94392507340b9ce1b745ffa39b71744045747b72365118.jpg", + "image_caption": [ + "(b) Epoch 35" + ], + "image_footnote": [], + "bbox": [ + 697, + 292, + 887, + 398 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "potential matching relation among mismatched pairs could be fully excavated to provide refined alignments. For example, one could see that the rematched caption, i.e., \"a man on a bicycle\" nicely expresses the semantic concept in Fig. 5(a). Although some rematched captions could not perfectly share the same semantics with images, they also contain some local similarities to the given images. For example, the image in Fig. 5(f) is correctly described with the words \"a motorcycle\" and our L2RM provides a relatively low refined alignment score as the target. In summary, our proposed rematching strategy could embrace better data efficiency and robustness against PMPs.", + "bbox": [ + 496, + 487, + 890, + 669 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 691, + 617, + 705 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work studies the challenge of cross-modal retrieval with partially mismatched pairs (PMPs). To address this problem, we propose L2RM, a generalized OT-based framework that learns to rematch mismatched pairs. Our key idea is to excavate the potential semantic similarity among unpaired samples. To formalize this idea through OT, first, we propose a self-supervised learner to automatically learn effective cost function. Second, we model a partial OT problem and restrict the transport among false positives to further boost refined alignments. Extensive experiments are conducted to verify that our L2RM can endow cross-modal retrieval models with strong robustness against PMPs.", + "bbox": [ + 496, + 719, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "26686", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Triantafyllos Afouras, Yuki M Asano, Francois Fagan, Andrea Vedaldi, and Florian Metze. Self-supervised object detection from audio-visual correspondence. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 10575–10586, 2022. 2", + "[2] Eric Arazo, Diego Ortego, Paul Albert, Noel O'Connor, and Kevin McGuinness. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 3536-3545, 2020. 2" + ], + "bbox": [ + 501, + 92, + 890, + 781 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "26688", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/fd35e1ac-d332-4502-a9ba-6902d0ab95b9_model.json b/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/fd35e1ac-d332-4502-a9ba-6902d0ab95b9_model.json new file mode 100644 index 0000000000000000000000000000000000000000..930407dfd3c24537e3d2bd1a402490844a69610e --- /dev/null +++ b/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/fd35e1ac-d332-4502-a9ba-6902d0ab95b9_model.json @@ -0,0 +1,2321 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.11, + 0.131, + 0.861, + 0.152 + ], + "angle": 0, + "content": "Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval" + }, + { + "type": "text", + "bbox": [ + 0.134, + 0.18, + 0.842, + 0.253 + ], + "angle": 0, + "content": "Haochen Han\\(^{1*}\\), Qinghua Zheng\\(^{1}\\), Guang Dai\\(^{2}\\), Minnan Luo\\(^{1\\dagger}\\), Jingdong Wang\\(^{3}\\) \n\\(^{1}\\) Xi'an Jiaotong University \\(^{2}\\) SGIT AI Lab, State Grid Corporation of China \\(^{3}\\) Baidu Inc \nhhc1997@stu.xjtu.edu.cn, {qhzheng, minluo}@xjtu.edu.cn \nguang.gdai@gmail.com, wangjingdong@baidu.com" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.287, + 0.314, + 0.303 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.319, + 0.474, + 0.711 + ], + "angle": 0, + "content": "Collecting well-matched multimedia datasets is crucial for training cross-modal retrieval models. However, in real-world scenarios, massive multimodal data are harvested from the Internet, which inevitably contains Partially Mismatched Pairs (PMPs). Undoubtedly, such semantical irrelevant data will remarkably harm the cross-modal retrieval performance. Previous efforts tend to mitigate this problem by estimating a soft correspondence to down-weight the contribution of PMPs. In this paper, we aim to address this challenge from a new perspective: the potential semantic similarity among unpaired samples makes it possible to excavate useful knowledge from mismatched pairs. To achieve this, we propose L2RM, a general framework based on Optimal Transport (OT) that learns to rematch mismatched pairs. In detail, L2RM aims to generate refined alignments by seeking a minimal-cost transport plan across different modalities. To formalize the rematching idea in OT, first, we propose a self-supervised cost function that automatically learns from explicit similarity-cost mapping relation. Second, we present to model a partial OT problem while restricting the transport among false positives to further boost refined alignments. Extensive experiments on three benchmarks demonstrate our L2RM significantly improves the robustness against PMPs for existing models. The code is available at https://github.com/hhc1997/L2RM." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.742, + 0.21, + 0.758 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.768, + 0.47, + 0.829 + ], + "angle": 0, + "content": "The pursuit of general intelligence has advanced the progress of multimodal learning, which aims to understand and integrate multiple sensory modalities like humans. Cross-modal retrieval is one of the most important" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.287, + 0.616, + 0.441 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.629, + 0.291, + 0.747, + 0.44 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.76, + 0.287, + 0.89, + 0.441 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.456, + 0.893, + 0.554 + ], + "angle": 0, + "content": "Figure 1. A toy example to illustrate our idea. The potential semantic similarity among unpaired samples makes it possible to excavate useful knowledge from mismatched pairs. Our L2RM aims to rematch PMPs by generating a refined alignment that brings relevant cross-modal samples (green links) together while repelling irrelevant ones (red links) away from each other. We also show some real-world rematched cases for our L2RM in Fig. 5." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.577, + 0.893, + 0.622 + ], + "angle": 0, + "content": "techniques in multimodal learning due to its flexibility in bridging different modalities [15, 20, 22, 25, 37, 42], which has powered various real-world applications." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.626, + 0.895, + 0.881 + ], + "angle": 0, + "content": "Despite the remarkable performance of previous methods, much of their success can be attributed to the voracious appetite for well-matched cross-modal pairs. In practice, collecting such ideal data [24] is notoriously labor-intensive and even impossible. Alternatively, several mainstream cross-modal datasets utilize the co-occurred information to crawl data from the Internet, especially for visual-text samples [11]. Although such a data collection way is free from expensive annotations, it will inevitably introduce partially mismatched pairs. For example, the standard image-caption dataset, Conceptual Captions [36], is estimated to contain about \\(3\\%\\) to \\(20\\%\\) mismatched pairs. Such semantically irrelevant data will be wrongly treated as the matched pairs for training, which undoubtedly impairs the performance of cross-modal retrieval models. Thus, endowing cross-modal learning with robustness against PMPs is crucial to suit real-world retrieval scenarios." + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.886, + 0.892, + 0.902 + ], + "angle": 0, + "content": "To alleviate the PMP problem, existing works [19,23,45]" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.839, + 0.441, + 0.852 + ], + "angle": 0, + "content": "*This work was completed during his internship at SGIT AI Lab." + }, + { + "type": "page_footnote", + "bbox": [ + 0.078, + 0.852, + 0.469, + 0.9 + ], + "angle": 0, + "content": "†Corresponding author. This work was supported by the National Key Research and Development Program of China (2022YFB3102600), and National Nature Science Foundation of China (62272374, 62192781, 62202367, 62250009, and 62137002)." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.839, + 0.469, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "26679" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.181 + ], + "angle": 0, + "content": "typically resort to recasting the estimated soft correspondence into a soft margin to adjust the distance in triplet ranking loss. However, the underuse of mismatched pairs, only limited to down-weighting their contribution, has led to sub-optimal retrieval performance. Hence, it is necessary to address the PMP issue in a data-efficient manner." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.183, + 0.473, + 0.59 + ], + "angle": 0, + "content": "A question naturally arises: Could cross-modal retrieval models even learn useful knowledge from mismatched pairs? To answer this question, this paper presents L2RM, a general framework that learns to rematch mismatched pairs for robust cross-modal retrieval. As illustrated in Fig. 1, our key idea is to excavate the potential matching relationship among mismatched cross-modal samples. Specifically, we first identify possibly mismatched pairs from training data by modeling the per-sample loss distribution. Then, we formalize the rematching idea as an OT problem to generate a new set of refined alignments for mismatched pairs in every minibatch. Notably, the cost function plays a paramount role when applying OT, which is typically designed as feature-driven distance [5, 10, 18]. However, the over-dependence on representations has led to a cycle of self-reinforcing errors—the existence of PMPs can generate corrupted representations—in turn, preventing the effective transport plan. To handle this problem, we propose a self-supervised learning solution to automatically learn the cost function from explicit similarity-cost mapping relation, which is unexplored in previous OT literature. Moreover, instead of exactly rematching all mismatched samples, we suggest modeling a partial OT problem while restricting the transport among false positives to boost the refined alignment. In practice, we show that our optimization objective could be solved by the Sinkhorn algorithm [9], which only incurs cheap computational overheads." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.59, + 0.472, + 0.803 + ], + "angle": 0, + "content": "Our main contributions are summarized as follows: (1) We propose a general OT-based framework to address the widely-existed PMP problem in cross-modal retrieval. The key to our method is learning to rematch mismatched pairs, which goes beyond previous efforts from the data-efficient view. (2) To address the error accumulation faced by the vanilla cost function, we propose a novel self-supervised learner that automatically learns the transport cost from explicit similarity-cost mapping relation. (3) To further boost the refined alignment, we present to model a partial OT problem and restrict the transport among false positives. (4) Extensive experiments on several benchmarks demonstrate our L2RM endows existing cross-modal retrieval methods with strong robustness against PMPs." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.815, + 0.22, + 0.831 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Cross-Modal Retrieval. Approaches for cross-modal retrieval aim to retrieve relevant items across different modalities for the query data. Current dominant methods project different modalities into a shared embedding space to mea" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.242 + ], + "angle": 0, + "content": "sure the similarity of cross-modal pairs, which generally follow two research lines: 1) Global Alignment focuses on learning the correspondence between whole cross-modal data. Existing studies usually propose a two-stream network to learn comparable global features [13, 30, 47]. 2) Local Alignment. It seeks to align the fine-grained regions for more precise cross-modal matching. For example, [26] employ the cross-attention mechanism to fully excavate the semantic region-word alignments. [43, 44] explore the intramodal relation to facilitate inter-modal alignments." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.243, + 0.893, + 0.44 + ], + "angle": 0, + "content": "Although these prior arts have achieved promising results, their success mainly relies on well-matched data, which is extremely expensive and even impossible to collect. To satisfy a more practical retrieval that is robust against the PMPs, [23, 33, 45] divide the mismatched pairs from training data and estimate a soft correspondence to downweight their training contribution. Recently, [21] resorts to complementary contrastive learning that only utilizes the negative information to avoid overfitting. However, these methods neglect the usage of either the negative information [23, 33, 45] or the positive one [21]. To fully leverage the training data, this paper proposes an OT-based method to rematch those partially mismatched pairs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.457, + 0.893, + 0.624 + ], + "angle": 0, + "content": "Optimal Transport. OT is used to seek a minimal-cost transport plan from one probability measure to another. The original OT model is a linear program that incurs expensive computational cost. [9] proposes the entropy-regularized OT to provide a computationally cheaper solver. Recently, OT has gained increasing attention from different fields in machine learning, including unsupervised learning [4, 29], semi-supervised learning [39], object detection [1, 17], domain adaptation [14, 35], and long-tailed recognition [32, 40]. To the best of our knowledge, we are the first to perform the PMP problem from an OT perspective." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.635, + 0.64, + 0.651 + ], + "angle": 0, + "content": "3. Preliminaries" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.66, + 0.685, + 0.675 + ], + "angle": 0, + "content": "3.1. Background on OT" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.683, + 0.892, + 0.85 + ], + "angle": 0, + "content": "OT provides a mechanism to infer the correspondence between two measures. We briefly introduce the OT theory to help us better view the PMP problem from an OT perspective. Consider \\( \\mathbf{X} = \\{x_{i}\\}_{i = 1}^{m} \\) and \\( \\mathbf{Y} = \\{y_{j}\\}_{j = 1}^{n} \\) as two discrete variables, and we denote their probability measures as \\( \\pmb {p} = \\sum_{i = 1}^{m}p_{i}\\delta (x_{i}) \\) and \\( \\pmb {q} = \\sum_{j = 1}^{n}q_{j}\\delta (y_{j}) \\) where \\( \\delta \\) is the Dirac function, \\( p_i \\) and \\( q_{j} \\) are the probability mass belonging to the probability simplex. When a meaningful cost function \\( c(\\cdot) \\) is defined, we can get the cost matrix \\( C\\in \\mathbb{R}^{m\\times n} \\) between \\( \\mathbf{X} \\) and \\( \\mathbf{Y} \\), where \\( C_{ij} = c(x_i,y_j) \\). Based on these, the OT distance can be expressed as:" + }, + { + "type": "equation", + "bbox": [ + 0.597, + 0.858, + 0.892, + 0.887 + ], + "angle": 0, + "content": "\\[\n\\mathrm {O T} (\\boldsymbol {p}, \\boldsymbol {q}) \\triangleq \\min _ {\\boldsymbol {\\pi} \\in \\Pi (\\boldsymbol {p}, \\boldsymbol {q})} \\left\\langle \\boldsymbol {\\pi}, \\boldsymbol {C} \\right\\rangle_ {F} \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.519, + 0.887, + 0.866, + 0.905 + ], + "angle": 0, + "content": "\\[\n\\text {s . t .} \\Pi (\\boldsymbol {p}, \\boldsymbol {q}) = \\left\\{\\boldsymbol {\\pi} \\in \\mathbb {R} _ {+} ^ {m \\times n} | \\boldsymbol {\\pi} \\mathbb {1} _ {n} = \\boldsymbol {p}, \\boldsymbol {\\pi} ^ {\\top} \\mathbb {1} _ {m} = \\boldsymbol {q} \\right\\},\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "26680" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.138 + ], + "angle": 0, + "content": "where \\(\\langle \\cdot, \\cdot \\rangle_F\\) is the Frobenius dot-product and \\(\\mathbb{1}_d\\) denotes a \\(d\\)-dimensional all-one vector. \\(\\pi\\) is called the optimal transport plan that transport \\(\\pmb{p}\\) towards \\(\\pmb{q}\\) at the smallest cost." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.148, + 0.262, + 0.163 + ], + "angle": 0, + "content": "3.2. Problem Definition" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.172, + 0.47, + 0.399 + ], + "angle": 0, + "content": "Without losing generality, we take the visual-text retrieval as an example to present the PMP problem in cross-modal retrieval. Consider a training dataset \\(\\mathbb{D} = \\{(V_i,T_i,m_i)\\}_{i=1}^N\\) consisting of \\(N\\) samples, where \\((V_i,T_i)\\) is the visual-text pair and \\(m_i \\in \\{1,0\\}\\) indicates whether the bimodal data is semantically matched or not. The key to cross-modal retrieval lies in measuring the similarity across distinct modalities. To achieve this, existing methods usually project the visual and textual modalities into a comparable feature space via the corresponding modal-specific networks \\(f_v\\) and \\(f_t\\), respectively. Then the similarity of a given visual-text pair is measured through \\(S_{ij} = g(f_v(V_i), f_t(T_j))\\), where \\(g\\) is a nonparametric or parametric mapping function. For convenience, we denote \\(g(f_v(V_i), f_t(T_j))\\) as \\(g(V_i, T_j)\\) in the following." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.4, + 0.472, + 0.476 + ], + "angle": 0, + "content": "Ideally, the positive (matched) pairs should have higher similarity while the negative (mismatched) pairs should have lower ones, which can be achieved by minimizing the triplet loss [13] or InfoNCE loss [31]. Consider a batch of \\( N_{b} \\) pairs \\( \\{(V_{i},T_{i})\\}_{i = 1}^{N_{b}} \\), the triplet loss is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.124, + 0.489, + 0.47, + 0.527 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) = [ \\alpha - g \\left(V _ {i}, T _ {i}\\right) + g \\left(V _ {i}, \\hat {T} _ {h}\\right) ] _ {+} \\tag {2} \\\\ + \\left[ \\alpha - g \\left(V _ {i}, T _ {i}\\right) + g \\left(\\hat {V} _ {h}, T _ {i}\\right) \\right] _ {+}, \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.542, + 0.469, + 0.603 + ], + "angle": 0, + "content": "where \\(\\alpha\\) is a margin and \\([x]_{+} = \\max (x,0)\\). \\(\\hat{V}_h\\) and \\(\\hat{T}_h\\) are the most similar negatives in the given batch corresponding to \\((V_i,T_i)\\). Eq.(2) aims to enforce the negative pairs to be distant from the positives by a certain margin value." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.604, + 0.469, + 0.813 + ], + "angle": 0, + "content": "Alternatively, InfoNCE loss is extended to cross-modal scenario [21,34] that encourages the similarity gap between positives and negatives as large as possible. Formally, the matching probability of \\(j\\)-th textual sample w.r.t. the \\(i\\)-th visual query is defined as \\(p_{ij}^{2t} = \\frac{\\exp(g(V_i,T_j) / \\tau)}{\\sum_{j' = 1}^{N_b}\\exp(g(V_i,T_{j'}) / \\tau)}\\), where \\(\\tau\\) is a temperature parameter. As InfoNCE loss is symmetric, the matching probability \\(p_{ij}^{t2v}\\) is defined similarly. For notation convenience, we denote \\(\\pmb{p}_i^{2t} = [p_{i1}^{2t},\\dots ,p_{iN_b}^{2t}]^\\top\\) and \\(\\pmb{p}_i^{t2v} = [p_{i1}^{t2v},\\dots ,p_{iN_b}^{t2v}]^\\top\\) as the probability vectors. To align cross-modal samples, the corresponding one-hot vector \\(\\pmb{y}_i = [y_{i1},\\dots ,y_{iN_b}]^\\top\\) is used as supervision, where \\(y_{ij}\\) equal to 1 if \\(i = j\\) while other elements are 0. Thus, the cross-modal InfoNCE loss is given by:" + }, + { + "type": "equation", + "bbox": [ + 0.121, + 0.824, + 0.469, + 0.843 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} ^ {\\text {I n f o N C E}} \\left(V _ {i}, T _ {i}\\right) = \\mathcal {H} \\left(\\boldsymbol {y} _ {i}, \\boldsymbol {p} _ {i} ^ {v 2 t}\\right) + \\mathcal {H} \\left(\\boldsymbol {y} _ {i}, \\boldsymbol {p} _ {i} ^ {t 2 v}\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.855, + 0.388, + 0.87 + ], + "angle": 0, + "content": "where \\(\\mathcal{H}\\) is the batched cross-entropy function." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.469, + 0.901 + ], + "angle": 0, + "content": "The success of both Eq.(2) and Eq.(3) relies on the well-matched pairs. However, in practice, the multimedia" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.892, + 0.151 + ], + "angle": 0, + "content": "datasets are usually web-collected, and thus inevitably contains an unknown portion of irrelevant pairs but are wrongly treated as matched (\\(m_i = 1\\)). Our goal is to combat such PMPs to facilitate robust cross-modal retrieval." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.165, + 0.635, + 0.182 + ], + "angle": 0, + "content": "4. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.19, + 0.892, + 0.387 + ], + "angle": 0, + "content": "To tackle the PMP problem, the mainstream pipeline first uses the memorization effect [3] of DNNs, i.e., DNNs learn simpler patterns before memorizing the difficult ones, to partition the dataset into a matched subset \\(\\mathbb{D}_m\\), and a mismatched subset \\(\\mathbb{D}_{\\widetilde{m}} = \\mathbb{D} / \\mathbb{D}_m\\). After that, \\(\\mathbb{D}_m\\) can be used for standard cross-modal training. To mitigate the impact of PMPs, recent advances [19, 23, 45] introduce a soft margin into Eq.(2) to down-weight the samples from \\(\\mathbb{D}_{\\widetilde{m}}\\). However, due to the underuse of mismatched pairs, the achieved performance by them is argued to be sub-optimal. In this work, we aim to fully leverage PMPs by trying to excavate the potential semantic similarity among mismatched pairs. In the following, we present the details of our method." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.396, + 0.766, + 0.412 + ], + "angle": 0, + "content": "4.1. Identifying Mismatched Pairs" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.419, + 0.892, + 0.57 + ], + "angle": 0, + "content": "Following the mainstream learning style, we first identify possibly mismatched pairs from all training data. The memorization effect of DNNs indicates that mismatched samples tend to have relatively higher loss during the early stage of training. Based on this, we use the difference in loss distribution between the matched and mismatched pairs to divide the training set. Empirically, we observe that the distribution of triplet loss is more distinguishable. Thus, given the retrieval model \\((f_v, f_t, g)\\), we compute the per-sample loss through Eq.(2):" + }, + { + "type": "equation", + "bbox": [ + 0.554, + 0.579, + 0.891, + 0.598 + ], + "angle": 0, + "content": "\\[\n\\ell_ {\\left(f _ {v}, f _ {t}, g\\right)} = \\left\\{\\ell_ {i} \\right\\} _ {i = 1} ^ {N} = \\left\\{\\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) \\right\\} _ {i = 1} ^ {N}. \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.607, + 0.892, + 0.728 + ], + "angle": 0, + "content": "Then, we fit a two-component beta mixture model [2,19,45] to \\(\\ell_{(f_v,f_t,g)}\\) using the Expectation-Maximization algorithm. For \\(i\\)-th pair, its probability \\(w_{i}\\) being mismatched is the posterior probability \\(p(b|\\ell_i)\\), where \\(b\\) is the beta component with a higher mean. By setting a threshold on \\(\\{w_{i}\\}_{i = 1}^{N}\\), we can divide the training data into the matched subset \\(\\mathbb{D}_m\\) and mismatched subset \\(\\mathbb{D}_{\\widetilde{m}}\\) (we set the threshold to 0.5 in all experiments for brevity)." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.728, + 0.892, + 0.834 + ], + "angle": 0, + "content": "For initial convergence of the algorithm, we warm up the model for a few epochs by training on all data with Eq.(2) or Eq.(3). However, for extreme mismatching rates, the model would quickly overfit to mismatched pairs and produce unreliable loss. To address this issue, we mitigate the overconfidence of the model by adding a reverse cross entropy [41] term to the InfoNCE loss during warm-up, i.e.," + }, + { + "type": "equation", + "bbox": [ + 0.554, + 0.843, + 0.891, + 0.862 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} ^ {\\mathrm {R C E}} \\left(V _ {i}, T _ {i}\\right) = \\mathcal {H} \\left(\\boldsymbol {p} _ {i} ^ {v 2 t}, \\boldsymbol {y} _ {i}\\right) + \\mathcal {H} \\left(\\boldsymbol {p} _ {i} ^ {t 2 v}, \\boldsymbol {y} _ {i}\\right). \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In the presence of PMPs, \\( y_{i} \\) may provide the wrong matching relation. Instead, the estimated probability could reflect" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.946, + 0.518, + 0.957 + ], + "angle": 0, + "content": "26681" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.089, + 0.895, + 0.292 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.303, + 0.895, + 0.348 + ], + "angle": 0, + "content": "Figure 2. Overview of the learnable cost function with self-supervised learning. The up part illustrates the reconstructed pairs that only \\((V_4, T_1)\\), \\((V_2, T_3)\\), and \\((V_{N_b}, T_{N_b})\\) are the reserved matching ones. Then, the matching matrix is viewed as supervision to guide the cost function from the explicit similarity-cost mapping relation through an OT loss (the down part)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.368, + 0.471, + 0.414 + ], + "angle": 0, + "content": "the truer distribution to a certain extent. Note that we bound the one-hot label into \\([\\epsilon, 1 - \\epsilon]\\) for computational feasibility. \\((\\epsilon = 10^{-7}\\) in our experiments)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.422, + 0.351, + 0.437 + ], + "angle": 0, + "content": "4.2. Rematching Mismatched Pairs" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.445, + 0.47, + 0.522 + ], + "angle": 0, + "content": "We formalize the rematching idea as an OT problem, generating refined alignments by seeking a minimal-cost transport plan. We will first introduce the novel learnable cost function to suit the PMP scenario, then we show how to boost the refined alignment by a relaxed OT model." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.539, + 0.47, + 0.765 + ], + "angle": 0, + "content": "Cost Function with Self-Supervised Learning. Cost function plays a crucial role when learning the transport plan for OT. In general, \\( C_{ij} \\) is set to a distance measure, e.g., \\( L_{2} \\)-distance [18] or cosine distance [10] to measure the expense of transporting a visual sample \\( i \\) to a textual sample \\( j \\). However, the existence of PMPs imposes formidable obstacles for these feature-driven distance measures. On the one hand, training with PMPs can wrongly bring irrelevant data together, which undoubtedly prevents effective representation learning. Even worse, different modalities will be embedded into separate regions of the shared space due to the inherent modality gap [27]. On the other hand, the refined alignments produced by those corrupted features would be used to guide subsequent training, leading to the cycle of self-reinforcing errors [8]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.766, + 0.471, + 0.903 + ], + "angle": 0, + "content": "To address the aforementioned limitations, we propose a novel self-supervised learning approach to automatically learn the cost function. Intuitively, for a given image and caption, the transport cost can be modeled as a function of similarity that higher similarity enjoys a lower cost. Thus, we formulate the cost function as a single-layer feedforward network with parameters \\(\\Theta_c\\), i.e., \\(f_c(\\cdot;\\Theta_c)\\), which takes the similarity matrix of the batched visual-text samples as input and attempts to learn the corresponding cost" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.368, + 0.895, + 0.61 + ], + "angle": 0, + "content": "matrix. To achieve this, we reconstruct the visual-text pairs to guide the cost function from explicit similarity-cost mapping relation. Specifically, for the matched pairs sampled from \\(\\mathbb{D}_m\\), we randomly reserve a part of the matching images and substitute the images from \\(\\mathbb{D}_{\\widetilde{m}}\\) for the remaining ones. With the reserved indexes, we could automatically obtain a matching matrix that indicates the ideal matching probability for each reconstructed pair. For the example illustrated in Fig. 2, \\((V_4,T_1)\\), \\((V_{2},T_{3})\\), and \\((V_{N_b},T_{N_b})\\) are the reserved matching pairs with a matching probability of 1, while the others could be considered as mismatched ones with a matching probability of 0. For convenience, let \\(\\mathbb{D}'\\) be the reconstructed data, and \\((V,T) \\in \\mathbb{D}'\\) be matrices that contain a batch of images and captions. To relate the similarity-cost mapping with the matching matrix, we optimize the cost function by the following OT loss:" + }, + { + "type": "equation", + "bbox": [ + 0.525, + 0.617, + 0.892, + 0.634 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {O T}} \\left(\\boldsymbol {\\pi} ^ {\\sup }, \\boldsymbol {V}, \\boldsymbol {T}\\right) = \\left\\langle \\boldsymbol {\\pi} ^ {\\sup }, f _ {c} \\left(g (\\boldsymbol {V}, \\boldsymbol {T}); \\Theta_ {c}\\right) \\right\\rangle_ {F}, \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.642, + 0.892, + 0.672 + ], + "angle": 0, + "content": "where \\(\\pi^{\\mathrm{sup}}\\) is the matching matrix, and \\(g(\\mathbf{V},\\mathbf{T})\\) denotes the similarity matrix for the batched visual-text pairs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.672, + 0.892, + 0.718 + ], + "angle": 0, + "content": "Eq.(6) seeks an effective cost function from a reverse perspective of OT, which views the ideal transport plan as the supervision to minimize the transport cost." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Boosting Refined Alignments with Relaxed OT. Given the defined cost function, we could generate the refined alignments for mismatched pairs following the OT objective described in Eq.(1). However, Eq.(1) requires the two distributions to have the same total mass and that all the mass of \\( p \\) should be transported to exactly match the mass of \\( q \\). In practice, due to the limited batch size, one caption may be irrelevant to all images in the batch and vice versa. To this end, we adopt the partial OT model [6, 16] to relax such strict all-to-all mass constraints, which seeks a minimal cost of only transporting \\( 0 \\leqslant \\rho \\leqslant \\min(\\|p\\|_1, \\|q\\|_1) \\)" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "26682" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.078, + 0.089, + 0.895, + 0.223 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.232, + 0.895, + 0.276 + ], + "angle": 0, + "content": "Figure 3. Illustration of the proposed rematching loss. For the mismatched pairs, we formalize a partial OT problem with positive pairs masked to generate the refined alignment in each batch. The refined alignment provides a more reliable matching relation to supervise the mismatched pairs. Then, we compute the symmetric KL-divergence to optimize the retrieval model \\((f_v, f_t, g)\\)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.287, + 0.47, + 0.302 + ], + "angle": 0, + "content": "unit mass between the visual and textual distribution, i.e.," + }, + { + "type": "equation", + "bbox": [ + 0.078, + 0.325, + 0.47, + 0.35 + ], + "angle": 0, + "content": "\\[\n\\min _ {\\boldsymbol {\\pi} \\in \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q})} \\left\\langle \\boldsymbol {\\pi}, \\boldsymbol {C} \\right\\rangle_ {F}, \\text {s . t .} \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q}) = \\left\\{\\boldsymbol {\\pi} \\in \\mathbb {R} _ {+} ^ {m \\times n} | \\boldsymbol {\\pi} \\mathbb {1} _ {n} \\leqslant \\boldsymbol {p}, \\right.\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.202, + 0.352, + 0.469, + 0.371 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {\\pi} ^ {\\top} \\mathbb {1} _ {m} \\leqslant \\boldsymbol {q}, \\mathbb {1} _ {m} ^ {\\top} \\pi \\mathbb {1} _ {n} = \\rho \\}. \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.379, + 0.47, + 0.499 + ], + "angle": 0, + "content": "Furthermore, the false positives contained in the mismatched pairs introduce an implicit constraint to our transport plan \\(\\pi\\) that the transport mass between the same element in two distributions should be limited. To this end, we propose to impose a mask operation on the transport plan that restricts the transport to only concentrate among the unpaired pairs. Specifically, the mask matrix \\(M\\in \\mathbb{R}^{m\\times n}\\) is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.19, + 0.505, + 0.47, + 0.546 + ], + "angle": 0, + "content": "\\[\nM _ {i j} \\triangleq \\left\\{ \\begin{array}{l l} 0, & \\text {i f} i = j, \\\\ 1, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.552, + 0.47, + 0.583 + ], + "angle": 0, + "content": "Then the masked transport plan is defined as the Hadamard product \\(\\tilde{\\pi} = M\\odot \\pi\\) and be optimized through Eq.(7)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.59, + 0.294, + 0.607 + ], + "angle": 0, + "content": "4.3. The Training Objective" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.612, + 0.47, + 0.725 + ], + "angle": 0, + "content": "Given the mismatched pairs \\(\\{(V_i, T_i)\\}_{i=1}^{N_b}\\) sampled from \\(\\mathbb{D}_{\\widetilde{m}}\\), if we don't have any prior knowledge, we could consider the visual and textual samples following the uniform distributions, i.e., \\(\\pmb{p} = \\sum_{i=1}^{N_b} \\frac{1}{N_b} \\delta(V_i)\\) and \\(\\pmb{q} = \\sum_{i=1}^{N_b} \\frac{1}{N_b} \\delta(T_i)\\), respectively. To guarantee the efficiency of our algorithm, we adopt an online strategy to update \\(\\Theta_c\\) and calculate \\(\\widetilde{\\pi}\\) through a single optimization loop:" + }, + { + "type": "equation", + "bbox": [ + 0.08, + 0.743, + 0.469, + 0.81 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\min _ {\\tilde {\\boldsymbol {\\pi}} \\in \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q})} \\mathbb {E} _ {(\\boldsymbol {V}, \\boldsymbol {T}) \\in \\mathbb {D} _ {\\tilde {m}}} \\left\\langle \\tilde {\\boldsymbol {\\pi}}, f _ {c} \\left(g \\left(\\boldsymbol {V}, \\boldsymbol {T}\\right); \\Theta_ {c} ^ {*}\\right) \\right\\rangle_ {F} - \\lambda H (\\tilde {\\boldsymbol {\\pi}}), \\\\ \\text {s . t .} \\Theta_ {c} ^ {*} = \\underset {\\Theta_ {c}} {\\arg \\min } \\mathbb {E} _ {(\\boldsymbol {V}, \\boldsymbol {T}, \\boldsymbol {\\pi} ^ {\\sup }) \\in \\mathbb {D} ^ {\\prime}} \\mathcal {L} _ {O T} (\\boldsymbol {\\pi} ^ {\\sup }, \\boldsymbol {V}, \\boldsymbol {T}) \\tag {9} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.47, + 0.902 + ], + "angle": 0, + "content": "where \\(\\lambda > 0\\) is a regularization parameter for the entropic constraint \\(H(\\tilde{\\pi}) = -\\sum_{ij} \\tilde{\\pi}_{ij} \\log \\tilde{\\pi}_{ij}\\). Note that Eq.(9) introduces an entropy regularization item to the OT model, which enables the transport plan to be solved by the computationally cheaper Sinkhorn-Knopp algorithm [9]. The detailed solution is presented in Appendix A." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.287, + 0.895, + 0.452 + ], + "angle": 0, + "content": "The optimal transport plan from Eq.(9) represents a refined alignment that provides a more reliable matching relation for those mismatched visual-text samples. As our refined alignment is generated dynamically, we adopt the KL-divergence to compute the rematching loss instead of the cross entropy. Besides, a reverse term is added to symmetrize the KL-divergence, which makes the training more stable. Formally, let \\(\\tilde{\\pi}_i^{v2t}\\) and \\(\\tilde{\\pi}_i^{t2v}\\) be the row-wise and column-wise normalized refined alignment for the \\(i\\)-th sample, respectively. Then, the rematching loss (see Fig. 3) is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.5, + 0.457, + 0.894, + 0.527 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} ^ {\\mathrm {r e}} \\left(V _ {i}, T _ {i}\\right) = \\frac {1}{2} \\left[ D _ {K L} \\left(\\tilde {\\boldsymbol {\\pi}} _ {i} ^ {v 2 t} \\parallel \\boldsymbol {p} _ {i} ^ {v 2 t}\\right) + D _ {K L} \\left(\\boldsymbol {p} _ {i} ^ {v 2 t} \\parallel \\tilde {\\boldsymbol {\\pi}} _ {i} ^ {v 2 t}\\right) \\right] \\\\ + \\frac {1}{2} \\left[ D _ {K L} \\left(\\tilde {\\boldsymbol {\\pi}} _ {i} ^ {t 2 v} \\| \\boldsymbol {p} _ {i} ^ {t 2 v}\\right) + D _ {K L} \\left(\\boldsymbol {p} _ {i} ^ {t 2 v} \\| \\tilde {\\boldsymbol {\\pi}} _ {i} ^ {t 2 v}\\right) \\right]. \\tag {10} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.529, + 0.894, + 0.573 + ], + "angle": 0, + "content": "For the pairs that are divided as matched, we use the triplet ranking loss to directly control the distance gap. Thus, our final objective function is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.52, + 0.58, + 0.892, + 0.615 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} ^ {\\text {F i n a l}} = \\sum_ {(V _ {i}, T _ {i}) \\in \\mathbb {D} _ {m}} \\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) + \\sum_ {(V _ {i}, T _ {i}) \\in \\mathbb {D} _ {\\tilde {m}}} \\mathcal {L} ^ {\\text {r e}} \\left(V _ {i}, T _ {i}\\right). \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.622, + 0.892, + 0.637 + ], + "angle": 0, + "content": "The detailed training pseudo-code is shown in Appendix B." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.649, + 0.625, + 0.666 + ], + "angle": 0, + "content": "5. Experiment" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.674, + 0.891, + 0.703 + ], + "angle": 0, + "content": "In this section, we experimentally analyze the effectiveness of L2RM in robust cross-modal retrieval." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.712, + 0.582, + 0.728 + ], + "angle": 0, + "content": "5.1. Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.894, + 0.902 + ], + "angle": 0, + "content": "Datasets. We apply our method to three image-text retrieval datasets varying in scale and scope. Specifically, Flickr30K [46] consists of 31,000 images with five corresponding text annotations for each image from the Flickr website. Following [23], we split 1,000 images for validation, 1,000 images for testing, and the rest for training. MS-COCO [28] is a large-scale cross-modal dataset, which collects 123,287 images with five sentences each. Following [23], we use 5,000 images for validation, 5,000 images for testing, and the rest for training. Conceptual Captions [36] is a web-crawled large-scale dataset containing" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "26683" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.093, + 0.088, + 0.891, + 0.63 + ], + "angle": 0, + "content": "
MRateMethodFlickr30KMS-COCO
Image-to-TextText-to-ImagerSumImage-to-TextText-to-ImagerSum
R@1R@5R@10R@1R@5R@10R@1R@5R@10R@1R@5R@10
0.2IMRAM59.185.491.944.571.479.4431.769.993.697.455.984.489.6490.8
NCR73.593.296.656.982.488.5491.176.695.698.260.888.895.0515.0
BiCro74.794.396.856.681.488.2492.076.695.498.261.388.894.8515.1
DECL-SGR74.592.997.153.679.586.8484.475.695.198.359.988.394.7511.9
DECL-SGRAF77.593.897.056.181.888.5494.777.595.998.461.789.395.4518.2
RCL-SGR74.291.896.955.681.287.5487.277.095.598.161.388.894.8515.5
RCL-SGRAF75.994.597.357.982.688.6496.878.996.098.462.889.995.4521.4
L2RM-SAF73.794.397.756.881.888.1492.477.996.098.362.189.294.9518.4
L2RM-SGR76.593.797.355.581.588.0492.578.495.798.362.189.194.9518.5
L2RM-SGRAF77.995.297.859.883.689.5503.880.296.398.564.290.195.4524.7
0.4IMRAM44.973.282.631.656.365.6354.251.882.490.938.470.378.9412.7
NCR68.189.694.851.478.484.8467.174.794.698.059.688.194.7509.7
BiCro70.792.095.551.977.785.4473.275.295.398.160.087.894.3510.7
DECL-SGR69.090.294.850.776.384.1465.173.694.697.957.886.993.9504.7
DECL-SGRAF72.792.395.453.479.486.4479.675.695.598.359.588.394.8512.0
RCL-SGR71.391.195.351.478.085.2472.373.994.997.959.087.493.9507.0
RCL-SGRAF72.792.796.154.880.087.1483.477.095.598.361.288.594.8515.3
L2RM-SAF72.192.196.152.778.885.9477.774.494.798.359.287.994.4508.9
L2RM-SGR73.192.496.352.379.486.3479.875.294.898.159.487.894.1509.4
L2RM-SGRAF75.893.296.956.381.087.3490.577.595.898.462.089.194.9517.7
0.6IMRAM16.438.250.97.519.225.3157.518.251.668.017.943.654.6253.9
NCR13.937.750.511.030.141.4184.60.10.30.40.10.51.02.4
BiCro64.187.192.747.274.082.3447.473.293.997.657.586.393.4501.9
DECL-SGR64.585.892.644.071.680.6439.169.793.497.554.585.292.6492.9
DECL-SGRAF65.288.494.046.874.082.2450.673.094.297.957.086.693.8502.5
RCL-SGR62.386.392.945.171.380.2438.171.493.297.155.484.792.3494.1
RCL-SGRAF67.789.193.648.074.983.3456.674.094.397.557.686.493.5503.3
L2RM-SAF66.188.893.847.874.282.2452.971.293.497.556.585.993.0497.5
L2RM-SGR65.187.893.647.073.581.5448.572.793.997.556.986.293.3500.5
L2RM-SGRAF70.090.895.451.376.483.7467.675.494.797.959.287.493.8508.4
0.8IMRAM3.19.75.20.30.91.921.11.35.08.30.20.61.316.7
NCR1.56.29.90.31.02.121.00.10.30.40.10.51.02.4
BiCro2.39.217.22.610.216.858.362.288.694.647.479.288.5460.5
DECL-SGR44.472.682.033.959.569.0361.460.088.794.545.978.888.3456.2
DECL-SGRAF53.478.886.937.663.873.9394.464.890.596.049.781.790.3473.0
RCL-SGR47.170.579.430.356.166.3349.763.289.395.247.678.788.0462.0
RCL-SGRAF51.775.884.434.561.270.7378.367.490.896.050.681.090.1475.9
L2RM-SAF50.877.985.535.662.672.7385.164.790.895.850.080.989.4471.6
L2RM-SGR50.577.283.934.261.171.6378.565.290.396.149.881.088.2470.6
L2RM-SGRAF55.780.887.839.465.474.9404.069.091.996.452.682.490.3482.6
" + }, + { + "type": "table_caption", + "bbox": [ + 0.141, + 0.64, + 0.825, + 0.655 + ], + "angle": 0, + "content": "Table 1. Image-text retrieval performance under different mismatching rates (MRate) on Flickr30K and MS-COCO." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.674, + 0.47, + 0.737 + ], + "angle": 0, + "content": "3.3M one-to-one images and captions. Following [23], we use the subset, i.e., CC152K to conduct experiments, which has 150,000 images for training, 1,000 images for validation, and 1,000 images for testing." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Implementation Details. As a general method, L2RM could be directly applied to almost all cross-modal retrieval methods to improve their robustness. Following [21, 33], we apply L2RM to SGR, SAF, and SGRAF for a comprehensive comparison. We evaluate the retrieval performance with the Recall@K (R@K) metric. Following [23], we save the best performance checkpoint on the validation set w.r.t. the sum of the evaluation scores and report its results on the testing set. We follow the same training setting as [23], our specific parameters setting can be found in Appendix C.1." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.674, + 0.892, + 0.797 + ], + "angle": 0, + "content": "Baselines. We compare L2RM with eight state-of-the-art cross-modal retrieval methods, including four general methods (i.e., IMRAM [7], SGR, SAF, and SGRAF [12]) and four robust learning methods against the PMPs (i.e., NCR [23], DECL [33], BiCro [45], and RCL [21]). Note that the original BiCro combines four models, i.e., two co-trained SGR, and two co-trained SAF. For a fair comparison, we report the results of 2 co-trained SGR for BiCro like [23]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.814, + 0.638, + 0.83 + ], + "angle": 0, + "content": "5.2. Main Results" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.903 + ], + "angle": 0, + "content": "In this section, we conduct comparison experiments with different mismatching rates on three datasets to evaluate the performance of our L2RM. As Flickr30K and MS-COCO are well-established datasets, we carry out experiments by" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "26684" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.228 + ], + "angle": 0, + "content": "generating the synthesized false positive pairs, i.e., the mismatching rate (MRate) increases from 0.2 to 0.8 in intervals of 0.2. Following [21, 33], we randomly select a specific percentage of images and randomly permute all their corresponding captions, which is more challenging and practical than the setting in [23, 45]. For the web-collected dataset CC152K, which naturally contains about \\(3\\% \\sim 20\\%\\) unknown mismatched pairs [36]. Thus we directly conduct experiments on it to evaluate the performance with real PMPs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.249, + 0.473, + 0.46 + ], + "angle": 0, + "content": "Results on Synthesized PMPs. Tab. 1 shows the experimental results on Flickr30K and MS-COCO. Note that for MS-COCO, the results are computed by averaging over 5 folds of 1K test images like [21, 33]. Due to space limitation, we omit the results of some general methods (SGR, SAF, and SGRAF), and the comparison on original datasets (0 MRate), which could be found in Appendix C.2. From the results, we can find that L2RM achieves the best results on all metrics than the other state-of-the-art methods, which shows the superior robustness of L2RM against PMPs. Moreover, when the mismatching rate is high, e.g., 0.6 and 0.8, the improvement of L2RM is more evident, proving that excavating mismatched pairs could effectively facilitate robust cross-modal retrieval." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.481, + 0.472, + 0.648 + ], + "angle": 0, + "content": "Results on Real-World PMPs. We validate our method on the real-world dataset CC152K, which contains an unknown portion of mismatched pairs. As shown in Tab. 2, our method considerably outperforms the best baseline in terms of sum in retrieval by \\(9.8\\%\\). Notably, our L2RM-SGR surpasses all SGR variants by a clear margin, achieving as much as a \\(16.9\\%\\) (rSum) absolute improvement over the best variant. It is because the real-world rematched pairs are more likely to involve only local alignments, e.g., Fig. 5(e)-Fig. 5(f), while the SGR model itself is adept at capturing the relationship between local alignments." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.661, + 0.472, + 0.874 + ], + "angle": 0, + "content": "
MethodImage-to-TextText-to-ImagerSum
R@1R@5R@10R@1R@5R@10
IMRAM27.852.460.929.251.561.2283.0
SAF32.559.570.032.560.768.7323.9
SGR14.535.548.913.736.147.9196.6
NCR39.564.573.540.364.673.2355.6
BiCro39.764.672.639.265.074.1355.2
DECL-SAF36.663.073.338.563.273.5348.1
DECL-SGR36.263.673.237.163.673.7347.4
DECL-SGRAF39.066.175.540.766.376.7364.3
RCL-SAF37.563.071.437.862.472.4344.5
RCL-SGR38.363.070.439.263.272.3346.4
RCL-SGRAF41.766.073.641.666.475.1364.4
L2RM-SAF37.362.771.738.865.774.8351.0
L2RM-SGR39.566.276.041.865.974.9364.3
L2RM-SGRAF43.067.575.742.868.077.2374.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.11, + 0.885, + 0.436, + 0.899 + ], + "angle": 0, + "content": "Table 2. Image-text retrieval performance on CC152K." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.091, + 0.655, + 0.108 + ], + "angle": 0, + "content": "5.3. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.113, + 0.895, + 0.386 + ], + "angle": 0, + "content": "Impact of Each Component. To study the influence of specific components in our method, we carry out the ablation study on the Flickr30K with 0.6 MRate. Specifically, we ablate the contributions of three key components of L2RM, i.e., partial OT, positives masked, and the learnable cost function (we use the cosine distance to measure the cost instead). Besides, we compare L2RM with different formulas of rematching loss: KL-divergence and InfoNCE. From Tab. 3, we observe the following conclusions: 1) The full L2RM could achieve the best overall performance, showing that all three components are important to improve the robustness against PMPs. 2) Using the learnable cost function substantially outperforms the variant with the cosine distance cost (e.g., +11.9 in terms of the rSum), which signifies the simple feature-driven cost is sub-optimal to the PMP situation. 3) Formulating different rematching loss could also achieve decent results, which verifies the ability of L2RM to provide effective matching relations." + }, + { + "type": "table", + "bbox": [ + 0.512, + 0.398, + 0.894, + 0.501 + ], + "angle": 0, + "content": "
AblationImage-to-TextText-to-Image
R@1R@5R@10R@1R@5R@10
L2RM65.187.893.647.073.581.5
L2RM w KL-divergence64.787.693.246.774.081.5
L2RM w InfoNCE Loss64.987.593.546.072.980.9
L2RM w/o Partial OT62.286.491.544.768.672.6
L2RM w/o Positives Masked64.987.692.746.473.281.1
L2RM w/o Cost Function61.385.691.444.972.481.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.529, + 0.512, + 0.862, + 0.525 + ], + "angle": 0, + "content": "Table 3. Ablation studies on Flickr30K with 0.6 MRate." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.538, + 0.892, + 0.659 + ], + "angle": 0, + "content": "Parameter Analysis. We now investigate the effect of the parameter \\(\\rho\\) by plotting the recall scores with incremental \\(\\rho\\) on Flickr30K. The figure shows that the overall performance tends to decrease as \\(\\rho\\) increases. We further analyze how untransported pairs benefit the model training in Appendix C.3. Experimentally, we find that the refined alignments for untransported pairs can be equivalent to the label smoothing strategy [38]." + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.671, + 0.697, + 0.782 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.558, + 0.784, + 0.652, + 0.797 + ], + "angle": 0, + "content": "(a) Image to Text" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.671, + 0.884, + 0.782 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.743, + 0.784, + 0.836, + 0.797 + ], + "angle": 0, + "content": "(b) Text to Image" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.805, + 0.892, + 0.833 + ], + "angle": 0, + "content": "Figure 4. Parameter analysis of L2RM-SGR in terms of recall scores on the testing set of Flickr30K under 0.2 MRate." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.9 + ], + "angle": 0, + "content": "Discussions on Warm-up Methods. We use different warm-up methods, i.e., triplet loss [13] and InfoNCE loss [31] for our L2RM-SGR. The experiments are conducted on the Flickr30K with 0.8 MRate and the CC152K with real" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "26685" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.091, + 0.213, + 0.17 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.085, + 0.173, + 0.192, + 0.189 + ], + "angle": 0, + "content": "Given: view bar out on the lounge chairs" + }, + { + "type": "image_caption", + "bbox": [ + 0.084, + 0.197, + 0.206, + 0.22 + ], + "angle": 0, + "content": "Rematched: the facade can be lit up at night using different coloured led lights (0.988)" + }, + { + "type": "image_caption", + "bbox": [ + 0.138, + 0.225, + 0.158, + 0.238 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.225, + 0.091, + 0.316, + 0.18 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.234, + 0.181, + 0.302, + 0.197 + ], + "angle": 0, + "content": "Given: the gift of the present" + }, + { + "type": "image_caption", + "bbox": [ + 0.234, + 0.204, + 0.311, + 0.219 + ], + "angle": 0, + "content": "Rematched: a man on a bicycle (0.996)" + }, + { + "type": "image_caption", + "bbox": [ + 0.261, + 0.224, + 0.28, + 0.238 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image", + "bbox": [ + 0.327, + 0.091, + 0.459, + 0.17 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.325, + 0.174, + 0.465, + 0.197 + ], + "angle": 0, + "content": "Given: a survey has revealed that a third would be less likely to travel if it was no longer a member" + }, + { + "type": "image_caption", + "bbox": [ + 0.325, + 0.203, + 0.447, + 0.219 + ], + "angle": 0, + "content": "Rematched: suspension bridge over a city (0.963)" + }, + { + "type": "image_caption", + "bbox": [ + 0.383, + 0.225, + 0.403, + 0.238 + ], + "angle": 0, + "content": "(c)" + }, + { + "type": "image", + "bbox": [ + 0.47, + 0.091, + 0.602, + 0.169 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.468, + 0.179, + 0.608, + 0.194 + ], + "angle": 0, + "content": "Given: video: fans sing composition after mic issue" + }, + { + "type": "image_caption", + "bbox": [ + 0.468, + 0.203, + 0.607, + 0.219 + ], + "angle": 0, + "content": "Rematched: most popular sports in the world - hockey (0.965)" + }, + { + "type": "image_caption", + "bbox": [ + 0.527, + 0.224, + 0.547, + 0.238 + ], + "angle": 0, + "content": "(d)" + }, + { + "type": "image", + "bbox": [ + 0.615, + 0.091, + 0.745, + 0.169 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.625, + 0.18, + 0.718, + 0.194 + ], + "angle": 0, + "content": "Given: day on the place unknown" + }, + { + "type": "image_caption", + "bbox": [ + 0.624, + 0.203, + 0.737, + 0.219 + ], + "angle": 0, + "content": "Rematched: a couple of men stand on a small hill (0.938)" + }, + { + "type": "image_caption", + "bbox": [ + 0.67, + 0.224, + 0.69, + 0.238 + ], + "angle": 0, + "content": "(e)" + }, + { + "type": "image", + "bbox": [ + 0.757, + 0.091, + 0.888, + 0.169 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.756, + 0.173, + 0.877, + 0.195 + ], + "angle": 0, + "content": "Given: a general view of atmosphere outside the diesel and launch party" + }, + { + "type": "image_caption", + "bbox": [ + 0.757, + 0.203, + 0.89, + 0.219 + ], + "angle": 0, + "content": "Rematched: a motorcycle winds their way through country (0.626)" + }, + { + "type": "image_caption", + "bbox": [ + 0.814, + 0.224, + 0.831, + 0.238 + ], + "angle": 0, + "content": "(f)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.254, + 0.892, + 0.281 + ], + "angle": 0, + "content": "Figure 5. The ability of our L2RM to rematch the mismatched visual-text samples. The figure shows some representative rematched pairs for L2RM-SGR on the training set of CC152K dataset. We highlight the matched words in green and the mismatched words in red." + }, + { + "type": "table", + "bbox": [ + 0.086, + 0.292, + 0.469, + 0.352 + ], + "angle": 0, + "content": "
MethodFlickr30KCC152K
Image-to-TextText-to-ImageImage-to-TextText-to-Image
R@1R@5R@10R@1R@5R@10R@1R@5R@10R@1R@5R@10
Triplet0.10.71.30.10.71.138.264.271.439.564.271.9
InfoNCE45.971.480.329.252.761.139.366.875.040.865.274.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.363, + 0.469, + 0.39 + ], + "angle": 0, + "content": "Table 4. Comparison with different warm-up methods on Flickr30K with 0.8 MRate and CC152K." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.411, + 0.469, + 0.531 + ], + "angle": 0, + "content": "PMPs. As shown in Tab. 4, one could see that the triplet loss cannot achieve satisfactory performance under the extreme mismatching rate. Compared with the results of the L2RM-SGR in Tab. 1, one could find that it is necessary to limit the overconfidence of the model during the warm-up process. The results on CC152K show that our method is robust to the choice of warm-up methods under a relatively low mismatching rate." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.541, + 0.317, + 0.557 + ], + "angle": 0, + "content": "5.4. Visualization and Analysis" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.565, + 0.469, + 0.731 + ], + "angle": 0, + "content": "Distribution of Transport Cost. To intuitively show the effectiveness of the learnable cost function, we illustrate the transport cost for matched and mismatched training pairs on Flickr30K with 0.8 MRate. From Fig. 6, one could see that our cost function first learns to assign higher transport costs to those mismatched pairs. Although the costs of matched pairs are distributed over a large range in the early stage, they gradually become smaller and tend toward 0 as training proceeds. In conclusion, our cost function could successfully learn to distinguish matched and mismatched data, which lays the foundation for the further OT model." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Visualizing Rematched Image-Text Pairs. To visually illustrate the rematching ability of our L2RM, we conduct the case study on CC152K to show real-world rematched examples. Specifically, the first two rows of Fig. 5 show the image and its original mismatched caption, respectively. The third row shows the rematched caption provided by our method, and we also show the refined alignment scores in brackets. In particular, we could find that some real-world visual-text pairs are completely uncorrelated (e.g., Fig. 5(a)-Fig. 5(b)) or contain only a few local similarities (e.g., Fig. 5(c)-Fig. 5(e)). Thanks to our L2RM, the" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.293, + 0.695, + 0.399 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.569, + 0.404, + 0.632, + 0.416 + ], + "angle": 0, + "content": "(a) Epoch 5" + }, + { + "type": "image", + "bbox": [ + 0.699, + 0.294, + 0.888, + 0.399 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.759, + 0.404, + 0.828, + 0.416 + ], + "angle": 0, + "content": "(b) Epoch 35" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.421, + 0.892, + 0.462 + ], + "angle": 0, + "content": "Figure 6. Transport cost distribution for matched and mismatched pairs at different training phases of our L2RM. The experiments are conducted on Flickr30K with 0.8 MRate." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.488, + 0.892, + 0.67 + ], + "angle": 0, + "content": "potential matching relation among mismatched pairs could be fully excavated to provide refined alignments. For example, one could see that the rematched caption, i.e., \"a man on a bicycle\" nicely expresses the semantic concept in Fig. 5(a). Although some rematched captions could not perfectly share the same semantics with images, they also contain some local similarities to the given images. For example, the image in Fig. 5(f) is correctly described with the words \"a motorcycle\" and our L2RM provides a relatively low refined alignment score as the target. In summary, our proposed rematching strategy could embrace better data efficiency and robustness against PMPs." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.692, + 0.619, + 0.707 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This work studies the challenge of cross-modal retrieval with partially mismatched pairs (PMPs). To address this problem, we propose L2RM, a generalized OT-based framework that learns to rematch mismatched pairs. Our key idea is to excavate the potential semantic similarity among unpaired samples. To formalize this idea through OT, first, we propose a self-supervised learner to automatically learn effective cost function. Second, we model a partial OT problem and restrict the transport among false positives to further boost refined alignments. Extensive experiments are conducted to verify that our L2RM can endow cross-modal retrieval models with strong robustness against PMPs." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "26686" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Triantafyllos Afouras, Yuki M Asano, Francois Fagan, Andrea Vedaldi, and Florian Metze. Self-supervised object detection from audio-visual correspondence. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 10575–10586, 2022. 2" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.186, + 0.472, + 0.242 + ], + "angle": 0, + "content": "[2] Eric Arazo, Diego Ortego, Paul Albert, Noel O'Connor, and Kevin McGuinness. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 3536-3545, 2020. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.782 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "26688" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/fd35e1ac-d332-4502-a9ba-6902d0ab95b9_origin.pdf b/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/fd35e1ac-d332-4502-a9ba-6902d0ab95b9_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..033adcb87527325b0aad43fdc93eb17539065bbd --- /dev/null +++ b/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/fd35e1ac-d332-4502-a9ba-6902d0ab95b9_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:1f9370e840a555a744694e6ef61c4d457134103b227522302b91bb276e7e8f06 +size 1333281 diff --git a/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/full.md b/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/full.md new file mode 100644 index 0000000000000000000000000000000000000000..5ae2ed9dcb55010248f0aa4608338465ffc91e4e --- /dev/null +++ b/2024/Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval/full.md @@ -0,0 +1,335 @@ +# Learning to Rematch Mismatched Pairs for Robust Cross-Modal Retrieval + +Haochen Han $^{1*}$ , Qinghua Zheng $^{1}$ , Guang Dai $^{2}$ , Minnan Luo $^{1\dagger}$ , Jingdong Wang $^{3}$ $^{1}$ Xi'an Jiaotong University $^{2}$ SGIT AI Lab, State Grid Corporation of China $^{3}$ Baidu Inc +hhc1997@stu.xjtu.edu.cn, {qhzheng, minluo}@xjtu.edu.cn +guang.gdai@gmail.com, wangjingdong@baidu.com + +# Abstract + +Collecting well-matched multimedia datasets is crucial for training cross-modal retrieval models. However, in real-world scenarios, massive multimodal data are harvested from the Internet, which inevitably contains Partially Mismatched Pairs (PMPs). Undoubtedly, such semantical irrelevant data will remarkably harm the cross-modal retrieval performance. Previous efforts tend to mitigate this problem by estimating a soft correspondence to down-weight the contribution of PMPs. In this paper, we aim to address this challenge from a new perspective: the potential semantic similarity among unpaired samples makes it possible to excavate useful knowledge from mismatched pairs. To achieve this, we propose L2RM, a general framework based on Optimal Transport (OT) that learns to rematch mismatched pairs. In detail, L2RM aims to generate refined alignments by seeking a minimal-cost transport plan across different modalities. To formalize the rematching idea in OT, first, we propose a self-supervised cost function that automatically learns from explicit similarity-cost mapping relation. Second, we present to model a partial OT problem while restricting the transport among false positives to further boost refined alignments. Extensive experiments on three benchmarks demonstrate our L2RM significantly improves the robustness against PMPs for existing models. The code is available at https://github.com/hhc1997/L2RM. + +# 1. Introduction + +The pursuit of general intelligence has advanced the progress of multimodal learning, which aims to understand and integrate multiple sensory modalities like humans. Cross-modal retrieval is one of the most important + +![](images/55074c0a0a7a8ba12a566525e996a168355222c66f22673d63b929d660d42c31.jpg) +Figure 1. A toy example to illustrate our idea. The potential semantic similarity among unpaired samples makes it possible to excavate useful knowledge from mismatched pairs. Our L2RM aims to rematch PMPs by generating a refined alignment that brings relevant cross-modal samples (green links) together while repelling irrelevant ones (red links) away from each other. We also show some real-world rematched cases for our L2RM in Fig. 5. + +![](images/ac434f70813a086843aba5986b2f069c2d72915be35a01928f6f0e1485c47cad.jpg) + +![](images/d91763d8d1cff34bdf79fa2ba4e62e0b25264462c4fa99a229c9eb5f6f69351a.jpg) + +techniques in multimodal learning due to its flexibility in bridging different modalities [15, 20, 22, 25, 37, 42], which has powered various real-world applications. + +Despite the remarkable performance of previous methods, much of their success can be attributed to the voracious appetite for well-matched cross-modal pairs. In practice, collecting such ideal data [24] is notoriously labor-intensive and even impossible. Alternatively, several mainstream cross-modal datasets utilize the co-occurred information to crawl data from the Internet, especially for visual-text samples [11]. Although such a data collection way is free from expensive annotations, it will inevitably introduce partially mismatched pairs. For example, the standard image-caption dataset, Conceptual Captions [36], is estimated to contain about $3\%$ to $20\%$ mismatched pairs. Such semantically irrelevant data will be wrongly treated as the matched pairs for training, which undoubtedly impairs the performance of cross-modal retrieval models. Thus, endowing cross-modal learning with robustness against PMPs is crucial to suit real-world retrieval scenarios. + +To alleviate the PMP problem, existing works [19,23,45] + +typically resort to recasting the estimated soft correspondence into a soft margin to adjust the distance in triplet ranking loss. However, the underuse of mismatched pairs, only limited to down-weighting their contribution, has led to sub-optimal retrieval performance. Hence, it is necessary to address the PMP issue in a data-efficient manner. + +A question naturally arises: Could cross-modal retrieval models even learn useful knowledge from mismatched pairs? To answer this question, this paper presents L2RM, a general framework that learns to rematch mismatched pairs for robust cross-modal retrieval. As illustrated in Fig. 1, our key idea is to excavate the potential matching relationship among mismatched cross-modal samples. Specifically, we first identify possibly mismatched pairs from training data by modeling the per-sample loss distribution. Then, we formalize the rematching idea as an OT problem to generate a new set of refined alignments for mismatched pairs in every minibatch. Notably, the cost function plays a paramount role when applying OT, which is typically designed as feature-driven distance [5, 10, 18]. However, the over-dependence on representations has led to a cycle of self-reinforcing errors—the existence of PMPs can generate corrupted representations—in turn, preventing the effective transport plan. To handle this problem, we propose a self-supervised learning solution to automatically learn the cost function from explicit similarity-cost mapping relation, which is unexplored in previous OT literature. Moreover, instead of exactly rematching all mismatched samples, we suggest modeling a partial OT problem while restricting the transport among false positives to boost the refined alignment. In practice, we show that our optimization objective could be solved by the Sinkhorn algorithm [9], which only incurs cheap computational overheads. + +Our main contributions are summarized as follows: (1) We propose a general OT-based framework to address the widely-existed PMP problem in cross-modal retrieval. The key to our method is learning to rematch mismatched pairs, which goes beyond previous efforts from the data-efficient view. (2) To address the error accumulation faced by the vanilla cost function, we propose a novel self-supervised learner that automatically learns the transport cost from explicit similarity-cost mapping relation. (3) To further boost the refined alignment, we present to model a partial OT problem and restrict the transport among false positives. (4) Extensive experiments on several benchmarks demonstrate our L2RM endows existing cross-modal retrieval methods with strong robustness against PMPs. + +# 2. Related Work + +Cross-Modal Retrieval. Approaches for cross-modal retrieval aim to retrieve relevant items across different modalities for the query data. Current dominant methods project different modalities into a shared embedding space to mea + +sure the similarity of cross-modal pairs, which generally follow two research lines: 1) Global Alignment focuses on learning the correspondence between whole cross-modal data. Existing studies usually propose a two-stream network to learn comparable global features [13, 30, 47]. 2) Local Alignment. It seeks to align the fine-grained regions for more precise cross-modal matching. For example, [26] employ the cross-attention mechanism to fully excavate the semantic region-word alignments. [43, 44] explore the intramodal relation to facilitate inter-modal alignments. + +Although these prior arts have achieved promising results, their success mainly relies on well-matched data, which is extremely expensive and even impossible to collect. To satisfy a more practical retrieval that is robust against the PMPs, [23, 33, 45] divide the mismatched pairs from training data and estimate a soft correspondence to downweight their training contribution. Recently, [21] resorts to complementary contrastive learning that only utilizes the negative information to avoid overfitting. However, these methods neglect the usage of either the negative information [23, 33, 45] or the positive one [21]. To fully leverage the training data, this paper proposes an OT-based method to rematch those partially mismatched pairs. + +Optimal Transport. OT is used to seek a minimal-cost transport plan from one probability measure to another. The original OT model is a linear program that incurs expensive computational cost. [9] proposes the entropy-regularized OT to provide a computationally cheaper solver. Recently, OT has gained increasing attention from different fields in machine learning, including unsupervised learning [4, 29], semi-supervised learning [39], object detection [1, 17], domain adaptation [14, 35], and long-tailed recognition [32, 40]. To the best of our knowledge, we are the first to perform the PMP problem from an OT perspective. + +# 3. Preliminaries + +# 3.1. Background on OT + +OT provides a mechanism to infer the correspondence between two measures. We briefly introduce the OT theory to help us better view the PMP problem from an OT perspective. Consider $\mathbf{X} = \{x_{i}\}_{i = 1}^{m}$ and $\mathbf{Y} = \{y_{j}\}_{j = 1}^{n}$ as two discrete variables, and we denote their probability measures as $\pmb {p} = \sum_{i = 1}^{m}p_{i}\delta (x_{i})$ and $\pmb {q} = \sum_{j = 1}^{n}q_{j}\delta (y_{j})$ where $\delta$ is the Dirac function, $p_i$ and $q_{j}$ are the probability mass belonging to the probability simplex. When a meaningful cost function $c(\cdot)$ is defined, we can get the cost matrix $C\in \mathbb{R}^{m\times n}$ between $\mathbf{X}$ and $\mathbf{Y}$ , where $C_{ij} = c(x_i,y_j)$ . Based on these, the OT distance can be expressed as: + +$$ +\mathrm {O T} (\boldsymbol {p}, \boldsymbol {q}) \triangleq \min _ {\boldsymbol {\pi} \in \Pi (\boldsymbol {p}, \boldsymbol {q})} \left\langle \boldsymbol {\pi}, \boldsymbol {C} \right\rangle_ {F} \tag {1} +$$ + +$$ +\text {s . t .} \Pi (\boldsymbol {p}, \boldsymbol {q}) = \left\{\boldsymbol {\pi} \in \mathbb {R} _ {+} ^ {m \times n} | \boldsymbol {\pi} \mathbb {1} _ {n} = \boldsymbol {p}, \boldsymbol {\pi} ^ {\top} \mathbb {1} _ {m} = \boldsymbol {q} \right\}, +$$ + +where $\langle \cdot, \cdot \rangle_F$ is the Frobenius dot-product and $\mathbb{1}_d$ denotes a $d$ -dimensional all-one vector. $\pi$ is called the optimal transport plan that transport $\pmb{p}$ towards $\pmb{q}$ at the smallest cost. + +# 3.2. Problem Definition + +Without losing generality, we take the visual-text retrieval as an example to present the PMP problem in cross-modal retrieval. Consider a training dataset $\mathbb{D} = \{(V_i,T_i,m_i)\}_{i=1}^N$ consisting of $N$ samples, where $(V_i,T_i)$ is the visual-text pair and $m_i \in \{1,0\}$ indicates whether the bimodal data is semantically matched or not. The key to cross-modal retrieval lies in measuring the similarity across distinct modalities. To achieve this, existing methods usually project the visual and textual modalities into a comparable feature space via the corresponding modal-specific networks $f_v$ and $f_t$ , respectively. Then the similarity of a given visual-text pair is measured through $S_{ij} = g(f_v(V_i), f_t(T_j))$ , where $g$ is a nonparametric or parametric mapping function. For convenience, we denote $g(f_v(V_i), f_t(T_j))$ as $g(V_i, T_j)$ in the following. + +Ideally, the positive (matched) pairs should have higher similarity while the negative (mismatched) pairs should have lower ones, which can be achieved by minimizing the triplet loss [13] or InfoNCE loss [31]. Consider a batch of $N_{b}$ pairs $\{(V_{i},T_{i})\}_{i = 1}^{N_{b}}$ , the triplet loss is defined as: + +$$ +\begin{array}{l} \mathcal {L} ^ {\text {t r i p l e t}} \left(V _ {i}, T _ {i}\right) = [ \alpha - g \left(V _ {i}, T _ {i}\right) + g \left(V _ {i}, \hat {T} _ {h}\right) ] _ {+} \tag {2} \\ + \left[ \alpha - g \left(V _ {i}, T _ {i}\right) + g \left(\hat {V} _ {h}, T _ {i}\right) \right] _ {+}, \\ \end{array} +$$ + +where $\alpha$ is a margin and $[x]_{+} = \max (x,0)$ . $\hat{V}_h$ and $\hat{T}_h$ are the most similar negatives in the given batch corresponding to $(V_i,T_i)$ . Eq.(2) aims to enforce the negative pairs to be distant from the positives by a certain margin value. + +Alternatively, InfoNCE loss is extended to cross-modal scenario [21,34] that encourages the similarity gap between positives and negatives as large as possible. Formally, the matching probability of $j$ -th textual sample w.r.t. the $i$ -th visual query is defined as $p_{ij}^{2t} = \frac{\exp(g(V_i,T_j) / \tau)}{\sum_{j' = 1}^{N_b}\exp(g(V_i,T_{j'}) / \tau)}$ , where $\tau$ is a temperature parameter. As InfoNCE loss is symmetric, the matching probability $p_{ij}^{t2v}$ is defined similarly. For notation convenience, we denote $\pmb{p}_i^{2t} = [p_{i1}^{2t},\dots ,p_{iN_b}^{2t}]^\top$ and $\pmb{p}_i^{t2v} = [p_{i1}^{t2v},\dots ,p_{iN_b}^{t2v}]^\top$ as the probability vectors. To align cross-modal samples, the corresponding one-hot vector $\pmb{y}_i = [y_{i1},\dots ,y_{iN_b}]^\top$ is used as supervision, where $y_{ij}$ equal to 1 if $i = j$ while other elements are 0. Thus, the cross-modal InfoNCE loss is given by: + +$$ +\mathcal {L} ^ {\text {I n f o N C E}} \left(V _ {i}, T _ {i}\right) = \mathcal {H} \left(\boldsymbol {y} _ {i}, \boldsymbol {p} _ {i} ^ {v 2 t}\right) + \mathcal {H} \left(\boldsymbol {y} _ {i}, \boldsymbol {p} _ {i} ^ {t 2 v}\right), \tag {3} +$$ + +where $\mathcal{H}$ is the batched cross-entropy function. + +The success of both Eq.(2) and Eq.(3) relies on the well-matched pairs. However, in practice, the multimedia + +datasets are usually web-collected, and thus inevitably contains an unknown portion of irrelevant pairs but are wrongly treated as matched ( $m_i = 1$ ). Our goal is to combat such PMPs to facilitate robust cross-modal retrieval. + +# 4. Methodology + +To tackle the PMP problem, the mainstream pipeline first uses the memorization effect [3] of DNNs, i.e., DNNs learn simpler patterns before memorizing the difficult ones, to partition the dataset into a matched subset $\mathbb{D}_m$ , and a mismatched subset $\mathbb{D}_{\widetilde{m}} = \mathbb{D} / \mathbb{D}_m$ . After that, $\mathbb{D}_m$ can be used for standard cross-modal training. To mitigate the impact of PMPs, recent advances [19, 23, 45] introduce a soft margin into Eq.(2) to down-weight the samples from $\mathbb{D}_{\widetilde{m}}$ . However, due to the underuse of mismatched pairs, the achieved performance by them is argued to be sub-optimal. In this work, we aim to fully leverage PMPs by trying to excavate the potential semantic similarity among mismatched pairs. In the following, we present the details of our method. + +# 4.1. Identifying Mismatched Pairs + +Following the mainstream learning style, we first identify possibly mismatched pairs from all training data. The memorization effect of DNNs indicates that mismatched samples tend to have relatively higher loss during the early stage of training. Based on this, we use the difference in loss distribution between the matched and mismatched pairs to divide the training set. Empirically, we observe that the distribution of triplet loss is more distinguishable. Thus, given the retrieval model $(f_v, f_t, g)$ , we compute the per-sample loss through Eq.(2): + +$$ +\ell_ {\left(f _ {v}, f _ {t}, g\right)} = \left\{\ell_ {i} \right\} _ {i = 1} ^ {N} = \left\{\mathcal {L} ^ {\text {t r i p l e t}} \left(V _ {i}, T _ {i}\right) \right\} _ {i = 1} ^ {N}. \tag {4} +$$ + +Then, we fit a two-component beta mixture model [2,19,45] to $\ell_{(f_v,f_t,g)}$ using the Expectation-Maximization algorithm. For $i$ -th pair, its probability $w_{i}$ being mismatched is the posterior probability $p(b|\ell_i)$ , where $b$ is the beta component with a higher mean. By setting a threshold on $\{w_{i}\}_{i = 1}^{N}$ , we can divide the training data into the matched subset $\mathbb{D}_m$ and mismatched subset $\mathbb{D}_{\widetilde{m}}$ (we set the threshold to 0.5 in all experiments for brevity). + +For initial convergence of the algorithm, we warm up the model for a few epochs by training on all data with Eq.(2) or Eq.(3). However, for extreme mismatching rates, the model would quickly overfit to mismatched pairs and produce unreliable loss. To address this issue, we mitigate the overconfidence of the model by adding a reverse cross entropy [41] term to the InfoNCE loss during warm-up, i.e., + +$$ +\mathcal {L} ^ {\mathrm {R C E}} \left(V _ {i}, T _ {i}\right) = \mathcal {H} \left(\boldsymbol {p} _ {i} ^ {v 2 t}, \boldsymbol {y} _ {i}\right) + \mathcal {H} \left(\boldsymbol {p} _ {i} ^ {t 2 v}, \boldsymbol {y} _ {i}\right). \tag {5} +$$ + +In the presence of PMPs, $y_{i}$ may provide the wrong matching relation. Instead, the estimated probability could reflect + +![](images/90f9e79f5dde2eb384dc91fad136b9f01a72f9429a3aef295e0d7760d83c19f9.jpg) +Figure 2. Overview of the learnable cost function with self-supervised learning. The up part illustrates the reconstructed pairs that only $(V_4, T_1)$ , $(V_2, T_3)$ , and $(V_{N_b}, T_{N_b})$ are the reserved matching ones. Then, the matching matrix is viewed as supervision to guide the cost function from the explicit similarity-cost mapping relation through an OT loss (the down part). + +the truer distribution to a certain extent. Note that we bound the one-hot label into $[\epsilon, 1 - \epsilon]$ for computational feasibility. $(\epsilon = 10^{-7}$ in our experiments). + +# 4.2. Rematching Mismatched Pairs + +We formalize the rematching idea as an OT problem, generating refined alignments by seeking a minimal-cost transport plan. We will first introduce the novel learnable cost function to suit the PMP scenario, then we show how to boost the refined alignment by a relaxed OT model. + +Cost Function with Self-Supervised Learning. Cost function plays a crucial role when learning the transport plan for OT. In general, $C_{ij}$ is set to a distance measure, e.g., $L_{2}$ -distance [18] or cosine distance [10] to measure the expense of transporting a visual sample $i$ to a textual sample $j$ . However, the existence of PMPs imposes formidable obstacles for these feature-driven distance measures. On the one hand, training with PMPs can wrongly bring irrelevant data together, which undoubtedly prevents effective representation learning. Even worse, different modalities will be embedded into separate regions of the shared space due to the inherent modality gap [27]. On the other hand, the refined alignments produced by those corrupted features would be used to guide subsequent training, leading to the cycle of self-reinforcing errors [8]. + +To address the aforementioned limitations, we propose a novel self-supervised learning approach to automatically learn the cost function. Intuitively, for a given image and caption, the transport cost can be modeled as a function of similarity that higher similarity enjoys a lower cost. Thus, we formulate the cost function as a single-layer feedforward network with parameters $\Theta_c$ , i.e., $f_c(\cdot;\Theta_c)$ , which takes the similarity matrix of the batched visual-text samples as input and attempts to learn the corresponding cost + +matrix. To achieve this, we reconstruct the visual-text pairs to guide the cost function from explicit similarity-cost mapping relation. Specifically, for the matched pairs sampled from $\mathbb{D}_m$ , we randomly reserve a part of the matching images and substitute the images from $\mathbb{D}_{\widetilde{m}}$ for the remaining ones. With the reserved indexes, we could automatically obtain a matching matrix that indicates the ideal matching probability for each reconstructed pair. For the example illustrated in Fig. 2, $(V_4,T_1)$ , $(V_{2},T_{3})$ , and $(V_{N_b},T_{N_b})$ are the reserved matching pairs with a matching probability of 1, while the others could be considered as mismatched ones with a matching probability of 0. For convenience, let $\mathbb{D}'$ be the reconstructed data, and $(V,T) \in \mathbb{D}'$ be matrices that contain a batch of images and captions. To relate the similarity-cost mapping with the matching matrix, we optimize the cost function by the following OT loss: + +$$ +\mathcal {L} _ {\mathrm {O T}} \left(\boldsymbol {\pi} ^ {\sup }, \boldsymbol {V}, \boldsymbol {T}\right) = \left\langle \boldsymbol {\pi} ^ {\sup }, f _ {c} \left(g (\boldsymbol {V}, \boldsymbol {T}); \Theta_ {c}\right) \right\rangle_ {F}, \tag {6} +$$ + +where $\pi^{\mathrm{sup}}$ is the matching matrix, and $g(\mathbf{V},\mathbf{T})$ denotes the similarity matrix for the batched visual-text pairs. + +Eq.(6) seeks an effective cost function from a reverse perspective of OT, which views the ideal transport plan as the supervision to minimize the transport cost. + +Boosting Refined Alignments with Relaxed OT. Given the defined cost function, we could generate the refined alignments for mismatched pairs following the OT objective described in Eq.(1). However, Eq.(1) requires the two distributions to have the same total mass and that all the mass of $p$ should be transported to exactly match the mass of $q$ . In practice, due to the limited batch size, one caption may be irrelevant to all images in the batch and vice versa. To this end, we adopt the partial OT model [6, 16] to relax such strict all-to-all mass constraints, which seeks a minimal cost of only transporting $0 \leqslant \rho \leqslant \min(\|p\|_1, \|q\|_1)$ + +![](images/6e5f6943323c0b5bd47309d6e844360e89d779947cb8bfb5d0bb7db2dd8c00da.jpg) +Figure 3. Illustration of the proposed rematching loss. For the mismatched pairs, we formalize a partial OT problem with positive pairs masked to generate the refined alignment in each batch. The refined alignment provides a more reliable matching relation to supervise the mismatched pairs. Then, we compute the symmetric KL-divergence to optimize the retrieval model $(f_v, f_t, g)$ . + +unit mass between the visual and textual distribution, i.e., + +$$ +\min _ {\boldsymbol {\pi} \in \Pi^ {\rho} (\boldsymbol {p}, \boldsymbol {q})} \left\langle \boldsymbol {\pi}, \boldsymbol {C} \right\rangle_ {F}, \text {s . t .} \Pi^ {\rho} (\boldsymbol {p}, \boldsymbol {q}) = \left\{\boldsymbol {\pi} \in \mathbb {R} _ {+} ^ {m \times n} | \boldsymbol {\pi} \mathbb {1} _ {n} \leqslant \boldsymbol {p}, \right. +$$ + +$$ +\boldsymbol {\pi} ^ {\top} \mathbb {1} _ {m} \leqslant \boldsymbol {q}, \mathbb {1} _ {m} ^ {\top} \pi \mathbb {1} _ {n} = \rho \}. \tag {7} +$$ + +Furthermore, the false positives contained in the mismatched pairs introduce an implicit constraint to our transport plan $\pi$ that the transport mass between the same element in two distributions should be limited. To this end, we propose to impose a mask operation on the transport plan that restricts the transport to only concentrate among the unpaired pairs. Specifically, the mask matrix $M\in \mathbb{R}^{m\times n}$ is defined as: + +$$ +M _ {i j} \triangleq \left\{ \begin{array}{l l} 0, & \text {i f} i = j, \\ 1, & \text {o t h e r w i s e .} \end{array} \right. \tag {8} +$$ + +Then the masked transport plan is defined as the Hadamard product $\tilde{\pi} = M\odot \pi$ and be optimized through Eq.(7). + +# 4.3. The Training Objective + +Given the mismatched pairs $\{(V_i, T_i)\}_{i=1}^{N_b}$ sampled from $\mathbb{D}_{\widetilde{m}}$ , if we don't have any prior knowledge, we could consider the visual and textual samples following the uniform distributions, i.e., $\pmb{p} = \sum_{i=1}^{N_b} \frac{1}{N_b} \delta(V_i)$ and $\pmb{q} = \sum_{i=1}^{N_b} \frac{1}{N_b} \delta(T_i)$ , respectively. To guarantee the efficiency of our algorithm, we adopt an online strategy to update $\Theta_c$ and calculate $\widetilde{\pi}$ through a single optimization loop: + +$$ +\begin{array}{l} \min _ {\tilde {\boldsymbol {\pi}} \in \Pi^ {\rho} (\boldsymbol {p}, \boldsymbol {q})} \mathbb {E} _ {(\boldsymbol {V}, \boldsymbol {T}) \in \mathbb {D} _ {\tilde {m}}} \left\langle \tilde {\boldsymbol {\pi}}, f _ {c} \left(g \left(\boldsymbol {V}, \boldsymbol {T}\right); \Theta_ {c} ^ {*}\right) \right\rangle_ {F} - \lambda H (\tilde {\boldsymbol {\pi}}), \\ \text {s . t .} \Theta_ {c} ^ {*} = \underset {\Theta_ {c}} {\arg \min } \mathbb {E} _ {(\boldsymbol {V}, \boldsymbol {T}, \boldsymbol {\pi} ^ {\sup }) \in \mathbb {D} ^ {\prime}} \mathcal {L} _ {O T} (\boldsymbol {\pi} ^ {\sup }, \boldsymbol {V}, \boldsymbol {T}) \tag {9} \\ \end{array} +$$ + +where $\lambda > 0$ is a regularization parameter for the entropic constraint $H(\tilde{\pi}) = -\sum_{ij} \tilde{\pi}_{ij} \log \tilde{\pi}_{ij}$ . Note that Eq.(9) introduces an entropy regularization item to the OT model, which enables the transport plan to be solved by the computationally cheaper Sinkhorn-Knopp algorithm [9]. The detailed solution is presented in Appendix A. + +The optimal transport plan from Eq.(9) represents a refined alignment that provides a more reliable matching relation for those mismatched visual-text samples. As our refined alignment is generated dynamically, we adopt the KL-divergence to compute the rematching loss instead of the cross entropy. Besides, a reverse term is added to symmetrize the KL-divergence, which makes the training more stable. Formally, let $\tilde{\pi}_i^{v2t}$ and $\tilde{\pi}_i^{t2v}$ be the row-wise and column-wise normalized refined alignment for the $i$ -th sample, respectively. Then, the rematching loss (see Fig. 3) is defined as: + +$$ +\begin{array}{l} \mathcal {L} ^ {\mathrm {r e}} \left(V _ {i}, T _ {i}\right) = \frac {1}{2} \left[ D _ {K L} \left(\tilde {\boldsymbol {\pi}} _ {i} ^ {v 2 t} \parallel \boldsymbol {p} _ {i} ^ {v 2 t}\right) + D _ {K L} \left(\boldsymbol {p} _ {i} ^ {v 2 t} \parallel \tilde {\boldsymbol {\pi}} _ {i} ^ {v 2 t}\right) \right] \\ + \frac {1}{2} \left[ D _ {K L} \left(\tilde {\boldsymbol {\pi}} _ {i} ^ {t 2 v} \| \boldsymbol {p} _ {i} ^ {t 2 v}\right) + D _ {K L} \left(\boldsymbol {p} _ {i} ^ {t 2 v} \| \tilde {\boldsymbol {\pi}} _ {i} ^ {t 2 v}\right) \right]. \tag {10} \\ \end{array} +$$ + +For the pairs that are divided as matched, we use the triplet ranking loss to directly control the distance gap. Thus, our final objective function is defined as: + +$$ +\mathcal {L} ^ {\text {F i n a l}} = \sum_ {(V _ {i}, T _ {i}) \in \mathbb {D} _ {m}} \mathcal {L} ^ {\text {t r i p l e t}} \left(V _ {i}, T _ {i}\right) + \sum_ {(V _ {i}, T _ {i}) \in \mathbb {D} _ {\tilde {m}}} \mathcal {L} ^ {\text {r e}} \left(V _ {i}, T _ {i}\right). \tag {11} +$$ + +The detailed training pseudo-code is shown in Appendix B. + +# 5. Experiment + +In this section, we experimentally analyze the effectiveness of L2RM in robust cross-modal retrieval. + +# 5.1. Setup + +Datasets. We apply our method to three image-text retrieval datasets varying in scale and scope. Specifically, Flickr30K [46] consists of 31,000 images with five corresponding text annotations for each image from the Flickr website. Following [23], we split 1,000 images for validation, 1,000 images for testing, and the rest for training. MS-COCO [28] is a large-scale cross-modal dataset, which collects 123,287 images with five sentences each. Following [23], we use 5,000 images for validation, 5,000 images for testing, and the rest for training. Conceptual Captions [36] is a web-crawled large-scale dataset containing + +
MRateMethodFlickr30KMS-COCO
Image-to-TextText-to-ImagerSumImage-to-TextText-to-ImagerSum
R@1R@5R@10R@1R@5R@10R@1R@5R@10R@1R@5R@10
0.2IMRAM59.185.491.944.571.479.4431.769.993.697.455.984.489.6490.8
NCR73.593.296.656.982.488.5491.176.695.698.260.888.895.0515.0
BiCro74.794.396.856.681.488.2492.076.695.498.261.388.894.8515.1
DECL-SGR74.592.997.153.679.586.8484.475.695.198.359.988.394.7511.9
DECL-SGRAF77.593.897.056.181.888.5494.777.595.998.461.789.395.4518.2
RCL-SGR74.291.896.955.681.287.5487.277.095.598.161.388.894.8515.5
RCL-SGRAF75.994.597.357.982.688.6496.878.996.098.462.889.995.4521.4
L2RM-SAF73.794.397.756.881.888.1492.477.996.098.362.189.294.9518.4
L2RM-SGR76.593.797.355.581.588.0492.578.495.798.362.189.194.9518.5
L2RM-SGRAF77.995.297.859.883.689.5503.880.296.398.564.290.195.4524.7
0.4IMRAM44.973.282.631.656.365.6354.251.882.490.938.470.378.9412.7
NCR68.189.694.851.478.484.8467.174.794.698.059.688.194.7509.7
BiCro70.792.095.551.977.785.4473.275.295.398.160.087.894.3510.7
DECL-SGR69.090.294.850.776.384.1465.173.694.697.957.886.993.9504.7
DECL-SGRAF72.792.395.453.479.486.4479.675.695.598.359.588.394.8512.0
RCL-SGR71.391.195.351.478.085.2472.373.994.997.959.087.493.9507.0
RCL-SGRAF72.792.796.154.880.087.1483.477.095.598.361.288.594.8515.3
L2RM-SAF72.192.196.152.778.885.9477.774.494.798.359.287.994.4508.9
L2RM-SGR73.192.496.352.379.486.3479.875.294.898.159.487.894.1509.4
L2RM-SGRAF75.893.296.956.381.087.3490.577.595.898.462.089.194.9517.7
0.6IMRAM16.438.250.97.519.225.3157.518.251.668.017.943.654.6253.9
NCR13.937.750.511.030.141.4184.60.10.30.40.10.51.02.4
BiCro64.187.192.747.274.082.3447.473.293.997.657.586.393.4501.9
DECL-SGR64.585.892.644.071.680.6439.169.793.497.554.585.292.6492.9
DECL-SGRAF65.288.494.046.874.082.2450.673.094.297.957.086.693.8502.5
RCL-SGR62.386.392.945.171.380.2438.171.493.297.155.484.792.3494.1
RCL-SGRAF67.789.193.648.074.983.3456.674.094.397.557.686.493.5503.3
L2RM-SAF66.188.893.847.874.282.2452.971.293.497.556.585.993.0497.5
L2RM-SGR65.187.893.647.073.581.5448.572.793.997.556.986.293.3500.5
L2RM-SGRAF70.090.895.451.376.483.7467.675.494.797.959.287.493.8508.4
0.8IMRAM3.19.75.20.30.91.921.11.35.08.30.20.61.316.7
NCR1.56.29.90.31.02.121.00.10.30.40.10.51.02.4
BiCro2.39.217.22.610.216.858.362.288.694.647.479.288.5460.5
DECL-SGR44.472.682.033.959.569.0361.460.088.794.545.978.888.3456.2
DECL-SGRAF53.478.886.937.663.873.9394.464.890.596.049.781.790.3473.0
RCL-SGR47.170.579.430.356.166.3349.763.289.395.247.678.788.0462.0
RCL-SGRAF51.775.884.434.561.270.7378.367.490.896.050.681.090.1475.9
L2RM-SAF50.877.985.535.662.672.7385.164.790.895.850.080.989.4471.6
L2RM-SGR50.577.283.934.261.171.6378.565.290.396.149.881.088.2470.6
L2RM-SGRAF55.780.887.839.465.474.9404.069.091.996.452.682.490.3482.6
+ +Table 1. Image-text retrieval performance under different mismatching rates (MRate) on Flickr30K and MS-COCO. + +3.3M one-to-one images and captions. Following [23], we use the subset, i.e., CC152K to conduct experiments, which has 150,000 images for training, 1,000 images for validation, and 1,000 images for testing. + +Implementation Details. As a general method, L2RM could be directly applied to almost all cross-modal retrieval methods to improve their robustness. Following [21, 33], we apply L2RM to SGR, SAF, and SGRAF for a comprehensive comparison. We evaluate the retrieval performance with the Recall@K (R@K) metric. Following [23], we save the best performance checkpoint on the validation set w.r.t. the sum of the evaluation scores and report its results on the testing set. We follow the same training setting as [23], our specific parameters setting can be found in Appendix C.1. + +Baselines. We compare L2RM with eight state-of-the-art cross-modal retrieval methods, including four general methods (i.e., IMRAM [7], SGR, SAF, and SGRAF [12]) and four robust learning methods against the PMPs (i.e., NCR [23], DECL [33], BiCro [45], and RCL [21]). Note that the original BiCro combines four models, i.e., two co-trained SGR, and two co-trained SAF. For a fair comparison, we report the results of 2 co-trained SGR for BiCro like [23]. + +# 5.2. Main Results + +In this section, we conduct comparison experiments with different mismatching rates on three datasets to evaluate the performance of our L2RM. As Flickr30K and MS-COCO are well-established datasets, we carry out experiments by + +generating the synthesized false positive pairs, i.e., the mismatching rate (MRate) increases from 0.2 to 0.8 in intervals of 0.2. Following [21, 33], we randomly select a specific percentage of images and randomly permute all their corresponding captions, which is more challenging and practical than the setting in [23, 45]. For the web-collected dataset CC152K, which naturally contains about $3\% \sim 20\%$ unknown mismatched pairs [36]. Thus we directly conduct experiments on it to evaluate the performance with real PMPs. + +Results on Synthesized PMPs. Tab. 1 shows the experimental results on Flickr30K and MS-COCO. Note that for MS-COCO, the results are computed by averaging over 5 folds of 1K test images like [21, 33]. Due to space limitation, we omit the results of some general methods (SGR, SAF, and SGRAF), and the comparison on original datasets (0 MRate), which could be found in Appendix C.2. From the results, we can find that L2RM achieves the best results on all metrics than the other state-of-the-art methods, which shows the superior robustness of L2RM against PMPs. Moreover, when the mismatching rate is high, e.g., 0.6 and 0.8, the improvement of L2RM is more evident, proving that excavating mismatched pairs could effectively facilitate robust cross-modal retrieval. + +Results on Real-World PMPs. We validate our method on the real-world dataset CC152K, which contains an unknown portion of mismatched pairs. As shown in Tab. 2, our method considerably outperforms the best baseline in terms of sum in retrieval by $9.8\%$ . Notably, our L2RM-SGR surpasses all SGR variants by a clear margin, achieving as much as a $16.9\%$ (rSum) absolute improvement over the best variant. It is because the real-world rematched pairs are more likely to involve only local alignments, e.g., Fig. 5(e)-Fig. 5(f), while the SGR model itself is adept at capturing the relationship between local alignments. + +
MethodImage-to-TextText-to-ImagerSum
R@1R@5R@10R@1R@5R@10
IMRAM27.852.460.929.251.561.2283.0
SAF32.559.570.032.560.768.7323.9
SGR14.535.548.913.736.147.9196.6
NCR39.564.573.540.364.673.2355.6
BiCro39.764.672.639.265.074.1355.2
DECL-SAF36.663.073.338.563.273.5348.1
DECL-SGR36.263.673.237.163.673.7347.4
DECL-SGRAF39.066.175.540.766.376.7364.3
RCL-SAF37.563.071.437.862.472.4344.5
RCL-SGR38.363.070.439.263.272.3346.4
RCL-SGRAF41.766.073.641.666.475.1364.4
L2RM-SAF37.362.771.738.865.774.8351.0
L2RM-SGR39.566.276.041.865.974.9364.3
L2RM-SGRAF43.067.575.742.868.077.2374.2
+ +# 5.3. Ablation Study + +Impact of Each Component. To study the influence of specific components in our method, we carry out the ablation study on the Flickr30K with 0.6 MRate. Specifically, we ablate the contributions of three key components of L2RM, i.e., partial OT, positives masked, and the learnable cost function (we use the cosine distance to measure the cost instead). Besides, we compare L2RM with different formulas of rematching loss: KL-divergence and InfoNCE. From Tab. 3, we observe the following conclusions: 1) The full L2RM could achieve the best overall performance, showing that all three components are important to improve the robustness against PMPs. 2) Using the learnable cost function substantially outperforms the variant with the cosine distance cost (e.g., +11.9 in terms of the rSum), which signifies the simple feature-driven cost is sub-optimal to the PMP situation. 3) Formulating different rematching loss could also achieve decent results, which verifies the ability of L2RM to provide effective matching relations. + +Table 2. Image-text retrieval performance on CC152K. + +
AblationImage-to-TextText-to-Image
R@1R@5R@10R@1R@5R@10
L2RM65.187.893.647.073.581.5
L2RM w KL-divergence64.787.693.246.774.081.5
L2RM w InfoNCE Loss64.987.593.546.072.980.9
L2RM w/o Partial OT62.286.491.544.768.672.6
L2RM w/o Positives Masked64.987.692.746.473.281.1
L2RM w/o Cost Function61.385.691.444.972.481.0
+ +Table 3. Ablation studies on Flickr30K with 0.6 MRate. + +Parameter Analysis. We now investigate the effect of the parameter $\rho$ by plotting the recall scores with incremental $\rho$ on Flickr30K. The figure shows that the overall performance tends to decrease as $\rho$ increases. We further analyze how untransported pairs benefit the model training in Appendix C.3. Experimentally, we find that the refined alignments for untransported pairs can be equivalent to the label smoothing strategy [38]. + +![](images/baa7dc4ae6e29bfd3f2c8659c63a9e87d57d7579e069a5c4ec279c043bdc0525.jpg) +(a) Image to Text + +![](images/a14098b1fbbcc991579b15d55b699c20c7f36f014395474a47fb3be546cb918a.jpg) +(b) Text to Image +Figure 4. Parameter analysis of L2RM-SGR in terms of recall scores on the testing set of Flickr30K under 0.2 MRate. + +Discussions on Warm-up Methods. We use different warm-up methods, i.e., triplet loss [13] and InfoNCE loss [31] for our L2RM-SGR. The experiments are conducted on the Flickr30K with 0.8 MRate and the CC152K with real + +![](images/63271031ab4ee06fc364b2dd7cd929e5067b476f8ead3963e750fb133aee4990.jpg) +Given: view bar out on the lounge chairs + +![](images/859227471a931c939cbd9d313b205bef614d6e9e5d48a7c8e795e802fc89b751.jpg) +Rematched: the facade can be lit up at night using different coloured led lights (0.988) +Given: the gift of the present +Rematched: a man on a bicycle (0.996) +(b) +Rematched: suspension bridge over a city (0.963) + +![](images/d1e6671c51c30a43d64de328f0969afccd66d2f189c42a10be234fb04dc8f0de.jpg) +(a) +Given: a survey has revealed that a third would be less likely to travel if it was no longer a member +(c) +Rematched: most popular sports in the world - hockey (0.965) + +![](images/fa716680cd2d0f75af90be62c18f5fd84d5508e0934c3ae8819b8cca967569b7.jpg) +Given: video: fans sing composition after mic issue +(d) + +![](images/41cc0394427109d593aa2e154534e04879e085fc5dd07604209d5e8ffc16cab4.jpg) +Given: day on the place unknown +Rematched: a couple of men stand on a small hill (0.938) +(e) + +![](images/83f32a9602eda87e3a948f62d2c4ecbc1d374f8f40d962f20309e3125905ca05.jpg) +Given: a general view of atmosphere outside the diesel and launch party +Rematched: a motorcycle winds their way through country (0.626) +(f) + +
MethodFlickr30KCC152K
Image-to-TextText-to-ImageImage-to-TextText-to-Image
R@1R@5R@10R@1R@5R@10R@1R@5R@10R@1R@5R@10
Triplet0.10.71.30.10.71.138.264.271.439.564.271.9
InfoNCE45.971.480.329.252.761.139.366.875.040.865.274.2
+ +Table 4. Comparison with different warm-up methods on Flickr30K with 0.8 MRate and CC152K. + +PMPs. As shown in Tab. 4, one could see that the triplet loss cannot achieve satisfactory performance under the extreme mismatching rate. Compared with the results of the L2RM-SGR in Tab. 1, one could find that it is necessary to limit the overconfidence of the model during the warm-up process. The results on CC152K show that our method is robust to the choice of warm-up methods under a relatively low mismatching rate. + +# 5.4. Visualization and Analysis + +Distribution of Transport Cost. To intuitively show the effectiveness of the learnable cost function, we illustrate the transport cost for matched and mismatched training pairs on Flickr30K with 0.8 MRate. From Fig. 6, one could see that our cost function first learns to assign higher transport costs to those mismatched pairs. Although the costs of matched pairs are distributed over a large range in the early stage, they gradually become smaller and tend toward 0 as training proceeds. In conclusion, our cost function could successfully learn to distinguish matched and mismatched data, which lays the foundation for the further OT model. + +Visualizing Rematched Image-Text Pairs. To visually illustrate the rematching ability of our L2RM, we conduct the case study on CC152K to show real-world rematched examples. Specifically, the first two rows of Fig. 5 show the image and its original mismatched caption, respectively. The third row shows the rematched caption provided by our method, and we also show the refined alignment scores in brackets. In particular, we could find that some real-world visual-text pairs are completely uncorrelated (e.g., Fig. 5(a)-Fig. 5(b)) or contain only a few local similarities (e.g., Fig. 5(c)-Fig. 5(e)). Thanks to our L2RM, the + +![](images/9e64827d05f2da7d9937006a34379cdb6d2ab8bb54e27df658a38ed946c6fd38.jpg) +Figure 5. The ability of our L2RM to rematch the mismatched visual-text samples. The figure shows some representative rematched pairs for L2RM-SGR on the training set of CC152K dataset. We highlight the matched words in green and the mismatched words in red. +(a) Epoch 5 +Figure 6. Transport cost distribution for matched and mismatched pairs at different training phases of our L2RM. The experiments are conducted on Flickr30K with 0.8 MRate. + +![](images/e238b617e4c7dbfe0a94392507340b9ce1b745ffa39b71744045747b72365118.jpg) +(b) Epoch 35 + +potential matching relation among mismatched pairs could be fully excavated to provide refined alignments. For example, one could see that the rematched caption, i.e., "a man on a bicycle" nicely expresses the semantic concept in Fig. 5(a). Although some rematched captions could not perfectly share the same semantics with images, they also contain some local similarities to the given images. For example, the image in Fig. 5(f) is correctly described with the words "a motorcycle" and our L2RM provides a relatively low refined alignment score as the target. In summary, our proposed rematching strategy could embrace better data efficiency and robustness against PMPs. + +# 6. Conclusion + +This work studies the challenge of cross-modal retrieval with partially mismatched pairs (PMPs). To address this problem, we propose L2RM, a generalized OT-based framework that learns to rematch mismatched pairs. Our key idea is to excavate the potential semantic similarity among unpaired samples. To formalize this idea through OT, first, we propose a self-supervised learner to automatically learn effective cost function. Second, we model a partial OT problem and restrict the transport among false positives to further boost refined alignments. Extensive experiments are conducted to verify that our L2RM can endow cross-modal retrieval models with strong robustness against PMPs. + +# References + +[1] Triantafyllos Afouras, Yuki M Asano, Francois Fagan, Andrea Vedaldi, and Florian Metze. Self-supervised object detection from audio-visual correspondence. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 10575–10586, 2022. 2 +[2] Eric Arazo, Diego Ortego, Paul Albert, Noel O'Connor, and Kevin McGuinness. Unsupervised label noise modeling and loss correction. In International conference on machine learning, pages 312-321. PMLR, 2019. 3 +[3] Devansh Arpit, Stanisław Jastrzebski, Nicolas Ballas, David Krueger, Emmanuel Bengio, Maxinder S Kanwal, Tegan Maharaj, Asja Fischer, Aaron Courville, Yoshua Bengio, et al. A closer look at memorization in deep networks. 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However, in real-world scenarios, massive multimodal data are harvested from the Internet, which inevitably contains Partially Mismatched Pairs (PMPs). Undoubtedly, such semantical irrelevant data will remarkably harm the cross-modal retrieval performance. Previous efforts tend to mitigate this problem by estimating a soft correspondence to down-weight the contribution of PMPs. In this paper, we aim to address this challenge from a new perspective: the potential semantic similarity among unpaired samples makes it possible to excavate useful knowledge from mismatched pairs. To achieve this, we propose L2RM, a general framework based on Optimal Transport (OT) that learns to rematch mismatched pairs. In detail, L2RM aims to generate refined alignments by seeking a minimal-cost transport plan across different modalities. To formalize the rematching idea in OT, first, we propose a self-supervised cost function that automatically learns from explicit similarity-cost mapping relation. Second, we present to model a partial OT problem while restricting the transport among false positives to further boost refined alignments. Extensive experiments on three benchmarks demonstrate our L2RM significantly improves the robustness against PMPs for existing models. The code is available at https://github.com/hhc1997/L2RM." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 587, + 128, + 600 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 587, + 128, + 600 + ], + "spans": [ + { + "bbox": [ + 47, + 587, + 128, + 600 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 608, + 287, + 656 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 608, + 287, + 656 + ], + "spans": [ + { + "bbox": [ + 46, + 608, + 287, + 656 + ], + "type": "text", + "content": "The pursuit of general intelligence has advanced the progress of multimodal learning, which aims to understand and integrate multiple sensory modalities like humans. Cross-modal retrieval is one of the most important" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 309, + 227, + 376, + 349 + ], + "blocks": [ + { + "bbox": [ + 309, + 227, + 376, + 349 + ], + "lines": [ + { + "bbox": [ + 309, + 227, + 376, + 349 + ], + "spans": [ + { + "bbox": [ + 309, + 227, + 376, + 349 + ], + "type": "image", + "image_path": "55074c0a0a7a8ba12a566525e996a168355222c66f22673d63b929d660d42c31.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 361, + 546, + 438 + ], + "lines": [ + { + "bbox": [ + 305, + 361, + 546, + 438 + ], + "spans": [ + { + "bbox": [ + 305, + 361, + 546, + 438 + ], + "type": "text", + "content": "Figure 1. A toy example to illustrate our idea. The potential semantic similarity among unpaired samples makes it possible to excavate useful knowledge from mismatched pairs. Our L2RM aims to rematch PMPs by generating a refined alignment that brings relevant cross-modal samples (green links) together while repelling irrelevant ones (red links) away from each other. We also show some real-world rematched cases for our L2RM in Fig. 5." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 384, + 230, + 457, + 348 + ], + "blocks": [ + { + "bbox": [ + 384, + 230, + 457, + 348 + ], + "lines": [ + { + "bbox": [ + 384, + 230, + 457, + 348 + ], + "spans": [ + { + "bbox": [ + 384, + 230, + 457, + 348 + ], + "type": "image", + "image_path": "ac434f70813a086843aba5986b2f069c2d72915be35a01928f6f0e1485c47cad.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 465, + 227, + 544, + 349 + ], + "blocks": [ + { + "bbox": [ + 465, + 227, + 544, + 349 + ], + "lines": [ + { + "bbox": [ + 465, + 227, + 544, + 349 + ], + "spans": [ + { + "bbox": [ + 465, + 227, + 544, + 349 + ], + "type": "image", + "image_path": "d91763d8d1cff34bdf79fa2ba4e62e0b25264462c4fa99a229c9eb5f6f69351a.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 456, + 546, + 492 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 456, + 546, + 492 + ], + "spans": [ + { + "bbox": [ + 304, + 456, + 546, + 492 + ], + "type": "text", + "content": "techniques in multimodal learning due to its flexibility in bridging different modalities [15, 20, 22, 25, 37, 42], which has powered various real-world applications." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 495, + 547, + 697 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 495, + 547, + 697 + ], + "spans": [ + { + "bbox": [ + 304, + 495, + 547, + 697 + ], + "type": "text", + "content": "Despite the remarkable performance of previous methods, much of their success can be attributed to the voracious appetite for well-matched cross-modal pairs. In practice, collecting such ideal data [24] is notoriously labor-intensive and even impossible. Alternatively, several mainstream cross-modal datasets utilize the co-occurred information to crawl data from the Internet, especially for visual-text samples [11]. Although such a data collection way is free from expensive annotations, it will inevitably introduce partially mismatched pairs. For example, the standard image-caption dataset, Conceptual Captions [36], is estimated to contain about " + }, + { + "bbox": [ + 304, + 495, + 547, + 697 + ], + "type": "inline_equation", + "content": "3\\%" + }, + { + "bbox": [ + 304, + 495, + 547, + 697 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 495, + 547, + 697 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 304, + 495, + 547, + 697 + ], + "type": "text", + "content": " mismatched pairs. Such semantically irrelevant data will be wrongly treated as the matched pairs for training, which undoubtedly impairs the performance of cross-modal retrieval models. Thus, endowing cross-modal learning with robustness against PMPs is crucial to suit real-world retrieval scenarios." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "content": "To alleviate the PMP problem, existing works [19,23,45]" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 664, + 269, + 674 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 664, + 269, + 674 + ], + "spans": [ + { + "bbox": [ + 58, + 664, + 269, + 674 + ], + "type": "text", + "content": "*This work was completed during his internship at SGIT AI Lab." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 47, + 674, + 287, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 674, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 674, + 287, + 712 + ], + "type": "text", + "content": "†Corresponding author. This work was supported by the National Key Research and Development Program of China (2022YFB3102600), and National Nature Science Foundation of China (62272374, 62192781, 62202367, 62250009, and 62137002)." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "26679" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 143 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 143 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 143 + ], + "type": "text", + "content": "typically resort to recasting the estimated soft correspondence into a soft margin to adjust the distance in triplet ranking loss. However, the underuse of mismatched pairs, only limited to down-weighting their contribution, has led to sub-optimal retrieval performance. Hence, it is necessary to address the PMP issue in a data-efficient manner." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 144, + 289, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 144, + 289, + 467 + ], + "spans": [ + { + "bbox": [ + 46, + 144, + 289, + 467 + ], + "type": "text", + "content": "A question naturally arises: Could cross-modal retrieval models even learn useful knowledge from mismatched pairs? To answer this question, this paper presents L2RM, a general framework that learns to rematch mismatched pairs for robust cross-modal retrieval. As illustrated in Fig. 1, our key idea is to excavate the potential matching relationship among mismatched cross-modal samples. Specifically, we first identify possibly mismatched pairs from training data by modeling the per-sample loss distribution. Then, we formalize the rematching idea as an OT problem to generate a new set of refined alignments for mismatched pairs in every minibatch. Notably, the cost function plays a paramount role when applying OT, which is typically designed as feature-driven distance [5, 10, 18]. However, the over-dependence on representations has led to a cycle of self-reinforcing errors—the existence of PMPs can generate corrupted representations—in turn, preventing the effective transport plan. To handle this problem, we propose a self-supervised learning solution to automatically learn the cost function from explicit similarity-cost mapping relation, which is unexplored in previous OT literature. Moreover, instead of exactly rematching all mismatched samples, we suggest modeling a partial OT problem while restricting the transport among false positives to boost the refined alignment. In practice, we show that our optimization objective could be solved by the Sinkhorn algorithm [9], which only incurs cheap computational overheads." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 467, + 288, + 635 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 467, + 288, + 635 + ], + "spans": [ + { + "bbox": [ + 46, + 467, + 288, + 635 + ], + "type": "text", + "content": "Our main contributions are summarized as follows: (1) We propose a general OT-based framework to address the widely-existed PMP problem in cross-modal retrieval. The key to our method is learning to rematch mismatched pairs, which goes beyond previous efforts from the data-efficient view. (2) To address the error accumulation faced by the vanilla cost function, we propose a novel self-supervised learner that automatically learns the transport cost from explicit similarity-cost mapping relation. (3) To further boost the refined alignment, we present to model a partial OT problem and restrict the transport among false positives. (4) Extensive experiments on several benchmarks demonstrate our L2RM endows existing cross-modal retrieval methods with strong robustness against PMPs." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 645, + 134, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 645, + 134, + 658 + ], + "spans": [ + { + "bbox": [ + 47, + 645, + 134, + 658 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "content": "Cross-Modal Retrieval. Approaches for cross-modal retrieval aim to retrieve relevant items across different modalities for the query data. Current dominant methods project different modalities into a shared embedding space to mea" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 191 + ], + "type": "text", + "content": "sure the similarity of cross-modal pairs, which generally follow two research lines: 1) Global Alignment focuses on learning the correspondence between whole cross-modal data. Existing studies usually propose a two-stream network to learn comparable global features [13, 30, 47]. 2) Local Alignment. It seeks to align the fine-grained regions for more precise cross-modal matching. For example, [26] employ the cross-attention mechanism to fully excavate the semantic region-word alignments. [43, 44] explore the intramodal relation to facilitate inter-modal alignments." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 192, + 546, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 192, + 546, + 348 + ], + "spans": [ + { + "bbox": [ + 304, + 192, + 546, + 348 + ], + "type": "text", + "content": "Although these prior arts have achieved promising results, their success mainly relies on well-matched data, which is extremely expensive and even impossible to collect. To satisfy a more practical retrieval that is robust against the PMPs, [23, 33, 45] divide the mismatched pairs from training data and estimate a soft correspondence to downweight their training contribution. Recently, [21] resorts to complementary contrastive learning that only utilizes the negative information to avoid overfitting. However, these methods neglect the usage of either the negative information [23, 33, 45] or the positive one [21]. To fully leverage the training data, this paper proposes an OT-based method to rematch those partially mismatched pairs." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 361, + 546, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 361, + 546, + 494 + ], + "spans": [ + { + "bbox": [ + 304, + 361, + 546, + 494 + ], + "type": "text", + "content": "Optimal Transport. OT is used to seek a minimal-cost transport plan from one probability measure to another. The original OT model is a linear program that incurs expensive computational cost. [9] proposes the entropy-regularized OT to provide a computationally cheaper solver. Recently, OT has gained increasing attention from different fields in machine learning, including unsupervised learning [4, 29], semi-supervised learning [39], object detection [1, 17], domain adaptation [14, 35], and long-tailed recognition [32, 40]. To the best of our knowledge, we are the first to perform the PMP problem from an OT perspective." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 502, + 391, + 515 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 502, + 391, + 515 + ], + "spans": [ + { + "bbox": [ + 306, + 502, + 391, + 515 + ], + "type": "text", + "content": "3. Preliminaries" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 522, + 419, + 534 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 522, + 419, + 534 + ], + "spans": [ + { + "bbox": [ + 306, + 522, + 419, + 534 + ], + "type": "text", + "content": "3.1. Background on OT" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "spans": [ + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": "OT provides a mechanism to infer the correspondence between two measures. We briefly introduce the OT theory to help us better view the PMP problem from an OT perspective. Consider " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "\\mathbf{X} = \\{x_{i}\\}_{i = 1}^{m}" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "\\mathbf{Y} = \\{y_{j}\\}_{j = 1}^{n}" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " as two discrete variables, and we denote their probability measures as " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "\\pmb {p} = \\sum_{i = 1}^{m}p_{i}\\delta (x_{i})" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "\\pmb {q} = \\sum_{j = 1}^{n}q_{j}\\delta (y_{j})" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "\\delta" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " is the Dirac function, " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "p_i" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "q_{j}" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " are the probability mass belonging to the probability simplex. When a meaningful cost function " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "c(\\cdot)" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " is defined, we can get the cost matrix " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "C\\in \\mathbb{R}^{m\\times n}" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " between " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "\\mathbf{X}" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "\\mathbf{Y}" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "inline_equation", + "content": "C_{ij} = c(x_i,y_j)" + }, + { + "bbox": [ + 304, + 540, + 545, + 673 + ], + "type": "text", + "content": ". Based on these, the OT distance can be expressed as:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 365, + 679, + 545, + 702 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 365, + 679, + 545, + 702 + ], + "spans": [ + { + "bbox": [ + 365, + 679, + 545, + 702 + ], + "type": "interline_equation", + "content": "\\mathrm {O T} (\\boldsymbol {p}, \\boldsymbol {q}) \\triangleq \\min _ {\\boldsymbol {\\pi} \\in \\Pi (\\boldsymbol {p}, \\boldsymbol {q})} \\left\\langle \\boldsymbol {\\pi}, \\boldsymbol {C} \\right\\rangle_ {F} \\tag {1}", + "image_path": "450fad17b4d8c87551ba116b92ba341322099075a4bdded82d6c2c7dd019e65f.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 317, + 702, + 529, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 702, + 529, + 716 + ], + "spans": [ + { + "bbox": [ + 317, + 702, + 529, + 716 + ], + "type": "interline_equation", + "content": "\\text {s . t .} \\Pi (\\boldsymbol {p}, \\boldsymbol {q}) = \\left\\{\\boldsymbol {\\pi} \\in \\mathbb {R} _ {+} ^ {m \\times n} | \\boldsymbol {\\pi} \\mathbb {1} _ {n} = \\boldsymbol {p}, \\boldsymbol {\\pi} ^ {\\top} \\mathbb {1} _ {m} = \\boldsymbol {q} \\right\\},", + "image_path": "46a9f1df7750eb80302a2aa22078bb6016c5c5cb467594840871ea067be18932.jpg" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "26680" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "\\langle \\cdot, \\cdot \\rangle_F" + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "text", + "content": " is the Frobenius dot-product and " + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "\\mathbb{1}_d" + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "text", + "content": " denotes a " + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "text", + "content": "-dimensional all-one vector. " + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "\\pi" + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "text", + "content": " is called the optimal transport plan that transport " + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "text", + "content": " towards " + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "inline_equation", + "content": "\\pmb{q}" + }, + { + "bbox": [ + 47, + 72, + 287, + 109 + ], + "type": "text", + "content": " at the smallest cost." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 117, + 160, + 129 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 117, + 160, + 129 + ], + "spans": [ + { + "bbox": [ + 47, + 117, + 160, + 129 + ], + "type": "text", + "content": "3.2. Problem Definition" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "spans": [ + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": "Without losing generality, we take the visual-text retrieval as an example to present the PMP problem in cross-modal retrieval. Consider a training dataset " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "\\mathbb{D} = \\{(V_i,T_i,m_i)\\}_{i=1}^N" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": " consisting of " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": " samples, where " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "(V_i,T_i)" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": " is the visual-text pair and " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "m_i \\in \\{1,0\\}" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": " indicates whether the bimodal data is semantically matched or not. The key to cross-modal retrieval lies in measuring the similarity across distinct modalities. To achieve this, existing methods usually project the visual and textual modalities into a comparable feature space via the corresponding modal-specific networks " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "f_v" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "f_t" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": ", respectively. Then the similarity of a given visual-text pair is measured through " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "S_{ij} = g(f_v(V_i), f_t(T_j))" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "g" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": " is a nonparametric or parametric mapping function. For convenience, we denote " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "g(f_v(V_i), f_t(T_j))" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": " as " + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "inline_equation", + "content": "g(V_i, T_j)" + }, + { + "bbox": [ + 47, + 136, + 287, + 316 + ], + "type": "text", + "content": " in the following." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 316, + 288, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 316, + 288, + 376 + ], + "spans": [ + { + "bbox": [ + 47, + 316, + 288, + 376 + ], + "type": "text", + "content": "Ideally, the positive (matched) pairs should have higher similarity while the negative (mismatched) pairs should have lower ones, which can be achieved by minimizing the triplet loss [13] or InfoNCE loss [31]. Consider a batch of " + }, + { + "bbox": [ + 47, + 316, + 288, + 376 + ], + "type": "inline_equation", + "content": "N_{b}" + }, + { + "bbox": [ + 47, + 316, + 288, + 376 + ], + "type": "text", + "content": " pairs " + }, + { + "bbox": [ + 47, + 316, + 288, + 376 + ], + "type": "inline_equation", + "content": "\\{(V_{i},T_{i})\\}_{i = 1}^{N_{b}}" + }, + { + "bbox": [ + 47, + 316, + 288, + 376 + ], + "type": "text", + "content": ", the triplet loss is defined as:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 75, + 387, + 287, + 417 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 75, + 387, + 287, + 417 + ], + "spans": [ + { + "bbox": [ + 75, + 387, + 287, + 417 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) = [ \\alpha - g \\left(V _ {i}, T _ {i}\\right) + g \\left(V _ {i}, \\hat {T} _ {h}\\right) ] _ {+} \\tag {2} \\\\ + \\left[ \\alpha - g \\left(V _ {i}, T _ {i}\\right) + g \\left(\\hat {V} _ {h}, T _ {i}\\right) \\right] _ {+}, \\\\ \\end{array}", + "image_path": "4b787ee891261fadfdfc4ca39488b4cdfa8fac528baa61399db85a965ddbf196.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "spans": [ + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "text", + "content": " is a margin and " + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "inline_equation", + "content": "[x]_{+} = \\max (x,0)" + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "inline_equation", + "content": "\\hat{V}_h" + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "inline_equation", + "content": "\\hat{T}_h" + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "text", + "content": " are the most similar negatives in the given batch corresponding to " + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "inline_equation", + "content": "(V_i,T_i)" + }, + { + "bbox": [ + 47, + 429, + 287, + 477 + ], + "type": "text", + "content": ". Eq.(2) aims to enforce the negative pairs to be distant from the positives by a certain margin value." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "spans": [ + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": "Alternatively, InfoNCE loss is extended to cross-modal scenario [21,34] that encourages the similarity gap between positives and negatives as large as possible. Formally, the matching probability of " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": "-th textual sample w.r.t. the " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": "-th visual query is defined as " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "p_{ij}^{2t} = \\frac{\\exp(g(V_i,T_j) / \\tau)}{\\sum_{j' = 1}^{N_b}\\exp(g(V_i,T_{j'}) / \\tau)}" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": " is a temperature parameter. As InfoNCE loss is symmetric, the matching probability " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "p_{ij}^{t2v}" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": " is defined similarly. For notation convenience, we denote " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "\\pmb{p}_i^{2t} = [p_{i1}^{2t},\\dots ,p_{iN_b}^{2t}]^\\top" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "\\pmb{p}_i^{t2v} = [p_{i1}^{t2v},\\dots ,p_{iN_b}^{t2v}]^\\top" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": " as the probability vectors. To align cross-modal samples, the corresponding one-hot vector " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "\\pmb{y}_i = [y_{i1},\\dots ,y_{iN_b}]^\\top" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": " is used as supervision, where " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "y_{ij}" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": " equal to 1 if " + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "inline_equation", + "content": "i = j" + }, + { + "bbox": [ + 47, + 478, + 287, + 643 + ], + "type": "text", + "content": " while other elements are 0. Thus, the cross-modal InfoNCE loss is given by:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 74, + 652, + 287, + 667 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 74, + 652, + 287, + 667 + ], + "spans": [ + { + "bbox": [ + 74, + 652, + 287, + 667 + ], + "type": "interline_equation", + "content": "\\mathcal {L} ^ {\\text {I n f o N C E}} \\left(V _ {i}, T _ {i}\\right) = \\mathcal {H} \\left(\\boldsymbol {y} _ {i}, \\boldsymbol {p} _ {i} ^ {v 2 t}\\right) + \\mathcal {H} \\left(\\boldsymbol {y} _ {i}, \\boldsymbol {p} _ {i} ^ {t 2 v}\\right), \\tag {3}", + "image_path": "5ca85c04ff00229bd45a54ff94c9aad1db806b6ecf0cbe674a95422454a5bf52.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 677, + 237, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 237, + 689 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 237, + 689 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 677, + 237, + 689 + ], + "type": "inline_equation", + "content": "\\mathcal{H}" + }, + { + "bbox": [ + 47, + 677, + 237, + 689 + ], + "type": "text", + "content": " is the batched cross-entropy function." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "The success of both Eq.(2) and Eq.(3) relies on the well-matched pairs. However, in practice, the multimedia" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 72, + 545, + 119 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 545, + 119 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 545, + 119 + ], + "type": "text", + "content": "datasets are usually web-collected, and thus inevitably contains an unknown portion of irrelevant pairs but are wrongly treated as matched (" + }, + { + "bbox": [ + 305, + 72, + 545, + 119 + ], + "type": "inline_equation", + "content": "m_i = 1" + }, + { + "bbox": [ + 305, + 72, + 545, + 119 + ], + "type": "text", + "content": "). Our goal is to combat such PMPs to facilitate robust cross-modal retrieval." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 130, + 388, + 144 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 130, + 388, + 144 + ], + "spans": [ + { + "bbox": [ + 306, + 130, + 388, + 144 + ], + "type": "text", + "content": "4. Methodology" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "spans": [ + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "text", + "content": "To tackle the PMP problem, the mainstream pipeline first uses the memorization effect [3] of DNNs, i.e., DNNs learn simpler patterns before memorizing the difficult ones, to partition the dataset into a matched subset " + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_m" + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "text", + "content": ", and a mismatched subset " + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_{\\widetilde{m}} = \\mathbb{D} / \\mathbb{D}_m" + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "text", + "content": ". After that, " + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_m" + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "text", + "content": " can be used for standard cross-modal training. To mitigate the impact of PMPs, recent advances [19, 23, 45] introduce a soft margin into Eq.(2) to down-weight the samples from " + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_{\\widetilde{m}}" + }, + { + "bbox": [ + 305, + 150, + 545, + 306 + ], + "type": "text", + "content": ". However, due to the underuse of mismatched pairs, the achieved performance by them is argued to be sub-optimal. In this work, we aim to fully leverage PMPs by trying to excavate the potential semantic similarity among mismatched pairs. In the following, we present the details of our method." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 313, + 468, + 326 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 313, + 468, + 326 + ], + "spans": [ + { + "bbox": [ + 306, + 313, + 468, + 326 + ], + "type": "text", + "content": "4.1. Identifying Mismatched Pairs" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 331, + 545, + 451 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 331, + 545, + 451 + ], + "spans": [ + { + "bbox": [ + 305, + 331, + 545, + 451 + ], + "type": "text", + "content": "Following the mainstream learning style, we first identify possibly mismatched pairs from all training data. The memorization effect of DNNs indicates that mismatched samples tend to have relatively higher loss during the early stage of training. Based on this, we use the difference in loss distribution between the matched and mismatched pairs to divide the training set. Empirically, we observe that the distribution of triplet loss is more distinguishable. Thus, given the retrieval model " + }, + { + "bbox": [ + 305, + 331, + 545, + 451 + ], + "type": "inline_equation", + "content": "(f_v, f_t, g)" + }, + { + "bbox": [ + 305, + 331, + 545, + 451 + ], + "type": "text", + "content": ", we compute the per-sample loss through Eq.(2):" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 339, + 458, + 545, + 473 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 339, + 458, + 545, + 473 + ], + "spans": [ + { + "bbox": [ + 339, + 458, + 545, + 473 + ], + "type": "interline_equation", + "content": "\\ell_ {\\left(f _ {v}, f _ {t}, g\\right)} = \\left\\{\\ell_ {i} \\right\\} _ {i = 1} ^ {N} = \\left\\{\\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) \\right\\} _ {i = 1} ^ {N}. \\tag {4}", + "image_path": "a8794e4569c4f84b297f68e461517398b2d83c8515a84a51435d556122303f7a.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "spans": [ + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": "Then, we fit a two-component beta mixture model [2,19,45] to " + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "inline_equation", + "content": "\\ell_{(f_v,f_t,g)}" + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": " using the Expectation-Maximization algorithm. For " + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": "-th pair, its probability " + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "inline_equation", + "content": "w_{i}" + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": " being mismatched is the posterior probability " + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "inline_equation", + "content": "p(b|\\ell_i)" + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": " is the beta component with a higher mean. By setting a threshold on " + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "inline_equation", + "content": "\\{w_{i}\\}_{i = 1}^{N}" + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": ", we can divide the training data into the matched subset " + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_m" + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": " and mismatched subset " + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_{\\widetilde{m}}" + }, + { + "bbox": [ + 305, + 480, + 545, + 576 + ], + "type": "text", + "content": " (we set the threshold to 0.5 in all experiments for brevity)." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 576, + 545, + 660 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 576, + 545, + 660 + ], + "spans": [ + { + "bbox": [ + 305, + 576, + 545, + 660 + ], + "type": "text", + "content": "For initial convergence of the algorithm, we warm up the model for a few epochs by training on all data with Eq.(2) or Eq.(3). However, for extreme mismatching rates, the model would quickly overfit to mismatched pairs and produce unreliable loss. To address this issue, we mitigate the overconfidence of the model by adding a reverse cross entropy [41] term to the InfoNCE loss during warm-up, i.e.," + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 339, + 667, + 545, + 682 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 339, + 667, + 545, + 682 + ], + "spans": [ + { + "bbox": [ + 339, + 667, + 545, + 682 + ], + "type": "interline_equation", + "content": "\\mathcal {L} ^ {\\mathrm {R C E}} \\left(V _ {i}, T _ {i}\\right) = \\mathcal {H} \\left(\\boldsymbol {p} _ {i} ^ {v 2 t}, \\boldsymbol {y} _ {i}\\right) + \\mathcal {H} \\left(\\boldsymbol {p} _ {i} ^ {t 2 v}, \\boldsymbol {y} _ {i}\\right). \\tag {5}", + "image_path": "49c02186ea948d92ab1c6aa02f7d3144d447eedf2e0f4d185529490f4d6086a8.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "In the presence of PMPs, " + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "inline_equation", + "content": "y_{i}" + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": " may provide the wrong matching relation. Instead, the estimated probability could reflect" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "26681" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 70, + 547, + 231 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 547, + 231 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 547, + 231 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 547, + 231 + ], + "type": "image", + "image_path": "90f9e79f5dde2eb384dc91fad136b9f01a72f9429a3aef295e0d7760d83c19f9.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "lines": [ + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "type": "text", + "content": "Figure 2. Overview of the learnable cost function with self-supervised learning. The up part illustrates the reconstructed pairs that only " + }, + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "type": "inline_equation", + "content": "(V_4, T_1)" + }, + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "type": "inline_equation", + "content": "(V_2, T_3)" + }, + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "type": "inline_equation", + "content": "(V_{N_b}, T_{N_b})" + }, + { + "bbox": [ + 46, + 239, + 547, + 275 + ], + "type": "text", + "content": " are the reserved matching ones. Then, the matching matrix is viewed as supervision to guide the cost function from the explicit similarity-cost mapping relation through an OT loss (the down part)." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 291, + 288, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 291, + 288, + 327 + ], + "spans": [ + { + "bbox": [ + 46, + 291, + 288, + 327 + ], + "type": "text", + "content": "the truer distribution to a certain extent. Note that we bound the one-hot label into " + }, + { + "bbox": [ + 46, + 291, + 288, + 327 + ], + "type": "inline_equation", + "content": "[\\epsilon, 1 - \\epsilon]" + }, + { + "bbox": [ + 46, + 291, + 288, + 327 + ], + "type": "text", + "content": " for computational feasibility. " + }, + { + "bbox": [ + 46, + 291, + 288, + 327 + ], + "type": "inline_equation", + "content": "(\\epsilon = 10^{-7}" + }, + { + "bbox": [ + 46, + 291, + 288, + 327 + ], + "type": "text", + "content": " in our experiments)." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 334, + 214, + 346 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 334, + 214, + 346 + ], + "spans": [ + { + "bbox": [ + 47, + 334, + 214, + 346 + ], + "type": "text", + "content": "4.2. Rematching Mismatched Pairs" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 352, + 287, + 413 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 352, + 287, + 413 + ], + "spans": [ + { + "bbox": [ + 46, + 352, + 287, + 413 + ], + "type": "text", + "content": "We formalize the rematching idea as an OT problem, generating refined alignments by seeking a minimal-cost transport plan. We will first introduce the novel learnable cost function to suit the PMP scenario, then we show how to boost the refined alignment by a relaxed OT model." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "text", + "content": "Cost Function with Self-Supervised Learning. Cost function plays a crucial role when learning the transport plan for OT. In general, " + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "inline_equation", + "content": "C_{ij}" + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "text", + "content": " is set to a distance measure, e.g., " + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "inline_equation", + "content": "L_{2}" + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "text", + "content": "-distance [18] or cosine distance [10] to measure the expense of transporting a visual sample " + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "text", + "content": " to a textual sample " + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 426, + 287, + 605 + ], + "type": "text", + "content": ". However, the existence of PMPs imposes formidable obstacles for these feature-driven distance measures. On the one hand, training with PMPs can wrongly bring irrelevant data together, which undoubtedly prevents effective representation learning. Even worse, different modalities will be embedded into separate regions of the shared space due to the inherent modality gap [27]. On the other hand, the refined alignments produced by those corrupted features would be used to guide subsequent training, leading to the cycle of self-reinforcing errors [8]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 606, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 606, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 606, + 288, + 715 + ], + "type": "text", + "content": "To address the aforementioned limitations, we propose a novel self-supervised learning approach to automatically learn the cost function. Intuitively, for a given image and caption, the transport cost can be modeled as a function of similarity that higher similarity enjoys a lower cost. Thus, we formulate the cost function as a single-layer feedforward network with parameters " + }, + { + "bbox": [ + 46, + 606, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\Theta_c" + }, + { + "bbox": [ + 46, + 606, + 288, + 715 + ], + "type": "text", + "content": ", i.e., " + }, + { + "bbox": [ + 46, + 606, + 288, + 715 + ], + "type": "inline_equation", + "content": "f_c(\\cdot;\\Theta_c)" + }, + { + "bbox": [ + 46, + 606, + 288, + 715 + ], + "type": "text", + "content": ", which takes the similarity matrix of the batched visual-text samples as input and attempts to learn the corresponding cost" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "spans": [ + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "content": "matrix. To achieve this, we reconstruct the visual-text pairs to guide the cost function from explicit similarity-cost mapping relation. Specifically, for the matched pairs sampled from " + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_m" + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "content": ", we randomly reserve a part of the matching images and substitute the images from " + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_{\\widetilde{m}}" + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "content": " for the remaining ones. With the reserved indexes, we could automatically obtain a matching matrix that indicates the ideal matching probability for each reconstructed pair. For the example illustrated in Fig. 2, " + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "inline_equation", + "content": "(V_4,T_1)" + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "inline_equation", + "content": "(V_{2},T_{3})" + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "inline_equation", + "content": "(V_{N_b},T_{N_b})" + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "content": " are the reserved matching pairs with a matching probability of 1, while the others could be considered as mismatched ones with a matching probability of 0. For convenience, let " + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "inline_equation", + "content": "\\mathbb{D}'" + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "content": " be the reconstructed data, and " + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "inline_equation", + "content": "(V,T) \\in \\mathbb{D}'" + }, + { + "bbox": [ + 304, + 291, + 547, + 483 + ], + "type": "text", + "content": " be matrices that contain a batch of images and captions. To relate the similarity-cost mapping with the matching matrix, we optimize the cost function by the following OT loss:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 321, + 488, + 545, + 502 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 321, + 488, + 545, + 502 + ], + "spans": [ + { + "bbox": [ + 321, + 488, + 545, + 502 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {O T}} \\left(\\boldsymbol {\\pi} ^ {\\sup }, \\boldsymbol {V}, \\boldsymbol {T}\\right) = \\left\\langle \\boldsymbol {\\pi} ^ {\\sup }, f _ {c} \\left(g (\\boldsymbol {V}, \\boldsymbol {T}); \\Theta_ {c}\\right) \\right\\rangle_ {F}, \\tag {6}", + "image_path": "eb4828f29bf65c0701d842e8ce024a38a07c6bd7aa7bde261c70eefa72d29218.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 508, + 545, + 532 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 508, + 545, + 532 + ], + "spans": [ + { + "bbox": [ + 304, + 508, + 545, + 532 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 508, + 545, + 532 + ], + "type": "inline_equation", + "content": "\\pi^{\\mathrm{sup}}" + }, + { + "bbox": [ + 304, + 508, + 545, + 532 + ], + "type": "text", + "content": " is the matching matrix, and " + }, + { + "bbox": [ + 304, + 508, + 545, + 532 + ], + "type": "inline_equation", + "content": "g(\\mathbf{V},\\mathbf{T})" + }, + { + "bbox": [ + 304, + 508, + 545, + 532 + ], + "type": "text", + "content": " denotes the similarity matrix for the batched visual-text pairs." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 532, + 545, + 568 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 532, + 545, + 568 + ], + "spans": [ + { + "bbox": [ + 304, + 532, + 545, + 568 + ], + "type": "text", + "content": "Eq.(6) seeks an effective cost function from a reverse perspective of OT, which views the ideal transport plan as the supervision to minimize the transport cost." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 582, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 715 + ], + "type": "text", + "content": "Boosting Refined Alignments with Relaxed OT. Given the defined cost function, we could generate the refined alignments for mismatched pairs following the OT objective described in Eq.(1). However, Eq.(1) requires the two distributions to have the same total mass and that all the mass of " + }, + { + "bbox": [ + 304, + 582, + 545, + 715 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 582, + 545, + 715 + ], + "type": "text", + "content": " should be transported to exactly match the mass of " + }, + { + "bbox": [ + 304, + 582, + 545, + 715 + ], + "type": "inline_equation", + "content": "q" + }, + { + "bbox": [ + 304, + 582, + 545, + 715 + ], + "type": "text", + "content": ". In practice, due to the limited batch size, one caption may be irrelevant to all images in the batch and vice versa. To this end, we adopt the partial OT model [6, 16] to relax such strict all-to-all mass constraints, which seeks a minimal cost of only transporting " + }, + { + "bbox": [ + 304, + 582, + 545, + 715 + ], + "type": "inline_equation", + "content": "0 \\leqslant \\rho \\leqslant \\min(\\|p\\|_1, \\|q\\|_1)" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "26682" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 70, + 547, + 176 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 547, + 176 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 547, + 176 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 547, + 176 + ], + "type": "image", + "image_path": "6e5f6943323c0b5bd47309d6e844360e89d779947cb8bfb5d0bb7db2dd8c00da.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 183, + 547, + 218 + ], + "lines": [ + { + "bbox": [ + 46, + 183, + 547, + 218 + ], + "spans": [ + { + "bbox": [ + 46, + 183, + 547, + 218 + ], + "type": "text", + "content": "Figure 3. Illustration of the proposed rematching loss. For the mismatched pairs, we formalize a partial OT problem with positive pairs masked to generate the refined alignment in each batch. The refined alignment provides a more reliable matching relation to supervise the mismatched pairs. Then, we compute the symmetric KL-divergence to optimize the retrieval model " + }, + { + "bbox": [ + 46, + 183, + 547, + 218 + ], + "type": "inline_equation", + "content": "(f_v, f_t, g)" + }, + { + "bbox": [ + 46, + 183, + 547, + 218 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 227, + 287, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 227, + 287, + 239 + ], + "spans": [ + { + "bbox": [ + 47, + 227, + 287, + 239 + ], + "type": "text", + "content": "unit mass between the visual and textual distribution, i.e.," + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 257, + 287, + 277 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 257, + 287, + 277 + ], + "spans": [ + { + "bbox": [ + 47, + 257, + 287, + 277 + ], + "type": "interline_equation", + "content": "\\min _ {\\boldsymbol {\\pi} \\in \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q})} \\left\\langle \\boldsymbol {\\pi}, \\boldsymbol {C} \\right\\rangle_ {F}, \\text {s . t .} \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q}) = \\left\\{\\boldsymbol {\\pi} \\in \\mathbb {R} _ {+} ^ {m \\times n} | \\boldsymbol {\\pi} \\mathbb {1} _ {n} \\leqslant \\boldsymbol {p}, \\right.", + "image_path": "8548c1d4765ae014492b5618dedc135cd98914a94094fa51c5f032ba660f46bb.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 123, + 278, + 287, + 293 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 123, + 278, + 287, + 293 + ], + "spans": [ + { + "bbox": [ + 123, + 278, + 287, + 293 + ], + "type": "interline_equation", + "content": "\\boldsymbol {\\pi} ^ {\\top} \\mathbb {1} _ {m} \\leqslant \\boldsymbol {q}, \\mathbb {1} _ {m} ^ {\\top} \\pi \\mathbb {1} _ {n} = \\rho \\}. \\tag {7}", + "image_path": "02cc7b280bb9091eb2ea4e33352018ab4744b22c319504574e037b59c6092dde.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 300, + 287, + 395 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 300, + 287, + 395 + ], + "spans": [ + { + "bbox": [ + 46, + 300, + 287, + 395 + ], + "type": "text", + "content": "Furthermore, the false positives contained in the mismatched pairs introduce an implicit constraint to our transport plan " + }, + { + "bbox": [ + 46, + 300, + 287, + 395 + ], + "type": "inline_equation", + "content": "\\pi" + }, + { + "bbox": [ + 46, + 300, + 287, + 395 + ], + "type": "text", + "content": " that the transport mass between the same element in two distributions should be limited. To this end, we propose to impose a mask operation on the transport plan that restricts the transport to only concentrate among the unpaired pairs. Specifically, the mask matrix " + }, + { + "bbox": [ + 46, + 300, + 287, + 395 + ], + "type": "inline_equation", + "content": "M\\in \\mathbb{R}^{m\\times n}" + }, + { + "bbox": [ + 46, + 300, + 287, + 395 + ], + "type": "text", + "content": " is defined as:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 116, + 399, + 287, + 432 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 116, + 399, + 287, + 432 + ], + "spans": [ + { + "bbox": [ + 116, + 399, + 287, + 432 + ], + "type": "interline_equation", + "content": "M _ {i j} \\triangleq \\left\\{ \\begin{array}{l l} 0, & \\text {i f} i = j, \\\\ 1, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {8}", + "image_path": "fd06feda0794159cc74d19df0c64fe86866863d9ba7ecd1ca3b15970d00e4370.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 437, + 287, + 461 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 287, + 461 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 287, + 461 + ], + "type": "text", + "content": "Then the masked transport plan is defined as the Hadamard product " + }, + { + "bbox": [ + 46, + 437, + 287, + 461 + ], + "type": "inline_equation", + "content": "\\tilde{\\pi} = M\\odot \\pi" + }, + { + "bbox": [ + 46, + 437, + 287, + 461 + ], + "type": "text", + "content": " and be optimized through Eq.(7)." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 467, + 179, + 480 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 467, + 179, + 480 + ], + "spans": [ + { + "bbox": [ + 47, + 467, + 179, + 480 + ], + "type": "text", + "content": "4.3. The Training Objective" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "spans": [ + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "text", + "content": "Given the mismatched pairs " + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "inline_equation", + "content": "\\{(V_i, T_i)\\}_{i=1}^{N_b}" + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "text", + "content": " sampled from " + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "inline_equation", + "content": "\\mathbb{D}_{\\widetilde{m}}" + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "text", + "content": ", if we don't have any prior knowledge, we could consider the visual and textual samples following the uniform distributions, i.e., " + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "inline_equation", + "content": "\\pmb{p} = \\sum_{i=1}^{N_b} \\frac{1}{N_b} \\delta(V_i)" + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "inline_equation", + "content": "\\pmb{q} = \\sum_{i=1}^{N_b} \\frac{1}{N_b} \\delta(T_i)" + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "text", + "content": ", respectively. To guarantee the efficiency of our algorithm, we adopt an online strategy to update " + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "inline_equation", + "content": "\\Theta_c" + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "text", + "content": " and calculate " + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "inline_equation", + "content": "\\widetilde{\\pi}" + }, + { + "bbox": [ + 47, + 484, + 287, + 574 + ], + "type": "text", + "content": " through a single optimization loop:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 48, + 588, + 287, + 641 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 588, + 287, + 641 + ], + "spans": [ + { + "bbox": [ + 48, + 588, + 287, + 641 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\min _ {\\tilde {\\boldsymbol {\\pi}} \\in \\Pi^ {\\rho} (\\boldsymbol {p}, \\boldsymbol {q})} \\mathbb {E} _ {(\\boldsymbol {V}, \\boldsymbol {T}) \\in \\mathbb {D} _ {\\tilde {m}}} \\left\\langle \\tilde {\\boldsymbol {\\pi}}, f _ {c} \\left(g \\left(\\boldsymbol {V}, \\boldsymbol {T}\\right); \\Theta_ {c} ^ {*}\\right) \\right\\rangle_ {F} - \\lambda H (\\tilde {\\boldsymbol {\\pi}}), \\\\ \\text {s . t .} \\Theta_ {c} ^ {*} = \\underset {\\Theta_ {c}} {\\arg \\min } \\mathbb {E} _ {(\\boldsymbol {V}, \\boldsymbol {T}, \\boldsymbol {\\pi} ^ {\\sup }) \\in \\mathbb {D} ^ {\\prime}} \\mathcal {L} _ {O T} (\\boldsymbol {\\pi} ^ {\\sup }, \\boldsymbol {V}, \\boldsymbol {T}) \\tag {9} \\\\ \\end{array}", + "image_path": "14403f6e872abf4f0694af04356086b349b165ab69580ca59000b8ff573ed02f.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\lambda > 0" + }, + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "type": "text", + "content": " is a regularization parameter for the entropic constraint " + }, + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "type": "inline_equation", + "content": "H(\\tilde{\\pi}) = -\\sum_{ij} \\tilde{\\pi}_{ij} \\log \\tilde{\\pi}_{ij}" + }, + { + "bbox": [ + 46, + 642, + 287, + 714 + ], + "type": "text", + "content": ". Note that Eq.(9) introduces an entropy regularization item to the OT model, which enables the transport plan to be solved by the computationally cheaper Sinkhorn-Knopp algorithm [9]. The detailed solution is presented in Appendix A." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "spans": [ + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "type": "text", + "content": "The optimal transport plan from Eq.(9) represents a refined alignment that provides a more reliable matching relation for those mismatched visual-text samples. As our refined alignment is generated dynamically, we adopt the KL-divergence to compute the rematching loss instead of the cross entropy. Besides, a reverse term is added to symmetrize the KL-divergence, which makes the training more stable. Formally, let " + }, + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "type": "inline_equation", + "content": "\\tilde{\\pi}_i^{v2t}" + }, + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "type": "inline_equation", + "content": "\\tilde{\\pi}_i^{t2v}" + }, + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "type": "text", + "content": " be the row-wise and column-wise normalized refined alignment for the " + }, + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 227, + 547, + 357 + ], + "type": "text", + "content": "-th sample, respectively. Then, the rematching loss (see Fig. 3) is defined as:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 361, + 547, + 417 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 361, + 547, + 417 + ], + "spans": [ + { + "bbox": [ + 306, + 361, + 547, + 417 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} ^ {\\mathrm {r e}} \\left(V _ {i}, T _ {i}\\right) = \\frac {1}{2} \\left[ D _ {K L} \\left(\\tilde {\\boldsymbol {\\pi}} _ {i} ^ {v 2 t} \\parallel \\boldsymbol {p} _ {i} ^ {v 2 t}\\right) + D _ {K L} \\left(\\boldsymbol {p} _ {i} ^ {v 2 t} \\parallel \\tilde {\\boldsymbol {\\pi}} _ {i} ^ {v 2 t}\\right) \\right] \\\\ + \\frac {1}{2} \\left[ D _ {K L} \\left(\\tilde {\\boldsymbol {\\pi}} _ {i} ^ {t 2 v} \\| \\boldsymbol {p} _ {i} ^ {t 2 v}\\right) + D _ {K L} \\left(\\boldsymbol {p} _ {i} ^ {t 2 v} \\| \\tilde {\\boldsymbol {\\pi}} _ {i} ^ {t 2 v}\\right) \\right]. \\tag {10} \\\\ \\end{array}", + "image_path": "aacc01c18c8e12ae610bbd29492ad75446f0c1cf3a8e8de68fcf8726321c040f.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 418, + 547, + 453 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 418, + 547, + 453 + ], + "spans": [ + { + "bbox": [ + 304, + 418, + 547, + 453 + ], + "type": "text", + "content": "For the pairs that are divided as matched, we use the triplet ranking loss to directly control the distance gap. Thus, our final objective function is defined as:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 318, + 459, + 545, + 487 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 459, + 545, + 487 + ], + "spans": [ + { + "bbox": [ + 318, + 459, + 545, + 487 + ], + "type": "interline_equation", + "content": "\\mathcal {L} ^ {\\text {F i n a l}} = \\sum_ {(V _ {i}, T _ {i}) \\in \\mathbb {D} _ {m}} \\mathcal {L} ^ {\\text {t r i p l e t}} \\left(V _ {i}, T _ {i}\\right) + \\sum_ {(V _ {i}, T _ {i}) \\in \\mathbb {D} _ {\\tilde {m}}} \\mathcal {L} ^ {\\text {r e}} \\left(V _ {i}, T _ {i}\\right). \\tag {11}", + "image_path": "fa75aa0a701c3e81bee78db65dc2f7eea8826237fcf891c0b487d767b17b415d.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 492, + 545, + 504 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 492, + 545, + 504 + ], + "spans": [ + { + "bbox": [ + 306, + 492, + 545, + 504 + ], + "type": "text", + "content": "The detailed training pseudo-code is shown in Appendix B." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 514, + 382, + 527 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 514, + 382, + 527 + ], + "spans": [ + { + "bbox": [ + 306, + 514, + 382, + 527 + ], + "type": "text", + "content": "5. Experiment" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 533, + 545, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 533, + 545, + 556 + ], + "spans": [ + { + "bbox": [ + 306, + 533, + 545, + 556 + ], + "type": "text", + "content": "In this section, we experimentally analyze the effectiveness of L2RM in robust cross-modal retrieval." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 563, + 356, + 576 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 563, + 356, + 576 + ], + "spans": [ + { + "bbox": [ + 306, + 563, + 356, + 576 + ], + "type": "text", + "content": "5.1. Setup" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 714 + ], + "type": "text", + "content": "Datasets. We apply our method to three image-text retrieval datasets varying in scale and scope. Specifically, Flickr30K [46] consists of 31,000 images with five corresponding text annotations for each image from the Flickr website. Following [23], we split 1,000 images for validation, 1,000 images for testing, and the rest for training. MS-COCO [28] is a large-scale cross-modal dataset, which collects 123,287 images with five sentences each. Following [23], we use 5,000 images for validation, 5,000 images for testing, and the rest for training. Conceptual Captions [36] is a web-crawled large-scale dataset containing" + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "26683" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 56, + 69, + 545, + 498 + ], + "blocks": [ + { + "bbox": [ + 56, + 69, + 545, + 498 + ], + "lines": [ + { + "bbox": [ + 56, + 69, + 545, + 498 + ], + "spans": [ + { + "bbox": [ + 56, + 69, + 545, + 498 + ], + "type": "table", + "html": "
MRateMethodFlickr30KMS-COCO
Image-to-TextText-to-ImagerSumImage-to-TextText-to-ImagerSum
R@1R@5R@10R@1R@5R@10R@1R@5R@10R@1R@5R@10
0.2IMRAM59.185.491.944.571.479.4431.769.993.697.455.984.489.6490.8
NCR73.593.296.656.982.488.5491.176.695.698.260.888.895.0515.0
BiCro74.794.396.856.681.488.2492.076.695.498.261.388.894.8515.1
DECL-SGR74.592.997.153.679.586.8484.475.695.198.359.988.394.7511.9
DECL-SGRAF77.593.897.056.181.888.5494.777.595.998.461.789.395.4518.2
RCL-SGR74.291.896.955.681.287.5487.277.095.598.161.388.894.8515.5
RCL-SGRAF75.994.597.357.982.688.6496.878.996.098.462.889.995.4521.4
L2RM-SAF73.794.397.756.881.888.1492.477.996.098.362.189.294.9518.4
L2RM-SGR76.593.797.355.581.588.0492.578.495.798.362.189.194.9518.5
L2RM-SGRAF77.995.297.859.883.689.5503.880.296.398.564.290.195.4524.7
0.4IMRAM44.973.282.631.656.365.6354.251.882.490.938.470.378.9412.7
NCR68.189.694.851.478.484.8467.174.794.698.059.688.194.7509.7
BiCro70.792.095.551.977.785.4473.275.295.398.160.087.894.3510.7
DECL-SGR69.090.294.850.776.384.1465.173.694.697.957.886.993.9504.7
DECL-SGRAF72.792.395.453.479.486.4479.675.695.598.359.588.394.8512.0
RCL-SGR71.391.195.351.478.085.2472.373.994.997.959.087.493.9507.0
RCL-SGRAF72.792.796.154.880.087.1483.477.095.598.361.288.594.8515.3
L2RM-SAF72.192.196.152.778.885.9477.774.494.798.359.287.994.4508.9
L2RM-SGR73.192.496.352.379.486.3479.875.294.898.159.487.894.1509.4
L2RM-SGRAF75.893.296.956.381.087.3490.577.595.898.462.089.194.9517.7
0.6IMRAM16.438.250.97.519.225.3157.518.251.668.017.943.654.6253.9
NCR13.937.750.511.030.141.4184.60.10.30.40.10.51.02.4
BiCro64.187.192.747.274.082.3447.473.293.997.657.586.393.4501.9
DECL-SGR64.585.892.644.071.680.6439.169.793.497.554.585.292.6492.9
DECL-SGRAF65.288.494.046.874.082.2450.673.094.297.957.086.693.8502.5
RCL-SGR62.386.392.945.171.380.2438.171.493.297.155.484.792.3494.1
RCL-SGRAF67.789.193.648.074.983.3456.674.094.397.557.686.493.5503.3
L2RM-SAF66.188.893.847.874.282.2452.971.293.497.556.585.993.0497.5
L2RM-SGR65.187.893.647.073.581.5448.572.793.997.556.986.293.3500.5
L2RM-SGRAF70.090.895.451.376.483.7467.675.494.797.959.287.493.8508.4
0.8IMRAM3.19.75.20.30.91.921.11.35.08.30.20.61.316.7
NCR1.56.29.90.31.02.121.00.10.30.40.10.51.02.4
BiCro2.39.217.22.610.216.858.362.288.694.647.479.288.5460.5
DECL-SGR44.472.682.033.959.569.0361.460.088.794.545.978.888.3456.2
DECL-SGRAF53.478.886.937.663.873.9394.464.890.596.049.781.790.3473.0
RCL-SGR47.170.579.430.356.166.3349.763.289.395.247.678.788.0462.0
RCL-SGRAF51.775.884.434.561.270.7378.367.490.896.050.681.090.1475.9
L2RM-SAF50.877.985.535.662.672.7385.164.790.895.850.080.989.4471.6
L2RM-SGR50.577.283.934.261.171.6378.565.290.396.149.881.088.2470.6
L2RM-SGRAF55.780.887.839.465.474.9404.069.091.996.452.682.490.3482.6
", + "image_path": "cb52478f98ecb0149f1025d7b0713cbfb24d614a61884fd6dbb06e5947d153cf.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 86, + 506, + 504, + 518 + ], + "lines": [ + { + "bbox": [ + 86, + 506, + 504, + 518 + ], + "spans": [ + { + "bbox": [ + 86, + 506, + 504, + 518 + ], + "type": "text", + "content": "Table 1. Image-text retrieval performance under different mismatching rates (MRate) on Flickr30K and MS-COCO." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 533, + 287, + 583 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 533, + 287, + 583 + ], + "spans": [ + { + "bbox": [ + 46, + 533, + 287, + 583 + ], + "type": "text", + "content": "3.3M one-to-one images and captions. Following [23], we use the subset, i.e., CC152K to conduct experiments, which has 150,000 images for training, 1,000 images for validation, and 1,000 images for testing." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 288, + 715 + ], + "type": "text", + "content": "Implementation Details. As a general method, L2RM could be directly applied to almost all cross-modal retrieval methods to improve their robustness. Following [21, 33], we apply L2RM to SGR, SAF, and SGRAF for a comprehensive comparison. We evaluate the retrieval performance with the Recall@K (R@K) metric. Following [23], we save the best performance checkpoint on the validation set w.r.t. the sum of the evaluation scores and report its results on the testing set. We follow the same training setting as [23], our specific parameters setting can be found in Appendix C.1." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 533, + 545, + 631 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 545, + 631 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 545, + 631 + ], + "type": "text", + "content": "Baselines. We compare L2RM with eight state-of-the-art cross-modal retrieval methods, including four general methods (i.e., IMRAM [7], SGR, SAF, and SGRAF [12]) and four robust learning methods against the PMPs (i.e., NCR [23], DECL [33], BiCro [45], and RCL [21]). Note that the original BiCro combines four models, i.e., two co-trained SGR, and two co-trained SAF. For a fair comparison, we report the results of 2 co-trained SGR for BiCro like [23]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 644, + 390, + 657 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 644, + 390, + 657 + ], + "spans": [ + { + "bbox": [ + 306, + 644, + 390, + 657 + ], + "type": "text", + "content": "5.2. Main Results" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 665, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 715 + ], + "type": "text", + "content": "In this section, we conduct comparison experiments with different mismatching rates on three datasets to evaluate the performance of our L2RM. As Flickr30K and MS-COCO are well-established datasets, we carry out experiments by" + } + ] + } + ], + "index": 6 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "26684" + } + ] + } + ], + "index": 7 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 180 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 180 + ], + "type": "text", + "content": "generating the synthesized false positive pairs, i.e., the mismatching rate (MRate) increases from 0.2 to 0.8 in intervals of 0.2. Following [21, 33], we randomly select a specific percentage of images and randomly permute all their corresponding captions, which is more challenging and practical than the setting in [23, 45]. For the web-collected dataset CC152K, which naturally contains about " + }, + { + "bbox": [ + 46, + 72, + 289, + 180 + ], + "type": "inline_equation", + "content": "3\\% \\sim 20\\%" + }, + { + "bbox": [ + 46, + 72, + 289, + 180 + ], + "type": "text", + "content": " unknown mismatched pairs [36]. Thus we directly conduct experiments on it to evaluate the performance with real PMPs." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 197, + 289, + 364 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 197, + 289, + 364 + ], + "spans": [ + { + "bbox": [ + 46, + 197, + 289, + 364 + ], + "type": "text", + "content": "Results on Synthesized PMPs. Tab. 1 shows the experimental results on Flickr30K and MS-COCO. Note that for MS-COCO, the results are computed by averaging over 5 folds of 1K test images like [21, 33]. Due to space limitation, we omit the results of some general methods (SGR, SAF, and SGRAF), and the comparison on original datasets (0 MRate), which could be found in Appendix C.2. From the results, we can find that L2RM achieves the best results on all metrics than the other state-of-the-art methods, which shows the superior robustness of L2RM against PMPs. Moreover, when the mismatching rate is high, e.g., 0.6 and 0.8, the improvement of L2RM is more evident, proving that excavating mismatched pairs could effectively facilitate robust cross-modal retrieval." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 380, + 288, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 380, + 288, + 513 + ], + "spans": [ + { + "bbox": [ + 46, + 380, + 288, + 513 + ], + "type": "text", + "content": "Results on Real-World PMPs. We validate our method on the real-world dataset CC152K, which contains an unknown portion of mismatched pairs. As shown in Tab. 2, our method considerably outperforms the best baseline in terms of sum in retrieval by " + }, + { + "bbox": [ + 46, + 380, + 288, + 513 + ], + "type": "inline_equation", + "content": "9.8\\%" + }, + { + "bbox": [ + 46, + 380, + 288, + 513 + ], + "type": "text", + "content": ". Notably, our L2RM-SGR surpasses all SGR variants by a clear margin, achieving as much as a " + }, + { + "bbox": [ + 46, + 380, + 288, + 513 + ], + "type": "inline_equation", + "content": "16.9\\%" + }, + { + "bbox": [ + 46, + 380, + 288, + 513 + ], + "type": "text", + "content": " (rSum) absolute improvement over the best variant. It is because the real-world rematched pairs are more likely to involve only local alignments, e.g., Fig. 5(e)-Fig. 5(f), while the SGR model itself is adept at capturing the relationship between local alignments." + } + ] + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 48, + 523, + 288, + 692 + ], + "blocks": [ + { + "bbox": [ + 48, + 523, + 288, + 692 + ], + "lines": [ + { + "bbox": [ + 48, + 523, + 288, + 692 + ], + "spans": [ + { + "bbox": [ + 48, + 523, + 288, + 692 + ], + "type": "table", + "html": "
MethodImage-to-TextText-to-ImagerSum
R@1R@5R@10R@1R@5R@10
IMRAM27.852.460.929.251.561.2283.0
SAF32.559.570.032.560.768.7323.9
SGR14.535.548.913.736.147.9196.6
NCR39.564.573.540.364.673.2355.6
BiCro39.764.672.639.265.074.1355.2
DECL-SAF36.663.073.338.563.273.5348.1
DECL-SGR36.263.673.237.163.673.7347.4
DECL-SGRAF39.066.175.540.766.376.7364.3
RCL-SAF37.563.071.437.862.472.4344.5
RCL-SGR38.363.070.439.263.272.3346.4
RCL-SGRAF41.766.073.641.666.475.1364.4
L2RM-SAF37.362.771.738.865.774.8351.0
L2RM-SGR39.566.276.041.865.974.9364.3
L2RM-SGRAF43.067.575.742.868.077.2374.2
", + "image_path": "d8667f3c7c787f6e9afb8799b615e2a6b15b02e61c92d51edd3b88810cde6a9b.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 306, + 72, + 400, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 400, + 85 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 400, + 85 + ], + "type": "text", + "content": "5.3. Ablation Study" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 89, + 547, + 305 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 89, + 547, + 305 + ], + "spans": [ + { + "bbox": [ + 304, + 89, + 547, + 305 + ], + "type": "text", + "content": "Impact of Each Component. To study the influence of specific components in our method, we carry out the ablation study on the Flickr30K with 0.6 MRate. Specifically, we ablate the contributions of three key components of L2RM, i.e., partial OT, positives masked, and the learnable cost function (we use the cosine distance to measure the cost instead). Besides, we compare L2RM with different formulas of rematching loss: KL-divergence and InfoNCE. From Tab. 3, we observe the following conclusions: 1) The full L2RM could achieve the best overall performance, showing that all three components are important to improve the robustness against PMPs. 2) Using the learnable cost function substantially outperforms the variant with the cosine distance cost (e.g., +11.9 in terms of the rSum), which signifies the simple feature-driven cost is sub-optimal to the PMP situation. 3) Formulating different rematching loss could also achieve decent results, which verifies the ability of L2RM to provide effective matching relations." + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 313, + 315, + 547, + 396 + ], + "blocks": [ + { + "bbox": [ + 67, + 700, + 266, + 712 + ], + "lines": [ + { + "bbox": [ + 67, + 700, + 266, + 712 + ], + "spans": [ + { + "bbox": [ + 67, + 700, + 266, + 712 + ], + "type": "text", + "content": "Table 2. Image-text retrieval performance on CC152K." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 313, + 315, + 547, + 396 + ], + "lines": [ + { + "bbox": [ + 313, + 315, + 547, + 396 + ], + "spans": [ + { + "bbox": [ + 313, + 315, + 547, + 396 + ], + "type": "table", + "html": "
AblationImage-to-TextText-to-Image
R@1R@5R@10R@1R@5R@10
L2RM65.187.893.647.073.581.5
L2RM w KL-divergence64.787.693.246.774.081.5
L2RM w InfoNCE Loss64.987.593.546.072.980.9
L2RM w/o Partial OT62.286.491.544.768.672.6
L2RM w/o Positives Masked64.987.692.746.473.281.1
L2RM w/o Cost Function61.385.691.444.972.481.0
", + "image_path": "be938b279f30c87190469202588ea6d0f8bb7b8ed5a8444a58c189462a9f242c.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 323, + 405, + 527, + 415 + ], + "lines": [ + { + "bbox": [ + 323, + 405, + 527, + 415 + ], + "spans": [ + { + "bbox": [ + 323, + 405, + 527, + 415 + ], + "type": "text", + "content": "Table 3. Ablation studies on Flickr30K with 0.6 MRate." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "type": "text", + "content": "Parameter Analysis. We now investigate the effect of the parameter " + }, + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "type": "inline_equation", + "content": "\\rho" + }, + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "type": "text", + "content": " by plotting the recall scores with incremental " + }, + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "type": "inline_equation", + "content": "\\rho" + }, + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "type": "text", + "content": " on Flickr30K. The figure shows that the overall performance tends to decrease as " + }, + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "type": "inline_equation", + "content": "\\rho" + }, + { + "bbox": [ + 304, + 426, + 545, + 521 + ], + "type": "text", + "content": " increases. We further analyze how untransported pairs benefit the model training in Appendix C.3. Experimentally, we find that the refined alignments for untransported pairs can be equivalent to the label smoothing strategy [38]." + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 310, + 531, + 426, + 619 + ], + "blocks": [ + { + "bbox": [ + 310, + 531, + 426, + 619 + ], + "lines": [ + { + "bbox": [ + 310, + 531, + 426, + 619 + ], + "spans": [ + { + "bbox": [ + 310, + 531, + 426, + 619 + ], + "type": "image", + "image_path": "baa7dc4ae6e29bfd3f2c8659c63a9e87d57d7579e069a5c4ec279c043bdc0525.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 341, + 620, + 399, + 631 + ], + "lines": [ + { + "bbox": [ + 341, + 620, + 399, + 631 + ], + "spans": [ + { + "bbox": [ + 341, + 620, + 399, + 631 + ], + "type": "text", + "content": "(a) Image to Text" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 425, + 531, + 541, + 619 + ], + "blocks": [ + { + "bbox": [ + 425, + 531, + 541, + 619 + ], + "lines": [ + { + "bbox": [ + 425, + 531, + 541, + 619 + ], + "spans": [ + { + "bbox": [ + 425, + 531, + 541, + 619 + ], + "type": "image", + "image_path": "a14098b1fbbcc991579b15d55b699c20c7f36f014395474a47fb3be546cb918a.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 454, + 620, + 511, + 631 + ], + "lines": [ + { + "bbox": [ + 454, + 620, + 511, + 631 + ], + "spans": [ + { + "bbox": [ + 454, + 620, + 511, + 631 + ], + "type": "text", + "content": "(b) Text to Image" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 637, + 545, + 659 + ], + "lines": [ + { + "bbox": [ + 304, + 637, + 545, + 659 + ], + "spans": [ + { + "bbox": [ + 304, + 637, + 545, + 659 + ], + "type": "text", + "content": "Figure 4. Parameter analysis of L2RM-SGR in terms of recall scores on the testing set of Flickr30K under 0.2 MRate." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 665, + 547, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 712 + ], + "type": "text", + "content": "Discussions on Warm-up Methods. We use different warm-up methods, i.e., triplet loss [13] and InfoNCE loss [31] for our L2RM-SGR. 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MethodFlickr30KCC152K
Image-to-TextText-to-ImageImage-to-TextText-to-Image
R@1R@5R@10R@1R@5R@10R@1R@5R@10R@1R@5R@10
Triplet0.10.71.30.10.71.138.264.271.439.564.271.9
InfoNCE45.971.480.329.252.761.139.366.875.040.865.274.2
", + "image_path": "88727890fb6081b9367905779781b13895d7f9fed443ac0d849c0ab4d6bd44b5.jpg" + } + ] + } + ], + "index": 25, + "angle": 0, + "type": "table_body" + } + ], + "index": 25 + }, + { + "bbox": [ + 46, + 287, + 287, + 308 + ], + "lines": [ + { + "bbox": [ + 46, + 287, + 287, + 308 + ], + "spans": [ + { + "bbox": [ + 46, + 287, + 287, + 308 + ], + "type": "text", + "content": "Table 4. Comparison with different warm-up methods on Flickr30K with 0.8 MRate and CC152K." + } + ] + } + ], + "index": 26, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 325, + 287, + 420 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 325, + 287, + 420 + ], + "spans": [ + { + "bbox": [ + 46, + 325, + 287, + 420 + ], + "type": "text", + "content": "PMPs. As shown in Tab. 4, one could see that the triplet loss cannot achieve satisfactory performance under the extreme mismatching rate. Compared with the results of the L2RM-SGR in Tab. 1, one could find that it is necessary to limit the overconfidence of the model during the warm-up process. The results on CC152K show that our method is robust to the choice of warm-up methods under a relatively low mismatching rate." + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 47, + 428, + 194, + 441 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 428, + 194, + 441 + ], + "spans": [ + { + "bbox": [ + 47, + 428, + 194, + 441 + ], + "type": "text", + "content": "5.4. Visualization and Analysis" + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 46, + 447, + 287, + 578 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 447, + 287, + 578 + ], + "spans": [ + { + "bbox": [ + 46, + 447, + 287, + 578 + ], + "type": "text", + "content": "Distribution of Transport Cost. To intuitively show the effectiveness of the learnable cost function, we illustrate the transport cost for matched and mismatched training pairs on Flickr30K with 0.8 MRate. From Fig. 6, one could see that our cost function first learns to assign higher transport costs to those mismatched pairs. Although the costs of matched pairs are distributed over a large range in the early stage, they gradually become smaller and tend toward 0 as training proceeds. In conclusion, our cost function could successfully learn to distinguish matched and mismatched data, which lays the foundation for the further OT model." + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 46, + 582, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 287, + 713 + ], + "type": "text", + "content": "Visualizing Rematched Image-Text Pairs. To visually illustrate the rematching ability of our L2RM, we conduct the case study on CC152K to show real-world rematched examples. Specifically, the first two rows of Fig. 5 show the image and its original mismatched caption, respectively. The third row shows the rematched caption provided by our method, and we also show the refined alignment scores in brackets. In particular, we could find that some real-world visual-text pairs are completely uncorrelated (e.g., Fig. 5(a)-Fig. 5(b)) or contain only a few local similarities (e.g., Fig. 5(c)-Fig. 5(e)). Thanks to our L2RM, the" + } + ] + } + ], + "index": 30 + }, + { + "type": "image", + "bbox": [ + 309, + 232, + 425, + 316 + ], + "blocks": [ + { + "bbox": [ + 46, + 201, + 545, + 222 + ], + "lines": [ + { + "bbox": [ + 46, + 201, + 545, + 222 + ], + "spans": [ + { + "bbox": [ + 46, + 201, + 545, + 222 + ], + "type": "text", + "content": "Figure 5. The ability of our L2RM to rematch the mismatched visual-text samples. The figure shows some representative rematched pairs for L2RM-SGR on the training set of CC152K dataset. We highlight the matched words in green and the mismatched words in red." + } + ] + } + ], + "index": 24, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 309, + 232, + 425, + 316 + ], + "lines": [ + { + "bbox": [ + 309, + 232, + 425, + 316 + ], + "spans": [ + { + "bbox": [ + 309, + 232, + 425, + 316 + ], + "type": "image", + "image_path": "9e64827d05f2da7d9937006a34379cdb6d2ab8bb54e27df658a38ed946c6fd38.jpg" + } + ] + } + ], + "index": 31, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 348, + 319, + 386, + 329 + ], + "lines": [ + { + "bbox": [ + 348, + 319, + 386, + 329 + ], + "spans": [ + { + "bbox": [ + 348, + 319, + 386, + 329 + ], + "type": "text", + "content": "(a) Epoch 5" + } + ] + } + ], + "index": 32, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 305, + 333, + 545, + 365 + ], + "lines": [ + { + "bbox": [ + 305, + 333, + 545, + 365 + ], + "spans": [ + { + "bbox": [ + 305, + 333, + 545, + 365 + ], + "type": "text", + "content": "Figure 6. Transport cost distribution for matched and mismatched pairs at different training phases of our L2RM. The experiments are conducted on Flickr30K with 0.8 MRate." + } + ] + } + ], + "index": 35, + "angle": 0, + "type": "image_caption" + } + ], + "index": 31 + }, + { + "type": "image", + "bbox": [ + 427, + 232, + 543, + 316 + ], + "blocks": [ + { + "bbox": [ + 427, + 232, + 543, + 316 + ], + "lines": [ + { + "bbox": [ + 427, + 232, + 543, + 316 + ], + "spans": [ + { + "bbox": [ + 427, + 232, + 543, + 316 + ], + "type": "image", + "image_path": "e238b617e4c7dbfe0a94392507340b9ce1b745ffa39b71744045747b72365118.jpg" + } + ] + } + ], + "index": 33, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 464, + 319, + 506, + 329 + ], + "lines": [ + { + "bbox": [ + 464, + 319, + 506, + 329 + ], + "spans": [ + { + "bbox": [ + 464, + 319, + 506, + 329 + ], + "type": "text", + "content": "(b) Epoch 35" + } + ] + } + ], + "index": 34, + "angle": 0, + "type": "image_caption" + } + ], + "index": 33 + }, + { + "bbox": [ + 304, + 386, + 545, + 530 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 386, + 545, + 530 + ], + "spans": [ + { + "bbox": [ + 304, + 386, + 545, + 530 + ], + "type": "text", + "content": "potential matching relation among mismatched pairs could be fully excavated to provide refined alignments. For example, one could see that the rematched caption, i.e., \"a man on a bicycle\" nicely expresses the semantic concept in Fig. 5(a). Although some rematched captions could not perfectly share the same semantics with images, they also contain some local similarities to the given images. For example, the image in Fig. 5(f) is correctly described with the words \"a motorcycle\" and our L2RM provides a relatively low refined alignment score as the target. In summary, our proposed rematching strategy could embrace better data efficiency and robustness against PMPs." + } + ] + } + ], + "index": 36 + }, + { + "bbox": [ + 306, + 548, + 378, + 559 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 548, + 378, + 559 + ], + "spans": [ + { + "bbox": [ + 306, + 548, + 378, + 559 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 37 + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "text", + "content": "This work studies the challenge of cross-modal retrieval with partially mismatched pairs (PMPs). To address this problem, we propose L2RM, a generalized OT-based framework that learns to rematch mismatched pairs. Our key idea is to excavate the potential semantic similarity among unpaired samples. To formalize this idea through OT, first, we propose a self-supervised learner to automatically learn effective cost function. Second, we model a partial OT problem and restrict the transport among false positives to further boost refined alignments. Extensive experiments are conducted to verify that our L2RM can endow cross-modal retrieval models with strong robustness against PMPs." + } + ] + } + ], + "index": 38 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "26686" + } + ] + } + ], + "index": 39 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 715 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Triantafyllos Afouras, Yuki M Asano, Francois Fagan, Andrea Vedaldi, and Florian Metze. 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Context-aware attention network for image-text retrieval. In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 3536-3545, 2020. 2" + } + ] + } + ], + "index": 22 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "26688" + } + ] + } + ], + "index": 24 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_content_list.json b/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..6009b1b2c0a03aebc1478b74c43441a9c4be6cb3 --- /dev/null +++ b/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_content_list.json @@ -0,0 +1,2267 @@ +[ + { + "type": "text", + "text": "Learning to Remove Wrinkled Transparent Film with Polarized Prior", + "text_level": 1, + "bbox": [ + 133, + 130, + 836, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Jiaqi Tang $^{1,2,3}$ Ruizheng Wu $^{4}$ Xiaogang Xu $^{5,6}$ Sixing Hu $^{4}$ Ying-Cong Chen $^{1,2,3*}$", + "bbox": [ + 143, + 179, + 831, + 199 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1The Hong Kong University of Science and Technology (Guangzhou)", + "bbox": [ + 210, + 199, + 759, + 215 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ The Hong Kong University of Science and Technology $^{3}$ HKUST(GZ) - SmartMore Joint Lab", + "bbox": [ + 107, + 215, + 861, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{4}$ SmartMore Corporation $^{5}$ The Chinese University of Hong Kong $^{6}$ Zhejiang University", + "bbox": [ + 135, + 233, + 834, + 252 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "jtan092@connect.hkust-gz.edu.cn, {ruizheng.wu, david.hu}@smartmore.com", + "bbox": [ + 169, + 253, + 797, + 268 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "xiaogangxu00@gmail.com, yingcongchen@ust.hk", + "bbox": [ + 290, + 272, + 673, + 286 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 321, + 313, + 338 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In this paper, we study a new problem, Film Removal (FR), which attempts to remove the interference of wrinkled transparent films and reconstruct the original information under films for industrial recognition systems. We first physically model the imaging of industrial materials covered by the film. Considering the specular highlight from the film can be effectively recorded by the polarized camera, we build a practical dataset with polarization information containing paired data with and without transparent film. We aim to remove interference from the film (specular highlights and other degradations) with an end-to-end framework. To locate the specular highlight, we use an angle estimation network to optimize the polarization angle with the minimized specular highlight. The image with minimized specular highlight is set as a prior for supporting the reconstruction network. Based on the prior and the polarized images, the reconstruction network can decouple all degradations from the film. Extensive experiments show that our framework achieves SOTA performance in both image reconstruction and industrial downstream tasks. Our code will be released at https://github.com/jqtangust/FilmRemoval.", + "bbox": [ + 75, + 353, + 473, + 686 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 715, + 209, + 729 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Various deep-learning-based recognition models have been employed in the industrial environment, e.g., defect detection [28], code recognition [25], etc. However, the model failures would sometimes happen due to the insufficient robustness [40] towards different perturbations [8, 10, 24, 32, 39]. The wrinkled transparent film is one of them, which is usually covered or packaged on industrial materials or products for protection. Its interference could cause the failure of varying downstream tasks, e.g., text OCR and", + "bbox": [ + 75, + 739, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/f9d5c24f8b2da7b9c871f2b8b5a1fe856eefb53d6d45db16a56022ea48d52c58.jpg", + "image_caption": [ + "Images with Wrinkled Transparent Film" + ], + "image_footnote": [], + "bbox": [ + 506, + 321, + 633, + 405 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/3efee36ca3efff82e45aac5c2f01b6a057d41b18da809042cd1333eb4e286c01.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 635, + 323, + 758, + 405 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/354bc7e64d4502e38e92d7f7a4e401369e59034f781d4872193f5098a2a86793.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 759, + 323, + 885, + 405 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/8d497d6b5004a6412afc1ae58ecc8dbc7980884fa6d7ec503d7edb6ba5d52b54.jpg", + "image_caption": [ + "Images without Wrinkled Transparent Film" + ], + "image_footnote": [], + "bbox": [ + 506, + 422, + 633, + 505 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/49611dbd0beb8dcafbebbefcac7252f1909527cebe390fa52db1833128b2c77e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 635, + 424, + 758, + 505 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/cf8b954e920d3349e40a3f00d1847c69126d03f7a7c2a24792b50f2c38c54b9a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 759, + 424, + 885, + 505 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Figure 1. The Red box presents a challenge in industrial recognition systems, where the product information is often hidden beneath the wrinkled transparent film. The Green box is the image we expect to generate, with the film layer removed. Removing the wrinkled film makes the information on industrial material clearer. QR code recognition, in Fig. 1. Regarding the wide usage of such films in industrial scenarios, it is worth opening the research direction to remove these films from images.", + "bbox": [ + 500, + 522, + 890, + 638 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "For the first time, we address a novel problem of wrinkle transparent Film Removal (FR), which aims to remove the transparent film and reveal the hidden information, benefiting the robustness of the industrial downstream models.", + "bbox": [ + 496, + 640, + 890, + 700 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Although some solutions have attempted to remove surface highlight [6, 31, 34], they have not accurately modeled the imaging of the wrinkled transparent film. Except for the highlight, they cannot remove the effects of other various degradations from the film, e.g., light transmittance and material texture. Therefore, they cannot remove the transparent film thoroughly.", + "bbox": [ + 496, + 702, + 890, + 808 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In this paper, we explicitly model the imaging of wrinkled transparent film into two parts: the specular highlight $I_{h}$ from the film, and the diffuse reflection $I_{md}$ from the materials under the film, as shown in Fig. 2. The diffuse reflection can be influenced by the properties of the film. Thus, it is divided into the original component $(I_{m})$ and various", + "bbox": [ + 496, + 810, + 890, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author.", + "bbox": [ + 94, + 886, + 220, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "24987", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/0dc39e4e71a4ee2c2532cbd38236a11e03e33e45e7bdaebaa9c6c32c4d34f9b7.jpg", + "image_caption": [ + "Figure 2. Wrinkled Transparent Film Model. (A) The polarized image. (B) The 3D physics model of the local region. The light is reflected through the transparent wrinkled film and captured by the polarization camera. (C) The light path diagram. Polarized cameras capture two components: Specular Reflection $(I_h)$ , and Diffuse Reflection $(I_{md})$ . The Original Diffuse Reflection $(I_m)$ would be interfered by various degradations $(I_{md} - I_m)$ from the film." + ], + "image_footnote": [], + "bbox": [ + 81, + 88, + 893, + 305 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "degradations $(I_{md} - I_m)$ . Therefore, our objective is to decouple the specular highlight and other degradations caused by the film and reconstruct the original diffuse reflection.", + "bbox": [ + 75, + 366, + 470, + 412 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We build an end-to-end framework for decoupling two different degradations in the Wrinkled Transparent Film Model (Fig. 2), which consists of the prior estimation and reconstruction network. We notice that specular highlight is significantly related to polarization angles, while other parts are not. Based on this observation, we use an Angle Estimation Network to learn the polar angle corresponding to the minimized specular highlight, which is driven by a Polarization-based Location Model. Images with minimized specular highlights are set as the priors for the later reconstruction network to remove all degradations.", + "bbox": [ + 75, + 412, + 468, + 578 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "There is currently no suitable dataset for the FR problem, since most of the existing datasets [5, 18, 34] are targeted towards specular reflection removal only. Also, most datasets do not consider the real industrial environment. Therefore, we build a new dataset that consists of paired images covered by the film and the uncovered ground truth in the industrial optical photography system. Moreover, it's proved that the specular highlight from the film can be effectively captured by the polarization camera [21, 34, 37], which is now cheap to be installed in industrial systems [22]. Thus, we follow the collection pipeline of existing polarization datasets [4, 9], and capture each object with four polarized images under four polar directions in one shot. It's empirically proved by our experiments that with the input of these polarization clues, networks can better locate the specular highlight and recover the hidden information under the film.", + "bbox": [ + 75, + 579, + 468, + 820 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Extensive experiments prove that our designed network achieves SOTA performance in the FR problem. Our contributions are summarized as follows:", + "bbox": [ + 75, + 821, + 468, + 866 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "- To the best of our knowledge, we are the first to address the new problem of Film Removal (FR), which", + "bbox": [ + 94, + 869, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "aims to remove the whole wrinkled transparent film in industrial scenarios.", + "bbox": [ + 529, + 366, + 890, + 396 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- To solve FR, we model the wrinkled film physically and propose an end-to-end reconstruction network for FR with a learnable polarization-based prior, which helps the network locate the specular highlight reflection in the film.", + "- We also build a new practical dataset in the real industrial optical photography system, which contains various polarized image pairs with and without the film.", + "- Extensive experiments are conducted to prove the effectiveness of our dataset and method, which achieves SOTA performance in both image reconstruction and downstream industrial tasks." + ], + "bbox": [ + 517, + 400, + 890, + 583 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 593, + 640, + 608 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Polarization Model and Application", + "text_level": 1, + "bbox": [ + 500, + 619, + 808, + 635 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Polarization refers to the property of the transverse wave oscillating in different directions. Since light is a kind of wave, this phenomenon describes the distribution of light waves in all directions [1]. Conventional cameras or human eyes are insensitive to polarization. Thus, polarization is often used as a way to supplement additional visual information. It is often used in a wide range of fields such as optics [29], materials science [27], and physics [7, 36], etc.", + "bbox": [ + 496, + 642, + 890, + 763 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In the field of computer vision, polarization provides different angles of view, hence allowing a more efficient interpretation of complex scenes. In recent years, polarization has been widely used for complex tasks such as Integral Imaging [38], Rendering [2], 3D Shape [44], Segmentation [14], and Reflection Removal [12, 15, 34], etc.", + "bbox": [ + 496, + 763, + 890, + 854 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In the real world, since natural light is mixed with multiple wavelengths, its refraction time is different when it is injected into an optically active material, thus, a phase shift", + "bbox": [ + 496, + 854, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "24988", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/f54454b49740c338119b479590ccf5140f5999bf6cd38d157da72552d781ebd2.jpg", + "image_caption": [ + "Figure 3. Model of elliptically polarized light. $E$ represents polarized light at any angle, which can be calculated by this model. $I_{max}$ and $I_{min}$ are two components indicating the maximum and minimum intensity of elliptically polarized light." + ], + "image_footnote": [], + "bbox": [ + 176, + 88, + 370, + 198 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "occurs. A physical description of this phenomenon is elliptically polarized light (i.e., partially polarized light), as shown in Eq. (1).", + "bbox": [ + 75, + 253, + 468, + 300 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{ \\begin{array}{l} E _ {x} = E _ {x 0} \\cos (\\omega t) \\\\ E _ {y} = E _ {y 0} \\cos (\\omega t - \\sigma) \\end{array} , \\right. \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 174, + 301, + 468, + 335 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $(x,y)$ is the Cartesian basis in the space of Jones vectors, $E_{x}$ and $E_{y}$ is the component of the light on the basis, $(x,y)$ . $\\omega$ is the frequency and $\\sigma$ is the phase difference of $E_{x}$ and $E_{y}$ . $E_{x0}$ and $E_{y0}$ are the field strength of a pair of orthogonal waves. Eq. (1) describes the vibration of the polarized light in different angles, $t$ . Based on this model, our solution only considers a simplified situation where $\\sigma = 90^{\\circ}$ . Eq. (1) can be simplified to Eq. (2),", + "bbox": [ + 75, + 337, + 468, + 458 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\frac {E _ {x} ^ {2}}{E _ {x 0} ^ {2}} + \\frac {E _ {y} ^ {2}}{E _ {y 0} ^ {2}} = 1. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 214, + 457, + 468, + 493 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Specular Highlight Removal via Polarization", + "text_level": 1, + "bbox": [ + 76, + 494, + 455, + 512 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Since the film includes unpredictable specular reflection, our task includes the procedure to remove these degradations. There have been several solutions to remove specular reflection using polarization information. Nayar et al. [21] first used polarization to determine the color of the specular component to separate the interfaces. Then, Umezama et al. [30] adopted independent component analysis to separate the diffuse and specular reflection components of surface reflection. Zhang et al. [42] considered the effect of polarization angle and attempted to get the appropriate global angle using Newton's method, but this method did not make full use of the local information. Wen et al. [34] separated specular reflection regions by using image chromaticity.", + "bbox": [ + 75, + 518, + 468, + 715 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Although conventional methods are available for removing specular highlight reflections, they are not able to accurately model the imaging of wrinkled transparent films, and thus do not adequately address the problem of eliminating all degradations from wrinkled transparent films.", + "bbox": [ + 75, + 715, + 468, + 790 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Dataset", + "text_level": 1, + "bbox": [ + 76, + 801, + 163, + 816 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "While some datasets exist for the removal of specular reflection [11, 13, 34], there is currently no dataset for film removal in the industrial environment. As shown in Fig. 2, the characteristics of the specular highlight information from the film can be effectively modeled by the polarized image.", + "bbox": [ + 75, + 824, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/1661310d5f0b9488bec08d2ee118303241d223d4ddb4bdc5c23894109197e519.jpg", + "image_caption": [ + "Figure 4. Prototype of industrial optical photography pipeline. We have built an optical pipeline for capturing the dataset in the industrial environment. As objects traverse the objective pipeline, the polarizing camera captures images continuously. Subsequently, the acquired data is sent to the monitor for pre-processing." + ], + "image_footnote": [], + "bbox": [ + 501, + 88, + 890, + 268 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Leveraging this polarization information can significantly enhance image reconstruction. Therefore, we construct a paired dataset based on polarized images. Polarized images can capture light amplitude information from wrinkled films at different angles, and making full use of this information will significantly facilitate the decoupling of degradation information occurring from the film.", + "bbox": [ + 496, + 339, + 890, + 446 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Industrial Optical Photography Pipeline", + "text_level": 1, + "bbox": [ + 498, + 453, + 844, + 470 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Fig. 4 illustrates the prototype of our pipeline. Within this industrial pipeline, we maintain a consistent posture and angle for both the camera and lighting resources. The objective pipeline sequentially passes different detected objects under the camera.", + "bbox": [ + 496, + 476, + 890, + 551 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To effectively capture optical information in multiple polarization directions within a single image, we employ the HIKROBOT MV-CH050-10UP camera1, which integrates the Sony IMX250MZR CMOS sensor2. This sensor contains four different angles of polarization $(0^{\\circ}, 45^{\\circ}, 90^{\\circ}$ , and $135^{\\circ}$ as Bayer pattern, allowing us to capture four polarization angles in high definition with a single shot.", + "bbox": [ + 496, + 551, + 890, + 657 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Finally, there is a monitor that controls the camera shutter and adjusts camera parameters. We utilize auto-exposure and auto-focus strategies to set the appropriate focal length, exposure time, and ISO for each specific scenario automatically. This is essential since the thickness and surface of the products on the industrial line may vary, requiring slight adjustments in camera parameters to ensure image quality.", + "bbox": [ + 496, + 657, + 890, + 763 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Capturing Polarized Images", + "text_level": 1, + "bbox": [ + 500, + 771, + 751, + 787 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "When capturing polarized images, the imaging system initially captures an image of the ground truth uncovered by the film, $I_{gt}^{raw}$ . Subsequently, with the complex transpar", + "bbox": [ + 496, + 794, + 890, + 842 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "1https://www.hikrobotics.com/cn/machinevision/productdetail?id=3886", + "bbox": [ + 500, + 849, + 890, + 875 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "2https://www.sony-semicon.com/en/products/is/industry/polarization.html", + "bbox": [ + 500, + 875, + 890, + 898 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "24989", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ent film placed over the ground truth, we capture the image $I_{input}^{raw}$ that needs to be recovered.", + "bbox": [ + 76, + 90, + 468, + 125 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Data Diversity and Robustness", + "text_level": 1, + "bbox": [ + 76, + 128, + 349, + 143 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To build a diverse and robust dataset, we follow the rules in industrial manufacturing. As depicted in Fig. 4, the current industrial pipeline includes 315 dynamic industrial scenarios, which can be categorized into three types: QR codes, text, and products. To enhance the diversity, we have different films with diverse material properties, coverage areas, film thicknesses, and levels of wrinkling. The film exhibits significant variability across each scenario.", + "bbox": [ + 75, + 150, + 468, + 271 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "On the other hand, to ensure the stability of the industrial imaging pipeline, we maintained a consistent intensity level for the industrial light source and fixed the distance between the camera and the object flow. This helps to minimize the influence of errors external to the industrial system.", + "bbox": [ + 75, + 271, + 468, + 347 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.4. Prepossessing", + "text_level": 1, + "bbox": [ + 76, + 353, + 220, + 369 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Each pixel of the image captured by the polarization sensor is represented by four-pixel dots, each corresponding to the intensity of light at four distinct polarization angles. We first need to decompose it into 4 subgraphs with different angles, and then we restore it to its original resolution using edge-aware residual interpolation (EARI) demosaicking [20]. This process is described in Eq. (3).", + "bbox": [ + 75, + 376, + 468, + 479 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{I _ {g t} ^ {0}, I _ {g t} ^ {4 5}, I _ {g t} ^ {9 0}, I _ {g t} ^ {1 3 5} \\right\\} = M \\left(F _ {d} \\left(I _ {g t} ^ {\\text {r a w}}\\right)\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 166, + 479, + 468, + 503 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{I _ {i n p u t} ^ {0}, I _ {i n p u t} ^ {4 5}, I _ {i n p u t} ^ {9 0}, I _ {i n p u t} ^ {1 3 5} \\right\\} = M \\left(F _ {d} \\left(I _ {i n p u t} ^ {r a w}\\right)\\right),\n$$\n", + "text_format": "latex", + "bbox": [ + 102, + 500, + 467, + 518 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $F_{d}(\\cdot)$ is the decomposing operator, $M(\\cdot)$ is EARI demosaicking. Taking $I_{gt}^{raw}$ and $I_{input}^{raw}$ as inputs, we obtain full-resolution polarized images with four different angles.", + "bbox": [ + 76, + 518, + 467, + 563 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To generate the ground truth image, we follow the standard procedure from the polarized image processing library, polanalyser3. Firstly, we introduce stokes parameters [3]. According to this physical model, the first stoke parameter $S_{0}$ describes the total intensity of the optical beam, and it can be calculated by Eq. (4).", + "bbox": [ + 76, + 564, + 468, + 652 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nS _ {0} = E _ {x 0} ^ {2} + E _ {y 0} ^ {2} = I ^ {x} + I ^ {y}, \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 174, + 652, + 468, + 670 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $I^x \\perp I^y$ . $E_{x0}^2$ and $E_{y0}^2$ are the field strength of a pair of orthogonal waves in Fig. 3, which can be calculated by a pair of orthogonal polarization components, $I^x$ and $I^y$ . Subsequently, we can calculate one ground truth $I_{gt}$ as", + "bbox": [ + 76, + 670, + 468, + 733 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nI _ {g t} = G \\left(\\frac {S 0}{2}\\right) = \\left(\\frac {I _ {g t} ^ {0} + I _ {g t} ^ {4 5} + I _ {g t} ^ {9 0} + I _ {g t} ^ {1 3 5}}{4}\\right) ^ {\\frac {1}{\\gamma}}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 122, + 732, + 468, + 765 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $G(\\cdot)$ is a gamma correction function, and we empirically set the gamma value, $\\gamma$ , to 2.2.", + "bbox": [ + 76, + 762, + 467, + 792 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.5. Training and Testing", + "text_level": 1, + "bbox": [ + 76, + 797, + 274, + 814 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "During training, our network mixed all the scenes for training, and the final network is applicable to data from all scenarios. Besides, to ensure the robustness and generalization of our dataset, we adopt 10-fold cross-validation [23]", + "bbox": [ + 76, + 818, + 468, + 878 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Specular Highlight, $I_{h}$", + "bbox": [ + 532, + 89, + 666, + 102 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Other Degradations, $I_{d}$", + "bbox": [ + 720, + 89, + 857, + 102 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/22e59a4aa7140b981bd111a9de60b95dcf71decb4ceb64c0b1636fba9e9479ae.jpg", + "image_caption": [ + "Figure 5. Two Decoupling Components. Specular highlight, $I_{h}$ and other degradations, $I_{d}$ . The Red box shows the degradations, the Green box is the Ground Truth." + ], + "image_footnote": [], + "bbox": [ + 506, + 103, + 890, + 179 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "to evaluate the results. The dataset is divided into ten parts, and nine of them are used as training data and one as test data in turn. Each test will yield a corresponding accuracy rate, which is then averaged as the final accuracy.", + "bbox": [ + 500, + 219, + 890, + 279 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Method", + "text_level": 1, + "bbox": [ + 500, + 287, + 589, + 301 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Although some conventional methods have used polarization information to remove surface specular highlight reflection, they assume the light intensity as a binary composition [34], i.e., transmission and reflection. However, the light intensity from the wrinkled film is more complex, which is not only influenced by film surface highlight but also mixed with various degradations, e.g., light transmittance and material texture.", + "bbox": [ + 498, + 306, + 890, + 426 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this section, we first model the wrinkled transparent film physically in Fig. 2, which is our method's motivation. Then, we use an end-to-end network for reconstructing the original information in Fig. 6. Besides, since the highlight region is more tricky to recover, we build a polarization-based prior into the end-to-end framework to assist in locating highlight regions.", + "bbox": [ + 498, + 426, + 890, + 532 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Modelling the Wrinkled Transparent Film", + "text_level": 1, + "bbox": [ + 500, + 537, + 859, + 554 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Based on the Industrial Optical Photography System in Sec. 3.1, the light intensity for materials covered with the wrinkled transparent film will be captured by the polarized camera in Fig. 2(A)(B). The captured light intensity consists of two parts, i.e., the specular highlight reflection of the film's polarized regions [19, 26], the diffuse reflection from the materials under the film, which could be influenced by light transmittance, the texture of the film in Fig. 2(C). Such a composition is written in Eq. (6).", + "bbox": [ + 498, + 558, + 890, + 691 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nI = I _ {m d} + I _ {h} \\stackrel {\\prime} {=} I _ {m} ^ {\\prime} + I _ {d} + I _ {h}, \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 589, + 691, + 888, + 705 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $+$ denotes the linear superposition of different light components, $I$ is the light intensity captured by the camera, $I_{md}$ is the diffuse reflection component of the material through various film degradations, $I_h$ is the specular reflection part from the film's highlighted regions. Then, $I_{md}$ can be decoupled to two parts, $I_m$ and $I_d$ . $I_m$ is the original diffuse reflection component of the material and $I_d$ is caused by other various degradations through film. In Fig. 2(C), the optical path diagram illustrates this process.", + "bbox": [ + 498, + 705, + 890, + 839 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Based on Eq. (6), the FR task can be implemented by retaining the information of $I_{m}$ and decoupling $I_{h}$ and $I_{d}$ (both of them are caused by the film layer). This is expressed in Eq. (7), as", + "bbox": [ + 498, + 839, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_footnote", + "text": "3https://github.com/elerac/polanalyser/wiki", + "bbox": [ + 93, + 886, + 433, + 898 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "24990", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/002a5cc0a1239822a6327c6682300817bbe04a9ed690eea61b885362c268ca25.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 81, + 88, + 893, + 385 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nI _ {m} = I - I _ {h} - I _ {d}, \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 207, + 449, + 467, + 464 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where - denotes the decoupling operator. Fig. 5 visualizes these two components for decoupling in our FR task.", + "bbox": [ + 75, + 464, + 468, + 494 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Based on this model, our whole framework is based on an end-to-end reconstruction network for decoupling these two parts in Sec. 4.3. Before that, to support the network for decoupling $I_{h}$ , we estimate a polarized prior for locating the highlight regions in Sec. 4.2.", + "bbox": [ + 75, + 494, + 468, + 570 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Estimating a Polarized Prior for Locating $I_{h}$", + "text_level": 1, + "bbox": [ + 76, + 575, + 450, + 590 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To decouple the specular reflection components, it is better to locate the highlight regions on the surface of the wrinkle film, which provides a prior to facilitate the decoupling network. However, these regions are hard to predict since images are captured in variable scenarios. To this end, we introduce the polarization information for this problem.", + "bbox": [ + 75, + 595, + 468, + 685 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Based on Fresnel's theory [35], the specular reflection component of optically active materials is an elliptically polarized light, which changes under different angles of polarization orientation, while the rest of the components remain almost constant. It can be employed in estimating $I_{h}$ , which is a specular reflection component. Thus, we propose a polarized prior $P$ , which is represented as the optimized $I$ with the minimized $I_{h}$ , as shown in Eq. (8). The difference between $P$ and the input $I$ indicates the regions of $I_{h}$ .", + "bbox": [ + 75, + 686, + 468, + 821 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nP = I _ {m} + I _ {d} + \\min I _ {h}. \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 189, + 823, + 467, + 838 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Eq. (8), i.e., the polarized version of Eq. (6), can be acquired with Malus's Law [16] and the elliptical polarization model in Sec. 2.1. We use a pair of orthogonal maximum and minimum components and the angle variable", + "bbox": [ + 75, + 840, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/810477355b9470e439b88bff24bf1db30f8f03685f4cb29fde60ccb69a1ae466.jpg", + "image_caption": [ + "Figure 6. Overall framework. The polarized images, AoP and DoP are fed into Angle Estimation Net (A-Net), denoted as $f_{A}$ , for estimating the angle, $A$ . Subsequently, the Polarization-based Location Model (PLM), represented as $I_{p}$ , takes $A$ as input to estimate the image prior, $P$ . This prior provides important highlight location information for the reconstruction network. Finally, the reconstruction network (R-Net) is trained to restore the original diffuse reflection in industrial materials.", + "Figure 7. Location of specular highlight. The $P$ is the polarized prior. We can calculate the location of highlight by $I_h - \\min I_h$ . $\\theta \\in [0,2\\pi)$ to rewrite Eq. (8) as" + ], + "image_footnote": [], + "bbox": [ + 506, + 444, + 632, + 534 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/5ea23c43b27475edfdded65597cd770453463193854a6b5c1ccecac7a0e599bc.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 635, + 441, + 759, + 534 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/fb1c65dfb556670d57181ce1329c6964f0ff5aab1d1643e35999abbc71be239c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 764, + 443, + 887, + 534 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nI _ {h} = I _ {p} (\\theta) = I _ {\\max } \\cos^ {2} \\theta + I _ {\\min } \\sin^ {2} \\theta , \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 558, + 579, + 890, + 595 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $I_{p}(\\theta)$ is the Polarization-based Location Model to describe the polarized light in the angle of $\\theta$ , $I_{max}$ and $I_{min}$ is a pair of orthogonal maximum and minimum components in Fig. 3. Given the input data $\\{I_{input}^{0}, I_{input}^{45}, I_{input}^{90}, I_{input}^{135}\\}$ , $I_{max}$ and $I_{min}$ can be computed by the Stokes parameters [3], from Eq. (10) and Eq. (11).", + "bbox": [ + 498, + 595, + 890, + 685 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} I _ {m a x} = S _ {0} + \\frac {\\sqrt {S _ {1} ^ {2} + S _ {2} ^ {2}}}{2}, I _ {m i n} = S _ {0} - \\frac {\\sqrt {S _ {1} ^ {2} + S _ {2} ^ {2}}}{2}, (10) \\\\ S _ {0} = E _ {x 0} ^ {2} - E _ {y 0} ^ {2} = I _ {\\text {i n p u t}} ^ {0} + I _ {\\text {i n p u t}} ^ {9 0}, \\\\ S _ {1} = E _ {x 0} ^ {2} - E _ {y 0} ^ {2} = I _ {\\text {i n p u t}} ^ {0} - I _ {\\text {i n p u t}} ^ {9 0}, (11) \\\\ S _ {2} = E _ {a 0} ^ {2} - E _ {b 0} ^ {2} = I _ {\\text {i n p u t}} ^ {4 5} - I _ {\\text {i n p u t}} ^ {1 3 5}, \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 684, + 890, + 765 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $(a,b)$ is the Cartesian basis rotated by $45^{\\circ}$ in the space of $(x,y)$ , and $E_{a0}^{2}$ as well as $E_{b0}^{2}$ are the field strengths under this basis.", + "bbox": [ + 496, + 763, + 890, + 806 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Since $I_{h}$ is the only polarized component that is determined by $\\theta$ , $P$ in Eq. (8) can also be formulated as Eq. (12).", + "bbox": [ + 496, + 809, + 890, + 838 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} P = I _ {m} + I _ {d} + \\min I _ {h} \\\\ = I _ {m} + I _ {d} + \\min _ {\\theta} I _ {p} (\\theta) \\tag {12} \\\\ = I _ {m} + I _ {d} + \\min _ {\\theta} \\left(I _ {m a x} \\cos^ {2} \\theta + I _ {m i n} \\sin^ {2} \\theta\\right). \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 838, + 890, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "24991", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Different pixels in one image correspond to varying optimized values for $\\theta$ . Thus, we estimate pixel-wise $\\theta$ with a learning-based network, obtaining the angle map $A$ . The input includes images with polarization information, i.e., $I_0$ , $I_{45}$ , $I_{90}$ , and $I_{135}$ . In addition, our input also includes two essential physics statistics, angle of polarization (AoP) and degree of polarization (DoP) [17]. The AoP provides information about the object's surface normal, which helps to analyze the difference in the surface structure between the object and film. The DoP offers information on the intensity of polarized light, so it can facilitate the network to utilize the polarized light accurately. Both of them can promote the model to learn the appropriate angle better. Eq. (13) describes this procedure.", + "bbox": [ + 75, + 90, + 472, + 301 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "$A = f_{A}(I_{input}^{0}\\oplus I_{input}^{45}\\oplus I_{input}^{90}\\oplus I_{input}^{135}\\oplus S_{AoP}\\oplus S_{DoP})$ (13) where, $A\\in \\mathbb{R}^{h\\times w\\times 1}$ is the pixel-wise angle map, $S_{AoP}\\in$ $\\mathbb{R}^{h\\times w\\times 1}$ and $S_{DoP}\\in \\mathbb{R}^{h\\times w\\times 1}$ indicate the AoP and DoP map respectively, $\\oplus$ is the concatenation operator, and $f_{A}(\\cdot)$ is angle estimation network. The network structure employs a lightweight Residual Dense Network [43] with a large perception field to capture more global information.", + "bbox": [ + 75, + 303, + 468, + 411 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "After obtaining the angle map $A$ , we can get the prior with minimized $I_h$ by Eq. (14).", + "bbox": [ + 76, + 411, + 468, + 440 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nP = I _ {m} + I _ {d} + I _ {\\max } \\cos^ {2} A + I _ {\\min } \\sin^ {2} A, \\tag {14}\n$$\n", + "text_format": "latex", + "bbox": [ + 109, + 440, + 468, + 455 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $P \\in \\mathbb{R}^{h \\times w \\times 1}$ . Fig. 7 visualize the Prior, $P$ , and the location of $I_h$ (highlighted). We can accurately estimate the location of the specular highlight.", + "bbox": [ + 75, + 455, + 468, + 503 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Reconstructing $I_{m}$ with a Prior", + "text_level": 1, + "bbox": [ + 76, + 508, + 352, + 526 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In this section, we set a reconstruction network $f_{r}$ to decouple both $I_{d}$ and $I_{h}$ , with the input of $I$ (i.e., $I_{input}^{0}, I_{input}^{45}, I_{input}^{90}$ , and $I_{input}^{135}$ ) and $P$ . The obtained prior $P$ from Sec. 4.2 can already provide the estimation of $I_{h}$ by comparing with $I$ . Thus, $f_{r}$ can be focused on the assessment of $I_{d}$ . The reconstruction network is implemented as a common Residual Dense Network [43]. The reconstruction process can be expressed as Eq. (15).", + "bbox": [ + 76, + 530, + 468, + 651 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nI _ {r e c} = f _ {r} \\left(I _ {i n p u t} ^ {0} \\oplus I _ {i n p u t} ^ {4 5} \\oplus I _ {i n p u t} ^ {9 0} \\oplus I _ {i n p u t} ^ {1 3 5} \\oplus P\\right), \\tag {15}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 651, + 468, + 670 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where, $I_{rec} \\in \\mathbb{R}^{h \\times w \\times 1}$ is the reconstructed image.", + "bbox": [ + 76, + 670, + 411, + 686 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.4. Details in Implementation", + "text_level": 1, + "bbox": [ + 76, + 691, + 313, + 708 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Our framework is implemented by PyTorch, and we use Polanalyser library4 to process the polarized images. It is trained with $L1$ loss between $I_{rec}$ and $I_{gt}$ in an end-to-end manner. Besides, the learning rate is $5 \\times 10^{-5}$ , and it decays to half of the original for every $2 \\times 10^{4}$ iterations.", + "bbox": [ + 75, + 712, + 468, + 787 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiment", + "text_level": 1, + "bbox": [ + 76, + 796, + 202, + 813 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In our experiment, we evaluate the performance of the proposed framework in three aspects. First, as an image reconstruction task, we conduct qualitative and quantitative evaluations with reconstruction-related metrics (e.g.,", + "bbox": [ + 75, + 816, + 468, + 878 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "PSNR, SSIM). Second, as an upstream task in the industry, two downstream scenarios (e.g., QR code reading, and Text OCR) are selected to evaluate the reliability of our proposed algorithm. Finally, we conduct ablation studies to analyze the roles of different components.", + "bbox": [ + 500, + 90, + 890, + 167 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Baselines", + "text_level": 1, + "bbox": [ + 500, + 174, + 607, + 188 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "There is no existing baseline for this new problem. Thus, we choose two general SOTA methods in image reconstruction, Uformer [33] and Restormer [41] to evaluate the performance. Considering the connection between the film removal and highlight removal, we also compare with two SOTA polarization and non-polarization highlight removal baselines, Polar-HR [34] and SHIQ [6], respectively.", + "bbox": [ + 498, + 194, + 890, + 299 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "To make a fair comparison, we follow the same training setting in our framework and input four polarized images to reconstruct one image without wrinkled transparent film in Uformer [33], Restormer [41]. In Polar-HR [34], it is a traditional training-free model and, therefore, shares the same input and output data as our approach. Besides, in SHIQ [6], since it cannot support polarized images, we convert four polarized images to one unpolarized image.", + "bbox": [ + 498, + 300, + 890, + 421 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Evaluation on Reconstruction Task", + "text_level": 1, + "bbox": [ + 500, + 429, + 805, + 443 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Quantitative Evaluation To measure the quantitative performance of the algorithm, we refer to commonly used metrics for Image Reconstruction: peak signal-to-noise ratio (PSNR) and structural similarity (SSIM). Also, to compare the overall performance of our dataset, we use 10-fold cross-validation during training and testing. This strategy ensures the evaluation's reliability and further proves the proposed algorithm's robustness.", + "bbox": [ + 498, + 448, + 890, + 568 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The quantitative results are shown in Table 1. In the last column of Table 1, $\\mu$ is the mean value, and $\\sigma$ is the variance of the 10-fold performance. These experimental results show the average PSNR is 36.48 and the average SSIM is 0.9824, and the results demonstrate the high quality of our reconstructed images. In addition, the variance of PSNR and SSIM are 0.57 and $1.23 \\times 10^{-5}$ , respectively, and this proves the proposed algorithm is stable and robust. Qualitative Evaluation To evaluate the reconstruction performance of the algorithm in a qualitative way, we show some visual results. Our results are shown in Fig. 8. Although Polar-HR [34] and SHIQ [6] can remove some of the highlights, their models cannot model the film correctly and, therefore, cannot remove the film itself. Besides, it can be observed that our algorithm can reconstruct regions where text or QR codes are corrupted by highlights through polarization information, while Uformer [33] and Restormer [41] produce fake artifacts in these regions.", + "bbox": [ + 498, + 569, + 890, + 843 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.3. Evaluation on Downstream Applications", + "text_level": 1, + "bbox": [ + 500, + 849, + 844, + 864 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In industrial environments, it is common to use transparent films to cover products, which may negatively im", + "bbox": [ + 498, + 869, + 890, + 901 + ], + "page_idx": 5 + }, + { + "type": "page_footnote", + "text": "4https://github.com/elerac/polanalyser/wiki", + "bbox": [ + 93, + 886, + 433, + 898 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "24992", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/074c6d0c66570e3d00b9dedffa0c604f0965699009b2d6bdfb56e94447f74812.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
K1K2K3K4K5K6K7K8K9K10μ↑σ↓
SHIQ [6]PSNR23.4722.1121.9521.6921.7721.0320.8620.4621.1021.3121.580.64
SSIM0.78990.76400.74160.74390.74590.74650.74990.74120.74650.73000.74992.41 × 10-4
Polar-HR [34]PSNR23.3122.8022.1321.5821.9422.0022.0321.9922.1821.9522.190.22
SSIM0.76420.74210.72200.70990.70640.70980.71280.70170.71020.69680.71763.80 × 10-4
Uformer [33]PSNR31.8531.9531.3931.1931.8132.0431.6831.9831.8531.0131.680.11
SSIM0.95190.94560.93710.93640.94340.94210.94380.94350.94570.93630.94262.17 × 10-5
Restormer [41]PSNR34.3535.0234.4433.7134.8835.1334.3134.3334.5132.4934.320.52
SSIM0.97710.97700.97210.96780.97570.97460.97420.97410.97590.96330.97311.75 × 10-5
OursPSNR36.7637.2936.6235.1236.9337.2136.2436.6736.9435.0236.480.57
SSIM0.98520.98590.98220.97670.98450.98330.98360.98300.98500.97490.98241.23 × 10-5
", + "bbox": [ + 81, + 88, + 893, + 268 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/44663d3ce12f288d19ff5c8db1a33f90c7ec6380d006ff78d02a418b4163963e.jpg", + "table_caption": [ + "Table 1. Quantitative evaluation in 10-fold cross-validation. The K- $I$ indicates the ${I}_{th}$ fold." + ], + "table_footnote": [], + "table_body": "
Input (Intensity)SHIQ [6]Polar-HR [34]Uformer [33]Restormer [41]OursGround Truth
", + "bbox": [ + 84, + 284, + 890, + 518 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/9f548df17fdc4109b59a419f35b1614a8f276f5c8c05c2ce9c9da4b660212a37.jpg", + "table_caption": [ + "Figure 8. Qualitative Evaluation. Compared with other baselines, our model can reconstruct more realistic details in highlight regions instead of fake artifacts. Please zoom in for more details." + ], + "table_footnote": [ + "Table 2. QR code reading rate. Compared with other baselines, our approach can improve the performance of QR codes scanner in the industrial environment." + ], + "table_body": "
SHIQ [6]Polar-HR [34]Uformer [33]
Read Number71718
Read Rate8.05%19.54%20.69%
Restormer [41]OursGround Truth
Read Number246387
Read Rate27.58%72.41%100%
", + "bbox": [ + 81, + 545, + 468, + 645 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "pact the robustness of downstream algorithms. To evaluate the effectiveness of our solution in such settings, we conduct two tests on two downstream tasks: QR Code Reading and Text Optical Character Recognition (Text OCR). These tasks are particularly relevant as they require access to raw information, which provides a rigorous test of the effectiveness of our algorithms in industrial scenarios.", + "bbox": [ + 75, + 686, + 468, + 792 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "QR Code Reading The read rate is a critical performance metric for manufacturing pipelines in industrial systems. In this experiment, we compare our method with other baselines in Table 2. Our upstream algorithm leads to a significant improvement in the performance of the QR code reading. The qualitative results in Fig. 9 demonstrate that our algorithm not only removes the film but also significantly", + "bbox": [ + 75, + 795, + 468, + 900 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "recovers the QR code information under the film.", + "bbox": [ + 498, + 547, + 823, + 561 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Text OCR Text OCR is also an important downstream industrial task. We compared our algorithm with other baselines, as shown in Fig. 10. Our method can restore more hidden text information accurately.", + "bbox": [ + 498, + 561, + 890, + 622 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.4. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 627, + 651, + 642 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We conduct ablation studies, which mainly validate the effectiveness of our proposed polarization dataset and one crucial component in our framework. To ensure that the experimental settings are consistent, we perform 10-fold cross-validation for the ablation experiments as well and draw two boxplots for further analysis.", + "bbox": [ + 496, + 643, + 890, + 733 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effectiveness of the Polarized Information To prove the effectiveness of polarized information, we eliminate all components that need polarization information, which include four polarization images. Since the Polarization-based Location Model is driven by the $I_{max}$ and $I_{min}$ , which need to be calculated with polarization images as input, this structure is also removed. Other settings remain constant. Without the support of polarized information, the quantitative performance has a considerable decrease, as shown in Fig. 11 (w/o Polarized information). Also, the performance of the network is limited by the lack of guidance", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "24993", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/e79188280e41b9a35a320d0737ba0e782432d516bf54db1e0ca4de9d326a7741.jpg", + "image_caption": [ + "Input (Intensity)" + ], + "image_footnote": [], + "bbox": [ + 86, + 95, + 209, + 174 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d16e29dbd899c279f1ae0f65a9b904667fbce9544f0f88dec782272a6717b535.jpg", + "image_caption": [ + "SHIQ [6]" + ], + "image_footnote": [], + "bbox": [ + 212, + 94, + 336, + 174 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/133d392a60bb38e1fab60f492cc99d0299c0cdbe83522dd64f80efbfc8477583.jpg", + "image_caption": [ + "Polar-HR [34]", + "Ours" + ], + "image_footnote": [], + "bbox": [ + 341, + 94, + 464, + 174 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a8b7364b60da3bd014d815c750ad7e5a8eda09936e67aadbfa31c359147d9713.jpg", + "image_caption": [ + "Uformer [33]", + "Figure 9. Performance of QR code reading in the industry. In the original image, the QR code scanner fails to detect QR code information. Polar-HR [34] and SHIQ [6] can only eliminate the specular reflection on the QR code, and Uformer [33] and Restormer [41] can only generate false artifacts in highlight regions. Our method can help industrial QR code scanners achieve a higher performance." + ], + "image_footnote": [], + "bbox": [ + 86, + 189, + 209, + 268 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/ca3ce774cb6fd4f5f00d547c1202cf443b2d0b894a792ed36606ba8cefb1cafc.jpg", + "image_caption": [ + "Restormer [41]" + ], + "image_footnote": [], + "bbox": [ + 212, + 189, + 336, + 268 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/b01f98b199edf300963e549b0fcdb67961623bc760bf736ed2c5cd02f9f81cf8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 341, + 189, + 464, + 268 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c7bf6dd855f94e9eaac1c5ef1a67f3926d03b8d02d27adedc62a53577dd5fc7f.jpg", + "image_caption": [ + "Input (Intensity)" + ], + "image_footnote": [], + "bbox": [ + 89, + 375, + 207, + 462 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/966102fc145d796445257115add9d981d9fc729af79bddd6c83cfbb59b265b9e.jpg", + "image_caption": [ + "SHIQ [6]" + ], + "image_footnote": [], + "bbox": [ + 212, + 375, + 328, + 462 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/6f6abcf37dfb2890151d5ef625ab13801c89e1af844416d86804e4db52cce93c.jpg", + "image_caption": [ + "Polar-HR [34]" + ], + "image_footnote": [], + "bbox": [ + 336, + 375, + 449, + 462 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/55ea3efd740049f05ef6ea1132a58b361dbc0091f6b6b48cd0dd0b04a9acd074.jpg", + "image_caption": [ + "Uformer [33]", + "Figure 10. Performance of text OCR in the industry. Compared to other baselines, our method can reconstruct more original text information for recognition." + ], + "image_footnote": [], + "bbox": [ + 89, + 476, + 207, + 563 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e564e808a6f0093c7d875d3b89dec8d306465d1f33747ec0fb074540e1e6dec7.jpg", + "image_caption": [ + "Restormer [41]" + ], + "image_footnote": [], + "bbox": [ + 212, + 476, + 328, + 561 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f3c7dd146dde70d980e073fbaff964a4412a7eb51946d9c073bb465f70468603.jpg", + "image_caption": [ + "Ours" + ], + "image_footnote": [], + "bbox": [ + 334, + 476, + 449, + 561 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/61431b6a8e4ac10e4a95a3ba00679228d7cbfaf03fb57cc4534fbc83a8fc97bc.jpg", + "image_caption": [ + "(A) PSNR", + "Figure 11. PSNR (A) and SSIM (B) in ablation study. We use two boxplots to describe the performance after $t$ -fold cross-validation. The results show that our dataset, the extracted prior, the AoP, and the DoP contribute to the framework performance improvement." + ], + "image_footnote": [ + "Ours $\\mathbb{w} / \\mathrm{o}$ AoP & DoP w/o Polarized Information w/o Prior" + ], + "bbox": [ + 91, + 619, + 271, + 705 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7d7103008bd7f424141c3cc74b9edd7fa34cf800fcf2842a253fa9ea32f32c83.jpg", + "image_caption": [ + "(B) SSIM" + ], + "image_footnote": [], + "bbox": [ + 272, + 619, + 449, + 705 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "information, so it cannot remove all degradation. Besides, removing the polarization information will induce artifacts in highlight regions, as shown in Fig. 12.", + "bbox": [ + 75, + 779, + 468, + 824 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effectiveness of AoP and DoP To prove the effectiveness of AoP and DoP, we eliminate AoP and DoP in the angle estimation network. The qualitative results presented in Fig. 13 demonstrate that AoP and DoP can help locate the highlight more significantly, and also improve overall", + "bbox": [ + 75, + 825, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/2ade62687f6dc0c6517dd5a28d6647b35374ff07766ca3ce022ec103be2526ba.jpg", + "image_caption": [ + "Figure 12. Qualitative evaluation of w/o Polarization Information. Compared with w/o polarization information (Red), introducing polarization information avoids the generation of artifacts and reconstructs the realistic details (Green)." + ], + "image_footnote": [], + "bbox": [ + 516, + 89, + 658, + 195 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e4232352b4ade2ca81c097bb3ccb5387328932e35c240fc49198bd158cd0f410.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 658, + 89, + 802, + 195 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/23b6601552e0a27e9fb9d6ed0a2e453e6c32ee122b0be7a53a2eabd516edce92.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 803, + 90, + 870, + 142 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c39f76310bdb4d734d3ef543a878ecd5ac91585b15d56924ba789593a16875b3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 803, + 142, + 870, + 195 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/bf36ebc847e6d2fe39d8476081a95cb29df247b57314ab6b93160fb17e9a6841.jpg", + "image_caption": [ + "Figure 13. Highlight location heatmap. Compared with \"w/o AoP & DoP\" (In Red Box), introducing AoP and DoP (In Green Box) can help the A-Net to infer more highlight regions." + ], + "image_footnote": [], + "bbox": [ + 511, + 251, + 604, + 323 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/1d7abcb5bc496e57b61e24c09298aa30da34021f11e2d29a98d6c73f461f6476.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 606, + 251, + 699, + 323 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a63ea703ce8facbcd7f5598125f23f84a4fda2b75f7e7c8980f49f3b85166e88.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 704, + 251, + 794, + 323 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/8aa2697b4681130cf29ade018d647ca48fc4cd10c100003f0c23c5c7b9aab800.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 795, + 251, + 883, + 323 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/cfb558be87ba53d9e5c92358f79efea1ff28b1c1d2a0ba0b7a52bd232056d010.jpg", + "image_caption": [ + "Figure 14. Qualitative Evaluation of w/o Prior. Compared with \"w/o Prior\" (In Red Box), our solution (In Green Box) is more effective to remove highlight and infer original information." + ], + "image_footnote": [], + "bbox": [ + 511, + 366, + 604, + 438 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/1cbfe6ce20b216e7247171f0a224bc23fad73f54bddbd09048e3953436ccc463.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 604, + 366, + 699, + 438 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/835f3ba4426d781e0669176da7df08c11279228e878c26bd14c524335f08881d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 704, + 366, + 794, + 438 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/3f840798e35ecc857c455afa381792a606457c91bb6e7f70ff40ffa44e7b98ea.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 795, + 366, + 883, + 438 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "performance in Fig. 11 (w/o AoP & DoP).", + "bbox": [ + 500, + 482, + 779, + 497 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effectiveness of Prior To prove the effectiveness of polarized prior, we eliminate the angle estimation network and the PLM in our network while retaining only the polarized images and the reconstruction network. In this case, the network can only implicitly facilitate the polarized information in the reconstruction network. Since there is no polarized prior that indicates highlight regions, this can lead to a decrease in the performance of the network to recover highlight regions (as shown in Fig. 14), while causing overall performance to decrease in Fig. 11 (w/o Prior).", + "bbox": [ + 500, + 498, + 890, + 648 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 654, + 617, + 667 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this study, we pioneer the investigation of the Film Removal (FR) problem, aiming to eliminate the disturbances caused by wrinkled transparent films and to restore the obscured information. We propose an end-to-end framework to effectively remove all degradations caused by the film with a polarized prior to minimizing highlight. Besides, we build a practical polarized dataset containing paired data for this problem. Experiments in the industry have demonstrated the potential application. We believe that the deployment of our algorithms will considerably improve the robustness of downstream industrial recognition systems.", + "bbox": [ + 500, + 672, + 890, + 839 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgment This work is supported by the National Natural Science Foundation of China (No. 62206068) and the Natural Science Foundation of Zhejiang Province, China under No. LD24F020002.", + "bbox": [ + 500, + 840, + 890, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "24994", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 106 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Gary A Atkinson. 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In CVPR, 2019. 2" + ], + "bbox": [ + 78, + 92, + 467, + 503 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "24996", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_model.json b/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_model.json new file mode 100644 index 0000000000000000000000000000000000000000..88144af0753752446c582fe7dbe1c31f8c92c87a --- /dev/null +++ b/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_model.json @@ -0,0 +1,2926 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.134, + 0.131, + 0.838, + 0.154 + ], + "angle": 0, + "content": "Learning to Remove Wrinkled Transparent Film with Polarized Prior" + }, + { + "type": "text", + "bbox": [ + 0.145, + 0.18, + 0.832, + 0.2 + ], + "angle": 0, + "content": "Jiaqi Tang\\(^{1,2,3}\\) Ruizheng Wu\\(^{4}\\) Xiaogang Xu\\(^{5,6}\\) Sixing Hu\\(^{4}\\) Ying-Cong Chen\\(^{1,2,3*}\\)" + }, + { + "type": "text", + "bbox": [ + 0.212, + 0.2, + 0.76, + 0.217 + ], + "angle": 0, + "content": "1The Hong Kong University of Science and Technology (Guangzhou)" + }, + { + "type": "text", + "bbox": [ + 0.109, + 0.217, + 0.862, + 0.234 + ], + "angle": 0, + "content": "\\(^{2}\\)The Hong Kong University of Science and Technology \\(^{3}\\)HKUST(GZ) - SmartMore Joint Lab" + }, + { + "type": "text", + "bbox": [ + 0.136, + 0.234, + 0.836, + 0.253 + ], + "angle": 0, + "content": "\\(^{4}\\)SmartMore Corporation \\(^{5}\\)The Chinese University of Hong Kong \\(^{6}\\)Zhejiang University" + }, + { + "type": "text", + "bbox": [ + 0.171, + 0.255, + 0.798, + 0.27 + ], + "angle": 0, + "content": "jtan092@connect.hkust-gz.edu.cn, {ruizheng.wu, david.hu}@smartmore.com" + }, + { + "type": "text", + "bbox": [ + 0.291, + 0.273, + 0.674, + 0.287 + ], + "angle": 0, + "content": "xiaogangxu00@gmail.com, yingcongchen@ust.hk" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.322, + 0.314, + 0.339 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.354, + 0.474, + 0.687 + ], + "angle": 0, + "content": "In this paper, we study a new problem, Film Removal (FR), which attempts to remove the interference of wrinkled transparent films and reconstruct the original information under films for industrial recognition systems. We first physically model the imaging of industrial materials covered by the film. Considering the specular highlight from the film can be effectively recorded by the polarized camera, we build a practical dataset with polarization information containing paired data with and without transparent film. We aim to remove interference from the film (specular highlights and other degradations) with an end-to-end framework. To locate the specular highlight, we use an angle estimation network to optimize the polarization angle with the minimized specular highlight. The image with minimized specular highlight is set as a prior for supporting the reconstruction network. Based on the prior and the polarized images, the reconstruction network can decouple all degradations from the film. Extensive experiments show that our framework achieves SOTA performance in both image reconstruction and industrial downstream tasks. Our code will be released at https://github.com/jqtangust/FilmRemoval." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.716, + 0.21, + 0.731 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.741, + 0.47, + 0.879 + ], + "angle": 0, + "content": "Various deep-learning-based recognition models have been employed in the industrial environment, e.g., defect detection [28], code recognition [25], etc. However, the model failures would sometimes happen due to the insufficient robustness [40] towards different perturbations [8, 10, 24, 32, 39]. The wrinkled transparent film is one of them, which is usually covered or packaged on industrial materials or products for protection. Its interference could cause the failure of varying downstream tasks, e.g., text OCR and" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.323, + 0.634, + 0.406 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.589, + 0.408, + 0.805, + 0.421 + ], + "angle": 0, + "content": "Images with Wrinkled Transparent Film" + }, + { + "type": "image", + "bbox": [ + 0.636, + 0.324, + 0.759, + 0.406 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.761, + 0.324, + 0.886, + 0.406 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.423, + 0.634, + 0.506 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.579, + 0.508, + 0.815, + 0.521 + ], + "angle": 0, + "content": "Images without Wrinkled Transparent Film" + }, + { + "type": "image", + "bbox": [ + 0.636, + 0.425, + 0.759, + 0.506 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.761, + 0.425, + 0.886, + 0.506 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.523, + 0.892, + 0.64 + ], + "angle": 0, + "content": "Figure 1. The Red box presents a challenge in industrial recognition systems, where the product information is often hidden beneath the wrinkled transparent film. The Green box is the image we expect to generate, with the film layer removed. Removing the wrinkled film makes the information on industrial material clearer. QR code recognition, in Fig. 1. Regarding the wide usage of such films in industrial scenarios, it is worth opening the research direction to remove these films from images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.641, + 0.892, + 0.702 + ], + "angle": 0, + "content": "For the first time, we address a novel problem of wrinkle transparent Film Removal (FR), which aims to remove the transparent film and reveal the hidden information, benefiting the robustness of the industrial downstream models." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.703, + 0.892, + 0.809 + ], + "angle": 0, + "content": "Although some solutions have attempted to remove surface highlight [6, 31, 34], they have not accurately modeled the imaging of the wrinkled transparent film. Except for the highlight, they cannot remove the effects of other various degradations from the film, e.g., light transmittance and material texture. Therefore, they cannot remove the transparent film thoroughly." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In this paper, we explicitly model the imaging of wrinkled transparent film into two parts: the specular highlight \\( I_{h} \\) from the film, and the diffuse reflection \\( I_{md} \\) from the materials under the film, as shown in Fig. 2. The diffuse reflection can be influenced by the properties of the film. Thus, it is divided into the original component \\( (I_{m}) \\) and various" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.222, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24987" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.089, + 0.895, + 0.306 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.308, + 0.895, + 0.365 + ], + "angle": 0, + "content": "Figure 2. Wrinkled Transparent Film Model. (A) The polarized image. (B) The 3D physics model of the local region. The light is reflected through the transparent wrinkled film and captured by the polarization camera. (C) The light path diagram. Polarized cameras capture two components: Specular Reflection \\((I_h)\\), and Diffuse Reflection \\((I_{md})\\). The Original Diffuse Reflection \\((I_m)\\) would be interfered by various degradations \\((I_{md} - I_m)\\) from the film." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.367, + 0.471, + 0.413 + ], + "angle": 0, + "content": "degradations \\((I_{md} - I_m)\\). Therefore, our objective is to decouple the specular highlight and other degradations caused by the film and reconstruct the original diffuse reflection." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.414, + 0.47, + 0.579 + ], + "angle": 0, + "content": "We build an end-to-end framework for decoupling two different degradations in the Wrinkled Transparent Film Model (Fig. 2), which consists of the prior estimation and reconstruction network. We notice that specular highlight is significantly related to polarization angles, while other parts are not. Based on this observation, we use an Angle Estimation Network to learn the polar angle corresponding to the minimized specular highlight, which is driven by a Polarization-based Location Model. Images with minimized specular highlights are set as the priors for the later reconstruction network to remove all degradations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.58, + 0.47, + 0.821 + ], + "angle": 0, + "content": "There is currently no suitable dataset for the FR problem, since most of the existing datasets [5, 18, 34] are targeted towards specular reflection removal only. Also, most datasets do not consider the real industrial environment. Therefore, we build a new dataset that consists of paired images covered by the film and the uncovered ground truth in the industrial optical photography system. Moreover, it's proved that the specular highlight from the film can be effectively captured by the polarization camera [21, 34, 37], which is now cheap to be installed in industrial systems [22]. Thus, we follow the collection pipeline of existing polarization datasets [4, 9], and capture each object with four polarized images under four polar directions in one shot. It's empirically proved by our experiments that with the input of these polarization clues, networks can better locate the specular highlight and recover the hidden information under the film." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.822, + 0.469, + 0.867 + ], + "angle": 0, + "content": "Extensive experiments prove that our designed network achieves SOTA performance in the FR problem. Our contributions are summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.096, + 0.871, + 0.47, + 0.902 + ], + "angle": 0, + "content": "- To the best of our knowledge, we are the first to address the new problem of Film Removal (FR), which" + }, + { + "type": "text", + "bbox": [ + 0.531, + 0.367, + 0.892, + 0.397 + ], + "angle": 0, + "content": "aims to remove the whole wrinkled transparent film in industrial scenarios." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.401, + 0.892, + 0.476 + ], + "angle": 0, + "content": "- To solve FR, we model the wrinkled film physically and propose an end-to-end reconstruction network for FR with a learnable polarization-based prior, which helps the network locate the specular highlight reflection in the film." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.48, + 0.892, + 0.525 + ], + "angle": 0, + "content": "- We also build a new practical dataset in the real industrial optical photography system, which contains various polarized image pairs with and without the film." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.526, + 0.892, + 0.584 + ], + "angle": 0, + "content": "- Extensive experiments are conducted to prove the effectiveness of our dataset and method, which achieves SOTA performance in both image reconstruction and downstream industrial tasks." + }, + { + "type": "list", + "bbox": [ + 0.518, + 0.401, + 0.892, + 0.584 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.594, + 0.642, + 0.609 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.62, + 0.81, + 0.636 + ], + "angle": 0, + "content": "2.1. Polarization Model and Application" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.892, + 0.764 + ], + "angle": 0, + "content": "Polarization refers to the property of the transverse wave oscillating in different directions. Since light is a kind of wave, this phenomenon describes the distribution of light waves in all directions [1]. Conventional cameras or human eyes are insensitive to polarization. Thus, polarization is often used as a way to supplement additional visual information. It is often used in a wide range of fields such as optics [29], materials science [27], and physics [7, 36], etc." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.855 + ], + "angle": 0, + "content": "In the field of computer vision, polarization provides different angles of view, hence allowing a more efficient interpretation of complex scenes. In recent years, polarization has been widely used for complex tasks such as Integral Imaging [38], Rendering [2], 3D Shape [44], Segmentation [14], and Reflection Removal [12, 15, 34], etc." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In the real world, since natural light is mixed with multiple wavelengths, its refraction time is different when it is injected into an optically active material, thus, a phase shift" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24988" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.177, + 0.089, + 0.372, + 0.199 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.196, + 0.47, + 0.253 + ], + "angle": 0, + "content": "Figure 3. Model of elliptically polarized light. \\(E\\) represents polarized light at any angle, which can be calculated by this model. \\(I_{max}\\) and \\(I_{min}\\) are two components indicating the maximum and minimum intensity of elliptically polarized light." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.255, + 0.47, + 0.301 + ], + "angle": 0, + "content": "occurs. A physical description of this phenomenon is elliptically polarized light (i.e., partially polarized light), as shown in Eq. (1)." + }, + { + "type": "equation", + "bbox": [ + 0.175, + 0.303, + 0.469, + 0.336 + ], + "angle": 0, + "content": "\\[\n\\left\\{ \\begin{array}{l} E _ {x} = E _ {x 0} \\cos (\\omega t) \\\\ E _ {y} = E _ {y 0} \\cos (\\omega t - \\sigma) \\end{array} , \\right. \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.338, + 0.469, + 0.459 + ], + "angle": 0, + "content": "where \\((x,y)\\) is the Cartesian basis in the space of Jones vectors, \\(E_{x}\\) and \\(E_{y}\\) is the component of the light on the basis, \\((x,y)\\). \\(\\omega\\) is the frequency and \\(\\sigma\\) is the phase difference of \\(E_{x}\\) and \\(E_{y}\\). \\(E_{x0}\\) and \\(E_{y0}\\) are the field strength of a pair of orthogonal waves. Eq. (1) describes the vibration of the polarized light in different angles, \\(t\\). Based on this model, our solution only considers a simplified situation where \\(\\sigma = 90^{\\circ}\\). Eq. (1) can be simplified to Eq. (2)," + }, + { + "type": "equation", + "bbox": [ + 0.215, + 0.458, + 0.469, + 0.494 + ], + "angle": 0, + "content": "\\[\n\\frac {E _ {x} ^ {2}}{E _ {x 0} ^ {2}} + \\frac {E _ {y} ^ {2}}{E _ {y 0} ^ {2}} = 1. \\tag {2}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.496, + 0.456, + 0.513 + ], + "angle": 0, + "content": "2.2. Specular Highlight Removal via Polarization" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.519, + 0.469, + 0.716 + ], + "angle": 0, + "content": "Since the film includes unpredictable specular reflection, our task includes the procedure to remove these degradations. There have been several solutions to remove specular reflection using polarization information. Nayar et al. [21] first used polarization to determine the color of the specular component to separate the interfaces. Then, Umezama et al. [30] adopted independent component analysis to separate the diffuse and specular reflection components of surface reflection. Zhang et al. [42] considered the effect of polarization angle and attempted to get the appropriate global angle using Newton's method, but this method did not make full use of the local information. Wen et al. [34] separated specular reflection regions by using image chromaticity." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.716, + 0.469, + 0.791 + ], + "angle": 0, + "content": "Although conventional methods are available for removing specular highlight reflections, they are not able to accurately model the imaging of wrinkled transparent films, and thus do not adequately address the problem of eliminating all degradations from wrinkled transparent films." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.803, + 0.165, + 0.818 + ], + "angle": 0, + "content": "3. Dataset" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.469, + 0.902 + ], + "angle": 0, + "content": "While some datasets exist for the removal of specular reflection [11, 13, 34], there is currently no dataset for film removal in the industrial environment. As shown in Fig. 2, the characteristics of the specular highlight information from the film can be effectively modeled by the polarized image." + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.089, + 0.892, + 0.269 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.269, + 0.892, + 0.338 + ], + "angle": 0, + "content": "Figure 4. Prototype of industrial optical photography pipeline. We have built an optical pipeline for capturing the dataset in the industrial environment. As objects traverse the objective pipeline, the polarizing camera captures images continuously. Subsequently, the acquired data is sent to the monitor for pre-processing." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.34, + 0.892, + 0.447 + ], + "angle": 0, + "content": "Leveraging this polarization information can significantly enhance image reconstruction. Therefore, we construct a paired dataset based on polarized images. Polarized images can capture light amplitude information from wrinkled films at different angles, and making full use of this information will significantly facilitate the decoupling of degradation information occurring from the film." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.454, + 0.845, + 0.471 + ], + "angle": 0, + "content": "3.1. Industrial Optical Photography Pipeline" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.477, + 0.892, + 0.552 + ], + "angle": 0, + "content": "Fig. 4 illustrates the prototype of our pipeline. Within this industrial pipeline, we maintain a consistent posture and angle for both the camera and lighting resources. The objective pipeline sequentially passes different detected objects under the camera." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.553, + 0.892, + 0.658 + ], + "angle": 0, + "content": "To effectively capture optical information in multiple polarization directions within a single image, we employ the HIKROBOT MV-CH050-10UP camera1, which integrates the Sony IMX250MZR CMOS sensor2. This sensor contains four different angles of polarization \\((0^{\\circ}, 45^{\\circ}, 90^{\\circ}\\), and \\(135^{\\circ}\\) as Bayer pattern, allowing us to capture four polarization angles in high definition with a single shot." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.658, + 0.892, + 0.765 + ], + "angle": 0, + "content": "Finally, there is a monitor that controls the camera shutter and adjusts camera parameters. We utilize auto-exposure and auto-focus strategies to set the appropriate focal length, exposure time, and ISO for each specific scenario automatically. This is essential since the thickness and surface of the products on the industrial line may vary, requiring slight adjustments in camera parameters to ensure image quality." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.772, + 0.753, + 0.789 + ], + "angle": 0, + "content": "3.2. Capturing Polarized Images" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.843 + ], + "angle": 0, + "content": "When capturing polarized images, the imaging system initially captures an image of the ground truth uncovered by the film, \\( I_{gt}^{raw} \\). Subsequently, with the complex transpar" + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.851, + 0.892, + 0.875 + ], + "angle": 0, + "content": "1https://www.hikrobotics.com/cn/machinevision/productdetail?id=3886" + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.876, + 0.892, + 0.9 + ], + "angle": 0, + "content": "2https://www.sony-semicon.com/en/products/is/industry/polarization.html" + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.851, + 0.892, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24989" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.125 + ], + "angle": 0, + "content": "ent film placed over the ground truth, we capture the image \\( I_{input}^{raw} \\) that needs to be recovered." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.129, + 0.35, + 0.145 + ], + "angle": 0, + "content": "3.3. Data Diversity and Robustness" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.151, + 0.469, + 0.272 + ], + "angle": 0, + "content": "To build a diverse and robust dataset, we follow the rules in industrial manufacturing. As depicted in Fig. 4, the current industrial pipeline includes 315 dynamic industrial scenarios, which can be categorized into three types: QR codes, text, and products. To enhance the diversity, we have different films with diverse material properties, coverage areas, film thicknesses, and levels of wrinkling. The film exhibits significant variability across each scenario." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.272, + 0.469, + 0.348 + ], + "angle": 0, + "content": "On the other hand, to ensure the stability of the industrial imaging pipeline, we maintained a consistent intensity level for the industrial light source and fixed the distance between the camera and the object flow. This helps to minimize the influence of errors external to the industrial system." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.354, + 0.221, + 0.371 + ], + "angle": 0, + "content": "3.4. Prepossessing" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.377, + 0.469, + 0.481 + ], + "angle": 0, + "content": "Each pixel of the image captured by the polarization sensor is represented by four-pixel dots, each corresponding to the intensity of light at four distinct polarization angles. We first need to decompose it into 4 subgraphs with different angles, and then we restore it to its original resolution using edge-aware residual interpolation (EARI) demosaicking [20]. This process is described in Eq. (3)." + }, + { + "type": "equation", + "bbox": [ + 0.168, + 0.481, + 0.469, + 0.505 + ], + "angle": 0, + "content": "\\[\n\\left\\{I _ {g t} ^ {0}, I _ {g t} ^ {4 5}, I _ {g t} ^ {9 0}, I _ {g t} ^ {1 3 5} \\right\\} = M \\left(F _ {d} \\left(I _ {g t} ^ {\\text {r a w}}\\right)\\right), \\tag {3}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.103, + 0.501, + 0.468, + 0.52 + ], + "angle": 0, + "content": "\\[\n\\left\\{I _ {i n p u t} ^ {0}, I _ {i n p u t} ^ {4 5}, I _ {i n p u t} ^ {9 0}, I _ {i n p u t} ^ {1 3 5} \\right\\} = M \\left(F _ {d} \\left(I _ {i n p u t} ^ {r a w}\\right)\\right),\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.519, + 0.468, + 0.564 + ], + "angle": 0, + "content": "where \\( F_{d}(\\cdot) \\) is the decomposing operator, \\( M(\\cdot) \\) is EARI demosaicking. Taking \\( I_{gt}^{raw} \\) and \\( I_{input}^{raw} \\) as inputs, we obtain full-resolution polarized images with four different angles." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.565, + 0.469, + 0.653 + ], + "angle": 0, + "content": "To generate the ground truth image, we follow the standard procedure from the polarized image processing library, polanalyser3. Firstly, we introduce stokes parameters [3]. According to this physical model, the first stoke parameter \\( S_{0} \\) describes the total intensity of the optical beam, and it can be calculated by Eq. (4)." + }, + { + "type": "equation", + "bbox": [ + 0.175, + 0.653, + 0.469, + 0.671 + ], + "angle": 0, + "content": "\\[\nS _ {0} = E _ {x 0} ^ {2} + E _ {y 0} ^ {2} = I ^ {x} + I ^ {y}, \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.671, + 0.469, + 0.734 + ], + "angle": 0, + "content": "where \\( I^x \\perp I^y \\). \\( E_{x0}^2 \\) and \\( E_{y0}^2 \\) are the field strength of a pair of orthogonal waves in Fig. 3, which can be calculated by a pair of orthogonal polarization components, \\( I^x \\) and \\( I^y \\). Subsequently, we can calculate one ground truth \\( I_{gt} \\) as" + }, + { + "type": "equation", + "bbox": [ + 0.123, + 0.733, + 0.469, + 0.766 + ], + "angle": 0, + "content": "\\[\nI _ {g t} = G \\left(\\frac {S 0}{2}\\right) = \\left(\\frac {I _ {g t} ^ {0} + I _ {g t} ^ {4 5} + I _ {g t} ^ {9 0} + I _ {g t} ^ {1 3 5}}{4}\\right) ^ {\\frac {1}{\\gamma}}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.763, + 0.468, + 0.793 + ], + "angle": 0, + "content": "where \\( G(\\cdot) \\) is a gamma correction function, and we empirically set the gamma value, \\( \\gamma \\), to 2.2." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.799, + 0.275, + 0.815 + ], + "angle": 0, + "content": "3.5. Training and Testing" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.819, + 0.469, + 0.879 + ], + "angle": 0, + "content": "During training, our network mixed all the scenes for training, and the final network is applicable to data from all scenarios. Besides, to ensure the robustness and generalization of our dataset, we adopt 10-fold cross-validation [23]" + }, + { + "type": "text", + "bbox": [ + 0.533, + 0.09, + 0.668, + 0.103 + ], + "angle": 0, + "content": "Specular Highlight, \\(I_{h}\\)" + }, + { + "type": "text", + "bbox": [ + 0.721, + 0.09, + 0.859, + 0.103 + ], + "angle": 0, + "content": "Other Degradations, \\(I_{d}\\)" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.104, + 0.892, + 0.18 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.18, + 0.892, + 0.219 + ], + "angle": 0, + "content": "Figure 5. Two Decoupling Components. Specular highlight, \\( I_{h} \\) and other degradations, \\( I_{d} \\). The Red box shows the degradations, the Green box is the Ground Truth." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.22, + 0.892, + 0.28 + ], + "angle": 0, + "content": "to evaluate the results. The dataset is divided into ten parts, and nine of them are used as training data and one as test data in turn. Each test will yield a corresponding accuracy rate, which is then averaged as the final accuracy." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.288, + 0.59, + 0.303 + ], + "angle": 0, + "content": "4. Method" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.307, + 0.892, + 0.427 + ], + "angle": 0, + "content": "Although some conventional methods have used polarization information to remove surface specular highlight reflection, they assume the light intensity as a binary composition [34], i.e., transmission and reflection. However, the light intensity from the wrinkled film is more complex, which is not only influenced by film surface highlight but also mixed with various degradations, e.g., light transmittance and material texture." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.428, + 0.892, + 0.534 + ], + "angle": 0, + "content": "In this section, we first model the wrinkled transparent film physically in Fig. 2, which is our method's motivation. Then, we use an end-to-end network for reconstructing the original information in Fig. 6. Besides, since the highlight region is more tricky to recover, we build a polarization-based prior into the end-to-end framework to assist in locating highlight regions." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.539, + 0.861, + 0.555 + ], + "angle": 0, + "content": "4.1. Modelling the Wrinkled Transparent Film" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.559, + 0.892, + 0.693 + ], + "angle": 0, + "content": "Based on the Industrial Optical Photography System in Sec. 3.1, the light intensity for materials covered with the wrinkled transparent film will be captured by the polarized camera in Fig. 2(A)(B). The captured light intensity consists of two parts, i.e., the specular highlight reflection of the film's polarized regions [19, 26], the diffuse reflection from the materials under the film, which could be influenced by light transmittance, the texture of the film in Fig. 2(C). Such a composition is written in Eq. (6)." + }, + { + "type": "equation", + "bbox": [ + 0.591, + 0.692, + 0.89, + 0.707 + ], + "angle": 0, + "content": "\\[\nI = I _ {m d} + I _ {h} \\stackrel {\\prime} {=} I _ {m} ^ {\\prime} + I _ {d} + I _ {h}, \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.706, + 0.892, + 0.84 + ], + "angle": 0, + "content": "where \\(+\\) denotes the linear superposition of different light components, \\(I\\) is the light intensity captured by the camera, \\(I_{md}\\) is the diffuse reflection component of the material through various film degradations, \\(I_h\\) is the specular reflection part from the film's highlighted regions. Then, \\(I_{md}\\) can be decoupled to two parts, \\(I_m\\) and \\(I_d\\). \\(I_m\\) is the original diffuse reflection component of the material and \\(I_d\\) is caused by other various degradations through film. In Fig. 2(C), the optical path diagram illustrates this process." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Based on Eq. (6), the FR task can be implemented by retaining the information of \\( I_{m} \\) and decoupling \\( I_{h} \\) and \\( I_{d} \\) (both of them are caused by the film layer). This is expressed in Eq. (7), as" + }, + { + "type": "page_footnote", + "bbox": [ + 0.094, + 0.887, + 0.434, + 0.9 + ], + "angle": 0, + "content": "3https://github.com/elerac/polanalyser/wiki" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "24990" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.089, + 0.895, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.39, + 0.893, + 0.446 + ], + "angle": 0, + "content": "Figure 6. Overall framework. The polarized images, AoP and DoP are fed into Angle Estimation Net (A-Net), denoted as \\( f_{A} \\), for estimating the angle, \\( A \\). Subsequently, the Polarization-based Location Model (PLM), represented as \\( I_{p} \\), takes \\( A \\) as input to estimate the image prior, \\( P \\). This prior provides important highlight location information for the reconstruction network. Finally, the reconstruction network (R-Net) is trained to restore the original diffuse reflection in industrial materials." + }, + { + "type": "equation", + "bbox": [ + 0.209, + 0.45, + 0.468, + 0.465 + ], + "angle": 0, + "content": "\\[\nI _ {m} = I - I _ {h} - I _ {d}, \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.465, + 0.469, + 0.495 + ], + "angle": 0, + "content": "where - denotes the decoupling operator. Fig. 5 visualizes these two components for decoupling in our FR task." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.495, + 0.469, + 0.571 + ], + "angle": 0, + "content": "Based on this model, our whole framework is based on an end-to-end reconstruction network for decoupling these two parts in Sec. 4.3. Before that, to support the network for decoupling \\( I_{h} \\), we estimate a polarized prior for locating the highlight regions in Sec. 4.2." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.576, + 0.451, + 0.592 + ], + "angle": 0, + "content": "4.2. Estimating a Polarized Prior for Locating \\( I_{h} \\)" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.596, + 0.469, + 0.686 + ], + "angle": 0, + "content": "To decouple the specular reflection components, it is better to locate the highlight regions on the surface of the wrinkle film, which provides a prior to facilitate the decoupling network. However, these regions are hard to predict since images are captured in variable scenarios. To this end, we introduce the polarization information for this problem." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.687, + 0.469, + 0.822 + ], + "angle": 0, + "content": "Based on Fresnel's theory [35], the specular reflection component of optically active materials is an elliptically polarized light, which changes under different angles of polarization orientation, while the rest of the components remain almost constant. It can be employed in estimating \\( I_{h} \\), which is a specular reflection component. Thus, we propose a polarized prior \\( P \\), which is represented as the optimized \\( I \\) with the minimized \\( I_{h} \\), as shown in Eq. (8). The difference between \\( P \\) and the input \\( I \\) indicates the regions of \\( I_{h} \\)." + }, + { + "type": "equation", + "bbox": [ + 0.191, + 0.824, + 0.468, + 0.839 + ], + "angle": 0, + "content": "\\[\nP = I _ {m} + I _ {d} + \\min I _ {h}. \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.841, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Eq. (8), i.e., the polarized version of Eq. (6), can be acquired with Malus's Law [16] and the elliptical polarization model in Sec. 2.1. We use a pair of orthogonal maximum and minimum components and the angle variable" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.445, + 0.633, + 0.535 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.636, + 0.443, + 0.76, + 0.535 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.765, + 0.444, + 0.888, + 0.535 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.535, + 0.892, + 0.58 + ], + "angle": 0, + "content": "Figure 7. Location of specular highlight. The \\(P\\) is the polarized prior. We can calculate the location of highlight by \\(I_h - \\min I_h\\). \\(\\theta \\in [0,2\\pi)\\) to rewrite Eq. (8) as" + }, + { + "type": "equation", + "bbox": [ + 0.56, + 0.58, + 0.891, + 0.597 + ], + "angle": 0, + "content": "\\[\nI _ {h} = I _ {p} (\\theta) = I _ {\\max } \\cos^ {2} \\theta + I _ {\\min } \\sin^ {2} \\theta , \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.597, + 0.892, + 0.686 + ], + "angle": 0, + "content": "where \\(I_{p}(\\theta)\\) is the Polarization-based Location Model to describe the polarized light in the angle of \\(\\theta\\), \\(I_{max}\\) and \\(I_{min}\\) is a pair of orthogonal maximum and minimum components in Fig. 3. Given the input data \\(\\{I_{input}^{0}, I_{input}^{45}, I_{input}^{90}, I_{input}^{135}\\}\\), \\(I_{max}\\) and \\(I_{min}\\) can be computed by the Stokes parameters [3], from Eq. (10) and Eq. (11)." + }, + { + "type": "equation", + "bbox": [ + 0.52, + 0.685, + 0.891, + 0.766 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} I _ {m a x} = S _ {0} + \\frac {\\sqrt {S _ {1} ^ {2} + S _ {2} ^ {2}}}{2}, I _ {m i n} = S _ {0} - \\frac {\\sqrt {S _ {1} ^ {2} + S _ {2} ^ {2}}}{2}, (10) \\\\ S _ {0} = E _ {x 0} ^ {2} - E _ {y 0} ^ {2} = I _ {\\text {i n p u t}} ^ {0} + I _ {\\text {i n p u t}} ^ {9 0}, \\\\ S _ {1} = E _ {x 0} ^ {2} - E _ {y 0} ^ {2} = I _ {\\text {i n p u t}} ^ {0} - I _ {\\text {i n p u t}} ^ {9 0}, (11) \\\\ S _ {2} = E _ {a 0} ^ {2} - E _ {b 0} ^ {2} = I _ {\\text {i n p u t}} ^ {4 5} - I _ {\\text {i n p u t}} ^ {1 3 5}, \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.891, + 0.808 + ], + "angle": 0, + "content": "where \\((a,b)\\) is the Cartesian basis rotated by \\(45^{\\circ}\\) in the space of \\((x,y)\\), and \\(E_{a0}^{2}\\) as well as \\(E_{b0}^{2}\\) are the field strengths under this basis." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.81, + 0.891, + 0.839 + ], + "angle": 0, + "content": "Since \\( I_{h} \\) is the only polarized component that is determined by \\( \\theta \\), \\( P \\) in Eq. (8) can also be formulated as Eq. (12)." + }, + { + "type": "equation", + "bbox": [ + 0.52, + 0.839, + 0.891, + 0.904 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} P = I _ {m} + I _ {d} + \\min I _ {h} \\\\ = I _ {m} + I _ {d} + \\min _ {\\theta} I _ {p} (\\theta) \\tag {12} \\\\ = I _ {m} + I _ {d} + \\min _ {\\theta} \\left(I _ {m a x} \\cos^ {2} \\theta + I _ {m i n} \\sin^ {2} \\theta\\right). \\\\ \\end{array}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "24991" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.302 + ], + "angle": 0, + "content": "Different pixels in one image correspond to varying optimized values for \\(\\theta\\). Thus, we estimate pixel-wise \\(\\theta\\) with a learning-based network, obtaining the angle map \\(A\\). The input includes images with polarization information, i.e., \\(I_0\\), \\(I_{45}\\), \\(I_{90}\\), and \\(I_{135}\\). In addition, our input also includes two essential physics statistics, angle of polarization (AoP) and degree of polarization (DoP) [17]. The AoP provides information about the object's surface normal, which helps to analyze the difference in the surface structure between the object and film. The DoP offers information on the intensity of polarized light, so it can facilitate the network to utilize the polarized light accurately. Both of them can promote the model to learn the appropriate angle better. Eq. (13) describes this procedure." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.304, + 0.47, + 0.412 + ], + "angle": 0, + "content": "\\(A = f_{A}(I_{input}^{0}\\oplus I_{input}^{45}\\oplus I_{input}^{90}\\oplus I_{input}^{135}\\oplus S_{AoP}\\oplus S_{DoP})\\) (13) where, \\(A\\in \\mathbb{R}^{h\\times w\\times 1}\\) is the pixel-wise angle map, \\(S_{AoP}\\in\\) \\(\\mathbb{R}^{h\\times w\\times 1}\\) and \\(S_{DoP}\\in \\mathbb{R}^{h\\times w\\times 1}\\) indicate the AoP and DoP map respectively, \\(\\oplus\\) is the concatenation operator, and \\(f_{A}(\\cdot)\\) is angle estimation network. The network structure employs a lightweight Residual Dense Network [43] with a large perception field to capture more global information." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.412, + 0.47, + 0.441 + ], + "angle": 0, + "content": "After obtaining the angle map \\(A\\), we can get the prior with minimized \\(I_h\\) by Eq. (14)." + }, + { + "type": "equation", + "bbox": [ + 0.111, + 0.441, + 0.469, + 0.457 + ], + "angle": 0, + "content": "\\[\nP = I _ {m} + I _ {d} + I _ {\\max } \\cos^ {2} A + I _ {\\min } \\sin^ {2} A, \\tag {14}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.457, + 0.47, + 0.504 + ], + "angle": 0, + "content": "where \\(P \\in \\mathbb{R}^{h \\times w \\times 1}\\). Fig. 7 visualize the Prior, \\(P\\), and the location of \\(I_h\\) (highlighted). We can accurately estimate the location of the specular highlight." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.51, + 0.353, + 0.527 + ], + "angle": 0, + "content": "4.3. Reconstructing \\( I_{m} \\) with a Prior" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.531, + 0.47, + 0.652 + ], + "angle": 0, + "content": "In this section, we set a reconstruction network \\( f_{r} \\) to decouple both \\( I_{d} \\) and \\( I_{h} \\), with the input of \\( I \\) (i.e., \\( I_{input}^{0}, I_{input}^{45}, I_{input}^{90} \\), and \\( I_{input}^{135} \\)) and \\( P \\). The obtained prior \\( P \\) from Sec. 4.2 can already provide the estimation of \\( I_{h} \\) by comparing with \\( I \\). Thus, \\( f_{r} \\) can be focused on the assessment of \\( I_{d} \\). The reconstruction network is implemented as a common Residual Dense Network [43]. The reconstruction process can be expressed as Eq. (15)." + }, + { + "type": "equation", + "bbox": [ + 0.09, + 0.652, + 0.469, + 0.671 + ], + "angle": 0, + "content": "\\[\nI _ {r e c} = f _ {r} \\left(I _ {i n p u t} ^ {0} \\oplus I _ {i n p u t} ^ {4 5} \\oplus I _ {i n p u t} ^ {9 0} \\oplus I _ {i n p u t} ^ {1 3 5} \\oplus P\\right), \\tag {15}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.671, + 0.412, + 0.687 + ], + "angle": 0, + "content": "where, \\(I_{rec} \\in \\mathbb{R}^{h \\times w \\times 1}\\) is the reconstructed image." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.693, + 0.314, + 0.709 + ], + "angle": 0, + "content": "4.4. Details in Implementation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.713, + 0.469, + 0.789 + ], + "angle": 0, + "content": "Our framework is implemented by PyTorch, and we use Polanalyser library4 to process the polarized images. It is trained with \\( L1 \\) loss between \\( I_{rec} \\) and \\( I_{gt} \\) in an end-to-end manner. Besides, the learning rate is \\( 5 \\times 10^{-5} \\), and it decays to half of the original for every \\( 2 \\times 10^{4} \\) iterations." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.797, + 0.203, + 0.814 + ], + "angle": 0, + "content": "5. Experiment" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.818, + 0.469, + 0.879 + ], + "angle": 0, + "content": "In our experiment, we evaluate the performance of the proposed framework in three aspects. First, as an image reconstruction task, we conduct qualitative and quantitative evaluations with reconstruction-related metrics (e.g.," + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.892, + 0.168 + ], + "angle": 0, + "content": "PSNR, SSIM). Second, as an upstream task in the industry, two downstream scenarios (e.g., QR code reading, and Text OCR) are selected to evaluate the reliability of our proposed algorithm. Finally, we conduct ablation studies to analyze the roles of different components." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.175, + 0.608, + 0.189 + ], + "angle": 0, + "content": "5.1. Baselines" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.195, + 0.892, + 0.3 + ], + "angle": 0, + "content": "There is no existing baseline for this new problem. Thus, we choose two general SOTA methods in image reconstruction, Uformer [33] and Restormer [41] to evaluate the performance. Considering the connection between the film removal and highlight removal, we also compare with two SOTA polarization and non-polarization highlight removal baselines, Polar-HR [34] and SHIQ [6], respectively." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.301, + 0.892, + 0.422 + ], + "angle": 0, + "content": "To make a fair comparison, we follow the same training setting in our framework and input four polarized images to reconstruct one image without wrinkled transparent film in Uformer [33], Restormer [41]. In Polar-HR [34], it is a traditional training-free model and, therefore, shares the same input and output data as our approach. Besides, in SHIQ [6], since it cannot support polarized images, we convert four polarized images to one unpolarized image." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.43, + 0.806, + 0.444 + ], + "angle": 0, + "content": "5.2. Evaluation on Reconstruction Task" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.449, + 0.892, + 0.569 + ], + "angle": 0, + "content": "Quantitative Evaluation To measure the quantitative performance of the algorithm, we refer to commonly used metrics for Image Reconstruction: peak signal-to-noise ratio (PSNR) and structural similarity (SSIM). Also, to compare the overall performance of our dataset, we use 10-fold cross-validation during training and testing. This strategy ensures the evaluation's reliability and further proves the proposed algorithm's robustness." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.57, + 0.892, + 0.844 + ], + "angle": 0, + "content": "The quantitative results are shown in Table 1. In the last column of Table 1, \\(\\mu\\) is the mean value, and \\(\\sigma\\) is the variance of the 10-fold performance. These experimental results show the average PSNR is 36.48 and the average SSIM is 0.9824, and the results demonstrate the high quality of our reconstructed images. In addition, the variance of PSNR and SSIM are 0.57 and \\(1.23 \\times 10^{-5}\\), respectively, and this proves the proposed algorithm is stable and robust. Qualitative Evaluation To evaluate the reconstruction performance of the algorithm in a qualitative way, we show some visual results. Our results are shown in Fig. 8. Although Polar-HR [34] and SHIQ [6] can remove some of the highlights, their models cannot model the film correctly and, therefore, cannot remove the film itself. Besides, it can be observed that our algorithm can reconstruct regions where text or QR codes are corrupted by highlights through polarization information, while Uformer [33] and Restormer [41] produce fake artifacts in these regions." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.85, + 0.846, + 0.866 + ], + "angle": 0, + "content": "5.3. Evaluation on Downstream Applications" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.892, + 0.902 + ], + "angle": 0, + "content": "In industrial environments, it is common to use transparent films to cover products, which may negatively im" + }, + { + "type": "page_footnote", + "bbox": [ + 0.094, + 0.887, + 0.434, + 0.9 + ], + "angle": 0, + "content": "4https://github.com/elerac/polanalyser/wiki" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "24992" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.082, + 0.089, + 0.894, + 0.269 + ], + "angle": 0, + "content": "
K1K2K3K4K5K6K7K8K9K10μ↑σ↓
SHIQ [6]PSNR23.4722.1121.9521.6921.7721.0320.8620.4621.1021.3121.580.64
SSIM0.78990.76400.74160.74390.74590.74650.74990.74120.74650.73000.74992.41 × 10-4
Polar-HR [34]PSNR23.3122.8022.1321.5821.9422.0022.0321.9922.1821.9522.190.22
SSIM0.76420.74210.72200.70990.70640.70980.71280.70170.71020.69680.71763.80 × 10-4
Uformer [33]PSNR31.8531.9531.3931.1931.8132.0431.6831.9831.8531.0131.680.11
SSIM0.95190.94560.93710.93640.94340.94210.94380.94350.94570.93630.94262.17 × 10-5
Restormer [41]PSNR34.3535.0234.4433.7134.8835.1334.3134.3334.5132.4934.320.52
SSIM0.97710.97700.97210.96780.97570.97460.97420.97410.97590.96330.97311.75 × 10-5
OursPSNR36.7637.2936.6235.1236.9337.2136.2436.6736.9435.0236.480.57
SSIM0.98520.98590.98220.97670.98450.98330.98360.98300.98500.97490.98241.23 × 10-5
" + }, + { + "type": "table_caption", + "bbox": [ + 0.216, + 0.271, + 0.754, + 0.284 + ], + "angle": 0, + "content": "Table 1. Quantitative evaluation in 10-fold cross-validation. The K- \\( I \\) indicates the \\( {I}_{th} \\) fold." + }, + { + "type": "table", + "bbox": [ + 0.086, + 0.285, + 0.891, + 0.519 + ], + "angle": 0, + "content": "
Input (Intensity)SHIQ [6]Polar-HR [34]Uformer [33]Restormer [41]OursGround Truth
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.518, + 0.891, + 0.544 + ], + "angle": 0, + "content": "Figure 8. Qualitative Evaluation. Compared with other baselines, our model can reconstruct more realistic details in highlight regions instead of fake artifacts. Please zoom in for more details." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.546, + 0.47, + 0.646 + ], + "angle": 0, + "content": "
SHIQ [6]Polar-HR [34]Uformer [33]
Read Number71718
Read Rate8.05%19.54%20.69%
Restormer [41]OursGround Truth
Read Number246387
Read Rate27.58%72.41%100%
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.077, + 0.647, + 0.469, + 0.687 + ], + "angle": 0, + "content": "Table 2. QR code reading rate. Compared with other baselines, our approach can improve the performance of QR codes scanner in the industrial environment." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.688, + 0.469, + 0.793 + ], + "angle": 0, + "content": "pact the robustness of downstream algorithms. To evaluate the effectiveness of our solution in such settings, we conduct two tests on two downstream tasks: QR Code Reading and Text Optical Character Recognition (Text OCR). These tasks are particularly relevant as they require access to raw information, which provides a rigorous test of the effectiveness of our algorithms in industrial scenarios." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.469, + 0.901 + ], + "angle": 0, + "content": "QR Code Reading The read rate is a critical performance metric for manufacturing pipelines in industrial systems. In this experiment, we compare our method with other baselines in Table 2. Our upstream algorithm leads to a significant improvement in the performance of the QR code reading. The qualitative results in Fig. 9 demonstrate that our algorithm not only removes the film but also significantly" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.549, + 0.825, + 0.562 + ], + "angle": 0, + "content": "recovers the QR code information under the film." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.563, + 0.891, + 0.623 + ], + "angle": 0, + "content": "Text OCR Text OCR is also an important downstream industrial task. We compared our algorithm with other baselines, as shown in Fig. 10. Our method can restore more hidden text information accurately." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.628, + 0.652, + 0.643 + ], + "angle": 0, + "content": "5.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.892, + 0.734 + ], + "angle": 0, + "content": "We conduct ablation studies, which mainly validate the effectiveness of our proposed polarization dataset and one crucial component in our framework. To ensure that the experimental settings are consistent, we perform 10-fold cross-validation for the ablation experiments as well and draw two boxplots for further analysis." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Effectiveness of the Polarized Information To prove the effectiveness of polarized information, we eliminate all components that need polarization information, which include four polarization images. Since the Polarization-based Location Model is driven by the \\( I_{max} \\) and \\( I_{min} \\), which need to be calculated with polarization images as input, this structure is also removed. Other settings remain constant. Without the support of polarized information, the quantitative performance has a considerable decrease, as shown in Fig. 11 (w/o Polarized information). Also, the performance of the network is limited by the lack of guidance" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "24993" + } + ], + [ + { + "type": "image_caption", + "bbox": [ + 0.104, + 0.083, + 0.193, + 0.095 + ], + "angle": 0, + "content": "Input (Intensity)" + }, + { + "type": "image", + "bbox": [ + 0.087, + 0.096, + 0.21, + 0.175 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.111, + 0.177, + 0.185, + 0.188 + ], + "angle": 0, + "content": "Uformer [33]" + }, + { + "type": "image_caption", + "bbox": [ + 0.249, + 0.083, + 0.301, + 0.095 + ], + "angle": 0, + "content": "SHIQ [6]" + }, + { + "type": "image", + "bbox": [ + 0.214, + 0.095, + 0.338, + 0.175 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.234, + 0.177, + 0.317, + 0.189 + ], + "angle": 0, + "content": "Restormer [41]" + }, + { + "type": "image_caption", + "bbox": [ + 0.365, + 0.083, + 0.443, + 0.095 + ], + "angle": 0, + "content": "Polar-HR [34]" + }, + { + "type": "image", + "bbox": [ + 0.342, + 0.095, + 0.465, + 0.175 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.389, + 0.177, + 0.418, + 0.188 + ], + "angle": 0, + "content": "Ours" + }, + { + "type": "image", + "bbox": [ + 0.087, + 0.19, + 0.21, + 0.269 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.214, + 0.19, + 0.338, + 0.269 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.342, + 0.19, + 0.465, + 0.269 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.27, + 0.469, + 0.364 + ], + "angle": 0, + "content": "Figure 9. Performance of QR code reading in the industry. In the original image, the QR code scanner fails to detect QR code information. Polar-HR [34] and SHIQ [6] can only eliminate the specular reflection on the QR code, and Uformer [33] and Restormer [41] can only generate false artifacts in highlight regions. Our method can help industrial QR code scanners achieve a higher performance." + }, + { + "type": "image_caption", + "bbox": [ + 0.106, + 0.365, + 0.192, + 0.376 + ], + "angle": 0, + "content": "Input (Intensity)" + }, + { + "type": "image", + "bbox": [ + 0.091, + 0.376, + 0.208, + 0.463 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.115, + 0.466, + 0.184, + 0.477 + ], + "angle": 0, + "content": "Uformer [33]" + }, + { + "type": "image_caption", + "bbox": [ + 0.245, + 0.364, + 0.296, + 0.375 + ], + "angle": 0, + "content": "SHIQ [6]" + }, + { + "type": "image", + "bbox": [ + 0.214, + 0.376, + 0.33, + 0.463 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.231, + 0.466, + 0.311, + 0.477 + ], + "angle": 0, + "content": "Restormer [41]" + }, + { + "type": "image_caption", + "bbox": [ + 0.355, + 0.364, + 0.429, + 0.375 + ], + "angle": 0, + "content": "Polar-HR [34]" + }, + { + "type": "image", + "bbox": [ + 0.338, + 0.376, + 0.45, + 0.463 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.379, + 0.466, + 0.405, + 0.477 + ], + "angle": 0, + "content": "Ours" + }, + { + "type": "image", + "bbox": [ + 0.091, + 0.477, + 0.208, + 0.564 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.213, + 0.477, + 0.33, + 0.563 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.335, + 0.477, + 0.45, + 0.563 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.565, + 0.469, + 0.605 + ], + "angle": 0, + "content": "Figure 10. Performance of text OCR in the industry. Compared to other baselines, our method can reconstruct more original text information for recognition." + }, + { + "type": "image_caption", + "bbox": [ + 0.16, + 0.607, + 0.208, + 0.618 + ], + "angle": 0, + "content": "(A) PSNR" + }, + { + "type": "image", + "bbox": [ + 0.092, + 0.62, + 0.272, + 0.707 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.341, + 0.608, + 0.386, + 0.618 + ], + "angle": 0, + "content": "(B) SSIM" + }, + { + "type": "image", + "bbox": [ + 0.274, + 0.621, + 0.45, + 0.707 + ], + "angle": 0, + "content": null + }, + { + "type": "image_footnote", + "bbox": [ + 0.119, + 0.708, + 0.427, + 0.718 + ], + "angle": 0, + "content": "Ours \\(\\mathbb{w} / \\mathrm{o}\\) AoP & DoP w/o Polarized Information w/o Prior" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.722, + 0.469, + 0.778 + ], + "angle": 0, + "content": "Figure 11. PSNR (A) and SSIM (B) in ablation study. We use two boxplots to describe the performance after \\( t \\)-fold cross-validation. The results show that our dataset, the extracted prior, the AoP, and the DoP contribute to the framework performance improvement." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.469, + 0.825 + ], + "angle": 0, + "content": "information, so it cannot remove all degradation. Besides, removing the polarization information will induce artifacts in highlight regions, as shown in Fig. 12." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.826, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Effectiveness of AoP and DoP To prove the effectiveness of AoP and DoP, we eliminate AoP and DoP in the angle estimation network. The qualitative results presented in Fig. 13 demonstrate that AoP and DoP can help locate the highlight more significantly, and also improve overall" + }, + { + "type": "image", + "bbox": [ + 0.517, + 0.09, + 0.659, + 0.196 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.66, + 0.09, + 0.803, + 0.196 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.805, + 0.091, + 0.872, + 0.143 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.805, + 0.143, + 0.872, + 0.196 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.196, + 0.892, + 0.249 + ], + "angle": 0, + "content": "Figure 12. Qualitative evaluation of w/o Polarization Information. Compared with w/o polarization information (Red), introducing polarization information avoids the generation of artifacts and reconstructs the realistic details (Green)." + }, + { + "type": "image", + "bbox": [ + 0.512, + 0.252, + 0.606, + 0.324 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.607, + 0.252, + 0.7, + 0.324 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.705, + 0.252, + 0.795, + 0.324 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.796, + 0.252, + 0.884, + 0.324 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.325, + 0.892, + 0.365 + ], + "angle": 0, + "content": "Figure 13. Highlight location heatmap. Compared with \"w/o AoP & DoP\" (In Red Box), introducing AoP and DoP (In Green Box) can help the A-Net to infer more highlight regions." + }, + { + "type": "image", + "bbox": [ + 0.512, + 0.367, + 0.605, + 0.439 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.606, + 0.367, + 0.7, + 0.439 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.705, + 0.367, + 0.795, + 0.439 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.796, + 0.367, + 0.884, + 0.439 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.44, + 0.892, + 0.481 + ], + "angle": 0, + "content": "Figure 14. Qualitative Evaluation of w/o Prior. Compared with \"w/o Prior\" (In Red Box), our solution (In Green Box) is more effective to remove highlight and infer original information." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.483, + 0.78, + 0.498 + ], + "angle": 0, + "content": "performance in Fig. 11 (w/o AoP & DoP)." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.499, + 0.892, + 0.65 + ], + "angle": 0, + "content": "Effectiveness of Prior To prove the effectiveness of polarized prior, we eliminate the angle estimation network and the PLM in our network while retaining only the polarized images and the reconstruction network. In this case, the network can only implicitly facilitate the polarized information in the reconstruction network. Since there is no polarized prior that indicates highlight regions, this can lead to a decrease in the performance of the network to recover highlight regions (as shown in Fig. 14), while causing overall performance to decrease in Fig. 11 (w/o Prior)." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.655, + 0.619, + 0.669 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.674, + 0.892, + 0.84 + ], + "angle": 0, + "content": "In this study, we pioneer the investigation of the Film Removal (FR) problem, aiming to eliminate the disturbances caused by wrinkled transparent films and to restore the obscured information. We propose an end-to-end framework to effectively remove all degradations caused by the film with a polarized prior to minimizing highlight. Besides, we build a practical polarized dataset containing paired data for this problem. Experiments in the industry have demonstrated the potential application. We believe that the deployment of our algorithms will considerably improve the robustness of downstream industrial recognition systems." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.841, + 0.892, + 0.899 + ], + "angle": 0, + "content": "Acknowledgment This work is supported by the National Natural Science Foundation of China (No. 62206068) and the Natural Science Foundation of Zhejiang Province, China under No. LD24F020002." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24994" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.079, + 0.09, + 0.176, + 0.107 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.116, + 0.47, + 0.158 + ], + "angle": 0, + "content": "[1] Gary A Atkinson. Polarized light in computer vision. In Computer Vision: A Reference Guide, pages 1005-1010. 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In CVPR, 2019. 2" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.093, + 0.468, + 0.504 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24996" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_origin.pdf b/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..baab8b0cfb5b7f446eb989b94ff50cf8e1ffb18e --- /dev/null +++ b/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/5e25a466-41ef-4842-a8b6-ee1cd66325a7_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:5c5fc52e40ca162174e11dc751b891a3dd6d85fcadfb366c77d980037623c621 +size 8567479 diff --git a/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/full.md b/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/full.md new file mode 100644 index 0000000000000000000000000000000000000000..f5b6f6685d872beacecc31280009d38f43c061e7 --- /dev/null +++ b/2024/Learning to Remove Wrinkled Transparent Film with Polarized Prior/full.md @@ -0,0 +1,440 @@ +# Learning to Remove Wrinkled Transparent Film with Polarized Prior + +Jiaqi Tang $^{1,2,3}$ Ruizheng Wu $^{4}$ Xiaogang Xu $^{5,6}$ Sixing Hu $^{4}$ Ying-Cong Chen $^{1,2,3*}$ + +1The Hong Kong University of Science and Technology (Guangzhou) + +$^{2}$ The Hong Kong University of Science and Technology $^{3}$ HKUST(GZ) - SmartMore Joint Lab + +$^{4}$ SmartMore Corporation $^{5}$ The Chinese University of Hong Kong $^{6}$ Zhejiang University + +jtan092@connect.hkust-gz.edu.cn, {ruizheng.wu, david.hu}@smartmore.com + +xiaogangxu00@gmail.com, yingcongchen@ust.hk + +# Abstract + +In this paper, we study a new problem, Film Removal (FR), which attempts to remove the interference of wrinkled transparent films and reconstruct the original information under films for industrial recognition systems. We first physically model the imaging of industrial materials covered by the film. Considering the specular highlight from the film can be effectively recorded by the polarized camera, we build a practical dataset with polarization information containing paired data with and without transparent film. We aim to remove interference from the film (specular highlights and other degradations) with an end-to-end framework. To locate the specular highlight, we use an angle estimation network to optimize the polarization angle with the minimized specular highlight. The image with minimized specular highlight is set as a prior for supporting the reconstruction network. Based on the prior and the polarized images, the reconstruction network can decouple all degradations from the film. Extensive experiments show that our framework achieves SOTA performance in both image reconstruction and industrial downstream tasks. Our code will be released at https://github.com/jqtangust/FilmRemoval. + +# 1. Introduction + +Various deep-learning-based recognition models have been employed in the industrial environment, e.g., defect detection [28], code recognition [25], etc. However, the model failures would sometimes happen due to the insufficient robustness [40] towards different perturbations [8, 10, 24, 32, 39]. The wrinkled transparent film is one of them, which is usually covered or packaged on industrial materials or products for protection. Its interference could cause the failure of varying downstream tasks, e.g., text OCR and + +![](images/f9d5c24f8b2da7b9c871f2b8b5a1fe856eefb53d6d45db16a56022ea48d52c58.jpg) +Images with Wrinkled Transparent Film + +![](images/3efee36ca3efff82e45aac5c2f01b6a057d41b18da809042cd1333eb4e286c01.jpg) + +![](images/354bc7e64d4502e38e92d7f7a4e401369e59034f781d4872193f5098a2a86793.jpg) + +![](images/8d497d6b5004a6412afc1ae58ecc8dbc7980884fa6d7ec503d7edb6ba5d52b54.jpg) +Images without Wrinkled Transparent Film + +![](images/49611dbd0beb8dcafbebbefcac7252f1909527cebe390fa52db1833128b2c77e.jpg) + +![](images/cf8b954e920d3349e40a3f00d1847c69126d03f7a7c2a24792b50f2c38c54b9a.jpg) + +Figure 1. The Red box presents a challenge in industrial recognition systems, where the product information is often hidden beneath the wrinkled transparent film. The Green box is the image we expect to generate, with the film layer removed. Removing the wrinkled film makes the information on industrial material clearer. QR code recognition, in Fig. 1. Regarding the wide usage of such films in industrial scenarios, it is worth opening the research direction to remove these films from images. + +For the first time, we address a novel problem of wrinkle transparent Film Removal (FR), which aims to remove the transparent film and reveal the hidden information, benefiting the robustness of the industrial downstream models. + +Although some solutions have attempted to remove surface highlight [6, 31, 34], they have not accurately modeled the imaging of the wrinkled transparent film. Except for the highlight, they cannot remove the effects of other various degradations from the film, e.g., light transmittance and material texture. Therefore, they cannot remove the transparent film thoroughly. + +In this paper, we explicitly model the imaging of wrinkled transparent film into two parts: the specular highlight $I_{h}$ from the film, and the diffuse reflection $I_{md}$ from the materials under the film, as shown in Fig. 2. The diffuse reflection can be influenced by the properties of the film. Thus, it is divided into the original component $(I_{m})$ and various + +![](images/0dc39e4e71a4ee2c2532cbd38236a11e03e33e45e7bdaebaa9c6c32c4d34f9b7.jpg) +Figure 2. Wrinkled Transparent Film Model. (A) The polarized image. (B) The 3D physics model of the local region. The light is reflected through the transparent wrinkled film and captured by the polarization camera. (C) The light path diagram. Polarized cameras capture two components: Specular Reflection $(I_h)$ , and Diffuse Reflection $(I_{md})$ . The Original Diffuse Reflection $(I_m)$ would be interfered by various degradations $(I_{md} - I_m)$ from the film. + +degradations $(I_{md} - I_m)$ . Therefore, our objective is to decouple the specular highlight and other degradations caused by the film and reconstruct the original diffuse reflection. + +We build an end-to-end framework for decoupling two different degradations in the Wrinkled Transparent Film Model (Fig. 2), which consists of the prior estimation and reconstruction network. We notice that specular highlight is significantly related to polarization angles, while other parts are not. Based on this observation, we use an Angle Estimation Network to learn the polar angle corresponding to the minimized specular highlight, which is driven by a Polarization-based Location Model. Images with minimized specular highlights are set as the priors for the later reconstruction network to remove all degradations. + +There is currently no suitable dataset for the FR problem, since most of the existing datasets [5, 18, 34] are targeted towards specular reflection removal only. Also, most datasets do not consider the real industrial environment. Therefore, we build a new dataset that consists of paired images covered by the film and the uncovered ground truth in the industrial optical photography system. Moreover, it's proved that the specular highlight from the film can be effectively captured by the polarization camera [21, 34, 37], which is now cheap to be installed in industrial systems [22]. Thus, we follow the collection pipeline of existing polarization datasets [4, 9], and capture each object with four polarized images under four polar directions in one shot. It's empirically proved by our experiments that with the input of these polarization clues, networks can better locate the specular highlight and recover the hidden information under the film. + +Extensive experiments prove that our designed network achieves SOTA performance in the FR problem. Our contributions are summarized as follows: + +- To the best of our knowledge, we are the first to address the new problem of Film Removal (FR), which + +aims to remove the whole wrinkled transparent film in industrial scenarios. + +- To solve FR, we model the wrinkled film physically and propose an end-to-end reconstruction network for FR with a learnable polarization-based prior, which helps the network locate the specular highlight reflection in the film. +- We also build a new practical dataset in the real industrial optical photography system, which contains various polarized image pairs with and without the film. +- Extensive experiments are conducted to prove the effectiveness of our dataset and method, which achieves SOTA performance in both image reconstruction and downstream industrial tasks. + +# 2. Related Work + +# 2.1. Polarization Model and Application + +Polarization refers to the property of the transverse wave oscillating in different directions. Since light is a kind of wave, this phenomenon describes the distribution of light waves in all directions [1]. Conventional cameras or human eyes are insensitive to polarization. Thus, polarization is often used as a way to supplement additional visual information. It is often used in a wide range of fields such as optics [29], materials science [27], and physics [7, 36], etc. + +In the field of computer vision, polarization provides different angles of view, hence allowing a more efficient interpretation of complex scenes. In recent years, polarization has been widely used for complex tasks such as Integral Imaging [38], Rendering [2], 3D Shape [44], Segmentation [14], and Reflection Removal [12, 15, 34], etc. + +In the real world, since natural light is mixed with multiple wavelengths, its refraction time is different when it is injected into an optically active material, thus, a phase shift + +![](images/f54454b49740c338119b479590ccf5140f5999bf6cd38d157da72552d781ebd2.jpg) +Figure 3. Model of elliptically polarized light. $E$ represents polarized light at any angle, which can be calculated by this model. $I_{max}$ and $I_{min}$ are two components indicating the maximum and minimum intensity of elliptically polarized light. + +occurs. A physical description of this phenomenon is elliptically polarized light (i.e., partially polarized light), as shown in Eq. (1). + +$$ +\left\{ \begin{array}{l} E _ {x} = E _ {x 0} \cos (\omega t) \\ E _ {y} = E _ {y 0} \cos (\omega t - \sigma) \end{array} , \right. \tag {1} +$$ + +where $(x,y)$ is the Cartesian basis in the space of Jones vectors, $E_{x}$ and $E_{y}$ is the component of the light on the basis, $(x,y)$ . $\omega$ is the frequency and $\sigma$ is the phase difference of $E_{x}$ and $E_{y}$ . $E_{x0}$ and $E_{y0}$ are the field strength of a pair of orthogonal waves. Eq. (1) describes the vibration of the polarized light in different angles, $t$ . Based on this model, our solution only considers a simplified situation where $\sigma = 90^{\circ}$ . Eq. (1) can be simplified to Eq. (2), + +$$ +\frac {E _ {x} ^ {2}}{E _ {x 0} ^ {2}} + \frac {E _ {y} ^ {2}}{E _ {y 0} ^ {2}} = 1. \tag {2} +$$ + +# 2.2. Specular Highlight Removal via Polarization + +Since the film includes unpredictable specular reflection, our task includes the procedure to remove these degradations. There have been several solutions to remove specular reflection using polarization information. Nayar et al. [21] first used polarization to determine the color of the specular component to separate the interfaces. Then, Umezama et al. [30] adopted independent component analysis to separate the diffuse and specular reflection components of surface reflection. Zhang et al. [42] considered the effect of polarization angle and attempted to get the appropriate global angle using Newton's method, but this method did not make full use of the local information. Wen et al. [34] separated specular reflection regions by using image chromaticity. + +Although conventional methods are available for removing specular highlight reflections, they are not able to accurately model the imaging of wrinkled transparent films, and thus do not adequately address the problem of eliminating all degradations from wrinkled transparent films. + +# 3. Dataset + +While some datasets exist for the removal of specular reflection [11, 13, 34], there is currently no dataset for film removal in the industrial environment. As shown in Fig. 2, the characteristics of the specular highlight information from the film can be effectively modeled by the polarized image. + +![](images/1661310d5f0b9488bec08d2ee118303241d223d4ddb4bdc5c23894109197e519.jpg) +Figure 4. Prototype of industrial optical photography pipeline. We have built an optical pipeline for capturing the dataset in the industrial environment. As objects traverse the objective pipeline, the polarizing camera captures images continuously. Subsequently, the acquired data is sent to the monitor for pre-processing. + +Leveraging this polarization information can significantly enhance image reconstruction. Therefore, we construct a paired dataset based on polarized images. Polarized images can capture light amplitude information from wrinkled films at different angles, and making full use of this information will significantly facilitate the decoupling of degradation information occurring from the film. + +# 3.1. Industrial Optical Photography Pipeline + +Fig. 4 illustrates the prototype of our pipeline. Within this industrial pipeline, we maintain a consistent posture and angle for both the camera and lighting resources. The objective pipeline sequentially passes different detected objects under the camera. + +To effectively capture optical information in multiple polarization directions within a single image, we employ the HIKROBOT MV-CH050-10UP camera1, which integrates the Sony IMX250MZR CMOS sensor2. This sensor contains four different angles of polarization $(0^{\circ}, 45^{\circ}, 90^{\circ}$ , and $135^{\circ}$ as Bayer pattern, allowing us to capture four polarization angles in high definition with a single shot. + +Finally, there is a monitor that controls the camera shutter and adjusts camera parameters. We utilize auto-exposure and auto-focus strategies to set the appropriate focal length, exposure time, and ISO for each specific scenario automatically. This is essential since the thickness and surface of the products on the industrial line may vary, requiring slight adjustments in camera parameters to ensure image quality. + +# 3.2. Capturing Polarized Images + +When capturing polarized images, the imaging system initially captures an image of the ground truth uncovered by the film, $I_{gt}^{raw}$ . Subsequently, with the complex transpar + +ent film placed over the ground truth, we capture the image $I_{input}^{raw}$ that needs to be recovered. + +# 3.3. Data Diversity and Robustness + +To build a diverse and robust dataset, we follow the rules in industrial manufacturing. As depicted in Fig. 4, the current industrial pipeline includes 315 dynamic industrial scenarios, which can be categorized into three types: QR codes, text, and products. To enhance the diversity, we have different films with diverse material properties, coverage areas, film thicknesses, and levels of wrinkling. The film exhibits significant variability across each scenario. + +On the other hand, to ensure the stability of the industrial imaging pipeline, we maintained a consistent intensity level for the industrial light source and fixed the distance between the camera and the object flow. This helps to minimize the influence of errors external to the industrial system. + +# 3.4. Prepossessing + +Each pixel of the image captured by the polarization sensor is represented by four-pixel dots, each corresponding to the intensity of light at four distinct polarization angles. We first need to decompose it into 4 subgraphs with different angles, and then we restore it to its original resolution using edge-aware residual interpolation (EARI) demosaicking [20]. This process is described in Eq. (3). + +$$ +\left\{I _ {g t} ^ {0}, I _ {g t} ^ {4 5}, I _ {g t} ^ {9 0}, I _ {g t} ^ {1 3 5} \right\} = M \left(F _ {d} \left(I _ {g t} ^ {\text {r a w}}\right)\right), \tag {3} +$$ + +$$ +\left\{I _ {i n p u t} ^ {0}, I _ {i n p u t} ^ {4 5}, I _ {i n p u t} ^ {9 0}, I _ {i n p u t} ^ {1 3 5} \right\} = M \left(F _ {d} \left(I _ {i n p u t} ^ {r a w}\right)\right), +$$ + +where $F_{d}(\cdot)$ is the decomposing operator, $M(\cdot)$ is EARI demosaicking. Taking $I_{gt}^{raw}$ and $I_{input}^{raw}$ as inputs, we obtain full-resolution polarized images with four different angles. + +To generate the ground truth image, we follow the standard procedure from the polarized image processing library, polanalyser3. Firstly, we introduce stokes parameters [3]. According to this physical model, the first stoke parameter $S_{0}$ describes the total intensity of the optical beam, and it can be calculated by Eq. (4). + +$$ +S _ {0} = E _ {x 0} ^ {2} + E _ {y 0} ^ {2} = I ^ {x} + I ^ {y}, \tag {4} +$$ + +where $I^x \perp I^y$ . $E_{x0}^2$ and $E_{y0}^2$ are the field strength of a pair of orthogonal waves in Fig. 3, which can be calculated by a pair of orthogonal polarization components, $I^x$ and $I^y$ . Subsequently, we can calculate one ground truth $I_{gt}$ as + +$$ +I _ {g t} = G \left(\frac {S 0}{2}\right) = \left(\frac {I _ {g t} ^ {0} + I _ {g t} ^ {4 5} + I _ {g t} ^ {9 0} + I _ {g t} ^ {1 3 5}}{4}\right) ^ {\frac {1}{\gamma}}, \tag {5} +$$ + +where $G(\cdot)$ is a gamma correction function, and we empirically set the gamma value, $\gamma$ , to 2.2. + +# 3.5. Training and Testing + +During training, our network mixed all the scenes for training, and the final network is applicable to data from all scenarios. Besides, to ensure the robustness and generalization of our dataset, we adopt 10-fold cross-validation [23] + +Specular Highlight, $I_{h}$ + +Other Degradations, $I_{d}$ + +![](images/22e59a4aa7140b981bd111a9de60b95dcf71decb4ceb64c0b1636fba9e9479ae.jpg) +Figure 5. Two Decoupling Components. Specular highlight, $I_{h}$ and other degradations, $I_{d}$ . The Red box shows the degradations, the Green box is the Ground Truth. + +to evaluate the results. The dataset is divided into ten parts, and nine of them are used as training data and one as test data in turn. Each test will yield a corresponding accuracy rate, which is then averaged as the final accuracy. + +# 4. Method + +Although some conventional methods have used polarization information to remove surface specular highlight reflection, they assume the light intensity as a binary composition [34], i.e., transmission and reflection. However, the light intensity from the wrinkled film is more complex, which is not only influenced by film surface highlight but also mixed with various degradations, e.g., light transmittance and material texture. + +In this section, we first model the wrinkled transparent film physically in Fig. 2, which is our method's motivation. Then, we use an end-to-end network for reconstructing the original information in Fig. 6. Besides, since the highlight region is more tricky to recover, we build a polarization-based prior into the end-to-end framework to assist in locating highlight regions. + +# 4.1. Modelling the Wrinkled Transparent Film + +Based on the Industrial Optical Photography System in Sec. 3.1, the light intensity for materials covered with the wrinkled transparent film will be captured by the polarized camera in Fig. 2(A)(B). The captured light intensity consists of two parts, i.e., the specular highlight reflection of the film's polarized regions [19, 26], the diffuse reflection from the materials under the film, which could be influenced by light transmittance, the texture of the film in Fig. 2(C). Such a composition is written in Eq. (6). + +$$ +I = I _ {m d} + I _ {h} \stackrel {\prime} {=} I _ {m} ^ {\prime} + I _ {d} + I _ {h}, \tag {6} +$$ + +where $+$ denotes the linear superposition of different light components, $I$ is the light intensity captured by the camera, $I_{md}$ is the diffuse reflection component of the material through various film degradations, $I_h$ is the specular reflection part from the film's highlighted regions. Then, $I_{md}$ can be decoupled to two parts, $I_m$ and $I_d$ . $I_m$ is the original diffuse reflection component of the material and $I_d$ is caused by other various degradations through film. In Fig. 2(C), the optical path diagram illustrates this process. + +Based on Eq. (6), the FR task can be implemented by retaining the information of $I_{m}$ and decoupling $I_{h}$ and $I_{d}$ (both of them are caused by the film layer). This is expressed in Eq. (7), as + +![](images/002a5cc0a1239822a6327c6682300817bbe04a9ed690eea61b885362c268ca25.jpg) + +$$ +I _ {m} = I - I _ {h} - I _ {d}, \tag {7} +$$ + +where - denotes the decoupling operator. Fig. 5 visualizes these two components for decoupling in our FR task. + +Based on this model, our whole framework is based on an end-to-end reconstruction network for decoupling these two parts in Sec. 4.3. Before that, to support the network for decoupling $I_{h}$ , we estimate a polarized prior for locating the highlight regions in Sec. 4.2. + +# 4.2. Estimating a Polarized Prior for Locating $I_{h}$ + +To decouple the specular reflection components, it is better to locate the highlight regions on the surface of the wrinkle film, which provides a prior to facilitate the decoupling network. However, these regions are hard to predict since images are captured in variable scenarios. To this end, we introduce the polarization information for this problem. + +Based on Fresnel's theory [35], the specular reflection component of optically active materials is an elliptically polarized light, which changes under different angles of polarization orientation, while the rest of the components remain almost constant. It can be employed in estimating $I_{h}$ , which is a specular reflection component. Thus, we propose a polarized prior $P$ , which is represented as the optimized $I$ with the minimized $I_{h}$ , as shown in Eq. (8). The difference between $P$ and the input $I$ indicates the regions of $I_{h}$ . + +$$ +P = I _ {m} + I _ {d} + \min I _ {h}. \tag {8} +$$ + +Eq. (8), i.e., the polarized version of Eq. (6), can be acquired with Malus's Law [16] and the elliptical polarization model in Sec. 2.1. We use a pair of orthogonal maximum and minimum components and the angle variable + +![](images/810477355b9470e439b88bff24bf1db30f8f03685f4cb29fde60ccb69a1ae466.jpg) +Figure 6. Overall framework. The polarized images, AoP and DoP are fed into Angle Estimation Net (A-Net), denoted as $f_{A}$ , for estimating the angle, $A$ . Subsequently, the Polarization-based Location Model (PLM), represented as $I_{p}$ , takes $A$ as input to estimate the image prior, $P$ . This prior provides important highlight location information for the reconstruction network. Finally, the reconstruction network (R-Net) is trained to restore the original diffuse reflection in industrial materials. +Figure 7. Location of specular highlight. The $P$ is the polarized prior. We can calculate the location of highlight by $I_h - \min I_h$ . $\theta \in [0,2\pi)$ to rewrite Eq. (8) as + +![](images/5ea23c43b27475edfdded65597cd770453463193854a6b5c1ccecac7a0e599bc.jpg) + +![](images/fb1c65dfb556670d57181ce1329c6964f0ff5aab1d1643e35999abbc71be239c.jpg) + +$$ +I _ {h} = I _ {p} (\theta) = I _ {\max } \cos^ {2} \theta + I _ {\min } \sin^ {2} \theta , \tag {9} +$$ + +where $I_{p}(\theta)$ is the Polarization-based Location Model to describe the polarized light in the angle of $\theta$ , $I_{max}$ and $I_{min}$ is a pair of orthogonal maximum and minimum components in Fig. 3. Given the input data $\{I_{input}^{0}, I_{input}^{45}, I_{input}^{90}, I_{input}^{135}\}$ , $I_{max}$ and $I_{min}$ can be computed by the Stokes parameters [3], from Eq. (10) and Eq. (11). + +$$ +\begin{array}{l} I _ {m a x} = S _ {0} + \frac {\sqrt {S _ {1} ^ {2} + S _ {2} ^ {2}}}{2}, I _ {m i n} = S _ {0} - \frac {\sqrt {S _ {1} ^ {2} + S _ {2} ^ {2}}}{2}, (10) \\ S _ {0} = E _ {x 0} ^ {2} - E _ {y 0} ^ {2} = I _ {\text {i n p u t}} ^ {0} + I _ {\text {i n p u t}} ^ {9 0}, \\ S _ {1} = E _ {x 0} ^ {2} - E _ {y 0} ^ {2} = I _ {\text {i n p u t}} ^ {0} - I _ {\text {i n p u t}} ^ {9 0}, (11) \\ S _ {2} = E _ {a 0} ^ {2} - E _ {b 0} ^ {2} = I _ {\text {i n p u t}} ^ {4 5} - I _ {\text {i n p u t}} ^ {1 3 5}, \\ \end{array} +$$ + +where $(a,b)$ is the Cartesian basis rotated by $45^{\circ}$ in the space of $(x,y)$ , and $E_{a0}^{2}$ as well as $E_{b0}^{2}$ are the field strengths under this basis. + +Since $I_{h}$ is the only polarized component that is determined by $\theta$ , $P$ in Eq. (8) can also be formulated as Eq. (12). + +$$ +\begin{array}{l} P = I _ {m} + I _ {d} + \min I _ {h} \\ = I _ {m} + I _ {d} + \min _ {\theta} I _ {p} (\theta) \tag {12} \\ = I _ {m} + I _ {d} + \min _ {\theta} \left(I _ {m a x} \cos^ {2} \theta + I _ {m i n} \sin^ {2} \theta\right). \\ \end{array} +$$ + +Different pixels in one image correspond to varying optimized values for $\theta$ . Thus, we estimate pixel-wise $\theta$ with a learning-based network, obtaining the angle map $A$ . The input includes images with polarization information, i.e., $I_0$ , $I_{45}$ , $I_{90}$ , and $I_{135}$ . In addition, our input also includes two essential physics statistics, angle of polarization (AoP) and degree of polarization (DoP) [17]. The AoP provides information about the object's surface normal, which helps to analyze the difference in the surface structure between the object and film. The DoP offers information on the intensity of polarized light, so it can facilitate the network to utilize the polarized light accurately. Both of them can promote the model to learn the appropriate angle better. Eq. (13) describes this procedure. + +$A = f_{A}(I_{input}^{0}\oplus I_{input}^{45}\oplus I_{input}^{90}\oplus I_{input}^{135}\oplus S_{AoP}\oplus S_{DoP})$ (13) where, $A\in \mathbb{R}^{h\times w\times 1}$ is the pixel-wise angle map, $S_{AoP}\in$ $\mathbb{R}^{h\times w\times 1}$ and $S_{DoP}\in \mathbb{R}^{h\times w\times 1}$ indicate the AoP and DoP map respectively, $\oplus$ is the concatenation operator, and $f_{A}(\cdot)$ is angle estimation network. The network structure employs a lightweight Residual Dense Network [43] with a large perception field to capture more global information. + +After obtaining the angle map $A$ , we can get the prior with minimized $I_h$ by Eq. (14). + +$$ +P = I _ {m} + I _ {d} + I _ {\max } \cos^ {2} A + I _ {\min } \sin^ {2} A, \tag {14} +$$ + +where $P \in \mathbb{R}^{h \times w \times 1}$ . Fig. 7 visualize the Prior, $P$ , and the location of $I_h$ (highlighted). We can accurately estimate the location of the specular highlight. + +# 4.3. Reconstructing $I_{m}$ with a Prior + +In this section, we set a reconstruction network $f_{r}$ to decouple both $I_{d}$ and $I_{h}$ , with the input of $I$ (i.e., $I_{input}^{0}, I_{input}^{45}, I_{input}^{90}$ , and $I_{input}^{135}$ ) and $P$ . The obtained prior $P$ from Sec. 4.2 can already provide the estimation of $I_{h}$ by comparing with $I$ . Thus, $f_{r}$ can be focused on the assessment of $I_{d}$ . The reconstruction network is implemented as a common Residual Dense Network [43]. The reconstruction process can be expressed as Eq. (15). + +$$ +I _ {r e c} = f _ {r} \left(I _ {i n p u t} ^ {0} \oplus I _ {i n p u t} ^ {4 5} \oplus I _ {i n p u t} ^ {9 0} \oplus I _ {i n p u t} ^ {1 3 5} \oplus P\right), \tag {15} +$$ + +where, $I_{rec} \in \mathbb{R}^{h \times w \times 1}$ is the reconstructed image. + +# 4.4. Details in Implementation + +Our framework is implemented by PyTorch, and we use Polanalyser library4 to process the polarized images. It is trained with $L1$ loss between $I_{rec}$ and $I_{gt}$ in an end-to-end manner. Besides, the learning rate is $5 \times 10^{-5}$ , and it decays to half of the original for every $2 \times 10^{4}$ iterations. + +# 5. Experiment + +In our experiment, we evaluate the performance of the proposed framework in three aspects. First, as an image reconstruction task, we conduct qualitative and quantitative evaluations with reconstruction-related metrics (e.g., + +PSNR, SSIM). Second, as an upstream task in the industry, two downstream scenarios (e.g., QR code reading, and Text OCR) are selected to evaluate the reliability of our proposed algorithm. Finally, we conduct ablation studies to analyze the roles of different components. + +# 5.1. Baselines + +There is no existing baseline for this new problem. Thus, we choose two general SOTA methods in image reconstruction, Uformer [33] and Restormer [41] to evaluate the performance. Considering the connection between the film removal and highlight removal, we also compare with two SOTA polarization and non-polarization highlight removal baselines, Polar-HR [34] and SHIQ [6], respectively. + +To make a fair comparison, we follow the same training setting in our framework and input four polarized images to reconstruct one image without wrinkled transparent film in Uformer [33], Restormer [41]. In Polar-HR [34], it is a traditional training-free model and, therefore, shares the same input and output data as our approach. Besides, in SHIQ [6], since it cannot support polarized images, we convert four polarized images to one unpolarized image. + +# 5.2. Evaluation on Reconstruction Task + +Quantitative Evaluation To measure the quantitative performance of the algorithm, we refer to commonly used metrics for Image Reconstruction: peak signal-to-noise ratio (PSNR) and structural similarity (SSIM). Also, to compare the overall performance of our dataset, we use 10-fold cross-validation during training and testing. This strategy ensures the evaluation's reliability and further proves the proposed algorithm's robustness. + +The quantitative results are shown in Table 1. In the last column of Table 1, $\mu$ is the mean value, and $\sigma$ is the variance of the 10-fold performance. These experimental results show the average PSNR is 36.48 and the average SSIM is 0.9824, and the results demonstrate the high quality of our reconstructed images. In addition, the variance of PSNR and SSIM are 0.57 and $1.23 \times 10^{-5}$ , respectively, and this proves the proposed algorithm is stable and robust. Qualitative Evaluation To evaluate the reconstruction performance of the algorithm in a qualitative way, we show some visual results. Our results are shown in Fig. 8. Although Polar-HR [34] and SHIQ [6] can remove some of the highlights, their models cannot model the film correctly and, therefore, cannot remove the film itself. Besides, it can be observed that our algorithm can reconstruct regions where text or QR codes are corrupted by highlights through polarization information, while Uformer [33] and Restormer [41] produce fake artifacts in these regions. + +# 5.3. Evaluation on Downstream Applications + +In industrial environments, it is common to use transparent films to cover products, which may negatively im + +
K1K2K3K4K5K6K7K8K9K10μ↑σ↓
SHIQ [6]PSNR23.4722.1121.9521.6921.7721.0320.8620.4621.1021.3121.580.64
SSIM0.78990.76400.74160.74390.74590.74650.74990.74120.74650.73000.74992.41 × 10-4
Polar-HR [34]PSNR23.3122.8022.1321.5821.9422.0022.0321.9922.1821.9522.190.22
SSIM0.76420.74210.72200.70990.70640.70980.71280.70170.71020.69680.71763.80 × 10-4
Uformer [33]PSNR31.8531.9531.3931.1931.8132.0431.6831.9831.8531.0131.680.11
SSIM0.95190.94560.93710.93640.94340.94210.94380.94350.94570.93630.94262.17 × 10-5
Restormer [41]PSNR34.3535.0234.4433.7134.8835.1334.3134.3334.5132.4934.320.52
SSIM0.97710.97700.97210.96780.97570.97460.97420.97410.97590.96330.97311.75 × 10-5
OursPSNR36.7637.2936.6235.1236.9337.2136.2436.6736.9435.0236.480.57
SSIM0.98520.98590.98220.97670.98450.98330.98360.98300.98500.97490.98241.23 × 10-5
+ +Table 1. Quantitative evaluation in 10-fold cross-validation. The K- $I$ indicates the ${I}_{th}$ fold. + +
Input (Intensity)SHIQ [6]Polar-HR [34]Uformer [33]Restormer [41]OursGround Truth
+ +Figure 8. Qualitative Evaluation. Compared with other baselines, our model can reconstruct more realistic details in highlight regions instead of fake artifacts. Please zoom in for more details. + +
SHIQ [6]Polar-HR [34]Uformer [33]
Read Number71718
Read Rate8.05%19.54%20.69%
Restormer [41]OursGround Truth
Read Number246387
Read Rate27.58%72.41%100%
+ +Table 2. QR code reading rate. Compared with other baselines, our approach can improve the performance of QR codes scanner in the industrial environment. + +pact the robustness of downstream algorithms. To evaluate the effectiveness of our solution in such settings, we conduct two tests on two downstream tasks: QR Code Reading and Text Optical Character Recognition (Text OCR). These tasks are particularly relevant as they require access to raw information, which provides a rigorous test of the effectiveness of our algorithms in industrial scenarios. + +QR Code Reading The read rate is a critical performance metric for manufacturing pipelines in industrial systems. In this experiment, we compare our method with other baselines in Table 2. Our upstream algorithm leads to a significant improvement in the performance of the QR code reading. The qualitative results in Fig. 9 demonstrate that our algorithm not only removes the film but also significantly + +recovers the QR code information under the film. + +Text OCR Text OCR is also an important downstream industrial task. We compared our algorithm with other baselines, as shown in Fig. 10. Our method can restore more hidden text information accurately. + +# 5.4. Ablation Study + +We conduct ablation studies, which mainly validate the effectiveness of our proposed polarization dataset and one crucial component in our framework. To ensure that the experimental settings are consistent, we perform 10-fold cross-validation for the ablation experiments as well and draw two boxplots for further analysis. + +Effectiveness of the Polarized Information To prove the effectiveness of polarized information, we eliminate all components that need polarization information, which include four polarization images. Since the Polarization-based Location Model is driven by the $I_{max}$ and $I_{min}$ , which need to be calculated with polarization images as input, this structure is also removed. Other settings remain constant. Without the support of polarized information, the quantitative performance has a considerable decrease, as shown in Fig. 11 (w/o Polarized information). Also, the performance of the network is limited by the lack of guidance + +![](images/e79188280e41b9a35a320d0737ba0e782432d516bf54db1e0ca4de9d326a7741.jpg) +Input (Intensity) + +![](images/d16e29dbd899c279f1ae0f65a9b904667fbce9544f0f88dec782272a6717b535.jpg) +SHIQ [6] + +![](images/133d392a60bb38e1fab60f492cc99d0299c0cdbe83522dd64f80efbfc8477583.jpg) +Polar-HR [34] +Ours + +![](images/a8b7364b60da3bd014d815c750ad7e5a8eda09936e67aadbfa31c359147d9713.jpg) +Uformer [33] +Figure 9. Performance of QR code reading in the industry. In the original image, the QR code scanner fails to detect QR code information. Polar-HR [34] and SHIQ [6] can only eliminate the specular reflection on the QR code, and Uformer [33] and Restormer [41] can only generate false artifacts in highlight regions. Our method can help industrial QR code scanners achieve a higher performance. + +![](images/ca3ce774cb6fd4f5f00d547c1202cf443b2d0b894a792ed36606ba8cefb1cafc.jpg) +Restormer [41] + +![](images/b01f98b199edf300963e549b0fcdb67961623bc760bf736ed2c5cd02f9f81cf8.jpg) + +![](images/c7bf6dd855f94e9eaac1c5ef1a67f3926d03b8d02d27adedc62a53577dd5fc7f.jpg) +Input (Intensity) + +![](images/966102fc145d796445257115add9d981d9fc729af79bddd6c83cfbb59b265b9e.jpg) +SHIQ [6] + +![](images/6f6abcf37dfb2890151d5ef625ab13801c89e1af844416d86804e4db52cce93c.jpg) +Polar-HR [34] + +![](images/55ea3efd740049f05ef6ea1132a58b361dbc0091f6b6b48cd0dd0b04a9acd074.jpg) +Uformer [33] +Figure 10. Performance of text OCR in the industry. Compared to other baselines, our method can reconstruct more original text information for recognition. + +![](images/e564e808a6f0093c7d875d3b89dec8d306465d1f33747ec0fb074540e1e6dec7.jpg) +Restormer [41] + +![](images/f3c7dd146dde70d980e073fbaff964a4412a7eb51946d9c073bb465f70468603.jpg) +Ours + +(A) PSNR +Figure 11. PSNR (A) and SSIM (B) in ablation study. We use two boxplots to describe the performance after $t$ -fold cross-validation. The results show that our dataset, the extracted prior, the AoP, and the DoP contribute to the framework performance improvement. +![](images/61431b6a8e4ac10e4a95a3ba00679228d7cbfaf03fb57cc4534fbc83a8fc97bc.jpg) +Ours $\mathbb{w} / \mathrm{o}$ AoP & DoP w/o Polarized Information w/o Prior + +![](images/7d7103008bd7f424141c3cc74b9edd7fa34cf800fcf2842a253fa9ea32f32c83.jpg) +(B) SSIM + +information, so it cannot remove all degradation. Besides, removing the polarization information will induce artifacts in highlight regions, as shown in Fig. 12. + +Effectiveness of AoP and DoP To prove the effectiveness of AoP and DoP, we eliminate AoP and DoP in the angle estimation network. The qualitative results presented in Fig. 13 demonstrate that AoP and DoP can help locate the highlight more significantly, and also improve overall + +![](images/2ade62687f6dc0c6517dd5a28d6647b35374ff07766ca3ce022ec103be2526ba.jpg) +Figure 12. Qualitative evaluation of w/o Polarization Information. Compared with w/o polarization information (Red), introducing polarization information avoids the generation of artifacts and reconstructs the realistic details (Green). + +![](images/e4232352b4ade2ca81c097bb3ccb5387328932e35c240fc49198bd158cd0f410.jpg) + +![](images/23b6601552e0a27e9fb9d6ed0a2e453e6c32ee122b0be7a53a2eabd516edce92.jpg) + +![](images/c39f76310bdb4d734d3ef543a878ecd5ac91585b15d56924ba789593a16875b3.jpg) + +![](images/bf36ebc847e6d2fe39d8476081a95cb29df247b57314ab6b93160fb17e9a6841.jpg) +Figure 13. Highlight location heatmap. Compared with "w/o AoP & DoP" (In Red Box), introducing AoP and DoP (In Green Box) can help the A-Net to infer more highlight regions. + +![](images/1d7abcb5bc496e57b61e24c09298aa30da34021f11e2d29a98d6c73f461f6476.jpg) + +![](images/a63ea703ce8facbcd7f5598125f23f84a4fda2b75f7e7c8980f49f3b85166e88.jpg) + +![](images/8aa2697b4681130cf29ade018d647ca48fc4cd10c100003f0c23c5c7b9aab800.jpg) + +![](images/cfb558be87ba53d9e5c92358f79efea1ff28b1c1d2a0ba0b7a52bd232056d010.jpg) +Figure 14. Qualitative Evaluation of w/o Prior. Compared with "w/o Prior" (In Red Box), our solution (In Green Box) is more effective to remove highlight and infer original information. + +![](images/1cbfe6ce20b216e7247171f0a224bc23fad73f54bddbd09048e3953436ccc463.jpg) + +![](images/835f3ba4426d781e0669176da7df08c11279228e878c26bd14c524335f08881d.jpg) + +![](images/3f840798e35ecc857c455afa381792a606457c91bb6e7f70ff40ffa44e7b98ea.jpg) + +performance in Fig. 11 (w/o AoP & DoP). + +Effectiveness of Prior To prove the effectiveness of polarized prior, we eliminate the angle estimation network and the PLM in our network while retaining only the polarized images and the reconstruction network. In this case, the network can only implicitly facilitate the polarized information in the reconstruction network. Since there is no polarized prior that indicates highlight regions, this can lead to a decrease in the performance of the network to recover highlight regions (as shown in Fig. 14), while causing overall performance to decrease in Fig. 11 (w/o Prior). + +# 6. Conclusion + +In this study, we pioneer the investigation of the Film Removal (FR) problem, aiming to eliminate the disturbances caused by wrinkled transparent films and to restore the obscured information. We propose an end-to-end framework to effectively remove all degradations caused by the film with a polarized prior to minimizing highlight. Besides, we build a practical polarized dataset containing paired data for this problem. Experiments in the industry have demonstrated the potential application. We believe that the deployment of our algorithms will considerably improve the robustness of downstream industrial recognition systems. + +Acknowledgment This work is supported by the National Natural Science Foundation of China (No. 62206068) and the Natural Science Foundation of Zhejiang Province, China under No. LD24F020002. + +# References + +[1] Gary A Atkinson. Polarized light in computer vision. In Computer Vision: A Reference Guide, pages 1005-1010. Springer, 2021. 2 +[2] Seung-Hwan Baek, Tizian Zeltner, Hyunjin Ku, Inseung Hwang, Xin Tong, Wenzel Jakob, and Min H Kim. Image-based acquisition and modeling of polarimetric reflectance. ACM TOG, 2020. 2 +[3] William S Bickel and Wilbur M Bailey. Stokes vectors, mueller matrices, and polarized scattered light. American Journal of Physics, 1985. 4, 5 +[4] DJ De Smet. Brewster's angle and optical anisotropy. American Journal of Physics, 1994. 2 +[5] Gang Fu, Qing Zhang, Qifeng Lin, Lei Zhu, and Chunxia Xiao. 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The Red box presents a challenge in industrial recognition systems, where the product information is often hidden beneath the wrinkled transparent film. The Green box is the image we expect to generate, with the film layer removed. Removing the wrinkled film makes the information on industrial material clearer. QR code recognition, in Fig. 1. Regarding the wide usage of such films in industrial scenarios, it is worth opening the research direction to remove these films from images." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 507, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 507, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 507, + 545, + 555 + ], + "type": "text", + "content": "For the first time, we address a novel problem of wrinkle transparent Film Removal (FR), which aims to remove the transparent film and reveal the hidden information, benefiting the robustness of the industrial downstream models." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 556, + 545, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 556, + 545, + 640 + ], + "spans": [ + { + "bbox": [ + 304, + 556, + 545, + 640 + ], + "type": "text", + "content": "Although some solutions have attempted to remove surface highlight [6, 31, 34], they have not accurately modeled the imaging of the wrinkled transparent film. Except for the highlight, they cannot remove the effects of other various degradations from the film, e.g., light transmittance and material texture. Therefore, they cannot remove the transparent film thoroughly." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": "In this paper, we explicitly model the imaging of wrinkled transparent film into two parts: the specular highlight " + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": " from the film, and the diffuse reflection " + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "inline_equation", + "content": "I_{md}" + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": " from the materials under the film, as shown in Fig. 2. The diffuse reflection can be influenced by the properties of the film. Thus, it is divided into the original component " + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "inline_equation", + "content": "(I_{m})" + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": " and various" + } + ] + } + ], + "index": 24 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 135, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 135, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 135, + 712 + ], + "type": "text", + "content": "*Corresponding author." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24987" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 70, + 547, + 242 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 547, + 242 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 547, + 242 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 547, + 242 + ], + "type": "image", + "image_path": "0dc39e4e71a4ee2c2532cbd38236a11e03e33e45e7bdaebaa9c6c32c4d34f9b7.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "lines": [ + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "spans": [ + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "text", + "content": "Figure 2. Wrinkled Transparent Film Model. (A) The polarized image. (B) The 3D physics model of the local region. The light is reflected through the transparent wrinkled film and captured by the polarization camera. (C) The light path diagram. Polarized cameras capture two components: Specular Reflection " + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "inline_equation", + "content": "(I_h)" + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "text", + "content": ", and Diffuse Reflection " + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "inline_equation", + "content": "(I_{md})" + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "text", + "content": ". The Original Diffuse Reflection " + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "inline_equation", + "content": "(I_m)" + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "text", + "content": " would be interfered by various degradations " + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "inline_equation", + "content": "(I_{md} - I_m)" + }, + { + "bbox": [ + 46, + 243, + 547, + 289 + ], + "type": "text", + "content": " from the film." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 290, + 288, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 290, + 288, + 327 + ], + "spans": [ + { + "bbox": [ + 46, + 290, + 288, + 327 + ], + "type": "text", + "content": "degradations " + }, + { + "bbox": [ + 46, + 290, + 288, + 327 + ], + "type": "inline_equation", + "content": "(I_{md} - I_m)" + }, + { + "bbox": [ + 46, + 290, + 288, + 327 + ], + "type": "text", + "content": ". Therefore, our objective is to decouple the specular highlight and other degradations caused by the film and reconstruct the original diffuse reflection." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 327, + 287, + 458 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 327, + 287, + 458 + ], + "spans": [ + { + "bbox": [ + 46, + 327, + 287, + 458 + ], + "type": "text", + "content": "We build an end-to-end framework for decoupling two different degradations in the Wrinkled Transparent Film Model (Fig. 2), which consists of the prior estimation and reconstruction network. We notice that specular highlight is significantly related to polarization angles, while other parts are not. Based on this observation, we use an Angle Estimation Network to learn the polar angle corresponding to the minimized specular highlight, which is driven by a Polarization-based Location Model. Images with minimized specular highlights are set as the priors for the later reconstruction network to remove all degradations." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 459, + 287, + 650 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 459, + 287, + 650 + ], + "spans": [ + { + "bbox": [ + 46, + 459, + 287, + 650 + ], + "type": "text", + "content": "There is currently no suitable dataset for the FR problem, since most of the existing datasets [5, 18, 34] are targeted towards specular reflection removal only. Also, most datasets do not consider the real industrial environment. Therefore, we build a new dataset that consists of paired images covered by the film and the uncovered ground truth in the industrial optical photography system. Moreover, it's proved that the specular highlight from the film can be effectively captured by the polarization camera [21, 34, 37], which is now cheap to be installed in industrial systems [22]. Thus, we follow the collection pipeline of existing polarization datasets [4, 9], and capture each object with four polarized images under four polar directions in one shot. It's empirically proved by our experiments that with the input of these polarization clues, networks can better locate the specular highlight and recover the hidden information under the film." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 651, + 287, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 651, + 287, + 686 + ], + "spans": [ + { + "bbox": [ + 46, + 651, + 287, + 686 + ], + "type": "text", + "content": "Extensive experiments prove that our designed network achieves SOTA performance in the FR problem. Our contributions are summarized as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 58, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 58, + 689, + 287, + 714 + ], + "type": "text", + "content": "- To the best of our knowledge, we are the first to address the new problem of Film Removal (FR), which" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 324, + 290, + 545, + 314 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 324, + 290, + 545, + 314 + ], + "spans": [ + { + "bbox": [ + 324, + 290, + 545, + 314 + ], + "type": "text", + "content": "aims to remove the whole wrinkled transparent film in industrial scenarios." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 317, + 317, + 545, + 462 + ], + "type": "list", + "angle": 0, + "index": 11, + "blocks": [ + { + "bbox": [ + 317, + 317, + 545, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 317, + 545, + 376 + ], + "spans": [ + { + "bbox": [ + 317, + 317, + 545, + 376 + ], + "type": "text", + "content": "- To solve FR, we model the wrinkled film physically and propose an end-to-end reconstruction network for FR with a learnable polarization-based prior, which helps the network locate the specular highlight reflection in the film." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 317, + 380, + 545, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 380, + 545, + 415 + ], + "spans": [ + { + "bbox": [ + 317, + 380, + 545, + 415 + ], + "type": "text", + "content": "- We also build a new practical dataset in the real industrial optical photography system, which contains various polarized image pairs with and without the film." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 317, + 416, + 545, + 462 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 416, + 545, + 462 + ], + "spans": [ + { + "bbox": [ + 317, + 416, + 545, + 462 + ], + "type": "text", + "content": "- Extensive experiments are conducted to prove the effectiveness of our dataset and method, which achieves SOTA performance in both image reconstruction and downstream industrial tasks." + } + ] + } + ], + "index": 10 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 470, + 392, + 482 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 470, + 392, + 482 + ], + "spans": [ + { + "bbox": [ + 306, + 470, + 392, + 482 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 491, + 495, + 503 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 491, + 495, + 503 + ], + "spans": [ + { + "bbox": [ + 306, + 491, + 495, + 503 + ], + "type": "text", + "content": "2.1. Polarization Model and Application" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 545, + 605 + ], + "type": "text", + "content": "Polarization refers to the property of the transverse wave oscillating in different directions. Since light is a kind of wave, this phenomenon describes the distribution of light waves in all directions [1]. Conventional cameras or human eyes are insensitive to polarization. Thus, polarization is often used as a way to supplement additional visual information. It is often used in a wide range of fields such as optics [29], materials science [27], and physics [7, 36], etc." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 605, + 545, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 677 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 677 + ], + "type": "text", + "content": "In the field of computer vision, polarization provides different angles of view, hence allowing a more efficient interpretation of complex scenes. In recent years, polarization has been widely used for complex tasks such as Integral Imaging [38], Rendering [2], 3D Shape [44], Segmentation [14], and Reflection Removal [12, 15, 34], etc." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "content": "In the real world, since natural light is mixed with multiple wavelengths, its refraction time is different when it is injected into an optically active material, thus, a phase shift" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24988" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 108, + 70, + 227, + 157 + ], + "blocks": [ + { + "bbox": [ + 108, + 70, + 227, + 157 + ], + "lines": [ + { + "bbox": [ + 108, + 70, + 227, + 157 + ], + "spans": [ + { + "bbox": [ + 108, + 70, + 227, + 157 + ], + "type": "image", + "image_path": "f54454b49740c338119b479590ccf5140f5999bf6cd38d157da72552d781ebd2.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "lines": [ + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "spans": [ + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "type": "text", + "content": "Figure 3. Model of elliptically polarized light. " + }, + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "type": "inline_equation", + "content": "E" + }, + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "type": "text", + "content": " represents polarized light at any angle, which can be calculated by this model. " + }, + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "type": "inline_equation", + "content": "I_{max}" + }, + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "type": "inline_equation", + "content": "I_{min}" + }, + { + "bbox": [ + 47, + 155, + 287, + 200 + ], + "type": "text", + "content": " are two components indicating the maximum and minimum intensity of elliptically polarized light." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "spans": [ + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "content": "occurs. A physical description of this phenomenon is elliptically polarized light (i.e., partially polarized light), as shown in Eq. (1)." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 107, + 239, + 287, + 266 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 107, + 239, + 287, + 266 + ], + "spans": [ + { + "bbox": [ + 107, + 239, + 287, + 266 + ], + "type": "interline_equation", + "content": "\\left\\{ \\begin{array}{l} E _ {x} = E _ {x 0} \\cos (\\omega t) \\\\ E _ {y} = E _ {y 0} \\cos (\\omega t - \\sigma) \\end{array} , \\right. \\tag {1}", + "image_path": "2e8d51d8914b850e0ffd3f5e2a82de25f1ad1c603bde18404790f56e7441043b.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "spans": [ + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "(x,y)" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": " is the Cartesian basis in the space of Jones vectors, " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "E_{x}" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "E_{y}" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": " is the component of the light on the basis, " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "(x,y)" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "\\omega" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": " is the frequency and " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": " is the phase difference of " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "E_{x}" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "E_{y}" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "E_{x0}" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "E_{y0}" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": " are the field strength of a pair of orthogonal waves. Eq. (1) describes the vibration of the polarized light in different angles, " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": ". Based on this model, our solution only considers a simplified situation where " + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "inline_equation", + "content": "\\sigma = 90^{\\circ}" + }, + { + "bbox": [ + 46, + 267, + 287, + 363 + ], + "type": "text", + "content": ". Eq. (1) can be simplified to Eq. (2)," + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 131, + 362, + 287, + 391 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 131, + 362, + 287, + 391 + ], + "spans": [ + { + "bbox": [ + 131, + 362, + 287, + 391 + ], + "type": "interline_equation", + "content": "\\frac {E _ {x} ^ {2}}{E _ {x 0} ^ {2}} + \\frac {E _ {y} ^ {2}}{E _ {y 0} ^ {2}} = 1. \\tag {2}", + "image_path": "9f53208029c65383758e127c2b12900d7dfd285d34317df885214a4f050e5088.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 392, + 279, + 406 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 392, + 279, + 406 + ], + "spans": [ + { + "bbox": [ + 47, + 392, + 279, + 406 + ], + "type": "text", + "content": "2.2. Specular Highlight Removal via Polarization" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 411, + 287, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 411, + 287, + 567 + ], + "spans": [ + { + "bbox": [ + 46, + 411, + 287, + 567 + ], + "type": "text", + "content": "Since the film includes unpredictable specular reflection, our task includes the procedure to remove these degradations. There have been several solutions to remove specular reflection using polarization information. Nayar et al. [21] first used polarization to determine the color of the specular component to separate the interfaces. Then, Umezama et al. [30] adopted independent component analysis to separate the diffuse and specular reflection components of surface reflection. Zhang et al. [42] considered the effect of polarization angle and attempted to get the appropriate global angle using Newton's method, but this method did not make full use of the local information. Wen et al. [34] separated specular reflection regions by using image chromaticity." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 567, + 287, + 626 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 567, + 287, + 626 + ], + "spans": [ + { + "bbox": [ + 46, + 567, + 287, + 626 + ], + "type": "text", + "content": "Although conventional methods are available for removing specular highlight reflections, they are not able to accurately model the imaging of wrinkled transparent films, and thus do not adequately address the problem of eliminating all degradations from wrinkled transparent films." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 635, + 100, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 635, + 100, + 647 + ], + "spans": [ + { + "bbox": [ + 47, + 635, + 100, + 647 + ], + "type": "text", + "content": "3. Dataset" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 653, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 287, + 714 + ], + "type": "text", + "content": "While some datasets exist for the removal of specular reflection [11, 13, 34], there is currently no dataset for film removal in the industrial environment. As shown in Fig. 2, the characteristics of the specular highlight information from the film can be effectively modeled by the polarized image." + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 307, + 70, + 545, + 213 + ], + "blocks": [ + { + "bbox": [ + 307, + 70, + 545, + 213 + ], + "lines": [ + { + "bbox": [ + 307, + 70, + 545, + 213 + ], + "spans": [ + { + "bbox": [ + 307, + 70, + 545, + 213 + ], + "type": "image", + "image_path": "1661310d5f0b9488bec08d2ee118303241d223d4ddb4bdc5c23894109197e519.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 213, + 545, + 267 + ], + "lines": [ + { + "bbox": [ + 304, + 213, + 545, + 267 + ], + "spans": [ + { + "bbox": [ + 304, + 213, + 545, + 267 + ], + "type": "text", + "content": "Figure 4. Prototype of industrial optical photography pipeline. We have built an optical pipeline for capturing the dataset in the industrial environment. As objects traverse the objective pipeline, the polarizing camera captures images continuously. Subsequently, the acquired data is sent to the monitor for pre-processing." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 269, + 545, + 354 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 269, + 545, + 354 + ], + "spans": [ + { + "bbox": [ + 304, + 269, + 545, + 354 + ], + "type": "text", + "content": "Leveraging this polarization information can significantly enhance image reconstruction. Therefore, we construct a paired dataset based on polarized images. Polarized images can capture light amplitude information from wrinkled films at different angles, and making full use of this information will significantly facilitate the decoupling of degradation information occurring from the film." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 359, + 517, + 373 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 359, + 517, + 373 + ], + "spans": [ + { + "bbox": [ + 305, + 359, + 517, + 373 + ], + "type": "text", + "content": "3.1. Industrial Optical Photography Pipeline" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 377, + 545, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 377, + 545, + 437 + ], + "spans": [ + { + "bbox": [ + 304, + 377, + 545, + 437 + ], + "type": "text", + "content": "Fig. 4 illustrates the prototype of our pipeline. Within this industrial pipeline, we maintain a consistent posture and angle for both the camera and lighting resources. The objective pipeline sequentially passes different detected objects under the camera." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 437, + 545, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 437, + 545, + 521 + ], + "spans": [ + { + "bbox": [ + 304, + 437, + 545, + 521 + ], + "type": "text", + "content": "To effectively capture optical information in multiple polarization directions within a single image, we employ the HIKROBOT MV-CH050-10UP camera1, which integrates the Sony IMX250MZR CMOS sensor2. This sensor contains four different angles of polarization " + }, + { + "bbox": [ + 304, + 437, + 545, + 521 + ], + "type": "inline_equation", + "content": "(0^{\\circ}, 45^{\\circ}, 90^{\\circ}" + }, + { + "bbox": [ + 304, + 437, + 545, + 521 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 437, + 545, + 521 + ], + "type": "inline_equation", + "content": "135^{\\circ}" + }, + { + "bbox": [ + 304, + 437, + 545, + 521 + ], + "type": "text", + "content": " as Bayer pattern, allowing us to capture four polarization angles in high definition with a single shot." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 521, + 545, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 545, + 605 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 545, + 605 + ], + "type": "text", + "content": "Finally, there is a monitor that controls the camera shutter and adjusts camera parameters. We utilize auto-exposure and auto-focus strategies to set the appropriate focal length, exposure time, and ISO for each specific scenario automatically. This is essential since the thickness and surface of the products on the industrial line may vary, requiring slight adjustments in camera parameters to ensure image quality." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 611, + 460, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 611, + 460, + 624 + ], + "spans": [ + { + "bbox": [ + 306, + 611, + 460, + 624 + ], + "type": "text", + "content": "3.2. Capturing Polarized Images" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 629, + 545, + 667 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 667 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 667 + ], + "type": "text", + "content": "When capturing polarized images, the imaging system initially captures an image of the ground truth uncovered by the film, " + }, + { + "bbox": [ + 304, + 629, + 545, + 667 + ], + "type": "inline_equation", + "content": "I_{gt}^{raw}" + }, + { + "bbox": [ + 304, + 629, + 545, + 667 + ], + "type": "text", + "content": ". Subsequently, with the complex transpar" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 306, + 673, + 545, + 693 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 673, + 545, + 693 + ], + "spans": [ + { + "bbox": [ + 306, + 673, + 545, + 693 + ], + "type": "text", + "content": "1https://www.hikrobotics.com/cn/machinevision/productdetail?id=3886" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 693, + 545, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 545, + 712 + ], + "type": "text", + "content": "2https://www.sony-semicon.com/en/products/is/industry/polarization.html" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24989" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 99 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 99 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 99 + ], + "type": "text", + "content": "ent film placed over the ground truth, we capture the image " + }, + { + "bbox": [ + 47, + 72, + 287, + 99 + ], + "type": "inline_equation", + "content": "I_{input}^{raw}" + }, + { + "bbox": [ + 47, + 72, + 287, + 99 + ], + "type": "text", + "content": " that needs to be recovered." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 102, + 214, + 114 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 102, + 214, + 114 + ], + "spans": [ + { + "bbox": [ + 47, + 102, + 214, + 114 + ], + "type": "text", + "content": "3.3. Data Diversity and Robustness" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 119, + 287, + 215 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 119, + 287, + 215 + ], + "spans": [ + { + "bbox": [ + 46, + 119, + 287, + 215 + ], + "type": "text", + "content": "To build a diverse and robust dataset, we follow the rules in industrial manufacturing. As depicted in Fig. 4, the current industrial pipeline includes 315 dynamic industrial scenarios, which can be categorized into three types: QR codes, text, and products. To enhance the diversity, we have different films with diverse material properties, coverage areas, film thicknesses, and levels of wrinkling. The film exhibits significant variability across each scenario." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 215, + 287, + 275 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 215, + 287, + 275 + ], + "spans": [ + { + "bbox": [ + 46, + 215, + 287, + 275 + ], + "type": "text", + "content": "On the other hand, to ensure the stability of the industrial imaging pipeline, we maintained a consistent intensity level for the industrial light source and fixed the distance between the camera and the object flow. This helps to minimize the influence of errors external to the industrial system." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 280, + 135, + 293 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 280, + 135, + 293 + ], + "spans": [ + { + "bbox": [ + 47, + 280, + 135, + 293 + ], + "type": "text", + "content": "3.4. Prepossessing" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 298, + 287, + 380 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 298, + 287, + 380 + ], + "spans": [ + { + "bbox": [ + 46, + 298, + 287, + 380 + ], + "type": "text", + "content": "Each pixel of the image captured by the polarization sensor is represented by four-pixel dots, each corresponding to the intensity of light at four distinct polarization angles. We first need to decompose it into 4 subgraphs with different angles, and then we restore it to its original resolution using edge-aware residual interpolation (EARI) demosaicking [20]. This process is described in Eq. (3)." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 102, + 380, + 287, + 399 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 102, + 380, + 287, + 399 + ], + "spans": [ + { + "bbox": [ + 102, + 380, + 287, + 399 + ], + "type": "interline_equation", + "content": "\\left\\{I _ {g t} ^ {0}, I _ {g t} ^ {4 5}, I _ {g t} ^ {9 0}, I _ {g t} ^ {1 3 5} \\right\\} = M \\left(F _ {d} \\left(I _ {g t} ^ {\\text {r a w}}\\right)\\right), \\tag {3}", + "image_path": "00312cfc845d0330e5586edc46384ddc917ddc3d75be78a3bde5937b52bc2d90.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 63, + 396, + 286, + 411 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 63, + 396, + 286, + 411 + ], + "spans": [ + { + "bbox": [ + 63, + 396, + 286, + 411 + ], + "type": "interline_equation", + "content": "\\left\\{I _ {i n p u t} ^ {0}, I _ {i n p u t} ^ {4 5}, I _ {i n p u t} ^ {9 0}, I _ {i n p u t} ^ {1 3 5} \\right\\} = M \\left(F _ {d} \\left(I _ {i n p u t} ^ {r a w}\\right)\\right),", + "image_path": "220bf8c85359daed048b544ef037de0eaf8278a03f7bda3ce05d36661b60eba3.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "spans": [ + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "inline_equation", + "content": "F_{d}(\\cdot)" + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "text", + "content": " is the decomposing operator, " + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "inline_equation", + "content": "M(\\cdot)" + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "text", + "content": " is EARI demosaicking. Taking " + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "inline_equation", + "content": "I_{gt}^{raw}" + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "inline_equation", + "content": "I_{input}^{raw}" + }, + { + "bbox": [ + 47, + 411, + 286, + 446 + ], + "type": "text", + "content": " as inputs, we obtain full-resolution polarized images with four different angles." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 447, + 287, + 517 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 447, + 287, + 517 + ], + "spans": [ + { + "bbox": [ + 47, + 447, + 287, + 517 + ], + "type": "text", + "content": "To generate the ground truth image, we follow the standard procedure from the polarized image processing library, polanalyser3. Firstly, we introduce stokes parameters [3]. According to this physical model, the first stoke parameter " + }, + { + "bbox": [ + 47, + 447, + 287, + 517 + ], + "type": "inline_equation", + "content": "S_{0}" + }, + { + "bbox": [ + 47, + 447, + 287, + 517 + ], + "type": "text", + "content": " describes the total intensity of the optical beam, and it can be calculated by Eq. (4)." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 107, + 517, + 287, + 531 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 107, + 517, + 287, + 531 + ], + "spans": [ + { + "bbox": [ + 107, + 517, + 287, + 531 + ], + "type": "interline_equation", + "content": "S _ {0} = E _ {x 0} ^ {2} + E _ {y 0} ^ {2} = I ^ {x} + I ^ {y}, \\tag {4}", + "image_path": "4b55392d58bb0d253c01a5d01887ced008c4de5acc4012a9fd9846d962ca6dec.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "spans": [ + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "inline_equation", + "content": "I^x \\perp I^y" + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "inline_equation", + "content": "E_{x0}^2" + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "inline_equation", + "content": "E_{y0}^2" + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "text", + "content": " are the field strength of a pair of orthogonal waves in Fig. 3, which can be calculated by a pair of orthogonal polarization components, " + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "inline_equation", + "content": "I^x" + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "inline_equation", + "content": "I^y" + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "text", + "content": ". Subsequently, we can calculate one ground truth " + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "inline_equation", + "content": "I_{gt}" + }, + { + "bbox": [ + 47, + 531, + 287, + 581 + ], + "type": "text", + "content": " as" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 75, + 580, + 287, + 606 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 75, + 580, + 287, + 606 + ], + "spans": [ + { + "bbox": [ + 75, + 580, + 287, + 606 + ], + "type": "interline_equation", + "content": "I _ {g t} = G \\left(\\frac {S 0}{2}\\right) = \\left(\\frac {I _ {g t} ^ {0} + I _ {g t} ^ {4 5} + I _ {g t} ^ {9 0} + I _ {g t} ^ {1 3 5}}{4}\\right) ^ {\\frac {1}{\\gamma}}, \\tag {5}", + "image_path": "68eb68d550bb7aa9f36b482d290972f4246ec2f5f4f9afefbd2a16c3d8679186.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 47, + 604, + 286, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 604, + 286, + 628 + ], + "spans": [ + { + "bbox": [ + 47, + 604, + 286, + 628 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 604, + 286, + 628 + ], + "type": "inline_equation", + "content": "G(\\cdot)" + }, + { + "bbox": [ + 47, + 604, + 286, + 628 + ], + "type": "text", + "content": " is a gamma correction function, and we empirically set the gamma value, " + }, + { + "bbox": [ + 47, + 604, + 286, + 628 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 47, + 604, + 286, + 628 + ], + "type": "text", + "content": ", to 2.2." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 632, + 168, + 645 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 632, + 168, + 645 + ], + "spans": [ + { + "bbox": [ + 47, + 632, + 168, + 645 + ], + "type": "text", + "content": "3.5. Training and Testing" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 47, + 648, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 648, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 47, + 648, + 287, + 696 + ], + "type": "text", + "content": "During training, our network mixed all the scenes for training, and the final network is applicable to data from all scenarios. Besides, to ensure the robustness and generalization of our dataset, we adopt 10-fold cross-validation [23]" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 326, + 71, + 408, + 81 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 326, + 71, + 408, + 81 + ], + "spans": [ + { + "bbox": [ + 326, + 71, + 408, + 81 + ], + "type": "text", + "content": "Specular Highlight, " + }, + { + "bbox": [ + 326, + 71, + 408, + 81 + ], + "type": "inline_equation", + "content": "I_{h}" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 441, + 71, + 525, + 81 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 441, + 71, + 525, + 81 + ], + "spans": [ + { + "bbox": [ + 441, + 71, + 525, + 81 + ], + "type": "text", + "content": "Other Degradations, " + }, + { + "bbox": [ + 441, + 71, + 525, + 81 + ], + "type": "inline_equation", + "content": "I_{d}" + } + ] + } + ], + "index": 17 + }, + { + "type": "image", + "bbox": [ + 310, + 82, + 545, + 142 + ], + "blocks": [ + { + "bbox": [ + 310, + 82, + 545, + 142 + ], + "lines": [ + { + "bbox": [ + 310, + 82, + 545, + 142 + ], + "spans": [ + { + "bbox": [ + 310, + 82, + 545, + 142 + ], + "type": "image", + "image_path": "22e59a4aa7140b981bd111a9de60b95dcf71decb4ceb64c0b1636fba9e9479ae.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 142, + 545, + 173 + ], + "lines": [ + { + "bbox": [ + 306, + 142, + 545, + 173 + ], + "spans": [ + { + "bbox": [ + 306, + 142, + 545, + 173 + ], + "type": "text", + "content": "Figure 5. Two Decoupling Components. Specular highlight, " + }, + { + "bbox": [ + 306, + 142, + 545, + 173 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 306, + 142, + 545, + 173 + ], + "type": "text", + "content": " and other degradations, " + }, + { + "bbox": [ + 306, + 142, + 545, + 173 + ], + "type": "inline_equation", + "content": "I_{d}" + }, + { + "bbox": [ + 306, + 142, + 545, + 173 + ], + "type": "text", + "content": ". The Red box shows the degradations, the Green box is the Ground Truth." + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 174, + 545, + 221 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 174, + 545, + 221 + ], + "spans": [ + { + "bbox": [ + 306, + 174, + 545, + 221 + ], + "type": "text", + "content": "to evaluate the results. The dataset is divided into ten parts, and nine of them are used as training data and one as test data in turn. Each test will yield a corresponding accuracy rate, which is then averaged as the final accuracy." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 228, + 361, + 239 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 228, + 361, + 239 + ], + "spans": [ + { + "bbox": [ + 306, + 228, + 361, + 239 + ], + "type": "text", + "content": "4. Method" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 305, + 243, + 545, + 338 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 243, + 545, + 338 + ], + "spans": [ + { + "bbox": [ + 305, + 243, + 545, + 338 + ], + "type": "text", + "content": "Although some conventional methods have used polarization information to remove surface specular highlight reflection, they assume the light intensity as a binary composition [34], i.e., transmission and reflection. However, the light intensity from the wrinkled film is more complex, which is not only influenced by film surface highlight but also mixed with various degradations, e.g., light transmittance and material texture." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 305, + 338, + 545, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 338, + 545, + 422 + ], + "spans": [ + { + "bbox": [ + 305, + 338, + 545, + 422 + ], + "type": "text", + "content": "In this section, we first model the wrinkled transparent film physically in Fig. 2, which is our method's motivation. Then, we use an end-to-end network for reconstructing the original information in Fig. 6. Besides, since the highlight region is more tricky to recover, we build a polarization-based prior into the end-to-end framework to assist in locating highlight regions." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 306, + 426, + 526, + 439 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 426, + 526, + 439 + ], + "spans": [ + { + "bbox": [ + 306, + 426, + 526, + 439 + ], + "type": "text", + "content": "4.1. Modelling the Wrinkled Transparent Film" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 305, + 442, + 545, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 442, + 545, + 548 + ], + "spans": [ + { + "bbox": [ + 305, + 442, + 545, + 548 + ], + "type": "text", + "content": "Based on the Industrial Optical Photography System in Sec. 3.1, the light intensity for materials covered with the wrinkled transparent film will be captured by the polarized camera in Fig. 2(A)(B). The captured light intensity consists of two parts, i.e., the specular highlight reflection of the film's polarized regions [19, 26], the diffuse reflection from the materials under the film, which could be influenced by light transmittance, the texture of the film in Fig. 2(C). Such a composition is written in Eq. (6)." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 361, + 548, + 544, + 559 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 361, + 548, + 544, + 559 + ], + "spans": [ + { + "bbox": [ + 361, + 548, + 544, + 559 + ], + "type": "interline_equation", + "content": "I = I _ {m d} + I _ {h} \\stackrel {\\prime} {=} I _ {m} ^ {\\prime} + I _ {d} + I _ {h}, \\tag {6}", + "image_path": "6ec3d76f9393a2316ce5d2b20c2006a7b2740ffddf7892e116819de7fa803529.jpg" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "spans": [ + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "+" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": " denotes the linear superposition of different light components, " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": " is the light intensity captured by the camera, " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "I_{md}" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": " is the diffuse reflection component of the material through various film degradations, " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "I_h" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": " is the specular reflection part from the film's highlighted regions. Then, " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "I_{md}" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": " can be decoupled to two parts, " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "I_m" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "I_d" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "I_m" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": " is the original diffuse reflection component of the material and " + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "inline_equation", + "content": "I_d" + }, + { + "bbox": [ + 305, + 559, + 545, + 665 + ], + "type": "text", + "content": " is caused by other various degradations through film. In Fig. 2(C), the optical path diagram illustrates this process." + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "content": "Based on Eq. (6), the FR task can be implemented by retaining the information of " + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "inline_equation", + "content": "I_{m}" + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "content": " and decoupling " + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "inline_equation", + "content": "I_{d}" + }, + { + "bbox": [ + 305, + 665, + 545, + 713 + ], + "type": "text", + "content": " (both of them are caused by the film layer). This is expressed in Eq. (7), as" + } + ] + } + ], + "index": 28 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 57, + 702, + 265, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 702, + 265, + 712 + ], + "spans": [ + { + "bbox": [ + 57, + 702, + 265, + 712 + ], + "type": "text", + "content": "3https://github.com/elerac/polanalyser/wiki" + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "24990" + } + ] + } + ], + "index": 30 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 70, + 547, + 305 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 547, + 305 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 547, + 305 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 547, + 305 + ], + "type": "image", + "image_path": "002a5cc0a1239822a6327c6682300817bbe04a9ed690eea61b885362c268ca25.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 127, + 356, + 286, + 368 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 127, + 356, + 286, + 368 + ], + "spans": [ + { + "bbox": [ + 127, + 356, + 286, + 368 + ], + "type": "interline_equation", + "content": "I _ {m} = I - I _ {h} - I _ {d}, \\tag {7}", + "image_path": "d117125168052ad120e726dface329e49140433d3ab8d4011c68a057362c5e03.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 368, + 287, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 368, + 287, + 392 + ], + "spans": [ + { + "bbox": [ + 46, + 368, + 287, + 392 + ], + "type": "text", + "content": "where - denotes the decoupling operator. Fig. 5 visualizes these two components for decoupling in our FR task." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 392, + 287, + 452 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 392, + 287, + 452 + ], + "spans": [ + { + "bbox": [ + 46, + 392, + 287, + 452 + ], + "type": "text", + "content": "Based on this model, our whole framework is based on an end-to-end reconstruction network for decoupling these two parts in Sec. 4.3. Before that, to support the network for decoupling " + }, + { + "bbox": [ + 46, + 392, + 287, + 452 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 46, + 392, + 287, + 452 + ], + "type": "text", + "content": ", we estimate a polarized prior for locating the highlight regions in Sec. 4.2." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 456, + 276, + 468 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 456, + 276, + 468 + ], + "spans": [ + { + "bbox": [ + 47, + 456, + 276, + 468 + ], + "type": "text", + "content": "4.2. Estimating a Polarized Prior for Locating " + }, + { + "bbox": [ + 47, + 456, + 276, + 468 + ], + "type": "inline_equation", + "content": "I_{h}" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 472, + 287, + 543 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 472, + 287, + 543 + ], + "spans": [ + { + "bbox": [ + 46, + 472, + 287, + 543 + ], + "type": "text", + "content": "To decouple the specular reflection components, it is better to locate the highlight regions on the surface of the wrinkle film, which provides a prior to facilitate the decoupling network. However, these regions are hard to predict since images are captured in variable scenarios. To this end, we introduce the polarization information for this problem." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "content": "Based on Fresnel's theory [35], the specular reflection component of optically active materials is an elliptically polarized light, which changes under different angles of polarization orientation, while the rest of the components remain almost constant. It can be employed in estimating " + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "content": ", which is a specular reflection component. Thus, we propose a polarized prior " + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "content": ", which is represented as the optimized " + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "content": " with the minimized " + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "content": ", as shown in Eq. (8). The difference between " + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "content": " and the input " + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "content": " indicates the regions of " + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 46, + 544, + 287, + 651 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 116, + 652, + 286, + 664 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 116, + 652, + 286, + 664 + ], + "spans": [ + { + "bbox": [ + 116, + 652, + 286, + 664 + ], + "type": "interline_equation", + "content": "P = I _ {m} + I _ {d} + \\min I _ {h}. \\tag {8}", + "image_path": "24aadfba2d4621dbbaa5f26843b822c8d1220a31b6814e96ff0a183cd6daf9c9.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 666, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 666, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 666, + 287, + 713 + ], + "type": "text", + "content": "Eq. (8), i.e., the polarized version of Eq. (6), can be acquired with Malus's Law [16] and the elliptical polarization model in Sec. 2.1. We use a pair of orthogonal maximum and minimum components and the angle variable" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 310, + 352, + 387, + 423 + ], + "blocks": [ + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "lines": [ + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "spans": [ + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "text", + "content": "Figure 6. Overall framework. The polarized images, AoP and DoP are fed into Angle Estimation Net (A-Net), denoted as " + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "inline_equation", + "content": "f_{A}" + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "text", + "content": ", for estimating the angle, " + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "inline_equation", + "content": "A" + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "text", + "content": ". Subsequently, the Polarization-based Location Model (PLM), represented as " + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "inline_equation", + "content": "I_{p}" + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "text", + "content": ", takes " + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "inline_equation", + "content": "A" + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "text", + "content": " as input to estimate the image prior, " + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 46, + 308, + 546, + 353 + ], + "type": "text", + "content": ". This prior provides important highlight location information for the reconstruction network. Finally, the reconstruction network (R-Net) is trained to restore the original diffuse reflection in industrial materials." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 310, + 352, + 387, + 423 + ], + "lines": [ + { + "bbox": [ + 310, + 352, + 387, + 423 + ], + "spans": [ + { + "bbox": [ + 310, + 352, + 387, + 423 + ], + "type": "image", + "image_path": "810477355b9470e439b88bff24bf1db30f8f03685f4cb29fde60ccb69a1ae466.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "lines": [ + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "spans": [ + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "type": "text", + "content": "Figure 7. Location of specular highlight. The " + }, + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "type": "text", + "content": " is the polarized prior. We can calculate the location of highlight by " + }, + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "type": "inline_equation", + "content": "I_h - \\min I_h" + }, + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "type": "inline_equation", + "content": "\\theta \\in [0,2\\pi)" + }, + { + "bbox": [ + 305, + 423, + 545, + 459 + ], + "type": "text", + "content": " to rewrite Eq. (8) as" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 389, + 350, + 465, + 423 + ], + "blocks": [ + { + "bbox": [ + 389, + 350, + 465, + 423 + ], + "lines": [ + { + "bbox": [ + 389, + 350, + 465, + 423 + ], + "spans": [ + { + "bbox": [ + 389, + 350, + 465, + 423 + ], + "type": "image", + "image_path": "5ea23c43b27475edfdded65597cd770453463193854a6b5c1ccecac7a0e599bc.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 468, + 351, + 543, + 423 + ], + "blocks": [ + { + "bbox": [ + 468, + 351, + 543, + 423 + ], + "lines": [ + { + "bbox": [ + 468, + 351, + 543, + 423 + ], + "spans": [ + { + "bbox": [ + 468, + 351, + 543, + 423 + ], + "type": "image", + "image_path": "fb1c65dfb556670d57181ce1329c6964f0ff5aab1d1643e35999abbc71be239c.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "bbox": [ + 342, + 459, + 545, + 472 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 342, + 459, + 545, + 472 + ], + "spans": [ + { + "bbox": [ + 342, + 459, + 545, + 472 + ], + "type": "interline_equation", + "content": "I _ {h} = I _ {p} (\\theta) = I _ {\\max } \\cos^ {2} \\theta + I _ {\\min } \\sin^ {2} \\theta , \\tag {9}", + "image_path": "34779830f62af912621f2a55f07bd3756d2db816c041c9073a4430586425d406.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "spans": [ + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "inline_equation", + "content": "I_{p}(\\theta)" + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "content": " is the Polarization-based Location Model to describe the polarized light in the angle of " + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "inline_equation", + "content": "I_{max}" + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "inline_equation", + "content": "I_{min}" + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "content": " is a pair of orthogonal maximum and minimum components in Fig. 3. Given the input data " + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "inline_equation", + "content": "\\{I_{input}^{0}, I_{input}^{45}, I_{input}^{90}, I_{input}^{135}\\}" + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "inline_equation", + "content": "I_{max}" + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "inline_equation", + "content": "I_{min}" + }, + { + "bbox": [ + 305, + 472, + 545, + 543 + ], + "type": "text", + "content": " can be computed by the Stokes parameters [3], from Eq. (10) and Eq. (11)." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 318, + 542, + 545, + 606 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 542, + 545, + 606 + ], + "spans": [ + { + "bbox": [ + 318, + 542, + 545, + 606 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} I _ {m a x} = S _ {0} + \\frac {\\sqrt {S _ {1} ^ {2} + S _ {2} ^ {2}}}{2}, I _ {m i n} = S _ {0} - \\frac {\\sqrt {S _ {1} ^ {2} + S _ {2} ^ {2}}}{2}, (10) \\\\ S _ {0} = E _ {x 0} ^ {2} - E _ {y 0} ^ {2} = I _ {\\text {i n p u t}} ^ {0} + I _ {\\text {i n p u t}} ^ {9 0}, \\\\ S _ {1} = E _ {x 0} ^ {2} - E _ {y 0} ^ {2} = I _ {\\text {i n p u t}} ^ {0} - I _ {\\text {i n p u t}} ^ {9 0}, (11) \\\\ S _ {2} = E _ {a 0} ^ {2} - E _ {b 0} ^ {2} = I _ {\\text {i n p u t}} ^ {4 5} - I _ {\\text {i n p u t}} ^ {1 3 5}, \\\\ \\end{array}", + "image_path": "eb7b2ba8d062869889369666fd7cc9fbe22a97833bb7aea74003364574888d29.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "inline_equation", + "content": "(a,b)" + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "text", + "content": " is the Cartesian basis rotated by " + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "inline_equation", + "content": "45^{\\circ}" + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "text", + "content": " in the space of " + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "inline_equation", + "content": "(x,y)" + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "inline_equation", + "content": "E_{a0}^{2}" + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "text", + "content": " as well as " + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "inline_equation", + "content": "E_{b0}^{2}" + }, + { + "bbox": [ + 304, + 605, + 545, + 639 + ], + "type": "text", + "content": " are the field strengths under this basis." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "spans": [ + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "type": "text", + "content": "Since " + }, + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "type": "text", + "content": " is the only polarized component that is determined by " + }, + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 304, + 641, + 545, + 664 + ], + "type": "text", + "content": " in Eq. (8) can also be formulated as Eq. (12)." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 318, + 664, + 545, + 715 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 664, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 318, + 664, + 545, + 715 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} P = I _ {m} + I _ {d} + \\min I _ {h} \\\\ = I _ {m} + I _ {d} + \\min _ {\\theta} I _ {p} (\\theta) \\tag {12} \\\\ = I _ {m} + I _ {d} + \\min _ {\\theta} \\left(I _ {m a x} \\cos^ {2} \\theta + I _ {m i n} \\sin^ {2} \\theta\\right). \\\\ \\end{array}", + "image_path": "5f837973c4fd0426725b0e31dcd3ec304fcba63fd4812900f085470d2cf7b1e7.jpg" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24991" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": "Different pixels in one image correspond to varying optimized values for " + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": ". Thus, we estimate pixel-wise " + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": " with a learning-based network, obtaining the angle map " + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "inline_equation", + "content": "A" + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": ". The input includes images with polarization information, i.e., " + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "inline_equation", + "content": "I_0" + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "inline_equation", + "content": "I_{45}" + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "inline_equation", + "content": "I_{90}" + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "inline_equation", + "content": "I_{135}" + }, + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": ". In addition, our input also includes two essential physics statistics, angle of polarization (AoP) and degree of polarization (DoP) [17]. The AoP provides information about the object's surface normal, which helps to analyze the difference in the surface structure between the object and film. The DoP offers information on the intensity of polarized light, so it can facilitate the network to utilize the polarized light accurately. Both of them can promote the model to learn the appropriate angle better. Eq. (13) describes this procedure." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "spans": [ + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "inline_equation", + "content": "A = f_{A}(I_{input}^{0}\\oplus I_{input}^{45}\\oplus I_{input}^{90}\\oplus I_{input}^{135}\\oplus S_{AoP}\\oplus S_{DoP})" + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "text", + "content": " (13) where, " + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "inline_equation", + "content": "A\\in \\mathbb{R}^{h\\times w\\times 1}" + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "text", + "content": " is the pixel-wise angle map, " + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "inline_equation", + "content": "S_{AoP}\\in" + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^{h\\times w\\times 1}" + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "inline_equation", + "content": "S_{DoP}\\in \\mathbb{R}^{h\\times w\\times 1}" + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "text", + "content": " indicate the AoP and DoP map respectively, " + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "inline_equation", + "content": "\\oplus" + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "text", + "content": " is the concatenation operator, and " + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "inline_equation", + "content": "f_{A}(\\cdot)" + }, + { + "bbox": [ + 46, + 240, + 287, + 326 + ], + "type": "text", + "content": " is angle estimation network. The network structure employs a lightweight Residual Dense Network [43] with a large perception field to capture more global information." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 326, + 287, + 349 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 326, + 287, + 349 + ], + "spans": [ + { + "bbox": [ + 47, + 326, + 287, + 349 + ], + "type": "text", + "content": "After obtaining the angle map " + }, + { + "bbox": [ + 47, + 326, + 287, + 349 + ], + "type": "inline_equation", + "content": "A" + }, + { + "bbox": [ + 47, + 326, + 287, + 349 + ], + "type": "text", + "content": ", we can get the prior with minimized " + }, + { + "bbox": [ + 47, + 326, + 287, + 349 + ], + "type": "inline_equation", + "content": "I_h" + }, + { + "bbox": [ + 47, + 326, + 287, + 349 + ], + "type": "text", + "content": " by Eq. (14)." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 67, + 349, + 287, + 361 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 349, + 287, + 361 + ], + "spans": [ + { + "bbox": [ + 67, + 349, + 287, + 361 + ], + "type": "interline_equation", + "content": "P = I _ {m} + I _ {d} + I _ {\\max } \\cos^ {2} A + I _ {\\min } \\sin^ {2} A, \\tag {14}", + "image_path": "540bea72f68f18a5f9fc37e28bd125fa257f65eb2c9cee1da7796f9908288171.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "spans": [ + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "type": "inline_equation", + "content": "P \\in \\mathbb{R}^{h \\times w \\times 1}" + }, + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "type": "text", + "content": ". Fig. 7 visualize the Prior, " + }, + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "type": "text", + "content": ", and the location of " + }, + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "type": "inline_equation", + "content": "I_h" + }, + { + "bbox": [ + 46, + 361, + 287, + 399 + ], + "type": "text", + "content": " (highlighted). We can accurately estimate the location of the specular highlight." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 403, + 216, + 417 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 403, + 216, + 417 + ], + "spans": [ + { + "bbox": [ + 47, + 403, + 216, + 417 + ], + "type": "text", + "content": "4.3. Reconstructing " + }, + { + "bbox": [ + 47, + 403, + 216, + 417 + ], + "type": "inline_equation", + "content": "I_{m}" + }, + { + "bbox": [ + 47, + 403, + 216, + 417 + ], + "type": "text", + "content": " with a Prior" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "spans": [ + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": "In this section, we set a reconstruction network " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "f_{r}" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": " to decouple both " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "I_{d}" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": ", with the input of " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": " (i.e., " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "I_{input}^{0}, I_{input}^{45}, I_{input}^{90}" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "I_{input}^{135}" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": ") and " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": ". The obtained prior " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "P" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": " from Sec. 4.2 can already provide the estimation of " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "I_{h}" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": " by comparing with " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": ". Thus, " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "f_{r}" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": " can be focused on the assessment of " + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "inline_equation", + "content": "I_{d}" + }, + { + "bbox": [ + 47, + 420, + 287, + 516 + ], + "type": "text", + "content": ". The reconstruction network is implemented as a common Residual Dense Network [43]. The reconstruction process can be expressed as Eq. (15)." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 55, + 516, + 287, + 531 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 516, + 287, + 531 + ], + "spans": [ + { + "bbox": [ + 55, + 516, + 287, + 531 + ], + "type": "interline_equation", + "content": "I _ {r e c} = f _ {r} \\left(I _ {i n p u t} ^ {0} \\oplus I _ {i n p u t} ^ {4 5} \\oplus I _ {i n p u t} ^ {9 0} \\oplus I _ {i n p u t} ^ {1 3 5} \\oplus P\\right), \\tag {15}", + "image_path": "552ba71bcd0555d943c9f86bd4a4ebe5f2993f30dbbe74cf3be7e9b558c5c61b.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 531, + 252, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 531, + 252, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 531, + 252, + 544 + ], + "type": "text", + "content": "where, " + }, + { + "bbox": [ + 47, + 531, + 252, + 544 + ], + "type": "inline_equation", + "content": "I_{rec} \\in \\mathbb{R}^{h \\times w \\times 1}" + }, + { + "bbox": [ + 47, + 531, + 252, + 544 + ], + "type": "text", + "content": " is the reconstructed image." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 548, + 192, + 561 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 548, + 192, + 561 + ], + "spans": [ + { + "bbox": [ + 47, + 548, + 192, + 561 + ], + "type": "text", + "content": "4.4. Details in Implementation" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "spans": [ + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "text", + "content": "Our framework is implemented by PyTorch, and we use Polanalyser library4 to process the polarized images. It is trained with " + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "inline_equation", + "content": "L1" + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "text", + "content": " loss between " + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "inline_equation", + "content": "I_{rec}" + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "inline_equation", + "content": "I_{gt}" + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "text", + "content": " in an end-to-end manner. Besides, the learning rate is " + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "inline_equation", + "content": "5 \\times 10^{-5}" + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "text", + "content": ", and it decays to half of the original for every " + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "inline_equation", + "content": "2 \\times 10^{4}" + }, + { + "bbox": [ + 46, + 564, + 287, + 624 + ], + "type": "text", + "content": " iterations." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 631, + 124, + 644 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 631, + 124, + 644 + ], + "spans": [ + { + "bbox": [ + 47, + 631, + 124, + 644 + ], + "type": "text", + "content": "5. Experiment" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "type": "text", + "content": "In our experiment, we evaluate the performance of the proposed framework in three aspects. First, as an image reconstruction task, we conduct qualitative and quantitative evaluations with reconstruction-related metrics (e.g.," + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 72, + 545, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 545, + 133 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 545, + 133 + ], + "type": "text", + "content": "PSNR, SSIM). Second, as an upstream task in the industry, two downstream scenarios (e.g., QR code reading, and Text OCR) are selected to evaluate the reliability of our proposed algorithm. Finally, we conduct ablation studies to analyze the roles of different components." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 138, + 372, + 149 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 138, + 372, + 149 + ], + "spans": [ + { + "bbox": [ + 306, + 138, + 372, + 149 + ], + "type": "text", + "content": "5.1. Baselines" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 154, + 545, + 237 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 154, + 545, + 237 + ], + "spans": [ + { + "bbox": [ + 305, + 154, + 545, + 237 + ], + "type": "text", + "content": "There is no existing baseline for this new problem. Thus, we choose two general SOTA methods in image reconstruction, Uformer [33] and Restormer [41] to evaluate the performance. Considering the connection between the film removal and highlight removal, we also compare with two SOTA polarization and non-polarization highlight removal baselines, Polar-HR [34] and SHIQ [6], respectively." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 238, + 545, + 334 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 238, + 545, + 334 + ], + "spans": [ + { + "bbox": [ + 305, + 238, + 545, + 334 + ], + "type": "text", + "content": "To make a fair comparison, we follow the same training setting in our framework and input four polarized images to reconstruct one image without wrinkled transparent film in Uformer [33], Restormer [41]. In Polar-HR [34], it is a traditional training-free model and, therefore, shares the same input and output data as our approach. Besides, in SHIQ [6], since it cannot support polarized images, we convert four polarized images to one unpolarized image." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 340, + 493, + 351 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 340, + 493, + 351 + ], + "spans": [ + { + "bbox": [ + 306, + 340, + 493, + 351 + ], + "type": "text", + "content": "5.2. Evaluation on Reconstruction Task" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 355, + 545, + 450 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 355, + 545, + 450 + ], + "spans": [ + { + "bbox": [ + 305, + 355, + 545, + 450 + ], + "type": "text", + "content": "Quantitative Evaluation To measure the quantitative performance of the algorithm, we refer to commonly used metrics for Image Reconstruction: peak signal-to-noise ratio (PSNR) and structural similarity (SSIM). Also, to compare the overall performance of our dataset, we use 10-fold cross-validation during training and testing. This strategy ensures the evaluation's reliability and further proves the proposed algorithm's robustness." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "spans": [ + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "type": "text", + "content": "The quantitative results are shown in Table 1. In the last column of Table 1, " + }, + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "type": "inline_equation", + "content": "\\mu" + }, + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "type": "text", + "content": " is the mean value, and " + }, + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "type": "text", + "content": " is the variance of the 10-fold performance. These experimental results show the average PSNR is 36.48 and the average SSIM is 0.9824, and the results demonstrate the high quality of our reconstructed images. In addition, the variance of PSNR and SSIM are 0.57 and " + }, + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "type": "inline_equation", + "content": "1.23 \\times 10^{-5}" + }, + { + "bbox": [ + 305, + 451, + 545, + 668 + ], + "type": "text", + "content": ", respectively, and this proves the proposed algorithm is stable and robust. Qualitative Evaluation To evaluate the reconstruction performance of the algorithm in a qualitative way, we show some visual results. Our results are shown in Fig. 8. Although Polar-HR [34] and SHIQ [6] can remove some of the highlights, their models cannot model the film correctly and, therefore, cannot remove the film itself. Besides, it can be observed that our algorithm can reconstruct regions where text or QR codes are corrupted by highlights through polarization information, while Uformer [33] and Restormer [41] produce fake artifacts in these regions." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 673, + 517, + 685 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 673, + 517, + 685 + ], + "spans": [ + { + "bbox": [ + 306, + 673, + 517, + 685 + ], + "type": "text", + "content": "5.3. Evaluation on Downstream Applications" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 714 + ], + "type": "text", + "content": "In industrial environments, it is common to use transparent films to cover products, which may negatively im" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 57, + 702, + 265, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 702, + 265, + 712 + ], + "spans": [ + { + "bbox": [ + 57, + 702, + 265, + 712 + ], + "type": "text", + "content": "4https://github.com/elerac/polanalyser/wiki" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "24992" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 70, + 547, + 213 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 547, + 213 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 547, + 213 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 547, + 213 + ], + "type": "table", + "html": "
K1K2K3K4K5K6K7K8K9K10μ↑σ↓
SHIQ [6]PSNR23.4722.1121.9521.6921.7721.0320.8620.4621.1021.3121.580.64
SSIM0.78990.76400.74160.74390.74590.74650.74990.74120.74650.73000.74992.41 × 10-4
Polar-HR [34]PSNR23.3122.8022.1321.5821.9422.0022.0321.9922.1821.9522.190.22
SSIM0.76420.74210.72200.70990.70640.70980.71280.70170.71020.69680.71763.80 × 10-4
Uformer [33]PSNR31.8531.9531.3931.1931.8132.0431.6831.9831.8531.0131.680.11
SSIM0.95190.94560.93710.93640.94340.94210.94380.94350.94570.93630.94262.17 × 10-5
Restormer [41]PSNR34.3535.0234.4433.7134.8835.1334.3134.3334.5132.4934.320.52
SSIM0.97710.97700.97210.96780.97570.97460.97420.97410.97590.96330.97311.75 × 10-5
OursPSNR36.7637.2936.6235.1236.9337.2136.2436.6736.9435.0236.480.57
SSIM0.98520.98590.98220.97670.98450.98330.98360.98300.98500.97490.98241.23 × 10-5
", + "image_path": "074c6d0c66570e3d00b9dedffa0c604f0965699009b2d6bdfb56e94447f74812.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 52, + 225, + 545, + 411 + ], + "blocks": [ + { + "bbox": [ + 132, + 214, + 461, + 224 + ], + "lines": [ + { + "bbox": [ + 132, + 214, + 461, + 224 + ], + "spans": [ + { + "bbox": [ + 132, + 214, + 461, + 224 + ], + "type": "text", + "content": "Table 1. Quantitative evaluation in 10-fold cross-validation. The K- " + }, + { + "bbox": [ + 132, + 214, + 461, + 224 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 132, + 214, + 461, + 224 + ], + "type": "text", + "content": " indicates the " + }, + { + "bbox": [ + 132, + 214, + 461, + 224 + ], + "type": "inline_equation", + "content": "{I}_{th}" + }, + { + "bbox": [ + 132, + 214, + 461, + 224 + ], + "type": "text", + "content": " fold." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 52, + 225, + 545, + 411 + ], + "lines": [ + { + "bbox": [ + 52, + 225, + 545, + 411 + ], + "spans": [ + { + "bbox": [ + 52, + 225, + 545, + 411 + ], + "type": "table", + "html": "
Input (Intensity)SHIQ [6]Polar-HR [34]Uformer [33]Restormer [41]OursGround Truth
", + "image_path": "44663d3ce12f288d19ff5c8db1a33f90c7ec6380d006ff78d02a418b4163963e.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 50, + 432, + 287, + 511 + ], + "blocks": [ + { + "bbox": [ + 47, + 410, + 545, + 430 + ], + "lines": [ + { + "bbox": [ + 47, + 410, + 545, + 430 + ], + "spans": [ + { + "bbox": [ + 47, + 410, + 545, + 430 + ], + "type": "text", + "content": "Figure 8. Qualitative Evaluation. Compared with other baselines, our model can reconstruct more realistic details in highlight regions instead of fake artifacts. Please zoom in for more details." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 432, + 287, + 511 + ], + "lines": [ + { + "bbox": [ + 50, + 432, + 287, + 511 + ], + "spans": [ + { + "bbox": [ + 50, + 432, + 287, + 511 + ], + "type": "table", + "html": "
SHIQ [6]Polar-HR [34]Uformer [33]
Read Number71718
Read Rate8.05%19.54%20.69%
Restormer [41]OursGround Truth
Read Number246387
Read Rate27.58%72.41%100%
", + "image_path": "9f548df17fdc4109b59a419f35b1614a8f276f5c8c05c2ce9c9da4b660212a37.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 47, + 512, + 287, + 544 + ], + "lines": [ + { + "bbox": [ + 47, + 512, + 287, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 512, + 287, + 544 + ], + "type": "text", + "content": "Table 2. QR code reading rate. Compared with other baselines, our approach can improve the performance of QR codes scanner in the industrial environment." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 544, + 287, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 287, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 287, + 628 + ], + "type": "text", + "content": "pact the robustness of downstream algorithms. To evaluate the effectiveness of our solution in such settings, we conduct two tests on two downstream tasks: QR Code Reading and Text Optical Character Recognition (Text OCR). These tasks are particularly relevant as they require access to raw information, which provides a rigorous test of the effectiveness of our algorithms in industrial scenarios." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 630, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 287, + 713 + ], + "type": "text", + "content": "QR Code Reading The read rate is a critical performance metric for manufacturing pipelines in industrial systems. In this experiment, we compare our method with other baselines in Table 2. Our upstream algorithm leads to a significant improvement in the performance of the QR code reading. The qualitative results in Fig. 9 demonstrate that our algorithm not only removes the film but also significantly" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 434, + 504, + 445 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 434, + 504, + 445 + ], + "spans": [ + { + "bbox": [ + 305, + 434, + 504, + 445 + ], + "type": "text", + "content": "recovers the QR code information under the film." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 445, + 545, + 493 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 445, + 545, + 493 + ], + "spans": [ + { + "bbox": [ + 305, + 445, + 545, + 493 + ], + "type": "text", + "content": "Text OCR Text OCR is also an important downstream industrial task. We compared our algorithm with other baselines, as shown in Fig. 10. Our method can restore more hidden text information accurately." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 497, + 399, + 509 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 497, + 399, + 509 + ], + "spans": [ + { + "bbox": [ + 306, + 497, + 399, + 509 + ], + "type": "text", + "content": "5.4. Ablation Study" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 510, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 545, + 581 + ], + "type": "text", + "content": "We conduct ablation studies, which mainly validate the effectiveness of our proposed polarization dataset and one crucial component in our framework. To ensure that the experimental settings are consistent, we perform 10-fold cross-validation for the ablation experiments as well and draw two boxplots for further analysis." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "Effectiveness of the Polarized Information To prove the effectiveness of polarized information, we eliminate all components that need polarization information, which include four polarization images. Since the Polarization-based Location Model is driven by the " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "I_{max}" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "I_{min}" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": ", which need to be calculated with polarization images as input, this structure is also removed. Other settings remain constant. Without the support of polarized information, the quantitative performance has a considerable decrease, as shown in Fig. 11 (w/o Polarized information). 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Performance of QR code reading in the industry. In the original image, the QR code scanner fails to detect QR code information. Polar-HR [34] and SHIQ [6] can only eliminate the specular reflection on the QR code, and Uformer [33] and Restormer [41] can only generate false artifacts in highlight regions. 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Performance of text OCR in the industry. 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PSNR (A) and SSIM (B) in ablation study. We use two boxplots to describe the performance after " + }, + { + "bbox": [ + 46, + 571, + 287, + 616 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 571, + 287, + 616 + ], + "type": "text", + "content": "-fold cross-validation. The results show that our dataset, the extracted prior, the AoP, and the DoP contribute to the framework performance improvement." + } + ] + } + ], + "index": 31, + "angle": 0, + "type": "image_caption" + } + ], + "index": 27 + }, + { + "type": "image", + "bbox": [ + 167, + 491, + 275, + 559 + ], + "blocks": [ + { + "bbox": [ + 208, + 481, + 236, + 489 + ], + "lines": [ + { + "bbox": [ + 208, + 481, + 236, + 489 + ], + "spans": [ + { + "bbox": [ + 208, + 481, + 236, + 489 + ], + "type": "text", + "content": "(B) SSIM" + } + ] + } + ], + "index": 28, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 167, + 491, + 275, + 559 + ], + "lines": [ + { + "bbox": [ + 167, + 491, + 275, + 559 + ], + "spans": [ + { + "bbox": [ + 167, + 491, + 275, + 559 + ], + "type": "image", + "image_path": "7d7103008bd7f424141c3cc74b9edd7fa34cf800fcf2842a253fa9ea32f32c83.jpg" + } + ] + } + ], + "index": 29, + "angle": 0, + "type": "image_body" + } + ], + "index": 29 + }, + { + "bbox": [ + 46, + 617, + 287, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 287, + 653 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 287, + 653 + ], + "type": "text", + "content": "information, so it cannot remove all degradation. Besides, removing the polarization information will induce artifacts in highlight regions, as shown in Fig. 12." + } + ] + } + ], + "index": 32 + }, + { + "bbox": [ + 46, + 654, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 654, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 654, + 287, + 713 + ], + "type": "text", + "content": "Effectiveness of AoP and DoP To prove the effectiveness of AoP and DoP, we eliminate AoP and DoP in the angle estimation network. The qualitative results presented in Fig. 13 demonstrate that AoP and DoP can help locate the highlight more significantly, and also improve overall" + } + ] + } + ], + "index": 33 + }, + { + "type": "image", + "bbox": [ + 316, + 71, + 403, + 155 + ], + "blocks": [ + { + "bbox": [ + 316, + 71, + 403, + 155 + ], + "lines": [ + { + "bbox": [ + 316, + 71, + 403, + 155 + ], + "spans": [ + { + "bbox": [ + 316, + 71, + 403, + 155 + ], + "type": "image", + "image_path": "2ade62687f6dc0c6517dd5a28d6647b35374ff07766ca3ce022ec103be2526ba.jpg" + } + ] + } + ], + "index": 34, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 155, + 545, + 197 + ], + "lines": [ + { + "bbox": [ + 306, + 155, + 545, + 197 + ], + "spans": [ + { + "bbox": [ + 306, + 155, + 545, + 197 + ], + "type": "text", + "content": "Figure 12. Qualitative evaluation of w/o Polarization Information. Compared with w/o polarization information (Red), introducing polarization information avoids the generation of artifacts and reconstructs the realistic details (Green)." + } + ] + } + ], + "index": 38, + "angle": 0, + "type": "image_caption" + } + ], + "index": 34 + }, + { + "type": "image", + "bbox": [ + 403, + 71, + 491, + 155 + ], + "blocks": [ + { + "bbox": [ + 403, + 71, + 491, + 155 + ], + "lines": [ + { + "bbox": [ + 403, + 71, + 491, + 155 + ], + "spans": [ + { + "bbox": [ + 403, + 71, + 491, + 155 + ], + "type": "image", + "image_path": "e4232352b4ade2ca81c097bb3ccb5387328932e35c240fc49198bd158cd0f410.jpg" + } + ] + } + ], + "index": 35, + "angle": 0, + "type": "image_body" + } + ], + "index": 35 + }, + { + "type": "image", + "bbox": [ + 492, + 72, + 533, + 113 + ], + "blocks": [ + { + "bbox": [ + 492, + 72, + 533, + 113 + ], + "lines": [ + { + "bbox": [ + 492, + 72, + 533, + 113 + ], + "spans": [ + { + "bbox": [ + 492, + 72, + 533, + 113 + ], + "type": "image", + "image_path": "23b6601552e0a27e9fb9d6ed0a2e453e6c32ee122b0be7a53a2eabd516edce92.jpg" + } + ] + } + ], + "index": 36, + "angle": 0, + "type": "image_body" + } + ], + "index": 36 + }, + { + "type": "image", + "bbox": [ + 492, + 113, + 533, + 155 + ], + "blocks": [ + { + "bbox": [ + 492, + 113, + 533, + 155 + ], + "lines": [ + { + "bbox": [ + 492, + 113, + 533, + 155 + ], + "spans": [ + { + "bbox": [ + 492, + 113, + 533, + 155 + ], + "type": "image", + "image_path": "c39f76310bdb4d734d3ef543a878ecd5ac91585b15d56924ba789593a16875b3.jpg" + } + ] + } + ], + "index": 37, + "angle": 0, + "type": "image_body" + } + ], + "index": 37 + }, + { + "type": "image", + "bbox": [ + 313, + 199, + 370, + 256 + ], + "blocks": [ + { + "bbox": [ + 313, + 199, + 370, + 256 + ], + "lines": [ + { + "bbox": [ + 313, + 199, + 370, + 256 + ], + "spans": [ + { + "bbox": [ + 313, + 199, + 370, + 256 + ], + "type": "image", + "image_path": "bf36ebc847e6d2fe39d8476081a95cb29df247b57314ab6b93160fb17e9a6841.jpg" + } + ] + } + ], + "index": 39, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 257, + 545, + 289 + ], + "lines": [ + { + "bbox": [ + 306, + 257, + 545, + 289 + ], + "spans": [ + { + "bbox": [ + 306, + 257, + 545, + 289 + ], + "type": "text", + "content": "Figure 13. Highlight location heatmap. Compared with \"w/o AoP & DoP\" (In Red Box), introducing AoP and DoP (In Green Box) can help the A-Net to infer more highlight regions." + } + ] + } + ], + "index": 43, + "angle": 0, + "type": "image_caption" + } + ], + "index": 39 + }, + { + "type": "image", + "bbox": [ + 371, + 199, + 428, + 256 + ], + "blocks": [ + { + "bbox": [ + 371, + 199, + 428, + 256 + ], + "lines": [ + { + "bbox": [ + 371, + 199, + 428, + 256 + ], + "spans": [ + { + "bbox": [ + 371, + 199, + 428, + 256 + ], + "type": "image", + "image_path": "1d7abcb5bc496e57b61e24c09298aa30da34021f11e2d29a98d6c73f461f6476.jpg" + } + ] + } + ], + "index": 40, + "angle": 0, + "type": "image_body" + } + ], + "index": 40 + }, + { + "type": "image", + "bbox": [ + 431, + 199, + 486, + 256 + ], + "blocks": [ + { + "bbox": [ + 431, + 199, + 486, + 256 + ], + "lines": [ + { + "bbox": [ + 431, + 199, + 486, + 256 + ], + "spans": [ + { + "bbox": [ + 431, + 199, + 486, + 256 + ], + "type": "image", + "image_path": "a63ea703ce8facbcd7f5598125f23f84a4fda2b75f7e7c8980f49f3b85166e88.jpg" + } + ] + } + ], + "index": 41, + "angle": 0, + "type": "image_body" + } + ], + "index": 41 + }, + { + "type": "image", + "bbox": [ + 487, + 199, + 541, + 256 + ], + "blocks": [ + { + "bbox": [ + 487, + 199, + 541, + 256 + ], + "lines": [ + { + "bbox": [ + 487, + 199, + 541, + 256 + ], + "spans": [ + { + "bbox": [ + 487, + 199, + 541, + 256 + ], + "type": "image", + "image_path": "8aa2697b4681130cf29ade018d647ca48fc4cd10c100003f0c23c5c7b9aab800.jpg" + } + ] + } + ], + "index": 42, + "angle": 0, + "type": "image_body" + } + ], + "index": 42 + }, + { + "type": "image", + "bbox": [ + 313, + 290, + 370, + 347 + ], + "blocks": [ + { + "bbox": [ + 313, + 290, + 370, + 347 + ], + "lines": [ + { + "bbox": [ + 313, + 290, + 370, + 347 + ], + "spans": [ + { + "bbox": [ + 313, + 290, + 370, + 347 + ], + "type": "image", + "image_path": "cfb558be87ba53d9e5c92358f79efea1ff28b1c1d2a0ba0b7a52bd232056d010.jpg" + } + ] + } + ], + "index": 44, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 306, + 348, + 545, + 380 + ], + "lines": [ + { + "bbox": [ + 306, + 348, + 545, + 380 + ], + "spans": [ + { + "bbox": [ + 306, + 348, + 545, + 380 + ], + "type": "text", + "content": "Figure 14. Qualitative Evaluation of w/o Prior. Compared with \"w/o Prior\" (In Red Box), our solution (In Green Box) is more effective to remove highlight and infer original information." + } + ] + } + ], + "index": 48, + "angle": 0, + "type": "image_caption" + } + ], + "index": 44 + }, + { + "type": "image", + "bbox": [ + 370, + 290, + 428, + 347 + ], + "blocks": [ + { + "bbox": [ + 370, + 290, + 428, + 347 + ], + "lines": [ + { + "bbox": [ + 370, + 290, + 428, + 347 + ], + "spans": [ + { + "bbox": [ + 370, + 290, + 428, + 347 + ], + "type": "image", + "image_path": "1cbfe6ce20b216e7247171f0a224bc23fad73f54bddbd09048e3953436ccc463.jpg" + } + ] + } + ], + "index": 45, + "angle": 0, + "type": "image_body" + } + ], + "index": 45 + }, + { + "type": "image", + "bbox": [ + 431, + 290, + 486, + 347 + ], + "blocks": [ + { + "bbox": [ + 431, + 290, + 486, + 347 + ], + "lines": [ + { + "bbox": [ + 431, + 290, + 486, + 347 + ], + "spans": [ + { + "bbox": [ + 431, + 290, + 486, + 347 + ], + "type": "image", + "image_path": "835f3ba4426d781e0669176da7df08c11279228e878c26bd14c524335f08881d.jpg" + } + ] + } + ], + "index": 46, + "angle": 0, + "type": "image_body" + } + ], + "index": 46 + }, + { + "type": "image", + "bbox": [ + 487, + 290, + 541, + 347 + ], + "blocks": [ + { + "bbox": [ + 487, + 290, + 541, + 347 + ], + "lines": [ + { + "bbox": [ + 487, + 290, + 541, + 347 + ], + "spans": [ + { + "bbox": [ + 487, + 290, + 541, + 347 + ], + "type": "image", + "image_path": "3f840798e35ecc857c455afa381792a606457c91bb6e7f70ff40ffa44e7b98ea.jpg" + } + ] + } + ], + "index": 47, + "angle": 0, + "type": "image_body" + } + ], + "index": 47 + }, + { + "bbox": [ + 306, + 382, + 477, + 394 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 382, + 477, + 394 + ], + "spans": [ + { + "bbox": [ + 306, + 382, + 477, + 394 + ], + "type": "text", + "content": "performance in Fig. 11 (w/o AoP & DoP)." + } + ] + } + ], + "index": 49 + }, + { + "bbox": [ + 306, + 395, + 545, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 395, + 545, + 514 + ], + "spans": [ + { + "bbox": [ + 306, + 395, + 545, + 514 + ], + "type": "text", + "content": "Effectiveness of Prior To prove the effectiveness of polarized prior, we eliminate the angle estimation network and the PLM in our network while retaining only the polarized images and the reconstruction network. In this case, the network can only implicitly facilitate the polarized information in the reconstruction network. Since there is no polarized prior that indicates highlight regions, this can lead to a decrease in the performance of the network to recover highlight regions (as shown in Fig. 14), while causing overall performance to decrease in Fig. 11 (w/o Prior)." + } + ] + } + ], + "index": 50 + }, + { + "bbox": [ + 306, + 518, + 378, + 529 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 518, + 378, + 529 + ], + "spans": [ + { + "bbox": [ + 306, + 518, + 378, + 529 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 51 + }, + { + "bbox": [ + 306, + 533, + 545, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 533, + 545, + 665 + ], + "spans": [ + { + "bbox": [ + 306, + 533, + 545, + 665 + ], + "type": "text", + "content": "In this study, we pioneer the investigation of the Film Removal (FR) problem, aiming to eliminate the disturbances caused by wrinkled transparent films and to restore the obscured information. We propose an end-to-end framework to effectively remove all degradations caused by the film with a polarized prior to minimizing highlight. Besides, we build a practical polarized dataset containing paired data for this problem. Experiments in the industry have demonstrated the potential application. We believe that the deployment of our algorithms will considerably improve the robustness of downstream industrial recognition systems." + } + ] + } + ], + "index": 52 + }, + { + "bbox": [ + 306, + 666, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 666, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 306, + 666, + 545, + 712 + ], + "type": "text", + "content": "Acknowledgment This work is supported by the National Natural Science Foundation of China (No. 62206068) and the Natural Science Foundation of Zhejiang Province, China under No. LD24F020002." + } + ] + } + ], + "index": 53 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "24994" + } + ] + } + ], + "index": 54 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 84 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 18, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 125 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 125 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 125 + ], + "type": "text", + "content": "[1] Gary A Atkinson. 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In CVPR, 2019. 2" + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "24996" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning to Segment Referred Objects from Narrated Egocentric Videos/13b15e2b-026f-47a4-a5c8-eb8241c9c8e2_content_list.json b/2024/Learning to Segment Referred Objects from Narrated Egocentric Videos/13b15e2b-026f-47a4-a5c8-eb8241c9c8e2_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..7cbe183346f65d7e5794fd050dad5484632c0d25 --- /dev/null +++ b/2024/Learning to Segment Referred Objects from Narrated Egocentric Videos/13b15e2b-026f-47a4-a5c8-eb8241c9c8e2_content_list.json @@ -0,0 +1,1646 @@ +[ + { + "type": "text", + "text": "Learning to Segment Referred Objects from Narrated Egocentric Videos", + "text_level": 1, + "bbox": [ + 117, + 130, + 849, + 151 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yuhan Shen $^{1,2*}$ Huiyu Wang $^{1}$ Xitong Yang $^{1}$ Matt Feiszli $^{1}$ Ehsan Elhamifar $^{2}$ Lorenzo Torresani $^{1}$ Effrosyni Mavroudi $^{1}$ FAIR, Meta, Northeastern University", + "bbox": [ + 230, + 179, + 733, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 268, + 310, + 282 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Egocentric videos provide a first-person perspective of the wearer's activities, involving simultaneous interactions with multiple objects. In this work, we propose the task of weakly-supervised Narration-based Video Object Segmentation (NVOS). Given an egocentric video clip and a narration of the wearer's activities, our aim is to segment object instances mentioned in the narration, without using any spatial annotations during training. Existing weakly-supervised video object grounding methods typically yield bounding boxes for referred objects. In contrast, we propose ROSA, a weakly-supervised pixel-level grounding framework learning alignments between referred objects and segmentation mask proposals. Our model harnesses vision-language models pre-trained on image-text pairs to embed region masks and object phrases. During training, we combine (a) a video-narration contrastive loss that implicitly supervises the alignment between regions and phrases, and (b) a region-phrase contrastive loss based on inferred latent alignments. To address the lack of annotated NVOS datasets in egocentric videos, we create a new evaluation benchmark, VISOR-NVOS, leveraging existing annotations of segmentation masks from VISOR alongside 14.6k newly-collected, object-based video clip narrations. Our approach achieves state-of-the-art zero-shot pixel-level grounding performance compared to strong baselines under similar supervision. Additionally, we demonstrate generalization capabilities for zero-shot video object grounding on YouCook2, a third-person instructional video dataset.", + "bbox": [ + 75, + 301, + 472, + 724 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 756, + 207, + 771 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Egocentric videos [6, 12, 42] capture human interactions with the surrounding environment from a first-person perspective. Recent datasets, such as Ego4D [12], have paired such interaction-rich visual signals with manually annotated textual narrations of the camera wearer's activities, catalyzing a surge in research at the intersection of vision", + "bbox": [ + 75, + 782, + 468, + 875 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/88bf2168a846b19194d5b2e0c3ddf6ee587d7e167f20c81d8bca90d4530bde2a.jpg", + "image_caption": [ + "\"C uses a spoon to spread the minced meat on the cheese mixture in a lasagna dish\"" + ], + "image_footnote": [], + "bbox": [ + 503, + 268, + 625, + 335 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e979369bb177fcd1c2ec61ac9a00b446d268b78b214737485c693a42ab48071d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 761, + 270, + 887, + 334 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/24bfe34ccb4117f7b9930e0ab16fa87d0239a6a7b000ff5730994f60768b838f.jpg", + "image_caption": [ + "(a) Narration-based Video Object Segmentation (Ours)" + ], + "image_footnote": [], + "bbox": [ + 504, + 335, + 625, + 397 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/d406f12679c126042568b583c569ae621a33d781bae4f39a2ff943ee3ed89310.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 630, + 337, + 758, + 369 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/8068da98d7996013deaff58625958a07df23b0be64bdfcfc371495092fcc8161.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 761, + 335, + 887, + 397 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/8d6a670ff6d2d7be34a9673424a760cf4a5aa79aa89e4393825e85e07bfd67c0.jpg", + "image_caption": [ + "(b) Video Object Grounding" + ], + "image_footnote": [], + "bbox": [ + 506, + 410, + 625, + 468 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/151a4ca9b7f1f2dfd5d502aeaa656384601c20b5574571183a3b5d59b47236e8.jpg", + "image_caption": [ + "\"the spoon used to spread the minced meat\"", + "(c) Referring Expression Segmentation" + ], + "image_footnote": [], + "bbox": [ + 638, + 436, + 751, + 469 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c451c63893c9f94c52242712e4b11d02f12fb52c2f501d472cb29e29fd587d36.jpg", + "image_caption": [ + "spoon; minced meat; \ncheese mixture; lasagna dish", + "(d) Video Object Segmentation", + "Figure 1. Overview of the Narration-based Video Object Segmentation (NVOS) task. Given a short video clip and a narration of the camera wearer's activities, our goal is to predict segmentation masks for each object phrase. This task requires more fine-grained video-language alignment (pixel-level and phrase-level) compared to popular grounding tasks, such as video object grounding and referring expression segmentation. Frames taken from the Epic-Kitchens [6] dataset." + ], + "image_footnote": [], + "bbox": [ + 767, + 436, + 880, + 469 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "and language. These efforts have primarily concentrated on coarse-grained, holistic video-language understanding, such as pairing a video clip with a narration of its content (video-text retrieval) [24, 35, 60], egocentric video question answering [2, 11, 18] and temporal localization of natural language queries [3, 15, 26, 37, 61], often lacking the fine-grained understanding at object level.", + "bbox": [ + 496, + 627, + 890, + 733 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In this work, we explore a more fine-grained connection between egocentric videos and language by introducing the Narration-based Video Object Segmentation (NVOS) task, linking noun phrases (objects) in narrations with segmentation masks in the video. For example, as shown in Figure 1, given an egocentric video clip and its narration \"C uses a spoon to spread the minced meat on the cheese mixture in a lasagna dish\", our goal is to predict a segmentation mask at each frame for each one of the referred objects (noun phrases): spoon, minced meat, cheese mixture, and lasagna dish. Our task requires models to effectively disambiguate", + "bbox": [ + 496, + 734, + 892, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Work done during an internship at FAIR, Meta.", + "bbox": [ + 94, + 886, + 351, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "14510", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "among multiple instances of the same object class (e.g., predict a segmentation mask for the spoon that the person uses and not for the spoon on the chopping board).", + "bbox": [ + 75, + 90, + 468, + 136 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "This task is related to, but different from other popular tasks that output segmentation masks, such as referring expression segmentation [50, 58] (Figure 1c), which generates a segmentation mask for only one object described in an input query sentence and open vocabulary segmentation [23, 38] (Figure 1d), which does not use narration context and is unable to disambiguate object instances of the same class. Besides, most prior approaches that address phrase-level grounding in images [4, 33] and videos [22, 41, 43, 64] were limited to predicting a single point or a bounding box per referred object. However, detecting the bounding boxes (Figure 1b) is not sufficient to localize highly-overlapping, occluded, or non-grid-aligned objects which frequently occur in egocentric procedural videos.", + "bbox": [ + 75, + 138, + 468, + 348 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Training models for pixel-level grounding typically requires spatial annotations (e.g., segmentation masks [16, 20] or mouse traces [45]) for the referred objects. However, obtaining precise annotations for every referred object in textual narrations is not only arduous but also prohibitively expensive for large-scale datasets like Ego4D [12]. Hence, in this work we present a weakly-supervised framework for NVOS, trained only with narrated egocentric videos, without any manual spatial annotations for referred objects. Our framework, called Referred Object-Segment Aligner (ROSA), leverages recent breakthroughs in class-agnostic segmentation mask generation [21] and casts grounding as a region-phrase alignment problem.", + "bbox": [ + 75, + 349, + 468, + 546 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Learning such alignments from uncurated narrated egocentric videos is very challenging, due to cluttered scenes, drastically changing object appearance (e.g., cheese getting shredded) and frequent occlusions. To address this, we propose: (a) bootstrapping from powerful joint imagetext models, such as CLIP [36], to get a prior about region-phrase alignments, and (b) formulating a global matching score between a video and a narration based on the local matching scores between the masks and noun phrases across different video frames. In particular, we design a CLIP-based Dual Encoder for obtaining context-aware embeddings for mask proposals and noun phrases. We also design a Global-Local Contrastive Learning framework that operates on ground-truth video-narration pairs and pseudolabelled region-phrase pairs.", + "bbox": [ + 75, + 547, + 468, + 773 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To address the lack of benchmarks for pixel-level grounding in egocentric videos, we introduce a new benchmark, VISOR-NVOS, through manual annotations of narrations referencing segmented objects from the VISOR dataset [7]. This benchmark comprises detailed object-based narrations for 14,612 video clips.", + "bbox": [ + 75, + 776, + 467, + 866 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We summarize the contributions of this work as follows:", + "bbox": [ + 76, + 868, + 467, + 882 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "- We introduce a new task of weakly-supervised NVOS,", + "bbox": [ + 76, + 885, + 467, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "and establish a new egocentric benchmark, VISOR-NVOS, by enriching the VISOR dataset [7] with detailed object-based narrations.", + "bbox": [ + 511, + 90, + 890, + 135 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose ROSA, a weakly-supervised framework that learns to align referred objects in narrations with mask proposals from narrated egocentric videos, without requiring spatial annotations for semantic concepts.", + "- We achieve state-of-the-art zero-shot NVOS grounding performance in two egocentric video datasets (VISOR-NVOS and VOST [44]) compared to baselines that use similar weak supervision or stronger spatial supervision. Additionally, we showcase generalization ability for zero-shot video object grounding on the YouCook2-BB [64] third-person video dataset." + ], + "bbox": [ + 500, + 136, + 890, + 301 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 316, + 640, + 333 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Video object grounding is an active research field in the intersection of vision and language that aims to localize objects referenced in visual descriptions of videos. Prior work has mostly focused on third-person video datasets, such as YouCook2-BB [64] and ActivityNet Entities [65], and on coarse-grained spatial localization of each object with a bounding box [28, 39, 41, 49, 64] or a single point [43]. Proposed models for referring expression or active object grounding [22, 51] in egocentric videos also output rectangular regions. Instead our work explores pixel-level grounding of referred objects in egocentric videos.", + "bbox": [ + 496, + 342, + 890, + 508 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our NVOS task is also closely related to the recently introduced Video Narration Grounding task [45], where the goal is to predict a segmentation mask for each noun in a collection of captions of a third-person video. Our work differs by grounding noun phrases on egocentric videos and by training models without any spatial annotations for referred objects (while [45] used mouse traces).", + "bbox": [ + 496, + 508, + 890, + 614 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Video object segmentation (VOS) is the problem of pixel-accurate separation of particular objects from the background in videos. The most related ones to our work are semi-supervised VOS [5, 14, 31, 55]. Given the segmentation masks of the objects in the first one or few frames, semi-supervised VOS aims to segment the target objects through the video. However, those methods merely use the visual modality to track and segment objects while our method segments objects based on the language narrations.", + "bbox": [ + 496, + 619, + 890, + 755 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Open-vocabulary segmentation aims to segment all object instances of the same category for a list of arbitrary categories described through textual input [9, 17, 23, 52, 57, 59]. Instead, our task aims to precisely identify particular instances of referred objects within the video.", + "bbox": [ + 496, + 760, + 890, + 835 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Image phrase grounding aims to localize corresponding objects in an image given a phrase in the image's caption [4, 13, 46, 47]. While related, we focus on pixel-wise grounding of phrases in videos than rather than bounding-", + "bbox": [ + 496, + 840, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "14511", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "box localization in images. To address the unique challenges of video context, we adaptively weigh various frames for establishing video-narration affinity scores during training, which has not been explored in those image-based works. Besides, most of those works apply contrastive learning only at image-caption level, with the exception of [4] which proposes a contrastive learning method at the phrase-bounding box level. Our framework is the first to combine both global and local contrastive learning losses for weakly-supervised region-phrase alignment.", + "bbox": [ + 75, + 90, + 472, + 242 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Vision-language pre-training, e.g., CLIP [36], has fueled a growing interest in knowledge transfer for various downstream tasks [25, 32, 52, 57]. Prior works [23, 57, 62, 63] have shown that naive ways to leverage pre-trained CLIP to represent bounding boxes or segmentation masks are not feasible as CLIP was pre-trained on image-text pairs without any pixel-level annotation. Our work explores ways of adapting CLIP to represent local regions and phrases, which is an exciting research question [23, 58, 63].", + "bbox": [ + 75, + 244, + 472, + 383 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. ROSA: Learning Region-Phrase Alignments", + "text_level": 1, + "bbox": [ + 76, + 395, + 470, + 414 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Task Formulation", + "text_level": 1, + "bbox": [ + 76, + 419, + 250, + 435 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given a video-narration pair $(\\mathcal{V},\\mathcal{S})$ , where the video clip $\\mathcal{V}$ consists of $T$ frames $\\{I_1,I_2,\\dots ,I_T\\}$ of size $H\\times W$ , and the narration $S$ describes the activities demonstrated in the video and refers to $N$ noun phrases (objects) $(o_{1},o_{2},\\ldots ,o_{N})$ , our goal is to output a set of binary segmentation masks $\\mathcal{M}_{tn}\\in \\{0,1\\}^{H\\times W}$ for the $n$ -th referred object at the $t$ -th frame. In this work, we focus on weakly-supervised training, i.e., training only with video-narration pairs without any pixel-level annotation. To achieve this, we extract $M$ mask proposals $\\{P_{tm}\\}_{t,m = 1}^{T,M}$ at each frame using the Segment Anything Model (SAM) [21] which is pre-trained on object segmentation masks without object labels. Then we use the video-narration pairs to supervise the learning of a similarity function between each mask proposal and each object phrase.", + "bbox": [ + 75, + 443, + 472, + 671 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Method overview. Figure 2 gives an overview of our proposed framework, Referred Object-Segment Aligner (ROSA). We propose a CLIP-based Dual Encoder to compute context-aware embeddings for mask regions and object phrases (Section 3.2). To train our model without ground-truth region-phrase alignments, we propose a Global-Local Contrastive Learning framework (Section 3.3). It optimizes two objectives: (1) a global contrastive objective, contrasting ground-truth positive and negative pairs of video clips and narrations, based on a Temporal Adaptive Pooling of region-phrase similarities, and (2) a local contrastive objective, contrasting pseudo-labelled positive and negative pairs of regions and phrases. After learning, grounding is achieved by finding the mask proposal that maximizes the region-phrase similarity (Section 3.4).", + "bbox": [ + 75, + 674, + 472, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. CLIP-based Dual Encoder", + "text_level": 1, + "bbox": [ + 500, + 90, + 740, + 106 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In order to effectively align phrases with mask proposals, we need discriminative region representations that align well with language and capture contextual nuances. We propose a Context-aware Region Encoder to embed each mask proposal, and a Context-aware Phrase Encoder to embed each groundable noun phrase (object), by leveraging the CLIP model [36] pretrained on large-scale image-text pairs.", + "bbox": [ + 496, + 114, + 890, + 220 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2.1 Context-Aware Region Encoder", + "text_level": 1, + "bbox": [ + 498, + 241, + 774, + 257 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The original Vision Transformer [10] (ViT) from CLIP consists of $L$ Transformer layers and embeds a whole image in its special CLS token of each last layer. To extract region-level features per mask proposal of a frame, we propose Mask-Guided Image CLIP. We pass the frame through the first $L - 1$ layers of ViT, and then compute a CLS token per mask proposal by applying a simple attention masking in the last Transformer layer, which ensures that the CLS token exclusively attends to the masked region. As this approach shares the computation of all hidden layers except for the last Transformer layer among all mask proposals, it is much more efficient than cropping and masking used in prior works [8, 23, 53]. Besides, as the visual encoder has access to the whole frame, it is able to capture contextual information, making it more suitable for grounding task that needs to disambiguate between object instances of the same class based on context. The final region embedding $\\mathbf{r}_{tm} \\in \\mathbb{R}^D$ for the $m$ -th mask proposal at the $t$ -th frame is computed by projecting the CLS token to a $D$ -dimensional vector with a shallow MLP, denoted as $\\mathbf{r}_{tm} = \\text{RegionEncoder}(P_{tm}, I_t)$ .", + "bbox": [ + 496, + 265, + 893, + 584 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2.2 Context-Aware Phrase Encoder", + "text_level": 1, + "bbox": [ + 498, + 604, + 774, + 619 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We use a language parser (spaCy [1]) to extract the noun phrases in each narration and then apply our Context-Aware Phrase Encoder to obtain a contextualized embedding for each phrase. A straight-forward way for obtaining phrase embeddings using CLIP is to pass the entire narration through its text encoder, and perform average pooling over the tokens corresponding to each referred object (Phrase Pooling) to get a narration-aware phrase embedding for each object. However, we observe that this embedding is often heavily influenced by the narration context, resulting in similar embeddings for nearby phrases, thus hurting disambiguation that is necessary for our grounding tasks. To address this limitation, we additionally input each object phrase to CLIP's text encoder and use the EOT (End of Text) token as a localized phrase embedding. The final phrase embedding $\\mathbf{w}_n\\in \\mathbb{R}^D$ for the $n$ -th object phrase in the input narration is computed as the average of the localized phrase embedding and narration-aware phrase embedding,", + "bbox": [ + 496, + 628, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "14512", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/ddf2890078bceb2f67db1c11eaf4d402a5bc426d7394950d86a27708e07943ec.jpg", + "image_caption": [ + "Figure 2. Framework Overview. We propose a CLIP-based Dual Encoder to embed mask proposals and noun phrases, and compute pairwise region-phrase similarities. We propose Global-Local Contrastive Learning via ground-truth Video-Narration Alignment and pseudo labelled Region-Phrase Alignment. Frames taken from Ego4D [12]." + ], + "image_footnote": [], + "bbox": [ + 80, + 88, + 890, + 349 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "denoted as $\\mathbf{w}_n = \\text{PhraseEncoder}(o_n, \\mathcal{S})$ ,", + "bbox": [ + 76, + 429, + 367, + 445 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Global-Local Contrastive Learning", + "text_level": 1, + "bbox": [ + 76, + 454, + 383, + 470 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In the weakly-supervised setting, we need to learn a similarity function between mask regions and object phrases, without ground-truth alignments of region-phrase pairs. We propose a Global-Local Contrastive Learning framework to learn the region-phrase similarities using the alignments at both video-narration (global) and region-phrase (local) levels. In Sec. 3.3.1, we detail how to compute the region-phrase similarities and aggregate them into a video-narration affinity score for global contrastive learning. In Sec. 3.3.2, we illustrate how we obtain the pseudo-labelled region-phrase pairs for local contrastive learning.", + "bbox": [ + 75, + 479, + 468, + 645 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3.1 Video-Narration Alignment", + "text_level": 1, + "bbox": [ + 76, + 662, + 323, + 678 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Since our only available supervision is at the video-narration level, we propose a standard contrastive loss for video-narration alignment, which is equipped with a region-based affinity score between videos and narrations. In particular, inspired by Multiple Instance Learning approaches for weakly-supervised phrase grounding [19], we formulate an affinity score $\\phi(\\mathcal{V},\\mathcal{S})$ between a video and a narration by aggregating individual region-phrase affinity scores. Intuitively, a video-narration pair should have a high affinity score if each referred object in the narration has a matched mask proposal in each frame of the video clip. Next, we detail how we aggregate the region-phrase similarities into frame-phrase affinity scores resulting in an overall affinity score between a video clip and a narration.", + "bbox": [ + 75, + 688, + 470, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Frame-phrase affinity score. Given a set of segmentation mask proposals $\\{P_{tm}\\}_{t,m=1}^{T,M}$ and a set of object phrases $\\{o_n\\}_{n=1}^N$ , we first compute the pairwise similarity $g(\\mathbf{r}_{tm}, \\mathbf{w}_n)$ between each mask proposal embedding $\\mathbf{r}_{tm}$ and each noun phrase embedding $\\mathbf{w}_n$ . In particular, our similarity function $g(\\cdot, \\cdot)$ is computed as the cosine similarity between the region embedding and phrase embedding, multiplied with the mask confidence score of the corresponding mask proposal. This multiplication prioritizes mask proposals with higher confidence scores when aligning the object phrase with mask proposals. The affinity score between a phrase and a frame is then defined based on the best matching region at each frame $I_t$ : $\\psi(I_t, o_n) = \\max_m g(\\mathbf{r}_{tm}, \\mathbf{w}_n)$ .", + "bbox": [ + 496, + 429, + 890, + 643 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Video-phrase affinity score. To compute the affinity score at the video-phrase level, we introduce a Temporal Adaptive Pooling of the frame-phrase affinity scores $\\psi(I_t, o_n)$ :", + "bbox": [ + 498, + 648, + 890, + 694 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\sigma (\\mathcal {V}, o _ {n}) = \\sum_ {t} \\frac {e ^ {\\psi \\left(I _ {t} , o _ {n}\\right) / \\alpha}}{\\sum_ {t ^ {\\prime}} e ^ {\\psi \\left(I _ {t ^ {\\prime}} , o _ {n}\\right) / \\alpha}} \\psi \\left(I _ {t}, o _ {n}\\right). \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 562, + 704, + 890, + 738 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The function involves a weighted sum across all temporal frames, where the weight for each frame is determined by the frame-phrase affinity scores divided by a temperature parameter $\\alpha$ . We dynamically adjust $\\alpha$ during training, following the schedule $\\alpha = \\alpha_0\\beta^{-s}$ , where $\\alpha_0$ is a small constant close to $0$ , $\\beta \\in (0,1)$ is a decay index, and $s$ is the iteration step. Intuitively, at the initial stage of training, the model may struggle to effectively segment objects undergoing occlusions or significant transformations. This dynamic adjustment allows the model to prioritize the most confident", + "bbox": [ + 496, + 750, + 892, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "14513", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "mask proposal in a single frame early in training (with low $\\alpha$ ) and gradually shift towards a smoother, more robust aggregation of region representations from multiple frames as training progresses (with a larger $\\alpha$ ).", + "bbox": [ + 76, + 90, + 468, + 151 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Video-narration affinity score. Finally, we compute the video-narration affinity score by averaging the videophrase affinity scores over all object phrases: $\\phi(\\mathcal{V},\\mathcal{S}) = \\frac{\\sum_{n}\\sigma(\\mathcal{V},o_{n})}{N}$ , which assumes that all referred objects in the narration should be present in the aligned video clip.", + "bbox": [ + 76, + 156, + 467, + 234 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Video-narration contrastive loss. Given a training batch of video-narration pairs $\\{(\\mathcal{V}_i, \\mathcal{S}_i)\\}_{i=1}^B$ , where $B$ is the batch size, we use an InfoNCE loss to train the model via weak supervision as follows:", + "bbox": [ + 76, + 239, + 467, + 301 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {V N A}} = \\frac {1}{B} \\sum_ {i = 1} ^ {B} - \\log \\frac {e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {i}\\right) / \\tau}}{\\sum_ {j} e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {j}\\right) / \\tau}} - \\log \\frac {e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {i}\\right) / \\tau}}{\\sum_ {j} e ^ {\\phi \\left(\\mathcal {V} _ {j} , \\mathcal {S} _ {i}\\right) / \\tau}}, \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 83, + 305, + 467, + 353 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\tau$ is a learnable temperature and $\\phi(\\mathcal{V}_i, \\mathcal{S}_j)$ is our custom video-narration affinity score defined above. We freeze the pre-trained CLIP image and text encoders, and optimize the parameters of the MLP to learn region representations better aligned with phrases.", + "bbox": [ + 76, + 354, + 467, + 431 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3.2 Region-Phrase Alignment", + "text_level": 1, + "bbox": [ + 76, + 453, + 310, + 468 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "While the aforementioned video-narration contrastive loss is effective at leveraging video-narration supervision, the loss is not directly applied to the alignment between region-phrase pairs. In order to learn a better alignment between mask regions and object phrases, we propose an additional local loss at region-phrase level. To do so, we first get pseudo-labelled alignments for region-phrase pairs. For each phrase embedding $\\mathbf{w}_n$ , we get the embedding of its best aligned mask proposal at each frame, denoted as $\\tilde{\\mathbf{r}}_{tn} = \\{\\mathbf{r}_{tm}|m = \\operatorname*{argmax}_{m'}g(\\mathbf{r}_{tm'},\\mathbf{w}_n)\\}$ .", + "bbox": [ + 76, + 478, + 467, + 637 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Region-phrase contrastive loss. Then we apply a region-phrase alignment loss over all object phrases and all aligned mask regions in a batch:", + "bbox": [ + 76, + 642, + 467, + 686 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} _ {\\mathrm {R P A}} = - \\sum_ {t} \\underbrace {\\log \\frac {e ^ {g \\left(\\tilde {\\mathbf {r}} _ {t n} , \\mathbf {w} _ {n}\\right) / \\tau}}{\\sum_ {n ^ {\\prime}} e ^ {g \\left(\\tilde {\\mathbf {r}} _ {t n} , \\mathbf {w} _ {n ^ {\\prime}}\\right) / \\tau}}} _ {\\text {r e g i o n t o p h r a s e}} \\tag {3} \\\\ - \\underbrace {\\log \\frac {\\sum_ {t} e ^ {g (\\mathbf {r} _ {t n} , \\mathbf {w} _ {n}) / \\tau}}{\\sum_ {n ^ {\\prime}} \\sum_ {t} e ^ {g (\\tilde {\\mathbf {r}} _ {t n ^ {\\prime}} , \\mathbf {w} _ {n}) / \\tau}}} _ {\\text {p h r a s e t o r i g i o n}}. \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 156, + 691, + 467, + 797 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The first term is a region to phrase (R2P) standard InfoNCE contrastive loss, which treats other object phrases as negative samples for a given mask region. The second term is a phrase to region (P2R) MIL-NCE-type [30] contrastive loss, which considers the aligned regions in all frames as positive pairs for a given object phrase, while", + "bbox": [ + 76, + 810, + 467, + 900 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/554a5be7f4c3c2114ed8e1b112025dd72e3a2af9de674bc47248db261a00843b.jpg", + "image_caption": [ + "Figure 3. An example of our annotated narration on the VISOR-NVOS benchmark. The annotators are instructed to write a detailed narration with [referred object] followed by $\\langle$ object ID $\\rangle$ ." + ], + "image_footnote": [], + "bbox": [ + 504, + 92, + 712, + 195 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/309bdaeb16109b4de6dd995d707135bc9dfb93f525bf1a45f38f25599b269db7.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 715, + 90, + 877, + 196 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "treating regions aligned with other object phrases as negative samples. Note that Eq. (3) is the loss for one object phrase, and we sum over all object phrases for training loss. This loss formulation facilitates the learning of robust region-phrase associations and enhances the quality of object segmentation and grounding. In the experiment section, we compare various strategies on selecting the negative samples for P2R contrastive learning and show the advantages of the proposed one. Our final training objective is: $\\mathcal{L} = \\mathcal{L}_{\\mathrm{VNA}} + \\lambda \\mathcal{L}_{\\mathrm{RPA}}$ , where $\\lambda$ is the weight for region-phrase alignment loss.", + "bbox": [ + 498, + 279, + 890, + 445 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Inference", + "text_level": 1, + "bbox": [ + 500, + 454, + 607, + 468 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We ground the $n$ -th noun phrase in the narration by selecting the mask proposal at each frame with the closest embedding in our learned, unified region-phrase embedding space:", + "bbox": [ + 498, + 477, + 890, + 523 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {M} _ {t n} = P _ {t m ^ {*}}, \\text {w h e r e} m ^ {*} = \\underset {m} {\\operatorname {a r g m a x}} g \\left(\\mathbf {r} _ {t m}, \\mathbf {w} _ {n}\\right) \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 526, + 535, + 890, + 559 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Evaluation Benchmarks for NVOS", + "text_level": 1, + "bbox": [ + 500, + 569, + 813, + 584 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "While our proposed weakly-supervised framework demonstrates the feasibility of training NVOS models without the need for mask annotation, evaluating the performance of such models is equally critical. Existing egocentric video datasets with segmentation mask annotations for objects, such as VISOR [7], VOST [44] and PACO [38], cannot be directly used for evaluation, since they lack narrations with referred objects associated with the annotated object masks.", + "bbox": [ + 498, + 595, + 890, + 715 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "VISOR-NVOS. To address these limitations, we create a new evaluation benchmark, VISOR-NVOS, by collecting object-based narration annotations for video clips from the VISOR [7] dataset. VISOR provides mask annotations for multiple active objects in egocentric videos of the EPIC-Kitchens [6] dataset. We pair these segmentation masks with narrations, by instructing annotators to describe activities explicitly referring to a set of objects of interest. As shown in Figure 3, provided with a short video clip and a list of objects of interest (with each object name associated with an object ID and a segmentation mask), the annotators are instructed to write a sentence describing the person's", + "bbox": [ + 498, + 719, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "14514", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/e26b6429522c6d572a958179de49e0096076bf05406a065e5c8c0114df978f52.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodSupervisionVISOR-NVOSVOST
Cross-ModalMask AnnotationEgo4D‡JFJ&FJunionJins
SAM [21] upper bound70.375.673.062.265.8
Trained w/ labeled regions
ODISE [52]mask-textclass-specific29.032.830.917.621.1
GroundedSAM [21, 27]bbox-textclass-agnostic37.341.839.521.825.3
Trained w/o labeled regions
SAM [21] + CLIP [36] (ViT-B/16)image-textclass-agnostic22.225.824.016.519.2
CoMMa† [43] + SAM [21]video-narrationclass-agnostic✓15.325.320.39.411.5
ROSA (ViT-B/16)video-narrationclass-agnostic✓34.941.238.122.225.4
ROSA (ViT-L/14)video-narrationclass-agnostic✓38.746.042.423.226.7
", + "bbox": [ + 99, + 88, + 874, + 262 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Comparison of grounding performance between our framework and strong baselines on our NVOS benchmarks. We report metrics on the test split of our proposed VISOR-NVOS and the validation split of VOST. $\\ddagger$ whether the model has been fine-tuned on Ego4D. \"Trained with labeled regions\": trained with annotations of bounding boxes or masks; \"Trained without labeled regions\": using video-level or image-level annotations.", + "bbox": [ + 75, + 263, + 893, + 321 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "activities in the video, linking noun phrases in the sentence with the associated object IDs. In total, we have collected detailed, object-based narrations for 14,612 video clips, including 37,170 referred objects. On average, each narration has 12.79 words, and 2.54 referred objects. The maximum number of referred objects in one narration is 9. We split the annotated videos into a validation set of 7,561 videos and a test set of 7,051 videos, and report the performance on the test set. We do not train our model on any of those videos or narrations. Please see the supplementary for more details about this benchmark.", + "bbox": [ + 75, + 345, + 472, + 512 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "VOST. VOST [44] is an egocentric video object segmentation dataset specifically designed to capture dramatic object transformations. To evaluate models for NVOS on VOST, we use the verb and noun pairs (e.g., \"peel banana\", \"mold clay\") as the narrations, with the nouns serving as the objects to ground. In contrast to VISOR, which encompasses multiple object classes in a single video, VOST contains annotations for a single object class (with one or multiple instances) per video. However, the uniqueness of VOST lies in the complexity of the transformations these objects undergo, e.g., the peeling of bananas. Hence, this benchmark allows us to evaluate the model's performance in grounding objects under complex transformations and its ability to comprehend actions that induce changes in object states.", + "bbox": [ + 75, + 517, + 472, + 731 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 76, + 744, + 209, + 762 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 76, + 770, + 267, + 787 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Training dataset. We train our model on video-narration pairs sourced from the Ego4D dataset [12]. Ego4D is a massive-scale egocentric video dataset that provides over 3M text narrations of the camera wearer's activities, synchronized with timestamps for 3,670 hours of video. We use a subset of Ego4D for our experiments, by selecting $250k$ video clips with narrations related to cooking objects.", + "bbox": [ + 75, + 794, + 470, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We sample four frames from each one-second clip, with an average of 1.6 narrations available per clip. During each training iteration, we construct video-narration pairs by randomly sampling one narration per video clip.", + "bbox": [ + 496, + 345, + 893, + 407 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation. After training on Ego4D, we evaluate on the VISOR-NVOS and VOST benchmarks without fine-tuning. Following [7, 34, 54], we use the Jaccard Index $(\\mathcal{J},$ also known as Intersection over Union, IoU), the Boundary F-Measure $(\\mathcal{F})$ , and the average of Jaccard Index and Boundary F-Measure $(\\mathcal{J}\\& \\mathcal{F})$ , as the evaluation metrics on VISOR-NVOS. On VOST, following [44], we only use the Jaccard Index as the contours are often not well-defined due to the dramatic transformations and motions involved on this dataset. As we described, VOST does not contain ground-truth alignments between annotated segmentation masks and referred objects. Hence, for some samples with multiple annotated object instances of the same object class, there is uncertainty for grounding evaluation. To mitigate this issue, we report two metrics: $\\mathcal{I}_{union}$ , i.e., the IoU between the predicted mask and the union of all annotated masks, and $\\mathcal{I}_{ins}$ , i.e., the IoU between the predicted mask and the most overlapping annotated mask instance.", + "bbox": [ + 496, + 410, + 895, + 683 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation details. We use SAM [21] to generate mask proposals on each frame using a $32 \\times 32$ point grid. We apply Non-Maximum Suppression (NMS) with a threshold of 0.9 to remove redundant mask proposals. Our best model uses a CLIP ViT-L/14 Image Encoder (while for ablations we use ViT-B/16). We set the weight for region-phrase alignment loss $\\lambda$ as 0.5 and use three-layer MLP in our Context-Aware Region Encoder. Please refer to the supplementary for more implementation details.", + "bbox": [ + 496, + 686, + 893, + 823 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Comparison with the State of the Art", + "text_level": 1, + "bbox": [ + 498, + 832, + 821, + 848 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We compare our method with strong baselines as well as state-of-the-art approaches from related tasks (narration grounding [43], open-vocabulary segmentation [52])", + "bbox": [ + 496, + 854, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "14515", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/ace2f394107033b09a3942127fcb67dfa82c3bc6854e9ac72995f23de04e5995.jpg", + "table_caption": [], + "table_footnote": [ + "(a) Impact of various losses." + ], + "table_body": "
VNAR2PP2RJFJ&F
24.831.328.1
✓32.439.636.0
✓✓33.940.137.0
✓✓33.940.637.3
✓✓✓34.941.238.1
", + "bbox": [ + 81, + 88, + 343, + 175 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/56caf458b87188f982fceff77cf6e7e325b4a27693ffdc75168aa016eb965e1d.jpg", + "table_caption": [], + "table_footnote": [ + "(b) Ablation for negative region sampling." + ], + "table_body": "
Negative samplesJFJ&F
same27.535.031.3
all27.434.831.1
other26.534.030.3
aligned (ours)34.941.238.1
", + "bbox": [ + 357, + 89, + 624, + 172 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/843a17c5e1bef78acb16f478515b0e485df14fe5b418d99e8a880770f42b2c00.jpg", + "table_caption": [], + "table_footnote": [ + "(c) Ablation of temporal aggregation functions." + ], + "table_body": "
JFJ&F
random frame33.339.836.6
max pooling33.740.537.1
softmax33.640.437.0
adaptive (ours)34.941.238.1
", + "bbox": [ + 642, + 89, + 887, + 172 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. Ablation studies on the Global-Local Contrastive Learning framework on the VISOR-NVOS test split.", + "bbox": [ + 153, + 194, + 812, + 208 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "adapted for our NVOS task. Baselines trained without labeled regions: \"SAM+CLIP\": For this simple baseline, we use SAM to generate mask proposals, input the cropped and masked images into CLIP image encoder and the object phrases into CLIP text encoder, and select the best matching mask proposal based on the cosine similarity of their embeddings. \"CoMMa†+SAM\": We adapt CoMMa [43], a state-of-the-art approach for weakly-supervised point-wise grounding of input language queries, for the NVOS task. We train CoMMa† with video-narration pairs (from the same Ego4D subset used to train our model), and during inference use the predicted point for each object phrase to prompt SAM and get the segmentation mask. Baselines trained with labeled regions: We also benchmark ODISE [52] and GroundedSAM [21, 27], two state-of-the-art, image-level, open-vocabulary segmentation approaches that are trained with segmentation masks/bounding boxes paired with semantic concepts, thus using stronger supervision than us. Since open-vocabulary segmentation outputs masks for all instances of an object class (e.g., all spoons), we select the mask with highest confidence score and compare it with the ground-truth mask.", + "bbox": [ + 75, + 234, + 472, + 566 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "As can be seen in Table 1, our model (with CLIP ViT-L/14 backbone) outperforms all compared baselines, including approaches that have been trained with strong spatial supervision (e.g., GroundedSAM is based on Grounding DINO [27], an open-set object detector that has been pre-trained on Objects365 [40], a large dataset with 10Mbbox annotations). Interestingly, the simple, out-of-the-box \"SAM+CLIP\" baseline, which has not been trained on egocentric video data, outperforms \"CoMMa†+SAM\", corroborating our intuition for using mask proposals and harnessing CLIP pre-training for representing them. Compared to this strong baseline, our model (with the same ViT-B/16 backbone) improves the $\\mathcal{J}\\&\\mathcal{F}$ by $14.1\\%$ on VISOR-NVOS, and improves the $\\mathcal{J}_{ins}$ by $6.2\\%$ on VOST, which demonstrates the effectiveness of our weakly-supervised framework that learns region-phrase alignments from egocentric video narrations.", + "bbox": [ + 75, + 569, + 468, + 825 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We note, however, that the performance of all compared models on our VISOR-NVOS benchmark lags behind the", + "bbox": [ + 76, + 828, + 468, + 858 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "upper bound performance that we could obtain based on the best-matching SAM mask proposal (reported in the first row of Table 1), highlighting the challenging nature of our proposed task and benchmark and the need for further research on learning better region-phrase alignments, e.g., by better modeling temporal consistency.", + "bbox": [ + 500, + 234, + 890, + 325 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Ablation Studies", + "text_level": 1, + "bbox": [ + 500, + 338, + 663, + 352 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "What is the effect of each component of our proposed training objective? We start by reporting the performance of our CLIP-based Dual Encoder before weakly-supervised training (i.e., we replace the MLP of our region encoder with the identity mapping and just use CLIP weights for our encoders) in the first row of Table 2a. Adding the MLP and fine-tuning it on Ego4D with our Global Contrastive Objective, that encourages video-narration alignment (VNA), leads to a significant performance improvement in $\\mathcal{J}\\&\\mathcal{F}$ (from $28.1\\%$ to $36.0\\%$ , rows 1 and 2). Adding our novel region-phrase alignment loss terms, i.e., region to phrase (R2P) and phrase to region (P2R) losses (Eq. (3)), further boosts performance. Both loss terms contribute to the improvement, and their combination improves $\\mathcal{J}\\&\\mathcal{F}$ by $2.1\\%$ , suggesting that our proposed loss function is able to learn a better region-phrase alignment by directly applying supervision on region-phrase pairs, instead of just contrasting video-narration pairs, as commonly done in prior work [64].", + "bbox": [ + 496, + 361, + 890, + 633 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "How to select negative region samples for region-phrase contrastive learning? As can be seen in Table 2b, using regions that are aligned with the other phrases in the batch (based on the pseudo-labeled alignments) is the only strategy that does not degrade the performance. We compare it with using the rest of regions from the same video, using the rest of regions from all the videos in the batch, and using all regions from other videos (as proposed for weakly-supervised image phrase grounding [4]). We conjecture that our proposed strategy avoids the issues of \"fake negative\" samples when the negative mask regions are also relevant to the object phrase if multiple mask proposals are overlapped, and \"easy negative\" samples when the mask regions are background regions irrelevant to active objects.", + "bbox": [ + 496, + 638, + 892, + 849 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "What is the effect of the temporal aggregation module? As we discussed, we aggregate region-phrase similarities from multiple frames to obtain a global video-narration", + "bbox": [ + 500, + 854, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_footnote", + "text": "1We use CoMMa† to denote the model we trained on Ego4D to differentiate with the original CoMMa model trained on HowTo100M.", + "bbox": [ + 76, + 875, + 467, + 898 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "14516", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/290c8b0b4154acfd0a6e11d5111daa1c923f163ac5bb518aab99f96bf25baa21.jpg", + "image_caption": [ + "Figure 4. Qualitative Results. Top: three examples from VISOR-NVOS. Bottom: an example from VOST showing the model's robustness to objects undergoing dramatic transformations." + ], + "image_footnote": [], + "bbox": [ + 83, + 89, + 467, + 270 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "affinity score for applying our global contrastive objective. Our proposed aggregation module starts by focusing on one frame for each phrase (the one with the best matching region) and then adaptively starts encouraging alignment with the regions of other frames. As can be seen in Table 2c, this approach (adaptive) better handles occlusions and motion blur and facilitates training compared to: (a) randomly selecting a frame of the video clip during each iteration (random frame), (b) using the frame with the highest frame-phrase affinity score (max), or (c) not adapting the frame weights (softmax).", + "bbox": [ + 75, + 334, + 472, + 501 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Qualitative Results", + "text_level": 1, + "bbox": [ + 76, + 510, + 261, + 526 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In Figure 4, we show some qualitative results. On the top, we show three examples from VISOR-NVOS. In the first example, our model is able to segment the referred objects in a complex environment featuring multiple spoons and pans. In the second example, the model successfully distinguishes between \"flour\" and \"flour package\". The third example highlights some limitations of our model, including ambiguity in mask size where the model only segments a portion of the fridge instead of the entire unit, and challenges in understanding plurals (the narration mentions \"containers\" but it only grounds one container). The bottom section showcases the model's predictions on three frames from a VOST video depicting the peeling of a banana. Remarkably, the model accurately segments the banana while the appearance of banana has changed significantly.", + "bbox": [ + 75, + 534, + 472, + 762 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.5. Exocentric Video Object Grounding", + "text_level": 1, + "bbox": [ + 76, + 770, + 393, + 787 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In Table 3, to further assess the generality of our model, we conduct evaluations on the third-person video object grounding dataset, YouCook2-BB [64], which includes bounding box annotations for referred objects. We convert the segmentation masks output by our model into bounding boxes for evaluation. Recall that our model is trained on egocentric videos with a goal to align object phrases", + "bbox": [ + 75, + 794, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/71e306e642286b46be0a692dc99fc85eba5f308b9abd4d0c3c226181f5f0214b.jpg", + "table_caption": [], + "table_footnote": [ + "(a) bounding box evaluation" + ], + "table_body": "
Methodbox accuracy
macromicro
Trained on YouCook2
Zhou et al. [64]35.0842.42
NAFAE [41]40.7146.33
STVG [56]41.6748.22
SCL [48]42.8048.60
Zero-Shot
CoMMa†+SAM6.638.98
Ours37.9344.96
", + "bbox": [ + 504, + 88, + 710, + 243 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/48deae8df8b65fadd32820d828ac36c0565ad35b4402c9e902b96360f5cd34ea.jpg", + "table_caption": [], + "table_footnote": [ + "(b) point prediction evaluation" + ], + "table_body": "
Methodpoint acc.
CoMMa†53.56
CoMMa [43]59.25
Ours69.35
", + "bbox": [ + 728, + 130, + 890, + 200 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. Object grounding evaluation on YouCook2-BB.", + "bbox": [ + 527, + 268, + 862, + 284 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "with segmentation masks. Despite a huge domain shift, our model achieves comparable performance with prior works [41, 48, 56, 64] that are trained on YouCook2 using bounding box proposals (Table 3a). In addition, we adopt the evaluation setup from CoMMa [43] to evaluate our model using point accuracy (see supplementary for more details). We use the center of the bounding box from our segmentation mask as the detected point. While CoMMa is trained on exocentric videos with a similar scale (HowTo100M [29]) for point-based grounding, our model outperforms CoMMa by a significant margin of $10.10\\%$ (Table 3b).", + "bbox": [ + 496, + 303, + 893, + 470 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Limitations", + "text_level": 1, + "bbox": [ + 500, + 484, + 622, + 500 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "A limitation of our framework is that we perform inference on each frame separately, neglecting temporal information. Integrating temporal context into our model has the potential to enhance performance and alleviate ambiguities, which is a promising direction for future work. Furthermore, we focused our training and evaluation on the cooking domain. In the supplementary, we show that our weakly-supervised training also improves grounding on non-cooking videos, such as DIY, but a performance gap still exists between the two domains.", + "bbox": [ + 496, + 508, + 890, + 660 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "7. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 674, + 617, + 689 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We have explored the task of Narration-based Video Object Segmentation and established a new evaluation benchmark, VISOR-NVOS. Our proposed framework, ROSA, has effectively learnt the alignment between referred objects and segmentation masks using weak supervision of video-narration alignments in egocentric videos. Our approach achieved state-of-the-art zero-shot pixel-level grounding performance on two egocentric video datasets compared to strong baselines.", + "bbox": [ + 496, + 699, + 890, + 835 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements. We thank Tushar Nagarajan, Triantafyllos Afouras, Yale Song, Austin Miller, and Jiabo Hu for helpful discussions and invaluable engineering support.", + "bbox": [ + 496, + 854, + 890, + 902 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "14517", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] spaCy. https://spacy.io/.3", + "[2] Leonard Bär mann and Alex Waibel. Where did i leave my keys? - episodic-memory-based question answering on egocentric videos. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR) Workshops, pages 1560-1568, 2022. 1", + "[3] Wayner Barrios, Mattia Soldan, Alberto Mario Ceballos-Arroyo, Fabian Caba Heilbron, and Bernard Ghanem. Localizing moments in long video via multimodal guidance. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 6578-6587, 2019. 2" + ], + "bbox": [ + 501, + 90, + 890, + 430 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "14520", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning to Segment Referred Objects from Narrated Egocentric Videos/13b15e2b-026f-47a4-a5c8-eb8241c9c8e2_model.json b/2024/Learning to Segment Referred Objects from Narrated Egocentric Videos/13b15e2b-026f-47a4-a5c8-eb8241c9c8e2_model.json new file mode 100644 index 0000000000000000000000000000000000000000..e9aaf2a88fce2c41d15b564310a3f4ffb458ce1a --- /dev/null +++ b/2024/Learning to Segment Referred Objects from Narrated Egocentric Videos/13b15e2b-026f-47a4-a5c8-eb8241c9c8e2_model.json @@ -0,0 +1,2422 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.119, + 0.131, + 0.851, + 0.152 + ], + "angle": 0, + "content": "Learning to Segment Referred Objects from Narrated Egocentric Videos" + }, + { + "type": "text", + "bbox": [ + 0.232, + 0.18, + 0.735, + 0.234 + ], + "angle": 0, + "content": "Yuhan Shen\\(^{1,2*}\\) Huiyu Wang\\(^{1}\\) Xitong Yang\\(^{1}\\) Matt Feiszli\\(^{1}\\) Ehsan Elhamifar\\(^{2}\\) Lorenzo Torresani\\(^{1}\\) Effrosyni Mavroudi\\(^{1}\\) FAIR, Meta, Northeastern University" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.312, + 0.284 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.302, + 0.473, + 0.725 + ], + "angle": 0, + "content": "Egocentric videos provide a first-person perspective of the wearer's activities, involving simultaneous interactions with multiple objects. In this work, we propose the task of weakly-supervised Narration-based Video Object Segmentation (NVOS). Given an egocentric video clip and a narration of the wearer's activities, our aim is to segment object instances mentioned in the narration, without using any spatial annotations during training. Existing weakly-supervised video object grounding methods typically yield bounding boxes for referred objects. In contrast, we propose ROSA, a weakly-supervised pixel-level grounding framework learning alignments between referred objects and segmentation mask proposals. Our model harnesses vision-language models pre-trained on image-text pairs to embed region masks and object phrases. During training, we combine (a) a video-narration contrastive loss that implicitly supervises the alignment between regions and phrases, and (b) a region-phrase contrastive loss based on inferred latent alignments. To address the lack of annotated NVOS datasets in egocentric videos, we create a new evaluation benchmark, VISOR-NVOS, leveraging existing annotations of segmentation masks from VISOR alongside 14.6k newly-collected, object-based video clip narrations. Our approach achieves state-of-the-art zero-shot pixel-level grounding performance compared to strong baselines under similar supervision. Additionally, we demonstrate generalization capabilities for zero-shot video object grounding on YouCook2, a third-person instructional video dataset." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.757, + 0.208, + 0.772 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.783, + 0.47, + 0.875 + ], + "angle": 0, + "content": "Egocentric videos [6, 12, 42] capture human interactions with the surrounding environment from a first-person perspective. Recent datasets, such as Ego4D [12], have paired such interaction-rich visual signals with manually annotated textual narrations of the camera wearer's activities, catalyzing a surge in research at the intersection of vision" + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.27, + 0.627, + 0.336 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.635, + 0.277, + 0.753, + 0.311 + ], + "angle": 0, + "content": "\"C uses a spoon to spread the minced meat on the cheese mixture in a lasagna dish\"" + }, + { + "type": "image", + "bbox": [ + 0.762, + 0.271, + 0.888, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.506, + 0.337, + 0.627, + 0.398 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.631, + 0.338, + 0.759, + 0.37 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.762, + 0.337, + 0.888, + 0.398 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.556, + 0.4, + 0.836, + 0.41 + ], + "angle": 0, + "content": "(a) Narration-based Video Object Segmentation (Ours)" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.411, + 0.627, + 0.469 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.526, + 0.471, + 0.61, + 0.489 + ], + "angle": 0, + "content": "(b) Video Object Grounding" + }, + { + "type": "image_caption", + "bbox": [ + 0.639, + 0.416, + 0.746, + 0.431 + ], + "angle": 0, + "content": "\"the spoon used to spread the minced meat\"" + }, + { + "type": "image", + "bbox": [ + 0.639, + 0.438, + 0.752, + 0.47 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.636, + 0.471, + 0.755, + 0.489 + ], + "angle": 0, + "content": "(c) Referring Expression Segmentation" + }, + { + "type": "image_caption", + "bbox": [ + 0.765, + 0.416, + 0.884, + 0.433 + ], + "angle": 0, + "content": "spoon; minced meat; \ncheese mixture; lasagna dish" + }, + { + "type": "image", + "bbox": [ + 0.769, + 0.438, + 0.882, + 0.47 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.785, + 0.472, + 0.866, + 0.49 + ], + "angle": 0, + "content": "(d) Video Object Segmentation" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.505, + 0.892, + 0.616 + ], + "angle": 0, + "content": "Figure 1. Overview of the Narration-based Video Object Segmentation (NVOS) task. Given a short video clip and a narration of the camera wearer's activities, our goal is to predict segmentation masks for each object phrase. This task requires more fine-grained video-language alignment (pixel-level and phrase-level) compared to popular grounding tasks, such as video object grounding and referring expression segmentation. Frames taken from the Epic-Kitchens [6] dataset." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.628, + 0.892, + 0.734 + ], + "angle": 0, + "content": "and language. These efforts have primarily concentrated on coarse-grained, holistic video-language understanding, such as pairing a video clip with a narration of its content (video-text retrieval) [24, 35, 60], egocentric video question answering [2, 11, 18] and temporal localization of natural language queries [3, 15, 26, 37, 61], often lacking the fine-grained understanding at object level." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.893, + 0.901 + ], + "angle": 0, + "content": "In this work, we explore a more fine-grained connection between egocentric videos and language by introducing the Narration-based Video Object Segmentation (NVOS) task, linking noun phrases (objects) in narrations with segmentation masks in the video. For example, as shown in Figure 1, given an egocentric video clip and its narration \"C uses a spoon to spread the minced meat on the cheese mixture in a lasagna dish\", our goal is to predict a segmentation mask at each frame for each one of the referred objects (noun phrases): spoon, minced meat, cheese mixture, and lasagna dish. Our task requires models to effectively disambiguate" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.352, + 0.9 + ], + "angle": 0, + "content": "*Work done during an internship at FAIR, Meta." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "14510" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.137 + ], + "angle": 0, + "content": "among multiple instances of the same object class (e.g., predict a segmentation mask for the spoon that the person uses and not for the spoon on the chopping board)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.139, + 0.47, + 0.349 + ], + "angle": 0, + "content": "This task is related to, but different from other popular tasks that output segmentation masks, such as referring expression segmentation [50, 58] (Figure 1c), which generates a segmentation mask for only one object described in an input query sentence and open vocabulary segmentation [23, 38] (Figure 1d), which does not use narration context and is unable to disambiguate object instances of the same class. Besides, most prior approaches that address phrase-level grounding in images [4, 33] and videos [22, 41, 43, 64] were limited to predicting a single point or a bounding box per referred object. However, detecting the bounding boxes (Figure 1b) is not sufficient to localize highly-overlapping, occluded, or non-grid-aligned objects which frequently occur in egocentric procedural videos." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.351, + 0.47, + 0.547 + ], + "angle": 0, + "content": "Training models for pixel-level grounding typically requires spatial annotations (e.g., segmentation masks [16, 20] or mouse traces [45]) for the referred objects. However, obtaining precise annotations for every referred object in textual narrations is not only arduous but also prohibitively expensive for large-scale datasets like Ego4D [12]. Hence, in this work we present a weakly-supervised framework for NVOS, trained only with narrated egocentric videos, without any manual spatial annotations for referred objects. Our framework, called Referred Object-Segment Aligner (ROSA), leverages recent breakthroughs in class-agnostic segmentation mask generation [21] and casts grounding as a region-phrase alignment problem." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.549, + 0.47, + 0.775 + ], + "angle": 0, + "content": "Learning such alignments from uncurated narrated egocentric videos is very challenging, due to cluttered scenes, drastically changing object appearance (e.g., cheese getting shredded) and frequent occlusions. To address this, we propose: (a) bootstrapping from powerful joint imagetext models, such as CLIP [36], to get a prior about region-phrase alignments, and (b) formulating a global matching score between a video and a narration based on the local matching scores between the masks and noun phrases across different video frames. In particular, we design a CLIP-based Dual Encoder for obtaining context-aware embeddings for mask proposals and noun phrases. We also design a Global-Local Contrastive Learning framework that operates on ground-truth video-narration pairs and pseudolabelled region-phrase pairs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.777, + 0.468, + 0.867 + ], + "angle": 0, + "content": "To address the lack of benchmarks for pixel-level grounding in egocentric videos, we introduce a new benchmark, VISOR-NVOS, through manual annotations of narrations referencing segmented objects from the VISOR dataset [7]. This benchmark comprises detailed object-based narrations for 14,612 video clips." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.869, + 0.468, + 0.883 + ], + "angle": 0, + "content": "We summarize the contributions of this work as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.886, + 0.468, + 0.901 + ], + "angle": 0, + "content": "- We introduce a new task of weakly-supervised NVOS," + }, + { + "type": "text", + "bbox": [ + 0.512, + 0.092, + 0.892, + 0.136 + ], + "angle": 0, + "content": "and establish a new egocentric benchmark, VISOR-NVOS, by enriching the VISOR dataset [7] with detailed object-based narrations." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.137, + 0.892, + 0.197 + ], + "angle": 0, + "content": "- We propose ROSA, a weakly-supervised framework that learns to align referred objects in narrations with mask proposals from narrated egocentric videos, without requiring spatial annotations for semantic concepts." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.198, + 0.892, + 0.303 + ], + "angle": 0, + "content": "- We achieve state-of-the-art zero-shot NVOS grounding performance in two egocentric video datasets (VISOR-NVOS and VOST [44]) compared to baselines that use similar weak supervision or stronger spatial supervision. Additionally, we showcase generalization ability for zero-shot video object grounding on the YouCook2-BB [64] third-person video dataset." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.137, + 0.892, + 0.303 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.318, + 0.642, + 0.334 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.343, + 0.892, + 0.509 + ], + "angle": 0, + "content": "Video object grounding is an active research field in the intersection of vision and language that aims to localize objects referenced in visual descriptions of videos. Prior work has mostly focused on third-person video datasets, such as YouCook2-BB [64] and ActivityNet Entities [65], and on coarse-grained spatial localization of each object with a bounding box [28, 39, 41, 49, 64] or a single point [43]. Proposed models for referring expression or active object grounding [22, 51] in egocentric videos also output rectangular regions. Instead our work explores pixel-level grounding of referred objects in egocentric videos." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.51, + 0.892, + 0.616 + ], + "angle": 0, + "content": "Our NVOS task is also closely related to the recently introduced Video Narration Grounding task [45], where the goal is to predict a segmentation mask for each noun in a collection of captions of a third-person video. Our work differs by grounding noun phrases on egocentric videos and by training models without any spatial annotations for referred objects (while [45] used mouse traces)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.62, + 0.892, + 0.756 + ], + "angle": 0, + "content": "Video object segmentation (VOS) is the problem of pixel-accurate separation of particular objects from the background in videos. The most related ones to our work are semi-supervised VOS [5, 14, 31, 55]. Given the segmentation masks of the objects in the first one or few frames, semi-supervised VOS aims to segment the target objects through the video. However, those methods merely use the visual modality to track and segment objects while our method segments objects based on the language narrations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.761, + 0.892, + 0.836 + ], + "angle": 0, + "content": "Open-vocabulary segmentation aims to segment all object instances of the same category for a list of arbitrary categories described through textual input [9, 17, 23, 52, 57, 59]. Instead, our task aims to precisely identify particular instances of referred objects within the video." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.841, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Image phrase grounding aims to localize corresponding objects in an image given a phrase in the image's caption [4, 13, 46, 47]. While related, we focus on pixel-wise grounding of phrases in videos than rather than bounding-" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "14511" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.243 + ], + "angle": 0, + "content": "box localization in images. To address the unique challenges of video context, we adaptively weigh various frames for establishing video-narration affinity scores during training, which has not been explored in those image-based works. Besides, most of those works apply contrastive learning only at image-caption level, with the exception of [4] which proposes a contrastive learning method at the phrase-bounding box level. Our framework is the first to combine both global and local contrastive learning losses for weakly-supervised region-phrase alignment." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.246, + 0.473, + 0.385 + ], + "angle": 0, + "content": "Vision-language pre-training, e.g., CLIP [36], has fueled a growing interest in knowledge transfer for various downstream tasks [25, 32, 52, 57]. Prior works [23, 57, 62, 63] have shown that naive ways to leverage pre-trained CLIP to represent bounding boxes or segmentation masks are not feasible as CLIP was pre-trained on image-text pairs without any pixel-level annotation. Our work explores ways of adapting CLIP to represent local regions and phrases, which is an exciting research question [23, 58, 63]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.396, + 0.471, + 0.415 + ], + "angle": 0, + "content": "3. ROSA: Learning Region-Phrase Alignments" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.42, + 0.251, + 0.436 + ], + "angle": 0, + "content": "3.1. Task Formulation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.444, + 0.473, + 0.672 + ], + "angle": 0, + "content": "Given a video-narration pair \\((\\mathcal{V},\\mathcal{S})\\), where the video clip \\(\\mathcal{V}\\) consists of \\(T\\) frames \\(\\{I_1,I_2,\\dots ,I_T\\}\\) of size \\(H\\times W\\), and the narration \\(S\\) describes the activities demonstrated in the video and refers to \\(N\\) noun phrases (objects) \\((o_{1},o_{2},\\ldots ,o_{N})\\), our goal is to output a set of binary segmentation masks \\(\\mathcal{M}_{tn}\\in \\{0,1\\}^{H\\times W}\\) for the \\(n\\)-th referred object at the \\(t\\)-th frame. In this work, we focus on weakly-supervised training, i.e., training only with video-narration pairs without any pixel-level annotation. To achieve this, we extract \\(M\\) mask proposals \\(\\{P_{tm}\\}_{t,m = 1}^{T,M}\\) at each frame using the Segment Anything Model (SAM) [21] which is pre-trained on object segmentation masks without object labels. Then we use the video-narration pairs to supervise the learning of a similarity function between each mask proposal and each object phrase." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.675, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Method overview. Figure 2 gives an overview of our proposed framework, Referred Object-Segment Aligner (ROSA). We propose a CLIP-based Dual Encoder to compute context-aware embeddings for mask regions and object phrases (Section 3.2). To train our model without ground-truth region-phrase alignments, we propose a Global-Local Contrastive Learning framework (Section 3.3). It optimizes two objectives: (1) a global contrastive objective, contrasting ground-truth positive and negative pairs of video clips and narrations, based on a Temporal Adaptive Pooling of region-phrase similarities, and (2) a local contrastive objective, contrasting pseudo-labelled positive and negative pairs of regions and phrases. After learning, grounding is achieved by finding the mask proposal that maximizes the region-phrase similarity (Section 3.4)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.091, + 0.741, + 0.107 + ], + "angle": 0, + "content": "3.2. CLIP-based Dual Encoder" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.115, + 0.892, + 0.222 + ], + "angle": 0, + "content": "In order to effectively align phrases with mask proposals, we need discriminative region representations that align well with language and capture contextual nuances. We propose a Context-aware Region Encoder to embed each mask proposal, and a Context-aware Phrase Encoder to embed each groundable noun phrase (object), by leveraging the CLIP model [36] pretrained on large-scale image-text pairs." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.242, + 0.776, + 0.258 + ], + "angle": 0, + "content": "3.2.1 Context-Aware Region Encoder" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.266, + 0.895, + 0.585 + ], + "angle": 0, + "content": "The original Vision Transformer [10] (ViT) from CLIP consists of \\(L\\) Transformer layers and embeds a whole image in its special CLS token of each last layer. To extract region-level features per mask proposal of a frame, we propose Mask-Guided Image CLIP. We pass the frame through the first \\(L - 1\\) layers of ViT, and then compute a CLS token per mask proposal by applying a simple attention masking in the last Transformer layer, which ensures that the CLS token exclusively attends to the masked region. As this approach shares the computation of all hidden layers except for the last Transformer layer among all mask proposals, it is much more efficient than cropping and masking used in prior works [8, 23, 53]. Besides, as the visual encoder has access to the whole frame, it is able to capture contextual information, making it more suitable for grounding task that needs to disambiguate between object instances of the same class based on context. The final region embedding \\(\\mathbf{r}_{tm} \\in \\mathbb{R}^D\\) for the \\(m\\)-th mask proposal at the \\(t\\)-th frame is computed by projecting the CLS token to a \\(D\\)-dimensional vector with a shallow MLP, denoted as \\(\\mathbf{r}_{tm} = \\text{RegionEncoder}(P_{tm}, I_t)\\)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.605, + 0.776, + 0.62 + ], + "angle": 0, + "content": "3.2.2 Context-Aware Phrase Encoder" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.895, + 0.903 + ], + "angle": 0, + "content": "We use a language parser (spaCy [1]) to extract the noun phrases in each narration and then apply our Context-Aware Phrase Encoder to obtain a contextualized embedding for each phrase. A straight-forward way for obtaining phrase embeddings using CLIP is to pass the entire narration through its text encoder, and perform average pooling over the tokens corresponding to each referred object (Phrase Pooling) to get a narration-aware phrase embedding for each object. However, we observe that this embedding is often heavily influenced by the narration context, resulting in similar embeddings for nearby phrases, thus hurting disambiguation that is necessary for our grounding tasks. To address this limitation, we additionally input each object phrase to CLIP's text encoder and use the EOT (End of Text) token as a localized phrase embedding. The final phrase embedding \\(\\mathbf{w}_n\\in \\mathbb{R}^D\\) for the \\(n\\)-th object phrase in the input narration is computed as the average of the localized phrase embedding and narration-aware phrase embedding," + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "14512" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.891, + 0.351 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.362, + 0.893, + 0.406 + ], + "angle": 0, + "content": "Figure 2. Framework Overview. We propose a CLIP-based Dual Encoder to embed mask proposals and noun phrases, and compute pairwise region-phrase similarities. We propose Global-Local Contrastive Learning via ground-truth Video-Narration Alignment and pseudo labelled Region-Phrase Alignment. Frames taken from Ego4D [12]." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.43, + 0.368, + 0.446 + ], + "angle": 0, + "content": "denoted as \\(\\mathbf{w}_n = \\text{PhraseEncoder}(o_n, \\mathcal{S})\\)," + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.455, + 0.384, + 0.472 + ], + "angle": 0, + "content": "3.3. Global-Local Contrastive Learning" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.48, + 0.47, + 0.646 + ], + "angle": 0, + "content": "In the weakly-supervised setting, we need to learn a similarity function between mask regions and object phrases, without ground-truth alignments of region-phrase pairs. We propose a Global-Local Contrastive Learning framework to learn the region-phrase similarities using the alignments at both video-narration (global) and region-phrase (local) levels. In Sec. 3.3.1, we detail how to compute the region-phrase similarities and aggregate them into a video-narration affinity score for global contrastive learning. In Sec. 3.3.2, we illustrate how we obtain the pseudo-labelled region-phrase pairs for local contrastive learning." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.664, + 0.325, + 0.679 + ], + "angle": 0, + "content": "3.3.1 Video-Narration Alignment" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Since our only available supervision is at the video-narration level, we propose a standard contrastive loss for video-narration alignment, which is equipped with a region-based affinity score between videos and narrations. In particular, inspired by Multiple Instance Learning approaches for weakly-supervised phrase grounding [19], we formulate an affinity score \\(\\phi(\\mathcal{V},\\mathcal{S})\\) between a video and a narration by aggregating individual region-phrase affinity scores. Intuitively, a video-narration pair should have a high affinity score if each referred object in the narration has a matched mask proposal in each frame of the video clip. Next, we detail how we aggregate the region-phrase similarities into frame-phrase affinity scores resulting in an overall affinity score between a video clip and a narration." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.43, + 0.892, + 0.644 + ], + "angle": 0, + "content": "Frame-phrase affinity score. Given a set of segmentation mask proposals \\(\\{P_{tm}\\}_{t,m=1}^{T,M}\\) and a set of object phrases \\(\\{o_n\\}_{n=1}^N\\), we first compute the pairwise similarity \\(g(\\mathbf{r}_{tm}, \\mathbf{w}_n)\\) between each mask proposal embedding \\(\\mathbf{r}_{tm}\\) and each noun phrase embedding \\(\\mathbf{w}_n\\). In particular, our similarity function \\(g(\\cdot, \\cdot)\\) is computed as the cosine similarity between the region embedding and phrase embedding, multiplied with the mask confidence score of the corresponding mask proposal. This multiplication prioritizes mask proposals with higher confidence scores when aligning the object phrase with mask proposals. The affinity score between a phrase and a frame is then defined based on the best matching region at each frame \\(I_t\\): \\(\\psi(I_t, o_n) = \\max_m g(\\mathbf{r}_{tm}, \\mathbf{w}_n)\\)." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.649, + 0.892, + 0.695 + ], + "angle": 0, + "content": "Video-phrase affinity score. To compute the affinity score at the video-phrase level, we introduce a Temporal Adaptive Pooling of the frame-phrase affinity scores \\(\\psi(I_t, o_n)\\):" + }, + { + "type": "equation", + "bbox": [ + 0.563, + 0.705, + 0.892, + 0.739 + ], + "angle": 0, + "content": "\\[\n\\sigma (\\mathcal {V}, o _ {n}) = \\sum_ {t} \\frac {e ^ {\\psi \\left(I _ {t} , o _ {n}\\right) / \\alpha}}{\\sum_ {t ^ {\\prime}} e ^ {\\psi \\left(I _ {t ^ {\\prime}} , o _ {n}\\right) / \\alpha}} \\psi \\left(I _ {t}, o _ {n}\\right). \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.893, + 0.901 + ], + "angle": 0, + "content": "The function involves a weighted sum across all temporal frames, where the weight for each frame is determined by the frame-phrase affinity scores divided by a temperature parameter \\(\\alpha\\). We dynamically adjust \\(\\alpha\\) during training, following the schedule \\(\\alpha = \\alpha_0\\beta^{-s}\\), where \\(\\alpha_0\\) is a small constant close to \\(0\\), \\(\\beta \\in (0,1)\\) is a decay index, and \\(s\\) is the iteration step. Intuitively, at the initial stage of training, the model may struggle to effectively segment objects undergoing occlusions or significant transformations. This dynamic adjustment allows the model to prioritize the most confident" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "14513" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.152 + ], + "angle": 0, + "content": "mask proposal in a single frame early in training (with low \\(\\alpha\\)) and gradually shift towards a smoother, more robust aggregation of region representations from multiple frames as training progresses (with a larger \\(\\alpha\\))." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.157, + 0.468, + 0.236 + ], + "angle": 0, + "content": "Video-narration affinity score. Finally, we compute the video-narration affinity score by averaging the videophrase affinity scores over all object phrases: \\(\\phi(\\mathcal{V},\\mathcal{S}) = \\frac{\\sum_{n}\\sigma(\\mathcal{V},o_{n})}{N}\\), which assumes that all referred objects in the narration should be present in the aligned video clip." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.241, + 0.468, + 0.302 + ], + "angle": 0, + "content": "Video-narration contrastive loss. Given a training batch of video-narration pairs \\(\\{(\\mathcal{V}_i, \\mathcal{S}_i)\\}_{i=1}^B\\), where \\(B\\) is the batch size, we use an InfoNCE loss to train the model via weak supervision as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.084, + 0.306, + 0.468, + 0.354 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {V N A}} = \\frac {1}{B} \\sum_ {i = 1} ^ {B} - \\log \\frac {e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {i}\\right) / \\tau}}{\\sum_ {j} e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {j}\\right) / \\tau}} - \\log \\frac {e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {i}\\right) / \\tau}}{\\sum_ {j} e ^ {\\phi \\left(\\mathcal {V} _ {j} , \\mathcal {S} _ {i}\\right) / \\tau}}, \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.356, + 0.468, + 0.432 + ], + "angle": 0, + "content": "where \\(\\tau\\) is a learnable temperature and \\(\\phi(\\mathcal{V}_i, \\mathcal{S}_j)\\) is our custom video-narration affinity score defined above. We freeze the pre-trained CLIP image and text encoders, and optimize the parameters of the MLP to learn region representations better aligned with phrases." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.454, + 0.312, + 0.469 + ], + "angle": 0, + "content": "3.3.2 Region-Phrase Alignment" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.479, + 0.468, + 0.638 + ], + "angle": 0, + "content": "While the aforementioned video-narration contrastive loss is effective at leveraging video-narration supervision, the loss is not directly applied to the alignment between region-phrase pairs. In order to learn a better alignment between mask regions and object phrases, we propose an additional local loss at region-phrase level. To do so, we first get pseudo-labelled alignments for region-phrase pairs. For each phrase embedding \\(\\mathbf{w}_n\\), we get the embedding of its best aligned mask proposal at each frame, denoted as \\(\\tilde{\\mathbf{r}}_{tn} = \\{\\mathbf{r}_{tm}|m = \\operatorname*{argmax}_{m'}g(\\mathbf{r}_{tm'},\\mathbf{w}_n)\\}\\)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.643, + 0.468, + 0.687 + ], + "angle": 0, + "content": "Region-phrase contrastive loss. Then we apply a region-phrase alignment loss over all object phrases and all aligned mask regions in a batch:" + }, + { + "type": "equation", + "bbox": [ + 0.158, + 0.693, + 0.468, + 0.798 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} _ {\\mathrm {R P A}} = - \\sum_ {t} \\underbrace {\\log \\frac {e ^ {g \\left(\\tilde {\\mathbf {r}} _ {t n} , \\mathbf {w} _ {n}\\right) / \\tau}}{\\sum_ {n ^ {\\prime}} e ^ {g \\left(\\tilde {\\mathbf {r}} _ {t n} , \\mathbf {w} _ {n ^ {\\prime}}\\right) / \\tau}}} _ {\\text {r e g i o n t o p h r a s e}} \\tag {3} \\\\ - \\underbrace {\\log \\frac {\\sum_ {t} e ^ {g (\\mathbf {r} _ {t n} , \\mathbf {w} _ {n}) / \\tau}}{\\sum_ {n ^ {\\prime}} \\sum_ {t} e ^ {g (\\tilde {\\mathbf {r}} _ {t n ^ {\\prime}} , \\mathbf {w} _ {n}) / \\tau}}} _ {\\text {p h r a s e t o r i g i o n}}. \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.811, + 0.468, + 0.901 + ], + "angle": 0, + "content": "The first term is a region to phrase (R2P) standard InfoNCE contrastive loss, which treats other object phrases as negative samples for a given mask region. The second term is a phrase to region (P2R) MIL-NCE-type [30] contrastive loss, which considers the aligned regions in all frames as positive pairs for a given object phrase, while" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.093, + 0.714, + 0.196 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.716, + 0.091, + 0.878, + 0.198 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.204, + 0.892, + 0.26 + ], + "angle": 0, + "content": "Figure 3. An example of our annotated narration on the VISOR-NVOS benchmark. The annotators are instructed to write a detailed narration with [referred object] followed by \\(\\langle\\)object ID \\(\\rangle\\)." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.28, + 0.892, + 0.446 + ], + "angle": 0, + "content": "treating regions aligned with other object phrases as negative samples. Note that Eq. (3) is the loss for one object phrase, and we sum over all object phrases for training loss. This loss formulation facilitates the learning of robust region-phrase associations and enhances the quality of object segmentation and grounding. In the experiment section, we compare various strategies on selecting the negative samples for P2R contrastive learning and show the advantages of the proposed one. Our final training objective is: \\(\\mathcal{L} = \\mathcal{L}_{\\mathrm{VNA}} + \\lambda \\mathcal{L}_{\\mathrm{RPA}}\\), where \\(\\lambda\\) is the weight for region-phrase alignment loss." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.455, + 0.609, + 0.469 + ], + "angle": 0, + "content": "3.4. Inference" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.478, + 0.891, + 0.524 + ], + "angle": 0, + "content": "We ground the \\(n\\)-th noun phrase in the narration by selecting the mask proposal at each frame with the closest embedding in our learned, unified region-phrase embedding space:" + }, + { + "type": "equation", + "bbox": [ + 0.527, + 0.536, + 0.891, + 0.56 + ], + "angle": 0, + "content": "\\[\n\\mathcal {M} _ {t n} = P _ {t m ^ {*}}, \\text {w h e r e} m ^ {*} = \\underset {m} {\\operatorname {a r g m a x}} g \\left(\\mathbf {r} _ {t m}, \\mathbf {w} _ {n}\\right) \\tag {4}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.57, + 0.814, + 0.585 + ], + "angle": 0, + "content": "4. Evaluation Benchmarks for NVOS" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.596, + 0.892, + 0.716 + ], + "angle": 0, + "content": "While our proposed weakly-supervised framework demonstrates the feasibility of training NVOS models without the need for mask annotation, evaluating the performance of such models is equally critical. Existing egocentric video datasets with segmentation mask annotations for objects, such as VISOR [7], VOST [44] and PACO [38], cannot be directly used for evaluation, since they lack narrations with referred objects associated with the annotated object masks." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.72, + 0.892, + 0.901 + ], + "angle": 0, + "content": "VISOR-NVOS. To address these limitations, we create a new evaluation benchmark, VISOR-NVOS, by collecting object-based narration annotations for video clips from the VISOR [7] dataset. VISOR provides mask annotations for multiple active objects in egocentric videos of the EPIC-Kitchens [6] dataset. We pair these segmentation masks with narrations, by instructing annotators to describe activities explicitly referring to a set of objects of interest. As shown in Figure 3, provided with a short video clip and a list of objects of interest (with each object name associated with an object ID and a segmentation mask), the annotators are instructed to write a sentence describing the person's" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "14514" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.1, + 0.089, + 0.875, + 0.263 + ], + "angle": 0, + "content": "
MethodSupervisionVISOR-NVOSVOST
Cross-ModalMask AnnotationEgo4D‡JFJ&FJunionJins
SAM [21] upper bound70.375.673.062.265.8
Trained w/ labeled regions
ODISE [52]mask-textclass-specific29.032.830.917.621.1
GroundedSAM [21, 27]bbox-textclass-agnostic37.341.839.521.825.3
Trained w/o labeled regions
SAM [21] + CLIP [36] (ViT-B/16)image-textclass-agnostic22.225.824.016.519.2
CoMMa† [43] + SAM [21]video-narrationclass-agnostic✓15.325.320.39.411.5
ROSA (ViT-B/16)video-narrationclass-agnostic✓34.941.238.122.225.4
ROSA (ViT-L/14)video-narrationclass-agnostic✓38.746.042.423.226.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.265, + 0.895, + 0.322 + ], + "angle": 0, + "content": "Table 1. Comparison of grounding performance between our framework and strong baselines on our NVOS benchmarks. We report metrics on the test split of our proposed VISOR-NVOS and the validation split of VOST. \\(\\ddagger\\) whether the model has been fine-tuned on Ego4D. \"Trained with labeled regions\": trained with annotations of bounding boxes or masks; \"Trained without labeled regions\": using video-level or image-level annotations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.347, + 0.473, + 0.513 + ], + "angle": 0, + "content": "activities in the video, linking noun phrases in the sentence with the associated object IDs. In total, we have collected detailed, object-based narrations for 14,612 video clips, including 37,170 referred objects. On average, each narration has 12.79 words, and 2.54 referred objects. The maximum number of referred objects in one narration is 9. We split the annotated videos into a validation set of 7,561 videos and a test set of 7,051 videos, and report the performance on the test set. We do not train our model on any of those videos or narrations. Please see the supplementary for more details about this benchmark." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.518, + 0.473, + 0.732 + ], + "angle": 0, + "content": "VOST. VOST [44] is an egocentric video object segmentation dataset specifically designed to capture dramatic object transformations. To evaluate models for NVOS on VOST, we use the verb and noun pairs (e.g., \"peel banana\", \"mold clay\") as the narrations, with the nouns serving as the objects to ground. In contrast to VISOR, which encompasses multiple object classes in a single video, VOST contains annotations for a single object class (with one or multiple instances) per video. However, the uniqueness of VOST lies in the complexity of the transformations these objects undergo, e.g., the peeling of bananas. Hence, this benchmark allows us to evaluate the model's performance in grounding objects under complex transformations and its ability to comprehend actions that induce changes in object states." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.746, + 0.21, + 0.763 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.771, + 0.268, + 0.789 + ], + "angle": 0, + "content": "5.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.472, + 0.903 + ], + "angle": 0, + "content": "Training dataset. We train our model on video-narration pairs sourced from the Ego4D dataset [12]. Ego4D is a massive-scale egocentric video dataset that provides over 3M text narrations of the camera wearer's activities, synchronized with timestamps for 3,670 hours of video. We use a subset of Ego4D for our experiments, by selecting \\(250k\\) video clips with narrations related to cooking objects." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.347, + 0.895, + 0.409 + ], + "angle": 0, + "content": "We sample four frames from each one-second clip, with an average of 1.6 narrations available per clip. During each training iteration, we construct video-narration pairs by randomly sampling one narration per video clip." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.411, + 0.896, + 0.684 + ], + "angle": 0, + "content": "Evaluation. After training on Ego4D, we evaluate on the VISOR-NVOS and VOST benchmarks without fine-tuning. Following [7, 34, 54], we use the Jaccard Index \\((\\mathcal{J},\\) also known as Intersection over Union, IoU), the Boundary F-Measure \\((\\mathcal{F})\\), and the average of Jaccard Index and Boundary F-Measure \\((\\mathcal{J}\\& \\mathcal{F})\\), as the evaluation metrics on VISOR-NVOS. On VOST, following [44], we only use the Jaccard Index as the contours are often not well-defined due to the dramatic transformations and motions involved on this dataset. As we described, VOST does not contain ground-truth alignments between annotated segmentation masks and referred objects. Hence, for some samples with multiple annotated object instances of the same object class, there is uncertainty for grounding evaluation. To mitigate this issue, we report two metrics: \\(\\mathcal{I}_{union}\\), i.e., the IoU between the predicted mask and the union of all annotated masks, and \\(\\mathcal{I}_{ins}\\), i.e., the IoU between the predicted mask and the most overlapping annotated mask instance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.687, + 0.895, + 0.824 + ], + "angle": 0, + "content": "Implementation details. We use SAM [21] to generate mask proposals on each frame using a \\(32 \\times 32\\) point grid. We apply Non-Maximum Suppression (NMS) with a threshold of 0.9 to remove redundant mask proposals. Our best model uses a CLIP ViT-L/14 Image Encoder (while for ablations we use ViT-B/16). We set the weight for region-phrase alignment loss \\(\\lambda\\) as 0.5 and use three-layer MLP in our Context-Aware Region Encoder. Please refer to the supplementary for more implementation details." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.833, + 0.822, + 0.849 + ], + "angle": 0, + "content": "5.2. Comparison with the State of the Art" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.895, + 0.903 + ], + "angle": 0, + "content": "We compare our method with strong baselines as well as state-of-the-art approaches from related tasks (narration grounding [43], open-vocabulary segmentation [52])" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "14515" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.082, + 0.089, + 0.344, + 0.176 + ], + "angle": 0, + "content": "
VNAR2PP2RJFJ&F
24.831.328.1
✓32.439.636.0
✓✓33.940.137.0
✓✓33.940.637.3
✓✓✓34.941.238.1
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.135, + 0.178, + 0.285, + 0.19 + ], + "angle": 0, + "content": "(a) Impact of various losses." + }, + { + "type": "table", + "bbox": [ + 0.359, + 0.09, + 0.625, + 0.174 + ], + "angle": 0, + "content": "
Negative samplesJFJ&F
same27.535.031.3
all27.434.831.1
other26.534.030.3
aligned (ours)34.941.238.1
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.379, + 0.176, + 0.602, + 0.189 + ], + "angle": 0, + "content": "(b) Ablation for negative region sampling." + }, + { + "type": "table", + "bbox": [ + 0.643, + 0.09, + 0.888, + 0.174 + ], + "angle": 0, + "content": "
JFJ&F
random frame33.339.836.6
max pooling33.740.537.1
softmax33.640.437.0
adaptive (ours)34.941.238.1
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.642, + 0.176, + 0.887, + 0.189 + ], + "angle": 0, + "content": "(c) Ablation of temporal aggregation functions." + }, + { + "type": "table_caption", + "bbox": [ + 0.155, + 0.195, + 0.813, + 0.209 + ], + "angle": 0, + "content": "Table 2. Ablation studies on the Global-Local Contrastive Learning framework on the VISOR-NVOS test split." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.235, + 0.473, + 0.568 + ], + "angle": 0, + "content": "adapted for our NVOS task. Baselines trained without labeled regions: \"SAM+CLIP\": For this simple baseline, we use SAM to generate mask proposals, input the cropped and masked images into CLIP image encoder and the object phrases into CLIP text encoder, and select the best matching mask proposal based on the cosine similarity of their embeddings. \"CoMMa†+SAM\": We adapt CoMMa [43], a state-of-the-art approach for weakly-supervised point-wise grounding of input language queries, for the NVOS task. We train CoMMa† with video-narration pairs (from the same Ego4D subset used to train our model), and during inference use the predicted point for each object phrase to prompt SAM and get the segmentation mask. Baselines trained with labeled regions: We also benchmark ODISE [52] and GroundedSAM [21, 27], two state-of-the-art, image-level, open-vocabulary segmentation approaches that are trained with segmentation masks/bounding boxes paired with semantic concepts, thus using stronger supervision than us. Since open-vocabulary segmentation outputs masks for all instances of an object class (e.g., all spoons), we select the mask with highest confidence score and compare it with the ground-truth mask." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.57, + 0.47, + 0.827 + ], + "angle": 0, + "content": "As can be seen in Table 1, our model (with CLIP ViT-L/14 backbone) outperforms all compared baselines, including approaches that have been trained with strong spatial supervision (e.g., GroundedSAM is based on Grounding DINO [27], an open-set object detector that has been pre-trained on Objects365 [40], a large dataset with 10Mbbox annotations). Interestingly, the simple, out-of-the-box \"SAM+CLIP\" baseline, which has not been trained on egocentric video data, outperforms \"CoMMa†+SAM\", corroborating our intuition for using mask proposals and harnessing CLIP pre-training for representing them. Compared to this strong baseline, our model (with the same ViT-B/16 backbone) improves the \\(\\mathcal{J}\\&\\mathcal{F}\\) by \\(14.1\\%\\) on VISOR-NVOS, and improves the \\(\\mathcal{J}_{ins}\\) by \\(6.2\\%\\) on VOST, which demonstrates the effectiveness of our weakly-supervised framework that learns region-phrase alignments from egocentric video narrations." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.829, + 0.47, + 0.859 + ], + "angle": 0, + "content": "We note, however, that the performance of all compared models on our VISOR-NVOS benchmark lags behind the" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.235, + 0.892, + 0.327 + ], + "angle": 0, + "content": "upper bound performance that we could obtain based on the best-matching SAM mask proposal (reported in the first row of Table 1), highlighting the challenging nature of our proposed task and benchmark and the need for further research on learning better region-phrase alignments, e.g., by better modeling temporal consistency." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.339, + 0.665, + 0.353 + ], + "angle": 0, + "content": "5.3. Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.362, + 0.892, + 0.635 + ], + "angle": 0, + "content": "What is the effect of each component of our proposed training objective? We start by reporting the performance of our CLIP-based Dual Encoder before weakly-supervised training (i.e., we replace the MLP of our region encoder with the identity mapping and just use CLIP weights for our encoders) in the first row of Table 2a. Adding the MLP and fine-tuning it on Ego4D with our Global Contrastive Objective, that encourages video-narration alignment (VNA), leads to a significant performance improvement in \\(\\mathcal{J}\\&\\mathcal{F}\\) (from \\(28.1\\%\\) to \\(36.0\\%\\), rows 1 and 2). Adding our novel region-phrase alignment loss terms, i.e., region to phrase (R2P) and phrase to region (P2R) losses (Eq. (3)), further boosts performance. Both loss terms contribute to the improvement, and their combination improves \\(\\mathcal{J}\\&\\mathcal{F}\\) by \\(2.1\\%\\), suggesting that our proposed loss function is able to learn a better region-phrase alignment by directly applying supervision on region-phrase pairs, instead of just contrasting video-narration pairs, as commonly done in prior work [64]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.639, + 0.893, + 0.851 + ], + "angle": 0, + "content": "How to select negative region samples for region-phrase contrastive learning? As can be seen in Table 2b, using regions that are aligned with the other phrases in the batch (based on the pseudo-labeled alignments) is the only strategy that does not degrade the performance. We compare it with using the rest of regions from the same video, using the rest of regions from all the videos in the batch, and using all regions from other videos (as proposed for weakly-supervised image phrase grounding [4]). We conjecture that our proposed strategy avoids the issues of \"fake negative\" samples when the negative mask regions are also relevant to the object phrase if multiple mask proposals are overlapped, and \"easy negative\" samples when the mask regions are background regions irrelevant to active objects." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "What is the effect of the temporal aggregation module? As we discussed, we aggregate region-phrase similarities from multiple frames to obtain a global video-narration" + }, + { + "type": "page_footnote", + "bbox": [ + 0.077, + 0.875, + 0.468, + 0.9 + ], + "angle": 0, + "content": "1We use CoMMa† to denote the model we trained on Ego4D to differentiate with the original CoMMa model trained on HowTo100M." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "14516" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.09, + 0.468, + 0.271 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.274, + 0.47, + 0.316 + ], + "angle": 0, + "content": "Figure 4. Qualitative Results. Top: three examples from VISOR-NVOS. Bottom: an example from VOST showing the model's robustness to objects undergoing dramatic transformations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.335, + 0.473, + 0.502 + ], + "angle": 0, + "content": "affinity score for applying our global contrastive objective. Our proposed aggregation module starts by focusing on one frame for each phrase (the one with the best matching region) and then adaptively starts encouraging alignment with the regions of other frames. As can be seen in Table 2c, this approach (adaptive) better handles occlusions and motion blur and facilitates training compared to: (a) randomly selecting a frame of the video clip during each iteration (random frame), (b) using the frame with the highest frame-phrase affinity score (max), or (c) not adapting the frame weights (softmax)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.511, + 0.262, + 0.527 + ], + "angle": 0, + "content": "5.4. Qualitative Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.535, + 0.473, + 0.763 + ], + "angle": 0, + "content": "In Figure 4, we show some qualitative results. On the top, we show three examples from VISOR-NVOS. In the first example, our model is able to segment the referred objects in a complex environment featuring multiple spoons and pans. In the second example, the model successfully distinguishes between \"flour\" and \"flour package\". The third example highlights some limitations of our model, including ambiguity in mask size where the model only segments a portion of the fridge instead of the entire unit, and challenges in understanding plurals (the narration mentions \"containers\" but it only grounds one container). The bottom section showcases the model's predictions on three frames from a VOST video depicting the peeling of a banana. Remarkably, the model accurately segments the banana while the appearance of banana has changed significantly." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.771, + 0.394, + 0.789 + ], + "angle": 0, + "content": "5.5. Exocentric Video Object Grounding" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.903 + ], + "angle": 0, + "content": "In Table 3, to further assess the generality of our model, we conduct evaluations on the third-person video object grounding dataset, YouCook2-BB [64], which includes bounding box annotations for referred objects. We convert the segmentation masks output by our model into bounding boxes for evaluation. Recall that our model is trained on egocentric videos with a goal to align object phrases" + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.089, + 0.712, + 0.244 + ], + "angle": 0, + "content": "
Methodbox accuracy
macromicro
Trained on YouCook2
Zhou et al. [64]35.0842.42
NAFAE [41]40.7146.33
STVG [56]41.6748.22
SCL [48]42.8048.60
Zero-Shot
CoMMa†+SAM6.638.98
Ours37.9344.96
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.532, + 0.246, + 0.684, + 0.258 + ], + "angle": 0, + "content": "(a) bounding box evaluation" + }, + { + "type": "table", + "bbox": [ + 0.729, + 0.131, + 0.892, + 0.202 + ], + "angle": 0, + "content": "
Methodpoint acc.
CoMMa†53.56
CoMMa [43]59.25
Ours69.35
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.729, + 0.203, + 0.89, + 0.216 + ], + "angle": 0, + "content": "(b) point prediction evaluation" + }, + { + "type": "table_caption", + "bbox": [ + 0.528, + 0.27, + 0.863, + 0.285 + ], + "angle": 0, + "content": "Table 3. Object grounding evaluation on YouCook2-BB." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.304, + 0.895, + 0.472 + ], + "angle": 0, + "content": "with segmentation masks. Despite a huge domain shift, our model achieves comparable performance with prior works [41, 48, 56, 64] that are trained on YouCook2 using bounding box proposals (Table 3a). In addition, we adopt the evaluation setup from CoMMa [43] to evaluate our model using point accuracy (see supplementary for more details). We use the center of the bounding box from our segmentation mask as the detected point. While CoMMa is trained on exocentric videos with a similar scale (HowTo100M [29]) for point-based grounding, our model outperforms CoMMa by a significant margin of \\(10.10\\%\\) (Table 3b)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.485, + 0.623, + 0.5 + ], + "angle": 0, + "content": "6. Limitations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.51, + 0.892, + 0.661 + ], + "angle": 0, + "content": "A limitation of our framework is that we perform inference on each frame separately, neglecting temporal information. Integrating temporal context into our model has the potential to enhance performance and alleviate ambiguities, which is a promising direction for future work. Furthermore, we focused our training and evaluation on the cooking domain. In the supplementary, we show that our weakly-supervised training also improves grounding on non-cooking videos, such as DIY, but a performance gap still exists between the two domains." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.675, + 0.619, + 0.69 + ], + "angle": 0, + "content": "7. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.7, + 0.892, + 0.837 + ], + "angle": 0, + "content": "We have explored the task of Narration-based Video Object Segmentation and established a new evaluation benchmark, VISOR-NVOS. Our proposed framework, ROSA, has effectively learnt the alignment between referred objects and segmentation masks using weak supervision of video-narration alignments in egocentric videos. Our approach achieved state-of-the-art zero-shot pixel-level grounding performance on two egocentric video datasets compared to strong baselines." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Acknowledgements. We thank Tushar Nagarajan, Triantafyllos Afouras, Yale Song, Austin Miller, and Jiabo Hu for helpful discussions and invaluable engineering support." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "14517" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.327, + 0.129 + ], + "angle": 0, + "content": "[1] spaCy. https://spacy.io/.3" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.131, + 0.469, + 0.201 + ], + "angle": 0, + "content": "[2] Leonard Bär mann and Alex Waibel. 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In this work, we propose the task of weakly-supervised Narration-based Video Object Segmentation (NVOS). Given an egocentric video clip and a narration of the wearer's activities, our aim is to segment object instances mentioned in the narration, without using any spatial annotations during training. Existing weakly-supervised video object grounding methods typically yield bounding boxes for referred objects. In contrast, we propose ROSA, a weakly-supervised pixel-level grounding framework learning alignments between referred objects and segmentation mask proposals. Our model harnesses vision-language models pre-trained on image-text pairs to embed region masks and object phrases. During training, we combine (a) a video-narration contrastive loss that implicitly supervises the alignment between regions and phrases, and (b) a region-phrase contrastive loss based on inferred latent alignments. To address the lack of annotated NVOS datasets in egocentric videos, we create a new evaluation benchmark, VISOR-NVOS, leveraging existing annotations of segmentation masks from VISOR alongside 14.6k newly-collected, object-based video clip narrations. Our approach achieves state-of-the-art zero-shot pixel-level grounding performance compared to strong baselines under similar supervision. Additionally, we demonstrate generalization capabilities for zero-shot video object grounding on YouCook2, a third-person instructional video dataset. + +# 1. Introduction + +Egocentric videos [6, 12, 42] capture human interactions with the surrounding environment from a first-person perspective. Recent datasets, such as Ego4D [12], have paired such interaction-rich visual signals with manually annotated textual narrations of the camera wearer's activities, catalyzing a surge in research at the intersection of vision + +![](images/88bf2168a846b19194d5b2e0c3ddf6ee587d7e167f20c81d8bca90d4530bde2a.jpg) +"C uses a spoon to spread the minced meat on the cheese mixture in a lasagna dish" + +![](images/e979369bb177fcd1c2ec61ac9a00b446d268b78b214737485c693a42ab48071d.jpg) + +![](images/24bfe34ccb4117f7b9930e0ab16fa87d0239a6a7b000ff5730994f60768b838f.jpg) +(a) Narration-based Video Object Segmentation (Ours) + +![](images/d406f12679c126042568b583c569ae621a33d781bae4f39a2ff943ee3ed89310.jpg) + +![](images/8068da98d7996013deaff58625958a07df23b0be64bdfcfc371495092fcc8161.jpg) + +![](images/8d6a670ff6d2d7be34a9673424a760cf4a5aa79aa89e4393825e85e07bfd67c0.jpg) +(b) Video Object Grounding + +![](images/151a4ca9b7f1f2dfd5d502aeaa656384601c20b5574571183a3b5d59b47236e8.jpg) +"the spoon used to spread the minced meat" +(c) Referring Expression Segmentation + +![](images/c451c63893c9f94c52242712e4b11d02f12fb52c2f501d472cb29e29fd587d36.jpg) +spoon; minced meat; +cheese mixture; lasagna dish +(d) Video Object Segmentation +Figure 1. Overview of the Narration-based Video Object Segmentation (NVOS) task. Given a short video clip and a narration of the camera wearer's activities, our goal is to predict segmentation masks for each object phrase. This task requires more fine-grained video-language alignment (pixel-level and phrase-level) compared to popular grounding tasks, such as video object grounding and referring expression segmentation. Frames taken from the Epic-Kitchens [6] dataset. + +and language. These efforts have primarily concentrated on coarse-grained, holistic video-language understanding, such as pairing a video clip with a narration of its content (video-text retrieval) [24, 35, 60], egocentric video question answering [2, 11, 18] and temporal localization of natural language queries [3, 15, 26, 37, 61], often lacking the fine-grained understanding at object level. + +In this work, we explore a more fine-grained connection between egocentric videos and language by introducing the Narration-based Video Object Segmentation (NVOS) task, linking noun phrases (objects) in narrations with segmentation masks in the video. For example, as shown in Figure 1, given an egocentric video clip and its narration "C uses a spoon to spread the minced meat on the cheese mixture in a lasagna dish", our goal is to predict a segmentation mask at each frame for each one of the referred objects (noun phrases): spoon, minced meat, cheese mixture, and lasagna dish. Our task requires models to effectively disambiguate + +among multiple instances of the same object class (e.g., predict a segmentation mask for the spoon that the person uses and not for the spoon on the chopping board). + +This task is related to, but different from other popular tasks that output segmentation masks, such as referring expression segmentation [50, 58] (Figure 1c), which generates a segmentation mask for only one object described in an input query sentence and open vocabulary segmentation [23, 38] (Figure 1d), which does not use narration context and is unable to disambiguate object instances of the same class. Besides, most prior approaches that address phrase-level grounding in images [4, 33] and videos [22, 41, 43, 64] were limited to predicting a single point or a bounding box per referred object. However, detecting the bounding boxes (Figure 1b) is not sufficient to localize highly-overlapping, occluded, or non-grid-aligned objects which frequently occur in egocentric procedural videos. + +Training models for pixel-level grounding typically requires spatial annotations (e.g., segmentation masks [16, 20] or mouse traces [45]) for the referred objects. However, obtaining precise annotations for every referred object in textual narrations is not only arduous but also prohibitively expensive for large-scale datasets like Ego4D [12]. Hence, in this work we present a weakly-supervised framework for NVOS, trained only with narrated egocentric videos, without any manual spatial annotations for referred objects. Our framework, called Referred Object-Segment Aligner (ROSA), leverages recent breakthroughs in class-agnostic segmentation mask generation [21] and casts grounding as a region-phrase alignment problem. + +Learning such alignments from uncurated narrated egocentric videos is very challenging, due to cluttered scenes, drastically changing object appearance (e.g., cheese getting shredded) and frequent occlusions. To address this, we propose: (a) bootstrapping from powerful joint imagetext models, such as CLIP [36], to get a prior about region-phrase alignments, and (b) formulating a global matching score between a video and a narration based on the local matching scores between the masks and noun phrases across different video frames. In particular, we design a CLIP-based Dual Encoder for obtaining context-aware embeddings for mask proposals and noun phrases. We also design a Global-Local Contrastive Learning framework that operates on ground-truth video-narration pairs and pseudolabelled region-phrase pairs. + +To address the lack of benchmarks for pixel-level grounding in egocentric videos, we introduce a new benchmark, VISOR-NVOS, through manual annotations of narrations referencing segmented objects from the VISOR dataset [7]. This benchmark comprises detailed object-based narrations for 14,612 video clips. + +We summarize the contributions of this work as follows: + +- We introduce a new task of weakly-supervised NVOS, + +and establish a new egocentric benchmark, VISOR-NVOS, by enriching the VISOR dataset [7] with detailed object-based narrations. + +- We propose ROSA, a weakly-supervised framework that learns to align referred objects in narrations with mask proposals from narrated egocentric videos, without requiring spatial annotations for semantic concepts. +- We achieve state-of-the-art zero-shot NVOS grounding performance in two egocentric video datasets (VISOR-NVOS and VOST [44]) compared to baselines that use similar weak supervision or stronger spatial supervision. Additionally, we showcase generalization ability for zero-shot video object grounding on the YouCook2-BB [64] third-person video dataset. + +# 2. Related Work + +Video object grounding is an active research field in the intersection of vision and language that aims to localize objects referenced in visual descriptions of videos. Prior work has mostly focused on third-person video datasets, such as YouCook2-BB [64] and ActivityNet Entities [65], and on coarse-grained spatial localization of each object with a bounding box [28, 39, 41, 49, 64] or a single point [43]. Proposed models for referring expression or active object grounding [22, 51] in egocentric videos also output rectangular regions. Instead our work explores pixel-level grounding of referred objects in egocentric videos. + +Our NVOS task is also closely related to the recently introduced Video Narration Grounding task [45], where the goal is to predict a segmentation mask for each noun in a collection of captions of a third-person video. Our work differs by grounding noun phrases on egocentric videos and by training models without any spatial annotations for referred objects (while [45] used mouse traces). + +Video object segmentation (VOS) is the problem of pixel-accurate separation of particular objects from the background in videos. The most related ones to our work are semi-supervised VOS [5, 14, 31, 55]. Given the segmentation masks of the objects in the first one or few frames, semi-supervised VOS aims to segment the target objects through the video. However, those methods merely use the visual modality to track and segment objects while our method segments objects based on the language narrations. + +Open-vocabulary segmentation aims to segment all object instances of the same category for a list of arbitrary categories described through textual input [9, 17, 23, 52, 57, 59]. Instead, our task aims to precisely identify particular instances of referred objects within the video. + +Image phrase grounding aims to localize corresponding objects in an image given a phrase in the image's caption [4, 13, 46, 47]. While related, we focus on pixel-wise grounding of phrases in videos than rather than bounding- + +box localization in images. To address the unique challenges of video context, we adaptively weigh various frames for establishing video-narration affinity scores during training, which has not been explored in those image-based works. Besides, most of those works apply contrastive learning only at image-caption level, with the exception of [4] which proposes a contrastive learning method at the phrase-bounding box level. Our framework is the first to combine both global and local contrastive learning losses for weakly-supervised region-phrase alignment. + +Vision-language pre-training, e.g., CLIP [36], has fueled a growing interest in knowledge transfer for various downstream tasks [25, 32, 52, 57]. Prior works [23, 57, 62, 63] have shown that naive ways to leverage pre-trained CLIP to represent bounding boxes or segmentation masks are not feasible as CLIP was pre-trained on image-text pairs without any pixel-level annotation. Our work explores ways of adapting CLIP to represent local regions and phrases, which is an exciting research question [23, 58, 63]. + +# 3. ROSA: Learning Region-Phrase Alignments + +# 3.1. Task Formulation + +Given a video-narration pair $(\mathcal{V},\mathcal{S})$ , where the video clip $\mathcal{V}$ consists of $T$ frames $\{I_1,I_2,\dots ,I_T\}$ of size $H\times W$ , and the narration $S$ describes the activities demonstrated in the video and refers to $N$ noun phrases (objects) $(o_{1},o_{2},\ldots ,o_{N})$ , our goal is to output a set of binary segmentation masks $\mathcal{M}_{tn}\in \{0,1\}^{H\times W}$ for the $n$ -th referred object at the $t$ -th frame. In this work, we focus on weakly-supervised training, i.e., training only with video-narration pairs without any pixel-level annotation. To achieve this, we extract $M$ mask proposals $\{P_{tm}\}_{t,m = 1}^{T,M}$ at each frame using the Segment Anything Model (SAM) [21] which is pre-trained on object segmentation masks without object labels. Then we use the video-narration pairs to supervise the learning of a similarity function between each mask proposal and each object phrase. + +Method overview. Figure 2 gives an overview of our proposed framework, Referred Object-Segment Aligner (ROSA). We propose a CLIP-based Dual Encoder to compute context-aware embeddings for mask regions and object phrases (Section 3.2). To train our model without ground-truth region-phrase alignments, we propose a Global-Local Contrastive Learning framework (Section 3.3). It optimizes two objectives: (1) a global contrastive objective, contrasting ground-truth positive and negative pairs of video clips and narrations, based on a Temporal Adaptive Pooling of region-phrase similarities, and (2) a local contrastive objective, contrasting pseudo-labelled positive and negative pairs of regions and phrases. After learning, grounding is achieved by finding the mask proposal that maximizes the region-phrase similarity (Section 3.4). + +# 3.2. CLIP-based Dual Encoder + +In order to effectively align phrases with mask proposals, we need discriminative region representations that align well with language and capture contextual nuances. We propose a Context-aware Region Encoder to embed each mask proposal, and a Context-aware Phrase Encoder to embed each groundable noun phrase (object), by leveraging the CLIP model [36] pretrained on large-scale image-text pairs. + +# 3.2.1 Context-Aware Region Encoder + +The original Vision Transformer [10] (ViT) from CLIP consists of $L$ Transformer layers and embeds a whole image in its special CLS token of each last layer. To extract region-level features per mask proposal of a frame, we propose Mask-Guided Image CLIP. We pass the frame through the first $L - 1$ layers of ViT, and then compute a CLS token per mask proposal by applying a simple attention masking in the last Transformer layer, which ensures that the CLS token exclusively attends to the masked region. As this approach shares the computation of all hidden layers except for the last Transformer layer among all mask proposals, it is much more efficient than cropping and masking used in prior works [8, 23, 53]. Besides, as the visual encoder has access to the whole frame, it is able to capture contextual information, making it more suitable for grounding task that needs to disambiguate between object instances of the same class based on context. The final region embedding $\mathbf{r}_{tm} \in \mathbb{R}^D$ for the $m$ -th mask proposal at the $t$ -th frame is computed by projecting the CLS token to a $D$ -dimensional vector with a shallow MLP, denoted as $\mathbf{r}_{tm} = \text{RegionEncoder}(P_{tm}, I_t)$ . + +# 3.2.2 Context-Aware Phrase Encoder + +We use a language parser (spaCy [1]) to extract the noun phrases in each narration and then apply our Context-Aware Phrase Encoder to obtain a contextualized embedding for each phrase. A straight-forward way for obtaining phrase embeddings using CLIP is to pass the entire narration through its text encoder, and perform average pooling over the tokens corresponding to each referred object (Phrase Pooling) to get a narration-aware phrase embedding for each object. However, we observe that this embedding is often heavily influenced by the narration context, resulting in similar embeddings for nearby phrases, thus hurting disambiguation that is necessary for our grounding tasks. To address this limitation, we additionally input each object phrase to CLIP's text encoder and use the EOT (End of Text) token as a localized phrase embedding. The final phrase embedding $\mathbf{w}_n\in \mathbb{R}^D$ for the $n$ -th object phrase in the input narration is computed as the average of the localized phrase embedding and narration-aware phrase embedding, + +![](images/ddf2890078bceb2f67db1c11eaf4d402a5bc426d7394950d86a27708e07943ec.jpg) +Figure 2. Framework Overview. We propose a CLIP-based Dual Encoder to embed mask proposals and noun phrases, and compute pairwise region-phrase similarities. We propose Global-Local Contrastive Learning via ground-truth Video-Narration Alignment and pseudo labelled Region-Phrase Alignment. Frames taken from Ego4D [12]. + +denoted as $\mathbf{w}_n = \text{PhraseEncoder}(o_n, \mathcal{S})$ , + +# 3.3. Global-Local Contrastive Learning + +In the weakly-supervised setting, we need to learn a similarity function between mask regions and object phrases, without ground-truth alignments of region-phrase pairs. We propose a Global-Local Contrastive Learning framework to learn the region-phrase similarities using the alignments at both video-narration (global) and region-phrase (local) levels. In Sec. 3.3.1, we detail how to compute the region-phrase similarities and aggregate them into a video-narration affinity score for global contrastive learning. In Sec. 3.3.2, we illustrate how we obtain the pseudo-labelled region-phrase pairs for local contrastive learning. + +# 3.3.1 Video-Narration Alignment + +Since our only available supervision is at the video-narration level, we propose a standard contrastive loss for video-narration alignment, which is equipped with a region-based affinity score between videos and narrations. In particular, inspired by Multiple Instance Learning approaches for weakly-supervised phrase grounding [19], we formulate an affinity score $\phi(\mathcal{V},\mathcal{S})$ between a video and a narration by aggregating individual region-phrase affinity scores. Intuitively, a video-narration pair should have a high affinity score if each referred object in the narration has a matched mask proposal in each frame of the video clip. Next, we detail how we aggregate the region-phrase similarities into frame-phrase affinity scores resulting in an overall affinity score between a video clip and a narration. + +Frame-phrase affinity score. Given a set of segmentation mask proposals $\{P_{tm}\}_{t,m=1}^{T,M}$ and a set of object phrases $\{o_n\}_{n=1}^N$ , we first compute the pairwise similarity $g(\mathbf{r}_{tm}, \mathbf{w}_n)$ between each mask proposal embedding $\mathbf{r}_{tm}$ and each noun phrase embedding $\mathbf{w}_n$ . In particular, our similarity function $g(\cdot, \cdot)$ is computed as the cosine similarity between the region embedding and phrase embedding, multiplied with the mask confidence score of the corresponding mask proposal. This multiplication prioritizes mask proposals with higher confidence scores when aligning the object phrase with mask proposals. The affinity score between a phrase and a frame is then defined based on the best matching region at each frame $I_t$ : $\psi(I_t, o_n) = \max_m g(\mathbf{r}_{tm}, \mathbf{w}_n)$ . + +Video-phrase affinity score. To compute the affinity score at the video-phrase level, we introduce a Temporal Adaptive Pooling of the frame-phrase affinity scores $\psi(I_t, o_n)$ : + +$$ +\sigma (\mathcal {V}, o _ {n}) = \sum_ {t} \frac {e ^ {\psi \left(I _ {t} , o _ {n}\right) / \alpha}}{\sum_ {t ^ {\prime}} e ^ {\psi \left(I _ {t ^ {\prime}} , o _ {n}\right) / \alpha}} \psi \left(I _ {t}, o _ {n}\right). \tag {1} +$$ + +The function involves a weighted sum across all temporal frames, where the weight for each frame is determined by the frame-phrase affinity scores divided by a temperature parameter $\alpha$ . We dynamically adjust $\alpha$ during training, following the schedule $\alpha = \alpha_0\beta^{-s}$ , where $\alpha_0$ is a small constant close to $0$ , $\beta \in (0,1)$ is a decay index, and $s$ is the iteration step. Intuitively, at the initial stage of training, the model may struggle to effectively segment objects undergoing occlusions or significant transformations. This dynamic adjustment allows the model to prioritize the most confident + +mask proposal in a single frame early in training (with low $\alpha$ ) and gradually shift towards a smoother, more robust aggregation of region representations from multiple frames as training progresses (with a larger $\alpha$ ). + +Video-narration affinity score. Finally, we compute the video-narration affinity score by averaging the videophrase affinity scores over all object phrases: $\phi(\mathcal{V},\mathcal{S}) = \frac{\sum_{n}\sigma(\mathcal{V},o_{n})}{N}$ , which assumes that all referred objects in the narration should be present in the aligned video clip. + +Video-narration contrastive loss. Given a training batch of video-narration pairs $\{(\mathcal{V}_i, \mathcal{S}_i)\}_{i=1}^B$ , where $B$ is the batch size, we use an InfoNCE loss to train the model via weak supervision as follows: + +$$ +\mathcal {L} _ {\mathrm {V N A}} = \frac {1}{B} \sum_ {i = 1} ^ {B} - \log \frac {e ^ {\phi \left(\mathcal {V} _ {i} , \mathcal {S} _ {i}\right) / \tau}}{\sum_ {j} e ^ {\phi \left(\mathcal {V} _ {i} , \mathcal {S} _ {j}\right) / \tau}} - \log \frac {e ^ {\phi \left(\mathcal {V} _ {i} , \mathcal {S} _ {i}\right) / \tau}}{\sum_ {j} e ^ {\phi \left(\mathcal {V} _ {j} , \mathcal {S} _ {i}\right) / \tau}}, \tag {2} +$$ + +where $\tau$ is a learnable temperature and $\phi(\mathcal{V}_i, \mathcal{S}_j)$ is our custom video-narration affinity score defined above. We freeze the pre-trained CLIP image and text encoders, and optimize the parameters of the MLP to learn region representations better aligned with phrases. + +# 3.3.2 Region-Phrase Alignment + +While the aforementioned video-narration contrastive loss is effective at leveraging video-narration supervision, the loss is not directly applied to the alignment between region-phrase pairs. In order to learn a better alignment between mask regions and object phrases, we propose an additional local loss at region-phrase level. To do so, we first get pseudo-labelled alignments for region-phrase pairs. For each phrase embedding $\mathbf{w}_n$ , we get the embedding of its best aligned mask proposal at each frame, denoted as $\tilde{\mathbf{r}}_{tn} = \{\mathbf{r}_{tm}|m = \operatorname*{argmax}_{m'}g(\mathbf{r}_{tm'},\mathbf{w}_n)\}$ . + +Region-phrase contrastive loss. Then we apply a region-phrase alignment loss over all object phrases and all aligned mask regions in a batch: + +$$ +\begin{array}{l} \mathcal {L} _ {\mathrm {R P A}} = - \sum_ {t} \underbrace {\log \frac {e ^ {g \left(\tilde {\mathbf {r}} _ {t n} , \mathbf {w} _ {n}\right) / \tau}}{\sum_ {n ^ {\prime}} e ^ {g \left(\tilde {\mathbf {r}} _ {t n} , \mathbf {w} _ {n ^ {\prime}}\right) / \tau}}} _ {\text {r e g i o n t o p h r a s e}} \tag {3} \\ - \underbrace {\log \frac {\sum_ {t} e ^ {g (\mathbf {r} _ {t n} , \mathbf {w} _ {n}) / \tau}}{\sum_ {n ^ {\prime}} \sum_ {t} e ^ {g (\tilde {\mathbf {r}} _ {t n ^ {\prime}} , \mathbf {w} _ {n}) / \tau}}} _ {\text {p h r a s e t o r i g i o n}}. \\ \end{array} +$$ + +The first term is a region to phrase (R2P) standard InfoNCE contrastive loss, which treats other object phrases as negative samples for a given mask region. The second term is a phrase to region (P2R) MIL-NCE-type [30] contrastive loss, which considers the aligned regions in all frames as positive pairs for a given object phrase, while + +![](images/554a5be7f4c3c2114ed8e1b112025dd72e3a2af9de674bc47248db261a00843b.jpg) +Figure 3. An example of our annotated narration on the VISOR-NVOS benchmark. The annotators are instructed to write a detailed narration with [referred object] followed by $\langle$ object ID $\rangle$ . + +![](images/309bdaeb16109b4de6dd995d707135bc9dfb93f525bf1a45f38f25599b269db7.jpg) + +treating regions aligned with other object phrases as negative samples. Note that Eq. (3) is the loss for one object phrase, and we sum over all object phrases for training loss. This loss formulation facilitates the learning of robust region-phrase associations and enhances the quality of object segmentation and grounding. In the experiment section, we compare various strategies on selecting the negative samples for P2R contrastive learning and show the advantages of the proposed one. Our final training objective is: $\mathcal{L} = \mathcal{L}_{\mathrm{VNA}} + \lambda \mathcal{L}_{\mathrm{RPA}}$ , where $\lambda$ is the weight for region-phrase alignment loss. + +# 3.4. Inference + +We ground the $n$ -th noun phrase in the narration by selecting the mask proposal at each frame with the closest embedding in our learned, unified region-phrase embedding space: + +$$ +\mathcal {M} _ {t n} = P _ {t m ^ {*}}, \text {w h e r e} m ^ {*} = \underset {m} {\operatorname {a r g m a x}} g \left(\mathbf {r} _ {t m}, \mathbf {w} _ {n}\right) \tag {4} +$$ + +# 4. Evaluation Benchmarks for NVOS + +While our proposed weakly-supervised framework demonstrates the feasibility of training NVOS models without the need for mask annotation, evaluating the performance of such models is equally critical. Existing egocentric video datasets with segmentation mask annotations for objects, such as VISOR [7], VOST [44] and PACO [38], cannot be directly used for evaluation, since they lack narrations with referred objects associated with the annotated object masks. + +VISOR-NVOS. To address these limitations, we create a new evaluation benchmark, VISOR-NVOS, by collecting object-based narration annotations for video clips from the VISOR [7] dataset. VISOR provides mask annotations for multiple active objects in egocentric videos of the EPIC-Kitchens [6] dataset. We pair these segmentation masks with narrations, by instructing annotators to describe activities explicitly referring to a set of objects of interest. As shown in Figure 3, provided with a short video clip and a list of objects of interest (with each object name associated with an object ID and a segmentation mask), the annotators are instructed to write a sentence describing the person's + +
MethodSupervisionVISOR-NVOSVOST
Cross-ModalMask AnnotationEgo4D‡JFJ&FJunionJins
SAM [21] upper bound70.375.673.062.265.8
Trained w/ labeled regions
ODISE [52]mask-textclass-specific29.032.830.917.621.1
GroundedSAM [21, 27]bbox-textclass-agnostic37.341.839.521.825.3
Trained w/o labeled regions
SAM [21] + CLIP [36] (ViT-B/16)image-textclass-agnostic22.225.824.016.519.2
CoMMa† [43] + SAM [21]video-narrationclass-agnostic✓15.325.320.39.411.5
ROSA (ViT-B/16)video-narrationclass-agnostic✓34.941.238.122.225.4
ROSA (ViT-L/14)video-narrationclass-agnostic✓38.746.042.423.226.7
+ +Table 1. Comparison of grounding performance between our framework and strong baselines on our NVOS benchmarks. We report metrics on the test split of our proposed VISOR-NVOS and the validation split of VOST. $\ddagger$ whether the model has been fine-tuned on Ego4D. "Trained with labeled regions": trained with annotations of bounding boxes or masks; "Trained without labeled regions": using video-level or image-level annotations. + +activities in the video, linking noun phrases in the sentence with the associated object IDs. In total, we have collected detailed, object-based narrations for 14,612 video clips, including 37,170 referred objects. On average, each narration has 12.79 words, and 2.54 referred objects. The maximum number of referred objects in one narration is 9. We split the annotated videos into a validation set of 7,561 videos and a test set of 7,051 videos, and report the performance on the test set. We do not train our model on any of those videos or narrations. Please see the supplementary for more details about this benchmark. + +VOST. VOST [44] is an egocentric video object segmentation dataset specifically designed to capture dramatic object transformations. To evaluate models for NVOS on VOST, we use the verb and noun pairs (e.g., "peel banana", "mold clay") as the narrations, with the nouns serving as the objects to ground. In contrast to VISOR, which encompasses multiple object classes in a single video, VOST contains annotations for a single object class (with one or multiple instances) per video. However, the uniqueness of VOST lies in the complexity of the transformations these objects undergo, e.g., the peeling of bananas. Hence, this benchmark allows us to evaluate the model's performance in grounding objects under complex transformations and its ability to comprehend actions that induce changes in object states. + +# 5. Experiments + +# 5.1. Experimental Setup + +Training dataset. We train our model on video-narration pairs sourced from the Ego4D dataset [12]. Ego4D is a massive-scale egocentric video dataset that provides over 3M text narrations of the camera wearer's activities, synchronized with timestamps for 3,670 hours of video. We use a subset of Ego4D for our experiments, by selecting $250k$ video clips with narrations related to cooking objects. + +We sample four frames from each one-second clip, with an average of 1.6 narrations available per clip. During each training iteration, we construct video-narration pairs by randomly sampling one narration per video clip. + +Evaluation. After training on Ego4D, we evaluate on the VISOR-NVOS and VOST benchmarks without fine-tuning. Following [7, 34, 54], we use the Jaccard Index $(\mathcal{J},$ also known as Intersection over Union, IoU), the Boundary F-Measure $(\mathcal{F})$ , and the average of Jaccard Index and Boundary F-Measure $(\mathcal{J}\& \mathcal{F})$ , as the evaluation metrics on VISOR-NVOS. On VOST, following [44], we only use the Jaccard Index as the contours are often not well-defined due to the dramatic transformations and motions involved on this dataset. As we described, VOST does not contain ground-truth alignments between annotated segmentation masks and referred objects. Hence, for some samples with multiple annotated object instances of the same object class, there is uncertainty for grounding evaluation. To mitigate this issue, we report two metrics: $\mathcal{I}_{union}$ , i.e., the IoU between the predicted mask and the union of all annotated masks, and $\mathcal{I}_{ins}$ , i.e., the IoU between the predicted mask and the most overlapping annotated mask instance. + +Implementation details. We use SAM [21] to generate mask proposals on each frame using a $32 \times 32$ point grid. We apply Non-Maximum Suppression (NMS) with a threshold of 0.9 to remove redundant mask proposals. Our best model uses a CLIP ViT-L/14 Image Encoder (while for ablations we use ViT-B/16). We set the weight for region-phrase alignment loss $\lambda$ as 0.5 and use three-layer MLP in our Context-Aware Region Encoder. Please refer to the supplementary for more implementation details. + +# 5.2. Comparison with the State of the Art + +We compare our method with strong baselines as well as state-of-the-art approaches from related tasks (narration grounding [43], open-vocabulary segmentation [52]) + +
VNAR2PP2RJFJ&F
24.831.328.1
✓32.439.636.0
✓✓33.940.137.0
✓✓33.940.637.3
✓✓✓34.941.238.1
+ +(a) Impact of various losses. + +
Negative samplesJFJ&F
same27.535.031.3
all27.434.831.1
other26.534.030.3
aligned (ours)34.941.238.1
+ +(b) Ablation for negative region sampling. + +
JFJ&F
random frame33.339.836.6
max pooling33.740.537.1
softmax33.640.437.0
adaptive (ours)34.941.238.1
+ +(c) Ablation of temporal aggregation functions. + +Table 2. Ablation studies on the Global-Local Contrastive Learning framework on the VISOR-NVOS test split. + +adapted for our NVOS task. Baselines trained without labeled regions: "SAM+CLIP": For this simple baseline, we use SAM to generate mask proposals, input the cropped and masked images into CLIP image encoder and the object phrases into CLIP text encoder, and select the best matching mask proposal based on the cosine similarity of their embeddings. "CoMMa†+SAM": We adapt CoMMa [43], a state-of-the-art approach for weakly-supervised point-wise grounding of input language queries, for the NVOS task. We train CoMMa† with video-narration pairs (from the same Ego4D subset used to train our model), and during inference use the predicted point for each object phrase to prompt SAM and get the segmentation mask. Baselines trained with labeled regions: We also benchmark ODISE [52] and GroundedSAM [21, 27], two state-of-the-art, image-level, open-vocabulary segmentation approaches that are trained with segmentation masks/bounding boxes paired with semantic concepts, thus using stronger supervision than us. Since open-vocabulary segmentation outputs masks for all instances of an object class (e.g., all spoons), we select the mask with highest confidence score and compare it with the ground-truth mask. + +As can be seen in Table 1, our model (with CLIP ViT-L/14 backbone) outperforms all compared baselines, including approaches that have been trained with strong spatial supervision (e.g., GroundedSAM is based on Grounding DINO [27], an open-set object detector that has been pre-trained on Objects365 [40], a large dataset with 10Mbbox annotations). Interestingly, the simple, out-of-the-box "SAM+CLIP" baseline, which has not been trained on egocentric video data, outperforms "CoMMa†+SAM", corroborating our intuition for using mask proposals and harnessing CLIP pre-training for representing them. Compared to this strong baseline, our model (with the same ViT-B/16 backbone) improves the $\mathcal{J}\&\mathcal{F}$ by $14.1\%$ on VISOR-NVOS, and improves the $\mathcal{J}_{ins}$ by $6.2\%$ on VOST, which demonstrates the effectiveness of our weakly-supervised framework that learns region-phrase alignments from egocentric video narrations. + +We note, however, that the performance of all compared models on our VISOR-NVOS benchmark lags behind the + +upper bound performance that we could obtain based on the best-matching SAM mask proposal (reported in the first row of Table 1), highlighting the challenging nature of our proposed task and benchmark and the need for further research on learning better region-phrase alignments, e.g., by better modeling temporal consistency. + +# 5.3. Ablation Studies + +What is the effect of each component of our proposed training objective? We start by reporting the performance of our CLIP-based Dual Encoder before weakly-supervised training (i.e., we replace the MLP of our region encoder with the identity mapping and just use CLIP weights for our encoders) in the first row of Table 2a. Adding the MLP and fine-tuning it on Ego4D with our Global Contrastive Objective, that encourages video-narration alignment (VNA), leads to a significant performance improvement in $\mathcal{J}\&\mathcal{F}$ (from $28.1\%$ to $36.0\%$ , rows 1 and 2). Adding our novel region-phrase alignment loss terms, i.e., region to phrase (R2P) and phrase to region (P2R) losses (Eq. (3)), further boosts performance. Both loss terms contribute to the improvement, and their combination improves $\mathcal{J}\&\mathcal{F}$ by $2.1\%$ , suggesting that our proposed loss function is able to learn a better region-phrase alignment by directly applying supervision on region-phrase pairs, instead of just contrasting video-narration pairs, as commonly done in prior work [64]. + +How to select negative region samples for region-phrase contrastive learning? As can be seen in Table 2b, using regions that are aligned with the other phrases in the batch (based on the pseudo-labeled alignments) is the only strategy that does not degrade the performance. We compare it with using the rest of regions from the same video, using the rest of regions from all the videos in the batch, and using all regions from other videos (as proposed for weakly-supervised image phrase grounding [4]). We conjecture that our proposed strategy avoids the issues of "fake negative" samples when the negative mask regions are also relevant to the object phrase if multiple mask proposals are overlapped, and "easy negative" samples when the mask regions are background regions irrelevant to active objects. + +What is the effect of the temporal aggregation module? As we discussed, we aggregate region-phrase similarities from multiple frames to obtain a global video-narration + +![](images/290c8b0b4154acfd0a6e11d5111daa1c923f163ac5bb518aab99f96bf25baa21.jpg) +Figure 4. Qualitative Results. Top: three examples from VISOR-NVOS. Bottom: an example from VOST showing the model's robustness to objects undergoing dramatic transformations. + +affinity score for applying our global contrastive objective. Our proposed aggregation module starts by focusing on one frame for each phrase (the one with the best matching region) and then adaptively starts encouraging alignment with the regions of other frames. As can be seen in Table 2c, this approach (adaptive) better handles occlusions and motion blur and facilitates training compared to: (a) randomly selecting a frame of the video clip during each iteration (random frame), (b) using the frame with the highest frame-phrase affinity score (max), or (c) not adapting the frame weights (softmax). + +# 5.4. Qualitative Results + +In Figure 4, we show some qualitative results. On the top, we show three examples from VISOR-NVOS. In the first example, our model is able to segment the referred objects in a complex environment featuring multiple spoons and pans. In the second example, the model successfully distinguishes between "flour" and "flour package". The third example highlights some limitations of our model, including ambiguity in mask size where the model only segments a portion of the fridge instead of the entire unit, and challenges in understanding plurals (the narration mentions "containers" but it only grounds one container). The bottom section showcases the model's predictions on three frames from a VOST video depicting the peeling of a banana. Remarkably, the model accurately segments the banana while the appearance of banana has changed significantly. + +# 5.5. Exocentric Video Object Grounding + +In Table 3, to further assess the generality of our model, we conduct evaluations on the third-person video object grounding dataset, YouCook2-BB [64], which includes bounding box annotations for referred objects. We convert the segmentation masks output by our model into bounding boxes for evaluation. Recall that our model is trained on egocentric videos with a goal to align object phrases + +
Methodbox accuracy
macromicro
Trained on YouCook2
Zhou et al. [64]35.0842.42
NAFAE [41]40.7146.33
STVG [56]41.6748.22
SCL [48]42.8048.60
Zero-Shot
CoMMa†+SAM6.638.98
Ours37.9344.96
+ +(a) bounding box evaluation + +
Methodpoint acc.
CoMMa†53.56
CoMMa [43]59.25
Ours69.35
+ +(b) point prediction evaluation + +Table 3. Object grounding evaluation on YouCook2-BB. + +with segmentation masks. Despite a huge domain shift, our model achieves comparable performance with prior works [41, 48, 56, 64] that are trained on YouCook2 using bounding box proposals (Table 3a). In addition, we adopt the evaluation setup from CoMMa [43] to evaluate our model using point accuracy (see supplementary for more details). We use the center of the bounding box from our segmentation mask as the detected point. While CoMMa is trained on exocentric videos with a similar scale (HowTo100M [29]) for point-based grounding, our model outperforms CoMMa by a significant margin of $10.10\%$ (Table 3b). + +# 6. Limitations + +A limitation of our framework is that we perform inference on each frame separately, neglecting temporal information. Integrating temporal context into our model has the potential to enhance performance and alleviate ambiguities, which is a promising direction for future work. Furthermore, we focused our training and evaluation on the cooking domain. In the supplementary, we show that our weakly-supervised training also improves grounding on non-cooking videos, such as DIY, but a performance gap still exists between the two domains. + +# 7. Conclusion + +We have explored the task of Narration-based Video Object Segmentation and established a new evaluation benchmark, VISOR-NVOS. Our proposed framework, ROSA, has effectively learnt the alignment between referred objects and segmentation masks using weak supervision of video-narration alignments in egocentric videos. Our approach achieved state-of-the-art zero-shot pixel-level grounding performance on two egocentric video datasets compared to strong baselines. + +Acknowledgements. We thank Tushar Nagarajan, Triantafyllos Afouras, Yale Song, Austin Miller, and Jiabo Hu for helpful discussions and invaluable engineering support. + +# References + +[1] spaCy. https://spacy.io/.3 +[2] Leonard Bär mann and Alex Waibel. Where did i leave my keys? - episodic-memory-based question answering on egocentric videos. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR) Workshops, pages 1560-1568, 2022. 1 +[3] Wayner Barrios, Mattia Soldan, Alberto Mario Ceballos-Arroyo, Fabian Caba Heilbron, and Bernard Ghanem. Localizing moments in long video via multimodal guidance. In Proceedings of the IEEE/CVF International Conference on Computer Vision (ICCV), pages 13667-13678, 2023. 1 +[4] Keqin Chen, Richong Zhang, Samuel Mensah, and Yongyi Mao. Contrastive learning with expectation-maximization for weakly supervised phrase grounding. 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+ "index": 19, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "type": "image", + "bbox": [ + 470, + 346, + 539, + 372 + ], + "blocks": [ + { + "bbox": [ + 468, + 329, + 541, + 342 + ], + "lines": [ + { + "bbox": [ + 468, + 329, + 541, + 342 + ], + "spans": [ + { + "bbox": [ + 468, + 329, + 541, + 342 + ], + "type": "text", + "content": "spoon; minced meat; \ncheese mixture; lasagna dish" + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 470, + 346, + 539, + 372 + ], + "lines": [ + { + "bbox": [ + 470, + 346, + 539, + 372 + ], + "spans": [ + { + "bbox": [ + 470, + 346, + 539, + 372 + ], + "type": "image", + "image_path": "c451c63893c9f94c52242712e4b11d02f12fb52c2f501d472cb29e29fd587d36.jpg" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 480, + 373, + 529, + 388 + ], + "lines": [ + { + "bbox": [ + 480, + 373, + 529, + 388 + ], + "spans": [ + { + "bbox": [ + 480, + 373, + 529, + 388 + ], + "type": "text", + "content": "(d) Video Object Segmentation" + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 399, + 545, + 487 + ], + "lines": [ + { + "bbox": [ + 304, + 399, + 545, + 487 + ], + "spans": [ + { + "bbox": [ + 304, + 399, + 545, + 487 + ], + "type": "text", + "content": "Figure 1. Overview of the Narration-based Video Object Segmentation (NVOS) task. Given a short video clip and a narration of the camera wearer's activities, our goal is to predict segmentation masks for each object phrase. This task requires more fine-grained video-language alignment (pixel-level and phrase-level) compared to popular grounding tasks, such as video object grounding and referring expression segmentation. Frames taken from the Epic-Kitchens [6] dataset." + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_caption" + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 497, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 497, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 497, + 545, + 581 + ], + "type": "text", + "content": "and language. These efforts have primarily concentrated on coarse-grained, holistic video-language understanding, such as pairing a video clip with a narration of its content (video-text retrieval) [24, 35, 60], egocentric video question answering [2, 11, 18] and temporal localization of natural language queries [3, 15, 26, 37, 61], often lacking the fine-grained understanding at object level." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 546, + 713 + ], + "type": "text", + "content": "In this work, we explore a more fine-grained connection between egocentric videos and language by introducing the Narration-based Video Object Segmentation (NVOS) task, linking noun phrases (objects) in narrations with segmentation masks in the video. For example, as shown in Figure 1, given an egocentric video clip and its narration \"C uses a spoon to spread the minced meat on the cheese mixture in a lasagna dish\", our goal is to predict a segmentation mask at each frame for each one of the referred objects (noun phrases): spoon, minced meat, cheese mixture, and lasagna dish. Our task requires models to effectively disambiguate" + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 215, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 215, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 215, + 712 + ], + "type": "text", + "content": "*Work done during an internship at FAIR, Meta." + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "14510" + } + ] + } + ], + "index": 27 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 108 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 108 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 108 + ], + "type": "text", + "content": "among multiple instances of the same object class (e.g., predict a segmentation mask for the spoon that the person uses and not for the spoon on the chopping board)." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 110, + 287, + 276 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 110, + 287, + 276 + ], + "spans": [ + { + "bbox": [ + 46, + 110, + 287, + 276 + ], + "type": "text", + "content": "This task is related to, but different from other popular tasks that output segmentation masks, such as referring expression segmentation [50, 58] (Figure 1c), which generates a segmentation mask for only one object described in an input query sentence and open vocabulary segmentation [23, 38] (Figure 1d), which does not use narration context and is unable to disambiguate object instances of the same class. Besides, most prior approaches that address phrase-level grounding in images [4, 33] and videos [22, 41, 43, 64] were limited to predicting a single point or a bounding box per referred object. However, detecting the bounding boxes (Figure 1b) is not sufficient to localize highly-overlapping, occluded, or non-grid-aligned objects which frequently occur in egocentric procedural videos." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 277, + 287, + 433 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 277, + 287, + 433 + ], + "spans": [ + { + "bbox": [ + 46, + 277, + 287, + 433 + ], + "type": "text", + "content": "Training models for pixel-level grounding typically requires spatial annotations (e.g., segmentation masks [16, 20] or mouse traces [45]) for the referred objects. However, obtaining precise annotations for every referred object in textual narrations is not only arduous but also prohibitively expensive for large-scale datasets like Ego4D [12]. Hence, in this work we present a weakly-supervised framework for NVOS, trained only with narrated egocentric videos, without any manual spatial annotations for referred objects. Our framework, called Referred Object-Segment Aligner (ROSA), leverages recent breakthroughs in class-agnostic segmentation mask generation [21] and casts grounding as a region-phrase alignment problem." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 434, + 287, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 434, + 287, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 434, + 287, + 613 + ], + "type": "text", + "content": "Learning such alignments from uncurated narrated egocentric videos is very challenging, due to cluttered scenes, drastically changing object appearance (e.g., cheese getting shredded) and frequent occlusions. To address this, we propose: (a) bootstrapping from powerful joint imagetext models, such as CLIP [36], to get a prior about region-phrase alignments, and (b) formulating a global matching score between a video and a narration based on the local matching scores between the masks and noun phrases across different video frames. In particular, we design a CLIP-based Dual Encoder for obtaining context-aware embeddings for mask proposals and noun phrases. We also design a Global-Local Contrastive Learning framework that operates on ground-truth video-narration pairs and pseudolabelled region-phrase pairs." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 615, + 286, + 686 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 615, + 286, + 686 + ], + "spans": [ + { + "bbox": [ + 46, + 615, + 286, + 686 + ], + "type": "text", + "content": "To address the lack of benchmarks for pixel-level grounding in egocentric videos, we introduce a new benchmark, VISOR-NVOS, through manual annotations of narrations referencing segmented objects from the VISOR dataset [7]. This benchmark comprises detailed object-based narrations for 14,612 video clips." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 688, + 286, + 699 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 688, + 286, + 699 + ], + "spans": [ + { + "bbox": [ + 47, + 688, + 286, + 699 + ], + "type": "text", + "content": "We summarize the contributions of this work as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 701, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 701, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 701, + 286, + 713 + ], + "type": "text", + "content": "- We introduce a new task of weakly-supervised NVOS," + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 313, + 72, + 545, + 107 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 72, + 545, + 107 + ], + "spans": [ + { + "bbox": [ + 313, + 72, + 545, + 107 + ], + "type": "text", + "content": "and establish a new egocentric benchmark, VISOR-NVOS, by enriching the VISOR dataset [7] with detailed object-based narrations." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 108, + 545, + 239 + ], + "type": "list", + "angle": 0, + "index": 10, + "blocks": [ + { + "bbox": [ + 306, + 108, + 545, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 108, + 545, + 156 + ], + "spans": [ + { + "bbox": [ + 306, + 108, + 545, + 156 + ], + "type": "text", + "content": "- We propose ROSA, a weakly-supervised framework that learns to align referred objects in narrations with mask proposals from narrated egocentric videos, without requiring spatial annotations for semantic concepts." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 156, + 545, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 156, + 545, + 239 + ], + "spans": [ + { + "bbox": [ + 306, + 156, + 545, + 239 + ], + "type": "text", + "content": "- We achieve state-of-the-art zero-shot NVOS grounding performance in two egocentric video datasets (VISOR-NVOS and VOST [44]) compared to baselines that use similar weak supervision or stronger spatial supervision. Additionally, we showcase generalization ability for zero-shot video object grounding on the YouCook2-BB [64] third-person video dataset." + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 251, + 392, + 264 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 251, + 392, + 264 + ], + "spans": [ + { + "bbox": [ + 306, + 251, + 392, + 264 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 271, + 545, + 403 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 271, + 545, + 403 + ], + "spans": [ + { + "bbox": [ + 304, + 271, + 545, + 403 + ], + "type": "text", + "content": "Video object grounding is an active research field in the intersection of vision and language that aims to localize objects referenced in visual descriptions of videos. Prior work has mostly focused on third-person video datasets, such as YouCook2-BB [64] and ActivityNet Entities [65], and on coarse-grained spatial localization of each object with a bounding box [28, 39, 41, 49, 64] or a single point [43]. Proposed models for referring expression or active object grounding [22, 51] in egocentric videos also output rectangular regions. Instead our work explores pixel-level grounding of referred objects in egocentric videos." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 403, + 545, + 487 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 545, + 487 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 545, + 487 + ], + "type": "text", + "content": "Our NVOS task is also closely related to the recently introduced Video Narration Grounding task [45], where the goal is to predict a segmentation mask for each noun in a collection of captions of a third-person video. Our work differs by grounding noun phrases on egocentric videos and by training models without any spatial annotations for referred objects (while [45] used mouse traces)." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 491, + 545, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 491, + 545, + 598 + ], + "spans": [ + { + "bbox": [ + 304, + 491, + 545, + 598 + ], + "type": "text", + "content": "Video object segmentation (VOS) is the problem of pixel-accurate separation of particular objects from the background in videos. The most related ones to our work are semi-supervised VOS [5, 14, 31, 55]. Given the segmentation masks of the objects in the first one or few frames, semi-supervised VOS aims to segment the target objects through the video. However, those methods merely use the visual modality to track and segment objects while our method segments objects based on the language narrations." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 602, + 545, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 602, + 545, + 662 + ], + "spans": [ + { + "bbox": [ + 304, + 602, + 545, + 662 + ], + "type": "text", + "content": "Open-vocabulary segmentation aims to segment all object instances of the same category for a list of arbitrary categories described through textual input [9, 17, 23, 52, 57, 59]. Instead, our task aims to precisely identify particular instances of referred objects within the video." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 666, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 666, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 666, + 545, + 713 + ], + "type": "text", + "content": "Image phrase grounding aims to localize corresponding objects in an image given a phrase in the image's caption [4, 13, 46, 47]. While related, we focus on pixel-wise grounding of phrases in videos than rather than bounding-" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "14511" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 192 + ], + "type": "text", + "content": "box localization in images. To address the unique challenges of video context, we adaptively weigh various frames for establishing video-narration affinity scores during training, which has not been explored in those image-based works. Besides, most of those works apply contrastive learning only at image-caption level, with the exception of [4] which proposes a contrastive learning method at the phrase-bounding box level. Our framework is the first to combine both global and local contrastive learning losses for weakly-supervised region-phrase alignment." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 194, + 289, + 304 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 194, + 289, + 304 + ], + "spans": [ + { + "bbox": [ + 46, + 194, + 289, + 304 + ], + "type": "text", + "content": "Vision-language pre-training, e.g., CLIP [36], has fueled a growing interest in knowledge transfer for various downstream tasks [25, 32, 52, 57]. Prior works [23, 57, 62, 63] have shown that naive ways to leverage pre-trained CLIP to represent bounding boxes or segmentation masks are not feasible as CLIP was pre-trained on image-text pairs without any pixel-level annotation. Our work explores ways of adapting CLIP to represent local regions and phrases, which is an exciting research question [23, 58, 63]." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 313, + 288, + 328 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 313, + 288, + 328 + ], + "spans": [ + { + "bbox": [ + 47, + 313, + 288, + 328 + ], + "type": "text", + "content": "3. ROSA: Learning Region-Phrase Alignments" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 332, + 153, + 345 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 332, + 153, + 345 + ], + "spans": [ + { + "bbox": [ + 47, + 332, + 153, + 345 + ], + "type": "text", + "content": "3.1. Task Formulation" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "spans": [ + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": "Given a video-narration pair " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "(\\mathcal{V},\\mathcal{S})" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": ", where the video clip " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": " consists of " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": " frames " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "\\{I_1,I_2,\\dots ,I_T\\}" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": " of size " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "H\\times W" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": ", and the narration " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": " describes the activities demonstrated in the video and refers to " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": " noun phrases (objects) " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "(o_{1},o_{2},\\ldots ,o_{N})" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": ", our goal is to output a set of binary segmentation masks " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "\\mathcal{M}_{tn}\\in \\{0,1\\}^{H\\times W}" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": " for the " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": "-th referred object at the " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": "-th frame. In this work, we focus on weakly-supervised training, i.e., training only with video-narration pairs without any pixel-level annotation. To achieve this, we extract " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": " mask proposals " + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "inline_equation", + "content": "\\{P_{tm}\\}_{t,m = 1}^{T,M}" + }, + { + "bbox": [ + 46, + 351, + 289, + 532 + ], + "type": "text", + "content": " at each frame using the Segment Anything Model (SAM) [21] which is pre-trained on object segmentation masks without object labels. Then we use the video-narration pairs to supervise the learning of a similarity function between each mask proposal and each object phrase." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 534, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 534, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 534, + 289, + 715 + ], + "type": "text", + "content": "Method overview. Figure 2 gives an overview of our proposed framework, Referred Object-Segment Aligner (ROSA). We propose a CLIP-based Dual Encoder to compute context-aware embeddings for mask regions and object phrases (Section 3.2). To train our model without ground-truth region-phrase alignments, we propose a Global-Local Contrastive Learning framework (Section 3.3). It optimizes two objectives: (1) a global contrastive objective, contrasting ground-truth positive and negative pairs of video clips and narrations, based on a Temporal Adaptive Pooling of region-phrase similarities, and (2) a local contrastive objective, contrasting pseudo-labelled positive and negative pairs of regions and phrases. After learning, grounding is achieved by finding the mask proposal that maximizes the region-phrase similarity (Section 3.4)." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 72, + 453, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 453, + 84 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 453, + 84 + ], + "type": "text", + "content": "3.2. CLIP-based Dual Encoder" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 91, + 545, + 175 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 545, + 175 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 545, + 175 + ], + "type": "text", + "content": "In order to effectively align phrases with mask proposals, we need discriminative region representations that align well with language and capture contextual nuances. We propose a Context-aware Region Encoder to embed each mask proposal, and a Context-aware Phrase Encoder to embed each groundable noun phrase (object), by leveraging the CLIP model [36] pretrained on large-scale image-text pairs." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 191, + 474, + 204 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 191, + 474, + 204 + ], + "spans": [ + { + "bbox": [ + 305, + 191, + 474, + 204 + ], + "type": "text", + "content": "3.2.1 Context-Aware Region Encoder" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "spans": [ + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "content": "The original Vision Transformer [10] (ViT) from CLIP consists of " + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "content": " Transformer layers and embeds a whole image in its special CLS token of each last layer. To extract region-level features per mask proposal of a frame, we propose Mask-Guided Image CLIP. We pass the frame through the first " + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "inline_equation", + "content": "L - 1" + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "content": " layers of ViT, and then compute a CLS token per mask proposal by applying a simple attention masking in the last Transformer layer, which ensures that the CLS token exclusively attends to the masked region. As this approach shares the computation of all hidden layers except for the last Transformer layer among all mask proposals, it is much more efficient than cropping and masking used in prior works [8, 23, 53]. Besides, as the visual encoder has access to the whole frame, it is able to capture contextual information, making it more suitable for grounding task that needs to disambiguate between object instances of the same class based on context. The final region embedding " + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_{tm} \\in \\mathbb{R}^D" + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "content": " for the " + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "content": "-th mask proposal at the " + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "content": "-th frame is computed by projecting the CLS token to a " + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "content": "-dimensional vector with a shallow MLP, denoted as " + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_{tm} = \\text{RegionEncoder}(P_{tm}, I_t)" + }, + { + "bbox": [ + 304, + 210, + 547, + 463 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 479, + 474, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 479, + 474, + 491 + ], + "spans": [ + { + "bbox": [ + 305, + 479, + 474, + 491 + ], + "type": "text", + "content": "3.2.2 Context-Aware Phrase Encoder" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 498, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 547, + 715 + ], + "type": "text", + "content": "We use a language parser (spaCy [1]) to extract the noun phrases in each narration and then apply our Context-Aware Phrase Encoder to obtain a contextualized embedding for each phrase. A straight-forward way for obtaining phrase embeddings using CLIP is to pass the entire narration through its text encoder, and perform average pooling over the tokens corresponding to each referred object (Phrase Pooling) to get a narration-aware phrase embedding for each object. However, we observe that this embedding is often heavily influenced by the narration context, resulting in similar embeddings for nearby phrases, thus hurting disambiguation that is necessary for our grounding tasks. To address this limitation, we additionally input each object phrase to CLIP's text encoder and use the EOT (End of Text) token as a localized phrase embedding. The final phrase embedding " + }, + { + "bbox": [ + 304, + 498, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_n\\in \\mathbb{R}^D" + }, + { + "bbox": [ + 304, + 498, + 547, + 715 + ], + "type": "text", + "content": " for the " + }, + { + "bbox": [ + 304, + 498, + 547, + 715 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 304, + 498, + 547, + 715 + ], + "type": "text", + "content": "-th object phrase in the input narration is computed as the average of the localized phrase embedding and narration-aware phrase embedding," + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "14512" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 70, + 545, + 277 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 545, + 277 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 545, + 277 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 545, + 277 + ], + "type": "image", + "image_path": "ddf2890078bceb2f67db1c11eaf4d402a5bc426d7394950d86a27708e07943ec.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 286, + 546, + 321 + ], + "lines": [ + { + "bbox": [ + 46, + 286, + 546, + 321 + ], + "spans": [ + { + "bbox": [ + 46, + 286, + 546, + 321 + ], + "type": "text", + "content": "Figure 2. Framework Overview. We propose a CLIP-based Dual Encoder to embed mask proposals and noun phrases, and compute pairwise region-phrase similarities. We propose Global-Local Contrastive Learning via ground-truth Video-Narration Alignment and pseudo labelled Region-Phrase Alignment. Frames taken from Ego4D [12]." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 340, + 225, + 353 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 340, + 225, + 353 + ], + "spans": [ + { + "bbox": [ + 47, + 340, + 225, + 353 + ], + "type": "text", + "content": "denoted as " + }, + { + "bbox": [ + 47, + 340, + 225, + 353 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_n = \\text{PhraseEncoder}(o_n, \\mathcal{S})" + }, + { + "bbox": [ + 47, + 340, + 225, + 353 + ], + "type": "text", + "content": "," + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 360, + 235, + 373 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 360, + 235, + 373 + ], + "spans": [ + { + "bbox": [ + 47, + 360, + 235, + 373 + ], + "type": "text", + "content": "3.3. Global-Local Contrastive Learning" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 380, + 287, + 511 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 380, + 287, + 511 + ], + "spans": [ + { + "bbox": [ + 46, + 380, + 287, + 511 + ], + "type": "text", + "content": "In the weakly-supervised setting, we need to learn a similarity function between mask regions and object phrases, without ground-truth alignments of region-phrase pairs. We propose a Global-Local Contrastive Learning framework to learn the region-phrase similarities using the alignments at both video-narration (global) and region-phrase (local) levels. In Sec. 3.3.1, we detail how to compute the region-phrase similarities and aggregate them into a video-narration affinity score for global contrastive learning. In Sec. 3.3.2, we illustrate how we obtain the pseudo-labelled region-phrase pairs for local contrastive learning." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 525, + 198, + 537 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 525, + 198, + 537 + ], + "spans": [ + { + "bbox": [ + 47, + 525, + 198, + 537 + ], + "type": "text", + "content": "3.3.1 Video-Narration Alignment" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "content": "Since our only available supervision is at the video-narration level, we propose a standard contrastive loss for video-narration alignment, which is equipped with a region-based affinity score between videos and narrations. In particular, inspired by Multiple Instance Learning approaches for weakly-supervised phrase grounding [19], we formulate an affinity score " + }, + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "inline_equation", + "content": "\\phi(\\mathcal{V},\\mathcal{S})" + }, + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "content": " between a video and a narration by aggregating individual region-phrase affinity scores. Intuitively, a video-narration pair should have a high affinity score if each referred object in the narration has a matched mask proposal in each frame of the video clip. Next, we detail how we aggregate the region-phrase similarities into frame-phrase affinity scores resulting in an overall affinity score between a video clip and a narration." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "spans": [ + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": "Frame-phrase affinity score. Given a set of segmentation mask proposals " + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "inline_equation", + "content": "\\{P_{tm}\\}_{t,m=1}^{T,M}" + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": " and a set of object phrases " + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "inline_equation", + "content": "\\{o_n\\}_{n=1}^N" + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": ", we first compute the pairwise similarity " + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "inline_equation", + "content": "g(\\mathbf{r}_{tm}, \\mathbf{w}_n)" + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": " between each mask proposal embedding " + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_{tm}" + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": " and each noun phrase embedding " + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_n" + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": ". In particular, our similarity function " + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "inline_equation", + "content": "g(\\cdot, \\cdot)" + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": " is computed as the cosine similarity between the region embedding and phrase embedding, multiplied with the mask confidence score of the corresponding mask proposal. This multiplication prioritizes mask proposals with higher confidence scores when aligning the object phrase with mask proposals. The affinity score between a phrase and a frame is then defined based on the best matching region at each frame " + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "inline_equation", + "content": "I_t" + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": ": " + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "inline_equation", + "content": "\\psi(I_t, o_n) = \\max_m g(\\mathbf{r}_{tm}, \\mathbf{w}_n)" + }, + { + "bbox": [ + 304, + 340, + 545, + 510 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 514, + 545, + 550 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 514, + 545, + 550 + ], + "spans": [ + { + "bbox": [ + 305, + 514, + 545, + 550 + ], + "type": "text", + "content": "Video-phrase affinity score. To compute the affinity score at the video-phrase level, we introduce a Temporal Adaptive Pooling of the frame-phrase affinity scores " + }, + { + "bbox": [ + 305, + 514, + 545, + 550 + ], + "type": "inline_equation", + "content": "\\psi(I_t, o_n)" + }, + { + "bbox": [ + 305, + 514, + 545, + 550 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 344, + 558, + 545, + 585 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 344, + 558, + 545, + 585 + ], + "spans": [ + { + "bbox": [ + 344, + 558, + 545, + 585 + ], + "type": "interline_equation", + "content": "\\sigma (\\mathcal {V}, o _ {n}) = \\sum_ {t} \\frac {e ^ {\\psi \\left(I _ {t} , o _ {n}\\right) / \\alpha}}{\\sum_ {t ^ {\\prime}} e ^ {\\psi \\left(I _ {t ^ {\\prime}} , o _ {n}\\right) / \\alpha}} \\psi \\left(I _ {t}, o _ {n}\\right). \\tag {1}", + "image_path": "249c5eb5dd259078c42ab6ead75dd55dad628e155ae6b37806d36501d1a3080d.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "content": "The function involves a weighted sum across all temporal frames, where the weight for each frame is determined by the frame-phrase affinity scores divided by a temperature parameter " + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "content": ". We dynamically adjust " + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "content": " during training, following the schedule " + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\alpha = \\alpha_0\\beta^{-s}" + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\alpha_0" + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "content": " is a small constant close to " + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "inline_equation", + "content": "0" + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "inline_equation", + "content": "\\beta \\in (0,1)" + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "content": " is a decay index, and " + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 304, + 594, + 546, + 713 + ], + "type": "text", + "content": " is the iteration step. Intuitively, at the initial stage of training, the model may struggle to effectively segment objects undergoing occlusions or significant transformations. This dynamic adjustment allows the model to prioritize the most confident" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "14513" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": "mask proposal in a single frame early in training (with low " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": ") and gradually shift towards a smoother, more robust aggregation of region representations from multiple frames as training progresses (with a larger " + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 47, + 72, + 287, + 120 + ], + "type": "text", + "content": ")." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 124, + 286, + 186 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 124, + 286, + 186 + ], + "spans": [ + { + "bbox": [ + 47, + 124, + 286, + 186 + ], + "type": "text", + "content": "Video-narration affinity score. Finally, we compute the video-narration affinity score by averaging the videophrase affinity scores over all object phrases: " + }, + { + "bbox": [ + 47, + 124, + 286, + 186 + ], + "type": "inline_equation", + "content": "\\phi(\\mathcal{V},\\mathcal{S}) = \\frac{\\sum_{n}\\sigma(\\mathcal{V},o_{n})}{N}" + }, + { + "bbox": [ + 47, + 124, + 286, + 186 + ], + "type": "text", + "content": ", which assumes that all referred objects in the narration should be present in the aligned video clip." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 190, + 286, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 190, + 286, + 239 + ], + "spans": [ + { + "bbox": [ + 47, + 190, + 286, + 239 + ], + "type": "text", + "content": "Video-narration contrastive loss. Given a training batch of video-narration pairs " + }, + { + "bbox": [ + 47, + 190, + 286, + 239 + ], + "type": "inline_equation", + "content": "\\{(\\mathcal{V}_i, \\mathcal{S}_i)\\}_{i=1}^B" + }, + { + "bbox": [ + 47, + 190, + 286, + 239 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 47, + 190, + 286, + 239 + ], + "type": "inline_equation", + "content": "B" + }, + { + "bbox": [ + 47, + 190, + 286, + 239 + ], + "type": "text", + "content": " is the batch size, we use an InfoNCE loss to train the model via weak supervision as follows:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 51, + 242, + 286, + 280 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 51, + 242, + 286, + 280 + ], + "spans": [ + { + "bbox": [ + 51, + 242, + 286, + 280 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {V N A}} = \\frac {1}{B} \\sum_ {i = 1} ^ {B} - \\log \\frac {e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {i}\\right) / \\tau}}{\\sum_ {j} e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {j}\\right) / \\tau}} - \\log \\frac {e ^ {\\phi \\left(\\mathcal {V} _ {i} , \\mathcal {S} _ {i}\\right) / \\tau}}{\\sum_ {j} e ^ {\\phi \\left(\\mathcal {V} _ {j} , \\mathcal {S} _ {i}\\right) / \\tau}}, \\tag {2}", + "image_path": "27b33de54cd31d7f48d970ec4a4eb5801b76abf6889fa04eb32d0ee7bc8d75ae.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 281, + 286, + 342 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 281, + 286, + 342 + ], + "spans": [ + { + "bbox": [ + 47, + 281, + 286, + 342 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 281, + 286, + 342 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 47, + 281, + 286, + 342 + ], + "type": "text", + "content": " is a learnable temperature and " + }, + { + "bbox": [ + 47, + 281, + 286, + 342 + ], + "type": "inline_equation", + "content": "\\phi(\\mathcal{V}_i, \\mathcal{S}_j)" + }, + { + "bbox": [ + 47, + 281, + 286, + 342 + ], + "type": "text", + "content": " is our custom video-narration affinity score defined above. We freeze the pre-trained CLIP image and text encoders, and optimize the parameters of the MLP to learn region representations better aligned with phrases." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 359, + 190, + 371 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 359, + 190, + 371 + ], + "spans": [ + { + "bbox": [ + 47, + 359, + 190, + 371 + ], + "type": "text", + "content": "3.3.2 Region-Phrase Alignment" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 379, + 286, + 505 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 379, + 286, + 505 + ], + "spans": [ + { + "bbox": [ + 47, + 379, + 286, + 505 + ], + "type": "text", + "content": "While the aforementioned video-narration contrastive loss is effective at leveraging video-narration supervision, the loss is not directly applied to the alignment between region-phrase pairs. In order to learn a better alignment between mask regions and object phrases, we propose an additional local loss at region-phrase level. To do so, we first get pseudo-labelled alignments for region-phrase pairs. For each phrase embedding " + }, + { + "bbox": [ + 47, + 379, + 286, + 505 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_n" + }, + { + "bbox": [ + 47, + 379, + 286, + 505 + ], + "type": "text", + "content": ", we get the embedding of its best aligned mask proposal at each frame, denoted as " + }, + { + "bbox": [ + 47, + 379, + 286, + 505 + ], + "type": "inline_equation", + "content": "\\tilde{\\mathbf{r}}_{tn} = \\{\\mathbf{r}_{tm}|m = \\operatorname*{argmax}_{m'}g(\\mathbf{r}_{tm'},\\mathbf{w}_n)\\}" + }, + { + "bbox": [ + 47, + 379, + 286, + 505 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 509, + 286, + 544 + ], + "type": "text", + "content": "Region-phrase contrastive loss. Then we apply a region-phrase alignment loss over all object phrases and all aligned mask regions in a batch:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 96, + 548, + 286, + 632 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 96, + 548, + 286, + 632 + ], + "spans": [ + { + "bbox": [ + 96, + 548, + 286, + 632 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} _ {\\mathrm {R P A}} = - \\sum_ {t} \\underbrace {\\log \\frac {e ^ {g \\left(\\tilde {\\mathbf {r}} _ {t n} , \\mathbf {w} _ {n}\\right) / \\tau}}{\\sum_ {n ^ {\\prime}} e ^ {g \\left(\\tilde {\\mathbf {r}} _ {t n} , \\mathbf {w} _ {n ^ {\\prime}}\\right) / \\tau}}} _ {\\text {r e g i o n t o p h r a s e}} \\tag {3} \\\\ - \\underbrace {\\log \\frac {\\sum_ {t} e ^ {g (\\mathbf {r} _ {t n} , \\mathbf {w} _ {n}) / \\tau}}{\\sum_ {n ^ {\\prime}} \\sum_ {t} e ^ {g (\\tilde {\\mathbf {r}} _ {t n ^ {\\prime}} , \\mathbf {w} _ {n}) / \\tau}}} _ {\\text {p h r a s e t o r i g i o n}}. \\\\ \\end{array}", + "image_path": "7475df256c85ef120fcfe94269f8a28f1f1f5051275c5943ec887805aa0a37eb.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 642, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 642, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 642, + 286, + 713 + ], + "type": "text", + "content": "The first term is a region to phrase (R2P) standard InfoNCE contrastive loss, which treats other object phrases as negative samples for a given mask region. The second term is a phrase to region (P2R) MIL-NCE-type [30] contrastive loss, which considers the aligned regions in all frames as positive pairs for a given object phrase, while" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 309, + 73, + 436, + 155 + ], + "blocks": [ + { + "bbox": [ + 309, + 73, + 436, + 155 + ], + "lines": [ + { + "bbox": [ + 309, + 73, + 436, + 155 + ], + "spans": [ + { + "bbox": [ + 309, + 73, + 436, + 155 + ], + "type": "image", + "image_path": "554a5be7f4c3c2114ed8e1b112025dd72e3a2af9de674bc47248db261a00843b.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 161, + 545, + 205 + ], + "lines": [ + { + "bbox": [ + 305, + 161, + 545, + 205 + ], + "spans": [ + { + "bbox": [ + 305, + 161, + 545, + 205 + ], + "type": "text", + "content": "Figure 3. An example of our annotated narration on the VISOR-NVOS benchmark. The annotators are instructed to write a detailed narration with [referred object] followed by " + }, + { + "bbox": [ + 305, + 161, + 545, + 205 + ], + "type": "inline_equation", + "content": "\\langle" + }, + { + "bbox": [ + 305, + 161, + 545, + 205 + ], + "type": "text", + "content": "object ID " + }, + { + "bbox": [ + 305, + 161, + 545, + 205 + ], + "type": "inline_equation", + "content": "\\rangle" + }, + { + "bbox": [ + 305, + 161, + 545, + 205 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 438, + 72, + 537, + 156 + ], + "blocks": [ + { + "bbox": [ + 438, + 72, + 537, + 156 + ], + "lines": [ + { + "bbox": [ + 438, + 72, + 537, + 156 + ], + "spans": [ + { + "bbox": [ + 438, + 72, + 537, + 156 + ], + "type": "image", + "image_path": "309bdaeb16109b4de6dd995d707135bc9dfb93f525bf1a45f38f25599b269db7.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 221, + 545, + 353 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 221, + 545, + 353 + ], + "spans": [ + { + "bbox": [ + 305, + 221, + 545, + 353 + ], + "type": "text", + "content": "treating regions aligned with other object phrases as negative samples. Note that Eq. (3) is the loss for one object phrase, and we sum over all object phrases for training loss. This loss formulation facilitates the learning of robust region-phrase associations and enhances the quality of object segmentation and grounding. In the experiment section, we compare various strategies on selecting the negative samples for P2R contrastive learning and show the advantages of the proposed one. Our final training objective is: " + }, + { + "bbox": [ + 305, + 221, + 545, + 353 + ], + "type": "inline_equation", + "content": "\\mathcal{L} = \\mathcal{L}_{\\mathrm{VNA}} + \\lambda \\mathcal{L}_{\\mathrm{RPA}}" + }, + { + "bbox": [ + 305, + 221, + 545, + 353 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 305, + 221, + 545, + 353 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 305, + 221, + 545, + 353 + ], + "type": "text", + "content": " is the weight for region-phrase alignment loss." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 360, + 372, + 371 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 360, + 372, + 371 + ], + "spans": [ + { + "bbox": [ + 306, + 360, + 372, + 371 + ], + "type": "text", + "content": "3.4. Inference" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 378, + 545, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 378, + 545, + 415 + ], + "spans": [ + { + "bbox": [ + 305, + 378, + 545, + 415 + ], + "type": "text", + "content": "We ground the " + }, + { + "bbox": [ + 305, + 378, + 545, + 415 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 305, + 378, + 545, + 415 + ], + "type": "text", + "content": "-th noun phrase in the narration by selecting the mask proposal at each frame with the closest embedding in our learned, unified region-phrase embedding space:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 322, + 424, + 545, + 443 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 322, + 424, + 545, + 443 + ], + "spans": [ + { + "bbox": [ + 322, + 424, + 545, + 443 + ], + "type": "interline_equation", + "content": "\\mathcal {M} _ {t n} = P _ {t m ^ {*}}, \\text {w h e r e} m ^ {*} = \\underset {m} {\\operatorname {a r g m a x}} g \\left(\\mathbf {r} _ {t m}, \\mathbf {w} _ {n}\\right) \\tag {4}", + "image_path": "b4d64ee4f78ac8f277ba3775a6f64f5fe652daef6114f79bae288331395f231b.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 451, + 498, + 463 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 451, + 498, + 463 + ], + "spans": [ + { + "bbox": [ + 306, + 451, + 498, + 463 + ], + "type": "text", + "content": "4. Evaluation Benchmarks for NVOS" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 472, + 545, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 472, + 545, + 567 + ], + "spans": [ + { + "bbox": [ + 305, + 472, + 545, + 567 + ], + "type": "text", + "content": "While our proposed weakly-supervised framework demonstrates the feasibility of training NVOS models without the need for mask annotation, evaluating the performance of such models is equally critical. Existing egocentric video datasets with segmentation mask annotations for objects, such as VISOR [7], VOST [44] and PACO [38], cannot be directly used for evaluation, since they lack narrations with referred objects associated with the annotated object masks." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 305, + 570, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 570, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 570, + 545, + 713 + ], + "type": "text", + "content": "VISOR-NVOS. To address these limitations, we create a new evaluation benchmark, VISOR-NVOS, by collecting object-based narration annotations for video clips from the VISOR [7] dataset. VISOR provides mask annotations for multiple active objects in egocentric videos of the EPIC-Kitchens [6] dataset. We pair these segmentation masks with narrations, by instructing annotators to describe activities explicitly referring to a set of objects of interest. As shown in Figure 3, provided with a short video clip and a list of objects of interest (with each object name associated with an object ID and a segmentation mask), the annotators are instructed to write a sentence describing the person's" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "14514" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 61, + 70, + 535, + 208 + ], + "blocks": [ + { + "bbox": [ + 61, + 70, + 535, + 208 + ], + "lines": [ + { + "bbox": [ + 61, + 70, + 535, + 208 + ], + "spans": [ + { + "bbox": [ + 61, + 70, + 535, + 208 + ], + "type": "table", + "html": "
MethodSupervisionVISOR-NVOSVOST
Cross-ModalMask AnnotationEgo4D‡JFJ&FJunionJins
SAM [21] upper bound70.375.673.062.265.8
Trained w/ labeled regions
ODISE [52]mask-textclass-specific29.032.830.917.621.1
GroundedSAM [21, 27]bbox-textclass-agnostic37.341.839.521.825.3
Trained w/o labeled regions
SAM [21] + CLIP [36] (ViT-B/16)image-textclass-agnostic22.225.824.016.519.2
CoMMa† [43] + SAM [21]video-narrationclass-agnostic✓15.325.320.39.411.5
ROSA (ViT-B/16)video-narrationclass-agnostic✓34.941.238.122.225.4
ROSA (ViT-L/14)video-narrationclass-agnostic✓38.746.042.423.226.7
", + "image_path": "e26b6429522c6d572a958179de49e0096076bf05406a065e5c8c0114df978f52.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 209, + 547, + 255 + ], + "lines": [ + { + "bbox": [ + 46, + 209, + 547, + 255 + ], + "spans": [ + { + "bbox": [ + 46, + 209, + 547, + 255 + ], + "type": "text", + "content": "Table 1. Comparison of grounding performance between our framework and strong baselines on our NVOS benchmarks. We report metrics on the test split of our proposed VISOR-NVOS and the validation split of VOST. " + }, + { + "bbox": [ + 46, + 209, + 547, + 255 + ], + "type": "inline_equation", + "content": "\\ddagger" + }, + { + "bbox": [ + 46, + 209, + 547, + 255 + ], + "type": "text", + "content": " whether the model has been fine-tuned on Ego4D. \"Trained with labeled regions\": trained with annotations of bounding boxes or masks; \"Trained without labeled regions\": using video-level or image-level annotations." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 274, + 289, + 406 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 274, + 289, + 406 + ], + "spans": [ + { + "bbox": [ + 46, + 274, + 289, + 406 + ], + "type": "text", + "content": "activities in the video, linking noun phrases in the sentence with the associated object IDs. In total, we have collected detailed, object-based narrations for 14,612 video clips, including 37,170 referred objects. On average, each narration has 12.79 words, and 2.54 referred objects. The maximum number of referred objects in one narration is 9. We split the annotated videos into a validation set of 7,561 videos and a test set of 7,051 videos, and report the performance on the test set. We do not train our model on any of those videos or narrations. Please see the supplementary for more details about this benchmark." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 410, + 289, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 410, + 289, + 579 + ], + "spans": [ + { + "bbox": [ + 46, + 410, + 289, + 579 + ], + "type": "text", + "content": "VOST. VOST [44] is an egocentric video object segmentation dataset specifically designed to capture dramatic object transformations. To evaluate models for NVOS on VOST, we use the verb and noun pairs (e.g., \"peel banana\", \"mold clay\") as the narrations, with the nouns serving as the objects to ground. In contrast to VISOR, which encompasses multiple object classes in a single video, VOST contains annotations for a single object class (with one or multiple instances) per video. However, the uniqueness of VOST lies in the complexity of the transformations these objects undergo, e.g., the peeling of bananas. Hence, this benchmark allows us to evaluate the model's performance in grounding objects under complex transformations and its ability to comprehend actions that induce changes in object states." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 590, + 128, + 604 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 590, + 128, + 604 + ], + "spans": [ + { + "bbox": [ + 47, + 590, + 128, + 604 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 610, + 164, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 610, + 164, + 624 + ], + "spans": [ + { + "bbox": [ + 47, + 610, + 164, + 624 + ], + "type": "text", + "content": "5.1. Experimental Setup" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": "Training dataset. We train our model on video-narration pairs sourced from the Ego4D dataset [12]. Ego4D is a massive-scale egocentric video dataset that provides over 3M text narrations of the camera wearer's activities, synchronized with timestamps for 3,670 hours of video. We use a subset of Ego4D for our experiments, by selecting " + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "inline_equation", + "content": "250k" + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": " video clips with narrations related to cooking objects." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 274, + 547, + 323 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 274, + 547, + 323 + ], + "spans": [ + { + "bbox": [ + 304, + 274, + 547, + 323 + ], + "type": "text", + "content": "We sample four frames from each one-second clip, with an average of 1.6 narrations available per clip. During each training iteration, we construct video-narration pairs by randomly sampling one narration per video clip." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "spans": [ + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "text", + "content": "Evaluation. After training on Ego4D, we evaluate on the VISOR-NVOS and VOST benchmarks without fine-tuning. Following [7, 34, 54], we use the Jaccard Index " + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "inline_equation", + "content": "(\\mathcal{J}," + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "text", + "content": " also known as Intersection over Union, IoU), the Boundary F-Measure " + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "inline_equation", + "content": "(\\mathcal{F})" + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "text", + "content": ", and the average of Jaccard Index and Boundary F-Measure " + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "inline_equation", + "content": "(\\mathcal{J}\\& \\mathcal{F})" + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "text", + "content": ", as the evaluation metrics on VISOR-NVOS. On VOST, following [44], we only use the Jaccard Index as the contours are often not well-defined due to the dramatic transformations and motions involved on this dataset. As we described, VOST does not contain ground-truth alignments between annotated segmentation masks and referred objects. Hence, for some samples with multiple annotated object instances of the same object class, there is uncertainty for grounding evaluation. To mitigate this issue, we report two metrics: " + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_{union}" + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "text", + "content": ", i.e., the IoU between the predicted mask and the union of all annotated masks, and " + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "inline_equation", + "content": "\\mathcal{I}_{ins}" + }, + { + "bbox": [ + 304, + 325, + 548, + 541 + ], + "type": "text", + "content": ", i.e., the IoU between the predicted mask and the most overlapping annotated mask instance." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 544, + 547, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 544, + 547, + 652 + ], + "spans": [ + { + "bbox": [ + 304, + 544, + 547, + 652 + ], + "type": "text", + "content": "Implementation details. We use SAM [21] to generate mask proposals on each frame using a " + }, + { + "bbox": [ + 304, + 544, + 547, + 652 + ], + "type": "inline_equation", + "content": "32 \\times 32" + }, + { + "bbox": [ + 304, + 544, + 547, + 652 + ], + "type": "text", + "content": " point grid. We apply Non-Maximum Suppression (NMS) with a threshold of 0.9 to remove redundant mask proposals. Our best model uses a CLIP ViT-L/14 Image Encoder (while for ablations we use ViT-B/16). We set the weight for region-phrase alignment loss " + }, + { + "bbox": [ + 304, + 544, + 547, + 652 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 304, + 544, + 547, + 652 + ], + "type": "text", + "content": " as 0.5 and use three-layer MLP in our Context-Aware Region Encoder. Please refer to the supplementary for more implementation details." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 659, + 503, + 672 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 659, + 503, + 672 + ], + "spans": [ + { + "bbox": [ + 305, + 659, + 503, + 672 + ], + "type": "text", + "content": "5.2. Comparison with the State of the Art" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 715 + ], + "type": "text", + "content": "We compare our method with strong baselines as well as state-of-the-art approaches from related tasks (narration grounding [43], open-vocabulary segmentation [52])" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "14515" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 70, + 210, + 139 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 210, + 139 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 210, + 139 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 210, + 139 + ], + "type": "table", + "html": "
VNAR2PP2RJFJ&F
24.831.328.1
✓32.439.636.0
✓✓33.940.137.0
✓✓33.940.637.3
✓✓✓34.941.238.1
", + "image_path": "ace2f394107033b09a3942127fcb67dfa82c3bc6854e9ac72995f23de04e5995.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 82, + 140, + 174, + 150 + ], + "lines": [ + { + "bbox": [ + 82, + 140, + 174, + 150 + ], + "spans": [ + { + "bbox": [ + 82, + 140, + 174, + 150 + ], + "type": "text", + "content": "(a) Impact of various losses." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 219, + 71, + 382, + 137 + ], + "blocks": [ + { + "bbox": [ + 219, + 71, + 382, + 137 + ], + "lines": [ + { + "bbox": [ + 219, + 71, + 382, + 137 + ], + "spans": [ + { + "bbox": [ + 219, + 71, + 382, + 137 + ], + "type": "table", + "html": "
Negative samplesJFJ&F
same27.535.031.3
all27.434.831.1
other26.534.030.3
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JFJ&F
random frame33.339.836.6
max pooling33.740.537.1
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", + "image_path": "843a17c5e1bef78acb16f478515b0e485df14fe5b418d99e8a880770f42b2c00.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 392, + 139, + 542, + 149 + ], + "lines": [ + { + "bbox": [ + 392, + 139, + 542, + 149 + ], + "spans": [ + { + "bbox": [ + 392, + 139, + 542, + 149 + ], + "type": "text", + "content": "(c) Ablation of temporal aggregation functions." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 4 + }, + { + "bbox": [ + 94, + 154, + 497, + 165 + ], + "lines": [ + { + "bbox": [ + 94, + 154, + 497, + 165 + ], + "spans": [ + { + "bbox": [ + 94, + 154, + 497, + 165 + ], + "type": "text", + "content": "Table 2. Ablation studies on the Global-Local Contrastive Learning framework on the VISOR-NVOS test split." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 186, + 289, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 186, + 289, + 449 + ], + "spans": [ + { + "bbox": [ + 46, + 186, + 289, + 449 + ], + "type": "text", + "content": "adapted for our NVOS task. Baselines trained without labeled regions: \"SAM+CLIP\": For this simple baseline, we use SAM to generate mask proposals, input the cropped and masked images into CLIP image encoder and the object phrases into CLIP text encoder, and select the best matching mask proposal based on the cosine similarity of their embeddings. \"CoMMa†+SAM\": We adapt CoMMa [43], a state-of-the-art approach for weakly-supervised point-wise grounding of input language queries, for the NVOS task. We train CoMMa† with video-narration pairs (from the same Ego4D subset used to train our model), and during inference use the predicted point for each object phrase to prompt SAM and get the segmentation mask. Baselines trained with labeled regions: We also benchmark ODISE [52] and GroundedSAM [21, 27], two state-of-the-art, image-level, open-vocabulary segmentation approaches that are trained with segmentation masks/bounding boxes paired with semantic concepts, thus using stronger supervision than us. Since open-vocabulary segmentation outputs masks for all instances of an object class (e.g., all spoons), we select the mask with highest confidence score and compare it with the ground-truth mask." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "spans": [ + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "text", + "content": "As can be seen in Table 1, our model (with CLIP ViT-L/14 backbone) outperforms all compared baselines, including approaches that have been trained with strong spatial supervision (e.g., GroundedSAM is based on Grounding DINO [27], an open-set object detector that has been pre-trained on Objects365 [40], a large dataset with 10Mbbox annotations). Interestingly, the simple, out-of-the-box \"SAM+CLIP\" baseline, which has not been trained on egocentric video data, outperforms \"CoMMa†+SAM\", corroborating our intuition for using mask proposals and harnessing CLIP pre-training for representing them. Compared to this strong baseline, our model (with the same ViT-B/16 backbone) improves the " + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "inline_equation", + "content": "\\mathcal{J}\\&\\mathcal{F}" + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "text", + "content": " by " + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "inline_equation", + "content": "14.1\\%" + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "text", + "content": " on VISOR-NVOS, and improves the " + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "inline_equation", + "content": "\\mathcal{J}_{ins}" + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "text", + "content": " by " + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "inline_equation", + "content": "6.2\\%" + }, + { + "bbox": [ + 46, + 451, + 287, + 654 + ], + "type": "text", + "content": " on VOST, which demonstrates the effectiveness of our weakly-supervised framework that learns region-phrase alignments from egocentric video narrations." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 656, + 287, + 680 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 656, + 287, + 680 + ], + "spans": [ + { + "bbox": [ + 47, + 656, + 287, + 680 + ], + "type": "text", + "content": "We note, however, that the performance of all compared models on our VISOR-NVOS benchmark lags behind the" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 186, + 545, + 258 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 186, + 545, + 258 + ], + "spans": [ + { + "bbox": [ + 306, + 186, + 545, + 258 + ], + "type": "text", + "content": "upper bound performance that we could obtain based on the best-matching SAM mask proposal (reported in the first row of Table 1), highlighting the challenging nature of our proposed task and benchmark and the need for further research on learning better region-phrase alignments, e.g., by better modeling temporal consistency." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 268, + 406, + 279 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 268, + 406, + 279 + ], + "spans": [ + { + "bbox": [ + 306, + 268, + 406, + 279 + ], + "type": "text", + "content": "5.3. Ablation Studies" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "spans": [ + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "text", + "content": "What is the effect of each component of our proposed training objective? We start by reporting the performance of our CLIP-based Dual Encoder before weakly-supervised training (i.e., we replace the MLP of our region encoder with the identity mapping and just use CLIP weights for our encoders) in the first row of Table 2a. Adding the MLP and fine-tuning it on Ego4D with our Global Contrastive Objective, that encourages video-narration alignment (VNA), leads to a significant performance improvement in " + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "inline_equation", + "content": "\\mathcal{J}\\&\\mathcal{F}" + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "text", + "content": " (from " + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "inline_equation", + "content": "28.1\\%" + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "inline_equation", + "content": "36.0\\%" + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "text", + "content": ", rows 1 and 2). Adding our novel region-phrase alignment loss terms, i.e., region to phrase (R2P) and phrase to region (P2R) losses (Eq. (3)), further boosts performance. Both loss terms contribute to the improvement, and their combination improves " + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "inline_equation", + "content": "\\mathcal{J}\\&\\mathcal{F}" + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "text", + "content": " by " + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "inline_equation", + "content": "2.1\\%" + }, + { + "bbox": [ + 304, + 286, + 545, + 502 + ], + "type": "text", + "content": ", suggesting that our proposed loss function is able to learn a better region-phrase alignment by directly applying supervision on region-phrase pairs, instead of just contrasting video-narration pairs, as commonly done in prior work [64]." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 506, + 546, + 673 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 506, + 546, + 673 + ], + "spans": [ + { + "bbox": [ + 304, + 506, + 546, + 673 + ], + "type": "text", + "content": "How to select negative region samples for region-phrase contrastive learning? As can be seen in Table 2b, using regions that are aligned with the other phrases in the batch (based on the pseudo-labeled alignments) is the only strategy that does not degrade the performance. We compare it with using the rest of regions from the same video, using the rest of regions from all the videos in the batch, and using all regions from other videos (as proposed for weakly-supervised image phrase grounding [4]). We conjecture that our proposed strategy avoids the issues of \"fake negative\" samples when the negative mask regions are also relevant to the object phrase if multiple mask proposals are overlapped, and \"easy negative\" samples when the mask regions are background regions irrelevant to active objects." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 677, + 545, + 713 + ], + "type": "text", + "content": "What is the effect of the temporal aggregation module? As we discussed, we aggregate region-phrase similarities from multiple frames to obtain a global video-narration" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 47, + 693, + 286, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 693, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 693, + 286, + 712 + ], + "type": "text", + "content": "1We use CoMMa† to denote the model we trained on Ego4D to differentiate with the original CoMMa model trained on HowTo100M." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "14516" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 71, + 286, + 214 + ], + "blocks": [ + { + "bbox": [ + 51, + 71, + 286, + 214 + ], + "lines": [ + { + "bbox": [ + 51, + 71, + 286, + 214 + ], + "spans": [ + { + "bbox": [ + 51, + 71, + 286, + 214 + ], + "type": "image", + "image_path": "290c8b0b4154acfd0a6e11d5111daa1c923f163ac5bb518aab99f96bf25baa21.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 217, + 287, + 250 + ], + "lines": [ + { + "bbox": [ + 46, + 217, + 287, + 250 + ], + "spans": [ + { + "bbox": [ + 46, + 217, + 287, + 250 + ], + "type": "text", + "content": "Figure 4. Qualitative Results. Top: three examples from VISOR-NVOS. Bottom: an example from VOST showing the model's robustness to objects undergoing dramatic transformations." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 265, + 289, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 265, + 289, + 397 + ], + "spans": [ + { + "bbox": [ + 46, + 265, + 289, + 397 + ], + "type": "text", + "content": "affinity score for applying our global contrastive objective. Our proposed aggregation module starts by focusing on one frame for each phrase (the one with the best matching region) and then adaptively starts encouraging alignment with the regions of other frames. As can be seen in Table 2c, this approach (adaptive) better handles occlusions and motion blur and facilitates training compared to: (a) randomly selecting a frame of the video clip during each iteration (random frame), (b) using the frame with the highest frame-phrase affinity score (max), or (c) not adapting the frame weights (softmax)." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 404, + 160, + 417 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 404, + 160, + 417 + ], + "spans": [ + { + "bbox": [ + 47, + 404, + 160, + 417 + ], + "type": "text", + "content": "5.4. Qualitative Results" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "spans": [ + { + "bbox": [ + 46, + 423, + 289, + 604 + ], + "type": "text", + "content": "In Figure 4, we show some qualitative results. On the top, we show three examples from VISOR-NVOS. In the first example, our model is able to segment the referred objects in a complex environment featuring multiple spoons and pans. In the second example, the model successfully distinguishes between \"flour\" and \"flour package\". The third example highlights some limitations of our model, including ambiguity in mask size where the model only segments a portion of the fridge instead of the entire unit, and challenges in understanding plurals (the narration mentions \"containers\" but it only grounds one container). The bottom section showcases the model's predictions on three frames from a VOST video depicting the peeling of a banana. Remarkably, the model accurately segments the banana while the appearance of banana has changed significantly." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 610, + 241, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 610, + 241, + 624 + ], + "spans": [ + { + "bbox": [ + 47, + 610, + 241, + 624 + ], + "type": "text", + "content": "5.5. Exocentric Video Object Grounding" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": "In Table 3, to further assess the generality of our model, we conduct evaluations on the third-person video object grounding dataset, YouCook2-BB [64], which includes bounding box annotations for referred objects. We convert the segmentation masks output by our model into bounding boxes for evaluation. Recall that our model is trained on egocentric videos with a goal to align object phrases" + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 309, + 70, + 435, + 193 + ], + "blocks": [ + { + "bbox": [ + 309, + 70, + 435, + 193 + ], + "lines": [ + { + "bbox": [ + 309, + 70, + 435, + 193 + ], + "spans": [ + { + "bbox": [ + 309, + 70, + 435, + 193 + ], + "type": "table", + "html": "
Methodbox accuracy
macromicro
Trained on YouCook2
Zhou et al. [64]35.0842.42
NAFAE [41]40.7146.33
STVG [56]41.6748.22
SCL [48]42.8048.60
Zero-Shot
CoMMa†+SAM6.638.98
Ours37.9344.96
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Methodpoint acc.
CoMMa†53.56
CoMMa [43]59.25
Ours69.35
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Object grounding evaluation on YouCook2-BB." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 240, + 547, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 240, + 547, + 373 + ], + "spans": [ + { + "bbox": [ + 304, + 240, + 547, + 373 + ], + "type": "text", + "content": "with segmentation masks. Despite a huge domain shift, our model achieves comparable performance with prior works [41, 48, 56, 64] that are trained on YouCook2 using bounding box proposals (Table 3a). In addition, we adopt the evaluation setup from CoMMa [43] to evaluate our model using point accuracy (see supplementary for more details). We use the center of the bounding box from our segmentation mask as the detected point. While CoMMa is trained on exocentric videos with a similar scale (HowTo100M [29]) for point-based grounding, our model outperforms CoMMa by a significant margin of " + }, + { + "bbox": [ + 304, + 240, + 547, + 373 + ], + "type": "inline_equation", + "content": "10.10\\%" + }, + { + "bbox": [ + 304, + 240, + 547, + 373 + ], + "type": "text", + "content": " (Table 3b)." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 384, + 381, + 396 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 384, + 381, + 396 + ], + "spans": [ + { + "bbox": [ + 306, + 384, + 381, + 396 + ], + "type": "text", + "content": "6. Limitations" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 403, + 545, + 523 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 403, + 545, + 523 + ], + "spans": [ + { + "bbox": [ + 304, + 403, + 545, + 523 + ], + "type": "text", + "content": "A limitation of our framework is that we perform inference on each frame separately, neglecting temporal information. Integrating temporal context into our model has the potential to enhance performance and alleviate ambiguities, which is a promising direction for future work. Furthermore, we focused our training and evaluation on the cooking domain. In the supplementary, we show that our weakly-supervised training also improves grounding on non-cooking videos, such as DIY, but a performance gap still exists between the two domains." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 534, + 378, + 546 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 534, + 378, + 546 + ], + "spans": [ + { + "bbox": [ + 306, + 534, + 378, + 546 + ], + "type": "text", + "content": "7. Conclusion" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 554, + 545, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 554, + 545, + 662 + ], + "spans": [ + { + "bbox": [ + 304, + 554, + 545, + 662 + ], + "type": "text", + "content": "We have explored the task of Narration-based Video Object Segmentation and established a new evaluation benchmark, VISOR-NVOS. Our proposed framework, ROSA, has effectively learnt the alignment between referred objects and segmentation masks using weak supervision of video-narration alignments in egocentric videos. Our approach achieved state-of-the-art zero-shot pixel-level grounding performance on two egocentric video datasets compared to strong baselines." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 677, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 545, + 715 + ], + "type": "text", + "content": "Acknowledgements. We thank Tushar Nagarajan, Triantafyllos Afouras, Yale Song, Austin Miller, and Jiabo Hu for helpful discussions and invaluable engineering support." + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "14517" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 711 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 200, + 102 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 200, + 102 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 200, + 102 + ], + "type": "text", + "content": "[1] spaCy. https://spacy.io/.3" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 53, + 103, + 287, + 159 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 103, + 287, + 159 + ], + "spans": [ + { + "bbox": [ + 53, + 103, + 287, + 159 + ], + "type": "text", + "content": "[2] Leonard Bär mann and Alex Waibel. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 6578-6587, 2019. 2" + } + ] + } + ], + "index": 19 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "14520" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning to Select Views for Efficient Multi-View Understanding/6f1ed185-f83a-4de1-ba41-bd094a6eccd2_content_list.json b/2024/Learning to Select Views for Efficient Multi-View Understanding/6f1ed185-f83a-4de1-ba41-bd094a6eccd2_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..2ab723bd264ca95420f3c9f0d9fe75ba02d62d29 --- /dev/null +++ b/2024/Learning to Select Views for Efficient Multi-View Understanding/6f1ed185-f83a-4de1-ba41-bd094a6eccd2_content_list.json @@ -0,0 +1,1734 @@ +[ + { + "type": "text", + "text": "Learning to Select Views for Efficient Multi-View Understanding", + "text_level": 1, + "bbox": [ + 158, + 130, + 813, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yunzhong Hou, Stephen Gould, and Liang Zheng \nAustralian National University", + "bbox": [ + 289, + 181, + 679, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{firstname.lastname}@anu.edu.au", + "bbox": [ + 346, + 219, + 619, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 268, + 313, + 284 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Multiple camera view (multi-view) setups have proven useful in many computer vision applications. However, the high computational cost associated with multiple views creates a significant challenge for end devices with limited computational resources. In modern CPU, pipelining breaks a longer job into steps and enables parallelism over sequential steps from multiple jobs. Inspired by this, we study selective view pipelining for efficient multi-view understanding, which breaks computation of multiple views into steps, and only computes the most helpful views/steps in a parallel manner for the best efficiency. To this end, we use reinforcement learning to learn a very light view selection module that analyzes the target object or scenario from initial views and selects the next-best-view for recognition or detection for pipeline computation. Experimental results on multi-view classification and detection tasks show that our approach achieves promising performance while using only 2 or 3 out of $N$ available views, significantly reducing computational costs while maintaining parallelism over GPU through selective view pipelining1.", + "bbox": [ + 76, + 301, + 473, + 603 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 635, + 209, + 651 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Multiple camera views (multi-view) are popular in computer vision systems for their ability to address challenges such as occlusions, ambiguities, and limited field-of-view (FoV) coverage. Tasks like classification [30, 37] and detection [6, 17] have shown significant benefits from using multiple cameras. With reduced hardware cost and easy deployment, real-world products now include more cameras at larger scales. However, the use of multiple cameras comes at a high computational cost, which can be a significant challenge for end devices with limited computational resources, especially with higher image resolutions and deeper neural network backbones. Limiting image resolution or using lighter networks [19, 27] are current options to reduce computation, but they may impede the", + "bbox": [ + 76, + 661, + 468, + 875 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/b3185fb8d2b880d2bd96d5a23a69d47661b35b02f35127c1b0c4b64e5d3c55d1.jpg", + "image_caption": [ + "(a) Piplining in modern CPU" + ], + "image_footnote": [], + "bbox": [ + 506, + 268, + 890, + 357 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/2f95de30ae0c21c683f1b4718782a97831d18286b5ea9d2bc7f66d0ed4aaba7d.jpg", + "image_caption": [ + "(b) Parallel in modern GPU" + ], + "image_footnote": [], + "bbox": [ + 504, + 377, + 888, + 455 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/3798442ec33fb7383a059fe7f97bd201620e5b009a0ef6ace239f144358766ff.jpg", + "image_caption": [ + "(c) Selective view pipelining", + "Figure 1. Demonstration of the proposed selective view pipelining. Inspired by instruction pipelining in modern CPU (a), selective view pipelining (c) breaks the multi-view perception task into sequential steps, and only computes the chosen views (see Fig. 2) to minimize the computation. At the same time, computation across multiple objects (different border colors) can still enjoy parallelism in GPU (b). In this example, for a $N = 6$ view system, traditional computation (b) on GPU hardware that only supports two images at the same time will produce a throughput of 2 instances during 6 time steps. In contrast, by taking advantage of the parallelism, selective view pipelining computes 6 instances within 7 time steps." + ], + "image_footnote": [], + "bbox": [ + 504, + 473, + 883, + 553 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "progress in camera sensors or neural network architecture.", + "bbox": [ + 496, + 763, + 883, + 779 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In modern CPU, instruction pipelining [10] breaks individual instructions into steps to enable parallelism across multiple instructions within the same CPU (see Fig. 1a). For multi-view perception, although computations for different images can be paralleled over GPU [9], the level of parallelism is still limited by hardware. As an example, the GPU in Fig. 1b might only support parallel computing for two images at a time, resulting in at least 3 time steps for", + "bbox": [ + 496, + 779, + 890, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "$^{1}$ Code available at https://github.com/hou-yz/MVSelect.", + "bbox": [ + 94, + 886, + 467, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "20135", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/85c1798479f0658128e78033dfca1d996f8590d7c5e9f59cda0b3ac4eac99397.jpg", + "image_caption": [ + "Figure 2. Efficient multi-view understanding with two glances. Instead of using all $N$ views at once, a more efficient approach is to first examine one view and then select another view to resolve ambiguities from the initial glance. If the initial side view cannot distinguish between a guitar and a mandolin (a round-shaped instrument that may also have a flat back), we can then query the front view. This sequential process can work in a pipeline to enable parallelism between multiple" + ], + "image_footnote": [], + "bbox": [ + 106, + 90, + 444, + 263 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "computing one object with 6 views.", + "bbox": [ + 76, + 410, + 313, + 425 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this work, we propose selective view pipelining, which breaks the multi-view perception task into a sequence of steps. Based on initial views, we estimate the most helpful views for this task, and only compute the selected views for maximum efficiency. The example in Fig. 1c shows that only selecting one additional view can greatly reduce the computation from 6 views to 2 views. By further taking advantage of the parallelism in GPUs, we can roughly improve the overall throughput by $3 \\times$ .", + "bbox": [ + 75, + 426, + 468, + 563 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To this end, this paper introduces a new angle to efficient multi-view understanding by selecting only the most useful views. To identify the best views, this approach leverages camera layouts, which is a key aspect overlooked by existing alternatives. With known camera layouts, networks should be able to infer what each camera view looks like and then choose accordingly, as previous works [20] have shown that networks can associate images with camera poses. Existing work on active vision [1, 8, 12] indicates that it is possible to find next-best-view (NBV) for reconstruction with 3D sensors. In this paper, we focus on recognition and detection problems using multiple RGB cameras, where a side view may confuse a guitar with a mandolin (Fig. 2). However, prior knowledge of the camera layout should inform the system that the front view can clear the ambiguities and should be queried.", + "bbox": [ + 75, + 566, + 470, + 808 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To achieve this goal, this paper proposes a novel view selection module, MVSelect, that chooses the best camera views from any initial view at minimal computational costs. Using the same feature extracted for the final task of classification or detection, the proposed module analyzes the target object or scenario from existing views and then selects the", + "bbox": [ + 75, + 810, + 470, + 901 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/23a312e7f3bd3b7eb5179a8d47e340c9e8e27da9059b6bd33ab2e3891ac06a44.jpg", + "image_caption": [ + "Figure 3. Multi-view classification with MVCNN [37]." + ], + "image_footnote": [], + "bbox": [ + 506, + 93, + 890, + 258 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "next view that best helps the task (classification or detection) network. To navigate through the non-differentiable view selection (the system only looks at selected cameras, so not-selected views cannot back propagate gradients to the controller), following Mnih et al. [26], we train the controller via trial-and-error. This process is formulated as a reinforcement learning problem aiming to maximize the final recognition or detection accuracy.", + "bbox": [ + 496, + 300, + 890, + 421 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "On both multi-view classification and detection tasks, our experimental results show that MVSelect can provide a good strategy for fixed task networks, while also capable of joint training with the task network for further performance improvements. Specifically, when joint training both MVSelect and the task network, the resulting system can achieve competitive performance to using all $N$ cameras, while using only 2 views for classification tasks and 3 views for detection tasks, respectively.", + "bbox": [ + 496, + 422, + 892, + 556 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The computational overhead of MVSelect is very small, as it shares the feature extraction backbone with the task network and only has a few learnable layers. For the entire system, the computational cost is roughly proportional to the number of views used, e.g., approximately $2 / N$ of the total computation when 2 views are used, a significant efficiency boost.", + "bbox": [ + 496, + 558, + 890, + 662 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The MVSelect policy also enables study on multi-view camera layout. In fact, we find that many of the $N$ cameras are rarely chosen and can be shut off for further operational cost improvements, which can serve as a starting point for future study on multi-view camera layout optimization.", + "bbox": [ + 496, + 664, + 890, + 739 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Background", + "text_level": 1, + "bbox": [ + 500, + 753, + 627, + 771 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Multi-view classification. One effective way for 3D shape recognition is to capture the object in multiple camera views. MVCNN [37] extracts feature vectors from the input views, and then uses max pooling to aggregate across multiple views for classification. Based on MVCNN, many alternative approaches are proposed. Qi et al. [30] propose sphere rendering at different volume resolutions. GVCNN [11] investigates hierarchical information between different", + "bbox": [ + 496, + 779, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "20136", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/845c2ac765a5d5f3f647519b198828dc12144adcddbcbdad5c9a646c7607f7e9.jpg", + "image_caption": [ + "Figure 4. Multi-view detection with MVDet [17]." + ], + "image_footnote": [], + "bbox": [ + 86, + 90, + 467, + 213 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "views by grouping the image features before the final aggregation. RotationNet [20] introduces a multi-task objective by jointly considering classification and camera poses. ViewGCN [42] uses a Graph Convolution Network (GCN) [23] instead of the max pooling layer to aggregate across views. Hamdi et al. [14] propose the MVTN network to estimate the best viewpoints for 3D point cloud models.", + "bbox": [ + 75, + 262, + 468, + 367 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Multi-view detection estimate pedestrian occupancy from the bird's-eye-view (BEV). For this task, some methods [13, 33, 45] aggregate single-view detection results. Others find single-view detection results unreliable and instead aggregate the features. Hou et al. [17] introduce MVDet, the first fully deep-learning approach, which projects feature maps from each camera view to the BEV. Based on MVDet, researchers develop other deep methods. SHOT [36] projects the image feature map at different heights and stacks them together to improve performance. MVDetr [16] deals with distinct distortion patterns from the projection. Qiu et al. [32] investigate data augmentation with simulated occlusion over multiple views.", + "bbox": [ + 75, + 369, + 468, + 565 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Camera viewpoint study. Cao and Snavely [5] investigate this for reconstruction with structure-from-motion. Active vision community investigates next-best-view planning with 3D sensors like RGBD cameras or LiDAR for scene reconstruction [4, 8, 35]. In multi-view classification, RotationNet [20] makes some pioneering work on limited view numbers by taking a random partial set of all $N$ views of the image. MVTN [14] uses the 3D point cloud as initial input and then estimates the best camera layout for multi-view classification, but its moving camera assumption is hard to meet in real-world systems. In multi-view detection, Vora et al. [41] investigate camera layout generalization by randomly dropping camera views from both training and testing. Hou et al. [18] investigate how to place cameras. For 3D human pose estimation, Pirinen et al. [28] actively select cameras over a dome.", + "bbox": [ + 75, + 566, + 470, + 806 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Reinforcement learning (RL) directs an agent to interact with the environment in a manner that maximizes cumulative rewards. State $s \\in S$ , action $a \\in \\mathcal{A}$ , and reward $r \\in \\mathcal{R}$ are key concepts to model the interaction between agent and environment. In a certain state $s$ , policy $\\pi(a|s)$ records the probability for each action, and state value func", + "bbox": [ + 75, + 810, + 468, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "tion $V(s)$ estimates the future rewards when following the corresponding policy. To learn the best policy, Q-learning and DQN [25] optimize the action value function $Q(s,a)$ , which describes the estimated future return for a specific action $a$ at state $s$ . Policy gradient methods like REINFORCE [43] and PPO [34] directly optimize for the polity $\\pi(a|s)$ .", + "bbox": [ + 496, + 90, + 890, + 183 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Multi-view Network Revisit", + "text_level": 1, + "bbox": [ + 498, + 195, + 756, + 210 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Multi-view Classification with MVCNN", + "text_level": 1, + "bbox": [ + 500, + 220, + 838, + 234 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "MVCNN [37] (Fig. 3) is a classic architecture which many multi-view classification networks build upon. Given $N$ input images $\\pmb{x}_n$ , $n \\in \\{1, \\dots, N\\}$ , first, MVCNN uses its feature extractor $f(\\cdot)$ to calculate the feature vectors,", + "bbox": [ + 496, + 242, + 890, + 304 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {h} _ {n} = f \\left(\\boldsymbol {x} _ {n}\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 643, + 316, + 890, + 333 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where the feature vector $\\pmb{h}_n \\in \\mathbb{R}^D$ is $D$ -dimensional. Secondly, it uses max pooling to aggregate multiple views into an overall feature descriptor $\\hat{\\pmb{h}} \\in \\mathbb{R}^{D}$ ,", + "bbox": [ + 496, + 344, + 890, + 390 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\boldsymbol {h}} = \\max _ {n} \\left\\{\\boldsymbol {h} _ {n} \\right\\}, \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 638, + 400, + 890, + 424 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\max \\{\\dots\\}$ takes the maximum along each of the $D$ dimensions. Lastly, it applies the output head $g(\\cdot)$ to produce the classification result $\\hat{\\pmb{y}}$ ,", + "bbox": [ + 496, + 434, + 890, + 479 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\boldsymbol {y}} = g (\\hat {\\boldsymbol {h}}). \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 651, + 489, + 890, + 516 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In training, the original design by Su et al. [37] adopts a 2-stage paradigm by first training on individual views and then considering multiple views. In this paper, we skip the first stage and directly train MVCNN on all $N$ views,", + "bbox": [ + 496, + 525, + 890, + 585 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {M V C N N}} = \\mathcal {L} _ {\\text {C E}} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}), \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 616, + 598, + 890, + 614 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathcal{L}_{\\mathrm{CE}}(\\cdot ,\\cdot)$ denotes the cross-entropy loss and $\\pmb{y}$ denotes the ground truth one-hot label.", + "bbox": [ + 496, + 626, + 890, + 656 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Multi-view Detection with MVDet", + "text_level": 1, + "bbox": [ + 500, + 665, + 797, + 680 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "MVDet [17] (Fig. 4) is a multi-view detection architecture that is followed by many recent works. To estimate human occupancy in bird's-eye-view (BEV), given input images $\\boldsymbol{x}_n, n \\in \\{1, \\dots, N\\}$ , MVDet first extracts $D$ -channel feature maps for each view and uses perspective transformation to project the camera views to the BEV. Together, these operations can be considered as the BEV feature extraction step under Eq. 1, with the exception that $\\boldsymbol{h}_n \\in \\mathbb{R}^{D \\times H \\times W}$ now denotes the $D$ -channel feature map for the BEV scenario of shape $H \\times W$ . Secondly, for multi-view aggregation, instead of the concatenation in the original design, we choose element-wise max pooling in Eq. 2, producing the overall feature description $\\hat{\\boldsymbol{h}} \\in \\mathbb{R}^{D \\times H \\times W}$ that fits arbitrary numbers of views. Lastly, we apply the output head as", + "bbox": [ + 496, + 688, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "20137", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/7b69fa980dec9ffa8a2d8b3d7d1c2597e090e0349f2649c2d313cf08b0c39613.jpg", + "image_caption": [ + "Figure 5. Efficient multi-view understanding with selective view pipelining using $T = 3$ glances. Solid lines indicate the network forward pass and dashed lines indicate the interaction between agent (MVSelect) and environment (multi-view system). The approach starts with a random initial view $a_1$ , and the feature extractor $f(\\cdot)$ computes its feature (Eq. 1). The state for this initial time step is recorded as $s_1$ (Eq. 6). Next, the proposed MVSelect module $d(\\cdot)$ is used to choose a second view $a_2$ , and the state is updated as $s_2$ . Then, by repeating the last step, a third view $a_3$ is chosen and the state is updated as $s_3$ . Finally, three views are aggregated into an overall descriptor $\\hat{h}$ (Eq. 2), and the task network output $\\hat{\\pmb{y}}$ is calculated using the output head $g(\\cdot)$ (Eq. 3). The final reward $r_3 = \\mathrm{MODA}(\\hat{\\pmb{y}},\\pmb{y})$ is set as the accuracy fir the task network (Eq. 7), and all other rewards are set as zero." + ], + "image_footnote": [], + "bbox": [ + 83, + 89, + 890, + 296 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Eq. 3 to generate a heatmap $\\hat{\\pmb{y}}\\in (0,1)^{H\\times W}$ that indicates the likelihood of human occupancy in each BEV location. The loss for MVDet can be written as,", + "bbox": [ + 75, + 431, + 470, + 481 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {M V D e t}} = \\mathcal {L} _ {\\mathrm {B E V}} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}) + \\frac {1}{N} \\sum_ {n = 1} ^ {N} \\mathcal {L} _ {n}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 148, + 492, + 468, + 534 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathcal{L}_{\\mathrm{BEV}}(\\cdot ,\\cdot)$ denotes BEV output loss; $\\pmb {y}\\in \\{0,1\\}^{H\\times W}$ denotes binary ground truth map; and $\\mathcal{L}_n$ denotes the auxiliary per-view loss with 2D bounding boxes.", + "bbox": [ + 76, + 546, + 468, + 597 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Efficient Multi-view Understanding", + "text_level": 1, + "bbox": [ + 76, + 611, + 400, + 628 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In a multi-view system with $N$ views, selective view planning uses a total of $T < N$ camera views $a_{t} \\in \\{1, \\dots, N\\}, t \\in \\{1, \\dots, T\\}$ for efficient understanding. To achieve this, we propose a view selection module, MVSelect, denoted as $d(\\cdot)$ , that sequentially selects camera views. Starting from a random initial view $a_{1}$ , MVSelect chooses the remaining $T - 1$ cameras by observing the target object or scene from existing views $a_{1}, \\dots, a_{t}$ at each time step $t$ and deciding which camera view $a_{t + 1}$ to select next for best performance. Once $T$ camera views have been gathered, we aggregate them into an overall description $\\hat{\\pmb{h}}$ using Eq. 2, and calculate the final output $\\hat{\\pmb{y}}$ using Eq. 3. Fig. 5 gives an overview of the proposed efficient multi-view approach.", + "bbox": [ + 75, + 637, + 472, + 835 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Problem Formulation", + "text_level": 1, + "bbox": [ + 76, + 845, + 279, + 861 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "While iteratively selecting camera views, it is impossible to know what is in the not-selected camera views. If view", + "bbox": [ + 75, + 869, + 470, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "selection was formulated as a prediction task in a supervised manner, the loss (final target metric at $t = T$ ) could not be back propagated to the not-selected views, making it non-differentiable and impossible to update the selection probability. Reinforcement learning, on the other hand, can update the controller even with the non-differentiable view selection. Therefore, we formulate this non-differentiable process as a reinforcement learning problem, where MVS-select is the agent and learns through trial and error, and the multi-view system is the environment.", + "bbox": [ + 496, + 434, + 893, + 584 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "State. In order to get a Markovian representation, we record the chosen camera views $a_1,\\dots ,a_t$ and the observations $h_{a_1},\\ldots ,h_{a_t}$ as state $s_t$ . We use the extracted features to represent the observations rather than the RGB camera views to reduce dimensionality and maximize efficiency, since these features will be used in the task network later (Eq. 2). Mathematically, we formulate the state $s_t$ as,", + "bbox": [ + 496, + 585, + 893, + 691 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ns _ {t} = \\left\\langle s _ {t} ^ {\\mathrm {c a m}}, s _ {t} ^ {\\mathrm {o b s}} \\right\\rangle ,\n$$\n", + "text_format": "latex", + "bbox": [ + 633, + 698, + 756, + 718 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ns _ {t} ^ {\\text {c a m}} = \\sum_ {\\tau = 1} ^ {t} \\text {o n e h o t} \\left(a _ {\\tau}\\right), \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 612, + 720, + 890, + 760 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ns _ {t} ^ {\\mathrm {o b s}} = \\max _ {\\tau = 1} ^ {t} \\left\\{\\boldsymbol {h} _ {a _ {\\tau}} \\right\\},\n$$\n", + "text_format": "latex", + "bbox": [ + 630, + 762, + 761, + 787 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where onehot $(\\cdot)$ is the one-hot function over $N$ cameras. This representation reflects both chosen cameras $s_t^{\\mathrm{cam}} \\in \\mathbb{R}^N$ and their observations $s_t^{\\mathrm{obs}} \\in \\mathbb{R}^D$ , and maintains the same dimensionality across different time steps. The observation part $s_t^{\\mathrm{obs}}$ also matches the overall representation in Eq. 2.", + "bbox": [ + 496, + 794, + 890, + 869 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Action. For state $s_t, t \\in \\{1, \\dots, T - 1\\}$ , MVSelect takes the next camera view $a_{t + 1}$ as action.", + "bbox": [ + 496, + 869, + 890, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "20138", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Algorithm 1 Joint training of MVSelect and task network.", + "bbox": [ + 78, + 90, + 464, + 106 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1: input: camera views $\\pmb{x}_n, n \\in \\{1, \\dots, N\\}$ , ground truth $\\pmb{y}$ , random initial view $a_1$ , number of total views $T$ , hyperparameter $\\epsilon$ .", + "2: update: feature extractor $f(\\cdot)$ and output head $g(\\cdot)$ of task network, and MVSelect controller $d(\\cdot)$ .", + "3: initialize the total loss $\\mathcal{L}_{\\mathrm{total}} = 0$", + "4: for $t \\in \\{1, \\dots, T - 1\\}$ do", + "5: select and apply the next action using $\\epsilon$ -greedy: with probability $\\epsilon$ adopt a random action, or else choose the action with highest value $a_{t+1} = \\arg \\max_a Q(s_t, a)$ ;", + "6: observe next state $s_{t + 1}$ (Eq. 6) and reward $r_{t + 1}$ (Eq. 7);", + "7: calculate the RL loss $\\mathcal{L}_{\\mathrm{RL}}$ (Eq. 9) and update the total loss $\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{total}} + \\mathcal{L}_{\\mathrm{RL}}$ ;", + "8: end for", + "9: calculate the task loss $\\mathcal{L}_{\\mathrm{task}}$ (Eq. 4 or Eq. 5) and update the total loss $\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{total}} + \\mathcal{L}_{\\mathrm{task}}$ ;", + "10: optimize for the total loss $\\mathcal{L}_{\\mathrm{total}}$" + ], + "bbox": [ + 81, + 109, + 468, + 345 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Reward. Upon taking action $a_{t+1}$ , the system receives reward $r_{t+1}$ and transitions into the next state $s_{t+1}$ . To achieve high task network performance, we consider the following as reward,", + "bbox": [ + 76, + 378, + 468, + 439 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} r _ {t} = 0, t \\in \\{1, \\dots , T - 1 \\}, \\\\ r _ {T} ^ {\\mathrm {M V C N N}} = \\mathbb {1} (\\hat {\\boldsymbol {y}} = \\boldsymbol {y}), r _ {T} ^ {\\mathrm {M V D e t}} = \\operatorname {M O D A} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}), \\tag {7} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 102, + 453, + 468, + 489 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathbb{1}(\\cdot)$ denotes the binary indicator function, MODA $(\\cdot ,\\cdot)$ is the evaluation metric for multi-view detection [21]. We also experiment with other reward designs in Section 5.4.", + "bbox": [ + 76, + 503, + 468, + 564 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. MVSelect Architecture", + "text_level": 1, + "bbox": [ + 76, + 577, + 289, + 590 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We design MVSelect architecture $d(\\cdot)$ with two branches. The first branch expands the camera selection result $s_t^{\\mathrm{cam}} \\in \\mathbb{R}^N$ into $D$ -dimensional learnable camera embeddings, and then sums over the selected embeddings to formulate a hidden vector. The second branch converts the observation $s_t^{\\mathrm{obs}} \\in \\mathbb{R}^D$ into another hidden vector. By combining the two hidden vectors, the controller network outputs the action-value $Q(s,a)$ , which measures the expected cumulative rewards for taking an action $a$ in a given state $s$ . See Supplementary Materials for figure illustrations.", + "bbox": [ + 76, + 599, + 468, + 752 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "During testing, MVSelect outputs the next action as,", + "bbox": [ + 96, + 753, + 442, + 768 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\na _ {t + 1} = \\underset {a} {\\arg \\max } Q \\left(s _ {t}, a\\right),\n$$\n", + "text_format": "latex", + "bbox": [ + 181, + 782, + 361, + 806 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "which maximizes the expected cumulative rewards.", + "bbox": [ + 76, + 818, + 416, + 833 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3. Training Scheme", + "text_level": 1, + "bbox": [ + 76, + 845, + 243, + 861 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We adopt Q-learning [38] for training MVSelect. Specifically, action-value function $Q(\\cdot ,\\cdot)$ should estimate the cu", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "mulative future rewards after taking action $a_{t+1}$ at state $s_t$ ,", + "bbox": [ + 500, + 125, + 887, + 138 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nQ \\left(s _ {t}, a _ {t + 1}\\right) = \\mathbb {E} \\left(\\sum_ {\\tau = t + 1} ^ {T} \\gamma^ {\\tau - t - 1} r _ {\\tau}\\right),\n$$\n", + "text_format": "latex", + "bbox": [ + 565, + 151, + 825, + 194 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathbb{E}(\\cdot)$ denotes the expectation, and $\\gamma \\in [0,1]$ denotes the discount factor. We take the temporal difference (TD) [38] target as supervision for the action value,", + "bbox": [ + 498, + 205, + 890, + 252 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nq _ {t} = \\left\\{ \\begin{array}{l l} r _ {t + 1} + \\gamma \\max _ {a} Q \\left(s _ {t + 1}, a\\right), & \\text {i f} t < T - 1 \\\\ r _ {T}, & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 514, + 263, + 890, + 305 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "and calculate the loss using the $L_{2}$ distance,", + "bbox": [ + 500, + 316, + 790, + 330 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {R L}} = \\sum_ {t = 1} ^ {T - 1} \\mathcal {L} _ {\\mathrm {M S E}} \\left(Q \\left(s _ {t}, a _ {t + 1}\\right), q _ {t}\\right), \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 573, + 342, + 890, + 383 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where the next action $a_{t + 1}$ is chosen using $\\epsilon$ -greedy for exploration-exploitation trade offs.", + "bbox": [ + 498, + 396, + 890, + 425 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In joint training, the task network takes supervision from $\\mathcal{L}_{\\mathrm{task}}$ (Eq. 4 and Eq. 5), and the selection module takes supervision from $\\mathcal{L}_{\\mathrm{RL}}$ (Eq. 9). A step-by-step demonstration of this process can be found in Algorithm 1.", + "bbox": [ + 498, + 426, + 890, + 487 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 502, + 632, + 518 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.1. Experiment Settings", + "text_level": 1, + "bbox": [ + 500, + 527, + 692, + 542 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. For multi-view classification, we use synthetic dataset ModelNet40 [44] under two different camera layouts (12 views and 20 views) and real-world dataset ScanObjectNN (12 views) [39]. For multi-view detection, we use real-world dataset Wildtrack (7 views) [6] and synthetic dataset MultiviewX (6 views) [17].", + "bbox": [ + 498, + 551, + 890, + 642 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Evaluation metrics. For multi-view classification, we report instance-averaged accuracy. Regarding multi-view detection, we report multi-object detection accuracy (MODA), which is calculated as $1 - \\frac{\\mathrm{FP} + \\mathrm{FN}}{\\mathrm{GT}}$ [21]. All metrics are reported in percentages.", + "bbox": [ + 498, + 643, + 890, + 718 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Implementation details. For multi-view classification, we input images of size $224 \\times 224$ to the MVCNN model. For multi-view detection, we use a resolution of $720 \\times 1280$ with view-coherent data augmentation [16], and downsample the BEV grid by a factor of 4. In terms of architecture, we use ResNet-18 [15] as feature extractor $f(\\cdot)$ .", + "bbox": [ + 498, + 719, + 890, + 809 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We train all networks for 10 epochs using the Adam optimizer [22]. We use learning rates of $5 \\times 10^{-5}$ and $5 \\times 10^{-4}$ , with batch sizes of 8 and 1 for MVCNN and MVDet, respectively. The MVSelect module is trained using a learning rate of $1 \\times 10^{-4}$ . For joint training, we decrease the learning rate for the task network to $1/5$ of its original value.", + "bbox": [ + 496, + 810, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "20139", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/c83b0d1c3eeba163fad5d94875e3e4323a54a8aaea8f9fa8bcdbbe1f7c0c5f4d.jpg", + "table_caption": [ + "Table 1. Performance comparison with state-of-the-art methods. Results are averaged from 5 runs. * indicates that the camera poses are dynamically chosen and do not follow a pre-defined layout. † indicates our implementation." + ], + "table_footnote": [], + "table_body": "
view selection (T=2)ModelNet40ScanObjNN
12 views20 views
MVCNN [37]N/A90.192.0-
GVCNN [11]N/A92.6--
MHBN [47]N/A93.4--
RotationNet [20]N/A-94.7-
RelationNet [46]N/A94.397.3-
ViewGCN [42]N/A-97.6-
MVCNN†N/A94.596.586.1
PointNet [31] + ViewGCNMVTN* (T=12 or 20) [14]93.893.592.6
MVCNN†SEE++† [3]79.270.375.5
MVCNN†Potthast and Sukhatme† [29]76.566.272.1
MVCNN†MVSelect88.279.680.0
MVCNN† (joint training)MVSelect94.394.484.1
", + "bbox": [ + 81, + 128, + 509, + 277 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/779c6add7c2a7fa249ef9f6a9ca9f9c89a8fb9092d5f93a7cbc44933ce9584fd.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
view selection (T=3)WildtrackMultiviewX
RCNN & cluster [45]N/A11.318.7
POM-CNN [13]N/A23.2-
DeepMCD [7]N/A67.870
Deep-Occlusion [2]N/A74.175.2
MVDet [17]N/A88.283.9
SHOT [36]N/A90.288.3
MVDetTr [16]N/A91.593.7
MVDet†N/A90.093.0
MVDet†SEE++[3]76.177.8
MVDet†Potthast and Sukhatme†[29]78.378.0
MVDet†max FoV†[35]78.073.9
MVDet†MVSelect80.078.7
MVDet† (joint training)MVSelect88.688.1
", + "bbox": [ + 524, + 128, + 890, + 277 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/86609035ec67b17c510c3b21899bbc4d4517e6aad6c36fc1d4b966908203214e.jpg", + "image_caption": [ + "Figure 6. Example of selected views on ModelNet40 (left) and Wildtrack (right)." + ], + "image_footnote": [], + "bbox": [ + 84, + 290, + 444, + 385 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/c1351cf7209250e17cca97a493e056134a6bedf5961c00a0b70566d2cbe2f206.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 460, + 290, + 885, + 385 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Regarding hyperparameters, we set the future reward discount factor $\\gamma = 0.99$ , and the exploration ratio $\\epsilon$ to gradually decrease from 0.95 to 0.05 during training. All experiments are conducted on a single RTX-3090 GPU and averaged across 5 repetitive runs.", + "bbox": [ + 75, + 436, + 468, + 511 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Experimental setups. First, we fix the task network. We compare with state-of-the-art methods including 1) NBV policy with depth-sensing enabled point-based occlusion estimation [3], 2) NBV policy with depth-sensing enabled voxel-based probabilistic representation [29], and 3) NBV policy to maximize field-of-view (FoV) coverage [35] (only applicable to multi-view detection). We also report two baselines: 1) random selection, 2) the best policy on the validation set; and two oracles: for a certain initial view, 1) choosing the overall best-performing camera for all instances in the dataset (dataset-level oracle) and 2) choosing specifically for each instance (instance-level oracle). For the two oracles, the former reflects the upper bound of performance achievable by human-designed heuristics, and the latter represents the theoretical performance ceiling when keeping the task network fixed.", + "bbox": [ + 75, + 513, + 468, + 753 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Second, we jointly train the proposed view selection module with the task networks. For this experiment, our goal is to achieve the highest possible performance using $T$ views. If not specified, we use a total of $T = 2$ views for multi-view classification and $T = 3$ views for detection.", + "bbox": [ + 75, + 756, + 470, + 830 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Evaluation of MVSelect", + "text_level": 1, + "bbox": [ + 76, + 845, + 295, + 861 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For multi-view classification, as in Table 1, MVSelect with fixed multi-view classification network achieves competi", + "bbox": [ + 75, + 869, + 470, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "tive performance compared to other state-of-the-art view selection methods. When compared with baselines and oracles in Table 2, the proposed view selection module, can choose the views effectively. Compared to dataset-level oracles (same policy for all instances with the same initial camera), MVSelect also turns out to be advantageous by $3.0\\%$ , $9.7\\%$ , and $1.5\\%$ across the two settings. This verifies that MVSelect can take the target object into consideration (see Fig. 2) and select different cameras for different instances under the same initial camera.", + "bbox": [ + 496, + 436, + 890, + 585 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "When joint training MVCNN with MVSelect, we witness large improvements. In fact, on two settings, the results are only $0.2\\%$ , $2.1\\%$ , and $2.0\\%$ behind compared to the full $N$ -view system. Overall, we believe that MVSelect and its joint training capabilities enable us to consider only 2 views without major performance drawbacks. We demonstrate an example of the selected views in Fig. 6, and the MVSelect policy in Fig. 7.", + "bbox": [ + 496, + 590, + 892, + 712 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For multi-view detection, MVSelect achieves competitive performance compared to existing NBV methods, some of them even require additional depth sensing (Table 1). Although the raw improvements are not as substantial as those in multi-view classification, they are statistically highly significant $(p$ -value $< 0.001)$ . This shows human designed heuristics like minimal occlusion or maximum FoV coverage cannot guarantee the best detection results.", + "bbox": [ + 496, + 715, + 890, + 837 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "When compared to baselines and oracles, MVSelect also shows to be competitive (see Table 2). Specifically, we observe that the instance-level oracle remains relatively low compared to that of multi-view classification tasks. This is", + "bbox": [ + 496, + 839, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "20140", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/f08efe14482e45dd62db44d1d414bcfdf79f3fbe74888298166e2d7769a96f52.jpg", + "table_caption": [ + "Table 2. Comparison with view selection baselines and oracles on multi-view classification and detection datasets." + ], + "table_footnote": [], + "table_body": "
view selection (T=2)ModelNet40ScanObjNN
12 views20 views
N/A: all N views94.596.586.1
dataset-lvl oracle85.2 ± 1.469.9 ± 1.978.5 ± 1.2
instance-lvl oracle96.5 ± 0.498.1 ± 1.993.4 ± 0.6
random selection71.5 ± 2.548.1 ± 3.174.2 ± 3.5
validation best policy85.1 ± 0.869.5 ± 1.077.5 ± 1.1
MVSelect88.2 ± 0.479.6 ± 1.880.0 ± 0.8
MVSelect + joint training94.3 ± 0.294.4 ± 0.284.1 ± 0.2
", + "bbox": [ + 81, + 114, + 517, + 256 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/9623e70d806015965f101cf757e0bf95a2b37311a06dad52bb2dc2fbde3f53fe.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
view selection (T=3)WildtrackMultiviewX
N/A: all N views90.093.0
dataset-lvl oracle82.5 ± 0.480.2 ± 0.3
instance-lvl oracle87.4 ± 0.482.3 ± 0.8
random selection74.9 ± 1.376.2 ± 1.4
validation best policy79.5 ± 1.178.0 ± 0.4
MVSelect80.0 ± 0.878.7 ± 0.5
MVSelect + joint training88.6 ± 0.288.1 ± 0.2
", + "bbox": [ + 534, + 122, + 888, + 250 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/fb5a7651b95a4fb120ccd9bc4d96570513386356d4e288aba040079d2120c5fb.jpg", + "image_caption": [ + "(a) Classification accuracy", + "Figure 7. Multi-view classification with $T = 2$ views on the 12-view setup of ModelNet40. The task network is fixed once trained. Left: test set accuracy of using two views. Right: MVSelect policy for the test set." + ], + "image_footnote": [], + "bbox": [ + 81, + 276, + 315, + 450 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a9f2da4b0ea3c10a150d3744bf47b0e65fba535ede4d0f0851a6deb470a767a9.jpg", + "image_caption": [ + "(b) MVSelect policy" + ], + "image_footnote": [], + "bbox": [ + 334, + 276, + 566, + 450 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/cad369f0e7290210c2dfc988f43e162afaee3784ca1cfd0523d5f8328db3fdfc.jpg", + "table_caption": [ + "Table 3. Computation efficiency." + ], + "table_footnote": [], + "table_body": "
viewsFLOPsthroughput (instance/s)
f(·)g(·)d(·)
ModelNet402036.5G20.5kN/A119.6
23.6G20.5k1.1M361.8
1221.9G20.5kN/A196.2
23.6G20.5k530.4k507.9
Wildtrack71.2T19.1GN/A8.4
3511.6G19.1G3.2G16.2
MultiviewX61.0T17.7GN/A9.8
3511.6G17.7G2.9G16.9
", + "bbox": [ + 588, + 285, + 885, + 402 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/64a2afab114da2264ec0153a7d8b72b4a54cf6b769f96801c8bfd599b853a7af.jpg", + "table_caption": [ + "Table 4. Ablation study." + ], + "table_footnote": [], + "table_body": "
ModelNet40Wildtrack
12 views
MVSelect88.280.0
w/o camera branch88.279.1
w/o feature branch85.079.7
w/ transformer87.078.7
reward=Δ task loss88.080.1
", + "bbox": [ + 588, + 428, + 885, + 530 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "likely due to the target scenarios not being fully captured by any single view, and the multi-view detection network needs multiple views to collaborate with each other for optimal results. Compared to the dataset-level oracles, we find the MVSelect policy lose its edge. In fact, we find that for multi-view detection, MVSelect tends to select the same camera for a given initial view, since it is not aware of the situation outside of the FoV coverage. As a result, it cannot choose cameras based on uncovered areas in different frames. Without this instance-aware advantage, the fixed camera policy learned during training (MVSelect) cannot outperform the dataset-level oracle, whose policy is computed on the test set.", + "bbox": [ + 75, + 556, + 472, + 751 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Joint training with MVDet once again leads to substantial performance improvements over keeping the task network fixed. In fact, the results even exceed the instance-level oracle for fixed task networks. Using $T = 3$ views, the joint training approach provides competitive results to using all $N$ views, and exceeds the reported performance in the original MVDet paper [17]. We present an example of the selected views in the Wildtrack dataset in Fig. 6.", + "bbox": [ + 75, + 779, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Efficiency Analysis", + "text_level": 1, + "bbox": [ + 500, + 555, + 683, + 571 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In Table 3, following previous works in efficient inference [19, 24], we detail the computational cost in FLOPs for task networks and MVSelect. Specifically, we find feature extraction $f(\\cdot)$ to take up the majority of the computation, while everything else is lighter by at least an order of magnitude. Overall, we verify that using $T = 2$ or 3 out of $N$ views can reduce the computational cost to roughly $T / N$ .", + "bbox": [ + 496, + 578, + 890, + 684 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In terms of inference speed, we find reduction in FLOPs results in monotonically increasing throughputs, ranging from $1.72 \\times$ to $3.03 \\times$ . Due to factors such as implementation, parallelization, and hardware limitations, actual speedups cannot actually reach the level of computational cost reduction, as suggested by previous study [27].", + "bbox": [ + 496, + 685, + 890, + 776 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.4. Variant Study", + "text_level": 1, + "bbox": [ + 500, + 786, + 643, + 801 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Ablation study. Regarding the MVSelect architecture design, Table 4 shows that removing the camera branch and feature branch primarily affects multi-view detection and multi-view classification performance, respectively. This aligns with the policy we learned for the two tasks. For multi-view detection, since the system has no clue about ar", + "bbox": [ + 496, + 809, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "20141", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/46b7cc7ab392afd0798d5a74f1cb8018e47e6c693d64ce66068a019859106ad8.jpg", + "image_caption": [ + "Figure 9. System performance under different number of total views $T$ . We report classification accuracy and MODA for the two tasks, respectively (same for Fig. 10 and Table. 4). Circle and triangle markers indicate whether the task network is fixed or not, respectively. Dotted lines represent oracle performance (not achievable)." + ], + "image_footnote": [], + "bbox": [ + 81, + 97, + 310, + 265 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/15f43b5dc456ea37de0697ff64d73ba717e477ec8e9a4e925ae24aecaece104d.jpg", + "image_caption": [ + "Figure 10. System evaluation under different settings. Except for the random pose* setting (where MVSelect variants are re-trained), all models are trained on the default setting." + ], + "image_footnote": [], + "bbox": [ + 331, + 95, + 563, + 265 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e1d47565d23c0e4be800f60083b5daa0138035ff3928733c635ed0bb1f03a6b4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 588, + 98, + 867, + 265 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "eas outside camera FoVs, the camera branch plays a more important role for encoding prior knowledge of the scene layout. For multi-view classification, however, target objects are fully observable, and MVSelect can make different decisions for each instance. Thus, the feature branch is more important, as it enables per-instance decision making.", + "bbox": [ + 73, + 359, + 468, + 450 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "When changing the MVSelect network architecture into transformer [40], we find that more parameters do not translate into better performance.", + "bbox": [ + 75, + 454, + 468, + 500 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Another option for the reward is the change in task loss. In our variant study, this reward design does not show any significant advantages over the current design.", + "bbox": [ + 75, + 502, + 468, + 547 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Influence of total view count. The performance curves in Fig. 9 demonstrate that the joint training variant achieves competitive performance with as few as $T = 2$ views for multi-view classification and $T = 3$ views for multi-view detection, beyond which point performance plateaus. By contrast, learning MVSelect for fixed task networks shows a less steep curve. The performance increases up to a total of $T = 5$ views, at which point the MVSelect policy performs comparably to the full $N$ -view system.", + "bbox": [ + 75, + 550, + 468, + 686 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Camera layout optimization. Determining the optimal camera locations is crucial for setting up an effective multiview system. In Fig.7, we observe that not all cameras are equally useful according to the MVSelect policy. To address this, we allocate a validation partition of the data to identify the more useful camera views and then disable half of the $N = 12$ cameras that are not frequently utilized. In testing, we find that some cameras are not as useful (\"policy shut-off\" in Fig. 10) and the proposed method can generalize to test-time disturbances including malfunctioning cameras (\"random shut-off\" in Fig.10). Although it is necessary to set up all $N$ cameras for the analysis, optimizing the multiview camera layout can be a crucial step towards achieving optimal performance, and merits further investigation.", + "bbox": [ + 75, + 689, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Random object pose. In real-world applications of multi-view systems, such as those found in iPhones and Tesla, the cameras may remain fixed in their relative positions while the entire system is in motion. To simulate this scenario in our experiments, we introduce the random object pose setting (Fig. 10) and re-train MVSelect. While there is no exact object pose as supervision, the reinforcement learning approach is able to roughly infer the relative poses between the object and the multi-view system, resulting in improved performance compared to random selection and dataset-level oracle (which is arguably inappropriate for this setup). In the future, we plan to estimate camera poses with respect to the object or the environment as an auxiliary supervision for moving setups.", + "bbox": [ + 496, + 359, + 890, + 571 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 594, + 617, + 609 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In conclusion, this paper proposes selective view pipelining, an efficient approach for multi-view understanding by limiting the number of views. To this end, a camera view selection module, MVSelect, is proposed along with a reinforcement learning based training scheme that can learn from the non-differentiable selection process. When jointly trained with the task network, the proposed approach demonstrates competitive performance on multi-view classification and detection tasks at fractions of the computational cost. Overall, the proposed efficient approach provides an alternative to reducing image resolution and using lighter networks, and paves ways for future multi-view camera layout optimization.", + "bbox": [ + 496, + 623, + 890, + 818 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement", + "text_level": 1, + "bbox": [ + 500, + 842, + 658, + 859 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by the ARC Discovery Project (DP210102801).", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "20142", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] John Aloimonos, Isaac Weiss, and Amit Bandyopadhyay. Active vision. 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In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 186-194, 2018. 6" + ], + "bbox": [ + 501, + 92, + 890, + 388 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "20144", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning to Select Views for Efficient Multi-View Understanding/6f1ed185-f83a-4de1-ba41-bd094a6eccd2_model.json b/2024/Learning to Select Views for Efficient Multi-View Understanding/6f1ed185-f83a-4de1-ba41-bd094a6eccd2_model.json new file mode 100644 index 0000000000000000000000000000000000000000..cf78544e5cb696ea547236d0405e10dd51805880 --- /dev/null +++ b/2024/Learning to Select Views for Efficient Multi-View Understanding/6f1ed185-f83a-4de1-ba41-bd094a6eccd2_model.json @@ -0,0 +1,2420 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.159, + 0.131, + 0.815, + 0.154 + ], + "angle": 0, + "content": "Learning to Select Views for Efficient Multi-View Understanding" + }, + { + "type": "text", + "bbox": [ + 0.29, + 0.182, + 0.681, + 0.218 + ], + "angle": 0, + "content": "Yunzhong Hou, Stephen Gould, and Liang Zheng \nAustralian National University" + }, + { + "type": "text", + "bbox": [ + 0.347, + 0.22, + 0.62, + 0.234 + ], + "angle": 0, + "content": "{firstname.lastname}@anu.edu.au" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.302, + 0.474, + 0.604 + ], + "angle": 0, + "content": "Multiple camera view (multi-view) setups have proven useful in many computer vision applications. However, the high computational cost associated with multiple views creates a significant challenge for end devices with limited computational resources. In modern CPU, pipelining breaks a longer job into steps and enables parallelism over sequential steps from multiple jobs. Inspired by this, we study selective view pipelining for efficient multi-view understanding, which breaks computation of multiple views into steps, and only computes the most helpful views/steps in a parallel manner for the best efficiency. To this end, we use reinforcement learning to learn a very light view selection module that analyzes the target object or scenario from initial views and selects the next-best-view for recognition or detection for pipeline computation. Experimental results on multi-view classification and detection tasks show that our approach achieves promising performance while using only 2 or 3 out of \\(N\\) available views, significantly reducing computational costs while maintaining parallelism over GPU through selective view pipelining1." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.636, + 0.21, + 0.652 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.662, + 0.47, + 0.875 + ], + "angle": 0, + "content": "Multiple camera views (multi-view) are popular in computer vision systems for their ability to address challenges such as occlusions, ambiguities, and limited field-of-view (FoV) coverage. Tasks like classification [30, 37] and detection [6, 17] have shown significant benefits from using multiple cameras. With reduced hardware cost and easy deployment, real-world products now include more cameras at larger scales. However, the use of multiple cameras comes at a high computational cost, which can be a significant challenge for end devices with limited computational resources, especially with higher image resolutions and deeper neural network backbones. Limiting image resolution or using lighter networks [19, 27] are current options to reduce computation, but they may impede the" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.269, + 0.891, + 0.358 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.619, + 0.362, + 0.774, + 0.375 + ], + "angle": 0, + "content": "(a) Piplining in modern CPU" + }, + { + "type": "image", + "bbox": [ + 0.506, + 0.378, + 0.889, + 0.457 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.624, + 0.46, + 0.771, + 0.472 + ], + "angle": 0, + "content": "(b) Parallel in modern GPU" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.474, + 0.885, + 0.554 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.62, + 0.557, + 0.774, + 0.571 + ], + "angle": 0, + "content": "(c) Selective view pipelining" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.581, + 0.892, + 0.749 + ], + "angle": 0, + "content": "Figure 1. Demonstration of the proposed selective view pipelining. Inspired by instruction pipelining in modern CPU (a), selective view pipelining (c) breaks the multi-view perception task into sequential steps, and only computes the chosen views (see Fig. 2) to minimize the computation. At the same time, computation across multiple objects (different border colors) can still enjoy parallelism in GPU (b). In this example, for a \\( N = 6 \\) view system, traditional computation (b) on GPU hardware that only supports two images at the same time will produce a throughput of 2 instances during 6 time steps. In contrast, by taking advantage of the parallelism, selective view pipelining computes 6 instances within 7 time steps." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.885, + 0.78 + ], + "angle": 0, + "content": "progress in camera sensors or neural network architecture." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In modern CPU, instruction pipelining [10] breaks individual instructions into steps to enable parallelism across multiple instructions within the same CPU (see Fig. 1a). For multi-view perception, although computations for different images can be paralleled over GPU [9], the level of parallelism is still limited by hardware. As an example, the GPU in Fig. 1b might only support parallel computing for two images at a time, resulting in at least 3 time steps for" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.468, + 0.9 + ], + "angle": 0, + "content": "\\(^{1}\\)Code available at https://github.com/hou-yz/MVSelect." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "20135" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.107, + 0.092, + 0.446, + 0.265 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.279, + 0.473, + 0.39 + ], + "angle": 0, + "content": "Figure 2. Efficient multi-view understanding with two glances. Instead of using all \\(N\\) views at once, a more efficient approach is to first examine one view and then select another view to resolve ambiguities from the initial glance. If the initial side view cannot distinguish between a guitar and a mandolin (a round-shaped instrument that may also have a flat back), we can then query the front view. This sequential process can work in a pipeline to enable parallelism between multiple" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.411, + 0.315, + 0.426 + ], + "angle": 0, + "content": "computing one object with 6 views." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.428, + 0.47, + 0.564 + ], + "angle": 0, + "content": "In this work, we propose selective view pipelining, which breaks the multi-view perception task into a sequence of steps. Based on initial views, we estimate the most helpful views for this task, and only compute the selected views for maximum efficiency. The example in Fig. 1c shows that only selecting one additional view can greatly reduce the computation from 6 views to 2 views. By further taking advantage of the parallelism in GPUs, we can roughly improve the overall throughput by \\(3 \\times\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.567, + 0.471, + 0.809 + ], + "angle": 0, + "content": "To this end, this paper introduces a new angle to efficient multi-view understanding by selecting only the most useful views. To identify the best views, this approach leverages camera layouts, which is a key aspect overlooked by existing alternatives. With known camera layouts, networks should be able to infer what each camera view looks like and then choose accordingly, as previous works [20] have shown that networks can associate images with camera poses. Existing work on active vision [1, 8, 12] indicates that it is possible to find next-best-view (NBV) for reconstruction with 3D sensors. In this paper, we focus on recognition and detection problems using multiple RGB cameras, where a side view may confuse a guitar with a mandolin (Fig. 2). However, prior knowledge of the camera layout should inform the system that the front view can clear the ambiguities and should be queried." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.471, + 0.902 + ], + "angle": 0, + "content": "To achieve this goal, this paper proposes a novel view selection module, MVSelect, that chooses the best camera views from any initial view at minimal computational costs. Using the same feature extracted for the final task of classification or detection, the proposed module analyzes the target object or scenario from existing views and then selects the" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.094, + 0.891, + 0.259 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.531, + 0.27, + 0.86, + 0.284 + ], + "angle": 0, + "content": "Figure 3. Multi-view classification with MVCNN [37]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.301, + 0.892, + 0.422 + ], + "angle": 0, + "content": "next view that best helps the task (classification or detection) network. To navigate through the non-differentiable view selection (the system only looks at selected cameras, so not-selected views cannot back propagate gradients to the controller), following Mnih et al. [26], we train the controller via trial-and-error. This process is formulated as a reinforcement learning problem aiming to maximize the final recognition or detection accuracy." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.423, + 0.893, + 0.558 + ], + "angle": 0, + "content": "On both multi-view classification and detection tasks, our experimental results show that MVSelect can provide a good strategy for fixed task networks, while also capable of joint training with the task network for further performance improvements. Specifically, when joint training both MVSelect and the task network, the resulting system can achieve competitive performance to using all \\(N\\) cameras, while using only 2 views for classification tasks and 3 views for detection tasks, respectively." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.559, + 0.892, + 0.663 + ], + "angle": 0, + "content": "The computational overhead of MVSelect is very small, as it shares the feature extraction backbone with the task network and only has a few learnable layers. For the entire system, the computational cost is roughly proportional to the number of views used, e.g., approximately \\(2 / N\\) of the total computation when 2 views are used, a significant efficiency boost." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.665, + 0.892, + 0.74 + ], + "angle": 0, + "content": "The MVSelect policy also enables study on multi-view camera layout. In fact, we find that many of the \\(N\\) cameras are rarely chosen and can be shut off for further operational cost improvements, which can serve as a starting point for future study on multi-view camera layout optimization." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.755, + 0.629, + 0.772 + ], + "angle": 0, + "content": "2. Background" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Multi-view classification. One effective way for 3D shape recognition is to capture the object in multiple camera views. MVCNN [37] extracts feature vectors from the input views, and then uses max pooling to aggregate across multiple views for classification. Based on MVCNN, many alternative approaches are proposed. Qi et al. [30] propose sphere rendering at different volume resolutions. GVCNN [11] investigates hierarchical information between different" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "20136" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.088, + 0.092, + 0.468, + 0.214 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.125, + 0.229, + 0.423, + 0.244 + ], + "angle": 0, + "content": "Figure 4. Multi-view detection with MVDet [17]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.263, + 0.47, + 0.368 + ], + "angle": 0, + "content": "views by grouping the image features before the final aggregation. RotationNet [20] introduces a multi-task objective by jointly considering classification and camera poses. ViewGCN [42] uses a Graph Convolution Network (GCN) [23] instead of the max pooling layer to aggregate across views. Hamdi et al. [14] propose the MVTN network to estimate the best viewpoints for 3D point cloud models." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.37, + 0.47, + 0.566 + ], + "angle": 0, + "content": "Multi-view detection estimate pedestrian occupancy from the bird's-eye-view (BEV). For this task, some methods [13, 33, 45] aggregate single-view detection results. Others find single-view detection results unreliable and instead aggregate the features. Hou et al. [17] introduce MVDet, the first fully deep-learning approach, which projects feature maps from each camera view to the BEV. Based on MVDet, researchers develop other deep methods. SHOT [36] projects the image feature map at different heights and stacks them together to improve performance. MVDetr [16] deals with distinct distortion patterns from the projection. Qiu et al. [32] investigate data augmentation with simulated occlusion over multiple views." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.567, + 0.471, + 0.808 + ], + "angle": 0, + "content": "Camera viewpoint study. Cao and Snavely [5] investigate this for reconstruction with structure-from-motion. Active vision community investigates next-best-view planning with 3D sensors like RGBD cameras or LiDAR for scene reconstruction [4, 8, 35]. In multi-view classification, RotationNet [20] makes some pioneering work on limited view numbers by taking a random partial set of all \\(N\\) views of the image. MVTN [14] uses the 3D point cloud as initial input and then estimates the best camera layout for multi-view classification, but its moving camera assumption is hard to meet in real-world systems. In multi-view detection, Vora et al. [41] investigate camera layout generalization by randomly dropping camera views from both training and testing. Hou et al. [18] investigate how to place cameras. For 3D human pose estimation, Pirinen et al. [28] actively select cameras over a dome." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Reinforcement learning (RL) directs an agent to interact with the environment in a manner that maximizes cumulative rewards. State \\( s \\in S \\), action \\( a \\in \\mathcal{A} \\), and reward \\( r \\in \\mathcal{R} \\) are key concepts to model the interaction between agent and environment. In a certain state \\( s \\), policy \\( \\pi(a|s) \\) records the probability for each action, and state value func" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.184 + ], + "angle": 0, + "content": "tion \\( V(s) \\) estimates the future rewards when following the corresponding policy. To learn the best policy, Q-learning and DQN [25] optimize the action value function \\( Q(s,a) \\), which describes the estimated future return for a specific action \\( a \\) at state \\( s \\). Policy gradient methods like REINFORCE [43] and PPO [34] directly optimize for the polity \\( \\pi(a|s) \\)." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.196, + 0.757, + 0.212 + ], + "angle": 0, + "content": "3. Multi-view Network Revisit" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.221, + 0.839, + 0.235 + ], + "angle": 0, + "content": "3.1. Multi-view Classification with MVCNN" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.243, + 0.892, + 0.305 + ], + "angle": 0, + "content": "MVCNN [37] (Fig. 3) is a classic architecture which many multi-view classification networks build upon. Given \\(N\\) input images \\(\\pmb{x}_n\\), \\(n \\in \\{1, \\dots, N\\}\\), first, MVCNN uses its feature extractor \\(f(\\cdot)\\) to calculate the feature vectors," + }, + { + "type": "equation", + "bbox": [ + 0.645, + 0.317, + 0.892, + 0.334 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {h} _ {n} = f \\left(\\boldsymbol {x} _ {n}\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.345, + 0.892, + 0.391 + ], + "angle": 0, + "content": "where the feature vector \\( \\pmb{h}_n \\in \\mathbb{R}^D \\) is \\( D \\)-dimensional. Secondly, it uses max pooling to aggregate multiple views into an overall feature descriptor \\( \\hat{\\pmb{h}} \\in \\mathbb{R}^{D} \\)," + }, + { + "type": "equation", + "bbox": [ + 0.64, + 0.401, + 0.892, + 0.425 + ], + "angle": 0, + "content": "\\[\n\\hat {\\boldsymbol {h}} = \\max _ {n} \\left\\{\\boldsymbol {h} _ {n} \\right\\}, \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.435, + 0.892, + 0.481 + ], + "angle": 0, + "content": "where \\(\\max \\{\\dots\\}\\) takes the maximum along each of the \\(D\\) dimensions. Lastly, it applies the output head \\(g(\\cdot)\\) to produce the classification result \\(\\hat{\\pmb{y}}\\)," + }, + { + "type": "equation", + "bbox": [ + 0.652, + 0.491, + 0.892, + 0.517 + ], + "angle": 0, + "content": "\\[\n\\hat {\\boldsymbol {y}} = g (\\hat {\\boldsymbol {h}}). \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.526, + 0.892, + 0.587 + ], + "angle": 0, + "content": "In training, the original design by Su et al. [37] adopts a 2-stage paradigm by first training on individual views and then considering multiple views. In this paper, we skip the first stage and directly train MVCNN on all \\(N\\) views," + }, + { + "type": "equation", + "bbox": [ + 0.617, + 0.599, + 0.892, + 0.616 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {M V C N N}} = \\mathcal {L} _ {\\text {C E}} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}), \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.627, + 0.892, + 0.657 + ], + "angle": 0, + "content": "where \\(\\mathcal{L}_{\\mathrm{CE}}(\\cdot ,\\cdot)\\) denotes the cross-entropy loss and \\(\\pmb{y}\\) denotes the ground truth one-hot label." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.666, + 0.798, + 0.681 + ], + "angle": 0, + "content": "3.2. Multi-view Detection with MVDet" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.892, + 0.901 + ], + "angle": 0, + "content": "MVDet [17] (Fig. 4) is a multi-view detection architecture that is followed by many recent works. To estimate human occupancy in bird's-eye-view (BEV), given input images \\( \\boldsymbol{x}_n, n \\in \\{1, \\dots, N\\} \\), MVDet first extracts \\( D \\)-channel feature maps for each view and uses perspective transformation to project the camera views to the BEV. Together, these operations can be considered as the BEV feature extraction step under Eq. 1, with the exception that \\( \\boldsymbol{h}_n \\in \\mathbb{R}^{D \\times H \\times W} \\) now denotes the \\( D \\)-channel feature map for the BEV scenario of shape \\( H \\times W \\). Secondly, for multi-view aggregation, instead of the concatenation in the original design, we choose element-wise max pooling in Eq. 2, producing the overall feature description \\( \\hat{\\boldsymbol{h}} \\in \\mathbb{R}^{D \\times H \\times W} \\) that fits arbitrary numbers of views. Lastly, we apply the output head as" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "20137" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.09, + 0.891, + 0.297 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.311, + 0.896, + 0.41 + ], + "angle": 0, + "content": "Figure 5. Efficient multi-view understanding with selective view pipelining using \\( T = 3 \\) glances. Solid lines indicate the network forward pass and dashed lines indicate the interaction between agent (MVSelect) and environment (multi-view system). The approach starts with a random initial view \\( a_1 \\), and the feature extractor \\( f(\\cdot) \\) computes its feature (Eq. 1). The state for this initial time step is recorded as \\( s_1 \\) (Eq. 6). Next, the proposed MVSelect module \\( d(\\cdot) \\) is used to choose a second view \\( a_2 \\), and the state is updated as \\( s_2 \\). Then, by repeating the last step, a third view \\( a_3 \\) is chosen and the state is updated as \\( s_3 \\). Finally, three views are aggregated into an overall descriptor \\( \\hat{h} \\) (Eq. 2), and the task network output \\( \\hat{\\pmb{y}} \\) is calculated using the output head \\( g(\\cdot) \\) (Eq. 3). The final reward \\( r_3 = \\mathrm{MODA}(\\hat{\\pmb{y}},\\pmb{y}) \\) is set as the accuracy fir the task network (Eq. 7), and all other rewards are set as zero." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.433, + 0.471, + 0.482 + ], + "angle": 0, + "content": "Eq. 3 to generate a heatmap \\(\\hat{\\pmb{y}}\\in (0,1)^{H\\times W}\\) that indicates the likelihood of human occupancy in each BEV location. The loss for MVDet can be written as," + }, + { + "type": "equation", + "bbox": [ + 0.15, + 0.493, + 0.47, + 0.535 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {M V D e t}} = \\mathcal {L} _ {\\mathrm {B E V}} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}) + \\frac {1}{N} \\sum_ {n = 1} ^ {N} \\mathcal {L} _ {n}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.547, + 0.47, + 0.598 + ], + "angle": 0, + "content": "where \\(\\mathcal{L}_{\\mathrm{BEV}}(\\cdot ,\\cdot)\\) denotes BEV output loss; \\(\\pmb {y}\\in \\{0,1\\}^{H\\times W}\\) denotes binary ground truth map; and \\(\\mathcal{L}_n\\) denotes the auxiliary per-view loss with 2D bounding boxes." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.612, + 0.401, + 0.63 + ], + "angle": 0, + "content": "4. Efficient Multi-view Understanding" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.638, + 0.473, + 0.837 + ], + "angle": 0, + "content": "In a multi-view system with \\(N\\) views, selective view planning uses a total of \\(T < N\\) camera views \\(a_{t} \\in \\{1, \\dots, N\\}, t \\in \\{1, \\dots, T\\}\\) for efficient understanding. To achieve this, we propose a view selection module, MVSelect, denoted as \\(d(\\cdot)\\), that sequentially selects camera views. Starting from a random initial view \\(a_{1}\\), MVSelect chooses the remaining \\(T - 1\\) cameras by observing the target object or scene from existing views \\(a_{1}, \\dots, a_{t}\\) at each time step \\(t\\) and deciding which camera view \\(a_{t + 1}\\) to select next for best performance. Once \\(T\\) camera views have been gathered, we aggregate them into an overall description \\(\\hat{\\pmb{h}}\\) using Eq. 2, and calculate the final output \\(\\hat{\\pmb{y}}\\) using Eq. 3. Fig. 5 gives an overview of the proposed efficient multi-view approach." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.847, + 0.281, + 0.862 + ], + "angle": 0, + "content": "4.1. Problem Formulation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.471, + 0.903 + ], + "angle": 0, + "content": "While iteratively selecting camera views, it is impossible to know what is in the not-selected camera views. If view" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.435, + 0.895, + 0.585 + ], + "angle": 0, + "content": "selection was formulated as a prediction task in a supervised manner, the loss (final target metric at \\( t = T \\)) could not be back propagated to the not-selected views, making it non-differentiable and impossible to update the selection probability. Reinforcement learning, on the other hand, can update the controller even with the non-differentiable view selection. Therefore, we formulate this non-differentiable process as a reinforcement learning problem, where MVS-select is the agent and learns through trial and error, and the multi-view system is the environment." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.587, + 0.895, + 0.693 + ], + "angle": 0, + "content": "State. In order to get a Markovian representation, we record the chosen camera views \\(a_1,\\dots ,a_t\\) and the observations \\(h_{a_1},\\ldots ,h_{a_t}\\) as state \\(s_t\\). We use the extracted features to represent the observations rather than the RGB camera views to reduce dimensionality and maximize efficiency, since these features will be used in the task network later (Eq. 2). Mathematically, we formulate the state \\(s_t\\) as," + }, + { + "type": "equation", + "bbox": [ + 0.634, + 0.699, + 0.758, + 0.719 + ], + "angle": 0, + "content": "\\[\ns _ {t} = \\left\\langle s _ {t} ^ {\\mathrm {c a m}}, s _ {t} ^ {\\mathrm {o b s}} \\right\\rangle ,\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.614, + 0.721, + 0.892, + 0.761 + ], + "angle": 0, + "content": "\\[\ns _ {t} ^ {\\text {c a m}} = \\sum_ {\\tau = 1} ^ {t} \\text {o n e h o t} \\left(a _ {\\tau}\\right), \\tag {6}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.631, + 0.763, + 0.762, + 0.789 + ], + "angle": 0, + "content": "\\[\ns _ {t} ^ {\\mathrm {o b s}} = \\max _ {\\tau = 1} ^ {t} \\left\\{\\boldsymbol {h} _ {a _ {\\tau}} \\right\\},\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.871 + ], + "angle": 0, + "content": "where onehot \\((\\cdot)\\) is the one-hot function over \\(N\\) cameras. This representation reflects both chosen cameras \\(s_t^{\\mathrm{cam}} \\in \\mathbb{R}^N\\) and their observations \\(s_t^{\\mathrm{obs}} \\in \\mathbb{R}^D\\), and maintains the same dimensionality across different time steps. The observation part \\(s_t^{\\mathrm{obs}}\\) also matches the overall representation in Eq. 2." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Action. For state \\( s_t, t \\in \\{1, \\dots, T - 1\\} \\), MVSelect takes the next camera view \\( a_{t + 1} \\) as action." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20138" + } + ], + [ + { + "type": "code_caption", + "bbox": [ + 0.08, + 0.092, + 0.465, + 0.107 + ], + "angle": 0, + "content": "Algorithm 1 Joint training of MVSelect and task network." + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.111, + 0.47, + 0.153 + ], + "angle": 0, + "content": "1: input: camera views \\( \\pmb{x}_n, n \\in \\{1, \\dots, N\\} \\), ground truth \\( \\pmb{y} \\), random initial view \\( a_1 \\), number of total views \\( T \\), hyperparameter \\( \\epsilon \\)." + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.154, + 0.469, + 0.181 + ], + "angle": 0, + "content": "2: update: feature extractor \\( f(\\cdot) \\) and output head \\( g(\\cdot) \\) of task network, and MVSelect controller \\( d(\\cdot) \\)." + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.181, + 0.303, + 0.194 + ], + "angle": 0, + "content": "3: initialize the total loss \\(\\mathcal{L}_{\\mathrm{total}} = 0\\)" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.195, + 0.269, + 0.208 + ], + "angle": 0, + "content": "4: for \\( t \\in \\{1, \\dots, T - 1\\} \\) do" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.209, + 0.469, + 0.25 + ], + "angle": 0, + "content": "5: select and apply the next action using \\(\\epsilon\\)-greedy: with probability \\(\\epsilon\\) adopt a random action, or else choose the action with highest value \\(a_{t+1} = \\arg \\max_a Q(s_t, a)\\);" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.251, + 0.456, + 0.264 + ], + "angle": 0, + "content": "6: observe next state \\( s_{t + 1} \\) (Eq. 6) and reward \\( r_{t + 1} \\) (Eq. 7);" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.265, + 0.469, + 0.291 + ], + "angle": 0, + "content": "7: calculate the RL loss \\(\\mathcal{L}_{\\mathrm{RL}}\\) (Eq. 9) and update the total loss \\(\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{total}} + \\mathcal{L}_{\\mathrm{RL}}\\);" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.293, + 0.155, + 0.304 + ], + "angle": 0, + "content": "8: end for" + }, + { + "type": "text", + "bbox": [ + 0.088, + 0.305, + 0.469, + 0.333 + ], + "angle": 0, + "content": "9: calculate the task loss \\(\\mathcal{L}_{\\mathrm{task}}\\) (Eq. 4 or Eq. 5) and update the total loss \\(\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{total}} + \\mathcal{L}_{\\mathrm{task}}\\);" + }, + { + "type": "text", + "bbox": [ + 0.082, + 0.334, + 0.296, + 0.347 + ], + "angle": 0, + "content": "10: optimize for the total loss \\(\\mathcal{L}_{\\mathrm{total}}\\)" + }, + { + "type": "list", + "bbox": [ + 0.082, + 0.111, + 0.47, + 0.347 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.38, + 0.469, + 0.44 + ], + "angle": 0, + "content": "Reward. Upon taking action \\( a_{t+1} \\), the system receives reward \\( r_{t+1} \\) and transitions into the next state \\( s_{t+1} \\). To achieve high task network performance, we consider the following as reward," + }, + { + "type": "equation", + "bbox": [ + 0.103, + 0.454, + 0.469, + 0.491 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} r _ {t} = 0, t \\in \\{1, \\dots , T - 1 \\}, \\\\ r _ {T} ^ {\\mathrm {M V C N N}} = \\mathbb {1} (\\hat {\\boldsymbol {y}} = \\boldsymbol {y}), r _ {T} ^ {\\mathrm {M V D e t}} = \\operatorname {M O D A} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}), \\tag {7} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.504, + 0.469, + 0.565 + ], + "angle": 0, + "content": "where \\(\\mathbb{1}(\\cdot)\\) denotes the binary indicator function, MODA \\((\\cdot ,\\cdot)\\) is the evaluation metric for multi-view detection [21]. We also experiment with other reward designs in Section 5.4." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.578, + 0.29, + 0.592 + ], + "angle": 0, + "content": "4.2. MVSelect Architecture" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.601, + 0.469, + 0.753 + ], + "angle": 0, + "content": "We design MVSelect architecture \\(d(\\cdot)\\) with two branches. The first branch expands the camera selection result \\(s_t^{\\mathrm{cam}} \\in \\mathbb{R}^N\\) into \\(D\\)-dimensional learnable camera embeddings, and then sums over the selected embeddings to formulate a hidden vector. The second branch converts the observation \\(s_t^{\\mathrm{obs}} \\in \\mathbb{R}^D\\) into another hidden vector. By combining the two hidden vectors, the controller network outputs the action-value \\(Q(s,a)\\), which measures the expected cumulative rewards for taking an action \\(a\\) in a given state \\(s\\). See Supplementary Materials for figure illustrations." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.754, + 0.443, + 0.769 + ], + "angle": 0, + "content": "During testing, MVSelect outputs the next action as," + }, + { + "type": "equation", + "bbox": [ + 0.183, + 0.783, + 0.362, + 0.807 + ], + "angle": 0, + "content": "\\[\na _ {t + 1} = \\underset {a} {\\arg \\max } Q \\left(s _ {t}, a\\right),\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.819, + 0.417, + 0.834 + ], + "angle": 0, + "content": "which maximizes the expected cumulative rewards." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.847, + 0.244, + 0.862 + ], + "angle": 0, + "content": "4.3. Training Scheme" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.469, + 0.901 + ], + "angle": 0, + "content": "We adopt Q-learning [38] for training MVSelect. Specifically, action-value function \\(Q(\\cdot ,\\cdot)\\) should estimate the cu" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.125, + 0.888, + 0.14 + ], + "angle": 0, + "content": "mulative future rewards after taking action \\( a_{t+1} \\) at state \\( s_t \\)," + }, + { + "type": "equation", + "bbox": [ + 0.566, + 0.152, + 0.826, + 0.195 + ], + "angle": 0, + "content": "\\[\nQ \\left(s _ {t}, a _ {t + 1}\\right) = \\mathbb {E} \\left(\\sum_ {\\tau = t + 1} ^ {T} \\gamma^ {\\tau - t - 1} r _ {\\tau}\\right),\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.206, + 0.892, + 0.253 + ], + "angle": 0, + "content": "where \\(\\mathbb{E}(\\cdot)\\) denotes the expectation, and \\(\\gamma \\in [0,1]\\) denotes the discount factor. We take the temporal difference (TD) [38] target as supervision for the action value," + }, + { + "type": "equation", + "bbox": [ + 0.515, + 0.265, + 0.892, + 0.306 + ], + "angle": 0, + "content": "\\[\nq _ {t} = \\left\\{ \\begin{array}{l l} r _ {t + 1} + \\gamma \\max _ {a} Q \\left(s _ {t + 1}, a\\right), & \\text {i f} t < T - 1 \\\\ r _ {T}, & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.317, + 0.792, + 0.332 + ], + "angle": 0, + "content": "and calculate the loss using the \\(L_{2}\\) distance," + }, + { + "type": "equation", + "bbox": [ + 0.575, + 0.343, + 0.892, + 0.385 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {R L}} = \\sum_ {t = 1} ^ {T - 1} \\mathcal {L} _ {\\mathrm {M S E}} \\left(Q \\left(s _ {t}, a _ {t + 1}\\right), q _ {t}\\right), \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.397, + 0.891, + 0.426 + ], + "angle": 0, + "content": "where the next action \\( a_{t + 1} \\) is chosen using \\( \\epsilon \\)-greedy for exploration-exploitation trade offs." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.428, + 0.892, + 0.488 + ], + "angle": 0, + "content": "In joint training, the task network takes supervision from \\(\\mathcal{L}_{\\mathrm{task}}\\) (Eq. 4 and Eq. 5), and the selection module takes supervision from \\(\\mathcal{L}_{\\mathrm{RL}}\\) (Eq. 9). A step-by-step demonstration of this process can be found in Algorithm 1." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.503, + 0.633, + 0.52 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.528, + 0.693, + 0.544 + ], + "angle": 0, + "content": "5.1. Experiment Settings" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.552, + 0.892, + 0.643 + ], + "angle": 0, + "content": "Datasets. For multi-view classification, we use synthetic dataset ModelNet40 [44] under two different camera layouts (12 views and 20 views) and real-world dataset ScanObjectNN (12 views) [39]. For multi-view detection, we use real-world dataset Wildtrack (7 views) [6] and synthetic dataset MultiviewX (6 views) [17]." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.644, + 0.892, + 0.719 + ], + "angle": 0, + "content": "Evaluation metrics. For multi-view classification, we report instance-averaged accuracy. Regarding multi-view detection, we report multi-object detection accuracy (MODA), which is calculated as \\(1 - \\frac{\\mathrm{FP} + \\mathrm{FN}}{\\mathrm{GT}}\\) [21]. All metrics are reported in percentages." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.72, + 0.892, + 0.81 + ], + "angle": 0, + "content": "Implementation details. For multi-view classification, we input images of size \\(224 \\times 224\\) to the MVCNN model. For multi-view detection, we use a resolution of \\(720 \\times 1280\\) with view-coherent data augmentation [16], and downsample the BEV grid by a factor of 4. In terms of architecture, we use ResNet-18 [15] as feature extractor \\(f(\\cdot)\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We train all networks for 10 epochs using the Adam optimizer [22]. We use learning rates of \\(5 \\times 10^{-5}\\) and \\(5 \\times 10^{-4}\\), with batch sizes of 8 and 1 for MVCNN and MVDet, respectively. The MVSelect module is trained using a learning rate of \\(1 \\times 10^{-4}\\). For joint training, we decrease the learning rate for the task network to \\(1/5\\) of its original value." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "20139" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.895, + 0.12 + ], + "angle": 0, + "content": "Table 1. Performance comparison with state-of-the-art methods. Results are averaged from 5 runs. * indicates that the camera poses are dynamically chosen and do not follow a pre-defined layout. † indicates our implementation." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.13, + 0.511, + 0.278 + ], + "angle": 0, + "content": "
view selection (T=2)ModelNet40ScanObjNN
12 views20 views
MVCNN [37]N/A90.192.0-
GVCNN [11]N/A92.6--
MHBN [47]N/A93.4--
RotationNet [20]N/A-94.7-
RelationNet [46]N/A94.397.3-
ViewGCN [42]N/A-97.6-
MVCNN†N/A94.596.586.1
PointNet [31] + ViewGCNMVTN* (T=12 or 20) [14]93.893.592.6
MVCNN†SEE++† [3]79.270.375.5
MVCNN†Potthast and Sukhatme† [29]76.566.272.1
MVCNN†MVSelect88.279.680.0
MVCNN† (joint training)MVSelect94.394.484.1
" + }, + { + "type": "table", + "bbox": [ + 0.526, + 0.13, + 0.892, + 0.278 + ], + "angle": 0, + "content": "
view selection (T=3)WildtrackMultiviewX
RCNN & cluster [45]N/A11.318.7
POM-CNN [13]N/A23.2-
DeepMCD [7]N/A67.870
Deep-Occlusion [2]N/A74.175.2
MVDet [17]N/A88.283.9
SHOT [36]N/A90.288.3
MVDetTr [16]N/A91.593.7
MVDet†N/A90.093.0
MVDet†SEE++[3]76.177.8
MVDet†Potthast and Sukhatme†[29]78.378.0
MVDet†max FoV†[35]78.073.9
MVDet†MVSelect80.078.7
MVDet† (joint training)MVSelect88.688.1
" + }, + { + "type": "image", + "bbox": [ + 0.086, + 0.291, + 0.446, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.461, + 0.291, + 0.886, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.244, + 0.395, + 0.725, + 0.41 + ], + "angle": 0, + "content": "Figure 6. Example of selected views on ModelNet40 (left) and Wildtrack (right)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.437, + 0.47, + 0.512 + ], + "angle": 0, + "content": "Regarding hyperparameters, we set the future reward discount factor \\(\\gamma = 0.99\\), and the exploration ratio \\(\\epsilon\\) to gradually decrease from 0.95 to 0.05 during training. All experiments are conducted on a single RTX-3090 GPU and averaged across 5 repetitive runs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.514, + 0.47, + 0.755 + ], + "angle": 0, + "content": "Experimental setups. First, we fix the task network. We compare with state-of-the-art methods including 1) NBV policy with depth-sensing enabled point-based occlusion estimation [3], 2) NBV policy with depth-sensing enabled voxel-based probabilistic representation [29], and 3) NBV policy to maximize field-of-view (FoV) coverage [35] (only applicable to multi-view detection). We also report two baselines: 1) random selection, 2) the best policy on the validation set; and two oracles: for a certain initial view, 1) choosing the overall best-performing camera for all instances in the dataset (dataset-level oracle) and 2) choosing specifically for each instance (instance-level oracle). For the two oracles, the former reflects the upper bound of performance achievable by human-designed heuristics, and the latter represents the theoretical performance ceiling when keeping the task network fixed." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.757, + 0.471, + 0.832 + ], + "angle": 0, + "content": "Second, we jointly train the proposed view selection module with the task networks. For this experiment, our goal is to achieve the highest possible performance using \\( T \\) views. If not specified, we use a total of \\( T = 2 \\) views for multi-view classification and \\( T = 3 \\) views for detection." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.846, + 0.296, + 0.862 + ], + "angle": 0, + "content": "5.2. Evaluation of MVSelect" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.471, + 0.903 + ], + "angle": 0, + "content": "For multi-view classification, as in Table 1, MVSelect with fixed multi-view classification network achieves competi" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.437, + 0.892, + 0.587 + ], + "angle": 0, + "content": "tive performance compared to other state-of-the-art view selection methods. When compared with baselines and oracles in Table 2, the proposed view selection module, can choose the views effectively. Compared to dataset-level oracles (same policy for all instances with the same initial camera), MVSelect also turns out to be advantageous by \\(3.0\\%\\), \\(9.7\\%\\), and \\(1.5\\%\\) across the two settings. This verifies that MVSelect can take the target object into consideration (see Fig. 2) and select different cameras for different instances under the same initial camera." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.591, + 0.893, + 0.713 + ], + "angle": 0, + "content": "When joint training MVCNN with MVSelect, we witness large improvements. In fact, on two settings, the results are only \\(0.2\\%\\), \\(2.1\\%\\), and \\(2.0\\%\\) behind compared to the full \\(N\\)-view system. Overall, we believe that MVSelect and its joint training capabilities enable us to consider only 2 views without major performance drawbacks. We demonstrate an example of the selected views in Fig. 6, and the MVSelect policy in Fig. 7." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.716, + 0.892, + 0.838 + ], + "angle": 0, + "content": "For multi-view detection, MVSelect achieves competitive performance compared to existing NBV methods, some of them even require additional depth sensing (Table 1). Although the raw improvements are not as substantial as those in multi-view classification, they are statistically highly significant \\((p\\)-value \\(< 0.001)\\). This shows human designed heuristics like minimal occlusion or maximum FoV coverage cannot guarantee the best detection results." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.901 + ], + "angle": 0, + "content": "When compared to baselines and oracles, MVSelect also shows to be competitive (see Table 2). Specifically, we observe that the instance-level oracle remains relatively low compared to that of multi-view classification tasks. This is" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20140" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.147, + 0.09, + 0.822, + 0.103 + ], + "angle": 0, + "content": "Table 2. Comparison with view selection baselines and oracles on multi-view classification and detection datasets." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.116, + 0.518, + 0.257 + ], + "angle": 0, + "content": "
view selection (T=2)ModelNet40ScanObjNN
12 views20 views
N/A: all N views94.596.586.1
dataset-lvl oracle85.2 ± 1.469.9 ± 1.978.5 ± 1.2
instance-lvl oracle96.5 ± 0.498.1 ± 1.993.4 ± 0.6
random selection71.5 ± 2.548.1 ± 3.174.2 ± 3.5
validation best policy85.1 ± 0.869.5 ± 1.077.5 ± 1.1
MVSelect88.2 ± 0.479.6 ± 1.880.0 ± 0.8
MVSelect + joint training94.3 ± 0.294.4 ± 0.284.1 ± 0.2
" + }, + { + "type": "table", + "bbox": [ + 0.535, + 0.123, + 0.89, + 0.25 + ], + "angle": 0, + "content": "
view selection (T=3)WildtrackMultiviewX
N/A: all N views90.093.0
dataset-lvl oracle82.5 ± 0.480.2 ± 0.3
instance-lvl oracle87.4 ± 0.482.3 ± 0.8
random selection74.9 ± 1.376.2 ± 1.4
validation best policy79.5 ± 1.178.0 ± 0.4
MVSelect80.0 ± 0.878.7 ± 0.5
MVSelect + joint training88.6 ± 0.288.1 ± 0.2
" + }, + { + "type": "image", + "bbox": [ + 0.083, + 0.277, + 0.316, + 0.452 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.128, + 0.458, + 0.268, + 0.47 + ], + "angle": 0, + "content": "(a) Classification accuracy" + }, + { + "type": "image", + "bbox": [ + 0.335, + 0.277, + 0.567, + 0.452 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.395, + 0.457, + 0.505, + 0.47 + ], + "angle": 0, + "content": "(b) MVSelect policy" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.482, + 0.571, + 0.525 + ], + "angle": 0, + "content": "Figure 7. Multi-view classification with \\( T = 2 \\) views on the 12-view setup of ModelNet40. The task network is fixed once trained. Left: test set accuracy of using two views. Right: MVSelect policy for the test set." + }, + { + "type": "table_caption", + "bbox": [ + 0.638, + 0.271, + 0.834, + 0.284 + ], + "angle": 0, + "content": "Table 3. Computation efficiency." + }, + { + "type": "table", + "bbox": [ + 0.589, + 0.286, + 0.887, + 0.403 + ], + "angle": 0, + "content": "
viewsFLOPsthroughput (instance/s)
f(·)g(·)d(·)
ModelNet402036.5G20.5kN/A119.6
23.6G20.5k1.1M361.8
1221.9G20.5kN/A196.2
23.6G20.5k530.4k507.9
Wildtrack71.2T19.1GN/A8.4
3511.6G19.1G3.2G16.2
MultiviewX61.0T17.7GN/A9.8
3511.6G17.7G2.9G16.9
" + }, + { + "type": "table_caption", + "bbox": [ + 0.663, + 0.414, + 0.807, + 0.427 + ], + "angle": 0, + "content": "Table 4. Ablation study." + }, + { + "type": "table", + "bbox": [ + 0.589, + 0.429, + 0.886, + 0.531 + ], + "angle": 0, + "content": "
ModelNet40Wildtrack
12 views
MVSelect88.280.0
w/o camera branch88.279.1
w/o feature branch85.079.7
w/ transformer87.078.7
reward=Δ task loss88.080.1
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.557, + 0.473, + 0.752 + ], + "angle": 0, + "content": "likely due to the target scenarios not being fully captured by any single view, and the multi-view detection network needs multiple views to collaborate with each other for optimal results. Compared to the dataset-level oracles, we find the MVSelect policy lose its edge. In fact, we find that for multi-view detection, MVSelect tends to select the same camera for a given initial view, since it is not aware of the situation outside of the FoV coverage. As a result, it cannot choose cameras based on uncovered areas in different frames. Without this instance-aware advantage, the fixed camera policy learned during training (MVSelect) cannot outperform the dataset-level oracle, whose policy is computed on the test set." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.472, + 0.903 + ], + "angle": 0, + "content": "Joint training with MVDet once again leads to substantial performance improvements over keeping the task network fixed. In fact, the results even exceed the instance-level oracle for fixed task networks. Using \\( T = 3 \\) views, the joint training approach provides competitive results to using all \\( N \\) views, and exceeds the reported performance in the original MVDet paper [17]. We present an example of the selected views in the Wildtrack dataset in Fig. 6." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.556, + 0.684, + 0.572 + ], + "angle": 0, + "content": "5.3. Efficiency Analysis" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.579, + 0.892, + 0.685 + ], + "angle": 0, + "content": "In Table 3, following previous works in efficient inference [19, 24], we detail the computational cost in FLOPs for task networks and MVSelect. Specifically, we find feature extraction \\( f(\\cdot) \\) to take up the majority of the computation, while everything else is lighter by at least an order of magnitude. Overall, we verify that using \\( T = 2 \\) or 3 out of \\( N \\) views can reduce the computational cost to roughly \\( T / N \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.686, + 0.892, + 0.777 + ], + "angle": 0, + "content": "In terms of inference speed, we find reduction in FLOPs results in monotonically increasing throughputs, ranging from \\(1.72 \\times\\) to \\(3.03 \\times\\). Due to factors such as implementation, parallelization, and hardware limitations, actual speedups cannot actually reach the level of computational cost reduction, as suggested by previous study [27]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.787, + 0.645, + 0.803 + ], + "angle": 0, + "content": "5.4. Variant Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.81, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Ablation study. Regarding the MVSelect architecture design, Table 4 shows that removing the camera branch and feature branch primarily affects multi-view detection and multi-view classification performance, respectively. This aligns with the policy we learned for the two tasks. For multi-view detection, since the system has no clue about ar" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "20141" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.098, + 0.312, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.332, + 0.097, + 0.565, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.589, + 0.099, + 0.868, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.279, + 0.571, + 0.336 + ], + "angle": 0, + "content": "Figure 9. System performance under different number of total views \\( T \\). We report classification accuracy and MODA for the two tasks, respectively (same for Fig. 10 and Table. 4). Circle and triangle markers indicate whether the task network is fixed or not, respectively. Dotted lines represent oracle performance (not achievable)." + }, + { + "type": "image_caption", + "bbox": [ + 0.582, + 0.279, + 0.874, + 0.335 + ], + "angle": 0, + "content": "Figure 10. System evaluation under different settings. Except for the random pose* setting (where MVSelect variants are re-trained), all models are trained on the default setting." + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.361, + 0.469, + 0.452 + ], + "angle": 0, + "content": "eas outside camera FoVs, the camera branch plays a more important role for encoding prior knowledge of the scene layout. For multi-view classification, however, target objects are fully observable, and MVSelect can make different decisions for each instance. Thus, the feature branch is more important, as it enables per-instance decision making." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.455, + 0.469, + 0.5 + ], + "angle": 0, + "content": "When changing the MVSelect network architecture into transformer [40], we find that more parameters do not translate into better performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.503, + 0.469, + 0.548 + ], + "angle": 0, + "content": "Another option for the reward is the change in task loss. In our variant study, this reward design does not show any significant advantages over the current design." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.551, + 0.469, + 0.687 + ], + "angle": 0, + "content": "Influence of total view count. The performance curves in Fig. 9 demonstrate that the joint training variant achieves competitive performance with as few as \\( T = 2 \\) views for multi-view classification and \\( T = 3 \\) views for multi-view detection, beyond which point performance plateaus. By contrast, learning MVSelect for fixed task networks shows a less steep curve. The performance increases up to a total of \\( T = 5 \\) views, at which point the MVSelect policy performs comparably to the full \\( N \\)-view system." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.69, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Camera layout optimization. Determining the optimal camera locations is crucial for setting up an effective multiview system. In Fig.7, we observe that not all cameras are equally useful according to the MVSelect policy. To address this, we allocate a validation partition of the data to identify the more useful camera views and then disable half of the \\(N = 12\\) cameras that are not frequently utilized. In testing, we find that some cameras are not as useful (\"policy shut-off\" in Fig. 10) and the proposed method can generalize to test-time disturbances including malfunctioning cameras (\"random shut-off\" in Fig.10). Although it is necessary to set up all \\(N\\) cameras for the analysis, optimizing the multiview camera layout can be a crucial step towards achieving optimal performance, and merits further investigation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.361, + 0.892, + 0.573 + ], + "angle": 0, + "content": "Random object pose. In real-world applications of multi-view systems, such as those found in iPhones and Tesla, the cameras may remain fixed in their relative positions while the entire system is in motion. To simulate this scenario in our experiments, we introduce the random object pose setting (Fig. 10) and re-train MVSelect. While there is no exact object pose as supervision, the reinforcement learning approach is able to roughly infer the relative poses between the object and the multi-view system, resulting in improved performance compared to random selection and dataset-level oracle (which is arguably inappropriate for this setup). In the future, we plan to estimate camera poses with respect to the object or the environment as an auxiliary supervision for moving setups." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.595, + 0.619, + 0.611 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.624, + 0.892, + 0.819 + ], + "angle": 0, + "content": "In conclusion, this paper proposes selective view pipelining, an efficient approach for multi-view understanding by limiting the number of views. To this end, a camera view selection module, MVSelect, is proposed along with a reinforcement learning based training scheme that can learn from the non-differentiable selection process. When jointly trained with the task network, the proposed approach demonstrates competitive performance on multi-view classification and detection tasks at fractions of the computational cost. Overall, the proposed efficient approach provides an alternative to reducing image resolution and using lighter networks, and paves ways for future multi-view camera layout optimization." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.843, + 0.66, + 0.86 + ], + "angle": 0, + "content": "Acknowledgement" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This work was supported by the ARC Discovery Project (DP210102801)." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "20142" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.156 + ], + "angle": 0, + "content": "[1] John Aloimonos, Isaac Weiss, and Amit Bandyopadhyay. Active vision. 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However, the high computational cost associated with multiple views creates a significant challenge for end devices with limited computational resources. In modern CPU, pipelining breaks a longer job into steps and enables parallelism over sequential steps from multiple jobs. Inspired by this, we study selective view pipelining for efficient multi-view understanding, which breaks computation of multiple views into steps, and only computes the most helpful views/steps in a parallel manner for the best efficiency. To this end, we use reinforcement learning to learn a very light view selection module that analyzes the target object or scenario from initial views and selects the next-best-view for recognition or detection for pipeline computation. Experimental results on multi-view classification and detection tasks show that our approach achieves promising performance while using only 2 or 3 out of $N$ available views, significantly reducing computational costs while maintaining parallelism over GPU through selective view pipelining1. + +# 1. Introduction + +Multiple camera views (multi-view) are popular in computer vision systems for their ability to address challenges such as occlusions, ambiguities, and limited field-of-view (FoV) coverage. Tasks like classification [30, 37] and detection [6, 17] have shown significant benefits from using multiple cameras. With reduced hardware cost and easy deployment, real-world products now include more cameras at larger scales. However, the use of multiple cameras comes at a high computational cost, which can be a significant challenge for end devices with limited computational resources, especially with higher image resolutions and deeper neural network backbones. Limiting image resolution or using lighter networks [19, 27] are current options to reduce computation, but they may impede the + +![](images/b3185fb8d2b880d2bd96d5a23a69d47661b35b02f35127c1b0c4b64e5d3c55d1.jpg) +(a) Piplining in modern CPU + +![](images/2f95de30ae0c21c683f1b4718782a97831d18286b5ea9d2bc7f66d0ed4aaba7d.jpg) +(b) Parallel in modern GPU + +![](images/3798442ec33fb7383a059fe7f97bd201620e5b009a0ef6ace239f144358766ff.jpg) +(c) Selective view pipelining +Figure 1. Demonstration of the proposed selective view pipelining. Inspired by instruction pipelining in modern CPU (a), selective view pipelining (c) breaks the multi-view perception task into sequential steps, and only computes the chosen views (see Fig. 2) to minimize the computation. At the same time, computation across multiple objects (different border colors) can still enjoy parallelism in GPU (b). In this example, for a $N = 6$ view system, traditional computation (b) on GPU hardware that only supports two images at the same time will produce a throughput of 2 instances during 6 time steps. In contrast, by taking advantage of the parallelism, selective view pipelining computes 6 instances within 7 time steps. + +progress in camera sensors or neural network architecture. + +In modern CPU, instruction pipelining [10] breaks individual instructions into steps to enable parallelism across multiple instructions within the same CPU (see Fig. 1a). For multi-view perception, although computations for different images can be paralleled over GPU [9], the level of parallelism is still limited by hardware. As an example, the GPU in Fig. 1b might only support parallel computing for two images at a time, resulting in at least 3 time steps for + +![](images/85c1798479f0658128e78033dfca1d996f8590d7c5e9f59cda0b3ac4eac99397.jpg) +Figure 2. Efficient multi-view understanding with two glances. Instead of using all $N$ views at once, a more efficient approach is to first examine one view and then select another view to resolve ambiguities from the initial glance. If the initial side view cannot distinguish between a guitar and a mandolin (a round-shaped instrument that may also have a flat back), we can then query the front view. This sequential process can work in a pipeline to enable parallelism between multiple + +computing one object with 6 views. + +In this work, we propose selective view pipelining, which breaks the multi-view perception task into a sequence of steps. Based on initial views, we estimate the most helpful views for this task, and only compute the selected views for maximum efficiency. The example in Fig. 1c shows that only selecting one additional view can greatly reduce the computation from 6 views to 2 views. By further taking advantage of the parallelism in GPUs, we can roughly improve the overall throughput by $3 \times$ . + +To this end, this paper introduces a new angle to efficient multi-view understanding by selecting only the most useful views. To identify the best views, this approach leverages camera layouts, which is a key aspect overlooked by existing alternatives. With known camera layouts, networks should be able to infer what each camera view looks like and then choose accordingly, as previous works [20] have shown that networks can associate images with camera poses. Existing work on active vision [1, 8, 12] indicates that it is possible to find next-best-view (NBV) for reconstruction with 3D sensors. In this paper, we focus on recognition and detection problems using multiple RGB cameras, where a side view may confuse a guitar with a mandolin (Fig. 2). However, prior knowledge of the camera layout should inform the system that the front view can clear the ambiguities and should be queried. + +To achieve this goal, this paper proposes a novel view selection module, MVSelect, that chooses the best camera views from any initial view at minimal computational costs. Using the same feature extracted for the final task of classification or detection, the proposed module analyzes the target object or scenario from existing views and then selects the + +![](images/23a312e7f3bd3b7eb5179a8d47e340c9e8e27da9059b6bd33ab2e3891ac06a44.jpg) +Figure 3. Multi-view classification with MVCNN [37]. + +next view that best helps the task (classification or detection) network. To navigate through the non-differentiable view selection (the system only looks at selected cameras, so not-selected views cannot back propagate gradients to the controller), following Mnih et al. [26], we train the controller via trial-and-error. This process is formulated as a reinforcement learning problem aiming to maximize the final recognition or detection accuracy. + +On both multi-view classification and detection tasks, our experimental results show that MVSelect can provide a good strategy for fixed task networks, while also capable of joint training with the task network for further performance improvements. Specifically, when joint training both MVSelect and the task network, the resulting system can achieve competitive performance to using all $N$ cameras, while using only 2 views for classification tasks and 3 views for detection tasks, respectively. + +The computational overhead of MVSelect is very small, as it shares the feature extraction backbone with the task network and only has a few learnable layers. For the entire system, the computational cost is roughly proportional to the number of views used, e.g., approximately $2 / N$ of the total computation when 2 views are used, a significant efficiency boost. + +The MVSelect policy also enables study on multi-view camera layout. In fact, we find that many of the $N$ cameras are rarely chosen and can be shut off for further operational cost improvements, which can serve as a starting point for future study on multi-view camera layout optimization. + +# 2. Background + +Multi-view classification. One effective way for 3D shape recognition is to capture the object in multiple camera views. MVCNN [37] extracts feature vectors from the input views, and then uses max pooling to aggregate across multiple views for classification. Based on MVCNN, many alternative approaches are proposed. Qi et al. [30] propose sphere rendering at different volume resolutions. GVCNN [11] investigates hierarchical information between different + +![](images/845c2ac765a5d5f3f647519b198828dc12144adcddbcbdad5c9a646c7607f7e9.jpg) +Figure 4. Multi-view detection with MVDet [17]. + +views by grouping the image features before the final aggregation. RotationNet [20] introduces a multi-task objective by jointly considering classification and camera poses. ViewGCN [42] uses a Graph Convolution Network (GCN) [23] instead of the max pooling layer to aggregate across views. Hamdi et al. [14] propose the MVTN network to estimate the best viewpoints for 3D point cloud models. + +Multi-view detection estimate pedestrian occupancy from the bird's-eye-view (BEV). For this task, some methods [13, 33, 45] aggregate single-view detection results. Others find single-view detection results unreliable and instead aggregate the features. Hou et al. [17] introduce MVDet, the first fully deep-learning approach, which projects feature maps from each camera view to the BEV. Based on MVDet, researchers develop other deep methods. SHOT [36] projects the image feature map at different heights and stacks them together to improve performance. MVDetr [16] deals with distinct distortion patterns from the projection. Qiu et al. [32] investigate data augmentation with simulated occlusion over multiple views. + +Camera viewpoint study. Cao and Snavely [5] investigate this for reconstruction with structure-from-motion. Active vision community investigates next-best-view planning with 3D sensors like RGBD cameras or LiDAR for scene reconstruction [4, 8, 35]. In multi-view classification, RotationNet [20] makes some pioneering work on limited view numbers by taking a random partial set of all $N$ views of the image. MVTN [14] uses the 3D point cloud as initial input and then estimates the best camera layout for multi-view classification, but its moving camera assumption is hard to meet in real-world systems. In multi-view detection, Vora et al. [41] investigate camera layout generalization by randomly dropping camera views from both training and testing. Hou et al. [18] investigate how to place cameras. For 3D human pose estimation, Pirinen et al. [28] actively select cameras over a dome. + +Reinforcement learning (RL) directs an agent to interact with the environment in a manner that maximizes cumulative rewards. State $s \in S$ , action $a \in \mathcal{A}$ , and reward $r \in \mathcal{R}$ are key concepts to model the interaction between agent and environment. In a certain state $s$ , policy $\pi(a|s)$ records the probability for each action, and state value func + +tion $V(s)$ estimates the future rewards when following the corresponding policy. To learn the best policy, Q-learning and DQN [25] optimize the action value function $Q(s,a)$ , which describes the estimated future return for a specific action $a$ at state $s$ . Policy gradient methods like REINFORCE [43] and PPO [34] directly optimize for the polity $\pi(a|s)$ . + +# 3. Multi-view Network Revisit + +# 3.1. Multi-view Classification with MVCNN + +MVCNN [37] (Fig. 3) is a classic architecture which many multi-view classification networks build upon. Given $N$ input images $\pmb{x}_n$ , $n \in \{1, \dots, N\}$ , first, MVCNN uses its feature extractor $f(\cdot)$ to calculate the feature vectors, + +$$ +\boldsymbol {h} _ {n} = f \left(\boldsymbol {x} _ {n}\right), \tag {1} +$$ + +where the feature vector $\pmb{h}_n \in \mathbb{R}^D$ is $D$ -dimensional. Secondly, it uses max pooling to aggregate multiple views into an overall feature descriptor $\hat{\pmb{h}} \in \mathbb{R}^{D}$ , + +$$ +\hat {\boldsymbol {h}} = \max _ {n} \left\{\boldsymbol {h} _ {n} \right\}, \tag {2} +$$ + +where $\max \{\dots\}$ takes the maximum along each of the $D$ dimensions. Lastly, it applies the output head $g(\cdot)$ to produce the classification result $\hat{\pmb{y}}$ , + +$$ +\hat {\boldsymbol {y}} = g (\hat {\boldsymbol {h}}). \tag {3} +$$ + +In training, the original design by Su et al. [37] adopts a 2-stage paradigm by first training on individual views and then considering multiple views. In this paper, we skip the first stage and directly train MVCNN on all $N$ views, + +$$ +\mathcal {L} _ {\text {M V C N N}} = \mathcal {L} _ {\text {C E}} (\hat {\boldsymbol {y}}, \boldsymbol {y}), \tag {4} +$$ + +where $\mathcal{L}_{\mathrm{CE}}(\cdot ,\cdot)$ denotes the cross-entropy loss and $\pmb{y}$ denotes the ground truth one-hot label. + +# 3.2. Multi-view Detection with MVDet + +MVDet [17] (Fig. 4) is a multi-view detection architecture that is followed by many recent works. To estimate human occupancy in bird's-eye-view (BEV), given input images $\boldsymbol{x}_n, n \in \{1, \dots, N\}$ , MVDet first extracts $D$ -channel feature maps for each view and uses perspective transformation to project the camera views to the BEV. Together, these operations can be considered as the BEV feature extraction step under Eq. 1, with the exception that $\boldsymbol{h}_n \in \mathbb{R}^{D \times H \times W}$ now denotes the $D$ -channel feature map for the BEV scenario of shape $H \times W$ . Secondly, for multi-view aggregation, instead of the concatenation in the original design, we choose element-wise max pooling in Eq. 2, producing the overall feature description $\hat{\boldsymbol{h}} \in \mathbb{R}^{D \times H \times W}$ that fits arbitrary numbers of views. Lastly, we apply the output head as + +![](images/7b69fa980dec9ffa8a2d8b3d7d1c2597e090e0349f2649c2d313cf08b0c39613.jpg) +Figure 5. Efficient multi-view understanding with selective view pipelining using $T = 3$ glances. Solid lines indicate the network forward pass and dashed lines indicate the interaction between agent (MVSelect) and environment (multi-view system). The approach starts with a random initial view $a_1$ , and the feature extractor $f(\cdot)$ computes its feature (Eq. 1). The state for this initial time step is recorded as $s_1$ (Eq. 6). Next, the proposed MVSelect module $d(\cdot)$ is used to choose a second view $a_2$ , and the state is updated as $s_2$ . Then, by repeating the last step, a third view $a_3$ is chosen and the state is updated as $s_3$ . Finally, three views are aggregated into an overall descriptor $\hat{h}$ (Eq. 2), and the task network output $\hat{\pmb{y}}$ is calculated using the output head $g(\cdot)$ (Eq. 3). The final reward $r_3 = \mathrm{MODA}(\hat{\pmb{y}},\pmb{y})$ is set as the accuracy fir the task network (Eq. 7), and all other rewards are set as zero. + +Eq. 3 to generate a heatmap $\hat{\pmb{y}}\in (0,1)^{H\times W}$ that indicates the likelihood of human occupancy in each BEV location. The loss for MVDet can be written as, + +$$ +\mathcal {L} _ {\mathrm {M V D e t}} = \mathcal {L} _ {\mathrm {B E V}} (\hat {\boldsymbol {y}}, \boldsymbol {y}) + \frac {1}{N} \sum_ {n = 1} ^ {N} \mathcal {L} _ {n}, \tag {5} +$$ + +where $\mathcal{L}_{\mathrm{BEV}}(\cdot ,\cdot)$ denotes BEV output loss; $\pmb {y}\in \{0,1\}^{H\times W}$ denotes binary ground truth map; and $\mathcal{L}_n$ denotes the auxiliary per-view loss with 2D bounding boxes. + +# 4. Efficient Multi-view Understanding + +In a multi-view system with $N$ views, selective view planning uses a total of $T < N$ camera views $a_{t} \in \{1, \dots, N\}, t \in \{1, \dots, T\}$ for efficient understanding. To achieve this, we propose a view selection module, MVSelect, denoted as $d(\cdot)$ , that sequentially selects camera views. Starting from a random initial view $a_{1}$ , MVSelect chooses the remaining $T - 1$ cameras by observing the target object or scene from existing views $a_{1}, \dots, a_{t}$ at each time step $t$ and deciding which camera view $a_{t + 1}$ to select next for best performance. Once $T$ camera views have been gathered, we aggregate them into an overall description $\hat{\pmb{h}}$ using Eq. 2, and calculate the final output $\hat{\pmb{y}}$ using Eq. 3. Fig. 5 gives an overview of the proposed efficient multi-view approach. + +# 4.1. Problem Formulation + +While iteratively selecting camera views, it is impossible to know what is in the not-selected camera views. If view + +selection was formulated as a prediction task in a supervised manner, the loss (final target metric at $t = T$ ) could not be back propagated to the not-selected views, making it non-differentiable and impossible to update the selection probability. Reinforcement learning, on the other hand, can update the controller even with the non-differentiable view selection. Therefore, we formulate this non-differentiable process as a reinforcement learning problem, where MVS-select is the agent and learns through trial and error, and the multi-view system is the environment. + +State. In order to get a Markovian representation, we record the chosen camera views $a_1,\dots ,a_t$ and the observations $h_{a_1},\ldots ,h_{a_t}$ as state $s_t$ . We use the extracted features to represent the observations rather than the RGB camera views to reduce dimensionality and maximize efficiency, since these features will be used in the task network later (Eq. 2). Mathematically, we formulate the state $s_t$ as, + +$$ +s _ {t} = \left\langle s _ {t} ^ {\mathrm {c a m}}, s _ {t} ^ {\mathrm {o b s}} \right\rangle , +$$ + +$$ +s _ {t} ^ {\text {c a m}} = \sum_ {\tau = 1} ^ {t} \text {o n e h o t} \left(a _ {\tau}\right), \tag {6} +$$ + +$$ +s _ {t} ^ {\mathrm {o b s}} = \max _ {\tau = 1} ^ {t} \left\{\boldsymbol {h} _ {a _ {\tau}} \right\}, +$$ + +where onehot $(\cdot)$ is the one-hot function over $N$ cameras. This representation reflects both chosen cameras $s_t^{\mathrm{cam}} \in \mathbb{R}^N$ and their observations $s_t^{\mathrm{obs}} \in \mathbb{R}^D$ , and maintains the same dimensionality across different time steps. The observation part $s_t^{\mathrm{obs}}$ also matches the overall representation in Eq. 2. + +Action. For state $s_t, t \in \{1, \dots, T - 1\}$ , MVSelect takes the next camera view $a_{t + 1}$ as action. + +Algorithm 1 Joint training of MVSelect and task network. + +1: input: camera views $\pmb{x}_n, n \in \{1, \dots, N\}$ , ground truth $\pmb{y}$ , random initial view $a_1$ , number of total views $T$ , hyperparameter $\epsilon$ . +2: update: feature extractor $f(\cdot)$ and output head $g(\cdot)$ of task network, and MVSelect controller $d(\cdot)$ . +3: initialize the total loss $\mathcal{L}_{\mathrm{total}} = 0$ +4: for $t \in \{1, \dots, T - 1\}$ do +5: select and apply the next action using $\epsilon$ -greedy: with probability $\epsilon$ adopt a random action, or else choose the action with highest value $a_{t+1} = \arg \max_a Q(s_t, a)$ ; +6: observe next state $s_{t + 1}$ (Eq. 6) and reward $r_{t + 1}$ (Eq. 7); +7: calculate the RL loss $\mathcal{L}_{\mathrm{RL}}$ (Eq. 9) and update the total loss $\mathcal{L}_{\mathrm{total}} = \mathcal{L}_{\mathrm{total}} + \mathcal{L}_{\mathrm{RL}}$ ; +8: end for +9: calculate the task loss $\mathcal{L}_{\mathrm{task}}$ (Eq. 4 or Eq. 5) and update the total loss $\mathcal{L}_{\mathrm{total}} = \mathcal{L}_{\mathrm{total}} + \mathcal{L}_{\mathrm{task}}$ ; +10: optimize for the total loss $\mathcal{L}_{\mathrm{total}}$ + +Reward. Upon taking action $a_{t+1}$ , the system receives reward $r_{t+1}$ and transitions into the next state $s_{t+1}$ . To achieve high task network performance, we consider the following as reward, + +$$ +\begin{array}{l} r _ {t} = 0, t \in \{1, \dots , T - 1 \}, \\ r _ {T} ^ {\mathrm {M V C N N}} = \mathbb {1} (\hat {\boldsymbol {y}} = \boldsymbol {y}), r _ {T} ^ {\mathrm {M V D e t}} = \operatorname {M O D A} (\hat {\boldsymbol {y}}, \boldsymbol {y}), \tag {7} \\ \end{array} +$$ + +where $\mathbb{1}(\cdot)$ denotes the binary indicator function, MODA $(\cdot ,\cdot)$ is the evaluation metric for multi-view detection [21]. We also experiment with other reward designs in Section 5.4. + +# 4.2. MVSelect Architecture + +We design MVSelect architecture $d(\cdot)$ with two branches. The first branch expands the camera selection result $s_t^{\mathrm{cam}} \in \mathbb{R}^N$ into $D$ -dimensional learnable camera embeddings, and then sums over the selected embeddings to formulate a hidden vector. The second branch converts the observation $s_t^{\mathrm{obs}} \in \mathbb{R}^D$ into another hidden vector. By combining the two hidden vectors, the controller network outputs the action-value $Q(s,a)$ , which measures the expected cumulative rewards for taking an action $a$ in a given state $s$ . See Supplementary Materials for figure illustrations. + +During testing, MVSelect outputs the next action as, + +$$ +a _ {t + 1} = \underset {a} {\arg \max } Q \left(s _ {t}, a\right), +$$ + +which maximizes the expected cumulative rewards. + +# 4.3. Training Scheme + +We adopt Q-learning [38] for training MVSelect. Specifically, action-value function $Q(\cdot ,\cdot)$ should estimate the cu + +mulative future rewards after taking action $a_{t+1}$ at state $s_t$ , + +$$ +Q \left(s _ {t}, a _ {t + 1}\right) = \mathbb {E} \left(\sum_ {\tau = t + 1} ^ {T} \gamma^ {\tau - t - 1} r _ {\tau}\right), +$$ + +where $\mathbb{E}(\cdot)$ denotes the expectation, and $\gamma \in [0,1]$ denotes the discount factor. We take the temporal difference (TD) [38] target as supervision for the action value, + +$$ +q _ {t} = \left\{ \begin{array}{l l} r _ {t + 1} + \gamma \max _ {a} Q \left(s _ {t + 1}, a\right), & \text {i f} t < T - 1 \\ r _ {T}, & \text {o t h e r w i s e} \end{array} , \right. \tag {8} +$$ + +and calculate the loss using the $L_{2}$ distance, + +$$ +\mathcal {L} _ {\mathrm {R L}} = \sum_ {t = 1} ^ {T - 1} \mathcal {L} _ {\mathrm {M S E}} \left(Q \left(s _ {t}, a _ {t + 1}\right), q _ {t}\right), \tag {9} +$$ + +where the next action $a_{t + 1}$ is chosen using $\epsilon$ -greedy for exploration-exploitation trade offs. + +In joint training, the task network takes supervision from $\mathcal{L}_{\mathrm{task}}$ (Eq. 4 and Eq. 5), and the selection module takes supervision from $\mathcal{L}_{\mathrm{RL}}$ (Eq. 9). A step-by-step demonstration of this process can be found in Algorithm 1. + +# 5. Experiments + +# 5.1. Experiment Settings + +Datasets. For multi-view classification, we use synthetic dataset ModelNet40 [44] under two different camera layouts (12 views and 20 views) and real-world dataset ScanObjectNN (12 views) [39]. For multi-view detection, we use real-world dataset Wildtrack (7 views) [6] and synthetic dataset MultiviewX (6 views) [17]. + +Evaluation metrics. For multi-view classification, we report instance-averaged accuracy. Regarding multi-view detection, we report multi-object detection accuracy (MODA), which is calculated as $1 - \frac{\mathrm{FP} + \mathrm{FN}}{\mathrm{GT}}$ [21]. All metrics are reported in percentages. + +Implementation details. For multi-view classification, we input images of size $224 \times 224$ to the MVCNN model. For multi-view detection, we use a resolution of $720 \times 1280$ with view-coherent data augmentation [16], and downsample the BEV grid by a factor of 4. In terms of architecture, we use ResNet-18 [15] as feature extractor $f(\cdot)$ . + +We train all networks for 10 epochs using the Adam optimizer [22]. We use learning rates of $5 \times 10^{-5}$ and $5 \times 10^{-4}$ , with batch sizes of 8 and 1 for MVCNN and MVDet, respectively. The MVSelect module is trained using a learning rate of $1 \times 10^{-4}$ . For joint training, we decrease the learning rate for the task network to $1/5$ of its original value. + +Table 1. Performance comparison with state-of-the-art methods. Results are averaged from 5 runs. * indicates that the camera poses are dynamically chosen and do not follow a pre-defined layout. † indicates our implementation. + +
view selection (T=2)ModelNet40ScanObjNN
12 views20 views
MVCNN [37]N/A90.192.0-
GVCNN [11]N/A92.6--
MHBN [47]N/A93.4--
RotationNet [20]N/A-94.7-
RelationNet [46]N/A94.397.3-
ViewGCN [42]N/A-97.6-
MVCNN†N/A94.596.586.1
PointNet [31] + ViewGCNMVTN* (T=12 or 20) [14]93.893.592.6
MVCNN†SEE++† [3]79.270.375.5
MVCNN†Potthast and Sukhatme† [29]76.566.272.1
MVCNN†MVSelect88.279.680.0
MVCNN† (joint training)MVSelect94.394.484.1
+ +
view selection (T=3)WildtrackMultiviewX
RCNN & cluster [45]N/A11.318.7
POM-CNN [13]N/A23.2-
DeepMCD [7]N/A67.870
Deep-Occlusion [2]N/A74.175.2
MVDet [17]N/A88.283.9
SHOT [36]N/A90.288.3
MVDetTr [16]N/A91.593.7
MVDet†N/A90.093.0
MVDet†SEE++[3]76.177.8
MVDet†Potthast and Sukhatme†[29]78.378.0
MVDet†max FoV†[35]78.073.9
MVDet†MVSelect80.078.7
MVDet† (joint training)MVSelect88.688.1
+ +![](images/86609035ec67b17c510c3b21899bbc4d4517e6aad6c36fc1d4b966908203214e.jpg) +Figure 6. Example of selected views on ModelNet40 (left) and Wildtrack (right). + +![](images/c1351cf7209250e17cca97a493e056134a6bedf5961c00a0b70566d2cbe2f206.jpg) + +Regarding hyperparameters, we set the future reward discount factor $\gamma = 0.99$ , and the exploration ratio $\epsilon$ to gradually decrease from 0.95 to 0.05 during training. All experiments are conducted on a single RTX-3090 GPU and averaged across 5 repetitive runs. + +Experimental setups. First, we fix the task network. We compare with state-of-the-art methods including 1) NBV policy with depth-sensing enabled point-based occlusion estimation [3], 2) NBV policy with depth-sensing enabled voxel-based probabilistic representation [29], and 3) NBV policy to maximize field-of-view (FoV) coverage [35] (only applicable to multi-view detection). We also report two baselines: 1) random selection, 2) the best policy on the validation set; and two oracles: for a certain initial view, 1) choosing the overall best-performing camera for all instances in the dataset (dataset-level oracle) and 2) choosing specifically for each instance (instance-level oracle). For the two oracles, the former reflects the upper bound of performance achievable by human-designed heuristics, and the latter represents the theoretical performance ceiling when keeping the task network fixed. + +Second, we jointly train the proposed view selection module with the task networks. For this experiment, our goal is to achieve the highest possible performance using $T$ views. If not specified, we use a total of $T = 2$ views for multi-view classification and $T = 3$ views for detection. + +# 5.2. Evaluation of MVSelect + +For multi-view classification, as in Table 1, MVSelect with fixed multi-view classification network achieves competi + +tive performance compared to other state-of-the-art view selection methods. When compared with baselines and oracles in Table 2, the proposed view selection module, can choose the views effectively. Compared to dataset-level oracles (same policy for all instances with the same initial camera), MVSelect also turns out to be advantageous by $3.0\%$ , $9.7\%$ , and $1.5\%$ across the two settings. This verifies that MVSelect can take the target object into consideration (see Fig. 2) and select different cameras for different instances under the same initial camera. + +When joint training MVCNN with MVSelect, we witness large improvements. In fact, on two settings, the results are only $0.2\%$ , $2.1\%$ , and $2.0\%$ behind compared to the full $N$ -view system. Overall, we believe that MVSelect and its joint training capabilities enable us to consider only 2 views without major performance drawbacks. We demonstrate an example of the selected views in Fig. 6, and the MVSelect policy in Fig. 7. + +For multi-view detection, MVSelect achieves competitive performance compared to existing NBV methods, some of them even require additional depth sensing (Table 1). Although the raw improvements are not as substantial as those in multi-view classification, they are statistically highly significant $(p$ -value $< 0.001)$ . This shows human designed heuristics like minimal occlusion or maximum FoV coverage cannot guarantee the best detection results. + +When compared to baselines and oracles, MVSelect also shows to be competitive (see Table 2). Specifically, we observe that the instance-level oracle remains relatively low compared to that of multi-view classification tasks. This is + +Table 2. Comparison with view selection baselines and oracles on multi-view classification and detection datasets. + +
view selection (T=2)ModelNet40ScanObjNN
12 views20 views
N/A: all N views94.596.586.1
dataset-lvl oracle85.2 ± 1.469.9 ± 1.978.5 ± 1.2
instance-lvl oracle96.5 ± 0.498.1 ± 1.993.4 ± 0.6
random selection71.5 ± 2.548.1 ± 3.174.2 ± 3.5
validation best policy85.1 ± 0.869.5 ± 1.077.5 ± 1.1
MVSelect88.2 ± 0.479.6 ± 1.880.0 ± 0.8
MVSelect + joint training94.3 ± 0.294.4 ± 0.284.1 ± 0.2
+ +
view selection (T=3)WildtrackMultiviewX
N/A: all N views90.093.0
dataset-lvl oracle82.5 ± 0.480.2 ± 0.3
instance-lvl oracle87.4 ± 0.482.3 ± 0.8
random selection74.9 ± 1.376.2 ± 1.4
validation best policy79.5 ± 1.178.0 ± 0.4
MVSelect80.0 ± 0.878.7 ± 0.5
MVSelect + joint training88.6 ± 0.288.1 ± 0.2
+ +![](images/fb5a7651b95a4fb120ccd9bc4d96570513386356d4e288aba040079d2120c5fb.jpg) +(a) Classification accuracy +Figure 7. Multi-view classification with $T = 2$ views on the 12-view setup of ModelNet40. The task network is fixed once trained. Left: test set accuracy of using two views. Right: MVSelect policy for the test set. + +![](images/a9f2da4b0ea3c10a150d3744bf47b0e65fba535ede4d0f0851a6deb470a767a9.jpg) +(b) MVSelect policy + +Table 3. Computation efficiency. + +
viewsFLOPsthroughput (instance/s)
f(·)g(·)d(·)
ModelNet402036.5G20.5kN/A119.6
23.6G20.5k1.1M361.8
1221.9G20.5kN/A196.2
23.6G20.5k530.4k507.9
Wildtrack71.2T19.1GN/A8.4
3511.6G19.1G3.2G16.2
MultiviewX61.0T17.7GN/A9.8
3511.6G17.7G2.9G16.9
+ +Table 4. Ablation study. + +
ModelNet40Wildtrack
12 views
MVSelect88.280.0
w/o camera branch88.279.1
w/o feature branch85.079.7
w/ transformer87.078.7
reward=Δ task loss88.080.1
+ +likely due to the target scenarios not being fully captured by any single view, and the multi-view detection network needs multiple views to collaborate with each other for optimal results. Compared to the dataset-level oracles, we find the MVSelect policy lose its edge. In fact, we find that for multi-view detection, MVSelect tends to select the same camera for a given initial view, since it is not aware of the situation outside of the FoV coverage. As a result, it cannot choose cameras based on uncovered areas in different frames. Without this instance-aware advantage, the fixed camera policy learned during training (MVSelect) cannot outperform the dataset-level oracle, whose policy is computed on the test set. + +Joint training with MVDet once again leads to substantial performance improvements over keeping the task network fixed. In fact, the results even exceed the instance-level oracle for fixed task networks. Using $T = 3$ views, the joint training approach provides competitive results to using all $N$ views, and exceeds the reported performance in the original MVDet paper [17]. We present an example of the selected views in the Wildtrack dataset in Fig. 6. + +# 5.3. Efficiency Analysis + +In Table 3, following previous works in efficient inference [19, 24], we detail the computational cost in FLOPs for task networks and MVSelect. Specifically, we find feature extraction $f(\cdot)$ to take up the majority of the computation, while everything else is lighter by at least an order of magnitude. Overall, we verify that using $T = 2$ or 3 out of $N$ views can reduce the computational cost to roughly $T / N$ . + +In terms of inference speed, we find reduction in FLOPs results in monotonically increasing throughputs, ranging from $1.72 \times$ to $3.03 \times$ . Due to factors such as implementation, parallelization, and hardware limitations, actual speedups cannot actually reach the level of computational cost reduction, as suggested by previous study [27]. + +# 5.4. Variant Study + +Ablation study. Regarding the MVSelect architecture design, Table 4 shows that removing the camera branch and feature branch primarily affects multi-view detection and multi-view classification performance, respectively. This aligns with the policy we learned for the two tasks. For multi-view detection, since the system has no clue about ar + +![](images/46b7cc7ab392afd0798d5a74f1cb8018e47e6c693d64ce66068a019859106ad8.jpg) +Figure 9. System performance under different number of total views $T$ . We report classification accuracy and MODA for the two tasks, respectively (same for Fig. 10 and Table. 4). Circle and triangle markers indicate whether the task network is fixed or not, respectively. Dotted lines represent oracle performance (not achievable). + +![](images/15f43b5dc456ea37de0697ff64d73ba717e477ec8e9a4e925ae24aecaece104d.jpg) +Figure 10. System evaluation under different settings. Except for the random pose* setting (where MVSelect variants are re-trained), all models are trained on the default setting. + +![](images/e1d47565d23c0e4be800f60083b5daa0138035ff3928733c635ed0bb1f03a6b4.jpg) + +eas outside camera FoVs, the camera branch plays a more important role for encoding prior knowledge of the scene layout. For multi-view classification, however, target objects are fully observable, and MVSelect can make different decisions for each instance. Thus, the feature branch is more important, as it enables per-instance decision making. + +When changing the MVSelect network architecture into transformer [40], we find that more parameters do not translate into better performance. + +Another option for the reward is the change in task loss. In our variant study, this reward design does not show any significant advantages over the current design. + +Influence of total view count. The performance curves in Fig. 9 demonstrate that the joint training variant achieves competitive performance with as few as $T = 2$ views for multi-view classification and $T = 3$ views for multi-view detection, beyond which point performance plateaus. By contrast, learning MVSelect for fixed task networks shows a less steep curve. The performance increases up to a total of $T = 5$ views, at which point the MVSelect policy performs comparably to the full $N$ -view system. + +Camera layout optimization. Determining the optimal camera locations is crucial for setting up an effective multiview system. In Fig.7, we observe that not all cameras are equally useful according to the MVSelect policy. To address this, we allocate a validation partition of the data to identify the more useful camera views and then disable half of the $N = 12$ cameras that are not frequently utilized. In testing, we find that some cameras are not as useful ("policy shut-off" in Fig. 10) and the proposed method can generalize to test-time disturbances including malfunctioning cameras ("random shut-off" in Fig.10). Although it is necessary to set up all $N$ cameras for the analysis, optimizing the multiview camera layout can be a crucial step towards achieving optimal performance, and merits further investigation. + +Random object pose. In real-world applications of multi-view systems, such as those found in iPhones and Tesla, the cameras may remain fixed in their relative positions while the entire system is in motion. To simulate this scenario in our experiments, we introduce the random object pose setting (Fig. 10) and re-train MVSelect. While there is no exact object pose as supervision, the reinforcement learning approach is able to roughly infer the relative poses between the object and the multi-view system, resulting in improved performance compared to random selection and dataset-level oracle (which is arguably inappropriate for this setup). In the future, we plan to estimate camera poses with respect to the object or the environment as an auxiliary supervision for moving setups. + +# 6. Conclusion + +In conclusion, this paper proposes selective view pipelining, an efficient approach for multi-view understanding by limiting the number of views. To this end, a camera view selection module, MVSelect, is proposed along with a reinforcement learning based training scheme that can learn from the non-differentiable selection process. When jointly trained with the task network, the proposed approach demonstrates competitive performance on multi-view classification and detection tasks at fractions of the computational cost. Overall, the proposed efficient approach provides an alternative to reducing image resolution and using lighter networks, and paves ways for future multi-view camera layout optimization. + +# Acknowledgement + +This work was supported by the ARC Discovery Project (DP210102801). + +# References + +[1] John Aloimonos, Isaac Weiss, and Amit Bandyopadhyay. Active vision. International journal of computer vision, 1: 333-356, 1988. 2 +[2] Pierre Baqué, François Fleuret, and Pascal Fua. Deep occlusion reasoning for multi-camera multi-target detection. In Proceedings of the IEEE International Conference on Computer Vision, pages 271-279, 2017. 6 +[3] Rowan Border and Jonathan D Gammell. Proactive estimation of occlusions and scene coverage for planning next best views in an unstructured representation. 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However, the high computational cost associated with multiple views creates a significant challenge for end devices with limited computational resources. In modern CPU, pipelining breaks a longer job into steps and enables parallelism over sequential steps from multiple jobs. Inspired by this, we study selective view pipelining for efficient multi-view understanding, which breaks computation of multiple views into steps, and only computes the most helpful views/steps in a parallel manner for the best efficiency. To this end, we use reinforcement learning to learn a very light view selection module that analyzes the target object or scenario from initial views and selects the next-best-view for recognition or detection for pipeline computation. 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Demonstration of the proposed selective view pipelining. Inspired by instruction pipelining in modern CPU (a), selective view pipelining (c) breaks the multi-view perception task into sequential steps, and only computes the chosen views (see Fig. 2) to minimize the computation. At the same time, computation across multiple objects (different border colors) can still enjoy parallelism in GPU (b). In this example, for a " + }, + { + "bbox": [ + 304, + 460, + 545, + 593 + ], + "type": "inline_equation", + "content": "N = 6" + }, + { + "bbox": [ + 304, + 460, + 545, + 593 + ], + "type": "text", + "content": " view system, traditional computation (b) on GPU hardware that only supports two images at the same time will produce a throughput of 2 instances during 6 time steps. 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Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 702, + 286, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 702, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 702, + 286, + 712 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 58, + 702, + 286, + 712 + ], + "type": "text", + "content": "Code available at https://github.com/hou-yz/MVSelect." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20135" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 65, + 72, + 272, + 209 + ], + "blocks": [ + { + "bbox": [ + 65, + 72, + 272, + 209 + ], + "lines": [ + { + "bbox": [ + 65, + 72, + 272, + 209 + ], + "spans": [ + { + "bbox": [ + 65, + 72, + 272, + 209 + ], + "type": "image", + "image_path": "85c1798479f0658128e78033dfca1d996f8590d7c5e9f59cda0b3ac4eac99397.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 220, + 289, + 308 + ], + "lines": [ + { + "bbox": [ + 46, + 220, + 289, + 308 + ], + "spans": [ + { + "bbox": [ + 46, + 220, + 289, + 308 + ], + "type": "text", + "content": "Figure 2. Efficient multi-view understanding with two glances. Instead of using all " + }, + { + "bbox": [ + 46, + 220, + 289, + 308 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 220, + 289, + 308 + ], + "type": "text", + "content": " views at once, a more efficient approach is to first examine one view and then select another view to resolve ambiguities from the initial glance. If the initial side view cannot distinguish between a guitar and a mandolin (a round-shaped instrument that may also have a flat back), we can then query the front view. This sequential process can work in a pipeline to enable parallelism between multiple" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 325, + 192, + 337 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 325, + 192, + 337 + ], + "spans": [ + { + "bbox": [ + 47, + 325, + 192, + 337 + ], + "type": "text", + "content": "computing one object with 6 views." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 338, + 287, + 446 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 338, + 287, + 446 + ], + "spans": [ + { + "bbox": [ + 46, + 338, + 287, + 446 + ], + "type": "text", + "content": "In this work, we propose selective view pipelining, which breaks the multi-view perception task into a sequence of steps. Based on initial views, we estimate the most helpful views for this task, and only compute the selected views for maximum efficiency. The example in Fig. 1c shows that only selecting one additional view can greatly reduce the computation from 6 views to 2 views. By further taking advantage of the parallelism in GPUs, we can roughly improve the overall throughput by " + }, + { + "bbox": [ + 46, + 338, + 287, + 446 + ], + "type": "inline_equation", + "content": "3 \\times" + }, + { + "bbox": [ + 46, + 338, + 287, + 446 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 449, + 288, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 449, + 288, + 640 + ], + "spans": [ + { + "bbox": [ + 46, + 449, + 288, + 640 + ], + "type": "text", + "content": "To this end, this paper introduces a new angle to efficient multi-view understanding by selecting only the most useful views. To identify the best views, this approach leverages camera layouts, which is a key aspect overlooked by existing alternatives. With known camera layouts, networks should be able to infer what each camera view looks like and then choose accordingly, as previous works [20] have shown that networks can associate images with camera poses. Existing work on active vision [1, 8, 12] indicates that it is possible to find next-best-view (NBV) for reconstruction with 3D sensors. In this paper, we focus on recognition and detection problems using multiple RGB cameras, where a side view may confuse a guitar with a mandolin (Fig. 2). However, prior knowledge of the camera layout should inform the system that the front view can clear the ambiguities and should be queried." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "content": "To achieve this goal, this paper proposes a novel view selection module, MVSelect, that chooses the best camera views from any initial view at minimal computational costs. Using the same feature extracted for the final task of classification or detection, the proposed module analyzes the target object or scenario from existing views and then selects the" + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 310, + 74, + 545, + 205 + ], + "blocks": [ + { + "bbox": [ + 310, + 74, + 545, + 205 + ], + "lines": [ + { + "bbox": [ + 310, + 74, + 545, + 205 + ], + "spans": [ + { + "bbox": [ + 310, + 74, + 545, + 205 + ], + "type": "image", + "image_path": "23a312e7f3bd3b7eb5179a8d47e340c9e8e27da9059b6bd33ab2e3891ac06a44.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 324, + 213, + 526, + 224 + ], + "lines": [ + { + "bbox": [ + 324, + 213, + 526, + 224 + ], + "spans": [ + { + "bbox": [ + 324, + 213, + 526, + 224 + ], + "type": "text", + "content": "Figure 3. Multi-view classification with MVCNN [37]." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 238, + 545, + 334 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 238, + 545, + 334 + ], + "spans": [ + { + "bbox": [ + 304, + 238, + 545, + 334 + ], + "type": "text", + "content": "next view that best helps the task (classification or detection) network. To navigate through the non-differentiable view selection (the system only looks at selected cameras, so not-selected views cannot back propagate gradients to the controller), following Mnih et al. [26], we train the controller via trial-and-error. This process is formulated as a reinforcement learning problem aiming to maximize the final recognition or detection accuracy." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 335, + 546, + 441 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 335, + 546, + 441 + ], + "spans": [ + { + "bbox": [ + 304, + 335, + 546, + 441 + ], + "type": "text", + "content": "On both multi-view classification and detection tasks, our experimental results show that MVSelect can provide a good strategy for fixed task networks, while also capable of joint training with the task network for further performance improvements. Specifically, when joint training both MVSelect and the task network, the resulting system can achieve competitive performance to using all " + }, + { + "bbox": [ + 304, + 335, + 546, + 441 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 335, + 546, + 441 + ], + "type": "text", + "content": " cameras, while using only 2 views for classification tasks and 3 views for detection tasks, respectively." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 442, + 545, + 525 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 442, + 545, + 525 + ], + "spans": [ + { + "bbox": [ + 304, + 442, + 545, + 525 + ], + "type": "text", + "content": "The computational overhead of MVSelect is very small, as it shares the feature extraction backbone with the task network and only has a few learnable layers. For the entire system, the computational cost is roughly proportional to the number of views used, e.g., approximately " + }, + { + "bbox": [ + 304, + 442, + 545, + 525 + ], + "type": "inline_equation", + "content": "2 / N" + }, + { + "bbox": [ + 304, + 442, + 545, + 525 + ], + "type": "text", + "content": " of the total computation when 2 views are used, a significant efficiency boost." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 526, + 545, + 586 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 526, + 545, + 586 + ], + "spans": [ + { + "bbox": [ + 304, + 526, + 545, + 586 + ], + "type": "text", + "content": "The MVSelect policy also enables study on multi-view camera layout. In fact, we find that many of the " + }, + { + "bbox": [ + 304, + 526, + 545, + 586 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 526, + 545, + 586 + ], + "type": "text", + "content": " cameras are rarely chosen and can be shut off for further operational cost improvements, which can serve as a starting point for future study on multi-view camera layout optimization." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 597, + 384, + 611 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 597, + 384, + 611 + ], + "spans": [ + { + "bbox": [ + 306, + 597, + 384, + 611 + ], + "type": "text", + "content": "2. Background" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 713 + ], + "type": "text", + "content": "Multi-view classification. One effective way for 3D shape recognition is to capture the object in multiple camera views. MVCNN [37] extracts feature vectors from the input views, and then uses max pooling to aggregate across multiple views for classification. Based on MVCNN, many alternative approaches are proposed. Qi et al. [30] propose sphere rendering at different volume resolutions. GVCNN [11] investigates hierarchical information between different" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "20136" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 72, + 286, + 169 + ], + "blocks": [ + { + "bbox": [ + 53, + 72, + 286, + 169 + ], + "lines": [ + { + "bbox": [ + 53, + 72, + 286, + 169 + ], + "spans": [ + { + "bbox": [ + 53, + 72, + 286, + 169 + ], + "type": "image", + "image_path": "845c2ac765a5d5f3f647519b198828dc12144adcddbcbdad5c9a646c7607f7e9.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 76, + 181, + 258, + 193 + ], + "lines": [ + { + "bbox": [ + 76, + 181, + 258, + 193 + ], + "spans": [ + { + "bbox": [ + 76, + 181, + 258, + 193 + ], + "type": "text", + "content": "Figure 4. Multi-view detection with MVDet [17]." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 208, + 287, + 291 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 208, + 287, + 291 + ], + "spans": [ + { + "bbox": [ + 46, + 208, + 287, + 291 + ], + "type": "text", + "content": "views by grouping the image features before the final aggregation. RotationNet [20] introduces a multi-task objective by jointly considering classification and camera poses. ViewGCN [42] uses a Graph Convolution Network (GCN) [23] instead of the max pooling layer to aggregate across views. Hamdi et al. [14] propose the MVTN network to estimate the best viewpoints for 3D point cloud models." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 293, + 287, + 448 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 293, + 287, + 448 + ], + "spans": [ + { + "bbox": [ + 46, + 293, + 287, + 448 + ], + "type": "text", + "content": "Multi-view detection estimate pedestrian occupancy from the bird's-eye-view (BEV). For this task, some methods [13, 33, 45] aggregate single-view detection results. Others find single-view detection results unreliable and instead aggregate the features. Hou et al. [17] introduce MVDet, the first fully deep-learning approach, which projects feature maps from each camera view to the BEV. Based on MVDet, researchers develop other deep methods. SHOT [36] projects the image feature map at different heights and stacks them together to improve performance. MVDetr [16] deals with distinct distortion patterns from the projection. Qiu et al. [32] investigate data augmentation with simulated occlusion over multiple views." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 449, + 288, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 449, + 288, + 639 + ], + "spans": [ + { + "bbox": [ + 46, + 449, + 288, + 639 + ], + "type": "text", + "content": "Camera viewpoint study. Cao and Snavely [5] investigate this for reconstruction with structure-from-motion. Active vision community investigates next-best-view planning with 3D sensors like RGBD cameras or LiDAR for scene reconstruction [4, 8, 35]. In multi-view classification, RotationNet [20] makes some pioneering work on limited view numbers by taking a random partial set of all " + }, + { + "bbox": [ + 46, + 449, + 288, + 639 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 449, + 288, + 639 + ], + "type": "text", + "content": " views of the image. MVTN [14] uses the 3D point cloud as initial input and then estimates the best camera layout for multi-view classification, but its moving camera assumption is hard to meet in real-world systems. In multi-view detection, Vora et al. [41] investigate camera layout generalization by randomly dropping camera views from both training and testing. Hou et al. [18] investigate how to place cameras. For 3D human pose estimation, Pirinen et al. [28] actively select cameras over a dome." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": "Reinforcement learning (RL) directs an agent to interact with the environment in a manner that maximizes cumulative rewards. State " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "s \\in S" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": ", action " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "a \\in \\mathcal{A}" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": ", and reward " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "r \\in \\mathcal{R}" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": " are key concepts to model the interaction between agent and environment. In a certain state " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": ", policy " + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pi(a|s)" + }, + { + "bbox": [ + 46, + 642, + 287, + 713 + ], + "type": "text", + "content": " records the probability for each action, and state value func" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "text", + "content": "tion " + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "inline_equation", + "content": "V(s)" + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "text", + "content": " estimates the future rewards when following the corresponding policy. To learn the best policy, Q-learning and DQN [25] optimize the action value function " + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "inline_equation", + "content": "Q(s,a)" + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "text", + "content": ", which describes the estimated future return for a specific action " + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "text", + "content": " at state " + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 304, + 72, + 545, + 145 + ], + "type": "text", + "content": ". 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Given " + }, + { + "bbox": [ + 304, + 192, + 545, + 241 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 192, + 545, + 241 + ], + "type": "text", + "content": " input images " + }, + { + "bbox": [ + 304, + 192, + 545, + 241 + ], + "type": "inline_equation", + "content": "\\pmb{x}_n" + }, + { + "bbox": [ + 304, + 192, + 545, + 241 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 192, + 545, + 241 + ], + "type": "inline_equation", + "content": "n \\in \\{1, \\dots, N\\}" + }, + { + "bbox": [ + 304, + 192, + 545, + 241 + ], + "type": "text", + "content": ", first, MVCNN uses its feature extractor " + }, + { + "bbox": [ + 304, + 192, + 545, + 241 + ], + "type": "inline_equation", + "content": "f(\\cdot)" + }, + { + "bbox": [ + 304, + 192, + 545, + 241 + ], + "type": "text", + "content": " to calculate the feature vectors," + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 394, + 251, + 545, + 264 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 394, + 251, + 545, + 264 + ], + "spans": [ + { + "bbox": [ + 394, + 251, + 545, + 264 + ], + "type": "interline_equation", + "content": "\\boldsymbol {h} _ {n} = f \\left(\\boldsymbol {x} _ {n}\\right), \\tag {1}", + "image_path": "9211f12308f8bff1c731843dee6a093c2dc31ffba9de67d1e6b7d5eec59ad32e.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "spans": [ + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "type": "text", + "content": "where the feature vector " + }, + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "type": "inline_equation", + "content": "\\pmb{h}_n \\in \\mathbb{R}^D" + }, + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "type": "text", + "content": " is " + }, + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "type": "text", + "content": "-dimensional. Secondly, it uses max pooling to aggregate multiple views into an overall feature descriptor " + }, + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "type": "inline_equation", + "content": "\\hat{\\pmb{h}} \\in \\mathbb{R}^{D}" + }, + { + "bbox": [ + 304, + 273, + 545, + 309 + ], + "type": "text", + "content": "," + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 391, + 317, + 545, + 336 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 391, + 317, + 545, + 336 + ], + "spans": [ + { + "bbox": [ + 391, + 317, + 545, + 336 + ], + "type": "interline_equation", + "content": "\\hat {\\boldsymbol {h}} = \\max _ {n} \\left\\{\\boldsymbol {h} _ {n} \\right\\}, \\tag {2}", + "image_path": "3a792b311e402aeab35f4f6798e1a6837634a3be56857a94b87c422cb15c6b33.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "spans": [ + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "inline_equation", + "content": "\\max \\{\\dots\\}" + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "text", + "content": " takes the maximum along each of the " + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "text", + "content": " dimensions. Lastly, it applies the output head " + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "inline_equation", + "content": "g(\\cdot)" + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "text", + "content": " to produce the classification result " + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "inline_equation", + "content": "\\hat{\\pmb{y}}" + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "text", + "content": "," + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 399, + 388, + 545, + 409 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 399, + 388, + 545, + 409 + ], + "spans": [ + { + "bbox": [ + 399, + 388, + 545, + 409 + ], + "type": "interline_equation", + "content": "\\hat {\\boldsymbol {y}} = g (\\hat {\\boldsymbol {h}}). \\tag {3}", + "image_path": "0247a16bf932afab89d2506a00292c5494234395250910986926e465f2336db5.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 416, + 545, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 416, + 545, + 464 + ], + "spans": [ + { + "bbox": [ + 304, + 416, + 545, + 464 + ], + "type": "text", + "content": "In training, the original design by Su et al. [37] adopts a 2-stage paradigm by first training on individual views and then considering multiple views. In this paper, we skip the first stage and directly train MVCNN on all " + }, + { + "bbox": [ + 304, + 416, + 545, + 464 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 416, + 545, + 464 + ], + "type": "text", + "content": " views," + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 377, + 474, + 545, + 487 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 377, + 474, + 545, + 487 + ], + "spans": [ + { + "bbox": [ + 377, + 474, + 545, + 487 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {M V C N N}} = \\mathcal {L} _ {\\text {C E}} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}), \\tag {4}", + "image_path": "fbe85d2ed1ccd2e22469996627a201f25fba572a541ca8ed2aa630cac772d45e.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 496, + 545, + 520 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 496, + 545, + 520 + ], + "spans": [ + { + "bbox": [ + 304, + 496, + 545, + 520 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 496, + 545, + 520 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{CE}}(\\cdot ,\\cdot)" + }, + { + "bbox": [ + 304, + 496, + 545, + 520 + ], + "type": "text", + "content": " denotes the cross-entropy loss and " + }, + { + "bbox": [ + 304, + 496, + 545, + 520 + ], + "type": "inline_equation", + "content": "\\pmb{y}" + }, + { + "bbox": [ + 304, + 496, + 545, + 520 + ], + "type": "text", + "content": " denotes the ground truth one-hot label." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 527, + 488, + 539 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 527, + 488, + 539 + ], + "spans": [ + { + "bbox": [ + 306, + 527, + 488, + 539 + ], + "type": "text", + "content": "3.2. Multi-view Detection with MVDet" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "text", + "content": "MVDet [17] (Fig. 4) is a multi-view detection architecture that is followed by many recent works. To estimate human occupancy in bird's-eye-view (BEV), given input images " + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\boldsymbol{x}_n, n \\in \\{1, \\dots, N\\}" + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "text", + "content": ", MVDet first extracts " + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "text", + "content": "-channel feature maps for each view and uses perspective transformation to project the camera views to the BEV. Together, these operations can be considered as the BEV feature extraction step under Eq. 1, with the exception that " + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\boldsymbol{h}_n \\in \\mathbb{R}^{D \\times H \\times W}" + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "text", + "content": " now denotes the " + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "text", + "content": "-channel feature map for the BEV scenario of shape " + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "inline_equation", + "content": "H \\times W" + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "text", + "content": ". Secondly, for multi-view aggregation, instead of the concatenation in the original design, we choose element-wise max pooling in Eq. 2, producing the overall feature description " + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\hat{\\boldsymbol{h}} \\in \\mathbb{R}^{D \\times H \\times W}" + }, + { + "bbox": [ + 304, + 545, + 545, + 713 + ], + "type": "text", + "content": " that fits arbitrary numbers of views. Lastly, we apply the output head as" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20137" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 71, + 545, + 235 + ], + "blocks": [ + { + "bbox": [ + 51, + 71, + 545, + 235 + ], + "lines": [ + { + "bbox": [ + 51, + 71, + 545, + 235 + ], + "spans": [ + { + "bbox": [ + 51, + 71, + 545, + 235 + ], + "type": "image", + "image_path": "7b69fa980dec9ffa8a2d8b3d7d1c2597e090e0349f2649c2d313cf08b0c39613.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "lines": [ + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "spans": [ + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": "Figure 5. Efficient multi-view understanding with selective view pipelining using " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "T = 3" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " glances. Solid lines indicate the network forward pass and dashed lines indicate the interaction between agent (MVSelect) and environment (multi-view system). The approach starts with a random initial view " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "a_1" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": ", and the feature extractor " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "f(\\cdot)" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " computes its feature (Eq. 1). The state for this initial time step is recorded as " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "s_1" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " (Eq. 6). Next, the proposed MVSelect module " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "d(\\cdot)" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " is used to choose a second view " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "a_2" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": ", and the state is updated as " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "s_2" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": ". Then, by repeating the last step, a third view " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "a_3" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " is chosen and the state is updated as " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "s_3" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": ". Finally, three views are aggregated into an overall descriptor " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "\\hat{h}" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " (Eq. 2), and the task network output " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "\\hat{\\pmb{y}}" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " is calculated using the output head " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "g(\\cdot)" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " (Eq. 3). The final reward " + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "inline_equation", + "content": "r_3 = \\mathrm{MODA}(\\hat{\\pmb{y}},\\pmb{y})" + }, + { + "bbox": [ + 46, + 246, + 548, + 324 + ], + "type": "text", + "content": " is set as the accuracy fir the task network (Eq. 7), and all other rewards are set as zero." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 342, + 288, + 381 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 342, + 288, + 381 + ], + "spans": [ + { + "bbox": [ + 46, + 342, + 288, + 381 + ], + "type": "text", + "content": "Eq. 3 to generate a heatmap " + }, + { + "bbox": [ + 46, + 342, + 288, + 381 + ], + "type": "inline_equation", + "content": "\\hat{\\pmb{y}}\\in (0,1)^{H\\times W}" + }, + { + "bbox": [ + 46, + 342, + 288, + 381 + ], + "type": "text", + "content": " that indicates the likelihood of human occupancy in each BEV location. The loss for MVDet can be written as," + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 91, + 390, + 287, + 423 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 91, + 390, + 287, + 423 + ], + "spans": [ + { + "bbox": [ + 91, + 390, + 287, + 423 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {M V D e t}} = \\mathcal {L} _ {\\mathrm {B E V}} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}) + \\frac {1}{N} \\sum_ {n = 1} ^ {N} \\mathcal {L} _ {n}, \\tag {5}", + "image_path": "80f864a33fef42e92db0a8bf4cbe91d5883f0d87b38564d3b56a32abea8d37ad.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "spans": [ + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{BEV}}(\\cdot ,\\cdot)" + }, + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "type": "text", + "content": " denotes BEV output loss; " + }, + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "type": "inline_equation", + "content": "\\pmb {y}\\in \\{0,1\\}^{H\\times W}" + }, + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "type": "text", + "content": " denotes binary ground truth map; and " + }, + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_n" + }, + { + "bbox": [ + 47, + 433, + 287, + 473 + ], + "type": "text", + "content": " denotes the auxiliary per-view loss with 2D bounding boxes." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 484, + 245, + 498 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 484, + 245, + 498 + ], + "spans": [ + { + "bbox": [ + 47, + 484, + 245, + 498 + ], + "type": "text", + "content": "4. Efficient Multi-view Understanding" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "spans": [ + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": "In a multi-view system with " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " views, selective view planning uses a total of " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "T < N" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " camera views " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "a_{t} \\in \\{1, \\dots, N\\}, t \\in \\{1, \\dots, T\\}" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " for efficient understanding. To achieve this, we propose a view selection module, MVSelect, denoted as " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "d(\\cdot)" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": ", that sequentially selects camera views. Starting from a random initial view " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "a_{1}" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": ", MVSelect chooses the remaining " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "T - 1" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " cameras by observing the target object or scene from existing views " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "a_{1}, \\dots, a_{t}" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " at each time step " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " and deciding which camera view " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "a_{t + 1}" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " to select next for best performance. Once " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " camera views have been gathered, we aggregate them into an overall description " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "\\hat{\\pmb{h}}" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " using Eq. 2, and calculate the final output " + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "inline_equation", + "content": "\\hat{\\pmb{y}}" + }, + { + "bbox": [ + 46, + 505, + 289, + 662 + ], + "type": "text", + "content": " using Eq. 3. Fig. 5 gives an overview of the proposed efficient multi-view approach." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 670, + 171, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 171, + 682 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 171, + 682 + ], + "type": "text", + "content": "4.1. Problem Formulation" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "content": "While iteratively selecting camera views, it is impossible to know what is in the not-selected camera views. If view" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 344, + 547, + 463 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 344, + 547, + 463 + ], + "spans": [ + { + "bbox": [ + 304, + 344, + 547, + 463 + ], + "type": "text", + "content": "selection was formulated as a prediction task in a supervised manner, the loss (final target metric at " + }, + { + "bbox": [ + 304, + 344, + 547, + 463 + ], + "type": "inline_equation", + "content": "t = T" + }, + { + "bbox": [ + 304, + 344, + 547, + 463 + ], + "type": "text", + "content": ") could not be back propagated to the not-selected views, making it non-differentiable and impossible to update the selection probability. Reinforcement learning, on the other hand, can update the controller even with the non-differentiable view selection. Therefore, we formulate this non-differentiable process as a reinforcement learning problem, where MVS-select is the agent and learns through trial and error, and the multi-view system is the environment." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "spans": [ + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "text", + "content": "State. In order to get a Markovian representation, we record the chosen camera views " + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "inline_equation", + "content": "a_1,\\dots ,a_t" + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "text", + "content": " and the observations " + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "inline_equation", + "content": "h_{a_1},\\ldots ,h_{a_t}" + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "text", + "content": " as state " + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "inline_equation", + "content": "s_t" + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "text", + "content": ". We use the extracted features to represent the observations rather than the RGB camera views to reduce dimensionality and maximize efficiency, since these features will be used in the task network later (Eq. 2). Mathematically, we formulate the state " + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "inline_equation", + "content": "s_t" + }, + { + "bbox": [ + 304, + 464, + 547, + 548 + ], + "type": "text", + "content": " as," + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 388, + 553, + 463, + 569 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 388, + 553, + 463, + 569 + ], + "spans": [ + { + "bbox": [ + 388, + 553, + 463, + 569 + ], + "type": "interline_equation", + "content": "s _ {t} = \\left\\langle s _ {t} ^ {\\mathrm {c a m}}, s _ {t} ^ {\\mathrm {o b s}} \\right\\rangle ,", + "image_path": "6bb521f180b4f4336f2ea00d077de9d7a00381216843625ed8655064eb914291.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 375, + 571, + 545, + 602 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 375, + 571, + 545, + 602 + ], + "spans": [ + { + "bbox": [ + 375, + 571, + 545, + 602 + ], + "type": "interline_equation", + "content": "s _ {t} ^ {\\text {c a m}} = \\sum_ {\\tau = 1} ^ {t} \\text {o n e h o t} \\left(a _ {\\tau}\\right), \\tag {6}", + "image_path": "2643b8bb4e2b0ae9c1d979d38f25385bf2944a4ece41b9223ea6c19fa0d8d70d.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 386, + 604, + 466, + 624 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 386, + 604, + 466, + 624 + ], + "spans": [ + { + "bbox": [ + 386, + 604, + 466, + 624 + ], + "type": "interline_equation", + "content": "s _ {t} ^ {\\mathrm {o b s}} = \\max _ {\\tau = 1} ^ {t} \\left\\{\\boldsymbol {h} _ {a _ {\\tau}} \\right\\},", + "image_path": "e7d16bbb1176bcb62ec6263363fccfe869b97d35a2fa1b2d6e911a50a97f25ef.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "text", + "content": "where onehot " + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "inline_equation", + "content": "(\\cdot)" + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "text", + "content": " is the one-hot function over " + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "text", + "content": " cameras. This representation reflects both chosen cameras " + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "inline_equation", + "content": "s_t^{\\mathrm{cam}} \\in \\mathbb{R}^N" + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "text", + "content": " and their observations " + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "inline_equation", + "content": "s_t^{\\mathrm{obs}} \\in \\mathbb{R}^D" + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "text", + "content": ", and maintains the same dimensionality across different time steps. The observation part " + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "inline_equation", + "content": "s_t^{\\mathrm{obs}}" + }, + { + "bbox": [ + 304, + 629, + 545, + 689 + ], + "type": "text", + "content": " also matches the overall representation in Eq. 2." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "content": "Action. For state " + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "inline_equation", + "content": "s_t, t \\in \\{1, \\dots, T - 1\\}" + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "content": ", MVSelect takes the next camera view " + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "inline_equation", + "content": "a_{t + 1}" + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "content": " as action." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20138" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 72, + 284, + 84 + ], + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 72, + 284, + 84 + ], + "spans": [ + { + "bbox": [ + 48, + 72, + 284, + 84 + ], + "type": "text", + "content": "Algorithm 1 Joint training of MVSelect and task network." + } + ] + } + ], + "index": 0, + "type": "text" + }, + { + "bbox": [ + 50, + 87, + 287, + 274 + ], + "type": "list", + "angle": 0, + "index": 11, + "blocks": [ + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "spans": [ + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "text", + "content": "1: input: camera views " + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "inline_equation", + "content": "\\pmb{x}_n, n \\in \\{1, \\dots, N\\}" + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "text", + "content": ", ground truth " + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "inline_equation", + "content": "\\pmb{y}" + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "text", + "content": ", random initial view " + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "inline_equation", + "content": "a_1" + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "text", + "content": ", number of total views " + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "text", + "content": ", hyperparameter " + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 53, + 87, + 287, + 121 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "spans": [ + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "type": "text", + "content": "2: update: feature extractor " + }, + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "type": "inline_equation", + "content": "f(\\cdot)" + }, + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "type": "text", + "content": " and output head " + }, + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "type": "inline_equation", + "content": "g(\\cdot)" + }, + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "type": "text", + "content": " of task network, and MVSelect controller " + }, + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "type": "inline_equation", + "content": "d(\\cdot)" + }, + { + "bbox": [ + 53, + 121, + 287, + 143 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 53, + 143, + 185, + 153 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 143, + 185, + 153 + ], + "spans": [ + { + "bbox": [ + 53, + 143, + 185, + 153 + ], + "type": "text", + "content": "3: initialize the total loss " + }, + { + "bbox": [ + 53, + 143, + 185, + 153 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{total}} = 0" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 53, + 154, + 164, + 164 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 154, + 164, + 164 + ], + "spans": [ + { + "bbox": [ + 53, + 154, + 164, + 164 + ], + "type": "text", + "content": "4: for " + }, + { + "bbox": [ + 53, + 154, + 164, + 164 + ], + "type": "inline_equation", + "content": "t \\in \\{1, \\dots, T - 1\\}" + }, + { + "bbox": [ + 53, + 154, + 164, + 164 + ], + "type": "text", + "content": " do" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "spans": [ + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "type": "text", + "content": "5: select and apply the next action using " + }, + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "type": "text", + "content": "-greedy: with probability " + }, + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "type": "text", + "content": " adopt a random action, or else choose the action with highest value " + }, + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "type": "inline_equation", + "content": "a_{t+1} = \\arg \\max_a Q(s_t, a)" + }, + { + "bbox": [ + 53, + 165, + 287, + 198 + ], + "type": "text", + "content": ";" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 53, + 198, + 279, + 209 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 198, + 279, + 209 + ], + "spans": [ + { + "bbox": [ + 53, + 198, + 279, + 209 + ], + "type": "text", + "content": "6: observe next state " + }, + { + "bbox": [ + 53, + 198, + 279, + 209 + ], + "type": "inline_equation", + "content": "s_{t + 1}" + }, + { + "bbox": [ + 53, + 198, + 279, + 209 + ], + "type": "text", + "content": " (Eq. 6) and reward " + }, + { + "bbox": [ + 53, + 198, + 279, + 209 + ], + "type": "inline_equation", + "content": "r_{t + 1}" + }, + { + "bbox": [ + 53, + 198, + 279, + 209 + ], + "type": "text", + "content": " (Eq. 7);" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 53, + 209, + 287, + 230 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 209, + 287, + 230 + ], + "spans": [ + { + "bbox": [ + 53, + 209, + 287, + 230 + ], + "type": "text", + "content": "7: calculate the RL loss " + }, + { + "bbox": [ + 53, + 209, + 287, + 230 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{RL}}" + }, + { + "bbox": [ + 53, + 209, + 287, + 230 + ], + "type": "text", + "content": " (Eq. 9) and update the total loss " + }, + { + "bbox": [ + 53, + 209, + 287, + 230 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{total}} + \\mathcal{L}_{\\mathrm{RL}}" + }, + { + "bbox": [ + 53, + 209, + 287, + 230 + ], + "type": "text", + "content": ";" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 53, + 232, + 94, + 240 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 232, + 94, + 240 + ], + "spans": [ + { + "bbox": [ + 53, + 232, + 94, + 240 + ], + "type": "text", + "content": "8: end for" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 53, + 241, + 287, + 263 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 241, + 287, + 263 + ], + "spans": [ + { + "bbox": [ + 53, + 241, + 287, + 263 + ], + "type": "text", + "content": "9: calculate the task loss " + }, + { + "bbox": [ + 53, + 241, + 287, + 263 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{task}}" + }, + { + "bbox": [ + 53, + 241, + 287, + 263 + ], + "type": "text", + "content": " (Eq. 4 or Eq. 5) and update the total loss " + }, + { + "bbox": [ + 53, + 241, + 287, + 263 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{total}} = \\mathcal{L}_{\\mathrm{total}} + \\mathcal{L}_{\\mathrm{task}}" + }, + { + "bbox": [ + 53, + 241, + 287, + 263 + ], + "type": "text", + "content": ";" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 50, + 264, + 181, + 274 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 50, + 264, + 181, + 274 + ], + "spans": [ + { + "bbox": [ + 50, + 264, + 181, + 274 + ], + "type": "text", + "content": "10: optimize for the total loss " + }, + { + "bbox": [ + 50, + 264, + 181, + 274 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{total}}" + } + ] + } + ], + "index": 10 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "spans": [ + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "type": "text", + "content": "Reward. Upon taking action " + }, + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "type": "inline_equation", + "content": "a_{t+1}" + }, + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "type": "text", + "content": ", the system receives reward " + }, + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "type": "inline_equation", + "content": "r_{t+1}" + }, + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "type": "text", + "content": " and transitions into the next state " + }, + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "type": "inline_equation", + "content": "s_{t+1}" + }, + { + "bbox": [ + 47, + 300, + 287, + 348 + ], + "type": "text", + "content": ". To achieve high task network performance, we consider the following as reward," + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 63, + 359, + 287, + 388 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 63, + 359, + 287, + 388 + ], + "spans": [ + { + "bbox": [ + 63, + 359, + 287, + 388 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} r _ {t} = 0, t \\in \\{1, \\dots , T - 1 \\}, \\\\ r _ {T} ^ {\\mathrm {M V C N N}} = \\mathbb {1} (\\hat {\\boldsymbol {y}} = \\boldsymbol {y}), r _ {T} ^ {\\mathrm {M V D e t}} = \\operatorname {M O D A} (\\hat {\\boldsymbol {y}}, \\boldsymbol {y}), \\tag {7} \\\\ \\end{array}", + "image_path": "6511e210646fb82369eeed83c85028a5fde413b1d365d3ea3954b79e740571ee.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 399, + 287, + 447 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 399, + 287, + 447 + ], + "spans": [ + { + "bbox": [ + 47, + 399, + 287, + 447 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 399, + 287, + 447 + ], + "type": "inline_equation", + "content": "\\mathbb{1}(\\cdot)" + }, + { + "bbox": [ + 47, + 399, + 287, + 447 + ], + "type": "text", + "content": " denotes the binary indicator function, MODA " + }, + { + "bbox": [ + 47, + 399, + 287, + 447 + ], + "type": "inline_equation", + "content": "(\\cdot ,\\cdot)" + }, + { + "bbox": [ + 47, + 399, + 287, + 447 + ], + "type": "text", + "content": " is the evaluation metric for multi-view detection [21]. We also experiment with other reward designs in Section 5.4." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 47, + 457, + 177, + 468 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 457, + 177, + 468 + ], + "spans": [ + { + "bbox": [ + 47, + 457, + 177, + 468 + ], + "type": "text", + "content": "4.2. MVSelect Architecture" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "spans": [ + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "content": "We design MVSelect architecture " + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "inline_equation", + "content": "d(\\cdot)" + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "content": " with two branches. The first branch expands the camera selection result " + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "inline_equation", + "content": "s_t^{\\mathrm{cam}} \\in \\mathbb{R}^N" + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "content": " into " + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "content": "-dimensional learnable camera embeddings, and then sums over the selected embeddings to formulate a hidden vector. The second branch converts the observation " + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "inline_equation", + "content": "s_t^{\\mathrm{obs}} \\in \\mathbb{R}^D" + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "content": " into another hidden vector. By combining the two hidden vectors, the controller network outputs the action-value " + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "inline_equation", + "content": "Q(s,a)" + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "content": ", which measures the expected cumulative rewards for taking an action " + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "content": " in a given state " + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "inline_equation", + "content": "s" + }, + { + "bbox": [ + 47, + 475, + 287, + 596 + ], + "type": "text", + "content": ". See Supplementary Materials for figure illustrations." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 59, + 597, + 271, + 609 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 597, + 271, + 609 + ], + "spans": [ + { + "bbox": [ + 59, + 597, + 271, + 609 + ], + "type": "text", + "content": "During testing, MVSelect outputs the next action as," + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 111, + 620, + 221, + 639 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 111, + 620, + 221, + 639 + ], + "spans": [ + { + "bbox": [ + 111, + 620, + 221, + 639 + ], + "type": "interline_equation", + "content": "a _ {t + 1} = \\underset {a} {\\arg \\max } Q \\left(s _ {t}, a\\right),", + "image_path": "bd0fecf0564387fc66f90db6eb2dc1bebd22140d5516a89f1488398de711c02b.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 47, + 648, + 255, + 660 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 648, + 255, + 660 + ], + "spans": [ + { + "bbox": [ + 47, + 648, + 255, + 660 + ], + "type": "text", + "content": "which maximizes the expected cumulative rewards." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 47, + 670, + 149, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 149, + 682 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 149, + 682 + ], + "type": "text", + "content": "4.3. Training Scheme" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "We adopt Q-learning [38] for training MVSelect. Specifically, action-value function " + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "inline_equation", + "content": "Q(\\cdot ,\\cdot)" + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": " should estimate the cu" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 306, + 99, + 543, + 110 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 99, + 543, + 110 + ], + "spans": [ + { + "bbox": [ + 306, + 99, + 543, + 110 + ], + "type": "text", + "content": "mulative future rewards after taking action " + }, + { + "bbox": [ + 306, + 99, + 543, + 110 + ], + "type": "inline_equation", + "content": "a_{t+1}" + }, + { + "bbox": [ + 306, + 99, + 543, + 110 + ], + "type": "text", + "content": " at state " + }, + { + "bbox": [ + 306, + 99, + 543, + 110 + ], + "type": "inline_equation", + "content": "s_t" + }, + { + "bbox": [ + 306, + 99, + 543, + 110 + ], + "type": "text", + "content": "," + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 346, + 120, + 505, + 154 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 346, + 120, + 505, + 154 + ], + "spans": [ + { + "bbox": [ + 346, + 120, + 505, + 154 + ], + "type": "interline_equation", + "content": "Q \\left(s _ {t}, a _ {t + 1}\\right) = \\mathbb {E} \\left(\\sum_ {\\tau = t + 1} ^ {T} \\gamma^ {\\tau - t - 1} r _ {\\tau}\\right),", + "image_path": "c35f6dc6ef34b204439024944ba6d412a4026c2fc53d6e202dc859ebfe2db441.jpg" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 305, + 163, + 545, + 200 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 163, + 545, + 200 + ], + "spans": [ + { + "bbox": [ + 305, + 163, + 545, + 200 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 163, + 545, + 200 + ], + "type": "inline_equation", + "content": "\\mathbb{E}(\\cdot)" + }, + { + "bbox": [ + 305, + 163, + 545, + 200 + ], + "type": "text", + "content": " denotes the expectation, and " + }, + { + "bbox": [ + 305, + 163, + 545, + 200 + ], + "type": "inline_equation", + "content": "\\gamma \\in [0,1]" + }, + { + "bbox": [ + 305, + 163, + 545, + 200 + ], + "type": "text", + "content": " denotes the discount factor. We take the temporal difference (TD) [38] target as supervision for the action value," + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 315, + 209, + 545, + 242 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 315, + 209, + 545, + 242 + ], + "spans": [ + { + "bbox": [ + 315, + 209, + 545, + 242 + ], + "type": "interline_equation", + "content": "q _ {t} = \\left\\{ \\begin{array}{l l} r _ {t + 1} + \\gamma \\max _ {a} Q \\left(s _ {t + 1}, a\\right), & \\text {i f} t < T - 1 \\\\ r _ {T}, & \\text {o t h e r w i s e} \\end{array} , \\right. \\tag {8}", + "image_path": "250da42d099525e6846e0104d983119354b38bb0c21e6b51cb52b8900a38eb96.jpg" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 306, + 251, + 484, + 262 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 251, + 484, + 262 + ], + "spans": [ + { + "bbox": [ + 306, + 251, + 484, + 262 + ], + "type": "text", + "content": "and calculate the loss using the " + }, + { + "bbox": [ + 306, + 251, + 484, + 262 + ], + "type": "inline_equation", + "content": "L_{2}" + }, + { + "bbox": [ + 306, + 251, + 484, + 262 + ], + "type": "text", + "content": " distance," + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 351, + 271, + 545, + 304 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 351, + 271, + 545, + 304 + ], + "spans": [ + { + "bbox": [ + 351, + 271, + 545, + 304 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {R L}} = \\sum_ {t = 1} ^ {T - 1} \\mathcal {L} _ {\\mathrm {M S E}} \\left(Q \\left(s _ {t}, a _ {t + 1}\\right), q _ {t}\\right), \\tag {9}", + "image_path": "670619e70b16da956427cfdd6f94696a2408a297ad511f7b0a386e9e66ca5c6a.jpg" + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 305, + 314, + 545, + 337 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 314, + 545, + 337 + ], + "spans": [ + { + "bbox": [ + 305, + 314, + 545, + 337 + ], + "type": "text", + "content": "where the next action " + }, + { + "bbox": [ + 305, + 314, + 545, + 337 + ], + "type": "inline_equation", + "content": "a_{t + 1}" + }, + { + "bbox": [ + 305, + 314, + 545, + 337 + ], + "type": "text", + "content": " is chosen using " + }, + { + "bbox": [ + 305, + 314, + 545, + 337 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 305, + 314, + 545, + 337 + ], + "type": "text", + "content": "-greedy for exploration-exploitation trade offs." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 305, + 338, + 545, + 386 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 338, + 545, + 386 + ], + "spans": [ + { + "bbox": [ + 305, + 338, + 545, + 386 + ], + "type": "text", + "content": "In joint training, the task network takes supervision from " + }, + { + "bbox": [ + 305, + 338, + 545, + 386 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{task}}" + }, + { + "bbox": [ + 305, + 338, + 545, + 386 + ], + "type": "text", + "content": " (Eq. 4 and Eq. 5), and the selection module takes supervision from " + }, + { + "bbox": [ + 305, + 338, + 545, + 386 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{RL}}" + }, + { + "bbox": [ + 305, + 338, + 545, + 386 + ], + "type": "text", + "content": " (Eq. 9). A step-by-step demonstration of this process can be found in Algorithm 1." + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 306, + 398, + 387, + 411 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 398, + 387, + 411 + ], + "spans": [ + { + "bbox": [ + 306, + 398, + 387, + 411 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 306, + 418, + 424, + 430 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 418, + 424, + 430 + ], + "spans": [ + { + "bbox": [ + 306, + 418, + 424, + 430 + ], + "type": "text", + "content": "5.1. Experiment Settings" + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 305, + 437, + 545, + 509 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 437, + 545, + 509 + ], + "spans": [ + { + "bbox": [ + 305, + 437, + 545, + 509 + ], + "type": "text", + "content": "Datasets. For multi-view classification, we use synthetic dataset ModelNet40 [44] under two different camera layouts (12 views and 20 views) and real-world dataset ScanObjectNN (12 views) [39]. For multi-view detection, we use real-world dataset Wildtrack (7 views) [6] and synthetic dataset MultiviewX (6 views) [17]." + } + ] + } + ], + "index": 32 + }, + { + "bbox": [ + 305, + 510, + 545, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 510, + 545, + 569 + ], + "spans": [ + { + "bbox": [ + 305, + 510, + 545, + 569 + ], + "type": "text", + "content": "Evaluation metrics. For multi-view classification, we report instance-averaged accuracy. Regarding multi-view detection, we report multi-object detection accuracy (MODA), which is calculated as " + }, + { + "bbox": [ + 305, + 510, + 545, + 569 + ], + "type": "inline_equation", + "content": "1 - \\frac{\\mathrm{FP} + \\mathrm{FN}}{\\mathrm{GT}}" + }, + { + "bbox": [ + 305, + 510, + 545, + 569 + ], + "type": "text", + "content": " [21]. All metrics are reported in percentages." + } + ] + } + ], + "index": 33 + }, + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "spans": [ + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "type": "text", + "content": "Implementation details. For multi-view classification, we input images of size " + }, + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "type": "inline_equation", + "content": "224 \\times 224" + }, + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "type": "text", + "content": " to the MVCNN model. For multi-view detection, we use a resolution of " + }, + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "type": "inline_equation", + "content": "720 \\times 1280" + }, + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "type": "text", + "content": " with view-coherent data augmentation [16], and downsample the BEV grid by a factor of 4. In terms of architecture, we use ResNet-18 [15] as feature extractor " + }, + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "type": "inline_equation", + "content": "f(\\cdot)" + }, + { + "bbox": [ + 305, + 570, + 545, + 641 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 34 + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": "We train all networks for 10 epochs using the Adam optimizer [22]. We use learning rates of " + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "inline_equation", + "content": "5 \\times 10^{-5}" + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "inline_equation", + "content": "5 \\times 10^{-4}" + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": ", with batch sizes of 8 and 1 for MVCNN and MVDet, respectively. The MVSelect module is trained using a learning rate of " + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "inline_equation", + "content": "1 \\times 10^{-4}" + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": ". For joint training, we decrease the learning rate for the task network to " + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "inline_equation", + "content": "1/5" + }, + { + "bbox": [ + 304, + 642, + 545, + 713 + ], + "type": "text", + "content": " of its original value." + } + ] + } + ], + "index": 35 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20139" + } + ] + } + ], + "index": 36 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 102, + 312, + 220 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 547, + 95 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 547, + 95 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 547, + 95 + ], + "type": "text", + "content": "Table 1. Performance comparison with state-of-the-art methods. Results are averaged from 5 runs. * indicates that the camera poses are dynamically chosen and do not follow a pre-defined layout. † indicates our implementation." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 102, + 312, + 220 + ], + "lines": [ + { + "bbox": [ + 50, + 102, + 312, + 220 + ], + "spans": [ + { + "bbox": [ + 50, + 102, + 312, + 220 + ], + "type": "table", + "html": "
view selection (T=2)ModelNet40ScanObjNN
12 views20 views
MVCNN [37]N/A90.192.0-
GVCNN [11]N/A92.6--
MHBN [47]N/A93.4--
RotationNet [20]N/A-94.7-
RelationNet [46]N/A94.397.3-
ViewGCN [42]N/A-97.6-
MVCNN†N/A94.596.586.1
PointNet [31] + ViewGCNMVTN* (T=12 or 20) [14]93.893.592.6
MVCNN†SEE++† [3]79.270.375.5
MVCNN†Potthast and Sukhatme† [29]76.566.272.1
MVCNN†MVSelect88.279.680.0
MVCNN† (joint training)MVSelect94.394.484.1
", + "image_path": "c83b0d1c3eeba163fad5d94875e3e4323a54a8aaea8f9fa8bcdbbe1f7c0c5f4d.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 321, + 102, + 545, + 220 + ], + "blocks": [ + { + "bbox": [ + 321, + 102, + 545, + 220 + ], + "lines": [ + { + "bbox": [ + 321, + 102, + 545, + 220 + ], + "spans": [ + { + "bbox": [ + 321, + 102, + 545, + 220 + ], + "type": "table", + "html": "
view selection (T=3)WildtrackMultiviewX
RCNN & cluster [45]N/A11.318.7
POM-CNN [13]N/A23.2-
DeepMCD [7]N/A67.870
Deep-Occlusion [2]N/A74.175.2
MVDet [17]N/A88.283.9
SHOT [36]N/A90.288.3
MVDetTr [16]N/A91.593.7
MVDet†N/A90.093.0
MVDet†SEE++[3]76.177.8
MVDet†Potthast and Sukhatme†[29]78.378.0
MVDet†max FoV†[35]78.073.9
MVDet†MVSelect80.078.7
MVDet† (joint training)MVSelect88.688.1
", + "image_path": "779c6add7c2a7fa249ef9f6a9ca9f9c89a8fb9092d5f93a7cbc44933ce9584fd.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 52, + 230, + 272, + 305 + ], + "blocks": [ + { + "bbox": [ + 52, + 230, + 272, + 305 + ], + "lines": [ + { + "bbox": [ + 52, + 230, + 272, + 305 + ], + "spans": [ + { + "bbox": [ + 52, + 230, + 272, + 305 + ], + "type": "image", + "image_path": "86609035ec67b17c510c3b21899bbc4d4517e6aad6c36fc1d4b966908203214e.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 149, + 312, + 443, + 324 + ], + "lines": [ + { + "bbox": [ + 149, + 312, + 443, + 324 + ], + "spans": [ + { + "bbox": [ + 149, + 312, + 443, + 324 + ], + "type": "text", + "content": "Figure 6. Example of selected views on ModelNet40 (left) and Wildtrack (right)." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 282, + 230, + 542, + 305 + ], + "blocks": [ + { + "bbox": [ + 282, + 230, + 542, + 305 + ], + "lines": [ + { + "bbox": [ + 282, + 230, + 542, + 305 + ], + "spans": [ + { + "bbox": [ + 282, + 230, + 542, + 305 + ], + "type": "image", + "image_path": "c1351cf7209250e17cca97a493e056134a6bedf5961c00a0b70566d2cbe2f206.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 346, + 287, + 405 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 346, + 287, + 405 + ], + "spans": [ + { + "bbox": [ + 46, + 346, + 287, + 405 + ], + "type": "text", + "content": "Regarding hyperparameters, we set the future reward discount factor " + }, + { + "bbox": [ + 46, + 346, + 287, + 405 + ], + "type": "inline_equation", + "content": "\\gamma = 0.99" + }, + { + "bbox": [ + 46, + 346, + 287, + 405 + ], + "type": "text", + "content": ", and the exploration ratio " + }, + { + "bbox": [ + 46, + 346, + 287, + 405 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 46, + 346, + 287, + 405 + ], + "type": "text", + "content": " to gradually decrease from 0.95 to 0.05 during training. All experiments are conducted on a single RTX-3090 GPU and averaged across 5 repetitive runs." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 407, + 287, + 597 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 407, + 287, + 597 + ], + "spans": [ + { + "bbox": [ + 46, + 407, + 287, + 597 + ], + "type": "text", + "content": "Experimental setups. First, we fix the task network. We compare with state-of-the-art methods including 1) NBV policy with depth-sensing enabled point-based occlusion estimation [3], 2) NBV policy with depth-sensing enabled voxel-based probabilistic representation [29], and 3) NBV policy to maximize field-of-view (FoV) coverage [35] (only applicable to multi-view detection). We also report two baselines: 1) random selection, 2) the best policy on the validation set; and two oracles: for a certain initial view, 1) choosing the overall best-performing camera for all instances in the dataset (dataset-level oracle) and 2) choosing specifically for each instance (instance-level oracle). For the two oracles, the former reflects the upper bound of performance achievable by human-designed heuristics, and the latter represents the theoretical performance ceiling when keeping the task network fixed." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "spans": [ + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "type": "text", + "content": "Second, we jointly train the proposed view selection module with the task networks. For this experiment, our goal is to achieve the highest possible performance using " + }, + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "type": "text", + "content": " views. If not specified, we use a total of " + }, + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "type": "inline_equation", + "content": "T = 2" + }, + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "type": "text", + "content": " views for multi-view classification and " + }, + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "type": "inline_equation", + "content": "T = 3" + }, + { + "bbox": [ + 46, + 599, + 288, + 658 + ], + "type": "text", + "content": " views for detection." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 670, + 181, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 181, + 682 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 181, + 682 + ], + "type": "text", + "content": "5.2. Evaluation of MVSelect" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "content": "For multi-view classification, as in Table 1, MVSelect with fixed multi-view classification network achieves competi" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "spans": [ + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "type": "text", + "content": "tive performance compared to other state-of-the-art view selection methods. When compared with baselines and oracles in Table 2, the proposed view selection module, can choose the views effectively. Compared to dataset-level oracles (same policy for all instances with the same initial camera), MVSelect also turns out to be advantageous by " + }, + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "type": "inline_equation", + "content": "3.0\\%" + }, + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "type": "inline_equation", + "content": "9.7\\%" + }, + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "type": "inline_equation", + "content": "1.5\\%" + }, + { + "bbox": [ + 304, + 346, + 545, + 464 + ], + "type": "text", + "content": " across the two settings. This verifies that MVSelect can take the target object into consideration (see Fig. 2) and select different cameras for different instances under the same initial camera." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "spans": [ + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "text", + "content": "When joint training MVCNN with MVSelect, we witness large improvements. In fact, on two settings, the results are only " + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "inline_equation", + "content": "0.2\\%" + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "inline_equation", + "content": "2.1\\%" + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "inline_equation", + "content": "2.0\\%" + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "text", + "content": " behind compared to the full " + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 468, + 546, + 564 + ], + "type": "text", + "content": "-view system. Overall, we believe that MVSelect and its joint training capabilities enable us to consider only 2 views without major performance drawbacks. We demonstrate an example of the selected views in Fig. 6, and the MVSelect policy in Fig. 7." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 567, + 545, + 663 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 567, + 545, + 663 + ], + "spans": [ + { + "bbox": [ + 304, + 567, + 545, + 663 + ], + "type": "text", + "content": "For multi-view detection, MVSelect achieves competitive performance compared to existing NBV methods, some of them even require additional depth sensing (Table 1). Although the raw improvements are not as substantial as those in multi-view classification, they are statistically highly significant " + }, + { + "bbox": [ + 304, + 567, + 545, + 663 + ], + "type": "inline_equation", + "content": "(p" + }, + { + "bbox": [ + 304, + 567, + 545, + 663 + ], + "type": "text", + "content": "-value " + }, + { + "bbox": [ + 304, + 567, + 545, + 663 + ], + "type": "inline_equation", + "content": "< 0.001)" + }, + { + "bbox": [ + 304, + 567, + 545, + 663 + ], + "type": "text", + "content": ". This shows human designed heuristics like minimal occlusion or maximum FoV coverage cannot guarantee the best detection results." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": "When compared to baselines and oracles, MVSelect also shows to be competitive (see Table 2). Specifically, we observe that the instance-level oracle remains relatively low compared to that of multi-view classification tasks. This is" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20140" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 91, + 317, + 203 + ], + "blocks": [ + { + "bbox": [ + 89, + 71, + 503, + 81 + ], + "lines": [ + { + "bbox": [ + 89, + 71, + 503, + 81 + ], + "spans": [ + { + "bbox": [ + 89, + 71, + 503, + 81 + ], + "type": "text", + "content": "Table 2. Comparison with view selection baselines and oracles on multi-view classification and detection datasets." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 91, + 317, + 203 + ], + "lines": [ + { + "bbox": [ + 50, + 91, + 317, + 203 + ], + "spans": [ + { + "bbox": [ + 50, + 91, + 317, + 203 + ], + "type": "table", + "html": "
view selection (T=2)ModelNet40ScanObjNN
12 views20 views
N/A: all N views94.596.586.1
dataset-lvl oracle85.2 ± 1.469.9 ± 1.978.5 ± 1.2
instance-lvl oracle96.5 ± 0.498.1 ± 1.993.4 ± 0.6
random selection71.5 ± 2.548.1 ± 3.174.2 ± 3.5
validation best policy85.1 ± 0.869.5 ± 1.077.5 ± 1.1
MVSelect88.2 ± 0.479.6 ± 1.880.0 ± 0.8
MVSelect + joint training94.3 ± 0.294.4 ± 0.284.1 ± 0.2
", + "image_path": "f08efe14482e45dd62db44d1d414bcfdf79f3fbe74888298166e2d7769a96f52.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 327, + 97, + 544, + 198 + ], + "blocks": [ + { + "bbox": [ + 327, + 97, + 544, + 198 + ], + "lines": [ + { + "bbox": [ + 327, + 97, + 544, + 198 + ], + "spans": [ + { + "bbox": [ + 327, + 97, + 544, + 198 + ], + "type": "table", + "html": "
view selection (T=3)WildtrackMultiviewX
N/A: all N views90.093.0
dataset-lvl oracle82.5 ± 0.480.2 ± 0.3
instance-lvl oracle87.4 ± 0.482.3 ± 0.8
random selection74.9 ± 1.376.2 ± 1.4
validation best policy79.5 ± 1.178.0 ± 0.4
MVSelect80.0 ± 0.878.7 ± 0.5
MVSelect + joint training88.6 ± 0.288.1 ± 0.2
", + "image_path": "9623e70d806015965f101cf757e0bf95a2b37311a06dad52bb2dc2fbde3f53fe.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 50, + 219, + 193, + 357 + ], + "blocks": [ + { + "bbox": [ + 50, + 219, + 193, + 357 + ], + "lines": [ + { + "bbox": [ + 50, + 219, + 193, + 357 + ], + "spans": [ + { + "bbox": [ + 50, + 219, + 193, + 357 + ], + "type": "image", + "image_path": "fb5a7651b95a4fb120ccd9bc4d96570513386356d4e288aba040079d2120c5fb.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 78, + 362, + 164, + 372 + ], + "lines": [ + { + "bbox": [ + 78, + 362, + 164, + 372 + ], + "spans": [ + { + "bbox": [ + 78, + 362, + 164, + 372 + ], + "type": "text", + "content": "(a) Classification accuracy" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 381, + 349, + 415 + ], + "lines": [ + { + "bbox": [ + 46, + 381, + 349, + 415 + ], + "spans": [ + { + "bbox": [ + 46, + 381, + 349, + 415 + ], + "type": "text", + "content": "Figure 7. Multi-view classification with " + }, + { + "bbox": [ + 46, + 381, + 349, + 415 + ], + "type": "inline_equation", + "content": "T = 2" + }, + { + "bbox": [ + 46, + 381, + 349, + 415 + ], + "type": "text", + "content": " views on the 12-view setup of ModelNet40. The task network is fixed once trained. Left: test set accuracy of using two views. Right: MVSelect policy for the test set." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 205, + 219, + 347, + 357 + ], + "blocks": [ + { + "bbox": [ + 205, + 219, + 347, + 357 + ], + "lines": [ + { + "bbox": [ + 205, + 219, + 347, + 357 + ], + "spans": [ + { + "bbox": [ + 205, + 219, + 347, + 357 + ], + "type": "image", + "image_path": "a9f2da4b0ea3c10a150d3744bf47b0e65fba535ede4d0f0851a6deb470a767a9.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 241, + 361, + 309, + 372 + ], + "lines": [ + { + "bbox": [ + 241, + 361, + 309, + 372 + ], + "spans": [ + { + "bbox": [ + 241, + 361, + 309, + 372 + ], + "type": "text", + "content": "(b) MVSelect policy" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 360, + 226, + 542, + 319 + ], + "blocks": [ + { + "bbox": [ + 390, + 214, + 510, + 224 + ], + "lines": [ + { + "bbox": [ + 390, + 214, + 510, + 224 + ], + "spans": [ + { + "bbox": [ + 390, + 214, + 510, + 224 + ], + "type": "text", + "content": "Table 3. Computation efficiency." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 360, + 226, + 542, + 319 + ], + "lines": [ + { + "bbox": [ + 360, + 226, + 542, + 319 + ], + "spans": [ + { + "bbox": [ + 360, + 226, + 542, + 319 + ], + "type": "table", + "html": "
viewsFLOPsthroughput (instance/s)
f(·)g(·)d(·)
ModelNet402036.5G20.5kN/A119.6
23.6G20.5k1.1M361.8
1221.9G20.5kN/A196.2
23.6G20.5k530.4k507.9
Wildtrack71.2T19.1GN/A8.4
3511.6G19.1G3.2G16.2
MultiviewX61.0T17.7GN/A9.8
3511.6G17.7G2.9G16.9
", + "image_path": "cad369f0e7290210c2dfc988f43e162afaee3784ca1cfd0523d5f8328db3fdfc.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 360, + 339, + 542, + 420 + ], + "blocks": [ + { + "bbox": [ + 405, + 327, + 493, + 338 + ], + "lines": [ + { + "bbox": [ + 405, + 327, + 493, + 338 + ], + "spans": [ + { + "bbox": [ + 405, + 327, + 493, + 338 + ], + "type": "text", + "content": "Table 4. Ablation study." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 360, + 339, + 542, + 420 + ], + "lines": [ + { + "bbox": [ + 360, + 339, + 542, + 420 + ], + "spans": [ + { + "bbox": [ + 360, + 339, + 542, + 420 + ], + "type": "table", + "html": "
ModelNet40Wildtrack
12 views
MVSelect88.280.0
w/o camera branch88.279.1
w/o feature branch85.079.7
w/ transformer87.078.7
reward=Δ task loss88.080.1
", + "image_path": "64a2afab114da2264ec0153a7d8b72b4a54cf6b769f96801c8bfd599b853a7af.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 441, + 289, + 595 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 441, + 289, + 595 + ], + "spans": [ + { + "bbox": [ + 46, + 441, + 289, + 595 + ], + "type": "text", + "content": "likely due to the target scenarios not being fully captured by any single view, and the multi-view detection network needs multiple views to collaborate with each other for optimal results. Compared to the dataset-level oracles, we find the MVSelect policy lose its edge. In fact, we find that for multi-view detection, MVSelect tends to select the same camera for a given initial view, since it is not aware of the situation outside of the FoV coverage. As a result, it cannot choose cameras based on uncovered areas in different frames. Without this instance-aware advantage, the fixed camera policy learned during training (MVSelect) cannot outperform the dataset-level oracle, whose policy is computed on the test set." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": "Joint training with MVDet once again leads to substantial performance improvements over keeping the task network fixed. In fact, the results even exceed the instance-level oracle for fixed task networks. Using " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "T = 3" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " views, the joint training approach provides competitive results to using all " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " views, and exceeds the reported performance in the original MVDet paper [17]. We present an example of the selected views in the Wildtrack dataset in Fig. 6." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 440, + 418, + 453 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 440, + 418, + 453 + ], + "spans": [ + { + "bbox": [ + 306, + 440, + 418, + 453 + ], + "type": "text", + "content": "5.3. Efficiency Analysis" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "spans": [ + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "text", + "content": "In Table 3, following previous works in efficient inference [19, 24], we detail the computational cost in FLOPs for task networks and MVSelect. Specifically, we find feature extraction " + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "inline_equation", + "content": "f(\\cdot)" + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "text", + "content": " to take up the majority of the computation, while everything else is lighter by at least an order of magnitude. Overall, we verify that using " + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "inline_equation", + "content": "T = 2" + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "text", + "content": " or 3 out of " + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "text", + "content": " views can reduce the computational cost to roughly " + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "inline_equation", + "content": "T / N" + }, + { + "bbox": [ + 304, + 458, + 545, + 542 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 543, + 545, + 615 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 543, + 545, + 615 + ], + "spans": [ + { + "bbox": [ + 304, + 543, + 545, + 615 + ], + "type": "text", + "content": "In terms of inference speed, we find reduction in FLOPs results in monotonically increasing throughputs, ranging from " + }, + { + "bbox": [ + 304, + 543, + 545, + 615 + ], + "type": "inline_equation", + "content": "1.72 \\times" + }, + { + "bbox": [ + 304, + 543, + 545, + 615 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 543, + 545, + 615 + ], + "type": "inline_equation", + "content": "3.03 \\times" + }, + { + "bbox": [ + 304, + 543, + 545, + 615 + ], + "type": "text", + "content": ". Due to factors such as implementation, parallelization, and hardware limitations, actual speedups cannot actually reach the level of computational cost reduction, as suggested by previous study [27]." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 623, + 394, + 635 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 623, + 394, + 635 + ], + "spans": [ + { + "bbox": [ + 306, + 623, + 394, + 635 + ], + "type": "text", + "content": "5.4. Variant Study" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": "Ablation study. Regarding the MVSelect architecture design, Table 4 shows that removing the camera branch and feature branch primarily affects multi-view detection and multi-view classification performance, respectively. This aligns with the policy we learned for the two tasks. For multi-view detection, since the system has no clue about ar" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20141" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 77, + 190, + 210 + ], + "blocks": [ + { + "bbox": [ + 50, + 77, + 190, + 210 + ], + "lines": [ + { + "bbox": [ + 50, + 77, + 190, + 210 + ], + "spans": [ + { + "bbox": [ + 50, + 77, + 190, + 210 + ], + "type": "image", + "image_path": "46b7cc7ab392afd0798d5a74f1cb8018e47e6c693d64ce66068a019859106ad8.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 220, + 349, + 266 + ], + "lines": [ + { + "bbox": [ + 46, + 220, + 349, + 266 + ], + "spans": [ + { + "bbox": [ + 46, + 220, + 349, + 266 + ], + "type": "text", + "content": "Figure 9. System performance under different number of total views " + }, + { + "bbox": [ + 46, + 220, + 349, + 266 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 220, + 349, + 266 + ], + "type": "text", + "content": ". We report classification accuracy and MODA for the two tasks, respectively (same for Fig. 10 and Table. 4). Circle and triangle markers indicate whether the task network is fixed or not, respectively. Dotted lines represent oracle performance (not achievable)." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 203, + 76, + 345, + 210 + ], + "blocks": [ + { + "bbox": [ + 203, + 76, + 345, + 210 + ], + "lines": [ + { + "bbox": [ + 203, + 76, + 345, + 210 + ], + "spans": [ + { + "bbox": [ + 203, + 76, + 345, + 210 + ], + "type": "image", + "image_path": "15f43b5dc456ea37de0697ff64d73ba717e477ec8e9a4e925ae24aecaece104d.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 356, + 220, + 534, + 265 + ], + "lines": [ + { + "bbox": [ + 356, + 220, + 534, + 265 + ], + "spans": [ + { + "bbox": [ + 356, + 220, + 534, + 265 + ], + "type": "text", + "content": "Figure 10. System evaluation under different settings. Except for the random pose* setting (where MVSelect variants are re-trained), all models are trained on the default setting." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 360, + 78, + 531, + 210 + ], + "blocks": [ + { + "bbox": [ + 360, + 78, + 531, + 210 + ], + "lines": [ + { + "bbox": [ + 360, + 78, + 531, + 210 + ], + "spans": [ + { + "bbox": [ + 360, + 78, + 531, + 210 + ], + "type": "image", + "image_path": "e1d47565d23c0e4be800f60083b5daa0138035ff3928733c635ed0bb1f03a6b4.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 45, + 285, + 287, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 285, + 287, + 357 + ], + "spans": [ + { + "bbox": [ + 45, + 285, + 287, + 357 + ], + "type": "text", + "content": "eas outside camera FoVs, the camera branch plays a more important role for encoding prior knowledge of the scene layout. For multi-view classification, however, target objects are fully observable, and MVSelect can make different decisions for each instance. Thus, the feature branch is more important, as it enables per-instance decision making." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 360, + 287, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 360, + 287, + 396 + ], + "spans": [ + { + "bbox": [ + 46, + 360, + 287, + 396 + ], + "type": "text", + "content": "When changing the MVSelect network architecture into transformer [40], we find that more parameters do not translate into better performance." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 398, + 287, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 398, + 287, + 434 + ], + "spans": [ + { + "bbox": [ + 46, + 398, + 287, + 434 + ], + "type": "text", + "content": "Another option for the reward is the change in task loss. In our variant study, this reward design does not show any significant advantages over the current design." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "content": "Influence of total view count. The performance curves in Fig. 9 demonstrate that the joint training variant achieves competitive performance with as few as " + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "inline_equation", + "content": "T = 2" + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "content": " views for multi-view classification and " + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "inline_equation", + "content": "T = 3" + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "content": " views for multi-view detection, beyond which point performance plateaus. By contrast, learning MVSelect for fixed task networks shows a less steep curve. The performance increases up to a total of " + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "inline_equation", + "content": "T = 5" + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "content": " views, at which point the MVSelect policy performs comparably to the full " + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 436, + 287, + 544 + ], + "type": "text", + "content": "-view system." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 546, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 546, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 546, + 287, + 713 + ], + "type": "text", + "content": "Camera layout optimization. Determining the optimal camera locations is crucial for setting up an effective multiview system. In Fig.7, we observe that not all cameras are equally useful according to the MVSelect policy. To address this, we allocate a validation partition of the data to identify the more useful camera views and then disable half of the " + }, + { + "bbox": [ + 46, + 546, + 287, + 713 + ], + "type": "inline_equation", + "content": "N = 12" + }, + { + "bbox": [ + 46, + 546, + 287, + 713 + ], + "type": "text", + "content": " cameras that are not frequently utilized. In testing, we find that some cameras are not as useful (\"policy shut-off\" in Fig. 10) and the proposed method can generalize to test-time disturbances including malfunctioning cameras (\"random shut-off\" in Fig.10). Although it is necessary to set up all " + }, + { + "bbox": [ + 46, + 546, + 287, + 713 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 546, + 287, + 713 + ], + "type": "text", + "content": " cameras for the analysis, optimizing the multiview camera layout can be a crucial step towards achieving optimal performance, and merits further investigation." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 285, + 545, + 453 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 285, + 545, + 453 + ], + "spans": [ + { + "bbox": [ + 304, + 285, + 545, + 453 + ], + "type": "text", + "content": "Random object pose. In real-world applications of multi-view systems, such as those found in iPhones and Tesla, the cameras may remain fixed in their relative positions while the entire system is in motion. To simulate this scenario in our experiments, we introduce the random object pose setting (Fig. 10) and re-train MVSelect. While there is no exact object pose as supervision, the reinforcement learning approach is able to roughly infer the relative poses between the object and the multi-view system, resulting in improved performance compared to random selection and dataset-level oracle (which is arguably inappropriate for this setup). In the future, we plan to estimate camera poses with respect to the object or the environment as an auxiliary supervision for moving setups." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 471, + 378, + 483 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 471, + 378, + 483 + ], + "spans": [ + { + "bbox": [ + 306, + 471, + 378, + 483 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 494, + 545, + 648 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 494, + 545, + 648 + ], + "spans": [ + { + "bbox": [ + 304, + 494, + 545, + 648 + ], + "type": "text", + "content": "In conclusion, this paper proposes selective view pipelining, an efficient approach for multi-view understanding by limiting the number of views. To this end, a camera view selection module, MVSelect, is proposed along with a reinforcement learning based training scheme that can learn from the non-differentiable selection process. When jointly trained with the task network, the proposed approach demonstrates competitive performance on multi-view classification and detection tasks at fractions of the computational cost. Overall, the proposed efficient approach provides an alternative to reducing image resolution and using lighter networks, and paves ways for future multi-view camera layout optimization." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 667, + 403, + 681 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 667, + 403, + 681 + ], + "spans": [ + { + "bbox": [ + 306, + 667, + 403, + 681 + ], + "type": "text", + "content": "Acknowledgement" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "This work was supported by the ARC Discovery Project (DP210102801)." + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20142" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 714 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "type": "text", + "content": "[1] John Aloimonos, Isaac Weiss, and Amit Bandyopadhyay. 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Recent studies identify the adversarial transferability across various models, i.e., the cross-model attack ability of adversarial samples. To enhance such adversarial transferability, existing input transformation-based methods diversify input data with transformation augmentation. However, their effectiveness is limited by the finite number of available transformations. In our study, we introduce a novel approach named Learning to Transform (L2T). L2T increases the diversity of transformed images by selecting the optimal combination of operations from a pool of candidates, consequently improving adversarial transferability. We conceptualize the selection of optimal transformation combinations as a trajectory optimization problem and employ a reinforcement learning strategy to effectively solve the problem. Comprehensive experiments on the ImageNet dataset, as well as practical tests with Google Vision and GPT-4V, reveal that L2T surpasses current methodologies in enhancing adversarial transferability, thereby confirming its effectiveness and practical significance. The code is available at https://github.com/ZhangAIP1/TransferAttack.", + "bbox": [ + 75, + 300, + 473, + 632 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 661, + 209, + 676 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Neural networks have been adopted as the building block for various real-world applications, such as face detection [37, 41], autonomous driving [12, 25], and medical diagnosis [1, 35]. However, neural networks are vulnerable to adversarial examples, which contain human imperceptible adversarial perturbations on the benign input. This issue is increasingly concerning researchers, as it is essential for ensuring the trustworthy use of neural networks [3, 19, 65, 66].", + "bbox": [ + 75, + 686, + 468, + 806 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In real-world scenarios of adversarial attacks, the target model is usually inaccessible. To attack these inaccessible models, many studies instead rely on surrogate models", + "bbox": [ + 75, + 808, + 470, + 853 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/3fc284a7eda7f1f3922cef808f6d2f611855a743022251725b1e4e94c7d12c8c.jpg", + "image_caption": [ + "Figure 1. For input transformation-based attacks, most works design a fixed transformation and use it to craft the adversarial perturbation. The learning-based methods preliminarily predict augmentation strategies for current images for better adversarial transferability. These methods cannot respond to the distribution shifts between benign images and adversarial examples. We propose Learning to Transform (L2T), which uses the dynamic of the optimal transformation in each iteration to further boost the adversarial transferability." + ], + "image_footnote": [], + "bbox": [ + 501, + 267, + 893, + 532 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "to generate adversarial examples [7, 57] and use generated samples to mislead the target model. This cross-model attack ability of samples generated on the surrogate models is called \"adversarial transferability.\" Numerous research studies are dedicated to enhancing adversarial transferability, which can be classified into four categories: gradient-based methods [7, 26, 44, 47], input transformation-based methods [8, 26, 46, 57], architecture-based methods [23, 52], and ensemble-based methods [28, 60]. Among these attack methodologies, input transformation-based methods gain much popularity because of their plug-n-play advantage, which can be seamlessly integrated into other attack techniques [7, 44]. However, we discover that existing input", + "bbox": [ + 496, + 703, + 895, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal contribution", + "bbox": [ + 94, + 862, + 202, + 875 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "†Project lead", + "bbox": [ + 96, + 875, + 166, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "$\\ddagger$ Corresponding author", + "bbox": [ + 96, + 887, + 218, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "24273", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "transformation-based methods adopt the same transformation when crafting adversarial examples, limiting the flexibility of transformation operations. We hypothesize that we should select the optimal transformation dynamically in each iteration to enhance the adversarial transferability.", + "bbox": [ + 75, + 90, + 470, + 167 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "As shown in Fig. 1, prior input transformation-based methods often revolve around designing fixed augmentation strategies like resizing inputs [57], block masking [10], or mix-up [46]. A more dynamic approach is presented by [63], advocating the precomputation of various sequences of augmentation strategies to apply to each iteration to enhance the attack performance. Complementing this, Wu et al. [53] proposes the use of generative models for image augmentation to boost the adversarial transferability. Some studies go further, combining multiple augmentation strategies to amplify input diversity to improve the performance. For example, Yuan et al. [64] introduces a neural network that generates a prediction of the optimal transformation strategy and applies the strategy to improve performance. A further improvement is hindered by the limited number of transformations.", + "bbox": [ + 75, + 169, + 470, + 396 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To fully utilize the limited number of transformations, a natural idea is to use a combination of operations. However, it is not always efficient to combine different transformations together for attack, as reported in [50]. We expect to find an optimal combination of transformations to achieve a tradeoff between operation diversity and adversarial transferability. Nonetheless, the enormity of the search space presents a significant challenge, impeding the identification of the most efficacious combination of transformations during an attack for optimal adversarial transferability. To surmount this hurdle, we conceptualize the search process of the optimal combination of transformations as a problem of optimal trajectory search. Each node within this trajectory represents an individual transformation, and each directed edge means a transfer of the optimal transformation from the current step to the next step. To effectively obtain the optimal trajectory in such a large search space, we design a reinforcement learning-based approach, capitalizing on its demonstrated efficacy in navigating expansive search domains.", + "bbox": [ + 75, + 398, + 470, + 686 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this paper, we introduce a novel framework called Learning to Transform (L2T) to improve the adversarial transferability of generated adversarial examples. L2T dynamically learns and applies the optimal input transformation in each iteration. Instead of exhaustively enumerating all possible input transformation methods, we employ a reinforcement learning-based approach to reduce the search space and better utilize the transformations to improve the diversity. In each iteration of the adversarial attack, we sample a subset of transformations and apply them to the adversarial examples. Subsequently, we update the sampling probabilities by conducting gradient ascent to maximize the loss. Our method effectively learns the dynamics of optimal transformations in attacks, leading to a significant enhancement in", + "bbox": [ + 75, + 688, + 470, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "adversarial transferability. Additionally, compared to other learn-based adversarial attack methods, our approach is more efficient for adversarial example generation, as it obviates the need for additional training modules.", + "bbox": [ + 496, + 90, + 890, + 151 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We summarize our contributions as follows,", + "bbox": [ + 517, + 152, + 810, + 166 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We formulate the problem of optimal transformation in adversarial attacks, which studies finding the optimal combination of transformations to increase the input diversities, thus improving the adversarial transferability.", + "- We propose Learning to Transform (L2T) that exploits the optimal transformation in each iteration and dynamically adjusts transformations to boost adversarial transferability.", + "- Extensive experiments on the ImageNet dataset demonstrate that L2T outperforms other baselines. We also validate L2T's superiority in real-world scenarios, such as Google Vision and GPT-4V." + ], + "bbox": [ + 500, + 167, + 893, + 334 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 349, + 640, + 366 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Adversarial Attack", + "text_level": 1, + "bbox": [ + 500, + 376, + 683, + 391 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Various adversarial attacks have been proposed, e.g., gradient-based attack [13, 20, 32], transfer-based attack [7, 31, 51, 57], score-based attack [4, 18, 22], decision-based attack [2, 21, 49], generation-based attack [45, 54]. Among these, transfer-based attacks do not require the information of the victim models, making it popular to attack the deep models in the real world and raise more research interests. To improve adversarial transferability, various momentum-based attacks have been proposed, such as MI-FGSM [7], NI-FGSM [26], VMI-FGSM [44], EMI-FGSM [47], etc. Several input transformation methods are also proposed, such as DIM [57], TIM [8], SIM [26], Admix [46], SIA [50], STM [11], BSR [43], etc., which augment images used for adversarial perturbation computation to boost transferability. The input transformation-based methods can be integrated into the gradient-based attacks for better performance.", + "bbox": [ + 496, + 401, + 893, + 643 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Delving into the input transformation-based methods, most works are limited to designing a fixed transformation to augment the images, which limits the diversity of transformed images and the adversarial transferability. To address this issue, some researchers [53, 63, 64] propose to augment the images with a set of multiple transformations predicted by a pre-trained network. Automatic Model Augmentation (AutoMA) [63] adopts a Proximal Policy Optimization (PPO) algorithm in search of a strong augmentation policy. Adversarial Transformation-enhanced Transfer Attack (ATTA) [53] proposes to employ an adversarial transformation network in modeling the most harmful distortions. Adaptive Image Transformation Learner (AITL) [64] incorporates different image transformations into a unified framework to learn adaptive transformations for each benign sample to boost adversarial transferability. By applying optimal multiple transformations, the adversarial attack per", + "bbox": [ + 496, + 643, + 895, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "24274", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "formance is largely improved.", + "bbox": [ + 76, + 90, + 277, + 104 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Adversarial Defense", + "text_level": 1, + "bbox": [ + 76, + 114, + 269, + 130 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Various defense approaches have been proposed to mitigate the threat of adversarial attacks, such as adversarial training [32, 40, 48], input preprocessing [33, 55], feature denoising [24, 56, 62], certified defense [6, 14, 34], etc. Liao et al. [24] train a denoising autoencoder, namely the High-level representation guided denoiser (HGD), to purify the adversarial perturbations. Xie et al. [55] propose to randomly resize the image and add padding to mitigate the adversarial effect, namely the Randomized resizing and padding (R&P). Xu et al. [61] propose the Bit depth reduction (Bit-Red) method, which reduces the number of bits for each pixel to squeeze the perturbation. Liu et al. [29] defend against adversarial attacks by applying a JPEG-based compression method to adversarial images. Cohen et al. [6] adopt randomized smoothing (RS) to train a certifiably robust classifier. Naseer et al. [33] propose a Neural Representation Purifier (NRP) to eliminate perturbation.", + "bbox": [ + 75, + 138, + 473, + 396 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Learning to Transform", + "text_level": 1, + "bbox": [ + 76, + 409, + 294, + 425 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Task definition", + "text_level": 1, + "bbox": [ + 76, + 434, + 227, + 449 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The crafting of adversarial examples usually takes an iterative framework to update the adversarial perturbation. Given a benign sample $\\pmb{x}$ and the corresponding label $y$ , a transferable attack takes a surrogate classifier $f_{\\theta}$ and iteratively updates the adversarial example $x^{adv}$ to maximize the loss of classifying $f_{\\theta}(x^{adv})$ to $y$ . Take I-FGSM [38] as an example. The adversarial example $x_{t}^{adv}$ at the $t$ -th iteration can be formulated as follows:", + "bbox": [ + 75, + 457, + 472, + 577 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {x} _ {t} ^ {a d v} = \\boldsymbol {x} _ {t - 1} ^ {a d v} + \\alpha \\cdot \\operatorname {s i g n} \\left(\\nabla_ {\\boldsymbol {x} _ {t - 1} ^ {a d v}} J \\left(f _ {\\boldsymbol {\\theta}} \\left(\\boldsymbol {x} _ {t - 1} ^ {a d v}, y\\right)\\right)\\right), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 101, + 588, + 468, + 609 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where we denote $\\alpha$ as the step size, $J(\\cdot ,\\cdot)$ as the classification loss function. As identified by previous studies, the adversarial example exhibits a characteristic of transferability, where the adversarial examples generated by the surrogate model can fool other neural networks.", + "bbox": [ + 75, + 619, + 468, + 695 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Input transformation-based methods are one of the most effective methods to boost adversarial transferability. With these methods, the adversarial samples are firstly transformed by a set of image transformations and then proceeded to gradient calculation. Let $\\varphi$ denote a set of image transformations operation $o$ , where $\\varphi = \\{o^i | i \\in \\{1, 2, \\dots, k\\}\\}$ . At the $t$ -th iteration, the adversarial example $\\boldsymbol{x}_t^{adv}$ is transformed sequentially by $o^i$ as follows,", + "bbox": [ + 75, + 696, + 470, + 818 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\varphi \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right) = o ^ {k} \\oplus o ^ {k - 1} \\oplus \\dots \\oplus o ^ {1} \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 135, + 830, + 468, + 849 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $o^2 \\oplus o^1(\\boldsymbol{x})$ denotes the operation $o^2(o^1(\\boldsymbol{x}))$ , $o^1, o^2 \\in \\varphi$ . We use the gradient of $\\varphi(\\boldsymbol{x}_t^{adv})$ with respect to the loss function to update the adversarial perturbation as Eq. (1).", + "bbox": [ + 76, + 854, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/a5b3a2732f3db3e76cd32a29ac9ad6490a3d811d4b7a52ac4daeb0d905e6966f.jpg", + "image_caption": [ + "(a) One iteration" + ], + "image_footnote": [], + "bbox": [ + 522, + 90, + 684, + 204 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/50e820cc6dffe34d9cf92467484de000dde6829eceef78172570e6e0bd8443e9.jpg", + "image_caption": [ + "(b) Two iteration", + "Figure 2. Comparison for different operations in boosting the adversarial transferability. The number in the box denotes the number of fooled models (Maximum: 9). In (a), the horizontal axis denotes different transformation operations and the vertical axis denotes different benign examples. In (b), the vertical axis denotes the transformation used in the first iteration and the horizontal axis denotes the transformation used in the second iteration" + ], + "image_footnote": [], + "bbox": [ + 702, + 89, + 870, + 207 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "There are two categories for selecting the operation set $\\varphi$ in the previous study. One line of research focuses on designing fixed transformation-based methods, which use a pre-defined transformation $\\varphi$ . For example, Admix chooses mixup and scaling for transformation $\\varphi$ . The other line of research proposes the learning-based transformation methods, which usually use a generative model to directly generate the transformed $\\varphi(x)$ . Compared with the fixed transformation-based methods, learning-based methods enjoy more diversity of transformed images, leading to a better performance in adversarial transferability. In our work, we study the learning-based transformation methods.", + "bbox": [ + 496, + 354, + 893, + 536 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Motivation", + "text_level": 1, + "bbox": [ + 500, + 547, + 620, + 563 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Previous research designs lots of transformations to improve the diversity of images, thus guiding the adversarial attacks to focus more on the invariant robust features. However, it does not always work by increasing the number of transformed images for attacks to boost the adversarial transferability. Because some combination of transformations can cause damage to original examples, losing massive amounts of information used for transferable attacks. A natural question occurs to us, for one image, does there exist the optimal combination of transformations for the best adversarial transferability?", + "bbox": [ + 496, + 573, + 893, + 738 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To answer this question, we start by generating adversarial examples in one iteration. We take an example of crafting adversarial examples using ResNet-18 to attack other 9 models1. We denote 5 operations for input transformation methods, namely the crop, rotation, shuffle, scaling, and mix-up. We use these operations on five images for attacks and report the number of models fooled. We report the results in Fig. 2. It can be seen that by shuffle, we can achieve the maximum", + "bbox": [ + 496, + 739, + 895, + 861 + ], + "page_idx": 2 + }, + { + "type": "page_footnote", + "text": "$^{1}$ ResNet-101, DenseNet-121, ResNext-50, Inception-v3, Inception-v4, ViT, PiT, Visformer, Swin", + "bbox": [ + 500, + 875, + 893, + 898 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "24275", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/83eed6cd4c482d0f56a2675065f8cf12b298c2b1897e4d469d33db568e70e186.jpg", + "image_caption": [ + "Figure 3. There exists an optimal transformation trajectory for boosting adversarial transferability. However, the search space increases exponentially with iteration number and operation number." + ], + "image_footnote": [], + "bbox": [ + 80, + 88, + 472, + 306 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "transferable attack success rates on a dog image, indicating the optimal transformations in all possible 5 operations.", + "bbox": [ + 75, + 383, + 468, + 412 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We continue our discussion in the two-iteration scenario. Following the same setting in one iteration, we report the number of fooled models. It can be seen that by choosing crop in the first iteration and scaling for the second iteration, which successfully fooled 6 models out of 9. We also notice that shuffle, the optimal transformation in one iteration, can not maintain the optimal performance. The average fooled model for shuffle is less than crop in 0.2.", + "bbox": [ + 75, + 414, + 470, + 532 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Following the aforementioned discussion, we move on to generating adversarial examples in 3 iterations, where we only take one operation as the image transformation to attack the image. As exemplified in Fig. 3, there are $5 \\times 5 \\times 5$ possible trajectories to transform the image for attacks. Among these trajectories, it can achieve the best performance by first shuffling, then rotating, and last shuffling the image. It should be noted it cannot consistently achieve the best performance by increasing the number of transformations for a higher diversity. As shown in Fig. 3, we respectively take the scaling, shuffle, and rotation operations at each iteration in trajectory 2. However, it has the worst attack success rate among the presented results.", + "bbox": [ + 75, + 535, + 472, + 731 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Generalizing the previous problem to common cases, we are motivated to identify an optimal transformation trajectory $\\mathcal{T}$ , which is defined as the sequence of transformation used in each iteration as $(\\varphi_{1},\\varphi_{2},\\dots,\\varphi_{T})$ , for the best adversarial transferability. Each element $\\varphi_T$ denotes the transformation used in iteration $t$ . It can be formulated as follows:", + "bbox": [ + 75, + 731, + 470, + 821 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {T} ^ {*} = \\underset {\\mathcal {T}} {\\operatorname {a r g m a x}} (\\mathbb {E} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\boldsymbol {x} _ {\\mathcal {T}} ^ {a d v}), y) ]), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 153, + 832, + 470, + 858 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where we denote $x_{\\mathcal{T}}^{adv}$ as the adversarial example generated by the surrogate model under transformation trajectory $\\mathcal{T}$ .", + "bbox": [ + 75, + 869, + 470, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "However, finding $\\mathcal{T}^*$ is hard. First, the search space is large. For example, supposing five candidate transformations, even if we only take one operation in one iteration to transform the image, we will still have an enormous search space for ten iterations that will be $5^{10}$ . The number of possible transformation trajectories grows exponentially with increasing the number of iterations and candidate transformations. Second, we can not access the black-box model $f$ , making it hard to optimize the Eq. (3) directly. Besides, as identified in the previous work [64], each image has a different optimal transformation to boost the adversarial transferability. There is no optimal transformation trajectory shared for all images.", + "bbox": [ + 496, + 90, + 893, + 287 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Methodology", + "text_level": 1, + "bbox": [ + 500, + 294, + 637, + 311 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The problem of Eq. (3) can be transformed into an optimal trajectory search problem, on which reinforcement learning has shown great compatibility. We are inspired to take a reinforcement learning-based approach in solving this optimization problem to enhance adversarial transferability.", + "bbox": [ + 496, + 318, + 893, + 393 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Supposing we have $M$ operations $\\{o^1,o^2,\\dots,o^M\\}$ in total, the optimal transformation trajectory $\\mathcal{T}$ is a temporal sequence of the combination of different operations. The probability $\\pmb{p}$ contains $M$ possibilities $\\{p_{o^1},p_{o^2},\\dots,p_{o^M}\\}$ for each iteration. Each element $p_{o^m}$ denotes the possibility of sampling operation $o^m$ , $m\\in \\{1,2,\\ldots,M\\}$ . And $p_{o^m}$ follows $\\sum_{m = 1}^{M}p_{o^m} = 1$ . A transformation $\\varphi$ consists $K$ operations $o^k$ , $k\\in \\{1,2,\\dots,M\\}$ . We sampled $K$ operations from $\\pmb{p}$ . We have the possibility of a transformation $\\varphi$ by $P(\\varphi) = \\prod_{k = 1}^{K}p_{o^k}$ .", + "bbox": [ + 496, + 393, + 893, + 578 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For each iteration $t$ , we sample a combination of transformation $\\varphi_t$ . Each transformation in $\\varphi_t$ is sampled from candidates depending on $\\pmb{p}$ . To get an optimal trajectory $\\mathcal{T} = (\\varphi_1, \\dots, \\varphi_T)$ , we need to dynamically optimize the sampling distribution $\\pmb{p}$ in each iteration $t$ . We formulate the problem of searching optima $\\pmb{p}^*$ in each iteration as follows,", + "bbox": [ + 496, + 579, + 893, + 669 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{r} \\boldsymbol {p} ^ {*} = \\underset {\\boldsymbol {p}} {\\arg \\max } \\mathbb {E} _ {\\varphi \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi (\\tilde {\\boldsymbol {x}} ^ {a d v})), y) ] \\\\ \\tilde {\\boldsymbol {x}} ^ {a d v} = \\underset {\\boldsymbol {x} ^ {a d v}} {\\arg \\max } \\mathbb {E} _ {\\varphi \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi (\\boldsymbol {x} ^ {a d v})), y) ], \\end{array} \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 545, + 675, + 893, + 727 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "which is a bi-level optimization. The inner optimization targets to optimize the adversarial example, and the outer optimization tries to find the optimal sampling probability. Following [27], we adopt an one-step optimization strategy to derive the approximated $p^*$ :", + "bbox": [ + 496, + 732, + 893, + 808 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {p} ^ {*} \\approx \\boldsymbol {p} + \\rho \\cdot \\boldsymbol {g} _ {\\boldsymbol {p}}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 635, + 816, + 893, + 834 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the $\\rho$ is the learning rate and $g_{p}$ is the gradient for $\\pmb{p}$ . Implementation details. We present the overview of our method in Fig. 4. First, we sample $L$ sequences of transformation $\\varphi_t^l,l\\in [1,2,\\dots,L]$ , depending on the sampling", + "bbox": [ + 496, + 840, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "24276", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Algorithm 1 Gradient policy for optimal augmentation search.", + "bbox": [ + 76, + 90, + 468, + 119 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Input: Classifier $f(\\cdot)$ ; The benign sample $x$ with ground-truth label $y$ ; Loss function $\\mathcal{L}(\\cdot, \\cdot)$ ; candidate operation pool $\\Gamma$ , the number of iterations $T$ , perturbation scale $\\epsilon$ , policy learning rate $\\rho$ , number of operations $K$ , number of transformations $L$ , decay factor $\\mu$ ;", + "bbox": [ + 78, + 123, + 470, + 199 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\alpha = \\epsilon / T, \\boldsymbol {g} _ {0} = 0, \\boldsymbol {x} _ {0} ^ {a d v} = \\boldsymbol {x}, \\boldsymbol {p} \\sim \\mathcal {N} (0, 1)\n$$\n", + "text_format": "latex", + "bbox": [ + 93, + 199, + 374, + 215 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "while $t = 1\\gets T$ do", + "bbox": [ + 94, + 215, + 233, + 227 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. Under the distribution $\\pmb{p}$ , sample $L$ transformation $\\varphi_t$ , each consisting of $K$ operations.", + "2. Transform adversarial examples:" + ], + "bbox": [ + 93, + 229, + 468, + 272 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\varphi_ {t} ^ {l} \\left(x _ {t} ^ {a d v}\\right) = o ^ {K} \\oplus o ^ {K - 1} \\overline {{\\oplus}} \\dots \\oplus o ^ {1} \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right).\n$$\n", + "text_format": "latex", + "bbox": [ + 158, + 273, + 444, + 290 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3. Calculate the average gradient:", + "bbox": [ + 117, + 290, + 339, + 304 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\bar {\\boldsymbol {g}} = \\frac {1}{L} \\sum_ {l = 1} ^ {L} \\nabla_ {\\boldsymbol {x} _ {t - 1} ^ {a d v}} \\mathcal {L} (\\varphi_ {t} ^ {l} (\\boldsymbol {x} _ {t - 1} ^ {a d v}), y).\n$$\n", + "text_format": "latex", + "bbox": [ + 156, + 305, + 380, + 335 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Update the momentum:", + "bbox": [ + 117, + 335, + 292, + 349 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {g} _ {t} = \\mu \\boldsymbol {g} _ {t - 1} + \\frac {\\bar {g}}{| | \\bar {g} | | _ {1}}.\n$$\n", + "text_format": "latex", + "bbox": [ + 158, + 349, + 297, + 368 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. Update the adversarial example:", + "bbox": [ + 117, + 368, + 349, + 381 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {x} _ {t} ^ {a d v} = \\operatorname {c l i p} \\left(\\boldsymbol {x} _ {t - 1} ^ {a d v} + \\alpha \\cdot \\operatorname {s i g n} \\left(\\boldsymbol {g} _ {t}\\right), 0, 1\\right).\n$$\n", + "text_format": "latex", + "bbox": [ + 158, + 381, + 418, + 397 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "6. Calculate the probability gradient:", + "bbox": [ + 117, + 397, + 362, + 411 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\pmb {g} _ {\\pmb {p}} = \\frac {\\partial \\left(\\frac {1}{L} \\sum_ {l = 1} ^ {L} \\mathbf {P} (\\varphi_ {t} ^ {l}) \\mathcal {L} (f _ {\\pmb {\\theta}} (\\varphi_ {t} ^ {l} (\\mathbf {x} _ {t} ^ {a d v})), y) ]\\right)}{\\partial \\mathbf {P} (\\varphi_ {t} ^ {l})}.\n$$\n", + "text_format": "latex", + "bbox": [ + 156, + 411, + 413, + 446 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "7. Update the probability:", + "bbox": [ + 117, + 446, + 290, + 460 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {p} = \\boldsymbol {p} + \\rho \\cdot \\boldsymbol {g} _ {\\boldsymbol {p}}.\n$$\n", + "text_format": "latex", + "bbox": [ + 158, + 462, + 264, + 476 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "end while", + "bbox": [ + 94, + 476, + 165, + 488 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Output: $x_{T}^{adv}$ .", + "bbox": [ + 76, + 489, + 181, + 506 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "distribution $\\pmb{p}$ . Next, we get the transformed examples denoted as $\\varphi_t^l(x_t^{adv})$ . The probability of each sequence $\\varphi_t^l$ is $P(\\varphi_t^l)$ . We use $\\varphi_t$ to denote all $L$ transformations, $\\varphi_t = \\{\\varphi_t^1, \\varphi_t^2, \\dots, \\varphi_t^L\\}$ . Then, we use Eq. (1) to update the adversarial examples for each iteration. The gradient is calculated by loss between $L$ transformed examples and their corresponding labels. Last, after updating the adversarial example, we recompute the approximate $\\pmb{p}$ . Specifically, we compute the gradient $g_{o^k}$ of each sampled operation $o^k$ as:", + "bbox": [ + 76, + 545, + 468, + 681 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} g _ {o ^ {k}} = \\frac {\\partial \\mathbb {E} _ {\\varphi_ {t} \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi_ {t} (\\mathbf {x} _ {t} ^ {a d v})), y) ]}{\\partial \\mathbf {P} (\\varphi_ {t})} \\cdot \\frac {\\partial \\mathbf {P} (\\varphi_ {l})}{\\partial p _ {o ^ {k}}} \\\\ = \\frac {\\partial \\sum_ {l = 1} ^ {L} \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right) \\mathcal {L} \\left( \\right.f _ {\\boldsymbol {\\theta}} \\left(\\varphi_ {t} ^ {l} \\left(\\mathbf {x} _ {t} ^ {a d v}\\right), y\\right)\\left. \\right]\\left. \\right)}{\\partial \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right)} \\cdot \\frac {\\partial \\mathbf {P} \\left(\\varphi_ {l}\\right)}{\\partial p _ {o k}} \\tag {6} \\\\ = \\sum_ {l = 1} ^ {L} \\mathcal {L} \\left(f _ {\\boldsymbol {\\theta}} \\left(\\varphi_ {t} ^ {l} \\left(\\mathbf {x} _ {t} ^ {a d v}\\right), y\\right)\\right) \\cdot \\frac {\\partial \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right)}{\\partial p _ {o ^ {k}}}. \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 94, + 700, + 468, + 832 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We concat the gradients for each operation as $[g_{o^1}, g_{o^2}, \\ldots, g_{o^K}]$ , which is denoted as $\\pmb{g_p}$ . We use gradient ascent to update $\\pmb{p}$ by $\\pmb{g_p}$ with the learning rate $\\rho$ .", + "bbox": [ + 76, + 854, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/504faf4781a9c5c340234ae9af207ad9ff9ce18d0e14335ec561c3cccedb634a.jpg", + "image_caption": [ + "Figure 4. Overview of the pipeline in L2T. We use probability in sampling $L$ transformations and update this probability through gradient ascent." + ], + "image_footnote": [], + "bbox": [ + 500, + 88, + 893, + 314 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 393, + 630, + 410 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Setup", + "text_level": 1, + "bbox": [ + 500, + 419, + 581, + 436 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Models. We evaluate the proposed method in three categories of target models. (1) Normally trained model: We select ten well-known models for experiments. ResNet-18 [15], ResNet-101 [15], ResNext-50 [59], DenseNet-121 [17], Inception-v3 [39], and Inception-v4 [39], ViT-B [9], PiT [16], Visformer [5], and Swin [30]. All of these models are pre-trained on the ImageNet dataset. (2) Adversarial trained models: we select four defense methods in our experiments. They are adversarial training (AT) [40], high-level representation guided denoiser (HGD) [24], neural representation purifier (NRP) [33], and randomized smoothing (RS) [6]. (3) Vision API: to imitate a practical scenario, we compare the attack performance on popular vision API. We chose Google Vision, Azure AI, GPT-4V, and Bard. For categories (2) and (3), we use ensemble-based attack. We choose two CNN-based models, ResNet18 and Inception-v4, and two transformer-based models, Visformer and Swin, to construct the ensemble surrogate model.", + "bbox": [ + 496, + 444, + 893, + 715 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Dataset. Following previous works [46, 50, 57], we randomly choose 1,000 images from ILSVRC 2012 validation set [36]. All images are classified correctly by the models.", + "bbox": [ + 496, + 717, + 893, + 762 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Baseline. We compare L2T with other input transformation adversarial methods. There are two categories of previous methods. The fixed transformation attack followed a fixed transformation scheme. We select TIM [8], SIM [26], Admix [46], DEM [67], IDE [58], Mask [10], $\\mathrm{S}^2\\mathrm{IM}$ [31], BSR [42], and SIA [50] for comparison. The learned transformation attack followed a set of transformations predicted by a trained network to generate adversarial examples. We also compare our method with learned transformation at-", + "bbox": [ + 496, + 763, + 893, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "24277", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/c41b5b9bc07d31b159df8bf6588d7f21189b3f75c538aba7fe135b7b283c593f.jpg", + "image_caption": [ + "(a) ResNet-18" + ], + "image_footnote": [], + "bbox": [ + 81, + 97, + 230, + 224 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/176cb3ac18f8d2d58e6b363586e2ac31e38b7af7fee699368a49caa9576b7b83.jpg", + "image_caption": [ + "(b) ResNet-101" + ], + "image_footnote": [], + "bbox": [ + 243, + 95, + 397, + 224 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/501d10e8988f843e618d74d4309de7fc7625070f13e1342db3fed83cf47ec093.jpg", + "image_caption": [ + "(c) Inception-v3" + ], + "image_footnote": [], + "bbox": [ + 408, + 95, + 562, + 224 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/db3120f9973d28cc592ca89a33bae2e1042dabf7e19c13b799d5aa4750fc0234.jpg", + "image_caption": [ + "(d) ResNeXt-50" + ], + "image_footnote": [], + "bbox": [ + 573, + 95, + 725, + 224 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e9ad13e8662adb6d7c7286a1dffcd7fee1bf4fa1ca8d2e0a1060f5e24bd4bfc4.jpg", + "image_caption": [ + "(e) Inception-v4" + ], + "image_footnote": [], + "bbox": [ + 738, + 99, + 890, + 224 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/bcd303bced0edf7fc4283c8f17d6f30528858b03691ef35b3e92971208b99654.jpg", + "image_caption": [ + "(f) DenseNet-121", + "Figure 5. Average attack success rates $(\\%)$ of ten models on the adversarial examples crafted on each model. The x-axis of each sub-figure denotes different attack methods. We include the detail number in our supplementary material." + ], + "image_footnote": [], + "bbox": [ + 81, + 238, + 230, + 364 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/4a34b0695c29712d3a89de51ddee09a0eca0f3f7274a3699802caa92e2a915e6.jpg", + "image_caption": [ + "(g) ViT" + ], + "image_footnote": [], + "bbox": [ + 243, + 237, + 397, + 364 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/6e564d3e49f66af2906bb7982c5641d8d73a626ac30d6fa7849130e02749b2e7.jpg", + "image_caption": [ + "(h) PiT" + ], + "image_footnote": [], + "bbox": [ + 408, + 237, + 562, + 364 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/2c79c877f8c011f884c1429c99b220b59a59078a220f199c6478c96116d4a9ad.jpg", + "image_caption": [ + "(i) Swin" + ], + "image_footnote": [], + "bbox": [ + 573, + 237, + 725, + 364 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/1c414049bbaa658d54791797e8eb8e9f010f6785219cec32f1ec561e71be4930.jpg", + "image_caption": [ + "(j) Visformer" + ], + "image_footnote": [], + "bbox": [ + 736, + 237, + 890, + 364 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/29aa9648852fec96de73791c40cea8ae5e80f3647bbe8b9be025df2507cc437d.jpg", + "image_caption": [ + "Figure 6. Attack success rates (ASR) $(\\%)$ of adversarial examples generated by L2T with various number of operations $K$ . We include the detail number in our supplementary material." + ], + "image_footnote": [], + "bbox": [ + 104, + 435, + 442, + 614 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "tacks, such as AutoMA [63], ATTA [53], and AITL [64]. All these methods are integrated with MI-FGSM [7] to generate adversarial examples.", + "bbox": [ + 75, + 702, + 468, + 747 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation Settings. We follow the hyper-parameter setting of MI-FGSM and set the perturbation budget $\\epsilon = 16$ , number of iteration $T = 10$ , step size $\\alpha = \\epsilon / T = 1.6$ and decay factor $\\mu = 1$ . For our method, we adopt the number of operations as 2, the number of samples as 10, and the learning rate $\\rho$ as 0.01. For the candidate operation, we chose ten categories of transformations. Each category contains ten specific operations with different parameters. We will discuss the detailed settings of our method and other baselines in the supplementary materials.", + "bbox": [ + 75, + 750, + 472, + 901 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Evaluations on single models", + "text_level": 1, + "bbox": [ + 500, + 431, + 756, + 449 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Our proposed L2T exhibits better adversarial transferability to various input transformation based attacks. We take a single model as the surrogate model and evaluate the average attack success rate (ASR), i.e., the average misclassification rates across ten models. We summarized our results in Figure 5. Each subfigure denotes the attacker generates the adversarial examples on the corresponding models and its x-axis denotes the attack algorithm used.", + "bbox": [ + 496, + 455, + 893, + 577 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "First, we observe that L2T consistently outperforms all other attackers, regardless of the surrogate model. Other baseline methods have various adversarial transferability according to the surrogate models. For example, the BSR performs to be the strongest baseline on ResNet-18. However, the BSR cannot remain efficient when the surrogate model is changed to Swin or PiT. In contrast, our proposed L2T is suitable for all the surrogate models being tested. These results also strengthen our argument that we should dynamically choose the transformation to fit the surrogate models. Specifically, in the worst case (subfig. c), our proposed L2T still outperforms the strongest baseline ( $S^2$ IM) by $2.1\\%$ . Overall, L2T outperforms the other baseline by $22.9\\%$ on average ASR.", + "bbox": [ + 496, + 578, + 893, + 790 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Evaluations on defense methods", + "text_level": 1, + "bbox": [ + 500, + 801, + 782, + 816 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "L2T is also capable of adversarial robust mechanisms. We test the attack performance of L2T against several defense mechanisms, including AT, HGD, NRP, and RS. We choose the ensemble setting to attack these defense approaches. We use the ensemble of four models, ResNet-18, Inception-v4,", + "bbox": [ + 496, + 824, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "24278", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/9b488102e2be5f25cc0462aa4c349cd5df40cd5fe883b1a818ca1b1218f37ad8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 89, + 269, + 224 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/471ffd6dc282826674386745ab8a2b280b4519b14b77d069f98f0ffe2b564a3b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 282, + 88, + 475, + 224 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/3aee0c8bee34960b93504958f1f980bfd30464cbf610f28264151af34f32d9a2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 493, + 88, + 684, + 224 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/da9a8af87a9f58af5b3871aa9ff477419915716bd15fd484c2d1fcabd98179f2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 88, + 890, + 224 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d8a2a1eef80e43edc86857d4cdada5d0b83380bcd2aa67705e48b9d570ca198d.jpg", + "image_caption": [ + "Figure 7. We integrate the ensemble-based attack with input transformation and evaluate the performance on defense methods and popular vision APIs. We include the detail number in our supplementary material." + ], + "image_footnote": [], + "bbox": [ + 78, + 227, + 271, + 366 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/336c0433addc40b44cdddfcd3a922382bafaf1c0dbf27de59b40d6801df180a6.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 284, + 227, + 477, + 366 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5a7a7d6c55d7f4408b1bf22a9f2dcf171d67732aad979767c6a5d61aa308b1f2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 490, + 227, + 684, + 366 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/0ae64566008047bbd7e854a91dfcedea6ea75f45341c8b9ed87e7d18489fe532.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 227, + 890, + 366 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Visformer, and Swin, as the surrogate model. We summarized our results in Figure 7 (a), (b), (c), and (d). Each subfigure denotes the model to be attacked and its x-axis denotes the attack algorithm used.", + "bbox": [ + 75, + 433, + 470, + 494 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "From Fig. 7, it is clear that L2T remains efficient. L2T consistently outperforms other methods against various defense methods. Notably, it achieves the attack success rate of $47.9\\%$ , $98.5\\%$ , $87.2\\%$ , and $46.7\\%$ on AT, HGD, NRP, and RS, respectively. Even on the certified defense RS, the strongest defense among the four, L2T achieves the attack success rate of $46.7\\%$ , which exceeds the best baseline (AITL) by $4.6\\%$ . This is also the biggest improvement L2T made compared to other defenses. This indicates that the dynamic of iteration also exists in the adversarial robust mechanism, which can be used to diminish the its performance.", + "bbox": [ + 75, + 494, + 472, + 662 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Evaluations on vision API", + "text_level": 1, + "bbox": [ + 76, + 676, + 313, + 691 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our proposed L2T can also perform well in realistic scenarios. To imitate the real-world application, we test the performance of L2T on Vision API. We use the same setting in sec. 4.3 to craft adversarial examples. We choose Google Vision (Figure 7 (e)) and Azure AI (Figure 7 (f)) to evaluate attacks on vision-only API. We also choose ChatGPT-4V (Figure 7 (g)) and Gemini (Figure 7 (f)) to evaluate attacks on the foundation model API.", + "bbox": [ + 75, + 702, + 470, + 821 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "As shown in Fig. 7, L2T is generally the best attacker to the real-world API. All attacks perform better on foundation model API than vision-only API. For vision-only API, L2T outperforms the strongest baseline by $8.7\\%$ and $12.6\\%$ , respectively. For foundation model API, L2T achieves nearly", + "bbox": [ + 75, + 824, + 472, + 902 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9daff0bbc13d8b1fe86e0cda8ed5ec8e3dbd3bc81c613de201765672216facfe.jpg", + "image_caption": [ + "Figure 8. Attack success rates (ASR) (\\%) of adversarial examples generated by L2T with various number of transformations $L$ . We include the detail number in our supplementary material." + ], + "image_footnote": [], + "bbox": [ + 526, + 435, + 867, + 641 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "$100\\%$ attack success rate on both GPT-4V and Gemini.", + "bbox": [ + 500, + 727, + 861, + 742 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.5. Ablation study", + "text_level": 1, + "bbox": [ + 500, + 755, + 648, + 771 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "On the numbers of operation $K$ . As shown in Fig. 6, we study the impact of $K$ on adversarial transferability. We craft the adversarial example on ResNet-18 and evaluate them on the other nine models. There is a clear difference between one operation and two operations. The average attack success rate increases by $8.09\\%$ , from $80.89\\%$ to $88.98\\%$ . However, when the $K \\geq 3$ , the improvement becomes marginal. The average attack success rate only", + "bbox": [ + 496, + 779, + 890, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "24279", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/14f15947b64781f248beed5bf8f2234f7159bb1a0eea0cb39442a38c87c4a653.jpg", + "table_caption": [ + "Table 1. Attack success rates (%) of adversarial examples by L2T and Rand (randomly choose transformation in each iteration)." + ], + "table_footnote": [], + "table_body": "
ResNet-18ResNet-101ResNeXt-50DenseNet-121Inception-v3Inception-v4ViTPiTVisformerswin
Rand52.3559.0653.1956.6443.0144.4158.4154.4865.08
L2T (Ours)90.0091.9091.0092.8078.8082.4090.1093.5096.20
", + "bbox": [ + 81, + 113, + 893, + 161 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/092e8e5b584399518885cebf74f038fb194824676e46b4e994c52745a4c93c0f.jpg", + "image_caption": [ + "Figure 9. Average attack success rates (ASR) (\\%) of adversarial examples generated by L2T with various number of steps $T$ . We include the detail number in our supplementary material." + ], + "image_footnote": [], + "bbox": [ + 106, + 188, + 444, + 369 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "increases by $2.29\\%$ when $K$ is increased from 2 to 5. Thus, $K$ should be moderately settled as 2.", + "bbox": [ + 75, + 458, + 470, + 488 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "On the number of transformations $L$ . We conducted experiments on the number of transformations $L$ . We craft the adversarial example on ResNet-18 and evaluate them on the other nine models. We choose $L$ from 1 to 50. From Fig. 8, we observe that the adversarial transferability improves steadily with the number of transformations. The increase is significant when the number of transformations grows from 1 to 20, which improves from an average attack success rate of $75.7\\%$ to an average attack success rate of $91.1\\%$ . However, transferability does not increase significantly after the number exceeds 20, where the average attack success rate only increases $1.5\\%$ . To keep the balance between computation efficiency and adversarial transferability, we suggest the number of samples set to 20.", + "bbox": [ + 75, + 489, + 473, + 700 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "On the number of iterations $T$ . We discuss the number of iterations among different attack approaches. We craft the adversarial example on ResNet-18 and compare the average attack success rate of 10 models. As shown in Fig. 9, for all the attack methods, the attack success rate increased steadily for the first 10 iterations. L2T achieves the fastest speed of increase, which reaches $89.47\\%$ at iteration 10. After 10 iterations, most of the methods struggled to make improvements. For example, the Admix goes around $71\\%$ . The performance of $\\mathrm{S}^2\\mathrm{IM}$ even decreases from $73\\%$ to $70\\%$ . Meanwhile, L2T still maintains a stable increase, from $89.47\\%$ to $94.77\\%$ .", + "bbox": [ + 75, + 703, + 470, + 868 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Comparison with random sampling. We compare the learnable strategy with random sampling. As shown in", + "bbox": [ + 75, + 869, + 470, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f01b02526a24712a74e031163d0b7d0ffba7f1f17c05b9b56ad3357203a2d0e5.jpg", + "image_caption": [ + "Figure 10. The average attack success rates $(\\%)$ of adversarial examples crafted by L2T and L2T without a single transformation. - indicates removing such transformation." + ], + "image_footnote": [], + "bbox": [ + 504, + 184, + 890, + 324 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Tab. 1, there is a clear gap of the attack success rate between random sampling and gradient-guided sampling. The minimum difference is $31.12\\%$ with setting Visformer as the surrogate model. For other surrogate models, the gap is even larger. This experiment indicates random sampling cannot effectively sample the best transformation trajectory, and the transformation in each iteration needs to be chosen carefully.", + "bbox": [ + 496, + 409, + 893, + 513 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Operation candidates analysis. We conducted an ablation study for the operation candidates. We subtract each operation in the candidates and conduct L2T on the updated operation candidates. From Fig. 10, we observe that subtracting any operations will lead to a performance decrease. For example, by subtracting the scale operation, the performance decreases for $23.5\\%$ . Meanwhile, subtracting mixup and translation only results in a $3.1\\%$ decrease.", + "bbox": [ + 496, + 515, + 893, + 636 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 654, + 619, + 669 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we study the dynamic property for input transformation. Utilizing this property, we propose L2T to optimize the input transformation in each iteration. By updating a sampling probability, our method provides an approximate solution to input transformation optimization. Our experiments further study the effectiveness of our methods. Our method performs consistently well among different targeted models. This paper provides a new perspective to understand the transferability of adversarial examples.", + "bbox": [ + 496, + 680, + 893, + 815 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement. This work was supported by NSF under grant 2202124 and the Center of Excellence in Data Science, an Empire State Development-designated Center of Excellence. The content of the information does not necessarily reflect the position of the Government, and no official endorsement should be inferred.", + "bbox": [ + 496, + 816, + 895, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "24280", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 121, + 173, + 136 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Mihalj Bakator and Dragica Radosav. Deep learning and medical diagnosis: A review of literature. Multimodal Technologies and Interaction, 2(3):47, 2018. 1", + "[2] Wieland Brendel, Jonas Rauber, and Matthias Bethge. Decision-Based Adversarial Attacks: Reliable Attacks Against Black-Box Machine Learning Models. 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Springer, 2020. 5" + ], + "bbox": [ + 501, + 92, + 893, + 332 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "24283", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning to Transform Dynamically for Better Adversarial Transferability/20178bd8-b1c9-4630-a7e2-243d8c197a2f_model.json b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/20178bd8-b1c9-4630-a7e2-243d8c197a2f_model.json new file mode 100644 index 0000000000000000000000000000000000000000..98ff1cb5bf9a6458ced876e7a4983ab520094699 --- /dev/null +++ b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/20178bd8-b1c9-4630-a7e2-243d8c197a2f_model.json @@ -0,0 +1,2785 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.11, + 0.131, + 0.861, + 0.154 + ], + "angle": 0, + "content": "Learning to Transform Dynamically for Better Adversarial Transferability" + }, + { + "type": "text", + "bbox": [ + 0.172, + 0.18, + 0.797, + 0.217 + ], + "angle": 0, + "content": "\\(^{\\ddagger}\\) Rongyi Zhu *†Zeliang Zhang Susan Liang Zhuo Liu ‡ Chenliang Xu University of Rochester" + }, + { + "type": "text", + "bbox": [ + 0.141, + 0.22, + 0.829, + 0.234 + ], + "angle": 0, + "content": "{rongyi.zhu, zeliang.zhang, susan.liang, zhuo.liu, chenliang.xu}@rochester.edu" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.301, + 0.474, + 0.633 + ], + "angle": 0, + "content": "Adversarial examples, crafted by adding perturbations imperceptible to humans, can deceive neural networks. Recent studies identify the adversarial transferability across various models, i.e., the cross-model attack ability of adversarial samples. To enhance such adversarial transferability, existing input transformation-based methods diversify input data with transformation augmentation. However, their effectiveness is limited by the finite number of available transformations. In our study, we introduce a novel approach named Learning to Transform (L2T). L2T increases the diversity of transformed images by selecting the optimal combination of operations from a pool of candidates, consequently improving adversarial transferability. We conceptualize the selection of optimal transformation combinations as a trajectory optimization problem and employ a reinforcement learning strategy to effectively solve the problem. Comprehensive experiments on the ImageNet dataset, as well as practical tests with Google Vision and GPT-4V, reveal that L2T surpasses current methodologies in enhancing adversarial transferability, thereby confirming its effectiveness and practical significance. The code is available at https://github.com/ZhangAIP1/TransferAttack." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.662, + 0.21, + 0.677 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.687, + 0.47, + 0.808 + ], + "angle": 0, + "content": "Neural networks have been adopted as the building block for various real-world applications, such as face detection [37, 41], autonomous driving [12, 25], and medical diagnosis [1, 35]. However, neural networks are vulnerable to adversarial examples, which contain human imperceptible adversarial perturbations on the benign input. This issue is increasingly concerning researchers, as it is essential for ensuring the trustworthy use of neural networks [3, 19, 65, 66]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.809, + 0.471, + 0.854 + ], + "angle": 0, + "content": "In real-world scenarios of adversarial attacks, the target model is usually inaccessible. To attack these inaccessible models, many studies instead rely on surrogate models" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.268, + 0.895, + 0.533 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.541, + 0.895, + 0.667 + ], + "angle": 0, + "content": "Figure 1. For input transformation-based attacks, most works design a fixed transformation and use it to craft the adversarial perturbation. The learning-based methods preliminarily predict augmentation strategies for current images for better adversarial transferability. These methods cannot respond to the distribution shifts between benign images and adversarial examples. We propose Learning to Transform (L2T), which uses the dynamic of the optimal transformation in each iteration to further boost the adversarial transferability." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.704, + 0.897, + 0.903 + ], + "angle": 0, + "content": "to generate adversarial examples [7, 57] and use generated samples to mislead the target model. This cross-model attack ability of samples generated on the surrogate models is called \"adversarial transferability.\" Numerous research studies are dedicated to enhancing adversarial transferability, which can be classified into four categories: gradient-based methods [7, 26, 44, 47], input transformation-based methods [8, 26, 46, 57], architecture-based methods [23, 52], and ensemble-based methods [28, 60]. Among these attack methodologies, input transformation-based methods gain much popularity because of their plug-n-play advantage, which can be seamlessly integrated into other attack techniques [7, 44]. However, we discover that existing input" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.863, + 0.203, + 0.875 + ], + "angle": 0, + "content": "*Equal contribution" + }, + { + "type": "page_footnote", + "bbox": [ + 0.098, + 0.876, + 0.168, + 0.888 + ], + "angle": 0, + "content": "†Project lead" + }, + { + "type": "page_footnote", + "bbox": [ + 0.098, + 0.888, + 0.22, + 0.9 + ], + "angle": 0, + "content": "\\(\\ddagger\\) Corresponding author" + }, + { + "type": "list", + "bbox": [ + 0.096, + 0.863, + 0.22, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24273" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.168 + ], + "angle": 0, + "content": "transformation-based methods adopt the same transformation when crafting adversarial examples, limiting the flexibility of transformation operations. We hypothesize that we should select the optimal transformation dynamically in each iteration to enhance the adversarial transferability." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.17, + 0.472, + 0.397 + ], + "angle": 0, + "content": "As shown in Fig. 1, prior input transformation-based methods often revolve around designing fixed augmentation strategies like resizing inputs [57], block masking [10], or mix-up [46]. A more dynamic approach is presented by [63], advocating the precomputation of various sequences of augmentation strategies to apply to each iteration to enhance the attack performance. Complementing this, Wu et al. [53] proposes the use of generative models for image augmentation to boost the adversarial transferability. Some studies go further, combining multiple augmentation strategies to amplify input diversity to improve the performance. For example, Yuan et al. [64] introduces a neural network that generates a prediction of the optimal transformation strategy and applies the strategy to improve performance. A further improvement is hindered by the limited number of transformations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.399, + 0.472, + 0.687 + ], + "angle": 0, + "content": "To fully utilize the limited number of transformations, a natural idea is to use a combination of operations. However, it is not always efficient to combine different transformations together for attack, as reported in [50]. We expect to find an optimal combination of transformations to achieve a tradeoff between operation diversity and adversarial transferability. Nonetheless, the enormity of the search space presents a significant challenge, impeding the identification of the most efficacious combination of transformations during an attack for optimal adversarial transferability. To surmount this hurdle, we conceptualize the search process of the optimal combination of transformations as a problem of optimal trajectory search. Each node within this trajectory represents an individual transformation, and each directed edge means a transfer of the optimal transformation from the current step to the next step. To effectively obtain the optimal trajectory in such a large search space, we design a reinforcement learning-based approach, capitalizing on its demonstrated efficacy in navigating expansive search domains." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.472, + 0.901 + ], + "angle": 0, + "content": "In this paper, we introduce a novel framework called Learning to Transform (L2T) to improve the adversarial transferability of generated adversarial examples. L2T dynamically learns and applies the optimal input transformation in each iteration. Instead of exhaustively enumerating all possible input transformation methods, we employ a reinforcement learning-based approach to reduce the search space and better utilize the transformations to improve the diversity. In each iteration of the adversarial attack, we sample a subset of transformations and apply them to the adversarial examples. Subsequently, we update the sampling probabilities by conducting gradient ascent to maximize the loss. Our method effectively learns the dynamics of optimal transformations in attacks, leading to a significant enhancement in" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.152 + ], + "angle": 0, + "content": "adversarial transferability. Additionally, compared to other learn-based adversarial attack methods, our approach is more efficient for adversarial example generation, as it obviates the need for additional training modules." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.153, + 0.812, + 0.167 + ], + "angle": 0, + "content": "We summarize our contributions as follows," + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.169, + 0.894, + 0.229 + ], + "angle": 0, + "content": "- We formulate the problem of optimal transformation in adversarial attacks, which studies finding the optimal combination of transformations to increase the input diversities, thus improving the adversarial transferability." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.23, + 0.894, + 0.274 + ], + "angle": 0, + "content": "- We propose Learning to Transform (L2T) that exploits the optimal transformation in each iteration and dynamically adjusts transformations to boost adversarial transferability." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.275, + 0.895, + 0.335 + ], + "angle": 0, + "content": "- Extensive experiments on the ImageNet dataset demonstrate that L2T outperforms other baselines. We also validate L2T's superiority in real-world scenarios, such as Google Vision and GPT-4V." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.169, + 0.895, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.351, + 0.642, + 0.367 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.377, + 0.684, + 0.392 + ], + "angle": 0, + "content": "2.1. Adversarial Attack" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.402, + 0.895, + 0.644 + ], + "angle": 0, + "content": "Various adversarial attacks have been proposed, e.g., gradient-based attack [13, 20, 32], transfer-based attack [7, 31, 51, 57], score-based attack [4, 18, 22], decision-based attack [2, 21, 49], generation-based attack [45, 54]. Among these, transfer-based attacks do not require the information of the victim models, making it popular to attack the deep models in the real world and raise more research interests. To improve adversarial transferability, various momentum-based attacks have been proposed, such as MI-FGSM [7], NI-FGSM [26], VMI-FGSM [44], EMI-FGSM [47], etc. Several input transformation methods are also proposed, such as DIM [57], TIM [8], SIM [26], Admix [46], SIA [50], STM [11], BSR [43], etc., which augment images used for adversarial perturbation computation to boost transferability. The input transformation-based methods can be integrated into the gradient-based attacks for better performance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.645, + 0.897, + 0.902 + ], + "angle": 0, + "content": "Delving into the input transformation-based methods, most works are limited to designing a fixed transformation to augment the images, which limits the diversity of transformed images and the adversarial transferability. To address this issue, some researchers [53, 63, 64] propose to augment the images with a set of multiple transformations predicted by a pre-trained network. Automatic Model Augmentation (AutoMA) [63] adopts a Proximal Policy Optimization (PPO) algorithm in search of a strong augmentation policy. Adversarial Transformation-enhanced Transfer Attack (ATTA) [53] proposes to employ an adversarial transformation network in modeling the most harmful distortions. Adaptive Image Transformation Learner (AITL) [64] incorporates different image transformations into a unified framework to learn adaptive transformations for each benign sample to boost adversarial transferability. By applying optimal multiple transformations, the adversarial attack per" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "24274" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.078, + 0.092, + 0.279, + 0.106 + ], + "angle": 0, + "content": "formance is largely improved." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.116, + 0.27, + 0.131 + ], + "angle": 0, + "content": "2.2. Adversarial Defense" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.139, + 0.474, + 0.397 + ], + "angle": 0, + "content": "Various defense approaches have been proposed to mitigate the threat of adversarial attacks, such as adversarial training [32, 40, 48], input preprocessing [33, 55], feature denoising [24, 56, 62], certified defense [6, 14, 34], etc. Liao et al. [24] train a denoising autoencoder, namely the High-level representation guided denoiser (HGD), to purify the adversarial perturbations. Xie et al. [55] propose to randomly resize the image and add padding to mitigate the adversarial effect, namely the Randomized resizing and padding (R&P). Xu et al. [61] propose the Bit depth reduction (Bit-Red) method, which reduces the number of bits for each pixel to squeeze the perturbation. Liu et al. [29] defend against adversarial attacks by applying a JPEG-based compression method to adversarial images. Cohen et al. [6] adopt randomized smoothing (RS) to train a certifiably robust classifier. Naseer et al. [33] propose a Neural Representation Purifier (NRP) to eliminate perturbation." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.41, + 0.295, + 0.426 + ], + "angle": 0, + "content": "3. Learning to Transform" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.435, + 0.228, + 0.45 + ], + "angle": 0, + "content": "3.1. Task definition" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.458, + 0.473, + 0.578 + ], + "angle": 0, + "content": "The crafting of adversarial examples usually takes an iterative framework to update the adversarial perturbation. Given a benign sample \\( \\pmb{x} \\) and the corresponding label \\( y \\), a transferable attack takes a surrogate classifier \\( f_{\\theta} \\) and iteratively updates the adversarial example \\( x^{adv} \\) to maximize the loss of classifying \\( f_{\\theta}(x^{adv}) \\) to \\( y \\). Take I-FGSM [38] as an example. The adversarial example \\( x_{t}^{adv} \\) at the \\( t \\)-th iteration can be formulated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.102, + 0.589, + 0.47, + 0.611 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {x} _ {t} ^ {a d v} = \\boldsymbol {x} _ {t - 1} ^ {a d v} + \\alpha \\cdot \\operatorname {s i g n} \\left(\\nabla_ {\\boldsymbol {x} _ {t - 1} ^ {a d v}} J \\left(f _ {\\boldsymbol {\\theta}} \\left(\\boldsymbol {x} _ {t - 1} ^ {a d v}, y\\right)\\right)\\right), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.621, + 0.47, + 0.696 + ], + "angle": 0, + "content": "where we denote \\(\\alpha\\) as the step size, \\(J(\\cdot ,\\cdot)\\) as the classification loss function. As identified by previous studies, the adversarial example exhibits a characteristic of transferability, where the adversarial examples generated by the surrogate model can fool other neural networks." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.697, + 0.472, + 0.819 + ], + "angle": 0, + "content": "Input transformation-based methods are one of the most effective methods to boost adversarial transferability. With these methods, the adversarial samples are firstly transformed by a set of image transformations and then proceeded to gradient calculation. Let \\(\\varphi\\) denote a set of image transformations operation \\(o\\), where \\(\\varphi = \\{o^i | i \\in \\{1, 2, \\dots, k\\}\\}\\). At the \\(t\\)-th iteration, the adversarial example \\(\\boldsymbol{x}_t^{adv}\\) is transformed sequentially by \\(o^i\\) as follows," + }, + { + "type": "equation", + "bbox": [ + 0.136, + 0.831, + 0.47, + 0.851 + ], + "angle": 0, + "content": "\\[\n\\varphi \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right) = o ^ {k} \\oplus o ^ {k - 1} \\oplus \\dots \\oplus o ^ {1} \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.855, + 0.47, + 0.902 + ], + "angle": 0, + "content": "where \\(o^2 \\oplus o^1(\\boldsymbol{x})\\) denotes the operation \\(o^2(o^1(\\boldsymbol{x}))\\), \\(o^1, o^2 \\in \\varphi\\). We use the gradient of \\(\\varphi(\\boldsymbol{x}_t^{adv})\\) with respect to the loss function to update the adversarial perturbation as Eq. (1)." + }, + { + "type": "image", + "bbox": [ + 0.523, + 0.092, + 0.685, + 0.205 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.573, + 0.208, + 0.642, + 0.218 + ], + "angle": 0, + "content": "(a) One iteration" + }, + { + "type": "image", + "bbox": [ + 0.704, + 0.09, + 0.871, + 0.208 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.766, + 0.209, + 0.837, + 0.219 + ], + "angle": 0, + "content": "(b) Two iteration" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.23, + 0.895, + 0.326 + ], + "angle": 0, + "content": "Figure 2. Comparison for different operations in boosting the adversarial transferability. The number in the box denotes the number of fooled models (Maximum: 9). In (a), the horizontal axis denotes different transformation operations and the vertical axis denotes different benign examples. In (b), the vertical axis denotes the transformation used in the first iteration and the horizontal axis denotes the transformation used in the second iteration" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.356, + 0.895, + 0.537 + ], + "angle": 0, + "content": "There are two categories for selecting the operation set \\(\\varphi\\) in the previous study. One line of research focuses on designing fixed transformation-based methods, which use a pre-defined transformation \\(\\varphi\\). For example, Admix chooses mixup and scaling for transformation \\(\\varphi\\). The other line of research proposes the learning-based transformation methods, which usually use a generative model to directly generate the transformed \\(\\varphi(x)\\). Compared with the fixed transformation-based methods, learning-based methods enjoy more diversity of transformed images, leading to a better performance in adversarial transferability. In our work, we study the learning-based transformation methods." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.549, + 0.622, + 0.564 + ], + "angle": 0, + "content": "3.2. Motivation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.574, + 0.895, + 0.739 + ], + "angle": 0, + "content": "Previous research designs lots of transformations to improve the diversity of images, thus guiding the adversarial attacks to focus more on the invariant robust features. However, it does not always work by increasing the number of transformed images for attacks to boost the adversarial transferability. Because some combination of transformations can cause damage to original examples, losing massive amounts of information used for transferable attacks. A natural question occurs to us, for one image, does there exist the optimal combination of transformations for the best adversarial transferability?" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.741, + 0.896, + 0.862 + ], + "angle": 0, + "content": "To answer this question, we start by generating adversarial examples in one iteration. We take an example of crafting adversarial examples using ResNet-18 to attack other 9 models1. We denote 5 operations for input transformation methods, namely the crop, rotation, shuffle, scaling, and mix-up. We use these operations on five images for attacks and report the number of models fooled. We report the results in Fig. 2. It can be seen that by shuffle, we can achieve the maximum" + }, + { + "type": "page_footnote", + "bbox": [ + 0.5, + 0.875, + 0.895, + 0.9 + ], + "angle": 0, + "content": "\\(^{1}\\)ResNet-101, DenseNet-121, ResNext-50, Inception-v3, Inception-v4, ViT, PiT, Visformer, Swin" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24275" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.473, + 0.308 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.316, + 0.473, + 0.358 + ], + "angle": 0, + "content": "Figure 3. There exists an optimal transformation trajectory for boosting adversarial transferability. However, the search space increases exponentially with iteration number and operation number." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.384, + 0.47, + 0.414 + ], + "angle": 0, + "content": "transferable attack success rates on a dog image, indicating the optimal transformations in all possible 5 operations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.415, + 0.472, + 0.534 + ], + "angle": 0, + "content": "We continue our discussion in the two-iteration scenario. Following the same setting in one iteration, we report the number of fooled models. It can be seen that by choosing crop in the first iteration and scaling for the second iteration, which successfully fooled 6 models out of 9. We also notice that shuffle, the optimal transformation in one iteration, can not maintain the optimal performance. The average fooled model for shuffle is less than crop in 0.2." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.536, + 0.473, + 0.732 + ], + "angle": 0, + "content": "Following the aforementioned discussion, we move on to generating adversarial examples in 3 iterations, where we only take one operation as the image transformation to attack the image. As exemplified in Fig. 3, there are \\(5 \\times 5 \\times 5\\) possible trajectories to transform the image for attacks. Among these trajectories, it can achieve the best performance by first shuffling, then rotating, and last shuffling the image. It should be noted it cannot consistently achieve the best performance by increasing the number of transformations for a higher diversity. As shown in Fig. 3, we respectively take the scaling, shuffle, and rotation operations at each iteration in trajectory 2. However, it has the worst attack success rate among the presented results." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.732, + 0.472, + 0.822 + ], + "angle": 0, + "content": "Generalizing the previous problem to common cases, we are motivated to identify an optimal transformation trajectory \\(\\mathcal{T}\\), which is defined as the sequence of transformation used in each iteration as \\((\\varphi_{1},\\varphi_{2},\\dots,\\varphi_{T})\\), for the best adversarial transferability. Each element \\(\\varphi_T\\) denotes the transformation used in iteration \\(t\\). It can be formulated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.154, + 0.833, + 0.471, + 0.859 + ], + "angle": 0, + "content": "\\[\n\\mathcal {T} ^ {*} = \\underset {\\mathcal {T}} {\\operatorname {a r g m a x}} (\\mathbb {E} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\boldsymbol {x} _ {\\mathcal {T}} ^ {a d v}), y) ]), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.471, + 0.903 + ], + "angle": 0, + "content": "where we denote \\(x_{\\mathcal{T}}^{adv}\\) as the adversarial example generated by the surrogate model under transformation trajectory \\(\\mathcal{T}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.289 + ], + "angle": 0, + "content": "However, finding \\(\\mathcal{T}^*\\) is hard. First, the search space is large. For example, supposing five candidate transformations, even if we only take one operation in one iteration to transform the image, we will still have an enormous search space for ten iterations that will be \\(5^{10}\\). The number of possible transformation trajectories grows exponentially with increasing the number of iterations and candidate transformations. Second, we can not access the black-box model \\(f\\), making it hard to optimize the Eq. (3) directly. Besides, as identified in the previous work [64], each image has a different optimal transformation to boost the adversarial transferability. There is no optimal transformation trajectory shared for all images." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.295, + 0.638, + 0.312 + ], + "angle": 0, + "content": "3.3. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.319, + 0.895, + 0.394 + ], + "angle": 0, + "content": "The problem of Eq. (3) can be transformed into an optimal trajectory search problem, on which reinforcement learning has shown great compatibility. We are inspired to take a reinforcement learning-based approach in solving this optimization problem to enhance adversarial transferability." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.394, + 0.895, + 0.579 + ], + "angle": 0, + "content": "Supposing we have \\(M\\) operations \\(\\{o^1,o^2,\\dots,o^M\\}\\) in total, the optimal transformation trajectory \\(\\mathcal{T}\\) is a temporal sequence of the combination of different operations. The probability \\(\\pmb{p}\\) contains \\(M\\) possibilities \\(\\{p_{o^1},p_{o^2},\\dots,p_{o^M}\\}\\) for each iteration. Each element \\(p_{o^m}\\) denotes the possibility of sampling operation \\(o^m\\), \\(m\\in \\{1,2,\\ldots,M\\}\\). And \\(p_{o^m}\\) follows \\(\\sum_{m = 1}^{M}p_{o^m} = 1\\). A transformation \\(\\varphi\\) consists \\(K\\) operations \\(o^k\\), \\(k\\in \\{1,2,\\dots,M\\}\\). We sampled \\(K\\) operations from \\(\\pmb{p}\\). We have the possibility of a transformation \\(\\varphi\\) by \\(P(\\varphi) = \\prod_{k = 1}^{K}p_{o^k}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.58, + 0.895, + 0.67 + ], + "angle": 0, + "content": "For each iteration \\(t\\), we sample a combination of transformation \\(\\varphi_t\\). Each transformation in \\(\\varphi_t\\) is sampled from candidates depending on \\(\\pmb{p}\\). To get an optimal trajectory \\(\\mathcal{T} = (\\varphi_1, \\dots, \\varphi_T)\\), we need to dynamically optimize the sampling distribution \\(\\pmb{p}\\) in each iteration \\(t\\). We formulate the problem of searching optima \\(\\pmb{p}^*\\) in each iteration as follows," + }, + { + "type": "equation", + "bbox": [ + 0.546, + 0.676, + 0.895, + 0.728 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{r} \\boldsymbol {p} ^ {*} = \\underset {\\boldsymbol {p}} {\\arg \\max } \\mathbb {E} _ {\\varphi \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi (\\tilde {\\boldsymbol {x}} ^ {a d v})), y) ] \\\\ \\tilde {\\boldsymbol {x}} ^ {a d v} = \\underset {\\boldsymbol {x} ^ {a d v}} {\\arg \\max } \\mathbb {E} _ {\\varphi \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi (\\boldsymbol {x} ^ {a d v})), y) ], \\end{array} \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.733, + 0.895, + 0.809 + ], + "angle": 0, + "content": "which is a bi-level optimization. The inner optimization targets to optimize the adversarial example, and the outer optimization tries to find the optimal sampling probability. Following [27], we adopt an one-step optimization strategy to derive the approximated \\( p^* \\):" + }, + { + "type": "equation", + "bbox": [ + 0.637, + 0.817, + 0.895, + 0.835 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {p} ^ {*} \\approx \\boldsymbol {p} + \\rho \\cdot \\boldsymbol {g} _ {\\boldsymbol {p}}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.841, + 0.895, + 0.903 + ], + "angle": 0, + "content": "where the \\(\\rho\\) is the learning rate and \\(g_{p}\\) is the gradient for \\(\\pmb{p}\\). Implementation details. We present the overview of our method in Fig. 4. First, we sample \\(L\\) sequences of transformation \\(\\varphi_t^l,l\\in [1,2,\\dots,L]\\), depending on the sampling" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "24276" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.078, + 0.091, + 0.47, + 0.12 + ], + "angle": 0, + "content": "Algorithm 1 Gradient policy for optimal augmentation search." + }, + { + "type": "text", + "bbox": [ + 0.079, + 0.124, + 0.472, + 0.2 + ], + "angle": 0, + "content": "Input: Classifier \\( f(\\cdot) \\); The benign sample \\( x \\) with ground-truth label \\( y \\); Loss function \\( \\mathcal{L}(\\cdot, \\cdot) \\); candidate operation pool \\( \\Gamma \\), the number of iterations \\( T \\), perturbation scale \\( \\epsilon \\), policy learning rate \\( \\rho \\), number of operations \\( K \\), number of transformations \\( L \\), decay factor \\( \\mu \\);" + }, + { + "type": "equation", + "bbox": [ + 0.094, + 0.2, + 0.375, + 0.216 + ], + "angle": 0, + "content": "\\[\n\\alpha = \\epsilon / T, \\boldsymbol {g} _ {0} = 0, \\boldsymbol {x} _ {0} ^ {a d v} = \\boldsymbol {x}, \\boldsymbol {p} \\sim \\mathcal {N} (0, 1)\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.095, + 0.216, + 0.235, + 0.228 + ], + "angle": 0, + "content": "while \\(t = 1\\gets T\\) do" + }, + { + "type": "text", + "bbox": [ + 0.094, + 0.23, + 0.469, + 0.26 + ], + "angle": 0, + "content": "1. Under the distribution \\( \\pmb{p} \\), sample \\( L \\) transformation \\( \\varphi_t \\), each consisting of \\( K \\) operations." + }, + { + "type": "text", + "bbox": [ + 0.118, + 0.261, + 0.354, + 0.273 + ], + "angle": 0, + "content": "2. Transform adversarial examples:" + }, + { + "type": "list", + "bbox": [ + 0.094, + 0.23, + 0.469, + 0.273 + ], + "angle": 0, + "content": null + }, + { + "type": "equation", + "bbox": [ + 0.16, + 0.274, + 0.445, + 0.291 + ], + "angle": 0, + "content": "\\[\n\\varphi_ {t} ^ {l} \\left(x _ {t} ^ {a d v}\\right) = o ^ {K} \\oplus o ^ {K - 1} \\overline {{\\oplus}} \\dots \\oplus o ^ {1} \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right).\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.118, + 0.291, + 0.341, + 0.305 + ], + "angle": 0, + "content": "3. Calculate the average gradient:" + }, + { + "type": "equation", + "bbox": [ + 0.158, + 0.306, + 0.382, + 0.337 + ], + "angle": 0, + "content": "\\[\n\\bar {\\boldsymbol {g}} = \\frac {1}{L} \\sum_ {l = 1} ^ {L} \\nabla_ {\\boldsymbol {x} _ {t - 1} ^ {a d v}} \\mathcal {L} (\\varphi_ {t} ^ {l} (\\boldsymbol {x} _ {t - 1} ^ {a d v}), y).\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.118, + 0.337, + 0.294, + 0.35 + ], + "angle": 0, + "content": "4. Update the momentum:" + }, + { + "type": "equation", + "bbox": [ + 0.159, + 0.35, + 0.298, + 0.369 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {g} _ {t} = \\mu \\boldsymbol {g} _ {t - 1} + \\frac {\\bar {g}}{| | \\bar {g} | | _ {1}}.\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.118, + 0.369, + 0.351, + 0.382 + ], + "angle": 0, + "content": "5. Update the adversarial example:" + }, + { + "type": "equation", + "bbox": [ + 0.16, + 0.382, + 0.419, + 0.398 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {x} _ {t} ^ {a d v} = \\operatorname {c l i p} \\left(\\boldsymbol {x} _ {t - 1} ^ {a d v} + \\alpha \\cdot \\operatorname {s i g n} \\left(\\boldsymbol {g} _ {t}\\right), 0, 1\\right).\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.118, + 0.398, + 0.363, + 0.412 + ], + "angle": 0, + "content": "6. Calculate the probability gradient:" + }, + { + "type": "equation", + "bbox": [ + 0.158, + 0.412, + 0.415, + 0.448 + ], + "angle": 0, + "content": "\\[\n\\pmb {g} _ {\\pmb {p}} = \\frac {\\partial \\left(\\frac {1}{L} \\sum_ {l = 1} ^ {L} \\mathbf {P} (\\varphi_ {t} ^ {l}) \\mathcal {L} (f _ {\\pmb {\\theta}} (\\varphi_ {t} ^ {l} (\\mathbf {x} _ {t} ^ {a d v})), y) ]\\right)}{\\partial \\mathbf {P} (\\varphi_ {t} ^ {l})}.\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.118, + 0.448, + 0.291, + 0.461 + ], + "angle": 0, + "content": "7. Update the probability:" + }, + { + "type": "equation", + "bbox": [ + 0.159, + 0.463, + 0.266, + 0.477 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {p} = \\boldsymbol {p} + \\rho \\cdot \\boldsymbol {g} _ {\\boldsymbol {p}}.\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.095, + 0.477, + 0.166, + 0.489 + ], + "angle": 0, + "content": "end while" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.49, + 0.182, + 0.507 + ], + "angle": 0, + "content": "Output: \\( x_{T}^{adv} \\)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.546, + 0.47, + 0.682 + ], + "angle": 0, + "content": "distribution \\(\\pmb{p}\\). Next, we get the transformed examples denoted as \\(\\varphi_t^l(x_t^{adv})\\). The probability of each sequence \\(\\varphi_t^l\\) is \\(P(\\varphi_t^l)\\). We use \\(\\varphi_t\\) to denote all \\(L\\) transformations, \\(\\varphi_t = \\{\\varphi_t^1, \\varphi_t^2, \\dots, \\varphi_t^L\\}\\). Then, we use Eq. (1) to update the adversarial examples for each iteration. The gradient is calculated by loss between \\(L\\) transformed examples and their corresponding labels. Last, after updating the adversarial example, we recompute the approximate \\(\\pmb{p}\\). Specifically, we compute the gradient \\(g_{o^k}\\) of each sampled operation \\(o^k\\) as:" + }, + { + "type": "equation", + "bbox": [ + 0.095, + 0.701, + 0.47, + 0.833 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} g _ {o ^ {k}} = \\frac {\\partial \\mathbb {E} _ {\\varphi_ {t} \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi_ {t} (\\mathbf {x} _ {t} ^ {a d v})), y) ]}{\\partial \\mathbf {P} (\\varphi_ {t})} \\cdot \\frac {\\partial \\mathbf {P} (\\varphi_ {l})}{\\partial p _ {o ^ {k}}} \\\\ = \\frac {\\partial \\sum_ {l = 1} ^ {L} \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right) \\mathcal {L} \\left( \\right.f _ {\\boldsymbol {\\theta}} \\left(\\varphi_ {t} ^ {l} \\left(\\mathbf {x} _ {t} ^ {a d v}\\right), y\\right)\\left. \\right]\\left. \\right)}{\\partial \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right)} \\cdot \\frac {\\partial \\mathbf {P} \\left(\\varphi_ {l}\\right)}{\\partial p _ {o k}} \\tag {6} \\\\ = \\sum_ {l = 1} ^ {L} \\mathcal {L} \\left(f _ {\\boldsymbol {\\theta}} \\left(\\varphi_ {t} ^ {l} \\left(\\mathbf {x} _ {t} ^ {a d v}\\right), y\\right)\\right) \\cdot \\frac {\\partial \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right)}{\\partial p _ {o ^ {k}}}. \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.856, + 0.47, + 0.902 + ], + "angle": 0, + "content": "We concat the gradients for each operation as \\([g_{o^1}, g_{o^2}, \\ldots, g_{o^K}]\\), which is denoted as \\(\\pmb{g_p}\\). We use gradient ascent to update \\(\\pmb{p}\\) by \\(\\pmb{g_p}\\) with the learning rate \\(\\rho\\)." + }, + { + "type": "image", + "bbox": [ + 0.501, + 0.089, + 0.895, + 0.315 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.323, + 0.892, + 0.366 + ], + "angle": 0, + "content": "Figure 4. Overview of the pipeline in L2T. We use probability in sampling \\(L\\) transformations and update this probability through gradient ascent." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.394, + 0.632, + 0.411 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.42, + 0.582, + 0.437 + ], + "angle": 0, + "content": "4.1. Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.445, + 0.895, + 0.717 + ], + "angle": 0, + "content": "Models. We evaluate the proposed method in three categories of target models. (1) Normally trained model: We select ten well-known models for experiments. ResNet-18 [15], ResNet-101 [15], ResNext-50 [59], DenseNet-121 [17], Inception-v3 [39], and Inception-v4 [39], ViT-B [9], PiT [16], Visformer [5], and Swin [30]. All of these models are pre-trained on the ImageNet dataset. (2) Adversarial trained models: we select four defense methods in our experiments. They are adversarial training (AT) [40], high-level representation guided denoiser (HGD) [24], neural representation purifier (NRP) [33], and randomized smoothing (RS) [6]. (3) Vision API: to imitate a practical scenario, we compare the attack performance on popular vision API. We chose Google Vision, Azure AI, GPT-4V, and Bard. For categories (2) and (3), we use ensemble-based attack. We choose two CNN-based models, ResNet18 and Inception-v4, and two transformer-based models, Visformer and Swin, to construct the ensemble surrogate model." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.718, + 0.894, + 0.763 + ], + "angle": 0, + "content": "Dataset. Following previous works [46, 50, 57], we randomly choose 1,000 images from ILSVRC 2012 validation set [36]. All images are classified correctly by the models." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Baseline. We compare L2T with other input transformation adversarial methods. There are two categories of previous methods. The fixed transformation attack followed a fixed transformation scheme. We select TIM [8], SIM [26], Admix [46], DEM [67], IDE [58], Mask [10], \\(\\mathrm{S}^2\\mathrm{IM}\\) [31], BSR [42], and SIA [50] for comparison. The learned transformation attack followed a set of transformations predicted by a trained network to generate adversarial examples. We also compare our method with learned transformation at-" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24277" + } + ], + [ + { + "type": "image_caption", + "bbox": [ + 0.128, + 0.09, + 0.197, + 0.1 + ], + "angle": 0, + "content": "(a) ResNet-18" + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.098, + 0.232, + 0.225 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.289, + 0.09, + 0.363, + 0.1 + ], + "angle": 0, + "content": "(b) ResNet-101" + }, + { + "type": "image", + "bbox": [ + 0.245, + 0.097, + 0.398, + 0.225 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.451, + 0.09, + 0.53, + 0.1 + ], + "angle": 0, + "content": "(c) Inception-v3" + }, + { + "type": "image", + "bbox": [ + 0.409, + 0.097, + 0.563, + 0.225 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.617, + 0.09, + 0.694, + 0.1 + ], + "angle": 0, + "content": "(d) ResNeXt-50" + }, + { + "type": "image", + "bbox": [ + 0.574, + 0.097, + 0.726, + 0.225 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.78, + 0.09, + 0.859, + 0.1 + ], + "angle": 0, + "content": "(e) Inception-v4" + }, + { + "type": "image", + "bbox": [ + 0.739, + 0.1, + 0.892, + 0.225 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.12, + 0.23, + 0.203, + 0.24 + ], + "angle": 0, + "content": "(f) DenseNet-121" + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.239, + 0.232, + 0.366 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.308, + 0.23, + 0.344, + 0.24 + ], + "angle": 0, + "content": "(g) ViT" + }, + { + "type": "image", + "bbox": [ + 0.245, + 0.238, + 0.398, + 0.365 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.473, + 0.23, + 0.509, + 0.24 + ], + "angle": 0, + "content": "(h) PiT" + }, + { + "type": "image", + "bbox": [ + 0.409, + 0.238, + 0.563, + 0.365 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.636, + 0.23, + 0.674, + 0.241 + ], + "angle": 0, + "content": "(i) Swin" + }, + { + "type": "image", + "bbox": [ + 0.574, + 0.238, + 0.726, + 0.365 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.786, + 0.23, + 0.853, + 0.24 + ], + "angle": 0, + "content": "(j) Visformer" + }, + { + "type": "image", + "bbox": [ + 0.737, + 0.238, + 0.892, + 0.366 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.379, + 0.893, + 0.407 + ], + "angle": 0, + "content": "Figure 5. Average attack success rates \\((\\%)\\) of ten models on the adversarial examples crafted on each model. The x-axis of each sub-figure denotes different attack methods. We include the detail number in our supplementary material." + }, + { + "type": "image", + "bbox": [ + 0.105, + 0.436, + 0.443, + 0.615 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.632, + 0.47, + 0.675 + ], + "angle": 0, + "content": "Figure 6. Attack success rates (ASR) \\((\\%)\\) of adversarial examples generated by L2T with various number of operations \\(K\\). We include the detail number in our supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.703, + 0.469, + 0.748 + ], + "angle": 0, + "content": "tacks, such as AutoMA [63], ATTA [53], and AITL [64]. All these methods are integrated with MI-FGSM [7] to generate adversarial examples." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.473, + 0.902 + ], + "angle": 0, + "content": "Evaluation Settings. We follow the hyper-parameter setting of MI-FGSM and set the perturbation budget \\(\\epsilon = 16\\), number of iteration \\(T = 10\\), step size \\(\\alpha = \\epsilon / T = 1.6\\) and decay factor \\(\\mu = 1\\). For our method, we adopt the number of operations as 2, the number of samples as 10, and the learning rate \\(\\rho\\) as 0.01. For the candidate operation, we chose ten categories of transformations. Each category contains ten specific operations with different parameters. We will discuss the detailed settings of our method and other baselines in the supplementary materials." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.433, + 0.757, + 0.45 + ], + "angle": 0, + "content": "4.2. Evaluations on single models" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.457, + 0.895, + 0.578 + ], + "angle": 0, + "content": "Our proposed L2T exhibits better adversarial transferability to various input transformation based attacks. We take a single model as the surrogate model and evaluate the average attack success rate (ASR), i.e., the average misclassification rates across ten models. We summarized our results in Figure 5. Each subfigure denotes the attacker generates the adversarial examples on the corresponding models and its x-axis denotes the attack algorithm used." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.579, + 0.895, + 0.791 + ], + "angle": 0, + "content": "First, we observe that L2T consistently outperforms all other attackers, regardless of the surrogate model. Other baseline methods have various adversarial transferability according to the surrogate models. For example, the BSR performs to be the strongest baseline on ResNet-18. However, the BSR cannot remain efficient when the surrogate model is changed to Swin or PiT. In contrast, our proposed L2T is suitable for all the surrogate models being tested. These results also strengthen our argument that we should dynamically choose the transformation to fit the surrogate models. Specifically, in the worst case (subfig. c), our proposed L2T still outperforms the strongest baseline (\\( S^2 \\)IM) by \\( 2.1\\% \\). Overall, L2T outperforms the other baseline by \\( 22.9\\% \\) on average ASR." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.802, + 0.783, + 0.817 + ], + "angle": 0, + "content": "4.3. Evaluations on defense methods" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.895, + 0.901 + ], + "angle": 0, + "content": "L2T is also capable of adversarial robust mechanisms. We test the attack performance of L2T against several defense mechanisms, including AT, HGD, NRP, and RS. We choose the ensemble setting to attack these defense approaches. We use the ensemble of four models, ResNet-18, Inception-v4," + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24278" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.09, + 0.271, + 0.226 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.089, + 0.477, + 0.226 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.494, + 0.089, + 0.685, + 0.226 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.699, + 0.089, + 0.892, + 0.226 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.079, + 0.228, + 0.272, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.285, + 0.228, + 0.478, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.491, + 0.228, + 0.685, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.699, + 0.228, + 0.892, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.379, + 0.893, + 0.407 + ], + "angle": 0, + "content": "Figure 7. We integrate the ensemble-based attack with input transformation and evaluate the performance on defense methods and popular vision APIs. We include the detail number in our supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.434, + 0.471, + 0.495 + ], + "angle": 0, + "content": "Visformer, and Swin, as the surrogate model. We summarized our results in Figure 7 (a), (b), (c), and (d). Each subfigure denotes the model to be attacked and its x-axis denotes the attack algorithm used." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.496, + 0.473, + 0.664 + ], + "angle": 0, + "content": "From Fig. 7, it is clear that L2T remains efficient. L2T consistently outperforms other methods against various defense methods. Notably, it achieves the attack success rate of \\(47.9\\%\\), \\(98.5\\%\\), \\(87.2\\%\\), and \\(46.7\\%\\) on AT, HGD, NRP, and RS, respectively. Even on the certified defense RS, the strongest defense among the four, L2T achieves the attack success rate of \\(46.7\\%\\), which exceeds the best baseline (AITL) by \\(4.6\\%\\). This is also the biggest improvement L2T made compared to other defenses. This indicates that the dynamic of iteration also exists in the adversarial robust mechanism, which can be used to diminish the its performance." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.678, + 0.314, + 0.693 + ], + "angle": 0, + "content": "4.4. Evaluations on vision API" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.703, + 0.471, + 0.822 + ], + "angle": 0, + "content": "Our proposed L2T can also perform well in realistic scenarios. To imitate the real-world application, we test the performance of L2T on Vision API. We use the same setting in sec. 4.3 to craft adversarial examples. We choose Google Vision (Figure 7 (e)) and Azure AI (Figure 7 (f)) to evaluate attacks on vision-only API. We also choose ChatGPT-4V (Figure 7 (g)) and Gemini (Figure 7 (f)) to evaluate attacks on the foundation model API." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.473, + 0.903 + ], + "angle": 0, + "content": "As shown in Fig. 7, L2T is generally the best attacker to the real-world API. All attacks perform better on foundation model API than vision-only API. For vision-only API, L2T outperforms the strongest baseline by \\(8.7\\%\\) and \\(12.6\\%\\), respectively. For foundation model API, L2T achieves nearly" + }, + { + "type": "image", + "bbox": [ + 0.527, + 0.436, + 0.868, + 0.642 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.657, + 0.892, + 0.7 + ], + "angle": 0, + "content": "Figure 8. Attack success rates (ASR) (\\%) of adversarial examples generated by L2T with various number of transformations \\(L\\). We include the detail number in our supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.728, + 0.862, + 0.743 + ], + "angle": 0, + "content": "\\(100\\%\\) attack success rate on both GPT-4V and Gemini." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.756, + 0.65, + 0.772 + ], + "angle": 0, + "content": "4.5. Ablation study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.892, + 0.903 + ], + "angle": 0, + "content": "On the numbers of operation \\( K \\). As shown in Fig. 6, we study the impact of \\( K \\) on adversarial transferability. We craft the adversarial example on ResNet-18 and evaluate them on the other nine models. There is a clear difference between one operation and two operations. The average attack success rate increases by \\( 8.09\\% \\), from \\( 80.89\\% \\) to \\( 88.98\\% \\). However, when the \\( K \\geq 3 \\), the improvement becomes marginal. The average attack success rate only" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24279" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.106, + 0.09, + 0.862, + 0.104 + ], + "angle": 0, + "content": "Table 1. Attack success rates (%) of adversarial examples by L2T and Rand (randomly choose transformation in each iteration)." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.114, + 0.895, + 0.162 + ], + "angle": 0, + "content": "
ResNet-18ResNet-101ResNeXt-50DenseNet-121Inception-v3Inception-v4ViTPiTVisformerswin
Rand52.3559.0653.1956.6443.0144.4158.4154.4865.08
L2T (Ours)90.0091.9091.0092.8078.8082.4090.1093.5096.20
" + }, + { + "type": "image", + "bbox": [ + 0.107, + 0.189, + 0.445, + 0.371 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.388, + 0.471, + 0.43 + ], + "angle": 0, + "content": "Figure 9. Average attack success rates (ASR) (\\%) of adversarial examples generated by L2T with various number of steps \\( T \\). We include the detail number in our supplementary material." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.459, + 0.471, + 0.489 + ], + "angle": 0, + "content": "increases by \\(2.29\\%\\) when \\(K\\) is increased from 2 to 5. Thus, \\(K\\) should be moderately settled as 2." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.491, + 0.474, + 0.702 + ], + "angle": 0, + "content": "On the number of transformations \\( L \\). We conducted experiments on the number of transformations \\( L \\). We craft the adversarial example on ResNet-18 and evaluate them on the other nine models. We choose \\( L \\) from 1 to 50. From Fig. 8, we observe that the adversarial transferability improves steadily with the number of transformations. The increase is significant when the number of transformations grows from 1 to 20, which improves from an average attack success rate of \\( 75.7\\% \\) to an average attack success rate of \\( 91.1\\% \\). However, transferability does not increase significantly after the number exceeds 20, where the average attack success rate only increases \\( 1.5\\% \\). To keep the balance between computation efficiency and adversarial transferability, we suggest the number of samples set to 20." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.704, + 0.471, + 0.869 + ], + "angle": 0, + "content": "On the number of iterations \\(T\\). We discuss the number of iterations among different attack approaches. We craft the adversarial example on ResNet-18 and compare the average attack success rate of 10 models. As shown in Fig. 9, for all the attack methods, the attack success rate increased steadily for the first 10 iterations. L2T achieves the fastest speed of increase, which reaches \\(89.47\\%\\) at iteration 10. After 10 iterations, most of the methods struggled to make improvements. For example, the Admix goes around \\(71\\%\\). The performance of \\(\\mathrm{S}^2\\mathrm{IM}\\) even decreases from \\(73\\%\\) to \\(70\\%\\). Meanwhile, L2T still maintains a stable increase, from \\(89.47\\%\\) to \\(94.77\\%\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Comparison with random sampling. We compare the learnable strategy with random sampling. As shown in" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.185, + 0.891, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.338, + 0.895, + 0.38 + ], + "angle": 0, + "content": "Figure 10. The average attack success rates \\((\\%)\\) of adversarial examples crafted by L2T and L2T without a single transformation. - indicates removing such transformation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.41, + 0.895, + 0.515 + ], + "angle": 0, + "content": "Tab. 1, there is a clear gap of the attack success rate between random sampling and gradient-guided sampling. The minimum difference is \\(31.12\\%\\) with setting Visformer as the surrogate model. For other surrogate models, the gap is even larger. This experiment indicates random sampling cannot effectively sample the best transformation trajectory, and the transformation in each iteration needs to be chosen carefully." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.516, + 0.895, + 0.637 + ], + "angle": 0, + "content": "Operation candidates analysis. We conducted an ablation study for the operation candidates. We subtract each operation in the candidates and conduct L2T on the updated operation candidates. From Fig. 10, we observe that subtracting any operations will lead to a performance decrease. For example, by subtracting the scale operation, the performance decreases for \\(23.5\\%\\). Meanwhile, subtracting mixup and translation only results in a \\(3.1\\%\\) decrease." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.655, + 0.62, + 0.67 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.681, + 0.895, + 0.816 + ], + "angle": 0, + "content": "In this paper, we study the dynamic property for input transformation. Utilizing this property, we propose L2T to optimize the input transformation in each iteration. By updating a sampling probability, our method provides an approximate solution to input transformation optimization. Our experiments further study the effectiveness of our methods. Our method performs consistently well among different targeted models. This paper provides a new perspective to understand the transferability of adversarial examples." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.817, + 0.897, + 0.9 + ], + "angle": 0, + "content": "Acknowledgement. This work was supported by NSF under grant 2202124 and the Center of Excellence in Data Science, an Empire State Development-designated Center of Excellence. The content of the information does not necessarily reflect the position of the Government, and no official endorsement should be inferred." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "24280" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.122, + 0.174, + 0.137 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.147, + 0.47, + 0.188 + ], + "angle": 0, + "content": "[1] Mihalj Bakator and Dragica Radosav. Deep learning and medical diagnosis: A review of literature. 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Springer, 2020. 5" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.894, + 0.333 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "24283" + } + ] +] \ No newline at end of file diff --git a/2024/Learning to Transform Dynamically for Better Adversarial Transferability/20178bd8-b1c9-4630-a7e2-243d8c197a2f_origin.pdf b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/20178bd8-b1c9-4630-a7e2-243d8c197a2f_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..a2e5f640351cbd14fe1b8309261e98e6f1f3aba9 --- /dev/null +++ b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/20178bd8-b1c9-4630-a7e2-243d8c197a2f_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:6adc5fd6a8ab8380ad999c551a21462b714c126eb3645234b4a9fcb1b0319c50 +size 2618114 diff --git a/2024/Learning to Transform Dynamically for Better Adversarial Transferability/full.md b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/full.md new file mode 100644 index 0000000000000000000000000000000000000000..22e113a02df99caab923c4bad9e441166539dcd5 --- /dev/null +++ b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/full.md @@ -0,0 +1,386 @@ +# Learning to Transform Dynamically for Better Adversarial Transferability + +$^{\ddagger}$ Rongyi Zhu *†Zeliang Zhang Susan Liang Zhuo Liu ‡ Chenliang Xu University of Rochester + +{rongyi.zhu, zeliang.zhang, susan.liang, zhuo.liu, chenliang.xu}@rochester.edu + +# Abstract + +Adversarial examples, crafted by adding perturbations imperceptible to humans, can deceive neural networks. Recent studies identify the adversarial transferability across various models, i.e., the cross-model attack ability of adversarial samples. To enhance such adversarial transferability, existing input transformation-based methods diversify input data with transformation augmentation. However, their effectiveness is limited by the finite number of available transformations. In our study, we introduce a novel approach named Learning to Transform (L2T). L2T increases the diversity of transformed images by selecting the optimal combination of operations from a pool of candidates, consequently improving adversarial transferability. We conceptualize the selection of optimal transformation combinations as a trajectory optimization problem and employ a reinforcement learning strategy to effectively solve the problem. Comprehensive experiments on the ImageNet dataset, as well as practical tests with Google Vision and GPT-4V, reveal that L2T surpasses current methodologies in enhancing adversarial transferability, thereby confirming its effectiveness and practical significance. The code is available at https://github.com/ZhangAIP1/TransferAttack. + +# 1. Introduction + +Neural networks have been adopted as the building block for various real-world applications, such as face detection [37, 41], autonomous driving [12, 25], and medical diagnosis [1, 35]. However, neural networks are vulnerable to adversarial examples, which contain human imperceptible adversarial perturbations on the benign input. This issue is increasingly concerning researchers, as it is essential for ensuring the trustworthy use of neural networks [3, 19, 65, 66]. + +In real-world scenarios of adversarial attacks, the target model is usually inaccessible. To attack these inaccessible models, many studies instead rely on surrogate models + +![](images/3fc284a7eda7f1f3922cef808f6d2f611855a743022251725b1e4e94c7d12c8c.jpg) +Figure 1. For input transformation-based attacks, most works design a fixed transformation and use it to craft the adversarial perturbation. The learning-based methods preliminarily predict augmentation strategies for current images for better adversarial transferability. These methods cannot respond to the distribution shifts between benign images and adversarial examples. We propose Learning to Transform (L2T), which uses the dynamic of the optimal transformation in each iteration to further boost the adversarial transferability. + +to generate adversarial examples [7, 57] and use generated samples to mislead the target model. This cross-model attack ability of samples generated on the surrogate models is called "adversarial transferability." Numerous research studies are dedicated to enhancing adversarial transferability, which can be classified into four categories: gradient-based methods [7, 26, 44, 47], input transformation-based methods [8, 26, 46, 57], architecture-based methods [23, 52], and ensemble-based methods [28, 60]. Among these attack methodologies, input transformation-based methods gain much popularity because of their plug-n-play advantage, which can be seamlessly integrated into other attack techniques [7, 44]. However, we discover that existing input + +transformation-based methods adopt the same transformation when crafting adversarial examples, limiting the flexibility of transformation operations. We hypothesize that we should select the optimal transformation dynamically in each iteration to enhance the adversarial transferability. + +As shown in Fig. 1, prior input transformation-based methods often revolve around designing fixed augmentation strategies like resizing inputs [57], block masking [10], or mix-up [46]. A more dynamic approach is presented by [63], advocating the precomputation of various sequences of augmentation strategies to apply to each iteration to enhance the attack performance. Complementing this, Wu et al. [53] proposes the use of generative models for image augmentation to boost the adversarial transferability. Some studies go further, combining multiple augmentation strategies to amplify input diversity to improve the performance. For example, Yuan et al. [64] introduces a neural network that generates a prediction of the optimal transformation strategy and applies the strategy to improve performance. A further improvement is hindered by the limited number of transformations. + +To fully utilize the limited number of transformations, a natural idea is to use a combination of operations. However, it is not always efficient to combine different transformations together for attack, as reported in [50]. We expect to find an optimal combination of transformations to achieve a tradeoff between operation diversity and adversarial transferability. Nonetheless, the enormity of the search space presents a significant challenge, impeding the identification of the most efficacious combination of transformations during an attack for optimal adversarial transferability. To surmount this hurdle, we conceptualize the search process of the optimal combination of transformations as a problem of optimal trajectory search. Each node within this trajectory represents an individual transformation, and each directed edge means a transfer of the optimal transformation from the current step to the next step. To effectively obtain the optimal trajectory in such a large search space, we design a reinforcement learning-based approach, capitalizing on its demonstrated efficacy in navigating expansive search domains. + +In this paper, we introduce a novel framework called Learning to Transform (L2T) to improve the adversarial transferability of generated adversarial examples. L2T dynamically learns and applies the optimal input transformation in each iteration. Instead of exhaustively enumerating all possible input transformation methods, we employ a reinforcement learning-based approach to reduce the search space and better utilize the transformations to improve the diversity. In each iteration of the adversarial attack, we sample a subset of transformations and apply them to the adversarial examples. Subsequently, we update the sampling probabilities by conducting gradient ascent to maximize the loss. Our method effectively learns the dynamics of optimal transformations in attacks, leading to a significant enhancement in + +adversarial transferability. Additionally, compared to other learn-based adversarial attack methods, our approach is more efficient for adversarial example generation, as it obviates the need for additional training modules. + +We summarize our contributions as follows, + +- We formulate the problem of optimal transformation in adversarial attacks, which studies finding the optimal combination of transformations to increase the input diversities, thus improving the adversarial transferability. +- We propose Learning to Transform (L2T) that exploits the optimal transformation in each iteration and dynamically adjusts transformations to boost adversarial transferability. +- Extensive experiments on the ImageNet dataset demonstrate that L2T outperforms other baselines. We also validate L2T's superiority in real-world scenarios, such as Google Vision and GPT-4V. + +# 2. Related Work + +# 2.1. Adversarial Attack + +Various adversarial attacks have been proposed, e.g., gradient-based attack [13, 20, 32], transfer-based attack [7, 31, 51, 57], score-based attack [4, 18, 22], decision-based attack [2, 21, 49], generation-based attack [45, 54]. Among these, transfer-based attacks do not require the information of the victim models, making it popular to attack the deep models in the real world and raise more research interests. To improve adversarial transferability, various momentum-based attacks have been proposed, such as MI-FGSM [7], NI-FGSM [26], VMI-FGSM [44], EMI-FGSM [47], etc. Several input transformation methods are also proposed, such as DIM [57], TIM [8], SIM [26], Admix [46], SIA [50], STM [11], BSR [43], etc., which augment images used for adversarial perturbation computation to boost transferability. The input transformation-based methods can be integrated into the gradient-based attacks for better performance. + +Delving into the input transformation-based methods, most works are limited to designing a fixed transformation to augment the images, which limits the diversity of transformed images and the adversarial transferability. To address this issue, some researchers [53, 63, 64] propose to augment the images with a set of multiple transformations predicted by a pre-trained network. Automatic Model Augmentation (AutoMA) [63] adopts a Proximal Policy Optimization (PPO) algorithm in search of a strong augmentation policy. Adversarial Transformation-enhanced Transfer Attack (ATTA) [53] proposes to employ an adversarial transformation network in modeling the most harmful distortions. Adaptive Image Transformation Learner (AITL) [64] incorporates different image transformations into a unified framework to learn adaptive transformations for each benign sample to boost adversarial transferability. By applying optimal multiple transformations, the adversarial attack per + +formance is largely improved. + +# 2.2. Adversarial Defense + +Various defense approaches have been proposed to mitigate the threat of adversarial attacks, such as adversarial training [32, 40, 48], input preprocessing [33, 55], feature denoising [24, 56, 62], certified defense [6, 14, 34], etc. Liao et al. [24] train a denoising autoencoder, namely the High-level representation guided denoiser (HGD), to purify the adversarial perturbations. Xie et al. [55] propose to randomly resize the image and add padding to mitigate the adversarial effect, namely the Randomized resizing and padding (R&P). Xu et al. [61] propose the Bit depth reduction (Bit-Red) method, which reduces the number of bits for each pixel to squeeze the perturbation. Liu et al. [29] defend against adversarial attacks by applying a JPEG-based compression method to adversarial images. Cohen et al. [6] adopt randomized smoothing (RS) to train a certifiably robust classifier. Naseer et al. [33] propose a Neural Representation Purifier (NRP) to eliminate perturbation. + +# 3. Learning to Transform + +# 3.1. Task definition + +The crafting of adversarial examples usually takes an iterative framework to update the adversarial perturbation. Given a benign sample $\pmb{x}$ and the corresponding label $y$ , a transferable attack takes a surrogate classifier $f_{\theta}$ and iteratively updates the adversarial example $x^{adv}$ to maximize the loss of classifying $f_{\theta}(x^{adv})$ to $y$ . Take I-FGSM [38] as an example. The adversarial example $x_{t}^{adv}$ at the $t$ -th iteration can be formulated as follows: + +$$ +\boldsymbol {x} _ {t} ^ {a d v} = \boldsymbol {x} _ {t - 1} ^ {a d v} + \alpha \cdot \operatorname {s i g n} \left(\nabla_ {\boldsymbol {x} _ {t - 1} ^ {a d v}} J \left(f _ {\boldsymbol {\theta}} \left(\boldsymbol {x} _ {t - 1} ^ {a d v}, y\right)\right)\right), \tag {1} +$$ + +where we denote $\alpha$ as the step size, $J(\cdot ,\cdot)$ as the classification loss function. As identified by previous studies, the adversarial example exhibits a characteristic of transferability, where the adversarial examples generated by the surrogate model can fool other neural networks. + +Input transformation-based methods are one of the most effective methods to boost adversarial transferability. With these methods, the adversarial samples are firstly transformed by a set of image transformations and then proceeded to gradient calculation. Let $\varphi$ denote a set of image transformations operation $o$ , where $\varphi = \{o^i | i \in \{1, 2, \dots, k\}\}$ . At the $t$ -th iteration, the adversarial example $\boldsymbol{x}_t^{adv}$ is transformed sequentially by $o^i$ as follows, + +$$ +\varphi \left(\boldsymbol {x} _ {t} ^ {a d v}\right) = o ^ {k} \oplus o ^ {k - 1} \oplus \dots \oplus o ^ {1} \left(\boldsymbol {x} _ {t} ^ {a d v}\right), \tag {2} +$$ + +where $o^2 \oplus o^1(\boldsymbol{x})$ denotes the operation $o^2(o^1(\boldsymbol{x}))$ , $o^1, o^2 \in \varphi$ . We use the gradient of $\varphi(\boldsymbol{x}_t^{adv})$ with respect to the loss function to update the adversarial perturbation as Eq. (1). + +![](images/a5b3a2732f3db3e76cd32a29ac9ad6490a3d811d4b7a52ac4daeb0d905e6966f.jpg) +(a) One iteration + +![](images/50e820cc6dffe34d9cf92467484de000dde6829eceef78172570e6e0bd8443e9.jpg) +(b) Two iteration +Figure 2. Comparison for different operations in boosting the adversarial transferability. The number in the box denotes the number of fooled models (Maximum: 9). In (a), the horizontal axis denotes different transformation operations and the vertical axis denotes different benign examples. In (b), the vertical axis denotes the transformation used in the first iteration and the horizontal axis denotes the transformation used in the second iteration + +There are two categories for selecting the operation set $\varphi$ in the previous study. One line of research focuses on designing fixed transformation-based methods, which use a pre-defined transformation $\varphi$ . For example, Admix chooses mixup and scaling for transformation $\varphi$ . The other line of research proposes the learning-based transformation methods, which usually use a generative model to directly generate the transformed $\varphi(x)$ . Compared with the fixed transformation-based methods, learning-based methods enjoy more diversity of transformed images, leading to a better performance in adversarial transferability. In our work, we study the learning-based transformation methods. + +# 3.2. Motivation + +Previous research designs lots of transformations to improve the diversity of images, thus guiding the adversarial attacks to focus more on the invariant robust features. However, it does not always work by increasing the number of transformed images for attacks to boost the adversarial transferability. Because some combination of transformations can cause damage to original examples, losing massive amounts of information used for transferable attacks. A natural question occurs to us, for one image, does there exist the optimal combination of transformations for the best adversarial transferability? + +To answer this question, we start by generating adversarial examples in one iteration. We take an example of crafting adversarial examples using ResNet-18 to attack other 9 models1. We denote 5 operations for input transformation methods, namely the crop, rotation, shuffle, scaling, and mix-up. We use these operations on five images for attacks and report the number of models fooled. We report the results in Fig. 2. It can be seen that by shuffle, we can achieve the maximum + +![](images/83eed6cd4c482d0f56a2675065f8cf12b298c2b1897e4d469d33db568e70e186.jpg) +Figure 3. There exists an optimal transformation trajectory for boosting adversarial transferability. However, the search space increases exponentially with iteration number and operation number. + +transferable attack success rates on a dog image, indicating the optimal transformations in all possible 5 operations. + +We continue our discussion in the two-iteration scenario. Following the same setting in one iteration, we report the number of fooled models. It can be seen that by choosing crop in the first iteration and scaling for the second iteration, which successfully fooled 6 models out of 9. We also notice that shuffle, the optimal transformation in one iteration, can not maintain the optimal performance. The average fooled model for shuffle is less than crop in 0.2. + +Following the aforementioned discussion, we move on to generating adversarial examples in 3 iterations, where we only take one operation as the image transformation to attack the image. As exemplified in Fig. 3, there are $5 \times 5 \times 5$ possible trajectories to transform the image for attacks. Among these trajectories, it can achieve the best performance by first shuffling, then rotating, and last shuffling the image. It should be noted it cannot consistently achieve the best performance by increasing the number of transformations for a higher diversity. As shown in Fig. 3, we respectively take the scaling, shuffle, and rotation operations at each iteration in trajectory 2. However, it has the worst attack success rate among the presented results. + +Generalizing the previous problem to common cases, we are motivated to identify an optimal transformation trajectory $\mathcal{T}$ , which is defined as the sequence of transformation used in each iteration as $(\varphi_{1},\varphi_{2},\dots,\varphi_{T})$ , for the best adversarial transferability. Each element $\varphi_T$ denotes the transformation used in iteration $t$ . It can be formulated as follows: + +$$ +\mathcal {T} ^ {*} = \underset {\mathcal {T}} {\operatorname {a r g m a x}} (\mathbb {E} [ \mathcal {L} (f _ {\boldsymbol {\theta}} (\boldsymbol {x} _ {\mathcal {T}} ^ {a d v}), y) ]), \tag {3} +$$ + +where we denote $x_{\mathcal{T}}^{adv}$ as the adversarial example generated by the surrogate model under transformation trajectory $\mathcal{T}$ . + +However, finding $\mathcal{T}^*$ is hard. First, the search space is large. For example, supposing five candidate transformations, even if we only take one operation in one iteration to transform the image, we will still have an enormous search space for ten iterations that will be $5^{10}$ . The number of possible transformation trajectories grows exponentially with increasing the number of iterations and candidate transformations. Second, we can not access the black-box model $f$ , making it hard to optimize the Eq. (3) directly. Besides, as identified in the previous work [64], each image has a different optimal transformation to boost the adversarial transferability. There is no optimal transformation trajectory shared for all images. + +# 3.3. Methodology + +The problem of Eq. (3) can be transformed into an optimal trajectory search problem, on which reinforcement learning has shown great compatibility. We are inspired to take a reinforcement learning-based approach in solving this optimization problem to enhance adversarial transferability. + +Supposing we have $M$ operations $\{o^1,o^2,\dots,o^M\}$ in total, the optimal transformation trajectory $\mathcal{T}$ is a temporal sequence of the combination of different operations. The probability $\pmb{p}$ contains $M$ possibilities $\{p_{o^1},p_{o^2},\dots,p_{o^M}\}$ for each iteration. Each element $p_{o^m}$ denotes the possibility of sampling operation $o^m$ , $m\in \{1,2,\ldots,M\}$ . And $p_{o^m}$ follows $\sum_{m = 1}^{M}p_{o^m} = 1$ . A transformation $\varphi$ consists $K$ operations $o^k$ , $k\in \{1,2,\dots,M\}$ . We sampled $K$ operations from $\pmb{p}$ . We have the possibility of a transformation $\varphi$ by $P(\varphi) = \prod_{k = 1}^{K}p_{o^k}$ . + +For each iteration $t$ , we sample a combination of transformation $\varphi_t$ . Each transformation in $\varphi_t$ is sampled from candidates depending on $\pmb{p}$ . To get an optimal trajectory $\mathcal{T} = (\varphi_1, \dots, \varphi_T)$ , we need to dynamically optimize the sampling distribution $\pmb{p}$ in each iteration $t$ . We formulate the problem of searching optima $\pmb{p}^*$ in each iteration as follows, + +$$ +\begin{array}{r} \boldsymbol {p} ^ {*} = \underset {\boldsymbol {p}} {\arg \max } \mathbb {E} _ {\varphi \sim \mathbf {p}} [ \mathcal {L} (f _ {\boldsymbol {\theta}} (\varphi (\tilde {\boldsymbol {x}} ^ {a d v})), y) ] \\ \tilde {\boldsymbol {x}} ^ {a d v} = \underset {\boldsymbol {x} ^ {a d v}} {\arg \max } \mathbb {E} _ {\varphi \sim \mathbf {p}} [ \mathcal {L} (f _ {\boldsymbol {\theta}} (\varphi (\boldsymbol {x} ^ {a d v})), y) ], \end{array} \tag {4} +$$ + +which is a bi-level optimization. The inner optimization targets to optimize the adversarial example, and the outer optimization tries to find the optimal sampling probability. Following [27], we adopt an one-step optimization strategy to derive the approximated $p^*$ : + +$$ +\boldsymbol {p} ^ {*} \approx \boldsymbol {p} + \rho \cdot \boldsymbol {g} _ {\boldsymbol {p}}, \tag {5} +$$ + +where the $\rho$ is the learning rate and $g_{p}$ is the gradient for $\pmb{p}$ . Implementation details. We present the overview of our method in Fig. 4. First, we sample $L$ sequences of transformation $\varphi_t^l,l\in [1,2,\dots,L]$ , depending on the sampling + +Algorithm 1 Gradient policy for optimal augmentation search. + +Input: Classifier $f(\cdot)$ ; The benign sample $x$ with ground-truth label $y$ ; Loss function $\mathcal{L}(\cdot, \cdot)$ ; candidate operation pool $\Gamma$ , the number of iterations $T$ , perturbation scale $\epsilon$ , policy learning rate $\rho$ , number of operations $K$ , number of transformations $L$ , decay factor $\mu$ ; + +$$ +\alpha = \epsilon / T, \boldsymbol {g} _ {0} = 0, \boldsymbol {x} _ {0} ^ {a d v} = \boldsymbol {x}, \boldsymbol {p} \sim \mathcal {N} (0, 1) +$$ + +while $t = 1\gets T$ do + +1. Under the distribution $\pmb{p}$ , sample $L$ transformation $\varphi_t$ , each consisting of $K$ operations. +2. Transform adversarial examples: + +$$ +\varphi_ {t} ^ {l} \left(x _ {t} ^ {a d v}\right) = o ^ {K} \oplus o ^ {K - 1} \overline {{\oplus}} \dots \oplus o ^ {1} \left(\boldsymbol {x} _ {t} ^ {a d v}\right). +$$ + +3. Calculate the average gradient: + +$$ +\bar {\boldsymbol {g}} = \frac {1}{L} \sum_ {l = 1} ^ {L} \nabla_ {\boldsymbol {x} _ {t - 1} ^ {a d v}} \mathcal {L} (\varphi_ {t} ^ {l} (\boldsymbol {x} _ {t - 1} ^ {a d v}), y). +$$ + +4. Update the momentum: + +$$ +\boldsymbol {g} _ {t} = \mu \boldsymbol {g} _ {t - 1} + \frac {\bar {g}}{| | \bar {g} | | _ {1}}. +$$ + +5. Update the adversarial example: + +$$ +\boldsymbol {x} _ {t} ^ {a d v} = \operatorname {c l i p} \left(\boldsymbol {x} _ {t - 1} ^ {a d v} + \alpha \cdot \operatorname {s i g n} \left(\boldsymbol {g} _ {t}\right), 0, 1\right). +$$ + +6. Calculate the probability gradient: + +$$ +\pmb {g} _ {\pmb {p}} = \frac {\partial \left(\frac {1}{L} \sum_ {l = 1} ^ {L} \mathbf {P} (\varphi_ {t} ^ {l}) \mathcal {L} (f _ {\pmb {\theta}} (\varphi_ {t} ^ {l} (\mathbf {x} _ {t} ^ {a d v})), y) ]\right)}{\partial \mathbf {P} (\varphi_ {t} ^ {l})}. +$$ + +7. Update the probability: + +$$ +\boldsymbol {p} = \boldsymbol {p} + \rho \cdot \boldsymbol {g} _ {\boldsymbol {p}}. +$$ + +end while + +Output: $x_{T}^{adv}$ . + +distribution $\pmb{p}$ . Next, we get the transformed examples denoted as $\varphi_t^l(x_t^{adv})$ . The probability of each sequence $\varphi_t^l$ is $P(\varphi_t^l)$ . We use $\varphi_t$ to denote all $L$ transformations, $\varphi_t = \{\varphi_t^1, \varphi_t^2, \dots, \varphi_t^L\}$ . Then, we use Eq. (1) to update the adversarial examples for each iteration. The gradient is calculated by loss between $L$ transformed examples and their corresponding labels. Last, after updating the adversarial example, we recompute the approximate $\pmb{p}$ . Specifically, we compute the gradient $g_{o^k}$ of each sampled operation $o^k$ as: + +$$ +\begin{array}{l} g _ {o ^ {k}} = \frac {\partial \mathbb {E} _ {\varphi_ {t} \sim \mathbf {p}} [ \mathcal {L} (f _ {\boldsymbol {\theta}} (\varphi_ {t} (\mathbf {x} _ {t} ^ {a d v})), y) ]}{\partial \mathbf {P} (\varphi_ {t})} \cdot \frac {\partial \mathbf {P} (\varphi_ {l})}{\partial p _ {o ^ {k}}} \\ = \frac {\partial \sum_ {l = 1} ^ {L} \mathbf {P} \left(\varphi_ {t} ^ {l}\right) \mathcal {L} \left( \right.f _ {\boldsymbol {\theta}} \left(\varphi_ {t} ^ {l} \left(\mathbf {x} _ {t} ^ {a d v}\right), y\right)\left. \right]\left. \right)}{\partial \mathbf {P} \left(\varphi_ {t} ^ {l}\right)} \cdot \frac {\partial \mathbf {P} \left(\varphi_ {l}\right)}{\partial p _ {o k}} \tag {6} \\ = \sum_ {l = 1} ^ {L} \mathcal {L} \left(f _ {\boldsymbol {\theta}} \left(\varphi_ {t} ^ {l} \left(\mathbf {x} _ {t} ^ {a d v}\right), y\right)\right) \cdot \frac {\partial \mathbf {P} \left(\varphi_ {t} ^ {l}\right)}{\partial p _ {o ^ {k}}}. \\ \end{array} +$$ + +We concat the gradients for each operation as $[g_{o^1}, g_{o^2}, \ldots, g_{o^K}]$ , which is denoted as $\pmb{g_p}$ . We use gradient ascent to update $\pmb{p}$ by $\pmb{g_p}$ with the learning rate $\rho$ . + +![](images/504faf4781a9c5c340234ae9af207ad9ff9ce18d0e14335ec561c3cccedb634a.jpg) +Figure 4. Overview of the pipeline in L2T. We use probability in sampling $L$ transformations and update this probability through gradient ascent. + +# 4. Experiments + +# 4.1. Setup + +Models. We evaluate the proposed method in three categories of target models. (1) Normally trained model: We select ten well-known models for experiments. ResNet-18 [15], ResNet-101 [15], ResNext-50 [59], DenseNet-121 [17], Inception-v3 [39], and Inception-v4 [39], ViT-B [9], PiT [16], Visformer [5], and Swin [30]. All of these models are pre-trained on the ImageNet dataset. (2) Adversarial trained models: we select four defense methods in our experiments. They are adversarial training (AT) [40], high-level representation guided denoiser (HGD) [24], neural representation purifier (NRP) [33], and randomized smoothing (RS) [6]. (3) Vision API: to imitate a practical scenario, we compare the attack performance on popular vision API. We chose Google Vision, Azure AI, GPT-4V, and Bard. For categories (2) and (3), we use ensemble-based attack. We choose two CNN-based models, ResNet18 and Inception-v4, and two transformer-based models, Visformer and Swin, to construct the ensemble surrogate model. + +Dataset. Following previous works [46, 50, 57], we randomly choose 1,000 images from ILSVRC 2012 validation set [36]. All images are classified correctly by the models. + +Baseline. We compare L2T with other input transformation adversarial methods. There are two categories of previous methods. The fixed transformation attack followed a fixed transformation scheme. We select TIM [8], SIM [26], Admix [46], DEM [67], IDE [58], Mask [10], $\mathrm{S}^2\mathrm{IM}$ [31], BSR [42], and SIA [50] for comparison. The learned transformation attack followed a set of transformations predicted by a trained network to generate adversarial examples. We also compare our method with learned transformation at- + +![](images/c41b5b9bc07d31b159df8bf6588d7f21189b3f75c538aba7fe135b7b283c593f.jpg) +(a) ResNet-18 + +![](images/176cb3ac18f8d2d58e6b363586e2ac31e38b7af7fee699368a49caa9576b7b83.jpg) +(b) ResNet-101 + +![](images/501d10e8988f843e618d74d4309de7fc7625070f13e1342db3fed83cf47ec093.jpg) +(c) Inception-v3 + +![](images/db3120f9973d28cc592ca89a33bae2e1042dabf7e19c13b799d5aa4750fc0234.jpg) +(d) ResNeXt-50 + +![](images/e9ad13e8662adb6d7c7286a1dffcd7fee1bf4fa1ca8d2e0a1060f5e24bd4bfc4.jpg) +(e) Inception-v4 + +![](images/bcd303bced0edf7fc4283c8f17d6f30528858b03691ef35b3e92971208b99654.jpg) +(f) DenseNet-121 +Figure 5. Average attack success rates $(\%)$ of ten models on the adversarial examples crafted on each model. The x-axis of each sub-figure denotes different attack methods. We include the detail number in our supplementary material. + +![](images/4a34b0695c29712d3a89de51ddee09a0eca0f3f7274a3699802caa92e2a915e6.jpg) +(g) ViT + +![](images/6e564d3e49f66af2906bb7982c5641d8d73a626ac30d6fa7849130e02749b2e7.jpg) +(h) PiT + +![](images/2c79c877f8c011f884c1429c99b220b59a59078a220f199c6478c96116d4a9ad.jpg) +(i) Swin + +![](images/1c414049bbaa658d54791797e8eb8e9f010f6785219cec32f1ec561e71be4930.jpg) +(j) Visformer + +![](images/29aa9648852fec96de73791c40cea8ae5e80f3647bbe8b9be025df2507cc437d.jpg) +Figure 6. Attack success rates (ASR) $(\%)$ of adversarial examples generated by L2T with various number of operations $K$ . We include the detail number in our supplementary material. + +tacks, such as AutoMA [63], ATTA [53], and AITL [64]. All these methods are integrated with MI-FGSM [7] to generate adversarial examples. + +Evaluation Settings. We follow the hyper-parameter setting of MI-FGSM and set the perturbation budget $\epsilon = 16$ , number of iteration $T = 10$ , step size $\alpha = \epsilon / T = 1.6$ and decay factor $\mu = 1$ . For our method, we adopt the number of operations as 2, the number of samples as 10, and the learning rate $\rho$ as 0.01. For the candidate operation, we chose ten categories of transformations. Each category contains ten specific operations with different parameters. We will discuss the detailed settings of our method and other baselines in the supplementary materials. + +# 4.2. Evaluations on single models + +Our proposed L2T exhibits better adversarial transferability to various input transformation based attacks. We take a single model as the surrogate model and evaluate the average attack success rate (ASR), i.e., the average misclassification rates across ten models. We summarized our results in Figure 5. Each subfigure denotes the attacker generates the adversarial examples on the corresponding models and its x-axis denotes the attack algorithm used. + +First, we observe that L2T consistently outperforms all other attackers, regardless of the surrogate model. Other baseline methods have various adversarial transferability according to the surrogate models. For example, the BSR performs to be the strongest baseline on ResNet-18. However, the BSR cannot remain efficient when the surrogate model is changed to Swin or PiT. In contrast, our proposed L2T is suitable for all the surrogate models being tested. These results also strengthen our argument that we should dynamically choose the transformation to fit the surrogate models. Specifically, in the worst case (subfig. c), our proposed L2T still outperforms the strongest baseline ( $S^2$ IM) by $2.1\%$ . Overall, L2T outperforms the other baseline by $22.9\%$ on average ASR. + +# 4.3. Evaluations on defense methods + +L2T is also capable of adversarial robust mechanisms. We test the attack performance of L2T against several defense mechanisms, including AT, HGD, NRP, and RS. We choose the ensemble setting to attack these defense approaches. We use the ensemble of four models, ResNet-18, Inception-v4, + +![](images/9b488102e2be5f25cc0462aa4c349cd5df40cd5fe883b1a818ca1b1218f37ad8.jpg) + +![](images/471ffd6dc282826674386745ab8a2b280b4519b14b77d069f98f0ffe2b564a3b.jpg) + +![](images/3aee0c8bee34960b93504958f1f980bfd30464cbf610f28264151af34f32d9a2.jpg) + +![](images/da9a8af87a9f58af5b3871aa9ff477419915716bd15fd484c2d1fcabd98179f2.jpg) + +![](images/d8a2a1eef80e43edc86857d4cdada5d0b83380bcd2aa67705e48b9d570ca198d.jpg) +Figure 7. We integrate the ensemble-based attack with input transformation and evaluate the performance on defense methods and popular vision APIs. We include the detail number in our supplementary material. + +![](images/336c0433addc40b44cdddfcd3a922382bafaf1c0dbf27de59b40d6801df180a6.jpg) + +![](images/5a7a7d6c55d7f4408b1bf22a9f2dcf171d67732aad979767c6a5d61aa308b1f2.jpg) + +![](images/0ae64566008047bbd7e854a91dfcedea6ea75f45341c8b9ed87e7d18489fe532.jpg) + +Visformer, and Swin, as the surrogate model. We summarized our results in Figure 7 (a), (b), (c), and (d). Each subfigure denotes the model to be attacked and its x-axis denotes the attack algorithm used. + +From Fig. 7, it is clear that L2T remains efficient. L2T consistently outperforms other methods against various defense methods. Notably, it achieves the attack success rate of $47.9\%$ , $98.5\%$ , $87.2\%$ , and $46.7\%$ on AT, HGD, NRP, and RS, respectively. Even on the certified defense RS, the strongest defense among the four, L2T achieves the attack success rate of $46.7\%$ , which exceeds the best baseline (AITL) by $4.6\%$ . This is also the biggest improvement L2T made compared to other defenses. This indicates that the dynamic of iteration also exists in the adversarial robust mechanism, which can be used to diminish the its performance. + +# 4.4. Evaluations on vision API + +Our proposed L2T can also perform well in realistic scenarios. To imitate the real-world application, we test the performance of L2T on Vision API. We use the same setting in sec. 4.3 to craft adversarial examples. We choose Google Vision (Figure 7 (e)) and Azure AI (Figure 7 (f)) to evaluate attacks on vision-only API. We also choose ChatGPT-4V (Figure 7 (g)) and Gemini (Figure 7 (f)) to evaluate attacks on the foundation model API. + +As shown in Fig. 7, L2T is generally the best attacker to the real-world API. All attacks perform better on foundation model API than vision-only API. For vision-only API, L2T outperforms the strongest baseline by $8.7\%$ and $12.6\%$ , respectively. For foundation model API, L2T achieves nearly + +![](images/9daff0bbc13d8b1fe86e0cda8ed5ec8e3dbd3bc81c613de201765672216facfe.jpg) +Figure 8. Attack success rates (ASR) (\%) of adversarial examples generated by L2T with various number of transformations $L$ . We include the detail number in our supplementary material. + +$100\%$ attack success rate on both GPT-4V and Gemini. + +# 4.5. Ablation study + +On the numbers of operation $K$ . As shown in Fig. 6, we study the impact of $K$ on adversarial transferability. We craft the adversarial example on ResNet-18 and evaluate them on the other nine models. There is a clear difference between one operation and two operations. The average attack success rate increases by $8.09\%$ , from $80.89\%$ to $88.98\%$ . However, when the $K \geq 3$ , the improvement becomes marginal. The average attack success rate only + +Table 1. Attack success rates (%) of adversarial examples by L2T and Rand (randomly choose transformation in each iteration). + +
ResNet-18ResNet-101ResNeXt-50DenseNet-121Inception-v3Inception-v4ViTPiTVisformerswin
Rand52.3559.0653.1956.6443.0144.4158.4154.4865.08
L2T (Ours)90.0091.9091.0092.8078.8082.4090.1093.5096.20
+ +![](images/092e8e5b584399518885cebf74f038fb194824676e46b4e994c52745a4c93c0f.jpg) +Figure 9. Average attack success rates (ASR) (\%) of adversarial examples generated by L2T with various number of steps $T$ . We include the detail number in our supplementary material. + +increases by $2.29\%$ when $K$ is increased from 2 to 5. Thus, $K$ should be moderately settled as 2. + +On the number of transformations $L$ . We conducted experiments on the number of transformations $L$ . We craft the adversarial example on ResNet-18 and evaluate them on the other nine models. We choose $L$ from 1 to 50. From Fig. 8, we observe that the adversarial transferability improves steadily with the number of transformations. The increase is significant when the number of transformations grows from 1 to 20, which improves from an average attack success rate of $75.7\%$ to an average attack success rate of $91.1\%$ . However, transferability does not increase significantly after the number exceeds 20, where the average attack success rate only increases $1.5\%$ . To keep the balance between computation efficiency and adversarial transferability, we suggest the number of samples set to 20. + +On the number of iterations $T$ . We discuss the number of iterations among different attack approaches. We craft the adversarial example on ResNet-18 and compare the average attack success rate of 10 models. As shown in Fig. 9, for all the attack methods, the attack success rate increased steadily for the first 10 iterations. L2T achieves the fastest speed of increase, which reaches $89.47\%$ at iteration 10. After 10 iterations, most of the methods struggled to make improvements. For example, the Admix goes around $71\%$ . The performance of $\mathrm{S}^2\mathrm{IM}$ even decreases from $73\%$ to $70\%$ . Meanwhile, L2T still maintains a stable increase, from $89.47\%$ to $94.77\%$ . + +Comparison with random sampling. We compare the learnable strategy with random sampling. As shown in + +![](images/f01b02526a24712a74e031163d0b7d0ffba7f1f17c05b9b56ad3357203a2d0e5.jpg) +Figure 10. The average attack success rates $(\%)$ of adversarial examples crafted by L2T and L2T without a single transformation. - indicates removing such transformation. + +Tab. 1, there is a clear gap of the attack success rate between random sampling and gradient-guided sampling. The minimum difference is $31.12\%$ with setting Visformer as the surrogate model. For other surrogate models, the gap is even larger. This experiment indicates random sampling cannot effectively sample the best transformation trajectory, and the transformation in each iteration needs to be chosen carefully. + +Operation candidates analysis. We conducted an ablation study for the operation candidates. We subtract each operation in the candidates and conduct L2T on the updated operation candidates. From Fig. 10, we observe that subtracting any operations will lead to a performance decrease. For example, by subtracting the scale operation, the performance decreases for $23.5\%$ . Meanwhile, subtracting mixup and translation only results in a $3.1\%$ decrease. + +# 5. Conclusion + +In this paper, we study the dynamic property for input transformation. Utilizing this property, we propose L2T to optimize the input transformation in each iteration. By updating a sampling probability, our method provides an approximate solution to input transformation optimization. Our experiments further study the effectiveness of our methods. Our method performs consistently well among different targeted models. This paper provides a new perspective to understand the transferability of adversarial examples. + +Acknowledgement. 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In European Conference on Computer Vision, pages 1-17. Springer, 2022. 2, 4, 6 +[65] Zeliang Zhang, Jinyang Jiang, Minjie Chen, Zhiyuan Wang, Yijie Peng, and Zhaofei Yu. A novel noise injection-based training scheme for better model robustness. arXiv preprint arXiv:2302.10802, 2023. 1 +[66] Zeliang Zhang, Wei Yao, Susan Liang, and Chenliang Xu. Random smooth-based certified defense against text adversarial attack. In Findings of the Association for Computational Linguistics: EACL 2024, pages 1251-1265, 2024. 1 +[67] Junhua Zou, Zhisong Pan, Junyang Qiu, Xin Liu, Ting Rui, and Wei Li. Improving the transferability of adversarial examples with resized-diverse-inputs, diversity-ensemble and region fitting. In European Conference on Computer Vision, pages 563–579. Springer, 2020. 5 \ No newline at end of file diff --git a/2024/Learning to Transform Dynamically for Better Adversarial Transferability/images.zip b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..aa7d690405b47b23b6a3c270b4edab6563dda8a5 --- /dev/null +++ b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:e426116f5e4e546892d4f8a1a0d677d7782259d8795e2b3a8e6a523d1bc156d0 +size 716958 diff --git a/2024/Learning to Transform Dynamically for Better Adversarial Transferability/layout.json b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..c1b1a9b96a6451bca8ef936ebde5f788d048ed4a --- /dev/null +++ b/2024/Learning to Transform Dynamically for Better Adversarial Transferability/layout.json @@ -0,0 +1,11615 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 67, + 103, + 526, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 103, + 526, + 121 + ], + "spans": [ + { + "bbox": [ + 67, + 103, + 526, + 121 + ], + "type": "text", + "content": "Learning to Transform Dynamically for Better Adversarial Transferability" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 105, + 142, + 487, + 171 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 105, + 142, + 487, + 171 + ], + "spans": [ + { + "bbox": [ + 105, + 142, + 487, + 171 + ], + "type": "inline_equation", + "content": "^{\\ddagger}" + }, + { + "bbox": [ + 105, + 142, + 487, + 171 + ], + "type": "text", + "content": " Rongyi Zhu *†Zeliang Zhang Susan Liang Zhuo Liu ‡ Chenliang Xu University of Rochester" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 86, + 174, + 507, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 86, + 174, + 507, + 185 + ], + "spans": [ + { + "bbox": [ + 86, + 174, + 507, + 185 + ], + "type": "text", + "content": "{rongyi.zhu, zeliang.zhang, susan.liang, zhuo.liu, chenliang.xu}@rochester.edu" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "spans": [ + { + "bbox": [ + 143, + 213, + 192, + 225 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 238, + 290, + 501 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 238, + 290, + 501 + ], + "spans": [ + { + "bbox": [ + 46, + 238, + 290, + 501 + ], + "type": "text", + "content": "Adversarial examples, crafted by adding perturbations imperceptible to humans, can deceive neural networks. Recent studies identify the adversarial transferability across various models, i.e., the cross-model attack ability of adversarial samples. To enhance such adversarial transferability, existing input transformation-based methods diversify input data with transformation augmentation. However, their effectiveness is limited by the finite number of available transformations. In our study, we introduce a novel approach named Learning to Transform (L2T). L2T increases the diversity of transformed images by selecting the optimal combination of operations from a pool of candidates, consequently improving adversarial transferability. We conceptualize the selection of optimal transformation combinations as a trajectory optimization problem and employ a reinforcement learning strategy to effectively solve the problem. Comprehensive experiments on the ImageNet dataset, as well as practical tests with Google Vision and GPT-4V, reveal that L2T surpasses current methodologies in enhancing adversarial transferability, thereby confirming its effectiveness and practical significance. The code is available at https://github.com/ZhangAIP1/TransferAttack." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 524, + 128, + 536 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 524, + 128, + 536 + ], + "spans": [ + { + "bbox": [ + 47, + 524, + 128, + 536 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 544, + 287, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 287, + 639 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 287, + 639 + ], + "type": "text", + "content": "Neural networks have been adopted as the building block for various real-world applications, such as face detection [37, 41], autonomous driving [12, 25], and medical diagnosis [1, 35]. However, neural networks are vulnerable to adversarial examples, which contain human imperceptible adversarial perturbations on the benign input. This issue is increasingly concerning researchers, as it is essential for ensuring the trustworthy use of neural networks [3, 19, 65, 66]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 640, + 288, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 640, + 288, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 640, + 288, + 676 + ], + "type": "text", + "content": "In real-world scenarios of adversarial attacks, the target model is usually inaccessible. To attack these inaccessible models, many studies instead rely on surrogate models" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 307, + 212, + 547, + 422 + ], + "blocks": [ + { + "bbox": [ + 307, + 212, + 547, + 422 + ], + "lines": [ + { + "bbox": [ + 307, + 212, + 547, + 422 + ], + "spans": [ + { + "bbox": [ + 307, + 212, + 547, + 422 + ], + "type": "image", + "image_path": "3fc284a7eda7f1f3922cef808f6d2f611855a743022251725b1e4e94c7d12c8c.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 428, + 547, + 528 + ], + "lines": [ + { + "bbox": [ + 304, + 428, + 547, + 528 + ], + "spans": [ + { + "bbox": [ + 304, + 428, + 547, + 528 + ], + "type": "text", + "content": "Figure 1. For input transformation-based attacks, most works design a fixed transformation and use it to craft the adversarial perturbation. The learning-based methods preliminarily predict augmentation strategies for current images for better adversarial transferability. These methods cannot respond to the distribution shifts between benign images and adversarial examples. We propose Learning to Transform (L2T), which uses the dynamic of the optimal transformation in each iteration to further boost the adversarial transferability." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 557, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 557, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 557, + 548, + 715 + ], + "type": "text", + "content": "to generate adversarial examples [7, 57] and use generated samples to mislead the target model. This cross-model attack ability of samples generated on the surrogate models is called \"adversarial transferability.\" Numerous research studies are dedicated to enhancing adversarial transferability, which can be classified into four categories: gradient-based methods [7, 26, 44, 47], input transformation-based methods [8, 26, 46, 57], architecture-based methods [23, 52], and ensemble-based methods [28, 60]. Among these attack methodologies, input transformation-based methods gain much popularity because of their plug-n-play advantage, which can be seamlessly integrated into other attack techniques [7, 44]. However, we discover that existing input" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 683, + 124, + 693 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 683, + 124, + 693 + ], + "spans": [ + { + "bbox": [ + 58, + 683, + 124, + 693 + ], + "type": "text", + "content": "*Equal contribution" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 59, + 693, + 102, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 693, + 102, + 703 + ], + "spans": [ + { + "bbox": [ + 59, + 693, + 102, + 703 + ], + "type": "text", + "content": "†Project lead" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "type": "inline_equation", + "content": "\\ddagger" + }, + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "type": "text", + "content": " Corresponding author" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24273" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "type": "text", + "content": "transformation-based methods adopt the same transformation when crafting adversarial examples, limiting the flexibility of transformation operations. We hypothesize that we should select the optimal transformation dynamically in each iteration to enhance the adversarial transferability." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 134, + 288, + 314 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 134, + 288, + 314 + ], + "spans": [ + { + "bbox": [ + 46, + 134, + 288, + 314 + ], + "type": "text", + "content": "As shown in Fig. 1, prior input transformation-based methods often revolve around designing fixed augmentation strategies like resizing inputs [57], block masking [10], or mix-up [46]. A more dynamic approach is presented by [63], advocating the precomputation of various sequences of augmentation strategies to apply to each iteration to enhance the attack performance. Complementing this, Wu et al. [53] proposes the use of generative models for image augmentation to boost the adversarial transferability. Some studies go further, combining multiple augmentation strategies to amplify input diversity to improve the performance. For example, Yuan et al. [64] introduces a neural network that generates a prediction of the optimal transformation strategy and applies the strategy to improve performance. A further improvement is hindered by the limited number of transformations." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 316, + 288, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 316, + 288, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 316, + 288, + 544 + ], + "type": "text", + "content": "To fully utilize the limited number of transformations, a natural idea is to use a combination of operations. However, it is not always efficient to combine different transformations together for attack, as reported in [50]. We expect to find an optimal combination of transformations to achieve a tradeoff between operation diversity and adversarial transferability. Nonetheless, the enormity of the search space presents a significant challenge, impeding the identification of the most efficacious combination of transformations during an attack for optimal adversarial transferability. To surmount this hurdle, we conceptualize the search process of the optimal combination of transformations as a problem of optimal trajectory search. Each node within this trajectory represents an individual transformation, and each directed edge means a transfer of the optimal transformation from the current step to the next step. To effectively obtain the optimal trajectory in such a large search space, we design a reinforcement learning-based approach, capitalizing on its demonstrated efficacy in navigating expansive search domains." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "content": "In this paper, we introduce a novel framework called Learning to Transform (L2T) to improve the adversarial transferability of generated adversarial examples. L2T dynamically learns and applies the optimal input transformation in each iteration. Instead of exhaustively enumerating all possible input transformation methods, we employ a reinforcement learning-based approach to reduce the search space and better utilize the transformations to improve the diversity. In each iteration of the adversarial attack, we sample a subset of transformations and apply them to the adversarial examples. Subsequently, we update the sampling probabilities by conducting gradient ascent to maximize the loss. Our method effectively learns the dynamics of optimal transformations in attacks, leading to a significant enhancement in" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "content": "adversarial transferability. Additionally, compared to other learn-based adversarial attack methods, our approach is more efficient for adversarial example generation, as it obviates the need for additional training modules." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 317, + 121, + 496, + 132 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 121, + 496, + 132 + ], + "spans": [ + { + "bbox": [ + 317, + 121, + 496, + 132 + ], + "type": "text", + "content": "We summarize our contributions as follows," + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 133, + 547, + 265 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 306, + 133, + 547, + 181 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 133, + 547, + 181 + ], + "spans": [ + { + "bbox": [ + 306, + 133, + 547, + 181 + ], + "type": "text", + "content": "- We formulate the problem of optimal transformation in adversarial attacks, which studies finding the optimal combination of transformations to increase the input diversities, thus improving the adversarial transferability." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 182, + 547, + 217 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 182, + 547, + 217 + ], + "spans": [ + { + "bbox": [ + 306, + 182, + 547, + 217 + ], + "type": "text", + "content": "- We propose Learning to Transform (L2T) that exploits the optimal transformation in each iteration and dynamically adjusts transformations to boost adversarial transferability." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 217, + 547, + 265 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 217, + 547, + 265 + ], + "spans": [ + { + "bbox": [ + 306, + 217, + 547, + 265 + ], + "type": "text", + "content": "- Extensive experiments on the ImageNet dataset demonstrate that L2T outperforms other baselines. We also validate L2T's superiority in real-world scenarios, such as Google Vision and GPT-4V." + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 277, + 392, + 290 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 277, + 392, + 290 + ], + "spans": [ + { + "bbox": [ + 306, + 277, + 392, + 290 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 298, + 418, + 310 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 298, + 418, + 310 + ], + "spans": [ + { + "bbox": [ + 306, + 298, + 418, + 310 + ], + "type": "text", + "content": "2.1. Adversarial Attack" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 318, + 547, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 318, + 547, + 510 + ], + "spans": [ + { + "bbox": [ + 304, + 318, + 547, + 510 + ], + "type": "text", + "content": "Various adversarial attacks have been proposed, e.g., gradient-based attack [13, 20, 32], transfer-based attack [7, 31, 51, 57], score-based attack [4, 18, 22], decision-based attack [2, 21, 49], generation-based attack [45, 54]. Among these, transfer-based attacks do not require the information of the victim models, making it popular to attack the deep models in the real world and raise more research interests. To improve adversarial transferability, various momentum-based attacks have been proposed, such as MI-FGSM [7], NI-FGSM [26], VMI-FGSM [44], EMI-FGSM [47], etc. Several input transformation methods are also proposed, such as DIM [57], TIM [8], SIM [26], Admix [46], SIA [50], STM [11], BSR [43], etc., which augment images used for adversarial perturbation computation to boost transferability. The input transformation-based methods can be integrated into the gradient-based attacks for better performance." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 510, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 548, + 714 + ], + "type": "text", + "content": "Delving into the input transformation-based methods, most works are limited to designing a fixed transformation to augment the images, which limits the diversity of transformed images and the adversarial transferability. To address this issue, some researchers [53, 63, 64] propose to augment the images with a set of multiple transformations predicted by a pre-trained network. Automatic Model Augmentation (AutoMA) [63] adopts a Proximal Policy Optimization (PPO) algorithm in search of a strong augmentation policy. Adversarial Transformation-enhanced Transfer Attack (ATTA) [53] proposes to employ an adversarial transformation network in modeling the most harmful distortions. Adaptive Image Transformation Learner (AITL) [64] incorporates different image transformations into a unified framework to learn adaptive transformations for each benign sample to boost adversarial transferability. By applying optimal multiple transformations, the adversarial attack per" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "24274" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 170, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 170, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 170, + 83 + ], + "type": "text", + "content": "formance is largely improved." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 91, + 165, + 103 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 91, + 165, + 103 + ], + "spans": [ + { + "bbox": [ + 47, + 91, + 165, + 103 + ], + "type": "text", + "content": "2.2. Adversarial Defense" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 110, + 290, + 314 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 110, + 290, + 314 + ], + "spans": [ + { + "bbox": [ + 46, + 110, + 290, + 314 + ], + "type": "text", + "content": "Various defense approaches have been proposed to mitigate the threat of adversarial attacks, such as adversarial training [32, 40, 48], input preprocessing [33, 55], feature denoising [24, 56, 62], certified defense [6, 14, 34], etc. Liao et al. [24] train a denoising autoencoder, namely the High-level representation guided denoiser (HGD), to purify the adversarial perturbations. Xie et al. [55] propose to randomly resize the image and add padding to mitigate the adversarial effect, namely the Randomized resizing and padding (R&P). Xu et al. [61] propose the Bit depth reduction (Bit-Red) method, which reduces the number of bits for each pixel to squeeze the perturbation. Liu et al. [29] defend against adversarial attacks by applying a JPEG-based compression method to adversarial images. Cohen et al. [6] adopt randomized smoothing (RS) to train a certifiably robust classifier. Naseer et al. [33] propose a Neural Representation Purifier (NRP) to eliminate perturbation." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 324, + 180, + 337 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 324, + 180, + 337 + ], + "spans": [ + { + "bbox": [ + 47, + 324, + 180, + 337 + ], + "type": "text", + "content": "3. Learning to Transform" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 344, + 139, + 356 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 344, + 139, + 356 + ], + "spans": [ + { + "bbox": [ + 47, + 344, + 139, + 356 + ], + "type": "text", + "content": "3.1. Task definition" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "spans": [ + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": "The crafting of adversarial examples usually takes an iterative framework to update the adversarial perturbation. Given a benign sample " + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "inline_equation", + "content": "\\pmb{x}" + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": " and the corresponding label " + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": ", a transferable attack takes a surrogate classifier " + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "inline_equation", + "content": "f_{\\theta}" + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": " and iteratively updates the adversarial example " + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "inline_equation", + "content": "x^{adv}" + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": " to maximize the loss of classifying " + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "inline_equation", + "content": "f_{\\theta}(x^{adv})" + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": ". Take I-FGSM [38] as an example. The adversarial example " + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "inline_equation", + "content": "x_{t}^{adv}" + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": " at the " + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 362, + 289, + 457 + ], + "type": "text", + "content": "-th iteration can be formulated as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 62, + 466, + 287, + 483 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 62, + 466, + 287, + 483 + ], + "spans": [ + { + "bbox": [ + 62, + 466, + 287, + 483 + ], + "type": "interline_equation", + "content": "\\boldsymbol {x} _ {t} ^ {a d v} = \\boldsymbol {x} _ {t - 1} ^ {a d v} + \\alpha \\cdot \\operatorname {s i g n} \\left(\\nabla_ {\\boldsymbol {x} _ {t - 1} ^ {a d v}} J \\left(f _ {\\boldsymbol {\\theta}} \\left(\\boldsymbol {x} _ {t - 1} ^ {a d v}, y\\right)\\right)\\right), \\tag {1}", + "image_path": "07d22699a8115a2b80773798075b08e292c5d9925ceba197c327b151dcb60fe3.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 491, + 287, + 551 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 491, + 287, + 551 + ], + "spans": [ + { + "bbox": [ + 46, + 491, + 287, + 551 + ], + "type": "text", + "content": "where we denote " + }, + { + "bbox": [ + 46, + 491, + 287, + 551 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 46, + 491, + 287, + 551 + ], + "type": "text", + "content": " as the step size, " + }, + { + "bbox": [ + 46, + 491, + 287, + 551 + ], + "type": "inline_equation", + "content": "J(\\cdot ,\\cdot)" + }, + { + "bbox": [ + 46, + 491, + 287, + 551 + ], + "type": "text", + "content": " as the classification loss function. As identified by previous studies, the adversarial example exhibits a characteristic of transferability, where the adversarial examples generated by the surrogate model can fool other neural networks." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "spans": [ + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "text", + "content": "Input transformation-based methods are one of the most effective methods to boost adversarial transferability. With these methods, the adversarial samples are firstly transformed by a set of image transformations and then proceeded to gradient calculation. Let " + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "inline_equation", + "content": "\\varphi" + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "text", + "content": " denote a set of image transformations operation " + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "inline_equation", + "content": "o" + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "inline_equation", + "content": "\\varphi = \\{o^i | i \\in \\{1, 2, \\dots, k\\}\\}" + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "text", + "content": ". At the " + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "text", + "content": "-th iteration, the adversarial example " + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "inline_equation", + "content": "\\boldsymbol{x}_t^{adv}" + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "text", + "content": " is transformed sequentially by " + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "inline_equation", + "content": "o^i" + }, + { + "bbox": [ + 46, + 552, + 288, + 648 + ], + "type": "text", + "content": " as follows," + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 83, + 658, + 287, + 673 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 83, + 658, + 287, + 673 + ], + "spans": [ + { + "bbox": [ + 83, + 658, + 287, + 673 + ], + "type": "interline_equation", + "content": "\\varphi \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right) = o ^ {k} \\oplus o ^ {k - 1} \\oplus \\dots \\oplus o ^ {1} \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right), \\tag {2}", + "image_path": "401b2d561c65fef8f4eb398623b6c17308cd989a413c6aa183a9906740e72e57.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "o^2 \\oplus o^1(\\boldsymbol{x})" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": " denotes the operation " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "o^2(o^1(\\boldsymbol{x}))" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "o^1, o^2 \\in \\varphi" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": ". We use the gradient of " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\varphi(\\boldsymbol{x}_t^{adv})" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": " with respect to the loss function to update the adversarial perturbation as Eq. (1)." + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 320, + 72, + 419, + 162 + ], + "blocks": [ + { + "bbox": [ + 320, + 72, + 419, + 162 + ], + "lines": [ + { + "bbox": [ + 320, + 72, + 419, + 162 + ], + "spans": [ + { + "bbox": [ + 320, + 72, + 419, + 162 + ], + "type": "image", + "image_path": "a5b3a2732f3db3e76cd32a29ac9ad6490a3d811d4b7a52ac4daeb0d905e6966f.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 350, + 164, + 392, + 172 + ], + "lines": [ + { + "bbox": [ + 350, + 164, + 392, + 172 + ], + "spans": [ + { + "bbox": [ + 350, + 164, + 392, + 172 + ], + "type": "text", + "content": "(a) One iteration" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 430, + 71, + 533, + 164 + ], + "blocks": [ + { + "bbox": [ + 430, + 71, + 533, + 164 + ], + "lines": [ + { + "bbox": [ + 430, + 71, + 533, + 164 + ], + "spans": [ + { + "bbox": [ + 430, + 71, + 533, + 164 + ], + "type": "image", + "image_path": "50e820cc6dffe34d9cf92467484de000dde6829eceef78172570e6e0bd8443e9.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 468, + 165, + 512, + 173 + ], + "lines": [ + { + "bbox": [ + 468, + 165, + 512, + 173 + ], + "spans": [ + { + "bbox": [ + 468, + 165, + 512, + 173 + ], + "type": "text", + "content": "(b) Two iteration" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 182, + 547, + 258 + ], + "lines": [ + { + "bbox": [ + 304, + 182, + 547, + 258 + ], + "spans": [ + { + "bbox": [ + 304, + 182, + 547, + 258 + ], + "type": "text", + "content": "Figure 2. Comparison for different operations in boosting the adversarial transferability. The number in the box denotes the number of fooled models (Maximum: 9). In (a), the horizontal axis denotes different transformation operations and the vertical axis denotes different benign examples. In (b), the vertical axis denotes the transformation used in the first iteration and the horizontal axis denotes the transformation used in the second iteration" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "spans": [ + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "text", + "content": "There are two categories for selecting the operation set " + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "inline_equation", + "content": "\\varphi" + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "text", + "content": " in the previous study. One line of research focuses on designing fixed transformation-based methods, which use a pre-defined transformation " + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "inline_equation", + "content": "\\varphi" + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "text", + "content": ". For example, Admix chooses mixup and scaling for transformation " + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "inline_equation", + "content": "\\varphi" + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "text", + "content": ". The other line of research proposes the learning-based transformation methods, which usually use a generative model to directly generate the transformed " + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "inline_equation", + "content": "\\varphi(x)" + }, + { + "bbox": [ + 304, + 281, + 547, + 425 + ], + "type": "text", + "content": ". Compared with the fixed transformation-based methods, learning-based methods enjoy more diversity of transformed images, leading to a better performance in adversarial transferability. In our work, we study the learning-based transformation methods." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 434, + 380, + 446 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 434, + 380, + 446 + ], + "spans": [ + { + "bbox": [ + 306, + 434, + 380, + 446 + ], + "type": "text", + "content": "3.2. Motivation" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 454, + 547, + 585 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 454, + 547, + 585 + ], + "spans": [ + { + "bbox": [ + 304, + 454, + 547, + 585 + ], + "type": "text", + "content": "Previous research designs lots of transformations to improve the diversity of images, thus guiding the adversarial attacks to focus more on the invariant robust features. However, it does not always work by increasing the number of transformed images for attacks to boost the adversarial transferability. Because some combination of transformations can cause damage to original examples, losing massive amounts of information used for transferable attacks. A natural question occurs to us, for one image, does there exist the optimal combination of transformations for the best adversarial transferability?" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 586, + 548, + 682 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 586, + 548, + 682 + ], + "spans": [ + { + "bbox": [ + 304, + 586, + 548, + 682 + ], + "type": "text", + "content": "To answer this question, we start by generating adversarial examples in one iteration. We take an example of crafting adversarial examples using ResNet-18 to attack other 9 models1. We denote 5 operations for input transformation methods, namely the crop, rotation, shuffle, scaling, and mix-up. We use these operations on five images for attacks and report the number of models fooled. We report the results in Fig. 2. It can be seen that by shuffle, we can achieve the maximum" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 306, + 693, + 547, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 693, + 547, + 712 + ], + "spans": [ + { + "bbox": [ + 306, + 693, + 547, + 712 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 306, + 693, + 547, + 712 + ], + "type": "text", + "content": "ResNet-101, DenseNet-121, ResNext-50, Inception-v3, Inception-v4, ViT, PiT, Visformer, Swin" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24275" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 70, + 289, + 243 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 289, + 243 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 289, + 243 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 289, + 243 + ], + "type": "image", + "image_path": "83eed6cd4c482d0f56a2675065f8cf12b298c2b1897e4d469d33db568e70e186.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 250, + 289, + 283 + ], + "lines": [ + { + "bbox": [ + 46, + 250, + 289, + 283 + ], + "spans": [ + { + "bbox": [ + 46, + 250, + 289, + 283 + ], + "type": "text", + "content": "Figure 3. There exists an optimal transformation trajectory for boosting adversarial transferability. However, the search space increases exponentially with iteration number and operation number." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 304, + 287, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 304, + 287, + 327 + ], + "spans": [ + { + "bbox": [ + 46, + 304, + 287, + 327 + ], + "type": "text", + "content": "transferable attack success rates on a dog image, indicating the optimal transformations in all possible 5 operations." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 328, + 288, + 422 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 328, + 288, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 328, + 288, + 422 + ], + "type": "text", + "content": "We continue our discussion in the two-iteration scenario. Following the same setting in one iteration, we report the number of fooled models. It can be seen that by choosing crop in the first iteration and scaling for the second iteration, which successfully fooled 6 models out of 9. We also notice that shuffle, the optimal transformation in one iteration, can not maintain the optimal performance. The average fooled model for shuffle is less than crop in 0.2." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 424, + 289, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 424, + 289, + 579 + ], + "spans": [ + { + "bbox": [ + 46, + 424, + 289, + 579 + ], + "type": "text", + "content": "Following the aforementioned discussion, we move on to generating adversarial examples in 3 iterations, where we only take one operation as the image transformation to attack the image. As exemplified in Fig. 3, there are " + }, + { + "bbox": [ + 46, + 424, + 289, + 579 + ], + "type": "inline_equation", + "content": "5 \\times 5 \\times 5" + }, + { + "bbox": [ + 46, + 424, + 289, + 579 + ], + "type": "text", + "content": " possible trajectories to transform the image for attacks. Among these trajectories, it can achieve the best performance by first shuffling, then rotating, and last shuffling the image. It should be noted it cannot consistently achieve the best performance by increasing the number of transformations for a higher diversity. As shown in Fig. 3, we respectively take the scaling, shuffle, and rotation operations at each iteration in trajectory 2. However, it has the worst attack success rate among the presented results." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "spans": [ + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "text", + "content": "Generalizing the previous problem to common cases, we are motivated to identify an optimal transformation trajectory " + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "text", + "content": ", which is defined as the sequence of transformation used in each iteration as " + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "inline_equation", + "content": "(\\varphi_{1},\\varphi_{2},\\dots,\\varphi_{T})" + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "text", + "content": ", for the best adversarial transferability. Each element " + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "inline_equation", + "content": "\\varphi_T" + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "text", + "content": " denotes the transformation used in iteration " + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 579, + 288, + 651 + ], + "type": "text", + "content": ". It can be formulated as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 94, + 659, + 288, + 680 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 94, + 659, + 288, + 680 + ], + "spans": [ + { + "bbox": [ + 94, + 659, + 288, + 680 + ], + "type": "interline_equation", + "content": "\\mathcal {T} ^ {*} = \\underset {\\mathcal {T}} {\\operatorname {a r g m a x}} (\\mathbb {E} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\boldsymbol {x} _ {\\mathcal {T}} ^ {a d v}), y) ]), \\tag {3}", + "image_path": "de5e768b1d0a16dbe597524c2ff47509a24a21ee86f45d3a87e51c18cebc7e2c.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "content": "where we denote " + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "inline_equation", + "content": "x_{\\mathcal{T}}^{adv}" + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "content": " as the adversarial example generated by the surrogate model under transformation trajectory " + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 46, + 689, + 288, + 715 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "text", + "content": "However, finding " + }, + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "inline_equation", + "content": "\\mathcal{T}^*" + }, + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "text", + "content": " is hard. First, the search space is large. For example, supposing five candidate transformations, even if we only take one operation in one iteration to transform the image, we will still have an enormous search space for ten iterations that will be " + }, + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "inline_equation", + "content": "5^{10}" + }, + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "text", + "content": ". The number of possible transformation trajectories grows exponentially with increasing the number of iterations and candidate transformations. Second, we can not access the black-box model " + }, + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 304, + 72, + 547, + 228 + ], + "type": "text", + "content": ", making it hard to optimize the Eq. (3) directly. Besides, as identified in the previous work [64], each image has a different optimal transformation to boost the adversarial transferability. There is no optimal transformation trajectory shared for all images." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 233, + 390, + 247 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 233, + 390, + 247 + ], + "spans": [ + { + "bbox": [ + 306, + 233, + 390, + 247 + ], + "type": "text", + "content": "3.3. Methodology" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 252, + 547, + 312 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 252, + 547, + 312 + ], + "spans": [ + { + "bbox": [ + 304, + 252, + 547, + 312 + ], + "type": "text", + "content": "The problem of Eq. (3) can be transformed into an optimal trajectory search problem, on which reinforcement learning has shown great compatibility. We are inspired to take a reinforcement learning-based approach in solving this optimization problem to enhance adversarial transferability." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "spans": [ + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": "Supposing we have " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " operations " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "\\{o^1,o^2,\\dots,o^M\\}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " in total, the optimal transformation trajectory " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "\\mathcal{T}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " is a temporal sequence of the combination of different operations. The probability " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " contains " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " possibilities " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "\\{p_{o^1},p_{o^2},\\dots,p_{o^M}\\}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " for each iteration. Each element " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "p_{o^m}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " denotes the possibility of sampling operation " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "o^m" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "m\\in \\{1,2,\\ldots,M\\}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": ". And " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "p_{o^m}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " follows " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "\\sum_{m = 1}^{M}p_{o^m} = 1" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": ". A transformation " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "\\varphi" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " consists " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " operations " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "o^k" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "k\\in \\{1,2,\\dots,M\\}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": ". We sampled " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " operations from " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": ". We have the possibility of a transformation " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "\\varphi" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": " by " + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "inline_equation", + "content": "P(\\varphi) = \\prod_{k = 1}^{K}p_{o^k}" + }, + { + "bbox": [ + 304, + 312, + 547, + 458 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "spans": [ + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": "For each iteration " + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": ", we sample a combination of transformation " + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "inline_equation", + "content": "\\varphi_t" + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": ". Each transformation in " + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "inline_equation", + "content": "\\varphi_t" + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": " is sampled from candidates depending on " + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": ". To get an optimal trajectory " + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "inline_equation", + "content": "\\mathcal{T} = (\\varphi_1, \\dots, \\varphi_T)" + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": ", we need to dynamically optimize the sampling distribution " + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": " in each iteration " + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": ". We formulate the problem of searching optima " + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "inline_equation", + "content": "\\pmb{p}^*" + }, + { + "bbox": [ + 304, + 459, + 547, + 530 + ], + "type": "text", + "content": " in each iteration as follows," + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 334, + 535, + 547, + 576 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 334, + 535, + 547, + 576 + ], + "spans": [ + { + "bbox": [ + 334, + 535, + 547, + 576 + ], + "type": "interline_equation", + "content": "\\begin{array}{r} \\boldsymbol {p} ^ {*} = \\underset {\\boldsymbol {p}} {\\arg \\max } \\mathbb {E} _ {\\varphi \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi (\\tilde {\\boldsymbol {x}} ^ {a d v})), y) ] \\\\ \\tilde {\\boldsymbol {x}} ^ {a d v} = \\underset {\\boldsymbol {x} ^ {a d v}} {\\arg \\max } \\mathbb {E} _ {\\varphi \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi (\\boldsymbol {x} ^ {a d v})), y) ], \\end{array} \\tag {4}", + "image_path": "3b7b9824b0d42f18600daba9dedc215c2ad1913ad6b3708996041104a7240b1a.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 580, + 547, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 580, + 547, + 640 + ], + "spans": [ + { + "bbox": [ + 304, + 580, + 547, + 640 + ], + "type": "text", + "content": "which is a bi-level optimization. The inner optimization targets to optimize the adversarial example, and the outer optimization tries to find the optimal sampling probability. Following [27], we adopt an one-step optimization strategy to derive the approximated " + }, + { + "bbox": [ + 304, + 580, + 547, + 640 + ], + "type": "inline_equation", + "content": "p^*" + }, + { + "bbox": [ + 304, + 580, + 547, + 640 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 389, + 647, + 547, + 661 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 389, + 647, + 547, + 661 + ], + "spans": [ + { + "bbox": [ + 389, + 647, + 547, + 661 + ], + "type": "interline_equation", + "content": "\\boldsymbol {p} ^ {*} \\approx \\boldsymbol {p} + \\rho \\cdot \\boldsymbol {g} _ {\\boldsymbol {p}}, \\tag {5}", + "image_path": "bd3123f07c7f88129a99123bb35ea95495a4b20e9e2ec490cffcb8d76db3c001.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "text", + "content": "where the " + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\rho" + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "text", + "content": " is the learning rate and " + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "inline_equation", + "content": "g_{p}" + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "text", + "content": " is the gradient for " + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "text", + "content": ". Implementation details. We present the overview of our method in Fig. 4. First, we sample " + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "text", + "content": " sequences of transformation " + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\varphi_t^l,l\\in [1,2,\\dots,L]" + }, + { + "bbox": [ + 304, + 666, + 547, + 715 + ], + "type": "text", + "content": ", depending on the sampling" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "24276" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 95 + ], + "type": "text", + "content": "Algorithm 1 Gradient policy for optimal augmentation search." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "spans": [ + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": "Input: Classifier " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "f(\\cdot)" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": "; The benign sample " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": " with ground-truth label " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": "; Loss function " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "\\mathcal{L}(\\cdot, \\cdot)" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": "; candidate operation pool " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "\\Gamma" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": ", the number of iterations " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": ", perturbation scale " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": ", policy learning rate " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "\\rho" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": ", number of operations " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": ", number of transformations " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": ", decay factor " + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "inline_equation", + "content": "\\mu" + }, + { + "bbox": [ + 48, + 98, + 288, + 158 + ], + "type": "text", + "content": ";" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 57, + 158, + 229, + 171 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 158, + 229, + 171 + ], + "spans": [ + { + "bbox": [ + 57, + 158, + 229, + 171 + ], + "type": "interline_equation", + "content": "\\alpha = \\epsilon / T, \\boldsymbol {g} _ {0} = 0, \\boldsymbol {x} _ {0} ^ {a d v} = \\boldsymbol {x}, \\boldsymbol {p} \\sim \\mathcal {N} (0, 1)", + "image_path": "799d8b7c6835bf23ac6eaa163beddca181ae71929f4a59bf43318e860ae6b932.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 58, + 171, + 143, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 171, + 143, + 180 + ], + "spans": [ + { + "bbox": [ + 58, + 171, + 143, + 180 + ], + "type": "text", + "content": "while " + }, + { + "bbox": [ + 58, + 171, + 143, + 180 + ], + "type": "inline_equation", + "content": "t = 1\\gets T" + }, + { + "bbox": [ + 58, + 171, + 143, + 180 + ], + "type": "text", + "content": " do" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 57, + 182, + 287, + 216 + ], + "type": "list", + "angle": 0, + "index": 6, + "blocks": [ + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "spans": [ + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "text", + "content": "1. Under the distribution " + }, + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "text", + "content": ", sample " + }, + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "text", + "content": " transformation " + }, + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "inline_equation", + "content": "\\varphi_t" + }, + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "text", + "content": ", each consisting of " + }, + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 57, + 182, + 287, + 205 + ], + "type": "text", + "content": " operations." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 72, + 206, + 216, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 72, + 206, + 216, + 216 + ], + "spans": [ + { + "bbox": [ + 72, + 206, + 216, + 216 + ], + "type": "text", + "content": "2. Transform adversarial examples:" + } + ] + } + ], + "index": 5 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 97, + 217, + 272, + 230 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 97, + 217, + 272, + 230 + ], + "spans": [ + { + "bbox": [ + 97, + 217, + 272, + 230 + ], + "type": "interline_equation", + "content": "\\varphi_ {t} ^ {l} \\left(x _ {t} ^ {a d v}\\right) = o ^ {K} \\oplus o ^ {K - 1} \\overline {{\\oplus}} \\dots \\oplus o ^ {1} \\left(\\boldsymbol {x} _ {t} ^ {a d v}\\right).", + "image_path": "b3a4cdb617a492f31431b944a219b9a968826a667b74d977f8990c23e9314159.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 72, + 230, + 208, + 241 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 72, + 230, + 208, + 241 + ], + "spans": [ + { + "bbox": [ + 72, + 230, + 208, + 241 + ], + "type": "text", + "content": "3. Calculate the average gradient:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 96, + 242, + 233, + 266 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 96, + 242, + 233, + 266 + ], + "spans": [ + { + "bbox": [ + 96, + 242, + 233, + 266 + ], + "type": "interline_equation", + "content": "\\bar {\\boldsymbol {g}} = \\frac {1}{L} \\sum_ {l = 1} ^ {L} \\nabla_ {\\boldsymbol {x} _ {t - 1} ^ {a d v}} \\mathcal {L} (\\varphi_ {t} ^ {l} (\\boldsymbol {x} _ {t - 1} ^ {a d v}), y).", + "image_path": "7566757d1a10c4d794a47dc00fde8dd78baf27d92eb9219938bbd386106580bb.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 72, + 266, + 179, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 72, + 266, + 179, + 277 + ], + "spans": [ + { + "bbox": [ + 72, + 266, + 179, + 277 + ], + "type": "text", + "content": "4. Update the momentum:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 97, + 277, + 182, + 292 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 97, + 277, + 182, + 292 + ], + "spans": [ + { + "bbox": [ + 97, + 277, + 182, + 292 + ], + "type": "interline_equation", + "content": "\\boldsymbol {g} _ {t} = \\mu \\boldsymbol {g} _ {t - 1} + \\frac {\\bar {g}}{| | \\bar {g} | | _ {1}}.", + "image_path": "5ba3db28eb0cf31ce42cf984b6ebf6d617571d074138343d80173bef9bf9f37b.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 72, + 292, + 214, + 302 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 72, + 292, + 214, + 302 + ], + "spans": [ + { + "bbox": [ + 72, + 292, + 214, + 302 + ], + "type": "text", + "content": "5. Update the adversarial example:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 97, + 302, + 256, + 315 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 97, + 302, + 256, + 315 + ], + "spans": [ + { + "bbox": [ + 97, + 302, + 256, + 315 + ], + "type": "interline_equation", + "content": "\\boldsymbol {x} _ {t} ^ {a d v} = \\operatorname {c l i p} \\left(\\boldsymbol {x} _ {t - 1} ^ {a d v} + \\alpha \\cdot \\operatorname {s i g n} \\left(\\boldsymbol {g} _ {t}\\right), 0, 1\\right).", + "image_path": "89dc76575df9a1e4fd8125e8963f166b92630fb6c700420f915467a9bf1a1cb7.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 72, + 315, + 222, + 326 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 72, + 315, + 222, + 326 + ], + "spans": [ + { + "bbox": [ + 72, + 315, + 222, + 326 + ], + "type": "text", + "content": "6. Calculate the probability gradient:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 96, + 326, + 253, + 354 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 96, + 326, + 253, + 354 + ], + "spans": [ + { + "bbox": [ + 96, + 326, + 253, + 354 + ], + "type": "interline_equation", + "content": "\\pmb {g} _ {\\pmb {p}} = \\frac {\\partial \\left(\\frac {1}{L} \\sum_ {l = 1} ^ {L} \\mathbf {P} (\\varphi_ {t} ^ {l}) \\mathcal {L} (f _ {\\pmb {\\theta}} (\\varphi_ {t} ^ {l} (\\mathbf {x} _ {t} ^ {a d v})), y) ]\\right)}{\\partial \\mathbf {P} (\\varphi_ {t} ^ {l})}.", + "image_path": "194820ab88b873e6b9c685de04652c1f02c154d3a28133b6099cc3e2ee0650ea.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 72, + 354, + 178, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 72, + 354, + 178, + 365 + ], + "spans": [ + { + "bbox": [ + 72, + 354, + 178, + 365 + ], + "type": "text", + "content": "7. Update the probability:" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 97, + 366, + 162, + 377 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 97, + 366, + 162, + 377 + ], + "spans": [ + { + "bbox": [ + 97, + 366, + 162, + 377 + ], + "type": "interline_equation", + "content": "\\boldsymbol {p} = \\boldsymbol {p} + \\rho \\cdot \\boldsymbol {g} _ {\\boldsymbol {p}}.", + "image_path": "3dd70b34da7338a54f0873b5c891188e47f8bf55801ab2e0e84bfbbfd73fa6e4.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 58, + 377, + 101, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 377, + 101, + 387 + ], + "spans": [ + { + "bbox": [ + 58, + 377, + 101, + 387 + ], + "type": "text", + "content": "end while" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 47, + 388, + 111, + 401 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 388, + 111, + 401 + ], + "spans": [ + { + "bbox": [ + 47, + 388, + 111, + 401 + ], + "type": "text", + "content": "Output: " + }, + { + "bbox": [ + 47, + 388, + 111, + 401 + ], + "type": "inline_equation", + "content": "x_{T}^{adv}" + }, + { + "bbox": [ + 47, + 388, + 111, + 401 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "spans": [ + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": "distribution " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": ". Next, we get the transformed examples denoted as " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "\\varphi_t^l(x_t^{adv})" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": ". The probability of each sequence " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "\\varphi_t^l" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": " is " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "P(\\varphi_t^l)" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": ". We use " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "\\varphi_t" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": " to denote all " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": " transformations, " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "\\varphi_t = \\{\\varphi_t^1, \\varphi_t^2, \\dots, \\varphi_t^L\\}" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": ". Then, we use Eq. (1) to update the adversarial examples for each iteration. The gradient is calculated by loss between " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": " transformed examples and their corresponding labels. Last, after updating the adversarial example, we recompute the approximate " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": ". Specifically, we compute the gradient " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "g_{o^k}" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": " of each sampled operation " + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "inline_equation", + "content": "o^k" + }, + { + "bbox": [ + 47, + 432, + 287, + 540 + ], + "type": "text", + "content": " as:" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 58, + 555, + 287, + 659 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 555, + 287, + 659 + ], + "spans": [ + { + "bbox": [ + 58, + 555, + 287, + 659 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} g _ {o ^ {k}} = \\frac {\\partial \\mathbb {E} _ {\\varphi_ {t} \\sim \\mathbf {p}} [ \\mathcal {L} (f _ {\\boldsymbol {\\theta}} (\\varphi_ {t} (\\mathbf {x} _ {t} ^ {a d v})), y) ]}{\\partial \\mathbf {P} (\\varphi_ {t})} \\cdot \\frac {\\partial \\mathbf {P} (\\varphi_ {l})}{\\partial p _ {o ^ {k}}} \\\\ = \\frac {\\partial \\sum_ {l = 1} ^ {L} \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right) \\mathcal {L} \\left( \\right.f _ {\\boldsymbol {\\theta}} \\left(\\varphi_ {t} ^ {l} \\left(\\mathbf {x} _ {t} ^ {a d v}\\right), y\\right)\\left. \\right]\\left. \\right)}{\\partial \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right)} \\cdot \\frac {\\partial \\mathbf {P} \\left(\\varphi_ {l}\\right)}{\\partial p _ {o k}} \\tag {6} \\\\ = \\sum_ {l = 1} ^ {L} \\mathcal {L} \\left(f _ {\\boldsymbol {\\theta}} \\left(\\varphi_ {t} ^ {l} \\left(\\mathbf {x} _ {t} ^ {a d v}\\right), y\\right)\\right) \\cdot \\frac {\\partial \\mathbf {P} \\left(\\varphi_ {t} ^ {l}\\right)}{\\partial p _ {o ^ {k}}}. \\\\ \\end{array}", + "image_path": "d96b1445f846aa6e24c8903ce944dccb47a68ba1e121273188255c6491caa018.jpg" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": "We concat the gradients for each operation as " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "[g_{o^1}, g_{o^2}, \\ldots, g_{o^K}]" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": ", which is denoted as " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\pmb{g_p}" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": ". We use gradient ascent to update " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\pmb{p}" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": " by " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\pmb{g_p}" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": " with the learning rate " + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\rho" + }, + { + "bbox": [ + 47, + 677, + 287, + 714 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 22 + }, + { + "type": "image", + "bbox": [ + 306, + 70, + 547, + 249 + ], + "blocks": [ + { + "bbox": [ + 306, + 70, + 547, + 249 + ], + "lines": [ + { + "bbox": [ + 306, + 70, + 547, + 249 + ], + "spans": [ + { + "bbox": [ + 306, + 70, + 547, + 249 + ], + "type": "image", + "image_path": "504faf4781a9c5c340234ae9af207ad9ff9ce18d0e14335ec561c3cccedb634a.jpg" + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 255, + 545, + 289 + ], + "lines": [ + { + "bbox": [ + 305, + 255, + 545, + 289 + ], + "spans": [ + { + "bbox": [ + 305, + 255, + 545, + 289 + ], + "type": "text", + "content": "Figure 4. Overview of the pipeline in L2T. We use probability in sampling " + }, + { + "bbox": [ + 305, + 255, + 545, + 289 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 305, + 255, + 545, + 289 + ], + "type": "text", + "content": " transformations and update this probability through gradient ascent." + } + ] + } + ], + "index": 24, + "angle": 0, + "type": "image_caption" + } + ], + "index": 23 + }, + { + "bbox": [ + 306, + 312, + 386, + 325 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 312, + 386, + 325 + ], + "spans": [ + { + "bbox": [ + 306, + 312, + 386, + 325 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 306, + 332, + 356, + 346 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 332, + 356, + 346 + ], + "spans": [ + { + "bbox": [ + 306, + 332, + 356, + 346 + ], + "type": "text", + "content": "4.1. Setup" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 304, + 352, + 547, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 352, + 547, + 567 + ], + "spans": [ + { + "bbox": [ + 304, + 352, + 547, + 567 + ], + "type": "text", + "content": "Models. We evaluate the proposed method in three categories of target models. (1) Normally trained model: We select ten well-known models for experiments. ResNet-18 [15], ResNet-101 [15], ResNext-50 [59], DenseNet-121 [17], Inception-v3 [39], and Inception-v4 [39], ViT-B [9], PiT [16], Visformer [5], and Swin [30]. All of these models are pre-trained on the ImageNet dataset. (2) Adversarial trained models: we select four defense methods in our experiments. They are adversarial training (AT) [40], high-level representation guided denoiser (HGD) [24], neural representation purifier (NRP) [33], and randomized smoothing (RS) [6]. (3) Vision API: to imitate a practical scenario, we compare the attack performance on popular vision API. We chose Google Vision, Azure AI, GPT-4V, and Bard. For categories (2) and (3), we use ensemble-based attack. We choose two CNN-based models, ResNet18 and Inception-v4, and two transformer-based models, Visformer and Swin, to construct the ensemble surrogate model." + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 304, + 568, + 547, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 568, + 547, + 604 + ], + "spans": [ + { + "bbox": [ + 304, + 568, + 547, + 604 + ], + "type": "text", + "content": "Dataset. Following previous works [46, 50, 57], we randomly choose 1,000 images from ILSVRC 2012 validation set [36]. All images are classified correctly by the models." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "content": "Baseline. We compare L2T with other input transformation adversarial methods. There are two categories of previous methods. The fixed transformation attack followed a fixed transformation scheme. We select TIM [8], SIM [26], Admix [46], DEM [67], IDE [58], Mask [10], " + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\mathrm{S}^2\\mathrm{IM}" + }, + { + "bbox": [ + 304, + 605, + 547, + 713 + ], + "type": "text", + "content": " [31], BSR [42], and SIA [50] for comparison. The learned transformation attack followed a set of transformations predicted by a trained network to generate adversarial examples. We also compare our method with learned transformation at-" + } + ] + } + ], + "index": 29 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24277" + } + ] + } + ], + "index": 30 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 77, + 141, + 178 + ], + "blocks": [ + { + "bbox": [ + 78, + 71, + 120, + 79 + ], + "lines": [ + { + "bbox": [ + 78, + 71, + 120, + 79 + ], + "spans": [ + { + "bbox": [ + 78, + 71, + 120, + 79 + ], + "type": "text", + "content": "(a) ResNet-18" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 50, + 77, + 141, + 178 + ], + "lines": [ + { + "bbox": [ + 50, + 77, + 141, + 178 + ], + "spans": [ + { + "bbox": [ + 50, + 77, 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Attack success rates (ASR) " + }, + { + "bbox": [ + 46, + 500, + 287, + 534 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 46, + 500, + 287, + 534 + ], + "type": "text", + "content": " of adversarial examples generated by L2T with various number of operations " + }, + { + "bbox": [ + 46, + 500, + 287, + 534 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 500, + 287, + 534 + ], + "type": "text", + "content": ". We include the detail number in our supplementary material." + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_caption" + } + ], + "index": 21 + }, + { + "bbox": [ + 46, + 556, + 287, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 556, + 287, + 592 + ], + "spans": [ + { + "bbox": [ + 46, + 556, + 287, + 592 + ], + "type": "text", + "content": "tacks, such as AutoMA [63], ATTA [53], and AITL [64]. All these methods are integrated with MI-FGSM [7] to generate adversarial examples." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "text", + "content": "Evaluation Settings. We follow the hyper-parameter setting of MI-FGSM and set the perturbation budget " + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\epsilon = 16" + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "text", + "content": ", number of iteration " + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "inline_equation", + "content": "T = 10" + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "text", + "content": ", step size " + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\alpha = \\epsilon / T = 1.6" + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "text", + "content": " and decay factor " + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\mu = 1" + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "text", + "content": ". For our method, we adopt the number of operations as 2, the number of samples as 10, and the learning rate " + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "inline_equation", + "content": "\\rho" + }, + { + "bbox": [ + 46, + 594, + 289, + 714 + ], + "type": "text", + "content": " as 0.01. For the candidate operation, we chose ten categories of transformations. Each category contains ten specific operations with different parameters. We will discuss the detailed settings of our method and other baselines in the supplementary materials." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 306, + 342, + 463, + 356 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 342, + 463, + 356 + ], + "spans": [ + { + "bbox": [ + 306, + 342, + 463, + 356 + ], + "type": "text", + "content": "4.2. Evaluations on single models" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 304, + 361, + 547, + 457 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 361, + 547, + 457 + ], + "spans": [ + { + "bbox": [ + 304, + 361, + 547, + 457 + ], + "type": "text", + "content": "Our proposed L2T exhibits better adversarial transferability to various input transformation based attacks. We take a single model as the surrogate model and evaluate the average attack success rate (ASR), i.e., the average misclassification rates across ten models. We summarized our results in Figure 5. Each subfigure denotes the attacker generates the adversarial examples on the corresponding models and its x-axis denotes the attack algorithm used." + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "spans": [ + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "type": "text", + "content": "First, we observe that L2T consistently outperforms all other attackers, regardless of the surrogate model. Other baseline methods have various adversarial transferability according to the surrogate models. For example, the BSR performs to be the strongest baseline on ResNet-18. However, the BSR cannot remain efficient when the surrogate model is changed to Swin or PiT. In contrast, our proposed L2T is suitable for all the surrogate models being tested. These results also strengthen our argument that we should dynamically choose the transformation to fit the surrogate models. Specifically, in the worst case (subfig. c), our proposed L2T still outperforms the strongest baseline (" + }, + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "type": "inline_equation", + "content": "S^2" + }, + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "type": "text", + "content": "IM) by " + }, + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "type": "inline_equation", + "content": "2.1\\%" + }, + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "type": "text", + "content": ". Overall, L2T outperforms the other baseline by " + }, + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "type": "inline_equation", + "content": "22.9\\%" + }, + { + "bbox": [ + 304, + 458, + 547, + 626 + ], + "type": "text", + "content": " on average ASR." + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 306, + 635, + 479, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 635, + 479, + 647 + ], + "spans": [ + { + "bbox": [ + 306, + 635, + 479, + 647 + ], + "type": "text", + "content": "4.3. Evaluations on defense methods" + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "content": "L2T is also capable of adversarial robust mechanisms. We test the attack performance of L2T against several defense mechanisms, including AT, HGD, NRP, and RS. We choose the ensemble setting to attack these defense approaches. We use the ensemble of four models, ResNet-18, Inception-v4," + } + ] + } + ], + "index": 29 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24278" + } + ] + } + ], + "index": 30 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 71, + 165, + 178 + ], + "blocks": [ + { + "bbox": [ + 49, + 71, + 165, + 178 + ], + "lines": [ + { + "bbox": [ + 49, + 71, + 165, + 178 + ], + "spans": [ + { + "bbox": [ + 49, + 71, + 165, + 178 + ], + "type": "image", + "image_path": "9b488102e2be5f25cc0462aa4c349cd5df40cd5fe883b1a818ca1b1218f37ad8.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 173, + 70, + 291, + 178 + ], + "blocks": [ + { + "bbox": [ + 173, + 70, + 291, + 178 + ], + "lines": [ + { + "bbox": [ + 173, + 70, + 291, + 178 + ], + "spans": [ + { + "bbox": [ + 173, + 70, + 291, + 178 + ], + "type": "image", + "image_path": "471ffd6dc282826674386745ab8a2b280b4519b14b77d069f98f0ffe2b564a3b.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 302, + 70, + 419, + 178 + ], + "blocks": [ + { + "bbox": [ + 302, + 70, + 419, + 178 + ], + "lines": [ + { + "bbox": [ + 302, + 70, + 419, + 178 + ], + "spans": [ + { + "bbox": [ + 302, + 70, + 419, + 178 + ], + "type": "image", + "image_path": "3aee0c8bee34960b93504958f1f980bfd30464cbf610f28264151af34f32d9a2.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 427, + 70, + 545, + 178 + ], + "blocks": [ + { + "bbox": [ + 427, + 70, + 545, + 178 + ], + "lines": [ + { + "bbox": [ + 427, + 70, + 545, + 178 + ], + "spans": [ + { + "bbox": [ + 427, + 70, + 545, + 178 + ], + "type": "image", + "image_path": "da9a8af87a9f58af5b3871aa9ff477419915716bd15fd484c2d1fcabd98179f2.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 48, + 180, + 166, + 290 + ], + "blocks": [ + { + "bbox": [ + 48, + 180, + 166, + 290 + ], + "lines": [ + { + "bbox": [ + 48, + 180, + 166, + 290 + ], + "spans": [ + { + "bbox": [ + 48, + 180, + 166, + 290 + ], + "type": "image", + "image_path": "d8a2a1eef80e43edc86857d4cdada5d0b83380bcd2aa67705e48b9d570ca198d.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 300, + 546, + 322 + ], + "lines": [ + { + "bbox": [ + 46, + 300, + 546, + 322 + ], + "spans": [ + { + "bbox": [ + 46, + 300, + 546, + 322 + ], + "type": "text", + "content": "Figure 7. We integrate the ensemble-based attack with input transformation and evaluate the performance on defense methods and popular vision APIs. We include the detail number in our supplementary material." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 174, + 180, + 292, + 290 + ], + "blocks": [ + { + "bbox": [ + 174, + 180, + 292, + 290 + ], + "lines": [ + { + "bbox": [ + 174, + 180, + 292, + 290 + ], + "spans": [ + { + "bbox": [ + 174, + 180, + 292, + 290 + ], + "type": "image", + "image_path": "336c0433addc40b44cdddfcd3a922382bafaf1c0dbf27de59b40d6801df180a6.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 300, + 180, + 419, + 290 + ], + "blocks": [ + { + "bbox": [ + 300, + 180, + 419, + 290 + ], + "lines": [ + { + "bbox": [ + 300, + 180, + 419, + 290 + ], + "spans": [ + { + "bbox": [ + 300, + 180, + 419, + 290 + ], + "type": "image", + "image_path": "5a7a7d6c55d7f4408b1bf22a9f2dcf171d67732aad979767c6a5d61aa308b1f2.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 427, + 180, + 545, + 290 + ], + "blocks": [ + { + "bbox": [ + 427, + 180, + 545, + 290 + ], + "lines": [ + { + "bbox": [ + 427, + 180, + 545, + 290 + ], + "spans": [ + { + "bbox": [ + 427, + 180, + 545, + 290 + ], + "type": "image", + "image_path": "0ae64566008047bbd7e854a91dfcedea6ea75f45341c8b9ed87e7d18489fe532.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 343, + 288, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 343, + 288, + 392 + ], + "spans": [ + { + "bbox": [ + 46, + 343, + 288, + 392 + ], + "type": "text", + "content": "Visformer, and Swin, as the surrogate model. We summarized our results in Figure 7 (a), (b), (c), and (d). Each subfigure denotes the model to be attacked and its x-axis denotes the attack algorithm used." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "spans": [ + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "text", + "content": "From Fig. 7, it is clear that L2T remains efficient. L2T consistently outperforms other methods against various defense methods. Notably, it achieves the attack success rate of " + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "inline_equation", + "content": "47.9\\%" + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "inline_equation", + "content": "98.5\\%" + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "inline_equation", + "content": "87.2\\%" + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "inline_equation", + "content": "46.7\\%" + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "text", + "content": " on AT, HGD, NRP, and RS, respectively. Even on the certified defense RS, the strongest defense among the four, L2T achieves the attack success rate of " + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "inline_equation", + "content": "46.7\\%" + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "text", + "content": ", which exceeds the best baseline (AITL) by " + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "inline_equation", + "content": "4.6\\%" + }, + { + "bbox": [ + 46, + 392, + 289, + 525 + ], + "type": "text", + "content": ". This is also the biggest improvement L2T made compared to other defenses. This indicates that the dynamic of iteration also exists in the adversarial robust mechanism, which can be used to diminish the its performance." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 536, + 192, + 548 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 536, + 192, + 548 + ], + "spans": [ + { + "bbox": [ + 47, + 536, + 192, + 548 + ], + "type": "text", + "content": "4.4. Evaluations on vision API" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 556, + 288, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 556, + 288, + 651 + ], + "spans": [ + { + "bbox": [ + 46, + 556, + 288, + 651 + ], + "type": "text", + "content": "Our proposed L2T can also perform well in realistic scenarios. To imitate the real-world application, we test the performance of L2T on Vision API. We use the same setting in sec. 4.3 to craft adversarial examples. We choose Google Vision (Figure 7 (e)) and Azure AI (Figure 7 (f)) to evaluate attacks on vision-only API. We also choose ChatGPT-4V (Figure 7 (g)) and Gemini (Figure 7 (f)) to evaluate attacks on the foundation model API." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 653, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 289, + 715 + ], + "type": "text", + "content": "As shown in Fig. 7, L2T is generally the best attacker to the real-world API. All attacks perform better on foundation model API than vision-only API. For vision-only API, L2T outperforms the strongest baseline by " + }, + { + "bbox": [ + 46, + 653, + 289, + 715 + ], + "type": "inline_equation", + "content": "8.7\\%" + }, + { + "bbox": [ + 46, + 653, + 289, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 653, + 289, + 715 + ], + "type": "inline_equation", + "content": "12.6\\%" + }, + { + "bbox": [ + 46, + 653, + 289, + 715 + ], + "type": "text", + "content": ", respectively. For foundation model API, L2T achieves nearly" + } + ] + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 322, + 345, + 531, + 508 + ], + "blocks": [ + { + "bbox": [ + 322, + 345, + 531, + 508 + ], + "lines": [ + { + "bbox": [ + 322, + 345, + 531, + 508 + ], + "spans": [ + { + "bbox": [ + 322, + 345, + 531, + 508 + ], + "type": "image", + "image_path": "9daff0bbc13d8b1fe86e0cda8ed5ec8e3dbd3bc81c613de201765672216facfe.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 520, + 545, + 554 + ], + "lines": [ + { + "bbox": [ + 305, + 520, + 545, + 554 + ], + "spans": [ + { + "bbox": [ + 305, + 520, + 545, + 554 + ], + "type": "text", + "content": "Figure 8. Attack success rates (ASR) (\\%) of adversarial examples generated by L2T with various number of transformations " + }, + { + "bbox": [ + 305, + 520, + 545, + 554 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 305, + 520, + 545, + 554 + ], + "type": "text", + "content": ". We include the detail number in our supplementary material." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 576, + 527, + 588 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 576, + 527, + 588 + ], + "spans": [ + { + "bbox": [ + 306, + 576, + 527, + 588 + ], + "type": "inline_equation", + "content": "100\\%" + }, + { + "bbox": [ + 306, + 576, + 527, + 588 + ], + "type": "text", + "content": " attack success rate on both GPT-4V and Gemini." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 598, + 397, + 611 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 598, + 397, + 611 + ], + "spans": [ + { + "bbox": [ + 306, + 598, + 397, + 611 + ], + "type": "text", + "content": "4.5. Ablation study" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "content": "On the numbers of operation " + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "content": ". As shown in Fig. 6, we study the impact of " + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "content": " on adversarial transferability. We craft the adversarial example on ResNet-18 and evaluate them on the other nine models. There is a clear difference between one operation and two operations. The average attack success rate increases by " + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "inline_equation", + "content": "8.09\\%" + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "content": ", from " + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "inline_equation", + "content": "80.89\\%" + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "inline_equation", + "content": "88.98\\%" + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "content": ". However, when the " + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "inline_equation", + "content": "K \\geq 3" + }, + { + "bbox": [ + 304, + 617, + 545, + 715 + ], + "type": "text", + "content": ", the improvement becomes marginal. The average attack success rate only" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "24279" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 90, + 547, + 128 + ], + "blocks": [ + { + "bbox": [ + 64, + 71, + 527, + 82 + ], + "lines": [ + { + "bbox": [ + 64, + 71, + 527, + 82 + ], + "spans": [ + { + "bbox": [ + 64, + 71, + 527, + 82 + ], + "type": "text", + "content": "Table 1. Attack success rates (%) of adversarial examples by L2T and Rand (randomly choose transformation in each iteration)." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 90, + 547, + 128 + ], + "lines": [ + { + "bbox": [ + 50, + 90, + 547, + 128 + ], + "spans": [ + { + "bbox": [ + 50, + 90, + 547, + 128 + ], + "type": "table", + "html": "
ResNet-18ResNet-101ResNeXt-50DenseNet-121Inception-v3Inception-v4ViTPiTVisformerswin
Rand52.3559.0653.1956.6443.0144.4158.4154.4865.08
L2T (Ours)90.0091.9091.0092.8078.8082.4090.1093.5096.20
", + "image_path": "14f15947b64781f248beed5bf8f2234f7159bb1a0eea0cb39442a38c87c4a653.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 65, + 149, + 272, + 293 + ], + "blocks": [ + { + "bbox": [ + 65, + 149, + 272, + 293 + ], + "lines": [ + { + "bbox": [ + 65, + 149, + 272, + 293 + ], + "spans": [ + { + "bbox": [ + 65, + 149, + 272, + 293 + ], + "type": "image", + "image_path": "092e8e5b584399518885cebf74f038fb194824676e46b4e994c52745a4c93c0f.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 307, + 288, + 340 + ], + "lines": [ + { + "bbox": [ + 46, + 307, + 288, + 340 + ], + "spans": [ + { + "bbox": [ + 46, + 307, + 288, + 340 + ], + "type": "text", + "content": "Figure 9. Average attack success rates (ASR) (\\%) of adversarial examples generated by L2T with various number of steps " + }, + { + "bbox": [ + 46, + 307, + 288, + 340 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 307, + 288, + 340 + ], + "type": "text", + "content": ". We include the detail number in our supplementary material." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "spans": [ + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "type": "text", + "content": "increases by " + }, + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "type": "inline_equation", + "content": "2.29\\%" + }, + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "type": "text", + "content": " when " + }, + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "type": "text", + "content": " is increased from 2 to 5. Thus, " + }, + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 363, + 288, + 387 + ], + "type": "text", + "content": " should be moderately settled as 2." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "spans": [ + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "text", + "content": "On the number of transformations " + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "text", + "content": ". We conducted experiments on the number of transformations " + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "text", + "content": ". We craft the adversarial example on ResNet-18 and evaluate them on the other nine models. We choose " + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "text", + "content": " from 1 to 50. From Fig. 8, we observe that the adversarial transferability improves steadily with the number of transformations. The increase is significant when the number of transformations grows from 1 to 20, which improves from an average attack success rate of " + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "inline_equation", + "content": "75.7\\%" + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "text", + "content": " to an average attack success rate of " + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "inline_equation", + "content": "91.1\\%" + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "text", + "content": ". However, transferability does not increase significantly after the number exceeds 20, where the average attack success rate only increases " + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "inline_equation", + "content": "1.5\\%" + }, + { + "bbox": [ + 46, + 388, + 290, + 555 + ], + "type": "text", + "content": ". To keep the balance between computation efficiency and adversarial transferability, we suggest the number of samples set to 20." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "spans": [ + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": "On the number of iterations " + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": ". We discuss the number of iterations among different attack approaches. We craft the adversarial example on ResNet-18 and compare the average attack success rate of 10 models. As shown in Fig. 9, for all the attack methods, the attack success rate increased steadily for the first 10 iterations. L2T achieves the fastest speed of increase, which reaches " + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "inline_equation", + "content": "89.47\\%" + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": " at iteration 10. After 10 iterations, most of the methods struggled to make improvements. For example, the Admix goes around " + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "inline_equation", + "content": "71\\%" + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": ". The performance of " + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "inline_equation", + "content": "\\mathrm{S}^2\\mathrm{IM}" + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": " even decreases from " + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "inline_equation", + "content": "73\\%" + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "inline_equation", + "content": "70\\%" + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": ". Meanwhile, L2T still maintains a stable increase, from " + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "inline_equation", + "content": "89.47\\%" + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "inline_equation", + "content": "94.77\\%" + }, + { + "bbox": [ + 46, + 557, + 288, + 688 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 689, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 288, + 714 + ], + "type": "text", + "content": "Comparison with random sampling. We compare the learnable strategy with random sampling. As shown in" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 309, + 146, + 545, + 257 + ], + "blocks": [ + { + "bbox": [ + 309, + 146, + 545, + 257 + ], + "lines": [ + { + "bbox": [ + 309, + 146, + 545, + 257 + ], + "spans": [ + { + "bbox": [ + 309, + 146, + 545, + 257 + ], + "type": "image", + "image_path": "f01b02526a24712a74e031163d0b7d0ffba7f1f17c05b9b56ad3357203a2d0e5.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 267, + 547, + 300 + ], + "lines": [ + { + "bbox": [ + 305, + 267, + 547, + 300 + ], + "spans": [ + { + "bbox": [ + 305, + 267, + 547, + 300 + ], + "type": "text", + "content": "Figure 10. The average attack success rates " + }, + { + "bbox": [ + 305, + 267, + 547, + 300 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 305, + 267, + 547, + 300 + ], + "type": "text", + "content": " of adversarial examples crafted by L2T and L2T without a single transformation. - indicates removing such transformation." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 324, + 547, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 324, + 547, + 407 + ], + "spans": [ + { + "bbox": [ + 304, + 324, + 547, + 407 + ], + "type": "text", + "content": "Tab. 1, there is a clear gap of the attack success rate between random sampling and gradient-guided sampling. The minimum difference is " + }, + { + "bbox": [ + 304, + 324, + 547, + 407 + ], + "type": "inline_equation", + "content": "31.12\\%" + }, + { + "bbox": [ + 304, + 324, + 547, + 407 + ], + "type": "text", + "content": " with setting Visformer as the surrogate model. For other surrogate models, the gap is even larger. This experiment indicates random sampling cannot effectively sample the best transformation trajectory, and the transformation in each iteration needs to be chosen carefully." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 408, + 547, + 504 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 408, + 547, + 504 + ], + "spans": [ + { + "bbox": [ + 304, + 408, + 547, + 504 + ], + "type": "text", + "content": "Operation candidates analysis. We conducted an ablation study for the operation candidates. We subtract each operation in the candidates and conduct L2T on the updated operation candidates. From Fig. 10, we observe that subtracting any operations will lead to a performance decrease. For example, by subtracting the scale operation, the performance decreases for " + }, + { + "bbox": [ + 304, + 408, + 547, + 504 + ], + "type": "inline_equation", + "content": "23.5\\%" + }, + { + "bbox": [ + 304, + 408, + 547, + 504 + ], + "type": "text", + "content": ". Meanwhile, subtracting mixup and translation only results in a " + }, + { + "bbox": [ + 304, + 408, + 547, + 504 + ], + "type": "inline_equation", + "content": "3.1\\%" + }, + { + "bbox": [ + 304, + 408, + 547, + 504 + ], + "type": "text", + "content": " decrease." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 518, + 379, + 530 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 518, + 379, + 530 + ], + "spans": [ + { + "bbox": [ + 306, + 518, + 379, + 530 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 539, + 547, + 646 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 539, + 547, + 646 + ], + "spans": [ + { + "bbox": [ + 304, + 539, + 547, + 646 + ], + "type": "text", + "content": "In this paper, we study the dynamic property for input transformation. Utilizing this property, we propose L2T to optimize the input transformation in each iteration. By updating a sampling probability, our method provides an approximate solution to input transformation optimization. Our experiments further study the effectiveness of our methods. Our method performs consistently well among different targeted models. This paper provides a new perspective to understand the transferability of adversarial examples." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 647, + 548, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 647, + 548, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 647, + 548, + 712 + ], + "type": "text", + "content": "Acknowledgement. This work was supported by NSF under grant 2202124 and the Center of Excellence in Data Science, an Empire State Development-designated Center of Excellence. 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Springer, 2020. 5" + } + ] + } + ], + "index": 17 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "24283" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/563474b5-06bb-4f08-b441-cc9dcf4bf078_content_list.json b/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/563474b5-06bb-4f08-b441-cc9dcf4bf078_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..7868515ac253759e0a5fb61125c77c07ad5d7060 --- /dev/null +++ b/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/563474b5-06bb-4f08-b441-cc9dcf4bf078_content_list.json @@ -0,0 +1,1523 @@ +[ + { + "type": "text", + "text": "Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge", + "text_level": 1, + "bbox": [ + 241, + 130, + 727, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Dongjin $\\mathrm{Kim}^{1,*}$ Sung Jin Um $^{1,*}$ Sangmin Lee $^{2,\\dagger}$ Jung Uk $\\mathrm{Kim}^{1,\\dagger}$ $^{1}$ Kyung Hee University $^{2}$ University of Illinois Urbana-Champaign \n{rlaehdwls310, sungzin1, ju.kim}@khu.ac.kr, sangminl@illinois.edu", + "bbox": [ + 184, + 202, + 789, + 256 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 291, + 313, + 306 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The goal of the multi-sound source localization task is to localize sound sources from the mixture individually. While recent multi-sound source localization methods have shown improved performance, they face challenges due to their reliance on prior information about the number of objects to be separated. In this paper, to overcome this limitation, we present a novel multi-sound source localization method that can perform localization without prior knowledge of the number of sound sources. To achieve this goal, we propose an iterative object identification (IOI) module, which can recognize sound-making objects in an iterative manner. After finding the regions of sound-making objects, we devise object similarity-aware clustering (OSC) loss to guide the IOI module to effectively combine regions of the same object but also distinguish between different objects and backgrounds. It enables our method to perform accurate localization of sound-making objects without any prior knowledge. Extensive experimental results on the MUSIC and VGGSound benchmarks show the significant performance improvements of the proposed method over the existing methods for both single and multi-source. Our code is available at: https://github.com/VisualAIKHU/NoPrior_MultiSSL.", + "bbox": [ + 75, + 324, + 473, + 672 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 686, + 209, + 702 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Humans naturally perceive various sounds and identify the origins of those sounds by using both visual sense (eyes) and auditory sense (ears) [12]. The sound source localization task aims to mimic the ability of humans to correlate auditory cues with visual information in order to identify sound-making objects. Due to this property, sound source localization is closely related to various real-world applications, including unmanned aerial vehicles [14, 30], robotics [20, 28], and speaker source localization [6, 31].", + "bbox": [ + 75, + 712, + 468, + 848 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The sound source localization task can be divided into", + "bbox": [ + 96, + 849, + 468, + 864 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/d55fda221c6f7fff4433f1736516056d532f8a00dd4f36261f598fa7485e2a17.jpg", + "image_caption": [ + "Figure 1. Conceptual comparison between (a) existing methods and (b) the proposed method. The existing methods require prior source knowledge of the number of sound-making objects. In contrast, our method can effectively localize multiple sound-making objects without the need for prior source knowledge." + ], + "image_footnote": [], + "bbox": [ + 501, + 285, + 893, + 483 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "two categories: (1) single sound source localization and (2) multi-sound source localization. The single sound source localization task [8, 11, 21, 22, 25, 32-36, 38, 39, 41, 44, 48] aims to find one source in a scene by utilizing cross-modal correlations [32, 40] between audio and visual cues. Various methods have been developed for the effective single sound source localization by introducing hard positive mining [8, 33], iterative learning [21], feature regularization [22], negative free learning [38], false negative aware learning [39], momentum target encoders [25], optical flow [11, 36], and spatial integration [41]. However, these methods focus primarily on locating a single sound source, which can be challenging in real-world environments where multiple sounds are often mixed together.", + "bbox": [ + 496, + 565, + 892, + 777 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In response to this challenge, several multi-sound source localization methods [16, 17, 26, 27] have been developed. The main goal of multi-sound source localization is to separate and localize individual sources from complex mixtures containing different sounds, such as self-supervised audio-visual matching [16], coarse-to-fine manner [27], contrastive random walker [17], and audio-visual grouping network [26]. However, a limitation of existing methods is", + "bbox": [ + 496, + 779, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal contribution", + "bbox": [ + 94, + 875, + 222, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "† Corresponding author", + "bbox": [ + 96, + 887, + 218, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "26467", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "their reliance on prior information about the number of objects that need to be separated. As shown in Figure 1(a), existing methods heavily rely on prior knowledge about the number of sound sources. If prior knowledge is incorrect, they are frequently failed to localize sound-making objects. Thus, they can only operate in constrained environments where prior source knowledge is available for sound source localization. Consequently, accurate localization of multisound sources becomes challenging when this prior knowledge is not available. In addition, since prior knowledge is generally not provided in real-world environments, it limits their applicability in practical scenarios.", + "bbox": [ + 75, + 90, + 472, + 272 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To address the aforementioned challenges, we introduce a novel method for multi-sound source localization that can identify multiple sound sources without the need for prior knowledge of the number of sources. As shown in Figure 1(b), our method can adapt to various numbers of sound sources by automatically recognizing the number of sound-making objects without relying on any prior knowledge. To this end, we propose an Iterative Object Identification (IOI) module. The goal of our IOI is to effectively automate object separation by repeatedly recognizing objects that make sounds from the mixtures in an iterative manner. By doing so, it continuously searches for sound-making regions until it determines that all relevant objects have been identified.", + "bbox": [ + 75, + 273, + 472, + 470 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To achieve this goal, we provide guidance to the IOI module for effective sound-making object identification. First, in the iterative process, we identify regions that are considered to be foreground objects and repeat this process until there are no more regions considered as foreground objects. At each iteration step, regions previously considered as foreground objects are eliminated in the subsequent iteration. Next, we employ a clustering process to merge regions belonging to the same object based on the foreground regions. To effectively carry out this process, we devise an object similarity-aware clustering (OSC) loss. This loss not only guides the IOI module to combine regions of the same object but also aids in distinguishing between different objects and backgrounds. By doing so, the proposed framework is able to distinguish between various objects with distinct sounds through the iterative process.", + "bbox": [ + 75, + 470, + 472, + 712 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Consequently, our method can precisely locate the sound-making objects without the need for prior source knowledge, and can effectively distinguish between multiple sound sources. As a result, our method shows significant improvements in sound source localization performance compared to existing methods.", + "bbox": [ + 75, + 713, + 470, + 804 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The major contributions of our paper are as follows:", + "bbox": [ + 96, + 805, + 441, + 821 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "- We introduce Iterative Object Identification (IOI) module to adaptively localize multiple sound sources without any prior source knowledge. To the best of our knowledge, this is the first attempt to perform multi-sound source localization without knowing the number of sound sources.", + "bbox": [ + 76, + 824, + 472, + 901 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose Object Similarity-aware Clustering (OSC) loss to guide the IOI module to merge regions belonging to the same object during the iteration process, while distinguishing between different objects and the background.", + "- Experimental results on MUSIC and VGGSound datasets demonstrate the effectiveness of the proposed method for both single-/multi-source sound localization." + ], + "bbox": [ + 500, + 90, + 893, + 196 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 213, + 640, + 229 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Sound Source Localization", + "text_level": 1, + "bbox": [ + 500, + 239, + 741, + 253 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The sound source localization focuses on finding the spatial location of sound sources within a video frame. It can be divided into two main streams: (1) single sound source localization and (2) multi-sound source localization.", + "bbox": [ + 496, + 263, + 893, + 323 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The single sound source localization [8, 9, 11, 21, 22, 25, 32-36, 38, 39, 41, 44, 48] leverages the cross-modal interrelations between auditory and visual modalities to localize a sound-making object. Senocak et al. [32] introduced an unsupervised method to incorporate an audio-visual two-stream network with attention mechanisms. Chen et al. [8] proposed a framework that automatically identifies hard samples through contrastive learning. Lin et al. [21] adopted iterative learning with pseudo-labels to refine the localization process. In addition, Fedorishin et al. [11] and Singh et al. [36] leveraged optical flow as a prior and introduced a cross-attention mechanism over the relevant video frame. Sun et al. [39] introduced the False Negative Aware Contrastive (FNAC) strategy to guide similar-looking samples to be more similar. Senocak et al. [34] improved localization accuracy through enhanced cross-modal semantic understanding. Um et al. [41] proposed the spatial knowledge integration of the audio-visual modalities, promoting recursive enhancement of localization. However, in real-world scenarios, they encounter limitations due to the frequent occurrence of mixed sounds from various sources.", + "bbox": [ + 496, + 324, + 892, + 641 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Recent studies focus on the multi-sound source localization [16, 17, 26, 27] to effectively find the location of sound sources from mixtures. Hu et al. [16] introduced a technique that constructs a supervisory signal to differentiate the sound-making entities within a scene. Qian et al. [27] developed a two-stage audiovisual learning approach that separates audio and visual representations of various categories from scenes in a coarse-to-fine manner. Hu et al. [17] made a graph model for robust multi-sound source localization. Mo et al. [26] proposed a way to simultaneously extract and assimilate category-specific semantic features for each sound source from auditory and visual inputs.", + "bbox": [ + 496, + 642, + 893, + 824 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "However, the existing multi-sound source localization methods also exhibit a limitation in real-world scenarios. They heavily rely on prior knowledge about the number of sound sources to differentiate between multi-sound sources. Thus, we propose a sound source localization framework", + "bbox": [ + 496, + 825, + 893, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "26468", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/5d59a73e652460bc359b217c335dccadcfe1822ad062c17ecf44accfa93cb366.jpg", + "image_caption": [ + "Figure 2. Network configuration of the proposed sound source localization framework. GAP denotes global average pooling." + ], + "image_footnote": [], + "bbox": [ + 94, + 56, + 877, + 385 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "that can autonomously recognize the number of objects within a scene and localize the objects without relying on annotations or prior knowledge.", + "bbox": [ + 75, + 415, + 468, + 460 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Iterative Methods in Computer Vision", + "text_level": 1, + "bbox": [ + 76, + 469, + 405, + 484 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Iterative techniques have been applied to various research fields [1, 4, 5, 19, 23, 29, 37, 42, 43, 45, 47] because they provide a refining solutions through repetitive cycles. For example, the iterative methods have been applied to image deblurring and denoising tasks [5, 19], showing significant improvements over traditional non-iterative techniques. In addition, for the mainstream computer vision tasks, e.g., object detection and segmentation tasks, various works [1, 37, 42, 45, 47] also adopt the iterative refinement techniques for more improved performance.", + "bbox": [ + 75, + 492, + 468, + 643 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The iterative technique possesses inherent characteristic of iteratively converging towards the desired solution. In this study, we adopt this technique to perform effective multi-sound source localization. Though this approach, we automatically and iteratively identify multiple sound sources, enhancing the localization for the same objects and allowing differentiation between different objects. As a result, our method demonstrates improved performance compared to conventional methods. Moreover, due to its automatic object-finding nature, our iterative approach is not constrained by prior source knowledge.", + "bbox": [ + 75, + 643, + 470, + 809 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Proposed Approach", + "text_level": 1, + "bbox": [ + 76, + 821, + 266, + 838 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Overall Architecture", + "text_level": 1, + "bbox": [ + 76, + 847, + 272, + 861 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Figure 2 shows the overall architecture of our framework. Similar to the previous works [8, 32], we adopt a two-stream", + "bbox": [ + 75, + 869, + 468, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "network to extract visual and audio features. Input image set $I_{v} \\in \\mathbb{R}^{B \\times W_{v} \\times H_{v} \\times 3}$ ( $B$ indicates batch number, $W_{v}$ and $H_{v}$ denote width and height of $I_{v}$ ) and the corresponding mixed audio spectrogram $I_{a} \\in \\mathbb{R}^{B \\times W_{a} \\times H_{a} \\times 1}$ ( $W_{a}$ and $H_{a}$ denote width and height of $I_{a}$ ) pass through each modal encoder (i.e., visual and audio encoders) to generate visual feature $\\mathbf{F}_{v}$ and audio feature $\\mathbf{F}_{a}$ , respectively. First, we identify all the sound-making regions associated with mixed audi-los to filter the regions of interest. We measure cosine similarity between $\\mathbf{F}_{v}$ and $l_{a}$ , derived from the global average pooling (GAP) of $\\mathbf{F}_{a}$ , to obtain a sound-associated map $\\mathbf{S}_{v}$ .", + "bbox": [ + 496, + 415, + 890, + 580 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Next, we obtain a sound-associated visual feature $\\hat{\\mathbf{F}}_v$ by the product of $\\mathbf{S}_v$ and $\\mathbf{F}_v$ to being aware of features for overall sound-making regions. The Iterative Object Identification (IOI) module receives $\\hat{\\mathbf{F}}_v$ to iteratively discriminate sound-associated grid cells and collect each cell in an object bank $\\mathbf{O}$ . Subsequently, sound-associated grid cells in $\\mathbf{O}$ are allocated into object groups (e.g., object 1, object 2, etc.), and the background regions are removed. Our method differentiates various objects without prior source knowledge (i.e., the number of sound sources).", + "bbox": [ + 496, + 580, + 890, + 731 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Sound-Associated Region Localization", + "text_level": 1, + "bbox": [ + 500, + 741, + 828, + 757 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To automatically localize sound-making objects in a visual scene without any annotation or prior knowledge, it is essential to measure the correspondence between audio and visual features. To achieve this, we try to distinguish sound-making regions from non-sound regions.", + "bbox": [ + 496, + 763, + 890, + 840 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We calculate the cosine similarity between $\\mathbf{F}_v \\in \\mathbb{R}^{B \\times w \\times h \\times c}$ ( $w, h$ , and $c$ are the width, height, and channel) and $l_a \\in \\mathbb{R}^{B \\times c}$ to generate sound-associated map $\\mathbf{S}_v = \\{S_{v_{ij}}\\}_{i=1,\\dots,h,j=1,\\dots,w} \\in \\mathbb{R}^{B \\times w \\times h}$ . To make $\\mathbf{S}_v$", + "bbox": [ + 496, + 840, + 890, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "26469", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "meaningful, our method allows positive audio-visual pairs to be attracted to each other and negative pairs to be repelled at training time. By doing so, it is possible to identify spatial regions associated with given sound (positive pairs) and regions which are not associated with that sound (negative pairs). We define $\\mathbf{S}_v^{n\\to m}$ as cosine similarity map between $n$ -th image and $m$ -th audio, and the $ij$ -th element of $\\mathbf{S}_v^{n\\to m}$ , which can be represented as:", + "bbox": [ + 76, + 90, + 472, + 212 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\operatorname {S i m} (A, B) = \\frac {\\langle A , B \\rangle}{| | A | | | | B | |}, \\\\ S _ {v _ {i j}} ^ {n \\rightarrow m} = \\frac {\\operatorname {S i m} \\left(\\mathbf {F} _ {v _ {i j}} ^ {n} , l _ {a} ^ {m}\\right)}{\\sum_ {i = 1} ^ {h} \\sum_ {j = 1} ^ {w} \\operatorname {S i m} \\left(\\mathbf {F} _ {v _ {i j}} ^ {n} , l _ {a} ^ {n}\\right)}, \\tag {1} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 145, + 218, + 468, + 294 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\langle \\cdot, \\cdot \\rangle$ denotes inner-product. Next, we obtain the mask of $n$ -th clip $M^n$ , represented as:", + "bbox": [ + 76, + 300, + 468, + 330 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nM ^ {n} = \\operatorname {s i g m o i d} \\left(\\left(S _ {v} ^ {n \\rightarrow n} - \\alpha\\right) / \\omega\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 156, + 337, + 468, + 354 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\alpha$ and $\\omega$ are the hyper-parameters. Based on $M^n$ , we aim to localize all the sound-making regions associated with mixed audios. Thus, motivated by [8], we employ an audiovisual contrastive loss $\\mathcal{L}_{avc}$ , which can be represented as:", + "bbox": [ + 76, + 362, + 468, + 422 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} P o s ^ {n} = \\frac {1}{| M ^ {n} |} \\langle M ^ {n}, S _ {v} ^ {n \\rightarrow n} \\rangle , \\\\ N e g ^ {n} = \\frac {\\left\\langle \\mathbf {1} - M ^ {n} , S _ {v} ^ {n \\rightarrow n} \\right\\rangle}{\\left| \\mathbf {1} - M ^ {n} \\right|} + \\frac {1}{h w} \\sum_ {n \\neq m} \\left\\langle \\mathbf {1}, S _ {v} ^ {n \\rightarrow m} \\right\\rangle , \\tag {3} \\\\ \\mathcal {L} _ {a v c} = - \\frac {1}{B} \\sum_ {n = 1} ^ {B} \\left[ \\log \\frac {\\exp (P o s ^ {n})}{\\exp (P o s ^ {n}) + \\exp (N e g ^ {n})} \\right]. \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 94, + 429, + 468, + 546 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "$Pos^n$ represents the average vector of highly correlated regions between the audio-visual pairs in the $n$ -th clip. In contrast, $Neg^n$ contains not only regions with low correlated between audio-visual pairs within the same clip but also includes correlation with other clips. Consequently, $\\mathcal{L}_{avc}$ allows the $\\mathbf{S}_v$ to effectively filter out the foreground regions associated with the mixed audio, separating from the background regions that do not produce sound.", + "bbox": [ + 76, + 551, + 468, + 674 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Iterative Object Identification Module", + "text_level": 1, + "bbox": [ + 76, + 681, + 406, + 696 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Through Section 3.2, the sound-associated map $\\mathbf{S}_v$ can contain knowledge of the sound-associated objects. We then multiply $\\mathbf{S}_v$ by the original visual feature $\\mathbf{F}_v$ to encode sound-associated visual feature $\\hat{\\mathbf{F}}_v\\in \\mathbb{R}^{B\\times w\\times h\\times c}$ . By doing so, background cells are removed, leaving all the sound-associated cells that represent the sound-making object.", + "bbox": [ + 76, + 703, + 468, + 795 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Next, the proposed Iterative Object Identification (IOI) module takes $\\hat{\\mathbf{F}}_v$ to identify sound-making objects in mixed audio-visual data. Using $\\hat{\\mathbf{F}}_v$ , the IOI module conducts a total of $T$ iterations to find all sound-associated cells, and in each iteration, it finds the area to localize around the position of the sound-associated cell identified. Each iteration consists of four steps: (1) Highest sound-associated cell", + "bbox": [ + 75, + 795, + 468, + 901 + ], + "page_idx": 3 + }, + { + "type": "code", + "sub_type": "algorithm", + "code_caption": [ + "Algorithm 1 Iterative Object Identification Algorithm" + ], + "code_body": "Require: $\\mathbf{S}_v,\\hat{\\mathbf{F}}_v$ \nEnsure: $\\mathbf{O} = [],t = 0$ \nwhile max(S>ε do $\\begin{array}{rl} & {\\mathbf{E}_p^t\\leftarrow \\hat{\\mathbf{F}}_v[\\mathrm{argmax}(\\mathbf{S}_v)]}\\\\ & {\\mathbf{R}_p\\leftarrow \\langle \\hat{\\mathbf{F}}_v,\\mathbf{E}_p^t\\rangle}\\\\ & {\\mathbf{R}_n\\leftarrow \\langle \\hat{\\mathbf{F}}_v,\\mathbf{E}_n\\rangle}\\\\ & {\\mathrm{sound\\_making\\_region}\\leftarrow \\mathbf{R}_p > \\mathbf{R}_n}\\\\ & {\\mathbf{S}_v\\leftarrow \\mathbf{S}_v\\cdot \\neg \\mathrm{sound\\_making\\_region}}\\\\ & {\\mathbf{O}.append(\\mathbf{E}_p^t)}\\\\ & {t\\leftarrow t + 1} \\end{array}$ ▷Inner Product \nend while \nResults: $T = t,\\mathbf{O} = [\\mathbf{E}_p^1,\\mathbf{E}_p^2,\\dots,\\mathbf{E}_p^T]$", + "bbox": [ + 500, + 111, + 890, + 287 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "selection, (2) foreground/background selection, (3) finding sound-making regions, and (4) identified sound-making region exclusion. After the end of $T$ iteration process, we cluster all sound-associated grid cells as each object or negative.", + "bbox": [ + 496, + 303, + 890, + 378 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Before starting iteration, we define a negative cell vector $\\mathbf{E}_n\\in \\mathbb{R}^{B\\times c}$ to represent background (non-sound-making objects). $\\mathbf{E}_n$ is obtained by averaging the background cells that were excluded during the creation of $\\hat{\\mathbf{F}}_v$ . This vector is essential for identifying regions that do not correspond to the sound, to provide contrast to the foreground.", + "bbox": [ + 496, + 378, + 890, + 469 + ], + "page_idx": 3 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "(1) Highest sound-associated cell selection. In the first step in $t$ -th iteration, we select the cell in $\\mathbf{S}_v$ with the highest value and select this cell as a starting point. This selection is based on the understanding that the highest value in $\\mathbf{S}_v$ indicates the strongest audio-visual correspondence in that cell. Therefore, we identify and mark the coordinates of this cell as $(i,j)$ . The vector $\\hat{\\mathbf{F}}_{v_{ij}}$ is then assigned as the sound-associated grid cell $\\mathbf{E}_p^t \\in \\mathbb{R}^{B \\times c}$ . Then, we store $\\mathbf{E}_p^t$ in the $i$ -th element of the object bank $\\mathbf{O} = \\{\\mathbf{E}_p^t\\}_{t=1}^T$ .", + "(2) Foreground/background selection. In the second step in $t$ -th iteration, we perform foreground and background selection using $\\mathbf{E}_p^t$ and $\\mathbf{E}_n$ . The similarity measurement is carried out by calculating the inner product of $\\hat{\\mathbf{F}}_v$ and $\\mathbf{E}_p^t$ . This result is used as foreground region $\\mathbf{R}_p^t \\in \\mathbb{R}^{B \\times w \\times h}$ . A higher value in $\\mathbf{R}_p^t$ indicates a higher likelihood of being the same object as $\\mathbf{E}_p^t$ . Similarly, the background region is calculated by inner product of $\\hat{\\mathbf{F}}_v$ and $\\mathbf{E}_n$ , resulting in $\\mathbf{R}_n^t \\in \\mathbb{R}^{B \\times w \\times h}$ . (3) Finding sound-making regions. In the third step in $t$ -th iteration, we compare $\\mathbf{R}_p^t$ and $\\mathbf{R}_n^t$ to localize sound-making regions. The choice of sound-making region sizes is based on the condition that the value of foreground region $\\mathbf{R}_p^t$ is higher than that of the background $\\mathbf{R}_n^t$ . Using these regions, we generate the $t$ -th localization map.", + "(4) Identified sound-making region exclusion. In the fourth step in $t$ -th iteration, to prevent redundancy in finding sound-associated grid cell vector $\\mathbf{E}_p^t$ , we need to modify $\\mathbf{S}_v$ for the next iteration. This involves setting the values of regions already localized to zero in $\\mathbf{S}_v$ , thereby excluding" + ], + "bbox": [ + 496, + 469, + 890, + 909 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "26470", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/ca7520bd762c9b887b71439177303f710ad6b7d4072fedf06d0e5e830e32c7d0.jpg", + "image_caption": [ + "Object Similarity-Aware Clustering (OSC) Loss $(N = 2$ Example)", + "Figure 3. Explanation of the proposed Object Similarity-Aware Clustering (OSC) loss ( $N = 2$ example)." + ], + "image_footnote": [], + "bbox": [ + 88, + 101, + 459, + 265 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "them from further iteration. After completing these steps, we move on to the next iteration. We repeat this process until we find all sound-associated grid cells. The pseudocode detailing this procedure is presented in Algorithm 1, offering a clear step-by-step guide.", + "bbox": [ + 75, + 303, + 467, + 378 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Object Identification and Final Localization.", + "text_level": 1, + "bbox": [ + 76, + 388, + 452, + 405 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "After finishing the iteration process, we identify all sound-associated grid cells as each object or negative. Each cell is evaluated to determine whether it represents a sound-making object or background. This classification is crucial as it ensures the accuracy of our object identification.", + "bbox": [ + 75, + 412, + 467, + 488 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "First, to eliminate cells that were identified as sound-associated grid cells but are actually background, we calculate cosine similarity between negative cell vector $\\mathbf{E}_n$ and each sound-associated grid cell $\\mathbf{E}_p^t$ in object bank $\\mathbf{O}$ . Cells with a similarity exceeding a threshold $\\tau_1$ are considered to be a part of the background and are eliminated from $\\mathbf{O}$ .", + "bbox": [ + 75, + 488, + 467, + 578 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Subsequently, to cluster the remaining sound-associated grid cells into each object, we calculate the cosine similarity between every pair of cells. This calculation helps us understand how similar or related these cells are to each other. If the similarity between any two cells is higher than the threshold $\\tau_{2}$ , we consider these cells to be part of the same object. To effectively cluster each object, we use the union-find algorithm [2]. It merges other cells into each group if they are determined to belong to the same object.", + "bbox": [ + 75, + 579, + 467, + 715 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Each identified group is labeled as object $k$ (where $k = 1,2,\\dots,K_b$ ). Here, $K_b$ is the number of objects in $b$ -th clip. Finally, we combine the localization maps from object $k$ to create the final localization map for each object.", + "bbox": [ + 76, + 715, + 467, + 776 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.5. Object Similarity-aware Clustering Loss", + "text_level": 1, + "bbox": [ + 76, + 786, + 421, + 801 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To effectively identify and separate multi-sound sources without any annotation and prior source knowledge in complex environments, we propose an Object Similarity-aware Clustering (OSC) loss. The OSC loss has an important role in guiding the IOI module to combine regions belonging to the same object while differentiating between distinct ob", + "bbox": [ + 75, + 809, + 467, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "jects and backgrounds. In the bank $\\mathbf{O}_b$ , the anchor cell $A_k^b$ is identified as the most representative cell of the object $k$ in the $b$ -th clip. $P_k^b$ and $N_k^b$ represent compositions of cells, where $P_k^b$ consists of cells attributed to the same object, and $N_k^b$ is from different objects or backgrounds ( $P_k^b$ and $N_k^b$ are distinguished though Section 3.4). The formulation of the OSC loss is structured as follows:", + "bbox": [ + 496, + 90, + 890, + 196 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} C _ {p k} ^ {b} = \\operatorname {S i m} \\left(A _ {k} ^ {b}, P _ {k} ^ {b}\\right), \\quad C _ {n k} ^ {b} = \\operatorname {S i m} \\left(A _ {k} ^ {b}, N _ {k} ^ {b}\\right), \\\\ \\mathcal {L} _ {k} ^ {b} = \\left(1 - C _ {p k} ^ {b}\\right) + C _ {n k} ^ {b}, \\tag {4} \\\\ \\mathcal {L} _ {o s c} = \\frac {1}{B} \\sum_ {b = 1} ^ {B} \\sum_ {k = 1} ^ {K _ {b}} \\frac {\\mathcal {L} _ {k} ^ {b}}{K _ {b}}, \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 540, + 204, + 890, + 289 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $C_{pk}^{b}$ and $C_{nk}^{b}$ represent the cosine similarity between the anchor and the positive, and the anchor and the negative, respectively. Through this loss, learning is directed in such a way that similarity between the anchor and positive cells is reinforced, while divergence between the anchor and negative cells is accentuated. As shown in Figure 3, this effectively clusters cells that are considered to be part of the same object, thereby aiding in the segmentation of objects. This approach reduces the number of iterations to distinguish objects, as detailed in our supplementary experiments.", + "bbox": [ + 496, + 301, + 890, + 454 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.6. Training Objective", + "text_level": 1, + "bbox": [ + 500, + 463, + 679, + 479 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To train our proposed method, we construct the total training loss function as follows:", + "bbox": [ + 496, + 486, + 890, + 516 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {T o t a l}} = \\lambda_ {1} \\mathcal {L} _ {\\text {a v c}} + \\lambda_ {2} \\mathcal {L} _ {\\text {o s c}}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 599, + 529, + 890, + 545 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\lambda_{1}$ and $\\lambda_{2}$ denote balancing parameters for each loss function. By using $\\mathcal{L}_{Total}$ , our method effectively performs multi-sound source localization, identifying sound sources from mixtures without the need for prior source knowledge.", + "bbox": [ + 496, + 556, + 890, + 617 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 626, + 632, + 642 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Datasets and Evaluation Metrics", + "text_level": 1, + "bbox": [ + 500, + 650, + 785, + 666 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "MUSIC. The MUSIC dataset [46] comprises 448 unedited YouTube music videos featuring solos and duets across 11 categories of musical instruments. To ensure a fair comparison with previous works, we use the same training/testing subset as utilized in AVGN [26]. Specifically, the MUSIC-Solo contains 358 solo videos that are applied for training, and 90 solo videos are for evaluation for single sound source localization. Similarly, the MUSIC-Duet contains 124 duet videos that are applied for training, and 17 duet videos are for evaluation for multi-sound source localization.", + "bbox": [ + 496, + 672, + 890, + 823 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "VGG-Sound. VGG-Sound dataset [7], which is denoted as VGGSound-Single consists of more than 200k videos from 221 different sound categories. We utilize 144k image-audio pairs as a training set. For single sound source localization, we use VGG-Sound Source [8] to evaluate our", + "bbox": [ + 496, + 824, + 890, + 898 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "26471", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/0a03f664905211f2cadbcf6bc9fad1f91ff0a38e21ee83cd9eaee160c6e579b2.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodMUSIC-Duet [46]VGGSound-Duet [7]
CAP(%)PIAP(%)CloU@0.3(%)AUC(%)CAP(%)PIAP(%)CloU@0.3(%)AUC(%)
Attention10k [32] (CVPR'18)--21.619.6--11.515.2
OTS [3] (ECCV'18)11.617.713.318.510.512.712.215.8
DMC [15] (CVPR'19)--17.521.1--13.817.1
CoarseToFine [27] (ECCV'20)--17.620.6--14.718.5
DSOL [16] (NeurIPS'20)--30.122.3--22.321.1
LVS [8] (CVPR'21)--22.520.9--17.319.5
EZ-VSL [24] (ECCV'22)--24.321.3--20.520.2
Mix-and-Localize [17] (CVPR'22)47.554.126.521.516.322.621.120.5
AVGN [26] (CVPR'23)50.657.232.524.621.928.126.223.8
Proposed Method52.172.538.630.132.544.446.929.2
", + "bbox": [ + 99, + 88, + 867, + 258 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/53901f5833055266f2f65baf917e72f89628add501ab92dd2b2cacfbb5c439ba.jpg", + "table_caption": [ + "Table 1. Experimental results on Music-Duet(left) and VGGSound-Duet(right) for multi-sound source localization. Bold/underlined fonts indicate the best/second-best results." + ], + "table_footnote": [], + "table_body": "
MethodMUSIC-Solo [46]VGGSound-Single [7]
AP(%)IoU@0.5(%)AUC(%)AP(%)IoU@0.5(%)AUC(%)
Attention10k [32] (CVPR'18)-37.238.7-19.230.6
OTS [3] (ECCV'18)69.326.135.829.832.835.7
DMC [15] (CVPR'19)-29.138.0-23.927.6
CoarseToFIne [27] (ECCV'20)70.733.639.828.229.134.8
DSOL [16] (NeurIPS'20)-51.443.7-35.737.2
LVS [8] (CVPR'21)70.641.940.329.634.438.2
EZ-VSL [24] (ECCV'22)71.545.841.231.338.939.5
Mix-and-Localize [17] (CVPR'22)68.630.540.832.536.338.9
AVGN [26] (CVPR'23)77.258.148.535.340.842.3
Proposed Method77.462.159.446.241.441.2
", + "bbox": [ + 101, + 301, + 867, + 484 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Experimental results on Music-Solo(left) and VGGSound-Single(right) for single sound source localization. Bold/underlined fonts indicate the best/second-best results.", + "bbox": [ + 75, + 484, + 892, + 513 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "method. In the training phase, for multi-sound source localization, we randomly concatenate two video frames to generate a single input image with dimensions of $448 \\times 224$ , and we combine the corresponding audio waveforms to generate a mixed audio signal. Following [26], we employ the VGGSound-Duet dataset for evaluation.", + "bbox": [ + 75, + 522, + 468, + 611 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation Metrics. Following the prior works [17, 26], we adopt metrics for a fair and comprehensive comparison. For single sound source localization, we employ Average Precision (AP), Intersection over Union (IoU), and Area Under Curve (AUC). Regarding multi-sound source localization, we employ Class-aware Average Precision (CAP), Permutation-Invariant Average Precision (PIAP), Class-aware IoU (CIoU), and Area Under Curve (AUC). Our method is self-supervised and does not use class labels, we follow [17] for the modified version of CAP and CIoU.", + "bbox": [ + 75, + 612, + 470, + 763 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.2. Implementation Details", + "text_level": 1, + "bbox": [ + 76, + 771, + 294, + 787 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For the visual modality input, we resize images to dimensions of $W_{v} = 224$ , $H_{v} = 224$ , extracting them from the central frame of 3-second video clips. For the audio modality, we resample the raw 3-second audio signal to $16\\mathrm{kHz}$ and convert it into a log-scale spectrogram.", + "bbox": [ + 75, + 794, + 468, + 869 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In accordance with the methods presented in [8], we utilize a ResNet-18 [13] for both the visual and audio feature", + "bbox": [ + 76, + 869, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "backbones to establish our model. Due to the sound spectrogram having only one channel, we adapt the first convolutional layer of the ResNet-18 [13] from 3 channels to 1. The visual encoder is pretrained using ImageNet [10]. Our method employs the Adam optimizer [18] with a learning rate of $10^{-4}$ and a batch size of 128. We train our model for 50 epochs on all experiments. The training is conducted using 1 RTX 4090 GPU. We use the weights of $\\tau_{1} = 0.7$ , $\\tau_{2} = 0.6$ . For our proposed loss function $\\mathcal{L}_{Total}$ , we set $\\lambda_{1} = 1$ and $\\lambda_{2} = 1$ . Following [8, 11], we utilize the implementation code and adopt the same other hyper-parameters.", + "bbox": [ + 496, + 522, + 890, + 689 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Comparison to Prior Works", + "text_level": 1, + "bbox": [ + 498, + 696, + 751, + 712 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Multi-Sound Source Localization. First, we conduct experiments on the multi-sound source localization scenarios. We compare our method with the state-of-the-art multisound source localization methods [3, 8, 15-17, 24, 26, 27, 32]. Table 1 shows the results of our method on MUSIC-Duet [46] and VGGSound-Duet [7]. For the MUSIC-Duet test set, our method demonstrates superior performance, achieving $1.5\\%$ , $15.3\\%$ , $6.1\\%$ , and $5.5\\%$ higher for CAP, PIAP, CIoU@0.3, and AUC, respectively. Furthermore, in the VGGSound-Duet dataset, our method significantly outperforms existing methods. It indicates that our OSC loss enables our method to effectively localize sound-making", + "bbox": [ + 496, + 719, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "26472", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/b58a4ce1db71f1325616adeb3dc0aa7ce724814594616e26903199280cfb05c3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 189, + 68, + 784, + 224 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ded77e4c1e8dcdbe6cf6d5eb524ee6bc690e882603a2e7b839cc2f8f4c3a2b0f.jpg", + "image_caption": [ + "(b)", + "Figure 4. Visualization results for (a) MUSIC-Duet, (b) VGGSound-Duet test set. We compare our method with AVGN [26]." + ], + "image_footnote": [], + "bbox": [ + 112, + 227, + 885, + 412 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/48903f2fc8ec74054c346c77ff05d2dbd1ff5f7e8a91a6da295552d79a4a5ee8.jpg", + "image_caption": [ + "Figure 5. Visualization results of our method on VGGSound-Trio test set." + ], + "image_footnote": [], + "bbox": [ + 138, + 436, + 831, + 580 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "objects through an iterative process.", + "bbox": [ + 76, + 612, + 315, + 626 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Single Sound Source Localization. For single sound source localization, we compare our method with other existing works [3, 8, 15-17, 24, 26, 27, 32]. Table 2 presents the performances on MUSIC-Solo [46] and VGGSound-Single datasets [7]. For the MUSIC-Solo test set, ours shows $0.2\\%$ higher for AP. $4.0\\%$ higher for IoU@0.5, and $10.9\\%$ higher for AUC, respectively. For the VGGSound-Single test set, ours outperforms most of the others. For AUC, ours achieves the second-best performance.", + "bbox": [ + 75, + 626, + 467, + 761 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The experimental results in Table 1 and Table 2 clearly demonstrate the significant advancements our method brings to single and multi-sound source localization. This progress is largely attributed to the capabilities of the IOI module and OSC loss in effectively distinguishing objects.", + "bbox": [ + 75, + 762, + 467, + 838 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.4. Visualization Results", + "text_level": 1, + "bbox": [ + 76, + 847, + 272, + 861 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We compare ours with the state-of-the-art approach, AVGN [26], in multi-sound source localization. This comparison", + "bbox": [ + 76, + 869, + 467, + 900 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "utilizes the MUSIC-Duet and VGGSound-Duet test sets for visualizing the localization results. The results are shown in Figure 4. The visualization highlights the efficacy of our method in accurately localizing sound-making objects within a mixture. Ground Truth (GT) annotations are used to denote regions where sound-making objects are present.", + "bbox": [ + 496, + 611, + 890, + 700 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Furthermore, Figure 5 offers additional visualization results from our method, showcasing its efficacy in differentiating objects in scenarios with three-source mixtures. We utilize VGGSound-Trio test set comprising a mixture of three sound sources from VGGSound-Single [7], following [26]. Our IOI module facilitates the repeated detection and distinction of objects in the audio-visual scene, culminating in highly accurate and refined localization maps.", + "bbox": [ + 496, + 702, + 890, + 821 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.5. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 832, + 651, + 847 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Effect of the Proposed Losses. We evaluate the performance impact of our two proposed losses $\\mathcal{L}_{\\text{ave}}$ and $\\mathcal{L}_{\\text{OSC}}$ . The results are shown in Table 3. When each loss is consid-", + "bbox": [ + 500, + 854, + 890, + 898 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "26473", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/7799232c3e5fba763fd6f570d8bc210fc6c3f5595cdae4f9d8e28f46b8a53d85.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Method\\( \\mathcal{L}_{auc} \\)\\( \\mathcal{L}_{osc} \\)PIAP(%)CloU@0.3(%)AUC(%)
AVGN [26]--28.126.223.8
Proposed Method✓-44.125.328.3
-✓44.343.027.0
✓✓44.446.929.2
", + "bbox": [ + 81, + 88, + 468, + 165 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/5a3bec7cb8435f4ebea25f13a12adb03ffc09987247c9fb10ba07fa6da6da77c.jpg", + "table_caption": [ + "Table 3. Effect of the proposed $\\mathcal{L}_{\\text{avg}}$ and $\\mathcal{L}_{\\text{osc}}$ loss on VGGSound-Duet test set." + ], + "table_footnote": [ + "Table 4. Experimental results on VGGSound-Duet test set according to the hyper-parameters ${\\tau }_{1}$ and ${\\tau }_{2}$ for IOI module in Sec 3.4." + ], + "table_body": "
τ1τ2PIAP(%)CloU@0.3(%)AUC(%)
0.644.446.929.2
0.70.744.143.927.5
0.844.345.028.2
0.644.346.328.9
0.70.644.446.929.2
0.844.246.829.1
", + "bbox": [ + 86, + 200, + 465, + 297 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ered, our method shows the improved performance against AVGN [26] which is currently a state-of-the-art method. When all the proposed losses are taken into account, we show the highest performance. By integrating the proposed losses into our training, ours achieves increased capacity for learning robust and discriminative features.", + "bbox": [ + 75, + 334, + 467, + 425 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Variation of $\\tau_{1}$ and $\\tau_{2}$ . We conduct an additional ablation study to investigate the effect of our method on the hyperparameters $\\tau_{1}$ and $\\tau_{2}$ as described in Section 3.3. The results in Table 4 indicate that we obtain the best results when $\\tau_{1} = 0.7$ and $\\tau_{2} = 0.6$ . Importantly, even when $\\tau_{1}$ and $\\tau_{2}$ are varied, our method still outperforms the existing methods. These results suggest that the proposed model is robust to the variations of hyperparameters.", + "bbox": [ + 75, + 426, + 467, + 547 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.6. Discussions", + "text_level": 1, + "bbox": [ + 76, + 559, + 202, + 571 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Sound Source Counting Accuracy. To validate the accuracy of counting the correct sound source for our model, we employed each VGGSound dataset, which comprises images containing varying sound sources (ranging from one to three per image). Respectively, our model achieved an impressive accuracy of $90.79\\%$ , $83.21\\%$ , and $68.94\\%$ for VGGSound-Single, Duet, and Trio test sets. These results not only highlight our performance in handling various numbers of sound sources but also demonstrate its potential applicability in diverse and dynamically changing audio-visual environments.", + "bbox": [ + 75, + 582, + 467, + 747 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Adaptability of Our Method to Varying Sound Sources. We present experiments designed to evaluate the adaptability of our method in scenarios with varied sound sources. For this purpose, we utilized two distinct test sets: VGGSound-Trio [26] and VGGSound-Mixed. VGGSound-Mixed is a resampled dataset encompassing sounds from VGGSound-Single, VGGSound-Duet, and VGGSound-Trio. VGGSound-Mixed allows us to demonstrate the capability of our method to localize sound sources effectively, regardless of their quantity. The results are shown in Ta", + "bbox": [ + 75, + 750, + 467, + 900 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/1db767b510278226fbd61b9483ede636b9cea06fe3bd9bbbdf82adc35e186a1a.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodTest SetCAP(%)PIAP(%)CloU@0.3(%)AUC(%)
AVGN [26]VGGSound-Trio18.523.722.721.8
Ours29.042.134.029.3
AVGN [26]VGGSound-MixedN/A22.9N/AN/A
Ours27.936.035.222.7
", + "bbox": [ + 504, + 88, + 888, + 152 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/f67a525b94f7513adf736161b726a58cc4cf13d6f98b4a14e26ff30fe3a6d922.jpg", + "table_caption": [ + "Table 5. Experimental results on VGGSound-Trio and VGGSound -Mixed test set. $N / A$ ’ denotes Not Available." + ], + "table_footnote": [ + "Table 6. The comparisons of training time, inference time, and the number of parameters." + ], + "table_body": "
MethodTraining (s) \n(per iter)Inference (s) \n(per image)#params
AVGN [26] (CVPR'23)0.420.03461.2M
Proposed Method0.450.02738.5M
", + "bbox": [ + 509, + 194, + 877, + 255 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ble 5. For the VGGSound-Trio test set, our method outperforms AVGN [26] across all evaluation metrics. For the VGGSound-Mixed test set, our approach achieves scores of $27.9\\%$ , $36.0\\%$ , $35.2\\%$ , and $22.7\\%$ for CAP, PIAP, CIoU@0.3, and AUC, respectively. Note that AVGN requires fixed prior source information, which limits its applicability. These results highlight our effectiveness in object localization, especially without prior source information, attributable to the efficacy of IOI module and loss function.", + "bbox": [ + 496, + 286, + 890, + 421 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Computational Costs. Table 6 presents comparisons of training time, inference time, and the number of parameters. We compare our method with AVGN [26] which shows the highest performance among the existing methods. Due to the iterative method, our training time is marginally increased (7.14%). However, inference time decreased by 28.3%, and the number of parameters significantly decreased compared to the existing method with transformers.", + "bbox": [ + 496, + 422, + 890, + 542 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 556, + 617, + 571 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we propose an innovative approach to multi-sound source localization that does not rely on prior knowledge. The core of our method is the Iterative Object Identification (IOI) module, which effectively identifies sound-making objects through iterative processes. Our object similarity-aware clustering (OSC) loss function successfully guides the IOI module not only to merge regions associated with the same object but also to discern distinct objects from the background. We believe that our approach, the iterative object identification method enhances accuracy and has diverse practical applications.", + "bbox": [ + 496, + 583, + 890, + 750 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements. This work was conducted by CARAI grant funded by DAPA and ADD (UD230017TD), and supported in part by the NRF grant funded by the Korea government (MSIT) (No. RS-2023-00252391) and by IITP grant (No. 2022-0-00124), IITP grant (IITP-2023-RS-2023-00266615), IITP grant (No. RS-2022-00155911) and by the MSIT (Ministry of Science and ICT), Korea, under the National Program for Excellence in SW (2023-0-00042) supervised by the IITP in 2024.", + "bbox": [ + 496, + 763, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "26474", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Bishwo Adhikari and Heikki Huttunen. Iterative bounding box annotation for object detection. In ICPR, 2021. 3", + "[2] Alfred V Aho and John E Hopcroft. 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In WACV, 2023. 1, 2" + ], + "bbox": [ + 78, + 90, + 468, + 742 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "26476", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/563474b5-06bb-4f08-b441-cc9dcf4bf078_model.json b/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/563474b5-06bb-4f08-b441-cc9dcf4bf078_model.json new file mode 100644 index 0000000000000000000000000000000000000000..ab7b586ac6b594ea4b9374115a9270d5c035109d --- /dev/null +++ b/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/563474b5-06bb-4f08-b441-cc9dcf4bf078_model.json @@ -0,0 +1,2134 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.243, + 0.131, + 0.728, + 0.177 + ], + "angle": 0, + "content": "Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge" + }, + { + "type": "text", + "bbox": [ + 0.186, + 0.203, + 0.79, + 0.257 + ], + "angle": 0, + "content": "Dongjin \\(\\mathrm{Kim}^{1,*}\\) Sung Jin Um\\(^{1,*}\\) Sangmin Lee\\(^{2,\\dagger}\\) Jung Uk \\(\\mathrm{Kim}^{1,\\dagger}\\) \n\\(^{1}\\)Kyung Hee University \\(^{2}\\)University of Illinois Urbana-Champaign \n{rlaehdwls310, sungzin1, ju.kim}@khu.ac.kr, sangminl@illinois.edu" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.292, + 0.314, + 0.308 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.325, + 0.474, + 0.673 + ], + "angle": 0, + "content": "The goal of the multi-sound source localization task is to localize sound sources from the mixture individually. While recent multi-sound source localization methods have shown improved performance, they face challenges due to their reliance on prior information about the number of objects to be separated. In this paper, to overcome this limitation, we present a novel multi-sound source localization method that can perform localization without prior knowledge of the number of sound sources. To achieve this goal, we propose an iterative object identification (IOI) module, which can recognize sound-making objects in an iterative manner. After finding the regions of sound-making objects, we devise object similarity-aware clustering (OSC) loss to guide the IOI module to effectively combine regions of the same object but also distinguish between different objects and backgrounds. It enables our method to perform accurate localization of sound-making objects without any prior knowledge. Extensive experimental results on the MUSIC and VGGSound benchmarks show the significant performance improvements of the proposed method over the existing methods for both single and multi-source. Our code is available at: https://github.com/VisualAIKHU/NoPrior_MultiSSL." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.687, + 0.21, + 0.703 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.713, + 0.47, + 0.849 + ], + "angle": 0, + "content": "Humans naturally perceive various sounds and identify the origins of those sounds by using both visual sense (eyes) and auditory sense (ears) [12]. The sound source localization task aims to mimic the ability of humans to correlate auditory cues with visual information in order to identify sound-making objects. Due to this property, sound source localization is closely related to various real-world applications, including unmanned aerial vehicles [14, 30], robotics [20, 28], and speaker source localization [6, 31]." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.85, + 0.469, + 0.865 + ], + "angle": 0, + "content": "The sound source localization task can be divided into" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.286, + 0.895, + 0.484 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.486, + 0.893, + 0.556 + ], + "angle": 0, + "content": "Figure 1. Conceptual comparison between (a) existing methods and (b) the proposed method. The existing methods require prior source knowledge of the number of sound-making objects. In contrast, our method can effectively localize multiple sound-making objects without the need for prior source knowledge." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.566, + 0.893, + 0.779 + ], + "angle": 0, + "content": "two categories: (1) single sound source localization and (2) multi-sound source localization. The single sound source localization task [8, 11, 21, 22, 25, 32-36, 38, 39, 41, 44, 48] aims to find one source in a scene by utilizing cross-modal correlations [32, 40] between audio and visual cues. Various methods have been developed for the effective single sound source localization by introducing hard positive mining [8, 33], iterative learning [21], feature regularization [22], negative free learning [38], false negative aware learning [39], momentum target encoders [25], optical flow [11, 36], and spatial integration [41]. However, these methods focus primarily on locating a single sound source, which can be challenging in real-world environments where multiple sounds are often mixed together." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.895, + 0.902 + ], + "angle": 0, + "content": "In response to this challenge, several multi-sound source localization methods [16, 17, 26, 27] have been developed. The main goal of multi-sound source localization is to separate and localize individual sources from complex mixtures containing different sounds, such as self-supervised audio-visual matching [16], coarse-to-fine manner [27], contrastive random walker [17], and audio-visual grouping network [26]. However, a limitation of existing methods is" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.875, + 0.223, + 0.888 + ], + "angle": 0, + "content": "*Equal contribution" + }, + { + "type": "page_footnote", + "bbox": [ + 0.097, + 0.888, + 0.22, + 0.9 + ], + "angle": 0, + "content": "† Corresponding author" + }, + { + "type": "list", + "bbox": [ + 0.096, + 0.875, + 0.223, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "26467" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.273 + ], + "angle": 0, + "content": "their reliance on prior information about the number of objects that need to be separated. As shown in Figure 1(a), existing methods heavily rely on prior knowledge about the number of sound sources. If prior knowledge is incorrect, they are frequently failed to localize sound-making objects. Thus, they can only operate in constrained environments where prior source knowledge is available for sound source localization. Consequently, accurate localization of multisound sources becomes challenging when this prior knowledge is not available. In addition, since prior knowledge is generally not provided in real-world environments, it limits their applicability in practical scenarios." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.274, + 0.473, + 0.472 + ], + "angle": 0, + "content": "To address the aforementioned challenges, we introduce a novel method for multi-sound source localization that can identify multiple sound sources without the need for prior knowledge of the number of sources. As shown in Figure 1(b), our method can adapt to various numbers of sound sources by automatically recognizing the number of sound-making objects without relying on any prior knowledge. To this end, we propose an Iterative Object Identification (IOI) module. The goal of our IOI is to effectively automate object separation by repeatedly recognizing objects that make sounds from the mixtures in an iterative manner. By doing so, it continuously searches for sound-making regions until it determines that all relevant objects have been identified." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.472, + 0.473, + 0.713 + ], + "angle": 0, + "content": "To achieve this goal, we provide guidance to the IOI module for effective sound-making object identification. First, in the iterative process, we identify regions that are considered to be foreground objects and repeat this process until there are no more regions considered as foreground objects. At each iteration step, regions previously considered as foreground objects are eliminated in the subsequent iteration. Next, we employ a clustering process to merge regions belonging to the same object based on the foreground regions. To effectively carry out this process, we devise an object similarity-aware clustering (OSC) loss. This loss not only guides the IOI module to combine regions of the same object but also aids in distinguishing between different objects and backgrounds. By doing so, the proposed framework is able to distinguish between various objects with distinct sounds through the iterative process." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.714, + 0.472, + 0.805 + ], + "angle": 0, + "content": "Consequently, our method can precisely locate the sound-making objects without the need for prior source knowledge, and can effectively distinguish between multiple sound sources. As a result, our method shows significant improvements in sound source localization performance compared to existing methods." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.806, + 0.442, + 0.822 + ], + "angle": 0, + "content": "The major contributions of our paper are as follows:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.825, + 0.473, + 0.902 + ], + "angle": 0, + "content": "- We introduce Iterative Object Identification (IOI) module to adaptively localize multiple sound sources without any prior source knowledge. To the best of our knowledge, this is the first attempt to perform multi-sound source localization without knowing the number of sound sources." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.894, + 0.152 + ], + "angle": 0, + "content": "- We propose Object Similarity-aware Clustering (OSC) loss to guide the IOI module to merge regions belonging to the same object during the iteration process, while distinguishing between different objects and the background." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.152, + 0.894, + 0.198 + ], + "angle": 0, + "content": "- Experimental results on MUSIC and VGGSound datasets demonstrate the effectiveness of the proposed method for both single-/multi-source sound localization." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.092, + 0.894, + 0.198 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.214, + 0.642, + 0.23 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.24, + 0.742, + 0.255 + ], + "angle": 0, + "content": "2.1. Sound Source Localization" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.264, + 0.894, + 0.324 + ], + "angle": 0, + "content": "The sound source localization focuses on finding the spatial location of sound sources within a video frame. It can be divided into two main streams: (1) single sound source localization and (2) multi-sound source localization." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.325, + 0.893, + 0.642 + ], + "angle": 0, + "content": "The single sound source localization [8, 9, 11, 21, 22, 25, 32-36, 38, 39, 41, 44, 48] leverages the cross-modal interrelations between auditory and visual modalities to localize a sound-making object. Senocak et al. [32] introduced an unsupervised method to incorporate an audio-visual two-stream network with attention mechanisms. Chen et al. [8] proposed a framework that automatically identifies hard samples through contrastive learning. Lin et al. [21] adopted iterative learning with pseudo-labels to refine the localization process. In addition, Fedorishin et al. [11] and Singh et al. [36] leveraged optical flow as a prior and introduced a cross-attention mechanism over the relevant video frame. Sun et al. [39] introduced the False Negative Aware Contrastive (FNAC) strategy to guide similar-looking samples to be more similar. Senocak et al. [34] improved localization accuracy through enhanced cross-modal semantic understanding. Um et al. [41] proposed the spatial knowledge integration of the audio-visual modalities, promoting recursive enhancement of localization. However, in real-world scenarios, they encounter limitations due to the frequent occurrence of mixed sounds from various sources." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.895, + 0.825 + ], + "angle": 0, + "content": "Recent studies focus on the multi-sound source localization [16, 17, 26, 27] to effectively find the location of sound sources from mixtures. Hu et al. [16] introduced a technique that constructs a supervisory signal to differentiate the sound-making entities within a scene. Qian et al. [27] developed a two-stage audiovisual learning approach that separates audio and visual representations of various categories from scenes in a coarse-to-fine manner. Hu et al. [17] made a graph model for robust multi-sound source localization. Mo et al. [26] proposed a way to simultaneously extract and assimilate category-specific semantic features for each sound source from auditory and visual inputs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.895, + 0.901 + ], + "angle": 0, + "content": "However, the existing multi-sound source localization methods also exhibit a limitation in real-world scenarios. They heavily rely on prior knowledge about the number of sound sources to differentiate between multi-sound sources. Thus, we propose a sound source localization framework" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "26468" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.096, + 0.058, + 0.878, + 0.386 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.115, + 0.389, + 0.851, + 0.404 + ], + "angle": 0, + "content": "Figure 2. Network configuration of the proposed sound source localization framework. GAP denotes global average pooling." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.416, + 0.47, + 0.462 + ], + "angle": 0, + "content": "that can autonomously recognize the number of objects within a scene and localize the objects without relying on annotations or prior knowledge." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.47, + 0.406, + 0.485 + ], + "angle": 0, + "content": "2.2. Iterative Methods in Computer Vision" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.493, + 0.47, + 0.644 + ], + "angle": 0, + "content": "Iterative techniques have been applied to various research fields [1, 4, 5, 19, 23, 29, 37, 42, 43, 45, 47] because they provide a refining solutions through repetitive cycles. For example, the iterative methods have been applied to image deblurring and denoising tasks [5, 19], showing significant improvements over traditional non-iterative techniques. In addition, for the mainstream computer vision tasks, e.g., object detection and segmentation tasks, various works [1, 37, 42, 45, 47] also adopt the iterative refinement techniques for more improved performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.645, + 0.471, + 0.81 + ], + "angle": 0, + "content": "The iterative technique possesses inherent characteristic of iteratively converging towards the desired solution. In this study, we adopt this technique to perform effective multi-sound source localization. Though this approach, we automatically and iteratively identify multiple sound sources, enhancing the localization for the same objects and allowing differentiation between different objects. As a result, our method demonstrates improved performance compared to conventional methods. Moreover, due to its automatic object-finding nature, our iterative approach is not constrained by prior source knowledge." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.823, + 0.267, + 0.839 + ], + "angle": 0, + "content": "3. Proposed Approach" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.848, + 0.273, + 0.862 + ], + "angle": 0, + "content": "3.1. Overall Architecture" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Figure 2 shows the overall architecture of our framework. Similar to the previous works [8, 32], we adopt a two-stream" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.416, + 0.892, + 0.581 + ], + "angle": 0, + "content": "network to extract visual and audio features. Input image set \\( I_{v} \\in \\mathbb{R}^{B \\times W_{v} \\times H_{v} \\times 3} \\) (\\( B \\) indicates batch number, \\( W_{v} \\) and \\( H_{v} \\) denote width and height of \\( I_{v} \\)) and the corresponding mixed audio spectrogram \\( I_{a} \\in \\mathbb{R}^{B \\times W_{a} \\times H_{a} \\times 1} \\) (\\( W_{a} \\) and \\( H_{a} \\) denote width and height of \\( I_{a} \\)) pass through each modal encoder (i.e., visual and audio encoders) to generate visual feature \\( \\mathbf{F}_{v} \\) and audio feature \\( \\mathbf{F}_{a} \\), respectively. First, we identify all the sound-making regions associated with mixed audi-los to filter the regions of interest. We measure cosine similarity between \\( \\mathbf{F}_{v} \\) and \\( l_{a} \\), derived from the global average pooling (GAP) of \\( \\mathbf{F}_{a} \\), to obtain a sound-associated map \\( \\mathbf{S}_{v} \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.582, + 0.892, + 0.732 + ], + "angle": 0, + "content": "Next, we obtain a sound-associated visual feature \\(\\hat{\\mathbf{F}}_v\\) by the product of \\(\\mathbf{S}_v\\) and \\(\\mathbf{F}_v\\) to being aware of features for overall sound-making regions. The Iterative Object Identification (IOI) module receives \\(\\hat{\\mathbf{F}}_v\\) to iteratively discriminate sound-associated grid cells and collect each cell in an object bank \\(\\mathbf{O}\\). Subsequently, sound-associated grid cells in \\(\\mathbf{O}\\) are allocated into object groups (e.g., object 1, object 2, etc.), and the background regions are removed. Our method differentiates various objects without prior source knowledge (i.e., the number of sound sources)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.742, + 0.83, + 0.758 + ], + "angle": 0, + "content": "3.2. Sound-Associated Region Localization" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.841 + ], + "angle": 0, + "content": "To automatically localize sound-making objects in a visual scene without any annotation or prior knowledge, it is essential to measure the correspondence between audio and visual features. To achieve this, we try to distinguish sound-making regions from non-sound regions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.841, + 0.892, + 0.903 + ], + "angle": 0, + "content": "We calculate the cosine similarity between \\(\\mathbf{F}_v \\in \\mathbb{R}^{B \\times w \\times h \\times c}\\) (\\(w, h\\), and \\(c\\) are the width, height, and channel) and \\(l_a \\in \\mathbb{R}^{B \\times c}\\) to generate sound-associated map \\(\\mathbf{S}_v = \\{S_{v_{ij}}\\}_{i=1,\\dots,h,j=1,\\dots,w} \\in \\mathbb{R}^{B \\times w \\times h}\\). To make \\(\\mathbf{S}_v\\)" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "26469" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.213 + ], + "angle": 0, + "content": "meaningful, our method allows positive audio-visual pairs to be attracted to each other and negative pairs to be repelled at training time. By doing so, it is possible to identify spatial regions associated with given sound (positive pairs) and regions which are not associated with that sound (negative pairs). We define \\(\\mathbf{S}_v^{n\\to m}\\) as cosine similarity map between \\(n\\)-th image and \\(m\\)-th audio, and the \\(ij\\)-th element of \\(\\mathbf{S}_v^{n\\to m}\\), which can be represented as:" + }, + { + "type": "equation", + "bbox": [ + 0.146, + 0.219, + 0.469, + 0.295 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\operatorname {S i m} (A, B) = \\frac {\\langle A , B \\rangle}{| | A | | | | B | |}, \\\\ S _ {v _ {i j}} ^ {n \\rightarrow m} = \\frac {\\operatorname {S i m} \\left(\\mathbf {F} _ {v _ {i j}} ^ {n} , l _ {a} ^ {m}\\right)}{\\sum_ {i = 1} ^ {h} \\sum_ {j = 1} ^ {w} \\operatorname {S i m} \\left(\\mathbf {F} _ {v _ {i j}} ^ {n} , l _ {a} ^ {n}\\right)}, \\tag {1} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.301, + 0.47, + 0.332 + ], + "angle": 0, + "content": "where \\(\\langle \\cdot, \\cdot \\rangle\\) denotes inner-product. Next, we obtain the mask of \\(n\\)-th clip \\(M^n\\), represented as:" + }, + { + "type": "equation", + "bbox": [ + 0.158, + 0.338, + 0.469, + 0.356 + ], + "angle": 0, + "content": "\\[\nM ^ {n} = \\operatorname {s i g m o i d} \\left(\\left(S _ {v} ^ {n \\rightarrow n} - \\alpha\\right) / \\omega\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.363, + 0.47, + 0.424 + ], + "angle": 0, + "content": "where \\(\\alpha\\) and \\(\\omega\\) are the hyper-parameters. Based on \\(M^n\\), we aim to localize all the sound-making regions associated with mixed audios. Thus, motivated by [8], we employ an audiovisual contrastive loss \\(\\mathcal{L}_{avc}\\), which can be represented as:" + }, + { + "type": "equation", + "bbox": [ + 0.095, + 0.43, + 0.469, + 0.547 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} P o s ^ {n} = \\frac {1}{| M ^ {n} |} \\langle M ^ {n}, S _ {v} ^ {n \\rightarrow n} \\rangle , \\\\ N e g ^ {n} = \\frac {\\left\\langle \\mathbf {1} - M ^ {n} , S _ {v} ^ {n \\rightarrow n} \\right\\rangle}{\\left| \\mathbf {1} - M ^ {n} \\right|} + \\frac {1}{h w} \\sum_ {n \\neq m} \\left\\langle \\mathbf {1}, S _ {v} ^ {n \\rightarrow m} \\right\\rangle , \\tag {3} \\\\ \\mathcal {L} _ {a v c} = - \\frac {1}{B} \\sum_ {n = 1} ^ {B} \\left[ \\log \\frac {\\exp (P o s ^ {n})}{\\exp (P o s ^ {n}) + \\exp (N e g ^ {n})} \\right]. \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.552, + 0.47, + 0.675 + ], + "angle": 0, + "content": "\\(Pos^n\\) represents the average vector of highly correlated regions between the audio-visual pairs in the \\(n\\)-th clip. In contrast, \\(Neg^n\\) contains not only regions with low correlated between audio-visual pairs within the same clip but also includes correlation with other clips. Consequently, \\(\\mathcal{L}_{avc}\\) allows the \\(\\mathbf{S}_v\\) to effectively filter out the foreground regions associated with the mixed audio, separating from the background regions that do not produce sound." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.682, + 0.407, + 0.698 + ], + "angle": 0, + "content": "3.3. Iterative Object Identification Module" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.704, + 0.469, + 0.796 + ], + "angle": 0, + "content": "Through Section 3.2, the sound-associated map \\(\\mathbf{S}_v\\) can contain knowledge of the sound-associated objects. We then multiply \\(\\mathbf{S}_v\\) by the original visual feature \\(\\mathbf{F}_v\\) to encode sound-associated visual feature \\(\\hat{\\mathbf{F}}_v\\in \\mathbb{R}^{B\\times w\\times h\\times c}\\). By doing so, background cells are removed, leaving all the sound-associated cells that represent the sound-making object." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Next, the proposed Iterative Object Identification (IOI) module takes \\(\\hat{\\mathbf{F}}_v\\) to identify sound-making objects in mixed audio-visual data. Using \\(\\hat{\\mathbf{F}}_v\\), the IOI module conducts a total of \\(T\\) iterations to find all sound-associated cells, and in each iteration, it finds the area to localize around the position of the sound-associated cell identified. Each iteration consists of four steps: (1) Highest sound-associated cell" + }, + { + "type": "code_caption", + "bbox": [ + 0.501, + 0.091, + 0.858, + 0.107 + ], + "angle": 0, + "content": "Algorithm 1 Iterative Object Identification Algorithm" + }, + { + "type": "algorithm", + "bbox": [ + 0.501, + 0.112, + 0.892, + 0.289 + ], + "angle": 0, + "content": "Require: \\(\\mathbf{S}_v,\\hat{\\mathbf{F}}_v\\) \nEnsure: \\(\\mathbf{O} = [],t = 0\\) \nwhile max(S>ε do \\(\\begin{array}{rl} & {\\mathbf{E}_p^t\\leftarrow \\hat{\\mathbf{F}}_v[\\mathrm{argmax}(\\mathbf{S}_v)]}\\\\ & {\\mathbf{R}_p\\leftarrow \\langle \\hat{\\mathbf{F}}_v,\\mathbf{E}_p^t\\rangle}\\\\ & {\\mathbf{R}_n\\leftarrow \\langle \\hat{\\mathbf{F}}_v,\\mathbf{E}_n\\rangle}\\\\ & {\\mathrm{sound\\_making\\_region}\\leftarrow \\mathbf{R}_p > \\mathbf{R}_n}\\\\ & {\\mathbf{S}_v\\leftarrow \\mathbf{S}_v\\cdot \\neg \\mathrm{sound\\_making\\_region}}\\\\ & {\\mathbf{O}.append(\\mathbf{E}_p^t)}\\\\ & {t\\leftarrow t + 1} \\end{array}\\) ▷Inner Product \nend while \nResults: \\(T = t,\\mathbf{O} = [\\mathbf{E}_p^1,\\mathbf{E}_p^2,\\dots,\\mathbf{E}_p^T]\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.304, + 0.892, + 0.379 + ], + "angle": 0, + "content": "selection, (2) foreground/background selection, (3) finding sound-making regions, and (4) identified sound-making region exclusion. After the end of \\( T \\) iteration process, we cluster all sound-associated grid cells as each object or negative." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.38, + 0.892, + 0.47 + ], + "angle": 0, + "content": "Before starting iteration, we define a negative cell vector \\(\\mathbf{E}_n\\in \\mathbb{R}^{B\\times c}\\) to represent background (non-sound-making objects). \\(\\mathbf{E}_n\\) is obtained by averaging the background cells that were excluded during the creation of \\(\\hat{\\mathbf{F}}_v\\). This vector is essential for identifying regions that do not correspond to the sound, to provide contrast to the foreground." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.47, + 0.892, + 0.61 + ], + "angle": 0, + "content": "(1) Highest sound-associated cell selection. In the first step in \\( t \\)-th iteration, we select the cell in \\( \\mathbf{S}_v \\) with the highest value and select this cell as a starting point. This selection is based on the understanding that the highest value in \\( \\mathbf{S}_v \\) indicates the strongest audio-visual correspondence in that cell. Therefore, we identify and mark the coordinates of this cell as \\( (i,j) \\). The vector \\( \\hat{\\mathbf{F}}_{v_{ij}} \\) is then assigned as the sound-associated grid cell \\( \\mathbf{E}_p^t \\in \\mathbb{R}^{B \\times c} \\). Then, we store \\( \\mathbf{E}_p^t \\) in the \\( i \\)-th element of the object bank \\( \\mathbf{O} = \\{\\mathbf{E}_p^t\\}_{t=1}^T \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.61, + 0.892, + 0.833 + ], + "angle": 0, + "content": "(2) Foreground/background selection. In the second step in \\(t\\)-th iteration, we perform foreground and background selection using \\(\\mathbf{E}_p^t\\) and \\(\\mathbf{E}_n\\). The similarity measurement is carried out by calculating the inner product of \\(\\hat{\\mathbf{F}}_v\\) and \\(\\mathbf{E}_p^t\\). This result is used as foreground region \\(\\mathbf{R}_p^t \\in \\mathbb{R}^{B \\times w \\times h}\\). A higher value in \\(\\mathbf{R}_p^t\\) indicates a higher likelihood of being the same object as \\(\\mathbf{E}_p^t\\). Similarly, the background region is calculated by inner product of \\(\\hat{\\mathbf{F}}_v\\) and \\(\\mathbf{E}_n\\), resulting in \\(\\mathbf{R}_n^t \\in \\mathbb{R}^{B \\times w \\times h}\\). (3) Finding sound-making regions. In the third step in \\(t\\)-th iteration, we compare \\(\\mathbf{R}_p^t\\) and \\(\\mathbf{R}_n^t\\) to localize sound-making regions. The choice of sound-making region sizes is based on the condition that the value of foreground region \\(\\mathbf{R}_p^t\\) is higher than that of the background \\(\\mathbf{R}_n^t\\). Using these regions, we generate the \\(t\\)-th localization map." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.833, + 0.892, + 0.91 + ], + "angle": 0, + "content": "(4) Identified sound-making region exclusion. In the fourth step in \\( t \\)-th iteration, to prevent redundancy in finding sound-associated grid cell vector \\( \\mathbf{E}_p^t \\), we need to modify \\( \\mathbf{S}_v \\) for the next iteration. This involves setting the values of regions already localized to zero in \\( \\mathbf{S}_v \\), thereby excluding" + }, + { + "type": "list", + "bbox": [ + 0.498, + 0.47, + 0.892, + 0.91 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "26470" + } + ], + [ + { + "type": "image_caption", + "bbox": [ + 0.108, + 0.088, + 0.438, + 0.1 + ], + "angle": 0, + "content": "Object Similarity-Aware Clustering (OSC) Loss \\((N = 2\\) Example)" + }, + { + "type": "image", + "bbox": [ + 0.089, + 0.102, + 0.46, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.27, + 0.468, + 0.298 + ], + "angle": 0, + "content": "Figure 3. Explanation of the proposed Object Similarity-Aware Clustering (OSC) loss (\\(N = 2\\) example)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.304, + 0.468, + 0.38 + ], + "angle": 0, + "content": "them from further iteration. After completing these steps, we move on to the next iteration. We repeat this process until we find all sound-associated grid cells. The pseudocode detailing this procedure is presented in Algorithm 1, offering a clear step-by-step guide." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.39, + 0.453, + 0.406 + ], + "angle": 0, + "content": "3.4. Object Identification and Final Localization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.413, + 0.468, + 0.489 + ], + "angle": 0, + "content": "After finishing the iteration process, we identify all sound-associated grid cells as each object or negative. Each cell is evaluated to determine whether it represents a sound-making object or background. This classification is crucial as it ensures the accuracy of our object identification." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.489, + 0.468, + 0.579 + ], + "angle": 0, + "content": "First, to eliminate cells that were identified as sound-associated grid cells but are actually background, we calculate cosine similarity between negative cell vector \\(\\mathbf{E}_n\\) and each sound-associated grid cell \\(\\mathbf{E}_p^t\\) in object bank \\(\\mathbf{O}\\). Cells with a similarity exceeding a threshold \\(\\tau_1\\) are considered to be a part of the background and are eliminated from \\(\\mathbf{O}\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.58, + 0.468, + 0.716 + ], + "angle": 0, + "content": "Subsequently, to cluster the remaining sound-associated grid cells into each object, we calculate the cosine similarity between every pair of cells. This calculation helps us understand how similar or related these cells are to each other. If the similarity between any two cells is higher than the threshold \\(\\tau_{2}\\), we consider these cells to be part of the same object. To effectively cluster each object, we use the union-find algorithm [2]. It merges other cells into each group if they are determined to belong to the same object." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.716, + 0.468, + 0.777 + ], + "angle": 0, + "content": "Each identified group is labeled as object \\( k \\) (where \\( k = 1,2,\\dots,K_b \\)). Here, \\( K_b \\) is the number of objects in \\( b \\)-th clip. Finally, we combine the localization maps from object \\( k \\) to create the final localization map for each object." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.787, + 0.423, + 0.803 + ], + "angle": 0, + "content": "3.5. Object Similarity-aware Clustering Loss" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.468, + 0.901 + ], + "angle": 0, + "content": "To effectively identify and separate multi-sound sources without any annotation and prior source knowledge in complex environments, we propose an Object Similarity-aware Clustering (OSC) loss. The OSC loss has an important role in guiding the IOI module to combine regions belonging to the same object while differentiating between distinct ob" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.091, + 0.892, + 0.197 + ], + "angle": 0, + "content": "jects and backgrounds. In the bank \\(\\mathbf{O}_b\\), the anchor cell \\(A_k^b\\) is identified as the most representative cell of the object \\(k\\) in the \\(b\\)-th clip. \\(P_k^b\\) and \\(N_k^b\\) represent compositions of cells, where \\(P_k^b\\) consists of cells attributed to the same object, and \\(N_k^b\\) is from different objects or backgrounds (\\(P_k^b\\) and \\(N_k^b\\) are distinguished though Section 3.4). The formulation of the OSC loss is structured as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.541, + 0.205, + 0.892, + 0.29 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} C _ {p k} ^ {b} = \\operatorname {S i m} \\left(A _ {k} ^ {b}, P _ {k} ^ {b}\\right), \\quad C _ {n k} ^ {b} = \\operatorname {S i m} \\left(A _ {k} ^ {b}, N _ {k} ^ {b}\\right), \\\\ \\mathcal {L} _ {k} ^ {b} = \\left(1 - C _ {p k} ^ {b}\\right) + C _ {n k} ^ {b}, \\tag {4} \\\\ \\mathcal {L} _ {o s c} = \\frac {1}{B} \\sum_ {b = 1} ^ {B} \\sum_ {k = 1} ^ {K _ {b}} \\frac {\\mathcal {L} _ {k} ^ {b}}{K _ {b}}, \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.302, + 0.892, + 0.455 + ], + "angle": 0, + "content": "where \\( C_{pk}^{b} \\) and \\( C_{nk}^{b} \\) represent the cosine similarity between the anchor and the positive, and the anchor and the negative, respectively. Through this loss, learning is directed in such a way that similarity between the anchor and positive cells is reinforced, while divergence between the anchor and negative cells is accentuated. As shown in Figure 3, this effectively clusters cells that are considered to be part of the same object, thereby aiding in the segmentation of objects. This approach reduces the number of iterations to distinguish objects, as detailed in our supplementary experiments." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.464, + 0.681, + 0.48 + ], + "angle": 0, + "content": "3.6. Training Objective" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.487, + 0.891, + 0.517 + ], + "angle": 0, + "content": "To train our proposed method, we construct the total training loss function as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.6, + 0.53, + 0.891, + 0.546 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {T o t a l}} = \\lambda_ {1} \\mathcal {L} _ {\\text {a v c}} + \\lambda_ {2} \\mathcal {L} _ {\\text {o s c}}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.558, + 0.891, + 0.618 + ], + "angle": 0, + "content": "where \\(\\lambda_{1}\\) and \\(\\lambda_{2}\\) denote balancing parameters for each loss function. By using \\(\\mathcal{L}_{Total}\\), our method effectively performs multi-sound source localization, identifying sound sources from mixtures without the need for prior source knowledge." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.627, + 0.633, + 0.643 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.651, + 0.787, + 0.667 + ], + "angle": 0, + "content": "4.1. Datasets and Evaluation Metrics" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.674, + 0.892, + 0.824 + ], + "angle": 0, + "content": "MUSIC. The MUSIC dataset [46] comprises 448 unedited YouTube music videos featuring solos and duets across 11 categories of musical instruments. To ensure a fair comparison with previous works, we use the same training/testing subset as utilized in AVGN [26]. Specifically, the MUSIC-Solo contains 358 solo videos that are applied for training, and 90 solo videos are for evaluation for single sound source localization. Similarly, the MUSIC-Duet contains 124 duet videos that are applied for training, and 17 duet videos are for evaluation for multi-sound source localization." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.892, + 0.9 + ], + "angle": 0, + "content": "VGG-Sound. VGG-Sound dataset [7], which is denoted as VGGSound-Single consists of more than 200k videos from 221 different sound categories. We utilize 144k image-audio pairs as a training set. For single sound source localization, we use VGG-Sound Source [8] to evaluate our" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "26471" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.1, + 0.089, + 0.868, + 0.26 + ], + "angle": 0, + "content": "
MethodMUSIC-Duet [46]VGGSound-Duet [7]
CAP(%)PIAP(%)CloU@0.3(%)AUC(%)CAP(%)PIAP(%)CloU@0.3(%)AUC(%)
Attention10k [32] (CVPR'18)--21.619.6--11.515.2
OTS [3] (ECCV'18)11.617.713.318.510.512.712.215.8
DMC [15] (CVPR'19)--17.521.1--13.817.1
CoarseToFine [27] (ECCV'20)--17.620.6--14.718.5
DSOL [16] (NeurIPS'20)--30.122.3--22.321.1
LVS [8] (CVPR'21)--22.520.9--17.319.5
EZ-VSL [24] (ECCV'22)--24.321.3--20.520.2
Mix-and-Localize [17] (CVPR'22)47.554.126.521.516.322.621.120.5
AVGN [26] (CVPR'23)50.657.232.524.621.928.126.223.8
Proposed Method52.172.538.630.132.544.446.929.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.262, + 0.892, + 0.289 + ], + "angle": 0, + "content": "Table 1. Experimental results on Music-Duet(left) and VGGSound-Duet(right) for multi-sound source localization. Bold/underlined fonts indicate the best/second-best results." + }, + { + "type": "table", + "bbox": [ + 0.102, + 0.302, + 0.869, + 0.485 + ], + "angle": 0, + "content": "
MethodMUSIC-Solo [46]VGGSound-Single [7]
AP(%)IoU@0.5(%)AUC(%)AP(%)IoU@0.5(%)AUC(%)
Attention10k [32] (CVPR'18)-37.238.7-19.230.6
OTS [3] (ECCV'18)69.326.135.829.832.835.7
DMC [15] (CVPR'19)-29.138.0-23.927.6
CoarseToFIne [27] (ECCV'20)70.733.639.828.229.134.8
DSOL [16] (NeurIPS'20)-51.443.7-35.737.2
LVS [8] (CVPR'21)70.641.940.329.634.438.2
EZ-VSL [24] (ECCV'22)71.545.841.231.338.939.5
Mix-and-Localize [17] (CVPR'22)68.630.540.832.536.338.9
AVGN [26] (CVPR'23)77.258.148.535.340.842.3
Proposed Method77.462.159.446.241.441.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.486, + 0.893, + 0.514 + ], + "angle": 0, + "content": "Table 2. Experimental results on Music-Solo(left) and VGGSound-Single(right) for single sound source localization. Bold/underlined fonts indicate the best/second-best results." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.523, + 0.47, + 0.612 + ], + "angle": 0, + "content": "method. In the training phase, for multi-sound source localization, we randomly concatenate two video frames to generate a single input image with dimensions of \\(448 \\times 224\\), and we combine the corresponding audio waveforms to generate a mixed audio signal. Following [26], we employ the VGGSound-Duet dataset for evaluation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.613, + 0.471, + 0.765 + ], + "angle": 0, + "content": "Evaluation Metrics. Following the prior works [17, 26], we adopt metrics for a fair and comprehensive comparison. For single sound source localization, we employ Average Precision (AP), Intersection over Union (IoU), and Area Under Curve (AUC). Regarding multi-sound source localization, we employ Class-aware Average Precision (CAP), Permutation-Invariant Average Precision (PIAP), Class-aware IoU (CIoU), and Area Under Curve (AUC). Our method is self-supervised and does not use class labels, we follow [17] for the modified version of CAP and CIoU." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.772, + 0.295, + 0.789 + ], + "angle": 0, + "content": "4.2. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.469, + 0.87 + ], + "angle": 0, + "content": "For the visual modality input, we resize images to dimensions of \\( W_{v} = 224 \\), \\( H_{v} = 224 \\), extracting them from the central frame of 3-second video clips. For the audio modality, we resample the raw 3-second audio signal to \\( 16\\mathrm{kHz} \\) and convert it into a log-scale spectrogram." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.901 + ], + "angle": 0, + "content": "In accordance with the methods presented in [8], we utilize a ResNet-18 [13] for both the visual and audio feature" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.523, + 0.892, + 0.69 + ], + "angle": 0, + "content": "backbones to establish our model. Due to the sound spectrogram having only one channel, we adapt the first convolutional layer of the ResNet-18 [13] from 3 channels to 1. The visual encoder is pretrained using ImageNet [10]. Our method employs the Adam optimizer [18] with a learning rate of \\(10^{-4}\\) and a batch size of 128. We train our model for 50 epochs on all experiments. The training is conducted using 1 RTX 4090 GPU. We use the weights of \\(\\tau_{1} = 0.7\\), \\(\\tau_{2} = 0.6\\). For our proposed loss function \\(\\mathcal{L}_{Total}\\), we set \\(\\lambda_{1} = 1\\) and \\(\\lambda_{2} = 1\\). Following [8, 11], we utilize the implementation code and adopt the same other hyper-parameters." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.697, + 0.753, + 0.713 + ], + "angle": 0, + "content": "4.3. Comparison to Prior Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Multi-Sound Source Localization. First, we conduct experiments on the multi-sound source localization scenarios. We compare our method with the state-of-the-art multisound source localization methods [3, 8, 15-17, 24, 26, 27, 32]. Table 1 shows the results of our method on MUSIC-Duet [46] and VGGSound-Duet [7]. For the MUSIC-Duet test set, our method demonstrates superior performance, achieving \\(1.5\\%\\), \\(15.3\\%\\), \\(6.1\\%\\), and \\(5.5\\%\\) higher for CAP, PIAP, CIoU@0.3, and AUC, respectively. Furthermore, in the VGGSound-Duet dataset, our method significantly outperforms existing methods. It indicates that our OSC loss enables our method to effectively localize sound-making" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "26472" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.19, + 0.069, + 0.785, + 0.226 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.085, + 0.325, + 0.102, + 0.337 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image", + "bbox": [ + 0.114, + 0.228, + 0.887, + 0.414 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.116, + 0.417, + 0.852, + 0.431 + ], + "angle": 0, + "content": "Figure 4. Visualization results for (a) MUSIC-Duet, (b) VGGSound-Duet test set. We compare our method with AVGN [26]." + }, + { + "type": "image", + "bbox": [ + 0.139, + 0.437, + 0.832, + 0.582 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.266, + 0.586, + 0.701, + 0.599 + ], + "angle": 0, + "content": "Figure 5. Visualization results of our method on VGGSound-Trio test set." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.613, + 0.316, + 0.627 + ], + "angle": 0, + "content": "objects through an iterative process." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.627, + 0.468, + 0.762 + ], + "angle": 0, + "content": "Single Sound Source Localization. For single sound source localization, we compare our method with other existing works [3, 8, 15-17, 24, 26, 27, 32]. Table 2 presents the performances on MUSIC-Solo [46] and VGGSound-Single datasets [7]. For the MUSIC-Solo test set, ours shows \\(0.2\\%\\) higher for AP. \\(4.0\\%\\) higher for IoU@0.5, and \\(10.9\\%\\) higher for AUC, respectively. For the VGGSound-Single test set, ours outperforms most of the others. For AUC, ours achieves the second-best performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.763, + 0.468, + 0.839 + ], + "angle": 0, + "content": "The experimental results in Table 1 and Table 2 clearly demonstrate the significant advancements our method brings to single and multi-sound source localization. This progress is largely attributed to the capabilities of the IOI module and OSC loss in effectively distinguishing objects." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.848, + 0.274, + 0.862 + ], + "angle": 0, + "content": "4.4. Visualization Results" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.468, + 0.901 + ], + "angle": 0, + "content": "We compare ours with the state-of-the-art approach, AVGN [26], in multi-sound source localization. This comparison" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.612, + 0.892, + 0.702 + ], + "angle": 0, + "content": "utilizes the MUSIC-Duet and VGGSound-Duet test sets for visualizing the localization results. The results are shown in Figure 4. The visualization highlights the efficacy of our method in accurately localizing sound-making objects within a mixture. Ground Truth (GT) annotations are used to denote regions where sound-making objects are present." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.703, + 0.892, + 0.823 + ], + "angle": 0, + "content": "Furthermore, Figure 5 offers additional visualization results from our method, showcasing its efficacy in differentiating objects in scenarios with three-source mixtures. We utilize VGGSound-Trio test set comprising a mixture of three sound sources from VGGSound-Single [7], following [26]. Our IOI module facilitates the repeated detection and distinction of objects in the audio-visual scene, culminating in highly accurate and refined localization maps." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.833, + 0.652, + 0.848 + ], + "angle": 0, + "content": "4.5. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.856, + 0.891, + 0.899 + ], + "angle": 0, + "content": "Effect of the Proposed Losses. We evaluate the performance impact of our two proposed losses \\(\\mathcal{L}_{\\text{ave}}\\) and \\(\\mathcal{L}_{\\text{OSC}}\\). The results are shown in Table 3. When each loss is consid-" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "26473" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.082, + 0.089, + 0.47, + 0.166 + ], + "angle": 0, + "content": "
Method\\( \\mathcal{L}_{auc} \\)\\( \\mathcal{L}_{osc} \\)PIAP(%)CloU@0.3(%)AUC(%)
AVGN [26]--28.126.223.8
Proposed Method✓-44.125.328.3
-✓44.343.027.0
✓✓44.446.929.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.078, + 0.169, + 0.468, + 0.196 + ], + "angle": 0, + "content": "Table 3. Effect of the proposed \\( \\mathcal{L}_{\\text{avg}} \\) and \\( \\mathcal{L}_{\\text{osc}} \\) loss on VGGSound-Duet test set." + }, + { + "type": "table", + "bbox": [ + 0.088, + 0.201, + 0.466, + 0.299 + ], + "angle": 0, + "content": "
τ1τ2PIAP(%)CloU@0.3(%)AUC(%)
0.644.446.929.2
0.70.744.143.927.5
0.844.345.028.2
0.644.346.328.9
0.70.644.446.929.2
0.844.246.829.1
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.077, + 0.301, + 0.468, + 0.33 + ], + "angle": 0, + "content": "Table 4. Experimental results on VGGSound-Duet test set according to the hyper-parameters \\( {\\tau }_{1} \\) and \\( {\\tau }_{2} \\) for IOI module in Sec 3.4." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.335, + 0.468, + 0.426 + ], + "angle": 0, + "content": "ered, our method shows the improved performance against AVGN [26] which is currently a state-of-the-art method. When all the proposed losses are taken into account, we show the highest performance. By integrating the proposed losses into our training, ours achieves increased capacity for learning robust and discriminative features." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.427, + 0.468, + 0.548 + ], + "angle": 0, + "content": "Variation of \\(\\tau_{1}\\) and \\(\\tau_{2}\\). We conduct an additional ablation study to investigate the effect of our method on the hyperparameters \\(\\tau_{1}\\) and \\(\\tau_{2}\\) as described in Section 3.3. The results in Table 4 indicate that we obtain the best results when \\(\\tau_{1} = 0.7\\) and \\(\\tau_{2} = 0.6\\). Importantly, even when \\(\\tau_{1}\\) and \\(\\tau_{2}\\) are varied, our method still outperforms the existing methods. These results suggest that the proposed model is robust to the variations of hyperparameters." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.56, + 0.203, + 0.573 + ], + "angle": 0, + "content": "4.6. Discussions" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.583, + 0.468, + 0.748 + ], + "angle": 0, + "content": "Sound Source Counting Accuracy. To validate the accuracy of counting the correct sound source for our model, we employed each VGGSound dataset, which comprises images containing varying sound sources (ranging from one to three per image). Respectively, our model achieved an impressive accuracy of \\(90.79\\%\\), \\(83.21\\%\\), and \\(68.94\\%\\) for VGGSound-Single, Duet, and Trio test sets. These results not only highlight our performance in handling various numbers of sound sources but also demonstrate its potential applicability in diverse and dynamically changing audio-visual environments." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Adaptability of Our Method to Varying Sound Sources. We present experiments designed to evaluate the adaptability of our method in scenarios with varied sound sources. For this purpose, we utilized two distinct test sets: VGGSound-Trio [26] and VGGSound-Mixed. VGGSound-Mixed is a resampled dataset encompassing sounds from VGGSound-Single, VGGSound-Duet, and VGGSound-Trio. VGGSound-Mixed allows us to demonstrate the capability of our method to localize sound sources effectively, regardless of their quantity. The results are shown in Ta" + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.089, + 0.89, + 0.153 + ], + "angle": 0, + "content": "
MethodTest SetCAP(%)PIAP(%)CloU@0.3(%)AUC(%)
AVGN [26]VGGSound-Trio18.523.722.721.8
Ours29.042.134.029.3
AVGN [26]VGGSound-MixedN/A22.9N/AN/A
Ours27.936.035.222.7
" + }, + { + "type": "table_caption", + "bbox": [ + 0.501, + 0.154, + 0.892, + 0.182 + ], + "angle": 0, + "content": "Table 5. Experimental results on VGGSound-Trio and VGGSound -Mixed test set. \\( N / A \\) ’ denotes Not Available." + }, + { + "type": "table", + "bbox": [ + 0.511, + 0.195, + 0.879, + 0.256 + ], + "angle": 0, + "content": "
MethodTraining (s) \n(per iter)Inference (s) \n(per image)#params
AVGN [26] (CVPR'23)0.420.03461.2M
Proposed Method0.450.02738.5M
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.5, + 0.257, + 0.891, + 0.284 + ], + "angle": 0, + "content": "Table 6. The comparisons of training time, inference time, and the number of parameters." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.287, + 0.892, + 0.422 + ], + "angle": 0, + "content": "ble 5. For the VGGSound-Trio test set, our method outperforms AVGN [26] across all evaluation metrics. For the VGGSound-Mixed test set, our approach achieves scores of \\(27.9\\%\\), \\(36.0\\%\\), \\(35.2\\%\\), and \\(22.7\\%\\) for CAP, PIAP, CIoU@0.3, and AUC, respectively. Note that AVGN requires fixed prior source information, which limits its applicability. These results highlight our effectiveness in object localization, especially without prior source information, attributable to the efficacy of IOI module and loss function." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.423, + 0.892, + 0.543 + ], + "angle": 0, + "content": "Computational Costs. Table 6 presents comparisons of training time, inference time, and the number of parameters. We compare our method with AVGN [26] which shows the highest performance among the existing methods. Due to the iterative method, our training time is marginally increased (7.14%). However, inference time decreased by 28.3%, and the number of parameters significantly decreased compared to the existing method with transformers." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.558, + 0.619, + 0.573 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.584, + 0.892, + 0.75 + ], + "angle": 0, + "content": "In this paper, we propose an innovative approach to multi-sound source localization that does not rely on prior knowledge. The core of our method is the Iterative Object Identification (IOI) module, which effectively identifies sound-making objects through iterative processes. Our object similarity-aware clustering (OSC) loss function successfully guides the IOI module not only to merge regions associated with the same object but also to discern distinct objects from the background. We believe that our approach, the iterative object identification method enhances accuracy and has diverse practical applications." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Acknowledgements. This work was conducted by CARAI grant funded by DAPA and ADD (UD230017TD), and supported in part by the NRF grant funded by the Korea government (MSIT) (No. RS-2023-00252391) and by IITP grant (No. 2022-0-00124), IITP grant (IITP-2023-RS-2023-00266615), IITP grant (No. RS-2022-00155911) and by the MSIT (Ministry of Science and ICT), Korea, under the National Program for Excellence in SW (2023-0-00042) supervised by the IITP in 2024." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "26474" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.175, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.468, + 0.143 + ], + "angle": 0, + "content": "[1] Bishwo Adhikari and Heikki Huttunen. Iterative bounding box annotation for object detection. 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While recent multi-sound source localization methods have shown improved performance, they face challenges due to their reliance on prior information about the number of objects to be separated. In this paper, to overcome this limitation, we present a novel multi-sound source localization method that can perform localization without prior knowledge of the number of sound sources. To achieve this goal, we propose an iterative object identification (IOI) module, which can recognize sound-making objects in an iterative manner. After finding the regions of sound-making objects, we devise object similarity-aware clustering (OSC) loss to guide the IOI module to effectively combine regions of the same object but also distinguish between different objects and backgrounds. It enables our method to perform accurate localization of sound-making objects without any prior knowledge. Extensive experimental results on the MUSIC and VGGSound benchmarks show the significant performance improvements of the proposed method over the existing methods for both single and multi-source. Our code is available at: https://github.com/VisualAIKHU/NoPrior_MultiSSL. + +# 1. Introduction + +Humans naturally perceive various sounds and identify the origins of those sounds by using both visual sense (eyes) and auditory sense (ears) [12]. The sound source localization task aims to mimic the ability of humans to correlate auditory cues with visual information in order to identify sound-making objects. Due to this property, sound source localization is closely related to various real-world applications, including unmanned aerial vehicles [14, 30], robotics [20, 28], and speaker source localization [6, 31]. + +The sound source localization task can be divided into + +![](images/d55fda221c6f7fff4433f1736516056d532f8a00dd4f36261f598fa7485e2a17.jpg) +Figure 1. Conceptual comparison between (a) existing methods and (b) the proposed method. The existing methods require prior source knowledge of the number of sound-making objects. In contrast, our method can effectively localize multiple sound-making objects without the need for prior source knowledge. + +two categories: (1) single sound source localization and (2) multi-sound source localization. The single sound source localization task [8, 11, 21, 22, 25, 32-36, 38, 39, 41, 44, 48] aims to find one source in a scene by utilizing cross-modal correlations [32, 40] between audio and visual cues. Various methods have been developed for the effective single sound source localization by introducing hard positive mining [8, 33], iterative learning [21], feature regularization [22], negative free learning [38], false negative aware learning [39], momentum target encoders [25], optical flow [11, 36], and spatial integration [41]. However, these methods focus primarily on locating a single sound source, which can be challenging in real-world environments where multiple sounds are often mixed together. + +In response to this challenge, several multi-sound source localization methods [16, 17, 26, 27] have been developed. The main goal of multi-sound source localization is to separate and localize individual sources from complex mixtures containing different sounds, such as self-supervised audio-visual matching [16], coarse-to-fine manner [27], contrastive random walker [17], and audio-visual grouping network [26]. However, a limitation of existing methods is + +their reliance on prior information about the number of objects that need to be separated. As shown in Figure 1(a), existing methods heavily rely on prior knowledge about the number of sound sources. If prior knowledge is incorrect, they are frequently failed to localize sound-making objects. Thus, they can only operate in constrained environments where prior source knowledge is available for sound source localization. Consequently, accurate localization of multisound sources becomes challenging when this prior knowledge is not available. In addition, since prior knowledge is generally not provided in real-world environments, it limits their applicability in practical scenarios. + +To address the aforementioned challenges, we introduce a novel method for multi-sound source localization that can identify multiple sound sources without the need for prior knowledge of the number of sources. As shown in Figure 1(b), our method can adapt to various numbers of sound sources by automatically recognizing the number of sound-making objects without relying on any prior knowledge. To this end, we propose an Iterative Object Identification (IOI) module. The goal of our IOI is to effectively automate object separation by repeatedly recognizing objects that make sounds from the mixtures in an iterative manner. By doing so, it continuously searches for sound-making regions until it determines that all relevant objects have been identified. + +To achieve this goal, we provide guidance to the IOI module for effective sound-making object identification. First, in the iterative process, we identify regions that are considered to be foreground objects and repeat this process until there are no more regions considered as foreground objects. At each iteration step, regions previously considered as foreground objects are eliminated in the subsequent iteration. Next, we employ a clustering process to merge regions belonging to the same object based on the foreground regions. To effectively carry out this process, we devise an object similarity-aware clustering (OSC) loss. This loss not only guides the IOI module to combine regions of the same object but also aids in distinguishing between different objects and backgrounds. By doing so, the proposed framework is able to distinguish between various objects with distinct sounds through the iterative process. + +Consequently, our method can precisely locate the sound-making objects without the need for prior source knowledge, and can effectively distinguish between multiple sound sources. As a result, our method shows significant improvements in sound source localization performance compared to existing methods. + +The major contributions of our paper are as follows: + +- We introduce Iterative Object Identification (IOI) module to adaptively localize multiple sound sources without any prior source knowledge. To the best of our knowledge, this is the first attempt to perform multi-sound source localization without knowing the number of sound sources. + +- We propose Object Similarity-aware Clustering (OSC) loss to guide the IOI module to merge regions belonging to the same object during the iteration process, while distinguishing between different objects and the background. +- Experimental results on MUSIC and VGGSound datasets demonstrate the effectiveness of the proposed method for both single-/multi-source sound localization. + +# 2. Related Work + +# 2.1. Sound Source Localization + +The sound source localization focuses on finding the spatial location of sound sources within a video frame. It can be divided into two main streams: (1) single sound source localization and (2) multi-sound source localization. + +The single sound source localization [8, 9, 11, 21, 22, 25, 32-36, 38, 39, 41, 44, 48] leverages the cross-modal interrelations between auditory and visual modalities to localize a sound-making object. Senocak et al. [32] introduced an unsupervised method to incorporate an audio-visual two-stream network with attention mechanisms. Chen et al. [8] proposed a framework that automatically identifies hard samples through contrastive learning. Lin et al. [21] adopted iterative learning with pseudo-labels to refine the localization process. In addition, Fedorishin et al. [11] and Singh et al. [36] leveraged optical flow as a prior and introduced a cross-attention mechanism over the relevant video frame. Sun et al. [39] introduced the False Negative Aware Contrastive (FNAC) strategy to guide similar-looking samples to be more similar. Senocak et al. [34] improved localization accuracy through enhanced cross-modal semantic understanding. Um et al. [41] proposed the spatial knowledge integration of the audio-visual modalities, promoting recursive enhancement of localization. However, in real-world scenarios, they encounter limitations due to the frequent occurrence of mixed sounds from various sources. + +Recent studies focus on the multi-sound source localization [16, 17, 26, 27] to effectively find the location of sound sources from mixtures. Hu et al. [16] introduced a technique that constructs a supervisory signal to differentiate the sound-making entities within a scene. Qian et al. [27] developed a two-stage audiovisual learning approach that separates audio and visual representations of various categories from scenes in a coarse-to-fine manner. Hu et al. [17] made a graph model for robust multi-sound source localization. Mo et al. [26] proposed a way to simultaneously extract and assimilate category-specific semantic features for each sound source from auditory and visual inputs. + +However, the existing multi-sound source localization methods also exhibit a limitation in real-world scenarios. They heavily rely on prior knowledge about the number of sound sources to differentiate between multi-sound sources. Thus, we propose a sound source localization framework + +![](images/5d59a73e652460bc359b217c335dccadcfe1822ad062c17ecf44accfa93cb366.jpg) +Figure 2. Network configuration of the proposed sound source localization framework. GAP denotes global average pooling. + +that can autonomously recognize the number of objects within a scene and localize the objects without relying on annotations or prior knowledge. + +# 2.2. Iterative Methods in Computer Vision + +Iterative techniques have been applied to various research fields [1, 4, 5, 19, 23, 29, 37, 42, 43, 45, 47] because they provide a refining solutions through repetitive cycles. For example, the iterative methods have been applied to image deblurring and denoising tasks [5, 19], showing significant improvements over traditional non-iterative techniques. In addition, for the mainstream computer vision tasks, e.g., object detection and segmentation tasks, various works [1, 37, 42, 45, 47] also adopt the iterative refinement techniques for more improved performance. + +The iterative technique possesses inherent characteristic of iteratively converging towards the desired solution. In this study, we adopt this technique to perform effective multi-sound source localization. Though this approach, we automatically and iteratively identify multiple sound sources, enhancing the localization for the same objects and allowing differentiation between different objects. As a result, our method demonstrates improved performance compared to conventional methods. Moreover, due to its automatic object-finding nature, our iterative approach is not constrained by prior source knowledge. + +# 3. Proposed Approach + +# 3.1. Overall Architecture + +Figure 2 shows the overall architecture of our framework. Similar to the previous works [8, 32], we adopt a two-stream + +network to extract visual and audio features. Input image set $I_{v} \in \mathbb{R}^{B \times W_{v} \times H_{v} \times 3}$ ( $B$ indicates batch number, $W_{v}$ and $H_{v}$ denote width and height of $I_{v}$ ) and the corresponding mixed audio spectrogram $I_{a} \in \mathbb{R}^{B \times W_{a} \times H_{a} \times 1}$ ( $W_{a}$ and $H_{a}$ denote width and height of $I_{a}$ ) pass through each modal encoder (i.e., visual and audio encoders) to generate visual feature $\mathbf{F}_{v}$ and audio feature $\mathbf{F}_{a}$ , respectively. First, we identify all the sound-making regions associated with mixed audi-los to filter the regions of interest. We measure cosine similarity between $\mathbf{F}_{v}$ and $l_{a}$ , derived from the global average pooling (GAP) of $\mathbf{F}_{a}$ , to obtain a sound-associated map $\mathbf{S}_{v}$ . + +Next, we obtain a sound-associated visual feature $\hat{\mathbf{F}}_v$ by the product of $\mathbf{S}_v$ and $\mathbf{F}_v$ to being aware of features for overall sound-making regions. The Iterative Object Identification (IOI) module receives $\hat{\mathbf{F}}_v$ to iteratively discriminate sound-associated grid cells and collect each cell in an object bank $\mathbf{O}$ . Subsequently, sound-associated grid cells in $\mathbf{O}$ are allocated into object groups (e.g., object 1, object 2, etc.), and the background regions are removed. Our method differentiates various objects without prior source knowledge (i.e., the number of sound sources). + +# 3.2. Sound-Associated Region Localization + +To automatically localize sound-making objects in a visual scene without any annotation or prior knowledge, it is essential to measure the correspondence between audio and visual features. To achieve this, we try to distinguish sound-making regions from non-sound regions. + +We calculate the cosine similarity between $\mathbf{F}_v \in \mathbb{R}^{B \times w \times h \times c}$ ( $w, h$ , and $c$ are the width, height, and channel) and $l_a \in \mathbb{R}^{B \times c}$ to generate sound-associated map $\mathbf{S}_v = \{S_{v_{ij}}\}_{i=1,\dots,h,j=1,\dots,w} \in \mathbb{R}^{B \times w \times h}$ . To make $\mathbf{S}_v$ + +meaningful, our method allows positive audio-visual pairs to be attracted to each other and negative pairs to be repelled at training time. By doing so, it is possible to identify spatial regions associated with given sound (positive pairs) and regions which are not associated with that sound (negative pairs). We define $\mathbf{S}_v^{n\to m}$ as cosine similarity map between $n$ -th image and $m$ -th audio, and the $ij$ -th element of $\mathbf{S}_v^{n\to m}$ , which can be represented as: + +$$ +\begin{array}{l} \operatorname {S i m} (A, B) = \frac {\langle A , B \rangle}{| | A | | | | B | |}, \\ S _ {v _ {i j}} ^ {n \rightarrow m} = \frac {\operatorname {S i m} \left(\mathbf {F} _ {v _ {i j}} ^ {n} , l _ {a} ^ {m}\right)}{\sum_ {i = 1} ^ {h} \sum_ {j = 1} ^ {w} \operatorname {S i m} \left(\mathbf {F} _ {v _ {i j}} ^ {n} , l _ {a} ^ {n}\right)}, \tag {1} \\ \end{array} +$$ + +where $\langle \cdot, \cdot \rangle$ denotes inner-product. Next, we obtain the mask of $n$ -th clip $M^n$ , represented as: + +$$ +M ^ {n} = \operatorname {s i g m o i d} \left(\left(S _ {v} ^ {n \rightarrow n} - \alpha\right) / \omega\right), \tag {2} +$$ + +where $\alpha$ and $\omega$ are the hyper-parameters. Based on $M^n$ , we aim to localize all the sound-making regions associated with mixed audios. Thus, motivated by [8], we employ an audiovisual contrastive loss $\mathcal{L}_{avc}$ , which can be represented as: + +$$ +\begin{array}{l} P o s ^ {n} = \frac {1}{| M ^ {n} |} \langle M ^ {n}, S _ {v} ^ {n \rightarrow n} \rangle , \\ N e g ^ {n} = \frac {\left\langle \mathbf {1} - M ^ {n} , S _ {v} ^ {n \rightarrow n} \right\rangle}{\left| \mathbf {1} - M ^ {n} \right|} + \frac {1}{h w} \sum_ {n \neq m} \left\langle \mathbf {1}, S _ {v} ^ {n \rightarrow m} \right\rangle , \tag {3} \\ \mathcal {L} _ {a v c} = - \frac {1}{B} \sum_ {n = 1} ^ {B} \left[ \log \frac {\exp (P o s ^ {n})}{\exp (P o s ^ {n}) + \exp (N e g ^ {n})} \right]. \\ \end{array} +$$ + +$Pos^n$ represents the average vector of highly correlated regions between the audio-visual pairs in the $n$ -th clip. In contrast, $Neg^n$ contains not only regions with low correlated between audio-visual pairs within the same clip but also includes correlation with other clips. Consequently, $\mathcal{L}_{avc}$ allows the $\mathbf{S}_v$ to effectively filter out the foreground regions associated with the mixed audio, separating from the background regions that do not produce sound. + +# 3.3. Iterative Object Identification Module + +Through Section 3.2, the sound-associated map $\mathbf{S}_v$ can contain knowledge of the sound-associated objects. We then multiply $\mathbf{S}_v$ by the original visual feature $\mathbf{F}_v$ to encode sound-associated visual feature $\hat{\mathbf{F}}_v\in \mathbb{R}^{B\times w\times h\times c}$ . By doing so, background cells are removed, leaving all the sound-associated cells that represent the sound-making object. + +Next, the proposed Iterative Object Identification (IOI) module takes $\hat{\mathbf{F}}_v$ to identify sound-making objects in mixed audio-visual data. Using $\hat{\mathbf{F}}_v$ , the IOI module conducts a total of $T$ iterations to find all sound-associated cells, and in each iteration, it finds the area to localize around the position of the sound-associated cell identified. Each iteration consists of four steps: (1) Highest sound-associated cell + +Algorithm 1 Iterative Object Identification Algorithm +Require: $\mathbf{S}_v,\hat{\mathbf{F}}_v$ +Ensure: $\mathbf{O} = [],t = 0$ +while max(S>ε do $\begin{array}{rl} & {\mathbf{E}_p^t\leftarrow \hat{\mathbf{F}}_v[\mathrm{argmax}(\mathbf{S}_v)]}\\ & {\mathbf{R}_p\leftarrow \langle \hat{\mathbf{F}}_v,\mathbf{E}_p^t\rangle}\\ & {\mathbf{R}_n\leftarrow \langle \hat{\mathbf{F}}_v,\mathbf{E}_n\rangle}\\ & {\mathrm{sound\_making\_region}\leftarrow \mathbf{R}_p > \mathbf{R}_n}\\ & {\mathbf{S}_v\leftarrow \mathbf{S}_v\cdot \neg \mathrm{sound\_making\_region}}\\ & {\mathbf{O}.append(\mathbf{E}_p^t)}\\ & {t\leftarrow t + 1} \end{array}$ ▷Inner Product +end while +Results: $T = t,\mathbf{O} = [\mathbf{E}_p^1,\mathbf{E}_p^2,\dots,\mathbf{E}_p^T]$ + +selection, (2) foreground/background selection, (3) finding sound-making regions, and (4) identified sound-making region exclusion. After the end of $T$ iteration process, we cluster all sound-associated grid cells as each object or negative. + +Before starting iteration, we define a negative cell vector $\mathbf{E}_n\in \mathbb{R}^{B\times c}$ to represent background (non-sound-making objects). $\mathbf{E}_n$ is obtained by averaging the background cells that were excluded during the creation of $\hat{\mathbf{F}}_v$ . This vector is essential for identifying regions that do not correspond to the sound, to provide contrast to the foreground. + +(1) Highest sound-associated cell selection. In the first step in $t$ -th iteration, we select the cell in $\mathbf{S}_v$ with the highest value and select this cell as a starting point. This selection is based on the understanding that the highest value in $\mathbf{S}_v$ indicates the strongest audio-visual correspondence in that cell. Therefore, we identify and mark the coordinates of this cell as $(i,j)$ . The vector $\hat{\mathbf{F}}_{v_{ij}}$ is then assigned as the sound-associated grid cell $\mathbf{E}_p^t \in \mathbb{R}^{B \times c}$ . Then, we store $\mathbf{E}_p^t$ in the $i$ -th element of the object bank $\mathbf{O} = \{\mathbf{E}_p^t\}_{t=1}^T$ . +(2) Foreground/background selection. In the second step in $t$ -th iteration, we perform foreground and background selection using $\mathbf{E}_p^t$ and $\mathbf{E}_n$ . The similarity measurement is carried out by calculating the inner product of $\hat{\mathbf{F}}_v$ and $\mathbf{E}_p^t$ . This result is used as foreground region $\mathbf{R}_p^t \in \mathbb{R}^{B \times w \times h}$ . A higher value in $\mathbf{R}_p^t$ indicates a higher likelihood of being the same object as $\mathbf{E}_p^t$ . Similarly, the background region is calculated by inner product of $\hat{\mathbf{F}}_v$ and $\mathbf{E}_n$ , resulting in $\mathbf{R}_n^t \in \mathbb{R}^{B \times w \times h}$ . (3) Finding sound-making regions. In the third step in $t$ -th iteration, we compare $\mathbf{R}_p^t$ and $\mathbf{R}_n^t$ to localize sound-making regions. The choice of sound-making region sizes is based on the condition that the value of foreground region $\mathbf{R}_p^t$ is higher than that of the background $\mathbf{R}_n^t$ . Using these regions, we generate the $t$ -th localization map. +(4) Identified sound-making region exclusion. In the fourth step in $t$ -th iteration, to prevent redundancy in finding sound-associated grid cell vector $\mathbf{E}_p^t$ , we need to modify $\mathbf{S}_v$ for the next iteration. This involves setting the values of regions already localized to zero in $\mathbf{S}_v$ , thereby excluding + +![](images/ca7520bd762c9b887b71439177303f710ad6b7d4072fedf06d0e5e830e32c7d0.jpg) +Object Similarity-Aware Clustering (OSC) Loss $(N = 2$ Example) +Figure 3. Explanation of the proposed Object Similarity-Aware Clustering (OSC) loss ( $N = 2$ example). + +them from further iteration. After completing these steps, we move on to the next iteration. We repeat this process until we find all sound-associated grid cells. The pseudocode detailing this procedure is presented in Algorithm 1, offering a clear step-by-step guide. + +# 3.4. Object Identification and Final Localization. + +After finishing the iteration process, we identify all sound-associated grid cells as each object or negative. Each cell is evaluated to determine whether it represents a sound-making object or background. This classification is crucial as it ensures the accuracy of our object identification. + +First, to eliminate cells that were identified as sound-associated grid cells but are actually background, we calculate cosine similarity between negative cell vector $\mathbf{E}_n$ and each sound-associated grid cell $\mathbf{E}_p^t$ in object bank $\mathbf{O}$ . Cells with a similarity exceeding a threshold $\tau_1$ are considered to be a part of the background and are eliminated from $\mathbf{O}$ . + +Subsequently, to cluster the remaining sound-associated grid cells into each object, we calculate the cosine similarity between every pair of cells. This calculation helps us understand how similar or related these cells are to each other. If the similarity between any two cells is higher than the threshold $\tau_{2}$ , we consider these cells to be part of the same object. To effectively cluster each object, we use the union-find algorithm [2]. It merges other cells into each group if they are determined to belong to the same object. + +Each identified group is labeled as object $k$ (where $k = 1,2,\dots,K_b$ ). Here, $K_b$ is the number of objects in $b$ -th clip. Finally, we combine the localization maps from object $k$ to create the final localization map for each object. + +# 3.5. Object Similarity-aware Clustering Loss + +To effectively identify and separate multi-sound sources without any annotation and prior source knowledge in complex environments, we propose an Object Similarity-aware Clustering (OSC) loss. The OSC loss has an important role in guiding the IOI module to combine regions belonging to the same object while differentiating between distinct ob + +jects and backgrounds. In the bank $\mathbf{O}_b$ , the anchor cell $A_k^b$ is identified as the most representative cell of the object $k$ in the $b$ -th clip. $P_k^b$ and $N_k^b$ represent compositions of cells, where $P_k^b$ consists of cells attributed to the same object, and $N_k^b$ is from different objects or backgrounds ( $P_k^b$ and $N_k^b$ are distinguished though Section 3.4). The formulation of the OSC loss is structured as follows: + +$$ +\begin{array}{l} C _ {p k} ^ {b} = \operatorname {S i m} \left(A _ {k} ^ {b}, P _ {k} ^ {b}\right), \quad C _ {n k} ^ {b} = \operatorname {S i m} \left(A _ {k} ^ {b}, N _ {k} ^ {b}\right), \\ \mathcal {L} _ {k} ^ {b} = \left(1 - C _ {p k} ^ {b}\right) + C _ {n k} ^ {b}, \tag {4} \\ \mathcal {L} _ {o s c} = \frac {1}{B} \sum_ {b = 1} ^ {B} \sum_ {k = 1} ^ {K _ {b}} \frac {\mathcal {L} _ {k} ^ {b}}{K _ {b}}, \\ \end{array} +$$ + +where $C_{pk}^{b}$ and $C_{nk}^{b}$ represent the cosine similarity between the anchor and the positive, and the anchor and the negative, respectively. Through this loss, learning is directed in such a way that similarity between the anchor and positive cells is reinforced, while divergence between the anchor and negative cells is accentuated. As shown in Figure 3, this effectively clusters cells that are considered to be part of the same object, thereby aiding in the segmentation of objects. This approach reduces the number of iterations to distinguish objects, as detailed in our supplementary experiments. + +# 3.6. Training Objective + +To train our proposed method, we construct the total training loss function as follows: + +$$ +\mathcal {L} _ {\text {T o t a l}} = \lambda_ {1} \mathcal {L} _ {\text {a v c}} + \lambda_ {2} \mathcal {L} _ {\text {o s c}}, \tag {5} +$$ + +where $\lambda_{1}$ and $\lambda_{2}$ denote balancing parameters for each loss function. By using $\mathcal{L}_{Total}$ , our method effectively performs multi-sound source localization, identifying sound sources from mixtures without the need for prior source knowledge. + +# 4. Experiments + +# 4.1. Datasets and Evaluation Metrics + +MUSIC. The MUSIC dataset [46] comprises 448 unedited YouTube music videos featuring solos and duets across 11 categories of musical instruments. To ensure a fair comparison with previous works, we use the same training/testing subset as utilized in AVGN [26]. Specifically, the MUSIC-Solo contains 358 solo videos that are applied for training, and 90 solo videos are for evaluation for single sound source localization. Similarly, the MUSIC-Duet contains 124 duet videos that are applied for training, and 17 duet videos are for evaluation for multi-sound source localization. + +VGG-Sound. VGG-Sound dataset [7], which is denoted as VGGSound-Single consists of more than 200k videos from 221 different sound categories. We utilize 144k image-audio pairs as a training set. For single sound source localization, we use VGG-Sound Source [8] to evaluate our + +
MethodMUSIC-Duet [46]VGGSound-Duet [7]
CAP(%)PIAP(%)CloU@0.3(%)AUC(%)CAP(%)PIAP(%)CloU@0.3(%)AUC(%)
Attention10k [32] (CVPR'18)--21.619.6--11.515.2
OTS [3] (ECCV'18)11.617.713.318.510.512.712.215.8
DMC [15] (CVPR'19)--17.521.1--13.817.1
CoarseToFine [27] (ECCV'20)--17.620.6--14.718.5
DSOL [16] (NeurIPS'20)--30.122.3--22.321.1
LVS [8] (CVPR'21)--22.520.9--17.319.5
EZ-VSL [24] (ECCV'22)--24.321.3--20.520.2
Mix-and-Localize [17] (CVPR'22)47.554.126.521.516.322.621.120.5
AVGN [26] (CVPR'23)50.657.232.524.621.928.126.223.8
Proposed Method52.172.538.630.132.544.446.929.2
+ +Table 1. Experimental results on Music-Duet(left) and VGGSound-Duet(right) for multi-sound source localization. Bold/underlined fonts indicate the best/second-best results. + +
MethodMUSIC-Solo [46]VGGSound-Single [7]
AP(%)IoU@0.5(%)AUC(%)AP(%)IoU@0.5(%)AUC(%)
Attention10k [32] (CVPR'18)-37.238.7-19.230.6
OTS [3] (ECCV'18)69.326.135.829.832.835.7
DMC [15] (CVPR'19)-29.138.0-23.927.6
CoarseToFIne [27] (ECCV'20)70.733.639.828.229.134.8
DSOL [16] (NeurIPS'20)-51.443.7-35.737.2
LVS [8] (CVPR'21)70.641.940.329.634.438.2
EZ-VSL [24] (ECCV'22)71.545.841.231.338.939.5
Mix-and-Localize [17] (CVPR'22)68.630.540.832.536.338.9
AVGN [26] (CVPR'23)77.258.148.535.340.842.3
Proposed Method77.462.159.446.241.441.2
+ +Table 2. Experimental results on Music-Solo(left) and VGGSound-Single(right) for single sound source localization. Bold/underlined fonts indicate the best/second-best results. + +method. In the training phase, for multi-sound source localization, we randomly concatenate two video frames to generate a single input image with dimensions of $448 \times 224$ , and we combine the corresponding audio waveforms to generate a mixed audio signal. Following [26], we employ the VGGSound-Duet dataset for evaluation. + +Evaluation Metrics. Following the prior works [17, 26], we adopt metrics for a fair and comprehensive comparison. For single sound source localization, we employ Average Precision (AP), Intersection over Union (IoU), and Area Under Curve (AUC). Regarding multi-sound source localization, we employ Class-aware Average Precision (CAP), Permutation-Invariant Average Precision (PIAP), Class-aware IoU (CIoU), and Area Under Curve (AUC). Our method is self-supervised and does not use class labels, we follow [17] for the modified version of CAP and CIoU. + +# 4.2. Implementation Details + +For the visual modality input, we resize images to dimensions of $W_{v} = 224$ , $H_{v} = 224$ , extracting them from the central frame of 3-second video clips. For the audio modality, we resample the raw 3-second audio signal to $16\mathrm{kHz}$ and convert it into a log-scale spectrogram. + +In accordance with the methods presented in [8], we utilize a ResNet-18 [13] for both the visual and audio feature + +backbones to establish our model. Due to the sound spectrogram having only one channel, we adapt the first convolutional layer of the ResNet-18 [13] from 3 channels to 1. The visual encoder is pretrained using ImageNet [10]. Our method employs the Adam optimizer [18] with a learning rate of $10^{-4}$ and a batch size of 128. We train our model for 50 epochs on all experiments. The training is conducted using 1 RTX 4090 GPU. We use the weights of $\tau_{1} = 0.7$ , $\tau_{2} = 0.6$ . For our proposed loss function $\mathcal{L}_{Total}$ , we set $\lambda_{1} = 1$ and $\lambda_{2} = 1$ . Following [8, 11], we utilize the implementation code and adopt the same other hyper-parameters. + +# 4.3. Comparison to Prior Works + +Multi-Sound Source Localization. First, we conduct experiments on the multi-sound source localization scenarios. We compare our method with the state-of-the-art multisound source localization methods [3, 8, 15-17, 24, 26, 27, 32]. Table 1 shows the results of our method on MUSIC-Duet [46] and VGGSound-Duet [7]. For the MUSIC-Duet test set, our method demonstrates superior performance, achieving $1.5\%$ , $15.3\%$ , $6.1\%$ , and $5.5\%$ higher for CAP, PIAP, CIoU@0.3, and AUC, respectively. Furthermore, in the VGGSound-Duet dataset, our method significantly outperforms existing methods. It indicates that our OSC loss enables our method to effectively localize sound-making + +![](images/b58a4ce1db71f1325616adeb3dc0aa7ce724814594616e26903199280cfb05c3.jpg) + +![](images/ded77e4c1e8dcdbe6cf6d5eb524ee6bc690e882603a2e7b839cc2f8f4c3a2b0f.jpg) +(b) +Figure 4. Visualization results for (a) MUSIC-Duet, (b) VGGSound-Duet test set. We compare our method with AVGN [26]. + +![](images/48903f2fc8ec74054c346c77ff05d2dbd1ff5f7e8a91a6da295552d79a4a5ee8.jpg) +Figure 5. Visualization results of our method on VGGSound-Trio test set. + +objects through an iterative process. + +Single Sound Source Localization. For single sound source localization, we compare our method with other existing works [3, 8, 15-17, 24, 26, 27, 32]. Table 2 presents the performances on MUSIC-Solo [46] and VGGSound-Single datasets [7]. For the MUSIC-Solo test set, ours shows $0.2\%$ higher for AP. $4.0\%$ higher for IoU@0.5, and $10.9\%$ higher for AUC, respectively. For the VGGSound-Single test set, ours outperforms most of the others. For AUC, ours achieves the second-best performance. + +The experimental results in Table 1 and Table 2 clearly demonstrate the significant advancements our method brings to single and multi-sound source localization. This progress is largely attributed to the capabilities of the IOI module and OSC loss in effectively distinguishing objects. + +# 4.4. Visualization Results + +We compare ours with the state-of-the-art approach, AVGN [26], in multi-sound source localization. This comparison + +utilizes the MUSIC-Duet and VGGSound-Duet test sets for visualizing the localization results. The results are shown in Figure 4. The visualization highlights the efficacy of our method in accurately localizing sound-making objects within a mixture. Ground Truth (GT) annotations are used to denote regions where sound-making objects are present. + +Furthermore, Figure 5 offers additional visualization results from our method, showcasing its efficacy in differentiating objects in scenarios with three-source mixtures. We utilize VGGSound-Trio test set comprising a mixture of three sound sources from VGGSound-Single [7], following [26]. Our IOI module facilitates the repeated detection and distinction of objects in the audio-visual scene, culminating in highly accurate and refined localization maps. + +# 4.5. Ablation Study + +Effect of the Proposed Losses. We evaluate the performance impact of our two proposed losses $\mathcal{L}_{\text{ave}}$ and $\mathcal{L}_{\text{OSC}}$ . The results are shown in Table 3. When each loss is consid- + +
Method\( \mathcal{L}_{auc} \)\( \mathcal{L}_{osc} \)PIAP(%)CloU@0.3(%)AUC(%)
AVGN [26]--28.126.223.8
Proposed Method✓-44.125.328.3
-✓44.343.027.0
✓✓44.446.929.2
+ +Table 3. Effect of the proposed $\mathcal{L}_{\text{avg}}$ and $\mathcal{L}_{\text{osc}}$ loss on VGGSound-Duet test set. + +
τ1τ2PIAP(%)CloU@0.3(%)AUC(%)
0.644.446.929.2
0.70.744.143.927.5
0.844.345.028.2
0.644.346.328.9
0.70.644.446.929.2
0.844.246.829.1
+ +Table 4. Experimental results on VGGSound-Duet test set according to the hyper-parameters ${\tau }_{1}$ and ${\tau }_{2}$ for IOI module in Sec 3.4. + +ered, our method shows the improved performance against AVGN [26] which is currently a state-of-the-art method. When all the proposed losses are taken into account, we show the highest performance. By integrating the proposed losses into our training, ours achieves increased capacity for learning robust and discriminative features. + +Variation of $\tau_{1}$ and $\tau_{2}$ . We conduct an additional ablation study to investigate the effect of our method on the hyperparameters $\tau_{1}$ and $\tau_{2}$ as described in Section 3.3. The results in Table 4 indicate that we obtain the best results when $\tau_{1} = 0.7$ and $\tau_{2} = 0.6$ . Importantly, even when $\tau_{1}$ and $\tau_{2}$ are varied, our method still outperforms the existing methods. These results suggest that the proposed model is robust to the variations of hyperparameters. + +# 4.6. Discussions + +Sound Source Counting Accuracy. To validate the accuracy of counting the correct sound source for our model, we employed each VGGSound dataset, which comprises images containing varying sound sources (ranging from one to three per image). Respectively, our model achieved an impressive accuracy of $90.79\%$ , $83.21\%$ , and $68.94\%$ for VGGSound-Single, Duet, and Trio test sets. These results not only highlight our performance in handling various numbers of sound sources but also demonstrate its potential applicability in diverse and dynamically changing audio-visual environments. + +Adaptability of Our Method to Varying Sound Sources. We present experiments designed to evaluate the adaptability of our method in scenarios with varied sound sources. For this purpose, we utilized two distinct test sets: VGGSound-Trio [26] and VGGSound-Mixed. VGGSound-Mixed is a resampled dataset encompassing sounds from VGGSound-Single, VGGSound-Duet, and VGGSound-Trio. VGGSound-Mixed allows us to demonstrate the capability of our method to localize sound sources effectively, regardless of their quantity. The results are shown in Ta + +
MethodTest SetCAP(%)PIAP(%)CloU@0.3(%)AUC(%)
AVGN [26]VGGSound-Trio18.523.722.721.8
Ours29.042.134.029.3
AVGN [26]VGGSound-MixedN/A22.9N/AN/A
Ours27.936.035.222.7
+ +Table 5. Experimental results on VGGSound-Trio and VGGSound -Mixed test set. $N / A$ ’ denotes Not Available. + +
MethodTraining (s) +(per iter)Inference (s) +(per image)#params
AVGN [26] (CVPR'23)0.420.03461.2M
Proposed Method0.450.02738.5M
+ +Table 6. The comparisons of training time, inference time, and the number of parameters. + +ble 5. For the VGGSound-Trio test set, our method outperforms AVGN [26] across all evaluation metrics. For the VGGSound-Mixed test set, our approach achieves scores of $27.9\%$ , $36.0\%$ , $35.2\%$ , and $22.7\%$ for CAP, PIAP, CIoU@0.3, and AUC, respectively. Note that AVGN requires fixed prior source information, which limits its applicability. These results highlight our effectiveness in object localization, especially without prior source information, attributable to the efficacy of IOI module and loss function. + +Computational Costs. Table 6 presents comparisons of training time, inference time, and the number of parameters. We compare our method with AVGN [26] which shows the highest performance among the existing methods. Due to the iterative method, our training time is marginally increased (7.14%). However, inference time decreased by 28.3%, and the number of parameters significantly decreased compared to the existing method with transformers. + +# 5. Conclusion + +In this paper, we propose an innovative approach to multi-sound source localization that does not rely on prior knowledge. The core of our method is the Iterative Object Identification (IOI) module, which effectively identifies sound-making objects through iterative processes. Our object similarity-aware clustering (OSC) loss function successfully guides the IOI module not only to merge regions associated with the same object but also to discern distinct objects from the background. We believe that our approach, the iterative object identification method enhances accuracy and has diverse practical applications. + +Acknowledgements. This work was conducted by CARAI grant funded by DAPA and ADD (UD230017TD), and supported in part by the NRF grant funded by the Korea government (MSIT) (No. RS-2023-00252391) and by IITP grant (No. 2022-0-00124), IITP grant (IITP-2023-RS-2023-00266615), IITP grant (No. RS-2022-00155911) and by the MSIT (Ministry of Science and ICT), Korea, under the National Program for Excellence in SW (2023-0-00042) supervised by the IITP in 2024. + +# References + +[1] Bishwo Adhikari and Heikki Huttunen. Iterative bounding box annotation for object detection. In ICPR, 2021. 3 +[2] Alfred V Aho and John E Hopcroft. The design and analysis of computer algorithms. Pearson Education India, 1974. 5 +[3] Relja Arandjelovic and Andrew Zisserman. Objects that sound. In ECCV, 2018. 6, 7 +[4] Gwangbin Bae, Ignas Budvytis, and Roberto Cipolla. Irondepth: Iterative refinement of single-view depth using surface normal and its uncertainty. arXiv preprint arXiv:2210.03676, 2022. 3 +[5] Jan Biemond, Reginald L. 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Audio-visual spatial integration and recursive attention for robust sound source localization. In ACM MM, 2023. 1, 2 +[42] Wenguan Wang, Jianbing Shen, Ming-Ming Cheng, and Ling Shao. An iterative and cooperative top-down and bottom-up inference network for salient object detection. In CVPR, 2019. 3 +[43] Xingkui Wei, Yinda Zhang, Xinlin Ren, Zhuwen Li, Yanwei Fu, and Xiangyang Xue. Deepsfm: Robust deep iterative refinement for structure from motion. TPAMI, 2023. 3 +[44] Hanyu Xuan, Zhiliang Wu, Jian Yang, Yan Yan, and Xavier Alameda-Pineda. A proposal-based paradigm for self-supervised sound source localization in videos. In CVPR, 2022. 1, 2 +[45] Chi Zhang, Guosheng Lin, Fayao Liu, Rui Yao, and Chunhua Shen. Canet: Class-agnostic segmentation networks with iterative refinement and attentive few-shot learning. In CVPR, 2019. 3 +[46] Hang Zhao, Chuang Gan, Andrew Rouditchenko, Carl Vondrick, Josh McDermott, and Antonio Torralba. The sound of pixels. In ECCV, 2018. 5, 6, 7 +[47] Mingmin Zhen, Jinglu Wang, Lei Zhou, Shiwei Li, Tianwei Shen, Jiaxiang Shang, Tian Fang, and Long Quan. Joint semantic segmentation and boundary detection using iterative pyramid contexts. In CVPR, 2020. 3 +[48] Xinchi Zhou, Dongzhan Zhou, Di Hu, Hang Zhou, and Wanli Ouyang. Exploiting visual context semantics for sound source localization. In WACV, 2023. 1, 2 \ No newline at end of file diff --git a/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/images.zip b/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..c09bcd05d7fb97fbcf44337309c92823fc668d5d --- /dev/null +++ b/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:51ec45f6eb52372b164a3db89ce95ae164fd9a5b46b91d1143d926ea88ff8505 +size 731869 diff --git a/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/layout.json b/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..657c13e8de9d079c12393d7b4e38ce4ca48d6f85 --- /dev/null +++ b/2024/Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge/layout.json @@ -0,0 +1,9692 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 148, + 103, + 445, + 140 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 148, + 103, + 445, + 140 + ], + "spans": [ + { + "bbox": [ + 148, + 103, + 445, + 140 + ], + "type": "text", + "content": "Learning to Visually Localize Sound Sources from Mixtures without Prior Source Knowledge" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "spans": [ + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "text", + "content": "Dongjin " + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "inline_equation", + "content": "\\mathrm{Kim}^{1,*}" + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "text", + "content": " Sung Jin Um" + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "inline_equation", + "content": "^{1,*}" + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "text", + "content": " Sangmin Lee" + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "inline_equation", + "content": "^{2,\\dagger}" + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "text", + "content": " Jung Uk " + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "inline_equation", + "content": "\\mathrm{Kim}^{1,\\dagger}" + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "text", + "content": "Kyung Hee University " + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "inline_equation", + "content": "^{2}" + }, + { + "bbox": [ + 113, + 160, + 483, + 203 + ], + "type": "text", + "content": "University of Illinois Urbana-Champaign \n{rlaehdwls310, sungzin1, ju.kim}@khu.ac.kr, sangminl@illinois.edu" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 143, + 231, + 192, + 243 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 231, + 192, + 243 + ], + "spans": [ + { + "bbox": [ + 143, + 231, + 192, + 243 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 257, + 290, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 257, + 290, + 533 + ], + "spans": [ + { + "bbox": [ + 46, + 257, + 290, + 533 + ], + "type": "text", + "content": "The goal of the multi-sound source localization task is to localize sound sources from the mixture individually. While recent multi-sound source localization methods have shown improved performance, they face challenges due to their reliance on prior information about the number of objects to be separated. In this paper, to overcome this limitation, we present a novel multi-sound source localization method that can perform localization without prior knowledge of the number of sound sources. To achieve this goal, we propose an iterative object identification (IOI) module, which can recognize sound-making objects in an iterative manner. After finding the regions of sound-making objects, we devise object similarity-aware clustering (OSC) loss to guide the IOI module to effectively combine regions of the same object but also distinguish between different objects and backgrounds. It enables our method to perform accurate localization of sound-making objects without any prior knowledge. Extensive experimental results on the MUSIC and VGGSound benchmarks show the significant performance improvements of the proposed method over the existing methods for both single and multi-source. Our code is available at: https://github.com/VisualAIKHU/NoPrior_MultiSSL." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 544, + 128, + 556 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 544, + 128, + 556 + ], + "spans": [ + { + "bbox": [ + 47, + 544, + 128, + 556 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 564, + 287, + 672 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 564, + 287, + 672 + ], + "spans": [ + { + "bbox": [ + 46, + 564, + 287, + 672 + ], + "type": "text", + "content": "Humans naturally perceive various sounds and identify the origins of those sounds by using both visual sense (eyes) and auditory sense (ears) [12]. The sound source localization task aims to mimic the ability of humans to correlate auditory cues with visual information in order to identify sound-making objects. Due to this property, sound source localization is closely related to various real-world applications, including unmanned aerial vehicles [14, 30], robotics [20, 28], and speaker source localization [6, 31]." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 59, + 673, + 287, + 685 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 673, + 287, + 685 + ], + "spans": [ + { + "bbox": [ + 59, + 673, + 287, + 685 + ], + "type": "text", + "content": "The sound source localization task can be divided into" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 307, + 226, + 547, + 383 + ], + "blocks": [ + { + "bbox": [ + 307, + 226, + 547, + 383 + ], + "lines": [ + { + "bbox": [ + 307, + 226, + 547, + 383 + ], + "spans": [ + { + "bbox": [ + 307, + 226, + 547, + 383 + ], + "type": "image", + "image_path": "d55fda221c6f7fff4433f1736516056d532f8a00dd4f36261f598fa7485e2a17.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 384, + 546, + 440 + ], + "lines": [ + { + "bbox": [ + 305, + 384, + 546, + 440 + ], + "spans": [ + { + "bbox": [ + 305, + 384, + 546, + 440 + ], + "type": "text", + "content": "Figure 1. Conceptual comparison between (a) existing methods and (b) the proposed method. The existing methods require prior source knowledge of the number of sound-making objects. In contrast, our method can effectively localize multiple sound-making objects without the need for prior source knowledge." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 448, + 546, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 448, + 546, + 616 + ], + "spans": [ + { + "bbox": [ + 304, + 448, + 546, + 616 + ], + "type": "text", + "content": "two categories: (1) single sound source localization and (2) multi-sound source localization. The single sound source localization task [8, 11, 21, 22, 25, 32-36, 38, 39, 41, 44, 48] aims to find one source in a scene by utilizing cross-modal correlations [32, 40] between audio and visual cues. Various methods have been developed for the effective single sound source localization by introducing hard positive mining [8, 33], iterative learning [21], feature regularization [22], negative free learning [38], false negative aware learning [39], momentum target encoders [25], optical flow [11, 36], and spatial integration [41]. However, these methods focus primarily on locating a single sound source, which can be challenging in real-world environments where multiple sounds are often mixed together." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "type": "text", + "content": "In response to this challenge, several multi-sound source localization methods [16, 17, 26, 27] have been developed. The main goal of multi-sound source localization is to separate and localize individual sources from complex mixtures containing different sounds, such as self-supervised audio-visual matching [16], coarse-to-fine manner [27], contrastive random walker [17], and audio-visual grouping network [26]. However, a limitation of existing methods is" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 693, + 136, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 693, + 136, + 703 + ], + "spans": [ + { + "bbox": [ + 58, + 693, + 136, + 703 + ], + "type": "text", + "content": "*Equal contribution" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "type": "text", + "content": "† Corresponding author" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "26467" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": "their reliance on prior information about the number of objects that need to be separated. As shown in Figure 1(a), existing methods heavily rely on prior knowledge about the number of sound sources. If prior knowledge is incorrect, they are frequently failed to localize sound-making objects. Thus, they can only operate in constrained environments where prior source knowledge is available for sound source localization. Consequently, accurate localization of multisound sources becomes challenging when this prior knowledge is not available. In addition, since prior knowledge is generally not provided in real-world environments, it limits their applicability in practical scenarios." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 217, + 289, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 217, + 289, + 373 + ], + "spans": [ + { + "bbox": [ + 46, + 217, + 289, + 373 + ], + "type": "text", + "content": "To address the aforementioned challenges, we introduce a novel method for multi-sound source localization that can identify multiple sound sources without the need for prior knowledge of the number of sources. As shown in Figure 1(b), our method can adapt to various numbers of sound sources by automatically recognizing the number of sound-making objects without relying on any prior knowledge. To this end, we propose an Iterative Object Identification (IOI) module. The goal of our IOI is to effectively automate object separation by repeatedly recognizing objects that make sounds from the mixtures in an iterative manner. By doing so, it continuously searches for sound-making regions until it determines that all relevant objects have been identified." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 373, + 289, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 373, + 289, + 564 + ], + "spans": [ + { + "bbox": [ + 46, + 373, + 289, + 564 + ], + "type": "text", + "content": "To achieve this goal, we provide guidance to the IOI module for effective sound-making object identification. First, in the iterative process, we identify regions that are considered to be foreground objects and repeat this process until there are no more regions considered as foreground objects. At each iteration step, regions previously considered as foreground objects are eliminated in the subsequent iteration. Next, we employ a clustering process to merge regions belonging to the same object based on the foreground regions. To effectively carry out this process, we devise an object similarity-aware clustering (OSC) loss. This loss not only guides the IOI module to combine regions of the same object but also aids in distinguishing between different objects and backgrounds. By doing so, the proposed framework is able to distinguish between various objects with distinct sounds through the iterative process." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 565, + 288, + 637 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 565, + 288, + 637 + ], + "spans": [ + { + "bbox": [ + 46, + 565, + 288, + 637 + ], + "type": "text", + "content": "Consequently, our method can precisely locate the sound-making objects without the need for prior source knowledge, and can effectively distinguish between multiple sound sources. As a result, our method shows significant improvements in sound source localization performance compared to existing methods." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 59, + 638, + 270, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 638, + 270, + 651 + ], + "spans": [ + { + "bbox": [ + 59, + 638, + 270, + 651 + ], + "type": "text", + "content": "The major contributions of our paper are as follows:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 653, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 653, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 653, + 289, + 714 + ], + "type": "text", + "content": "- We introduce Iterative Object Identification (IOI) module to adaptively localize multiple sound sources without any prior source knowledge. To the best of our knowledge, this is the first attempt to perform multi-sound source localization without knowing the number of sound sources." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 72, + 547, + 156 + ], + "type": "list", + "angle": 0, + "index": 8, + "blocks": [ + { + "bbox": [ + 306, + 72, + 547, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 547, + 120 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 547, + 120 + ], + "type": "text", + "content": "- We propose Object Similarity-aware Clustering (OSC) loss to guide the IOI module to merge regions belonging to the same object during the iteration process, while distinguishing between different objects and the background." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 120, + 547, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 120, + 547, + 156 + ], + "spans": [ + { + "bbox": [ + 306, + 120, + 547, + 156 + ], + "type": "text", + "content": "- Experimental results on MUSIC and VGGSound datasets demonstrate the effectiveness of the proposed method for both single-/multi-source sound localization." + } + ] + } + ], + "index": 7 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 169, + 392, + 182 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 169, + 392, + 182 + ], + "spans": [ + { + "bbox": [ + 306, + 169, + 392, + 182 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 190, + 454, + 201 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 190, + 454, + 201 + ], + "spans": [ + { + "bbox": [ + 306, + 190, + 454, + 201 + ], + "type": "text", + "content": "2.1. Sound Source Localization" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 209, + 547, + 256 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 209, + 547, + 256 + ], + "spans": [ + { + "bbox": [ + 304, + 209, + 547, + 256 + ], + "type": "text", + "content": "The sound source localization focuses on finding the spatial location of sound sources within a video frame. It can be divided into two main streams: (1) single sound source localization and (2) multi-sound source localization." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "spans": [ + { + "bbox": [ + 304, + 257, + 546, + 508 + ], + "type": "text", + "content": "The single sound source localization [8, 9, 11, 21, 22, 25, 32-36, 38, 39, 41, 44, 48] leverages the cross-modal interrelations between auditory and visual modalities to localize a sound-making object. Senocak et al. [32] introduced an unsupervised method to incorporate an audio-visual two-stream network with attention mechanisms. Chen et al. [8] proposed a framework that automatically identifies hard samples through contrastive learning. Lin et al. [21] adopted iterative learning with pseudo-labels to refine the localization process. In addition, Fedorishin et al. [11] and Singh et al. [36] leveraged optical flow as a prior and introduced a cross-attention mechanism over the relevant video frame. Sun et al. [39] introduced the False Negative Aware Contrastive (FNAC) strategy to guide similar-looking samples to be more similar. Senocak et al. [34] improved localization accuracy through enhanced cross-modal semantic understanding. Um et al. [41] proposed the spatial knowledge integration of the audio-visual modalities, promoting recursive enhancement of localization. However, in real-world scenarios, they encounter limitations due to the frequent occurrence of mixed sounds from various sources." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 509, + 547, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 547, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 547, + 653 + ], + "type": "text", + "content": "Recent studies focus on the multi-sound source localization [16, 17, 26, 27] to effectively find the location of sound sources from mixtures. Hu et al. [16] introduced a technique that constructs a supervisory signal to differentiate the sound-making entities within a scene. Qian et al. [27] developed a two-stage audiovisual learning approach that separates audio and visual representations of various categories from scenes in a coarse-to-fine manner. Hu et al. [17] made a graph model for robust multi-sound source localization. Mo et al. [26] proposed a way to simultaneously extract and assimilate category-specific semantic features for each sound source from auditory and visual inputs." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": "However, the existing multi-sound source localization methods also exhibit a limitation in real-world scenarios. They heavily rely on prior knowledge about the number of sound sources to differentiate between multi-sound sources. Thus, we propose a sound source localization framework" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "26468" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 58, + 45, + 537, + 305 + ], + "blocks": [ + { + "bbox": [ + 58, + 45, + 537, + 305 + ], + "lines": [ + { + "bbox": [ + 58, + 45, + 537, + 305 + ], + "spans": [ + { + "bbox": [ + 58, + 45, + 537, + 305 + ], + "type": "image", + "image_path": "5d59a73e652460bc359b217c335dccadcfe1822ad062c17ecf44accfa93cb366.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 70, + 308, + 520, + 319 + ], + "lines": [ + { + "bbox": [ + 70, + 308, + 520, + 319 + ], + "spans": [ + { + "bbox": [ + 70, + 308, + 520, + 319 + ], + "type": "text", + "content": "Figure 2. Network configuration of the proposed sound source localization framework. GAP denotes global average pooling." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 329, + 287, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 329, + 287, + 365 + ], + "spans": [ + { + "bbox": [ + 46, + 329, + 287, + 365 + ], + "type": "text", + "content": "that can autonomously recognize the number of objects within a scene and localize the objects without relying on annotations or prior knowledge." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 372, + 248, + 384 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 372, + 248, + 384 + ], + "spans": [ + { + "bbox": [ + 47, + 372, + 248, + 384 + ], + "type": "text", + "content": "2.2. Iterative Methods in Computer Vision" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 390, + 287, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 390, + 287, + 510 + ], + "spans": [ + { + "bbox": [ + 46, + 390, + 287, + 510 + ], + "type": "text", + "content": "Iterative techniques have been applied to various research fields [1, 4, 5, 19, 23, 29, 37, 42, 43, 45, 47] because they provide a refining solutions through repetitive cycles. For example, the iterative methods have been applied to image deblurring and denoising tasks [5, 19], showing significant improvements over traditional non-iterative techniques. In addition, for the mainstream computer vision tasks, e.g., object detection and segmentation tasks, various works [1, 37, 42, 45, 47] also adopt the iterative refinement techniques for more improved performance." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 510, + 288, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 288, + 641 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 288, + 641 + ], + "type": "text", + "content": "The iterative technique possesses inherent characteristic of iteratively converging towards the desired solution. In this study, we adopt this technique to perform effective multi-sound source localization. Though this approach, we automatically and iteratively identify multiple sound sources, enhancing the localization for the same objects and allowing differentiation between different objects. As a result, our method demonstrates improved performance compared to conventional methods. Moreover, due to its automatic object-finding nature, our iterative approach is not constrained by prior source knowledge." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 651, + 163, + 664 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 651, + 163, + 664 + ], + "spans": [ + { + "bbox": [ + 47, + 651, + 163, + 664 + ], + "type": "text", + "content": "3. Proposed Approach" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 671, + 167, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 671, + 167, + 682 + ], + "spans": [ + { + "bbox": [ + 47, + 671, + 167, + 682 + ], + "type": "text", + "content": "3.1. Overall Architecture" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "type": "text", + "content": "Figure 2 shows the overall architecture of our framework. Similar to the previous works [8, 32], we adopt a two-stream" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "spans": [ + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": "network to extract visual and audio features. Input image set " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "I_{v} \\in \\mathbb{R}^{B \\times W_{v} \\times H_{v} \\times 3}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "B" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " indicates batch number, " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "W_{v}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "H_{v}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " denote width and height of " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "I_{v}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": ") and the corresponding mixed audio spectrogram " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "I_{a} \\in \\mathbb{R}^{B \\times W_{a} \\times H_{a} \\times 1}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "W_{a}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "H_{a}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " denote width and height of " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "I_{a}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": ") pass through each modal encoder (i.e., visual and audio encoders) to generate visual feature " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{v}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " and audio feature " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{a}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": ", respectively. First, we identify all the sound-making regions associated with mixed audi-los to filter the regions of interest. We measure cosine similarity between " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{v}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "l_{a}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": ", derived from the global average pooling (GAP) of " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{a}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": ", to obtain a sound-associated map " + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_{v}" + }, + { + "bbox": [ + 304, + 329, + 545, + 460 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "text", + "content": "Next, we obtain a sound-associated visual feature " + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_v" + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "text", + "content": " by the product of " + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_v" + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "text", + "content": " to being aware of features for overall sound-making regions. The Iterative Object Identification (IOI) module receives " + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_v" + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "text", + "content": " to iteratively discriminate sound-associated grid cells and collect each cell in an object bank " + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "inline_equation", + "content": "\\mathbf{O}" + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "text", + "content": ". Subsequently, sound-associated grid cells in " + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "inline_equation", + "content": "\\mathbf{O}" + }, + { + "bbox": [ + 304, + 460, + 545, + 579 + ], + "type": "text", + "content": " are allocated into object groups (e.g., object 1, object 2, etc.), and the background regions are removed. Our method differentiates various objects without prior source knowledge (i.e., the number of sound sources)." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 587, + 507, + 600 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 587, + 507, + 600 + ], + "spans": [ + { + "bbox": [ + 306, + 587, + 507, + 600 + ], + "type": "text", + "content": "3.2. Sound-Associated Region Localization" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 666 + ], + "type": "text", + "content": "To automatically localize sound-making objects in a visual scene without any annotation or prior knowledge, it is essential to measure the correspondence between audio and visual features. To achieve this, we try to distinguish sound-making regions from non-sound regions." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "text", + "content": "We calculate the cosine similarity between " + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_v \\in \\mathbb{R}^{B \\times w \\times h \\times c}" + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "inline_equation", + "content": "w, h" + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "text", + "content": " are the width, height, and channel) and " + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "inline_equation", + "content": "l_a \\in \\mathbb{R}^{B \\times c}" + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "text", + "content": " to generate sound-associated map " + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v = \\{S_{v_{ij}}\\}_{i=1,\\dots,h,j=1,\\dots,w} \\in \\mathbb{R}^{B \\times w \\times h}" + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "text", + "content": ". To make " + }, + { + "bbox": [ + 304, + 666, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "26469" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "text", + "content": "meaningful, our method allows positive audio-visual pairs to be attracted to each other and negative pairs to be repelled at training time. By doing so, it is possible to identify spatial regions associated with given sound (positive pairs) and regions which are not associated with that sound (negative pairs). We define " + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v^{n\\to m}" + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "text", + "content": " as cosine similarity map between " + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "text", + "content": "-th image and " + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "text", + "content": "-th audio, and the " + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "inline_equation", + "content": "ij" + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "text", + "content": "-th element of " + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v^{n\\to m}" + }, + { + "bbox": [ + 47, + 72, + 289, + 168 + ], + "type": "text", + "content": ", which can be represented as:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 89, + 173, + 287, + 233 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 89, + 173, + 287, + 233 + ], + "spans": [ + { + "bbox": [ + 89, + 173, + 287, + 233 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\operatorname {S i m} (A, B) = \\frac {\\langle A , B \\rangle}{| | A | | | | B | |}, \\\\ S _ {v _ {i j}} ^ {n \\rightarrow m} = \\frac {\\operatorname {S i m} \\left(\\mathbf {F} _ {v _ {i j}} ^ {n} , l _ {a} ^ {m}\\right)}{\\sum_ {i = 1} ^ {h} \\sum_ {j = 1} ^ {w} \\operatorname {S i m} \\left(\\mathbf {F} _ {v _ {i j}} ^ {n} , l _ {a} ^ {n}\\right)}, \\tag {1} \\\\ \\end{array}", + "image_path": "414570b80b561f3d54885744d102baa57b619592dd0df8bf65f26e174487ada0.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "spans": [ + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "type": "inline_equation", + "content": "\\langle \\cdot, \\cdot \\rangle" + }, + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "type": "text", + "content": " denotes inner-product. Next, we obtain the mask of " + }, + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "type": "text", + "content": "-th clip " + }, + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "type": "inline_equation", + "content": "M^n" + }, + { + "bbox": [ + 47, + 238, + 287, + 262 + ], + "type": "text", + "content": ", represented as:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 96, + 267, + 287, + 281 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 96, + 267, + 287, + 281 + ], + "spans": [ + { + "bbox": [ + 96, + 267, + 287, + 281 + ], + "type": "interline_equation", + "content": "M ^ {n} = \\operatorname {s i g m o i d} \\left(\\left(S _ {v} ^ {n \\rightarrow n} - \\alpha\\right) / \\omega\\right), \\tag {2}", + "image_path": "69eab4ed4f7e71c1eb923cb45b5650f6652c7d6468ec1d2f71030957456a0886.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "spans": [ + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "inline_equation", + "content": "\\omega" + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "text", + "content": " are the hyper-parameters. Based on " + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "inline_equation", + "content": "M^n" + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "text", + "content": ", we aim to localize all the sound-making regions associated with mixed audios. Thus, motivated by [8], we employ an audiovisual contrastive loss " + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{avc}" + }, + { + "bbox": [ + 47, + 287, + 287, + 335 + ], + "type": "text", + "content": ", which can be represented as:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 58, + 340, + 287, + 433 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 340, + 287, + 433 + ], + "spans": [ + { + "bbox": [ + 58, + 340, + 287, + 433 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} P o s ^ {n} = \\frac {1}{| M ^ {n} |} \\langle M ^ {n}, S _ {v} ^ {n \\rightarrow n} \\rangle , \\\\ N e g ^ {n} = \\frac {\\left\\langle \\mathbf {1} - M ^ {n} , S _ {v} ^ {n \\rightarrow n} \\right\\rangle}{\\left| \\mathbf {1} - M ^ {n} \\right|} + \\frac {1}{h w} \\sum_ {n \\neq m} \\left\\langle \\mathbf {1}, S _ {v} ^ {n \\rightarrow m} \\right\\rangle , \\tag {3} \\\\ \\mathcal {L} _ {a v c} = - \\frac {1}{B} \\sum_ {n = 1} ^ {B} \\left[ \\log \\frac {\\exp (P o s ^ {n})}{\\exp (P o s ^ {n}) + \\exp (N e g ^ {n})} \\right]. \\\\ \\end{array}", + "image_path": "ff17e8f6a15ba0e8a2521add8e18dcd5339c75abe7858c0d827044f586c96e84.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "spans": [ + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "inline_equation", + "content": "Pos^n" + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "text", + "content": " represents the average vector of highly correlated regions between the audio-visual pairs in the " + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "text", + "content": "-th clip. In contrast, " + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "inline_equation", + "content": "Neg^n" + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "text", + "content": " contains not only regions with low correlated between audio-visual pairs within the same clip but also includes correlation with other clips. Consequently, " + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{avc}" + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "text", + "content": " allows the " + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + }, + { + "bbox": [ + 47, + 437, + 287, + 534 + ], + "type": "text", + "content": " to effectively filter out the foreground regions associated with the mixed audio, separating from the background regions that do not produce sound." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 540, + 249, + 552 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 540, + 249, + 552 + ], + "spans": [ + { + "bbox": [ + 47, + 540, + 249, + 552 + ], + "type": "text", + "content": "3.3. Iterative Object Identification Module" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "spans": [ + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "text", + "content": "Through Section 3.2, the sound-associated map " + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "text", + "content": " can contain knowledge of the sound-associated objects. We then multiply " + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "text", + "content": " by the original visual feature " + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_v" + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "text", + "content": " to encode sound-associated visual feature " + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_v\\in \\mathbb{R}^{B\\times w\\times h\\times c}" + }, + { + "bbox": [ + 47, + 557, + 287, + 630 + ], + "type": "text", + "content": ". By doing so, background cells are removed, leaving all the sound-associated cells that represent the sound-making object." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "type": "text", + "content": "Next, the proposed Iterative Object Identification (IOI) module takes " + }, + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_v" + }, + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "type": "text", + "content": " to identify sound-making objects in mixed audio-visual data. Using " + }, + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_v" + }, + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "type": "text", + "content": ", the IOI module conducts a total of " + }, + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 46, + 630, + 287, + 714 + ], + "type": "text", + "content": " iterations to find all sound-associated cells, and in each iteration, it finds the area to localize around the position of the sound-associated cell identified. Each iteration consists of four steps: (1) Highest sound-associated cell" + } + ] + } + ], + "index": 9 + }, + { + "type": "code", + "bbox": [ + 306, + 88, + 545, + 228 + ], + "blocks": [ + { + "bbox": [ + 306, + 72, + 525, + 84 + ], + "lines": [ + { + "bbox": [ + 306, + 72, + 525, + 84 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 525, + 84 + ], + "type": "text", + "content": "Algorithm 1 Iterative Object Identification Algorithm" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "code_caption" + }, + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "lines": [ + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "spans": [ + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "type": "text", + "content": "Require: " + }, + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v,\\hat{\\mathbf{F}}_v" + }, + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "type": "text", + "content": " \nEnsure: " + }, + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{O} = [],t = 0" + }, + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "type": "text", + "content": " \nwhile max(S>ε do " + }, + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "type": "inline_equation", + "content": "\\begin{array}{rl} & {\\mathbf{E}_p^t\\leftarrow \\hat{\\mathbf{F}}_v[\\mathrm{argmax}(\\mathbf{S}_v)]}\\\\ & {\\mathbf{R}_p\\leftarrow \\langle \\hat{\\mathbf{F}}_v,\\mathbf{E}_p^t\\rangle}\\\\ & {\\mathbf{R}_n\\leftarrow \\langle \\hat{\\mathbf{F}}_v,\\mathbf{E}_n\\rangle}\\\\ & {\\mathrm{sound\\_making\\_region}\\leftarrow \\mathbf{R}_p > \\mathbf{R}_n}\\\\ & {\\mathbf{S}_v\\leftarrow \\mathbf{S}_v\\cdot \\neg \\mathrm{sound\\_making\\_region}}\\\\ & {\\mathbf{O}.append(\\mathbf{E}_p^t)}\\\\ & {t\\leftarrow t + 1} \\end{array}" + }, + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "type": "text", + "content": " ▷Inner Product \nend while \nResults: " + }, + { + "bbox": [ + 306, + 88, + 545, + 228 + ], + "type": "inline_equation", + "content": "T = t,\\mathbf{O} = [\\mathbf{E}_p^1,\\mathbf{E}_p^2,\\dots,\\mathbf{E}_p^T]" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "code_body" + } + ], + "index": 11, + "sub_type": "algorithm" + }, + { + "bbox": [ + 304, + 240, + 545, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 240, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 304, + 240, + 545, + 300 + ], + "type": "text", + "content": "selection, (2) foreground/background selection, (3) finding sound-making regions, and (4) identified sound-making region exclusion. After the end of " + }, + { + "bbox": [ + 304, + 240, + 545, + 300 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 240, + 545, + 300 + ], + "type": "text", + "content": " iteration process, we cluster all sound-associated grid cells as each object or negative." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "spans": [ + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "content": "Before starting iteration, we define a negative cell vector " + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_n\\in \\mathbb{R}^{B\\times c}" + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "content": " to represent background (non-sound-making objects). " + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_n" + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "content": " is obtained by averaging the background cells that were excluded during the creation of " + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_v" + }, + { + "bbox": [ + 304, + 300, + 545, + 372 + ], + "type": "text", + "content": ". This vector is essential for identifying regions that do not correspond to the sound, to provide contrast to the foreground." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 372, + 545, + 720 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "spans": [ + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": "(1) Highest sound-associated cell selection. In the first step in " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": "-th iteration, we select the cell in " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": " with the highest value and select this cell as a starting point. This selection is based on the understanding that the highest value in " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": " indicates the strongest audio-visual correspondence in that cell. Therefore, we identify and mark the coordinates of this cell as " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "(i,j)" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": ". The vector " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_{v_{ij}}" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": " is then assigned as the sound-associated grid cell " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_p^t \\in \\mathbb{R}^{B \\times c}" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": ". Then, we store " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_p^t" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": " in the " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": "-th element of the object bank " + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "inline_equation", + "content": "\\mathbf{O} = \\{\\mathbf{E}_p^t\\}_{t=1}^T" + }, + { + "bbox": [ + 304, + 372, + 545, + 483 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "spans": [ + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": "(2) Foreground/background selection. In the second step in " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": "-th iteration, we perform foreground and background selection using " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_p^t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_n" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": ". The similarity measurement is carried out by calculating the inner product of " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_v" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_p^t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": ". This result is used as foreground region " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{R}_p^t \\in \\mathbb{R}^{B \\times w \\times h}" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": ". A higher value in " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{R}_p^t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": " indicates a higher likelihood of being the same object as " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_p^t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": ". Similarly, the background region is calculated by inner product of " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{F}}_v" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_n" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": ", resulting in " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{R}_n^t \\in \\mathbb{R}^{B \\times w \\times h}" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": ". (3) Finding sound-making regions. In the third step in " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": "-th iteration, we compare " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{R}_p^t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{R}_n^t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": " to localize sound-making regions. The choice of sound-making region sizes is based on the condition that the value of foreground region " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{R}_p^t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": " is higher than that of the background " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "\\mathbf{R}_n^t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": ". Using these regions, we generate the " + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 483, + 545, + 659 + ], + "type": "text", + "content": "-th localization map." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "spans": [ + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "text", + "content": "(4) Identified sound-making region exclusion. In the fourth step in " + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "text", + "content": "-th iteration, to prevent redundancy in finding sound-associated grid cell vector " + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_p^t" + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "text", + "content": ", we need to modify " + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "text", + "content": " for the next iteration. This involves setting the values of regions already localized to zero in " + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "inline_equation", + "content": "\\mathbf{S}_v" + }, + { + "bbox": [ + 304, + 659, + 545, + 720 + ], + "type": "text", + "content": ", thereby excluding" + } + ] + } + ], + "index": 16 + } + ], + "sub_type": "text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "26470" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 54, + 80, + 281, + 210 + ], + "blocks": [ + { + "bbox": [ + 66, + 69, + 268, + 79 + ], + "lines": [ + { + "bbox": [ + 66, + 69, + 268, + 79 + ], + "spans": [ + { + "bbox": [ + 66, + 69, + 268, + 79 + ], + "type": "text", + "content": "Object Similarity-Aware Clustering (OSC) Loss " + }, + { + "bbox": [ + 66, + 69, + 268, + 79 + ], + "type": "inline_equation", + "content": "(N = 2" + }, + { + "bbox": [ + 66, + 69, + 268, + 79 + ], + "type": "text", + "content": " Example)" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 54, + 80, + 281, + 210 + ], + "lines": [ + { + "bbox": [ + 54, + 80, + 281, + 210 + ], + "spans": [ + { + "bbox": [ + 54, + 80, + 281, + 210 + ], + "type": "image", + "image_path": "ca7520bd762c9b887b71439177303f710ad6b7d4072fedf06d0e5e830e32c7d0.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 213, + 286, + 236 + ], + "lines": [ + { + "bbox": [ + 46, + 213, + 286, + 236 + ], + "spans": [ + { + "bbox": [ + 46, + 213, + 286, + 236 + ], + "type": "text", + "content": "Figure 3. Explanation of the proposed Object Similarity-Aware Clustering (OSC) loss (" + }, + { + "bbox": [ + 46, + 213, + 286, + 236 + ], + "type": "inline_equation", + "content": "N = 2" + }, + { + "bbox": [ + 46, + 213, + 286, + 236 + ], + "type": "text", + "content": " example)." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 240, + 286, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 240, + 286, + 300 + ], + "spans": [ + { + "bbox": [ + 46, + 240, + 286, + 300 + ], + "type": "text", + "content": "them from further iteration. After completing these steps, we move on to the next iteration. We repeat this process until we find all sound-associated grid cells. The pseudocode detailing this procedure is presented in Algorithm 1, offering a clear step-by-step guide." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 308, + 277, + 321 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 308, + 277, + 321 + ], + "spans": [ + { + "bbox": [ + 47, + 308, + 277, + 321 + ], + "type": "text", + "content": "3.4. Object Identification and Final Localization." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 327, + 286, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 327, + 286, + 387 + ], + "spans": [ + { + "bbox": [ + 46, + 327, + 286, + 387 + ], + "type": "text", + "content": "After finishing the iteration process, we identify all sound-associated grid cells as each object or negative. Each cell is evaluated to determine whether it represents a sound-making object or background. This classification is crucial as it ensures the accuracy of our object identification." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "spans": [ + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "text", + "content": "First, to eliminate cells that were identified as sound-associated grid cells but are actually background, we calculate cosine similarity between negative cell vector " + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_n" + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "text", + "content": " and each sound-associated grid cell " + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "inline_equation", + "content": "\\mathbf{E}_p^t" + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "text", + "content": " in object bank " + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "inline_equation", + "content": "\\mathbf{O}" + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "text", + "content": ". Cells with a similarity exceeding a threshold " + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "inline_equation", + "content": "\\tau_1" + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "text", + "content": " are considered to be a part of the background and are eliminated from " + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "inline_equation", + "content": "\\mathbf{O}" + }, + { + "bbox": [ + 46, + 387, + 286, + 458 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 459, + 286, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 459, + 286, + 567 + ], + "spans": [ + { + "bbox": [ + 46, + 459, + 286, + 567 + ], + "type": "text", + "content": "Subsequently, to cluster the remaining sound-associated grid cells into each object, we calculate the cosine similarity between every pair of cells. This calculation helps us understand how similar or related these cells are to each other. If the similarity between any two cells is higher than the threshold " + }, + { + "bbox": [ + 46, + 459, + 286, + 567 + ], + "type": "inline_equation", + "content": "\\tau_{2}" + }, + { + "bbox": [ + 46, + 459, + 286, + 567 + ], + "type": "text", + "content": ", we consider these cells to be part of the same object. To effectively cluster each object, we use the union-find algorithm [2]. It merges other cells into each group if they are determined to belong to the same object." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "spans": [ + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "text", + "content": "Each identified group is labeled as object " + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "text", + "content": " (where " + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "inline_equation", + "content": "k = 1,2,\\dots,K_b" + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "text", + "content": "). Here, " + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "inline_equation", + "content": "K_b" + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "text", + "content": " is the number of objects in " + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "text", + "content": "-th clip. Finally, we combine the localization maps from object " + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 47, + 567, + 286, + 615 + ], + "type": "text", + "content": " to create the final localization map for each object." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 623, + 258, + 635 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 623, + 258, + 635 + ], + "spans": [ + { + "bbox": [ + 47, + 623, + 258, + 635 + ], + "type": "text", + "content": "3.5. Object Similarity-aware Clustering Loss" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "content": "To effectively identify and separate multi-sound sources without any annotation and prior source knowledge in complex environments, we propose an Object Similarity-aware Clustering (OSC) loss. The OSC loss has an important role in guiding the IOI module to combine regions belonging to the same object while differentiating between distinct ob" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": "jects and backgrounds. In the bank " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "\\mathbf{O}_b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": ", the anchor cell " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "A_k^b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": " is identified as the most representative cell of the object " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": " in the " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": "-th clip. " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "P_k^b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "N_k^b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": " represent compositions of cells, where " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "P_k^b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": " consists of cells attributed to the same object, and " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "N_k^b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": " is from different objects or backgrounds (" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "P_k^b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "inline_equation", + "content": "N_k^b" + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": " are distinguished though Section 3.4). The formulation of the OSC loss is structured as follows:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 331, + 162, + 545, + 229 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 331, + 162, + 545, + 229 + ], + "spans": [ + { + "bbox": [ + 331, + 162, + 545, + 229 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} C _ {p k} ^ {b} = \\operatorname {S i m} \\left(A _ {k} ^ {b}, P _ {k} ^ {b}\\right), \\quad C _ {n k} ^ {b} = \\operatorname {S i m} \\left(A _ {k} ^ {b}, N _ {k} ^ {b}\\right), \\\\ \\mathcal {L} _ {k} ^ {b} = \\left(1 - C _ {p k} ^ {b}\\right) + C _ {n k} ^ {b}, \\tag {4} \\\\ \\mathcal {L} _ {o s c} = \\frac {1}{B} \\sum_ {b = 1} ^ {B} \\sum_ {k = 1} ^ {K _ {b}} \\frac {\\mathcal {L} _ {k} ^ {b}}{K _ {b}}, \\\\ \\end{array}", + "image_path": "b49de5510a92270caa445aa2f8dabb64397a7c9a9ed748975c2cb1e8a9087e73.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 239, + 545, + 360 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 239, + 545, + 360 + ], + "spans": [ + { + "bbox": [ + 304, + 239, + 545, + 360 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 239, + 545, + 360 + ], + "type": "inline_equation", + "content": "C_{pk}^{b}" + }, + { + "bbox": [ + 304, + 239, + 545, + 360 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 239, + 545, + 360 + ], + "type": "inline_equation", + "content": "C_{nk}^{b}" + }, + { + "bbox": [ + 304, + 239, + 545, + 360 + ], + "type": "text", + "content": " represent the cosine similarity between the anchor and the positive, and the anchor and the negative, respectively. Through this loss, learning is directed in such a way that similarity between the anchor and positive cells is reinforced, while divergence between the anchor and negative cells is accentuated. As shown in Figure 3, this effectively clusters cells that are considered to be part of the same object, thereby aiding in the segmentation of objects. This approach reduces the number of iterations to distinguish objects, as detailed in our supplementary experiments." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 367, + 416, + 380 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 367, + 416, + 380 + ], + "spans": [ + { + "bbox": [ + 306, + 367, + 416, + 380 + ], + "type": "text", + "content": "3.6. Training Objective" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 385, + 545, + 409 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 385, + 545, + 409 + ], + "spans": [ + { + "bbox": [ + 304, + 385, + 545, + 409 + ], + "type": "text", + "content": "To train our proposed method, we construct the total training loss function as follows:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 367, + 419, + 545, + 432 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 367, + 419, + 545, + 432 + ], + "spans": [ + { + "bbox": [ + 367, + 419, + 545, + 432 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {T o t a l}} = \\lambda_ {1} \\mathcal {L} _ {\\text {a v c}} + \\lambda_ {2} \\mathcal {L} _ {\\text {o s c}}, \\tag {5}", + "image_path": "0f35396f2fb754422c45192c07e156a478fbfc74409c5611de883edf02d2cb9d.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "spans": [ + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "inline_equation", + "content": "\\lambda_{1}" + }, + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "inline_equation", + "content": "\\lambda_{2}" + }, + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "text", + "content": " denote balancing parameters for each loss function. By using " + }, + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{Total}" + }, + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "text", + "content": ", our method effectively performs multi-sound source localization, identifying sound sources from mixtures without the need for prior source knowledge." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 496, + 387, + 509 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 496, + 387, + 509 + ], + "spans": [ + { + "bbox": [ + 306, + 496, + 387, + 509 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 515, + 481, + 528 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 515, + 481, + 528 + ], + "spans": [ + { + "bbox": [ + 306, + 515, + 481, + 528 + ], + "type": "text", + "content": "4.1. Datasets and Evaluation Metrics" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 533, + 545, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 545, + 652 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 545, + 652 + ], + "type": "text", + "content": "MUSIC. The MUSIC dataset [46] comprises 448 unedited YouTube music videos featuring solos and duets across 11 categories of musical instruments. To ensure a fair comparison with previous works, we use the same training/testing subset as utilized in AVGN [26]. Specifically, the MUSIC-Solo contains 358 solo videos that are applied for training, and 90 solo videos are for evaluation for single sound source localization. Similarly, the MUSIC-Duet contains 124 duet videos that are applied for training, and 17 duet videos are for evaluation for multi-sound source localization." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 653, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 545, + 712 + ], + "type": "text", + "content": "VGG-Sound. VGG-Sound dataset [7], which is denoted as VGGSound-Single consists of more than 200k videos from 221 different sound categories. We utilize 144k image-audio pairs as a training set. For single sound source localization, we use VGG-Sound Source [8] to evaluate our" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "26471" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 61, + 70, + 531, + 205 + ], + "blocks": [ + { + "bbox": [ + 61, + 70, + 531, + 205 + ], + "lines": [ + { + "bbox": [ + 61, + 70, + 531, + 205 + ], + "spans": [ + { + "bbox": [ + 61, + 70, + 531, + 205 + ], + "type": "table", + "html": "
MethodMUSIC-Duet [46]VGGSound-Duet [7]
CAP(%)PIAP(%)CloU@0.3(%)AUC(%)CAP(%)PIAP(%)CloU@0.3(%)AUC(%)
Attention10k [32] (CVPR'18)--21.619.6--11.515.2
OTS [3] (ECCV'18)11.617.713.318.510.512.712.215.8
DMC [15] (CVPR'19)--17.521.1--13.817.1
CoarseToFine [27] (ECCV'20)--17.620.6--14.718.5
DSOL [16] (NeurIPS'20)--30.122.3--22.321.1
LVS [8] (CVPR'21)--22.520.9--17.319.5
EZ-VSL [24] (ECCV'22)--24.321.3--20.520.2
Mix-and-Localize [17] (CVPR'22)47.554.126.521.516.322.621.120.5
AVGN [26] (CVPR'23)50.657.232.524.621.928.126.223.8
Proposed Method52.172.538.630.132.544.446.929.2
", + "image_path": "0a03f664905211f2cadbcf6bc9fad1f91ff0a38e21ee83cd9eaee160c6e579b2.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 62, + 239, + 531, + 384 + ], + "blocks": [ + { + "bbox": [ + 47, + 207, + 545, + 228 + ], + "lines": [ + { + "bbox": [ + 47, + 207, + 545, + 228 + ], + "spans": [ + { + "bbox": [ + 47, + 207, + 545, + 228 + ], + "type": "text", + "content": "Table 1. Experimental results on Music-Duet(left) and VGGSound-Duet(right) for multi-sound source localization. Bold/underlined fonts indicate the best/second-best results." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 62, + 239, + 531, + 384 + ], + "lines": [ + { + "bbox": [ + 62, + 239, + 531, + 384 + ], + "spans": [ + { + "bbox": [ + 62, + 239, + 531, + 384 + ], + "type": "table", + "html": "
MethodMUSIC-Solo [46]VGGSound-Single [7]
AP(%)IoU@0.5(%)AUC(%)AP(%)IoU@0.5(%)AUC(%)
Attention10k [32] (CVPR'18)-37.238.7-19.230.6
OTS [3] (ECCV'18)69.326.135.829.832.835.7
DMC [15] (CVPR'19)-29.138.0-23.927.6
CoarseToFIne [27] (ECCV'20)70.733.639.828.229.134.8
DSOL [16] (NeurIPS'20)-51.443.7-35.737.2
LVS [8] (CVPR'21)70.641.940.329.634.438.2
EZ-VSL [24] (ECCV'22)71.545.841.231.338.939.5
Mix-and-Localize [17] (CVPR'22)68.630.540.832.536.338.9
AVGN [26] (CVPR'23)77.258.148.535.340.842.3
Proposed Method77.462.159.446.241.441.2
", + "image_path": "53901f5833055266f2f65baf917e72f89628add501ab92dd2b2cacfbb5c439ba.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 384, + 546, + 407 + ], + "lines": [ + { + "bbox": [ + 46, + 384, + 546, + 407 + ], + "spans": [ + { + "bbox": [ + 46, + 384, + 546, + 407 + ], + "type": "text", + "content": "Table 2. Experimental results on Music-Solo(left) and VGGSound-Single(right) for single sound source localization. Bold/underlined fonts indicate the best/second-best results." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 414, + 287, + 484 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 414, + 287, + 484 + ], + "spans": [ + { + "bbox": [ + 46, + 414, + 287, + 484 + ], + "type": "text", + "content": "method. In the training phase, for multi-sound source localization, we randomly concatenate two video frames to generate a single input image with dimensions of " + }, + { + "bbox": [ + 46, + 414, + 287, + 484 + ], + "type": "inline_equation", + "content": "448 \\times 224" + }, + { + "bbox": [ + 46, + 414, + 287, + 484 + ], + "type": "text", + "content": ", and we combine the corresponding audio waveforms to generate a mixed audio signal. Following [26], we employ the VGGSound-Duet dataset for evaluation." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 485, + 288, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 485, + 288, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 485, + 288, + 605 + ], + "type": "text", + "content": "Evaluation Metrics. Following the prior works [17, 26], we adopt metrics for a fair and comprehensive comparison. For single sound source localization, we employ Average Precision (AP), Intersection over Union (IoU), and Area Under Curve (AUC). Regarding multi-sound source localization, we employ Class-aware Average Precision (CAP), Permutation-Invariant Average Precision (PIAP), Class-aware IoU (CIoU), and Area Under Curve (AUC). Our method is self-supervised and does not use class labels, we follow [17] for the modified version of CAP and CIoU." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 611, + 180, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 611, + 180, + 624 + ], + "spans": [ + { + "bbox": [ + 47, + 611, + 180, + 624 + ], + "type": "text", + "content": "4.2. Implementation Details" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "type": "text", + "content": "For the visual modality input, we resize images to dimensions of " + }, + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "type": "inline_equation", + "content": "W_{v} = 224" + }, + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "type": "inline_equation", + "content": "H_{v} = 224" + }, + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "type": "text", + "content": ", extracting them from the central frame of 3-second video clips. For the audio modality, we resample the raw 3-second audio signal to " + }, + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "type": "inline_equation", + "content": "16\\mathrm{kHz}" + }, + { + "bbox": [ + 46, + 629, + 287, + 689 + ], + "type": "text", + "content": " and convert it into a log-scale spectrogram." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "In accordance with the methods presented in [8], we utilize a ResNet-18 [13] for both the visual and audio feature" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "spans": [ + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "text", + "content": "backbones to establish our model. Due to the sound spectrogram having only one channel, we adapt the first convolutional layer of the ResNet-18 [13] from 3 channels to 1. The visual encoder is pretrained using ImageNet [10]. Our method employs the Adam optimizer [18] with a learning rate of " + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "inline_equation", + "content": "10^{-4}" + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "text", + "content": " and a batch size of 128. We train our model for 50 epochs on all experiments. The training is conducted using 1 RTX 4090 GPU. We use the weights of " + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "inline_equation", + "content": "\\tau_{1} = 0.7" + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "inline_equation", + "content": "\\tau_{2} = 0.6" + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "text", + "content": ". For our proposed loss function " + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{Total}" + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "text", + "content": ", we set " + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "inline_equation", + "content": "\\lambda_{1} = 1" + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "inline_equation", + "content": "\\lambda_{2} = 1" + }, + { + "bbox": [ + 304, + 414, + 545, + 546 + ], + "type": "text", + "content": ". Following [8, 11], we utilize the implementation code and adopt the same other hyper-parameters." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 552, + 460, + 564 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 552, + 460, + 564 + ], + "spans": [ + { + "bbox": [ + 305, + 552, + 460, + 564 + ], + "type": "text", + "content": "4.3. Comparison to Prior Works" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "text", + "content": "Multi-Sound Source Localization. First, we conduct experiments on the multi-sound source localization scenarios. We compare our method with the state-of-the-art multisound source localization methods [3, 8, 15-17, 24, 26, 27, 32]. Table 1 shows the results of our method on MUSIC-Duet [46] and VGGSound-Duet [7]. For the MUSIC-Duet test set, our method demonstrates superior performance, achieving " + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "inline_equation", + "content": "1.5\\%" + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "inline_equation", + "content": "15.3\\%" + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "inline_equation", + "content": "6.1\\%" + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "inline_equation", + "content": "5.5\\%" + }, + { + "bbox": [ + 304, + 570, + 545, + 713 + ], + "type": "text", + "content": " higher for CAP, PIAP, CIoU@0.3, and AUC, respectively. Furthermore, in the VGGSound-Duet dataset, our method significantly outperforms existing methods. It indicates that our OSC loss enables our method to effectively localize sound-making" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "26472" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 116, + 54, + 480, + 178 + ], + "blocks": [ + { + "bbox": [ + 116, + 54, + 480, + 178 + ], + "lines": [ + { + "bbox": [ + 116, + 54, + 480, + 178 + ], + "spans": [ + { + "bbox": [ + 116, + 54, + 480, + 178 + ], + "type": "image", + "image_path": "b58a4ce1db71f1325616adeb3dc0aa7ce724814594616e26903199280cfb05c3.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 69, + 180, + 542, + 327 + ], + "blocks": [ + { + "bbox": [ + 52, + 257, + 62, + 266 + ], + "lines": [ + { + "bbox": [ + 52, + 257, + 62, + 266 + ], + "spans": [ + { + "bbox": [ + 52, + 257, + 62, + 266 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 69, + 180, + 542, + 327 + ], + "lines": [ + { + "bbox": [ + 69, + 180, + 542, + 327 + ], + "spans": [ + { + "bbox": [ + 69, + 180, + 542, + 327 + ], + "type": "image", + "image_path": "ded77e4c1e8dcdbe6cf6d5eb524ee6bc690e882603a2e7b839cc2f8f4c3a2b0f.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 70, + 330, + 521, + 341 + ], + "lines": [ + { + "bbox": [ + 70, + 330, + 521, + 341 + ], + "spans": [ + { + "bbox": [ + 70, + 330, + 521, + 341 + ], + "type": "text", + "content": "Figure 4. Visualization results for (a) MUSIC-Duet, (b) VGGSound-Duet test set. We compare our method with AVGN [26]." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 85, + 346, + 509, + 460 + ], + "blocks": [ + { + "bbox": [ + 85, + 346, + 509, + 460 + ], + "lines": [ + { + "bbox": [ + 85, + 346, + 509, + 460 + ], + "spans": [ + { + "bbox": [ + 85, + 346, + 509, + 460 + ], + "type": "image", + "image_path": "48903f2fc8ec74054c346c77ff05d2dbd1ff5f7e8a91a6da295552d79a4a5ee8.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 162, + 464, + 429, + 474 + ], + "lines": [ + { + "bbox": [ + 162, + 464, + 429, + 474 + ], + "spans": [ + { + "bbox": [ + 162, + 464, + 429, + 474 + ], + "type": "text", + "content": "Figure 5. Visualization results of our method on VGGSound-Trio test set." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 485, + 193, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 485, + 193, + 496 + ], + "spans": [ + { + "bbox": [ + 47, + 485, + 193, + 496 + ], + "type": "text", + "content": "objects through an iterative process." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "spans": [ + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "type": "text", + "content": "Single Sound Source Localization. For single sound source localization, we compare our method with other existing works [3, 8, 15-17, 24, 26, 27, 32]. Table 2 presents the performances on MUSIC-Solo [46] and VGGSound-Single datasets [7]. For the MUSIC-Solo test set, ours shows " + }, + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "type": "inline_equation", + "content": "0.2\\%" + }, + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "type": "text", + "content": " higher for AP. " + }, + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "type": "inline_equation", + "content": "4.0\\%" + }, + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "type": "text", + "content": " higher for IoU@0.5, and " + }, + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "type": "inline_equation", + "content": "10.9\\%" + }, + { + "bbox": [ + 46, + 496, + 286, + 603 + ], + "type": "text", + "content": " higher for AUC, respectively. For the VGGSound-Single test set, ours outperforms most of the others. For AUC, ours achieves the second-best performance." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 604, + 286, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 604, + 286, + 664 + ], + "spans": [ + { + "bbox": [ + 46, + 604, + 286, + 664 + ], + "type": "text", + "content": "The experimental results in Table 1 and Table 2 clearly demonstrate the significant advancements our method brings to single and multi-sound source localization. This progress is largely attributed to the capabilities of the IOI module and OSC loss in effectively distinguishing objects." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 671, + 167, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 671, + 167, + 682 + ], + "spans": [ + { + "bbox": [ + 47, + 671, + 167, + 682 + ], + "type": "text", + "content": "4.4. Visualization Results" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 286, + 713 + ], + "type": "text", + "content": "We compare ours with the state-of-the-art approach, AVGN [26], in multi-sound source localization. This comparison" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 484, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 484, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 484, + 545, + 555 + ], + "type": "text", + "content": "utilizes the MUSIC-Duet and VGGSound-Duet test sets for visualizing the localization results. The results are shown in Figure 4. The visualization highlights the efficacy of our method in accurately localizing sound-making objects within a mixture. Ground Truth (GT) annotations are used to denote regions where sound-making objects are present." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 556, + 545, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 556, + 545, + 651 + ], + "spans": [ + { + "bbox": [ + 304, + 556, + 545, + 651 + ], + "type": "text", + "content": "Furthermore, Figure 5 offers additional visualization results from our method, showcasing its efficacy in differentiating objects in scenarios with three-source mixtures. We utilize VGGSound-Trio test set comprising a mixture of three sound sources from VGGSound-Single [7], following [26]. Our IOI module facilitates the repeated detection and distinction of objects in the audio-visual scene, culminating in highly accurate and refined localization maps." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 659, + 399, + 671 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 659, + 399, + 671 + ], + "spans": [ + { + "bbox": [ + 306, + 659, + 399, + 671 + ], + "type": "text", + "content": "4.5. Ablation Study" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 677, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 677, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 306, + 677, + 545, + 712 + ], + "type": "text", + "content": "Effect of the Proposed Losses. We evaluate the performance impact of our two proposed losses " + }, + { + "bbox": [ + 306, + 677, + 545, + 712 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\text{ave}}" + }, + { + "bbox": [ + 306, + 677, + 545, + 712 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 306, + 677, + 545, + 712 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\text{OSC}}" + }, + { + "bbox": [ + 306, + 677, + 545, + 712 + ], + "type": "text", + "content": ". The results are shown in Table 3. When each loss is consid-" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "26473" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 70, + 287, + 131 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 287, + 131 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 287, + 131 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 287, + 131 + ], + "type": "table", + "html": "
Method\\( \\mathcal{L}_{auc} \\)\\( \\mathcal{L}_{osc} \\)PIAP(%)CloU@0.3(%)AUC(%)
AVGN [26]--28.126.223.8
Proposed Method✓-44.125.328.3
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τ1τ2PIAP(%)CloU@0.3(%)AUC(%)
0.644.446.929.2
0.70.744.143.927.5
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", + "image_path": "5a3bec7cb8435f4ebea25f13a12adb03ffc09987247c9fb10ba07fa6da6da77c.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 47, + 238, + 286, + 261 + ], + "lines": [ + { + "bbox": [ + 47, + 238, + 286, + 261 + ], + "spans": [ + { + "bbox": [ + 47, + 238, + 286, + 261 + ], + "type": "text", + "content": "Table 4. Experimental results on VGGSound-Duet test set according to the hyper-parameters " + }, + { + "bbox": [ + 47, + 238, + 286, + 261 + ], + "type": "inline_equation", + "content": "{\\tau }_{1}" + }, + { + "bbox": [ + 47, + 238, + 286, + 261 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 238, + 286, + 261 + ], + "type": "inline_equation", + "content": "{\\tau }_{2}" + }, + { + "bbox": [ + 47, + 238, + 286, + 261 + ], + "type": "text", + "content": " for IOI module in Sec 3.4." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 265, + 286, + 337 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 265, + 286, + 337 + ], + "spans": [ + { + "bbox": [ + 46, + 265, + 286, + 337 + ], + "type": "text", + "content": "ered, our method shows the improved performance against AVGN [26] which is currently a state-of-the-art method. When all the proposed losses are taken into account, we show the highest performance. By integrating the proposed losses into our training, ours achieves increased capacity for learning robust and discriminative features." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "spans": [ + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": "Variation of " + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "inline_equation", + "content": "\\tau_{1}" + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "inline_equation", + "content": "\\tau_{2}" + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": ". We conduct an additional ablation study to investigate the effect of our method on the hyperparameters " + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "inline_equation", + "content": "\\tau_{1}" + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "inline_equation", + "content": "\\tau_{2}" + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": " as described in Section 3.3. The results in Table 4 indicate that we obtain the best results when " + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "inline_equation", + "content": "\\tau_{1} = 0.7" + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "inline_equation", + "content": "\\tau_{2} = 0.6" + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": ". Importantly, even when " + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "inline_equation", + "content": "\\tau_{1}" + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "inline_equation", + "content": "\\tau_{2}" + }, + { + "bbox": [ + 46, + 338, + 286, + 434 + ], + "type": "text", + "content": " are varied, our method still outperforms the existing methods. These results suggest that the proposed model is robust to the variations of hyperparameters." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 443, + 124, + 453 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 443, + 124, + 453 + ], + "spans": [ + { + "bbox": [ + 47, + 443, + 124, + 453 + ], + "type": "text", + "content": "4.6. Discussions" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "spans": [ + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "type": "text", + "content": "Sound Source Counting Accuracy. To validate the accuracy of counting the correct sound source for our model, we employed each VGGSound dataset, which comprises images containing varying sound sources (ranging from one to three per image). Respectively, our model achieved an impressive accuracy of " + }, + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "type": "inline_equation", + "content": "90.79\\%" + }, + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "type": "inline_equation", + "content": "83.21\\%" + }, + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "type": "inline_equation", + "content": "68.94\\%" + }, + { + "bbox": [ + 46, + 461, + 286, + 592 + ], + "type": "text", + "content": " for VGGSound-Single, Duet, and Trio test sets. These results not only highlight our performance in handling various numbers of sound sources but also demonstrate its potential applicability in diverse and dynamically changing audio-visual environments." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 286, + 713 + ], + "type": "text", + "content": "Adaptability of Our Method to Varying Sound Sources. We present experiments designed to evaluate the adaptability of our method in scenarios with varied sound sources. For this purpose, we utilized two distinct test sets: VGGSound-Trio [26] and VGGSound-Mixed. VGGSound-Mixed is a resampled dataset encompassing sounds from VGGSound-Single, VGGSound-Duet, and VGGSound-Trio. VGGSound-Mixed allows us to demonstrate the capability of our method to localize sound sources effectively, regardless of their quantity. The results are shown in Ta" + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 309, + 70, + 544, + 121 + ], + "blocks": [ + { + "bbox": [ + 309, + 70, + 544, + 121 + ], + "lines": [ + { + "bbox": [ + 309, + 70, + 544, + 121 + ], + "spans": [ + { + "bbox": [ + 309, + 70, + 544, + 121 + ], + "type": "table", + "html": "
MethodTest SetCAP(%)PIAP(%)CloU@0.3(%)AUC(%)
AVGN [26]VGGSound-Trio18.523.722.721.8
Ours29.042.134.029.3
AVGN [26]VGGSound-MixedN/A22.9N/AN/A
Ours27.936.035.222.7
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MethodTraining (s) \n(per iter)Inference (s) \n(per image)#params
AVGN [26] (CVPR'23)0.420.03461.2M
Proposed Method0.450.02738.5M
", + "image_path": "f67a525b94f7513adf736161b726a58cc4cf13d6f98b4a14e26ff30fe3a6d922.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 306, + 203, + 545, + 224 + ], + "lines": [ + { + "bbox": [ + 306, + 203, + 545, + 224 + ], + "spans": [ + { + "bbox": [ + 306, + 203, + 545, + 224 + ], + "type": "text", + "content": "Table 6. The comparisons of training time, inference time, and the number of parameters." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "spans": [ + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "text", + "content": "ble 5. For the VGGSound-Trio test set, our method outperforms AVGN [26] across all evaluation metrics. For the VGGSound-Mixed test set, our approach achieves scores of " + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "inline_equation", + "content": "27.9\\%" + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "inline_equation", + "content": "36.0\\%" + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "inline_equation", + "content": "35.2\\%" + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "inline_equation", + "content": "22.7\\%" + }, + { + "bbox": [ + 304, + 227, + 545, + 334 + ], + "type": "text", + "content": " for CAP, PIAP, CIoU@0.3, and AUC, respectively. Note that AVGN requires fixed prior source information, which limits its applicability. These results highlight our effectiveness in object localization, especially without prior source information, attributable to the efficacy of IOI module and loss function." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 335, + 545, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 335, + 545, + 430 + ], + "spans": [ + { + "bbox": [ + 304, + 335, + 545, + 430 + ], + "type": "text", + "content": "Computational Costs. Table 6 presents comparisons of training time, inference time, and the number of parameters. We compare our method with AVGN [26] which shows the highest performance among the existing methods. Due to the iterative method, our training time is marginally increased (7.14%). However, inference time decreased by 28.3%, and the number of parameters significantly decreased compared to the existing method with transformers." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 441, + 378, + 453 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 441, + 378, + 453 + ], + "spans": [ + { + "bbox": [ + 306, + 441, + 378, + 453 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 462, + 545, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 462, + 545, + 594 + ], + "spans": [ + { + "bbox": [ + 304, + 462, + 545, + 594 + ], + "type": "text", + "content": "In this paper, we propose an innovative approach to multi-sound source localization that does not rely on prior knowledge. The core of our method is the Iterative Object Identification (IOI) module, which effectively identifies sound-making objects through iterative processes. Our object similarity-aware clustering (OSC) loss function successfully guides the IOI module not only to merge regions associated with the same object but also to discern distinct objects from the background. We believe that our approach, the iterative object identification method enhances accuracy and has diverse practical applications." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 713 + ], + "type": "text", + "content": "Acknowledgements. This work was conducted by CARAI grant funded by DAPA and ADD (UD230017TD), and supported in part by the NRF grant funded by the Korea government (MSIT) (No. RS-2023-00252391) and by IITP grant (No. 2022-0-00124), IITP grant (IITP-2023-RS-2023-00266615), IITP grant (No. RS-2022-00155911) and by the MSIT (Ministry of Science and ICT), Korea, under the National Program for Excellence in SW (2023-0-00042) supervised by the IITP in 2024." + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "26474" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 286, + 712 + ], + "type": "list", + "angle": 0, + "index": 18, + "blocks": [ + { + "bbox": [ + 53, + 91, + 286, + 113 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 286, + 113 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 286, + 113 + ], + "type": "text", + "content": "[1] Bishwo Adhikari and Heikki Huttunen. 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In WACV, 2023. 1, 2" + } + ] + } + ], + "index": 12 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "text", + "content": "26476" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning with Structural Labels for Learning with Noisy Labels/7cf38337-93d1-4b9d-ac46-50f09fbdcf75_content_list.json b/2024/Learning with Structural Labels for Learning with Noisy Labels/7cf38337-93d1-4b9d-ac46-50f09fbdcf75_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..88fa14a1e4ed30d4fad344c89de7cfd4269c35c0 --- /dev/null +++ b/2024/Learning with Structural Labels for Learning with Noisy Labels/7cf38337-93d1-4b9d-ac46-50f09fbdcf75_content_list.json @@ -0,0 +1,1670 @@ +[ + { + "type": "text", + "text": "Learning with Structural Labels for Learning with Noisy Labels", + "text_level": 1, + "bbox": [ + 161, + 130, + 810, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Noo-ri Kim* Jin-Seop Lee* Jee-Hyong Lee† Sungkyunkwan University, Suwon, South Korea", + "bbox": [ + 285, + 180, + 689, + 215 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{pd99j, wlstjq0602, john}@skku.edu", + "bbox": [ + 331, + 219, + 632, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 268, + 313, + 284 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Deep Neural Networks (DNNs) have demonstrated remarkable performance across diverse domains and tasks with large-scale datasets. To reduce labeling costs for large-scale datasets, semi-automated and crowdsourcing labeling methods are developed, but their labels are inevitably noisy. Learning with Noisy Labels (LNL) approaches aim to train DNNs despite the presence of noisy labels. These approaches utilize the memorization effect to select correct labels and refine noisy ones, which are then used for subsequent training. However, these methods encounter a significant decrease in the model's generalization performance due to the inevitably existing noise labels. To overcome this limitation, we propose a new approach to enhance learning with noisy labels by incorporating additional distribution information—structural labels. In order to leverage additional distribution information for generalization, we employ a reverse $k$ -NN, which helps the model in achieving a better feature manifold and mitigating overfitting to noisy labels. The proposed method shows outperformed performance in multiple benchmark datasets with IDN and real-world noisy datasets.", + "bbox": [ + 75, + 300, + 473, + 618 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 645, + 209, + 660 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Deep neural networks (DNNs) have achieved high performance in various domains such as computer vision [13, 14, 20, 25, 29, 52], natural language processing [3, 7, 12, 40], and signal processing [18, 48, 50] across diverse tasks. To achieve the high performance of DNNs, well-curated large-scale datasets are necessary. However, labeling large-scale data requires a significant cost. In order to reduce these labeling costs, semi-automated [35, 42] and crowdsourcing methods [28] are used, but their labels are inevitably noisy. When trained on data with noisy labels, DNNs suffer degraded performance because they tend to easily overfit noisy labeled samples [72]. To address these issues, methods for learning with noisy labels (LNL), which aim to ef", + "bbox": [ + 75, + 670, + 468, + 867 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/f1904d0b8e89ece55e0d0e8ec2cc1e55b212a5adbe258a2f3166020ba0cfc16a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 514, + 268, + 697, + 407 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/30cbf27f1847dcd27d77d62db50eafecfcd74390bd66795409f878429b1e3c9d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 700, + 268, + 882, + 407 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e1e4136705dd34f465c9f7739e1fbf43b1b9097fbb09b5ff40871de7aa8dd0a2.jpg", + "image_caption": [ + "(a)", + "(c)", + "Figure 1. Comparison of t-SNE visualization on CIFAR10 IDN at noise rate 0.50. (a) DivideMix on training samples with golden labels. (b) DivdieMix on training samples with predicted labels. (c) SSR on training samples with golden labels. (d) SSR on training samples with predicted labels. The black-outlined box represents areas where samples overlap, similar samples are learned as different classes, or clusters are not separable." + ], + "image_footnote": [], + "bbox": [ + 513, + 428, + 697, + 569 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/2a8befe5fa23211a8b020303168d0178dbf6239f4efc8919f1b725f68f533e53.jpg", + "image_caption": [ + "(b)", + "(d)" + ], + "image_footnote": [], + "bbox": [ + 700, + 428, + 883, + 569 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "fectively train DNN models in environments with noisy labeled samples, have been proposed [1, 15, 17, 23, 31, 41, 45, 75].", + "bbox": [ + 496, + 729, + 892, + 775 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Most methods for learning with noisy labels (LNL) are based on the fact that DNNs tend to learn from clean samples with simple patterns earlier than from wrong-labeled samples [1, 69]. Based on the observation, most approaches adopted an iterative process. Initially, they trained the model with the entire dataset. The model would learned some patterns from clean samples rather than noisy samples. Then, they selected confident samples based on the", + "bbox": [ + 496, + 779, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal contribution", + "bbox": [ + 94, + 875, + 202, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "† Corresponding author", + "bbox": [ + 96, + 887, + 218, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "27610", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "output of the trained model, most of which would be clean samples. Subsequently, they retrained the model with the selected samples. They repeat the selection and training. Consequently, the model can avoid noisy samples and focus on clean samples. Previous approaches proposed various clean sample selection methods based on the model prediction, such as the small-loss trick [23] and the k-Nearest Neighbor (k-NN) method [9, 16]. Additionally, relabeling methods are utilized to leverage a larger number of clean samples by modifying model outputs deemed unreliable. These learning strategies performed quite well in a noisy environment, but they still have a critical limitation—they heavily depend on the model's predictions for relabeling and selection.", + "bbox": [ + 75, + 90, + 472, + 301 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Essentially, the models guide themselves based on their own predictions in a noisy environment. If an incorrectly predicted sample is chosen, the model may learn from it in the subsequent training step. Therefore, in this self-guided process, inevitable inaccurate predictions arise from learning based on previous inaccuracies. By learning from these inevitable noisy labels, the model not only degrades its generalization performance but also declines its ability to extract features, making the feature manifold more complex.", + "bbox": [ + 75, + 305, + 472, + 441 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Figure 1 shows that the learned feature manifolds are complex due to a degradation of generalization performance. It presents t-SNE [60] visualization for DivideMix [31], SSR [15]. Figures 1a and 1b display features of training samples extracted by DivideMix with golden labels and predictions, respectively. In DivideMix, a considerable number of samples from different classes exist in a single cluster, and the model tends to predict them with the same label, incorrectly. In Fig. 1c and 1d, SSR shows better results compared to DivideMix, but clusters have more complex forms. Furthermore, SSR incorrectly predicts some samples, and it seems that classes are not separable. They made efforts to improve generalization by incorporating additional objectives, such as consistency regularization [15] and unsupervised loss [17, 31, 75], but still demonstrate poor generalization performance.", + "bbox": [ + 75, + 444, + 472, + 686 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "It is a fact that deep learning models trained with all cleanly labeled samples exhibit good generalization behavior [44], and their feature distributions are well-discriminated by class. These well-generalized models have preserved the following structural characteristics: 1) When two samples are similar, it is highly probable that they share the same label. 2) If certain samples form a cluster, they are likely to have the same label. These are also consistent with the smoothness/cluster assumptions [4, 61, 76] in the context of semi-supervised learning. We aim to develop a method for training a LNL model by consider the characteristics of well-generalized models. In order to incorporate the characteristics, we aim to extract structural information based on the distribution of the data and directly integrate it", + "bbox": [ + 75, + 688, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "into the training process.", + "bbox": [ + 498, + 92, + 666, + 106 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this paper, we present a simple approach to enhance learning with noisy labels by incorporating additional distribution information, structural labels. If a model preserves the structural assumption, it can avoid overfitting to noisy labels and achieve better generalized. By extracting the structural information of data and integrating it into model training, we can efficiently train models with minimized bias towards noisy samples. To extract structural labels, we estimate the data distribution based on Reverse k-Nearest Neighbor (Reverse k-NN) [57]. And then, the structural labels are learned with cross-entropy based on strong augmentation [10] and mixup [73] methods, which help to avoid overfitting noisy samples.", + "bbox": [ + 496, + 107, + 890, + 301 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To verify our proposed method, we conduct experiments on IDN and real-world noisy datasets including CIFAR10 and CIFAR100 with IDN [66], CIFAR-N [63], Animal-10N [53], Red Mini-Imagenet from CNWL [24], Mini-WebVision [35], andImagenet ILSVRC12 [11]. Our method shows the state-of-the-art performance on various datasets.", + "bbox": [ + 496, + 303, + 890, + 407 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 421, + 640, + 436 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Deep neural networks (DNNs) tend to overfit to label datasets so that they also overfit to noisy label samples and it leads to degraded performance. Many studies have been conducted to learn datasets with noisy labels. To prevent overfitting to noisy labels and learn effectively from datasets with noisy labels, early studies utilized a given small set of clean samples and relabeled noisy samples based on their modeling [5, 30, 36, 59, 62, 67]. Subsequently, instead of using a given small set of clean samples, several studies focus to distinguish clean samples from the given noisy datasets [1, 15, 17, 26, 31, 51, 58, 75].", + "bbox": [ + 496, + 446, + 890, + 613 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "These methods rely on DNNs initially learn from cleanly labeled samples with simple patterns before overfitting to noisy label samples [72], and use the small-loss trick to select clean-label samples [17, 23, 31, 51, 75]. DivideMix [31] treats samples with small losses as labeled samples and the others as unlabeled then trains the model using MixMatch [2], a semi-supervised learning technique. C2D [75] leverages self-supervised models to tackle the instability during the warm-up phase of DivideMix, and InstanceGM [17] proposes a graphical modeling approach to address the more realistic noise, Instance-Dependent Noise (IDN).", + "bbox": [ + 496, + 614, + 890, + 794 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Contrary to the loss-based approaches, some methods utilize the model's feature representation [15, 34, 64, 71]. TopoFilter [64] proposes a label noise filtering strategy based on spatial topological patterns, and SSR [15] leverages the model's high-confident predictions for relabeling samples and employs a k-NN classifier [9] within the feature representation space for selecting clean samples.", + "bbox": [ + 496, + 795, + 890, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "27611", + "bbox": [ + 478, + 944, + 517, + 957 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In conclusion, recent LNL methods mainly focus on relabeling and selecting based on their own predictions. However, it is challenging to expect good generalization performance due to the excessive reliance on the predictions of a model that may have errors.", + "bbox": [ + 76, + 90, + 468, + 167 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Proposed Method", + "text_level": 1, + "bbox": [ + 76, + 178, + 250, + 195 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Since existing methods heavily depend on uncertain models' predictions, they struggle to form good representations and do not preserve structural information. Wellgeneralized models should preserve the assumption that closer features are likely to be located on the same manifold and have the same label. Therefore, it is necessary not only to get accurate predictions from the model but also to consider the distribution of features.", + "bbox": [ + 75, + 203, + 468, + 323 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we propose Learning with Structural Label (LSL), a new approach for learning structural information in LNLs. To learn structural information, we estimate the data distribution based on the Reverse k-NN algorithm, which is less influenced by outlier samples compared to k-NN [21, 49], and calculate the probability of belonging to a class distribution. Then, we extract structural labels $l_{st}$ from the estimated distribution for all samples and train the model using a strong augmentation [10] and mixup [73] strategy. In contrast to traditional relabeling methods, which depend on uncertain models' predictions learned from selected samples with simple patterns, our approach considers the feature distribution for learning on all samples, not only selected samples.", + "bbox": [ + 75, + 325, + 468, + 536 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Structural Labels based on Reverse k-NN", + "text_level": 1, + "bbox": [ + 76, + 542, + 429, + 558 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In order to obtain more reliable information from noisy predictions of the model, we define the structural labels, $l_{st}$ , which are the soft labels of each sample based on sample distributions. We first obtain class prediction for each sample from the model, and estimate the distribution of samples predicted as class $c$ . We estimate the probability of $x$ given $c$ , $P(x|c)$ , based on the similarity of feature representations and reverse k-NN. We emit $k$ arrows from each sample predicted as class $c$ to its $k$ nearest neighbors including itself. For a sample $x$ , $P(x|c)$ can be approximated as follows:", + "bbox": [ + 75, + 566, + 468, + 717 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nP (x \\mid c) = \\frac {\\# \\text {o f A r r o w s} _ {x , c}}{k \\cdot | X ^ {c} |} \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 183, + 724, + 468, + 758 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\#$ of $\\operatorname{Arrows}_{x,c}$ is the total number of arrows received by $x$ from samples predicted as $c$ , and $|X^c|$ is the total number of samples predicted as $c$ . If $x$ exists in the region where $c$ class samples densely exist, it may receive more arrows, and vice versa. Consequently, when divided by the total number of arrows from $c$ class samples, it is an approximation for $P(x|c)$ .", + "bbox": [ + 75, + 763, + 468, + 869 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Figure 2 shows estimation examples of 2-d Gaussian and Moon data [47]. Figures 2a and 2c show distributions by", + "bbox": [ + 76, + 869, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/02cfa054df0ce573ac75f1ed72ea6697726e260433bf7c7c46667d781154aa68.jpg", + "image_caption": [ + "(a) Gaussian modeling for Gaussian samples" + ], + "image_footnote": [], + "bbox": [ + 524, + 92, + 687, + 191 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/5240b0fa410ea26be34c55149cff2c0ff1ebb2d8034c923364bfbc516f161751.jpg", + "image_caption": [ + "(b) Modeling based on reverse k-NN for Gaussian samples" + ], + "image_footnote": [], + "bbox": [ + 707, + 90, + 870, + 191 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/c00f286017f081a3154b33733fd00f82e1bcde720f4a4e0418090d0ac58f815c.jpg", + "image_caption": [ + "(c) Gaussian modeling for Moon dataset" + ], + "image_footnote": [], + "bbox": [ + 524, + 224, + 687, + 324 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/2105415bbd86a229732f4fe0f3b08fe11a1957ee00d5f38ad0d662cf7ef17592.jpg", + "image_caption": [ + "(d) Modeling based on reverse k-NN for Moon dataset", + "Figure 2. Comparison of distributions between Gaussian modeling and reverse k-NN modeling in 2-D Gaussian dataset and Moon dataset. Figure 2a shows the Gaussian modeling effectively estimates distribution for Gaussian samples. However, the Gaussian modeling fails to fit the distribution of the Moon dataset in Fig. 2c. Figure 2b and Fig. 2d show Reverse k-NN effectively approximates the data distribution for both Gaussian and Moon datasets." + ], + "image_footnote": [], + "bbox": [ + 707, + 223, + 870, + 324 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Gaussian modeling, and 2b and 2d show distributions by our modeling based on reverse k-NN. The Gaussian modeling can efficiently estimates the distributions, but it is hard to accurately model complex data distributions like the Moon dataset. In contrast, the distribution estimation based on reverse k-NN effectively approximates not only the simple distribution, Gaussian, but also the complex data distribution, Moon dataset.", + "bbox": [ + 496, + 487, + 890, + 606 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Based on the feature distribution, we define the structural label of $x$ , which is the soft label representing the probability of $c$ given $x$ :", + "bbox": [ + 496, + 608, + 890, + 652 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nP (c | x) = \\frac {P (x | c) P (c)}{\\sum_ {c \\in C} P (x | c) P (c)}. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 591, + 659, + 890, + 694 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The prior $P(c)$ represents the probability of observing class $c$ , which can be determined from the number of samples in each class:", + "bbox": [ + 496, + 700, + 888, + 743 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nP (c) = \\frac {\\left| X ^ {c} \\right|}{\\sum_ {c = 1} ^ {C} \\left| X ^ {c} \\right|}. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 624, + 741, + 890, + 777 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Then, Eq. (2) can be reformulated as follows:", + "bbox": [ + 500, + 780, + 800, + 795 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nP (c | x) = \\frac {P (x | c) \\left| X ^ {c} \\right|}{\\sum_ {c = 1} ^ {C} P (x | c) \\left| X ^ {c} \\right|}. \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 593, + 801, + 890, + 838 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "From Eqs. (1) and (4), $P(c|x)$ is approximated as follows:", + "bbox": [ + 500, + 844, + 883, + 859 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nP (c | x) = \\frac {\\# \\text {o f A r r o w s} _ {x , c}}{\\sum_ {c = 1} ^ {C} \\# \\text {o f A r r o w s} _ {x , c}}. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 581, + 866, + 890, + 904 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "27612", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "code", + "sub_type": "algorithm", + "code_caption": [ + "Algorithm 1: Extracting Structural Labels based on reverse k-NN distribution estimation" + ], + "code_body": "Input : model encoder $\\theta$ training dataset $\\mathcal{X},\\mathcal{V} = \\{(x_i,y_i^r)_{i = 1}^N\\}$ Parameter: number of reverse nearest neighbors $k_{st}$ Output : structural labels by $st\\mathcal{Y}^{st} = \\{(y^{st})_{i = 1}^N\\}$ \n1 T = torch.zeros[N, K] \n2 # $K$ is the number of classes \n3 #T indicates edge count table \n4 $\\mathcal{F} = \\mathrm{Normalize}(\\theta (\\mathcal{X}))$ #Normalize all features \n5 for $i\\gets 1$ to $N$ do \n6 score $=$ Cosine $(f_i,\\mathcal{F})$ indices $=$ score.topk $(k_{st})$ \n8 # Emit k edges to $k_{st}$ nearest neighbors \n9 T [indices, $y_i^r ] + = 1$ \n10 # Propagate its label to k nearest neighbors \n11 end \n12 $\\mathcal{V}^{st} = \\mathrm{T} / \\mathrm{T}.\\mathrm{sum}(\\mathrm{dim} = 1$ ,keepdim=True) \n13 # Aggregate from received labels and normalize these labels \n14 return $\\mathcal{V}^{st}$", + "bbox": [ + 76, + 125, + 491, + 400 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Since $P(c|x)$ is estimated from noisy prediction of the model, it can be affected by wrong predictions. However, if we assume that the uniform noise over the sample space, it is clear that the probability is free from the uniform noise. Even though the noise is not uniform, it can be easily smoothed if we use enough large $k_{st}$ . However, if $k_{st}$ is too large, the number of arrows received from samples of classes other than $c$ will increase. It can lead to over-smoothing of $l_{st}$ and lose the structural information. To avoid over-dilution of structural information, we need to choose an appropriate value of $k_{st}$ , and it is discussed in Sec. 5.2.", + "bbox": [ + 75, + 434, + 473, + 613 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In conclusion, the structural label of $x$ estimated by reverse k-NN effectively reflects the distribution information of the samples in noisy data environments. Algorithm 1 shows how to obtain the structural labels.", + "bbox": [ + 75, + 616, + 468, + 676 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Learning with Structural Labels (LSL)", + "text_level": 1, + "bbox": [ + 76, + 689, + 413, + 707 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To learn structural information, we utilize structural labels $l_{st}$ to effectively reflect feature distribution with SSR [15]. It is one of the LNL methods that considers feature representation. The procedure for the proposed method is described in Algorithm 2.", + "bbox": [ + 75, + 713, + 468, + 789 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In Algorithm 2, line 2 indicates relabeling based on model prediction with Eq. (6), and line 3 indicates sample selection based on k-NN.", + "bbox": [ + 75, + 791, + 468, + 835 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ny _ {i} ^ {r} = \\left\\{ \\begin{array}{l l} \\operatorname {a r g m a x} _ {l} f (\\alpha (x _ {i})), & \\text {i f} \\max _ {l} f (\\alpha (x _ {i})) > \\tau_ {r} \\\\ y _ {i}, & \\text {o t h e r w i s e} \\end{array} \\right. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 88, + 863, + 468, + 904 + ], + "page_idx": 3 + }, + { + "type": "code", + "sub_type": "algorithm", + "code_caption": [ + "Algorithm 2: Learning with Structural Labels (LSL)" + ], + "code_body": "Input : model encoder $\\theta$ multi-layer neural network $\\phi$ training dataset $(\\mathcal{X},\\mathcal{Y}) = \\{(x_i,y_i)\\}_{i = 1}^N$ \nParameter: sample relabelling threshold $\\tau_r$ feature consistency loss weight $\\lambda_{fc}$ structural loss weight $\\lambda_{st}$ \n1 while eMethodIDN - CIFAR10IDN - CIFAR1000.200.300.400.450.500.200.300.400.450.50CE [70]75.8169.1562.4551.7239.4230.4224.1521.4515.2314.42Mixup [73]73.1772.0261.5656.4548.9532.9229.7625.9223.1321.31Forward [46]74.6469.7560.2148.8146.2736.3833.1726.7521.9319.27Reweight [39]76.2370.1262.5851.5445.4636.7331.9128.3924.1220.23Decoupling [43]78.7175.1761.7358.6150.4336.5330.9327.8523.8119.59Co-teaching [19]80.9678.5673.4171.6045.9237.9633.4328.0425.6023.97MentorNet [23]81.0377.2271.8366.1847.8938.9134.2331.8927.5324.15DivideMix [31]94.8094.6094.5394.0893.0477.0776.3370.8057.7858.61SSR* [15]96.4996.5296.3395.8994.0678.8478.6076.9574.9872.83InstanceGM [17]96.6896.5296.3696.1595.9079.6979.2178.4777.4977.19LSL (Ours)97.1396.8596.5396.5895.8180.9479.9078.6078.0877.95", + "bbox": [ + 78, + 88, + 893, + 349 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Table 1. Test accuracy (%) of different methods on CIFAR10-IDN and CIFAR100-IDN [66] under various IDN noise rates. Most of the experimental results are extracted from state-of-the-art methods [15, 17, 31]. Bold values indicate the best performances. The reproduced result is marked with $*$ .", + "bbox": [ + 75, + 361, + 892, + 405 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We describe these datasets in Sec. 4.1 and provide the implementation details in Sec. 4.2. In Sec. 4.3, we compare our approach with state-of-the-art models in various IDN benchmarks and real-world noisy datasets.", + "bbox": [ + 75, + 430, + 470, + 491 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Datasets", + "text_level": 1, + "bbox": [ + 76, + 500, + 181, + 513 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "CIFAR10 and CIFAR100 both datasets [27] consist of 50,000 training images and 10,000 testing images, and each image has dimensions of $32 \\times 32 \\times 3$ . The CIFAR10 has 10 classes, while CIFAR100 has 100 classes. To conduct experiments in the instance-dependent noise (IDN) environment, we obtained noisy labels of the CIFAR10 and CIFAR100 datasets according to [66]. We set the noise rate for IDN settings at values of 0.20, 0.30, 0.40, 0.45, and 0.50.", + "bbox": [ + 75, + 522, + 468, + 643 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The CIFAR10N and CIFAR100N datasets [63] consist of human-annotated noisy labels obtained from Amazon Mechanical Turk. CIFAR10N and CIFAR100N datasets include 5 and 2 noisy label types, respectively. In this paper, we evaluate the settings with the highest noise rates, specifically CIFAR10N Worst (CIFAR10N-W, a noise rate of $40.21\\%$ ) and CIFAR100N Fine (CIFAR100N-F, a noise rate of $40.20\\%$ ).", + "bbox": [ + 75, + 643, + 470, + 763 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Animal-10N dataset [53] consists of 50,000 training images and 10,000 test images, with each image having a resolution of $64 \\times 64 \\times 3$ . The dataset has 10 animal categories, including 5 pairs of animals with similar appearances and the estimated noise rate of the dataset is $8\\%$ .", + "bbox": [ + 75, + 763, + 468, + 839 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Red Mini-Imagenet from CNWL [24] dataset is annotated by 3-5 labeling professionals using Google Cloud Data Labeling Service. The dataset comprises 600 training samples for each of its 100 classes. While the origi", + "bbox": [ + 75, + 839, + 470, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "nal image size is $84 \\times 84 \\times 3$ , we resize it to $32 \\times 32 \\times 3$ for a fair comparison with other experiments [17, 68]. It supports noise ratios ranging from $0\\%$ to $80\\%$ , and we validate our model on training data with noise ratios of $20\\%$ , $40\\%$ , $60\\%$ , $80\\%$ .", + "bbox": [ + 496, + 430, + 892, + 503 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "WebVision [35] is a large-scale dataset with 2.4 million images collected from the web across 1k categories, and Mini-WebVision is a dataset composed of the initial 50 categories from the WebVision dataset. Mini-WebVision contains 65,994 training images, and we resized the images to $256 \\times 256 \\times 3$ . For validation, we use not only Mini-WebVision but also ImageNet ILSVRC12 dataset [11], which shares the same subset of categories.", + "bbox": [ + 496, + 505, + 893, + 628 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Implementation Details", + "text_level": 1, + "bbox": [ + 498, + 635, + 718, + 651 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "All experiments are conducted using the PyTorch framework on an NVIDIA RTX 3090Ti GPU. Unless otherwise specified, all hyperparameter values mentioned below are followed from SSR [15].", + "bbox": [ + 496, + 657, + 892, + 718 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For CIFAR10 and CIFAR100 with IDN datasets, we use a PreAct-ResNet-18 [20] following DivideMix [31]. We use SGD optimizer for 300 epochs with a momentum of 0.9, a weight decay of 5e-4, an initial learning rate of 0.02, and the cosine annealing function as a learning scheduler. We set a relabeling threshold, $\\tau_r$ , from 0.55 to 0.8 for CIFAR10 and CIFAR100 with IDN as the noise ratio decreases, and the batch size to 128. For CIFAR-N datasets, we set $\\tau_r$ to 0.8 for CIFAR10-N and CIFAR100-N, and all other details are consistent with CIFAR10/100 with IDN configurations. For Red Mini-Imagenet from CNWL [24], we set $\\tau_r$ to 0.8, and all other details are consistent with CIFAR10/100 with", + "bbox": [ + 496, + 719, + 893, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "27614", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/f1cf5d5ef99bad05cb2a15e22672bad1f86e267b9eb4a4cc05b782806a097cee.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodCIFAR10N-WCIFAR100N-F
CE [70]77.6955.50
CAL [77]85.3661.73
ELR [37]91.0966.72
SOP+ [38]93.2467.81
DivideMix [31]92.5671.13
SSR* [15]93.5071.99
LSL (Ours)94.5774.46
", + "bbox": [ + 81, + 88, + 460, + 253 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "IDN configurations.", + "bbox": [ + 76, + 318, + 212, + 334 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For Animal-10N, we use a VGG-19 with batch-normalization [55]. We use SGD optimizer for 150 epochs with a momentum of 0.9, a weight decay of 5e-4, an initial learning rate of 0.02, and the step function as a learning scheduler with a reduction factor of 10 and a step size of 50 epochs. We set $\\tau_r$ to 0.8, and the batch size of 128.", + "bbox": [ + 75, + 334, + 468, + 425 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For Mini-WebVision, we use an InceptionResNetv2 [56] following [31]. We use SGD optimizer for 150 epochs with a momentum of 0.9, a weight decay of 1e-4, an initial learning rate of 0.01, and the step function as a learning scheduler with a reduction factor of 10 and a step size of 50 epochs. We set $\\tau_r$ to 0.8, and the batch size to 64.", + "bbox": [ + 75, + 426, + 468, + 516 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For mixup interpolation, we set both $\\alpha$ and $\\beta$ to 4 for beta mixture on IDN datasets, CIFAR-N and Red MiniImageNet, and to 0.5 on other datasets. We set the consistency loss weight $\\lambda_{fc}$ and the structural loss weight $\\lambda_{st}$ to 1.0, and the number of reverse nearest neighbors $k_{st}$ to 20.", + "bbox": [ + 75, + 517, + 468, + 606 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Experimental Results", + "text_level": 1, + "bbox": [ + 76, + 619, + 279, + 635 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The results for CIFAR10 and CIFAR100 with IDN benchmark datasets are shown in Tab. 1. Our proposed method exhibits the best performance in all cases except for CIFAR10 with an IDN noise ratio of 0.5. Even in CIFAR10 with an IDN noise ratio of 0.5, our method demonstrates comparable performance to the baseline, within a margin of $0.1\\%$ points. These results demonstrate that our method is consistently effective across various IDN environments.", + "bbox": [ + 75, + 642, + 468, + 763 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Tables 2 to 5 show the results for real-world noisy datasets. The performance on CIFAR10N-W and CIFAR100N-F is presented in Tab. 2. For both datasets, which have a noise rate of approximately $40\\%$ , our proposed method shows significant improvements by $1.1\\%$ and $3.4\\%$ , respectively, compared to the baseline methods. These results confirm the effectiveness of our approach, not only with synthetic IDN noise but also with human-annotated real-world noisy labels.", + "bbox": [ + 75, + 763, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/7d84289320c9571f9bf3d703d0f3bee6e5f55ee6c17c553f97918e5af321686f.jpg", + "table_caption": [ + "Table 2. Test accuracy $(\\%)$ of CIFAR-N [63]. Bold values indicate the best performances and the reproduced result is marked with $*$" + ], + "table_footnote": [], + "table_body": "
MethodNoise rate
0.20.40.60.8
CE [70]47.3642.7037.3029.79
Mixup [73]49.1046.4040.5833.58
Mentormix [24]51.0247.1443.8033.46
FaMUS [68]51.4248.0645.1035.50
DivideMix [31]50.9646.7243.1434.50
SSR* [15]52.1848.9642.4233.20
InstanceGM [17]58.3852.2447.9639.62
LSL (Ours)54.6849.8045.4636.78
", + "bbox": [ + 504, + 88, + 883, + 292 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/e262bb7a0c8088a5f2f2491df38496643b54f18aa22e1d97e41997a38ce9e893.jpg", + "table_caption": [ + "Table 3. Test accuracy $(\\%)$ of Red Mini-Imagenet (CNWL) [24]. Bold values indicate the best performances and the reproduced result is marked with $*$" + ], + "table_footnote": [], + "table_body": "
MethodTest Accuracy (%)
CE [70]79.4
Nested-Dropout [6]81.8
CE+Dropout [6]81.3
SELFIE [54]81.3
PLC [74]83.4
Nested-CE [6]84.1
SSR [15]88.5
InstanceGM [17]84.6
LSL (Ours)89.1
", + "bbox": [ + 540, + 378, + 848, + 583 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 4. Test accuracy $(\\%)$ of ANIMAL-10N [53]. Bold values indicate the best performances.", + "bbox": [ + 498, + 593, + 890, + 621 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The experimental results on the Red Mini-ImageNet from CNWL dataset are presented in Tab. 3. Our proposed method demonstrates the second-best performances.", + "bbox": [ + 498, + 667, + 890, + 714 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Animal-10N is a challenging dataset consisting of 5 pairs of easily confused animals and has a relatively low noise ratio of approximately $8\\%$ compared to other real-world noisy labels. For this dataset, our method outperforms other approaches, as shown in Tab. 4.", + "bbox": [ + 496, + 724, + 890, + 800 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Lastly, Tab. 5 shows performance on the large-scale WebVision and ImageNet datasets. Our method achieves the best performance on all cases in Top1 accuracy. Especially, our proposed method shows best performance on the Top1 accuracy of ImageNet, and it shows that our method generalizes very well to other datasets.", + "bbox": [ + 496, + 809, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "27615", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/766380d89922fdebe95537252c46b8dff9482f532f310621b2384ddf9d5f44e9.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodWebVisionIISVRC2012
Top-1Top-5Top-1Top-5
Co-teaching [19]63.5885.2061.4884.70
ELR+ [37]77.7891.6870.2989.76
NGC [65]79.1691.8474.4491.04
LongReMix [8]78.9292.32--
RRL [32]76.3091.5073.3091.20
Sel-CL+ [33]79.9692.6476.8493.04
TCL [22]79.1092.3075.4092.40
DivideMix [31]77.3291.6475.2090.84
SSR [15]80.9292.8075.7691.76
LSL (Ours)81.4093.0077.0091.84
", + "bbox": [ + 78, + 88, + 472, + 330 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 5. Test accuracy $(\\%)$ of WebVision [35] and IISVRC2012 [11]. Bold values indicate the best performances.", + "bbox": [ + 76, + 340, + 468, + 369 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/bd6ce2bc74906c36d46195060eec04cfc1c3c06ae11ad45b87af9e12bcc5e681.jpg", + "image_caption": [ + "Figure 3. Comparison of training accuracy. Our proposed method outperforms existing approaches. Through the proposed structural labels based on the feature distribution, the model can effectively leverage the entire training dataset." + ], + "image_footnote": [], + "bbox": [ + 94, + 391, + 460, + 558 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5. Ablation Studies", + "text_level": 1, + "bbox": [ + 76, + 659, + 240, + 674 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In this section, we analyze the effectiveness of our proposed method and introduce its details. All ablation studies are conducted on the CIFAR10 with IDN dataset [66].", + "bbox": [ + 75, + 684, + 468, + 731 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.1. Effectiveness of learning structural labels", + "text_level": 1, + "bbox": [ + 76, + 739, + 429, + 757 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Figure 3 shows the accuracy of training data, the agreement between the model's predictions and the original clean labels as training progresses. The original clean labels are used only for evaluation, not for training. In LNL, the accuracy typically does not reach $100\\%$ by the end of training as models cannot fully generalize from noisy training data. Our proposed method shows a higher training accuracy compared to other approaches such as DivideMix [31] and SSR [15]. Existing methods are difficult to accurately", + "bbox": [ + 75, + 763, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/52598a88b603274e6f771327c7a1cc744254ce798c8146a933e78fa504fb1d70.jpg", + "image_caption": [ + "(a) Histogram of logits by SSR" + ], + "image_footnote": [], + "bbox": [ + 506, + 93, + 888, + 287 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/2b1160e05e828fbd4d4aeda636de7dd8a91ffa14c9107eb0bd703ead726ead41.jpg", + "image_caption": [ + "(b) Histogram of logits by the proposed method", + "Figure 4. Histogram of Logits for the Training Dataset of CIFAR10 with IDN at noise rate 0.50." + ], + "image_footnote": [], + "bbox": [ + 504, + 318, + 888, + 513 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "relabel and select more samples with complex patterns, so they only learn a fraction of the training data and struggle to generalize. In contrast, our proposed method, which utilizes structural labels $l_{st}$ based on feature distribution, effectively leverages more samples and achieves better generalization performance.", + "bbox": [ + 496, + 598, + 890, + 686 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Figure 4 shows the distribution of logits for SSR and our proposed method on CIFAR10 with IDN at noise rate 0.50. In SSR, the total number of misclassified samples is 3238. Among them, 1248 samples are misclassified as given noisy labels, accounting for 0.39 percent of the total misclassified samples. On the other hand, in our method, the total number of misclassified samples is 2107. Among them, the number of misclassified samples as given noisy labels is 646. The percentage of them is 0.31. Thus, our proposed method exhibits fewer total misclassified samples and a lower percentage of misclassified samples as given noisy labels. Also, The logit distribution of misclassified samples with given noise (red) is skewed to the right relative to the logit distribution of misclassified samples (orange) in SSR, whereas", + "bbox": [ + 496, + 688, + 892, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "27616", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ac98a9b7fd700611a26fdc676a35bc4d9f2e0deaca63a5fb07cc384410ac12f5.jpg", + "image_caption": [ + "(a) Accuracy with respect to different values of the $k_{st}$ ." + ], + "image_footnote": [], + "bbox": [ + 86, + 93, + 455, + 205 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e954e65f73f600d27e3f3d3fa1b000aa92a2ca048a8a2a1c4d1be5a2e3d74bf1.jpg", + "image_caption": [ + "(b) Accuracy with respect to different values of the $\\lambda_{st}$ .", + "Figure 5. Accuracy with respect to hyperparameters on CIFAR10 with IDN at noise rate 0.20. The red dashed line represents the performance of the state-of-the-art (SOTA)." + ], + "image_footnote": [], + "bbox": [ + 86, + 238, + 455, + 349 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ours is not. As these statistics demonstrate, our method avoids overfitting to given noisy labels and achieves better generalization performance.", + "bbox": [ + 75, + 454, + 468, + 500 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.2. Hyperparameters", + "text_level": 1, + "bbox": [ + 76, + 518, + 250, + 536 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To validate the sensitivity of the hyperparameters, experiments are conducted using various values of $k_{st}$ for reverse k-NN and the weight of the structural loss, $\\lambda_{st}$ . The results are shown in Fig. 5.", + "bbox": [ + 75, + 546, + 468, + 606 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Figure 5a shows the model's accuracy with respect to different values of the hyperparameter $k_{st}$ . Based on the feature distribution, the model can be trained by smoothing over the correct answer labels of its neighboring samples in a noisy environment. However, if $k_{st}$ is too small, our method cannot fully incorporate the feature distribution. On the contrary, if $k_{st}$ is too large, the number of arrows received from samples of classes other than $c$ will increase, and then structural labels $l_{st}$ are over-smoothed. To avoid over-dilution of structural information, we need to choose an appropriate value of $k_{st}$ . Therefore, we experiment with various values to determine the optimal $k_{st}$ . Our proposed model shows the best performances at a $k_{st}$ of 20.", + "bbox": [ + 75, + 609, + 468, + 806 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Figure 5b shows the performance of our proposed method with respect to value of $\\lambda_{st}$ , the weight of the structural loss. When applying structural loss, there is a clear performance improvement compared to the case where it is not applied, $\\lambda_{st}$ is 0. Additionally, it demonstrates stable, improved performance regardless of changes in the value.", + "bbox": [ + 75, + 809, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c6c2f0af9773de86858968d50be1a95cbba2f19da90db4eb57a4ba65190c6410.jpg", + "image_caption": [ + "(a)", + "Figure 6. Comparison of t-SNE visualization on CIFAR10 with IDN at noise rate 0.50. (a) Ours on training samples with golden labels. (b) Ours on training samples with predicted labels. There are only smaller amounts of wrongly trained samples than DivideMix and SSR." + ], + "image_footnote": [], + "bbox": [ + 509, + 90, + 694, + 233 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/77c05a1b11c896782f5bd8faf07a6ff9c6507f34e5b997523249e816130cf75f.jpg", + "image_caption": [ + "(b)" + ], + "image_footnote": [], + "bbox": [ + 697, + 90, + 883, + 233 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.3. The t-SNE visualization", + "text_level": 1, + "bbox": [ + 500, + 359, + 718, + 375 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Figure 6 shows t-SNE visualization of features for the proposed method. Unlike DivideMix and SSR in Fig. 1, our method not only learned a relatively simple manifold but also exhibits well-separated clusters, each predominantly representing one class. This confirms that our method demonstrates superior generalization performance.", + "bbox": [ + 498, + 383, + 890, + 474 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 491, + 617, + 507 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we explored the generalization problem in learning with noisy labels (LNL) and proposed a simple yet effective approach to address these challenges. While existing LNL methods, our proposed method employed a reverse k-NN to leverage structural information based on feature distribution. And by learning the structural information, the model had a better feature manifold and robustness against overfitting to noisy labels, thus achieving better generalization performance. The proposed method demonstrated outperformed performance across various datasets including CIFAR10 and CIFAR100 with IDN, CIFAR-N, Animal10N, Red Mini-Imagenet, Mini-WebVision, and ImageNet.", + "bbox": [ + 498, + 517, + 890, + 699 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments. This work was partly supported by Institute of Information & communications Technology Planning & Evaluation (IITP) grant funded by the Korea government (MSIT) (No.2019-0-00421, AI Graduate School Support Program, Sungkyunkwan University, and No.RS-2023-00228970, Development of Flexible SW-HW Conjunctive Solution for On-edge Self-supervised Learning).", + "bbox": [ + 498, + 719, + 890, + 816 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 500, + 847, + 596, + 863 + ], + "page_idx": 7 + }, + { + "type": "ref_text", + "text": "[1] Eric Arazo, Diego Ortego, Paul Albert, Noel O'Connor, and Kevin McGuinness. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 10113-10123, 2021. 6" + ], + "bbox": [ + 501, + 92, + 890, + 656 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "27620", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning with Structural Labels for Learning with Noisy Labels/7cf38337-93d1-4b9d-ac46-50f09fbdcf75_model.json b/2024/Learning with Structural Labels for Learning with Noisy Labels/7cf38337-93d1-4b9d-ac46-50f09fbdcf75_model.json new file mode 100644 index 0000000000000000000000000000000000000000..4c8a4ecd88a2f09ab52a14af3b683d3ca7cc124d --- /dev/null +++ b/2024/Learning with Structural Labels for Learning with Noisy Labels/7cf38337-93d1-4b9d-ac46-50f09fbdcf75_model.json @@ -0,0 +1,2642 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.162, + 0.131, + 0.812, + 0.154 + ], + "angle": 0, + "content": "Learning with Structural Labels for Learning with Noisy Labels" + }, + { + "type": "text", + "bbox": [ + 0.287, + 0.181, + 0.69, + 0.217 + ], + "angle": 0, + "content": "Noo-ri Kim* Jin-Seop Lee* Jee-Hyong Lee† Sungkyunkwan University, Suwon, South Korea" + }, + { + "type": "text", + "bbox": [ + 0.332, + 0.22, + 0.633, + 0.234 + ], + "angle": 0, + "content": "{pd99j, wlstjq0602, john}@skku.edu" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.301, + 0.474, + 0.619 + ], + "angle": 0, + "content": "Deep Neural Networks (DNNs) have demonstrated remarkable performance across diverse domains and tasks with large-scale datasets. To reduce labeling costs for large-scale datasets, semi-automated and crowdsourcing labeling methods are developed, but their labels are inevitably noisy. Learning with Noisy Labels (LNL) approaches aim to train DNNs despite the presence of noisy labels. These approaches utilize the memorization effect to select correct labels and refine noisy ones, which are then used for subsequent training. However, these methods encounter a significant decrease in the model's generalization performance due to the inevitably existing noise labels. To overcome this limitation, we propose a new approach to enhance learning with noisy labels by incorporating additional distribution information—structural labels. In order to leverage additional distribution information for generalization, we employ a reverse \\( k \\)-NN, which helps the model in achieving a better feature manifold and mitigating overfitting to noisy labels. The proposed method shows outperformed performance in multiple benchmark datasets with IDN and real-world noisy datasets." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.646, + 0.21, + 0.661 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.671, + 0.47, + 0.868 + ], + "angle": 0, + "content": "Deep neural networks (DNNs) have achieved high performance in various domains such as computer vision [13, 14, 20, 25, 29, 52], natural language processing [3, 7, 12, 40], and signal processing [18, 48, 50] across diverse tasks. To achieve the high performance of DNNs, well-curated large-scale datasets are necessary. However, labeling large-scale data requires a significant cost. In order to reduce these labeling costs, semi-automated [35, 42] and crowdsourcing methods [28] are used, but their labels are inevitably noisy. When trained on data with noisy labels, DNNs suffer degraded performance because they tend to easily overfit noisy labeled samples [72]. To address these issues, methods for learning with noisy labels (LNL), which aim to ef" + }, + { + "type": "image", + "bbox": [ + 0.515, + 0.269, + 0.698, + 0.409 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.594, + 0.416, + 0.611, + 0.427 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.701, + 0.269, + 0.883, + 0.409 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.779, + 0.415, + 0.797, + 0.427 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image", + "bbox": [ + 0.514, + 0.429, + 0.698, + 0.57 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.594, + 0.575, + 0.612, + 0.586 + ], + "angle": 0, + "content": "(c)" + }, + { + "type": "image", + "bbox": [ + 0.701, + 0.429, + 0.885, + 0.57 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.781, + 0.575, + 0.799, + 0.586 + ], + "angle": 0, + "content": "(d)" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.599, + 0.895, + 0.697 + ], + "angle": 0, + "content": "Figure 1. Comparison of t-SNE visualization on CIFAR10 IDN at noise rate 0.50. (a) DivideMix on training samples with golden labels. (b) DivdieMix on training samples with predicted labels. (c) SSR on training samples with golden labels. (d) SSR on training samples with predicted labels. The black-outlined box represents areas where samples overlap, similar samples are learned as different classes, or clusters are not separable." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.731, + 0.893, + 0.776 + ], + "angle": 0, + "content": "fectively train DNN models in environments with noisy labeled samples, have been proposed [1, 15, 17, 23, 31, 41, 45, 75]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Most methods for learning with noisy labels (LNL) are based on the fact that DNNs tend to learn from clean samples with simple patterns earlier than from wrong-labeled samples [1, 69]. Based on the observation, most approaches adopted an iterative process. Initially, they trained the model with the entire dataset. The model would learned some patterns from clean samples rather than noisy samples. Then, they selected confident samples based on the" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.875, + 0.204, + 0.888 + ], + "angle": 0, + "content": "*Equal contribution" + }, + { + "type": "page_footnote", + "bbox": [ + 0.098, + 0.888, + 0.22, + 0.9 + ], + "angle": 0, + "content": "† Corresponding author" + }, + { + "type": "list", + "bbox": [ + 0.096, + 0.875, + 0.22, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27610" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.302 + ], + "angle": 0, + "content": "output of the trained model, most of which would be clean samples. Subsequently, they retrained the model with the selected samples. They repeat the selection and training. Consequently, the model can avoid noisy samples and focus on clean samples. Previous approaches proposed various clean sample selection methods based on the model prediction, such as the small-loss trick [23] and the k-Nearest Neighbor (k-NN) method [9, 16]. Additionally, relabeling methods are utilized to leverage a larger number of clean samples by modifying model outputs deemed unreliable. These learning strategies performed quite well in a noisy environment, but they still have a critical limitation—they heavily depend on the model's predictions for relabeling and selection." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.306, + 0.473, + 0.442 + ], + "angle": 0, + "content": "Essentially, the models guide themselves based on their own predictions in a noisy environment. If an incorrectly predicted sample is chosen, the model may learn from it in the subsequent training step. Therefore, in this self-guided process, inevitable inaccurate predictions arise from learning based on previous inaccuracies. By learning from these inevitable noisy labels, the model not only degrades its generalization performance but also declines its ability to extract features, making the feature manifold more complex." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.445, + 0.473, + 0.688 + ], + "angle": 0, + "content": "Figure 1 shows that the learned feature manifolds are complex due to a degradation of generalization performance. It presents t-SNE [60] visualization for DivideMix [31], SSR [15]. Figures 1a and 1b display features of training samples extracted by DivideMix with golden labels and predictions, respectively. In DivideMix, a considerable number of samples from different classes exist in a single cluster, and the model tends to predict them with the same label, incorrectly. In Fig. 1c and 1d, SSR shows better results compared to DivideMix, but clusters have more complex forms. Furthermore, SSR incorrectly predicts some samples, and it seems that classes are not separable. They made efforts to improve generalization by incorporating additional objectives, such as consistency regularization [15] and unsupervised loss [17, 31, 75], but still demonstrate poor generalization performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.473, + 0.903 + ], + "angle": 0, + "content": "It is a fact that deep learning models trained with all cleanly labeled samples exhibit good generalization behavior [44], and their feature distributions are well-discriminated by class. These well-generalized models have preserved the following structural characteristics: 1) When two samples are similar, it is highly probable that they share the same label. 2) If certain samples form a cluster, they are likely to have the same label. These are also consistent with the smoothness/cluster assumptions [4, 61, 76] in the context of semi-supervised learning. We aim to develop a method for training a LNL model by consider the characteristics of well-generalized models. In order to incorporate the characteristics, we aim to extract structural information based on the distribution of the data and directly integrate it" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.093, + 0.668, + 0.107 + ], + "angle": 0, + "content": "into the training process." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.108, + 0.892, + 0.303 + ], + "angle": 0, + "content": "In this paper, we present a simple approach to enhance learning with noisy labels by incorporating additional distribution information, structural labels. If a model preserves the structural assumption, it can avoid overfitting to noisy labels and achieve better generalized. By extracting the structural information of data and integrating it into model training, we can efficiently train models with minimized bias towards noisy samples. To extract structural labels, we estimate the data distribution based on Reverse k-Nearest Neighbor (Reverse k-NN) [57]. And then, the structural labels are learned with cross-entropy based on strong augmentation [10] and mixup [73] methods, which help to avoid overfitting noisy samples." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.304, + 0.892, + 0.408 + ], + "angle": 0, + "content": "To verify our proposed method, we conduct experiments on IDN and real-world noisy datasets including CIFAR10 and CIFAR100 with IDN [66], CIFAR-N [63], Animal-10N [53], Red Mini-Imagenet from CNWL [24], Mini-WebVision [35], andImagenet ILSVRC12 [11]. Our method shows the state-of-the-art performance on various datasets." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.422, + 0.642, + 0.438 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.448, + 0.892, + 0.614 + ], + "angle": 0, + "content": "Deep neural networks (DNNs) tend to overfit to label datasets so that they also overfit to noisy label samples and it leads to degraded performance. Many studies have been conducted to learn datasets with noisy labels. To prevent overfitting to noisy labels and learn effectively from datasets with noisy labels, early studies utilized a given small set of clean samples and relabeled noisy samples based on their modeling [5, 30, 36, 59, 62, 67]. Subsequently, instead of using a given small set of clean samples, several studies focus to distinguish clean samples from the given noisy datasets [1, 15, 17, 26, 31, 51, 58, 75]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.615, + 0.892, + 0.795 + ], + "angle": 0, + "content": "These methods rely on DNNs initially learn from cleanly labeled samples with simple patterns before overfitting to noisy label samples [72], and use the small-loss trick to select clean-label samples [17, 23, 31, 51, 75]. DivideMix [31] treats samples with small losses as labeled samples and the others as unlabeled then trains the model using MixMatch [2], a semi-supervised learning technique. C2D [75] leverages self-supervised models to tackle the instability during the warm-up phase of DivideMix, and InstanceGM [17] proposes a graphical modeling approach to address the more realistic noise, Instance-Dependent Noise (IDN)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Contrary to the loss-based approaches, some methods utilize the model's feature representation [15, 34, 64, 71]. TopoFilter [64] proposes a label noise filtering strategy based on spatial topological patterns, and SSR [15] leverages the model's high-confident predictions for relabeling samples and employs a k-NN classifier [9] within the feature representation space for selecting clean samples." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.958 + ], + "angle": 0, + "content": "27611" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.168 + ], + "angle": 0, + "content": "In conclusion, recent LNL methods mainly focus on relabeling and selecting based on their own predictions. However, it is challenging to expect good generalization performance due to the excessive reliance on the predictions of a model that may have errors." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.179, + 0.251, + 0.196 + ], + "angle": 0, + "content": "3. Proposed Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.204, + 0.469, + 0.324 + ], + "angle": 0, + "content": "Since existing methods heavily depend on uncertain models' predictions, they struggle to form good representations and do not preserve structural information. Wellgeneralized models should preserve the assumption that closer features are likely to be located on the same manifold and have the same label. Therefore, it is necessary not only to get accurate predictions from the model but also to consider the distribution of features." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.326, + 0.47, + 0.537 + ], + "angle": 0, + "content": "In this section, we propose Learning with Structural Label (LSL), a new approach for learning structural information in LNLs. To learn structural information, we estimate the data distribution based on the Reverse k-NN algorithm, which is less influenced by outlier samples compared to k-NN [21, 49], and calculate the probability of belonging to a class distribution. Then, we extract structural labels \\( l_{st} \\) from the estimated distribution for all samples and train the model using a strong augmentation [10] and mixup [73] strategy. In contrast to traditional relabeling methods, which depend on uncertain models' predictions learned from selected samples with simple patterns, our approach considers the feature distribution for learning on all samples, not only selected samples." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.544, + 0.431, + 0.559 + ], + "angle": 0, + "content": "3.1. Structural Labels based on Reverse k-NN" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.567, + 0.469, + 0.718 + ], + "angle": 0, + "content": "In order to obtain more reliable information from noisy predictions of the model, we define the structural labels, \\( l_{st} \\), which are the soft labels of each sample based on sample distributions. We first obtain class prediction for each sample from the model, and estimate the distribution of samples predicted as class \\( c \\). We estimate the probability of \\( x \\) given \\( c \\), \\( P(x|c) \\), based on the similarity of feature representations and reverse k-NN. We emit \\( k \\) arrows from each sample predicted as class \\( c \\) to its \\( k \\) nearest neighbors including itself. For a sample \\( x \\), \\( P(x|c) \\) can be approximated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.184, + 0.725, + 0.469, + 0.759 + ], + "angle": 0, + "content": "\\[\nP (x \\mid c) = \\frac {\\# \\text {o f A r r o w s} _ {x , c}}{k \\cdot | X ^ {c} |} \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.469, + 0.87 + ], + "angle": 0, + "content": "where \\(\\#\\) of \\(\\operatorname{Arrows}_{x,c}\\) is the total number of arrows received by \\(x\\) from samples predicted as \\(c\\), and \\(|X^c|\\) is the total number of samples predicted as \\(c\\). If \\(x\\) exists in the region where \\(c\\) class samples densely exist, it may receive more arrows, and vice versa. Consequently, when divided by the total number of arrows from \\(c\\) class samples, it is an approximation for \\(P(x|c)\\)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.469, + 0.902 + ], + "angle": 0, + "content": "Figure 2 shows estimation examples of 2-d Gaussian and Moon data [47]. Figures 2a and 2c show distributions by" + }, + { + "type": "image", + "bbox": [ + 0.525, + 0.093, + 0.688, + 0.193 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.534, + 0.197, + 0.677, + 0.222 + ], + "angle": 0, + "content": "(a) Gaussian modeling for Gaussian samples" + }, + { + "type": "image", + "bbox": [ + 0.708, + 0.092, + 0.871, + 0.193 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.709, + 0.197, + 0.869, + 0.222 + ], + "angle": 0, + "content": "(b) Modeling based on reverse k-NN for Gaussian samples" + }, + { + "type": "image", + "bbox": [ + 0.525, + 0.226, + 0.688, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.534, + 0.33, + 0.676, + 0.354 + ], + "angle": 0, + "content": "(c) Gaussian modeling for Moon dataset" + }, + { + "type": "image", + "bbox": [ + 0.709, + 0.224, + 0.871, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.709, + 0.33, + 0.869, + 0.354 + ], + "angle": 0, + "content": "(d) Modeling based on reverse k-NN for Moon dataset" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.367, + 0.892, + 0.464 + ], + "angle": 0, + "content": "Figure 2. Comparison of distributions between Gaussian modeling and reverse k-NN modeling in 2-D Gaussian dataset and Moon dataset. Figure 2a shows the Gaussian modeling effectively estimates distribution for Gaussian samples. However, the Gaussian modeling fails to fit the distribution of the Moon dataset in Fig. 2c. Figure 2b and Fig. 2d show Reverse k-NN effectively approximates the data distribution for both Gaussian and Moon datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.488, + 0.891, + 0.607 + ], + "angle": 0, + "content": "Gaussian modeling, and 2b and 2d show distributions by our modeling based on reverse k-NN. The Gaussian modeling can efficiently estimates the distributions, but it is hard to accurately model complex data distributions like the Moon dataset. In contrast, the distribution estimation based on reverse k-NN effectively approximates not only the simple distribution, Gaussian, but also the complex data distribution, Moon dataset." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.609, + 0.891, + 0.654 + ], + "angle": 0, + "content": "Based on the feature distribution, we define the structural label of \\( x \\), which is the soft label representing the probability of \\( c \\) given \\( x \\):" + }, + { + "type": "equation", + "bbox": [ + 0.593, + 0.66, + 0.891, + 0.695 + ], + "angle": 0, + "content": "\\[\nP (c | x) = \\frac {P (x | c) P (c)}{\\sum_ {c \\in C} P (x | c) P (c)}. \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.702, + 0.89, + 0.744 + ], + "angle": 0, + "content": "The prior \\( P(c) \\) represents the probability of observing class \\( c \\), which can be determined from the number of samples in each class:" + }, + { + "type": "equation", + "bbox": [ + 0.625, + 0.742, + 0.891, + 0.779 + ], + "angle": 0, + "content": "\\[\nP (c) = \\frac {\\left| X ^ {c} \\right|}{\\sum_ {c = 1} ^ {C} \\left| X ^ {c} \\right|}. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.781, + 0.801, + 0.796 + ], + "angle": 0, + "content": "Then, Eq. (2) can be reformulated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.594, + 0.802, + 0.891, + 0.839 + ], + "angle": 0, + "content": "\\[\nP (c | x) = \\frac {P (x | c) \\left| X ^ {c} \\right|}{\\sum_ {c = 1} ^ {C} P (x | c) \\left| X ^ {c} \\right|}. \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.845, + 0.885, + 0.861 + ], + "angle": 0, + "content": "From Eqs. (1) and (4), \\( P(c|x) \\) is approximated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.582, + 0.867, + 0.891, + 0.905 + ], + "angle": 0, + "content": "\\[\nP (c | x) = \\frac {\\# \\text {o f A r r o w s} _ {x , c}}{\\sum_ {c = 1} ^ {C} \\# \\text {o f A r r o w s} _ {x , c}}. \\tag {5}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27612" + } + ], + [ + { + "type": "code_caption", + "bbox": [ + 0.084, + 0.096, + 0.429, + 0.123 + ], + "angle": 0, + "content": "Algorithm 1: Extracting Structural Labels based on reverse k-NN distribution estimation" + }, + { + "type": "algorithm", + "bbox": [ + 0.078, + 0.125, + 0.493, + 0.401 + ], + "angle": 0, + "content": "Input : model encoder \\(\\theta\\) training dataset \\(\\mathcal{X},\\mathcal{V} = \\{(x_i,y_i^r)_{i = 1}^N\\}\\) Parameter: number of reverse nearest neighbors \\(k_{st}\\) Output : structural labels by \\(st\\mathcal{Y}^{st} = \\{(y^{st})_{i = 1}^N\\}\\) \n1 T = torch.zeros[N, K] \n2 # \\(K\\) is the number of classes \n3 #T indicates edge count table \n4 \\(\\mathcal{F} = \\mathrm{Normalize}(\\theta (\\mathcal{X}))\\) #Normalize all features \n5 for \\(i\\gets 1\\) to \\(N\\) do \n6 score \\(=\\) Cosine \\((f_i,\\mathcal{F})\\) indices \\(=\\) score.topk \\((k_{st})\\) \n8 # Emit k edges to \\(k_{st}\\) nearest neighbors \n9 T [indices, \\(y_i^r ] + = 1\\) \n10 # Propagate its label to k nearest neighbors \n11 end \n12 \\(\\mathcal{V}^{st} = \\mathrm{T} / \\mathrm{T}.\\mathrm{sum}(\\mathrm{dim} = 1\\) ,keepdim=True) \n13 # Aggregate from received labels and normalize these labels \n14 return \\(\\mathcal{V}^{st}\\)" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.435, + 0.474, + 0.614 + ], + "angle": 0, + "content": "Since \\( P(c|x) \\) is estimated from noisy prediction of the model, it can be affected by wrong predictions. However, if we assume that the uniform noise over the sample space, it is clear that the probability is free from the uniform noise. Even though the noise is not uniform, it can be easily smoothed if we use enough large \\( k_{st} \\). However, if \\( k_{st} \\) is too large, the number of arrows received from samples of classes other than \\( c \\) will increase. It can lead to over-smoothing of \\( l_{st} \\) and lose the structural information. To avoid over-dilution of structural information, we need to choose an appropriate value of \\( k_{st} \\), and it is discussed in Sec. 5.2." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.617, + 0.47, + 0.678 + ], + "angle": 0, + "content": "In conclusion, the structural label of \\( x \\) estimated by reverse k-NN effectively reflects the distribution information of the samples in noisy data environments. Algorithm 1 shows how to obtain the structural labels." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.69, + 0.414, + 0.708 + ], + "angle": 0, + "content": "3.2. Learning with Structural Labels (LSL)" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.714, + 0.47, + 0.79 + ], + "angle": 0, + "content": "To learn structural information, we utilize structural labels \\( l_{st} \\) to effectively reflect feature distribution with SSR [15]. It is one of the LNL methods that considers feature representation. The procedure for the proposed method is described in Algorithm 2." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.792, + 0.47, + 0.837 + ], + "angle": 0, + "content": "In Algorithm 2, line 2 indicates relabeling based on model prediction with Eq. (6), and line 3 indicates sample selection based on k-NN." + }, + { + "type": "equation", + "bbox": [ + 0.089, + 0.864, + 0.47, + 0.905 + ], + "angle": 0, + "content": "\\[\ny _ {i} ^ {r} = \\left\\{ \\begin{array}{l l} \\operatorname {a r g m a x} _ {l} f (\\alpha (x _ {i})), & \\text {i f} \\max _ {l} f (\\alpha (x _ {i})) > \\tau_ {r} \\\\ y _ {i}, & \\text {o t h e r w i s e} \\end{array} \\right. \\tag {6}\n\\]" + }, + { + "type": "code_caption", + "bbox": [ + 0.508, + 0.095, + 0.853, + 0.125 + ], + "angle": 0, + "content": "Algorithm 2: Learning with Structural Labels (LSL)" + }, + { + "type": "algorithm", + "bbox": [ + 0.501, + 0.126, + 0.892, + 0.576 + ], + "angle": 0, + "content": "Input : model encoder \\(\\theta\\) multi-layer neural network \\(\\phi\\) training dataset \\((\\mathcal{X},\\mathcal{Y}) = \\{(x_i,y_i)\\}_{i = 1}^N\\) \nParameter: sample relabelling threshold \\(\\tau_r\\) feature consistency loss weight \\(\\lambda_{fc}\\) structural loss weight \\(\\lambda_{st}\\) \n1 while eMethodIDN - CIFAR10IDN - CIFAR1000.200.300.400.450.500.200.300.400.450.50CE [70]75.8169.1562.4551.7239.4230.4224.1521.4515.2314.42Mixup [73]73.1772.0261.5656.4548.9532.9229.7625.9223.1321.31Forward [46]74.6469.7560.2148.8146.2736.3833.1726.7521.9319.27Reweight [39]76.2370.1262.5851.5445.4636.7331.9128.3924.1220.23Decoupling [43]78.7175.1761.7358.6150.4336.5330.9327.8523.8119.59Co-teaching [19]80.9678.5673.4171.6045.9237.9633.4328.0425.6023.97MentorNet [23]81.0377.2271.8366.1847.8938.9134.2331.8927.5324.15DivideMix [31]94.8094.6094.5394.0893.0477.0776.3370.8057.7858.61SSR* [15]96.4996.5296.3395.8994.0678.8478.6076.9574.9872.83InstanceGM [17]96.6896.5296.3696.1595.9079.6979.2178.4777.4977.19LSL (Ours)97.1396.8596.5396.5895.8180.9479.9078.6078.0877.95" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.362, + 0.893, + 0.406 + ], + "angle": 0, + "content": "Table 1. Test accuracy (%) of different methods on CIFAR10-IDN and CIFAR100-IDN [66] under various IDN noise rates. Most of the experimental results are extracted from state-of-the-art methods [15, 17, 31]. Bold values indicate the best performances. The reproduced result is marked with \\(*\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.431, + 0.471, + 0.492 + ], + "angle": 0, + "content": "We describe these datasets in Sec. 4.1 and provide the implementation details in Sec. 4.2. In Sec. 4.3, we compare our approach with state-of-the-art models in various IDN benchmarks and real-world noisy datasets." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.5, + 0.182, + 0.515 + ], + "angle": 0, + "content": "4.1. Datasets" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.523, + 0.47, + 0.644 + ], + "angle": 0, + "content": "CIFAR10 and CIFAR100 both datasets [27] consist of 50,000 training images and 10,000 testing images, and each image has dimensions of \\(32 \\times 32 \\times 3\\). The CIFAR10 has 10 classes, while CIFAR100 has 100 classes. To conduct experiments in the instance-dependent noise (IDN) environment, we obtained noisy labels of the CIFAR10 and CIFAR100 datasets according to [66]. We set the noise rate for IDN settings at values of 0.20, 0.30, 0.40, 0.45, and 0.50." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.644, + 0.471, + 0.765 + ], + "angle": 0, + "content": "The CIFAR10N and CIFAR100N datasets [63] consist of human-annotated noisy labels obtained from Amazon Mechanical Turk. CIFAR10N and CIFAR100N datasets include 5 and 2 noisy label types, respectively. In this paper, we evaluate the settings with the highest noise rates, specifically CIFAR10N Worst (CIFAR10N-W, a noise rate of \\(40.21\\%\\)) and CIFAR100N Fine (CIFAR100N-F, a noise rate of \\(40.20\\%\\))." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.47, + 0.84 + ], + "angle": 0, + "content": "Animal-10N dataset [53] consists of 50,000 training images and 10,000 test images, with each image having a resolution of \\(64 \\times 64 \\times 3\\). The dataset has 10 animal categories, including 5 pairs of animals with similar appearances and the estimated noise rate of the dataset is \\(8\\%\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Red Mini-Imagenet from CNWL [24] dataset is annotated by 3-5 labeling professionals using Google Cloud Data Labeling Service. The dataset comprises 600 training samples for each of its 100 classes. While the origi" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.431, + 0.893, + 0.505 + ], + "angle": 0, + "content": "nal image size is \\(84 \\times 84 \\times 3\\), we resize it to \\(32 \\times 32 \\times 3\\) for a fair comparison with other experiments [17, 68]. It supports noise ratios ranging from \\(0\\%\\) to \\(80\\%\\), and we validate our model on training data with noise ratios of \\(20\\%\\), \\(40\\%\\), \\(60\\%\\), \\(80\\%\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.506, + 0.894, + 0.629 + ], + "angle": 0, + "content": "WebVision [35] is a large-scale dataset with 2.4 million images collected from the web across 1k categories, and Mini-WebVision is a dataset composed of the initial 50 categories from the WebVision dataset. Mini-WebVision contains 65,994 training images, and we resized the images to \\(256 \\times 256 \\times 3\\). For validation, we use not only Mini-WebVision but also ImageNet ILSVRC12 dataset [11], which shares the same subset of categories." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.636, + 0.719, + 0.652 + ], + "angle": 0, + "content": "4.2. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.893, + 0.719 + ], + "angle": 0, + "content": "All experiments are conducted using the PyTorch framework on an NVIDIA RTX 3090Ti GPU. Unless otherwise specified, all hyperparameter values mentioned below are followed from SSR [15]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.901 + ], + "angle": 0, + "content": "For CIFAR10 and CIFAR100 with IDN datasets, we use a PreAct-ResNet-18 [20] following DivideMix [31]. We use SGD optimizer for 300 epochs with a momentum of 0.9, a weight decay of 5e-4, an initial learning rate of 0.02, and the cosine annealing function as a learning scheduler. We set a relabeling threshold, \\(\\tau_r\\), from 0.55 to 0.8 for CIFAR10 and CIFAR100 with IDN as the noise ratio decreases, and the batch size to 128. For CIFAR-N datasets, we set \\(\\tau_r\\) to 0.8 for CIFAR10-N and CIFAR100-N, and all other details are consistent with CIFAR10/100 with IDN configurations. For Red Mini-Imagenet from CNWL [24], we set \\(\\tau_r\\) to 0.8, and all other details are consistent with CIFAR10/100 with" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27614" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.082, + 0.089, + 0.462, + 0.254 + ], + "angle": 0, + "content": "
MethodCIFAR10N-WCIFAR100N-F
CE [70]77.6955.50
CAL [77]85.3661.73
ELR [37]91.0966.72
SOP+ [38]93.2467.81
DivideMix [31]92.5671.13
SSR* [15]93.5071.99
LSL (Ours)94.5774.46
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.263, + 0.47, + 0.293 + ], + "angle": 0, + "content": "Table 2. Test accuracy \\((\\%)\\) of CIFAR-N [63]. Bold values indicate the best performances and the reproduced result is marked with \\(*\\)" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.319, + 0.214, + 0.335 + ], + "angle": 0, + "content": "IDN configurations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.335, + 0.469, + 0.426 + ], + "angle": 0, + "content": "For Animal-10N, we use a VGG-19 with batch-normalization [55]. We use SGD optimizer for 150 epochs with a momentum of 0.9, a weight decay of 5e-4, an initial learning rate of 0.02, and the step function as a learning scheduler with a reduction factor of 10 and a step size of 50 epochs. We set \\(\\tau_r\\) to 0.8, and the batch size of 128." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.427, + 0.469, + 0.517 + ], + "angle": 0, + "content": "For Mini-WebVision, we use an InceptionResNetv2 [56] following [31]. We use SGD optimizer for 150 epochs with a momentum of 0.9, a weight decay of 1e-4, an initial learning rate of 0.01, and the step function as a learning scheduler with a reduction factor of 10 and a step size of 50 epochs. We set \\(\\tau_r\\) to 0.8, and the batch size to 64." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.518, + 0.469, + 0.607 + ], + "angle": 0, + "content": "For mixup interpolation, we set both \\(\\alpha\\) and \\(\\beta\\) to 4 for beta mixture on IDN datasets, CIFAR-N and Red MiniImageNet, and to 0.5 on other datasets. We set the consistency loss weight \\(\\lambda_{fc}\\) and the structural loss weight \\(\\lambda_{st}\\) to 1.0, and the number of reverse nearest neighbors \\(k_{st}\\) to 20." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.62, + 0.28, + 0.636 + ], + "angle": 0, + "content": "4.3. Experimental Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.643, + 0.469, + 0.764 + ], + "angle": 0, + "content": "The results for CIFAR10 and CIFAR100 with IDN benchmark datasets are shown in Tab. 1. Our proposed method exhibits the best performance in all cases except for CIFAR10 with an IDN noise ratio of 0.5. Even in CIFAR10 with an IDN noise ratio of 0.5, our method demonstrates comparable performance to the baseline, within a margin of \\(0.1\\%\\) points. These results demonstrate that our method is consistently effective across various IDN environments." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Tables 2 to 5 show the results for real-world noisy datasets. The performance on CIFAR10N-W and CIFAR100N-F is presented in Tab. 2. For both datasets, which have a noise rate of approximately \\(40\\%\\), our proposed method shows significant improvements by \\(1.1\\%\\) and \\(3.4\\%\\), respectively, compared to the baseline methods. These results confirm the effectiveness of our approach, not only with synthetic IDN noise but also with human-annotated real-world noisy labels." + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.089, + 0.885, + 0.293 + ], + "angle": 0, + "content": "
MethodNoise rate
0.20.40.60.8
CE [70]47.3642.7037.3029.79
Mixup [73]49.1046.4040.5833.58
Mentormix [24]51.0247.1443.8033.46
FaMUS [68]51.4248.0645.1035.50
DivideMix [31]50.9646.7243.1434.50
SSR* [15]52.1848.9642.4233.20
InstanceGM [17]58.3852.2447.9639.62
LSL (Ours)54.6849.8045.4636.78
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.304, + 0.892, + 0.345 + ], + "angle": 0, + "content": "Table 3. Test accuracy \\((\\%)\\) of Red Mini-Imagenet (CNWL) [24]. Bold values indicate the best performances and the reproduced result is marked with \\(*\\)" + }, + { + "type": "table", + "bbox": [ + 0.541, + 0.38, + 0.849, + 0.584 + ], + "angle": 0, + "content": "
MethodTest Accuracy (%)
CE [70]79.4
Nested-Dropout [6]81.8
CE+Dropout [6]81.3
SELFIE [54]81.3
PLC [74]83.4
Nested-CE [6]84.1
SSR [15]88.5
InstanceGM [17]84.6
LSL (Ours)89.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.594, + 0.892, + 0.622 + ], + "angle": 0, + "content": "Table 4. Test accuracy \\((\\%)\\) of ANIMAL-10N [53]. Bold values indicate the best performances." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.669, + 0.892, + 0.715 + ], + "angle": 0, + "content": "The experimental results on the Red Mini-ImageNet from CNWL dataset are presented in Tab. 3. Our proposed method demonstrates the second-best performances." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.725, + 0.892, + 0.801 + ], + "angle": 0, + "content": "Animal-10N is a challenging dataset consisting of 5 pairs of easily confused animals and has a relatively low noise ratio of approximately \\(8\\%\\) compared to other real-world noisy labels. For this dataset, our method outperforms other approaches, as shown in Tab. 4." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.81, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Lastly, Tab. 5 shows performance on the large-scale WebVision and ImageNet datasets. Our method achieves the best performance on all cases in Top1 accuracy. Especially, our proposed method shows best performance on the Top1 accuracy of ImageNet, and it shows that our method generalizes very well to other datasets." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27615" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.08, + 0.089, + 0.473, + 0.332 + ], + "angle": 0, + "content": "
MethodWebVisionIISVRC2012
Top-1Top-5Top-1Top-5
Co-teaching [19]63.5885.2061.4884.70
ELR+ [37]77.7891.6870.2989.76
NGC [65]79.1691.8474.4491.04
LongReMix [8]78.9292.32--
RRL [32]76.3091.5073.3091.20
Sel-CL+ [33]79.9692.6476.8493.04
TCL [22]79.1092.3075.4092.40
DivideMix [31]77.3291.6475.2090.84
SSR [15]80.9292.8075.7691.76
LSL (Ours)81.4093.0077.0091.84
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.342, + 0.47, + 0.371 + ], + "angle": 0, + "content": "Table 5. Test accuracy \\((\\%)\\) of WebVision [35] and IISVRC2012 [11]. Bold values indicate the best performances." + }, + { + "type": "image", + "bbox": [ + 0.095, + 0.392, + 0.462, + 0.559 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.578, + 0.47, + 0.634 + ], + "angle": 0, + "content": "Figure 3. Comparison of training accuracy. Our proposed method outperforms existing approaches. Through the proposed structural labels based on the feature distribution, the model can effectively leverage the entire training dataset." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.66, + 0.241, + 0.675 + ], + "angle": 0, + "content": "5. Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.685, + 0.47, + 0.732 + ], + "angle": 0, + "content": "In this section, we analyze the effectiveness of our proposed method and introduce its details. All ablation studies are conducted on the CIFAR10 with IDN dataset [66]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.741, + 0.431, + 0.758 + ], + "angle": 0, + "content": "5.1. Effectiveness of learning structural labels" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Figure 3 shows the accuracy of training data, the agreement between the model's predictions and the original clean labels as training progresses. The original clean labels are used only for evaluation, not for training. In LNL, the accuracy typically does not reach \\(100\\%\\) by the end of training as models cannot fully generalize from noisy training data. Our proposed method shows a higher training accuracy compared to other approaches such as DivideMix [31] and SSR [15]. Existing methods are difficult to accurately" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.094, + 0.889, + 0.288 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.615, + 0.291, + 0.78, + 0.306 + ], + "angle": 0, + "content": "(a) Histogram of logits by SSR" + }, + { + "type": "image", + "bbox": [ + 0.506, + 0.319, + 0.889, + 0.514 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.571, + 0.518, + 0.824, + 0.531 + ], + "angle": 0, + "content": "(b) Histogram of logits by the proposed method" + }, + { + "type": "image_caption", + "bbox": [ + 0.5, + 0.542, + 0.892, + 0.571 + ], + "angle": 0, + "content": "Figure 4. Histogram of Logits for the Training Dataset of CIFAR10 with IDN at noise rate 0.50." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.892, + 0.688 + ], + "angle": 0, + "content": "relabel and select more samples with complex patterns, so they only learn a fraction of the training data and struggle to generalize. In contrast, our proposed method, which utilizes structural labels \\( l_{st} \\) based on feature distribution, effectively leverages more samples and achieves better generalization performance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.893, + 0.901 + ], + "angle": 0, + "content": "Figure 4 shows the distribution of logits for SSR and our proposed method on CIFAR10 with IDN at noise rate 0.50. In SSR, the total number of misclassified samples is 3238. Among them, 1248 samples are misclassified as given noisy labels, accounting for 0.39 percent of the total misclassified samples. On the other hand, in our method, the total number of misclassified samples is 2107. Among them, the number of misclassified samples as given noisy labels is 646. The percentage of them is 0.31. Thus, our proposed method exhibits fewer total misclassified samples and a lower percentage of misclassified samples as given noisy labels. Also, The logit distribution of misclassified samples with given noise (red) is skewed to the right relative to the logit distribution of misclassified samples (orange) in SSR, whereas" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "27616" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.088, + 0.094, + 0.457, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.128, + 0.211, + 0.42, + 0.224 + ], + "angle": 0, + "content": "(a) Accuracy with respect to different values of the \\(k_{st}\\)." + }, + { + "type": "image", + "bbox": [ + 0.088, + 0.239, + 0.456, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.128, + 0.355, + 0.42, + 0.368 + ], + "angle": 0, + "content": "(b) Accuracy with respect to different values of the \\(\\lambda_{st}\\)." + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.38, + 0.47, + 0.422 + ], + "angle": 0, + "content": "Figure 5. Accuracy with respect to hyperparameters on CIFAR10 with IDN at noise rate 0.20. The red dashed line represents the performance of the state-of-the-art (SOTA)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.455, + 0.47, + 0.501 + ], + "angle": 0, + "content": "ours is not. As these statistics demonstrate, our method avoids overfitting to given noisy labels and achieves better generalization performance." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.52, + 0.251, + 0.537 + ], + "angle": 0, + "content": "5.2. Hyperparameters" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.547, + 0.469, + 0.607 + ], + "angle": 0, + "content": "To validate the sensitivity of the hyperparameters, experiments are conducted using various values of \\( k_{st} \\) for reverse k-NN and the weight of the structural loss, \\( \\lambda_{st} \\). The results are shown in Fig. 5." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.611, + 0.469, + 0.807 + ], + "angle": 0, + "content": "Figure 5a shows the model's accuracy with respect to different values of the hyperparameter \\( k_{st} \\). Based on the feature distribution, the model can be trained by smoothing over the correct answer labels of its neighboring samples in a noisy environment. However, if \\( k_{st} \\) is too small, our method cannot fully incorporate the feature distribution. On the contrary, if \\( k_{st} \\) is too large, the number of arrows received from samples of classes other than \\( c \\) will increase, and then structural labels \\( l_{st} \\) are over-smoothed. To avoid over-dilution of structural information, we need to choose an appropriate value of \\( k_{st} \\). Therefore, we experiment with various values to determine the optimal \\( k_{st} \\). Our proposed model shows the best performances at a \\( k_{st} \\) of 20." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Figure 5b shows the performance of our proposed method with respect to value of \\(\\lambda_{st}\\), the weight of the structural loss. When applying structural loss, there is a clear performance improvement compared to the case where it is not applied, \\(\\lambda_{st}\\) is 0. Additionally, it demonstrates stable, improved performance regardless of changes in the value." + }, + { + "type": "image", + "bbox": [ + 0.511, + 0.091, + 0.696, + 0.234 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.592, + 0.239, + 0.61, + 0.251 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.699, + 0.091, + 0.885, + 0.234 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.781, + 0.239, + 0.799, + 0.25 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.263, + 0.892, + 0.332 + ], + "angle": 0, + "content": "Figure 6. Comparison of t-SNE visualization on CIFAR10 with IDN at noise rate 0.50. (a) Ours on training samples with golden labels. (b) Ours on training samples with predicted labels. There are only smaller amounts of wrongly trained samples than DivideMix and SSR." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.36, + 0.719, + 0.375 + ], + "angle": 0, + "content": "5.3. The t-SNE visualization" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.385, + 0.892, + 0.476 + ], + "angle": 0, + "content": "Figure 6 shows t-SNE visualization of features for the proposed method. Unlike DivideMix and SSR in Fig. 1, our method not only learned a relatively simple manifold but also exhibits well-separated clusters, each predominantly representing one class. This confirms that our method demonstrates superior generalization performance." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.492, + 0.619, + 0.508 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.518, + 0.892, + 0.7 + ], + "angle": 0, + "content": "In this paper, we explored the generalization problem in learning with noisy labels (LNL) and proposed a simple yet effective approach to address these challenges. While existing LNL methods, our proposed method employed a reverse k-NN to leverage structural information based on feature distribution. And by learning the structural information, the model had a better feature manifold and robustness against overfitting to noisy labels, thus achieving better generalization performance. The proposed method demonstrated outperformed performance across various datasets including CIFAR10 and CIFAR100 with IDN, CIFAR-N, Animal10N, Red Mini-Imagenet, Mini-WebVision, and ImageNet." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.72, + 0.892, + 0.818 + ], + "angle": 0, + "content": "Acknowledgments. This work was partly supported by Institute of Information & communications Technology Planning & Evaluation (IITP) grant funded by the Korea government (MSIT) (No.2019-0-00421, AI Graduate School Support Program, Sungkyunkwan University, and No.RS-2023-00228970, Development of Flexible SW-HW Conjunctive Solution for On-edge Self-supervised Learning)." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.848, + 0.597, + 0.864 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.508, + 0.873, + 0.892, + 0.901 + ], + "angle": 0, + "content": "[1] Eric Arazo, Diego Ortego, Paul Albert, Noel O'Connor, and Kevin McGuinness. Unsupervised label noise modeling" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27617" + } + ], + [ + { + "type": "ref_text", + "bbox": [ + 0.108, + 0.092, + 0.469, + 0.12 + ], + "angle": 0, + "content": "and loss correction. 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To reduce labeling costs for large-scale datasets, semi-automated and crowdsourcing labeling methods are developed, but their labels are inevitably noisy. Learning with Noisy Labels (LNL) approaches aim to train DNNs despite the presence of noisy labels. These approaches utilize the memorization effect to select correct labels and refine noisy ones, which are then used for subsequent training. However, these methods encounter a significant decrease in the model's generalization performance due to the inevitably existing noise labels. To overcome this limitation, we propose a new approach to enhance learning with noisy labels by incorporating additional distribution information—structural labels. In order to leverage additional distribution information for generalization, we employ a reverse $k$ -NN, which helps the model in achieving a better feature manifold and mitigating overfitting to noisy labels. The proposed method shows outperformed performance in multiple benchmark datasets with IDN and real-world noisy datasets. + +# 1. Introduction + +Deep neural networks (DNNs) have achieved high performance in various domains such as computer vision [13, 14, 20, 25, 29, 52], natural language processing [3, 7, 12, 40], and signal processing [18, 48, 50] across diverse tasks. To achieve the high performance of DNNs, well-curated large-scale datasets are necessary. However, labeling large-scale data requires a significant cost. In order to reduce these labeling costs, semi-automated [35, 42] and crowdsourcing methods [28] are used, but their labels are inevitably noisy. When trained on data with noisy labels, DNNs suffer degraded performance because they tend to easily overfit noisy labeled samples [72]. To address these issues, methods for learning with noisy labels (LNL), which aim to ef + +![](images/f1904d0b8e89ece55e0d0e8ec2cc1e55b212a5adbe258a2f3166020ba0cfc16a.jpg) + +![](images/30cbf27f1847dcd27d77d62db50eafecfcd74390bd66795409f878429b1e3c9d.jpg) + +![](images/e1e4136705dd34f465c9f7739e1fbf43b1b9097fbb09b5ff40871de7aa8dd0a2.jpg) +(a) +(c) +Figure 1. Comparison of t-SNE visualization on CIFAR10 IDN at noise rate 0.50. (a) DivideMix on training samples with golden labels. (b) DivdieMix on training samples with predicted labels. (c) SSR on training samples with golden labels. (d) SSR on training samples with predicted labels. The black-outlined box represents areas where samples overlap, similar samples are learned as different classes, or clusters are not separable. + +![](images/2a8befe5fa23211a8b020303168d0178dbf6239f4efc8919f1b725f68f533e53.jpg) +(b) +(d) + +fectively train DNN models in environments with noisy labeled samples, have been proposed [1, 15, 17, 23, 31, 41, 45, 75]. + +Most methods for learning with noisy labels (LNL) are based on the fact that DNNs tend to learn from clean samples with simple patterns earlier than from wrong-labeled samples [1, 69]. Based on the observation, most approaches adopted an iterative process. Initially, they trained the model with the entire dataset. The model would learned some patterns from clean samples rather than noisy samples. Then, they selected confident samples based on the + +output of the trained model, most of which would be clean samples. Subsequently, they retrained the model with the selected samples. They repeat the selection and training. Consequently, the model can avoid noisy samples and focus on clean samples. Previous approaches proposed various clean sample selection methods based on the model prediction, such as the small-loss trick [23] and the k-Nearest Neighbor (k-NN) method [9, 16]. Additionally, relabeling methods are utilized to leverage a larger number of clean samples by modifying model outputs deemed unreliable. These learning strategies performed quite well in a noisy environment, but they still have a critical limitation—they heavily depend on the model's predictions for relabeling and selection. + +Essentially, the models guide themselves based on their own predictions in a noisy environment. If an incorrectly predicted sample is chosen, the model may learn from it in the subsequent training step. Therefore, in this self-guided process, inevitable inaccurate predictions arise from learning based on previous inaccuracies. By learning from these inevitable noisy labels, the model not only degrades its generalization performance but also declines its ability to extract features, making the feature manifold more complex. + +Figure 1 shows that the learned feature manifolds are complex due to a degradation of generalization performance. It presents t-SNE [60] visualization for DivideMix [31], SSR [15]. Figures 1a and 1b display features of training samples extracted by DivideMix with golden labels and predictions, respectively. In DivideMix, a considerable number of samples from different classes exist in a single cluster, and the model tends to predict them with the same label, incorrectly. In Fig. 1c and 1d, SSR shows better results compared to DivideMix, but clusters have more complex forms. Furthermore, SSR incorrectly predicts some samples, and it seems that classes are not separable. They made efforts to improve generalization by incorporating additional objectives, such as consistency regularization [15] and unsupervised loss [17, 31, 75], but still demonstrate poor generalization performance. + +It is a fact that deep learning models trained with all cleanly labeled samples exhibit good generalization behavior [44], and their feature distributions are well-discriminated by class. These well-generalized models have preserved the following structural characteristics: 1) When two samples are similar, it is highly probable that they share the same label. 2) If certain samples form a cluster, they are likely to have the same label. These are also consistent with the smoothness/cluster assumptions [4, 61, 76] in the context of semi-supervised learning. We aim to develop a method for training a LNL model by consider the characteristics of well-generalized models. In order to incorporate the characteristics, we aim to extract structural information based on the distribution of the data and directly integrate it + +into the training process. + +In this paper, we present a simple approach to enhance learning with noisy labels by incorporating additional distribution information, structural labels. If a model preserves the structural assumption, it can avoid overfitting to noisy labels and achieve better generalized. By extracting the structural information of data and integrating it into model training, we can efficiently train models with minimized bias towards noisy samples. To extract structural labels, we estimate the data distribution based on Reverse k-Nearest Neighbor (Reverse k-NN) [57]. And then, the structural labels are learned with cross-entropy based on strong augmentation [10] and mixup [73] methods, which help to avoid overfitting noisy samples. + +To verify our proposed method, we conduct experiments on IDN and real-world noisy datasets including CIFAR10 and CIFAR100 with IDN [66], CIFAR-N [63], Animal-10N [53], Red Mini-Imagenet from CNWL [24], Mini-WebVision [35], andImagenet ILSVRC12 [11]. Our method shows the state-of-the-art performance on various datasets. + +# 2. Related Work + +Deep neural networks (DNNs) tend to overfit to label datasets so that they also overfit to noisy label samples and it leads to degraded performance. Many studies have been conducted to learn datasets with noisy labels. To prevent overfitting to noisy labels and learn effectively from datasets with noisy labels, early studies utilized a given small set of clean samples and relabeled noisy samples based on their modeling [5, 30, 36, 59, 62, 67]. Subsequently, instead of using a given small set of clean samples, several studies focus to distinguish clean samples from the given noisy datasets [1, 15, 17, 26, 31, 51, 58, 75]. + +These methods rely on DNNs initially learn from cleanly labeled samples with simple patterns before overfitting to noisy label samples [72], and use the small-loss trick to select clean-label samples [17, 23, 31, 51, 75]. DivideMix [31] treats samples with small losses as labeled samples and the others as unlabeled then trains the model using MixMatch [2], a semi-supervised learning technique. C2D [75] leverages self-supervised models to tackle the instability during the warm-up phase of DivideMix, and InstanceGM [17] proposes a graphical modeling approach to address the more realistic noise, Instance-Dependent Noise (IDN). + +Contrary to the loss-based approaches, some methods utilize the model's feature representation [15, 34, 64, 71]. TopoFilter [64] proposes a label noise filtering strategy based on spatial topological patterns, and SSR [15] leverages the model's high-confident predictions for relabeling samples and employs a k-NN classifier [9] within the feature representation space for selecting clean samples. + +In conclusion, recent LNL methods mainly focus on relabeling and selecting based on their own predictions. However, it is challenging to expect good generalization performance due to the excessive reliance on the predictions of a model that may have errors. + +# 3. Proposed Method + +Since existing methods heavily depend on uncertain models' predictions, they struggle to form good representations and do not preserve structural information. Wellgeneralized models should preserve the assumption that closer features are likely to be located on the same manifold and have the same label. Therefore, it is necessary not only to get accurate predictions from the model but also to consider the distribution of features. + +In this section, we propose Learning with Structural Label (LSL), a new approach for learning structural information in LNLs. To learn structural information, we estimate the data distribution based on the Reverse k-NN algorithm, which is less influenced by outlier samples compared to k-NN [21, 49], and calculate the probability of belonging to a class distribution. Then, we extract structural labels $l_{st}$ from the estimated distribution for all samples and train the model using a strong augmentation [10] and mixup [73] strategy. In contrast to traditional relabeling methods, which depend on uncertain models' predictions learned from selected samples with simple patterns, our approach considers the feature distribution for learning on all samples, not only selected samples. + +# 3.1. Structural Labels based on Reverse k-NN + +In order to obtain more reliable information from noisy predictions of the model, we define the structural labels, $l_{st}$ , which are the soft labels of each sample based on sample distributions. We first obtain class prediction for each sample from the model, and estimate the distribution of samples predicted as class $c$ . We estimate the probability of $x$ given $c$ , $P(x|c)$ , based on the similarity of feature representations and reverse k-NN. We emit $k$ arrows from each sample predicted as class $c$ to its $k$ nearest neighbors including itself. For a sample $x$ , $P(x|c)$ can be approximated as follows: + +$$ +P (x \mid c) = \frac {\# \text {o f A r r o w s} _ {x , c}}{k \cdot | X ^ {c} |} \tag {1} +$$ + +where $\#$ of $\operatorname{Arrows}_{x,c}$ is the total number of arrows received by $x$ from samples predicted as $c$ , and $|X^c|$ is the total number of samples predicted as $c$ . If $x$ exists in the region where $c$ class samples densely exist, it may receive more arrows, and vice versa. Consequently, when divided by the total number of arrows from $c$ class samples, it is an approximation for $P(x|c)$ . + +Figure 2 shows estimation examples of 2-d Gaussian and Moon data [47]. Figures 2a and 2c show distributions by + +![](images/02cfa054df0ce573ac75f1ed72ea6697726e260433bf7c7c46667d781154aa68.jpg) +(a) Gaussian modeling for Gaussian samples + +![](images/5240b0fa410ea26be34c55149cff2c0ff1ebb2d8034c923364bfbc516f161751.jpg) +(b) Modeling based on reverse k-NN for Gaussian samples + +![](images/c00f286017f081a3154b33733fd00f82e1bcde720f4a4e0418090d0ac58f815c.jpg) +(c) Gaussian modeling for Moon dataset + +![](images/2105415bbd86a229732f4fe0f3b08fe11a1957ee00d5f38ad0d662cf7ef17592.jpg) +(d) Modeling based on reverse k-NN for Moon dataset +Figure 2. Comparison of distributions between Gaussian modeling and reverse k-NN modeling in 2-D Gaussian dataset and Moon dataset. Figure 2a shows the Gaussian modeling effectively estimates distribution for Gaussian samples. However, the Gaussian modeling fails to fit the distribution of the Moon dataset in Fig. 2c. Figure 2b and Fig. 2d show Reverse k-NN effectively approximates the data distribution for both Gaussian and Moon datasets. + +Gaussian modeling, and 2b and 2d show distributions by our modeling based on reverse k-NN. The Gaussian modeling can efficiently estimates the distributions, but it is hard to accurately model complex data distributions like the Moon dataset. In contrast, the distribution estimation based on reverse k-NN effectively approximates not only the simple distribution, Gaussian, but also the complex data distribution, Moon dataset. + +Based on the feature distribution, we define the structural label of $x$ , which is the soft label representing the probability of $c$ given $x$ : + +$$ +P (c | x) = \frac {P (x | c) P (c)}{\sum_ {c \in C} P (x | c) P (c)}. \tag {2} +$$ + +The prior $P(c)$ represents the probability of observing class $c$ , which can be determined from the number of samples in each class: + +$$ +P (c) = \frac {\left| X ^ {c} \right|}{\sum_ {c = 1} ^ {C} \left| X ^ {c} \right|}. \tag {3} +$$ + +Then, Eq. (2) can be reformulated as follows: + +$$ +P (c | x) = \frac {P (x | c) \left| X ^ {c} \right|}{\sum_ {c = 1} ^ {C} P (x | c) \left| X ^ {c} \right|}. \tag {4} +$$ + +From Eqs. (1) and (4), $P(c|x)$ is approximated as follows: + +$$ +P (c | x) = \frac {\# \text {o f A r r o w s} _ {x , c}}{\sum_ {c = 1} ^ {C} \# \text {o f A r r o w s} _ {x , c}}. \tag {5} +$$ + +Algorithm 1: Extracting Structural Labels based on reverse k-NN distribution estimation +Input : model encoder $\theta$ training dataset $\mathcal{X},\mathcal{V} = \{(x_i,y_i^r)_{i = 1}^N\}$ Parameter: number of reverse nearest neighbors $k_{st}$ Output : structural labels by $st\mathcal{Y}^{st} = \{(y^{st})_{i = 1}^N\}$ +1 T = torch.zeros[N, K] +2 # $K$ is the number of classes +3 #T indicates edge count table +4 $\mathcal{F} = \mathrm{Normalize}(\theta (\mathcal{X}))$ #Normalize all features +5 for $i\gets 1$ to $N$ do +6 score $=$ Cosine $(f_i,\mathcal{F})$ indices $=$ score.topk $(k_{st})$ +8 # Emit k edges to $k_{st}$ nearest neighbors +9 T [indices, $y_i^r ] + = 1$ +10 # Propagate its label to k nearest neighbors +11 end +12 $\mathcal{V}^{st} = \mathrm{T} / \mathrm{T}.\mathrm{sum}(\mathrm{dim} = 1$ ,keepdim=True) +13 # Aggregate from received labels and normalize these labels +14 return $\mathcal{V}^{st}$ + +Since $P(c|x)$ is estimated from noisy prediction of the model, it can be affected by wrong predictions. However, if we assume that the uniform noise over the sample space, it is clear that the probability is free from the uniform noise. Even though the noise is not uniform, it can be easily smoothed if we use enough large $k_{st}$ . However, if $k_{st}$ is too large, the number of arrows received from samples of classes other than $c$ will increase. It can lead to over-smoothing of $l_{st}$ and lose the structural information. To avoid over-dilution of structural information, we need to choose an appropriate value of $k_{st}$ , and it is discussed in Sec. 5.2. + +In conclusion, the structural label of $x$ estimated by reverse k-NN effectively reflects the distribution information of the samples in noisy data environments. Algorithm 1 shows how to obtain the structural labels. + +# 3.2. Learning with Structural Labels (LSL) + +To learn structural information, we utilize structural labels $l_{st}$ to effectively reflect feature distribution with SSR [15]. It is one of the LNL methods that considers feature representation. The procedure for the proposed method is described in Algorithm 2. + +In Algorithm 2, line 2 indicates relabeling based on model prediction with Eq. (6), and line 3 indicates sample selection based on k-NN. + +$$ +y _ {i} ^ {r} = \left\{ \begin{array}{l l} \operatorname {a r g m a x} _ {l} f (\alpha (x _ {i})), & \text {i f} \max _ {l} f (\alpha (x _ {i})) > \tau_ {r} \\ y _ {i}, & \text {o t h e r w i s e} \end{array} \right. \tag {6} +$$ + +Algorithm 2: Learning with Structural Labels (LSL) +Input : model encoder $\theta$ multi-layer neural network $\phi$ training dataset $(\mathcal{X},\mathcal{Y}) = \{(x_i,y_i)\}_{i = 1}^N$ +Parameter: sample relabelling threshold $\tau_r$ feature consistency loss weight $\lambda_{fc}$ structural loss weight $\lambda_{st}$ +1 while eMethodIDN - CIFAR10IDN - CIFAR1000.200.300.400.450.500.200.300.400.450.50CE [70]75.8169.1562.4551.7239.4230.4224.1521.4515.2314.42Mixup [73]73.1772.0261.5656.4548.9532.9229.7625.9223.1321.31Forward [46]74.6469.7560.2148.8146.2736.3833.1726.7521.9319.27Reweight [39]76.2370.1262.5851.5445.4636.7331.9128.3924.1220.23Decoupling [43]78.7175.1761.7358.6150.4336.5330.9327.8523.8119.59Co-teaching [19]80.9678.5673.4171.6045.9237.9633.4328.0425.6023.97MentorNet [23]81.0377.2271.8366.1847.8938.9134.2331.8927.5324.15DivideMix [31]94.8094.6094.5394.0893.0477.0776.3370.8057.7858.61SSR* [15]96.4996.5296.3395.8994.0678.8478.6076.9574.9872.83InstanceGM [17]96.6896.5296.3696.1595.9079.6979.2178.4777.4977.19LSL (Ours)97.1396.8596.5396.5895.8180.9479.9078.6078.0877.95 + +Table 1. Test accuracy (%) of different methods on CIFAR10-IDN and CIFAR100-IDN [66] under various IDN noise rates. Most of the experimental results are extracted from state-of-the-art methods [15, 17, 31]. Bold values indicate the best performances. The reproduced result is marked with $*$ . + +We describe these datasets in Sec. 4.1 and provide the implementation details in Sec. 4.2. In Sec. 4.3, we compare our approach with state-of-the-art models in various IDN benchmarks and real-world noisy datasets. + +# 4.1. Datasets + +CIFAR10 and CIFAR100 both datasets [27] consist of 50,000 training images and 10,000 testing images, and each image has dimensions of $32 \times 32 \times 3$ . The CIFAR10 has 10 classes, while CIFAR100 has 100 classes. To conduct experiments in the instance-dependent noise (IDN) environment, we obtained noisy labels of the CIFAR10 and CIFAR100 datasets according to [66]. We set the noise rate for IDN settings at values of 0.20, 0.30, 0.40, 0.45, and 0.50. + +The CIFAR10N and CIFAR100N datasets [63] consist of human-annotated noisy labels obtained from Amazon Mechanical Turk. CIFAR10N and CIFAR100N datasets include 5 and 2 noisy label types, respectively. In this paper, we evaluate the settings with the highest noise rates, specifically CIFAR10N Worst (CIFAR10N-W, a noise rate of $40.21\%$ ) and CIFAR100N Fine (CIFAR100N-F, a noise rate of $40.20\%$ ). + +Animal-10N dataset [53] consists of 50,000 training images and 10,000 test images, with each image having a resolution of $64 \times 64 \times 3$ . The dataset has 10 animal categories, including 5 pairs of animals with similar appearances and the estimated noise rate of the dataset is $8\%$ . + +Red Mini-Imagenet from CNWL [24] dataset is annotated by 3-5 labeling professionals using Google Cloud Data Labeling Service. The dataset comprises 600 training samples for each of its 100 classes. While the origi + +nal image size is $84 \times 84 \times 3$ , we resize it to $32 \times 32 \times 3$ for a fair comparison with other experiments [17, 68]. It supports noise ratios ranging from $0\%$ to $80\%$ , and we validate our model on training data with noise ratios of $20\%$ , $40\%$ , $60\%$ , $80\%$ . + +WebVision [35] is a large-scale dataset with 2.4 million images collected from the web across 1k categories, and Mini-WebVision is a dataset composed of the initial 50 categories from the WebVision dataset. Mini-WebVision contains 65,994 training images, and we resized the images to $256 \times 256 \times 3$ . For validation, we use not only Mini-WebVision but also ImageNet ILSVRC12 dataset [11], which shares the same subset of categories. + +# 4.2. Implementation Details + +All experiments are conducted using the PyTorch framework on an NVIDIA RTX 3090Ti GPU. Unless otherwise specified, all hyperparameter values mentioned below are followed from SSR [15]. + +For CIFAR10 and CIFAR100 with IDN datasets, we use a PreAct-ResNet-18 [20] following DivideMix [31]. We use SGD optimizer for 300 epochs with a momentum of 0.9, a weight decay of 5e-4, an initial learning rate of 0.02, and the cosine annealing function as a learning scheduler. We set a relabeling threshold, $\tau_r$ , from 0.55 to 0.8 for CIFAR10 and CIFAR100 with IDN as the noise ratio decreases, and the batch size to 128. For CIFAR-N datasets, we set $\tau_r$ to 0.8 for CIFAR10-N and CIFAR100-N, and all other details are consistent with CIFAR10/100 with IDN configurations. For Red Mini-Imagenet from CNWL [24], we set $\tau_r$ to 0.8, and all other details are consistent with CIFAR10/100 with + +
MethodCIFAR10N-WCIFAR100N-F
CE [70]77.6955.50
CAL [77]85.3661.73
ELR [37]91.0966.72
SOP+ [38]93.2467.81
DivideMix [31]92.5671.13
SSR* [15]93.5071.99
LSL (Ours)94.5774.46
+ +IDN configurations. + +For Animal-10N, we use a VGG-19 with batch-normalization [55]. We use SGD optimizer for 150 epochs with a momentum of 0.9, a weight decay of 5e-4, an initial learning rate of 0.02, and the step function as a learning scheduler with a reduction factor of 10 and a step size of 50 epochs. We set $\tau_r$ to 0.8, and the batch size of 128. + +For Mini-WebVision, we use an InceptionResNetv2 [56] following [31]. We use SGD optimizer for 150 epochs with a momentum of 0.9, a weight decay of 1e-4, an initial learning rate of 0.01, and the step function as a learning scheduler with a reduction factor of 10 and a step size of 50 epochs. We set $\tau_r$ to 0.8, and the batch size to 64. + +For mixup interpolation, we set both $\alpha$ and $\beta$ to 4 for beta mixture on IDN datasets, CIFAR-N and Red MiniImageNet, and to 0.5 on other datasets. We set the consistency loss weight $\lambda_{fc}$ and the structural loss weight $\lambda_{st}$ to 1.0, and the number of reverse nearest neighbors $k_{st}$ to 20. + +# 4.3. Experimental Results + +The results for CIFAR10 and CIFAR100 with IDN benchmark datasets are shown in Tab. 1. Our proposed method exhibits the best performance in all cases except for CIFAR10 with an IDN noise ratio of 0.5. Even in CIFAR10 with an IDN noise ratio of 0.5, our method demonstrates comparable performance to the baseline, within a margin of $0.1\%$ points. These results demonstrate that our method is consistently effective across various IDN environments. + +Tables 2 to 5 show the results for real-world noisy datasets. The performance on CIFAR10N-W and CIFAR100N-F is presented in Tab. 2. For both datasets, which have a noise rate of approximately $40\%$ , our proposed method shows significant improvements by $1.1\%$ and $3.4\%$ , respectively, compared to the baseline methods. These results confirm the effectiveness of our approach, not only with synthetic IDN noise but also with human-annotated real-world noisy labels. + +Table 2. Test accuracy $(\%)$ of CIFAR-N [63]. Bold values indicate the best performances and the reproduced result is marked with $*$ + +
MethodNoise rate
0.20.40.60.8
CE [70]47.3642.7037.3029.79
Mixup [73]49.1046.4040.5833.58
Mentormix [24]51.0247.1443.8033.46
FaMUS [68]51.4248.0645.1035.50
DivideMix [31]50.9646.7243.1434.50
SSR* [15]52.1848.9642.4233.20
InstanceGM [17]58.3852.2447.9639.62
LSL (Ours)54.6849.8045.4636.78
+ +Table 3. Test accuracy $(\%)$ of Red Mini-Imagenet (CNWL) [24]. Bold values indicate the best performances and the reproduced result is marked with $*$ + +
MethodTest Accuracy (%)
CE [70]79.4
Nested-Dropout [6]81.8
CE+Dropout [6]81.3
SELFIE [54]81.3
PLC [74]83.4
Nested-CE [6]84.1
SSR [15]88.5
InstanceGM [17]84.6
LSL (Ours)89.1
+ +Table 4. Test accuracy $(\%)$ of ANIMAL-10N [53]. Bold values indicate the best performances. + +The experimental results on the Red Mini-ImageNet from CNWL dataset are presented in Tab. 3. Our proposed method demonstrates the second-best performances. + +Animal-10N is a challenging dataset consisting of 5 pairs of easily confused animals and has a relatively low noise ratio of approximately $8\%$ compared to other real-world noisy labels. For this dataset, our method outperforms other approaches, as shown in Tab. 4. + +Lastly, Tab. 5 shows performance on the large-scale WebVision and ImageNet datasets. Our method achieves the best performance on all cases in Top1 accuracy. Especially, our proposed method shows best performance on the Top1 accuracy of ImageNet, and it shows that our method generalizes very well to other datasets. + +
MethodWebVisionIISVRC2012
Top-1Top-5Top-1Top-5
Co-teaching [19]63.5885.2061.4884.70
ELR+ [37]77.7891.6870.2989.76
NGC [65]79.1691.8474.4491.04
LongReMix [8]78.9292.32--
RRL [32]76.3091.5073.3091.20
Sel-CL+ [33]79.9692.6476.8493.04
TCL [22]79.1092.3075.4092.40
DivideMix [31]77.3291.6475.2090.84
SSR [15]80.9292.8075.7691.76
LSL (Ours)81.4093.0077.0091.84
+ +Table 5. Test accuracy $(\%)$ of WebVision [35] and IISVRC2012 [11]. Bold values indicate the best performances. + +![](images/bd6ce2bc74906c36d46195060eec04cfc1c3c06ae11ad45b87af9e12bcc5e681.jpg) +Figure 3. Comparison of training accuracy. Our proposed method outperforms existing approaches. Through the proposed structural labels based on the feature distribution, the model can effectively leverage the entire training dataset. + +# 5. Ablation Studies + +In this section, we analyze the effectiveness of our proposed method and introduce its details. All ablation studies are conducted on the CIFAR10 with IDN dataset [66]. + +# 5.1. Effectiveness of learning structural labels + +Figure 3 shows the accuracy of training data, the agreement between the model's predictions and the original clean labels as training progresses. The original clean labels are used only for evaluation, not for training. In LNL, the accuracy typically does not reach $100\%$ by the end of training as models cannot fully generalize from noisy training data. Our proposed method shows a higher training accuracy compared to other approaches such as DivideMix [31] and SSR [15]. Existing methods are difficult to accurately + +![](images/52598a88b603274e6f771327c7a1cc744254ce798c8146a933e78fa504fb1d70.jpg) +(a) Histogram of logits by SSR + +![](images/2b1160e05e828fbd4d4aeda636de7dd8a91ffa14c9107eb0bd703ead726ead41.jpg) +(b) Histogram of logits by the proposed method +Figure 4. Histogram of Logits for the Training Dataset of CIFAR10 with IDN at noise rate 0.50. + +relabel and select more samples with complex patterns, so they only learn a fraction of the training data and struggle to generalize. In contrast, our proposed method, which utilizes structural labels $l_{st}$ based on feature distribution, effectively leverages more samples and achieves better generalization performance. + +Figure 4 shows the distribution of logits for SSR and our proposed method on CIFAR10 with IDN at noise rate 0.50. In SSR, the total number of misclassified samples is 3238. Among them, 1248 samples are misclassified as given noisy labels, accounting for 0.39 percent of the total misclassified samples. On the other hand, in our method, the total number of misclassified samples is 2107. Among them, the number of misclassified samples as given noisy labels is 646. The percentage of them is 0.31. Thus, our proposed method exhibits fewer total misclassified samples and a lower percentage of misclassified samples as given noisy labels. Also, The logit distribution of misclassified samples with given noise (red) is skewed to the right relative to the logit distribution of misclassified samples (orange) in SSR, whereas + +![](images/ac98a9b7fd700611a26fdc676a35bc4d9f2e0deaca63a5fb07cc384410ac12f5.jpg) +(a) Accuracy with respect to different values of the $k_{st}$ . + +![](images/e954e65f73f600d27e3f3d3fa1b000aa92a2ca048a8a2a1c4d1be5a2e3d74bf1.jpg) +(b) Accuracy with respect to different values of the $\lambda_{st}$ . +Figure 5. Accuracy with respect to hyperparameters on CIFAR10 with IDN at noise rate 0.20. The red dashed line represents the performance of the state-of-the-art (SOTA). + +ours is not. As these statistics demonstrate, our method avoids overfitting to given noisy labels and achieves better generalization performance. + +# 5.2. Hyperparameters + +To validate the sensitivity of the hyperparameters, experiments are conducted using various values of $k_{st}$ for reverse k-NN and the weight of the structural loss, $\lambda_{st}$ . The results are shown in Fig. 5. + +Figure 5a shows the model's accuracy with respect to different values of the hyperparameter $k_{st}$ . Based on the feature distribution, the model can be trained by smoothing over the correct answer labels of its neighboring samples in a noisy environment. However, if $k_{st}$ is too small, our method cannot fully incorporate the feature distribution. On the contrary, if $k_{st}$ is too large, the number of arrows received from samples of classes other than $c$ will increase, and then structural labels $l_{st}$ are over-smoothed. To avoid over-dilution of structural information, we need to choose an appropriate value of $k_{st}$ . Therefore, we experiment with various values to determine the optimal $k_{st}$ . Our proposed model shows the best performances at a $k_{st}$ of 20. + +Figure 5b shows the performance of our proposed method with respect to value of $\lambda_{st}$ , the weight of the structural loss. When applying structural loss, there is a clear performance improvement compared to the case where it is not applied, $\lambda_{st}$ is 0. Additionally, it demonstrates stable, improved performance regardless of changes in the value. + +![](images/c6c2f0af9773de86858968d50be1a95cbba2f19da90db4eb57a4ba65190c6410.jpg) +(a) +Figure 6. Comparison of t-SNE visualization on CIFAR10 with IDN at noise rate 0.50. (a) Ours on training samples with golden labels. (b) Ours on training samples with predicted labels. There are only smaller amounts of wrongly trained samples than DivideMix and SSR. + +![](images/77c05a1b11c896782f5bd8faf07a6ff9c6507f34e5b997523249e816130cf75f.jpg) +(b) + +# 5.3. The t-SNE visualization + +Figure 6 shows t-SNE visualization of features for the proposed method. Unlike DivideMix and SSR in Fig. 1, our method not only learned a relatively simple manifold but also exhibits well-separated clusters, each predominantly representing one class. This confirms that our method demonstrates superior generalization performance. + +# 6. Conclusion + +In this paper, we explored the generalization problem in learning with noisy labels (LNL) and proposed a simple yet effective approach to address these challenges. While existing LNL methods, our proposed method employed a reverse k-NN to leverage structural information based on feature distribution. And by learning the structural information, the model had a better feature manifold and robustness against overfitting to noisy labels, thus achieving better generalization performance. The proposed method demonstrated outperformed performance across various datasets including CIFAR10 and CIFAR100 with IDN, CIFAR-N, Animal10N, Red Mini-Imagenet, Mini-WebVision, and ImageNet. + +Acknowledgments. 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Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 531, + 287, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 531, + 287, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 531, + 287, + 687 + ], + "type": "text", + "content": "Deep neural networks (DNNs) have achieved high performance in various domains such as computer vision [13, 14, 20, 25, 29, 52], natural language processing [3, 7, 12, 40], and signal processing [18, 48, 50] across diverse tasks. To achieve the high performance of DNNs, well-curated large-scale datasets are necessary. However, labeling large-scale data requires a significant cost. In order to reduce these labeling costs, semi-automated [35, 42] and crowdsourcing methods [28] are used, but their labels are inevitably noisy. When trained on data with noisy labels, DNNs suffer degraded performance because they tend to easily overfit noisy labeled samples [72]. 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Comparison of t-SNE visualization on CIFAR10 IDN at noise rate 0.50. (a) DivideMix on training samples with golden labels. (b) DivdieMix on training samples with predicted labels. (c) SSR on training samples with golden labels. (d) SSR on training samples with predicted labels. The black-outlined box represents areas where samples overlap, similar samples are learned as different classes, or clusters are not separable." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 429, + 339, + 541, + 451 + ], + "blocks": [ + { + "bbox": [ + 476, + 328, + 487, + 338 + ], + "lines": [ + { + "bbox": [ + 476, + 328, + 487, + 338 + ], + "spans": [ + { + "bbox": [ + 476, + 328, + 487, + 338 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 429, + 339, + 541, + 451 + ], + "lines": [ + { + "bbox": [ + 429, + 339, + 541, + 451 + ], + "spans": [ + { + "bbox": [ + 429, + 339, + 541, + 451 + ], + "type": "image", + "image_path": "2a8befe5fa23211a8b020303168d0178dbf6239f4efc8919f1b725f68f533e53.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 477, + 455, + 488, + 464 + ], + "lines": [ + { + "bbox": [ + 477, + 455, + 488, + 464 + ], + "spans": [ + { + "bbox": [ + 477, + 455, + 488, + 464 + ], + "type": "text", + "content": "(d)" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 578, + 546, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 578, + 546, + 614 + ], + "spans": [ + { + "bbox": [ + 304, + 578, + 546, + 614 + ], + "type": "text", + "content": "fectively train DNN models in environments with noisy labeled samples, have been proposed [1, 15, 17, 23, 31, 41, 45, 75]." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": "Most methods for learning with noisy labels (LNL) are based on the fact that DNNs tend to learn from clean samples with simple patterns earlier than from wrong-labeled samples [1, 69]. Based on the observation, most approaches adopted an iterative process. Initially, they trained the model with the entire dataset. The model would learned some patterns from clean samples rather than noisy samples. Then, they selected confident samples based on the" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 693, + 124, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 693, + 124, + 703 + ], + "spans": [ + { + "bbox": [ + 58, + 693, + 124, + 703 + ], + "type": "text", + "content": "*Equal contribution" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 134, + 712 + ], + "type": "text", + "content": "† Corresponding author" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27610" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 239 + ], + "type": "text", + "content": "output of the trained model, most of which would be clean samples. Subsequently, they retrained the model with the selected samples. They repeat the selection and training. Consequently, the model can avoid noisy samples and focus on clean samples. Previous approaches proposed various clean sample selection methods based on the model prediction, such as the small-loss trick [23] and the k-Nearest Neighbor (k-NN) method [9, 16]. Additionally, relabeling methods are utilized to leverage a larger number of clean samples by modifying model outputs deemed unreliable. These learning strategies performed quite well in a noisy environment, but they still have a critical limitation—they heavily depend on the model's predictions for relabeling and selection." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 242, + 289, + 350 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 242, + 289, + 350 + ], + "spans": [ + { + "bbox": [ + 46, + 242, + 289, + 350 + ], + "type": "text", + "content": "Essentially, the models guide themselves based on their own predictions in a noisy environment. If an incorrectly predicted sample is chosen, the model may learn from it in the subsequent training step. Therefore, in this self-guided process, inevitable inaccurate predictions arise from learning based on previous inaccuracies. By learning from these inevitable noisy labels, the model not only degrades its generalization performance but also declines its ability to extract features, making the feature manifold more complex." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 352, + 289, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 352, + 289, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 352, + 289, + 544 + ], + "type": "text", + "content": "Figure 1 shows that the learned feature manifolds are complex due to a degradation of generalization performance. It presents t-SNE [60] visualization for DivideMix [31], SSR [15]. Figures 1a and 1b display features of training samples extracted by DivideMix with golden labels and predictions, respectively. In DivideMix, a considerable number of samples from different classes exist in a single cluster, and the model tends to predict them with the same label, incorrectly. In Fig. 1c and 1d, SSR shows better results compared to DivideMix, but clusters have more complex forms. Furthermore, SSR incorrectly predicts some samples, and it seems that classes are not separable. They made efforts to improve generalization by incorporating additional objectives, such as consistency regularization [15] and unsupervised loss [17, 31, 75], but still demonstrate poor generalization performance." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 545, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 289, + 715 + ], + "type": "text", + "content": "It is a fact that deep learning models trained with all cleanly labeled samples exhibit good generalization behavior [44], and their feature distributions are well-discriminated by class. These well-generalized models have preserved the following structural characteristics: 1) When two samples are similar, it is highly probable that they share the same label. 2) If certain samples form a cluster, they are likely to have the same label. These are also consistent with the smoothness/cluster assumptions [4, 61, 76] in the context of semi-supervised learning. We aim to develop a method for training a LNL model by consider the characteristics of well-generalized models. In order to incorporate the characteristics, we aim to extract structural information based on the distribution of the data and directly integrate it" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 305, + 73, + 408, + 84 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 73, + 408, + 84 + ], + "spans": [ + { + "bbox": [ + 305, + 73, + 408, + 84 + ], + "type": "text", + "content": "into the training process." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 85, + 545, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 85, + 545, + 239 + ], + "spans": [ + { + "bbox": [ + 304, + 85, + 545, + 239 + ], + "type": "text", + "content": "In this paper, we present a simple approach to enhance learning with noisy labels by incorporating additional distribution information, structural labels. If a model preserves the structural assumption, it can avoid overfitting to noisy labels and achieve better generalized. By extracting the structural information of data and integrating it into model training, we can efficiently train models with minimized bias towards noisy samples. To extract structural labels, we estimate the data distribution based on Reverse k-Nearest Neighbor (Reverse k-NN) [57]. And then, the structural labels are learned with cross-entropy based on strong augmentation [10] and mixup [73] methods, which help to avoid overfitting noisy samples." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 240, + 545, + 323 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 240, + 545, + 323 + ], + "spans": [ + { + "bbox": [ + 304, + 240, + 545, + 323 + ], + "type": "text", + "content": "To verify our proposed method, we conduct experiments on IDN and real-world noisy datasets including CIFAR10 and CIFAR100 with IDN [66], CIFAR-N [63], Animal-10N [53], Red Mini-Imagenet from CNWL [24], Mini-WebVision [35], andImagenet ILSVRC12 [11]. Our method shows the state-of-the-art performance on various datasets." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 334, + 392, + 346 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 334, + 392, + 346 + ], + "spans": [ + { + "bbox": [ + 306, + 334, + 392, + 346 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 354, + 545, + 486 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 354, + 545, + 486 + ], + "spans": [ + { + "bbox": [ + 304, + 354, + 545, + 486 + ], + "type": "text", + "content": "Deep neural networks (DNNs) tend to overfit to label datasets so that they also overfit to noisy label samples and it leads to degraded performance. Many studies have been conducted to learn datasets with noisy labels. To prevent overfitting to noisy labels and learn effectively from datasets with noisy labels, early studies utilized a given small set of clean samples and relabeled noisy samples based on their modeling [5, 30, 36, 59, 62, 67]. Subsequently, instead of using a given small set of clean samples, several studies focus to distinguish clean samples from the given noisy datasets [1, 15, 17, 26, 31, 51, 58, 75]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 487, + 545, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 487, + 545, + 629 + ], + "spans": [ + { + "bbox": [ + 304, + 487, + 545, + 629 + ], + "type": "text", + "content": "These methods rely on DNNs initially learn from cleanly labeled samples with simple patterns before overfitting to noisy label samples [72], and use the small-loss trick to select clean-label samples [17, 23, 31, 51, 75]. DivideMix [31] treats samples with small losses as labeled samples and the others as unlabeled then trains the model using MixMatch [2], a semi-supervised learning technique. C2D [75] leverages self-supervised models to tackle the instability during the warm-up phase of DivideMix, and InstanceGM [17] proposes a graphical modeling approach to address the more realistic noise, Instance-Dependent Noise (IDN)." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 630, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 545, + 715 + ], + "type": "text", + "content": "Contrary to the loss-based approaches, some methods utilize the model's feature representation [15, 34, 64, 71]. TopoFilter [64] proposes a label noise filtering strategy based on spatial topological patterns, and SSR [15] leverages the model's high-confident predictions for relabeling samples and employs a k-NN classifier [9] within the feature representation space for selecting clean samples." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 758 + ], + "type": "text", + "content": "27611" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 133 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 133 + ], + "type": "text", + "content": "In conclusion, recent LNL methods mainly focus on relabeling and selecting based on their own predictions. However, it is challenging to expect good generalization performance due to the excessive reliance on the predictions of a model that may have errors." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 141, + 153, + 155 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 141, + 153, + 155 + ], + "spans": [ + { + "bbox": [ + 47, + 141, + 153, + 155 + ], + "type": "text", + "content": "3. Proposed Method" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 161, + 287, + 256 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 161, + 287, + 256 + ], + "spans": [ + { + "bbox": [ + 46, + 161, + 287, + 256 + ], + "type": "text", + "content": "Since existing methods heavily depend on uncertain models' predictions, they struggle to form good representations and do not preserve structural information. Wellgeneralized models should preserve the assumption that closer features are likely to be located on the same manifold and have the same label. Therefore, it is necessary not only to get accurate predictions from the model but also to consider the distribution of features." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 258, + 287, + 425 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 258, + 287, + 425 + ], + "spans": [ + { + "bbox": [ + 46, + 258, + 287, + 425 + ], + "type": "text", + "content": "In this section, we propose Learning with Structural Label (LSL), a new approach for learning structural information in LNLs. To learn structural information, we estimate the data distribution based on the Reverse k-NN algorithm, which is less influenced by outlier samples compared to k-NN [21, 49], and calculate the probability of belonging to a class distribution. Then, we extract structural labels " + }, + { + "bbox": [ + 46, + 258, + 287, + 425 + ], + "type": "inline_equation", + "content": "l_{st}" + }, + { + "bbox": [ + 46, + 258, + 287, + 425 + ], + "type": "text", + "content": " from the estimated distribution for all samples and train the model using a strong augmentation [10] and mixup [73] strategy. In contrast to traditional relabeling methods, which depend on uncertain models' predictions learned from selected samples with simple patterns, our approach considers the feature distribution for learning on all samples, not only selected samples." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 430, + 263, + 442 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 430, + 263, + 442 + ], + "spans": [ + { + "bbox": [ + 47, + 430, + 263, + 442 + ], + "type": "text", + "content": "3.1. Structural Labels based on Reverse k-NN" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "spans": [ + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": "In order to obtain more reliable information from noisy predictions of the model, we define the structural labels, " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "l_{st}" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": ", which are the soft labels of each sample based on sample distributions. We first obtain class prediction for each sample from the model, and estimate the distribution of samples predicted as class " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": ". We estimate the probability of " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": " given " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "P(x|c)" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": ", based on the similarity of feature representations and reverse k-NN. We emit " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": " arrows from each sample predicted as class " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": " to its " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": " nearest neighbors including itself. For a sample " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "inline_equation", + "content": "P(x|c)" + }, + { + "bbox": [ + 46, + 449, + 287, + 568 + ], + "type": "text", + "content": " can be approximated as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 112, + 574, + 287, + 601 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 112, + 574, + 287, + 601 + ], + "spans": [ + { + "bbox": [ + 112, + 574, + 287, + 601 + ], + "type": "interline_equation", + "content": "P (x \\mid c) = \\frac {\\# \\text {o f A r r o w s} _ {x , c}}{k \\cdot | X ^ {c} |} \\tag {1}", + "image_path": "5b8e3139c26ef21cf1b9c53f7a15d16f3469b09718ac4afc0a7ab43fedf65618.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "\\#" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "\\operatorname{Arrows}_{x,c}" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": " is the total number of arrows received by " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": " from samples predicted as " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "|X^c|" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": " is the total number of samples predicted as " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": ". If " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": " exists in the region where " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": " class samples densely exist, it may receive more arrows, and vice versa. Consequently, when divided by the total number of arrows from " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": " class samples, it is an approximation for " + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "inline_equation", + "content": "P(x|c)" + }, + { + "bbox": [ + 46, + 605, + 287, + 689 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 714 + ], + "type": "text", + "content": "Figure 2 shows estimation examples of 2-d Gaussian and Moon data [47]. Figures 2a and 2c show distributions by" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 321, + 73, + 421, + 152 + ], + "blocks": [ + { + "bbox": [ + 321, + 73, + 421, + 152 + ], + "lines": [ + { + "bbox": [ + 321, + 73, + 421, + 152 + ], + "spans": [ + { + "bbox": [ + 321, + 73, + 421, + 152 + ], + "type": "image", + "image_path": "02cfa054df0ce573ac75f1ed72ea6697726e260433bf7c7c46667d781154aa68.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 326, + 156, + 414, + 175 + ], + "lines": [ + { + "bbox": [ + 326, + 156, + 414, + 175 + ], + "spans": [ + { + "bbox": [ + 326, + 156, + 414, + 175 + ], + "type": "text", + "content": "(a) Gaussian modeling for Gaussian samples" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 433, + 72, + 533, + 152 + ], + "blocks": [ + { + "bbox": [ + 433, + 72, + 533, + 152 + ], + "lines": [ + { + "bbox": [ + 433, + 72, + 533, + 152 + ], + "spans": [ + { + "bbox": [ + 433, + 72, + 533, + 152 + ], + "type": "image", + "image_path": "5240b0fa410ea26be34c55149cff2c0ff1ebb2d8034c923364bfbc516f161751.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 433, + 156, + 531, + 175 + ], + "lines": [ + { + "bbox": [ + 433, + 156, + 531, + 175 + ], + "spans": [ + { + "bbox": [ + 433, + 156, + 531, + 175 + ], + "type": "text", + "content": "(b) Modeling based on reverse k-NN for Gaussian samples" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 321, + 178, + 421, + 257 + ], + "blocks": [ + { + "bbox": [ + 321, + 178, + 421, + 257 + ], + "lines": [ + { + "bbox": [ + 321, + 178, + 421, + 257 + ], + "spans": [ + { + "bbox": [ + 321, + 178, + 421, + 257 + ], + "type": "image", + "image_path": "c00f286017f081a3154b33733fd00f82e1bcde720f4a4e0418090d0ac58f815c.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 326, + 261, + 413, + 280 + ], + "lines": [ + { + "bbox": [ + 326, + 261, + 413, + 280 + ], + "spans": [ + { + "bbox": [ + 326, + 261, + 413, + 280 + ], + "type": "text", + "content": "(c) Gaussian modeling for Moon dataset" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 433, + 177, + 533, + 257 + ], + "blocks": [ + { + "bbox": [ + 433, + 177, + 533, + 257 + ], + "lines": [ + { + "bbox": [ + 433, + 177, + 533, + 257 + ], + "spans": [ + { + "bbox": [ + 433, + 177, + 533, + 257 + ], + "type": "image", + "image_path": "2105415bbd86a229732f4fe0f3b08fe11a1957ee00d5f38ad0d662cf7ef17592.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 433, + 261, + 531, + 280 + ], + "lines": [ + { + "bbox": [ + 433, + 261, + 531, + 280 + ], + "spans": [ + { + "bbox": [ + 433, + 261, + 531, + 280 + ], + "type": "text", + "content": "(d) Modeling based on reverse k-NN for Moon dataset" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 290, + 545, + 367 + ], + "lines": [ + { + "bbox": [ + 304, + 290, + 545, + 367 + ], + "spans": [ + { + "bbox": [ + 304, + 290, + 545, + 367 + ], + "type": "text", + "content": "Figure 2. Comparison of distributions between Gaussian modeling and reverse k-NN modeling in 2-D Gaussian dataset and Moon dataset. Figure 2a shows the Gaussian modeling effectively estimates distribution for Gaussian samples. However, the Gaussian modeling fails to fit the distribution of the Moon dataset in Fig. 2c. Figure 2b and Fig. 2d show Reverse k-NN effectively approximates the data distribution for both Gaussian and Moon datasets." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 386, + 545, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 386, + 545, + 480 + ], + "spans": [ + { + "bbox": [ + 304, + 386, + 545, + 480 + ], + "type": "text", + "content": "Gaussian modeling, and 2b and 2d show distributions by our modeling based on reverse k-NN. The Gaussian modeling can efficiently estimates the distributions, but it is hard to accurately model complex data distributions like the Moon dataset. In contrast, the distribution estimation based on reverse k-NN effectively approximates not only the simple distribution, Gaussian, but also the complex data distribution, Moon dataset." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "spans": [ + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "type": "text", + "content": "Based on the feature distribution, we define the structural label of " + }, + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "type": "text", + "content": ", which is the soft label representing the probability of " + }, + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "type": "text", + "content": " given " + }, + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 304, + 482, + 545, + 517 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 362, + 522, + 545, + 550 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 362, + 522, + 545, + 550 + ], + "spans": [ + { + "bbox": [ + 362, + 522, + 545, + 550 + ], + "type": "interline_equation", + "content": "P (c | x) = \\frac {P (x | c) P (c)}{\\sum_ {c \\in C} P (x | c) P (c)}. \\tag {2}", + "image_path": "263ccfa82191fdd9cef48684e7b2ab1f904b8b050134e69b8e25d99c14ee0b32.jpg" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 555, + 544, + 589 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 555, + 544, + 589 + ], + "spans": [ + { + "bbox": [ + 304, + 555, + 544, + 589 + ], + "type": "text", + "content": "The prior " + }, + { + "bbox": [ + 304, + 555, + 544, + 589 + ], + "type": "inline_equation", + "content": "P(c)" + }, + { + "bbox": [ + 304, + 555, + 544, + 589 + ], + "type": "text", + "content": " represents the probability of observing class " + }, + { + "bbox": [ + 304, + 555, + 544, + 589 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 555, + 544, + 589 + ], + "type": "text", + "content": ", which can be determined from the number of samples in each class:" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 382, + 587, + 545, + 616 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 382, + 587, + 545, + 616 + ], + "spans": [ + { + "bbox": [ + 382, + 587, + 545, + 616 + ], + "type": "interline_equation", + "content": "P (c) = \\frac {\\left| X ^ {c} \\right|}{\\sum_ {c = 1} ^ {C} \\left| X ^ {c} \\right|}. \\tag {3}", + "image_path": "563211bfda8ce0dacc0528bf8bf21a1edd90676ab93ed318fbe1c512a57fbeee.jpg" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 618, + 490, + 630 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 618, + 490, + 630 + ], + "spans": [ + { + "bbox": [ + 306, + 618, + 490, + 630 + ], + "type": "text", + "content": "Then, Eq. (2) can be reformulated as follows:" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 363, + 635, + 545, + 664 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 363, + 635, + 545, + 664 + ], + "spans": [ + { + "bbox": [ + 363, + 635, + 545, + 664 + ], + "type": "interline_equation", + "content": "P (c | x) = \\frac {P (x | c) \\left| X ^ {c} \\right|}{\\sum_ {c = 1} ^ {C} P (x | c) \\left| X ^ {c} \\right|}. \\tag {4}", + "image_path": "b4a5213bc6a9af08e00007a7e8ca4fd9e4807e1a2bd45a0225bbedc86507ed58.jpg" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 306, + 669, + 541, + 681 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 669, + 541, + 681 + ], + "spans": [ + { + "bbox": [ + 306, + 669, + 541, + 681 + ], + "type": "text", + "content": "From Eqs. (1) and (4), " + }, + { + "bbox": [ + 306, + 669, + 541, + 681 + ], + "type": "inline_equation", + "content": "P(c|x)" + }, + { + "bbox": [ + 306, + 669, + 541, + 681 + ], + "type": "text", + "content": " is approximated as follows:" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 356, + 686, + 545, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 356, + 686, + 545, + 716 + ], + "spans": [ + { + "bbox": [ + 356, + 686, + 545, + 716 + ], + "type": "interline_equation", + "content": "P (c | x) = \\frac {\\# \\text {o f A r r o w s} _ {x , c}}{\\sum_ {c = 1} ^ {C} \\# \\text {o f A r r o w s} _ {x , c}}. \\tag {5}", + "image_path": "b8607af21d268b4b538850ed622c5249e7961882fb3250716e12c1fddad269b9.jpg" + } + ] + } + ], + "index": 26 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27612" + } + ] + } + ], + "index": 27 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "code", + "bbox": [ + 47, + 99, + 301, + 317 + ], + "blocks": [ + { + "bbox": [ + 51, + 76, + 262, + 97 + ], + "lines": [ + { + "bbox": [ + 51, + 76, + 262, + 97 + ], + "spans": [ + { + "bbox": [ + 51, + 76, + 262, + 97 + ], + "type": "text", + "content": "Algorithm 1: Extracting Structural Labels based on reverse k-NN distribution estimation" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "code_caption" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "lines": [ + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "spans": [ + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": "Input : model encoder " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " training dataset " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "\\mathcal{X},\\mathcal{V} = \\{(x_i,y_i^r)_{i = 1}^N\\}" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " Parameter: number of reverse nearest neighbors " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " Output : structural labels by " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "st\\mathcal{Y}^{st} = \\{(y^{st})_{i = 1}^N\\}" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " \n1 T = torch.zeros[N, K] \n2 # " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " is the number of classes \n3 #T indicates edge count table \n4 " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "\\mathcal{F} = \\mathrm{Normalize}(\\theta (\\mathcal{X}))" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " #Normalize all features \n5 for " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "i\\gets 1" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " do \n6 score " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "=" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " Cosine " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "(f_i,\\mathcal{F})" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " indices " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "=" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " score.topk " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "(k_{st})" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " \n8 # Emit k edges to " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " nearest neighbors \n9 T [indices, " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "y_i^r ] + = 1" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " \n10 # Propagate its label to k nearest neighbors \n11 end \n12 " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "\\mathcal{V}^{st} = \\mathrm{T} / \\mathrm{T}.\\mathrm{sum}(\\mathrm{dim} = 1" + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "text", + "content": " ,keepdim=True) \n13 # Aggregate from received labels and normalize these labels \n14 return " + }, + { + "bbox": [ + 47, + 99, + 301, + 317 + ], + "type": "inline_equation", + "content": "\\mathcal{V}^{st}" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "code_body" + } + ], + "index": 1, + "sub_type": "algorithm" + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "spans": [ + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "text", + "content": "Since " + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "inline_equation", + "content": "P(c|x)" + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "text", + "content": " is estimated from noisy prediction of the model, it can be affected by wrong predictions. However, if we assume that the uniform noise over the sample space, it is clear that the probability is free from the uniform noise. Even though the noise is not uniform, it can be easily smoothed if we use enough large " + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "text", + "content": ". However, if " + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "text", + "content": " is too large, the number of arrows received from samples of classes other than " + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "text", + "content": " will increase. It can lead to over-smoothing of " + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "inline_equation", + "content": "l_{st}" + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "text", + "content": " and lose the structural information. To avoid over-dilution of structural information, we need to choose an appropriate value of " + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 344, + 290, + 486 + ], + "type": "text", + "content": ", and it is discussed in Sec. 5.2." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 488, + 287, + 536 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 488, + 287, + 536 + ], + "spans": [ + { + "bbox": [ + 46, + 488, + 287, + 536 + ], + "type": "text", + "content": "In conclusion, the structural label of " + }, + { + "bbox": [ + 46, + 488, + 287, + 536 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 488, + 287, + 536 + ], + "type": "text", + "content": " estimated by reverse k-NN effectively reflects the distribution information of the samples in noisy data environments. Algorithm 1 shows how to obtain the structural labels." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 546, + 253, + 560 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 546, + 253, + 560 + ], + "spans": [ + { + "bbox": [ + 47, + 546, + 253, + 560 + ], + "type": "text", + "content": "3.2. Learning with Structural Labels (LSL)" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 565, + 287, + 625 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 565, + 287, + 625 + ], + "spans": [ + { + "bbox": [ + 46, + 565, + 287, + 625 + ], + "type": "text", + "content": "To learn structural information, we utilize structural labels " + }, + { + "bbox": [ + 46, + 565, + 287, + 625 + ], + "type": "inline_equation", + "content": "l_{st}" + }, + { + "bbox": [ + 46, + 565, + 287, + 625 + ], + "type": "text", + "content": " to effectively reflect feature distribution with SSR [15]. It is one of the LNL methods that considers feature representation. The procedure for the proposed method is described in Algorithm 2." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 627, + 287, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 627, + 287, + 662 + ], + "spans": [ + { + "bbox": [ + 46, + 627, + 287, + 662 + ], + "type": "text", + "content": "In Algorithm 2, line 2 indicates relabeling based on model prediction with Eq. (6), and line 3 indicates sample selection based on k-NN." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 54, + 684, + 287, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 54, + 684, + 287, + 716 + ], + "spans": [ + { + "bbox": [ + 54, + 684, + 287, + 716 + ], + "type": "interline_equation", + "content": "y _ {i} ^ {r} = \\left\\{ \\begin{array}{l l} \\operatorname {a r g m a x} _ {l} f (\\alpha (x _ {i})), & \\text {i f} \\max _ {l} f (\\alpha (x _ {i})) > \\tau_ {r} \\\\ y _ {i}, & \\text {o t h e r w i s e} \\end{array} \\right. \\tag {6}", + "image_path": "03342ff4a351c76fbba073bd3491b5be1d8c931bd5f48b80162589e458d7a657.jpg" + } + ] + } + ], + "index": 7 + }, + { + "type": "code", + "bbox": [ + 306, + 99, + 545, + 456 + ], + "blocks": [ + { + "bbox": [ + 310, + 75, + 522, + 99 + ], + "lines": [ + { + "bbox": [ + 310, + 75, + 522, + 99 + ], + "spans": [ + { + "bbox": [ + 310, + 75, + 522, + 99 + ], + "type": "text", + "content": "Algorithm 2: Learning with Structural Labels (LSL)" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "code_caption" + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "lines": [ + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "text", + "content": "Input : model encoder " + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "text", + "content": " multi-layer neural network " + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "text", + "content": " training dataset " + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "inline_equation", + "content": "(\\mathcal{X},\\mathcal{Y}) = \\{(x_i,y_i)\\}_{i = 1}^N" + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "text", + "content": " \nParameter: sample relabelling threshold " + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "inline_equation", + "content": "\\tau_r" + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "text", + "content": " feature consistency loss weight " + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "inline_equation", + "content": "\\lambda_{fc}" + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "text", + "content": " structural loss weight " + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "inline_equation", + "content": "\\lambda_{st}" + }, + { + "bbox": [ + 306, + 99, + 545, + 456 + ], + "type": "text", + "content": " \n1 while eMethodIDN - CIFAR10IDN - CIFAR1000.200.300.400.450.500.200.300.400.450.50CE [70]75.8169.1562.4551.7239.4230.4224.1521.4515.2314.42Mixup [73]73.1772.0261.5656.4548.9532.9229.7625.9223.1321.31Forward [46]74.6469.7560.2148.8146.2736.3833.1726.7521.9319.27Reweight [39]76.2370.1262.5851.5445.4636.7331.9128.3924.1220.23Decoupling [43]78.7175.1761.7358.6150.4336.5330.9327.8523.8119.59Co-teaching [19]80.9678.5673.4171.6045.9237.9633.4328.0425.6023.97MentorNet [23]81.0377.2271.8366.1847.8938.9134.2331.8927.5324.15DivideMix [31]94.8094.6094.5394.0893.0477.0776.3370.8057.7858.61SSR* [15]96.4996.5296.3395.8994.0678.8478.6076.9574.9872.83InstanceGM [17]96.6896.5296.3696.1595.9079.6979.2178.4777.4977.19LSL (Ours)97.1396.8596.5396.5895.8180.9479.9078.6078.0877.95", + "image_path": "59d375aeb00144d0b46d09bf345cf7a357dc5bcfadfc0a31d6ffe11207b8a0b2.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 286, + 546, + 321 + ], + "lines": [ + { + "bbox": [ + 46, + 286, + 546, + 321 + ], + "spans": [ + { + "bbox": [ + 46, + 286, + 546, + 321 + ], + "type": "text", + "content": "Table 1. Test accuracy (%) of different methods on CIFAR10-IDN and CIFAR100-IDN [66] under various IDN noise rates. Most of the experimental results are extracted from state-of-the-art methods [15, 17, 31]. Bold values indicate the best performances. The reproduced result is marked with " + }, + { + "bbox": [ + 46, + 286, + 546, + 321 + ], + "type": "inline_equation", + "content": "*" + }, + { + "bbox": [ + 46, + 286, + 546, + 321 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 341, + 288, + 389 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 341, + 288, + 389 + ], + "spans": [ + { + "bbox": [ + 46, + 341, + 288, + 389 + ], + "type": "text", + "content": "We describe these datasets in Sec. 4.1 and provide the implementation details in Sec. 4.2. In Sec. 4.3, we compare our approach with state-of-the-art models in various IDN benchmarks and real-world noisy datasets." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 396, + 111, + 407 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 396, + 111, + 407 + ], + "spans": [ + { + "bbox": [ + 47, + 396, + 111, + 407 + ], + "type": "text", + "content": "4.1. Datasets" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 414, + 287, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 414, + 287, + 510 + ], + "spans": [ + { + "bbox": [ + 46, + 414, + 287, + 510 + ], + "type": "text", + "content": "CIFAR10 and CIFAR100 both datasets [27] consist of 50,000 training images and 10,000 testing images, and each image has dimensions of " + }, + { + "bbox": [ + 46, + 414, + 287, + 510 + ], + "type": "inline_equation", + "content": "32 \\times 32 \\times 3" + }, + { + "bbox": [ + 46, + 414, + 287, + 510 + ], + "type": "text", + "content": ". The CIFAR10 has 10 classes, while CIFAR100 has 100 classes. To conduct experiments in the instance-dependent noise (IDN) environment, we obtained noisy labels of the CIFAR10 and CIFAR100 datasets according to [66]. We set the noise rate for IDN settings at values of 0.20, 0.30, 0.40, 0.45, and 0.50." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 510, + 288, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 288, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 288, + 605 + ], + "type": "text", + "content": "The CIFAR10N and CIFAR100N datasets [63] consist of human-annotated noisy labels obtained from Amazon Mechanical Turk. CIFAR10N and CIFAR100N datasets include 5 and 2 noisy label types, respectively. In this paper, we evaluate the settings with the highest noise rates, specifically CIFAR10N Worst (CIFAR10N-W, a noise rate of " + }, + { + "bbox": [ + 46, + 510, + 288, + 605 + ], + "type": "inline_equation", + "content": "40.21\\%" + }, + { + "bbox": [ + 46, + 510, + 288, + 605 + ], + "type": "text", + "content": ") and CIFAR100N Fine (CIFAR100N-F, a noise rate of " + }, + { + "bbox": [ + 46, + 510, + 288, + 605 + ], + "type": "inline_equation", + "content": "40.20\\%" + }, + { + "bbox": [ + 46, + 510, + 288, + 605 + ], + "type": "text", + "content": ")." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 605, + 287, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 665 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 665 + ], + "type": "text", + "content": "Animal-10N dataset [53] consists of 50,000 training images and 10,000 test images, with each image having a resolution of " + }, + { + "bbox": [ + 46, + 605, + 287, + 665 + ], + "type": "inline_equation", + "content": "64 \\times 64 \\times 3" + }, + { + "bbox": [ + 46, + 605, + 287, + 665 + ], + "type": "text", + "content": ". The dataset has 10 animal categories, including 5 pairs of animals with similar appearances and the estimated noise rate of the dataset is " + }, + { + "bbox": [ + 46, + 605, + 287, + 665 + ], + "type": "inline_equation", + "content": "8\\%" + }, + { + "bbox": [ + 46, + 605, + 287, + 665 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "content": "Red Mini-Imagenet from CNWL [24] dataset is annotated by 3-5 labeling professionals using Google Cloud Data Labeling Service. The dataset comprises 600 training samples for each of its 100 classes. While the origi" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "spans": [ + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": "nal image size is " + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "inline_equation", + "content": "84 \\times 84 \\times 3" + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": ", we resize it to " + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "inline_equation", + "content": "32 \\times 32 \\times 3" + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": " for a fair comparison with other experiments [17, 68]. It supports noise ratios ranging from " + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "inline_equation", + "content": "0\\%" + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "inline_equation", + "content": "80\\%" + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": ", and we validate our model on training data with noise ratios of " + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "inline_equation", + "content": "20\\%" + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "inline_equation", + "content": "40\\%" + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "inline_equation", + "content": "60\\%" + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "inline_equation", + "content": "80\\%" + }, + { + "bbox": [ + 304, + 341, + 546, + 399 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 400, + 547, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 400, + 547, + 498 + ], + "spans": [ + { + "bbox": [ + 304, + 400, + 547, + 498 + ], + "type": "text", + "content": "WebVision [35] is a large-scale dataset with 2.4 million images collected from the web across 1k categories, and Mini-WebVision is a dataset composed of the initial 50 categories from the WebVision dataset. Mini-WebVision contains 65,994 training images, and we resized the images to " + }, + { + "bbox": [ + 304, + 400, + 547, + 498 + ], + "type": "inline_equation", + "content": "256 \\times 256 \\times 3" + }, + { + "bbox": [ + 304, + 400, + 547, + 498 + ], + "type": "text", + "content": ". For validation, we use not only Mini-WebVision but also ImageNet ILSVRC12 dataset [11], which shares the same subset of categories." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 503, + 440, + 516 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 503, + 440, + 516 + ], + "spans": [ + { + "bbox": [ + 305, + 503, + 440, + 516 + ], + "type": "text", + "content": "4.2. Implementation Details" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 521, + 546, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 546, + 569 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 546, + 569 + ], + "type": "text", + "content": "All experiments are conducted using the PyTorch framework on an NVIDIA RTX 3090Ti GPU. Unless otherwise specified, all hyperparameter values mentioned below are followed from SSR [15]." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": "For CIFAR10 and CIFAR100 with IDN datasets, we use a PreAct-ResNet-18 [20] following DivideMix [31]. We use SGD optimizer for 300 epochs with a momentum of 0.9, a weight decay of 5e-4, an initial learning rate of 0.02, and the cosine annealing function as a learning scheduler. We set a relabeling threshold, " + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\tau_r" + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": ", from 0.55 to 0.8 for CIFAR10 and CIFAR100 with IDN as the noise ratio decreases, and the batch size to 128. For CIFAR-N datasets, we set " + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\tau_r" + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": " to 0.8 for CIFAR10-N and CIFAR100-N, and all other details are consistent with CIFAR10/100 with IDN configurations. For Red Mini-Imagenet from CNWL [24], we set " + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\tau_r" + }, + { + "bbox": [ + 304, + 570, + 547, + 713 + ], + "type": "text", + "content": " to 0.8, and all other details are consistent with CIFAR10/100 with" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27614" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 70, + 282, + 201 + ], + "blocks": [ + { + "bbox": [ + 50, + 70, + 282, + 201 + ], + "lines": [ + { + "bbox": [ + 50, + 70, + 282, + 201 + ], + "spans": [ + { + "bbox": [ + 50, + 70, + 282, + 201 + ], + "type": "table", + "html": "
MethodCIFAR10N-WCIFAR100N-F
CE [70]77.6955.50
CAL [77]85.3661.73
ELR [37]91.0966.72
SOP+ [38]93.2467.81
DivideMix [31]92.5671.13
SSR* [15]93.5071.99
LSL (Ours)94.5774.46
", + "image_path": "f1cf5d5ef99bad05cb2a15e22672bad1f86e267b9eb4a4cc05b782806a097cee.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 252, + 130, + 265 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 252, + 130, + 265 + ], + "spans": [ + { + "bbox": [ + 47, + 252, + 130, + 265 + ], + "type": "text", + "content": "IDN configurations." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 265, + 287, + 337 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 265, + 287, + 337 + ], + "spans": [ + { + "bbox": [ + 46, + 265, + 287, + 337 + ], + "type": "text", + "content": "For Animal-10N, we use a VGG-19 with batch-normalization [55]. We use SGD optimizer for 150 epochs with a momentum of 0.9, a weight decay of 5e-4, an initial learning rate of 0.02, and the step function as a learning scheduler with a reduction factor of 10 and a step size of 50 epochs. We set " + }, + { + "bbox": [ + 46, + 265, + 287, + 337 + ], + "type": "inline_equation", + "content": "\\tau_r" + }, + { + "bbox": [ + 46, + 265, + 287, + 337 + ], + "type": "text", + "content": " to 0.8, and the batch size of 128." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 338, + 287, + 409 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 338, + 287, + 409 + ], + "spans": [ + { + "bbox": [ + 46, + 338, + 287, + 409 + ], + "type": "text", + "content": "For Mini-WebVision, we use an InceptionResNetv2 [56] following [31]. We use SGD optimizer for 150 epochs with a momentum of 0.9, a weight decay of 1e-4, an initial learning rate of 0.01, and the step function as a learning scheduler with a reduction factor of 10 and a step size of 50 epochs. We set " + }, + { + "bbox": [ + 46, + 338, + 287, + 409 + ], + "type": "inline_equation", + "content": "\\tau_r" + }, + { + "bbox": [ + 46, + 338, + 287, + 409 + ], + "type": "text", + "content": " to 0.8, and the batch size to 64." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "spans": [ + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "text", + "content": "For mixup interpolation, we set both " + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "text", + "content": " to 4 for beta mixture on IDN datasets, CIFAR-N and Red MiniImageNet, and to 0.5 on other datasets. We set the consistency loss weight " + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "inline_equation", + "content": "\\lambda_{fc}" + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "text", + "content": " and the structural loss weight " + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "inline_equation", + "content": "\\lambda_{st}" + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "text", + "content": " to 1.0, and the number of reverse nearest neighbors " + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 410, + 287, + 480 + ], + "type": "text", + "content": " to 20." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 491, + 171, + 503 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 491, + 171, + 503 + ], + "spans": [ + { + "bbox": [ + 47, + 491, + 171, + 503 + ], + "type": "text", + "content": "4.3. Experimental Results" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 509, + 287, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 509, + 287, + 605 + ], + "spans": [ + { + "bbox": [ + 46, + 509, + 287, + 605 + ], + "type": "text", + "content": "The results for CIFAR10 and CIFAR100 with IDN benchmark datasets are shown in Tab. 1. Our proposed method exhibits the best performance in all cases except for CIFAR10 with an IDN noise ratio of 0.5. Even in CIFAR10 with an IDN noise ratio of 0.5, our method demonstrates comparable performance to the baseline, within a margin of " + }, + { + "bbox": [ + 46, + 509, + 287, + 605 + ], + "type": "inline_equation", + "content": "0.1\\%" + }, + { + "bbox": [ + 46, + 509, + 287, + 605 + ], + "type": "text", + "content": " points. These results demonstrate that our method is consistently effective across various IDN environments." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "content": "Tables 2 to 5 show the results for real-world noisy datasets. The performance on CIFAR10N-W and CIFAR100N-F is presented in Tab. 2. For both datasets, which have a noise rate of approximately " + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "inline_equation", + "content": "40\\%" + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "content": ", our proposed method shows significant improvements by " + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "inline_equation", + "content": "1.1\\%" + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "inline_equation", + "content": "3.4\\%" + }, + { + "bbox": [ + 46, + 605, + 287, + 713 + ], + "type": "text", + "content": ", respectively, compared to the baseline methods. These results confirm the effectiveness of our approach, not only with synthetic IDN noise but also with human-annotated real-world noisy labels." + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 309, + 70, + 541, + 232 + ], + "blocks": [ + { + "bbox": [ + 47, + 208, + 287, + 232 + ], + "lines": [ + { + "bbox": [ + 47, + 208, + 287, + 232 + ], + "spans": [ + { + "bbox": [ + 47, + 208, + 287, + 232 + ], + "type": "text", + "content": "Table 2. Test accuracy " + }, + { + "bbox": [ + 47, + 208, + 287, + 232 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 47, + 208, + 287, + 232 + ], + "type": "text", + "content": " of CIFAR-N [63]. Bold values indicate the best performances and the reproduced result is marked with " + }, + { + "bbox": [ + 47, + 208, + 287, + 232 + ], + "type": "inline_equation", + "content": "*" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 309, + 70, + 541, + 232 + ], + "lines": [ + { + "bbox": [ + 309, + 70, + 541, + 232 + ], + "spans": [ + { + "bbox": [ + 309, + 70, + 541, + 232 + ], + "type": "table", + "html": "
MethodNoise rate
0.20.40.60.8
CE [70]47.3642.7037.3029.79
Mixup [73]49.1046.4040.5833.58
Mentormix [24]51.0247.1443.8033.46
FaMUS [68]51.4248.0645.1035.50
DivideMix [31]50.9646.7243.1434.50
SSR* [15]52.1848.9642.4233.20
InstanceGM [17]58.3852.2447.9639.62
LSL (Ours)54.6849.8045.4636.78
", + "image_path": "7d84289320c9571f9bf3d703d0f3bee6e5f55ee6c17c553f97918e5af321686f.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 331, + 300, + 519, + 462 + ], + "blocks": [ + { + "bbox": [ + 305, + 240, + 545, + 273 + ], + "lines": [ + { + "bbox": [ + 305, + 240, + 545, + 273 + ], + "spans": [ + { + "bbox": [ + 305, + 240, + 545, + 273 + ], + "type": "text", + "content": "Table 3. Test accuracy " + }, + { + "bbox": [ + 305, + 240, + 545, + 273 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 305, + 240, + 545, + 273 + ], + "type": "text", + "content": " of Red Mini-Imagenet (CNWL) [24]. Bold values indicate the best performances and the reproduced result is marked with " + }, + { + "bbox": [ + 305, + 240, + 545, + 273 + ], + "type": "inline_equation", + "content": "*" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 331, + 300, + 519, + 462 + ], + "lines": [ + { + "bbox": [ + 331, + 300, + 519, + 462 + ], + "spans": [ + { + "bbox": [ + 331, + 300, + 519, + 462 + ], + "type": "table", + "html": "
MethodTest Accuracy (%)
CE [70]79.4
Nested-Dropout [6]81.8
CE+Dropout [6]81.3
SELFIE [54]81.3
PLC [74]83.4
Nested-CE [6]84.1
SSR [15]88.5
InstanceGM [17]84.6
LSL (Ours)89.1
", + "image_path": "e262bb7a0c8088a5f2f2491df38496643b54f18aa22e1d97e41997a38ce9e893.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 470, + 545, + 492 + ], + "lines": [ + { + "bbox": [ + 305, + 470, + 545, + 492 + ], + "spans": [ + { + "bbox": [ + 305, + 470, + 545, + 492 + ], + "type": "text", + "content": "Table 4. Test accuracy " + }, + { + "bbox": [ + 305, + 470, + 545, + 492 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 305, + 470, + 545, + 492 + ], + "type": "text", + "content": " of ANIMAL-10N [53]. Bold values indicate the best performances." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 305, + 529, + 545, + 566 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 529, + 545, + 566 + ], + "spans": [ + { + "bbox": [ + 305, + 529, + 545, + 566 + ], + "type": "text", + "content": "The experimental results on the Red Mini-ImageNet from CNWL dataset are presented in Tab. 3. Our proposed method demonstrates the second-best performances." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 574, + 545, + 634 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 574, + 545, + 634 + ], + "spans": [ + { + "bbox": [ + 304, + 574, + 545, + 634 + ], + "type": "text", + "content": "Animal-10N is a challenging dataset consisting of 5 pairs of easily confused animals and has a relatively low noise ratio of approximately " + }, + { + "bbox": [ + 304, + 574, + 545, + 634 + ], + "type": "inline_equation", + "content": "8\\%" + }, + { + "bbox": [ + 304, + 574, + 545, + 634 + ], + "type": "text", + "content": " compared to other real-world noisy labels. For this dataset, our method outperforms other approaches, as shown in Tab. 4." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 641, + 545, + 713 + ], + "type": "text", + "content": "Lastly, Tab. 5 shows performance on the large-scale WebVision and ImageNet datasets. Our method achieves the best performance on all cases in Top1 accuracy. Especially, our proposed method shows best performance on the Top1 accuracy of ImageNet, and it shows that our method generalizes very well to other datasets." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27615" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 48, + 70, + 289, + 262 + ], + "blocks": [ + { + "bbox": [ + 48, + 70, + 289, + 262 + ], + "lines": [ + { + "bbox": [ + 48, + 70, + 289, + 262 + ], + "spans": [ + { + "bbox": [ + 48, + 70, + 289, + 262 + ], + "type": "table", + "html": "
MethodWebVisionIISVRC2012
Top-1Top-5Top-1Top-5
Co-teaching [19]63.5885.2061.4884.70
ELR+ [37]77.7891.6870.2989.76
NGC [65]79.1691.8474.4491.04
LongReMix [8]78.9292.32--
RRL [32]76.3091.5073.3091.20
Sel-CL+ [33]79.9692.6476.8493.04
TCL [22]79.1092.3075.4092.40
DivideMix [31]77.3291.6475.2090.84
SSR [15]80.9292.8075.7691.76
LSL (Ours)81.4093.0077.0091.84
", + "image_path": "766380d89922fdebe95537252c46b8dff9482f532f310621b2384ddf9d5f44e9.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 270, + 287, + 293 + ], + "lines": [ + { + "bbox": [ + 47, + 270, + 287, + 293 + ], + "spans": [ + { + "bbox": [ + 47, + 270, + 287, + 293 + ], + "type": "text", + "content": "Table 5. Test accuracy " + }, + { + "bbox": [ + 47, + 270, + 287, + 293 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 47, + 270, + 287, + 293 + ], + "type": "text", + "content": " of WebVision [35] and IISVRC2012 [11]. Bold values indicate the best performances." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 58, + 310, + 282, + 442 + ], + "blocks": [ + { + "bbox": [ + 58, + 310, + 282, + 442 + ], + "lines": [ + { + "bbox": [ + 58, + 310, + 282, + 442 + ], + "spans": [ + { + "bbox": [ + 58, + 310, + 282, + 442 + ], + "type": "image", + "image_path": "bd6ce2bc74906c36d46195060eec04cfc1c3c06ae11ad45b87af9e12bcc5e681.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 457, + 287, + 502 + ], + "lines": [ + { + "bbox": [ + 46, + 457, + 287, + 502 + ], + "spans": [ + { + "bbox": [ + 46, + 457, + 287, + 502 + ], + "type": "text", + "content": "Figure 3. Comparison of training accuracy. Our proposed method outperforms existing approaches. Through the proposed structural labels based on the feature distribution, the model can effectively leverage the entire training dataset." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 522, + 147, + 534 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 522, + 147, + 534 + ], + "spans": [ + { + "bbox": [ + 47, + 522, + 147, + 534 + ], + "type": "text", + "content": "5. Ablation Studies" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 542, + 287, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 542, + 287, + 579 + ], + "spans": [ + { + "bbox": [ + 46, + 542, + 287, + 579 + ], + "type": "text", + "content": "In this section, we analyze the effectiveness of our proposed method and introduce its details. All ablation studies are conducted on the CIFAR10 with IDN dataset [66]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 586, + 263, + 600 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 586, + 263, + 600 + ], + "spans": [ + { + "bbox": [ + 47, + 586, + 263, + 600 + ], + "type": "text", + "content": "5.1. Effectiveness of learning structural labels" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": "Figure 3 shows the accuracy of training data, the agreement between the model's predictions and the original clean labels as training progresses. The original clean labels are used only for evaluation, not for training. In LNL, the accuracy typically does not reach " + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "inline_equation", + "content": "100\\%" + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": " by the end of training as models cannot fully generalize from noisy training data. Our proposed method shows a higher training accuracy compared to other approaches such as DivideMix [31] and SSR [15]. Existing methods are difficult to accurately" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 310, + 74, + 544, + 228 + ], + "blocks": [ + { + "bbox": [ + 310, + 74, + 544, + 228 + ], + "lines": [ + { + "bbox": [ + 310, + 74, + 544, + 228 + ], + "spans": [ + { + "bbox": [ + 310, + 74, + 544, + 228 + ], + "type": "image", + "image_path": "52598a88b603274e6f771327c7a1cc744254ce798c8146a933e78fa504fb1d70.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 376, + 230, + 477, + 242 + ], + "lines": [ + { + "bbox": [ + 376, + 230, + 477, + 242 + ], + "spans": [ + { + "bbox": [ + 376, + 230, + 477, + 242 + ], + "type": "text", + "content": "(a) Histogram of logits by SSR" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 309, + 252, + 544, + 407 + ], + "blocks": [ + { + "bbox": [ + 309, + 252, + 544, + 407 + ], + "lines": [ + { + "bbox": [ + 309, + 252, + 544, + 407 + ], + "spans": [ + { + "bbox": [ + 309, + 252, + 544, + 407 + ], + "type": "image", + "image_path": "2b1160e05e828fbd4d4aeda636de7dd8a91ffa14c9107eb0bd703ead726ead41.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 349, + 410, + 504, + 420 + ], + "lines": [ + { + "bbox": [ + 349, + 410, + 504, + 420 + ], + "spans": [ + { + "bbox": [ + 349, + 410, + 504, + 420 + ], + "type": "text", + "content": "(b) Histogram of logits by the proposed method" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 306, + 429, + 545, + 452 + ], + "lines": [ + { + "bbox": [ + 306, + 429, + 545, + 452 + ], + "spans": [ + { + "bbox": [ + 306, + 429, + 545, + 452 + ], + "type": "text", + "content": "Figure 4. Histogram of Logits for the Training Dataset of CIFAR10 with IDN at noise rate 0.50." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 474, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 545, + 544 + ], + "type": "text", + "content": "relabel and select more samples with complex patterns, so they only learn a fraction of the training data and struggle to generalize. In contrast, our proposed method, which utilizes structural labels " + }, + { + "bbox": [ + 304, + 474, + 545, + 544 + ], + "type": "inline_equation", + "content": "l_{st}" + }, + { + "bbox": [ + 304, + 474, + 545, + 544 + ], + "type": "text", + "content": " based on feature distribution, effectively leverages more samples and achieves better generalization performance." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 545, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 546, + 713 + ], + "type": "text", + "content": "Figure 4 shows the distribution of logits for SSR and our proposed method on CIFAR10 with IDN at noise rate 0.50. In SSR, the total number of misclassified samples is 3238. Among them, 1248 samples are misclassified as given noisy labels, accounting for 0.39 percent of the total misclassified samples. On the other hand, in our method, the total number of misclassified samples is 2107. Among them, the number of misclassified samples as given noisy labels is 646. The percentage of them is 0.31. Thus, our proposed method exhibits fewer total misclassified samples and a lower percentage of misclassified samples as given noisy labels. Also, The logit distribution of misclassified samples with given noise (red) is skewed to the right relative to the logit distribution of misclassified samples (orange) in SSR, whereas" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "27616" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 74, + 279, + 163 + ], + "blocks": [ + { + "bbox": [ + 53, + 74, + 279, + 163 + ], + "lines": [ + { + "bbox": [ + 53, + 74, + 279, + 163 + ], + "spans": [ + { + "bbox": [ + 53, + 74, + 279, + 163 + ], + "type": "image", + "image_path": "ac98a9b7fd700611a26fdc676a35bc4d9f2e0deaca63a5fb07cc384410ac12f5.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 78, + 167, + 257, + 177 + ], + "lines": [ + { + "bbox": [ + 78, + 167, + 257, + 177 + ], + "spans": [ + { + "bbox": [ + 78, + 167, + 257, + 177 + ], + "type": "text", + "content": "(a) Accuracy with respect to different values of the " + }, + { + "bbox": [ + 78, + 167, + 257, + 177 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 78, + 167, + 257, + 177 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 53, + 189, + 279, + 277 + ], + "blocks": [ + { + "bbox": [ + 53, + 189, + 279, + 277 + ], + "lines": [ + { + "bbox": [ + 53, + 189, + 279, + 277 + ], + "spans": [ + { + "bbox": [ + 53, + 189, + 279, + 277 + ], + "type": "image", + "image_path": "e954e65f73f600d27e3f3d3fa1b000aa92a2ca048a8a2a1c4d1be5a2e3d74bf1.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 78, + 281, + 257, + 291 + ], + "lines": [ + { + "bbox": [ + 78, + 281, + 257, + 291 + ], + "spans": [ + { + "bbox": [ + 78, + 281, + 257, + 291 + ], + "type": "text", + "content": "(b) Accuracy with respect to different values of the " + }, + { + "bbox": [ + 78, + 281, + 257, + 291 + ], + "type": "inline_equation", + "content": "\\lambda_{st}" + }, + { + "bbox": [ + 78, + 281, + 257, + 291 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 300, + 287, + 334 + ], + "lines": [ + { + "bbox": [ + 46, + 300, + 287, + 334 + ], + "spans": [ + { + "bbox": [ + 46, + 300, + 287, + 334 + ], + "type": "text", + "content": "Figure 5. Accuracy with respect to hyperparameters on CIFAR10 with IDN at noise rate 0.20. The red dashed line represents the performance of the state-of-the-art (SOTA)." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 360, + 287, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 360, + 287, + 396 + ], + "spans": [ + { + "bbox": [ + 46, + 360, + 287, + 396 + ], + "type": "text", + "content": "ours is not. As these statistics demonstrate, our method avoids overfitting to given noisy labels and achieves better generalization performance." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 411, + 153, + 425 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 411, + 153, + 425 + ], + "spans": [ + { + "bbox": [ + 47, + 411, + 153, + 425 + ], + "type": "text", + "content": "5.2. Hyperparameters" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 433, + 287, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 433, + 287, + 480 + ], + "spans": [ + { + "bbox": [ + 46, + 433, + 287, + 480 + ], + "type": "text", + "content": "To validate the sensitivity of the hyperparameters, experiments are conducted using various values of " + }, + { + "bbox": [ + 46, + 433, + 287, + 480 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 433, + 287, + 480 + ], + "type": "text", + "content": " for reverse k-NN and the weight of the structural loss, " + }, + { + "bbox": [ + 46, + 433, + 287, + 480 + ], + "type": "inline_equation", + "content": "\\lambda_{st}" + }, + { + "bbox": [ + 46, + 433, + 287, + 480 + ], + "type": "text", + "content": ". The results are shown in Fig. 5." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "spans": [ + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": "Figure 5a shows the model's accuracy with respect to different values of the hyperparameter " + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": ". Based on the feature distribution, the model can be trained by smoothing over the correct answer labels of its neighboring samples in a noisy environment. However, if " + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": " is too small, our method cannot fully incorporate the feature distribution. On the contrary, if " + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": " is too large, the number of arrows received from samples of classes other than " + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": " will increase, and then structural labels " + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "inline_equation", + "content": "l_{st}" + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": " are over-smoothed. To avoid over-dilution of structural information, we need to choose an appropriate value of " + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": ". Therefore, we experiment with various values to determine the optimal " + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": ". Our proposed model shows the best performances at a " + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "inline_equation", + "content": "k_{st}" + }, + { + "bbox": [ + 46, + 483, + 287, + 639 + ], + "type": "text", + "content": " of 20." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "type": "text", + "content": "Figure 5b shows the performance of our proposed method with respect to value of " + }, + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\lambda_{st}" + }, + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "type": "text", + "content": ", the weight of the structural loss. When applying structural loss, there is a clear performance improvement compared to the case where it is not applied, " + }, + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\lambda_{st}" + }, + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "type": "text", + "content": " is 0. Additionally, it demonstrates stable, improved performance regardless of changes in the value." + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 312, + 72, + 425, + 185 + ], + "blocks": [ + { + "bbox": [ + 312, + 72, + 425, + 185 + ], + "lines": [ + { + "bbox": [ + 312, + 72, + 425, + 185 + ], + "spans": [ + { + "bbox": [ + 312, + 72, + 425, + 185 + ], + "type": "image", + "image_path": "c6c2f0af9773de86858968d50be1a95cbba2f19da90db4eb57a4ba65190c6410.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 362, + 189, + 373, + 198 + ], + "lines": [ + { + "bbox": [ + 362, + 189, + 373, + 198 + ], + "spans": [ + { + "bbox": [ + 362, + 189, + 373, + 198 + ], + "type": "text", + "content": "(a)" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 305, + 208, + 545, + 262 + ], + "lines": [ + { + "bbox": [ + 305, + 208, + 545, + 262 + ], + "spans": [ + { + "bbox": [ + 305, + 208, + 545, + 262 + ], + "type": "text", + "content": "Figure 6. Comparison of t-SNE visualization on CIFAR10 with IDN at noise rate 0.50. (a) Ours on training samples with golden labels. (b) Ours on training samples with predicted labels. There are only smaller amounts of wrongly trained samples than DivideMix and SSR." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 427, + 72, + 541, + 185 + ], + "blocks": [ + { + "bbox": [ + 427, + 72, + 541, + 185 + ], + "lines": [ + { + "bbox": [ + 427, + 72, + 541, + 185 + ], + "spans": [ + { + "bbox": [ + 427, + 72, + 541, + 185 + ], + "type": "image", + "image_path": "77c05a1b11c896782f5bd8faf07a6ff9c6507f34e5b997523249e816130cf75f.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 477, + 189, + 488, + 198 + ], + "lines": [ + { + "bbox": [ + 477, + 189, + 488, + 198 + ], + "spans": [ + { + "bbox": [ + 477, + 189, + 488, + 198 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 285, + 440, + 297 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 285, + 440, + 297 + ], + "spans": [ + { + "bbox": [ + 306, + 285, + 440, + 297 + ], + "type": "text", + "content": "5.3. The t-SNE visualization" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 304, + 545, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 304, + 545, + 376 + ], + "spans": [ + { + "bbox": [ + 305, + 304, + 545, + 376 + ], + "type": "text", + "content": "Figure 6 shows t-SNE visualization of features for the proposed method. Unlike DivideMix and SSR in Fig. 1, our method not only learned a relatively simple manifold but also exhibits well-separated clusters, each predominantly representing one class. This confirms that our method demonstrates superior generalization performance." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 389, + 378, + 402 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 389, + 378, + 402 + ], + "spans": [ + { + "bbox": [ + 306, + 389, + 378, + 402 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 410, + 545, + 554 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 410, + 545, + 554 + ], + "spans": [ + { + "bbox": [ + 305, + 410, + 545, + 554 + ], + "type": "text", + "content": "In this paper, we explored the generalization problem in learning with noisy labels (LNL) and proposed a simple yet effective approach to address these challenges. While existing LNL methods, our proposed method employed a reverse k-NN to leverage structural information based on feature distribution. And by learning the structural information, the model had a better feature manifold and robustness against overfitting to noisy labels, thus achieving better generalization performance. The proposed method demonstrated outperformed performance across various datasets including CIFAR10 and CIFAR100 with IDN, CIFAR-N, Animal10N, Red Mini-Imagenet, Mini-WebVision, and ImageNet." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 305, + 570, + 545, + 647 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 570, + 545, + 647 + ], + "spans": [ + { + "bbox": [ + 305, + 570, + 545, + 647 + ], + "type": "text", + "content": "Acknowledgments. This work was partly supported by Institute of Information & communications Technology Planning & Evaluation (IITP) grant funded by the Korea government (MSIT) (No.2019-0-00421, AI Graduate School Support Program, Sungkyunkwan University, and No.RS-2023-00228970, Development of Flexible SW-HW Conjunctive Solution for On-edge Self-supervised Learning)." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 671, + 365, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 671, + 365, + 684 + ], + "spans": [ + { + "bbox": [ + 306, + 671, + 365, + 684 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 310, + 691, + 545, + 713 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 691, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 310, + 691, + 545, + 713 + ], + "type": "text", + "content": "[1] Eric Arazo, Diego Ortego, Paul Albert, Noel O'Connor, and Kevin McGuinness. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 10113-10123, 2021. 6" + } + ] + } + ], + "index": 25 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "27620" + } + ] + } + ], + "index": 27 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_content_list.json b/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..4b44078a34dc7de19bf092950a05c7aac98d55cc --- /dev/null +++ b/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_content_list.json @@ -0,0 +1,1746 @@ +[ + { + "type": "text", + "text": "Learning with Unreliability: Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency", + "text_level": 1, + "bbox": [ + 153, + 130, + 818, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Yingjie Xu $^{1,2*}$ Bangzhen Liu $^{2*}$ Hao Tang $^{1,3}$ Bailin Deng $^{4}$ Shengfeng He $^{1\\dagger}$ $^{1}$ Singapore Management University $^{2}$ South China University of Technology $^{3}$ Nanjing University of Science and Technology $^{4}$ Cardiff University", + "bbox": [ + 169, + 186, + 805, + 244 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c9186a2448aed9889ca0b6c76469d6a456318e81e6eb6a7620a063f3c7286ec8.jpg", + "image_caption": [ + "Figure 1. We present ReVoRF, a voxel-based framework designed to capitalize on the unreliability inherent in warped novel views. (b) demonstrates the warping outcomes, where black holes signify unmatched pixels from the original view. (c) illustrates the results of training when these holes are masked out, which unfortunately results in ambiguous geometric structures. In contrast, (d) showcases our approach's ability to maintain correct geometric consistency. ReVoRF achieves this by leveraging relational depth prior knowledge within these unreliable hole regions. Our approach demonstrates the best reconstruction quality while being one of the fastest few-shot approaches in (e)." + ], + "image_footnote": [], + "bbox": [ + 84, + 250, + 550, + 465 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/727c259f2677aff1171c8faa5d058d09ba6db414f06c2a5d437069ff1edea320.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 571, + 282, + 857, + 465 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 547, + 313, + 561 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "We propose a voxel-based optimization framework, ReVoRF, for few-shot radiance fields that strategically address the unreliability in pseudo novel view synthesis. Our method pivots on the insight that relative depth relationships within neighboring regions are more reliable than the absolute color values in disoccluded areas. Consequently, we devise a bilateral geometric consistency loss that carefully navigates the trade-off between color fidelity and geometric accuracy in the context of depth consistency for uncertain regions. Moreover, we present a reliability-guided learning strategy to discern and utilize the variable quality across synthesized views, complemented by a reliability-aware voxel smoothing algorithm that smoothens the transition between reliable and unreliable data patches. Our approach allows for a more nuanced use of all available data, promoting enhanced learning from regions previously considered unsuitable for high-quality reconstruction. Extensive experiments across diverse datasets reveal that our approach attains significant gains in efficiency and accuracy, delivering rendering speeds of 3 FPS, 7 mins to train a $360^{\\circ}$ scene, and", + "bbox": [ + 75, + 564, + 473, + 867 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "a $5\\%$ improvement in PSNR over existing few-shot methods. Code is available at https://github.com/HKCLynn/ReVoRF.", + "bbox": [ + 500, + 547, + 893, + 580 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 500, + 603, + 632, + 619 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Neural Radiance Fields (NeRF) have revolutionized the fields of novel view synthesis and 3D reconstruction by leveraging an implicit function optimized from a collection of 2D images [2, 13, 24, 27]. Despite their remarkable rendering capabilities, NeRFs are hampered by the substantial cost and time required to gather dense image sets for a given scene [6,41,47]. This challenge has spurred the development of Few-shot NeRF, an emerging domain focused on reconstructing 3D scenes with minimal image data [6,8, 12, 18].", + "bbox": [ + 496, + 628, + 893, + 763 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The performance of NeRF in accurately reconstructing geometry and texture diminishes when faced with sparse observations, as it tends to overfit the limited views available [8, 49]. To address this issue, there has been a push in recent studies to fortify NeRF with additional priors [46, 47], including semantic relations [14], depth cues [49], and entropy constraints [17]. These enhancements strive to extract maximum information from limited data. However, the reconstructions are inherently limited by the insufficient", + "bbox": [ + 496, + 765, + 895, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*The first two authors contributed equally.", + "bbox": [ + 94, + 875, + 344, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "† Corresponding author (shengfenghe@smu.edu.sg).", + "bbox": [ + 96, + 887, + 369, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "20342", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "coherence of the sparse views provided.", + "bbox": [ + 76, + 90, + 341, + 104 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Recent research has explored overcoming the challenges posed by very limited observations through pseudo-view synthesis [3, 18]. By using known camera poses and coarse depth estimates, these methods generate warped images from sparse viewpoints to enhance cross-view consistency. However, as shown in Fig. 1b, these generated images often include noisy areas with artifacts, which, if used for learning, can lead to inconsistent training signals and compromise scene integrity. To address this, Kwak et al. [18] implement self-occlusion aware masking to exclude unreliable regions. While this selective masking successfully filters out areas of uncertainty, it also introduces voids, presenting a conundrum: refining these images can bring in inconsistent noise and floaters, as illustrated in Fig. 1c, yet the limited number of usable samples necessitates using all available pseudo supervision for quality reconstruction.", + "bbox": [ + 75, + 109, + 470, + 349 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In light of the issues identified with unreliable warped areas, our paper proposes a novel method for fully exploiting these uncertain regions to achieve multi-view consistency learning. The rationale behind our method is that, although absolute supervision is not reliable in those disoccluded regions, we observe that they maintain consistent relative depth relationships. The unreliability of certain regions in warped images can still bear geometric resemblances to their original view counterparts. We find that local depth information within these images can indicate geometric disparities, offering a self-supervised signal that aids in discerning the geometry of regions lacking precise textural information. While reliable regions offer more accurate supervision, our approach seeks to fully utilize all the information present, exploiting depth cues in coarsely warped images to inform the learning process across both reliable and traditionally discarded unreliable areas.", + "bbox": [ + 75, + 354, + 470, + 609 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Drawing from the insights above, we propose a novel voxel-based optimization framework, ReVoRF, tailored for fast and multi-view consistent reconstruction of few-shot radiance fields, which incorporates the relative depth priors from several aspects. The objective of this work is to concurrently explore information from both dependable and less reliable regions within the warped novel view images. In the first step, we randomly warp the sparse images onto a series of novel views, subsequently delineating reliable and unreliable regions based on the pixel-wise correlation between the input and novel view. We then introduce a bilateral geometric consistency loss to enable self-training on novel synthesized images. This loss encompasses a reconstruction term in a bilateral manner, including a color and density regularization term for reliable regions and a relative depth consistency term for unreliable regions, respectively. While the former term aims at explicitly learning the geometric context of the reliable regions, the relative depth regularization is applied for implicitly exploring the geometric consistency guided", + "bbox": [ + 75, + 613, + 470, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "by relative depth. Moreover, we integrate unreliability into our voxelization of scene features: 1) a reliability-guided learning strategy that dynamically adjusts learning priorities towards more reliable regions; 2) a reliability-aware voxel smoothing procedure that preserves structural integrity in reliable zones and mitigates inconsistencies in less reliable ones, ensuring a balanced and coherent scene reconstruction. As illustrated in Fig. 1e, assisted by both bilateral geometric consistency loss and reliability-aware regularization, our method is the second fastest while achieving the best reconstruction fidelity, with a large margin over the others.", + "bbox": [ + 496, + 90, + 893, + 257 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our contributions can be summarized as follows:", + "bbox": [ + 517, + 257, + 843, + 271 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We present the first attempt to explore pseudo-views unreliability within few-shot radiance fields, presenting the first framework to incorporate these areas for enhanced multi-view consistency learning with a bilateral geometric consistency loss.", + "- We introduce a reliability-guided learning strategy and voxelization smoothing procedure that tailors the learning process to the reliability of data, thus optimizing the training emphasis for improved reconstruction quality in few-shot radiance fields.", + "- We demonstrate superior performance of our approach against existing state-of-the-art few-shot methods in efficiency and accuracy, through extensive experiments on both synthetic and real-world datasets." + ], + "bbox": [ + 517, + 279, + 890, + 507 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 520, + 640, + 536 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Neural Radiance Fields (NeRF). NeRF [2,5,13,22,24] have emerged as a significant advancement in 3D reconstruction and novel view synthesis. These methods employ an implicit function to represent a 3D scene, enabling the extraction of detailed geometric and textural information from a set of multi-view images. Subsequent researchers have broadened the scope of NeRF applications, including generative modeling [11,40], video synthesis [9,20,34], and scene editing [21,48]. Despite the impressive rendering quality, the training of vanilla NeRF often spans several days for a single scene reconstruction. Recent advancements [10,27,37,38] have endeavored to mitigate this computational burden. Approaches such as DVGO [4,37,38] employ dense voxel grids in conjunction with shallow multilayer perceptrons to expedite the reconstruction process. Similarly, Plenoxels [10] utilizes sparse voxel grids, and Instant-NGP [27] employs a multi-resolution hash table to delineate the radiance field more efficiently. Diverse from these methods, which typically require dense inputs, we aim to address the challenge of achieving fast and high-fidelity scene reconstruction in the case where only a few observed views are available.", + "bbox": [ + 496, + 545, + 893, + 863 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Few-Shot NeRFs. Recent advances [5, 14, 17, 47, 49, 51] have sought to reduce the dependency on densely collected", + "bbox": [ + 496, + 869, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "20343", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "data for scene reconstruction, leveraging sparse inputs and scene priors. Notably, PixelNeRF [47] and StereoRF [7] utilize local semantic relationships across multiple scenes, while MVSNeRF [5] incorporates cost volume to enhance performance. These methodologies, however, require pretraining on numerous scenes to acquire necessary scene priors. Further developments [14, 17, 31, 39, 46] have introduced various regularization techniques to maximize the utility of sparse input views. InfoNeRF [17] enhances ray adjacency consistency through entropy regularization. DietNeRF [14] facilitates cross-view semantic consistency by harnessing the semantic space of the pretrained CLIP [31], while DiffusioNeRF [44] explores the diffusion prior of pretrained diffusion models. Additionally, FreeNeRF [46] applies frequency regularization, and VGOS [39] introduces voxel regularization to optimize both feature representation and density. Another group of research focuses on augmenting sparse inputs with synthetically generated views. RapNeRF [49] utilizes geometric re-projection for novel view extrapolation, while VmNeRF [3] employs depth maps for view-morphing. GeCoNeRF [18] aims to refine geometric consistency by separating reliable regions from warped images and discarding unreliable areas prone to self-occlusion. Our work diverges from these approaches by considering the inherent information of both reliable and unreliable regions of the novel view images, facilitating cross-view geometric consistency.", + "bbox": [ + 76, + 90, + 472, + 484 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Unreliability/Uncertainty Modeling. In the rapid development of NeRF, the incorporation of uncertainty modeling has become crucial for achieving robustness in 3D reconstruction from sparse views. Previous efforts have employed diverse strategies, including Bayesian approaches [15, 28] and evidential neural networks [1,33], to quantify uncertainty in neural networks. In the context of NeRF, uncertainty has been harnessed to enhance rendering and guide input capture. Some methods assume Gaussian noise in RGB space for pixel-wise uncertainty [22, 30], employ volumetric entropy for scene geometry [19, 45], or adopt variational inference or Latent Variable Modeling for radiance field uncertainty as seen in S-NeRF [36] and CF-NeRF [35]. However, these approaches have not comprehensively addressed uncertainty quantification in unseen regions. Our approach differs from these methods by not only capturing uncertainty in the geometry and appearance of visible areas but also explicitly accounting for unseen spaces, including occluded points, which previous methods have not considered. This distinction allows for a more nuanced and accurate reconstruction, promising to elevate the fidelity of few-shot NeRF models.", + "bbox": [ + 76, + 491, + 470, + 809 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Methodology", + "text_level": 1, + "bbox": [ + 76, + 821, + 210, + 838 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Preliminaries", + "text_level": 1, + "bbox": [ + 76, + 847, + 217, + 861 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "NeRF [24] represents a scene as a continuously differentiable function $f$ via a Multi-Layer Perceptron (MLP).", + "bbox": [ + 76, + 869, + 470, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Given a 3D position $\\mathbf{x} \\in \\mathbb{R}^3$ and the associated 2D viewing directions $\\mathbf{d} \\in \\mathbb{R}^2$ , NeRF maps them into a volume density $\\sigma \\in \\mathbb{R}$ and an RGB value $\\mathbf{c} \\in \\mathbb{R}^3$ , such that: $(\\mathbf{c}, \\sigma) = f(\\gamma(\\mathbf{x}), \\gamma(\\mathbf{d}))$ , where the $\\gamma$ is a positional encoding that projects $\\mathbf{x}$ and $\\mathbf{d}$ into a higher dimensional feature space [42]. With a ray parameterized as $\\mathbf{r}_p(t) = \\mathbf{o} + t\\mathbf{d}_p$ cast from the camera's optical center $\\mathbf{o}$ along direction $\\mathbf{d}_p$ , the expected color $\\hat{C}(\\mathbf{r}_p)$ of pixel $p$ is rendered as follows:", + "bbox": [ + 496, + 90, + 893, + 214 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {C} (\\mathbf {r} _ {p}) = \\int_ {t _ {n}} ^ {t _ {f}} T (t) \\sigma (\\mathbf {r} _ {p} (t)) \\mathbf {c} (\\mathbf {r} _ {p} (t), \\mathbf {d} _ {p}) d t, \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 550, + 227, + 893, + 262 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $t_n$ and $t_f$ are the near and far bounds of the ray for sampling, and $T(t) = \\exp \\left(-\\int_{t_n}^t \\sigma(\\mathbf{r}(s)) ds\\right)$ denotes the cumulative transparency along the ray from $t_n$ to $t$ . Therefore, the NeRF can be optimized by a reconstruction loss between the rendered color $\\hat{C}(\\mathbf{r})$ and the real color $C(\\mathbf{r})$ :", + "bbox": [ + 496, + 273, + 893, + 357 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nL _ {r g b} = \\sum_ {\\mathbf {r} \\in \\mathcal {R}} \\| \\hat {C} (\\mathbf {r}) - C (\\mathbf {r}) \\| ^ {2}, \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 594, + 369, + 892, + 402 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathcal{R}$ denotes the set of training rays.", + "bbox": [ + 498, + 415, + 769, + 430 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2. Overview", + "text_level": 1, + "bbox": [ + 500, + 443, + 609, + 455 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We propose ReVoRF, a novel voxel-based optimization framework tailored for fast and multi-view consistent scene reconstruction from sparse input views. Our key idea is to incorporate the unreliability information for fully exploring the warped novel view images. By treating depth priors as the unreliability metrics, ReVoRF facilitates the reconstruction of the few-shot radiance field from several aspects, including the multi-view consistency learning (Sec. 3.3) and the regularization of voxel features (Sec. 3.4). The overall pipeline of ReVoRF is displayed in Fig. 2.", + "bbox": [ + 496, + 467, + 893, + 619 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.3. Unreliability for Multi-view Consistency", + "text_level": 1, + "bbox": [ + 500, + 630, + 844, + 646 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we explore the potential of unreliability in facilitating multi-view geometric consistency via the proposed bilateral geometric consistency loss.", + "bbox": [ + 496, + 654, + 893, + 700 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Novel View Warping. Starting from a set of sparse input images $I_r^i$ for $i \\in 1, \\dots, N_r$ , where $i$ represents the view number and $N_r$ is a small number, e.g., $N_r = 3$ or $N_r = 4$ , we propose to synthesize novel view images $I_{s \\leftarrow r}^{i,j}$ through a fast and flexible warping process on several novel views $j \\in 1, \\dots, N_s$ . To preserve the cross-view consistency, the warping is guided by a coarse depth map $D_r^i$ , where the depth value on each pixel $p$ is accumulated by the density along each ray $r_p$ omitted from the camera: $D_r^i(p) = \\int_{t_f}^{t_n} T(t) \\sigma(r_p(t)) t dt$ . Subsequently, we obtain the warped image $I_{s \\leftarrow r}^{i,j}$ through a cross-view transformation $H_{s \\leftarrow r}$ , which deforms each pixel $p_r$ of $I_r^i$ to its correspond", + "bbox": [ + 496, + 713, + 895, + 901 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "20344", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/91a2121fb48de591d43840e5e63b49e3b4f5ff9b41d079d4792c03957da6eeb1.jpg", + "image_caption": [ + "Figure 2. Overview of our proposed ReVoRF. Specifically, we first warp the sparse images onto several novel views and determine both the dependable and unreliable regions. Based on the dependability of each image region, we introduce a bilateral geometric consistency loss for multi-view consistent learning, which is composed of a color and density regularization term for reliable regions and a relative depth consistency term for unreliable regions. These two terms are responsible for explicitly learning the reliable geometric contents and implicitly exploring the geometric consistency via the guidance of relative depth, respectively. For voxel feature regularization, we integrate the unreliability through a reliability-guided learning strategy and a reliability-aware voxel smoothing procedure. By prioritizing the learning of more reliable regions and mitigating the inconsistencies in less reliable ones, ReVoRF ensures a more balanced and coherent reconstruction." + ], + "image_footnote": [], + "bbox": [ + 81, + 85, + 893, + 397 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "ing position $p_{s}$ on the target view:", + "bbox": [ + 76, + 518, + 305, + 534 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} p _ {s \\leftarrow r} = H _ {s \\leftarrow r} \\left(p _ {r}\\right) \\tag {3} \\\\ = f _ {s \\leftarrow w} \\left(f _ {w \\leftarrow r} \\left(p _ {r}\\right)\\right), \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 179, + 550, + 468, + 585 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "$f_{w\\leftarrow r}$ is a mapping matrix from the pixel coordinate of $I_r^i$ to the world coordinate and $f_{s\\leftarrow w}$ is the inverse operation to the coordinate of $I_{s\\leftarrow r}^{i,j}$ , such that:", + "bbox": [ + 76, + 603, + 468, + 650 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nf _ {w \\leftarrow r} \\left(p _ {r}\\right) = D _ {r} ^ {i} \\left(p _ {r}\\right) T _ {r} ^ {- 1} K _ {r} ^ {- 1} p _ {r}, \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 161, + 665, + 468, + 683 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nf _ {s \\leftarrow w} \\left(p _ {w}\\right) = K _ {s} T _ {s} \\left(p _ {w}\\right), \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 161, + 686, + 468, + 703 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $K$ and $T$ represent the camera's intrinsic and extrinsic parameter matrices in their corresponding views, respectively. Since the warping function is not surjective, voids may occur in $I_{s\\leftarrow r}^{i,j}$ . We empirically obtain a binary mask $M_{\\text{warp}}$ , where the pixels of void areas are set as 1 to identify the initial unreliable regions. To further refine the mask, we employ the cross-view pixel correspondences within the world coordinate of $I_r^i$ and $I_{s\\leftarrow r}^{i,j}$ . To achieve this, we obtain the pseudo depth $D_s^j$ of view $j$ by rendering from the radiance fields. Following Eq. 4, we map the pixel of $I_r^i$ and $I_{s\\leftarrow r}^{i,j}$ into the same coordinate and obtain the correlation map $M_{\\text{cor}}$ by comparing the distance between each pixel", + "bbox": [ + 76, + 719, + 472, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "pair $(p_r,p_{s\\leftarrow r})$", + "bbox": [ + 500, + 518, + 609, + 534 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nM _ {c o r} \\left(p _ {s \\leftarrow r}\\right) = \\left\\{ \\begin{array}{l l} 1, & \\| f _ {w \\leftarrow r} \\left(p _ {r}\\right) - f _ {w \\leftarrow s} \\left(p _ {s \\leftarrow r}\\right) \\| _ {2} > \\epsilon . \\\\ 0, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 504, + 542, + 890, + 595 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this way, the final unreliability mask can be calculated as follows:", + "bbox": [ + 498, + 595, + 890, + 623 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nM _ {s \\leftarrow r} = M _ {c o r} \\cup M _ {w a r p}. \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 609, + 626, + 890, + 642 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Bilateral Geometric Consistency Loss. According to the obtained unreliability mask $M_{s \\leftarrow r}$ , we categorize the warped novel view image into reliable regions $R_{rel}$ and unreliable regions $R_{unr}$ . Subsequently, we propose a bilateral geometric consistency loss to facilitate the self-training. Since the contents within $R_{rel}$ are considered reliable, we explicitly constrain the appearance of rendered image $I_{s}^{j}$ on view $j$ via a reconstruction loss defined as:", + "bbox": [ + 496, + 655, + 893, + 775 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nL _ {r e l} = \\sum_ {p \\in \\mathcal {R} _ {r e l}} \\| I _ {s \\leftarrow r} ^ {i, j} (p) - I _ {s} ^ {j} (p) \\| ^ {2}. \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 575, + 782, + 890, + 816 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For $R_{unr}$ , we propose to leverage the relative depth prior of the warped $I_{s\\leftarrow r}^{i,j}$ to improve the geometric consistency. Specifically, we extract the depth map $D_{s\\leftarrow r}$ with a powerful pretrained depth estimation model DPT [32]. By analyzing the semantics of the surrounding context, we could inpaint", + "bbox": [ + 496, + 825, + 893, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "20345", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "the voids occurring in $D_{s \\leftarrow r}$ . Subsequently, a relative depth regularization loss [23] is introduced to constrain the geometric consistency on the rendered depth $D_{s}$ , which is defined as:", + "bbox": [ + 75, + 90, + 470, + 148 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {u n r} = \\sum_ {p \\in R _ {u n r}} \\sum_ {\\hat {p} \\in N \\left(D _ {s \\leftarrow r} ^ {p}\\right)} h (p, \\hat {p}), \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 155, + 160, + 470, + 195 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where", + "bbox": [ + 76, + 205, + 122, + 219 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} h (p, \\hat {p}) = \\\\ \\left\\{ \\begin{array}{l l} \\max \\left(\\left| D _ {s} ^ {\\hat {p}} - D _ {s} ^ {p} \\right| - m, 0\\right) & \\text {i f} \\left(D _ {s \\leftarrow r} ^ {\\hat {p}} - D _ {s \\leftarrow r} ^ {p}\\right) \\\\ & \\times \\left(D _ {s} ^ {\\hat {p}} - D _ {s} ^ {p}\\right) < 0, \\\\ 0 & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {10} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 231, + 468, + 306 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Here $p$ denotes any pixel within the unreliable region $R_{unr}$ ; $\\hat{p}$ represents each pixel within a neighborhood $N(D_{s\\leftarrow r}^{p})$ of $p$ , where $N(D_{s\\leftarrow r}^{p})$ is obtained by calculating pixels that have close depth values with $D_{s\\leftarrow r}^{p}$ in the warped depth map; $D_{s}^{p}, D_{s}^{\\hat{p}}$ and $D_{s\\leftarrow r}^{p}, D_{s\\leftarrow r}^{\\hat{p}}$ denote the depth values of $p$ and $\\hat{p}$ within the rendered depth map $D_{s}$ and estimated depth map $D_{s\\leftarrow r}$ , respectively. The function $h(p, \\hat{p})$ penalizes inconsistent relative ordering between the depth values of $p$ and $\\hat{p}$ in the two depth maps. Specifically, if $D_{s}^{p} < D_{s}^{\\hat{p}}$ but $D_{s\\leftarrow r}^{p} > D_{s\\leftarrow r}^{\\hat{p}}$ , or $D_{s}^{p} > D_{s}^{\\hat{p}}$ but $D_{s\\leftarrow r}^{p} < D_{s\\leftarrow r}^{\\hat{p}}$ , then $h(p, \\hat{p})$ penalizes the depth difference $|D_{s}^{\\hat{p}} - D_{s}^{p}|$ beyond a threshold $m$ , to prevent the depth values from shifting dramatically.", + "bbox": [ + 75, + 316, + 470, + 513 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Our bilateral geometric consistency loss is then defined as a weighted sum of $L_{rel}$ and $L_{unr}$ :", + "bbox": [ + 75, + 513, + 468, + 545 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {b g c} = \\lambda_ {r e l} L _ {r e l} + \\lambda_ {u n r} L _ {u n r}. \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 169, + 556, + 468, + 574 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "This loss enables us to thoroughly explore the information from both reliable and unreliable regions, facilitating the learning of cross-view consistency. Note that we also apply Eq. 9 on input views $I_{r}$ as a depth regularization between the rendered depth and $D_{r}$ for fully exploring the depth prior.", + "bbox": [ + 75, + 585, + 468, + 662 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Unreliability for Voxel Feature Regularization", + "text_level": 1, + "bbox": [ + 76, + 670, + 465, + 686 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this section, we incorporate the unreliability on regularizing the feature of each position of the voxel grid. With a proper design of reliability-aware voxel smoothing and reliability-aware learning adjustment, we further improve the quality of the rendered image, avoiding suboptimal scene reconstruction.", + "bbox": [ + 75, + 695, + 468, + 785 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Reliability-aware Voxel Smoothing. Employing voxelized feature representations [37, 38] can significantly improve the training and rendering speed of NeRF, by storing the RGB features $f_{c}$ and density $\\sigma$ in a voxel grids. To facilitate the learning of voxel representation, DVGO [37, 38] propose a differentiable voxel smoothing loss, which regularizes the difference of $f_{c}$ and $\\sigma$ between a given voxel v", + "bbox": [ + 75, + 794, + 470, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "with its six adjacent points $V$ as follows:", + "bbox": [ + 498, + 90, + 769, + 106 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL (\\mathbf {v}) = \\sum_ {\\hat {\\mathbf {v}} \\in V} \\Delta_ {f _ {c}} (\\mathbf {v}, \\hat {\\mathbf {v}}) + \\Delta_ {\\sigma} (\\mathbf {v}, \\hat {\\mathbf {v}}), \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 573, + 113, + 892, + 143 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\Delta (\\cdot ,\\cdot)$ denotes an error metric for the difference (e.g., $L_{1},L_{2}$ , or Huber loss).", + "bbox": [ + 500, + 152, + 892, + 183 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "However, under the few-shot scenario, learning on the sparse input views can easily overfit the view-specific image, which could lead to a degenerated voxel grid that may contain fluctuant features. To address this issue, we propose to regularize the voxel features for balanced and smooth learning. By taking the unreliability of each synthesized novel view image into consideration, we mitigate the influence of unreliable regions while promoting learning in more reliable areas. We design a reliability-aware smooth factor $\\rho (\\mathbf{v})$ for each voxel in the grid. Specifically, given a warped image, we cast $O$ rays $\\mathbf{r}$ through each pixel of the reliable regions $R_{rel}$ . For each voxel $\\mathbf{v}$ , we obtain a reliability score by accumulating the number of rays that pass this voxel, denoted by $S(\\mathbf{v})$ . The maximum number of times being passed by rays is denoted as $S(\\mathbf{v})_{max}$ . Then the reliability-aware smooth factor is defined as $\\rho (v) = \\frac{S(\\mathbf{v})}{S(\\mathbf{v})_{max}}$ . Finally, we formulate the reliability-aware voxel smoothing losses on $f_{c}$ and $\\sigma$ as:", + "bbox": [ + 498, + 184, + 893, + 444 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {f _ {c}} = \\sum_ {\\mathbf {v}} \\sum_ {\\hat {\\mathbf {v}} \\in V} (1 + e ^ {- \\rho (\\mathbf {v})}) \\Delta_ {f _ {c}} (\\mathbf {v}, \\hat {\\mathbf {v}}), \\tag {13}\n$$\n", + "text_format": "latex", + "bbox": [ + 563, + 450, + 892, + 489 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {\\sigma} = \\sum_ {\\mathbf {v}} \\sum_ {\\hat {\\mathbf {v}} \\in V} (1 + e ^ {- \\rho (\\mathbf {v})}) \\Delta_ {\\sigma} (\\mathbf {v}, \\hat {\\mathbf {v}}).\n$$\n", + "text_format": "latex", + "bbox": [ + 570, + 487, + 818, + 517 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The final regularization loss is defined as follows:", + "bbox": [ + 500, + 525, + 826, + 540 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nL _ {r s} = \\lambda_ {f} L _ {f c} + \\lambda_ {d} L _ {\\sigma}. \\tag {14}\n$$\n", + "text_format": "latex", + "bbox": [ + 617, + 549, + 890, + 566 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this case, the unreliable regions will have smoother supervision during training, mitigating the inconsistency caused by potential overfitting.", + "bbox": [ + 498, + 571, + 893, + 618 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Reliability-guided Learning Adjustment. To further facilitate the learning of geometric and appearance information, we apply a reliability-guided learning strategy to dynamically prioritize the learning towards the reliable zones, while eliminating the false supervision of unreliable regions at the beginning of training. Concretely, we adjust the importance of each voxel $\\mathbf{v}$ with a reliability weight $\\mathbf{w}_{\\mathbf{v}} = 1 + \\rho (\\mathbf{v})$ , to control the gradients of each voxel during the back-propagation.", + "bbox": [ + 498, + 625, + 893, + 762 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.5. Optimization of ReVoRF", + "text_level": 1, + "bbox": [ + 500, + 768, + 725, + 784 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To avoid dramatic variation of the unreliable depth, we further adopt a depth smoothness loss function [29] as an extra regularization for better relative depth supervision:", + "bbox": [ + 498, + 792, + 890, + 839 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} L _ {d s} = \\frac {1}{| R |} \\sum_ {r \\in R} \\sum_ {(x, y) \\in D} \\| d (x, y) - d (x, y + 1) \\| _ {2} ^ {2} \\tag {15} \\\\ + \\left\\| d (x, y) - d (x + 1, y) \\right\\| _ {2} ^ {2}, \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 509, + 844, + 892, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "20346", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/34e704c7bbc557b2cc0aea634386231206762ca28cc7f7a5ba26425ba5d0f4b3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 96, + 85, + 253, + 157 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/67953f65e3bfaf16a95751315d1576b3150547758bf83c41430d208ca47d5f6f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 96, + 164, + 254, + 261 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/eb4c5af9f426d79205ef3573a8e5ef8f7e6563e6635fb8d8965246dd0b88965a.jpg", + "image_caption": [ + "Diet-NeRF [14]", + "Figure 3. 4-views reconstructions on Realistic Synthetic $360^{\\circ}$ [26]. ReVoRF enables more consistent reconstruction with detailed appearance." + ], + "image_footnote": [], + "bbox": [ + 122, + 273, + 254, + 330 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/1157a21e45b6b2fabbcc29b7427f4f5af9aaa52afef161c71795b4840d3caf78.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 259, + 126, + 400, + 199 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/f7b95f595c67f4533ec41d6cfc700b5fbd292b521073c209927ff032c48bc2b6.jpg", + "image_caption": [ + "InfoNeRF [17]" + ], + "image_footnote": [], + "bbox": [ + 272, + 212, + 380, + 306 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/bb85b821bad12407d2e2935e95d6bf8bb50fcf427413a5e4cf1392d95cdd9802.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 415, + 126, + 552, + 190 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/be284e27d22dc72d674d854053e2fcbd2f3b50e82535b805e5909a3a8993355e.jpg", + "image_caption": [ + "VGOS [39]" + ], + "image_footnote": [], + "bbox": [ + 426, + 215, + 535, + 311 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/d8143693e9e95f1fda6b73721b748909906dc28a1558627e5a1ca73907a331c1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 566, + 126, + 705, + 190 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e03ac08eabf960eb27d7cb1d3374096dfe54878d00758cd31ca40d26e7caa39f.jpg", + "image_caption": [ + "ReVoRF (Ours)" + ], + "image_footnote": [], + "bbox": [ + 581, + 217, + 691, + 311 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/fe50330791af82f21f2eade031f26e608e5001a389e14a9acdea170301dad840.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 722, + 126, + 859, + 190 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/1c9a4891dd50d629cd499a1d0b315e752c8d77adf7ccc4dedfc23d8318895d58.jpg", + "image_caption": [ + "GT" + ], + "image_footnote": [], + "bbox": [ + 735, + 217, + 844, + 311 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/72df23a26e6273a8c3b1774e093f85de3790219f635aae45a5ca2d297ffe1d0f.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Realistic Synthetic 360° dataset
MethodsPSNR↑SSIM↑LPIPS↓Training Time↓
NeRF [24]15.930.7800.3202 hrs
PixelNeRF [47]16.090.7380.3903-4 days* + 10 hrs
DietNeRF [14]16.060.7930.30619 hrs
3DGS [16]17.550.7010.2503 mins
InfoNeRF [17]18.620.8110.2304 hrs
VGOS [39]18.910.8250.2053 mins
GeCoNeRF [18]19.780.8800.185>2 hrs
Ours20.720.8480.1797 mins
", + "bbox": [ + 81, + 369, + 483, + 507 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 1. Quantitative comparison for 4-views setting in the Realistic Synthetic $360^{\\circ}$ dataset [24]. The best and the second-best results are highlighted in bold and underlined, respectively. (*) denotes the time cost of pre-training.", + "bbox": [ + 76, + 507, + 470, + 563 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $R$ represents the set of rays emanating from the sampled views, $D$ refers to the depth patch that is centered around $r$ , and $d(x,y)$ is of the depth value in position $(x,y)$ .", + "bbox": [ + 76, + 571, + 470, + 618 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The final objective of ReVoRF is formulated as:", + "bbox": [ + 96, + 618, + 413, + 632 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\nL _ {\\text {t o t a l}} = L _ {r g b} + L _ {b g c} + L _ {r s} + \\lambda_ {d s} L _ {d s}. \\tag {16}\n$$\n", + "text_format": "latex", + "bbox": [ + 140, + 641, + 468, + 657 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 691, + 209, + 709 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In this section, we demonstrate the superiority of the proposed ReVoRF through extensive experiments. The details of experiment settings are discussed in Sec. 4.1. Analysis on comparison experiments and ablation study are performed in Sec. 4.2 and Sec. 4.3, respectively.", + "bbox": [ + 75, + 717, + 470, + 794 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.1. Experiment Settings", + "text_level": 1, + "bbox": [ + 76, + 801, + 269, + 816 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Datasets. The experiments are conducted on inward-facing scenes from the Realistic Synthetic $360^{\\circ}$ dataset [26] and forward-facing scenes from the LLFF dataset [25].", + "bbox": [ + 76, + 824, + 468, + 869 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Realistic Synthetic $360^{\\circ}$ comprises path-traced images from 8 synthetic scenes, which are characterized by their", + "bbox": [ + 76, + 869, + 470, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "complex geometry and realistic rendering of non-Lambertian materials. Each scene is represented by 400 images, rendered by inward-facing virtual cameras positioned at varying viewpoints. We adhere to the protocol established by InfoNeRF [17] and randomly select 4 views from 100 training images as sparse inputs. The model's performance is then evaluated on a set of 200 testing images.", + "bbox": [ + 496, + 372, + 893, + 477 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "LLFF consists of 8 real-world scenes captured with a handheld cellphone, featuring 20 to 62 forward-facing images per scene. These scenes encompass a range of complex environments. In line with the standard protocol [26], we reserve 1/8 of these images for testing purposes. The remaining images are used for training, from which we randomly sample three views for input into our model.", + "bbox": [ + 496, + 479, + 893, + 585 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation Details. Following DVGO [37, 38], we adopt a coarse-to-fine optimization scheme to stabilize the training of ReVoRF and gradually improve the geometric details. During the whole training period, we set the values of $\\lambda_{rel}$ and $\\lambda_{unr}$ in Eq. 11 as $10^{-1}$ and $10^{-2}$ , respectively. The values of $\\lambda_d$ , $\\lambda_f$ in Eq. 14, and $\\lambda_{ds}$ in Eq. 15 are set as $5\\cdot 10^{-4}$ , $5\\cdot 10^{-5}$ , and $5\\cdot 10^{-5}$ in the coarse stage, and decreased to $5\\cdot 10^{-5}$ , $10^{-5}$ , and $5\\cdot 10^{-5}$ in the fine stage. The warping poses collected for the Realistic Synthetic $360^{\\circ}$ dataset [24] and the LLFF dataset [20] are different. For Realistic Synthetic $360^{\\circ}$ , we randomly vary the polar angle $\\theta$ and azimuthal angle $\\phi$ in the range of $[5^{\\circ}, 10^{\\circ}]$ based on the input view, and subsequently warp each input sparse view to its four neighboring views defined by $\\{(\\theta, \\phi), (-\\theta, \\phi), (\\theta, -\\phi), (-\\theta, -\\phi)\\}$ . For the LLFF dataset, the warped views are obtained by randomly interpolating between every adjacent input view. To speed up the training stage and improve the quality of depth supervision, the warping is performed periodically, which updates the warped depth maps and RGB images every 1000 training steps.", + "bbox": [ + 496, + 604, + 893, + 909 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "20347", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/cf8dd9c562fa92a11be0bda80ea3c98de83bab810303a1b68ff92424d9448a0e.jpg", + "image_caption": [ + "Figure 4. Comparisons on the LLFF dataset [25] in 3-view setting. The red and blue boxes denote compared regions. Our approach achieves better results in reconstructing fine details with enhanced clarity. Please zoom in for details." + ], + "image_footnote": [], + "bbox": [ + 81, + 88, + 883, + 287 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/e0750cdbe3c92b5f7a2dff00ed4897141cbf1e885f3c070bcb1f7a109898c3e0.jpg", + "table_caption": [], + "table_footnote": [ + "Table 2. Quantitative comparison for 3-views setting on LLFF [20]. The best and the second-best results are highlighted in bold and underlined, respectively. (*) signifies the pre-training time." + ], + "table_body": "
NeRF LLFF dataset
MethodsPSNR↑SSIM↑LPIPS↓Training Time↓
PixelNeRF [47]16.170.4380.5123-4 days* + 10 hrs
SRF [7]17.070.4360.5292-3 days* + 43mins
MVSNeRF [5]17.880.5840.3271-2 days* + 10mins
Mip-NeRF [2]14.620.3510.49514 hrs
DietNeRF [14]14.940.3700.49618 hrs
3DGS [16]13.050.4070.38813 mins
RegNeRF [29]19.080.5870.3364 hrs
VGOS [39]19.350.6200.4325 mins
SparseNeRF [12]19.860.6240.328>2 hrs
Ours19.260.6440.31611 mins
", + "bbox": [ + 81, + 330, + 483, + 488 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Evaluation Metrics. To assess the effectiveness of our method, we employ several established metrics, including PSNR (Peak Signal-to-Noise Ratio) for assessing image reconstruction accuracy, SSIM (Structural Similarity Index Measure) [43] for evaluating changes in luminance and contrast that affect structural integrity, and LPIPS (Learned Perceptual Image Patch Similarity) [50], which uses deep learning to approximate human visual perception. These metrics provide a comprehensive analysis of our model's performance, covering aspects of accuracy, perceptual quality, and structural fidelity in the reconstructed images.", + "bbox": [ + 75, + 542, + 470, + 710 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Comparisons", + "text_level": 1, + "bbox": [ + 76, + 719, + 217, + 734 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "On the Realistic Synthetic $360^{\\circ}$ dataset [24], we compare our method with state-of-the-art approaches, including RegNeRF [29], DietNeRF [14], infoNeRF [17], VGOS [39], PixelNeRF [47], and GeCoNeRF [18], in a 4-view setting. On the LLFF dataset [20], we implement our method in a 3-view setting and compare with SRF [7], MVSNeRF [5], mip-NeRF [2], DietNeRF [14], RegNeRF [29], VGOS [39], SparseNeRF [12] and GeCoNeRF [18]. We adopt the reported results from VGOS [39], sparseNeRF [12], and GeCoNeRF [18]. Besides, we also compare with the advanced reconstruction method 3DGS [16].", + "bbox": [ + 75, + 742, + 472, + 909 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Qualitative Experiments. Fig. 3 compares our approach with some recent methods on the Realistic Synthetic $360^{\\circ}$ dataset [24]. Diet-NeRF [14] performs poorly in the setting of 4 views, while infoNeRF [17] and VGOS [39] are inferior to our method in terms of both geometric shapes and detail resolution. Our approach demonstrates superior performance in both geometry and details.", + "bbox": [ + 496, + 333, + 893, + 438 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Fig. 4 shows a qualitative comparison on a scene from the LLFF dataset [20]. While all methods can recover the overall structure of the scene, our approach excels at the quality of details as shown in the magnified regions. Our method incorporates smoothness while retaining fine details, achieving the most natural results.", + "bbox": [ + 496, + 439, + 893, + 529 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Quantitative Experiments. Table 1 shows quantitative results from different methods on the Realistic Synthetic $360^{\\circ}$ dataset [24]. In terms of training time, our method is at least an order of magnitude faster than all other methods except for VGOS [39]. Although our method is slightly lower than VGOS [39], it significantly enhances the PSNR, LPIPS [50], and SSIM [43] of the rendered images. Our method achieves state-of-the-art accuracy in PSNR and LPIPS [50]. Additionally, despite not utilizing a pre-trained model or perceptual loss for high-level semantic information extraction, our method still achieves the second-best performance in perceived SSIM [43].", + "bbox": [ + 496, + 537, + 893, + 718 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2 shows a quantitative comparison on the LLFF dataset [20]. Our method achieves the highest scores in both SSIM [43] and LPIPS [50], indicating that our images exhibit the best performance in terms of human perceptual reconstruction. We also achieve the third-highest PSNR, which, together with our state-of-the-art performance in SSIM [43] and LPIPS [50], demonstrates that our approach has made improvements in certain aspects of image rendering.", + "bbox": [ + 496, + 718, + 893, + 840 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 847, + 653, + 863 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our ablation study is segmented into five distinct groups with Table 3, with DVGO [37, 38] serving", + "bbox": [ + 500, + 869, + 892, + 901 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "20348", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/2785d3dbbe3277c2ec433c3cee91061c2416cc98f381fa11e45033e0651525e9.jpg", + "image_caption": [ + "Baseline" + ], + "image_footnote": [], + "bbox": [ + 133, + 99, + 220, + 204 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e624199123eecc53c7716e35ed4b67b6cc204cf2ad08b49dfd17f3ab11e82c59.jpg", + "image_caption": [ + "Baseline $+L_{rel}$", + "Figure 5. Visualizations of the ablation on Chair scene from the Realistic Synthetic $360^{\\circ}$ [26] dataset in 4 views setting. With the proposed losses, our methods could gradually improve the cross-view consistency and reduce the noise compared with the baseline." + ], + "image_footnote": [], + "bbox": [ + 285, + 101, + 375, + 207 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/1cfb2111e597c0414c937bc4db59a0913658abaad11e1faa64896460b9ea4218.jpg", + "image_caption": [ + "Baseline $+L_{rel} + L_{unr}$" + ], + "image_footnote": [], + "bbox": [ + 437, + 101, + 529, + 200 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/186207c7eb38dd4ff8774aefe41db8c661aaa88b175c15720d61045dae9fed9c.jpg", + "image_caption": [ + "Baseline $+L_{rel} + L_{unr} + L_{ds}$" + ], + "image_footnote": [], + "bbox": [ + 593, + 101, + 684, + 200 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5e7236f892ecd712fc54ad3887616e6fd7115007eba54e38e499b5ae3dac60e3.jpg", + "image_caption": [ + "Full Model" + ], + "image_footnote": [], + "bbox": [ + 748, + 101, + 836, + 202 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/9e5c093b14d595fbafd25ff7828689f67bb8f0e190db6e43b48fea999165bec6.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
LrsLdsUnrRelPSNR↑SSIM↑LPIPS↓
17.190.7670.223
✓17.790.7800.243
✓✓19.010.8050.228
✓✓✓19.230.8110.220
✓✓✓✓20.720.8480.179
", + "bbox": [ + 109, + 266, + 431, + 349 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "as the baseline. We incrementally introduce our proposed contributions along with various regularization methods to enhance the model's rendering quality. The groups are delineated as: baseline, baseline $+L_{rel}$ , baseline $+L_{rel} + L_{unr}$ , baseline $+L_{rel} + L_{unr} + L_{ds}$ , and baseline $+L_{rel} + L_{unr} + L_{ds} + L_{rs}$ . The ablation results reveal that each incremental contribution positively impacts the rendering quality in various aspects. After the addition of $L_{rel}$ , our PSNR increased by 0.6. Subsequent inclusion of $L_{unr}$ led to a further rise in PSNR by 1.22. With the incorporation of $L_{ds}$ , the PSNR went from 19.01 to 19.23. Finally, after adding $L_{rs}$ , our PSNR peaked at 20.72, SSIM [43] reached 0.848, and LPIPS [50] arrived at 0.179, marking a significant enhancement.", + "bbox": [ + 75, + 430, + 472, + 642 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Besides, we explore the potential of ReVoRF under the settings where more input views are available. We report extra results for 6-view and 9-view settings in Table 4, demonstrating that increased input views generally enhance performance. ReVoRF maintains superiority across these settings.", + "bbox": [ + 75, + 650, + 470, + 726 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Fig. 5 presents the visualization of our ablation study on the Chair scene. We incorporated $L_{rel}$ to enhance the texture quality of the model, which, however, introduced some noise artifacts. To mitigate these artifacts, $L_{unr}$ and $L_{ds}$ were subsequently integrated. These adjustments successfully reduced noise but at the cost of blurring the geometric structures in the process. The issue of maintaining geometric consistency while eliminating noise was addressed through the implementation of $L_{rs}$ . We observe that our method effectively prevents the collapse of new views caused by overfitting due to a limited number of viewpoints.", + "bbox": [ + 75, + 734, + 472, + 902 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/8d4903dddc1ebb95a3219643f9f7b1a34254ce4283b48d670f51ba1f73f14021.jpg", + "table_caption": [ + "Table 3. Ablation study on the Realistic Synthetic $360^{\\circ}$ dataset [24] in the 4-view setting. The best and the second-best results are highlighted in bold and underlined, respectively." + ], + "table_footnote": [], + "table_body": "
MethodsPSNR↑SSIM↑LPIPS↓
3-view6-view9-view3-view6-view9-view3-view6-view9-view
SRF [7]17.0716.7517.390.4360.4380.4650.5290.5210.503
PixelNeRF [47]16.1717.0318.920.4380.4730.5350.5120.4770.430
MVSNeRF [5]17.8819.9920.470.5840.6600.6950.3270.2640.244
DVGO [37]16.6021.2522.890.5600.7040.7460.4220.2460.228
VGOS [39]19.3521.5522.390.6200.6710.6920.4320.3280.325
Ours19.2622.2123.040.6440.7200.7530.3160.2690.225
", + "bbox": [ + 503, + 267, + 890, + 364 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 4. Comparison of 3, 6, and 9 input views on LLFF [20]. The best and the second-best results are highlighted in bold and underlined, respectively.", + "bbox": [ + 500, + 366, + 893, + 407 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion, Limitation, and Future Work", + "text_level": 1, + "bbox": [ + 500, + 426, + 872, + 444 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we address the challenge of view deformation by discerning reliable and unreliable areas, subsequently introducing a bilateral geometric consistency regularization. This approach maximizes the use of reliable regions while delicately exploring the depth in unreliable areas, applying a more lenient constraint to these zones. Further extending our method into voxel space, we transform 2D reliable areas into 3D space through a reliability-aware voxelization smoothing process. Our method, when applied to various datasets, has proven to be highly precise, significantly bolstering geometric consistency and demonstrating its efficacy in intricate 3D reconstruction tasks.", + "bbox": [ + 496, + 455, + 893, + 636 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Our method shares a common limitation of the voxel-based method: the tendency to produce smoothed results, leading to a loss in fine details. Besides, the exceptionally challenging context for NeRF with sparse input also limits its application in more complex scenes, such as large-scale scene reconstruction. For future work, we aim to refine the voxelization technique to better preserve details, potentially exploring hybrid models that combine voxel-based methods with alternative geometric representations for a more detailed reconstruction.", + "bbox": [ + 496, + 642, + 893, + 792 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement. The work is supported by the Guangdong Natural Science Funds for Distinguished Young Scholar (No. 2023B1515020097), Singapore MOE Tier 1 Funds (MSS23C002), and the NRF Singapore under the AI Singapore Programme (No. AISG3-GV-2023-011).", + "bbox": [ + 496, + 825, + 893, + 902 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "20349", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Alexander Amini, Wilko Schwarting, Ava Soleimany, and Daniela Rus. Deep evidential regression. In NeurIPS, volume 33, pages 14927-14937, 2020. 3", + "[2] Jonathan T Barron, Ben Mildenhall, Matthew Tancik, Peter Hedman, Ricardo Martin-Brualla, and Pratul P Srinivasan. Mip-nerf: A multiscale representation for anti-aliasing neural radiance fields. 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IEEE TVCG, 2024. 2" + ], + "bbox": [ + 501, + 92, + 893, + 415 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "20351", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_model.json b/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_model.json new file mode 100644 index 0000000000000000000000000000000000000000..d7158ed3943dac7ec6bf72ac842f30b051509e13 --- /dev/null +++ b/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_model.json @@ -0,0 +1,2387 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.155, + 0.131, + 0.819, + 0.178 + ], + "angle": 0, + "content": "Learning with Unreliability: Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency" + }, + { + "type": "text", + "bbox": [ + 0.171, + 0.188, + 0.807, + 0.245 + ], + "angle": 0, + "content": "Yingjie Xu\\(^{1,2*}\\) Bangzhen Liu\\(^{2*}\\) Hao Tang\\(^{1,3}\\) Bailin Deng\\(^{4}\\) Shengfeng He\\(^{1\\dagger}\\) \n\\(^{1}\\)Singapore Management University \\(^{2}\\)South China University of Technology \\(^{3}\\)Nanjing University of Science and Technology \\(^{4}\\)Cardiff University" + }, + { + "type": "image", + "bbox": [ + 0.086, + 0.25, + 0.552, + 0.467 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.572, + 0.283, + 0.858, + 0.467 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.468, + 0.895, + 0.539 + ], + "angle": 0, + "content": "Figure 1. We present ReVoRF, a voxel-based framework designed to capitalize on the unreliability inherent in warped novel views. (b) demonstrates the warping outcomes, where black holes signify unmatched pixels from the original view. (c) illustrates the results of training when these holes are masked out, which unfortunately results in ambiguous geometric structures. In contrast, (d) showcases our approach's ability to maintain correct geometric consistency. ReVoRF achieves this by leveraging relational depth prior knowledge within these unreliable hole regions. Our approach demonstrates the best reconstruction quality while being one of the fastest few-shot approaches in (e)." + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.548, + 0.314, + 0.563 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.565, + 0.474, + 0.868 + ], + "angle": 0, + "content": "We propose a voxel-based optimization framework, ReVoRF, for few-shot radiance fields that strategically address the unreliability in pseudo novel view synthesis. Our method pivots on the insight that relative depth relationships within neighboring regions are more reliable than the absolute color values in disoccluded areas. Consequently, we devise a bilateral geometric consistency loss that carefully navigates the trade-off between color fidelity and geometric accuracy in the context of depth consistency for uncertain regions. Moreover, we present a reliability-guided learning strategy to discern and utilize the variable quality across synthesized views, complemented by a reliability-aware voxel smoothing algorithm that smoothens the transition between reliable and unreliable data patches. Our approach allows for a more nuanced use of all available data, promoting enhanced learning from regions previously considered unsuitable for high-quality reconstruction. Extensive experiments across diverse datasets reveal that our approach attains significant gains in efficiency and accuracy, delivering rendering speeds of 3 FPS, 7 mins to train a \\(360^{\\circ}\\) scene, and" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.549, + 0.895, + 0.581 + ], + "angle": 0, + "content": "a \\(5\\%\\) improvement in PSNR over existing few-shot methods. Code is available at https://github.com/HKCLynn/ReVoRF." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.604, + 0.633, + 0.62 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.895, + 0.765 + ], + "angle": 0, + "content": "Neural Radiance Fields (NeRF) have revolutionized the fields of novel view synthesis and 3D reconstruction by leveraging an implicit function optimized from a collection of 2D images [2, 13, 24, 27]. Despite their remarkable rendering capabilities, NeRFs are hampered by the substantial cost and time required to gather dense image sets for a given scene [6,41,47]. This challenge has spurred the development of Few-shot NeRF, an emerging domain focused on reconstructing 3D scenes with minimal image data [6,8, 12, 18]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.766, + 0.896, + 0.902 + ], + "angle": 0, + "content": "The performance of NeRF in accurately reconstructing geometry and texture diminishes when faced with sparse observations, as it tends to overfit the limited views available [8, 49]. To address this issue, there has been a push in recent studies to fortify NeRF with additional priors [46, 47], including semantic relations [14], depth cues [49], and entropy constraints [17]. These enhancements strive to extract maximum information from limited data. However, the reconstructions are inherently limited by the insufficient" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.875, + 0.345, + 0.888 + ], + "angle": 0, + "content": "*The first two authors contributed equally." + }, + { + "type": "page_footnote", + "bbox": [ + 0.097, + 0.888, + 0.37, + 0.901 + ], + "angle": 0, + "content": "† Corresponding author (shengfenghe@smu.edu.sg)." + }, + { + "type": "list", + "bbox": [ + 0.096, + 0.875, + 0.37, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "20342" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.342, + 0.106 + ], + "angle": 0, + "content": "coherence of the sparse views provided." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.11, + 0.471, + 0.351 + ], + "angle": 0, + "content": "Recent research has explored overcoming the challenges posed by very limited observations through pseudo-view synthesis [3, 18]. By using known camera poses and coarse depth estimates, these methods generate warped images from sparse viewpoints to enhance cross-view consistency. However, as shown in Fig. 1b, these generated images often include noisy areas with artifacts, which, if used for learning, can lead to inconsistent training signals and compromise scene integrity. To address this, Kwak et al. [18] implement self-occlusion aware masking to exclude unreliable regions. While this selective masking successfully filters out areas of uncertainty, it also introduces voids, presenting a conundrum: refining these images can bring in inconsistent noise and floaters, as illustrated in Fig. 1c, yet the limited number of usable samples necessitates using all available pseudo supervision for quality reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.355, + 0.471, + 0.61 + ], + "angle": 0, + "content": "In light of the issues identified with unreliable warped areas, our paper proposes a novel method for fully exploiting these uncertain regions to achieve multi-view consistency learning. The rationale behind our method is that, although absolute supervision is not reliable in those disoccluded regions, we observe that they maintain consistent relative depth relationships. The unreliability of certain regions in warped images can still bear geometric resemblances to their original view counterparts. We find that local depth information within these images can indicate geometric disparities, offering a self-supervised signal that aids in discerning the geometry of regions lacking precise textural information. While reliable regions offer more accurate supervision, our approach seeks to fully utilize all the information present, exploiting depth cues in coarsely warped images to inform the learning process across both reliable and traditionally discarded unreliable areas." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.614, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Drawing from the insights above, we propose a novel voxel-based optimization framework, ReVoRF, tailored for fast and multi-view consistent reconstruction of few-shot radiance fields, which incorporates the relative depth priors from several aspects. The objective of this work is to concurrently explore information from both dependable and less reliable regions within the warped novel view images. In the first step, we randomly warp the sparse images onto a series of novel views, subsequently delineating reliable and unreliable regions based on the pixel-wise correlation between the input and novel view. We then introduce a bilateral geometric consistency loss to enable self-training on novel synthesized images. This loss encompasses a reconstruction term in a bilateral manner, including a color and density regularization term for reliable regions and a relative depth consistency term for unreliable regions, respectively. While the former term aims at explicitly learning the geometric context of the reliable regions, the relative depth regularization is applied for implicitly exploring the geometric consistency guided" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.258 + ], + "angle": 0, + "content": "by relative depth. Moreover, we integrate unreliability into our voxelization of scene features: 1) a reliability-guided learning strategy that dynamically adjusts learning priorities towards more reliable regions; 2) a reliability-aware voxel smoothing procedure that preserves structural integrity in reliable zones and mitigates inconsistencies in less reliable ones, ensuring a balanced and coherent scene reconstruction. As illustrated in Fig. 1e, assisted by both bilateral geometric consistency loss and reliability-aware regularization, our method is the second fastest while achieving the best reconstruction fidelity, with a large margin over the others." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.258, + 0.844, + 0.272 + ], + "angle": 0, + "content": "Our contributions can be summarized as follows:" + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.28, + 0.892, + 0.356 + ], + "angle": 0, + "content": "- We present the first attempt to explore pseudo-views unreliability within few-shot radiance fields, presenting the first framework to incorporate these areas for enhanced multi-view consistency learning with a bilateral geometric consistency loss." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.364, + 0.892, + 0.439 + ], + "angle": 0, + "content": "- We introduce a reliability-guided learning strategy and voxelization smoothing procedure that tailors the learning process to the reliability of data, thus optimizing the training emphasis for improved reconstruction quality in few-shot radiance fields." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.448, + 0.892, + 0.508 + ], + "angle": 0, + "content": "- We demonstrate superior performance of our approach against existing state-of-the-art few-shot methods in efficiency and accuracy, through extensive experiments on both synthetic and real-world datasets." + }, + { + "type": "list", + "bbox": [ + 0.519, + 0.28, + 0.892, + 0.508 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.521, + 0.642, + 0.537 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.546, + 0.895, + 0.864 + ], + "angle": 0, + "content": "Neural Radiance Fields (NeRF). NeRF [2,5,13,22,24] have emerged as a significant advancement in 3D reconstruction and novel view synthesis. These methods employ an implicit function to represent a 3D scene, enabling the extraction of detailed geometric and textural information from a set of multi-view images. Subsequent researchers have broadened the scope of NeRF applications, including generative modeling [11,40], video synthesis [9,20,34], and scene editing [21,48]. Despite the impressive rendering quality, the training of vanilla NeRF often spans several days for a single scene reconstruction. Recent advancements [10,27,37,38] have endeavored to mitigate this computational burden. Approaches such as DVGO [4,37,38] employ dense voxel grids in conjunction with shallow multilayer perceptrons to expedite the reconstruction process. Similarly, Plenoxels [10] utilizes sparse voxel grids, and Instant-NGP [27] employs a multi-resolution hash table to delineate the radiance field more efficiently. Diverse from these methods, which typically require dense inputs, we aim to address the challenge of achieving fast and high-fidelity scene reconstruction in the case where only a few observed views are available." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Few-Shot NeRFs. Recent advances [5, 14, 17, 47, 49, 51] have sought to reduce the dependency on densely collected" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "20343" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.485 + ], + "angle": 0, + "content": "data for scene reconstruction, leveraging sparse inputs and scene priors. Notably, PixelNeRF [47] and StereoRF [7] utilize local semantic relationships across multiple scenes, while MVSNeRF [5] incorporates cost volume to enhance performance. These methodologies, however, require pretraining on numerous scenes to acquire necessary scene priors. Further developments [14, 17, 31, 39, 46] have introduced various regularization techniques to maximize the utility of sparse input views. InfoNeRF [17] enhances ray adjacency consistency through entropy regularization. DietNeRF [14] facilitates cross-view semantic consistency by harnessing the semantic space of the pretrained CLIP [31], while DiffusioNeRF [44] explores the diffusion prior of pretrained diffusion models. Additionally, FreeNeRF [46] applies frequency regularization, and VGOS [39] introduces voxel regularization to optimize both feature representation and density. Another group of research focuses on augmenting sparse inputs with synthetically generated views. RapNeRF [49] utilizes geometric re-projection for novel view extrapolation, while VmNeRF [3] employs depth maps for view-morphing. GeCoNeRF [18] aims to refine geometric consistency by separating reliable regions from warped images and discarding unreliable areas prone to self-occlusion. Our work diverges from these approaches by considering the inherent information of both reliable and unreliable regions of the novel view images, facilitating cross-view geometric consistency." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.492, + 0.472, + 0.81 + ], + "angle": 0, + "content": "Unreliability/Uncertainty Modeling. In the rapid development of NeRF, the incorporation of uncertainty modeling has become crucial for achieving robustness in 3D reconstruction from sparse views. Previous efforts have employed diverse strategies, including Bayesian approaches [15, 28] and evidential neural networks [1,33], to quantify uncertainty in neural networks. In the context of NeRF, uncertainty has been harnessed to enhance rendering and guide input capture. Some methods assume Gaussian noise in RGB space for pixel-wise uncertainty [22, 30], employ volumetric entropy for scene geometry [19, 45], or adopt variational inference or Latent Variable Modeling for radiance field uncertainty as seen in S-NeRF [36] and CF-NeRF [35]. However, these approaches have not comprehensively addressed uncertainty quantification in unseen regions. Our approach differs from these methods by not only capturing uncertainty in the geometry and appearance of visible areas but also explicitly accounting for unseen spaces, including occluded points, which previous methods have not considered. This distinction allows for a more nuanced and accurate reconstruction, promising to elevate the fidelity of few-shot NeRF models." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.822, + 0.212, + 0.839 + ], + "angle": 0, + "content": "3. Methodology" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.848, + 0.218, + 0.862 + ], + "angle": 0, + "content": "3.1. Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.472, + 0.901 + ], + "angle": 0, + "content": "NeRF [24] represents a scene as a continuously differentiable function \\( f \\) via a Multi-Layer Perceptron (MLP)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.215 + ], + "angle": 0, + "content": "Given a 3D position \\(\\mathbf{x} \\in \\mathbb{R}^3\\) and the associated 2D viewing directions \\(\\mathbf{d} \\in \\mathbb{R}^2\\), NeRF maps them into a volume density \\(\\sigma \\in \\mathbb{R}\\) and an RGB value \\(\\mathbf{c} \\in \\mathbb{R}^3\\), such that: \\((\\mathbf{c}, \\sigma) = f(\\gamma(\\mathbf{x}), \\gamma(\\mathbf{d}))\\), where the \\(\\gamma\\) is a positional encoding that projects \\(\\mathbf{x}\\) and \\(\\mathbf{d}\\) into a higher dimensional feature space [42]. With a ray parameterized as \\(\\mathbf{r}_p(t) = \\mathbf{o} + t\\mathbf{d}_p\\) cast from the camera's optical center \\(\\mathbf{o}\\) along direction \\(\\mathbf{d}_p\\), the expected color \\(\\hat{C}(\\mathbf{r}_p)\\) of pixel \\(p\\) is rendered as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.551, + 0.228, + 0.894, + 0.263 + ], + "angle": 0, + "content": "\\[\n\\hat {C} (\\mathbf {r} _ {p}) = \\int_ {t _ {n}} ^ {t _ {f}} T (t) \\sigma (\\mathbf {r} _ {p} (t)) \\mathbf {c} (\\mathbf {r} _ {p} (t), \\mathbf {d} _ {p}) d t, \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.275, + 0.895, + 0.358 + ], + "angle": 0, + "content": "where \\( t_n \\) and \\( t_f \\) are the near and far bounds of the ray for sampling, and \\( T(t) = \\exp \\left(-\\int_{t_n}^t \\sigma(\\mathbf{r}(s)) ds\\right) \\) denotes the cumulative transparency along the ray from \\( t_n \\) to \\( t \\). Therefore, the NeRF can be optimized by a reconstruction loss between the rendered color \\( \\hat{C}(\\mathbf{r}) \\) and the real color \\( C(\\mathbf{r}) \\):" + }, + { + "type": "equation", + "bbox": [ + 0.595, + 0.371, + 0.893, + 0.403 + ], + "angle": 0, + "content": "\\[\nL _ {r g b} = \\sum_ {\\mathbf {r} \\in \\mathcal {R}} \\| \\hat {C} (\\mathbf {r}) - C (\\mathbf {r}) \\| ^ {2}, \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.416, + 0.771, + 0.431 + ], + "angle": 0, + "content": "where \\(\\mathcal{R}\\) denotes the set of training rays." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.444, + 0.611, + 0.457 + ], + "angle": 0, + "content": "3.2. Overview" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.468, + 0.895, + 0.62 + ], + "angle": 0, + "content": "We propose ReVoRF, a novel voxel-based optimization framework tailored for fast and multi-view consistent scene reconstruction from sparse input views. Our key idea is to incorporate the unreliability information for fully exploring the warped novel view images. By treating depth priors as the unreliability metrics, ReVoRF facilitates the reconstruction of the few-shot radiance field from several aspects, including the multi-view consistency learning (Sec. 3.3) and the regularization of voxel features (Sec. 3.4). The overall pipeline of ReVoRF is displayed in Fig. 2." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.631, + 0.845, + 0.647 + ], + "angle": 0, + "content": "3.3. Unreliability for Multi-view Consistency" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.655, + 0.895, + 0.701 + ], + "angle": 0, + "content": "In this section, we explore the potential of unreliability in facilitating multi-view geometric consistency via the proposed bilateral geometric consistency loss." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.714, + 0.896, + 0.902 + ], + "angle": 0, + "content": "Novel View Warping. Starting from a set of sparse input images \\( I_r^i \\) for \\( i \\in 1, \\dots, N_r \\), where \\( i \\) represents the view number and \\( N_r \\) is a small number, e.g., \\( N_r = 3 \\) or \\( N_r = 4 \\), we propose to synthesize novel view images \\( I_{s \\leftarrow r}^{i,j} \\) through a fast and flexible warping process on several novel views \\( j \\in 1, \\dots, N_s \\). To preserve the cross-view consistency, the warping is guided by a coarse depth map \\( D_r^i \\), where the depth value on each pixel \\( p \\) is accumulated by the density along each ray \\( r_p \\) omitted from the camera: \\( D_r^i(p) = \\int_{t_f}^{t_n} T(t) \\sigma(r_p(t)) t dt \\). Subsequently, we obtain the warped image \\( I_{s \\leftarrow r}^{i,j} \\) through a cross-view transformation \\( H_{s \\leftarrow r} \\), which deforms each pixel \\( p_r \\) of \\( I_r^i \\) to its correspond" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "20344" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.087, + 0.895, + 0.398 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.405, + 0.895, + 0.504 + ], + "angle": 0, + "content": "Figure 2. Overview of our proposed ReVoRF. Specifically, we first warp the sparse images onto several novel views and determine both the dependable and unreliable regions. Based on the dependability of each image region, we introduce a bilateral geometric consistency loss for multi-view consistent learning, which is composed of a color and density regularization term for reliable regions and a relative depth consistency term for unreliable regions. These two terms are responsible for explicitly learning the reliable geometric contents and implicitly exploring the geometric consistency via the guidance of relative depth, respectively. For voxel feature regularization, we integrate the unreliability through a reliability-guided learning strategy and a reliability-aware voxel smoothing procedure. By prioritizing the learning of more reliable regions and mitigating the inconsistencies in less reliable ones, ReVoRF ensures a more balanced and coherent reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.519, + 0.306, + 0.535 + ], + "angle": 0, + "content": "ing position \\(p_{s}\\) on the target view:" + }, + { + "type": "equation", + "bbox": [ + 0.18, + 0.551, + 0.47, + 0.587 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} p _ {s \\leftarrow r} = H _ {s \\leftarrow r} \\left(p _ {r}\\right) \\tag {3} \\\\ = f _ {s \\leftarrow w} \\left(f _ {w \\leftarrow r} \\left(p _ {r}\\right)\\right), \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.604, + 0.47, + 0.651 + ], + "angle": 0, + "content": "\\(f_{w\\leftarrow r}\\) is a mapping matrix from the pixel coordinate of \\(I_r^i\\) to the world coordinate and \\(f_{s\\leftarrow w}\\) is the inverse operation to the coordinate of \\(I_{s\\leftarrow r}^{i,j}\\), such that:" + }, + { + "type": "equation", + "bbox": [ + 0.162, + 0.666, + 0.47, + 0.684 + ], + "angle": 0, + "content": "\\[\nf _ {w \\leftarrow r} \\left(p _ {r}\\right) = D _ {r} ^ {i} \\left(p _ {r}\\right) T _ {r} ^ {- 1} K _ {r} ^ {- 1} p _ {r}, \\tag {4}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.162, + 0.687, + 0.47, + 0.704 + ], + "angle": 0, + "content": "\\[\nf _ {s \\leftarrow w} \\left(p _ {w}\\right) = K _ {s} T _ {s} \\left(p _ {w}\\right), \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.72, + 0.473, + 0.902 + ], + "angle": 0, + "content": "where \\(K\\) and \\(T\\) represent the camera's intrinsic and extrinsic parameter matrices in their corresponding views, respectively. Since the warping function is not surjective, voids may occur in \\(I_{s\\leftarrow r}^{i,j}\\). We empirically obtain a binary mask \\(M_{\\text{warp}}\\), where the pixels of void areas are set as 1 to identify the initial unreliable regions. To further refine the mask, we employ the cross-view pixel correspondences within the world coordinate of \\(I_r^i\\) and \\(I_{s\\leftarrow r}^{i,j}\\). To achieve this, we obtain the pseudo depth \\(D_s^j\\) of view \\(j\\) by rendering from the radiance fields. Following Eq. 4, we map the pixel of \\(I_r^i\\) and \\(I_{s\\leftarrow r}^{i,j}\\) into the same coordinate and obtain the correlation map \\(M_{\\text{cor}}\\) by comparing the distance between each pixel" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.519, + 0.61, + 0.535 + ], + "angle": 0, + "content": "pair \\((p_r,p_{s\\leftarrow r})\\)" + }, + { + "type": "equation", + "bbox": [ + 0.506, + 0.543, + 0.892, + 0.596 + ], + "angle": 0, + "content": "\\[\nM _ {c o r} \\left(p _ {s \\leftarrow r}\\right) = \\left\\{ \\begin{array}{l l} 1, & \\| f _ {w \\leftarrow r} \\left(p _ {r}\\right) - f _ {w \\leftarrow s} \\left(p _ {s \\leftarrow r}\\right) \\| _ {2} > \\epsilon . \\\\ 0, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.597, + 0.892, + 0.624 + ], + "angle": 0, + "content": "In this way, the final unreliability mask can be calculated as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.61, + 0.627, + 0.892, + 0.643 + ], + "angle": 0, + "content": "\\[\nM _ {s \\leftarrow r} = M _ {c o r} \\cup M _ {w a r p}. \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.656, + 0.895, + 0.776 + ], + "angle": 0, + "content": "Bilateral Geometric Consistency Loss. According to the obtained unreliability mask \\( M_{s \\leftarrow r} \\), we categorize the warped novel view image into reliable regions \\( R_{rel} \\) and unreliable regions \\( R_{unr} \\). Subsequently, we propose a bilateral geometric consistency loss to facilitate the self-training. Since the contents within \\( R_{rel} \\) are considered reliable, we explicitly constrain the appearance of rendered image \\( I_{s}^{j} \\) on view \\( j \\) via a reconstruction loss defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.576, + 0.784, + 0.892, + 0.817 + ], + "angle": 0, + "content": "\\[\nL _ {r e l} = \\sum_ {p \\in \\mathcal {R} _ {r e l}} \\| I _ {s \\leftarrow r} ^ {i, j} (p) - I _ {s} ^ {j} (p) \\| ^ {2}. \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.895, + 0.902 + ], + "angle": 0, + "content": "For \\( R_{unr} \\), we propose to leverage the relative depth prior of the warped \\( I_{s\\leftarrow r}^{i,j} \\) to improve the geometric consistency. Specifically, we extract the depth map \\( D_{s\\leftarrow r} \\) with a powerful pretrained depth estimation model DPT [32]. By analyzing the semantics of the surrounding context, we could inpaint" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "20345" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.15 + ], + "angle": 0, + "content": "the voids occurring in \\( D_{s \\leftarrow r} \\). Subsequently, a relative depth regularization loss [23] is introduced to constrain the geometric consistency on the rendered depth \\( D_{s} \\), which is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.156, + 0.161, + 0.471, + 0.196 + ], + "angle": 0, + "content": "\\[\nL _ {u n r} = \\sum_ {p \\in R _ {u n r}} \\sum_ {\\hat {p} \\in N \\left(D _ {s \\leftarrow r} ^ {p}\\right)} h (p, \\hat {p}), \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.207, + 0.124, + 0.22 + ], + "angle": 0, + "content": "where" + }, + { + "type": "equation", + "bbox": [ + 0.09, + 0.232, + 0.47, + 0.307 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} h (p, \\hat {p}) = \\\\ \\left\\{ \\begin{array}{l l} \\max \\left(\\left| D _ {s} ^ {\\hat {p}} - D _ {s} ^ {p} \\right| - m, 0\\right) & \\text {i f} \\left(D _ {s \\leftarrow r} ^ {\\hat {p}} - D _ {s \\leftarrow r} ^ {p}\\right) \\\\ & \\times \\left(D _ {s} ^ {\\hat {p}} - D _ {s} ^ {p}\\right) < 0, \\\\ 0 & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {10} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.318, + 0.471, + 0.514 + ], + "angle": 0, + "content": "Here \\( p \\) denotes any pixel within the unreliable region \\( R_{unr} \\); \\( \\hat{p} \\) represents each pixel within a neighborhood \\( N(D_{s\\leftarrow r}^{p}) \\) of \\( p \\), where \\( N(D_{s\\leftarrow r}^{p}) \\) is obtained by calculating pixels that have close depth values with \\( D_{s\\leftarrow r}^{p} \\) in the warped depth map; \\( D_{s}^{p}, D_{s}^{\\hat{p}} \\) and \\( D_{s\\leftarrow r}^{p}, D_{s\\leftarrow r}^{\\hat{p}} \\) denote the depth values of \\( p \\) and \\( \\hat{p} \\) within the rendered depth map \\( D_{s} \\) and estimated depth map \\( D_{s\\leftarrow r} \\), respectively. The function \\( h(p, \\hat{p}) \\) penalizes inconsistent relative ordering between the depth values of \\( p \\) and \\( \\hat{p} \\) in the two depth maps. Specifically, if \\( D_{s}^{p} < D_{s}^{\\hat{p}} \\) but \\( D_{s\\leftarrow r}^{p} > D_{s\\leftarrow r}^{\\hat{p}} \\), or \\( D_{s}^{p} > D_{s}^{\\hat{p}} \\) but \\( D_{s\\leftarrow r}^{p} < D_{s\\leftarrow r}^{\\hat{p}} \\), then \\( h(p, \\hat{p}) \\) penalizes the depth difference \\( |D_{s}^{\\hat{p}} - D_{s}^{p}| \\) beyond a threshold \\( m \\), to prevent the depth values from shifting dramatically." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.515, + 0.47, + 0.546 + ], + "angle": 0, + "content": "Our bilateral geometric consistency loss is then defined as a weighted sum of \\( L_{rel} \\) and \\( L_{unr} \\):" + }, + { + "type": "equation", + "bbox": [ + 0.171, + 0.558, + 0.47, + 0.575 + ], + "angle": 0, + "content": "\\[\nL _ {b g c} = \\lambda_ {r e l} L _ {r e l} + \\lambda_ {u n r} L _ {u n r}. \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.587, + 0.469, + 0.663 + ], + "angle": 0, + "content": "This loss enables us to thoroughly explore the information from both reliable and unreliable regions, facilitating the learning of cross-view consistency. Note that we also apply Eq. 9 on input views \\( I_{r} \\) as a depth regularization between the rendered depth and \\( D_{r} \\) for fully exploring the depth prior." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.671, + 0.467, + 0.687 + ], + "angle": 0, + "content": "3.4. Unreliability for Voxel Feature Regularization" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.696, + 0.47, + 0.786 + ], + "angle": 0, + "content": "In this section, we incorporate the unreliability on regularizing the feature of each position of the voxel grid. With a proper design of reliability-aware voxel smoothing and reliability-aware learning adjustment, we further improve the quality of the rendered image, avoiding suboptimal scene reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Reliability-aware Voxel Smoothing. Employing voxelized feature representations [37, 38] can significantly improve the training and rendering speed of NeRF, by storing the RGB features \\( f_{c} \\) and density \\( \\sigma \\) in a voxel grids. To facilitate the learning of voxel representation, DVGO [37, 38] propose a differentiable voxel smoothing loss, which regularizes the difference of \\( f_{c} \\) and \\( \\sigma \\) between a given voxel v" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.771, + 0.107 + ], + "angle": 0, + "content": "with its six adjacent points \\(V\\) as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.574, + 0.114, + 0.893, + 0.145 + ], + "angle": 0, + "content": "\\[\nL (\\mathbf {v}) = \\sum_ {\\hat {\\mathbf {v}} \\in V} \\Delta_ {f _ {c}} (\\mathbf {v}, \\hat {\\mathbf {v}}) + \\Delta_ {\\sigma} (\\mathbf {v}, \\hat {\\mathbf {v}}), \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.154, + 0.893, + 0.184 + ], + "angle": 0, + "content": "where \\(\\Delta (\\cdot ,\\cdot)\\) denotes an error metric for the difference (e.g., \\(L_{1},L_{2}\\), or Huber loss)." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.185, + 0.895, + 0.445 + ], + "angle": 0, + "content": "However, under the few-shot scenario, learning on the sparse input views can easily overfit the view-specific image, which could lead to a degenerated voxel grid that may contain fluctuant features. To address this issue, we propose to regularize the voxel features for balanced and smooth learning. By taking the unreliability of each synthesized novel view image into consideration, we mitigate the influence of unreliable regions while promoting learning in more reliable areas. We design a reliability-aware smooth factor \\(\\rho (\\mathbf{v})\\) for each voxel in the grid. Specifically, given a warped image, we cast \\(O\\) rays \\(\\mathbf{r}\\) through each pixel of the reliable regions \\(R_{rel}\\). For each voxel \\(\\mathbf{v}\\), we obtain a reliability score by accumulating the number of rays that pass this voxel, denoted by \\(S(\\mathbf{v})\\). The maximum number of times being passed by rays is denoted as \\(S(\\mathbf{v})_{max}\\). Then the reliability-aware smooth factor is defined as \\(\\rho (v) = \\frac{S(\\mathbf{v})}{S(\\mathbf{v})_{max}}\\). Finally, we formulate the reliability-aware voxel smoothing losses on \\(f_{c}\\) and \\(\\sigma\\) as:" + }, + { + "type": "equation", + "bbox": [ + 0.565, + 0.452, + 0.893, + 0.491 + ], + "angle": 0, + "content": "\\[\nL _ {f _ {c}} = \\sum_ {\\mathbf {v}} \\sum_ {\\hat {\\mathbf {v}} \\in V} (1 + e ^ {- \\rho (\\mathbf {v})}) \\Delta_ {f _ {c}} (\\mathbf {v}, \\hat {\\mathbf {v}}), \\tag {13}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.571, + 0.488, + 0.82, + 0.518 + ], + "angle": 0, + "content": "\\[\nL _ {\\sigma} = \\sum_ {\\mathbf {v}} \\sum_ {\\hat {\\mathbf {v}} \\in V} (1 + e ^ {- \\rho (\\mathbf {v})}) \\Delta_ {\\sigma} (\\mathbf {v}, \\hat {\\mathbf {v}}).\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.526, + 0.828, + 0.541 + ], + "angle": 0, + "content": "The final regularization loss is defined as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.619, + 0.55, + 0.892, + 0.567 + ], + "angle": 0, + "content": "\\[\nL _ {r s} = \\lambda_ {f} L _ {f c} + \\lambda_ {d} L _ {\\sigma}. \\tag {14}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.573, + 0.894, + 0.619 + ], + "angle": 0, + "content": "In this case, the unreliable regions will have smoother supervision during training, mitigating the inconsistency caused by potential overfitting." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.626, + 0.895, + 0.763 + ], + "angle": 0, + "content": "Reliability-guided Learning Adjustment. To further facilitate the learning of geometric and appearance information, we apply a reliability-guided learning strategy to dynamically prioritize the learning towards the reliable zones, while eliminating the false supervision of unreliable regions at the beginning of training. Concretely, we adjust the importance of each voxel \\(\\mathbf{v}\\) with a reliability weight \\(\\mathbf{w}_{\\mathbf{v}} = 1 + \\rho (\\mathbf{v})\\), to control the gradients of each voxel during the back-propagation." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.77, + 0.727, + 0.785 + ], + "angle": 0, + "content": "3.5. Optimization of ReVoRF" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.793, + 0.892, + 0.84 + ], + "angle": 0, + "content": "To avoid dramatic variation of the unreliable depth, we further adopt a depth smoothness loss function [29] as an extra regularization for better relative depth supervision:" + }, + { + "type": "equation", + "bbox": [ + 0.511, + 0.845, + 0.893, + 0.904 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} L _ {d s} = \\frac {1}{| R |} \\sum_ {r \\in R} \\sum_ {(x, y) \\in D} \\| d (x, y) - d (x, y + 1) \\| _ {2} ^ {2} \\tag {15} \\\\ + \\left\\| d (x, y) - d (x + 1, y) \\right\\| _ {2} ^ {2}, \\\\ \\end{array}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "20346" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.097, + 0.087, + 0.254, + 0.158 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.098, + 0.165, + 0.255, + 0.262 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.124, + 0.274, + 0.255, + 0.331 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.133, + 0.332, + 0.219, + 0.344 + ], + "angle": 0, + "content": "Diet-NeRF [14]" + }, + { + "type": "image", + "bbox": [ + 0.261, + 0.127, + 0.401, + 0.2 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.274, + 0.213, + 0.382, + 0.308 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.289, + 0.332, + 0.371, + 0.345 + ], + "angle": 0, + "content": "InfoNeRF [17]" + }, + { + "type": "image", + "bbox": [ + 0.416, + 0.127, + 0.553, + 0.191 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.427, + 0.217, + 0.537, + 0.312 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.452, + 0.332, + 0.515, + 0.344 + ], + "angle": 0, + "content": "VGOS [39]" + }, + { + "type": "image", + "bbox": [ + 0.568, + 0.127, + 0.707, + 0.191 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.582, + 0.218, + 0.692, + 0.313 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.595, + 0.332, + 0.68, + 0.344 + ], + "angle": 0, + "content": "ReVoRF (Ours)" + }, + { + "type": "image", + "bbox": [ + 0.723, + 0.127, + 0.861, + 0.191 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.736, + 0.218, + 0.846, + 0.313 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.781, + 0.332, + 0.802, + 0.343 + ], + "angle": 0, + "content": "GT" + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.346, + 0.892, + 0.361 + ], + "angle": 0, + "content": "Figure 3. 4-views reconstructions on Realistic Synthetic \\(360^{\\circ}\\) [26]. ReVoRF enables more consistent reconstruction with detailed appearance." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.37, + 0.485, + 0.508 + ], + "angle": 0, + "content": "
Realistic Synthetic 360° dataset
MethodsPSNR↑SSIM↑LPIPS↓Training Time↓
NeRF [24]15.930.7800.3202 hrs
PixelNeRF [47]16.090.7380.3903-4 days* + 10 hrs
DietNeRF [14]16.060.7930.30619 hrs
3DGS [16]17.550.7010.2503 mins
InfoNeRF [17]18.620.8110.2304 hrs
VGOS [39]18.910.8250.2053 mins
GeCoNeRF [18]19.780.8800.185>2 hrs
Ours20.720.8480.1797 mins
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.508, + 0.471, + 0.564 + ], + "angle": 0, + "content": "Table 1. Quantitative comparison for 4-views setting in the Realistic Synthetic \\(360^{\\circ}\\) dataset [24]. The best and the second-best results are highlighted in bold and underlined, respectively. (*) denotes the time cost of pre-training." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.573, + 0.472, + 0.619 + ], + "angle": 0, + "content": "where \\( R \\) represents the set of rays emanating from the sampled views, \\( D \\) refers to the depth patch that is centered around \\( r \\), and \\( d(x,y) \\) is of the depth value in position \\( (x,y) \\)." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.619, + 0.414, + 0.633 + ], + "angle": 0, + "content": "The final objective of ReVoRF is formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.141, + 0.642, + 0.47, + 0.658 + ], + "angle": 0, + "content": "\\[\nL _ {\\text {t o t a l}} = L _ {r g b} + L _ {b g c} + L _ {r s} + \\lambda_ {d s} L _ {d s}. \\tag {16}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.693, + 0.21, + 0.71 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.718, + 0.471, + 0.795 + ], + "angle": 0, + "content": "In this section, we demonstrate the superiority of the proposed ReVoRF through extensive experiments. The details of experiment settings are discussed in Sec. 4.1. Analysis on comparison experiments and ablation study are performed in Sec. 4.2 and Sec. 4.3, respectively." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.802, + 0.271, + 0.818 + ], + "angle": 0, + "content": "4.1. Experiment Settings" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.825, + 0.47, + 0.871 + ], + "angle": 0, + "content": "Datasets. The experiments are conducted on inward-facing scenes from the Realistic Synthetic \\(360^{\\circ}\\) dataset [26] and forward-facing scenes from the LLFF dataset [25]." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Realistic Synthetic \\(360^{\\circ}\\) comprises path-traced images from 8 synthetic scenes, which are characterized by their" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.373, + 0.895, + 0.478 + ], + "angle": 0, + "content": "complex geometry and realistic rendering of non-Lambertian materials. Each scene is represented by 400 images, rendered by inward-facing virtual cameras positioned at varying viewpoints. We adhere to the protocol established by InfoNeRF [17] and randomly select 4 views from 100 training images as sparse inputs. The model's performance is then evaluated on a set of 200 testing images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.48, + 0.895, + 0.587 + ], + "angle": 0, + "content": "LLFF consists of 8 real-world scenes captured with a handheld cellphone, featuring 20 to 62 forward-facing images per scene. These scenes encompass a range of complex environments. In line with the standard protocol [26], we reserve 1/8 of these images for testing purposes. The remaining images are used for training, from which we randomly sample three views for input into our model." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.606, + 0.895, + 0.91 + ], + "angle": 0, + "content": "Implementation Details. Following DVGO [37, 38], we adopt a coarse-to-fine optimization scheme to stabilize the training of ReVoRF and gradually improve the geometric details. During the whole training period, we set the values of \\(\\lambda_{rel}\\) and \\(\\lambda_{unr}\\) in Eq. 11 as \\(10^{-1}\\) and \\(10^{-2}\\), respectively. The values of \\(\\lambda_d\\), \\(\\lambda_f\\) in Eq. 14, and \\(\\lambda_{ds}\\) in Eq. 15 are set as \\(5\\cdot 10^{-4}\\), \\(5\\cdot 10^{-5}\\), and \\(5\\cdot 10^{-5}\\) in the coarse stage, and decreased to \\(5\\cdot 10^{-5}\\), \\(10^{-5}\\), and \\(5\\cdot 10^{-5}\\) in the fine stage. The warping poses collected for the Realistic Synthetic \\(360^{\\circ}\\) dataset [24] and the LLFF dataset [20] are different. For Realistic Synthetic \\(360^{\\circ}\\), we randomly vary the polar angle \\(\\theta\\) and azimuthal angle \\(\\phi\\) in the range of \\([5^{\\circ}, 10^{\\circ}]\\) based on the input view, and subsequently warp each input sparse view to its four neighboring views defined by \\(\\{(\\theta, \\phi), (-\\theta, \\phi), (\\theta, -\\phi), (-\\theta, -\\phi)\\}\\). For the LLFF dataset, the warped views are obtained by randomly interpolating between every adjacent input view. To speed up the training stage and improve the quality of depth supervision, the warping is performed periodically, which updates the warped depth maps and RGB images every 1000 training steps." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "20347" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.089, + 0.885, + 0.289 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.293, + 0.893, + 0.322 + ], + "angle": 0, + "content": "Figure 4. Comparisons on the LLFF dataset [25] in 3-view setting. The red and blue boxes denote compared regions. Our approach achieves better results in reconstructing fine details with enhanced clarity. Please zoom in for details." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.332, + 0.485, + 0.489 + ], + "angle": 0, + "content": "
NeRF LLFF dataset
MethodsPSNR↑SSIM↑LPIPS↓Training Time↓
PixelNeRF [47]16.170.4380.5123-4 days* + 10 hrs
SRF [7]17.070.4360.5292-3 days* + 43mins
MVSNeRF [5]17.880.5840.3271-2 days* + 10mins
Mip-NeRF [2]14.620.3510.49514 hrs
DietNeRF [14]14.940.3700.49618 hrs
3DGS [16]13.050.4070.38813 mins
RegNeRF [29]19.080.5870.3364 hrs
VGOS [39]19.350.6200.4325 mins
SparseNeRF [12]19.860.6240.328>2 hrs
Ours19.260.6440.31611 mins
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.076, + 0.49, + 0.472, + 0.533 + ], + "angle": 0, + "content": "Table 2. Quantitative comparison for 3-views setting on LLFF [20]. The best and the second-best results are highlighted in bold and underlined, respectively. (*) signifies the pre-training time." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.544, + 0.472, + 0.711 + ], + "angle": 0, + "content": "Evaluation Metrics. To assess the effectiveness of our method, we employ several established metrics, including PSNR (Peak Signal-to-Noise Ratio) for assessing image reconstruction accuracy, SSIM (Structural Similarity Index Measure) [43] for evaluating changes in luminance and contrast that affect structural integrity, and LPIPS (Learned Perceptual Image Patch Similarity) [50], which uses deep learning to approximate human visual perception. These metrics provide a comprehensive analysis of our model's performance, covering aspects of accuracy, perceptual quality, and structural fidelity in the reconstructed images." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.72, + 0.218, + 0.736 + ], + "angle": 0, + "content": "4.2. Comparisons" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.743, + 0.473, + 0.91 + ], + "angle": 0, + "content": "On the Realistic Synthetic \\(360^{\\circ}\\) dataset [24], we compare our method with state-of-the-art approaches, including RegNeRF [29], DietNeRF [14], infoNeRF [17], VGOS [39], PixelNeRF [47], and GeCoNeRF [18], in a 4-view setting. On the LLFF dataset [20], we implement our method in a 3-view setting and compare with SRF [7], MVSNeRF [5], mip-NeRF [2], DietNeRF [14], RegNeRF [29], VGOS [39], SparseNeRF [12] and GeCoNeRF [18]. We adopt the reported results from VGOS [39], sparseNeRF [12], and GeCoNeRF [18]. Besides, we also compare with the advanced reconstruction method 3DGS [16]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.334, + 0.895, + 0.439 + ], + "angle": 0, + "content": "Qualitative Experiments. Fig. 3 compares our approach with some recent methods on the Realistic Synthetic \\(360^{\\circ}\\) dataset [24]. Diet-NeRF [14] performs poorly in the setting of 4 views, while infoNeRF [17] and VGOS [39] are inferior to our method in terms of both geometric shapes and detail resolution. Our approach demonstrates superior performance in both geometry and details." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.44, + 0.895, + 0.53 + ], + "angle": 0, + "content": "Fig. 4 shows a qualitative comparison on a scene from the LLFF dataset [20]. While all methods can recover the overall structure of the scene, our approach excels at the quality of details as shown in the magnified regions. Our method incorporates smoothness while retaining fine details, achieving the most natural results." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.538, + 0.895, + 0.719 + ], + "angle": 0, + "content": "Quantitative Experiments. Table 1 shows quantitative results from different methods on the Realistic Synthetic \\(360^{\\circ}\\) dataset [24]. In terms of training time, our method is at least an order of magnitude faster than all other methods except for VGOS [39]. Although our method is slightly lower than VGOS [39], it significantly enhances the PSNR, LPIPS [50], and SSIM [43] of the rendered images. Our method achieves state-of-the-art accuracy in PSNR and LPIPS [50]. Additionally, despite not utilizing a pre-trained model or perceptual loss for high-level semantic information extraction, our method still achieves the second-best performance in perceived SSIM [43]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.719, + 0.895, + 0.841 + ], + "angle": 0, + "content": "Table 2 shows a quantitative comparison on the LLFF dataset [20]. Our method achieves the highest scores in both SSIM [43] and LPIPS [50], indicating that our images exhibit the best performance in terms of human perceptual reconstruction. We also achieve the third-highest PSNR, which, together with our state-of-the-art performance in SSIM [43] and LPIPS [50], demonstrates that our approach has made improvements in certain aspects of image rendering." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.848, + 0.655, + 0.864 + ], + "angle": 0, + "content": "4.3. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.893, + 0.902 + ], + "angle": 0, + "content": "Our ablation study is segmented into five distinct groups with Table 3, with DVGO [37, 38] serving" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "20348" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.134, + 0.101, + 0.222, + 0.205 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.151, + 0.212, + 0.201, + 0.224 + ], + "angle": 0, + "content": "Baseline" + }, + { + "type": "image", + "bbox": [ + 0.286, + 0.102, + 0.377, + 0.208 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.29, + 0.213, + 0.369, + 0.224 + ], + "angle": 0, + "content": "Baseline \\(+L_{rel}\\)" + }, + { + "type": "image", + "bbox": [ + 0.439, + 0.102, + 0.53, + 0.202 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.426, + 0.213, + 0.541, + 0.225 + ], + "angle": 0, + "content": "Baseline \\(+L_{rel} + L_{unr}\\)" + }, + { + "type": "image", + "bbox": [ + 0.594, + 0.102, + 0.685, + 0.201 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.566, + 0.212, + 0.708, + 0.225 + ], + "angle": 0, + "content": "Baseline \\(+L_{rel} + L_{unr} + L_{ds}\\)" + }, + { + "type": "image", + "bbox": [ + 0.749, + 0.102, + 0.837, + 0.203 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.76, + 0.212, + 0.822, + 0.223 + ], + "angle": 0, + "content": "Full Model" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.23, + 0.894, + 0.258 + ], + "angle": 0, + "content": "Figure 5. Visualizations of the ablation on Chair scene from the Realistic Synthetic \\(360^{\\circ}\\) [26] dataset in 4 views setting. With the proposed losses, our methods could gradually improve the cross-view consistency and reduce the noise compared with the baseline." + }, + { + "type": "table", + "bbox": [ + 0.111, + 0.267, + 0.432, + 0.35 + ], + "angle": 0, + "content": "
LrsLdsUnrRelPSNR↑SSIM↑LPIPS↓
17.190.7670.223
✓17.790.7800.243
✓✓19.010.8050.228
✓✓✓19.230.8110.220
✓✓✓✓20.720.8480.179
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.352, + 0.47, + 0.395 + ], + "angle": 0, + "content": "Table 3. Ablation study on the Realistic Synthetic \\(360^{\\circ}\\) dataset [24] in the 4-view setting. The best and the second-best results are highlighted in bold and underlined, respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.431, + 0.473, + 0.643 + ], + "angle": 0, + "content": "as the baseline. We incrementally introduce our proposed contributions along with various regularization methods to enhance the model's rendering quality. The groups are delineated as: baseline, baseline \\(+L_{rel}\\), baseline \\(+L_{rel} + L_{unr}\\), baseline \\(+L_{rel} + L_{unr} + L_{ds}\\), and baseline \\(+L_{rel} + L_{unr} + L_{ds} + L_{rs}\\). The ablation results reveal that each incremental contribution positively impacts the rendering quality in various aspects. After the addition of \\(L_{rel}\\), our PSNR increased by 0.6. Subsequent inclusion of \\(L_{unr}\\) led to a further rise in PSNR by 1.22. With the incorporation of \\(L_{ds}\\), the PSNR went from 19.01 to 19.23. Finally, after adding \\(L_{rs}\\), our PSNR peaked at 20.72, SSIM [43] reached 0.848, and LPIPS [50] arrived at 0.179, marking a significant enhancement." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.651, + 0.472, + 0.727 + ], + "angle": 0, + "content": "Besides, we explore the potential of ReVoRF under the settings where more input views are available. We report extra results for 6-view and 9-view settings in Table 4, demonstrating that increased input views generally enhance performance. ReVoRF maintains superiority across these settings." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Fig. 5 presents the visualization of our ablation study on the Chair scene. We incorporated \\( L_{rel} \\) to enhance the texture quality of the model, which, however, introduced some noise artifacts. To mitigate these artifacts, \\( L_{unr} \\) and \\( L_{ds} \\) were subsequently integrated. These adjustments successfully reduced noise but at the cost of blurring the geometric structures in the process. The issue of maintaining geometric consistency while eliminating noise was addressed through the implementation of \\( L_{rs} \\). We observe that our method effectively prevents the collapse of new views caused by overfitting due to a limited number of viewpoints." + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.268, + 0.892, + 0.366 + ], + "angle": 0, + "content": "
MethodsPSNR↑SSIM↑LPIPS↓
3-view6-view9-view3-view6-view9-view3-view6-view9-view
SRF [7]17.0716.7517.390.4360.4380.4650.5290.5210.503
PixelNeRF [47]16.1717.0318.920.4380.4730.5350.5120.4770.430
MVSNeRF [5]17.8819.9920.470.5840.6600.6950.3270.2640.244
DVGO [37]16.6021.2522.890.5600.7040.7460.4220.2460.228
VGOS [39]19.3521.5522.390.6200.6710.6920.4320.3280.325
Ours19.2622.2123.040.6440.7200.7530.3160.2690.225
" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.367, + 0.894, + 0.408 + ], + "angle": 0, + "content": "Table 4. Comparison of 3, 6, and 9 input views on LLFF [20]. The best and the second-best results are highlighted in bold and underlined, respectively." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.428, + 0.874, + 0.445 + ], + "angle": 0, + "content": "5. Conclusion, Limitation, and Future Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.457, + 0.895, + 0.637 + ], + "angle": 0, + "content": "In this paper, we address the challenge of view deformation by discerning reliable and unreliable areas, subsequently introducing a bilateral geometric consistency regularization. This approach maximizes the use of reliable regions while delicately exploring the depth in unreliable areas, applying a more lenient constraint to these zones. Further extending our method into voxel space, we transform 2D reliable areas into 3D space through a reliability-aware voxelization smoothing process. Our method, when applied to various datasets, has proven to be highly precise, significantly bolstering geometric consistency and demonstrating its efficacy in intricate 3D reconstruction tasks." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.895, + 0.793 + ], + "angle": 0, + "content": "Our method shares a common limitation of the voxel-based method: the tendency to produce smoothed results, leading to a loss in fine details. Besides, the exceptionally challenging context for NeRF with sparse input also limits its application in more complex scenes, such as large-scale scene reconstruction. For future work, we aim to refine the voxelization technique to better preserve details, potentially exploring hybrid models that combine voxel-based methods with alternative geometric representations for a more detailed reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Acknowledgement. The work is supported by the Guangdong Natural Science Funds for Distinguished Young Scholar (No. 2023B1515020097), Singapore MOE Tier 1 Funds (MSS23C002), and the NRF Singapore under the AI Singapore Programme (No. AISG3-GV-2023-011)." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "20349" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.175, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.116, + 0.471, + 0.157 + ], + "angle": 0, + "content": "[1] Alexander Amini, Wilko Schwarting, Ava Soleimany, and Daniela Rus. Deep evidential regression. In NeurIPS, volume 33, pages 14927-14937, 2020. 3" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.159, + 0.472, + 0.213 + ], + "angle": 0, + "content": "[2] Jonathan T Barron, Ben Mildenhall, Matthew Tancik, Peter Hedman, Ricardo Martin-Brualla, and Pratul P Srinivasan. 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IEEE TVCG, 2024. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.894, + 0.416 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "20351" + } + ] +] \ No newline at end of file diff --git a/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_origin.pdf b/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..c759b0b365c1c6be947b27ab4b99337f7102d217 --- /dev/null +++ b/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/c9a1770c-6e1c-4c1e-859d-d8ada4bc155c_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:7b991f69149cb4f14dbf977ea87f83ca3e93d4fdc5987b45823237ff941fbc27 +size 2887915 diff --git a/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/full.md b/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/full.md new file mode 100644 index 0000000000000000000000000000000000000000..23f2784b53a8e792fceb18f1c96ffa3020f72c36 --- /dev/null +++ b/2024/Learning with Unreliability_ Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency/full.md @@ -0,0 +1,358 @@ +# Learning with Unreliability: Fast Few-shot Voxel Radiance Fields with Relative Geometric Consistency + +Yingjie Xu $^{1,2*}$ Bangzhen Liu $^{2*}$ Hao Tang $^{1,3}$ Bailin Deng $^{4}$ Shengfeng He $^{1\dagger}$ $^{1}$ Singapore Management University $^{2}$ South China University of Technology $^{3}$ Nanjing University of Science and Technology $^{4}$ Cardiff University + +![](images/c9186a2448aed9889ca0b6c76469d6a456318e81e6eb6a7620a063f3c7286ec8.jpg) +Figure 1. We present ReVoRF, a voxel-based framework designed to capitalize on the unreliability inherent in warped novel views. (b) demonstrates the warping outcomes, where black holes signify unmatched pixels from the original view. (c) illustrates the results of training when these holes are masked out, which unfortunately results in ambiguous geometric structures. In contrast, (d) showcases our approach's ability to maintain correct geometric consistency. ReVoRF achieves this by leveraging relational depth prior knowledge within these unreliable hole regions. Our approach demonstrates the best reconstruction quality while being one of the fastest few-shot approaches in (e). + +![](images/727c259f2677aff1171c8faa5d058d09ba6db414f06c2a5d437069ff1edea320.jpg) + +# Abstract + +We propose a voxel-based optimization framework, ReVoRF, for few-shot radiance fields that strategically address the unreliability in pseudo novel view synthesis. Our method pivots on the insight that relative depth relationships within neighboring regions are more reliable than the absolute color values in disoccluded areas. Consequently, we devise a bilateral geometric consistency loss that carefully navigates the trade-off between color fidelity and geometric accuracy in the context of depth consistency for uncertain regions. Moreover, we present a reliability-guided learning strategy to discern and utilize the variable quality across synthesized views, complemented by a reliability-aware voxel smoothing algorithm that smoothens the transition between reliable and unreliable data patches. Our approach allows for a more nuanced use of all available data, promoting enhanced learning from regions previously considered unsuitable for high-quality reconstruction. Extensive experiments across diverse datasets reveal that our approach attains significant gains in efficiency and accuracy, delivering rendering speeds of 3 FPS, 7 mins to train a $360^{\circ}$ scene, and + +a $5\%$ improvement in PSNR over existing few-shot methods. Code is available at https://github.com/HKCLynn/ReVoRF. + +# 1. Introduction + +Neural Radiance Fields (NeRF) have revolutionized the fields of novel view synthesis and 3D reconstruction by leveraging an implicit function optimized from a collection of 2D images [2, 13, 24, 27]. Despite their remarkable rendering capabilities, NeRFs are hampered by the substantial cost and time required to gather dense image sets for a given scene [6,41,47]. This challenge has spurred the development of Few-shot NeRF, an emerging domain focused on reconstructing 3D scenes with minimal image data [6,8, 12, 18]. + +The performance of NeRF in accurately reconstructing geometry and texture diminishes when faced with sparse observations, as it tends to overfit the limited views available [8, 49]. To address this issue, there has been a push in recent studies to fortify NeRF with additional priors [46, 47], including semantic relations [14], depth cues [49], and entropy constraints [17]. These enhancements strive to extract maximum information from limited data. However, the reconstructions are inherently limited by the insufficient + +coherence of the sparse views provided. + +Recent research has explored overcoming the challenges posed by very limited observations through pseudo-view synthesis [3, 18]. By using known camera poses and coarse depth estimates, these methods generate warped images from sparse viewpoints to enhance cross-view consistency. However, as shown in Fig. 1b, these generated images often include noisy areas with artifacts, which, if used for learning, can lead to inconsistent training signals and compromise scene integrity. To address this, Kwak et al. [18] implement self-occlusion aware masking to exclude unreliable regions. While this selective masking successfully filters out areas of uncertainty, it also introduces voids, presenting a conundrum: refining these images can bring in inconsistent noise and floaters, as illustrated in Fig. 1c, yet the limited number of usable samples necessitates using all available pseudo supervision for quality reconstruction. + +In light of the issues identified with unreliable warped areas, our paper proposes a novel method for fully exploiting these uncertain regions to achieve multi-view consistency learning. The rationale behind our method is that, although absolute supervision is not reliable in those disoccluded regions, we observe that they maintain consistent relative depth relationships. The unreliability of certain regions in warped images can still bear geometric resemblances to their original view counterparts. We find that local depth information within these images can indicate geometric disparities, offering a self-supervised signal that aids in discerning the geometry of regions lacking precise textural information. While reliable regions offer more accurate supervision, our approach seeks to fully utilize all the information present, exploiting depth cues in coarsely warped images to inform the learning process across both reliable and traditionally discarded unreliable areas. + +Drawing from the insights above, we propose a novel voxel-based optimization framework, ReVoRF, tailored for fast and multi-view consistent reconstruction of few-shot radiance fields, which incorporates the relative depth priors from several aspects. The objective of this work is to concurrently explore information from both dependable and less reliable regions within the warped novel view images. In the first step, we randomly warp the sparse images onto a series of novel views, subsequently delineating reliable and unreliable regions based on the pixel-wise correlation between the input and novel view. We then introduce a bilateral geometric consistency loss to enable self-training on novel synthesized images. This loss encompasses a reconstruction term in a bilateral manner, including a color and density regularization term for reliable regions and a relative depth consistency term for unreliable regions, respectively. While the former term aims at explicitly learning the geometric context of the reliable regions, the relative depth regularization is applied for implicitly exploring the geometric consistency guided + +by relative depth. Moreover, we integrate unreliability into our voxelization of scene features: 1) a reliability-guided learning strategy that dynamically adjusts learning priorities towards more reliable regions; 2) a reliability-aware voxel smoothing procedure that preserves structural integrity in reliable zones and mitigates inconsistencies in less reliable ones, ensuring a balanced and coherent scene reconstruction. As illustrated in Fig. 1e, assisted by both bilateral geometric consistency loss and reliability-aware regularization, our method is the second fastest while achieving the best reconstruction fidelity, with a large margin over the others. + +Our contributions can be summarized as follows: + +- We present the first attempt to explore pseudo-views unreliability within few-shot radiance fields, presenting the first framework to incorporate these areas for enhanced multi-view consistency learning with a bilateral geometric consistency loss. +- We introduce a reliability-guided learning strategy and voxelization smoothing procedure that tailors the learning process to the reliability of data, thus optimizing the training emphasis for improved reconstruction quality in few-shot radiance fields. +- We demonstrate superior performance of our approach against existing state-of-the-art few-shot methods in efficiency and accuracy, through extensive experiments on both synthetic and real-world datasets. + +# 2. Related Work + +Neural Radiance Fields (NeRF). NeRF [2,5,13,22,24] have emerged as a significant advancement in 3D reconstruction and novel view synthesis. These methods employ an implicit function to represent a 3D scene, enabling the extraction of detailed geometric and textural information from a set of multi-view images. Subsequent researchers have broadened the scope of NeRF applications, including generative modeling [11,40], video synthesis [9,20,34], and scene editing [21,48]. Despite the impressive rendering quality, the training of vanilla NeRF often spans several days for a single scene reconstruction. Recent advancements [10,27,37,38] have endeavored to mitigate this computational burden. Approaches such as DVGO [4,37,38] employ dense voxel grids in conjunction with shallow multilayer perceptrons to expedite the reconstruction process. Similarly, Plenoxels [10] utilizes sparse voxel grids, and Instant-NGP [27] employs a multi-resolution hash table to delineate the radiance field more efficiently. Diverse from these methods, which typically require dense inputs, we aim to address the challenge of achieving fast and high-fidelity scene reconstruction in the case where only a few observed views are available. + +Few-Shot NeRFs. Recent advances [5, 14, 17, 47, 49, 51] have sought to reduce the dependency on densely collected + +data for scene reconstruction, leveraging sparse inputs and scene priors. Notably, PixelNeRF [47] and StereoRF [7] utilize local semantic relationships across multiple scenes, while MVSNeRF [5] incorporates cost volume to enhance performance. These methodologies, however, require pretraining on numerous scenes to acquire necessary scene priors. Further developments [14, 17, 31, 39, 46] have introduced various regularization techniques to maximize the utility of sparse input views. InfoNeRF [17] enhances ray adjacency consistency through entropy regularization. DietNeRF [14] facilitates cross-view semantic consistency by harnessing the semantic space of the pretrained CLIP [31], while DiffusioNeRF [44] explores the diffusion prior of pretrained diffusion models. Additionally, FreeNeRF [46] applies frequency regularization, and VGOS [39] introduces voxel regularization to optimize both feature representation and density. Another group of research focuses on augmenting sparse inputs with synthetically generated views. RapNeRF [49] utilizes geometric re-projection for novel view extrapolation, while VmNeRF [3] employs depth maps for view-morphing. GeCoNeRF [18] aims to refine geometric consistency by separating reliable regions from warped images and discarding unreliable areas prone to self-occlusion. Our work diverges from these approaches by considering the inherent information of both reliable and unreliable regions of the novel view images, facilitating cross-view geometric consistency. + +Unreliability/Uncertainty Modeling. In the rapid development of NeRF, the incorporation of uncertainty modeling has become crucial for achieving robustness in 3D reconstruction from sparse views. Previous efforts have employed diverse strategies, including Bayesian approaches [15, 28] and evidential neural networks [1,33], to quantify uncertainty in neural networks. In the context of NeRF, uncertainty has been harnessed to enhance rendering and guide input capture. Some methods assume Gaussian noise in RGB space for pixel-wise uncertainty [22, 30], employ volumetric entropy for scene geometry [19, 45], or adopt variational inference or Latent Variable Modeling for radiance field uncertainty as seen in S-NeRF [36] and CF-NeRF [35]. However, these approaches have not comprehensively addressed uncertainty quantification in unseen regions. Our approach differs from these methods by not only capturing uncertainty in the geometry and appearance of visible areas but also explicitly accounting for unseen spaces, including occluded points, which previous methods have not considered. This distinction allows for a more nuanced and accurate reconstruction, promising to elevate the fidelity of few-shot NeRF models. + +# 3. Methodology + +# 3.1. Preliminaries + +NeRF [24] represents a scene as a continuously differentiable function $f$ via a Multi-Layer Perceptron (MLP). + +Given a 3D position $\mathbf{x} \in \mathbb{R}^3$ and the associated 2D viewing directions $\mathbf{d} \in \mathbb{R}^2$ , NeRF maps them into a volume density $\sigma \in \mathbb{R}$ and an RGB value $\mathbf{c} \in \mathbb{R}^3$ , such that: $(\mathbf{c}, \sigma) = f(\gamma(\mathbf{x}), \gamma(\mathbf{d}))$ , where the $\gamma$ is a positional encoding that projects $\mathbf{x}$ and $\mathbf{d}$ into a higher dimensional feature space [42]. With a ray parameterized as $\mathbf{r}_p(t) = \mathbf{o} + t\mathbf{d}_p$ cast from the camera's optical center $\mathbf{o}$ along direction $\mathbf{d}_p$ , the expected color $\hat{C}(\mathbf{r}_p)$ of pixel $p$ is rendered as follows: + +$$ +\hat {C} (\mathbf {r} _ {p}) = \int_ {t _ {n}} ^ {t _ {f}} T (t) \sigma (\mathbf {r} _ {p} (t)) \mathbf {c} (\mathbf {r} _ {p} (t), \mathbf {d} _ {p}) d t, \tag {1} +$$ + +where $t_n$ and $t_f$ are the near and far bounds of the ray for sampling, and $T(t) = \exp \left(-\int_{t_n}^t \sigma(\mathbf{r}(s)) ds\right)$ denotes the cumulative transparency along the ray from $t_n$ to $t$ . Therefore, the NeRF can be optimized by a reconstruction loss between the rendered color $\hat{C}(\mathbf{r})$ and the real color $C(\mathbf{r})$ : + +$$ +L _ {r g b} = \sum_ {\mathbf {r} \in \mathcal {R}} \| \hat {C} (\mathbf {r}) - C (\mathbf {r}) \| ^ {2}, \tag {2} +$$ + +where $\mathcal{R}$ denotes the set of training rays. + +# 3.2. Overview + +We propose ReVoRF, a novel voxel-based optimization framework tailored for fast and multi-view consistent scene reconstruction from sparse input views. Our key idea is to incorporate the unreliability information for fully exploring the warped novel view images. By treating depth priors as the unreliability metrics, ReVoRF facilitates the reconstruction of the few-shot radiance field from several aspects, including the multi-view consistency learning (Sec. 3.3) and the regularization of voxel features (Sec. 3.4). The overall pipeline of ReVoRF is displayed in Fig. 2. + +# 3.3. Unreliability for Multi-view Consistency + +In this section, we explore the potential of unreliability in facilitating multi-view geometric consistency via the proposed bilateral geometric consistency loss. + +Novel View Warping. Starting from a set of sparse input images $I_r^i$ for $i \in 1, \dots, N_r$ , where $i$ represents the view number and $N_r$ is a small number, e.g., $N_r = 3$ or $N_r = 4$ , we propose to synthesize novel view images $I_{s \leftarrow r}^{i,j}$ through a fast and flexible warping process on several novel views $j \in 1, \dots, N_s$ . To preserve the cross-view consistency, the warping is guided by a coarse depth map $D_r^i$ , where the depth value on each pixel $p$ is accumulated by the density along each ray $r_p$ omitted from the camera: $D_r^i(p) = \int_{t_f}^{t_n} T(t) \sigma(r_p(t)) t dt$ . Subsequently, we obtain the warped image $I_{s \leftarrow r}^{i,j}$ through a cross-view transformation $H_{s \leftarrow r}$ , which deforms each pixel $p_r$ of $I_r^i$ to its correspond + +![](images/91a2121fb48de591d43840e5e63b49e3b4f5ff9b41d079d4792c03957da6eeb1.jpg) +Figure 2. Overview of our proposed ReVoRF. Specifically, we first warp the sparse images onto several novel views and determine both the dependable and unreliable regions. Based on the dependability of each image region, we introduce a bilateral geometric consistency loss for multi-view consistent learning, which is composed of a color and density regularization term for reliable regions and a relative depth consistency term for unreliable regions. These two terms are responsible for explicitly learning the reliable geometric contents and implicitly exploring the geometric consistency via the guidance of relative depth, respectively. For voxel feature regularization, we integrate the unreliability through a reliability-guided learning strategy and a reliability-aware voxel smoothing procedure. By prioritizing the learning of more reliable regions and mitigating the inconsistencies in less reliable ones, ReVoRF ensures a more balanced and coherent reconstruction. + +ing position $p_{s}$ on the target view: + +$$ +\begin{array}{l} p _ {s \leftarrow r} = H _ {s \leftarrow r} \left(p _ {r}\right) \tag {3} \\ = f _ {s \leftarrow w} \left(f _ {w \leftarrow r} \left(p _ {r}\right)\right), \\ \end{array} +$$ + +$f_{w\leftarrow r}$ is a mapping matrix from the pixel coordinate of $I_r^i$ to the world coordinate and $f_{s\leftarrow w}$ is the inverse operation to the coordinate of $I_{s\leftarrow r}^{i,j}$ , such that: + +$$ +f _ {w \leftarrow r} \left(p _ {r}\right) = D _ {r} ^ {i} \left(p _ {r}\right) T _ {r} ^ {- 1} K _ {r} ^ {- 1} p _ {r}, \tag {4} +$$ + +$$ +f _ {s \leftarrow w} \left(p _ {w}\right) = K _ {s} T _ {s} \left(p _ {w}\right), \tag {5} +$$ + +where $K$ and $T$ represent the camera's intrinsic and extrinsic parameter matrices in their corresponding views, respectively. Since the warping function is not surjective, voids may occur in $I_{s\leftarrow r}^{i,j}$ . We empirically obtain a binary mask $M_{\text{warp}}$ , where the pixels of void areas are set as 1 to identify the initial unreliable regions. To further refine the mask, we employ the cross-view pixel correspondences within the world coordinate of $I_r^i$ and $I_{s\leftarrow r}^{i,j}$ . To achieve this, we obtain the pseudo depth $D_s^j$ of view $j$ by rendering from the radiance fields. Following Eq. 4, we map the pixel of $I_r^i$ and $I_{s\leftarrow r}^{i,j}$ into the same coordinate and obtain the correlation map $M_{\text{cor}}$ by comparing the distance between each pixel + +pair $(p_r,p_{s\leftarrow r})$ + +$$ +M _ {c o r} \left(p _ {s \leftarrow r}\right) = \left\{ \begin{array}{l l} 1, & \| f _ {w \leftarrow r} \left(p _ {r}\right) - f _ {w \leftarrow s} \left(p _ {s \leftarrow r}\right) \| _ {2} > \epsilon . \\ 0, & \text {o t h e r w i s e .} \end{array} \right. \tag {6} +$$ + +In this way, the final unreliability mask can be calculated as follows: + +$$ +M _ {s \leftarrow r} = M _ {c o r} \cup M _ {w a r p}. \tag {7} +$$ + +Bilateral Geometric Consistency Loss. According to the obtained unreliability mask $M_{s \leftarrow r}$ , we categorize the warped novel view image into reliable regions $R_{rel}$ and unreliable regions $R_{unr}$ . Subsequently, we propose a bilateral geometric consistency loss to facilitate the self-training. Since the contents within $R_{rel}$ are considered reliable, we explicitly constrain the appearance of rendered image $I_{s}^{j}$ on view $j$ via a reconstruction loss defined as: + +$$ +L _ {r e l} = \sum_ {p \in \mathcal {R} _ {r e l}} \| I _ {s \leftarrow r} ^ {i, j} (p) - I _ {s} ^ {j} (p) \| ^ {2}. \tag {8} +$$ + +For $R_{unr}$ , we propose to leverage the relative depth prior of the warped $I_{s\leftarrow r}^{i,j}$ to improve the geometric consistency. Specifically, we extract the depth map $D_{s\leftarrow r}$ with a powerful pretrained depth estimation model DPT [32]. By analyzing the semantics of the surrounding context, we could inpaint + +the voids occurring in $D_{s \leftarrow r}$ . Subsequently, a relative depth regularization loss [23] is introduced to constrain the geometric consistency on the rendered depth $D_{s}$ , which is defined as: + +$$ +L _ {u n r} = \sum_ {p \in R _ {u n r}} \sum_ {\hat {p} \in N \left(D _ {s \leftarrow r} ^ {p}\right)} h (p, \hat {p}), \tag {9} +$$ + +where + +$$ +\begin{array}{l} h (p, \hat {p}) = \\ \left\{ \begin{array}{l l} \max \left(\left| D _ {s} ^ {\hat {p}} - D _ {s} ^ {p} \right| - m, 0\right) & \text {i f} \left(D _ {s \leftarrow r} ^ {\hat {p}} - D _ {s \leftarrow r} ^ {p}\right) \\ & \times \left(D _ {s} ^ {\hat {p}} - D _ {s} ^ {p}\right) < 0, \\ 0 & \text {o t h e r w i s e .} \end{array} \right. \tag {10} \\ \end{array} +$$ + +Here $p$ denotes any pixel within the unreliable region $R_{unr}$ ; $\hat{p}$ represents each pixel within a neighborhood $N(D_{s\leftarrow r}^{p})$ of $p$ , where $N(D_{s\leftarrow r}^{p})$ is obtained by calculating pixels that have close depth values with $D_{s\leftarrow r}^{p}$ in the warped depth map; $D_{s}^{p}, D_{s}^{\hat{p}}$ and $D_{s\leftarrow r}^{p}, D_{s\leftarrow r}^{\hat{p}}$ denote the depth values of $p$ and $\hat{p}$ within the rendered depth map $D_{s}$ and estimated depth map $D_{s\leftarrow r}$ , respectively. The function $h(p, \hat{p})$ penalizes inconsistent relative ordering between the depth values of $p$ and $\hat{p}$ in the two depth maps. Specifically, if $D_{s}^{p} < D_{s}^{\hat{p}}$ but $D_{s\leftarrow r}^{p} > D_{s\leftarrow r}^{\hat{p}}$ , or $D_{s}^{p} > D_{s}^{\hat{p}}$ but $D_{s\leftarrow r}^{p} < D_{s\leftarrow r}^{\hat{p}}$ , then $h(p, \hat{p})$ penalizes the depth difference $|D_{s}^{\hat{p}} - D_{s}^{p}|$ beyond a threshold $m$ , to prevent the depth values from shifting dramatically. + +Our bilateral geometric consistency loss is then defined as a weighted sum of $L_{rel}$ and $L_{unr}$ : + +$$ +L _ {b g c} = \lambda_ {r e l} L _ {r e l} + \lambda_ {u n r} L _ {u n r}. \tag {11} +$$ + +This loss enables us to thoroughly explore the information from both reliable and unreliable regions, facilitating the learning of cross-view consistency. Note that we also apply Eq. 9 on input views $I_{r}$ as a depth regularization between the rendered depth and $D_{r}$ for fully exploring the depth prior. + +# 3.4. Unreliability for Voxel Feature Regularization + +In this section, we incorporate the unreliability on regularizing the feature of each position of the voxel grid. With a proper design of reliability-aware voxel smoothing and reliability-aware learning adjustment, we further improve the quality of the rendered image, avoiding suboptimal scene reconstruction. + +Reliability-aware Voxel Smoothing. Employing voxelized feature representations [37, 38] can significantly improve the training and rendering speed of NeRF, by storing the RGB features $f_{c}$ and density $\sigma$ in a voxel grids. To facilitate the learning of voxel representation, DVGO [37, 38] propose a differentiable voxel smoothing loss, which regularizes the difference of $f_{c}$ and $\sigma$ between a given voxel v + +with its six adjacent points $V$ as follows: + +$$ +L (\mathbf {v}) = \sum_ {\hat {\mathbf {v}} \in V} \Delta_ {f _ {c}} (\mathbf {v}, \hat {\mathbf {v}}) + \Delta_ {\sigma} (\mathbf {v}, \hat {\mathbf {v}}), \tag {12} +$$ + +where $\Delta (\cdot ,\cdot)$ denotes an error metric for the difference (e.g., $L_{1},L_{2}$ , or Huber loss). + +However, under the few-shot scenario, learning on the sparse input views can easily overfit the view-specific image, which could lead to a degenerated voxel grid that may contain fluctuant features. To address this issue, we propose to regularize the voxel features for balanced and smooth learning. By taking the unreliability of each synthesized novel view image into consideration, we mitigate the influence of unreliable regions while promoting learning in more reliable areas. We design a reliability-aware smooth factor $\rho (\mathbf{v})$ for each voxel in the grid. Specifically, given a warped image, we cast $O$ rays $\mathbf{r}$ through each pixel of the reliable regions $R_{rel}$ . For each voxel $\mathbf{v}$ , we obtain a reliability score by accumulating the number of rays that pass this voxel, denoted by $S(\mathbf{v})$ . The maximum number of times being passed by rays is denoted as $S(\mathbf{v})_{max}$ . Then the reliability-aware smooth factor is defined as $\rho (v) = \frac{S(\mathbf{v})}{S(\mathbf{v})_{max}}$ . Finally, we formulate the reliability-aware voxel smoothing losses on $f_{c}$ and $\sigma$ as: + +$$ +L _ {f _ {c}} = \sum_ {\mathbf {v}} \sum_ {\hat {\mathbf {v}} \in V} (1 + e ^ {- \rho (\mathbf {v})}) \Delta_ {f _ {c}} (\mathbf {v}, \hat {\mathbf {v}}), \tag {13} +$$ + +$$ +L _ {\sigma} = \sum_ {\mathbf {v}} \sum_ {\hat {\mathbf {v}} \in V} (1 + e ^ {- \rho (\mathbf {v})}) \Delta_ {\sigma} (\mathbf {v}, \hat {\mathbf {v}}). +$$ + +The final regularization loss is defined as follows: + +$$ +L _ {r s} = \lambda_ {f} L _ {f c} + \lambda_ {d} L _ {\sigma}. \tag {14} +$$ + +In this case, the unreliable regions will have smoother supervision during training, mitigating the inconsistency caused by potential overfitting. + +Reliability-guided Learning Adjustment. To further facilitate the learning of geometric and appearance information, we apply a reliability-guided learning strategy to dynamically prioritize the learning towards the reliable zones, while eliminating the false supervision of unreliable regions at the beginning of training. Concretely, we adjust the importance of each voxel $\mathbf{v}$ with a reliability weight $\mathbf{w}_{\mathbf{v}} = 1 + \rho (\mathbf{v})$ , to control the gradients of each voxel during the back-propagation. + +# 3.5. Optimization of ReVoRF + +To avoid dramatic variation of the unreliable depth, we further adopt a depth smoothness loss function [29] as an extra regularization for better relative depth supervision: + +$$ +\begin{array}{l} L _ {d s} = \frac {1}{| R |} \sum_ {r \in R} \sum_ {(x, y) \in D} \| d (x, y) - d (x, y + 1) \| _ {2} ^ {2} \tag {15} \\ + \left\| d (x, y) - d (x + 1, y) \right\| _ {2} ^ {2}, \\ \end{array} +$$ + +![](images/34e704c7bbc557b2cc0aea634386231206762ca28cc7f7a5ba26425ba5d0f4b3.jpg) + +![](images/67953f65e3bfaf16a95751315d1576b3150547758bf83c41430d208ca47d5f6f.jpg) + +![](images/eb4c5af9f426d79205ef3573a8e5ef8f7e6563e6635fb8d8965246dd0b88965a.jpg) +Diet-NeRF [14] +Figure 3. 4-views reconstructions on Realistic Synthetic $360^{\circ}$ [26]. ReVoRF enables more consistent reconstruction with detailed appearance. + +![](images/1157a21e45b6b2fabbcc29b7427f4f5af9aaa52afef161c71795b4840d3caf78.jpg) + +![](images/f7b95f595c67f4533ec41d6cfc700b5fbd292b521073c209927ff032c48bc2b6.jpg) +InfoNeRF [17] + +![](images/bb85b821bad12407d2e2935e95d6bf8bb50fcf427413a5e4cf1392d95cdd9802.jpg) + +![](images/be284e27d22dc72d674d854053e2fcbd2f3b50e82535b805e5909a3a8993355e.jpg) +VGOS [39] + +![](images/d8143693e9e95f1fda6b73721b748909906dc28a1558627e5a1ca73907a331c1.jpg) + +![](images/e03ac08eabf960eb27d7cb1d3374096dfe54878d00758cd31ca40d26e7caa39f.jpg) +ReVoRF (Ours) + +![](images/fe50330791af82f21f2eade031f26e608e5001a389e14a9acdea170301dad840.jpg) + +![](images/1c9a4891dd50d629cd499a1d0b315e752c8d77adf7ccc4dedfc23d8318895d58.jpg) +GT + +
Realistic Synthetic 360° dataset
MethodsPSNR↑SSIM↑LPIPS↓Training Time↓
NeRF [24]15.930.7800.3202 hrs
PixelNeRF [47]16.090.7380.3903-4 days* + 10 hrs
DietNeRF [14]16.060.7930.30619 hrs
3DGS [16]17.550.7010.2503 mins
InfoNeRF [17]18.620.8110.2304 hrs
VGOS [39]18.910.8250.2053 mins
GeCoNeRF [18]19.780.8800.185>2 hrs
Ours20.720.8480.1797 mins
+ +Table 1. Quantitative comparison for 4-views setting in the Realistic Synthetic $360^{\circ}$ dataset [24]. The best and the second-best results are highlighted in bold and underlined, respectively. (*) denotes the time cost of pre-training. + +where $R$ represents the set of rays emanating from the sampled views, $D$ refers to the depth patch that is centered around $r$ , and $d(x,y)$ is of the depth value in position $(x,y)$ . + +The final objective of ReVoRF is formulated as: + +$$ +L _ {\text {t o t a l}} = L _ {r g b} + L _ {b g c} + L _ {r s} + \lambda_ {d s} L _ {d s}. \tag {16} +$$ + +# 4. Experiments + +In this section, we demonstrate the superiority of the proposed ReVoRF through extensive experiments. The details of experiment settings are discussed in Sec. 4.1. Analysis on comparison experiments and ablation study are performed in Sec. 4.2 and Sec. 4.3, respectively. + +# 4.1. Experiment Settings + +Datasets. The experiments are conducted on inward-facing scenes from the Realistic Synthetic $360^{\circ}$ dataset [26] and forward-facing scenes from the LLFF dataset [25]. + +Realistic Synthetic $360^{\circ}$ comprises path-traced images from 8 synthetic scenes, which are characterized by their + +complex geometry and realistic rendering of non-Lambertian materials. Each scene is represented by 400 images, rendered by inward-facing virtual cameras positioned at varying viewpoints. We adhere to the protocol established by InfoNeRF [17] and randomly select 4 views from 100 training images as sparse inputs. The model's performance is then evaluated on a set of 200 testing images. + +LLFF consists of 8 real-world scenes captured with a handheld cellphone, featuring 20 to 62 forward-facing images per scene. These scenes encompass a range of complex environments. In line with the standard protocol [26], we reserve 1/8 of these images for testing purposes. The remaining images are used for training, from which we randomly sample three views for input into our model. + +Implementation Details. Following DVGO [37, 38], we adopt a coarse-to-fine optimization scheme to stabilize the training of ReVoRF and gradually improve the geometric details. During the whole training period, we set the values of $\lambda_{rel}$ and $\lambda_{unr}$ in Eq. 11 as $10^{-1}$ and $10^{-2}$ , respectively. The values of $\lambda_d$ , $\lambda_f$ in Eq. 14, and $\lambda_{ds}$ in Eq. 15 are set as $5\cdot 10^{-4}$ , $5\cdot 10^{-5}$ , and $5\cdot 10^{-5}$ in the coarse stage, and decreased to $5\cdot 10^{-5}$ , $10^{-5}$ , and $5\cdot 10^{-5}$ in the fine stage. The warping poses collected for the Realistic Synthetic $360^{\circ}$ dataset [24] and the LLFF dataset [20] are different. For Realistic Synthetic $360^{\circ}$ , we randomly vary the polar angle $\theta$ and azimuthal angle $\phi$ in the range of $[5^{\circ}, 10^{\circ}]$ based on the input view, and subsequently warp each input sparse view to its four neighboring views defined by $\{(\theta, \phi), (-\theta, \phi), (\theta, -\phi), (-\theta, -\phi)\}$ . For the LLFF dataset, the warped views are obtained by randomly interpolating between every adjacent input view. To speed up the training stage and improve the quality of depth supervision, the warping is performed periodically, which updates the warped depth maps and RGB images every 1000 training steps. + +![](images/cf8dd9c562fa92a11be0bda80ea3c98de83bab810303a1b68ff92424d9448a0e.jpg) +Figure 4. Comparisons on the LLFF dataset [25] in 3-view setting. The red and blue boxes denote compared regions. Our approach achieves better results in reconstructing fine details with enhanced clarity. Please zoom in for details. + +
NeRF LLFF dataset
MethodsPSNR↑SSIM↑LPIPS↓Training Time↓
PixelNeRF [47]16.170.4380.5123-4 days* + 10 hrs
SRF [7]17.070.4360.5292-3 days* + 43mins
MVSNeRF [5]17.880.5840.3271-2 days* + 10mins
Mip-NeRF [2]14.620.3510.49514 hrs
DietNeRF [14]14.940.3700.49618 hrs
3DGS [16]13.050.4070.38813 mins
RegNeRF [29]19.080.5870.3364 hrs
VGOS [39]19.350.6200.4325 mins
SparseNeRF [12]19.860.6240.328>2 hrs
Ours19.260.6440.31611 mins
+ +Table 2. Quantitative comparison for 3-views setting on LLFF [20]. The best and the second-best results are highlighted in bold and underlined, respectively. (*) signifies the pre-training time. + +Evaluation Metrics. To assess the effectiveness of our method, we employ several established metrics, including PSNR (Peak Signal-to-Noise Ratio) for assessing image reconstruction accuracy, SSIM (Structural Similarity Index Measure) [43] for evaluating changes in luminance and contrast that affect structural integrity, and LPIPS (Learned Perceptual Image Patch Similarity) [50], which uses deep learning to approximate human visual perception. These metrics provide a comprehensive analysis of our model's performance, covering aspects of accuracy, perceptual quality, and structural fidelity in the reconstructed images. + +# 4.2. Comparisons + +On the Realistic Synthetic $360^{\circ}$ dataset [24], we compare our method with state-of-the-art approaches, including RegNeRF [29], DietNeRF [14], infoNeRF [17], VGOS [39], PixelNeRF [47], and GeCoNeRF [18], in a 4-view setting. On the LLFF dataset [20], we implement our method in a 3-view setting and compare with SRF [7], MVSNeRF [5], mip-NeRF [2], DietNeRF [14], RegNeRF [29], VGOS [39], SparseNeRF [12] and GeCoNeRF [18]. We adopt the reported results from VGOS [39], sparseNeRF [12], and GeCoNeRF [18]. Besides, we also compare with the advanced reconstruction method 3DGS [16]. + +Qualitative Experiments. Fig. 3 compares our approach with some recent methods on the Realistic Synthetic $360^{\circ}$ dataset [24]. Diet-NeRF [14] performs poorly in the setting of 4 views, while infoNeRF [17] and VGOS [39] are inferior to our method in terms of both geometric shapes and detail resolution. Our approach demonstrates superior performance in both geometry and details. + +Fig. 4 shows a qualitative comparison on a scene from the LLFF dataset [20]. While all methods can recover the overall structure of the scene, our approach excels at the quality of details as shown in the magnified regions. Our method incorporates smoothness while retaining fine details, achieving the most natural results. + +Quantitative Experiments. Table 1 shows quantitative results from different methods on the Realistic Synthetic $360^{\circ}$ dataset [24]. In terms of training time, our method is at least an order of magnitude faster than all other methods except for VGOS [39]. Although our method is slightly lower than VGOS [39], it significantly enhances the PSNR, LPIPS [50], and SSIM [43] of the rendered images. Our method achieves state-of-the-art accuracy in PSNR and LPIPS [50]. Additionally, despite not utilizing a pre-trained model or perceptual loss for high-level semantic information extraction, our method still achieves the second-best performance in perceived SSIM [43]. + +Table 2 shows a quantitative comparison on the LLFF dataset [20]. Our method achieves the highest scores in both SSIM [43] and LPIPS [50], indicating that our images exhibit the best performance in terms of human perceptual reconstruction. We also achieve the third-highest PSNR, which, together with our state-of-the-art performance in SSIM [43] and LPIPS [50], demonstrates that our approach has made improvements in certain aspects of image rendering. + +# 4.3. Ablation Study + +Our ablation study is segmented into five distinct groups with Table 3, with DVGO [37, 38] serving + +![](images/2785d3dbbe3277c2ec433c3cee91061c2416cc98f381fa11e45033e0651525e9.jpg) +Baseline + +![](images/e624199123eecc53c7716e35ed4b67b6cc204cf2ad08b49dfd17f3ab11e82c59.jpg) +Baseline $+L_{rel}$ +Figure 5. Visualizations of the ablation on Chair scene from the Realistic Synthetic $360^{\circ}$ [26] dataset in 4 views setting. With the proposed losses, our methods could gradually improve the cross-view consistency and reduce the noise compared with the baseline. + +![](images/1cfb2111e597c0414c937bc4db59a0913658abaad11e1faa64896460b9ea4218.jpg) +Baseline $+L_{rel} + L_{unr}$ + +![](images/186207c7eb38dd4ff8774aefe41db8c661aaa88b175c15720d61045dae9fed9c.jpg) +Baseline $+L_{rel} + L_{unr} + L_{ds}$ + +![](images/5e7236f892ecd712fc54ad3887616e6fd7115007eba54e38e499b5ae3dac60e3.jpg) +Full Model + +
LrsLdsUnrRelPSNR↑SSIM↑LPIPS↓
17.190.7670.223
✓17.790.7800.243
✓✓19.010.8050.228
✓✓✓19.230.8110.220
✓✓✓✓20.720.8480.179
+ +as the baseline. We incrementally introduce our proposed contributions along with various regularization methods to enhance the model's rendering quality. The groups are delineated as: baseline, baseline $+L_{rel}$ , baseline $+L_{rel} + L_{unr}$ , baseline $+L_{rel} + L_{unr} + L_{ds}$ , and baseline $+L_{rel} + L_{unr} + L_{ds} + L_{rs}$ . The ablation results reveal that each incremental contribution positively impacts the rendering quality in various aspects. After the addition of $L_{rel}$ , our PSNR increased by 0.6. Subsequent inclusion of $L_{unr}$ led to a further rise in PSNR by 1.22. With the incorporation of $L_{ds}$ , the PSNR went from 19.01 to 19.23. Finally, after adding $L_{rs}$ , our PSNR peaked at 20.72, SSIM [43] reached 0.848, and LPIPS [50] arrived at 0.179, marking a significant enhancement. + +Besides, we explore the potential of ReVoRF under the settings where more input views are available. We report extra results for 6-view and 9-view settings in Table 4, demonstrating that increased input views generally enhance performance. ReVoRF maintains superiority across these settings. + +Fig. 5 presents the visualization of our ablation study on the Chair scene. We incorporated $L_{rel}$ to enhance the texture quality of the model, which, however, introduced some noise artifacts. To mitigate these artifacts, $L_{unr}$ and $L_{ds}$ were subsequently integrated. These adjustments successfully reduced noise but at the cost of blurring the geometric structures in the process. The issue of maintaining geometric consistency while eliminating noise was addressed through the implementation of $L_{rs}$ . We observe that our method effectively prevents the collapse of new views caused by overfitting due to a limited number of viewpoints. + +Table 3. Ablation study on the Realistic Synthetic $360^{\circ}$ dataset [24] in the 4-view setting. The best and the second-best results are highlighted in bold and underlined, respectively. + +
MethodsPSNR↑SSIM↑LPIPS↓
3-view6-view9-view3-view6-view9-view3-view6-view9-view
SRF [7]17.0716.7517.390.4360.4380.4650.5290.5210.503
PixelNeRF [47]16.1717.0318.920.4380.4730.5350.5120.4770.430
MVSNeRF [5]17.8819.9920.470.5840.6600.6950.3270.2640.244
DVGO [37]16.6021.2522.890.5600.7040.7460.4220.2460.228
VGOS [39]19.3521.5522.390.6200.6710.6920.4320.3280.325
Ours19.2622.2123.040.6440.7200.7530.3160.2690.225
+ +Table 4. Comparison of 3, 6, and 9 input views on LLFF [20]. The best and the second-best results are highlighted in bold and underlined, respectively. + +# 5. Conclusion, Limitation, and Future Work + +In this paper, we address the challenge of view deformation by discerning reliable and unreliable areas, subsequently introducing a bilateral geometric consistency regularization. This approach maximizes the use of reliable regions while delicately exploring the depth in unreliable areas, applying a more lenient constraint to these zones. Further extending our method into voxel space, we transform 2D reliable areas into 3D space through a reliability-aware voxelization smoothing process. Our method, when applied to various datasets, has proven to be highly precise, significantly bolstering geometric consistency and demonstrating its efficacy in intricate 3D reconstruction tasks. + +Our method shares a common limitation of the voxel-based method: the tendency to produce smoothed results, leading to a loss in fine details. Besides, the exceptionally challenging context for NeRF with sparse input also limits its application in more complex scenes, such as large-scale scene reconstruction. For future work, we aim to refine the voxelization technique to better preserve details, potentially exploring hybrid models that combine voxel-based methods with alternative geometric representations for a more detailed reconstruction. + +Acknowledgement. The work is supported by the Guangdong Natural Science Funds for Distinguished Young Scholar (No. 2023B1515020097), Singapore MOE Tier 1 Funds (MSS23C002), and the NRF Singapore under the AI Singapore Programme (No. AISG3-GV-2023-011). + +# References + +[1] Alexander Amini, Wilko Schwarting, Ava Soleimany, and Daniela Rus. Deep evidential regression. In NeurIPS, volume 33, pages 14927-14937, 2020. 3 +[2] Jonathan T Barron, Ben Mildenhall, Matthew Tancik, Peter Hedman, Ricardo Martin-Brualla, and Pratul P Srinivasan. Mip-nerf: A multiscale representation for anti-aliasing neural radiance fields. In ICCV, pages 5855–5864, 2021. 1, 2, 7 +[3] Matteo Bortolon, Alessio Del Bue, and Fabio Poiesi. Vmnerf: Tackling sparsity in nerf with view morphing. In ICIAP, pages 63-74. Springer, 2023. 2, 3 +[4] Ang Cao and Justin Johnson. Hexplane: A fast representation for dynamic scenes. 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Fourier features let networks learn high frequency functions in low dimensional domains. In NeurIPS, volume 33, pages 7537–7547, 2020. 3 +[43] Zhou Wang, Alan C. Bovik, Hamid R. Sheikh, and Eero P. Simoncelli. Image quality assessment: from error visibility to structural similarity. IEEE TIP, 13(4):600-612, 2004. 7, 8 +[44] Jamie Wynn and Daniyar Turmukhambetov. DiffusioNeRF: Regularizing Neural Radiance Fields with Denoising Diffusion Models. In CVPR, 2023. 3 +[45] Dongyu Yan, Jianheng Liu, Fengyu Quan, Haoyao Chen, and Mengmeng Fu. Active implicit object reconstruction using uncertainty-guided next-best-view optimization. IEEE Robotics Autom. Lett., 8(10):6395-6402, 2023. 3 + +[46] Jiawei Yang, Marco Pavone, and Yue Wang. Freenerf: Improving few-shot neural rendering with free frequency regularization. In CVPR, pages 8254-8263, 2023. 1, 3 +[47] Alex Yu, Vickie Ye, Matthew Tancik, and Angjoo Kanazawa. pixelnerf: Neural radiance fields from one or few images. In CVPR, pages 4578-4587, 2021. 1, 2, 3, 6, 7, 8 +[48] Yu-Jie Yuan, Yang-Tian Sun, Yu-Kun Lai, Yuewen Ma, Rongfei Jia, and Lin Gao. Nerf-editing: geometry editing of neural radiance fields. In CVPR, pages 18353-18364, 2022. 2 +[49] Jian Zhang, Yuanqing Zhang, Huan Fu, Xiaowei Zhou, Bowen Cai, Jinchi Huang, Rongfei Jia, Binqiang Zhao, and Xing Tang. Ray priors through reprojection: Improving neural radiance fields for novel view extrapolation. In CVPR, pages 18376-18386, 2022. 1, 2, 3 +[50] Richard Zhang, Phillip Isola, Alexei A. Efros, Eli Shechtman, and Oliver Wang. The unreasonable effectiveness of deep features as a perceptual metric. In CVPR, pages 586-595, 2018. 7, 8 +[51] Chenxi Zheng, Bangzhen Liu, Xuemiao Xu, Huaidong Zhang, and Shengfeng He. Learning an interpretable stylized subspace for 3d-aware animatable artforms. 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Our method pivots on the insight that relative depth relationships within neighboring regions are more reliable than the absolute color values in disoccluded areas. Consequently, we devise a bilateral geometric consistency loss that carefully navigates the trade-off between color fidelity and geometric accuracy in the context of depth consistency for uncertain regions. Moreover, we present a reliability-guided learning strategy to discern and utilize the variable quality across synthesized views, complemented by a reliability-aware voxel smoothing algorithm that smoothens the transition between reliable and unreliable data patches. Our approach allows for a more nuanced use of all available data, promoting enhanced learning from regions previously considered unsuitable for high-quality reconstruction. 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This challenge has spurred the development of Few-shot NeRF, an emerging domain focused on reconstructing 3D scenes with minimal image data [6,8, 12, 18]." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 606, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 606, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 606, + 548, + 714 + ], + "type": "text", + "content": "The performance of NeRF in accurately reconstructing geometry and texture diminishes when faced with sparse observations, as it tends to overfit the limited views available [8, 49]. To address this issue, there has been a push in recent studies to fortify NeRF with additional priors [46, 47], including semantic relations [14], depth cues [49], and entropy constraints [17]. These enhancements strive to extract maximum information from limited data. However, the reconstructions are inherently limited by the insufficient" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 693, + 211, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 693, + 211, + 703 + ], + "spans": [ + { + "bbox": [ + 58, + 693, + 211, + 703 + ], + "type": "text", + "content": "*The first two authors contributed equally." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 59, + 703, + 226, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 226, + 713 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 226, + 713 + ], + "type": "text", + "content": "† Corresponding author (shengfenghe@smu.edu.sg)." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "20342" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 209, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 209, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 209, + 83 + ], + "type": "text", + "content": "coherence of the sparse views provided." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 87, + 288, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 87, + 288, + 277 + ], + "spans": [ + { + "bbox": [ + 46, + 87, + 288, + 277 + ], + "type": "text", + "content": "Recent research has explored overcoming the challenges posed by very limited observations through pseudo-view synthesis [3, 18]. By using known camera poses and coarse depth estimates, these methods generate warped images from sparse viewpoints to enhance cross-view consistency. However, as shown in Fig. 1b, these generated images often include noisy areas with artifacts, which, if used for learning, can lead to inconsistent training signals and compromise scene integrity. To address this, Kwak et al. [18] implement self-occlusion aware masking to exclude unreliable regions. While this selective masking successfully filters out areas of uncertainty, it also introduces voids, presenting a conundrum: refining these images can bring in inconsistent noise and floaters, as illustrated in Fig. 1c, yet the limited number of usable samples necessitates using all available pseudo supervision for quality reconstruction." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 281, + 288, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 281, + 288, + 483 + ], + "spans": [ + { + "bbox": [ + 46, + 281, + 288, + 483 + ], + "type": "text", + "content": "In light of the issues identified with unreliable warped areas, our paper proposes a novel method for fully exploiting these uncertain regions to achieve multi-view consistency learning. The rationale behind our method is that, although absolute supervision is not reliable in those disoccluded regions, we observe that they maintain consistent relative depth relationships. The unreliability of certain regions in warped images can still bear geometric resemblances to their original view counterparts. We find that local depth information within these images can indicate geometric disparities, offering a self-supervised signal that aids in discerning the geometry of regions lacking precise textural information. While reliable regions offer more accurate supervision, our approach seeks to fully utilize all the information present, exploiting depth cues in coarsely warped images to inform the learning process across both reliable and traditionally discarded unreliable areas." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 486, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 486, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 486, + 288, + 713 + ], + "type": "text", + "content": "Drawing from the insights above, we propose a novel voxel-based optimization framework, ReVoRF, tailored for fast and multi-view consistent reconstruction of few-shot radiance fields, which incorporates the relative depth priors from several aspects. The objective of this work is to concurrently explore information from both dependable and less reliable regions within the warped novel view images. In the first step, we randomly warp the sparse images onto a series of novel views, subsequently delineating reliable and unreliable regions based on the pixel-wise correlation between the input and novel view. We then introduce a bilateral geometric consistency loss to enable self-training on novel synthesized images. This loss encompasses a reconstruction term in a bilateral manner, including a color and density regularization term for reliable regions and a relative depth consistency term for unreliable regions, respectively. While the former term aims at explicitly learning the geometric context of the reliable regions, the relative depth regularization is applied for implicitly exploring the geometric consistency guided" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "text", + "content": "by relative depth. Moreover, we integrate unreliability into our voxelization of scene features: 1) a reliability-guided learning strategy that dynamically adjusts learning priorities towards more reliable regions; 2) a reliability-aware voxel smoothing procedure that preserves structural integrity in reliable zones and mitigates inconsistencies in less reliable ones, ensuring a balanced and coherent scene reconstruction. As illustrated in Fig. 1e, assisted by both bilateral geometric consistency loss and reliability-aware regularization, our method is the second fastest while achieving the best reconstruction fidelity, with a large margin over the others." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 317, + 204, + 516, + 215 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 204, + 516, + 215 + ], + "spans": [ + { + "bbox": [ + 317, + 204, + 516, + 215 + ], + "type": "text", + "content": "Our contributions can be summarized as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 317, + 221, + 545, + 402 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 317, + 221, + 545, + 281 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 221, + 545, + 281 + ], + "spans": [ + { + "bbox": [ + 317, + 221, + 545, + 281 + ], + "type": "text", + "content": "- We present the first attempt to explore pseudo-views unreliability within few-shot radiance fields, presenting the first framework to incorporate these areas for enhanced multi-view consistency learning with a bilateral geometric consistency loss." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 317, + 288, + 545, + 347 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 288, + 545, + 347 + ], + "spans": [ + { + "bbox": [ + 317, + 288, + 545, + 347 + ], + "type": "text", + "content": "- We introduce a reliability-guided learning strategy and voxelization smoothing procedure that tailors the learning process to the reliability of data, thus optimizing the training emphasis for improved reconstruction quality in few-shot radiance fields." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 317, + 354, + 545, + 402 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 354, + 545, + 402 + ], + "spans": [ + { + "bbox": [ + 317, + 354, + 545, + 402 + ], + "type": "text", + "content": "- We demonstrate superior performance of our approach against existing state-of-the-art few-shot methods in efficiency and accuracy, through extensive experiments on both synthetic and real-world datasets." + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 412, + 392, + 425 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 412, + 392, + 425 + ], + "spans": [ + { + "bbox": [ + 306, + 412, + 392, + 425 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 432, + 547, + 684 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 432, + 547, + 684 + ], + "spans": [ + { + "bbox": [ + 304, + 432, + 547, + 684 + ], + "type": "text", + "content": "Neural Radiance Fields (NeRF). NeRF [2,5,13,22,24] have emerged as a significant advancement in 3D reconstruction and novel view synthesis. These methods employ an implicit function to represent a 3D scene, enabling the extraction of detailed geometric and textural information from a set of multi-view images. Subsequent researchers have broadened the scope of NeRF applications, including generative modeling [11,40], video synthesis [9,20,34], and scene editing [21,48]. Despite the impressive rendering quality, the training of vanilla NeRF often spans several days for a single scene reconstruction. Recent advancements [10,27,37,38] have endeavored to mitigate this computational burden. Approaches such as DVGO [4,37,38] employ dense voxel grids in conjunction with shallow multilayer perceptrons to expedite the reconstruction process. Similarly, Plenoxels [10] utilizes sparse voxel grids, and Instant-NGP [27] employs a multi-resolution hash table to delineate the radiance field more efficiently. Diverse from these methods, which typically require dense inputs, we aim to address the challenge of achieving fast and high-fidelity scene reconstruction in the case where only a few observed views are available." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 545, + 713 + ], + "type": "text", + "content": "Few-Shot NeRFs. Recent advances [5, 14, 17, 47, 49, 51] have sought to reduce the dependency on densely collected" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20343" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 384 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 384 + ], + "type": "text", + "content": "data for scene reconstruction, leveraging sparse inputs and scene priors. Notably, PixelNeRF [47] and StereoRF [7] utilize local semantic relationships across multiple scenes, while MVSNeRF [5] incorporates cost volume to enhance performance. These methodologies, however, require pretraining on numerous scenes to acquire necessary scene priors. Further developments [14, 17, 31, 39, 46] have introduced various regularization techniques to maximize the utility of sparse input views. InfoNeRF [17] enhances ray adjacency consistency through entropy regularization. DietNeRF [14] facilitates cross-view semantic consistency by harnessing the semantic space of the pretrained CLIP [31], while DiffusioNeRF [44] explores the diffusion prior of pretrained diffusion models. Additionally, FreeNeRF [46] applies frequency regularization, and VGOS [39] introduces voxel regularization to optimize both feature representation and density. Another group of research focuses on augmenting sparse inputs with synthetically generated views. RapNeRF [49] utilizes geometric re-projection for novel view extrapolation, while VmNeRF [3] employs depth maps for view-morphing. GeCoNeRF [18] aims to refine geometric consistency by separating reliable regions from warped images and discarding unreliable areas prone to self-occlusion. Our work diverges from these approaches by considering the inherent information of both reliable and unreliable regions of the novel view images, facilitating cross-view geometric consistency." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 389, + 288, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 389, + 288, + 641 + ], + "spans": [ + { + "bbox": [ + 47, + 389, + 288, + 641 + ], + "type": "text", + "content": "Unreliability/Uncertainty Modeling. In the rapid development of NeRF, the incorporation of uncertainty modeling has become crucial for achieving robustness in 3D reconstruction from sparse views. Previous efforts have employed diverse strategies, including Bayesian approaches [15, 28] and evidential neural networks [1,33], to quantify uncertainty in neural networks. In the context of NeRF, uncertainty has been harnessed to enhance rendering and guide input capture. Some methods assume Gaussian noise in RGB space for pixel-wise uncertainty [22, 30], employ volumetric entropy for scene geometry [19, 45], or adopt variational inference or Latent Variable Modeling for radiance field uncertainty as seen in S-NeRF [36] and CF-NeRF [35]. However, these approaches have not comprehensively addressed uncertainty quantification in unseen regions. Our approach differs from these methods by not only capturing uncertainty in the geometry and appearance of visible areas but also explicitly accounting for unseen spaces, including occluded points, which previous methods have not considered. This distinction allows for a more nuanced and accurate reconstruction, promising to elevate the fidelity of few-shot NeRF models." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 651, + 129, + 664 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 651, + 129, + 664 + ], + "spans": [ + { + "bbox": [ + 47, + 651, + 129, + 664 + ], + "type": "text", + "content": "3. Methodology" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 671, + 133, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 671, + 133, + 682 + ], + "spans": [ + { + "bbox": [ + 47, + 671, + 133, + 682 + ], + "type": "text", + "content": "3.1. Preliminaries" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "content": "NeRF [24] represents a scene as a continuously differentiable function " + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "content": " via a Multi-Layer Perceptron (MLP)." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": "Given a 3D position " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\mathbf{x} \\in \\mathbb{R}^3" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " and the associated 2D viewing directions " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\mathbf{d} \\in \\mathbb{R}^2" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": ", NeRF maps them into a volume density " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\sigma \\in \\mathbb{R}" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " and an RGB value " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\mathbf{c} \\in \\mathbb{R}^3" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": ", such that: " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "(\\mathbf{c}, \\sigma) = f(\\gamma(\\mathbf{x}), \\gamma(\\mathbf{d}))" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": ", where the " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " is a positional encoding that projects " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\mathbf{d}" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " into a higher dimensional feature space [42]. With a ray parameterized as " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\mathbf{r}_p(t) = \\mathbf{o} + t\\mathbf{d}_p" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " cast from the camera's optical center " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\mathbf{o}" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " along direction " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\mathbf{d}_p" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": ", the expected color " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "\\hat{C}(\\mathbf{r}_p)" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " of pixel " + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 72, + 547, + 170 + ], + "type": "text", + "content": " is rendered as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 337, + 180, + 547, + 208 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 337, + 180, + 547, + 208 + ], + "spans": [ + { + "bbox": [ + 337, + 180, + 547, + 208 + ], + "type": "interline_equation", + "content": "\\hat {C} (\\mathbf {r} _ {p}) = \\int_ {t _ {n}} ^ {t _ {f}} T (t) \\sigma (\\mathbf {r} _ {p} (t)) \\mathbf {c} (\\mathbf {r} _ {p} (t), \\mathbf {d} _ {p}) d t, \\tag {1}", + "image_path": "0c6792debcee0d31c9fb724a480d067fb1a463e18671da3ea86fe30e8355042f.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "spans": [ + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "inline_equation", + "content": "t_n" + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "inline_equation", + "content": "t_f" + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "content": " are the near and far bounds of the ray for sampling, and " + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "inline_equation", + "content": "T(t) = \\exp \\left(-\\int_{t_n}^t \\sigma(\\mathbf{r}(s)) ds\\right)" + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "content": " denotes the cumulative transparency along the ray from " + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "inline_equation", + "content": "t_n" + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "content": ". Therefore, the NeRF can be optimized by a reconstruction loss between the rendered color " + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "inline_equation", + "content": "\\hat{C}(\\mathbf{r})" + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "content": " and the real color " + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "inline_equation", + "content": "C(\\mathbf{r})" + }, + { + "bbox": [ + 304, + 217, + 547, + 283 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 364, + 293, + 546, + 319 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 364, + 293, + 546, + 319 + ], + "spans": [ + { + "bbox": [ + 364, + 293, + 546, + 319 + ], + "type": "interline_equation", + "content": "L _ {r g b} = \\sum_ {\\mathbf {r} \\in \\mathcal {R}} \\| \\hat {C} (\\mathbf {r}) - C (\\mathbf {r}) \\| ^ {2}, \\tag {2}", + "image_path": "016ca3b3a67bba30bc8ec35be23298d3152dc136c4a9acefd0a18ba3f4f4643e.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 329, + 471, + 341 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 329, + 471, + 341 + ], + "spans": [ + { + "bbox": [ + 305, + 329, + 471, + 341 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 329, + 471, + 341 + ], + "type": "inline_equation", + "content": "\\mathcal{R}" + }, + { + "bbox": [ + 305, + 329, + 471, + 341 + ], + "type": "text", + "content": " denotes the set of training rays." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 351, + 373, + 361 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 351, + 373, + 361 + ], + "spans": [ + { + "bbox": [ + 306, + 351, + 373, + 361 + ], + "type": "text", + "content": "3.2. Overview" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 370, + 547, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 370, + 547, + 491 + ], + "spans": [ + { + "bbox": [ + 304, + 370, + 547, + 491 + ], + "type": "text", + "content": "We propose ReVoRF, a novel voxel-based optimization framework tailored for fast and multi-view consistent scene reconstruction from sparse input views. Our key idea is to incorporate the unreliability information for fully exploring the warped novel view images. By treating depth priors as the unreliability metrics, ReVoRF facilitates the reconstruction of the few-shot radiance field from several aspects, including the multi-view consistency learning (Sec. 3.3) and the regularization of voxel features (Sec. 3.4). The overall pipeline of ReVoRF is displayed in Fig. 2." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 499, + 517, + 512 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 499, + 517, + 512 + ], + "spans": [ + { + "bbox": [ + 306, + 499, + 517, + 512 + ], + "type": "text", + "content": "3.3. Unreliability for Multi-view Consistency" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 518, + 547, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 518, + 547, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 518, + 547, + 555 + ], + "type": "text", + "content": "In this section, we explore the potential of unreliability in facilitating multi-view geometric consistency via the proposed bilateral geometric consistency loss." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": "Novel View Warping. Starting from a set of sparse input images " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "I_r^i" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " for " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "i \\in 1, \\dots, N_r" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " represents the view number and " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "N_r" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " is a small number, e.g., " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "N_r = 3" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " or " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "N_r = 4" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": ", we propose to synthesize novel view images " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "I_{s \\leftarrow r}^{i,j}" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " through a fast and flexible warping process on several novel views " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "j \\in 1, \\dots, N_s" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": ". To preserve the cross-view consistency, the warping is guided by a coarse depth map " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "D_r^i" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": ", where the depth value on each pixel " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " is accumulated by the density along each ray " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "r_p" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " omitted from the camera: " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "D_r^i(p) = \\int_{t_f}^{t_n} T(t) \\sigma(r_p(t)) t dt" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": ". Subsequently, we obtain the warped image " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "I_{s \\leftarrow r}^{i,j}" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " through a cross-view transformation " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "H_{s \\leftarrow r}" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": ", which deforms each pixel " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "p_r" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "inline_equation", + "content": "I_r^i" + }, + { + "bbox": [ + 304, + 565, + 548, + 714 + ], + "type": "text", + "content": " to its correspond" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "20344" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 68, + 547, + 315 + ], + "blocks": [ + { + "bbox": [ + 50, + 68, + 547, + 315 + ], + "lines": [ + { + "bbox": [ + 50, + 68, + 547, + 315 + ], + "spans": [ + { + "bbox": [ + 50, + 68, + 547, + 315 + ], + "type": "image", + "image_path": "91a2121fb48de591d43840e5e63b49e3b4f5ff9b41d079d4792c03957da6eeb1.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 320, + 547, + 399 + ], + "lines": [ + { + "bbox": [ + 46, + 320, + 547, + 399 + ], + "spans": [ + { + "bbox": [ + 46, + 320, + 547, + 399 + ], + "type": "text", + "content": "Figure 2. Overview of our proposed ReVoRF. Specifically, we first warp the sparse images onto several novel views and determine both the dependable and unreliable regions. Based on the dependability of each image region, we introduce a bilateral geometric consistency loss for multi-view consistent learning, which is composed of a color and density regularization term for reliable regions and a relative depth consistency term for unreliable regions. These two terms are responsible for explicitly learning the reliable geometric contents and implicitly exploring the geometric consistency via the guidance of relative depth, respectively. For voxel feature regularization, we integrate the unreliability through a reliability-guided learning strategy and a reliability-aware voxel smoothing procedure. By prioritizing the learning of more reliable regions and mitigating the inconsistencies in less reliable ones, ReVoRF ensures a more balanced and coherent reconstruction." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 411, + 187, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 411, + 187, + 423 + ], + "spans": [ + { + "bbox": [ + 47, + 411, + 187, + 423 + ], + "type": "text", + "content": "ing position " + }, + { + "bbox": [ + 47, + 411, + 187, + 423 + ], + "type": "inline_equation", + "content": "p_{s}" + }, + { + "bbox": [ + 47, + 411, + 187, + 423 + ], + "type": "text", + "content": " on the target view:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 110, + 436, + 287, + 464 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 110, + 436, + 287, + 464 + ], + "spans": [ + { + "bbox": [ + 110, + 436, + 287, + 464 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} p _ {s \\leftarrow r} = H _ {s \\leftarrow r} \\left(p _ {r}\\right) \\tag {3} \\\\ = f _ {s \\leftarrow w} \\left(f _ {w \\leftarrow r} \\left(p _ {r}\\right)\\right), \\\\ \\end{array}", + "image_path": "03559480abae79506dfe2b18c1d050ae8a358661ed8208e1f68a8148e3e8e60f.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "spans": [ + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "inline_equation", + "content": "f_{w\\leftarrow r}" + }, + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "text", + "content": " is a mapping matrix from the pixel coordinate of " + }, + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "inline_equation", + "content": "I_r^i" + }, + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "text", + "content": " to the world coordinate and " + }, + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "inline_equation", + "content": "f_{s\\leftarrow w}" + }, + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "text", + "content": " is the inverse operation to the coordinate of " + }, + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "inline_equation", + "content": "I_{s\\leftarrow r}^{i,j}" + }, + { + "bbox": [ + 47, + 478, + 287, + 515 + ], + "type": "text", + "content": ", such that:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 99, + 527, + 287, + 541 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 99, + 527, + 287, + 541 + ], + "spans": [ + { + "bbox": [ + 99, + 527, + 287, + 541 + ], + "type": "interline_equation", + "content": "f _ {w \\leftarrow r} \\left(p _ {r}\\right) = D _ {r} ^ {i} \\left(p _ {r}\\right) T _ {r} ^ {- 1} K _ {r} ^ {- 1} p _ {r}, \\tag {4}", + "image_path": "a761b956ce94d52fa11bf871ab0039a3415725df3b663afd2eb9b38329a20fd1.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 99, + 544, + 287, + 557 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 99, + 544, + 287, + 557 + ], + "spans": [ + { + "bbox": [ + 99, + 544, + 287, + 557 + ], + "type": "interline_equation", + "content": "f _ {s \\leftarrow w} \\left(p _ {w}\\right) = K _ {s} T _ {s} \\left(p _ {w}\\right), \\tag {5}", + "image_path": "79e3a1f3f23b4d9ff6d0d625fd1084a36b24032a0bb3ca3b2ef8c8973faaaf8f.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": " represent the camera's intrinsic and extrinsic parameter matrices in their corresponding views, respectively. Since the warping function is not surjective, voids may occur in " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "I_{s\\leftarrow r}^{i,j}" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": ". We empirically obtain a binary mask " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "M_{\\text{warp}}" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": ", where the pixels of void areas are set as 1 to identify the initial unreliable regions. To further refine the mask, we employ the cross-view pixel correspondences within the world coordinate of " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "I_r^i" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "I_{s\\leftarrow r}^{i,j}" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": ". To achieve this, we obtain the pseudo depth " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "D_s^j" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": " of view " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": " by rendering from the radiance fields. Following Eq. 4, we map the pixel of " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "I_r^i" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "I_{s\\leftarrow r}^{i,j}" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": " into the same coordinate and obtain the correlation map " + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "inline_equation", + "content": "M_{\\text{cor}}" + }, + { + "bbox": [ + 47, + 570, + 289, + 714 + ], + "type": "text", + "content": " by comparing the distance between each pixel" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 411, + 373, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 411, + 373, + 423 + ], + "spans": [ + { + "bbox": [ + 306, + 411, + 373, + 423 + ], + "type": "text", + "content": "pair " + }, + { + "bbox": [ + 306, + 411, + 373, + 423 + ], + "type": "inline_equation", + "content": "(p_r,p_{s\\leftarrow r})" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 309, + 430, + 545, + 472 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 430, + 545, + 472 + ], + "spans": [ + { + "bbox": [ + 309, + 430, + 545, + 472 + ], + "type": "interline_equation", + "content": "M _ {c o r} \\left(p _ {s \\leftarrow r}\\right) = \\left\\{ \\begin{array}{l l} 1, & \\| f _ {w \\leftarrow r} \\left(p _ {r}\\right) - f _ {w \\leftarrow s} \\left(p _ {s \\leftarrow r}\\right) \\| _ {2} > \\epsilon . \\\\ 0, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {6}", + "image_path": "f38142c21e12dee89db471b79b4f2d91de1169363c7970fc425f40b4f9dbd86a.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 472, + 545, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 472, + 545, + 494 + ], + "spans": [ + { + "bbox": [ + 305, + 472, + 545, + 494 + ], + "type": "text", + "content": "In this way, the final unreliability mask can be calculated as follows:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 373, + 496, + 545, + 509 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 373, + 496, + 545, + 509 + ], + "spans": [ + { + "bbox": [ + 373, + 496, + 545, + 509 + ], + "type": "interline_equation", + "content": "M _ {s \\leftarrow r} = M _ {c o r} \\cup M _ {w a r p}. \\tag {7}", + "image_path": "f5643bc9bd05b3bbd34b63c795ee602ed182249312768606b8ca36f4dc43e247.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "spans": [ + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "text", + "content": "Bilateral Geometric Consistency Loss. According to the obtained unreliability mask " + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "inline_equation", + "content": "M_{s \\leftarrow r}" + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "text", + "content": ", we categorize the warped novel view image into reliable regions " + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "inline_equation", + "content": "R_{rel}" + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "text", + "content": " and unreliable regions " + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "inline_equation", + "content": "R_{unr}" + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "text", + "content": ". Subsequently, we propose a bilateral geometric consistency loss to facilitate the self-training. Since the contents within " + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "inline_equation", + "content": "R_{rel}" + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "text", + "content": " are considered reliable, we explicitly constrain the appearance of rendered image " + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "inline_equation", + "content": "I_{s}^{j}" + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "text", + "content": " on view " + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 304, + 519, + 547, + 614 + ], + "type": "text", + "content": " via a reconstruction loss defined as:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 352, + 620, + 545, + 647 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 352, + 620, + 545, + 647 + ], + "spans": [ + { + "bbox": [ + 352, + 620, + 545, + 647 + ], + "type": "interline_equation", + "content": "L _ {r e l} = \\sum_ {p \\in \\mathcal {R} _ {r e l}} \\| I _ {s \\leftarrow r} ^ {i, j} (p) - I _ {s} ^ {j} (p) \\| ^ {2}. \\tag {8}", + "image_path": "566b16713b0410044166ef811f7cd1b7db814b3025fb226909e81eb621c16a76.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "type": "text", + "content": "For " + }, + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "type": "inline_equation", + "content": "R_{unr}" + }, + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "type": "text", + "content": ", we propose to leverage the relative depth prior of the warped " + }, + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "type": "inline_equation", + "content": "I_{s\\leftarrow r}^{i,j}" + }, + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "type": "text", + "content": " to improve the geometric consistency. Specifically, we extract the depth map " + }, + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "type": "inline_equation", + "content": "D_{s\\leftarrow r}" + }, + { + "bbox": [ + 304, + 654, + 547, + 714 + ], + "type": "text", + "content": " with a powerful pretrained depth estimation model DPT [32]. By analyzing the semantics of the surrounding context, we could inpaint" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20345" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 118 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 118 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 118 + ], + "type": "text", + "content": "the voids occurring in " + }, + { + "bbox": [ + 46, + 72, + 288, + 118 + ], + "type": "inline_equation", + "content": "D_{s \\leftarrow r}" + }, + { + "bbox": [ + 46, + 72, + 288, + 118 + ], + "type": "text", + "content": ". Subsequently, a relative depth regularization loss [23] is introduced to constrain the geometric consistency on the rendered depth " + }, + { + "bbox": [ + 46, + 72, + 288, + 118 + ], + "type": "inline_equation", + "content": "D_{s}" + }, + { + "bbox": [ + 46, + 72, + 288, + 118 + ], + "type": "text", + "content": ", which is defined as:" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 95, + 127, + 288, + 155 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 95, + 127, + 288, + 155 + ], + "spans": [ + { + "bbox": [ + 95, + 127, + 288, + 155 + ], + "type": "interline_equation", + "content": "L _ {u n r} = \\sum_ {p \\in R _ {u n r}} \\sum_ {\\hat {p} \\in N \\left(D _ {s \\leftarrow r} ^ {p}\\right)} h (p, \\hat {p}), \\tag {9}", + "image_path": "37b0b616583acbe5ea29540d1bf53530a02b0884ce8aff856ce8cbd29acd470d.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 163, + 75, + 174 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 163, + 75, + 174 + ], + "spans": [ + { + "bbox": [ + 47, + 163, + 75, + 174 + ], + "type": "text", + "content": "where" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 55, + 183, + 287, + 243 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 183, + 287, + 243 + ], + "spans": [ + { + "bbox": [ + 55, + 183, + 287, + 243 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} h (p, \\hat {p}) = \\\\ \\left\\{ \\begin{array}{l l} \\max \\left(\\left| D _ {s} ^ {\\hat {p}} - D _ {s} ^ {p} \\right| - m, 0\\right) & \\text {i f} \\left(D _ {s \\leftarrow r} ^ {\\hat {p}} - D _ {s \\leftarrow r} ^ {p}\\right) \\\\ & \\times \\left(D _ {s} ^ {\\hat {p}} - D _ {s} ^ {p}\\right) < 0, \\\\ 0 & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {10} \\\\ \\end{array}", + "image_path": "140d26512218c0d86e792e66958b33ebbf15f32c6d2d3e18a74b57578079bdf3.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": "Here " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " denotes any pixel within the unreliable region " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "R_{unr}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": "; " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "\\hat{p}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " represents each pixel within a neighborhood " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "N(D_{s\\leftarrow r}^{p})" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "N(D_{s\\leftarrow r}^{p})" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " is obtained by calculating pixels that have close depth values with " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s\\leftarrow r}^{p}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " in the warped depth map; " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s}^{p}, D_{s}^{\\hat{p}}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s\\leftarrow r}^{p}, D_{s\\leftarrow r}^{\\hat{p}}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " denote the depth values of " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "\\hat{p}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " within the rendered depth map " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " and estimated depth map " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s\\leftarrow r}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": ", respectively. The function " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "h(p, \\hat{p})" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " penalizes inconsistent relative ordering between the depth values of " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "\\hat{p}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " in the two depth maps. Specifically, if " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s}^{p} < D_{s}^{\\hat{p}}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " but " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s\\leftarrow r}^{p} > D_{s\\leftarrow r}^{\\hat{p}}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": ", or " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s}^{p} > D_{s}^{\\hat{p}}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " but " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "D_{s\\leftarrow r}^{p} < D_{s\\leftarrow r}^{\\hat{p}}" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": ", then " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "h(p, \\hat{p})" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " penalizes the depth difference " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "|D_{s}^{\\hat{p}} - D_{s}^{p}|" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": " beyond a threshold " + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 46, + 251, + 288, + 407 + ], + "type": "text", + "content": ", to prevent the depth values from shifting dramatically." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 407, + 287, + 432 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 407, + 287, + 432 + ], + "spans": [ + { + "bbox": [ + 46, + 407, + 287, + 432 + ], + "type": "text", + "content": "Our bilateral geometric consistency loss is then defined as a weighted sum of " + }, + { + "bbox": [ + 46, + 407, + 287, + 432 + ], + "type": "inline_equation", + "content": "L_{rel}" + }, + { + "bbox": [ + 46, + 407, + 287, + 432 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 407, + 287, + 432 + ], + "type": "inline_equation", + "content": "L_{unr}" + }, + { + "bbox": [ + 46, + 407, + 287, + 432 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 104, + 441, + 287, + 455 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 104, + 441, + 287, + 455 + ], + "spans": [ + { + "bbox": [ + 104, + 441, + 287, + 455 + ], + "type": "interline_equation", + "content": "L _ {b g c} = \\lambda_ {r e l} L _ {r e l} + \\lambda_ {u n r} L _ {u n r}. \\tag {11}", + "image_path": "16dea4491d22d2486c8189738446af770b7bc7f4f0f549e6fe66acf47aec5c5b.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 464, + 287, + 525 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 464, + 287, + 525 + ], + "spans": [ + { + "bbox": [ + 46, + 464, + 287, + 525 + ], + "type": "text", + "content": "This loss enables us to thoroughly explore the information from both reliable and unreliable regions, facilitating the learning of cross-view consistency. Note that we also apply Eq. 9 on input views " + }, + { + "bbox": [ + 46, + 464, + 287, + 525 + ], + "type": "inline_equation", + "content": "I_{r}" + }, + { + "bbox": [ + 46, + 464, + 287, + 525 + ], + "type": "text", + "content": " as a depth regularization between the rendered depth and " + }, + { + "bbox": [ + 46, + 464, + 287, + 525 + ], + "type": "inline_equation", + "content": "D_{r}" + }, + { + "bbox": [ + 46, + 464, + 287, + 525 + ], + "type": "text", + "content": " for fully exploring the depth prior." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 531, + 285, + 544 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 531, + 285, + 544 + ], + "spans": [ + { + "bbox": [ + 47, + 531, + 285, + 544 + ], + "type": "text", + "content": "3.4. Unreliability for Voxel Feature Regularization" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 551, + 287, + 622 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 551, + 287, + 622 + ], + "spans": [ + { + "bbox": [ + 46, + 551, + 287, + 622 + ], + "type": "text", + "content": "In this section, we incorporate the unreliability on regularizing the feature of each position of the voxel grid. With a proper design of reliability-aware voxel smoothing and reliability-aware learning adjustment, we further improve the quality of the rendered image, avoiding suboptimal scene reconstruction." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "content": "Reliability-aware Voxel Smoothing. Employing voxelized feature representations [37, 38] can significantly improve the training and rendering speed of NeRF, by storing the RGB features " + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "inline_equation", + "content": "f_{c}" + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "content": " and density " + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "content": " in a voxel grids. To facilitate the learning of voxel representation, DVGO [37, 38] propose a differentiable voxel smoothing loss, which regularizes the difference of " + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "inline_equation", + "content": "f_{c}" + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "content": " between a given voxel v" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 72, + 471, + 84 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 471, + 84 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 471, + 84 + ], + "type": "text", + "content": "with its six adjacent points " + }, + { + "bbox": [ + 305, + 72, + 471, + 84 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 305, + 72, + 471, + 84 + ], + "type": "text", + "content": " as follows:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 351, + 90, + 546, + 114 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 351, + 90, + 546, + 114 + ], + "spans": [ + { + "bbox": [ + 351, + 90, + 546, + 114 + ], + "type": "interline_equation", + "content": "L (\\mathbf {v}) = \\sum_ {\\hat {\\mathbf {v}} \\in V} \\Delta_ {f _ {c}} (\\mathbf {v}, \\hat {\\mathbf {v}}) + \\Delta_ {\\sigma} (\\mathbf {v}, \\hat {\\mathbf {v}}), \\tag {12}", + "image_path": "87242abdbf20272e941b7cd0558a8031963bd447d0c0a42214a9a465ec0511ac.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 121, + 546, + 145 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 121, + 546, + 145 + ], + "spans": [ + { + "bbox": [ + 306, + 121, + 546, + 145 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 306, + 121, + 546, + 145 + ], + "type": "inline_equation", + "content": "\\Delta (\\cdot ,\\cdot)" + }, + { + "bbox": [ + 306, + 121, + 546, + 145 + ], + "type": "text", + "content": " denotes an error metric for the difference (e.g., " + }, + { + "bbox": [ + 306, + 121, + 546, + 145 + ], + "type": "inline_equation", + "content": "L_{1},L_{2}" + }, + { + "bbox": [ + 306, + 121, + 546, + 145 + ], + "type": "text", + "content": ", or Huber loss)." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "spans": [ + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": "However, under the few-shot scenario, learning on the sparse input views can easily overfit the view-specific image, which could lead to a degenerated voxel grid that may contain fluctuant features. To address this issue, we propose to regularize the voxel features for balanced and smooth learning. By taking the unreliability of each synthesized novel view image into consideration, we mitigate the influence of unreliable regions while promoting learning in more reliable areas. We design a reliability-aware smooth factor " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "\\rho (\\mathbf{v})" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": " for each voxel in the grid. Specifically, given a warped image, we cast " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "O" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": " rays " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "\\mathbf{r}" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": " through each pixel of the reliable regions " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "R_{rel}" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": ". For each voxel " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "\\mathbf{v}" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": ", we obtain a reliability score by accumulating the number of rays that pass this voxel, denoted by " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "S(\\mathbf{v})" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": ". The maximum number of times being passed by rays is denoted as " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "S(\\mathbf{v})_{max}" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": ". Then the reliability-aware smooth factor is defined as " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "\\rho (v) = \\frac{S(\\mathbf{v})}{S(\\mathbf{v})_{max}}" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": ". Finally, we formulate the reliability-aware voxel smoothing losses on " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "f_{c}" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 305, + 146, + 547, + 352 + ], + "type": "text", + "content": " as:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 345, + 357, + 546, + 388 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 345, + 357, + 546, + 388 + ], + "spans": [ + { + "bbox": [ + 345, + 357, + 546, + 388 + ], + "type": "interline_equation", + "content": "L _ {f _ {c}} = \\sum_ {\\mathbf {v}} \\sum_ {\\hat {\\mathbf {v}} \\in V} (1 + e ^ {- \\rho (\\mathbf {v})}) \\Delta_ {f _ {c}} (\\mathbf {v}, \\hat {\\mathbf {v}}), \\tag {13}", + "image_path": "a45df1b3e283bdee9244103ab01eee995c6b1a07e88fe9813409b40724d86292.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 349, + 386, + 501, + 410 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 349, + 386, + 501, + 410 + ], + "spans": [ + { + "bbox": [ + 349, + 386, + 501, + 410 + ], + "type": "interline_equation", + "content": "L _ {\\sigma} = \\sum_ {\\mathbf {v}} \\sum_ {\\hat {\\mathbf {v}} \\in V} (1 + e ^ {- \\rho (\\mathbf {v})}) \\Delta_ {\\sigma} (\\mathbf {v}, \\hat {\\mathbf {v}}).", + "image_path": "a0f8c42eb1c7860d256065913724244b267049bb03565a77d7aa843ebc919a9e.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 416, + 506, + 428 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 416, + 506, + 428 + ], + "spans": [ + { + "bbox": [ + 306, + 416, + 506, + 428 + ], + "type": "text", + "content": "The final regularization loss is defined as follows:" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 378, + 435, + 545, + 449 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 378, + 435, + 545, + 449 + ], + "spans": [ + { + "bbox": [ + 378, + 435, + 545, + 449 + ], + "type": "interline_equation", + "content": "L _ {r s} = \\lambda_ {f} L _ {f c} + \\lambda_ {d} L _ {\\sigma}. \\tag {14}", + "image_path": "e13b4807f5c44658cf90350e3568199e178749445ab6cd7ad332fb03d6c64446.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 305, + 453, + 547, + 490 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 453, + 547, + 490 + ], + "spans": [ + { + "bbox": [ + 305, + 453, + 547, + 490 + ], + "type": "text", + "content": "In this case, the unreliable regions will have smoother supervision during training, mitigating the inconsistency caused by potential overfitting." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 495, + 547, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 495, + 547, + 604 + ], + "spans": [ + { + "bbox": [ + 305, + 495, + 547, + 604 + ], + "type": "text", + "content": "Reliability-guided Learning Adjustment. To further facilitate the learning of geometric and appearance information, we apply a reliability-guided learning strategy to dynamically prioritize the learning towards the reliable zones, while eliminating the false supervision of unreliable regions at the beginning of training. Concretely, we adjust the importance of each voxel " + }, + { + "bbox": [ + 305, + 495, + 547, + 604 + ], + "type": "inline_equation", + "content": "\\mathbf{v}" + }, + { + "bbox": [ + 305, + 495, + 547, + 604 + ], + "type": "text", + "content": " with a reliability weight " + }, + { + "bbox": [ + 305, + 495, + 547, + 604 + ], + "type": "inline_equation", + "content": "\\mathbf{w}_{\\mathbf{v}} = 1 + \\rho (\\mathbf{v})" + }, + { + "bbox": [ + 305, + 495, + 547, + 604 + ], + "type": "text", + "content": ", to control the gradients of each voxel during the back-propagation." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 609, + 444, + 621 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 609, + 444, + 621 + ], + "spans": [ + { + "bbox": [ + 306, + 609, + 444, + 621 + ], + "type": "text", + "content": "3.5. 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Realistic Synthetic 360° dataset
MethodsPSNR↑SSIM↑LPIPS↓Training Time↓
NeRF [24]15.930.7800.3202 hrs
PixelNeRF [47]16.090.7380.3903-4 days* + 10 hrs
DietNeRF [14]16.060.7930.30619 hrs
3DGS [16]17.550.7010.2503 mins
InfoNeRF [17]18.620.8110.2304 hrs
VGOS [39]18.910.8250.2053 mins
GeCoNeRF [18]19.780.8800.185>2 hrs
Ours20.720.8480.1797 mins
", + "image_path": "72df23a26e6273a8c3b1774e093f85de3790219f635aae45a5ca2d297ffe1d0f.jpg" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "table_body" + } + ], + "index": 17 + }, + { + "bbox": [ + 47, + 402, + 288, + 446 + ], + "lines": [ + { + "bbox": [ + 47, + 402, + 288, + 446 + ], + "spans": [ + { + "bbox": [ + 47, + 402, + 288, + 446 + ], + "type": "text", + "content": "Table 1. Quantitative comparison for 4-views setting in the Realistic Synthetic " + }, + { + "bbox": [ + 47, + 402, + 288, + 446 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 47, + 402, + 288, + 446 + ], + "type": "text", + "content": " dataset [24]. The best and the second-best results are highlighted in bold and underlined, respectively. (*) denotes the time cost of pre-training." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "spans": [ + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "inline_equation", + "content": "R" + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "text", + "content": " represents the set of rays emanating from the sampled views, " + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "text", + "content": " refers to the depth patch that is centered around " + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "inline_equation", + "content": "r" + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "inline_equation", + "content": "d(x,y)" + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "text", + "content": " is of the depth value in position " + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "inline_equation", + "content": "(x,y)" + }, + { + "bbox": [ + 47, + 453, + 288, + 490 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 59, + 490, + 253, + 501 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 490, + 253, + 501 + ], + "spans": [ + { + "bbox": [ + 59, + 490, + 253, + 501 + ], + "type": "text", + "content": "The final objective of ReVoRF is formulated as:" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 86, + 508, + 287, + 521 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 86, + 508, + 287, + 521 + ], + "spans": [ + { + "bbox": [ + 86, + 508, + 287, + 521 + ], + "type": "interline_equation", + "content": "L _ {\\text {t o t a l}} = L _ {r g b} + L _ {b g c} + L _ {r s} + \\lambda_ {d s} L _ {d s}. \\tag {16}", + "image_path": "72f6c1c6bb6c79cc7ba0d8e78eced4e575008c0425bf41f8e266192bb221d394.jpg" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 47, + 548, + 128, + 562 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 548, + 128, + 562 + ], + "spans": [ + { + "bbox": [ + 47, + 548, + 128, + 562 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 46, + 568, + 288, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 568, + 288, + 629 + ], + "spans": [ + { + "bbox": [ + 46, + 568, + 288, + 629 + ], + "type": "text", + "content": "In this section, we demonstrate the superiority of the proposed ReVoRF through extensive experiments. The details of experiment settings are discussed in Sec. 4.1. Analysis on comparison experiments and ablation study are performed in Sec. 4.2 and Sec. 4.3, respectively." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 47, + 635, + 165, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 635, + 165, + 647 + ], + "spans": [ + { + "bbox": [ + 47, + 635, + 165, + 647 + ], + "type": "text", + "content": "4.1. Experiment Settings" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 47, + 653, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 653, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 47, + 653, + 287, + 689 + ], + "type": "text", + "content": "Datasets. The experiments are conducted on inward-facing scenes from the Realistic Synthetic " + }, + { + "bbox": [ + 47, + 653, + 287, + 689 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 47, + 653, + 287, + 689 + ], + "type": "text", + "content": " dataset [26] and forward-facing scenes from the LLFF dataset [25]." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "content": "Realistic Synthetic " + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 47, + 689, + 288, + 713 + ], + "type": "text", + "content": " comprises path-traced images from 8 synthetic scenes, which are characterized by their" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 304, + 295, + 547, + 378 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 295, + 547, + 378 + ], + "spans": [ + { + "bbox": [ + 304, + 295, + 547, + 378 + ], + "type": "text", + "content": "complex geometry and realistic rendering of non-Lambertian materials. Each scene is represented by 400 images, rendered by inward-facing virtual cameras positioned at varying viewpoints. We adhere to the protocol established by InfoNeRF [17] and randomly select 4 views from 100 training images as sparse inputs. The model's performance is then evaluated on a set of 200 testing images." + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 304, + 380, + 547, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 380, + 547, + 464 + ], + "spans": [ + { + "bbox": [ + 304, + 380, + 547, + 464 + ], + "type": "text", + "content": "LLFF consists of 8 real-world scenes captured with a handheld cellphone, featuring 20 to 62 forward-facing images per scene. These scenes encompass a range of complex environments. In line with the standard protocol [26], we reserve 1/8 of these images for testing purposes. The remaining images are used for training, from which we randomly sample three views for input into our model." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "spans": [ + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": "Implementation Details. Following DVGO [37, 38], we adopt a coarse-to-fine optimization scheme to stabilize the training of ReVoRF and gradually improve the geometric details. During the whole training period, we set the values of " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "\\lambda_{rel}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "\\lambda_{unr}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " in Eq. 11 as " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "10^{-1}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "10^{-2}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": ", respectively. The values of " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "\\lambda_d" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "\\lambda_f" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " in Eq. 14, and " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "\\lambda_{ds}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " in Eq. 15 are set as " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "5\\cdot 10^{-4}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "5\\cdot 10^{-5}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "5\\cdot 10^{-5}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " in the coarse stage, and decreased to " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "5\\cdot 10^{-5}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "10^{-5}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "5\\cdot 10^{-5}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " in the fine stage. The warping poses collected for the Realistic Synthetic " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " dataset [24] and the LLFF dataset [20] are different. For Realistic Synthetic " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": ", we randomly vary the polar angle " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " and azimuthal angle " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " in the range of " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "[5^{\\circ}, 10^{\\circ}]" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": " based on the input view, and subsequently warp each input sparse view to its four neighboring views defined by " + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "inline_equation", + "content": "\\{(\\theta, \\phi), (-\\theta, \\phi), (\\theta, -\\phi), (-\\theta, -\\phi)\\}" + }, + { + "bbox": [ + 304, + 479, + 547, + 720 + ], + "type": "text", + "content": ". For the LLFF dataset, the warped views are obtained by randomly interpolating between every adjacent input view. 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Comparisons on the LLFF dataset [25] in 3-view setting. The red and blue boxes denote compared regions. Our approach achieves better results in reconstructing fine details with enhanced clarity. Please zoom in for details." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 50, + 262, + 296, + 387 + ], + "blocks": [ + { + "bbox": [ + 50, + 262, + 296, + 387 + ], + "lines": [ + { + "bbox": [ + 50, + 262, + 296, + 387 + ], + "spans": [ + { + "bbox": [ + 50, + 262, + 296, + 387 + ], + "type": "table", + "html": "
NeRF LLFF dataset
MethodsPSNR↑SSIM↑LPIPS↓Training Time↓
PixelNeRF [47]16.170.4380.5123-4 days* + 10 hrs
SRF [7]17.070.4360.5292-3 days* + 43mins
MVSNeRF [5]17.880.5840.3271-2 days* + 10mins
Mip-NeRF [2]14.620.3510.49514 hrs
DietNeRF [14]14.940.3700.49618 hrs
3DGS [16]13.050.4070.38813 mins
RegNeRF [29]19.080.5870.3364 hrs
VGOS [39]19.350.6200.4325 mins
SparseNeRF [12]19.860.6240.328>2 hrs
Ours19.260.6440.31611 mins
", + "image_path": "e0750cdbe3c92b5f7a2dff00ed4897141cbf1e885f3c070bcb1f7a109898c3e0.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 46, + 388, + 288, + 422 + ], + "lines": [ + { + "bbox": [ + 46, + 388, + 288, + 422 + ], + "spans": [ + { + "bbox": [ + 46, + 388, + 288, + 422 + ], + "type": "text", + "content": "Table 2. Quantitative comparison for 3-views setting on LLFF [20]. The best and the second-best results are highlighted in bold and underlined, respectively. (*) signifies the pre-training time." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 430, + 288, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 430, + 288, + 563 + ], + "spans": [ + { + "bbox": [ + 46, + 430, + 288, + 563 + ], + "type": "text", + "content": "Evaluation Metrics. To assess the effectiveness of our method, we employ several established metrics, including PSNR (Peak Signal-to-Noise Ratio) for assessing image reconstruction accuracy, SSIM (Structural Similarity Index Measure) [43] for evaluating changes in luminance and contrast that affect structural integrity, and LPIPS (Learned Perceptual Image Patch Similarity) [50], which uses deep learning to approximate human visual perception. These metrics provide a comprehensive analysis of our model's performance, covering aspects of accuracy, perceptual quality, and structural fidelity in the reconstructed images." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 570, + 133, + 582 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 570, + 133, + 582 + ], + "spans": [ + { + "bbox": [ + 47, + 570, + 133, + 582 + ], + "type": "text", + "content": "4.2. Comparisons" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 588, + 289, + 720 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 588, + 289, + 720 + ], + "spans": [ + { + "bbox": [ + 46, + 588, + 289, + 720 + ], + "type": "text", + "content": "On the Realistic Synthetic " + }, + { + "bbox": [ + 46, + 588, + 289, + 720 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 46, + 588, + 289, + 720 + ], + "type": "text", + "content": " dataset [24], we compare our method with state-of-the-art approaches, including RegNeRF [29], DietNeRF [14], infoNeRF [17], VGOS [39], PixelNeRF [47], and GeCoNeRF [18], in a 4-view setting. On the LLFF dataset [20], we implement our method in a 3-view setting and compare with SRF [7], MVSNeRF [5], mip-NeRF [2], DietNeRF [14], RegNeRF [29], VGOS [39], SparseNeRF [12] and GeCoNeRF [18]. We adopt the reported results from VGOS [39], sparseNeRF [12], and GeCoNeRF [18]. Besides, we also compare with the advanced reconstruction method 3DGS [16]." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 264, + 547, + 347 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 264, + 547, + 347 + ], + "spans": [ + { + "bbox": [ + 304, + 264, + 547, + 347 + ], + "type": "text", + "content": "Qualitative Experiments. Fig. 3 compares our approach with some recent methods on the Realistic Synthetic " + }, + { + "bbox": [ + 304, + 264, + 547, + 347 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 304, + 264, + 547, + 347 + ], + "type": "text", + "content": " dataset [24]. Diet-NeRF [14] performs poorly in the setting of 4 views, while infoNeRF [17] and VGOS [39] are inferior to our method in terms of both geometric shapes and detail resolution. Our approach demonstrates superior performance in both geometry and details." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 348, + 547, + 419 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 348, + 547, + 419 + ], + "spans": [ + { + "bbox": [ + 304, + 348, + 547, + 419 + ], + "type": "text", + "content": "Fig. 4 shows a qualitative comparison on a scene from the LLFF dataset [20]. While all methods can recover the overall structure of the scene, our approach excels at the quality of details as shown in the magnified regions. Our method incorporates smoothness while retaining fine details, achieving the most natural results." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 426, + 547, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 426, + 547, + 569 + ], + "spans": [ + { + "bbox": [ + 304, + 426, + 547, + 569 + ], + "type": "text", + "content": "Quantitative Experiments. Table 1 shows quantitative results from different methods on the Realistic Synthetic " + }, + { + "bbox": [ + 304, + 426, + 547, + 569 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 304, + 426, + 547, + 569 + ], + "type": "text", + "content": " dataset [24]. In terms of training time, our method is at least an order of magnitude faster than all other methods except for VGOS [39]. Although our method is slightly lower than VGOS [39], it significantly enhances the PSNR, LPIPS [50], and SSIM [43] of the rendered images. Our method achieves state-of-the-art accuracy in PSNR and LPIPS [50]. Additionally, despite not utilizing a pre-trained model or perceptual loss for high-level semantic information extraction, our method still achieves the second-best performance in perceived SSIM [43]." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 569, + 547, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 569, + 547, + 666 + ], + "spans": [ + { + "bbox": [ + 304, + 569, + 547, + 666 + ], + "type": "text", + "content": "Table 2 shows a quantitative comparison on the LLFF dataset [20]. Our method achieves the highest scores in both SSIM [43] and LPIPS [50], indicating that our images exhibit the best performance in terms of human perceptual reconstruction. We also achieve the third-highest PSNR, which, together with our state-of-the-art performance in SSIM [43] and LPIPS [50], demonstrates that our approach has made improvements in certain aspects of image rendering." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 671, + 400, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 671, + 400, + 684 + ], + "spans": [ + { + "bbox": [ + 306, + 671, + 400, + 684 + ], + "type": "text", + "content": "4.3. 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LrsLdsUnrRelPSNR↑SSIM↑LPIPS↓
17.190.7670.223
✓17.790.7800.243
✓✓19.010.8050.228
✓✓✓19.230.8110.220
✓✓✓✓20.720.8480.179
", + "image_path": "9e5c093b14d595fbafd25ff7828689f67bb8f0e190db6e43b48fea999165bec6.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "spans": [ + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": "as the baseline. We incrementally introduce our proposed contributions along with various regularization methods to enhance the model's rendering quality. The groups are delineated as: baseline, baseline " + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "inline_equation", + "content": "+L_{rel}" + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": ", baseline " + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "inline_equation", + "content": "+L_{rel} + L_{unr}" + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": ", baseline " + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "inline_equation", + "content": "+L_{rel} + L_{unr} + L_{ds}" + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": ", and baseline " + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "inline_equation", + "content": "+L_{rel} + L_{unr} + L_{ds} + L_{rs}" + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": ". The ablation results reveal that each incremental contribution positively impacts the rendering quality in various aspects. After the addition of " + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "inline_equation", + "content": "L_{rel}" + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": ", our PSNR increased by 0.6. Subsequent inclusion of " + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "inline_equation", + "content": "L_{unr}" + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": " led to a further rise in PSNR by 1.22. With the incorporation of " + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "inline_equation", + "content": "L_{ds}" + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": ", the PSNR went from 19.01 to 19.23. Finally, after adding " + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "inline_equation", + "content": "L_{rs}" + }, + { + "bbox": [ + 46, + 341, + 289, + 509 + ], + "type": "text", + "content": ", our PSNR peaked at 20.72, SSIM [43] reached 0.848, and LPIPS [50] arrived at 0.179, marking a significant enhancement." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 515, + 288, + 575 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 515, + 288, + 575 + ], + "spans": [ + { + "bbox": [ + 46, + 515, + 288, + 575 + ], + "type": "text", + "content": "Besides, we explore the potential of ReVoRF under the settings where more input views are available. We report extra results for 6-view and 9-view settings in Table 4, demonstrating that increased input views generally enhance performance. ReVoRF maintains superiority across these settings." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "content": "Fig. 5 presents the visualization of our ablation study on the Chair scene. We incorporated " + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "L_{rel}" + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "content": " to enhance the texture quality of the model, which, however, introduced some noise artifacts. To mitigate these artifacts, " + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "L_{unr}" + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "L_{ds}" + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "content": " were subsequently integrated. These adjustments successfully reduced noise but at the cost of blurring the geometric structures in the process. The issue of maintaining geometric consistency while eliminating noise was addressed through the implementation of " + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "inline_equation", + "content": "L_{rs}" + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "content": ". We observe that our method effectively prevents the collapse of new views caused by overfitting due to a limited number of viewpoints." + } + ] + } + ], + "index": 15 + }, + { + "type": "table", + "bbox": [ + 308, + 212, + 545, + 289 + ], + "blocks": [ + { + "bbox": [ + 46, + 278, + 287, + 312 + ], + "lines": [ + { + "bbox": [ + 46, + 278, + 287, + 312 + ], + "spans": [ + { + "bbox": [ + 46, + 278, + 287, + 312 + ], + "type": "text", + "content": "Table 3. Ablation study on the Realistic Synthetic " + }, + { + "bbox": [ + 46, + 278, + 287, + 312 + ], + "type": "inline_equation", + "content": "360^{\\circ}" + }, + { + "bbox": [ + 46, + 278, + 287, + 312 + ], + "type": "text", + "content": " dataset [24] in the 4-view setting. The best and the second-best results are highlighted in bold and underlined, respectively." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 308, + 212, + 545, + 289 + ], + "lines": [ + { + "bbox": [ + 308, + 212, + 545, + 289 + ], + "spans": [ + { + "bbox": [ + 308, + 212, + 545, + 289 + ], + "type": "table", + "html": "
MethodsPSNR↑SSIM↑LPIPS↓
3-view6-view9-view3-view6-view9-view3-view6-view9-view
SRF [7]17.0716.7517.390.4360.4380.4650.5290.5210.503
PixelNeRF [47]16.1717.0318.920.4380.4730.5350.5120.4770.430
MVSNeRF [5]17.8819.9920.470.5840.6600.6950.3270.2640.244
DVGO [37]16.6021.2522.890.5600.7040.7460.4220.2460.228
VGOS [39]19.3521.5522.390.6200.6710.6920.4320.3280.325
Ours19.2622.2123.040.6440.7200.7530.3160.2690.225
", + "image_path": "8d4903dddc1ebb95a3219643f9f7b1a34254ce4283b48d670f51ba1f73f14021.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "table_body" + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 290, + 547, + 323 + ], + "lines": [ + { + "bbox": [ + 306, + 290, + 547, + 323 + ], + "spans": [ + { + "bbox": [ + 306, + 290, + 547, + 323 + ], + "type": "text", + "content": "Table 4. Comparison of 3, 6, and 9 input views on LLFF [20]. The best and the second-best results are highlighted in bold and underlined, respectively." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 306, + 338, + 534, + 352 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 338, + 534, + 352 + ], + "spans": [ + { + "bbox": [ + 306, + 338, + 534, + 352 + ], + "type": "text", + "content": "5. Conclusion, Limitation, and Future Work" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 361, + 547, + 504 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 361, + 547, + 504 + ], + "spans": [ + { + "bbox": [ + 304, + 361, + 547, + 504 + ], + "type": "text", + "content": "In this paper, we address the challenge of view deformation by discerning reliable and unreliable areas, subsequently introducing a bilateral geometric consistency regularization. This approach maximizes the use of reliable regions while delicately exploring the depth in unreliable areas, applying a more lenient constraint to these zones. Further extending our method into voxel space, we transform 2D reliable areas into 3D space through a reliability-aware voxelization smoothing process. Our method, when applied to various datasets, has proven to be highly precise, significantly bolstering geometric consistency and demonstrating its efficacy in intricate 3D reconstruction tasks." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 509, + 547, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 547, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 547, + 628 + ], + "type": "text", + "content": "Our method shares a common limitation of the voxel-based method: the tendency to produce smoothed results, leading to a loss in fine details. Besides, the exceptionally challenging context for NeRF with sparse input also limits its application in more complex scenes, such as large-scale scene reconstruction. For future work, we aim to refine the voxelization technique to better preserve details, potentially exploring hybrid models that combine voxel-based methods with alternative geometric representations for a more detailed reconstruction." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "type": "text", + "content": "Acknowledgement. The work is supported by the Guangdong Natural Science Funds for Distinguished Young Scholar (No. 2023B1515020097), Singapore MOE Tier 1 Funds (MSS23C002), and the NRF Singapore under the AI Singapore Programme (No. AISG3-GV-2023-011)." + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "20349" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 53, + 91, + 288, + 124 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 288, + 124 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 288, + 124 + ], + "type": "text", + "content": "[1] Alexander Amini, Wilko Schwarting, Ava Soleimany, and Daniela Rus. 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IEEE TVCG, 2024. 2" + } + ] + } + ], + "index": 21 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "20351" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_content_list.json b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..7192a07cd0a90c65254f9876f54503cac2efa36e --- /dev/null +++ b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_content_list.json @@ -0,0 +1,1795 @@ +[ + { + "type": "text", + "text": "Learning without Exact Guidance: Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels", + "text_level": 1, + "bbox": [ + 86, + 130, + 883, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Zhuohong $\\mathsf{Li}^{1*}$ , Wei $\\mathsf{He}^{1*}$ , Jiepan $\\mathsf{Li}^1$ , Fangxiao $\\mathsf{Lu}^1$ , Hongyan Zhang $^{1,2\\dagger}$", + "bbox": [ + 196, + 202, + 769, + 220 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1Wuhan University 2China University of Geosciences", + "bbox": [ + 263, + 220, + 705, + 239 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{ashelee, weihe1990, jiepanli, fangxiaolu}@whu.edu.cn, zhanghongyan@cug.edu.cn", + "bbox": [ + 135, + 241, + 823, + 257 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 291, + 313, + 306 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Large-scale high-resolution (HR) land-cover mapping is a vital task to survey the Earth's surface and resolve many challenges facing humanity. However, it is still a nontrivial task hindered by complex ground details, various landforms, and the scarcity of accurate training labels over a wide-span geographic area. In this paper, we propose an efficient, weakly supervised framework (Paraformer) to guide large-scale HR land-cover mapping with easy-access historical land-cover data of low resolution (LR). Specifically, existing land-cover mapping approaches reveal the dominance of CNNs in preserving local ground details but still suffer from insufficient global modeling in various landforms. Therefore, we design a parallel CNN-Transformer feature extractor in Paraformer, consisting of a downsampling-free CNN branch and a Transformer branch, to jointly capture local and global contextual information. Besides, facing the spatial mismatch of training data, a pseudo-label-assisted training (PLAT) module is adopted to reasonably refine LR labels for weakly supervised semantic segmentation of HR images. Experiments on two large-scale datasets demonstrate the superiority of Paraformer over other state-of-the-art methods for automatically updating HR land-cover maps from LR historical labels.", + "bbox": [ + 75, + 323, + 473, + 672 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 704, + 209, + 720 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Land-cover mapping is a semantic segmentation task that gives each pixel of remote-sensing images a land-cover class such as \"cropland\" or \"building\" [14]. The land-cover data should be continuously updated since nature and human activities frequently change the landscape [37]. As sensors and satellites developed, massive high-resolution (HR) remote-sensing images ( $\\leq 1$ meter/pixel) could be easily obtained [1]. Rapid large-scale HR land-cover map", + "bbox": [ + 75, + 729, + 468, + 852 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/0de6bd4d0462bf8c96115bc0b558cb70c0cd3568bbb7d49692fff76d4baf143b.jpg", + "image_caption": [ + "Figure 1. Illustration of resolution mismatched issue in using the HR remote-sensing image (Source) and LR historical labels (Guide) to generate HR land-cover results (Target)." + ], + "image_footnote": [], + "bbox": [ + 503, + 292, + 890, + 523 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "ping is even more critical to facilitate downstream applications as the up-to-date HR land-cover data can accurately describe the land surface [21, 27, 55]. However, the complex ground details reflected by HR images and various landforms over wide-span areas still challenge the periodic updating of large-scale HR land-cover maps [28].", + "bbox": [ + 496, + 580, + 890, + 672 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The advanced methods for HR land-cover mapping have been dominated by the convolutional neural network (CNN) for many years. Although CNN-based models can finely capture local details for semantic segmentation of HR images, the intrinsic locality of convolution operations still limits their implementation in various landforms across larger areas [2]. Recently, Transformer has achieved tremendous success in semantic segmentation [5, 18, 34] and large-scale applications of Earth observation [11, 41, 48]. It adopts multi-head self-attention mechanisms to model global contexts but struggles in the representation of local details due to the shortage of low-level features [10, 48]. Besides, current methods with either CNN or Transformer structures generally rely on sufficient exact training labels by adopting a fully supervised strategy", + "bbox": [ + 496, + 674, + 892, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Indicates equal contribution. †Corresponding author. The code and data are released at https://github.com/LiZhuoHong/Paraformer", + "bbox": [ + 75, + 862, + 468, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "27717", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/22b7d38cf58280c9649a725065a17606c526bac7804888b12ba22f040f85aa84.jpg", + "image_caption": [ + "(a) Existing mode" + ], + "image_footnote": [], + "bbox": [ + 143, + 88, + 398, + 166 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/5b674f92572eb55929905f410c2415fbf85fb93048caf6667e42aac433a6a98d.jpg", + "image_caption": [ + "(b) HR-label-free, end-to-end mode", + "Figure 2. Two modes of large-scale HR land-cover mapping with LR labels. (a) Existing modes either reply on partial HR labels or require non-end-to-end training with human interventions. (b) Paraformer aims to form a mode that is HR-label-free and end-to-end trainable." + ], + "image_footnote": [], + "bbox": [ + 143, + 181, + 398, + 260 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "[20, 32, 39]. However, creating accurate HR land-cover labels for large-scale geographic areas is extremely time-consuming and laborious [6, 37].", + "bbox": [ + 75, + 340, + 468, + 385 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Fortunately, many low-resolution (LR) land-cover data with large coverage have already emerged in the past decades [9, 22, 44, 56]. Utilizing these LR historical land-cover data as alternative guidance is a way to alleviate the scarcity of HR labels [29]. Nevertheless, the unmatched training pairs of HR images and inexact LR labels posed a challenge for fully supervised methods. Moreover, due to the different applied scenarios, existing weakly supervised semantic segmentation methods for natural scenes (e.g., learning from bounding box or image-level labels) are not applicable in handling the challenge as well [15, 23, 24, 57].", + "bbox": [ + 75, + 386, + 468, + 551 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Distinctively, the incorrect samples of LR land-cover labels are brought by satellites in different spatial resolutions during Earth observation. As shown in Figure 1, the objects in a $60m \\times 60m$ area can be clearly observed from the HR (1 m/pixel) image $\\mathbf{X}$ . However, in the LR (30 m/pixel) label $\\mathbf{Y}$ , the area is only labeled by four pixels. To produce the 1-m land-cover result $\\hat{\\mathbf{Y}}$ , a labeled pixel $y_{1}$ needs to provide guiding information for 900 target pixels $\\{\\hat{y}_1, \\hat{y}_2 \\dots \\hat{y}_{900}\\}$ , which raises a serious geospatial mismatch. How to reasonably exploit LR labels as the only guidance for semantic segmentation of large-scale HR satellite images is a particular problem shared in the fields of Earth observation and computer vision [28, 31, 37]. By summarizing the state-of-the-art methods of exploiting LR labels for large-scale HR land-cover mapping, there are still two main problems:", + "bbox": [ + 75, + 551, + 468, + 777 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. For the wide-span application areas, existing feature extractors are difficult to jointly capture local details from HR images and model global contexts in various landforms at once [29, 54].", + "2. For the mismatch of training pairs, existing pipelines, as shown in Figure 2 (a), either still rely on partial HR labels or require non-end-to-end optimization with human interventions [12, 27]." + ], + "bbox": [ + 76, + 780, + 467, + 898 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To resolve these problems, as shown in Figure 2 (b), we propose the Paraformer as an HR-label-free, end-to-end framework to guide large-scale HR land-cover mapping with LR land-cover labels. Specifically, Paraformer parallelly hybrids a downsampling-free CNN branch with a Transformer branch to jointly capture local and global contexts from the large-scale HR images and adopts a pseudolabel-assisted training (PLAT) module to dig up reliable information from LR labels for framework training.", + "bbox": [ + 496, + 90, + 890, + 226 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The main contributions of this study are summarized as follows: (a) We introduce an efficient, weakly supervised Paraformer to facilitate large-scale HR land-cover mapping by getting rid of the well-annotated HR labels and human interventions during framework training; (b) a downsampling-free CNN branch is parallelly hybridized with a Transformer branch to capture features with both high spatial resolution and deep-level representation. The structure aims to globally adapt large-scale, various landforms and locally preserve HR ground details; (c) the PLAT module iteratively intersects primal predictions and LR labels to constantly refine labeled samples for guiding the framework training. It provides a concise way to update large-scale HR land-cover maps from LR historical data.", + "bbox": [ + 496, + 228, + 890, + 439 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 450, + 640, + 467 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Land-cover mapping approach: In the early stage, pixel-to-pixel classification methods, such as decision tree [19], random forest [7], and support vector machine [40], were popular in the land-cover mapping of multi-spectral LR images. However, these methods generally ignore contextual information and have fragmented results in HR cases, as optical HR images contain abundant spatial details but limited spectral features [29]. With the development of data-driven semantic segmentation, many CNN-based models were widely used in land-cover mapping of HR images [37, 52, 53]. Besides, as an alternative architecture, Transformer shows great power in capturing global contexts with sequence-to-sequence modeling [3, 10, 30] and demonstrates outstanding performance in many large-scale applications of Earth observation, such as building extraction [25, 41], road detection [11], and land-object classification [47]. Besides, many works developed new ways by saving labor to produce finer labels with the Segment Anything Model (SAM) [35, 50]. However, sufficient exact training labels are the foundation for large-scale applications of both CNN- and Transformer-based methods. The scarcity of HR labels still impedes these fully supervised approaches from large-scale HR land-cover mapping.", + "bbox": [ + 496, + 477, + 890, + 824 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Land-cover labeled data: Creating large-scale HR labels via manual and semi-manual annotations is extremely time-consuming and expensive [17, 36]. Therefore, exiting HR land-cover data is generally limited to small scales. E.g., the LoveDA dataset contains $0.3\\mathrm{-m}$ land-cover data, covering", + "bbox": [ + 496, + 825, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "27718", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/48ec693be6caeb544f4d9d62e1c0b008de968d41a23628aefdfd3283e6301c6c.jpg", + "image_caption": [ + "Figure 3. Overall workflow of Paraformer. The framework only takes the HR images and LR labels as training input and includes three components: (a) CNN-based resolution-preserving branch, (b) Transformer-based global-modeling branch, and (c) Pseudo-Label-Assisted Training (PLAT) module." + ], + "image_footnote": [], + "bbox": [ + 178, + 88, + 795, + 378 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "536.15 $km^2$ of China [46]. The Agri-vision dataset contained 0.1-m labeled data, covering $560~km^2$ of the USA [13]. In the contract, the LR land-cover data generally has a larger coverage. E.g., the United States Geological Survey cyclically updates 30-m land-cover data covering the whole USA [49]. The European Space Agency (ESA) has updated an annual 10-m global land-cover data since 2020 [44]. These LR data can be seen as an alternative label source for guiding large-scale HR land-cover mapping. However, massive in exactly labeled samples still hinder them from being practicable.", + "bbox": [ + 75, + 424, + 472, + 590 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Strategies for LR historical label mining: To alleviate the scarcity of accurate labels in large-scale HR land-cover mapping, many studies have made efforts to mine reliable information from LR labels. E.g., a label super-resolution network was designed to constrain the inexact parts of LR labels by using the statistical distribution inferred from HR labels [31, 37]. A multi-stage framework, named WESUP, was built for $10\\mathrm{-m}$ land-cover mapping with $30\\mathrm{-m}$ labels [12]. In WESUP, multi-models were trained to refine clean samples from LR labels. Similarly, the winner approach of the 2021 IEEE GRSS Data Fusion Contest (DFC) deployed a shallow CNN to refine the $30\\mathrm{-m}$ labels, and then multi-model were trained with pseudo-labels to create the $1\\mathrm{-m}$ land-cover map of Maryland, USA [27]. Moreover, a low-to-high network (L2HNet) was proposed to select confident parts of LR labels via weakly supervised loss functions [28]. To produce $1\\mathrm{-m}$ land-cover maps across China with available $10\\mathrm{-m}$ labels, seven L2HNets were selectively trained to adapt wide-span geographic areas [29].", + "bbox": [ + 75, + 590, + 472, + 878 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Different from these approaches that either still rely on", + "bbox": [ + 96, + 885, + 470, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "partial HR labels or require human interventions, Pafaromer is designed as an HR-label-free end-to-end framework to facilitate large-scale HR land-cover mapping.", + "bbox": [ + 498, + 425, + 893, + 472 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Methodology", + "text_level": 1, + "bbox": [ + 500, + 481, + 635, + 500 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To jointly capture local and global contexts and reasonably exploit LR labels for large-scale HR land-cover mapping, Paraformer combines parallel CNN and Transformer branches with a PLAT module. In this section, the three components are introduced sequentially.", + "bbox": [ + 498, + 507, + 892, + 583 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. CNN-based resolution-preserving branch", + "text_level": 1, + "bbox": [ + 498, + 590, + 852, + 606 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As a basic feature extractor of Paraformer and also the main structure of previous L2HNet V1 [28], the CNN branch is designed to capture local contexts from HR images and preserve the spatial details by preventing feature downsampling. As shown in Figure 3 (a), the CNN branch is constructed by five serially connected resolution-preserving (RP) blocks. Each RP block contains parallel convolution layers with the sizes of $1 \\times 1$ , $3 \\times 3$ , and $5 \\times 5$ , whose steps are set to 1 for feature size maintaining. Partly similar to the inception module [42], the channel numbers of different scales' layers in each block are inversely proportional to their kernel sizes, which are set to 128, 64, and 32. Based on the setting, the RP blocks can capture features with a proper receptive field instead of downsampling the feature maps with a deep encoder-decoder pattern. The serial blocks aim at sufficiently preserving the spatial resolution of features by using the majority of $1 \\times 1$ kernels. The $3 \\times 3$ and $5 \\times 5$ kernels capture necessary surrounding information. Furthermore, the multi-scale feature maps are", + "bbox": [ + 496, + 613, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "27719", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/9075bbdad61d2a8a8a84992ed0af9912a38b871ab6fc414d2bb8c17a63241004.jpg", + "image_caption": [ + "Figure 4. Example of the local mismatch/match in two regions. The edge of water is marked with yellow boundaries. Region 1 shows dispersed lakes around urban areas with unmatched annotation. Region 2 shows a large-scale river with matched annotation." + ], + "image_footnote": [], + "bbox": [ + 80, + 90, + 467, + 349 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "concatenated and reduced to 128 channels for branch lightening. Besides, a shortcut connection is adopted between blocks for residual learning and detail preserving.", + "bbox": [ + 76, + 412, + 468, + 459 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Transformer-based global-modeling branch", + "text_level": 1, + "bbox": [ + 76, + 467, + 447, + 484 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The ground objects with the same land-cover class may have distinctive attributes in HR images and are differently annotated in LR labels. Figure 4 shows typical cases of lakes and rivers located in different areas. By considering that the CNN branch with intrinsic locality hinders the adaptation of various landforms over large-scale areas, we further hybrid the CNN branch with a Transformer branch which aims at capturing global contexts and building long-range support among dispersed geographic areas. As shown in Figure 3 (b), the Transformer branch contains 12 transformer layers. Each layer includes layer normalization, multi-head self-attention, and multi-layer perception. The feature maps extracted by each RP block are concatenated and inputted to the Transformer branch. Specifically, the extracted features from the CNN branch are downsampled and embedded in a hidden feature layer. And then the Transformer branch encodes the dense feature patches to capture global contexts. Subsequently, the encoded features are constantly upsampled to the size of HR images and classified to the final results. During the upsampling process, the outputted features of each stage are concatenated with the pre-encoded features, which bring massive local contextual information to the final feature maps.", + "bbox": [ + 76, + 491, + 468, + 838 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.3. Pseudo-Label-Assisted Training module", + "text_level": 1, + "bbox": [ + 76, + 847, + 419, + 864 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To reasonably guide the large-scale HR land-cover mapping with weak LR labels, as shown in Figure 3 (c), a weakly", + "bbox": [ + 76, + 869, + 468, + 902 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "supervised PLAT module is adopted to optimize the framework training. The PLAT module aims to screen out uncertain samples and dig up reliable information from the LR labels. Specifically, the two parts of the PLAT module are explained as follows. For the CNN branch, we use classifier $^{(1)}$ , which is constructed by $3 \\times 3$ convolution layers, to generate the primal prediction $^{(1)}$ based on the extracted HR feature maps. Then we calculate the Cross-Entropy (CE) loss between prediction $^{(1)}$ , represented as $\\hat{\\mathbf{Y}}'$ , and the LR label, represented as $\\mathbf{Y}$ . Formally, by regarding $H$ , $W$ , and $L$ as the height, weight, and land-cover class of the patch, the CE loss of the CNN branch is written as:", + "bbox": [ + 496, + 90, + 893, + 272 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {c e}} (\\mathbf {Y}, \\hat {\\mathbf {Y}} ^ {\\prime}) = \\frac {\\sum_ {i = 0} ^ {W} \\sum_ {j = 0} ^ {H} \\left[ \\sum_ {l = 1} ^ {L} y _ {i j} ^ {(l)} \\log \\left(\\hat {y} _ {i j} ^ {\\prime (l)}\\right) \\right]}{H \\times W}. \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 535, + 282, + 890, + 319 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "As the final output of the framework, prediction $^{(2)}$ is classified from the concatenated feature maps of CNN and Transformer branches, which is represented as $\\hat{\\mathbf{Y}}''$ . During each training iteration, we take the simple but effective intersection of prediction $^{(1)}$ and LR label to generate mask labels. Specifically, the inconsistent samples in mask labels are set as void values to remove them from loss calculations. Moreover, since predictions of the CNN branch contain HR textual information that is highly consistent with the images, the mask labels also outline fine edges and retain stable labeled samples. Finally, the proposed Mask-Cross-Entropy (MCE) loss is calculated between prediction $^{(2)}$ and mask labels. Formally, the MCE loss is written as:", + "bbox": [ + 496, + 330, + 893, + 527 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {m c e}} (\\mathbf {M} \\cdot \\mathbf {Y}, \\hat {\\mathbf {Y}} ^ {\\prime \\prime}) = \\frac {\\sum_ {i = 0} ^ {W} \\sum_ {j = 0} ^ {H} \\left[ \\sum_ {l = 1} ^ {L} y _ {i j} ^ {(l)} m _ {i j} \\log \\left(\\hat {y} _ {i j} ^ {\\prime \\prime (l)}\\right) \\right]}{\\operatorname {S u m} (\\mathbf {M} (i , j) = 1)}. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 501, + 537, + 890, + 585 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In Eqs. 2, $\\mathbf{M}$ is the intersected mask with the size of $H\\times W$ . $m_{ij},i\\in [0,H],j\\in [0,W]$ is the element of $\\mathbf{M}(i,j)$ which can be simply represented as:", + "bbox": [ + 500, + 587, + 890, + 633 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nm _ {i j} = \\left\\{ \\begin{array}{l l} 1 | Y _ {i j} = Y ^ {\\prime} _ {i j} \\\\ 0 | Y _ {i j} \\neq Y ^ {\\prime} _ {i j}. \\end{array} \\right. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 612, + 642, + 890, + 672 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The total loss of the Paraformer is the combination of two branches' losses, which is written as:", + "bbox": [ + 498, + 681, + 890, + 712 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {t o t a l}} = \\mathcal {L} _ {\\mathrm {c e}} + \\mathcal {L} _ {\\mathrm {m c e}}. \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 625, + 724, + 890, + 739 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 752, + 633, + 768 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Study areas and using data", + "text_level": 1, + "bbox": [ + 500, + 777, + 743, + 792 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To comprehensively evaluate Paraformer on various landforms and different LR labels, the experiments are conducted on two large-scale datasets.", + "bbox": [ + 496, + 795, + 890, + 839 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The Chesapeake Bay dataset is sampled from the largest estuary in the USA and organized into 732 non-overlapping tiles, where each tile has a size of $6000 \\times 7500$ pixels [37]. The specific data includes:", + "bbox": [ + 496, + 839, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "27720", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/9f7b34ba42c0f1eab6ff067cfeb0cda7dec1b4b5aef068c6a144667954f297f3.jpg", + "image_caption": [ + "(a) Source (1m/pixel)" + ], + "image_footnote": [], + "bbox": [ + 84, + 88, + 282, + 202 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/d4b09fc44a89b6b9d5ffa92810ae83319ab934c96470f795a437391741f13549.jpg", + "image_caption": [ + "(b) Guide (30/pixel)" + ], + "image_footnote": [], + "bbox": [ + 282, + 88, + 480, + 202 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/2100d1bb5f8b8a7106d283d685b7418555e909d5e1cddf20e96058b830d35a87.jpg", + "image_caption": [ + "(c) Paraformer (ours)" + ], + "image_footnote": [], + "bbox": [ + 480, + 88, + 679, + 202 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/09b97ba7f3e2b028105d0dc3bcac08d20111ea385dda9f0bd5865f5757ff2890.jpg", + "image_caption": [ + "(d) L2HNet" + ], + "image_footnote": [], + "bbox": [ + 681, + 88, + 880, + 202 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/cedf9421240131565fc077ceb567cf01ffd60d9c5ac4b471a715887088fff120.jpg", + "image_caption": [ + "(e) RF" + ], + "image_footnote": [], + "bbox": [ + 84, + 214, + 282, + 328 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/36eb09911538b2f97bfe6e2501f3e64e4dc5e05d16b8b57964aa945a275c2260.jpg", + "image_caption": [ + "(f) UNet" + ], + "image_footnote": [], + "bbox": [ + 282, + 214, + 480, + 327 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/071302de548a4fc231a2c8d94a72beb1cfdab1743633c5817db0f470f198f4fe.jpg", + "image_caption": [ + "(g) HRNet" + ], + "image_footnote": [], + "bbox": [ + 480, + 214, + 679, + 327 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/5ce9bec037b40ba72f7deb74d5dcd486b97f11eb1a586671b969b86b3ad04610.jpg", + "image_caption": [ + "(h) TransUNet" + ], + "image_footnote": [], + "bbox": [ + 681, + 214, + 880, + 327 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/ee0e18ff0408b04290fc8ac3a55bb262b8060960e792cdc0d72fe93635d2132d.jpg", + "image_caption": [ + "Figure 5. Demonstration of the training data and visual comparisons of the Paraformer and other typical methods on the Chesapeake Bay dataset with 16 classes. (a) HR image. (b) LR label. (c) land-cover mapping result of Paraformer. (d-h) land-cover mapping results of five typical methods." + ], + "image_footnote": [], + "bbox": [ + 169, + 344, + 784, + 366 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/8c77fd3ad40212a2cce100e7e5b740aeb468749545ed4f2858ff79d82b3aff0f.jpg", + "image_caption": [ + "(a)", + "(b)", + "(c)", + "(d)", + "(e)", + "Figure 6. Six typical areas with finer observation scale on the Chesapeake Bay dataset. The first row shows the LR labels (Guide). The second row shows the HR images (Source). Third row shows the HR results (Target) produced by Paraformer." + ], + "image_footnote": [], + "bbox": [ + 93, + 400, + 883, + 640 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1. The HR images (1 m/pixel) are from the U.S. Department of Agriculture's National Agriculture Imagery Program (NAIP). The images contained four bands of red, green, blue, and near-infrared [33].", + "2. The LR historical labels (30 m/pixel) are from the USGS's National Land Cover Database (NLCD) [49], including 16 land-cover classes.", + "3. The ground truths (1 m/pixel) are from the Chesapeake Bay Conservancy Land Cover (CCLC) project." + ], + "bbox": [ + 76, + 689, + 468, + 824 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The Poland dataset contains 14 provinces of Poland and is organized into 403 non-overlapping tiles, where each tile has a size of $1024 \\times 1024$ pixels. The specific data includes:", + "bbox": [ + 75, + 832, + 468, + 877 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "1. The HR images (0.25m and 0.5 m/pixel) are from the", + "bbox": [ + 76, + 885, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "LandCover.ai [4] dataset. The images contained three bands of red, green, and blue.", + "bbox": [ + 517, + 689, + 890, + 718 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "2. The LR historical labels are collected from three types of 10-m land-cover data and one type of 30-m data, which are named FROM_GLC10 [9], ESA_GLC10 [44], ESRI_GLC10 [22], and GLC_FCS30 [56].", + "3. The HR ground truths are from the OpenEarthMap [51] dataset with seven land-cover classes." + ], + "bbox": [ + 500, + 719, + 890, + 808 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Implementation Detail and Metrics", + "text_level": 1, + "bbox": [ + 500, + 821, + 805, + 837 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In the experiments, all methods only take LR land-cover data as training labels. Paraformer is trained by the AdamW optimizer with a patch size of $224 \\times 224$ and batch size of 8. The learning rate is set to 0.01 and would decrease by $10\\%$", + "bbox": [ + 496, + 840, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "27721", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/496d5c6b98744a6fdfc289855ce20ce59ed6321b5fb12786d819c4f228c32aff.jpg", + "image_caption": [ + "Large-scale region" + ], + "image_footnote": [], + "bbox": [ + 83, + 89, + 225, + 310 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/2d7551d405046a87f8c3de9a3d3df96829d71066def350284c613c11271b5226.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 225, + 92, + 352, + 212 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/6195077f55556a80e4211fdfe7e308d9a4bd0a428f455dba11949090270dc621.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 228, + 215, + 354, + 321 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/5669d3f207888ef1800b5e197d088c9965851c3c126fbff5062c8010a9ffa6ed.jpg", + "image_caption": [ + "(b) LR label 1" + ], + "image_footnote": [], + "bbox": [ + 362, + 90, + 485, + 199 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/cebcffa540743dc37f6207e1ab6a16a2b9d343b1bf6f00044c4b6bc2abefed2f.jpg", + "image_caption": [ + "(c) LR label 2" + ], + "image_footnote": [], + "bbox": [ + 493, + 92, + 616, + 199 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/76e816b7c2d4af44d48b49e2d719708774fc768267087e4c53c0e41447de496b.jpg", + "image_caption": [ + "(d) LR label 3" + ], + "image_footnote": [], + "bbox": [ + 625, + 92, + 746, + 199 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/91b3f0249601862c2c1d65b5949b1bfe755efa10db9912ec6c8e03f9ad055678.jpg", + "image_caption": [ + "(e) LR label 4" + ], + "image_footnote": [], + "bbox": [ + 754, + 92, + 879, + 199 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/30d663c663bcdc848217fc11e04f7642c408818012254253d7484f50670712ad.jpg", + "image_caption": [ + "(g) Result 1" + ], + "image_footnote": [], + "bbox": [ + 361, + 215, + 485, + 310 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e64e18311db668eaa625c21846bc687d73f83fd56d4ea261c7a6c0f8acb09774.jpg", + "image_caption": [ + "(h) Result 2" + ], + "image_footnote": [], + "bbox": [ + 491, + 215, + 616, + 310 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/0e54219dfb7281e0fea51a1d3541a22cc56b513efdf0913707c3721bf602c695.jpg", + "image_caption": [ + "(i) Result 3" + ], + "image_footnote": [], + "bbox": [ + 622, + 215, + 746, + 310 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/15400ac7f7597c95ab38386d66f2a4900e88319952a4b92b4a459d2a7866fd45.jpg", + "image_caption": [ + "(j) Result 4" + ], + "image_footnote": [], + "bbox": [ + 754, + 215, + 879, + 311 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/f4bd38a9c47c25e3dde113cbaa0933c085cfc0d14f9cd6848c5a345a51642873.jpg", + "image_caption": [ + "Figure 7. Visual results of Paraformer in the Poland dataset. The demonstration area is one of the training pieces sampled from large-scale training regions. (a-e) the training pairs of HR images (0.5 m/pixel) and four types of LR labels including ESA_GLC (10 m/pixel), FROM_GLc (10 m/pixel), Esri_GLC (10 m/pixel), and GLC_FCS30 (30 m/pixel). (f-g) the ground truth (0.5 m/pixel) and the mapping results of Paraformer with different LR labels." + ], + "image_footnote": [], + "bbox": [ + 367, + 325, + 421, + 335 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/8166721f6f53b0f2b30dae99cbc598957d009f151739a333bd94ecfe8dca20e8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 468, + 325, + 540, + 335 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/1097eb77b778eed086425aafc61db41551789087a3715c07bd4730ce8bcfc9ea.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 575, + 325, + 656, + 335 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/2ef9e140fd12f1016353dce25bb99b7ed1ee17d69f4e905d830af7d3bb7ce408.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 325, + 741, + 335 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/608253bff3c977c2bcfb0eeb0e503b089e5078da12cde0a79866e964b10a9514.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Resolution gapMethodmIoU (%) of six states in the Chesapeake Bay watershed
DelawareNew YorkMarylandPennsylvaniaVirginiaWest VirginiaAverage
30×Paraformer65.5771.4370.2060.0468.0152.6264.65
L2HNet [28]61.7768.1265.2458.5269.3955.4363.08
TransUNet [10]53.1560.5360.4251.0866.2147.5256.49
ConViT [18]55.2660.7161.5853.9459.8049.1156.73
CoAtNet [16]56.8962.8361.2553.5765.6751.3458.59
MobileViT[34]58.0361.3261.8455.5357.0448.6457.07
EfficientViT[5]53.7261.2859.4851.3857.3448.7655.33
UNetFormer[48]58.8565.1161.3459.1060.8447.2058.74
DC-Swin[47]59.6565.9958.6058.0664.1148.1559.09
UNet [38]54.1658.7956.4253.2157.3446.1154.34
HRNet [45]52.1156.2150.7650.0357.4845.4252.00
LinkNet [8]58.2762.0552.9652.1148.7148.9353.84
SkipFCN [26]60.9764.8359.4455.3764.7254.6660.00
SSDA [43]57.9161.5454.8551.7157.7147.1555.15
RF [7]59.3555.0355.2651.0752.2954.3654.56
", + "bbox": [ + 119, + 388, + 846, + 595 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/d5b800961327a447ff85b96c2927bdae920a9442de93712399ba5dc5f1a549a0.jpg", + "table_caption": [ + "Table 1. The quantitative comparison of the Paraformer and other methods on six states of the Chesapeake Bay watershed. All methods were trained with the 1-m images and 30-m labels. The mIoU (\\%) of different methods was calculated between their results and the 1-m ground truth." + ], + "table_footnote": [], + "table_body": "
Max gapLR labelParaformer (ours)mIoU (%) of different methods
L2HNet [28]TransUNet [10]ConViT [18]MobileViT [34]DC-Swin [47]HRNet [45]SkipFCN [26]RF [7]
40×FROM_GLC10 [9]56.5750.1538.4439.3641.0343.5643.6627.1421.48
ESA_GLC10 [44]55.1952.1335.5836.0938.4240.0549.8128.3426.97
Esri_GLC10 [22]55.0750.7837.7938.7838.5039.9146.6528.1819.36
120×GLC_FCS30 [56]49.3943.6226.2029.1629.5730.1441.4623.6717.02
", + "bbox": [ + 86, + 637, + 879, + 724 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. The quantitative comparison on the Poland dataset. The mIoU (%) of the Paraformer and other methods that trained with three types of 10-m labels (i.e., FROM_GLCL10, ESA_GLCL10, and Esri_GLCL10) and one type of 30-m label (i.e., GLC_FCS30) are demonstrated.", + "bbox": [ + 75, + 727, + 892, + 751 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "when the loss stopped dropping over eight epochs. The metric of mean intersection over union (mIoU) is calculated between the results and the HR ground truths after their land-cover classes are unified into four base classes. The compared methods include: Random Forest (RF) is a pixel-to-pixel method widely used in large-scale land-cover mapping [7]. TransUNet [10], ConViT [18], CoAtNet [16], MobileViT [34], and EfficientViT [5] are CNN-Transformer hy", + "bbox": [ + 75, + 768, + 468, + 888 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "brid methods for semantic segmentation. UNetformer [48] and DC-Swin [47] are dedicated CNN-Transformer methods for remote-sensing images. UNet [38], HRNet [45], and LinkNet [8] are typical CNN-based semantic segmentation methods which are widely adopted in HR land-cover mapping [37, 52, 53]. SkipFCN [26] and SSDA [43] are shallow CNN-based methods for updating 1-m land-cover change maps from 30-m labels, which won first and second place", + "bbox": [ + 496, + 768, + 890, + 888 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "27722", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e71ae878de8f982c02a4e64ad6f521f886cc3d12a9ff8bfa4cef24f7f12c6fcd.jpg", + "image_caption": [ + "(a) Source (1m/pixel)" + ], + "image_footnote": [], + "bbox": [ + 117, + 88, + 300, + 205 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/98533551fb2817b555fa7eb67d2dc5f04ffccfaffb2ea4ec411b12a7dbff731c.jpg", + "image_caption": [ + "(b) Guide (30m/pixel)" + ], + "image_footnote": [], + "bbox": [ + 300, + 88, + 480, + 205 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a90e67ac8735c6b14ada1bd3191f323d6465a3e41ff2ba6b454049e8393ea001.jpg", + "image_caption": [ + "(c) Prediction(1) from the CNN branch" + ], + "image_footnote": [], + "bbox": [ + 482, + 88, + 663, + 205 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/3b97701294340fc345022557b737b3083317658a81175f5819eb8a1cc8530230.jpg", + "image_caption": [ + "(d) Mask label" + ], + "image_footnote": [], + "bbox": [ + 666, + 88, + 846, + 205 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/77ef88ccd697fbbd77fb4f4da23f08a15aa0409bcca2d47a4c5d54163e93a473.jpg", + "image_caption": [ + "(e) Mismatch of LR label" + ], + "image_footnote": [], + "bbox": [ + 117, + 217, + 299, + 334 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/caff7e7774357df18f7a202fadd16d6f0713bae3c2d26ff8989755151aa8f21e.jpg", + "image_caption": [ + "(f) Mismatch of mask label", + "Tree canopy" + ], + "image_footnote": [], + "bbox": [ + 300, + 217, + 480, + 334 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ab8fc4735b6a364f1c56d774b234984f318d21b790206ff956061fe74e34511f.jpg", + "image_caption": [ + "(g) Paraformer", + "Water" + ], + "image_footnote": [], + "bbox": [ + 483, + 217, + 663, + 334 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/3816d83d922694a41c1ca5f0d127943c90a36ebaabb63e4d41eae74f92a496de.jpg", + "image_caption": [ + "(h) GT (1m/pixel)" + ], + "image_footnote": [], + "bbox": [ + 666, + 217, + 846, + 334 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1d523fb9ffd99e9805d82dbb32abe3d3c4b9b3d31aef8f428362eff2670556e2.jpg", + "image_caption": [ + "Figure 8. Example of training data and different outputs of Paraformer sampled from the Chesapeake Bay dataset with four unified classes. (a) HR images. (b) LR labels. (c) the primal prediction from the CNN branch. (d) Mask label, as the intersection parts of (b) and (c). The black areas are set to void without supervised information. (e–f) the incorrect samples (with pink color) of LR label and mask label. (g) the final results of Paraformer. (h) HR ground truth." + ], + "image_footnote": [], + "bbox": [ + 267, + 348, + 326, + 361 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5ac1967144410ced333559ef866f388383e7cc085388c1a56f5c677b75a129a3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 496, + 348, + 589, + 359 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "in the 2021 IEEE GRSS DFC [27]. L2HNet is a state-of-the-art method designed for weakly supervised land-cover mapping [28].", + "bbox": [ + 75, + 424, + 468, + 470 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.3. Comparison Results", + "text_level": 1, + "bbox": [ + 76, + 488, + 267, + 503 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparison on the Chesapeake Bay dataset: Table 1 and Figure 5 show the comparisons on the Chesapeake Bay dataset. From the quantitative results, Paraformer shows superiority in the states of Delaware, New York, Maryland, and Pennsylvania. The L2HNet shows better results in Virginia and West Virginia. On average, Paraformer has the most accurate HR land-cover mapping results over the entire area, with a mIoU of $64.65\\%$ . As shown in Figure 5 (c), the visual result of Paraformer is more consistent with the HR image compared with other methods. Unlike the fully supervised semantic segmentation task, the unmatched training pairs can cause serious misguidedness during the model training. E.g., as the rough results shown in Figure 5 (f) and (g), UNet and HRNet over-downsample the features and encourage results to fit LR labels instead of being consistent with the HR images. Furthermore, quantitative results reveal that UNet, LinkNet, and HRNet have insufficient performance, with mIoU of $54.34\\%$ , $53.84\\%$ , and $52.00\\%$ . Although the compared CNN-Transformer methods (e.g., TransUNet) combine local and global contextual information, the structure does not focus on preserving the feature resolution or dealing with the geospatial mismatch. As a result, TransUNet shows a weak performance in visual results, shown in Figure 5 (h), and has a mIoU of $56.49\\%$ . Furthermore, SkipFCN, SSDA, and RF use small receptive fields or pixel-to-pixel strategies to ex", + "bbox": [ + 75, + 507, + 472, + 901 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "tract features with fine land details. However, due to the lack of deep-level feature representation and global contextual information, SkipFCN, SSDA, and RF obtain a mIoU of $59.99\\%$ , $55.15\\%$ , and $54.56\\%$ , respectively. As an example shown in Figure 5 (e), RF finely predicts ground details but incorrectly classifies rivers, lakes, and pastures. To further demonstrate the effect of Paraformer on different landscapes, we sample six typical areas in Figure 6. The visual results indicate that the complex ground details among various landforms of HR land-cover maps can be well updated from the LR historical land-cover labels.", + "bbox": [ + 496, + 424, + 890, + 590 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparison on the Poland dataset: In the experiments with the Poland dataset, all methods were used to produce $0.25 / 0.5$ -m land-cover maps of 14 provinces of Poland by exploiting four LR labels separately. These LR labels include 10-m FROM_GLC10, ESA_GLC10, Esri_GLC10, and 30-m GLC_FCS30. As shown in Table 2, Paraformer is compared with eight representative methods (i.e., weakly supervised, CNN-Transformer, CNN-based, pixel-to-pixel approaches) in a more extreme geospatial mismatch. Compared with the state-of-the-art method, the Paraformer has an increase in mIoU of $6.42\\%$ , $3.06\\%$ , and $4.29\\%$ in exploiting 10-m labels. By resolving 30-m labels with a max resolution gap of $120\\times$ , Paraformer has a mIoU of $49.39\\%$ with an increase of $5.77\\%$ compared with L2HNet. The typical CNN-based method has an average mIoU of $46.71\\%$ among the 10-m cases and $41.46\\%$ in the 30-m case. Skip_FCN and RF have the lowest mIoU among all methods, which shows the difficulty of dealing with extremely unmatched situations. Moreover, the quantitative results of Paraformer shown in the four cases reveal that the proposed frame", + "bbox": [ + 496, + 597, + 892, + 898 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "27723", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/d016777d72856b078e8a12fc3be12d96e8121922e946a8cde2e31bb12afb85f7.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Ablation methodmIoU (%) of six states in the Chesapeake Bay watershed
DelawareNew YourMarylandPennsylvaniaVirginiaWest VirginiaAverageParamsFLOPs
Paraformer65.5771.4370.2060.0468.0152.6264.65109.4M141.3G
Sole CNN branch59.5767.8764.3053.8665.2650.0160.154.5M56.1G
Sole Transformer branch53.1560.5360.4251.0866.2247.5256.4996.9M83.3G
Hybrid without PLAT62.6970.3967.1558.3367.4750.8362.81109.4M141.3G
", + "bbox": [ + 88, + 88, + 879, + 164 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. The ablation results of the Paraformer on six states of the Chesapeake Bay watershed. The sole CNN branch, sole Transformer branch, and Hybrid without PLAT aim to investigate the contribution of the CNN branch, Transformer branch, and PLAT module, respectively.", + "bbox": [ + 76, + 170, + 893, + 196 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/df9f523b4eaf4ba6ba45a81dd5813642b9d3cace6224107d2dd5f5eaf1840b44.jpg", + "image_caption": [ + "(a) 1-m image" + ], + "image_footnote": [], + "bbox": [ + 80, + 210, + 274, + 305 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/bd0e7630b9ff14e9c5103b41cfacb4a934ebfd3a407008303812bf21258d8c13.jpg", + "image_caption": [ + "(b) CNN-branch context" + ], + "image_footnote": [], + "bbox": [ + 274, + 209, + 467, + 304 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e9827db31527091a470156b00054916d6007b23ac1ff94b1e4bd8828187c48bc.jpg", + "image_caption": [ + "(c) Transformer-branch context", + "Figure 9. Demonstration of the extracted contexts from the ablation methods. (a) the original HR image. (b) the contexts extracted by the sole CNN branch. (c) the contexts extracted by the sole Transformer branch. (d) the contexts extracted by the CNN-Transformer hybrid backbone." + ], + "image_footnote": [], + "bbox": [ + 78, + 315, + 272, + 409 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/daa5eb2d357136b5303c7a7f7783d901b98100f4eea0282112326779e440279c.jpg", + "image_caption": [ + "(d) Hybrid-structure context" + ], + "image_footnote": [], + "bbox": [ + 274, + 315, + 468, + 409 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "work obtains stable results from different LR labels. Figure 7 shows the visual results of Paraformer among four cases. With the parallel CNN-Transformer structure and PLAT module, Paraformer is able to refine the clear ground details (e.g., vegetation and roads) even if they are roughly labeled in local areas. In general, Paraformer shows the potential to robustly update large-scale HR land-cover maps from available LR historical labels.", + "bbox": [ + 75, + 496, + 468, + 617 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.4. Ablation experiments", + "text_level": 1, + "bbox": [ + 76, + 619, + 279, + 636 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this section, ablation experiments were conducted on the Chesapeake Bay dataset to evaluate different components of Paraformer. Each ablation in Table 3 is explained as follows: (1) the sole CNN branch is dependently trained by calculating CE loss with LR labels; (2) the sole Transformer branch embeds HR images instead of features from the CNN branch and calculates CE loss with LR labels; (3) the hybrid structure without PLAT directly calculates CE loss with the LR labels.", + "bbox": [ + 75, + 643, + 468, + 777 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "By ablating the PLAT module, the results obtained an average mIoU of $62.81\\%$ , which indicates a $1.84\\%$ decrease compared with the $64.65\\%$ of Paraformer. By ablating the CNN and Transformer branches, the results of the sole CNN branch obtained a mIoU of $60.15\\%$ and had a $4.5\\%$ decrease. Results of the sole Transformer branch obtained the lowest mIoU of $56.49\\%$ and had the most obvious decrease $(8.16\\%)$ . Figure 8 shows different outputs of Paraformer,", + "bbox": [ + 75, + 780, + 470, + 901 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "where the inexact LR labels are gradually refined during framework training. The final result shown in Figure 8 (g) indicates both fine ground details and accurate land-cover patterns that are consistent with the ground truth. Moreover, Figure 9 shows the visualized contexts captured by the CNN branch, Transformer branch, and hybrid structure. Figure 9 (b) indicates that the CNN branch mostly focuses on capturing local details (e.g., the edges of roads, single houses, and shrubs). Figure 9 (c) indicates that the Transformer branch captures the feature in object scale, focusing on intact land objects of building areas and parking spots. The hybrid structure shows a strong response to the obvious objects with both fine edges and intact areas.", + "bbox": [ + 496, + 212, + 890, + 407 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In general, the ablation results demonstrate two findings: (1) The PLAT module can stably optimize the framework training and reasonably exploit the LR labels during the large-scale HR land-cover mapping process. (2) The parallel CNN and Transformer branches are indispensable parts of the framework, which construct a more robust feature extractor to bridge local and global contextual information.", + "bbox": [ + 496, + 409, + 890, + 513 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 498, + 530, + 619, + 545 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, a weakly supervised CNN-Transformer framework, Paraformer, is proposed to update large-scale HR land-cover maps in an HR-label-free, end-to-end manner. Experiments on two datasets show that Paraformer outperforms other approaches in guiding semantic segmentation of large-scale HR remote-sensing images with easy-access LR land-cover data. Further analysis reveals that the Paraformer can robustly adapt various landforms of wide-span areas and stably exploit different LR labels in producing accurate HR land-cover maps. The ablation studies demonstrate the effectiveness of the parallel CNN-Transformer structure and the PLAT module. Moreover, intermediate results of each training process and visualized contexts of each branch are demonstrated to transparently explain the components of Paraformer. In general, the proposed Paraformer has the potential to become an effective method for facilitating large-scale HR land-cover mapping.", + "bbox": [ + 496, + 549, + 890, + 806 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments", + "text_level": 1, + "bbox": [ + 500, + 816, + 658, + 834 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work has been supported by the National Key Research and Development Program of China (grant no. 2022YFB3903605) and the National Natural Science Foundation of China (grant no.42071322).", + "bbox": [ + 496, + 839, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "27724", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Land-cover classification with high-resolution remote sensing images using transferable deep models. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 4299-4309, 2022. 2" + ], + "bbox": [ + 78, + 90, + 470, + 852 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "27727", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_model.json b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_model.json new file mode 100644 index 0000000000000000000000000000000000000000..414d6431d7792ca9a4cbc8bab3d47b6fe06053e9 --- /dev/null +++ b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_model.json @@ -0,0 +1,2785 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.087, + 0.131, + 0.885, + 0.177 + ], + "angle": 0, + "content": "Learning without Exact Guidance: Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels" + }, + { + "type": "text", + "bbox": [ + 0.197, + 0.203, + 0.77, + 0.222 + ], + "angle": 0, + "content": "Zhuohong \\(\\mathsf{Li}^{1*}\\), Wei \\(\\mathsf{He}^{1*}\\), Jiepan \\(\\mathsf{Li}^1\\), Fangxiao \\(\\mathsf{Lu}^1\\), Hongyan Zhang\\(^{1,2\\dagger}\\)" + }, + { + "type": "text", + "bbox": [ + 0.264, + 0.222, + 0.706, + 0.24 + ], + "angle": 0, + "content": "1Wuhan University 2China University of Geosciences" + }, + { + "type": "text", + "bbox": [ + 0.136, + 0.242, + 0.825, + 0.258 + ], + "angle": 0, + "content": "{ashelee, weihe1990, jiepanli, fangxiaolu}@whu.edu.cn, zhanghongyan@cug.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.292, + 0.314, + 0.308 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.324, + 0.474, + 0.673 + ], + "angle": 0, + "content": "Large-scale high-resolution (HR) land-cover mapping is a vital task to survey the Earth's surface and resolve many challenges facing humanity. However, it is still a nontrivial task hindered by complex ground details, various landforms, and the scarcity of accurate training labels over a wide-span geographic area. In this paper, we propose an efficient, weakly supervised framework (Paraformer) to guide large-scale HR land-cover mapping with easy-access historical land-cover data of low resolution (LR). Specifically, existing land-cover mapping approaches reveal the dominance of CNNs in preserving local ground details but still suffer from insufficient global modeling in various landforms. Therefore, we design a parallel CNN-Transformer feature extractor in Paraformer, consisting of a downsampling-free CNN branch and a Transformer branch, to jointly capture local and global contextual information. Besides, facing the spatial mismatch of training data, a pseudo-label-assisted training (PLAT) module is adopted to reasonably refine LR labels for weakly supervised semantic segmentation of HR images. Experiments on two large-scale datasets demonstrate the superiority of Paraformer over other state-of-the-art methods for automatically updating HR land-cover maps from LR historical labels." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.705, + 0.21, + 0.721 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.731, + 0.47, + 0.853 + ], + "angle": 0, + "content": "Land-cover mapping is a semantic segmentation task that gives each pixel of remote-sensing images a land-cover class such as \"cropland\" or \"building\" [14]. The land-cover data should be continuously updated since nature and human activities frequently change the landscape [37]. As sensors and satellites developed, massive high-resolution (HR) remote-sensing images (\\(\\leq 1\\) meter/pixel) could be easily obtained [1]. Rapid large-scale HR land-cover map" + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.294, + 0.892, + 0.524 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.528, + 0.894, + 0.566 + ], + "angle": 0, + "content": "Figure 1. Illustration of resolution mismatched issue in using the HR remote-sensing image (Source) and LR historical labels (Guide) to generate HR land-cover results (Target)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.582, + 0.892, + 0.674 + ], + "angle": 0, + "content": "ping is even more critical to facilitate downstream applications as the up-to-date HR land-cover data can accurately describe the land surface [21, 27, 55]. However, the complex ground details reflected by HR images and various landforms over wide-span areas still challenge the periodic updating of large-scale HR land-cover maps [28]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.893, + 0.903 + ], + "angle": 0, + "content": "The advanced methods for HR land-cover mapping have been dominated by the convolutional neural network (CNN) for many years. Although CNN-based models can finely capture local details for semantic segmentation of HR images, the intrinsic locality of convolution operations still limits their implementation in various landforms across larger areas [2]. Recently, Transformer has achieved tremendous success in semantic segmentation [5, 18, 34] and large-scale applications of Earth observation [11, 41, 48]. It adopts multi-head self-attention mechanisms to model global contexts but struggles in the representation of local details due to the shortage of low-level features [10, 48]. Besides, current methods with either CNN or Transformer structures generally rely on sufficient exact training labels by adopting a fully supervised strategy" + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.863, + 0.47, + 0.9 + ], + "angle": 0, + "content": "*Indicates equal contribution. †Corresponding author. The code and data are released at https://github.com/LiZhuoHong/Paraformer" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27717" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.145, + 0.089, + 0.4, + 0.167 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.228, + 0.168, + 0.317, + 0.179 + ], + "angle": 0, + "content": "(a) Existing mode" + }, + { + "type": "image", + "bbox": [ + 0.144, + 0.182, + 0.399, + 0.261 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.185, + 0.262, + 0.361, + 0.272 + ], + "angle": 0, + "content": "(b) HR-label-free, end-to-end mode" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.277, + 0.47, + 0.326 + ], + "angle": 0, + "content": "Figure 2. Two modes of large-scale HR land-cover mapping with LR labels. (a) Existing modes either reply on partial HR labels or require non-end-to-end training with human interventions. (b) Paraformer aims to form a mode that is HR-label-free and end-to-end trainable." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.341, + 0.469, + 0.386 + ], + "angle": 0, + "content": "[20, 32, 39]. However, creating accurate HR land-cover labels for large-scale geographic areas is extremely time-consuming and laborious [6, 37]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.387, + 0.469, + 0.552 + ], + "angle": 0, + "content": "Fortunately, many low-resolution (LR) land-cover data with large coverage have already emerged in the past decades [9, 22, 44, 56]. Utilizing these LR historical land-cover data as alternative guidance is a way to alleviate the scarcity of HR labels [29]. Nevertheless, the unmatched training pairs of HR images and inexact LR labels posed a challenge for fully supervised methods. Moreover, due to the different applied scenarios, existing weakly supervised semantic segmentation methods for natural scenes (e.g., learning from bounding box or image-level labels) are not applicable in handling the challenge as well [15, 23, 24, 57]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.553, + 0.469, + 0.779 + ], + "angle": 0, + "content": "Distinctively, the incorrect samples of LR land-cover labels are brought by satellites in different spatial resolutions during Earth observation. As shown in Figure 1, the objects in a \\(60m \\times 60m\\) area can be clearly observed from the HR (1 m/pixel) image \\(\\mathbf{X}\\). However, in the LR (30 m/pixel) label \\(\\mathbf{Y}\\), the area is only labeled by four pixels. To produce the 1-m land-cover result \\(\\hat{\\mathbf{Y}}\\), a labeled pixel \\(y_{1}\\) needs to provide guiding information for 900 target pixels \\(\\{\\hat{y}_1, \\hat{y}_2 \\dots \\hat{y}_{900}\\}\\), which raises a serious geospatial mismatch. How to reasonably exploit LR labels as the only guidance for semantic segmentation of large-scale HR satellite images is a particular problem shared in the fields of Earth observation and computer vision [28, 31, 37]. By summarizing the state-of-the-art methods of exploiting LR labels for large-scale HR land-cover mapping, there are still two main problems:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.781, + 0.468, + 0.839 + ], + "angle": 0, + "content": "1. For the wide-span application areas, existing feature extractors are difficult to jointly capture local details from HR images and model global contexts in various landforms at once [29, 54]." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.841, + 0.468, + 0.899 + ], + "angle": 0, + "content": "2. For the mismatch of training pairs, existing pipelines, as shown in Figure 2 (a), either still rely on partial HR labels or require non-end-to-end optimization with human interventions [12, 27]." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.781, + 0.468, + 0.899 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.227 + ], + "angle": 0, + "content": "To resolve these problems, as shown in Figure 2 (b), we propose the Paraformer as an HR-label-free, end-to-end framework to guide large-scale HR land-cover mapping with LR land-cover labels. Specifically, Paraformer parallelly hybrids a downsampling-free CNN branch with a Transformer branch to jointly capture local and global contexts from the large-scale HR images and adopts a pseudolabel-assisted training (PLAT) module to dig up reliable information from LR labels for framework training." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.229, + 0.892, + 0.44 + ], + "angle": 0, + "content": "The main contributions of this study are summarized as follows: (a) We introduce an efficient, weakly supervised Paraformer to facilitate large-scale HR land-cover mapping by getting rid of the well-annotated HR labels and human interventions during framework training; (b) a downsampling-free CNN branch is parallelly hybridized with a Transformer branch to capture features with both high spatial resolution and deep-level representation. The structure aims to globally adapt large-scale, various landforms and locally preserve HR ground details; (c) the PLAT module iteratively intersects primal predictions and LR labels to constantly refine labeled samples for guiding the framework training. It provides a concise way to update large-scale HR land-cover maps from LR historical data." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.452, + 0.642, + 0.468 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.478, + 0.892, + 0.825 + ], + "angle": 0, + "content": "Land-cover mapping approach: In the early stage, pixel-to-pixel classification methods, such as decision tree [19], random forest [7], and support vector machine [40], were popular in the land-cover mapping of multi-spectral LR images. However, these methods generally ignore contextual information and have fragmented results in HR cases, as optical HR images contain abundant spatial details but limited spectral features [29]. With the development of data-driven semantic segmentation, many CNN-based models were widely used in land-cover mapping of HR images [37, 52, 53]. Besides, as an alternative architecture, Transformer shows great power in capturing global contexts with sequence-to-sequence modeling [3, 10, 30] and demonstrates outstanding performance in many large-scale applications of Earth observation, such as building extraction [25, 41], road detection [11], and land-object classification [47]. Besides, many works developed new ways by saving labor to produce finer labels with the Segment Anything Model (SAM) [35, 50]. However, sufficient exact training labels are the foundation for large-scale applications of both CNN- and Transformer-based methods. The scarcity of HR labels still impedes these fully supervised approaches from large-scale HR land-cover mapping." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Land-cover labeled data: Creating large-scale HR labels via manual and semi-manual annotations is extremely time-consuming and expensive [17, 36]. Therefore, exiting HR land-cover data is generally limited to small scales. E.g., the LoveDA dataset contains \\(0.3\\mathrm{-m}\\) land-cover data, covering" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "27718" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.179, + 0.089, + 0.797, + 0.379 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.387, + 0.893, + 0.414 + ], + "angle": 0, + "content": "Figure 3. Overall workflow of Paraformer. The framework only takes the HR images and LR labels as training input and includes three components: (a) CNN-based resolution-preserving branch, (b) Transformer-based global-modeling branch, and (c) Pseudo-Label-Assisted Training (PLAT) module." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.425, + 0.473, + 0.591 + ], + "angle": 0, + "content": "536.15 \\(km^2\\) of China [46]. The Agri-vision dataset contained 0.1-m labeled data, covering \\(560~km^2\\) of the USA [13]. In the contract, the LR land-cover data generally has a larger coverage. E.g., the United States Geological Survey cyclically updates 30-m land-cover data covering the whole USA [49]. The European Space Agency (ESA) has updated an annual 10-m global land-cover data since 2020 [44]. These LR data can be seen as an alternative label source for guiding large-scale HR land-cover mapping. However, massive in exactly labeled samples still hinder them from being practicable." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.592, + 0.473, + 0.88 + ], + "angle": 0, + "content": "Strategies for LR historical label mining: To alleviate the scarcity of accurate labels in large-scale HR land-cover mapping, many studies have made efforts to mine reliable information from LR labels. E.g., a label super-resolution network was designed to constrain the inexact parts of LR labels by using the statistical distribution inferred from HR labels [31, 37]. A multi-stage framework, named WESUP, was built for \\(10\\mathrm{-m}\\) land-cover mapping with \\(30\\mathrm{-m}\\) labels [12]. In WESUP, multi-models were trained to refine clean samples from LR labels. Similarly, the winner approach of the 2021 IEEE GRSS Data Fusion Contest (DFC) deployed a shallow CNN to refine the \\(30\\mathrm{-m}\\) labels, and then multi-model were trained with pseudo-labels to create the \\(1\\mathrm{-m}\\) land-cover map of Maryland, USA [27]. Moreover, a low-to-high network (L2HNet) was proposed to select confident parts of LR labels via weakly supervised loss functions [28]. To produce \\(1\\mathrm{-m}\\) land-cover maps across China with available \\(10\\mathrm{-m}\\) labels, seven L2HNets were selectively trained to adapt wide-span geographic areas [29]." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.886, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Different from these approaches that either still rely on" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.426, + 0.895, + 0.473 + ], + "angle": 0, + "content": "partial HR labels or require human interventions, Pafaromer is designed as an HR-label-free end-to-end framework to facilitate large-scale HR land-cover mapping." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.482, + 0.637, + 0.5 + ], + "angle": 0, + "content": "3. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.508, + 0.893, + 0.584 + ], + "angle": 0, + "content": "To jointly capture local and global contexts and reasonably exploit LR labels for large-scale HR land-cover mapping, Paraformer combines parallel CNN and Transformer branches with a PLAT module. In this section, the three components are introduced sequentially." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.591, + 0.854, + 0.607 + ], + "angle": 0, + "content": "3.1. CNN-based resolution-preserving branch" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.614, + 0.895, + 0.903 + ], + "angle": 0, + "content": "As a basic feature extractor of Paraformer and also the main structure of previous L2HNet V1 [28], the CNN branch is designed to capture local contexts from HR images and preserve the spatial details by preventing feature downsampling. As shown in Figure 3 (a), the CNN branch is constructed by five serially connected resolution-preserving (RP) blocks. Each RP block contains parallel convolution layers with the sizes of \\(1 \\times 1\\), \\(3 \\times 3\\), and \\(5 \\times 5\\), whose steps are set to 1 for feature size maintaining. Partly similar to the inception module [42], the channel numbers of different scales' layers in each block are inversely proportional to their kernel sizes, which are set to 128, 64, and 32. Based on the setting, the RP blocks can capture features with a proper receptive field instead of downsampling the feature maps with a deep encoder-decoder pattern. The serial blocks aim at sufficiently preserving the spatial resolution of features by using the majority of \\(1 \\times 1\\) kernels. The \\(3 \\times 3\\) and \\(5 \\times 5\\) kernels capture necessary surrounding information. Furthermore, the multi-scale feature maps are" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27719" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.092, + 0.468, + 0.35 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.354, + 0.472, + 0.404 + ], + "angle": 0, + "content": "Figure 4. Example of the local mismatch/match in two regions. The edge of water is marked with yellow boundaries. Region 1 shows dispersed lakes around urban areas with unmatched annotation. Region 2 shows a large-scale river with matched annotation." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.414, + 0.47, + 0.46 + ], + "angle": 0, + "content": "concatenated and reduced to 128 channels for branch lightening. Besides, a shortcut connection is adopted between blocks for residual learning and detail preserving." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.468, + 0.449, + 0.485 + ], + "angle": 0, + "content": "3.2. Transformer-based global-modeling branch" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.492, + 0.47, + 0.839 + ], + "angle": 0, + "content": "The ground objects with the same land-cover class may have distinctive attributes in HR images and are differently annotated in LR labels. Figure 4 shows typical cases of lakes and rivers located in different areas. By considering that the CNN branch with intrinsic locality hinders the adaptation of various landforms over large-scale areas, we further hybrid the CNN branch with a Transformer branch which aims at capturing global contexts and building long-range support among dispersed geographic areas. As shown in Figure 3 (b), the Transformer branch contains 12 transformer layers. Each layer includes layer normalization, multi-head self-attention, and multi-layer perception. The feature maps extracted by each RP block are concatenated and inputted to the Transformer branch. Specifically, the extracted features from the CNN branch are downsampled and embedded in a hidden feature layer. And then the Transformer branch encodes the dense feature patches to capture global contexts. Subsequently, the encoded features are constantly upsampled to the size of HR images and classified to the final results. During the upsampling process, the outputted features of each stage are concatenated with the pre-encoded features, which bring massive local contextual information to the final feature maps." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.848, + 0.421, + 0.865 + ], + "angle": 0, + "content": "3.3. Pseudo-Label-Assisted Training module" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.903 + ], + "angle": 0, + "content": "To reasonably guide the large-scale HR land-cover mapping with weak LR labels, as shown in Figure 3 (c), a weakly" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.273 + ], + "angle": 0, + "content": "supervised PLAT module is adopted to optimize the framework training. The PLAT module aims to screen out uncertain samples and dig up reliable information from the LR labels. Specifically, the two parts of the PLAT module are explained as follows. For the CNN branch, we use classifier\\(^{(1)}\\), which is constructed by \\(3 \\times 3\\) convolution layers, to generate the primal prediction\\(^{(1)}\\) based on the extracted HR feature maps. Then we calculate the Cross-Entropy (CE) loss between prediction\\(^{(1)}\\), represented as \\(\\hat{\\mathbf{Y}}'\\), and the LR label, represented as \\(\\mathbf{Y}\\). Formally, by regarding \\(H\\), \\(W\\), and \\(L\\) as the height, weight, and land-cover class of the patch, the CE loss of the CNN branch is written as:" + }, + { + "type": "equation", + "bbox": [ + 0.537, + 0.283, + 0.892, + 0.32 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {c e}} (\\mathbf {Y}, \\hat {\\mathbf {Y}} ^ {\\prime}) = \\frac {\\sum_ {i = 0} ^ {W} \\sum_ {j = 0} ^ {H} \\left[ \\sum_ {l = 1} ^ {L} y _ {i j} ^ {(l)} \\log \\left(\\hat {y} _ {i j} ^ {\\prime (l)}\\right) \\right]}{H \\times W}. \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.331, + 0.895, + 0.528 + ], + "angle": 0, + "content": "As the final output of the framework, prediction\\(^{(2)}\\) is classified from the concatenated feature maps of CNN and Transformer branches, which is represented as \\(\\hat{\\mathbf{Y}}''\\). During each training iteration, we take the simple but effective intersection of prediction\\(^{(1)}\\) and LR label to generate mask labels. Specifically, the inconsistent samples in mask labels are set as void values to remove them from loss calculations. Moreover, since predictions of the CNN branch contain HR textual information that is highly consistent with the images, the mask labels also outline fine edges and retain stable labeled samples. Finally, the proposed Mask-Cross-Entropy (MCE) loss is calculated between prediction\\(^{(2)}\\) and mask labels. Formally, the MCE loss is written as:" + }, + { + "type": "equation", + "bbox": [ + 0.502, + 0.538, + 0.892, + 0.587 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {m c e}} (\\mathbf {M} \\cdot \\mathbf {Y}, \\hat {\\mathbf {Y}} ^ {\\prime \\prime}) = \\frac {\\sum_ {i = 0} ^ {W} \\sum_ {j = 0} ^ {H} \\left[ \\sum_ {l = 1} ^ {L} y _ {i j} ^ {(l)} m _ {i j} \\log \\left(\\hat {y} _ {i j} ^ {\\prime \\prime (l)}\\right) \\right]}{\\operatorname {S u m} (\\mathbf {M} (i , j) = 1)}. \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.588, + 0.892, + 0.634 + ], + "angle": 0, + "content": "In Eqs. 2, \\(\\mathbf{M}\\) is the intersected mask with the size of \\(H\\times W\\). \\(m_{ij},i\\in [0,H],j\\in [0,W]\\) is the element of \\(\\mathbf{M}(i,j)\\) which can be simply represented as:" + }, + { + "type": "equation", + "bbox": [ + 0.613, + 0.643, + 0.892, + 0.673 + ], + "angle": 0, + "content": "\\[\nm _ {i j} = \\left\\{ \\begin{array}{l l} 1 | Y _ {i j} = Y ^ {\\prime} _ {i j} \\\\ 0 | Y _ {i j} \\neq Y ^ {\\prime} _ {i j}. \\end{array} \\right. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.683, + 0.892, + 0.713 + ], + "angle": 0, + "content": "The total loss of the Paraformer is the combination of two branches' losses, which is written as:" + }, + { + "type": "equation", + "bbox": [ + 0.627, + 0.725, + 0.892, + 0.74 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {t o t a l}} = \\mathcal {L} _ {\\mathrm {c e}} + \\mathcal {L} _ {\\mathrm {m c e}}. \\tag {4}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.753, + 0.634, + 0.77 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.778, + 0.745, + 0.794 + ], + "angle": 0, + "content": "4.1. Study areas and using data" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.892, + 0.84 + ], + "angle": 0, + "content": "To comprehensively evaluate Paraformer on various landforms and different LR labels, the experiments are conducted on two large-scale datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "The Chesapeake Bay dataset is sampled from the largest estuary in the USA and organized into 732 non-overlapping tiles, where each tile has a size of \\(6000 \\times 7500\\) pixels [37]. The specific data includes:" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27720" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.086, + 0.089, + 0.284, + 0.203 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.137, + 0.204, + 0.234, + 0.213 + ], + "angle": 0, + "content": "(a) Source (1m/pixel)" + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.089, + 0.482, + 0.203 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.339, + 0.204, + 0.428, + 0.213 + ], + "angle": 0, + "content": "(b) Guide (30/pixel)" + }, + { + "type": "image", + "bbox": [ + 0.482, + 0.089, + 0.681, + 0.203 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.532, + 0.204, + 0.634, + 0.213 + ], + "angle": 0, + "content": "(c) Paraformer (ours)" + }, + { + "type": "image", + "bbox": [ + 0.682, + 0.089, + 0.882, + 0.203 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.757, + 0.204, + 0.808, + 0.213 + ], + "angle": 0, + "content": "(d) L2HNet" + }, + { + "type": "image", + "bbox": [ + 0.086, + 0.215, + 0.284, + 0.329 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.17, + 0.329, + 0.2, + 0.338 + ], + "angle": 0, + "content": "(e) RF" + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.215, + 0.482, + 0.328 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.365, + 0.329, + 0.403, + 0.338 + ], + "angle": 0, + "content": "(f) UNet" + }, + { + "type": "image", + "bbox": [ + 0.482, + 0.215, + 0.681, + 0.328 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.559, + 0.329, + 0.606, + 0.338 + ], + "angle": 0, + "content": "(g) HRNet" + }, + { + "type": "image", + "bbox": [ + 0.682, + 0.215, + 0.882, + 0.328 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.747, + 0.329, + 0.813, + 0.338 + ], + "angle": 0, + "content": "(h) TransUNet" + }, + { + "type": "image", + "bbox": [ + 0.171, + 0.345, + 0.785, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.37, + 0.893, + 0.396 + ], + "angle": 0, + "content": "Figure 5. Demonstration of the training data and visual comparisons of the Paraformer and other typical methods on the Chesapeake Bay dataset with 16 classes. (a) HR image. (b) LR label. (c) land-cover mapping result of Paraformer. (d-h) land-cover mapping results of five typical methods." + }, + { + "type": "image", + "bbox": [ + 0.094, + 0.401, + 0.885, + 0.641 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.208, + 0.642, + 0.225, + 0.652 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image_caption", + "bbox": [ + 0.328, + 0.643, + 0.344, + 0.652 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image_caption", + "bbox": [ + 0.451, + 0.643, + 0.467, + 0.652 + ], + "angle": 0, + "content": "(c)" + }, + { + "type": "image_caption", + "bbox": [ + 0.573, + 0.643, + 0.587, + 0.652 + ], + "angle": 0, + "content": "(d)" + }, + { + "type": "image_caption", + "bbox": [ + 0.693, + 0.643, + 0.708, + 0.652 + ], + "angle": 0, + "content": "(e)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.652, + 0.893, + 0.676 + ], + "angle": 0, + "content": "Figure 6. Six typical areas with finer observation scale on the Chesapeake Bay dataset. The first row shows the LR labels (Guide). The second row shows the HR images (Source). Third row shows the HR results (Target) produced by Paraformer." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.69, + 0.469, + 0.749 + ], + "angle": 0, + "content": "1. The HR images (1 m/pixel) are from the U.S. Department of Agriculture's National Agriculture Imagery Program (NAIP). The images contained four bands of red, green, blue, and near-infrared [33]." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.75, + 0.469, + 0.795 + ], + "angle": 0, + "content": "2. The LR historical labels (30 m/pixel) are from the USGS's National Land Cover Database (NLCD) [49], including 16 land-cover classes." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.796, + 0.468, + 0.825 + ], + "angle": 0, + "content": "3. The ground truths (1 m/pixel) are from the Chesapeake Bay Conservancy Land Cover (CCLC) project." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.69, + 0.469, + 0.825 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.833, + 0.469, + 0.878 + ], + "angle": 0, + "content": "The Poland dataset contains 14 provinces of Poland and is organized into 403 non-overlapping tiles, where each tile has a size of \\(1024 \\times 1024\\) pixels. The specific data includes:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.886, + 0.469, + 0.901 + ], + "angle": 0, + "content": "1. The HR images (0.25m and 0.5 m/pixel) are from the" + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.69, + 0.891, + 0.719 + ], + "angle": 0, + "content": "LandCover.ai [4] dataset. The images contained three bands of red, green, and blue." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.72, + 0.891, + 0.78 + ], + "angle": 0, + "content": "2. The LR historical labels are collected from three types of 10-m land-cover data and one type of 30-m data, which are named FROM_GLC10 [9], ESA_GLC10 [44], ESRI_GLC10 [22], and GLC_FCS30 [56]." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.781, + 0.891, + 0.809 + ], + "angle": 0, + "content": "3. The HR ground truths are from the OpenEarthMap [51] dataset with seven land-cover classes." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.72, + 0.891, + 0.809 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.823, + 0.806, + 0.838 + ], + "angle": 0, + "content": "4.2. Implementation Detail and Metrics" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.841, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In the experiments, all methods only take LR land-cover data as training labels. Paraformer is trained by the AdamW optimizer with a patch size of \\(224 \\times 224\\) and batch size of 8. The learning rate is set to 0.01 and would decrease by \\(10\\%\\)" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "27721" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.09, + 0.226, + 0.311 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.104, + 0.312, + 0.207, + 0.323 + ], + "angle": 0, + "content": "Large-scale region" + }, + { + "type": "image", + "bbox": [ + 0.227, + 0.093, + 0.354, + 0.213 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.23, + 0.216, + 0.355, + 0.322 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.364, + 0.092, + 0.486, + 0.2 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.388, + 0.201, + 0.461, + 0.213 + ], + "angle": 0, + "content": "(b) LR label 1" + }, + { + "type": "image", + "bbox": [ + 0.494, + 0.093, + 0.617, + 0.2 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.518, + 0.201, + 0.593, + 0.213 + ], + "angle": 0, + "content": "(c) LR label 2" + }, + { + "type": "image", + "bbox": [ + 0.627, + 0.093, + 0.747, + 0.2 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.649, + 0.201, + 0.724, + 0.213 + ], + "angle": 0, + "content": "(d) LR label 3" + }, + { + "type": "image", + "bbox": [ + 0.756, + 0.093, + 0.88, + 0.2 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.78, + 0.201, + 0.855, + 0.213 + ], + "angle": 0, + "content": "(e) LR label 4" + }, + { + "type": "image", + "bbox": [ + 0.362, + 0.216, + 0.486, + 0.311 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.392, + 0.312, + 0.456, + 0.322 + ], + "angle": 0, + "content": "(g) Result 1" + }, + { + "type": "image", + "bbox": [ + 0.493, + 0.216, + 0.617, + 0.311 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.523, + 0.312, + 0.588, + 0.322 + ], + "angle": 0, + "content": "(h) Result 2" + }, + { + "type": "image", + "bbox": [ + 0.624, + 0.216, + 0.748, + 0.311 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.656, + 0.312, + 0.716, + 0.322 + ], + "angle": 0, + "content": "(i) Result 3" + }, + { + "type": "image", + "bbox": [ + 0.756, + 0.216, + 0.88, + 0.312 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.785, + 0.313, + 0.85, + 0.322 + ], + "angle": 0, + "content": "(j) Result 4" + }, + { + "type": "image", + "bbox": [ + 0.368, + 0.327, + 0.422, + 0.337 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.47, + 0.327, + 0.542, + 0.337 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.576, + 0.327, + 0.658, + 0.337 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.327, + 0.743, + 0.337 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.34, + 0.893, + 0.378 + ], + "angle": 0, + "content": "Figure 7. Visual results of Paraformer in the Poland dataset. The demonstration area is one of the training pieces sampled from large-scale training regions. (a-e) the training pairs of HR images (0.5 m/pixel) and four types of LR labels including ESA_GLC (10 m/pixel), FROM_GLc (10 m/pixel), Esri_GLC (10 m/pixel), and GLC_FCS30 (30 m/pixel). (f-g) the ground truth (0.5 m/pixel) and the mapping results of Paraformer with different LR labels." + }, + { + "type": "table", + "bbox": [ + 0.12, + 0.39, + 0.848, + 0.597 + ], + "angle": 0, + "content": "
Resolution gapMethodmIoU (%) of six states in the Chesapeake Bay watershed
DelawareNew YorkMarylandPennsylvaniaVirginiaWest VirginiaAverage
30×Paraformer65.5771.4370.2060.0468.0152.6264.65
L2HNet [28]61.7768.1265.2458.5269.3955.4363.08
TransUNet [10]53.1560.5360.4251.0866.2147.5256.49
ConViT [18]55.2660.7161.5853.9459.8049.1156.73
CoAtNet [16]56.8962.8361.2553.5765.6751.3458.59
MobileViT[34]58.0361.3261.8455.5357.0448.6457.07
EfficientViT[5]53.7261.2859.4851.3857.3448.7655.33
UNetFormer[48]58.8565.1161.3459.1060.8447.2058.74
DC-Swin[47]59.6565.9958.6058.0664.1148.1559.09
UNet [38]54.1658.7956.4253.2157.3446.1154.34
HRNet [45]52.1156.2150.7650.0357.4845.4252.00
LinkNet [8]58.2762.0552.9652.1148.7148.9353.84
SkipFCN [26]60.9764.8359.4455.3764.7254.6660.00
SSDA [43]57.9161.5454.8551.7157.7147.1555.15
RF [7]59.3555.0355.2651.0752.2954.3654.56
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.6, + 0.893, + 0.625 + ], + "angle": 0, + "content": "Table 1. The quantitative comparison of the Paraformer and other methods on six states of the Chesapeake Bay watershed. All methods were trained with the 1-m images and 30-m labels. The mIoU (\\%) of different methods was calculated between their results and the 1-m ground truth." + }, + { + "type": "table", + "bbox": [ + 0.087, + 0.638, + 0.88, + 0.726 + ], + "angle": 0, + "content": "
Max gapLR labelParaformer (ours)mIoU (%) of different methods
L2HNet [28]TransUNet [10]ConViT [18]MobileViT [34]DC-Swin [47]HRNet [45]SkipFCN [26]RF [7]
40×FROM_GLC10 [9]56.5750.1538.4439.3641.0343.5643.6627.1421.48
ESA_GLC10 [44]55.1952.1335.5836.0938.4240.0549.8128.3426.97
Esri_GLC10 [22]55.0750.7837.7938.7838.5039.9146.6528.1819.36
120×GLC_FCS30 [56]49.3943.6226.2029.1629.5730.1441.4623.6717.02
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.728, + 0.893, + 0.752 + ], + "angle": 0, + "content": "Table 2. The quantitative comparison on the Poland dataset. The mIoU (%) of the Paraformer and other methods that trained with three types of 10-m labels (i.e., FROM_GLCL10, ESA_GLCL10, and Esri_GLCL10) and one type of 30-m label (i.e., GLC_FCS30) are demonstrated." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.769, + 0.47, + 0.89 + ], + "angle": 0, + "content": "when the loss stopped dropping over eight epochs. The metric of mean intersection over union (mIoU) is calculated between the results and the HR ground truths after their land-cover classes are unified into four base classes. The compared methods include: Random Forest (RF) is a pixel-to-pixel method widely used in large-scale land-cover mapping [7]. TransUNet [10], ConViT [18], CoAtNet [16], MobileViT [34], and EfficientViT [5] are CNN-Transformer hy" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.769, + 0.892, + 0.89 + ], + "angle": 0, + "content": "brid methods for semantic segmentation. UNetformer [48] and DC-Swin [47] are dedicated CNN-Transformer methods for remote-sensing images. UNet [38], HRNet [45], and LinkNet [8] are typical CNN-based semantic segmentation methods which are widely adopted in HR land-cover mapping [37, 52, 53]. SkipFCN [26] and SSDA [43] are shallow CNN-based methods for updating 1-m land-cover change maps from 30-m labels, which won first and second place" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27722" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.118, + 0.089, + 0.301, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.161, + 0.207, + 0.257, + 0.216 + ], + "angle": 0, + "content": "(a) Source (1m/pixel)" + }, + { + "type": "image", + "bbox": [ + 0.302, + 0.089, + 0.481, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.344, + 0.207, + 0.44, + 0.217 + ], + "angle": 0, + "content": "(b) Guide (30m/pixel)" + }, + { + "type": "image", + "bbox": [ + 0.483, + 0.089, + 0.665, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.491, + 0.207, + 0.658, + 0.216 + ], + "angle": 0, + "content": "(c) Prediction(1) from the CNN branch" + }, + { + "type": "image", + "bbox": [ + 0.668, + 0.089, + 0.848, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.725, + 0.207, + 0.79, + 0.216 + ], + "angle": 0, + "content": "(d) Mask label" + }, + { + "type": "image", + "bbox": [ + 0.118, + 0.218, + 0.3, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.155, + 0.336, + 0.264, + 0.344 + ], + "angle": 0, + "content": "(e) Mismatch of LR label" + }, + { + "type": "image", + "bbox": [ + 0.302, + 0.218, + 0.482, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.333, + 0.336, + 0.451, + 0.344 + ], + "angle": 0, + "content": "(f) Mismatch of mask label" + }, + { + "type": "image", + "bbox": [ + 0.484, + 0.218, + 0.664, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.54, + 0.336, + 0.61, + 0.344 + ], + "angle": 0, + "content": "(g) Paraformer" + }, + { + "type": "image", + "bbox": [ + 0.667, + 0.218, + 0.848, + 0.335 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.72, + 0.336, + 0.796, + 0.344 + ], + "angle": 0, + "content": "(h) GT (1m/pixel)" + }, + { + "type": "image", + "bbox": [ + 0.269, + 0.349, + 0.328, + 0.362 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.382, + 0.35, + 0.461, + 0.361 + ], + "angle": 0, + "content": "Tree canopy" + }, + { + "type": "image", + "bbox": [ + 0.498, + 0.349, + 0.59, + 0.361 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.631, + 0.35, + 0.682, + 0.36 + ], + "angle": 0, + "content": "Water" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.371, + 0.894, + 0.409 + ], + "angle": 0, + "content": "Figure 8. Example of training data and different outputs of Paraformer sampled from the Chesapeake Bay dataset with four unified classes. (a) HR images. (b) LR labels. (c) the primal prediction from the CNN branch. (d) Mask label, as the intersection parts of (b) and (c). The black areas are set to void without supervised information. (e–f) the incorrect samples (with pink color) of LR label and mask label. (g) the final results of Paraformer. (h) HR ground truth." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.425, + 0.47, + 0.471 + ], + "angle": 0, + "content": "in the 2021 IEEE GRSS DFC [27]. L2HNet is a state-of-the-art method designed for weakly supervised land-cover mapping [28]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.489, + 0.268, + 0.505 + ], + "angle": 0, + "content": "4.3. Comparison Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.508, + 0.473, + 0.902 + ], + "angle": 0, + "content": "Comparison on the Chesapeake Bay dataset: Table 1 and Figure 5 show the comparisons on the Chesapeake Bay dataset. From the quantitative results, Paraformer shows superiority in the states of Delaware, New York, Maryland, and Pennsylvania. The L2HNet shows better results in Virginia and West Virginia. On average, Paraformer has the most accurate HR land-cover mapping results over the entire area, with a mIoU of \\(64.65\\%\\). As shown in Figure 5 (c), the visual result of Paraformer is more consistent with the HR image compared with other methods. Unlike the fully supervised semantic segmentation task, the unmatched training pairs can cause serious misguidedness during the model training. E.g., as the rough results shown in Figure 5 (f) and (g), UNet and HRNet over-downsample the features and encourage results to fit LR labels instead of being consistent with the HR images. Furthermore, quantitative results reveal that UNet, LinkNet, and HRNet have insufficient performance, with mIoU of \\(54.34\\%\\), \\(53.84\\%\\), and \\(52.00\\%\\). Although the compared CNN-Transformer methods (e.g., TransUNet) combine local and global contextual information, the structure does not focus on preserving the feature resolution or dealing with the geospatial mismatch. As a result, TransUNet shows a weak performance in visual results, shown in Figure 5 (h), and has a mIoU of \\(56.49\\%\\). Furthermore, SkipFCN, SSDA, and RF use small receptive fields or pixel-to-pixel strategies to ex" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.425, + 0.892, + 0.591 + ], + "angle": 0, + "content": "tract features with fine land details. However, due to the lack of deep-level feature representation and global contextual information, SkipFCN, SSDA, and RF obtain a mIoU of \\(59.99\\%\\), \\(55.15\\%\\), and \\(54.56\\%\\), respectively. As an example shown in Figure 5 (e), RF finely predicts ground details but incorrectly classifies rivers, lakes, and pastures. To further demonstrate the effect of Paraformer on different landscapes, we sample six typical areas in Figure 6. The visual results indicate that the complex ground details among various landforms of HR land-cover maps can be well updated from the LR historical land-cover labels." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.893, + 0.9 + ], + "angle": 0, + "content": "Comparison on the Poland dataset: In the experiments with the Poland dataset, all methods were used to produce \\(0.25 / 0.5\\)-m land-cover maps of 14 provinces of Poland by exploiting four LR labels separately. These LR labels include 10-m FROM_GLC10, ESA_GLC10, Esri_GLC10, and 30-m GLC_FCS30. As shown in Table 2, Paraformer is compared with eight representative methods (i.e., weakly supervised, CNN-Transformer, CNN-based, pixel-to-pixel approaches) in a more extreme geospatial mismatch. Compared with the state-of-the-art method, the Paraformer has an increase in mIoU of \\(6.42\\%\\), \\(3.06\\%\\), and \\(4.29\\%\\) in exploiting 10-m labels. By resolving 30-m labels with a max resolution gap of \\(120\\times\\), Paraformer has a mIoU of \\(49.39\\%\\) with an increase of \\(5.77\\%\\) compared with L2HNet. The typical CNN-based method has an average mIoU of \\(46.71\\%\\) among the 10-m cases and \\(41.46\\%\\) in the 30-m case. Skip_FCN and RF have the lowest mIoU among all methods, which shows the difficulty of dealing with extremely unmatched situations. Moreover, the quantitative results of Paraformer shown in the four cases reveal that the proposed frame" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "27723" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.089, + 0.089, + 0.88, + 0.165 + ], + "angle": 0, + "content": "
Ablation methodmIoU (%) of six states in the Chesapeake Bay watershed
DelawareNew YourMarylandPennsylvaniaVirginiaWest VirginiaAverageParamsFLOPs
Paraformer65.5771.4370.2060.0468.0152.6264.65109.4M141.3G
Sole CNN branch59.5767.8764.3053.8665.2650.0160.154.5M56.1G
Sole Transformer branch53.1560.5360.4251.0866.2247.5256.4996.9M83.3G
Hybrid without PLAT62.6970.3967.1558.3367.4750.8362.81109.4M141.3G
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.171, + 0.894, + 0.198 + ], + "angle": 0, + "content": "Table 3. The ablation results of the Paraformer on six states of the Chesapeake Bay watershed. The sole CNN branch, sole Transformer branch, and Hybrid without PLAT aim to investigate the contribution of the CNN branch, Transformer branch, and PLAT module, respectively." + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.211, + 0.275, + 0.306 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.142, + 0.306, + 0.212, + 0.315 + ], + "angle": 0, + "content": "(a) 1-m image" + }, + { + "type": "image", + "bbox": [ + 0.276, + 0.21, + 0.468, + 0.305 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.312, + 0.306, + 0.431, + 0.315 + ], + "angle": 0, + "content": "(b) CNN-branch context" + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.316, + 0.274, + 0.41 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.1, + 0.411, + 0.254, + 0.421 + ], + "angle": 0, + "content": "(c) Transformer-branch context" + }, + { + "type": "image", + "bbox": [ + 0.276, + 0.316, + 0.469, + 0.41 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.304, + 0.411, + 0.44, + 0.421 + ], + "angle": 0, + "content": "(d) Hybrid-structure context" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.429, + 0.471, + 0.477 + ], + "angle": 0, + "content": "Figure 9. Demonstration of the extracted contexts from the ablation methods. (a) the original HR image. (b) the contexts extracted by the sole CNN branch. (c) the contexts extracted by the sole Transformer branch. (d) the contexts extracted by the CNN-Transformer hybrid backbone." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.497, + 0.47, + 0.618 + ], + "angle": 0, + "content": "work obtains stable results from different LR labels. Figure 7 shows the visual results of Paraformer among four cases. With the parallel CNN-Transformer structure and PLAT module, Paraformer is able to refine the clear ground details (e.g., vegetation and roads) even if they are roughly labeled in local areas. In general, Paraformer shows the potential to robustly update large-scale HR land-cover maps from available LR historical labels." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.621, + 0.281, + 0.637 + ], + "angle": 0, + "content": "4.4. Ablation experiments" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.645, + 0.47, + 0.779 + ], + "angle": 0, + "content": "In this section, ablation experiments were conducted on the Chesapeake Bay dataset to evaluate different components of Paraformer. Each ablation in Table 3 is explained as follows: (1) the sole CNN branch is dependently trained by calculating CE loss with LR labels; (2) the sole Transformer branch embeds HR images instead of features from the CNN branch and calculates CE loss with LR labels; (3) the hybrid structure without PLAT directly calculates CE loss with the LR labels." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.471, + 0.902 + ], + "angle": 0, + "content": "By ablating the PLAT module, the results obtained an average mIoU of \\(62.81\\%\\), which indicates a \\(1.84\\%\\) decrease compared with the \\(64.65\\%\\) of Paraformer. By ablating the CNN and Transformer branches, the results of the sole CNN branch obtained a mIoU of \\(60.15\\%\\) and had a \\(4.5\\%\\) decrease. Results of the sole Transformer branch obtained the lowest mIoU of \\(56.49\\%\\) and had the most obvious decrease \\((8.16\\%)\\). Figure 8 shows different outputs of Paraformer," + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.213, + 0.892, + 0.409 + ], + "angle": 0, + "content": "where the inexact LR labels are gradually refined during framework training. The final result shown in Figure 8 (g) indicates both fine ground details and accurate land-cover patterns that are consistent with the ground truth. Moreover, Figure 9 shows the visualized contexts captured by the CNN branch, Transformer branch, and hybrid structure. Figure 9 (b) indicates that the CNN branch mostly focuses on capturing local details (e.g., the edges of roads, single houses, and shrubs). Figure 9 (c) indicates that the Transformer branch captures the feature in object scale, focusing on intact land objects of building areas and parking spots. The hybrid structure shows a strong response to the obvious objects with both fine edges and intact areas." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.41, + 0.892, + 0.515 + ], + "angle": 0, + "content": "In general, the ablation results demonstrate two findings: (1) The PLAT module can stably optimize the framework training and reasonably exploit the LR labels during the large-scale HR land-cover mapping process. (2) The parallel CNN and Transformer branches are indispensable parts of the framework, which construct a more robust feature extractor to bridge local and global contextual information." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.531, + 0.62, + 0.546 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.55, + 0.892, + 0.807 + ], + "angle": 0, + "content": "In this paper, a weakly supervised CNN-Transformer framework, Paraformer, is proposed to update large-scale HR land-cover maps in an HR-label-free, end-to-end manner. Experiments on two datasets show that Paraformer outperforms other approaches in guiding semantic segmentation of large-scale HR remote-sensing images with easy-access LR land-cover data. Further analysis reveals that the Paraformer can robustly adapt various landforms of wide-span areas and stably exploit different LR labels in producing accurate HR land-cover maps. The ablation studies demonstrate the effectiveness of the parallel CNN-Transformer structure and the PLAT module. Moreover, intermediate results of each training process and visualized contexts of each branch are demonstrated to transparently explain the components of Paraformer. In general, the proposed Paraformer has the potential to become an effective method for facilitating large-scale HR land-cover mapping." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.818, + 0.66, + 0.835 + ], + "angle": 0, + "content": "Acknowledgments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This work has been supported by the National Key Research and Development Program of China (grant no. 2022YFB3903605) and the National Natural Science Foundation of China (grant no.42071322)." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27724" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.157 + ], + "angle": 0, + "content": "[1] Land-cover classification with high-resolution remote sensing images using transferable deep models. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 4299-4309, 2022. 2" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.472, + 0.853 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "27727" + } + ] +] \ No newline at end of file diff --git a/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_origin.pdf b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..88fd503ed833626a0a974d5d858562b681eb2b1a --- /dev/null +++ b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/29f9f1d2-f3f8-470f-b021-c1331e97eff4_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:6a490dafea983954ccde26efaecf3e072463c0568bf367d9ad759845cf235fbb +size 8791065 diff --git a/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/full.md b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/full.md new file mode 100644 index 0000000000000000000000000000000000000000..3ecd33bbb3e4155464ddb45519d6590ca22f079c --- /dev/null +++ b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/full.md @@ -0,0 +1,360 @@ +# Learning without Exact Guidance: Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels + +Zhuohong $\mathsf{Li}^{1*}$ , Wei $\mathsf{He}^{1*}$ , Jiepan $\mathsf{Li}^1$ , Fangxiao $\mathsf{Lu}^1$ , Hongyan Zhang $^{1,2\dagger}$ + +1Wuhan University 2China University of Geosciences + +{ashelee, weihe1990, jiepanli, fangxiaolu}@whu.edu.cn, zhanghongyan@cug.edu.cn + +# Abstract + +Large-scale high-resolution (HR) land-cover mapping is a vital task to survey the Earth's surface and resolve many challenges facing humanity. However, it is still a nontrivial task hindered by complex ground details, various landforms, and the scarcity of accurate training labels over a wide-span geographic area. In this paper, we propose an efficient, weakly supervised framework (Paraformer) to guide large-scale HR land-cover mapping with easy-access historical land-cover data of low resolution (LR). Specifically, existing land-cover mapping approaches reveal the dominance of CNNs in preserving local ground details but still suffer from insufficient global modeling in various landforms. Therefore, we design a parallel CNN-Transformer feature extractor in Paraformer, consisting of a downsampling-free CNN branch and a Transformer branch, to jointly capture local and global contextual information. Besides, facing the spatial mismatch of training data, a pseudo-label-assisted training (PLAT) module is adopted to reasonably refine LR labels for weakly supervised semantic segmentation of HR images. Experiments on two large-scale datasets demonstrate the superiority of Paraformer over other state-of-the-art methods for automatically updating HR land-cover maps from LR historical labels. + +# 1. Introduction + +Land-cover mapping is a semantic segmentation task that gives each pixel of remote-sensing images a land-cover class such as "cropland" or "building" [14]. The land-cover data should be continuously updated since nature and human activities frequently change the landscape [37]. As sensors and satellites developed, massive high-resolution (HR) remote-sensing images ( $\leq 1$ meter/pixel) could be easily obtained [1]. Rapid large-scale HR land-cover map + +![](images/0de6bd4d0462bf8c96115bc0b558cb70c0cd3568bbb7d49692fff76d4baf143b.jpg) +Figure 1. Illustration of resolution mismatched issue in using the HR remote-sensing image (Source) and LR historical labels (Guide) to generate HR land-cover results (Target). + +ping is even more critical to facilitate downstream applications as the up-to-date HR land-cover data can accurately describe the land surface [21, 27, 55]. However, the complex ground details reflected by HR images and various landforms over wide-span areas still challenge the periodic updating of large-scale HR land-cover maps [28]. + +The advanced methods for HR land-cover mapping have been dominated by the convolutional neural network (CNN) for many years. Although CNN-based models can finely capture local details for semantic segmentation of HR images, the intrinsic locality of convolution operations still limits their implementation in various landforms across larger areas [2]. Recently, Transformer has achieved tremendous success in semantic segmentation [5, 18, 34] and large-scale applications of Earth observation [11, 41, 48]. It adopts multi-head self-attention mechanisms to model global contexts but struggles in the representation of local details due to the shortage of low-level features [10, 48]. Besides, current methods with either CNN or Transformer structures generally rely on sufficient exact training labels by adopting a fully supervised strategy + +![](images/22b7d38cf58280c9649a725065a17606c526bac7804888b12ba22f040f85aa84.jpg) +(a) Existing mode + +![](images/5b674f92572eb55929905f410c2415fbf85fb93048caf6667e42aac433a6a98d.jpg) +(b) HR-label-free, end-to-end mode +Figure 2. Two modes of large-scale HR land-cover mapping with LR labels. (a) Existing modes either reply on partial HR labels or require non-end-to-end training with human interventions. (b) Paraformer aims to form a mode that is HR-label-free and end-to-end trainable. + +[20, 32, 39]. However, creating accurate HR land-cover labels for large-scale geographic areas is extremely time-consuming and laborious [6, 37]. + +Fortunately, many low-resolution (LR) land-cover data with large coverage have already emerged in the past decades [9, 22, 44, 56]. Utilizing these LR historical land-cover data as alternative guidance is a way to alleviate the scarcity of HR labels [29]. Nevertheless, the unmatched training pairs of HR images and inexact LR labels posed a challenge for fully supervised methods. Moreover, due to the different applied scenarios, existing weakly supervised semantic segmentation methods for natural scenes (e.g., learning from bounding box or image-level labels) are not applicable in handling the challenge as well [15, 23, 24, 57]. + +Distinctively, the incorrect samples of LR land-cover labels are brought by satellites in different spatial resolutions during Earth observation. As shown in Figure 1, the objects in a $60m \times 60m$ area can be clearly observed from the HR (1 m/pixel) image $\mathbf{X}$ . However, in the LR (30 m/pixel) label $\mathbf{Y}$ , the area is only labeled by four pixels. To produce the 1-m land-cover result $\hat{\mathbf{Y}}$ , a labeled pixel $y_{1}$ needs to provide guiding information for 900 target pixels $\{\hat{y}_1, \hat{y}_2 \dots \hat{y}_{900}\}$ , which raises a serious geospatial mismatch. How to reasonably exploit LR labels as the only guidance for semantic segmentation of large-scale HR satellite images is a particular problem shared in the fields of Earth observation and computer vision [28, 31, 37]. By summarizing the state-of-the-art methods of exploiting LR labels for large-scale HR land-cover mapping, there are still two main problems: + +1. For the wide-span application areas, existing feature extractors are difficult to jointly capture local details from HR images and model global contexts in various landforms at once [29, 54]. +2. For the mismatch of training pairs, existing pipelines, as shown in Figure 2 (a), either still rely on partial HR labels or require non-end-to-end optimization with human interventions [12, 27]. + +To resolve these problems, as shown in Figure 2 (b), we propose the Paraformer as an HR-label-free, end-to-end framework to guide large-scale HR land-cover mapping with LR land-cover labels. Specifically, Paraformer parallelly hybrids a downsampling-free CNN branch with a Transformer branch to jointly capture local and global contexts from the large-scale HR images and adopts a pseudolabel-assisted training (PLAT) module to dig up reliable information from LR labels for framework training. + +The main contributions of this study are summarized as follows: (a) We introduce an efficient, weakly supervised Paraformer to facilitate large-scale HR land-cover mapping by getting rid of the well-annotated HR labels and human interventions during framework training; (b) a downsampling-free CNN branch is parallelly hybridized with a Transformer branch to capture features with both high spatial resolution and deep-level representation. The structure aims to globally adapt large-scale, various landforms and locally preserve HR ground details; (c) the PLAT module iteratively intersects primal predictions and LR labels to constantly refine labeled samples for guiding the framework training. It provides a concise way to update large-scale HR land-cover maps from LR historical data. + +# 2. Related Work + +Land-cover mapping approach: In the early stage, pixel-to-pixel classification methods, such as decision tree [19], random forest [7], and support vector machine [40], were popular in the land-cover mapping of multi-spectral LR images. However, these methods generally ignore contextual information and have fragmented results in HR cases, as optical HR images contain abundant spatial details but limited spectral features [29]. With the development of data-driven semantic segmentation, many CNN-based models were widely used in land-cover mapping of HR images [37, 52, 53]. Besides, as an alternative architecture, Transformer shows great power in capturing global contexts with sequence-to-sequence modeling [3, 10, 30] and demonstrates outstanding performance in many large-scale applications of Earth observation, such as building extraction [25, 41], road detection [11], and land-object classification [47]. Besides, many works developed new ways by saving labor to produce finer labels with the Segment Anything Model (SAM) [35, 50]. However, sufficient exact training labels are the foundation for large-scale applications of both CNN- and Transformer-based methods. The scarcity of HR labels still impedes these fully supervised approaches from large-scale HR land-cover mapping. + +Land-cover labeled data: Creating large-scale HR labels via manual and semi-manual annotations is extremely time-consuming and expensive [17, 36]. Therefore, exiting HR land-cover data is generally limited to small scales. E.g., the LoveDA dataset contains $0.3\mathrm{-m}$ land-cover data, covering + +![](images/48ec693be6caeb544f4d9d62e1c0b008de968d41a23628aefdfd3283e6301c6c.jpg) +Figure 3. Overall workflow of Paraformer. The framework only takes the HR images and LR labels as training input and includes three components: (a) CNN-based resolution-preserving branch, (b) Transformer-based global-modeling branch, and (c) Pseudo-Label-Assisted Training (PLAT) module. + +536.15 $km^2$ of China [46]. The Agri-vision dataset contained 0.1-m labeled data, covering $560~km^2$ of the USA [13]. In the contract, the LR land-cover data generally has a larger coverage. E.g., the United States Geological Survey cyclically updates 30-m land-cover data covering the whole USA [49]. The European Space Agency (ESA) has updated an annual 10-m global land-cover data since 2020 [44]. These LR data can be seen as an alternative label source for guiding large-scale HR land-cover mapping. However, massive in exactly labeled samples still hinder them from being practicable. + +Strategies for LR historical label mining: To alleviate the scarcity of accurate labels in large-scale HR land-cover mapping, many studies have made efforts to mine reliable information from LR labels. E.g., a label super-resolution network was designed to constrain the inexact parts of LR labels by using the statistical distribution inferred from HR labels [31, 37]. A multi-stage framework, named WESUP, was built for $10\mathrm{-m}$ land-cover mapping with $30\mathrm{-m}$ labels [12]. In WESUP, multi-models were trained to refine clean samples from LR labels. Similarly, the winner approach of the 2021 IEEE GRSS Data Fusion Contest (DFC) deployed a shallow CNN to refine the $30\mathrm{-m}$ labels, and then multi-model were trained with pseudo-labels to create the $1\mathrm{-m}$ land-cover map of Maryland, USA [27]. Moreover, a low-to-high network (L2HNet) was proposed to select confident parts of LR labels via weakly supervised loss functions [28]. To produce $1\mathrm{-m}$ land-cover maps across China with available $10\mathrm{-m}$ labels, seven L2HNets were selectively trained to adapt wide-span geographic areas [29]. + +Different from these approaches that either still rely on + +partial HR labels or require human interventions, Pafaromer is designed as an HR-label-free end-to-end framework to facilitate large-scale HR land-cover mapping. + +# 3. Methodology + +To jointly capture local and global contexts and reasonably exploit LR labels for large-scale HR land-cover mapping, Paraformer combines parallel CNN and Transformer branches with a PLAT module. In this section, the three components are introduced sequentially. + +# 3.1. CNN-based resolution-preserving branch + +As a basic feature extractor of Paraformer and also the main structure of previous L2HNet V1 [28], the CNN branch is designed to capture local contexts from HR images and preserve the spatial details by preventing feature downsampling. As shown in Figure 3 (a), the CNN branch is constructed by five serially connected resolution-preserving (RP) blocks. Each RP block contains parallel convolution layers with the sizes of $1 \times 1$ , $3 \times 3$ , and $5 \times 5$ , whose steps are set to 1 for feature size maintaining. Partly similar to the inception module [42], the channel numbers of different scales' layers in each block are inversely proportional to their kernel sizes, which are set to 128, 64, and 32. Based on the setting, the RP blocks can capture features with a proper receptive field instead of downsampling the feature maps with a deep encoder-decoder pattern. The serial blocks aim at sufficiently preserving the spatial resolution of features by using the majority of $1 \times 1$ kernels. The $3 \times 3$ and $5 \times 5$ kernels capture necessary surrounding information. Furthermore, the multi-scale feature maps are + +![](images/9075bbdad61d2a8a8a84992ed0af9912a38b871ab6fc414d2bb8c17a63241004.jpg) +Figure 4. Example of the local mismatch/match in two regions. The edge of water is marked with yellow boundaries. Region 1 shows dispersed lakes around urban areas with unmatched annotation. Region 2 shows a large-scale river with matched annotation. + +concatenated and reduced to 128 channels for branch lightening. Besides, a shortcut connection is adopted between blocks for residual learning and detail preserving. + +# 3.2. Transformer-based global-modeling branch + +The ground objects with the same land-cover class may have distinctive attributes in HR images and are differently annotated in LR labels. Figure 4 shows typical cases of lakes and rivers located in different areas. By considering that the CNN branch with intrinsic locality hinders the adaptation of various landforms over large-scale areas, we further hybrid the CNN branch with a Transformer branch which aims at capturing global contexts and building long-range support among dispersed geographic areas. As shown in Figure 3 (b), the Transformer branch contains 12 transformer layers. Each layer includes layer normalization, multi-head self-attention, and multi-layer perception. The feature maps extracted by each RP block are concatenated and inputted to the Transformer branch. Specifically, the extracted features from the CNN branch are downsampled and embedded in a hidden feature layer. And then the Transformer branch encodes the dense feature patches to capture global contexts. Subsequently, the encoded features are constantly upsampled to the size of HR images and classified to the final results. During the upsampling process, the outputted features of each stage are concatenated with the pre-encoded features, which bring massive local contextual information to the final feature maps. + +# 3.3. Pseudo-Label-Assisted Training module + +To reasonably guide the large-scale HR land-cover mapping with weak LR labels, as shown in Figure 3 (c), a weakly + +supervised PLAT module is adopted to optimize the framework training. The PLAT module aims to screen out uncertain samples and dig up reliable information from the LR labels. Specifically, the two parts of the PLAT module are explained as follows. For the CNN branch, we use classifier $^{(1)}$ , which is constructed by $3 \times 3$ convolution layers, to generate the primal prediction $^{(1)}$ based on the extracted HR feature maps. Then we calculate the Cross-Entropy (CE) loss between prediction $^{(1)}$ , represented as $\hat{\mathbf{Y}}'$ , and the LR label, represented as $\mathbf{Y}$ . Formally, by regarding $H$ , $W$ , and $L$ as the height, weight, and land-cover class of the patch, the CE loss of the CNN branch is written as: + +$$ +\mathcal {L} _ {\mathrm {c e}} (\mathbf {Y}, \hat {\mathbf {Y}} ^ {\prime}) = \frac {\sum_ {i = 0} ^ {W} \sum_ {j = 0} ^ {H} \left[ \sum_ {l = 1} ^ {L} y _ {i j} ^ {(l)} \log \left(\hat {y} _ {i j} ^ {\prime (l)}\right) \right]}{H \times W}. \tag {1} +$$ + +As the final output of the framework, prediction $^{(2)}$ is classified from the concatenated feature maps of CNN and Transformer branches, which is represented as $\hat{\mathbf{Y}}''$ . During each training iteration, we take the simple but effective intersection of prediction $^{(1)}$ and LR label to generate mask labels. Specifically, the inconsistent samples in mask labels are set as void values to remove them from loss calculations. Moreover, since predictions of the CNN branch contain HR textual information that is highly consistent with the images, the mask labels also outline fine edges and retain stable labeled samples. Finally, the proposed Mask-Cross-Entropy (MCE) loss is calculated between prediction $^{(2)}$ and mask labels. Formally, the MCE loss is written as: + +$$ +\mathcal {L} _ {\mathrm {m c e}} (\mathbf {M} \cdot \mathbf {Y}, \hat {\mathbf {Y}} ^ {\prime \prime}) = \frac {\sum_ {i = 0} ^ {W} \sum_ {j = 0} ^ {H} \left[ \sum_ {l = 1} ^ {L} y _ {i j} ^ {(l)} m _ {i j} \log \left(\hat {y} _ {i j} ^ {\prime \prime (l)}\right) \right]}{\operatorname {S u m} (\mathbf {M} (i , j) = 1)}. \tag {2} +$$ + +In Eqs. 2, $\mathbf{M}$ is the intersected mask with the size of $H\times W$ . $m_{ij},i\in [0,H],j\in [0,W]$ is the element of $\mathbf{M}(i,j)$ which can be simply represented as: + +$$ +m _ {i j} = \left\{ \begin{array}{l l} 1 | Y _ {i j} = Y ^ {\prime} _ {i j} \\ 0 | Y _ {i j} \neq Y ^ {\prime} _ {i j}. \end{array} \right. \tag {3} +$$ + +The total loss of the Paraformer is the combination of two branches' losses, which is written as: + +$$ +\mathcal {L} _ {\text {t o t a l}} = \mathcal {L} _ {\mathrm {c e}} + \mathcal {L} _ {\mathrm {m c e}}. \tag {4} +$$ + +# 4. Experiments + +# 4.1. Study areas and using data + +To comprehensively evaluate Paraformer on various landforms and different LR labels, the experiments are conducted on two large-scale datasets. + +The Chesapeake Bay dataset is sampled from the largest estuary in the USA and organized into 732 non-overlapping tiles, where each tile has a size of $6000 \times 7500$ pixels [37]. The specific data includes: + +![](images/9f7b34ba42c0f1eab6ff067cfeb0cda7dec1b4b5aef068c6a144667954f297f3.jpg) +(a) Source (1m/pixel) + +![](images/d4b09fc44a89b6b9d5ffa92810ae83319ab934c96470f795a437391741f13549.jpg) +(b) Guide (30/pixel) + +![](images/2100d1bb5f8b8a7106d283d685b7418555e909d5e1cddf20e96058b830d35a87.jpg) +(c) Paraformer (ours) + +![](images/09b97ba7f3e2b028105d0dc3bcac08d20111ea385dda9f0bd5865f5757ff2890.jpg) +(d) L2HNet + +![](images/cedf9421240131565fc077ceb567cf01ffd60d9c5ac4b471a715887088fff120.jpg) +(e) RF + +![](images/36eb09911538b2f97bfe6e2501f3e64e4dc5e05d16b8b57964aa945a275c2260.jpg) +(f) UNet + +![](images/071302de548a4fc231a2c8d94a72beb1cfdab1743633c5817db0f470f198f4fe.jpg) +(g) HRNet + +![](images/5ce9bec037b40ba72f7deb74d5dcd486b97f11eb1a586671b969b86b3ad04610.jpg) +(h) TransUNet + +![](images/ee0e18ff0408b04290fc8ac3a55bb262b8060960e792cdc0d72fe93635d2132d.jpg) +Figure 5. Demonstration of the training data and visual comparisons of the Paraformer and other typical methods on the Chesapeake Bay dataset with 16 classes. (a) HR image. (b) LR label. (c) land-cover mapping result of Paraformer. (d-h) land-cover mapping results of five typical methods. + +![](images/8c77fd3ad40212a2cce100e7e5b740aeb468749545ed4f2858ff79d82b3aff0f.jpg) +(a) +(b) +(c) +(d) +(e) +Figure 6. Six typical areas with finer observation scale on the Chesapeake Bay dataset. The first row shows the LR labels (Guide). The second row shows the HR images (Source). Third row shows the HR results (Target) produced by Paraformer. + +1. The HR images (1 m/pixel) are from the U.S. Department of Agriculture's National Agriculture Imagery Program (NAIP). The images contained four bands of red, green, blue, and near-infrared [33]. +2. The LR historical labels (30 m/pixel) are from the USGS's National Land Cover Database (NLCD) [49], including 16 land-cover classes. +3. The ground truths (1 m/pixel) are from the Chesapeake Bay Conservancy Land Cover (CCLC) project. + +The Poland dataset contains 14 provinces of Poland and is organized into 403 non-overlapping tiles, where each tile has a size of $1024 \times 1024$ pixels. The specific data includes: + +1. The HR images (0.25m and 0.5 m/pixel) are from the + +LandCover.ai [4] dataset. The images contained three bands of red, green, and blue. + +2. The LR historical labels are collected from three types of 10-m land-cover data and one type of 30-m data, which are named FROM_GLC10 [9], ESA_GLC10 [44], ESRI_GLC10 [22], and GLC_FCS30 [56]. +3. The HR ground truths are from the OpenEarthMap [51] dataset with seven land-cover classes. + +# 4.2. Implementation Detail and Metrics + +In the experiments, all methods only take LR land-cover data as training labels. Paraformer is trained by the AdamW optimizer with a patch size of $224 \times 224$ and batch size of 8. The learning rate is set to 0.01 and would decrease by $10\%$ + +![](images/496d5c6b98744a6fdfc289855ce20ce59ed6321b5fb12786d819c4f228c32aff.jpg) +Large-scale region + +![](images/2d7551d405046a87f8c3de9a3d3df96829d71066def350284c613c11271b5226.jpg) + +![](images/6195077f55556a80e4211fdfe7e308d9a4bd0a428f455dba11949090270dc621.jpg) + +![](images/5669d3f207888ef1800b5e197d088c9965851c3c126fbff5062c8010a9ffa6ed.jpg) +(b) LR label 1 + +![](images/cebcffa540743dc37f6207e1ab6a16a2b9d343b1bf6f00044c4b6bc2abefed2f.jpg) +(c) LR label 2 + +![](images/76e816b7c2d4af44d48b49e2d719708774fc768267087e4c53c0e41447de496b.jpg) +(d) LR label 3 + +![](images/91b3f0249601862c2c1d65b5949b1bfe755efa10db9912ec6c8e03f9ad055678.jpg) +(e) LR label 4 + +![](images/30d663c663bcdc848217fc11e04f7642c408818012254253d7484f50670712ad.jpg) +(g) Result 1 + +![](images/e64e18311db668eaa625c21846bc687d73f83fd56d4ea261c7a6c0f8acb09774.jpg) +(h) Result 2 + +![](images/0e54219dfb7281e0fea51a1d3541a22cc56b513efdf0913707c3721bf602c695.jpg) +(i) Result 3 + +![](images/15400ac7f7597c95ab38386d66f2a4900e88319952a4b92b4a459d2a7866fd45.jpg) +(j) Result 4 + +![](images/f4bd38a9c47c25e3dde113cbaa0933c085cfc0d14f9cd6848c5a345a51642873.jpg) +Figure 7. Visual results of Paraformer in the Poland dataset. The demonstration area is one of the training pieces sampled from large-scale training regions. (a-e) the training pairs of HR images (0.5 m/pixel) and four types of LR labels including ESA_GLC (10 m/pixel), FROM_GLc (10 m/pixel), Esri_GLC (10 m/pixel), and GLC_FCS30 (30 m/pixel). (f-g) the ground truth (0.5 m/pixel) and the mapping results of Paraformer with different LR labels. + +![](images/8166721f6f53b0f2b30dae99cbc598957d009f151739a333bd94ecfe8dca20e8.jpg) + +![](images/1097eb77b778eed086425aafc61db41551789087a3715c07bd4730ce8bcfc9ea.jpg) + +![](images/2ef9e140fd12f1016353dce25bb99b7ed1ee17d69f4e905d830af7d3bb7ce408.jpg) + +
Resolution gapMethodmIoU (%) of six states in the Chesapeake Bay watershed
DelawareNew YorkMarylandPennsylvaniaVirginiaWest VirginiaAverage
30×Paraformer65.5771.4370.2060.0468.0152.6264.65
L2HNet [28]61.7768.1265.2458.5269.3955.4363.08
TransUNet [10]53.1560.5360.4251.0866.2147.5256.49
ConViT [18]55.2660.7161.5853.9459.8049.1156.73
CoAtNet [16]56.8962.8361.2553.5765.6751.3458.59
MobileViT[34]58.0361.3261.8455.5357.0448.6457.07
EfficientViT[5]53.7261.2859.4851.3857.3448.7655.33
UNetFormer[48]58.8565.1161.3459.1060.8447.2058.74
DC-Swin[47]59.6565.9958.6058.0664.1148.1559.09
UNet [38]54.1658.7956.4253.2157.3446.1154.34
HRNet [45]52.1156.2150.7650.0357.4845.4252.00
LinkNet [8]58.2762.0552.9652.1148.7148.9353.84
SkipFCN [26]60.9764.8359.4455.3764.7254.6660.00
SSDA [43]57.9161.5454.8551.7157.7147.1555.15
RF [7]59.3555.0355.2651.0752.2954.3654.56
+ +Table 1. The quantitative comparison of the Paraformer and other methods on six states of the Chesapeake Bay watershed. All methods were trained with the 1-m images and 30-m labels. The mIoU (\%) of different methods was calculated between their results and the 1-m ground truth. + +
Max gapLR labelParaformer (ours)mIoU (%) of different methods
L2HNet [28]TransUNet [10]ConViT [18]MobileViT [34]DC-Swin [47]HRNet [45]SkipFCN [26]RF [7]
40×FROM_GLC10 [9]56.5750.1538.4439.3641.0343.5643.6627.1421.48
ESA_GLC10 [44]55.1952.1335.5836.0938.4240.0549.8128.3426.97
Esri_GLC10 [22]55.0750.7837.7938.7838.5039.9146.6528.1819.36
120×GLC_FCS30 [56]49.3943.6226.2029.1629.5730.1441.4623.6717.02
+ +Table 2. The quantitative comparison on the Poland dataset. The mIoU (%) of the Paraformer and other methods that trained with three types of 10-m labels (i.e., FROM_GLCL10, ESA_GLCL10, and Esri_GLCL10) and one type of 30-m label (i.e., GLC_FCS30) are demonstrated. + +when the loss stopped dropping over eight epochs. The metric of mean intersection over union (mIoU) is calculated between the results and the HR ground truths after their land-cover classes are unified into four base classes. The compared methods include: Random Forest (RF) is a pixel-to-pixel method widely used in large-scale land-cover mapping [7]. TransUNet [10], ConViT [18], CoAtNet [16], MobileViT [34], and EfficientViT [5] are CNN-Transformer hy + +brid methods for semantic segmentation. UNetformer [48] and DC-Swin [47] are dedicated CNN-Transformer methods for remote-sensing images. UNet [38], HRNet [45], and LinkNet [8] are typical CNN-based semantic segmentation methods which are widely adopted in HR land-cover mapping [37, 52, 53]. SkipFCN [26] and SSDA [43] are shallow CNN-based methods for updating 1-m land-cover change maps from 30-m labels, which won first and second place + +![](images/e71ae878de8f982c02a4e64ad6f521f886cc3d12a9ff8bfa4cef24f7f12c6fcd.jpg) +(a) Source (1m/pixel) + +![](images/98533551fb2817b555fa7eb67d2dc5f04ffccfaffb2ea4ec411b12a7dbff731c.jpg) +(b) Guide (30m/pixel) + +![](images/a90e67ac8735c6b14ada1bd3191f323d6465a3e41ff2ba6b454049e8393ea001.jpg) +(c) Prediction(1) from the CNN branch + +![](images/3b97701294340fc345022557b737b3083317658a81175f5819eb8a1cc8530230.jpg) +(d) Mask label + +![](images/77ef88ccd697fbbd77fb4f4da23f08a15aa0409bcca2d47a4c5d54163e93a473.jpg) +(e) Mismatch of LR label + +![](images/caff7e7774357df18f7a202fadd16d6f0713bae3c2d26ff8989755151aa8f21e.jpg) +(f) Mismatch of mask label +Tree canopy + +![](images/ab8fc4735b6a364f1c56d774b234984f318d21b790206ff956061fe74e34511f.jpg) +(g) Paraformer +Water + +![](images/3816d83d922694a41c1ca5f0d127943c90a36ebaabb63e4d41eae74f92a496de.jpg) +(h) GT (1m/pixel) + +![](images/1d523fb9ffd99e9805d82dbb32abe3d3c4b9b3d31aef8f428362eff2670556e2.jpg) +Figure 8. Example of training data and different outputs of Paraformer sampled from the Chesapeake Bay dataset with four unified classes. (a) HR images. (b) LR labels. (c) the primal prediction from the CNN branch. (d) Mask label, as the intersection parts of (b) and (c). The black areas are set to void without supervised information. (e–f) the incorrect samples (with pink color) of LR label and mask label. (g) the final results of Paraformer. (h) HR ground truth. + +![](images/5ac1967144410ced333559ef866f388383e7cc085388c1a56f5c677b75a129a3.jpg) + +in the 2021 IEEE GRSS DFC [27]. L2HNet is a state-of-the-art method designed for weakly supervised land-cover mapping [28]. + +# 4.3. Comparison Results + +Comparison on the Chesapeake Bay dataset: Table 1 and Figure 5 show the comparisons on the Chesapeake Bay dataset. From the quantitative results, Paraformer shows superiority in the states of Delaware, New York, Maryland, and Pennsylvania. The L2HNet shows better results in Virginia and West Virginia. On average, Paraformer has the most accurate HR land-cover mapping results over the entire area, with a mIoU of $64.65\%$ . As shown in Figure 5 (c), the visual result of Paraformer is more consistent with the HR image compared with other methods. Unlike the fully supervised semantic segmentation task, the unmatched training pairs can cause serious misguidedness during the model training. E.g., as the rough results shown in Figure 5 (f) and (g), UNet and HRNet over-downsample the features and encourage results to fit LR labels instead of being consistent with the HR images. Furthermore, quantitative results reveal that UNet, LinkNet, and HRNet have insufficient performance, with mIoU of $54.34\%$ , $53.84\%$ , and $52.00\%$ . Although the compared CNN-Transformer methods (e.g., TransUNet) combine local and global contextual information, the structure does not focus on preserving the feature resolution or dealing with the geospatial mismatch. As a result, TransUNet shows a weak performance in visual results, shown in Figure 5 (h), and has a mIoU of $56.49\%$ . Furthermore, SkipFCN, SSDA, and RF use small receptive fields or pixel-to-pixel strategies to ex + +tract features with fine land details. However, due to the lack of deep-level feature representation and global contextual information, SkipFCN, SSDA, and RF obtain a mIoU of $59.99\%$ , $55.15\%$ , and $54.56\%$ , respectively. As an example shown in Figure 5 (e), RF finely predicts ground details but incorrectly classifies rivers, lakes, and pastures. To further demonstrate the effect of Paraformer on different landscapes, we sample six typical areas in Figure 6. The visual results indicate that the complex ground details among various landforms of HR land-cover maps can be well updated from the LR historical land-cover labels. + +Comparison on the Poland dataset: In the experiments with the Poland dataset, all methods were used to produce $0.25 / 0.5$ -m land-cover maps of 14 provinces of Poland by exploiting four LR labels separately. These LR labels include 10-m FROM_GLC10, ESA_GLC10, Esri_GLC10, and 30-m GLC_FCS30. As shown in Table 2, Paraformer is compared with eight representative methods (i.e., weakly supervised, CNN-Transformer, CNN-based, pixel-to-pixel approaches) in a more extreme geospatial mismatch. Compared with the state-of-the-art method, the Paraformer has an increase in mIoU of $6.42\%$ , $3.06\%$ , and $4.29\%$ in exploiting 10-m labels. By resolving 30-m labels with a max resolution gap of $120\times$ , Paraformer has a mIoU of $49.39\%$ with an increase of $5.77\%$ compared with L2HNet. The typical CNN-based method has an average mIoU of $46.71\%$ among the 10-m cases and $41.46\%$ in the 30-m case. Skip_FCN and RF have the lowest mIoU among all methods, which shows the difficulty of dealing with extremely unmatched situations. Moreover, the quantitative results of Paraformer shown in the four cases reveal that the proposed frame + +
Ablation methodmIoU (%) of six states in the Chesapeake Bay watershed
DelawareNew YourMarylandPennsylvaniaVirginiaWest VirginiaAverageParamsFLOPs
Paraformer65.5771.4370.2060.0468.0152.6264.65109.4M141.3G
Sole CNN branch59.5767.8764.3053.8665.2650.0160.154.5M56.1G
Sole Transformer branch53.1560.5360.4251.0866.2247.5256.4996.9M83.3G
Hybrid without PLAT62.6970.3967.1558.3367.4750.8362.81109.4M141.3G
+ +Table 3. The ablation results of the Paraformer on six states of the Chesapeake Bay watershed. The sole CNN branch, sole Transformer branch, and Hybrid without PLAT aim to investigate the contribution of the CNN branch, Transformer branch, and PLAT module, respectively. + +![](images/df9f523b4eaf4ba6ba45a81dd5813642b9d3cace6224107d2dd5f5eaf1840b44.jpg) +(a) 1-m image + +![](images/bd0e7630b9ff14e9c5103b41cfacb4a934ebfd3a407008303812bf21258d8c13.jpg) +(b) CNN-branch context + +![](images/e9827db31527091a470156b00054916d6007b23ac1ff94b1e4bd8828187c48bc.jpg) +(c) Transformer-branch context +Figure 9. Demonstration of the extracted contexts from the ablation methods. (a) the original HR image. (b) the contexts extracted by the sole CNN branch. (c) the contexts extracted by the sole Transformer branch. (d) the contexts extracted by the CNN-Transformer hybrid backbone. + +![](images/daa5eb2d357136b5303c7a7f7783d901b98100f4eea0282112326779e440279c.jpg) +(d) Hybrid-structure context + +work obtains stable results from different LR labels. Figure 7 shows the visual results of Paraformer among four cases. With the parallel CNN-Transformer structure and PLAT module, Paraformer is able to refine the clear ground details (e.g., vegetation and roads) even if they are roughly labeled in local areas. In general, Paraformer shows the potential to robustly update large-scale HR land-cover maps from available LR historical labels. + +# 4.4. Ablation experiments + +In this section, ablation experiments were conducted on the Chesapeake Bay dataset to evaluate different components of Paraformer. Each ablation in Table 3 is explained as follows: (1) the sole CNN branch is dependently trained by calculating CE loss with LR labels; (2) the sole Transformer branch embeds HR images instead of features from the CNN branch and calculates CE loss with LR labels; (3) the hybrid structure without PLAT directly calculates CE loss with the LR labels. + +By ablating the PLAT module, the results obtained an average mIoU of $62.81\%$ , which indicates a $1.84\%$ decrease compared with the $64.65\%$ of Paraformer. By ablating the CNN and Transformer branches, the results of the sole CNN branch obtained a mIoU of $60.15\%$ and had a $4.5\%$ decrease. Results of the sole Transformer branch obtained the lowest mIoU of $56.49\%$ and had the most obvious decrease $(8.16\%)$ . Figure 8 shows different outputs of Paraformer, + +where the inexact LR labels are gradually refined during framework training. The final result shown in Figure 8 (g) indicates both fine ground details and accurate land-cover patterns that are consistent with the ground truth. Moreover, Figure 9 shows the visualized contexts captured by the CNN branch, Transformer branch, and hybrid structure. Figure 9 (b) indicates that the CNN branch mostly focuses on capturing local details (e.g., the edges of roads, single houses, and shrubs). Figure 9 (c) indicates that the Transformer branch captures the feature in object scale, focusing on intact land objects of building areas and parking spots. The hybrid structure shows a strong response to the obvious objects with both fine edges and intact areas. + +In general, the ablation results demonstrate two findings: (1) The PLAT module can stably optimize the framework training and reasonably exploit the LR labels during the large-scale HR land-cover mapping process. (2) The parallel CNN and Transformer branches are indispensable parts of the framework, which construct a more robust feature extractor to bridge local and global contextual information. + +# 5. Conclusion + +In this paper, a weakly supervised CNN-Transformer framework, Paraformer, is proposed to update large-scale HR land-cover maps in an HR-label-free, end-to-end manner. Experiments on two datasets show that Paraformer outperforms other approaches in guiding semantic segmentation of large-scale HR remote-sensing images with easy-access LR land-cover data. Further analysis reveals that the Paraformer can robustly adapt various landforms of wide-span areas and stably exploit different LR labels in producing accurate HR land-cover maps. The ablation studies demonstrate the effectiveness of the parallel CNN-Transformer structure and the PLAT module. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 4299-4309, 2022. 2 \ No newline at end of file diff --git a/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/images.zip b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..6cc00feb105473b088d8b1a469a8caae6d5ccf3f --- /dev/null +++ b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:d4e6edd8626df06134758742df4fb74b9502c4dccd2c385679d92107992db359 +size 1201505 diff --git a/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/layout.json b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..7ee2b7617f73b23606362f91a872733c1e25ff91 --- /dev/null +++ b/2024/Learning without Exact Guidance_ Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels/layout.json @@ -0,0 +1,10309 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 53, + 103, + 541, + 140 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 103, + 541, + 140 + ], + "spans": [ + { + "bbox": [ + 53, + 103, + 541, + 140 + ], + "type": "text", + "content": "Learning without Exact Guidance: Updating Large-scale High-resolution Land Cover Maps from Low-resolution Historical Labels" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "spans": [ + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "text", + "content": "Zhuohong " + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "inline_equation", + "content": "\\mathsf{Li}^{1*}" + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "text", + "content": ", Wei " + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "inline_equation", + "content": "\\mathsf{He}^{1*}" + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "text", + "content": ", Jiepan " + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "inline_equation", + "content": "\\mathsf{Li}^1" + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "text", + "content": ", Fangxiao " + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "inline_equation", + "content": "\\mathsf{Lu}^1" + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "text", + "content": ", Hongyan Zhang" + }, + { + "bbox": [ + 120, + 160, + 471, + 175 + ], + "type": "inline_equation", + "content": "^{1,2\\dagger}" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 161, + 175, + 432, + 190 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 161, + 175, + 432, + 190 + ], + "spans": [ + { + "bbox": [ + 161, + 175, + 432, + 190 + ], + "type": "text", + "content": "1Wuhan University 2China University of Geosciences" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 83, + 191, + 504, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 83, + 191, + 504, + 204 + ], + "spans": [ + { + "bbox": [ + 83, + 191, + 504, + 204 + ], + "type": "text", + "content": "{ashelee, weihe1990, jiepanli, fangxiaolu}@whu.edu.cn, zhanghongyan@cug.edu.cn" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 143, + 231, + 192, + 243 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 231, + 192, + 243 + ], + "spans": [ + { + "bbox": [ + 143, + 231, + 192, + 243 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 256, + 290, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 256, + 290, + 533 + ], + "spans": [ + { + "bbox": [ + 46, + 256, + 290, + 533 + ], + "type": "text", + "content": "Large-scale high-resolution (HR) land-cover mapping is a vital task to survey the Earth's surface and resolve many challenges facing humanity. However, it is still a nontrivial task hindered by complex ground details, various landforms, and the scarcity of accurate training labels over a wide-span geographic area. In this paper, we propose an efficient, weakly supervised framework (Paraformer) to guide large-scale HR land-cover mapping with easy-access historical land-cover data of low resolution (LR). Specifically, existing land-cover mapping approaches reveal the dominance of CNNs in preserving local ground details but still suffer from insufficient global modeling in various landforms. Therefore, we design a parallel CNN-Transformer feature extractor in Paraformer, consisting of a downsampling-free CNN branch and a Transformer branch, to jointly capture local and global contextual information. Besides, facing the spatial mismatch of training data, a pseudo-label-assisted training (PLAT) module is adopted to reasonably refine LR labels for weakly supervised semantic segmentation of HR images. Experiments on two large-scale datasets demonstrate the superiority of Paraformer over other state-of-the-art methods for automatically updating HR land-cover maps from LR historical labels." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 558, + 128, + 571 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 558, + 128, + 571 + ], + "spans": [ + { + "bbox": [ + 47, + 558, + 128, + 571 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 578, + 287, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 578, + 287, + 675 + ], + "spans": [ + { + "bbox": [ + 46, + 578, + 287, + 675 + ], + "type": "text", + "content": "Land-cover mapping is a semantic segmentation task that gives each pixel of remote-sensing images a land-cover class such as \"cropland\" or \"building\" [14]. The land-cover data should be continuously updated since nature and human activities frequently change the landscape [37]. As sensors and satellites developed, massive high-resolution (HR) remote-sensing images (" + }, + { + "bbox": [ + 46, + 578, + 287, + 675 + ], + "type": "inline_equation", + "content": "\\leq 1" + }, + { + "bbox": [ + 46, + 578, + 287, + 675 + ], + "type": "text", + "content": " meter/pixel) could be easily obtained [1]. Rapid large-scale HR land-cover map" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 308, + 232, + 545, + 415 + ], + "blocks": [ + { + "bbox": [ + 308, + 232, + 545, + 415 + ], + "lines": [ + { + "bbox": [ + 308, + 232, + 545, + 415 + ], + "spans": [ + { + "bbox": [ + 308, + 232, + 545, + 415 + ], + "type": "image", + "image_path": "0de6bd4d0462bf8c96115bc0b558cb70c0cd3568bbb7d49692fff76d4baf143b.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 418, + 547, + 448 + ], + "lines": [ + { + "bbox": [ + 305, + 418, + 547, + 448 + ], + "spans": [ + { + "bbox": [ + 305, + 418, + 547, + 448 + ], + "type": "text", + "content": "Figure 1. Illustration of resolution mismatched issue in using the HR remote-sensing image (Source) and LR historical labels (Guide) to generate HR land-cover results (Target)." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 460, + 545, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 545, + 533 + ], + "type": "text", + "content": "ping is even more critical to facilitate downstream applications as the up-to-date HR land-cover data can accurately describe the land surface [21, 27, 55]. However, the complex ground details reflected by HR images and various landforms over wide-span areas still challenge the periodic updating of large-scale HR land-cover maps [28]." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 534, + 546, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 546, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 546, + 715 + ], + "type": "text", + "content": "The advanced methods for HR land-cover mapping have been dominated by the convolutional neural network (CNN) for many years. Although CNN-based models can finely capture local details for semantic segmentation of HR images, the intrinsic locality of convolution operations still limits their implementation in various landforms across larger areas [2]. Recently, Transformer has achieved tremendous success in semantic segmentation [5, 18, 34] and large-scale applications of Earth observation [11, 41, 48]. It adopts multi-head self-attention mechanisms to model global contexts but struggles in the representation of local details due to the shortage of low-level features [10, 48]. Besides, current methods with either CNN or Transformer structures generally rely on sufficient exact training labels by adopting a fully supervised strategy" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 683, + 287, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 683, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 683, + 287, + 712 + ], + "type": "text", + "content": "*Indicates equal contribution. †Corresponding author. The code and data are released at https://github.com/LiZhuoHong/Paraformer" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27717" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 88, + 70, + 244, + 132 + ], + "blocks": [ + { + "bbox": [ + 88, + 70, + 244, + 132 + ], + "lines": [ + { + "bbox": [ + 88, + 70, + 244, + 132 + ], + "spans": [ + { + "bbox": [ + 88, + 70, + 244, + 132 + ], + "type": "image", + "image_path": "22b7d38cf58280c9649a725065a17606c526bac7804888b12ba22f040f85aa84.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 139, + 133, + 194, + 141 + ], + "lines": [ + { + "bbox": [ + 139, + 133, + 194, + 141 + ], + "spans": [ + { + "bbox": [ + 139, + 133, + 194, + 141 + ], + "type": "text", + "content": "(a) Existing mode" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 88, + 144, + 244, + 206 + ], + "blocks": [ + { + "bbox": [ + 88, + 144, + 244, + 206 + ], + "lines": [ + { + "bbox": [ + 88, + 144, + 244, + 206 + ], + "spans": [ + { + "bbox": [ + 88, + 144, + 244, + 206 + ], + "type": "image", + "image_path": "5b674f92572eb55929905f410c2415fbf85fb93048caf6667e42aac433a6a98d.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 113, + 207, + 220, + 215 + ], + "lines": [ + { + "bbox": [ + 113, + 207, + 220, + 215 + ], + "spans": [ + { + "bbox": [ + 113, + 207, + 220, + 215 + ], + "type": "text", + "content": "(b) HR-label-free, end-to-end mode" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 219, + 287, + 258 + ], + "lines": [ + { + "bbox": [ + 46, + 219, + 287, + 258 + ], + "spans": [ + { + "bbox": [ + 46, + 219, + 287, + 258 + ], + "type": "text", + "content": "Figure 2. Two modes of large-scale HR land-cover mapping with LR labels. (a) Existing modes either reply on partial HR labels or require non-end-to-end training with human interventions. (b) Paraformer aims to form a mode that is HR-label-free and end-to-end trainable." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 270, + 287, + 305 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 270, + 287, + 305 + ], + "spans": [ + { + "bbox": [ + 46, + 270, + 287, + 305 + ], + "type": "text", + "content": "[20, 32, 39]. However, creating accurate HR land-cover labels for large-scale geographic areas is extremely time-consuming and laborious [6, 37]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 306, + 287, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 306, + 287, + 437 + ], + "spans": [ + { + "bbox": [ + 46, + 306, + 287, + 437 + ], + "type": "text", + "content": "Fortunately, many low-resolution (LR) land-cover data with large coverage have already emerged in the past decades [9, 22, 44, 56]. Utilizing these LR historical land-cover data as alternative guidance is a way to alleviate the scarcity of HR labels [29]. Nevertheless, the unmatched training pairs of HR images and inexact LR labels posed a challenge for fully supervised methods. Moreover, due to the different applied scenarios, existing weakly supervised semantic segmentation methods for natural scenes (e.g., learning from bounding box or image-level labels) are not applicable in handling the challenge as well [15, 23, 24, 57]." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "text", + "content": "Distinctively, the incorrect samples of LR land-cover labels are brought by satellites in different spatial resolutions during Earth observation. As shown in Figure 1, the objects in a " + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "inline_equation", + "content": "60m \\times 60m" + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "text", + "content": " area can be clearly observed from the HR (1 m/pixel) image " + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\mathbf{X}" + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "text", + "content": ". However, in the LR (30 m/pixel) label " + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\mathbf{Y}" + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "text", + "content": ", the area is only labeled by four pixels. To produce the 1-m land-cover result " + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{Y}}" + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "text", + "content": ", a labeled pixel " + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "inline_equation", + "content": "y_{1}" + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "text", + "content": " needs to provide guiding information for 900 target pixels " + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\{\\hat{y}_1, \\hat{y}_2 \\dots \\hat{y}_{900}\\}" + }, + { + "bbox": [ + 46, + 437, + 287, + 616 + ], + "type": "text", + "content": ", which raises a serious geospatial mismatch. How to reasonably exploit LR labels as the only guidance for semantic segmentation of large-scale HR satellite images is a particular problem shared in the fields of Earth observation and computer vision [28, 31, 37]. By summarizing the state-of-the-art methods of exploiting LR labels for large-scale HR land-cover mapping, there are still two main problems:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 618, + 286, + 712 + ], + "type": "list", + "angle": 0, + "index": 10, + "blocks": [ + { + "bbox": [ + 47, + 618, + 286, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 618, + 286, + 664 + ], + "spans": [ + { + "bbox": [ + 47, + 618, + 286, + 664 + ], + "type": "text", + "content": "1. For the wide-span application areas, existing feature extractors are difficult to jointly capture local details from HR images and model global contexts in various landforms at once [29, 54]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 666, + 286, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 666, + 286, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 666, + 286, + 712 + ], + "type": "text", + "content": "2. For the mismatch of training pairs, existing pipelines, as shown in Figure 2 (a), either still rely on partial HR labels or require non-end-to-end optimization with human interventions [12, 27]." + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 304, + 72, + 545, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 179 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 179 + ], + "type": "text", + "content": "To resolve these problems, as shown in Figure 2 (b), we propose the Paraformer as an HR-label-free, end-to-end framework to guide large-scale HR land-cover mapping with LR land-cover labels. Specifically, Paraformer parallelly hybrids a downsampling-free CNN branch with a Transformer branch to jointly capture local and global contexts from the large-scale HR images and adopts a pseudolabel-assisted training (PLAT) module to dig up reliable information from LR labels for framework training." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 181, + 545, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 181, + 545, + 348 + ], + "spans": [ + { + "bbox": [ + 304, + 181, + 545, + 348 + ], + "type": "text", + "content": "The main contributions of this study are summarized as follows: (a) We introduce an efficient, weakly supervised Paraformer to facilitate large-scale HR land-cover mapping by getting rid of the well-annotated HR labels and human interventions during framework training; (b) a downsampling-free CNN branch is parallelly hybridized with a Transformer branch to capture features with both high spatial resolution and deep-level representation. The structure aims to globally adapt large-scale, various landforms and locally preserve HR ground details; (c) the PLAT module iteratively intersects primal predictions and LR labels to constantly refine labeled samples for guiding the framework training. It provides a concise way to update large-scale HR land-cover maps from LR historical data." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 357, + 392, + 370 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 357, + 392, + 370 + ], + "spans": [ + { + "bbox": [ + 306, + 357, + 392, + 370 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 378, + 545, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 378, + 545, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 378, + 545, + 653 + ], + "type": "text", + "content": "Land-cover mapping approach: In the early stage, pixel-to-pixel classification methods, such as decision tree [19], random forest [7], and support vector machine [40], were popular in the land-cover mapping of multi-spectral LR images. However, these methods generally ignore contextual information and have fragmented results in HR cases, as optical HR images contain abundant spatial details but limited spectral features [29]. With the development of data-driven semantic segmentation, many CNN-based models were widely used in land-cover mapping of HR images [37, 52, 53]. Besides, as an alternative architecture, Transformer shows great power in capturing global contexts with sequence-to-sequence modeling [3, 10, 30] and demonstrates outstanding performance in many large-scale applications of Earth observation, such as building extraction [25, 41], road detection [11], and land-object classification [47]. Besides, many works developed new ways by saving labor to produce finer labels with the Segment Anything Model (SAM) [35, 50]. However, sufficient exact training labels are the foundation for large-scale applications of both CNN- and Transformer-based methods. The scarcity of HR labels still impedes these fully supervised approaches from large-scale HR land-cover mapping." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": "Land-cover labeled data: Creating large-scale HR labels via manual and semi-manual annotations is extremely time-consuming and expensive [17, 36]. Therefore, exiting HR land-cover data is generally limited to small scales. E.g., the LoveDA dataset contains " + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "inline_equation", + "content": "0.3\\mathrm{-m}" + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": " land-cover data, covering" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "27718" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 109, + 70, + 487, + 300 + ], + "blocks": [ + { + "bbox": [ + 109, + 70, + 487, + 300 + ], + "lines": [ + { + "bbox": [ + 109, + 70, + 487, + 300 + ], + "spans": [ + { + "bbox": [ + 109, + 70, + 487, + 300 + ], + "type": "image", + "image_path": "48ec693be6caeb544f4d9d62e1c0b008de968d41a23628aefdfd3283e6301c6c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 306, + 546, + 327 + ], + "lines": [ + { + "bbox": [ + 46, + 306, + 546, + 327 + ], + "spans": [ + { + "bbox": [ + 46, + 306, + 546, + 327 + ], + "type": "text", + "content": "Figure 3. Overall workflow of Paraformer. The framework only takes the HR images and LR labels as training input and includes three components: (a) CNN-based resolution-preserving branch, (b) Transformer-based global-modeling branch, and (c) Pseudo-Label-Assisted Training (PLAT) module." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 336, + 289, + 468 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 336, + 289, + 468 + ], + "spans": [ + { + "bbox": [ + 46, + 336, + 289, + 468 + ], + "type": "text", + "content": "536.15 " + }, + { + "bbox": [ + 46, + 336, + 289, + 468 + ], + "type": "inline_equation", + "content": "km^2" + }, + { + "bbox": [ + 46, + 336, + 289, + 468 + ], + "type": "text", + "content": " of China [46]. The Agri-vision dataset contained 0.1-m labeled data, covering " + }, + { + "bbox": [ + 46, + 336, + 289, + 468 + ], + "type": "inline_equation", + "content": "560~km^2" + }, + { + "bbox": [ + 46, + 336, + 289, + 468 + ], + "type": "text", + "content": " of the USA [13]. In the contract, the LR land-cover data generally has a larger coverage. E.g., the United States Geological Survey cyclically updates 30-m land-cover data covering the whole USA [49]. The European Space Agency (ESA) has updated an annual 10-m global land-cover data since 2020 [44]. These LR data can be seen as an alternative label source for guiding large-scale HR land-cover mapping. However, massive in exactly labeled samples still hinder them from being practicable." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "text", + "content": "Strategies for LR historical label mining: To alleviate the scarcity of accurate labels in large-scale HR land-cover mapping, many studies have made efforts to mine reliable information from LR labels. E.g., a label super-resolution network was designed to constrain the inexact parts of LR labels by using the statistical distribution inferred from HR labels [31, 37]. A multi-stage framework, named WESUP, was built for " + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "inline_equation", + "content": "10\\mathrm{-m}" + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "text", + "content": " land-cover mapping with " + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "inline_equation", + "content": "30\\mathrm{-m}" + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "text", + "content": " labels [12]. In WESUP, multi-models were trained to refine clean samples from LR labels. Similarly, the winner approach of the 2021 IEEE GRSS Data Fusion Contest (DFC) deployed a shallow CNN to refine the " + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "inline_equation", + "content": "30\\mathrm{-m}" + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "text", + "content": " labels, and then multi-model were trained with pseudo-labels to create the " + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "inline_equation", + "content": "1\\mathrm{-m}" + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "text", + "content": " land-cover map of Maryland, USA [27]. Moreover, a low-to-high network (L2HNet) was proposed to select confident parts of LR labels via weakly supervised loss functions [28]. To produce " + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "inline_equation", + "content": "1\\mathrm{-m}" + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "text", + "content": " land-cover maps across China with available " + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "inline_equation", + "content": "10\\mathrm{-m}" + }, + { + "bbox": [ + 46, + 468, + 289, + 696 + ], + "type": "text", + "content": " labels, seven L2HNets were selectively trained to adapt wide-span geographic areas [29]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 59, + 701, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 701, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 59, + 701, + 288, + 714 + ], + "type": "text", + "content": "Different from these approaches that either still rely on" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 305, + 337, + 547, + 374 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 337, + 547, + 374 + ], + "spans": [ + { + "bbox": [ + 305, + 337, + 547, + 374 + ], + "type": "text", + "content": "partial HR labels or require human interventions, Pafaromer is designed as an HR-label-free end-to-end framework to facilitate large-scale HR land-cover mapping." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 381, + 389, + 396 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 381, + 389, + 396 + ], + "spans": [ + { + "bbox": [ + 306, + 381, + 389, + 396 + ], + "type": "text", + "content": "3. Methodology" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 402, + 546, + 462 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 402, + 546, + 462 + ], + "spans": [ + { + "bbox": [ + 305, + 402, + 546, + 462 + ], + "type": "text", + "content": "To jointly capture local and global contexts and reasonably exploit LR labels for large-scale HR land-cover mapping, Paraformer combines parallel CNN and Transformer branches with a PLAT module. In this section, the three components are introduced sequentially." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 468, + 522, + 480 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 468, + 522, + 480 + ], + "spans": [ + { + "bbox": [ + 305, + 468, + 522, + 480 + ], + "type": "text", + "content": "3.1. CNN-based resolution-preserving branch" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "text", + "content": "As a basic feature extractor of Paraformer and also the main structure of previous L2HNet V1 [28], the CNN branch is designed to capture local contexts from HR images and preserve the spatial details by preventing feature downsampling. As shown in Figure 3 (a), the CNN branch is constructed by five serially connected resolution-preserving (RP) blocks. Each RP block contains parallel convolution layers with the sizes of " + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "inline_equation", + "content": "1 \\times 1" + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "inline_equation", + "content": "3 \\times 3" + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "inline_equation", + "content": "5 \\times 5" + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "text", + "content": ", whose steps are set to 1 for feature size maintaining. Partly similar to the inception module [42], the channel numbers of different scales' layers in each block are inversely proportional to their kernel sizes, which are set to 128, 64, and 32. Based on the setting, the RP blocks can capture features with a proper receptive field instead of downsampling the feature maps with a deep encoder-decoder pattern. The serial blocks aim at sufficiently preserving the spatial resolution of features by using the majority of " + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "inline_equation", + "content": "1 \\times 1" + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "text", + "content": " kernels. The " + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "inline_equation", + "content": "3 \\times 3" + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "inline_equation", + "content": "5 \\times 5" + }, + { + "bbox": [ + 304, + 486, + 547, + 715 + ], + "type": "text", + "content": " kernels capture necessary surrounding information. Furthermore, the multi-scale feature maps are" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27719" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 72, + 286, + 277 + ], + "blocks": [ + { + "bbox": [ + 49, + 72, + 286, + 277 + ], + "lines": [ + { + "bbox": [ + 49, + 72, + 286, + 277 + ], + "spans": [ + { + "bbox": [ + 49, + 72, + 286, + 277 + ], + "type": "image", + "image_path": "9075bbdad61d2a8a8a84992ed0af9912a38b871ab6fc414d2bb8c17a63241004.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 280, + 288, + 319 + ], + "lines": [ + { + "bbox": [ + 47, + 280, + 288, + 319 + ], + "spans": [ + { + "bbox": [ + 47, + 280, + 288, + 319 + ], + "type": "text", + "content": "Figure 4. Example of the local mismatch/match in two regions. The edge of water is marked with yellow boundaries. Region 1 shows dispersed lakes around urban areas with unmatched annotation. Region 2 shows a large-scale river with matched annotation." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 327, + 287, + 364 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 327, + 287, + 364 + ], + "spans": [ + { + "bbox": [ + 47, + 327, + 287, + 364 + ], + "type": "text", + "content": "concatenated and reduced to 128 channels for branch lightening. Besides, a shortcut connection is adopted between blocks for residual learning and detail preserving." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 370, + 274, + 384 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 370, + 274, + 384 + ], + "spans": [ + { + "bbox": [ + 47, + 370, + 274, + 384 + ], + "type": "text", + "content": "3.2. Transformer-based global-modeling branch" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 389, + 287, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 389, + 287, + 664 + ], + "spans": [ + { + "bbox": [ + 47, + 389, + 287, + 664 + ], + "type": "text", + "content": "The ground objects with the same land-cover class may have distinctive attributes in HR images and are differently annotated in LR labels. Figure 4 shows typical cases of lakes and rivers located in different areas. By considering that the CNN branch with intrinsic locality hinders the adaptation of various landforms over large-scale areas, we further hybrid the CNN branch with a Transformer branch which aims at capturing global contexts and building long-range support among dispersed geographic areas. As shown in Figure 3 (b), the Transformer branch contains 12 transformer layers. Each layer includes layer normalization, multi-head self-attention, and multi-layer perception. The feature maps extracted by each RP block are concatenated and inputted to the Transformer branch. Specifically, the extracted features from the CNN branch are downsampled and embedded in a hidden feature layer. And then the Transformer branch encodes the dense feature patches to capture global contexts. Subsequently, the encoded features are constantly upsampled to the size of HR images and classified to the final results. During the upsampling process, the outputted features of each stage are concatenated with the pre-encoded features, which bring massive local contextual information to the final feature maps." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 671, + 257, + 685 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 671, + 257, + 685 + ], + "spans": [ + { + "bbox": [ + 47, + 671, + 257, + 685 + ], + "type": "text", + "content": "3.3. Pseudo-Label-Assisted Training module" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": "To reasonably guide the large-scale HR land-cover mapping with weak LR labels, as shown in Figure 3 (c), a weakly" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": "supervised PLAT module is adopted to optimize the framework training. The PLAT module aims to screen out uncertain samples and dig up reliable information from the LR labels. Specifically, the two parts of the PLAT module are explained as follows. For the CNN branch, we use classifier" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "^{(1)}" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": ", which is constructed by " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "3 \\times 3" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " convolution layers, to generate the primal prediction" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "^{(1)}" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " based on the extracted HR feature maps. Then we calculate the Cross-Entropy (CE) loss between prediction" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "^{(1)}" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": ", represented as " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{Y}}'" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": ", and the LR label, represented as " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "\\mathbf{Y}" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": ". Formally, by regarding " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "H" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "W" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 304, + 72, + 547, + 216 + ], + "type": "text", + "content": " as the height, weight, and land-cover class of the patch, the CE loss of the CNN branch is written as:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 328, + 224, + 545, + 253 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 328, + 224, + 545, + 253 + ], + "spans": [ + { + "bbox": [ + 328, + 224, + 545, + 253 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {c e}} (\\mathbf {Y}, \\hat {\\mathbf {Y}} ^ {\\prime}) = \\frac {\\sum_ {i = 0} ^ {W} \\sum_ {j = 0} ^ {H} \\left[ \\sum_ {l = 1} ^ {L} y _ {i j} ^ {(l)} \\log \\left(\\hat {y} _ {i j} ^ {\\prime (l)}\\right) \\right]}{H \\times W}. \\tag {1}", + "image_path": "adbc9c65e3e681877b648444f43d7b8a6bb6c7a78a0e1a15b5319017ce383fa7.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "spans": [ + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "text", + "content": "As the final output of the framework, prediction" + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "inline_equation", + "content": "^{(2)}" + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "text", + "content": " is classified from the concatenated feature maps of CNN and Transformer branches, which is represented as " + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{Y}}''" + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "text", + "content": ". During each training iteration, we take the simple but effective intersection of prediction" + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "inline_equation", + "content": "^{(1)}" + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "text", + "content": " and LR label to generate mask labels. Specifically, the inconsistent samples in mask labels are set as void values to remove them from loss calculations. Moreover, since predictions of the CNN branch contain HR textual information that is highly consistent with the images, the mask labels also outline fine edges and retain stable labeled samples. Finally, the proposed Mask-Cross-Entropy (MCE) loss is calculated between prediction" + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "inline_equation", + "content": "^{(2)}" + }, + { + "bbox": [ + 304, + 262, + 547, + 418 + ], + "type": "text", + "content": " and mask labels. Formally, the MCE loss is written as:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 307, + 426, + 545, + 464 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 307, + 426, + 545, + 464 + ], + "spans": [ + { + "bbox": [ + 307, + 426, + 545, + 464 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {m c e}} (\\mathbf {M} \\cdot \\mathbf {Y}, \\hat {\\mathbf {Y}} ^ {\\prime \\prime}) = \\frac {\\sum_ {i = 0} ^ {W} \\sum_ {j = 0} ^ {H} \\left[ \\sum_ {l = 1} ^ {L} y _ {i j} ^ {(l)} m _ {i j} \\log \\left(\\hat {y} _ {i j} ^ {\\prime \\prime (l)}\\right) \\right]}{\\operatorname {S u m} (\\mathbf {M} (i , j) = 1)}. \\tag {2}", + "image_path": "78628c98adf5bdb26d3295e183c70713d93cc60c273f4eaf152fb995005b73d7.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "spans": [ + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "text", + "content": "In Eqs. 2, " + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "inline_equation", + "content": "\\mathbf{M}" + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "text", + "content": " is the intersected mask with the size of " + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "inline_equation", + "content": "H\\times W" + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "inline_equation", + "content": "m_{ij},i\\in [0,H],j\\in [0,W]" + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "text", + "content": " is the element of " + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "inline_equation", + "content": "\\mathbf{M}(i,j)" + }, + { + "bbox": [ + 306, + 465, + 545, + 502 + ], + "type": "text", + "content": " which can be simply represented as:" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 375, + 509, + 545, + 533 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 375, + 509, + 545, + 533 + ], + "spans": [ + { + "bbox": [ + 375, + 509, + 545, + 533 + ], + "type": "interline_equation", + "content": "m _ {i j} = \\left\\{ \\begin{array}{l l} 1 | Y _ {i j} = Y ^ {\\prime} _ {i j} \\\\ 0 | Y _ {i j} \\neq Y ^ {\\prime} _ {i j}. \\end{array} \\right. \\tag {3}", + "image_path": "54b009669e0bdd25b04c2a634faaf12c5fe67b8588bd228565d40aaf86c62fff.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 540, + 545, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 540, + 545, + 564 + ], + "spans": [ + { + "bbox": [ + 305, + 540, + 545, + 564 + ], + "type": "text", + "content": "The total loss of the Paraformer is the combination of two branches' losses, which is written as:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 383, + 574, + 545, + 586 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 383, + 574, + 545, + 586 + ], + "spans": [ + { + "bbox": [ + 383, + 574, + 545, + 586 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {t o t a l}} = \\mathcal {L} _ {\\mathrm {c e}} + \\mathcal {L} _ {\\mathrm {m c e}}. \\tag {4}", + "image_path": "f987cc8821813bf575773980aa95d522e8b816efcd9c69e9dc2d1cea3f30a22f.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 596, + 388, + 609 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 596, + 388, + 609 + ], + "spans": [ + { + "bbox": [ + 306, + 596, + 388, + 609 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 616, + 455, + 628 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 616, + 455, + 628 + ], + "spans": [ + { + "bbox": [ + 306, + 616, + 455, + 628 + ], + "type": "text", + "content": "4.1. Study areas and using data" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 630, + 545, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 545, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 545, + 665 + ], + "type": "text", + "content": "To comprehensively evaluate Paraformer on various landforms and different LR labels, the experiments are conducted on two large-scale datasets." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": "The Chesapeake Bay dataset is sampled from the largest estuary in the USA and organized into 732 non-overlapping tiles, where each tile has a size of " + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "inline_equation", + "content": "6000 \\times 7500" + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": " pixels [37]. 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Demonstration of the training data and visual comparisons of the Paraformer and other typical methods on the Chesapeake Bay dataset with 16 classes. (a) HR image. (b) LR label. (c) land-cover mapping result of Paraformer. (d-h) land-cover mapping results of five typical methods." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 16 + }, + { + "type": "image", + "bbox": [ + 57, + 317, + 541, + 507 + ], + "blocks": [ + { + "bbox": [ + 57, + 317, + 541, + 507 + ], + "lines": [ + { + "bbox": [ + 57, + 317, + 541, + 507 + ], + "spans": [ + { + "bbox": [ + 57, + 317, + 541, + 507 + ], + "type": "image", + "image_path": "8c77fd3ad40212a2cce100e7e5b740aeb468749545ed4f2858ff79d82b3aff0f.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 127, + 508, + 137, + 516 + ], + "lines": [ + { + "bbox": [ + 127, + 508, + 137, + 516 + ], + "spans": [ + { + "bbox": [ + 127, + 508, + 137, + 516 + ], + "type": "text", + "content": "(a)" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 200, + 509, + 210, + 516 + ], + "lines": [ + { + "bbox": [ + 200, + 509, + 210, + 516 + ], + "spans": [ + { + "bbox": [ + 200, + 509, + 210, + 516 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 276, + 509, + 285, + 516 + ], + "lines": [ + { + "bbox": [ + 276, + 509, + 285, + 516 + ], + "spans": [ + { + "bbox": [ + 276, + 509, + 285, + 516 + ], + "type": "text", + "content": "(c)" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 350, + 509, + 359, + 516 + ], + "lines": [ + { + "bbox": [ + 350, + 509, + 359, + 516 + ], + "spans": [ + { + "bbox": [ + 350, + 509, + 359, + 516 + ], + "type": "text", + "content": "(d)" + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 424, + 509, + 433, + 516 + ], + "lines": [ + { + "bbox": [ + 424, + 509, + 433, + 516 + ], + "spans": [ + { + "bbox": [ + 424, + 509, + 433, + 516 + ], + "type": "text", + "content": "(e)" + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 516, + 546, + 535 + ], + "lines": [ + { + "bbox": [ + 46, + 516, + 546, + 535 + ], + "spans": [ + { + "bbox": [ + 46, + 516, + 546, + 535 + ], + "type": "text", + "content": "Figure 6. Six typical areas with finer observation scale on the Chesapeake Bay dataset. The first row shows the LR labels (Guide). The second row shows the HR images (Source). Third row shows the HR results (Target) produced by Paraformer." + } + ] + } + ], + "index": 24, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "bbox": [ + 47, + 546, + 287, + 653 + ], + "type": "list", + "angle": 0, + "index": 28, + "blocks": [ + { + "bbox": [ + 47, + 546, + 287, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 546, + 287, + 593 + ], + "spans": [ + { + "bbox": [ + 47, + 546, + 287, + 593 + ], + "type": "text", + "content": "1. The HR images (1 m/pixel) are from the U.S. Department of Agriculture's National Agriculture Imagery Program (NAIP). The images contained four bands of red, green, blue, and near-infrared [33]." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 47, + 594, + 287, + 629 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 594, + 287, + 629 + ], + "spans": [ + { + "bbox": [ + 47, + 594, + 287, + 629 + ], + "type": "text", + "content": "2. The LR historical labels (30 m/pixel) are from the USGS's National Land Cover Database (NLCD) [49], including 16 land-cover classes." + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 47, + 630, + 286, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 630, + 286, + 653 + ], + "spans": [ + { + "bbox": [ + 47, + 630, + 286, + 653 + ], + "type": "text", + "content": "3. The ground truths (1 m/pixel) are from the Chesapeake Bay Conservancy Land Cover (CCLC) project." + } + ] + } + ], + "index": 27 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 46, + 659, + 287, + 695 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 659, + 287, + 695 + ], + "spans": [ + { + "bbox": [ + 46, + 659, + 287, + 695 + ], + "type": "text", + "content": "The Poland dataset contains 14 provinces of Poland and is organized into 403 non-overlapping tiles, where each tile has a size of " + }, + { + "bbox": [ + 46, + 659, + 287, + 695 + ], + "type": "inline_equation", + "content": "1024 \\times 1024" + }, + { + "bbox": [ + 46, + 659, + 287, + 695 + ], + "type": "text", + "content": " pixels. The specific data includes:" + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 47, + 701, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 701, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 701, + 287, + 713 + ], + "type": "text", + "content": "1. The HR images (0.25m and 0.5 m/pixel) are from the" + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 317, + 546, + 545, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 546, + 545, + 569 + ], + "spans": [ + { + "bbox": [ + 317, + 546, + 545, + 569 + ], + "type": "text", + "content": "LandCover.ai [4] dataset. 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Visual results of Paraformer in the Poland dataset. The demonstration area is one of the training pieces sampled from large-scale training regions. (a-e) the training pairs of HR images (0.5 m/pixel) and four types of LR labels including ESA_GLC (10 m/pixel), FROM_GLc (10 m/pixel), Esri_GLC (10 m/pixel), and GLC_FCS30 (30 m/pixel). 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Resolution gapMethodmIoU (%) of six states in the Chesapeake Bay watershed
DelawareNew YorkMarylandPennsylvaniaVirginiaWest VirginiaAverage
30×Paraformer65.5771.4370.2060.0468.0152.6264.65
L2HNet [28]61.7768.1265.2458.5269.3955.4363.08
TransUNet [10]53.1560.5360.4251.0866.2147.5256.49
ConViT [18]55.2660.7161.5853.9459.8049.1156.73
CoAtNet [16]56.8962.8361.2553.5765.6751.3458.59
MobileViT[34]58.0361.3261.8455.5357.0448.6457.07
EfficientViT[5]53.7261.2859.4851.3857.3448.7655.33
UNetFormer[48]58.8565.1161.3459.1060.8447.2058.74
DC-Swin[47]59.6565.9958.6058.0664.1148.1559.09
UNet [38]54.1658.7956.4253.2157.3446.1154.34
HRNet [45]52.1156.2150.7650.0357.4845.4252.00
LinkNet [8]58.2762.0552.9652.1148.7148.9353.84
SkipFCN [26]60.9764.8359.4455.3764.7254.6660.00
SSDA [43]57.9161.5454.8551.7157.7147.1555.15
RF [7]59.3555.0355.2651.0752.2954.3654.56
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Max gapLR labelParaformer (ours)mIoU (%) of different methods
L2HNet [28]TransUNet [10]ConViT [18]MobileViT [34]DC-Swin [47]HRNet [45]SkipFCN [26]RF [7]
40×FROM_GLC10 [9]56.5750.1538.4439.3641.0343.5643.6627.1421.48
ESA_GLC10 [44]55.1952.1335.5836.0938.4240.0549.8128.3426.97
Esri_GLC10 [22]55.0750.7837.7938.7838.5039.9146.6528.1819.36
120×GLC_FCS30 [56]49.3943.6226.2029.1629.5730.1441.4623.6717.02
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The mIoU (%) of the Paraformer and other methods that trained with three types of 10-m labels (i.e., FROM_GLCL10, ESA_GLCL10, and Esri_GLCL10) and one type of 30-m label (i.e., GLC_FCS30) are demonstrated." + } + ] + } + ], + "index": 28, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 609, + 287, + 704 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 609, + 287, + 704 + ], + "spans": [ + { + "bbox": [ + 46, + 609, + 287, + 704 + ], + "type": "text", + "content": "when the loss stopped dropping over eight epochs. The metric of mean intersection over union (mIoU) is calculated between the results and the HR ground truths after their land-cover classes are unified into four base classes. The compared methods include: Random Forest (RF) is a pixel-to-pixel method widely used in large-scale land-cover mapping [7]. TransUNet [10], ConViT [18], CoAtNet [16], MobileViT [34], and EfficientViT [5] are CNN-Transformer hy" + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 304, + 609, + 545, + 704 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 609, + 545, + 704 + ], + "spans": [ + { + "bbox": [ + 304, + 609, + 545, + 704 + ], + "type": "text", + "content": "brid methods for semantic segmentation. UNetformer [48] and DC-Swin [47] are dedicated CNN-Transformer methods for remote-sensing images. UNet [38], HRNet [45], and LinkNet [8] are typical CNN-based semantic segmentation methods which are widely adopted in HR land-cover mapping [37, 52, 53]. 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Example of training data and different outputs of Paraformer sampled from the Chesapeake Bay dataset with four unified classes. (a) HR images. (b) LR labels. (c) the primal prediction from the CNN branch. (d) Mask label, as the intersection parts of (b) and (c). The black areas are set to void without supervised information. (e–f) the incorrect samples (with pink color) of LR label and mask label. (g) the final results of Paraformer. (h) HR ground truth." + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_caption" + } + ], + "index": 16 + }, + { + "type": "image", + "bbox": [ + 304, + 276, + 361, + 285 + ], + "blocks": [ + { + "bbox": [ + 304, + 276, + 361, + 285 + ], + "lines": [ + { + "bbox": [ + 304, + 276, + 361, + 285 + ], + "spans": [ + { + "bbox": [ + 304, + 276, + 361, + 285 + ], + "type": "image", + "image_path": "5ac1967144410ced333559ef866f388383e7cc085388c1a56f5c677b75a129a3.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + } + ], + "index": 18 + }, + { + "bbox": [ + 46, + 336, + 287, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 336, + 287, + 373 + ], + "spans": [ + { + "bbox": [ + 46, + 336, + 287, + 373 + ], + "type": "text", + "content": "in the 2021 IEEE GRSS DFC [27]. L2HNet is a state-of-the-art method designed for weakly supervised land-cover mapping [28]." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 47, + 387, + 164, + 399 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 387, + 164, + 399 + ], + "spans": [ + { + "bbox": [ + 47, + 387, + 164, + 399 + ], + "type": "text", + "content": "4.3. Comparison Results" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "text", + "content": "Comparison on the Chesapeake Bay dataset: Table 1 and Figure 5 show the comparisons on the Chesapeake Bay dataset. From the quantitative results, Paraformer shows superiority in the states of Delaware, New York, Maryland, and Pennsylvania. The L2HNet shows better results in Virginia and West Virginia. On average, Paraformer has the most accurate HR land-cover mapping results over the entire area, with a mIoU of " + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "inline_equation", + "content": "64.65\\%" + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "text", + "content": ". As shown in Figure 5 (c), the visual result of Paraformer is more consistent with the HR image compared with other methods. Unlike the fully supervised semantic segmentation task, the unmatched training pairs can cause serious misguidedness during the model training. E.g., as the rough results shown in Figure 5 (f) and (g), UNet and HRNet over-downsample the features and encourage results to fit LR labels instead of being consistent with the HR images. Furthermore, quantitative results reveal that UNet, LinkNet, and HRNet have insufficient performance, with mIoU of " + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "inline_equation", + "content": "54.34\\%" + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "inline_equation", + "content": "53.84\\%" + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "inline_equation", + "content": "52.00\\%" + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "text", + "content": ". Although the compared CNN-Transformer methods (e.g., TransUNet) combine local and global contextual information, the structure does not focus on preserving the feature resolution or dealing with the geospatial mismatch. As a result, TransUNet shows a weak performance in visual results, shown in Figure 5 (h), and has a mIoU of " + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "inline_equation", + "content": "56.49\\%" + }, + { + "bbox": [ + 46, + 402, + 289, + 714 + ], + "type": "text", + "content": ". Furthermore, SkipFCN, SSDA, and RF use small receptive fields or pixel-to-pixel strategies to ex" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "spans": [ + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "type": "text", + "content": "tract features with fine land details. However, due to the lack of deep-level feature representation and global contextual information, SkipFCN, SSDA, and RF obtain a mIoU of " + }, + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "type": "inline_equation", + "content": "59.99\\%" + }, + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "type": "inline_equation", + "content": "55.15\\%" + }, + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "type": "inline_equation", + "content": "54.56\\%" + }, + { + "bbox": [ + 304, + 336, + 545, + 468 + ], + "type": "text", + "content": ", respectively. As an example shown in Figure 5 (e), RF finely predicts ground details but incorrectly classifies rivers, lakes, and pastures. To further demonstrate the effect of Paraformer on different landscapes, we sample six typical areas in Figure 6. The visual results indicate that the complex ground details among various landforms of HR land-cover maps can be well updated from the LR historical land-cover labels." + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": "Comparison on the Poland dataset: In the experiments with the Poland dataset, all methods were used to produce " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "0.25 / 0.5" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": "-m land-cover maps of 14 provinces of Poland by exploiting four LR labels separately. These LR labels include 10-m FROM_GLC10, ESA_GLC10, Esri_GLC10, and 30-m GLC_FCS30. As shown in Table 2, Paraformer is compared with eight representative methods (i.e., weakly supervised, CNN-Transformer, CNN-based, pixel-to-pixel approaches) in a more extreme geospatial mismatch. Compared with the state-of-the-art method, the Paraformer has an increase in mIoU of " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "6.42\\%" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "3.06\\%" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "4.29\\%" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": " in exploiting 10-m labels. By resolving 30-m labels with a max resolution gap of " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "120\\times" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": ", Paraformer has a mIoU of " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "49.39\\%" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": " with an increase of " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "5.77\\%" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": " compared with L2HNet. The typical CNN-based method has an average mIoU of " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "46.71\\%" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": " among the 10-m cases and " + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "inline_equation", + "content": "41.46\\%" + }, + { + "bbox": [ + 304, + 473, + 546, + 712 + ], + "type": "text", + "content": " in the 30-m case. Skip_FCN and RF have the lowest mIoU among all methods, which shows the difficulty of dealing with extremely unmatched situations. Moreover, the quantitative results of Paraformer shown in the four cases reveal that the proposed frame" + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27723" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 54, + 70, + 538, + 130 + ], + "blocks": [ + { + "bbox": [ + 54, + 70, + 538, + 130 + ], + "lines": [ + { + "bbox": [ + 54, + 70, + 538, + 130 + ], + "spans": [ + { + "bbox": [ + 54, + 70, + 538, + 130 + ], + "type": "table", + "html": "
Ablation methodmIoU (%) of six states in the Chesapeake Bay watershed
DelawareNew YourMarylandPennsylvaniaVirginiaWest VirginiaAverageParamsFLOPs
Paraformer65.5771.4370.2060.0468.0152.6264.65109.4M141.3G
Sole CNN branch59.5767.8764.3053.8665.2650.0160.154.5M56.1G
Sole Transformer branch53.1560.5360.4251.0866.2247.5256.4996.9M83.3G
Hybrid without PLAT62.6970.3967.1558.3367.4750.8362.81109.4M141.3G
", + "image_path": "d016777d72856b078e8a12fc3be12d96e8121922e946a8cde2e31bb12afb85f7.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 135, + 547, + 156 + ], + "lines": [ + { + "bbox": [ + 47, + 135, + 547, + 156 + ], + "spans": [ + { + "bbox": [ + 47, + 135, + 547, + 156 + ], + "type": "text", + "content": "Table 3. The ablation results of the Paraformer on six states of the Chesapeake Bay watershed. The sole CNN branch, sole Transformer branch, and Hybrid without PLAT aim to investigate the contribution of the CNN branch, Transformer branch, and PLAT module, respectively." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 49, + 167, + 168, + 242 + ], + "blocks": [ + { + "bbox": [ + 49, + 167, + 168, + 242 + ], + "lines": [ + { + "bbox": [ + 49, + 167, + 168, + 242 + ], + "spans": [ + { + "bbox": [ + 49, + 167, + 168, + 242 + ], + "type": "image", + "image_path": "df9f523b4eaf4ba6ba45a81dd5813642b9d3cace6224107d2dd5f5eaf1840b44.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 86, + 242, + 129, + 249 + ], + "lines": [ + { + "bbox": [ + 86, + 242, + 129, + 249 + ], + "spans": [ + { + "bbox": [ + 86, + 242, + 129, + 249 + ], + "type": "text", + "content": "(a) 1-m image" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 168, + 166, + 286, + 241 + ], + "blocks": [ + { + "bbox": [ + 168, + 166, + 286, + 241 + ], + "lines": [ + { + "bbox": [ + 168, + 166, + 286, + 241 + ], + "spans": [ + { + "bbox": [ + 168, + 166, + 286, + 241 + ], + "type": "image", + "image_path": "bd0e7630b9ff14e9c5103b41cfacb4a934ebfd3a407008303812bf21258d8c13.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 190, + 242, + 263, + 249 + ], + "lines": [ + { + "bbox": [ + 190, + 242, + 263, + 249 + ], + "spans": [ + { + "bbox": [ + 190, + 242, + 263, + 249 + ], + "type": "text", + "content": "(b) CNN-branch context" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 48, + 250, + 167, + 324 + ], + "blocks": [ + { + "bbox": [ + 48, + 250, + 167, + 324 + ], + "lines": [ + { + "bbox": [ + 48, + 250, + 167, + 324 + ], + "spans": [ + { + "bbox": [ + 48, + 250, + 167, + 324 + ], + "type": "image", + "image_path": "e9827db31527091a470156b00054916d6007b23ac1ff94b1e4bd8828187c48bc.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 61, + 325, + 155, + 333 + ], + "lines": [ + { + "bbox": [ + 61, + 325, + 155, + 333 + ], + "spans": [ + { + "bbox": [ + 61, + 325, + 155, + 333 + ], + "type": "text", + "content": "(c) Transformer-branch context" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 339, + 288, + 377 + ], + "lines": [ + { + "bbox": [ + 46, + 339, + 288, + 377 + ], + "spans": [ + { + "bbox": [ + 46, + 339, + 288, + 377 + ], + "type": "text", + "content": "Figure 9. Demonstration of the extracted contexts from the ablation methods. (a) the original HR image. (b) the contexts extracted by the sole CNN branch. (c) the contexts extracted by the sole Transformer branch. (d) the contexts extracted by the CNN-Transformer hybrid backbone." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 168, + 250, + 287, + 324 + ], + "blocks": [ + { + "bbox": [ + 168, + 250, + 287, + 324 + ], + "lines": [ + { + "bbox": [ + 168, + 250, + 287, + 324 + ], + "spans": [ + { + "bbox": [ + 168, + 250, + 287, + 324 + ], + "type": "image", + "image_path": "daa5eb2d357136b5303c7a7f7783d901b98100f4eea0282112326779e440279c.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 186, + 325, + 269, + 333 + ], + "lines": [ + { + "bbox": [ + 186, + 325, + 269, + 333 + ], + "spans": [ + { + "bbox": [ + 186, + 325, + 269, + 333 + ], + "type": "text", + "content": "(d) Hybrid-structure context" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 393, + 287, + 489 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 393, + 287, + 489 + ], + "spans": [ + { + "bbox": [ + 46, + 393, + 287, + 489 + ], + "type": "text", + "content": "work obtains stable results from different LR labels. Figure 7 shows the visual results of Paraformer among four cases. With the parallel CNN-Transformer structure and PLAT module, Paraformer is able to refine the clear ground details (e.g., vegetation and roads) even if they are roughly labeled in local areas. In general, Paraformer shows the potential to robustly update large-scale HR land-cover maps from available LR historical labels." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 491, + 171, + 504 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 491, + 171, + 504 + ], + "spans": [ + { + "bbox": [ + 47, + 491, + 171, + 504 + ], + "type": "text", + "content": "4.4. Ablation experiments" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 510, + 287, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 287, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 287, + 616 + ], + "type": "text", + "content": "In this section, ablation experiments were conducted on the Chesapeake Bay dataset to evaluate different components of Paraformer. Each ablation in Table 3 is explained as follows: (1) the sole CNN branch is dependently trained by calculating CE loss with LR labels; (2) the sole Transformer branch embeds HR images instead of features from the CNN branch and calculates CE loss with LR labels; (3) the hybrid structure without PLAT directly calculates CE loss with the LR labels." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": "By ablating the PLAT module, the results obtained an average mIoU of " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "62.81\\%" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": ", which indicates a " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "1.84\\%" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " decrease compared with the " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "64.65\\%" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " of Paraformer. By ablating the CNN and Transformer branches, the results of the sole CNN branch obtained a mIoU of " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "60.15\\%" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " and had a " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "4.5\\%" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " decrease. Results of the sole Transformer branch obtained the lowest mIoU of " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "56.49\\%" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " and had the most obvious decrease " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "(8.16\\%)" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": ". Figure 8 shows different outputs of Paraformer," + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 168, + 545, + 323 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 168, + 545, + 323 + ], + "spans": [ + { + "bbox": [ + 304, + 168, + 545, + 323 + ], + "type": "text", + "content": "where the inexact LR labels are gradually refined during framework training. The final result shown in Figure 8 (g) indicates both fine ground details and accurate land-cover patterns that are consistent with the ground truth. Moreover, Figure 9 shows the visualized contexts captured by the CNN branch, Transformer branch, and hybrid structure. Figure 9 (b) indicates that the CNN branch mostly focuses on capturing local details (e.g., the edges of roads, single houses, and shrubs). Figure 9 (c) indicates that the Transformer branch captures the feature in object scale, focusing on intact land objects of building areas and parking spots. The hybrid structure shows a strong response to the obvious objects with both fine edges and intact areas." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 324, + 545, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 324, + 545, + 407 + ], + "spans": [ + { + "bbox": [ + 304, + 324, + 545, + 407 + ], + "type": "text", + "content": "In general, the ablation results demonstrate two findings: (1) The PLAT module can stably optimize the framework training and reasonably exploit the LR labels during the large-scale HR land-cover mapping process. (2) The parallel CNN and Transformer branches are indispensable parts of the framework, which construct a more robust feature extractor to bridge local and global contextual information." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 420, + 379, + 432 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 420, + 379, + 432 + ], + "spans": [ + { + "bbox": [ + 305, + 420, + 379, + 432 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 435, + 545, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 435, + 545, + 639 + ], + "spans": [ + { + "bbox": [ + 304, + 435, + 545, + 639 + ], + "type": "text", + "content": "In this paper, a weakly supervised CNN-Transformer framework, Paraformer, is proposed to update large-scale HR land-cover maps in an HR-label-free, end-to-end manner. Experiments on two datasets show that Paraformer outperforms other approaches in guiding semantic segmentation of large-scale HR remote-sensing images with easy-access LR land-cover data. Further analysis reveals that the Paraformer can robustly adapt various landforms of wide-span areas and stably exploit different LR labels in producing accurate HR land-cover maps. The ablation studies demonstrate the effectiveness of the parallel CNN-Transformer structure and the PLAT module. Moreover, intermediate results of each training process and visualized contexts of each branch are demonstrated to transparently explain the components of Paraformer. In general, the proposed Paraformer has the potential to become an effective method for facilitating large-scale HR land-cover mapping." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 647, + 403, + 661 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 647, + 403, + 661 + ], + "spans": [ + { + "bbox": [ + 306, + 647, + 403, + 661 + ], + "type": "text", + "content": "Acknowledgments" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": "This work has been supported by the National Key Research and Development Program of China (grant no. 2022YFB3903605) and the National Natural Science Foundation of China (grant no.42071322)." + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27724" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 124 + ], + "type": "text", + "content": "[1] Land-cover classification with high-resolution remote sensing images using transferable deep models. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), pages 4299-4309, 2022. 2" + } + ] + } + ], + "index": 10 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "27727" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/LeftRefill_ Filling Right Canvas based on Left Reference through Generalized Text-to-Image Diffusion Model/908a3914-e513-461a-933d-8314753d5fc2_content_list.json b/2024/LeftRefill_ Filling Right Canvas based on Left Reference through Generalized Text-to-Image Diffusion Model/908a3914-e513-461a-933d-8314753d5fc2_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..661560d10e482f186262171ad3328a3a41f1295e --- /dev/null +++ b/2024/LeftRefill_ Filling Right Canvas based on Left Reference through Generalized Text-to-Image Diffusion Model/908a3914-e513-461a-933d-8314753d5fc2_content_list.json @@ -0,0 +1,1336 @@ +[ + { + "type": "text", + "text": "LeftRefill: Filling Right Canvas based on Left Reference through Generalized Text-to-Image Diffusion Model", + "text_level": 1, + "bbox": [ + 156, + 130, + 816, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Chenjie Cao $^{1,2*}$ , Yunuo Cai $^{1}$ , Qiaole Dong $^{1}$ , Yikai Wang $^{1}$ , Yanwei Fu $^{1\\dagger}$ , Fudan University, $^{2}$ Alibaba Group", + "bbox": [ + 207, + 202, + 769, + 239 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/b1036f552a07ad16762225fb827519dc4c6312f0a1b94675a2dbe959d70e5628.jpg", + "image_caption": [ + "Figure 1. LetRefill addresses the generation on the right canvas conditioned by left references. We can re-formulate several existing tasks in the LeftRefill manner, including (a) reference-guided inpainting, (b) novel view synthesis. The reference and target can be further extended to multi-view scenes, forming (c) multi-view reference inpainting and (d) multi-view synthesis, respectively. Green frames indicate stitched inputs. Reference views are placed on the left side, while masked target views are placed on the right side. Violet frames only show enlarged right-side generations produced by LeftRefill. Note that we omit some input details in (c) and (d) for simplicity." + ], + "image_footnote": [], + "bbox": [ + 98, + 276, + 869, + 527 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 614, + 313, + 630 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "This paper introduces LeftRefill, an innovative approach to efficiently harness large Text-to-Image (T2I) diffusion models for reference-guided image synthesis. As the name implies, LeftRefill horizontally stitches reference and target views together as a whole input. The reference image occupies the left side, while the target canvas is positioned on the right. Then, LeftRefill paints the right-side target canvas based on the left-side reference and specific task instructions. Such a task formulation shares some similarities with contextual inpainting, akin to the actions of a human painter. This novel formulation efficiently learns both structural and textured correspondence between reference and target without other image encoders", + "bbox": [ + 75, + 646, + 472, + 843 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "or adapters. We inject task and view information through cross-attention modules in T2I models, and further exhibit multi-view reference ability via the re-arranged self-attention modules. These enable LeftRefill to perform consistent generation as a generalized model without requiring test-time fine-tuning or model modifications. Thus, LeftRefill can be seen as a simple yet unified framework to address reference-guided synthesis. As an exemplar, we leverage LeftRefill to address two different challenges: reference-guided inpainting and novel view synthesis, based on the pre-trained StableDiffusion. Codes&models are released at https://github.com/ewrfcas/LeftRefill.", + "bbox": [ + 500, + 616, + 893, + 797 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 500, + 828, + 632, + 844 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Imagine you are a right-handed painter with a task that requires you to draw or modify a target image based on a reference picture. How would you approach it? Intuitively,", + "bbox": [ + 500, + 854, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "$^*$ Dr. Chenjie Cao is at Alibaba Group. This work was accomplished while Dr. Chenjie Cao was at Fudan University. \n† Corresponding author: yanweifu@fudan.edu.cn \nOther emails: {cjcao20,yncai20,qldong18,yikaiwang19} @fudan.edu.cn", + "bbox": [ + 75, + 849, + 470, + 901 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "7705", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "you would likely place the reference image on your left side and paint or modify the target view on the right side conditioned on the left one. If we regard the large Text-to-Image (T2I) models [6, 37, 41, 44, 46, 48] as skillful painters, could they also follow such simple and intuitive task formulation to handle complex reference-guided synthesis tasks? In this paper, we explore this problem with two challenging tasks: 1) Inpainting masked target views conditioned on reference images, i.e., reference-guided inpainting (Ref-inpainting) [67, 68] as in Figure 1(a). 2) Generating new views based on known images of specific objects, i.e., Novel View Synthesis (NVS) [30] as in Figure 1(b).", + "bbox": [ + 75, + 90, + 472, + 272 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "It seems straightforward to harness the power of T2I generative models to directly address these image-reference tasks by training additional adapters [21, 36, 64] or replacing textual encoders with visual ones [30, 62] and optimize them for full fine-tuning of the entire T2I model. We should clarify that training these large T2I models with unfamiliar visual encoders is computationally intensive and challenging to converge, particularly when working with limited batch sizes. Additionally, most visual encoders, such as image CLIP [43], tend to emphasize the learning of semantic features rather than the intricately spatial details that are essential for tasks involving Ref-inpainting as verified in our experiments.", + "bbox": [ + 75, + 273, + 472, + 453 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To prevent the heavy modification to T2I models mentioned above, we rethink the human painting habit and propose LeftRefill, a unified approach for both Ref-inpainting and NVS. LeftRefill is built upon the inpainting fine-tuned StableDiffusion2.0 (SD) [46]*, which ingeniously reformulates reference-based synthesis as a contextual inpainting process. Specifically, LeftRefill horizontally stitches reference and target views as a whole input. As shown in Figure 1, reference images are positioned on the left side, while masked targets are on the right side. This simple yet effective formulation eliminates the dependency on additional image feature encoders, as both reference and target views have been stitched into the same canvas. As an \"experienced painter\", LeftRefill is driven by specific instructions, called task and view prompt tuning. These instructions infuse crucial information for specific generative tasks and desired view orders to cross-attention modules, guiding the generation of SD. Note that LeftRefill is a generalized framework, so we can train two LeftRefill models for Ref-inpainting and NVS separately without any test-time fine-tuning.", + "bbox": [ + 75, + 454, + 472, + 755 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "On the other hand, we emphasize that LeftRefill further enjoys extension into multi-view synthesis scenarios, including image inpainting conditioned on multi-view references in Figure 1(c) and consistent NVS from a single view in Figure 1(d). Formally, we rearrange the tensor shape before the self-attention modules, enabling self-attention to capture cross-view information. Moreover, to tackle the more intricate NVS task, we propose the novel technique of block", + "bbox": [ + 75, + 756, + 472, + 878 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "causal masking, facilitating self-attention-based T2I models in achieving consistent autoregressive (AR) generation. All improvements are integrated into the off-the-shelf SD components, involving no additional image encoder, prompt tuning based on cross-attention, self-attention rearranging and block causal masking. LeftRefill emerges as a unified architecture for addressing reference-guided synthesis, requiring only minor model modifications.", + "bbox": [ + 496, + 90, + 893, + 210 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We highlight the key contributions of LeftRefill as follows: 1) Lightweight and generalized task formulation based on off-the-shelf T2I models: Benefiting from the novel contextual inpainting formulation and inherent attention mechanisms from SD, LeftRefill provides an efficient solution for reference-guided synthesis without thoroughly re-training T2I models and test-time fine-tuning. 2) Task and view-specific prompt tuning: Our work pioneers the use of task and view-specific prompt tuning, allowing for precise control over generative tasks and view orders. 3) End-to-end Ref-inpainting: Notably, our LeftRefill addresses the challenging Ref-inpainting end-to-end, without complex 3D geometrical warping and 2D inpainting techniques [65, 67, 68]. 4) Autoregressive NVS with block causal masking: For the intricate NVS task, we introduce the novel concept of block causal masking, enabling self-attention-based T2I models to achieve AR generation for geometric consistency.", + "bbox": [ + 496, + 212, + 895, + 469 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 482, + 640, + 498 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Personalization and Controllability of T2I Models. Recent achievements on T2I have produced impressive visual generations [2, 36, 42], which could be further extended into local editing [1, 8, 18]. However, these models could only be controlled by natural languages. As \"an image is worth hundreds of words\", T2I models based on natural texts fail to produce images with specific textures, locations, identities, and appearances [15]. Textual inversion [15, 35] and fine-tuning techniques [47] are proposed for personalized T2I. Meanwhile, many works pay attention to image-guided generations [26, 34, 58]. ControlNet [64] and T2I-Adapter [36] learn trainable adapters [20] to inject visual clues to pretrained T2I models without losing generalization and diversity. But these moderate methods only work for simple style transfers. More spatially complex tasks, such as Refinpainting, are difficult to handle by ControlNet as verified in Section 4. In contrast, T2I-based exemplar-editing and NVS have to be fine-tuned on large-scale datasets with strong data augmentation [62] and large batch size [30]. Compared with these aforementioned manners, LeftRefill enjoys both spatial modeling capability and computational efficiency.", + "bbox": [ + 496, + 507, + 895, + 824 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Prompt Tuning [24, 32, 33] indicates fine-tuning token embeddings for transformers with frozen backbone to preserve the capacity. Prompt tuning is first explored for adaptively learning suitable prompt features for language models rather than manually selecting them for different downstream", + "bbox": [ + 496, + 825, + 893, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_footnote", + "text": "*https://github.com/Stability-AI/stablediffusion.", + "bbox": [ + 94, + 887, + 431, + 898 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "7706", + "bbox": [ + 482, + 945, + 516, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "tasks [29]. Moreover, prompt tuning has been further investigated in vision-language models [16, 43] and discriminative vision models [23, 28]. Visual prompt tuning in [53] prepends trainable tokens before the visual sequence for transferred generations. Though both LeftRefill and [53] aim to tackle image synthesis, our prompt tuning is used for controlling text encoders rather than visual ones. Thus LeftRefill enjoys more intuitive prompt initialization from task-related textual descriptions.", + "bbox": [ + 75, + 90, + 472, + 226 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Reference-guided Image Inpainting. Image inpainting is a long-standing vision task, which aims to fill missing image regions with coherent results. Both traditional methods [3, 9, 17] and learning-based ones [11, 25, 54, 63, 66] achieved great progress in image inpainting. Furthermore, Ref-inpainting requires recovering a target image with one or several reference views from different viewpoints [40], which is useful for repairing old buildings or removing occlusions in popular attractions. But Ref-inpainting usually suffers from a sophisticated pipeline [65, 67, 68], including depth estimation, pose estimation, homography warping, and single-view inpainting. Limited by large holes, the estimated geometric pose is not reliable, largely degrading the pipeline. Thus an end-to-end Ref-inpainting pipeline is meaningful. To the best of our knowledge, we are the first ones to tackle such a difficult reference-guided task with T2I models.", + "bbox": [ + 75, + 227, + 473, + 467 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Novel View Synthesis from a Single Image. NVs based on a single image is an intractable ill-posed problem, requiring both sufficient geometry understanding and expressive textural presentation [14]. Many previous works could partially tackle this problem through single view 3D reconstruction [7, 31, 59–61], 2D generative models [39, 45, 52], feature cost volumes [5], and GAN-based methods [4, 38, 51]. However, these manners still suffer from limited generalization or small angle variations. To address this issue, Zero123 [30] uses another image CLIP encoder to inject image features from the reference view to unlock the capacity from 2D diffusion-based T2I models for NVs. But Zero123 requires a large batch size and expensive computational resources to stabilize the training stage with an unknown reference image encoder. Moreover, the image encoder in Zero123 can only tackle one reference image, which fails to generate consistent multi-view images.", + "bbox": [ + 75, + 468, + 473, + 726 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 737, + 168, + 752 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Overview. LeftRefill is first formulated in Section 3.1. Then we explain using self-attention to capture multi-view correspondence, and AR generation based on block casual masking (Section 3.2). Finally, we discuss the task and view-specific prompt tuning for cross-attention (Section 3.3).", + "bbox": [ + 75, + 762, + 472, + 839 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Framework of LeftRefill", + "text_level": 1, + "bbox": [ + 76, + 847, + 302, + 861 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Motivations. As depicted in Figure 2(a), our LeftRefill is built upon the inpainting fine-tuned SD [46]. There are two", + "bbox": [ + 75, + 869, + 470, + 900 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/d77961d4d0de9be420d970a11ebc876d2fc8714c1741d01be228984565159520.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 506, + 92, + 707, + 247 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/cab02103fb24fdd6b39cab60ff5e28bdb09eb8c6e4046a802ade808695b096e3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 717, + 93, + 888, + 250 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/621d30d98338a9ddfa77bcf6a357056e0af02fd1dc2c967111f731d9074554d8.jpg", + "image_caption": [ + "Figure 3. Illustration about multi-view training inputs $(v\\times H\\times 2W$ , $v = 4)$ of LeftRefill, where $v,H,2W$ indicate the view number, height, and width of stitching images. All views of Ref-inpainting (a) share the same masked target, while the multi-view NVS (b) should be trained with the AR generation." + ], + "image_footnote": [], + "bbox": [ + 522, + 332, + 705, + 569 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/64457f794ffd18376e1a53c22db3a5e8cfe51bc3be9fdbac782f6a6aee30f503.jpg", + "image_caption": [ + "Figure 2. (a) The overview of LeftRefill. Inputs of Ref-inpainting and NVs are shown in (b). Task and view prompt embedding and pose features (optional for NVS) are infused to CLIP-H for cross-attention learning in U-net. For the output of LeftRefill, we discard the left-side reference and take the right-side generation." + ], + "image_footnote": [], + "bbox": [ + 718, + 330, + 856, + 569 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "primary motivations that make us stitch reference and target images together and reformulate both Ref-inpainting and NVS as a contextual image inpainting problem. 1) LeftRefill just considers a single input image, eliminating the requirement of additional image encoders and avoiding major architectural alterations and extensive re-training. 2) Since all T2I models are only pre-trained on single-view images, the left-right stitched input could implicitly reactivate the essential capacity from large T2I models of modeling the correlation of the single-view image. Particularly, the left-right stitching input enables the self-attention modules to focus on correct parts from left-side reference at the early stage of diffusion sampling (Figure 10). We also thoroughly evaluate different alterations of reference-guided SD in Section 4.1. LeftRefill substantially outperforms other competitors with high efficiency and negligible trainable weights.", + "bbox": [ + 496, + 643, + 893, + 883 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Single-view Formulation (1-to-1). Thanks to the convo", + "bbox": [ + 500, + 885, + 893, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "7707", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/27ae7e58841500d2fc8856ce19193b8ce8a1996c54996c5e3196fb41a84996fa.jpg", + "image_caption": [ + "Figure 4. Detailed architecture of LeftRefill for multi-view synthesis. Both CNN and cross-attention modules are encoded separately for each stitched view, while all views share the same self-attention for multi-view correlation learning." + ], + "image_footnote": [], + "bbox": [ + 127, + 90, + 421, + 300 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/439739df524b24ed65641efbba3b86b3be2a0f0766a0c6586f8056fd0a36162b.jpg", + "image_caption": [ + "(a) Illustration about the shape rearranging of LeftRefill" + ], + "image_footnote": [], + "bbox": [ + 117, + 359, + 390, + 412 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/07b28d4f6b5dc1bc985436580972ae02e11085eb6ddc972a3d543f9cf0ba105d.jpg", + "image_caption": [ + "(b) Block causal masking used for autoregressive training", + "Figure 5. (a) Feature rearranging, and (b) block causal masking of LeftRefill, where $b, v, h, w, c$ indicate the batch size, view number, height, width, and channels of features, where $w$ is the width of stitching features (downsampled from $2W$ )." + ], + "image_footnote": [], + "bbox": [ + 114, + 426, + 424, + 545 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "lutional U-net architecture in the Latent Diffusion Model (LDM), we can expand the input image in the spatial dimensions without any modification. Let's consider a scenario with a single reference image at first, i.e., 1-to-1. Our input $\\mathbf{I}'$ is a stitching image of $\\mathbf{I}_{ref}$ and the masked target $\\hat{\\mathbf{I}}_{tar}$ , forming as $\\mathbf{I}' = [\\mathbf{I}_{ref};\\hat{\\mathbf{I}}_{tar}] \\in \\mathbb{R}^{H \\times 2W}$ as shown in Figure 2(a). In practice, we take the reference image on the left side, while the target one is placed on the right side. We just take the right-side output as the final generation while the left-side output is discarded. Note that the diffusion optimization is based on the whole stitched image without any modification. For the masked target $\\hat{\\mathbf{I}}_{tar}$ , we treat Ref-inpainting's input targets as partially masked images, while NVS's input targets are entirely masked through the objective segmentation and bounding box. More details about the processing of data and masks are discussed in the supplementary.", + "bbox": [ + 75, + 625, + 468, + 868 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Multi-view Formulation (V-to-1). For the multi-view references, we stitch each reference with the specific target", + "bbox": [ + 75, + 869, + 470, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "as shown in Figure 3. All views are learned separately for convolutions and cross-attention, while they share the same self-attention processing as shown in Figure 4 and detailed in Section 3.2. From Figure 3(a), the multi-view Ref-inpainting leverages information from different reference views to repair the same target, i.e., $v$ -to-1, where $v$ means the view number. We simply take the generation of the first view as the final inpainted output in $v$ -to-1. For the multi-view NVS, it could be seen as an AR generation for sequentially consistent view synthesis, as depicted in Figure 3(b), i.e., $n$ -to-1 ( $n = 1,2,\\dots,v$ ). During the inference, we apply the generated targets as new references for the subsequent view synthesis, while the training phase is accomplished parallelly as detailed in the block casual masking of Section 3.2.", + "bbox": [ + 496, + 90, + 893, + 301 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Controlling Generation for LeftRefill. Although the self-attention modules in SD have the potential to enable the correlation between left reference and right target, SD is not trained to explicitly activate this capacity. The most intuitive way to guide the SD in capturing the correlation among left-right stitched images is to apply suitable text prompts to drive the diffusion model for the desired generation. However, it is non-trivial to define Ref-inpainting and NVS with natural languages. Furthermore, it is beneficial to have a non-instance-level prompt to generally guide the diffusion model to accomplish specific tasks. To this end, we propose to use prompt tuning to learn task and view-specific prompts as detailed in Section 3.3. Except for the prompt tuning, all weights in LDM are frozen in Ref-inpainting to maintain the proper generalization as shown in Figure 2(a). For NVS, we fine-tune the whole LDM to achieve essentially precise pose control, but LeftRefill enjoys much better convergence compared with other fine-tuning based methods [30].", + "bbox": [ + 496, + 301, + 893, + 574 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Reactivating Self-Attention for Multi-View", + "text_level": 1, + "bbox": [ + 500, + 583, + 862, + 598 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "As shown in Figure 5(a), given multi-view features $\\mathbf{F}_i$ of layer $i$ , all MLP, convolutional, and cross-attention layers encode $\\mathbf{F}_i$ separately. We can simply achieve the separate feature encoding by reshaping the view $v$ and batch $b$ dimension together as $bv$ . Before the self-attention, we rearrange the feature shape as $\\tilde{\\mathbf{F}}_i \\in \\mathbb{R}^{b \\times vhw \\times c}$ , thus features across different views could be learned together. To further incorporate positional clues for distinguishing different sides of reference and target in NVS, we incrementally add positional encoding $P_i$ to $\\tilde{\\mathbf{F}}_i$ before each self-attention block as", + "bbox": [ + 496, + 606, + 893, + 757 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nP _ {i} = \\gamma_ {i} \\cdot \\operatorname {c a t} ([ P _ {v}; P _ {\\text {F o u r i e r}} ]), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 594, + 768, + 890, + 785 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $P_{v}, P_{Fourier}$ indicate the trainable view embedding and Fourier absolute positional encoding [57] respectively; $\\gamma_{i}$ is a zero-initialized learnable coefficient for each layer.", + "bbox": [ + 496, + 794, + 890, + 840 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For the Ref-inpainting, no masking strategy should be considered in self-attention modules. All reference views share the same target one, thus it is unnecessary for LeftRefill to sequentially repair target views. In contrast, for the", + "bbox": [ + 496, + 840, + 893, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "7708", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "multi-view NVs, generating consistent novel views from a single image needs our model to handle the sequential generation with dynamic reference views. For example, the same LeftRefill should accomplish the NVS from one view, two views, and even more. So the AR generation [13, 49, 56] is suitable to formulate this task.", + "bbox": [ + 75, + 90, + 470, + 180 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Block Causal Masking. LeftRefill requires a certain finetuning for LDM to effectively tackle challenging NVS as shown in Figure 2(a). The intuitive solution is to train an AR-based generative model that can generalize across various view numbers for multi-view synthesis. Converting a pretrained diffusion model to an AR-based generative model is non-trivial. However, the inpainting formulation of Left-Refill makes this conversion feasible. Specifically, we just need to adjust the masking strategy during the self-attention learning. We propose the block casual masking as shown in Figure 5(b), while the block side-length of each view is $h w$ , matching the size of the stitched reference and target pair. Different from the traditional casual mask which is a lower triangular matrix, the block casual mask enlarges the minimal unit from one token to a $h w \\times h w$ block, ensuring reasonable block-wise receptive fields. In practice, all uncolored tokens in the attention score are masked with “—inf” before the softmax operation. The block casual mask can be implemented parallelly and efficiently as in supplementary.", + "bbox": [ + 75, + 181, + 473, + 470 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Task&View Prompt Tuning", + "text_level": 1, + "bbox": [ + 76, + 477, + 326, + 494 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The prompt embedding is adopted as the textual branch to CLIP-H [43] of SD, being applied to cross-attention as shown in Figure 2(a). Specifically, we prepare a set of trainable text embeddings for different generative tasks, which are further categorized into task and view prompts. Specifically, task prompt embeddings are shared in the same task, e.g., all views of Ref-inpainting using the same task embeddings. In contrast, different view prompt embeddings are applied to inject various view-order information through cross-attention modules to the specific input view. Though there are only a few trainable parameters (0.05M to 0.065M), we astonishingly find that prompt tuning is sufficient to drive complex generative tasks such as Ref-inpainting, even with a frozen LDM backbone. The trainable task and view prompt embeddings $p_t$ , $p_v$ are initialized as the averaged embedding of the natural task description. The optimization target is:", + "bbox": [ + 75, + 500, + 470, + 743 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{p _ {t}, p _ {v} \\right\\} _ {*} = \\underset {\\left\\{p _ {t}, p _ {v} \\right\\}} {\\arg \\min } \\mathbb {E} \\left[ \\left\\| \\varepsilon - \\varepsilon_ {\\theta} \\left([ z _ {t}; \\hat {z} _ {0}; \\mathbf {M} ], c _ {\\phi} \\left(p _ {t}, p _ {v}\\right), t\\right) \\right\\| ^ {2} \\right], (2)\n$$\n", + "text_format": "latex", + "bbox": [ + 81, + 747, + 470, + 773 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\varepsilon_{\\theta}(\\cdot)$ is the estimated noise by LDM; $c_{\\phi}(\\cdot)$ means the frozen CLIP-H; $z_{t}$ is a noisy latent feature of input $z_{0}$ in step $t$ ; $\\hat{z}_0 = z_0\\odot (1 - \\mathbf{M})$ are masked latent features concatenated to $z_{t}$ with mask $\\mathbf{M}$ . Task and view-specific prompt tuning enjoy not only training efficiency but also lightweight saving [24]. For example, we share the same LeftRefill to address Ref-inpainting with different reference views, while only $0.01\\%$ additional weights of $\\{p_t,p_v\\}_{*}$ are", + "bbox": [ + 75, + 779, + 470, + 902 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/67b9ebb73031ed78fa72984ac29a1ac30df2aba086864c8e6e1e7c1f2f18e84c.jpg", + "table_caption": [ + "Table 1. Quantitative results for Ref-inpainting on MegaDepth [27] test set based on matching and manual masks (upper: 1-view; lower: multi-view). 'ExParams': the scale of extra trainable parameters. * means that the uncorrupted ground truth is visible for the matching. 'No stitching': reference and target views are separate without spatial stitching, and only self-attention are learned across them." + ], + "table_footnote": [], + "table_body": "
MethodsPSNR↑SSIM↑FID↓LPIPS↓ExParams
SD ( inpainting) [46]19.8410.81930.2600.1349+0
ControlNet [64]19.0720.74433.6640.1816+364.2M
ControlNet+NewCrossAttn19.0270.74334.1700.1805+463.4M
ControlNet+Matching* [55]20.5920.76329.5560.1565+364.3M
Perceiver+ImageCLIP [22]19.3380.74532.9110.1751+52.01M
Paint-by-Example [62]18.3510.79734.7110.1604+865.9M
TransFill [68]22.7440.87526.2910.1102-
LeftRefill (no stitching)20.4890.82720.1250.1085+0.05M
LeftRefill20.9260.83618.6800.0961+0.05M
LeftRefill (2-view)21.0920.83618.3890.0969+0.055M
LeftRefill (3-view)21.3560.84016.8380.0901+0.06M
LeftRefill (4-view)21.7790.84716.6320.0839+0.065M
", + "bbox": [ + 501, + 159, + 898, + 337 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "changed for each view condition. In NVS, we further provide relative poses to LeftRefill. Following [30], we calculate the 4-channel relative pose in the polar coordinate for each view, which is encoded by a two-layer FC. Then the pose feature replaces the last padding token in the prompt embeddings before being applied to the CLIP-H.", + "bbox": [ + 496, + 343, + 893, + 434 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 450, + 633, + 467 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. For Ref-inpainting, we use the resized $512 \\times 512$ image pairs from MegaDepth [27], which includes many multi-view famous scenes collected from the Internet. To trade-off between the image correlation and the inpainting difficulty, we empirically retain image pairs with $40\\%$ to $70\\%$ co-occurrence with about 80k images and 820k pairs. The validation of Ref-inpainting also includes some manual masks from ETH3D scenes [50] to verify the generalization. For the NVS, we use Objaverse [10] rendered by [30] including 800k various scenes with object masks. We resize all images to $256 \\times 256$ as [30]. Note that some extreme views with elevation angles less than $-10^{\\circ}$ are filtered due to excessive ambiguity. More details about the masking and datasets are introduced in the supplementary.", + "bbox": [ + 496, + 476, + 893, + 688 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Implementation Details. Our LeftRefill is based on the inpainting fine-tuned SD [46] with 0.8 billion parameters. For the task and view prompt tuning, there are 50 trainable prompt tokens at all. We use $90\\%$ tokens to represent the task embeddings, while $10\\%$ tokens indicate each view respectively. We use the AdamW optimizer with a weight decay of 0.01 to optimize LeftRefill. For the Ref-inpainting, the prompt tuning's learning rate is 3e-5. Moreover, $75\\%$ masks are randomly generated, and $25\\%$ of them are matching-based masks. For the NVS, LeftRefill could be tested with the adaptive masking strengthened by the foreground segmentation model. Concretely, we first enlarge the reference segmentation mask and generate a coarse target with fewer DDIM steps. We extract the new mask from the coarse tar", + "bbox": [ + 496, + 688, + 895, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "7709", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/7c15677a34c9c7b41a21181a3760afebf27794db80489ddcf176d7a2456d22ad.jpg", + "image_caption": [ + "Figure 6. Qualitative Ref-inpainting results on MegaDepth [27]. More results are in the supplementary." + ], + "image_footnote": [], + "bbox": [ + 138, + 88, + 830, + 368 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/2e95a83d2211106fd2cc4309847af7455c14020cb81ca0dc4513ec5615adc280.jpg", + "image_caption": [ + "Figure 7. Multi-view Ref-inpainting qualitative results. Increasing the reference view number improves the quality of repaired targets." + ], + "image_footnote": [], + "bbox": [ + 78, + 404, + 468, + 536 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "get and then further randomly enlarge it as the final target mask. The NVS LeftRefill is trained with 512 batch size and learning rate 3e-5. We show that a simplified LeftRefill with just 48 batch size can also be converged for NVS, which breaks through the limitation of Zero123 [30]. More details about matching-based masks, adaptive masking, and training schedules are discussed in the supplementary.", + "bbox": [ + 75, + 592, + 468, + 698 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.1. Results of Reference-guided Inpainting", + "text_level": 1, + "bbox": [ + 76, + 710, + 413, + 726 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Results of One-view Reference. We thoroughly compared the specific Ref-inpainting method [68] and existing image reference-based variants of SD with one-view reference in Table 1 and Figure 6. Note that ControlNet [64] fails to learn the correct spatial correlation between reference images and masked targets, even enhanced with trainable cross-attention learned between reference and target features. Furthermore, we try to warp ground-truth latent features with image matching [55] as the reference guidance for ControlNet, but the improvement is not prominent. Perceiver [22] and Paint-by-Example [62] align and learn image features from Image", + "bbox": [ + 75, + 734, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/aa32d35428ca39fb87ad941b72b69032d5f4ea8ed6739084f321b457771f6dc8.jpg", + "image_caption": [ + "Figure 8. NVS results on Objaverse [10] (row1, 2) and Google Scanned Objects [12] (row3, 4) from a single reference image." + ], + "image_footnote": [], + "bbox": [ + 537, + 410, + 856, + 676 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "CLIP. Since image features from CLIP contain high-level semantics, they fail to deal with the fine-grained Ref-inpainting as shown in Figure 6(e)(f). Though TransFill [68] achieves proper results in PSNR and SSIM, it suffers from blur and color difference as in Figure 6(g) with challenging viewpoints. LeftRefill enjoys substantial advantages in both qualitative and quantitative comparisons with negligible trainable weights. Particularly, spatially stitching reference and target views together achieves consistent improvements. Thus it is intuitive and convincing that all U-net modules contribute to improved inpainting results with a whole stitched image, as", + "bbox": [ + 496, + 734, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "7710", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/c18132f3ab236168abce7c33dc02ebe98f39f35bc62e142941f8ef8de2d3d749.jpg", + "image_caption": [ + "Figure 9. Sequential generative results from a single view. Zero123 [30] are conditioned on real reference (first view) and last generated view (last view), while LeftRefill is based on AR." + ], + "image_footnote": [], + "bbox": [ + 101, + 94, + 444, + 455 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "opposed to using only attention modules. We further compare LeftRefill with TransFill on their officially provided real-world dataset in the supplementary.", + "bbox": [ + 75, + 517, + 470, + 561 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results of Multi-view Ref-inpainting. We verified models trained with different numbers of reference views in Table 1 (lower). As the number of reference views increases, there is a notable enhancement in inpainting capability. As qualitatively compared in Figure 7, more consistent references lead to robust inpainting results with sensible structures.", + "bbox": [ + 75, + 563, + 470, + 652 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Results of Novel View Synthesis", + "text_level": 1, + "bbox": [ + 76, + 664, + 356, + 681 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results of Single-view NVs. We compare the quantitative NVs results on Objaverse in Table 2. The qualitative results for both Objaverse and Google Scanned Objects are compared in Figure 8. Without specific annotations, all NVs results are based on adaptive masking. The CLIP score [43] is compared to evaluate the similarity between the generation and the target. Specifically, LeftRefill fine-tuned with the whole LDM enjoys substantial achievements compared to the state-of-the-art competitor Zero123 [30], even though Zero123 might have seen our validation in Objaverse. Moreover, the LoRA-based LeftRefill [21] is still competitive with a very moderate training setting (batch size 48 with 2 A6000 GPUs) in Table 2. We further compare the training log of LeftRefill and Zero123 in the supplementary to investigate", + "bbox": [ + 75, + 688, + 470, + 900 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/85d91010444793bad639a6a47cc6fe2b528cb46a9a26c220d435cdcf4a9fb638.jpg", + "table_caption": [ + "Table 2. Results of 1-view NVS conditioned on different numbers of reference views on Objaverse [10]. 'w.o. AM' indicates NVS results without Adaptive Masking (AM)." + ], + "table_footnote": [], + "table_body": "
MethodsRef-ViewPSNR↑SSIM↑LPIPS↓CLIP↑
Zero123 [30]119.4020.8580.13090.7816
LeftRefill (LoRA)119.5140.8690.15340.7589
LeftRefill (w.o. AM)121.6750.8870.10890.7959
LeftRefill121.4040.8820.11510.7972
LeftRefill222.9350.8950.08710.8280
LeftRefill324.1070.9080.07220.8432
LeftRefill424.6850.9110.06340.8495
", + "bbox": [ + 501, + 128, + 895, + 262 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/9709f3ef11da66ade0195061d341e3d5aa29c753c205774b66049ab8721dd395.jpg", + "table_caption": [ + "Table 3. Results of 4-view NVS generations based on 1 reference view on Objaverse [10]. P-CLIP means pairwise CLIP score showing consistency of generated views. The reference (Ref) can be categorized into the first ground-truth view and the last generated view, while we also provide the AR results of LeftRefill." + ], + "table_footnote": [], + "table_body": "
MethodsRefPSNR↑SSIM↑LPIPS↓CLIP↑P-CLIP↑
Zero123First19.2650.8550.13660.77230.7756
Zero123Last14.6210.7670.25690.69210.7667
LeftRefillFirst21.5730.8830.11430.79640.7709
LeftRefillAR21.2710.8820.11950.78820.7958
", + "bbox": [ + 503, + 335, + 885, + 419 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/24225828d4b1a20f2f28dd2b8224dc532f80e628dd2b7acec1c25cb2e535af26.jpg", + "image_caption": [ + "Figure 10. Visualization of attention scores in LeftRefill for Refinpainting across different DDIM steps. We show scores from reference views attended by masked regions. The upper row shows attention scores from the 8th self-attention (1/32 scale), while the bottom row shows ones from the 14th self-attention (1/8 scale)." + ], + "image_footnote": [], + "bbox": [ + 509, + 421, + 879, + 565 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "the training convergence for NVs. The contextual inpainting-based LeftRefill enjoys a substantially faster convergence and superior image quality. So LeftRefill enjoys a good balance between training efficiency and performance.", + "bbox": [ + 496, + 657, + 893, + 718 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Results of Multi-view NVs. Quantitative results of multi-view NVs are shown in the lower of Table 2. Obviously, more reference views lead to better reconstruction quality of LeftRefill. Moreover, additional reference images could substantially alleviate the ambiguity, improving the final results with consistent geometry. Benefited by AR, LeftRefill can be also generalized to synthesize a group of consistent images with different viewpoints from a single view as shown in Figure 9 and Table 3. We introduce the pairwise CLIP score (P-CLIP) to verify the consistency of all generated samples. LeftRefill outperforms Zero123 in most metrics, while AR could prominently improve the consistency with just a little", + "bbox": [ + 496, + 719, + 893, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "7711", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/2fa34c680a2de8a44fee803ea3c4ed5a77ed489bf8672c25cc3ff2cb311e0937.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Prompt TypeLengthPSNR↑SSIM↑LPIPS↓Params
Shallow2520.350.8270.104+0.025M
Shallow5020.490.8290.103+0.05M
Shallow7520.380.8300.104+0.075M
Deep (×16)25(400)20.150.8250.106+0.4M
", + "bbox": [ + 163, + 138, + 514, + 227 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/b94b0f90d48ed3474a5ca9e415deeb37887ef36ad883d0c11eb710c1f16870e2.jpg", + "table_caption": [ + "Table 4. Ablation studies for the setting of prompt tuning in Ref-inpainting. Left: 'Shallow' means only prompt tuning to text embedding, while 'Deep' indicates tuning additional embedding features to different cross-attention layers (16 layers) in SD. Right: validating the influence of the length of shared (Task) and unshared (View) prompts with 3-view Ref-inpainting." + ], + "table_footnote": [], + "table_body": "
TaskViewPSNR↑SSIM↑LPIPS↓Params
50021.2240.8380.0941+0.05M
45521.3560.8400.0901+0.06M
252521.1270.8360.0950+0.11M
54520.7440.8320.1040+0.14M
05020.5630.8310.1110+0.15M
", + "bbox": [ + 531, + 133, + 807, + 232 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/5495d4ae049348b0b8c1cb145ceb8446447a4985cc5a6f1f5fdca9ba1fb0157c.jpg", + "table_caption": [ + "Table 5. NVS results of LeftRefill-simple with different reference views with/without incremental Positional Encoding (PE)." + ], + "table_footnote": [], + "table_body": "
Ref-ViewPEPSNR↑SSIM↑LPIPS↓
1×20.3520.8730.132
1✓20.5080.8750.128
4×22.0970.8880.099
4✓22.3240.8900.095
", + "bbox": [ + 120, + 263, + 426, + 356 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "quality degradation. Our method can also be generalized to real-world data as shown in the supplementary.", + "bbox": [ + 75, + 382, + 468, + 412 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3. Analysis and Ablation Studies", + "text_level": 1, + "bbox": [ + 76, + 422, + 344, + 438 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Self-Attention Analysis. We show the visualization of self-attention scores attended by masked regions for Refinpainting across different DDIM steps in Figure 10. Self-attention can capture correct feature correlations without any backbone fine-tuning. As diffusion sampling progresses, self-attention modules gradually shift their focus from specific key points to broader related regions, which is convincing and intuitive. Because the key landmarks help to swiftly locate the spatial correlation between the reference and target, while the extended receptive fields further refine the generation for the following sampling steps. More analysis about the attention visualization with increased reference views is shown in the supplementary.", + "bbox": [ + 75, + 446, + 472, + 643 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Prompt Settings. The length and depth used in the task and view prompt tuning are explored in Table 4. Different from [23], we find that LeftRefill is relatively robust in the length selection. Thus we select 50 for both Ref-inpainting and NVS. Moreover, the deep prompt with much more trainable prompts for different cross-attention layers does not perform well, which may suffer from a little overfitting. For the multi-view scene, we empirically evaluate the 3-view-based Ref-inpainting performance with various proportions of task&view prompt lengths in the right of Table 4. Increasing the proportion of view tokens initially improves the results, followed by a subsequent decline. We think that a few unshared view tokens contribute valuable view orders, while too many unshared tokens would increase the learning difficulty, leading to an inferior prompt tuning performance. Incremental Positional Encoding. We incrementally add the concatenation of learnable view embedding and absolute", + "bbox": [ + 75, + 643, + 472, + 900 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9d691f7011ef37fe3912624be3788692bcd78850ed3047c7a74d91526165a604.jpg", + "image_caption": [ + "Figure 11. Ref-inpainting results with different CFG weights, which take a trade-off between structural and textural recoveries." + ], + "image_footnote": [], + "bbox": [ + 514, + 243, + 875, + 368 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "positional encoding to each attention block for NVs (Equation (1)), improving the performance of both single-view and multi-view-based NVs as verified in Table 5.", + "bbox": [ + 496, + 415, + 893, + 460 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Classifier-Free Guidance (CFG) [19]. We find that CFG can enhance the performance of Ref-inpainting even without training with prompt dropout as in Figure 11. The adjusting of CFG could be seen as the trade-off between structural and textural recoveries. High CFG scales lead to over-saturated results with superior structure. We empirically set CFG to 2.0 and 2.5 for Ref-inpainting and NVs respectively. More quantitative results and details about the CFG setting of NVs are discussed in the supplementary.", + "bbox": [ + 496, + 460, + 893, + 599 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 614, + 617, + 631 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we propose LeftRefill, formulating reference-based synthesis as inpainting tasks and addressing them end-to-end as a human painter. Benefiting from the prompt tuning and the well-learned attention modules in large T2I models, LeftRefill can address the spatially sophisticated Ref-inpainting and NVs efficiently. Moreover, LeftRefill could be easily extended to tackle multi-view generation tasks. We also propose block casual masking to accomplish NVs with consistent results autoregressively. Comprehensive experiments on Ref-inpainting and NVs show the effectiveness and efficiency of LeftRefill.", + "bbox": [ + 496, + 642, + 893, + 808 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements: Yanwei Fu is the corresponding author. Yanwei Fu is with the School of Data Science, Shanghai Key Lab of Intelligent Information Processing, Fudan University, and Fudan ISTBI-ZJNU Algorithm Centre for Brain-inspired Intelligence, Zhejiang Normal University. The computations in this research were performed using the CFFF platform of Fudan University.", + "bbox": [ + 496, + 810, + 895, + 901 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "7712", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Omri Avrahami, Dani Lischinski, and Ohad Fried. Blended diffusion for text-driven editing of natural images. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 18208-18218, 2022. 2", + "[2] Omer Bar-Tal, Lior Yariv, Yaron Lipman, and Tali Dekel. Multidiffusion: Fusing diffusion paths for controlled image generation. arXiv preprint arXiv:2302.08113, 2, 2023. 2", + "[3] Marcelo Bertalmio, Guillermo Sapiro, Vincent Caseles, and Coloma Ballester. Image inpainting. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 2266-2276, 2021. 2, 3, 5, 6" + ], + "bbox": [ + 501, + 92, + 893, + 273 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "7715", + "bbox": [ + 482, + 945, + 514, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/LeftRefill_ Filling Right Canvas based on Left Reference through Generalized Text-to-Image Diffusion Model/908a3914-e513-461a-933d-8314753d5fc2_model.json b/2024/LeftRefill_ Filling Right Canvas based on Left Reference through Generalized Text-to-Image Diffusion Model/908a3914-e513-461a-933d-8314753d5fc2_model.json new file mode 100644 index 0000000000000000000000000000000000000000..2976d4a2093a638f9f31f3d16c23dce2186a22e3 --- /dev/null +++ b/2024/LeftRefill_ Filling Right Canvas based on Left Reference through Generalized Text-to-Image Diffusion Model/908a3914-e513-461a-933d-8314753d5fc2_model.json @@ -0,0 +1,2147 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.044 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.158, + 0.131, + 0.817, + 0.177 + ], + "angle": 0, + "content": "LeftRefill: Filling Right Canvas based on Left Reference through Generalized Text-to-Image Diffusion Model" + }, + { + "type": "text", + "bbox": [ + 0.209, + 0.203, + 0.77, + 0.241 + ], + "angle": 0, + "content": "Chenjie Cao\\(^{1,2*}\\), Yunuo Cai\\(^{1}\\), Qiaole Dong\\(^{1}\\), Yikai Wang\\(^{1}\\), Yanwei Fu\\(^{1\\dagger}\\), Fudan University, \\(^{2}\\)Alibaba Group" + }, + { + "type": "image", + "bbox": [ + 0.099, + 0.277, + 0.87, + 0.529 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.534, + 0.895, + 0.604 + ], + "angle": 0, + "content": "Figure 1. LetRefill addresses the generation on the right canvas conditioned by left references. We can re-formulate several existing tasks in the LeftRefill manner, including (a) reference-guided inpainting, (b) novel view synthesis. The reference and target can be further extended to multi-view scenes, forming (c) multi-view reference inpainting and (d) multi-view synthesis, respectively. Green frames indicate stitched inputs. Reference views are placed on the left side, while masked target views are placed on the right side. Violet frames only show enlarged right-side generations produced by LeftRefill. Note that we omit some input details in (c) and (d) for simplicity." + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.616, + 0.314, + 0.631 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.647, + 0.473, + 0.844 + ], + "angle": 0, + "content": "This paper introduces LeftRefill, an innovative approach to efficiently harness large Text-to-Image (T2I) diffusion models for reference-guided image synthesis. As the name implies, LeftRefill horizontally stitches reference and target views together as a whole input. The reference image occupies the left side, while the target canvas is positioned on the right. Then, LeftRefill paints the right-side target canvas based on the left-side reference and specific task instructions. Such a task formulation shares some similarities with contextual inpainting, akin to the actions of a human painter. This novel formulation efficiently learns both structural and textured correspondence between reference and target without other image encoders" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.617, + 0.895, + 0.799 + ], + "angle": 0, + "content": "or adapters. We inject task and view information through cross-attention modules in T2I models, and further exhibit multi-view reference ability via the re-arranged self-attention modules. These enable LeftRefill to perform consistent generation as a generalized model without requiring test-time fine-tuning or model modifications. Thus, LeftRefill can be seen as a simple yet unified framework to address reference-guided synthesis. As an exemplar, we leverage LeftRefill to address two different challenges: reference-guided inpainting and novel view synthesis, based on the pre-trained StableDiffusion. Codes&models are released at https://github.com/ewrfcas/LeftRefill." + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.829, + 0.633, + 0.845 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.856, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Imagine you are a right-handed painter with a task that requires you to draw or modify a target image based on a reference picture. How would you approach it? Intuitively," + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.851, + 0.471, + 0.902 + ], + "angle": 0, + "content": "\\(^*\\) Dr. Chenjie Cao is at Alibaba Group. This work was accomplished while Dr. Chenjie Cao was at Fudan University. \n† Corresponding author: yanweifu@fudan.edu.cn \nOther emails: {cjcao20,yncai20,qldong18,yikaiwang19} @fudan.edu.cn" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7705" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.273 + ], + "angle": 0, + "content": "you would likely place the reference image on your left side and paint or modify the target view on the right side conditioned on the left one. If we regard the large Text-to-Image (T2I) models [6, 37, 41, 44, 46, 48] as skillful painters, could they also follow such simple and intuitive task formulation to handle complex reference-guided synthesis tasks? In this paper, we explore this problem with two challenging tasks: 1) Inpainting masked target views conditioned on reference images, i.e., reference-guided inpainting (Ref-inpainting) [67, 68] as in Figure 1(a). 2) Generating new views based on known images of specific objects, i.e., Novel View Synthesis (NVS) [30] as in Figure 1(b)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.274, + 0.473, + 0.454 + ], + "angle": 0, + "content": "It seems straightforward to harness the power of T2I generative models to directly address these image-reference tasks by training additional adapters [21, 36, 64] or replacing textual encoders with visual ones [30, 62] and optimize them for full fine-tuning of the entire T2I model. We should clarify that training these large T2I models with unfamiliar visual encoders is computationally intensive and challenging to converge, particularly when working with limited batch sizes. Additionally, most visual encoders, such as image CLIP [43], tend to emphasize the learning of semantic features rather than the intricately spatial details that are essential for tasks involving Ref-inpainting as verified in our experiments." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.455, + 0.473, + 0.756 + ], + "angle": 0, + "content": "To prevent the heavy modification to T2I models mentioned above, we rethink the human painting habit and propose LeftRefill, a unified approach for both Ref-inpainting and NVS. LeftRefill is built upon the inpainting fine-tuned StableDiffusion2.0 (SD) [46]*, which ingeniously reformulates reference-based synthesis as a contextual inpainting process. Specifically, LeftRefill horizontally stitches reference and target views as a whole input. As shown in Figure 1, reference images are positioned on the left side, while masked targets are on the right side. This simple yet effective formulation eliminates the dependency on additional image feature encoders, as both reference and target views have been stitched into the same canvas. As an \"experienced painter\", LeftRefill is driven by specific instructions, called task and view prompt tuning. These instructions infuse crucial information for specific generative tasks and desired view orders to cross-attention modules, guiding the generation of SD. Note that LeftRefill is a generalized framework, so we can train two LeftRefill models for Ref-inpainting and NVS separately without any test-time fine-tuning." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.757, + 0.473, + 0.879 + ], + "angle": 0, + "content": "On the other hand, we emphasize that LeftRefill further enjoys extension into multi-view synthesis scenarios, including image inpainting conditioned on multi-view references in Figure 1(c) and consistent NVS from a single view in Figure 1(d). Formally, we rearrange the tensor shape before the self-attention modules, enabling self-attention to capture cross-view information. Moreover, to tackle the more intricate NVS task, we propose the novel technique of block" + }, + { + "type": "text", + "bbox": [ + 0.497, + 0.092, + 0.895, + 0.212 + ], + "angle": 0, + "content": "causal masking, facilitating self-attention-based T2I models in achieving consistent autoregressive (AR) generation. All improvements are integrated into the off-the-shelf SD components, involving no additional image encoder, prompt tuning based on cross-attention, self-attention rearranging and block causal masking. LeftRefill emerges as a unified architecture for addressing reference-guided synthesis, requiring only minor model modifications." + }, + { + "type": "text", + "bbox": [ + 0.497, + 0.213, + 0.897, + 0.47 + ], + "angle": 0, + "content": "We highlight the key contributions of LeftRefill as follows: 1) Lightweight and generalized task formulation based on off-the-shelf T2I models: Benefiting from the novel contextual inpainting formulation and inherent attention mechanisms from SD, LeftRefill provides an efficient solution for reference-guided synthesis without thoroughly re-training T2I models and test-time fine-tuning. 2) Task and view-specific prompt tuning: Our work pioneers the use of task and view-specific prompt tuning, allowing for precise control over generative tasks and view orders. 3) End-to-end Ref-inpainting: Notably, our LeftRefill addresses the challenging Ref-inpainting end-to-end, without complex 3D geometrical warping and 2D inpainting techniques [65, 67, 68]. 4) Autoregressive NVS with block causal masking: For the intricate NVS task, we introduce the novel concept of block causal masking, enabling self-attention-based T2I models to achieve AR generation for geometric consistency." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.483, + 0.642, + 0.499 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.497, + 0.508, + 0.897, + 0.825 + ], + "angle": 0, + "content": "Personalization and Controllability of T2I Models. Recent achievements on T2I have produced impressive visual generations [2, 36, 42], which could be further extended into local editing [1, 8, 18]. However, these models could only be controlled by natural languages. As \"an image is worth hundreds of words\", T2I models based on natural texts fail to produce images with specific textures, locations, identities, and appearances [15]. Textual inversion [15, 35] and fine-tuning techniques [47] are proposed for personalized T2I. Meanwhile, many works pay attention to image-guided generations [26, 34, 58]. ControlNet [64] and T2I-Adapter [36] learn trainable adapters [20] to inject visual clues to pretrained T2I models without losing generalization and diversity. But these moderate methods only work for simple style transfers. More spatially complex tasks, such as Refinpainting, are difficult to handle by ControlNet as verified in Section 4. In contrast, T2I-based exemplar-editing and NVS have to be fine-tuned on large-scale datasets with strong data augmentation [62] and large batch size [30]. Compared with these aforementioned manners, LeftRefill enjoys both spatial modeling capability and computational efficiency." + }, + { + "type": "text", + "bbox": [ + 0.497, + 0.826, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Prompt Tuning [24, 32, 33] indicates fine-tuning token embeddings for transformers with frozen backbone to preserve the capacity. Prompt tuning is first explored for adaptively learning suitable prompt features for language models rather than manually selecting them for different downstream" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.888, + 0.432, + 0.9 + ], + "angle": 0, + "content": "*https://github.com/Stability-AI/stablediffusion." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.946, + 0.517, + 0.957 + ], + "angle": 0, + "content": "7706" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.227 + ], + "angle": 0, + "content": "tasks [29]. Moreover, prompt tuning has been further investigated in vision-language models [16, 43] and discriminative vision models [23, 28]. Visual prompt tuning in [53] prepends trainable tokens before the visual sequence for transferred generations. Though both LeftRefill and [53] aim to tackle image synthesis, our prompt tuning is used for controlling text encoders rather than visual ones. Thus LeftRefill enjoys more intuitive prompt initialization from task-related textual descriptions." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.228, + 0.474, + 0.468 + ], + "angle": 0, + "content": "Reference-guided Image Inpainting. Image inpainting is a long-standing vision task, which aims to fill missing image regions with coherent results. Both traditional methods [3, 9, 17] and learning-based ones [11, 25, 54, 63, 66] achieved great progress in image inpainting. Furthermore, Ref-inpainting requires recovering a target image with one or several reference views from different viewpoints [40], which is useful for repairing old buildings or removing occlusions in popular attractions. But Ref-inpainting usually suffers from a sophisticated pipeline [65, 67, 68], including depth estimation, pose estimation, homography warping, and single-view inpainting. Limited by large holes, the estimated geometric pose is not reliable, largely degrading the pipeline. Thus an end-to-end Ref-inpainting pipeline is meaningful. To the best of our knowledge, we are the first ones to tackle such a difficult reference-guided task with T2I models." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.469, + 0.474, + 0.727 + ], + "angle": 0, + "content": "Novel View Synthesis from a Single Image. NVs based on a single image is an intractable ill-posed problem, requiring both sufficient geometry understanding and expressive textural presentation [14]. Many previous works could partially tackle this problem through single view 3D reconstruction [7, 31, 59–61], 2D generative models [39, 45, 52], feature cost volumes [5], and GAN-based methods [4, 38, 51]. However, these manners still suffer from limited generalization or small angle variations. To address this issue, Zero123 [30] uses another image CLIP encoder to inject image features from the reference view to unlock the capacity from 2D diffusion-based T2I models for NVs. But Zero123 requires a large batch size and expensive computational resources to stabilize the training stage with an unknown reference image encoder. Moreover, the image encoder in Zero123 can only tackle one reference image, which fails to generate consistent multi-view images." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.738, + 0.169, + 0.753 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.763, + 0.473, + 0.84 + ], + "angle": 0, + "content": "Overview. LeftRefill is first formulated in Section 3.1. Then we explain using self-attention to capture multi-view correspondence, and AR generation based on block casual masking (Section 3.2). Finally, we discuss the task and view-specific prompt tuning for cross-attention (Section 3.3)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.848, + 0.303, + 0.862 + ], + "angle": 0, + "content": "3.1. Framework of LeftRefill" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Motivations. As depicted in Figure 2(a), our LeftRefill is built upon the inpainting fine-tuned SD [46]. There are two" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.093, + 0.709, + 0.248 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.718, + 0.094, + 0.89, + 0.25 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.26, + 0.895, + 0.33 + ], + "angle": 0, + "content": "Figure 2. (a) The overview of LeftRefill. Inputs of Ref-inpainting and NVs are shown in (b). Task and view prompt embedding and pose features (optional for NVS) are infused to CLIP-H for cross-attention learning in U-net. For the output of LeftRefill, we discard the left-side reference and take the right-side generation." + }, + { + "type": "image", + "bbox": [ + 0.523, + 0.333, + 0.707, + 0.57 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.719, + 0.332, + 0.857, + 0.57 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.571, + 0.894, + 0.64 + ], + "angle": 0, + "content": "Figure 3. Illustration about multi-view training inputs \\((v\\times H\\times 2W\\), \\(v = 4)\\) of LeftRefill, where \\(v,H,2W\\) indicate the view number, height, and width of stitching images. All views of Ref-inpainting (a) share the same masked target, while the multi-view NVS (b) should be trained with the AR generation." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.895, + 0.885 + ], + "angle": 0, + "content": "primary motivations that make us stitch reference and target images together and reformulate both Ref-inpainting and NVS as a contextual image inpainting problem. 1) LeftRefill just considers a single input image, eliminating the requirement of additional image encoders and avoiding major architectural alterations and extensive re-training. 2) Since all T2I models are only pre-trained on single-view images, the left-right stitched input could implicitly reactivate the essential capacity from large T2I models of modeling the correlation of the single-view image. Particularly, the left-right stitching input enables the self-attention modules to focus on correct parts from left-side reference at the early stage of diffusion sampling (Figure 10). We also thoroughly evaluate different alterations of reference-guided SD in Section 4.1. LeftRefill substantially outperforms other competitors with high efficiency and negligible trainable weights." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.886, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Single-view Formulation (1-to-1). Thanks to the convo" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7707" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.129, + 0.091, + 0.422, + 0.301 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.302, + 0.471, + 0.357 + ], + "angle": 0, + "content": "Figure 4. Detailed architecture of LeftRefill for multi-view synthesis. Both CNN and cross-attention modules are encoded separately for each stitched view, while all views share the same self-attention for multi-view correlation learning." + }, + { + "type": "image", + "bbox": [ + 0.118, + 0.361, + 0.391, + 0.414 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.158, + 0.416, + 0.393, + 0.426 + ], + "angle": 0, + "content": "(a) Illustration about the shape rearranging of LeftRefill" + }, + { + "type": "image", + "bbox": [ + 0.115, + 0.427, + 0.426, + 0.546 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.152, + 0.55, + 0.396, + 0.561 + ], + "angle": 0, + "content": "(b) Block causal masking used for autoregressive training" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.564, + 0.471, + 0.62 + ], + "angle": 0, + "content": "Figure 5. (a) Feature rearranging, and (b) block causal masking of LeftRefill, where \\( b, v, h, w, c \\) indicate the batch size, view number, height, width, and channels of features, where \\( w \\) is the width of stitching features (downsampled from \\( 2W \\))." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.626, + 0.47, + 0.869 + ], + "angle": 0, + "content": "lutional U-net architecture in the Latent Diffusion Model (LDM), we can expand the input image in the spatial dimensions without any modification. Let's consider a scenario with a single reference image at first, i.e., 1-to-1. Our input \\(\\mathbf{I}'\\) is a stitching image of \\(\\mathbf{I}_{ref}\\) and the masked target \\(\\hat{\\mathbf{I}}_{tar}\\), forming as \\(\\mathbf{I}' = [\\mathbf{I}_{ref};\\hat{\\mathbf{I}}_{tar}] \\in \\mathbb{R}^{H \\times 2W}\\) as shown in Figure 2(a). In practice, we take the reference image on the left side, while the target one is placed on the right side. We just take the right-side output as the final generation while the left-side output is discarded. Note that the diffusion optimization is based on the whole stitched image without any modification. For the masked target \\(\\hat{\\mathbf{I}}_{tar}\\), we treat Ref-inpainting's input targets as partially masked images, while NVS's input targets are entirely masked through the objective segmentation and bounding box. More details about the processing of data and masks are discussed in the supplementary." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Multi-view Formulation (V-to-1). For the multi-view references, we stitch each reference with the specific target" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.302 + ], + "angle": 0, + "content": "as shown in Figure 3. All views are learned separately for convolutions and cross-attention, while they share the same self-attention processing as shown in Figure 4 and detailed in Section 3.2. From Figure 3(a), the multi-view Ref-inpainting leverages information from different reference views to repair the same target, i.e., \\( v \\)-to-1, where \\( v \\) means the view number. We simply take the generation of the first view as the final inpainted output in \\( v \\)-to-1. For the multi-view NVS, it could be seen as an AR generation for sequentially consistent view synthesis, as depicted in Figure 3(b), i.e., \\( n \\)-to-1 (\\( n = 1,2,\\dots,v \\)). During the inference, we apply the generated targets as new references for the subsequent view synthesis, while the training phase is accomplished parallelly as detailed in the block casual masking of Section 3.2." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.303, + 0.895, + 0.575 + ], + "angle": 0, + "content": "Controlling Generation for LeftRefill. Although the self-attention modules in SD have the potential to enable the correlation between left reference and right target, SD is not trained to explicitly activate this capacity. The most intuitive way to guide the SD in capturing the correlation among left-right stitched images is to apply suitable text prompts to drive the diffusion model for the desired generation. However, it is non-trivial to define Ref-inpainting and NVS with natural languages. Furthermore, it is beneficial to have a non-instance-level prompt to generally guide the diffusion model to accomplish specific tasks. To this end, we propose to use prompt tuning to learn task and view-specific prompts as detailed in Section 3.3. Except for the prompt tuning, all weights in LDM are frozen in Ref-inpainting to maintain the proper generalization as shown in Figure 2(a). For NVS, we fine-tune the whole LDM to achieve essentially precise pose control, but LeftRefill enjoys much better convergence compared with other fine-tuning based methods [30]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.584, + 0.863, + 0.599 + ], + "angle": 0, + "content": "3.2. Reactivating Self-Attention for Multi-View" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.607, + 0.894, + 0.758 + ], + "angle": 0, + "content": "As shown in Figure 5(a), given multi-view features \\(\\mathbf{F}_i\\) of layer \\(i\\), all MLP, convolutional, and cross-attention layers encode \\(\\mathbf{F}_i\\) separately. We can simply achieve the separate feature encoding by reshaping the view \\(v\\) and batch \\(b\\) dimension together as \\(bv\\). Before the self-attention, we rearrange the feature shape as \\(\\tilde{\\mathbf{F}}_i \\in \\mathbb{R}^{b \\times vhw \\times c}\\), thus features across different views could be learned together. To further incorporate positional clues for distinguishing different sides of reference and target in NVS, we incrementally add positional encoding \\(P_i\\) to \\(\\tilde{\\mathbf{F}}_i\\) before each self-attention block as" + }, + { + "type": "equation", + "bbox": [ + 0.596, + 0.769, + 0.892, + 0.786 + ], + "angle": 0, + "content": "\\[\nP _ {i} = \\gamma_ {i} \\cdot \\operatorname {c a t} ([ P _ {v}; P _ {\\text {F o u r i e r}} ]), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.892, + 0.841 + ], + "angle": 0, + "content": "where \\(P_{v}, P_{Fourier}\\) indicate the trainable view embedding and Fourier absolute positional encoding [57] respectively; \\(\\gamma_{i}\\) is a zero-initialized learnable coefficient for each layer." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.841, + 0.894, + 0.901 + ], + "angle": 0, + "content": "For the Ref-inpainting, no masking strategy should be considered in self-attention modules. All reference views share the same target one, thus it is unnecessary for LeftRefill to sequentially repair target views. In contrast, for the" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "7708" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.181 + ], + "angle": 0, + "content": "multi-view NVs, generating consistent novel views from a single image needs our model to handle the sequential generation with dynamic reference views. For example, the same LeftRefill should accomplish the NVS from one view, two views, and even more. So the AR generation [13, 49, 56] is suitable to formulate this task." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.182, + 0.474, + 0.471 + ], + "angle": 0, + "content": "Block Causal Masking. LeftRefill requires a certain finetuning for LDM to effectively tackle challenging NVS as shown in Figure 2(a). The intuitive solution is to train an AR-based generative model that can generalize across various view numbers for multi-view synthesis. Converting a pretrained diffusion model to an AR-based generative model is non-trivial. However, the inpainting formulation of Left-Refill makes this conversion feasible. Specifically, we just need to adjust the masking strategy during the self-attention learning. We propose the block casual masking as shown in Figure 5(b), while the block side-length of each view is \\( h w \\), matching the size of the stitched reference and target pair. Different from the traditional casual mask which is a lower triangular matrix, the block casual mask enlarges the minimal unit from one token to a \\( h w \\times h w \\) block, ensuring reasonable block-wise receptive fields. In practice, all uncolored tokens in the attention score are masked with “—inf” before the softmax operation. The block casual mask can be implemented parallelly and efficiently as in supplementary." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.478, + 0.327, + 0.495 + ], + "angle": 0, + "content": "3.3. Task&View Prompt Tuning" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.501, + 0.471, + 0.744 + ], + "angle": 0, + "content": "The prompt embedding is adopted as the textual branch to CLIP-H [43] of SD, being applied to cross-attention as shown in Figure 2(a). Specifically, we prepare a set of trainable text embeddings for different generative tasks, which are further categorized into task and view prompts. Specifically, task prompt embeddings are shared in the same task, e.g., all views of Ref-inpainting using the same task embeddings. In contrast, different view prompt embeddings are applied to inject various view-order information through cross-attention modules to the specific input view. Though there are only a few trainable parameters (0.05M to 0.065M), we astonishingly find that prompt tuning is sufficient to drive complex generative tasks such as Ref-inpainting, even with a frozen LDM backbone. The trainable task and view prompt embeddings \\( p_t \\), \\( p_v \\) are initialized as the averaged embedding of the natural task description. The optimization target is:" + }, + { + "type": "equation", + "bbox": [ + 0.082, + 0.748, + 0.471, + 0.775 + ], + "angle": 0, + "content": "\\[\n\\left\\{p _ {t}, p _ {v} \\right\\} _ {*} = \\underset {\\left\\{p _ {t}, p _ {v} \\right\\}} {\\arg \\min } \\mathbb {E} \\left[ \\left\\| \\varepsilon - \\varepsilon_ {\\theta} \\left([ z _ {t}; \\hat {z} _ {0}; \\mathbf {M} ], c _ {\\phi} \\left(p _ {t}, p _ {v}\\right), t\\right) \\right\\| ^ {2} \\right], (2)\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.471, + 0.903 + ], + "angle": 0, + "content": "where \\(\\varepsilon_{\\theta}(\\cdot)\\) is the estimated noise by LDM; \\(c_{\\phi}(\\cdot)\\) means the frozen CLIP-H; \\(z_{t}\\) is a noisy latent feature of input \\(z_{0}\\) in step \\(t\\); \\(\\hat{z}_0 = z_0\\odot (1 - \\mathbf{M})\\) are masked latent features concatenated to \\(z_{t}\\) with mask \\(\\mathbf{M}\\). Task and view-specific prompt tuning enjoy not only training efficiency but also lightweight saving [24]. For example, we share the same LeftRefill to address Ref-inpainting with different reference views, while only \\(0.01\\%\\) additional weights of \\(\\{p_t,p_v\\}_{*}\\) are" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.076, + 0.895, + 0.16 + ], + "angle": 0, + "content": "Table 1. Quantitative results for Ref-inpainting on MegaDepth [27] test set based on matching and manual masks (upper: 1-view; lower: multi-view). 'ExParams': the scale of extra trainable parameters. * means that the uncorrupted ground truth is visible for the matching. 'No stitching': reference and target views are separate without spatial stitching, and only self-attention are learned across them." + }, + { + "type": "table", + "bbox": [ + 0.502, + 0.16, + 0.9, + 0.338 + ], + "angle": 0, + "content": "
MethodsPSNR↑SSIM↑FID↓LPIPS↓ExParams
SD ( inpainting) [46]19.8410.81930.2600.1349+0
ControlNet [64]19.0720.74433.6640.1816+364.2M
ControlNet+NewCrossAttn19.0270.74334.1700.1805+463.4M
ControlNet+Matching* [55]20.5920.76329.5560.1565+364.3M
Perceiver+ImageCLIP [22]19.3380.74532.9110.1751+52.01M
Paint-by-Example [62]18.3510.79734.7110.1604+865.9M
TransFill [68]22.7440.87526.2910.1102-
LeftRefill (no stitching)20.4890.82720.1250.1085+0.05M
LeftRefill20.9260.83618.6800.0961+0.05M
LeftRefill (2-view)21.0920.83618.3890.0969+0.055M
LeftRefill (3-view)21.3560.84016.8380.0901+0.06M
LeftRefill (4-view)21.7790.84716.6320.0839+0.065M
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.344, + 0.895, + 0.435 + ], + "angle": 0, + "content": "changed for each view condition. In NVS, we further provide relative poses to LeftRefill. Following [30], we calculate the 4-channel relative pose in the polar coordinate for each view, which is encoded by a two-layer FC. Then the pose feature replaces the last padding token in the prompt embeddings before being applied to the CLIP-H." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.451, + 0.634, + 0.468 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.477, + 0.895, + 0.689 + ], + "angle": 0, + "content": "Datasets. For Ref-inpainting, we use the resized \\(512 \\times 512\\) image pairs from MegaDepth [27], which includes many multi-view famous scenes collected from the Internet. To trade-off between the image correlation and the inpainting difficulty, we empirically retain image pairs with \\(40\\%\\) to \\(70\\%\\) co-occurrence with about 80k images and 820k pairs. The validation of Ref-inpainting also includes some manual masks from ETH3D scenes [50] to verify the generalization. For the NVS, we use Objaverse [10] rendered by [30] including 800k various scenes with object masks. We resize all images to \\(256 \\times 256\\) as [30]. Note that some extreme views with elevation angles less than \\(-10^{\\circ}\\) are filtered due to excessive ambiguity. More details about the masking and datasets are introduced in the supplementary." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.897, + 0.901 + ], + "angle": 0, + "content": "Implementation Details. Our LeftRefill is based on the inpainting fine-tuned SD [46] with 0.8 billion parameters. For the task and view prompt tuning, there are 50 trainable prompt tokens at all. We use \\(90\\%\\) tokens to represent the task embeddings, while \\(10\\%\\) tokens indicate each view respectively. We use the AdamW optimizer with a weight decay of 0.01 to optimize LeftRefill. For the Ref-inpainting, the prompt tuning's learning rate is 3e-5. Moreover, \\(75\\%\\) masks are randomly generated, and \\(25\\%\\) of them are matching-based masks. For the NVS, LeftRefill could be tested with the adaptive masking strengthened by the foreground segmentation model. Concretely, we first enlarge the reference segmentation mask and generate a coarse target with fewer DDIM steps. We extract the new mask from the coarse tar" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7709" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.139, + 0.089, + 0.831, + 0.369 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.177, + 0.378, + 0.788, + 0.393 + ], + "angle": 0, + "content": "Figure 6. Qualitative Ref-inpainting results on MegaDepth [27]. More results are in the supplementary." + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.405, + 0.47, + 0.537 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.549, + 0.471, + 0.577 + ], + "angle": 0, + "content": "Figure 7. Multi-view Ref-inpainting qualitative results. Increasing the reference view number improves the quality of repaired targets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.593, + 0.47, + 0.699 + ], + "angle": 0, + "content": "get and then further randomly enlarge it as the final target mask. The NVS LeftRefill is trained with 512 batch size and learning rate 3e-5. We show that a simplified LeftRefill with just 48 batch size can also be converged for NVS, which breaks through the limitation of Zero123 [30]. More details about matching-based masks, adaptive masking, and training schedules are discussed in the supplementary." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.711, + 0.414, + 0.727 + ], + "angle": 0, + "content": "4.1. Results of Reference-guided Inpainting" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Results of One-view Reference. We thoroughly compared the specific Ref-inpainting method [68] and existing image reference-based variants of SD with one-view reference in Table 1 and Figure 6. Note that ControlNet [64] fails to learn the correct spatial correlation between reference images and masked targets, even enhanced with trainable cross-attention learned between reference and target features. Furthermore, we try to warp ground-truth latent features with image matching [55] as the reference guidance for ControlNet, but the improvement is not prominent. Perceiver [22] and Paint-by-Example [62] align and learn image features from Image" + }, + { + "type": "image", + "bbox": [ + 0.539, + 0.411, + 0.857, + 0.678 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.686, + 0.892, + 0.715 + ], + "angle": 0, + "content": "Figure 8. NVS results on Objaverse [10] (row1, 2) and Google Scanned Objects [12] (row3, 4) from a single reference image." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.903 + ], + "angle": 0, + "content": "CLIP. Since image features from CLIP contain high-level semantics, they fail to deal with the fine-grained Ref-inpainting as shown in Figure 6(e)(f). Though TransFill [68] achieves proper results in PSNR and SSIM, it suffers from blur and color difference as in Figure 6(g) with challenging viewpoints. LeftRefill enjoys substantial advantages in both qualitative and quantitative comparisons with negligible trainable weights. Particularly, spatially stitching reference and target views together achieves consistent improvements. Thus it is intuitive and convincing that all U-net modules contribute to improved inpainting results with a whole stitched image, as" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7710" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.102, + 0.095, + 0.445, + 0.457 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.466, + 0.472, + 0.507 + ], + "angle": 0, + "content": "Figure 9. Sequential generative results from a single view. Zero123 [30] are conditioned on real reference (first view) and last generated view (last view), while LeftRefill is based on AR." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.518, + 0.472, + 0.562 + ], + "angle": 0, + "content": "opposed to using only attention modules. We further compare LeftRefill with TransFill on their officially provided real-world dataset in the supplementary." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.564, + 0.472, + 0.654 + ], + "angle": 0, + "content": "Results of Multi-view Ref-inpainting. We verified models trained with different numbers of reference views in Table 1 (lower). As the number of reference views increases, there is a notable enhancement in inpainting capability. As qualitatively compared in Figure 7, more consistent references lead to robust inpainting results with sensible structures." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.665, + 0.357, + 0.682 + ], + "angle": 0, + "content": "4.2. Results of Novel View Synthesis" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.472, + 0.901 + ], + "angle": 0, + "content": "Results of Single-view NVs. We compare the quantitative NVs results on Objaverse in Table 2. The qualitative results for both Objaverse and Google Scanned Objects are compared in Figure 8. Without specific annotations, all NVs results are based on adaptive masking. The CLIP score [43] is compared to evaluate the similarity between the generation and the target. Specifically, LeftRefill fine-tuned with the whole LDM enjoys substantial achievements compared to the state-of-the-art competitor Zero123 [30], even though Zero123 might have seen our validation in Objaverse. Moreover, the LoRA-based LeftRefill [21] is still competitive with a very moderate training setting (batch size 48 with 2 A6000 GPUs) in Table 2. We further compare the training log of LeftRefill and Zero123 in the supplementary to investigate" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.085, + 0.892, + 0.127 + ], + "angle": 0, + "content": "Table 2. Results of 1-view NVS conditioned on different numbers of reference views on Objaverse [10]. 'w.o. AM' indicates NVS results without Adaptive Masking (AM)." + }, + { + "type": "table", + "bbox": [ + 0.502, + 0.13, + 0.897, + 0.263 + ], + "angle": 0, + "content": "
MethodsRef-ViewPSNR↑SSIM↑LPIPS↓CLIP↑
Zero123 [30]119.4020.8580.13090.7816
LeftRefill (LoRA)119.5140.8690.15340.7589
LeftRefill (w.o. AM)121.6750.8870.10890.7959
LeftRefill121.4040.8820.11510.7972
LeftRefill222.9350.8950.08710.8280
LeftRefill324.1070.9080.07220.8432
LeftRefill424.6850.9110.06340.8495
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.265, + 0.895, + 0.334 + ], + "angle": 0, + "content": "Table 3. Results of 4-view NVS generations based on 1 reference view on Objaverse [10]. P-CLIP means pairwise CLIP score showing consistency of generated views. The reference (Ref) can be categorized into the first ground-truth view and the last generated view, while we also provide the AR results of LeftRefill." + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.337, + 0.887, + 0.42 + ], + "angle": 0, + "content": "
MethodsRefPSNR↑SSIM↑LPIPS↓CLIP↑P-CLIP↑
Zero123First19.2650.8550.13660.77230.7756
Zero123Last14.6210.7670.25690.69210.7667
LeftRefillFirst21.5730.8830.11430.79640.7709
LeftRefillAR21.2710.8820.11950.78820.7958
" + }, + { + "type": "image", + "bbox": [ + 0.51, + 0.422, + 0.88, + 0.566 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.571, + 0.895, + 0.641 + ], + "angle": 0, + "content": "Figure 10. Visualization of attention scores in LeftRefill for Refinpainting across different DDIM steps. We show scores from reference views attended by masked regions. The upper row shows attention scores from the 8th self-attention (1/32 scale), while the bottom row shows ones from the 14th self-attention (1/8 scale)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.894, + 0.719 + ], + "angle": 0, + "content": "the training convergence for NVs. The contextual inpainting-based LeftRefill enjoys a substantially faster convergence and superior image quality. So LeftRefill enjoys a good balance between training efficiency and performance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Results of Multi-view NVs. Quantitative results of multi-view NVs are shown in the lower of Table 2. Obviously, more reference views lead to better reconstruction quality of LeftRefill. Moreover, additional reference images could substantially alleviate the ambiguity, improving the final results with consistent geometry. Benefited by AR, LeftRefill can be also generalized to synthesize a group of consistent images with different viewpoints from a single view as shown in Figure 9 and Table 3. We introduce the pairwise CLIP score (P-CLIP) to verify the consistency of all generated samples. LeftRefill outperforms Zero123 in most metrics, while AR could prominently improve the consistency with just a little" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.514, + 0.957 + ], + "angle": 0, + "content": "7711" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.089, + 0.895, + 0.132 + ], + "angle": 0, + "content": "Table 4. Ablation studies for the setting of prompt tuning in Ref-inpainting. Left: 'Shallow' means only prompt tuning to text embedding, while 'Deep' indicates tuning additional embedding features to different cross-attention layers (16 layers) in SD. Right: validating the influence of the length of shared (Task) and unshared (View) prompts with 3-view Ref-inpainting." + }, + { + "type": "table", + "bbox": [ + 0.164, + 0.139, + 0.516, + 0.228 + ], + "angle": 0, + "content": "
Prompt TypeLengthPSNR↑SSIM↑LPIPS↓Params
Shallow2520.350.8270.104+0.025M
Shallow5020.490.8290.103+0.05M
Shallow7520.380.8300.104+0.075M
Deep (×16)25(400)20.150.8250.106+0.4M
" + }, + { + "type": "table", + "bbox": [ + 0.532, + 0.135, + 0.808, + 0.233 + ], + "angle": 0, + "content": "
TaskViewPSNR↑SSIM↑LPIPS↓Params
50021.2240.8380.0941+0.05M
45521.3560.8400.0901+0.06M
252521.1270.8360.0950+0.11M
54520.7440.8320.1040+0.14M
05020.5630.8310.1110+0.15M
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.234, + 0.47, + 0.262 + ], + "angle": 0, + "content": "Table 5. NVS results of LeftRefill-simple with different reference views with/without incremental Positional Encoding (PE)." + }, + { + "type": "table", + "bbox": [ + 0.121, + 0.264, + 0.428, + 0.357 + ], + "angle": 0, + "content": "
Ref-ViewPEPSNR↑SSIM↑LPIPS↓
1×20.3520.8730.132
1✓20.5080.8750.128
4×22.0970.8880.099
4✓22.3240.8900.095
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.383, + 0.47, + 0.414 + ], + "angle": 0, + "content": "quality degradation. Our method can also be generalized to real-world data as shown in the supplementary." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.423, + 0.345, + 0.439 + ], + "angle": 0, + "content": "4.3. Analysis and Ablation Studies" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.447, + 0.473, + 0.644 + ], + "angle": 0, + "content": "Self-Attention Analysis. We show the visualization of self-attention scores attended by masked regions for Refinpainting across different DDIM steps in Figure 10. Self-attention can capture correct feature correlations without any backbone fine-tuning. As diffusion sampling progresses, self-attention modules gradually shift their focus from specific key points to broader related regions, which is convincing and intuitive. Because the key landmarks help to swiftly locate the spatial correlation between the reference and target, while the extended receptive fields further refine the generation for the following sampling steps. More analysis about the attention visualization with increased reference views is shown in the supplementary." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.644, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Prompt Settings. The length and depth used in the task and view prompt tuning are explored in Table 4. Different from [23], we find that LeftRefill is relatively robust in the length selection. Thus we select 50 for both Ref-inpainting and NVS. Moreover, the deep prompt with much more trainable prompts for different cross-attention layers does not perform well, which may suffer from a little overfitting. For the multi-view scene, we empirically evaluate the 3-view-based Ref-inpainting performance with various proportions of task&view prompt lengths in the right of Table 4. Increasing the proportion of view tokens initially improves the results, followed by a subsequent decline. We think that a few unshared view tokens contribute valuable view orders, while too many unshared tokens would increase the learning difficulty, leading to an inferior prompt tuning performance. Incremental Positional Encoding. We incrementally add the concatenation of learnable view embedding and absolute" + }, + { + "type": "image", + "bbox": [ + 0.515, + 0.244, + 0.877, + 0.369 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.372, + 0.894, + 0.401 + ], + "angle": 0, + "content": "Figure 11. Ref-inpainting results with different CFG weights, which take a trade-off between structural and textural recoveries." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.416, + 0.895, + 0.461 + ], + "angle": 0, + "content": "positional encoding to each attention block for NVs (Equation (1)), improving the performance of both single-view and multi-view-based NVs as verified in Table 5." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.462, + 0.895, + 0.6 + ], + "angle": 0, + "content": "Classifier-Free Guidance (CFG) [19]. We find that CFG can enhance the performance of Ref-inpainting even without training with prompt dropout as in Figure 11. The adjusting of CFG could be seen as the trade-off between structural and textural recoveries. High CFG scales lead to over-saturated results with superior structure. We empirically set CFG to 2.0 and 2.5 for Ref-inpainting and NVs respectively. More quantitative results and details about the CFG setting of NVs are discussed in the supplementary." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.616, + 0.619, + 0.632 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.895, + 0.809 + ], + "angle": 0, + "content": "In this paper, we propose LeftRefill, formulating reference-based synthesis as inpainting tasks and addressing them end-to-end as a human painter. Benefiting from the prompt tuning and the well-learned attention modules in large T2I models, LeftRefill can address the spatially sophisticated Ref-inpainting and NVs efficiently. Moreover, LeftRefill could be easily extended to tackle multi-view generation tasks. We also propose block casual masking to accomplish NVs with consistent results autoregressively. Comprehensive experiments on Ref-inpainting and NVs show the effectiveness and efficiency of LeftRefill." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.897, + 0.902 + ], + "angle": 0, + "content": "Acknowledgements: Yanwei Fu is the corresponding author. Yanwei Fu is with the School of Data Science, Shanghai Key Lab of Intelligent Information Processing, Fudan University, and Fudan ISTBI-ZJNU Algorithm Centre for Brain-inspired Intelligence, Zhejiang Normal University. The computations in this research were performed using the CFFF platform of Fudan University." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "7712" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.171 + ], + "angle": 0, + "content": "[1] Omri Avrahami, Dani Lischinski, and Ohad Fried. 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LetRefill addresses the generation on the right canvas conditioned by left references. We can re-formulate several existing tasks in the LeftRefill manner, including (a) reference-guided inpainting, (b) novel view synthesis. The reference and target can be further extended to multi-view scenes, forming (c) multi-view reference inpainting and (d) multi-view synthesis, respectively. Green frames indicate stitched inputs. Reference views are placed on the left side, while masked target views are placed on the right side. Violet frames only show enlarged right-side generations produced by LeftRefill. Note that we omit some input details in (c) and (d) for simplicity. + +# Abstract + +This paper introduces LeftRefill, an innovative approach to efficiently harness large Text-to-Image (T2I) diffusion models for reference-guided image synthesis. As the name implies, LeftRefill horizontally stitches reference and target views together as a whole input. The reference image occupies the left side, while the target canvas is positioned on the right. Then, LeftRefill paints the right-side target canvas based on the left-side reference and specific task instructions. Such a task formulation shares some similarities with contextual inpainting, akin to the actions of a human painter. This novel formulation efficiently learns both structural and textured correspondence between reference and target without other image encoders + +or adapters. We inject task and view information through cross-attention modules in T2I models, and further exhibit multi-view reference ability via the re-arranged self-attention modules. These enable LeftRefill to perform consistent generation as a generalized model without requiring test-time fine-tuning or model modifications. Thus, LeftRefill can be seen as a simple yet unified framework to address reference-guided synthesis. As an exemplar, we leverage LeftRefill to address two different challenges: reference-guided inpainting and novel view synthesis, based on the pre-trained StableDiffusion. Codes&models are released at https://github.com/ewrfcas/LeftRefill. + +# 1. Introduction + +Imagine you are a right-handed painter with a task that requires you to draw or modify a target image based on a reference picture. How would you approach it? Intuitively, + +you would likely place the reference image on your left side and paint or modify the target view on the right side conditioned on the left one. If we regard the large Text-to-Image (T2I) models [6, 37, 41, 44, 46, 48] as skillful painters, could they also follow such simple and intuitive task formulation to handle complex reference-guided synthesis tasks? In this paper, we explore this problem with two challenging tasks: 1) Inpainting masked target views conditioned on reference images, i.e., reference-guided inpainting (Ref-inpainting) [67, 68] as in Figure 1(a). 2) Generating new views based on known images of specific objects, i.e., Novel View Synthesis (NVS) [30] as in Figure 1(b). + +It seems straightforward to harness the power of T2I generative models to directly address these image-reference tasks by training additional adapters [21, 36, 64] or replacing textual encoders with visual ones [30, 62] and optimize them for full fine-tuning of the entire T2I model. We should clarify that training these large T2I models with unfamiliar visual encoders is computationally intensive and challenging to converge, particularly when working with limited batch sizes. Additionally, most visual encoders, such as image CLIP [43], tend to emphasize the learning of semantic features rather than the intricately spatial details that are essential for tasks involving Ref-inpainting as verified in our experiments. + +To prevent the heavy modification to T2I models mentioned above, we rethink the human painting habit and propose LeftRefill, a unified approach for both Ref-inpainting and NVS. LeftRefill is built upon the inpainting fine-tuned StableDiffusion2.0 (SD) [46]*, which ingeniously reformulates reference-based synthesis as a contextual inpainting process. Specifically, LeftRefill horizontally stitches reference and target views as a whole input. As shown in Figure 1, reference images are positioned on the left side, while masked targets are on the right side. This simple yet effective formulation eliminates the dependency on additional image feature encoders, as both reference and target views have been stitched into the same canvas. As an "experienced painter", LeftRefill is driven by specific instructions, called task and view prompt tuning. These instructions infuse crucial information for specific generative tasks and desired view orders to cross-attention modules, guiding the generation of SD. Note that LeftRefill is a generalized framework, so we can train two LeftRefill models for Ref-inpainting and NVS separately without any test-time fine-tuning. + +On the other hand, we emphasize that LeftRefill further enjoys extension into multi-view synthesis scenarios, including image inpainting conditioned on multi-view references in Figure 1(c) and consistent NVS from a single view in Figure 1(d). Formally, we rearrange the tensor shape before the self-attention modules, enabling self-attention to capture cross-view information. Moreover, to tackle the more intricate NVS task, we propose the novel technique of block + +causal masking, facilitating self-attention-based T2I models in achieving consistent autoregressive (AR) generation. All improvements are integrated into the off-the-shelf SD components, involving no additional image encoder, prompt tuning based on cross-attention, self-attention rearranging and block causal masking. LeftRefill emerges as a unified architecture for addressing reference-guided synthesis, requiring only minor model modifications. + +We highlight the key contributions of LeftRefill as follows: 1) Lightweight and generalized task formulation based on off-the-shelf T2I models: Benefiting from the novel contextual inpainting formulation and inherent attention mechanisms from SD, LeftRefill provides an efficient solution for reference-guided synthesis without thoroughly re-training T2I models and test-time fine-tuning. 2) Task and view-specific prompt tuning: Our work pioneers the use of task and view-specific prompt tuning, allowing for precise control over generative tasks and view orders. 3) End-to-end Ref-inpainting: Notably, our LeftRefill addresses the challenging Ref-inpainting end-to-end, without complex 3D geometrical warping and 2D inpainting techniques [65, 67, 68]. 4) Autoregressive NVS with block causal masking: For the intricate NVS task, we introduce the novel concept of block causal masking, enabling self-attention-based T2I models to achieve AR generation for geometric consistency. + +# 2. Related Work + +Personalization and Controllability of T2I Models. Recent achievements on T2I have produced impressive visual generations [2, 36, 42], which could be further extended into local editing [1, 8, 18]. However, these models could only be controlled by natural languages. As "an image is worth hundreds of words", T2I models based on natural texts fail to produce images with specific textures, locations, identities, and appearances [15]. Textual inversion [15, 35] and fine-tuning techniques [47] are proposed for personalized T2I. Meanwhile, many works pay attention to image-guided generations [26, 34, 58]. ControlNet [64] and T2I-Adapter [36] learn trainable adapters [20] to inject visual clues to pretrained T2I models without losing generalization and diversity. But these moderate methods only work for simple style transfers. More spatially complex tasks, such as Refinpainting, are difficult to handle by ControlNet as verified in Section 4. In contrast, T2I-based exemplar-editing and NVS have to be fine-tuned on large-scale datasets with strong data augmentation [62] and large batch size [30]. Compared with these aforementioned manners, LeftRefill enjoys both spatial modeling capability and computational efficiency. + +Prompt Tuning [24, 32, 33] indicates fine-tuning token embeddings for transformers with frozen backbone to preserve the capacity. Prompt tuning is first explored for adaptively learning suitable prompt features for language models rather than manually selecting them for different downstream + +tasks [29]. Moreover, prompt tuning has been further investigated in vision-language models [16, 43] and discriminative vision models [23, 28]. Visual prompt tuning in [53] prepends trainable tokens before the visual sequence for transferred generations. Though both LeftRefill and [53] aim to tackle image synthesis, our prompt tuning is used for controlling text encoders rather than visual ones. Thus LeftRefill enjoys more intuitive prompt initialization from task-related textual descriptions. + +Reference-guided Image Inpainting. Image inpainting is a long-standing vision task, which aims to fill missing image regions with coherent results. Both traditional methods [3, 9, 17] and learning-based ones [11, 25, 54, 63, 66] achieved great progress in image inpainting. Furthermore, Ref-inpainting requires recovering a target image with one or several reference views from different viewpoints [40], which is useful for repairing old buildings or removing occlusions in popular attractions. But Ref-inpainting usually suffers from a sophisticated pipeline [65, 67, 68], including depth estimation, pose estimation, homography warping, and single-view inpainting. Limited by large holes, the estimated geometric pose is not reliable, largely degrading the pipeline. Thus an end-to-end Ref-inpainting pipeline is meaningful. To the best of our knowledge, we are the first ones to tackle such a difficult reference-guided task with T2I models. + +Novel View Synthesis from a Single Image. NVs based on a single image is an intractable ill-posed problem, requiring both sufficient geometry understanding and expressive textural presentation [14]. Many previous works could partially tackle this problem through single view 3D reconstruction [7, 31, 59–61], 2D generative models [39, 45, 52], feature cost volumes [5], and GAN-based methods [4, 38, 51]. However, these manners still suffer from limited generalization or small angle variations. To address this issue, Zero123 [30] uses another image CLIP encoder to inject image features from the reference view to unlock the capacity from 2D diffusion-based T2I models for NVs. But Zero123 requires a large batch size and expensive computational resources to stabilize the training stage with an unknown reference image encoder. Moreover, the image encoder in Zero123 can only tackle one reference image, which fails to generate consistent multi-view images. + +# 3. Method + +Overview. LeftRefill is first formulated in Section 3.1. Then we explain using self-attention to capture multi-view correspondence, and AR generation based on block casual masking (Section 3.2). Finally, we discuss the task and view-specific prompt tuning for cross-attention (Section 3.3). + +# 3.1. Framework of LeftRefill + +Motivations. As depicted in Figure 2(a), our LeftRefill is built upon the inpainting fine-tuned SD [46]. There are two + +![](images/d77961d4d0de9be420d970a11ebc876d2fc8714c1741d01be228984565159520.jpg) + +![](images/cab02103fb24fdd6b39cab60ff5e28bdb09eb8c6e4046a802ade808695b096e3.jpg) + +![](images/621d30d98338a9ddfa77bcf6a357056e0af02fd1dc2c967111f731d9074554d8.jpg) +Figure 3. Illustration about multi-view training inputs $(v\times H\times 2W$ , $v = 4)$ of LeftRefill, where $v,H,2W$ indicate the view number, height, and width of stitching images. All views of Ref-inpainting (a) share the same masked target, while the multi-view NVS (b) should be trained with the AR generation. + +![](images/64457f794ffd18376e1a53c22db3a5e8cfe51bc3be9fdbac782f6a6aee30f503.jpg) +Figure 2. (a) The overview of LeftRefill. Inputs of Ref-inpainting and NVs are shown in (b). Task and view prompt embedding and pose features (optional for NVS) are infused to CLIP-H for cross-attention learning in U-net. For the output of LeftRefill, we discard the left-side reference and take the right-side generation. + +primary motivations that make us stitch reference and target images together and reformulate both Ref-inpainting and NVS as a contextual image inpainting problem. 1) LeftRefill just considers a single input image, eliminating the requirement of additional image encoders and avoiding major architectural alterations and extensive re-training. 2) Since all T2I models are only pre-trained on single-view images, the left-right stitched input could implicitly reactivate the essential capacity from large T2I models of modeling the correlation of the single-view image. Particularly, the left-right stitching input enables the self-attention modules to focus on correct parts from left-side reference at the early stage of diffusion sampling (Figure 10). We also thoroughly evaluate different alterations of reference-guided SD in Section 4.1. LeftRefill substantially outperforms other competitors with high efficiency and negligible trainable weights. + +Single-view Formulation (1-to-1). Thanks to the convo + +![](images/27ae7e58841500d2fc8856ce19193b8ce8a1996c54996c5e3196fb41a84996fa.jpg) +Figure 4. Detailed architecture of LeftRefill for multi-view synthesis. Both CNN and cross-attention modules are encoded separately for each stitched view, while all views share the same self-attention for multi-view correlation learning. + +![](images/439739df524b24ed65641efbba3b86b3be2a0f0766a0c6586f8056fd0a36162b.jpg) +(a) Illustration about the shape rearranging of LeftRefill + +![](images/07b28d4f6b5dc1bc985436580972ae02e11085eb6ddc972a3d543f9cf0ba105d.jpg) +(b) Block causal masking used for autoregressive training +Figure 5. (a) Feature rearranging, and (b) block causal masking of LeftRefill, where $b, v, h, w, c$ indicate the batch size, view number, height, width, and channels of features, where $w$ is the width of stitching features (downsampled from $2W$ ). + +lutional U-net architecture in the Latent Diffusion Model (LDM), we can expand the input image in the spatial dimensions without any modification. Let's consider a scenario with a single reference image at first, i.e., 1-to-1. Our input $\mathbf{I}'$ is a stitching image of $\mathbf{I}_{ref}$ and the masked target $\hat{\mathbf{I}}_{tar}$ , forming as $\mathbf{I}' = [\mathbf{I}_{ref};\hat{\mathbf{I}}_{tar}] \in \mathbb{R}^{H \times 2W}$ as shown in Figure 2(a). In practice, we take the reference image on the left side, while the target one is placed on the right side. We just take the right-side output as the final generation while the left-side output is discarded. Note that the diffusion optimization is based on the whole stitched image without any modification. For the masked target $\hat{\mathbf{I}}_{tar}$ , we treat Ref-inpainting's input targets as partially masked images, while NVS's input targets are entirely masked through the objective segmentation and bounding box. More details about the processing of data and masks are discussed in the supplementary. + +Multi-view Formulation (V-to-1). For the multi-view references, we stitch each reference with the specific target + +as shown in Figure 3. All views are learned separately for convolutions and cross-attention, while they share the same self-attention processing as shown in Figure 4 and detailed in Section 3.2. From Figure 3(a), the multi-view Ref-inpainting leverages information from different reference views to repair the same target, i.e., $v$ -to-1, where $v$ means the view number. We simply take the generation of the first view as the final inpainted output in $v$ -to-1. For the multi-view NVS, it could be seen as an AR generation for sequentially consistent view synthesis, as depicted in Figure 3(b), i.e., $n$ -to-1 ( $n = 1,2,\dots,v$ ). During the inference, we apply the generated targets as new references for the subsequent view synthesis, while the training phase is accomplished parallelly as detailed in the block casual masking of Section 3.2. + +Controlling Generation for LeftRefill. Although the self-attention modules in SD have the potential to enable the correlation between left reference and right target, SD is not trained to explicitly activate this capacity. The most intuitive way to guide the SD in capturing the correlation among left-right stitched images is to apply suitable text prompts to drive the diffusion model for the desired generation. However, it is non-trivial to define Ref-inpainting and NVS with natural languages. Furthermore, it is beneficial to have a non-instance-level prompt to generally guide the diffusion model to accomplish specific tasks. To this end, we propose to use prompt tuning to learn task and view-specific prompts as detailed in Section 3.3. Except for the prompt tuning, all weights in LDM are frozen in Ref-inpainting to maintain the proper generalization as shown in Figure 2(a). For NVS, we fine-tune the whole LDM to achieve essentially precise pose control, but LeftRefill enjoys much better convergence compared with other fine-tuning based methods [30]. + +# 3.2. Reactivating Self-Attention for Multi-View + +As shown in Figure 5(a), given multi-view features $\mathbf{F}_i$ of layer $i$ , all MLP, convolutional, and cross-attention layers encode $\mathbf{F}_i$ separately. We can simply achieve the separate feature encoding by reshaping the view $v$ and batch $b$ dimension together as $bv$ . Before the self-attention, we rearrange the feature shape as $\tilde{\mathbf{F}}_i \in \mathbb{R}^{b \times vhw \times c}$ , thus features across different views could be learned together. To further incorporate positional clues for distinguishing different sides of reference and target in NVS, we incrementally add positional encoding $P_i$ to $\tilde{\mathbf{F}}_i$ before each self-attention block as + +$$ +P _ {i} = \gamma_ {i} \cdot \operatorname {c a t} ([ P _ {v}; P _ {\text {F o u r i e r}} ]), \tag {1} +$$ + +where $P_{v}, P_{Fourier}$ indicate the trainable view embedding and Fourier absolute positional encoding [57] respectively; $\gamma_{i}$ is a zero-initialized learnable coefficient for each layer. + +For the Ref-inpainting, no masking strategy should be considered in self-attention modules. All reference views share the same target one, thus it is unnecessary for LeftRefill to sequentially repair target views. In contrast, for the + +multi-view NVs, generating consistent novel views from a single image needs our model to handle the sequential generation with dynamic reference views. For example, the same LeftRefill should accomplish the NVS from one view, two views, and even more. So the AR generation [13, 49, 56] is suitable to formulate this task. + +Block Causal Masking. LeftRefill requires a certain finetuning for LDM to effectively tackle challenging NVS as shown in Figure 2(a). The intuitive solution is to train an AR-based generative model that can generalize across various view numbers for multi-view synthesis. Converting a pretrained diffusion model to an AR-based generative model is non-trivial. However, the inpainting formulation of Left-Refill makes this conversion feasible. Specifically, we just need to adjust the masking strategy during the self-attention learning. We propose the block casual masking as shown in Figure 5(b), while the block side-length of each view is $h w$ , matching the size of the stitched reference and target pair. Different from the traditional casual mask which is a lower triangular matrix, the block casual mask enlarges the minimal unit from one token to a $h w \times h w$ block, ensuring reasonable block-wise receptive fields. In practice, all uncolored tokens in the attention score are masked with “—inf” before the softmax operation. The block casual mask can be implemented parallelly and efficiently as in supplementary. + +# 3.3. Task&View Prompt Tuning + +The prompt embedding is adopted as the textual branch to CLIP-H [43] of SD, being applied to cross-attention as shown in Figure 2(a). Specifically, we prepare a set of trainable text embeddings for different generative tasks, which are further categorized into task and view prompts. Specifically, task prompt embeddings are shared in the same task, e.g., all views of Ref-inpainting using the same task embeddings. In contrast, different view prompt embeddings are applied to inject various view-order information through cross-attention modules to the specific input view. Though there are only a few trainable parameters (0.05M to 0.065M), we astonishingly find that prompt tuning is sufficient to drive complex generative tasks such as Ref-inpainting, even with a frozen LDM backbone. The trainable task and view prompt embeddings $p_t$ , $p_v$ are initialized as the averaged embedding of the natural task description. The optimization target is: + +$$ +\left\{p _ {t}, p _ {v} \right\} _ {*} = \underset {\left\{p _ {t}, p _ {v} \right\}} {\arg \min } \mathbb {E} \left[ \left\| \varepsilon - \varepsilon_ {\theta} \left([ z _ {t}; \hat {z} _ {0}; \mathbf {M} ], c _ {\phi} \left(p _ {t}, p _ {v}\right), t\right) \right\| ^ {2} \right], (2) +$$ + +where $\varepsilon_{\theta}(\cdot)$ is the estimated noise by LDM; $c_{\phi}(\cdot)$ means the frozen CLIP-H; $z_{t}$ is a noisy latent feature of input $z_{0}$ in step $t$ ; $\hat{z}_0 = z_0\odot (1 - \mathbf{M})$ are masked latent features concatenated to $z_{t}$ with mask $\mathbf{M}$ . Task and view-specific prompt tuning enjoy not only training efficiency but also lightweight saving [24]. For example, we share the same LeftRefill to address Ref-inpainting with different reference views, while only $0.01\%$ additional weights of $\{p_t,p_v\}_{*}$ are + +Table 1. Quantitative results for Ref-inpainting on MegaDepth [27] test set based on matching and manual masks (upper: 1-view; lower: multi-view). 'ExParams': the scale of extra trainable parameters. * means that the uncorrupted ground truth is visible for the matching. 'No stitching': reference and target views are separate without spatial stitching, and only self-attention are learned across them. + +
MethodsPSNR↑SSIM↑FID↓LPIPS↓ExParams
SD ( inpainting) [46]19.8410.81930.2600.1349+0
ControlNet [64]19.0720.74433.6640.1816+364.2M
ControlNet+NewCrossAttn19.0270.74334.1700.1805+463.4M
ControlNet+Matching* [55]20.5920.76329.5560.1565+364.3M
Perceiver+ImageCLIP [22]19.3380.74532.9110.1751+52.01M
Paint-by-Example [62]18.3510.79734.7110.1604+865.9M
TransFill [68]22.7440.87526.2910.1102-
LeftRefill (no stitching)20.4890.82720.1250.1085+0.05M
LeftRefill20.9260.83618.6800.0961+0.05M
LeftRefill (2-view)21.0920.83618.3890.0969+0.055M
LeftRefill (3-view)21.3560.84016.8380.0901+0.06M
LeftRefill (4-view)21.7790.84716.6320.0839+0.065M
+ +changed for each view condition. In NVS, we further provide relative poses to LeftRefill. Following [30], we calculate the 4-channel relative pose in the polar coordinate for each view, which is encoded by a two-layer FC. Then the pose feature replaces the last padding token in the prompt embeddings before being applied to the CLIP-H. + +# 4. Experiments + +Datasets. For Ref-inpainting, we use the resized $512 \times 512$ image pairs from MegaDepth [27], which includes many multi-view famous scenes collected from the Internet. To trade-off between the image correlation and the inpainting difficulty, we empirically retain image pairs with $40\%$ to $70\%$ co-occurrence with about 80k images and 820k pairs. The validation of Ref-inpainting also includes some manual masks from ETH3D scenes [50] to verify the generalization. For the NVS, we use Objaverse [10] rendered by [30] including 800k various scenes with object masks. We resize all images to $256 \times 256$ as [30]. Note that some extreme views with elevation angles less than $-10^{\circ}$ are filtered due to excessive ambiguity. More details about the masking and datasets are introduced in the supplementary. + +Implementation Details. Our LeftRefill is based on the inpainting fine-tuned SD [46] with 0.8 billion parameters. For the task and view prompt tuning, there are 50 trainable prompt tokens at all. We use $90\%$ tokens to represent the task embeddings, while $10\%$ tokens indicate each view respectively. We use the AdamW optimizer with a weight decay of 0.01 to optimize LeftRefill. For the Ref-inpainting, the prompt tuning's learning rate is 3e-5. Moreover, $75\%$ masks are randomly generated, and $25\%$ of them are matching-based masks. For the NVS, LeftRefill could be tested with the adaptive masking strengthened by the foreground segmentation model. Concretely, we first enlarge the reference segmentation mask and generate a coarse target with fewer DDIM steps. We extract the new mask from the coarse tar + +![](images/7c15677a34c9c7b41a21181a3760afebf27794db80489ddcf176d7a2456d22ad.jpg) +Figure 6. Qualitative Ref-inpainting results on MegaDepth [27]. More results are in the supplementary. + +![](images/2e95a83d2211106fd2cc4309847af7455c14020cb81ca0dc4513ec5615adc280.jpg) +Figure 7. Multi-view Ref-inpainting qualitative results. Increasing the reference view number improves the quality of repaired targets. + +get and then further randomly enlarge it as the final target mask. The NVS LeftRefill is trained with 512 batch size and learning rate 3e-5. We show that a simplified LeftRefill with just 48 batch size can also be converged for NVS, which breaks through the limitation of Zero123 [30]. More details about matching-based masks, adaptive masking, and training schedules are discussed in the supplementary. + +# 4.1. Results of Reference-guided Inpainting + +Results of One-view Reference. We thoroughly compared the specific Ref-inpainting method [68] and existing image reference-based variants of SD with one-view reference in Table 1 and Figure 6. Note that ControlNet [64] fails to learn the correct spatial correlation between reference images and masked targets, even enhanced with trainable cross-attention learned between reference and target features. Furthermore, we try to warp ground-truth latent features with image matching [55] as the reference guidance for ControlNet, but the improvement is not prominent. Perceiver [22] and Paint-by-Example [62] align and learn image features from Image + +![](images/aa32d35428ca39fb87ad941b72b69032d5f4ea8ed6739084f321b457771f6dc8.jpg) +Figure 8. NVS results on Objaverse [10] (row1, 2) and Google Scanned Objects [12] (row3, 4) from a single reference image. + +CLIP. Since image features from CLIP contain high-level semantics, they fail to deal with the fine-grained Ref-inpainting as shown in Figure 6(e)(f). Though TransFill [68] achieves proper results in PSNR and SSIM, it suffers from blur and color difference as in Figure 6(g) with challenging viewpoints. LeftRefill enjoys substantial advantages in both qualitative and quantitative comparisons with negligible trainable weights. Particularly, spatially stitching reference and target views together achieves consistent improvements. Thus it is intuitive and convincing that all U-net modules contribute to improved inpainting results with a whole stitched image, as + +![](images/c18132f3ab236168abce7c33dc02ebe98f39f35bc62e142941f8ef8de2d3d749.jpg) +Figure 9. Sequential generative results from a single view. Zero123 [30] are conditioned on real reference (first view) and last generated view (last view), while LeftRefill is based on AR. + +opposed to using only attention modules. We further compare LeftRefill with TransFill on their officially provided real-world dataset in the supplementary. + +Results of Multi-view Ref-inpainting. We verified models trained with different numbers of reference views in Table 1 (lower). As the number of reference views increases, there is a notable enhancement in inpainting capability. As qualitatively compared in Figure 7, more consistent references lead to robust inpainting results with sensible structures. + +# 4.2. Results of Novel View Synthesis + +Results of Single-view NVs. We compare the quantitative NVs results on Objaverse in Table 2. The qualitative results for both Objaverse and Google Scanned Objects are compared in Figure 8. Without specific annotations, all NVs results are based on adaptive masking. The CLIP score [43] is compared to evaluate the similarity between the generation and the target. Specifically, LeftRefill fine-tuned with the whole LDM enjoys substantial achievements compared to the state-of-the-art competitor Zero123 [30], even though Zero123 might have seen our validation in Objaverse. Moreover, the LoRA-based LeftRefill [21] is still competitive with a very moderate training setting (batch size 48 with 2 A6000 GPUs) in Table 2. We further compare the training log of LeftRefill and Zero123 in the supplementary to investigate + +Table 2. Results of 1-view NVS conditioned on different numbers of reference views on Objaverse [10]. 'w.o. AM' indicates NVS results without Adaptive Masking (AM). + +
MethodsRef-ViewPSNR↑SSIM↑LPIPS↓CLIP↑
Zero123 [30]119.4020.8580.13090.7816
LeftRefill (LoRA)119.5140.8690.15340.7589
LeftRefill (w.o. AM)121.6750.8870.10890.7959
LeftRefill121.4040.8820.11510.7972
LeftRefill222.9350.8950.08710.8280
LeftRefill324.1070.9080.07220.8432
LeftRefill424.6850.9110.06340.8495
+ +Table 3. Results of 4-view NVS generations based on 1 reference view on Objaverse [10]. P-CLIP means pairwise CLIP score showing consistency of generated views. The reference (Ref) can be categorized into the first ground-truth view and the last generated view, while we also provide the AR results of LeftRefill. + +
MethodsRefPSNR↑SSIM↑LPIPS↓CLIP↑P-CLIP↑
Zero123First19.2650.8550.13660.77230.7756
Zero123Last14.6210.7670.25690.69210.7667
LeftRefillFirst21.5730.8830.11430.79640.7709
LeftRefillAR21.2710.8820.11950.78820.7958
+ +![](images/24225828d4b1a20f2f28dd2b8224dc532f80e628dd2b7acec1c25cb2e535af26.jpg) +Figure 10. Visualization of attention scores in LeftRefill for Refinpainting across different DDIM steps. We show scores from reference views attended by masked regions. The upper row shows attention scores from the 8th self-attention (1/32 scale), while the bottom row shows ones from the 14th self-attention (1/8 scale). + +the training convergence for NVs. The contextual inpainting-based LeftRefill enjoys a substantially faster convergence and superior image quality. So LeftRefill enjoys a good balance between training efficiency and performance. + +Results of Multi-view NVs. Quantitative results of multi-view NVs are shown in the lower of Table 2. Obviously, more reference views lead to better reconstruction quality of LeftRefill. Moreover, additional reference images could substantially alleviate the ambiguity, improving the final results with consistent geometry. Benefited by AR, LeftRefill can be also generalized to synthesize a group of consistent images with different viewpoints from a single view as shown in Figure 9 and Table 3. We introduce the pairwise CLIP score (P-CLIP) to verify the consistency of all generated samples. LeftRefill outperforms Zero123 in most metrics, while AR could prominently improve the consistency with just a little + +
Prompt TypeLengthPSNR↑SSIM↑LPIPS↓Params
Shallow2520.350.8270.104+0.025M
Shallow5020.490.8290.103+0.05M
Shallow7520.380.8300.104+0.075M
Deep (×16)25(400)20.150.8250.106+0.4M
+ +Table 4. Ablation studies for the setting of prompt tuning in Ref-inpainting. Left: 'Shallow' means only prompt tuning to text embedding, while 'Deep' indicates tuning additional embedding features to different cross-attention layers (16 layers) in SD. Right: validating the influence of the length of shared (Task) and unshared (View) prompts with 3-view Ref-inpainting. + +
TaskViewPSNR↑SSIM↑LPIPS↓Params
50021.2240.8380.0941+0.05M
45521.3560.8400.0901+0.06M
252521.1270.8360.0950+0.11M
54520.7440.8320.1040+0.14M
05020.5630.8310.1110+0.15M
+ +Table 5. NVS results of LeftRefill-simple with different reference views with/without incremental Positional Encoding (PE). + +
Ref-ViewPEPSNR↑SSIM↑LPIPS↓
1×20.3520.8730.132
1✓20.5080.8750.128
4×22.0970.8880.099
4✓22.3240.8900.095
+ +quality degradation. Our method can also be generalized to real-world data as shown in the supplementary. + +# 4.3. Analysis and Ablation Studies + +Self-Attention Analysis. We show the visualization of self-attention scores attended by masked regions for Refinpainting across different DDIM steps in Figure 10. Self-attention can capture correct feature correlations without any backbone fine-tuning. As diffusion sampling progresses, self-attention modules gradually shift their focus from specific key points to broader related regions, which is convincing and intuitive. Because the key landmarks help to swiftly locate the spatial correlation between the reference and target, while the extended receptive fields further refine the generation for the following sampling steps. More analysis about the attention visualization with increased reference views is shown in the supplementary. + +Prompt Settings. The length and depth used in the task and view prompt tuning are explored in Table 4. Different from [23], we find that LeftRefill is relatively robust in the length selection. Thus we select 50 for both Ref-inpainting and NVS. Moreover, the deep prompt with much more trainable prompts for different cross-attention layers does not perform well, which may suffer from a little overfitting. For the multi-view scene, we empirically evaluate the 3-view-based Ref-inpainting performance with various proportions of task&view prompt lengths in the right of Table 4. Increasing the proportion of view tokens initially improves the results, followed by a subsequent decline. We think that a few unshared view tokens contribute valuable view orders, while too many unshared tokens would increase the learning difficulty, leading to an inferior prompt tuning performance. Incremental Positional Encoding. We incrementally add the concatenation of learnable view embedding and absolute + +![](images/9d691f7011ef37fe3912624be3788692bcd78850ed3047c7a74d91526165a604.jpg) +Figure 11. Ref-inpainting results with different CFG weights, which take a trade-off between structural and textural recoveries. + +positional encoding to each attention block for NVs (Equation (1)), improving the performance of both single-view and multi-view-based NVs as verified in Table 5. + +Classifier-Free Guidance (CFG) [19]. We find that CFG can enhance the performance of Ref-inpainting even without training with prompt dropout as in Figure 11. The adjusting of CFG could be seen as the trade-off between structural and textural recoveries. High CFG scales lead to over-saturated results with superior structure. We empirically set CFG to 2.0 and 2.5 for Ref-inpainting and NVs respectively. More quantitative results and details about the CFG setting of NVs are discussed in the supplementary. + +# 5. Conclusion + +In this paper, we propose LeftRefill, formulating reference-based synthesis as inpainting tasks and addressing them end-to-end as a human painter. Benefiting from the prompt tuning and the well-learned attention modules in large T2I models, LeftRefill can address the spatially sophisticated Ref-inpainting and NVs efficiently. Moreover, LeftRefill could be easily extended to tackle multi-view generation tasks. We also propose block casual masking to accomplish NVs with consistent results autoregressively. Comprehensive experiments on Ref-inpainting and NVs show the effectiveness and efficiency of LeftRefill. + +Acknowledgements: Yanwei Fu is the corresponding author. Yanwei Fu is with the School of Data Science, Shanghai Key Lab of Intelligent Information Processing, Fudan University, and Fudan ISTBI-ZJNU Algorithm Centre for Brain-inspired Intelligence, Zhejiang Normal University. 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LetRefill addresses the generation on the right canvas conditioned by left references. We can re-formulate several existing tasks in the LeftRefill manner, including (a) reference-guided inpainting, (b) novel view synthesis. The reference and target can be further extended to multi-view scenes, forming (c) multi-view reference inpainting and (d) multi-view synthesis, respectively. Green frames indicate stitched inputs. Reference views are placed on the left side, while masked target views are placed on the right side. Violet frames only show enlarged right-side generations produced by LeftRefill. Note that we omit some input details in (c) and (d) for simplicity." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 487, + 192, + 499 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 487, + 192, + 499 + ], + "spans": [ + { + "bbox": [ + 143, + 487, + 192, + 499 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 512, + 289, + 668 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 512, + 289, + 668 + ], + "spans": [ + { + "bbox": [ + 46, + 512, + 289, + 668 + ], + "type": "text", + "content": "This paper introduces LeftRefill, an innovative approach to efficiently harness large Text-to-Image (T2I) diffusion models for reference-guided image synthesis. As the name implies, LeftRefill horizontally stitches reference and target views together as a whole input. The reference image occupies the left side, while the target canvas is positioned on the right. Then, LeftRefill paints the right-side target canvas based on the left-side reference and specific task instructions. Such a task formulation shares some similarities with contextual inpainting, akin to the actions of a human painter. This novel formulation efficiently learns both structural and textured correspondence between reference and target without other image encoders" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 488, + 547, + 632 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 488, + 547, + 632 + ], + "spans": [ + { + "bbox": [ + 306, + 488, + 547, + 632 + ], + "type": "text", + "content": "or adapters. We inject task and view information through cross-attention modules in T2I models, and further exhibit multi-view reference ability via the re-arranged self-attention modules. These enable LeftRefill to perform consistent generation as a generalized model without requiring test-time fine-tuning or model modifications. Thus, LeftRefill can be seen as a simple yet unified framework to address reference-guided synthesis. As an exemplar, we leverage LeftRefill to address two different challenges: reference-guided inpainting and novel view synthesis, based on the pre-trained StableDiffusion. Codes&models are released at https://github.com/ewrfcas/LeftRefill." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 656, + 387, + 669 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 656, + 387, + 669 + ], + "spans": [ + { + "bbox": [ + 306, + 656, + 387, + 669 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 677, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 677, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 306, + 677, + 547, + 715 + ], + "type": "text", + "content": "Imagine you are a right-handed painter with a task that requires you to draw or modify a target image based on a reference picture. How would you approach it? Intuitively," + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 673, + 288, + 714 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 673, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 673, + 288, + 714 + ], + "type": "inline_equation", + "content": "^*" + }, + { + "bbox": [ + 46, + 673, + 288, + 714 + ], + "type": "text", + "content": " Dr. Chenjie Cao is at Alibaba Group. This work was accomplished while Dr. Chenjie Cao was at Fudan University. \n† Corresponding author: yanweifu@fudan.edu.cn \nOther emails: {cjcao20,yncai20,qldong18,yikaiwang19} @fudan.edu.cn" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7705" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 216 + ], + "type": "text", + "content": "you would likely place the reference image on your left side and paint or modify the target view on the right side conditioned on the left one. If we regard the large Text-to-Image (T2I) models [6, 37, 41, 44, 46, 48] as skillful painters, could they also follow such simple and intuitive task formulation to handle complex reference-guided synthesis tasks? In this paper, we explore this problem with two challenging tasks: 1) Inpainting masked target views conditioned on reference images, i.e., reference-guided inpainting (Ref-inpainting) [67, 68] as in Figure 1(a). 2) Generating new views based on known images of specific objects, i.e., Novel View Synthesis (NVS) [30] as in Figure 1(b)." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 217, + 289, + 359 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 217, + 289, + 359 + ], + "spans": [ + { + "bbox": [ + 46, + 217, + 289, + 359 + ], + "type": "text", + "content": "It seems straightforward to harness the power of T2I generative models to directly address these image-reference tasks by training additional adapters [21, 36, 64] or replacing textual encoders with visual ones [30, 62] and optimize them for full fine-tuning of the entire T2I model. We should clarify that training these large T2I models with unfamiliar visual encoders is computationally intensive and challenging to converge, particularly when working with limited batch sizes. Additionally, most visual encoders, such as image CLIP [43], tend to emphasize the learning of semantic features rather than the intricately spatial details that are essential for tasks involving Ref-inpainting as verified in our experiments." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 360, + 289, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 360, + 289, + 598 + ], + "spans": [ + { + "bbox": [ + 46, + 360, + 289, + 598 + ], + "type": "text", + "content": "To prevent the heavy modification to T2I models mentioned above, we rethink the human painting habit and propose LeftRefill, a unified approach for both Ref-inpainting and NVS. LeftRefill is built upon the inpainting fine-tuned StableDiffusion2.0 (SD) [46]*, which ingeniously reformulates reference-based synthesis as a contextual inpainting process. Specifically, LeftRefill horizontally stitches reference and target views as a whole input. As shown in Figure 1, reference images are positioned on the left side, while masked targets are on the right side. This simple yet effective formulation eliminates the dependency on additional image feature encoders, as both reference and target views have been stitched into the same canvas. As an \"experienced painter\", LeftRefill is driven by specific instructions, called task and view prompt tuning. These instructions infuse crucial information for specific generative tasks and desired view orders to cross-attention modules, guiding the generation of SD. Note that LeftRefill is a generalized framework, so we can train two LeftRefill models for Ref-inpainting and NVS separately without any test-time fine-tuning." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 599, + 289, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 599, + 289, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 599, + 289, + 696 + ], + "type": "text", + "content": "On the other hand, we emphasize that LeftRefill further enjoys extension into multi-view synthesis scenarios, including image inpainting conditioned on multi-view references in Figure 1(c) and consistent NVS from a single view in Figure 1(d). Formally, we rearrange the tensor shape before the self-attention modules, enabling self-attention to capture cross-view information. Moreover, to tackle the more intricate NVS task, we propose the novel technique of block" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 72, + 547, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 167 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 167 + ], + "type": "text", + "content": "causal masking, facilitating self-attention-based T2I models in achieving consistent autoregressive (AR) generation. All improvements are integrated into the off-the-shelf SD components, involving no additional image encoder, prompt tuning based on cross-attention, self-attention rearranging and block causal masking. LeftRefill emerges as a unified architecture for addressing reference-guided synthesis, requiring only minor model modifications." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 168, + 548, + 372 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 168, + 548, + 372 + ], + "spans": [ + { + "bbox": [ + 304, + 168, + 548, + 372 + ], + "type": "text", + "content": "We highlight the key contributions of LeftRefill as follows: 1) Lightweight and generalized task formulation based on off-the-shelf T2I models: Benefiting from the novel contextual inpainting formulation and inherent attention mechanisms from SD, LeftRefill provides an efficient solution for reference-guided synthesis without thoroughly re-training T2I models and test-time fine-tuning. 2) Task and view-specific prompt tuning: Our work pioneers the use of task and view-specific prompt tuning, allowing for precise control over generative tasks and view orders. 3) End-to-end Ref-inpainting: Notably, our LeftRefill addresses the challenging Ref-inpainting end-to-end, without complex 3D geometrical warping and 2D inpainting techniques [65, 67, 68]. 4) Autoregressive NVS with block causal masking: For the intricate NVS task, we introduce the novel concept of block causal masking, enabling self-attention-based T2I models to achieve AR generation for geometric consistency." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 382, + 392, + 395 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 382, + 392, + 395 + ], + "spans": [ + { + "bbox": [ + 306, + 382, + 392, + 395 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 402, + 548, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 402, + 548, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 402, + 548, + 653 + ], + "type": "text", + "content": "Personalization and Controllability of T2I Models. Recent achievements on T2I have produced impressive visual generations [2, 36, 42], which could be further extended into local editing [1, 8, 18]. However, these models could only be controlled by natural languages. As \"an image is worth hundreds of words\", T2I models based on natural texts fail to produce images with specific textures, locations, identities, and appearances [15]. Textual inversion [15, 35] and fine-tuning techniques [47] are proposed for personalized T2I. Meanwhile, many works pay attention to image-guided generations [26, 34, 58]. ControlNet [64] and T2I-Adapter [36] learn trainable adapters [20] to inject visual clues to pretrained T2I models without losing generalization and diversity. But these moderate methods only work for simple style transfers. More spatially complex tasks, such as Refinpainting, are difficult to handle by ControlNet as verified in Section 4. In contrast, T2I-based exemplar-editing and NVS have to be fine-tuned on large-scale datasets with strong data augmentation [62] and large batch size [30]. Compared with these aforementioned manners, LeftRefill enjoys both spatial modeling capability and computational efficiency." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 713 + ], + "type": "text", + "content": "Prompt Tuning [24, 32, 33] indicates fine-tuning token embeddings for transformers with frozen backbone to preserve the capacity. Prompt tuning is first explored for adaptively learning suitable prompt features for language models rather than manually selecting them for different downstream" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 58, + 703, + 264, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 703, + 264, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 703, + 264, + 712 + ], + "type": "text", + "content": "*https://github.com/Stability-AI/stablediffusion." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 295, + 749, + 316, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 316, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 316, + 757 + ], + "type": "text", + "content": "7706" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 179 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 179 + ], + "type": "text", + "content": "tasks [29]. Moreover, prompt tuning has been further investigated in vision-language models [16, 43] and discriminative vision models [23, 28]. Visual prompt tuning in [53] prepends trainable tokens before the visual sequence for transferred generations. Though both LeftRefill and [53] aim to tackle image synthesis, our prompt tuning is used for controlling text encoders rather than visual ones. Thus LeftRefill enjoys more intuitive prompt initialization from task-related textual descriptions." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 180, + 290, + 370 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 180, + 290, + 370 + ], + "spans": [ + { + "bbox": [ + 46, + 180, + 290, + 370 + ], + "type": "text", + "content": "Reference-guided Image Inpainting. Image inpainting is a long-standing vision task, which aims to fill missing image regions with coherent results. Both traditional methods [3, 9, 17] and learning-based ones [11, 25, 54, 63, 66] achieved great progress in image inpainting. Furthermore, Ref-inpainting requires recovering a target image with one or several reference views from different viewpoints [40], which is useful for repairing old buildings or removing occlusions in popular attractions. But Ref-inpainting usually suffers from a sophisticated pipeline [65, 67, 68], including depth estimation, pose estimation, homography warping, and single-view inpainting. Limited by large holes, the estimated geometric pose is not reliable, largely degrading the pipeline. Thus an end-to-end Ref-inpainting pipeline is meaningful. To the best of our knowledge, we are the first ones to tackle such a difficult reference-guided task with T2I models." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 371, + 290, + 575 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 371, + 290, + 575 + ], + "spans": [ + { + "bbox": [ + 46, + 371, + 290, + 575 + ], + "type": "text", + "content": "Novel View Synthesis from a Single Image. NVs based on a single image is an intractable ill-posed problem, requiring both sufficient geometry understanding and expressive textural presentation [14]. Many previous works could partially tackle this problem through single view 3D reconstruction [7, 31, 59–61], 2D generative models [39, 45, 52], feature cost volumes [5], and GAN-based methods [4, 38, 51]. However, these manners still suffer from limited generalization or small angle variations. To address this issue, Zero123 [30] uses another image CLIP encoder to inject image features from the reference view to unlock the capacity from 2D diffusion-based T2I models for NVs. But Zero123 requires a large batch size and expensive computational resources to stabilize the training stage with an unknown reference image encoder. Moreover, the image encoder in Zero123 can only tackle one reference image, which fails to generate consistent multi-view images." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 584, + 103, + 596 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 584, + 103, + 596 + ], + "spans": [ + { + "bbox": [ + 47, + 584, + 103, + 596 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 604, + 289, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 604, + 289, + 665 + ], + "spans": [ + { + "bbox": [ + 46, + 604, + 289, + 665 + ], + "type": "text", + "content": "Overview. LeftRefill is first formulated in Section 3.1. Then we explain using self-attention to capture multi-view correspondence, and AR generation based on block casual masking (Section 3.2). Finally, we discuss the task and view-specific prompt tuning for cross-attention (Section 3.3)." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 671, + 185, + 682 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 671, + 185, + 682 + ], + "spans": [ + { + "bbox": [ + 47, + 671, + 185, + 682 + ], + "type": "text", + "content": "3.1. Framework of LeftRefill" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 689, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 288, + 713 + ], + "type": "text", + "content": "Motivations. As depicted in Figure 2(a), our LeftRefill is built upon the inpainting fine-tuned SD [46]. There are two" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 310, + 73, + 433, + 196 + ], + "blocks": [ + { + "bbox": [ + 310, + 73, + 433, + 196 + ], + "lines": [ + { + "bbox": [ + 310, + 73, + 433, + 196 + ], + "spans": [ + { + "bbox": [ + 310, + 73, + 433, + 196 + ], + "type": "image", + "image_path": "d77961d4d0de9be420d970a11ebc876d2fc8714c1741d01be228984565159520.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 439, + 74, + 544, + 198 + ], + "blocks": [ + { + "bbox": [ + 439, + 74, + 544, + 198 + ], + "lines": [ + { + "bbox": [ + 439, + 74, + 544, + 198 + ], + "spans": [ + { + "bbox": [ + 439, + 74, + 544, + 198 + ], + "type": "image", + "image_path": "cab02103fb24fdd6b39cab60ff5e28bdb09eb8c6e4046a802ade808695b096e3.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 320, + 263, + 432, + 451 + ], + "blocks": [ + { + "bbox": [ + 320, + 263, + 432, + 451 + ], + "lines": [ + { + "bbox": [ + 320, + 263, + 432, + 451 + ], + "spans": [ + { + "bbox": [ + 320, + 263, + 432, + 451 + ], + "type": "image", + "image_path": "621d30d98338a9ddfa77bcf6a357056e0af02fd1dc2c967111f731d9074554d8.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "lines": [ + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "spans": [ + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "type": "text", + "content": "Figure 3. Illustration about multi-view training inputs " + }, + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "type": "inline_equation", + "content": "(v\\times H\\times 2W" + }, + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "type": "inline_equation", + "content": "v = 4)" + }, + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "type": "text", + "content": " of LeftRefill, where " + }, + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "type": "inline_equation", + "content": "v,H,2W" + }, + { + "bbox": [ + 304, + 452, + 547, + 506 + ], + "type": "text", + "content": " indicate the view number, height, and width of stitching images. All views of Ref-inpainting (a) share the same masked target, while the multi-view NVS (b) should be trained with the AR generation." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 440, + 262, + 524, + 451 + ], + "blocks": [ + { + "bbox": [ + 304, + 205, + 547, + 261 + ], + "lines": [ + { + "bbox": [ + 304, + 205, + 547, + 261 + ], + "spans": [ + { + "bbox": [ + 304, + 205, + 547, + 261 + ], + "type": "text", + "content": "Figure 2. (a) The overview of LeftRefill. Inputs of Ref-inpainting and NVs are shown in (b). Task and view prompt embedding and pose features (optional for NVS) are infused to CLIP-H for cross-attention learning in U-net. For the output of LeftRefill, we discard the left-side reference and take the right-side generation." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 440, + 262, + 524, + 451 + ], + "lines": [ + { + "bbox": [ + 440, + 262, + 524, + 451 + ], + "spans": [ + { + "bbox": [ + 440, + 262, + 524, + 451 + ], + "type": "image", + "image_path": "64457f794ffd18376e1a53c22db3a5e8cfe51bc3be9fdbac782f6a6aee30f503.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 510, + 547, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 547, + 700 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 547, + 700 + ], + "type": "text", + "content": "primary motivations that make us stitch reference and target images together and reformulate both Ref-inpainting and NVS as a contextual image inpainting problem. 1) LeftRefill just considers a single input image, eliminating the requirement of additional image encoders and avoiding major architectural alterations and extensive re-training. 2) Since all T2I models are only pre-trained on single-view images, the left-right stitched input could implicitly reactivate the essential capacity from large T2I models of modeling the correlation of the single-view image. Particularly, the left-right stitching input enables the self-attention modules to focus on correct parts from left-side reference at the early stage of diffusion sampling (Figure 10). We also thoroughly evaluate different alterations of reference-guided SD in Section 4.1. LeftRefill substantially outperforms other competitors with high efficiency and negligible trainable weights." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 701, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 701, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 701, + 547, + 713 + ], + "type": "text", + "content": "Single-view Formulation (1-to-1). Thanks to the convo" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7707" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 78, + 72, + 258, + 238 + ], + "blocks": [ + { + "bbox": [ + 78, + 72, + 258, + 238 + ], + "lines": [ + { + "bbox": [ + 78, + 72, + 258, + 238 + ], + "spans": [ + { + "bbox": [ + 78, + 72, + 258, + 238 + ], + "type": "image", + "image_path": "27ae7e58841500d2fc8856ce19193b8ce8a1996c54996c5e3196fb41a84996fa.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 239, + 288, + 282 + ], + "lines": [ + { + "bbox": [ + 46, + 239, + 288, + 282 + ], + "spans": [ + { + "bbox": [ + 46, + 239, + 288, + 282 + ], + "type": "text", + "content": "Figure 4. Detailed architecture of LeftRefill for multi-view synthesis. Both CNN and cross-attention modules are encoded separately for each stitched view, while all views share the same self-attention for multi-view correlation learning." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 72, + 285, + 239, + 327 + ], + "blocks": [ + { + "bbox": [ + 72, + 285, + 239, + 327 + ], + "lines": [ + { + "bbox": [ + 72, + 285, + 239, + 327 + ], + "spans": [ + { + "bbox": [ + 72, + 285, + 239, + 327 + ], + "type": "image", + "image_path": "439739df524b24ed65641efbba3b86b3be2a0f0766a0c6586f8056fd0a36162b.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 96, + 329, + 240, + 337 + ], + "lines": [ + { + "bbox": [ + 96, + 329, + 240, + 337 + ], + "spans": [ + { + "bbox": [ + 96, + 329, + 240, + 337 + ], + "type": "text", + "content": "(a) Illustration about the shape rearranging of LeftRefill" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 70, + 338, + 260, + 432 + ], + "blocks": [ + { + "bbox": [ + 70, + 338, + 260, + 432 + ], + "lines": [ + { + "bbox": [ + 70, + 338, + 260, + 432 + ], + "spans": [ + { + "bbox": [ + 70, + 338, + 260, + 432 + ], + "type": "image", + "image_path": "07b28d4f6b5dc1bc985436580972ae02e11085eb6ddc972a3d543f9cf0ba105d.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 93, + 435, + 242, + 444 + ], + "lines": [ + { + "bbox": [ + 93, + 435, + 242, + 444 + ], + "spans": [ + { + "bbox": [ + 93, + 435, + 242, + 444 + ], + "type": "text", + "content": "(b) Block causal masking used for autoregressive training" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "lines": [ + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "spans": [ + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "type": "text", + "content": "Figure 5. (a) Feature rearranging, and (b) block causal masking of LeftRefill, where " + }, + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "type": "inline_equation", + "content": "b, v, h, w, c" + }, + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "type": "text", + "content": " indicate the batch size, view number, height, width, and channels of features, where " + }, + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "type": "text", + "content": " is the width of stitching features (downsampled from " + }, + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "type": "inline_equation", + "content": "2W" + }, + { + "bbox": [ + 46, + 446, + 288, + 491 + ], + "type": "text", + "content": ")." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "spans": [ + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "text", + "content": "lutional U-net architecture in the Latent Diffusion Model (LDM), we can expand the input image in the spatial dimensions without any modification. Let's consider a scenario with a single reference image at first, i.e., 1-to-1. Our input " + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "inline_equation", + "content": "\\mathbf{I}'" + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "text", + "content": " is a stitching image of " + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_{ref}" + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "text", + "content": " and the masked target " + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}_{tar}" + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "text", + "content": ", forming as " + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "inline_equation", + "content": "\\mathbf{I}' = [\\mathbf{I}_{ref};\\hat{\\mathbf{I}}_{tar}] \\in \\mathbb{R}^{H \\times 2W}" + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "text", + "content": " as shown in Figure 2(a). In practice, we take the reference image on the left side, while the target one is placed on the right side. We just take the right-side output as the final generation while the left-side output is discarded. Note that the diffusion optimization is based on the whole stitched image without any modification. For the masked target " + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "inline_equation", + "content": "\\hat{\\mathbf{I}}_{tar}" + }, + { + "bbox": [ + 46, + 495, + 287, + 688 + ], + "type": "text", + "content": ", we treat Ref-inpainting's input targets as partially masked images, while NVS's input targets are entirely masked through the objective segmentation and bounding box. More details about the processing of data and masks are discussed in the supplementary." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 689, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 288, + 713 + ], + "type": "text", + "content": "Multi-view Formulation (V-to-1). For the multi-view references, we stitch each reference with the specific target" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "content": "as shown in Figure 3. All views are learned separately for convolutions and cross-attention, while they share the same self-attention processing as shown in Figure 4 and detailed in Section 3.2. From Figure 3(a), the multi-view Ref-inpainting leverages information from different reference views to repair the same target, i.e., " + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "content": "-to-1, where " + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "content": " means the view number. We simply take the generation of the first view as the final inpainted output in " + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "content": "-to-1. For the multi-view NVS, it could be seen as an AR generation for sequentially consistent view synthesis, as depicted in Figure 3(b), i.e., " + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "content": "-to-1 (" + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "inline_equation", + "content": "n = 1,2,\\dots,v" + }, + { + "bbox": [ + 304, + 72, + 547, + 239 + ], + "type": "text", + "content": "). During the inference, we apply the generated targets as new references for the subsequent view synthesis, while the training phase is accomplished parallelly as detailed in the block casual masking of Section 3.2." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 239, + 547, + 455 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 239, + 547, + 455 + ], + "spans": [ + { + "bbox": [ + 304, + 239, + 547, + 455 + ], + "type": "text", + "content": "Controlling Generation for LeftRefill. Although the self-attention modules in SD have the potential to enable the correlation between left reference and right target, SD is not trained to explicitly activate this capacity. The most intuitive way to guide the SD in capturing the correlation among left-right stitched images is to apply suitable text prompts to drive the diffusion model for the desired generation. However, it is non-trivial to define Ref-inpainting and NVS with natural languages. Furthermore, it is beneficial to have a non-instance-level prompt to generally guide the diffusion model to accomplish specific tasks. To this end, we propose to use prompt tuning to learn task and view-specific prompts as detailed in Section 3.3. Except for the prompt tuning, all weights in LDM are frozen in Ref-inpainting to maintain the proper generalization as shown in Figure 2(a). For NVS, we fine-tune the whole LDM to achieve essentially precise pose control, but LeftRefill enjoys much better convergence compared with other fine-tuning based methods [30]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 462, + 528, + 474 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 462, + 528, + 474 + ], + "spans": [ + { + "bbox": [ + 306, + 462, + 528, + 474 + ], + "type": "text", + "content": "3.2. Reactivating Self-Attention for Multi-View" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "spans": [ + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": "As shown in Figure 5(a), given multi-view features " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_i" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": " of layer " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": ", all MLP, convolutional, and cross-attention layers encode " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_i" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": " separately. We can simply achieve the separate feature encoding by reshaping the view " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "v" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": " and batch " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": " dimension together as " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "bv" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": ". Before the self-attention, we rearrange the feature shape as " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\tilde{\\mathbf{F}}_i \\in \\mathbb{R}^{b \\times vhw \\times c}" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": ", thus features across different views could be learned together. To further incorporate positional clues for distinguishing different sides of reference and target in NVS, we incrementally add positional encoding " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "P_i" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\tilde{\\mathbf{F}}_i" + }, + { + "bbox": [ + 304, + 480, + 547, + 600 + ], + "type": "text", + "content": " before each self-attention block as" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 364, + 609, + 545, + 622 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 364, + 609, + 545, + 622 + ], + "spans": [ + { + "bbox": [ + 364, + 609, + 545, + 622 + ], + "type": "interline_equation", + "content": "P _ {i} = \\gamma_ {i} \\cdot \\operatorname {c a t} ([ P _ {v}; P _ {\\text {F o u r i e r}} ]), \\tag {1}", + "image_path": "1a7917c70b2a77d25b1608dd4d70395e376dcdba8056bca51ceef8622a7f1121.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 629, + 545, + 666 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 545, + 666 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 545, + 666 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 629, + 545, + 666 + ], + "type": "inline_equation", + "content": "P_{v}, P_{Fourier}" + }, + { + "bbox": [ + 304, + 629, + 545, + 666 + ], + "type": "text", + "content": " indicate the trainable view embedding and Fourier absolute positional encoding [57] respectively; " + }, + { + "bbox": [ + 304, + 629, + 545, + 666 + ], + "type": "inline_equation", + "content": "\\gamma_{i}" + }, + { + "bbox": [ + 304, + 629, + 545, + 666 + ], + "type": "text", + "content": " is a zero-initialized learnable coefficient for each layer." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 666, + 547, + 713 + ], + "type": "text", + "content": "For the Ref-inpainting, no masking strategy should be considered in self-attention modules. All reference views share the same target one, thus it is unnecessary for LeftRefill to sequentially repair target views. In contrast, for the" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7708" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 143 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 143 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 143 + ], + "type": "text", + "content": "multi-view NVs, generating consistent novel views from a single image needs our model to handle the sequential generation with dynamic reference views. For example, the same LeftRefill should accomplish the NVS from one view, two views, and even more. So the AR generation [13, 49, 56] is suitable to formulate this task." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 144, + 290, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 144, + 290, + 373 + ], + "spans": [ + { + "bbox": [ + 46, + 144, + 290, + 373 + ], + "type": "text", + "content": "Block Causal Masking. LeftRefill requires a certain finetuning for LDM to effectively tackle challenging NVS as shown in Figure 2(a). The intuitive solution is to train an AR-based generative model that can generalize across various view numbers for multi-view synthesis. Converting a pretrained diffusion model to an AR-based generative model is non-trivial. However, the inpainting formulation of Left-Refill makes this conversion feasible. Specifically, we just need to adjust the masking strategy during the self-attention learning. We propose the block casual masking as shown in Figure 5(b), while the block side-length of each view is " + }, + { + "bbox": [ + 46, + 144, + 290, + 373 + ], + "type": "inline_equation", + "content": "h w" + }, + { + "bbox": [ + 46, + 144, + 290, + 373 + ], + "type": "text", + "content": ", matching the size of the stitched reference and target pair. Different from the traditional casual mask which is a lower triangular matrix, the block casual mask enlarges the minimal unit from one token to a " + }, + { + "bbox": [ + 46, + 144, + 290, + 373 + ], + "type": "inline_equation", + "content": "h w \\times h w" + }, + { + "bbox": [ + 46, + 144, + 290, + 373 + ], + "type": "text", + "content": " block, ensuring reasonable block-wise receptive fields. In practice, all uncolored tokens in the attention score are masked with “—inf” before the softmax operation. The block casual mask can be implemented parallelly and efficiently as in supplementary." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 378, + 200, + 392 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 378, + 200, + 392 + ], + "spans": [ + { + "bbox": [ + 47, + 378, + 200, + 392 + ], + "type": "text", + "content": "3.3. Task&View Prompt Tuning" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 396, + 288, + 589 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 396, + 288, + 589 + ], + "spans": [ + { + "bbox": [ + 46, + 396, + 288, + 589 + ], + "type": "text", + "content": "The prompt embedding is adopted as the textual branch to CLIP-H [43] of SD, being applied to cross-attention as shown in Figure 2(a). Specifically, we prepare a set of trainable text embeddings for different generative tasks, which are further categorized into task and view prompts. Specifically, task prompt embeddings are shared in the same task, e.g., all views of Ref-inpainting using the same task embeddings. In contrast, different view prompt embeddings are applied to inject various view-order information through cross-attention modules to the specific input view. Though there are only a few trainable parameters (0.05M to 0.065M), we astonishingly find that prompt tuning is sufficient to drive complex generative tasks such as Ref-inpainting, even with a frozen LDM backbone. The trainable task and view prompt embeddings " + }, + { + "bbox": [ + 46, + 396, + 288, + 589 + ], + "type": "inline_equation", + "content": "p_t" + }, + { + "bbox": [ + 46, + 396, + 288, + 589 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 396, + 288, + 589 + ], + "type": "inline_equation", + "content": "p_v" + }, + { + "bbox": [ + 46, + 396, + 288, + 589 + ], + "type": "text", + "content": " are initialized as the averaged embedding of the natural task description. The optimization target is:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 50, + 592, + 288, + 613 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 50, + 592, + 288, + 613 + ], + "spans": [ + { + "bbox": [ + 50, + 592, + 288, + 613 + ], + "type": "interline_equation", + "content": "\\left\\{p _ {t}, p _ {v} \\right\\} _ {*} = \\underset {\\left\\{p _ {t}, p _ {v} \\right\\}} {\\arg \\min } \\mathbb {E} \\left[ \\left\\| \\varepsilon - \\varepsilon_ {\\theta} \\left([ z _ {t}; \\hat {z} _ {0}; \\mathbf {M} ], c _ {\\phi} \\left(p _ {t}, p _ {v}\\right), t\\right) \\right\\| ^ {2} \\right], (2)", + "image_path": "904f8e833f63578ade6ba435a2eb262c26418a2fac4511204d93d2c5c0e7aa86.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\varepsilon_{\\theta}(\\cdot)" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " is the estimated noise by LDM; " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "c_{\\phi}(\\cdot)" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " means the frozen CLIP-H; " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "z_{t}" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " is a noisy latent feature of input " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "z_{0}" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " in step " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": "; " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\hat{z}_0 = z_0\\odot (1 - \\mathbf{M})" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " are masked latent features concatenated to " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "z_{t}" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " with mask " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{M}" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": ". Task and view-specific prompt tuning enjoy not only training efficiency but also lightweight saving [24]. For example, we share the same LeftRefill to address Ref-inpainting with different reference views, while only " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "0.01\\%" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " additional weights of " + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\{p_t,p_v\\}_{*}" + }, + { + "bbox": [ + 46, + 617, + 288, + 715 + ], + "type": "text", + "content": " are" + } + ] + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 307, + 126, + 550, + 267 + ], + "blocks": [ + { + "bbox": [ + 304, + 60, + 547, + 126 + ], + "lines": [ + { + "bbox": [ + 304, + 60, + 547, + 126 + ], + "spans": [ + { + "bbox": [ + 304, + 60, + 547, + 126 + ], + "type": "text", + "content": "Table 1. Quantitative results for Ref-inpainting on MegaDepth [27] test set based on matching and manual masks (upper: 1-view; lower: multi-view). 'ExParams': the scale of extra trainable parameters. * means that the uncorrupted ground truth is visible for the matching. 'No stitching': reference and target views are separate without spatial stitching, and only self-attention are learned across them." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 307, + 126, + 550, + 267 + ], + "lines": [ + { + "bbox": [ + 307, + 126, + 550, + 267 + ], + "spans": [ + { + "bbox": [ + 307, + 126, + 550, + 267 + ], + "type": "table", + "html": "
MethodsPSNR↑SSIM↑FID↓LPIPS↓ExParams
SD ( inpainting) [46]19.8410.81930.2600.1349+0
ControlNet [64]19.0720.74433.6640.1816+364.2M
ControlNet+NewCrossAttn19.0270.74334.1700.1805+463.4M
ControlNet+Matching* [55]20.5920.76329.5560.1565+364.3M
Perceiver+ImageCLIP [22]19.3380.74532.9110.1751+52.01M
Paint-by-Example [62]18.3510.79734.7110.1604+865.9M
TransFill [68]22.7440.87526.2910.1102-
LeftRefill (no stitching)20.4890.82720.1250.1085+0.05M
LeftRefill20.9260.83618.6800.0961+0.05M
LeftRefill (2-view)21.0920.83618.3890.0969+0.055M
LeftRefill (3-view)21.3560.84016.8380.0901+0.06M
LeftRefill (4-view)21.7790.84716.6320.0839+0.065M
", + "image_path": "67b9ebb73031ed78fa72984ac29a1ac30df2aba086864c8e6e1e7c1f2f18e84c.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 272, + 547, + 344 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 272, + 547, + 344 + ], + "spans": [ + { + "bbox": [ + 304, + 272, + 547, + 344 + ], + "type": "text", + "content": "changed for each view condition. In NVS, we further provide relative poses to LeftRefill. Following [30], we calculate the 4-channel relative pose in the polar coordinate for each view, which is encoded by a two-layer FC. Then the pose feature replaces the last padding token in the prompt embeddings before being applied to the CLIP-H." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 357, + 388, + 370 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 357, + 388, + 370 + ], + "spans": [ + { + "bbox": [ + 306, + 357, + 388, + 370 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "spans": [ + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "text", + "content": "Datasets. For Ref-inpainting, we use the resized " + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "inline_equation", + "content": "512 \\times 512" + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "text", + "content": " image pairs from MegaDepth [27], which includes many multi-view famous scenes collected from the Internet. To trade-off between the image correlation and the inpainting difficulty, we empirically retain image pairs with " + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "inline_equation", + "content": "40\\%" + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "inline_equation", + "content": "70\\%" + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "text", + "content": " co-occurrence with about 80k images and 820k pairs. The validation of Ref-inpainting also includes some manual masks from ETH3D scenes [50] to verify the generalization. For the NVS, we use Objaverse [10] rendered by [30] including 800k various scenes with object masks. We resize all images to " + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "inline_equation", + "content": "256 \\times 256" + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "text", + "content": " as [30]. Note that some extreme views with elevation angles less than " + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "inline_equation", + "content": "-10^{\\circ}" + }, + { + "bbox": [ + 304, + 377, + 547, + 545 + ], + "type": "text", + "content": " are filtered due to excessive ambiguity. More details about the masking and datasets are introduced in the supplementary." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "text", + "content": "Implementation Details. Our LeftRefill is based on the inpainting fine-tuned SD [46] with 0.8 billion parameters. For the task and view prompt tuning, there are 50 trainable prompt tokens at all. We use " + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "inline_equation", + "content": "90\\%" + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "text", + "content": " tokens to represent the task embeddings, while " + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "inline_equation", + "content": "10\\%" + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "text", + "content": " tokens indicate each view respectively. We use the AdamW optimizer with a weight decay of 0.01 to optimize LeftRefill. For the Ref-inpainting, the prompt tuning's learning rate is 3e-5. Moreover, " + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "inline_equation", + "content": "75\\%" + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "text", + "content": " masks are randomly generated, and " + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "inline_equation", + "content": "25\\%" + }, + { + "bbox": [ + 304, + 545, + 548, + 713 + ], + "type": "text", + "content": " of them are matching-based masks. For the NVS, LeftRefill could be tested with the adaptive masking strengthened by the foreground segmentation model. Concretely, we first enlarge the reference segmentation mask and generate a coarse target with fewer DDIM steps. We extract the new mask from the coarse tar" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7709" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 85, + 70, + 508, + 292 + ], + "blocks": [ + { + "bbox": [ + 85, + 70, + 508, + 292 + ], + "lines": [ + { + "bbox": [ + 85, + 70, + 508, + 292 + ], + "spans": [ + { + "bbox": [ + 85, + 70, + 508, + 292 + ], + "type": "image", + "image_path": "7c15677a34c9c7b41a21181a3760afebf27794db80489ddcf176d7a2456d22ad.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 108, + 299, + 482, + 311 + ], + "lines": [ + { + "bbox": [ + 108, + 299, + 482, + 311 + ], + "spans": [ + { + "bbox": [ + 108, + 299, + 482, + 311 + ], + "type": "text", + "content": "Figure 6. Qualitative Ref-inpainting results on MegaDepth [27]. More results are in the supplementary." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 48, + 320, + 287, + 425 + ], + "blocks": [ + { + "bbox": [ + 48, + 320, + 287, + 425 + ], + "lines": [ + { + "bbox": [ + 48, + 320, + 287, + 425 + ], + "spans": [ + { + "bbox": [ + 48, + 320, + 287, + 425 + ], + "type": "image", + "image_path": "2e95a83d2211106fd2cc4309847af7455c14020cb81ca0dc4513ec5615adc280.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 434, + 288, + 456 + ], + "lines": [ + { + "bbox": [ + 47, + 434, + 288, + 456 + ], + "spans": [ + { + "bbox": [ + 47, + 434, + 288, + 456 + ], + "type": "text", + "content": "Figure 7. Multi-view Ref-inpainting qualitative results. Increasing the reference view number improves the quality of repaired targets." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 469, + 287, + 553 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 469, + 287, + 553 + ], + "spans": [ + { + "bbox": [ + 46, + 469, + 287, + 553 + ], + "type": "text", + "content": "get and then further randomly enlarge it as the final target mask. The NVS LeftRefill is trained with 512 batch size and learning rate 3e-5. We show that a simplified LeftRefill with just 48 batch size can also be converged for NVS, which breaks through the limitation of Zero123 [30]. More details about matching-based masks, adaptive masking, and training schedules are discussed in the supplementary." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 563, + 253, + 575 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 563, + 253, + 575 + ], + "spans": [ + { + "bbox": [ + 47, + 563, + 253, + 575 + ], + "type": "text", + "content": "4.1. Results of Reference-guided Inpainting" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 288, + 714 + ], + "type": "text", + "content": "Results of One-view Reference. We thoroughly compared the specific Ref-inpainting method [68] and existing image reference-based variants of SD with one-view reference in Table 1 and Figure 6. Note that ControlNet [64] fails to learn the correct spatial correlation between reference images and masked targets, even enhanced with trainable cross-attention learned between reference and target features. Furthermore, we try to warp ground-truth latent features with image matching [55] as the reference guidance for ControlNet, but the improvement is not prominent. Perceiver [22] and Paint-by-Example [62] align and learn image features from Image" + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 329, + 325, + 524, + 536 + ], + "blocks": [ + { + "bbox": [ + 329, + 325, + 524, + 536 + ], + "lines": [ + { + "bbox": [ + 329, + 325, + 524, + 536 + ], + "spans": [ + { + "bbox": [ + 329, + 325, + 524, + 536 + ], + "type": "image", + "image_path": "aa32d35428ca39fb87ad941b72b69032d5f4ea8ed6739084f321b457771f6dc8.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 543, + 545, + 566 + ], + "lines": [ + { + "bbox": [ + 305, + 543, + 545, + 566 + ], + "spans": [ + { + "bbox": [ + 305, + 543, + 545, + 566 + ], + "type": "text", + "content": "Figure 8. NVS results on Objaverse [10] (row1, 2) and Google Scanned Objects [12] (row3, 4) from a single reference image." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": "CLIP. Since image features from CLIP contain high-level semantics, they fail to deal with the fine-grained Ref-inpainting as shown in Figure 6(e)(f). Though TransFill [68] achieves proper results in PSNR and SSIM, it suffers from blur and color difference as in Figure 6(g) with challenging viewpoints. LeftRefill enjoys substantial advantages in both qualitative and quantitative comparisons with negligible trainable weights. Particularly, spatially stitching reference and target views together achieves consistent improvements. Thus it is intuitive and convincing that all U-net modules contribute to improved inpainting results with a whole stitched image, as" + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7710" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 62, + 75, + 272, + 361 + ], + "blocks": [ + { + "bbox": [ + 62, + 75, + 272, + 361 + ], + "lines": [ + { + "bbox": [ + 62, + 75, + 272, + 361 + ], + "spans": [ + { + "bbox": [ + 62, + 75, + 272, + 361 + ], + "type": "image", + "image_path": "c18132f3ab236168abce7c33dc02ebe98f39f35bc62e142941f8ef8de2d3d749.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 369, + 288, + 401 + ], + "lines": [ + { + "bbox": [ + 46, + 369, + 288, + 401 + ], + "spans": [ + { + "bbox": [ + 46, + 369, + 288, + 401 + ], + "type": "text", + "content": "Figure 9. Sequential generative results from a single view. Zero123 [30] are conditioned on real reference (first view) and last generated view (last view), while LeftRefill is based on AR." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 410, + 288, + 445 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 410, + 288, + 445 + ], + "spans": [ + { + "bbox": [ + 46, + 410, + 288, + 445 + ], + "type": "text", + "content": "opposed to using only attention modules. We further compare LeftRefill with TransFill on their officially provided real-world dataset in the supplementary." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 446, + 288, + 517 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 446, + 288, + 517 + ], + "spans": [ + { + "bbox": [ + 46, + 446, + 288, + 517 + ], + "type": "text", + "content": "Results of Multi-view Ref-inpainting. We verified models trained with different numbers of reference views in Table 1 (lower). As the number of reference views increases, there is a notable enhancement in inpainting capability. As qualitatively compared in Figure 7, more consistent references lead to robust inpainting results with sensible structures." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 526, + 218, + 540 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 526, + 218, + 540 + ], + "spans": [ + { + "bbox": [ + 47, + 526, + 218, + 540 + ], + "type": "text", + "content": "4.2. Results of Novel View Synthesis" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 288, + 713 + ], + "type": "text", + "content": "Results of Single-view NVs. We compare the quantitative NVs results on Objaverse in Table 2. The qualitative results for both Objaverse and Google Scanned Objects are compared in Figure 8. Without specific annotations, all NVs results are based on adaptive masking. The CLIP score [43] is compared to evaluate the similarity between the generation and the target. Specifically, LeftRefill fine-tuned with the whole LDM enjoys substantial achievements compared to the state-of-the-art competitor Zero123 [30], even though Zero123 might have seen our validation in Objaverse. Moreover, the LoRA-based LeftRefill [21] is still competitive with a very moderate training setting (batch size 48 with 2 A6000 GPUs) in Table 2. We further compare the training log of LeftRefill and Zero123 in the supplementary to investigate" + } + ] + } + ], + "index": 5 + }, + { + "type": "table", + "bbox": [ + 307, + 102, + 548, + 208 + ], + "blocks": [ + { + "bbox": [ + 305, + 67, + 545, + 100 + ], + "lines": [ + { + "bbox": [ + 305, + 67, + 545, + 100 + ], + "spans": [ + { + "bbox": [ + 305, + 67, + 545, + 100 + ], + "type": "text", + "content": "Table 2. Results of 1-view NVS conditioned on different numbers of reference views on Objaverse [10]. 'w.o. AM' indicates NVS results without Adaptive Masking (AM)." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 307, + 102, + 548, + 208 + ], + "lines": [ + { + "bbox": [ + 307, + 102, + 548, + 208 + ], + "spans": [ + { + "bbox": [ + 307, + 102, + 548, + 208 + ], + "type": "table", + "html": "
MethodsRef-ViewPSNR↑SSIM↑LPIPS↓CLIP↑
Zero123 [30]119.4020.8580.13090.7816
LeftRefill (LoRA)119.5140.8690.15340.7589
LeftRefill (w.o. AM)121.6750.8870.10890.7959
LeftRefill121.4040.8820.11510.7972
LeftRefill222.9350.8950.08710.8280
LeftRefill324.1070.9080.07220.8432
LeftRefill424.6850.9110.06340.8495
", + "image_path": "85d91010444793bad639a6a47cc6fe2b528cb46a9a26c220d435cdcf4a9fb638.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 308, + 266, + 542, + 332 + ], + "blocks": [ + { + "bbox": [ + 305, + 209, + 547, + 264 + ], + "lines": [ + { + "bbox": [ + 305, + 209, + 547, + 264 + ], + "spans": [ + { + "bbox": [ + 305, + 209, + 547, + 264 + ], + "type": "text", + "content": "Table 3. Results of 4-view NVS generations based on 1 reference view on Objaverse [10]. P-CLIP means pairwise CLIP score showing consistency of generated views. The reference (Ref) can be categorized into the first ground-truth view and the last generated view, while we also provide the AR results of LeftRefill." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 308, + 266, + 542, + 332 + ], + "lines": [ + { + "bbox": [ + 308, + 266, + 542, + 332 + ], + "spans": [ + { + "bbox": [ + 308, + 266, + 542, + 332 + ], + "type": "table", + "html": "
MethodsRefPSNR↑SSIM↑LPIPS↓CLIP↑P-CLIP↑
Zero123First19.2650.8550.13660.77230.7756
Zero123Last14.6210.7670.25690.69210.7667
LeftRefillFirst21.5730.8830.11430.79640.7709
LeftRefillAR21.2710.8820.11950.78820.7958
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Prompt TypeLengthPSNR↑SSIM↑LPIPS↓Params
Shallow2520.350.8270.104+0.025M
Shallow5020.490.8290.103+0.05M
Shallow7520.380.8300.104+0.075M
Deep (×16)25(400)20.150.8250.106+0.4M
", + "image_path": "2fa34c680a2de8a44fee803ea3c4ed5a77ed489bf8672c25cc3ff2cb311e0937.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 325, + 106, + 494, + 184 + ], + "blocks": [ + { + "bbox": [ + 46, + 70, + 547, + 104 + ], + "lines": [ + { + "bbox": [ + 46, + 70, + 547, + 104 + ], + "spans": [ + { + "bbox": [ + 46, + 70, + 547, + 104 + ], + "type": "text", + "content": "Table 4. Ablation studies for the setting of prompt tuning in Ref-inpainting. Left: 'Shallow' means only prompt tuning to text embedding, while 'Deep' indicates tuning additional embedding features to different cross-attention layers (16 layers) in SD. Right: validating the influence of the length of shared (Task) and unshared (View) prompts with 3-view Ref-inpainting." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 325, + 106, + 494, + 184 + ], + "lines": [ + { + "bbox": [ + 325, + 106, + 494, + 184 + ], + "spans": [ + { + "bbox": [ + 325, + 106, + 494, + 184 + ], + "type": "table", + "html": "
TaskViewPSNR↑SSIM↑LPIPS↓Params
50021.2240.8380.0941+0.05M
45521.3560.8400.0901+0.06M
252521.1270.8360.0950+0.11M
54520.7440.8320.1040+0.14M
05020.5630.8310.1110+0.15M
", + "image_path": "b94b0f90d48ed3474a5ca9e415deeb37887ef36ad883d0c11eb710c1f16870e2.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 74, + 209, + 261, + 282 + ], + "blocks": [ + { + "bbox": [ + 47, + 185, + 287, + 207 + ], + "lines": [ + { + "bbox": [ + 47, + 185, + 287, + 207 + ], + "spans": [ + { + "bbox": [ + 47, + 185, + 287, + 207 + ], + "type": "text", + "content": "Table 5. NVS results of LeftRefill-simple with different reference views with/without incremental Positional Encoding (PE)." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 74, + 209, + 261, + 282 + ], + "lines": [ + { + "bbox": [ + 74, + 209, + 261, + 282 + ], + "spans": [ + { + "bbox": [ + 74, + 209, + 261, + 282 + ], + "type": "table", + "html": "
Ref-ViewPEPSNR↑SSIM↑LPIPS↓
1×20.3520.8730.132
1✓20.5080.8750.128
4×22.0970.8880.099
4✓22.3240.8900.095
", + "image_path": "5495d4ae049348b0b8c1cb145ceb8446447a4985cc5a6f1f5fdca9ba1fb0157c.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 303, + 287, + 327 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 303, + 287, + 327 + ], + "spans": [ + { + "bbox": [ + 46, + 303, + 287, + 327 + ], + "type": "text", + "content": "quality degradation. Our method can also be generalized to real-world data as shown in the supplementary." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 335, + 211, + 347 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 335, + 211, + 347 + ], + "spans": [ + { + "bbox": [ + 47, + 335, + 211, + 347 + ], + "type": "text", + "content": "4.3. Analysis and Ablation Studies" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 354, + 289, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 354, + 289, + 510 + ], + "spans": [ + { + "bbox": [ + 46, + 354, + 289, + 510 + ], + "type": "text", + "content": "Self-Attention Analysis. We show the visualization of self-attention scores attended by masked regions for Refinpainting across different DDIM steps in Figure 10. Self-attention can capture correct feature correlations without any backbone fine-tuning. As diffusion sampling progresses, self-attention modules gradually shift their focus from specific key points to broader related regions, which is convincing and intuitive. Because the key landmarks help to swiftly locate the spatial correlation between the reference and target, while the extended receptive fields further refine the generation for the following sampling steps. More analysis about the attention visualization with increased reference views is shown in the supplementary." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 510, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 289, + 713 + ], + "type": "text", + "content": "Prompt Settings. The length and depth used in the task and view prompt tuning are explored in Table 4. Different from [23], we find that LeftRefill is relatively robust in the length selection. Thus we select 50 for both Ref-inpainting and NVS. Moreover, the deep prompt with much more trainable prompts for different cross-attention layers does not perform well, which may suffer from a little overfitting. For the multi-view scene, we empirically evaluate the 3-view-based Ref-inpainting performance with various proportions of task&view prompt lengths in the right of Table 4. Increasing the proportion of view tokens initially improves the results, followed by a subsequent decline. We think that a few unshared view tokens contribute valuable view orders, while too many unshared tokens would increase the learning difficulty, leading to an inferior prompt tuning performance. Incremental Positional Encoding. We incrementally add the concatenation of learnable view embedding and absolute" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 315, + 193, + 536, + 292 + ], + "blocks": [ + { + "bbox": [ + 315, + 193, + 536, + 292 + ], + "lines": [ + { + "bbox": [ + 315, + 193, + 536, + 292 + ], + "spans": [ + { + "bbox": [ + 315, + 193, + 536, + 292 + ], + "type": "image", + "image_path": "9d691f7011ef37fe3912624be3788692bcd78850ed3047c7a74d91526165a604.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 294, + 547, + 317 + ], + "lines": [ + { + "bbox": [ + 305, + 294, + 547, + 317 + ], + "spans": [ + { + "bbox": [ + 305, + 294, + 547, + 317 + ], + "type": "text", + "content": "Figure 11. Ref-inpainting results with different CFG weights, which take a trade-off between structural and textural recoveries." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 329, + 547, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 329, + 547, + 365 + ], + "spans": [ + { + "bbox": [ + 304, + 329, + 547, + 365 + ], + "type": "text", + "content": "positional encoding to each attention block for NVs (Equation (1)), improving the performance of both single-view and multi-view-based NVs as verified in Table 5." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 365, + 547, + 475 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 365, + 547, + 475 + ], + "spans": [ + { + "bbox": [ + 304, + 365, + 547, + 475 + ], + "type": "text", + "content": "Classifier-Free Guidance (CFG) [19]. We find that CFG can enhance the performance of Ref-inpainting even without training with prompt dropout as in Figure 11. The adjusting of CFG could be seen as the trade-off between structural and textural recoveries. High CFG scales lead to over-saturated results with superior structure. We empirically set CFG to 2.0 and 2.5 for Ref-inpainting and NVs respectively. More quantitative results and details about the CFG setting of NVs are discussed in the supplementary." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 487, + 378, + 500 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 487, + 378, + 500 + ], + "spans": [ + { + "bbox": [ + 306, + 487, + 378, + 500 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 509, + 547, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 547, + 640 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 547, + 640 + ], + "type": "text", + "content": "In this paper, we propose LeftRefill, formulating reference-based synthesis as inpainting tasks and addressing them end-to-end as a human painter. Benefiting from the prompt tuning and the well-learned attention modules in large T2I models, LeftRefill can address the spatially sophisticated Ref-inpainting and NVs efficiently. Moreover, LeftRefill could be easily extended to tackle multi-view generation tasks. We also propose block casual masking to accomplish NVs with consistent results autoregressively. Comprehensive experiments on Ref-inpainting and NVs show the effectiveness and efficiency of LeftRefill." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 642, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 548, + 714 + ], + "type": "text", + "content": "Acknowledgements: Yanwei Fu is the corresponding author. Yanwei Fu is with the School of Data Science, Shanghai Key Lab of Intelligent Information Processing, Fudan University, and Fudan ISTBI-ZJNU Algorithm Centre for Brain-inspired Intelligence, Zhejiang Normal University. The computations in this research were performed using the CFFF platform of Fudan University." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "7712" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 135 + ], + "type": "text", + "content": "[1] Omri Avrahami, Dani Lischinski, and Ohad Fried. 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In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, pages 2266-2276, 2021. 2, 3, 5, 6" + } + ] + } + ], + "index": 16 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 749, + 315, + 757 + ], + "type": "text", + "content": "7715" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_content_list.json b/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..4144d8c82ffe891ba99f94b8f1c096104ff87456 --- /dev/null +++ b/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_content_list.json @@ -0,0 +1,2298 @@ +[ + { + "type": "image", + "img_path": "images/067735d14749de563bfd8fb9faff2ec4ea77b95a2f0614ec090b1e2c61319e58.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 129, + 125, + 166, + 154 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Let's Think Outside the Box: Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation", + "text_level": 1, + "bbox": [ + 169, + 137, + 844, + 183 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Shanshan Zhong $^{1,3*}$ Zhongzhan Huang $^{1,3*}$ Shanghua Gao $^{4}$ Wushao Wen $^{1}$ Liang Lin $^{1}$ Marinka Zitnik $^{4}$ Pan Zhou $^{2,3\\dagger}$", + "bbox": [ + 145, + 209, + 821, + 246 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1 Sun Yat-Sen University, 2 Singapore Management University, 3 Sea AI Lab, 4 Harvard University", + "bbox": [ + 96, + 246, + 872, + 265 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "*Co-first author: {zhongshsh5,huangzhzh23}@mail2.sysu.edu.cn", + "bbox": [ + 215, + 266, + 743, + 281 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "†Corresponding author: panzhou@smu.edu.sg", + "bbox": [ + 300, + 284, + 661, + 299 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c22c2c0d8a93fe4cf40ce7bf29efcc1b43ea64795695264b3bc3d5a05e0adb80.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 96, + 308, + 344, + 386 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/d70d32c8f597e543d5a78b3c0da0972d10fd200ad0966991d4c5e351138d5ac9.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 99, + 397, + 122, + 410 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Qwen-VL", + "bbox": [ + 122, + 398, + 179, + 410 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/1224980760705167e40cec79b03d1981b9887f46636910d295f052f2b11b5925.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 179, + 398, + 202, + 410 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Qwen- $\\mathrm{VL}_{+}$ CLoT (Ours)", + "bbox": [ + 202, + 398, + 323, + 411 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Image&Text to Text (IT2T)", + "bbox": [ + 137, + 417, + 303, + 430 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/6104469f6d2d041dd41ccd7e33a4380cef44f26cb41df968852fe2d1d9a5167a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 102, + 435, + 344, + 554 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/d63c2d6f49b503c5fb614b6b7547a33a4f2d808ffa193e222369d5f9cf542cc6.jpg", + "image_caption": [ + "Figure 1. Comparison between (multimodal) large language model (LLM, red) and its CLoT-integrated version (blue) for Oogiri-style multimodal humor generation. According to the model input that can be image, text or both, there are three Oogiri tasks, \"Image&Text to Text (IT2T)\", \"Image to Text (I2T)\", and \"Text to Text (T2T)\", where text can be English (EN), Chinese (CN), and Japanese (JP). \"@\" denotes translations. The baseline LLM is Qwen-VL [1]. While humor is subjective, these examples demonstrate CLoT's leap-of-thought capacity of using excellent creative thinking to produce high-quality humor responses. See more examples in Appendix." + ], + "image_footnote": [], + "bbox": [ + 102, + 560, + 189, + 647 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(CN) ①求婚者 ②被求婚者 ③", + "bbox": [ + 192, + 569, + 333, + 594 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@①Proposer②Proposee③?", + "bbox": [ + 194, + 597, + 320, + 609 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/5e17acc6ac711ae2f7e1ea41b0eae7b2952b20175f3ee9c288d2920ec27363af.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 194, + 625, + 225, + 638 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "牧师 @ Pastor", + "bbox": [ + 225, + 627, + 285, + 638 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/a9c736c8fd84ccf4ec06b12c056e44caba3c85865bfcd3fbd92e43576d6b4092.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 289, + 626, + 336, + 642 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/fa6c0b4ebdafc11a8feae62a1b183dcff275568fe8f21ce51699d793e53a5ec3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 194, + 648, + 233, + 660 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "译员@Translator", + "bbox": [ + 235, + 648, + 310, + 660 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/8efb454dfa4a2d3cf6d59e6f7436f17ddabff85189e7750084214d815591434d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 313, + 648, + 338, + 664 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Image to Text (12T)", + "text_level": 1, + "bbox": [ + 421, + 316, + 539, + 329 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c3a972ab0f0de8aef1eabaa54e09a82cdf859adddd6af2726f2bc0424923ae8b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 362, + 349, + 431, + 414 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(EN) Forgot to remove glasses while swimming.", + "bbox": [ + 437, + 345, + 586, + 369 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(EN) An apple a day keep the doctor away.", + "bbox": [ + 437, + 386, + 580, + 409 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/cba9f5d00011ca5a7d0664082e567d0bc325049c4f66d4ce6783f4bdae288762.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 570, + 398, + 596, + 421 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/0c09d7e434c10a54520e501a1c4ea5b40ab4883326fbec4029b07c87a1beacaf.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 364, + 454, + 431, + 518 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(JP) ああ、やと運転が始のをるた", + "bbox": [ + 437, + 450, + 591, + 472 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ Oh, I can finally start driving.", + "bbox": [ + 437, + 473, + 558, + 484 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/084978b7506c146f8036b8e39f550aadd61c01e4a54ae1b9921bc682aa21f035.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 570, + 470, + 594, + 486 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(JP)心配ないて、すてが青信号です", + "bbox": [ + 437, + 500, + 591, + 523 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ Don't worry, they're all green lig", + "bbox": [ + 437, + 525, + 566, + 535 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/b11cdd71293582f013eda1219a3919e10cda0fc20e30a2277ec27b7b4d5ffd30.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 570, + 529, + 594, + 551 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/9367f80eb07b1591e1549cc747197716bac66d65211ee3a4c5f44b96f06142d0.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 364, + 574, + 431, + 637 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(CN)哈哈这是一只快乐的猫咪,它张着嘴巴...", + "bbox": [ + 437, + 568, + 583, + 590 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ Haha this is a happy cat with his mouth open ....", + "bbox": [ + 437, + 590, + 568, + 608 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/6b1bb6426cb93fa0ae4131542759251f3951a54ee69d77f181472256158948ac.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 570, + 590, + 594, + 609 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(CN) 什么?! 现在要去宠物医院做绝育手术?!", + "bbox": [ + 436, + 617, + 596, + 638 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ What?! Going to the pet hospital now for a neutering surgery!?", + "bbox": [ + 436, + 640, + 586, + 660 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/929e3f229f02ae223cf8c65a0a783201f24b6b12e24065d509359944fc0f42f2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 570, + 648, + 594, + 667 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Text to Text (T2T)", + "text_level": 1, + "bbox": [ + 681, + 316, + 792, + 330 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(EN) What else can wake you up besides coffee when you are coding?", + "bbox": [ + 622, + 340, + 818, + 364 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(EN) Maybe you need to enlist the help of some angry bees.", + "bbox": [ + 622, + 372, + 852, + 396 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(EN) A cup of deadline.", + "bbox": [ + 622, + 406, + 738, + 419 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/b2229c2ae3bd3f04a0127b9b6cfdb6664c3689e9eed11314d352099f58eba399.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 823, + 383, + 849, + 398 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/1edb29ff96c2e8521ded080f92669fdccf134e58fe6cd80d94a72cd9e158a2c1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 823, + 405, + 851, + 422 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(JP)一番絕望的だと思うさは何てすか?", + "bbox": [ + 622, + 448, + 848, + 460 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ What's the most desperate thing you've ever heard?", + "bbox": [ + 622, + 463, + 825, + 473 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(JP)犬が私の比を食てまた", + "bbox": [ + 622, + 479, + 789, + 492 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ The dog ate my pizza.", + "bbox": [ + 622, + 496, + 718, + 506 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/989c26291bdf788217439357ce751ca7592e81c579960e367cb0049049ec0423.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 825, + 493, + 851, + 511 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(JP)月曜日だし、仕事に行く時間だね", + "bbox": [ + 622, + 516, + 823, + 527 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ It's Monday and time to go to work.", + "bbox": [ + 622, + 532, + 767, + 541 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/11c1603049fcfebd67168cb922ac6e6c3a1b908022310fe0bd6d04012fec144e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 825, + 529, + 851, + 547 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(CN)你觉得完成一篇深度学习论文辛苦吗?@Do you think writing a DL paper is exhausting?", + "bbox": [ + 622, + 570, + 849, + 595 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(CN) 完成一篇论文其实很快乐", + "bbox": [ + 622, + 603, + 782, + 614 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ Completing a paper is actually very enjoyable.", + "bbox": [ + 622, + 617, + 808, + 626 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/e44220eef6a3d516f209231f6ecf97df24a7b1d02593cd2b8723aa353aa5e3d3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 825, + 613, + 851, + 632 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "(CN) 不辛苦,辛苦的是我的导师", + "bbox": [ + 622, + 638, + 795, + 651 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "@ Not for me, but it's hard for my supervisor.", + "bbox": [ + 622, + 652, + 797, + 662 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/3dca93164eb197c856254a4275df2a87a1f8d3b2e19bf3107e34b2ac54aa4af3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 823, + 648, + 851, + 667 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 770, + 313, + 786 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Chain-of-Thought (CoT) [2, 3] guides large language models (LLMs) to reason step-by-step, and can motivate their logical reasoning ability. While effective for logical tasks, CoT is not conducive to creative problem-solving which often requires out-of-box thoughts and is crucial for innovation advancements. In this paper, we explore the Leap-of-Thought (LoT) abilities within LLMs — a non-", + "bbox": [ + 75, + 794, + 470, + 900 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "sequential, creative paradigm involving strong associations and knowledge leaps. To this end, we study LLMs on the popular Oogiri game which needs participants to have good creativity and strong associative thinking for responding unexpectedly and humorously to the given image, text, or both, and thus is suitable for LoT study. Then to investigate LLMs' LoT ability in the Oogiri game, we first build a multimodal and multilingual Oogiri-GO dataset which con", + "bbox": [ + 496, + 772, + 893, + 893 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "13246", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "tains over 130,000 samples from the Oogiri game, and observe the insufficient LoT ability or failures of most existing LLMs on the Oogiri game. Accordingly, we introduce a creative Leap-of-Thought (CLoT) paradigm to improve LLM's LoT ability. CLoT first formulates the Oogiri-GO dataset into LoT-oriented instruction tuning data to train pretrained LLM for achieving certain LoT humor generation and discrimination abilities. Then CLoT designs an explorative self-refinement that encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts and selects high-quality data to train itself for self-refinement. CLoT not only excels in humor generation in the Oogiri game as shown in Fig. 1 but also boosts creative abilities in various tasks like \"cloud guessing game\" and \"divergent association task\". These findings advance our understanding and offer a pathway to improve LLMs' creative capacities for innovative applications across domains. The dataset, code, and models have been released online: https://zhongshsh.github.io/CLoT.", + "bbox": [ + 75, + 90, + 472, + 380 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 386, + 209, + 402 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Large language models (LLMs) [4-13] have catalyzed a transformative era in problem-solving abilities, revolutionizing various domains within artificial intelligence. The advent of the Chain-of-Thought (CoT) paradigm [3] and its further enhancements [2, 14-16] have equipped these LLMs with a human-like step-by-step reasoning capacity. This augmentation has enabled LLMs to excel in intricate reasoning tasks spanning from language comprehension to visual understanding. As shown in Fig. 2 (Left), CoT instills LLMs with a sequential thinking process wherein each subsequent thought builds upon the previous one. This paradigm enhances the precision and rigor in logical processing, making it exceedingly effective for problems that demand closely linked logical reasoning.", + "bbox": [ + 75, + 412, + 468, + 625 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "However, the sequential nature of CoT might fall short in nurturing creativity and innovation, potentially limiting solutions in creative problem-solving scenarios [17, 18]. For instance, proving an algebraic inequality often follows a step-by-step CoT process that progresses from one inequality to the next. Yet, an intuitive flash, e.g., a geometric interpretation, can yield a more creative solution. This type of insight, known as \"Leap-of-Thought\" (LoT) [19, 20], a.k.a. mental leap [21-24]—the art of non-sequential thinking by association, drawing parallels between seemingly unrelated concepts, and facilitating a \"leap\" of knowledge transfer. In contrast to CoT reasoning, LoT as depicted in Fig. 2 (Right), fosters associative reasoning and encourages thinking outside the box, which bridges disparate ideas and facilitates conceptual leaps. Embracing LLMs with a strong LoT ability can unlock significant potential for innovation, contributing to advancements in creative applications.", + "bbox": [ + 75, + 627, + 470, + 883 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this paper, we aim to initially explore and enhance the", + "bbox": [ + 96, + 885, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/ce4d1416dba78d56d9ae78f62670046c27fa2380efd5684481522dd20fcd4b06.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 521, + 93, + 684, + 156 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/77b4f81e9935d793d97abb64de157c2fd268113d96c167e6962dfc0d05d5ca03.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 707, + 93, + 870, + 156 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/b8ed2352ab5d0669e4cbb2c6fee2b7b63255733d83960a0004a60418aadb6ea0.jpg", + "image_caption": [ + "Figure 2. Comparison of CoT and LoT. “ $\\bigcirc$ ” denotes the thought and “ $\\rightarrow$ ” represents the connection between two thoughts." + ], + "image_footnote": [], + "bbox": [ + 522, + 205, + 656, + 320 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/abdf5574cf2356069b6138ee1980df427a84cbf2570ebab3262f42bc6d338384.jpg", + "image_caption": [ + "Figure 3. Examples of the three types of LoT-based Oogiri games. Players are required to make surprising and creative humorous responses (blue box) to the given multimodal information e.g., images, text, or both." + ], + "image_footnote": [], + "bbox": [ + 658, + 205, + 782, + 319 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/d81e82f8ba942c0d806c691b9ecee58d55993e42ec09f145a04e9e023e0cbd1b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 785, + 207, + 869, + 316 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "LoT ability of LLMs. However, thoroughly assessing LoT is challenging due to the complexity of measuring creative thinking [25-27] and the difficulty in gathering pertinent data, since generating novel ideas is challenging, even for humans [17]. Given these constraints, we propose studying LoT in LLMs through the lens of Oogiri-style humor generation. Oogiri, a traditional Japanese creative game [28], requires participants to provide unexpected and humorous responses to prompts in the form of images, text, or a combination of both, as shown in Fig. 3. This game challenges LLMs to demonstrate a sudden burst of insight and strong associative thinking, presenting a unique challenge for CoT-based methods, making it an ideal testbed for assessing the leap-of-thought abilities of LLMs. Moreover, the extensive online presence of Oogiri guarantees a wealth of human-generated creative content, ideal for compiling an expansive leap-of-thought dataset.", + "bbox": [ + 496, + 402, + 892, + 657 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To investigate the LoT ability of LLMs in the Oogiri game, we present the multilingual and multimodal Oogiri-GO dataset which comprises more than 130,000 high-quality Oogiri samples in English, Chinese, and Japanese, and curated to prompt textual humor in response to inputs that can be images, text, or both. Through extensive experiments, we discover that even the advanced LLMs and reasoning frameworks [2, 4, 6, 29], such as GPT-4 and CoT, despite their exceptional reasoning capabilities, possessing a rich prior knowledge of diverse forms of humor [2], still struggle to exhibit sufficient LoT ability for creative humor generation. Moreover, directly fine-tuning LLMs on the Oogiri-GO is not easy to improve the LoT ability. The more efficient utilization of humorous knowledge is needed to help LLM elicit creative responses.", + "bbox": [ + 496, + 659, + 893, + 885 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Motivated by the human mental leap exercise process", + "bbox": [ + 517, + 886, + 890, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "13247", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "of \"remote association & self-refinement\" [30], to enable LLMs with strong LoT ability for creation, we propose the Creative Leap-of-Thought (CLoT) paradigm which relies on two LoT-boosting stages. The first one is the associable instruction tuning stage which designs an associative instruction template to formulate the Oogiri-GO dataset into instruction data and trains an LLM to improve its LoT ability. The core here is the instruction template with a dual purpose: it randomly provides LLM with clues to establish connections between game inputs and creative responses, while also introducing empty clues to encourage LLM for unrestrained exploration and remote association thinking.", + "bbox": [ + 75, + 90, + 472, + 271 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The second stage is explorative self-refinement which encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts under weakly-associated conditions, and selects high-quality data to train itself for self-refinement. These weakly-associated conditions can either be empty, or randomly sampled from an object noun set collected from the Oogiri-GO dataset. The former empty conditions to allow LLM to operate freely, and the latter ones help the LLM to link seemingly-unrelated and weakly-related concepts, and encourage the LLM to explore knowledge outside of traditional cognitive limitations. This exploration strategy can help generate diverse high-quality data for self-refinement.", + "bbox": [ + 75, + 272, + 472, + 468 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Experimental results show that CLoT can greatly enhance the LoT ability of LLMs like Qwen [1] and CogVLM [29] across several types of Oogiri games. Specifically, CLoT can help LLMs to generate much better humors in Fig. 1. Moreover, CLoT-integrated LLMs achieve higher quantitative performance than the corresponding vanilla and CoT-integrated LLMs across the multiple-choice and ranking questions in the Oogiri game. Also, CLoT can boost creative abilities on other tasks like \"cloud guessing game\" and \"divergent association task\" [31-33], showing its remarkable generalization ability.", + "bbox": [ + 75, + 469, + 472, + 636 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 76, + 648, + 227, + 664 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "(1) Oogiri game (大喜利) is a general term for a series of traditional Japanese comedy games. In ancient times, there were different types of Oogiri, such as actors performing sumo wrestling, telling ghost stories, etc. The modern Oogiri game mainly refers to one specific type known as Tonchi (頓智), typically presented in the format of game shows or intellectual quiz programs [28]. Players are provided with various multimodal contents, which can be simple questions, random images, etc., and are then prompted to come up with humorous, creative responses to achieve surprising comedic effects, as the examples are shown in Fig. 3. It is worth noting that the character “頓” in both Japanese and Chinese denote “sudden”, while “智” means “intelligence, insight or intuition”. This highlights the connection between the Oogiri game and the requirement for", + "bbox": [ + 75, + 672, + 472, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "strong associative abilities in LoT, making Oogiri an ideal platform for exploring LoT capabilities within LLMs.", + "bbox": [ + 496, + 90, + 890, + 121 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "(2) Multimodal LLMs and their creativity. Recently, multimodal Language Models [1, 29, 34, 35] have garnered significant attention, particularly due to their impressive reasoning abilities [7-12, 36]. Moreover, there is a growing focus on exploring the creativity [37-40] of LLMs for applications such as scientific discovery [18, 41-44], creative writing [45-49], etc.", + "bbox": [ + 496, + 122, + 893, + 227 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "(3) Computational humor is a branch of computational linguistics and artificial intelligence that uses computers in humor research [50], which encompasses various tasks, including humor detection [51-58], humor interpretation [58-61], and humor generation [62-66], etc. With the advancement of generative LLMs [1, 4, 29], humor generation has become a popular focus while humor generation still faces challenges such as insufficient punchlines [67] and limited in multimodal contexts [68-70].", + "bbox": [ + 496, + 229, + 893, + 364 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "(4) Chain-of-Thought based Methods provide the models with \"chain of thoughts\" [2, 3, 14-16], i.e., reasoning exemplars [3], or a simple prompt \"Let's think step by step\" [2], to encourage LLMs to engage in reasoning rather than simply providing answers directly [71].", + "bbox": [ + 496, + 366, + 893, + 441 + ], + "page_idx": 2 + }, + { + "type": "table", + "img_path": "images/a7b800e02cc9a1f104546ae6d18de6c5b52338af243cf6b5cbb68ea65cc17dc4.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
CategoryEnglishChineseJapaneseTotal
I2T17,33632,13040,27889,744
T2T6,43315,79711,84234,072
IT2T—9129,42010,332
", + "bbox": [ + 532, + 449, + 864, + 516 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Table 1. Data distribution of the Oogiri-GO dataset. For the IT2T task, its English version is not available due to cultural preference.", + "bbox": [ + 496, + 526, + 893, + 555 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Oogiri-GO Dataset", + "text_level": 1, + "bbox": [ + 498, + 571, + 687, + 588 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As introduced in Sec. 2, in the Oogiri game, the participants need to unexpectedly and humorously respond to the given images, text, or both. See three types of examples in Fig. 3. This game requests a sudden burst of insight and strong associative thinking to the given context, and provides an ideal platform to assess the leap-of-thought (LoT) ability of LLMs. Accordingly, we collect Oogiri game data to build a large-scale Oogiri-GO dataset which serves as a benchmark to evaluate and improve LoT ability.", + "bbox": [ + 496, + 597, + 890, + 733 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Specifically, Oogiri-GO is a multimodal and multilingual humor dataset, and contains more than 130,000 Oogiri samples in English, Chinese, and Japanese. Notably, in Oogiri-GO, $77.95\\%$ of samples are annotated with human preferences, namely the number of likes, indicating the popularity of a response. As illustrated in Fig. 3, Oogiri-GO contains three types of Oogiri games according to the input that can be images, text, or both, and are respectively called \"Text to Text\" (T2T), \"Image to Text\" (I2T), and \"Image & Text to Text\" (IT2T) for brevity. See more examples in Fig. 1. Table 1 summarizes the distribution of these game types.", + "bbox": [ + 496, + 734, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "13248", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/115f9de2241c1d1d6ad2de6941a882e89743f9fb1632dba7de29a8291b697fc2.jpg", + "image_caption": [ + "Figure 4. The overview of proposed Creative Leap-of-Thought." + ], + "image_footnote": [], + "bbox": [ + 99, + 89, + 447, + 257 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For training purposes, $95\\%$ of the samples are randomly selected to construct the training dataset, while the remaining $5\\%$ form the test dataset for validation and analysis.", + "bbox": [ + 76, + 285, + 468, + 330 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To create the Oogiri-GO dataset, there are three main steps, including online data collection, machine filtering by LLM, and manual screening. Firstly, to collect sufficient data, we source Oogiri game data from the official Oogiri game platform, Bokete, and other popular platforms, such as Twitter and Weibo which also host some Oogiri-game-like data. Then, to guard against the inclusion of bias, violence, explicit content, offensive language, etc., we have placed a strong emphasis on rigorous safety checks during both machine and manual screening. We first use the multimodal LLM Qwen-VL [1] to do the initial screening of the raw data by constructing safety-checking prompts. Then, manual checking is performed on the remaining data. See more details about the dataset creation in the Appendix.", + "bbox": [ + 75, + 330, + 468, + 542 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Creative Leap-of-Thought (CLoT)", + "text_level": 1, + "bbox": [ + 76, + 551, + 388, + 568 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To augment the Leap-of-Thought (LoT) ability in (multimodal) Large Language Models (LLMs) for creative generation, we propose a novel Creative LoT framework (CLoT). As shown in Fig. 4, CLoT relies on two LoT-boosting stages. The first one is associative instruction tuning that formulates the Oogiri-GO dataset into instruction tuning data for training an LLM to improve its LoT ability (Sec. 4.1). The second one is explorative self-refinement that encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts, and selects high-quality data to train itself for self-refinement (Sec. 4.2). Finally, we present the CLoT inference to induce the LoT ability of the trained LLM (Sec. 4.3).", + "bbox": [ + 75, + 577, + 468, + 773 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Associable Instruction Tuning", + "text_level": 1, + "bbox": [ + 76, + 785, + 344, + 801 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "LoT ability mainly includes associable generation and discrimination ability [30]. Given an input, associative generation draws its parallels with seemingly unrelated concepts via remote association and then generates innovative responses, e.g., the unexpected humor for the Oogiri input. Associable discrimination is to judge the matchiness among", + "bbox": [ + 75, + 809, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "input and responses though they are seemingly unrelated, and then to select the most creative response.", + "bbox": [ + 498, + 90, + 890, + 119 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Unfortunately, both associative generation and discrimination are not present in current LLMs, e.g., poor performance of GPT4v [72] in the Oogiri game observed in Sec. 5. Moreover, it is hard to improve these two LoT abilities via popular CoT-like prompt techniques. Indeed, as shown in Sec. 5, CoT even sometimes impairs the LoT performance of the LLMs like Qwen-VL [1] in the Oogiri game.", + "bbox": [ + 496, + 121, + 890, + 226 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To address this issue, we propose associable instruction tuning which trains LoRA [73] for LLMs on the OogiriGO dataset to achieve certain associable generation and discrimination abilities. It has two steps, including instruction generation and discrimination template design, and associative instruction learning.", + "bbox": [ + 496, + 227, + 890, + 316 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "(1) Instruction Generation & Discrimination Templates. We design LoT-oriented instruction templates to transform the Oogiri-GO dataset into instruction tuning data, and then train LLM to achieve associable generation and discrimination abilities. Our templates primarily comprise two components in Fig. 5: task-specific prompt and response. For different abilities, the templates need some special design.", + "bbox": [ + 498, + 316, + 890, + 422 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/f4e92f5a4b61c30fb2f3da03ca7bca6d43a6238f4f6bc154d962c18a1fcc1e7c.jpg", + "image_caption": [ + "Figure 5. The LoT-oriented instruction templates." + ], + "image_footnote": [], + "bbox": [ + 549, + 428, + 821, + 469 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For associable generation, \"USER-INPUTs\" contains \"Task-specific Prompt\" along with two optional conditions, \"Image\" and \"Condition\". For \"Task-specific Prompt\", we elaborately design several templates for different types of Oogiri game. See the Appendix for details and there is an image-2-text (I2T) Oogiri example in Fig. 6. For \"Image\" condition, it relies on the type of Oogiri game, e.g., being the image embeddings in I2T game and empty in T2T type. For the \"condition\" option, it's set to empty with a probability of $\\rho_{c}$ , and otherwise is randomly set as one noun in \"task-specific responses\". This design gives the LLM a clue to connect the game input and the correct responses while also encouraging LLM to explore and unleash its creative thinking with probability $\\rho_{c}$ . Finally, \"Task-specific Responses\" are the ground truth responses of an Oogiri-GO data, and need to be predicted by LLM during training. This task enforces the LLM to draw parallels between seemingly unrelated concepts in inputs and responses for giving innovative responses, e.g., the humor for the Oogiri input. This associative generation ability can assist the LLM to think outside the box and learn remote association thinking.", + "bbox": [ + 496, + 492, + 890, + 809 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Regarding associable discrimination, we aim to develop fundamental LoT discrimination skills for LLM. Based on the Oogiri-GO data, we design choice questions to enhance LLM's LoT discrimination ability, i.e., selection skill. Besides, as $77.95\\%$ of the Oogiri-GO data have human preference annotations, i.e., the number of likes of several re", + "bbox": [ + 496, + 810, + 890, + 898 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "13249", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/656c6608f80b4c86e5462f5ea6e64ac75d63df4df74d337e7fb4ef37f715bb18.jpg", + "image_caption": [ + "Figure 6. The details of LoT-oriented instructions templates. We take \"Image to Text\" as an example, see the Appendix for the details of other categories' instructions. (a) and (b) are the instruction templates with/without conditions for associable generation. (c) and (d) are the two instructions about the selection and ranking of associable discrimination. All templates follow the formats in Fig. 5." + ], + "image_footnote": [], + "bbox": [ + 83, + 107, + 279, + 215 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/63beecebd6dbbe8744ab05e258fff39d4350a27b988a9089496728e380683810.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 282, + 107, + 483, + 215 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/d87022c4c0e05f8658f9fa04da4032fcc24bb2a5058b23d9881326935f077f89.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 488, + 107, + 689, + 215 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/cd0113a459e8b5457796874c70a3236c8f6e42bd1e0dfdcf3f3be7c3b1b7dcfc.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 692, + 107, + 890, + 215 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "sponses (see Sec. 3), we design ranking questions to improve another discrimination skill, i.e., ranking ability.", + "bbox": [ + 75, + 280, + 468, + 310 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For a choice question, as shown in Fig. 6 (c), the options in \"Task-specific Prompt\" contain the random permutations of ground truth response (GTR), image captions generated by BLIP2 [74], GTR from other images, rewrites of GTR by Qwen-14B [5]. See details in Appendix. For \"task-specific responses\", it is the GTR. This design is to train LLM to improve its LoT selection ability. For a ranking question, as shown in Fig. 6 (d), it is to enforce LLM to rank multiple distinct responses of a given input to match their human preferences. By training on the choice and ranking questions, LLM is encouraged to distinguish LoT responses and align human creative preferences, improving its LoT discriminative selection and ranking abilities.", + "bbox": [ + 75, + 311, + 468, + 505 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "(2) Associable Instruction Learning. By using the above instruction templates, we augment the 130,000 samples in the Oogiri-GO dataset to more than 500,000 instructions whose formulation is in Fig. 5. During training, LLM is required to predict the \"task-specific responses\" according to the \"USER-INPUTs\" which include \"Task-specific Prompt\" and two additional optional conditions like image and text condition. To avoid over-fitting, we only train standard LoRA [73] for the LLM with the associable instruction data. See more details in Appendix.", + "bbox": [ + 75, + 507, + 468, + 657 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Explorative Self-Refinement", + "text_level": 1, + "bbox": [ + 76, + 665, + 330, + 681 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "After associable instruction tuning, we aim to generate more high-quality creative data by LLM which are then used to train LLM for self-refinement. To this end, we introduce an innovative stage called explorative self-refinement, inspired by human LoT exercise process of \"remote association & self-refinement\", also known as mental leap [21, 24, 30]. The remote association process refers to generating new ideas by associating remote concepts or thoughts, and self-refinement uses the generated data to enhance one's own LoT ability. In the following, we design two similar LoT exercise processes for LLM to improve its LoT ability.", + "bbox": [ + 75, + 689, + 468, + 853 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "(1) Explorative Remote Association. The core here is to prompt the LLM to generate a diverse array of creative responses under weakly-associated conditions. To implement", + "bbox": [ + 75, + 854, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "this, we extract a set of object nouns, denoted as $\\mathcal{S}$ , from the text in the Oogiri-GO training data. See details in Appendix. Then, for each user-input $I$ (see Fig. 5), we generate $n$ weakly-associated conditions $\\{C_i\\}_{i=1}^n$ . These conditions can either be empty with a probability $\\rho \\in (0,1)$ to give freedom to LLM, or uniformly randomly sampled from the noun set $\\mathcal{S}$ to enforce LLM to build connections between different concepts. Next, we add the condition $C_i$ into user-input $I$ , and feed $I$ into the LLM to generate a humor candidate $R_i$ . Repeating this process with different conditions $C_i$ can generate a total of $n$ candidates $\\{R_i\\}_{i=1}^n$ .", + "bbox": [ + 496, + 280, + 890, + 446 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Then the LLM ranks these candidates by its discriminative ranking ability learned in Sec. 4.1. Next, it mixes the top-2 candidates with the ground truth responses (GTR), and selects the top-1 as the final response. Finally, if the selected top-1 response is the GTR, we discard this sample. Here first filtering out low-quality responses can improve the accuracy of subsequent top-1 selection, since $(n + 1)$ -choice problem is often more challenging than 3-choice problem as shown in Sec. 5. By repeating this process, we progressively gather sufficient new high-quality data.", + "bbox": [ + 496, + 446, + 890, + 598 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The core of this approach is the weakly-associated conditions $\\{C_i\\}_{i=1}^n$ which can encourage the LLM to engage in remote associations. This is because the empty conditions allow LLM to operate freely, while the object noun conditions compel the LLM to draw connections between seemingly unrelated concepts. This mechanism facilitates the establishment of links between seemingly-unrelated and weakly-related concepts, encouraging the LLM to explore knowledge outside of traditional cognitive limitations. The exploration ability distinguishes our CLoT from CoT which primarily guides the LLM to exploit its inherent reasoning ability without emphasizing knowledge exploration.", + "bbox": [ + 496, + 598, + 890, + 779 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "(2) Self-refinement. Here we combine the above generated instructions with vanilla instruction tuning samples in Sec. 4.1 to form a dataset with more than 550,000 samples to train our LLM again. Since the above generated data is of high diversity because of its exploration strategy, they prevent performance collapse [76, 77] during self-refinement phase, and can improve the LoT performance across several creative tasks as shown in Sec. 5. See the ablation study and", + "bbox": [ + 496, + 780, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "header", + "text": "Associable Generation", + "bbox": [ + 218, + 93, + 346, + 104 + ], + "page_idx": 4 + }, + { + "type": "header", + "text": "Associable discrimination", + "bbox": [ + 616, + 93, + 759, + 104 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "13250", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/1f67766d80c9f87ec2865f4e16443f7ab510cf622cf33ec6c5fb9b9ce59a7ac5.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelSizeImage&Text to Text (IT2T)Image to Text (I2T)Text to Text (T2T)
3T14T15T2RankAvg.3T14T15T2RankAvg.3T14T15T2RankAvg.
GPT4v [72]-19.314.93.256.723.529.115.13.960.427.127.116.86.853.526.1
LLaVA-1.5 [34]13B13.213.713.968.127.229.322.73.960.929.233.825.24.062.631.4
MiniGPT-v2 [35]7B6.13.44.060.718.65.34.03.860.518.410.87.33.559.420.3
mPLUG-OwlMultilingual [12]7B28.126.010.564.432.219.218.66.060.526.124.422.210.760.129.4
VisualGLM-6B [75]6B24.122.59.767.430.914.320.48.861.926.413.120.27.161.325.4
Qwen-VL [1]7B30.226.010.467.733.623.223.111.962.230.123.425.013.359.630.3
Qwen-VL+Alt(Ours)7B39.738.915.767.340.4+ 6.838.830.515.762.336.8+ 6.730.628.716.762.634.6+ 4.3
Qwen-VL+CLoT(Ours)7B41.838.721.668.542.7+ 9.139.835.122.764.440.5+10.438.829.421.064.738.5+ 8.2
", + "bbox": [ + 101, + 88, + 874, + 218 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/644d7a62fecbdcb904b88da6e6e11276e10ee76f156880bd108e783dac385330.jpg", + "table_caption": [ + "Table 2. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on multil-modal multilingual models. mTn choice question selects $n$ correct answers from $m$ options. \"Avg.\" is the average of all metrics. \"AIT\" denotes associable instruction tuning." + ], + "table_footnote": [], + "table_body": "
Algorithm 1 Inference Step of CLoT
Input: Input I, CLoT-trained LLM A, response number n
Output: Creative response R.
1:▷ Creating the candidate responses
2: construct n weakly-associated conditions {Ci}n{i=1}
3: {Ri}n{i=1} ← A([I, {Ci}n{i=1}])
4:▷ Choosing most creative response
5: Top-2 R1', R2' ← A([I, {Ri}n{i=1}]) with ranking ability
6: Best R ← A([I, R1', R2']) with selection ability
7: return Best response R.
", + "bbox": [ + 76, + 260, + 468, + 406 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "more discussions in Sec. 5.5.", + "bbox": [ + 76, + 431, + 272, + 448 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. CLoT Inference", + "text_level": 1, + "bbox": [ + 76, + 453, + 238, + 469 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "After the two LoT-boosting phases in Sec. 4.1 and 4.2, the LLM acquires sufficient LoT ability. Now we introduce the inference steps of LLM to release its LoT ability. Formally, given an Oogiri user-input $\\pmb{I}$ of the formation in Fig. 5, LLM first uses explorative remote association in Sec. 4.2 to construct $n$ weakly-associated conditions (these conditions can be empty since the training paradigm in Section 4), and then follows Sec. 4.2 to generate $n$ responses $\\{R_i\\}_{i=1}^n$ . Next, LLM ranks these responses by using its learned ranking skill and finally selects the top-1 one from the ranked top-2 response via its selection skill. The reason to first use ranking before selection is that as shown by experimental results in Sec. 5, directly choosing the best one from a large number of options has poor accuracy, and ranking can filter out low-quality candidates to improve the selection accuracy. See Algorithm 1 for an overview of CLoT inference steps.", + "bbox": [ + 75, + 477, + 472, + 720 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 76, + 731, + 210, + 750 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Evaluation Questions and Metrics", + "text_level": 1, + "bbox": [ + 76, + 756, + 375, + 772 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Inspired by the humor benchmarks in [81], we first develop choice and ranking questions as introduced in Sec. 4.1 (see examples in Fig. 6 (c-d)), and then quantitatively evaluate the LoT ability of LLMs on the Oogiri-GO test dataset. For the choice questions, $mTn$ for short, they need LLMs to choose $n$ \"leap-of-thought\" humor responses from $m$ options given the input. Here we build four types of $mTn$ questions, including 2T1, 3T1, 4T1, and 5T2. 2T1 means", + "bbox": [ + 75, + 779, + 472, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "two options, the ground-truth response (GTR) and an image caption generated by BLIP2 [74]. 3T1 adds unrelated answers, e.g., other image captions. 4T1 further adds the GTR rewrite by Qwen-14B [5]. 5T2 has an extra GTR. For these questions, their difficulty increases progressively, and is diverse to ensure comprehensive evaluation. For choice questions, we use accuracy as the evaluation metric. Additionally, for the questions in test set whose responses have ground-truth human preference, e.g., the number of likes, we develop the ranking questions that always rank five candidates. For evaluation, we adopt the top-1 accuracy and the widely used ranking metric, i.e., Normalized Discounted Cumulative Gain (NDCG) [82, 83]. We provide more experimental details in the Appendix.", + "bbox": [ + 496, + 262, + 893, + 474 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Evaluation by Choice and Ranking Questions", + "text_level": 1, + "bbox": [ + 498, + 483, + 885, + 501 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation on Multimodal Multilingual LLMs. We plug our associative instruction tuning (AIT) and our CLoT into the SoTA open-source multimodal multilingual model Qwen-VL [1] to obtain Qwen- $\\mathrm{VL}_{+\\mathrm{AIT}}$ and Qwen- $\\mathrm{VL}_{+\\mathrm{CLoT}}$ , respectively. Table 2 shows that, on three tasks (IT2T, I2T and T2T) which include English, Chinese and Japanese questions, Qwen-VL achieves the best LoT performance among all baselines in most cases. In comparison, Qwen- $\\mathrm{VL}_{+\\mathrm{AIT}}$ achieves a noticeable improvement on the SoTA Qwen with average accuracy enhancements of $6.8\\%$ , $6.7\\%$ , and $4.3\\%$ on the three tasks, respectively. Importantly, Qwen- $\\mathrm{VL}_{+\\mathrm{CLoT}}$ further enhances Qwen-VL, showing improvements of $9.1\\%$ , $10.4\\%$ , and $8.2\\%$ in accuracy across these tasks. These results demonstrate the efficacy of the two stages in CLoT, i.e., associative instruction tuning and explorative self-refinement.", + "bbox": [ + 496, + 507, + 893, + 748 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation on Multimodal Non-multilingual LLMs. Here we integrate our CLoT with the SoTA multimodal non-multilingual model, CogVLM-17B [29], and evaluate it on the English I2T and T2T tasks. Table 3 shows that $\\mathrm{CogVLM - 17B}_{+\\mathrm{AIT}}$ achieves remarkable improvements over the standard $\\mathrm{CogVLM - 17B}$ , and $\\mathrm{CogVLM - 17B}_{+\\mathrm{CLoT}}$ consistently demonstrates significantly superior performance compared to $\\mathrm{CogVLM - 17B}$ .", + "bbox": [ + 496, + 750, + 893, + 869 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation on Single-Modal LLMs. Now we test LLMs that can handle only pure texts, using the English T2T task", + "bbox": [ + 498, + 869, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "13251", + "bbox": [ + 480, + 944, + 517, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/1b15fa3d9f9ce54d1fe0d57fa4d5dc1704e9c5eba92ab46cb0815bbbfce44f56.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelSizeImage to Text (I2T)Text to Text (T2T)
2T13T14T15T2RankAvg.2T13T14T15T2RankAvg.
InstructionBLIP [78]13B19.813.715.51.165.523.122.316.017.00.759.523.1
mPLUG-OwlLLaMA2 [12]7B22.312.715.04.259.922.824.213.712.63.159.222.6
Otter [79]7B15.89.98.57.161.320.53.83.34.85.458.515.1
CogVLM-17B [29]7B37.626.418.32.564.629.935.127.824.87.564.131.9
CogVLM-17B+AIT(Ours)7B57.437.433.521.864.642.9+13.155.446.526.418.264.442.2+10.3
CogVLM-17B+CLoT(Ours)7B66.947.643.430.769.451.6+21.764.852.933.621.868.648.3+16.4
", + "bbox": [ + 84, + 75, + 893, + 195 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/4e0dbf050d2fb69404d4c66cc287dc21602af7a5094f1bf7681ee070e42f0f8e.jpg", + "table_caption": [ + "Table 3. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on various mulilmodal non-multilingual models (English). See notations in Table 2. We only consider I2T and T2T since English IT2T is not available due to cultural preference." + ], + "table_footnote": [], + "table_body": "
ModelSize3T14T15T2RankAvg.
GPT-3.5 [72]-45.330.46.761.636.0
GPT-4 [72]-49.220.43.654.732.0
LLAMA2 [4]7B18.913.51.160.423.5
13B15.620.01.860.524.5
70B27.816.13.862.027.4
Baichuan2 [80]7B28.322.611.664.631.8
13B21.718.38.961.527.6
Qwen [5]7B23.120.48.061.428.2
14B27.422.212.359.530.3
ChatGLM3 [75]6B15.617.05.459.424.3
Vicuna-v1.5 [6]7B32.623.50.063.029.8
13B30.223.02.762.229.5
Qwen-VL+CLoT(Ours)7B51.732.324.865.043.4
CogVLM-17B+CLoT(Ours)7B52.933.621.868.644.2
", + "bbox": [ + 81, + 244, + 468, + 468 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 4. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on various large language models. Here we use English T2T task for test. See notations in Table 2.", + "bbox": [ + 76, + 478, + 468, + 521 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "for evaluation. Table 4 also indicates the insufficient LoT ability within existing LLMs, ranging from small to large models. Fortunately, our CLoT significantly improves the LoT ability of these LLMs, as demonstrated by the notable improvement in accuracy.", + "bbox": [ + 76, + 530, + 468, + 606 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparison with CoT-alike Reasoning Frameworks. We also find that existing reasoning frameworks are not as effective as CLoT in enhancing LoT ability. Fig. 8 compares CLoT with CoT [2, 3], CoT-SC [84], and prompted-based LoT (PLoT) with the prompt \"let's think outside the box\". The results reveal that CoT-alike frameworks do not enhance LoT performance of LLMs, while CLoT demonstrates the ability to consistently enhance LLMs.", + "bbox": [ + 75, + 609, + 468, + 731 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Our experiments and analysis reveal that, unlike CoT-based methods, LoT cannot be directly achieved by prompting alone. This is because the inherent reasoning capabilities and extensive knowledge of LLMs are not sufficient to enable LoT ability. However, when trained with our proposed CLoT method, LLMs can effectively engage in a range of creative tasks. Additionally, the use of specific prompting techniques can enhance the LoT ability of CLoT-trained LLMs. These findings suggest that LoT could potentially be considered an additional general reasoning ability for LLMs that is not contained in current LLMs.", + "bbox": [ + 75, + 734, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/93ba7dc25772108bb8a64619b8da5ef7ee612648ee2c04f73a49639e6b58804c.jpg", + "image_caption": [ + "Figure 7. User study with voting $(\\%)$ for Oogiri-style creative responses by different models and improved methods." + ], + "image_footnote": [], + "bbox": [ + 521, + 243, + 870, + 351 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Human Evaluation", + "text_level": 1, + "bbox": [ + 500, + 391, + 683, + 404 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We conduct a user preference study to test creativity of LLMs. Here we select six LLMs to generate responses for a total of eighteen questions across three tasks (IT2T, I2T and T2T). We use choice questions, and ask users to choose the most creative and humorous responses. Fig. 7 summarizes the statistical analysis of 154 valid surveys. The results show that users have a strong inclination towards selecting the results of CLoT across three tasks, highlighting the high-quality creative content generated by CLoT. See more user study details in Appendix.", + "bbox": [ + 496, + 414, + 892, + 566 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.4. Evaluation on Other Creative Tasks", + "text_level": 1, + "bbox": [ + 500, + 575, + 812, + 589 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "To evaluate the generalization ability of CLoT, we test CLoT on another two creative tasks, including Cloud Guessing Game (CGG) and Divergent Association Task (DAT). In CGG, the LLM is to identify the shape of white clouds, and then to select the corresponding shapes from given options. For instance, the white clouds in Fig. 9 (c) has a shape of a cat, and the one in Fig. 9 (d) is similar to a human. These white cloud images are generated by a control diffusion model [31, 32, 85, 86], guided by masks shown in Fig. 9 (b). We use top-1 accuracy as metric. See more details in Appendix. For DAT, it is a classic creativity test [33, 87] which needs participants to choose words with larger semantic distances among 10 unrelated nouns. Here for test easily, we transfer the DAT benchmark [33] to a series of choice questions and take the standard average semantic distance (ASD) as a metric. These questions can challenge the LLM to select the one word from nine options that differs from the given word most. See more details in Appendix. CGG and DAT can test the LoT ability of LLMs, specifically their remote association thinking ability,", + "bbox": [ + 496, + 598, + 893, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "13252", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ad4ccd4921cee3c2d8368978a0c0b30dbd2030ea75df1d8d30fc777bcb808d2e.jpg", + "image_caption": [ + "Figure 8. The accuracy $(\\%)$ of choice questions and the NDCG $(\\%)$ of ranking questions on our CLoT and various reasoning frameworks. The baseline is Qwen-VL on multilingual I2T task. For $mTn$ choice questions, one needs to select $n$ correct answers from $m$ options." + ], + "image_footnote": [], + "bbox": [ + 117, + 90, + 297, + 196 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/945cadf00ecea58f84a7f0b6251a1d3116ce04ff5d50823a61b0ce5aa34cc0e9.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 313, + 90, + 429, + 196 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/3605fab232944da02d04d77d1d13dcc663a13a149e921c6c1aa5225493f63256.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 442, + 90, + 558, + 196 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/fbfcdfc05caba4a497f6930f2c1aa50ab065728c20ba1325a90a0e799cc0bb2c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 578, + 90, + 694, + 196 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/454e67bd787a32b5be4f4acd03015ed7c10f3513c6460947820cf22801e6f9bb.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 710, + 90, + 823, + 196 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/988142eb1d9aa3591b54ba23ba850ad81d0be793a0652d6b1f7ded5a5f7859e1.jpg", + "image_caption": [ + "Figure 9. Evaluation of CLoT on the creative CGG (e) and DAT (f) tasks. (c-d): examples of cloud guessing games. (b): conditional masks of image (a) for generating cloud images." + ], + "image_footnote": [], + "bbox": [ + 107, + 237, + 267, + 397 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c1a9f07fc95283174686b870c6123ea40c5afe8b728b34f49f34296d4125a930.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 269, + 237, + 433, + 397 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "and provide quite different evaluation platforms. As shown in Fig. 9 (e-f), CLoT can also significantly enhance the performance of the SoTA Qwen-VL on both CGG and DAT tasks. Specifically, CLoT-integrated Qwen-VL improves the vanilla Qwen-VL by about $8\\%$ on the CGG task and $5\\%$ on the DAT task. These results well demonstrate the good generalization and transferability of CLoT.", + "bbox": [ + 75, + 459, + 468, + 565 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.5. Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 574, + 230, + 590 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Weakly-associated Conditions. By default, to encourage remote association, we use weakly-associated conditions randomly sampled from the noun set on the whole dataset in Sec. 4.2. To verify the effectiveness of weakly-associated conditions, now we resort to strongly-associated conditions sampled from the noun set of the current image caption. Results in Fig. 10 (Left) show that using weakly-associated conditions is superior and more conducive to fostering the creativity of LLMs. The weakly-associated conditions enable the LLM to generate more diverse LoT responses, while the strong clue from the strongly-associated conditions limit the diversity of LoT generations.", + "bbox": [ + 75, + 598, + 468, + 779 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Round of Self-refinement. By default, we run one-round self-refinement for the Oogiri game. Here we explore whether more rounds of the self-refinement can further improve the LoT ability. Fig. 10 (Right) shows that a single round of self-refinement already yields promising performance, whereas additional rounds do not yield significant further improvements. As shown in Fig. 10 (Left), the diversity of the condition set $\\mathcal{S}$ is crucial to self-refinement, since", + "bbox": [ + 75, + 780, + 470, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f38f0db91012536c4fcd339eba26b85260d5be2177e8e272e2fe14337567bb7b.jpg", + "image_caption": [ + "Figure 10. The ablation study of CLoT. We use CogVLM as baseline on the English I2T task. Left: weakly-associated condition v.s. strongly-associated condition during explorative remote association. Right: The effect of rounds of self-refinement." + ], + "image_footnote": [], + "bbox": [ + 519, + 237, + 692, + 330 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7f4b62c5f9ae11c6cabd4439192523065874bf7873b1c26041db48845511e20a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 696, + 237, + 870, + 330 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "it decides whether the associable remote stage can generate high quality and diverse data. However, the condition set $\\mathcal{S}$ is not expanded during the second-round self-refinement, which consequently limits further improvements in performance. Effectively increasing the scale of the condition set is an effective way for further improvement. See more discussion in Appendix. But its exploration falls outside the scope of this work and is left for our future research.", + "bbox": [ + 498, + 405, + 892, + 526 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 536, + 617, + 551 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we propose a Creative Leap-of-Thought (CLoT) paradigm to improve LLM's leap-of-thought (LoT) ability. CLoT first collects a multimodal Oogiri-GO dataset, and formulates it into instruction tuning data to train LLM to improve its LoT ability. Then CLoT designs an explorative self-refinement that lets LLM generate more creative LoT data via exploring parallels among different concepts and selects high-quality data to train itself for self-refinement. Experimental results show the effectiveness and generalization ability of CLoT across several creative tasks.", + "bbox": [ + 498, + 561, + 890, + 713 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "7. Acknowledgments", + "text_level": 1, + "bbox": [ + 500, + 722, + 679, + 739 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by National Science and Technology Major Project (No.2021ZD0111601), National Natural Science Foundation of China (No.62325605, U1711264), and Guangdong Basic and Applied Basic Research Foundation (No.2023A1515011374), and Guangzhou Science and Technology Program (No.2024A04J6365), and Guangdong Province Key Laboratory of Information Security Technology. Pan Zhou acknowledges support from the Singapore Ministry of Education (MOE) Academic Research Fund (AcRF) Tier 1 grant.", + "bbox": [ + 496, + 747, + 893, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "13253", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Jinze Bai, Shuai Bai, Shusheng Yang, Shijie Wang, Sinan Tan, Peng Wang, Junyang Lin, Chang Zhou, and Jingren Zhou. Qwen-vl: A versatile vision-language model for understanding, localization, text reading, and beyond. arXiv preprint arXiv:2308.12966, 2023. 1, 3, 4, 6", + "[2] Takeshi Kojima, Shixiang Shane Gu, Machel Reid, Yutaka Matsuo, and Yusuke Iwasawa. Large language models are zero-shot reasoners. 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Europe's journal of psychology, 12(2):210, 2016. 7" + ], + "bbox": [ + 78, + 90, + 468, + 275 + ], + "page_idx": 11 + }, + { + "type": "page_number", + "text": "13257", + "bbox": [ + 480, + 945, + 517, + 955 + ], + "page_idx": 11 + } +] \ No newline at end of file diff --git a/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_model.json b/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_model.json new file mode 100644 index 0000000000000000000000000000000000000000..9d22022cc202a1e2790aeb9ef4a9a229dac2d98b --- /dev/null +++ b/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_model.json @@ -0,0 +1,3161 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "image", + "bbox": [ + 0.13, + 0.125, + 0.168, + 0.155 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.17, + 0.138, + 0.845, + 0.184 + ], + "angle": 0, + "content": "Let's Think Outside the Box: Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation" + }, + { + "type": "text", + "bbox": [ + 0.147, + 0.21, + 0.822, + 0.247 + ], + "angle": 0, + "content": "Shanshan Zhong\\(^{1,3*}\\) Zhongzhan Huang\\(^{1,3*}\\) Shanghua Gao\\(^{4}\\) Wushao Wen\\(^{1}\\) Liang Lin\\(^{1}\\) Marinka Zitnik\\(^{4}\\) Pan Zhou\\(^{2,3\\dagger}\\)" + }, + { + "type": "text", + "bbox": [ + 0.098, + 0.247, + 0.873, + 0.266 + ], + "angle": 0, + "content": "1 Sun Yat-Sen University, 2 Singapore Management University, 3 Sea AI Lab, 4 Harvard University" + }, + { + "type": "text", + "bbox": [ + 0.217, + 0.267, + 0.744, + 0.282 + ], + "angle": 0, + "content": "*Co-first author: {zhongshsh5,huangzhzh23}@mail2.sysu.edu.cn" + }, + { + "type": "text", + "bbox": [ + 0.302, + 0.285, + 0.663, + 0.3 + ], + "angle": 0, + "content": "†Corresponding author: panzhou@smu.edu.sg" + }, + { + "type": "image", + "bbox": [ + 0.098, + 0.309, + 0.345, + 0.387 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.101, + 0.398, + 0.123, + 0.411 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.123, + 0.399, + 0.18, + 0.411 + ], + "angle": 0, + "content": "Qwen-VL" + }, + { + "type": "image", + "bbox": [ + 0.181, + 0.399, + 0.203, + 0.411 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.204, + 0.399, + 0.324, + 0.412 + ], + "angle": 0, + "content": "Qwen- \\(\\mathrm{VL}_{+}\\) CLoT (Ours)" + }, + { + "type": "text", + "bbox": [ + 0.138, + 0.418, + 0.304, + 0.431 + ], + "angle": 0, + "content": "Image&Text to Text (IT2T)" + }, + { + "type": "image", + "bbox": [ + 0.104, + 0.436, + 0.345, + 0.555 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.104, + 0.561, + 0.19, + 0.648 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.194, + 0.57, + 0.334, + 0.595 + ], + "angle": 0, + "content": "(CN) ①求婚者 ②被求婚者 ③" + }, + { + "type": "text", + "bbox": [ + 0.196, + 0.598, + 0.321, + 0.61 + ], + "angle": 0, + "content": "@①Proposer②Proposee③?" + }, + { + "type": "image", + "bbox": [ + 0.196, + 0.626, + 0.226, + 0.64 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.227, + 0.628, + 0.287, + 0.639 + ], + "angle": 0, + "content": "牧师 @ Pastor" + }, + { + "type": "image", + "bbox": [ + 0.29, + 0.627, + 0.338, + 0.643 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.196, + 0.649, + 0.234, + 0.661 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.236, + 0.649, + 0.312, + 0.661 + ], + "angle": 0, + "content": "译员@Translator" + }, + { + "type": "image", + "bbox": [ + 0.314, + 0.649, + 0.339, + 0.665 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.422, + 0.317, + 0.54, + 0.33 + ], + "angle": 0, + "content": "Image to Text (12T)" + }, + { + "type": "image", + "bbox": [ + 0.363, + 0.35, + 0.432, + 0.415 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.439, + 0.346, + 0.588, + 0.37 + ], + "angle": 0, + "content": "(EN) Forgot to remove glasses while swimming." + }, + { + "type": "text", + "bbox": [ + 0.438, + 0.387, + 0.581, + 0.41 + ], + "angle": 0, + "content": "(EN) An apple a day keep the doctor away." + }, + { + "type": "image", + "bbox": [ + 0.571, + 0.399, + 0.597, + 0.422 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.365, + 0.455, + 0.433, + 0.52 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.438, + 0.451, + 0.592, + 0.473 + ], + "angle": 0, + "content": "(JP) ああ、やと運転が始のをるた" + }, + { + "type": "text", + "bbox": [ + 0.438, + 0.474, + 0.559, + 0.485 + ], + "angle": 0, + "content": "@ Oh, I can finally start driving." + }, + { + "type": "image", + "bbox": [ + 0.571, + 0.472, + 0.596, + 0.487 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.438, + 0.501, + 0.593, + 0.524 + ], + "angle": 0, + "content": "(JP)心配ないて、すてが青信号です" + }, + { + "type": "text", + "bbox": [ + 0.438, + 0.526, + 0.568, + 0.536 + ], + "angle": 0, + "content": "@ Don't worry, they're all green lig" + }, + { + "type": "image", + "bbox": [ + 0.571, + 0.53, + 0.596, + 0.552 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.365, + 0.575, + 0.433, + 0.638 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.438, + 0.569, + 0.584, + 0.591 + ], + "angle": 0, + "content": "(CN)哈哈这是一只快乐的猫咪,它张着嘴巴..." + }, + { + "type": "text", + "bbox": [ + 0.438, + 0.592, + 0.57, + 0.609 + ], + "angle": 0, + "content": "@ Haha this is a happy cat with his mouth open ...." + }, + { + "type": "image", + "bbox": [ + 0.571, + 0.592, + 0.596, + 0.61 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.437, + 0.618, + 0.597, + 0.639 + ], + "angle": 0, + "content": "(CN) 什么?! 现在要去宠物医院做绝育手术?!" + }, + { + "type": "text", + "bbox": [ + 0.437, + 0.641, + 0.588, + 0.661 + ], + "angle": 0, + "content": "@ What?! Going to the pet hospital now for a neutering surgery!?" + }, + { + "type": "image", + "bbox": [ + 0.571, + 0.649, + 0.596, + 0.669 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.683, + 0.318, + 0.793, + 0.331 + ], + "angle": 0, + "content": "Text to Text (T2T)" + }, + { + "type": "text", + "bbox": [ + 0.623, + 0.341, + 0.82, + 0.365 + ], + "angle": 0, + "content": "(EN) What else can wake you up besides coffee when you are coding?" + }, + { + "type": "text", + "bbox": [ + 0.623, + 0.373, + 0.853, + 0.397 + ], + "angle": 0, + "content": "(EN) Maybe you need to enlist the help of some angry bees." + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.407, + 0.739, + 0.42 + ], + "angle": 0, + "content": "(EN) A cup of deadline." + }, + { + "type": "image", + "bbox": [ + 0.825, + 0.384, + 0.851, + 0.399 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.825, + 0.406, + 0.852, + 0.423 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.449, + 0.849, + 0.461 + ], + "angle": 0, + "content": "(JP)一番絕望的だと思うさは何てすか?" + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.464, + 0.826, + 0.474 + ], + "angle": 0, + "content": "@ What's the most desperate thing you've ever heard?" + }, + { + "type": "text", + "bbox": [ + 0.623, + 0.481, + 0.79, + 0.493 + ], + "angle": 0, + "content": "(JP)犬が私の比を食てまた" + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.497, + 0.719, + 0.507 + ], + "angle": 0, + "content": "@ The dog ate my pizza." + }, + { + "type": "image", + "bbox": [ + 0.826, + 0.494, + 0.852, + 0.512 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.623, + 0.517, + 0.825, + 0.529 + ], + "angle": 0, + "content": "(JP)月曜日だし、仕事に行く時間だね" + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.533, + 0.769, + 0.542 + ], + "angle": 0, + "content": "@ It's Monday and time to go to work." + }, + { + "type": "image", + "bbox": [ + 0.826, + 0.53, + 0.852, + 0.548 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.571, + 0.85, + 0.597 + ], + "angle": 0, + "content": "(CN)你觉得完成一篇深度学习论文辛苦吗?@Do you think writing a DL paper is exhausting?" + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.604, + 0.784, + 0.616 + ], + "angle": 0, + "content": "(CN) 完成一篇论文其实很快乐" + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.618, + 0.81, + 0.627 + ], + "angle": 0, + "content": "@ Completing a paper is actually very enjoyable." + }, + { + "type": "image", + "bbox": [ + 0.826, + 0.614, + 0.852, + 0.633 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.639, + 0.797, + 0.652 + ], + "angle": 0, + "content": "(CN) 不辛苦,辛苦的是我的导师" + }, + { + "type": "text", + "bbox": [ + 0.624, + 0.653, + 0.798, + 0.663 + ], + "angle": 0, + "content": "@ Not for me, but it's hard for my supervisor." + }, + { + "type": "image", + "bbox": [ + 0.825, + 0.649, + 0.852, + 0.668 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.075, + 0.688, + 0.894, + 0.759 + ], + "angle": 0, + "content": "Figure 1. Comparison between (multimodal) large language model (LLM, red) and its CLoT-integrated version (blue) for Oogiri-style multimodal humor generation. According to the model input that can be image, text or both, there are three Oogiri tasks, \"Image&Text to Text (IT2T)\", \"Image to Text (I2T)\", and \"Text to Text (T2T)\", where text can be English (EN), Chinese (CN), and Japanese (JP). \"@\" denotes translations. The baseline LLM is Qwen-VL [1]. While humor is subjective, these examples demonstrate CLoT's leap-of-thought capacity of using excellent creative thinking to produce high-quality humor responses. See more examples in Appendix." + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.771, + 0.314, + 0.787 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Chain-of-Thought (CoT) [2, 3] guides large language models (LLMs) to reason step-by-step, and can motivate their logical reasoning ability. While effective for logical tasks, CoT is not conducive to creative problem-solving which often requires out-of-box thoughts and is crucial for innovation advancements. In this paper, we explore the Leap-of-Thought (LoT) abilities within LLMs — a non-" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.773, + 0.895, + 0.894 + ], + "angle": 0, + "content": "sequential, creative paradigm involving strong associations and knowledge leaps. To this end, we study LLMs on the popular Oogiri game which needs participants to have good creativity and strong associative thinking for responding unexpectedly and humorously to the given image, text, or both, and thus is suitable for LoT study. Then to investigate LLMs' LoT ability in the Oogiri game, we first build a multimodal and multilingual Oogiri-GO dataset which con" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "13246" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.381 + ], + "angle": 0, + "content": "tains over 130,000 samples from the Oogiri game, and observe the insufficient LoT ability or failures of most existing LLMs on the Oogiri game. Accordingly, we introduce a creative Leap-of-Thought (CLoT) paradigm to improve LLM's LoT ability. CLoT first formulates the Oogiri-GO dataset into LoT-oriented instruction tuning data to train pretrained LLM for achieving certain LoT humor generation and discrimination abilities. Then CLoT designs an explorative self-refinement that encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts and selects high-quality data to train itself for self-refinement. CLoT not only excels in humor generation in the Oogiri game as shown in Fig. 1 but also boosts creative abilities in various tasks like \"cloud guessing game\" and \"divergent association task\". These findings advance our understanding and offer a pathway to improve LLMs' creative capacities for innovative applications across domains. The dataset, code, and models have been released online: https://zhongshsh.github.io/CLoT." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.387, + 0.21, + 0.403 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.414, + 0.47, + 0.626 + ], + "angle": 0, + "content": "Large language models (LLMs) [4-13] have catalyzed a transformative era in problem-solving abilities, revolutionizing various domains within artificial intelligence. The advent of the Chain-of-Thought (CoT) paradigm [3] and its further enhancements [2, 14-16] have equipped these LLMs with a human-like step-by-step reasoning capacity. This augmentation has enabled LLMs to excel in intricate reasoning tasks spanning from language comprehension to visual understanding. As shown in Fig. 2 (Left), CoT instills LLMs with a sequential thinking process wherein each subsequent thought builds upon the previous one. This paradigm enhances the precision and rigor in logical processing, making it exceedingly effective for problems that demand closely linked logical reasoning." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.628, + 0.471, + 0.884 + ], + "angle": 0, + "content": "However, the sequential nature of CoT might fall short in nurturing creativity and innovation, potentially limiting solutions in creative problem-solving scenarios [17, 18]. For instance, proving an algebraic inequality often follows a step-by-step CoT process that progresses from one inequality to the next. Yet, an intuitive flash, e.g., a geometric interpretation, can yield a more creative solution. This type of insight, known as \"Leap-of-Thought\" (LoT) [19, 20], a.k.a. mental leap [21-24]—the art of non-sequential thinking by association, drawing parallels between seemingly unrelated concepts, and facilitating a \"leap\" of knowledge transfer. In contrast to CoT reasoning, LoT as depicted in Fig. 2 (Right), fosters associative reasoning and encourages thinking outside the box, which bridges disparate ideas and facilitates conceptual leaps. Embracing LLMs with a strong LoT ability can unlock significant potential for innovation, contributing to advancements in creative applications." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.886, + 0.47, + 0.901 + ], + "angle": 0, + "content": "In this paper, we aim to initially explore and enhance the" + }, + { + "type": "image", + "bbox": [ + 0.522, + 0.094, + 0.686, + 0.157 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.708, + 0.094, + 0.872, + 0.157 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.174, + 0.892, + 0.203 + ], + "angle": 0, + "content": "Figure 2. Comparison of CoT and LoT. “\\(\\bigcirc\\)” denotes the thought and “\\(\\rightarrow\\)” represents the connection between two thoughts." + }, + { + "type": "image", + "bbox": [ + 0.524, + 0.206, + 0.658, + 0.321 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.66, + 0.206, + 0.783, + 0.32 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.786, + 0.208, + 0.87, + 0.318 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.333, + 0.892, + 0.388 + ], + "angle": 0, + "content": "Figure 3. Examples of the three types of LoT-based Oogiri games. Players are required to make surprising and creative humorous responses (blue box) to the given multimodal information e.g., images, text, or both." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.403, + 0.893, + 0.659 + ], + "angle": 0, + "content": "LoT ability of LLMs. However, thoroughly assessing LoT is challenging due to the complexity of measuring creative thinking [25-27] and the difficulty in gathering pertinent data, since generating novel ideas is challenging, even for humans [17]. Given these constraints, we propose studying LoT in LLMs through the lens of Oogiri-style humor generation. Oogiri, a traditional Japanese creative game [28], requires participants to provide unexpected and humorous responses to prompts in the form of images, text, or a combination of both, as shown in Fig. 3. This game challenges LLMs to demonstrate a sudden burst of insight and strong associative thinking, presenting a unique challenge for CoT-based methods, making it an ideal testbed for assessing the leap-of-thought abilities of LLMs. Moreover, the extensive online presence of Oogiri guarantees a wealth of human-generated creative content, ideal for compiling an expansive leap-of-thought dataset." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.66, + 0.895, + 0.886 + ], + "angle": 0, + "content": "To investigate the LoT ability of LLMs in the Oogiri game, we present the multilingual and multimodal Oogiri-GO dataset which comprises more than 130,000 high-quality Oogiri samples in English, Chinese, and Japanese, and curated to prompt textual humor in response to inputs that can be images, text, or both. Through extensive experiments, we discover that even the advanced LLMs and reasoning frameworks [2, 4, 6, 29], such as GPT-4 and CoT, despite their exceptional reasoning capabilities, possessing a rich prior knowledge of diverse forms of humor [2], still struggle to exhibit sufficient LoT ability for creative humor generation. Moreover, directly fine-tuning LLMs on the Oogiri-GO is not easy to improve the LoT ability. The more efficient utilization of humorous knowledge is needed to help LLM elicit creative responses." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.887, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Motivated by the human mental leap exercise process" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13247" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.272 + ], + "angle": 0, + "content": "of \"remote association & self-refinement\" [30], to enable LLMs with strong LoT ability for creation, we propose the Creative Leap-of-Thought (CLoT) paradigm which relies on two LoT-boosting stages. The first one is the associable instruction tuning stage which designs an associative instruction template to formulate the Oogiri-GO dataset into instruction data and trains an LLM to improve its LoT ability. The core here is the instruction template with a dual purpose: it randomly provides LLM with clues to establish connections between game inputs and creative responses, while also introducing empty clues to encourage LLM for unrestrained exploration and remote association thinking." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.273, + 0.473, + 0.469 + ], + "angle": 0, + "content": "The second stage is explorative self-refinement which encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts under weakly-associated conditions, and selects high-quality data to train itself for self-refinement. These weakly-associated conditions can either be empty, or randomly sampled from an object noun set collected from the Oogiri-GO dataset. The former empty conditions to allow LLM to operate freely, and the latter ones help the LLM to link seemingly-unrelated and weakly-related concepts, and encourage the LLM to explore knowledge outside of traditional cognitive limitations. This exploration strategy can help generate diverse high-quality data for self-refinement." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.47, + 0.473, + 0.637 + ], + "angle": 0, + "content": "Experimental results show that CLoT can greatly enhance the LoT ability of LLMs like Qwen [1] and CogVLM [29] across several types of Oogiri games. Specifically, CLoT can help LLMs to generate much better humors in Fig. 1. Moreover, CLoT-integrated LLMs achieve higher quantitative performance than the corresponding vanilla and CoT-integrated LLMs across the multiple-choice and ranking questions in the Oogiri game. Also, CLoT can boost creative abilities on other tasks like \"cloud guessing game\" and \"divergent association task\" [31-33], showing its remarkable generalization ability." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.649, + 0.228, + 0.665 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.674, + 0.473, + 0.902 + ], + "angle": 0, + "content": "(1) Oogiri game (大喜利) is a general term for a series of traditional Japanese comedy games. In ancient times, there were different types of Oogiri, such as actors performing sumo wrestling, telling ghost stories, etc. The modern Oogiri game mainly refers to one specific type known as Tonchi (頓智), typically presented in the format of game shows or intellectual quiz programs [28]. Players are provided with various multimodal contents, which can be simple questions, random images, etc., and are then prompted to come up with humorous, creative responses to achieve surprising comedic effects, as the examples are shown in Fig. 3. It is worth noting that the character “頓” in both Japanese and Chinese denote “sudden”, while “智” means “intelligence, insight or intuition”. This highlights the connection between the Oogiri game and the requirement for" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.122 + ], + "angle": 0, + "content": "strong associative abilities in LoT, making Oogiri an ideal platform for exploring LoT capabilities within LLMs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.123, + 0.894, + 0.228 + ], + "angle": 0, + "content": "(2) Multimodal LLMs and their creativity. Recently, multimodal Language Models [1, 29, 34, 35] have garnered significant attention, particularly due to their impressive reasoning abilities [7-12, 36]. Moreover, there is a growing focus on exploring the creativity [37-40] of LLMs for applications such as scientific discovery [18, 41-44], creative writing [45-49], etc." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.23, + 0.895, + 0.365 + ], + "angle": 0, + "content": "(3) Computational humor is a branch of computational linguistics and artificial intelligence that uses computers in humor research [50], which encompasses various tasks, including humor detection [51-58], humor interpretation [58-61], and humor generation [62-66], etc. With the advancement of generative LLMs [1, 4, 29], humor generation has become a popular focus while humor generation still faces challenges such as insufficient punchlines [67] and limited in multimodal contexts [68-70]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.367, + 0.894, + 0.443 + ], + "angle": 0, + "content": "(4) Chain-of-Thought based Methods provide the models with \"chain of thoughts\" [2, 3, 14-16], i.e., reasoning exemplars [3], or a simple prompt \"Let's think step by step\" [2], to encourage LLMs to engage in reasoning rather than simply providing answers directly [71]." + }, + { + "type": "table", + "bbox": [ + 0.534, + 0.45, + 0.866, + 0.517 + ], + "angle": 0, + "content": "
CategoryEnglishChineseJapaneseTotal
I2T17,33632,13040,27889,744
T2T6,43315,79711,84234,072
IT2T—9129,42010,332
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.527, + 0.894, + 0.556 + ], + "angle": 0, + "content": "Table 1. Data distribution of the Oogiri-GO dataset. For the IT2T task, its English version is not available due to cultural preference." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.572, + 0.688, + 0.589 + ], + "angle": 0, + "content": "3. Oogiri-GO Dataset" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.892, + 0.734 + ], + "angle": 0, + "content": "As introduced in Sec. 2, in the Oogiri game, the participants need to unexpectedly and humorously respond to the given images, text, or both. See three types of examples in Fig. 3. This game requests a sudden burst of insight and strong associative thinking to the given context, and provides an ideal platform to assess the leap-of-thought (LoT) ability of LLMs. Accordingly, we collect Oogiri game data to build a large-scale Oogiri-GO dataset which serves as a benchmark to evaluate and improve LoT ability." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Specifically, Oogiri-GO is a multimodal and multilingual humor dataset, and contains more than 130,000 Oogiri samples in English, Chinese, and Japanese. Notably, in Oogiri-GO, \\(77.95\\%\\) of samples are annotated with human preferences, namely the number of likes, indicating the popularity of a response. As illustrated in Fig. 3, Oogiri-GO contains three types of Oogiri games according to the input that can be images, text, or both, and are respectively called \"Text to Text\" (T2T), \"Image to Text\" (I2T), and \"Image & Text to Text\" (IT2T) for brevity. See more examples in Fig. 1. Table 1 summarizes the distribution of these game types." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "13248" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.1, + 0.09, + 0.449, + 0.258 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.081, + 0.268, + 0.462, + 0.283 + ], + "angle": 0, + "content": "Figure 4. The overview of proposed Creative Leap-of-Thought." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.286, + 0.469, + 0.331 + ], + "angle": 0, + "content": "For training purposes, \\(95\\%\\) of the samples are randomly selected to construct the training dataset, while the remaining \\(5\\%\\) form the test dataset for validation and analysis." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.332, + 0.469, + 0.544 + ], + "angle": 0, + "content": "To create the Oogiri-GO dataset, there are three main steps, including online data collection, machine filtering by LLM, and manual screening. Firstly, to collect sufficient data, we source Oogiri game data from the official Oogiri game platform, Bokete, and other popular platforms, such as Twitter and Weibo which also host some Oogiri-game-like data. Then, to guard against the inclusion of bias, violence, explicit content, offensive language, etc., we have placed a strong emphasis on rigorous safety checks during both machine and manual screening. We first use the multimodal LLM Qwen-VL [1] to do the initial screening of the raw data by constructing safety-checking prompts. Then, manual checking is performed on the remaining data. See more details about the dataset creation in the Appendix." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.552, + 0.39, + 0.569 + ], + "angle": 0, + "content": "4. Creative Leap-of-Thought (CLoT)" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.578, + 0.47, + 0.775 + ], + "angle": 0, + "content": "To augment the Leap-of-Thought (LoT) ability in (multimodal) Large Language Models (LLMs) for creative generation, we propose a novel Creative LoT framework (CLoT). As shown in Fig. 4, CLoT relies on two LoT-boosting stages. The first one is associative instruction tuning that formulates the Oogiri-GO dataset into instruction tuning data for training an LLM to improve its LoT ability (Sec. 4.1). The second one is explorative self-refinement that encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts, and selects high-quality data to train itself for self-refinement (Sec. 4.2). Finally, we present the CLoT inference to induce the LoT ability of the trained LLM (Sec. 4.3)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.786, + 0.345, + 0.803 + ], + "angle": 0, + "content": "4.1. Associable Instruction Tuning" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.469, + 0.901 + ], + "angle": 0, + "content": "LoT ability mainly includes associable generation and discrimination ability [30]. Given an input, associative generation draws its parallels with seemingly unrelated concepts via remote association and then generates innovative responses, e.g., the unexpected humor for the Oogiri input. Associable discrimination is to judge the matchiness among" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.891, + 0.121 + ], + "angle": 0, + "content": "input and responses though they are seemingly unrelated, and then to select the most creative response." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.122, + 0.892, + 0.227 + ], + "angle": 0, + "content": "Unfortunately, both associative generation and discrimination are not present in current LLMs, e.g., poor performance of GPT4v [72] in the Oogiri game observed in Sec. 5. Moreover, it is hard to improve these two LoT abilities via popular CoT-like prompt techniques. Indeed, as shown in Sec. 5, CoT even sometimes impairs the LoT performance of the LLMs like Qwen-VL [1] in the Oogiri game." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.228, + 0.892, + 0.317 + ], + "angle": 0, + "content": "To address this issue, we propose associable instruction tuning which trains LoRA [73] for LLMs on the OogiriGO dataset to achieve certain associable generation and discrimination abilities. It has two steps, including instruction generation and discrimination template design, and associative instruction learning." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.318, + 0.892, + 0.424 + ], + "angle": 0, + "content": "(1) Instruction Generation & Discrimination Templates. We design LoT-oriented instruction templates to transform the Oogiri-GO dataset into instruction tuning data, and then train LLM to achieve associable generation and discrimination abilities. Our templates primarily comprise two components in Fig. 5: task-specific prompt and response. For different abilities, the templates need some special design." + }, + { + "type": "image", + "bbox": [ + 0.55, + 0.429, + 0.822, + 0.47 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.548, + 0.475, + 0.843, + 0.489 + ], + "angle": 0, + "content": "Figure 5. The LoT-oriented instruction templates." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.493, + 0.892, + 0.81 + ], + "angle": 0, + "content": "For associable generation, \"USER-INPUTs\" contains \"Task-specific Prompt\" along with two optional conditions, \"Image\" and \"Condition\". For \"Task-specific Prompt\", we elaborately design several templates for different types of Oogiri game. See the Appendix for details and there is an image-2-text (I2T) Oogiri example in Fig. 6. For \"Image\" condition, it relies on the type of Oogiri game, e.g., being the image embeddings in I2T game and empty in T2T type. For the \"condition\" option, it's set to empty with a probability of \\(\\rho_{c}\\), and otherwise is randomly set as one noun in \"task-specific responses\". This design gives the LLM a clue to connect the game input and the correct responses while also encouraging LLM to explore and unleash its creative thinking with probability \\(\\rho_{c}\\). Finally, \"Task-specific Responses\" are the ground truth responses of an Oogiri-GO data, and need to be predicted by LLM during training. This task enforces the LLM to draw parallels between seemingly unrelated concepts in inputs and responses for giving innovative responses, e.g., the humor for the Oogiri input. This associative generation ability can assist the LLM to think outside the box and learn remote association thinking." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.892, + 0.9 + ], + "angle": 0, + "content": "Regarding associable discrimination, we aim to develop fundamental LoT discrimination skills for LLM. Based on the Oogiri-GO data, we design choice questions to enhance LLM's LoT discrimination ability, i.e., selection skill. Besides, as \\(77.95\\%\\) of the Oogiri-GO data have human preference annotations, i.e., the number of likes of several re" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13249" + } + ], + [ + { + "type": "header", + "bbox": [ + 0.219, + 0.094, + 0.347, + 0.105 + ], + "angle": 0, + "content": "Associable Generation" + }, + { + "type": "header", + "bbox": [ + 0.617, + 0.094, + 0.761, + 0.105 + ], + "angle": 0, + "content": "Associable discrimination" + }, + { + "type": "image", + "bbox": [ + 0.084, + 0.108, + 0.28, + 0.216 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.108, + 0.484, + 0.216 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.489, + 0.108, + 0.691, + 0.216 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.693, + 0.108, + 0.891, + 0.216 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.231, + 0.894, + 0.274 + ], + "angle": 0, + "content": "Figure 6. The details of LoT-oriented instructions templates. We take \"Image to Text\" as an example, see the Appendix for the details of other categories' instructions. (a) and (b) are the instruction templates with/without conditions for associable generation. (c) and (d) are the two instructions about the selection and ranking of associable discrimination. All templates follow the formats in Fig. 5." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.281, + 0.469, + 0.311 + ], + "angle": 0, + "content": "sponses (see Sec. 3), we design ranking questions to improve another discrimination skill, i.e., ranking ability." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.312, + 0.469, + 0.506 + ], + "angle": 0, + "content": "For a choice question, as shown in Fig. 6 (c), the options in \"Task-specific Prompt\" contain the random permutations of ground truth response (GTR), image captions generated by BLIP2 [74], GTR from other images, rewrites of GTR by Qwen-14B [5]. See details in Appendix. For \"task-specific responses\", it is the GTR. This design is to train LLM to improve its LoT selection ability. For a ranking question, as shown in Fig. 6 (d), it is to enforce LLM to rank multiple distinct responses of a given input to match their human preferences. By training on the choice and ranking questions, LLM is encouraged to distinguish LoT responses and align human creative preferences, improving its LoT discriminative selection and ranking abilities." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.508, + 0.47, + 0.659 + ], + "angle": 0, + "content": "(2) Associable Instruction Learning. By using the above instruction templates, we augment the 130,000 samples in the Oogiri-GO dataset to more than 500,000 instructions whose formulation is in Fig. 5. During training, LLM is required to predict the \"task-specific responses\" according to the \"USER-INPUTs\" which include \"Task-specific Prompt\" and two additional optional conditions like image and text condition. To avoid over-fitting, we only train standard LoRA [73] for the LLM with the associable instruction data. See more details in Appendix." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.666, + 0.331, + 0.683 + ], + "angle": 0, + "content": "4.2. Explorative Self-Refinement" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.69, + 0.469, + 0.854 + ], + "angle": 0, + "content": "After associable instruction tuning, we aim to generate more high-quality creative data by LLM which are then used to train LLM for self-refinement. To this end, we introduce an innovative stage called explorative self-refinement, inspired by human LoT exercise process of \"remote association & self-refinement\", also known as mental leap [21, 24, 30]. The remote association process refers to generating new ideas by associating remote concepts or thoughts, and self-refinement uses the generated data to enhance one's own LoT ability. In the following, we design two similar LoT exercise processes for LLM to improve its LoT ability." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.469, + 0.901 + ], + "angle": 0, + "content": "(1) Explorative Remote Association. The core here is to prompt the LLM to generate a diverse array of creative responses under weakly-associated conditions. To implement" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.281, + 0.892, + 0.447 + ], + "angle": 0, + "content": "this, we extract a set of object nouns, denoted as \\(\\mathcal{S}\\), from the text in the Oogiri-GO training data. See details in Appendix. Then, for each user-input \\(I\\) (see Fig. 5), we generate \\(n\\) weakly-associated conditions \\(\\{C_i\\}_{i=1}^n\\). These conditions can either be empty with a probability \\(\\rho \\in (0,1)\\) to give freedom to LLM, or uniformly randomly sampled from the noun set \\(\\mathcal{S}\\) to enforce LLM to build connections between different concepts. Next, we add the condition \\(C_i\\) into user-input \\(I\\), and feed \\(I\\) into the LLM to generate a humor candidate \\(R_i\\). Repeating this process with different conditions \\(C_i\\) can generate a total of \\(n\\) candidates \\(\\{R_i\\}_{i=1}^n\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.448, + 0.892, + 0.599 + ], + "angle": 0, + "content": "Then the LLM ranks these candidates by its discriminative ranking ability learned in Sec. 4.1. Next, it mixes the top-2 candidates with the ground truth responses (GTR), and selects the top-1 as the final response. Finally, if the selected top-1 response is the GTR, we discard this sample. Here first filtering out low-quality responses can improve the accuracy of subsequent top-1 selection, since \\((n + 1)\\)-choice problem is often more challenging than 3-choice problem as shown in Sec. 5. By repeating this process, we progressively gather sufficient new high-quality data." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.892, + 0.78 + ], + "angle": 0, + "content": "The core of this approach is the weakly-associated conditions \\(\\{C_i\\}_{i=1}^n\\) which can encourage the LLM to engage in remote associations. This is because the empty conditions allow LLM to operate freely, while the object noun conditions compel the LLM to draw connections between seemingly unrelated concepts. This mechanism facilitates the establishment of links between seemingly-unrelated and weakly-related concepts, encouraging the LLM to explore knowledge outside of traditional cognitive limitations. The exploration ability distinguishes our CLoT from CoT which primarily guides the LLM to exploit its inherent reasoning ability without emphasizing knowledge exploration." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.781, + 0.892, + 0.901 + ], + "angle": 0, + "content": "(2) Self-refinement. Here we combine the above generated instructions with vanilla instruction tuning samples in Sec. 4.1 to form a dataset with more than 550,000 samples to train our LLM again. Since the above generated data is of high diversity because of its exploration strategy, they prevent performance collapse [76, 77] during self-refinement phase, and can improve the LoT performance across several creative tasks as shown in Sec. 5. See the ablation study and" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13250" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.102, + 0.089, + 0.875, + 0.219 + ], + "angle": 0, + "content": "
ModelSizeImage&Text to Text (IT2T)Image to Text (I2T)Text to Text (T2T)
3T14T15T2RankAvg.3T14T15T2RankAvg.3T14T15T2RankAvg.
GPT4v [72]-19.314.93.256.723.529.115.13.960.427.127.116.86.853.526.1
LLaVA-1.5 [34]13B13.213.713.968.127.229.322.73.960.929.233.825.24.062.631.4
MiniGPT-v2 [35]7B6.13.44.060.718.65.34.03.860.518.410.87.33.559.420.3
mPLUG-OwlMultilingual [12]7B28.126.010.564.432.219.218.66.060.526.124.422.210.760.129.4
VisualGLM-6B [75]6B24.122.59.767.430.914.320.48.861.926.413.120.27.161.325.4
Qwen-VL [1]7B30.226.010.467.733.623.223.111.962.230.123.425.013.359.630.3
Qwen-VL+Alt(Ours)7B39.738.915.767.340.4+ 6.838.830.515.762.336.8+ 6.730.628.716.762.634.6+ 4.3
Qwen-VL+CLoT(Ours)7B41.838.721.668.542.7+ 9.139.835.122.764.440.5+10.438.829.421.064.738.5+ 8.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.227, + 0.895, + 0.259 + ], + "angle": 0, + "content": "Table 2. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on multil-modal multilingual models. mTn choice question selects \\( n \\) correct answers from \\( m \\) options. \"Avg.\" is the average of all metrics. \"AIT\" denotes associable instruction tuning." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.261, + 0.47, + 0.407 + ], + "angle": 0, + "content": "
Algorithm 1 Inference Step of CLoT
Input: Input I, CLoT-trained LLM A, response number n
Output: Creative response R.
1:▷ Creating the candidate responses
2: construct n weakly-associated conditions {Ci}n{i=1}
3: {Ri}n{i=1} ← A([I, {Ci}n{i=1}])
4:▷ Choosing most creative response
5: Top-2 R1', R2' ← A([I, {Ri}n{i=1}]) with ranking ability
6: Best R ← A([I, R1', R2']) with selection ability
7: return Best response R.
" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.433, + 0.274, + 0.449 + ], + "angle": 0, + "content": "more discussions in Sec. 5.5." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.454, + 0.24, + 0.47 + ], + "angle": 0, + "content": "4.3. CLoT Inference" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.478, + 0.473, + 0.721 + ], + "angle": 0, + "content": "After the two LoT-boosting phases in Sec. 4.1 and 4.2, the LLM acquires sufficient LoT ability. Now we introduce the inference steps of LLM to release its LoT ability. Formally, given an Oogiri user-input \\( \\pmb{I} \\) of the formation in Fig. 5, LLM first uses explorative remote association in Sec. 4.2 to construct \\( n \\) weakly-associated conditions (these conditions can be empty since the training paradigm in Section 4), and then follows Sec. 4.2 to generate \\( n \\) responses \\( \\{R_i\\}_{i=1}^n \\). Next, LLM ranks these responses by using its learned ranking skill and finally selects the top-1 one from the ranked top-2 response via its selection skill. The reason to first use ranking before selection is that as shown by experimental results in Sec. 5, directly choosing the best one from a large number of options has poor accuracy, and ranking can filter out low-quality candidates to improve the selection accuracy. See Algorithm 1 for an overview of CLoT inference steps." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.732, + 0.212, + 0.75 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.757, + 0.376, + 0.773 + ], + "angle": 0, + "content": "5.1. Evaluation Questions and Metrics" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.78, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Inspired by the humor benchmarks in [81], we first develop choice and ranking questions as introduced in Sec. 4.1 (see examples in Fig. 6 (c-d)), and then quantitatively evaluate the LoT ability of LLMs on the Oogiri-GO test dataset. For the choice questions, \\( mTn \\) for short, they need LLMs to choose \\( n \\) \"leap-of-thought\" humor responses from \\( m \\) options given the input. Here we build four types of \\( mTn \\) questions, including 2T1, 3T1, 4T1, and 5T2. 2T1 means" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.263, + 0.895, + 0.476 + ], + "angle": 0, + "content": "two options, the ground-truth response (GTR) and an image caption generated by BLIP2 [74]. 3T1 adds unrelated answers, e.g., other image captions. 4T1 further adds the GTR rewrite by Qwen-14B [5]. 5T2 has an extra GTR. For these questions, their difficulty increases progressively, and is diverse to ensure comprehensive evaluation. For choice questions, we use accuracy as the evaluation metric. Additionally, for the questions in test set whose responses have ground-truth human preference, e.g., the number of likes, we develop the ranking questions that always rank five candidates. For evaluation, we adopt the top-1 accuracy and the widely used ranking metric, i.e., Normalized Discounted Cumulative Gain (NDCG) [82, 83]. We provide more experimental details in the Appendix." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.484, + 0.886, + 0.502 + ], + "angle": 0, + "content": "5.2. Evaluation by Choice and Ranking Questions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.508, + 0.895, + 0.749 + ], + "angle": 0, + "content": "Evaluation on Multimodal Multilingual LLMs. We plug our associative instruction tuning (AIT) and our CLoT into the SoTA open-source multimodal multilingual model Qwen-VL [1] to obtain Qwen- \\(\\mathrm{VL}_{+\\mathrm{AIT}}\\) and Qwen- \\(\\mathrm{VL}_{+\\mathrm{CLoT}}\\), respectively. Table 2 shows that, on three tasks (IT2T, I2T and T2T) which include English, Chinese and Japanese questions, Qwen-VL achieves the best LoT performance among all baselines in most cases. In comparison, Qwen- \\(\\mathrm{VL}_{+\\mathrm{AIT}}\\) achieves a noticeable improvement on the SoTA Qwen with average accuracy enhancements of \\(6.8\\%\\), \\(6.7\\%\\), and \\(4.3\\%\\) on the three tasks, respectively. Importantly, Qwen- \\(\\mathrm{VL}_{+\\mathrm{CLoT}}\\) further enhances Qwen-VL, showing improvements of \\(9.1\\%\\), \\(10.4\\%\\), and \\(8.2\\%\\) in accuracy across these tasks. These results demonstrate the efficacy of the two stages in CLoT, i.e., associative instruction tuning and explorative self-refinement." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.895, + 0.87 + ], + "angle": 0, + "content": "Evaluation on Multimodal Non-multilingual LLMs. Here we integrate our CLoT with the SoTA multimodal non-multilingual model, CogVLM-17B [29], and evaluate it on the English I2T and T2T tasks. Table 3 shows that \\(\\mathrm{CogVLM - 17B}_{+\\mathrm{AIT}}\\) achieves remarkable improvements over the standard \\(\\mathrm{CogVLM - 17B}\\), and \\(\\mathrm{CogVLM - 17B}_{+\\mathrm{CLoT}}\\) consistently demonstrates significantly superior performance compared to \\(\\mathrm{CogVLM - 17B}\\)." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Evaluation on Single-Modal LLMs. Now we test LLMs that can handle only pure texts, using the English T2T task" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.958 + ], + "angle": 0, + "content": "13251" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.085, + 0.077, + 0.894, + 0.196 + ], + "angle": 0, + "content": "
ModelSizeImage to Text (I2T)Text to Text (T2T)
2T13T14T15T2RankAvg.2T13T14T15T2RankAvg.
InstructionBLIP [78]13B19.813.715.51.165.523.122.316.017.00.759.523.1
mPLUG-OwlLLaMA2 [12]7B22.312.715.04.259.922.824.213.712.63.159.222.6
Otter [79]7B15.89.98.57.161.320.53.83.34.85.458.515.1
CogVLM-17B [29]7B37.626.418.32.564.629.935.127.824.87.564.131.9
CogVLM-17B+AIT(Ours)7B57.437.433.521.864.642.9+13.155.446.526.418.264.442.2+10.3
CogVLM-17B+CLoT(Ours)7B66.947.643.430.769.451.6+21.764.852.933.621.868.648.3+16.4
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.205, + 0.893, + 0.234 + ], + "angle": 0, + "content": "Table 3. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on various mulilmodal non-multilingual models (English). See notations in Table 2. We only consider I2T and T2T since English IT2T is not available due to cultural preference." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.245, + 0.47, + 0.469 + ], + "angle": 0, + "content": "
ModelSize3T14T15T2RankAvg.
GPT-3.5 [72]-45.330.46.761.636.0
GPT-4 [72]-49.220.43.654.732.0
LLAMA2 [4]7B18.913.51.160.423.5
13B15.620.01.860.524.5
70B27.816.13.862.027.4
Baichuan2 [80]7B28.322.611.664.631.8
13B21.718.38.961.527.6
Qwen [5]7B23.120.48.061.428.2
14B27.422.212.359.530.3
ChatGLM3 [75]6B15.617.05.459.424.3
Vicuna-v1.5 [6]7B32.623.50.063.029.8
13B30.223.02.762.229.5
Qwen-VL+CLoT(Ours)7B51.732.324.865.043.4
CogVLM-17B+CLoT(Ours)7B52.933.621.868.644.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.479, + 0.47, + 0.522 + ], + "angle": 0, + "content": "Table 4. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on various large language models. Here we use English T2T task for test. See notations in Table 2." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.531, + 0.47, + 0.607 + ], + "angle": 0, + "content": "for evaluation. Table 4 also indicates the insufficient LoT ability within existing LLMs, ranging from small to large models. Fortunately, our CLoT significantly improves the LoT ability of these LLMs, as demonstrated by the notable improvement in accuracy." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.61, + 0.47, + 0.732 + ], + "angle": 0, + "content": "Comparison with CoT-alike Reasoning Frameworks. We also find that existing reasoning frameworks are not as effective as CLoT in enhancing LoT ability. Fig. 8 compares CLoT with CoT [2, 3], CoT-SC [84], and prompted-based LoT (PLoT) with the prompt \"let's think outside the box\". The results reveal that CoT-alike frameworks do not enhance LoT performance of LLMs, while CLoT demonstrates the ability to consistently enhance LLMs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Our experiments and analysis reveal that, unlike CoT-based methods, LoT cannot be directly achieved by prompting alone. This is because the inherent reasoning capabilities and extensive knowledge of LLMs are not sufficient to enable LoT ability. However, when trained with our proposed CLoT method, LLMs can effectively engage in a range of creative tasks. Additionally, the use of specific prompting techniques can enhance the LoT ability of CLoT-trained LLMs. These findings suggest that LoT could potentially be considered an additional general reasoning ability for LLMs that is not contained in current LLMs." + }, + { + "type": "image", + "bbox": [ + 0.522, + 0.244, + 0.871, + 0.352 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.361, + 0.892, + 0.39 + ], + "angle": 0, + "content": "Figure 7. User study with voting \\((\\%)\\) for Oogiri-style creative responses by different models and improved methods." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.392, + 0.684, + 0.405 + ], + "angle": 0, + "content": "5.3. Human Evaluation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.415, + 0.893, + 0.567 + ], + "angle": 0, + "content": "We conduct a user preference study to test creativity of LLMs. Here we select six LLMs to generate responses for a total of eighteen questions across three tasks (IT2T, I2T and T2T). We use choice questions, and ask users to choose the most creative and humorous responses. Fig. 7 summarizes the statistical analysis of 154 valid surveys. The results show that users have a strong inclination towards selecting the results of CLoT across three tasks, highlighting the high-quality creative content generated by CLoT. See more user study details in Appendix." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.576, + 0.813, + 0.59 + ], + "angle": 0, + "content": "5.4. Evaluation on Other Creative Tasks" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.895, + 0.903 + ], + "angle": 0, + "content": "To evaluate the generalization ability of CLoT, we test CLoT on another two creative tasks, including Cloud Guessing Game (CGG) and Divergent Association Task (DAT). In CGG, the LLM is to identify the shape of white clouds, and then to select the corresponding shapes from given options. For instance, the white clouds in Fig. 9 (c) has a shape of a cat, and the one in Fig. 9 (d) is similar to a human. These white cloud images are generated by a control diffusion model [31, 32, 85, 86], guided by masks shown in Fig. 9 (b). We use top-1 accuracy as metric. See more details in Appendix. For DAT, it is a classic creativity test [33, 87] which needs participants to choose words with larger semantic distances among 10 unrelated nouns. Here for test easily, we transfer the DAT benchmark [33] to a series of choice questions and take the standard average semantic distance (ASD) as a metric. These questions can challenge the LLM to select the one word from nine options that differs from the given word most. See more details in Appendix. CGG and DAT can test the LoT ability of LLMs, specifically their remote association thinking ability," + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "13252" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.118, + 0.091, + 0.298, + 0.198 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.315, + 0.091, + 0.43, + 0.198 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.443, + 0.091, + 0.559, + 0.198 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.579, + 0.092, + 0.696, + 0.198 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.712, + 0.092, + 0.825, + 0.198 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.199, + 0.891, + 0.226 + ], + "angle": 0, + "content": "Figure 8. The accuracy \\((\\%)\\) of choice questions and the NDCG \\((\\%)\\) of ranking questions on our CLoT and various reasoning frameworks. The baseline is Qwen-VL on multilingual I2T task. For \\(mTn\\) choice questions, one needs to select \\(n\\) correct answers from \\(m\\) options." + }, + { + "type": "image", + "bbox": [ + 0.108, + 0.238, + 0.268, + 0.398 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.27, + 0.238, + 0.434, + 0.398 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.403, + 0.47, + 0.446 + ], + "angle": 0, + "content": "Figure 9. Evaluation of CLoT on the creative CGG (e) and DAT (f) tasks. (c-d): examples of cloud guessing games. (b): conditional masks of image (a) for generating cloud images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.46, + 0.47, + 0.566 + ], + "angle": 0, + "content": "and provide quite different evaluation platforms. As shown in Fig. 9 (e-f), CLoT can also significantly enhance the performance of the SoTA Qwen-VL on both CGG and DAT tasks. Specifically, CLoT-integrated Qwen-VL improves the vanilla Qwen-VL by about \\(8\\%\\) on the CGG task and \\(5\\%\\) on the DAT task. These results well demonstrate the good generalization and transferability of CLoT." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.575, + 0.231, + 0.592 + ], + "angle": 0, + "content": "5.5. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.599, + 0.47, + 0.78 + ], + "angle": 0, + "content": "Weakly-associated Conditions. By default, to encourage remote association, we use weakly-associated conditions randomly sampled from the noun set on the whole dataset in Sec. 4.2. To verify the effectiveness of weakly-associated conditions, now we resort to strongly-associated conditions sampled from the noun set of the current image caption. Results in Fig. 10 (Left) show that using weakly-associated conditions is superior and more conducive to fostering the creativity of LLMs. The weakly-associated conditions enable the LLM to generate more diverse LoT responses, while the strong clue from the strongly-associated conditions limit the diversity of LoT generations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Round of Self-refinement. By default, we run one-round self-refinement for the Oogiri game. Here we explore whether more rounds of the self-refinement can further improve the LoT ability. Fig. 10 (Right) shows that a single round of self-refinement already yields promising performance, whereas additional rounds do not yield significant further improvements. As shown in Fig. 10 (Left), the diversity of the condition set \\(\\mathcal{S}\\) is crucial to self-refinement, since" + }, + { + "type": "image", + "bbox": [ + 0.52, + 0.238, + 0.693, + 0.332 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.697, + 0.238, + 0.871, + 0.332 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.336, + 0.893, + 0.392 + ], + "angle": 0, + "content": "Figure 10. The ablation study of CLoT. We use CogVLM as baseline on the English I2T task. Left: weakly-associated condition v.s. strongly-associated condition during explorative remote association. Right: The effect of rounds of self-refinement." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.406, + 0.893, + 0.527 + ], + "angle": 0, + "content": "it decides whether the associable remote stage can generate high quality and diverse data. However, the condition set \\(\\mathcal{S}\\) is not expanded during the second-round self-refinement, which consequently limits further improvements in performance. Effectively increasing the scale of the condition set is an effective way for further improvement. See more discussion in Appendix. But its exploration falls outside the scope of this work and is left for our future research." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.537, + 0.619, + 0.552 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.562, + 0.892, + 0.714 + ], + "angle": 0, + "content": "In this paper, we propose a Creative Leap-of-Thought (CLoT) paradigm to improve LLM's leap-of-thought (LoT) ability. CLoT first collects a multimodal Oogiri-GO dataset, and formulates it into instruction tuning data to train LLM to improve its LoT ability. Then CLoT designs an explorative self-refinement that lets LLM generate more creative LoT data via exploring parallels among different concepts and selects high-quality data to train itself for self-refinement. Experimental results show the effectiveness and generalization ability of CLoT across several creative tasks." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.723, + 0.68, + 0.74 + ], + "angle": 0, + "content": "7. Acknowledgments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.748, + 0.894, + 0.9 + ], + "angle": 0, + "content": "This work was supported by National Science and Technology Major Project (No.2021ZD0111601), National Natural Science Foundation of China (No.62325605, U1711264), and Guangdong Basic and Applied Basic Research Foundation (No.2023A1515011374), and Guangzhou Science and Technology Program (No.2024A04J6365), and Guangdong Province Key Laboratory of Information Security Technology. Pan Zhou acknowledges support from the Singapore Ministry of Education (MOE) Academic Research Fund (AcRF) Tier 1 grant." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "13253" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Jinze Bai, Shuai Bai, Shusheng Yang, Shijie Wang, Sinan Tan, Peng Wang, Junyang Lin, Chang Zhou, and Jingren Zhou. Qwen-vl: A versatile vision-language model for understanding, localization, text reading, and beyond. arXiv preprint arXiv:2308.12966, 2023. 1, 3, 4, 6" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.187, + 0.472, + 0.243 + ], + "angle": 0, + "content": "[2] Takeshi Kojima, Shixiang Shane Gu, Machel Reid, Yutaka Matsuo, and Yusuke Iwasawa. Large language models are zero-shot reasoners. 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Europe's journal of psychology, 12(2):210, 2016. 7" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.47, + 0.276 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.946, + 0.519, + 0.956 + ], + "angle": 0, + "content": "13257" + } + ] +] \ No newline at end of file diff --git a/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_origin.pdf b/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..e7e3d0a732b6381dc2581ebde5584cc9aaebc607 --- /dev/null +++ b/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/1c2a1ffb-0d92-41f0-bf24-e35e48d25ef2_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:1f39d7b32f1148dd8d4cee76fb1b9631f5fd82f0b9a92a3358e08677763892a1 +size 4717741 diff --git a/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/full.md b/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/full.md new file mode 100644 index 0000000000000000000000000000000000000000..b1fe0229b8233c9ae6e2bbb72ad403c577847e97 --- /dev/null +++ b/2024/Let's Think Outside the Box_ Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation/full.md @@ -0,0 +1,433 @@ +![](images/067735d14749de563bfd8fb9faff2ec4ea77b95a2f0614ec090b1e2c61319e58.jpg) + +# Let's Think Outside the Box: Exploring Leap-of-Thought in Large Language Models with Creative Humor Generation + +Shanshan Zhong $^{1,3*}$ Zhongzhan Huang $^{1,3*}$ Shanghua Gao $^{4}$ Wushao Wen $^{1}$ Liang Lin $^{1}$ Marinka Zitnik $^{4}$ Pan Zhou $^{2,3\dagger}$ + +1 Sun Yat-Sen University, 2 Singapore Management University, 3 Sea AI Lab, 4 Harvard University + +*Co-first author: {zhongshsh5,huangzhzh23}@mail2.sysu.edu.cn + +†Corresponding author: panzhou@smu.edu.sg + +![](images/c22c2c0d8a93fe4cf40ce7bf29efcc1b43ea64795695264b3bc3d5a05e0adb80.jpg) + +![](images/d70d32c8f597e543d5a78b3c0da0972d10fd200ad0966991d4c5e351138d5ac9.jpg) + +Qwen-VL + +![](images/1224980760705167e40cec79b03d1981b9887f46636910d295f052f2b11b5925.jpg) + +Qwen- $\mathrm{VL}_{+}$ CLoT (Ours) + +Image&Text to Text (IT2T) + +![](images/6104469f6d2d041dd41ccd7e33a4380cef44f26cb41df968852fe2d1d9a5167a.jpg) + +![](images/d63c2d6f49b503c5fb614b6b7547a33a4f2d808ffa193e222369d5f9cf542cc6.jpg) +Figure 1. Comparison between (multimodal) large language model (LLM, red) and its CLoT-integrated version (blue) for Oogiri-style multimodal humor generation. According to the model input that can be image, text or both, there are three Oogiri tasks, "Image&Text to Text (IT2T)", "Image to Text (I2T)", and "Text to Text (T2T)", where text can be English (EN), Chinese (CN), and Japanese (JP). "@" denotes translations. The baseline LLM is Qwen-VL [1]. While humor is subjective, these examples demonstrate CLoT's leap-of-thought capacity of using excellent creative thinking to produce high-quality humor responses. See more examples in Appendix. + +(CN) ①求婚者 ②被求婚者 ③ + +@①Proposer②Proposee③? + +![](images/5e17acc6ac711ae2f7e1ea41b0eae7b2952b20175f3ee9c288d2920ec27363af.jpg) + +牧师 @ Pastor + +![](images/a9c736c8fd84ccf4ec06b12c056e44caba3c85865bfcd3fbd92e43576d6b4092.jpg) + +![](images/fa6c0b4ebdafc11a8feae62a1b183dcff275568fe8f21ce51699d793e53a5ec3.jpg) + +译员@Translator + +![](images/8efb454dfa4a2d3cf6d59e6f7436f17ddabff85189e7750084214d815591434d.jpg) + +# Image to Text (12T) + +![](images/c3a972ab0f0de8aef1eabaa54e09a82cdf859adddd6af2726f2bc0424923ae8b.jpg) + +(EN) Forgot to remove glasses while swimming. + +(EN) An apple a day keep the doctor away. + +![](images/cba9f5d00011ca5a7d0664082e567d0bc325049c4f66d4ce6783f4bdae288762.jpg) + +![](images/0c09d7e434c10a54520e501a1c4ea5b40ab4883326fbec4029b07c87a1beacaf.jpg) + +(JP) ああ、やと運転が始のをるた + +@ Oh, I can finally start driving. + +![](images/084978b7506c146f8036b8e39f550aadd61c01e4a54ae1b9921bc682aa21f035.jpg) + +(JP)心配ないて、すてが青信号です + +@ Don't worry, they're all green lig + +![](images/b11cdd71293582f013eda1219a3919e10cda0fc20e30a2277ec27b7b4d5ffd30.jpg) + +![](images/9367f80eb07b1591e1549cc747197716bac66d65211ee3a4c5f44b96f06142d0.jpg) + +(CN)哈哈这是一只快乐的猫咪,它张着嘴巴... + +@ Haha this is a happy cat with his mouth open .... + +![](images/6b1bb6426cb93fa0ae4131542759251f3951a54ee69d77f181472256158948ac.jpg) + +(CN) 什么?! 现在要去宠物医院做绝育手术?! + +@ What?! Going to the pet hospital now for a neutering surgery!? + +![](images/929e3f229f02ae223cf8c65a0a783201f24b6b12e24065d509359944fc0f42f2.jpg) + +# Text to Text (T2T) + +(EN) What else can wake you up besides coffee when you are coding? + +(EN) Maybe you need to enlist the help of some angry bees. + +(EN) A cup of deadline. + +![](images/b2229c2ae3bd3f04a0127b9b6cfdb6664c3689e9eed11314d352099f58eba399.jpg) + +![](images/1edb29ff96c2e8521ded080f92669fdccf134e58fe6cd80d94a72cd9e158a2c1.jpg) + +(JP)一番絕望的だと思うさは何てすか? + +@ What's the most desperate thing you've ever heard? + +(JP)犬が私の比を食てまた + +@ The dog ate my pizza. + +![](images/989c26291bdf788217439357ce751ca7592e81c579960e367cb0049049ec0423.jpg) + +(JP)月曜日だし、仕事に行く時間だね + +@ It's Monday and time to go to work. + +![](images/11c1603049fcfebd67168cb922ac6e6c3a1b908022310fe0bd6d04012fec144e.jpg) + +(CN)你觉得完成一篇深度学习论文辛苦吗?@Do you think writing a DL paper is exhausting? + +(CN) 完成一篇论文其实很快乐 + +@ Completing a paper is actually very enjoyable. + +![](images/e44220eef6a3d516f209231f6ecf97df24a7b1d02593cd2b8723aa353aa5e3d3.jpg) + +(CN) 不辛苦,辛苦的是我的导师 + +@ Not for me, but it's hard for my supervisor. + +![](images/3dca93164eb197c856254a4275df2a87a1f8d3b2e19bf3107e34b2ac54aa4af3.jpg) + +# Abstract + +Chain-of-Thought (CoT) [2, 3] guides large language models (LLMs) to reason step-by-step, and can motivate their logical reasoning ability. While effective for logical tasks, CoT is not conducive to creative problem-solving which often requires out-of-box thoughts and is crucial for innovation advancements. In this paper, we explore the Leap-of-Thought (LoT) abilities within LLMs — a non- + +sequential, creative paradigm involving strong associations and knowledge leaps. To this end, we study LLMs on the popular Oogiri game which needs participants to have good creativity and strong associative thinking for responding unexpectedly and humorously to the given image, text, or both, and thus is suitable for LoT study. Then to investigate LLMs' LoT ability in the Oogiri game, we first build a multimodal and multilingual Oogiri-GO dataset which con + +tains over 130,000 samples from the Oogiri game, and observe the insufficient LoT ability or failures of most existing LLMs on the Oogiri game. Accordingly, we introduce a creative Leap-of-Thought (CLoT) paradigm to improve LLM's LoT ability. CLoT first formulates the Oogiri-GO dataset into LoT-oriented instruction tuning data to train pretrained LLM for achieving certain LoT humor generation and discrimination abilities. Then CLoT designs an explorative self-refinement that encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts and selects high-quality data to train itself for self-refinement. CLoT not only excels in humor generation in the Oogiri game as shown in Fig. 1 but also boosts creative abilities in various tasks like "cloud guessing game" and "divergent association task". These findings advance our understanding and offer a pathway to improve LLMs' creative capacities for innovative applications across domains. The dataset, code, and models have been released online: https://zhongshsh.github.io/CLoT. + +# 1. Introduction + +Large language models (LLMs) [4-13] have catalyzed a transformative era in problem-solving abilities, revolutionizing various domains within artificial intelligence. The advent of the Chain-of-Thought (CoT) paradigm [3] and its further enhancements [2, 14-16] have equipped these LLMs with a human-like step-by-step reasoning capacity. This augmentation has enabled LLMs to excel in intricate reasoning tasks spanning from language comprehension to visual understanding. As shown in Fig. 2 (Left), CoT instills LLMs with a sequential thinking process wherein each subsequent thought builds upon the previous one. This paradigm enhances the precision and rigor in logical processing, making it exceedingly effective for problems that demand closely linked logical reasoning. + +However, the sequential nature of CoT might fall short in nurturing creativity and innovation, potentially limiting solutions in creative problem-solving scenarios [17, 18]. For instance, proving an algebraic inequality often follows a step-by-step CoT process that progresses from one inequality to the next. Yet, an intuitive flash, e.g., a geometric interpretation, can yield a more creative solution. This type of insight, known as "Leap-of-Thought" (LoT) [19, 20], a.k.a. mental leap [21-24]—the art of non-sequential thinking by association, drawing parallels between seemingly unrelated concepts, and facilitating a "leap" of knowledge transfer. In contrast to CoT reasoning, LoT as depicted in Fig. 2 (Right), fosters associative reasoning and encourages thinking outside the box, which bridges disparate ideas and facilitates conceptual leaps. Embracing LLMs with a strong LoT ability can unlock significant potential for innovation, contributing to advancements in creative applications. + +In this paper, we aim to initially explore and enhance the + +![](images/ce4d1416dba78d56d9ae78f62670046c27fa2380efd5684481522dd20fcd4b06.jpg) + +![](images/77b4f81e9935d793d97abb64de157c2fd268113d96c167e6962dfc0d05d5ca03.jpg) + +![](images/b8ed2352ab5d0669e4cbb2c6fee2b7b63255733d83960a0004a60418aadb6ea0.jpg) +Figure 2. Comparison of CoT and LoT. “ $\bigcirc$ ” denotes the thought and “ $\rightarrow$ ” represents the connection between two thoughts. + +![](images/abdf5574cf2356069b6138ee1980df427a84cbf2570ebab3262f42bc6d338384.jpg) +Figure 3. Examples of the three types of LoT-based Oogiri games. Players are required to make surprising and creative humorous responses (blue box) to the given multimodal information e.g., images, text, or both. + +![](images/d81e82f8ba942c0d806c691b9ecee58d55993e42ec09f145a04e9e023e0cbd1b.jpg) + +LoT ability of LLMs. However, thoroughly assessing LoT is challenging due to the complexity of measuring creative thinking [25-27] and the difficulty in gathering pertinent data, since generating novel ideas is challenging, even for humans [17]. Given these constraints, we propose studying LoT in LLMs through the lens of Oogiri-style humor generation. Oogiri, a traditional Japanese creative game [28], requires participants to provide unexpected and humorous responses to prompts in the form of images, text, or a combination of both, as shown in Fig. 3. This game challenges LLMs to demonstrate a sudden burst of insight and strong associative thinking, presenting a unique challenge for CoT-based methods, making it an ideal testbed for assessing the leap-of-thought abilities of LLMs. Moreover, the extensive online presence of Oogiri guarantees a wealth of human-generated creative content, ideal for compiling an expansive leap-of-thought dataset. + +To investigate the LoT ability of LLMs in the Oogiri game, we present the multilingual and multimodal Oogiri-GO dataset which comprises more than 130,000 high-quality Oogiri samples in English, Chinese, and Japanese, and curated to prompt textual humor in response to inputs that can be images, text, or both. Through extensive experiments, we discover that even the advanced LLMs and reasoning frameworks [2, 4, 6, 29], such as GPT-4 and CoT, despite their exceptional reasoning capabilities, possessing a rich prior knowledge of diverse forms of humor [2], still struggle to exhibit sufficient LoT ability for creative humor generation. Moreover, directly fine-tuning LLMs on the Oogiri-GO is not easy to improve the LoT ability. The more efficient utilization of humorous knowledge is needed to help LLM elicit creative responses. + +Motivated by the human mental leap exercise process + +of "remote association & self-refinement" [30], to enable LLMs with strong LoT ability for creation, we propose the Creative Leap-of-Thought (CLoT) paradigm which relies on two LoT-boosting stages. The first one is the associable instruction tuning stage which designs an associative instruction template to formulate the Oogiri-GO dataset into instruction data and trains an LLM to improve its LoT ability. The core here is the instruction template with a dual purpose: it randomly provides LLM with clues to establish connections between game inputs and creative responses, while also introducing empty clues to encourage LLM for unrestrained exploration and remote association thinking. + +The second stage is explorative self-refinement which encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts under weakly-associated conditions, and selects high-quality data to train itself for self-refinement. These weakly-associated conditions can either be empty, or randomly sampled from an object noun set collected from the Oogiri-GO dataset. The former empty conditions to allow LLM to operate freely, and the latter ones help the LLM to link seemingly-unrelated and weakly-related concepts, and encourage the LLM to explore knowledge outside of traditional cognitive limitations. This exploration strategy can help generate diverse high-quality data for self-refinement. + +Experimental results show that CLoT can greatly enhance the LoT ability of LLMs like Qwen [1] and CogVLM [29] across several types of Oogiri games. Specifically, CLoT can help LLMs to generate much better humors in Fig. 1. Moreover, CLoT-integrated LLMs achieve higher quantitative performance than the corresponding vanilla and CoT-integrated LLMs across the multiple-choice and ranking questions in the Oogiri game. Also, CLoT can boost creative abilities on other tasks like "cloud guessing game" and "divergent association task" [31-33], showing its remarkable generalization ability. + +# 2. Related Works + +(1) Oogiri game (大喜利) is a general term for a series of traditional Japanese comedy games. In ancient times, there were different types of Oogiri, such as actors performing sumo wrestling, telling ghost stories, etc. The modern Oogiri game mainly refers to one specific type known as Tonchi (頓智), typically presented in the format of game shows or intellectual quiz programs [28]. Players are provided with various multimodal contents, which can be simple questions, random images, etc., and are then prompted to come up with humorous, creative responses to achieve surprising comedic effects, as the examples are shown in Fig. 3. It is worth noting that the character “頓” in both Japanese and Chinese denote “sudden”, while “智” means “intelligence, insight or intuition”. This highlights the connection between the Oogiri game and the requirement for + +strong associative abilities in LoT, making Oogiri an ideal platform for exploring LoT capabilities within LLMs. + +(2) Multimodal LLMs and their creativity. Recently, multimodal Language Models [1, 29, 34, 35] have garnered significant attention, particularly due to their impressive reasoning abilities [7-12, 36]. Moreover, there is a growing focus on exploring the creativity [37-40] of LLMs for applications such as scientific discovery [18, 41-44], creative writing [45-49], etc. + +(3) Computational humor is a branch of computational linguistics and artificial intelligence that uses computers in humor research [50], which encompasses various tasks, including humor detection [51-58], humor interpretation [58-61], and humor generation [62-66], etc. With the advancement of generative LLMs [1, 4, 29], humor generation has become a popular focus while humor generation still faces challenges such as insufficient punchlines [67] and limited in multimodal contexts [68-70]. + +(4) Chain-of-Thought based Methods provide the models with "chain of thoughts" [2, 3, 14-16], i.e., reasoning exemplars [3], or a simple prompt "Let's think step by step" [2], to encourage LLMs to engage in reasoning rather than simply providing answers directly [71]. + +
CategoryEnglishChineseJapaneseTotal
I2T17,33632,13040,27889,744
T2T6,43315,79711,84234,072
IT2T—9129,42010,332
+ +Table 1. Data distribution of the Oogiri-GO dataset. For the IT2T task, its English version is not available due to cultural preference. + +# 3. Oogiri-GO Dataset + +As introduced in Sec. 2, in the Oogiri game, the participants need to unexpectedly and humorously respond to the given images, text, or both. See three types of examples in Fig. 3. This game requests a sudden burst of insight and strong associative thinking to the given context, and provides an ideal platform to assess the leap-of-thought (LoT) ability of LLMs. Accordingly, we collect Oogiri game data to build a large-scale Oogiri-GO dataset which serves as a benchmark to evaluate and improve LoT ability. + +Specifically, Oogiri-GO is a multimodal and multilingual humor dataset, and contains more than 130,000 Oogiri samples in English, Chinese, and Japanese. Notably, in Oogiri-GO, $77.95\%$ of samples are annotated with human preferences, namely the number of likes, indicating the popularity of a response. As illustrated in Fig. 3, Oogiri-GO contains three types of Oogiri games according to the input that can be images, text, or both, and are respectively called "Text to Text" (T2T), "Image to Text" (I2T), and "Image & Text to Text" (IT2T) for brevity. See more examples in Fig. 1. Table 1 summarizes the distribution of these game types. + +![](images/115f9de2241c1d1d6ad2de6941a882e89743f9fb1632dba7de29a8291b697fc2.jpg) +Figure 4. The overview of proposed Creative Leap-of-Thought. + +For training purposes, $95\%$ of the samples are randomly selected to construct the training dataset, while the remaining $5\%$ form the test dataset for validation and analysis. + +To create the Oogiri-GO dataset, there are three main steps, including online data collection, machine filtering by LLM, and manual screening. Firstly, to collect sufficient data, we source Oogiri game data from the official Oogiri game platform, Bokete, and other popular platforms, such as Twitter and Weibo which also host some Oogiri-game-like data. Then, to guard against the inclusion of bias, violence, explicit content, offensive language, etc., we have placed a strong emphasis on rigorous safety checks during both machine and manual screening. We first use the multimodal LLM Qwen-VL [1] to do the initial screening of the raw data by constructing safety-checking prompts. Then, manual checking is performed on the remaining data. See more details about the dataset creation in the Appendix. + +# 4. Creative Leap-of-Thought (CLoT) + +To augment the Leap-of-Thought (LoT) ability in (multimodal) Large Language Models (LLMs) for creative generation, we propose a novel Creative LoT framework (CLoT). As shown in Fig. 4, CLoT relies on two LoT-boosting stages. The first one is associative instruction tuning that formulates the Oogiri-GO dataset into instruction tuning data for training an LLM to improve its LoT ability (Sec. 4.1). The second one is explorative self-refinement that encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts, and selects high-quality data to train itself for self-refinement (Sec. 4.2). Finally, we present the CLoT inference to induce the LoT ability of the trained LLM (Sec. 4.3). + +# 4.1. Associable Instruction Tuning + +LoT ability mainly includes associable generation and discrimination ability [30]. Given an input, associative generation draws its parallels with seemingly unrelated concepts via remote association and then generates innovative responses, e.g., the unexpected humor for the Oogiri input. Associable discrimination is to judge the matchiness among + +input and responses though they are seemingly unrelated, and then to select the most creative response. + +Unfortunately, both associative generation and discrimination are not present in current LLMs, e.g., poor performance of GPT4v [72] in the Oogiri game observed in Sec. 5. Moreover, it is hard to improve these two LoT abilities via popular CoT-like prompt techniques. Indeed, as shown in Sec. 5, CoT even sometimes impairs the LoT performance of the LLMs like Qwen-VL [1] in the Oogiri game. + +To address this issue, we propose associable instruction tuning which trains LoRA [73] for LLMs on the OogiriGO dataset to achieve certain associable generation and discrimination abilities. It has two steps, including instruction generation and discrimination template design, and associative instruction learning. + +(1) Instruction Generation & Discrimination Templates. We design LoT-oriented instruction templates to transform the Oogiri-GO dataset into instruction tuning data, and then train LLM to achieve associable generation and discrimination abilities. Our templates primarily comprise two components in Fig. 5: task-specific prompt and response. For different abilities, the templates need some special design. + +![](images/f4e92f5a4b61c30fb2f3da03ca7bca6d43a6238f4f6bc154d962c18a1fcc1e7c.jpg) +Figure 5. The LoT-oriented instruction templates. + +For associable generation, "USER-INPUTs" contains "Task-specific Prompt" along with two optional conditions, "Image" and "Condition". For "Task-specific Prompt", we elaborately design several templates for different types of Oogiri game. See the Appendix for details and there is an image-2-text (I2T) Oogiri example in Fig. 6. For "Image" condition, it relies on the type of Oogiri game, e.g., being the image embeddings in I2T game and empty in T2T type. For the "condition" option, it's set to empty with a probability of $\rho_{c}$ , and otherwise is randomly set as one noun in "task-specific responses". This design gives the LLM a clue to connect the game input and the correct responses while also encouraging LLM to explore and unleash its creative thinking with probability $\rho_{c}$ . Finally, "Task-specific Responses" are the ground truth responses of an Oogiri-GO data, and need to be predicted by LLM during training. This task enforces the LLM to draw parallels between seemingly unrelated concepts in inputs and responses for giving innovative responses, e.g., the humor for the Oogiri input. This associative generation ability can assist the LLM to think outside the box and learn remote association thinking. + +Regarding associable discrimination, we aim to develop fundamental LoT discrimination skills for LLM. Based on the Oogiri-GO data, we design choice questions to enhance LLM's LoT discrimination ability, i.e., selection skill. Besides, as $77.95\%$ of the Oogiri-GO data have human preference annotations, i.e., the number of likes of several re + +![](images/656c6608f80b4c86e5462f5ea6e64ac75d63df4df74d337e7fb4ef37f715bb18.jpg) +Figure 6. The details of LoT-oriented instructions templates. We take "Image to Text" as an example, see the Appendix for the details of other categories' instructions. (a) and (b) are the instruction templates with/without conditions for associable generation. (c) and (d) are the two instructions about the selection and ranking of associable discrimination. All templates follow the formats in Fig. 5. + +![](images/63beecebd6dbbe8744ab05e258fff39d4350a27b988a9089496728e380683810.jpg) + +![](images/d87022c4c0e05f8658f9fa04da4032fcc24bb2a5058b23d9881326935f077f89.jpg) + +![](images/cd0113a459e8b5457796874c70a3236c8f6e42bd1e0dfdcf3f3be7c3b1b7dcfc.jpg) + +sponses (see Sec. 3), we design ranking questions to improve another discrimination skill, i.e., ranking ability. + +For a choice question, as shown in Fig. 6 (c), the options in "Task-specific Prompt" contain the random permutations of ground truth response (GTR), image captions generated by BLIP2 [74], GTR from other images, rewrites of GTR by Qwen-14B [5]. See details in Appendix. For "task-specific responses", it is the GTR. This design is to train LLM to improve its LoT selection ability. For a ranking question, as shown in Fig. 6 (d), it is to enforce LLM to rank multiple distinct responses of a given input to match their human preferences. By training on the choice and ranking questions, LLM is encouraged to distinguish LoT responses and align human creative preferences, improving its LoT discriminative selection and ranking abilities. + +(2) Associable Instruction Learning. By using the above instruction templates, we augment the 130,000 samples in the Oogiri-GO dataset to more than 500,000 instructions whose formulation is in Fig. 5. During training, LLM is required to predict the "task-specific responses" according to the "USER-INPUTs" which include "Task-specific Prompt" and two additional optional conditions like image and text condition. To avoid over-fitting, we only train standard LoRA [73] for the LLM with the associable instruction data. See more details in Appendix. + +# 4.2. Explorative Self-Refinement + +After associable instruction tuning, we aim to generate more high-quality creative data by LLM which are then used to train LLM for self-refinement. To this end, we introduce an innovative stage called explorative self-refinement, inspired by human LoT exercise process of "remote association & self-refinement", also known as mental leap [21, 24, 30]. The remote association process refers to generating new ideas by associating remote concepts or thoughts, and self-refinement uses the generated data to enhance one's own LoT ability. In the following, we design two similar LoT exercise processes for LLM to improve its LoT ability. + +(1) Explorative Remote Association. The core here is to prompt the LLM to generate a diverse array of creative responses under weakly-associated conditions. To implement + +this, we extract a set of object nouns, denoted as $\mathcal{S}$ , from the text in the Oogiri-GO training data. See details in Appendix. Then, for each user-input $I$ (see Fig. 5), we generate $n$ weakly-associated conditions $\{C_i\}_{i=1}^n$ . These conditions can either be empty with a probability $\rho \in (0,1)$ to give freedom to LLM, or uniformly randomly sampled from the noun set $\mathcal{S}$ to enforce LLM to build connections between different concepts. Next, we add the condition $C_i$ into user-input $I$ , and feed $I$ into the LLM to generate a humor candidate $R_i$ . Repeating this process with different conditions $C_i$ can generate a total of $n$ candidates $\{R_i\}_{i=1}^n$ . + +Then the LLM ranks these candidates by its discriminative ranking ability learned in Sec. 4.1. Next, it mixes the top-2 candidates with the ground truth responses (GTR), and selects the top-1 as the final response. Finally, if the selected top-1 response is the GTR, we discard this sample. Here first filtering out low-quality responses can improve the accuracy of subsequent top-1 selection, since $(n + 1)$ -choice problem is often more challenging than 3-choice problem as shown in Sec. 5. By repeating this process, we progressively gather sufficient new high-quality data. + +The core of this approach is the weakly-associated conditions $\{C_i\}_{i=1}^n$ which can encourage the LLM to engage in remote associations. This is because the empty conditions allow LLM to operate freely, while the object noun conditions compel the LLM to draw connections between seemingly unrelated concepts. This mechanism facilitates the establishment of links between seemingly-unrelated and weakly-related concepts, encouraging the LLM to explore knowledge outside of traditional cognitive limitations. The exploration ability distinguishes our CLoT from CoT which primarily guides the LLM to exploit its inherent reasoning ability without emphasizing knowledge exploration. + +(2) Self-refinement. Here we combine the above generated instructions with vanilla instruction tuning samples in Sec. 4.1 to form a dataset with more than 550,000 samples to train our LLM again. Since the above generated data is of high diversity because of its exploration strategy, they prevent performance collapse [76, 77] during self-refinement phase, and can improve the LoT performance across several creative tasks as shown in Sec. 5. See the ablation study and + +
ModelSizeImage&Text to Text (IT2T)Image to Text (I2T)Text to Text (T2T)
3T14T15T2RankAvg.3T14T15T2RankAvg.3T14T15T2RankAvg.
GPT4v [72]-19.314.93.256.723.529.115.13.960.427.127.116.86.853.526.1
LLaVA-1.5 [34]13B13.213.713.968.127.229.322.73.960.929.233.825.24.062.631.4
MiniGPT-v2 [35]7B6.13.44.060.718.65.34.03.860.518.410.87.33.559.420.3
mPLUG-OwlMultilingual [12]7B28.126.010.564.432.219.218.66.060.526.124.422.210.760.129.4
VisualGLM-6B [75]6B24.122.59.767.430.914.320.48.861.926.413.120.27.161.325.4
Qwen-VL [1]7B30.226.010.467.733.623.223.111.962.230.123.425.013.359.630.3
Qwen-VL+Alt(Ours)7B39.738.915.767.340.4+ 6.838.830.515.762.336.8+ 6.730.628.716.762.634.6+ 4.3
Qwen-VL+CLoT(Ours)7B41.838.721.668.542.7+ 9.139.835.122.764.440.5+10.438.829.421.064.738.5+ 8.2
+ +Table 2. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on multil-modal multilingual models. mTn choice question selects $n$ correct answers from $m$ options. "Avg." is the average of all metrics. "AIT" denotes associable instruction tuning. + +
Algorithm 1 Inference Step of CLoT
Input: Input I, CLoT-trained LLM A, response number n
Output: Creative response R.
1:▷ Creating the candidate responses
2: construct n weakly-associated conditions {Ci}n{i=1}
3: {Ri}n{i=1} ← A([I, {Ci}n{i=1}])
4:▷ Choosing most creative response
5: Top-2 R1', R2' ← A([I, {Ri}n{i=1}]) with ranking ability
6: Best R ← A([I, R1', R2']) with selection ability
7: return Best response R.
+ +more discussions in Sec. 5.5. + +# 4.3. CLoT Inference + +After the two LoT-boosting phases in Sec. 4.1 and 4.2, the LLM acquires sufficient LoT ability. Now we introduce the inference steps of LLM to release its LoT ability. Formally, given an Oogiri user-input $\pmb{I}$ of the formation in Fig. 5, LLM first uses explorative remote association in Sec. 4.2 to construct $n$ weakly-associated conditions (these conditions can be empty since the training paradigm in Section 4), and then follows Sec. 4.2 to generate $n$ responses $\{R_i\}_{i=1}^n$ . Next, LLM ranks these responses by using its learned ranking skill and finally selects the top-1 one from the ranked top-2 response via its selection skill. The reason to first use ranking before selection is that as shown by experimental results in Sec. 5, directly choosing the best one from a large number of options has poor accuracy, and ranking can filter out low-quality candidates to improve the selection accuracy. See Algorithm 1 for an overview of CLoT inference steps. + +# 5. Experiments + +# 5.1. Evaluation Questions and Metrics + +Inspired by the humor benchmarks in [81], we first develop choice and ranking questions as introduced in Sec. 4.1 (see examples in Fig. 6 (c-d)), and then quantitatively evaluate the LoT ability of LLMs on the Oogiri-GO test dataset. For the choice questions, $mTn$ for short, they need LLMs to choose $n$ "leap-of-thought" humor responses from $m$ options given the input. Here we build four types of $mTn$ questions, including 2T1, 3T1, 4T1, and 5T2. 2T1 means + +two options, the ground-truth response (GTR) and an image caption generated by BLIP2 [74]. 3T1 adds unrelated answers, e.g., other image captions. 4T1 further adds the GTR rewrite by Qwen-14B [5]. 5T2 has an extra GTR. For these questions, their difficulty increases progressively, and is diverse to ensure comprehensive evaluation. For choice questions, we use accuracy as the evaluation metric. Additionally, for the questions in test set whose responses have ground-truth human preference, e.g., the number of likes, we develop the ranking questions that always rank five candidates. For evaluation, we adopt the top-1 accuracy and the widely used ranking metric, i.e., Normalized Discounted Cumulative Gain (NDCG) [82, 83]. We provide more experimental details in the Appendix. + +# 5.2. Evaluation by Choice and Ranking Questions + +Evaluation on Multimodal Multilingual LLMs. We plug our associative instruction tuning (AIT) and our CLoT into the SoTA open-source multimodal multilingual model Qwen-VL [1] to obtain Qwen- $\mathrm{VL}_{+\mathrm{AIT}}$ and Qwen- $\mathrm{VL}_{+\mathrm{CLoT}}$ , respectively. Table 2 shows that, on three tasks (IT2T, I2T and T2T) which include English, Chinese and Japanese questions, Qwen-VL achieves the best LoT performance among all baselines in most cases. In comparison, Qwen- $\mathrm{VL}_{+\mathrm{AIT}}$ achieves a noticeable improvement on the SoTA Qwen with average accuracy enhancements of $6.8\%$ , $6.7\%$ , and $4.3\%$ on the three tasks, respectively. Importantly, Qwen- $\mathrm{VL}_{+\mathrm{CLoT}}$ further enhances Qwen-VL, showing improvements of $9.1\%$ , $10.4\%$ , and $8.2\%$ in accuracy across these tasks. These results demonstrate the efficacy of the two stages in CLoT, i.e., associative instruction tuning and explorative self-refinement. + +Evaluation on Multimodal Non-multilingual LLMs. Here we integrate our CLoT with the SoTA multimodal non-multilingual model, CogVLM-17B [29], and evaluate it on the English I2T and T2T tasks. Table 3 shows that $\mathrm{CogVLM - 17B}_{+\mathrm{AIT}}$ achieves remarkable improvements over the standard $\mathrm{CogVLM - 17B}$ , and $\mathrm{CogVLM - 17B}_{+\mathrm{CLoT}}$ consistently demonstrates significantly superior performance compared to $\mathrm{CogVLM - 17B}$ . + +Evaluation on Single-Modal LLMs. Now we test LLMs that can handle only pure texts, using the English T2T task + +
ModelSizeImage to Text (I2T)Text to Text (T2T)
2T13T14T15T2RankAvg.2T13T14T15T2RankAvg.
InstructionBLIP [78]13B19.813.715.51.165.523.122.316.017.00.759.523.1
mPLUG-OwlLLaMA2 [12]7B22.312.715.04.259.922.824.213.712.63.159.222.6
Otter [79]7B15.89.98.57.161.320.53.83.34.85.458.515.1
CogVLM-17B [29]7B37.626.418.32.564.629.935.127.824.87.564.131.9
CogVLM-17B+AIT(Ours)7B57.437.433.521.864.642.9+13.155.446.526.418.264.442.2+10.3
CogVLM-17B+CLoT(Ours)7B66.947.643.430.769.451.6+21.764.852.933.621.868.648.3+16.4
+ +Table 3. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on various mulilmodal non-multilingual models (English). See notations in Table 2. We only consider I2T and T2T since English IT2T is not available due to cultural preference. + +
ModelSize3T14T15T2RankAvg.
GPT-3.5 [72]-45.330.46.761.636.0
GPT-4 [72]-49.220.43.654.732.0
LLAMA2 [4]7B18.913.51.160.423.5
13B15.620.01.860.524.5
70B27.816.13.862.027.4
Baichuan2 [80]7B28.322.611.664.631.8
13B21.718.38.961.527.6
Qwen [5]7B23.120.48.061.428.2
14B27.422.212.359.530.3
ChatGLM3 [75]6B15.617.05.459.424.3
Vicuna-v1.5 [6]7B32.623.50.063.029.8
13B30.223.02.762.229.5
Qwen-VL+CLoT(Ours)7B51.732.324.865.043.4
CogVLM-17B+CLoT(Ours)7B52.933.621.868.644.2
+ +Table 4. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on various large language models. Here we use English T2T task for test. See notations in Table 2. + +for evaluation. Table 4 also indicates the insufficient LoT ability within existing LLMs, ranging from small to large models. Fortunately, our CLoT significantly improves the LoT ability of these LLMs, as demonstrated by the notable improvement in accuracy. + +Comparison with CoT-alike Reasoning Frameworks. We also find that existing reasoning frameworks are not as effective as CLoT in enhancing LoT ability. Fig. 8 compares CLoT with CoT [2, 3], CoT-SC [84], and prompted-based LoT (PLoT) with the prompt "let's think outside the box". The results reveal that CoT-alike frameworks do not enhance LoT performance of LLMs, while CLoT demonstrates the ability to consistently enhance LLMs. + +Our experiments and analysis reveal that, unlike CoT-based methods, LoT cannot be directly achieved by prompting alone. This is because the inherent reasoning capabilities and extensive knowledge of LLMs are not sufficient to enable LoT ability. However, when trained with our proposed CLoT method, LLMs can effectively engage in a range of creative tasks. Additionally, the use of specific prompting techniques can enhance the LoT ability of CLoT-trained LLMs. These findings suggest that LoT could potentially be considered an additional general reasoning ability for LLMs that is not contained in current LLMs. + +![](images/93ba7dc25772108bb8a64619b8da5ef7ee612648ee2c04f73a49639e6b58804c.jpg) +Figure 7. User study with voting $(\%)$ for Oogiri-style creative responses by different models and improved methods. + +# 5.3. Human Evaluation + +We conduct a user preference study to test creativity of LLMs. Here we select six LLMs to generate responses for a total of eighteen questions across three tasks (IT2T, I2T and T2T). We use choice questions, and ask users to choose the most creative and humorous responses. Fig. 7 summarizes the statistical analysis of 154 valid surveys. The results show that users have a strong inclination towards selecting the results of CLoT across three tasks, highlighting the high-quality creative content generated by CLoT. See more user study details in Appendix. + +# 5.4. Evaluation on Other Creative Tasks + +To evaluate the generalization ability of CLoT, we test CLoT on another two creative tasks, including Cloud Guessing Game (CGG) and Divergent Association Task (DAT). In CGG, the LLM is to identify the shape of white clouds, and then to select the corresponding shapes from given options. For instance, the white clouds in Fig. 9 (c) has a shape of a cat, and the one in Fig. 9 (d) is similar to a human. These white cloud images are generated by a control diffusion model [31, 32, 85, 86], guided by masks shown in Fig. 9 (b). We use top-1 accuracy as metric. See more details in Appendix. For DAT, it is a classic creativity test [33, 87] which needs participants to choose words with larger semantic distances among 10 unrelated nouns. Here for test easily, we transfer the DAT benchmark [33] to a series of choice questions and take the standard average semantic distance (ASD) as a metric. These questions can challenge the LLM to select the one word from nine options that differs from the given word most. See more details in Appendix. CGG and DAT can test the LoT ability of LLMs, specifically their remote association thinking ability, + +![](images/ad4ccd4921cee3c2d8368978a0c0b30dbd2030ea75df1d8d30fc777bcb808d2e.jpg) +Figure 8. The accuracy $(\%)$ of choice questions and the NDCG $(\%)$ of ranking questions on our CLoT and various reasoning frameworks. The baseline is Qwen-VL on multilingual I2T task. For $mTn$ choice questions, one needs to select $n$ correct answers from $m$ options. + +![](images/945cadf00ecea58f84a7f0b6251a1d3116ce04ff5d50823a61b0ce5aa34cc0e9.jpg) + +![](images/3605fab232944da02d04d77d1d13dcc663a13a149e921c6c1aa5225493f63256.jpg) + +![](images/fbfcdfc05caba4a497f6930f2c1aa50ab065728c20ba1325a90a0e799cc0bb2c.jpg) + +![](images/454e67bd787a32b5be4f4acd03015ed7c10f3513c6460947820cf22801e6f9bb.jpg) + +![](images/988142eb1d9aa3591b54ba23ba850ad81d0be793a0652d6b1f7ded5a5f7859e1.jpg) +Figure 9. Evaluation of CLoT on the creative CGG (e) and DAT (f) tasks. (c-d): examples of cloud guessing games. (b): conditional masks of image (a) for generating cloud images. + +![](images/c1a9f07fc95283174686b870c6123ea40c5afe8b728b34f49f34296d4125a930.jpg) + +and provide quite different evaluation platforms. As shown in Fig. 9 (e-f), CLoT can also significantly enhance the performance of the SoTA Qwen-VL on both CGG and DAT tasks. Specifically, CLoT-integrated Qwen-VL improves the vanilla Qwen-VL by about $8\%$ on the CGG task and $5\%$ on the DAT task. These results well demonstrate the good generalization and transferability of CLoT. + +# 5.5. Ablation Study + +Weakly-associated Conditions. By default, to encourage remote association, we use weakly-associated conditions randomly sampled from the noun set on the whole dataset in Sec. 4.2. To verify the effectiveness of weakly-associated conditions, now we resort to strongly-associated conditions sampled from the noun set of the current image caption. Results in Fig. 10 (Left) show that using weakly-associated conditions is superior and more conducive to fostering the creativity of LLMs. The weakly-associated conditions enable the LLM to generate more diverse LoT responses, while the strong clue from the strongly-associated conditions limit the diversity of LoT generations. + +Round of Self-refinement. By default, we run one-round self-refinement for the Oogiri game. Here we explore whether more rounds of the self-refinement can further improve the LoT ability. Fig. 10 (Right) shows that a single round of self-refinement already yields promising performance, whereas additional rounds do not yield significant further improvements. As shown in Fig. 10 (Left), the diversity of the condition set $\mathcal{S}$ is crucial to self-refinement, since + +![](images/f38f0db91012536c4fcd339eba26b85260d5be2177e8e272e2fe14337567bb7b.jpg) +Figure 10. The ablation study of CLoT. We use CogVLM as baseline on the English I2T task. Left: weakly-associated condition v.s. strongly-associated condition during explorative remote association. Right: The effect of rounds of self-refinement. + +![](images/7f4b62c5f9ae11c6cabd4439192523065874bf7873b1c26041db48845511e20a.jpg) + +it decides whether the associable remote stage can generate high quality and diverse data. However, the condition set $\mathcal{S}$ is not expanded during the second-round self-refinement, which consequently limits further improvements in performance. Effectively increasing the scale of the condition set is an effective way for further improvement. See more discussion in Appendix. But its exploration falls outside the scope of this work and is left for our future research. + +# 6. Conclusion + +In this paper, we propose a Creative Leap-of-Thought (CLoT) paradigm to improve LLM's leap-of-thought (LoT) ability. CLoT first collects a multimodal Oogiri-GO dataset, and formulates it into instruction tuning data to train LLM to improve its LoT ability. Then CLoT designs an explorative self-refinement that lets LLM generate more creative LoT data via exploring parallels among different concepts and selects high-quality data to train itself for self-refinement. Experimental results show the effectiveness and generalization ability of CLoT across several creative tasks. + +# 7. Acknowledgments + +This work was supported by National Science and Technology Major Project (No.2021ZD0111601), National Natural Science Foundation of China (No.62325605, U1711264), and Guangdong Basic and Applied Basic Research Foundation (No.2023A1515011374), and Guangzhou Science and Technology Program (No.2024A04J6365), and Guangdong Province Key Laboratory of Information Security Technology. Pan Zhou acknowledges support from the Singapore Ministry of Education (MOE) Academic Research Fund (AcRF) Tier 1 grant. + +# References + +[1] Jinze Bai, Shuai Bai, Shusheng Yang, Shijie Wang, Sinan Tan, Peng Wang, Junyang Lin, Chang Zhou, and Jingren Zhou. 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} + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 45, + 544, + 547, + 601 + ], + "lines": [ + { + "bbox": [ + 45, + 544, + 547, + 601 + ], + "spans": [ + { + "bbox": [ + 45, + 544, + 547, + 601 + ], + "type": "text", + "content": "Figure 1. Comparison between (multimodal) large language model (LLM, red) and its CLoT-integrated version (blue) for Oogiri-style multimodal humor generation. According to the model input that can be image, text or both, there are three Oogiri tasks, \"Image&Text to Text (IT2T)\", \"Image to Text (I2T)\", and \"Text to Text (T2T)\", where text can be English (EN), Chinese (CN), and Japanese (JP). \"@\" denotes translations. The baseline LLM is Qwen-VL [1]. While humor is subjective, these examples demonstrate CLoT's leap-of-thought capacity of using excellent creative thinking to produce high-quality humor responses. See more examples in Appendix." + } + ] + } + ], + "index": 64, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "bbox": [ + 118, + 451, + 204, + 471 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 118, + 451, + 204, + 471 + ], + "spans": [ + { + "bbox": [ + 118, + 451, + 204, + 471 + ], + "type": "text", + "content": "(CN) ①求婚者 ②被求婚者 ③" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 119, + 473, + 196, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 119, + 473, + 196, + 483 + ], + "spans": [ + { + "bbox": [ + 119, + 473, + 196, + 483 + ], + "type": "text", + "content": "@①Proposer②Proposee③?" + } + ] + } + ], + "index": 17 + }, + { + "type": "image", + "bbox": [ + 119, + 495, + 138, + 506 + ], + "blocks": [ + { + "bbox": [ + 119, + 495, + 138, + 506 + ], + "lines": [ + { + "bbox": [ + 119, + 495, + 138, + 506 + ], + "spans": [ + { + "bbox": [ + 119, + 495, + 138, + 506 + ], + "type": "image", + "image_path": 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Going to the pet hospital now for a neutering surgery!?" + } + ] + } + ], + "index": 41 + }, + { + "type": "image", + "bbox": [ + 349, + 514, + 364, + 529 + ], + "blocks": [ + { + "bbox": [ + 349, + 514, + 364, + 529 + ], + "lines": [ + { + "bbox": [ + 349, + 514, + 364, + 529 + ], + "spans": [ + { + "bbox": [ + 349, + 514, + 364, + 529 + ], + "type": "image", + "image_path": "929e3f229f02ae223cf8c65a0a783201f24b6b12e24065d509359944fc0f42f2.jpg" + } + ] + } + ], + "index": 42, + "angle": 0, + "type": "image_body" + } + ], + "index": 42 + }, + { + "bbox": [ + 417, + 251, + 485, + 262 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 417, + 251, + 485, + 262 + ], + "spans": [ + { + "bbox": [ + 417, + 251, + 485, + 262 + ], + "type": "text", + "content": "Text to Text (T2T)" + } + ] + } + ], + "index": 43 + }, + { + "bbox": [ + 381, + 270, + 501, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 381, + 270, + 501, + 289 + ], + "spans": [ + { + 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完成一篇论文其实很快乐" + } + ] + } + ], + "index": 58 + }, + { + "bbox": [ + 381, + 489, + 495, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 381, + 489, + 495, + 496 + ], + "spans": [ + { + "bbox": [ + 381, + 489, + 495, + 496 + ], + "type": "text", + "content": "@ Completing a paper is actually very enjoyable." + } + ] + } + ], + "index": 59 + }, + { + "type": "image", + "bbox": [ + 505, + 486, + 521, + 501 + ], + "blocks": [ + { + "bbox": [ + 505, + 486, + 521, + 501 + ], + "lines": [ + { + "bbox": [ + 505, + 486, + 521, + 501 + ], + "spans": [ + { + "bbox": [ + 505, + 486, + 521, + 501 + ], + "type": "image", + "image_path": "e44220eef6a3d516f209231f6ecf97df24a7b1d02593cd2b8723aa353aa5e3d3.jpg" + } + ] + } + ], + "index": 60, + "angle": 0, + "type": "image_body" + } + ], + "index": 60 + }, + { + "bbox": [ + 381, + 506, + 487, + 516 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 381, + 506, + 487, + 516 + ], + "spans": [ + { + "bbox": [ + 381, + 506, + 487, + 516 + ], + "type": "text", + "content": "(CN) 不辛苦,辛苦的是我的导师" + } + ] + } + ], + "index": 61 + }, + { + "bbox": [ + 381, + 517, + 488, + 525 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 381, + 517, + 488, + 525 + ], + "spans": [ + { + "bbox": [ + 381, + 517, + 488, + 525 + ], + "type": "text", + "content": "@ Not for me, but it's hard for my supervisor." + } + ] + } + ], + "index": 62 + }, + { + "type": "image", + "bbox": [ + 504, + 514, + 521, + 529 + ], + "blocks": [ + { + "bbox": [ + 504, + 514, + 521, + 529 + ], + "lines": [ + { + "bbox": [ + 504, + 514, + 521, + 529 + ], + "spans": [ + { + "bbox": [ + 504, + 514, + 521, + 529 + ], + "type": "image", + "image_path": "3dca93164eb197c856254a4275df2a87a1f8d3b2e19bf3107e34b2ac54aa4af3.jpg" + } + ] + } + ], + "index": 63, + "angle": 0, + "type": "image_body" + } + ], + "index": 63 + }, + { + "bbox": [ + 143, + 610, + 192, + 623 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 610, + 192, + 623 + ], + "spans": [ + { + "bbox": [ + 143, + 610, + 192, + 623 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 65 + }, + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 713 + ], + "type": "text", + "content": "Chain-of-Thought (CoT) [2, 3] guides large language models (LLMs) to reason step-by-step, and can motivate their logical reasoning ability. While effective for logical tasks, CoT is not conducive to creative problem-solving which often requires out-of-box thoughts and is crucial for innovation advancements. In this paper, we explore the Leap-of-Thought (LoT) abilities within LLMs — a non-" + } + ] + } + ], + "index": 66 + }, + { + "bbox": [ + 304, + 612, + 547, + 708 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 612, + 547, + 708 + ], + "spans": [ + { + "bbox": [ + 304, + 612, + 547, + 708 + ], + "type": "text", + "content": "sequential, creative paradigm involving strong associations and knowledge leaps. To this end, we study LLMs on the popular Oogiri game which needs participants to have good creativity and strong associative thinking for responding unexpectedly and humorously to the given image, text, or both, and thus is suitable for LoT study. Then to investigate LLMs' LoT ability in the Oogiri game, we first build a multimodal and multilingual Oogiri-GO dataset which con" + } + ] + } + ], + "index": 67 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "13246" + } + ] + } + ], + "index": 68 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 301 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 301 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 301 + ], + "type": "text", + "content": "tains over 130,000 samples from the Oogiri game, and observe the insufficient LoT ability or failures of most existing LLMs on the Oogiri game. Accordingly, we introduce a creative Leap-of-Thought (CLoT) paradigm to improve LLM's LoT ability. CLoT first formulates the Oogiri-GO dataset into LoT-oriented instruction tuning data to train pretrained LLM for achieving certain LoT humor generation and discrimination abilities. Then CLoT designs an explorative self-refinement that encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts and selects high-quality data to train itself for self-refinement. CLoT not only excels in humor generation in the Oogiri game as shown in Fig. 1 but also boosts creative abilities in various tasks like \"cloud guessing game\" and \"divergent association task\". These findings advance our understanding and offer a pathway to improve LLMs' creative capacities for innovative applications across domains. The dataset, code, and models have been released online: https://zhongshsh.github.io/CLoT." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 306, + 128, + 319 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 306, + 128, + 319 + ], + "spans": [ + { + "bbox": [ + 47, + 306, + 128, + 319 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 327, + 287, + 495 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 327, + 287, + 495 + ], + "spans": [ + { + "bbox": [ + 46, + 327, + 287, + 495 + ], + "type": "text", + "content": "Large language models (LLMs) [4-13] have catalyzed a transformative era in problem-solving abilities, revolutionizing various domains within artificial intelligence. The advent of the Chain-of-Thought (CoT) paradigm [3] and its further enhancements [2, 14-16] have equipped these LLMs with a human-like step-by-step reasoning capacity. This augmentation has enabled LLMs to excel in intricate reasoning tasks spanning from language comprehension to visual understanding. As shown in Fig. 2 (Left), CoT instills LLMs with a sequential thinking process wherein each subsequent thought builds upon the previous one. This paradigm enhances the precision and rigor in logical processing, making it exceedingly effective for problems that demand closely linked logical reasoning." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 497, + 288, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 497, + 288, + 700 + ], + "spans": [ + { + "bbox": [ + 46, + 497, + 288, + 700 + ], + "type": "text", + "content": "However, the sequential nature of CoT might fall short in nurturing creativity and innovation, potentially limiting solutions in creative problem-solving scenarios [17, 18]. For instance, proving an algebraic inequality often follows a step-by-step CoT process that progresses from one inequality to the next. Yet, an intuitive flash, e.g., a geometric interpretation, can yield a more creative solution. This type of insight, known as \"Leap-of-Thought\" (LoT) [19, 20], a.k.a. mental leap [21-24]—the art of non-sequential thinking by association, drawing parallels between seemingly unrelated concepts, and facilitating a \"leap\" of knowledge transfer. In contrast to CoT reasoning, LoT as depicted in Fig. 2 (Right), fosters associative reasoning and encourages thinking outside the box, which bridges disparate ideas and facilitates conceptual leaps. Embracing LLMs with a strong LoT ability can unlock significant potential for innovation, contributing to advancements in creative applications." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 59, + 701, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 701, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 59, + 701, + 287, + 713 + ], + "type": "text", + "content": "In this paper, we aim to initially explore and enhance the" + } + ] + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 319, + 74, + 419, + 124 + ], + "blocks": [ + { + "bbox": [ + 319, + 74, + 419, + 124 + ], + "lines": [ + { + "bbox": [ + 319, + 74, + 419, + 124 + ], + "spans": [ + { + "bbox": [ + 319, + 74, + 419, + 124 + ], + "type": "image", + "image_path": "ce4d1416dba78d56d9ae78f62670046c27fa2380efd5684481522dd20fcd4b06.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 433, + 74, + 533, + 124 + ], + "blocks": [ + { + "bbox": [ + 433, + 74, + 533, + 124 + ], + "lines": [ + { + "bbox": [ + 433, + 74, + 533, + 124 + ], + "spans": [ + { + "bbox": [ + 433, + 74, + 533, + 124 + ], + "type": "image", + "image_path": "77b4f81e9935d793d97abb64de157c2fd268113d96c167e6962dfc0d05d5ca03.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 320, + 163, + 402, + 254 + ], + "blocks": [ + { + "bbox": [ + 305, + 137, + 545, + 160 + ], + "lines": [ + { + "bbox": [ + 305, + 137, + 545, + 160 + ], + "spans": [ + { + "bbox": [ + 305, + 137, + 545, + 160 + ], + "type": "text", + "content": "Figure 2. Comparison of CoT and LoT. “" + }, + { + "bbox": [ + 305, + 137, + 545, + 160 + ], + "type": "inline_equation", + "content": "\\bigcirc" + }, + { + "bbox": [ + 305, + 137, + 545, + 160 + ], + "type": "text", + "content": "” denotes the thought and “" + }, + { + "bbox": [ + 305, + 137, + 545, + 160 + ], + "type": "inline_equation", + "content": "\\rightarrow" + }, + { + "bbox": [ + 305, + 137, + 545, + 160 + ], + "type": "text", + "content": "” represents the connection between two thoughts." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 320, + 163, + 402, + 254 + ], + "lines": [ + { + "bbox": [ + 320, + 163, + 402, + 254 + ], + "spans": [ + { + "bbox": [ + 320, + 163, + 402, + 254 + ], + "type": "image", + "image_path": "b8ed2352ab5d0669e4cbb2c6fee2b7b63255733d83960a0004a60418aadb6ea0.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 403, + 163, + 479, + 253 + ], + "blocks": [ + { + "bbox": [ + 403, + 163, + 479, + 253 + ], + "lines": [ + { + "bbox": [ + 403, + 163, + 479, + 253 + ], + "spans": [ + { + "bbox": [ + 403, + 163, + 479, + 253 + ], + "type": "image", + "image_path": "abdf5574cf2356069b6138ee1980df427a84cbf2570ebab3262f42bc6d338384.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 263, + 545, + 307 + ], + "lines": [ + { + "bbox": [ + 305, + 263, + 545, + 307 + ], + "spans": [ + { + "bbox": [ + 305, + 263, + 545, + 307 + ], + "type": "text", + "content": "Figure 3. Examples of the three types of LoT-based Oogiri games. Players are required to make surprising and creative humorous responses (blue box) to the given multimodal information e.g., images, text, or both." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 481, + 164, + 532, + 251 + ], + "blocks": [ + { + "bbox": [ + 481, + 164, + 532, + 251 + ], + "lines": [ + { + "bbox": [ + 481, + 164, + 532, + 251 + ], + "spans": [ + { + "bbox": [ + 481, + 164, + 532, + 251 + ], + "type": "image", + "image_path": "d81e82f8ba942c0d806c691b9ecee58d55993e42ec09f145a04e9e023e0cbd1b.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 319, + 546, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 319, + 546, + 521 + ], + "spans": [ + { + "bbox": [ + 304, + 319, + 546, + 521 + ], + "type": "text", + "content": "LoT ability of LLMs. However, thoroughly assessing LoT is challenging due to the complexity of measuring creative thinking [25-27] and the difficulty in gathering pertinent data, since generating novel ideas is challenging, even for humans [17]. Given these constraints, we propose studying LoT in LLMs through the lens of Oogiri-style humor generation. Oogiri, a traditional Japanese creative game [28], requires participants to provide unexpected and humorous responses to prompts in the form of images, text, or a combination of both, as shown in Fig. 3. This game challenges LLMs to demonstrate a sudden burst of insight and strong associative thinking, presenting a unique challenge for CoT-based methods, making it an ideal testbed for assessing the leap-of-thought abilities of LLMs. Moreover, the extensive online presence of Oogiri guarantees a wealth of human-generated creative content, ideal for compiling an expansive leap-of-thought dataset." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 522, + 547, + 701 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 522, + 547, + 701 + ], + "spans": [ + { + "bbox": [ + 304, + 522, + 547, + 701 + ], + "type": "text", + "content": "To investigate the LoT ability of LLMs in the Oogiri game, we present the multilingual and multimodal Oogiri-GO dataset which comprises more than 130,000 high-quality Oogiri samples in English, Chinese, and Japanese, and curated to prompt textual humor in response to inputs that can be images, text, or both. Through extensive experiments, we discover that even the advanced LLMs and reasoning frameworks [2, 4, 6, 29], such as GPT-4 and CoT, despite their exceptional reasoning capabilities, possessing a rich prior knowledge of diverse forms of humor [2], still struggle to exhibit sufficient LoT ability for creative humor generation. Moreover, directly fine-tuning LLMs on the Oogiri-GO is not easy to improve the LoT ability. The more efficient utilization of humorous knowledge is needed to help LLM elicit creative responses." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 317, + 702, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 702, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 317, + 702, + 545, + 714 + ], + "type": "text", + "content": "Motivated by the human mental leap exercise process" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13247" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": "of \"remote association & self-refinement\" [30], to enable LLMs with strong LoT ability for creation, we propose the Creative Leap-of-Thought (CLoT) paradigm which relies on two LoT-boosting stages. The first one is the associable instruction tuning stage which designs an associative instruction template to formulate the Oogiri-GO dataset into instruction data and trains an LLM to improve its LoT ability. The core here is the instruction template with a dual purpose: it randomly provides LLM with clues to establish connections between game inputs and creative responses, while also introducing empty clues to encourage LLM for unrestrained exploration and remote association thinking." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 216, + 289, + 371 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 216, + 289, + 371 + ], + "spans": [ + { + "bbox": [ + 46, + 216, + 289, + 371 + ], + "type": "text", + "content": "The second stage is explorative self-refinement which encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts under weakly-associated conditions, and selects high-quality data to train itself for self-refinement. These weakly-associated conditions can either be empty, or randomly sampled from an object noun set collected from the Oogiri-GO dataset. The former empty conditions to allow LLM to operate freely, and the latter ones help the LLM to link seemingly-unrelated and weakly-related concepts, and encourage the LLM to explore knowledge outside of traditional cognitive limitations. This exploration strategy can help generate diverse high-quality data for self-refinement." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 372, + 289, + 504 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 372, + 289, + 504 + ], + "spans": [ + { + "bbox": [ + 46, + 372, + 289, + 504 + ], + "type": "text", + "content": "Experimental results show that CLoT can greatly enhance the LoT ability of LLMs like Qwen [1] and CogVLM [29] across several types of Oogiri games. Specifically, CLoT can help LLMs to generate much better humors in Fig. 1. Moreover, CLoT-integrated LLMs achieve higher quantitative performance than the corresponding vanilla and CoT-integrated LLMs across the multiple-choice and ranking questions in the Oogiri game. Also, CLoT can boost creative abilities on other tasks like \"cloud guessing game\" and \"divergent association task\" [31-33], showing its remarkable generalization ability." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 514, + 139, + 526 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 514, + 139, + 526 + ], + "spans": [ + { + "bbox": [ + 47, + 514, + 139, + 526 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 533, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 533, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 533, + 289, + 714 + ], + "type": "text", + "content": "(1) Oogiri game (大喜利) is a general term for a series of traditional Japanese comedy games. In ancient times, there were different types of Oogiri, such as actors performing sumo wrestling, telling ghost stories, etc. The modern Oogiri game mainly refers to one specific type known as Tonchi (頓智), typically presented in the format of game shows or intellectual quiz programs [28]. Players are provided with various multimodal contents, which can be simple questions, random images, etc., and are then prompted to come up with humorous, creative responses to achieve surprising comedic effects, as the examples are shown in Fig. 3. It is worth noting that the character “頓” in both Japanese and Chinese denote “sudden”, while “智” means “intelligence, insight or intuition”. This highlights the connection between the Oogiri game and the requirement for" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 545, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 96 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 96 + ], + "type": "text", + "content": "strong associative abilities in LoT, making Oogiri an ideal platform for exploring LoT capabilities within LLMs." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 97, + 547, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 97, + 547, + 180 + ], + "spans": [ + { + "bbox": [ + 304, + 97, + 547, + 180 + ], + "type": "text", + "content": "(2) Multimodal LLMs and their creativity. Recently, multimodal Language Models [1, 29, 34, 35] have garnered significant attention, particularly due to their impressive reasoning abilities [7-12, 36]. Moreover, there is a growing focus on exploring the creativity [37-40] of LLMs for applications such as scientific discovery [18, 41-44], creative writing [45-49], etc." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 182, + 547, + 289 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 182, + 547, + 289 + ], + "spans": [ + { + "bbox": [ + 304, + 182, + 547, + 289 + ], + "type": "text", + "content": "(3) Computational humor is a branch of computational linguistics and artificial intelligence that uses computers in humor research [50], which encompasses various tasks, including humor detection [51-58], humor interpretation [58-61], and humor generation [62-66], etc. With the advancement of generative LLMs [1, 4, 29], humor generation has become a popular focus while humor generation still faces challenges such as insufficient punchlines [67] and limited in multimodal contexts [68-70]." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 290, + 547, + 350 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 290, + 547, + 350 + ], + "spans": [ + { + "bbox": [ + 304, + 290, + 547, + 350 + ], + "type": "text", + "content": "(4) Chain-of-Thought based Methods provide the models with \"chain of thoughts\" [2, 3, 14-16], i.e., reasoning exemplars [3], or a simple prompt \"Let's think step by step\" [2], to encourage LLMs to engage in reasoning rather than simply providing answers directly [71]." + } + ] + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 326, + 356, + 529, + 409 + ], + "blocks": [ + { + "bbox": [ + 326, + 356, + 529, + 409 + ], + "lines": [ + { + "bbox": [ + 326, + 356, + 529, + 409 + ], + "spans": [ + { + "bbox": [ + 326, + 356, + 529, + 409 + ], + "type": "table", + "html": "
CategoryEnglishChineseJapaneseTotal
I2T17,33632,13040,27889,744
T2T6,43315,79711,84234,072
IT2T—9129,42010,332
", + "image_path": "a7b800e02cc9a1f104546ae6d18de6c5b52338af243cf6b5cbb68ea65cc17dc4.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 417, + 547, + 440 + ], + "lines": [ + { + "bbox": [ + 304, + 417, + 547, + 440 + ], + "spans": [ + { + "bbox": [ + 304, + 417, + 547, + 440 + ], + "type": "text", + "content": "Table 1. Data distribution of the Oogiri-GO dataset. For the IT2T task, its English version is not available due to cultural preference." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 305, + 453, + 421, + 466 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 453, + 421, + 466 + ], + "spans": [ + { + "bbox": [ + 305, + 453, + 421, + 466 + ], + "type": "text", + "content": "3. Oogiri-GO Dataset" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 473, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 545, + 581 + ], + "type": "text", + "content": "As introduced in Sec. 2, in the Oogiri game, the participants need to unexpectedly and humorously respond to the given images, text, or both. See three types of examples in Fig. 3. This game requests a sudden burst of insight and strong associative thinking to the given context, and provides an ideal platform to assess the leap-of-thought (LoT) ability of LLMs. Accordingly, we collect Oogiri game data to build a large-scale Oogiri-GO dataset which serves as a benchmark to evaluate and improve LoT ability." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": "Specifically, Oogiri-GO is a multimodal and multilingual humor dataset, and contains more than 130,000 Oogiri samples in English, Chinese, and Japanese. Notably, in Oogiri-GO, " + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "inline_equation", + "content": "77.95\\%" + }, + { + "bbox": [ + 304, + 582, + 547, + 715 + ], + "type": "text", + "content": " of samples are annotated with human preferences, namely the number of likes, indicating the popularity of a response. As illustrated in Fig. 3, Oogiri-GO contains three types of Oogiri games according to the input that can be images, text, or both, and are respectively called \"Text to Text\" (T2T), \"Image to Text\" (I2T), and \"Image & Text to Text\" (IT2T) for brevity. See more examples in Fig. 1. Table 1 summarizes the distribution of these game types." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "13248" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 61, + 71, + 274, + 204 + ], + "blocks": [ + { + "bbox": [ + 61, + 71, + 274, + 204 + ], + "lines": [ + { + "bbox": [ + 61, + 71, + 274, + 204 + ], + "spans": [ + { + "bbox": [ + 61, + 71, + 274, + 204 + ], + "type": "image", + "image_path": "115f9de2241c1d1d6ad2de6941a882e89743f9fb1632dba7de29a8291b697fc2.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 49, + 212, + 282, + 224 + ], + "lines": [ + { + "bbox": [ + 49, + 212, + 282, + 224 + ], + "spans": [ + { + "bbox": [ + 49, + 212, + 282, + 224 + ], + "type": "text", + "content": "Figure 4. The overview of proposed Creative Leap-of-Thought." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 226, + 287, + 262 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 226, + 287, + 262 + ], + "spans": [ + { + "bbox": [ + 47, + 226, + 287, + 262 + ], + "type": "text", + "content": "For training purposes, " + }, + { + "bbox": [ + 47, + 226, + 287, + 262 + ], + "type": "inline_equation", + "content": "95\\%" + }, + { + "bbox": [ + 47, + 226, + 287, + 262 + ], + "type": "text", + "content": " of the samples are randomly selected to construct the training dataset, while the remaining " + }, + { + "bbox": [ + 47, + 226, + 287, + 262 + ], + "type": "inline_equation", + "content": "5\\%" + }, + { + "bbox": [ + 47, + 226, + 287, + 262 + ], + "type": "text", + "content": " form the test dataset for validation and analysis." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 262, + 287, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 262, + 287, + 430 + ], + "spans": [ + { + "bbox": [ + 46, + 262, + 287, + 430 + ], + "type": "text", + "content": "To create the Oogiri-GO dataset, there are three main steps, including online data collection, machine filtering by LLM, and manual screening. Firstly, to collect sufficient data, we source Oogiri game data from the official Oogiri game platform, Bokete, and other popular platforms, such as Twitter and Weibo which also host some Oogiri-game-like data. Then, to guard against the inclusion of bias, violence, explicit content, offensive language, etc., we have placed a strong emphasis on rigorous safety checks during both machine and manual screening. We first use the multimodal LLM Qwen-VL [1] to do the initial screening of the raw data by constructing safety-checking prompts. Then, manual checking is performed on the remaining data. See more details about the dataset creation in the Appendix." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 437, + 238, + 450 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 437, + 238, + 450 + ], + "spans": [ + { + "bbox": [ + 47, + 437, + 238, + 450 + ], + "type": "text", + "content": "4. Creative Leap-of-Thought (CLoT)" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 457, + 287, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 457, + 287, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 457, + 287, + 613 + ], + "type": "text", + "content": "To augment the Leap-of-Thought (LoT) ability in (multimodal) Large Language Models (LLMs) for creative generation, we propose a novel Creative LoT framework (CLoT). As shown in Fig. 4, CLoT relies on two LoT-boosting stages. The first one is associative instruction tuning that formulates the Oogiri-GO dataset into instruction tuning data for training an LLM to improve its LoT ability (Sec. 4.1). The second one is explorative self-refinement that encourages the LLM to generate more creative LoT data via exploring parallels between seemingly unrelated concepts, and selects high-quality data to train itself for self-refinement (Sec. 4.2). Finally, we present the CLoT inference to induce the LoT ability of the trained LLM (Sec. 4.3)." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 622, + 211, + 635 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 622, + 211, + 635 + ], + "spans": [ + { + "bbox": [ + 47, + 622, + 211, + 635 + ], + "type": "text", + "content": "4.1. Associable Instruction Tuning" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 287, + 713 + ], + "type": "text", + "content": "LoT ability mainly includes associable generation and discrimination ability [30]. Given an input, associative generation draws its parallels with seemingly unrelated concepts via remote association and then generates innovative responses, e.g., the unexpected humor for the Oogiri input. Associable discrimination is to judge the matchiness among" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 72, + 545, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 545, + 95 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 545, + 95 + ], + "type": "text", + "content": "input and responses though they are seemingly unrelated, and then to select the most creative response." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 96, + 545, + 179 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 96, + 545, + 179 + ], + "spans": [ + { + "bbox": [ + 304, + 96, + 545, + 179 + ], + "type": "text", + "content": "Unfortunately, both associative generation and discrimination are not present in current LLMs, e.g., poor performance of GPT4v [72] in the Oogiri game observed in Sec. 5. Moreover, it is hard to improve these two LoT abilities via popular CoT-like prompt techniques. Indeed, as shown in Sec. 5, CoT even sometimes impairs the LoT performance of the LLMs like Qwen-VL [1] in the Oogiri game." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 180, + 545, + 251 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 180, + 545, + 251 + ], + "spans": [ + { + "bbox": [ + 304, + 180, + 545, + 251 + ], + "type": "text", + "content": "To address this issue, we propose associable instruction tuning which trains LoRA [73] for LLMs on the OogiriGO dataset to achieve certain associable generation and discrimination abilities. It has two steps, including instruction generation and discrimination template design, and associative instruction learning." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 251, + 545, + 335 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 251, + 545, + 335 + ], + "spans": [ + { + "bbox": [ + 305, + 251, + 545, + 335 + ], + "type": "text", + "content": "(1) Instruction Generation & Discrimination Templates. We design LoT-oriented instruction templates to transform the Oogiri-GO dataset into instruction tuning data, and then train LLM to achieve associable generation and discrimination abilities. Our templates primarily comprise two components in Fig. 5: task-specific prompt and response. For different abilities, the templates need some special design." + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 336, + 339, + 503, + 372 + ], + "blocks": [ + { + "bbox": [ + 336, + 339, + 503, + 372 + ], + "lines": [ + { + "bbox": [ + 336, + 339, + 503, + 372 + ], + "spans": [ + { + "bbox": [ + 336, + 339, + 503, + 372 + ], + "type": "image", + "image_path": "f4e92f5a4b61c30fb2f3da03ca7bca6d43a6238f4f6bc154d962c18a1fcc1e7c.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 335, + 376, + 515, + 387 + ], + "lines": [ + { + "bbox": [ + 335, + 376, + 515, + 387 + ], + "spans": [ + { + "bbox": [ + 335, + 376, + 515, + 387 + ], + "type": "text", + "content": "Figure 5. The LoT-oriented instruction templates." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 390, + 545, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 390, + 545, + 641 + ], + "spans": [ + { + "bbox": [ + 304, + 390, + 545, + 641 + ], + "type": "text", + "content": "For associable generation, \"USER-INPUTs\" contains \"Task-specific Prompt\" along with two optional conditions, \"Image\" and \"Condition\". For \"Task-specific Prompt\", we elaborately design several templates for different types of Oogiri game. See the Appendix for details and there is an image-2-text (I2T) Oogiri example in Fig. 6. For \"Image\" condition, it relies on the type of Oogiri game, e.g., being the image embeddings in I2T game and empty in T2T type. For the \"condition\" option, it's set to empty with a probability of " + }, + { + "bbox": [ + 304, + 390, + 545, + 641 + ], + "type": "inline_equation", + "content": "\\rho_{c}" + }, + { + "bbox": [ + 304, + 390, + 545, + 641 + ], + "type": "text", + "content": ", and otherwise is randomly set as one noun in \"task-specific responses\". This design gives the LLM a clue to connect the game input and the correct responses while also encouraging LLM to explore and unleash its creative thinking with probability " + }, + { + "bbox": [ + 304, + 390, + 545, + 641 + ], + "type": "inline_equation", + "content": "\\rho_{c}" + }, + { + "bbox": [ + 304, + 390, + 545, + 641 + ], + "type": "text", + "content": ". Finally, \"Task-specific Responses\" are the ground truth responses of an Oogiri-GO data, and need to be predicted by LLM during training. This task enforces the LLM to draw parallels between seemingly unrelated concepts in inputs and responses for giving innovative responses, e.g., the humor for the Oogiri input. This associative generation ability can assist the LLM to think outside the box and learn remote association thinking." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 642, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 545, + 712 + ], + "type": "text", + "content": "Regarding associable discrimination, we aim to develop fundamental LoT discrimination skills for LLM. Based on the Oogiri-GO data, we design choice questions to enhance LLM's LoT discrimination ability, i.e., selection skill. Besides, as " + }, + { + "bbox": [ + 304, + 642, + 545, + 712 + ], + "type": "inline_equation", + "content": "77.95\\%" + }, + { + "bbox": [ + 304, + 642, + 545, + 712 + ], + "type": "text", + "content": " of the Oogiri-GO data have human preference annotations, i.e., the number of likes of several re" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13249" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 85, + 171, + 171 + ], + "blocks": [ + { + "bbox": [ + 51, + 85, + 171, + 171 + ], + "lines": [ + { + "bbox": [ + 51, + 85, + 171, + 171 + ], + "spans": [ + { + "bbox": [ + 51, + 85, + 171, + 171 + ], + "type": "image", + "image_path": "656c6608f80b4c86e5462f5ea6e64ac75d63df4df74d337e7fb4ef37f715bb18.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 182, + 547, + 217 + ], + "lines": [ + { + "bbox": [ + 46, + 182, + 547, + 217 + ], + "spans": [ + { + "bbox": [ + 46, + 182, + 547, + 217 + ], + "type": "text", + "content": "Figure 6. The details of LoT-oriented instructions templates. We take \"Image to Text\" as an example, see the Appendix for the details of other categories' instructions. (a) and (b) are the instruction templates with/without conditions for associable generation. (c) and (d) are the two instructions about the selection and ranking of associable discrimination. All templates follow the formats in Fig. 5." + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 173, + 85, + 296, + 171 + ], + "blocks": [ + { + "bbox": [ + 173, + 85, + 296, + 171 + ], + "lines": [ + { + "bbox": [ + 173, + 85, + 296, + 171 + ], + "spans": [ + { + "bbox": [ + 173, + 85, + 296, + 171 + ], + "type": "image", + "image_path": "63beecebd6dbbe8744ab05e258fff39d4350a27b988a9089496728e380683810.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 299, + 85, + 422, + 171 + ], + "blocks": [ + { + "bbox": [ + 299, + 85, + 422, + 171 + ], + "lines": [ + { + "bbox": [ + 299, + 85, + 422, + 171 + ], + "spans": [ + { + "bbox": [ + 299, + 85, + 422, + 171 + ], + "type": "image", + "image_path": "d87022c4c0e05f8658f9fa04da4032fcc24bb2a5058b23d9881326935f077f89.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 424, + 85, + 545, + 171 + ], + "blocks": [ + { + "bbox": [ + 424, + 85, + 545, + 171 + ], + "lines": [ + { + "bbox": [ + 424, + 85, + 545, + 171 + ], + "spans": [ + { + "bbox": [ + 424, + 85, + 545, + 171 + ], + "type": "image", + "image_path": "cd0113a459e8b5457796874c70a3236c8f6e42bd1e0dfdcf3f3be7c3b1b7dcfc.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 222, + 287, + 246 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 222, + 287, + 246 + ], + "spans": [ + { + "bbox": [ + 46, + 222, + 287, + 246 + ], + "type": "text", + "content": "sponses (see Sec. 3), we design ranking questions to improve another discrimination skill, i.e., ranking ability." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 247, + 287, + 400 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 247, + 287, + 400 + ], + "spans": [ + { + "bbox": [ + 46, + 247, + 287, + 400 + ], + "type": "text", + "content": "For a choice question, as shown in Fig. 6 (c), the options in \"Task-specific Prompt\" contain the random permutations of ground truth response (GTR), image captions generated by BLIP2 [74], GTR from other images, rewrites of GTR by Qwen-14B [5]. See details in Appendix. For \"task-specific responses\", it is the GTR. This design is to train LLM to improve its LoT selection ability. For a ranking question, as shown in Fig. 6 (d), it is to enforce LLM to rank multiple distinct responses of a given input to match their human preferences. By training on the choice and ranking questions, LLM is encouraged to distinguish LoT responses and align human creative preferences, improving its LoT discriminative selection and ranking abilities." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 402, + 287, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 402, + 287, + 521 + ], + "spans": [ + { + "bbox": [ + 46, + 402, + 287, + 521 + ], + "type": "text", + "content": "(2) Associable Instruction Learning. By using the above instruction templates, we augment the 130,000 samples in the Oogiri-GO dataset to more than 500,000 instructions whose formulation is in Fig. 5. During training, LLM is required to predict the \"task-specific responses\" according to the \"USER-INPUTs\" which include \"Task-specific Prompt\" and two additional optional conditions like image and text condition. To avoid over-fitting, we only train standard LoRA [73] for the LLM with the associable instruction data. See more details in Appendix." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 527, + 202, + 540 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 527, + 202, + 540 + ], + "spans": [ + { + "bbox": [ + 47, + 527, + 202, + 540 + ], + "type": "text", + "content": "4.2. Explorative Self-Refinement" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 546, + 287, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 546, + 287, + 676 + ], + "spans": [ + { + "bbox": [ + 46, + 546, + 287, + 676 + ], + "type": "text", + "content": "After associable instruction tuning, we aim to generate more high-quality creative data by LLM which are then used to train LLM for self-refinement. To this end, we introduce an innovative stage called explorative self-refinement, inspired by human LoT exercise process of \"remote association & self-refinement\", also known as mental leap [21, 24, 30]. The remote association process refers to generating new ideas by associating remote concepts or thoughts, and self-refinement uses the generated data to enhance one's own LoT ability. In the following, we design two similar LoT exercise processes for LLM to improve its LoT ability." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": "(1) Explorative Remote Association. The core here is to prompt the LLM to generate a diverse array of creative responses under weakly-associated conditions. To implement" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "spans": [ + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": "this, we extract a set of object nouns, denoted as " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\mathcal{S}" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": ", from the text in the Oogiri-GO training data. See details in Appendix. Then, for each user-input " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": " (see Fig. 5), we generate " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": " weakly-associated conditions " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\{C_i\\}_{i=1}^n" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": ". These conditions can either be empty with a probability " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\rho \\in (0,1)" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": " to give freedom to LLM, or uniformly randomly sampled from the noun set " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\mathcal{S}" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": " to enforce LLM to build connections between different concepts. Next, we add the condition " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "C_i" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": " into user-input " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": ", and feed " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "I" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": " into the LLM to generate a humor candidate " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "R_i" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": ". Repeating this process with different conditions " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "C_i" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": " can generate a total of " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": " candidates " + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "inline_equation", + "content": "\\{R_i\\}_{i=1}^n" + }, + { + "bbox": [ + 304, + 222, + 545, + 354 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 354, + 545, + 474 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 354, + 545, + 474 + ], + "spans": [ + { + "bbox": [ + 304, + 354, + 545, + 474 + ], + "type": "text", + "content": "Then the LLM ranks these candidates by its discriminative ranking ability learned in Sec. 4.1. Next, it mixes the top-2 candidates with the ground truth responses (GTR), and selects the top-1 as the final response. Finally, if the selected top-1 response is the GTR, we discard this sample. Here first filtering out low-quality responses can improve the accuracy of subsequent top-1 selection, since " + }, + { + "bbox": [ + 304, + 354, + 545, + 474 + ], + "type": "inline_equation", + "content": "(n + 1)" + }, + { + "bbox": [ + 304, + 354, + 545, + 474 + ], + "type": "text", + "content": "-choice problem is often more challenging than 3-choice problem as shown in Sec. 5. By repeating this process, we progressively gather sufficient new high-quality data." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 474, + 545, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 545, + 617 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 545, + 617 + ], + "type": "text", + "content": "The core of this approach is the weakly-associated conditions " + }, + { + "bbox": [ + 304, + 474, + 545, + 617 + ], + "type": "inline_equation", + "content": "\\{C_i\\}_{i=1}^n" + }, + { + "bbox": [ + 304, + 474, + 545, + 617 + ], + "type": "text", + "content": " which can encourage the LLM to engage in remote associations. This is because the empty conditions allow LLM to operate freely, while the object noun conditions compel the LLM to draw connections between seemingly unrelated concepts. This mechanism facilitates the establishment of links between seemingly-unrelated and weakly-related concepts, encouraging the LLM to explore knowledge outside of traditional cognitive limitations. The exploration ability distinguishes our CLoT from CoT which primarily guides the LLM to exploit its inherent reasoning ability without emphasizing knowledge exploration." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 618, + 545, + 713 + ], + "type": "text", + "content": "(2) Self-refinement. Here we combine the above generated instructions with vanilla instruction tuning samples in Sec. 4.1 to form a dataset with more than 550,000 samples to train our LLM again. Since the above generated data is of high diversity because of its exploration strategy, they prevent performance collapse [76, 77] during self-refinement phase, and can improve the LoT performance across several creative tasks as shown in Sec. 5. See the ablation study and" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 134, + 74, + 212, + 83 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 134, + 74, + 212, + 83 + ], + "spans": [ + { + "bbox": [ + 134, + 74, + 212, + 83 + ], + "type": "text", + "content": "Associable Generation" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 377, + 74, + 465, + 83 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 377, + 74, + 465, + 83 + ], + "spans": [ + { + "bbox": [ + 377, + 74, + 465, + 83 + ], + "type": "text", + "content": "Associable discrimination" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13250" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 62, + 70, + 535, + 173 + ], + "blocks": [ + { + "bbox": [ + 62, + 70, + 535, + 173 + ], + "lines": [ + { + "bbox": [ + 62, + 70, + 535, + 173 + ], + "spans": [ + { + "bbox": [ + 62, + 70, + 535, + 173 + ], + "type": "table", + "html": "
ModelSizeImage&Text to Text (IT2T)Image to Text (I2T)Text to Text (T2T)
3T14T15T2RankAvg.3T14T15T2RankAvg.3T14T15T2RankAvg.
GPT4v [72]-19.314.93.256.723.529.115.13.960.427.127.116.86.853.526.1
LLaVA-1.5 [34]13B13.213.713.968.127.229.322.73.960.929.233.825.24.062.631.4
MiniGPT-v2 [35]7B6.13.44.060.718.65.34.03.860.518.410.87.33.559.420.3
mPLUG-OwlMultilingual [12]7B28.126.010.564.432.219.218.66.060.526.124.422.210.760.129.4
VisualGLM-6B [75]6B24.122.59.767.430.914.320.48.861.926.413.120.27.161.325.4
Qwen-VL [1]7B30.226.010.467.733.623.223.111.962.230.123.425.013.359.630.3
Qwen-VL+Alt(Ours)7B39.738.915.767.340.4+ 6.838.830.515.762.336.8+ 6.730.628.716.762.634.6+ 4.3
Qwen-VL+CLoT(Ours)7B41.838.721.668.542.7+ 9.139.835.122.764.440.5+10.438.829.421.064.738.5+ 8.2
", + "image_path": "1f67766d80c9f87ec2865f4e16443f7ab510cf622cf33ec6c5fb9b9ce59a7ac5.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 47, + 206, + 287, + 322 + ], + "blocks": [ + { + "bbox": [ + 46, + 179, + 547, + 205 + ], + "lines": [ + { + "bbox": [ + 46, + 179, + 547, + 205 + ], + "spans": [ + { + "bbox": [ + 46, + 179, + 547, + 205 + ], + "type": "text", + "content": "Table 2. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on multil-modal multilingual models. mTn choice question selects " + }, + { + "bbox": [ + 46, + 179, + 547, + 205 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 179, + 547, + 205 + ], + "type": "text", + "content": " correct answers from " + }, + { + "bbox": [ + 46, + 179, + 547, + 205 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 46, + 179, + 547, + 205 + ], + "type": "text", + "content": " options. \"Avg.\" is the average of all metrics. \"AIT\" denotes associable instruction tuning." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 206, + 287, + 322 + ], + "lines": [ + { + "bbox": [ + 47, + 206, + 287, + 322 + ], + "spans": [ + { + "bbox": [ + 47, + 206, + 287, + 322 + ], + "type": "table", + "html": "
Algorithm 1 Inference Step of CLoT
Input: Input I, CLoT-trained LLM A, response number n
Output: Creative response R.
1:▷ Creating the candidate responses
2: construct n weakly-associated conditions {Ci}n{i=1}
3: {Ri}n{i=1} ← A([I, {Ci}n{i=1}])
4:▷ Choosing most creative response
5: Top-2 R1', R2' ← A([I, {Ri}n{i=1}]) with ranking ability
6: Best R ← A([I, R1', R2']) with selection ability
7: return Best response R.
", + "image_path": "644d7a62fecbdcb904b88da6e6e11276e10ee76f156880bd108e783dac385330.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 342, + 167, + 355 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 342, + 167, + 355 + ], + "spans": [ + { + "bbox": [ + 47, + 342, + 167, + 355 + ], + "type": "text", + "content": "more discussions in Sec. 5.5." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 359, + 146, + 372 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 359, + 146, + 372 + ], + "spans": [ + { + "bbox": [ + 47, + 359, + 146, + 372 + ], + "type": "text", + "content": "4.3. CLoT Inference" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "spans": [ + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "text", + "content": "After the two LoT-boosting phases in Sec. 4.1 and 4.2, the LLM acquires sufficient LoT ability. Now we introduce the inference steps of LLM to release its LoT ability. Formally, given an Oogiri user-input " + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "inline_equation", + "content": "\\pmb{I}" + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "text", + "content": " of the formation in Fig. 5, LLM first uses explorative remote association in Sec. 4.2 to construct " + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "text", + "content": " weakly-associated conditions (these conditions can be empty since the training paradigm in Section 4), and then follows Sec. 4.2 to generate " + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "text", + "content": " responses " + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "inline_equation", + "content": "\\{R_i\\}_{i=1}^n" + }, + { + "bbox": [ + 46, + 378, + 289, + 571 + ], + "type": "text", + "content": ". Next, LLM ranks these responses by using its learned ranking skill and finally selects the top-1 one from the ranked top-2 response via its selection skill. The reason to first use ranking before selection is that as shown by experimental results in Sec. 5, directly choosing the best one from a large number of options has poor accuracy, and ranking can filter out low-quality candidates to improve the selection accuracy. See Algorithm 1 for an overview of CLoT inference steps." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 579, + 129, + 594 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 579, + 129, + 594 + ], + "spans": [ + { + "bbox": [ + 47, + 579, + 129, + 594 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 599, + 230, + 612 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 599, + 230, + 612 + ], + "spans": [ + { + "bbox": [ + 47, + 599, + 230, + 612 + ], + "type": "text", + "content": "5.1. Evaluation Questions and Metrics" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "content": "Inspired by the humor benchmarks in [81], we first develop choice and ranking questions as introduced in Sec. 4.1 (see examples in Fig. 6 (c-d)), and then quantitatively evaluate the LoT ability of LLMs on the Oogiri-GO test dataset. For the choice questions, " + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "inline_equation", + "content": "mTn" + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "content": " for short, they need LLMs to choose " + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "content": " \"leap-of-thought\" humor responses from " + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "content": " options given the input. Here we build four types of " + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "inline_equation", + "content": "mTn" + }, + { + "bbox": [ + 46, + 617, + 289, + 715 + ], + "type": "text", + "content": " questions, including 2T1, 3T1, 4T1, and 5T2. 2T1 means" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 208, + 547, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 208, + 547, + 376 + ], + "spans": [ + { + "bbox": [ + 304, + 208, + 547, + 376 + ], + "type": "text", + "content": "two options, the ground-truth response (GTR) and an image caption generated by BLIP2 [74]. 3T1 adds unrelated answers, e.g., other image captions. 4T1 further adds the GTR rewrite by Qwen-14B [5]. 5T2 has an extra GTR. For these questions, their difficulty increases progressively, and is diverse to ensure comprehensive evaluation. For choice questions, we use accuracy as the evaluation metric. Additionally, for the questions in test set whose responses have ground-truth human preference, e.g., the number of likes, we develop the ranking questions that always rank five candidates. For evaluation, we adopt the top-1 accuracy and the widely used ranking metric, i.e., Normalized Discounted Cumulative Gain (NDCG) [82, 83]. We provide more experimental details in the Appendix." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 383, + 542, + 397 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 383, + 542, + 397 + ], + "spans": [ + { + "bbox": [ + 305, + 383, + 542, + 397 + ], + "type": "text", + "content": "5.2. Evaluation by Choice and Ranking Questions" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "spans": [ + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": "Evaluation on Multimodal Multilingual LLMs. We plug our associative instruction tuning (AIT) and our CLoT into the SoTA open-source multimodal multilingual model Qwen-VL [1] to obtain Qwen- " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\mathrm{VL}_{+\\mathrm{AIT}}" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": " and Qwen- " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\mathrm{VL}_{+\\mathrm{CLoT}}" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": ", respectively. Table 2 shows that, on three tasks (IT2T, I2T and T2T) which include English, Chinese and Japanese questions, Qwen-VL achieves the best LoT performance among all baselines in most cases. In comparison, Qwen- " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\mathrm{VL}_{+\\mathrm{AIT}}" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": " achieves a noticeable improvement on the SoTA Qwen with average accuracy enhancements of " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "6.8\\%" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "6.7\\%" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "4.3\\%" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": " on the three tasks, respectively. Importantly, Qwen- " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "\\mathrm{VL}_{+\\mathrm{CLoT}}" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": " further enhances Qwen-VL, showing improvements of " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "9.1\\%" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "10.4\\%" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "inline_equation", + "content": "8.2\\%" + }, + { + "bbox": [ + 304, + 402, + 547, + 593 + ], + "type": "text", + "content": " in accuracy across these tasks. These results demonstrate the efficacy of the two stages in CLoT, i.e., associative instruction tuning and explorative self-refinement." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "text", + "content": "Evaluation on Multimodal Non-multilingual LLMs. Here we integrate our CLoT with the SoTA multimodal non-multilingual model, CogVLM-17B [29], and evaluate it on the English I2T and T2T tasks. Table 3 shows that " + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "inline_equation", + "content": "\\mathrm{CogVLM - 17B}_{+\\mathrm{AIT}}" + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "text", + "content": " achieves remarkable improvements over the standard " + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "inline_equation", + "content": "\\mathrm{CogVLM - 17B}" + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "inline_equation", + "content": "\\mathrm{CogVLM - 17B}_{+\\mathrm{CLoT}}" + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "text", + "content": " consistently demonstrates significantly superior performance compared to " + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "inline_equation", + "content": "\\mathrm{CogVLM - 17B}" + }, + { + "bbox": [ + 304, + 594, + 547, + 689 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 689, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 547, + 715 + ], + "type": "text", + "content": "Evaluation on Single-Modal LLMs. Now we test LLMs that can handle only pure texts, using the English T2T task" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 758 + ], + "type": "text", + "content": "13251" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 52, + 60, + 547, + 155 + ], + "blocks": [ + { + "bbox": [ + 52, + 60, + 547, + 155 + ], + "lines": [ + { + "bbox": [ + 52, + 60, + 547, + 155 + ], + "spans": [ + { + "bbox": [ + 52, + 60, + 547, + 155 + ], + "type": "table", + "html": "
ModelSizeImage to Text (I2T)Text to Text (T2T)
2T13T14T15T2RankAvg.2T13T14T15T2RankAvg.
InstructionBLIP [78]13B19.813.715.51.165.523.122.316.017.00.759.523.1
mPLUG-OwlLLaMA2 [12]7B22.312.715.04.259.922.824.213.712.63.159.222.6
Otter [79]7B15.89.98.57.161.320.53.83.34.85.458.515.1
CogVLM-17B [29]7B37.626.418.32.564.629.935.127.824.87.564.131.9
CogVLM-17B+AIT(Ours)7B57.437.433.521.864.642.9+13.155.446.526.418.264.442.2+10.3
CogVLM-17B+CLoT(Ours)7B66.947.643.430.769.451.6+21.764.852.933.621.868.648.3+16.4
", + "image_path": "1b15fa3d9f9ce54d1fe0d57fa4d5dc1704e9c5eba92ab46cb0815bbbfce44f56.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 50, + 194, + 287, + 371 + ], + "blocks": [ + { + "bbox": [ + 47, + 162, + 546, + 185 + ], + "lines": [ + { + "bbox": [ + 47, + 162, + 546, + 185 + ], + "spans": [ + { + "bbox": [ + 47, + 162, + 546, + 185 + ], + "type": "text", + "content": "Table 3. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on various mulilmodal non-multilingual models (English). See notations in Table 2. We only consider I2T and T2T since English IT2T is not available due to cultural preference." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 194, + 287, + 371 + ], + "lines": [ + { + "bbox": [ + 50, + 194, + 287, + 371 + ], + "spans": [ + { + "bbox": [ + 50, + 194, + 287, + 371 + ], + "type": "table", + "html": "
ModelSize3T14T15T2RankAvg.
GPT-3.5 [72]-45.330.46.761.636.0
GPT-4 [72]-49.220.43.654.732.0
LLAMA2 [4]7B18.913.51.160.423.5
13B15.620.01.860.524.5
70B27.816.13.862.027.4
Baichuan2 [80]7B28.322.611.664.631.8
13B21.718.38.961.527.6
Qwen [5]7B23.120.48.061.428.2
14B27.422.212.359.530.3
ChatGLM3 [75]6B15.617.05.459.424.3
Vicuna-v1.5 [6]7B32.623.50.063.029.8
13B30.223.02.762.229.5
Qwen-VL+CLoT(Ours)7B51.732.324.865.043.4
CogVLM-17B+CLoT(Ours)7B52.933.621.868.644.2
", + "image_path": "4e0dbf050d2fb69404d4c66cc287dc21602af7a5094f1bf7681ee070e42f0f8e.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 379, + 287, + 413 + ], + "lines": [ + { + "bbox": [ + 47, + 379, + 287, + 413 + ], + "spans": [ + { + "bbox": [ + 47, + 379, + 287, + 413 + ], + "type": "text", + "content": "Table 4. The accuracy (%) of choice questions and the NDCG (%) of ranking questions on various large language models. Here we use English T2T task for test. See notations in Table 2." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 47, + 420, + 287, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 420, + 287, + 480 + ], + "spans": [ + { + "bbox": [ + 47, + 420, + 287, + 480 + ], + "type": "text", + "content": "for evaluation. Table 4 also indicates the insufficient LoT ability within existing LLMs, ranging from small to large models. Fortunately, our CLoT significantly improves the LoT ability of these LLMs, as demonstrated by the notable improvement in accuracy." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 483, + 287, + 579 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 483, + 287, + 579 + ], + "spans": [ + { + "bbox": [ + 46, + 483, + 287, + 579 + ], + "type": "text", + "content": "Comparison with CoT-alike Reasoning Frameworks. We also find that existing reasoning frameworks are not as effective as CLoT in enhancing LoT ability. Fig. 8 compares CLoT with CoT [2, 3], CoT-SC [84], and prompted-based LoT (PLoT) with the prompt \"let's think outside the box\". The results reveal that CoT-alike frameworks do not enhance LoT performance of LLMs, while CLoT demonstrates the ability to consistently enhance LLMs." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "type": "text", + "content": "Our experiments and analysis reveal that, unlike CoT-based methods, LoT cannot be directly achieved by prompting alone. This is because the inherent reasoning capabilities and extensive knowledge of LLMs are not sufficient to enable LoT ability. However, when trained with our proposed CLoT method, LLMs can effectively engage in a range of creative tasks. Additionally, the use of specific prompting techniques can enhance the LoT ability of CLoT-trained LLMs. These findings suggest that LoT could potentially be considered an additional general reasoning ability for LLMs that is not contained in current LLMs." + } + ] + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 319, + 193, + 533, + 278 + ], + "blocks": [ + { + "bbox": [ + 319, + 193, + 533, + 278 + ], + "lines": [ + { + "bbox": [ + 319, + 193, + 533, + 278 + ], + "spans": [ + { + "bbox": [ + 319, + 193, + 533, + 278 + ], + "type": "image", + "image_path": "93ba7dc25772108bb8a64619b8da5ef7ee612648ee2c04f73a49639e6b58804c.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 285, + 545, + 308 + ], + "lines": [ + { + "bbox": [ + 305, + 285, + 545, + 308 + ], + "spans": [ + { + "bbox": [ + 305, + 285, + 545, + 308 + ], + "type": "text", + "content": "Figure 7. User study with voting " + }, + { + "bbox": [ + 305, + 285, + 545, + 308 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 305, + 285, + 545, + 308 + ], + "type": "text", + "content": " for Oogiri-style creative responses by different models and improved methods." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 310, + 418, + 320 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 310, + 418, + 320 + ], + "spans": [ + { + "bbox": [ + 306, + 310, + 418, + 320 + ], + "type": "text", + "content": "5.3. Human Evaluation" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 328, + 546, + 449 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 328, + 546, + 449 + ], + "spans": [ + { + "bbox": [ + 304, + 328, + 546, + 449 + ], + "type": "text", + "content": "We conduct a user preference study to test creativity of LLMs. Here we select six LLMs to generate responses for a total of eighteen questions across three tasks (IT2T, I2T and T2T). We use choice questions, and ask users to choose the most creative and humorous responses. Fig. 7 summarizes the statistical analysis of 154 valid surveys. The results show that users have a strong inclination towards selecting the results of CLoT across three tasks, highlighting the high-quality creative content generated by CLoT. See more user study details in Appendix." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 456, + 497, + 467 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 456, + 497, + 467 + ], + "spans": [ + { + "bbox": [ + 306, + 456, + 497, + 467 + ], + "type": "text", + "content": "5.4. Evaluation on Other Creative Tasks" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 474, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 547, + 715 + ], + "type": "text", + "content": "To evaluate the generalization ability of CLoT, we test CLoT on another two creative tasks, including Cloud Guessing Game (CGG) and Divergent Association Task (DAT). In CGG, the LLM is to identify the shape of white clouds, and then to select the corresponding shapes from given options. For instance, the white clouds in Fig. 9 (c) has a shape of a cat, and the one in Fig. 9 (d) is similar to a human. These white cloud images are generated by a control diffusion model [31, 32, 85, 86], guided by masks shown in Fig. 9 (b). We use top-1 accuracy as metric. See more details in Appendix. For DAT, it is a classic creativity test [33, 87] which needs participants to choose words with larger semantic distances among 10 unrelated nouns. Here for test easily, we transfer the DAT benchmark [33] to a series of choice questions and take the standard average semantic distance (ASD) as a metric. These questions can challenge the LLM to select the one word from nine options that differs from the given word most. See more details in Appendix. CGG and DAT can test the LoT ability of LLMs, specifically their remote association thinking ability," + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "13252" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 72, + 72, + 182, + 156 + ], + "blocks": [ + { + "bbox": [ + 72, + 72, + 182, + 156 + ], + "lines": [ + { + "bbox": [ + 72, + 72, + 182, + 156 + ], + "spans": [ + { + "bbox": [ + 72, + 72, + 182, + 156 + ], + "type": "image", + "image_path": "ad4ccd4921cee3c2d8368978a0c0b30dbd2030ea75df1d8d30fc777bcb808d2e.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "lines": [ + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "spans": [ + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "text", + "content": "Figure 8. The accuracy " + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "text", + "content": " of choice questions and the NDCG " + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "text", + "content": " of ranking questions on our CLoT and various reasoning frameworks. The baseline is Qwen-VL on multilingual I2T task. For " + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "inline_equation", + "content": "mTn" + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "text", + "content": " choice questions, one needs to select " + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "text", + "content": " correct answers from " + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 46, + 157, + 545, + 178 + ], + "type": "text", + "content": " options." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 192, + 72, + 263, + 156 + ], + "blocks": [ + { + "bbox": [ + 192, + 72, + 263, + 156 + ], + "lines": [ + { + "bbox": [ + 192, + 72, + 263, + 156 + ], + "spans": [ + { + "bbox": [ + 192, + 72, + 263, + 156 + ], + "type": "image", + "image_path": "945cadf00ecea58f84a7f0b6251a1d3116ce04ff5d50823a61b0ce5aa34cc0e9.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 271, + 72, + 342, + 156 + ], + "blocks": [ + { + "bbox": [ + 271, + 72, + 342, + 156 + ], + "lines": [ + { + "bbox": [ + 271, + 72, + 342, + 156 + ], + "spans": [ + { + "bbox": [ + 271, + 72, + 342, + 156 + ], + "type": "image", + "image_path": "3605fab232944da02d04d77d1d13dcc663a13a149e921c6c1aa5225493f63256.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 354, + 72, + 425, + 156 + ], + "blocks": [ + { + "bbox": [ + 354, + 72, + 425, + 156 + ], + "lines": [ + { + "bbox": [ + 354, + 72, + 425, + 156 + ], + "spans": [ + { + "bbox": [ + 354, + 72, + 425, + 156 + ], + "type": "image", + "image_path": "fbfcdfc05caba4a497f6930f2c1aa50ab065728c20ba1325a90a0e799cc0bb2c.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 435, + 72, + 504, + 156 + ], + "blocks": [ + { + "bbox": [ + 435, + 72, + 504, + 156 + ], + "lines": [ + { + "bbox": [ + 435, + 72, + 504, + 156 + ], + "spans": [ + { + "bbox": [ + 435, + 72, + 504, + 156 + ], + "type": "image", + "image_path": "454e67bd787a32b5be4f4acd03015ed7c10f3513c6460947820cf22801e6f9bb.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 66, + 188, + 164, + 315 + ], + "blocks": [ + { + "bbox": [ + 66, + 188, + 164, + 315 + ], + "lines": [ + { + "bbox": [ + 66, + 188, + 164, + 315 + ], + "spans": [ + { + "bbox": [ + 66, + 188, + 164, + 315 + ], + "type": "image", + "image_path": "988142eb1d9aa3591b54ba23ba850ad81d0be793a0652d6b1f7ded5a5f7859e1.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 319, + 287, + 353 + ], + "lines": [ + { + "bbox": [ + 46, + 319, + 287, + 353 + ], + "spans": [ + { + "bbox": [ + 46, + 319, + 287, + 353 + ], + "type": "text", + "content": "Figure 9. Evaluation of CLoT on the creative CGG (e) and DAT (f) tasks. (c-d): examples of cloud guessing games. (b): conditional masks of image (a) for generating cloud images." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 165, + 188, + 265, + 315 + ], + "blocks": [ + { + "bbox": [ + 165, + 188, + 265, + 315 + ], + "lines": [ + { + "bbox": [ + 165, + 188, + 265, + 315 + ], + "spans": [ + { + "bbox": [ + 165, + 188, + 265, + 315 + ], + "type": "image", + "image_path": "c1a9f07fc95283174686b870c6123ea40c5afe8b728b34f49f34296d4125a930.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 364, + 287, + 448 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 364, + 287, + 448 + ], + "spans": [ + { + "bbox": [ + 46, + 364, + 287, + 448 + ], + "type": "text", + "content": "and provide quite different evaluation platforms. As shown in Fig. 9 (e-f), CLoT can also significantly enhance the performance of the SoTA Qwen-VL on both CGG and DAT tasks. Specifically, CLoT-integrated Qwen-VL improves the vanilla Qwen-VL by about " + }, + { + "bbox": [ + 46, + 364, + 287, + 448 + ], + "type": "inline_equation", + "content": "8\\%" + }, + { + "bbox": [ + 46, + 364, + 287, + 448 + ], + "type": "text", + "content": " on the CGG task and " + }, + { + "bbox": [ + 46, + 364, + 287, + 448 + ], + "type": "inline_equation", + "content": "5\\%" + }, + { + "bbox": [ + 46, + 364, + 287, + 448 + ], + "type": "text", + "content": " on the DAT task. These results well demonstrate the good generalization and transferability of CLoT." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 455, + 141, + 468 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 455, + 141, + 468 + ], + "spans": [ + { + "bbox": [ + 47, + 455, + 141, + 468 + ], + "type": "text", + "content": "5.5. Ablation Study" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 474, + 287, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 474, + 287, + 617 + ], + "spans": [ + { + "bbox": [ + 46, + 474, + 287, + 617 + ], + "type": "text", + "content": "Weakly-associated Conditions. By default, to encourage remote association, we use weakly-associated conditions randomly sampled from the noun set on the whole dataset in Sec. 4.2. To verify the effectiveness of weakly-associated conditions, now we resort to strongly-associated conditions sampled from the noun set of the current image caption. Results in Fig. 10 (Left) show that using weakly-associated conditions is superior and more conducive to fostering the creativity of LLMs. The weakly-associated conditions enable the LLM to generate more diverse LoT responses, while the strong clue from the strongly-associated conditions limit the diversity of LoT generations." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": "Round of Self-refinement. By default, we run one-round self-refinement for the Oogiri game. Here we explore whether more rounds of the self-refinement can further improve the LoT ability. Fig. 10 (Right) shows that a single round of self-refinement already yields promising performance, whereas additional rounds do not yield significant further improvements. As shown in Fig. 10 (Left), the diversity of the condition set " + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{S}" + }, + { + "bbox": [ + 46, + 618, + 288, + 714 + ], + "type": "text", + "content": " is crucial to self-refinement, since" + } + ] + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 318, + 188, + 424, + 262 + ], + "blocks": [ + { + "bbox": [ + 318, + 188, + 424, + 262 + ], + "lines": [ + { + "bbox": [ + 318, + 188, + 424, + 262 + ], + "spans": [ + { + "bbox": [ + 318, + 188, + 424, + 262 + ], + "type": "image", + "image_path": "f38f0db91012536c4fcd339eba26b85260d5be2177e8e272e2fe14337567bb7b.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 266, + 546, + 310 + ], + "lines": [ + { + "bbox": [ + 305, + 266, + 546, + 310 + ], + "spans": [ + { + "bbox": [ + 305, + 266, + 546, + 310 + ], + "type": "text", + "content": "Figure 10. The ablation study of CLoT. We use CogVLM as baseline on the English I2T task. Left: weakly-associated condition v.s. strongly-associated condition during explorative remote association. Right: The effect of rounds of self-refinement." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 426, + 188, + 533, + 262 + ], + "blocks": [ + { + "bbox": [ + 426, + 188, + 533, + 262 + ], + "lines": [ + { + "bbox": [ + 426, + 188, + 533, + 262 + ], + "spans": [ + { + "bbox": [ + 426, + 188, + 533, + 262 + ], + "type": "image", + "image_path": "7f4b62c5f9ae11c6cabd4439192523065874bf7873b1c26041db48845511e20a.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 321, + 546, + 417 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 321, + 546, + 417 + ], + "spans": [ + { + "bbox": [ + 305, + 321, + 546, + 417 + ], + "type": "text", + "content": "it decides whether the associable remote stage can generate high quality and diverse data. However, the condition set " + }, + { + "bbox": [ + 305, + 321, + 546, + 417 + ], + "type": "inline_equation", + "content": "\\mathcal{S}" + }, + { + "bbox": [ + 305, + 321, + 546, + 417 + ], + "type": "text", + "content": " is not expanded during the second-round self-refinement, which consequently limits further improvements in performance. Effectively increasing the scale of the condition set is an effective way for further improvement. See more discussion in Appendix. But its exploration falls outside the scope of this work and is left for our future research." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 425, + 378, + 437 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 425, + 378, + 437 + ], + "spans": [ + { + "bbox": [ + 306, + 425, + 378, + 437 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 305, + 445, + 545, + 565 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 445, + 545, + 565 + ], + "spans": [ + { + "bbox": [ + 305, + 445, + 545, + 565 + ], + "type": "text", + "content": "In this paper, we propose a Creative Leap-of-Thought (CLoT) paradigm to improve LLM's leap-of-thought (LoT) ability. CLoT first collects a multimodal Oogiri-GO dataset, and formulates it into instruction tuning data to train LLM to improve its LoT ability. Then CLoT designs an explorative self-refinement that lets LLM generate more creative LoT data via exploring parallels among different concepts and selects high-quality data to train itself for self-refinement. Experimental results show the effectiveness and generalization ability of CLoT across several creative tasks." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 572, + 416, + 586 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 572, + 416, + 586 + ], + "spans": [ + { + "bbox": [ + 306, + 572, + 416, + 586 + ], + "type": "text", + "content": "7. Acknowledgments" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 592, + 547, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 592, + 547, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 592, + 547, + 712 + ], + "type": "text", + "content": "This work was supported by National Science and Technology Major Project (No.2021ZD0111601), National Natural Science Foundation of China (No.62325605, U1711264), and Guangdong Basic and Applied Basic Research Foundation (No.2023A1515011374), and Guangzhou Science and Technology Program (No.2024A04J6365), and Guangdong Province Key Laboratory of Information Security Technology. Pan Zhou acknowledges support from the Singapore Ministry of Education (MOE) Academic Research Fund (AcRF) Tier 1 grant." + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "13253" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Jinze Bai, Shuai Bai, Shusheng Yang, Shijie Wang, Sinan Tan, Peng Wang, Junyang Lin, Chang Zhou, and Jingren Zhou. 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Europe's journal of psychology, 12(2):210, 2016. 7" + } + ] + } + ], + "index": 2 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 749, + 317, + 757 + ], + "type": "text", + "content": "13257" + } + ] + } + ], + "index": 4 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 11 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Leveraging Camera Triplets for Efficient and Accurate Structure-from-Motion/a217b793-2629-4522-9467-ef3937164206_content_list.json b/2024/Leveraging Camera Triplets for Efficient and Accurate Structure-from-Motion/a217b793-2629-4522-9467-ef3937164206_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..c833c509f8fc87ef874bdcd5bb7de273d331534f --- /dev/null +++ b/2024/Leveraging Camera Triplets for Efficient and Accurate Structure-from-Motion/a217b793-2629-4522-9467-ef3937164206_content_list.json @@ -0,0 +1,1307 @@ +[ + { + "type": "text", + "text": "Leveraging Camera Triplets for Efficient and Accurate Structure-from-Motion", + "text_level": 1, + "bbox": [ + 86, + 130, + 880, + 151 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Lalit Manam and Venu Madhav Govindu \nIndian Institute of Science \nBengaluru - 560012, INDIA \n{lalitmanam,venug}@iisc.ac.in", + "bbox": [ + 321, + 181, + 645, + 251 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 286, + 313, + 301 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In Structure-from-Motion (SfM), the underlying viewgraphs of unordered image collections generally have a highly redundant set of edges that can be sparsified for efficiency without significant loss of reconstruction quality. Often, there are also false edges due to incorrect image retrieval and repeated structures (symmetries) that give rise to ghosting and superimposed reconstruction artifacts. We present a unified method to simultaneously sparsify the viewgraph and remove false edges. We propose a scoring mechanism based on camera triplets that identifies edge redundancy as well as false edges. Our edge selection is formulated as an optimization problem which can be provably solved using a simple thresholding scheme. This results in a highly efficient algorithm which can be incorporated as a pre-processing step into any SfM pipeline, making it practically usable. We demonstrate the utility of our method on generic and ambiguous datasets that cover the range of small, medium and large-scale datasets, all with different statistical properties. Sparsification of generic datasets using our method significantly reduces reconstruction time while maintaining the accuracy of the reconstructions as well as removing ghosting artifacts. For ambiguous datasets, our method removes false edges, thereby avoiding incorrect superimposed reconstructions.", + "bbox": [ + 75, + 316, + 472, + 681 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 709, + 209, + 724 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Structure-from-Motion (SfM) [13] has been a long-studied problem in computer vision. It aims to reconstruct a 3D structure and estimate camera motions given images of a scene. The first step in SfM is to identify the pairs of images that capture the same part of the scene. For unordered image collections, especially for large-scale datasets, image retrieval techniques [1, 14, 23, 31, 32] are used where each image is assigned with a descriptor and then matched with other images. The relationships between the pairs of images can be represented as a graph (also called a viewgraph in the SfM literature), with nodes representing", + "bbox": [ + 75, + 733, + 472, + 902 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "cameras and edges representing an overlap of the scene in the images captured by the two cameras, implying that their relative geometry can be recovered. This graph is further processed to extract keypoints in the images, which are then matched with keypoints in other images based on the connectivity of the graph [2, 7, 8, 25, 27, 34, 35, 44, 50]. Subsequently, the relative motion for every edge is obtained by estimating epipolar geometry [13] using inlier keypoint matches. We refer to such matches as epipolar inliers. The obtained graph in this fashion is used by either incremental [36, 39, 40, 48] or global methods [9-11, 42] to get a 3D reconstruction of the scene along with camera motions.", + "bbox": [ + 496, + 287, + 893, + 470 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The underlying viewgraphs obtained from unordered image collections generally contain a redundant set of images (equivalently nodes) since popular views of the scene are captured more frequently [41]. As a consequence, a large number of pairs of images (equivalently edges) are identified to capture the same part of the scene, resulting in a highly redundant set of edges in the viewgraphs [16]. We refer to the datasets with the above-mentioned properties as generic datasets. Many methods [15, 16, 37, 38, 41] have been proposed to sparsify the viewgraphs while maintaining the accuracy of the reconstructions by considering only the nodes and edges which are distinguished to be important.", + "bbox": [ + 496, + 488, + 893, + 684 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "When scenes contain repeated structures leading to different symmetries [26], a significant number of false edges occur between the cameras viewing repeated structures. This is because such images look similar and, thus, are identified as belonging to the same part of the scene, even if they capture physically different parts of the scene. The presence of such false edges leads to superimposed reconstructions. We refer to these datasets as ambiguous datasets. Methods based on viewgraph properties and loop consistency checks in the viewgraphs [3, 4, 17-19, 21, 33, 37, 38, 45, 46, 49, 51, 52] have been proposed to tackle false edges.", + "bbox": [ + 496, + 704, + 895, + 886 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "4959", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/f6c6aaf1a12bd06c8250ffe5ffd38ba25c524109962a9525d928733d140aeb20.jpg", + "image_caption": [ + "(a) Generic case (Union Square [47])." + ], + "image_footnote": [], + "bbox": [ + 96, + 89, + 344, + 228 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/72acfadf51418a0fec0eacb0a420e88c4d1af6aff5374652d3a1a69054519286.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 346, + 142, + 482, + 210 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/4c9b8d5baa31eb99b2c833844dfd810c13a508d6386c93c4b45566c5c5c4262c.jpg", + "image_caption": [ + "(b) Ambiguous case (Alexander Nevsky Cathedral [17]).", + "Figure 1. Camera triplets in different cases. The number of epipolar inliers are shown for the respective edges. The part of the image where most of the inliers are matched is shown in rectangular boxes with colours corresponding to the edge colours. The red dots on the images show the detected keypoints. (a) A triplet in a generic dataset where the edge marked green has fewer inliers than other edges due to low overlap, thus, can potentially be removed to sparsify the viewgraph. (b) A triplet in an ambiguous dataset where two different facades of a building are matched, giving false edges (marked green and blue). The false edges have a low number of inliers compared to the true edge (marked orange), thus giving a cue about ambiguity." + ], + "image_footnote": [], + "bbox": [ + 490, + 90, + 872, + 226 + ], + "page_idx": 1 + }, + { + "type": "table", + "img_path": "images/93a7228eab0752106ea356c000e7be5daf318b9ee0044a0b930c9c7861dbddb3.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodsScenarios in viewgraphs
Mostly True EdgesMany False Edges
Graph Sparsification✓✗
Disambiguation✗✓
Ours✓✓
", + "bbox": [ + 81, + 364, + 470, + 458 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Table 1. Summary of different scenarios in viewgraphs handled by methods designed for specific tasks.", + "bbox": [ + 76, + 468, + 468, + 497 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We note that generic datasets can also contain a small fraction of false edges due to incorrect images retrieved, which leads to ghost artifacts in reconstructions. On the other hand, ambiguous datasets contain repeated structures which give rise to a significant number of false edges.", + "bbox": [ + 76, + 531, + 468, + 606 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Both the problems, viewgraph sparsification and disambiguation of repeated structures, have mostly been dealt with independently in the literature. The underlying assumptions of both the problems are very much opposed. For viewgraph sparsification, most of the edges are considered to be reliable (or true). Thus, the removal of a few edges does not severely affect the accuracy of reconstruction. On the other hand, for the disambiguation problem, a significant number of edges are false, which must be weeded out to obtain a proper reconstruction. Our objective is to solve both problems together by a single scheme, which is summarized in Table 1.", + "bbox": [ + 75, + 625, + 468, + 805 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Our contributions: In this paper, we simultaneously target both the problems of viewgraph sparsification and disambiguation of repeated structures. A fundamental design attribute of our approach is the idea that camera triplets are more informative than individual edges [41, 51] and are", + "bbox": [ + 75, + 825, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "easy to analyze since they form loops of the smallest possible length. For the problems on hand, triplets provide an important indication of an edge being redundant or ambiguous based on matched keypoints (see Fig. 1). We propose a single scheme for both tasks by leveraging camera triplets. We identify redundant and false edges based on a scoring mechanism that aggregates information about 3D point connectivity of the triplets globally over the whole graph without requiring intermediate partial reconstructions and remove them based on a single threshold. The proposed method can be incorporated into any SfM pipeline, either incremental or global, making it practical for usage. Experiments on viewgraph sparsification show a significant improvement in reconstruction time while maintaining accuracy on large-scale datasets. Our method also removes ghost artifacts in the reconstructions of generic datasets and shows disambiguation capability on ambiguous datasets.", + "bbox": [ + 496, + 368, + 890, + 625 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Literature Review", + "text_level": 1, + "bbox": [ + 500, + 646, + 674, + 661 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Viewgraph sparsification: Snavely et al. [41] constructed skeletal graphs based on the approximate covariance of camera motions. Havlena et al. [15] used image level descriptors to carefully choose camera triplets for independent reconstructions and then merged them. Havlena et al. [16] also relied on image level descriptors and selected a minimally connected dominating set of the image collection. Shen et al. [38] used an online algorithm to get a spanning tree, expanded the graph based on triplets and finally enforced a community-based graph structure. Shah et al. [37] selected edges on the graph based on a minimum cost network flow problem. Many methods rely on intermediate partial reconstructions [15, 16, 41], have multiple hyperparameters [37, 38], or design their own specific SfM pipeline [15, 16, 41] but we provide a solution", + "bbox": [ + 496, + 674, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "4960", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "based on a single hyperparameter without any intermediate reconstruction, and can be used in any pipeline.", + "bbox": [ + 76, + 90, + 468, + 121 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Disambiguation of repeated structures: Zach et al. [51] reasoned about false edges based on missing correspondences in triplets using Bayesian inference. Zach et al. [52] further extended [51] on longer loops using relative camera motions. Roberts et al. [33] also inferred false edges based on relative motions using an expectation-maximization framework [29]. Cohen et al. [4] detected symmetries by estimating similarity transforms and removing false edges to reduce drift. Jiang et al. [19] measured reconstruction quality based on missing correspondences and used it for edge selection. Wilson et al. [46] split the camera-point relation graph based on its covering subgraphs. Heinly et al. [17] proposed a post-processing step to split the reconstruction based on conflicting observations and then merge the disconnected epipolar inliers. Heinly et al. [18] also proposed a post-processing step to isolate 3D points connecting separate parts of the reconstruction incorrectly by analyzing the clustering behaviour of 3D point connectivity. Cui et al. [6] merged two-view reconstructions locally to find missing correspondences. Yan et al. [49] constructed a path network where a few anchor images are selected and other images are related to them with paths for clean image correspondences. Wang et al. [45] grouped the images based on viewgraph and scored edges on their ability to expand the reconstruction. Kataria et al. [21] considered keypoints which are only matched across a few images for resectioning cameras to obtain a reliable reconstruction. Cai et al. [3] proposed Doppelgangers, where a neural network detects false edges based on images, keypoints and matches. Some graph sparsification methods also disambiguated repeated structures either by checking geometric consistency along loops [38] or by modifying their cost function for handling ambiguous datasets [37]. Some other methods [22, 43] avoided incorrect fetching of images containing repetitive structures during the image retrieval phase by specific designs of image descriptors. Many of these methods assume specific probability distributions on missing correspondences [51, 52], exploit intermediate reconstructions [6, 33], involve multiple hyperparameters [18, 19, 21, 37, 38, 46, 49] or are designed for specific pipelines [21, 51]. Our method does not assume any probability distribution for missing correspondences, can be used in any pipeline, and uses only a single hyperparameter without requiring any intermediate reconstruction.", + "bbox": [ + 76, + 137, + 472, + 803 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Proposed Method", + "text_level": 1, + "bbox": [ + 76, + 815, + 250, + 832 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The goal of graph sparsification is to recover most of the cameras and 3D points with a sparsified graph compared to the original graph while maintaining accuracy and significantly reducing reconstruction time. Dealing with", + "bbox": [ + 76, + 839, + 468, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ambiguities in the scene requires distinguishing between repeated structures. Our aim is to handle both the tasks of graph sparsification and disambiguation of repeated structures using a single scheme with as few hyperparameters as possible without needing any intermediate partial reconstructions. We also seek to build a scheme which can be used as a pre-processing step for any pipeline, either incremental or global. To achieve our goals, we present a scheme for scoring edge quality and then formulate an optimization problem which can be provably solved based on thresholding leading to our proposed algorithm.", + "bbox": [ + 496, + 90, + 893, + 258 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Edge quality score: Edges contain limited information about the pairs of cameras they connect. An individual edge alone cannot validate its importance in the graph, and thus, scoring them meaningfully requires considering other connected edges in the graph. We take recourse to camera triplets, which provide much more information about an edge based on the other two edges in a triplet (see Fig. 1). Triplets have been widely used for sparsification [15, 16, 37, 38, 41] and disambiguation [19, 33, 51, 52]. Let $\\mathcal{G} = (\\mathcal{V},\\mathcal{E})$ be a viewgraph, with $\\mathcal{V}$ and $\\mathcal{E}$ denote the set of nodes and edges in $\\mathcal{G}$ , respectively. We first determine a quality score, $q_{ij} > 0$ , for each edge $(i,j)\\in \\mathcal{E}$ before processing the viewgraph. Since we aim to get a 3D reconstruction, to sparsify the viewgraph, we want to score the edges based on how well they are connected via 3D points. One way to get an idea of 3D point connectivity without access to 3D reconstruction is to check for epipolar inliers on the edges since inliers are the candidate keypoints for reconstruction. One could check for common inliers in all three cameras and assign a score to each edge on the triplet based on the fraction of common inliers to that of the total inliers belonging to that edge. Such a scoring mechanism favours edges with a low number of inliers, which conflicts with our aim to score based on 3D point connectivity.", + "bbox": [ + 496, + 275, + 893, + 654 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Therefore, we score edges based on the number of inliers instead of common inliers across all three edges of the triplet, which adheres to our aim of 3D point connectivity-based scores. The indication for graph sparsification and disambiguation in the triplets is given by the relative number of inliers between the three edges (also seen in Fig. 1) and not by the actual number of inliers. To score edges, we take the ratio of the number of inliers in each edge to the maximum number of inliers among all three edges in a triplet. This assigns scores to edges based on relative 3D point connectivity in the triplet and is also considerate of the cases where all images in triplets have a low number of inliers due to occlusion or lack of texture.", + "bbox": [ + 496, + 671, + 893, + 867 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Inherently, our scoring mechanism based on the relative", + "bbox": [ + 519, + 885, + 890, + 901 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "4961", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "number of inliers in triplets is also useful for disambiguation. [3] empirically noted that the actual number of epipolar inliers does not provide useful information about ambiguity. Missing correspondences [19, 33, 49, 51] and the statistics of matched keypoints [49] provide a cue about the presence of false edges. They are generally detected using loops of small lengths like triplets since the likelihood of viewing the same 3D points on larger loops reduces. But the implicit assumption is the repeatability of the keypoints for the same 3D point, which can be violated in case of noisy images, occlusion or drastic changes in viewpoint [17, 30, 51]. Scoring based on the number of inliers instead of common inliers in the loops reduces the effect of unmatched keypoints due to repeatability concerns. This is because there can be other matched keypoints on the edges which will compensate for reduced edge scores due to non-repeatable keypoints. Moreover, we consider only inliers on the edges for computing scores. This ensures that only keypoints, which are proven to have discriminative capabilities for matching, are used for inference instead of all the keypoints (as used in [3, 33]).", + "bbox": [ + 75, + 90, + 472, + 409 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "A given edge can be a part of many triplets and, thus, have as many scores. To aggregate information about the edge over the whole graph, for each edge, we take the average of the scores obtained from all the triplets it participates in. This ensures that edge scores reflect global information about the edge in the graph. Since our scoring mechanism is based only on triplets, we remove edges which are not a part of any triplet, as such edges cannot be scored. In practice, the viewgraphs for unordered image collections are well connected and losing edges not contributing to triplets has minimal impact on the reconstructions (please refer to Sec. 4 for details).", + "bbox": [ + 75, + 426, + 470, + 608 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Handling graphs consisting only of triplets: For graphs containing only triplets, there can be cases when two triplets are connected by a node and do not share a common edge. We call such a connection between two triplets a joint. In Fig. 2a, we present a scenario where the triplets $T5$ and $T6$ have a common node but no common edge. Also, there are no other triplets that share common edges with both green and red edges. In such cases, the edges marked in the two colours are effectively being scored independently since edges marked in each colour do not participate in the scoring of edges in the other colour. Although, we can continue with such independent scoring, for ambiguous datasets, it is not possible to infer whether the joints are valid connections or not. So, we separate the joints, which ensures that inference on edges is not based on independent scores.", + "bbox": [ + 75, + 626, + 472, + 867 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We construct a triplet graph $\\mathcal{G}_T = (\\mathcal{V}_T,\\mathcal{E}_T)$ , as done", + "bbox": [ + 96, + 885, + 470, + 901 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/aa4696287ffefe6f518fda13825b37209f47737baa703e729ec11ce232474de9.jpg", + "image_caption": [ + "(a) Graph $(\\mathcal{G})$ containing only triplets." + ], + "image_footnote": [], + "bbox": [ + 540, + 95, + 857, + 233 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/522b1c4fc57873dc432282e9a9d46c47637f79e86dd21179c07a0ba37a9a8854.jpg", + "image_caption": [ + "(b) Corresponding triplet graph $(\\mathcal{G}_T)$ .", + "Figure 2. Graph $(\\mathcal{G})$ containing only triplets with a joint and its corresponding triplet graph $(\\mathcal{G}_T)$ . The edges marked in green and red can be scored independently due to the absence of triplets sharing common edges across them. The triplet graph separates the joint and disconnects such graphs." + ], + "image_footnote": [], + "bbox": [ + 527, + 263, + 854, + 335 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "in [20, 28], where nodes, $\\mathcal{V}_T$ , denote triplets in $\\mathcal{G}$ and edges, $\\mathcal{E}_T$ , connect the nodes if an edge is common between the triplets in $\\mathcal{G}$ . By construction, the triplets connected by the joints in the viewgraph $\\mathcal{G}$ are not connected in the triplet graph $\\mathcal{G}_T$ . If there are no common triplets between the set of edges separated by joints, it results in multiple connected components in the triplet graph $\\mathcal{G}_T$ , as can be seen in Fig. 2b. For each connected component of $\\mathcal{G}_T$ , the triplets in $\\mathcal{G}$ will have at least one common edge with the other triplets in the same connected component and no common edges across different components of $\\mathcal{G}_T$ . Thus, the edges participating in different connected components of $\\mathcal{G}_T$ can be scored independently. So, we only retain the edges in $\\mathcal{G}$ corresponding to the largest connected component of $\\mathcal{G}_T$ (denoting it as $\\mathcal{G}_{LCT}$ ) since our aim is to assign scores based on global reasoning. We empirically observe that separating the joints has a minor effect on the reconstructions (see Sec. 4).", + "bbox": [ + 496, + 484, + 893, + 757 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Formulation: Given a quality score $q_{ij}$ for each edge, we aim to select those edges which will increase the average quality score taken across all the edges. To avoid having the degenerate case of selecting edges only with the highest score (which could be as low as one edge in realistic scenarios), we need to regularize the cost by penalizing the loss of edges. Let $s_{ij} \\in \\{0,1\\}$ , be the binary variables denoting selection $(s_{ij} = 1)$ or removal $(s_{ij} = 0)$ of edges. Then, the", + "bbox": [ + 496, + 780, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "4962", + "bbox": [ + 480, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "optimization problem can be formulated as", + "bbox": [ + 76, + 90, + 362, + 104 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\max_{\\substack{s_{ij}\\in \\{0,1\\} ,\\\\ (i,j)\\in \\mathcal{E}}}\\frac{\\sum_{(i,j)\\in\\mathcal{E}}s_{ij}q_{ij}}{\\sum_{(i,j)\\in\\mathcal{E}}s_{ij}} -\\lambda \\frac{\\sum_{(i,j)\\in\\mathcal{E}}(1 - s_{ij})q_{ij}}{\\sum_{(i,j)\\in\\mathcal{E}}(1 - s_{ij})}, \\tag{1}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 116, + 468, + 162 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\lambda \\geq 0$ is a regularization parameter which avoids degenerate solutions for the optimization problem. $\\lambda$ also acts as a tuning parameter for the aggressiveness of edge removal, where reducing $\\lambda$ increases the number of edges removed. The second term in Eqn. 1 suggests the average of quality scores of the removed edges should not be high, thus regularizing the first term. The strict positiveness of $q_{ij}$ ensures that edges are either selected or removed for any given $\\lambda \\geq 0$ . Although the problem in Eqn. 1 does not enforce the graph structure, the quality scores obtained for edges are based on all the triplets they are members of. Let Trp be the set of all triplets in $\\mathcal{G}_{LCT}$ , $trp(i,j) \\subseteq Trp$ be the set of triplets for which the edge $(i,j)$ is a member, and $q_{ij}^{t}$ be the score obtained from the triplet $t \\in trp(i,j)$ . Replacing the scores $q_{ij}$ in Eqn. 1 with $\\frac{\\sum_{t \\in trp(i,j)} q_{ij}^{t}}{|trp(i,j)|}$ discloses the dependence of Eqn. 1 on the graph structure more explicitly. While the optimization problem in Eqn. 1 is combinatorial, we provide a simple thresholding scheme to solve it, which is shown as follows:", + "bbox": [ + 76, + 172, + 472, + 467 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\ns _ {i j} = \\left\\{ \\begin{array}{l l} 1 & \\text {i f} q _ {i j} \\geq \\tau , \\\\ 0 & \\text {o t h e r w i s e}, \\end{array} \\right. \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 192, + 474, + 468, + 516 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\tau$ denotes a threshold. This thresholding scheme is equivalent to optimizing the problem in Eqn. 1 with $\\tau$ acting as a regularizer, as shown by the following theorem:", + "bbox": [ + 76, + 526, + 468, + 571 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Theorem 1. For a given $\\lambda$ in Eqn. 1, there exists a threshold $\\tau$ such that the values of $s_{ij}$ obtained by solving the problems given by Eqn. 1 and Eqn. 2 are the same.", + "bbox": [ + 75, + 582, + 468, + 628 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Please refer to supplementary material for the proof of Thm. 1. In practice, finding a threshold is not easy for a given dataset, and a single threshold is not suitable for all datasets. We choose a threshold adaptively based on the connectivity of the graph. Specifically, given maximum node degree of the graph as $d_{max}$ , we get a threshold as", + "bbox": [ + 75, + 638, + 468, + 729 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\tau = m \\left(1 - \\frac {d _ {\\text {m a x}}}{| \\mathcal {V} |}\\right) + \\left(\\frac {d _ {\\text {m a x}}}{| \\mathcal {V} |}\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 153, + 739, + 468, + 773 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $|\\mathcal{V}|$ is the number of nodes and $m$ is the minimum score which edges should satisfy. We deliberately choose $|\\mathcal{V}|$ as the denominator since for a connected graph, $0 \\leq d_{max} \\leq |\\mathcal{V}| - 1$ , thus $m \\leq \\tau < 1$ . This ensures that $\\tau = 1$ is never chosen which only retains edges scored exactly as 1. Such a scenario with many edges scored as 1 is seldom true in practice. We now summarize our procedure in Algo. 1. Efficient implementations exist to get the list", + "bbox": [ + 76, + 779, + 470, + 901 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Algorithm 1: Edge Selection using Triplets", + "text_level": 1, + "bbox": [ + 509, + 94, + 802, + 109 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Input: Viewgraph $\\mathcal{G} = (\\mathcal{V},\\mathcal{E})$ , with geometrically verified edges and a minimum edge score $m$", + "bbox": [ + 519, + 112, + 866, + 142 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Output: Sparsified viewgraph $\\mathcal{G}_F = (\\mathcal{V}_F,\\mathcal{E}_F)$ with ambiguous edges removed.", + "bbox": [ + 519, + 143, + 862, + 172 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "1 Construct triplet graph $\\mathcal{G}_T$ from $\\mathcal{G}$", + "2 Retain edges in $\\mathcal{G}$ participating in largest connected component of $\\mathcal{G}_T$ , denoting it $\\mathcal{G}_{LCT}$ .", + "3 Find the list of all triplets $Trp$ in $\\mathcal{G}_{LCT}$ .", + "4 for each triplet $t$ in Trp do" + ], + "bbox": [ + 504, + 172, + 859, + 248 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "5 Get the number of inliers for all three edges as $n_{ij}, (i,j) \\in t$ .", + "6 Assign a score to each edge based on triplet $t$ $q_{ij}^{t} = \\frac{n_{ij}}{\\max_{(k,l)\\in t}n_{kl}}.$" + ], + "bbox": [ + 506, + 250, + 851, + 314 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "7 end", + "bbox": [ + 506, + 314, + 550, + 325 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "$\\S$ Assign $q_{ij}$ to each edge: $q_{ij} = \\frac{\\sum_{t\\in trp(i,j)}q_{ij}^t}{|trp(i,j)|}$ .", + "9 Compute $\\tau$ from $m$ using Eqn. 3.", + "10 Remove edges in $\\mathcal{G}_{LCT}$ with $q_{ij} < \\tau$ giving $\\mathcal{G}_F$ .", + "11 Extract the largest connected component of $\\mathcal{G}_F$ ." + ], + "bbox": [ + 503, + 329, + 838, + 398 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "of all triplets [12, 42]. We note that steps 4-8 in Algo. 1 are performed using CPU parallelization (20 threads) and vectorized operations, which makes it efficient.", + "bbox": [ + 496, + 434, + 890, + 479 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 494, + 632, + 513 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We present experimental results on publicly available generic and ambiguous datasets in individual subsections. We use COLMAP [36] to obtain the original viewgraph and also use it to get 3D reconstructions under different scenarios. All experiments are performed on a PC with Intel Xeon Silver 4210 processor with 128 GB RAM and two RTX 2080Ti GPUs. Our code is implemented in MATLAB and does not require any $\\mathbf{GPU}^1$ . We only consider the largest connected component of the viewgraphs for reporting values. We state the notations for graphs below (same as used in Algo. 1), for further usage:", + "bbox": [ + 496, + 521, + 890, + 686 + ], + "page_idx": 4 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "$\\mathcal{G}$ Original viewgraph.", + "- $\\mathcal{G}_{LCT}$ : Graph containing edges contributing to the largest connected component of the triplet graph $\\mathcal{G}_T$ .", + "- $\\mathcal{G}_{Dopp}$ : Graph obtained after applying Doppelgangers [3] on the original graph $\\mathcal{G}$ .", + "- $\\mathcal{G}_F(m)$ : Graph obtained after applying Algo. 1 with minimum edge score $m$ ." + ], + "bbox": [ + 500, + 688, + 890, + 792 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Generic Datasets", + "text_level": 1, + "bbox": [ + 500, + 805, + 666, + 819 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this subsection, we provide results for graph sparsification on generic datasets. We consider datasets provided by [5, 24, 47] and apply Algo. 1 to sparsify viewgraphs.", + "bbox": [ + 496, + 829, + 890, + 876 + ], + "page_idx": 4 + }, + { + "type": "page_footnote", + "text": "1 GPUs are used only for Doppelgangers [3] and COLMAP [36].", + "bbox": [ + 517, + 886, + 859, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "4963", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/b5944b709fd6af4cd6ef68ef4500d07c0a5eac0649548ae25f59d09362fcc0dd.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DatasetClean Reconstruction# Cameras Reconstructed (#NCR)# 3D Points Reconstructed (in 103)Mean Reprojection Errors (px)Reconstruction Time (mins) (tr)
GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)
Alamo [47]✓✓✓✓8998756526121611571281260.660.660.620.5944442825
Gendarmenmark [47]XX✓✓104210458998572072061601510.760.760.610.74372339144103
Madrid Metropolis [47]✓✓✓✓471453274232747247330.620.610.570.5888902221
Montreal Notre Dame [47]✓✓✓✓5755704113981451461081030.860.860.800.791141005052
Notre Dame [47]XX✓✓14071406129510933483483322880.760.760.700.68205421311323758
NYC Library [47]✓✓✓✓63561450939611010993840.740.740.710.701051014040
Piccadilly [47]XX✓✓32083110278626453743683112880.760.760.740.721969140910601000
Roman Forum [47]✓✓✓✓15871565136512953243232782630.760.760.730.72784810477453
Tower of London [47]✓✓✓✓7357185354951651651371290.630.630.620.6195864442
Trafalgar [47]✓✓✓✓78677532653862567066955735450.740.740.730.726875560138523698
Union Square [47]✓✓✓✓11601150891805828162550.740.730.690.692201858086
Vienna Cathedral [47]XX✓✓1197116110109653043012582480.750.750.740.73793703398376
Dubrovnik [24]✓✓✓✓588358505576546412521250112710730.760.760.730.72582556521428
Rome [24]✓✓✓✓18121812180717283953953893890.900.900.870.85284280279265
Quad [5]✓✓✓✓57295569436038431295127710418820.690.690.670.66417418318249
", + "bbox": [ + 80, + 88, + 885, + 250 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Reconstruction statistics on generic datasets. $\\checkmark / \\times$ : Removed/Existing ghost artifacts. Bold values indicate best in the respective category. Our method sparsifies the viewgraphs, reconstructing most cameras and 3D points with reduced reprojection errors and reconstruction time.", + "bbox": [ + 75, + 260, + 893, + 303 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/32094ad333aeda59afbd3914a31afce8f9b981d8920f6b31f2502a351edb57b5.jpg", + "image_caption": [ + "[47]" + ], + "image_footnote": [], + "bbox": [ + 104, + 330, + 295, + 424 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/a18f02dd55e3a080c51dfc317f403a9c68b6ebb93ead52ae3fc496d94cdcb54e.jpg", + "image_caption": [ + "$\\# N_{CR} = 1045, t_R = 339$ mins." + ], + "image_footnote": [], + "bbox": [ + 299, + 330, + 493, + 424 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/727b5f2474aff265600d5036c5ecc60d8cd18a29b7651733c81063c9f08318a0.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 504, + 337, + 694, + 398 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/a52bc88b4995134b28086848d996f13afe97070a2226c1bf750002036659c8fc.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 707, + 337, + 892, + 398 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e0168581abacbab7e4cddad520d190f723d98e3997b7ef854e9924b57a1c0114.jpg", + "image_caption": [ + "$N_{CR} = 1042, t_R = 372$ mins.", + "$N_{CR} = 5883, t_R = 582$ mins.", + "Original Graph $(\\mathcal{G})$" + ], + "image_footnote": [], + "bbox": [ + 76, + 445, + 295, + 537 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/348416e0e1c7701a49eabc2bcf4bb0271521a55cc4a75ae6979e827270afffbd.jpg", + "image_caption": [ + "Graph with Triplets $(\\mathcal{G}_{LCT})$" + ], + "image_footnote": [], + "bbox": [ + 299, + 445, + 495, + 536 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/f2b5ab384ba9a6e9395bdf9480c193c9c57dfdc7ae6ee235351f80d0685e302d.jpg", + "image_caption": [ + "$\\# N_{CR} = 899, t_R = 144$ mins.", + "$\\# N_{CR} = 5850, t_R = 556 \\mathrm{~min}$", + "$\\# N_{CR} = 5576, t_R = 521$ mins.", + "Sparsified Graph [Ours] $(\\mathcal{G}_F(0.6))$", + "Figure 3. Reconstructed obtained with different graphs on generic datasets. $\\# N_{CR}$ : Number of cameras reconstructed, $t_R$ : Reconstruction time using COLMAP [36]. Top row: Dataset creating ghost artifacts in reconstructions (marked in blue). Applying our method removes such artifacts with other parts of the reconstructions intact. Bottom row: Dataset with many redundant cameras and edges. Our method sparsifies the graphs, giving visually similar reconstructions in reduced reconstruction time." + ], + "image_footnote": [], + "bbox": [ + 496, + 445, + 692, + 540 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/46d0e4e7e81e145c8ca06c3501875cbcb34acacb0eff6e1838fa1fa3fbbba265.jpg", + "image_caption": [ + "$N_{CR} = 857,t_R = 103$ mins.", + "$\\# N_{CR} = 5464, t_R = 428$ mins.", + "Sparsified Graph [Ours] $(\\mathcal{G}_F(0.7))$" + ], + "image_footnote": [], + "bbox": [ + 694, + 445, + 893, + 540 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In Table 2, we compare results of the original viewgraph $\\mathcal{G}$ and the sparsified viewgraphs $\\mathcal{G}_F$ with different values of minimum edge score, $m = \\{0.6, 0.7\\}$ . We also show the results for the viewgraph $\\mathcal{G}_{LCT}$ , since Algo. 1 extracts this graph before scoring the edges. It can be seen that the number of cameras and 3D points reconstructed with $\\mathcal{G}$ and $\\mathcal{G}_{LCT}$ are similar, with mean reprojection errors being close. This shows that the removal of edges not participating in the largest connected component of the triplet graph has minimal impact on the 3D reconstructions. The sparsified viewgraphs $(\\mathcal{G}_F)$ , using Algo. 1, also have most cameras and 3D points reconstructed compared to $\\mathcal{G}_{LCT}$ . Although the number of 3D points reconstructed is reduced compared to $\\mathcal{G}_{LCT}$ , they have lower reprojection", + "bbox": [ + 75, + 680, + 472, + 893 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "errors, indicating that the estimated camera parameters (intrinsic and motions) and 3D points in $\\mathcal{G}_F$ are more consistent with the observations (epipolar inliers on the edges) compared to the original graph. Moreover, the ghost artifacts in the reconstructions are also removed in sparsified graphs, along with a significant reduction in the reconstruction time using COLMAP, by a margin of $50\\%$ to $80\\%$ . Our method takes $< 1\\%$ of the reconstruction time to execute in most cases. More details are provided in the supplementary material. These results are in accordance with the goals of sparsification to obtain a reconstruction with most cameras and 3D points recovered with similar or improved accuracy with reduced reconstruction time using a time-efficient method.", + "bbox": [ + 496, + 680, + 893, + 891 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "4964", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/8a7401909f88443027537642a63e46a3f96ac7fe182d382e5e62d322222316db.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
DatasetDisambiguated# Cameras Reconstructed (#NCR)# 3D Points Reconstructed (in 103)Mean Reprojection Errors (px)Reconstruction Time (mins) (tR)
GGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF Ours
Louvre [46]✓✓✓✓3673593201861281291081130.600.600.600.6095907952
Notre Dame [46]XX✓✓795277785481542017851775131413060.730.740.740.721558168611601059
Sacre Coeur [46]XX✓✓44924443379619847117065483470.700.710.710.61385405347156
Seville [46]XX✓✓151014984474753533531091170.680.680.640.622031138724
Ellis Island [47]XX✓✓88091031433316417184890.760.750.800.792121953326
Piazza del Popolo [47]XX✓✓102310129228651381361231100.690.690.680.6717818412899
Yorkminster [47]XX✓✓106510275855202842801731620.750.750.770.7638341211386
Alexander Nevsky Cathedral [17]XX✓✓44744744542910010090830.670.670.680.6232283113
Arc de Triompe [17]XX✓✓427425392394818169700.660.660.660.6422181715
Berliner Dom [17]XX✓✓16031603160015882422422382340.700.700.700.68142118126104
Big Ben [17]XX✓✓397398394379747473670.640.640.640.6140364333
Brandenburg Gate [17]XX✓*✓*172172151129242421140.840.840.870.738892
Church on Spilled Blood [17]XXX✓273274258136696964300.610.610.610.521818165
Indoor [17]XX✓✓1521521524273735890.520.550.530.409881
Radcliffe Camera [17]XX✓*✓*27928094177767628400.640.640.600.58181866
Books [49]XXX✓*212121988720.410.410.410.310.30.30.30.1
Cereal [49]XXX✓*252525712121230.410.410.410.300.50.50.50.1
Cup [49]XX✓X6464634066650.610.610.390.420.50.60.30.3
Desk [49]✓✓✓✓*3131311214141230.490.490.480.401.01.10.80.2
Oats [49]XXX✓*232323988730.400.390.370.250.40.50.40.1
Street [49]XX✓*✓1919101944120.500.500.370.350.20.20.10.1
Temple of Heaven [49]✓✓✓✓3383383383381921921851960.650.650.630.6578763254
", + "bbox": [ + 80, + 88, + 885, + 330 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 3. Reconstruction statistics on ambiguous datasets. Please refer to text for details on probability threshold $(p)$ used for Doppelgangers [3] and minimum edge score $(m)$ for our method (Algo. 1). $\\sqrt{/\\sqrt{*}/X}$ : Disambiguated/Disambiguated but oversplit/Nondisambiguated reconstructions. Bold values indicate best in the respective category. The best value is checked only across disambiguated/disambiguated but oversplit reconstructions. Our method disambiguates all datasets except Cup (and also sparsifies them), reconstructing most cameras and 3D points with reduced reprojection errors and reconstruction time.", + "bbox": [ + 75, + 340, + 892, + 411 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In Fig. 3, we show the reconstructions of two datasets, with Gendarmenmarkt containing a ghost artifact. It can be seen that extracting $\\mathcal{G}_{LCT}$ from $\\mathcal{G}$ does not remove the ghost artifact and requires further processing to avoid it. The reconstructions obtained with sparsified viewgraphs are visually similar to those from $\\mathcal{G}$ and $\\mathcal{G}_{LCT}$ (after removing ghost artifacts, if present), even with some lost cameras, in significantly less time. This reveals the advantage of scoring edges based on the number of epipolar inliers.", + "bbox": [ + 75, + 453, + 470, + 589 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Ambiguous Datasets", + "text_level": 1, + "bbox": [ + 76, + 604, + 272, + 619 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In this subsection, we evaluate the performance of our method on ambiguous datasets. At first, we study how well the edge scores reflect the presence of false edges. We take datasets provided by Doppelgangers [3] since they provide ground truth labels for true and false edges. We obtain viewgraphs using COLMAP and compute the edge quality scores based on Algo. 1. In Fig. 4, we provide separate histograms of the edge quality scores for true (non-ambiguous) and false (ambiguous) edges for all the datasets. We only use those edges for the histograms whose labels are provided in the datasets. It can be seen that the ambiguous edges are scored low, which is desired for their removal using our method. For non-ambiguous edges, the edge scores are distributed more uniformly, which helps in the uniform removal of edges for graph sparsification with our method. Thus, our edge scoring mechanism is able to capture the presence of false edges and redundancy of the graph based on connectivity via 3D points.", + "bbox": [ + 75, + 628, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/f9be05bef23336d8c9924dec3a91125154711707b75bb804662a3d7eaa5a3518.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 563, + 444, + 823, + 517 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/e94c0585d57c9ac94a1200c70c65f6e6c092607947f522c725d7bbea8339d105.jpg", + "image_caption": [ + "Figure 4. Histograms of edge quality scores over all datasets from Doppelgangers [3]. Top: Only non-ambiguous edges. Bottom: Only ambiguous edges. Ambiguous edges have low scores. Non-ambiguous edges are scored more uniformly, which aids uniform edge removal for graph sparsification." + ], + "image_footnote": [], + "bbox": [ + 563, + 525, + 825, + 599 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Next, we present results on ambiguous datasets provided by [17, 46, 47, 49]. In Table 3, we compare results of the disambiguated viewgraph $\\mathcal{G}_F$ to those of viewgraphs $\\mathcal{G}$ and $\\mathcal{G}_{LCT}$ . We use $m = 0.6$ for large-scale datasets [46, 47], the same as used for generic datasets, except for highly ambiguous datasets (Louvre and Sacre Coeur), where we use $m = 0.9$ . We use $m = 0.3$ for medium and small-scale datasets [17, 49]. We also provide reconstruction statistics after applying Doppelgangers [3] on $\\mathcal{G}$ , where we use probability threshold $p = 0.8$ for all datasets (as suggested in [3]) except for Louvre, where $p = 0.9$ . No value of $p$ worked for the datasets not disambiguated by [3]. We", + "bbox": [ + 496, + 719, + 893, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "4965", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5d7767d156c4ccc453869052ef6b793d6aa431f5aedc148764e6de421ec3f2c6.jpg", + "image_caption": [ + "Figure 5. Reconstructions obtained with different graphs on ambiguous datasets. $\\# N_{CR}$ : Number of cameras reconstructed, $t_R$ : Reconstruction time using COLMAP [36]. Datasets resulting in superimposed reconstructions (marked in blue) are corrected after applying our method with faster reconstruction time compared to Doppelgangers [3] due to the sparsification behaviour of our method." + ], + "image_footnote": [], + "bbox": [ + 76, + 85, + 890, + 415 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "note that $\\mathcal{G}_{LCT}$ still contains false edges, due to which no dataset is disambiguated by extracting $\\mathcal{G}_{LCT}$ from $\\mathcal{G}$ . Our method is able to disambiguate repeated structures for all large and medium-scale datasets, recovering most of the cameras and 3D points when compared to Doppelgangers reconstructions, with similar or better reprojection errors for almost all the datasets. For Louvre, although many cameras are lost, we still reconstruct more 3D points than Doppelgangers with reprojection errors close to each other, showing the effectiveness of our edge-scoring mechanism. Additionally, apart from removing false edges, our method also sparsifies the graphs, which reduces the reconstruction times for most datasets. More details are given in the supplementary material. Although similar observations can be made for small-scale datasets [49], some scenes are over-split due to graph sparsification by our method because these datasets [49], being sequential, have a low redundancy of edges.", + "bbox": [ + 75, + 496, + 472, + 770 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In Fig. 5, we show reconstructions of two datasets, one large-scale and another medium-scale. Both $\\mathcal{G}$ and $\\mathcal{G}_{LCT}$ lead to superimposed reconstructions due to the presence of false edges. Our method is able to disambiguate different facades of the buildings, leading to correct reconstruction, as validated by Doppelgangers reconstruction. Moreover, due to graph sparsification, our method significantly", + "bbox": [ + 75, + 794, + 468, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "reduces reconstruction time compared to Doppelgangers. More results are provided in the supplementary material.", + "bbox": [ + 498, + 496, + 888, + 527 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 542, + 617, + 556 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we present a single method based on camera triplets to solve both the problems of viewgraph sparsification and disambiguation of repeated structures. We propose a scoring mechanism for the edges in a viewgraph based on epipolar inliers, which captures both the redundancy of the edges and the presence of ambiguous edges based on global information of 3D point connectivity. We formulate an optimization problem whose solution is proven to be a thresholding scheme. This leads us to an efficient algorithm which can be incorporated into any SfM pipeline as a pre-processing step. Applying our method reduces the reconstruction time significantly while maintaining accuracy and also removes ghost artifacts on generic datasets. Our method also disambiguates repeated structures in the scenes along with sparsifying viewgraphs of ambiguous datasets, resulting in reduced reconstruction time.", + "bbox": [ + 496, + 566, + 890, + 811 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments: Lalit Manam is supported by a Prime Minister's Research Fellowship, Government of India. This research was supported in part by a Core Research Grant from the Science and Engineering Research Board, Department of Science and Technology, Government of India.", + "bbox": [ + 496, + 825, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "4966", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. Netvlad: Cnn architecture for weakly supervised place recognition. In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 5297-5307, 2016. 1", + "[2] Herbert Bay, Andreas Ess, Tinne Tuytelaars, and Luc Van Gool. Speeded-up robust features (surf). 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IEEE, 2010. 1, 3" + ], + "bbox": [ + 501, + 92, + 890, + 797 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "4968", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Leveraging Camera Triplets for Efficient and Accurate Structure-from-Motion/a217b793-2629-4522-9467-ef3937164206_model.json b/2024/Leveraging Camera Triplets for Efficient and Accurate Structure-from-Motion/a217b793-2629-4522-9467-ef3937164206_model.json new file mode 100644 index 0000000000000000000000000000000000000000..2d609f613cfd8b1ee3ae3bfd186398d97ed9868c --- /dev/null +++ b/2024/Leveraging Camera Triplets for Efficient and Accurate Structure-from-Motion/a217b793-2629-4522-9467-ef3937164206_model.json @@ -0,0 +1,2134 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.088, + 0.131, + 0.882, + 0.152 + ], + "angle": 0, + "content": "Leveraging Camera Triplets for Efficient and Accurate Structure-from-Motion" + }, + { + "type": "text", + "bbox": [ + 0.322, + 0.182, + 0.647, + 0.252 + ], + "angle": 0, + "content": "Lalit Manam and Venu Madhav Govindu \nIndian Institute of Science \nBengaluru - 560012, INDIA \n{lalitmanam,venug}@iisc.ac.in" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.287, + 0.314, + 0.303 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.318, + 0.473, + 0.683 + ], + "angle": 0, + "content": "In Structure-from-Motion (SfM), the underlying viewgraphs of unordered image collections generally have a highly redundant set of edges that can be sparsified for efficiency without significant loss of reconstruction quality. Often, there are also false edges due to incorrect image retrieval and repeated structures (symmetries) that give rise to ghosting and superimposed reconstruction artifacts. We present a unified method to simultaneously sparsify the viewgraph and remove false edges. We propose a scoring mechanism based on camera triplets that identifies edge redundancy as well as false edges. Our edge selection is formulated as an optimization problem which can be provably solved using a simple thresholding scheme. This results in a highly efficient algorithm which can be incorporated as a pre-processing step into any SfM pipeline, making it practically usable. We demonstrate the utility of our method on generic and ambiguous datasets that cover the range of small, medium and large-scale datasets, all with different statistical properties. Sparsification of generic datasets using our method significantly reduces reconstruction time while maintaining the accuracy of the reconstructions as well as removing ghosting artifacts. For ambiguous datasets, our method removes false edges, thereby avoiding incorrect superimposed reconstructions." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.71, + 0.21, + 0.725 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.734, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Structure-from-Motion (SfM) [13] has been a long-studied problem in computer vision. It aims to reconstruct a 3D structure and estimate camera motions given images of a scene. The first step in SfM is to identify the pairs of images that capture the same part of the scene. For unordered image collections, especially for large-scale datasets, image retrieval techniques [1, 14, 23, 31, 32] are used where each image is assigned with a descriptor and then matched with other images. The relationships between the pairs of images can be represented as a graph (also called a viewgraph in the SfM literature), with nodes representing" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.288, + 0.895, + 0.471 + ], + "angle": 0, + "content": "cameras and edges representing an overlap of the scene in the images captured by the two cameras, implying that their relative geometry can be recovered. This graph is further processed to extract keypoints in the images, which are then matched with keypoints in other images based on the connectivity of the graph [2, 7, 8, 25, 27, 34, 35, 44, 50]. Subsequently, the relative motion for every edge is obtained by estimating epipolar geometry [13] using inlier keypoint matches. We refer to such matches as epipolar inliers. The obtained graph in this fashion is used by either incremental [36, 39, 40, 48] or global methods [9-11, 42] to get a 3D reconstruction of the scene along with camera motions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.489, + 0.895, + 0.685 + ], + "angle": 0, + "content": "The underlying viewgraphs obtained from unordered image collections generally contain a redundant set of images (equivalently nodes) since popular views of the scene are captured more frequently [41]. As a consequence, a large number of pairs of images (equivalently edges) are identified to capture the same part of the scene, resulting in a highly redundant set of edges in the viewgraphs [16]. We refer to the datasets with the above-mentioned properties as generic datasets. Many methods [15, 16, 37, 38, 41] have been proposed to sparsify the viewgraphs while maintaining the accuracy of the reconstructions by considering only the nodes and edges which are distinguished to be important." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.896, + 0.887 + ], + "angle": 0, + "content": "When scenes contain repeated structures leading to different symmetries [26], a significant number of false edges occur between the cameras viewing repeated structures. This is because such images look similar and, thus, are identified as belonging to the same part of the scene, even if they capture physically different parts of the scene. The presence of such false edges leads to superimposed reconstructions. We refer to these datasets as ambiguous datasets. Methods based on viewgraph properties and loop consistency checks in the viewgraphs [3, 4, 17-19, 21, 33, 37, 38, 45, 46, 49, 51, 52] have been proposed to tackle false edges." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4959" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.097, + 0.09, + 0.345, + 0.229 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.189, + 0.234, + 0.388, + 0.247 + ], + "angle": 0, + "content": "(a) Generic case (Union Square [47])." + }, + { + "type": "image", + "bbox": [ + 0.347, + 0.143, + 0.483, + 0.212 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.491, + 0.091, + 0.874, + 0.227 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.532, + 0.233, + 0.831, + 0.246 + ], + "angle": 0, + "content": "(b) Ambiguous case (Alexander Nevsky Cathedral [17])." + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.259, + 0.892, + 0.343 + ], + "angle": 0, + "content": "Figure 1. Camera triplets in different cases. The number of epipolar inliers are shown for the respective edges. The part of the image where most of the inliers are matched is shown in rectangular boxes with colours corresponding to the edge colours. The red dots on the images show the detected keypoints. (a) A triplet in a generic dataset where the edge marked green has fewer inliers than other edges due to low overlap, thus, can potentially be removed to sparsify the viewgraph. (b) A triplet in an ambiguous dataset where two different facades of a building are matched, giving false edges (marked green and blue). The false edges have a low number of inliers compared to the true edge (marked orange), thus giving a cue about ambiguity." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.366, + 0.472, + 0.459 + ], + "angle": 0, + "content": "
MethodsScenarios in viewgraphs
Mostly True EdgesMany False Edges
Graph Sparsification✓✗
Disambiguation✗✓
Ours✓✓
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.469, + 0.469, + 0.498 + ], + "angle": 0, + "content": "Table 1. Summary of different scenarios in viewgraphs handled by methods designed for specific tasks." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.532, + 0.469, + 0.607 + ], + "angle": 0, + "content": "We note that generic datasets can also contain a small fraction of false edges due to incorrect images retrieved, which leads to ghost artifacts in reconstructions. On the other hand, ambiguous datasets contain repeated structures which give rise to a significant number of false edges." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.626, + 0.469, + 0.806 + ], + "angle": 0, + "content": "Both the problems, viewgraph sparsification and disambiguation of repeated structures, have mostly been dealt with independently in the literature. The underlying assumptions of both the problems are very much opposed. For viewgraph sparsification, most of the edges are considered to be reliable (or true). Thus, the removal of a few edges does not severely affect the accuracy of reconstruction. On the other hand, for the disambiguation problem, a significant number of edges are false, which must be weeded out to obtain a proper reconstruction. Our objective is to solve both problems together by a single scheme, which is summarized in Table 1." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.826, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Our contributions: In this paper, we simultaneously target both the problems of viewgraph sparsification and disambiguation of repeated structures. A fundamental design attribute of our approach is the idea that camera triplets are more informative than individual edges [41, 51] and are" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.369, + 0.892, + 0.626 + ], + "angle": 0, + "content": "easy to analyze since they form loops of the smallest possible length. For the problems on hand, triplets provide an important indication of an edge being redundant or ambiguous based on matched keypoints (see Fig. 1). We propose a single scheme for both tasks by leveraging camera triplets. We identify redundant and false edges based on a scoring mechanism that aggregates information about 3D point connectivity of the triplets globally over the whole graph without requiring intermediate partial reconstructions and remove them based on a single threshold. The proposed method can be incorporated into any SfM pipeline, either incremental or global, making it practical for usage. Experiments on viewgraph sparsification show a significant improvement in reconstruction time while maintaining accuracy on large-scale datasets. Our method also removes ghost artifacts in the reconstructions of generic datasets and shows disambiguation capability on ambiguous datasets." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.647, + 0.676, + 0.662 + ], + "angle": 0, + "content": "2. Literature Review" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Viewgraph sparsification: Snavely et al. [41] constructed skeletal graphs based on the approximate covariance of camera motions. Havlena et al. [15] used image level descriptors to carefully choose camera triplets for independent reconstructions and then merged them. Havlena et al. [16] also relied on image level descriptors and selected a minimally connected dominating set of the image collection. Shen et al. [38] used an online algorithm to get a spanning tree, expanded the graph based on triplets and finally enforced a community-based graph structure. Shah et al. [37] selected edges on the graph based on a minimum cost network flow problem. Many methods rely on intermediate partial reconstructions [15, 16, 41], have multiple hyperparameters [37, 38], or design their own specific SfM pipeline [15, 16, 41] but we provide a solution" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.956 + ], + "angle": 0, + "content": "4960" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.122 + ], + "angle": 0, + "content": "based on a single hyperparameter without any intermediate reconstruction, and can be used in any pipeline." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.138, + 0.473, + 0.804 + ], + "angle": 0, + "content": "Disambiguation of repeated structures: Zach et al. [51] reasoned about false edges based on missing correspondences in triplets using Bayesian inference. Zach et al. [52] further extended [51] on longer loops using relative camera motions. Roberts et al. [33] also inferred false edges based on relative motions using an expectation-maximization framework [29]. Cohen et al. [4] detected symmetries by estimating similarity transforms and removing false edges to reduce drift. Jiang et al. [19] measured reconstruction quality based on missing correspondences and used it for edge selection. Wilson et al. [46] split the camera-point relation graph based on its covering subgraphs. Heinly et al. [17] proposed a post-processing step to split the reconstruction based on conflicting observations and then merge the disconnected epipolar inliers. Heinly et al. [18] also proposed a post-processing step to isolate 3D points connecting separate parts of the reconstruction incorrectly by analyzing the clustering behaviour of 3D point connectivity. Cui et al. [6] merged two-view reconstructions locally to find missing correspondences. Yan et al. [49] constructed a path network where a few anchor images are selected and other images are related to them with paths for clean image correspondences. Wang et al. [45] grouped the images based on viewgraph and scored edges on their ability to expand the reconstruction. Kataria et al. [21] considered keypoints which are only matched across a few images for resectioning cameras to obtain a reliable reconstruction. Cai et al. [3] proposed Doppelgangers, where a neural network detects false edges based on images, keypoints and matches. Some graph sparsification methods also disambiguated repeated structures either by checking geometric consistency along loops [38] or by modifying their cost function for handling ambiguous datasets [37]. Some other methods [22, 43] avoided incorrect fetching of images containing repetitive structures during the image retrieval phase by specific designs of image descriptors. Many of these methods assume specific probability distributions on missing correspondences [51, 52], exploit intermediate reconstructions [6, 33], involve multiple hyperparameters [18, 19, 21, 37, 38, 46, 49] or are designed for specific pipelines [21, 51]. Our method does not assume any probability distribution for missing correspondences, can be used in any pipeline, and uses only a single hyperparameter without requiring any intermediate reconstruction." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.816, + 0.251, + 0.833 + ], + "angle": 0, + "content": "3. Proposed Method" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.84, + 0.47, + 0.903 + ], + "angle": 0, + "content": "The goal of graph sparsification is to recover most of the cameras and 3D points with a sparsified graph compared to the original graph while maintaining accuracy and significantly reducing reconstruction time. Dealing with" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.26 + ], + "angle": 0, + "content": "ambiguities in the scene requires distinguishing between repeated structures. Our aim is to handle both the tasks of graph sparsification and disambiguation of repeated structures using a single scheme with as few hyperparameters as possible without needing any intermediate partial reconstructions. We also seek to build a scheme which can be used as a pre-processing step for any pipeline, either incremental or global. To achieve our goals, we present a scheme for scoring edge quality and then formulate an optimization problem which can be provably solved based on thresholding leading to our proposed algorithm." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.276, + 0.895, + 0.655 + ], + "angle": 0, + "content": "Edge quality score: Edges contain limited information about the pairs of cameras they connect. An individual edge alone cannot validate its importance in the graph, and thus, scoring them meaningfully requires considering other connected edges in the graph. We take recourse to camera triplets, which provide much more information about an edge based on the other two edges in a triplet (see Fig. 1). Triplets have been widely used for sparsification [15, 16, 37, 38, 41] and disambiguation [19, 33, 51, 52]. Let \\(\\mathcal{G} = (\\mathcal{V},\\mathcal{E})\\) be a viewgraph, with \\(\\mathcal{V}\\) and \\(\\mathcal{E}\\) denote the set of nodes and edges in \\(\\mathcal{G}\\), respectively. We first determine a quality score, \\(q_{ij} > 0\\), for each edge \\((i,j)\\in \\mathcal{E}\\) before processing the viewgraph. Since we aim to get a 3D reconstruction, to sparsify the viewgraph, we want to score the edges based on how well they are connected via 3D points. One way to get an idea of 3D point connectivity without access to 3D reconstruction is to check for epipolar inliers on the edges since inliers are the candidate keypoints for reconstruction. One could check for common inliers in all three cameras and assign a score to each edge on the triplet based on the fraction of common inliers to that of the total inliers belonging to that edge. Such a scoring mechanism favours edges with a low number of inliers, which conflicts with our aim to score based on 3D point connectivity." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.672, + 0.895, + 0.868 + ], + "angle": 0, + "content": "Therefore, we score edges based on the number of inliers instead of common inliers across all three edges of the triplet, which adheres to our aim of 3D point connectivity-based scores. The indication for graph sparsification and disambiguation in the triplets is given by the relative number of inliers between the three edges (also seen in Fig. 1) and not by the actual number of inliers. To score edges, we take the ratio of the number of inliers in each edge to the maximum number of inliers among all three edges in a triplet. This assigns scores to edges based on relative 3D point connectivity in the triplet and is also considerate of the cases where all images in triplets have a low number of inliers due to occlusion or lack of texture." + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.886, + 0.892, + 0.902 + ], + "angle": 0, + "content": "Inherently, our scoring mechanism based on the relative" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.514, + 0.957 + ], + "angle": 0, + "content": "4961" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.41 + ], + "angle": 0, + "content": "number of inliers in triplets is also useful for disambiguation. [3] empirically noted that the actual number of epipolar inliers does not provide useful information about ambiguity. Missing correspondences [19, 33, 49, 51] and the statistics of matched keypoints [49] provide a cue about the presence of false edges. They are generally detected using loops of small lengths like triplets since the likelihood of viewing the same 3D points on larger loops reduces. But the implicit assumption is the repeatability of the keypoints for the same 3D point, which can be violated in case of noisy images, occlusion or drastic changes in viewpoint [17, 30, 51]. Scoring based on the number of inliers instead of common inliers in the loops reduces the effect of unmatched keypoints due to repeatability concerns. This is because there can be other matched keypoints on the edges which will compensate for reduced edge scores due to non-repeatable keypoints. Moreover, we consider only inliers on the edges for computing scores. This ensures that only keypoints, which are proven to have discriminative capabilities for matching, are used for inference instead of all the keypoints (as used in [3, 33])." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.427, + 0.472, + 0.609 + ], + "angle": 0, + "content": "A given edge can be a part of many triplets and, thus, have as many scores. To aggregate information about the edge over the whole graph, for each edge, we take the average of the scores obtained from all the triplets it participates in. This ensures that edge scores reflect global information about the edge in the graph. Since our scoring mechanism is based only on triplets, we remove edges which are not a part of any triplet, as such edges cannot be scored. In practice, the viewgraphs for unordered image collections are well connected and losing edges not contributing to triplets has minimal impact on the reconstructions (please refer to Sec. 4 for details)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.627, + 0.473, + 0.868 + ], + "angle": 0, + "content": "Handling graphs consisting only of triplets: For graphs containing only triplets, there can be cases when two triplets are connected by a node and do not share a common edge. We call such a connection between two triplets a joint. In Fig. 2a, we present a scenario where the triplets \\( T5 \\) and \\( T6 \\) have a common node but no common edge. Also, there are no other triplets that share common edges with both green and red edges. In such cases, the edges marked in the two colours are effectively being scored independently since edges marked in each colour do not participate in the scoring of edges in the other colour. Although, we can continue with such independent scoring, for ambiguous datasets, it is not possible to infer whether the joints are valid connections or not. So, we separate the joints, which ensures that inference on edges is not based on independent scores." + }, + { + "type": "text", + "bbox": [ + 0.097, + 0.886, + 0.471, + 0.902 + ], + "angle": 0, + "content": "We construct a triplet graph \\(\\mathcal{G}_T = (\\mathcal{V}_T,\\mathcal{E}_T)\\), as done" + }, + { + "type": "image", + "bbox": [ + 0.541, + 0.097, + 0.859, + 0.234 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.595, + 0.244, + 0.796, + 0.257 + ], + "angle": 0, + "content": "(a) Graph \\((\\mathcal{G})\\) containing only triplets." + }, + { + "type": "image", + "bbox": [ + 0.529, + 0.264, + 0.855, + 0.337 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.597, + 0.348, + 0.796, + 0.361 + ], + "angle": 0, + "content": "(b) Corresponding triplet graph \\((\\mathcal{G}_T)\\)." + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.372, + 0.895, + 0.442 + ], + "angle": 0, + "content": "Figure 2. Graph \\((\\mathcal{G})\\) containing only triplets with a joint and its corresponding triplet graph \\((\\mathcal{G}_T)\\). The edges marked in green and red can be scored independently due to the absence of triplets sharing common edges across them. The triplet graph separates the joint and disconnects such graphs." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.485, + 0.895, + 0.758 + ], + "angle": 0, + "content": "in [20, 28], where nodes, \\(\\mathcal{V}_T\\), denote triplets in \\(\\mathcal{G}\\) and edges, \\(\\mathcal{E}_T\\), connect the nodes if an edge is common between the triplets in \\(\\mathcal{G}\\). By construction, the triplets connected by the joints in the viewgraph \\(\\mathcal{G}\\) are not connected in the triplet graph \\(\\mathcal{G}_T\\). If there are no common triplets between the set of edges separated by joints, it results in multiple connected components in the triplet graph \\(\\mathcal{G}_T\\), as can be seen in Fig. 2b. For each connected component of \\(\\mathcal{G}_T\\), the triplets in \\(\\mathcal{G}\\) will have at least one common edge with the other triplets in the same connected component and no common edges across different components of \\(\\mathcal{G}_T\\). Thus, the edges participating in different connected components of \\(\\mathcal{G}_T\\) can be scored independently. So, we only retain the edges in \\(\\mathcal{G}\\) corresponding to the largest connected component of \\(\\mathcal{G}_T\\) (denoting it as \\(\\mathcal{G}_{LCT}\\)) since our aim is to assign scores based on global reasoning. We empirically observe that separating the joints has a minor effect on the reconstructions (see Sec. 4)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.781, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Formulation: Given a quality score \\( q_{ij} \\) for each edge, we aim to select those edges which will increase the average quality score taken across all the edges. To avoid having the degenerate case of selecting edges only with the highest score (which could be as low as one edge in realistic scenarios), we need to regularize the cost by penalizing the loss of edges. Let \\( s_{ij} \\in \\{0,1\\} \\), be the binary variables denoting selection \\( (s_{ij} = 1) \\) or removal \\( (s_{ij} = 0) \\) of edges. Then, the" + }, + { + "type": "page_number", + "bbox": [ + 0.482, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4962" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.078, + 0.092, + 0.364, + 0.106 + ], + "angle": 0, + "content": "optimization problem can be formulated as" + }, + { + "type": "equation", + "bbox": [ + 0.09, + 0.117, + 0.47, + 0.164 + ], + "angle": 0, + "content": "\\[\n\\max_{\\substack{s_{ij}\\in \\{0,1\\} ,\\\\ (i,j)\\in \\mathcal{E}}}\\frac{\\sum_{(i,j)\\in\\mathcal{E}}s_{ij}q_{ij}}{\\sum_{(i,j)\\in\\mathcal{E}}s_{ij}} -\\lambda \\frac{\\sum_{(i,j)\\in\\mathcal{E}}(1 - s_{ij})q_{ij}}{\\sum_{(i,j)\\in\\mathcal{E}}(1 - s_{ij})}, \\tag{1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.174, + 0.473, + 0.468 + ], + "angle": 0, + "content": "where \\(\\lambda \\geq 0\\) is a regularization parameter which avoids degenerate solutions for the optimization problem. \\(\\lambda\\) also acts as a tuning parameter for the aggressiveness of edge removal, where reducing \\(\\lambda\\) increases the number of edges removed. The second term in Eqn. 1 suggests the average of quality scores of the removed edges should not be high, thus regularizing the first term. The strict positiveness of \\(q_{ij}\\) ensures that edges are either selected or removed for any given \\(\\lambda \\geq 0\\). Although the problem in Eqn. 1 does not enforce the graph structure, the quality scores obtained for edges are based on all the triplets they are members of. Let Trp be the set of all triplets in \\(\\mathcal{G}_{LCT}\\), \\(trp(i,j) \\subseteq Trp\\) be the set of triplets for which the edge \\((i,j)\\) is a member, and \\(q_{ij}^{t}\\) be the score obtained from the triplet \\(t \\in trp(i,j)\\). Replacing the scores \\(q_{ij}\\) in Eqn. 1 with \\(\\frac{\\sum_{t \\in trp(i,j)} q_{ij}^{t}}{|trp(i,j)|}\\) discloses the dependence of Eqn. 1 on the graph structure more explicitly. While the optimization problem in Eqn. 1 is combinatorial, we provide a simple thresholding scheme to solve it, which is shown as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.194, + 0.476, + 0.47, + 0.517 + ], + "angle": 0, + "content": "\\[\ns _ {i j} = \\left\\{ \\begin{array}{l l} 1 & \\text {i f} q _ {i j} \\geq \\tau , \\\\ 0 & \\text {o t h e r w i s e}, \\end{array} \\right. \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.527, + 0.47, + 0.573 + ], + "angle": 0, + "content": "where \\(\\tau\\) denotes a threshold. This thresholding scheme is equivalent to optimizing the problem in Eqn. 1 with \\(\\tau\\) acting as a regularizer, as shown by the following theorem:" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.583, + 0.47, + 0.63 + ], + "angle": 0, + "content": "Theorem 1. For a given \\(\\lambda\\) in Eqn. 1, there exists a threshold \\(\\tau\\) such that the values of \\(s_{ij}\\) obtained by solving the problems given by Eqn. 1 and Eqn. 2 are the same." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.639, + 0.47, + 0.731 + ], + "angle": 0, + "content": "Please refer to supplementary material for the proof of Thm. 1. In practice, finding a threshold is not easy for a given dataset, and a single threshold is not suitable for all datasets. We choose a threshold adaptively based on the connectivity of the graph. Specifically, given maximum node degree of the graph as \\( d_{max} \\), we get a threshold as" + }, + { + "type": "equation", + "bbox": [ + 0.155, + 0.74, + 0.47, + 0.775 + ], + "angle": 0, + "content": "\\[\n\\tau = m \\left(1 - \\frac {d _ {\\text {m a x}}}{| \\mathcal {V} |}\\right) + \\left(\\frac {d _ {\\text {m a x}}}{| \\mathcal {V} |}\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.78, + 0.471, + 0.902 + ], + "angle": 0, + "content": "where \\( |\\mathcal{V}| \\) is the number of nodes and \\( m \\) is the minimum score which edges should satisfy. We deliberately choose \\( |\\mathcal{V}| \\) as the denominator since for a connected graph, \\( 0 \\leq d_{max} \\leq |\\mathcal{V}| - 1 \\), thus \\( m \\leq \\tau < 1 \\). This ensures that \\( \\tau = 1 \\) is never chosen which only retains edges scored exactly as 1. Such a scenario with many edges scored as 1 is seldom true in practice. We now summarize our procedure in Algo. 1. Efficient implementations exist to get the list" + }, + { + "type": "title", + "bbox": [ + 0.51, + 0.095, + 0.803, + 0.11 + ], + "angle": 0, + "content": "Algorithm 1: Edge Selection using Triplets" + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.113, + 0.867, + 0.143 + ], + "angle": 0, + "content": "Input: Viewgraph \\(\\mathcal{G} = (\\mathcal{V},\\mathcal{E})\\) , with geometrically verified edges and a minimum edge score \\(m\\)" + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.144, + 0.863, + 0.173 + ], + "angle": 0, + "content": "Output: Sparsified viewgraph \\(\\mathcal{G}_F = (\\mathcal{V}_F,\\mathcal{E}_F)\\) with ambiguous edges removed." + }, + { + "type": "text", + "bbox": [ + 0.507, + 0.174, + 0.751, + 0.189 + ], + "angle": 0, + "content": "1 Construct triplet graph \\(\\mathcal{G}_T\\) from \\(\\mathcal{G}\\)" + }, + { + "type": "text", + "bbox": [ + 0.506, + 0.189, + 0.86, + 0.219 + ], + "angle": 0, + "content": "2 Retain edges in \\(\\mathcal{G}\\) participating in largest connected component of \\(\\mathcal{G}_T\\), denoting it \\(\\mathcal{G}_{LCT}\\)." + }, + { + "type": "text", + "bbox": [ + 0.506, + 0.22, + 0.786, + 0.234 + ], + "angle": 0, + "content": "3 Find the list of all triplets \\(Trp\\) in \\(\\mathcal{G}_{LCT}\\)." + }, + { + "type": "text", + "bbox": [ + 0.507, + 0.235, + 0.704, + 0.249 + ], + "angle": 0, + "content": "4 for each triplet \\(t\\) in Trp do" + }, + { + "type": "list", + "bbox": [ + 0.506, + 0.174, + 0.86, + 0.249 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.507, + 0.25, + 0.852, + 0.28 + ], + "angle": 0, + "content": "5 Get the number of inliers for all three edges as \\(n_{ij}, (i,j) \\in t\\)." + }, + { + "type": "text", + "bbox": [ + 0.507, + 0.28, + 0.849, + 0.315 + ], + "angle": 0, + "content": "6 Assign a score to each edge based on triplet \\(t\\) \\(q_{ij}^{t} = \\frac{n_{ij}}{\\max_{(k,l)\\in t}n_{kl}}.\\)" + }, + { + "type": "list", + "bbox": [ + 0.507, + 0.25, + 0.852, + 0.315 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.507, + 0.315, + 0.551, + 0.327 + ], + "angle": 0, + "content": "7 end" + }, + { + "type": "text", + "bbox": [ + 0.506, + 0.33, + 0.819, + 0.354 + ], + "angle": 0, + "content": "\\(\\S\\) Assign \\(q_{ij}\\) to each edge: \\(q_{ij} = \\frac{\\sum_{t\\in trp(i,j)}q_{ij}^t}{|trp(i,j)|}\\)." + }, + { + "type": "text", + "bbox": [ + 0.506, + 0.355, + 0.742, + 0.369 + ], + "angle": 0, + "content": "9 Compute \\(\\tau\\) from \\(m\\) using Eqn. 3." + }, + { + "type": "text", + "bbox": [ + 0.505, + 0.37, + 0.839, + 0.385 + ], + "angle": 0, + "content": "10 Remove edges in \\(\\mathcal{G}_{LCT}\\) with \\(q_{ij} < \\tau\\) giving \\(\\mathcal{G}_F\\)." + }, + { + "type": "text", + "bbox": [ + 0.504, + 0.385, + 0.835, + 0.399 + ], + "angle": 0, + "content": "11 Extract the largest connected component of \\(\\mathcal{G}_F\\)." + }, + { + "type": "list", + "bbox": [ + 0.504, + 0.33, + 0.839, + 0.399 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.435, + 0.892, + 0.481 + ], + "angle": 0, + "content": "of all triplets [12, 42]. We note that steps 4-8 in Algo. 1 are performed using CPU parallelization (20 threads) and vectorized operations, which makes it efficient." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.496, + 0.633, + 0.514 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.522, + 0.892, + 0.688 + ], + "angle": 0, + "content": "We present experimental results on publicly available generic and ambiguous datasets in individual subsections. We use COLMAP [36] to obtain the original viewgraph and also use it to get 3D reconstructions under different scenarios. All experiments are performed on a PC with Intel Xeon Silver 4210 processor with 128 GB RAM and two RTX 2080Ti GPUs. Our code is implemented in MATLAB and does not require any \\(\\mathbf{GPU}^1\\). We only consider the largest connected component of the viewgraphs for reporting values. We state the notations for graphs below (same as used in Algo. 1), for further usage:" + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.689, + 0.671, + 0.704 + ], + "angle": 0, + "content": "\\(\\mathcal{G}\\) Original viewgraph." + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.705, + 0.891, + 0.734 + ], + "angle": 0, + "content": "- \\(\\mathcal{G}_{LCT}\\): Graph containing edges contributing to the largest connected component of the triplet graph \\(\\mathcal{G}_T\\)." + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.735, + 0.891, + 0.765 + ], + "angle": 0, + "content": "- \\(\\mathcal{G}_{Dopp}\\): Graph obtained after applying Doppelgangers [3] on the original graph \\(\\mathcal{G}\\)." + }, + { + "type": "text", + "bbox": [ + 0.501, + 0.765, + 0.891, + 0.794 + ], + "angle": 0, + "content": "- \\(\\mathcal{G}_F(m)\\): Graph obtained after applying Algo. 1 with minimum edge score \\(m\\)." + }, + { + "type": "list", + "bbox": [ + 0.501, + 0.689, + 0.891, + 0.794 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.806, + 0.667, + 0.82 + ], + "angle": 0, + "content": "4.1. Generic Datasets" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.83, + 0.892, + 0.877 + ], + "angle": 0, + "content": "In this subsection, we provide results for graph sparsification on generic datasets. We consider datasets provided by [5, 24, 47] and apply Algo. 1 to sparsify viewgraphs." + }, + { + "type": "page_footnote", + "bbox": [ + 0.518, + 0.887, + 0.86, + 0.901 + ], + "angle": 0, + "content": "1 GPUs are used only for Doppelgangers [3] and COLMAP [36]." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4963" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.081, + 0.089, + 0.887, + 0.251 + ], + "angle": 0, + "content": "
DatasetClean Reconstruction# Cameras Reconstructed (#NCR)# 3D Points Reconstructed (in 103)Mean Reprojection Errors (px)Reconstruction Time (mins) (tr)
GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)
Alamo [47]✓✓✓✓8998756526121611571281260.660.660.620.5944442825
Gendarmenmark [47]XX✓✓104210458998572072061601510.760.760.610.74372339144103
Madrid Metropolis [47]✓✓✓✓471453274232747247330.620.610.570.5888902221
Montreal Notre Dame [47]✓✓✓✓5755704113981451461081030.860.860.800.791141005052
Notre Dame [47]XX✓✓14071406129510933483483322880.760.760.700.68205421311323758
NYC Library [47]✓✓✓✓63561450939611010993840.740.740.710.701051014040
Piccadilly [47]XX✓✓32083110278626453743683112880.760.760.740.721969140910601000
Roman Forum [47]✓✓✓✓15871565136512953243232782630.760.760.730.72784810477453
Tower of London [47]✓✓✓✓7357185354951651651371290.630.630.620.6195864442
Trafalgar [47]✓✓✓✓78677532653862567066955735450.740.740.730.726875560138523698
Union Square [47]✓✓✓✓11601150891805828162550.740.730.690.692201858086
Vienna Cathedral [47]XX✓✓1197116110109653043012582480.750.750.740.73793703398376
Dubrovnik [24]✓✓✓✓588358505576546412521250112710730.760.760.730.72582556521428
Rome [24]✓✓✓✓18121812180717283953953893890.900.900.870.85284280279265
Quad [5]✓✓✓✓57295569436038431295127710418820.690.690.670.66417418318249
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.261, + 0.895, + 0.304 + ], + "angle": 0, + "content": "Table 2. Reconstruction statistics on generic datasets. \\( \\checkmark / \\times \\) : Removed/Existing ghost artifacts. Bold values indicate best in the respective category. Our method sparsifies the viewgraphs, reconstructing most cameras and 3D points with reduced reprojection errors and reconstruction time." + }, + { + "type": "image_caption", + "bbox": [ + 0.078, + 0.317, + 0.097, + 0.431 + ], + "angle": 0, + "content": "[47]" + }, + { + "type": "image", + "bbox": [ + 0.105, + 0.331, + 0.296, + 0.425 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.3, + 0.331, + 0.495, + 0.425 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.506, + 0.338, + 0.695, + 0.4 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.709, + 0.338, + 0.893, + 0.4 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.106, + 0.43, + 0.291, + 0.444 + ], + "angle": 0, + "content": "\\(N_{CR} = 1042, t_R = 372\\) mins." + }, + { + "type": "image_caption", + "bbox": [ + 0.305, + 0.431, + 0.487, + 0.444 + ], + "angle": 0, + "content": "\\(\\# N_{CR} = 1045, t_R = 339\\) mins." + }, + { + "type": "image_caption", + "bbox": [ + 0.507, + 0.431, + 0.683, + 0.444 + ], + "angle": 0, + "content": "\\(\\# N_{CR} = 899, t_R = 144\\) mins." + }, + { + "type": "image_caption", + "bbox": [ + 0.705, + 0.431, + 0.881, + 0.444 + ], + "angle": 0, + "content": "\\(N_{CR} = 857,t_R = 103\\) mins." + }, + { + "type": "image", + "bbox": [ + 0.078, + 0.446, + 0.297, + 0.539 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.3, + 0.446, + 0.496, + 0.537 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.498, + 0.446, + 0.694, + 0.541 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.446, + 0.894, + 0.541 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.106, + 0.553, + 0.29, + 0.567 + ], + "angle": 0, + "content": "\\(N_{CR} = 5883, t_R = 582\\) mins." + }, + { + "type": "image_caption", + "bbox": [ + 0.306, + 0.553, + 0.488, + 0.567 + ], + "angle": 0, + "content": "\\(\\# N_{CR} = 5850, t_R = 556 \\mathrm{~min}\\)" + }, + { + "type": "image_caption", + "bbox": [ + 0.503, + 0.554, + 0.686, + 0.567 + ], + "angle": 0, + "content": "\\(\\# N_{CR} = 5576, t_R = 521\\) mins." + }, + { + "type": "image_caption", + "bbox": [ + 0.702, + 0.554, + 0.884, + 0.567 + ], + "angle": 0, + "content": "\\(\\# N_{CR} = 5464, t_R = 428\\) mins." + }, + { + "type": "image_caption", + "bbox": [ + 0.145, + 0.571, + 0.251, + 0.583 + ], + "angle": 0, + "content": "Original Graph \\((\\mathcal{G})\\)" + }, + { + "type": "image_caption", + "bbox": [ + 0.318, + 0.571, + 0.474, + 0.584 + ], + "angle": 0, + "content": "Graph with Triplets \\((\\mathcal{G}_{LCT})\\)" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.571, + 0.689, + 0.584 + ], + "angle": 0, + "content": "Sparsified Graph [Ours] \\((\\mathcal{G}_F(0.6))\\)" + }, + { + "type": "image_caption", + "bbox": [ + 0.698, + 0.571, + 0.887, + 0.584 + ], + "angle": 0, + "content": "Sparsified Graph [Ours] \\((\\mathcal{G}_F(0.7))\\)" + }, + { + "type": "image_caption", + "bbox": [ + 0.075, + 0.599, + 0.895, + 0.656 + ], + "angle": 0, + "content": "Figure 3. Reconstructed obtained with different graphs on generic datasets. \\(\\# N_{CR}\\): Number of cameras reconstructed, \\(t_R\\): Reconstruction time using COLMAP [36]. Top row: Dataset creating ghost artifacts in reconstructions (marked in blue). Applying our method removes such artifacts with other parts of the reconstructions intact. Bottom row: Dataset with many redundant cameras and edges. Our method sparsifies the graphs, giving visually similar reconstructions in reduced reconstruction time." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.681, + 0.473, + 0.894 + ], + "angle": 0, + "content": "In Table 2, we compare results of the original viewgraph \\(\\mathcal{G}\\) and the sparsified viewgraphs \\(\\mathcal{G}_F\\) with different values of minimum edge score, \\(m = \\{0.6, 0.7\\}\\). We also show the results for the viewgraph \\(\\mathcal{G}_{LCT}\\), since Algo. 1 extracts this graph before scoring the edges. It can be seen that the number of cameras and 3D points reconstructed with \\(\\mathcal{G}\\) and \\(\\mathcal{G}_{LCT}\\) are similar, with mean reprojection errors being close. This shows that the removal of edges not participating in the largest connected component of the triplet graph has minimal impact on the 3D reconstructions. The sparsified viewgraphs \\((\\mathcal{G}_F)\\), using Algo. 1, also have most cameras and 3D points reconstructed compared to \\(\\mathcal{G}_{LCT}\\). Although the number of 3D points reconstructed is reduced compared to \\(\\mathcal{G}_{LCT}\\), they have lower reprojection" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.681, + 0.895, + 0.892 + ], + "angle": 0, + "content": "errors, indicating that the estimated camera parameters (intrinsic and motions) and 3D points in \\(\\mathcal{G}_F\\) are more consistent with the observations (epipolar inliers on the edges) compared to the original graph. Moreover, the ghost artifacts in the reconstructions are also removed in sparsified graphs, along with a significant reduction in the reconstruction time using COLMAP, by a margin of \\(50\\%\\) to \\(80\\%\\). Our method takes \\(< 1\\%\\) of the reconstruction time to execute in most cases. More details are provided in the supplementary material. These results are in accordance with the goals of sparsification to obtain a reconstruction with most cameras and 3D points recovered with similar or improved accuracy with reduced reconstruction time using a time-efficient method." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4964" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.081, + 0.089, + 0.887, + 0.332 + ], + "angle": 0, + "content": "
DatasetDisambiguated# Cameras Reconstructed (#NCR)# 3D Points Reconstructed (in 103)Mean Reprojection Errors (px)Reconstruction Time (mins) (tR)
GGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF Ours
Louvre [46]✓✓✓✓3673593201861281291081130.600.600.600.6095907952
Notre Dame [46]XX✓✓795277785481542017851775131413060.730.740.740.721558168611601059
Sacre Coeur [46]XX✓✓44924443379619847117065483470.700.710.710.61385405347156
Seville [46]XX✓✓151014984474753533531091170.680.680.640.622031138724
Ellis Island [47]XX✓✓88091031433316417184890.760.750.800.792121953326
Piazza del Popolo [47]XX✓✓102310129228651381361231100.690.690.680.6717818412899
Yorkminster [47]XX✓✓106510275855202842801731620.750.750.770.7638341211386
Alexander Nevsky Cathedral [17]XX✓✓44744744542910010090830.670.670.680.6232283113
Arc de Triompe [17]XX✓✓427425392394818169700.660.660.660.6422181715
Berliner Dom [17]XX✓✓16031603160015882422422382340.700.700.700.68142118126104
Big Ben [17]XX✓✓397398394379747473670.640.640.640.6140364333
Brandenburg Gate [17]XX✓*✓*172172151129242421140.840.840.870.738892
Church on Spilled Blood [17]XXX✓273274258136696964300.610.610.610.521818165
Indoor [17]XX✓✓1521521524273735890.520.550.530.409881
Radcliffe Camera [17]XX✓*✓*27928094177767628400.640.640.600.58181866
Books [49]XXX✓*212121988720.410.410.410.310.30.30.30.1
Cereal [49]XXX✓*252525712121230.410.410.410.300.50.50.50.1
Cup [49]XX✓X6464634066650.610.610.390.420.50.60.30.3
Desk [49]✓✓✓✓*3131311214141230.490.490.480.401.01.10.80.2
Oats [49]XXX✓*232323988730.400.390.370.250.40.50.40.1
Street [49]XX✓*✓1919101944120.500.500.370.350.20.20.10.1
Temple of Heaven [49]✓✓✓✓3383383383381921921851960.650.650.630.6578763254
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.341, + 0.893, + 0.412 + ], + "angle": 0, + "content": "Table 3. Reconstruction statistics on ambiguous datasets. Please refer to text for details on probability threshold \\((p)\\) used for Doppelgangers [3] and minimum edge score \\((m)\\) for our method (Algo. 1). \\(\\sqrt{/\\sqrt{*}/X}\\): Disambiguated/Disambiguated but oversplit/Nondisambiguated reconstructions. Bold values indicate best in the respective category. The best value is checked only across disambiguated/disambiguated but oversplit reconstructions. Our method disambiguates all datasets except Cup (and also sparsifies them), reconstructing most cameras and 3D points with reduced reprojection errors and reconstruction time." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.454, + 0.472, + 0.59 + ], + "angle": 0, + "content": "In Fig. 3, we show the reconstructions of two datasets, with Gendarmenmarkt containing a ghost artifact. It can be seen that extracting \\(\\mathcal{G}_{LCT}\\) from \\(\\mathcal{G}\\) does not remove the ghost artifact and requires further processing to avoid it. The reconstructions obtained with sparsified viewgraphs are visually similar to those from \\(\\mathcal{G}\\) and \\(\\mathcal{G}_{LCT}\\) (after removing ghost artifacts, if present), even with some lost cameras, in significantly less time. This reveals the advantage of scoring edges based on the number of epipolar inliers." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.605, + 0.273, + 0.62 + ], + "angle": 0, + "content": "4.2. Ambiguous Datasets" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.471, + 0.903 + ], + "angle": 0, + "content": "In this subsection, we evaluate the performance of our method on ambiguous datasets. At first, we study how well the edge scores reflect the presence of false edges. We take datasets provided by Doppelgangers [3] since they provide ground truth labels for true and false edges. We obtain viewgraphs using COLMAP and compute the edge quality scores based on Algo. 1. In Fig. 4, we provide separate histograms of the edge quality scores for true (non-ambiguous) and false (ambiguous) edges for all the datasets. We only use those edges for the histograms whose labels are provided in the datasets. It can be seen that the ambiguous edges are scored low, which is desired for their removal using our method. For non-ambiguous edges, the edge scores are distributed more uniformly, which helps in the uniform removal of edges for graph sparsification with our method. Thus, our edge scoring mechanism is able to capture the presence of false edges and redundancy of the graph based on connectivity via 3D points." + }, + { + "type": "image", + "bbox": [ + 0.565, + 0.445, + 0.825, + 0.518 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.564, + 0.526, + 0.826, + 0.6 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.621, + 0.895, + 0.69 + ], + "angle": 0, + "content": "Figure 4. Histograms of edge quality scores over all datasets from Doppelgangers [3]. Top: Only non-ambiguous edges. Bottom: Only ambiguous edges. Ambiguous edges have low scores. Non-ambiguous edges are scored more uniformly, which aids uniform edge removal for graph sparsification." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Next, we present results on ambiguous datasets provided by [17, 46, 47, 49]. In Table 3, we compare results of the disambiguated viewgraph \\(\\mathcal{G}_F\\) to those of viewgraphs \\(\\mathcal{G}\\) and \\(\\mathcal{G}_{LCT}\\). We use \\(m = 0.6\\) for large-scale datasets [46, 47], the same as used for generic datasets, except for highly ambiguous datasets (Louvre and Sacre Coeur), where we use \\(m = 0.9\\). We use \\(m = 0.3\\) for medium and small-scale datasets [17, 49]. We also provide reconstruction statistics after applying Doppelgangers [3] on \\(\\mathcal{G}\\), where we use probability threshold \\(p = 0.8\\) for all datasets (as suggested in [3]) except for Louvre, where \\(p = 0.9\\). No value of \\(p\\) worked for the datasets not disambiguated by [3]. We" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "4965" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.077, + 0.087, + 0.892, + 0.416 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.429, + 0.893, + 0.471 + ], + "angle": 0, + "content": "Figure 5. Reconstructions obtained with different graphs on ambiguous datasets. \\(\\# N_{CR}\\): Number of cameras reconstructed, \\(t_R\\): Reconstruction time using COLMAP [36]. Datasets resulting in superimposed reconstructions (marked in blue) are corrected after applying our method with faster reconstruction time compared to Doppelgangers [3] due to the sparsification behaviour of our method." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.497, + 0.473, + 0.771 + ], + "angle": 0, + "content": "note that \\(\\mathcal{G}_{LCT}\\) still contains false edges, due to which no dataset is disambiguated by extracting \\(\\mathcal{G}_{LCT}\\) from \\(\\mathcal{G}\\). Our method is able to disambiguate repeated structures for all large and medium-scale datasets, recovering most of the cameras and 3D points when compared to Doppelgangers reconstructions, with similar or better reprojection errors for almost all the datasets. For Louvre, although many cameras are lost, we still reconstruct more 3D points than Doppelgangers with reprojection errors close to each other, showing the effectiveness of our edge-scoring mechanism. Additionally, apart from removing false edges, our method also sparsifies the graphs, which reduces the reconstruction times for most datasets. More details are given in the supplementary material. Although similar observations can be made for small-scale datasets [49], some scenes are over-split due to graph sparsification by our method because these datasets [49], being sequential, have a low redundancy of edges." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.47, + 0.903 + ], + "angle": 0, + "content": "In Fig. 5, we show reconstructions of two datasets, one large-scale and another medium-scale. Both \\(\\mathcal{G}\\) and \\(\\mathcal{G}_{LCT}\\) lead to superimposed reconstructions due to the presence of false edges. Our method is able to disambiguate different facades of the buildings, leading to correct reconstruction, as validated by Doppelgangers reconstruction. Moreover, due to graph sparsification, our method significantly" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.497, + 0.89, + 0.528 + ], + "angle": 0, + "content": "reduces reconstruction time compared to Doppelgangers. More results are provided in the supplementary material." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.543, + 0.619, + 0.558 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.568, + 0.892, + 0.812 + ], + "angle": 0, + "content": "In this paper, we present a single method based on camera triplets to solve both the problems of viewgraph sparsification and disambiguation of repeated structures. We propose a scoring mechanism for the edges in a viewgraph based on epipolar inliers, which captures both the redundancy of the edges and the presence of ambiguous edges based on global information of 3D point connectivity. We formulate an optimization problem whose solution is proven to be a thresholding scheme. This leads us to an efficient algorithm which can be incorporated into any SfM pipeline as a pre-processing step. Applying our method reduces the reconstruction time significantly while maintaining accuracy and also removes ghost artifacts on generic datasets. Our method also disambiguates repeated structures in the scenes along with sparsifying viewgraphs of ambiguous datasets, resulting in reduced reconstruction time." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Acknowledgments: Lalit Manam is supported by a Prime Minister's Research Fellowship, Government of India. 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Often, there are also false edges due to incorrect image retrieval and repeated structures (symmetries) that give rise to ghosting and superimposed reconstruction artifacts. We present a unified method to simultaneously sparsify the viewgraph and remove false edges. We propose a scoring mechanism based on camera triplets that identifies edge redundancy as well as false edges. Our edge selection is formulated as an optimization problem which can be provably solved using a simple thresholding scheme. This results in a highly efficient algorithm which can be incorporated as a pre-processing step into any SfM pipeline, making it practically usable. We demonstrate the utility of our method on generic and ambiguous datasets that cover the range of small, medium and large-scale datasets, all with different statistical properties. Sparsification of generic datasets using our method significantly reduces reconstruction time while maintaining the accuracy of the reconstructions as well as removing ghosting artifacts. For ambiguous datasets, our method removes false edges, thereby avoiding incorrect superimposed reconstructions. + +# 1. Introduction + +Structure-from-Motion (SfM) [13] has been a long-studied problem in computer vision. It aims to reconstruct a 3D structure and estimate camera motions given images of a scene. The first step in SfM is to identify the pairs of images that capture the same part of the scene. For unordered image collections, especially for large-scale datasets, image retrieval techniques [1, 14, 23, 31, 32] are used where each image is assigned with a descriptor and then matched with other images. The relationships between the pairs of images can be represented as a graph (also called a viewgraph in the SfM literature), with nodes representing + +cameras and edges representing an overlap of the scene in the images captured by the two cameras, implying that their relative geometry can be recovered. This graph is further processed to extract keypoints in the images, which are then matched with keypoints in other images based on the connectivity of the graph [2, 7, 8, 25, 27, 34, 35, 44, 50]. Subsequently, the relative motion for every edge is obtained by estimating epipolar geometry [13] using inlier keypoint matches. We refer to such matches as epipolar inliers. The obtained graph in this fashion is used by either incremental [36, 39, 40, 48] or global methods [9-11, 42] to get a 3D reconstruction of the scene along with camera motions. + +The underlying viewgraphs obtained from unordered image collections generally contain a redundant set of images (equivalently nodes) since popular views of the scene are captured more frequently [41]. As a consequence, a large number of pairs of images (equivalently edges) are identified to capture the same part of the scene, resulting in a highly redundant set of edges in the viewgraphs [16]. We refer to the datasets with the above-mentioned properties as generic datasets. Many methods [15, 16, 37, 38, 41] have been proposed to sparsify the viewgraphs while maintaining the accuracy of the reconstructions by considering only the nodes and edges which are distinguished to be important. + +When scenes contain repeated structures leading to different symmetries [26], a significant number of false edges occur between the cameras viewing repeated structures. This is because such images look similar and, thus, are identified as belonging to the same part of the scene, even if they capture physically different parts of the scene. The presence of such false edges leads to superimposed reconstructions. We refer to these datasets as ambiguous datasets. Methods based on viewgraph properties and loop consistency checks in the viewgraphs [3, 4, 17-19, 21, 33, 37, 38, 45, 46, 49, 51, 52] have been proposed to tackle false edges. + +![](images/f6c6aaf1a12bd06c8250ffe5ffd38ba25c524109962a9525d928733d140aeb20.jpg) +(a) Generic case (Union Square [47]). + +![](images/72acfadf51418a0fec0eacb0a420e88c4d1af6aff5374652d3a1a69054519286.jpg) + +![](images/4c9b8d5baa31eb99b2c833844dfd810c13a508d6386c93c4b45566c5c5c4262c.jpg) +(b) Ambiguous case (Alexander Nevsky Cathedral [17]). +Figure 1. Camera triplets in different cases. The number of epipolar inliers are shown for the respective edges. The part of the image where most of the inliers are matched is shown in rectangular boxes with colours corresponding to the edge colours. The red dots on the images show the detected keypoints. (a) A triplet in a generic dataset where the edge marked green has fewer inliers than other edges due to low overlap, thus, can potentially be removed to sparsify the viewgraph. (b) A triplet in an ambiguous dataset where two different facades of a building are matched, giving false edges (marked green and blue). The false edges have a low number of inliers compared to the true edge (marked orange), thus giving a cue about ambiguity. + +
MethodsScenarios in viewgraphs
Mostly True EdgesMany False Edges
Graph Sparsification✓✗
Disambiguation✗✓
Ours✓✓
+ +Table 1. Summary of different scenarios in viewgraphs handled by methods designed for specific tasks. + +We note that generic datasets can also contain a small fraction of false edges due to incorrect images retrieved, which leads to ghost artifacts in reconstructions. On the other hand, ambiguous datasets contain repeated structures which give rise to a significant number of false edges. + +Both the problems, viewgraph sparsification and disambiguation of repeated structures, have mostly been dealt with independently in the literature. The underlying assumptions of both the problems are very much opposed. For viewgraph sparsification, most of the edges are considered to be reliable (or true). Thus, the removal of a few edges does not severely affect the accuracy of reconstruction. On the other hand, for the disambiguation problem, a significant number of edges are false, which must be weeded out to obtain a proper reconstruction. Our objective is to solve both problems together by a single scheme, which is summarized in Table 1. + +Our contributions: In this paper, we simultaneously target both the problems of viewgraph sparsification and disambiguation of repeated structures. A fundamental design attribute of our approach is the idea that camera triplets are more informative than individual edges [41, 51] and are + +easy to analyze since they form loops of the smallest possible length. For the problems on hand, triplets provide an important indication of an edge being redundant or ambiguous based on matched keypoints (see Fig. 1). We propose a single scheme for both tasks by leveraging camera triplets. We identify redundant and false edges based on a scoring mechanism that aggregates information about 3D point connectivity of the triplets globally over the whole graph without requiring intermediate partial reconstructions and remove them based on a single threshold. The proposed method can be incorporated into any SfM pipeline, either incremental or global, making it practical for usage. Experiments on viewgraph sparsification show a significant improvement in reconstruction time while maintaining accuracy on large-scale datasets. Our method also removes ghost artifacts in the reconstructions of generic datasets and shows disambiguation capability on ambiguous datasets. + +# 2. Literature Review + +Viewgraph sparsification: Snavely et al. [41] constructed skeletal graphs based on the approximate covariance of camera motions. Havlena et al. [15] used image level descriptors to carefully choose camera triplets for independent reconstructions and then merged them. Havlena et al. [16] also relied on image level descriptors and selected a minimally connected dominating set of the image collection. Shen et al. [38] used an online algorithm to get a spanning tree, expanded the graph based on triplets and finally enforced a community-based graph structure. Shah et al. [37] selected edges on the graph based on a minimum cost network flow problem. Many methods rely on intermediate partial reconstructions [15, 16, 41], have multiple hyperparameters [37, 38], or design their own specific SfM pipeline [15, 16, 41] but we provide a solution + +based on a single hyperparameter without any intermediate reconstruction, and can be used in any pipeline. + +Disambiguation of repeated structures: Zach et al. [51] reasoned about false edges based on missing correspondences in triplets using Bayesian inference. Zach et al. [52] further extended [51] on longer loops using relative camera motions. Roberts et al. [33] also inferred false edges based on relative motions using an expectation-maximization framework [29]. Cohen et al. [4] detected symmetries by estimating similarity transforms and removing false edges to reduce drift. Jiang et al. [19] measured reconstruction quality based on missing correspondences and used it for edge selection. Wilson et al. [46] split the camera-point relation graph based on its covering subgraphs. Heinly et al. [17] proposed a post-processing step to split the reconstruction based on conflicting observations and then merge the disconnected epipolar inliers. Heinly et al. [18] also proposed a post-processing step to isolate 3D points connecting separate parts of the reconstruction incorrectly by analyzing the clustering behaviour of 3D point connectivity. Cui et al. [6] merged two-view reconstructions locally to find missing correspondences. Yan et al. [49] constructed a path network where a few anchor images are selected and other images are related to them with paths for clean image correspondences. Wang et al. [45] grouped the images based on viewgraph and scored edges on their ability to expand the reconstruction. Kataria et al. [21] considered keypoints which are only matched across a few images for resectioning cameras to obtain a reliable reconstruction. Cai et al. [3] proposed Doppelgangers, where a neural network detects false edges based on images, keypoints and matches. Some graph sparsification methods also disambiguated repeated structures either by checking geometric consistency along loops [38] or by modifying their cost function for handling ambiguous datasets [37]. Some other methods [22, 43] avoided incorrect fetching of images containing repetitive structures during the image retrieval phase by specific designs of image descriptors. Many of these methods assume specific probability distributions on missing correspondences [51, 52], exploit intermediate reconstructions [6, 33], involve multiple hyperparameters [18, 19, 21, 37, 38, 46, 49] or are designed for specific pipelines [21, 51]. Our method does not assume any probability distribution for missing correspondences, can be used in any pipeline, and uses only a single hyperparameter without requiring any intermediate reconstruction. + +# 3. Proposed Method + +The goal of graph sparsification is to recover most of the cameras and 3D points with a sparsified graph compared to the original graph while maintaining accuracy and significantly reducing reconstruction time. Dealing with + +ambiguities in the scene requires distinguishing between repeated structures. Our aim is to handle both the tasks of graph sparsification and disambiguation of repeated structures using a single scheme with as few hyperparameters as possible without needing any intermediate partial reconstructions. We also seek to build a scheme which can be used as a pre-processing step for any pipeline, either incremental or global. To achieve our goals, we present a scheme for scoring edge quality and then formulate an optimization problem which can be provably solved based on thresholding leading to our proposed algorithm. + +Edge quality score: Edges contain limited information about the pairs of cameras they connect. An individual edge alone cannot validate its importance in the graph, and thus, scoring them meaningfully requires considering other connected edges in the graph. We take recourse to camera triplets, which provide much more information about an edge based on the other two edges in a triplet (see Fig. 1). Triplets have been widely used for sparsification [15, 16, 37, 38, 41] and disambiguation [19, 33, 51, 52]. Let $\mathcal{G} = (\mathcal{V},\mathcal{E})$ be a viewgraph, with $\mathcal{V}$ and $\mathcal{E}$ denote the set of nodes and edges in $\mathcal{G}$ , respectively. We first determine a quality score, $q_{ij} > 0$ , for each edge $(i,j)\in \mathcal{E}$ before processing the viewgraph. Since we aim to get a 3D reconstruction, to sparsify the viewgraph, we want to score the edges based on how well they are connected via 3D points. One way to get an idea of 3D point connectivity without access to 3D reconstruction is to check for epipolar inliers on the edges since inliers are the candidate keypoints for reconstruction. One could check for common inliers in all three cameras and assign a score to each edge on the triplet based on the fraction of common inliers to that of the total inliers belonging to that edge. Such a scoring mechanism favours edges with a low number of inliers, which conflicts with our aim to score based on 3D point connectivity. + +Therefore, we score edges based on the number of inliers instead of common inliers across all three edges of the triplet, which adheres to our aim of 3D point connectivity-based scores. The indication for graph sparsification and disambiguation in the triplets is given by the relative number of inliers between the three edges (also seen in Fig. 1) and not by the actual number of inliers. To score edges, we take the ratio of the number of inliers in each edge to the maximum number of inliers among all three edges in a triplet. This assigns scores to edges based on relative 3D point connectivity in the triplet and is also considerate of the cases where all images in triplets have a low number of inliers due to occlusion or lack of texture. + +Inherently, our scoring mechanism based on the relative + +number of inliers in triplets is also useful for disambiguation. [3] empirically noted that the actual number of epipolar inliers does not provide useful information about ambiguity. Missing correspondences [19, 33, 49, 51] and the statistics of matched keypoints [49] provide a cue about the presence of false edges. They are generally detected using loops of small lengths like triplets since the likelihood of viewing the same 3D points on larger loops reduces. But the implicit assumption is the repeatability of the keypoints for the same 3D point, which can be violated in case of noisy images, occlusion or drastic changes in viewpoint [17, 30, 51]. Scoring based on the number of inliers instead of common inliers in the loops reduces the effect of unmatched keypoints due to repeatability concerns. This is because there can be other matched keypoints on the edges which will compensate for reduced edge scores due to non-repeatable keypoints. Moreover, we consider only inliers on the edges for computing scores. This ensures that only keypoints, which are proven to have discriminative capabilities for matching, are used for inference instead of all the keypoints (as used in [3, 33]). + +A given edge can be a part of many triplets and, thus, have as many scores. To aggregate information about the edge over the whole graph, for each edge, we take the average of the scores obtained from all the triplets it participates in. This ensures that edge scores reflect global information about the edge in the graph. Since our scoring mechanism is based only on triplets, we remove edges which are not a part of any triplet, as such edges cannot be scored. In practice, the viewgraphs for unordered image collections are well connected and losing edges not contributing to triplets has minimal impact on the reconstructions (please refer to Sec. 4 for details). + +Handling graphs consisting only of triplets: For graphs containing only triplets, there can be cases when two triplets are connected by a node and do not share a common edge. We call such a connection between two triplets a joint. In Fig. 2a, we present a scenario where the triplets $T5$ and $T6$ have a common node but no common edge. Also, there are no other triplets that share common edges with both green and red edges. In such cases, the edges marked in the two colours are effectively being scored independently since edges marked in each colour do not participate in the scoring of edges in the other colour. Although, we can continue with such independent scoring, for ambiguous datasets, it is not possible to infer whether the joints are valid connections or not. So, we separate the joints, which ensures that inference on edges is not based on independent scores. + +We construct a triplet graph $\mathcal{G}_T = (\mathcal{V}_T,\mathcal{E}_T)$ , as done + +![](images/aa4696287ffefe6f518fda13825b37209f47737baa703e729ec11ce232474de9.jpg) +(a) Graph $(\mathcal{G})$ containing only triplets. + +![](images/522b1c4fc57873dc432282e9a9d46c47637f79e86dd21179c07a0ba37a9a8854.jpg) +(b) Corresponding triplet graph $(\mathcal{G}_T)$ . +Figure 2. Graph $(\mathcal{G})$ containing only triplets with a joint and its corresponding triplet graph $(\mathcal{G}_T)$ . The edges marked in green and red can be scored independently due to the absence of triplets sharing common edges across them. The triplet graph separates the joint and disconnects such graphs. + +in [20, 28], where nodes, $\mathcal{V}_T$ , denote triplets in $\mathcal{G}$ and edges, $\mathcal{E}_T$ , connect the nodes if an edge is common between the triplets in $\mathcal{G}$ . By construction, the triplets connected by the joints in the viewgraph $\mathcal{G}$ are not connected in the triplet graph $\mathcal{G}_T$ . If there are no common triplets between the set of edges separated by joints, it results in multiple connected components in the triplet graph $\mathcal{G}_T$ , as can be seen in Fig. 2b. For each connected component of $\mathcal{G}_T$ , the triplets in $\mathcal{G}$ will have at least one common edge with the other triplets in the same connected component and no common edges across different components of $\mathcal{G}_T$ . Thus, the edges participating in different connected components of $\mathcal{G}_T$ can be scored independently. So, we only retain the edges in $\mathcal{G}$ corresponding to the largest connected component of $\mathcal{G}_T$ (denoting it as $\mathcal{G}_{LCT}$ ) since our aim is to assign scores based on global reasoning. We empirically observe that separating the joints has a minor effect on the reconstructions (see Sec. 4). + +Formulation: Given a quality score $q_{ij}$ for each edge, we aim to select those edges which will increase the average quality score taken across all the edges. To avoid having the degenerate case of selecting edges only with the highest score (which could be as low as one edge in realistic scenarios), we need to regularize the cost by penalizing the loss of edges. Let $s_{ij} \in \{0,1\}$ , be the binary variables denoting selection $(s_{ij} = 1)$ or removal $(s_{ij} = 0)$ of edges. Then, the + +optimization problem can be formulated as + +$$ +\max_{\substack{s_{ij}\in \{0,1\} ,\\ (i,j)\in \mathcal{E}}}\frac{\sum_{(i,j)\in\mathcal{E}}s_{ij}q_{ij}}{\sum_{(i,j)\in\mathcal{E}}s_{ij}} -\lambda \frac{\sum_{(i,j)\in\mathcal{E}}(1 - s_{ij})q_{ij}}{\sum_{(i,j)\in\mathcal{E}}(1 - s_{ij})}, \tag{1} +$$ + +where $\lambda \geq 0$ is a regularization parameter which avoids degenerate solutions for the optimization problem. $\lambda$ also acts as a tuning parameter for the aggressiveness of edge removal, where reducing $\lambda$ increases the number of edges removed. The second term in Eqn. 1 suggests the average of quality scores of the removed edges should not be high, thus regularizing the first term. The strict positiveness of $q_{ij}$ ensures that edges are either selected or removed for any given $\lambda \geq 0$ . Although the problem in Eqn. 1 does not enforce the graph structure, the quality scores obtained for edges are based on all the triplets they are members of. Let Trp be the set of all triplets in $\mathcal{G}_{LCT}$ , $trp(i,j) \subseteq Trp$ be the set of triplets for which the edge $(i,j)$ is a member, and $q_{ij}^{t}$ be the score obtained from the triplet $t \in trp(i,j)$ . Replacing the scores $q_{ij}$ in Eqn. 1 with $\frac{\sum_{t \in trp(i,j)} q_{ij}^{t}}{|trp(i,j)|}$ discloses the dependence of Eqn. 1 on the graph structure more explicitly. While the optimization problem in Eqn. 1 is combinatorial, we provide a simple thresholding scheme to solve it, which is shown as follows: + +$$ +s _ {i j} = \left\{ \begin{array}{l l} 1 & \text {i f} q _ {i j} \geq \tau , \\ 0 & \text {o t h e r w i s e}, \end{array} \right. \tag {2} +$$ + +where $\tau$ denotes a threshold. This thresholding scheme is equivalent to optimizing the problem in Eqn. 1 with $\tau$ acting as a regularizer, as shown by the following theorem: + +Theorem 1. For a given $\lambda$ in Eqn. 1, there exists a threshold $\tau$ such that the values of $s_{ij}$ obtained by solving the problems given by Eqn. 1 and Eqn. 2 are the same. + +Please refer to supplementary material for the proof of Thm. 1. In practice, finding a threshold is not easy for a given dataset, and a single threshold is not suitable for all datasets. We choose a threshold adaptively based on the connectivity of the graph. Specifically, given maximum node degree of the graph as $d_{max}$ , we get a threshold as + +$$ +\tau = m \left(1 - \frac {d _ {\text {m a x}}}{| \mathcal {V} |}\right) + \left(\frac {d _ {\text {m a x}}}{| \mathcal {V} |}\right), \tag {3} +$$ + +where $|\mathcal{V}|$ is the number of nodes and $m$ is the minimum score which edges should satisfy. We deliberately choose $|\mathcal{V}|$ as the denominator since for a connected graph, $0 \leq d_{max} \leq |\mathcal{V}| - 1$ , thus $m \leq \tau < 1$ . This ensures that $\tau = 1$ is never chosen which only retains edges scored exactly as 1. Such a scenario with many edges scored as 1 is seldom true in practice. We now summarize our procedure in Algo. 1. Efficient implementations exist to get the list + +# Algorithm 1: Edge Selection using Triplets + +Input: Viewgraph $\mathcal{G} = (\mathcal{V},\mathcal{E})$ , with geometrically verified edges and a minimum edge score $m$ + +Output: Sparsified viewgraph $\mathcal{G}_F = (\mathcal{V}_F,\mathcal{E}_F)$ with ambiguous edges removed. + +1 Construct triplet graph $\mathcal{G}_T$ from $\mathcal{G}$ +2 Retain edges in $\mathcal{G}$ participating in largest connected component of $\mathcal{G}_T$ , denoting it $\mathcal{G}_{LCT}$ . +3 Find the list of all triplets $Trp$ in $\mathcal{G}_{LCT}$ . +4 for each triplet $t$ in Trp do + +5 Get the number of inliers for all three edges as $n_{ij}, (i,j) \in t$ . +6 Assign a score to each edge based on triplet $t$ $q_{ij}^{t} = \frac{n_{ij}}{\max_{(k,l)\in t}n_{kl}}.$ + +7 end + +$\S$ Assign $q_{ij}$ to each edge: $q_{ij} = \frac{\sum_{t\in trp(i,j)}q_{ij}^t}{|trp(i,j)|}$ . +9 Compute $\tau$ from $m$ using Eqn. 3. +10 Remove edges in $\mathcal{G}_{LCT}$ with $q_{ij} < \tau$ giving $\mathcal{G}_F$ . +11 Extract the largest connected component of $\mathcal{G}_F$ . + +of all triplets [12, 42]. We note that steps 4-8 in Algo. 1 are performed using CPU parallelization (20 threads) and vectorized operations, which makes it efficient. + +# 4. Experiments + +We present experimental results on publicly available generic and ambiguous datasets in individual subsections. We use COLMAP [36] to obtain the original viewgraph and also use it to get 3D reconstructions under different scenarios. All experiments are performed on a PC with Intel Xeon Silver 4210 processor with 128 GB RAM and two RTX 2080Ti GPUs. Our code is implemented in MATLAB and does not require any $\mathbf{GPU}^1$ . We only consider the largest connected component of the viewgraphs for reporting values. We state the notations for graphs below (same as used in Algo. 1), for further usage: + +$\mathcal{G}$ Original viewgraph. +- $\mathcal{G}_{LCT}$ : Graph containing edges contributing to the largest connected component of the triplet graph $\mathcal{G}_T$ . +- $\mathcal{G}_{Dopp}$ : Graph obtained after applying Doppelgangers [3] on the original graph $\mathcal{G}$ . +- $\mathcal{G}_F(m)$ : Graph obtained after applying Algo. 1 with minimum edge score $m$ . + +# 4.1. Generic Datasets + +In this subsection, we provide results for graph sparsification on generic datasets. We consider datasets provided by [5, 24, 47] and apply Algo. 1 to sparsify viewgraphs. + +
DatasetClean Reconstruction# Cameras Reconstructed (#NCR)# 3D Points Reconstructed (in 103)Mean Reprojection Errors (px)Reconstruction Time (mins) (tr)
GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)
Alamo [47]✓✓✓✓8998756526121611571281260.660.660.620.5944442825
Gendarmenmark [47]XX✓✓104210458998572072061601510.760.760.610.74372339144103
Madrid Metropolis [47]✓✓✓✓471453274232747247330.620.610.570.5888902221
Montreal Notre Dame [47]✓✓✓✓5755704113981451461081030.860.860.800.791141005052
Notre Dame [47]XX✓✓14071406129510933483483322880.760.760.700.68205421311323758
NYC Library [47]✓✓✓✓63561450939611010993840.740.740.710.701051014040
Piccadilly [47]XX✓✓32083110278626453743683112880.760.760.740.721969140910601000
Roman Forum [47]✓✓✓✓15871565136512953243232782630.760.760.730.72784810477453
Tower of London [47]✓✓✓✓7357185354951651651371290.630.630.620.6195864442
Trafalgar [47]✓✓✓✓78677532653862567066955735450.740.740.730.726875560138523698
Union Square [47]✓✓✓✓11601150891805828162550.740.730.690.692201858086
Vienna Cathedral [47]XX✓✓1197116110109653043012582480.750.750.740.73793703398376
Dubrovnik [24]✓✓✓✓588358505576546412521250112710730.760.760.730.72582556521428
Rome [24]✓✓✓✓18121812180717283953953893890.900.900.870.85284280279265
Quad [5]✓✓✓✓57295569436038431295127710418820.690.690.670.66417418318249
+ +Table 2. Reconstruction statistics on generic datasets. $\checkmark / \times$ : Removed/Existing ghost artifacts. Bold values indicate best in the respective category. Our method sparsifies the viewgraphs, reconstructing most cameras and 3D points with reduced reprojection errors and reconstruction time. + +![](images/32094ad333aeda59afbd3914a31afce8f9b981d8920f6b31f2502a351edb57b5.jpg) +[47] + +![](images/a18f02dd55e3a080c51dfc317f403a9c68b6ebb93ead52ae3fc496d94cdcb54e.jpg) +$\# N_{CR} = 1045, t_R = 339$ mins. + +![](images/727b5f2474aff265600d5036c5ecc60d8cd18a29b7651733c81063c9f08318a0.jpg) + +![](images/a52bc88b4995134b28086848d996f13afe97070a2226c1bf750002036659c8fc.jpg) + +![](images/e0168581abacbab7e4cddad520d190f723d98e3997b7ef854e9924b57a1c0114.jpg) +$N_{CR} = 1042, t_R = 372$ mins. +$N_{CR} = 5883, t_R = 582$ mins. +Original Graph $(\mathcal{G})$ + +![](images/348416e0e1c7701a49eabc2bcf4bb0271521a55cc4a75ae6979e827270afffbd.jpg) +Graph with Triplets $(\mathcal{G}_{LCT})$ + +![](images/f2b5ab384ba9a6e9395bdf9480c193c9c57dfdc7ae6ee235351f80d0685e302d.jpg) +$\# N_{CR} = 899, t_R = 144$ mins. +$\# N_{CR} = 5850, t_R = 556 \mathrm{~min}$ +$\# N_{CR} = 5576, t_R = 521$ mins. +Sparsified Graph [Ours] $(\mathcal{G}_F(0.6))$ +Figure 3. Reconstructed obtained with different graphs on generic datasets. $\# N_{CR}$ : Number of cameras reconstructed, $t_R$ : Reconstruction time using COLMAP [36]. Top row: Dataset creating ghost artifacts in reconstructions (marked in blue). Applying our method removes such artifacts with other parts of the reconstructions intact. Bottom row: Dataset with many redundant cameras and edges. Our method sparsifies the graphs, giving visually similar reconstructions in reduced reconstruction time. + +![](images/46d0e4e7e81e145c8ca06c3501875cbcb34acacb0eff6e1838fa1fa3fbbba265.jpg) +$N_{CR} = 857,t_R = 103$ mins. +$\# N_{CR} = 5464, t_R = 428$ mins. +Sparsified Graph [Ours] $(\mathcal{G}_F(0.7))$ + +In Table 2, we compare results of the original viewgraph $\mathcal{G}$ and the sparsified viewgraphs $\mathcal{G}_F$ with different values of minimum edge score, $m = \{0.6, 0.7\}$ . We also show the results for the viewgraph $\mathcal{G}_{LCT}$ , since Algo. 1 extracts this graph before scoring the edges. It can be seen that the number of cameras and 3D points reconstructed with $\mathcal{G}$ and $\mathcal{G}_{LCT}$ are similar, with mean reprojection errors being close. This shows that the removal of edges not participating in the largest connected component of the triplet graph has minimal impact on the 3D reconstructions. The sparsified viewgraphs $(\mathcal{G}_F)$ , using Algo. 1, also have most cameras and 3D points reconstructed compared to $\mathcal{G}_{LCT}$ . Although the number of 3D points reconstructed is reduced compared to $\mathcal{G}_{LCT}$ , they have lower reprojection + +errors, indicating that the estimated camera parameters (intrinsic and motions) and 3D points in $\mathcal{G}_F$ are more consistent with the observations (epipolar inliers on the edges) compared to the original graph. Moreover, the ghost artifacts in the reconstructions are also removed in sparsified graphs, along with a significant reduction in the reconstruction time using COLMAP, by a margin of $50\%$ to $80\%$ . Our method takes $< 1\%$ of the reconstruction time to execute in most cases. More details are provided in the supplementary material. These results are in accordance with the goals of sparsification to obtain a reconstruction with most cameras and 3D points recovered with similar or improved accuracy with reduced reconstruction time using a time-efficient method. + +
DatasetDisambiguated# Cameras Reconstructed (#NCR)# 3D Points Reconstructed (in 103)Mean Reprojection Errors (px)Reconstruction Time (mins) (tR)
GGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF Ours
Louvre [46]✓✓✓✓3673593201861281291081130.600.600.600.6095907952
Notre Dame [46]XX✓✓795277785481542017851775131413060.730.740.740.721558168611601059
Sacre Coeur [46]XX✓✓44924443379619847117065483470.700.710.710.61385405347156
Seville [46]XX✓✓151014984474753533531091170.680.680.640.622031138724
Ellis Island [47]XX✓✓88091031433316417184890.760.750.800.792121953326
Piazza del Popolo [47]XX✓✓102310129228651381361231100.690.690.680.6717818412899
Yorkminster [47]XX✓✓106510275855202842801731620.750.750.770.7638341211386
Alexander Nevsky Cathedral [17]XX✓✓44744744542910010090830.670.670.680.6232283113
Arc de Triompe [17]XX✓✓427425392394818169700.660.660.660.6422181715
Berliner Dom [17]XX✓✓16031603160015882422422382340.700.700.700.68142118126104
Big Ben [17]XX✓✓397398394379747473670.640.640.640.6140364333
Brandenburg Gate [17]XX✓*✓*172172151129242421140.840.840.870.738892
Church on Spilled Blood [17]XXX✓273274258136696964300.610.610.610.521818165
Indoor [17]XX✓✓1521521524273735890.520.550.530.409881
Radcliffe Camera [17]XX✓*✓*27928094177767628400.640.640.600.58181866
Books [49]XXX✓*212121988720.410.410.410.310.30.30.30.1
Cereal [49]XXX✓*252525712121230.410.410.410.300.50.50.50.1
Cup [49]XX✓X6464634066650.610.610.390.420.50.60.30.3
Desk [49]✓✓✓✓*3131311214141230.490.490.480.401.01.10.80.2
Oats [49]XXX✓*232323988730.400.390.370.250.40.50.40.1
Street [49]XX✓*✓1919101944120.500.500.370.350.20.20.10.1
Temple of Heaven [49]✓✓✓✓3383383383381921921851960.650.650.630.6578763254
+ +Table 3. Reconstruction statistics on ambiguous datasets. Please refer to text for details on probability threshold $(p)$ used for Doppelgangers [3] and minimum edge score $(m)$ for our method (Algo. 1). $\sqrt{/\sqrt{*}/X}$ : Disambiguated/Disambiguated but oversplit/Nondisambiguated reconstructions. Bold values indicate best in the respective category. The best value is checked only across disambiguated/disambiguated but oversplit reconstructions. Our method disambiguates all datasets except Cup (and also sparsifies them), reconstructing most cameras and 3D points with reduced reprojection errors and reconstruction time. + +In Fig. 3, we show the reconstructions of two datasets, with Gendarmenmarkt containing a ghost artifact. It can be seen that extracting $\mathcal{G}_{LCT}$ from $\mathcal{G}$ does not remove the ghost artifact and requires further processing to avoid it. The reconstructions obtained with sparsified viewgraphs are visually similar to those from $\mathcal{G}$ and $\mathcal{G}_{LCT}$ (after removing ghost artifacts, if present), even with some lost cameras, in significantly less time. This reveals the advantage of scoring edges based on the number of epipolar inliers. + +# 4.2. Ambiguous Datasets + +In this subsection, we evaluate the performance of our method on ambiguous datasets. At first, we study how well the edge scores reflect the presence of false edges. We take datasets provided by Doppelgangers [3] since they provide ground truth labels for true and false edges. We obtain viewgraphs using COLMAP and compute the edge quality scores based on Algo. 1. In Fig. 4, we provide separate histograms of the edge quality scores for true (non-ambiguous) and false (ambiguous) edges for all the datasets. We only use those edges for the histograms whose labels are provided in the datasets. It can be seen that the ambiguous edges are scored low, which is desired for their removal using our method. For non-ambiguous edges, the edge scores are distributed more uniformly, which helps in the uniform removal of edges for graph sparsification with our method. Thus, our edge scoring mechanism is able to capture the presence of false edges and redundancy of the graph based on connectivity via 3D points. + +![](images/f9be05bef23336d8c9924dec3a91125154711707b75bb804662a3d7eaa5a3518.jpg) + +![](images/e94c0585d57c9ac94a1200c70c65f6e6c092607947f522c725d7bbea8339d105.jpg) +Figure 4. Histograms of edge quality scores over all datasets from Doppelgangers [3]. Top: Only non-ambiguous edges. Bottom: Only ambiguous edges. Ambiguous edges have low scores. Non-ambiguous edges are scored more uniformly, which aids uniform edge removal for graph sparsification. + +Next, we present results on ambiguous datasets provided by [17, 46, 47, 49]. In Table 3, we compare results of the disambiguated viewgraph $\mathcal{G}_F$ to those of viewgraphs $\mathcal{G}$ and $\mathcal{G}_{LCT}$ . We use $m = 0.6$ for large-scale datasets [46, 47], the same as used for generic datasets, except for highly ambiguous datasets (Louvre and Sacre Coeur), where we use $m = 0.9$ . We use $m = 0.3$ for medium and small-scale datasets [17, 49]. We also provide reconstruction statistics after applying Doppelgangers [3] on $\mathcal{G}$ , where we use probability threshold $p = 0.8$ for all datasets (as suggested in [3]) except for Louvre, where $p = 0.9$ . No value of $p$ worked for the datasets not disambiguated by [3]. We + +![](images/5d7767d156c4ccc453869052ef6b793d6aa431f5aedc148764e6de421ec3f2c6.jpg) +Figure 5. Reconstructions obtained with different graphs on ambiguous datasets. $\# N_{CR}$ : Number of cameras reconstructed, $t_R$ : Reconstruction time using COLMAP [36]. Datasets resulting in superimposed reconstructions (marked in blue) are corrected after applying our method with faster reconstruction time compared to Doppelgangers [3] due to the sparsification behaviour of our method. + +note that $\mathcal{G}_{LCT}$ still contains false edges, due to which no dataset is disambiguated by extracting $\mathcal{G}_{LCT}$ from $\mathcal{G}$ . Our method is able to disambiguate repeated structures for all large and medium-scale datasets, recovering most of the cameras and 3D points when compared to Doppelgangers reconstructions, with similar or better reprojection errors for almost all the datasets. For Louvre, although many cameras are lost, we still reconstruct more 3D points than Doppelgangers with reprojection errors close to each other, showing the effectiveness of our edge-scoring mechanism. Additionally, apart from removing false edges, our method also sparsifies the graphs, which reduces the reconstruction times for most datasets. More details are given in the supplementary material. Although similar observations can be made for small-scale datasets [49], some scenes are over-split due to graph sparsification by our method because these datasets [49], being sequential, have a low redundancy of edges. + +In Fig. 5, we show reconstructions of two datasets, one large-scale and another medium-scale. Both $\mathcal{G}$ and $\mathcal{G}_{LCT}$ lead to superimposed reconstructions due to the presence of false edges. Our method is able to disambiguate different facades of the buildings, leading to correct reconstruction, as validated by Doppelgangers reconstruction. Moreover, due to graph sparsification, our method significantly + +reduces reconstruction time compared to Doppelgangers. More results are provided in the supplementary material. + +# 5. Conclusion + +In this paper, we present a single method based on camera triplets to solve both the problems of viewgraph sparsification and disambiguation of repeated structures. We propose a scoring mechanism for the edges in a viewgraph based on epipolar inliers, which captures both the redundancy of the edges and the presence of ambiguous edges based on global information of 3D point connectivity. We formulate an optimization problem whose solution is proven to be a thresholding scheme. This leads us to an efficient algorithm which can be incorporated into any SfM pipeline as a pre-processing step. Applying our method reduces the reconstruction time significantly while maintaining accuracy and also removes ghost artifacts on generic datasets. Our method also disambiguates repeated structures in the scenes along with sparsifying viewgraphs of ambiguous datasets, resulting in reduced reconstruction time. + +Acknowledgments: Lalit Manam is supported by a Prime Minister's Research Fellowship, Government of India. This research was supported in part by a Core Research Grant from the Science and Engineering Research Board, Department of Science and Technology, Government of India. + +# References + +[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. Netvlad: Cnn architecture for weakly supervised place recognition. In Proceedings of the IEEE conference on computer vision and pattern recognition, pages 5297-5307, 2016. 1 +[2] Herbert Bay, Andreas Ess, Tinne Tuytelaars, and Luc Van Gool. Speeded-up robust features (surf). Computer vision and image understanding, 110(3):346-359, 2008. 1 +[3] Ruojin Cai, Joseph Tung, Qianqian Wang, Hadar Averbuch-Elor, Bharath Hariharan, and Noah Snavely. 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Often, there are also false edges due to incorrect image retrieval and repeated structures (symmetries) that give rise to ghosting and superimposed reconstruction artifacts. We present a unified method to simultaneously sparsify the viewgraph and remove false edges. We propose a scoring mechanism based on camera triplets that identifies edge redundancy as well as false edges. Our edge selection is formulated as an optimization problem which can be provably solved using a simple thresholding scheme. This results in a highly efficient algorithm which can be incorporated as a pre-processing step into any SfM pipeline, making it practically usable. We demonstrate the utility of our method on generic and ambiguous datasets that cover the range of small, medium and large-scale datasets, all with different statistical properties. Sparsification of generic datasets using our method significantly reduces reconstruction time while maintaining the accuracy of the reconstructions as well as removing ghosting artifacts. For ambiguous datasets, our method removes false edges, thereby avoiding incorrect superimposed reconstructions." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 562, + 128, + 574 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 562, + 128, + 574 + ], + "spans": [ + { + "bbox": [ + 47, + 562, + 128, + 574 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 581, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 581, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 581, + 289, + 715 + ], + "type": "text", + "content": "Structure-from-Motion (SfM) [13] has been a long-studied problem in computer vision. It aims to reconstruct a 3D structure and estimate camera motions given images of a scene. The first step in SfM is to identify the pairs of images that capture the same part of the scene. For unordered image collections, especially for large-scale datasets, image retrieval techniques [1, 14, 23, 31, 32] are used where each image is assigned with a descriptor and then matched with other images. The relationships between the pairs of images can be represented as a graph (also called a viewgraph in the SfM literature), with nodes representing" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 228, + 547, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 228, + 547, + 373 + ], + "spans": [ + { + "bbox": [ + 304, + 228, + 547, + 373 + ], + "type": "text", + "content": "cameras and edges representing an overlap of the scene in the images captured by the two cameras, implying that their relative geometry can be recovered. This graph is further processed to extract keypoints in the images, which are then matched with keypoints in other images based on the connectivity of the graph [2, 7, 8, 25, 27, 34, 35, 44, 50]. Subsequently, the relative motion for every edge is obtained by estimating epipolar geometry [13] using inlier keypoint matches. We refer to such matches as epipolar inliers. The obtained graph in this fashion is used by either incremental [36, 39, 40, 48] or global methods [9-11, 42] to get a 3D reconstruction of the scene along with camera motions." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 387, + 547, + 542 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 387, + 547, + 542 + ], + "spans": [ + { + "bbox": [ + 304, + 387, + 547, + 542 + ], + "type": "text", + "content": "The underlying viewgraphs obtained from unordered image collections generally contain a redundant set of images (equivalently nodes) since popular views of the scene are captured more frequently [41]. As a consequence, a large number of pairs of images (equivalently edges) are identified to capture the same part of the scene, resulting in a highly redundant set of edges in the viewgraphs [16]. We refer to the datasets with the above-mentioned properties as generic datasets. Many methods [15, 16, 37, 38, 41] have been proposed to sparsify the viewgraphs while maintaining the accuracy of the reconstructions by considering only the nodes and edges which are distinguished to be important." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 558, + 548, + 702 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 548, + 702 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 548, + 702 + ], + "type": "text", + "content": "When scenes contain repeated structures leading to different symmetries [26], a significant number of false edges occur between the cameras viewing repeated structures. This is because such images look similar and, thus, are identified as belonging to the same part of the scene, even if they capture physically different parts of the scene. The presence of such false edges leads to superimposed reconstructions. We refer to these datasets as ambiguous datasets. Methods based on viewgraph properties and loop consistency checks in the viewgraphs [3, 4, 17-19, 21, 33, 37, 38, 45, 46, 49, 51, 52] have been proposed to tackle false edges." + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4959" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 59, + 71, + 211, + 181 + ], + "blocks": [ + { + "bbox": [ + 59, + 71, + 211, + 181 + ], + "lines": [ + { + "bbox": [ + 59, + 71, + 211, + 181 + ], + "spans": [ + { + "bbox": [ + 59, + 71, + 211, + 181 + ], + "type": "image", + "image_path": "f6c6aaf1a12bd06c8250ffe5ffd38ba25c524109962a9525d928733d140aeb20.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 115, + 185, + 237, + 195 + ], + "lines": [ + { + "bbox": [ + 115, + 185, + 237, + 195 + ], + "spans": [ + { + "bbox": [ + 115, + 185, + 237, + 195 + ], + "type": "text", + "content": "(a) Generic case (Union Square [47])." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 212, + 113, + 295, + 167 + ], + "blocks": [ + { + "bbox": [ + 212, + 113, + 295, + 167 + ], + "lines": [ + { + "bbox": [ + 212, + 113, + 295, + 167 + ], + "spans": [ + { + "bbox": [ + 212, + 113, + 295, + 167 + ], + "type": "image", + "image_path": "72acfadf51418a0fec0eacb0a420e88c4d1af6aff5374652d3a1a69054519286.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 300, + 72, + 534, + 179 + ], + "blocks": [ + { + "bbox": [ + 300, + 72, + 534, + 179 + ], + "lines": [ + { + "bbox": [ + 300, + 72, + 534, + 179 + ], + "spans": [ + { + "bbox": [ + 300, + 72, + 534, + 179 + ], + "type": "image", + "image_path": "4c9b8d5baa31eb99b2c833844dfd810c13a508d6386c93c4b45566c5c5c4262c.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 325, + 184, + 508, + 194 + ], + "lines": [ + { + "bbox": [ + 325, + 184, + 508, + 194 + ], + "spans": [ + { + "bbox": [ + 325, + 184, + 508, + 194 + ], + "type": "text", + "content": "(b) Ambiguous case (Alexander Nevsky Cathedral [17])." + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 205, + 545, + 271 + ], + "lines": [ + { + "bbox": [ + 46, + 205, + 545, + 271 + ], + "spans": [ + { + "bbox": [ + 46, + 205, + 545, + 271 + ], + "type": "text", + "content": "Figure 1. Camera triplets in different cases. The number of epipolar inliers are shown for the respective edges. The part of the image where most of the inliers are matched is shown in rectangular boxes with colours corresponding to the edge colours. The red dots on the images show the detected keypoints. (a) A triplet in a generic dataset where the edge marked green has fewer inliers than other edges due to low overlap, thus, can potentially be removed to sparsify the viewgraph. (b) A triplet in an ambiguous dataset where two different facades of a building are matched, giving false edges (marked green and blue). The false edges have a low number of inliers compared to the true edge (marked orange), thus giving a cue about ambiguity." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "type": "table", + "bbox": [ + 50, + 289, + 288, + 363 + ], + "blocks": [ + { + "bbox": [ + 50, + 289, + 288, + 363 + ], + "lines": [ + { + "bbox": [ + 50, + 289, + 288, + 363 + ], + "spans": [ + { + "bbox": [ + 50, + 289, + 288, + 363 + ], + "type": "table", + "html": "
MethodsScenarios in viewgraphs
Mostly True EdgesMany False Edges
Graph Sparsification✓✗
Disambiguation✗✓
Ours✓✓
", + "image_path": "93a7228eab0752106ea356c000e7be5daf318b9ee0044a0b930c9c7861dbddb3.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "table_body" + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 371, + 287, + 394 + ], + "lines": [ + { + "bbox": [ + 47, + 371, + 287, + 394 + ], + "spans": [ + { + "bbox": [ + 47, + 371, + 287, + 394 + ], + "type": "text", + "content": "Table 1. Summary of different scenarios in viewgraphs handled by methods designed for specific tasks." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 47, + 421, + 287, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 421, + 287, + 480 + ], + "spans": [ + { + "bbox": [ + 47, + 421, + 287, + 480 + ], + "type": "text", + "content": "We note that generic datasets can also contain a small fraction of false edges due to incorrect images retrieved, which leads to ghost artifacts in reconstructions. On the other hand, ambiguous datasets contain repeated structures which give rise to a significant number of false edges." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 495, + 287, + 638 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 495, + 287, + 638 + ], + "spans": [ + { + "bbox": [ + 46, + 495, + 287, + 638 + ], + "type": "text", + "content": "Both the problems, viewgraph sparsification and disambiguation of repeated structures, have mostly been dealt with independently in the literature. The underlying assumptions of both the problems are very much opposed. For viewgraph sparsification, most of the edges are considered to be reliable (or true). Thus, the removal of a few edges does not severely affect the accuracy of reconstruction. On the other hand, for the disambiguation problem, a significant number of edges are false, which must be weeded out to obtain a proper reconstruction. Our objective is to solve both problems together by a single scheme, which is summarized in Table 1." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 654, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 654, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 654, + 287, + 713 + ], + "type": "text", + "content": "Our contributions: In this paper, we simultaneously target both the problems of viewgraph sparsification and disambiguation of repeated structures. A fundamental design attribute of our approach is the idea that camera triplets are more informative than individual edges [41, 51] and are" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 292, + 545, + 495 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 292, + 545, + 495 + ], + "spans": [ + { + "bbox": [ + 304, + 292, + 545, + 495 + ], + "type": "text", + "content": "easy to analyze since they form loops of the smallest possible length. For the problems on hand, triplets provide an important indication of an edge being redundant or ambiguous based on matched keypoints (see Fig. 1). We propose a single scheme for both tasks by leveraging camera triplets. We identify redundant and false edges based on a scoring mechanism that aggregates information about 3D point connectivity of the triplets globally over the whole graph without requiring intermediate partial reconstructions and remove them based on a single threshold. The proposed method can be incorporated into any SfM pipeline, either incremental or global, making it practical for usage. Experiments on viewgraph sparsification show a significant improvement in reconstruction time while maintaining accuracy on large-scale datasets. Our method also removes ghost artifacts in the reconstructions of generic datasets and shows disambiguation capability on ambiguous datasets." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 512, + 413, + 524 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 512, + 413, + 524 + ], + "spans": [ + { + "bbox": [ + 306, + 512, + 413, + 524 + ], + "type": "text", + "content": "2. Literature Review" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 534, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 545, + 713 + ], + "type": "text", + "content": "Viewgraph sparsification: Snavely et al. [41] constructed skeletal graphs based on the approximate covariance of camera motions. Havlena et al. [15] used image level descriptors to carefully choose camera triplets for independent reconstructions and then merged them. Havlena et al. [16] also relied on image level descriptors and selected a minimally connected dominating set of the image collection. Shen et al. [38] used an online algorithm to get a spanning tree, expanded the graph based on triplets and finally enforced a community-based graph structure. Shah et al. [37] selected edges on the graph based on a minimum cost network flow problem. Many methods rely on intermediate partial reconstructions [15, 16, 41], have multiple hyperparameters [37, 38], or design their own specific SfM pipeline [15, 16, 41] but we provide a solution" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4960" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "content": "based on a single hyperparameter without any intermediate reconstruction, and can be used in any pipeline." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 109, + 289, + 636 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 109, + 289, + 636 + ], + "spans": [ + { + "bbox": [ + 47, + 109, + 289, + 636 + ], + "type": "text", + "content": "Disambiguation of repeated structures: Zach et al. [51] reasoned about false edges based on missing correspondences in triplets using Bayesian inference. Zach et al. [52] further extended [51] on longer loops using relative camera motions. Roberts et al. [33] also inferred false edges based on relative motions using an expectation-maximization framework [29]. Cohen et al. [4] detected symmetries by estimating similarity transforms and removing false edges to reduce drift. Jiang et al. [19] measured reconstruction quality based on missing correspondences and used it for edge selection. Wilson et al. [46] split the camera-point relation graph based on its covering subgraphs. Heinly et al. [17] proposed a post-processing step to split the reconstruction based on conflicting observations and then merge the disconnected epipolar inliers. Heinly et al. [18] also proposed a post-processing step to isolate 3D points connecting separate parts of the reconstruction incorrectly by analyzing the clustering behaviour of 3D point connectivity. Cui et al. [6] merged two-view reconstructions locally to find missing correspondences. Yan et al. [49] constructed a path network where a few anchor images are selected and other images are related to them with paths for clean image correspondences. Wang et al. [45] grouped the images based on viewgraph and scored edges on their ability to expand the reconstruction. Kataria et al. [21] considered keypoints which are only matched across a few images for resectioning cameras to obtain a reliable reconstruction. Cai et al. [3] proposed Doppelgangers, where a neural network detects false edges based on images, keypoints and matches. Some graph sparsification methods also disambiguated repeated structures either by checking geometric consistency along loops [38] or by modifying their cost function for handling ambiguous datasets [37]. Some other methods [22, 43] avoided incorrect fetching of images containing repetitive structures during the image retrieval phase by specific designs of image descriptors. Many of these methods assume specific probability distributions on missing correspondences [51, 52], exploit intermediate reconstructions [6, 33], involve multiple hyperparameters [18, 19, 21, 37, 38, 46, 49] or are designed for specific pipelines [21, 51]. Our method does not assume any probability distribution for missing correspondences, can be used in any pipeline, and uses only a single hyperparameter without requiring any intermediate reconstruction." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 646, + 153, + 659 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 646, + 153, + 659 + ], + "spans": [ + { + "bbox": [ + 47, + 646, + 153, + 659 + ], + "type": "text", + "content": "3. Proposed Method" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 665, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 665, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 665, + 287, + 715 + ], + "type": "text", + "content": "The goal of graph sparsification is to recover most of the cameras and 3D points with a sparsified graph compared to the original graph while maintaining accuracy and significantly reducing reconstruction time. Dealing with" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 205 + ], + "type": "text", + "content": "ambiguities in the scene requires distinguishing between repeated structures. Our aim is to handle both the tasks of graph sparsification and disambiguation of repeated structures using a single scheme with as few hyperparameters as possible without needing any intermediate partial reconstructions. We also seek to build a scheme which can be used as a pre-processing step for any pipeline, either incremental or global. To achieve our goals, we present a scheme for scoring edge quality and then formulate an optimization problem which can be provably solved based on thresholding leading to our proposed algorithm." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "spans": [ + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "text", + "content": "Edge quality score: Edges contain limited information about the pairs of cameras they connect. An individual edge alone cannot validate its importance in the graph, and thus, scoring them meaningfully requires considering other connected edges in the graph. We take recourse to camera triplets, which provide much more information about an edge based on the other two edges in a triplet (see Fig. 1). Triplets have been widely used for sparsification [15, 16, 37, 38, 41] and disambiguation [19, 33, 51, 52]. Let " + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "inline_equation", + "content": "\\mathcal{G} = (\\mathcal{V},\\mathcal{E})" + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "text", + "content": " be a viewgraph, with " + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "text", + "content": " denote the set of nodes and edges in " + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "text", + "content": ", respectively. We first determine a quality score, " + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "inline_equation", + "content": "q_{ij} > 0" + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "text", + "content": ", for each edge " + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "inline_equation", + "content": "(i,j)\\in \\mathcal{E}" + }, + { + "bbox": [ + 304, + 218, + 547, + 518 + ], + "type": "text", + "content": " before processing the viewgraph. Since we aim to get a 3D reconstruction, to sparsify the viewgraph, we want to score the edges based on how well they are connected via 3D points. One way to get an idea of 3D point connectivity without access to 3D reconstruction is to check for epipolar inliers on the edges since inliers are the candidate keypoints for reconstruction. One could check for common inliers in all three cameras and assign a score to each edge on the triplet based on the fraction of common inliers to that of the total inliers belonging to that edge. Such a scoring mechanism favours edges with a low number of inliers, which conflicts with our aim to score based on 3D point connectivity." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 532, + 547, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 532, + 547, + 687 + ], + "spans": [ + { + "bbox": [ + 304, + 532, + 547, + 687 + ], + "type": "text", + "content": "Therefore, we score edges based on the number of inliers instead of common inliers across all three edges of the triplet, which adheres to our aim of 3D point connectivity-based scores. The indication for graph sparsification and disambiguation in the triplets is given by the relative number of inliers between the three edges (also seen in Fig. 1) and not by the actual number of inliers. To score edges, we take the ratio of the number of inliers in each edge to the maximum number of inliers among all three edges in a triplet. This assigns scores to edges based on relative 3D point connectivity in the triplet and is also considerate of the cases where all images in triplets have a low number of inliers due to occlusion or lack of texture." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "content": "Inherently, our scoring mechanism based on the relative" + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "text", + "content": "4961" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "type": "text", + "content": "number of inliers in triplets is also useful for disambiguation. [3] empirically noted that the actual number of epipolar inliers does not provide useful information about ambiguity. Missing correspondences [19, 33, 49, 51] and the statistics of matched keypoints [49] provide a cue about the presence of false edges. They are generally detected using loops of small lengths like triplets since the likelihood of viewing the same 3D points on larger loops reduces. But the implicit assumption is the repeatability of the keypoints for the same 3D point, which can be violated in case of noisy images, occlusion or drastic changes in viewpoint [17, 30, 51]. Scoring based on the number of inliers instead of common inliers in the loops reduces the effect of unmatched keypoints due to repeatability concerns. This is because there can be other matched keypoints on the edges which will compensate for reduced edge scores due to non-repeatable keypoints. Moreover, we consider only inliers on the edges for computing scores. This ensures that only keypoints, which are proven to have discriminative capabilities for matching, are used for inference instead of all the keypoints (as used in [3, 33])." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 338, + 288, + 482 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 338, + 288, + 482 + ], + "spans": [ + { + "bbox": [ + 46, + 338, + 288, + 482 + ], + "type": "text", + "content": "A given edge can be a part of many triplets and, thus, have as many scores. To aggregate information about the edge over the whole graph, for each edge, we take the average of the scores obtained from all the triplets it participates in. This ensures that edge scores reflect global information about the edge in the graph. Since our scoring mechanism is based only on triplets, we remove edges which are not a part of any triplet, as such edges cannot be scored. In practice, the viewgraphs for unordered image collections are well connected and losing edges not contributing to triplets has minimal impact on the reconstructions (please refer to Sec. 4 for details)." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 496, + 289, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 496, + 289, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 496, + 289, + 687 + ], + "type": "text", + "content": "Handling graphs consisting only of triplets: For graphs containing only triplets, there can be cases when two triplets are connected by a node and do not share a common edge. We call such a connection between two triplets a joint. In Fig. 2a, we present a scenario where the triplets " + }, + { + "bbox": [ + 46, + 496, + 289, + 687 + ], + "type": "inline_equation", + "content": "T5" + }, + { + "bbox": [ + 46, + 496, + 289, + 687 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 496, + 289, + 687 + ], + "type": "inline_equation", + "content": "T6" + }, + { + "bbox": [ + 46, + 496, + 289, + 687 + ], + "type": "text", + "content": " have a common node but no common edge. Also, there are no other triplets that share common edges with both green and red edges. In such cases, the edges marked in the two colours are effectively being scored independently since edges marked in each colour do not participate in the scoring of edges in the other colour. Although, we can continue with such independent scoring, for ambiguous datasets, it is not possible to infer whether the joints are valid connections or not. So, we separate the joints, which ensures that inference on edges is not based on independent scores." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 59, + 701, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 701, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 59, + 701, + 288, + 714 + ], + "type": "text", + "content": "We construct a triplet graph " + }, + { + "bbox": [ + 59, + 701, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T = (\\mathcal{V}_T,\\mathcal{E}_T)" + }, + { + "bbox": [ + 59, + 701, + 288, + 714 + ], + "type": "text", + "content": ", as done" + } + ] + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 331, + 76, + 525, + 185 + ], + "blocks": [ + { + "bbox": [ + 331, + 76, + 525, + 185 + ], + "lines": [ + { + "bbox": [ + 331, + 76, + 525, + 185 + ], + "spans": [ + { + "bbox": [ + 331, + 76, + 525, + 185 + ], + "type": "image", + "image_path": "aa4696287ffefe6f518fda13825b37209f47737baa703e729ec11ce232474de9.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 364, + 193, + 487, + 203 + ], + "lines": [ + { + "bbox": [ + 364, + 193, + 487, + 203 + ], + "spans": [ + { + "bbox": [ + 364, + 193, + 487, + 203 + ], + "type": "text", + "content": "(a) Graph " + }, + { + "bbox": [ + 364, + 193, + 487, + 203 + ], + "type": "inline_equation", + "content": "(\\mathcal{G})" + }, + { + "bbox": [ + 364, + 193, + 487, + 203 + ], + "type": "text", + "content": " containing only triplets." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 323, + 209, + 523, + 266 + ], + "blocks": [ + { + "bbox": [ + 323, + 209, + 523, + 266 + ], + "lines": [ + { + "bbox": [ + 323, + 209, + 523, + 266 + ], + "spans": [ + { + "bbox": [ + 323, + 209, + 523, + 266 + ], + "type": "image", + "image_path": "522b1c4fc57873dc432282e9a9d46c47637f79e86dd21179c07a0ba37a9a8854.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 365, + 275, + 487, + 285 + ], + "lines": [ + { + "bbox": [ + 365, + 275, + 487, + 285 + ], + "spans": [ + { + "bbox": [ + 365, + 275, + 487, + 285 + ], + "type": "text", + "content": "(b) Corresponding triplet graph " + }, + { + "bbox": [ + 365, + 275, + 487, + 285 + ], + "type": "inline_equation", + "content": "(\\mathcal{G}_T)" + }, + { + "bbox": [ + 365, + 275, + 487, + 285 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 294, + 547, + 350 + ], + "lines": [ + { + "bbox": [ + 304, + 294, + 547, + 350 + ], + "spans": [ + { + "bbox": [ + 304, + 294, + 547, + 350 + ], + "type": "text", + "content": "Figure 2. Graph " + }, + { + "bbox": [ + 304, + 294, + 547, + 350 + ], + "type": "inline_equation", + "content": "(\\mathcal{G})" + }, + { + "bbox": [ + 304, + 294, + 547, + 350 + ], + "type": "text", + "content": " containing only triplets with a joint and its corresponding triplet graph " + }, + { + "bbox": [ + 304, + 294, + 547, + 350 + ], + "type": "inline_equation", + "content": "(\\mathcal{G}_T)" + }, + { + "bbox": [ + 304, + 294, + 547, + 350 + ], + "type": "text", + "content": ". The edges marked in green and red can be scored independently due to the absence of triplets sharing common edges across them. The triplet graph separates the joint and disconnects such graphs." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "spans": [ + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": "in [20, 28], where nodes, " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{V}_T" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": ", denote triplets in " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": " and edges, " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{E}_T" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": ", connect the nodes if an edge is common between the triplets in " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": ". By construction, the triplets connected by the joints in the viewgraph " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": " are not connected in the triplet graph " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": ". If there are no common triplets between the set of edges separated by joints, it results in multiple connected components in the triplet graph " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": ", as can be seen in Fig. 2b. For each connected component of " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": ", the triplets in " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": " will have at least one common edge with the other triplets in the same connected component and no common edges across different components of " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": ". Thus, the edges participating in different connected components of " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": " can be scored independently. So, we only retain the edges in " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": " corresponding to the largest connected component of " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": " (denoting it as " + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 304, + 384, + 547, + 600 + ], + "type": "text", + "content": ") since our aim is to assign scores based on global reasoning. We empirically observe that separating the joints has a minor effect on the reconstructions (see Sec. 4)." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "text", + "content": "Formulation: Given a quality score " + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "inline_equation", + "content": "q_{ij}" + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "text", + "content": " for each edge, we aim to select those edges which will increase the average quality score taken across all the edges. To avoid having the degenerate case of selecting edges only with the highest score (which could be as low as one edge in realistic scenarios), we need to regularize the cost by penalizing the loss of edges. Let " + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "inline_equation", + "content": "s_{ij} \\in \\{0,1\\}" + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "text", + "content": ", be the binary variables denoting selection " + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "inline_equation", + "content": "(s_{ij} = 1)" + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "text", + "content": " or removal " + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "inline_equation", + "content": "(s_{ij} = 0)" + }, + { + "bbox": [ + 304, + 618, + 547, + 715 + ], + "type": "text", + "content": " of edges. Then, the" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 315, + 757 + ], + "type": "text", + "content": "4962" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 222, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 222, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 222, + 83 + ], + "type": "text", + "content": "optimization problem can be formulated as" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 55, + 92, + 287, + 129 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 92, + 287, + 129 + ], + "spans": [ + { + "bbox": [ + 55, + 92, + 287, + 129 + ], + "type": "interline_equation", + "content": "\\max_{\\substack{s_{ij}\\in \\{0,1\\} ,\\\\ (i,j)\\in \\mathcal{E}}}\\frac{\\sum_{(i,j)\\in\\mathcal{E}}s_{ij}q_{ij}}{\\sum_{(i,j)\\in\\mathcal{E}}s_{ij}} -\\lambda \\frac{\\sum_{(i,j)\\in\\mathcal{E}}(1 - s_{ij})q_{ij}}{\\sum_{(i,j)\\in\\mathcal{E}}(1 - s_{ij})}, \\tag{1}", + "image_path": "8c4ceb5b8bd2eb89b14250771c711fe3f0f1b8158a6299c3d9f4494dc6f0d681.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "spans": [ + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "\\lambda \\geq 0" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " is a regularization parameter which avoids degenerate solutions for the optimization problem. " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " also acts as a tuning parameter for the aggressiveness of edge removal, where reducing " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " increases the number of edges removed. The second term in Eqn. 1 suggests the average of quality scores of the removed edges should not be high, thus regularizing the first term. The strict positiveness of " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "q_{ij}" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " ensures that edges are either selected or removed for any given " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "\\lambda \\geq 0" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": ". Although the problem in Eqn. 1 does not enforce the graph structure, the quality scores obtained for edges are based on all the triplets they are members of. Let Trp be the set of all triplets in " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "trp(i,j) \\subseteq Trp" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " be the set of triplets for which the edge " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "(i,j)" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " is a member, and " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "q_{ij}^{t}" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " be the score obtained from the triplet " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "t \\in trp(i,j)" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": ". Replacing the scores " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "q_{ij}" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " in Eqn. 1 with " + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "inline_equation", + "content": "\\frac{\\sum_{t \\in trp(i,j)} q_{ij}^{t}}{|trp(i,j)|}" + }, + { + "bbox": [ + 47, + 137, + 289, + 370 + ], + "type": "text", + "content": " discloses the dependence of Eqn. 1 on the graph structure more explicitly. While the optimization problem in Eqn. 1 is combinatorial, we provide a simple thresholding scheme to solve it, which is shown as follows:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 118, + 376, + 287, + 409 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 118, + 376, + 287, + 409 + ], + "spans": [ + { + "bbox": [ + 118, + 376, + 287, + 409 + ], + "type": "interline_equation", + "content": "s _ {i j} = \\left\\{ \\begin{array}{l l} 1 & \\text {i f} q _ {i j} \\geq \\tau , \\\\ 0 & \\text {o t h e r w i s e}, \\end{array} \\right. \\tag {2}", + "image_path": "12bdf3f728da4584afbef314d2986fcad660b4a5488e97a950a24b4e2f0db2d3.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 417, + 287, + 453 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 417, + 287, + 453 + ], + "spans": [ + { + "bbox": [ + 47, + 417, + 287, + 453 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 417, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 47, + 417, + 287, + 453 + ], + "type": "text", + "content": " denotes a threshold. This thresholding scheme is equivalent to optimizing the problem in Eqn. 1 with " + }, + { + "bbox": [ + 47, + 417, + 287, + 453 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 47, + 417, + 287, + 453 + ], + "type": "text", + "content": " acting as a regularizer, as shown by the following theorem:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "spans": [ + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "type": "text", + "content": "Theorem 1. For a given " + }, + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "type": "text", + "content": " in Eqn. 1, there exists a threshold " + }, + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "type": "text", + "content": " such that the values of " + }, + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "type": "inline_equation", + "content": "s_{ij}" + }, + { + "bbox": [ + 46, + 461, + 287, + 498 + ], + "type": "text", + "content": " obtained by solving the problems given by Eqn. 1 and Eqn. 2 are the same." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 506, + 287, + 578 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 506, + 287, + 578 + ], + "spans": [ + { + "bbox": [ + 46, + 506, + 287, + 578 + ], + "type": "text", + "content": "Please refer to supplementary material for the proof of Thm. 1. In practice, finding a threshold is not easy for a given dataset, and a single threshold is not suitable for all datasets. We choose a threshold adaptively based on the connectivity of the graph. Specifically, given maximum node degree of the graph as " + }, + { + "bbox": [ + 46, + 506, + 287, + 578 + ], + "type": "inline_equation", + "content": "d_{max}" + }, + { + "bbox": [ + 46, + 506, + 287, + 578 + ], + "type": "text", + "content": ", we get a threshold as" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 94, + 586, + 287, + 613 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 94, + 586, + 287, + 613 + ], + "spans": [ + { + "bbox": [ + 94, + 586, + 287, + 613 + ], + "type": "interline_equation", + "content": "\\tau = m \\left(1 - \\frac {d _ {\\text {m a x}}}{| \\mathcal {V} |}\\right) + \\left(\\frac {d _ {\\text {m a x}}}{| \\mathcal {V} |}\\right), \\tag {3}", + "image_path": "8cdd84a383b944894f86d0008b906fdfab83f0b87018fada71726ee928cf36e9.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "|\\mathcal{V}|" + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "text", + "content": " is the number of nodes and " + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "text", + "content": " is the minimum score which edges should satisfy. We deliberately choose " + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "|\\mathcal{V}|" + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "text", + "content": " as the denominator since for a connected graph, " + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "0 \\leq d_{max} \\leq |\\mathcal{V}| - 1" + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "text", + "content": ", thus " + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "m \\leq \\tau < 1" + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "text", + "content": ". This ensures that " + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "inline_equation", + "content": "\\tau = 1" + }, + { + "bbox": [ + 47, + 617, + 288, + 714 + ], + "type": "text", + "content": " is never chosen which only retains edges scored exactly as 1. Such a scenario with many edges scored as 1 is seldom true in practice. We now summarize our procedure in Algo. 1. Efficient implementations exist to get the list" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 312, + 75, + 491, + 87 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 312, + 75, + 491, + 87 + ], + "spans": [ + { + "bbox": [ + 312, + 75, + 491, + 87 + ], + "type": "text", + "content": "Algorithm 1: Edge Selection using Triplets" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 318, + 89, + 530, + 113 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 89, + 530, + 113 + ], + "spans": [ + { + "bbox": [ + 318, + 89, + 530, + 113 + ], + "type": "text", + "content": "Input: Viewgraph " + }, + { + "bbox": [ + 318, + 89, + 530, + 113 + ], + "type": "inline_equation", + "content": "\\mathcal{G} = (\\mathcal{V},\\mathcal{E})" + }, + { + "bbox": [ + 318, + 89, + 530, + 113 + ], + "type": "text", + "content": " , with geometrically verified edges and a minimum edge score " + }, + { + "bbox": [ + 318, + 89, + 530, + 113 + ], + "type": "inline_equation", + "content": "m" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 318, + 114, + 528, + 137 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 114, + 528, + 137 + ], + "spans": [ + { + "bbox": [ + 318, + 114, + 528, + 137 + ], + "type": "text", + "content": "Output: Sparsified viewgraph " + }, + { + "bbox": [ + 318, + 114, + 528, + 137 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_F = (\\mathcal{V}_F,\\mathcal{E}_F)" + }, + { + "bbox": [ + 318, + 114, + 528, + 137 + ], + "type": "text", + "content": " with ambiguous edges removed." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 309, + 137, + 526, + 197 + ], + "type": "list", + "angle": 0, + "index": 16, + "blocks": [ + { + "bbox": [ + 310, + 137, + 459, + 149 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 137, + 459, + 149 + ], + "spans": [ + { + "bbox": [ + 310, + 137, + 459, + 149 + ], + "type": "text", + "content": "1 Construct triplet graph " + }, + { + "bbox": [ + 310, + 137, + 459, + 149 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 310, + 137, + 459, + 149 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 310, + 137, + 459, + 149 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "spans": [ + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "type": "text", + "content": "2 Retain edges in " + }, + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "type": "text", + "content": " participating in largest connected component of " + }, + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "type": "text", + "content": ", denoting it " + }, + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 309, + 149, + 526, + 173 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 309, + 174, + 481, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 174, + 481, + 185 + ], + "spans": [ + { + "bbox": [ + 309, + 174, + 481, + 185 + ], + "type": "text", + "content": "3 Find the list of all triplets " + }, + { + "bbox": [ + 309, + 174, + 481, + 185 + ], + "type": "inline_equation", + "content": "Trp" + }, + { + "bbox": [ + 309, + 174, + 481, + 185 + ], + "type": "text", + "content": " in " + }, + { + "bbox": [ + 309, + 174, + 481, + 185 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 309, + 174, + 481, + 185 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 310, + 186, + 430, + 197 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 186, + 430, + 197 + ], + "spans": [ + { + "bbox": [ + 310, + 186, + 430, + 197 + ], + "type": "text", + "content": "4 for each triplet " + }, + { + "bbox": [ + 310, + 186, + 430, + 197 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 310, + 186, + 430, + 197 + ], + "type": "text", + "content": " in Trp do" + } + ] + } + ], + "index": 15 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 310, + 198, + 521, + 249 + ], + "type": "list", + "angle": 0, + "index": 19, + "blocks": [ + { + "bbox": [ + 310, + 198, + 521, + 221 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 198, + 521, + 221 + ], + "spans": [ + { + "bbox": [ + 310, + 198, + 521, + 221 + ], + "type": "text", + "content": "5 Get the number of inliers for all three edges as " + }, + { + "bbox": [ + 310, + 198, + 521, + 221 + ], + "type": "inline_equation", + "content": "n_{ij}, (i,j) \\in t" + }, + { + "bbox": [ + 310, + 198, + 521, + 221 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 310, + 221, + 519, + 249 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 221, + 519, + 249 + ], + "spans": [ + { + "bbox": [ + 310, + 221, + 519, + 249 + ], + "type": "text", + "content": "6 Assign a score to each edge based on triplet " + }, + { + "bbox": [ + 310, + 221, + 519, + 249 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 310, + 221, + 519, + 249 + ], + "type": "inline_equation", + "content": "q_{ij}^{t} = \\frac{n_{ij}}{\\max_{(k,l)\\in t}n_{kl}}." + } + ] + } + ], + "index": 18 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 310, + 249, + 337, + 258 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 310, + 249, + 337, + 258 + ], + "spans": [ + { + "bbox": [ + 310, + 249, + 337, + 258 + ], + "type": "text", + "content": "7 end" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 308, + 261, + 513, + 316 + ], + "type": "list", + "angle": 0, + "index": 25, + "blocks": [ + { + "bbox": [ + 309, + 261, + 501, + 280 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 261, + 501, + 280 + ], + "spans": [ + { + "bbox": [ + 309, + 261, + 501, + 280 + ], + "type": "inline_equation", + "content": "\\S" + }, + { + "bbox": [ + 309, + 261, + 501, + 280 + ], + "type": "text", + "content": " Assign " + }, + { + "bbox": [ + 309, + 261, + 501, + 280 + ], + "type": "inline_equation", + "content": "q_{ij}" + }, + { + "bbox": [ + 309, + 261, + 501, + 280 + ], + "type": "text", + "content": " to each edge: " + }, + { + "bbox": [ + 309, + 261, + 501, + 280 + ], + "type": "inline_equation", + "content": "q_{ij} = \\frac{\\sum_{t\\in trp(i,j)}q_{ij}^t}{|trp(i,j)|}" + }, + { + "bbox": [ + 309, + 261, + 501, + 280 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 309, + 281, + 454, + 292 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 281, + 454, + 292 + ], + "spans": [ + { + "bbox": [ + 309, + 281, + 454, + 292 + ], + "type": "text", + "content": "9 Compute " + }, + { + "bbox": [ + 309, + 281, + 454, + 292 + ], + "type": "inline_equation", + "content": "\\tau" + }, + { + "bbox": [ + 309, + 281, + 454, + 292 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 309, + 281, + 454, + 292 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 309, + 281, + 454, + 292 + ], + "type": "text", + "content": " using Eqn. 3." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "spans": [ + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "type": "text", + "content": "10 Remove edges in " + }, + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "type": "text", + "content": " with " + }, + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "type": "inline_equation", + "content": "q_{ij} < \\tau" + }, + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "type": "text", + "content": " giving " + }, + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_F" + }, + { + "bbox": [ + 309, + 293, + 513, + 304 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 308, + 304, + 511, + 316 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 308, + 304, + 511, + 316 + ], + "spans": [ + { + "bbox": [ + 308, + 304, + 511, + 316 + ], + "type": "text", + "content": "11 Extract the largest connected component of " + }, + { + "bbox": [ + 308, + 304, + 511, + 316 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_F" + }, + { + "bbox": [ + 308, + 304, + 511, + 316 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 24 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "spans": [ + { + "bbox": [ + 304, + 344, + 545, + 380 + ], + "type": "text", + "content": "of all triplets [12, 42]. We note that steps 4-8 in Algo. 1 are performed using CPU parallelization (20 threads) and vectorized operations, which makes it efficient." + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 306, + 392, + 387, + 407 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 392, + 387, + 407 + ], + "spans": [ + { + "bbox": [ + 306, + 392, + 387, + 407 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 304, + 413, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 413, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 413, + 545, + 544 + ], + "type": "text", + "content": "We present experimental results on publicly available generic and ambiguous datasets in individual subsections. We use COLMAP [36] to obtain the original viewgraph and also use it to get 3D reconstructions under different scenarios. All experiments are performed on a PC with Intel Xeon Silver 4210 processor with 128 GB RAM and two RTX 2080Ti GPUs. Our code is implemented in MATLAB and does not require any " + }, + { + "bbox": [ + 304, + 413, + 545, + 544 + ], + "type": "inline_equation", + "content": "\\mathbf{GPU}^1" + }, + { + "bbox": [ + 304, + 413, + 545, + 544 + ], + "type": "text", + "content": ". We only consider the largest connected component of the viewgraphs for reporting values. We state the notations for graphs below (same as used in Algo. 1), for further usage:" + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 306, + 545, + 545, + 628 + ], + "type": "list", + "angle": 0, + "index": 33, + "blocks": [ + { + "bbox": [ + 306, + 545, + 410, + 557 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 545, + 410, + 557 + ], + "spans": [ + { + "bbox": [ + 306, + 545, + 410, + 557 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 306, + 545, + 410, + 557 + ], + "type": "text", + "content": " Original viewgraph." + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 306, + 558, + 545, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 558, + 545, + 581 + ], + "spans": [ + { + "bbox": [ + 306, + 558, + 545, + 581 + ], + "type": "text", + "content": "- " + }, + { + "bbox": [ + 306, + 558, + 545, + 581 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 306, + 558, + 545, + 581 + ], + "type": "text", + "content": ": Graph containing edges contributing to the largest connected component of the triplet graph " + }, + { + "bbox": [ + 306, + 558, + 545, + 581 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_T" + }, + { + "bbox": [ + 306, + 558, + 545, + 581 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 306, + 582, + 545, + 605 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 582, + 545, + 605 + ], + "spans": [ + { + "bbox": [ + 306, + 582, + 545, + 605 + ], + "type": "text", + "content": "- " + }, + { + "bbox": [ + 306, + 582, + 545, + 605 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{Dopp}" + }, + { + "bbox": [ + 306, + 582, + 545, + 605 + ], + "type": "text", + "content": ": Graph obtained after applying Doppelgangers [3] on the original graph " + }, + { + "bbox": [ + 306, + 582, + 545, + 605 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 306, + 582, + 545, + 605 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 306, + 605, + 545, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 605, + 545, + 628 + ], + "spans": [ + { + "bbox": [ + 306, + 605, + 545, + 628 + ], + "type": "text", + "content": "- " + }, + { + "bbox": [ + 306, + 605, + 545, + 628 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_F(m)" + }, + { + "bbox": [ + 306, + 605, + 545, + 628 + ], + "type": "text", + "content": ": Graph obtained after applying Algo. 1 with minimum edge score " + }, + { + "bbox": [ + 306, + 605, + 545, + 628 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 306, + 605, + 545, + 628 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 32 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 638, + 408, + 649 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 638, + 408, + 649 + ], + "spans": [ + { + "bbox": [ + 306, + 638, + 408, + 649 + ], + "type": "text", + "content": "4.1. Generic Datasets" + } + ] + } + ], + "index": 34 + }, + { + "bbox": [ + 304, + 657, + 545, + 694 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 657, + 545, + 694 + ], + "spans": [ + { + "bbox": [ + 304, + 657, + 545, + 694 + ], + "type": "text", + "content": "In this subsection, we provide results for graph sparsification on generic datasets. We consider datasets provided by [5, 24, 47] and apply Algo. 1 to sparsify viewgraphs." + } + ] + } + ], + "index": 35 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 317, + 702, + 526, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 702, + 526, + 713 + ], + "spans": [ + { + "bbox": [ + 317, + 702, + 526, + 713 + ], + "type": "text", + "content": "1 GPUs are used only for Doppelgangers [3] and COLMAP [36]." + } + ] + } + ], + "index": 36 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4963" + } + ] + } + ], + "index": 37 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 49, + 70, + 542, + 198 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 542, + 198 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 542, + 198 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 542, + 198 + ], + "type": "table", + "html": "
DatasetClean Reconstruction# Cameras Reconstructed (#NCR)# 3D Points Reconstructed (in 103)Mean Reprojection Errors (px)Reconstruction Time (mins) (tr)
GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)GGLCTGF(0.6)GF(0.7)
Alamo [47]✓✓✓✓8998756526121611571281260.660.660.620.5944442825
Gendarmenmark [47]XX✓✓104210458998572072061601510.760.760.610.74372339144103
Madrid Metropolis [47]✓✓✓✓471453274232747247330.620.610.570.5888902221
Montreal Notre Dame [47]✓✓✓✓5755704113981451461081030.860.860.800.791141005052
Notre Dame [47]XX✓✓14071406129510933483483322880.760.760.700.68205421311323758
NYC Library [47]✓✓✓✓63561450939611010993840.740.740.710.701051014040
Piccadilly [47]XX✓✓32083110278626453743683112880.760.760.740.721969140910601000
Roman Forum [47]✓✓✓✓15871565136512953243232782630.760.760.730.72784810477453
Tower of London [47]✓✓✓✓7357185354951651651371290.630.630.620.6195864442
Trafalgar [47]✓✓✓✓78677532653862567066955735450.740.740.730.726875560138523698
Union Square [47]✓✓✓✓11601150891805828162550.740.730.690.692201858086
Vienna Cathedral [47]XX✓✓1197116110109653043012582480.750.750.740.73793703398376
Dubrovnik [24]✓✓✓✓588358505576546412521250112710730.760.760.730.72582556521428
Rome [24]✓✓✓✓18121812180717283953953893890.900.900.870.85284280279265
Quad [5]✓✓✓✓57295569436038431295127710418820.690.690.670.66417418318249
", + "image_path": "b5944b709fd6af4cd6ef68ef4500d07c0a5eac0649548ae25f59d09362fcc0dd.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 206, + 547, + 240 + ], + "lines": [ + { + "bbox": [ + 46, + 206, + 547, + 240 + ], + "spans": [ + { + "bbox": [ + 46, + 206, + 547, + 240 + ], + "type": "text", + "content": "Table 2. Reconstruction statistics on generic datasets. " + }, + { + "bbox": [ + 46, + 206, + 547, + 240 + ], + "type": "inline_equation", + "content": "\\checkmark / \\times" + }, + { + "bbox": [ + 46, + 206, + 547, + 240 + ], + "type": "text", + "content": " : Removed/Existing ghost artifacts. Bold values indicate best in the respective category. Our method sparsifies the viewgraphs, reconstructing most cameras and 3D points with reduced reprojection errors and reconstruction time." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 64, + 262, + 181, + 336 + ], + "blocks": [ + { + "bbox": [ + 47, + 251, + 59, + 341 + ], + "lines": [ + { + "bbox": [ + 47, + 251, + 59, + 341 + ], + "spans": [ + { + "bbox": [ + 47, + 251, + 59, + 341 + ], + "type": "text", + "content": "[47]" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 64, + 262, + 181, + 336 + ], + "lines": [ + { + "bbox": [ + 64, + 262, + 181, + 336 + ], + "spans": [ + { + "bbox": [ + 64, + 262, + 181, + 336 + ], + "type": "image", + "image_path": "32094ad333aeda59afbd3914a31afce8f9b981d8920f6b31f2502a351edb57b5.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 183, + 262, + 302, + 336 + ], + "blocks": [ + { + "bbox": [ + 183, + 262, + 302, + 336 + ], + "lines": [ + { + "bbox": [ + 183, + 262, + 302, + 336 + ], + "spans": [ + { + "bbox": [ + 183, + 262, + 302, + 336 + ], + "type": "image", + "image_path": "a18f02dd55e3a080c51dfc317f403a9c68b6ebb93ead52ae3fc496d94cdcb54e.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 186, + 341, + 298, + 351 + ], + "lines": [ + { + "bbox": [ + 186, + 341, + 298, + 351 + ], + "spans": [ + { + "bbox": [ + 186, + 341, + 298, + 351 + ], + "type": "inline_equation", + "content": "\\# N_{CR} = 1045, t_R = 339" + }, + { + "bbox": [ + 186, + 341, + 298, + 351 + ], + "type": "text", + "content": " mins." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 309, + 267, + 425, + 316 + ], + "blocks": [ + { + "bbox": [ + 309, + 267, + 425, + 316 + ], + "lines": [ + { + "bbox": [ + 309, + 267, + 425, + 316 + ], + "spans": [ + 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1042, t_R = 372" + }, + { + "bbox": [ + 64, + 340, + 178, + 351 + ], + "type": "text", + "content": " mins." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 47, + 353, + 181, + 426 + ], + "lines": [ + { + "bbox": [ + 47, + 353, + 181, + 426 + ], + "spans": [ + { + "bbox": [ + 47, + 353, + 181, + 426 + ], + "type": "image", + "image_path": "e0168581abacbab7e4cddad520d190f723d98e3997b7ef854e9924b57a1c0114.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 64, + 437, + 177, + 449 + ], + "lines": [ + { + "bbox": [ + 64, + 437, + 177, + 449 + ], + "spans": [ + { + "bbox": [ + 64, + 437, + 177, + 449 + ], + "type": "inline_equation", + "content": "N_{CR} = 5883, t_R = 582" + }, + { + "bbox": [ + 64, + 437, + 177, + 449 + ], + "type": "text", + "content": " mins." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 88, + 452, + 153, + 461 + ], + "lines": [ + { + "bbox": [ + 88, + 452, + 153, + 461 + ], + "spans": [ + { + "bbox": [ + 88, + 452, + 153, + 461 + ], + "type": "text", + "content": "Original Graph " + }, + { + "bbox": [ + 88, + 452, + 153, + 461 + ], + "type": "inline_equation", + "content": "(\\mathcal{G})" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 183, + 353, + 303, + 425 + ], + "blocks": [ + { + "bbox": [ + 183, + 353, + 303, + 425 + ], + "lines": [ + { + "bbox": [ + 183, + 353, + 303, + 425 + ], + "spans": [ + { + "bbox": [ + 183, + 353, + 303, + 425 + ], + "type": "image", + "image_path": "348416e0e1c7701a49eabc2bcf4bb0271521a55cc4a75ae6979e827270afffbd.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 194, + 452, + 290, + 462 + ], + "lines": [ + { + "bbox": [ + 194, + 452, + 290, + 462 + ], + "spans": [ + { + "bbox": [ + 194, + 452, + 290, + 462 + ], + "type": "text", + "content": "Graph with Triplets " + }, + { + "bbox": [ + 194, + 452, + 290, + 462 + ], + "type": "inline_equation", + "content": "(\\mathcal{G}_{LCT})" + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 304, + 353, + 424, + 428 + ], + "blocks": [ + { + "bbox": [ + 310, + 341, + 417, + 351 + ], + "lines": [ + { + "bbox": [ + 310, + 341, + 417, + 351 + ], + "spans": [ + { + "bbox": [ + 310, + 341, + 417, + 351 + ], + "type": "inline_equation", + "content": "\\# N_{CR} = 899, t_R = 144" + }, + { + "bbox": [ + 310, + 341, + 417, + 351 + ], + "type": "text", + "content": " mins." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 353, + 424, + 428 + ], + "lines": [ + { + "bbox": [ + 304, + 353, + 424, + 428 + ], + "spans": [ + { + "bbox": [ + 304, + 353, + 424, + 428 + ], + "type": "image", + "image_path": "f2b5ab384ba9a6e9395bdf9480c193c9c57dfdc7ae6ee235351f80d0685e302d.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 187, + 437, + 298, + 449 + ], + "lines": [ + { + "bbox": [ + 187, + 437, + 298, + 449 + ], + "spans": [ + { + "bbox": [ + 187, + 437, + 298, + 449 + ], + "type": "inline_equation", + "content": "\\# N_{CR} = 5850, t_R = 556 \\mathrm{~min}" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 307, + 438, + 419, + 449 + ], + "lines": [ + { + "bbox": [ + 307, + 438, + 419, + 449 + ], + "spans": [ + { + "bbox": [ + 307, + 438, + 419, + 449 + ], + "type": "inline_equation", + "content": "\\# N_{CR} = 5576, t_R = 521" + }, + { + "bbox": [ + 307, + 438, + 419, + 449 + ], + "type": "text", + "content": " mins." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 452, + 421, + 462 + ], + "lines": [ + { + "bbox": [ + 304, + 452, + 421, + 462 + ], + "spans": [ + { + "bbox": [ + 304, + 452, + 421, + 462 + ], + "type": "text", + "content": "Sparsified Graph [Ours] " + }, + { + "bbox": [ + 304, + 452, + 421, + 462 + ], + "type": "inline_equation", + "content": "(\\mathcal{G}_F(0.6))" + } + ] + } + ], + "index": 21, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 45, + 474, + 547, + 519 + ], + "lines": [ + { + "bbox": [ + 45, + 474, + 547, + 519 + ], + "spans": [ + { + "bbox": [ + 45, + 474, + 547, + 519 + ], + "type": "text", + "content": "Figure 3. Reconstructed obtained with different graphs on generic datasets. " + }, + { + "bbox": [ + 45, + 474, + 547, + 519 + ], + "type": "inline_equation", + "content": "\\# N_{CR}" + }, + { + "bbox": [ + 45, + 474, + 547, + 519 + ], + "type": "text", + "content": ": Number of cameras reconstructed, " + }, + { + "bbox": [ + 45, + 474, + 547, + 519 + ], + "type": "inline_equation", + "content": "t_R" + }, + { + "bbox": [ + 45, + 474, + 547, + 519 + ], + "type": "text", + "content": ": Reconstruction time using COLMAP [36]. Top row: Dataset creating ghost artifacts in reconstructions (marked in blue). Applying our method removes such artifacts with other parts of the reconstructions intact. Bottom row: Dataset with many redundant cameras and edges. Our method sparsifies the graphs, giving visually similar reconstructions in reduced reconstruction time." + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 425, + 353, + 547, + 428 + ], + "blocks": [ + { + "bbox": [ + 431, + 341, + 539, + 351 + ], + "lines": [ + { + "bbox": [ + 431, + 341, + 539, + 351 + ], + "spans": [ + { + "bbox": [ + 431, + 341, + 539, + 351 + ], + "type": "inline_equation", + "content": "N_{CR} = 857,t_R = 103" + }, + { + "bbox": [ + 431, + 341, + 539, + 351 + ], + "type": "text", + "content": " mins." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 425, + 353, + 547, + 428 + ], + "lines": [ + { + "bbox": [ + 425, + 353, + 547, + 428 + ], + "spans": [ + { + "bbox": [ + 425, + 353, + 547, + 428 + ], + "type": "image", + "image_path": "46d0e4e7e81e145c8ca06c3501875cbcb34acacb0eff6e1838fa1fa3fbbba265.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 429, + 438, + 541, + 449 + ], + "lines": [ + { + "bbox": [ + 429, + 438, + 541, + 449 + ], + "spans": [ + { + "bbox": [ + 429, + 438, + 541, + 449 + ], + "type": "inline_equation", + "content": "\\# N_{CR} = 5464, t_R = 428" + }, + { + "bbox": [ + 429, + 438, + 541, + 449 + ], + "type": "text", + "content": " mins." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 427, + 452, + 542, + 462 + ], + "lines": [ + { + "bbox": [ + 427, + 452, + 542, + 462 + ], + "spans": [ + { + "bbox": [ + 427, + 452, + 542, + 462 + ], + "type": "text", + "content": "Sparsified Graph [Ours] " + }, + { + "bbox": [ + 427, + 452, + 542, + 462 + ], + "type": "inline_equation", + "content": "(\\mathcal{G}_F(0.7))" + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "spans": [ + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": "In Table 2, we compare results of the original viewgraph " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": " and the sparsified viewgraphs " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_F" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": " with different values of minimum edge score, " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "m = \\{0.6, 0.7\\}" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": ". We also show the results for the viewgraph " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": ", since Algo. 1 extracts this graph before scoring the edges. It can be seen that the number of cameras and 3D points reconstructed with " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": " are similar, with mean reprojection errors being close. This shows that the removal of edges not participating in the largest connected component of the triplet graph has minimal impact on the 3D reconstructions. The sparsified viewgraphs " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "(\\mathcal{G}_F)" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": ", using Algo. 1, also have most cameras and 3D points reconstructed compared to " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": ". Although the number of 3D points reconstructed is reduced compared to " + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 539, + 289, + 708 + ], + "type": "text", + "content": ", they have lower reprojection" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "spans": [ + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "text", + "content": "errors, indicating that the estimated camera parameters (intrinsic and motions) and 3D points in " + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_F" + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "text", + "content": " are more consistent with the observations (epipolar inliers on the edges) compared to the original graph. Moreover, the ghost artifacts in the reconstructions are also removed in sparsified graphs, along with a significant reduction in the reconstruction time using COLMAP, by a margin of " + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "inline_equation", + "content": "50\\%" + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "inline_equation", + "content": "80\\%" + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "text", + "content": ". Our method takes " + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "inline_equation", + "content": "< 1\\%" + }, + { + "bbox": [ + 304, + 539, + 547, + 706 + ], + "type": "text", + "content": " of the reconstruction time to execute in most cases. More details are provided in the supplementary material. These results are in accordance with the goals of sparsification to obtain a reconstruction with most cameras and 3D points recovered with similar or improved accuracy with reduced reconstruction time using a time-efficient method." + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4964" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 49, + 70, + 542, + 262 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 542, + 262 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 542, + 262 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 542, + 262 + ], + "type": "table", + "html": "
DatasetDisambiguated# Cameras Reconstructed (#NCR)# 3D Points Reconstructed (in 103)Mean Reprojection Errors (px)Reconstruction Time (mins) (tR)
GGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF OursGGLCTGDopp[3]GF Ours
Louvre [46]✓✓✓✓3673593201861281291081130.600.600.600.6095907952
Notre Dame [46]XX✓✓795277785481542017851775131413060.730.740.740.721558168611601059
Sacre Coeur [46]XX✓✓44924443379619847117065483470.700.710.710.61385405347156
Seville [46]XX✓✓151014984474753533531091170.680.680.640.622031138724
Ellis Island [47]XX✓✓88091031433316417184890.760.750.800.792121953326
Piazza del Popolo [47]XX✓✓102310129228651381361231100.690.690.680.6717818412899
Yorkminster [47]XX✓✓106510275855202842801731620.750.750.770.7638341211386
Alexander Nevsky Cathedral [17]XX✓✓44744744542910010090830.670.670.680.6232283113
Arc de Triompe [17]XX✓✓427425392394818169700.660.660.660.6422181715
Berliner Dom [17]XX✓✓16031603160015882422422382340.700.700.700.68142118126104
Big Ben [17]XX✓✓397398394379747473670.640.640.640.6140364333
Brandenburg Gate [17]XX✓*✓*172172151129242421140.840.840.870.738892
Church on Spilled Blood [17]XXX✓273274258136696964300.610.610.610.521818165
Indoor [17]XX✓✓1521521524273735890.520.550.530.409881
Radcliffe Camera [17]XX✓*✓*27928094177767628400.640.640.600.58181866
Books [49]XXX✓*212121988720.410.410.410.310.30.30.30.1
Cereal [49]XXX✓*252525712121230.410.410.410.300.50.50.50.1
Cup [49]XX✓X6464634066650.610.610.390.420.50.60.30.3
Desk [49]✓✓✓✓*3131311214141230.490.490.480.401.01.10.80.2
Oats [49]XXX✓*232323988730.400.390.370.250.40.50.40.1
Street [49]XX✓*✓1919101944120.500.500.370.350.20.20.10.1
Temple of Heaven [49]✓✓✓✓3383383383381921921851960.650.650.630.6578763254
", + "image_path": "8a7401909f88443027537642a63e46a3f96ac7fe182d382e5e62d322222316db.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "lines": [ + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "spans": [ + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "type": "text", + "content": "Table 3. Reconstruction statistics on ambiguous datasets. Please refer to text for details on probability threshold " + }, + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "type": "inline_equation", + "content": "(p)" + }, + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "type": "text", + "content": " used for Doppelgangers [3] and minimum edge score " + }, + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "type": "inline_equation", + "content": "(m)" + }, + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "type": "text", + "content": " for our method (Algo. 1). " + }, + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "type": "inline_equation", + "content": "\\sqrt{/\\sqrt{*}/X}" + }, + { + "bbox": [ + 46, + 270, + 546, + 326 + ], + "type": "text", + "content": ": Disambiguated/Disambiguated but oversplit/Nondisambiguated reconstructions. Bold values indicate best in the respective category. The best value is checked only across disambiguated/disambiguated but oversplit reconstructions. Our method disambiguates all datasets except Cup (and also sparsifies them), reconstructing most cameras and 3D points with reduced reprojection errors and reconstruction time." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "spans": [ + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "text", + "content": "In Fig. 3, we show the reconstructions of two datasets, with Gendarmenmarkt containing a ghost artifact. It can be seen that extracting " + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "text", + "content": " does not remove the ghost artifact and requires further processing to avoid it. The reconstructions obtained with sparsified viewgraphs are visually similar to those from " + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 359, + 288, + 467 + ], + "type": "text", + "content": " (after removing ghost artifacts, if present), even with some lost cameras, in significantly less time. This reveals the advantage of scoring edges based on the number of epipolar inliers." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 479, + 167, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 479, + 167, + 491 + ], + "spans": [ + { + "bbox": [ + 47, + 479, + 167, + 491 + ], + "type": "text", + "content": "4.2. Ambiguous Datasets" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 498, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 288, + 715 + ], + "type": "text", + "content": "In this subsection, we evaluate the performance of our method on ambiguous datasets. At first, we study how well the edge scores reflect the presence of false edges. We take datasets provided by Doppelgangers [3] since they provide ground truth labels for true and false edges. We obtain viewgraphs using COLMAP and compute the edge quality scores based on Algo. 1. In Fig. 4, we provide separate histograms of the edge quality scores for true (non-ambiguous) and false (ambiguous) edges for all the datasets. We only use those edges for the histograms whose labels are provided in the datasets. It can be seen that the ambiguous edges are scored low, which is desired for their removal using our method. For non-ambiguous edges, the edge scores are distributed more uniformly, which helps in the uniform removal of edges for graph sparsification with our method. Thus, our edge scoring mechanism is able to capture the presence of false edges and redundancy of the graph based on connectivity via 3D points." + } + ] + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 345, + 352, + 504, + 410 + ], + "blocks": [ + { + "bbox": [ + 345, + 352, + 504, + 410 + ], + "lines": [ + { + "bbox": [ + 345, + 352, + 504, + 410 + ], + "spans": [ + { + "bbox": [ + 345, + 352, + 504, + 410 + ], + "type": "image", + "image_path": "f9be05bef23336d8c9924dec3a91125154711707b75bb804662a3d7eaa5a3518.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 345, + 416, + 505, + 475 + ], + "blocks": [ + { + "bbox": [ + 345, + 416, + 505, + 475 + ], + "lines": [ + { + "bbox": [ + 345, + 416, + 505, + 475 + ], + "spans": [ + { + "bbox": [ + 345, + 416, + 505, + 475 + ], + "type": "image", + "image_path": "e94c0585d57c9ac94a1200c70c65f6e6c092607947f522c725d7bbea8339d105.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 491, + 547, + 546 + ], + "lines": [ + { + "bbox": [ + 304, + 491, + 547, + 546 + ], + "spans": [ + { + "bbox": [ + 304, + 491, + 547, + 546 + ], + "type": "text", + "content": "Figure 4. Histograms of edge quality scores over all datasets from Doppelgangers [3]. Top: Only non-ambiguous edges. Bottom: Only ambiguous edges. Ambiguous edges have low scores. Non-ambiguous edges are scored more uniformly, which aids uniform edge removal for graph sparsification." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": "Next, we present results on ambiguous datasets provided by [17, 46, 47, 49]. In Table 3, we compare results of the disambiguated viewgraph " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_F" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": " to those of viewgraphs " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": ". We use " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "m = 0.6" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": " for large-scale datasets [46, 47], the same as used for generic datasets, except for highly ambiguous datasets (Louvre and Sacre Coeur), where we use " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "m = 0.9" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": ". We use " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "m = 0.3" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": " for medium and small-scale datasets [17, 49]. We also provide reconstruction statistics after applying Doppelgangers [3] on " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": ", where we use probability threshold " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "p = 0.8" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": " for all datasets (as suggested in [3]) except for Louvre, where " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "p = 0.9" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": ". No value of " + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "inline_equation", + "content": "p" + }, + { + "bbox": [ + 304, + 570, + 547, + 715 + ], + "type": "text", + "content": " worked for the datasets not disambiguated by [3]. We" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4965" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 47, + 68, + 545, + 329 + ], + "blocks": [ + { + "bbox": [ + 47, + 68, + 545, + 329 + ], + "lines": [ + { + "bbox": [ + 47, + 68, + 545, + 329 + ], + "spans": [ + { + "bbox": [ + 47, + 68, + 545, + 329 + ], + "type": "image", + "image_path": "5d7767d156c4ccc453869052ef6b793d6aa431f5aedc148764e6de421ec3f2c6.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 339, + 546, + 373 + ], + "lines": [ + { + "bbox": [ + 46, + 339, + 546, + 373 + ], + "spans": [ + { + "bbox": [ + 46, + 339, + 546, + 373 + ], + "type": "text", + "content": "Figure 5. Reconstructions obtained with different graphs on ambiguous datasets. " + }, + { + "bbox": [ + 46, + 339, + 546, + 373 + ], + "type": "inline_equation", + "content": "\\# N_{CR}" + }, + { + "bbox": [ + 46, + 339, + 546, + 373 + ], + "type": "text", + "content": ": Number of cameras reconstructed, " + }, + { + "bbox": [ + 46, + 339, + 546, + 373 + ], + "type": "inline_equation", + "content": "t_R" + }, + { + "bbox": [ + 46, + 339, + 546, + 373 + ], + "type": "text", + "content": ": Reconstruction time using COLMAP [36]. Datasets resulting in superimposed reconstructions (marked in blue) are corrected after applying our method with faster reconstruction time compared to Doppelgangers [3] due to the sparsification behaviour of our method." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "spans": [ + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "type": "text", + "content": "note that " + }, + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "type": "text", + "content": " still contains false edges, due to which no dataset is disambiguated by extracting " + }, + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "type": "text", + "content": " from " + }, + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 46, + 393, + 289, + 610 + ], + "type": "text", + "content": ". Our method is able to disambiguate repeated structures for all large and medium-scale datasets, recovering most of the cameras and 3D points when compared to Doppelgangers reconstructions, with similar or better reprojection errors for almost all the datasets. For Louvre, although many cameras are lost, we still reconstruct more 3D points than Doppelgangers with reprojection errors close to each other, showing the effectiveness of our edge-scoring mechanism. Additionally, apart from removing false edges, our method also sparsifies the graphs, which reduces the reconstruction times for most datasets. More details are given in the supplementary material. Although similar observations can be made for small-scale datasets [49], some scenes are over-split due to graph sparsification by our method because these datasets [49], being sequential, have a low redundancy of edges." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": "In Fig. 5, we show reconstructions of two datasets, one large-scale and another medium-scale. Both " + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{G}" + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{G}_{LCT}" + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": " lead to superimposed reconstructions due to the presence of false edges. Our method is able to disambiguate different facades of the buildings, leading to correct reconstruction, as validated by Doppelgangers reconstruction. Moreover, due to graph sparsification, our method significantly" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 305, + 393, + 544, + 418 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 393, + 544, + 418 + ], + "spans": [ + { + "bbox": [ + 305, + 393, + 544, + 418 + ], + "type": "text", + "content": "reduces reconstruction time compared to Doppelgangers. More results are provided in the supplementary material." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 430, + 378, + 441 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 430, + 378, + 441 + ], + "spans": [ + { + "bbox": [ + 306, + 430, + 378, + 441 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 449, + 545, + 643 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 449, + 545, + 643 + ], + "spans": [ + { + "bbox": [ + 304, + 449, + 545, + 643 + ], + "type": "text", + "content": "In this paper, we present a single method based on camera triplets to solve both the problems of viewgraph sparsification and disambiguation of repeated structures. We propose a scoring mechanism for the edges in a viewgraph based on epipolar inliers, which captures both the redundancy of the edges and the presence of ambiguous edges based on global information of 3D point connectivity. We formulate an optimization problem whose solution is proven to be a thresholding scheme. This leads us to an efficient algorithm which can be incorporated into any SfM pipeline as a pre-processing step. Applying our method reduces the reconstruction time significantly while maintaining accuracy and also removes ghost artifacts on generic datasets. Our method also disambiguates repeated structures in the scenes along with sparsifying viewgraphs of ambiguous datasets, resulting in reduced reconstruction time." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": "Acknowledgments: Lalit Manam is supported by a Prime Minister's Research Fellowship, Government of India. This research was supported in part by a Core Research Grant from the Science and Engineering Research Board, Department of Science and Technology, Government of India." + } + ] + } + ], + "index": 7 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4966" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. 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IEEE, 2010. 1, 3" + } + ] + } + ], + "index": 28 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "4968" + } + ] + } + ], + "index": 30 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_content_list.json b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..61c687b0b61989a3cc6d013954910ea7201663e1 --- /dev/null +++ b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_content_list.json @@ -0,0 +1,1702 @@ +[ + { + "type": "text", + "text": "Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification", + "text_level": 1, + "bbox": [ + 230, + 130, + 738, + 174 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Chao Yi, Lu Ren, De-Chuan Zhan, Han-Jia Ye $(\\boxtimes)$ \nNational Key Laboratory for Novel Software Technology, Nanjing University, China \nSchool of Artificial Intelligence, Nanjing University, China \n{yic, renl, zhandc, yehj}@lamda.nju.edu.cn", + "bbox": [ + 151, + 203, + 815, + 273 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 308, + 313, + 325 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "CLIP showcases exceptional cross-modal matching capabilities due to its training on image-text contrastive learning tasks. However, without specific optimization for unimodal scenarios, its performance in single-modality feature extraction might be suboptimal. Despite this, some studies have directly used CLIP's image encoder for tasks like few-shot classification, introducing a misalignment between its pre-training objectives and feature extraction methods. This inconsistency can diminish the quality of the image's feature representation, adversely affecting CLIP's effectiveness in target tasks. In this paper, we view text features as precise neighbors of image features in CLIP's space and present a novel CrOss-moDal nEighbor Representation (CODER) based on the distance structure between images and their neighbor texts. This feature extraction method aligns better with CLIP's pre-training objectives, thereby fully leveraging CLIP's robust cross-modal capabilities. The key to construct a high-quality CODER lies in how to create a vast amount of high-quality and diverse texts to match with images. We introduce the Auto Text Generator (ATG) to automatically generate the required texts in a data-free and training-free manner. We apply CODER to CLIP's zero-shot and few-shot image classification tasks. Experiment results across various datasets and models confirm CODER's effectiveness. Code is available at: https://github.com/YCaigogogo/CVPR24-CODER.", + "bbox": [ + 76, + 342, + 472, + 734 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 767, + 207, + 782 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In recent years, vision-language models have garnered widespread attention, with CLIP [16] standing out as a notably powerful exemplar. Trained on a vast array of image-text pairs through the image-text contrastive learning tasks, CLIP boasts impressive cross-modal matching capabilities. And it has been applied to fields like image classification [16], object detection [3], semantic segmen", + "bbox": [ + 75, + 794, + 468, + 902 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "tation [7, 25], video understanding [10], voice classification [4], text-to-image generation [19, 34], model pretraining [23], and beyond [17, 31].", + "bbox": [ + 496, + 310, + 890, + 354 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Some existing works [21, 23, 32] extract image features directly from CLIP's image encoder for intra-modal operation, like calculating similarity between images in few-shot classification [32]. However, these methods overlook CLIP's multi-modal capabilities, leading to a misalignment with CLIP's pre-training objectives. Furthermore, since CLIP isn't optimized for uni-modal scenarios, its performance in intra-modal tasks isn't guaranteed. To optimize the image features extracted by CLIP, we ask:", + "bbox": [ + 496, + 354, + 892, + 491 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Can we leverage CLIP's powerful cross-modal matching capabilities to extract better image features, thereby improving CLIP's performance on downstream tasks?", + "bbox": [ + 529, + 500, + 859, + 559 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In this paper, we introduce an enhanced image representation based on the distance between images and their neighboring texts in CLIP's feature space. This idea stems from our re-examination of CLIP's robust zero-shot classification capability from the perspective of nearest neighboring: The previous approaches consider the text features extracted by CLIP as classifiers and use them to get the classification results. Different from this perspective, we interpret CLIP's zero-shot image classification as a 1NN problem, as shown in the left part of Figure 1. We treat texts as the images' neighbors in the CLIP's feature space. Then for each image, CLIP identifies its closest text and assigns this text's class as the image's predicted class. This 1NN approach shows good performance because CLIP's robust image-text matching capabilities ensure images are closer to their semantically related texts. This suggests that the cross-modal distance between an image and its neighboring texts captures information about the image, such as its class.", + "bbox": [ + 496, + 568, + 892, + 839 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In zero-shot image classification, CLIP only considers the distance between an image and its nearest neighbor text, which loses the information implied in the distance between the image and other texts. To make full use of this infor", + "bbox": [ + 496, + 839, + 890, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "27402", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/4d4a48acd8ebf7cdb5f8a0dc3828ea36b23dde31c9d839d66bffd84f74ea3e79.jpg", + "image_caption": [ + "Figure 1. Illustration of image's CrOss-moDal nEighbor Representation (CODER). CLIP's powerful text-image matching capabilities endows it with a favorable cross-modal neighbor distance relation. And CLIP's Zero-Shot Image Classification process can be interpreted as using a 1NN algorithm to find the image's nearest text, with the text's class determining the image's predicted class. Inspired by this idea, we expand the image's neighbor range to leverage its distance to all texts for constructing the CODER. Here $d_{ij}$ refers to the distance between the $i$ -th image and the $j$ -th text." + ], + "image_footnote": [], + "bbox": [ + 120, + 87, + 848, + 272 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "mation, we expand each image's neighbor range to utilize its distance to $K$ Nearest Neighbor (KNN) texts for constructing image representation, as depicted in the right half of Figure 1. Here $K$ denotes the total number of texts. We refer to this representation as CrOss-moDal nEighbor Representation (CODER). We believe images with closer CODER values are more similar in semantics. This aligns with intuition: If two objects share the same sets of similar and dissimilar items, they're likely similar to each other.", + "bbox": [ + 75, + 371, + 468, + 505 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Previous work [24, 33] has noted that dense sampling of neighbor samples is critical for building neighbor representations. This inspires us to use various high-quality texts for dense sampling. Considering that Large Models have rich knowledge and are widely used in many ways [9, 14, 27], we introduce the Auto Text Generator (ATG) based on Large Language Models like ChatGPT [13] to automatically generate various high-quality texts. Without the need for image data and the training process, ATG can produce a diverse and effective set of texts based on the target dataset's class names. These diverse, high-quality texts enhance the density of neighboring texts for images in CLIP's feature space, helping to build a better CODER.", + "bbox": [ + 75, + 507, + 468, + 703 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We apply CODER to CLIP's zero-shot and few-shot image classification tasks to prove CODER's superiority. For the zero-shot image classification task, we use CODER in a two-stage manner. In the first stage, we use ATG to acquire general class-specific texts for constructing general CODER. Then we employ a heuristic classifier to the image's general CODER. In the second stage, we utilize ATG to generate one-to-one specific texts for comparing two distinct classes, concentrating on their most distinguishing features. These texts are then used to construct the one-to-one specific CODER, which is used to rerank the preliminary classification results. For the few-shot situation, we calculate the similarity between test images and the support set's", + "bbox": [ + 75, + 704, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "images using those images' general CODER. By ensembling the similarity and CLIP's original zero-shot classification logits, we determine the classification results. Experiment results on various datasets and different CLIP models confirm that CODER enhances CLIP's performance in both zero-shot and few-shot image classification.", + "bbox": [ + 496, + 371, + 890, + 460 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 479, + 640, + 494 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Vision-Language Models. Vision-Language Models (VLMs) represent a class of multimodal models adept at correlating textual and visual information. Prominent models in this domain include CLIP [16], ALIGN [6], FLAVA [18] and Florence [30], among others. These models typically comprise two main components: an image encoder and a text encoder. Some models also have multimodal fusion modules [8, 22]. VLMs are trained on extensive text-image pairs through tasks like image-text contrastive learning, endowing them with powerful text-image matching capabilities. In this paper, we leverage these capabilities of CLIP to generate our cross-modal neighbor representations (CODER) for images.", + "bbox": [ + 496, + 506, + 890, + 702 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Using LLMs as Experts to Improve VLMs. Large Language Models (LLMs) are widely used in many tasks, such as in-context learning. LLMs can serve as experts by outputting their knowledge in text form. This text-based knowledge can be harnessed by VLMs to enhance their capabilities. Previous work has explored using LLMs' knowledge to optimize VLMs' pre-training [1], prediction interpretability [12, 26, 28], and classifier quality [2, 11, 12, 15]. Recently, some work [29, 35] uses LLMs to select the best VLMs from a VLM zoo for specific target tasks. In this paper, we use the semantic information provided by LLMs to optimize CLIP's features during the inference stage in a training-free manner.", + "bbox": [ + 496, + 704, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "27403", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/45895adcd1b6d2aae32b50facffa21736363d4283c4be28e266393c2f8c7e478.jpg", + "image_caption": [ + "Figure 2. An example of CODER correcting wrong distance relation between images. $d_{ij}^{img}$ refers to the cosine distance between the $i$ -th and the $j$ -th image. $r_1$ and $r_2$ refer to the cosine distance between the text and different images, while $1 - r_1$ and $1 - r_2$ refer to the cosine similarity. The left side of the figure indicates that even though images of the same class share similar distance to a text, this doesn't ensure that their features are closely similar. The right side of the figure shows that CODER corrects the wrong distance relation by utilizing the text-image distance." + ], + "image_footnote": [], + "bbox": [ + 127, + 93, + 839, + 292 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Notations and Background", + "text_level": 1, + "bbox": [ + 76, + 388, + 326, + 407 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Using CLIP to match text and image. CLIP encodes both images and texts into a joint space using its image encoder $f^{\\prime}$ or text encoder $f^{T}$ , shown in Equation 1. Here $\\hat{x}_i$ and $\\hat{t}_j$ refers to the feature of image $x_i$ and text $t_j$ , respectively. $D_{1}$ refers to the dimension of CLIP's feature space.", + "bbox": [ + 76, + 415, + 470, + 492 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\boldsymbol {x}} _ {i} = f ^ {I} \\left(\\boldsymbol {x} _ {i}\\right) \\in \\mathbb {R} ^ {D _ {1}}, \\hat {\\boldsymbol {t}} _ {j} = f ^ {T} \\left(\\boldsymbol {t} _ {j}\\right) \\in \\mathbb {R} ^ {D _ {1}}. \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 130, + 501, + 468, + 520 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {\\boldsymbol {t}} = \\underset {j \\in [ 1, \\dots , K ]} {\\arg \\max } \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {j}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot \\| \\hat {\\boldsymbol {t}} _ {j} \\|.} \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 181, + 541, + 468, + 579 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Then we can compute the cosine similarity between the features of various texts and images. These similarity scores represent the matching degree between different images and texts. Given an image $\\boldsymbol{x}_i$ , its best matched text $\\tilde{t}$ is identified by the highest similarity scores with the image, as shown in Equation 2. Here $K$ refers to the number of texts.", + "bbox": [ + 75, + 584, + 468, + 675 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Cross-Modal Neighbor Representation", + "text_level": 1, + "bbox": [ + 75, + 688, + 424, + 707 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. Understand the Advantage of CODER.", + "text_level": 1, + "bbox": [ + 75, + 713, + 398, + 729 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We construct the CODER for the current image by tapping into the precise image-text distance relationship within the CLIP feature space. This process is shown in Equation 3. We use the CODER construct function $\\phi$ to build image's CODER $\\phi (\\hat{x}_i)$ based on its original feature $\\hat{x}_i$ .", + "bbox": [ + 75, + 736, + 468, + 813 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\left[ \\psi (d (\\hat {\\boldsymbol {x}} _ {i}, \\hat {\\boldsymbol {t}} _ {1})), \\dots , \\psi (d (\\hat {\\boldsymbol {x}} _ {i}, \\hat {\\boldsymbol {t}} _ {K})) \\right] \\in \\mathbb {R} ^ {K}. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 89, + 821, + 468, + 854 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The specific implementation of $\\phi$ depends on the similarity or distance function $d$ and the subsequent mapping function $\\psi$ applied to this distance. In this paper, we use cosine", + "bbox": [ + 75, + 854, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "similarity for $d$ and identity mapping for $\\psi$ . Then we can rewrite Equation 3 as Equation 4. We emphasize that the implementation of $d$ and $\\psi$ can be further researched.", + "bbox": [ + 498, + 391, + 892, + 436 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\left[ \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {1}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot \\| \\hat {\\boldsymbol {t}} _ {1} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {K}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot | \\hat {\\boldsymbol {t}} _ {K} |} \\right] \\in \\mathbb {R} ^ {K}. \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 452, + 890, + 491 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We highlight CODER's advantages over CLIP's original image features using an example. Figure 2's left side depicts a bad case for CLIP. For simplicity, we consider a situation where test images share the same neighboring text in CLIP's feature space. While CLIP's cross-modal pre-training ensures accurate image-text distances, it doesn't always capture precise distances between images. This results in cases where the distance for same-class images $d_{21}^{img}$ exceeds that of different-class images $d_{23}^{img}$ . To solve this problem, CODER uses CLIP's accurate text-image distance to build image features. As images of the same class have similar distance to their neighboring texts, their CODER align more closely. Thus, CODER addresses the wrong distance relation between images.", + "bbox": [ + 496, + 503, + 892, + 717 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We then focus on the key element of building a good CODER. Previous studies have emphasized that dense sampling of neighboring samples is vital for algorithms based on nearest neighbor. For example, only when the training samples are densely sampled will the error rate of the KNN classifier remain within twice that of the Bayes optimal classifier. And some studies [24, 33] have observed that greater sampling density of neighboring samples can lead to better neighbor representations. Inspired by these works, we try to optimize our CODER by increasing the number of texts. For increasing the number of texts, we use our Auto Text Generator (ATG) to achieve this objective.", + "bbox": [ + 496, + 719, + 893, + 901 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "27404", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.2. Use Auto Text Generator to Generate Texts", + "text_level": 1, + "bbox": [ + 76, + 90, + 444, + 104 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Accurate and diverse class-specific texts provide a comprehensive description of object classes from various perspectives, enhancing the sampling density of images' neighbor texts for constructing better CODER. To automatically generate a plethora of high-quality class-specific texts adaptive to target tasks, we introduce the Auto Text Generator (ATG). It uses different query prompts to extract diverse insights from external experts like ChatGPT [13]. Then it leverages that knowledge to construct various high-quality texts. These texts are instrumental in generating high-quality CODER.", + "bbox": [ + 75, + 114, + 467, + 280 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In our implementation, ATG can construct five types of texts: (1) Class Name-based Texts; (2) Attribute-based Texts; (3) Analogous Class-based Texts; (4) Synonym-based Texts; (5) One-to-One Texts. The first two types of texts are proposed by previous work[12, 16], while the latter three are innovations introduced in this paper. We will then delve deeper into the design rationale and generation process of these last three types of texts.", + "bbox": [ + 75, + 281, + 467, + 402 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "(1) Analogous Class-based Texts. If someone describes a clouded leopard as resembling a cheetah, you can envision its appearance even if you've never seen a clouded leopard. This scenario illustrates how inter-object similarities help humans leverage their experience with known object classes to recognize new ones. Inspired by this, we query ChatGPT to obtain analogous categories for a given object by asking:", + "bbox": [ + 75, + 402, + 467, + 508 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Q: What other categories are {class} visually similar to?", + "bbox": [ + 86, + 527, + 413, + 555 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given that the generated class names might exist within the target dataset's class names, we address this issue by filtering out those generated class names whose cosine similarity with existing class names surpass a defined threshold. Next, we insert each analogous class name into some templates like \"a {target class} similar to {analogous class}\" to form a complete text.", + "bbox": [ + 75, + 566, + 467, + 672 + ], + "page_idx": 3 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "(2) Synonym-based Texts. An object can have several names. For example, both \"forest\" and \"woodland\" refer to \"land covered with trees and shrubs\". Due to varying frequencies of synonyms in CLIP's training data, the model might favor more common terms and undervalue lesser-known synonyms, despite their equivalent meanings. To mitigate this bias, we query WordNet for synonyms of the current class. Subsequently, we insert the obtained synonym class names into templates like \"a photo of {synonym class}\".", + "(3) One-to-One Texts: Due to similar classes often share common features, the ATG may generate nearly identical attribute descriptions for these classes. For example, the ATG might generate attributes such as \"two pairs of wings\" for both \"butterfly\" and \"dragonfly\". Such identical" + ], + "bbox": [ + 75, + 672, + 467, + 901 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "attributes can hinder CLIP's ability to distinguish closely related classes. To tackle this problem, we introduce the one-to-one texts. We use the following query prompt to guide ChatGPT in generating the most distinguishing features between similar classes A and B:", + "bbox": [ + 498, + 90, + 890, + 165 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Q: What are different visual features between a {class 1} and a {class 2} in a photo? Focus on their key differences.", + "bbox": [ + 508, + 169, + 859, + 210 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Using the prompt, we generate distinguishing attributes that differentiate butterfly from dragonfly. For butterfly, some of the exemplified attributes include: [\"Butterflies typically have larger and more colorful wings compared to dragonflies.'] For dragonfly, some of the descriptors produced are: [\"They have transparent wings that are typically held out horizontally when at rest.'] From these newly created attributes, we can make two main observations: (1) The attributes underscore the key differences between butterfly and dragonfly, such as their wing characteristics. (2) The new attributes accentuate the comparison between the two classes, evident from terms like \"larger\", and \"compared to\" found within the descriptors.", + "bbox": [ + 498, + 220, + 890, + 417 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Finally, we insert the obtained one-to-one texts into some templates like \"Because of {1v1 text}, {class 1} is different from {class 2}\"", + "bbox": [ + 498, + 417, + 890, + 463 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.3. Use CODER on Downstream Tasks", + "text_level": 1, + "bbox": [ + 500, + 472, + 792, + 487 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We apply CODER in zero-shot and few-shot image classification tasks to enhance the performance of CLIP.", + "bbox": [ + 498, + 496, + 888, + 526 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Zero-Shot Image Classification. In the first stage, we utilize a general text set generated by ATG to construct the general CODER for images. These texts can be considered as descriptions of general characteristics for a certain class in comparison to most other classes. We can derive preliminary classification results based on the general CODER of the images. In the second stage, we employ ATG to create distinct one-to-one specific text sets for the top five classes, each pair-wise. These texts serve as descriptions of the key distinguishing features between the classes. Utilizing these, we then develop corresponding one-to-one specific CODER for images. Subsequently, we rerank the initial top five classification results using these one-to-one specific CODER. Figure 3 shows the process of our zero-shot image classification method.", + "bbox": [ + 498, + 527, + 890, + 752 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We first utilize all texts generated by ATG, excluding the one-to-one texts, as the general text set $\\mathcal{P} = [t_1,\\dots ,t_K]$ to construct the general CODER for test images. This process is shown in Equation 5 and Equation 6. Here $\\pmb {W}\\in \\mathbb{R}^{D_1\\times K}$ refers to the texts' features in the CLIP feature space. And $s_i\\in \\mathbb{R}^K$ represents the CODER of test image $\\pmb{x}_i$ . $K$ refers to the total number of texts in $\\mathcal{P}$ .", + "bbox": [ + 498, + 753, + 890, + 859 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {W} = \\left[ \\frac {\\hat {\\boldsymbol {t}} _ {1}}{\\| \\hat {\\boldsymbol {t}} _ {1} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K}}{\\| \\hat {\\boldsymbol {t}} _ {K} \\|} \\right] \\in \\mathbb {R} ^ {D _ {1} \\times K}. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 868, + 890, + 905 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "27405", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/9cda19fd5a8a3babf33f85372154a10c858cef5fdcb9a321c25ca5dfe607e78b.jpg", + "image_caption": [ + "Stage 1: Use General CODER for Preliminary Classification" + ], + "image_footnote": [], + "bbox": [ + 153, + 107, + 566, + 253 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/ee842a6032038daf61d9806e7ee5c0b5496e4900aff80dd1c5264bfde1163d42.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 571, + 89, + 821, + 252 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/d4f5fef52f43eecbb7c35d5b866ebad6338b23c83f33053e7eb6200eeca6b745.jpg", + "image_caption": [ + "Stage 2: Use One-to-One Specific CODER for Reranking Top 5 Classes", + "Figure 3. Illustration of two-stage zero-shot image classification process based on image's CODER. In the first stage, we use the Auto Text Generator to create a General Text Set, which contains general descriptions of classes. This set is utilized to construct the image's general CODER, and we use it for preliminary classification. In the second stage, we construct One-to-One Text Sets in pairs for the top five predicted classes of the preliminary classification results, focusing on attributes where the two specific classes differ most. We build one-to-one specific CODER for the image based on these One-to-One Text Sets and use heuristic classifier to get each class's classification score. Then we rerank the top five preliminary results based on the classification score gaps $gap_i^{c,j}$ between classes. Here $gap_i^{c,j}$ represents the difference obtained by subtracting the score of the class $c$ from that of the class $j$ for image $x_i$ ." + ], + "image_footnote": [], + "bbox": [ + 158, + 275, + 816, + 426 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {s} _ {i} = \\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\|} \\boldsymbol {W} \\in \\mathbb {R} ^ {K}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 166, + 558, + 468, + 594 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Then, we employ a heuristic classifier $h$ on the test image's general CODER $s_i$ to obtain the preliminary classification logits vector $o_i$ . We use $s_{ij}$ to represent the portion of the test image's general CODER $s_i$ corresponding to the text of the $j$ -th category. $s_{ij}$ consists of several parts, as shown in Equation 7. Here $s_{ij}^{ori}, s_{ij}^{att}, s_{ij}^{ana}, s_{ij}^{syn}$ refers to $s_{ij}$ 's portion of class name-based texts, attribute-based texts, analogous class-based texts and synonym-based texts, respectively. $\\oplus$ refers to the vector concatenation operation.", + "bbox": [ + 75, + 595, + 468, + 733 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {s} _ {i j} = \\boldsymbol {s} _ {i j} ^ {\\text {o r i}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a t t}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a n a}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {s y n}}. \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 158, + 739, + 468, + 760 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For each class, the heuristic classifier $h$ first gets the largest element in the test image's CODER portion corresponding to the class name-based texts and synonym-based texts. This step is intuitive: Humans can recognize an object by knowing just one of its names. Then $h$ calculates the mean of $\\max(s_{ij}^{ori} \\oplus s_{ij}^{syn})$ and all elements in the $s_{ij}$ 's portion corresponding to the attribute-based texts and synonym-based texts. This value can be seen as the preliminary classification logit value $o_{ij}$ belonging to class $j$ . The process", + "bbox": [ + 75, + 763, + 470, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "is shown in the following Equation:", + "bbox": [ + 500, + 549, + 736, + 564 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\no _ {i j} = h \\left(\\boldsymbol {s} _ {i j}\\right) = \\operatorname {m e a n} \\left(\\boldsymbol {s} _ {i j} ^ {\\text {a t t}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a n a}} \\oplus \\left[ \\max \\left(\\boldsymbol {s} _ {i j} ^ {\\text {o r i}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {s y n}}\\right) \\right]\\right). \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 500, + 574, + 903, + 606 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "After obtaining the preliminary classification results $\\boldsymbol{o}_i$ , we extract the top five classes from the prediction results, forming a set named $\\mathcal{C}_5$ . Subsequently, we draw all pairwise combinations from these five classes in set $\\mathcal{C}_5$ , creating a new set $\\mathcal{P}_{1v1}$ comprised of these pairs. This process can be described by Equation 9 and Equation 10:", + "bbox": [ + 496, + 607, + 890, + 698 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {C} _ {5} = \\operatorname {T o p} 5 \\left(\\boldsymbol {o} _ {i}\\right) = \\left\\{c _ {1}, c _ {2}, c _ {3}, c _ {4}, c _ {5} \\right\\}. \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 566, + 709, + 890, + 727 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {P} _ {1 v 1} = \\left\\{\\left\\{c _ {a}, c _ {b} \\right\\} \\mid c _ {a}, c _ {b} \\in \\mathcal {C} _ {5}, a \\neq b \\right\\}. \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 566, + 741, + 890, + 758 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In the second stage, we use ATG to generate the one-to-one specific texts for each pair in $\\mathcal{P}_{1v1}$ , resulting in a total of $C_5^2 = 10$ text sets. For each one-to-one specific text set, we can construct a one-to-one specific CODER for the image. We first use CLIP's text encoder $f^{T}$ to extract the text features of the one-to-one text set $\\boldsymbol{W}^{a,b} \\in \\mathbb{R}^{D_{1} \\times (K_{1} + K_{2})}$ . Here $K_{1}$ and $K_{2}$ represent the number of one-to-one texts for each of the two classes. Equation 11 shows the composition of $\\boldsymbol{W}^{a,b}$ , where $\\hat{\\boldsymbol{t}}_i^a$ and $\\hat{\\boldsymbol{t}}_i^b$ refers to the $i$ -th one-to-one", + "bbox": [ + 496, + 763, + 890, + 901 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "27406", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "text feature of class $a$ and class $b$ , respectively.", + "bbox": [ + 76, + 90, + 385, + 107 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {W} ^ {a, b} = \\left[ \\frac {\\hat {\\boldsymbol {t}} _ {1} ^ {a}}{\\| \\hat {\\boldsymbol {t}} _ {1} ^ {a} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K _ {1}} ^ {a}}{\\| \\hat {\\boldsymbol {t}} _ {K _ {1}} ^ {a} \\|}, \\frac {\\hat {\\boldsymbol {t}} _ {1} ^ {b}}{\\| \\hat {\\boldsymbol {t}} _ {1} ^ {b} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K _ {2}} ^ {b}}{\\| \\hat {\\boldsymbol {t}} _ {K _ {2}} ^ {b} \\|} \\right]. \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 91, + 116, + 468, + 159 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Then we use the one-to-one text features $W^{a,b}$ to construct the image's one-to-one specific CODER $s_i^{a,b} \\in \\mathbb{R}^{K_1 + K_2}$ :", + "bbox": [ + 76, + 169, + 468, + 202 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {s} _ {i} ^ {a, b} = \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\|} \\boldsymbol {W} ^ {a, b} = \\boldsymbol {s} _ {i a} ^ {a, b} \\oplus \\boldsymbol {s} _ {i b} ^ {a, b}. \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 158, + 210, + 468, + 246 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Here $s_{ia}^{a,b} \\in \\mathbb{R}^{K_1}$ and $s_{ib}^{a,b} \\in \\mathbb{R}^{K_2}$ represent the part of CODER pertaining to the one-to-one texts for class $a$ and class $b$ , respectively.", + "bbox": [ + 76, + 256, + 468, + 304 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Based on the one-to-one specific CODER $s_i^{a,b}$ of the image $\\pmb{x}_i$ , we employ a heuristic classifier $h$ to obtain image's classification scores for class $a$ and $b$ , denoted as $o_{ia}^{a,b}$ and $o_{ib}^{a,b}$ , respectively:", + "bbox": [ + 76, + 303, + 468, + 368 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\no _ {i a} ^ {a, b} = h \\left(\\boldsymbol {s} _ {i a} ^ {a, b}\\right) = \\operatorname {m e a n} \\left(\\boldsymbol {s} _ {i a} ^ {a, b}\\right), \\tag {13}\n$$\n", + "text_format": "latex", + "bbox": [ + 163, + 378, + 468, + 410 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\no _ {i b} ^ {a, b} = h (\\pmb {s} _ {i b} ^ {a, b}) = \\mathrm {m e a n} \\left(\\pmb {s} _ {i b} ^ {a, b}\\right).\n$$\n", + "text_format": "latex", + "bbox": [ + 166, + 407, + 380, + 431 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Then we calculate the image's classification score gap for each class relative to another class:", + "bbox": [ + 76, + 441, + 468, + 470 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\ng a p _ {i} ^ {a b} = o _ {i a} ^ {a, b} - o _ {i b} ^ {a, b}, \\quad g a p _ {i} ^ {b a} = o _ {i b} ^ {a, b} - o _ {i a} ^ {a, b}. \\tag {14}\n$$\n", + "text_format": "latex", + "bbox": [ + 109, + 481, + 468, + 502 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For each class, we sum up all the score gaps between it and other classes. Then we select the class with the largest sum of score gaps as the final predicted class $\\hat{c}_i$ of the image:", + "bbox": [ + 76, + 512, + 468, + 558 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {c} _ {i} = \\underset {c \\in \\mathcal {C} _ {5}} {\\operatorname {a r g m a x}} \\sum_ {j \\in \\mathcal {C} _ {5} / \\{c \\}} \\operatorname {g a p} _ {i} ^ {c j}. \\tag {15}\n$$\n", + "text_format": "latex", + "bbox": [ + 174, + 568, + 468, + 603 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We use the method based on score gaps instead of the traditional voting method to reorder initial prediction results. The reason is that score gaps provide quantified information about the relative advantages between classes. Unlike voting, which only considers each class's number of wins in pairwise classification, score gaps better capture the model's uncertainty in the classification tasks. For example, a small score gap might indicate that the model is uncertain about the correct class for the image, suggesting that the classification result may be unreliable. This can lead to errors in the outcomes derived from voting methods.", + "bbox": [ + 75, + 613, + 468, + 779 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "This two-phase image classification process illustrates that by changing the neighbor text set, we can dynamically build image's feature that focus on different semantics according to task requirements. In coarse-grained image classification, we focus on the general semantics of a class, such as whether an animal has wings. In fine-grained image classification, we aim to focus on more detailed features that differentiate between two specific classes, such as the color", + "bbox": [ + 75, + 780, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "of wings when distinguishing between dragonfly and butterfly. However, the original image features extracted by the CLIP's image encoder cannot dynamically adapt to specific classification task requirements.", + "bbox": [ + 496, + 90, + 890, + 151 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Few-Shot Image Classification. For Few-Shot Image Classification, we improve the Tip-Adapter [32] by replacing the original CLIP's image features with our CODER to calculate the similarity between the test image and the support set's images. We refer to the improved method as CrOss-MoDal NEighbor Representation CLIP Adapter (CODER-Adapter). Given the $N$ -way $M$ -shot support image set $\\mathcal{I}$ , we first calculate the CODER of the images in the support set, represented by $S_{train} \\in \\mathbb{R}^{NM \\times K}$ . Equation 16 shows the calculation process, where $f^I(\\mathcal{I}) \\in \\mathbb{R}^{NM \\times D_1}$ refers to the support images' original features and $W \\in \\mathbb{R}^{D_1 \\times K}$ refers to the features of texts in the general text set $\\mathcal{P}$ , as defined in Equation 5.", + "bbox": [ + 496, + 151, + 892, + 348 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {S} _ {\\text {t r a i n}} = f ^ {I} (\\mathcal {I}) \\boldsymbol {W}. \\tag {16}\n$$\n", + "text_format": "latex", + "bbox": [ + 624, + 361, + 890, + 378 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Then we perform one-hot encoding on the support images' labels $\\pmb{L}$ to get one-hot labels matrix $L_{train} \\in \\mathbb{R}^{NM \\times C}$ . Each row of $L_{train}$ is a one-hot vector.", + "bbox": [ + 498, + 383, + 890, + 429 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {L} _ {\\text {t r a i n}} = \\operatorname {O n e H o t} (\\boldsymbol {L}). \\tag {17}\n$$\n", + "text_format": "latex", + "bbox": [ + 614, + 436, + 890, + 454 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For the test image $\\pmb{x}_i$ , we also construct its CODER $s_i \\in \\mathbb{R}^K$ similarly to the support set's images.", + "bbox": [ + 498, + 460, + 890, + 492 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {s} _ {i} = f ^ {I} \\left(\\boldsymbol {x} _ {i}\\right) \\boldsymbol {W}. \\tag {18}\n$$\n", + "text_format": "latex", + "bbox": [ + 637, + 498, + 890, + 516 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We then calculate the affinity matrix $\\mathbf{A} \\in \\mathbb{R}^{1 \\times NM}$ between the test image's CODER $s_i \\in \\mathbb{R}^K$ and the support set images' CODER $S_{train} \\in \\mathbb{R}^{NM \\times K}$ using the Equation 19. Here $\\mathrm{Norm}(\\cdot)$ refers to the data normalization operation like L2 or min-max normalization. $\\beta$ and $T$ are hyperparameters to control the sharpness of $\\mathbf{A}$ 's distribution.", + "bbox": [ + 496, + 523, + 890, + 614 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {A} = \\exp \\left(- \\beta \\cdot \\left(1 - \\frac {\\operatorname {N o r m} \\left(\\boldsymbol {s} _ {i} \\boldsymbol {S} _ {\\text {t r a i n}} ^ {\\top}\\right)}{T}\\right)\\right). \\tag {19}\n$$\n", + "text_format": "latex", + "bbox": [ + 527, + 621, + 890, + 664 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The affinity $\\mathbf{A} \\in \\mathbb{R}^{1 \\times NM}$ serves as a weight factor for $L_{train}$ . By calculating the weighted sum of images' labels in $L_{train}$ , we can refine the CLIP's original zero-shot prediction results $o_i^{zs}$ using Equation 20. Here $\\alpha$ controls the degree of correction.", + "bbox": [ + 496, + 670, + 890, + 747 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {o} _ {i} = \\alpha \\cdot \\boldsymbol {A} \\boldsymbol {L} _ {\\text {t r a i n}} + \\boldsymbol {o} _ {i} ^ {z s}. \\tag {20}\n$$\n", + "text_format": "latex", + "bbox": [ + 609, + 755, + 890, + 772 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Finally, we select the class corresponding to the largest logits in $\\pmb{o}_i$ as the predicted class of image $\\pmb{x}_i$ .", + "bbox": [ + 496, + 780, + 890, + 810 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 821, + 633, + 839 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Zero-Shot Image Classification Performance", + "text_level": 1, + "bbox": [ + 500, + 847, + 877, + 863 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For zero-shot image classification, we compare our method with two baselines: Vanilla CLIP [16] and VCD [12]. Ta", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "27407", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/c73144797a260cb4cef4fff1bda28fa228b02dd03f005d6a31f3c7599a3120d8.jpg", + "table_caption": [ + "Table 1. Accuracy gains over VCD and CLIP baseline. The \"CODER\" column shows the classification accuracy before rerank stage, while the \"CODER*\" column shows the accuracy after rerank stage. $\\Delta$ represents the improvement of our method over VCD." + ], + "table_footnote": [], + "table_body": "
ImageNetCUB200EuroSAT
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3259.0762.9664.3866.863.9051.8151.7853.0055.043.2644.8946.5752.8354.938.36
ViT-B/1663.5368.1069.6171.463.3655.7557.5458.3059.922.3849.5256.4655.3060.544.08
ViT-L/1470.5874.9676.1577.382.4262.1063.2964.6465.762.4753.5459.5762.9868.248.67
ViT-L/14@336px71.8176.1177.2778.492.3863.4864.7966.2967.362.5754.9359.4664.9469.9610.50
Describable TexturesPlaces365Food101
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3241.2845.2748.7852.717.4436.4738.9240.3740.271.4580.2784.1384.7285.501.37
ViT-B/1643.1945.6448.6755.6910.0537.3139.8741.3941.701.8385.9989.2589.2989.820.57
ViT-L/1452.1857.1860.7461.864.6837.0638.5541.2141.593.0489.8593.3393.6693.930.60
ViT-L/14@336px52.1257.4561.1262.875.4237.2739.8842.0942.502.6291.1094.0694.4894.750.69
Caltech101Oxford PetsImageNetV2
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3279.9089.8091.2491.421.6281.6385.9188.4789.263.3551.7955.2956.7556.421.46
ViT-B/1680.1892.2894.0793.951.7983.9589.3491.5092.012.6757.2561.5362.9462.971.44
ViT-L/1479.7893.9595.7995.681.8487.9093.1894.1994.361.1864.3169.2170.3570.371.16
ViT-L/14@336px80.3694.3596.3196.372.0287.8293.6294.2294.881.2665.6170.4171.4571.281.04
", + "bbox": [ + 76, + 121, + 890, + 356 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ble 1 displays zero-shot image classification experiment results. By analyzing the results, we can draw the following conclusions: (1) Our proposed CODER consistently boosts CLIP's zero-shot image classification accuracy across various datasets and model architectures; (2) The rerank stage based on the one-to-one specific CODER can further enhance CLIP's performance, demonstrating the effectiveness of our proposed two-stage zero-shot classification method.", + "bbox": [ + 75, + 375, + 468, + 494 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.2. Few-Shot Image Classification Performance", + "text_level": 1, + "bbox": [ + 76, + 510, + 447, + 526 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "For few-shot image classification, we use ResNet 50[5] as the backbone for CLIP's image encoder, consistent with previous methods. We use two CLIP's training-free few-shot image classification methods TIP-Adapter [32] and TIP-X [20] as our baselines. TIP-Adapter leverages features extracted by CLIP's image encoder for calculating the similarity between test images and support set's images. While TIP-X uses features based on similarity scores between images and texts generated by CUPL [15] to do it.", + "bbox": [ + 75, + 536, + 467, + 671 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Figure 4 shows the few-shot image classification experiment results. We use the experimental results of TIP-Adapter and TIP-X presented in [20] and ensure that our random seeds are consistent with them. Our method surpasses the previous CLIP few-shot training-free image classification methods on most datasets across different shot scenarios. We notice that CODER-Adapter's performance on EuroSAT is unsatisfactory, which results in our method not having a significant advantage in average accuracy across 11 datasets compared to previous methods. But this meets our expectations. Since EuroSAT has only 10 classes and 95 texts generated by ATG, this small number of texts fails to satisfy CODER's need for dense text sampling, impacting the adapter's performance. This highlights the importance of dense sampling for CODER.", + "bbox": [ + 75, + 674, + 467, + 900 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 2. The accuracy of the zero-shot image classification experiments using different texts. Meaning of symbols: P: Using class name-based texts. Att: Using attribute-based texts. Ana: Using analogous class-based texts. We use CLIP ViT-B-32.", + "bbox": [ + 498, + 372, + 890, + 428 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/1f9154e9243820c86f4fc91378de3e577f4438be94afb6f4940e39d1c368b580.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
TextCaltech101Oxford PetsDescribable TexturesEuroSAT
P79.9081.6341.2844.89
P+Att89.8085.9145.2746.57
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TextCaltech101Oxford PetsDescribable TexturesEuroSAT
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", + "bbox": [ + 500, + 545, + 890, + 601 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Contrasting to previous work [20, 32], we innovatively interpret the superiority of CLIP's cross-modal relative feature representation from the perspective of neighbor representation. Additionally, by drawing an analogy to neighbor-based algorithms like KNN, which require dense sampling of neighbor samples to ensure superior performance, we provide an intuitive explanation for our need to use a more diverse and higher-quality text set to construct our CODER. Motivated by this conclusion, we develop the Auto Text Generator for the automated creation of varied, high-quality texts to meet CODER's dense sampling needs. The experiments demonstrate the validity of our method.", + "bbox": [ + 496, + 609, + 890, + 790 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. The Importance of Dense Sampling for CODER", + "text_level": 1, + "bbox": [ + 498, + 801, + 890, + 816 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Nearest neighbor algorithms like KNN depend on dense sampling for good performance. We view our CODER as a cross-modal neighbor representation. Hence, as the diversity and quantity of high-quality cross-modal neighbor texts increase, the constructed CODER should correspond", + "bbox": [ + 496, + 824, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "27408", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/8e505bb6850852a0bf4acbe3510ca2435395bca781ae4cb18a3aa5a23b99537e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 106, + 92, + 294, + 205 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/9d1f22043b2fa421b13f61f0d0b3eef2f60705cf63814f38f0468f22ffbc15ae.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 295, + 92, + 483, + 205 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/388065c011561aa9f35138b7b3f7ee444f68055e7d2e49f03263c8d55324fad0.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 486, + 90, + 673, + 205 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/50b41990085c2496c4fce85a9fe1aefbeeccaa57a11f87a2615e9cf9cc70287e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 676, + 90, + 864, + 205 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7a0b2a9053c9bd109b8f695094308494b9ec3adf0f7a90c76ce73db0e9e0a754.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 102, + 208, + 292, + 324 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a4deb8b9188dcffd85f21f6d307b8bb40bf756c7fa6241267abc23132b486786.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 297, + 208, + 483, + 324 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/32fd0a9c632d23b112e0dd1ea1ece1a24bc150f167734d96d8b898f6b10f7cc5.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 486, + 208, + 674, + 324 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/10df6792c2e702f3129fb20b49600505bf894b9058fcfbc852b98e6cc7a8ea7d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 676, + 208, + 864, + 324 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/24d128f4ba5878e5c21b7407f47672c691fcc442c9e189b439cc6a72e2fa57c6.jpg", + "image_caption": [ + "Figure 4. Results for the training-free few-shot regime across 11 datasets. We compare the CODER-Adapter with the previous CLIP few-shot image classification methods. Our CODER-Adapter achieves the best performance on most datasets." + ], + "image_footnote": [], + "bbox": [ + 102, + 325, + 294, + 444 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/96c39b524cc94188e903182a4688ce53af230b0dfa0ca25fd4f0b27e2225b927.jpg", + "image_caption": [], + "image_footnote": [ + "Zero-shot CLIP TIP-Adapter TIP-X CODER-Adapter (Ours)" + ], + "bbox": [ + 297, + 325, + 483, + 443 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/1c527fcaa3ff06eb4ba2cddec23651766139b0b55cb57eec92bd4c760fcaf5d4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 486, + 325, + 674, + 443 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/dccb78d0fa6254e723c93a05646196ee538225ad07617a18b396644fc60b611b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 676, + 329, + 864, + 443 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f606b8ca39bef0b8dde5c3985382abd3d0df4486398c7b853f1800e6d5fee531.jpg", + "image_caption": [ + "Figure 5. The t-SNE Visualization of the Oxford-Pets dataset. Left: Original CLIP Images' Features; Right: CODER." + ], + "image_footnote": [], + "bbox": [ + 86, + 512, + 272, + 625 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/5dd786495e3298e7e69cb40824a91d12eaceaa7a88240be3edf11ca276b6822d.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 276, + 512, + 460, + 625 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ingly improve. We validate this idea through experiments. We use three different text sets for constructing the image's CODER: (1) CLIP's original class name-based texts; (2) class name-based texts and VCD's attribute-based texts; (3) our analogous class-based texts added to (2). Our experiments in zero-shot and few-shot image classification, as detailed in Table 2 and Table 3, show that CODER performance enhances with the increasing diversity and number of texts. This highlights the importance of dense neighbor text sampling in improving CODER quality.", + "bbox": [ + 75, + 670, + 472, + 823 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Visualization results of CODER", + "text_level": 1, + "bbox": [ + 76, + 830, + 352, + 847 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Figure 5 presents a t-SNE visualization comparing original image features from the CLIP image encoder with those of our proposed CODER on the Oxford-Pets dataset. Our", + "bbox": [ + 75, + 854, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "CODER achieves tighter clustering of same-class images' features and clearer separation of different classes.", + "bbox": [ + 498, + 513, + 890, + 546 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 560, + 619, + 575 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we address the misalignment between CLIP's image feature extraction method and its pretraining paradigm. We present a novel perspective based on the nearest neighbors to comprehend CLIP's strong zero-shot image classification capability. Our key insight is that CLIP's effective text-image matching capability embeds image information in image-text distances. This leads us to propose the CrOss-moDal nEighbor Representation (CODER), utilizing these image-text distances for image representation. We introduce the Auto Text Generator to automatically generate texts, ensuring dense sampling of neighbor texts for better CODER construction. Experiment results in zero-shot and few-shot image classification show the superiority of our method.", + "bbox": [ + 496, + 585, + 892, + 799 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments", + "text_level": 1, + "bbox": [ + 500, + 814, + 658, + 830 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work is partially supported by National Key R&D Program of China (2022ZD0114805), NSFC (62376118, 62006112, 62250069, 61921006), Collaborative Innovation Center of Novel Software Technology and Industrialization.", + "bbox": [ + 496, + 839, + 893, + 902 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "27409", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Lijie Fan, Dilip Krishnan, Phillip Isola, Dina Katabi, and Yonglong Tian. 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In NeurIPS, 2023. 2" + ], + "bbox": [ + 78, + 90, + 467, + 484 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "27411", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_model.json b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_model.json new file mode 100644 index 0000000000000000000000000000000000000000..909d96b71c62f18c0bcbb4b28c334caf662429f8 --- /dev/null +++ b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_model.json @@ -0,0 +1,2090 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.231, + 0.131, + 0.74, + 0.175 + ], + "angle": 0, + "content": "Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification" + }, + { + "type": "text", + "bbox": [ + 0.152, + 0.204, + 0.816, + 0.275 + ], + "angle": 0, + "content": "Chao Yi, Lu Ren, De-Chuan Zhan, Han-Jia Ye\\((\\boxtimes)\\) \nNational Key Laboratory for Novel Software Technology, Nanjing University, China \nSchool of Artificial Intelligence, Nanjing University, China \n{yic, renl, zhandc, yehj}@lamda.nju.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.309, + 0.314, + 0.327 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.343, + 0.473, + 0.735 + ], + "angle": 0, + "content": "CLIP showcases exceptional cross-modal matching capabilities due to its training on image-text contrastive learning tasks. However, without specific optimization for unimodal scenarios, its performance in single-modality feature extraction might be suboptimal. Despite this, some studies have directly used CLIP's image encoder for tasks like few-shot classification, introducing a misalignment between its pre-training objectives and feature extraction methods. This inconsistency can diminish the quality of the image's feature representation, adversely affecting CLIP's effectiveness in target tasks. In this paper, we view text features as precise neighbors of image features in CLIP's space and present a novel CrOss-moDal nEighbor Representation (CODER) based on the distance structure between images and their neighbor texts. This feature extraction method aligns better with CLIP's pre-training objectives, thereby fully leveraging CLIP's robust cross-modal capabilities. The key to construct a high-quality CODER lies in how to create a vast amount of high-quality and diverse texts to match with images. We introduce the Auto Text Generator (ATG) to automatically generate the required texts in a data-free and training-free manner. We apply CODER to CLIP's zero-shot and few-shot image classification tasks. Experiment results across various datasets and models confirm CODER's effectiveness. Code is available at: https://github.com/YCaigogogo/CVPR24-CODER." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.768, + 0.208, + 0.784 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.47, + 0.903 + ], + "angle": 0, + "content": "In recent years, vision-language models have garnered widespread attention, with CLIP [16] standing out as a notably powerful exemplar. Trained on a vast array of image-text pairs through the image-text contrastive learning tasks, CLIP boasts impressive cross-modal matching capabilities. And it has been applied to fields like image classification [16], object detection [3], semantic segmen" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.311, + 0.892, + 0.356 + ], + "angle": 0, + "content": "tation [7, 25], video understanding [10], voice classification [4], text-to-image generation [19, 34], model pretraining [23], and beyond [17, 31]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.356, + 0.893, + 0.492 + ], + "angle": 0, + "content": "Some existing works [21, 23, 32] extract image features directly from CLIP's image encoder for intra-modal operation, like calculating similarity between images in few-shot classification [32]. However, these methods overlook CLIP's multi-modal capabilities, leading to a misalignment with CLIP's pre-training objectives. Furthermore, since CLIP isn't optimized for uni-modal scenarios, its performance in intra-modal tasks isn't guaranteed. To optimize the image features extracted by CLIP, we ask:" + }, + { + "type": "text", + "bbox": [ + 0.531, + 0.5, + 0.86, + 0.56 + ], + "angle": 0, + "content": "Can we leverage CLIP's powerful cross-modal matching capabilities to extract better image features, thereby improving CLIP's performance on downstream tasks?" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.569, + 0.893, + 0.84 + ], + "angle": 0, + "content": "In this paper, we introduce an enhanced image representation based on the distance between images and their neighboring texts in CLIP's feature space. This idea stems from our re-examination of CLIP's robust zero-shot classification capability from the perspective of nearest neighboring: The previous approaches consider the text features extracted by CLIP as classifiers and use them to get the classification results. Different from this perspective, we interpret CLIP's zero-shot image classification as a 1NN problem, as shown in the left part of Figure 1. We treat texts as the images' neighbors in the CLIP's feature space. Then for each image, CLIP identifies its closest text and assigns this text's class as the image's predicted class. This 1NN approach shows good performance because CLIP's robust image-text matching capabilities ensure images are closer to their semantically related texts. This suggests that the cross-modal distance between an image and its neighboring texts captures information about the image, such as its class." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In zero-shot image classification, CLIP only considers the distance between an image and its nearest neighbor text, which loses the information implied in the distance between the image and other texts. To make full use of this infor" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27402" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.121, + 0.088, + 0.849, + 0.273 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.285, + 0.892, + 0.356 + ], + "angle": 0, + "content": "Figure 1. Illustration of image's CrOss-moDal nEighbor Representation (CODER). CLIP's powerful text-image matching capabilities endows it with a favorable cross-modal neighbor distance relation. And CLIP's Zero-Shot Image Classification process can be interpreted as using a 1NN algorithm to find the image's nearest text, with the text's class determining the image's predicted class. Inspired by this idea, we expand the image's neighbor range to leverage its distance to all texts for constructing the CODER. Here \\(d_{ij}\\) refers to the distance between the \\(i\\)-th image and the \\(j\\)-th text." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.372, + 0.47, + 0.506 + ], + "angle": 0, + "content": "mation, we expand each image's neighbor range to utilize its distance to \\( K \\) Nearest Neighbor (KNN) texts for constructing image representation, as depicted in the right half of Figure 1. Here \\( K \\) denotes the total number of texts. We refer to this representation as CrOss-moDal nEighbor Representation (CODER). We believe images with closer CODER values are more similar in semantics. This aligns with intuition: If two objects share the same sets of similar and dissimilar items, they're likely similar to each other." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.508, + 0.47, + 0.704 + ], + "angle": 0, + "content": "Previous work [24, 33] has noted that dense sampling of neighbor samples is critical for building neighbor representations. This inspires us to use various high-quality texts for dense sampling. Considering that Large Models have rich knowledge and are widely used in many ways [9, 14, 27], we introduce the Auto Text Generator (ATG) based on Large Language Models like ChatGPT [13] to automatically generate various high-quality texts. Without the need for image data and the training process, ATG can produce a diverse and effective set of texts based on the target dataset's class names. These diverse, high-quality texts enhance the density of neighboring texts for images in CLIP's feature space, helping to build a better CODER." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.705, + 0.47, + 0.902 + ], + "angle": 0, + "content": "We apply CODER to CLIP's zero-shot and few-shot image classification tasks to prove CODER's superiority. For the zero-shot image classification task, we use CODER in a two-stage manner. In the first stage, we use ATG to acquire general class-specific texts for constructing general CODER. Then we employ a heuristic classifier to the image's general CODER. In the second stage, we utilize ATG to generate one-to-one specific texts for comparing two distinct classes, concentrating on their most distinguishing features. These texts are then used to construct the one-to-one specific CODER, which is used to rerank the preliminary classification results. For the few-shot situation, we calculate the similarity between test images and the support set's" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.372, + 0.892, + 0.462 + ], + "angle": 0, + "content": "images using those images' general CODER. By ensembling the similarity and CLIP's original zero-shot classification logits, we determine the classification results. Experiment results on various datasets and different CLIP models confirm that CODER enhances CLIP's performance in both zero-shot and few-shot image classification." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.48, + 0.642, + 0.495 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.507, + 0.892, + 0.703 + ], + "angle": 0, + "content": "Vision-Language Models. Vision-Language Models (VLMs) represent a class of multimodal models adept at correlating textual and visual information. Prominent models in this domain include CLIP [16], ALIGN [6], FLAVA [18] and Florence [30], among others. These models typically comprise two main components: an image encoder and a text encoder. Some models also have multimodal fusion modules [8, 22]. VLMs are trained on extensive text-image pairs through tasks like image-text contrastive learning, endowing them with powerful text-image matching capabilities. In this paper, we leverage these capabilities of CLIP to generate our cross-modal neighbor representations (CODER) for images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Using LLMs as Experts to Improve VLMs. Large Language Models (LLMs) are widely used in many tasks, such as in-context learning. LLMs can serve as experts by outputting their knowledge in text form. This text-based knowledge can be harnessed by VLMs to enhance their capabilities. Previous work has explored using LLMs' knowledge to optimize VLMs' pre-training [1], prediction interpretability [12, 26, 28], and classifier quality [2, 11, 12, 15]. Recently, some work [29, 35] uses LLMs to select the best VLMs from a VLM zoo for specific target tasks. In this paper, we use the semantic information provided by LLMs to optimize CLIP's features during the inference stage in a training-free manner." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27403" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.129, + 0.094, + 0.84, + 0.293 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.306, + 0.895, + 0.378 + ], + "angle": 0, + "content": "Figure 2. An example of CODER correcting wrong distance relation between images. \\( d_{ij}^{img} \\) refers to the cosine distance between the \\( i \\)-th and the \\( j \\)-th image. \\( r_1 \\) and \\( r_2 \\) refer to the cosine distance between the text and different images, while \\( 1 - r_1 \\) and \\( 1 - r_2 \\) refer to the cosine similarity. The left side of the figure indicates that even though images of the same class share similar distance to a text, this doesn't ensure that their features are closely similar. The right side of the figure shows that CODER corrects the wrong distance relation by utilizing the text-image distance." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.39, + 0.327, + 0.408 + ], + "angle": 0, + "content": "3. Notations and Background" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.416, + 0.471, + 0.493 + ], + "angle": 0, + "content": "Using CLIP to match text and image. CLIP encodes both images and texts into a joint space using its image encoder \\( f^{\\prime} \\) or text encoder \\( f^{T} \\), shown in Equation 1. Here \\( \\hat{x}_i \\) and \\( \\hat{t}_j \\) refers to the feature of image \\( x_i \\) and text \\( t_j \\), respectively. \\( D_{1} \\) refers to the dimension of CLIP's feature space." + }, + { + "type": "equation", + "bbox": [ + 0.132, + 0.502, + 0.47, + 0.521 + ], + "angle": 0, + "content": "\\[\n\\hat {\\boldsymbol {x}} _ {i} = f ^ {I} \\left(\\boldsymbol {x} _ {i}\\right) \\in \\mathbb {R} ^ {D _ {1}}, \\hat {\\boldsymbol {t}} _ {j} = f ^ {T} \\left(\\boldsymbol {t} _ {j}\\right) \\in \\mathbb {R} ^ {D _ {1}}. \\tag {1}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.182, + 0.542, + 0.469, + 0.58 + ], + "angle": 0, + "content": "\\[\n\\tilde {\\boldsymbol {t}} = \\underset {j \\in [ 1, \\dots , K ]} {\\arg \\max } \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {j}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot \\| \\hat {\\boldsymbol {t}} _ {j} \\|.} \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.585, + 0.47, + 0.676 + ], + "angle": 0, + "content": "Then we can compute the cosine similarity between the features of various texts and images. These similarity scores represent the matching degree between different images and texts. Given an image \\( \\boldsymbol{x}_i \\), its best matched text \\( \\tilde{t} \\) is identified by the highest similarity scores with the image, as shown in Equation 2. Here \\( K \\) refers to the number of texts." + }, + { + "type": "title", + "bbox": [ + 0.076, + 0.689, + 0.426, + 0.708 + ], + "angle": 0, + "content": "4. Cross-Modal Neighbor Representation" + }, + { + "type": "title", + "bbox": [ + 0.076, + 0.714, + 0.4, + 0.731 + ], + "angle": 0, + "content": "4.1. Understand the Advantage of CODER." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.737, + 0.469, + 0.814 + ], + "angle": 0, + "content": "We construct the CODER for the current image by tapping into the precise image-text distance relationship within the CLIP feature space. This process is shown in Equation 3. We use the CODER construct function \\(\\phi\\) to build image's CODER \\(\\phi (\\hat{x}_i)\\) based on its original feature \\(\\hat{x}_i\\)." + }, + { + "type": "equation", + "bbox": [ + 0.091, + 0.823, + 0.469, + 0.855 + ], + "angle": 0, + "content": "\\[\n\\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\left[ \\psi (d (\\hat {\\boldsymbol {x}} _ {i}, \\hat {\\boldsymbol {t}} _ {1})), \\dots , \\psi (d (\\hat {\\boldsymbol {x}} _ {i}, \\hat {\\boldsymbol {t}} _ {K})) \\right] \\in \\mathbb {R} ^ {K}. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.902 + ], + "angle": 0, + "content": "The specific implementation of \\(\\phi\\) depends on the similarity or distance function \\(d\\) and the subsequent mapping function \\(\\psi\\) applied to this distance. In this paper, we use cosine" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.392, + 0.893, + 0.438 + ], + "angle": 0, + "content": "similarity for \\(d\\) and identity mapping for \\(\\psi\\). Then we can rewrite Equation 3 as Equation 4. We emphasize that the implementation of \\(d\\) and \\(\\psi\\) can be further researched." + }, + { + "type": "equation", + "bbox": [ + 0.52, + 0.453, + 0.892, + 0.492 + ], + "angle": 0, + "content": "\\[\n\\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\left[ \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {1}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot \\| \\hat {\\boldsymbol {t}} _ {1} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {K}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot | \\hat {\\boldsymbol {t}} _ {K} |} \\right] \\in \\mathbb {R} ^ {K}. \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.504, + 0.893, + 0.718 + ], + "angle": 0, + "content": "We highlight CODER's advantages over CLIP's original image features using an example. Figure 2's left side depicts a bad case for CLIP. For simplicity, we consider a situation where test images share the same neighboring text in CLIP's feature space. While CLIP's cross-modal pre-training ensures accurate image-text distances, it doesn't always capture precise distances between images. This results in cases where the distance for same-class images \\( d_{21}^{img} \\) exceeds that of different-class images \\( d_{23}^{img} \\). To solve this problem, CODER uses CLIP's accurate text-image distance to build image features. As images of the same class have similar distance to their neighboring texts, their CODER align more closely. Thus, CODER addresses the wrong distance relation between images." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.895, + 0.902 + ], + "angle": 0, + "content": "We then focus on the key element of building a good CODER. Previous studies have emphasized that dense sampling of neighboring samples is vital for algorithms based on nearest neighbor. For example, only when the training samples are densely sampled will the error rate of the KNN classifier remain within twice that of the Bayes optimal classifier. And some studies [24, 33] have observed that greater sampling density of neighboring samples can lead to better neighbor representations. Inspired by these works, we try to optimize our CODER by increasing the number of texts. For increasing the number of texts, we use our Auto Text Generator (ATG) to achieve this objective." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27404" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.077, + 0.091, + 0.445, + 0.106 + ], + "angle": 0, + "content": "4.2. Use Auto Text Generator to Generate Texts" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.115, + 0.468, + 0.281 + ], + "angle": 0, + "content": "Accurate and diverse class-specific texts provide a comprehensive description of object classes from various perspectives, enhancing the sampling density of images' neighbor texts for constructing better CODER. To automatically generate a plethora of high-quality class-specific texts adaptive to target tasks, we introduce the Auto Text Generator (ATG). It uses different query prompts to extract diverse insights from external experts like ChatGPT [13]. Then it leverages that knowledge to construct various high-quality texts. These texts are instrumental in generating high-quality CODER." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.282, + 0.468, + 0.403 + ], + "angle": 0, + "content": "In our implementation, ATG can construct five types of texts: (1) Class Name-based Texts; (2) Attribute-based Texts; (3) Analogous Class-based Texts; (4) Synonym-based Texts; (5) One-to-One Texts. The first two types of texts are proposed by previous work[12, 16], while the latter three are innovations introduced in this paper. We will then delve deeper into the design rationale and generation process of these last three types of texts." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.403, + 0.468, + 0.509 + ], + "angle": 0, + "content": "(1) Analogous Class-based Texts. If someone describes a clouded leopard as resembling a cheetah, you can envision its appearance even if you've never seen a clouded leopard. This scenario illustrates how inter-object similarities help humans leverage their experience with known object classes to recognize new ones. Inspired by this, we query ChatGPT to obtain analogous categories for a given object by asking:" + }, + { + "type": "text", + "bbox": [ + 0.087, + 0.528, + 0.414, + 0.556 + ], + "angle": 0, + "content": "Q: What other categories are {class} visually similar to?" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.568, + 0.468, + 0.674 + ], + "angle": 0, + "content": "Given that the generated class names might exist within the target dataset's class names, we address this issue by filtering out those generated class names whose cosine similarity with existing class names surpass a defined threshold. Next, we insert each analogous class name into some templates like \"a {target class} similar to {analogous class}\" to form a complete text." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.674, + 0.468, + 0.825 + ], + "angle": 0, + "content": "(2) Synonym-based Texts. An object can have several names. For example, both \"forest\" and \"woodland\" refer to \"land covered with trees and shrubs\". Due to varying frequencies of synonyms in CLIP's training data, the model might favor more common terms and undervalue lesser-known synonyms, despite their equivalent meanings. To mitigate this bias, we query WordNet for synonyms of the current class. Subsequently, we insert the obtained synonym class names into templates like \"a photo of {synonym class}\"." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.825, + 0.468, + 0.902 + ], + "angle": 0, + "content": "(3) One-to-One Texts: Due to similar classes often share common features, the ATG may generate nearly identical attribute descriptions for these classes. For example, the ATG might generate attributes such as \"two pairs of wings\" for both \"butterfly\" and \"dragonfly\". Such identical" + }, + { + "type": "list", + "bbox": [ + 0.076, + 0.674, + 0.468, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.092, + 0.892, + 0.166 + ], + "angle": 0, + "content": "attributes can hinder CLIP's ability to distinguish closely related classes. To tackle this problem, we introduce the one-to-one texts. We use the following query prompt to guide ChatGPT in generating the most distinguishing features between similar classes A and B:" + }, + { + "type": "text", + "bbox": [ + 0.509, + 0.17, + 0.86, + 0.212 + ], + "angle": 0, + "content": "Q: What are different visual features between a {class 1} and a {class 2} in a photo? Focus on their key differences." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.221, + 0.892, + 0.418 + ], + "angle": 0, + "content": "Using the prompt, we generate distinguishing attributes that differentiate butterfly from dragonfly. For butterfly, some of the exemplified attributes include: [\"Butterflies typically have larger and more colorful wings compared to dragonflies.'] For dragonfly, some of the descriptors produced are: [\"They have transparent wings that are typically held out horizontally when at rest.'] From these newly created attributes, we can make two main observations: (1) The attributes underscore the key differences between butterfly and dragonfly, such as their wing characteristics. (2) The new attributes accentuate the comparison between the two classes, evident from terms like \"larger\", and \"compared to\" found within the descriptors." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.419, + 0.891, + 0.464 + ], + "angle": 0, + "content": "Finally, we insert the obtained one-to-one texts into some templates like \"Because of {1v1 text}, {class 1} is different from {class 2}\"" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.473, + 0.794, + 0.488 + ], + "angle": 0, + "content": "4.3. Use CODER on Downstream Tasks" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.497, + 0.89, + 0.527 + ], + "angle": 0, + "content": "We apply CODER in zero-shot and few-shot image classification tasks to enhance the performance of CLIP." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.528, + 0.892, + 0.753 + ], + "angle": 0, + "content": "Zero-Shot Image Classification. In the first stage, we utilize a general text set generated by ATG to construct the general CODER for images. These texts can be considered as descriptions of general characteristics for a certain class in comparison to most other classes. We can derive preliminary classification results based on the general CODER of the images. In the second stage, we employ ATG to create distinct one-to-one specific text sets for the top five classes, each pair-wise. These texts serve as descriptions of the key distinguishing features between the classes. Utilizing these, we then develop corresponding one-to-one specific CODER for images. Subsequently, we rerank the initial top five classification results using these one-to-one specific CODER. Figure 3 shows the process of our zero-shot image classification method." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.754, + 0.892, + 0.86 + ], + "angle": 0, + "content": "We first utilize all texts generated by ATG, excluding the one-to-one texts, as the general text set \\(\\mathcal{P} = [t_1,\\dots ,t_K]\\) to construct the general CODER for test images. This process is shown in Equation 5 and Equation 6. Here \\(\\pmb {W}\\in \\mathbb{R}^{D_1\\times K}\\) refers to the texts' features in the CLIP feature space. And \\(s_i\\in \\mathbb{R}^K\\) represents the CODER of test image \\(\\pmb{x}_i\\). \\(K\\) refers to the total number of texts in \\(\\mathcal{P}\\)." + }, + { + "type": "equation", + "bbox": [ + 0.57, + 0.869, + 0.892, + 0.906 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {W} = \\left[ \\frac {\\hat {\\boldsymbol {t}} _ {1}}{\\| \\hat {\\boldsymbol {t}} _ {1} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K}}{\\| \\hat {\\boldsymbol {t}} _ {K} \\|} \\right] \\in \\mathbb {R} ^ {D _ {1} \\times K}. \\tag {5}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "27405" + } + ], + [ + { + "type": "image_caption", + "bbox": [ + 0.155, + 0.09, + 0.568, + 0.105 + ], + "angle": 0, + "content": "Stage 1: Use General CODER for Preliminary Classification" + }, + { + "type": "image", + "bbox": [ + 0.154, + 0.108, + 0.568, + 0.255 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.572, + 0.09, + 0.822, + 0.253 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.165, + 0.26, + 0.654, + 0.274 + ], + "angle": 0, + "content": "Stage 2: Use One-to-One Specific CODER for Reranking Top 5 Classes" + }, + { + "type": "image", + "bbox": [ + 0.159, + 0.276, + 0.818, + 0.427 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.438, + 0.892, + 0.536 + ], + "angle": 0, + "content": "Figure 3. Illustration of two-stage zero-shot image classification process based on image's CODER. In the first stage, we use the Auto Text Generator to create a General Text Set, which contains general descriptions of classes. This set is utilized to construct the image's general CODER, and we use it for preliminary classification. In the second stage, we construct One-to-One Text Sets in pairs for the top five predicted classes of the preliminary classification results, focusing on attributes where the two specific classes differ most. We build one-to-one specific CODER for the image based on these One-to-One Text Sets and use heuristic classifier to get each class's classification score. Then we rerank the top five preliminary results based on the classification score gaps \\( gap_i^{c,j} \\) between classes. Here \\( gap_i^{c,j} \\) represents the difference obtained by subtracting the score of the class \\( c \\) from that of the class \\( j \\) for image \\( x_i \\)." + }, + { + "type": "equation", + "bbox": [ + 0.168, + 0.559, + 0.47, + 0.595 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {s} _ {i} = \\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\|} \\boldsymbol {W} \\in \\mathbb {R} ^ {K}. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.597, + 0.47, + 0.734 + ], + "angle": 0, + "content": "Then, we employ a heuristic classifier \\( h \\) on the test image's general CODER \\( s_i \\) to obtain the preliminary classification logits vector \\( o_i \\). We use \\( s_{ij} \\) to represent the portion of the test image's general CODER \\( s_i \\) corresponding to the text of the \\( j \\)-th category. \\( s_{ij} \\) consists of several parts, as shown in Equation 7. Here \\( s_{ij}^{ori}, s_{ij}^{att}, s_{ij}^{ana}, s_{ij}^{syn} \\) refers to \\( s_{ij} \\)'s portion of class name-based texts, attribute-based texts, analogous class-based texts and synonym-based texts, respectively. \\( \\oplus \\) refers to the vector concatenation operation." + }, + { + "type": "equation", + "bbox": [ + 0.16, + 0.74, + 0.469, + 0.761 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {s} _ {i j} = \\boldsymbol {s} _ {i j} ^ {\\text {o r i}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a t t}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a n a}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {s y n}}. \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.765, + 0.471, + 0.903 + ], + "angle": 0, + "content": "For each class, the heuristic classifier \\( h \\) first gets the largest element in the test image's CODER portion corresponding to the class name-based texts and synonym-based texts. This step is intuitive: Humans can recognize an object by knowing just one of its names. Then \\( h \\) calculates the mean of \\( \\max(s_{ij}^{ori} \\oplus s_{ij}^{syn}) \\) and all elements in the \\( s_{ij} \\)'s portion corresponding to the attribute-based texts and synonym-based texts. This value can be seen as the preliminary classification logit value \\( o_{ij} \\) belonging to class \\( j \\). The process" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.55, + 0.738, + 0.565 + ], + "angle": 0, + "content": "is shown in the following Equation:" + }, + { + "type": "equation", + "bbox": [ + 0.5, + 0.575, + 0.904, + 0.607 + ], + "angle": 0, + "content": "\\[\no _ {i j} = h \\left(\\boldsymbol {s} _ {i j}\\right) = \\operatorname {m e a n} \\left(\\boldsymbol {s} _ {i j} ^ {\\text {a t t}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a n a}} \\oplus \\left[ \\max \\left(\\boldsymbol {s} _ {i j} ^ {\\text {o r i}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {s y n}}\\right) \\right]\\right). \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.608, + 0.892, + 0.699 + ], + "angle": 0, + "content": "After obtaining the preliminary classification results \\( \\boldsymbol{o}_i \\), we extract the top five classes from the prediction results, forming a set named \\( \\mathcal{C}_5 \\). Subsequently, we draw all pairwise combinations from these five classes in set \\( \\mathcal{C}_5 \\), creating a new set \\( \\mathcal{P}_{1v1} \\) comprised of these pairs. This process can be described by Equation 9 and Equation 10:" + }, + { + "type": "equation", + "bbox": [ + 0.568, + 0.71, + 0.892, + 0.728 + ], + "angle": 0, + "content": "\\[\n\\mathcal {C} _ {5} = \\operatorname {T o p} 5 \\left(\\boldsymbol {o} _ {i}\\right) = \\left\\{c _ {1}, c _ {2}, c _ {3}, c _ {4}, c _ {5} \\right\\}. \\tag {9}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.567, + 0.742, + 0.892, + 0.759 + ], + "angle": 0, + "content": "\\[\n\\mathcal {P} _ {1 v 1} = \\left\\{\\left\\{c _ {a}, c _ {b} \\right\\} \\mid c _ {a}, c _ {b} \\in \\mathcal {C} _ {5}, a \\neq b \\right\\}. \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.892, + 0.902 + ], + "angle": 0, + "content": "In the second stage, we use ATG to generate the one-to-one specific texts for each pair in \\(\\mathcal{P}_{1v1}\\), resulting in a total of \\(C_5^2 = 10\\) text sets. For each one-to-one specific text set, we can construct a one-to-one specific CODER for the image. We first use CLIP's text encoder \\(f^{T}\\) to extract the text features of the one-to-one text set \\(\\boldsymbol{W}^{a,b} \\in \\mathbb{R}^{D_{1} \\times (K_{1} + K_{2})}\\). Here \\(K_{1}\\) and \\(K_{2}\\) represent the number of one-to-one texts for each of the two classes. Equation 11 shows the composition of \\(\\boldsymbol{W}^{a,b}\\), where \\(\\hat{\\boldsymbol{t}}_i^a\\) and \\(\\hat{\\boldsymbol{t}}_i^b\\) refers to the \\(i\\)-th one-to-one" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "27406" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.387, + 0.108 + ], + "angle": 0, + "content": "text feature of class \\(a\\) and class \\(b\\), respectively." + }, + { + "type": "equation", + "bbox": [ + 0.092, + 0.117, + 0.47, + 0.16 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {W} ^ {a, b} = \\left[ \\frac {\\hat {\\boldsymbol {t}} _ {1} ^ {a}}{\\| \\hat {\\boldsymbol {t}} _ {1} ^ {a} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K _ {1}} ^ {a}}{\\| \\hat {\\boldsymbol {t}} _ {K _ {1}} ^ {a} \\|}, \\frac {\\hat {\\boldsymbol {t}} _ {1} ^ {b}}{\\| \\hat {\\boldsymbol {t}} _ {1} ^ {b} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K _ {2}} ^ {b}}{\\| \\hat {\\boldsymbol {t}} _ {K _ {2}} ^ {b} \\|} \\right]. \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.17, + 0.47, + 0.203 + ], + "angle": 0, + "content": "Then we use the one-to-one text features \\( W^{a,b} \\) to construct the image's one-to-one specific CODER \\( s_i^{a,b} \\in \\mathbb{R}^{K_1 + K_2} \\):" + }, + { + "type": "equation", + "bbox": [ + 0.16, + 0.212, + 0.469, + 0.247 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {s} _ {i} ^ {a, b} = \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\|} \\boldsymbol {W} ^ {a, b} = \\boldsymbol {s} _ {i a} ^ {a, b} \\oplus \\boldsymbol {s} _ {i b} ^ {a, b}. \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.257, + 0.47, + 0.305 + ], + "angle": 0, + "content": "Here \\( s_{ia}^{a,b} \\in \\mathbb{R}^{K_1} \\) and \\( s_{ib}^{a,b} \\in \\mathbb{R}^{K_2} \\) represent the part of CODER pertaining to the one-to-one texts for class \\( a \\) and class \\( b \\), respectively." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.304, + 0.469, + 0.369 + ], + "angle": 0, + "content": "Based on the one-to-one specific CODER \\( s_i^{a,b} \\) of the image \\( \\pmb{x}_i \\), we employ a heuristic classifier \\( h \\) to obtain image's classification scores for class \\( a \\) and \\( b \\), denoted as \\( o_{ia}^{a,b} \\) and \\( o_{ib}^{a,b} \\), respectively:" + }, + { + "type": "equation", + "bbox": [ + 0.164, + 0.379, + 0.469, + 0.411 + ], + "angle": 0, + "content": "\\[\no _ {i a} ^ {a, b} = h \\left(\\boldsymbol {s} _ {i a} ^ {a, b}\\right) = \\operatorname {m e a n} \\left(\\boldsymbol {s} _ {i a} ^ {a, b}\\right), \\tag {13}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.168, + 0.409, + 0.381, + 0.433 + ], + "angle": 0, + "content": "\\[\no _ {i b} ^ {a, b} = h (\\pmb {s} _ {i b} ^ {a, b}) = \\mathrm {m e a n} \\left(\\pmb {s} _ {i b} ^ {a, b}\\right).\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.443, + 0.47, + 0.472 + ], + "angle": 0, + "content": "Then we calculate the image's classification score gap for each class relative to another class:" + }, + { + "type": "equation", + "bbox": [ + 0.111, + 0.482, + 0.469, + 0.503 + ], + "angle": 0, + "content": "\\[\ng a p _ {i} ^ {a b} = o _ {i a} ^ {a, b} - o _ {i b} ^ {a, b}, \\quad g a p _ {i} ^ {b a} = o _ {i b} ^ {a, b} - o _ {i a} ^ {a, b}. \\tag {14}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.513, + 0.47, + 0.559 + ], + "angle": 0, + "content": "For each class, we sum up all the score gaps between it and other classes. Then we select the class with the largest sum of score gaps as the final predicted class \\(\\hat{c}_i\\) of the image:" + }, + { + "type": "equation", + "bbox": [ + 0.175, + 0.569, + 0.469, + 0.604 + ], + "angle": 0, + "content": "\\[\n\\hat {c} _ {i} = \\underset {c \\in \\mathcal {C} _ {5}} {\\operatorname {a r g m a x}} \\sum_ {j \\in \\mathcal {C} _ {5} / \\{c \\}} \\operatorname {g a p} _ {i} ^ {c j}. \\tag {15}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.614, + 0.469, + 0.78 + ], + "angle": 0, + "content": "We use the method based on score gaps instead of the traditional voting method to reorder initial prediction results. The reason is that score gaps provide quantified information about the relative advantages between classes. Unlike voting, which only considers each class's number of wins in pairwise classification, score gaps better capture the model's uncertainty in the classification tasks. For example, a small score gap might indicate that the model is uncertain about the correct class for the image, suggesting that the classification result may be unreliable. This can lead to errors in the outcomes derived from voting methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.781, + 0.47, + 0.901 + ], + "angle": 0, + "content": "This two-phase image classification process illustrates that by changing the neighbor text set, we can dynamically build image's feature that focus on different semantics according to task requirements. In coarse-grained image classification, we focus on the general semantics of a class, such as whether an animal has wings. In fine-grained image classification, we aim to focus on more detailed features that differentiate between two specific classes, such as the color" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.152 + ], + "angle": 0, + "content": "of wings when distinguishing between dragonfly and butterfly. However, the original image features extracted by the CLIP's image encoder cannot dynamically adapt to specific classification task requirements." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.152, + 0.893, + 0.349 + ], + "angle": 0, + "content": "Few-Shot Image Classification. For Few-Shot Image Classification, we improve the Tip-Adapter [32] by replacing the original CLIP's image features with our CODER to calculate the similarity between the test image and the support set's images. We refer to the improved method as CrOss-MoDal NEighbor Representation CLIP Adapter (CODER-Adapter). Given the \\(N\\)-way \\(M\\)-shot support image set \\(\\mathcal{I}\\), we first calculate the CODER of the images in the support set, represented by \\(S_{train} \\in \\mathbb{R}^{NM \\times K}\\). Equation 16 shows the calculation process, where \\(f^I(\\mathcal{I}) \\in \\mathbb{R}^{NM \\times D_1}\\) refers to the support images' original features and \\(W \\in \\mathbb{R}^{D_1 \\times K}\\) refers to the features of texts in the general text set \\(\\mathcal{P}\\), as defined in Equation 5." + }, + { + "type": "equation", + "bbox": [ + 0.625, + 0.362, + 0.892, + 0.379 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {S} _ {\\text {t r a i n}} = f ^ {I} (\\mathcal {I}) \\boldsymbol {W}. \\tag {16}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.384, + 0.892, + 0.43 + ], + "angle": 0, + "content": "Then we perform one-hot encoding on the support images' labels \\(\\pmb{L}\\) to get one-hot labels matrix \\(L_{train} \\in \\mathbb{R}^{NM \\times C}\\). Each row of \\(L_{train}\\) is a one-hot vector." + }, + { + "type": "equation", + "bbox": [ + 0.616, + 0.438, + 0.892, + 0.455 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {L} _ {\\text {t r a i n}} = \\operatorname {O n e H o t} (\\boldsymbol {L}). \\tag {17}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.462, + 0.892, + 0.493 + ], + "angle": 0, + "content": "For the test image \\( \\pmb{x}_i \\), we also construct its CODER \\( s_i \\in \\mathbb{R}^K \\) similarly to the support set's images." + }, + { + "type": "equation", + "bbox": [ + 0.638, + 0.499, + 0.892, + 0.517 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {s} _ {i} = f ^ {I} \\left(\\boldsymbol {x} _ {i}\\right) \\boldsymbol {W}. \\tag {18}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.524, + 0.892, + 0.616 + ], + "angle": 0, + "content": "We then calculate the affinity matrix \\( \\mathbf{A} \\in \\mathbb{R}^{1 \\times NM} \\) between the test image's CODER \\( s_i \\in \\mathbb{R}^K \\) and the support set images' CODER \\( S_{train} \\in \\mathbb{R}^{NM \\times K} \\) using the Equation 19. Here \\( \\mathrm{Norm}(\\cdot) \\) refers to the data normalization operation like L2 or min-max normalization. \\( \\beta \\) and \\( T \\) are hyperparameters to control the sharpness of \\( \\mathbf{A} \\)'s distribution." + }, + { + "type": "equation", + "bbox": [ + 0.528, + 0.622, + 0.892, + 0.665 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {A} = \\exp \\left(- \\beta \\cdot \\left(1 - \\frac {\\operatorname {N o r m} \\left(\\boldsymbol {s} _ {i} \\boldsymbol {S} _ {\\text {t r a i n}} ^ {\\top}\\right)}{T}\\right)\\right). \\tag {19}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.671, + 0.892, + 0.748 + ], + "angle": 0, + "content": "The affinity \\( \\mathbf{A} \\in \\mathbb{R}^{1 \\times NM} \\) serves as a weight factor for \\( L_{train} \\). By calculating the weighted sum of images' labels in \\( L_{train} \\), we can refine the CLIP's original zero-shot prediction results \\( o_i^{zs} \\) using Equation 20. Here \\( \\alpha \\) controls the degree of correction." + }, + { + "type": "equation", + "bbox": [ + 0.611, + 0.756, + 0.892, + 0.773 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {o} _ {i} = \\alpha \\cdot \\boldsymbol {A} \\boldsymbol {L} _ {\\text {t r a i n}} + \\boldsymbol {o} _ {i} ^ {z s}. \\tag {20}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.781, + 0.891, + 0.811 + ], + "angle": 0, + "content": "Finally, we select the class corresponding to the largest logits in \\( \\pmb{o}_i \\) as the predicted class of image \\( \\pmb{x}_i \\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.823, + 0.634, + 0.84 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.848, + 0.878, + 0.864 + ], + "angle": 0, + "content": "5.1. Zero-Shot Image Classification Performance" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "For zero-shot image classification, we compare our method with two baselines: Vanilla CLIP [16] and VCD [12]. Ta" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27407" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.892, + 0.118 + ], + "angle": 0, + "content": "Table 1. Accuracy gains over VCD and CLIP baseline. The \"CODER\" column shows the classification accuracy before rerank stage, while the \"CODER*\" column shows the accuracy after rerank stage. \\( \\Delta \\) represents the improvement of our method over VCD." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.122, + 0.892, + 0.357 + ], + "angle": 0, + "content": "
ImageNetCUB200EuroSAT
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3259.0762.9664.3866.863.9051.8151.7853.0055.043.2644.8946.5752.8354.938.36
ViT-B/1663.5368.1069.6171.463.3655.7557.5458.3059.922.3849.5256.4655.3060.544.08
ViT-L/1470.5874.9676.1577.382.4262.1063.2964.6465.762.4753.5459.5762.9868.248.67
ViT-L/14@336px71.8176.1177.2778.492.3863.4864.7966.2967.362.5754.9359.4664.9469.9610.50
Describable TexturesPlaces365Food101
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3241.2845.2748.7852.717.4436.4738.9240.3740.271.4580.2784.1384.7285.501.37
ViT-B/1643.1945.6448.6755.6910.0537.3139.8741.3941.701.8385.9989.2589.2989.820.57
ViT-L/1452.1857.1860.7461.864.6837.0638.5541.2141.593.0489.8593.3393.6693.930.60
ViT-L/14@336px52.1257.4561.1262.875.4237.2739.8842.0942.502.6291.1094.0694.4894.750.69
Caltech101Oxford PetsImageNetV2
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3279.9089.8091.2491.421.6281.6385.9188.4789.263.3551.7955.2956.7556.421.46
ViT-B/1680.1892.2894.0793.951.7983.9589.3491.5092.012.6757.2561.5362.9462.971.44
ViT-L/1479.7893.9595.7995.681.8487.9093.1894.1994.361.1864.3169.2170.3570.371.16
ViT-L/14@336px80.3694.3596.3196.372.0287.8293.6294.2294.881.2665.6170.4171.4571.281.04
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.375, + 0.47, + 0.496 + ], + "angle": 0, + "content": "ble 1 displays zero-shot image classification experiment results. By analyzing the results, we can draw the following conclusions: (1) Our proposed CODER consistently boosts CLIP's zero-shot image classification accuracy across various datasets and model architectures; (2) The rerank stage based on the one-to-one specific CODER can further enhance CLIP's performance, demonstrating the effectiveness of our proposed two-stage zero-shot classification method." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.511, + 0.449, + 0.527 + ], + "angle": 0, + "content": "5.2. Few-Shot Image Classification Performance" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.537, + 0.468, + 0.672 + ], + "angle": 0, + "content": "For few-shot image classification, we use ResNet 50[5] as the backbone for CLIP's image encoder, consistent with previous methods. We use two CLIP's training-free few-shot image classification methods TIP-Adapter [32] and TIP-X [20] as our baselines. TIP-Adapter leverages features extracted by CLIP's image encoder for calculating the similarity between test images and support set's images. While TIP-X uses features based on similarity scores between images and texts generated by CUPL [15] to do it." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.675, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Figure 4 shows the few-shot image classification experiment results. We use the experimental results of TIP-Adapter and TIP-X presented in [20] and ensure that our random seeds are consistent with them. Our method surpasses the previous CLIP few-shot training-free image classification methods on most datasets across different shot scenarios. We notice that CODER-Adapter's performance on EuroSAT is unsatisfactory, which results in our method not having a significant advantage in average accuracy across 11 datasets compared to previous methods. But this meets our expectations. Since EuroSAT has only 10 classes and 95 texts generated by ATG, this small number of texts fails to satisfy CODER's need for dense text sampling, impacting the adapter's performance. This highlights the importance of dense sampling for CODER." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.373, + 0.892, + 0.429 + ], + "angle": 0, + "content": "Table 2. The accuracy of the zero-shot image classification experiments using different texts. Meaning of symbols: P: Using class name-based texts. Att: Using attribute-based texts. Ana: Using analogous class-based texts. We use CLIP ViT-B-32." + }, + { + "type": "table", + "bbox": [ + 0.501, + 0.44, + 0.891, + 0.496 + ], + "angle": 0, + "content": "
TextCaltech101Oxford PetsDescribable TexturesEuroSAT
P79.9081.6341.2844.89
P+Att89.8085.9145.2746.57
P+Att+Ana91.0188.5548.7352.77
" + }, + { + "type": "table_caption", + "bbox": [ + 0.5, + 0.507, + 0.89, + 0.534 + ], + "angle": 0, + "content": "Table 3. The accuracy of the 16-shot image classification experiments using different texts. We use CLIP ResNet-50." + }, + { + "type": "table", + "bbox": [ + 0.501, + 0.546, + 0.891, + 0.602 + ], + "angle": 0, + "content": "
TextCaltech101Oxford PetsDescribable TexturesEuroSAT
P90.3489.8362.3558.44
P+Att90.4790.363.0665.36
P+Att+Ana90.9990.2664.1867.11
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.61, + 0.892, + 0.791 + ], + "angle": 0, + "content": "Contrasting to previous work [20, 32], we innovatively interpret the superiority of CLIP's cross-modal relative feature representation from the perspective of neighbor representation. Additionally, by drawing an analogy to neighbor-based algorithms like KNN, which require dense sampling of neighbor samples to ensure superior performance, we provide an intuitive explanation for our need to use a more diverse and higher-quality text set to construct our CODER. Motivated by this conclusion, we develop the Auto Text Generator for the automated creation of varied, high-quality texts to meet CODER's dense sampling needs. The experiments demonstrate the validity of our method." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.802, + 0.891, + 0.818 + ], + "angle": 0, + "content": "5.3. The Importance of Dense Sampling for CODER" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Nearest neighbor algorithms like KNN depend on dense sampling for good performance. We view our CODER as a cross-modal neighbor representation. Hence, as the diversity and quantity of high-quality cross-modal neighbor texts increase, the constructed CODER should correspond" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "27408" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.107, + 0.093, + 0.295, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.297, + 0.093, + 0.484, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.487, + 0.091, + 0.674, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.678, + 0.091, + 0.865, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.104, + 0.209, + 0.294, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.298, + 0.209, + 0.484, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.488, + 0.209, + 0.675, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.678, + 0.209, + 0.865, + 0.325 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.104, + 0.327, + 0.295, + 0.445 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.298, + 0.327, + 0.484, + 0.444 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.488, + 0.327, + 0.675, + 0.444 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.678, + 0.33, + 0.865, + 0.444 + ], + "angle": 0, + "content": null + }, + { + "type": "image_footnote", + "bbox": [ + 0.324, + 0.451, + 0.651, + 0.461 + ], + "angle": 0, + "content": "Zero-shot CLIP TIP-Adapter TIP-X CODER-Adapter (Ours)" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.471, + 0.893, + 0.501 + ], + "angle": 0, + "content": "Figure 4. Results for the training-free few-shot regime across 11 datasets. We compare the CODER-Adapter with the previous CLIP few-shot image classification methods. Our CODER-Adapter achieves the best performance on most datasets." + }, + { + "type": "image", + "bbox": [ + 0.088, + 0.513, + 0.273, + 0.626 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.277, + 0.513, + 0.462, + 0.626 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.637, + 0.47, + 0.667 + ], + "angle": 0, + "content": "Figure 5. The t-SNE Visualization of the Oxford-Pets dataset. Left: Original CLIP Images' Features; Right: CODER." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.671, + 0.473, + 0.824 + ], + "angle": 0, + "content": "ingly improve. We validate this idea through experiments. We use three different text sets for constructing the image's CODER: (1) CLIP's original class name-based texts; (2) class name-based texts and VCD's attribute-based texts; (3) our analogous class-based texts added to (2). Our experiments in zero-shot and few-shot image classification, as detailed in Table 2 and Table 3, show that CODER performance enhances with the increasing diversity and number of texts. This highlights the importance of dense neighbor text sampling in improving CODER quality." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.832, + 0.353, + 0.848 + ], + "angle": 0, + "content": "5.4. Visualization results of CODER" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Figure 5 presents a t-SNE visualization comparing original image features from the CLIP image encoder with those of our proposed CODER on the Oxford-Pets dataset. Our" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.515, + 0.892, + 0.547 + ], + "angle": 0, + "content": "CODER achieves tighter clustering of same-class images' features and clearer separation of different classes." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.561, + 0.62, + 0.577 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.587, + 0.893, + 0.8 + ], + "angle": 0, + "content": "In this paper, we address the misalignment between CLIP's image feature extraction method and its pretraining paradigm. We present a novel perspective based on the nearest neighbors to comprehend CLIP's strong zero-shot image classification capability. Our key insight is that CLIP's effective text-image matching capability embeds image information in image-text distances. This leads us to propose the CrOss-moDal nEighbor Representation (CODER), utilizing these image-text distances for image representation. We introduce the Auto Text Generator to automatically generate texts, ensuring dense sampling of neighbor texts for better CODER construction. Experiment results in zero-shot and few-shot image classification show the superiority of our method." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.815, + 0.66, + 0.832 + ], + "angle": 0, + "content": "Acknowledgments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.894, + 0.903 + ], + "angle": 0, + "content": "This work is partially supported by National Key R&D Program of China (2022ZD0114805), NSFC (62376118, 62006112, 62250069, 61921006), Collaborative Innovation Center of Novel Software Technology and Industrialization." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "27409" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.156 + ], + "angle": 0, + "content": "[1] Lijie Fan, Dilip Krishnan, Phillip Isola, Dina Katabi, and Yonglong Tian. 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In NeurIPS, 2023. 2" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.468, + 0.486 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.518, + 0.956 + ], + "angle": 0, + "content": "27411" + } + ] +] \ No newline at end of file diff --git a/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_origin.pdf b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..17f2f209c88bb21b362109c29cdf3799b40a5c9e --- /dev/null +++ b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/a3f70eee-6e9c-43f6-ae6b-71319cbe101f_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:b62332b9601c8f9d5770c312f159bb17c2c17950e152c29cc65eaf5f8e65ad8b +size 4381145 diff --git a/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/full.md b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/full.md new file mode 100644 index 0000000000000000000000000000000000000000..8d2cccb9663a98e2c3ee081a0b84e547343cecf8 --- /dev/null +++ b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/full.md @@ -0,0 +1,347 @@ +# Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification + +Chao Yi, Lu Ren, De-Chuan Zhan, Han-Jia Ye $(\boxtimes)$ +National Key Laboratory for Novel Software Technology, Nanjing University, China +School of Artificial Intelligence, Nanjing University, China +{yic, renl, zhandc, yehj}@lamda.nju.edu.cn + +# Abstract + +CLIP showcases exceptional cross-modal matching capabilities due to its training on image-text contrastive learning tasks. However, without specific optimization for unimodal scenarios, its performance in single-modality feature extraction might be suboptimal. Despite this, some studies have directly used CLIP's image encoder for tasks like few-shot classification, introducing a misalignment between its pre-training objectives and feature extraction methods. This inconsistency can diminish the quality of the image's feature representation, adversely affecting CLIP's effectiveness in target tasks. In this paper, we view text features as precise neighbors of image features in CLIP's space and present a novel CrOss-moDal nEighbor Representation (CODER) based on the distance structure between images and their neighbor texts. This feature extraction method aligns better with CLIP's pre-training objectives, thereby fully leveraging CLIP's robust cross-modal capabilities. The key to construct a high-quality CODER lies in how to create a vast amount of high-quality and diverse texts to match with images. We introduce the Auto Text Generator (ATG) to automatically generate the required texts in a data-free and training-free manner. We apply CODER to CLIP's zero-shot and few-shot image classification tasks. Experiment results across various datasets and models confirm CODER's effectiveness. Code is available at: https://github.com/YCaigogogo/CVPR24-CODER. + +# 1. Introduction + +In recent years, vision-language models have garnered widespread attention, with CLIP [16] standing out as a notably powerful exemplar. Trained on a vast array of image-text pairs through the image-text contrastive learning tasks, CLIP boasts impressive cross-modal matching capabilities. And it has been applied to fields like image classification [16], object detection [3], semantic segmen + +tation [7, 25], video understanding [10], voice classification [4], text-to-image generation [19, 34], model pretraining [23], and beyond [17, 31]. + +Some existing works [21, 23, 32] extract image features directly from CLIP's image encoder for intra-modal operation, like calculating similarity between images in few-shot classification [32]. However, these methods overlook CLIP's multi-modal capabilities, leading to a misalignment with CLIP's pre-training objectives. Furthermore, since CLIP isn't optimized for uni-modal scenarios, its performance in intra-modal tasks isn't guaranteed. To optimize the image features extracted by CLIP, we ask: + +Can we leverage CLIP's powerful cross-modal matching capabilities to extract better image features, thereby improving CLIP's performance on downstream tasks? + +In this paper, we introduce an enhanced image representation based on the distance between images and their neighboring texts in CLIP's feature space. This idea stems from our re-examination of CLIP's robust zero-shot classification capability from the perspective of nearest neighboring: The previous approaches consider the text features extracted by CLIP as classifiers and use them to get the classification results. Different from this perspective, we interpret CLIP's zero-shot image classification as a 1NN problem, as shown in the left part of Figure 1. We treat texts as the images' neighbors in the CLIP's feature space. Then for each image, CLIP identifies its closest text and assigns this text's class as the image's predicted class. This 1NN approach shows good performance because CLIP's robust image-text matching capabilities ensure images are closer to their semantically related texts. This suggests that the cross-modal distance between an image and its neighboring texts captures information about the image, such as its class. + +In zero-shot image classification, CLIP only considers the distance between an image and its nearest neighbor text, which loses the information implied in the distance between the image and other texts. To make full use of this infor + +![](images/4d4a48acd8ebf7cdb5f8a0dc3828ea36b23dde31c9d839d66bffd84f74ea3e79.jpg) +Figure 1. Illustration of image's CrOss-moDal nEighbor Representation (CODER). CLIP's powerful text-image matching capabilities endows it with a favorable cross-modal neighbor distance relation. And CLIP's Zero-Shot Image Classification process can be interpreted as using a 1NN algorithm to find the image's nearest text, with the text's class determining the image's predicted class. Inspired by this idea, we expand the image's neighbor range to leverage its distance to all texts for constructing the CODER. Here $d_{ij}$ refers to the distance between the $i$ -th image and the $j$ -th text. + +mation, we expand each image's neighbor range to utilize its distance to $K$ Nearest Neighbor (KNN) texts for constructing image representation, as depicted in the right half of Figure 1. Here $K$ denotes the total number of texts. We refer to this representation as CrOss-moDal nEighbor Representation (CODER). We believe images with closer CODER values are more similar in semantics. This aligns with intuition: If two objects share the same sets of similar and dissimilar items, they're likely similar to each other. + +Previous work [24, 33] has noted that dense sampling of neighbor samples is critical for building neighbor representations. This inspires us to use various high-quality texts for dense sampling. Considering that Large Models have rich knowledge and are widely used in many ways [9, 14, 27], we introduce the Auto Text Generator (ATG) based on Large Language Models like ChatGPT [13] to automatically generate various high-quality texts. Without the need for image data and the training process, ATG can produce a diverse and effective set of texts based on the target dataset's class names. These diverse, high-quality texts enhance the density of neighboring texts for images in CLIP's feature space, helping to build a better CODER. + +We apply CODER to CLIP's zero-shot and few-shot image classification tasks to prove CODER's superiority. For the zero-shot image classification task, we use CODER in a two-stage manner. In the first stage, we use ATG to acquire general class-specific texts for constructing general CODER. Then we employ a heuristic classifier to the image's general CODER. In the second stage, we utilize ATG to generate one-to-one specific texts for comparing two distinct classes, concentrating on their most distinguishing features. These texts are then used to construct the one-to-one specific CODER, which is used to rerank the preliminary classification results. For the few-shot situation, we calculate the similarity between test images and the support set's + +images using those images' general CODER. By ensembling the similarity and CLIP's original zero-shot classification logits, we determine the classification results. Experiment results on various datasets and different CLIP models confirm that CODER enhances CLIP's performance in both zero-shot and few-shot image classification. + +# 2. Related Work + +Vision-Language Models. Vision-Language Models (VLMs) represent a class of multimodal models adept at correlating textual and visual information. Prominent models in this domain include CLIP [16], ALIGN [6], FLAVA [18] and Florence [30], among others. These models typically comprise two main components: an image encoder and a text encoder. Some models also have multimodal fusion modules [8, 22]. VLMs are trained on extensive text-image pairs through tasks like image-text contrastive learning, endowing them with powerful text-image matching capabilities. In this paper, we leverage these capabilities of CLIP to generate our cross-modal neighbor representations (CODER) for images. + +Using LLMs as Experts to Improve VLMs. Large Language Models (LLMs) are widely used in many tasks, such as in-context learning. LLMs can serve as experts by outputting their knowledge in text form. This text-based knowledge can be harnessed by VLMs to enhance their capabilities. Previous work has explored using LLMs' knowledge to optimize VLMs' pre-training [1], prediction interpretability [12, 26, 28], and classifier quality [2, 11, 12, 15]. Recently, some work [29, 35] uses LLMs to select the best VLMs from a VLM zoo for specific target tasks. In this paper, we use the semantic information provided by LLMs to optimize CLIP's features during the inference stage in a training-free manner. + +![](images/45895adcd1b6d2aae32b50facffa21736363d4283c4be28e266393c2f8c7e478.jpg) +Figure 2. An example of CODER correcting wrong distance relation between images. $d_{ij}^{img}$ refers to the cosine distance between the $i$ -th and the $j$ -th image. $r_1$ and $r_2$ refer to the cosine distance between the text and different images, while $1 - r_1$ and $1 - r_2$ refer to the cosine similarity. The left side of the figure indicates that even though images of the same class share similar distance to a text, this doesn't ensure that their features are closely similar. The right side of the figure shows that CODER corrects the wrong distance relation by utilizing the text-image distance. + +# 3. Notations and Background + +Using CLIP to match text and image. CLIP encodes both images and texts into a joint space using its image encoder $f^{\prime}$ or text encoder $f^{T}$ , shown in Equation 1. Here $\hat{x}_i$ and $\hat{t}_j$ refers to the feature of image $x_i$ and text $t_j$ , respectively. $D_{1}$ refers to the dimension of CLIP's feature space. + +$$ +\hat {\boldsymbol {x}} _ {i} = f ^ {I} \left(\boldsymbol {x} _ {i}\right) \in \mathbb {R} ^ {D _ {1}}, \hat {\boldsymbol {t}} _ {j} = f ^ {T} \left(\boldsymbol {t} _ {j}\right) \in \mathbb {R} ^ {D _ {1}}. \tag {1} +$$ + +$$ +\tilde {\boldsymbol {t}} = \underset {j \in [ 1, \dots , K ]} {\arg \max } \frac {\hat {\boldsymbol {x}} _ {i} ^ {\top} \hat {\boldsymbol {t}} _ {j}}{\| \hat {\boldsymbol {x}} _ {i} \| \cdot \| \hat {\boldsymbol {t}} _ {j} \|.} \tag {2} +$$ + +Then we can compute the cosine similarity between the features of various texts and images. These similarity scores represent the matching degree between different images and texts. Given an image $\boldsymbol{x}_i$ , its best matched text $\tilde{t}$ is identified by the highest similarity scores with the image, as shown in Equation 2. Here $K$ refers to the number of texts. + +# 4. Cross-Modal Neighbor Representation + +# 4.1. Understand the Advantage of CODER. + +We construct the CODER for the current image by tapping into the precise image-text distance relationship within the CLIP feature space. This process is shown in Equation 3. We use the CODER construct function $\phi$ to build image's CODER $\phi (\hat{x}_i)$ based on its original feature $\hat{x}_i$ . + +$$ +\phi (\hat {\boldsymbol {x}} _ {i}) = \left[ \psi (d (\hat {\boldsymbol {x}} _ {i}, \hat {\boldsymbol {t}} _ {1})), \dots , \psi (d (\hat {\boldsymbol {x}} _ {i}, \hat {\boldsymbol {t}} _ {K})) \right] \in \mathbb {R} ^ {K}. \tag {3} +$$ + +The specific implementation of $\phi$ depends on the similarity or distance function $d$ and the subsequent mapping function $\psi$ applied to this distance. In this paper, we use cosine + +similarity for $d$ and identity mapping for $\psi$ . Then we can rewrite Equation 3 as Equation 4. We emphasize that the implementation of $d$ and $\psi$ can be further researched. + +$$ +\phi (\hat {\boldsymbol {x}} _ {i}) = \left[ \frac {\hat {\boldsymbol {x}} _ {i} ^ {\top} \hat {\boldsymbol {t}} _ {1}}{\| \hat {\boldsymbol {x}} _ {i} \| \cdot \| \hat {\boldsymbol {t}} _ {1} \|}, \dots , \frac {\hat {\boldsymbol {x}} _ {i} ^ {\top} \hat {\boldsymbol {t}} _ {K}}{\| \hat {\boldsymbol {x}} _ {i} \| \cdot | \hat {\boldsymbol {t}} _ {K} |} \right] \in \mathbb {R} ^ {K}. \tag {4} +$$ + +We highlight CODER's advantages over CLIP's original image features using an example. Figure 2's left side depicts a bad case for CLIP. For simplicity, we consider a situation where test images share the same neighboring text in CLIP's feature space. While CLIP's cross-modal pre-training ensures accurate image-text distances, it doesn't always capture precise distances between images. This results in cases where the distance for same-class images $d_{21}^{img}$ exceeds that of different-class images $d_{23}^{img}$ . To solve this problem, CODER uses CLIP's accurate text-image distance to build image features. As images of the same class have similar distance to their neighboring texts, their CODER align more closely. Thus, CODER addresses the wrong distance relation between images. + +We then focus on the key element of building a good CODER. Previous studies have emphasized that dense sampling of neighboring samples is vital for algorithms based on nearest neighbor. For example, only when the training samples are densely sampled will the error rate of the KNN classifier remain within twice that of the Bayes optimal classifier. And some studies [24, 33] have observed that greater sampling density of neighboring samples can lead to better neighbor representations. Inspired by these works, we try to optimize our CODER by increasing the number of texts. For increasing the number of texts, we use our Auto Text Generator (ATG) to achieve this objective. + +# 4.2. Use Auto Text Generator to Generate Texts + +Accurate and diverse class-specific texts provide a comprehensive description of object classes from various perspectives, enhancing the sampling density of images' neighbor texts for constructing better CODER. To automatically generate a plethora of high-quality class-specific texts adaptive to target tasks, we introduce the Auto Text Generator (ATG). It uses different query prompts to extract diverse insights from external experts like ChatGPT [13]. Then it leverages that knowledge to construct various high-quality texts. These texts are instrumental in generating high-quality CODER. + +In our implementation, ATG can construct five types of texts: (1) Class Name-based Texts; (2) Attribute-based Texts; (3) Analogous Class-based Texts; (4) Synonym-based Texts; (5) One-to-One Texts. The first two types of texts are proposed by previous work[12, 16], while the latter three are innovations introduced in this paper. We will then delve deeper into the design rationale and generation process of these last three types of texts. + +(1) Analogous Class-based Texts. If someone describes a clouded leopard as resembling a cheetah, you can envision its appearance even if you've never seen a clouded leopard. This scenario illustrates how inter-object similarities help humans leverage their experience with known object classes to recognize new ones. Inspired by this, we query ChatGPT to obtain analogous categories for a given object by asking: + +Q: What other categories are {class} visually similar to? + +Given that the generated class names might exist within the target dataset's class names, we address this issue by filtering out those generated class names whose cosine similarity with existing class names surpass a defined threshold. Next, we insert each analogous class name into some templates like "a {target class} similar to {analogous class}" to form a complete text. + +(2) Synonym-based Texts. An object can have several names. For example, both "forest" and "woodland" refer to "land covered with trees and shrubs". Due to varying frequencies of synonyms in CLIP's training data, the model might favor more common terms and undervalue lesser-known synonyms, despite their equivalent meanings. To mitigate this bias, we query WordNet for synonyms of the current class. Subsequently, we insert the obtained synonym class names into templates like "a photo of {synonym class}". +(3) One-to-One Texts: Due to similar classes often share common features, the ATG may generate nearly identical attribute descriptions for these classes. For example, the ATG might generate attributes such as "two pairs of wings" for both "butterfly" and "dragonfly". Such identical + +attributes can hinder CLIP's ability to distinguish closely related classes. To tackle this problem, we introduce the one-to-one texts. We use the following query prompt to guide ChatGPT in generating the most distinguishing features between similar classes A and B: + +Q: What are different visual features between a {class 1} and a {class 2} in a photo? Focus on their key differences. + +Using the prompt, we generate distinguishing attributes that differentiate butterfly from dragonfly. For butterfly, some of the exemplified attributes include: ["Butterflies typically have larger and more colorful wings compared to dragonflies.'] For dragonfly, some of the descriptors produced are: ["They have transparent wings that are typically held out horizontally when at rest.'] From these newly created attributes, we can make two main observations: (1) The attributes underscore the key differences between butterfly and dragonfly, such as their wing characteristics. (2) The new attributes accentuate the comparison between the two classes, evident from terms like "larger", and "compared to" found within the descriptors. + +Finally, we insert the obtained one-to-one texts into some templates like "Because of {1v1 text}, {class 1} is different from {class 2}" + +# 4.3. Use CODER on Downstream Tasks + +We apply CODER in zero-shot and few-shot image classification tasks to enhance the performance of CLIP. + +Zero-Shot Image Classification. In the first stage, we utilize a general text set generated by ATG to construct the general CODER for images. These texts can be considered as descriptions of general characteristics for a certain class in comparison to most other classes. We can derive preliminary classification results based on the general CODER of the images. In the second stage, we employ ATG to create distinct one-to-one specific text sets for the top five classes, each pair-wise. These texts serve as descriptions of the key distinguishing features between the classes. Utilizing these, we then develop corresponding one-to-one specific CODER for images. Subsequently, we rerank the initial top five classification results using these one-to-one specific CODER. Figure 3 shows the process of our zero-shot image classification method. + +We first utilize all texts generated by ATG, excluding the one-to-one texts, as the general text set $\mathcal{P} = [t_1,\dots ,t_K]$ to construct the general CODER for test images. This process is shown in Equation 5 and Equation 6. Here $\pmb {W}\in \mathbb{R}^{D_1\times K}$ refers to the texts' features in the CLIP feature space. And $s_i\in \mathbb{R}^K$ represents the CODER of test image $\pmb{x}_i$ . $K$ refers to the total number of texts in $\mathcal{P}$ . + +$$ +\boldsymbol {W} = \left[ \frac {\hat {\boldsymbol {t}} _ {1}}{\| \hat {\boldsymbol {t}} _ {1} \|}, \dots , \frac {\hat {\boldsymbol {t}} _ {K}}{\| \hat {\boldsymbol {t}} _ {K} \|} \right] \in \mathbb {R} ^ {D _ {1} \times K}. \tag {5} +$$ + +![](images/9cda19fd5a8a3babf33f85372154a10c858cef5fdcb9a321c25ca5dfe607e78b.jpg) +Stage 1: Use General CODER for Preliminary Classification + +![](images/ee842a6032038daf61d9806e7ee5c0b5496e4900aff80dd1c5264bfde1163d42.jpg) + +![](images/d4f5fef52f43eecbb7c35d5b866ebad6338b23c83f33053e7eb6200eeca6b745.jpg) +Stage 2: Use One-to-One Specific CODER for Reranking Top 5 Classes +Figure 3. Illustration of two-stage zero-shot image classification process based on image's CODER. In the first stage, we use the Auto Text Generator to create a General Text Set, which contains general descriptions of classes. This set is utilized to construct the image's general CODER, and we use it for preliminary classification. In the second stage, we construct One-to-One Text Sets in pairs for the top five predicted classes of the preliminary classification results, focusing on attributes where the two specific classes differ most. We build one-to-one specific CODER for the image based on these One-to-One Text Sets and use heuristic classifier to get each class's classification score. Then we rerank the top five preliminary results based on the classification score gaps $gap_i^{c,j}$ between classes. Here $gap_i^{c,j}$ represents the difference obtained by subtracting the score of the class $c$ from that of the class $j$ for image $x_i$ . + +$$ +\boldsymbol {s} _ {i} = \phi (\hat {\boldsymbol {x}} _ {i}) = \frac {\hat {\boldsymbol {x}} _ {i} ^ {\top}}{\| \hat {\boldsymbol {x}} _ {i} \|} \boldsymbol {W} \in \mathbb {R} ^ {K}. \tag {6} +$$ + +Then, we employ a heuristic classifier $h$ on the test image's general CODER $s_i$ to obtain the preliminary classification logits vector $o_i$ . We use $s_{ij}$ to represent the portion of the test image's general CODER $s_i$ corresponding to the text of the $j$ -th category. $s_{ij}$ consists of several parts, as shown in Equation 7. Here $s_{ij}^{ori}, s_{ij}^{att}, s_{ij}^{ana}, s_{ij}^{syn}$ refers to $s_{ij}$ 's portion of class name-based texts, attribute-based texts, analogous class-based texts and synonym-based texts, respectively. $\oplus$ refers to the vector concatenation operation. + +$$ +\boldsymbol {s} _ {i j} = \boldsymbol {s} _ {i j} ^ {\text {o r i}} \oplus \boldsymbol {s} _ {i j} ^ {\text {a t t}} \oplus \boldsymbol {s} _ {i j} ^ {\text {a n a}} \oplus \boldsymbol {s} _ {i j} ^ {\text {s y n}}. \tag {7} +$$ + +For each class, the heuristic classifier $h$ first gets the largest element in the test image's CODER portion corresponding to the class name-based texts and synonym-based texts. This step is intuitive: Humans can recognize an object by knowing just one of its names. Then $h$ calculates the mean of $\max(s_{ij}^{ori} \oplus s_{ij}^{syn})$ and all elements in the $s_{ij}$ 's portion corresponding to the attribute-based texts and synonym-based texts. This value can be seen as the preliminary classification logit value $o_{ij}$ belonging to class $j$ . The process + +is shown in the following Equation: + +$$ +o _ {i j} = h \left(\boldsymbol {s} _ {i j}\right) = \operatorname {m e a n} \left(\boldsymbol {s} _ {i j} ^ {\text {a t t}} \oplus \boldsymbol {s} _ {i j} ^ {\text {a n a}} \oplus \left[ \max \left(\boldsymbol {s} _ {i j} ^ {\text {o r i}} \oplus \boldsymbol {s} _ {i j} ^ {\text {s y n}}\right) \right]\right). \tag {8} +$$ + +After obtaining the preliminary classification results $\boldsymbol{o}_i$ , we extract the top five classes from the prediction results, forming a set named $\mathcal{C}_5$ . Subsequently, we draw all pairwise combinations from these five classes in set $\mathcal{C}_5$ , creating a new set $\mathcal{P}_{1v1}$ comprised of these pairs. This process can be described by Equation 9 and Equation 10: + +$$ +\mathcal {C} _ {5} = \operatorname {T o p} 5 \left(\boldsymbol {o} _ {i}\right) = \left\{c _ {1}, c _ {2}, c _ {3}, c _ {4}, c _ {5} \right\}. \tag {9} +$$ + +$$ +\mathcal {P} _ {1 v 1} = \left\{\left\{c _ {a}, c _ {b} \right\} \mid c _ {a}, c _ {b} \in \mathcal {C} _ {5}, a \neq b \right\}. \tag {10} +$$ + +In the second stage, we use ATG to generate the one-to-one specific texts for each pair in $\mathcal{P}_{1v1}$ , resulting in a total of $C_5^2 = 10$ text sets. For each one-to-one specific text set, we can construct a one-to-one specific CODER for the image. We first use CLIP's text encoder $f^{T}$ to extract the text features of the one-to-one text set $\boldsymbol{W}^{a,b} \in \mathbb{R}^{D_{1} \times (K_{1} + K_{2})}$ . Here $K_{1}$ and $K_{2}$ represent the number of one-to-one texts for each of the two classes. Equation 11 shows the composition of $\boldsymbol{W}^{a,b}$ , where $\hat{\boldsymbol{t}}_i^a$ and $\hat{\boldsymbol{t}}_i^b$ refers to the $i$ -th one-to-one + +text feature of class $a$ and class $b$ , respectively. + +$$ +\boldsymbol {W} ^ {a, b} = \left[ \frac {\hat {\boldsymbol {t}} _ {1} ^ {a}}{\| \hat {\boldsymbol {t}} _ {1} ^ {a} \|}, \dots , \frac {\hat {\boldsymbol {t}} _ {K _ {1}} ^ {a}}{\| \hat {\boldsymbol {t}} _ {K _ {1}} ^ {a} \|}, \frac {\hat {\boldsymbol {t}} _ {1} ^ {b}}{\| \hat {\boldsymbol {t}} _ {1} ^ {b} \|}, \dots , \frac {\hat {\boldsymbol {t}} _ {K _ {2}} ^ {b}}{\| \hat {\boldsymbol {t}} _ {K _ {2}} ^ {b} \|} \right]. \tag {11} +$$ + +Then we use the one-to-one text features $W^{a,b}$ to construct the image's one-to-one specific CODER $s_i^{a,b} \in \mathbb{R}^{K_1 + K_2}$ : + +$$ +\boldsymbol {s} _ {i} ^ {a, b} = \frac {\hat {\boldsymbol {x}} _ {i} ^ {\top}}{\| \hat {\boldsymbol {x}} _ {i} \|} \boldsymbol {W} ^ {a, b} = \boldsymbol {s} _ {i a} ^ {a, b} \oplus \boldsymbol {s} _ {i b} ^ {a, b}. \tag {12} +$$ + +Here $s_{ia}^{a,b} \in \mathbb{R}^{K_1}$ and $s_{ib}^{a,b} \in \mathbb{R}^{K_2}$ represent the part of CODER pertaining to the one-to-one texts for class $a$ and class $b$ , respectively. + +Based on the one-to-one specific CODER $s_i^{a,b}$ of the image $\pmb{x}_i$ , we employ a heuristic classifier $h$ to obtain image's classification scores for class $a$ and $b$ , denoted as $o_{ia}^{a,b}$ and $o_{ib}^{a,b}$ , respectively: + +$$ +o _ {i a} ^ {a, b} = h \left(\boldsymbol {s} _ {i a} ^ {a, b}\right) = \operatorname {m e a n} \left(\boldsymbol {s} _ {i a} ^ {a, b}\right), \tag {13} +$$ + +$$ +o _ {i b} ^ {a, b} = h (\pmb {s} _ {i b} ^ {a, b}) = \mathrm {m e a n} \left(\pmb {s} _ {i b} ^ {a, b}\right). +$$ + +Then we calculate the image's classification score gap for each class relative to another class: + +$$ +g a p _ {i} ^ {a b} = o _ {i a} ^ {a, b} - o _ {i b} ^ {a, b}, \quad g a p _ {i} ^ {b a} = o _ {i b} ^ {a, b} - o _ {i a} ^ {a, b}. \tag {14} +$$ + +For each class, we sum up all the score gaps between it and other classes. Then we select the class with the largest sum of score gaps as the final predicted class $\hat{c}_i$ of the image: + +$$ +\hat {c} _ {i} = \underset {c \in \mathcal {C} _ {5}} {\operatorname {a r g m a x}} \sum_ {j \in \mathcal {C} _ {5} / \{c \}} \operatorname {g a p} _ {i} ^ {c j}. \tag {15} +$$ + +We use the method based on score gaps instead of the traditional voting method to reorder initial prediction results. The reason is that score gaps provide quantified information about the relative advantages between classes. Unlike voting, which only considers each class's number of wins in pairwise classification, score gaps better capture the model's uncertainty in the classification tasks. For example, a small score gap might indicate that the model is uncertain about the correct class for the image, suggesting that the classification result may be unreliable. This can lead to errors in the outcomes derived from voting methods. + +This two-phase image classification process illustrates that by changing the neighbor text set, we can dynamically build image's feature that focus on different semantics according to task requirements. In coarse-grained image classification, we focus on the general semantics of a class, such as whether an animal has wings. In fine-grained image classification, we aim to focus on more detailed features that differentiate between two specific classes, such as the color + +of wings when distinguishing between dragonfly and butterfly. However, the original image features extracted by the CLIP's image encoder cannot dynamically adapt to specific classification task requirements. + +Few-Shot Image Classification. For Few-Shot Image Classification, we improve the Tip-Adapter [32] by replacing the original CLIP's image features with our CODER to calculate the similarity between the test image and the support set's images. We refer to the improved method as CrOss-MoDal NEighbor Representation CLIP Adapter (CODER-Adapter). Given the $N$ -way $M$ -shot support image set $\mathcal{I}$ , we first calculate the CODER of the images in the support set, represented by $S_{train} \in \mathbb{R}^{NM \times K}$ . Equation 16 shows the calculation process, where $f^I(\mathcal{I}) \in \mathbb{R}^{NM \times D_1}$ refers to the support images' original features and $W \in \mathbb{R}^{D_1 \times K}$ refers to the features of texts in the general text set $\mathcal{P}$ , as defined in Equation 5. + +$$ +\boldsymbol {S} _ {\text {t r a i n}} = f ^ {I} (\mathcal {I}) \boldsymbol {W}. \tag {16} +$$ + +Then we perform one-hot encoding on the support images' labels $\pmb{L}$ to get one-hot labels matrix $L_{train} \in \mathbb{R}^{NM \times C}$ . Each row of $L_{train}$ is a one-hot vector. + +$$ +\boldsymbol {L} _ {\text {t r a i n}} = \operatorname {O n e H o t} (\boldsymbol {L}). \tag {17} +$$ + +For the test image $\pmb{x}_i$ , we also construct its CODER $s_i \in \mathbb{R}^K$ similarly to the support set's images. + +$$ +\boldsymbol {s} _ {i} = f ^ {I} \left(\boldsymbol {x} _ {i}\right) \boldsymbol {W}. \tag {18} +$$ + +We then calculate the affinity matrix $\mathbf{A} \in \mathbb{R}^{1 \times NM}$ between the test image's CODER $s_i \in \mathbb{R}^K$ and the support set images' CODER $S_{train} \in \mathbb{R}^{NM \times K}$ using the Equation 19. Here $\mathrm{Norm}(\cdot)$ refers to the data normalization operation like L2 or min-max normalization. $\beta$ and $T$ are hyperparameters to control the sharpness of $\mathbf{A}$ 's distribution. + +$$ +\boldsymbol {A} = \exp \left(- \beta \cdot \left(1 - \frac {\operatorname {N o r m} \left(\boldsymbol {s} _ {i} \boldsymbol {S} _ {\text {t r a i n}} ^ {\top}\right)}{T}\right)\right). \tag {19} +$$ + +The affinity $\mathbf{A} \in \mathbb{R}^{1 \times NM}$ serves as a weight factor for $L_{train}$ . By calculating the weighted sum of images' labels in $L_{train}$ , we can refine the CLIP's original zero-shot prediction results $o_i^{zs}$ using Equation 20. Here $\alpha$ controls the degree of correction. + +$$ +\boldsymbol {o} _ {i} = \alpha \cdot \boldsymbol {A} \boldsymbol {L} _ {\text {t r a i n}} + \boldsymbol {o} _ {i} ^ {z s}. \tag {20} +$$ + +Finally, we select the class corresponding to the largest logits in $\pmb{o}_i$ as the predicted class of image $\pmb{x}_i$ . + +# 5. Experiments + +# 5.1. Zero-Shot Image Classification Performance + +For zero-shot image classification, we compare our method with two baselines: Vanilla CLIP [16] and VCD [12]. Ta + +Table 1. Accuracy gains over VCD and CLIP baseline. The "CODER" column shows the classification accuracy before rerank stage, while the "CODER*" column shows the accuracy after rerank stage. $\Delta$ represents the improvement of our method over VCD. + +
ImageNetCUB200EuroSAT
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3259.0762.9664.3866.863.9051.8151.7853.0055.043.2644.8946.5752.8354.938.36
ViT-B/1663.5368.1069.6171.463.3655.7557.5458.3059.922.3849.5256.4655.3060.544.08
ViT-L/1470.5874.9676.1577.382.4262.1063.2964.6465.762.4753.5459.5762.9868.248.67
ViT-L/14@336px71.8176.1177.2778.492.3863.4864.7966.2967.362.5754.9359.4664.9469.9610.50
Describable TexturesPlaces365Food101
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3241.2845.2748.7852.717.4436.4738.9240.3740.271.4580.2784.1384.7285.501.37
ViT-B/1643.1945.6448.6755.6910.0537.3139.8741.3941.701.8385.9989.2589.2989.820.57
ViT-L/1452.1857.1860.7461.864.6837.0638.5541.2141.593.0489.8593.3393.6693.930.60
ViT-L/14@336px52.1257.4561.1262.875.4237.2739.8842.0942.502.6291.1094.0694.4894.750.69
Caltech101Oxford PetsImageNetV2
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3279.9089.8091.2491.421.6281.6385.9188.4789.263.3551.7955.2956.7556.421.46
ViT-B/1680.1892.2894.0793.951.7983.9589.3491.5092.012.6757.2561.5362.9462.971.44
ViT-L/1479.7893.9595.7995.681.8487.9093.1894.1994.361.1864.3169.2170.3570.371.16
ViT-L/14@336px80.3694.3596.3196.372.0287.8293.6294.2294.881.2665.6170.4171.4571.281.04
+ +ble 1 displays zero-shot image classification experiment results. By analyzing the results, we can draw the following conclusions: (1) Our proposed CODER consistently boosts CLIP's zero-shot image classification accuracy across various datasets and model architectures; (2) The rerank stage based on the one-to-one specific CODER can further enhance CLIP's performance, demonstrating the effectiveness of our proposed two-stage zero-shot classification method. + +# 5.2. Few-Shot Image Classification Performance + +For few-shot image classification, we use ResNet 50[5] as the backbone for CLIP's image encoder, consistent with previous methods. We use two CLIP's training-free few-shot image classification methods TIP-Adapter [32] and TIP-X [20] as our baselines. TIP-Adapter leverages features extracted by CLIP's image encoder for calculating the similarity between test images and support set's images. While TIP-X uses features based on similarity scores between images and texts generated by CUPL [15] to do it. + +Figure 4 shows the few-shot image classification experiment results. We use the experimental results of TIP-Adapter and TIP-X presented in [20] and ensure that our random seeds are consistent with them. Our method surpasses the previous CLIP few-shot training-free image classification methods on most datasets across different shot scenarios. We notice that CODER-Adapter's performance on EuroSAT is unsatisfactory, which results in our method not having a significant advantage in average accuracy across 11 datasets compared to previous methods. But this meets our expectations. Since EuroSAT has only 10 classes and 95 texts generated by ATG, this small number of texts fails to satisfy CODER's need for dense text sampling, impacting the adapter's performance. This highlights the importance of dense sampling for CODER. + +Table 2. The accuracy of the zero-shot image classification experiments using different texts. Meaning of symbols: P: Using class name-based texts. Att: Using attribute-based texts. Ana: Using analogous class-based texts. We use CLIP ViT-B-32. + +
TextCaltech101Oxford PetsDescribable TexturesEuroSAT
P79.9081.6341.2844.89
P+Att89.8085.9145.2746.57
P+Att+Ana91.0188.5548.7352.77
+ +Table 3. The accuracy of the 16-shot image classification experiments using different texts. We use CLIP ResNet-50. + +
TextCaltech101Oxford PetsDescribable TexturesEuroSAT
P90.3489.8362.3558.44
P+Att90.4790.363.0665.36
P+Att+Ana90.9990.2664.1867.11
+ +Contrasting to previous work [20, 32], we innovatively interpret the superiority of CLIP's cross-modal relative feature representation from the perspective of neighbor representation. Additionally, by drawing an analogy to neighbor-based algorithms like KNN, which require dense sampling of neighbor samples to ensure superior performance, we provide an intuitive explanation for our need to use a more diverse and higher-quality text set to construct our CODER. Motivated by this conclusion, we develop the Auto Text Generator for the automated creation of varied, high-quality texts to meet CODER's dense sampling needs. The experiments demonstrate the validity of our method. + +# 5.3. The Importance of Dense Sampling for CODER + +Nearest neighbor algorithms like KNN depend on dense sampling for good performance. We view our CODER as a cross-modal neighbor representation. Hence, as the diversity and quantity of high-quality cross-modal neighbor texts increase, the constructed CODER should correspond + +![](images/8e505bb6850852a0bf4acbe3510ca2435395bca781ae4cb18a3aa5a23b99537e.jpg) + +![](images/9d1f22043b2fa421b13f61f0d0b3eef2f60705cf63814f38f0468f22ffbc15ae.jpg) + +![](images/388065c011561aa9f35138b7b3f7ee444f68055e7d2e49f03263c8d55324fad0.jpg) + +![](images/50b41990085c2496c4fce85a9fe1aefbeeccaa57a11f87a2615e9cf9cc70287e.jpg) + +![](images/7a0b2a9053c9bd109b8f695094308494b9ec3adf0f7a90c76ce73db0e9e0a754.jpg) + +![](images/a4deb8b9188dcffd85f21f6d307b8bb40bf756c7fa6241267abc23132b486786.jpg) + +![](images/32fd0a9c632d23b112e0dd1ea1ece1a24bc150f167734d96d8b898f6b10f7cc5.jpg) + +![](images/10df6792c2e702f3129fb20b49600505bf894b9058fcfbc852b98e6cc7a8ea7d.jpg) + +![](images/24d128f4ba5878e5c21b7407f47672c691fcc442c9e189b439cc6a72e2fa57c6.jpg) +Figure 4. Results for the training-free few-shot regime across 11 datasets. We compare the CODER-Adapter with the previous CLIP few-shot image classification methods. Our CODER-Adapter achieves the best performance on most datasets. + +![](images/96c39b524cc94188e903182a4688ce53af230b0dfa0ca25fd4f0b27e2225b927.jpg) +Zero-shot CLIP TIP-Adapter TIP-X CODER-Adapter (Ours) + +![](images/1c527fcaa3ff06eb4ba2cddec23651766139b0b55cb57eec92bd4c760fcaf5d4.jpg) + +![](images/dccb78d0fa6254e723c93a05646196ee538225ad07617a18b396644fc60b611b.jpg) + +![](images/f606b8ca39bef0b8dde5c3985382abd3d0df4486398c7b853f1800e6d5fee531.jpg) +Figure 5. The t-SNE Visualization of the Oxford-Pets dataset. Left: Original CLIP Images' Features; Right: CODER. + +![](images/5dd786495e3298e7e69cb40824a91d12eaceaa7a88240be3edf11ca276b6822d.jpg) + +ingly improve. We validate this idea through experiments. We use three different text sets for constructing the image's CODER: (1) CLIP's original class name-based texts; (2) class name-based texts and VCD's attribute-based texts; (3) our analogous class-based texts added to (2). Our experiments in zero-shot and few-shot image classification, as detailed in Table 2 and Table 3, show that CODER performance enhances with the increasing diversity and number of texts. This highlights the importance of dense neighbor text sampling in improving CODER quality. + +# 5.4. Visualization results of CODER + +Figure 5 presents a t-SNE visualization comparing original image features from the CLIP image encoder with those of our proposed CODER on the Oxford-Pets dataset. Our + +CODER achieves tighter clustering of same-class images' features and clearer separation of different classes. + +# 6. Conclusion + +In this paper, we address the misalignment between CLIP's image feature extraction method and its pretraining paradigm. We present a novel perspective based on the nearest neighbors to comprehend CLIP's strong zero-shot image classification capability. Our key insight is that CLIP's effective text-image matching capability embeds image information in image-text distances. This leads us to propose the CrOss-moDal nEighbor Representation (CODER), utilizing these image-text distances for image representation. We introduce the Auto Text Generator to automatically generate texts, ensuring dense sampling of neighbor texts for better CODER construction. Experiment results in zero-shot and few-shot image classification show the superiority of our method. + +# Acknowledgments + +This work is partially supported by National Key R&D Program of China (2022ZD0114805), NSFC (62376118, 62006112, 62250069, 61921006), Collaborative Innovation Center of Novel Software Technology and Industrialization. + +# References + +[1] Lijie Fan, Dilip Krishnan, Phillip Isola, Dina Katabi, and Yonglong Tian. 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In NeurIPS, 2023. 2 \ No newline at end of file diff --git a/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/images.zip b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..1987b4b8121177c9191db76a1b61c380b23b46b9 --- /dev/null +++ b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:e0934babd9f153815164dca38f4479e0641bdef0fbe5588f75de2f1962856e8b +size 651539 diff --git a/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/layout.json b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..ba3721af3bd005ce3aab4ed2d372ad5eda711ddc --- /dev/null +++ b/2024/Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification/layout.json @@ -0,0 +1,8912 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 141, + 103, + 452, + 138 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 141, + 103, + 452, + 138 + ], + "spans": [ + { + "bbox": [ + 141, + 103, + 452, + 138 + ], + "type": "text", + "content": "Leveraging Cross-Modal Neighbor Representation for Improved CLIP Classification" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 93, + 161, + 499, + 217 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 93, + 161, + 499, + 217 + ], + "spans": [ + { + "bbox": [ + 93, + 161, + 499, + 217 + ], + "type": "text", + "content": "Chao Yi, Lu Ren, De-Chuan Zhan, Han-Jia Ye" + }, + { + "bbox": [ + 93, + 161, + 499, + 217 + ], + "type": "inline_equation", + "content": "(\\boxtimes)" + }, + { + "bbox": [ + 93, + 161, + 499, + 217 + ], + "type": "text", + "content": " \nNational Key Laboratory for Novel Software Technology, Nanjing University, China \nSchool of Artificial Intelligence, Nanjing University, China \n{yic, renl, zhandc, yehj}@lamda.nju.edu.cn" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 143, + 244, + 192, + 258 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 244, + 192, + 258 + ], + "spans": [ + { + "bbox": [ + 143, + 244, + 192, + 258 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 271, + 289, + 582 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 271, + 289, + 582 + ], + "spans": [ + { + "bbox": [ + 47, + 271, + 289, + 582 + ], + "type": "text", + "content": "CLIP showcases exceptional cross-modal matching capabilities due to its training on image-text contrastive learning tasks. However, without specific optimization for unimodal scenarios, its performance in single-modality feature extraction might be suboptimal. Despite this, some studies have directly used CLIP's image encoder for tasks like few-shot classification, introducing a misalignment between its pre-training objectives and feature extraction methods. This inconsistency can diminish the quality of the image's feature representation, adversely affecting CLIP's effectiveness in target tasks. In this paper, we view text features as precise neighbors of image features in CLIP's space and present a novel CrOss-moDal nEighbor Representation (CODER) based on the distance structure between images and their neighbor texts. This feature extraction method aligns better with CLIP's pre-training objectives, thereby fully leveraging CLIP's robust cross-modal capabilities. The key to construct a high-quality CODER lies in how to create a vast amount of high-quality and diverse texts to match with images. We introduce the Auto Text Generator (ATG) to automatically generate the required texts in a data-free and training-free manner. We apply CODER to CLIP's zero-shot and few-shot image classification tasks. Experiment results across various datasets and models confirm CODER's effectiveness. Code is available at: https://github.com/YCaigogogo/CVPR24-CODER." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 608, + 127, + 620 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 608, + 127, + 620 + ], + "spans": [ + { + "bbox": [ + 47, + 608, + 127, + 620 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": "In recent years, vision-language models have garnered widespread attention, with CLIP [16] standing out as a notably powerful exemplar. Trained on a vast array of image-text pairs through the image-text contrastive learning tasks, CLIP boasts impressive cross-modal matching capabilities. And it has been applied to fields like image classification [16], object detection [3], semantic segmen" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 246, + 545, + 281 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 246, + 545, + 281 + ], + "spans": [ + { + "bbox": [ + 304, + 246, + 545, + 281 + ], + "type": "text", + "content": "tation [7, 25], video understanding [10], voice classification [4], text-to-image generation [19, 34], model pretraining [23], and beyond [17, 31]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "spans": [ + { + "bbox": [ + 304, + 281, + 546, + 389 + ], + "type": "text", + "content": "Some existing works [21, 23, 32] extract image features directly from CLIP's image encoder for intra-modal operation, like calculating similarity between images in few-shot classification [32]. However, these methods overlook CLIP's multi-modal capabilities, leading to a misalignment with CLIP's pre-training objectives. Furthermore, since CLIP isn't optimized for uni-modal scenarios, its performance in intra-modal tasks isn't guaranteed. To optimize the image features extracted by CLIP, we ask:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 324, + 396, + 526, + 443 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 324, + 396, + 526, + 443 + ], + "spans": [ + { + "bbox": [ + 324, + 396, + 526, + 443 + ], + "type": "text", + "content": "Can we leverage CLIP's powerful cross-modal matching capabilities to extract better image features, thereby improving CLIP's performance on downstream tasks?" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 450, + 546, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 450, + 546, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 450, + 546, + 665 + ], + "type": "text", + "content": "In this paper, we introduce an enhanced image representation based on the distance between images and their neighboring texts in CLIP's feature space. This idea stems from our re-examination of CLIP's robust zero-shot classification capability from the perspective of nearest neighboring: The previous approaches consider the text features extracted by CLIP as classifiers and use them to get the classification results. Different from this perspective, we interpret CLIP's zero-shot image classification as a 1NN problem, as shown in the left part of Figure 1. We treat texts as the images' neighbors in the CLIP's feature space. Then for each image, CLIP identifies its closest text and assigns this text's class as the image's predicted class. This 1NN approach shows good performance because CLIP's robust image-text matching capabilities ensure images are closer to their semantically related texts. This suggests that the cross-modal distance between an image and its neighboring texts captures information about the image, such as its class." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": "In zero-shot image classification, CLIP only considers the distance between an image and its nearest neighbor text, which loses the information implied in the distance between the image and other texts. To make full use of this infor" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27402" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 74, + 69, + 519, + 216 + ], + "blocks": [ + { + "bbox": [ + 74, + 69, + 519, + 216 + ], + "lines": [ + { + "bbox": [ + 74, + 69, + 519, + 216 + ], + "spans": [ + { + "bbox": [ + 74, + 69, + 519, + 216 + ], + "type": "image", + "image_path": "4d4a48acd8ebf7cdb5f8a0dc3828ea36b23dde31c9d839d66bffd84f74ea3e79.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "lines": [ + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "spans": [ + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "type": "text", + "content": "Figure 1. Illustration of image's CrOss-moDal nEighbor Representation (CODER). CLIP's powerful text-image matching capabilities endows it with a favorable cross-modal neighbor distance relation. And CLIP's Zero-Shot Image Classification process can be interpreted as using a 1NN algorithm to find the image's nearest text, with the text's class determining the image's predicted class. Inspired by this idea, we expand the image's neighbor range to leverage its distance to all texts for constructing the CODER. Here " + }, + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "type": "inline_equation", + "content": "d_{ij}" + }, + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "type": "text", + "content": " refers to the distance between the " + }, + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "type": "text", + "content": "-th image and the " + }, + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 225, + 545, + 281 + ], + "type": "text", + "content": "-th text." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 294, + 287, + 400 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 294, + 287, + 400 + ], + "spans": [ + { + "bbox": [ + 46, + 294, + 287, + 400 + ], + "type": "text", + "content": "mation, we expand each image's neighbor range to utilize its distance to " + }, + { + "bbox": [ + 46, + 294, + 287, + 400 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 294, + 287, + 400 + ], + "type": "text", + "content": " Nearest Neighbor (KNN) texts for constructing image representation, as depicted in the right half of Figure 1. Here " + }, + { + "bbox": [ + 46, + 294, + 287, + 400 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 294, + 287, + 400 + ], + "type": "text", + "content": " denotes the total number of texts. We refer to this representation as CrOss-moDal nEighbor Representation (CODER). We believe images with closer CODER values are more similar in semantics. This aligns with intuition: If two objects share the same sets of similar and dissimilar items, they're likely similar to each other." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 402, + 287, + 557 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 402, + 287, + 557 + ], + "spans": [ + { + "bbox": [ + 46, + 402, + 287, + 557 + ], + "type": "text", + "content": "Previous work [24, 33] has noted that dense sampling of neighbor samples is critical for building neighbor representations. This inspires us to use various high-quality texts for dense sampling. Considering that Large Models have rich knowledge and are widely used in many ways [9, 14, 27], we introduce the Auto Text Generator (ATG) based on Large Language Models like ChatGPT [13] to automatically generate various high-quality texts. Without the need for image data and the training process, ATG can produce a diverse and effective set of texts based on the target dataset's class names. These diverse, high-quality texts enhance the density of neighboring texts for images in CLIP's feature space, helping to build a better CODER." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 558, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 558, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 558, + 287, + 714 + ], + "type": "text", + "content": "We apply CODER to CLIP's zero-shot and few-shot image classification tasks to prove CODER's superiority. For the zero-shot image classification task, we use CODER in a two-stage manner. In the first stage, we use ATG to acquire general class-specific texts for constructing general CODER. Then we employ a heuristic classifier to the image's general CODER. In the second stage, we utilize ATG to generate one-to-one specific texts for comparing two distinct classes, concentrating on their most distinguishing features. These texts are then used to construct the one-to-one specific CODER, which is used to rerank the preliminary classification results. For the few-shot situation, we calculate the similarity between test images and the support set's" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 294, + 545, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 294, + 545, + 365 + ], + "spans": [ + { + "bbox": [ + 304, + 294, + 545, + 365 + ], + "type": "text", + "content": "images using those images' general CODER. By ensembling the similarity and CLIP's original zero-shot classification logits, we determine the classification results. Experiment results on various datasets and different CLIP models confirm that CODER enhances CLIP's performance in both zero-shot and few-shot image classification." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 380, + 392, + 392 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 380, + 392, + 392 + ], + "spans": [ + { + "bbox": [ + 306, + 380, + 392, + 392 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 401, + 545, + 556 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 401, + 545, + 556 + ], + "spans": [ + { + "bbox": [ + 304, + 401, + 545, + 556 + ], + "type": "text", + "content": "Vision-Language Models. Vision-Language Models (VLMs) represent a class of multimodal models adept at correlating textual and visual information. Prominent models in this domain include CLIP [16], ALIGN [6], FLAVA [18] and Florence [30], among others. These models typically comprise two main components: an image encoder and a text encoder. Some models also have multimodal fusion modules [8, 22]. VLMs are trained on extensive text-image pairs through tasks like image-text contrastive learning, endowing them with powerful text-image matching capabilities. In this paper, we leverage these capabilities of CLIP to generate our cross-modal neighbor representations (CODER) for images." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 545, + 713 + ], + "type": "text", + "content": "Using LLMs as Experts to Improve VLMs. Large Language Models (LLMs) are widely used in many tasks, such as in-context learning. LLMs can serve as experts by outputting their knowledge in text form. This text-based knowledge can be harnessed by VLMs to enhance their capabilities. Previous work has explored using LLMs' knowledge to optimize VLMs' pre-training [1], prediction interpretability [12, 26, 28], and classifier quality [2, 11, 12, 15]. Recently, some work [29, 35] uses LLMs to select the best VLMs from a VLM zoo for specific target tasks. In this paper, we use the semantic information provided by LLMs to optimize CLIP's features during the inference stage in a training-free manner." + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27403" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 78, + 74, + 514, + 232 + ], + "blocks": [ + { + "bbox": [ + 78, + 74, + 514, + 232 + ], + "lines": [ + { + "bbox": [ + 78, + 74, + 514, + 232 + ], + "spans": [ + { + "bbox": [ + 78, + 74, + 514, + 232 + ], + "type": "image", + "image_path": "45895adcd1b6d2aae32b50facffa21736363d4283c4be28e266393c2f8c7e478.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "lines": [ + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "spans": [ + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "text", + "content": "Figure 2. An example of CODER correcting wrong distance relation between images. " + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "inline_equation", + "content": "d_{ij}^{img}" + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "text", + "content": " refers to the cosine distance between the " + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "text", + "content": "-th and the " + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "text", + "content": "-th image. " + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "inline_equation", + "content": "r_1" + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "inline_equation", + "content": "r_2" + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "text", + "content": " refer to the cosine distance between the text and different images, while " + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "inline_equation", + "content": "1 - r_1" + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "inline_equation", + "content": "1 - r_2" + }, + { + "bbox": [ + 46, + 242, + 547, + 299 + ], + "type": "text", + "content": " refer to the cosine similarity. The left side of the figure indicates that even though images of the same class share similar distance to a text, this doesn't ensure that their features are closely similar. The right side of the figure shows that CODER corrects the wrong distance relation by utilizing the text-image distance." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 308, + 200, + 323 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 308, + 200, + 323 + ], + "spans": [ + { + "bbox": [ + 47, + 308, + 200, + 323 + ], + "type": "text", + "content": "3. Notations and Background" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "spans": [ + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "content": "Using CLIP to match text and image. CLIP encodes both images and texts into a joint space using its image encoder " + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "inline_equation", + "content": "f^{\\prime}" + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "content": " or text encoder " + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "inline_equation", + "content": "f^{T}" + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "content": ", shown in Equation 1. Here " + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "inline_equation", + "content": "\\hat{x}_i" + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "inline_equation", + "content": "\\hat{t}_j" + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "content": " refers to the feature of image " + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "inline_equation", + "content": "x_i" + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "content": " and text " + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "inline_equation", + "content": "t_j" + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "content": ", respectively. " + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "inline_equation", + "content": "D_{1}" + }, + { + "bbox": [ + 47, + 329, + 288, + 390 + ], + "type": "text", + "content": " refers to the dimension of CLIP's feature space." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 80, + 397, + 287, + 412 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 80, + 397, + 287, + 412 + ], + "spans": [ + { + "bbox": [ + 80, + 397, + 287, + 412 + ], + "type": "interline_equation", + "content": "\\hat {\\boldsymbol {x}} _ {i} = f ^ {I} \\left(\\boldsymbol {x} _ {i}\\right) \\in \\mathbb {R} ^ {D _ {1}}, \\hat {\\boldsymbol {t}} _ {j} = f ^ {T} \\left(\\boldsymbol {t} _ {j}\\right) \\in \\mathbb {R} ^ {D _ {1}}. \\tag {1}", + "image_path": "aced2e3b8706a0153ca19bc7a7d8f97002e983d7adcaf5816725f1a10e57bd53.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 111, + 429, + 287, + 459 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 111, + 429, + 287, + 459 + ], + "spans": [ + { + "bbox": [ + 111, + 429, + 287, + 459 + ], + "type": "interline_equation", + "content": "\\tilde {\\boldsymbol {t}} = \\underset {j \\in [ 1, \\dots , K ]} {\\arg \\max } \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {j}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot \\| \\hat {\\boldsymbol {t}} _ {j} \\|.} \\tag {2}", + "image_path": "089bbb060fbb5a3378e71cf0caef9f3fe623f1b2a937b31010c53f69917ab2e0.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "spans": [ + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "type": "text", + "content": "Then we can compute the cosine similarity between the features of various texts and images. These similarity scores represent the matching degree between different images and texts. Given an image " + }, + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "type": "inline_equation", + "content": "\\boldsymbol{x}_i" + }, + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "type": "text", + "content": ", its best matched text " + }, + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "type": "inline_equation", + "content": "\\tilde{t}" + }, + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "type": "text", + "content": " is identified by the highest similarity scores with the image, as shown in Equation 2. Here " + }, + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 46, + 463, + 287, + 535 + ], + "type": "text", + "content": " refers to the number of texts." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 545, + 260, + 560 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 260, + 560 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 260, + 560 + ], + "type": "text", + "content": "4. Cross-Modal Neighbor Representation" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 565, + 244, + 578 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 565, + 244, + 578 + ], + "spans": [ + { + "bbox": [ + 46, + 565, + 244, + 578 + ], + "type": "text", + "content": "4.1. Understand the Advantage of CODER." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "spans": [ + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "type": "text", + "content": "We construct the CODER for the current image by tapping into the precise image-text distance relationship within the CLIP feature space. This process is shown in Equation 3. We use the CODER construct function " + }, + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "type": "text", + "content": " to build image's CODER " + }, + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "type": "inline_equation", + "content": "\\phi (\\hat{x}_i)" + }, + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "type": "text", + "content": " based on its original feature " + }, + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "type": "inline_equation", + "content": "\\hat{x}_i" + }, + { + "bbox": [ + 46, + 583, + 287, + 644 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 55, + 651, + 287, + 677 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 55, + 651, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 55, + 651, + 287, + 677 + ], + "type": "interline_equation", + "content": "\\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\left[ \\psi (d (\\hat {\\boldsymbol {x}} _ {i}, \\hat {\\boldsymbol {t}} _ {1})), \\dots , \\psi (d (\\hat {\\boldsymbol {x}} _ {i}, \\hat {\\boldsymbol {t}} _ {K})) \\right] \\in \\mathbb {R} ^ {K}. \\tag {3}", + "image_path": "07a1488317c8744391c94cec39455dd673ddeeee7877b03b84a5f302b964ffaa.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": "The specific implementation of " + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": " depends on the similarity or distance function " + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": " and the subsequent mapping function " + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\psi" + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": " applied to this distance. In this paper, we use cosine" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "spans": [ + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "text", + "content": "similarity for " + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "text", + "content": " and identity mapping for " + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "inline_equation", + "content": "\\psi" + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "text", + "content": ". Then we can rewrite Equation 3 as Equation 4. We emphasize that the implementation of " + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "inline_equation", + "content": "\\psi" + }, + { + "bbox": [ + 305, + 310, + 546, + 346 + ], + "type": "text", + "content": " can be further researched." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 318, + 358, + 545, + 389 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 358, + 545, + 389 + ], + "spans": [ + { + "bbox": [ + 318, + 358, + 545, + 389 + ], + "type": "interline_equation", + "content": "\\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\left[ \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {1}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot \\| \\hat {\\boldsymbol {t}} _ {1} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top} \\hat {\\boldsymbol {t}} _ {K}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\| \\cdot | \\hat {\\boldsymbol {t}} _ {K} |} \\right] \\in \\mathbb {R} ^ {K}. \\tag {4}", + "image_path": "ecfec773e0b68816eef4775627aa890bf1c34363ac87a99fd7ddfc5396674f6a.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 399, + 546, + 568 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 399, + 546, + 568 + ], + "spans": [ + { + "bbox": [ + 304, + 399, + 546, + 568 + ], + "type": "text", + "content": "We highlight CODER's advantages over CLIP's original image features using an example. Figure 2's left side depicts a bad case for CLIP. For simplicity, we consider a situation where test images share the same neighboring text in CLIP's feature space. While CLIP's cross-modal pre-training ensures accurate image-text distances, it doesn't always capture precise distances between images. This results in cases where the distance for same-class images " + }, + { + "bbox": [ + 304, + 399, + 546, + 568 + ], + "type": "inline_equation", + "content": "d_{21}^{img}" + }, + { + "bbox": [ + 304, + 399, + 546, + 568 + ], + "type": "text", + "content": " exceeds that of different-class images " + }, + { + "bbox": [ + 304, + 399, + 546, + 568 + ], + "type": "inline_equation", + "content": "d_{23}^{img}" + }, + { + "bbox": [ + 304, + 399, + 546, + 568 + ], + "type": "text", + "content": ". To solve this problem, CODER uses CLIP's accurate text-image distance to build image features. As images of the same class have similar distance to their neighboring texts, their CODER align more closely. Thus, CODER addresses the wrong distance relation between images." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 570, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 547, + 714 + ], + "type": "text", + "content": "We then focus on the key element of building a good CODER. Previous studies have emphasized that dense sampling of neighboring samples is vital for algorithms based on nearest neighbor. For example, only when the training samples are densely sampled will the error rate of the KNN classifier remain within twice that of the Bayes optimal classifier. And some studies [24, 33] have observed that greater sampling density of neighboring samples can lead to better neighbor representations. Inspired by these works, we try to optimize our CODER by increasing the number of texts. For increasing the number of texts, we use our Auto Text Generator (ATG) to achieve this objective." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27404" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 272, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 272, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 272, + 83 + ], + "type": "text", + "content": "4.2. Use Auto Text Generator to Generate Texts" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 91, + 286, + 222 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 91, + 286, + 222 + ], + "spans": [ + { + "bbox": [ + 46, + 91, + 286, + 222 + ], + "type": "text", + "content": "Accurate and diverse class-specific texts provide a comprehensive description of object classes from various perspectives, enhancing the sampling density of images' neighbor texts for constructing better CODER. To automatically generate a plethora of high-quality class-specific texts adaptive to target tasks, we introduce the Auto Text Generator (ATG). It uses different query prompts to extract diverse insights from external experts like ChatGPT [13]. Then it leverages that knowledge to construct various high-quality texts. These texts are instrumental in generating high-quality CODER." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 223, + 286, + 319 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 223, + 286, + 319 + ], + "spans": [ + { + "bbox": [ + 46, + 223, + 286, + 319 + ], + "type": "text", + "content": "In our implementation, ATG can construct five types of texts: (1) Class Name-based Texts; (2) Attribute-based Texts; (3) Analogous Class-based Texts; (4) Synonym-based Texts; (5) One-to-One Texts. The first two types of texts are proposed by previous work[12, 16], while the latter three are innovations introduced in this paper. We will then delve deeper into the design rationale and generation process of these last three types of texts." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 319, + 286, + 403 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 319, + 286, + 403 + ], + "spans": [ + { + "bbox": [ + 46, + 319, + 286, + 403 + ], + "type": "text", + "content": "(1) Analogous Class-based Texts. If someone describes a clouded leopard as resembling a cheetah, you can envision its appearance even if you've never seen a clouded leopard. This scenario illustrates how inter-object similarities help humans leverage their experience with known object classes to recognize new ones. Inspired by this, we query ChatGPT to obtain analogous categories for a given object by asking:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 53, + 418, + 253, + 440 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 418, + 253, + 440 + ], + "spans": [ + { + "bbox": [ + 53, + 418, + 253, + 440 + ], + "type": "text", + "content": "Q: What other categories are {class} visually similar to?" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 449, + 286, + 533 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 449, + 286, + 533 + ], + "spans": [ + { + "bbox": [ + 46, + 449, + 286, + 533 + ], + "type": "text", + "content": "Given that the generated class names might exist within the target dataset's class names, we address this issue by filtering out those generated class names whose cosine similarity with existing class names surpass a defined threshold. Next, we insert each analogous class name into some templates like \"a {target class} similar to {analogous class}\" to form a complete text." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 533, + 286, + 714 + ], + "type": "list", + "angle": 0, + "index": 8, + "blocks": [ + { + "bbox": [ + 46, + 533, + 286, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 533, + 286, + 653 + ], + "spans": [ + { + "bbox": [ + 46, + 533, + 286, + 653 + ], + "type": "text", + "content": "(2) Synonym-based Texts. An object can have several names. For example, both \"forest\" and \"woodland\" refer to \"land covered with trees and shrubs\". Due to varying frequencies of synonyms in CLIP's training data, the model might favor more common terms and undervalue lesser-known synonyms, despite their equivalent meanings. To mitigate this bias, we query WordNet for synonyms of the current class. Subsequently, we insert the obtained synonym class names into templates like \"a photo of {synonym class}\"." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 653, + 286, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 653, + 286, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 653, + 286, + 714 + ], + "type": "text", + "content": "(3) One-to-One Texts: Due to similar classes often share common features, the ATG may generate nearly identical attribute descriptions for these classes. For example, the ATG might generate attributes such as \"two pairs of wings\" for both \"butterfly\" and \"dragonfly\". Such identical" + } + ] + } + ], + "index": 7 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 305, + 72, + 545, + 131 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 72, + 545, + 131 + ], + "spans": [ + { + "bbox": [ + 305, + 72, + 545, + 131 + ], + "type": "text", + "content": "attributes can hinder CLIP's ability to distinguish closely related classes. To tackle this problem, we introduce the one-to-one texts. We use the following query prompt to guide ChatGPT in generating the most distinguishing features between similar classes A and B:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 311, + 134, + 526, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 311, + 134, + 526, + 167 + ], + "spans": [ + { + "bbox": [ + 311, + 134, + 526, + 167 + ], + "type": "text", + "content": "Q: What are different visual features between a {class 1} and a {class 2} in a photo? Focus on their key differences." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 175, + 545, + 331 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 175, + 545, + 331 + ], + "spans": [ + { + "bbox": [ + 305, + 175, + 545, + 331 + ], + "type": "text", + "content": "Using the prompt, we generate distinguishing attributes that differentiate butterfly from dragonfly. For butterfly, some of the exemplified attributes include: [\"Butterflies typically have larger and more colorful wings compared to dragonflies.'] For dragonfly, some of the descriptors produced are: [\"They have transparent wings that are typically held out horizontally when at rest.'] From these newly created attributes, we can make two main observations: (1) The attributes underscore the key differences between butterfly and dragonfly, such as their wing characteristics. (2) The new attributes accentuate the comparison between the two classes, evident from terms like \"larger\", and \"compared to\" found within the descriptors." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 331, + 545, + 367 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 331, + 545, + 367 + ], + "spans": [ + { + "bbox": [ + 305, + 331, + 545, + 367 + ], + "type": "text", + "content": "Finally, we insert the obtained one-to-one texts into some templates like \"Because of {1v1 text}, {class 1} is different from {class 2}\"" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 374, + 485, + 386 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 374, + 485, + 386 + ], + "spans": [ + { + "bbox": [ + 306, + 374, + 485, + 386 + ], + "type": "text", + "content": "4.3. Use CODER on Downstream Tasks" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 393, + 544, + 417 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 393, + 544, + 417 + ], + "spans": [ + { + "bbox": [ + 305, + 393, + 544, + 417 + ], + "type": "text", + "content": "We apply CODER in zero-shot and few-shot image classification tasks to enhance the performance of CLIP." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 418, + 545, + 596 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 418, + 545, + 596 + ], + "spans": [ + { + "bbox": [ + 305, + 418, + 545, + 596 + ], + "type": "text", + "content": "Zero-Shot Image Classification. In the first stage, we utilize a general text set generated by ATG to construct the general CODER for images. These texts can be considered as descriptions of general characteristics for a certain class in comparison to most other classes. We can derive preliminary classification results based on the general CODER of the images. In the second stage, we employ ATG to create distinct one-to-one specific text sets for the top five classes, each pair-wise. These texts serve as descriptions of the key distinguishing features between the classes. Utilizing these, we then develop corresponding one-to-one specific CODER for images. Subsequently, we rerank the initial top five classification results using these one-to-one specific CODER. Figure 3 shows the process of our zero-shot image classification method." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "spans": [ + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "text", + "content": "We first utilize all texts generated by ATG, excluding the one-to-one texts, as the general text set " + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "inline_equation", + "content": "\\mathcal{P} = [t_1,\\dots ,t_K]" + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "text", + "content": " to construct the general CODER for test images. This process is shown in Equation 5 and Equation 6. Here " + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "inline_equation", + "content": "\\pmb {W}\\in \\mathbb{R}^{D_1\\times K}" + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "text", + "content": " refers to the texts' features in the CLIP feature space. And " + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "inline_equation", + "content": "s_i\\in \\mathbb{R}^K" + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "text", + "content": " represents the CODER of test image " + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "inline_equation", + "content": "\\pmb{x}_i" + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "text", + "content": " refers to the total number of texts in " + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 305, + 597, + 545, + 681 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 348, + 688, + 545, + 717 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 688, + 545, + 717 + ], + "spans": [ + { + "bbox": [ + 348, + 688, + 545, + 717 + ], + "type": "interline_equation", + "content": "\\boldsymbol {W} = \\left[ \\frac {\\hat {\\boldsymbol {t}} _ {1}}{\\| \\hat {\\boldsymbol {t}} _ {1} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K}}{\\| \\hat {\\boldsymbol {t}} _ {K} \\|} \\right] \\in \\mathbb {R} ^ {D _ {1} \\times K}. \\tag {5}", + "image_path": "f121e5aec9ede5bcb5a617f9ad18649156bd61f3a041016f1f86f84c4ca8352a.jpg" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27405" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 94, + 85, + 347, + 201 + ], + "blocks": [ + { + "bbox": [ + 94, + 71, + 347, + 83 + ], + "lines": [ + { + "bbox": [ + 94, + 71, + 347, + 83 + ], + "spans": [ + { + "bbox": [ + 94, + 71, + 347, + 83 + ], + "type": "text", + "content": "Stage 1: Use General CODER for Preliminary Classification" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 94, + 85, + 347, + 201 + ], + "lines": [ + { + "bbox": [ + 94, + 85, + 347, + 201 + ], + "spans": [ + { + "bbox": [ + 94, + 85, + 347, + 201 + ], + "type": "image", + "image_path": "9cda19fd5a8a3babf33f85372154a10c858cef5fdcb9a321c25ca5dfe607e78b.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 350, + 71, + 503, + 200 + ], + "blocks": [ + { + "bbox": [ + 350, + 71, + 503, + 200 + ], + "lines": [ + { + "bbox": [ + 350, + 71, + 503, + 200 + ], + "spans": [ + { + "bbox": [ + 350, + 71, + 503, + 200 + ], + "type": "image", + "image_path": "ee842a6032038daf61d9806e7ee5c0b5496e4900aff80dd1c5264bfde1163d42.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 97, + 218, + 500, + 338 + ], + "blocks": [ + { + "bbox": [ + 100, + 205, + 400, + 217 + ], + "lines": [ + { + "bbox": [ + 100, + 205, + 400, + 217 + ], + "spans": [ + { + "bbox": [ + 100, + 205, + 400, + 217 + ], + "type": "text", + "content": "Stage 2: Use One-to-One Specific CODER for Reranking Top 5 Classes" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 97, + 218, + 500, + 338 + ], + "lines": [ + { + "bbox": [ + 97, + 218, + 500, + 338 + ], + "spans": [ + { + "bbox": [ + 97, + 218, + 500, + 338 + ], + "type": "image", + "image_path": "d4f5fef52f43eecbb7c35d5b866ebad6338b23c83f33053e7eb6200eeca6b745.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "lines": [ + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "spans": [ + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "text", + "content": "Figure 3. Illustration of two-stage zero-shot image classification process based on image's CODER. In the first stage, we use the Auto Text Generator to create a General Text Set, which contains general descriptions of classes. This set is utilized to construct the image's general CODER, and we use it for preliminary classification. In the second stage, we construct One-to-One Text Sets in pairs for the top five predicted classes of the preliminary classification results, focusing on attributes where the two specific classes differ most. We build one-to-one specific CODER for the image based on these One-to-One Text Sets and use heuristic classifier to get each class's classification score. Then we rerank the top five preliminary results based on the classification score gaps " + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "inline_equation", + "content": "gap_i^{c,j}" + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "text", + "content": " between classes. Here " + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "inline_equation", + "content": "gap_i^{c,j}" + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "text", + "content": " represents the difference obtained by subtracting the score of the class " + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "text", + "content": " from that of the class " + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "text", + "content": " for image " + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "inline_equation", + "content": "x_i" + }, + { + "bbox": [ + 46, + 346, + 545, + 424 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 102, + 442, + 287, + 471 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 102, + 442, + 287, + 471 + ], + "spans": [ + { + "bbox": [ + 102, + 442, + 287, + 471 + ], + "type": "interline_equation", + "content": "\\boldsymbol {s} _ {i} = \\phi (\\hat {\\boldsymbol {x}} _ {i}) = \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\|} \\boldsymbol {W} \\in \\mathbb {R} ^ {K}. \\tag {6}", + "image_path": "471d59deb0fe42d8071324453b2d8c749eaebbfe2a5b257302635fbe3355f4df.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "spans": [ + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": "Then, we employ a heuristic classifier " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": " on the test image's general CODER " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "s_i" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": " to obtain the preliminary classification logits vector " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "o_i" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": ". We use " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "s_{ij}" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": " to represent the portion of the test image's general CODER " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "s_i" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": " corresponding to the text of the " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": "-th category. " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "s_{ij}" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": " consists of several parts, as shown in Equation 7. Here " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "s_{ij}^{ori}, s_{ij}^{att}, s_{ij}^{ana}, s_{ij}^{syn}" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": " refers to " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "s_{ij}" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": "'s portion of class name-based texts, attribute-based texts, analogous class-based texts and synonym-based texts, respectively. " + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "inline_equation", + "content": "\\oplus" + }, + { + "bbox": [ + 46, + 472, + 287, + 581 + ], + "type": "text", + "content": " refers to the vector concatenation operation." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 97, + 586, + 287, + 602 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 97, + 586, + 287, + 602 + ], + "spans": [ + { + "bbox": [ + 97, + 586, + 287, + 602 + ], + "type": "interline_equation", + "content": "\\boldsymbol {s} _ {i j} = \\boldsymbol {s} _ {i j} ^ {\\text {o r i}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a t t}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a n a}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {s y n}}. \\tag {7}", + "image_path": "a5af58f16faddc2b059e8b28ed64e5525c73723f2b78341d90ab64c598edc839.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": "For each class, the heuristic classifier " + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": " first gets the largest element in the test image's CODER portion corresponding to the class name-based texts and synonym-based texts. This step is intuitive: Humans can recognize an object by knowing just one of its names. Then " + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": " calculates the mean of " + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\max(s_{ij}^{ori} \\oplus s_{ij}^{syn})" + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": " and all elements in the " + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "inline_equation", + "content": "s_{ij}" + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": "'s portion corresponding to the attribute-based texts and synonym-based texts. This value can be seen as the preliminary classification logit value " + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "inline_equation", + "content": "o_{ij}" + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": " belonging to class " + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 605, + 288, + 715 + ], + "type": "text", + "content": ". The process" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 435, + 451, + 447 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 435, + 451, + 447 + ], + "spans": [ + { + "bbox": [ + 306, + 435, + 451, + 447 + ], + "type": "text", + "content": "is shown in the following Equation:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 455, + 553, + 480 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 455, + 553, + 480 + ], + "spans": [ + { + "bbox": [ + 306, + 455, + 553, + 480 + ], + "type": "interline_equation", + "content": "o _ {i j} = h \\left(\\boldsymbol {s} _ {i j}\\right) = \\operatorname {m e a n} \\left(\\boldsymbol {s} _ {i j} ^ {\\text {a t t}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {a n a}} \\oplus \\left[ \\max \\left(\\boldsymbol {s} _ {i j} ^ {\\text {o r i}} \\oplus \\boldsymbol {s} _ {i j} ^ {\\text {s y n}}\\right) \\right]\\right). \\tag {8}", + "image_path": "13cf31e8320cdeae873884a3bd9950e004a68b9be1d53bde364a92a59d5a7350.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "spans": [ + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "text", + "content": "After obtaining the preliminary classification results " + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "inline_equation", + "content": "\\boldsymbol{o}_i" + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "text", + "content": ", we extract the top five classes from the prediction results, forming a set named " + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_5" + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "text", + "content": ". Subsequently, we draw all pairwise combinations from these five classes in set " + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "inline_equation", + "content": "\\mathcal{C}_5" + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "text", + "content": ", creating a new set " + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "inline_equation", + "content": "\\mathcal{P}_{1v1}" + }, + { + "bbox": [ + 304, + 481, + 545, + 553 + ], + "type": "text", + "content": " comprised of these pairs. This process can be described by Equation 9 and Equation 10:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 347, + 562, + 545, + 576 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 347, + 562, + 545, + 576 + ], + "spans": [ + { + "bbox": [ + 347, + 562, + 545, + 576 + ], + "type": "interline_equation", + "content": "\\mathcal {C} _ {5} = \\operatorname {T o p} 5 \\left(\\boldsymbol {o} _ {i}\\right) = \\left\\{c _ {1}, c _ {2}, c _ {3}, c _ {4}, c _ {5} \\right\\}. \\tag {9}", + "image_path": "468774f188a6f29e004804a01c586804c5ff713e73100c592db1e8543c000093.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 347, + 587, + 545, + 601 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 347, + 587, + 545, + 601 + ], + "spans": [ + { + "bbox": [ + 347, + 587, + 545, + 601 + ], + "type": "interline_equation", + "content": "\\mathcal {P} _ {1 v 1} = \\left\\{\\left\\{c _ {a}, c _ {b} \\right\\} \\mid c _ {a}, c _ {b} \\in \\mathcal {C} _ {5}, a \\neq b \\right\\}. \\tag {10}", + "image_path": "24390c5ff6a5ff97a547b586afe63efecf18f081d36f181050fef0ad7af62306.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": "In the second stage, we use ATG to generate the one-to-one specific texts for each pair in " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{P}_{1v1}" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": ", resulting in a total of " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "C_5^2 = 10" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": " text sets. For each one-to-one specific text set, we can construct a one-to-one specific CODER for the image. We first use CLIP's text encoder " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "f^{T}" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": " to extract the text features of the one-to-one text set " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\boldsymbol{W}^{a,b} \\in \\mathbb{R}^{D_{1} \\times (K_{1} + K_{2})}" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": ". Here " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "K_{1}" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "K_{2}" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": " represent the number of one-to-one texts for each of the two classes. Equation 11 shows the composition of " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\boldsymbol{W}^{a,b}" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\hat{\\boldsymbol{t}}_i^a" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\hat{\\boldsymbol{t}}_i^b" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": " refers to the " + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 605, + 545, + 714 + ], + "type": "text", + "content": "-th one-to-one" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27406" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 236, + 85 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 236, + 85 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 236, + 85 + ], + "type": "text", + "content": "text feature of class " + }, + { + "bbox": [ + 47, + 72, + 236, + 85 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 47, + 72, + 236, + 85 + ], + "type": "text", + "content": " and class " + }, + { + "bbox": [ + 47, + 72, + 236, + 85 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 47, + 72, + 236, + 85 + ], + "type": "text", + "content": ", respectively." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 56, + 92, + 287, + 126 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 56, + 92, + 287, + 126 + ], + "spans": [ + { + "bbox": [ + 56, + 92, + 287, + 126 + ], + "type": "interline_equation", + "content": "\\boldsymbol {W} ^ {a, b} = \\left[ \\frac {\\hat {\\boldsymbol {t}} _ {1} ^ {a}}{\\| \\hat {\\boldsymbol {t}} _ {1} ^ {a} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K _ {1}} ^ {a}}{\\| \\hat {\\boldsymbol {t}} _ {K _ {1}} ^ {a} \\|}, \\frac {\\hat {\\boldsymbol {t}} _ {1} ^ {b}}{\\| \\hat {\\boldsymbol {t}} _ {1} ^ {b} \\|}, \\dots , \\frac {\\hat {\\boldsymbol {t}} _ {K _ {2}} ^ {b}}{\\| \\hat {\\boldsymbol {t}} _ {K _ {2}} ^ {b} \\|} \\right]. \\tag {11}", + "image_path": "f6b763b359e42e88e8e4dc56cddcd4b95e853a02b76e44fd0f12757bd26f4905.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 134, + 287, + 160 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 134, + 287, + 160 + ], + "spans": [ + { + "bbox": [ + 47, + 134, + 287, + 160 + ], + "type": "text", + "content": "Then we use the one-to-one text features " + }, + { + "bbox": [ + 47, + 134, + 287, + 160 + ], + "type": "inline_equation", + "content": "W^{a,b}" + }, + { + "bbox": [ + 47, + 134, + 287, + 160 + ], + "type": "text", + "content": " to construct the image's one-to-one specific CODER " + }, + { + "bbox": [ + 47, + 134, + 287, + 160 + ], + "type": "inline_equation", + "content": "s_i^{a,b} \\in \\mathbb{R}^{K_1 + K_2}" + }, + { + "bbox": [ + 47, + 134, + 287, + 160 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 97, + 167, + 287, + 195 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 97, + 167, + 287, + 195 + ], + "spans": [ + { + "bbox": [ + 97, + 167, + 287, + 195 + ], + "type": "interline_equation", + "content": "\\boldsymbol {s} _ {i} ^ {a, b} = \\frac {\\hat {\\boldsymbol {x}} _ {i} ^ {\\top}}{\\| \\hat {\\boldsymbol {x}} _ {i} \\|} \\boldsymbol {W} ^ {a, b} = \\boldsymbol {s} _ {i a} ^ {a, b} \\oplus \\boldsymbol {s} _ {i b} ^ {a, b}. \\tag {12}", + "image_path": "630ae08c40c7be2dfc4a9b0013174624b9fdf39a1017a44ea659b06e129e1d40.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "spans": [ + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "text", + "content": "Here " + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "inline_equation", + "content": "s_{ia}^{a,b} \\in \\mathbb{R}^{K_1}" + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "inline_equation", + "content": "s_{ib}^{a,b} \\in \\mathbb{R}^{K_2}" + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "text", + "content": " represent the part of CODER pertaining to the one-to-one texts for class " + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "text", + "content": " and class " + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 47, + 203, + 287, + 241 + ], + "type": "text", + "content": ", respectively." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "spans": [ + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "content": "Based on the one-to-one specific CODER " + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "inline_equation", + "content": "s_i^{a,b}" + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "content": " of the image " + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "inline_equation", + "content": "\\pmb{x}_i" + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "content": ", we employ a heuristic classifier " + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "inline_equation", + "content": "h" + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "content": " to obtain image's classification scores for class " + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "inline_equation", + "content": "a" + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "inline_equation", + "content": "b" + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "content": ", denoted as " + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "inline_equation", + "content": "o_{ia}^{a,b}" + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "inline_equation", + "content": "o_{ib}^{a,b}" + }, + { + "bbox": [ + 47, + 240, + 287, + 292 + ], + "type": "text", + "content": ", respectively:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 100, + 300, + 287, + 325 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 100, + 300, + 287, + 325 + ], + "spans": [ + { + "bbox": [ + 100, + 300, + 287, + 325 + ], + "type": "interline_equation", + "content": "o _ {i a} ^ {a, b} = h \\left(\\boldsymbol {s} _ {i a} ^ {a, b}\\right) = \\operatorname {m e a n} \\left(\\boldsymbol {s} _ {i a} ^ {a, b}\\right), \\tag {13}", + "image_path": "434594e8363bb7ac52af67859fe0a054e766e7db248af7ddad0ff77e3b905912.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 102, + 323, + 233, + 342 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 102, + 323, + 233, + 342 + ], + "spans": [ + { + "bbox": [ + 102, + 323, + 233, + 342 + ], + "type": "interline_equation", + "content": "o _ {i b} ^ {a, b} = h (\\pmb {s} _ {i b} ^ {a, b}) = \\mathrm {m e a n} \\left(\\pmb {s} _ {i b} ^ {a, b}\\right).", + "image_path": "e7d74baa60277246297f5294e07d3f27aabf9061c32053484cd0e309147a2fc4.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 350, + 287, + 373 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 350, + 287, + 373 + ], + "spans": [ + { + "bbox": [ + 47, + 350, + 287, + 373 + ], + "type": "text", + "content": "Then we calculate the image's classification score gap for each class relative to another class:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 67, + 381, + 287, + 398 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 67, + 381, + 287, + 398 + ], + "spans": [ + { + "bbox": [ + 67, + 381, + 287, + 398 + ], + "type": "interline_equation", + "content": "g a p _ {i} ^ {a b} = o _ {i a} ^ {a, b} - o _ {i b} ^ {a, b}, \\quad g a p _ {i} ^ {b a} = o _ {i b} ^ {a, b} - o _ {i a} ^ {a, b}. \\tag {14}", + "image_path": "2183b79ce517a3b8dcb3b96f355cede52a178b82526662cc9aa370205dfe15ba.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 406, + 287, + 442 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 406, + 287, + 442 + ], + "spans": [ + { + "bbox": [ + 47, + 406, + 287, + 442 + ], + "type": "text", + "content": "For each class, we sum up all the score gaps between it and other classes. Then we select the class with the largest sum of score gaps as the final predicted class " + }, + { + "bbox": [ + 47, + 406, + 287, + 442 + ], + "type": "inline_equation", + "content": "\\hat{c}_i" + }, + { + "bbox": [ + 47, + 406, + 287, + 442 + ], + "type": "text", + "content": " of the image:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 107, + 450, + 287, + 478 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 107, + 450, + 287, + 478 + ], + "spans": [ + { + "bbox": [ + 107, + 450, + 287, + 478 + ], + "type": "interline_equation", + "content": "\\hat {c} _ {i} = \\underset {c \\in \\mathcal {C} _ {5}} {\\operatorname {a r g m a x}} \\sum_ {j \\in \\mathcal {C} _ {5} / \\{c \\}} \\operatorname {g a p} _ {i} ^ {c j}. \\tag {15}", + "image_path": "7c48b135961e8d7740de432cb061be224402a717ee8ffcb7a36de04b79cdef3d.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 486, + 287, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 486, + 287, + 617 + ], + "spans": [ + { + "bbox": [ + 46, + 486, + 287, + 617 + ], + "type": "text", + "content": "We use the method based on score gaps instead of the traditional voting method to reorder initial prediction results. The reason is that score gaps provide quantified information about the relative advantages between classes. Unlike voting, which only considers each class's number of wins in pairwise classification, score gaps better capture the model's uncertainty in the classification tasks. For example, a small score gap might indicate that the model is uncertain about the correct class for the image, suggesting that the classification result may be unreliable. This can lead to errors in the outcomes derived from voting methods." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 618, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 618, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 618, + 287, + 713 + ], + "type": "text", + "content": "This two-phase image classification process illustrates that by changing the neighbor text set, we can dynamically build image's feature that focus on different semantics according to task requirements. In coarse-grained image classification, we focus on the general semantics of a class, such as whether an animal has wings. In fine-grained image classification, we aim to focus on more detailed features that differentiate between two specific classes, such as the color" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "content": "of wings when distinguishing between dragonfly and butterfly. However, the original image features extracted by the CLIP's image encoder cannot dynamically adapt to specific classification task requirements." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "spans": [ + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "content": "Few-Shot Image Classification. For Few-Shot Image Classification, we improve the Tip-Adapter [32] by replacing the original CLIP's image features with our CODER to calculate the similarity between the test image and the support set's images. We refer to the improved method as CrOss-MoDal NEighbor Representation CLIP Adapter (CODER-Adapter). Given the " + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "content": "-way " + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "content": "-shot support image set " + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "inline_equation", + "content": "\\mathcal{I}" + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "content": ", we first calculate the CODER of the images in the support set, represented by " + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "inline_equation", + "content": "S_{train} \\in \\mathbb{R}^{NM \\times K}" + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "content": ". Equation 16 shows the calculation process, where " + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "inline_equation", + "content": "f^I(\\mathcal{I}) \\in \\mathbb{R}^{NM \\times D_1}" + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "content": " refers to the support images' original features and " + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "inline_equation", + "content": "W \\in \\mathbb{R}^{D_1 \\times K}" + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "content": " refers to the features of texts in the general text set " + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 304, + 120, + 546, + 276 + ], + "type": "text", + "content": ", as defined in Equation 5." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 382, + 286, + 545, + 300 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 382, + 286, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 382, + 286, + 545, + 300 + ], + "type": "interline_equation", + "content": "\\boldsymbol {S} _ {\\text {t r a i n}} = f ^ {I} (\\mathcal {I}) \\boldsymbol {W}. \\tag {16}", + "image_path": "9ee9a7a88f5087d6b6c102eaea2c023de9f1932bb8213e617de8bb5661d86380.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "spans": [ + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "type": "text", + "content": "Then we perform one-hot encoding on the support images' labels " + }, + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "type": "inline_equation", + "content": "\\pmb{L}" + }, + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "type": "text", + "content": " to get one-hot labels matrix " + }, + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "type": "inline_equation", + "content": "L_{train} \\in \\mathbb{R}^{NM \\times C}" + }, + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "type": "text", + "content": ". Each row of " + }, + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "type": "inline_equation", + "content": "L_{train}" + }, + { + "bbox": [ + 305, + 304, + 545, + 340 + ], + "type": "text", + "content": " is a one-hot vector." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 376, + 346, + 545, + 360 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 376, + 346, + 545, + 360 + ], + "spans": [ + { + "bbox": [ + 376, + 346, + 545, + 360 + ], + "type": "interline_equation", + "content": "\\boldsymbol {L} _ {\\text {t r a i n}} = \\operatorname {O n e H o t} (\\boldsymbol {L}). \\tag {17}", + "image_path": "8e8ca82b09ed8e05200a9702e5e1ca9ce1e05bc1a7fcacba1778790ccd3900b0.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 305, + 365, + 545, + 390 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 365, + 545, + 390 + ], + "spans": [ + { + "bbox": [ + 305, + 365, + 545, + 390 + ], + "type": "text", + "content": "For the test image " + }, + { + "bbox": [ + 305, + 365, + 545, + 390 + ], + "type": "inline_equation", + "content": "\\pmb{x}_i" + }, + { + "bbox": [ + 305, + 365, + 545, + 390 + ], + "type": "text", + "content": ", we also construct its CODER " + }, + { + "bbox": [ + 305, + 365, + 545, + 390 + ], + "type": "inline_equation", + "content": "s_i \\in \\mathbb{R}^K" + }, + { + "bbox": [ + 305, + 365, + 545, + 390 + ], + "type": "text", + "content": " similarly to the support set's images." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 390, + 395, + 545, + 409 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 390, + 395, + 545, + 409 + ], + "spans": [ + { + "bbox": [ + 390, + 395, + 545, + 409 + ], + "type": "interline_equation", + "content": "\\boldsymbol {s} _ {i} = f ^ {I} \\left(\\boldsymbol {x} _ {i}\\right) \\boldsymbol {W}. \\tag {18}", + "image_path": "b77fe0c1f6c9293f96ec80f9868c8475659f250d268452d5cd1b13d26566a697.jpg" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "spans": [ + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "content": "We then calculate the affinity matrix " + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "inline_equation", + "content": "\\mathbf{A} \\in \\mathbb{R}^{1 \\times NM}" + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "content": " between the test image's CODER " + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "inline_equation", + "content": "s_i \\in \\mathbb{R}^K" + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "content": " and the support set images' CODER " + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "inline_equation", + "content": "S_{train} \\in \\mathbb{R}^{NM \\times K}" + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "content": " using the Equation 19. Here " + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "inline_equation", + "content": "\\mathrm{Norm}(\\cdot)" + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "content": " refers to the data normalization operation like L2 or min-max normalization. " + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "content": " are hyperparameters to control the sharpness of " + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "inline_equation", + "content": "\\mathbf{A}" + }, + { + "bbox": [ + 304, + 415, + 545, + 487 + ], + "type": "text", + "content": "'s distribution." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 323, + 492, + 545, + 526 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 323, + 492, + 545, + 526 + ], + "spans": [ + { + "bbox": [ + 323, + 492, + 545, + 526 + ], + "type": "interline_equation", + "content": "\\boldsymbol {A} = \\exp \\left(- \\beta \\cdot \\left(1 - \\frac {\\operatorname {N o r m} \\left(\\boldsymbol {s} _ {i} \\boldsymbol {S} _ {\\text {t r a i n}} ^ {\\top}\\right)}{T}\\right)\\right). \\tag {19}", + "image_path": "04210de98bb38015f6241a31ef81f2f36ac4b08790714745c6f3c2a86f961d54.jpg" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "spans": [ + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "text", + "content": "The affinity " + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "inline_equation", + "content": "\\mathbf{A} \\in \\mathbb{R}^{1 \\times NM}" + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "text", + "content": " serves as a weight factor for " + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "inline_equation", + "content": "L_{train}" + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "text", + "content": ". By calculating the weighted sum of images' labels in " + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "inline_equation", + "content": "L_{train}" + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "text", + "content": ", we can refine the CLIP's original zero-shot prediction results " + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "inline_equation", + "content": "o_i^{zs}" + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "text", + "content": " using Equation 20. Here " + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 304, + 531, + 545, + 592 + ], + "type": "text", + "content": " controls the degree of correction." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 373, + 598, + 545, + 612 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 373, + 598, + 545, + 612 + ], + "spans": [ + { + "bbox": [ + 373, + 598, + 545, + 612 + ], + "type": "interline_equation", + "content": "\\boldsymbol {o} _ {i} = \\alpha \\cdot \\boldsymbol {A} \\boldsymbol {L} _ {\\text {t r a i n}} + \\boldsymbol {o} _ {i} ^ {z s}. \\tag {20}", + "image_path": "28a5832c32d03f531794bdc9d7ec124c43d03a2516a9e854a4f7a09c7d94e1ff.jpg" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 304, + 618, + 545, + 642 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 618, + 545, + 642 + ], + "spans": [ + { + "bbox": [ + 304, + 618, + 545, + 642 + ], + "type": "text", + "content": "Finally, we select the class corresponding to the largest logits in " + }, + { + "bbox": [ + 304, + 618, + 545, + 642 + ], + "type": "inline_equation", + "content": "\\pmb{o}_i" + }, + { + "bbox": [ + 304, + 618, + 545, + 642 + ], + "type": "text", + "content": " as the predicted class of image " + }, + { + "bbox": [ + 304, + 618, + 545, + 642 + ], + "type": "inline_equation", + "content": "\\pmb{x}_i" + }, + { + "bbox": [ + 304, + 618, + 545, + 642 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 306, + 651, + 388, + 665 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 651, + 388, + 665 + ], + "spans": [ + { + "bbox": [ + 306, + 651, + 388, + 665 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 306, + 671, + 537, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 671, + 537, + 684 + ], + "spans": [ + { + "bbox": [ + 306, + 671, + 537, + 684 + ], + "type": "text", + "content": "5.1. Zero-Shot Image Classification Performance" + } + ] + } + ], + "index": 27 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "For zero-shot image classification, we compare our method with two baselines: Vanilla CLIP [16] and VCD [12]. Ta" + } + ] + } + ], + "index": 28 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27407" + } + ] + } + ], + "index": 29 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 47, + 96, + 545, + 282 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 545, + 93 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 545, + 93 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 545, + 93 + ], + "type": "text", + "content": "Table 1. Accuracy gains over VCD and CLIP baseline. The \"CODER\" column shows the classification accuracy before rerank stage, while the \"CODER*\" column shows the accuracy after rerank stage. " + }, + { + "bbox": [ + 47, + 70, + 545, + 93 + ], + "type": "inline_equation", + "content": "\\Delta" + }, + { + "bbox": [ + 47, + 70, + 545, + 93 + ], + "type": "text", + "content": " represents the improvement of our method over VCD." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 96, + 545, + 282 + ], + "lines": [ + { + "bbox": [ + 47, + 96, + 545, + 282 + ], + "spans": [ + { + "bbox": [ + 47, + 96, + 545, + 282 + ], + "type": "table", + "html": "
ImageNetCUB200EuroSAT
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3259.0762.9664.3866.863.9051.8151.7853.0055.043.2644.8946.5752.8354.938.36
ViT-B/1663.5368.1069.6171.463.3655.7557.5458.3059.922.3849.5256.4655.3060.544.08
ViT-L/1470.5874.9676.1577.382.4262.1063.2964.6465.762.4753.5459.5762.9868.248.67
ViT-L/14@336px71.8176.1177.2778.492.3863.4864.7966.2967.362.5754.9359.4664.9469.9610.50
Describable TexturesPlaces365Food101
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3241.2845.2748.7852.717.4436.4738.9240.3740.271.4580.2784.1384.7285.501.37
ViT-B/1643.1945.6448.6755.6910.0537.3139.8741.3941.701.8385.9989.2589.2989.820.57
ViT-L/1452.1857.1860.7461.864.6837.0638.5541.2141.593.0489.8593.3393.6693.930.60
ViT-L/14@336px52.1257.4561.1262.875.4237.2739.8842.0942.502.6291.1094.0694.4894.750.69
Caltech101Oxford PetsImageNetV2
ArchitectureCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*ΔCLIPVCDCODERCODER*Δ
ViT-B/3279.9089.8091.2491.421.6281.6385.9188.4789.263.3551.7955.2956.7556.421.46
ViT-B/1680.1892.2894.0793.951.7983.9589.3491.5092.012.6757.2561.5362.9462.971.44
ViT-L/1479.7893.9595.7995.681.8487.9093.1894.1994.361.1864.3169.2170.3570.371.16
ViT-L/14@336px80.3694.3596.3196.372.0287.8293.6294.2294.881.2665.6170.4171.4571.281.04
", + "image_path": "c73144797a260cb4cef4fff1bda28fa228b02dd03f005d6a31f3c7599a3120d8.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 297, + 287, + 392 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 297, + 287, + 392 + ], + "spans": [ + { + "bbox": [ + 46, + 297, + 287, + 392 + ], + "type": "text", + "content": "ble 1 displays zero-shot image classification experiment results. By analyzing the results, we can draw the following conclusions: (1) Our proposed CODER consistently boosts CLIP's zero-shot image classification accuracy across various datasets and model architectures; (2) The rerank stage based on the one-to-one specific CODER can further enhance CLIP's performance, demonstrating the effectiveness of our proposed two-stage zero-shot classification method." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 404, + 274, + 417 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 404, + 274, + 417 + ], + "spans": [ + { + "bbox": [ + 47, + 404, + 274, + 417 + ], + "type": "text", + "content": "5.2. Few-Shot Image Classification Performance" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 425, + 286, + 532 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 425, + 286, + 532 + ], + "spans": [ + { + "bbox": [ + 46, + 425, + 286, + 532 + ], + "type": "text", + "content": "For few-shot image classification, we use ResNet 50[5] as the backbone for CLIP's image encoder, consistent with previous methods. We use two CLIP's training-free few-shot image classification methods TIP-Adapter [32] and TIP-X [20] as our baselines. TIP-Adapter leverages features extracted by CLIP's image encoder for calculating the similarity between test images and support set's images. While TIP-X uses features based on similarity scores between images and texts generated by CUPL [15] to do it." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 534, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 534, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 534, + 286, + 713 + ], + "type": "text", + "content": "Figure 4 shows the few-shot image classification experiment results. We use the experimental results of TIP-Adapter and TIP-X presented in [20] and ensure that our random seeds are consistent with them. Our method surpasses the previous CLIP few-shot training-free image classification methods on most datasets across different shot scenarios. We notice that CODER-Adapter's performance on EuroSAT is unsatisfactory, which results in our method not having a significant advantage in average accuracy across 11 datasets compared to previous methods. But this meets our expectations. Since EuroSAT has only 10 classes and 95 texts generated by ATG, this small number of texts fails to satisfy CODER's need for dense text sampling, impacting the adapter's performance. This highlights the importance of dense sampling for CODER." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 295, + 545, + 339 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 295, + 545, + 339 + ], + "spans": [ + { + "bbox": [ + 305, + 295, + 545, + 339 + ], + "type": "text", + "content": "Table 2. The accuracy of the zero-shot image classification experiments using different texts. Meaning of symbols: P: Using class name-based texts. Att: Using attribute-based texts. Ana: Using analogous class-based texts. We use CLIP ViT-B-32." + } + ] + } + ], + "index": 6 + }, + { + "type": "table", + "bbox": [ + 306, + 348, + 545, + 392 + ], + "blocks": [ + { + "bbox": [ + 306, + 348, + 545, + 392 + ], + "lines": [ + { + "bbox": [ + 306, + 348, + 545, + 392 + ], + "spans": [ + { + "bbox": [ + 306, + 348, + 545, + 392 + ], + "type": "table", + "html": "
TextCaltech101Oxford PetsDescribable TexturesEuroSAT
P79.9081.6341.2844.89
P+Att89.8085.9145.2746.57
P+Att+Ana91.0188.5548.7352.77
", + "image_path": "1f9154e9243820c86f4fc91378de3e577f4438be94afb6f4940e39d1c368b580.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "table_body" + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 306, + 432, + 545, + 476 + ], + "blocks": [ + { + "bbox": [ + 306, + 401, + 544, + 422 + ], + "lines": [ + { + "bbox": [ + 306, + 401, + 544, + 422 + ], + "spans": [ + { + "bbox": [ + 306, + 401, + 544, + 422 + ], + "type": "text", + "content": "Table 3. The accuracy of the 16-shot image classification experiments using different texts. We use CLIP ResNet-50." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 306, + 432, + 545, + 476 + ], + "lines": [ + { + "bbox": [ + 306, + 432, + 545, + 476 + ], + "spans": [ + { + "bbox": [ + 306, + 432, + 545, + 476 + ], + "type": "table", + "html": "
TextCaltech101Oxford PetsDescribable TexturesEuroSAT
P90.3489.8362.3558.44
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P+Att+Ana90.9990.2664.1867.11
", + "image_path": "f54fdd09ecc59ce692fdd5a54f40c5b18710dfb41276999a162216f7cda182c5.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "table_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 483, + 545, + 626 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 483, + 545, + 626 + ], + "spans": [ + { + "bbox": [ + 304, + 483, + 545, + 626 + ], + "type": "text", + "content": "Contrasting to previous work [20, 32], we innovatively interpret the superiority of CLIP's cross-modal relative feature representation from the perspective of neighbor representation. Additionally, by drawing an analogy to neighbor-based algorithms like KNN, which require dense sampling of neighbor samples to ensure superior performance, we provide an intuitive explanation for our need to use a more diverse and higher-quality text set to construct our CODER. Motivated by this conclusion, we develop the Auto Text Generator for the automated creation of varied, high-quality texts to meet CODER's dense sampling needs. The experiments demonstrate the validity of our method." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 635, + 545, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 635, + 545, + 647 + ], + "spans": [ + { + "bbox": [ + 305, + 635, + 545, + 647 + ], + "type": "text", + "content": "5.3. The Importance of Dense Sampling for CODER" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 545, + 713 + ], + "type": "text", + "content": "Nearest neighbor algorithms like KNN depend on dense sampling for good performance. We view our CODER as a cross-modal neighbor representation. Hence, as the diversity and quantity of high-quality cross-modal neighbor texts increase, the constructed CODER should correspond" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "27408" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 65, + 73, + 180, + 163 + ], + "blocks": [ + { + "bbox": [ + 65, + 73, + 180, + 163 + ], + "lines": [ + { + "bbox": [ + 65, + 73, + 180, + 163 + ], + "spans": [ + { + "bbox": [ + 65, + 73, + 180, + 163 + ], + "type": "image", + "image_path": "8e505bb6850852a0bf4acbe3510ca2435395bca781ae4cb18a3aa5a23b99537e.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 181, + 73, + 296, + 163 + ], + "blocks": [ + { + "bbox": [ + 181, + 73, + 296, + 163 + ], + "lines": [ + { + "bbox": [ + 181, + 73, + 296, + 163 + ], + "spans": [ + { + "bbox": [ + 181, + 73, + 296, + 163 + ], + "type": "image", + "image_path": "9d1f22043b2fa421b13f61f0d0b3eef2f60705cf63814f38f0468f22ffbc15ae.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 298, + 72, + 412, + 163 + ], + "blocks": [ + { + "bbox": [ + 298, + 72, + 412, + 163 + ], + "lines": [ + { + "bbox": [ + 298, + 72, + 412, + 163 + ], + "spans": [ + { + "bbox": [ + 298, + 72, + 412, + 163 + ], + "type": "image", + "image_path": "388065c011561aa9f35138b7b3f7ee444f68055e7d2e49f03263c8d55324fad0.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 414, + 72, + 529, + 163 + ], + "blocks": [ + { + "bbox": [ + 414, + 72, + 529, + 163 + ], + "lines": [ + { + "bbox": [ + 414, + 72, + 529, + 163 + ], + "spans": [ + { + "bbox": [ + 414, + 72, + 529, + 163 + ], + "type": "image", + "image_path": "50b41990085c2496c4fce85a9fe1aefbeeccaa57a11f87a2615e9cf9cc70287e.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 63, + 165, + 179, + 257 + ], + "blocks": [ + { + "bbox": [ + 63, + 165, + 179, + 257 + ], + "lines": [ + { + "bbox": [ + 63, + 165, + 179, + 257 + ], + "spans": [ + { + "bbox": [ + 63, + 165, + 179, + 257 + ], + "type": "image", + "image_path": "7a0b2a9053c9bd109b8f695094308494b9ec3adf0f7a90c76ce73db0e9e0a754.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 182, + 165, + 296, + 257 + ], + "blocks": [ + { + "bbox": [ + 182, + 165, + 296, + 257 + ], + "lines": [ + { + "bbox": [ + 182, + 165, + 296, + 257 + ], + "spans": [ + { + "bbox": [ + 182, + 165, + 296, + 257 + ], + "type": "image", + "image_path": "a4deb8b9188dcffd85f21f6d307b8bb40bf756c7fa6241267abc23132b486786.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 298, + 165, + 413, + 257 + ], + "blocks": [ + { + "bbox": [ + 298, + 165, + 413, + 257 + ], + "lines": [ + { + "bbox": [ + 298, + 165, + 413, + 257 + ], + "spans": [ + { + "bbox": [ + 298, + 165, + 413, + 257 + ], + "type": "image", + "image_path": "32fd0a9c632d23b112e0dd1ea1ece1a24bc150f167734d96d8b898f6b10f7cc5.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 414, + 165, + 529, + 257 + ], + "blocks": [ + { + "bbox": [ + 414, + 165, + 529, + 257 + ], + "lines": [ + { + "bbox": [ + 414, + 165, + 529, + 257 + ], + "spans": [ + { + "bbox": [ + 414, + 165, + 529, + 257 + ], + "type": "image", + "image_path": "10df6792c2e702f3129fb20b49600505bf894b9058fcfbc852b98e6cc7a8ea7d.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 63, + 258, + 180, + 352 + ], + "blocks": [ + { + "bbox": [ + 63, + 258, + 180, + 352 + ], + "lines": [ + { + "bbox": [ + 63, + 258, + 180, + 352 + ], + "spans": [ + { + "bbox": [ + 63, + 258, + 180, + 352 + ], + "type": "image", + "image_path": "24d128f4ba5878e5c21b7407f47672c691fcc442c9e189b439cc6a72e2fa57c6.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 373, + 546, + 396 + ], + "lines": [ + { + "bbox": [ + 46, + 373, + 546, + 396 + ], + "spans": [ + { + "bbox": [ + 46, + 373, + 546, + 396 + ], + "type": "text", + "content": "Figure 4. Results for the training-free few-shot regime across 11 datasets. We compare the CODER-Adapter with the previous CLIP few-shot image classification methods. Our CODER-Adapter achieves the best performance on most datasets." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 182, + 258, + 296, + 351 + ], + "blocks": [ + { + "bbox": [ + 182, + 258, + 296, + 351 + ], + "lines": [ + { + "bbox": [ + 182, + 258, + 296, + 351 + ], + "spans": [ + { + "bbox": [ + 182, + 258, + 296, + 351 + ], + "type": "image", + "image_path": "96c39b524cc94188e903182a4688ce53af230b0dfa0ca25fd4f0b27e2225b927.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 198, + 357, + 398, + 365 + ], + "lines": [ + { + "bbox": [ + 198, + 357, + 398, + 365 + ], + "spans": [ + { + "bbox": [ + 198, + 357, + 398, + 365 + ], + "type": "text", + "content": "Zero-shot CLIP TIP-Adapter TIP-X CODER-Adapter (Ours)" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_footnote" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 298, + 258, + 413, + 351 + ], + "blocks": [ + { + "bbox": [ + 298, + 258, + 413, + 351 + ], + "lines": [ + { + "bbox": [ + 298, + 258, + 413, + 351 + ], + "spans": [ + { + "bbox": [ + 298, + 258, + 413, + 351 + ], + "type": "image", + "image_path": "1c527fcaa3ff06eb4ba2cddec23651766139b0b55cb57eec92bd4c760fcaf5d4.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 414, + 261, + 529, + 351 + ], + "blocks": [ + { + "bbox": [ + 414, + 261, + 529, + 351 + ], + "lines": [ + { + "bbox": [ + 414, + 261, + 529, + 351 + ], + "spans": [ + { + "bbox": [ + 414, + 261, + 529, + 351 + ], + "type": "image", + "image_path": "dccb78d0fa6254e723c93a05646196ee538225ad07617a18b396644fc60b611b.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 53, + 406, + 167, + 495 + ], + "blocks": [ + { + "bbox": [ + 53, + 406, + 167, + 495 + ], + "lines": [ + { + "bbox": [ + 53, + 406, + 167, + 495 + ], + "spans": [ + { + "bbox": [ + 53, + 406, + 167, + 495 + ], + "type": "image", + "image_path": "f606b8ca39bef0b8dde5c3985382abd3d0df4486398c7b853f1800e6d5fee531.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 504, + 287, + 528 + ], + "lines": [ + { + "bbox": [ + 46, + 504, + 287, + 528 + ], + "spans": [ + { + "bbox": [ + 46, + 504, + 287, + 528 + ], + "type": "text", + "content": "Figure 5. The t-SNE Visualization of the Oxford-Pets dataset. Left: Original CLIP Images' Features; Right: CODER." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 169, + 406, + 282, + 495 + ], + "blocks": [ + { + "bbox": [ + 169, + 406, + 282, + 495 + ], + "lines": [ + { + "bbox": [ + 169, + 406, + 282, + 495 + ], + "spans": [ + { + "bbox": [ + 169, + 406, + 282, + 495 + ], + "type": "image", + "image_path": "5dd786495e3298e7e69cb40824a91d12eaceaa7a88240be3edf11ca276b6822d.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + } + ], + "index": 15 + }, + { + "bbox": [ + 46, + 531, + 289, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 531, + 289, + 652 + ], + "spans": [ + { + "bbox": [ + 46, + 531, + 289, + 652 + ], + "type": "text", + "content": "ingly improve. We validate this idea through experiments. We use three different text sets for constructing the image's CODER: (1) CLIP's original class name-based texts; (2) class name-based texts and VCD's attribute-based texts; (3) our analogous class-based texts added to (2). Our experiments in zero-shot and few-shot image classification, as detailed in Table 2 and Table 3, show that CODER performance enhances with the increasing diversity and number of texts. This highlights the importance of dense neighbor text sampling in improving CODER quality." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 47, + 658, + 216, + 671 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 658, + 216, + 671 + ], + "spans": [ + { + "bbox": [ + 47, + 658, + 216, + 671 + ], + "type": "text", + "content": "5.4. Visualization results of CODER" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 288, + 715 + ], + "type": "text", + "content": "Figure 5 presents a t-SNE visualization comparing original image features from the CLIP image encoder with those of our proposed CODER on the Oxford-Pets dataset. Our" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 305, + 407, + 545, + 433 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 407, + 545, + 433 + ], + "spans": [ + { + "bbox": [ + 305, + 407, + 545, + 433 + ], + "type": "text", + "content": "CODER achieves tighter clustering of same-class images' features and clearer separation of different classes." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 444, + 379, + 456 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 444, + 379, + 456 + ], + "spans": [ + { + "bbox": [ + 306, + 444, + 379, + 456 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 464, + 546, + 633 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 464, + 546, + 633 + ], + "spans": [ + { + "bbox": [ + 304, + 464, + 546, + 633 + ], + "type": "text", + "content": "In this paper, we address the misalignment between CLIP's image feature extraction method and its pretraining paradigm. We present a novel perspective based on the nearest neighbors to comprehend CLIP's strong zero-shot image classification capability. Our key insight is that CLIP's effective text-image matching capability embeds image information in image-text distances. This leads us to propose the CrOss-moDal nEighbor Representation (CODER), utilizing these image-text distances for image representation. We introduce the Auto Text Generator to automatically generate texts, ensuring dense sampling of neighbor texts for better CODER construction. Experiment results in zero-shot and few-shot image classification show the superiority of our method." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 645, + 403, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 645, + 403, + 658 + ], + "spans": [ + { + "bbox": [ + 306, + 645, + 403, + 658 + ], + "type": "text", + "content": "Acknowledgments" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 715 + ], + "type": "text", + "content": "This work is partially supported by National Key R&D Program of China (2022ZD0114805), NSFC (62376118, 62006112, 62250069, 61921006), Collaborative Innovation Center of Novel Software Technology and Industrialization." + } + ] + } + ], + "index": 24 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "27409" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 15, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "type": "text", + "content": "[1] Lijie Fan, Dilip Krishnan, Phillip Isola, Dina Katabi, and Yonglong Tian. 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In NeurIPS, 2023. 2" + } + ] + } + ], + "index": 6 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "27411" + } + ] + } + ], + "index": 8 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_content_list.json b/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..b8a451a01e4cafaed65f471c68f6e02df34e3249 --- /dev/null +++ b/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_content_list.json @@ -0,0 +1,1767 @@ +[ + { + "type": "text", + "text": "Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering", + "text_level": 1, + "bbox": [ + 151, + 130, + 818, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Chen Zhang $^{1*}$ , Wencheng Han $^{2*}$ , Yang Zhou $^{1}$ , Jianbing Shen $^{2\\dagger}$ , Cheng-zhong Xu $^{2}$ , Wentao Liu $^{1\\dagger}$ $^{1}$ SenseTime Research and Tetras.AI, $^{2}$ SKL-IOTSC, CIS, University of Macau.", + "bbox": [ + 101, + 179, + 866, + 215 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "zhangchen2@tetras.ai{wencheng256, shenjiangbingcg}@gmail.com {zhouyang, liuwentao}@sensetime.com czxu@um.edu.mo", + "bbox": [ + 215, + 219, + 754, + 251 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 286, + 313, + 301 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Unprocessed RAW video has shown distinct advantages over sRGB video in video editing and computer vision tasks. However, capturing RAW video is challenging due to limitations in bandwidth and storage. Various methods have been proposed to address similar issues in single image RAW capture through de-rendering. These methods utilize both the metadata and the sRGB image to perform sRGB-to-RAW de-rendering and recover high-quality single-frame RAW data. However, metadata-based methods always require additional computation for online metadata generation, imposing severe burden on mobile camera device for high frame rate RAW video capture. To address this issue, we propose a framework that utilizes frame affinity to achieve high-quality sRGB-to-RAW video reconstruction. Our approach consists of two main steps. The first step, temporal affinity prior extraction, uses motion information between adjacent frames to obtain a reference RAW image. The second step, spatial feature fusion and mapping, learns a pixel-level mapping function using scene-specific and position-specific features provided by the previous frame. Our method can be easily applied to current mobile camera equipment without complicated adaptations or added burden. To demonstrate the effectiveness of our approach, we introduce the first RAW Video De-rendering Benchmark. In this benchmark, our method outperforms state-of-the-art RAW image reconstruction methods, even without image-level metadata.", + "bbox": [ + 75, + 316, + 473, + 727 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 770, + 209, + 786 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In recent years, RAW videos have become increasingly popular among professional videographers due to their ability to capture unprocessed signals from the camera at a 10-16", + "bbox": [ + 75, + 795, + 468, + 842 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/94ff3dff4faa8bce0937ef7b3b17dde41db141efb07ff7d526ae37a4bf0b1bb0.jpg", + "image_caption": [ + "(a) RAW video capturing procedure" + ], + "image_footnote": [], + "bbox": [ + 522, + 284, + 879, + 386 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/27d7935ca505f2e9245f64bd7d38ab1d402d279d77c5eec5ff9d2f03398a867b.jpg", + "image_caption": [ + "(b) Meta-data based method" + ], + "image_footnote": [], + "bbox": [ + 516, + 402, + 696, + 503 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/0d15c1adc76b1127e901137ba88408e1280bd5bccb15202210d58c59ce8d5558.jpg", + "image_caption": [ + "(c) Our method", + "Figure 1. Comparison of Different RAW Video Capture Methods. (a) Saving the entire RAW video would cause significant strain on bandwidth and storage resources. (b) Sampling metadata for every frame in the video would burden the camera's computation. (c) Our method only requires saving a single extra RAW frame, which does not significantly burden the camera." + ], + "image_footnote": [], + "bbox": [ + 705, + 402, + 883, + 503 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "bit depth. This enables the production of video sequences with superior visual effects compared to sRGB videos. In addition, recent research has explored the benefits of using RAW data in computer vision tasks. Some studies have discovered that the linear relationship between scene irradiance and RAW data is better suited for tasks such as image denoising [2, 9, 12, 39], image super-resolution [7, 13, 34, 40], and low-light enhancement [5, 8, 11]. Additionally, the wide tolerance of RAW data makes perception tasks more robust in high-dynamic scenes [6, 22, 33, 36]. However, the high cost of RAW video capturing limits the widespread use of this technology. On one hand, the abundant and detailed information encoded in the RAW data takes up a huge amount of storage, increasing storage costs for users. On the other hand, real-time capturing of RAW video data puts a significant strain on the camera's bandwidth, as shown in Figure 1 (a).", + "bbox": [ + 496, + 627, + 893, + 883 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To address similar issues, many techniques have been", + "bbox": [ + 519, + 885, + 890, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal contribution. † Corresponding author. This work was supported in part by the FDCT grants 0154/2022/A3, 0002/2023/AKP, 0102/2023/RIA2, and 001/2024/SKL, the MYRG-CRG2022-00013-IOTSC-ICI grant and the SRG2022-00023-IOTSC grant.", + "bbox": [ + 75, + 849, + 468, + 900 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "25659", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "proposed for de-rendering single-frame sRGB images to RAW data. Some approaches utilize only the sRGB data as input and learn to recover the corresponding RAW data [2, 7, 31]. These methods are convenient for various applications, as they do not require any additional information from the camera besides the sRGB images. However, since some critical information may have been lost during the ISP processing, the de-rendering from only sRGB inputs still suffers from limited performance. In contrast, other methods attempt to extract a small portion of crucial information from the RAW data as metadata and learn to recover the original RAW images from both the sRGB images and the metadata [14, 19, 23, 27]. Although these methods can produce more accurate RAW images, they require an additional sampling method to run on the camera for producing the metadata. These sampling techniques impose additional pressure on the camera, and the burden will be much more severe for RAW video capturing. The complexity of sampling metadata from RAW video is $O(WHL)$ , where $W$ and $H$ are the width and height of the image, and $L$ is the length of the video sequence, as shown in Figure 1 (b).", + "bbox": [ + 76, + 90, + 472, + 407 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "This paper presents a novel approach for RAW video de-rendering, which overcomes the limitations of previous methods and enhances storage and computation efficiency. Unlike metadata-based approaches, our method eliminates the need for an online sampler on the camera side. Instead, it utilizes a single RAW frame from the video sequence as prior information to efficiently recover detailed information from the RAW data, as depicted in Figure 1 (c). The additional select operation only incurs $O(1)$ extra computation cost. Specifically, our method utilizes the provided RAW frame and the relationship between adjacent frames to guide the reconstruction of the remaining RAW frames. By designing a deep neural network with Temporal Affinity Prior Extraction and Spatial Feature Fusion and Mapping, our method effectively leverages the prior information from the previous frame and efficiently de-renders the RAW video.", + "bbox": [ + 76, + 410, + 472, + 651 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To assess the effectiveness of our proposed method, we introduce the first RAW Video De-rendering benchmark, the RVD dataset. We then evaluate the performance of the proposed method and compare it with other sRGB-to-RAW de-rendering methods. The results demonstrate that our method can produce high-fidelity RAW video sequences and outperform other methods, without relying on per-image metadata. In conclusion, the contributions we have made in this paper can be summarized into five points:", + "bbox": [ + 76, + 652, + 472, + 789 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose a new architecture for RAW video de- rendering. This architecture can efficiently de-render RAW video sequences using only one RAW frame and sRGB videos as input. By adopting this method, both storage and computation efficiency for RAW video capturing can be significantly improved.", + "- We propose a module for extracting a temporal affinity" + ], + "bbox": [ + 76, + 795, + 468, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "prior to obtain a reliable reference RAW frame. This module utilizes motion information between adjacent frames. The reference RAW frame can accurately serve as a reference for recovering the lost RAW information.", + "bbox": [ + 511, + 90, + 890, + 151 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose a module called Global and Local feature Aggregation (GLA) to extract and combine the globalized and localized features encoded in the prior information.", + "- We propose a new benchmark for RAW video de-earning to comprehensively evaluate the methods for this task. To our knowledge, this is the first benchmark specifically designed for the RAW video de-rendering task.", + "- Our method significantly outperforms state-of-the-art image RAW de-rendering methods and achieves high-quality RAW video sequences without relying on per-image metadata." + ], + "bbox": [ + 500, + 152, + 890, + 332 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related work", + "text_level": 1, + "bbox": [ + 500, + 347, + 637, + 363 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. RAW Data Application", + "text_level": 1, + "bbox": [ + 500, + 373, + 712, + 388 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "RAW data, as a direct capture of raw information from a scene by a camera, has long been favored by computational photography and certain low-level vision tasks. These tasks include image super-resolution [7, 16, 30, 40], image denoising [2, 9, 10, 41-43], image deblur [4, 15], and low-light enhancement [5, 8, 11]. The main advantage of RAW data is that it is not processed by ISP (Image Signal Processor) and its response value has a linear relationship with scene irradiance. This simplifies the modeling process for degradation or enhancement models.", + "bbox": [ + 496, + 397, + 890, + 547 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Recently, the advantages of RAW in visual perception tasks have been gradually discovered and explored. One basic point is that high-bit-depth RAW data retains more scene information. Another point is that ISP processing does not always have a positive effect. In the early stages, the work in [3, 17, 29, 35] examined the role of the ISP pipeline in computer vision tasks. An interesting conclusion is that most ISP processing is focused on improving visual effects and has little to do with the DNN model, and may even have a negative impact. Furthermore, some methods [18, 25, 37] used proxy networks or parameter searching to redefine ISP as a learnable process, improving the performance of RAW data in downstream tasks. The work in [6] focused on the instance segmentation task in dark scenes, and its results show that higher bit-depth is usually associated with better segmentation results. Xu et al. [33] proposed a new benchmark for RAW object detection in driving scenes and demonstrated the important influence of dynamic range on the detector.", + "bbox": [ + 496, + 547, + 890, + 834 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.2. sRGB-to-RAW Image De-rendering", + "text_level": 1, + "bbox": [ + 500, + 845, + 810, + 863 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "There are generally two categories of single image sRGB-to-RAW de-rendering methods, based on whether metadata", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "25660", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "is used or not.", + "bbox": [ + 76, + 92, + 171, + 104 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "De-rendering without metadata. Such methods are often designed for a specific camera or for vision tasks that require imprecise de-rendering. For example, Brooks et al. [2] proposed a generic process to model and invert the key steps of ISP. They then used synthesized RAW data to train a denoising network. Conde et al. [7] improved upon the aforementioned method by modeling the ISP steps as a learnable dictionary. The work in [31] introduced the normalizing flow to this task, relying on the inherent reversibility of this structure. It is approximated by a two-way process of learning rendering and de-rendering.", + "bbox": [ + 75, + 106, + 467, + 271 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "De-rendering with metadata. For metadata-based methods, the typical approach is to reconstruct the complete RAW image by saving a small amount of sampled data. Yuan and Sun [38] proposed a hybrid capture mode that reduces storage costs and continuous shooting burdens by saving low-resolution RAW images. The method described in [23] saves a small number of uniformly sampled pixels as metadata during capture, and uses RBF interpolation to obtain the full-resolution image during the reconstruction phase. Subsequently, [19] proposed a content-aware superpixel prediction network to improve the sampling strategy, while [14] introduced more expressive implicit neural functions to replace the RBF interpolation algorithm and achieve better performance. In addition to sampling-based methods, Nguyen and Brown's work [20] [21] proposed encoding the necessary parameters of ISP into an sRGB-JPEG file. The work of [27] considered an adaptive and learnable metadata construction method, which uses a compact representation of the latent space as metadata.", + "bbox": [ + 75, + 272, + 467, + 558 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Unlike previous single image de-rendering methods, the proposed method does not impose any additional burden on the camera side. Instead, it utilizes inter-frame relationships to guide the de-rendering process, resulting in improved performance and greater efficiency.", + "bbox": [ + 75, + 559, + 467, + 633 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. RAW Video De-rendering Dataset", + "text_level": 1, + "bbox": [ + 76, + 648, + 383, + 665 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "RAW Video De-rendering is a computer vision task that aims to reconstruct RAW video sequences using sRGB frames and other additional information. This task is valuable as it helps reduce the storage and bandwidth requirements associated with capturing RAW videos. Currently, there is a lack of a dedicated benchmark specifically designed for evaluating and developing RAW video de-rendering methods. To address this issue, we propose the introduction of the first-ever RAW Video De-rendering (RVD) benchmark. This benchmark consists of over 200 videos, captured using different devices in various scenarios. Additionally, we have included videos in challenging scenes, such as fast motion and low lighting, to provide a comprehensive evaluation of de-rendering methods even in extreme conditions. In the remaining content of this section,", + "bbox": [ + 75, + 672, + 467, + 900 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/253b820f3739df1dec478b79c7e0f58a5432c0596e5cc263380649932378f711.jpg", + "image_caption": [ + "Figure 2. Typical challenging scenarios of RVD dataset. (a) contains fast moving vehicles, (b) has drastic scene change, and (c) is a high-light scenario. For each video, we list the sRGB of the first two frames and the last frame, and the corresponding RAW images which are demosaiced for visualization." + ], + "image_footnote": [], + "bbox": [ + 506, + 92, + 880, + 251 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "we will provide a detailed introduction to the Data Collection and Data Processing of the proposed benchmark.", + "bbox": [ + 498, + 340, + 890, + 371 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Data Collection. We collect the data used in this benchmark from two different sources. In the first part, we gather RAW-sRGB video pairs from existing RAW video-based tasks [40]. There are two reasons why we choose to reuse this data in our benchmark. Firstly, this data is of high quality, captured in various scenarios by different devices. By reusing this data, we can increase the diversity of the proposed benchmark without incurring additional data collection costs. Secondly, these datasets are widely recognized benchmarks for RAW video-based tasks, such as Video RAW Super-resolution. Therefore, this data can be easily used to evaluate the de-rendered RAW videos in these tasks.", + "bbox": [ + 498, + 372, + 890, + 551 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "However, simply relying on the data from the existing RAW video dataset is not sufficient for evaluating the RAW video de-rendering tasks. These data are not specifically collected for this task and lack comprehensive evaluations. Therefore, we manually collected some new videos from various challenging scenarios for the RAW video de-rendering task. Specifically, we collected these RAW videos using a Canon 5D Mark III DSLR camera. All videos were shot using fixed focus lenses, specifically the Canon EF $50\\mathrm{mm}$ f/1.8 STM. We used the automatic setting on the camera, where the aperture, shutter, and ISO were adjusted automatically based on the scene. Each video has a duration of 4 to 6 seconds, resulting in a total of 100 videos. The RAW videos are recorded with a resolution of $1600\\times 900$ pixels at a frame rate of 30 frames per second. The camera sensor's color filter array (CFA) follows the widely used RGGB Bayer format, and the RAW data is recorded with a 14-bit depth.", + "bbox": [ + 498, + 553, + 890, + 824 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "For the scenarios, we select some common challenges in the RAW video de-rendering task. These challenges include fast motion, high/low illumination, and more. After collecting this data, we manually label each video with the corresponding attributes. It is possible for a video to be as-", + "bbox": [ + 498, + 825, + 890, + 898 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "25661", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "signed with more than one attribute.", + "bbox": [ + 76, + 90, + 316, + 104 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Data Processing. Typically, different camera devices use different Image Signal Processing (ISP) types to generate sRGB images, resulting in significant variations in sRGB image quality. In order to ensure a fair comparison with previous works, we choose not to use the sRGB images produced by the camera itself. Instead, we employ a software ISP algorithm that has been widely used in previous RAW-image datasets to generate the sRGB videos. Our data processing involves two steps: converting the RAW video format data (in .MLV format for Canon 5D Mark III) into RAW image sequences, and using an external ISP algorithm to render the sRGB image sequences.", + "bbox": [ + 75, + 107, + 467, + 287 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "For the first step, we use MLV App[1] - a professional magic lantern video processing software - to convert the RAW video into a RAW image sequence in DNG format (an open and lossless RAW image format). Since the quality of the first few frames of a handheld shot may not be very high, we delete some of the early frames. For convenience, we retain 120 consecutive frames from each video, resulting in a total of 12,000 retained images for the device. To obtain a rendered sRGB image sequence, we follow the methods described in [31] and [15]. We use the rawpy toolbox, a Python version of the LibRaw library, to process all the RAW images into PNG format using the default settings. This process includes typical operations of a modern ISP, such as demosaicking, auto white balance, denoising, gamma correction, color correction, and more. Some sample images can be seen in Figure 2.", + "bbox": [ + 75, + 289, + 467, + 531 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Method", + "text_level": 1, + "bbox": [ + 76, + 547, + 166, + 561 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Overview", + "text_level": 1, + "bbox": [ + 76, + 574, + 187, + 588 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Given a video sequence $x$ from the sRGB domain, and the corresponding RAW video $y$ from the RAW domain. The sRGB generation procedure $f$ is:", + "bbox": [ + 75, + 598, + 467, + 643 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nx, \\varepsilon^ {\\prime} = f (y), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 225, + 647, + 467, + 664 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\varepsilon^{\\prime}$ represents the extra data saved at capture time. And the invert function of this procedure is defined as the RAW video de-rendering task:", + "bbox": [ + 75, + 666, + 467, + 710 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\ny = f ^ {- 1} (x \\mid \\varepsilon). \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 220, + 714, + 467, + 729 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In previous works on single image RAW de-rendering, additional data $\\varepsilon$ typically consists of sampled RAW pixels from the original RAW image, i.e. the metadata. This data has proven to be highly effective in recovering lost detailed information during the sRGB generation process. However, when it comes to video de-rendering, sampling additional metadata from every frame in the RAW video could impose an excessively high computational burden on the camera, making implementation difficult. To alleviate the need for extra computational burden on the camera device and boost de-rendering efficiency, we propose a new pipeline for the", + "bbox": [ + 75, + 734, + 467, + 900 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/13144f184cea177dbe58667dd0baf63d374106e3d7c80e392c80ee171a0e59b7.jpg", + "image_caption": [ + "Figure 3. Video capture and inference procedure. In the capture time, we save the first frame RAW image and complete sRGB sequence. In the inference phase, except for the first frame, which uses the real RAW image, the rest use the predicted RAW image from the previous frame." + ], + "image_footnote": [], + "bbox": [ + 506, + 95, + 883, + 304 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "RAW video de-rendering. In this pipeline, we utilize the first RAW frame from the RAW video $y$ as additional data:", + "bbox": [ + 498, + 392, + 890, + 422 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\varepsilon = y _ {1}. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 668, + 426, + 890, + 441 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Figure 3 shows an overview of the proposed pipeline. When capturing the video, we only need the camera to save the sRGB frames and an additional first RAW frame, which is easily achievable. When de-rendering the RAW video, our pipeline employs a chained structure to accomplish this. Specifically, in the initialization step, our model takes sRGB frames $x_{1}, x_{2}$ and the first RAW frame $y_{1}$ as input and produces the well-de-rendered RAW frame $\\hat{y}_{2}$ as output. In the subsequent steps, our model takes $x_{t}, x_{t + 1}$ , and the $\\hat{y}_t$ produced in the last step as input and produces $\\hat{y}_{t + 1}$ until the entire RAW video is de-rendered. As shown in this figure, the Frame Affinity Guided De-rendering Network (FAGDN) is the core of our pipeline. In the following subsection, we will provide a detailed introduction to it.", + "bbox": [ + 498, + 445, + 890, + 655 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.2. Frame Affinity Guided De-rendering Network", + "text_level": 1, + "bbox": [ + 498, + 665, + 888, + 681 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Figure 4 illustrates the structure of the proposed Frame Affinity Guided De-rendering Network, which consists of two main steps. The first step is the extraction of temporal affinity priors. In this step, we combine the motion relationship between adjacent frames and the input from the previous frame RAW to construct a reference RAW. This is based on the observation that most parts of adjacent frames describe similar scenes. Therefore, the pixels in the previous RAW frame can provide accurate prior information for de-rendering the corresponding pixels in the subsequent frames.", + "bbox": [ + 496, + 688, + 890, + 852 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The second step involves spatial feature fusion and mapping. Using the reference RAW extracted in the first step as auxiliary information, we utilize an encoder-decoder struc", + "bbox": [ + 498, + 854, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "25662", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/6828309f8fa2f33cfa58ae4a669d93cd62959074d2d2c48b65b4f5b4c011a270.jpg", + "image_caption": [ + "Figure 4. Overview of the proposed Frame Affinity Guided De-rendering network. It contains two main steps, the Temporal Affinity Prior Extraction step generates an reference RAW by utilizing the motion information between adjacent frames. Here, we evaluate the quality of reference RAW through a confidence map. The second step is Spatial Feature Fusion and Mapping, using the reference RAW as starting status, we learn a pixel-level mapping function with the help of sRGB image and previous frames to further repair pixels predicted inaccurately in the first stage." + ], + "image_footnote": [], + "bbox": [ + 86, + 92, + 877, + 362 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/6d1d15c39e269b3ac362639e9e131c77a34d0b88030e6ee21363829edb535927.jpg", + "image_caption": [ + "(a) sRGB", + "Figure 5. From left to right are the sRGB image $x_{t}$ , the optical flow image $o_{t\\rightarrow t + 1}$ , the warping sRGB image $\\tilde{x}_{t + 1}$ and the error map of $\\tilde{x}_{t + 1}$ and $x_{t + 1}$ . The red box lists errors caused by the optical flow algorithm." + ], + "image_footnote": [], + "bbox": [ + 78, + 450, + 168, + 506 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/1310ef262533212d139236465106b4407ea31e5612bfa49f84a9ab7e884aeb92.jpg", + "image_caption": [ + "(b) Optical Flow" + ], + "image_footnote": [], + "bbox": [ + 171, + 450, + 259, + 505 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/08bbdb35fc4d368a4b590a48fae0dd3394ebf130bb639c5767feb7d42d52c293.jpg", + "image_caption": [ + "(c) Warping sRGB" + ], + "image_footnote": [], + "bbox": [ + 264, + 450, + 356, + 505 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/d3b3f0fdf5f153e100dd331972ec16589ea59ce7fc799cd96c3608caa3fad28a.jpg", + "image_caption": [ + "(d) Error Map" + ], + "image_footnote": [], + "bbox": [ + 357, + 450, + 468, + 505 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "ture to learn a mapping function of sRGB-to-RAW by incorporating the previous frame. To effectively utilize the scene-specific and position-specific prior information encoded in the previous frame, we introduce a Global and Local Feature Aggregation (GLA) module. This module is integrated with the encoder-decoder network, which will be further discussed later.", + "bbox": [ + 75, + 594, + 468, + 698 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Temporal Affinity Prior Extraction. In order to take full advantage of the temporal relationship between the adjacent frames, we need to generate the affinity between two frames. We accomplish this by using an off-the-shelf optical flow algorithm $\\Theta$ [32]. This algorithm takes the sRGB frames $(x_{t}, x_{t+1})$ as input and produces the transfer matrix $o_{t \\to t+1}$ :", + "bbox": [ + 75, + 699, + 468, + 805 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\no _ {t \\rightarrow t + 1} = \\Theta \\left(x _ {t}, x _ {t + 1}\\right). \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 192, + 805, + 468, + 821 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Using this transfer matrix and the previous RAW image $y_{t}$ we can apply a wrapping technique to generate a warping RAW image $\\tilde{y}_{t + 1}$ as an reference RAW:", + "bbox": [ + 76, + 825, + 468, + 871 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\tilde {y} _ {t + 1} = \\Omega \\left(y _ {t}, o _ {t \\rightarrow t + 1}\\right), \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 194, + 880, + 468, + 897 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\Omega$ represents a warping function that applies an offset to the original pixels to obtain new coordinates. It then completes the image using an interpolation algorithm.", + "bbox": [ + 498, + 453, + 890, + 501 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "However, there is a natural limitation where some pixels in the subsequent frame do not have corresponding pixels in the previous frame, making the reference pixels unreliable. Figure 5 illustrates a typical example of this limitation. To overcome this issue, we propose generating a confidence map to suppress areas where matching errors occur and select reliable reference features from the reference RAW frame. This generation process is based on the observation that regions with matching errors result in high error values when warping the sRGB image, as shown in Figure 5 (d). Subsequently, we utilize a multi-layer convolutional network to generate the confidence map $M$ :", + "bbox": [ + 496, + 506, + 892, + 686 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\tilde {x} _ {t + 1} = \\Omega \\left(x _ {t}, o _ {t \\rightarrow t + 1}\\right), \\\\ M = \\sigma (\\operatorname {c o n v} ([ \\tilde {x} _ {t + 1}, x _ {t + 1} ])), \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 596, + 690, + 792, + 724 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where, the $conv$ and $\\sigma$ represent the convolutional network and sigmoid function, respectively. The reference RAW image $\\tilde{y}_{t+1}$ and confidence map $M$ will be fed to the second step for accurate RAW image reconstruction.", + "bbox": [ + 496, + 727, + 890, + 787 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Spatial Feature Fusion and Mapping. Using the current sRGB frame and reference RAW, we develop a neural network that learns the final RAW image de-rendering process. Following the previous method for sRGB-to-RAW de-rendering [19], we utilize an encoder-decoder structure, specifically U-Net [24] like structure, to learn the mapping function in an end-to-end manner.", + "bbox": [ + 496, + 794, + 892, + 898 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "25663", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/5debf8583cf175ff4b200939d8c4a6aa908434eafbe6b6c700d926c19cf42caf.jpg", + "image_caption": [ + "Figure 6. The implementation of Global and Local Feature Aggregation(GLA) module. Global information guidance models the dependencies between all patches, while local information guidance limits the relationship modeling within each pair of patches." + ], + "image_footnote": [], + "bbox": [ + 81, + 89, + 467, + 265 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "However, the mapping function often presents two types of challenges. Firstly, the sRGB-to-RAW mapping is scene-specific, meaning that even the same RAW pixel can be mapped to different sRGB values under different scenes. Secondly, the sRGB-to-RAW mapping is position-specific, as described in [23], due to local operations in the ISP. This means that the same RAW value can be mapped to different sRGB values even within a single image. Therefore, our structure includes two branches in the encoder. The first branch takes the current frame information $[x_{t + 1},\\tilde{y}_{t + 1},M]$ as input, providing realistic information about the current status, such as lighting conditions and object position. The second branch takes the previous frame input $[x_t,y_t]$ , aiming to extract global (scene-specific) and local (position-specific) prior information from the previous RAW and sRGB pair.", + "bbox": [ + 75, + 344, + 468, + 585 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "As shown in Figure 4, we utilize two encoder networks to extract deep features from the two input branches individually. These branches have identical structures but do not share parameters:", + "bbox": [ + 75, + 585, + 468, + 646 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} f _ {l} ^ {r} = \\operatorname {E n c o d e r} _ {\\text {r e f}} ([ x _ {t}, y _ {t} ]), \\\\ f _ {l} ^ {c} = \\operatorname {E n c o d e r} _ {\\mathrm {c u r}} ([ x _ {t + 1}, y _ {t + 1}, M ]), \\tag {7} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 155, + 650, + 467, + 686 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where Encoder represents encoder network. The intermediate features are denoted as $f_{l}^{r}$ and $f_{l}^{c}$ , where $l$ indexes the layer of the network. To efficiently utilize the features of the previous frame from global and local perspectives, we propose a global and local feature aggregation module, as shown in Figure 6. Specifically, for the feature $f_{l}^{r} \\in \\mathbb{R}^{C \\times H \\times W}$ and $f_{l}^{c} \\in \\mathbb{R}^{C \\times H \\times W}$ , we divide them into non-overlapping patches with a size of $C \\times p \\times p$ . To introduce scene-related features from a global perspective, we embed each patch as a vector, forming a sequence of length $\\frac{HW}{p^2}$ . Similar to the transformer approach[26], we use the embedding vector of the current frame as the Query and the embedding vector of the previous frame as the Key to learn an affinity matrix. This matrix is then used to ex", + "bbox": [ + 75, + 689, + 470, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "tract global relevant information from the previous frame features (Value). For local information guidance, we implement information interaction within each patch pair. Similarly, we still use the current frame as the Query vector to model pixel-level dependencies. The information interaction within the patch allows the network to pay attention to neighboring pixels, making use of the video characteristics and reducing computational cost. Finally, the global and local supplementary information is added to each layer of the Encodercur sequentially.", + "bbox": [ + 496, + 90, + 890, + 242 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "During the decoding stage, we use an equal number of convolutional and sampling layers to gradually merge features and restore resolution. At the same time, we incorporate the multi-level features of the current encoder $(\\mathrm{Encoder}_{\\mathrm{cur}})$ into the decoding process through skip connections. The resulting output of the decoder is considered the final reconstructed RAW image $(\\hat{y}_{t + 1})$", + "bbox": [ + 496, + 243, + 890, + 348 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Loss Function. The overall network is trained in an end-to-end manner, using $\\ell$ , the combination of $L_{2}$ loss and SSIM [28] loss, to measure the accuracy of the reconstructed RAW. In addition to supervising the output of the last layer of the decoder, we also impose additional constraints on the intermediate features. The entire loss function can be expressed by the following formula:", + "bbox": [ + 496, + 349, + 890, + 455 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\ell \\left(\\hat {y} _ {t + 1}, y _ {t + 1}\\right) + \\lambda \\sum_ {n = 1} ^ {3} \\ell \\left(\\hat {y} _ {t + 1} ^ {n}, y _ {t + 1} ^ {n}\\right). \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 547, + 458, + 890, + 498 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "$\\hat{y}_{t+1}^n$ denotes the output of different levels of the decoder, while $y_{t+1}^n$ is the downsampled image of the ground truth, maintaining the same resolution. $\\lambda$ is a hyperparameter used to balance the contribution of the auxiliary loss and is set to 0.5.", + "bbox": [ + 496, + 500, + 890, + 575 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 592, + 632, + 609 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 500, + 618, + 689, + 633 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Dataset. We conduct experiments on the proposed RVD dataset. For convenience, we call the actually collected data RVD-Part1, and the data collected from [40] is called RVD-Part2. For RVD-Part1, we carefully select 15 videos (including difficult scenes such as fast motion, drastic scene changes, HDR) for testing, and remaining 85 videos for training. Each video is 120 frames with $1600 \\times 900$ resolution. For the RVD-part2, we maintain the original division of training sets and test sets. Specifically, the training set contains 130 videos, each video has about 50 frames, and a total of 6308 images. The testing set has 20 videos, and 983 images. All images have resolution $1440 \\times 640$ .", + "bbox": [ + 496, + 642, + 890, + 823 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation details. We are committed to converting sRGB to the original RAW data, which has not undergone any ISP operations such as demosaic and AWB. As a common practice, we package the single-channel RAW data into a four-channel [R, Gr, Gb, B] format, which serves as the", + "bbox": [ + 496, + 825, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "25664", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/62257dabdbed74433e7d872610cb3292dc01d295ca8cae29ade566d623e4e517.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodPub.YearMetadataRVD-Part1RVD-Part2
PSNR ↑SSIM ↑PSNR ↑SSIM ↑
CAM [19]CVPR2022✓41.850.983242.250.9856
CAM w/ fine-tuning [19]CVPR2022✓41.870.983642.260.9858
INF [14]CVPR2023✓47.670.994846.250.9939
Ours--X48.860.998049.710.9983
", + "bbox": [ + 120, + 89, + 851, + 193 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 1. Quantitative comparison with sRGB-to-RAW image de-rendering methods on the proposed RVD dataset. The $\\uparrow$ represents that the larger the value, the better, and best results are marked in bold.", + "bbox": [ + 75, + 196, + 893, + 224 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5469e8dd8c508b42eb3b98c88cb9f3ba3029c13de645c42d7ae84c3d6c2ad945.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 78, + 233, + 228, + 301 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d65f45571cf0a4815da4519c2ae9aaded7d4b8d45c70b34d1e84c536d298302b.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 301, + 227, + 369 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9e62e5dd3350bdc1b3770761a905c704ef7e54334d7ca7e854a184269443139f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 80, + 369, + 227, + 424 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/c2157c792de1d35af5aa6e9780a12fe2ab9f9995c1c4854c68d2eb1c107be557.jpg", + "image_caption": [ + "sRGB" + ], + "image_footnote": [], + "bbox": [ + 78, + 426, + 227, + 479 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/97047dbba97dec7a2fabcc8396f62e9dee70873f473026c0cb604aa6490e5364.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 233, + 233, + 382, + 300 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/27b58671a39e0e8a8a4c3d3b5cd13e6896977d5d51d23da636712079b22bf6f8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 233, + 301, + 382, + 369 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/2fe5791090f97a2b4fc50509f67be4f478fc06700178af2a47311410cf00a5e7.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 233, + 369, + 382, + 424 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/1306b0ca31db9af6982a80393d5a08e113fec82795d4c3e30aa9c208ccbd6ce7.jpg", + "image_caption": [ + "GT" + ], + "image_footnote": [], + "bbox": [ + 233, + 425, + 380, + 478 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/29da1fe936e32d59a09058850201f350b054546a4cb0fb19c42cd76590ff44ec.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 388, + 233, + 537, + 300 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/2c30b7159179bcff850f9e75e42cf0905bb101a2244ae6ddbebfd8d2aa4c11ff.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 388, + 301, + 535, + 369 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/35707941e55cd1b456297f1b97c979bec56514a7595cceaab9907c2d42fe1a83.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 388, + 369, + 535, + 424 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a32b065f308323642f652060b8e656105d4c64919f8c6c9b6c1bf6b32329f18d.jpg", + "image_caption": [ + "CAM w/ fine-tuning" + ], + "image_footnote": [], + "bbox": [ + 388, + 425, + 535, + 478 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/909fde616ad2b97d34de4a95b3f4753303481d87a2f7b7b847f724435a96b295.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 542, + 233, + 691, + 300 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/0f5a71cc0baf01dc8ffc554c7c207ddb07f9e22bcfb59b5111c9625aa413172f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 542, + 301, + 691, + 369 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/25d5c6a61e6ec0dfcea3c8020bfaa27cd5bc779005fa80f878e46795423c596e.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 542, + 369, + 691, + 424 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/b0f3c98870facc2f9f80897ba2e8fd702e4a544cf594c3936f46cfde054d379c.jpg", + "image_caption": [ + "INF", + "Figure 7. Visual comparison with sRGB-to-RAW image de-rendering methods. We calculate the pixel-level error maps of different methods and GT, and the RAW images are demosaiced for visualization." + ], + "image_footnote": [], + "bbox": [ + 542, + 425, + 691, + 479 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/f792df724a70b7d3d25c1e6313cadcf698708b30dd9e4692c3b0c67f03e64387.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 696, + 233, + 893, + 300 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/3ae35ccb212ebe93f984587176cef404183cbd3396384dc8385377133c09ee37.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 696, + 301, + 893, + 369 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a13161773c191f4fde13d2200d870a74b2912687887fc5ab2db1042745687855.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 696, + 369, + 893, + 424 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/df16ff6c445d5b89ae53b6798f6a61e14bb22adc5a247a2671329193a8f1be4c.jpg", + "image_caption": [ + "Ours" + ], + "image_footnote": [], + "bbox": [ + 696, + 425, + 893, + 479 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "basic format for training and inference. It is also easy to unpack it back to single-channel RAW for downstream tasks. The proposed method is implemented using the PyTorch framework. During training, we randomly crop patches of size $256 \\times 256$ from the original input and apply random rotation and flipping as data augmentation techniques. The model is optimized using the Adam optimizer, with an initial learning rate of $1e - 3$ . The learning rate is reduced to one-tenth every 20 epochs. We train the model for a total of 60 epochs and select the model from the last epoch for testing. During testing, we maintain the original resolution of the image as the input. Considering the differences in sensors among different devices, we train and test the model separately on each subset.", + "bbox": [ + 75, + 542, + 472, + 755 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.2. Comparison with Image De-rendering Methods", + "text_level": 1, + "bbox": [ + 76, + 768, + 468, + 787 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Since our method is the first proposed for sRGB-to-RAW video de-rendering, we compare it with state-of-the-art sRGB-to-RAW image de-rendering methods: CAM [19], CAM with fine-tuning [19], and INF [14]. The source code of these methods has been made public, and since most of the sRGB-to-RAW methods are camera-dependent, we retrain and test on the new dataset.", + "bbox": [ + 75, + 794, + 470, + 898 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 1 illustrates the quantitative comparison results of different methods. We use peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) metrics to evaluate the quality of reconstructed RAW. The results demonstrate that the proposed method achieves the best performance, even when compared to per-image metadata-based methods. Moreover, we also compute the pixel-wise difference between the reconstructed RAW and the ground truth to visually compare the performance of different methods, which can be seen in Figure 7. Overall, our method achieves satisfactory results in most scenarios. We also notice that the sampling-based method INF obtains comparable results to our method but performs poorly in the edge areas of objects. This means that interpolation-based functions have difficulty processing areas with large gradient changes.", + "bbox": [ + 496, + 542, + 893, + 771 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Comparison under Challenging Scenarios", + "text_level": 1, + "bbox": [ + 498, + 784, + 857, + 801 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In the actual photography process, the camera faces complex and diverse scenes. Therefore, we aim to explore the robustness of the model in different challenging scenarios. Low resolution is a common phenomenon in post-processing or when using low-cost storage. Previous research [14] has shown that sampling-based methods tend", + "bbox": [ + 496, + 810, + 893, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "25665", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/6592ce6f03154cffd37af1e5874891e6a36aa278b5bf64fc89c09fa69d366d5a.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ConditionMethodPSNRSSIM
Low resolutionOurs47.900.9978
INF45.500.9944
Fast motionOurs46.360.9976
INF45.790.9936
Dark lightingOurs53.600.9989
INF51.420.9969
", + "bbox": [ + 111, + 88, + 433, + 207 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/8aad4702eec5878463d15536ed916134c4ce1a2591957b717c5a8901be6ac476.jpg", + "table_caption": [ + "Table 2. Comparison under challenging scenarios on RVD-Part1." + ], + "table_footnote": [], + "table_body": "
warpingMGLA\\( \\ell_{aux} \\)PSNRSSIM
✓✓42.600.9972
✓✓✓47.680.9978
✓✓✓46.120.9979
✓✓✓47.910.9983
✓✓✓✓49.710.9983
", + "bbox": [ + 111, + 239, + 434, + 338 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. Ablation study on RVD-Part2 dataset.", + "bbox": [ + 133, + 342, + 410, + 356 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "to be sensitive to resolution. To test the performance of our method and INF, we construct a low-resolution version by downsampling the original dataset to half the resolution. The results indicate that our method is more robust to resolution changes, with a $1.8\\%$ PSNR drop compared to the $4.6\\%$ drop observed in INF. Fast motion is often regarded as a challenging scene for our method, as the first RAW frame only provides limited information for subsequent RAW reconstruction. In comparison to INF, our method shows a gain of $1.2\\%$ in the fast motion scene, which is lower than the $2.3\\%$ gain observed on the full test set. This suggests that fast motion still poses a challenge for our method. Dark lighting is a typical harsh environment for shooting. However, our research has found that it is not actually difficult for the sRGB-to-RAW methods, as the recovery quality in these scenarios is well above average.", + "bbox": [ + 75, + 369, + 472, + 611 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 619, + 228, + 636 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We conduct ablation experiments to verify the effectiveness of key designs in the proposed method, and the quantitative results are shown in Table 3. We first investigate the role of the temporal affinity prior extraction, which generates a reference RAW image by utilizing the motion information. We remove this step and directly input the sRGB image $x_{t+1}$ into Encoders to do the verification. The results in first line show this step is all-important to our pipeline, that is, PSNR decreased by 6.17. The second line represents that we do not consider the quality of the RAW and directly input the reference RAW image $\\tilde{y}_{t+1}$ to the next stage.", + "bbox": [ + 75, + 643, + 468, + 810 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In the spatial feature fusion and mapping step, the previous frame provides global and local supplementary information for image reconstruction by the GLA module. To demonstrate the necessity of introducing a previous frame into this step, we remove the previous frame encoder $\\mathrm{Encoder}_{\\mathrm{ref}}$ and directly learn the mapping function from the", + "bbox": [ + 75, + 810, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7cd5b6c25e5a0d92063948a5d9bc41b66c7e3be99459fa0360428ed293e411c4.jpg", + "image_caption": [ + "Figure 8. Average PSNR and SSIM in time dimension." + ], + "image_footnote": [], + "bbox": [ + 501, + 89, + 689, + 207 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/07c16ab097f601663d3d8b96730fa7febd83508a6d6ec9a1bf86c1bbee3a970c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 89, + 887, + 207 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "current frame inputs. The result can be seen in the third line of Table 3. Furthermore, we add the auxiliary loss function to constraint the intermediate outputs, and the results can be seen in the fourth line when deleting it from the pipeline.", + "bbox": [ + 496, + 234, + 890, + 297 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.5. Robustness over Time", + "text_level": 1, + "bbox": [ + 500, + 305, + 705, + 320 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Our method relies on the first frame RAW to provide real reference information in the chained inference phase. However, as time increases, there will inevitably be accumulated information loss. In Figure 8, we calculate the average PSNR $(psnr^i = (\\sum_{v=1}^{V} psnr_v^i) / V)$ and SSIM $(ssim^i = (\\sum_{v=1}^{V} ssim_v^i) / V)$ along the time dimension. Here, $i \\in [2,120]$ indexes the order of frames, and $V$ represents the number of all testing videos.", + "bbox": [ + 496, + 328, + 890, + 450 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "As depicted in the curve, our method exhibits good robustness over time within a relatively long period of 100 frames. In comparison to INF, the method based on single-image metadata, our method still maintains a relatively high quality. However, the performance noticeably declines when the period becomes too long. This phenomenon is attributed to the inherent characteristics of our method. As an optional solution and for future work, we intend to investigate a previous frame selection strategy. This strategy would involve saving reference RAW frames at intervals to achieve a stable reconstruction quality.", + "bbox": [ + 496, + 452, + 892, + 619 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 633, + 617, + 648 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we introduce a new task called sRGB-to-RAW video de-rendering. Existing methods for converting sRGB images to RAW format are not applicable when applied to the new video de-rendering task. To address this, we propose a frame affinity guided reconstructed network with two main steps. The first step involves extracting temporal affinity prior by utilizing motion information between adjacent frames to obtain a reference RAW image. The second step focuses on spatial feature fusion and mapping, where a pixel-level mapping function is learned using scene-specific and position-specific prior information from the previous frame. To evaluate our proposed method, we create a benchmark dataset that includes a wide range of RAW-sRGB videos. Experimental results on this dataset demonstrate the superior reconstruction quality achieved by our method.", + "bbox": [ + 496, + 657, + 890, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "25666", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 90, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] https://mlv.app/.", + "[2] Tim Brooks, Ben Mildenhall, Tianfan Xue, Jiawen Chen, Dillon Sharlet, and Jonathan T Barron. Unprocessing images for learned raw denoising. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 11036-11045, 2019.", + "[3] Mark Buckler, Suren Jayasuriya, and Adrian Sampson. Reconfiguring the imaging pipeline for computer vision. 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In Proceedings of the IEEE/CVF International Conference on Computer Vision, pages 4593-4601, 2021." + ], + "bbox": [ + 501, + 92, + 890, + 228 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "25668", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_model.json b/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_model.json new file mode 100644 index 0000000000000000000000000000000000000000..da791b1e8dee27284b306a351d4b9aaaba9d7bf6 --- /dev/null +++ b/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_model.json @@ -0,0 +1,2376 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.044 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.152, + 0.131, + 0.82, + 0.154 + ], + "angle": 0, + "content": "Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering" + }, + { + "type": "text", + "bbox": [ + 0.102, + 0.18, + 0.867, + 0.217 + ], + "angle": 0, + "content": "Chen Zhang\\(^{1*}\\), Wencheng Han\\(^{2*}\\), Yang Zhou\\(^{1}\\), Jianbing Shen\\(^{2\\dagger}\\), Cheng-zhong Xu\\(^{2}\\), Wentao Liu\\(^{1\\dagger}\\) \n\\(^{1}\\)SenseTime Research and Tetras.AI, \\(^{2}\\)SKL-IOTSC, CIS, University of Macau." + }, + { + "type": "text", + "bbox": [ + 0.217, + 0.22, + 0.755, + 0.252 + ], + "angle": 0, + "content": "zhangchen2@tetras.ai{wencheng256, shenjiangbingcg}@gmail.com {zhouyang, liuwentao}@sensetime.com czxu@um.edu.mo" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.287, + 0.314, + 0.303 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.318, + 0.474, + 0.728 + ], + "angle": 0, + "content": "Unprocessed RAW video has shown distinct advantages over sRGB video in video editing and computer vision tasks. However, capturing RAW video is challenging due to limitations in bandwidth and storage. Various methods have been proposed to address similar issues in single image RAW capture through de-rendering. These methods utilize both the metadata and the sRGB image to perform sRGB-to-RAW de-rendering and recover high-quality single-frame RAW data. However, metadata-based methods always require additional computation for online metadata generation, imposing severe burden on mobile camera device for high frame rate RAW video capture. To address this issue, we propose a framework that utilizes frame affinity to achieve high-quality sRGB-to-RAW video reconstruction. Our approach consists of two main steps. The first step, temporal affinity prior extraction, uses motion information between adjacent frames to obtain a reference RAW image. The second step, spatial feature fusion and mapping, learns a pixel-level mapping function using scene-specific and position-specific features provided by the previous frame. Our method can be easily applied to current mobile camera equipment without complicated adaptations or added burden. To demonstrate the effectiveness of our approach, we introduce the first RAW Video De-rendering Benchmark. In this benchmark, our method outperforms state-of-the-art RAW image reconstruction methods, even without image-level metadata." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.771, + 0.21, + 0.787 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.47, + 0.843 + ], + "angle": 0, + "content": "In recent years, RAW videos have become increasingly popular among professional videographers due to their ability to capture unprocessed signals from the camera at a 10-16" + }, + { + "type": "image", + "bbox": [ + 0.523, + 0.285, + 0.88, + 0.387 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.615, + 0.39, + 0.784, + 0.402 + ], + "angle": 0, + "content": "(a) RAW video capturing procedure" + }, + { + "type": "image", + "bbox": [ + 0.517, + 0.404, + 0.697, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.536, + 0.51, + 0.668, + 0.521 + ], + "angle": 0, + "content": "(b) Meta-data based method" + }, + { + "type": "image", + "bbox": [ + 0.706, + 0.403, + 0.884, + 0.505 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.751, + 0.51, + 0.825, + 0.521 + ], + "angle": 0, + "content": "(c) Our method" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.53, + 0.895, + 0.614 + ], + "angle": 0, + "content": "Figure 1. Comparison of Different RAW Video Capture Methods. (a) Saving the entire RAW video would cause significant strain on bandwidth and storage resources. (b) Sampling metadata for every frame in the video would burden the camera's computation. (c) Our method only requires saving a single extra RAW frame, which does not significantly burden the camera." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.628, + 0.895, + 0.884 + ], + "angle": 0, + "content": "bit depth. This enables the production of video sequences with superior visual effects compared to sRGB videos. In addition, recent research has explored the benefits of using RAW data in computer vision tasks. Some studies have discovered that the linear relationship between scene irradiance and RAW data is better suited for tasks such as image denoising [2, 9, 12, 39], image super-resolution [7, 13, 34, 40], and low-light enhancement [5, 8, 11]. Additionally, the wide tolerance of RAW data makes perception tasks more robust in high-dynamic scenes [6, 22, 33, 36]. However, the high cost of RAW video capturing limits the widespread use of this technology. On one hand, the abundant and detailed information encoded in the RAW data takes up a huge amount of storage, increasing storage costs for users. On the other hand, real-time capturing of RAW video data puts a significant strain on the camera's bandwidth, as shown in Figure 1 (a)." + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.886, + 0.892, + 0.902 + ], + "angle": 0, + "content": "To address similar issues, many techniques have been" + }, + { + "type": "page_footnote", + "bbox": [ + 0.076, + 0.851, + 0.47, + 0.901 + ], + "angle": 0, + "content": "*Equal contribution. † Corresponding author. This work was supported in part by the FDCT grants 0154/2022/A3, 0002/2023/AKP, 0102/2023/RIA2, and 001/2024/SKL, the MYRG-CRG2022-00013-IOTSC-ICI grant and the SRG2022-00023-IOTSC grant." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "25659" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.409 + ], + "angle": 0, + "content": "proposed for de-rendering single-frame sRGB images to RAW data. Some approaches utilize only the sRGB data as input and learn to recover the corresponding RAW data [2, 7, 31]. These methods are convenient for various applications, as they do not require any additional information from the camera besides the sRGB images. However, since some critical information may have been lost during the ISP processing, the de-rendering from only sRGB inputs still suffers from limited performance. In contrast, other methods attempt to extract a small portion of crucial information from the RAW data as metadata and learn to recover the original RAW images from both the sRGB images and the metadata [14, 19, 23, 27]. Although these methods can produce more accurate RAW images, they require an additional sampling method to run on the camera for producing the metadata. These sampling techniques impose additional pressure on the camera, and the burden will be much more severe for RAW video capturing. The complexity of sampling metadata from RAW video is \\( O(WHL) \\), where \\( W \\) and \\( H \\) are the width and height of the image, and \\( L \\) is the length of the video sequence, as shown in Figure 1 (b)." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.411, + 0.473, + 0.652 + ], + "angle": 0, + "content": "This paper presents a novel approach for RAW video de-rendering, which overcomes the limitations of previous methods and enhances storage and computation efficiency. Unlike metadata-based approaches, our method eliminates the need for an online sampler on the camera side. Instead, it utilizes a single RAW frame from the video sequence as prior information to efficiently recover detailed information from the RAW data, as depicted in Figure 1 (c). The additional select operation only incurs \\( O(1) \\) extra computation cost. Specifically, our method utilizes the provided RAW frame and the relationship between adjacent frames to guide the reconstruction of the remaining RAW frames. By designing a deep neural network with Temporal Affinity Prior Extraction and Spatial Feature Fusion and Mapping, our method effectively leverages the prior information from the previous frame and efficiently de-renders the RAW video." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.654, + 0.473, + 0.79 + ], + "angle": 0, + "content": "To assess the effectiveness of our proposed method, we introduce the first RAW Video De-rendering benchmark, the RVD dataset. We then evaluate the performance of the proposed method and compare it with other sRGB-to-RAW de-rendering methods. The results demonstrate that our method can produce high-fidelity RAW video sequences and outperform other methods, without relying on per-image metadata. In conclusion, the contributions we have made in this paper can be summarized into five points:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.796, + 0.47, + 0.886 + ], + "angle": 0, + "content": "- We propose a new architecture for RAW video de- rendering. This architecture can efficiently de-render RAW video sequences using only one RAW frame and sRGB videos as input. By adopting this method, both storage and computation efficiency for RAW video capturing can be significantly improved." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.886, + 0.469, + 0.902 + ], + "angle": 0, + "content": "- We propose a module for extracting a temporal affinity" + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.796, + 0.47, + 0.902 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.513, + 0.092, + 0.892, + 0.152 + ], + "angle": 0, + "content": "prior to obtain a reliable reference RAW frame. This module utilizes motion information between adjacent frames. The reference RAW frame can accurately serve as a reference for recovering the lost RAW information." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.153, + 0.892, + 0.197 + ], + "angle": 0, + "content": "- We propose a module called Global and Local feature Aggregation (GLA) to extract and combine the globalized and localized features encoded in the prior information." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.198, + 0.892, + 0.271 + ], + "angle": 0, + "content": "- We propose a new benchmark for RAW video de-earning to comprehensively evaluate the methods for this task. To our knowledge, this is the first benchmark specifically designed for the RAW video de-rendering task." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.273, + 0.892, + 0.333 + ], + "angle": 0, + "content": "- Our method significantly outperforms state-of-the-art image RAW de-rendering methods and achieves high-quality RAW video sequences without relying on per-image metadata." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.153, + 0.892, + 0.333 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.348, + 0.638, + 0.364 + ], + "angle": 0, + "content": "2. Related work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.374, + 0.714, + 0.39 + ], + "angle": 0, + "content": "2.1. RAW Data Application" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.398, + 0.892, + 0.548 + ], + "angle": 0, + "content": "RAW data, as a direct capture of raw information from a scene by a camera, has long been favored by computational photography and certain low-level vision tasks. These tasks include image super-resolution [7, 16, 30, 40], image denoising [2, 9, 10, 41-43], image deblur [4, 15], and low-light enhancement [5, 8, 11]. The main advantage of RAW data is that it is not processed by ISP (Image Signal Processor) and its response value has a linear relationship with scene irradiance. This simplifies the modeling process for degradation or enhancement models." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.549, + 0.892, + 0.835 + ], + "angle": 0, + "content": "Recently, the advantages of RAW in visual perception tasks have been gradually discovered and explored. One basic point is that high-bit-depth RAW data retains more scene information. Another point is that ISP processing does not always have a positive effect. In the early stages, the work in [3, 17, 29, 35] examined the role of the ISP pipeline in computer vision tasks. An interesting conclusion is that most ISP processing is focused on improving visual effects and has little to do with the DNN model, and may even have a negative impact. Furthermore, some methods [18, 25, 37] used proxy networks or parameter searching to redefine ISP as a learnable process, improving the performance of RAW data in downstream tasks. The work in [6] focused on the instance segmentation task in dark scenes, and its results show that higher bit-depth is usually associated with better segmentation results. Xu et al. [33] proposed a new benchmark for RAW object detection in driving scenes and demonstrated the important influence of dynamic range on the detector." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.847, + 0.812, + 0.864 + ], + "angle": 0, + "content": "2.2. sRGB-to-RAW Image De-rendering" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "There are generally two categories of single image sRGB-to-RAW de-rendering methods, based on whether metadata" + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25660" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.093, + 0.173, + 0.105 + ], + "angle": 0, + "content": "is used or not." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.107, + 0.468, + 0.272 + ], + "angle": 0, + "content": "De-rendering without metadata. Such methods are often designed for a specific camera or for vision tasks that require imprecise de-rendering. For example, Brooks et al. [2] proposed a generic process to model and invert the key steps of ISP. They then used synthesized RAW data to train a denoising network. Conde et al. [7] improved upon the aforementioned method by modeling the ISP steps as a learnable dictionary. The work in [31] introduced the normalizing flow to this task, relying on the inherent reversibility of this structure. It is approximated by a two-way process of learning rendering and de-rendering." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.273, + 0.468, + 0.559 + ], + "angle": 0, + "content": "De-rendering with metadata. For metadata-based methods, the typical approach is to reconstruct the complete RAW image by saving a small amount of sampled data. Yuan and Sun [38] proposed a hybrid capture mode that reduces storage costs and continuous shooting burdens by saving low-resolution RAW images. The method described in [23] saves a small number of uniformly sampled pixels as metadata during capture, and uses RBF interpolation to obtain the full-resolution image during the reconstruction phase. Subsequently, [19] proposed a content-aware superpixel prediction network to improve the sampling strategy, while [14] introduced more expressive implicit neural functions to replace the RBF interpolation algorithm and achieve better performance. In addition to sampling-based methods, Nguyen and Brown's work [20] [21] proposed encoding the necessary parameters of ISP into an sRGB-JPEG file. The work of [27] considered an adaptive and learnable metadata construction method, which uses a compact representation of the latent space as metadata." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.56, + 0.468, + 0.635 + ], + "angle": 0, + "content": "Unlike previous single image de-rendering methods, the proposed method does not impose any additional burden on the camera side. Instead, it utilizes inter-frame relationships to guide the de-rendering process, resulting in improved performance and greater efficiency." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.649, + 0.384, + 0.666 + ], + "angle": 0, + "content": "3. RAW Video De-rendering Dataset" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.674, + 0.468, + 0.901 + ], + "angle": 0, + "content": "RAW Video De-rendering is a computer vision task that aims to reconstruct RAW video sequences using sRGB frames and other additional information. This task is valuable as it helps reduce the storage and bandwidth requirements associated with capturing RAW videos. Currently, there is a lack of a dedicated benchmark specifically designed for evaluating and developing RAW video de-rendering methods. To address this issue, we propose the introduction of the first-ever RAW Video De-rendering (RVD) benchmark. This benchmark consists of over 200 videos, captured using different devices in various scenarios. Additionally, we have included videos in challenging scenes, such as fast motion and low lighting, to provide a comprehensive evaluation of de-rendering methods even in extreme conditions. In the remaining content of this section," + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.093, + 0.882, + 0.252 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.26, + 0.892, + 0.329 + ], + "angle": 0, + "content": "Figure 2. Typical challenging scenarios of RVD dataset. (a) contains fast moving vehicles, (b) has drastic scene change, and (c) is a high-light scenario. For each video, we list the sRGB of the first two frames and the last frame, and the corresponding RAW images which are demosaiced for visualization." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.342, + 0.891, + 0.372 + ], + "angle": 0, + "content": "we will provide a detailed introduction to the Data Collection and Data Processing of the proposed benchmark." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.373, + 0.892, + 0.553 + ], + "angle": 0, + "content": "Data Collection. We collect the data used in this benchmark from two different sources. In the first part, we gather RAW-sRGB video pairs from existing RAW video-based tasks [40]. There are two reasons why we choose to reuse this data in our benchmark. Firstly, this data is of high quality, captured in various scenarios by different devices. By reusing this data, we can increase the diversity of the proposed benchmark without incurring additional data collection costs. Secondly, these datasets are widely recognized benchmarks for RAW video-based tasks, such as Video RAW Super-resolution. Therefore, this data can be easily used to evaluate the de-rendered RAW videos in these tasks." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.554, + 0.892, + 0.825 + ], + "angle": 0, + "content": "However, simply relying on the data from the existing RAW video dataset is not sufficient for evaluating the RAW video de-rendering tasks. These data are not specifically collected for this task and lack comprehensive evaluations. Therefore, we manually collected some new videos from various challenging scenarios for the RAW video de-rendering task. Specifically, we collected these RAW videos using a Canon 5D Mark III DSLR camera. All videos were shot using fixed focus lenses, specifically the Canon EF \\(50\\mathrm{mm}\\) f/1.8 STM. We used the automatic setting on the camera, where the aperture, shutter, and ISO were adjusted automatically based on the scene. Each video has a duration of 4 to 6 seconds, resulting in a total of 100 videos. The RAW videos are recorded with a resolution of \\(1600\\times 900\\) pixels at a frame rate of 30 frames per second. The camera sensor's color filter array (CFA) follows the widely used RGGB Bayer format, and the RAW data is recorded with a 14-bit depth." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.826, + 0.892, + 0.9 + ], + "angle": 0, + "content": "For the scenarios, we select some common challenges in the RAW video de-rendering task. These challenges include fast motion, high/low illumination, and more. After collecting this data, we manually label each video with the corresponding attributes. It is possible for a video to be as-" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "25661" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.317, + 0.106 + ], + "angle": 0, + "content": "signed with more than one attribute." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.108, + 0.468, + 0.289 + ], + "angle": 0, + "content": "Data Processing. Typically, different camera devices use different Image Signal Processing (ISP) types to generate sRGB images, resulting in significant variations in sRGB image quality. In order to ensure a fair comparison with previous works, we choose not to use the sRGB images produced by the camera itself. Instead, we employ a software ISP algorithm that has been widely used in previous RAW-image datasets to generate the sRGB videos. Our data processing involves two steps: converting the RAW video format data (in .MLV format for Canon 5D Mark III) into RAW image sequences, and using an external ISP algorithm to render the sRGB image sequences." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.29, + 0.468, + 0.532 + ], + "angle": 0, + "content": "For the first step, we use MLV App[1] - a professional magic lantern video processing software - to convert the RAW video into a RAW image sequence in DNG format (an open and lossless RAW image format). Since the quality of the first few frames of a handheld shot may not be very high, we delete some of the early frames. For convenience, we retain 120 consecutive frames from each video, resulting in a total of 12,000 retained images for the device. To obtain a rendered sRGB image sequence, we follow the methods described in [31] and [15]. We use the rawpy toolbox, a Python version of the LibRaw library, to process all the RAW images into PNG format using the default settings. This process includes typical operations of a modern ISP, such as demosaicking, auto white balance, denoising, gamma correction, color correction, and more. Some sample images can be seen in Figure 2." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.549, + 0.168, + 0.563 + ], + "angle": 0, + "content": "4. Method" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.575, + 0.188, + 0.589 + ], + "angle": 0, + "content": "4.1. Overview" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.599, + 0.468, + 0.644 + ], + "angle": 0, + "content": "Given a video sequence \\( x \\) from the sRGB domain, and the corresponding RAW video \\( y \\) from the RAW domain. The sRGB generation procedure \\( f \\) is:" + }, + { + "type": "equation", + "bbox": [ + 0.227, + 0.648, + 0.468, + 0.665 + ], + "angle": 0, + "content": "\\[\nx, \\varepsilon^ {\\prime} = f (y), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.667, + 0.468, + 0.711 + ], + "angle": 0, + "content": "where \\(\\varepsilon^{\\prime}\\) represents the extra data saved at capture time. And the invert function of this procedure is defined as the RAW video de-rendering task:" + }, + { + "type": "equation", + "bbox": [ + 0.222, + 0.715, + 0.468, + 0.731 + ], + "angle": 0, + "content": "\\[\ny = f ^ {- 1} (x \\mid \\varepsilon). \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.468, + 0.901 + ], + "angle": 0, + "content": "In previous works on single image RAW de-rendering, additional data \\(\\varepsilon\\) typically consists of sampled RAW pixels from the original RAW image, i.e. the metadata. This data has proven to be highly effective in recovering lost detailed information during the sRGB generation process. However, when it comes to video de-rendering, sampling additional metadata from every frame in the RAW video could impose an excessively high computational burden on the camera, making implementation difficult. To alleviate the need for extra computational burden on the camera device and boost de-rendering efficiency, we propose a new pipeline for the" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.096, + 0.885, + 0.305 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.31, + 0.892, + 0.38 + ], + "angle": 0, + "content": "Figure 3. Video capture and inference procedure. In the capture time, we save the first frame RAW image and complete sRGB sequence. In the inference phase, except for the first frame, which uses the real RAW image, the rest use the predicted RAW image from the previous frame." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.393, + 0.891, + 0.423 + ], + "angle": 0, + "content": "RAW video de-rendering. In this pipeline, we utilize the first RAW frame from the RAW video \\( y \\) as additional data:" + }, + { + "type": "equation", + "bbox": [ + 0.669, + 0.428, + 0.891, + 0.442 + ], + "angle": 0, + "content": "\\[\n\\varepsilon = y _ {1}. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.446, + 0.892, + 0.656 + ], + "angle": 0, + "content": "Figure 3 shows an overview of the proposed pipeline. When capturing the video, we only need the camera to save the sRGB frames and an additional first RAW frame, which is easily achievable. When de-rendering the RAW video, our pipeline employs a chained structure to accomplish this. Specifically, in the initialization step, our model takes sRGB frames \\( x_{1}, x_{2} \\) and the first RAW frame \\( y_{1} \\) as input and produces the well-de-rendered RAW frame \\( \\hat{y}_{2} \\) as output. In the subsequent steps, our model takes \\( x_{t}, x_{t + 1} \\), and the \\( \\hat{y}_t \\) produced in the last step as input and produces \\( \\hat{y}_{t + 1} \\) until the entire RAW video is de-rendered. As shown in this figure, the Frame Affinity Guided De-rendering Network (FAGDN) is the core of our pipeline. In the following subsection, we will provide a detailed introduction to it." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.666, + 0.889, + 0.682 + ], + "angle": 0, + "content": "4.2. Frame Affinity Guided De-rendering Network" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.892, + 0.853 + ], + "angle": 0, + "content": "Figure 4 illustrates the structure of the proposed Frame Affinity Guided De-rendering Network, which consists of two main steps. The first step is the extraction of temporal affinity priors. In this step, we combine the motion relationship between adjacent frames and the input from the previous frame RAW to construct a reference RAW. This is based on the observation that most parts of adjacent frames describe similar scenes. Therefore, the pixels in the previous RAW frame can provide accurate prior information for de-rendering the corresponding pixels in the subsequent frames." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "The second step involves spatial feature fusion and mapping. Using the reference RAW extracted in the first step as auxiliary information, we utilize an encoder-decoder struc" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "25662" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.087, + 0.093, + 0.878, + 0.363 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.365, + 0.893, + 0.437 + ], + "angle": 0, + "content": "Figure 4. Overview of the proposed Frame Affinity Guided De-rendering network. It contains two main steps, the Temporal Affinity Prior Extraction step generates an reference RAW by utilizing the motion information between adjacent frames. Here, we evaluate the quality of reference RAW through a confidence map. The second step is Spatial Feature Fusion and Mapping, using the reference RAW as starting status, we learn a pixel-level mapping function with the help of sRGB image and previous frames to further repair pixels predicted inaccurately in the first stage." + }, + { + "type": "image", + "bbox": [ + 0.079, + 0.451, + 0.169, + 0.507 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.102, + 0.507, + 0.142, + 0.516 + ], + "angle": 0, + "content": "(a) sRGB" + }, + { + "type": "image", + "bbox": [ + 0.172, + 0.452, + 0.26, + 0.506 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.182, + 0.507, + 0.251, + 0.516 + ], + "angle": 0, + "content": "(b) Optical Flow" + }, + { + "type": "image", + "bbox": [ + 0.266, + 0.452, + 0.357, + 0.506 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.274, + 0.507, + 0.351, + 0.516 + ], + "angle": 0, + "content": "(c) Warping sRGB" + }, + { + "type": "image", + "bbox": [ + 0.358, + 0.452, + 0.469, + 0.506 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.376, + 0.507, + 0.435, + 0.516 + ], + "angle": 0, + "content": "(d) Error Map" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.525, + 0.47, + 0.582 + ], + "angle": 0, + "content": "Figure 5. From left to right are the sRGB image \\( x_{t} \\), the optical flow image \\( o_{t\\rightarrow t + 1} \\), the warping sRGB image \\( \\tilde{x}_{t + 1} \\) and the error map of \\( \\tilde{x}_{t + 1} \\) and \\( x_{t + 1} \\). The red box lists errors caused by the optical flow algorithm." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.595, + 0.469, + 0.699 + ], + "angle": 0, + "content": "ture to learn a mapping function of sRGB-to-RAW by incorporating the previous frame. To effectively utilize the scene-specific and position-specific prior information encoded in the previous frame, we introduce a Global and Local Feature Aggregation (GLA) module. This module is integrated with the encoder-decoder network, which will be further discussed later." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.7, + 0.469, + 0.806 + ], + "angle": 0, + "content": "Temporal Affinity Prior Extraction. In order to take full advantage of the temporal relationship between the adjacent frames, we need to generate the affinity between two frames. We accomplish this by using an off-the-shelf optical flow algorithm \\(\\Theta\\) [32]. This algorithm takes the sRGB frames \\((x_{t}, x_{t+1})\\) as input and produces the transfer matrix \\(o_{t \\to t+1}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.194, + 0.806, + 0.469, + 0.822 + ], + "angle": 0, + "content": "\\[\no _ {t \\rightarrow t + 1} = \\Theta \\left(x _ {t}, x _ {t + 1}\\right). \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.827, + 0.469, + 0.872 + ], + "angle": 0, + "content": "Using this transfer matrix and the previous RAW image \\( y_{t} \\) we can apply a wrapping technique to generate a warping RAW image \\( \\tilde{y}_{t + 1} \\) as an reference RAW:" + }, + { + "type": "equation", + "bbox": [ + 0.195, + 0.881, + 0.469, + 0.898 + ], + "angle": 0, + "content": "\\[\n\\tilde {y} _ {t + 1} = \\Omega \\left(y _ {t}, o _ {t \\rightarrow t + 1}\\right), \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.454, + 0.892, + 0.502 + ], + "angle": 0, + "content": "where \\(\\Omega\\) represents a warping function that applies an offset to the original pixels to obtain new coordinates. It then completes the image using an interpolation algorithm." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.507, + 0.893, + 0.688 + ], + "angle": 0, + "content": "However, there is a natural limitation where some pixels in the subsequent frame do not have corresponding pixels in the previous frame, making the reference pixels unreliable. Figure 5 illustrates a typical example of this limitation. To overcome this issue, we propose generating a confidence map to suppress areas where matching errors occur and select reliable reference features from the reference RAW frame. This generation process is based on the observation that regions with matching errors result in high error values when warping the sRGB image, as shown in Figure 5 (d). Subsequently, we utilize a multi-layer convolutional network to generate the confidence map \\( M \\):" + }, + { + "type": "equation", + "bbox": [ + 0.597, + 0.691, + 0.794, + 0.726 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\tilde {x} _ {t + 1} = \\Omega \\left(x _ {t}, o _ {t \\rightarrow t + 1}\\right), \\\\ M = \\sigma (\\operatorname {c o n v} ([ \\tilde {x} _ {t + 1}, x _ {t + 1} ])), \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.728, + 0.892, + 0.789 + ], + "angle": 0, + "content": "where, the \\( conv \\) and \\( \\sigma \\) represent the convolutional network and sigmoid function, respectively. The reference RAW image \\( \\tilde{y}_{t+1} \\) and confidence map \\( M \\) will be fed to the second step for accurate RAW image reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.893, + 0.9 + ], + "angle": 0, + "content": "Spatial Feature Fusion and Mapping. Using the current sRGB frame and reference RAW, we develop a neural network that learns the final RAW image de-rendering process. Following the previous method for sRGB-to-RAW de-rendering [19], we utilize an encoder-decoder structure, specifically U-Net [24] like structure, to learn the mapping function in an end-to-end manner." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "25663" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.09, + 0.468, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.275, + 0.47, + 0.332 + ], + "angle": 0, + "content": "Figure 6. The implementation of Global and Local Feature Aggregation(GLA) module. Global information guidance models the dependencies between all patches, while local information guidance limits the relationship modeling within each pair of patches." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.345, + 0.47, + 0.586 + ], + "angle": 0, + "content": "However, the mapping function often presents two types of challenges. Firstly, the sRGB-to-RAW mapping is scene-specific, meaning that even the same RAW pixel can be mapped to different sRGB values under different scenes. Secondly, the sRGB-to-RAW mapping is position-specific, as described in [23], due to local operations in the ISP. This means that the same RAW value can be mapped to different sRGB values even within a single image. Therefore, our structure includes two branches in the encoder. The first branch takes the current frame information \\([x_{t + 1},\\tilde{y}_{t + 1},M]\\) as input, providing realistic information about the current status, such as lighting conditions and object position. The second branch takes the previous frame input \\([x_t,y_t]\\), aiming to extract global (scene-specific) and local (position-specific) prior information from the previous RAW and sRGB pair." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.587, + 0.47, + 0.647 + ], + "angle": 0, + "content": "As shown in Figure 4, we utilize two encoder networks to extract deep features from the two input branches individually. These branches have identical structures but do not share parameters:" + }, + { + "type": "equation", + "bbox": [ + 0.156, + 0.651, + 0.468, + 0.687 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} f _ {l} ^ {r} = \\operatorname {E n c o d e r} _ {\\text {r e f}} ([ x _ {t}, y _ {t} ]), \\\\ f _ {l} ^ {c} = \\operatorname {E n c o d e r} _ {\\mathrm {c u r}} ([ x _ {t + 1}, y _ {t + 1}, M ]), \\tag {7} \\\\ \\end{array}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.69, + 0.471, + 0.901 + ], + "angle": 0, + "content": "where Encoder represents encoder network. The intermediate features are denoted as \\( f_{l}^{r} \\) and \\( f_{l}^{c} \\), where \\( l \\) indexes the layer of the network. To efficiently utilize the features of the previous frame from global and local perspectives, we propose a global and local feature aggregation module, as shown in Figure 6. Specifically, for the feature \\( f_{l}^{r} \\in \\mathbb{R}^{C \\times H \\times W} \\) and \\( f_{l}^{c} \\in \\mathbb{R}^{C \\times H \\times W} \\), we divide them into non-overlapping patches with a size of \\( C \\times p \\times p \\). To introduce scene-related features from a global perspective, we embed each patch as a vector, forming a sequence of length \\( \\frac{HW}{p^2} \\). Similar to the transformer approach[26], we use the embedding vector of the current frame as the Query and the embedding vector of the previous frame as the Key to learn an affinity matrix. This matrix is then used to ex" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.243 + ], + "angle": 0, + "content": "tract global relevant information from the previous frame features (Value). For local information guidance, we implement information interaction within each patch pair. Similarly, we still use the current frame as the Query vector to model pixel-level dependencies. The information interaction within the patch allows the network to pay attention to neighboring pixels, making use of the video characteristics and reducing computational cost. Finally, the global and local supplementary information is added to each layer of the Encodercur sequentially." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.244, + 0.892, + 0.349 + ], + "angle": 0, + "content": "During the decoding stage, we use an equal number of convolutional and sampling layers to gradually merge features and restore resolution. At the same time, we incorporate the multi-level features of the current encoder \\((\\mathrm{Encoder}_{\\mathrm{cur}})\\) into the decoding process through skip connections. The resulting output of the decoder is considered the final reconstructed RAW image \\((\\hat{y}_{t + 1})\\)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.35, + 0.892, + 0.456 + ], + "angle": 0, + "content": "Loss Function. The overall network is trained in an end-to-end manner, using \\(\\ell\\), the combination of \\(L_{2}\\) loss and SSIM [28] loss, to measure the accuracy of the reconstructed RAW. In addition to supervising the output of the last layer of the decoder, we also impose additional constraints on the intermediate features. The entire loss function can be expressed by the following formula:" + }, + { + "type": "equation", + "bbox": [ + 0.549, + 0.459, + 0.892, + 0.499 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\ell \\left(\\hat {y} _ {t + 1}, y _ {t + 1}\\right) + \\lambda \\sum_ {n = 1} ^ {3} \\ell \\left(\\hat {y} _ {t + 1} ^ {n}, y _ {t + 1} ^ {n}\\right). \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.501, + 0.892, + 0.576 + ], + "angle": 0, + "content": "\\(\\hat{y}_{t+1}^n\\) denotes the output of different levels of the decoder, while \\(y_{t+1}^n\\) is the downsampled image of the ground truth, maintaining the same resolution. \\(\\lambda\\) is a hyperparameter used to balance the contribution of the auxiliary loss and is set to 0.5." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.593, + 0.633, + 0.61 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.619, + 0.691, + 0.635 + ], + "angle": 0, + "content": "5.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.643, + 0.892, + 0.824 + ], + "angle": 0, + "content": "Dataset. We conduct experiments on the proposed RVD dataset. For convenience, we call the actually collected data RVD-Part1, and the data collected from [40] is called RVD-Part2. For RVD-Part1, we carefully select 15 videos (including difficult scenes such as fast motion, drastic scene changes, HDR) for testing, and remaining 85 videos for training. Each video is 120 frames with \\(1600 \\times 900\\) resolution. For the RVD-part2, we maintain the original division of training sets and test sets. Specifically, the training set contains 130 videos, each video has about 50 frames, and a total of 6308 images. The testing set has 20 videos, and 983 images. All images have resolution \\(1440 \\times 640\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Implementation details. We are committed to converting sRGB to the original RAW data, which has not undergone any ISP operations such as demosaic and AWB. As a common practice, we package the single-channel RAW data into a four-channel [R, Gr, Gb, B] format, which serves as the" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25664" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.122, + 0.09, + 0.852, + 0.194 + ], + "angle": 0, + "content": "
MethodPub.YearMetadataRVD-Part1RVD-Part2
PSNR ↑SSIM ↑PSNR ↑SSIM ↑
CAM [19]CVPR2022✓41.850.983242.250.9856
CAM w/ fine-tuning [19]CVPR2022✓41.870.983642.260.9858
INF [14]CVPR2023✓47.670.994846.250.9939
Ours--X48.860.998049.710.9983
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.197, + 0.895, + 0.226 + ], + "angle": 0, + "content": "Table 1. Quantitative comparison with sRGB-to-RAW image de-rendering methods on the proposed RVD dataset. The \\(\\uparrow\\) represents that the larger the value, the better, and best results are marked in bold." + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.234, + 0.229, + 0.302 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.303, + 0.228, + 0.37 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.081, + 0.371, + 0.228, + 0.425 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.427, + 0.228, + 0.481 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.135, + 0.482, + 0.176, + 0.494 + ], + "angle": 0, + "content": "sRGB" + }, + { + "type": "image", + "bbox": [ + 0.235, + 0.234, + 0.383, + 0.301 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.235, + 0.303, + 0.383, + 0.37 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.235, + 0.371, + 0.383, + 0.425 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.235, + 0.426, + 0.382, + 0.479 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.297, + 0.481, + 0.319, + 0.493 + ], + "angle": 0, + "content": "GT" + }, + { + "type": "image", + "bbox": [ + 0.389, + 0.234, + 0.538, + 0.301 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.389, + 0.303, + 0.537, + 0.37 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.389, + 0.371, + 0.537, + 0.425 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.389, + 0.426, + 0.537, + 0.479 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.402, + 0.481, + 0.529, + 0.495 + ], + "angle": 0, + "content": "CAM w/ fine-tuning" + }, + { + "type": "image", + "bbox": [ + 0.543, + 0.234, + 0.692, + 0.301 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.543, + 0.303, + 0.692, + 0.37 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.543, + 0.371, + 0.692, + 0.425 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.543, + 0.426, + 0.692, + 0.48 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.603, + 0.482, + 0.628, + 0.493 + ], + "angle": 0, + "content": "INF" + }, + { + "type": "image", + "bbox": [ + 0.697, + 0.234, + 0.895, + 0.301 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.697, + 0.303, + 0.895, + 0.37 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.697, + 0.371, + 0.895, + 0.425 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.697, + 0.426, + 0.895, + 0.48 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.756, + 0.482, + 0.789, + 0.493 + ], + "angle": 0, + "content": "Ours" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.501, + 0.893, + 0.53 + ], + "angle": 0, + "content": "Figure 7. Visual comparison with sRGB-to-RAW image de-rendering methods. We calculate the pixel-level error maps of different methods and GT, and the RAW images are demosaiced for visualization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.543, + 0.473, + 0.756 + ], + "angle": 0, + "content": "basic format for training and inference. It is also easy to unpack it back to single-channel RAW for downstream tasks. The proposed method is implemented using the PyTorch framework. During training, we randomly crop patches of size \\(256 \\times 256\\) from the original input and apply random rotation and flipping as data augmentation techniques. The model is optimized using the Adam optimizer, with an initial learning rate of \\(1e - 3\\). The learning rate is reduced to one-tenth every 20 epochs. We train the model for a total of 60 epochs and select the model from the last epoch for testing. During testing, we maintain the original resolution of the image as the input. Considering the differences in sensors among different devices, we train and test the model separately on each subset." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.77, + 0.47, + 0.788 + ], + "angle": 0, + "content": "5.2. Comparison with Image De-rendering Methods" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.9 + ], + "angle": 0, + "content": "Since our method is the first proposed for sRGB-to-RAW video de-rendering, we compare it with state-of-the-art sRGB-to-RAW image de-rendering methods: CAM [19], CAM with fine-tuning [19], and INF [14]. The source code of these methods has been made public, and since most of the sRGB-to-RAW methods are camera-dependent, we retrain and test on the new dataset." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.543, + 0.895, + 0.772 + ], + "angle": 0, + "content": "Table 1 illustrates the quantitative comparison results of different methods. We use peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) metrics to evaluate the quality of reconstructed RAW. The results demonstrate that the proposed method achieves the best performance, even when compared to per-image metadata-based methods. Moreover, we also compute the pixel-wise difference between the reconstructed RAW and the ground truth to visually compare the performance of different methods, which can be seen in Figure 7. Overall, our method achieves satisfactory results in most scenarios. We also notice that the sampling-based method INF obtains comparable results to our method but performs poorly in the edge areas of objects. This means that interpolation-based functions have difficulty processing areas with large gradient changes." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.785, + 0.859, + 0.803 + ], + "angle": 0, + "content": "5.3. Comparison under Challenging Scenarios" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.895, + 0.903 + ], + "angle": 0, + "content": "In the actual photography process, the camera faces complex and diverse scenes. Therefore, we aim to explore the robustness of the model in different challenging scenarios. Low resolution is a common phenomenon in post-processing or when using low-cost storage. Previous research [14] has shown that sampling-based methods tend" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25665" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.112, + 0.089, + 0.434, + 0.208 + ], + "angle": 0, + "content": "
ConditionMethodPSNRSSIM
Low resolutionOurs47.900.9978
INF45.500.9944
Fast motionOurs46.360.9976
INF45.790.9936
Dark lightingOurs53.600.9989
INF51.420.9969
" + }, + { + "type": "table_caption", + "bbox": [ + 0.08, + 0.212, + 0.466, + 0.227 + ], + "angle": 0, + "content": "Table 2. Comparison under challenging scenarios on RVD-Part1." + }, + { + "type": "table", + "bbox": [ + 0.112, + 0.241, + 0.436, + 0.339 + ], + "angle": 0, + "content": "
warpingMGLA\\( \\ell_{aux} \\)PSNRSSIM
✓✓42.600.9972
✓✓✓47.680.9978
✓✓✓46.120.9979
✓✓✓47.910.9983
✓✓✓✓49.710.9983
" + }, + { + "type": "table_caption", + "bbox": [ + 0.134, + 0.343, + 0.411, + 0.357 + ], + "angle": 0, + "content": "Table 3. Ablation study on RVD-Part2 dataset." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.37, + 0.473, + 0.612 + ], + "angle": 0, + "content": "to be sensitive to resolution. To test the performance of our method and INF, we construct a low-resolution version by downsampling the original dataset to half the resolution. The results indicate that our method is more robust to resolution changes, with a \\(1.8\\%\\) PSNR drop compared to the \\(4.6\\%\\) drop observed in INF. Fast motion is often regarded as a challenging scene for our method, as the first RAW frame only provides limited information for subsequent RAW reconstruction. In comparison to INF, our method shows a gain of \\(1.2\\%\\) in the fast motion scene, which is lower than the \\(2.3\\%\\) gain observed on the full test set. This suggests that fast motion still poses a challenge for our method. Dark lighting is a typical harsh environment for shooting. However, our research has found that it is not actually difficult for the sRGB-to-RAW methods, as the recovery quality in these scenarios is well above average." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.621, + 0.23, + 0.637 + ], + "angle": 0, + "content": "5.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.644, + 0.47, + 0.811 + ], + "angle": 0, + "content": "We conduct ablation experiments to verify the effectiveness of key designs in the proposed method, and the quantitative results are shown in Table 3. We first investigate the role of the temporal affinity prior extraction, which generates a reference RAW image by utilizing the motion information. We remove this step and directly input the sRGB image \\( x_{t+1} \\) into Encoders to do the verification. The results in first line show this step is all-important to our pipeline, that is, PSNR decreased by 6.17. The second line represents that we do not consider the quality of the RAW and directly input the reference RAW image \\( \\tilde{y}_{t+1} \\) to the next stage." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.471, + 0.903 + ], + "angle": 0, + "content": "In the spatial feature fusion and mapping step, the previous frame provides global and local supplementary information for image reconstruction by the GLA module. To demonstrate the necessity of introducing a previous frame into this step, we remove the previous frame encoder \\(\\mathrm{Encoder}_{\\mathrm{ref}}\\) and directly learn the mapping function from the" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.09, + 0.691, + 0.208 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.09, + 0.888, + 0.208 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.532, + 0.211, + 0.859, + 0.226 + ], + "angle": 0, + "content": "Figure 8. Average PSNR and SSIM in time dimension." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.235, + 0.892, + 0.298 + ], + "angle": 0, + "content": "current frame inputs. The result can be seen in the third line of Table 3. Furthermore, we add the auxiliary loss function to constraint the intermediate outputs, and the results can be seen in the fourth line when deleting it from the pipeline." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.306, + 0.706, + 0.321 + ], + "angle": 0, + "content": "5.5. Robustness over Time" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.329, + 0.892, + 0.452 + ], + "angle": 0, + "content": "Our method relies on the first frame RAW to provide real reference information in the chained inference phase. However, as time increases, there will inevitably be accumulated information loss. In Figure 8, we calculate the average PSNR \\((psnr^i = (\\sum_{v=1}^{V} psnr_v^i) / V)\\) and SSIM \\((ssim^i = (\\sum_{v=1}^{V} ssim_v^i) / V)\\) along the time dimension. Here, \\(i \\in [2,120]\\) indexes the order of frames, and \\(V\\) represents the number of all testing videos." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.453, + 0.893, + 0.62 + ], + "angle": 0, + "content": "As depicted in the curve, our method exhibits good robustness over time within a relatively long period of 100 frames. In comparison to INF, the method based on single-image metadata, our method still maintains a relatively high quality. However, the performance noticeably declines when the period becomes too long. This phenomenon is attributed to the inherent characteristics of our method. As an optional solution and for future work, we intend to investigate a previous frame selection strategy. This strategy would involve saving reference RAW frames at intervals to achieve a stable reconstruction quality." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.634, + 0.619, + 0.65 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.659, + 0.892, + 0.901 + ], + "angle": 0, + "content": "In this paper, we introduce a new task called sRGB-to-RAW video de-rendering. Existing methods for converting sRGB images to RAW format are not applicable when applied to the new video de-rendering task. To address this, we propose a frame affinity guided reconstructed network with two main steps. The first step involves extracting temporal affinity prior by utilizing motion information between adjacent frames to obtain a reference RAW image. The second step focuses on spatial feature fusion and mapping, where a pixel-level mapping function is learned using scene-specific and position-specific prior information from the previous frame. To evaluate our proposed method, we create a benchmark dataset that includes a wide range of RAW-sRGB videos. Experimental results on this dataset demonstrate the superior reconstruction quality achieved by our method." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "25666" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.091, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.088, + 0.116, + 0.21, + 0.129 + ], + "angle": 0, + "content": "[1] https://mlv.app/." + }, + { + "type": "ref_text", + "bbox": [ + 0.088, + 0.129, + 0.47, + 0.196 + ], + "angle": 0, + "content": "[2] Tim Brooks, Ben Mildenhall, Tianfan Xue, Jiawen Chen, Dillon Sharlet, and Jonathan T Barron. Unprocessing images for learned raw denoising. 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In Proceedings of the IEEE/CVF International Conference on Computer Vision, pages 4593-4601, 2021." + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.892, + 0.229 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.518, + 0.956 + ], + "angle": 0, + "content": "25668" + } + ] +] \ No newline at end of file diff --git a/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_origin.pdf b/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..447aad07499b674af581e4c835c1032867ae8557 --- /dev/null +++ b/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/e20bf1ce-fabe-4b72-8cff-e86075845d22_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:0b8f743275fcfe1bf81c0ebb13fad798e5a8238a85c12239369db020e9ec4a23 +size 5025394 diff --git a/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/full.md b/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/full.md new file mode 100644 index 0000000000000000000000000000000000000000..0cdd54c09c171f3f5a1861e5cc27c00475776a19 --- /dev/null +++ b/2024/Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering/full.md @@ -0,0 +1,340 @@ +# Leveraging Frame Affinity for sRGB-to-RAW Video De-rendering + +Chen Zhang $^{1*}$ , Wencheng Han $^{2*}$ , Yang Zhou $^{1}$ , Jianbing Shen $^{2\dagger}$ , Cheng-zhong Xu $^{2}$ , Wentao Liu $^{1\dagger}$ $^{1}$ SenseTime Research and Tetras.AI, $^{2}$ SKL-IOTSC, CIS, University of Macau. + +zhangchen2@tetras.ai{wencheng256, shenjiangbingcg}@gmail.com {zhouyang, liuwentao}@sensetime.com czxu@um.edu.mo + +# Abstract + +Unprocessed RAW video has shown distinct advantages over sRGB video in video editing and computer vision tasks. However, capturing RAW video is challenging due to limitations in bandwidth and storage. Various methods have been proposed to address similar issues in single image RAW capture through de-rendering. These methods utilize both the metadata and the sRGB image to perform sRGB-to-RAW de-rendering and recover high-quality single-frame RAW data. However, metadata-based methods always require additional computation for online metadata generation, imposing severe burden on mobile camera device for high frame rate RAW video capture. To address this issue, we propose a framework that utilizes frame affinity to achieve high-quality sRGB-to-RAW video reconstruction. Our approach consists of two main steps. The first step, temporal affinity prior extraction, uses motion information between adjacent frames to obtain a reference RAW image. The second step, spatial feature fusion and mapping, learns a pixel-level mapping function using scene-specific and position-specific features provided by the previous frame. Our method can be easily applied to current mobile camera equipment without complicated adaptations or added burden. To demonstrate the effectiveness of our approach, we introduce the first RAW Video De-rendering Benchmark. In this benchmark, our method outperforms state-of-the-art RAW image reconstruction methods, even without image-level metadata. + +# 1. Introduction + +In recent years, RAW videos have become increasingly popular among professional videographers due to their ability to capture unprocessed signals from the camera at a 10-16 + +![](images/94ff3dff4faa8bce0937ef7b3b17dde41db141efb07ff7d526ae37a4bf0b1bb0.jpg) +(a) RAW video capturing procedure + +![](images/27d7935ca505f2e9245f64bd7d38ab1d402d279d77c5eec5ff9d2f03398a867b.jpg) +(b) Meta-data based method + +![](images/0d15c1adc76b1127e901137ba88408e1280bd5bccb15202210d58c59ce8d5558.jpg) +(c) Our method +Figure 1. Comparison of Different RAW Video Capture Methods. (a) Saving the entire RAW video would cause significant strain on bandwidth and storage resources. (b) Sampling metadata for every frame in the video would burden the camera's computation. (c) Our method only requires saving a single extra RAW frame, which does not significantly burden the camera. + +bit depth. This enables the production of video sequences with superior visual effects compared to sRGB videos. In addition, recent research has explored the benefits of using RAW data in computer vision tasks. Some studies have discovered that the linear relationship between scene irradiance and RAW data is better suited for tasks such as image denoising [2, 9, 12, 39], image super-resolution [7, 13, 34, 40], and low-light enhancement [5, 8, 11]. Additionally, the wide tolerance of RAW data makes perception tasks more robust in high-dynamic scenes [6, 22, 33, 36]. However, the high cost of RAW video capturing limits the widespread use of this technology. On one hand, the abundant and detailed information encoded in the RAW data takes up a huge amount of storage, increasing storage costs for users. On the other hand, real-time capturing of RAW video data puts a significant strain on the camera's bandwidth, as shown in Figure 1 (a). + +To address similar issues, many techniques have been + +proposed for de-rendering single-frame sRGB images to RAW data. Some approaches utilize only the sRGB data as input and learn to recover the corresponding RAW data [2, 7, 31]. These methods are convenient for various applications, as they do not require any additional information from the camera besides the sRGB images. However, since some critical information may have been lost during the ISP processing, the de-rendering from only sRGB inputs still suffers from limited performance. In contrast, other methods attempt to extract a small portion of crucial information from the RAW data as metadata and learn to recover the original RAW images from both the sRGB images and the metadata [14, 19, 23, 27]. Although these methods can produce more accurate RAW images, they require an additional sampling method to run on the camera for producing the metadata. These sampling techniques impose additional pressure on the camera, and the burden will be much more severe for RAW video capturing. The complexity of sampling metadata from RAW video is $O(WHL)$ , where $W$ and $H$ are the width and height of the image, and $L$ is the length of the video sequence, as shown in Figure 1 (b). + +This paper presents a novel approach for RAW video de-rendering, which overcomes the limitations of previous methods and enhances storage and computation efficiency. Unlike metadata-based approaches, our method eliminates the need for an online sampler on the camera side. Instead, it utilizes a single RAW frame from the video sequence as prior information to efficiently recover detailed information from the RAW data, as depicted in Figure 1 (c). The additional select operation only incurs $O(1)$ extra computation cost. Specifically, our method utilizes the provided RAW frame and the relationship between adjacent frames to guide the reconstruction of the remaining RAW frames. By designing a deep neural network with Temporal Affinity Prior Extraction and Spatial Feature Fusion and Mapping, our method effectively leverages the prior information from the previous frame and efficiently de-renders the RAW video. + +To assess the effectiveness of our proposed method, we introduce the first RAW Video De-rendering benchmark, the RVD dataset. We then evaluate the performance of the proposed method and compare it with other sRGB-to-RAW de-rendering methods. The results demonstrate that our method can produce high-fidelity RAW video sequences and outperform other methods, without relying on per-image metadata. In conclusion, the contributions we have made in this paper can be summarized into five points: + +- We propose a new architecture for RAW video de- rendering. This architecture can efficiently de-render RAW video sequences using only one RAW frame and sRGB videos as input. By adopting this method, both storage and computation efficiency for RAW video capturing can be significantly improved. +- We propose a module for extracting a temporal affinity + +prior to obtain a reliable reference RAW frame. This module utilizes motion information between adjacent frames. The reference RAW frame can accurately serve as a reference for recovering the lost RAW information. + +- We propose a module called Global and Local feature Aggregation (GLA) to extract and combine the globalized and localized features encoded in the prior information. +- We propose a new benchmark for RAW video de-earning to comprehensively evaluate the methods for this task. To our knowledge, this is the first benchmark specifically designed for the RAW video de-rendering task. +- Our method significantly outperforms state-of-the-art image RAW de-rendering methods and achieves high-quality RAW video sequences without relying on per-image metadata. + +# 2. Related work + +# 2.1. RAW Data Application + +RAW data, as a direct capture of raw information from a scene by a camera, has long been favored by computational photography and certain low-level vision tasks. These tasks include image super-resolution [7, 16, 30, 40], image denoising [2, 9, 10, 41-43], image deblur [4, 15], and low-light enhancement [5, 8, 11]. The main advantage of RAW data is that it is not processed by ISP (Image Signal Processor) and its response value has a linear relationship with scene irradiance. This simplifies the modeling process for degradation or enhancement models. + +Recently, the advantages of RAW in visual perception tasks have been gradually discovered and explored. One basic point is that high-bit-depth RAW data retains more scene information. Another point is that ISP processing does not always have a positive effect. In the early stages, the work in [3, 17, 29, 35] examined the role of the ISP pipeline in computer vision tasks. An interesting conclusion is that most ISP processing is focused on improving visual effects and has little to do with the DNN model, and may even have a negative impact. Furthermore, some methods [18, 25, 37] used proxy networks or parameter searching to redefine ISP as a learnable process, improving the performance of RAW data in downstream tasks. The work in [6] focused on the instance segmentation task in dark scenes, and its results show that higher bit-depth is usually associated with better segmentation results. Xu et al. [33] proposed a new benchmark for RAW object detection in driving scenes and demonstrated the important influence of dynamic range on the detector. + +# 2.2. sRGB-to-RAW Image De-rendering + +There are generally two categories of single image sRGB-to-RAW de-rendering methods, based on whether metadata + +is used or not. + +De-rendering without metadata. Such methods are often designed for a specific camera or for vision tasks that require imprecise de-rendering. For example, Brooks et al. [2] proposed a generic process to model and invert the key steps of ISP. They then used synthesized RAW data to train a denoising network. Conde et al. [7] improved upon the aforementioned method by modeling the ISP steps as a learnable dictionary. The work in [31] introduced the normalizing flow to this task, relying on the inherent reversibility of this structure. It is approximated by a two-way process of learning rendering and de-rendering. + +De-rendering with metadata. For metadata-based methods, the typical approach is to reconstruct the complete RAW image by saving a small amount of sampled data. Yuan and Sun [38] proposed a hybrid capture mode that reduces storage costs and continuous shooting burdens by saving low-resolution RAW images. The method described in [23] saves a small number of uniformly sampled pixels as metadata during capture, and uses RBF interpolation to obtain the full-resolution image during the reconstruction phase. Subsequently, [19] proposed a content-aware superpixel prediction network to improve the sampling strategy, while [14] introduced more expressive implicit neural functions to replace the RBF interpolation algorithm and achieve better performance. In addition to sampling-based methods, Nguyen and Brown's work [20] [21] proposed encoding the necessary parameters of ISP into an sRGB-JPEG file. The work of [27] considered an adaptive and learnable metadata construction method, which uses a compact representation of the latent space as metadata. + +Unlike previous single image de-rendering methods, the proposed method does not impose any additional burden on the camera side. Instead, it utilizes inter-frame relationships to guide the de-rendering process, resulting in improved performance and greater efficiency. + +# 3. RAW Video De-rendering Dataset + +RAW Video De-rendering is a computer vision task that aims to reconstruct RAW video sequences using sRGB frames and other additional information. This task is valuable as it helps reduce the storage and bandwidth requirements associated with capturing RAW videos. Currently, there is a lack of a dedicated benchmark specifically designed for evaluating and developing RAW video de-rendering methods. To address this issue, we propose the introduction of the first-ever RAW Video De-rendering (RVD) benchmark. This benchmark consists of over 200 videos, captured using different devices in various scenarios. Additionally, we have included videos in challenging scenes, such as fast motion and low lighting, to provide a comprehensive evaluation of de-rendering methods even in extreme conditions. In the remaining content of this section, + +![](images/253b820f3739df1dec478b79c7e0f58a5432c0596e5cc263380649932378f711.jpg) +Figure 2. Typical challenging scenarios of RVD dataset. (a) contains fast moving vehicles, (b) has drastic scene change, and (c) is a high-light scenario. For each video, we list the sRGB of the first two frames and the last frame, and the corresponding RAW images which are demosaiced for visualization. + +we will provide a detailed introduction to the Data Collection and Data Processing of the proposed benchmark. + +Data Collection. We collect the data used in this benchmark from two different sources. In the first part, we gather RAW-sRGB video pairs from existing RAW video-based tasks [40]. There are two reasons why we choose to reuse this data in our benchmark. Firstly, this data is of high quality, captured in various scenarios by different devices. By reusing this data, we can increase the diversity of the proposed benchmark without incurring additional data collection costs. Secondly, these datasets are widely recognized benchmarks for RAW video-based tasks, such as Video RAW Super-resolution. Therefore, this data can be easily used to evaluate the de-rendered RAW videos in these tasks. + +However, simply relying on the data from the existing RAW video dataset is not sufficient for evaluating the RAW video de-rendering tasks. These data are not specifically collected for this task and lack comprehensive evaluations. Therefore, we manually collected some new videos from various challenging scenarios for the RAW video de-rendering task. Specifically, we collected these RAW videos using a Canon 5D Mark III DSLR camera. All videos were shot using fixed focus lenses, specifically the Canon EF $50\mathrm{mm}$ f/1.8 STM. We used the automatic setting on the camera, where the aperture, shutter, and ISO were adjusted automatically based on the scene. Each video has a duration of 4 to 6 seconds, resulting in a total of 100 videos. The RAW videos are recorded with a resolution of $1600\times 900$ pixels at a frame rate of 30 frames per second. The camera sensor's color filter array (CFA) follows the widely used RGGB Bayer format, and the RAW data is recorded with a 14-bit depth. + +For the scenarios, we select some common challenges in the RAW video de-rendering task. These challenges include fast motion, high/low illumination, and more. After collecting this data, we manually label each video with the corresponding attributes. It is possible for a video to be as- + +signed with more than one attribute. + +Data Processing. Typically, different camera devices use different Image Signal Processing (ISP) types to generate sRGB images, resulting in significant variations in sRGB image quality. In order to ensure a fair comparison with previous works, we choose not to use the sRGB images produced by the camera itself. Instead, we employ a software ISP algorithm that has been widely used in previous RAW-image datasets to generate the sRGB videos. Our data processing involves two steps: converting the RAW video format data (in .MLV format for Canon 5D Mark III) into RAW image sequences, and using an external ISP algorithm to render the sRGB image sequences. + +For the first step, we use MLV App[1] - a professional magic lantern video processing software - to convert the RAW video into a RAW image sequence in DNG format (an open and lossless RAW image format). Since the quality of the first few frames of a handheld shot may not be very high, we delete some of the early frames. For convenience, we retain 120 consecutive frames from each video, resulting in a total of 12,000 retained images for the device. To obtain a rendered sRGB image sequence, we follow the methods described in [31] and [15]. We use the rawpy toolbox, a Python version of the LibRaw library, to process all the RAW images into PNG format using the default settings. This process includes typical operations of a modern ISP, such as demosaicking, auto white balance, denoising, gamma correction, color correction, and more. Some sample images can be seen in Figure 2. + +# 4. Method + +# 4.1. Overview + +Given a video sequence $x$ from the sRGB domain, and the corresponding RAW video $y$ from the RAW domain. The sRGB generation procedure $f$ is: + +$$ +x, \varepsilon^ {\prime} = f (y), \tag {1} +$$ + +where $\varepsilon^{\prime}$ represents the extra data saved at capture time. And the invert function of this procedure is defined as the RAW video de-rendering task: + +$$ +y = f ^ {- 1} (x \mid \varepsilon). \tag {2} +$$ + +In previous works on single image RAW de-rendering, additional data $\varepsilon$ typically consists of sampled RAW pixels from the original RAW image, i.e. the metadata. This data has proven to be highly effective in recovering lost detailed information during the sRGB generation process. However, when it comes to video de-rendering, sampling additional metadata from every frame in the RAW video could impose an excessively high computational burden on the camera, making implementation difficult. To alleviate the need for extra computational burden on the camera device and boost de-rendering efficiency, we propose a new pipeline for the + +![](images/13144f184cea177dbe58667dd0baf63d374106e3d7c80e392c80ee171a0e59b7.jpg) +Figure 3. Video capture and inference procedure. In the capture time, we save the first frame RAW image and complete sRGB sequence. In the inference phase, except for the first frame, which uses the real RAW image, the rest use the predicted RAW image from the previous frame. + +RAW video de-rendering. In this pipeline, we utilize the first RAW frame from the RAW video $y$ as additional data: + +$$ +\varepsilon = y _ {1}. \tag {3} +$$ + +Figure 3 shows an overview of the proposed pipeline. When capturing the video, we only need the camera to save the sRGB frames and an additional first RAW frame, which is easily achievable. When de-rendering the RAW video, our pipeline employs a chained structure to accomplish this. Specifically, in the initialization step, our model takes sRGB frames $x_{1}, x_{2}$ and the first RAW frame $y_{1}$ as input and produces the well-de-rendered RAW frame $\hat{y}_{2}$ as output. In the subsequent steps, our model takes $x_{t}, x_{t + 1}$ , and the $\hat{y}_t$ produced in the last step as input and produces $\hat{y}_{t + 1}$ until the entire RAW video is de-rendered. As shown in this figure, the Frame Affinity Guided De-rendering Network (FAGDN) is the core of our pipeline. In the following subsection, we will provide a detailed introduction to it. + +# 4.2. Frame Affinity Guided De-rendering Network + +Figure 4 illustrates the structure of the proposed Frame Affinity Guided De-rendering Network, which consists of two main steps. The first step is the extraction of temporal affinity priors. In this step, we combine the motion relationship between adjacent frames and the input from the previous frame RAW to construct a reference RAW. This is based on the observation that most parts of adjacent frames describe similar scenes. Therefore, the pixels in the previous RAW frame can provide accurate prior information for de-rendering the corresponding pixels in the subsequent frames. + +The second step involves spatial feature fusion and mapping. Using the reference RAW extracted in the first step as auxiliary information, we utilize an encoder-decoder struc + +![](images/6828309f8fa2f33cfa58ae4a669d93cd62959074d2d2c48b65b4f5b4c011a270.jpg) +Figure 4. Overview of the proposed Frame Affinity Guided De-rendering network. It contains two main steps, the Temporal Affinity Prior Extraction step generates an reference RAW by utilizing the motion information between adjacent frames. Here, we evaluate the quality of reference RAW through a confidence map. The second step is Spatial Feature Fusion and Mapping, using the reference RAW as starting status, we learn a pixel-level mapping function with the help of sRGB image and previous frames to further repair pixels predicted inaccurately in the first stage. + +![](images/6d1d15c39e269b3ac362639e9e131c77a34d0b88030e6ee21363829edb535927.jpg) +(a) sRGB +Figure 5. From left to right are the sRGB image $x_{t}$ , the optical flow image $o_{t\rightarrow t + 1}$ , the warping sRGB image $\tilde{x}_{t + 1}$ and the error map of $\tilde{x}_{t + 1}$ and $x_{t + 1}$ . The red box lists errors caused by the optical flow algorithm. + +![](images/1310ef262533212d139236465106b4407ea31e5612bfa49f84a9ab7e884aeb92.jpg) +(b) Optical Flow + +![](images/08bbdb35fc4d368a4b590a48fae0dd3394ebf130bb639c5767feb7d42d52c293.jpg) +(c) Warping sRGB + +![](images/d3b3f0fdf5f153e100dd331972ec16589ea59ce7fc799cd96c3608caa3fad28a.jpg) +(d) Error Map + +ture to learn a mapping function of sRGB-to-RAW by incorporating the previous frame. To effectively utilize the scene-specific and position-specific prior information encoded in the previous frame, we introduce a Global and Local Feature Aggregation (GLA) module. This module is integrated with the encoder-decoder network, which will be further discussed later. + +Temporal Affinity Prior Extraction. In order to take full advantage of the temporal relationship between the adjacent frames, we need to generate the affinity between two frames. We accomplish this by using an off-the-shelf optical flow algorithm $\Theta$ [32]. This algorithm takes the sRGB frames $(x_{t}, x_{t+1})$ as input and produces the transfer matrix $o_{t \to t+1}$ : + +$$ +o _ {t \rightarrow t + 1} = \Theta \left(x _ {t}, x _ {t + 1}\right). \tag {4} +$$ + +Using this transfer matrix and the previous RAW image $y_{t}$ we can apply a wrapping technique to generate a warping RAW image $\tilde{y}_{t + 1}$ as an reference RAW: + +$$ +\tilde {y} _ {t + 1} = \Omega \left(y _ {t}, o _ {t \rightarrow t + 1}\right), \tag {5} +$$ + +where $\Omega$ represents a warping function that applies an offset to the original pixels to obtain new coordinates. It then completes the image using an interpolation algorithm. + +However, there is a natural limitation where some pixels in the subsequent frame do not have corresponding pixels in the previous frame, making the reference pixels unreliable. Figure 5 illustrates a typical example of this limitation. To overcome this issue, we propose generating a confidence map to suppress areas where matching errors occur and select reliable reference features from the reference RAW frame. This generation process is based on the observation that regions with matching errors result in high error values when warping the sRGB image, as shown in Figure 5 (d). Subsequently, we utilize a multi-layer convolutional network to generate the confidence map $M$ : + +$$ +\begin{array}{l} \tilde {x} _ {t + 1} = \Omega \left(x _ {t}, o _ {t \rightarrow t + 1}\right), \\ M = \sigma (\operatorname {c o n v} ([ \tilde {x} _ {t + 1}, x _ {t + 1} ])), \\ \end{array} +$$ + +where, the $conv$ and $\sigma$ represent the convolutional network and sigmoid function, respectively. The reference RAW image $\tilde{y}_{t+1}$ and confidence map $M$ will be fed to the second step for accurate RAW image reconstruction. + +Spatial Feature Fusion and Mapping. Using the current sRGB frame and reference RAW, we develop a neural network that learns the final RAW image de-rendering process. Following the previous method for sRGB-to-RAW de-rendering [19], we utilize an encoder-decoder structure, specifically U-Net [24] like structure, to learn the mapping function in an end-to-end manner. + +![](images/5debf8583cf175ff4b200939d8c4a6aa908434eafbe6b6c700d926c19cf42caf.jpg) +Figure 6. The implementation of Global and Local Feature Aggregation(GLA) module. Global information guidance models the dependencies between all patches, while local information guidance limits the relationship modeling within each pair of patches. + +However, the mapping function often presents two types of challenges. Firstly, the sRGB-to-RAW mapping is scene-specific, meaning that even the same RAW pixel can be mapped to different sRGB values under different scenes. Secondly, the sRGB-to-RAW mapping is position-specific, as described in [23], due to local operations in the ISP. This means that the same RAW value can be mapped to different sRGB values even within a single image. Therefore, our structure includes two branches in the encoder. The first branch takes the current frame information $[x_{t + 1},\tilde{y}_{t + 1},M]$ as input, providing realistic information about the current status, such as lighting conditions and object position. The second branch takes the previous frame input $[x_t,y_t]$ , aiming to extract global (scene-specific) and local (position-specific) prior information from the previous RAW and sRGB pair. + +As shown in Figure 4, we utilize two encoder networks to extract deep features from the two input branches individually. These branches have identical structures but do not share parameters: + +$$ +\begin{array}{l} f _ {l} ^ {r} = \operatorname {E n c o d e r} _ {\text {r e f}} ([ x _ {t}, y _ {t} ]), \\ f _ {l} ^ {c} = \operatorname {E n c o d e r} _ {\mathrm {c u r}} ([ x _ {t + 1}, y _ {t + 1}, M ]), \tag {7} \\ \end{array} +$$ + +where Encoder represents encoder network. The intermediate features are denoted as $f_{l}^{r}$ and $f_{l}^{c}$ , where $l$ indexes the layer of the network. To efficiently utilize the features of the previous frame from global and local perspectives, we propose a global and local feature aggregation module, as shown in Figure 6. Specifically, for the feature $f_{l}^{r} \in \mathbb{R}^{C \times H \times W}$ and $f_{l}^{c} \in \mathbb{R}^{C \times H \times W}$ , we divide them into non-overlapping patches with a size of $C \times p \times p$ . To introduce scene-related features from a global perspective, we embed each patch as a vector, forming a sequence of length $\frac{HW}{p^2}$ . Similar to the transformer approach[26], we use the embedding vector of the current frame as the Query and the embedding vector of the previous frame as the Key to learn an affinity matrix. This matrix is then used to ex + +tract global relevant information from the previous frame features (Value). For local information guidance, we implement information interaction within each patch pair. Similarly, we still use the current frame as the Query vector to model pixel-level dependencies. The information interaction within the patch allows the network to pay attention to neighboring pixels, making use of the video characteristics and reducing computational cost. Finally, the global and local supplementary information is added to each layer of the Encodercur sequentially. + +During the decoding stage, we use an equal number of convolutional and sampling layers to gradually merge features and restore resolution. At the same time, we incorporate the multi-level features of the current encoder $(\mathrm{Encoder}_{\mathrm{cur}})$ into the decoding process through skip connections. The resulting output of the decoder is considered the final reconstructed RAW image $(\hat{y}_{t + 1})$ + +Loss Function. The overall network is trained in an end-to-end manner, using $\ell$ , the combination of $L_{2}$ loss and SSIM [28] loss, to measure the accuracy of the reconstructed RAW. In addition to supervising the output of the last layer of the decoder, we also impose additional constraints on the intermediate features. The entire loss function can be expressed by the following formula: + +$$ +\mathcal {L} = \ell \left(\hat {y} _ {t + 1}, y _ {t + 1}\right) + \lambda \sum_ {n = 1} ^ {3} \ell \left(\hat {y} _ {t + 1} ^ {n}, y _ {t + 1} ^ {n}\right). \tag {8} +$$ + +$\hat{y}_{t+1}^n$ denotes the output of different levels of the decoder, while $y_{t+1}^n$ is the downsampled image of the ground truth, maintaining the same resolution. $\lambda$ is a hyperparameter used to balance the contribution of the auxiliary loss and is set to 0.5. + +# 5. Experiments + +# 5.1. Experimental Setup + +Dataset. We conduct experiments on the proposed RVD dataset. For convenience, we call the actually collected data RVD-Part1, and the data collected from [40] is called RVD-Part2. For RVD-Part1, we carefully select 15 videos (including difficult scenes such as fast motion, drastic scene changes, HDR) for testing, and remaining 85 videos for training. Each video is 120 frames with $1600 \times 900$ resolution. For the RVD-part2, we maintain the original division of training sets and test sets. Specifically, the training set contains 130 videos, each video has about 50 frames, and a total of 6308 images. The testing set has 20 videos, and 983 images. All images have resolution $1440 \times 640$ . + +Implementation details. We are committed to converting sRGB to the original RAW data, which has not undergone any ISP operations such as demosaic and AWB. As a common practice, we package the single-channel RAW data into a four-channel [R, Gr, Gb, B] format, which serves as the + +
MethodPub.YearMetadataRVD-Part1RVD-Part2
PSNR ↑SSIM ↑PSNR ↑SSIM ↑
CAM [19]CVPR2022✓41.850.983242.250.9856
CAM w/ fine-tuning [19]CVPR2022✓41.870.983642.260.9858
INF [14]CVPR2023✓47.670.994846.250.9939
Ours--X48.860.998049.710.9983
+ +Table 1. Quantitative comparison with sRGB-to-RAW image de-rendering methods on the proposed RVD dataset. The $\uparrow$ represents that the larger the value, the better, and best results are marked in bold. + +![](images/5469e8dd8c508b42eb3b98c88cb9f3ba3029c13de645c42d7ae84c3d6c2ad945.jpg) + +![](images/d65f45571cf0a4815da4519c2ae9aaded7d4b8d45c70b34d1e84c536d298302b.jpg) + +![](images/9e62e5dd3350bdc1b3770761a905c704ef7e54334d7ca7e854a184269443139f.jpg) + +![](images/c2157c792de1d35af5aa6e9780a12fe2ab9f9995c1c4854c68d2eb1c107be557.jpg) +sRGB + +![](images/97047dbba97dec7a2fabcc8396f62e9dee70873f473026c0cb604aa6490e5364.jpg) + +![](images/27b58671a39e0e8a8a4c3d3b5cd13e6896977d5d51d23da636712079b22bf6f8.jpg) + +![](images/2fe5791090f97a2b4fc50509f67be4f478fc06700178af2a47311410cf00a5e7.jpg) + +![](images/1306b0ca31db9af6982a80393d5a08e113fec82795d4c3e30aa9c208ccbd6ce7.jpg) +GT + +![](images/29da1fe936e32d59a09058850201f350b054546a4cb0fb19c42cd76590ff44ec.jpg) + +![](images/2c30b7159179bcff850f9e75e42cf0905bb101a2244ae6ddbebfd8d2aa4c11ff.jpg) + +![](images/35707941e55cd1b456297f1b97c979bec56514a7595cceaab9907c2d42fe1a83.jpg) + +![](images/a32b065f308323642f652060b8e656105d4c64919f8c6c9b6c1bf6b32329f18d.jpg) +CAM w/ fine-tuning + +![](images/909fde616ad2b97d34de4a95b3f4753303481d87a2f7b7b847f724435a96b295.jpg) + +![](images/0f5a71cc0baf01dc8ffc554c7c207ddb07f9e22bcfb59b5111c9625aa413172f.jpg) + +![](images/25d5c6a61e6ec0dfcea3c8020bfaa27cd5bc779005fa80f878e46795423c596e.jpg) + +![](images/b0f3c98870facc2f9f80897ba2e8fd702e4a544cf594c3936f46cfde054d379c.jpg) +INF +Figure 7. Visual comparison with sRGB-to-RAW image de-rendering methods. We calculate the pixel-level error maps of different methods and GT, and the RAW images are demosaiced for visualization. + +![](images/f792df724a70b7d3d25c1e6313cadcf698708b30dd9e4692c3b0c67f03e64387.jpg) + +![](images/3ae35ccb212ebe93f984587176cef404183cbd3396384dc8385377133c09ee37.jpg) + +![](images/a13161773c191f4fde13d2200d870a74b2912687887fc5ab2db1042745687855.jpg) + +![](images/df16ff6c445d5b89ae53b6798f6a61e14bb22adc5a247a2671329193a8f1be4c.jpg) +Ours + +basic format for training and inference. It is also easy to unpack it back to single-channel RAW for downstream tasks. The proposed method is implemented using the PyTorch framework. During training, we randomly crop patches of size $256 \times 256$ from the original input and apply random rotation and flipping as data augmentation techniques. The model is optimized using the Adam optimizer, with an initial learning rate of $1e - 3$ . The learning rate is reduced to one-tenth every 20 epochs. We train the model for a total of 60 epochs and select the model from the last epoch for testing. During testing, we maintain the original resolution of the image as the input. Considering the differences in sensors among different devices, we train and test the model separately on each subset. + +# 5.2. Comparison with Image De-rendering Methods + +Since our method is the first proposed for sRGB-to-RAW video de-rendering, we compare it with state-of-the-art sRGB-to-RAW image de-rendering methods: CAM [19], CAM with fine-tuning [19], and INF [14]. The source code of these methods has been made public, and since most of the sRGB-to-RAW methods are camera-dependent, we retrain and test on the new dataset. + +Table 1 illustrates the quantitative comparison results of different methods. We use peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) metrics to evaluate the quality of reconstructed RAW. The results demonstrate that the proposed method achieves the best performance, even when compared to per-image metadata-based methods. Moreover, we also compute the pixel-wise difference between the reconstructed RAW and the ground truth to visually compare the performance of different methods, which can be seen in Figure 7. Overall, our method achieves satisfactory results in most scenarios. We also notice that the sampling-based method INF obtains comparable results to our method but performs poorly in the edge areas of objects. This means that interpolation-based functions have difficulty processing areas with large gradient changes. + +# 5.3. Comparison under Challenging Scenarios + +In the actual photography process, the camera faces complex and diverse scenes. Therefore, we aim to explore the robustness of the model in different challenging scenarios. Low resolution is a common phenomenon in post-processing or when using low-cost storage. Previous research [14] has shown that sampling-based methods tend + +
ConditionMethodPSNRSSIM
Low resolutionOurs47.900.9978
INF45.500.9944
Fast motionOurs46.360.9976
INF45.790.9936
Dark lightingOurs53.600.9989
INF51.420.9969
+ +Table 2. Comparison under challenging scenarios on RVD-Part1. + +
warpingMGLA\( \ell_{aux} \)PSNRSSIM
✓✓42.600.9972
✓✓✓47.680.9978
✓✓✓46.120.9979
✓✓✓47.910.9983
✓✓✓✓49.710.9983
+ +Table 3. Ablation study on RVD-Part2 dataset. + +to be sensitive to resolution. To test the performance of our method and INF, we construct a low-resolution version by downsampling the original dataset to half the resolution. The results indicate that our method is more robust to resolution changes, with a $1.8\%$ PSNR drop compared to the $4.6\%$ drop observed in INF. Fast motion is often regarded as a challenging scene for our method, as the first RAW frame only provides limited information for subsequent RAW reconstruction. In comparison to INF, our method shows a gain of $1.2\%$ in the fast motion scene, which is lower than the $2.3\%$ gain observed on the full test set. This suggests that fast motion still poses a challenge for our method. Dark lighting is a typical harsh environment for shooting. However, our research has found that it is not actually difficult for the sRGB-to-RAW methods, as the recovery quality in these scenarios is well above average. + +# 5.4. Ablation Study + +We conduct ablation experiments to verify the effectiveness of key designs in the proposed method, and the quantitative results are shown in Table 3. We first investigate the role of the temporal affinity prior extraction, which generates a reference RAW image by utilizing the motion information. We remove this step and directly input the sRGB image $x_{t+1}$ into Encoders to do the verification. The results in first line show this step is all-important to our pipeline, that is, PSNR decreased by 6.17. The second line represents that we do not consider the quality of the RAW and directly input the reference RAW image $\tilde{y}_{t+1}$ to the next stage. + +In the spatial feature fusion and mapping step, the previous frame provides global and local supplementary information for image reconstruction by the GLA module. To demonstrate the necessity of introducing a previous frame into this step, we remove the previous frame encoder $\mathrm{Encoder}_{\mathrm{ref}}$ and directly learn the mapping function from the + +![](images/7cd5b6c25e5a0d92063948a5d9bc41b66c7e3be99459fa0360428ed293e411c4.jpg) +Figure 8. Average PSNR and SSIM in time dimension. + +![](images/07c16ab097f601663d3d8b96730fa7febd83508a6d6ec9a1bf86c1bbee3a970c.jpg) + +current frame inputs. The result can be seen in the third line of Table 3. Furthermore, we add the auxiliary loss function to constraint the intermediate outputs, and the results can be seen in the fourth line when deleting it from the pipeline. + +# 5.5. Robustness over Time + +Our method relies on the first frame RAW to provide real reference information in the chained inference phase. However, as time increases, there will inevitably be accumulated information loss. In Figure 8, we calculate the average PSNR $(psnr^i = (\sum_{v=1}^{V} psnr_v^i) / V)$ and SSIM $(ssim^i = (\sum_{v=1}^{V} ssim_v^i) / V)$ along the time dimension. Here, $i \in [2,120]$ indexes the order of frames, and $V$ represents the number of all testing videos. + +As depicted in the curve, our method exhibits good robustness over time within a relatively long period of 100 frames. In comparison to INF, the method based on single-image metadata, our method still maintains a relatively high quality. However, the performance noticeably declines when the period becomes too long. This phenomenon is attributed to the inherent characteristics of our method. As an optional solution and for future work, we intend to investigate a previous frame selection strategy. This strategy would involve saving reference RAW frames at intervals to achieve a stable reconstruction quality. + +# 6. Conclusion + +In this paper, we introduce a new task called sRGB-to-RAW video de-rendering. Existing methods for converting sRGB images to RAW format are not applicable when applied to the new video de-rendering task. To address this, we propose a frame affinity guided reconstructed network with two main steps. The first step involves extracting temporal affinity prior by utilizing motion information between adjacent frames to obtain a reference RAW image. The second step focuses on spatial feature fusion and mapping, where a pixel-level mapping function is learned using scene-specific and position-specific prior information from the previous frame. To evaluate our proposed method, we create a benchmark dataset that includes a wide range of RAW-sRGB videos. Experimental results on this dataset demonstrate the superior reconstruction quality achieved by our method. + +# References + +[1] https://mlv.app/. +[2] Tim Brooks, Ben Mildenhall, Tianfan Xue, Jiawen Chen, Dillon Sharlet, and Jonathan T Barron. Unprocessing images for learned raw denoising. 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Dynamicisp: dynamically controlled image signal processor for image recognition. In Proceedings of the IEEE/CVF International Conference on Computer Vision, pages 12866-12876, 2023. +[36] Masakazu Yoshimura, Junji Otsuka, Atsushi Irie, and Takeshi Ohashi. Rawgment: noise-accounted raw augmentation enables recognition in a wide variety of environments. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 14007-14017, 2023. +[37] Ke Yu, Zexian Li, Yue Peng, Chen Change Loy, and Jinwei Gu. Reconfigisp: Reconfigurable camera image processing pipeline. In Proceedings of the IEEE/CVF International Conference on Computer Vision, pages 4248-4257, 2021. +[38] Lu Yuan and Jian Sun. High quality image reconstruction from raw and JPEG image pair. In 2011 International Conference on Computer Vision, pages 2158-2165. IEEE, 2011. +[39] Huanjing Yue, Cong Cao, Lei Liao, Ronghe Chu, and Jingyu Yang. 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However, capturing RAW video is challenging due to limitations in bandwidth and storage. Various methods have been proposed to address similar issues in single image RAW capture through de-rendering. These methods utilize both the metadata and the sRGB image to perform sRGB-to-RAW de-rendering and recover high-quality single-frame RAW data. However, metadata-based methods always require additional computation for online metadata generation, imposing severe burden on mobile camera device for high frame rate RAW video capture. To address this issue, we propose a framework that utilizes frame affinity to achieve high-quality sRGB-to-RAW video reconstruction. Our approach consists of two main steps. The first step, temporal affinity prior extraction, uses motion information between adjacent frames to obtain a reference RAW image. 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Comparison of Different RAW Video Capture Methods. (a) Saving the entire RAW video would cause significant strain on bandwidth and storage resources. (b) Sampling metadata for every frame in the video would burden the camera's computation. (c) Our method only requires saving a single extra RAW frame, which does not significantly burden the camera." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 497, + 547, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 497, + 547, + 700 + ], + "spans": [ + { + "bbox": [ + 304, + 497, + 547, + 700 + ], + "type": "text", + "content": "bit depth. This enables the production of video sequences with superior visual effects compared to sRGB videos. In addition, recent research has explored the benefits of using RAW data in computer vision tasks. Some studies have discovered that the linear relationship between scene irradiance and RAW data is better suited for tasks such as image denoising [2, 9, 12, 39], image super-resolution [7, 13, 34, 40], and low-light enhancement [5, 8, 11]. Additionally, the wide tolerance of RAW data makes perception tasks more robust in high-dynamic scenes [6, 22, 33, 36]. However, the high cost of RAW video capturing limits the widespread use of this technology. On one hand, the abundant and detailed information encoded in the RAW data takes up a huge amount of storage, increasing storage costs for users. On the other hand, real-time capturing of RAW video data puts a significant strain on the camera's bandwidth, as shown in Figure 1 (a)." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 318, + 701, + 545, + 714 + ], + "type": "text", + "content": "To address similar issues, many techniques have been" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 673, + 287, + 713 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 673, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 673, + 287, + 713 + ], + "type": "text", + "content": "*Equal contribution. † Corresponding author. This work was supported in part by the FDCT grants 0154/2022/A3, 0002/2023/AKP, 0102/2023/RIA2, and 001/2024/SKL, the MYRG-CRG2022-00013-IOTSC-ICI grant and the SRG2022-00023-IOTSC grant." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25659" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "text", + "content": "proposed for de-rendering single-frame sRGB images to RAW data. Some approaches utilize only the sRGB data as input and learn to recover the corresponding RAW data [2, 7, 31]. These methods are convenient for various applications, as they do not require any additional information from the camera besides the sRGB images. However, since some critical information may have been lost during the ISP processing, the de-rendering from only sRGB inputs still suffers from limited performance. In contrast, other methods attempt to extract a small portion of crucial information from the RAW data as metadata and learn to recover the original RAW images from both the sRGB images and the metadata [14, 19, 23, 27]. Although these methods can produce more accurate RAW images, they require an additional sampling method to run on the camera for producing the metadata. These sampling techniques impose additional pressure on the camera, and the burden will be much more severe for RAW video capturing. The complexity of sampling metadata from RAW video is " + }, + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "inline_equation", + "content": "O(WHL)" + }, + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "inline_equation", + "content": "W" + }, + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "inline_equation", + "content": "H" + }, + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "text", + "content": " are the width and height of the image, and " + }, + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "inline_equation", + "content": "L" + }, + { + "bbox": [ + 47, + 72, + 289, + 323 + ], + "type": "text", + "content": " is the length of the video sequence, as shown in Figure 1 (b)." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 325, + 289, + 516 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 325, + 289, + 516 + ], + "spans": [ + { + "bbox": [ + 47, + 325, + 289, + 516 + ], + "type": "text", + "content": "This paper presents a novel approach for RAW video de-rendering, which overcomes the limitations of previous methods and enhances storage and computation efficiency. Unlike metadata-based approaches, our method eliminates the need for an online sampler on the camera side. Instead, it utilizes a single RAW frame from the video sequence as prior information to efficiently recover detailed information from the RAW data, as depicted in Figure 1 (c). The additional select operation only incurs " + }, + { + "bbox": [ + 47, + 325, + 289, + 516 + ], + "type": "inline_equation", + "content": "O(1)" + }, + { + "bbox": [ + 47, + 325, + 289, + 516 + ], + "type": "text", + "content": " extra computation cost. Specifically, our method utilizes the provided RAW frame and the relationship between adjacent frames to guide the reconstruction of the remaining RAW frames. By designing a deep neural network with Temporal Affinity Prior Extraction and Spatial Feature Fusion and Mapping, our method effectively leverages the prior information from the previous frame and efficiently de-renders the RAW video." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 517, + 289, + 625 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 517, + 289, + 625 + ], + "spans": [ + { + "bbox": [ + 47, + 517, + 289, + 625 + ], + "type": "text", + "content": "To assess the effectiveness of our proposed method, we introduce the first RAW Video De-rendering benchmark, the RVD dataset. We then evaluate the performance of the proposed method and compare it with other sRGB-to-RAW de-rendering methods. The results demonstrate that our method can produce high-fidelity RAW video sequences and outperform other methods, without relying on per-image metadata. In conclusion, the contributions we have made in this paper can be summarized into five points:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 630, + 287, + 714 + ], + "type": "list", + "angle": 0, + "index": 5, + "blocks": [ + { + "bbox": [ + 47, + 630, + 287, + 701 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 630, + 287, + 701 + ], + "spans": [ + { + "bbox": [ + 47, + 630, + 287, + 701 + ], + "type": "text", + "content": "- We propose a new architecture for RAW video de- rendering. This architecture can efficiently de-render RAW video sequences using only one RAW frame and sRGB videos as input. By adopting this method, both storage and computation efficiency for RAW video capturing can be significantly improved." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 701, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 701, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 47, + 701, + 287, + 714 + ], + "type": "text", + "content": "- We propose a module for extracting a temporal affinity" + } + ] + } + ], + "index": 4 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 313, + 72, + 545, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 72, + 545, + 120 + ], + "spans": [ + { + "bbox": [ + 313, + 72, + 545, + 120 + ], + "type": "text", + "content": "prior to obtain a reliable reference RAW frame. This module utilizes motion information between adjacent frames. The reference RAW frame can accurately serve as a reference for recovering the lost RAW information." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 121, + 545, + 263 + ], + "type": "list", + "angle": 0, + "index": 10, + "blocks": [ + { + "bbox": [ + 306, + 121, + 545, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 121, + 545, + 156 + ], + "spans": [ + { + "bbox": [ + 306, + 121, + 545, + 156 + ], + "type": "text", + "content": "- We propose a module called Global and Local feature Aggregation (GLA) to extract and combine the globalized and localized features encoded in the prior information." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 156, + 545, + 214 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 156, + 545, + 214 + ], + "spans": [ + { + "bbox": [ + 306, + 156, + 545, + 214 + ], + "type": "text", + "content": "- We propose a new benchmark for RAW video de-earning to comprehensively evaluate the methods for this task. To our knowledge, this is the first benchmark specifically designed for the RAW video de-rendering task." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 216, + 545, + 263 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 216, + 545, + 263 + ], + "spans": [ + { + "bbox": [ + 306, + 216, + 545, + 263 + ], + "type": "text", + "content": "- Our method significantly outperforms state-of-the-art image RAW de-rendering methods and achieves high-quality RAW video sequences without relying on per-image metadata." + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 275, + 390, + 288 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 275, + 390, + 288 + ], + "spans": [ + { + "bbox": [ + 306, + 275, + 390, + 288 + ], + "type": "text", + "content": "2. Related work" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 296, + 436, + 308 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 296, + 436, + 308 + ], + "spans": [ + { + "bbox": [ + 306, + 296, + 436, + 308 + ], + "type": "text", + "content": "2.1. RAW Data Application" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 315, + 545, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 315, + 545, + 434 + ], + "spans": [ + { + "bbox": [ + 304, + 315, + 545, + 434 + ], + "type": "text", + "content": "RAW data, as a direct capture of raw information from a scene by a camera, has long been favored by computational photography and certain low-level vision tasks. These tasks include image super-resolution [7, 16, 30, 40], image denoising [2, 9, 10, 41-43], image deblur [4, 15], and low-light enhancement [5, 8, 11]. The main advantage of RAW data is that it is not processed by ISP (Image Signal Processor) and its response value has a linear relationship with scene irradiance. This simplifies the modeling process for degradation or enhancement models." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 434, + 545, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 434, + 545, + 661 + ], + "spans": [ + { + "bbox": [ + 304, + 434, + 545, + 661 + ], + "type": "text", + "content": "Recently, the advantages of RAW in visual perception tasks have been gradually discovered and explored. One basic point is that high-bit-depth RAW data retains more scene information. Another point is that ISP processing does not always have a positive effect. In the early stages, the work in [3, 17, 29, 35] examined the role of the ISP pipeline in computer vision tasks. An interesting conclusion is that most ISP processing is focused on improving visual effects and has little to do with the DNN model, and may even have a negative impact. Furthermore, some methods [18, 25, 37] used proxy networks or parameter searching to redefine ISP as a learnable process, improving the performance of RAW data in downstream tasks. The work in [6] focused on the instance segmentation task in dark scenes, and its results show that higher bit-depth is usually associated with better segmentation results. Xu et al. [33] proposed a new benchmark for RAW object detection in driving scenes and demonstrated the important influence of dynamic range on the detector." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 670, + 496, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 670, + 496, + 684 + ], + "spans": [ + { + "bbox": [ + 306, + 670, + 496, + 684 + ], + "type": "text", + "content": "2.2. sRGB-to-RAW Image De-rendering" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "There are generally two categories of single image sRGB-to-RAW de-rendering methods, based on whether metadata" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25660" + } + ] + } + ], + "index": 17 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 73, + 105, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 73, + 105, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 73, + 105, + 83 + ], + "type": "text", + "content": "is used or not." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 84, + 286, + 215 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 84, + 286, + 215 + ], + "spans": [ + { + "bbox": [ + 46, + 84, + 286, + 215 + ], + "type": "text", + "content": "De-rendering without metadata. Such methods are often designed for a specific camera or for vision tasks that require imprecise de-rendering. For example, Brooks et al. [2] proposed a generic process to model and invert the key steps of ISP. They then used synthesized RAW data to train a denoising network. Conde et al. [7] improved upon the aforementioned method by modeling the ISP steps as a learnable dictionary. The work in [31] introduced the normalizing flow to this task, relying on the inherent reversibility of this structure. It is approximated by a two-way process of learning rendering and de-rendering." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 216, + 286, + 442 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 216, + 286, + 442 + ], + "spans": [ + { + "bbox": [ + 46, + 216, + 286, + 442 + ], + "type": "text", + "content": "De-rendering with metadata. For metadata-based methods, the typical approach is to reconstruct the complete RAW image by saving a small amount of sampled data. Yuan and Sun [38] proposed a hybrid capture mode that reduces storage costs and continuous shooting burdens by saving low-resolution RAW images. The method described in [23] saves a small number of uniformly sampled pixels as metadata during capture, and uses RBF interpolation to obtain the full-resolution image during the reconstruction phase. Subsequently, [19] proposed a content-aware superpixel prediction network to improve the sampling strategy, while [14] introduced more expressive implicit neural functions to replace the RBF interpolation algorithm and achieve better performance. In addition to sampling-based methods, Nguyen and Brown's work [20] [21] proposed encoding the necessary parameters of ISP into an sRGB-JPEG file. The work of [27] considered an adaptive and learnable metadata construction method, which uses a compact representation of the latent space as metadata." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 443, + 286, + 502 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 443, + 286, + 502 + ], + "spans": [ + { + "bbox": [ + 46, + 443, + 286, + 502 + ], + "type": "text", + "content": "Unlike previous single image de-rendering methods, the proposed method does not impose any additional burden on the camera side. Instead, it utilizes inter-frame relationships to guide the de-rendering process, resulting in improved performance and greater efficiency." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 514, + 235, + 527 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 514, + 235, + 527 + ], + "spans": [ + { + "bbox": [ + 47, + 514, + 235, + 527 + ], + "type": "text", + "content": "3. RAW Video De-rendering Dataset" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 533, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 533, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 533, + 286, + 713 + ], + "type": "text", + "content": "RAW Video De-rendering is a computer vision task that aims to reconstruct RAW video sequences using sRGB frames and other additional information. This task is valuable as it helps reduce the storage and bandwidth requirements associated with capturing RAW videos. Currently, there is a lack of a dedicated benchmark specifically designed for evaluating and developing RAW video de-rendering methods. To address this issue, we propose the introduction of the first-ever RAW Video De-rendering (RVD) benchmark. This benchmark consists of over 200 videos, captured using different devices in various scenarios. Additionally, we have included videos in challenging scenes, such as fast motion and low lighting, to provide a comprehensive evaluation of de-rendering methods even in extreme conditions. In the remaining content of this section," + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 310, + 73, + 539, + 199 + ], + "blocks": [ + { + "bbox": [ + 310, + 73, + 539, + 199 + ], + "lines": [ + { + "bbox": [ + 310, + 73, + 539, + 199 + ], + "spans": [ + { + "bbox": [ + 310, + 73, + 539, + 199 + ], + "type": "image", + "image_path": "253b820f3739df1dec478b79c7e0f58a5432c0596e5cc263380649932378f711.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 205, + 545, + 260 + ], + "lines": [ + { + "bbox": [ + 305, + 205, + 545, + 260 + ], + "spans": [ + { + "bbox": [ + 305, + 205, + 545, + 260 + ], + "type": "text", + "content": "Figure 2. Typical challenging scenarios of RVD dataset. (a) contains fast moving vehicles, (b) has drastic scene change, and (c) is a high-light scenario. For each video, we list the sRGB of the first two frames and the last frame, and the corresponding RAW images which are demosaiced for visualization." + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 270, + 545, + 294 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 270, + 545, + 294 + ], + "spans": [ + { + "bbox": [ + 305, + 270, + 545, + 294 + ], + "type": "text", + "content": "we will provide a detailed introduction to the Data Collection and Data Processing of the proposed benchmark." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 295, + 545, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 295, + 545, + 437 + ], + "spans": [ + { + "bbox": [ + 305, + 295, + 545, + 437 + ], + "type": "text", + "content": "Data Collection. We collect the data used in this benchmark from two different sources. In the first part, we gather RAW-sRGB video pairs from existing RAW video-based tasks [40]. There are two reasons why we choose to reuse this data in our benchmark. Firstly, this data is of high quality, captured in various scenarios by different devices. By reusing this data, we can increase the diversity of the proposed benchmark without incurring additional data collection costs. Secondly, these datasets are widely recognized benchmarks for RAW video-based tasks, such as Video RAW Super-resolution. Therefore, this data can be easily used to evaluate the de-rendered RAW videos in these tasks." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 438, + 545, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 438, + 545, + 653 + ], + "spans": [ + { + "bbox": [ + 305, + 438, + 545, + 653 + ], + "type": "text", + "content": "However, simply relying on the data from the existing RAW video dataset is not sufficient for evaluating the RAW video de-rendering tasks. These data are not specifically collected for this task and lack comprehensive evaluations. Therefore, we manually collected some new videos from various challenging scenarios for the RAW video de-rendering task. Specifically, we collected these RAW videos using a Canon 5D Mark III DSLR camera. All videos were shot using fixed focus lenses, specifically the Canon EF " + }, + { + "bbox": [ + 305, + 438, + 545, + 653 + ], + "type": "inline_equation", + "content": "50\\mathrm{mm}" + }, + { + "bbox": [ + 305, + 438, + 545, + 653 + ], + "type": "text", + "content": " f/1.8 STM. We used the automatic setting on the camera, where the aperture, shutter, and ISO were adjusted automatically based on the scene. Each video has a duration of 4 to 6 seconds, resulting in a total of 100 videos. The RAW videos are recorded with a resolution of " + }, + { + "bbox": [ + 305, + 438, + 545, + 653 + ], + "type": "inline_equation", + "content": "1600\\times 900" + }, + { + "bbox": [ + 305, + 438, + 545, + 653 + ], + "type": "text", + "content": " pixels at a frame rate of 30 frames per second. The camera sensor's color filter array (CFA) follows the widely used RGGB Bayer format, and the RAW data is recorded with a 14-bit depth." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 654, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 654, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 305, + 654, + 545, + 712 + ], + "type": "text", + "content": "For the scenarios, we select some common challenges in the RAW video de-rendering task. These challenges include fast motion, high/low illumination, and more. After collecting this data, we manually label each video with the corresponding attributes. It is possible for a video to be as-" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25661" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 194, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 194, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 194, + 83 + ], + "type": "text", + "content": "signed with more than one attribute." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 85, + 286, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 85, + 286, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 85, + 286, + 228 + ], + "type": "text", + "content": "Data Processing. Typically, different camera devices use different Image Signal Processing (ISP) types to generate sRGB images, resulting in significant variations in sRGB image quality. In order to ensure a fair comparison with previous works, we choose not to use the sRGB images produced by the camera itself. Instead, we employ a software ISP algorithm that has been widely used in previous RAW-image datasets to generate the sRGB videos. Our data processing involves two steps: converting the RAW video format data (in .MLV format for Canon 5D Mark III) into RAW image sequences, and using an external ISP algorithm to render the sRGB image sequences." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 229, + 286, + 421 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 229, + 286, + 421 + ], + "spans": [ + { + "bbox": [ + 46, + 229, + 286, + 421 + ], + "type": "text", + "content": "For the first step, we use MLV App[1] - a professional magic lantern video processing software - to convert the RAW video into a RAW image sequence in DNG format (an open and lossless RAW image format). Since the quality of the first few frames of a handheld shot may not be very high, we delete some of the early frames. For convenience, we retain 120 consecutive frames from each video, resulting in a total of 12,000 retained images for the device. To obtain a rendered sRGB image sequence, we follow the methods described in [31] and [15]. We use the rawpy toolbox, a Python version of the LibRaw library, to process all the RAW images into PNG format using the default settings. This process includes typical operations of a modern ISP, such as demosaicking, auto white balance, denoising, gamma correction, color correction, and more. Some sample images can be seen in Figure 2." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 434, + 102, + 445 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 434, + 102, + 445 + ], + "spans": [ + { + "bbox": [ + 47, + 434, + 102, + 445 + ], + "type": "text", + "content": "4. Method" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 455, + 115, + 466 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 455, + 115, + 466 + ], + "spans": [ + { + "bbox": [ + 47, + 455, + 115, + 466 + ], + "type": "text", + "content": "4.1. Overview" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "spans": [ + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "type": "text", + "content": "Given a video sequence " + }, + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "type": "text", + "content": " from the sRGB domain, and the corresponding RAW video " + }, + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "type": "text", + "content": " from the RAW domain. The sRGB generation procedure " + }, + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "type": "inline_equation", + "content": "f" + }, + { + "bbox": [ + 46, + 474, + 286, + 510 + ], + "type": "text", + "content": " is:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 138, + 513, + 286, + 526 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 138, + 513, + 286, + 526 + ], + "spans": [ + { + "bbox": [ + 138, + 513, + 286, + 526 + ], + "type": "interline_equation", + "content": "x, \\varepsilon^ {\\prime} = f (y), \\tag {1}", + "image_path": "f2928279f00ccedcdb35105457ddde62e107b6045728c69424c2436472bf8985.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 528, + 286, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 528, + 286, + 563 + ], + "spans": [ + { + "bbox": [ + 46, + 528, + 286, + 563 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 528, + 286, + 563 + ], + "type": "inline_equation", + "content": "\\varepsilon^{\\prime}" + }, + { + "bbox": [ + 46, + 528, + 286, + 563 + ], + "type": "text", + "content": " represents the extra data saved at capture time. And the invert function of this procedure is defined as the RAW video de-rendering task:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 135, + 566, + 286, + 578 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 135, + 566, + 286, + 578 + ], + "spans": [ + { + "bbox": [ + 135, + 566, + 286, + 578 + ], + "type": "interline_equation", + "content": "y = f ^ {- 1} (x \\mid \\varepsilon). \\tag {2}", + "image_path": "8ad2892aeff73f091b3c63d1d18d4f2d5d5f8486f01da131cf0d65652de5e29f.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 582, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 286, + 713 + ], + "type": "text", + "content": "In previous works on single image RAW de-rendering, additional data " + }, + { + "bbox": [ + 46, + 582, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\varepsilon" + }, + { + "bbox": [ + 46, + 582, + 286, + 713 + ], + "type": "text", + "content": " typically consists of sampled RAW pixels from the original RAW image, i.e. the metadata. This data has proven to be highly effective in recovering lost detailed information during the sRGB generation process. However, when it comes to video de-rendering, sampling additional metadata from every frame in the RAW video could impose an excessively high computational burden on the camera, making implementation difficult. To alleviate the need for extra computational burden on the camera device and boost de-rendering efficiency, we propose a new pipeline for the" + } + ] + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 310, + 76, + 541, + 241 + ], + "blocks": [ + { + "bbox": [ + 310, + 76, + 541, + 241 + ], + "lines": [ + { + "bbox": [ + 310, + 76, + 541, + 241 + ], + "spans": [ + { + "bbox": [ + 310, + 76, + 541, + 241 + ], + "type": "image", + "image_path": "13144f184cea177dbe58667dd0baf63d374106e3d7c80e392c80ee171a0e59b7.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 245, + 545, + 300 + ], + "lines": [ + { + "bbox": [ + 305, + 245, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 305, + 245, + 545, + 300 + ], + "type": "text", + "content": "Figure 3. Video capture and inference procedure. In the capture time, we save the first frame RAW image and complete sRGB sequence. In the inference phase, except for the first frame, which uses the real RAW image, the rest use the predicted RAW image from the previous frame." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 311, + 545, + 335 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 311, + 545, + 335 + ], + "spans": [ + { + "bbox": [ + 305, + 311, + 545, + 335 + ], + "type": "text", + "content": "RAW video de-rendering. In this pipeline, we utilize the first RAW frame from the RAW video " + }, + { + "bbox": [ + 305, + 311, + 545, + 335 + ], + "type": "inline_equation", + "content": "y" + }, + { + "bbox": [ + 305, + 311, + 545, + 335 + ], + "type": "text", + "content": " as additional data:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 409, + 338, + 545, + 350 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 409, + 338, + 545, + 350 + ], + "spans": [ + { + "bbox": [ + 409, + 338, + 545, + 350 + ], + "type": "interline_equation", + "content": "\\varepsilon = y _ {1}. \\tag {3}", + "image_path": "368e306bcb91ad1fc12ffa13ad253ac38082f61060f0018660474ae6f76c118f.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "spans": [ + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "text", + "content": "Figure 3 shows an overview of the proposed pipeline. When capturing the video, we only need the camera to save the sRGB frames and an additional first RAW frame, which is easily achievable. When de-rendering the RAW video, our pipeline employs a chained structure to accomplish this. Specifically, in the initialization step, our model takes sRGB frames " + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "inline_equation", + "content": "x_{1}, x_{2}" + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "text", + "content": " and the first RAW frame " + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "inline_equation", + "content": "y_{1}" + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "text", + "content": " as input and produces the well-de-rendered RAW frame " + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "inline_equation", + "content": "\\hat{y}_{2}" + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "text", + "content": " as output. In the subsequent steps, our model takes " + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "inline_equation", + "content": "x_{t}, x_{t + 1}" + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "text", + "content": ", and the " + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "inline_equation", + "content": "\\hat{y}_t" + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "text", + "content": " produced in the last step as input and produces " + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "inline_equation", + "content": "\\hat{y}_{t + 1}" + }, + { + "bbox": [ + 305, + 353, + 545, + 519 + ], + "type": "text", + "content": " until the entire RAW video is de-rendered. As shown in this figure, the Frame Affinity Guided De-rendering Network (FAGDN) is the core of our pipeline. In the following subsection, we will provide a detailed introduction to it." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 527, + 544, + 540 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 527, + 544, + 540 + ], + "spans": [ + { + "bbox": [ + 305, + 527, + 544, + 540 + ], + "type": "text", + "content": "4.2. Frame Affinity Guided De-rendering Network" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 545, + 545, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 545, + 675 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 545, + 675 + ], + "type": "text", + "content": "Figure 4 illustrates the structure of the proposed Frame Affinity Guided De-rendering Network, which consists of two main steps. The first step is the extraction of temporal affinity priors. In this step, we combine the motion relationship between adjacent frames and the input from the previous frame RAW to construct a reference RAW. This is based on the observation that most parts of adjacent frames describe similar scenes. Therefore, the pixels in the previous RAW frame can provide accurate prior information for de-rendering the corresponding pixels in the subsequent frames." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 677, + 545, + 713 + ], + "type": "text", + "content": "The second step involves spatial feature fusion and mapping. Using the reference RAW extracted in the first step as auxiliary information, we utilize an encoder-decoder struc" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25662" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 53, + 73, + 537, + 287 + ], + "blocks": [ + { + "bbox": [ + 53, + 73, + 537, + 287 + ], + "lines": [ + { + "bbox": [ + 53, + 73, + 537, + 287 + ], + "spans": [ + { + "bbox": [ + 53, + 73, + 537, + 287 + ], + "type": "image", + "image_path": "6828309f8fa2f33cfa58ae4a669d93cd62959074d2d2c48b65b4f5b4c011a270.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 289, + 546, + 346 + ], + "lines": [ + { + "bbox": [ + 46, + 289, + 546, + 346 + ], + "spans": [ + { + "bbox": [ + 46, + 289, + 546, + 346 + ], + "type": "text", + "content": "Figure 4. Overview of the proposed Frame Affinity Guided De-rendering network. It contains two main steps, the Temporal Affinity Prior Extraction step generates an reference RAW by utilizing the motion information between adjacent frames. Here, we evaluate the quality of reference RAW through a confidence map. The second step is Spatial Feature Fusion and Mapping, using the reference RAW as starting status, we learn a pixel-level mapping function with the help of sRGB image and previous frames to further repair pixels predicted inaccurately in the first stage." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 48, + 357, + 103, + 401 + ], + "blocks": [ + { + "bbox": [ + 48, + 357, + 103, + 401 + ], + "lines": [ + { + "bbox": [ + 48, + 357, + 103, + 401 + ], + "spans": [ + { + "bbox": [ + 48, + 357, + 103, + 401 + ], + "type": "image", + "image_path": "6d1d15c39e269b3ac362639e9e131c77a34d0b88030e6ee21363829edb535927.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 62, + 401, + 86, + 408 + ], + "lines": [ + { + "bbox": [ + 62, + 401, + 86, + 408 + ], + "spans": [ + { + "bbox": [ + 62, + 401, + 86, + 408 + ], + "type": "text", + "content": "(a) sRGB" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "lines": [ + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "spans": [ + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "text", + "content": "Figure 5. From left to right are the sRGB image " + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "inline_equation", + "content": "x_{t}" + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "text", + "content": ", the optical flow image " + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "inline_equation", + "content": "o_{t\\rightarrow t + 1}" + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "text", + "content": ", the warping sRGB image " + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "inline_equation", + "content": "\\tilde{x}_{t + 1}" + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "text", + "content": " and the error map of " + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "inline_equation", + "content": "\\tilde{x}_{t + 1}" + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "inline_equation", + "content": "x_{t + 1}" + }, + { + "bbox": [ + 46, + 415, + 287, + 460 + ], + "type": "text", + "content": ". The red box lists errors caused by the optical flow algorithm." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 105, + 357, + 159, + 400 + ], + "blocks": [ + { + "bbox": [ + 105, + 357, + 159, + 400 + ], + "lines": [ + { + "bbox": [ + 105, + 357, + 159, + 400 + ], + "spans": [ + { + "bbox": [ + 105, + 357, + 159, + 400 + ], + "type": "image", + "image_path": "1310ef262533212d139236465106b4407ea31e5612bfa49f84a9ab7e884aeb92.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 111, + 401, + 153, + 408 + ], + "lines": [ + { + "bbox": [ + 111, + 401, + 153, + 408 + ], + "spans": [ + { + "bbox": [ + 111, + 401, + 153, + 408 + ], + "type": "text", + "content": "(b) Optical Flow" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 162, + 357, + 218, + 400 + ], + "blocks": [ + { + "bbox": [ + 162, + 357, + 218, + 400 + ], + "lines": [ + { + "bbox": [ + 162, + 357, + 218, + 400 + ], + "spans": [ + { + "bbox": [ + 162, + 357, + 218, + 400 + ], + "type": "image", + "image_path": "08bbdb35fc4d368a4b590a48fae0dd3394ebf130bb639c5767feb7d42d52c293.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 167, + 401, + 214, + 408 + ], + "lines": [ + { + "bbox": [ + 167, + 401, + 214, + 408 + ], + "spans": [ + { + "bbox": [ + 167, + 401, + 214, + 408 + ], + "type": "text", + "content": "(c) Warping sRGB" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 219, + 357, + 287, + 400 + ], + "blocks": [ + { + "bbox": [ + 219, + 357, + 287, + 400 + ], + "lines": [ + { + "bbox": [ + 219, + 357, + 287, + 400 + ], + "spans": [ + { + "bbox": [ + 219, + 357, + 287, + 400 + ], + "type": "image", + "image_path": "d3b3f0fdf5f153e100dd331972ec16589ea59ce7fc799cd96c3608caa3fad28a.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 230, + 401, + 266, + 408 + ], + "lines": [ + { + "bbox": [ + 230, + 401, + 266, + 408 + ], + "spans": [ + { + "bbox": [ + 230, + 401, + 266, + 408 + ], + "type": "text", + "content": "(d) Error Map" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 471, + 287, + 553 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 471, + 287, + 553 + ], + "spans": [ + { + "bbox": [ + 46, + 471, + 287, + 553 + ], + "type": "text", + "content": "ture to learn a mapping function of sRGB-to-RAW by incorporating the previous frame. To effectively utilize the scene-specific and position-specific prior information encoded in the previous frame, we introduce a Global and Local Feature Aggregation (GLA) module. This module is integrated with the encoder-decoder network, which will be further discussed later." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "spans": [ + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "type": "text", + "content": "Temporal Affinity Prior Extraction. In order to take full advantage of the temporal relationship between the adjacent frames, we need to generate the affinity between two frames. We accomplish this by using an off-the-shelf optical flow algorithm " + }, + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "type": "inline_equation", + "content": "\\Theta" + }, + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "type": "text", + "content": " [32]. This algorithm takes the sRGB frames " + }, + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "type": "inline_equation", + "content": "(x_{t}, x_{t+1})" + }, + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "type": "text", + "content": " as input and produces the transfer matrix " + }, + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "type": "inline_equation", + "content": "o_{t \\to t+1}" + }, + { + "bbox": [ + 46, + 554, + 287, + 638 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 118, + 638, + 287, + 651 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 118, + 638, + 287, + 651 + ], + "spans": [ + { + "bbox": [ + 118, + 638, + 287, + 651 + ], + "type": "interline_equation", + "content": "o _ {t \\rightarrow t + 1} = \\Theta \\left(x _ {t}, x _ {t + 1}\\right). \\tag {4}", + "image_path": "5f08e0b43b431886ee726e3956ef8417c8940c8babcaef35efd598529d1090cb.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 654, + 287, + 690 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 654, + 287, + 690 + ], + "spans": [ + { + "bbox": [ + 47, + 654, + 287, + 690 + ], + "type": "text", + "content": "Using this transfer matrix and the previous RAW image " + }, + { + "bbox": [ + 47, + 654, + 287, + 690 + ], + "type": "inline_equation", + "content": "y_{t}" + }, + { + "bbox": [ + 47, + 654, + 287, + 690 + ], + "type": "text", + "content": " we can apply a wrapping technique to generate a warping RAW image " + }, + { + "bbox": [ + 47, + 654, + 287, + 690 + ], + "type": "inline_equation", + "content": "\\tilde{y}_{t + 1}" + }, + { + "bbox": [ + 47, + 654, + 287, + 690 + ], + "type": "text", + "content": " as an reference RAW:" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 119, + 697, + 287, + 711 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 119, + 697, + 287, + 711 + ], + "spans": [ + { + "bbox": [ + 119, + 697, + 287, + 711 + ], + "type": "interline_equation", + "content": "\\tilde {y} _ {t + 1} = \\Omega \\left(y _ {t}, o _ {t \\rightarrow t + 1}\\right), \\tag {5}", + "image_path": "ce71abd0bc4c241fca39253cd508d7ccc42b047db0e44815cbc14b05ddb97b43.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 359, + 545, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 359, + 545, + 397 + ], + "spans": [ + { + "bbox": [ + 305, + 359, + 545, + 397 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 359, + 545, + 397 + ], + "type": "inline_equation", + "content": "\\Omega" + }, + { + "bbox": [ + 305, + 359, + 545, + 397 + ], + "type": "text", + "content": " represents a warping function that applies an offset to the original pixels to obtain new coordinates. It then completes the image using an interpolation algorithm." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 401, + 546, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 401, + 546, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 401, + 546, + 544 + ], + "type": "text", + "content": "However, there is a natural limitation where some pixels in the subsequent frame do not have corresponding pixels in the previous frame, making the reference pixels unreliable. Figure 5 illustrates a typical example of this limitation. To overcome this issue, we propose generating a confidence map to suppress areas where matching errors occur and select reliable reference features from the reference RAW frame. This generation process is based on the observation that regions with matching errors result in high error values when warping the sRGB image, as shown in Figure 5 (d). Subsequently, we utilize a multi-layer convolutional network to generate the confidence map " + }, + { + "bbox": [ + 304, + 401, + 546, + 544 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 401, + 546, + 544 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 365, + 547, + 485, + 574 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 365, + 547, + 485, + 574 + ], + "spans": [ + { + "bbox": [ + 365, + 547, + 485, + 574 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\tilde {x} _ {t + 1} = \\Omega \\left(x _ {t}, o _ {t \\rightarrow t + 1}\\right), \\\\ M = \\sigma (\\operatorname {c o n v} ([ \\tilde {x} _ {t + 1}, x _ {t + 1} ])), \\\\ \\end{array}", + "image_path": "498d8c2dc75ec4df87241a292ff0795c137a6289f2d409ba8fce1ede4d8f46e1.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "spans": [ + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "text", + "content": "where, the " + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "inline_equation", + "content": "conv" + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "text", + "content": " represent the convolutional network and sigmoid function, respectively. The reference RAW image " + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "inline_equation", + "content": "\\tilde{y}_{t+1}" + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "text", + "content": " and confidence map " + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 576, + 545, + 624 + ], + "type": "text", + "content": " will be fed to the second step for accurate RAW image reconstruction." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 629, + 546, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 546, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 546, + 712 + ], + "type": "text", + "content": "Spatial Feature Fusion and Mapping. Using the current sRGB frame and reference RAW, we develop a neural network that learns the final RAW image de-rendering process. Following the previous method for sRGB-to-RAW de-rendering [19], we utilize an encoder-decoder structure, specifically U-Net [24] like structure, to learn the mapping function in an end-to-end manner." + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "25663" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 71, + 286, + 210 + ], + "blocks": [ + { + "bbox": [ + 50, + 71, + 286, + 210 + ], + "lines": [ + { + "bbox": [ + 50, + 71, + 286, + 210 + ], + "spans": [ + { + "bbox": [ + 50, + 71, + 286, + 210 + ], + "type": "image", + "image_path": "5debf8583cf175ff4b200939d8c4a6aa908434eafbe6b6c700d926c19cf42caf.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 217, + 287, + 262 + ], + "lines": [ + { + "bbox": [ + 46, + 217, + 287, + 262 + ], + "spans": [ + { + "bbox": [ + 46, + 217, + 287, + 262 + ], + "type": "text", + "content": "Figure 6. The implementation of Global and Local Feature Aggregation(GLA) module. Global information guidance models the dependencies between all patches, while local information guidance limits the relationship modeling within each pair of patches." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 273, + 287, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 273, + 287, + 464 + ], + "spans": [ + { + "bbox": [ + 46, + 273, + 287, + 464 + ], + "type": "text", + "content": "However, the mapping function often presents two types of challenges. Firstly, the sRGB-to-RAW mapping is scene-specific, meaning that even the same RAW pixel can be mapped to different sRGB values under different scenes. Secondly, the sRGB-to-RAW mapping is position-specific, as described in [23], due to local operations in the ISP. This means that the same RAW value can be mapped to different sRGB values even within a single image. Therefore, our structure includes two branches in the encoder. The first branch takes the current frame information " + }, + { + "bbox": [ + 46, + 273, + 287, + 464 + ], + "type": "inline_equation", + "content": "[x_{t + 1},\\tilde{y}_{t + 1},M]" + }, + { + "bbox": [ + 46, + 273, + 287, + 464 + ], + "type": "text", + "content": " as input, providing realistic information about the current status, such as lighting conditions and object position. The second branch takes the previous frame input " + }, + { + "bbox": [ + 46, + 273, + 287, + 464 + ], + "type": "inline_equation", + "content": "[x_t,y_t]" + }, + { + "bbox": [ + 46, + 273, + 287, + 464 + ], + "type": "text", + "content": ", aiming to extract global (scene-specific) and local (position-specific) prior information from the previous RAW and sRGB pair." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 464, + 287, + 512 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 464, + 287, + 512 + ], + "spans": [ + { + "bbox": [ + 46, + 464, + 287, + 512 + ], + "type": "text", + "content": "As shown in Figure 4, we utilize two encoder networks to extract deep features from the two input branches individually. These branches have identical structures but do not share parameters:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 95, + 515, + 286, + 544 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 95, + 515, + 286, + 544 + ], + "spans": [ + { + "bbox": [ + 95, + 515, + 286, + 544 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} f _ {l} ^ {r} = \\operatorname {E n c o d e r} _ {\\text {r e f}} ([ x _ {t}, y _ {t} ]), \\\\ f _ {l} ^ {c} = \\operatorname {E n c o d e r} _ {\\mathrm {c u r}} ([ x _ {t + 1}, y _ {t + 1}, M ]), \\tag {7} \\\\ \\end{array}", + "image_path": "29c9fae86a991c677bd7c62a90416a021cd419de62e1c8b27d3bb488150ffdf3.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "content": "where Encoder represents encoder network. The intermediate features are denoted as " + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "inline_equation", + "content": "f_{l}^{r}" + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "inline_equation", + "content": "f_{l}^{c}" + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "content": " indexes the layer of the network. To efficiently utilize the features of the previous frame from global and local perspectives, we propose a global and local feature aggregation module, as shown in Figure 6. Specifically, for the feature " + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "inline_equation", + "content": "f_{l}^{r} \\in \\mathbb{R}^{C \\times H \\times W}" + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "inline_equation", + "content": "f_{l}^{c} \\in \\mathbb{R}^{C \\times H \\times W}" + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "content": ", we divide them into non-overlapping patches with a size of " + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "inline_equation", + "content": "C \\times p \\times p" + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "content": ". To introduce scene-related features from a global perspective, we embed each patch as a vector, forming a sequence of length " + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "inline_equation", + "content": "\\frac{HW}{p^2}" + }, + { + "bbox": [ + 46, + 546, + 288, + 713 + ], + "type": "text", + "content": ". Similar to the transformer approach[26], we use the embedding vector of the current frame as the Query and the embedding vector of the previous frame as the Key to learn an affinity matrix. This matrix is then used to ex" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 72, + 545, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 192 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 192 + ], + "type": "text", + "content": "tract global relevant information from the previous frame features (Value). For local information guidance, we implement information interaction within each patch pair. Similarly, we still use the current frame as the Query vector to model pixel-level dependencies. The information interaction within the patch allows the network to pay attention to neighboring pixels, making use of the video characteristics and reducing computational cost. Finally, the global and local supplementary information is added to each layer of the Encodercur sequentially." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 193, + 545, + 276 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 193, + 545, + 276 + ], + "spans": [ + { + "bbox": [ + 304, + 193, + 545, + 276 + ], + "type": "text", + "content": "During the decoding stage, we use an equal number of convolutional and sampling layers to gradually merge features and restore resolution. At the same time, we incorporate the multi-level features of the current encoder " + }, + { + "bbox": [ + 304, + 193, + 545, + 276 + ], + "type": "inline_equation", + "content": "(\\mathrm{Encoder}_{\\mathrm{cur}})" + }, + { + "bbox": [ + 304, + 193, + 545, + 276 + ], + "type": "text", + "content": " into the decoding process through skip connections. The resulting output of the decoder is considered the final reconstructed RAW image " + }, + { + "bbox": [ + 304, + 193, + 545, + 276 + ], + "type": "inline_equation", + "content": "(\\hat{y}_{t + 1})" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 277, + 545, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 277, + 545, + 361 + ], + "spans": [ + { + "bbox": [ + 304, + 277, + 545, + 361 + ], + "type": "text", + "content": "Loss Function. The overall network is trained in an end-to-end manner, using " + }, + { + "bbox": [ + 304, + 277, + 545, + 361 + ], + "type": "inline_equation", + "content": "\\ell" + }, + { + "bbox": [ + 304, + 277, + 545, + 361 + ], + "type": "text", + "content": ", the combination of " + }, + { + "bbox": [ + 304, + 277, + 545, + 361 + ], + "type": "inline_equation", + "content": "L_{2}" + }, + { + "bbox": [ + 304, + 277, + 545, + 361 + ], + "type": "text", + "content": " loss and SSIM [28] loss, to measure the accuracy of the reconstructed RAW. In addition to supervising the output of the last layer of the decoder, we also impose additional constraints on the intermediate features. The entire loss function can be expressed by the following formula:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 335, + 363, + 545, + 395 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 335, + 363, + 545, + 395 + ], + "spans": [ + { + "bbox": [ + 335, + 363, + 545, + 395 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\ell \\left(\\hat {y} _ {t + 1}, y _ {t + 1}\\right) + \\lambda \\sum_ {n = 1} ^ {3} \\ell \\left(\\hat {y} _ {t + 1} ^ {n}, y _ {t + 1} ^ {n}\\right). \\tag {8}", + "image_path": "9ce01c847e9cf9d411c424356bedc998744cd9cd7b51422ff27963e75e6e51e1.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "inline_equation", + "content": "\\hat{y}_{t+1}^n" + }, + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "text", + "content": " denotes the output of different levels of the decoder, while " + }, + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "inline_equation", + "content": "y_{t+1}^n" + }, + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "text", + "content": " is the downsampled image of the ground truth, maintaining the same resolution. " + }, + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "inline_equation", + "content": "\\lambda" + }, + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "text", + "content": " is a hyperparameter used to balance the contribution of the auxiliary loss and is set to 0.5." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 469, + 387, + 483 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 469, + 387, + 483 + ], + "spans": [ + { + "bbox": [ + 306, + 469, + 387, + 483 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 490, + 422, + 502 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 490, + 422, + 502 + ], + "spans": [ + { + "bbox": [ + 306, + 490, + 422, + 502 + ], + "type": "text", + "content": "5.1. Experimental Setup" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 509, + 545, + 652 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 509, + 545, + 652 + ], + "spans": [ + { + "bbox": [ + 304, + 509, + 545, + 652 + ], + "type": "text", + "content": "Dataset. We conduct experiments on the proposed RVD dataset. For convenience, we call the actually collected data RVD-Part1, and the data collected from [40] is called RVD-Part2. For RVD-Part1, we carefully select 15 videos (including difficult scenes such as fast motion, drastic scene changes, HDR) for testing, and remaining 85 videos for training. Each video is 120 frames with " + }, + { + "bbox": [ + 304, + 509, + 545, + 652 + ], + "type": "inline_equation", + "content": "1600 \\times 900" + }, + { + "bbox": [ + 304, + 509, + 545, + 652 + ], + "type": "text", + "content": " resolution. For the RVD-part2, we maintain the original division of training sets and test sets. Specifically, the training set contains 130 videos, each video has about 50 frames, and a total of 6308 images. The testing set has 20 videos, and 983 images. All images have resolution " + }, + { + "bbox": [ + 304, + 509, + 545, + 652 + ], + "type": "inline_equation", + "content": "1440 \\times 640" + }, + { + "bbox": [ + 304, + 509, + 545, + 652 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": "Implementation details. We are committed to converting sRGB to the original RAW data, which has not undergone any ISP operations such as demosaic and AWB. As a common practice, we package the single-channel RAW data into a four-channel [R, Gr, Gb, B] format, which serves as the" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25664" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 74, + 71, + 521, + 153 + ], + "blocks": [ + { + "bbox": [ + 74, + 71, + 521, + 153 + ], + "lines": [ + { + "bbox": [ + 74, + 71, + 521, + 153 + ], + "spans": [ + { + "bbox": [ + 74, + 71, + 521, + 153 + ], + "type": "table", + "html": "
MethodPub.YearMetadataRVD-Part1RVD-Part2
PSNR ↑SSIM ↑PSNR ↑SSIM ↑
CAM [19]CVPR2022✓41.850.983242.250.9856
CAM w/ fine-tuning [19]CVPR2022✓41.870.983642.260.9858
INF [14]CVPR2023✓47.670.994846.250.9939
Ours--X48.860.998049.710.9983
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7. Visual comparison with sRGB-to-RAW image de-rendering methods. We calculate the pixel-level error maps of different methods and GT, and the RAW images are demosaiced for visualization." + } + ] + } + ], + "index": 27, + "angle": 0, + "type": "image_caption" + } + ], + "index": 20 + }, + { + "type": "image", + "bbox": [ + 426, + 185, + 547, + 238 + ], + "blocks": [ + { + "bbox": [ + 426, + 185, + 547, + 238 + ], + "lines": [ + { + "bbox": [ + 426, + 185, + 547, + 238 + ], + "spans": [ + { + "bbox": [ + 426, + 185, + 547, + 238 + ], + "type": "image", + "image_path": "f792df724a70b7d3d25c1e6313cadcf698708b30dd9e4692c3b0c67f03e64387.jpg" + } + ] + } + ], + "index": 22, + "angle": 0, + "type": "image_body" + } + ], + "index": 22 + }, + { + "type": "image", + "bbox": [ + 426, + 239, + 547, + 293 + ], + "blocks": [ + { + "bbox": [ + 426, + 239, + 547, + 293 + ], + "lines": [ + { + "bbox": [ + 426, + 239, + 547, + 293 + ], + "spans": [ + { + "bbox": [ + 426, + 239, + 547, + 293 + ], + "type": "image", + "image_path": "3ae35ccb212ebe93f984587176cef404183cbd3396384dc8385377133c09ee37.jpg" + } + ] + } + ], + "index": 23, + "angle": 0, + "type": "image_body" + } + ], + "index": 23 + }, + { + "type": "image", + "bbox": [ + 426, + 293, + 547, + 336 + ], + "blocks": [ + { + "bbox": [ + 426, + 293, + 547, + 336 + ], + "lines": [ + { + "bbox": [ + 426, + 293, + 547, + 336 + ], + "spans": [ + { + "bbox": [ + 426, + 293, + 547, + 336 + ], + "type": "image", + "image_path": "a13161773c191f4fde13d2200d870a74b2912687887fc5ab2db1042745687855.jpg" + } + ] + } + ], + "index": 24, + "angle": 0, + "type": "image_body" + } + ], + "index": 24 + }, + { + "type": "image", + "bbox": [ + 426, + 337, + 547, + 380 + ], + "blocks": [ + { + "bbox": [ + 426, + 337, + 547, + 380 + ], + "lines": [ + { + "bbox": [ + 426, + 337, + 547, + 380 + ], + "spans": [ + { + "bbox": [ + 426, + 337, + 547, + 380 + ], + "type": "image", + "image_path": "df16ff6c445d5b89ae53b6798f6a61e14bb22adc5a247a2671329193a8f1be4c.jpg" + } + ] + } + ], + "index": 25, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 462, + 381, + 482, + 390 + ], + "lines": [ + { + "bbox": [ + 462, + 381, + 482, + 390 + ], + "spans": [ + { + "bbox": [ + 462, + 381, + 482, + 390 + ], + "type": "text", + "content": "Ours" + } + ] + } + ], + "index": 26, + "angle": 0, + "type": "image_caption" + } + ], + "index": 25 + }, + { + "bbox": [ + 46, + 430, + 289, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 430, + 289, + 598 + ], + "spans": [ + { + "bbox": [ + 46, + 430, + 289, + 598 + ], + "type": "text", + "content": "basic format for training and inference. It is also easy to unpack it back to single-channel RAW for downstream tasks. The proposed method is implemented using the PyTorch framework. During training, we randomly crop patches of size " + }, + { + "bbox": [ + 46, + 430, + 289, + 598 + ], + "type": "inline_equation", + "content": "256 \\times 256" + }, + { + "bbox": [ + 46, + 430, + 289, + 598 + ], + "type": "text", + "content": " from the original input and apply random rotation and flipping as data augmentation techniques. The model is optimized using the Adam optimizer, with an initial learning rate of " + }, + { + "bbox": [ + 46, + 430, + 289, + 598 + ], + "type": "inline_equation", + "content": "1e - 3" + }, + { + "bbox": [ + 46, + 430, + 289, + 598 + ], + "type": "text", + "content": ". The learning rate is reduced to one-tenth every 20 epochs. We train the model for a total of 60 epochs and select the model from the last epoch for testing. During testing, we maintain the original resolution of the image as the input. Considering the differences in sensors among different devices, we train and test the model separately on each subset." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 47, + 609, + 287, + 624 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 609, + 287, + 624 + ], + "spans": [ + { + "bbox": [ + 47, + 609, + 287, + 624 + ], + "type": "text", + "content": "5.2. Comparison with Image De-rendering Methods" + } + ] + } + ], + "index": 29 + }, + { + "bbox": [ + 46, + 629, + 288, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 712 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 712 + ], + "type": "text", + "content": "Since our method is the first proposed for sRGB-to-RAW video de-rendering, we compare it with state-of-the-art sRGB-to-RAW image de-rendering methods: CAM [19], CAM with fine-tuning [19], and INF [14]. The source code of these methods has been made public, and since most of the sRGB-to-RAW methods are camera-dependent, we retrain and test on the new dataset." + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 304, + 430, + 547, + 611 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 430, + 547, + 611 + ], + "spans": [ + { + "bbox": [ + 304, + 430, + 547, + 611 + ], + "type": "text", + "content": "Table 1 illustrates the quantitative comparison results of different methods. We use peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) metrics to evaluate the quality of reconstructed RAW. The results demonstrate that the proposed method achieves the best performance, even when compared to per-image metadata-based methods. Moreover, we also compute the pixel-wise difference between the reconstructed RAW and the ground truth to visually compare the performance of different methods, which can be seen in Figure 7. Overall, our method achieves satisfactory results in most scenarios. We also notice that the sampling-based method INF obtains comparable results to our method but performs poorly in the edge areas of objects. This means that interpolation-based functions have difficulty processing areas with large gradient changes." + } + ] + } + ], + "index": 31 + }, + { + "bbox": [ + 305, + 621, + 525, + 635 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 621, + 525, + 635 + ], + "spans": [ + { + "bbox": [ + 305, + 621, + 525, + 635 + ], + "type": "text", + "content": "5.3. Comparison under Challenging Scenarios" + } + ] + } + ], + "index": 32 + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "content": "In the actual photography process, the camera faces complex and diverse scenes. Therefore, we aim to explore the robustness of the model in different challenging scenarios. Low resolution is a common phenomenon in post-processing or when using low-cost storage. Previous research [14] has shown that sampling-based methods tend" + } + ] + } + ], + "index": 33 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "25665" + } + ] + } + ], + "index": 34 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 68, + 70, + 265, + 164 + ], + "blocks": [ + { + "bbox": [ + 68, + 70, + 265, + 164 + ], + "lines": [ + { + "bbox": [ + 68, + 70, + 265, + 164 + ], + "spans": [ + { + "bbox": [ + 68, + 70, + 265, + 164 + ], + "type": "table", + "html": "
ConditionMethodPSNRSSIM
Low resolutionOurs47.900.9978
INF45.500.9944
Fast motionOurs46.360.9976
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Dark lightingOurs53.600.9989
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warpingMGLA\\( \\ell_{aux} \\)PSNRSSIM
✓✓42.600.9972
✓✓✓47.680.9978
✓✓✓46.120.9979
✓✓✓47.910.9983
✓✓✓✓49.710.9983
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The results indicate that our method is more robust to resolution changes, with a " + }, + { + "bbox": [ + 46, + 293, + 289, + 484 + ], + "type": "inline_equation", + "content": "1.8\\%" + }, + { + "bbox": [ + 46, + 293, + 289, + 484 + ], + "type": "text", + "content": " PSNR drop compared to the " + }, + { + "bbox": [ + 46, + 293, + 289, + 484 + ], + "type": "inline_equation", + "content": "4.6\\%" + }, + { + "bbox": [ + 46, + 293, + 289, + 484 + ], + "type": "text", + "content": " drop observed in INF. Fast motion is often regarded as a challenging scene for our method, as the first RAW frame only provides limited information for subsequent RAW reconstruction. In comparison to INF, our method shows a gain of " + }, + { + "bbox": [ + 46, + 293, + 289, + 484 + ], + "type": "inline_equation", + "content": "1.2\\%" + }, + { + "bbox": [ + 46, + 293, + 289, + 484 + ], + "type": "text", + "content": " in the fast motion scene, which is lower than the " + }, + { + "bbox": [ + 46, + 293, + 289, + 484 + ], + "type": "inline_equation", + "content": "2.3\\%" + }, + { + "bbox": [ + 46, + 293, + 289, + 484 + ], + "type": "text", + "content": " gain observed on the full test set. This suggests that fast motion still poses a challenge for our method. Dark lighting is a typical harsh environment for shooting. However, our research has found that it is not actually difficult for the sRGB-to-RAW methods, as the recovery quality in these scenarios is well above average." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 491, + 140, + 504 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 491, + 140, + 504 + ], + "spans": [ + { + "bbox": [ + 47, + 491, + 140, + 504 + ], + "type": "text", + "content": "5.4. Ablation Study" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 510, + 287, + 642 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 287, + 642 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 287, + 642 + ], + "type": "text", + "content": "We conduct ablation experiments to verify the effectiveness of key designs in the proposed method, and the quantitative results are shown in Table 3. We first investigate the role of the temporal affinity prior extraction, which generates a reference RAW image by utilizing the motion information. We remove this step and directly input the sRGB image " + }, + { + "bbox": [ + 46, + 510, + 287, + 642 + ], + "type": "inline_equation", + "content": "x_{t+1}" + }, + { + "bbox": [ + 46, + 510, + 287, + 642 + ], + "type": "text", + "content": " into Encoders to do the verification. The results in first line show this step is all-important to our pipeline, that is, PSNR decreased by 6.17. The second line represents that we do not consider the quality of the RAW and directly input the reference RAW image " + }, + { + "bbox": [ + 46, + 510, + 287, + 642 + ], + "type": "inline_equation", + "content": "\\tilde{y}_{t+1}" + }, + { + "bbox": [ + 46, + 510, + 287, + 642 + ], + "type": "text", + "content": " to the next stage." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 642, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 288, + 715 + ], + "type": "text", + "content": "In the spatial feature fusion and mapping step, the previous frame provides global and local supplementary information for image reconstruction by the GLA module. To demonstrate the necessity of introducing a previous frame into this step, we remove the previous frame encoder " + }, + { + "bbox": [ + 46, + 642, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathrm{Encoder}_{\\mathrm{ref}}" + }, + { + "bbox": [ + 46, + 642, + 288, + 715 + ], + "type": "text", + "content": " and directly learn the mapping function from the" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 307, + 71, + 422, + 164 + ], + "blocks": [ + { + "bbox": [ + 307, + 71, + 422, + 164 + ], + "lines": [ + { + "bbox": [ + 307, + 71, + 422, + 164 + ], + "spans": [ + { + "bbox": [ + 307, + 71, + 422, + 164 + ], + "type": "image", + "image_path": "7cd5b6c25e5a0d92063948a5d9bc41b66c7e3be99459fa0360428ed293e411c4.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 325, + 167, + 525, + 178 + ], + "lines": [ + { + "bbox": [ + 325, + 167, + 525, + 178 + ], + "spans": [ + { + "bbox": [ + 325, + 167, + 525, + 178 + ], + "type": "text", + "content": "Figure 8. Average PSNR and SSIM in time dimension." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 425, + 71, + 543, + 164 + ], + "blocks": [ + { + "bbox": [ + 425, + 71, + 543, + 164 + ], + "lines": [ + { + "bbox": [ + 425, + 71, + 543, + 164 + ], + "spans": [ + { + "bbox": [ + 425, + 71, + 543, + 164 + ], + "type": "image", + "image_path": "07c16ab097f601663d3d8b96730fa7febd83508a6d6ec9a1bf86c1bbee3a970c.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 186, + 545, + 236 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 186, + 545, + 236 + ], + "spans": [ + { + "bbox": [ + 304, + 186, + 545, + 236 + ], + "type": "text", + "content": "current frame inputs. The result can be seen in the third line of Table 3. Furthermore, we add the auxiliary loss function to constraint the intermediate outputs, and the results can be seen in the fourth line when deleting it from the pipeline." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 242, + 432, + 254 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 242, + 432, + 254 + ], + "spans": [ + { + "bbox": [ + 306, + 242, + 432, + 254 + ], + "type": "text", + "content": "5.5. Robustness over Time" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "spans": [ + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "text", + "content": "Our method relies on the first frame RAW to provide real reference information in the chained inference phase. However, as time increases, there will inevitably be accumulated information loss. In Figure 8, we calculate the average PSNR " + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "inline_equation", + "content": "(psnr^i = (\\sum_{v=1}^{V} psnr_v^i) / V)" + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "text", + "content": " and SSIM " + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "inline_equation", + "content": "(ssim^i = (\\sum_{v=1}^{V} ssim_v^i) / V)" + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "text", + "content": " along the time dimension. Here, " + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "inline_equation", + "content": "i \\in [2,120]" + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "text", + "content": " indexes the order of frames, and " + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "inline_equation", + "content": "V" + }, + { + "bbox": [ + 304, + 260, + 545, + 357 + ], + "type": "text", + "content": " represents the number of all testing videos." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 358, + 546, + 491 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 358, + 546, + 491 + ], + "spans": [ + { + "bbox": [ + 304, + 358, + 546, + 491 + ], + "type": "text", + "content": "As depicted in the curve, our method exhibits good robustness over time within a relatively long period of 100 frames. In comparison to INF, the method based on single-image metadata, our method still maintains a relatively high quality. However, the performance noticeably declines when the period becomes too long. This phenomenon is attributed to the inherent characteristics of our method. As an optional solution and for future work, we intend to investigate a previous frame selection strategy. This strategy would involve saving reference RAW frames at intervals to achieve a stable reconstruction quality." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 502, + 378, + 514 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 502, + 378, + 514 + ], + "spans": [ + { + "bbox": [ + 306, + 502, + 378, + 514 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 521, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 521, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 521, + 545, + 713 + ], + "type": "text", + "content": "In this paper, we introduce a new task called sRGB-to-RAW video de-rendering. Existing methods for converting sRGB images to RAW format are not applicable when applied to the new video de-rendering task. To address this, we propose a frame affinity guided reconstructed network with two main steps. The first step involves extracting temporal affinity prior by utilizing motion information between adjacent frames to obtain a reference RAW image. The second step focuses on spatial feature fusion and mapping, where a pixel-level mapping function is learned using scene-specific and position-specific prior information from the previous frame. To evaluate our proposed method, we create a benchmark dataset that includes a wide range of RAW-sRGB videos. 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In Proceedings of the IEEE/CVF International Conference on Computer Vision, pages 4593-4601, 2021." + } + ] + } + ], + "index": 17 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "25668" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Leveraging Predicate and Triplet Learning for Scene Graph Generation/24e4e41a-71a3-4905-abbc-d74d18828d82_content_list.json b/2024/Leveraging Predicate and Triplet Learning for Scene Graph Generation/24e4e41a-71a3-4905-abbc-d74d18828d82_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..2f25aff5f854a8a10ff165ef2fa459fbd55fc07a --- /dev/null +++ b/2024/Leveraging Predicate and Triplet Learning for Scene Graph Generation/24e4e41a-71a3-4905-abbc-d74d18828d82_content_list.json @@ -0,0 +1,1608 @@ +[ + { + "type": "text", + "text": "Leveraging Predicate and Triplet Learning for Scene Graph Generation", + "text_level": 1, + "bbox": [ + 122, + 130, + 846, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Jiankai $\\mathsf{Li}^{1,2,3}$ Yunhong Wang $^{1}$ Xiefan Guo $^{1}$ Ruijie Yang $^{1}$ Weixin Li $^{1,2,3*}$", + "bbox": [ + 174, + 179, + 834, + 198 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1 IRIP Lab, School of Computer Science and Engineering, Beihang University, Beijing, China", + "bbox": [ + 132, + 198, + 872, + 215 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{2}$ State Key Laboratory of Complex & Critical Software Environment, Beihang University, Beijing, China", + "bbox": [ + 88, + 215, + 916, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "$^{3}$ Shanghai Artificial Intelligence Laboratory, Shanghai, China", + "bbox": [ + 256, + 233, + 750, + 252 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{lijiankai, yhwang, xfguo, rjyang, weixinli}@buaa.edu.cn", + "bbox": [ + 253, + 253, + 746, + 268 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 304, + 312, + 319 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Scene Graph Generation (SGG) aims to identify entities and predict the relationship triplets $<$ subject, predicate, object> in visual scenes. Given the prevalence of large visual variations of subject-object pairs even in the same predicate, it can be quite challenging to model and refine predicate representations directly across such pairs, which is however a common strategy adopted by most existing SGG methods. We observe that visual variations within the identical triplet are relatively small and certain relation cues are shared in the same type of triplet, which can potentially facilitate the relation learning in SGG. Moreover, for the long-tail problem widely studied in SGG task, it is also crucial to deal with the limited types and quantity of triplets in tail predicates. Accordingly, in this paper, we propose a Dual-granularity Relation Modeling (DRM) network to leverage fine-grained triplet cues besides the coarse-grained predicate ones. DRM utilizes contexts and semantics of predicate and triplet with Dual-granularity Constraints, generating compact and balanced representations from two perspectives to facilitate relation recognition. Furthermore, a Dual-granularity Knowledge Transfer (DKT) strategy is introduced to transfer variation from head predicates/triplets to tail ones, aiming to enrich the pattern diversity of tail classes to alleviate the long-tail problem. Extensive experiments demonstrate the effectiveness of our method, which establishes new state-of-the-art performance on Visual Genome, Open Image, and GQA datasets. Our code is available at https://github.com/jkli1998/DRM", + "bbox": [ + 75, + 335, + 472, + 773 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 790, + 207, + 806 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Entities and their associated relationships form the cornerstones of visual contents in images [14]. Scene Graph Generation (SGG), a fundamental task in visual scene understanding, is designed to detect these entities and predict", + "bbox": [ + 75, + 816, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/8f7ae5ebc3d0278e38ab426a8e54d9685e23f0564ad35bb736e4a448d2bfaced.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 532, + 305, + 692, + 377 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/a46604bea033176331e283214f3412fb9322f436c1fdf548f08ae056fcd02013.jpg", + "image_caption": [ + "" + ], + "image_footnote": [], + "bbox": [ + 694, + 305, + 854, + 378 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c1cc7f4ebc25de4e119ae4e18314881e2dcb7727d7615536a6c2fdb60dd10733.jpg", + "image_caption": [ + "", + "", + "Figure 1. The illustration of large visual variations within the predicate \"eating\". Identical predicate can appear differently under distinct subject-object pairs, encompassing a different set of visual cues within each manifestation. Identifying discriminative relation cues that are shared across diverse subject-object pairs within the same predicate can be challenging. Yet, they can be easily captured when the scope is narrowed to the identical triplet." + ], + "image_footnote": [], + "bbox": [ + 532, + 391, + 691, + 464 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ebf13cd0eb7eb695ba95014740645796d1d1af3f72a2f198f4d3d255af473df3.jpg", + "image_caption": [ + "" + ], + "image_footnote": [], + "bbox": [ + 694, + 391, + 854, + 464 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "their pairwise relationships, encapsulating them into $<\\text{subject}, \\text{predicate}, \\text{object}>$ triplets [4, 26, 51]. The generated compact graph-structured image representation can be utilized in a range of applications, e.g. embodied navigation [7, 33], image retrieval [5, 8], visual question answering [1, 32], etc., so the SGG task has received widespread attention in recent years [12, 16, 22, 45].", + "bbox": [ + 496, + 597, + 890, + 703 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Existing SGG methods are mostly dedicated to generating discriminative predicate representations for the detected entities, based on their appearances, relative positions, contextual cues, etc. [15, 19, 37, 44, 54]. However, as shown in Figure 1, large visual variations due to different subject-object combinations are inherent even in the same predicate, presenting an obstacle for SGG methods to capture robust predicate cues across distinct triplet types. To alleviate this problem, PE-Net [54] utilizes textual semantics of predicate categories as the prototype and model predicate cues by reducing the intra-class variance and inter-class similarity. Despite the improved prediction accuracy, PE-Net still follows the previous strategy of straightforwardly amalga", + "bbox": [ + 496, + 704, + 892, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author", + "bbox": [ + 94, + 887, + 220, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "28369", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "mating predicate cues that probably contain extensive visual variations of diverse triplets.", + "bbox": [ + 76, + 90, + 468, + 121 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Moreover, many recent efforts have been devoted to the long-tail problem in SGG task. Insufficient samples with limited triplet types lead to the reduced diversity observed in tail predicate categories, making it a challenging task to learn and adapt to their distributions. Existing methods boost model's attention towards tail predicate categories through re-sampling [19], re-weighting[28], or the utilization of mixture of experts [6, 34]. However, they mostly fall short of directly tackling the core of the long-tail issue, i.e., the insufficient patterns for tail predicates, leaving space for further improvement.", + "bbox": [ + 75, + 125, + 468, + 290 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Reflecting on similarities and differences among predicates, we find that despite the non-negligible or even large variations inherent in the same predicate, the visual diversity of the same triplet is relatively small (e.g. the two instances of in Figure 1). Accordingly, considering the more fine-grained triplet cues in addition to the coarse-grained predicate ones can help prevent the model from getting stuck in the refinement process of predicate features with potentially large variations, and promote it to strike a balance between different granularities during the relationship learning process. For the long-tail problem in SGG task which primarily emerges due to the insufficient tail predicate patterns and corresponding limited types and quantity of triplets, it then becomes a natural choice to enrich tail predicate patterns using head predicates and their triplets.", + "bbox": [ + 75, + 292, + 468, + 534 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Based on the aforementioned insights, we propose a Dual-granularity Relation Modeling (DRM) network that models triplet cues to facilitate predicate learning and transfer knowledge from the head classes to tail classes for relation recognition. In our DRM network, as shown in Figure 2, 1) besides a predicate branch that models coarse-grained predicate cues by leveraging their contextual predicates and subject-object pairs, a triplet branch is also presented to strengthen fine-grained triplet representations via jointly exploring their visual contents and corresponding label semantics. We also devise dual-granularity constraints to prevent the degradation of predicate and triplet feature spaces during model training. Subsequently, 2) the Dual-granularity Knowledge Transfer (DKT) strategy is proposed to transfer the class variance from head classes to tail ones from both the predicate and triplet perspectives for unbiased SGG. Distributions of tail predicates/triplets are designed to be calibrated using variance from head ones that are most similar to them. New predicate/triplet samples are generated as well based on the calibrated distributions to enrich the pattern diversity of tail predicates/triplets. Extensive experiments conducted on the widely used Visual Genome [14], Open Image [13], and GQA [10] datasets for SGG demonstrate the state-of-the-art performance of our method.", + "bbox": [ + 75, + 537, + 470, + 900 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/3cbacaa1f43b5b7d1d6854804eb4b04225626966f3a7514af108c210cfd49534.jpg", + "image_caption": [ + "Figure 2. Comparison of different pipelines for relation recognition. Previous methods focus on learning predicate cues shared across various triplets with diverse visual appearance. Our method learns and leverages both triplet cues within the same triplet and predicate cues across triplets, to better handle the visual diversity." + ], + "image_footnote": [], + "bbox": [ + 513, + 90, + 879, + 224 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Contributions of this paper can be summarized as:", + "bbox": [ + 517, + 311, + 849, + 325 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose to learn scene graphs in a dual-granularity manner, integrating both coarse-grained predicate cues and fine-grained triplet cues.", + "- We introduce the DRM network to model predicate and triplet cues, and propose the DKT strategy to propagate knowledge from head predicates/triplets to tail ones to mitigate the long-tail problem in SGG.", + "- We comprehensively evaluate the proposed method and demonstrate its superior performance." + ], + "bbox": [ + 500, + 325, + 890, + 460 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 474, + 640, + 489 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. Scene Graph Generation", + "text_level": 1, + "bbox": [ + 500, + 500, + 725, + 515 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Scene graph is a structured representation of the image content, where its essential constituents are the relationships (or triplets $<$ subject, predicate, object $\\succ$ ). The direct prediction of triplet categories presents a significant challenge given the extensive combinations of subjects, predicates, and objects. Existing Scene Graph Generation (SGG) methods [11, 16, 25, 42, 52, 54] decompose this prediction target into two components: entities and predicates. Early SGG approaches [26, 49, 51] explore to integrate multiple modalities like positional information and linguistic features into relationships. Later methodologies [11, 27, 35, 36, 39] identify the value of visual context in SGG. Some of them encode contextual information utilizing techniques e.g. message passing [43], LSTM [37, 41, 49], graph neural networks [19, 44], and self-attention modules [3, 6, 20]. Others [27, 39] refine the detected scene graph and optimize the features of refined predicates based on high-confidence predictions. PE-Net [54] proposes to utilize text embeddings as the centroid of predicates, aiming to minimize the intraclass variance and the inter-class similarity. Despite the improved prediction accuracy, it is still hard to extract discriminative relation cues across the various subject-object pairs in the same predicate. The core of this issue lies in the fact that the identical predicates can manifest differently under distinct subject-object pairs, encompassing a unique array", + "bbox": [ + 496, + 523, + 890, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "28370", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/93588ba668c62405ba1e6021b6514d9a0c3dd7780ad7bb0e7460754447974968.jpg", + "image_caption": [ + "Figure 3. Illustration of the proposed Dual-granularity Relation Modeling (DRM) network. The learning procedure of DRM is composed of two stages. In the first stage, we capture the coarse-grained predicate cues shared across different subject-object pairs and learn the fine-grained triplet cues under specific subject-object pairs. In the second stage, the Dual-granularity Knowledge Transfer (DKT) strategy transfers the variation from head predicates with their associate triplets to the tail. Then DRM exploits the real instances along with synthetic samples from the calibrated tail distribution to fine-tune the relation classifier, which alleviates the long-tail problem in SGG." + ], + "image_footnote": [], + "bbox": [ + 83, + 92, + 888, + 407 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "of visual cues within each manifestation. The direct aggregation of predicate features tends to overlook the inherent triplet cues present under the various subject-object pairs. We propose to explicitly model both coarse-grained predicate cues and fine-grained triplet cues for biased and unbiased SGG.", + "bbox": [ + 75, + 500, + 470, + 589 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Unbiased Scene Graph Generation", + "text_level": 1, + "bbox": [ + 76, + 604, + 380, + 619 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Real-world data tends to obey a long-tailed distribution, and imbalanced samples in scene graph present the challenge to learn and adapt to the distribution in the tail predicates [37, 38, 48, 53]. Recently, many methods have been proposed to deal with the biased prediction problem in scene graphs, which can be roughly divided into three categories. The first category of methods use re-balancing strategies that alleviate the long-tail problem by re-sampling images and triplet samples to enhance the performance of tail predicates [19] or by enhancing the loss weights of tail predicates and easily misclassified categories through the pre-defined Predicate Lattice [28]. The second category of methods utilize noisy label learning to explicitly re-label relational triplets missed by annotators and correct the unlabeled predicates [17, 50]. The last category exploit the mixture of experts to let different experts separately deal with a subpart of predicates and merge their outputs [6, 34]. Different from these approaches, we mitigate the long-tail problem", + "bbox": [ + 75, + 628, + 470, + 900 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "in SGG by exploiting knowledge from the head predicates and triplets. Our method involves transferring the abundant variations from the head predicates and their associate triplets to the tail, thus enriching patterns of the tail predicates.", + "bbox": [ + 496, + 500, + 890, + 575 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 500, + 587, + 589, + 602 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "An overview of our Dual-granularity Relation Modeling (DRM) network is illustrated in Figure 3. DRM aims to balance and integrate coarse-grained predicate cues and fine-grained triplet cues for relation recognition. To this end, a predicate cue modeling module and a triplet cue modeling module are designed to extract predicate cues shared across diverse subject and object pairs, and triplet cues shared by specific subject-object pairs, respectively. Moreover, the Dual-granularity Knowledge Transfer (DKT) strategy is proposed for unbiased SGG. This strategy transfers the knowledge of both predicates and triplets from head categories to tail ones, with the objective of enriching the pattern of tail predicates and their associated triplets.", + "bbox": [ + 496, + 612, + 890, + 809 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. The DRM Network Backbone", + "text_level": 1, + "bbox": [ + 500, + 816, + 764, + 830 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The backbone of our DRM network is composed of a proposal network and an entity encoder. Features generated by the backbone are further fed into subsequent predicate and triplet cue modeling modules.", + "bbox": [ + 496, + 839, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "28371", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Proposal Network. Given an image $\\mathcal{I}$ , the proposal network generates $N$ entities along with their corresponding visual features, label predictions, and spatial features from their bounding boxes. A pre-trained Faster RCNN [31] is adopted as the proposal network in this paper. And following previous works [6, 19, 37, 49], we initialize the entity representations $\\{\\mathbf{v}_i\\}_{i=1}^N$ with their visual and spatial features, encode the union feature $\\mathbf{u}_{i,j}$ between the $i$ -th entity and the $j$ -th entity with their relative spatial representation and the ROI feature of their union box, and obtain the semantic features $\\{\\mathbf{s}_i\\}_{i=1}^N$ of entities using word embeddings of their class labels.", + "bbox": [ + 75, + 90, + 472, + 271 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Entity Encoder. The entity encoder is designed to refine features of entities with their contexts for further predictions. Inspired by Dong et al. [6], we utilize the Hybrid Attention (HA) to incorporate semantic cues $\\{\\mathbf{s}_i\\}_{i=1}^N$ into entities $\\{\\mathbf{v}_i\\}_{i=1}^N$ while modeling the scene context. Each layer of Hybrid Attention is composed of two Self-Attention (SA) units and two Cross-Attention (CA) units, which is built upon the multi-head attention module [40]. The Hybrid Attention at the $l$ -th layer can be formulated as:", + "bbox": [ + 75, + 272, + 472, + 409 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{ \\begin{array}{l} \\mathbf {X} ^ {(l)} = S A \\left(\\mathbf {X} ^ {(l - 1)}\\right) + C A \\left(\\mathbf {X} ^ {(l - 1)}, \\mathbf {Y} ^ {(l - 1)}\\right), \\\\ \\mathbf {Y} ^ {(l)} = S A \\left(\\mathbf {Y} ^ {(l - 1)}\\right) + C A \\left(\\mathbf {Y} ^ {(l - 1)}, \\mathbf {X} ^ {(l - 1)}\\right), \\end{array} \\right. \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 106, + 419, + 468, + 462 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathbf{X}^{(l - 1)}$ and $\\mathbf{Y}^{(l - 1)}$ are inputs of the $l$ -th HA layer. We directly fuse outputs of SA and CA units with an addition operation.", + "bbox": [ + 75, + 473, + 468, + 518 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Our entity encoder $Enc_{ent}$ is consisted of a stacked 4-layer Hybrid Attention, and we have $\\mathbf{X}^{(0)} = \\{\\mathbf{v}_i\\}_{i=1}^N$ , $\\mathbf{Y}^{(0)} = \\{\\mathbf{s}_i\\}_{i=1}^N$ , and:", + "bbox": [ + 76, + 520, + 468, + 568 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{\\mathbf {v} _ {i} ^ {\\prime} \\right\\} _ {i = 1} ^ {N} = E n c _ {e n t} \\left(\\left\\{\\mathbf {v} _ {i} \\right\\} _ {i = 1} ^ {N}, \\left\\{\\mathbf {s} _ {i} \\right\\} _ {i = 1} ^ {N}\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 143, + 578, + 468, + 595 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the refined entity representations $\\{\\mathbf{v}_i^{\\prime}\\}_{i = 1}^{N}$ are obtained by summing up of outputs from the last HA layer.", + "bbox": [ + 75, + 608, + 468, + 640 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Predicate and Triplet Cue Modeling", + "text_level": 1, + "bbox": [ + 76, + 650, + 390, + 666 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Previous approaches tend to categorize predicates in a coarse manner, most of which only focus on predicate cues shared among various subject-object pairs, and thus cannot effectively deal with the potentially large visual variations inherent in the identical predicate. In contrast to these approaches, our method considers both coarse-grained predicate cues and fine-grained triplet cues, leveraging and striking a balance between the dual-grained cues for accurate predicate categorization. Our DRM network involves a Predicate Cue Modeling module and a Triplet Cue Modeling module for extracting features at these two granularities respectively. Additionally, we introduce Dual-Granularity Constraints to decrease the intra-class variance and increase inter-class distinguishability, explicitly enforcing the predicate and triplet branches to concentrate on cues from their", + "bbox": [ + 75, + 674, + 472, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "corresponding granularities and preventing the degradation of dual-granularity space.", + "bbox": [ + 496, + 90, + 890, + 119 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Predicate Cue Modeling. Our predicate cue modeling module Encprd, comprising a 2-layer Hybrid Attention, aims to capture predicate cues across different subject-object pairs. In each HA layer of Encprd, the two Self-Attention units are designed to model predicate and entity contextual information. And the two Cross-Attention units are designed to capture the dependency between entities and predicates, where the predicate $\\mathbf{p}_{i,j}$ solely queries the contexts of its corresponding subject $\\mathbf{e}_i$ and object $\\mathbf{e}_j$ , and the entity $\\mathbf{e}_i$ only queries predicates related to it. Our Predicate Cue Modeling process can thus be formulated as:", + "bbox": [ + 496, + 119, + 893, + 287 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{\\mathbf {p} _ {i, j} ^ {\\prime} \\right\\} _ {i \\neq j} ^ {M} = E n c _ {p r d} \\left(\\left\\{\\mathbf {p} _ {i, j} \\right\\} _ {i \\neq j} ^ {M}, \\left\\{\\mathbf {e} _ {i} \\right\\} _ {i = 1} ^ {N}\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 555, + 292, + 890, + 313 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the predicate representation $\\mathbf{p}_{i,j}$ is initialized with the union feature $\\mathbf{u}_{i,j}$ , the entity representation $\\mathbf{e}_i$ is obtained with the concatenation of $\\mathbf{v}_i'$ and $\\mathbf{v}_i$ , $M = N \\times (N - 1)$ is the number of subject-object pairs, and $\\mathbf{p}_{i,j}'$ is the corresponding output of $\\mathbf{p}_{i,j}$ at the last HA layer.", + "bbox": [ + 496, + 319, + 890, + 393 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Triplet Cue Modeling. Our triplet cue modeling module $Enc_{tpt}$ is also constructed using a 2-layer Hybrid Attention. This module is responsible for obtaining fine-grained triplet cues that are shared by specific subject-object pairs. The two Self-Attention units in each HA layer of $Enc_{tpt}$ are designed to model visual and semantic contextual information of triplets, respectively, and the two Cross-Attention units aim at fusing semantic cues into the visual information of triplets. We initialize the triplet representation $\\mathbf{t}_{i,j}$ with the concatenation of the subject representation $\\mathbf{e}_i$ , predicate representation $\\mathbf{p}_{i,j}$ , and object representation $\\mathbf{e}_j$ . Our Triplet Cue Modeling process is formulated as:", + "bbox": [ + 496, + 393, + 892, + 575 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\left\\{\\mathbf {t} _ {i, j} ^ {\\prime} \\right\\} _ {i \\neq j} ^ {M} = E n c _ {t p t} \\left(\\left\\{\\mathbf {t} _ {i, j} \\right\\} _ {i \\neq j} ^ {M}, \\left\\{\\left[ \\mathbf {s} _ {i} ^ {\\prime}, \\mathbf {s} _ {j} ^ {\\prime} \\right] \\right\\} _ {i \\neq j} ^ {M}\\right), \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 545, + 580, + 890, + 602 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathbf{s}_i^{\\prime}$ is the word embedding of predicted entity label, and $[\\cdot ,\\cdot ]$ denotes the concatenate operation. $\\mathbf{t}_{i,j}^{\\prime}$ is the contextually and semantically aware triplet feature, and is derived from the addition of outputs from the last HA layer.", + "bbox": [ + 496, + 607, + 890, + 667 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Dual-granularity Constraints. Although we explicitly model predicate and triplet cues with $Enc_{prd}$ and $Enc_{pt}$ , they may degrade beyond our desires with a single predicate cross-entropy loss. To prevent this degradation, we propose the dual-granularity constraints to guide the predicate and triplet cue modeling modules to refine representations in their desired granularities. Specifically, we generate two views of an input relation and impose a predicate category-aware supervised contrastive learning loss on predicate representations to capture the coarse-grained predicate cues as:", + "bbox": [ + 496, + 667, + 893, + 819 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {p} = - \\log \\frac {\\exp \\left(\\left\\langle \\mathbf {p} _ {i , j} ^ {\\prime \\prime} , \\mathbf {p} _ {p o s _ {p}} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {p}\\right)}{\\sum_ {b \\in \\mathcal {B} (i , j)} \\exp \\left(\\left\\langle \\mathbf {p} _ {i , j} ^ {\\prime \\prime} , \\mathbf {p} _ {b} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {p}\\right)}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 550, + 828, + 890, + 867 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathbf{p}_{i,j}^{\\prime \\prime}$ is obtained by passing $\\mathbf{p}_{i,j}^{\\prime}$ through a projection layer comprising two fully connected layers, $\\tau_{p}$ is the tem", + "bbox": [ + 496, + 869, + 890, + 901 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "28372", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "perature, $pos_{p}$ denotes the subscripts of positive samples belonging to the same predicate category as $\\mathbf{p}_{i,j}^{\\prime \\prime},\\langle \\cdot ,\\cdot \\rangle$ is the cosine similarity function, and $\\mathcal{B}(i,j)$ denotes the subscript set of samples within the same batch.", + "bbox": [ + 75, + 90, + 468, + 150 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Similarly, a triplet category-aware supervised contrastive learning loss is applied on triplet representations, aiming at capturing the fine-grained triplet cues as:", + "bbox": [ + 75, + 151, + 468, + 196 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {t} = - \\log \\frac {\\exp \\left(\\left\\langle \\mathbf {t} _ {i , j} ^ {\\prime \\prime} , \\mathbf {t} _ {p o s _ {t}} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {t}\\right)}{\\sum_ {b \\in \\mathcal {B} (i , j)} \\exp \\left(\\left\\langle \\mathbf {t} _ {i , j} ^ {\\prime \\prime} , \\mathbf {t} _ {b} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {t}\\right)}, \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 133, + 205, + 468, + 244 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\tau_{t}$ is the temperature, $pos_{t}$ denotes subscripts of positive samples from the same triplet category as $\\mathbf{t}_{i,j}^{\\prime \\prime}$ , and $\\mathbf{t}_{i,j}^{\\prime \\prime}$ is obtained by passing $\\mathbf{t}_{i,j}^{\\prime}$ through a projection layer.", + "bbox": [ + 75, + 253, + 468, + 300 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Scene Graph Prediction. For each relationship proposal, our predicate classifier utilizes two fully connected layers to integrate the coarse-grained and fine-grained cues, i.e. $\\mathbf{p}_{i,j}^{\\prime}$ and $\\mathbf{t}_{i,j}^{\\prime}$ , to obtain the final relation label prediction. For each entity, we also introduce a fully connected layer with softmax function to get its refined label prediction.", + "bbox": [ + 76, + 300, + 468, + 388 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Training Loss. During the training in the first stage of DRM, the overall loss function $\\mathcal{L}$ is defined as:", + "bbox": [ + 76, + 390, + 468, + 420 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\lambda_ {e} \\mathcal {L} _ {e} + \\lambda_ {r} \\mathcal {L} _ {r} + \\lambda_ {p} \\mathcal {L} _ {p} + \\lambda_ {t} \\mathcal {L} _ {t}, \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 151, + 431, + 468, + 450 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{L}_e$ and $\\mathcal{L}_r$ are cross-entropy losses of entities and relationships respectively. $\\lambda_e, \\lambda_r, \\lambda_p,$ and $\\lambda_t$ are pre-defined weight hyper-parameters for corresponding loss terms.", + "bbox": [ + 75, + 460, + 468, + 506 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Dual-granularity Knowledge Transfer", + "text_level": 1, + "bbox": [ + 76, + 513, + 405, + 531 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The SGG task typically suffers from the long-tail distribution problem. This problem primarily originates from the tail predicate classes, which possesses limited types and quantities of triplets. The head predicate classes contain a relatively larger number of samples and an abundance of triplet types. Thus to alleviate the long-tail problem, we propose the Dual-granularity Knowledge Transfer (DKT) strategy to transfer knowledge in predicate and triplet feature spaces from head predicate class to the tail one. DKT generates samples belonging to the tail predicates with their associated predicate and triplet features, thereby enriching and diversifying the patterns of tail predicates.", + "bbox": [ + 75, + 537, + 468, + 718 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Specifically, DKT first calculates the distributions of predicate and triplet features. We assume that the distribution of each category $\\Omega_c$ follows a multidimensional Gaussian distribution. Formally, it can be expressed as $\\{\\Omega_c = \\mathcal{N}(\\pmb{\\mu}_c, \\pmb{\\sigma}_c) | c \\in \\mathcal{C}\\}$ , where $\\pmb{\\mu}_c$ and $\\pmb{\\sigma}_c$ denote the mean and covariance of $\\Omega_c$ , and $c$ denotes the predicate or triplet category. After the first-stage pre-training of DRM network, we freeze the proposal network, entity encoder, and the predicate and triplet cue modeling modules. Subsequently, the compact predicate and triplet features, i.e. $\\mathbf{p}'$ and $\\mathbf{t}'$ , are extracted to calculate the predicate and triplet feature distributions, respectively. The mean, denoted as $\\pmb{\\mu}_c$ , is calculated", + "bbox": [ + 75, + 719, + 468, + 900 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "as $\\pmb{\\mu}_{c} = \\frac{1}{N_{c}}\\sum_{k}^{N_{c}}\\mathbf{x}_{k}^{c}$ . The covariance, symbolized as $\\pmb{\\sigma}_{c}$ , is calculated as $\\pmb{\\sigma}_{c} = \\frac{1}{N_{c} - 1}\\sum_{k}^{N_{c}}(\\mathbf{x}_{k}^{c} - \\pmb{\\mu}_{c})(\\mathbf{x}_{k}^{c} - \\pmb{\\mu}_{c})^{T}$ . Here, $\\mathbf{x}_i^c$ denotes the feature of category $c$ , and $N_{c}$ is the number of $\\mathbf{x}_k^c$ . The feature $\\mathbf{x}$ can be either $\\mathbf{p}'$ or $\\mathbf{t}'$ .", + "bbox": [ + 496, + 89, + 890, + 155 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "We then transfer knowledge of feature distributions of head predicate classes to the tail ones. Specifically, we arrange the predicate classes in descending order based on their sample numbers, choosing half of the predicate classes as head predicates and the remaining ones as tail predicates. We further select triplets that appear more than certain times in the head predicates to be the head triplets (we use 64 times as the threshold in this paper), and those in the tail predicates to be the tail triplets. For each tail category $i \\in \\mathcal{C}$ we compute the euclidean distance $d_{i,j}$ between its center $\\pmb{\\mu}_i$ and the center $\\pmb{\\mu}_j$ of head category $j \\in \\mathcal{C}$ . The closer the centers of two categories are to each other in either predicate or triplet space, the more similar they are, which also increases the likelihood of knowledge sharing between them. Based on $d_{i,j}$ , we achieve the knowledge transfer as:", + "bbox": [ + 496, + 155, + 892, + 382 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\boldsymbol {\\sigma} _ {i} ^ {\\prime} = \\frac {N _ {i}}{Q _ {i}} \\boldsymbol {\\sigma} _ {i} + \\left(1 - \\frac {N _ {i}}{Q _ {i}}\\right) \\sum_ {j} \\alpha_ {i, j} \\boldsymbol {\\sigma} _ {j}, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 573, + 391, + 890, + 429 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\alpha_{i,j}$ denotes the softmax normalized form of $d_{i,j}$ , $Q_{i}$ denotes the desired number of predicate/triplet instances of tail class $i$ and it is identical for every predicates in the tail. It suggests that the tail category with fewer samples requires more knowledge from the head for calibration.", + "bbox": [ + 496, + 439, + 890, + 513 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "After dual-granularity knowledge transfer, we generate synthetic samples in tail predicate using corresponding predicate and triplet features from calibrated distributions:", + "bbox": [ + 496, + 515, + 890, + 560 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\{\\hat {\\boldsymbol {x}} | \\hat {\\boldsymbol {x}} \\sim \\Omega_ {c} ^ {\\prime} = \\mathcal {N} \\left(\\boldsymbol {\\mu} _ {c}, \\boldsymbol {\\sigma} _ {c} ^ {\\prime}\\right) \\}. \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 602, + 570, + 890, + 588 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Finally, we under-sample head predicates to form a balanced dataset and input the real instances together with synthetic ones into the relation classifier for fine-tuning. Benefiting from the dual-granularity knowledge transfer, the patterns of tail predicates and their associate triplets can be enriched, thus alleviating the long-tail problem.", + "bbox": [ + 496, + 597, + 890, + 688 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 700, + 633, + 718 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Experimental Settings", + "text_level": 1, + "bbox": [ + 500, + 726, + 705, + 742 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Datasets. We evaluate our method on three commonly used SGG datasets, namely Visual Genome [14], Open Image [13], and GQA [10]. For the Visual Genome dataset, we adopt the VG150 split following previous approaches [23, 29, 37, 43, 49], which contains the most frequent 150 object categories and 50 predicate categories. We use $70\\%$ of images for training, $30\\%$ images for testing and $5\\mathrm{k}$ images from the training set for validation. As for Open Image, we apply the Open Image V6 protocol, which has 301 object categories and 31 predicate categories. It contains", + "bbox": [ + 496, + 750, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "28373", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/b4651264ee2902730820870439328e617a0c2f8dbc02373dfd9f9eb1c736552f.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelsPredClsSGClsSGDet
R@50/100mR@50/100R@50/100mR@50/100R@50/100mR@50/100
IMP [43]CVPR'1761.1 / 63.111.0 / 11.837.5 / 38.56.2 / 6.525.9 / 31.24.2 / 5.3
VTransE [51]CVPR'1765.7 / 67.614.7 / 15.838.6 / 39.48.2 / 8.729.7 / 34.35.0 / 6.1
MOTIFS [49]CVPR'1866.0 / 67.914.6 / 15.839.1 / 39.98.0 / 8.532.1 / 36.95.5 / 6.8
G-RCNN [44]ECCV'1865.4 / 67.216.4 / 17.237.0 / 38.59.0 / 9.529.7 / 32.85.8 / 6.6
VCTREE [37]CVPR'1965.5 / 67.416.7 / 17.940.3 / 41.67.9 / 8.331.9 / 36.06.4 / 7.3
GPS-Net [22]CVPR'2065.2 / 67.115.2 / 16.637.8 / 39.28.5 / 9.131.3 / 35.96.7 / 8.6
RU-Net [24]CVPR'2267.7 / 69.6- / 24.242.4 / 43.3- / 14.632.9 / 37.5- / 10.8
HL-Net [23]CVPR'2267.0 / 68.9- / 22.842.6 / 43.5- / 13.533.7 / 38.1- / 9.2
PE-Net(P) [54]CVPR'2368.2 / 70.123.1 / 25.441.3 / 42.313.1 / 14.832.4 / 36.98.9 / 11.0
VETO [34]ICCV'2364.2 / 66.322.8 / 24.735.7 / 36.911.1 / 11.927.5 / 31.58.1 / 9.5
TDE° [38]CVPR'2046.2 / 51.425.5 / 29.127.7 / 29.913.1 / 14.916.9 / 20.38.2 / 9.8
CogTree° [47]IJCAI'2135.6 / 36.826.4 / 29.021.6 / 22.214.9 / 16.120.0 / 22.110.4 / 11.8
BPL-SA° [9]ICCV'2150.7 / 52.529.7 / 31.730.1 / 31.016.5 / 17.523.0 / 26.913.5 / 15.6
VisualDS° [46]ICCV'21- / -16.1 / 17.5- / -9.3 / 9.9- / -7.0 / 8.3
NICE° [17]CVPR'2255.1 / 57.229.9 / 32.333.1 / 34.016.6 / 17.927.8 / 31.812.2 / 14.4
PPDL° [21]CVPR'2247.2 / 47.632.2 / 33.328.4 / 29.317.5 / 18.221.2 / 23.911.4 / 13.5
GCL° [6]CVPR'2242.7 / 44.436.1 / 38.226.1 / 27.120.8 / 21.818.4 / 22.016.8 / 19.3
IETrans° [50]ECCV'22- / -35.8 / 39.1- / -21.5 / 22.8- / -15.5 / 18.0
INF° [2]CVPR'2351.5 / 55.124.7 / 30.732.2 / 33.814.5 / 17.423.9 / 27.19.4 / 11.7
CFA° [18]ICCV'2354.1 / 56.635.7 / 38.234.9 / 36.117.0 / 18.427.4 / 31.813.2 / 15.5
EICR° [29]ICCV'2355.3 / 57.434.9 / 37.034.5 / 35.420.8 / 21.827.9 / 32.215.5 / 18.2
BGNN [19]CVPR'2159.2 / 61.330.4 / 32.937.4 / 38.514.3 / 16.531.0 / 35.810.7 / 12.6
SHA+GCL [6]CVPR'2235.1 / 37.241.6 / 44.122.8 / 23.923.0 / 24.314.9 / 18.217.9 / 20.9
PE-Net [54]CVPR'2364.9 / 67.231.5 / 33.839.4 / 40.717.8 / 18.930.7 / 35.212.4 / 14.5
SQUAT [12]ICCV'2355.7 / 57.930.9 / 33.433.1 / 34.417.5 / 18.824.5 / 28.914.1 / 16.5
CaCao [48]ICCV'23- / -41.7 / 43.7- / -24.0 / 25.0- / -18.3 / 22.1
DRM w/o DKT70.2 / 72.123.3 / 25.644.3 / 45.213.5 / 14.634.0 / 38.99.0 / 11.2
DRM43.9 / 45.847.1 / 49.627.5 / 28.427.8 / 29.219.0 / 22.920.4 / 24.1
", + "bbox": [ + 140, + 88, + 826, + 503 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/291852691992eea2eaddfb534555a94dffd2107724e9b4f6329a23f94cd4bff1.jpg", + "table_caption": [ + "Table 1. Comparison results with state-of-the-art SGG methods on the VG150 dataset. \"◇\" denotes the combination of MOTIFS with a model-agnostic unbiased strategy. The best and second best results under each setting are respectively marked in red and underline blue." + ], + "table_footnote": [], + "table_body": "
ModelR@50WmAPscorewtd
relphr
MOTIFS [49]CVPR'1871.629.931.638.9
G-RCNN [44]ECCV'1874.533.234.241.8
VCTREE [37]CVPR'1974.134.233.140.2
GPS-Net [22]CVPR'2074.832.934.041.7
BGNN [19]CVPR'2175.033.534.242.1
RU-Net [24]CVPR'2276.935.434.943.5
HL-Net [23]CVPR'2276.535.134.743.2
PE-Net [54]CVPR'2376.536.637.444.9
SQUAT [12]ICCV'2375.834.935.943.5
DRM w/o DKT75.940.541.447.9
", + "bbox": [ + 91, + 553, + 450, + 723 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Comparison results with state-of-the-art SGG methods on Open Image V6. The best and second best results under each metric are respectively marked in red and underline blue.", + "bbox": [ + 75, + 728, + 468, + 770 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "126,368, 1,183, and 5,322 images for training, validation, and testing, respectively. For the GQA dataset, we follow previous works [6, 34] and utilize the GQA200 split, which includes 200 object categories and 100 predicate categories.", + "bbox": [ + 75, + 790, + 468, + 852 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Tasks. We adopt three SGG tasks for evaluation: 1) Predicate Classification (Predcls) infers the predicates of entity pairs with ground-truth bounding boxes and cate", + "bbox": [ + 75, + 854, + 468, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "gories. 2) Scene Graph Classification (SGCls) aims to predict the triplet categories with ground-truth bounding boxes. 3) Scene Graph Detection (SGDet) detects bounding boxes of entity pairs and infers their predicate categories.", + "bbox": [ + 496, + 556, + 890, + 617 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation Metrics. We use Recall@K (R@K) and mean Recall@K (mR@K) as evaluation metrics on VG150 and GQA200 datasets, following recent works [6, 34, 54]. R@K tends to prioritize frequent predicates, while mR@K exhibits a preference for less frequent predicates. Results on Open Image dataset are evaluated using Recall@50 (R@50), weighted mean AP of relations (wmAPrel) weighted mean AP of phrase (wmAPphr), and a weighted score of them scorewtd = 0.2 × R@50 + 0.4 × wAPrel + 0.4 × wAPphr, following previous works [19, 23, 52].", + "bbox": [ + 496, + 622, + 892, + 773 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation Details. Following previous works [6, 34, 54], we adopt the pre-trained Faster RCNN with ResNeXt-101-RPN in the proposal network to detect entities in the image. GloVe [30] is applied to embed the semantic features. We set the loss weight parameters $\\lambda_r$ , $\\lambda_e$ , $\\lambda_t$ , and $\\lambda_p$ as 3, 0.5, 0.1, and 0.1, respectively. Temperatures $\\tau_p$ and $\\tau_t$ are set as 0.2, and 0.1 considering that the predicate feature space exhibits greater variety than its asso", + "bbox": [ + 496, + 779, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "28374", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/63c292bb61bb9741f89f8169b1548a83239153ae690d6ff1f7bd0d7a182da1d4.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
ModelsPredClsSGClsSGDet
R@50/100mR@50/100R@50/100mR@50/100R@50/100mR@50/100
VTransE [51]CVPR'1755.7 / 57.914.0 / 15.033.4 / 34.28.1 / 8.727.2 / 30.75.8 / 6.6
MOTIFS [49]CVPR'1865.3 / 66.816.4 / 17.134.2 / 34.98.2 / 8.628.9 / 33.16.4 / 7.7
VCTREE [37]CVPR'1963.8 / 65.716.6 / 17.434.1 / 34.87.9 / 8.328.3 / 31.96.5 / 7.4
SHA [6]CVPR'2263.3 / 65.219.5 / 21.132.7 / 33.68.5 / 9.025.5 / 29.16.6 / 7.8
VETO [34]ICCV'2364.5 / 66.021.2 / 22.130.4 / 31.58.6 / 9.126.1 / 29.07.0 / 8.1
VTransE+GCL [6]CVPR'2235.5 / 37.430.4 / 32.322.9 / 23.616.6 / 17.415.3 / 18.014.7 / 16.4
MOTIFS+GCL [6]CVPR'2244.5 / 46.236.7 / 38.123.2 / 24.017.3 / 18.118.5 / 21.816.8 / 18.8
VCTREE+GCL [6]CVPR'2244.8 / 46.635.4 / 36.723.7 / 24.517.3 / 18.017.6 / 20.715.6 / 17.8
SHA+GCL [6]CVPR'2242.7 / 44.541.0 / 42.721.4 / 22.220.6 / 21.314.8 / 17.917.8 / 20.1
DRM w/o DKT66.9 / 68.418.1 / 19.036.4 / 37.27.1 / 7.430.6 / 34.66.9 / 8.4
DRM43.2 / 44.441.9 / 43.523.3 / 23.919.9 / 20.718.6 / 21.718.9 / 21.0
", + "bbox": [ + 132, + 88, + 834, + 272 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/2fb9d53967ed89f96a8fe87946cc15463b183338c162f5a1038f653d3e694b59.jpg", + "table_caption": [ + "Table 3. Comparison results with state-of-the-art SGG methods on the GQA200 dataset. The best and second best results under each setting are respectively marked in red and underline blue." + ], + "table_footnote": [], + "table_body": "
ModulePredClsSGCls
PTACR@50/100mR@50/100R@50/100
56.5/60.415.5/17.437.5/39.310.1/11.3
✓67.6/69.518.1/19.941.8/42.710.8/11.8
✓67.6/69.820.5/22.542.3/43.212.6/13.6
✓✓69.3/71.320.8/22.842.8/43.812.8/13.9
✓✓✓69.8/71.620.4/22.343.4/44.412.8/13.8
✓✓✓69.8/71.622.0/24.043.4/44.312.3/13.3
✓✓✓69.7/71.521.9/24.343.8/44.812.7/13.9
✓✓✓70.2/72.123.3/25.644.3/45.213.5/14.6
", + "bbox": [ + 81, + 316, + 468, + 463 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/eea2ef689c9ea3d1dab8872625a72d894e88c2349ce54dc991edce27c120d436.jpg", + "table_caption": [ + "Table 4. Ablation studies on predicate and triplet cues learning. \"P\", \"T\", \"A\", and \"C\" denote the predicate cue modeling module, triplet cue modeling module, augmentation in dual-granularity constraints, and the dual-granularity constraints loss, respectively." + ], + "table_footnote": [], + "table_body": "
ModulePredClsSGCls
R@50/100mR@50/100R@50/100mR@50/100
None70.2/72.123.3/25.644.3/45.213.5/14.6
DKT-P42.4/44.245.0/47.326.8/27.826.9/28.1
DKT-T40.4/42.246.1/48.724.3/25.326.4/28.0
DKT43.9/45.847.1/49.627.5/28.427.8/29.2
", + "bbox": [ + 83, + 534, + 464, + 623 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 5. Ablation studies on dual-granularity knowledge transfer. \"DKT-P\" and \"DKT-T\" denote the predicate knowledge transfer and triplet knowledge transfer.", + "bbox": [ + 75, + 628, + 468, + 672 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ciated triplet one. We optimize our method via SGD, using an initial leaning late of $10^{-4}$ with a batch size of 16.", + "bbox": [ + 75, + 681, + 468, + 712 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "4.2. Comparison with State-of-the-art Methods", + "text_level": 1, + "bbox": [ + 75, + 724, + 441, + 742 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "To evaluate the performance our model, we compare it with several state-of-the-art SGG approaches on Visual Genome, Open Image, and GQA datasets. The comparison methods include IMP [43], MOTIFS [49], VCTREE [37], RU-Net [24], HL-Net [23], PE-Net [54], and VETO [34], which focus on the prediction of every relationship in an image. We also compare with methods for unbiased scene graph generation, including TDE [38], CogTree [47], NICE [17], INF [2], CFA [18], EICR [29], BGNN [19], SHA+GCL [6], SQUAT [12], and CaCao[48]. In addition, we compare", + "bbox": [ + 75, + 750, + 468, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "our method with VETO+MEET [34] in the setting without graph constraint in the Supplementary Material.", + "bbox": [ + 496, + 319, + 890, + 349 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Visual Genome. Table 1 shows the comparison results of different approaches on VG150. From these results, we have the following observations: 1) our proposed method significantly outperforms all baselines on all three tasks. More specifically, our DRM w/o DKT outperforms the recent PE-Net [54] by $2.0\\%$ , $2.9\\%$ , and $2.0\\%$ at R@100 on PredCls, SGCls, and SGDet, respectively. Unlike approaches such as MOTIFS [49] and VCTREE [37], which only utilize a predicate classifier to predict predicates and overlook the triplet cues, our method leverages coarse-grained predicate cues and fine-grained triplet cues for relation recognition and thus achieves superior results. 2) Our DRM method also has considerably better performance compared to the baseline unbiased SGG methods. Notably, based on the proposed DKT strategy in DRM, our method outperforms the recent multi-expert method SHA+GCL [6] by $5.5\\%$ , $4.9\\%$ , and $3.2\\%$ at mR@100 on three tasks. This demonstrates that transferring knowledge from head predicates to tail predicates at dual granularities and enriching the patterns in tail predicates can effectively mitigate the long-tail problem.", + "bbox": [ + 496, + 352, + 892, + 669 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Open Image. Compared to the VG dataset, Open Image provides a relatively complete labeling of relationships in the images. Consequently, the model's capability to generate scene graphs can be evaluated at a fine-grained level utilizing the AP metric. To evaluate the generalizability of our method across various datasets, we conduct experiments on Open Image V6. Since the metrics in Open Image V6 tend to prioritize frequent predicates, we just compare our DRM w/o DKT with state-of-the-art approaches. The comparison results shown in Table 2 indicate that our DRM w/o DKT significantly outperforms the recent approaches, i.e., SQUAT [12] and PE-Net [54].", + "bbox": [ + 496, + 671, + 890, + 852 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "GQA. Compared to Visual Genome and Open Image datasets, GQA200 contains a broader range of predicates. So we further confirm the generality of our model on the", + "bbox": [ + 496, + 854, + 890, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "28375", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/fb1f74fcc34a696ae95cc298fccddb16b444d3cae279c05261d9caa319d51904.jpg", + "image_caption": [ + "(a) MOTIFS, Triplet" + ], + "image_footnote": [], + "bbox": [ + 83, + 90, + 236, + 204 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e193cbcac6da00784390bbd73a2c352b3d1b4467504e57313b110760c508ca00.jpg", + "image_caption": [ + "(b) DRM w/o DKT, Triplet" + ], + "image_footnote": [], + "bbox": [ + 243, + 90, + 397, + 205 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/2d5f2a6106667f987a0d8c943d5a00e2b36a7e8484b91f7c15b665f4923a67b5.jpg", + "image_caption": [ + "(c) DRM, Triplet", + "Figure 4. The comparison of t-SNE visualization results on predicate and triplet feature distributions within the VG dataset. \"MOTIFS, Triplet\" and \"DRM w/o DKT, Triplet\" visualize the same set of samples, where each unique color represents a different type of triplet." + ], + "image_footnote": [], + "bbox": [ + 406, + 90, + 560, + 205 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/edc6eaebf09caba9c3d91b03e24084e28aff9f0c288ab809fe758a82e0ec9876.jpg", + "image_caption": [ + "(d) DRM w/o DKT, Predicate" + ], + "image_footnote": [], + "bbox": [ + 568, + 90, + 720, + 205 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/fae206042c6cdfaa0904f7c334b247a4ff230c879b025fd7319b09f367c557d7.jpg", + "image_caption": [ + "(e) DRM, Predicate" + ], + "image_footnote": [], + "bbox": [ + 730, + 90, + 882, + 205 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "GQA200 dataset. As shown in Table 3, our method significantly outperforms the recent VETO [34] at R@100 on three tasks. When equipped with DKT, our DRM outperforms $\\mathrm{SHA + GCL}$ [6] by an average of $0.4\\%$ at mR@100 across three tasks. These results demonstrate the consistent effectiveness of our method in handling relation recognition under different data distributions.", + "bbox": [ + 75, + 268, + 468, + 375 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3. Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 383, + 230, + 400 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To verify the contributions of different components in our DRM network, we conduct the following ablation studies.", + "bbox": [ + 75, + 409, + 468, + 439 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Predicate and Triplet Cue Learning. We first perform an ablation study on the leverage of predicate and triplet cues. As shown in Table 4, we incrementally incorporate one component into the baseline to verify their effectiveness. Compared with the application of predicate or triplet cue modeling in isolation, leveraging both predicate and triplet together improves the performance. Our dual-granularity constraints include a constraint loss component and a two-view augmentation component to generate positive pairs in each training batch. The constraints compel predicate and triplet cue modeling to concentrate on corresponding granularities. We observe from the results that both the loss component and augmentation component contribute to the performance improvements.", + "bbox": [ + 75, + 439, + 468, + 651 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Dual-Granularity Knowledge Transfer. As shown in Table 5, we conduct an ablation study for the DKT. We observe an obvious performance gain on $\\mathrm{mR}@\\mathrm{K}$ when transferring knowledge at either predicate or triplet granularity. The $\\mathrm{mR}@\\mathrm{K}$ is further improved when predicate and triplet granularities are simultaneously employed. In comparison to the scenario without the application of DKT, we observe a performance decrease in $\\mathrm{R}@\\mathrm{K}$ when using it. This is attributed to the capability of our model to reasonably classify ambiguous head predicates, e.g. \"on\", into more specific tail predicates, e.g. \"sitting on\". Consequently, decreases at the $\\mathrm{R}@\\mathrm{K}$ for these head predicates are inevitable [17, 54].", + "bbox": [ + 75, + 652, + 468, + 834 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.4. Visualization Analysis", + "text_level": 1, + "bbox": [ + 76, + 845, + 284, + 862 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "To illustrate the ability our method to learn triplet cues and impact of the DKT strategy, we visualize the predicate and", + "bbox": [ + 75, + 869, + 468, + 901 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "triplet feature distributions using t-SNE. The visualization results are shown in Figure 4. Comparing Figure 4a with Figure 4b, we observe that our DRM generates compact and distinguishable triplet representations, while MOTIFS [49] appears to overlook the triplet cues, leading to a challenge in distinguishing various triplet types. By comparing Figure 4b with Figure 4c, it can be observed that DKT can generate synthetic samples with diverse distributions for the tail triplets. Figures 4d and 4e demonstrate that DKT also transfers the knowledge of head predicates to tail predicates, increasing the tail predicate patterns. The visualization of predicate and triplet feature distributions demonstrates the interpretability of our method in leveraging predicate and triplet cues and transferring the dual-granularity knowledge.", + "bbox": [ + 496, + 268, + 893, + 482 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 502, + 617, + 517 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we propose a Dual-granularity Relation Modeling (DRM) network to address two issues in SGG, i.e. the diverse visual appearance within the same predicate and the lack of patterns in tail predicates. Our DRM network captures the coarse-grained predicate cues shared across different subject-object pairs and fine-grained triplet cues under specific subject-object pairs for relationship recognition. The Dual-granularity Knowledge Transfer (DKT) is further proposed to transfer the variation from head predicates to the tail to enrich the tail predicate patterns. Quantitative and qualitative experiments demonstrate that our method establishes new state-of-the-art performances on Visual Genome, Open Image and GQA datasets.", + "bbox": [ + 496, + 530, + 890, + 727 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement", + "text_level": 1, + "bbox": [ + 500, + 748, + 660, + 765 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported in part by the National Key R&D Program of China under Grant 2022ZD0161901, the National Natural Science Foundation of China under Grants 62276018 and U20B2069, the Beijing Nova Program under Grant 20230484297, the Fundamental Research Funds for the Central Universities, and Research Program of State Key Laboratory of Complex & Critical Software Environment.", + "bbox": [ + 496, + 773, + 890, + 887 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "28376", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Hedi Ben-Younes, Remi Cadene, Nicolas Thome, and Matthieu Cord. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 22783-22792, 2023. 1, 2, 6, 7, 8" + ], + "bbox": [ + 78, + 90, + 468, + 444 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "28379", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Leveraging Predicate and Triplet Learning for Scene Graph Generation/24e4e41a-71a3-4905-abbc-d74d18828d82_model.json b/2024/Leveraging Predicate and Triplet Learning for Scene Graph Generation/24e4e41a-71a3-4905-abbc-d74d18828d82_model.json new file mode 100644 index 0000000000000000000000000000000000000000..9ca896d83bc9e361b3bf5eb928d4bd635f44c860 --- /dev/null +++ b/2024/Leveraging Predicate and Triplet Learning for Scene Graph Generation/24e4e41a-71a3-4905-abbc-d74d18828d82_model.json @@ -0,0 +1,2301 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.812, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.123, + 0.131, + 0.848, + 0.154 + ], + "angle": 0, + "content": "Leveraging Predicate and Triplet Learning for Scene Graph Generation" + }, + { + "type": "text", + "bbox": [ + 0.175, + 0.18, + 0.836, + 0.199 + ], + "angle": 0, + "content": "Jiankai \\(\\mathsf{Li}^{1,2,3}\\) Yunhong Wang\\(^{1}\\) Xiefan Guo\\(^{1}\\) Ruijie Yang\\(^{1}\\) Weixin Li\\(^{1,2,3*}\\)" + }, + { + "type": "text", + "bbox": [ + 0.133, + 0.199, + 0.874, + 0.217 + ], + "angle": 0, + "content": "1 IRIP Lab, School of Computer Science and Engineering, Beihang University, Beijing, China" + }, + { + "type": "text", + "bbox": [ + 0.089, + 0.217, + 0.918, + 0.234 + ], + "angle": 0, + "content": "\\(^{2}\\) State Key Laboratory of Complex & Critical Software Environment, Beihang University, Beijing, China" + }, + { + "type": "text", + "bbox": [ + 0.258, + 0.234, + 0.75, + 0.253 + ], + "angle": 0, + "content": "\\(^{3}\\) Shanghai Artificial Intelligence Laboratory, Shanghai, China" + }, + { + "type": "text", + "bbox": [ + 0.254, + 0.255, + 0.748, + 0.27 + ], + "angle": 0, + "content": "{lijiankai, yhwang, xfguo, rjyang, weixinli}@buaa.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.305, + 0.313, + 0.32 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.337, + 0.473, + 0.775 + ], + "angle": 0, + "content": "Scene Graph Generation (SGG) aims to identify entities and predict the relationship triplets \\(<\\) subject, predicate, object> in visual scenes. Given the prevalence of large visual variations of subject-object pairs even in the same predicate, it can be quite challenging to model and refine predicate representations directly across such pairs, which is however a common strategy adopted by most existing SGG methods. We observe that visual variations within the identical triplet are relatively small and certain relation cues are shared in the same type of triplet, which can potentially facilitate the relation learning in SGG. Moreover, for the long-tail problem widely studied in SGG task, it is also crucial to deal with the limited types and quantity of triplets in tail predicates. Accordingly, in this paper, we propose a Dual-granularity Relation Modeling (DRM) network to leverage fine-grained triplet cues besides the coarse-grained predicate ones. DRM utilizes contexts and semantics of predicate and triplet with Dual-granularity Constraints, generating compact and balanced representations from two perspectives to facilitate relation recognition. Furthermore, a Dual-granularity Knowledge Transfer (DKT) strategy is introduced to transfer variation from head predicates/triplets to tail ones, aiming to enrich the pattern diversity of tail classes to alleviate the long-tail problem. Extensive experiments demonstrate the effectiveness of our method, which establishes new state-of-the-art performance on Visual Genome, Open Image, and GQA datasets. Our code is available at https://github.com/jkli1998/DRM" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.791, + 0.208, + 0.807 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.817, + 0.47, + 0.879 + ], + "angle": 0, + "content": "Entities and their associated relationships form the cornerstones of visual contents in images [14]. Scene Graph Generation (SGG), a fundamental task in visual scene understanding, is designed to detect these entities and predict" + }, + { + "type": "image", + "bbox": [ + 0.534, + 0.306, + 0.693, + 0.378 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.561, + 0.379, + 0.668, + 0.392 + ], + "angle": 0, + "content": "" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.306, + 0.855, + 0.379 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.718, + 0.38, + 0.834, + 0.392 + ], + "angle": 0, + "content": "" + }, + { + "type": "image", + "bbox": [ + 0.534, + 0.392, + 0.692, + 0.465 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.548, + 0.467, + 0.68, + 0.478 + ], + "angle": 0, + "content": "" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.392, + 0.855, + 0.465 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.709, + 0.467, + 0.841, + 0.478 + ], + "angle": 0, + "content": "" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.485, + 0.892, + 0.583 + ], + "angle": 0, + "content": "Figure 1. The illustration of large visual variations within the predicate \"eating\". Identical predicate can appear differently under distinct subject-object pairs, encompassing a different set of visual cues within each manifestation. Identifying discriminative relation cues that are shared across diverse subject-object pairs within the same predicate can be challenging. Yet, they can be easily captured when the scope is narrowed to the identical triplet." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.892, + 0.704 + ], + "angle": 0, + "content": "their pairwise relationships, encapsulating them into \\(<\\text{subject}, \\text{predicate}, \\text{object}>\\) triplets [4, 26, 51]. The generated compact graph-structured image representation can be utilized in a range of applications, e.g. embodied navigation [7, 33], image retrieval [5, 8], visual question answering [1, 32], etc., so the SGG task has received widespread attention in recent years [12, 16, 22, 45]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.893, + 0.902 + ], + "angle": 0, + "content": "Existing SGG methods are mostly dedicated to generating discriminative predicate representations for the detected entities, based on their appearances, relative positions, contextual cues, etc. [15, 19, 37, 44, 54]. However, as shown in Figure 1, large visual variations due to different subject-object combinations are inherent even in the same predicate, presenting an obstacle for SGG methods to capture robust predicate cues across distinct triplet types. To alleviate this problem, PE-Net [54] utilizes textual semantics of predicate categories as the prototype and model predicate cues by reducing the intra-class variance and inter-class similarity. Despite the improved prediction accuracy, PE-Net still follows the previous strategy of straightforwardly amalga" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.888, + 0.221, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "28369" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.122 + ], + "angle": 0, + "content": "mating predicate cues that probably contain extensive visual variations of diverse triplets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.125, + 0.469, + 0.291 + ], + "angle": 0, + "content": "Moreover, many recent efforts have been devoted to the long-tail problem in SGG task. Insufficient samples with limited triplet types lead to the reduced diversity observed in tail predicate categories, making it a challenging task to learn and adapt to their distributions. Existing methods boost model's attention towards tail predicate categories through re-sampling [19], re-weighting[28], or the utilization of mixture of experts [6, 34]. However, they mostly fall short of directly tackling the core of the long-tail issue, i.e., the insufficient patterns for tail predicates, leaving space for further improvement." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.294, + 0.47, + 0.535 + ], + "angle": 0, + "content": "Reflecting on similarities and differences among predicates, we find that despite the non-negligible or even large variations inherent in the same predicate, the visual diversity of the same triplet is relatively small (e.g. the two instances of in Figure 1). Accordingly, considering the more fine-grained triplet cues in addition to the coarse-grained predicate ones can help prevent the model from getting stuck in the refinement process of predicate features with potentially large variations, and promote it to strike a balance between different granularities during the relationship learning process. For the long-tail problem in SGG task which primarily emerges due to the insufficient tail predicate patterns and corresponding limited types and quantity of triplets, it then becomes a natural choice to enrich tail predicate patterns using head predicates and their triplets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.539, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Based on the aforementioned insights, we propose a Dual-granularity Relation Modeling (DRM) network that models triplet cues to facilitate predicate learning and transfer knowledge from the head classes to tail classes for relation recognition. In our DRM network, as shown in Figure 2, 1) besides a predicate branch that models coarse-grained predicate cues by leveraging their contextual predicates and subject-object pairs, a triplet branch is also presented to strengthen fine-grained triplet representations via jointly exploring their visual contents and corresponding label semantics. We also devise dual-granularity constraints to prevent the degradation of predicate and triplet feature spaces during model training. Subsequently, 2) the Dual-granularity Knowledge Transfer (DKT) strategy is proposed to transfer the class variance from head classes to tail ones from both the predicate and triplet perspectives for unbiased SGG. Distributions of tail predicates/triplets are designed to be calibrated using variance from head ones that are most similar to them. New predicate/triplet samples are generated as well based on the calibrated distributions to enrich the pattern diversity of tail predicates/triplets. Extensive experiments conducted on the widely used Visual Genome [14], Open Image [13], and GQA [10] datasets for SGG demonstrate the state-of-the-art performance of our method." + }, + { + "type": "image", + "bbox": [ + 0.514, + 0.091, + 0.88, + 0.226 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.228, + 0.892, + 0.299 + ], + "angle": 0, + "content": "Figure 2. Comparison of different pipelines for relation recognition. Previous methods focus on learning predicate cues shared across various triplets with diverse visual appearance. Our method learns and leverages both triplet cues within the same triplet and predicate cues across triplets, to better handle the visual diversity." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.312, + 0.851, + 0.326 + ], + "angle": 0, + "content": "Contributions of this paper can be summarized as:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.327, + 0.891, + 0.371 + ], + "angle": 0, + "content": "- We propose to learn scene graphs in a dual-granularity manner, integrating both coarse-grained predicate cues and fine-grained triplet cues." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.372, + 0.891, + 0.432 + ], + "angle": 0, + "content": "- We introduce the DRM network to model predicate and triplet cues, and propose the DKT strategy to propagate knowledge from head predicates/triplets to tail ones to mitigate the long-tail problem in SGG." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.433, + 0.891, + 0.462 + ], + "angle": 0, + "content": "- We comprehensively evaluate the proposed method and demonstrate its superior performance." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.327, + 0.891, + 0.462 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.476, + 0.642, + 0.491 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.5, + 0.727, + 0.516 + ], + "angle": 0, + "content": "2.1. Scene Graph Generation" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.524, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Scene graph is a structured representation of the image content, where its essential constituents are the relationships (or triplets \\(<\\) subject, predicate, object \\(\\succ\\)). The direct prediction of triplet categories presents a significant challenge given the extensive combinations of subjects, predicates, and objects. Existing Scene Graph Generation (SGG) methods [11, 16, 25, 42, 52, 54] decompose this prediction target into two components: entities and predicates. Early SGG approaches [26, 49, 51] explore to integrate multiple modalities like positional information and linguistic features into relationships. Later methodologies [11, 27, 35, 36, 39] identify the value of visual context in SGG. Some of them encode contextual information utilizing techniques e.g. message passing [43], LSTM [37, 41, 49], graph neural networks [19, 44], and self-attention modules [3, 6, 20]. Others [27, 39] refine the detected scene graph and optimize the features of refined predicates based on high-confidence predictions. PE-Net [54] proposes to utilize text embeddings as the centroid of predicates, aiming to minimize the intraclass variance and the inter-class similarity. Despite the improved prediction accuracy, it is still hard to extract discriminative relation cues across the various subject-object pairs in the same predicate. The core of this issue lies in the fact that the identical predicates can manifest differently under distinct subject-object pairs, encompassing a unique array" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "28370" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.093, + 0.89, + 0.409 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.417, + 0.893, + 0.488 + ], + "angle": 0, + "content": "Figure 3. Illustration of the proposed Dual-granularity Relation Modeling (DRM) network. The learning procedure of DRM is composed of two stages. In the first stage, we capture the coarse-grained predicate cues shared across different subject-object pairs and learn the fine-grained triplet cues under specific subject-object pairs. In the second stage, the Dual-granularity Knowledge Transfer (DKT) strategy transfers the variation from head predicates with their associate triplets to the tail. Then DRM exploits the real instances along with synthetic samples from the calibrated tail distribution to fine-tune the relation classifier, which alleviates the long-tail problem in SGG." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.501, + 0.471, + 0.59 + ], + "angle": 0, + "content": "of visual cues within each manifestation. The direct aggregation of predicate features tends to overlook the inherent triplet cues present under the various subject-object pairs. We propose to explicitly model both coarse-grained predicate cues and fine-grained triplet cues for biased and unbiased SGG." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.605, + 0.382, + 0.621 + ], + "angle": 0, + "content": "2.2. Unbiased Scene Graph Generation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.629, + 0.471, + 0.901 + ], + "angle": 0, + "content": "Real-world data tends to obey a long-tailed distribution, and imbalanced samples in scene graph present the challenge to learn and adapt to the distribution in the tail predicates [37, 38, 48, 53]. Recently, many methods have been proposed to deal with the biased prediction problem in scene graphs, which can be roughly divided into three categories. The first category of methods use re-balancing strategies that alleviate the long-tail problem by re-sampling images and triplet samples to enhance the performance of tail predicates [19] or by enhancing the loss weights of tail predicates and easily misclassified categories through the pre-defined Predicate Lattice [28]. The second category of methods utilize noisy label learning to explicitly re-label relational triplets missed by annotators and correct the unlabeled predicates [17, 50]. The last category exploit the mixture of experts to let different experts separately deal with a subpart of predicates and merge their outputs [6, 34]. Different from these approaches, we mitigate the long-tail problem" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.501, + 0.892, + 0.576 + ], + "angle": 0, + "content": "in SGG by exploiting knowledge from the head predicates and triplets. Our method involves transferring the abundant variations from the head predicates and their associate triplets to the tail, thus enriching patterns of the tail predicates." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.588, + 0.591, + 0.603 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.613, + 0.892, + 0.81 + ], + "angle": 0, + "content": "An overview of our Dual-granularity Relation Modeling (DRM) network is illustrated in Figure 3. DRM aims to balance and integrate coarse-grained predicate cues and fine-grained triplet cues for relation recognition. To this end, a predicate cue modeling module and a triplet cue modeling module are designed to extract predicate cues shared across diverse subject and object pairs, and triplet cues shared by specific subject-object pairs, respectively. Moreover, the Dual-granularity Knowledge Transfer (DKT) strategy is proposed for unbiased SGG. This strategy transfers the knowledge of both predicates and triplets from head categories to tail ones, with the objective of enriching the pattern of tail predicates and their associated triplets." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.818, + 0.766, + 0.832 + ], + "angle": 0, + "content": "3.1. The DRM Network Backbone" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "The backbone of our DRM network is composed of a proposal network and an entity encoder. Features generated by the backbone are further fed into subsequent predicate and triplet cue modeling modules." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "28371" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.272 + ], + "angle": 0, + "content": "Proposal Network. Given an image \\(\\mathcal{I}\\), the proposal network generates \\(N\\) entities along with their corresponding visual features, label predictions, and spatial features from their bounding boxes. A pre-trained Faster RCNN [31] is adopted as the proposal network in this paper. And following previous works [6, 19, 37, 49], we initialize the entity representations \\(\\{\\mathbf{v}_i\\}_{i=1}^N\\) with their visual and spatial features, encode the union feature \\(\\mathbf{u}_{i,j}\\) between the \\(i\\)-th entity and the \\(j\\)-th entity with their relative spatial representation and the ROI feature of their union box, and obtain the semantic features \\(\\{\\mathbf{s}_i\\}_{i=1}^N\\) of entities using word embeddings of their class labels." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.273, + 0.473, + 0.41 + ], + "angle": 0, + "content": "Entity Encoder. The entity encoder is designed to refine features of entities with their contexts for further predictions. Inspired by Dong et al. [6], we utilize the Hybrid Attention (HA) to incorporate semantic cues \\(\\{\\mathbf{s}_i\\}_{i=1}^N\\) into entities \\(\\{\\mathbf{v}_i\\}_{i=1}^N\\) while modeling the scene context. Each layer of Hybrid Attention is composed of two Self-Attention (SA) units and two Cross-Attention (CA) units, which is built upon the multi-head attention module [40]. The Hybrid Attention at the \\(l\\)-th layer can be formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.107, + 0.42, + 0.47, + 0.463 + ], + "angle": 0, + "content": "\\[\n\\left\\{ \\begin{array}{l} \\mathbf {X} ^ {(l)} = S A \\left(\\mathbf {X} ^ {(l - 1)}\\right) + C A \\left(\\mathbf {X} ^ {(l - 1)}, \\mathbf {Y} ^ {(l - 1)}\\right), \\\\ \\mathbf {Y} ^ {(l)} = S A \\left(\\mathbf {Y} ^ {(l - 1)}\\right) + C A \\left(\\mathbf {Y} ^ {(l - 1)}, \\mathbf {X} ^ {(l - 1)}\\right), \\end{array} \\right. \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.474, + 0.47, + 0.52 + ], + "angle": 0, + "content": "where \\(\\mathbf{X}^{(l - 1)}\\) and \\(\\mathbf{Y}^{(l - 1)}\\) are inputs of the \\(l\\)-th HA layer. We directly fuse outputs of SA and CA units with an addition operation." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.521, + 0.47, + 0.569 + ], + "angle": 0, + "content": "Our entity encoder \\( Enc_{ent} \\) is consisted of a stacked 4-layer Hybrid Attention, and we have \\( \\mathbf{X}^{(0)} = \\{\\mathbf{v}_i\\}_{i=1}^N \\), \\( \\mathbf{Y}^{(0)} = \\{\\mathbf{s}_i\\}_{i=1}^N \\), and:" + }, + { + "type": "equation", + "bbox": [ + 0.144, + 0.579, + 0.469, + 0.597 + ], + "angle": 0, + "content": "\\[\n\\left\\{\\mathbf {v} _ {i} ^ {\\prime} \\right\\} _ {i = 1} ^ {N} = E n c _ {e n t} \\left(\\left\\{\\mathbf {v} _ {i} \\right\\} _ {i = 1} ^ {N}, \\left\\{\\mathbf {s} _ {i} \\right\\} _ {i = 1} ^ {N}\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.609, + 0.47, + 0.641 + ], + "angle": 0, + "content": "where the refined entity representations \\(\\{\\mathbf{v}_i^{\\prime}\\}_{i = 1}^{N}\\) are obtained by summing up of outputs from the last HA layer." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.651, + 0.391, + 0.667 + ], + "angle": 0, + "content": "3.2. Predicate and Triplet Cue Modeling" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.675, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Previous approaches tend to categorize predicates in a coarse manner, most of which only focus on predicate cues shared among various subject-object pairs, and thus cannot effectively deal with the potentially large visual variations inherent in the identical predicate. In contrast to these approaches, our method considers both coarse-grained predicate cues and fine-grained triplet cues, leveraging and striking a balance between the dual-grained cues for accurate predicate categorization. Our DRM network involves a Predicate Cue Modeling module and a Triplet Cue Modeling module for extracting features at these two granularities respectively. Additionally, we introduce Dual-Granularity Constraints to decrease the intra-class variance and increase inter-class distinguishability, explicitly enforcing the predicate and triplet branches to concentrate on cues from their" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.121 + ], + "angle": 0, + "content": "corresponding granularities and preventing the degradation of dual-granularity space." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.121, + 0.894, + 0.288 + ], + "angle": 0, + "content": "Predicate Cue Modeling. Our predicate cue modeling module Encprd, comprising a 2-layer Hybrid Attention, aims to capture predicate cues across different subject-object pairs. In each HA layer of Encprd, the two Self-Attention units are designed to model predicate and entity contextual information. And the two Cross-Attention units are designed to capture the dependency between entities and predicates, where the predicate \\(\\mathbf{p}_{i,j}\\) solely queries the contexts of its corresponding subject \\(\\mathbf{e}_i\\) and object \\(\\mathbf{e}_j\\), and the entity \\(\\mathbf{e}_i\\) only queries predicates related to it. Our Predicate Cue Modeling process can thus be formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.556, + 0.294, + 0.892, + 0.314 + ], + "angle": 0, + "content": "\\[\n\\left\\{\\mathbf {p} _ {i, j} ^ {\\prime} \\right\\} _ {i \\neq j} ^ {M} = E n c _ {p r d} \\left(\\left\\{\\mathbf {p} _ {i, j} \\right\\} _ {i \\neq j} ^ {M}, \\left\\{\\mathbf {e} _ {i} \\right\\} _ {i = 1} ^ {N}\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.32, + 0.892, + 0.395 + ], + "angle": 0, + "content": "where the predicate representation \\(\\mathbf{p}_{i,j}\\) is initialized with the union feature \\(\\mathbf{u}_{i,j}\\), the entity representation \\(\\mathbf{e}_i\\) is obtained with the concatenation of \\(\\mathbf{v}_i'\\) and \\(\\mathbf{v}_i\\), \\(M = N \\times (N - 1)\\) is the number of subject-object pairs, and \\(\\mathbf{p}_{i,j}'\\) is the corresponding output of \\(\\mathbf{p}_{i,j}\\) at the last HA layer." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.395, + 0.893, + 0.577 + ], + "angle": 0, + "content": "Triplet Cue Modeling. Our triplet cue modeling module \\( Enc_{tpt} \\) is also constructed using a 2-layer Hybrid Attention. This module is responsible for obtaining fine-grained triplet cues that are shared by specific subject-object pairs. The two Self-Attention units in each HA layer of \\( Enc_{tpt} \\) are designed to model visual and semantic contextual information of triplets, respectively, and the two Cross-Attention units aim at fusing semantic cues into the visual information of triplets. We initialize the triplet representation \\( \\mathbf{t}_{i,j} \\) with the concatenation of the subject representation \\( \\mathbf{e}_i \\), predicate representation \\( \\mathbf{p}_{i,j} \\), and object representation \\( \\mathbf{e}_j \\). Our Triplet Cue Modeling process is formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.547, + 0.582, + 0.891, + 0.603 + ], + "angle": 0, + "content": "\\[\n\\left\\{\\mathbf {t} _ {i, j} ^ {\\prime} \\right\\} _ {i \\neq j} ^ {M} = E n c _ {t p t} \\left(\\left\\{\\mathbf {t} _ {i, j} \\right\\} _ {i \\neq j} ^ {M}, \\left\\{\\left[ \\mathbf {s} _ {i} ^ {\\prime}, \\mathbf {s} _ {j} ^ {\\prime} \\right] \\right\\} _ {i \\neq j} ^ {M}\\right), \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.608, + 0.892, + 0.668 + ], + "angle": 0, + "content": "where \\(\\mathbf{s}_i^{\\prime}\\) is the word embedding of predicted entity label, and \\([\\cdot ,\\cdot ]\\) denotes the concatenate operation. \\(\\mathbf{t}_{i,j}^{\\prime}\\) is the contextually and semantically aware triplet feature, and is derived from the addition of outputs from the last HA layer." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.669, + 0.894, + 0.82 + ], + "angle": 0, + "content": "Dual-granularity Constraints. Although we explicitly model predicate and triplet cues with \\( Enc_{prd} \\) and \\( Enc_{pt} \\), they may degrade beyond our desires with a single predicate cross-entropy loss. To prevent this degradation, we propose the dual-granularity constraints to guide the predicate and triplet cue modeling modules to refine representations in their desired granularities. Specifically, we generate two views of an input relation and impose a predicate category-aware supervised contrastive learning loss on predicate representations to capture the coarse-grained predicate cues as:" + }, + { + "type": "equation", + "bbox": [ + 0.552, + 0.829, + 0.892, + 0.868 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {p} = - \\log \\frac {\\exp \\left(\\left\\langle \\mathbf {p} _ {i , j} ^ {\\prime \\prime} , \\mathbf {p} _ {p o s _ {p}} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {p}\\right)}{\\sum_ {b \\in \\mathcal {B} (i , j)} \\exp \\left(\\left\\langle \\mathbf {p} _ {i , j} ^ {\\prime \\prime} , \\mathbf {p} _ {b} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {p}\\right)}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.892, + 0.902 + ], + "angle": 0, + "content": "where \\(\\mathbf{p}_{i,j}^{\\prime \\prime}\\) is obtained by passing \\(\\mathbf{p}_{i,j}^{\\prime}\\) through a projection layer comprising two fully connected layers, \\(\\tau_{p}\\) is the tem" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "28372" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.151 + ], + "angle": 0, + "content": "perature, \\(pos_{p}\\) denotes the subscripts of positive samples belonging to the same predicate category as \\(\\mathbf{p}_{i,j}^{\\prime \\prime},\\langle \\cdot ,\\cdot \\rangle\\) is the cosine similarity function, and \\(\\mathcal{B}(i,j)\\) denotes the subscript set of samples within the same batch." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.152, + 0.47, + 0.198 + ], + "angle": 0, + "content": "Similarly, a triplet category-aware supervised contrastive learning loss is applied on triplet representations, aiming at capturing the fine-grained triplet cues as:" + }, + { + "type": "equation", + "bbox": [ + 0.135, + 0.207, + 0.47, + 0.245 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {t} = - \\log \\frac {\\exp \\left(\\left\\langle \\mathbf {t} _ {i , j} ^ {\\prime \\prime} , \\mathbf {t} _ {p o s _ {t}} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {t}\\right)}{\\sum_ {b \\in \\mathcal {B} (i , j)} \\exp \\left(\\left\\langle \\mathbf {t} _ {i , j} ^ {\\prime \\prime} , \\mathbf {t} _ {b} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {t}\\right)}, \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.255, + 0.469, + 0.301 + ], + "angle": 0, + "content": "where \\(\\tau_{t}\\) is the temperature, \\(pos_{t}\\) denotes subscripts of positive samples from the same triplet category as \\(\\mathbf{t}_{i,j}^{\\prime \\prime}\\), and \\(\\mathbf{t}_{i,j}^{\\prime \\prime}\\) is obtained by passing \\(\\mathbf{t}_{i,j}^{\\prime}\\) through a projection layer." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.301, + 0.469, + 0.39 + ], + "angle": 0, + "content": "Scene Graph Prediction. For each relationship proposal, our predicate classifier utilizes two fully connected layers to integrate the coarse-grained and fine-grained cues, i.e. \\(\\mathbf{p}_{i,j}^{\\prime}\\) and \\(\\mathbf{t}_{i,j}^{\\prime}\\), to obtain the final relation label prediction. For each entity, we also introduce a fully connected layer with softmax function to get its refined label prediction." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.391, + 0.47, + 0.421 + ], + "angle": 0, + "content": "Training Loss. During the training in the first stage of DRM, the overall loss function \\(\\mathcal{L}\\) is defined as:" + }, + { + "type": "equation", + "bbox": [ + 0.152, + 0.433, + 0.469, + 0.451 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\lambda_ {e} \\mathcal {L} _ {e} + \\lambda_ {r} \\mathcal {L} _ {r} + \\lambda_ {p} \\mathcal {L} _ {p} + \\lambda_ {t} \\mathcal {L} _ {t}, \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.461, + 0.469, + 0.507 + ], + "angle": 0, + "content": "where \\(\\mathcal{L}_e\\) and \\(\\mathcal{L}_r\\) are cross-entropy losses of entities and relationships respectively. \\(\\lambda_e, \\lambda_r, \\lambda_p,\\) and \\(\\lambda_t\\) are pre-defined weight hyper-parameters for corresponding loss terms." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.515, + 0.406, + 0.532 + ], + "angle": 0, + "content": "3.3. Dual-granularity Knowledge Transfer" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.538, + 0.469, + 0.719 + ], + "angle": 0, + "content": "The SGG task typically suffers from the long-tail distribution problem. This problem primarily originates from the tail predicate classes, which possesses limited types and quantities of triplets. The head predicate classes contain a relatively larger number of samples and an abundance of triplet types. Thus to alleviate the long-tail problem, we propose the Dual-granularity Knowledge Transfer (DKT) strategy to transfer knowledge in predicate and triplet feature spaces from head predicate class to the tail one. DKT generates samples belonging to the tail predicates with their associated predicate and triplet features, thereby enriching and diversifying the patterns of tail predicates." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Specifically, DKT first calculates the distributions of predicate and triplet features. We assume that the distribution of each category \\(\\Omega_c\\) follows a multidimensional Gaussian distribution. Formally, it can be expressed as \\(\\{\\Omega_c = \\mathcal{N}(\\pmb{\\mu}_c, \\pmb{\\sigma}_c) | c \\in \\mathcal{C}\\}\\), where \\(\\pmb{\\mu}_c\\) and \\(\\pmb{\\sigma}_c\\) denote the mean and covariance of \\(\\Omega_c\\), and \\(c\\) denotes the predicate or triplet category. After the first-stage pre-training of DRM network, we freeze the proposal network, entity encoder, and the predicate and triplet cue modeling modules. Subsequently, the compact predicate and triplet features, i.e. \\(\\mathbf{p}'\\) and \\(\\mathbf{t}'\\), are extracted to calculate the predicate and triplet feature distributions, respectively. The mean, denoted as \\(\\pmb{\\mu}_c\\), is calculated" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.09, + 0.892, + 0.156 + ], + "angle": 0, + "content": "as \\(\\pmb{\\mu}_{c} = \\frac{1}{N_{c}}\\sum_{k}^{N_{c}}\\mathbf{x}_{k}^{c}\\). The covariance, symbolized as \\(\\pmb{\\sigma}_{c}\\), is calculated as \\(\\pmb{\\sigma}_{c} = \\frac{1}{N_{c} - 1}\\sum_{k}^{N_{c}}(\\mathbf{x}_{k}^{c} - \\pmb{\\mu}_{c})(\\mathbf{x}_{k}^{c} - \\pmb{\\mu}_{c})^{T}\\). Here, \\(\\mathbf{x}_i^c\\) denotes the feature of category \\(c\\), and \\(N_{c}\\) is the number of \\(\\mathbf{x}_k^c\\). The feature \\(\\mathbf{x}\\) can be either \\(\\mathbf{p}'\\) or \\(\\mathbf{t}'\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.156, + 0.893, + 0.383 + ], + "angle": 0, + "content": "We then transfer knowledge of feature distributions of head predicate classes to the tail ones. Specifically, we arrange the predicate classes in descending order based on their sample numbers, choosing half of the predicate classes as head predicates and the remaining ones as tail predicates. We further select triplets that appear more than certain times in the head predicates to be the head triplets (we use 64 times as the threshold in this paper), and those in the tail predicates to be the tail triplets. For each tail category \\( i \\in \\mathcal{C} \\) we compute the euclidean distance \\( d_{i,j} \\) between its center \\( \\pmb{\\mu}_i \\) and the center \\( \\pmb{\\mu}_j \\) of head category \\( j \\in \\mathcal{C} \\). The closer the centers of two categories are to each other in either predicate or triplet space, the more similar they are, which also increases the likelihood of knowledge sharing between them. Based on \\( d_{i,j} \\), we achieve the knowledge transfer as:" + }, + { + "type": "equation", + "bbox": [ + 0.574, + 0.392, + 0.892, + 0.43 + ], + "angle": 0, + "content": "\\[\n\\boldsymbol {\\sigma} _ {i} ^ {\\prime} = \\frac {N _ {i}}{Q _ {i}} \\boldsymbol {\\sigma} _ {i} + \\left(1 - \\frac {N _ {i}}{Q _ {i}}\\right) \\sum_ {j} \\alpha_ {i, j} \\boldsymbol {\\sigma} _ {j}, \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.44, + 0.892, + 0.515 + ], + "angle": 0, + "content": "where \\(\\alpha_{i,j}\\) denotes the softmax normalized form of \\(d_{i,j}\\), \\(Q_{i}\\) denotes the desired number of predicate/triplet instances of tail class \\(i\\) and it is identical for every predicates in the tail. It suggests that the tail category with fewer samples requires more knowledge from the head for calibration." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.516, + 0.892, + 0.561 + ], + "angle": 0, + "content": "After dual-granularity knowledge transfer, we generate synthetic samples in tail predicate using corresponding predicate and triplet features from calibrated distributions:" + }, + { + "type": "equation", + "bbox": [ + 0.604, + 0.571, + 0.891, + 0.589 + ], + "angle": 0, + "content": "\\[\n\\{\\hat {\\boldsymbol {x}} | \\hat {\\boldsymbol {x}} \\sim \\Omega_ {c} ^ {\\prime} = \\mathcal {N} \\left(\\boldsymbol {\\mu} _ {c}, \\boldsymbol {\\sigma} _ {c} ^ {\\prime}\\right) \\}. \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.892, + 0.689 + ], + "angle": 0, + "content": "Finally, we under-sample head predicates to form a balanced dataset and input the real instances together with synthetic ones into the relation classifier for fine-tuning. Benefiting from the dual-granularity knowledge transfer, the patterns of tail predicates and their associate triplets can be enriched, thus alleviating the long-tail problem." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.702, + 0.634, + 0.719 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.727, + 0.707, + 0.743 + ], + "angle": 0, + "content": "4.1. Experimental Settings" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Datasets. We evaluate our method on three commonly used SGG datasets, namely Visual Genome [14], Open Image [13], and GQA [10]. For the Visual Genome dataset, we adopt the VG150 split following previous approaches [23, 29, 37, 43, 49], which contains the most frequent 150 object categories and 50 predicate categories. We use \\(70\\%\\) of images for training, \\(30\\%\\) images for testing and \\(5\\mathrm{k}\\) images from the training set for validation. As for Open Image, we apply the Open Image V6 protocol, which has 301 object categories and 31 predicate categories. It contains" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28373" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.141, + 0.089, + 0.827, + 0.504 + ], + "angle": 0, + "content": "
ModelsPredClsSGClsSGDet
R@50/100mR@50/100R@50/100mR@50/100R@50/100mR@50/100
IMP [43]CVPR'1761.1 / 63.111.0 / 11.837.5 / 38.56.2 / 6.525.9 / 31.24.2 / 5.3
VTransE [51]CVPR'1765.7 / 67.614.7 / 15.838.6 / 39.48.2 / 8.729.7 / 34.35.0 / 6.1
MOTIFS [49]CVPR'1866.0 / 67.914.6 / 15.839.1 / 39.98.0 / 8.532.1 / 36.95.5 / 6.8
G-RCNN [44]ECCV'1865.4 / 67.216.4 / 17.237.0 / 38.59.0 / 9.529.7 / 32.85.8 / 6.6
VCTREE [37]CVPR'1965.5 / 67.416.7 / 17.940.3 / 41.67.9 / 8.331.9 / 36.06.4 / 7.3
GPS-Net [22]CVPR'2065.2 / 67.115.2 / 16.637.8 / 39.28.5 / 9.131.3 / 35.96.7 / 8.6
RU-Net [24]CVPR'2267.7 / 69.6- / 24.242.4 / 43.3- / 14.632.9 / 37.5- / 10.8
HL-Net [23]CVPR'2267.0 / 68.9- / 22.842.6 / 43.5- / 13.533.7 / 38.1- / 9.2
PE-Net(P) [54]CVPR'2368.2 / 70.123.1 / 25.441.3 / 42.313.1 / 14.832.4 / 36.98.9 / 11.0
VETO [34]ICCV'2364.2 / 66.322.8 / 24.735.7 / 36.911.1 / 11.927.5 / 31.58.1 / 9.5
TDE° [38]CVPR'2046.2 / 51.425.5 / 29.127.7 / 29.913.1 / 14.916.9 / 20.38.2 / 9.8
CogTree° [47]IJCAI'2135.6 / 36.826.4 / 29.021.6 / 22.214.9 / 16.120.0 / 22.110.4 / 11.8
BPL-SA° [9]ICCV'2150.7 / 52.529.7 / 31.730.1 / 31.016.5 / 17.523.0 / 26.913.5 / 15.6
VisualDS° [46]ICCV'21- / -16.1 / 17.5- / -9.3 / 9.9- / -7.0 / 8.3
NICE° [17]CVPR'2255.1 / 57.229.9 / 32.333.1 / 34.016.6 / 17.927.8 / 31.812.2 / 14.4
PPDL° [21]CVPR'2247.2 / 47.632.2 / 33.328.4 / 29.317.5 / 18.221.2 / 23.911.4 / 13.5
GCL° [6]CVPR'2242.7 / 44.436.1 / 38.226.1 / 27.120.8 / 21.818.4 / 22.016.8 / 19.3
IETrans° [50]ECCV'22- / -35.8 / 39.1- / -21.5 / 22.8- / -15.5 / 18.0
INF° [2]CVPR'2351.5 / 55.124.7 / 30.732.2 / 33.814.5 / 17.423.9 / 27.19.4 / 11.7
CFA° [18]ICCV'2354.1 / 56.635.7 / 38.234.9 / 36.117.0 / 18.427.4 / 31.813.2 / 15.5
EICR° [29]ICCV'2355.3 / 57.434.9 / 37.034.5 / 35.420.8 / 21.827.9 / 32.215.5 / 18.2
BGNN [19]CVPR'2159.2 / 61.330.4 / 32.937.4 / 38.514.3 / 16.531.0 / 35.810.7 / 12.6
SHA+GCL [6]CVPR'2235.1 / 37.241.6 / 44.122.8 / 23.923.0 / 24.314.9 / 18.217.9 / 20.9
PE-Net [54]CVPR'2364.9 / 67.231.5 / 33.839.4 / 40.717.8 / 18.930.7 / 35.212.4 / 14.5
SQUAT [12]ICCV'2355.7 / 57.930.9 / 33.433.1 / 34.417.5 / 18.824.5 / 28.914.1 / 16.5
CaCao [48]ICCV'23- / -41.7 / 43.7- / -24.0 / 25.0- / -18.3 / 22.1
DRM w/o DKT70.2 / 72.123.3 / 25.644.3 / 45.213.5 / 14.634.0 / 38.99.0 / 11.2
DRM43.9 / 45.847.1 / 49.627.5 / 28.427.8 / 29.219.0 / 22.920.4 / 24.1
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.508, + 0.892, + 0.537 + ], + "angle": 0, + "content": "Table 1. Comparison results with state-of-the-art SGG methods on the VG150 dataset. \"◇\" denotes the combination of MOTIFS with a model-agnostic unbiased strategy. The best and second best results under each setting are respectively marked in red and underline blue." + }, + { + "type": "table", + "bbox": [ + 0.092, + 0.554, + 0.452, + 0.724 + ], + "angle": 0, + "content": "
ModelR@50WmAPscorewtd
relphr
MOTIFS [49]CVPR'1871.629.931.638.9
G-RCNN [44]ECCV'1874.533.234.241.8
VCTREE [37]CVPR'1974.134.233.140.2
GPS-Net [22]CVPR'2074.832.934.041.7
BGNN [19]CVPR'2175.033.534.242.1
RU-Net [24]CVPR'2276.935.434.943.5
HL-Net [23]CVPR'2276.535.134.743.2
PE-Net [54]CVPR'2376.536.637.444.9
SQUAT [12]ICCV'2375.834.935.943.5
DRM w/o DKT75.940.541.447.9
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.729, + 0.47, + 0.771 + ], + "angle": 0, + "content": "Table 2. Comparison results with state-of-the-art SGG methods on Open Image V6. The best and second best results under each metric are respectively marked in red and underline blue." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.791, + 0.469, + 0.853 + ], + "angle": 0, + "content": "126,368, 1,183, and 5,322 images for training, validation, and testing, respectively. For the GQA dataset, we follow previous works [6, 34] and utilize the GQA200 split, which includes 200 object categories and 100 predicate categories." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Tasks. We adopt three SGG tasks for evaluation: 1) Predicate Classification (Predcls) infers the predicates of entity pairs with ground-truth bounding boxes and cate" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.557, + 0.892, + 0.618 + ], + "angle": 0, + "content": "gories. 2) Scene Graph Classification (SGCls) aims to predict the triplet categories with ground-truth bounding boxes. 3) Scene Graph Detection (SGDet) detects bounding boxes of entity pairs and infers their predicate categories." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.623, + 0.893, + 0.775 + ], + "angle": 0, + "content": "Evaluation Metrics. We use Recall@K (R@K) and mean Recall@K (mR@K) as evaluation metrics on VG150 and GQA200 datasets, following recent works [6, 34, 54]. R@K tends to prioritize frequent predicates, while mR@K exhibits a preference for less frequent predicates. Results on Open Image dataset are evaluated using Recall@50 (R@50), weighted mean AP of relations (wmAPrel) weighted mean AP of phrase (wmAPphr), and a weighted score of them scorewtd = 0.2 × R@50 + 0.4 × wAPrel + 0.4 × wAPphr, following previous works [19, 23, 52]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.894, + 0.903 + ], + "angle": 0, + "content": "Implementation Details. Following previous works [6, 34, 54], we adopt the pre-trained Faster RCNN with ResNeXt-101-RPN in the proposal network to detect entities in the image. GloVe [30] is applied to embed the semantic features. We set the loss weight parameters \\(\\lambda_r\\), \\(\\lambda_e\\), \\(\\lambda_t\\), and \\(\\lambda_p\\) as 3, 0.5, 0.1, and 0.1, respectively. Temperatures \\(\\tau_p\\) and \\(\\tau_t\\) are set as 0.2, and 0.1 considering that the predicate feature space exhibits greater variety than its asso" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "28374" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.133, + 0.089, + 0.835, + 0.273 + ], + "angle": 0, + "content": "
ModelsPredClsSGClsSGDet
R@50/100mR@50/100R@50/100mR@50/100R@50/100mR@50/100
VTransE [51]CVPR'1755.7 / 57.914.0 / 15.033.4 / 34.28.1 / 8.727.2 / 30.75.8 / 6.6
MOTIFS [49]CVPR'1865.3 / 66.816.4 / 17.134.2 / 34.98.2 / 8.628.9 / 33.16.4 / 7.7
VCTREE [37]CVPR'1963.8 / 65.716.6 / 17.434.1 / 34.87.9 / 8.328.3 / 31.96.5 / 7.4
SHA [6]CVPR'2263.3 / 65.219.5 / 21.132.7 / 33.68.5 / 9.025.5 / 29.16.6 / 7.8
VETO [34]ICCV'2364.5 / 66.021.2 / 22.130.4 / 31.58.6 / 9.126.1 / 29.07.0 / 8.1
VTransE+GCL [6]CVPR'2235.5 / 37.430.4 / 32.322.9 / 23.616.6 / 17.415.3 / 18.014.7 / 16.4
MOTIFS+GCL [6]CVPR'2244.5 / 46.236.7 / 38.123.2 / 24.017.3 / 18.118.5 / 21.816.8 / 18.8
VCTREE+GCL [6]CVPR'2244.8 / 46.635.4 / 36.723.7 / 24.517.3 / 18.017.6 / 20.715.6 / 17.8
SHA+GCL [6]CVPR'2242.7 / 44.541.0 / 42.721.4 / 22.220.6 / 21.314.8 / 17.917.8 / 20.1
DRM w/o DKT66.9 / 68.418.1 / 19.036.4 / 37.27.1 / 7.430.6 / 34.66.9 / 8.4
DRM43.2 / 44.441.9 / 43.523.3 / 23.919.9 / 20.718.6 / 21.718.9 / 21.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.278, + 0.893, + 0.308 + ], + "angle": 0, + "content": "Table 3. Comparison results with state-of-the-art SGG methods on the GQA200 dataset. The best and second best results under each setting are respectively marked in red and underline blue." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.317, + 0.47, + 0.464 + ], + "angle": 0, + "content": "
ModulePredClsSGCls
PTACR@50/100mR@50/100R@50/100
56.5/60.415.5/17.437.5/39.310.1/11.3
✓67.6/69.518.1/19.941.8/42.710.8/11.8
✓67.6/69.820.5/22.542.3/43.212.6/13.6
✓✓69.3/71.320.8/22.842.8/43.812.8/13.9
✓✓✓69.8/71.620.4/22.343.4/44.412.8/13.8
✓✓✓69.8/71.622.0/24.043.4/44.312.3/13.3
✓✓✓69.7/71.521.9/24.343.8/44.812.7/13.9
✓✓✓70.2/72.123.3/25.644.3/45.213.5/14.6
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.47, + 0.47, + 0.526 + ], + "angle": 0, + "content": "Table 4. Ablation studies on predicate and triplet cues learning. \"P\", \"T\", \"A\", and \"C\" denote the predicate cue modeling module, triplet cue modeling module, augmentation in dual-granularity constraints, and the dual-granularity constraints loss, respectively." + }, + { + "type": "table", + "bbox": [ + 0.084, + 0.535, + 0.465, + 0.624 + ], + "angle": 0, + "content": "
ModulePredClsSGCls
R@50/100mR@50/100R@50/100mR@50/100
None70.2/72.123.3/25.644.3/45.213.5/14.6
DKT-P42.4/44.245.0/47.326.8/27.826.9/28.1
DKT-T40.4/42.246.1/48.724.3/25.326.4/28.0
DKT43.9/45.847.1/49.627.5/28.427.8/29.2
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.63, + 0.47, + 0.673 + ], + "angle": 0, + "content": "Table 5. Ablation studies on dual-granularity knowledge transfer. \"DKT-P\" and \"DKT-T\" denote the predicate knowledge transfer and triplet knowledge transfer." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.682, + 0.469, + 0.713 + ], + "angle": 0, + "content": "ciated triplet one. We optimize our method via SGD, using an initial leaning late of \\(10^{-4}\\) with a batch size of 16." + }, + { + "type": "title", + "bbox": [ + 0.076, + 0.726, + 0.442, + 0.743 + ], + "angle": 0, + "content": "4.2. Comparison with State-of-the-art Methods" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.47, + 0.903 + ], + "angle": 0, + "content": "To evaluate the performance our model, we compare it with several state-of-the-art SGG approaches on Visual Genome, Open Image, and GQA datasets. The comparison methods include IMP [43], MOTIFS [49], VCTREE [37], RU-Net [24], HL-Net [23], PE-Net [54], and VETO [34], which focus on the prediction of every relationship in an image. We also compare with methods for unbiased scene graph generation, including TDE [38], CogTree [47], NICE [17], INF [2], CFA [18], EICR [29], BGNN [19], SHA+GCL [6], SQUAT [12], and CaCao[48]. In addition, we compare" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.32, + 0.892, + 0.351 + ], + "angle": 0, + "content": "our method with VETO+MEET [34] in the setting without graph constraint in the Supplementary Material." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.353, + 0.893, + 0.67 + ], + "angle": 0, + "content": "Visual Genome. Table 1 shows the comparison results of different approaches on VG150. From these results, we have the following observations: 1) our proposed method significantly outperforms all baselines on all three tasks. More specifically, our DRM w/o DKT outperforms the recent PE-Net [54] by \\(2.0\\%\\), \\(2.9\\%\\), and \\(2.0\\%\\) at R@100 on PredCls, SGCls, and SGDet, respectively. Unlike approaches such as MOTIFS [49] and VCTREE [37], which only utilize a predicate classifier to predict predicates and overlook the triplet cues, our method leverages coarse-grained predicate cues and fine-grained triplet cues for relation recognition and thus achieves superior results. 2) Our DRM method also has considerably better performance compared to the baseline unbiased SGG methods. Notably, based on the proposed DKT strategy in DRM, our method outperforms the recent multi-expert method SHA+GCL [6] by \\(5.5\\%\\), \\(4.9\\%\\), and \\(3.2\\%\\) at mR@100 on three tasks. This demonstrates that transferring knowledge from head predicates to tail predicates at dual granularities and enriching the patterns in tail predicates can effectively mitigate the long-tail problem." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.672, + 0.892, + 0.853 + ], + "angle": 0, + "content": "Open Image. Compared to the VG dataset, Open Image provides a relatively complete labeling of relationships in the images. Consequently, the model's capability to generate scene graphs can be evaluated at a fine-grained level utilizing the AP metric. To evaluate the generalizability of our method across various datasets, we conduct experiments on Open Image V6. Since the metrics in Open Image V6 tend to prioritize frequent predicates, we just compare our DRM w/o DKT with state-of-the-art approaches. The comparison results shown in Table 2 indicate that our DRM w/o DKT significantly outperforms the recent approaches, i.e., SQUAT [12] and PE-Net [54]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "GQA. Compared to Visual Genome and Open Image datasets, GQA200 contains a broader range of predicates. So we further confirm the generality of our model on the" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "28375" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.091, + 0.237, + 0.205 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.105, + 0.209, + 0.215, + 0.222 + ], + "angle": 0, + "content": "(a) MOTIFS, Triplet" + }, + { + "type": "image", + "bbox": [ + 0.245, + 0.092, + 0.398, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.25, + 0.209, + 0.395, + 0.222 + ], + "angle": 0, + "content": "(b) DRM w/o DKT, Triplet" + }, + { + "type": "image", + "bbox": [ + 0.408, + 0.092, + 0.561, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.438, + 0.209, + 0.53, + 0.222 + ], + "angle": 0, + "content": "(c) DRM, Triplet" + }, + { + "type": "image", + "bbox": [ + 0.569, + 0.092, + 0.722, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.567, + 0.209, + 0.724, + 0.221 + ], + "angle": 0, + "content": "(d) DRM w/o DKT, Predicate" + }, + { + "type": "image", + "bbox": [ + 0.732, + 0.092, + 0.883, + 0.206 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.754, + 0.209, + 0.86, + 0.221 + ], + "angle": 0, + "content": "(e) DRM, Predicate" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.228, + 0.892, + 0.257 + ], + "angle": 0, + "content": "Figure 4. The comparison of t-SNE visualization results on predicate and triplet feature distributions within the VG dataset. \"MOTIFS, Triplet\" and \"DRM w/o DKT, Triplet\" visualize the same set of samples, where each unique color represents a different type of triplet." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.27, + 0.47, + 0.376 + ], + "angle": 0, + "content": "GQA200 dataset. As shown in Table 3, our method significantly outperforms the recent VETO [34] at R@100 on three tasks. When equipped with DKT, our DRM outperforms \\(\\mathrm{SHA + GCL}\\) [6] by an average of \\(0.4\\%\\) at mR@100 across three tasks. These results demonstrate the consistent effectiveness of our method in handling relation recognition under different data distributions." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.385, + 0.231, + 0.401 + ], + "angle": 0, + "content": "4.3. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.41, + 0.47, + 0.44 + ], + "angle": 0, + "content": "To verify the contributions of different components in our DRM network, we conduct the following ablation studies." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.44, + 0.47, + 0.652 + ], + "angle": 0, + "content": "Predicate and Triplet Cue Learning. We first perform an ablation study on the leverage of predicate and triplet cues. As shown in Table 4, we incrementally incorporate one component into the baseline to verify their effectiveness. Compared with the application of predicate or triplet cue modeling in isolation, leveraging both predicate and triplet together improves the performance. Our dual-granularity constraints include a constraint loss component and a two-view augmentation component to generate positive pairs in each training batch. The constraints compel predicate and triplet cue modeling to concentrate on corresponding granularities. We observe from the results that both the loss component and augmentation component contribute to the performance improvements." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.653, + 0.47, + 0.835 + ], + "angle": 0, + "content": "Dual-Granularity Knowledge Transfer. As shown in Table 5, we conduct an ablation study for the DKT. We observe an obvious performance gain on \\(\\mathrm{mR}@\\mathrm{K}\\) when transferring knowledge at either predicate or triplet granularity. The \\(\\mathrm{mR}@\\mathrm{K}\\) is further improved when predicate and triplet granularities are simultaneously employed. In comparison to the scenario without the application of DKT, we observe a performance decrease in \\(\\mathrm{R}@\\mathrm{K}\\) when using it. This is attributed to the capability of our model to reasonably classify ambiguous head predicates, e.g. \"on\", into more specific tail predicates, e.g. \"sitting on\". Consequently, decreases at the \\(\\mathrm{R}@\\mathrm{K}\\) for these head predicates are inevitable [17, 54]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.847, + 0.285, + 0.863 + ], + "angle": 0, + "content": "4.4. Visualization Analysis" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.47, + 0.902 + ], + "angle": 0, + "content": "To illustrate the ability our method to learn triplet cues and impact of the DKT strategy, we visualize the predicate and" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.27, + 0.895, + 0.483 + ], + "angle": 0, + "content": "triplet feature distributions using t-SNE. The visualization results are shown in Figure 4. Comparing Figure 4a with Figure 4b, we observe that our DRM generates compact and distinguishable triplet representations, while MOTIFS [49] appears to overlook the triplet cues, leading to a challenge in distinguishing various triplet types. By comparing Figure 4b with Figure 4c, it can be observed that DKT can generate synthetic samples with diverse distributions for the tail triplets. Figures 4d and 4e demonstrate that DKT also transfers the knowledge of head predicates to tail predicates, increasing the tail predicate patterns. The visualization of predicate and triplet feature distributions demonstrates the interpretability of our method in leveraging predicate and triplet cues and transferring the dual-granularity knowledge." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.503, + 0.619, + 0.518 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.531, + 0.892, + 0.728 + ], + "angle": 0, + "content": "In this paper, we propose a Dual-granularity Relation Modeling (DRM) network to address two issues in SGG, i.e. the diverse visual appearance within the same predicate and the lack of patterns in tail predicates. Our DRM network captures the coarse-grained predicate cues shared across different subject-object pairs and fine-grained triplet cues under specific subject-object pairs for relationship recognition. The Dual-granularity Knowledge Transfer (DKT) is further proposed to transfer the variation from head predicates to the tail to enrich the tail predicate patterns. Quantitative and qualitative experiments demonstrate that our method establishes new state-of-the-art performances on Visual Genome, Open Image and GQA datasets." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.749, + 0.661, + 0.766 + ], + "angle": 0, + "content": "Acknowledgement" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.775, + 0.892, + 0.888 + ], + "angle": 0, + "content": "This work was supported in part by the National Key R&D Program of China under Grant 2022ZD0161901, the National Natural Science Foundation of China under Grants 62276018 and U20B2069, the Beijing Nova Program under Grant 20230484297, the Fundamental Research Funds for the Central Universities, and Research Program of State Key Laboratory of Complex & Critical Software Environment." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "28376" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.105 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Hedi Ben-Younes, Remi Cadene, Nicolas Thome, and Matthieu Cord. 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Given the prevalence of large visual variations of subject-object pairs even in the same predicate, it can be quite challenging to model and refine predicate representations directly across such pairs, which is however a common strategy adopted by most existing SGG methods. We observe that visual variations within the identical triplet are relatively small and certain relation cues are shared in the same type of triplet, which can potentially facilitate the relation learning in SGG. Moreover, for the long-tail problem widely studied in SGG task, it is also crucial to deal with the limited types and quantity of triplets in tail predicates. Accordingly, in this paper, we propose a Dual-granularity Relation Modeling (DRM) network to leverage fine-grained triplet cues besides the coarse-grained predicate ones. DRM utilizes contexts and semantics of predicate and triplet with Dual-granularity Constraints, generating compact and balanced representations from two perspectives to facilitate relation recognition. Furthermore, a Dual-granularity Knowledge Transfer (DKT) strategy is introduced to transfer variation from head predicates/triplets to tail ones, aiming to enrich the pattern diversity of tail classes to alleviate the long-tail problem. Extensive experiments demonstrate the effectiveness of our method, which establishes new state-of-the-art performance on Visual Genome, Open Image, and GQA datasets. Our code is available at https://github.com/jkli1998/DRM + +# 1. Introduction + +Entities and their associated relationships form the cornerstones of visual contents in images [14]. Scene Graph Generation (SGG), a fundamental task in visual scene understanding, is designed to detect these entities and predict + +![](images/8f7ae5ebc3d0278e38ab426a8e54d9685e23f0564ad35bb736e4a448d2bfaced.jpg) + +![](images/a46604bea033176331e283214f3412fb9322f436c1fdf548f08ae056fcd02013.jpg) + + +![](images/c1cc7f4ebc25de4e119ae4e18314881e2dcb7727d7615536a6c2fdb60dd10733.jpg) + + +Figure 1. The illustration of large visual variations within the predicate "eating". Identical predicate can appear differently under distinct subject-object pairs, encompassing a different set of visual cues within each manifestation. Identifying discriminative relation cues that are shared across diverse subject-object pairs within the same predicate can be challenging. Yet, they can be easily captured when the scope is narrowed to the identical triplet. + +![](images/ebf13cd0eb7eb695ba95014740645796d1d1af3f72a2f198f4d3d255af473df3.jpg) + + +their pairwise relationships, encapsulating them into $<\text{subject}, \text{predicate}, \text{object}>$ triplets [4, 26, 51]. The generated compact graph-structured image representation can be utilized in a range of applications, e.g. embodied navigation [7, 33], image retrieval [5, 8], visual question answering [1, 32], etc., so the SGG task has received widespread attention in recent years [12, 16, 22, 45]. + +Existing SGG methods are mostly dedicated to generating discriminative predicate representations for the detected entities, based on their appearances, relative positions, contextual cues, etc. [15, 19, 37, 44, 54]. However, as shown in Figure 1, large visual variations due to different subject-object combinations are inherent even in the same predicate, presenting an obstacle for SGG methods to capture robust predicate cues across distinct triplet types. To alleviate this problem, PE-Net [54] utilizes textual semantics of predicate categories as the prototype and model predicate cues by reducing the intra-class variance and inter-class similarity. Despite the improved prediction accuracy, PE-Net still follows the previous strategy of straightforwardly amalga + +mating predicate cues that probably contain extensive visual variations of diverse triplets. + +Moreover, many recent efforts have been devoted to the long-tail problem in SGG task. Insufficient samples with limited triplet types lead to the reduced diversity observed in tail predicate categories, making it a challenging task to learn and adapt to their distributions. Existing methods boost model's attention towards tail predicate categories through re-sampling [19], re-weighting[28], or the utilization of mixture of experts [6, 34]. However, they mostly fall short of directly tackling the core of the long-tail issue, i.e., the insufficient patterns for tail predicates, leaving space for further improvement. + +Reflecting on similarities and differences among predicates, we find that despite the non-negligible or even large variations inherent in the same predicate, the visual diversity of the same triplet is relatively small (e.g. the two instances of in Figure 1). Accordingly, considering the more fine-grained triplet cues in addition to the coarse-grained predicate ones can help prevent the model from getting stuck in the refinement process of predicate features with potentially large variations, and promote it to strike a balance between different granularities during the relationship learning process. For the long-tail problem in SGG task which primarily emerges due to the insufficient tail predicate patterns and corresponding limited types and quantity of triplets, it then becomes a natural choice to enrich tail predicate patterns using head predicates and their triplets. + +Based on the aforementioned insights, we propose a Dual-granularity Relation Modeling (DRM) network that models triplet cues to facilitate predicate learning and transfer knowledge from the head classes to tail classes for relation recognition. In our DRM network, as shown in Figure 2, 1) besides a predicate branch that models coarse-grained predicate cues by leveraging their contextual predicates and subject-object pairs, a triplet branch is also presented to strengthen fine-grained triplet representations via jointly exploring their visual contents and corresponding label semantics. We also devise dual-granularity constraints to prevent the degradation of predicate and triplet feature spaces during model training. Subsequently, 2) the Dual-granularity Knowledge Transfer (DKT) strategy is proposed to transfer the class variance from head classes to tail ones from both the predicate and triplet perspectives for unbiased SGG. Distributions of tail predicates/triplets are designed to be calibrated using variance from head ones that are most similar to them. New predicate/triplet samples are generated as well based on the calibrated distributions to enrich the pattern diversity of tail predicates/triplets. Extensive experiments conducted on the widely used Visual Genome [14], Open Image [13], and GQA [10] datasets for SGG demonstrate the state-of-the-art performance of our method. + +![](images/3cbacaa1f43b5b7d1d6854804eb4b04225626966f3a7514af108c210cfd49534.jpg) +Figure 2. Comparison of different pipelines for relation recognition. Previous methods focus on learning predicate cues shared across various triplets with diverse visual appearance. Our method learns and leverages both triplet cues within the same triplet and predicate cues across triplets, to better handle the visual diversity. + +Contributions of this paper can be summarized as: + +- We propose to learn scene graphs in a dual-granularity manner, integrating both coarse-grained predicate cues and fine-grained triplet cues. +- We introduce the DRM network to model predicate and triplet cues, and propose the DKT strategy to propagate knowledge from head predicates/triplets to tail ones to mitigate the long-tail problem in SGG. +- We comprehensively evaluate the proposed method and demonstrate its superior performance. + +# 2. Related Work + +# 2.1. Scene Graph Generation + +Scene graph is a structured representation of the image content, where its essential constituents are the relationships (or triplets $<$ subject, predicate, object $\succ$ ). The direct prediction of triplet categories presents a significant challenge given the extensive combinations of subjects, predicates, and objects. Existing Scene Graph Generation (SGG) methods [11, 16, 25, 42, 52, 54] decompose this prediction target into two components: entities and predicates. Early SGG approaches [26, 49, 51] explore to integrate multiple modalities like positional information and linguistic features into relationships. Later methodologies [11, 27, 35, 36, 39] identify the value of visual context in SGG. Some of them encode contextual information utilizing techniques e.g. message passing [43], LSTM [37, 41, 49], graph neural networks [19, 44], and self-attention modules [3, 6, 20]. Others [27, 39] refine the detected scene graph and optimize the features of refined predicates based on high-confidence predictions. PE-Net [54] proposes to utilize text embeddings as the centroid of predicates, aiming to minimize the intraclass variance and the inter-class similarity. Despite the improved prediction accuracy, it is still hard to extract discriminative relation cues across the various subject-object pairs in the same predicate. The core of this issue lies in the fact that the identical predicates can manifest differently under distinct subject-object pairs, encompassing a unique array + +![](images/93588ba668c62405ba1e6021b6514d9a0c3dd7780ad7bb0e7460754447974968.jpg) +Figure 3. Illustration of the proposed Dual-granularity Relation Modeling (DRM) network. The learning procedure of DRM is composed of two stages. In the first stage, we capture the coarse-grained predicate cues shared across different subject-object pairs and learn the fine-grained triplet cues under specific subject-object pairs. In the second stage, the Dual-granularity Knowledge Transfer (DKT) strategy transfers the variation from head predicates with their associate triplets to the tail. Then DRM exploits the real instances along with synthetic samples from the calibrated tail distribution to fine-tune the relation classifier, which alleviates the long-tail problem in SGG. + +of visual cues within each manifestation. The direct aggregation of predicate features tends to overlook the inherent triplet cues present under the various subject-object pairs. We propose to explicitly model both coarse-grained predicate cues and fine-grained triplet cues for biased and unbiased SGG. + +# 2.2. Unbiased Scene Graph Generation + +Real-world data tends to obey a long-tailed distribution, and imbalanced samples in scene graph present the challenge to learn and adapt to the distribution in the tail predicates [37, 38, 48, 53]. Recently, many methods have been proposed to deal with the biased prediction problem in scene graphs, which can be roughly divided into three categories. The first category of methods use re-balancing strategies that alleviate the long-tail problem by re-sampling images and triplet samples to enhance the performance of tail predicates [19] or by enhancing the loss weights of tail predicates and easily misclassified categories through the pre-defined Predicate Lattice [28]. The second category of methods utilize noisy label learning to explicitly re-label relational triplets missed by annotators and correct the unlabeled predicates [17, 50]. The last category exploit the mixture of experts to let different experts separately deal with a subpart of predicates and merge their outputs [6, 34]. Different from these approaches, we mitigate the long-tail problem + +in SGG by exploiting knowledge from the head predicates and triplets. Our method involves transferring the abundant variations from the head predicates and their associate triplets to the tail, thus enriching patterns of the tail predicates. + +# 3. Method + +An overview of our Dual-granularity Relation Modeling (DRM) network is illustrated in Figure 3. DRM aims to balance and integrate coarse-grained predicate cues and fine-grained triplet cues for relation recognition. To this end, a predicate cue modeling module and a triplet cue modeling module are designed to extract predicate cues shared across diverse subject and object pairs, and triplet cues shared by specific subject-object pairs, respectively. Moreover, the Dual-granularity Knowledge Transfer (DKT) strategy is proposed for unbiased SGG. This strategy transfers the knowledge of both predicates and triplets from head categories to tail ones, with the objective of enriching the pattern of tail predicates and their associated triplets. + +# 3.1. The DRM Network Backbone + +The backbone of our DRM network is composed of a proposal network and an entity encoder. Features generated by the backbone are further fed into subsequent predicate and triplet cue modeling modules. + +Proposal Network. Given an image $\mathcal{I}$ , the proposal network generates $N$ entities along with their corresponding visual features, label predictions, and spatial features from their bounding boxes. A pre-trained Faster RCNN [31] is adopted as the proposal network in this paper. And following previous works [6, 19, 37, 49], we initialize the entity representations $\{\mathbf{v}_i\}_{i=1}^N$ with their visual and spatial features, encode the union feature $\mathbf{u}_{i,j}$ between the $i$ -th entity and the $j$ -th entity with their relative spatial representation and the ROI feature of their union box, and obtain the semantic features $\{\mathbf{s}_i\}_{i=1}^N$ of entities using word embeddings of their class labels. + +Entity Encoder. The entity encoder is designed to refine features of entities with their contexts for further predictions. Inspired by Dong et al. [6], we utilize the Hybrid Attention (HA) to incorporate semantic cues $\{\mathbf{s}_i\}_{i=1}^N$ into entities $\{\mathbf{v}_i\}_{i=1}^N$ while modeling the scene context. Each layer of Hybrid Attention is composed of two Self-Attention (SA) units and two Cross-Attention (CA) units, which is built upon the multi-head attention module [40]. The Hybrid Attention at the $l$ -th layer can be formulated as: + +$$ +\left\{ \begin{array}{l} \mathbf {X} ^ {(l)} = S A \left(\mathbf {X} ^ {(l - 1)}\right) + C A \left(\mathbf {X} ^ {(l - 1)}, \mathbf {Y} ^ {(l - 1)}\right), \\ \mathbf {Y} ^ {(l)} = S A \left(\mathbf {Y} ^ {(l - 1)}\right) + C A \left(\mathbf {Y} ^ {(l - 1)}, \mathbf {X} ^ {(l - 1)}\right), \end{array} \right. \tag {1} +$$ + +where $\mathbf{X}^{(l - 1)}$ and $\mathbf{Y}^{(l - 1)}$ are inputs of the $l$ -th HA layer. We directly fuse outputs of SA and CA units with an addition operation. + +Our entity encoder $Enc_{ent}$ is consisted of a stacked 4-layer Hybrid Attention, and we have $\mathbf{X}^{(0)} = \{\mathbf{v}_i\}_{i=1}^N$ , $\mathbf{Y}^{(0)} = \{\mathbf{s}_i\}_{i=1}^N$ , and: + +$$ +\left\{\mathbf {v} _ {i} ^ {\prime} \right\} _ {i = 1} ^ {N} = E n c _ {e n t} \left(\left\{\mathbf {v} _ {i} \right\} _ {i = 1} ^ {N}, \left\{\mathbf {s} _ {i} \right\} _ {i = 1} ^ {N}\right), \tag {2} +$$ + +where the refined entity representations $\{\mathbf{v}_i^{\prime}\}_{i = 1}^{N}$ are obtained by summing up of outputs from the last HA layer. + +# 3.2. Predicate and Triplet Cue Modeling + +Previous approaches tend to categorize predicates in a coarse manner, most of which only focus on predicate cues shared among various subject-object pairs, and thus cannot effectively deal with the potentially large visual variations inherent in the identical predicate. In contrast to these approaches, our method considers both coarse-grained predicate cues and fine-grained triplet cues, leveraging and striking a balance between the dual-grained cues for accurate predicate categorization. Our DRM network involves a Predicate Cue Modeling module and a Triplet Cue Modeling module for extracting features at these two granularities respectively. Additionally, we introduce Dual-Granularity Constraints to decrease the intra-class variance and increase inter-class distinguishability, explicitly enforcing the predicate and triplet branches to concentrate on cues from their + +corresponding granularities and preventing the degradation of dual-granularity space. + +Predicate Cue Modeling. Our predicate cue modeling module Encprd, comprising a 2-layer Hybrid Attention, aims to capture predicate cues across different subject-object pairs. In each HA layer of Encprd, the two Self-Attention units are designed to model predicate and entity contextual information. And the two Cross-Attention units are designed to capture the dependency between entities and predicates, where the predicate $\mathbf{p}_{i,j}$ solely queries the contexts of its corresponding subject $\mathbf{e}_i$ and object $\mathbf{e}_j$ , and the entity $\mathbf{e}_i$ only queries predicates related to it. Our Predicate Cue Modeling process can thus be formulated as: + +$$ +\left\{\mathbf {p} _ {i, j} ^ {\prime} \right\} _ {i \neq j} ^ {M} = E n c _ {p r d} \left(\left\{\mathbf {p} _ {i, j} \right\} _ {i \neq j} ^ {M}, \left\{\mathbf {e} _ {i} \right\} _ {i = 1} ^ {N}\right), \tag {3} +$$ + +where the predicate representation $\mathbf{p}_{i,j}$ is initialized with the union feature $\mathbf{u}_{i,j}$ , the entity representation $\mathbf{e}_i$ is obtained with the concatenation of $\mathbf{v}_i'$ and $\mathbf{v}_i$ , $M = N \times (N - 1)$ is the number of subject-object pairs, and $\mathbf{p}_{i,j}'$ is the corresponding output of $\mathbf{p}_{i,j}$ at the last HA layer. + +Triplet Cue Modeling. Our triplet cue modeling module $Enc_{tpt}$ is also constructed using a 2-layer Hybrid Attention. This module is responsible for obtaining fine-grained triplet cues that are shared by specific subject-object pairs. The two Self-Attention units in each HA layer of $Enc_{tpt}$ are designed to model visual and semantic contextual information of triplets, respectively, and the two Cross-Attention units aim at fusing semantic cues into the visual information of triplets. We initialize the triplet representation $\mathbf{t}_{i,j}$ with the concatenation of the subject representation $\mathbf{e}_i$ , predicate representation $\mathbf{p}_{i,j}$ , and object representation $\mathbf{e}_j$ . Our Triplet Cue Modeling process is formulated as: + +$$ +\left\{\mathbf {t} _ {i, j} ^ {\prime} \right\} _ {i \neq j} ^ {M} = E n c _ {t p t} \left(\left\{\mathbf {t} _ {i, j} \right\} _ {i \neq j} ^ {M}, \left\{\left[ \mathbf {s} _ {i} ^ {\prime}, \mathbf {s} _ {j} ^ {\prime} \right] \right\} _ {i \neq j} ^ {M}\right), \tag {4} +$$ + +where $\mathbf{s}_i^{\prime}$ is the word embedding of predicted entity label, and $[\cdot ,\cdot ]$ denotes the concatenate operation. $\mathbf{t}_{i,j}^{\prime}$ is the contextually and semantically aware triplet feature, and is derived from the addition of outputs from the last HA layer. + +Dual-granularity Constraints. Although we explicitly model predicate and triplet cues with $Enc_{prd}$ and $Enc_{pt}$ , they may degrade beyond our desires with a single predicate cross-entropy loss. To prevent this degradation, we propose the dual-granularity constraints to guide the predicate and triplet cue modeling modules to refine representations in their desired granularities. Specifically, we generate two views of an input relation and impose a predicate category-aware supervised contrastive learning loss on predicate representations to capture the coarse-grained predicate cues as: + +$$ +\mathcal {L} _ {p} = - \log \frac {\exp \left(\left\langle \mathbf {p} _ {i , j} ^ {\prime \prime} , \mathbf {p} _ {p o s _ {p}} ^ {\prime \prime} \right\rangle / \tau_ {p}\right)}{\sum_ {b \in \mathcal {B} (i , j)} \exp \left(\left\langle \mathbf {p} _ {i , j} ^ {\prime \prime} , \mathbf {p} _ {b} ^ {\prime \prime} \right\rangle / \tau_ {p}\right)}, \tag {5} +$$ + +where $\mathbf{p}_{i,j}^{\prime \prime}$ is obtained by passing $\mathbf{p}_{i,j}^{\prime}$ through a projection layer comprising two fully connected layers, $\tau_{p}$ is the tem + +perature, $pos_{p}$ denotes the subscripts of positive samples belonging to the same predicate category as $\mathbf{p}_{i,j}^{\prime \prime},\langle \cdot ,\cdot \rangle$ is the cosine similarity function, and $\mathcal{B}(i,j)$ denotes the subscript set of samples within the same batch. + +Similarly, a triplet category-aware supervised contrastive learning loss is applied on triplet representations, aiming at capturing the fine-grained triplet cues as: + +$$ +\mathcal {L} _ {t} = - \log \frac {\exp \left(\left\langle \mathbf {t} _ {i , j} ^ {\prime \prime} , \mathbf {t} _ {p o s _ {t}} ^ {\prime \prime} \right\rangle / \tau_ {t}\right)}{\sum_ {b \in \mathcal {B} (i , j)} \exp \left(\left\langle \mathbf {t} _ {i , j} ^ {\prime \prime} , \mathbf {t} _ {b} ^ {\prime \prime} \right\rangle / \tau_ {t}\right)}, \tag {6} +$$ + +where $\tau_{t}$ is the temperature, $pos_{t}$ denotes subscripts of positive samples from the same triplet category as $\mathbf{t}_{i,j}^{\prime \prime}$ , and $\mathbf{t}_{i,j}^{\prime \prime}$ is obtained by passing $\mathbf{t}_{i,j}^{\prime}$ through a projection layer. + +Scene Graph Prediction. For each relationship proposal, our predicate classifier utilizes two fully connected layers to integrate the coarse-grained and fine-grained cues, i.e. $\mathbf{p}_{i,j}^{\prime}$ and $\mathbf{t}_{i,j}^{\prime}$ , to obtain the final relation label prediction. For each entity, we also introduce a fully connected layer with softmax function to get its refined label prediction. + +Training Loss. During the training in the first stage of DRM, the overall loss function $\mathcal{L}$ is defined as: + +$$ +\mathcal {L} = \lambda_ {e} \mathcal {L} _ {e} + \lambda_ {r} \mathcal {L} _ {r} + \lambda_ {p} \mathcal {L} _ {p} + \lambda_ {t} \mathcal {L} _ {t}, \tag {7} +$$ + +where $\mathcal{L}_e$ and $\mathcal{L}_r$ are cross-entropy losses of entities and relationships respectively. $\lambda_e, \lambda_r, \lambda_p,$ and $\lambda_t$ are pre-defined weight hyper-parameters for corresponding loss terms. + +# 3.3. Dual-granularity Knowledge Transfer + +The SGG task typically suffers from the long-tail distribution problem. This problem primarily originates from the tail predicate classes, which possesses limited types and quantities of triplets. The head predicate classes contain a relatively larger number of samples and an abundance of triplet types. Thus to alleviate the long-tail problem, we propose the Dual-granularity Knowledge Transfer (DKT) strategy to transfer knowledge in predicate and triplet feature spaces from head predicate class to the tail one. DKT generates samples belonging to the tail predicates with their associated predicate and triplet features, thereby enriching and diversifying the patterns of tail predicates. + +Specifically, DKT first calculates the distributions of predicate and triplet features. We assume that the distribution of each category $\Omega_c$ follows a multidimensional Gaussian distribution. Formally, it can be expressed as $\{\Omega_c = \mathcal{N}(\pmb{\mu}_c, \pmb{\sigma}_c) | c \in \mathcal{C}\}$ , where $\pmb{\mu}_c$ and $\pmb{\sigma}_c$ denote the mean and covariance of $\Omega_c$ , and $c$ denotes the predicate or triplet category. After the first-stage pre-training of DRM network, we freeze the proposal network, entity encoder, and the predicate and triplet cue modeling modules. Subsequently, the compact predicate and triplet features, i.e. $\mathbf{p}'$ and $\mathbf{t}'$ , are extracted to calculate the predicate and triplet feature distributions, respectively. The mean, denoted as $\pmb{\mu}_c$ , is calculated + +as $\pmb{\mu}_{c} = \frac{1}{N_{c}}\sum_{k}^{N_{c}}\mathbf{x}_{k}^{c}$ . The covariance, symbolized as $\pmb{\sigma}_{c}$ , is calculated as $\pmb{\sigma}_{c} = \frac{1}{N_{c} - 1}\sum_{k}^{N_{c}}(\mathbf{x}_{k}^{c} - \pmb{\mu}_{c})(\mathbf{x}_{k}^{c} - \pmb{\mu}_{c})^{T}$ . Here, $\mathbf{x}_i^c$ denotes the feature of category $c$ , and $N_{c}$ is the number of $\mathbf{x}_k^c$ . The feature $\mathbf{x}$ can be either $\mathbf{p}'$ or $\mathbf{t}'$ . + +We then transfer knowledge of feature distributions of head predicate classes to the tail ones. Specifically, we arrange the predicate classes in descending order based on their sample numbers, choosing half of the predicate classes as head predicates and the remaining ones as tail predicates. We further select triplets that appear more than certain times in the head predicates to be the head triplets (we use 64 times as the threshold in this paper), and those in the tail predicates to be the tail triplets. For each tail category $i \in \mathcal{C}$ we compute the euclidean distance $d_{i,j}$ between its center $\pmb{\mu}_i$ and the center $\pmb{\mu}_j$ of head category $j \in \mathcal{C}$ . The closer the centers of two categories are to each other in either predicate or triplet space, the more similar they are, which also increases the likelihood of knowledge sharing between them. Based on $d_{i,j}$ , we achieve the knowledge transfer as: + +$$ +\boldsymbol {\sigma} _ {i} ^ {\prime} = \frac {N _ {i}}{Q _ {i}} \boldsymbol {\sigma} _ {i} + \left(1 - \frac {N _ {i}}{Q _ {i}}\right) \sum_ {j} \alpha_ {i, j} \boldsymbol {\sigma} _ {j}, \tag {8} +$$ + +where $\alpha_{i,j}$ denotes the softmax normalized form of $d_{i,j}$ , $Q_{i}$ denotes the desired number of predicate/triplet instances of tail class $i$ and it is identical for every predicates in the tail. It suggests that the tail category with fewer samples requires more knowledge from the head for calibration. + +After dual-granularity knowledge transfer, we generate synthetic samples in tail predicate using corresponding predicate and triplet features from calibrated distributions: + +$$ +\{\hat {\boldsymbol {x}} | \hat {\boldsymbol {x}} \sim \Omega_ {c} ^ {\prime} = \mathcal {N} \left(\boldsymbol {\mu} _ {c}, \boldsymbol {\sigma} _ {c} ^ {\prime}\right) \}. \tag {9} +$$ + +Finally, we under-sample head predicates to form a balanced dataset and input the real instances together with synthetic ones into the relation classifier for fine-tuning. Benefiting from the dual-granularity knowledge transfer, the patterns of tail predicates and their associate triplets can be enriched, thus alleviating the long-tail problem. + +# 4. Experiments + +# 4.1. Experimental Settings + +Datasets. We evaluate our method on three commonly used SGG datasets, namely Visual Genome [14], Open Image [13], and GQA [10]. For the Visual Genome dataset, we adopt the VG150 split following previous approaches [23, 29, 37, 43, 49], which contains the most frequent 150 object categories and 50 predicate categories. We use $70\%$ of images for training, $30\%$ images for testing and $5\mathrm{k}$ images from the training set for validation. As for Open Image, we apply the Open Image V6 protocol, which has 301 object categories and 31 predicate categories. It contains + +
ModelsPredClsSGClsSGDet
R@50/100mR@50/100R@50/100mR@50/100R@50/100mR@50/100
IMP [43]CVPR'1761.1 / 63.111.0 / 11.837.5 / 38.56.2 / 6.525.9 / 31.24.2 / 5.3
VTransE [51]CVPR'1765.7 / 67.614.7 / 15.838.6 / 39.48.2 / 8.729.7 / 34.35.0 / 6.1
MOTIFS [49]CVPR'1866.0 / 67.914.6 / 15.839.1 / 39.98.0 / 8.532.1 / 36.95.5 / 6.8
G-RCNN [44]ECCV'1865.4 / 67.216.4 / 17.237.0 / 38.59.0 / 9.529.7 / 32.85.8 / 6.6
VCTREE [37]CVPR'1965.5 / 67.416.7 / 17.940.3 / 41.67.9 / 8.331.9 / 36.06.4 / 7.3
GPS-Net [22]CVPR'2065.2 / 67.115.2 / 16.637.8 / 39.28.5 / 9.131.3 / 35.96.7 / 8.6
RU-Net [24]CVPR'2267.7 / 69.6- / 24.242.4 / 43.3- / 14.632.9 / 37.5- / 10.8
HL-Net [23]CVPR'2267.0 / 68.9- / 22.842.6 / 43.5- / 13.533.7 / 38.1- / 9.2
PE-Net(P) [54]CVPR'2368.2 / 70.123.1 / 25.441.3 / 42.313.1 / 14.832.4 / 36.98.9 / 11.0
VETO [34]ICCV'2364.2 / 66.322.8 / 24.735.7 / 36.911.1 / 11.927.5 / 31.58.1 / 9.5
TDE° [38]CVPR'2046.2 / 51.425.5 / 29.127.7 / 29.913.1 / 14.916.9 / 20.38.2 / 9.8
CogTree° [47]IJCAI'2135.6 / 36.826.4 / 29.021.6 / 22.214.9 / 16.120.0 / 22.110.4 / 11.8
BPL-SA° [9]ICCV'2150.7 / 52.529.7 / 31.730.1 / 31.016.5 / 17.523.0 / 26.913.5 / 15.6
VisualDS° [46]ICCV'21- / -16.1 / 17.5- / -9.3 / 9.9- / -7.0 / 8.3
NICE° [17]CVPR'2255.1 / 57.229.9 / 32.333.1 / 34.016.6 / 17.927.8 / 31.812.2 / 14.4
PPDL° [21]CVPR'2247.2 / 47.632.2 / 33.328.4 / 29.317.5 / 18.221.2 / 23.911.4 / 13.5
GCL° [6]CVPR'2242.7 / 44.436.1 / 38.226.1 / 27.120.8 / 21.818.4 / 22.016.8 / 19.3
IETrans° [50]ECCV'22- / -35.8 / 39.1- / -21.5 / 22.8- / -15.5 / 18.0
INF° [2]CVPR'2351.5 / 55.124.7 / 30.732.2 / 33.814.5 / 17.423.9 / 27.19.4 / 11.7
CFA° [18]ICCV'2354.1 / 56.635.7 / 38.234.9 / 36.117.0 / 18.427.4 / 31.813.2 / 15.5
EICR° [29]ICCV'2355.3 / 57.434.9 / 37.034.5 / 35.420.8 / 21.827.9 / 32.215.5 / 18.2
BGNN [19]CVPR'2159.2 / 61.330.4 / 32.937.4 / 38.514.3 / 16.531.0 / 35.810.7 / 12.6
SHA+GCL [6]CVPR'2235.1 / 37.241.6 / 44.122.8 / 23.923.0 / 24.314.9 / 18.217.9 / 20.9
PE-Net [54]CVPR'2364.9 / 67.231.5 / 33.839.4 / 40.717.8 / 18.930.7 / 35.212.4 / 14.5
SQUAT [12]ICCV'2355.7 / 57.930.9 / 33.433.1 / 34.417.5 / 18.824.5 / 28.914.1 / 16.5
CaCao [48]ICCV'23- / -41.7 / 43.7- / -24.0 / 25.0- / -18.3 / 22.1
DRM w/o DKT70.2 / 72.123.3 / 25.644.3 / 45.213.5 / 14.634.0 / 38.99.0 / 11.2
DRM43.9 / 45.847.1 / 49.627.5 / 28.427.8 / 29.219.0 / 22.920.4 / 24.1
+ +Table 1. Comparison results with state-of-the-art SGG methods on the VG150 dataset. "◇" denotes the combination of MOTIFS with a model-agnostic unbiased strategy. The best and second best results under each setting are respectively marked in red and underline blue. + +
ModelR@50WmAPscorewtd
relphr
MOTIFS [49]CVPR'1871.629.931.638.9
G-RCNN [44]ECCV'1874.533.234.241.8
VCTREE [37]CVPR'1974.134.233.140.2
GPS-Net [22]CVPR'2074.832.934.041.7
BGNN [19]CVPR'2175.033.534.242.1
RU-Net [24]CVPR'2276.935.434.943.5
HL-Net [23]CVPR'2276.535.134.743.2
PE-Net [54]CVPR'2376.536.637.444.9
SQUAT [12]ICCV'2375.834.935.943.5
DRM w/o DKT75.940.541.447.9
+ +Table 2. Comparison results with state-of-the-art SGG methods on Open Image V6. The best and second best results under each metric are respectively marked in red and underline blue. + +126,368, 1,183, and 5,322 images for training, validation, and testing, respectively. For the GQA dataset, we follow previous works [6, 34] and utilize the GQA200 split, which includes 200 object categories and 100 predicate categories. + +Tasks. We adopt three SGG tasks for evaluation: 1) Predicate Classification (Predcls) infers the predicates of entity pairs with ground-truth bounding boxes and cate + +gories. 2) Scene Graph Classification (SGCls) aims to predict the triplet categories with ground-truth bounding boxes. 3) Scene Graph Detection (SGDet) detects bounding boxes of entity pairs and infers their predicate categories. + +Evaluation Metrics. We use Recall@K (R@K) and mean Recall@K (mR@K) as evaluation metrics on VG150 and GQA200 datasets, following recent works [6, 34, 54]. R@K tends to prioritize frequent predicates, while mR@K exhibits a preference for less frequent predicates. Results on Open Image dataset are evaluated using Recall@50 (R@50), weighted mean AP of relations (wmAPrel) weighted mean AP of phrase (wmAPphr), and a weighted score of them scorewtd = 0.2 × R@50 + 0.4 × wAPrel + 0.4 × wAPphr, following previous works [19, 23, 52]. + +Implementation Details. Following previous works [6, 34, 54], we adopt the pre-trained Faster RCNN with ResNeXt-101-RPN in the proposal network to detect entities in the image. GloVe [30] is applied to embed the semantic features. We set the loss weight parameters $\lambda_r$ , $\lambda_e$ , $\lambda_t$ , and $\lambda_p$ as 3, 0.5, 0.1, and 0.1, respectively. Temperatures $\tau_p$ and $\tau_t$ are set as 0.2, and 0.1 considering that the predicate feature space exhibits greater variety than its asso + +
ModelsPredClsSGClsSGDet
R@50/100mR@50/100R@50/100mR@50/100R@50/100mR@50/100
VTransE [51]CVPR'1755.7 / 57.914.0 / 15.033.4 / 34.28.1 / 8.727.2 / 30.75.8 / 6.6
MOTIFS [49]CVPR'1865.3 / 66.816.4 / 17.134.2 / 34.98.2 / 8.628.9 / 33.16.4 / 7.7
VCTREE [37]CVPR'1963.8 / 65.716.6 / 17.434.1 / 34.87.9 / 8.328.3 / 31.96.5 / 7.4
SHA [6]CVPR'2263.3 / 65.219.5 / 21.132.7 / 33.68.5 / 9.025.5 / 29.16.6 / 7.8
VETO [34]ICCV'2364.5 / 66.021.2 / 22.130.4 / 31.58.6 / 9.126.1 / 29.07.0 / 8.1
VTransE+GCL [6]CVPR'2235.5 / 37.430.4 / 32.322.9 / 23.616.6 / 17.415.3 / 18.014.7 / 16.4
MOTIFS+GCL [6]CVPR'2244.5 / 46.236.7 / 38.123.2 / 24.017.3 / 18.118.5 / 21.816.8 / 18.8
VCTREE+GCL [6]CVPR'2244.8 / 46.635.4 / 36.723.7 / 24.517.3 / 18.017.6 / 20.715.6 / 17.8
SHA+GCL [6]CVPR'2242.7 / 44.541.0 / 42.721.4 / 22.220.6 / 21.314.8 / 17.917.8 / 20.1
DRM w/o DKT66.9 / 68.418.1 / 19.036.4 / 37.27.1 / 7.430.6 / 34.66.9 / 8.4
DRM43.2 / 44.441.9 / 43.523.3 / 23.919.9 / 20.718.6 / 21.718.9 / 21.0
+ +Table 3. Comparison results with state-of-the-art SGG methods on the GQA200 dataset. The best and second best results under each setting are respectively marked in red and underline blue. + +
ModulePredClsSGCls
PTACR@50/100mR@50/100R@50/100
56.5/60.415.5/17.437.5/39.310.1/11.3
✓67.6/69.518.1/19.941.8/42.710.8/11.8
✓67.6/69.820.5/22.542.3/43.212.6/13.6
✓✓69.3/71.320.8/22.842.8/43.812.8/13.9
✓✓✓69.8/71.620.4/22.343.4/44.412.8/13.8
✓✓✓69.8/71.622.0/24.043.4/44.312.3/13.3
✓✓✓69.7/71.521.9/24.343.8/44.812.7/13.9
✓✓✓70.2/72.123.3/25.644.3/45.213.5/14.6
+ +Table 4. Ablation studies on predicate and triplet cues learning. "P", "T", "A", and "C" denote the predicate cue modeling module, triplet cue modeling module, augmentation in dual-granularity constraints, and the dual-granularity constraints loss, respectively. + +
ModulePredClsSGCls
R@50/100mR@50/100R@50/100mR@50/100
None70.2/72.123.3/25.644.3/45.213.5/14.6
DKT-P42.4/44.245.0/47.326.8/27.826.9/28.1
DKT-T40.4/42.246.1/48.724.3/25.326.4/28.0
DKT43.9/45.847.1/49.627.5/28.427.8/29.2
+ +Table 5. Ablation studies on dual-granularity knowledge transfer. "DKT-P" and "DKT-T" denote the predicate knowledge transfer and triplet knowledge transfer. + +ciated triplet one. We optimize our method via SGD, using an initial leaning late of $10^{-4}$ with a batch size of 16. + +# 4.2. Comparison with State-of-the-art Methods + +To evaluate the performance our model, we compare it with several state-of-the-art SGG approaches on Visual Genome, Open Image, and GQA datasets. The comparison methods include IMP [43], MOTIFS [49], VCTREE [37], RU-Net [24], HL-Net [23], PE-Net [54], and VETO [34], which focus on the prediction of every relationship in an image. We also compare with methods for unbiased scene graph generation, including TDE [38], CogTree [47], NICE [17], INF [2], CFA [18], EICR [29], BGNN [19], SHA+GCL [6], SQUAT [12], and CaCao[48]. In addition, we compare + +our method with VETO+MEET [34] in the setting without graph constraint in the Supplementary Material. + +Visual Genome. Table 1 shows the comparison results of different approaches on VG150. From these results, we have the following observations: 1) our proposed method significantly outperforms all baselines on all three tasks. More specifically, our DRM w/o DKT outperforms the recent PE-Net [54] by $2.0\%$ , $2.9\%$ , and $2.0\%$ at R@100 on PredCls, SGCls, and SGDet, respectively. Unlike approaches such as MOTIFS [49] and VCTREE [37], which only utilize a predicate classifier to predict predicates and overlook the triplet cues, our method leverages coarse-grained predicate cues and fine-grained triplet cues for relation recognition and thus achieves superior results. 2) Our DRM method also has considerably better performance compared to the baseline unbiased SGG methods. Notably, based on the proposed DKT strategy in DRM, our method outperforms the recent multi-expert method SHA+GCL [6] by $5.5\%$ , $4.9\%$ , and $3.2\%$ at mR@100 on three tasks. This demonstrates that transferring knowledge from head predicates to tail predicates at dual granularities and enriching the patterns in tail predicates can effectively mitigate the long-tail problem. + +Open Image. Compared to the VG dataset, Open Image provides a relatively complete labeling of relationships in the images. Consequently, the model's capability to generate scene graphs can be evaluated at a fine-grained level utilizing the AP metric. To evaluate the generalizability of our method across various datasets, we conduct experiments on Open Image V6. Since the metrics in Open Image V6 tend to prioritize frequent predicates, we just compare our DRM w/o DKT with state-of-the-art approaches. The comparison results shown in Table 2 indicate that our DRM w/o DKT significantly outperforms the recent approaches, i.e., SQUAT [12] and PE-Net [54]. + +GQA. Compared to Visual Genome and Open Image datasets, GQA200 contains a broader range of predicates. So we further confirm the generality of our model on the + +![](images/fb1f74fcc34a696ae95cc298fccddb16b444d3cae279c05261d9caa319d51904.jpg) +(a) MOTIFS, Triplet + +![](images/e193cbcac6da00784390bbd73a2c352b3d1b4467504e57313b110760c508ca00.jpg) +(b) DRM w/o DKT, Triplet + +![](images/2d5f2a6106667f987a0d8c943d5a00e2b36a7e8484b91f7c15b665f4923a67b5.jpg) +(c) DRM, Triplet +Figure 4. The comparison of t-SNE visualization results on predicate and triplet feature distributions within the VG dataset. "MOTIFS, Triplet" and "DRM w/o DKT, Triplet" visualize the same set of samples, where each unique color represents a different type of triplet. + +![](images/edc6eaebf09caba9c3d91b03e24084e28aff9f0c288ab809fe758a82e0ec9876.jpg) +(d) DRM w/o DKT, Predicate + +![](images/fae206042c6cdfaa0904f7c334b247a4ff230c879b025fd7319b09f367c557d7.jpg) +(e) DRM, Predicate + +GQA200 dataset. As shown in Table 3, our method significantly outperforms the recent VETO [34] at R@100 on three tasks. When equipped with DKT, our DRM outperforms $\mathrm{SHA + GCL}$ [6] by an average of $0.4\%$ at mR@100 across three tasks. These results demonstrate the consistent effectiveness of our method in handling relation recognition under different data distributions. + +# 4.3. Ablation Study + +To verify the contributions of different components in our DRM network, we conduct the following ablation studies. + +Predicate and Triplet Cue Learning. We first perform an ablation study on the leverage of predicate and triplet cues. As shown in Table 4, we incrementally incorporate one component into the baseline to verify their effectiveness. Compared with the application of predicate or triplet cue modeling in isolation, leveraging both predicate and triplet together improves the performance. Our dual-granularity constraints include a constraint loss component and a two-view augmentation component to generate positive pairs in each training batch. The constraints compel predicate and triplet cue modeling to concentrate on corresponding granularities. We observe from the results that both the loss component and augmentation component contribute to the performance improvements. + +Dual-Granularity Knowledge Transfer. As shown in Table 5, we conduct an ablation study for the DKT. We observe an obvious performance gain on $\mathrm{mR}@\mathrm{K}$ when transferring knowledge at either predicate or triplet granularity. The $\mathrm{mR}@\mathrm{K}$ is further improved when predicate and triplet granularities are simultaneously employed. In comparison to the scenario without the application of DKT, we observe a performance decrease in $\mathrm{R}@\mathrm{K}$ when using it. This is attributed to the capability of our model to reasonably classify ambiguous head predicates, e.g. "on", into more specific tail predicates, e.g. "sitting on". Consequently, decreases at the $\mathrm{R}@\mathrm{K}$ for these head predicates are inevitable [17, 54]. + +# 4.4. Visualization Analysis + +To illustrate the ability our method to learn triplet cues and impact of the DKT strategy, we visualize the predicate and + +triplet feature distributions using t-SNE. The visualization results are shown in Figure 4. Comparing Figure 4a with Figure 4b, we observe that our DRM generates compact and distinguishable triplet representations, while MOTIFS [49] appears to overlook the triplet cues, leading to a challenge in distinguishing various triplet types. By comparing Figure 4b with Figure 4c, it can be observed that DKT can generate synthetic samples with diverse distributions for the tail triplets. Figures 4d and 4e demonstrate that DKT also transfers the knowledge of head predicates to tail predicates, increasing the tail predicate patterns. The visualization of predicate and triplet feature distributions demonstrates the interpretability of our method in leveraging predicate and triplet cues and transferring the dual-granularity knowledge. + +# 5. Conclusion + +In this paper, we propose a Dual-granularity Relation Modeling (DRM) network to address two issues in SGG, i.e. the diverse visual appearance within the same predicate and the lack of patterns in tail predicates. Our DRM network captures the coarse-grained predicate cues shared across different subject-object pairs and fine-grained triplet cues under specific subject-object pairs for relationship recognition. The Dual-granularity Knowledge Transfer (DKT) is further proposed to transfer the variation from head predicates to the tail to enrich the tail predicate patterns. Quantitative and qualitative experiments demonstrate that our method establishes new state-of-the-art performances on Visual Genome, Open Image and GQA datasets. + +# Acknowledgement + +This work was supported in part by the National Key R&D Program of China under Grant 2022ZD0161901, the National Natural Science Foundation of China under Grants 62276018 and U20B2069, the Beijing Nova Program under Grant 20230484297, the Fundamental Research Funds for the Central Universities, and Research Program of State Key Laboratory of Complex & Critical Software Environment. + +# References + +[1] Hedi Ben-Younes, Remi Cadene, Nicolas Thome, and Matthieu Cord. Block: Bilinear superdiagonal fusion for visual question answering and visual relationship detection. In Proceedings of the AAAI Conference on Artificial Intelligence, pages 8102-8109, 2019. 1 +[2] Bashirul Azam Biswas and Qiang Ji. Probabilistic debiasing of scene graphs. 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Given the prevalence of large visual variations of subject-object pairs even in the same predicate, it can be quite challenging to model and refine predicate representations directly across such pairs, which is however a common strategy adopted by most existing SGG methods. We observe that visual variations within the identical triplet are relatively small and certain relation cues are shared in the same type of triplet, which can potentially facilitate the relation learning in SGG. Moreover, for the long-tail problem widely studied in SGG task, it is also crucial to deal with the limited types and quantity of triplets in tail predicates. Accordingly, in this paper, we propose a Dual-granularity Relation Modeling (DRM) network to leverage fine-grained triplet cues besides the coarse-grained predicate ones. DRM utilizes contexts and semantics of predicate and triplet with Dual-granularity Constraints, generating compact and balanced representations from two perspectives to facilitate relation recognition. Furthermore, a Dual-granularity Knowledge Transfer (DKT) strategy is introduced to transfer variation from head predicates/triplets to tail ones, aiming to enrich the pattern diversity of tail classes to alleviate the long-tail problem. Extensive experiments demonstrate the effectiveness of our method, which establishes new state-of-the-art performance on Visual Genome, Open Image, and GQA datasets. Our code is available at https://github.com/jkli1998/DRM" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 626, + 127, + 639 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 626, + 127, + 639 + ], + "spans": [ + { + "bbox": [ + 47, + 626, + 127, + 639 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "spans": [ + { + "bbox": [ + 46, + 647, + 287, + 696 + ], + "type": "text", + "content": "Entities and their associated relationships form the cornerstones of visual contents in images [14]. Scene Graph Generation (SGG), a fundamental task in visual scene understanding, is designed to detect these entities and predict" + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 326, + 242, + 424, + 299 + ], + "blocks": [ + { + "bbox": [ + 326, + 242, + 424, + 299 + ], + "lines": [ + { + "bbox": [ + 326, + 242, + 424, + 299 + ], + "spans": [ + { + "bbox": [ + 326, + 242, + 424, + 299 + ], + "type": "image", + "image_path": "8f7ae5ebc3d0278e38ab426a8e54d9685e23f0564ad35bb736e4a448d2bfaced.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 425, + 242, + 523, + 300 + ], + "blocks": [ + { + "bbox": [ + 425, + 242, + 523, + 300 + ], + "lines": [ + { + "bbox": [ + 425, + 242, + 523, + 300 + ], + "spans": [ + { + "bbox": [ + 425, + 242, + 523, + 300 + ], + "type": "image", + "image_path": "a46604bea033176331e283214f3412fb9322f436c1fdf548f08ae056fcd02013.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 439, + 300, + 510, + 310 + ], + "lines": [ + { + "bbox": [ + 439, + 300, + 510, + 310 + ], + "spans": [ + { + "bbox": [ + 439, + 300, + 510, + 310 + ], + "type": "text", + "content": "" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 326, + 310, + 423, + 368 + ], + "blocks": [ + { + "bbox": [ + 343, + 300, + 408, + 310 + ], + "lines": [ + { + "bbox": [ + 343, + 300, + 408, + 310 + ], + "spans": [ + { + "bbox": [ + 343, + 300, + 408, + 310 + ], + "type": "text", + "content": "" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 326, + 310, + 423, + 368 + ], + "lines": [ + { + "bbox": [ + 326, + 310, + 423, + 368 + ], + "spans": [ + { + "bbox": [ + 326, + 310, + 423, + 368 + ], + "type": "image", + "image_path": "c1cc7f4ebc25de4e119ae4e18314881e2dcb7727d7615536a6c2fdb60dd10733.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 335, + 369, + 416, + 378 + ], + "lines": [ + { + "bbox": [ + 335, + 369, + 416, + 378 + ], + "spans": [ + { + "bbox": [ + 335, + 369, + 416, + 378 + ], + "type": "text", + "content": "" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 384, + 545, + 461 + ], + "lines": [ + { + "bbox": [ + 304, + 384, + 545, + 461 + ], + "spans": [ + { + "bbox": [ + 304, + 384, + 545, + 461 + ], + "type": "text", + "content": "Figure 1. The illustration of large visual variations within the predicate \"eating\". Identical predicate can appear differently under distinct subject-object pairs, encompassing a different set of visual cues within each manifestation. Identifying discriminative relation cues that are shared across diverse subject-object pairs within the same predicate can be challenging. Yet, they can be easily captured when the scope is narrowed to the identical triplet." + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_caption" + } + ], + "index": 16 + }, + { + "type": "image", + "bbox": [ + 425, + 310, + 523, + 368 + ], + "blocks": [ + { + "bbox": [ + 425, + 310, + 523, + 368 + ], + "lines": [ + { + "bbox": [ + 425, + 310, + 523, + 368 + ], + "spans": [ + { + "bbox": [ + 425, + 310, + 523, + 368 + ], + "type": "image", + "image_path": "ebf13cd0eb7eb695ba95014740645796d1d1af3f72a2f198f4d3d255af473df3.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 433, + 369, + 514, + 378 + ], + "lines": [ + { + "bbox": [ + 433, + 369, + 514, + 378 + ], + "spans": [ + { + "bbox": [ + 433, + 369, + 514, + 378 + ], + "type": "text", + "content": "" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 473, + 545, + 557 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 545, + 557 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 545, + 557 + ], + "type": "text", + "content": "their pairwise relationships, encapsulating them into " + }, + { + "bbox": [ + 304, + 473, + 545, + 557 + ], + "type": "inline_equation", + "content": "<\\text{subject}, \\text{predicate}, \\text{object}>" + }, + { + "bbox": [ + 304, + 473, + 545, + 557 + ], + "type": "text", + "content": " triplets [4, 26, 51]. The generated compact graph-structured image representation can be utilized in a range of applications, e.g. embodied navigation [7, 33], image retrieval [5, 8], visual question answering [1, 32], etc., so the SGG task has received widespread attention in recent years [12, 16, 22, 45]." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 558, + 546, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 546, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 546, + 714 + ], + "type": "text", + "content": "Existing SGG methods are mostly dedicated to generating discriminative predicate representations for the detected entities, based on their appearances, relative positions, contextual cues, etc. [15, 19, 37, 44, 54]. However, as shown in Figure 1, large visual variations due to different subject-object combinations are inherent even in the same predicate, presenting an obstacle for SGG methods to capture robust predicate cues across distinct triplet types. To alleviate this problem, PE-Net [54] utilizes textual semantics of predicate categories as the prototype and model predicate cues by reducing the intra-class variance and inter-class similarity. Despite the improved prediction accuracy, PE-Net still follows the previous strategy of straightforwardly amalga" + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "type": "text", + "content": "*Corresponding author" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "28369" + } + ] + } + ], + "index": 24 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "content": "mating predicate cues that probably contain extensive visual variations of diverse triplets." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 99, + 287, + 230 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 99, + 287, + 230 + ], + "spans": [ + { + "bbox": [ + 46, + 99, + 287, + 230 + ], + "type": "text", + "content": "Moreover, many recent efforts have been devoted to the long-tail problem in SGG task. Insufficient samples with limited triplet types lead to the reduced diversity observed in tail predicate categories, making it a challenging task to learn and adapt to their distributions. Existing methods boost model's attention towards tail predicate categories through re-sampling [19], re-weighting[28], or the utilization of mixture of experts [6, 34]. However, they mostly fall short of directly tackling the core of the long-tail issue, i.e., the insufficient patterns for tail predicates, leaving space for further improvement." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 232, + 287, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 232, + 287, + 423 + ], + "spans": [ + { + "bbox": [ + 46, + 232, + 287, + 423 + ], + "type": "text", + "content": "Reflecting on similarities and differences among predicates, we find that despite the non-negligible or even large variations inherent in the same predicate, the visual diversity of the same triplet is relatively small (e.g. the two instances of in Figure 1). Accordingly, considering the more fine-grained triplet cues in addition to the coarse-grained predicate ones can help prevent the model from getting stuck in the refinement process of predicate features with potentially large variations, and promote it to strike a balance between different granularities during the relationship learning process. For the long-tail problem in SGG task which primarily emerges due to the insufficient tail predicate patterns and corresponding limited types and quantity of triplets, it then becomes a natural choice to enrich tail predicate patterns using head predicates and their triplets." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 426, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 426, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 426, + 288, + 713 + ], + "type": "text", + "content": "Based on the aforementioned insights, we propose a Dual-granularity Relation Modeling (DRM) network that models triplet cues to facilitate predicate learning and transfer knowledge from the head classes to tail classes for relation recognition. In our DRM network, as shown in Figure 2, 1) besides a predicate branch that models coarse-grained predicate cues by leveraging their contextual predicates and subject-object pairs, a triplet branch is also presented to strengthen fine-grained triplet representations via jointly exploring their visual contents and corresponding label semantics. We also devise dual-granularity constraints to prevent the degradation of predicate and triplet feature spaces during model training. Subsequently, 2) the Dual-granularity Knowledge Transfer (DKT) strategy is proposed to transfer the class variance from head classes to tail ones from both the predicate and triplet perspectives for unbiased SGG. Distributions of tail predicates/triplets are designed to be calibrated using variance from head ones that are most similar to them. New predicate/triplet samples are generated as well based on the calibrated distributions to enrich the pattern diversity of tail predicates/triplets. Extensive experiments conducted on the widely used Visual Genome [14], Open Image [13], and GQA [10] datasets for SGG demonstrate the state-of-the-art performance of our method." + } + ] + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 314, + 72, + 538, + 178 + ], + "blocks": [ + { + "bbox": [ + 314, + 72, + 538, + 178 + ], + "lines": [ + { + "bbox": [ + 314, + 72, + 538, + 178 + ], + "spans": [ + { + "bbox": [ + 314, + 72, + 538, + 178 + ], + "type": "image", + "image_path": "3cbacaa1f43b5b7d1d6854804eb4b04225626966f3a7514af108c210cfd49534.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 180, + 545, + 236 + ], + "lines": [ + { + "bbox": [ + 304, + 180, + 545, + 236 + ], + "spans": [ + { + "bbox": [ + 304, + 180, + 545, + 236 + ], + "type": "text", + "content": "Figure 2. Comparison of different pipelines for relation recognition. Previous methods focus on learning predicate cues shared across various triplets with diverse visual appearance. Our method learns and leverages both triplet cues within the same triplet and predicate cues across triplets, to better handle the visual diversity." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "bbox": [ + 317, + 247, + 520, + 258 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 247, + 520, + 258 + ], + "spans": [ + { + "bbox": [ + 317, + 247, + 520, + 258 + ], + "type": "text", + "content": "Contributions of this paper can be summarized as:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 258, + 545, + 365 + ], + "type": "list", + "angle": 0, + "index": 10, + "blocks": [ + { + "bbox": [ + 306, + 258, + 545, + 293 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 258, + 545, + 293 + ], + "spans": [ + { + "bbox": [ + 306, + 258, + 545, + 293 + ], + "type": "text", + "content": "- We propose to learn scene graphs in a dual-granularity manner, integrating both coarse-grained predicate cues and fine-grained triplet cues." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 294, + 545, + 342 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 294, + 545, + 342 + ], + "spans": [ + { + "bbox": [ + 306, + 294, + 545, + 342 + ], + "type": "text", + "content": "- We introduce the DRM network to model predicate and triplet cues, and propose the DKT strategy to propagate knowledge from head predicates/triplets to tail ones to mitigate the long-tail problem in SGG." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 342, + 545, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 342, + 545, + 365 + ], + "spans": [ + { + "bbox": [ + 306, + 342, + 545, + 365 + ], + "type": "text", + "content": "- We comprehensively evaluate the proposed method and demonstrate its superior performance." + } + ] + } + ], + "index": 9 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 376, + 392, + 388 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 376, + 392, + 388 + ], + "spans": [ + { + "bbox": [ + 306, + 376, + 392, + 388 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 306, + 396, + 444, + 408 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 396, + 444, + 408 + ], + "spans": [ + { + "bbox": [ + 306, + 396, + 444, + 408 + ], + "type": "text", + "content": "2.1. Scene Graph Generation" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 415, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 415, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 415, + 545, + 715 + ], + "type": "text", + "content": "Scene graph is a structured representation of the image content, where its essential constituents are the relationships (or triplets " + }, + { + "bbox": [ + 304, + 415, + 545, + 715 + ], + "type": "inline_equation", + "content": "<" + }, + { + "bbox": [ + 304, + 415, + 545, + 715 + ], + "type": "text", + "content": " subject, predicate, object " + }, + { + "bbox": [ + 304, + 415, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\succ" + }, + { + "bbox": [ + 304, + 415, + 545, + 715 + ], + "type": "text", + "content": "). The direct prediction of triplet categories presents a significant challenge given the extensive combinations of subjects, predicates, and objects. Existing Scene Graph Generation (SGG) methods [11, 16, 25, 42, 52, 54] decompose this prediction target into two components: entities and predicates. Early SGG approaches [26, 49, 51] explore to integrate multiple modalities like positional information and linguistic features into relationships. Later methodologies [11, 27, 35, 36, 39] identify the value of visual context in SGG. Some of them encode contextual information utilizing techniques e.g. message passing [43], LSTM [37, 41, 49], graph neural networks [19, 44], and self-attention modules [3, 6, 20]. Others [27, 39] refine the detected scene graph and optimize the features of refined predicates based on high-confidence predictions. PE-Net [54] proposes to utilize text embeddings as the centroid of predicates, aiming to minimize the intraclass variance and the inter-class similarity. Despite the improved prediction accuracy, it is still hard to extract discriminative relation cues across the various subject-object pairs in the same predicate. The core of this issue lies in the fact that the identical predicates can manifest differently under distinct subject-object pairs, encompassing a unique array" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "28370" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 73, + 544, + 323 + ], + "blocks": [ + { + "bbox": [ + 51, + 73, + 544, + 323 + ], + "lines": [ + { + "bbox": [ + 51, + 73, + 544, + 323 + ], + "spans": [ + { + "bbox": [ + 51, + 73, + 544, + 323 + ], + "type": "image", + "image_path": "93588ba668c62405ba1e6021b6514d9a0c3dd7780ad7bb0e7460754447974968.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 330, + 546, + 386 + ], + "lines": [ + { + "bbox": [ + 46, + 330, + 546, + 386 + ], + "spans": [ + { + "bbox": [ + 46, + 330, + 546, + 386 + ], + "type": "text", + "content": "Figure 3. Illustration of the proposed Dual-granularity Relation Modeling (DRM) network. The learning procedure of DRM is composed of two stages. In the first stage, we capture the coarse-grained predicate cues shared across different subject-object pairs and learn the fine-grained triplet cues under specific subject-object pairs. In the second stage, the Dual-granularity Knowledge Transfer (DKT) strategy transfers the variation from head predicates with their associate triplets to the tail. Then DRM exploits the real instances along with synthetic samples from the calibrated tail distribution to fine-tune the relation classifier, which alleviates the long-tail problem in SGG." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 396, + 288, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 396, + 288, + 467 + ], + "spans": [ + { + "bbox": [ + 46, + 396, + 288, + 467 + ], + "type": "text", + "content": "of visual cues within each manifestation. The direct aggregation of predicate features tends to overlook the inherent triplet cues present under the various subject-object pairs. We propose to explicitly model both coarse-grained predicate cues and fine-grained triplet cues for biased and unbiased SGG." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 479, + 233, + 491 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 479, + 233, + 491 + ], + "spans": [ + { + "bbox": [ + 47, + 479, + 233, + 491 + ], + "type": "text", + "content": "2.2. Unbiased Scene Graph Generation" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 498, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 498, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 288, + 713 + ], + "type": "text", + "content": "Real-world data tends to obey a long-tailed distribution, and imbalanced samples in scene graph present the challenge to learn and adapt to the distribution in the tail predicates [37, 38, 48, 53]. Recently, many methods have been proposed to deal with the biased prediction problem in scene graphs, which can be roughly divided into three categories. The first category of methods use re-balancing strategies that alleviate the long-tail problem by re-sampling images and triplet samples to enhance the performance of tail predicates [19] or by enhancing the loss weights of tail predicates and easily misclassified categories through the pre-defined Predicate Lattice [28]. The second category of methods utilize noisy label learning to explicitly re-label relational triplets missed by annotators and correct the unlabeled predicates [17, 50]. The last category exploit the mixture of experts to let different experts separately deal with a subpart of predicates and merge their outputs [6, 34]. Different from these approaches, we mitigate the long-tail problem" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 304, + 396, + 545, + 456 + ], + "type": "text", + "content": "in SGG by exploiting knowledge from the head predicates and triplets. Our method involves transferring the abundant variations from the head predicates and their associate triplets to the tail, thus enriching patterns of the tail predicates." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 465, + 361, + 477 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 465, + 361, + 477 + ], + "spans": [ + { + "bbox": [ + 306, + 465, + 361, + 477 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 485, + 545, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 485, + 545, + 641 + ], + "spans": [ + { + "bbox": [ + 304, + 485, + 545, + 641 + ], + "type": "text", + "content": "An overview of our Dual-granularity Relation Modeling (DRM) network is illustrated in Figure 3. DRM aims to balance and integrate coarse-grained predicate cues and fine-grained triplet cues for relation recognition. To this end, a predicate cue modeling module and a triplet cue modeling module are designed to extract predicate cues shared across diverse subject and object pairs, and triplet cues shared by specific subject-object pairs, respectively. Moreover, the Dual-granularity Knowledge Transfer (DKT) strategy is proposed for unbiased SGG. This strategy transfers the knowledge of both predicates and triplets from head categories to tail ones, with the objective of enriching the pattern of tail predicates and their associated triplets." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 647, + 468, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 647, + 468, + 658 + ], + "spans": [ + { + "bbox": [ + 306, + 647, + 468, + 658 + ], + "type": "text", + "content": "3.1. The DRM Network Backbone" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": "The backbone of our DRM network is composed of a proposal network and an entity encoder. Features generated by the backbone are further fed into subsequent predicate and triplet cue modeling modules." + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28371" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": "Proposal Network. Given an image " + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "inline_equation", + "content": "\\mathcal{I}" + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": ", the proposal network generates " + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": " entities along with their corresponding visual features, label predictions, and spatial features from their bounding boxes. A pre-trained Faster RCNN [31] is adopted as the proposal network in this paper. And following previous works [6, 19, 37, 49], we initialize the entity representations " + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{v}_i\\}_{i=1}^N" + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": " with their visual and spatial features, encode the union feature " + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "inline_equation", + "content": "\\mathbf{u}_{i,j}" + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": " between the " + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": "-th entity and the " + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "inline_equation", + "content": "j" + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": "-th entity with their relative spatial representation and the ROI feature of their union box, and obtain the semantic features " + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{s}_i\\}_{i=1}^N" + }, + { + "bbox": [ + 46, + 72, + 289, + 215 + ], + "type": "text", + "content": " of entities using word embeddings of their class labels." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "spans": [ + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "type": "text", + "content": "Entity Encoder. The entity encoder is designed to refine features of entities with their contexts for further predictions. Inspired by Dong et al. [6], we utilize the Hybrid Attention (HA) to incorporate semantic cues " + }, + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{s}_i\\}_{i=1}^N" + }, + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "type": "text", + "content": " into entities " + }, + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{v}_i\\}_{i=1}^N" + }, + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "type": "text", + "content": " while modeling the scene context. Each layer of Hybrid Attention is composed of two Self-Attention (SA) units and two Cross-Attention (CA) units, which is built upon the multi-head attention module [40]. The Hybrid Attention at the " + }, + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 46, + 216, + 289, + 324 + ], + "type": "text", + "content": "-th layer can be formulated as:" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 65, + 332, + 287, + 366 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 332, + 287, + 366 + ], + "spans": [ + { + "bbox": [ + 65, + 332, + 287, + 366 + ], + "type": "interline_equation", + "content": "\\left\\{ \\begin{array}{l} \\mathbf {X} ^ {(l)} = S A \\left(\\mathbf {X} ^ {(l - 1)}\\right) + C A \\left(\\mathbf {X} ^ {(l - 1)}, \\mathbf {Y} ^ {(l - 1)}\\right), \\\\ \\mathbf {Y} ^ {(l)} = S A \\left(\\mathbf {Y} ^ {(l - 1)}\\right) + C A \\left(\\mathbf {Y} ^ {(l - 1)}, \\mathbf {X} ^ {(l - 1)}\\right), \\end{array} \\right. \\tag {1}", + "image_path": "e29caf926997fd2cd44b7af7b5e365f8d1aa87095fa1f27d5bc9fe0a8fdbf9b8.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "spans": [ + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\mathbf{X}^{(l - 1)}" + }, + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\mathbf{Y}^{(l - 1)}" + }, + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "type": "text", + "content": " are inputs of the " + }, + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "type": "inline_equation", + "content": "l" + }, + { + "bbox": [ + 46, + 375, + 287, + 411 + ], + "type": "text", + "content": "-th HA layer. We directly fuse outputs of SA and CA units with an addition operation." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "spans": [ + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "type": "text", + "content": "Our entity encoder " + }, + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "type": "inline_equation", + "content": "Enc_{ent}" + }, + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "type": "text", + "content": " is consisted of a stacked 4-layer Hybrid Attention, and we have " + }, + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "type": "inline_equation", + "content": "\\mathbf{X}^{(0)} = \\{\\mathbf{v}_i\\}_{i=1}^N" + }, + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "type": "inline_equation", + "content": "\\mathbf{Y}^{(0)} = \\{\\mathbf{s}_i\\}_{i=1}^N" + }, + { + "bbox": [ + 47, + 412, + 287, + 450 + ], + "type": "text", + "content": ", and:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 88, + 458, + 287, + 472 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 88, + 458, + 287, + 472 + ], + "spans": [ + { + "bbox": [ + 88, + 458, + 287, + 472 + ], + "type": "interline_equation", + "content": "\\left\\{\\mathbf {v} _ {i} ^ {\\prime} \\right\\} _ {i = 1} ^ {N} = E n c _ {e n t} \\left(\\left\\{\\mathbf {v} _ {i} \\right\\} _ {i = 1} ^ {N}, \\left\\{\\mathbf {s} _ {i} \\right\\} _ {i = 1} ^ {N}\\right), \\tag {2}", + "image_path": "16644c13b3e6ab6e587a639876644fb9d56fa89cffdd8a9a203231c521e16886.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 482, + 287, + 507 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 482, + 287, + 507 + ], + "spans": [ + { + "bbox": [ + 46, + 482, + 287, + 507 + ], + "type": "text", + "content": "where the refined entity representations " + }, + { + "bbox": [ + 46, + 482, + 287, + 507 + ], + "type": "inline_equation", + "content": "\\{\\mathbf{v}_i^{\\prime}\\}_{i = 1}^{N}" + }, + { + "bbox": [ + 46, + 482, + 287, + 507 + ], + "type": "text", + "content": " are obtained by summing up of outputs from the last HA layer." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 515, + 239, + 528 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 515, + 239, + 528 + ], + "spans": [ + { + "bbox": [ + 47, + 515, + 239, + 528 + ], + "type": "text", + "content": "3.2. Predicate and Triplet Cue Modeling" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 534, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 534, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 534, + 289, + 713 + ], + "type": "text", + "content": "Previous approaches tend to categorize predicates in a coarse manner, most of which only focus on predicate cues shared among various subject-object pairs, and thus cannot effectively deal with the potentially large visual variations inherent in the identical predicate. In contrast to these approaches, our method considers both coarse-grained predicate cues and fine-grained triplet cues, leveraging and striking a balance between the dual-grained cues for accurate predicate categorization. Our DRM network involves a Predicate Cue Modeling module and a Triplet Cue Modeling module for extracting features at these two granularities respectively. Additionally, we introduce Dual-Granularity Constraints to decrease the intra-class variance and increase inter-class distinguishability, explicitly enforcing the predicate and triplet branches to concentrate on cues from their" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 72, + 545, + 95 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 95 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 95 + ], + "type": "text", + "content": "corresponding granularities and preventing the degradation of dual-granularity space." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "spans": [ + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "text", + "content": "Predicate Cue Modeling. Our predicate cue modeling module Encprd, comprising a 2-layer Hybrid Attention, aims to capture predicate cues across different subject-object pairs. In each HA layer of Encprd, the two Self-Attention units are designed to model predicate and entity contextual information. And the two Cross-Attention units are designed to capture the dependency between entities and predicates, where the predicate " + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}" + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "text", + "content": " solely queries the contexts of its corresponding subject " + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{e}_i" + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "text", + "content": " and object " + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{e}_j" + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "text", + "content": ", and the entity " + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "inline_equation", + "content": "\\mathbf{e}_i" + }, + { + "bbox": [ + 304, + 95, + 547, + 228 + ], + "type": "text", + "content": " only queries predicates related to it. Our Predicate Cue Modeling process can thus be formulated as:" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 340, + 232, + 545, + 248 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 340, + 232, + 545, + 248 + ], + "spans": [ + { + "bbox": [ + 340, + 232, + 545, + 248 + ], + "type": "interline_equation", + "content": "\\left\\{\\mathbf {p} _ {i, j} ^ {\\prime} \\right\\} _ {i \\neq j} ^ {M} = E n c _ {p r d} \\left(\\left\\{\\mathbf {p} _ {i, j} \\right\\} _ {i \\neq j} ^ {M}, \\left\\{\\mathbf {e} _ {i} \\right\\} _ {i = 1} ^ {N}\\right), \\tag {3}", + "image_path": "255c7abc7b00f2122a68d77b66552d26c0951f4678adbeeacf61536c8fd16cc0.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "spans": [ + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": "where the predicate representation " + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}" + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": " is initialized with the union feature " + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "inline_equation", + "content": "\\mathbf{u}_{i,j}" + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": ", the entity representation " + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "inline_equation", + "content": "\\mathbf{e}_i" + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": " is obtained with the concatenation of " + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "inline_equation", + "content": "\\mathbf{v}_i'" + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "inline_equation", + "content": "\\mathbf{v}_i" + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "inline_equation", + "content": "M = N \\times (N - 1)" + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": " is the number of subject-object pairs, and " + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}'" + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": " is the corresponding output of " + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}" + }, + { + "bbox": [ + 304, + 253, + 545, + 312 + ], + "type": "text", + "content": " at the last HA layer." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "spans": [ + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "text", + "content": "Triplet Cue Modeling. Our triplet cue modeling module " + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "inline_equation", + "content": "Enc_{tpt}" + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "text", + "content": " is also constructed using a 2-layer Hybrid Attention. This module is responsible for obtaining fine-grained triplet cues that are shared by specific subject-object pairs. The two Self-Attention units in each HA layer of " + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "inline_equation", + "content": "Enc_{tpt}" + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "text", + "content": " are designed to model visual and semantic contextual information of triplets, respectively, and the two Cross-Attention units aim at fusing semantic cues into the visual information of triplets. We initialize the triplet representation " + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{i,j}" + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "text", + "content": " with the concatenation of the subject representation " + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "inline_equation", + "content": "\\mathbf{e}_i" + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "text", + "content": ", predicate representation " + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}" + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "text", + "content": ", and object representation " + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "inline_equation", + "content": "\\mathbf{e}_j" + }, + { + "bbox": [ + 304, + 312, + 546, + 456 + ], + "type": "text", + "content": ". Our Triplet Cue Modeling process is formulated as:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 334, + 460, + 545, + 477 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 334, + 460, + 545, + 477 + ], + "spans": [ + { + "bbox": [ + 334, + 460, + 545, + 477 + ], + "type": "interline_equation", + "content": "\\left\\{\\mathbf {t} _ {i, j} ^ {\\prime} \\right\\} _ {i \\neq j} ^ {M} = E n c _ {t p t} \\left(\\left\\{\\mathbf {t} _ {i, j} \\right\\} _ {i \\neq j} ^ {M}, \\left\\{\\left[ \\mathbf {s} _ {i} ^ {\\prime}, \\mathbf {s} _ {j} ^ {\\prime} \\right] \\right\\} _ {i \\neq j} ^ {M}\\right), \\tag {4}", + "image_path": "8d81f9098527f40d4139c256fc7eef69af4b43320b8e0439e93d16d4464bb374.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "spans": [ + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "type": "inline_equation", + "content": "\\mathbf{s}_i^{\\prime}" + }, + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "type": "text", + "content": " is the word embedding of predicted entity label, and " + }, + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "type": "inline_equation", + "content": "[\\cdot ,\\cdot ]" + }, + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "type": "text", + "content": " denotes the concatenate operation. " + }, + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{i,j}^{\\prime}" + }, + { + "bbox": [ + 304, + 481, + 545, + 529 + ], + "type": "text", + "content": " is the contextually and semantically aware triplet feature, and is derived from the addition of outputs from the last HA layer." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 529, + 547, + 649 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 529, + 547, + 649 + ], + "spans": [ + { + "bbox": [ + 304, + 529, + 547, + 649 + ], + "type": "text", + "content": "Dual-granularity Constraints. Although we explicitly model predicate and triplet cues with " + }, + { + "bbox": [ + 304, + 529, + 547, + 649 + ], + "type": "inline_equation", + "content": "Enc_{prd}" + }, + { + "bbox": [ + 304, + 529, + 547, + 649 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 529, + 547, + 649 + ], + "type": "inline_equation", + "content": "Enc_{pt}" + }, + { + "bbox": [ + 304, + 529, + 547, + 649 + ], + "type": "text", + "content": ", they may degrade beyond our desires with a single predicate cross-entropy loss. To prevent this degradation, we propose the dual-granularity constraints to guide the predicate and triplet cue modeling modules to refine representations in their desired granularities. Specifically, we generate two views of an input relation and impose a predicate category-aware supervised contrastive learning loss on predicate representations to capture the coarse-grained predicate cues as:" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 337, + 656, + 545, + 687 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 337, + 656, + 545, + 687 + ], + "spans": [ + { + "bbox": [ + 337, + 656, + 545, + 687 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {p} = - \\log \\frac {\\exp \\left(\\left\\langle \\mathbf {p} _ {i , j} ^ {\\prime \\prime} , \\mathbf {p} _ {p o s _ {p}} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {p}\\right)}{\\sum_ {b \\in \\mathcal {B} (i , j)} \\exp \\left(\\left\\langle \\mathbf {p} _ {i , j} ^ {\\prime \\prime} , \\mathbf {p} _ {b} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {p}\\right)}, \\tag {5}", + "image_path": "7b339b5f5933d89c03943f793a0373a59fb0f849123f7ab375034f678cc81b64.jpg" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}^{\\prime \\prime}" + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "content": " is obtained by passing " + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}^{\\prime}" + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "content": " through a projection layer comprising two fully connected layers, " + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "inline_equation", + "content": "\\tau_{p}" + }, + { + "bbox": [ + 304, + 689, + 545, + 714 + ], + "type": "text", + "content": " is the tem" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "28372" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "content": "perature, " + }, + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "inline_equation", + "content": "pos_{p}" + }, + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "content": " denotes the subscripts of positive samples belonging to the same predicate category as " + }, + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}^{\\prime \\prime},\\langle \\cdot ,\\cdot \\rangle" + }, + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "content": " is the cosine similarity function, and " + }, + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "inline_equation", + "content": "\\mathcal{B}(i,j)" + }, + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "content": " denotes the subscript set of samples within the same batch." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 120, + 287, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 120, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 46, + 120, + 287, + 156 + ], + "type": "text", + "content": "Similarly, a triplet category-aware supervised contrastive learning loss is applied on triplet representations, aiming at capturing the fine-grained triplet cues as:" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 82, + 163, + 287, + 194 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 82, + 163, + 287, + 194 + ], + "spans": [ + { + "bbox": [ + 82, + 163, + 287, + 194 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {t} = - \\log \\frac {\\exp \\left(\\left\\langle \\mathbf {t} _ {i , j} ^ {\\prime \\prime} , \\mathbf {t} _ {p o s _ {t}} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {t}\\right)}{\\sum_ {b \\in \\mathcal {B} (i , j)} \\exp \\left(\\left\\langle \\mathbf {t} _ {i , j} ^ {\\prime \\prime} , \\mathbf {t} _ {b} ^ {\\prime \\prime} \\right\\rangle / \\tau_ {t}\\right)}, \\tag {6}", + "image_path": "0c3cc8c62d6bd8ef4fb1f280875cd2e655a802e568fc7212377a6617d9ea4890.jpg" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "spans": [ + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "inline_equation", + "content": "\\tau_{t}" + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "content": " is the temperature, " + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "inline_equation", + "content": "pos_{t}" + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "content": " denotes subscripts of positive samples from the same triplet category as " + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{i,j}^{\\prime \\prime}" + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{i,j}^{\\prime \\prime}" + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "content": " is obtained by passing " + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{i,j}^{\\prime}" + }, + { + "bbox": [ + 46, + 201, + 287, + 238 + ], + "type": "text", + "content": " through a projection layer." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 238, + 287, + 308 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 238, + 287, + 308 + ], + "spans": [ + { + "bbox": [ + 47, + 238, + 287, + 308 + ], + "type": "text", + "content": "Scene Graph Prediction. For each relationship proposal, our predicate classifier utilizes two fully connected layers to integrate the coarse-grained and fine-grained cues, i.e. " + }, + { + "bbox": [ + 47, + 238, + 287, + 308 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i,j}^{\\prime}" + }, + { + "bbox": [ + 47, + 238, + 287, + 308 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 238, + 287, + 308 + ], + "type": "inline_equation", + "content": "\\mathbf{t}_{i,j}^{\\prime}" + }, + { + "bbox": [ + 47, + 238, + 287, + 308 + ], + "type": "text", + "content": ", to obtain the final relation label prediction. For each entity, we also introduce a fully connected layer with softmax function to get its refined label prediction." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 309, + 287, + 333 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 309, + 287, + 333 + ], + "spans": [ + { + "bbox": [ + 47, + 309, + 287, + 333 + ], + "type": "text", + "content": "Training Loss. During the training in the first stage of DRM, the overall loss function " + }, + { + "bbox": [ + 47, + 309, + 287, + 333 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 47, + 309, + 287, + 333 + ], + "type": "text", + "content": " is defined as:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 93, + 342, + 287, + 357 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 93, + 342, + 287, + 357 + ], + "spans": [ + { + "bbox": [ + 93, + 342, + 287, + 357 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\lambda_ {e} \\mathcal {L} _ {e} + \\lambda_ {r} \\mathcal {L} _ {r} + \\lambda_ {p} \\mathcal {L} _ {p} + \\lambda_ {t} \\mathcal {L} _ {t}, \\tag {7}", + "image_path": "369b4fb5ec53232d9d0baa565a63949ee76f11499f9d4a7eea23e64957f7688c.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "spans": [ + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_e" + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_r" + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "text", + "content": " are cross-entropy losses of entities and relationships respectively. " + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "inline_equation", + "content": "\\lambda_e, \\lambda_r, \\lambda_p," + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "inline_equation", + "content": "\\lambda_t" + }, + { + "bbox": [ + 46, + 365, + 287, + 401 + ], + "type": "text", + "content": " are pre-defined weight hyper-parameters for corresponding loss terms." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 407, + 248, + 421 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 407, + 248, + 421 + ], + "spans": [ + { + "bbox": [ + 47, + 407, + 248, + 421 + ], + "type": "text", + "content": "3.3. Dual-granularity Knowledge Transfer" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 426, + 287, + 569 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 426, + 287, + 569 + ], + "spans": [ + { + "bbox": [ + 46, + 426, + 287, + 569 + ], + "type": "text", + "content": "The SGG task typically suffers from the long-tail distribution problem. This problem primarily originates from the tail predicate classes, which possesses limited types and quantities of triplets. The head predicate classes contain a relatively larger number of samples and an abundance of triplet types. Thus to alleviate the long-tail problem, we propose the Dual-granularity Knowledge Transfer (DKT) strategy to transfer knowledge in predicate and triplet feature spaces from head predicate class to the tail one. DKT generates samples belonging to the tail predicates with their associated predicate and triplet features, thereby enriching and diversifying the patterns of tail predicates." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": "Specifically, DKT first calculates the distributions of predicate and triplet features. We assume that the distribution of each category " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\Omega_c" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": " follows a multidimensional Gaussian distribution. Formally, it can be expressed as " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\{\\Omega_c = \\mathcal{N}(\\pmb{\\mu}_c, \\pmb{\\sigma}_c) | c \\in \\mathcal{C}\\}" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{\\mu}_c" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{\\sigma}_c" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": " denote the mean and covariance of " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\Omega_c" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": " denotes the predicate or triplet category. After the first-stage pre-training of DRM network, we freeze the proposal network, entity encoder, and the predicate and triplet cue modeling modules. Subsequently, the compact predicate and triplet features, i.e. " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{p}'" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{t}'" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": ", are extracted to calculate the predicate and triplet feature distributions, respectively. The mean, denoted as " + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "inline_equation", + "content": "\\pmb{\\mu}_c" + }, + { + "bbox": [ + 46, + 570, + 287, + 713 + ], + "type": "text", + "content": ", is calculated" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "spans": [ + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": "as " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "\\pmb{\\mu}_{c} = \\frac{1}{N_{c}}\\sum_{k}^{N_{c}}\\mathbf{x}_{k}^{c}" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": ". The covariance, symbolized as " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "\\pmb{\\sigma}_{c}" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": ", is calculated as " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "\\pmb{\\sigma}_{c} = \\frac{1}{N_{c} - 1}\\sum_{k}^{N_{c}}(\\mathbf{x}_{k}^{c} - \\pmb{\\mu}_{c})(\\mathbf{x}_{k}^{c} - \\pmb{\\mu}_{c})^{T}" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": ". Here, " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_i^c" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": " denotes the feature of category " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "N_{c}" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": " is the number of " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "\\mathbf{x}_k^c" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": ". The feature " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": " can be either " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "\\mathbf{p}'" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": " or " + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "inline_equation", + "content": "\\mathbf{t}'" + }, + { + "bbox": [ + 304, + 71, + 545, + 123 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "spans": [ + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "text", + "content": "We then transfer knowledge of feature distributions of head predicate classes to the tail ones. Specifically, we arrange the predicate classes in descending order based on their sample numbers, choosing half of the predicate classes as head predicates and the remaining ones as tail predicates. We further select triplets that appear more than certain times in the head predicates to be the head triplets (we use 64 times as the threshold in this paper), and those in the tail predicates to be the tail triplets. For each tail category " + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "inline_equation", + "content": "i \\in \\mathcal{C}" + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "text", + "content": " we compute the euclidean distance " + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "inline_equation", + "content": "d_{i,j}" + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "text", + "content": " between its center " + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "inline_equation", + "content": "\\pmb{\\mu}_i" + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "text", + "content": " and the center " + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "inline_equation", + "content": "\\pmb{\\mu}_j" + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "text", + "content": " of head category " + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "inline_equation", + "content": "j \\in \\mathcal{C}" + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "text", + "content": ". The closer the centers of two categories are to each other in either predicate or triplet space, the more similar they are, which also increases the likelihood of knowledge sharing between them. Based on " + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "inline_equation", + "content": "d_{i,j}" + }, + { + "bbox": [ + 304, + 123, + 546, + 303 + ], + "type": "text", + "content": ", we achieve the knowledge transfer as:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 351, + 310, + 545, + 340 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 351, + 310, + 545, + 340 + ], + "spans": [ + { + "bbox": [ + 351, + 310, + 545, + 340 + ], + "type": "interline_equation", + "content": "\\boldsymbol {\\sigma} _ {i} ^ {\\prime} = \\frac {N _ {i}}{Q _ {i}} \\boldsymbol {\\sigma} _ {i} + \\left(1 - \\frac {N _ {i}}{Q _ {i}}\\right) \\sum_ {j} \\alpha_ {i, j} \\boldsymbol {\\sigma} _ {j}, \\tag {8}", + "image_path": "561dc42868ff922377edd7ba699f082e237298edcd6b88147dde0dc0ecbbc9a0.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "spans": [ + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "inline_equation", + "content": "\\alpha_{i,j}" + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "text", + "content": " denotes the softmax normalized form of " + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "inline_equation", + "content": "d_{i,j}" + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "inline_equation", + "content": "Q_{i}" + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "text", + "content": " denotes the desired number of predicate/triplet instances of tail class " + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 348, + 545, + 407 + ], + "type": "text", + "content": " and it is identical for every predicates in the tail. It suggests that the tail category with fewer samples requires more knowledge from the head for calibration." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 408, + 545, + 444 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 408, + 545, + 444 + ], + "spans": [ + { + "bbox": [ + 304, + 408, + 545, + 444 + ], + "type": "text", + "content": "After dual-granularity knowledge transfer, we generate synthetic samples in tail predicate using corresponding predicate and triplet features from calibrated distributions:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 369, + 452, + 545, + 466 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 369, + 452, + 545, + 466 + ], + "spans": [ + { + "bbox": [ + 369, + 452, + 545, + 466 + ], + "type": "interline_equation", + "content": "\\{\\hat {\\boldsymbol {x}} | \\hat {\\boldsymbol {x}} \\sim \\Omega_ {c} ^ {\\prime} = \\mathcal {N} \\left(\\boldsymbol {\\mu} _ {c}, \\boldsymbol {\\sigma} _ {c} ^ {\\prime}\\right) \\}. \\tag {9}", + "image_path": "70bb30dc0d9c410e7104d30b559fe5d7653d85bd00982c92b9c856d7d2d2030d.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 473, + 545, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 545, + 545 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 545, + 545 + ], + "type": "text", + "content": "Finally, we under-sample head predicates to form a balanced dataset and input the real instances together with synthetic ones into the relation classifier for fine-tuning. Benefiting from the dual-granularity knowledge transfer, the patterns of tail predicates and their associate triplets can be enriched, thus alleviating the long-tail problem." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 555, + 388, + 569 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 555, + 388, + 569 + ], + "spans": [ + { + "bbox": [ + 306, + 555, + 388, + 569 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 575, + 432, + 588 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 575, + 432, + 588 + ], + "spans": [ + { + "bbox": [ + 306, + 575, + 432, + 588 + ], + "type": "text", + "content": "4.1. Experimental Settings" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": "Datasets. We evaluate our method on three commonly used SGG datasets, namely Visual Genome [14], Open Image [13], and GQA [10]. For the Visual Genome dataset, we adopt the VG150 split following previous approaches [23, 29, 37, 43, 49], which contains the most frequent 150 object categories and 50 predicate categories. We use " + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "inline_equation", + "content": "70\\%" + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": " of images for training, " + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "inline_equation", + "content": "30\\%" + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": " images for testing and " + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "inline_equation", + "content": "5\\mathrm{k}" + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": " images from the training set for validation. As for Open Image, we apply the Open Image V6 protocol, which has 301 object categories and 31 predicate categories. It contains" + } + ] + } + ], + "index": 20 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28373" + } + ] + } + ], + "index": 21 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 86, + 70, + 506, + 399 + ], + "blocks": [ + { + "bbox": [ + 86, + 70, + 506, + 399 + ], + "lines": [ + { + "bbox": [ + 86, + 70, + 506, + 399 + ], + "spans": [ + { + "bbox": [ + 86, + 70, + 506, + 399 + ], + "type": "table", + "html": "
ModelsPredClsSGClsSGDet
R@50/100mR@50/100R@50/100mR@50/100R@50/100mR@50/100
IMP [43]CVPR'1761.1 / 63.111.0 / 11.837.5 / 38.56.2 / 6.525.9 / 31.24.2 / 5.3
VTransE [51]CVPR'1765.7 / 67.614.7 / 15.838.6 / 39.48.2 / 8.729.7 / 34.35.0 / 6.1
MOTIFS [49]CVPR'1866.0 / 67.914.6 / 15.839.1 / 39.98.0 / 8.532.1 / 36.95.5 / 6.8
G-RCNN [44]ECCV'1865.4 / 67.216.4 / 17.237.0 / 38.59.0 / 9.529.7 / 32.85.8 / 6.6
VCTREE [37]CVPR'1965.5 / 67.416.7 / 17.940.3 / 41.67.9 / 8.331.9 / 36.06.4 / 7.3
GPS-Net [22]CVPR'2065.2 / 67.115.2 / 16.637.8 / 39.28.5 / 9.131.3 / 35.96.7 / 8.6
RU-Net [24]CVPR'2267.7 / 69.6- / 24.242.4 / 43.3- / 14.632.9 / 37.5- / 10.8
HL-Net [23]CVPR'2267.0 / 68.9- / 22.842.6 / 43.5- / 13.533.7 / 38.1- / 9.2
PE-Net(P) [54]CVPR'2368.2 / 70.123.1 / 25.441.3 / 42.313.1 / 14.832.4 / 36.98.9 / 11.0
VETO [34]ICCV'2364.2 / 66.322.8 / 24.735.7 / 36.911.1 / 11.927.5 / 31.58.1 / 9.5
TDE° [38]CVPR'2046.2 / 51.425.5 / 29.127.7 / 29.913.1 / 14.916.9 / 20.38.2 / 9.8
CogTree° [47]IJCAI'2135.6 / 36.826.4 / 29.021.6 / 22.214.9 / 16.120.0 / 22.110.4 / 11.8
BPL-SA° [9]ICCV'2150.7 / 52.529.7 / 31.730.1 / 31.016.5 / 17.523.0 / 26.913.5 / 15.6
VisualDS° [46]ICCV'21- / -16.1 / 17.5- / -9.3 / 9.9- / -7.0 / 8.3
NICE° [17]CVPR'2255.1 / 57.229.9 / 32.333.1 / 34.016.6 / 17.927.8 / 31.812.2 / 14.4
PPDL° [21]CVPR'2247.2 / 47.632.2 / 33.328.4 / 29.317.5 / 18.221.2 / 23.911.4 / 13.5
GCL° [6]CVPR'2242.7 / 44.436.1 / 38.226.1 / 27.120.8 / 21.818.4 / 22.016.8 / 19.3
IETrans° [50]ECCV'22- / -35.8 / 39.1- / -21.5 / 22.8- / -15.5 / 18.0
INF° [2]CVPR'2351.5 / 55.124.7 / 30.732.2 / 33.814.5 / 17.423.9 / 27.19.4 / 11.7
CFA° [18]ICCV'2354.1 / 56.635.7 / 38.234.9 / 36.117.0 / 18.427.4 / 31.813.2 / 15.5
EICR° [29]ICCV'2355.3 / 57.434.9 / 37.034.5 / 35.420.8 / 21.827.9 / 32.215.5 / 18.2
BGNN [19]CVPR'2159.2 / 61.330.4 / 32.937.4 / 38.514.3 / 16.531.0 / 35.810.7 / 12.6
SHA+GCL [6]CVPR'2235.1 / 37.241.6 / 44.122.8 / 23.923.0 / 24.314.9 / 18.217.9 / 20.9
PE-Net [54]CVPR'2364.9 / 67.231.5 / 33.839.4 / 40.717.8 / 18.930.7 / 35.212.4 / 14.5
SQUAT [12]ICCV'2355.7 / 57.930.9 / 33.433.1 / 34.417.5 / 18.824.5 / 28.914.1 / 16.5
CaCao [48]ICCV'23- / -41.7 / 43.7- / -24.0 / 25.0- / -18.3 / 22.1
DRM w/o DKT70.2 / 72.123.3 / 25.644.3 / 45.213.5 / 14.634.0 / 38.99.0 / 11.2
DRM43.9 / 45.847.1 / 49.627.5 / 28.427.8 / 29.219.0 / 22.920.4 / 24.1
", + "image_path": "b4651264ee2902730820870439328e617a0c2f8dbc02373dfd9f9eb1c736552f.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 56, + 438, + 276, + 573 + ], + "blocks": [ + { + "bbox": [ + 47, + 402, + 545, + 425 + ], + "lines": [ + { + "bbox": [ + 47, + 402, + 545, + 425 + ], + "spans": [ + { + "bbox": [ + 47, + 402, + 545, + 425 + ], + "type": "text", + "content": "Table 1. Comparison results with state-of-the-art SGG methods on the VG150 dataset. \"◇\" denotes the combination of MOTIFS with a model-agnostic unbiased strategy. The best and second best results under each setting are respectively marked in red and underline blue." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 56, + 438, + 276, + 573 + ], + "lines": [ + { + "bbox": [ + 56, + 438, + 276, + 573 + ], + "spans": [ + { + "bbox": [ + 56, + 438, + 276, + 573 + ], + "type": "table", + "html": "
ModelR@50WmAPscorewtd
relphr
MOTIFS [49]CVPR'1871.629.931.638.9
G-RCNN [44]ECCV'1874.533.234.241.8
VCTREE [37]CVPR'1974.134.233.140.2
GPS-Net [22]CVPR'2074.832.934.041.7
BGNN [19]CVPR'2175.033.534.242.1
RU-Net [24]CVPR'2276.935.434.943.5
HL-Net [23]CVPR'2276.535.134.743.2
PE-Net [54]CVPR'2376.536.637.444.9
SQUAT [12]ICCV'2375.834.935.943.5
DRM w/o DKT75.940.541.447.9
", + "image_path": "291852691992eea2eaddfb534555a94dffd2107724e9b4f6329a23f94cd4bff1.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 577, + 287, + 610 + ], + "lines": [ + { + "bbox": [ + 46, + 577, + 287, + 610 + ], + "spans": [ + { + "bbox": [ + 46, + 577, + 287, + 610 + ], + "type": "text", + "content": "Table 2. Comparison results with state-of-the-art SGG methods on Open Image V6. The best and second best results under each metric are respectively marked in red and underline blue." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 626, + 287, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 626, + 287, + 675 + ], + "spans": [ + { + "bbox": [ + 46, + 626, + 287, + 675 + ], + "type": "text", + "content": "126,368, 1,183, and 5,322 images for training, validation, and testing, respectively. For the GQA dataset, we follow previous works [6, 34] and utilize the GQA200 split, which includes 200 object categories and 100 predicate categories." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "content": "Tasks. We adopt three SGG tasks for evaluation: 1) Predicate Classification (Predcls) infers the predicates of entity pairs with ground-truth bounding boxes and cate" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "spans": [ + { + "bbox": [ + 304, + 441, + 545, + 489 + ], + "type": "text", + "content": "gories. 2) Scene Graph Classification (SGCls) aims to predict the triplet categories with ground-truth bounding boxes. 3) Scene Graph Detection (SGDet) detects bounding boxes of entity pairs and infers their predicate categories." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 493, + 546, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 493, + 546, + 613 + ], + "spans": [ + { + "bbox": [ + 304, + 493, + 546, + 613 + ], + "type": "text", + "content": "Evaluation Metrics. We use Recall@K (R@K) and mean Recall@K (mR@K) as evaluation metrics on VG150 and GQA200 datasets, following recent works [6, 34, 54]. R@K tends to prioritize frequent predicates, while mR@K exhibits a preference for less frequent predicates. Results on Open Image dataset are evaluated using Recall@50 (R@50), weighted mean AP of relations (wmAPrel) weighted mean AP of phrase (wmAPphr), and a weighted score of them scorewtd = 0.2 × R@50 + 0.4 × wAPrel + 0.4 × wAPphr, following previous works [19, 23, 52]." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": "Implementation Details. Following previous works [6, 34, 54], we adopt the pre-trained Faster RCNN with ResNeXt-101-RPN in the proposal network to detect entities in the image. GloVe [30] is applied to embed the semantic features. We set the loss weight parameters " + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\lambda_r" + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\lambda_e" + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\lambda_t" + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\lambda_p" + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": " as 3, 0.5, 0.1, and 0.1, respectively. Temperatures " + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\tau_p" + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\tau_t" + }, + { + "bbox": [ + 304, + 617, + 547, + 715 + ], + "type": "text", + "content": " are set as 0.2, and 0.1 considering that the predicate feature space exhibits greater variety than its asso" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "28374" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 81, + 70, + 511, + 216 + ], + "blocks": [ + { + "bbox": [ + 81, + 70, + 511, + 216 + ], + "lines": [ + { + "bbox": [ + 81, + 70, + 511, + 216 + ], + "spans": [ + { + "bbox": [ + 81, + 70, + 511, + 216 + ], + "type": "table", + "html": "
ModelsPredClsSGClsSGDet
R@50/100mR@50/100R@50/100mR@50/100R@50/100mR@50/100
VTransE [51]CVPR'1755.7 / 57.914.0 / 15.033.4 / 34.28.1 / 8.727.2 / 30.75.8 / 6.6
MOTIFS [49]CVPR'1865.3 / 66.816.4 / 17.134.2 / 34.98.2 / 8.628.9 / 33.16.4 / 7.7
VCTREE [37]CVPR'1963.8 / 65.716.6 / 17.434.1 / 34.87.9 / 8.328.3 / 31.96.5 / 7.4
SHA [6]CVPR'2263.3 / 65.219.5 / 21.132.7 / 33.68.5 / 9.025.5 / 29.16.6 / 7.8
VETO [34]ICCV'2364.5 / 66.021.2 / 22.130.4 / 31.58.6 / 9.126.1 / 29.07.0 / 8.1
VTransE+GCL [6]CVPR'2235.5 / 37.430.4 / 32.322.9 / 23.616.6 / 17.415.3 / 18.014.7 / 16.4
MOTIFS+GCL [6]CVPR'2244.5 / 46.236.7 / 38.123.2 / 24.017.3 / 18.118.5 / 21.816.8 / 18.8
VCTREE+GCL [6]CVPR'2244.8 / 46.635.4 / 36.723.7 / 24.517.3 / 18.017.6 / 20.715.6 / 17.8
SHA+GCL [6]CVPR'2242.7 / 44.541.0 / 42.721.4 / 22.220.6 / 21.314.8 / 17.917.8 / 20.1
DRM w/o DKT66.9 / 68.418.1 / 19.036.4 / 37.27.1 / 7.430.6 / 34.66.9 / 8.4
DRM43.2 / 44.441.9 / 43.523.3 / 23.919.9 / 20.718.6 / 21.718.9 / 21.0
", + "image_path": "63c292bb61bb9741f89f8169b1548a83239153ae690d6ff1f7bd0d7a182da1d4.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 50, + 251, + 287, + 367 + ], + "blocks": [ + { + "bbox": [ + 46, + 220, + 546, + 243 + ], + "lines": [ + { + "bbox": [ + 46, + 220, + 546, + 243 + ], + "spans": [ + { + "bbox": [ + 46, + 220, + 546, + 243 + ], + "type": "text", + "content": "Table 3. Comparison results with state-of-the-art SGG methods on the GQA200 dataset. The best and second best results under each setting are respectively marked in red and underline blue." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 251, + 287, + 367 + ], + "lines": [ + { + "bbox": [ + 50, + 251, + 287, + 367 + ], + "spans": [ + { + "bbox": [ + 50, + 251, + 287, + 367 + ], + "type": "table", + "html": "
ModulePredClsSGCls
PTACR@50/100mR@50/100R@50/100
56.5/60.415.5/17.437.5/39.310.1/11.3
✓67.6/69.518.1/19.941.8/42.710.8/11.8
✓67.6/69.820.5/22.542.3/43.212.6/13.6
✓✓69.3/71.320.8/22.842.8/43.812.8/13.9
✓✓✓69.8/71.620.4/22.343.4/44.412.8/13.8
✓✓✓69.8/71.622.0/24.043.4/44.312.3/13.3
✓✓✓69.7/71.521.9/24.343.8/44.812.7/13.9
✓✓✓70.2/72.123.3/25.644.3/45.213.5/14.6
", + "image_path": "2fb9d53967ed89f96a8fe87946cc15463b183338c162f5a1038f653d3e694b59.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 51, + 423, + 284, + 494 + ], + "blocks": [ + { + "bbox": [ + 46, + 372, + 287, + 416 + ], + "lines": [ + { + "bbox": [ + 46, + 372, + 287, + 416 + ], + "spans": [ + { + "bbox": [ + 46, + 372, + 287, + 416 + ], + "type": "text", + "content": "Table 4. Ablation studies on predicate and triplet cues learning. \"P\", \"T\", \"A\", and \"C\" denote the predicate cue modeling module, triplet cue modeling module, augmentation in dual-granularity constraints, and the dual-granularity constraints loss, respectively." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 51, + 423, + 284, + 494 + ], + "lines": [ + { + "bbox": [ + 51, + 423, + 284, + 494 + ], + "spans": [ + { + "bbox": [ + 51, + 423, + 284, + 494 + ], + "type": "table", + "html": "
ModulePredClsSGCls
R@50/100mR@50/100R@50/100mR@50/100
None70.2/72.123.3/25.644.3/45.213.5/14.6
DKT-P42.4/44.245.0/47.326.8/27.826.9/28.1
DKT-T40.4/42.246.1/48.724.3/25.326.4/28.0
DKT43.9/45.847.1/49.627.5/28.427.8/29.2
", + "image_path": "eea2ef689c9ea3d1dab8872625a72d894e88c2349ce54dc991edce27c120d436.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 498, + 287, + 533 + ], + "lines": [ + { + "bbox": [ + 46, + 498, + 287, + 533 + ], + "spans": [ + { + "bbox": [ + 46, + 498, + 287, + 533 + ], + "type": "text", + "content": "Table 5. Ablation studies on dual-granularity knowledge transfer. \"DKT-P\" and \"DKT-T\" denote the predicate knowledge transfer and triplet knowledge transfer." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 540, + 287, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 540, + 287, + 564 + ], + "spans": [ + { + "bbox": [ + 46, + 540, + 287, + 564 + ], + "type": "text", + "content": "ciated triplet one. We optimize our method via SGD, using an initial leaning late of " + }, + { + "bbox": [ + 46, + 540, + 287, + 564 + ], + "type": "inline_equation", + "content": "10^{-4}" + }, + { + "bbox": [ + 46, + 540, + 287, + 564 + ], + "type": "text", + "content": " with a batch size of 16." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 574, + 270, + 588 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 574, + 270, + 588 + ], + "spans": [ + { + "bbox": [ + 46, + 574, + 270, + 588 + ], + "type": "text", + "content": "4.2. Comparison with State-of-the-art Methods" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 594, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 287, + 715 + ], + "type": "text", + "content": "To evaluate the performance our model, we compare it with several state-of-the-art SGG approaches on Visual Genome, Open Image, and GQA datasets. The comparison methods include IMP [43], MOTIFS [49], VCTREE [37], RU-Net [24], HL-Net [23], PE-Net [54], and VETO [34], which focus on the prediction of every relationship in an image. We also compare with methods for unbiased scene graph generation, including TDE [38], CogTree [47], NICE [17], INF [2], CFA [18], EICR [29], BGNN [19], SHA+GCL [6], SQUAT [12], and CaCao[48]. In addition, we compare" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 253, + 545, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 253, + 545, + 277 + ], + "spans": [ + { + "bbox": [ + 304, + 253, + 545, + 277 + ], + "type": "text", + "content": "our method with VETO+MEET [34] in the setting without graph constraint in the Supplementary Material." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "spans": [ + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "text", + "content": "Visual Genome. Table 1 shows the comparison results of different approaches on VG150. From these results, we have the following observations: 1) our proposed method significantly outperforms all baselines on all three tasks. More specifically, our DRM w/o DKT outperforms the recent PE-Net [54] by " + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "inline_equation", + "content": "2.0\\%" + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "inline_equation", + "content": "2.9\\%" + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "inline_equation", + "content": "2.0\\%" + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "text", + "content": " at R@100 on PredCls, SGCls, and SGDet, respectively. Unlike approaches such as MOTIFS [49] and VCTREE [37], which only utilize a predicate classifier to predict predicates and overlook the triplet cues, our method leverages coarse-grained predicate cues and fine-grained triplet cues for relation recognition and thus achieves superior results. 2) Our DRM method also has considerably better performance compared to the baseline unbiased SGG methods. Notably, based on the proposed DKT strategy in DRM, our method outperforms the recent multi-expert method SHA+GCL [6] by " + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "inline_equation", + "content": "5.5\\%" + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "inline_equation", + "content": "4.9\\%" + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "inline_equation", + "content": "3.2\\%" + }, + { + "bbox": [ + 304, + 279, + 546, + 530 + ], + "type": "text", + "content": " at mR@100 on three tasks. This demonstrates that transferring knowledge from head predicates to tail predicates at dual granularities and enriching the patterns in tail predicates can effectively mitigate the long-tail problem." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 532, + 545, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 532, + 545, + 675 + ], + "spans": [ + { + "bbox": [ + 304, + 532, + 545, + 675 + ], + "type": "text", + "content": "Open Image. Compared to the VG dataset, Open Image provides a relatively complete labeling of relationships in the images. Consequently, the model's capability to generate scene graphs can be evaluated at a fine-grained level utilizing the AP metric. To evaluate the generalizability of our method across various datasets, we conduct experiments on Open Image V6. Since the metrics in Open Image V6 tend to prioritize frequent predicates, we just compare our DRM w/o DKT with state-of-the-art approaches. The comparison results shown in Table 2 indicate that our DRM w/o DKT significantly outperforms the recent approaches, i.e., SQUAT [12] and PE-Net [54]." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "content": "GQA. Compared to Visual Genome and Open Image datasets, GQA200 contains a broader range of predicates. So we further confirm the generality of our model on the" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "28375" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 72, + 145, + 162 + ], + "blocks": [ + { + "bbox": [ + 51, + 72, + 145, + 162 + ], + "lines": [ + { + "bbox": [ + 51, + 72, + 145, + 162 + ], + "spans": [ + { + "bbox": [ + 51, + 72, + 145, + 162 + ], + "type": "image", + "image_path": "fb1f74fcc34a696ae95cc298fccddb16b444d3cae279c05261d9caa319d51904.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 64, + 165, + 131, + 175 + ], + "lines": [ + { + "bbox": [ + 64, + 165, + 131, + 175 + ], + "spans": [ + { + "bbox": [ + 64, + 165, + 131, + 175 + ], + "type": "text", + "content": "(a) MOTIFS, Triplet" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 149, + 72, + 243, + 163 + ], + "blocks": [ + { + "bbox": [ + 149, + 72, + 243, + 163 + ], + "lines": [ + { + "bbox": [ + 149, + 72, + 243, + 163 + ], + "spans": [ + { + "bbox": [ + 149, + 72, + 243, + 163 + ], + "type": "image", + "image_path": "e193cbcac6da00784390bbd73a2c352b3d1b4467504e57313b110760c508ca00.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 153, + 165, + 241, + 175 + ], + "lines": [ + { + "bbox": [ + 153, + 165, + 241, + 175 + ], + "spans": [ + { + "bbox": [ + 153, + 165, + 241, + 175 + ], + "type": "text", + "content": "(b) DRM w/o DKT, Triplet" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 249, + 72, + 343, + 163 + ], + "blocks": [ + { + "bbox": [ + 249, + 72, + 343, + 163 + ], + "lines": [ + { + "bbox": [ + 249, + 72, + 343, + 163 + ], + "spans": [ + { + "bbox": [ + 249, + 72, + 343, + 163 + ], + "type": "image", + "image_path": "2d5f2a6106667f987a0d8c943d5a00e2b36a7e8484b91f7c15b665f4923a67b5.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 268, + 165, + 324, + 175 + ], + "lines": [ + { + "bbox": [ + 268, + 165, + 324, + 175 + ], + "spans": [ + { + "bbox": [ + 268, + 165, + 324, + 175 + ], + "type": "text", + "content": "(c) DRM, Triplet" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 180, + 545, + 203 + ], + "lines": [ + { + "bbox": [ + 46, + 180, + 545, + 203 + ], + "spans": [ + { + "bbox": [ + 46, + 180, + 545, + 203 + ], + "type": "text", + "content": "Figure 4. The comparison of t-SNE visualization results on predicate and triplet feature distributions within the VG dataset. \"MOTIFS, Triplet\" and \"DRM w/o DKT, Triplet\" visualize the same set of samples, where each unique color represents a different type of triplet." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 348, + 72, + 441, + 163 + ], + "blocks": [ + { + "bbox": [ + 348, + 72, + 441, + 163 + ], + "lines": [ + { + "bbox": [ + 348, + 72, + 441, + 163 + ], + "spans": [ + { + "bbox": [ + 348, + 72, + 441, + 163 + ], + "type": "image", + "image_path": "edc6eaebf09caba9c3d91b03e24084e28aff9f0c288ab809fe758a82e0ec9876.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 347, + 165, + 443, + 175 + ], + "lines": [ + { + "bbox": [ + 347, + 165, + 443, + 175 + ], + "spans": [ + { + "bbox": [ + 347, + 165, + 443, + 175 + ], + "type": "text", + "content": "(d) DRM w/o DKT, Predicate" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 447, + 72, + 540, + 163 + ], + "blocks": [ + { + "bbox": [ + 447, + 72, + 540, + 163 + ], + "lines": [ + { + "bbox": [ + 447, + 72, + 540, + 163 + ], + "spans": [ + { + "bbox": [ + 447, + 72, + 540, + 163 + ], + "type": "image", + "image_path": "fae206042c6cdfaa0904f7c334b247a4ff230c879b025fd7319b09f367c557d7.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 461, + 165, + 526, + 175 + ], + "lines": [ + { + "bbox": [ + 461, + 165, + 526, + 175 + ], + "spans": [ + { + "bbox": [ + 461, + 165, + 526, + 175 + ], + "type": "text", + "content": "(e) DRM, Predicate" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 213, + 287, + 297 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 213, + 287, + 297 + ], + "spans": [ + { + "bbox": [ + 46, + 213, + 287, + 297 + ], + "type": "text", + "content": "GQA200 dataset. As shown in Table 3, our method significantly outperforms the recent VETO [34] at R@100 on three tasks. When equipped with DKT, our DRM outperforms " + }, + { + "bbox": [ + 46, + 213, + 287, + 297 + ], + "type": "inline_equation", + "content": "\\mathrm{SHA + GCL}" + }, + { + "bbox": [ + 46, + 213, + 287, + 297 + ], + "type": "text", + "content": " [6] by an average of " + }, + { + "bbox": [ + 46, + 213, + 287, + 297 + ], + "type": "inline_equation", + "content": "0.4\\%" + }, + { + "bbox": [ + 46, + 213, + 287, + 297 + ], + "type": "text", + "content": " at mR@100 across three tasks. These results demonstrate the consistent effectiveness of our method in handling relation recognition under different data distributions." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 304, + 141, + 317 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 304, + 141, + 317 + ], + "spans": [ + { + "bbox": [ + 47, + 304, + 141, + 317 + ], + "type": "text", + "content": "4.3. Ablation Study" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 324, + 287, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 324, + 287, + 348 + ], + "spans": [ + { + "bbox": [ + 46, + 324, + 287, + 348 + ], + "type": "text", + "content": "To verify the contributions of different components in our DRM network, we conduct the following ablation studies." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 348, + 287, + 516 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 348, + 287, + 516 + ], + "spans": [ + { + "bbox": [ + 46, + 348, + 287, + 516 + ], + "type": "text", + "content": "Predicate and Triplet Cue Learning. We first perform an ablation study on the leverage of predicate and triplet cues. As shown in Table 4, we incrementally incorporate one component into the baseline to verify their effectiveness. Compared with the application of predicate or triplet cue modeling in isolation, leveraging both predicate and triplet together improves the performance. Our dual-granularity constraints include a constraint loss component and a two-view augmentation component to generate positive pairs in each training batch. The constraints compel predicate and triplet cue modeling to concentrate on corresponding granularities. We observe from the results that both the loss component and augmentation component contribute to the performance improvements." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "spans": [ + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "text", + "content": "Dual-Granularity Knowledge Transfer. As shown in Table 5, we conduct an ablation study for the DKT. We observe an obvious performance gain on " + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "inline_equation", + "content": "\\mathrm{mR}@\\mathrm{K}" + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "text", + "content": " when transferring knowledge at either predicate or triplet granularity. The " + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "inline_equation", + "content": "\\mathrm{mR}@\\mathrm{K}" + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "text", + "content": " is further improved when predicate and triplet granularities are simultaneously employed. In comparison to the scenario without the application of DKT, we observe a performance decrease in " + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "inline_equation", + "content": "\\mathrm{R}@\\mathrm{K}" + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "text", + "content": " when using it. This is attributed to the capability of our model to reasonably classify ambiguous head predicates, e.g. \"on\", into more specific tail predicates, e.g. \"sitting on\". Consequently, decreases at the " + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "inline_equation", + "content": "\\mathrm{R}@\\mathrm{K}" + }, + { + "bbox": [ + 46, + 517, + 287, + 661 + ], + "type": "text", + "content": " for these head predicates are inevitable [17, 54]." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 47, + 670, + 174, + 683 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 670, + 174, + 683 + ], + "spans": [ + { + "bbox": [ + 47, + 670, + 174, + 683 + ], + "type": "text", + "content": "4.4. Visualization Analysis" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": "To illustrate the ability our method to learn triplet cues and impact of the DKT strategy, we visualize the predicate and" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 213, + 547, + 382 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 213, + 547, + 382 + ], + "spans": [ + { + "bbox": [ + 304, + 213, + 547, + 382 + ], + "type": "text", + "content": "triplet feature distributions using t-SNE. The visualization results are shown in Figure 4. Comparing Figure 4a with Figure 4b, we observe that our DRM generates compact and distinguishable triplet representations, while MOTIFS [49] appears to overlook the triplet cues, leading to a challenge in distinguishing various triplet types. By comparing Figure 4b with Figure 4c, it can be observed that DKT can generate synthetic samples with diverse distributions for the tail triplets. Figures 4d and 4e demonstrate that DKT also transfers the knowledge of head predicates to tail predicates, increasing the tail predicate patterns. The visualization of predicate and triplet feature distributions demonstrates the interpretability of our method in leveraging predicate and triplet cues and transferring the dual-granularity knowledge." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 398, + 378, + 410 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 398, + 378, + 410 + ], + "spans": [ + { + "bbox": [ + 306, + 398, + 378, + 410 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 420, + 545, + 576 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 420, + 545, + 576 + ], + "spans": [ + { + "bbox": [ + 304, + 420, + 545, + 576 + ], + "type": "text", + "content": "In this paper, we propose a Dual-granularity Relation Modeling (DRM) network to address two issues in SGG, i.e. the diverse visual appearance within the same predicate and the lack of patterns in tail predicates. Our DRM network captures the coarse-grained predicate cues shared across different subject-object pairs and fine-grained triplet cues under specific subject-object pairs for relationship recognition. The Dual-granularity Knowledge Transfer (DKT) is further proposed to transfer the variation from head predicates to the tail to enrich the tail predicate patterns. Quantitative and qualitative experiments demonstrate that our method establishes new state-of-the-art performances on Visual Genome, Open Image and GQA datasets." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 593, + 404, + 606 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 593, + 404, + 606 + ], + "spans": [ + { + "bbox": [ + 306, + 593, + 404, + 606 + ], + "type": "text", + "content": "Acknowledgement" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 613, + 545, + 703 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 613, + 545, + 703 + ], + "spans": [ + { + "bbox": [ + 304, + 613, + 545, + 703 + ], + "type": "text", + "content": "This work was supported in part by the National Key R&D Program of China under Grant 2022ZD0161901, the National Natural Science Foundation of China under Grants 62276018 and U20B2069, the Beijing Nova Program under Grant 20230484297, the Fundamental Research Funds for the Central Universities, and Research Program of State Key Laboratory of Complex & Critical Software Environment." + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "28376" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Hedi Ben-Younes, Remi Cadene, Nicolas Thome, and Matthieu Cord. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 22783-22792, 2023. 1, 2, 6, 7, 8" + } + ] + } + ], + "index": 5 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "28379" + } + ] + } + ], + "index": 7 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_content_list.json b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..fe5fc6f8ae069549f935e5cc4a702dbeb20f8135 --- /dev/null +++ b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_content_list.json @@ -0,0 +1,1283 @@ +[ + { + "type": "text", + "text": "Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification", + "text_level": 1, + "bbox": [ + 225, + 130, + 746, + 176 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Sravanti Addepalli * Ashish Ramayee Asokan * Lakshay Sharma R. Venkatesh Babu Vision and AI Lab, Indian Institute of Science, Bangalore", + "bbox": [ + 127, + 203, + 841, + 239 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 273, + 313, + 289 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Vision-Language Models (VLMs) such as CLIP are trained on large amounts of image-text pairs, resulting in remarkable generalization across several data distributions. However, in several cases, their expensive training and data collection/curation costs do not justify the end application. This motivates a vendor-client paradigm, where a vendor trains a large-scale VLM and grants only input-output access to clients on a pay-per-query basis in a black-box setting. The client aims to minimize inference cost by distilling the VLM to a student model using the limited available task-specific data, and further deploying this student model in the downstream application. While naive distillation largely improves the In-Domain (ID) accuracy of the student, it fails to transfer the superior out-of-distribution (OOD) generalization of the VLM teacher using the limited available labeled images. To mitigate this, we propose Vision-Language to Vision - Align, Distill, Predict (VL2V-ADiP), which first aligns the vision and language modalities of the teacher model with the vision modality of a pre-trained student model, and further distills the aligned VLM representations to the student. This maximally retains the pre-trained features of the student, while also incorporating the rich representations of the VLM image encoder and the superior generalization of the text embeddings. The proposed approach achieves state-of-the-art results on the standard Domain Generalization benchmarks in a black-box teacher setting as well as a white-box setting where the weights of the VLM are accessible. Project page: http://val.cds.iisc.ac.in/VL2V-ADiP/", + "bbox": [ + 76, + 305, + 473, + 743 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 753, + 209, + 768 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "While the initial success of Deep Learning was predominantly driven by training specialized models for each task or dataset [26, 29], recent research on foundation models [24, 34, 47, 65] eliminates the need for this by training generic models jointly over several modalities using large-", + "bbox": [ + 75, + 777, + 468, + 854 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/139f047a9cc70387e0c8325960c851b3c4c5d6493ca2e3dbd0fd6766c3d67f88.jpg", + "image_caption": [ + "Figure 1. Schematic diagram showing class and domain distributions in the shared text/ image embedding space of a VLM: VLMs learn highly specialized image representations that are not domain invariant. Thus, a linear classifier (red decision boundary) that is trained over the vision encoder using limited training data cannot generalize well to the target domain (shown in purple). On the other hand, generic text embeddings such as \"A photo of a class\" represent the core concept of a class by virtue of their training method and vast training data. Thus, they generalize effectively across domains, and a zero-shot classifier (green decision boundary) aligns better with the true distribution of classes." + ], + "image_footnote": [], + "bbox": [ + 519, + 271, + 870, + 513 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "scale data. The use of both image and language modalities in large-scale Vision-Language Models (VLMs) enables their use in several applications including zero-shot classification, where the embedding of an image is compared with text embeddings for \"a photo of a {class}\" corresponding to every class during inference and the class with highest similarity is predicted. For example, the LiT (private) model [65] has been trained on 4 billion image-text pairs scraped from the web, and it achieves $85.2\\%$ zero-shot accuracy on ImageNet. VLMs also demonstrate extraordinary performance across several distributions, owing to the vast diversity of distributions seen during their training [47].", + "bbox": [ + 496, + 686, + 893, + 868 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "The remarkable OOD generalization of VLMs makes them suitable for use in several applications, either directly", + "bbox": [ + 498, + 869, + 893, + 901 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal Contribution.", + "bbox": [ + 94, + 863, + 209, + 875 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "Correspondence to Sravanti Addepalli , Ashish Ramayee Asokan ", + "bbox": [ + 76, + 876, + 468, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "23922", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "or after finetuning on the downstream target dataset. Although several open-sourced models such as CLIP [47] are easily accessible, they may not be suitable for use in specialized applications. For example, the training data may have to be curated to reduce biases in the model or to ensure data privacy. It may also be important to ensure that the web-crawled data is clean for adoption in critical applications such as autonomous driving, to avoid data-poisoning attacks [4, 7]. Further, general-purpose models cannot be used in specialized applications such as medical diagnosis, where a VLM trained on data containing expert comments can be invaluable. This motivates the need for training highly specialized VLMs, which can be expensive due to the high costs associated with data collection/ curation and training.", + "bbox": [ + 75, + 90, + 472, + 303 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "A given downstream application may not always justify the cost associated with training such large-scale models. However, since these VLMs are generic and applicable to several downstream applications, one vendor could train such a model, and make it available to several clients in a black-box setting on a pay-per-query basis. In this case, the client can minimize their inference time costs by distilling the VLM to a student model using the limited available data specific to the downstream task, and deploying the distilled model rather than the VLM. Since the key motivation of using VLMs is their generalization to several domains, reliable OOD performance of the distilled model is crucial.", + "bbox": [ + 75, + 305, + 472, + 487 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this work, we consider the problem of distilling a multimodal Vision-Language model to a unimodal Vision model using limited task-specific downstream data, targeted toward better OOD performance with respect to the training domains used for distillation. While standard distillation of VLMs would require training data comprising of images and their associated text, in this case, the training data consists of only labeled images, similar to a classification task. Moreover, since the superior generalization abilities of VLMs are a result of the large-scale data ( $\\sim 400$ million in the case of CLIP) used for their training, it is challenging to transfer these generalization abilities using a limited dataset comprising around 10,000 (0.01 million) images [16, 30, 60]. Lastly, since the VLM is considered to be a black box, the image encoder's weights cannot be used as initialization to the vision model for further fine-tuning. However, since the downstream task-specific data is limited and is insufficient to train models from scratch, we assume that the student is initialized with weights from a model pretrained on a publicly available dataset such as ImageNet-1K [26], as is common in a domain-generalization setting [19].", + "bbox": [ + 75, + 489, + 472, + 808 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "While knowledge distillation [20] using the labeled task-specific images improves the In-Domain accuracy on the downstream task, the improvement in OOD accuracy is marginal due to the limited size of the dataset. To address this, we first analyze the robustness of the text and image embeddings from the VLM and highlight the impor", + "bbox": [ + 75, + 810, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "tance of text embeddings for better OOD generalization (see Fig.1). Further, we propose VL2V-ADiP: Vision-Language to Vision - Align, Distill, Predict, to firstly align the features of the pre-trained student model with the text and image modalities of the VLM teacher, and further fine-tune the student backbone in a distillation framework. This improves the robustness of the student, while also aligning the student embeddings to the VLM's text embeddings corresponding to the respective class, thereby making the latter suitable for use as a classifier in the student without the need for further training. We summarize our contributions below:", + "bbox": [ + 496, + 90, + 893, + 257 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We investigate the robustness of image and text embeddings of VLMs, and highlight the importance of the text embeddings for better OOD generalization.", + "- To demonstrate the superior generalization of text embeddings, we propose VL2V-SD - a self-distillation approach, that improves the OOD generalization of the VLM's pre-trained vision encoder using supervision from its own text encoder in a white-box VLM setting.", + "- We further propose VL2V-ADiP - a black-box distillation approach that effectively combines the features of a pretrained vision model with the text and vision encoders of a VLM teacher for better OOD generalization.", + "- We demonstrate state-of-the-art results on standard Domain Generalization benchmark datasets in both white-box and black-box settings of the VLM teacher." + ], + "bbox": [ + 500, + 258, + 890, + 484 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Works", + "text_level": 1, + "bbox": [ + 500, + 497, + 650, + 513 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Vision-Language Models (VLMs): VLMs are trained on large-scale datasets of image-text pairs crawled from the web [10, 53, 58]. Contrastive pre-training methods [24, 34, 47, 65] maximize the similarity between the embeddings of matching image-text pairs. More recent efforts focus on scaling up image-text pre-training to larger datasets [34], better supervision with unimodal and multimodal data [56], data-efficient pre-training [36], and fine-tuning VLMs for downstream tasks [18, 28, 63]. Another line of work focuses on leveraging CLIP [47] to improve the OOD generalization in image classification [40, 55].", + "bbox": [ + 496, + 522, + 893, + 688 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Domain Generalization (DG): Prior works learn domain invariant representations by using augmentations [41, 42, 50], feature alignment across domains [17, 33, 35, 57], and disentangling domain-specific and domain-invariant features [11, 38, 45]. Gulrajani et.al [19] demonstrate that a well-tuned ERM model is comparable to several past DG algorithms [1, 5, 21, 27, 31, 32, 52, 62, 66]. SWAD [8] is a generic strategy that performs weight-averaging across different model snapshots in the optimal basin during training. MIRO [9] proposes Mutual Information (MI) regularization to maximally retain the pre-trained model's representations. SAGM [61] aligns gradient directions between the $\\epsilon$ -perturbed loss and the empirical risk. We demonstrate performance gains when compared to the existing DG methods", + "bbox": [ + 496, + 688, + 895, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "23923", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "table", + "img_path": "images/4d6650973924a2f144e405c068ee814a8ac39f5f8facb943cd2c420c746597b6.jpg", + "table_caption": [ + "Table 1. CLIP on DG datasets: Performance $(\\%)$ of CLIP ViT-B/16 model on using different embeddings in the classifier head for computing similarity w.r.t. the test image during inference (T.E.: Text Embedding, I.E.: Image Embedding)." + ], + "table_footnote": [], + "table_body": "
Embedding used for computing similarityOHTIVLCSPACSAvg.
E1: Text embedding for "A photo of a {class}"82.3634.1982.0896.1073.68
E2: Avg. text embedding for "A {domain} of a {class}" across all train domains83.7035.5582.2896.2174.44
E3: Avg. image embedding of each class (Source)71.3733.9948.2179.0358.15
E4: Avg. image embedding of each class (Target)78.2138.6969.3193.0869.82
E5: Avg. image embedding of 10 images per class closest to test image (Source)76.4239.3376.4292.1571.08
E6: Avg. image embedding of 10 images per class closest to test image (Target)84.8685.3887.8898.3289.11
", + "bbox": [ + 76, + 148, + 470, + 303 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "in both white-box and black-box settings of the VLM. More recently, several methods perform diverse training of multiple models, followed by weight-averaging to improve OOD generalization [2, 23, 48, 49]. However, they incur the enormous expense of training several diverse models. We thus restrict our comparison to DART [23], where the number of models trained is lower than the others. Another direction has been the generation of better prompts for improved generalization of VLMs [39, 54, 67]. These methods can be integrated with the proposed approach.", + "bbox": [ + 75, + 324, + 468, + 474 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Knowledge Distillation (KD): Knowledge distillation aims to transfer knowledge from a powerful teacher model to a compact student model. Output-distillation [20] uses the teacher's softmax outputs as guidance for the student. Feature-distillation methods [12-14, 37, 43, 51] use the teacher's intermediate representations as guidance since they contain richer information. The proposed method operates in the black box distillation setup that allows only input-output access to the teacher network and restricts access to intermediate features. We thus compare the proposed black-box approach only with methods that do not access intermediate features [13, 20, 22].", + "bbox": [ + 75, + 478, + 468, + 659 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Notations", + "text_level": 1, + "bbox": [ + 76, + 675, + 183, + 691 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We consider the problem of Knowledge Distillation (KD) from VLMs (teacher) to vision models (student) for improved OOD generalization. We denote the VLM's text embedding for the input, \"A photo of a {class}\" for class $c$ as $\\mathbf{T}_c$ . The image embedding corresponding to the image $x$ is denoted as $\\mathbf{I}_x$ . The student model's features corresponding to an input $x$ are denoted as $\\mathbf{F}_x$ . These features when projected to the same dimension as the VLM embeddings $(\\mathbf{I}_x$ and $\\mathbf{T}_c)$ , are denoted as $\\mathbf{P}\\mathbf{F}_x$ . The cosine similarity between two vectors $\\mathbf{a}$ and $\\mathbf{b}$ is denoted as $\\cos(\\mathbf{a},\\mathbf{b})$ . While we use CLIP [47] as the teacher for most of our analysis and experiments, we show the compatibility of the proposed approach with other VLMs [34, 36, 56, 64] in Suppl. Sec-3.3.", + "bbox": [ + 75, + 703, + 470, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Robustness of CLIP embeddings", + "text_level": 1, + "bbox": [ + 498, + 89, + 797, + 107 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we present an overview of the training and zero-shot evaluation of the CLIP model, followed by a study on the robustness of its image and text embeddings.", + "bbox": [ + 496, + 114, + 892, + 161 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. CLIP training and zero-shot prediction", + "text_level": 1, + "bbox": [ + 498, + 169, + 836, + 186 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "CLIP is a VLM that consists of an image encoder and a text encoder trained jointly on 400 million web-scraped image-text pairs [47]. The outputs of CLIP are the text and image embeddings for the respective text and image inputs. CLIP is trained using a contrastive loss which enforces similarity between the representations of positive image-text pairs and disparity between the representations of negative image-text pairs in the training minibatch. The training objective of CLIP is shown in Eq.1, where the embeddings of the $i^{th}$ image-text pair are represented as $\\mathbf{I}_i$ and $\\mathbf{T}_i$ respectively.:", + "bbox": [ + 496, + 191, + 892, + 345 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {C L I P}} \\left(x _ {i}\\right) = - \\log \\frac {\\exp \\left(\\cos \\left(\\mathbf {I} _ {i} , \\mathbf {T} _ {i}\\right)\\right)}{\\sum_ {c = 1} ^ {C} \\exp \\left(\\cos \\left(\\mathbf {I} _ {i} , \\mathbf {T} _ {c}\\right)\\right)} \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 549, + 353, + 890, + 392 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The use of both text and image modalities during training enables the effective use of text embeddings as a zero-shot classifier, where inference can be performed directly without access to training data. For this, the text embeddings $\\mathbf{T}_c$ corresponding to the captions \"A photo of a {class}\" for each of the $C$ classes are compared with the image embedding $\\mathbf{I}_i$ , and the class with maximum similarity is predicted as shown in Eq.2. Thus, the text embeddings $\\mathbf{T}_c$ can be viewed as the weights of a classifier for a CLIP backbone.", + "bbox": [ + 496, + 398, + 892, + 536 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {y} _ {i} = \\operatorname {a r g m a x} _ {c} \\cos \\left(\\mathbf {I} _ {i}, \\mathbf {T} _ {c}\\right) \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 606, + 547, + 890, + 564 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.2. Characteristics of image and text embeddings", + "text_level": 1, + "bbox": [ + 498, + 574, + 885, + 590 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "CLIP [47] shows remarkable zero-shot performance as shown in Table-1 (E1), and outperforms even an ImageNet pre-trained model that is explicitly fine-tuned using the downstream dataset (Table-3) on several DG datasets. To understand its superior zero-shot performance, we discuss below the robustness of its image and text embeddings.", + "bbox": [ + 496, + 598, + 890, + 688 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Characteristics of the Image Encoder: In image classification tasks, the representations learned using standard ERM training are expected to exhibit invariances to several factors of variation due to: (a) the classification objective that enforces similar representations for different variations within a given class, which are different from the representations for other classes and (b) augmentations such as color jitter that enforce additional invariance. However, CLIP is trained using detailed captions for each image, such as \"A brown cat sitting on a sofa\", \"A black cat standing on two limbs\", and \"A black dog with long ears and a lot of fur\". This allows CLIP to learn rich specialized representations for each attribute, with higher intra-class variance when compared to standard ERM training.", + "bbox": [ + 496, + 689, + 893, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "23924", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Characteristics of the Text Encoder: Robustness to distribution shifts can be achieved either by incorporating the required domain-invariance in the feature extractor, or by domain-invariant feature selection at the classification head. As discussed, CLIP's image encoder produces input-specific representations and is not domain invariant. The superior generalization of CLIP on different datasets and domains is thus a result of the robust text embeddings. Although descriptive captions such as \"A brown cat sitting on a sofa\" are expected to have unique embeddings based on pose, location, etc., generic captions such as \"A photo of a {class}\" represent the core concept of the class.", + "bbox": [ + 76, + 90, + 472, + 272 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Empirical observations: In Table-1, we present results to demonstrate the robustness of CLIP text embeddings on the multi-source Domain Generalization benchmarks, where each dataset consists of images from $n$ domains. The results presented are an average of $n$ cases, where each case corresponds to the training on a given set of $n - 1$ domains and testing on the remaining unseen domain referred to as the target domain. Firstly, CLIP zero-shot results (E1) show the robustness of text embeddings across different distributions. The robustness of the text embeddings can be improved by explicitly enforcing domain invariance for better generalization to unseen domains (E2). However, the same level of robustness is not seen when we use an average of all image embeddings across the same domains for a given class, as shown in E3. This is due to the fact that while the text embeddings for \"A {domain} of a {class}\" are obtained by training over a large dataset (400 million images), the image embeddings are an average of $\\sim 0.01$ million images on the downstream dataset. This is illustrated in Fig.1, where the red decision boundary trained using image embeddings misclassifies images from the unseen target domain, while the green classifier trained using the generic text embeddings is closer to an ideal decision boundary. However, an average image embedding on the target domain improves results significantly (E4). The accuracy improves further when an average embedding corresponding to a few (10) source domain images closest (in terms of cosine similarity of image embeddings) to the target image is used for each class during prediction (E5). A similar experiment using images from the target domain (E6), achieves considerable improvements over the zero-shot accuracy in E1. We can consider E6 as an In-(target)-Domain setting where a labeled hold-out validation set is used during prediction for obtaining the average embeddings. Therefore, it is possible to outperform the generalized representations of the text embeddings only when labeled images from the target domain are available. Thus, in a DG setting where the target domain is inaccessible, the generic text embeddings provide the best robustness across distribution shifts. We therefore use the text embeddings to maximally transfer their robustness to the student model.", + "bbox": [ + 76, + 281, + 472, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "5. Proposed Approach: VL2V-ADiP", + "text_level": 1, + "bbox": [ + 498, + 89, + 805, + 107 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In this section, we first present the knowledge distillation framework adapted to a VLM-to-vision distillation setting. We further propose a self-distillation approach VL2V-SD, to enhance the robustness of the VLM image encoder, which motivates the proposed approach VL2V-ADiP.", + "bbox": [ + 496, + 114, + 890, + 191 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "5.1. Distillation from VLMs to Vision models", + "text_level": 1, + "bbox": [ + 498, + 199, + 846, + 214 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The standard framework of Knowledge Distillation (KD) [20] applies in the unimodal setting, for instance, where the teacher and student are both vision models. To adapt this to a VLM-to-vision distillation setting, a classification model (which we refer to as a VLM-classifier) is first constructed using the VLM. The feature extractor of the VLM-classifier comes from the image encoder of the VLM, and the linear classifier head obtains its weights from the text embeddings $\\mathbf{T}_c$ corresponding to the captions \"a photo of a {class}\" for all $C$ classes. For every image-label pair $(x_i,y_i)$ , the VLM-classifier first computes the image embedding $\\mathbf{I}_{x_i}$ , and further computes its similarity w.r.t. each of the text embeddings $\\mathbf{T}_c$ . The similarity scores $\\cos (\\mathbf{I}_{x_i},\\mathbf{T}_c)$ are considered to be analogous to the logit layer, over which the softmax function is applied. The final distillation loss of the student that is minimized during training is shown below in Eq.4 for a minibatch of size $n$ . Here, $f_{S}(.)$ and $f_{\\mathrm{T}}(.)$ represent the softmax representations of the student and teacher respectively, CE represents the Cross-Entropy loss, and KL represents the Kullback-Leibler divergence. Temperature scaling is applied to the logits before computing softmax [20]. We tune over the range - $\\{0.1,1,10\\}$ on the in-domain validation set, and report the baseline best results in Table-3.", + "bbox": [ + 496, + 222, + 890, + 569 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nf _ {\\mathrm {T}} \\left(x _ {i}\\right) = \\operatorname {s o f t m a x} \\left(\\cos \\left(\\mathbf {I} _ {x _ {i}}, \\mathbf {T} _ {c}\\right)\\right) \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 584, + 580, + 890, + 598 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {K D}} = \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\left\\{\\mathrm {C E} \\left(f _ {S} \\left(x _ {i}\\right), y _ {i}\\right) + \\lambda \\cdot \\mathrm {K L} \\left(f _ {\\mathrm {T}} \\left(x _ {i}\\right) \\mid \\mid f _ {S} \\left(x _ {i}\\right)\\right) \\right\\} \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 500, + 608, + 890, + 660 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "5.2. Self-Distillation from Text to Image encoders", + "text_level": 1, + "bbox": [ + 500, + 666, + 879, + 681 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "As discussed in Section-4.2, the image encoder of CLIP is trained to represent all factors of variations in an image that are described in the corresponding caption used during its training. Therefore, it does not exhibit the invariances to factors such as color, texture, lighting, and pose, that are required for an image classification task. On the other hand, text prompts allow much better control over invariances in text-embeddings. For example, a prompt such as \"A brown cat sitting on a sofa\" uniquely represents the color, location, and pose of the cat in addition to the object itself, whereas a prompt \"A photo of a cat\" is invariant to such variations.", + "bbox": [ + 496, + 688, + 890, + 853 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Motivated by this, we propose Vision-Language to Vision Self Distillation (VL2V-SD), where the invariances of generic text embeddings are distilled to the image encoder", + "bbox": [ + 498, + 854, + 893, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "23925", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/acd36f423afd1c11c334bf958b24fb564dba25f4c41db84ae644060a3c2cb124.jpg", + "image_caption": [ + "CLIP image encoder/features", + "CLIP text encoder / features" + ], + "image_footnote": [], + "bbox": [ + 80, + 88, + 344, + 284 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/d2859f37a8966683bad4313b867da91d69a96a8ad0f0f51e7beb38cc126287ed.jpg", + "image_caption": [ + "Networkfrozen", + "Network trainable", + "Student network / features", + "CLIP zero-shot classifier" + ], + "image_footnote": [], + "bbox": [ + 351, + 88, + 612, + 282 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/0e3b70fed9340deff4ce250aa2b3be45f860afab729bb8242c1420753e3bd614.jpg", + "image_caption": [ + "Stage 3 (Predict)", + "Figure 2. Overview of the proposed approach VL2V-ADiP, consisting of (a) Align, (b) Distill and (c) Predict Stages for Black-Box Distillation from Vision-Language to Vision (VL2V) models." + ], + "image_footnote": [], + "bbox": [ + 620, + 119, + 887, + 250 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "using the downstream dataset. We minimize the loss shown in Eq.5 for training, where $\\mathbf{T}_{y_i}$ represents the embedding for \"A photo of a {class}\" corresponding to the ground truth class $y_{i}$ , and $\\mathbf{I}_{x_i}^t$ , $\\mathbf{I}_{x_i}^s$ represent the image embeddings of the teacher and student respectively for an image $x_{i}$ .", + "bbox": [ + 75, + 382, + 468, + 458 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {S D}} = - \\frac {1}{2 n} \\sum_ {i = 1} ^ {n} \\left\\{\\cos \\left(\\mathbf {I} _ {x _ {i}} ^ {s}, \\mathbf {T} _ {y _ {i}}\\right) + \\cos \\left(\\mathbf {I} _ {x _ {i}} ^ {s}, \\mathbf {I} _ {x _ {i}} ^ {t}\\right) \\right\\} \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 99, + 464, + 468, + 503 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The image encoders of both teacher and student are the same (VLM's image encoder) initially, and the student's image encoder is updated during training. The text encoder is frozen during training. While the first term enforces the image encoder to learn representations that match the corresponding text embeddings more accurately on the given dataset, the second term ensures that there is no representation collapse, and retains the rich features learned by the image encoder. The classifier is composed of text embeddings corresponding to the prompts \"a photo of a {class}\" for all classes, as was the case in the VLM-classifier discussed in Section-5.1. We present the results of VL2V-SD in Table2, where we note significant improvements over both CLIP zero-shot and the SOTA DG methods - SWAD [8], MIRO [9], DART [23], and SAGM [61] on the ViT-B/16 architecture with CLIP initialization. We demonstrate significant gains over the CLIP fine-tuning methods LP-FT [28], FLYP [18], CLIPood [55], and WiSE-FT [63]. We also achieve significant gains over a distillation method RISE [22], despite using the standard text prompt while RISE uses an expanded set of prompts. For WiSE-FT, we present the results with the optimal $\\alpha$ that achieves the best performance by using the search space $\\alpha = [0.1 - 0.9]$ . Similarly, for RISE, we present the results with the optimal hyperparameters $\\lambda_1, \\lambda_2, \\lambda_3$ based on their search space. We incorporate SWAD [8] in all our runs for the baselines as well", + "bbox": [ + 75, + 507, + 472, + 900 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/6cd0bf2058dbce024c064dfecb7ba65de9e24800329eb5cfcda48ff0370f919f.jpg", + "table_caption": [ + "Table 2. White-Box setting (CLIP initialization): Performance $(\\%)$ of the proposed approach VLV2-SD, compared to the existing methods. ViT-B/16 architecture is used. (S) denotes SWAD [8]." + ], + "table_footnote": [], + "table_body": "
MethodOHTIVLCSPACSDNAvg-IDAvg-OOD
Zero-shot [47]82.4034.1082.3096.5057.70-70.60
SWAD [8]81.0142.9279.1391.3557.9289.0570.47
MIRO (S) [9]84.8059.3082.3096.4460.4791.0076.66
DART (S) [23]80.9351.2480.3893.4359.3289.2573.06
SAGM (S) [61]83.4058.6482.0594.3159.0589.7475.49
LP-FT (S) [28]81.1747.2680.8892.9257.0488.9771.85
FLYP (S) [18]82.7633.2566.6478.5357.4178.9463.72
CLIPood (S) [55]83.3146.2877.1993.1657.7869.9071.55
WiSE-FT (S) [63]86.3254.5082.8897.2958.0188.3575.80
RISE (S) [22]78.3949.6180.6293.2555.3787.9171.45
VL2V-SD (Ours)87.3858.5483.2596.6862.7989.9977.73
", + "bbox": [ + 501, + 426, + 890, + 564 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "as the proposed approach (denoted by “(S)”) since it is a generic technique that improves the generalization of any given method. However, we do not incorporate SWAD with WiSE-FT since it already performs weight averaging of the pre-trained and fine-tuned models. We present the results without SWAD in Suppl. Sec-3.2.", + "bbox": [ + 496, + 575, + 890, + 667 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5.3. VL2V - Align, Distill, Predict (VL2V-ADiP)", + "text_level": 1, + "bbox": [ + 498, + 678, + 867, + 695 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "While VL2V-SD is very effective in improving the performance of the VLM in a white-box setting, it does not address the problem of black-box distillation that we consider in this work, since it assumes access to the weights of the VLM model. In this section, we discuss how this method can be adapted to the black-box setting and present the proposed approach VL2V-ADiP. Since the amount of downstream task-specific data is assumed to be limited, the student is initialized with the best available pre-trained model such as ImageNet [26].", + "bbox": [ + 496, + 702, + 890, + 853 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In the self-distillation case seen in Section-5.2, the goal was to induce domain invariance from the text encoder to the image encoder, while ensuring that the rich features", + "bbox": [ + 496, + 854, + 892, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "23926", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "learned by the image encoder are not lost. Whereas, in the black-box setting, the goal is to distill the rich features learned by the image-encoder of the VLM and the domain invariance from the text embeddings. While the two cases can have a similar loss formulation as shown in Eq.5, the method VL2V-SD cannot directly be applied here since the feature dimension of the student model may be different from the dimension of VLM's image and text embeddings. Even if the dimensions had matched, the features of the ImageNet pre-trained backbone and VLM's embeddings would be misaligned. Directly enforcing a similarity loss in such a case would lead to forgetting of the pretrained features. To address this, we propose VL2V-ADiP, Vision-Language to Vision - Align, Distill, Predict as shown in Fig.2 (Ref: Alg. 1 in Suppl.). We propose to first Align the features of the pre-trained student model with VLM embeddings using a linear projection head on the student backbone in Stage-1, as shown in Fig.2(a). For this, the student backbone is frozen and only the projection head is trained using the following loss, where $\\mathbf{PF}_{x_i}^s$ represents the projected features of the student model for the input $x_{i}$ :", + "bbox": [ + 75, + 90, + 472, + 409 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {A D i P}} = - \\frac {1}{2 n} \\sum_ {i = 1} ^ {n} \\left\\{\\cos \\left(\\mathbf {P F} _ {x _ {i}} ^ {s}, \\mathbf {T} _ {y _ {i}}\\right) + \\cos \\left(\\mathbf {P F} _ {x _ {i}} ^ {s}, \\mathbf {I} _ {x _ {i}} ^ {t}\\right) \\right\\} \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 86, + 424, + 468, + 474 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Next, the aligned student features are refined using the VLM's image and text embeddings in the Distill step as shown in Fig.2(b) (Stage-2). For this step, the linear projection head is frozen, and the feature extractor is trained using the same loss as Stage-1, as shown in Eq.6. While we give equal weight to both loss terms in Eq.6, we present the impact of varying this in Suppl. Sec-4. Finally, in Stage-3 (Predict), the VLM's embeddings corresponding to \"a photo of a {class}\" for all $C$ classes are used as weights of the classification head, and the class with the highest similarity to the given image embedding is predicted, as shown in Eq.2. In addition to learning the rich features from the VLM teacher's image-encoder and invariances from its text encoder, enforcing similarity between the features of the student backbone and the text embeddings of the corresponding classes also makes the text embeddings more suitable for use as a classifier in Stage-3 (Predict). Thus, although Stages 1 and 2 explicitly train only the student backbone and projection head, they implicitly impact the effectiveness of the classification head as well. This facilitates the use of these embeddings directly as a classifier without the need for fine-tuning further on the downstream dataset. As shown in Table-5, further fine-tuning degrades the performance, since only In-Domain (ID) data is available for fine-tuning, which would make the classifier forget the domain invariance that it inherently possesses. However, fine-tuning with limited In-Domain data improves the ID accuracy as shown in the table.", + "bbox": [ + 75, + 478, + 472, + 900 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "6. Experiments and Results", + "text_level": 1, + "bbox": [ + 500, + 90, + 733, + 107 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "6.1. Evaluation Details", + "text_level": 1, + "bbox": [ + 500, + 114, + 679, + 130 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Towards evaluating the OOD generalization of image classification models, we consider the five popular Domain Generalization (DG) datasets - OfficeHome (OH) [60], PACS [30], VLCS [16], Terra-Incognita (TI) [3] and DomainNet (DN) [44]. Each of the datasets consists of $d$ domains, where $d = 4$ for the first four datasets and $d = 6$ for DomainNet. We present more details on the datasets in Suppl. Sec-2. We follow the DomainBed [19] framework for training and evaluation, where each domain is split into training and validation sets, and training is performed on $d - 1$ domains while evaluation is done on the $d^{th}$ unseen domain. Thus, for every dataset, $d$ models are trained, by leaving one domain out for evaluation each time. The average accuracy across these $d$ runs on the unseen test domain (OOD accuracy) and the average In-domain (ID) validation split accuracy are reported. The unseen test domain is neither used for training nor for hyperparameter tuning [19].", + "bbox": [ + 496, + 137, + 893, + 396 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "6.2. Training Details", + "text_level": 1, + "bbox": [ + 500, + 405, + 661, + 421 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "The number of training iterations is set to 5000 for OfficeHome, PACS, VLCS, and Terra-Incognita, and to 15000 for DomainNet, as is standard [8, 9]. We use the Adam optimizer with a constant learning rate of $5 \\times 10^{-5}$ for all our experiments except CLIPood (S) in Table-2, for which we use the AdamW optimizer as specified in [55]. These settings are fixed for all datasets, and we do not introduce any additional hyperparameters in the proposed algorithm. Our primary evaluations consider a ViT-B/16 architecture [15] for both the VLM (teacher) Image-encoder and the student model to enable a fair comparison with existing methods, that use the same architecture. Since one of the key motivations of distillation is to train a low-capacity model, we present results with lower-capacity student architectures as well. We use a CLIP teacher model, which uses a Transformer architecture [59] with modifications described by Radford et al. [46] for the text encoder. The student model and our primary baselines for VL2V-ADiP use an ImageNet pre-trained initialization [26], as is standard in DG [19]. We obtain the results of baseline methods on ViTs in Tables 2 and 3 by integrating the official code of the respective method with the MIRO [9] code base to ensure a fair comparison. Additionally, we show results with other teacher VLMs in Suppl. Sec-3.3.", + "bbox": [ + 496, + 429, + 893, + 792 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "6.3. Comparison with the SOTA", + "text_level": 1, + "bbox": [ + 500, + 801, + 750, + 816 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We present the ID and OOD results of the proposed approach VL2V-ADiP when compared to the DG and KD baselines in Table-3. Gulrajani and Lopez-Paz [19] show that ERM training is a very strong baseline in DG and outperforms several older methods that were proposed. Thus,", + "bbox": [ + 496, + 825, + 893, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "23927", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/849e0129d16d1eff8ea2fce5633bb3fddc0e1f4663e0bc7bc4c92dd7b9f18c35.jpg", + "table_caption": [ + "Table 3. SOTA comparison with ImageNet initialization: Performance (%) of the proposed approach VL2V-ADiP, compared to existing KD and DG methods with SWAD (S). ViT-B/16 with ImageNet-1K initialization is used as the student." + ], + "table_footnote": [], + "table_body": "
MethodOHTIVLCSPACSDNAvg-IDAvg-OOD
ERM-LP (S)71.4831.3577.5267.0236.6573.9956.81
ERM Full Fine-tuning (S)83.2250.0580.3390.2856.1089.3172.00
LP-FT (S) [28]81.5551.6180.1791.2056.0390.0372.11
SimKD (S) [13]66.7681.0183.9228.2449.4268.2461.87
KD (S) [20]82.7348.4080.4891.4656.1189.2071.84
MIRO (S) [9]80.0950.2981.1089.5055.7588.7171.35
DART (S) [23]83.7549.6877.2990.5558.0588.5471.86
SAGM (S) [61]82.2253.2479.6090.0255.6689.2272.15
Text2Concept (S) [40]70.2426.4664.7779.0323.2653.1552.82
RISE (S) [22]83.4852.5583.7093.5456.5888.9173.97
VL2V-ADiP (Ours)85.7455.4381.9094.9459.3889.0275.48
", + "bbox": [ + 76, + 146, + 470, + 270 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/4959eedefc4f193f4625ee8d8073f2c1b136fa7e49ed9759aad57b811076f939.jpg", + "table_caption": [ + "Table 4. Distillation to lower capacity student models: Performance (\\%) of the proposed approach VL2V-ADiP (denoted as Ours), when compared to the KD baseline [20] and ERM (S) or SWAD [8] with different student architectures. The teacher architecture is ViT-B/16. (S) denotes SWAD." + ], + "table_footnote": [], + "table_body": "
StudentMethodOHTIVLCSPACSDNAvg-IDAvg-OOD
ViT-B/16 (86M)ERM (S)83.2250.0580.3390.2856.1089.3172.00
KD (S)82.7348.4080.4891.4656.1789.2071.85
Ours (S)85.7455.4381.9094.9459.3889.0275.48
ViT-S/16 (22M)ERM (S)78.5849.4078.7285.8052.0985.6668.92
KD (S)78.1450.1179.1485.9752.0587.4369.08
Ours (S)81.2252.4781.4489.3254.2386.5971.73
DeiT-S/16 (22M)ERM (S)74.9547.8579.3789.2249.1886.5868.12
KD (S)74.6548.1178.8688.1449.1086.6667.77
Ours (S)77.6348.7281.8988.9750.3785.2869.52
ResNet-50 (26M)ERM (S)70.8549.4779.5088.0546.4384.8866.86
KD (S)70.6751.2278.6387.2346.3185.0466.81
Ours (S)74.4253.4679.2386.7247.7484.7368.31
", + "bbox": [ + 76, + 358, + 470, + 515 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "ERM training of only the linear layer (ERM-LP) and ERM full fine-tuning (ERM-FFT) are two important baselines we consider. Further, we present the results of important SOTA DG methods - SWAD [8], MIRO [9], DART [23], and SAGM [61]. Additionally, we also show results with Text2Concept [40] and LP-FT [28] - simple fine-tuning strategies for improved OOD generalization on downstream tasks. While there are several methods that outperform ERM [6, 25, 41, 57], we do not present all of them here since the above-listed recent methods outperform them. Since we incorporate SWAD in the proposed approach, we present all the baseline results by integrating SWAD with each of them and denote them with a suffix \"S\" in the tables. Additionally, we also present three distillation results - (a) knowledge distillation from the VLM teacher to the vision student model as discussed in Section-5.1 and (b) distillation from the VLM teacher using SimKD [13], and (c) distillation from the VLM teacher using RISE [22]. Since the feature distillation methods listed in Sec. 2 cannot be extended to the black box distillation setting, we do not compare with them. The proposed approach VL2V-ADiP achieves $\\sim 1.5\\%$ improvement on average OOD accuracy across all datasets with respect to the best baselines, with comparable ID accuracy. We note that Text2Concept scales", + "bbox": [ + 75, + 537, + 472, + 902 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "poorly on smaller datasets compared to the results shown in the paper [40]. SimKD [13] is a method intended for unimodal distillation and thus fails for the multimodal setup. Furthermore, we outperform the method RISE [22] by a large margin despite the latter using expanded text prompts. This shows that the proposed distillation method VL2V-ADiP effectively distills from VLMs with lesser prompt engineering and text supervision compared to RISE.", + "bbox": [ + 496, + 90, + 893, + 213 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "6.4. Distillation to lower capacity student models", + "text_level": 1, + "bbox": [ + 498, + 223, + 877, + 239 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We present results of distilling from a CLIP ViT-B/16 teacher to different student architectures and capacities (ViT-S/16, DeiT-S, ResNet-50) in Table-4. We observe substantial gains over the Knowledge Distillation and ERM (S) or SWAD baseline across all student architectures. We note that the distillation performance is best when the architecture (ViT) of the teacher matches that of the student. For example, although ViT-S/16, DeiT-S/16, and ResNet-50 have a similar number of parameters, the performance of the ViT-S/16 student is the best, showing the architecture plays a role in the nature of representations learned, thereby allowing better transfer when they match.", + "bbox": [ + 496, + 246, + 893, + 429 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "6.5. Ablation Study", + "text_level": 1, + "bbox": [ + 498, + 438, + 653, + 455 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "We present an ablation study of the proposed method in Table-5. Firstly, we study the impact of combining stages-1 (Align) and 2 (Distill), i.e., training the linear projection layer and the backbone jointly in A1. This results in a $2.2\\%$ drop in ID accuracy and a $6.3\\%$ drop in OOD accuracy, highlighting that the pre-trained ImageNet features are retained better when they are aligned before distillation. In A2, the linear projection head is also trained in Stage-2. The results of this case are similar to the proposed approach, showing that even when the linear head is changed, it does not get updated much after Stage-1 (Align). We next analyze the importance of distilling from both image and text encoders of CLIP by using only one of them individually in A3 and A4. In both cases, we note a significant drop in the OOD accuracy highlighting the importance of distilling from both encoders. Distilling only from the Image encoder has a larger drop due to the lack of alignment between the representations and the classifier head which is composed of CLIP text embeddings corresponding to each of the classes.", + "bbox": [ + 496, + 462, + 893, + 750 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "In Stage-3 (Predict) of the proposed approach, the CLIP text embeddings corresponding to the classes are directly used as the classifier weights. We explore the impact of training this classifier further using cross-entropy loss over the softmax representations shown in Eq.3, in experiments A5-A8. In A5 and A6, the classifier head is first initialized using the text embeddings of CLIP, and in A7 and A8, a random initialization is used for the classification head. In A5 and A7, only the classifier head is trained, whereas in A6 and A8, the full network is trained. All these experi", + "bbox": [ + 496, + 750, + 895, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "23928", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/22b5203a29e5948ea1c3f7c1c78b954bd9b460092513f241566a908e17c8e81d.jpg", + "table_caption": [ + "Table 5. Ablation Study of the proposed VL2V-ADiP: Performance (%) on ViT-B/16 model with ImageNet initialization." + ], + "table_footnote": [], + "table_body": "
Method - Changes done w.r.t. VL2V-ADiP (Ours)OHTIVLCSPACSAvg-IDAvg-OOD
VL2V-ADiP (Ours)85.7455.4381.9094.9492.7479.50
A1: Combining "Align" and "Distill" stages74.5552.9980.1485.2990.5573.24
A2: Without freezing projection head in Stage-286.1356.6881.7893.7593.0079.59
A3: Distilling only from Text encoder in Stages-1 and 283.1847.0279.8390.8691.8775.22
A4: Distilling only from Image encoder in Stages-1 and 278.9728.9782.2489.9774.0970.04
A5: Finetuning CLIP classifier-head in Stage-3 (CE loss) - CLIP init classifier84.4749.2881.3093.5493.0677.15
A6: Finetuning full network in Stage-3 (CE loss) - CLIP init classifier83.8849.8380.1392.2593.3776.52
A7: Finetuning classifier-head in Stage-3 (CE loss) - random init classifier84.6349.5581.2993.5793.0277.26
A8: Finetuning full network in Stage-3 (CE loss) - random init classifier83.1650.0379.7892.1593.1476.28
", + "bbox": [ + 81, + 107, + 893, + 247 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/6f84f9fcf6ec76d60916a8d979d0197c2f10c1cda186f4ffc424a97248b2f52c.jpg", + "image_caption": [ + "Figure 3. OOD accuracy $(\\%)$ of the proposed approach when compared to KD and ERM baselines for select classes/ domains in Office-Home and Terra-Incognita datasets, where the (a) ERM-IN (linear) (b) CLIP Zero-shot (c) ERM-CLIP (linear) performance is poor." + ], + "image_footnote": [], + "bbox": [ + 76, + 257, + 890, + 409 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ments result in a drop in the OOD accuracy, indicating that training on the downstream dataset using the cross-entropy loss can destroy the domain invariances learned from CLIP. Since the impact of training the full network is higher, the drop is higher in this case when compared to finetuning only the classification head. In all cases, the In-Domain accuracy improves when compared to the proposed approach, with higher gains in the case when the full network is trained, confirming that training without the supervision of the CLIP teacher indeed overfits to the training domains.", + "bbox": [ + 75, + 453, + 472, + 604 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "We also compare the ERM and KD baselines with the proposed approach in some of the extreme cases in Fig.3, where the CLIP Image encoder is significantly better than the ERM model (a), and vice-versa (c). For this, we select the classes/domains with the highest difference $(40 - 50\\%)$ between the ERM-CLIP (Linear) and ERM-ImageNet (IN) (Linear) baselines from the OfficeHome dataset. We also present the case where the CLIP zero-shot accuracy is poor in OfficeHome $(22\\%)$ and Terra-Incognita datasets $(0\\%)$ in Fig.3 (b). The KD baseline relies a lot on the ImageNet pre-trained backbone, hence it is poor when ERM-IN is poor, and is close to our approach when ERM-IN is good. The ERM fine-tuning baseline is best when the ImageNet features are much better than CLIP Image encoder's features, but it is poor in the other case, as expected. Lastly, even when CLIP zero-shot accuracy is poor (close to $0\\%$ ), the proposed approach achieves reasonable accuracy, since Stages-1 and 2 align the text embeddings better to the feature extractor, making them more suitable as a classifier.", + "bbox": [ + 75, + 613, + 472, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "7. Conclusion", + "text_level": 1, + "bbox": [ + 498, + 450, + 619, + 467 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we aim to leverage the superior generalization of large-scale Vision-Language Models towards improving the OOD generalization of Vision models. We consider a practical scenario where a client gets only black-box access to the model on a pay-per-query basis from the vendor, motivating the need for distilling the model first, and further using the student model during inference. Towards this, we first highlight the unique aspects of the image and text encoders of VLMs and further propose a self-distillation (SD) approach - VL2V-SD, to distill the superior generalization of the VLM's text encoder to its image encoder, while retaining the rich representations of the latter. We further adapt this to a black-box distillation setting, by firstly projecting the representations of the pre-trained feature-extractor (student) to a space that is aligned with embeddings of the VLM teacher, and further finetuning the backbone using the same. The use of both text and image embeddings induces the rich representations of the VLM and its superior generalization to the student model, while also making the text embeddings more suitable for use in the classification head. Both proposed approaches (VL2V-SD and VL2V-ADiP) achieve substantial gains over prior methods on the popular Domain Generalization datasets.", + "bbox": [ + 496, + 477, + 890, + 824 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements. This work is supported by the Kotak IISc AI-ML Center and a research grant CRG/2021/005925 from SERB, DST, Govt. of India. Sravanti Addepalli is supported by the Google PhD Fellowship and CII-SERB Prime Minister's Fellowship for Doctoral Research.", + "bbox": [ + 496, + 824, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "23929", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Martin Arjovsky, Léon Bottou, Ishaan Gulrajani, and David Lopez-Paz. Invariant risk minimization. arXiv preprint arXiv:1907.02893, 2019. 2", + "[2] Devansh Arpit, Huan Wang, Yingbo Zhou, and Caiming Xiong. Ensemble of averages: Improving model selection and boosting performance in domain generalization. NeurIPS, 2022. 3", + "[3] Sara Beery, Grant Van Horn, and Pietro Perona. Recognition in terra incognita. In ECCV. 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IJCV, 2022. 3" + ], + "bbox": [ + 78, + 90, + 468, + 189 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "23932", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_model.json b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_model.json new file mode 100644 index 0000000000000000000000000000000000000000..f5b533295e120b708016d64e7563f2091167c81e --- /dev/null +++ b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_model.json @@ -0,0 +1,2103 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.226, + 0.131, + 0.748, + 0.177 + ], + "angle": 0, + "content": "Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification" + }, + { + "type": "text", + "bbox": [ + 0.129, + 0.204, + 0.842, + 0.24 + ], + "angle": 0, + "content": "Sravanti Addepalli * Ashish Ramayee Asokan * Lakshay Sharma R. Venkatesh Babu Vision and AI Lab, Indian Institute of Science, Bangalore" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.274, + 0.314, + 0.29 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.306, + 0.474, + 0.744 + ], + "angle": 0, + "content": "Vision-Language Models (VLMs) such as CLIP are trained on large amounts of image-text pairs, resulting in remarkable generalization across several data distributions. However, in several cases, their expensive training and data collection/curation costs do not justify the end application. This motivates a vendor-client paradigm, where a vendor trains a large-scale VLM and grants only input-output access to clients on a pay-per-query basis in a black-box setting. The client aims to minimize inference cost by distilling the VLM to a student model using the limited available task-specific data, and further deploying this student model in the downstream application. While naive distillation largely improves the In-Domain (ID) accuracy of the student, it fails to transfer the superior out-of-distribution (OOD) generalization of the VLM teacher using the limited available labeled images. To mitigate this, we propose Vision-Language to Vision - Align, Distill, Predict (VL2V-ADiP), which first aligns the vision and language modalities of the teacher model with the vision modality of a pre-trained student model, and further distills the aligned VLM representations to the student. This maximally retains the pre-trained features of the student, while also incorporating the rich representations of the VLM image encoder and the superior generalization of the text embeddings. The proposed approach achieves state-of-the-art results on the standard Domain Generalization benchmarks in a black-box teacher setting as well as a white-box setting where the weights of the VLM are accessible. Project page: http://val.cds.iisc.ac.in/VL2V-ADiP/" + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.754, + 0.21, + 0.769 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.779, + 0.47, + 0.856 + ], + "angle": 0, + "content": "While the initial success of Deep Learning was predominantly driven by training specialized models for each task or dataset [26, 29], recent research on foundation models [24, 34, 47, 65] eliminates the need for this by training generic models jointly over several modalities using large-" + }, + { + "type": "image", + "bbox": [ + 0.521, + 0.272, + 0.871, + 0.515 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.521, + 0.895, + 0.676 + ], + "angle": 0, + "content": "Figure 1. Schematic diagram showing class and domain distributions in the shared text/ image embedding space of a VLM: VLMs learn highly specialized image representations that are not domain invariant. Thus, a linear classifier (red decision boundary) that is trained over the vision encoder using limited training data cannot generalize well to the target domain (shown in purple). On the other hand, generic text embeddings such as \"A photo of a class\" represent the core concept of a class by virtue of their training method and vast training data. Thus, they generalize effectively across domains, and a zero-shot classifier (green decision boundary) aligns better with the true distribution of classes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.687, + 0.895, + 0.869 + ], + "angle": 0, + "content": "scale data. The use of both image and language modalities in large-scale Vision-Language Models (VLMs) enables their use in several applications including zero-shot classification, where the embedding of an image is compared with text embeddings for \"a photo of a {class}\" corresponding to every class during inference and the class with highest similarity is predicted. For example, the LiT (private) model [65] has been trained on 4 billion image-text pairs scraped from the web, and it achieves \\(85.2\\%\\) zero-shot accuracy on ImageNet. VLMs also demonstrate extraordinary performance across several distributions, owing to the vast diversity of distributions seen during their training [47]." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.87, + 0.895, + 0.902 + ], + "angle": 0, + "content": "The remarkable OOD generalization of VLMs makes them suitable for use in several applications, either directly" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.864, + 0.21, + 0.876 + ], + "angle": 0, + "content": "*Equal Contribution." + }, + { + "type": "page_footnote", + "bbox": [ + 0.078, + 0.877, + 0.47, + 0.899 + ], + "angle": 0, + "content": "Correspondence to Sravanti Addepalli , Ashish Ramayee Asokan " + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.864, + 0.47, + 0.899 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23922" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.304 + ], + "angle": 0, + "content": "or after finetuning on the downstream target dataset. Although several open-sourced models such as CLIP [47] are easily accessible, they may not be suitable for use in specialized applications. For example, the training data may have to be curated to reduce biases in the model or to ensure data privacy. It may also be important to ensure that the web-crawled data is clean for adoption in critical applications such as autonomous driving, to avoid data-poisoning attacks [4, 7]. Further, general-purpose models cannot be used in specialized applications such as medical diagnosis, where a VLM trained on data containing expert comments can be invaluable. This motivates the need for training highly specialized VLMs, which can be expensive due to the high costs associated with data collection/ curation and training." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.306, + 0.473, + 0.488 + ], + "angle": 0, + "content": "A given downstream application may not always justify the cost associated with training such large-scale models. However, since these VLMs are generic and applicable to several downstream applications, one vendor could train such a model, and make it available to several clients in a black-box setting on a pay-per-query basis. In this case, the client can minimize their inference time costs by distilling the VLM to a student model using the limited available data specific to the downstream task, and deploying the distilled model rather than the VLM. Since the key motivation of using VLMs is their generalization to several domains, reliable OOD performance of the distilled model is crucial." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.491, + 0.473, + 0.809 + ], + "angle": 0, + "content": "In this work, we consider the problem of distilling a multimodal Vision-Language model to a unimodal Vision model using limited task-specific downstream data, targeted toward better OOD performance with respect to the training domains used for distillation. While standard distillation of VLMs would require training data comprising of images and their associated text, in this case, the training data consists of only labeled images, similar to a classification task. Moreover, since the superior generalization abilities of VLMs are a result of the large-scale data (\\(\\sim 400\\) million in the case of CLIP) used for their training, it is challenging to transfer these generalization abilities using a limited dataset comprising around 10,000 (0.01 million) images [16, 30, 60]. Lastly, since the VLM is considered to be a black box, the image encoder's weights cannot be used as initialization to the vision model for further fine-tuning. However, since the downstream task-specific data is limited and is insufficient to train models from scratch, we assume that the student is initialized with weights from a model pretrained on a publicly available dataset such as ImageNet-1K [26], as is common in a domain-generalization setting [19]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.473, + 0.903 + ], + "angle": 0, + "content": "While knowledge distillation [20] using the labeled task-specific images improves the In-Domain accuracy on the downstream task, the improvement in OOD accuracy is marginal due to the limited size of the dataset. To address this, we first analyze the robustness of the text and image embeddings from the VLM and highlight the impor" + }, + { + "type": "text", + "bbox": [ + 0.497, + 0.092, + 0.895, + 0.258 + ], + "angle": 0, + "content": "tance of text embeddings for better OOD generalization (see Fig.1). Further, we propose VL2V-ADiP: Vision-Language to Vision - Align, Distill, Predict, to firstly align the features of the pre-trained student model with the text and image modalities of the VLM teacher, and further fine-tune the student backbone in a distillation framework. This improves the robustness of the student, while also aligning the student embeddings to the VLM's text embeddings corresponding to the respective class, thereby making the latter suitable for use as a classifier in the student without the need for further training. We summarize our contributions below:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.26, + 0.892, + 0.304 + ], + "angle": 0, + "content": "- We investigate the robustness of image and text embeddings of VLMs, and highlight the importance of the text embeddings for better OOD generalization." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.305, + 0.892, + 0.379 + ], + "angle": 0, + "content": "- To demonstrate the superior generalization of text embeddings, we propose VL2V-SD - a self-distillation approach, that improves the OOD generalization of the VLM's pre-trained vision encoder using supervision from its own text encoder in a white-box VLM setting." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.381, + 0.892, + 0.44 + ], + "angle": 0, + "content": "- We further propose VL2V-ADiP - a black-box distillation approach that effectively combines the features of a pretrained vision model with the text and vision encoders of a VLM teacher for better OOD generalization." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.442, + 0.892, + 0.486 + ], + "angle": 0, + "content": "- We demonstrate state-of-the-art results on standard Domain Generalization benchmark datasets in both white-box and black-box settings of the VLM teacher." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.26, + 0.892, + 0.486 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.498, + 0.651, + 0.514 + ], + "angle": 0, + "content": "2. Related Works" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.523, + 0.895, + 0.689 + ], + "angle": 0, + "content": "Vision-Language Models (VLMs): VLMs are trained on large-scale datasets of image-text pairs crawled from the web [10, 53, 58]. Contrastive pre-training methods [24, 34, 47, 65] maximize the similarity between the embeddings of matching image-text pairs. More recent efforts focus on scaling up image-text pre-training to larger datasets [34], better supervision with unimodal and multimodal data [56], data-efficient pre-training [36], and fine-tuning VLMs for downstream tasks [18, 28, 63]. Another line of work focuses on leveraging CLIP [47] to improve the OOD generalization in image classification [40, 55]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.897, + 0.902 + ], + "angle": 0, + "content": "Domain Generalization (DG): Prior works learn domain invariant representations by using augmentations [41, 42, 50], feature alignment across domains [17, 33, 35, 57], and disentangling domain-specific and domain-invariant features [11, 38, 45]. Gulrajani et.al [19] demonstrate that a well-tuned ERM model is comparable to several past DG algorithms [1, 5, 21, 27, 31, 32, 52, 62, 66]. SWAD [8] is a generic strategy that performs weight-averaging across different model snapshots in the optimal basin during training. MIRO [9] proposes Mutual Information (MI) regularization to maximally retain the pre-trained model's representations. SAGM [61] aligns gradient directions between the \\(\\epsilon\\)-perturbed loss and the empirical risk. We demonstrate performance gains when compared to the existing DG methods" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23923" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.47, + 0.146 + ], + "angle": 0, + "content": "Table 1. CLIP on DG datasets: Performance \\((\\%)\\) of CLIP ViT-B/16 model on using different embeddings in the classifier head for computing similarity w.r.t. the test image during inference (T.E.: Text Embedding, I.E.: Image Embedding)." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.149, + 0.472, + 0.304 + ], + "angle": 0, + "content": "
Embedding used for computing similarityOHTIVLCSPACSAvg.
E1: Text embedding for "A photo of a {class}"82.3634.1982.0896.1073.68
E2: Avg. text embedding for "A {domain} of a {class}" across all train domains83.7035.5582.2896.2174.44
E3: Avg. image embedding of each class (Source)71.3733.9948.2179.0358.15
E4: Avg. image embedding of each class (Target)78.2138.6969.3193.0869.82
E5: Avg. image embedding of 10 images per class closest to test image (Source)76.4239.3376.4292.1571.08
E6: Avg. image embedding of 10 images per class closest to test image (Target)84.8685.3887.8898.3289.11
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.325, + 0.47, + 0.476 + ], + "angle": 0, + "content": "in both white-box and black-box settings of the VLM. More recently, several methods perform diverse training of multiple models, followed by weight-averaging to improve OOD generalization [2, 23, 48, 49]. However, they incur the enormous expense of training several diverse models. We thus restrict our comparison to DART [23], where the number of models trained is lower than the others. Another direction has been the generation of better prompts for improved generalization of VLMs [39, 54, 67]. These methods can be integrated with the proposed approach." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.479, + 0.47, + 0.66 + ], + "angle": 0, + "content": "Knowledge Distillation (KD): Knowledge distillation aims to transfer knowledge from a powerful teacher model to a compact student model. Output-distillation [20] uses the teacher's softmax outputs as guidance for the student. Feature-distillation methods [12-14, 37, 43, 51] use the teacher's intermediate representations as guidance since they contain richer information. The proposed method operates in the black box distillation setup that allows only input-output access to the teacher network and restricts access to intermediate features. We thus compare the proposed black-box approach only with methods that do not access intermediate features [13, 20, 22]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.676, + 0.184, + 0.692 + ], + "angle": 0, + "content": "3. Notations" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.704, + 0.471, + 0.903 + ], + "angle": 0, + "content": "We consider the problem of Knowledge Distillation (KD) from VLMs (teacher) to vision models (student) for improved OOD generalization. We denote the VLM's text embedding for the input, \"A photo of a {class}\" for class \\( c \\) as \\( \\mathbf{T}_c \\). The image embedding corresponding to the image \\( x \\) is denoted as \\( \\mathbf{I}_x \\). The student model's features corresponding to an input \\( x \\) are denoted as \\( \\mathbf{F}_x \\). These features when projected to the same dimension as the VLM embeddings \\( (\\mathbf{I}_x \\) and \\( \\mathbf{T}_c) \\), are denoted as \\( \\mathbf{P}\\mathbf{F}_x \\). The cosine similarity between two vectors \\( \\mathbf{a} \\) and \\( \\mathbf{b} \\) is denoted as \\( \\cos(\\mathbf{a},\\mathbf{b}) \\). While we use CLIP [47] as the teacher for most of our analysis and experiments, we show the compatibility of the proposed approach with other VLMs [34, 36, 56, 64] in Suppl. Sec-3.3." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.09, + 0.798, + 0.108 + ], + "angle": 0, + "content": "4. Robustness of CLIP embeddings" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.115, + 0.893, + 0.162 + ], + "angle": 0, + "content": "In this section, we present an overview of the training and zero-shot evaluation of the CLIP model, followed by a study on the robustness of its image and text embeddings." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.17, + 0.837, + 0.187 + ], + "angle": 0, + "content": "4.1. CLIP training and zero-shot prediction" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.193, + 0.893, + 0.346 + ], + "angle": 0, + "content": "CLIP is a VLM that consists of an image encoder and a text encoder trained jointly on 400 million web-scraped image-text pairs [47]. The outputs of CLIP are the text and image embeddings for the respective text and image inputs. CLIP is trained using a contrastive loss which enforces similarity between the representations of positive image-text pairs and disparity between the representations of negative image-text pairs in the training minibatch. The training objective of CLIP is shown in Eq.1, where the embeddings of the \\( i^{th} \\) image-text pair are represented as \\( \\mathbf{I}_i \\) and \\( \\mathbf{T}_i \\) respectively.:" + }, + { + "type": "equation", + "bbox": [ + 0.55, + 0.354, + 0.892, + 0.393 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {C L I P}} \\left(x _ {i}\\right) = - \\log \\frac {\\exp \\left(\\cos \\left(\\mathbf {I} _ {i} , \\mathbf {T} _ {i}\\right)\\right)}{\\sum_ {c = 1} ^ {C} \\exp \\left(\\cos \\left(\\mathbf {I} _ {i} , \\mathbf {T} _ {c}\\right)\\right)} \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.4, + 0.893, + 0.537 + ], + "angle": 0, + "content": "The use of both text and image modalities during training enables the effective use of text embeddings as a zero-shot classifier, where inference can be performed directly without access to training data. For this, the text embeddings \\(\\mathbf{T}_c\\) corresponding to the captions \"A photo of a {class}\" for each of the \\(C\\) classes are compared with the image embedding \\(\\mathbf{I}_i\\), and the class with maximum similarity is predicted as shown in Eq.2. Thus, the text embeddings \\(\\mathbf{T}_c\\) can be viewed as the weights of a classifier for a CLIP backbone." + }, + { + "type": "equation", + "bbox": [ + 0.607, + 0.549, + 0.892, + 0.565 + ], + "angle": 0, + "content": "\\[\n\\hat {y} _ {i} = \\operatorname {a r g m a x} _ {c} \\cos \\left(\\mathbf {I} _ {i}, \\mathbf {T} _ {c}\\right) \\tag {2}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.575, + 0.886, + 0.592 + ], + "angle": 0, + "content": "4.2. Characteristics of image and text embeddings" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.599, + 0.892, + 0.689 + ], + "angle": 0, + "content": "CLIP [47] shows remarkable zero-shot performance as shown in Table-1 (E1), and outperforms even an ImageNet pre-trained model that is explicitly fine-tuned using the downstream dataset (Table-3) on several DG datasets. To understand its superior zero-shot performance, we discuss below the robustness of its image and text embeddings." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.69, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Characteristics of the Image Encoder: In image classification tasks, the representations learned using standard ERM training are expected to exhibit invariances to several factors of variation due to: (a) the classification objective that enforces similar representations for different variations within a given class, which are different from the representations for other classes and (b) augmentations such as color jitter that enforce additional invariance. However, CLIP is trained using detailed captions for each image, such as \"A brown cat sitting on a sofa\", \"A black cat standing on two limbs\", and \"A black dog with long ears and a lot of fur\". This allows CLIP to learn rich specialized representations for each attribute, with higher intra-class variance when compared to standard ERM training." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23924" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.273 + ], + "angle": 0, + "content": "Characteristics of the Text Encoder: Robustness to distribution shifts can be achieved either by incorporating the required domain-invariance in the feature extractor, or by domain-invariant feature selection at the classification head. As discussed, CLIP's image encoder produces input-specific representations and is not domain invariant. The superior generalization of CLIP on different datasets and domains is thus a result of the robust text embeddings. Although descriptive captions such as \"A brown cat sitting on a sofa\" are expected to have unique embeddings based on pose, location, etc., generic captions such as \"A photo of a {class}\" represent the core concept of the class." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.282, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Empirical observations: In Table-1, we present results to demonstrate the robustness of CLIP text embeddings on the multi-source Domain Generalization benchmarks, where each dataset consists of images from \\( n \\) domains. The results presented are an average of \\( n \\) cases, where each case corresponds to the training on a given set of \\( n - 1 \\) domains and testing on the remaining unseen domain referred to as the target domain. Firstly, CLIP zero-shot results (E1) show the robustness of text embeddings across different distributions. The robustness of the text embeddings can be improved by explicitly enforcing domain invariance for better generalization to unseen domains (E2). However, the same level of robustness is not seen when we use an average of all image embeddings across the same domains for a given class, as shown in E3. This is due to the fact that while the text embeddings for \"A {domain} of a {class}\" are obtained by training over a large dataset (400 million images), the image embeddings are an average of \\( \\sim 0.01 \\) million images on the downstream dataset. This is illustrated in Fig.1, where the red decision boundary trained using image embeddings misclassifies images from the unseen target domain, while the green classifier trained using the generic text embeddings is closer to an ideal decision boundary. However, an average image embedding on the target domain improves results significantly (E4). The accuracy improves further when an average embedding corresponding to a few (10) source domain images closest (in terms of cosine similarity of image embeddings) to the target image is used for each class during prediction (E5). A similar experiment using images from the target domain (E6), achieves considerable improvements over the zero-shot accuracy in E1. We can consider E6 as an In-(target)-Domain setting where a labeled hold-out validation set is used during prediction for obtaining the average embeddings. Therefore, it is possible to outperform the generalized representations of the text embeddings only when labeled images from the target domain are available. Thus, in a DG setting where the target domain is inaccessible, the generic text embeddings provide the best robustness across distribution shifts. We therefore use the text embeddings to maximally transfer their robustness to the student model." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.09, + 0.807, + 0.108 + ], + "angle": 0, + "content": "5. Proposed Approach: VL2V-ADiP" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.115, + 0.892, + 0.192 + ], + "angle": 0, + "content": "In this section, we first present the knowledge distillation framework adapted to a VLM-to-vision distillation setting. We further propose a self-distillation approach VL2V-SD, to enhance the robustness of the VLM image encoder, which motivates the proposed approach VL2V-ADiP." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.2, + 0.848, + 0.215 + ], + "angle": 0, + "content": "5.1. Distillation from VLMs to Vision models" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.223, + 0.892, + 0.57 + ], + "angle": 0, + "content": "The standard framework of Knowledge Distillation (KD) [20] applies in the unimodal setting, for instance, where the teacher and student are both vision models. To adapt this to a VLM-to-vision distillation setting, a classification model (which we refer to as a VLM-classifier) is first constructed using the VLM. The feature extractor of the VLM-classifier comes from the image encoder of the VLM, and the linear classifier head obtains its weights from the text embeddings \\(\\mathbf{T}_c\\) corresponding to the captions \"a photo of a {class}\" for all \\(C\\) classes. For every image-label pair \\((x_i,y_i)\\), the VLM-classifier first computes the image embedding \\(\\mathbf{I}_{x_i}\\), and further computes its similarity w.r.t. each of the text embeddings \\(\\mathbf{T}_c\\). The similarity scores \\(\\cos (\\mathbf{I}_{x_i},\\mathbf{T}_c)\\) are considered to be analogous to the logit layer, over which the softmax function is applied. The final distillation loss of the student that is minimized during training is shown below in Eq.4 for a minibatch of size \\(n\\). Here, \\(f_{S}(.)\\) and \\(f_{\\mathrm{T}}(.)\\) represent the softmax representations of the student and teacher respectively, CE represents the Cross-Entropy loss, and KL represents the Kullback-Leibler divergence. Temperature scaling is applied to the logits before computing softmax [20]. We tune over the range - \\(\\{0.1,1,10\\}\\) on the in-domain validation set, and report the baseline best results in Table-3." + }, + { + "type": "equation", + "bbox": [ + 0.586, + 0.582, + 0.891, + 0.599 + ], + "angle": 0, + "content": "\\[\nf _ {\\mathrm {T}} \\left(x _ {i}\\right) = \\operatorname {s o f t m a x} \\left(\\cos \\left(\\mathbf {I} _ {x _ {i}}, \\mathbf {T} _ {c}\\right)\\right) \\tag {3}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.5, + 0.609, + 0.891, + 0.661 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {K D}} = \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\left\\{\\mathrm {C E} \\left(f _ {S} \\left(x _ {i}\\right), y _ {i}\\right) + \\lambda \\cdot \\mathrm {K L} \\left(f _ {\\mathrm {T}} \\left(x _ {i}\\right) \\mid \\mid f _ {S} \\left(x _ {i}\\right)\\right) \\right\\} \\tag {4}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.667, + 0.88, + 0.683 + ], + "angle": 0, + "content": "5.2. Self-Distillation from Text to Image encoders" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.689, + 0.892, + 0.854 + ], + "angle": 0, + "content": "As discussed in Section-4.2, the image encoder of CLIP is trained to represent all factors of variations in an image that are described in the corresponding caption used during its training. Therefore, it does not exhibit the invariances to factors such as color, texture, lighting, and pose, that are required for an image classification task. On the other hand, text prompts allow much better control over invariances in text-embeddings. For example, a prompt such as \"A brown cat sitting on a sofa\" uniquely represents the color, location, and pose of the cat in addition to the object itself, whereas a prompt \"A photo of a cat\" is invariant to such variations." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.856, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Motivated by this, we propose Vision-Language to Vision Self Distillation (VL2V-SD), where the invariances of generic text embeddings are distilled to the image encoder" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "23925" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.081, + 0.089, + 0.345, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.245, + 0.289, + 0.422, + 0.302 + ], + "angle": 0, + "content": "CLIP image encoder/features" + }, + { + "type": "image_caption", + "bbox": [ + 0.245, + 0.306, + 0.407, + 0.319 + ], + "angle": 0, + "content": "CLIP text encoder / features" + }, + { + "type": "image", + "bbox": [ + 0.352, + 0.089, + 0.613, + 0.284 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.43, + 0.289, + 0.533, + 0.301 + ], + "angle": 0, + "content": "Networkfrozen" + }, + { + "type": "image_caption", + "bbox": [ + 0.428, + 0.306, + 0.545, + 0.319 + ], + "angle": 0, + "content": "Network trainable" + }, + { + "type": "image_caption", + "bbox": [ + 0.556, + 0.289, + 0.715, + 0.302 + ], + "angle": 0, + "content": "Student network / features" + }, + { + "type": "image_caption", + "bbox": [ + 0.556, + 0.306, + 0.7, + 0.318 + ], + "angle": 0, + "content": "CLIP zero-shot classifier" + }, + { + "type": "image_caption", + "bbox": [ + 0.674, + 0.094, + 0.8, + 0.107 + ], + "angle": 0, + "content": "Stage 3 (Predict)" + }, + { + "type": "image", + "bbox": [ + 0.622, + 0.121, + 0.888, + 0.25 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.335, + 0.894, + 0.364 + ], + "angle": 0, + "content": "Figure 2. Overview of the proposed approach VL2V-ADiP, consisting of (a) Align, (b) Distill and (c) Predict Stages for Black-Box Distillation from Vision-Language to Vision (VL2V) models." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.383, + 0.47, + 0.459 + ], + "angle": 0, + "content": "using the downstream dataset. We minimize the loss shown in Eq.5 for training, where \\(\\mathbf{T}_{y_i}\\) represents the embedding for \"A photo of a {class}\" corresponding to the ground truth class \\(y_{i}\\), and \\(\\mathbf{I}_{x_i}^t\\), \\(\\mathbf{I}_{x_i}^s\\) represent the image embeddings of the teacher and student respectively for an image \\(x_{i}\\)." + }, + { + "type": "equation", + "bbox": [ + 0.1, + 0.465, + 0.47, + 0.504 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {S D}} = - \\frac {1}{2 n} \\sum_ {i = 1} ^ {n} \\left\\{\\cos \\left(\\mathbf {I} _ {x _ {i}} ^ {s}, \\mathbf {T} _ {y _ {i}}\\right) + \\cos \\left(\\mathbf {I} _ {x _ {i}} ^ {s}, \\mathbf {I} _ {x _ {i}} ^ {t}\\right) \\right\\} \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.508, + 0.473, + 0.901 + ], + "angle": 0, + "content": "The image encoders of both teacher and student are the same (VLM's image encoder) initially, and the student's image encoder is updated during training. The text encoder is frozen during training. While the first term enforces the image encoder to learn representations that match the corresponding text embeddings more accurately on the given dataset, the second term ensures that there is no representation collapse, and retains the rich features learned by the image encoder. The classifier is composed of text embeddings corresponding to the prompts \"a photo of a {class}\" for all classes, as was the case in the VLM-classifier discussed in Section-5.1. We present the results of VL2V-SD in Table2, where we note significant improvements over both CLIP zero-shot and the SOTA DG methods - SWAD [8], MIRO [9], DART [23], and SAGM [61] on the ViT-B/16 architecture with CLIP initialization. We demonstrate significant gains over the CLIP fine-tuning methods LP-FT [28], FLYP [18], CLIPood [55], and WiSE-FT [63]. We also achieve significant gains over a distillation method RISE [22], despite using the standard text prompt while RISE uses an expanded set of prompts. For WiSE-FT, we present the results with the optimal \\(\\alpha\\) that achieves the best performance by using the search space \\(\\alpha = [0.1 - 0.9]\\). Similarly, for RISE, we present the results with the optimal hyperparameters \\(\\lambda_1, \\lambda_2, \\lambda_3\\) based on their search space. We incorporate SWAD [8] in all our runs for the baselines as well" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.381, + 0.893, + 0.424 + ], + "angle": 0, + "content": "Table 2. White-Box setting (CLIP initialization): Performance \\((\\%)\\) of the proposed approach VLV2-SD, compared to the existing methods. ViT-B/16 architecture is used. (S) denotes SWAD [8]." + }, + { + "type": "table", + "bbox": [ + 0.502, + 0.427, + 0.892, + 0.565 + ], + "angle": 0, + "content": "
MethodOHTIVLCSPACSDNAvg-IDAvg-OOD
Zero-shot [47]82.4034.1082.3096.5057.70-70.60
SWAD [8]81.0142.9279.1391.3557.9289.0570.47
MIRO (S) [9]84.8059.3082.3096.4460.4791.0076.66
DART (S) [23]80.9351.2480.3893.4359.3289.2573.06
SAGM (S) [61]83.4058.6482.0594.3159.0589.7475.49
LP-FT (S) [28]81.1747.2680.8892.9257.0488.9771.85
FLYP (S) [18]82.7633.2566.6478.5357.4178.9463.72
CLIPood (S) [55]83.3146.2877.1993.1657.7869.9071.55
WiSE-FT (S) [63]86.3254.5082.8897.2958.0188.3575.80
RISE (S) [22]78.3949.6180.6293.2555.3787.9171.45
VL2V-SD (Ours)87.3858.5483.2596.6862.7989.9977.73
" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.577, + 0.892, + 0.669 + ], + "angle": 0, + "content": "as the proposed approach (denoted by “(S)”) since it is a generic technique that improves the generalization of any given method. However, we do not incorporate SWAD with WiSE-FT since it already performs weight averaging of the pre-trained and fine-tuned models. We present the results without SWAD in Suppl. Sec-3.2." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.679, + 0.869, + 0.696 + ], + "angle": 0, + "content": "5.3. VL2V - Align, Distill, Predict (VL2V-ADiP)" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.703, + 0.892, + 0.854 + ], + "angle": 0, + "content": "While VL2V-SD is very effective in improving the performance of the VLM in a white-box setting, it does not address the problem of black-box distillation that we consider in this work, since it assumes access to the weights of the VLM model. In this section, we discuss how this method can be adapted to the black-box setting and present the proposed approach VL2V-ADiP. Since the amount of downstream task-specific data is assumed to be limited, the student is initialized with the best available pre-trained model such as ImageNet [26]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.893, + 0.901 + ], + "angle": 0, + "content": "In the self-distillation case seen in Section-5.2, the goal was to induce domain invariance from the text encoder to the image encoder, while ensuring that the rich features" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23926" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.41 + ], + "angle": 0, + "content": "learned by the image encoder are not lost. Whereas, in the black-box setting, the goal is to distill the rich features learned by the image-encoder of the VLM and the domain invariance from the text embeddings. While the two cases can have a similar loss formulation as shown in Eq.5, the method VL2V-SD cannot directly be applied here since the feature dimension of the student model may be different from the dimension of VLM's image and text embeddings. Even if the dimensions had matched, the features of the ImageNet pre-trained backbone and VLM's embeddings would be misaligned. Directly enforcing a similarity loss in such a case would lead to forgetting of the pretrained features. To address this, we propose VL2V-ADiP, Vision-Language to Vision - Align, Distill, Predict as shown in Fig.2 (Ref: Alg. 1 in Suppl.). We propose to first Align the features of the pre-trained student model with VLM embeddings using a linear projection head on the student backbone in Stage-1, as shown in Fig.2(a). For this, the student backbone is frozen and only the projection head is trained using the following loss, where \\(\\mathbf{PF}_{x_i}^s\\) represents the projected features of the student model for the input \\(x_{i}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.088, + 0.425, + 0.469, + 0.476 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {A D i P}} = - \\frac {1}{2 n} \\sum_ {i = 1} ^ {n} \\left\\{\\cos \\left(\\mathbf {P F} _ {x _ {i}} ^ {s}, \\mathbf {T} _ {y _ {i}}\\right) + \\cos \\left(\\mathbf {P F} _ {x _ {i}} ^ {s}, \\mathbf {I} _ {x _ {i}} ^ {t}\\right) \\right\\} \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.479, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Next, the aligned student features are refined using the VLM's image and text embeddings in the Distill step as shown in Fig.2(b) (Stage-2). For this step, the linear projection head is frozen, and the feature extractor is trained using the same loss as Stage-1, as shown in Eq.6. While we give equal weight to both loss terms in Eq.6, we present the impact of varying this in Suppl. Sec-4. Finally, in Stage-3 (Predict), the VLM's embeddings corresponding to \"a photo of a {class}\" for all \\( C \\) classes are used as weights of the classification head, and the class with the highest similarity to the given image embedding is predicted, as shown in Eq.2. In addition to learning the rich features from the VLM teacher's image-encoder and invariances from its text encoder, enforcing similarity between the features of the student backbone and the text embeddings of the corresponding classes also makes the text embeddings more suitable for use as a classifier in Stage-3 (Predict). Thus, although Stages 1 and 2 explicitly train only the student backbone and projection head, they implicitly impact the effectiveness of the classification head as well. This facilitates the use of these embeddings directly as a classifier without the need for fine-tuning further on the downstream dataset. As shown in Table-5, further fine-tuning degrades the performance, since only In-Domain (ID) data is available for fine-tuning, which would make the classifier forget the domain invariance that it inherently possesses. However, fine-tuning with limited In-Domain data improves the ID accuracy as shown in the table." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.091, + 0.735, + 0.108 + ], + "angle": 0, + "content": "6. Experiments and Results" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.115, + 0.68, + 0.131 + ], + "angle": 0, + "content": "6.1. Evaluation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.138, + 0.895, + 0.397 + ], + "angle": 0, + "content": "Towards evaluating the OOD generalization of image classification models, we consider the five popular Domain Generalization (DG) datasets - OfficeHome (OH) [60], PACS [30], VLCS [16], Terra-Incognita (TI) [3] and DomainNet (DN) [44]. Each of the datasets consists of \\(d\\) domains, where \\(d = 4\\) for the first four datasets and \\(d = 6\\) for DomainNet. We present more details on the datasets in Suppl. Sec-2. We follow the DomainBed [19] framework for training and evaluation, where each domain is split into training and validation sets, and training is performed on \\(d - 1\\) domains while evaluation is done on the \\(d^{th}\\) unseen domain. Thus, for every dataset, \\(d\\) models are trained, by leaving one domain out for evaluation each time. The average accuracy across these \\(d\\) runs on the unseen test domain (OOD accuracy) and the average In-domain (ID) validation split accuracy are reported. The unseen test domain is neither used for training nor for hyperparameter tuning [19]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.406, + 0.663, + 0.422 + ], + "angle": 0, + "content": "6.2. Training Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.43, + 0.895, + 0.793 + ], + "angle": 0, + "content": "The number of training iterations is set to 5000 for OfficeHome, PACS, VLCS, and Terra-Incognita, and to 15000 for DomainNet, as is standard [8, 9]. We use the Adam optimizer with a constant learning rate of \\(5 \\times 10^{-5}\\) for all our experiments except CLIPood (S) in Table-2, for which we use the AdamW optimizer as specified in [55]. These settings are fixed for all datasets, and we do not introduce any additional hyperparameters in the proposed algorithm. Our primary evaluations consider a ViT-B/16 architecture [15] for both the VLM (teacher) Image-encoder and the student model to enable a fair comparison with existing methods, that use the same architecture. Since one of the key motivations of distillation is to train a low-capacity model, we present results with lower-capacity student architectures as well. We use a CLIP teacher model, which uses a Transformer architecture [59] with modifications described by Radford et al. [46] for the text encoder. The student model and our primary baselines for VL2V-ADiP use an ImageNet pre-trained initialization [26], as is standard in DG [19]. We obtain the results of baseline methods on ViTs in Tables 2 and 3 by integrating the official code of the respective method with the MIRO [9] code base to ensure a fair comparison. Additionally, we show results with other teacher VLMs in Suppl. Sec-3.3." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.802, + 0.75, + 0.818 + ], + "angle": 0, + "content": "6.3. Comparison with the SOTA" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.894, + 0.903 + ], + "angle": 0, + "content": "We present the ID and OOD results of the proposed approach VL2V-ADiP when compared to the DG and KD baselines in Table-3. Gulrajani and Lopez-Paz [19] show that ERM training is a very strong baseline in DG and outperforms several older methods that were proposed. Thus," + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23927" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.089, + 0.472, + 0.146 + ], + "angle": 0, + "content": "Table 3. SOTA comparison with ImageNet initialization: Performance (%) of the proposed approach VL2V-ADiP, compared to existing KD and DG methods with SWAD (S). ViT-B/16 with ImageNet-1K initialization is used as the student." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.147, + 0.472, + 0.271 + ], + "angle": 0, + "content": "
MethodOHTIVLCSPACSDNAvg-IDAvg-OOD
ERM-LP (S)71.4831.3577.5267.0236.6573.9956.81
ERM Full Fine-tuning (S)83.2250.0580.3390.2856.1089.3172.00
LP-FT (S) [28]81.5551.6180.1791.2056.0390.0372.11
SimKD (S) [13]66.7681.0183.9228.2449.4268.2461.87
KD (S) [20]82.7348.4080.4891.4656.1189.2071.84
MIRO (S) [9]80.0950.2981.1089.5055.7588.7171.35
DART (S) [23]83.7549.6877.2990.5558.0588.5471.86
SAGM (S) [61]82.2253.2479.6090.0255.6689.2272.15
Text2Concept (S) [40]70.2426.4664.7779.0323.2653.1552.82
RISE (S) [22]83.4852.5583.7093.5456.5888.9173.97
VL2V-ADiP (Ours)85.7455.4381.9094.9459.3889.0275.48
" + }, + { + "type": "table_caption", + "bbox": [ + 0.077, + 0.288, + 0.472, + 0.357 + ], + "angle": 0, + "content": "Table 4. Distillation to lower capacity student models: Performance (\\%) of the proposed approach VL2V-ADiP (denoted as Ours), when compared to the KD baseline [20] and ERM (S) or SWAD [8] with different student architectures. The teacher architecture is ViT-B/16. (S) denotes SWAD." + }, + { + "type": "table", + "bbox": [ + 0.078, + 0.359, + 0.472, + 0.516 + ], + "angle": 0, + "content": "
StudentMethodOHTIVLCSPACSDNAvg-IDAvg-OOD
ViT-B/16 (86M)ERM (S)83.2250.0580.3390.2856.1089.3172.00
KD (S)82.7348.4080.4891.4656.1789.2071.85
Ours (S)85.7455.4381.9094.9459.3889.0275.48
ViT-S/16 (22M)ERM (S)78.5849.4078.7285.8052.0985.6668.92
KD (S)78.1450.1179.1485.9752.0587.4369.08
Ours (S)81.2252.4781.4489.3254.2386.5971.73
DeiT-S/16 (22M)ERM (S)74.9547.8579.3789.2249.1886.5868.12
KD (S)74.6548.1178.8688.1449.1086.6667.77
Ours (S)77.6348.7281.8988.9750.3785.2869.52
ResNet-50 (26M)ERM (S)70.8549.4779.5088.0546.4384.8866.86
KD (S)70.6751.2278.6387.2346.3185.0466.81
Ours (S)74.4253.4679.2386.7247.7484.7368.31
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.539, + 0.473, + 0.903 + ], + "angle": 0, + "content": "ERM training of only the linear layer (ERM-LP) and ERM full fine-tuning (ERM-FFT) are two important baselines we consider. Further, we present the results of important SOTA DG methods - SWAD [8], MIRO [9], DART [23], and SAGM [61]. Additionally, we also show results with Text2Concept [40] and LP-FT [28] - simple fine-tuning strategies for improved OOD generalization on downstream tasks. While there are several methods that outperform ERM [6, 25, 41, 57], we do not present all of them here since the above-listed recent methods outperform them. Since we incorporate SWAD in the proposed approach, we present all the baseline results by integrating SWAD with each of them and denote them with a suffix \"S\" in the tables. Additionally, we also present three distillation results - (a) knowledge distillation from the VLM teacher to the vision student model as discussed in Section-5.1 and (b) distillation from the VLM teacher using SimKD [13], and (c) distillation from the VLM teacher using RISE [22]. Since the feature distillation methods listed in Sec. 2 cannot be extended to the black box distillation setting, we do not compare with them. The proposed approach VL2V-ADiP achieves \\(\\sim 1.5\\%\\) improvement on average OOD accuracy across all datasets with respect to the best baselines, with comparable ID accuracy. We note that Text2Concept scales" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.214 + ], + "angle": 0, + "content": "poorly on smaller datasets compared to the results shown in the paper [40]. SimKD [13] is a method intended for unimodal distillation and thus fails for the multimodal setup. Furthermore, we outperform the method RISE [22] by a large margin despite the latter using expanded text prompts. This shows that the proposed distillation method VL2V-ADiP effectively distills from VLMs with lesser prompt engineering and text supervision compared to RISE." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.224, + 0.878, + 0.24 + ], + "angle": 0, + "content": "6.4. Distillation to lower capacity student models" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.247, + 0.895, + 0.43 + ], + "angle": 0, + "content": "We present results of distilling from a CLIP ViT-B/16 teacher to different student architectures and capacities (ViT-S/16, DeiT-S, ResNet-50) in Table-4. We observe substantial gains over the Knowledge Distillation and ERM (S) or SWAD baseline across all student architectures. We note that the distillation performance is best when the architecture (ViT) of the teacher matches that of the student. For example, although ViT-S/16, DeiT-S/16, and ResNet-50 have a similar number of parameters, the performance of the ViT-S/16 student is the best, showing the architecture plays a role in the nature of representations learned, thereby allowing better transfer when they match." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.439, + 0.654, + 0.456 + ], + "angle": 0, + "content": "6.5. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.463, + 0.895, + 0.75 + ], + "angle": 0, + "content": "We present an ablation study of the proposed method in Table-5. Firstly, we study the impact of combining stages-1 (Align) and 2 (Distill), i.e., training the linear projection layer and the backbone jointly in A1. This results in a \\(2.2\\%\\) drop in ID accuracy and a \\(6.3\\%\\) drop in OOD accuracy, highlighting that the pre-trained ImageNet features are retained better when they are aligned before distillation. In A2, the linear projection head is also trained in Stage-2. The results of this case are similar to the proposed approach, showing that even when the linear head is changed, it does not get updated much after Stage-1 (Align). We next analyze the importance of distilling from both image and text encoders of CLIP by using only one of them individually in A3 and A4. In both cases, we note a significant drop in the OOD accuracy highlighting the importance of distilling from both encoders. Distilling only from the Image encoder has a larger drop due to the lack of alignment between the representations and the classifier head which is composed of CLIP text embeddings corresponding to each of the classes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.897, + 0.903 + ], + "angle": 0, + "content": "In Stage-3 (Predict) of the proposed approach, the CLIP text embeddings corresponding to the classes are directly used as the classifier weights. We explore the impact of training this classifier further using cross-entropy loss over the softmax representations shown in Eq.3, in experiments A5-A8. In A5 and A6, the classifier head is first initialized using the text embeddings of CLIP, and in A7 and A8, a random initialization is used for the classification head. In A5 and A7, only the classifier head is trained, whereas in A6 and A8, the full network is trained. All these experi" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.946, + 0.521, + 0.957 + ], + "angle": 0, + "content": "23928" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.12, + 0.089, + 0.85, + 0.104 + ], + "angle": 0, + "content": "Table 5. Ablation Study of the proposed VL2V-ADiP: Performance (%) on ViT-B/16 model with ImageNet initialization." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.108, + 0.895, + 0.248 + ], + "angle": 0, + "content": "
Method - Changes done w.r.t. VL2V-ADiP (Ours)OHTIVLCSPACSAvg-IDAvg-OOD
VL2V-ADiP (Ours)85.7455.4381.9094.9492.7479.50
A1: Combining "Align" and "Distill" stages74.5552.9980.1485.2990.5573.24
A2: Without freezing projection head in Stage-286.1356.6881.7893.7593.0079.59
A3: Distilling only from Text encoder in Stages-1 and 283.1847.0279.8390.8691.8775.22
A4: Distilling only from Image encoder in Stages-1 and 278.9728.9782.2489.9774.0970.04
A5: Finetuning CLIP classifier-head in Stage-3 (CE loss) - CLIP init classifier84.4749.2881.3093.5493.0677.15
A6: Finetuning full network in Stage-3 (CE loss) - CLIP init classifier83.8849.8380.1392.2593.3776.52
A7: Finetuning classifier-head in Stage-3 (CE loss) - random init classifier84.6349.5581.2993.5793.0277.26
A8: Finetuning full network in Stage-3 (CE loss) - random init classifier83.1650.0379.7892.1593.1476.28
" + }, + { + "type": "image", + "bbox": [ + 0.078, + 0.258, + 0.891, + 0.41 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.413, + 0.893, + 0.444 + ], + "angle": 0, + "content": "Figure 3. OOD accuracy \\((\\%)\\) of the proposed approach when compared to KD and ERM baselines for select classes/ domains in Office-Home and Terra-Incognita datasets, where the (a) ERM-IN (linear) (b) CLIP Zero-shot (c) ERM-CLIP (linear) performance is poor." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.454, + 0.473, + 0.606 + ], + "angle": 0, + "content": "ments result in a drop in the OOD accuracy, indicating that training on the downstream dataset using the cross-entropy loss can destroy the domain invariances learned from CLIP. Since the impact of training the full network is higher, the drop is higher in this case when compared to finetuning only the classification head. In all cases, the In-Domain accuracy improves when compared to the proposed approach, with higher gains in the case when the full network is trained, confirming that training without the supervision of the CLIP teacher indeed overfits to the training domains." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.614, + 0.473, + 0.903 + ], + "angle": 0, + "content": "We also compare the ERM and KD baselines with the proposed approach in some of the extreme cases in Fig.3, where the CLIP Image encoder is significantly better than the ERM model (a), and vice-versa (c). For this, we select the classes/domains with the highest difference \\((40 - 50\\%)\\) between the ERM-CLIP (Linear) and ERM-ImageNet (IN) (Linear) baselines from the OfficeHome dataset. We also present the case where the CLIP zero-shot accuracy is poor in OfficeHome \\((22\\%)\\) and Terra-Incognita datasets \\((0\\%)\\) in Fig.3 (b). The KD baseline relies a lot on the ImageNet pre-trained backbone, hence it is poor when ERM-IN is poor, and is close to our approach when ERM-IN is good. The ERM fine-tuning baseline is best when the ImageNet features are much better than CLIP Image encoder's features, but it is poor in the other case, as expected. Lastly, even when CLIP zero-shot accuracy is poor (close to \\(0\\%\\)), the proposed approach achieves reasonable accuracy, since Stages-1 and 2 align the text embeddings better to the feature extractor, making them more suitable as a classifier." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.452, + 0.62, + 0.468 + ], + "angle": 0, + "content": "7. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.478, + 0.892, + 0.825 + ], + "angle": 0, + "content": "In this work, we aim to leverage the superior generalization of large-scale Vision-Language Models towards improving the OOD generalization of Vision models. We consider a practical scenario where a client gets only black-box access to the model on a pay-per-query basis from the vendor, motivating the need for distilling the model first, and further using the student model during inference. Towards this, we first highlight the unique aspects of the image and text encoders of VLMs and further propose a self-distillation (SD) approach - VL2V-SD, to distill the superior generalization of the VLM's text encoder to its image encoder, while retaining the rich representations of the latter. We further adapt this to a black-box distillation setting, by firstly projecting the representations of the pre-trained feature-extractor (student) to a space that is aligned with embeddings of the VLM teacher, and further finetuning the backbone using the same. The use of both text and image embeddings induces the rich representations of the VLM and its superior generalization to the student model, while also making the text embeddings more suitable for use in the classification head. Both proposed approaches (VL2V-SD and VL2V-ADiP) achieve substantial gains over prior methods on the popular Domain Generalization datasets." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Acknowledgements. This work is supported by the Kotak IISc AI-ML Center and a research grant CRG/2021/005925 from SERB, DST, Govt. of India. Sravanti Addepalli is supported by the Google PhD Fellowship and CII-SERB Prime Minister's Fellowship for Doctoral Research." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "23929" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.175, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.156 + ], + "angle": 0, + "content": "[1] Martin Arjovsky, Léon Bottou, Ishaan Gulrajani, and David Lopez-Paz. Invariant risk minimization. arXiv preprint arXiv:1907.02893, 2019. 2" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.159, + 0.47, + 0.213 + ], + "angle": 0, + "content": "[2] Devansh Arpit, Huan Wang, Yingbo Zhou, and Caiming Xiong. Ensemble of averages: Improving model selection and boosting performance in domain generalization. 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IJCV, 2022. 3" + }, + { + "type": "list", + "bbox": [ + 0.08, + 0.092, + 0.47, + 0.19 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "23932" + } + ] +] \ No newline at end of file diff --git a/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_origin.pdf b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..910856c092be11743de09965bee5b34e70f424a2 --- /dev/null +++ b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/229a1582-b514-420e-a818-a61870d35925_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:7a3a279e7e252751a48a0411d522aa2d0ee5292fcb64fa0380e32cc011c145e7 +size 509060 diff --git a/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/full.md b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/full.md new file mode 100644 index 0000000000000000000000000000000000000000..4de0cfddc2c869559a6421d4d826eaf9ad616e4f --- /dev/null +++ b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/full.md @@ -0,0 +1,270 @@ +# Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification + +Sravanti Addepalli * Ashish Ramayee Asokan * Lakshay Sharma R. Venkatesh Babu Vision and AI Lab, Indian Institute of Science, Bangalore + +# Abstract + +Vision-Language Models (VLMs) such as CLIP are trained on large amounts of image-text pairs, resulting in remarkable generalization across several data distributions. However, in several cases, their expensive training and data collection/curation costs do not justify the end application. This motivates a vendor-client paradigm, where a vendor trains a large-scale VLM and grants only input-output access to clients on a pay-per-query basis in a black-box setting. The client aims to minimize inference cost by distilling the VLM to a student model using the limited available task-specific data, and further deploying this student model in the downstream application. While naive distillation largely improves the In-Domain (ID) accuracy of the student, it fails to transfer the superior out-of-distribution (OOD) generalization of the VLM teacher using the limited available labeled images. To mitigate this, we propose Vision-Language to Vision - Align, Distill, Predict (VL2V-ADiP), which first aligns the vision and language modalities of the teacher model with the vision modality of a pre-trained student model, and further distills the aligned VLM representations to the student. This maximally retains the pre-trained features of the student, while also incorporating the rich representations of the VLM image encoder and the superior generalization of the text embeddings. The proposed approach achieves state-of-the-art results on the standard Domain Generalization benchmarks in a black-box teacher setting as well as a white-box setting where the weights of the VLM are accessible. Project page: http://val.cds.iisc.ac.in/VL2V-ADiP/ + +# 1. Introduction + +While the initial success of Deep Learning was predominantly driven by training specialized models for each task or dataset [26, 29], recent research on foundation models [24, 34, 47, 65] eliminates the need for this by training generic models jointly over several modalities using large- + +![](images/139f047a9cc70387e0c8325960c851b3c4c5d6493ca2e3dbd0fd6766c3d67f88.jpg) +Figure 1. Schematic diagram showing class and domain distributions in the shared text/ image embedding space of a VLM: VLMs learn highly specialized image representations that are not domain invariant. Thus, a linear classifier (red decision boundary) that is trained over the vision encoder using limited training data cannot generalize well to the target domain (shown in purple). On the other hand, generic text embeddings such as "A photo of a class" represent the core concept of a class by virtue of their training method and vast training data. Thus, they generalize effectively across domains, and a zero-shot classifier (green decision boundary) aligns better with the true distribution of classes. + +scale data. The use of both image and language modalities in large-scale Vision-Language Models (VLMs) enables their use in several applications including zero-shot classification, where the embedding of an image is compared with text embeddings for "a photo of a {class}" corresponding to every class during inference and the class with highest similarity is predicted. For example, the LiT (private) model [65] has been trained on 4 billion image-text pairs scraped from the web, and it achieves $85.2\%$ zero-shot accuracy on ImageNet. VLMs also demonstrate extraordinary performance across several distributions, owing to the vast diversity of distributions seen during their training [47]. + +The remarkable OOD generalization of VLMs makes them suitable for use in several applications, either directly + +or after finetuning on the downstream target dataset. Although several open-sourced models such as CLIP [47] are easily accessible, they may not be suitable for use in specialized applications. For example, the training data may have to be curated to reduce biases in the model or to ensure data privacy. It may also be important to ensure that the web-crawled data is clean for adoption in critical applications such as autonomous driving, to avoid data-poisoning attacks [4, 7]. Further, general-purpose models cannot be used in specialized applications such as medical diagnosis, where a VLM trained on data containing expert comments can be invaluable. This motivates the need for training highly specialized VLMs, which can be expensive due to the high costs associated with data collection/ curation and training. + +A given downstream application may not always justify the cost associated with training such large-scale models. However, since these VLMs are generic and applicable to several downstream applications, one vendor could train such a model, and make it available to several clients in a black-box setting on a pay-per-query basis. In this case, the client can minimize their inference time costs by distilling the VLM to a student model using the limited available data specific to the downstream task, and deploying the distilled model rather than the VLM. Since the key motivation of using VLMs is their generalization to several domains, reliable OOD performance of the distilled model is crucial. + +In this work, we consider the problem of distilling a multimodal Vision-Language model to a unimodal Vision model using limited task-specific downstream data, targeted toward better OOD performance with respect to the training domains used for distillation. While standard distillation of VLMs would require training data comprising of images and their associated text, in this case, the training data consists of only labeled images, similar to a classification task. Moreover, since the superior generalization abilities of VLMs are a result of the large-scale data ( $\sim 400$ million in the case of CLIP) used for their training, it is challenging to transfer these generalization abilities using a limited dataset comprising around 10,000 (0.01 million) images [16, 30, 60]. Lastly, since the VLM is considered to be a black box, the image encoder's weights cannot be used as initialization to the vision model for further fine-tuning. However, since the downstream task-specific data is limited and is insufficient to train models from scratch, we assume that the student is initialized with weights from a model pretrained on a publicly available dataset such as ImageNet-1K [26], as is common in a domain-generalization setting [19]. + +While knowledge distillation [20] using the labeled task-specific images improves the In-Domain accuracy on the downstream task, the improvement in OOD accuracy is marginal due to the limited size of the dataset. To address this, we first analyze the robustness of the text and image embeddings from the VLM and highlight the impor + +tance of text embeddings for better OOD generalization (see Fig.1). Further, we propose VL2V-ADiP: Vision-Language to Vision - Align, Distill, Predict, to firstly align the features of the pre-trained student model with the text and image modalities of the VLM teacher, and further fine-tune the student backbone in a distillation framework. This improves the robustness of the student, while also aligning the student embeddings to the VLM's text embeddings corresponding to the respective class, thereby making the latter suitable for use as a classifier in the student without the need for further training. We summarize our contributions below: + +- We investigate the robustness of image and text embeddings of VLMs, and highlight the importance of the text embeddings for better OOD generalization. +- To demonstrate the superior generalization of text embeddings, we propose VL2V-SD - a self-distillation approach, that improves the OOD generalization of the VLM's pre-trained vision encoder using supervision from its own text encoder in a white-box VLM setting. +- We further propose VL2V-ADiP - a black-box distillation approach that effectively combines the features of a pretrained vision model with the text and vision encoders of a VLM teacher for better OOD generalization. +- We demonstrate state-of-the-art results on standard Domain Generalization benchmark datasets in both white-box and black-box settings of the VLM teacher. + +# 2. Related Works + +Vision-Language Models (VLMs): VLMs are trained on large-scale datasets of image-text pairs crawled from the web [10, 53, 58]. Contrastive pre-training methods [24, 34, 47, 65] maximize the similarity between the embeddings of matching image-text pairs. More recent efforts focus on scaling up image-text pre-training to larger datasets [34], better supervision with unimodal and multimodal data [56], data-efficient pre-training [36], and fine-tuning VLMs for downstream tasks [18, 28, 63]. Another line of work focuses on leveraging CLIP [47] to improve the OOD generalization in image classification [40, 55]. + +Domain Generalization (DG): Prior works learn domain invariant representations by using augmentations [41, 42, 50], feature alignment across domains [17, 33, 35, 57], and disentangling domain-specific and domain-invariant features [11, 38, 45]. Gulrajani et.al [19] demonstrate that a well-tuned ERM model is comparable to several past DG algorithms [1, 5, 21, 27, 31, 32, 52, 62, 66]. SWAD [8] is a generic strategy that performs weight-averaging across different model snapshots in the optimal basin during training. MIRO [9] proposes Mutual Information (MI) regularization to maximally retain the pre-trained model's representations. SAGM [61] aligns gradient directions between the $\epsilon$ -perturbed loss and the empirical risk. We demonstrate performance gains when compared to the existing DG methods + +Table 1. CLIP on DG datasets: Performance $(\%)$ of CLIP ViT-B/16 model on using different embeddings in the classifier head for computing similarity w.r.t. the test image during inference (T.E.: Text Embedding, I.E.: Image Embedding). + +
Embedding used for computing similarityOHTIVLCSPACSAvg.
E1: Text embedding for "A photo of a {class}"82.3634.1982.0896.1073.68
E2: Avg. text embedding for "A {domain} of a {class}" across all train domains83.7035.5582.2896.2174.44
E3: Avg. image embedding of each class (Source)71.3733.9948.2179.0358.15
E4: Avg. image embedding of each class (Target)78.2138.6969.3193.0869.82
E5: Avg. image embedding of 10 images per class closest to test image (Source)76.4239.3376.4292.1571.08
E6: Avg. image embedding of 10 images per class closest to test image (Target)84.8685.3887.8898.3289.11
+ +in both white-box and black-box settings of the VLM. More recently, several methods perform diverse training of multiple models, followed by weight-averaging to improve OOD generalization [2, 23, 48, 49]. However, they incur the enormous expense of training several diverse models. We thus restrict our comparison to DART [23], where the number of models trained is lower than the others. Another direction has been the generation of better prompts for improved generalization of VLMs [39, 54, 67]. These methods can be integrated with the proposed approach. + +Knowledge Distillation (KD): Knowledge distillation aims to transfer knowledge from a powerful teacher model to a compact student model. Output-distillation [20] uses the teacher's softmax outputs as guidance for the student. Feature-distillation methods [12-14, 37, 43, 51] use the teacher's intermediate representations as guidance since they contain richer information. The proposed method operates in the black box distillation setup that allows only input-output access to the teacher network and restricts access to intermediate features. We thus compare the proposed black-box approach only with methods that do not access intermediate features [13, 20, 22]. + +# 3. Notations + +We consider the problem of Knowledge Distillation (KD) from VLMs (teacher) to vision models (student) for improved OOD generalization. We denote the VLM's text embedding for the input, "A photo of a {class}" for class $c$ as $\mathbf{T}_c$ . The image embedding corresponding to the image $x$ is denoted as $\mathbf{I}_x$ . The student model's features corresponding to an input $x$ are denoted as $\mathbf{F}_x$ . These features when projected to the same dimension as the VLM embeddings $(\mathbf{I}_x$ and $\mathbf{T}_c)$ , are denoted as $\mathbf{P}\mathbf{F}_x$ . The cosine similarity between two vectors $\mathbf{a}$ and $\mathbf{b}$ is denoted as $\cos(\mathbf{a},\mathbf{b})$ . While we use CLIP [47] as the teacher for most of our analysis and experiments, we show the compatibility of the proposed approach with other VLMs [34, 36, 56, 64] in Suppl. Sec-3.3. + +# 4. Robustness of CLIP embeddings + +In this section, we present an overview of the training and zero-shot evaluation of the CLIP model, followed by a study on the robustness of its image and text embeddings. + +# 4.1. CLIP training and zero-shot prediction + +CLIP is a VLM that consists of an image encoder and a text encoder trained jointly on 400 million web-scraped image-text pairs [47]. The outputs of CLIP are the text and image embeddings for the respective text and image inputs. CLIP is trained using a contrastive loss which enforces similarity between the representations of positive image-text pairs and disparity between the representations of negative image-text pairs in the training minibatch. The training objective of CLIP is shown in Eq.1, where the embeddings of the $i^{th}$ image-text pair are represented as $\mathbf{I}_i$ and $\mathbf{T}_i$ respectively.: + +$$ +\mathcal {L} _ {\mathrm {C L I P}} \left(x _ {i}\right) = - \log \frac {\exp \left(\cos \left(\mathbf {I} _ {i} , \mathbf {T} _ {i}\right)\right)}{\sum_ {c = 1} ^ {C} \exp \left(\cos \left(\mathbf {I} _ {i} , \mathbf {T} _ {c}\right)\right)} \tag {1} +$$ + +The use of both text and image modalities during training enables the effective use of text embeddings as a zero-shot classifier, where inference can be performed directly without access to training data. For this, the text embeddings $\mathbf{T}_c$ corresponding to the captions "A photo of a {class}" for each of the $C$ classes are compared with the image embedding $\mathbf{I}_i$ , and the class with maximum similarity is predicted as shown in Eq.2. Thus, the text embeddings $\mathbf{T}_c$ can be viewed as the weights of a classifier for a CLIP backbone. + +$$ +\hat {y} _ {i} = \operatorname {a r g m a x} _ {c} \cos \left(\mathbf {I} _ {i}, \mathbf {T} _ {c}\right) \tag {2} +$$ + +# 4.2. Characteristics of image and text embeddings + +CLIP [47] shows remarkable zero-shot performance as shown in Table-1 (E1), and outperforms even an ImageNet pre-trained model that is explicitly fine-tuned using the downstream dataset (Table-3) on several DG datasets. To understand its superior zero-shot performance, we discuss below the robustness of its image and text embeddings. + +Characteristics of the Image Encoder: In image classification tasks, the representations learned using standard ERM training are expected to exhibit invariances to several factors of variation due to: (a) the classification objective that enforces similar representations for different variations within a given class, which are different from the representations for other classes and (b) augmentations such as color jitter that enforce additional invariance. However, CLIP is trained using detailed captions for each image, such as "A brown cat sitting on a sofa", "A black cat standing on two limbs", and "A black dog with long ears and a lot of fur". This allows CLIP to learn rich specialized representations for each attribute, with higher intra-class variance when compared to standard ERM training. + +Characteristics of the Text Encoder: Robustness to distribution shifts can be achieved either by incorporating the required domain-invariance in the feature extractor, or by domain-invariant feature selection at the classification head. As discussed, CLIP's image encoder produces input-specific representations and is not domain invariant. The superior generalization of CLIP on different datasets and domains is thus a result of the robust text embeddings. Although descriptive captions such as "A brown cat sitting on a sofa" are expected to have unique embeddings based on pose, location, etc., generic captions such as "A photo of a {class}" represent the core concept of the class. + +Empirical observations: In Table-1, we present results to demonstrate the robustness of CLIP text embeddings on the multi-source Domain Generalization benchmarks, where each dataset consists of images from $n$ domains. The results presented are an average of $n$ cases, where each case corresponds to the training on a given set of $n - 1$ domains and testing on the remaining unseen domain referred to as the target domain. Firstly, CLIP zero-shot results (E1) show the robustness of text embeddings across different distributions. The robustness of the text embeddings can be improved by explicitly enforcing domain invariance for better generalization to unseen domains (E2). However, the same level of robustness is not seen when we use an average of all image embeddings across the same domains for a given class, as shown in E3. This is due to the fact that while the text embeddings for "A {domain} of a {class}" are obtained by training over a large dataset (400 million images), the image embeddings are an average of $\sim 0.01$ million images on the downstream dataset. This is illustrated in Fig.1, where the red decision boundary trained using image embeddings misclassifies images from the unseen target domain, while the green classifier trained using the generic text embeddings is closer to an ideal decision boundary. However, an average image embedding on the target domain improves results significantly (E4). The accuracy improves further when an average embedding corresponding to a few (10) source domain images closest (in terms of cosine similarity of image embeddings) to the target image is used for each class during prediction (E5). A similar experiment using images from the target domain (E6), achieves considerable improvements over the zero-shot accuracy in E1. We can consider E6 as an In-(target)-Domain setting where a labeled hold-out validation set is used during prediction for obtaining the average embeddings. Therefore, it is possible to outperform the generalized representations of the text embeddings only when labeled images from the target domain are available. Thus, in a DG setting where the target domain is inaccessible, the generic text embeddings provide the best robustness across distribution shifts. We therefore use the text embeddings to maximally transfer their robustness to the student model. + +# 5. Proposed Approach: VL2V-ADiP + +In this section, we first present the knowledge distillation framework adapted to a VLM-to-vision distillation setting. We further propose a self-distillation approach VL2V-SD, to enhance the robustness of the VLM image encoder, which motivates the proposed approach VL2V-ADiP. + +# 5.1. Distillation from VLMs to Vision models + +The standard framework of Knowledge Distillation (KD) [20] applies in the unimodal setting, for instance, where the teacher and student are both vision models. To adapt this to a VLM-to-vision distillation setting, a classification model (which we refer to as a VLM-classifier) is first constructed using the VLM. The feature extractor of the VLM-classifier comes from the image encoder of the VLM, and the linear classifier head obtains its weights from the text embeddings $\mathbf{T}_c$ corresponding to the captions "a photo of a {class}" for all $C$ classes. For every image-label pair $(x_i,y_i)$ , the VLM-classifier first computes the image embedding $\mathbf{I}_{x_i}$ , and further computes its similarity w.r.t. each of the text embeddings $\mathbf{T}_c$ . The similarity scores $\cos (\mathbf{I}_{x_i},\mathbf{T}_c)$ are considered to be analogous to the logit layer, over which the softmax function is applied. The final distillation loss of the student that is minimized during training is shown below in Eq.4 for a minibatch of size $n$ . Here, $f_{S}(.)$ and $f_{\mathrm{T}}(.)$ represent the softmax representations of the student and teacher respectively, CE represents the Cross-Entropy loss, and KL represents the Kullback-Leibler divergence. Temperature scaling is applied to the logits before computing softmax [20]. We tune over the range - $\{0.1,1,10\}$ on the in-domain validation set, and report the baseline best results in Table-3. + +$$ +f _ {\mathrm {T}} \left(x _ {i}\right) = \operatorname {s o f t m a x} \left(\cos \left(\mathbf {I} _ {x _ {i}}, \mathbf {T} _ {c}\right)\right) \tag {3} +$$ + +$$ +\mathcal {L} _ {\mathrm {K D}} = \frac {1}{n} \sum_ {i = 1} ^ {n} \left\{\mathrm {C E} \left(f _ {S} \left(x _ {i}\right), y _ {i}\right) + \lambda \cdot \mathrm {K L} \left(f _ {\mathrm {T}} \left(x _ {i}\right) \mid \mid f _ {S} \left(x _ {i}\right)\right) \right\} \tag {4} +$$ + +# 5.2. Self-Distillation from Text to Image encoders + +As discussed in Section-4.2, the image encoder of CLIP is trained to represent all factors of variations in an image that are described in the corresponding caption used during its training. Therefore, it does not exhibit the invariances to factors such as color, texture, lighting, and pose, that are required for an image classification task. On the other hand, text prompts allow much better control over invariances in text-embeddings. For example, a prompt such as "A brown cat sitting on a sofa" uniquely represents the color, location, and pose of the cat in addition to the object itself, whereas a prompt "A photo of a cat" is invariant to such variations. + +Motivated by this, we propose Vision-Language to Vision Self Distillation (VL2V-SD), where the invariances of generic text embeddings are distilled to the image encoder + +![](images/acd36f423afd1c11c334bf958b24fb564dba25f4c41db84ae644060a3c2cb124.jpg) +CLIP image encoder/features +CLIP text encoder / features + +![](images/d2859f37a8966683bad4313b867da91d69a96a8ad0f0f51e7beb38cc126287ed.jpg) +Networkfrozen +Network trainable +Student network / features +CLIP zero-shot classifier + +![](images/0e3b70fed9340deff4ce250aa2b3be45f860afab729bb8242c1420753e3bd614.jpg) +Stage 3 (Predict) +Figure 2. Overview of the proposed approach VL2V-ADiP, consisting of (a) Align, (b) Distill and (c) Predict Stages for Black-Box Distillation from Vision-Language to Vision (VL2V) models. + +using the downstream dataset. We minimize the loss shown in Eq.5 for training, where $\mathbf{T}_{y_i}$ represents the embedding for "A photo of a {class}" corresponding to the ground truth class $y_{i}$ , and $\mathbf{I}_{x_i}^t$ , $\mathbf{I}_{x_i}^s$ represent the image embeddings of the teacher and student respectively for an image $x_{i}$ . + +$$ +\mathcal {L} _ {\mathrm {S D}} = - \frac {1}{2 n} \sum_ {i = 1} ^ {n} \left\{\cos \left(\mathbf {I} _ {x _ {i}} ^ {s}, \mathbf {T} _ {y _ {i}}\right) + \cos \left(\mathbf {I} _ {x _ {i}} ^ {s}, \mathbf {I} _ {x _ {i}} ^ {t}\right) \right\} \tag {5} +$$ + +The image encoders of both teacher and student are the same (VLM's image encoder) initially, and the student's image encoder is updated during training. The text encoder is frozen during training. While the first term enforces the image encoder to learn representations that match the corresponding text embeddings more accurately on the given dataset, the second term ensures that there is no representation collapse, and retains the rich features learned by the image encoder. The classifier is composed of text embeddings corresponding to the prompts "a photo of a {class}" for all classes, as was the case in the VLM-classifier discussed in Section-5.1. We present the results of VL2V-SD in Table2, where we note significant improvements over both CLIP zero-shot and the SOTA DG methods - SWAD [8], MIRO [9], DART [23], and SAGM [61] on the ViT-B/16 architecture with CLIP initialization. We demonstrate significant gains over the CLIP fine-tuning methods LP-FT [28], FLYP [18], CLIPood [55], and WiSE-FT [63]. We also achieve significant gains over a distillation method RISE [22], despite using the standard text prompt while RISE uses an expanded set of prompts. For WiSE-FT, we present the results with the optimal $\alpha$ that achieves the best performance by using the search space $\alpha = [0.1 - 0.9]$ . Similarly, for RISE, we present the results with the optimal hyperparameters $\lambda_1, \lambda_2, \lambda_3$ based on their search space. We incorporate SWAD [8] in all our runs for the baselines as well + +Table 2. White-Box setting (CLIP initialization): Performance $(\%)$ of the proposed approach VLV2-SD, compared to the existing methods. ViT-B/16 architecture is used. (S) denotes SWAD [8]. + +
MethodOHTIVLCSPACSDNAvg-IDAvg-OOD
Zero-shot [47]82.4034.1082.3096.5057.70-70.60
SWAD [8]81.0142.9279.1391.3557.9289.0570.47
MIRO (S) [9]84.8059.3082.3096.4460.4791.0076.66
DART (S) [23]80.9351.2480.3893.4359.3289.2573.06
SAGM (S) [61]83.4058.6482.0594.3159.0589.7475.49
LP-FT (S) [28]81.1747.2680.8892.9257.0488.9771.85
FLYP (S) [18]82.7633.2566.6478.5357.4178.9463.72
CLIPood (S) [55]83.3146.2877.1993.1657.7869.9071.55
WiSE-FT (S) [63]86.3254.5082.8897.2958.0188.3575.80
RISE (S) [22]78.3949.6180.6293.2555.3787.9171.45
VL2V-SD (Ours)87.3858.5483.2596.6862.7989.9977.73
+ +as the proposed approach (denoted by “(S)”) since it is a generic technique that improves the generalization of any given method. However, we do not incorporate SWAD with WiSE-FT since it already performs weight averaging of the pre-trained and fine-tuned models. We present the results without SWAD in Suppl. Sec-3.2. + +# 5.3. VL2V - Align, Distill, Predict (VL2V-ADiP) + +While VL2V-SD is very effective in improving the performance of the VLM in a white-box setting, it does not address the problem of black-box distillation that we consider in this work, since it assumes access to the weights of the VLM model. In this section, we discuss how this method can be adapted to the black-box setting and present the proposed approach VL2V-ADiP. Since the amount of downstream task-specific data is assumed to be limited, the student is initialized with the best available pre-trained model such as ImageNet [26]. + +In the self-distillation case seen in Section-5.2, the goal was to induce domain invariance from the text encoder to the image encoder, while ensuring that the rich features + +learned by the image encoder are not lost. Whereas, in the black-box setting, the goal is to distill the rich features learned by the image-encoder of the VLM and the domain invariance from the text embeddings. While the two cases can have a similar loss formulation as shown in Eq.5, the method VL2V-SD cannot directly be applied here since the feature dimension of the student model may be different from the dimension of VLM's image and text embeddings. Even if the dimensions had matched, the features of the ImageNet pre-trained backbone and VLM's embeddings would be misaligned. Directly enforcing a similarity loss in such a case would lead to forgetting of the pretrained features. To address this, we propose VL2V-ADiP, Vision-Language to Vision - Align, Distill, Predict as shown in Fig.2 (Ref: Alg. 1 in Suppl.). We propose to first Align the features of the pre-trained student model with VLM embeddings using a linear projection head on the student backbone in Stage-1, as shown in Fig.2(a). For this, the student backbone is frozen and only the projection head is trained using the following loss, where $\mathbf{PF}_{x_i}^s$ represents the projected features of the student model for the input $x_{i}$ : + +$$ +\mathcal {L} _ {\mathrm {A D i P}} = - \frac {1}{2 n} \sum_ {i = 1} ^ {n} \left\{\cos \left(\mathbf {P F} _ {x _ {i}} ^ {s}, \mathbf {T} _ {y _ {i}}\right) + \cos \left(\mathbf {P F} _ {x _ {i}} ^ {s}, \mathbf {I} _ {x _ {i}} ^ {t}\right) \right\} \tag {6} +$$ + +Next, the aligned student features are refined using the VLM's image and text embeddings in the Distill step as shown in Fig.2(b) (Stage-2). For this step, the linear projection head is frozen, and the feature extractor is trained using the same loss as Stage-1, as shown in Eq.6. While we give equal weight to both loss terms in Eq.6, we present the impact of varying this in Suppl. Sec-4. Finally, in Stage-3 (Predict), the VLM's embeddings corresponding to "a photo of a {class}" for all $C$ classes are used as weights of the classification head, and the class with the highest similarity to the given image embedding is predicted, as shown in Eq.2. In addition to learning the rich features from the VLM teacher's image-encoder and invariances from its text encoder, enforcing similarity between the features of the student backbone and the text embeddings of the corresponding classes also makes the text embeddings more suitable for use as a classifier in Stage-3 (Predict). Thus, although Stages 1 and 2 explicitly train only the student backbone and projection head, they implicitly impact the effectiveness of the classification head as well. This facilitates the use of these embeddings directly as a classifier without the need for fine-tuning further on the downstream dataset. As shown in Table-5, further fine-tuning degrades the performance, since only In-Domain (ID) data is available for fine-tuning, which would make the classifier forget the domain invariance that it inherently possesses. However, fine-tuning with limited In-Domain data improves the ID accuracy as shown in the table. + +# 6. Experiments and Results + +# 6.1. Evaluation Details + +Towards evaluating the OOD generalization of image classification models, we consider the five popular Domain Generalization (DG) datasets - OfficeHome (OH) [60], PACS [30], VLCS [16], Terra-Incognita (TI) [3] and DomainNet (DN) [44]. Each of the datasets consists of $d$ domains, where $d = 4$ for the first four datasets and $d = 6$ for DomainNet. We present more details on the datasets in Suppl. Sec-2. We follow the DomainBed [19] framework for training and evaluation, where each domain is split into training and validation sets, and training is performed on $d - 1$ domains while evaluation is done on the $d^{th}$ unseen domain. Thus, for every dataset, $d$ models are trained, by leaving one domain out for evaluation each time. The average accuracy across these $d$ runs on the unseen test domain (OOD accuracy) and the average In-domain (ID) validation split accuracy are reported. The unseen test domain is neither used for training nor for hyperparameter tuning [19]. + +# 6.2. Training Details + +The number of training iterations is set to 5000 for OfficeHome, PACS, VLCS, and Terra-Incognita, and to 15000 for DomainNet, as is standard [8, 9]. We use the Adam optimizer with a constant learning rate of $5 \times 10^{-5}$ for all our experiments except CLIPood (S) in Table-2, for which we use the AdamW optimizer as specified in [55]. These settings are fixed for all datasets, and we do not introduce any additional hyperparameters in the proposed algorithm. Our primary evaluations consider a ViT-B/16 architecture [15] for both the VLM (teacher) Image-encoder and the student model to enable a fair comparison with existing methods, that use the same architecture. Since one of the key motivations of distillation is to train a low-capacity model, we present results with lower-capacity student architectures as well. We use a CLIP teacher model, which uses a Transformer architecture [59] with modifications described by Radford et al. [46] for the text encoder. The student model and our primary baselines for VL2V-ADiP use an ImageNet pre-trained initialization [26], as is standard in DG [19]. We obtain the results of baseline methods on ViTs in Tables 2 and 3 by integrating the official code of the respective method with the MIRO [9] code base to ensure a fair comparison. Additionally, we show results with other teacher VLMs in Suppl. Sec-3.3. + +# 6.3. Comparison with the SOTA + +We present the ID and OOD results of the proposed approach VL2V-ADiP when compared to the DG and KD baselines in Table-3. Gulrajani and Lopez-Paz [19] show that ERM training is a very strong baseline in DG and outperforms several older methods that were proposed. Thus, + +Table 3. SOTA comparison with ImageNet initialization: Performance (%) of the proposed approach VL2V-ADiP, compared to existing KD and DG methods with SWAD (S). ViT-B/16 with ImageNet-1K initialization is used as the student. + +
MethodOHTIVLCSPACSDNAvg-IDAvg-OOD
ERM-LP (S)71.4831.3577.5267.0236.6573.9956.81
ERM Full Fine-tuning (S)83.2250.0580.3390.2856.1089.3172.00
LP-FT (S) [28]81.5551.6180.1791.2056.0390.0372.11
SimKD (S) [13]66.7681.0183.9228.2449.4268.2461.87
KD (S) [20]82.7348.4080.4891.4656.1189.2071.84
MIRO (S) [9]80.0950.2981.1089.5055.7588.7171.35
DART (S) [23]83.7549.6877.2990.5558.0588.5471.86
SAGM (S) [61]82.2253.2479.6090.0255.6689.2272.15
Text2Concept (S) [40]70.2426.4664.7779.0323.2653.1552.82
RISE (S) [22]83.4852.5583.7093.5456.5888.9173.97
VL2V-ADiP (Ours)85.7455.4381.9094.9459.3889.0275.48
+ +Table 4. Distillation to lower capacity student models: Performance (\%) of the proposed approach VL2V-ADiP (denoted as Ours), when compared to the KD baseline [20] and ERM (S) or SWAD [8] with different student architectures. The teacher architecture is ViT-B/16. (S) denotes SWAD. + +
StudentMethodOHTIVLCSPACSDNAvg-IDAvg-OOD
ViT-B/16 (86M)ERM (S)83.2250.0580.3390.2856.1089.3172.00
KD (S)82.7348.4080.4891.4656.1789.2071.85
Ours (S)85.7455.4381.9094.9459.3889.0275.48
ViT-S/16 (22M)ERM (S)78.5849.4078.7285.8052.0985.6668.92
KD (S)78.1450.1179.1485.9752.0587.4369.08
Ours (S)81.2252.4781.4489.3254.2386.5971.73
DeiT-S/16 (22M)ERM (S)74.9547.8579.3789.2249.1886.5868.12
KD (S)74.6548.1178.8688.1449.1086.6667.77
Ours (S)77.6348.7281.8988.9750.3785.2869.52
ResNet-50 (26M)ERM (S)70.8549.4779.5088.0546.4384.8866.86
KD (S)70.6751.2278.6387.2346.3185.0466.81
Ours (S)74.4253.4679.2386.7247.7484.7368.31
+ +ERM training of only the linear layer (ERM-LP) and ERM full fine-tuning (ERM-FFT) are two important baselines we consider. Further, we present the results of important SOTA DG methods - SWAD [8], MIRO [9], DART [23], and SAGM [61]. Additionally, we also show results with Text2Concept [40] and LP-FT [28] - simple fine-tuning strategies for improved OOD generalization on downstream tasks. While there are several methods that outperform ERM [6, 25, 41, 57], we do not present all of them here since the above-listed recent methods outperform them. Since we incorporate SWAD in the proposed approach, we present all the baseline results by integrating SWAD with each of them and denote them with a suffix "S" in the tables. Additionally, we also present three distillation results - (a) knowledge distillation from the VLM teacher to the vision student model as discussed in Section-5.1 and (b) distillation from the VLM teacher using SimKD [13], and (c) distillation from the VLM teacher using RISE [22]. Since the feature distillation methods listed in Sec. 2 cannot be extended to the black box distillation setting, we do not compare with them. The proposed approach VL2V-ADiP achieves $\sim 1.5\%$ improvement on average OOD accuracy across all datasets with respect to the best baselines, with comparable ID accuracy. We note that Text2Concept scales + +poorly on smaller datasets compared to the results shown in the paper [40]. SimKD [13] is a method intended for unimodal distillation and thus fails for the multimodal setup. Furthermore, we outperform the method RISE [22] by a large margin despite the latter using expanded text prompts. This shows that the proposed distillation method VL2V-ADiP effectively distills from VLMs with lesser prompt engineering and text supervision compared to RISE. + +# 6.4. Distillation to lower capacity student models + +We present results of distilling from a CLIP ViT-B/16 teacher to different student architectures and capacities (ViT-S/16, DeiT-S, ResNet-50) in Table-4. We observe substantial gains over the Knowledge Distillation and ERM (S) or SWAD baseline across all student architectures. We note that the distillation performance is best when the architecture (ViT) of the teacher matches that of the student. For example, although ViT-S/16, DeiT-S/16, and ResNet-50 have a similar number of parameters, the performance of the ViT-S/16 student is the best, showing the architecture plays a role in the nature of representations learned, thereby allowing better transfer when they match. + +# 6.5. Ablation Study + +We present an ablation study of the proposed method in Table-5. Firstly, we study the impact of combining stages-1 (Align) and 2 (Distill), i.e., training the linear projection layer and the backbone jointly in A1. This results in a $2.2\%$ drop in ID accuracy and a $6.3\%$ drop in OOD accuracy, highlighting that the pre-trained ImageNet features are retained better when they are aligned before distillation. In A2, the linear projection head is also trained in Stage-2. The results of this case are similar to the proposed approach, showing that even when the linear head is changed, it does not get updated much after Stage-1 (Align). We next analyze the importance of distilling from both image and text encoders of CLIP by using only one of them individually in A3 and A4. In both cases, we note a significant drop in the OOD accuracy highlighting the importance of distilling from both encoders. Distilling only from the Image encoder has a larger drop due to the lack of alignment between the representations and the classifier head which is composed of CLIP text embeddings corresponding to each of the classes. + +In Stage-3 (Predict) of the proposed approach, the CLIP text embeddings corresponding to the classes are directly used as the classifier weights. We explore the impact of training this classifier further using cross-entropy loss over the softmax representations shown in Eq.3, in experiments A5-A8. In A5 and A6, the classifier head is first initialized using the text embeddings of CLIP, and in A7 and A8, a random initialization is used for the classification head. In A5 and A7, only the classifier head is trained, whereas in A6 and A8, the full network is trained. All these experi + +Table 5. Ablation Study of the proposed VL2V-ADiP: Performance (%) on ViT-B/16 model with ImageNet initialization. + +
Method - Changes done w.r.t. VL2V-ADiP (Ours)OHTIVLCSPACSAvg-IDAvg-OOD
VL2V-ADiP (Ours)85.7455.4381.9094.9492.7479.50
A1: Combining "Align" and "Distill" stages74.5552.9980.1485.2990.5573.24
A2: Without freezing projection head in Stage-286.1356.6881.7893.7593.0079.59
A3: Distilling only from Text encoder in Stages-1 and 283.1847.0279.8390.8691.8775.22
A4: Distilling only from Image encoder in Stages-1 and 278.9728.9782.2489.9774.0970.04
A5: Finetuning CLIP classifier-head in Stage-3 (CE loss) - CLIP init classifier84.4749.2881.3093.5493.0677.15
A6: Finetuning full network in Stage-3 (CE loss) - CLIP init classifier83.8849.8380.1392.2593.3776.52
A7: Finetuning classifier-head in Stage-3 (CE loss) - random init classifier84.6349.5581.2993.5793.0277.26
A8: Finetuning full network in Stage-3 (CE loss) - random init classifier83.1650.0379.7892.1593.1476.28
+ +![](images/6f84f9fcf6ec76d60916a8d979d0197c2f10c1cda186f4ffc424a97248b2f52c.jpg) +Figure 3. OOD accuracy $(\%)$ of the proposed approach when compared to KD and ERM baselines for select classes/ domains in Office-Home and Terra-Incognita datasets, where the (a) ERM-IN (linear) (b) CLIP Zero-shot (c) ERM-CLIP (linear) performance is poor. + +ments result in a drop in the OOD accuracy, indicating that training on the downstream dataset using the cross-entropy loss can destroy the domain invariances learned from CLIP. Since the impact of training the full network is higher, the drop is higher in this case when compared to finetuning only the classification head. In all cases, the In-Domain accuracy improves when compared to the proposed approach, with higher gains in the case when the full network is trained, confirming that training without the supervision of the CLIP teacher indeed overfits to the training domains. + +We also compare the ERM and KD baselines with the proposed approach in some of the extreme cases in Fig.3, where the CLIP Image encoder is significantly better than the ERM model (a), and vice-versa (c). For this, we select the classes/domains with the highest difference $(40 - 50\%)$ between the ERM-CLIP (Linear) and ERM-ImageNet (IN) (Linear) baselines from the OfficeHome dataset. We also present the case where the CLIP zero-shot accuracy is poor in OfficeHome $(22\%)$ and Terra-Incognita datasets $(0\%)$ in Fig.3 (b). The KD baseline relies a lot on the ImageNet pre-trained backbone, hence it is poor when ERM-IN is poor, and is close to our approach when ERM-IN is good. The ERM fine-tuning baseline is best when the ImageNet features are much better than CLIP Image encoder's features, but it is poor in the other case, as expected. Lastly, even when CLIP zero-shot accuracy is poor (close to $0\%$ ), the proposed approach achieves reasonable accuracy, since Stages-1 and 2 align the text embeddings better to the feature extractor, making them more suitable as a classifier. + +# 7. Conclusion + +In this work, we aim to leverage the superior generalization of large-scale Vision-Language Models towards improving the OOD generalization of Vision models. We consider a practical scenario where a client gets only black-box access to the model on a pay-per-query basis from the vendor, motivating the need for distilling the model first, and further using the student model during inference. Towards this, we first highlight the unique aspects of the image and text encoders of VLMs and further propose a self-distillation (SD) approach - VL2V-SD, to distill the superior generalization of the VLM's text encoder to its image encoder, while retaining the rich representations of the latter. We further adapt this to a black-box distillation setting, by firstly projecting the representations of the pre-trained feature-extractor (student) to a space that is aligned with embeddings of the VLM teacher, and further finetuning the backbone using the same. The use of both text and image embeddings induces the rich representations of the VLM and its superior generalization to the student model, while also making the text embeddings more suitable for use in the classification head. Both proposed approaches (VL2V-SD and VL2V-ADiP) achieve substantial gains over prior methods on the popular Domain Generalization datasets. + +Acknowledgements. This work is supported by the Kotak IISc AI-ML Center and a research grant CRG/2021/005925 from SERB, DST, Govt. of India. Sravanti Addepalli is supported by the Google PhD Fellowship and CII-SERB Prime Minister's Fellowship for Doctoral Research. + +# References + +[1] Martin Arjovsky, Léon Bottou, Ishaan Gulrajani, and David Lopez-Paz. Invariant risk minimization. arXiv preprint arXiv:1907.02893, 2019. 2 +[2] Devansh Arpit, Huan Wang, Yingbo Zhou, and Caiming Xiong. Ensemble of averages: Improving model selection and boosting performance in domain generalization. NeurIPS, 2022. 3 +[3] Sara Beery, Grant Van Horn, and Pietro Perona. Recognition in terra incognita. In ECCV. Springer, 2018. 6 +[4] Battista Biggio, Blaine Nelson, and Pavel Laskov. Poisoning attacks against support vector machines. In ICML. PMLR, 2012. 2 +[5] Gilles Blanchard, Aniket Anand Deshmukh, Ürun Dogan, Gyemin Lee, and Clayton Scott. Domain generalization by marginal transfer learning. 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IJCV, 2022. 3 \ No newline at end of file diff --git a/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/images.zip b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..bfe38514637240a6ac6eebe4657aa17850b13a50 --- /dev/null +++ b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:9aa8c8b8fc54ae5ea663003c76afea1804458e03a3b29fab90b7d2a6e436d46f +size 482732 diff --git a/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/layout.json b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..1272473bc9d702a9101e9c7d1054de43c3228976 --- /dev/null +++ b/2024/Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification/layout.json @@ -0,0 +1,7668 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 138, + 103, + 457, + 140 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 138, + 103, + 457, + 140 + ], + "spans": [ + { + "bbox": [ + 138, + 103, + 457, + 140 + ], + "type": "text", + "content": "Leveraging Vision-Language Models for Improving Domain Generalization in Image Classification" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 78, + 161, + 515, + 190 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 78, + 161, + 515, + 190 + ], + "spans": [ + { + "bbox": [ + 78, + 161, + 515, + 190 + ], + "type": "text", + "content": "Sravanti Addepalli * Ashish Ramayee Asokan * Lakshay Sharma R. Venkatesh Babu Vision and AI Lab, Indian Institute of Science, Bangalore" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 143, + 217, + 192, + 229 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 217, + 192, + 229 + ], + "spans": [ + { + "bbox": [ + 143, + 217, + 192, + 229 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 242, + 290, + 589 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 242, + 290, + 589 + ], + "spans": [ + { + "bbox": [ + 47, + 242, + 290, + 589 + ], + "type": "text", + "content": "Vision-Language Models (VLMs) such as CLIP are trained on large amounts of image-text pairs, resulting in remarkable generalization across several data distributions. However, in several cases, their expensive training and data collection/curation costs do not justify the end application. This motivates a vendor-client paradigm, where a vendor trains a large-scale VLM and grants only input-output access to clients on a pay-per-query basis in a black-box setting. The client aims to minimize inference cost by distilling the VLM to a student model using the limited available task-specific data, and further deploying this student model in the downstream application. While naive distillation largely improves the In-Domain (ID) accuracy of the student, it fails to transfer the superior out-of-distribution (OOD) generalization of the VLM teacher using the limited available labeled images. To mitigate this, we propose Vision-Language to Vision - Align, Distill, Predict (VL2V-ADiP), which first aligns the vision and language modalities of the teacher model with the vision modality of a pre-trained student model, and further distills the aligned VLM representations to the student. This maximally retains the pre-trained features of the student, while also incorporating the rich representations of the VLM image encoder and the superior generalization of the text embeddings. The proposed approach achieves state-of-the-art results on the standard Domain Generalization benchmarks in a black-box teacher setting as well as a white-box setting where the weights of the VLM are accessible. Project page: http://val.cds.iisc.ac.in/VL2V-ADiP/" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 597, + 128, + 609 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 597, + 128, + 609 + ], + "spans": [ + { + "bbox": [ + 47, + 597, + 128, + 609 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 616, + 287, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 616, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 46, + 616, + 287, + 677 + ], + "type": "text", + "content": "While the initial success of Deep Learning was predominantly driven by training specialized models for each task or dataset [26, 29], recent research on foundation models [24, 34, 47, 65] eliminates the need for this by training generic models jointly over several modalities using large-" + } + ] + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 318, + 215, + 533, + 407 + ], + "blocks": [ + { + "bbox": [ + 318, + 215, + 533, + 407 + ], + "lines": [ + { + "bbox": [ + 318, + 215, + 533, + 407 + ], + "spans": [ + { + "bbox": [ + 318, + 215, + 533, + 407 + ], + "type": "image", + "image_path": "139f047a9cc70387e0c8325960c851b3c4c5d6493ca2e3dbd0fd6766c3d67f88.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 412, + 547, + 535 + ], + "lines": [ + { + "bbox": [ + 304, + 412, + 547, + 535 + ], + "spans": [ + { + "bbox": [ + 304, + 412, + 547, + 535 + ], + "type": "text", + "content": "Figure 1. Schematic diagram showing class and domain distributions in the shared text/ image embedding space of a VLM: VLMs learn highly specialized image representations that are not domain invariant. Thus, a linear classifier (red decision boundary) that is trained over the vision encoder using limited training data cannot generalize well to the target domain (shown in purple). On the other hand, generic text embeddings such as \"A photo of a class\" represent the core concept of a class by virtue of their training method and vast training data. Thus, they generalize effectively across domains, and a zero-shot classifier (green decision boundary) aligns better with the true distribution of classes." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 544, + 547, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 544, + 547, + 688 + ], + "spans": [ + { + "bbox": [ + 304, + 544, + 547, + 688 + ], + "type": "text", + "content": "scale data. The use of both image and language modalities in large-scale Vision-Language Models (VLMs) enables their use in several applications including zero-shot classification, where the embedding of an image is compared with text embeddings for \"a photo of a {class}\" corresponding to every class during inference and the class with highest similarity is predicted. For example, the LiT (private) model [65] has been trained on 4 billion image-text pairs scraped from the web, and it achieves " + }, + { + "bbox": [ + 304, + 544, + 547, + 688 + ], + "type": "inline_equation", + "content": "85.2\\%" + }, + { + "bbox": [ + 304, + 544, + 547, + 688 + ], + "type": "text", + "content": " zero-shot accuracy on ImageNet. VLMs also demonstrate extraordinary performance across several distributions, owing to the vast diversity of distributions seen during their training [47]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 689, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 547, + 714 + ], + "type": "text", + "content": "The remarkable OOD generalization of VLMs makes them suitable for use in several applications, either directly" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 496, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 684, + 128, + 693 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 684, + 128, + 693 + ], + "spans": [ + { + "bbox": [ + 58, + 684, + 128, + 693 + ], + "type": "text", + "content": "*Equal Contribution." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 47, + 694, + 287, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 694, + 287, + 712 + ], + "spans": [ + { + "bbox": [ + 47, + 694, + 287, + 712 + ], + "type": "text", + "content": "Correspondence to Sravanti Addepalli , Ashish Ramayee Asokan " + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23922" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 240 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 240 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 240 + ], + "type": "text", + "content": "or after finetuning on the downstream target dataset. Although several open-sourced models such as CLIP [47] are easily accessible, they may not be suitable for use in specialized applications. For example, the training data may have to be curated to reduce biases in the model or to ensure data privacy. It may also be important to ensure that the web-crawled data is clean for adoption in critical applications such as autonomous driving, to avoid data-poisoning attacks [4, 7]. Further, general-purpose models cannot be used in specialized applications such as medical diagnosis, where a VLM trained on data containing expert comments can be invaluable. This motivates the need for training highly specialized VLMs, which can be expensive due to the high costs associated with data collection/ curation and training." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 242, + 289, + 386 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 242, + 289, + 386 + ], + "spans": [ + { + "bbox": [ + 46, + 242, + 289, + 386 + ], + "type": "text", + "content": "A given downstream application may not always justify the cost associated with training such large-scale models. However, since these VLMs are generic and applicable to several downstream applications, one vendor could train such a model, and make it available to several clients in a black-box setting on a pay-per-query basis. In this case, the client can minimize their inference time costs by distilling the VLM to a student model using the limited available data specific to the downstream task, and deploying the distilled model rather than the VLM. Since the key motivation of using VLMs is their generalization to several domains, reliable OOD performance of the distilled model is crucial." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 388, + 289, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 388, + 289, + 640 + ], + "spans": [ + { + "bbox": [ + 46, + 388, + 289, + 640 + ], + "type": "text", + "content": "In this work, we consider the problem of distilling a multimodal Vision-Language model to a unimodal Vision model using limited task-specific downstream data, targeted toward better OOD performance with respect to the training domains used for distillation. While standard distillation of VLMs would require training data comprising of images and their associated text, in this case, the training data consists of only labeled images, similar to a classification task. Moreover, since the superior generalization abilities of VLMs are a result of the large-scale data (" + }, + { + "bbox": [ + 46, + 388, + 289, + 640 + ], + "type": "inline_equation", + "content": "\\sim 400" + }, + { + "bbox": [ + 46, + 388, + 289, + 640 + ], + "type": "text", + "content": " million in the case of CLIP) used for their training, it is challenging to transfer these generalization abilities using a limited dataset comprising around 10,000 (0.01 million) images [16, 30, 60]. Lastly, since the VLM is considered to be a black box, the image encoder's weights cannot be used as initialization to the vision model for further fine-tuning. However, since the downstream task-specific data is limited and is insufficient to train models from scratch, we assume that the student is initialized with weights from a model pretrained on a publicly available dataset such as ImageNet-1K [26], as is common in a domain-generalization setting [19]." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 642, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 289, + 715 + ], + "type": "text", + "content": "While knowledge distillation [20] using the labeled task-specific images improves the In-Domain accuracy on the downstream task, the improvement in OOD accuracy is marginal due to the limited size of the dataset. To address this, we first analyze the robustness of the text and image embeddings from the VLM and highlight the impor" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 204 + ], + "type": "text", + "content": "tance of text embeddings for better OOD generalization (see Fig.1). Further, we propose VL2V-ADiP: Vision-Language to Vision - Align, Distill, Predict, to firstly align the features of the pre-trained student model with the text and image modalities of the VLM teacher, and further fine-tune the student backbone in a distillation framework. This improves the robustness of the student, while also aligning the student embeddings to the VLM's text embeddings corresponding to the respective class, thereby making the latter suitable for use as a classifier in the student without the need for further training. We summarize our contributions below:" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 205, + 545, + 384 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 306, + 205, + 545, + 240 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 205, + 545, + 240 + ], + "spans": [ + { + "bbox": [ + 306, + 205, + 545, + 240 + ], + "type": "text", + "content": "- We investigate the robustness of image and text embeddings of VLMs, and highlight the importance of the text embeddings for better OOD generalization." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 241, + 545, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 241, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 306, + 241, + 545, + 300 + ], + "type": "text", + "content": "- To demonstrate the superior generalization of text embeddings, we propose VL2V-SD - a self-distillation approach, that improves the OOD generalization of the VLM's pre-trained vision encoder using supervision from its own text encoder in a white-box VLM setting." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 301, + 545, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 301, + 545, + 348 + ], + "spans": [ + { + "bbox": [ + 306, + 301, + 545, + 348 + ], + "type": "text", + "content": "- We further propose VL2V-ADiP - a black-box distillation approach that effectively combines the features of a pretrained vision model with the text and vision encoders of a VLM teacher for better OOD generalization." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 350, + 545, + 384 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 350, + 545, + 384 + ], + "spans": [ + { + "bbox": [ + 306, + 350, + 545, + 384 + ], + "type": "text", + "content": "- We demonstrate state-of-the-art results on standard Domain Generalization benchmark datasets in both white-box and black-box settings of the VLM teacher." + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 394, + 398, + 407 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 394, + 398, + 407 + ], + "spans": [ + { + "bbox": [ + 306, + 394, + 398, + 407 + ], + "type": "text", + "content": "2. Related Works" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 414, + 547, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 414, + 547, + 545 + ], + "spans": [ + { + "bbox": [ + 304, + 414, + 547, + 545 + ], + "type": "text", + "content": "Vision-Language Models (VLMs): VLMs are trained on large-scale datasets of image-text pairs crawled from the web [10, 53, 58]. Contrastive pre-training methods [24, 34, 47, 65] maximize the similarity between the embeddings of matching image-text pairs. More recent efforts focus on scaling up image-text pre-training to larger datasets [34], better supervision with unimodal and multimodal data [56], data-efficient pre-training [36], and fine-tuning VLMs for downstream tasks [18, 28, 63]. Another line of work focuses on leveraging CLIP [47] to improve the OOD generalization in image classification [40, 55]." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 545, + 548, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 548, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 548, + 714 + ], + "type": "text", + "content": "Domain Generalization (DG): Prior works learn domain invariant representations by using augmentations [41, 42, 50], feature alignment across domains [17, 33, 35, 57], and disentangling domain-specific and domain-invariant features [11, 38, 45]. Gulrajani et.al [19] demonstrate that a well-tuned ERM model is comparable to several past DG algorithms [1, 5, 21, 27, 31, 32, 52, 62, 66]. SWAD [8] is a generic strategy that performs weight-averaging across different model snapshots in the optimal basin during training. MIRO [9] proposes Mutual Information (MI) regularization to maximally retain the pre-trained model's representations. SAGM [61] aligns gradient directions between the " + }, + { + "bbox": [ + 304, + 545, + 548, + 714 + ], + "type": "inline_equation", + "content": "\\epsilon" + }, + { + "bbox": [ + 304, + 545, + 548, + 714 + ], + "type": "text", + "content": "-perturbed loss and the empirical risk. We demonstrate performance gains when compared to the existing DG methods" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23923" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 47, + 118, + 288, + 240 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 287, + 115 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 287, + 115 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 287, + 115 + ], + "type": "text", + "content": "Table 1. CLIP on DG datasets: Performance " + }, + { + "bbox": [ + 47, + 70, + 287, + 115 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 47, + 70, + 287, + 115 + ], + "type": "text", + "content": " of CLIP ViT-B/16 model on using different embeddings in the classifier head for computing similarity w.r.t. the test image during inference (T.E.: Text Embedding, I.E.: Image Embedding)." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 118, + 288, + 240 + ], + "lines": [ + { + "bbox": [ + 47, + 118, + 288, + 240 + ], + "spans": [ + { + "bbox": [ + 47, + 118, + 288, + 240 + ], + "type": "table", + "html": "
Embedding used for computing similarityOHTIVLCSPACSAvg.
E1: Text embedding for "A photo of a {class}"82.3634.1982.0896.1073.68
E2: Avg. text embedding for "A {domain} of a {class}" across all train domains83.7035.5582.2896.2174.44
E3: Avg. image embedding of each class (Source)71.3733.9948.2179.0358.15
E4: Avg. image embedding of each class (Target)78.2138.6969.3193.0869.82
E5: Avg. image embedding of 10 images per class closest to test image (Source)76.4239.3376.4292.1571.08
E6: Avg. image embedding of 10 images per class closest to test image (Target)84.8685.3887.8898.3289.11
", + "image_path": "4d6650973924a2f144e405c068ee814a8ac39f5f8facb943cd2c420c746597b6.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 257, + 287, + 376 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 257, + 287, + 376 + ], + "spans": [ + { + "bbox": [ + 46, + 257, + 287, + 376 + ], + "type": "text", + "content": "in both white-box and black-box settings of the VLM. More recently, several methods perform diverse training of multiple models, followed by weight-averaging to improve OOD generalization [2, 23, 48, 49]. However, they incur the enormous expense of training several diverse models. We thus restrict our comparison to DART [23], where the number of models trained is lower than the others. Another direction has been the generation of better prompts for improved generalization of VLMs [39, 54, 67]. These methods can be integrated with the proposed approach." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 379, + 287, + 522 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 379, + 287, + 522 + ], + "spans": [ + { + "bbox": [ + 46, + 379, + 287, + 522 + ], + "type": "text", + "content": "Knowledge Distillation (KD): Knowledge distillation aims to transfer knowledge from a powerful teacher model to a compact student model. Output-distillation [20] uses the teacher's softmax outputs as guidance for the student. Feature-distillation methods [12-14, 37, 43, 51] use the teacher's intermediate representations as guidance since they contain richer information. The proposed method operates in the black box distillation setup that allows only input-output access to the teacher network and restricts access to intermediate features. We thus compare the proposed black-box approach only with methods that do not access intermediate features [13, 20, 22]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 535, + 112, + 548 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 535, + 112, + 548 + ], + "spans": [ + { + "bbox": [ + 47, + 535, + 112, + 548 + ], + "type": "text", + "content": "3. Notations" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": "We consider the problem of Knowledge Distillation (KD) from VLMs (teacher) to vision models (student) for improved OOD generalization. We denote the VLM's text embedding for the input, \"A photo of a {class}\" for class " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": " as " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_c" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": ". The image embedding corresponding to the image " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": " is denoted as " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_x" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": ". The student model's features corresponding to an input " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": " are denoted as " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_x" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": ". These features when projected to the same dimension as the VLM embeddings " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "(\\mathbf{I}_x" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_c)" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": ", are denoted as " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{P}\\mathbf{F}_x" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": ". The cosine similarity between two vectors " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{a}" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{b}" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": " is denoted as " + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "inline_equation", + "content": "\\cos(\\mathbf{a},\\mathbf{b})" + }, + { + "bbox": [ + 46, + 557, + 288, + 715 + ], + "type": "text", + "content": ". While we use CLIP [47] as the teacher for most of our analysis and experiments, we show the compatibility of the proposed approach with other VLMs [34, 36, 56, 64] in Suppl. Sec-3.3." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 71, + 488, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 71, + 488, + 85 + ], + "spans": [ + { + "bbox": [ + 305, + 71, + 488, + 85 + ], + "type": "text", + "content": "4. Robustness of CLIP embeddings" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 91, + 546, + 128 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 546, + 128 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 546, + 128 + ], + "type": "text", + "content": "In this section, we present an overview of the training and zero-shot evaluation of the CLIP model, followed by a study on the robustness of its image and text embeddings." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 134, + 512, + 148 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 134, + 512, + 148 + ], + "spans": [ + { + "bbox": [ + 305, + 134, + 512, + 148 + ], + "type": "text", + "content": "4.1. CLIP training and zero-shot prediction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "spans": [ + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "type": "text", + "content": "CLIP is a VLM that consists of an image encoder and a text encoder trained jointly on 400 million web-scraped image-text pairs [47]. The outputs of CLIP are the text and image embeddings for the respective text and image inputs. CLIP is trained using a contrastive loss which enforces similarity between the representations of positive image-text pairs and disparity between the representations of negative image-text pairs in the training minibatch. The training objective of CLIP is shown in Eq.1, where the embeddings of the " + }, + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "type": "inline_equation", + "content": "i^{th}" + }, + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "type": "text", + "content": " image-text pair are represented as " + }, + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_i" + }, + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_i" + }, + { + "bbox": [ + 304, + 152, + 546, + 274 + ], + "type": "text", + "content": " respectively.:" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 336, + 280, + 545, + 311 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 336, + 280, + 545, + 311 + ], + "spans": [ + { + "bbox": [ + 336, + 280, + 545, + 311 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {C L I P}} \\left(x _ {i}\\right) = - \\log \\frac {\\exp \\left(\\cos \\left(\\mathbf {I} _ {i} , \\mathbf {T} _ {i}\\right)\\right)}{\\sum_ {c = 1} ^ {C} \\exp \\left(\\cos \\left(\\mathbf {I} _ {i} , \\mathbf {T} _ {c}\\right)\\right)} \\tag {1}", + "image_path": "e14000b58a0356e006c237f5e3426f5aa7d4ca7d0a59d4afd7d7bf1de3e89a7e.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "spans": [ + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "text", + "content": "The use of both text and image modalities during training enables the effective use of text embeddings as a zero-shot classifier, where inference can be performed directly without access to training data. For this, the text embeddings " + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_c" + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "text", + "content": " corresponding to the captions \"A photo of a {class}\" for each of the " + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "text", + "content": " classes are compared with the image embedding " + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_i" + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "text", + "content": ", and the class with maximum similarity is predicted as shown in Eq.2. Thus, the text embeddings " + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_c" + }, + { + "bbox": [ + 304, + 316, + 546, + 425 + ], + "type": "text", + "content": " can be viewed as the weights of a classifier for a CLIP backbone." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 371, + 434, + 545, + 447 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 371, + 434, + 545, + 447 + ], + "spans": [ + { + "bbox": [ + 371, + 434, + 545, + 447 + ], + "type": "interline_equation", + "content": "\\hat {y} _ {i} = \\operatorname {a r g m a x} _ {c} \\cos \\left(\\mathbf {I} _ {i}, \\mathbf {T} _ {c}\\right) \\tag {2}", + "image_path": "d8799d177ef7101d8c08672af66b2f581b64429ea2811203f7030c67af51e81c.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 455, + 542, + 468 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 455, + 542, + 468 + ], + "spans": [ + { + "bbox": [ + 305, + 455, + 542, + 468 + ], + "type": "text", + "content": "4.2. Characteristics of image and text embeddings" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 474, + 545, + 545 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 474, + 545, + 545 + ], + "spans": [ + { + "bbox": [ + 304, + 474, + 545, + 545 + ], + "type": "text", + "content": "CLIP [47] shows remarkable zero-shot performance as shown in Table-1 (E1), and outperforms even an ImageNet pre-trained model that is explicitly fine-tuned using the downstream dataset (Table-3) on several DG datasets. To understand its superior zero-shot performance, we discuss below the robustness of its image and text embeddings." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 546, + 547, + 713 + ], + "type": "text", + "content": "Characteristics of the Image Encoder: In image classification tasks, the representations learned using standard ERM training are expected to exhibit invariances to several factors of variation due to: (a) the classification objective that enforces similar representations for different variations within a given class, which are different from the representations for other classes and (b) augmentations such as color jitter that enforce additional invariance. However, CLIP is trained using detailed captions for each image, such as \"A brown cat sitting on a sofa\", \"A black cat standing on two limbs\", and \"A black dog with long ears and a lot of fur\". This allows CLIP to learn rich specialized representations for each attribute, with higher intra-class variance when compared to standard ERM training." + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23924" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 216 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 216 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 216 + ], + "type": "text", + "content": "Characteristics of the Text Encoder: Robustness to distribution shifts can be achieved either by incorporating the required domain-invariance in the feature extractor, or by domain-invariant feature selection at the classification head. As discussed, CLIP's image encoder produces input-specific representations and is not domain invariant. The superior generalization of CLIP on different datasets and domains is thus a result of the robust text embeddings. Although descriptive captions such as \"A brown cat sitting on a sofa\" are expected to have unique embeddings based on pose, location, etc., generic captions such as \"A photo of a {class}\" represent the core concept of the class." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "text", + "content": "Empirical observations: In Table-1, we present results to demonstrate the robustness of CLIP text embeddings on the multi-source Domain Generalization benchmarks, where each dataset consists of images from " + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "text", + "content": " domains. The results presented are an average of " + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "text", + "content": " cases, where each case corresponds to the training on a given set of " + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "inline_equation", + "content": "n - 1" + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "text", + "content": " domains and testing on the remaining unseen domain referred to as the target domain. Firstly, CLIP zero-shot results (E1) show the robustness of text embeddings across different distributions. The robustness of the text embeddings can be improved by explicitly enforcing domain invariance for better generalization to unseen domains (E2). However, the same level of robustness is not seen when we use an average of all image embeddings across the same domains for a given class, as shown in E3. This is due to the fact that while the text embeddings for \"A {domain} of a {class}\" are obtained by training over a large dataset (400 million images), the image embeddings are an average of " + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\sim 0.01" + }, + { + "bbox": [ + 47, + 223, + 289, + 713 + ], + "type": "text", + "content": " million images on the downstream dataset. This is illustrated in Fig.1, where the red decision boundary trained using image embeddings misclassifies images from the unseen target domain, while the green classifier trained using the generic text embeddings is closer to an ideal decision boundary. However, an average image embedding on the target domain improves results significantly (E4). The accuracy improves further when an average embedding corresponding to a few (10) source domain images closest (in terms of cosine similarity of image embeddings) to the target image is used for each class during prediction (E5). A similar experiment using images from the target domain (E6), achieves considerable improvements over the zero-shot accuracy in E1. We can consider E6 as an In-(target)-Domain setting where a labeled hold-out validation set is used during prediction for obtaining the average embeddings. Therefore, it is possible to outperform the generalized representations of the text embeddings only when labeled images from the target domain are available. Thus, in a DG setting where the target domain is inaccessible, the generic text embeddings provide the best robustness across distribution shifts. We therefore use the text embeddings to maximally transfer their robustness to the student model." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 305, + 71, + 493, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 71, + 493, + 85 + ], + "spans": [ + { + "bbox": [ + 305, + 71, + 493, + 85 + ], + "type": "text", + "content": "5. Proposed Approach: VL2V-ADiP" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 304, + 91, + 545, + 152 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 545, + 152 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 545, + 152 + ], + "type": "text", + "content": "In this section, we first present the knowledge distillation framework adapted to a VLM-to-vision distillation setting. We further propose a self-distillation approach VL2V-SD, to enhance the robustness of the VLM image encoder, which motivates the proposed approach VL2V-ADiP." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 305, + 158, + 518, + 170 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 158, + 518, + 170 + ], + "spans": [ + { + "bbox": [ + 305, + 158, + 518, + 170 + ], + "type": "text", + "content": "5.1. Distillation from VLMs to Vision models" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "spans": [ + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": "The standard framework of Knowledge Distillation (KD) [20] applies in the unimodal setting, for instance, where the teacher and student are both vision models. To adapt this to a VLM-to-vision distillation setting, a classification model (which we refer to as a VLM-classifier) is first constructed using the VLM. The feature extractor of the VLM-classifier comes from the image encoder of the VLM, and the linear classifier head obtains its weights from the text embeddings " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_c" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": " corresponding to the captions \"a photo of a {class}\" for all " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": " classes. For every image-label pair " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "(x_i,y_i)" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": ", the VLM-classifier first computes the image embedding " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_{x_i}" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": ", and further computes its similarity w.r.t. each of the text embeddings " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_c" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": ". The similarity scores " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "\\cos (\\mathbf{I}_{x_i},\\mathbf{T}_c)" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": " are considered to be analogous to the logit layer, over which the softmax function is applied. The final distillation loss of the student that is minimized during training is shown below in Eq.4 for a minibatch of size " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": ". Here, " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "f_{S}(.)" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{T}}(.)" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": " represent the softmax representations of the student and teacher respectively, CE represents the Cross-Entropy loss, and KL represents the Kullback-Leibler divergence. Temperature scaling is applied to the logits before computing softmax [20]. We tune over the range - " + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "inline_equation", + "content": "\\{0.1,1,10\\}" + }, + { + "bbox": [ + 304, + 176, + 545, + 451 + ], + "type": "text", + "content": " on the in-domain validation set, and report the baseline best results in Table-3." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 358, + 460, + 545, + 474 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 358, + 460, + 545, + 474 + ], + "spans": [ + { + "bbox": [ + 358, + 460, + 545, + 474 + ], + "type": "interline_equation", + "content": "f _ {\\mathrm {T}} \\left(x _ {i}\\right) = \\operatorname {s o f t m a x} \\left(\\cos \\left(\\mathbf {I} _ {x _ {i}}, \\mathbf {T} _ {c}\\right)\\right) \\tag {3}", + "image_path": "db2c5fd3208becb58572e779673a3ef9f7300a3d56fb64ee70e6e48207922ec4.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 482, + 545, + 523 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 482, + 545, + 523 + ], + "spans": [ + { + "bbox": [ + 306, + 482, + 545, + 523 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {K D}} = \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\left\\{\\mathrm {C E} \\left(f _ {S} \\left(x _ {i}\\right), y _ {i}\\right) + \\lambda \\cdot \\mathrm {K L} \\left(f _ {\\mathrm {T}} \\left(x _ {i}\\right) \\mid \\mid f _ {S} \\left(x _ {i}\\right)\\right) \\right\\} \\tag {4}", + "image_path": "2714011f652c73f82c211b03ac3fcef17d37af19db489cee2a32b1e6f3fe2d2c.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 528, + 538, + 540 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 528, + 538, + 540 + ], + "spans": [ + { + "bbox": [ + 306, + 528, + 538, + 540 + ], + "type": "text", + "content": "5.2. Self-Distillation from Text to Image encoders" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 545, + 545, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 545, + 545, + 676 + ], + "spans": [ + { + "bbox": [ + 304, + 545, + 545, + 676 + ], + "type": "text", + "content": "As discussed in Section-4.2, the image encoder of CLIP is trained to represent all factors of variations in an image that are described in the corresponding caption used during its training. Therefore, it does not exhibit the invariances to factors such as color, texture, lighting, and pose, that are required for an image classification task. On the other hand, text prompts allow much better control over invariances in text-embeddings. For example, a prompt such as \"A brown cat sitting on a sofa\" uniquely represents the color, location, and pose of the cat in addition to the object itself, whereas a prompt \"A photo of a cat\" is invariant to such variations." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 305, + 677, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 677, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 677, + 547, + 713 + ], + "type": "text", + "content": "Motivated by this, we propose Vision-Language to Vision Self Distillation (VL2V-SD), where the invariances of generic text embeddings are distilled to the image encoder" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "23925" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 49, + 70, + 211, + 225 + ], + "blocks": [ + { + "bbox": [ + 49, + 70, + 211, + 225 + ], + "lines": [ + { + "bbox": [ + 49, + 70, + 211, + 225 + ], + "spans": [ + { + "bbox": [ + 49, + 70, + 211, + 225 + ], + "type": "image", + "image_path": "acd36f423afd1c11c334bf958b24fb564dba25f4c41db84ae644060a3c2cb124.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 149, + 228, + 258, + 239 + ], + "lines": [ + { + "bbox": [ + 149, + 228, + 258, + 239 + ], + "spans": [ + { + "bbox": [ + 149, + 228, + 258, + 239 + ], + "type": "text", + "content": "CLIP image encoder/features" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 149, + 242, + 249, + 252 + ], + "lines": [ + { + "bbox": [ + 149, + 242, + 249, + 252 + ], + "spans": [ + { + "bbox": [ + 149, + 242, + 249, + 252 + ], + "type": "text", + "content": "CLIP text encoder / features" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 215, + 70, + 375, + 224 + ], + "blocks": [ + { + "bbox": [ + 215, + 70, + 375, + 224 + ], + "lines": [ + { + "bbox": [ + 215, + 70, + 375, + 224 + ], + "spans": [ + { + "bbox": [ + 215, + 70, + 375, + 224 + ], + "type": "image", + "image_path": "d2859f37a8966683bad4313b867da91d69a96a8ad0f0f51e7beb38cc126287ed.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 263, + 228, + 326, + 238 + ], + "lines": [ + { + "bbox": [ + 263, + 228, + 326, + 238 + ], + "spans": [ + { + "bbox": [ + 263, + 228, + 326, + 238 + ], + "type": "text", + "content": "Networkfrozen" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 261, + 242, + 333, + 252 + ], + "lines": [ + { + "bbox": [ + 261, + 242, + 333, + 252 + ], + "spans": [ + { + "bbox": [ + 261, + 242, + 333, + 252 + ], + "type": "text", + "content": "Network trainable" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 340, + 228, + 437, + 239 + ], + "lines": [ + { + "bbox": [ + 340, + 228, + 437, + 239 + ], + "spans": [ + { + "bbox": [ + 340, + 228, + 437, + 239 + ], + "type": "text", + "content": "Student network / features" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 340, + 242, + 428, + 251 + ], + "lines": [ + { + "bbox": [ + 340, + 242, + 428, + 251 + ], + "spans": [ + { + "bbox": [ + 340, + 242, + 428, + 251 + ], + "type": "text", + "content": "CLIP zero-shot classifier" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 380, + 95, + 543, + 198 + ], + "blocks": [ + { + "bbox": [ + 412, + 74, + 489, + 84 + ], + "lines": [ + { + "bbox": [ + 412, + 74, + 489, + 84 + ], + "spans": [ + { + "bbox": [ + 412, + 74, + 489, + 84 + ], + "type": "text", + "content": "Stage 3 (Predict)" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 380, + 95, + 543, + 198 + ], + "lines": [ + { + "bbox": [ + 380, + 95, + 543, + 198 + ], + "spans": [ + { + "bbox": [ + 380, + 95, + 543, + 198 + ], + "type": "image", + "image_path": "0e3b70fed9340deff4ce250aa2b3be45f860afab729bb8242c1420753e3bd614.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 265, + 547, + 288 + ], + "lines": [ + { + "bbox": [ + 46, + 265, + 547, + 288 + ], + "spans": [ + { + "bbox": [ + 46, + 265, + 547, + 288 + ], + "type": "text", + "content": "Figure 2. Overview of the proposed approach VL2V-ADiP, consisting of (a) Align, (b) Distill and (c) Predict Stages for Black-Box Distillation from Vision-Language to Vision (VL2V) models." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "spans": [ + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "text", + "content": "using the downstream dataset. We minimize the loss shown in Eq.5 for training, where " + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "inline_equation", + "content": "\\mathbf{T}_{y_i}" + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "text", + "content": " represents the embedding for \"A photo of a {class}\" corresponding to the ground truth class " + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "inline_equation", + "content": "y_{i}" + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_{x_i}^t" + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "inline_equation", + "content": "\\mathbf{I}_{x_i}^s" + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "text", + "content": " represent the image embeddings of the teacher and student respectively for an image " + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "inline_equation", + "content": "x_{i}" + }, + { + "bbox": [ + 46, + 303, + 287, + 363 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 61, + 368, + 287, + 399 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 368, + 287, + 399 + ], + "spans": [ + { + "bbox": [ + 61, + 368, + 287, + 399 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {S D}} = - \\frac {1}{2 n} \\sum_ {i = 1} ^ {n} \\left\\{\\cos \\left(\\mathbf {I} _ {x _ {i}} ^ {s}, \\mathbf {T} _ {y _ {i}}\\right) + \\cos \\left(\\mathbf {I} _ {x _ {i}} ^ {s}, \\mathbf {I} _ {x _ {i}} ^ {t}\\right) \\right\\} \\tag {5}", + "image_path": "75cbd0911f70d55d3b2cad704d6eaf9ed9f4c4355505ebb7984c3cd1f851e273.jpg" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "type": "text", + "content": "The image encoders of both teacher and student are the same (VLM's image encoder) initially, and the student's image encoder is updated during training. The text encoder is frozen during training. While the first term enforces the image encoder to learn representations that match the corresponding text embeddings more accurately on the given dataset, the second term ensures that there is no representation collapse, and retains the rich features learned by the image encoder. The classifier is composed of text embeddings corresponding to the prompts \"a photo of a {class}\" for all classes, as was the case in the VLM-classifier discussed in Section-5.1. We present the results of VL2V-SD in Table2, where we note significant improvements over both CLIP zero-shot and the SOTA DG methods - SWAD [8], MIRO [9], DART [23], and SAGM [61] on the ViT-B/16 architecture with CLIP initialization. We demonstrate significant gains over the CLIP fine-tuning methods LP-FT [28], FLYP [18], CLIPood [55], and WiSE-FT [63]. We also achieve significant gains over a distillation method RISE [22], despite using the standard text prompt while RISE uses an expanded set of prompts. For WiSE-FT, we present the results with the optimal " + }, + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "type": "text", + "content": " that achieves the best performance by using the search space " + }, + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\alpha = [0.1 - 0.9]" + }, + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "type": "text", + "content": ". Similarly, for RISE, we present the results with the optimal hyperparameters " + }, + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "type": "inline_equation", + "content": "\\lambda_1, \\lambda_2, \\lambda_3" + }, + { + "bbox": [ + 46, + 402, + 289, + 713 + ], + "type": "text", + "content": " based on their search space. We incorporate SWAD [8] in all our runs for the baselines as well" + } + ] + } + ], + "index": 13 + }, + { + "type": "table", + "bbox": [ + 307, + 338, + 545, + 447 + ], + "blocks": [ + { + "bbox": [ + 305, + 301, + 546, + 335 + ], + "lines": [ + { + "bbox": [ + 305, + 301, + 546, + 335 + ], + "spans": [ + { + "bbox": [ + 305, + 301, + 546, + 335 + ], + "type": "text", + "content": "Table 2. White-Box setting (CLIP initialization): Performance " + }, + { + "bbox": [ + 305, + 301, + 546, + 335 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 305, + 301, + 546, + 335 + ], + "type": "text", + "content": " of the proposed approach VLV2-SD, compared to the existing methods. ViT-B/16 architecture is used. (S) denotes SWAD [8]." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 307, + 338, + 545, + 447 + ], + "lines": [ + { + "bbox": [ + 307, + 338, + 545, + 447 + ], + "spans": [ + { + "bbox": [ + 307, + 338, + 545, + 447 + ], + "type": "table", + "html": "
MethodOHTIVLCSPACSDNAvg-IDAvg-OOD
Zero-shot [47]82.4034.1082.3096.5057.70-70.60
SWAD [8]81.0142.9279.1391.3557.9289.0570.47
MIRO (S) [9]84.8059.3082.3096.4460.4791.0076.66
DART (S) [23]80.9351.2480.3893.4359.3289.2573.06
SAGM (S) [61]83.4058.6482.0594.3159.0589.7475.49
LP-FT (S) [28]81.1747.2680.8892.9257.0488.9771.85
FLYP (S) [18]82.7633.2566.6478.5357.4178.9463.72
CLIPood (S) [55]83.3146.2877.1993.1657.7869.9071.55
WiSE-FT (S) [63]86.3254.5082.8897.2958.0188.3575.80
RISE (S) [22]78.3949.6180.6293.2555.3787.9171.45
VL2V-SD (Ours)87.3858.5483.2596.6862.7989.9977.73
", + "image_path": "6cd0bf2058dbce024c064dfecb7ba65de9e24800329eb5cfcda48ff0370f919f.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "table_body" + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 456, + 545, + 529 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 456, + 545, + 529 + ], + "spans": [ + { + "bbox": [ + 304, + 456, + 545, + 529 + ], + "type": "text", + "content": "as the proposed approach (denoted by “(S)”) since it is a generic technique that improves the generalization of any given method. However, we do not incorporate SWAD with WiSE-FT since it already performs weight averaging of the pre-trained and fine-tuned models. We present the results without SWAD in Suppl. Sec-3.2." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 537, + 531, + 551 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 537, + 531, + 551 + ], + "spans": [ + { + "bbox": [ + 305, + 537, + 531, + 551 + ], + "type": "text", + "content": "5.3. VL2V - Align, Distill, Predict (VL2V-ADiP)" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 556, + 545, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 556, + 545, + 676 + ], + "spans": [ + { + "bbox": [ + 304, + 556, + 545, + 676 + ], + "type": "text", + "content": "While VL2V-SD is very effective in improving the performance of the VLM in a white-box setting, it does not address the problem of black-box distillation that we consider in this work, since it assumes access to the weights of the VLM model. In this section, we discuss how this method can be adapted to the black-box setting and present the proposed approach VL2V-ADiP. Since the amount of downstream task-specific data is assumed to be limited, the student is initialized with the best available pre-trained model such as ImageNet [26]." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 677, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 546, + 713 + ], + "type": "text", + "content": "In the self-distillation case seen in Section-5.2, the goal was to induce domain invariance from the text encoder to the image encoder, while ensuring that the rich features" + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23926" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "type": "text", + "content": "learned by the image encoder are not lost. Whereas, in the black-box setting, the goal is to distill the rich features learned by the image-encoder of the VLM and the domain invariance from the text embeddings. While the two cases can have a similar loss formulation as shown in Eq.5, the method VL2V-SD cannot directly be applied here since the feature dimension of the student model may be different from the dimension of VLM's image and text embeddings. Even if the dimensions had matched, the features of the ImageNet pre-trained backbone and VLM's embeddings would be misaligned. Directly enforcing a similarity loss in such a case would lead to forgetting of the pretrained features. To address this, we propose VL2V-ADiP, Vision-Language to Vision - Align, Distill, Predict as shown in Fig.2 (Ref: Alg. 1 in Suppl.). We propose to first Align the features of the pre-trained student model with VLM embeddings using a linear projection head on the student backbone in Stage-1, as shown in Fig.2(a). For this, the student backbone is frozen and only the projection head is trained using the following loss, where " + }, + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "type": "inline_equation", + "content": "\\mathbf{PF}_{x_i}^s" + }, + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "type": "text", + "content": " represents the projected features of the student model for the input " + }, + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "type": "inline_equation", + "content": "x_{i}" + }, + { + "bbox": [ + 46, + 72, + 289, + 324 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 53, + 336, + 287, + 376 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 336, + 287, + 376 + ], + "spans": [ + { + "bbox": [ + 53, + 336, + 287, + 376 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {A D i P}} = - \\frac {1}{2 n} \\sum_ {i = 1} ^ {n} \\left\\{\\cos \\left(\\mathbf {P F} _ {x _ {i}} ^ {s}, \\mathbf {T} _ {y _ {i}}\\right) + \\cos \\left(\\mathbf {P F} _ {x _ {i}} ^ {s}, \\mathbf {I} _ {x _ {i}} ^ {t}\\right) \\right\\} \\tag {6}", + "image_path": "fba178dee3def0f19f222df16a5d85f7d7cf8fcb33f65e96a3ee23da6730e2b9.jpg" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 379, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 379, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 379, + 289, + 713 + ], + "type": "text", + "content": "Next, the aligned student features are refined using the VLM's image and text embeddings in the Distill step as shown in Fig.2(b) (Stage-2). For this step, the linear projection head is frozen, and the feature extractor is trained using the same loss as Stage-1, as shown in Eq.6. While we give equal weight to both loss terms in Eq.6, we present the impact of varying this in Suppl. Sec-4. Finally, in Stage-3 (Predict), the VLM's embeddings corresponding to \"a photo of a {class}\" for all " + }, + { + "bbox": [ + 46, + 379, + 289, + 713 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 46, + 379, + 289, + 713 + ], + "type": "text", + "content": " classes are used as weights of the classification head, and the class with the highest similarity to the given image embedding is predicted, as shown in Eq.2. In addition to learning the rich features from the VLM teacher's image-encoder and invariances from its text encoder, enforcing similarity between the features of the student backbone and the text embeddings of the corresponding classes also makes the text embeddings more suitable for use as a classifier in Stage-3 (Predict). Thus, although Stages 1 and 2 explicitly train only the student backbone and projection head, they implicitly impact the effectiveness of the classification head as well. This facilitates the use of these embeddings directly as a classifier without the need for fine-tuning further on the downstream dataset. As shown in Table-5, further fine-tuning degrades the performance, since only In-Domain (ID) data is available for fine-tuning, which would make the classifier forget the domain invariance that it inherently possesses. However, fine-tuning with limited In-Domain data improves the ID accuracy as shown in the table." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 306, + 72, + 449, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 449, + 85 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 449, + 85 + ], + "type": "text", + "content": "6. Experiments and Results" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 306, + 91, + 416, + 103 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 91, + 416, + 103 + ], + "spans": [ + { + "bbox": [ + 306, + 91, + 416, + 103 + ], + "type": "text", + "content": "6.1. Evaluation Details" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "spans": [ + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "content": "Towards evaluating the OOD generalization of image classification models, we consider the five popular Domain Generalization (DG) datasets - OfficeHome (OH) [60], PACS [30], VLCS [16], Terra-Incognita (TI) [3] and DomainNet (DN) [44]. Each of the datasets consists of " + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "content": " domains, where " + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "inline_equation", + "content": "d = 4" + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "content": " for the first four datasets and " + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "inline_equation", + "content": "d = 6" + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "content": " for DomainNet. We present more details on the datasets in Suppl. Sec-2. We follow the DomainBed [19] framework for training and evaluation, where each domain is split into training and validation sets, and training is performed on " + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "inline_equation", + "content": "d - 1" + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "content": " domains while evaluation is done on the " + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "inline_equation", + "content": "d^{th}" + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "content": " unseen domain. Thus, for every dataset, " + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "content": " models are trained, by leaving one domain out for evaluation each time. The average accuracy across these " + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 304, + 109, + 547, + 314 + ], + "type": "text", + "content": " runs on the unseen test domain (OOD accuracy) and the average In-domain (ID) validation split accuracy are reported. The unseen test domain is neither used for training nor for hyperparameter tuning [19]." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 321, + 405, + 334 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 321, + 405, + 334 + ], + "spans": [ + { + "bbox": [ + 306, + 321, + 405, + 334 + ], + "type": "text", + "content": "6.2. Training Details" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 340, + 547, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 340, + 547, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 340, + 547, + 628 + ], + "type": "text", + "content": "The number of training iterations is set to 5000 for OfficeHome, PACS, VLCS, and Terra-Incognita, and to 15000 for DomainNet, as is standard [8, 9]. We use the Adam optimizer with a constant learning rate of " + }, + { + "bbox": [ + 304, + 340, + 547, + 628 + ], + "type": "inline_equation", + "content": "5 \\times 10^{-5}" + }, + { + "bbox": [ + 304, + 340, + 547, + 628 + ], + "type": "text", + "content": " for all our experiments except CLIPood (S) in Table-2, for which we use the AdamW optimizer as specified in [55]. These settings are fixed for all datasets, and we do not introduce any additional hyperparameters in the proposed algorithm. Our primary evaluations consider a ViT-B/16 architecture [15] for both the VLM (teacher) Image-encoder and the student model to enable a fair comparison with existing methods, that use the same architecture. Since one of the key motivations of distillation is to train a low-capacity model, we present results with lower-capacity student architectures as well. We use a CLIP teacher model, which uses a Transformer architecture [59] with modifications described by Radford et al. [46] for the text encoder. The student model and our primary baselines for VL2V-ADiP use an ImageNet pre-trained initialization [26], as is standard in DG [19]. We obtain the results of baseline methods on ViTs in Tables 2 and 3 by integrating the official code of the respective method with the MIRO [9] code base to ensure a fair comparison. Additionally, we show results with other teacher VLMs in Suppl. Sec-3.3." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 635, + 459, + 647 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 635, + 459, + 647 + ], + "spans": [ + { + "bbox": [ + 306, + 635, + 459, + 647 + ], + "type": "text", + "content": "6.3. Comparison with the SOTA" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 547, + 715 + ], + "type": "text", + "content": "We present the ID and OOD results of the proposed approach VL2V-ADiP when compared to the DG and KD baselines in Table-3. Gulrajani and Lopez-Paz [19] show that ERM training is a very strong baseline in DG and outperforms several older methods that were proposed. Thus," + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23927" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 47, + 116, + 288, + 214 + ], + "blocks": [ + { + "bbox": [ + 47, + 70, + 288, + 115 + ], + "lines": [ + { + "bbox": [ + 47, + 70, + 288, + 115 + ], + "spans": [ + { + "bbox": [ + 47, + 70, + 288, + 115 + ], + "type": "text", + "content": "Table 3. SOTA comparison with ImageNet initialization: Performance (%) of the proposed approach VL2V-ADiP, compared to existing KD and DG methods with SWAD (S). ViT-B/16 with ImageNet-1K initialization is used as the student." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 116, + 288, + 214 + ], + "lines": [ + { + "bbox": [ + 47, + 116, + 288, + 214 + ], + "spans": [ + { + "bbox": [ + 47, + 116, + 288, + 214 + ], + "type": "table", + "html": "
MethodOHTIVLCSPACSDNAvg-IDAvg-OOD
ERM-LP (S)71.4831.3577.5267.0236.6573.9956.81
ERM Full Fine-tuning (S)83.2250.0580.3390.2856.1089.3172.00
LP-FT (S) [28]81.5551.6180.1791.2056.0390.0372.11
SimKD (S) [13]66.7681.0183.9228.2449.4268.2461.87
KD (S) [20]82.7348.4080.4891.4656.1189.2071.84
MIRO (S) [9]80.0950.2981.1089.5055.7588.7171.35
DART (S) [23]83.7549.6877.2990.5558.0588.5471.86
SAGM (S) [61]82.2253.2479.6090.0255.6689.2272.15
Text2Concept (S) [40]70.2426.4664.7779.0323.2653.1552.82
RISE (S) [22]83.4852.5583.7093.5456.5888.9173.97
VL2V-ADiP (Ours)85.7455.4381.9094.9459.3889.0275.48
", + "image_path": "849e0129d16d1eff8ea2fce5633bb3fddc0e1f4663e0bc7bc4c92dd7b9f18c35.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 47, + 284, + 288, + 408 + ], + "blocks": [ + { + "bbox": [ + 47, + 228, + 288, + 282 + ], + "lines": [ + { + "bbox": [ + 47, + 228, + 288, + 282 + ], + "spans": [ + { + "bbox": [ + 47, + 228, + 288, + 282 + ], + "type": "text", + "content": "Table 4. Distillation to lower capacity student models: Performance (\\%) of the proposed approach VL2V-ADiP (denoted as Ours), when compared to the KD baseline [20] and ERM (S) or SWAD [8] with different student architectures. The teacher architecture is ViT-B/16. (S) denotes SWAD." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 47, + 284, + 288, + 408 + ], + "lines": [ + { + "bbox": [ + 47, + 284, + 288, + 408 + ], + "spans": [ + { + "bbox": [ + 47, + 284, + 288, + 408 + ], + "type": "table", + "html": "
StudentMethodOHTIVLCSPACSDNAvg-IDAvg-OOD
ViT-B/16 (86M)ERM (S)83.2250.0580.3390.2856.1089.3172.00
KD (S)82.7348.4080.4891.4656.1789.2071.85
Ours (S)85.7455.4381.9094.9459.3889.0275.48
ViT-S/16 (22M)ERM (S)78.5849.4078.7285.8052.0985.6668.92
KD (S)78.1450.1179.1485.9752.0587.4369.08
Ours (S)81.2252.4781.4489.3254.2386.5971.73
DeiT-S/16 (22M)ERM (S)74.9547.8579.3789.2249.1886.5868.12
KD (S)74.6548.1178.8688.1449.1086.6667.77
Ours (S)77.6348.7281.8988.9750.3785.2869.52
ResNet-50 (26M)ERM (S)70.8549.4779.5088.0546.4384.8866.86
KD (S)70.6751.2278.6387.2346.3185.0466.81
Ours (S)74.4253.4679.2386.7247.7484.7368.31
", + "image_path": "4959eedefc4f193f4625ee8d8073f2c1b136fa7e49ed9759aad57b811076f939.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 426, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 426, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 426, + 289, + 715 + ], + "type": "text", + "content": "ERM training of only the linear layer (ERM-LP) and ERM full fine-tuning (ERM-FFT) are two important baselines we consider. Further, we present the results of important SOTA DG methods - SWAD [8], MIRO [9], DART [23], and SAGM [61]. Additionally, we also show results with Text2Concept [40] and LP-FT [28] - simple fine-tuning strategies for improved OOD generalization on downstream tasks. While there are several methods that outperform ERM [6, 25, 41, 57], we do not present all of them here since the above-listed recent methods outperform them. Since we incorporate SWAD in the proposed approach, we present all the baseline results by integrating SWAD with each of them and denote them with a suffix \"S\" in the tables. Additionally, we also present three distillation results - (a) knowledge distillation from the VLM teacher to the vision student model as discussed in Section-5.1 and (b) distillation from the VLM teacher using SimKD [13], and (c) distillation from the VLM teacher using RISE [22]. Since the feature distillation methods listed in Sec. 2 cannot be extended to the black box distillation setting, we do not compare with them. The proposed approach VL2V-ADiP achieves " + }, + { + "bbox": [ + 46, + 426, + 289, + 715 + ], + "type": "inline_equation", + "content": "\\sim 1.5\\%" + }, + { + "bbox": [ + 46, + 426, + 289, + 715 + ], + "type": "text", + "content": " improvement on average OOD accuracy across all datasets with respect to the best baselines, with comparable ID accuracy. We note that Text2Concept scales" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 169 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 169 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 169 + ], + "type": "text", + "content": "poorly on smaller datasets compared to the results shown in the paper [40]. SimKD [13] is a method intended for unimodal distillation and thus fails for the multimodal setup. Furthermore, we outperform the method RISE [22] by a large margin despite the latter using expanded text prompts. This shows that the proposed distillation method VL2V-ADiP effectively distills from VLMs with lesser prompt engineering and text supervision compared to RISE." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 177, + 537, + 190 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 177, + 537, + 190 + ], + "spans": [ + { + "bbox": [ + 305, + 177, + 537, + 190 + ], + "type": "text", + "content": "6.4. Distillation to lower capacity student models" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 195, + 547, + 340 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 195, + 547, + 340 + ], + "spans": [ + { + "bbox": [ + 304, + 195, + 547, + 340 + ], + "type": "text", + "content": "We present results of distilling from a CLIP ViT-B/16 teacher to different student architectures and capacities (ViT-S/16, DeiT-S, ResNet-50) in Table-4. We observe substantial gains over the Knowledge Distillation and ERM (S) or SWAD baseline across all student architectures. We note that the distillation performance is best when the architecture (ViT) of the teacher matches that of the student. For example, although ViT-S/16, DeiT-S/16, and ResNet-50 have a similar number of parameters, the performance of the ViT-S/16 student is the best, showing the architecture plays a role in the nature of representations learned, thereby allowing better transfer when they match." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 347, + 400, + 361 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 347, + 400, + 361 + ], + "spans": [ + { + "bbox": [ + 305, + 347, + 400, + 361 + ], + "type": "text", + "content": "6.5. Ablation Study" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 366, + 547, + 594 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 366, + 547, + 594 + ], + "spans": [ + { + "bbox": [ + 304, + 366, + 547, + 594 + ], + "type": "text", + "content": "We present an ablation study of the proposed method in Table-5. Firstly, we study the impact of combining stages-1 (Align) and 2 (Distill), i.e., training the linear projection layer and the backbone jointly in A1. This results in a " + }, + { + "bbox": [ + 304, + 366, + 547, + 594 + ], + "type": "inline_equation", + "content": "2.2\\%" + }, + { + "bbox": [ + 304, + 366, + 547, + 594 + ], + "type": "text", + "content": " drop in ID accuracy and a " + }, + { + "bbox": [ + 304, + 366, + 547, + 594 + ], + "type": "inline_equation", + "content": "6.3\\%" + }, + { + "bbox": [ + 304, + 366, + 547, + 594 + ], + "type": "text", + "content": " drop in OOD accuracy, highlighting that the pre-trained ImageNet features are retained better when they are aligned before distillation. In A2, the linear projection head is also trained in Stage-2. The results of this case are similar to the proposed approach, showing that even when the linear head is changed, it does not get updated much after Stage-1 (Align). We next analyze the importance of distilling from both image and text encoders of CLIP by using only one of them individually in A3 and A4. In both cases, we note a significant drop in the OOD accuracy highlighting the importance of distilling from both encoders. Distilling only from the Image encoder has a larger drop due to the lack of alignment between the representations and the classifier head which is composed of CLIP text embeddings corresponding to each of the classes." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 594, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 548, + 715 + ], + "type": "text", + "content": "In Stage-3 (Predict) of the proposed approach, the CLIP text embeddings corresponding to the classes are directly used as the classifier weights. We explore the impact of training this classifier further using cross-entropy loss over the softmax representations shown in Eq.3, in experiments A5-A8. In A5 and A6, the classifier head is first initialized using the text embeddings of CLIP, and in A7 and A8, a random initialization is used for the classification head. In A5 and A7, only the classifier head is trained, whereas in A6 and A8, the full network is trained. All these experi" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 318, + 757 + ], + "type": "text", + "content": "23928" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 85, + 547, + 196 + ], + "blocks": [ + { + "bbox": [ + 73, + 70, + 520, + 82 + ], + "lines": [ + { + "bbox": [ + 73, + 70, + 520, + 82 + ], + "spans": [ + { + "bbox": [ + 73, + 70, + 520, + 82 + ], + "type": "text", + "content": "Table 5. Ablation Study of the proposed VL2V-ADiP: Performance (%) on ViT-B/16 model with ImageNet initialization." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 85, + 547, + 196 + ], + "lines": [ + { + "bbox": [ + 50, + 85, + 547, + 196 + ], + "spans": [ + { + "bbox": [ + 50, + 85, + 547, + 196 + ], + "type": "table", + "html": "
Method - Changes done w.r.t. VL2V-ADiP (Ours)OHTIVLCSPACSAvg-IDAvg-OOD
VL2V-ADiP (Ours)85.7455.4381.9094.9492.7479.50
A1: Combining "Align" and "Distill" stages74.5552.9980.1485.2990.5573.24
A2: Without freezing projection head in Stage-286.1356.6881.7893.7593.0079.59
A3: Distilling only from Text encoder in Stages-1 and 283.1847.0279.8390.8691.8775.22
A4: Distilling only from Image encoder in Stages-1 and 278.9728.9782.2489.9774.0970.04
A5: Finetuning CLIP classifier-head in Stage-3 (CE loss) - CLIP init classifier84.4749.2881.3093.5493.0677.15
A6: Finetuning full network in Stage-3 (CE loss) - CLIP init classifier83.8849.8380.1392.2593.3776.52
A7: Finetuning classifier-head in Stage-3 (CE loss) - random init classifier84.6349.5581.2993.5793.0277.26
A8: Finetuning full network in Stage-3 (CE loss) - random init classifier83.1650.0379.7892.1593.1476.28
", + "image_path": "22b5203a29e5948ea1c3f7c1c78b954bd9b460092513f241566a908e17c8e81d.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 47, + 204, + 545, + 324 + ], + "blocks": [ + { + "bbox": [ + 47, + 204, + 545, + 324 + ], + "lines": [ + { + "bbox": [ + 47, + 204, + 545, + 324 + ], + "spans": [ + { + "bbox": [ + 47, + 204, + 545, + 324 + ], + "type": "image", + "image_path": "6f84f9fcf6ec76d60916a8d979d0197c2f10c1cda186f4ffc424a97248b2f52c.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 327, + 546, + 351 + ], + "lines": [ + { + "bbox": [ + 46, + 327, + 546, + 351 + ], + "spans": [ + { + "bbox": [ + 46, + 327, + 546, + 351 + ], + "type": "text", + "content": "Figure 3. OOD accuracy " + }, + { + "bbox": [ + 46, + 327, + 546, + 351 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 46, + 327, + 546, + 351 + ], + "type": "text", + "content": " of the proposed approach when compared to KD and ERM baselines for select classes/ domains in Office-Home and Terra-Incognita datasets, where the (a) ERM-IN (linear) (b) CLIP Zero-shot (c) ERM-CLIP (linear) performance is poor." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 359, + 289, + 479 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 359, + 289, + 479 + ], + "spans": [ + { + "bbox": [ + 46, + 359, + 289, + 479 + ], + "type": "text", + "content": "ments result in a drop in the OOD accuracy, indicating that training on the downstream dataset using the cross-entropy loss can destroy the domain invariances learned from CLIP. Since the impact of training the full network is higher, the drop is higher in this case when compared to finetuning only the classification head. In all cases, the In-Domain accuracy improves when compared to the proposed approach, with higher gains in the case when the full network is trained, confirming that training without the supervision of the CLIP teacher indeed overfits to the training domains." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "text", + "content": "We also compare the ERM and KD baselines with the proposed approach in some of the extreme cases in Fig.3, where the CLIP Image encoder is significantly better than the ERM model (a), and vice-versa (c). For this, we select the classes/domains with the highest difference " + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "inline_equation", + "content": "(40 - 50\\%)" + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "text", + "content": " between the ERM-CLIP (Linear) and ERM-ImageNet (IN) (Linear) baselines from the OfficeHome dataset. We also present the case where the CLIP zero-shot accuracy is poor in OfficeHome " + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "inline_equation", + "content": "(22\\%)" + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "text", + "content": " and Terra-Incognita datasets " + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "inline_equation", + "content": "(0\\%)" + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "text", + "content": " in Fig.3 (b). The KD baseline relies a lot on the ImageNet pre-trained backbone, hence it is poor when ERM-IN is poor, and is close to our approach when ERM-IN is good. The ERM fine-tuning baseline is best when the ImageNet features are much better than CLIP Image encoder's features, but it is poor in the other case, as expected. Lastly, even when CLIP zero-shot accuracy is poor (close to " + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "inline_equation", + "content": "0\\%" + }, + { + "bbox": [ + 46, + 486, + 289, + 715 + ], + "type": "text", + "content": "), the proposed approach achieves reasonable accuracy, since Stages-1 and 2 align the text embeddings better to the feature extractor, making them more suitable as a classifier." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 305, + 357, + 379, + 370 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 357, + 379, + 370 + ], + "spans": [ + { + "bbox": [ + 305, + 357, + 379, + 370 + ], + "type": "text", + "content": "7. Conclusion" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 378, + 545, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 378, + 545, + 653 + ], + "spans": [ + { + "bbox": [ + 304, + 378, + 545, + 653 + ], + "type": "text", + "content": "In this work, we aim to leverage the superior generalization of large-scale Vision-Language Models towards improving the OOD generalization of Vision models. We consider a practical scenario where a client gets only black-box access to the model on a pay-per-query basis from the vendor, motivating the need for distilling the model first, and further using the student model during inference. Towards this, we first highlight the unique aspects of the image and text encoders of VLMs and further propose a self-distillation (SD) approach - VL2V-SD, to distill the superior generalization of the VLM's text encoder to its image encoder, while retaining the rich representations of the latter. We further adapt this to a black-box distillation setting, by firstly projecting the representations of the pre-trained feature-extractor (student) to a space that is aligned with embeddings of the VLM teacher, and further finetuning the backbone using the same. The use of both text and image embeddings induces the rich representations of the VLM and its superior generalization to the student model, while also making the text embeddings more suitable for use in the classification head. Both proposed approaches (VL2V-SD and VL2V-ADiP) achieve substantial gains over prior methods on the popular Domain Generalization datasets." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 713 + ], + "type": "text", + "content": "Acknowledgements. This work is supported by the Kotak IISc AI-ML Center and a research grant CRG/2021/005925 from SERB, DST, Govt. of India. Sravanti Addepalli is supported by the Google PhD Fellowship and CII-SERB Prime Minister's Fellowship for Doctoral Research." + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "23929" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 287, + 713 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 123 + ], + "type": "text", + "content": "[1] Martin Arjovsky, Léon Bottou, Ishaan Gulrajani, and David Lopez-Paz. 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It encompasses three prevalent daily environments, including learning scenes, working scenes, and living scenes. LiDAR-Net is characterized by its nonuniform point distribution, e.g., scanning holes and scanning lines. Additionally, it meticulously records and annotates scanning anomalies, including reflection noise and ghost. These anomalies stem from specular reflections on glass or metal, as well as distortions due to moving persons. LiDAR-Net's realistic representation of non-uniform distribution and anomalies significantly enhances the training of deep learning models, leading to improved generalization in practical applications. We thoroughly evaluate the performance of state-of-the-art algorithms on LiDAR-Net and provide a detailed analysis of the results. Crucially, our research identifies several fundamental challenges in understanding indoor point clouds, contributing essential insights to future explorations in this field. Our dataset can be found online: http://lidar-net.njumeta.com.", + "bbox": [ + 75, + 407, + 473, + 724 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 756, + 209, + 771 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Owing to its reliability and accuracy, Light Detection And Ranging (LiDAR) technology becomes increasingly popular, finding broad applications in autonomous vehicles for perception and localization [23, 26, 54] as well as expanding its applications in consumer electronics [3, 34, 37]. Introduced in 2020, the LiDAR scanner on the iPhone has en", + "bbox": [ + 75, + 782, + 468, + 875 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/c56edca1fc4969c1ae2755a12889581f4080f285592a4336ef251ff860e8fa72.jpg", + "image_caption": [ + "Figure 1. LiDAR-Net comprises 3.6 billion real-scanned points, each annotated with semantic and instance labels. Points of LiDAR-Net have real-scanned characteristics including scanning holes, scanning lines, and anomalies such as ghosts (indicated by red points) caused by moving persons. These characteristics significantly enhance the ability of trained deep models to generalize to real-world applications." + ], + "image_footnote": [], + "bbox": [ + 506, + 375, + 888, + 510 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "abled a multitude of innovative applications in virtual reality (VR) and 3D measurements. Deep learning has achieved remarkable success in computer vision, particularly in analyzing and understanding 3D scenes [35, 36, 49, 56]. Datasets undoubtedly have played a critical role in this process, since training a deep models usually requires extensive annotated datasets, especially for supervised learning [2, 8, 11, 19, 42, 53]. In the domain of 3D computer vision for indoor scenes, the most widely recognized datasets in the academic community are S3DIS [2], ScanNet [11], and the recent ScanNet++ [53], etc. S3DIS and ScanNet have been used to train models for various 3D scene understanding tasks, such as 3D object detection, along with semantic and instance segmentation. S3DIS and ScanNet collect RGB-D images, and then reconstruct and annotate textured meshes. ScanNet++ relies on a scanner to capture point clouds, however, the provided annotations are attached to the Poisson reconstruction instead of raw points.", + "bbox": [ + 496, + 628, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 810, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author.", + "bbox": [ + 94, + 886, + 220, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "21989", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 0 + }, + { + "type": "table", + "img_path": "images/70e7d204d1332a46f7bf45305578e92024fede75571bbec2fbd2d5055480b1f7.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
#Name#Year#Spatial size#Classes#Points# Raw points# Anomalies#Sensors
S3DIS [1]20176×103m213273MXXMatterport
ScanNet [11]20173.4×104m220242MXXRGB-D
ScanNet++ [53]20231.5×104m21000+446MXXTLS
LiDAR-Net (Ours)20233.0×104m2243619M✓✓MLS
", + "bbox": [ + 140, + 87, + 831, + 170 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Table 1. In comparison with well-known indoor scene datasets, LiDAR-Net exceeds both S3DIS and ScanNet++ regarding spatial size and resolution. Although ScanNet covers a larger spatial size than ours, we provide points with annotations at a higher resolution. TLS is Terrestrial Laser Scanning system. MLS is Mobile Laser Scanning system.", + "bbox": [ + 75, + 172, + 893, + 217 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/747abd6b5228f2c1f1fdb116d074b1a6ff0819ad73fe21dcc182eafb9e4dee6f.jpg", + "image_caption": [ + "Original points", + "Figure 2. Illustration of reflection noise. These noise points usually suspend in the air. Purple highlights reflection noise in the semantic label figures" + ], + "image_footnote": [], + "bbox": [ + 83, + 224, + 176, + 301 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/7b8d0110e3b8e1799ffb9e54dd547eeee1b79de3aefd76650165e2fc090f1001.jpg", + "image_caption": [ + "Semantic labels" + ], + "image_footnote": [], + "bbox": [ + 176, + 224, + 267, + 300 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/1f65431e5e3566136ca242a60dfbdb5ad4be585218e60ef2bf50130734467f91.jpg", + "image_caption": [ + "Original points" + ], + "image_footnote": [], + "bbox": [ + 269, + 224, + 364, + 300 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/010f8f032920a18597c5f2baf6140b4ab6aa031dd1948329e5dabe204cb2681f.jpg", + "image_caption": [ + "Semantic labels" + ], + "image_footnote": [], + "bbox": [ + 364, + 224, + 464, + 300 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "The 3D accuracy of these datasets is inferior to that of raw point clouds directly collected using laser scanners. Annotated data in existing datasets also lack characteristic distributions of real-scanned points, including scanning lines and scanning holes, as illustrated in Fig. 1. Consequently, deep models trained on these datasets tend to perform poorly when applied to actual, real-scanned point cloud data, significantly impeding their practical applicability.", + "bbox": [ + 75, + 380, + 468, + 501 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In this paper, we contribute a new dataset, LiDAR-Net, to the academic community. Distinct from existing indoor scene datasets, LiDAR-Net is captured by real laser scanners and contains precise semantic and instance annotations for each raw point. LiDAR-Net encompasses three common daily scenes: learning, working, and living environments. It contains 3.6 billion 3D points, covering $30,000m^2$ of indoor space. Using professional LiDAR scanning systems, the 3D point clouds the dataset ensures the high authenticity of its 3D point clouds. Detailed information about the data collection process is provided in Section 3. Across all scenes, each point is carefully annotated and classified into 24 semantic categories, such as floor, ceiling, and window.", + "bbox": [ + 75, + 503, + 468, + 699 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Compared to previous indoor scene datasets primarily collected using RGB-D cameras or annotated on reconstructed meshes, LiDAR-Net offers several advantages:", + "bbox": [ + 75, + 700, + 468, + 746 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- Firstly, LiDAR-Net distinguishes itself by its authentically captured point cloud data, which leads to non-uniform point distributions, characterized by scanning holes and lines, as depicted in Fig. 1.", + "- Secondly, LiDAR-Net includes comprehensive annotations of scanning anomalies including reflection noises (purple points in Fig. 2) and ghosts caused by moving objects, particularly persons (red points in Fig. 1).", + "- Thirdly, LiDAR-Net covers corridors and stairs connecting each room, creating seamless and complete spaces" + ], + "bbox": [ + 76, + 750, + 468, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "crucial for integrated tasks across entire areas.", + "bbox": [ + 511, + 227, + 818, + 242 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Table 1 presents a comparative analysis with other popular indoor scene datasets. While many outdoor point cloud datasets [43, 44] contain real-scanned data, the significant disparity in scene characteristics presents challenges for adapting outdoor datasets to indoor tasks. Moreover, outdoor point clouds generally show a higher level of sparsity and incompleteness compared to LiDAR-Net.", + "bbox": [ + 496, + 244, + 890, + 349 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Using LiDAR-Net, we recognize several challenges and conduct studies on them, as outlined in Section 5. We first investigate the process of annotating a large indoor point cloud dataset. Then, we discuss the significance of real-scanned point cloud data for semantic learning, emphasizing the advantages of raw LiDAR-based point clouds over those from depth cameras or from reconstructed meshes. Additionally, we investigate the imbalance of semantic classes in indoor environments. While this paper does not provide exhaustive solutions, it introduces these challenges for further exploration by the research community. Our discussion on the complexities of multi-task learning in indoor 3D point clouds aims to spur developments in fields such as intelligent home systems, digital twins, indoor robotic navigation, asset management in extensive indoor infrastructures, and smart construction sites, etc. To summarize, our work makes the following contributions:", + "bbox": [ + 496, + 352, + 892, + 609 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We introduce LiDAR-Net, a comprehensive large-scale 3D point cloud dataset. This dataset is equipped with point-level semantic and instance annotations, making it ideal for multi-task training and testing.", + "- LiDAR-Net is characterized by its distinct features such as non-uniform point distributions, scanning anomalies, and seamless spatial coverage. These attributes notably enhance the generalization capabilities of trained deep models for real-world applications.", + "- We assess the efficacy of current algorithms within real-scanned point cloud environments and identify key challenges in this field." + ], + "bbox": [ + 500, + 609, + 890, + 791 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 804, + 640, + 820 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Booming deep learning-based 3D scene understanding methods desire various 3D scene datasets. Guo et al. [15] give a comprehensive survey on this topic. We briefly summary 3D scene datasets and 3D point cloud scene understanding methods below.", + "bbox": [ + 496, + 825, + 890, + 900 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "21990", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2.1. 3D Scene Datasets", + "text_level": 1, + "bbox": [ + 76, + 90, + 253, + 104 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "According to the application scenario, existing 3D datasets can be divided into three categories: (i) 3D objects, (ii) indoor scenes, (iii) outdoor scenes.", + "bbox": [ + 76, + 113, + 468, + 157 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3D objects. ModelNet [50] and ShapeNet [9] are both 3D synthetic mesh datasets for shape classification. Mo et al. [32] propose PartNet containing hierarchical labels for part segmentation. ABC dataset [22] contains 1M CAD models with structure information. Deitke et al. [12] propose Objaverse-XL, which is a universe of $10\\mathrm{M} + 3\\mathrm{D}$ objects.", + "bbox": [ + 75, + 159, + 468, + 265 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Indoor scenes. Early indoor 3D datasets are acquired by using commodity short-range depth scanners such as NYUv2 [41] and SUN RGB-D [42], comprising short RGB-D sequences with limited resolution. While SceneNN [19] and PiGraphs [39] provide reconstructed and labeled scenes, their scene counts are restricted. Armeni et al. [2] propose S3DIS, which is a widely used benchmark in many tasks, by collecting RGB-D images and reconstructing 3D textured mesh model for each scene. The colored 3D point clouds in S3DIS are densely and uniformly sampled from the textured meshes. ScanNet [11] also provide 3D reconstructions captured by an iPad equipped with a structure sensor, accompanied by annotations. Matterport3D [8] generates low-resolution meshes from panoramic RGB-D images. ARKitScenes [5] offers high-resolution ground truth geometry by using laser scans, but it only provides bounding box annotations. Novel view synthesis methods, such as neural radiance fields (NeRFs) [31], development rapidly in recent years [4, 28]. Yeshwanth et al. [53] propose ScanNet++, containing 460 scenes with DSLR images and iPhone RGB-D frames. They obtain each scene by using the Faro Focus Premium laser scanner and implementing Poisson reconstruction [20, 21] to obtain meshes. Then the meshes are annotated. Comparing to S3DIS [2], ScanNet [11], and ScanNet++ [53], LiDAR-Net provides annotated raw points, which can be directly employed for training deep models specializing in 3D point cloud scene understanding. LiDAR-Net meticulously preserves the characteristics of raw point clouds captured by sensors, encompassing non-uniform distributions like scanning holes and lines, as well as anomalies like reflection noises and ghosts.", + "bbox": [ + 75, + 265, + 470, + 734 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Outdoor scenes. These datasets are usually captured by static Terrestrial Laser Scanners (TLS), Mobile Laser Scanners (MLS), and Airborne Laser Scanners (ALS). The representative datasets in this domain comprise roadway-level datasets, such as KITTI [14], Paris-rue-Madame [40], IQmulus [46], Semantic3D [16], Paris-Lille-3D [38], Ar-goverse [10], SemanticKITTI [6], SemanticPOSS [33], Toronto-3D [44], nuScenes [7], and Waymo dataset [43]. Additionally, urban-level aerial 3D point cloud datasets include DublinCity [57], DALES [47], LASDU [52], Campus3D [24], and SensatUrban [18].", + "bbox": [ + 75, + 734, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "2.2. Deep Learning on 3D Scene Understanding", + "text_level": 1, + "bbox": [ + 500, + 90, + 867, + 107 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Pioneered by PointNet [35], neural networks are used to process the unordered point cloud data [25, 36, 49, 56], leading to numerous innovative applications [13, 27, 30, 55]. We choose three representative tasks to evaluate LiDAR-Net dataset. 1) Semantic segmentation. Thomas et al. [45] propose Kernel Point Convolution (KPCConv) operators for 3D point clouds using a set of learnable kernel points. Hu et al. [17] propose RandLA-Net utilizing random point sampling to achieve remarkably high efficiency. 2) Instance segmentation. ASIS [48] uses a feature fusion structure to enhance both semantic and instance branches by leveraging information from each other. Yang et al. [51] propose a single-stage and anchor-free network called 3D-BoNet for instance segmentation. 3) Object detection. VoteNet [37] implements a unique voting scheme among points to infer object bounding box centers. GroupFree3D [29] leverages a sophisticated attention mechanism that obviates the need for point candidate grouping, enabling direct inference of object instances.", + "bbox": [ + 496, + 114, + 890, + 405 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Dataset Acquisition and Annotation", + "text_level": 1, + "bbox": [ + 498, + 424, + 823, + 441 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Point Cloud Acquisition", + "text_level": 1, + "bbox": [ + 500, + 452, + 720, + 468 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Acknowledging the marked advantages of LiDAR technology in securing authentic three-dimensional data over traditional RGBD data acquisition methods, our research utilizes Leica BLK2GO, a device combining dual-axis LiDAR technology. The BLK2GO is equipped not only with a commercial dual-axis LiDAR and a 12-megapixel detail camera but also with a 4.8-megapixel, 3-shot panoramic camera. This integration enables stable collection of point cloud data with an accuracy of $\\pm 3\\text{mm} @10m$ and a capture speed of 420,000 points/second within a $0.5\\sim 25m$ range, while simultaneously obtaining high-resolution color images. Significantly, the BLK2GO implements GrandSLAM dual-positioning technology, seamlessly blending laser SLAM and visual SLAM. This approach involves using point cloud from LiDAR and inertial navigation from IMU for one aspect of positioning, and determining the current position and orientation by analyzing disparities between consecutive frames captured by the panoramic camera. For the LiDAR-Net, all data acquisition routes are meticulously pre-planned by professional surveyors, ensuring comprehensive and consistent coverage of the targeted area. To mirror the various interferences typical in real-world point cloud acquisition scenarios, all data are manually collected by human surveyors. Due to the device's battery capacity constraints, each data collection session is strategically limited to approximately one hour. To encompass the entire area, data from multiple individual sessions are manually integrated.", + "bbox": [ + 496, + 477, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "21991", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/6de1bc955587ab42b9fd077a5ea14f4c042a938945441650f434bc02625cd3f7.jpg", + "image_caption": [ + "Figure 3. Semantic and instance labels. LiDAR-Net provides point-level annotations directly associated with each raw data point." + ], + "image_footnote": [], + "bbox": [ + 101, + 80, + 869, + 601 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. Point Cloud Annotation", + "text_level": 1, + "bbox": [ + 76, + 637, + 295, + 651 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "In the dataset, we address three sub-tasks: semantic segmentation, instance segmentation, and object detection. The categorization criteria are based on two key principles: 1) Each category should possess a distinct and unambiguous semantic meaning, aligning with both academic research and practical business applications. This alignment facilitates advanced visual tasks such as 3D reconstruction, point cloud completion, and applications in virtual reality, building upon baseline tasks. 2) The categories should exhibit significant geometric or appearance differences, ensuring clear distinction across different groups. We provide a Point Cloud AnnoTation system (PCAT system) to annotate all point clouds in the LiDAR-Net with both semantic and instance labels. Subsequently, object detection labels, in the form of bounding boxes, are derived from these instances", + "bbox": [ + 75, + 674, + 472, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "labels. The PCAT system is set to be released, allowing users to easily modify or subdivide labels according to their specific requirements. Each label in LiDAR-Net is rigorously manually annotated and verified, ensuring the consistency and high quality of the semantic categories. The entire dataset labeling consumes approximately 550 working hours. Illustrative examples of our annotations are displayed in Fig. 3.", + "bbox": [ + 496, + 637, + 890, + 758 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "We annotate various indoor components, including floors, stairs, and ceilings, as well as a wide range of furniture and fixtures such as tables, chairs, and sofas. Additionally, we carefully annotate anomalies captured by LiDAR, encompassing reflection noises and ghosts, as they introduce inaccuracies into the data and present challenges in data analysis. Specular reflections from smooth surfaces like glass or metal can disrupt LiDAR systems, resulting in reflection noise points. LiDAR systems would capture", + "bbox": [ + 496, + 763, + 892, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "21992", + "bbox": [ + 478, + 944, + 519, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "incomplete and repetitive ghosts when persons or other objects move in front of the scanner. These anomalies, commonly encountered in real-world applications like robotics and consumer electronics, are accurately recorded in our LiDAR-Net dataset to aid in training deep learning models capable of handling these challenges.", + "bbox": [ + 75, + 90, + 470, + 183 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Benchmark", + "text_level": 1, + "bbox": [ + 76, + 194, + 204, + 209 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "LiDAR-Net contains classrooms, study lounges, seminar rooms, auditoriums for learning scenes, offices, meeting rooms, lounges for working scenes, and living rooms, bedrooms, dining rooms, washrooms for living scenes. Fig. 4 shows the diversity of scenes. Furthermore, We record world coordinates of rooms to form connecting areas, including 2, 7, and 5 seamless areas of learning, working and living scenes, which facilitate navigation and understanding large-scale indoor scenes.", + "bbox": [ + 75, + 218, + 468, + 354 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For the facilitation of GPU-accelerated batch training and testing, we divide the point clouds from various scenes into individual rooms based on their primary structural features, particularly the wall orientations. It is important to note that we provide coordinate correspondences for each room to facilitate tasks working in a whole area. Point clouds from learning scenes are divided into 216 rooms, including 173 rooms for training and 43 for testing. Similarly, we split the working scenes into 206 rooms, including 169 and 37 for training and testing, each room covering approximately $100m^2$ . In living scenes, of the 43 rooms analyzed, 33 are used for training and 10 for testing. The distribution of room areas is illustrated in Fig. 5.", + "bbox": [ + 75, + 354, + 470, + 551 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "LiDAR-Net contains 24 semantic categories, including houseplant (low potted plants), tree (tall trees typically positioned on the floor), person, floor, stair, ceiling, pipe, wall, pillar, window, curtain, door, table, chair, sofa, blackboard (common in learning or working scenes), monitor, bookshelf, wardrobe, bed, light, tabletop others (miscellaneous small objects on tables), reflection noise, ghost (resulting from moving entities, such as people). Additionally, an 'unknown' class exists outside these 24 categories, encompassing points not classified into any specific category. Each point within the 24 semantic categories is assigned instance labels. 17 categories are used for object detection. Floors, ceilings, pipes, walls, pillars, reflection noises and ghosts, which lack definite boundaries, are excluded from object detection task, following [29, 37]. It is important to note that instance labels are provided for these excluded categories, facilitating use cases like smart construction sites and vectorized indoor modeling. The LiDAR-Net dataset will be publicly released, with the goal of establishing benchmarks in indoor point cloud semantic segmentation, instance segmentation, and object detection, which will be evaluated through an online public platform. Following ScanNet [11] and ScanNet++ [53], labels of the test", + "bbox": [ + 75, + 551, + 470, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "set will remain hidden.", + "bbox": [ + 500, + 90, + 653, + 104 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 500, + 119, + 632, + 137 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.1. Representative Baselines", + "text_level": 1, + "bbox": [ + 500, + 145, + 725, + 161 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In Section 2.2, we explore the three main tasks in learning-based 3D point cloud scene understanding. To comprehensively evaluate our LiDAR-Net dataset, we carefully select eight emblematic methods, applying them as benchmarks across different tasks to conduct an extensive benchmark test on our dataset. Precisely, we utilize PointNet [35], PointNet++ [36], KPCov [45], and RandLA-Net [17], for point cloud semantic segmentation, ASIS [48] and 3D-BoNet [51] for instance segmentation, VoteNet [37] and GroupFree3D [29] for object detection.", + "bbox": [ + 496, + 167, + 890, + 320 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Evaluation Metrics", + "text_level": 1, + "bbox": [ + 500, + 330, + 683, + 344 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Consistent with prevailing benchmarks, our evaluation framework is designed for a thorough assessment across various segmentation and detection tasks. For semantic segmentation, we focus primarily on mean Intersection-over-Union (mIoU) as the key evaluation metric, following [17, 45]. In instance segmentation, our analysis emphasizes mean precision (mPre) and mean recall rate (mRec) to measure algorithmic performance, following [48, 51]. Moreover, within the domain of object detection, we concentrate on the mean of per-category object detection average precision with 3D IoU threshold 0.25 and 0.5, denoted as mAP@0.25 and mAP@0.5, following [29, 37].", + "bbox": [ + 496, + 353, + 890, + 534 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.3. Benchmark Results", + "text_level": 1, + "bbox": [ + 500, + 544, + 686, + 559 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To ensure a fair comparison, we rigorously follow the experimental settings outlined in the original publications of each benchmark algorithm. Table 2 presents the quantitative results across three tasks. The overall performances in segmentation and detection has not reached a satisfactory level. For instance, examining RandLA-Net [17] and KPCov [45], which show the best performance in semantic segmentation, Table 3 details the IoU for each semantic category of the two methods. Table 3 reveals that certain key categories, such as window and bookshelf, were poorly segmented. RandLA-Net achieves $42.02\\%$ for the IoU of tree, which is higher than $7.94\\%$ of KPCov, however for the IoU of sofa, performance of KPCov is much better than that of RandLA-Net. There is a significant variation in performance across different algorithms within these challenging categories, and no single algorithm consistently outperforms the other. Comprehensive quantitative results of other semantic segmentation, instance segmentation and object detection methods for each category are given in the supplementary materials.", + "bbox": [ + 496, + 566, + 890, + 869 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "A key advantage of our LiDAR-Net is that its annotated raw points closely mirror the distribution of real-scanned", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "21993", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/c04539faf3784505505d106906593d59c369211c7e48c91c5650677a15df8080.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 98, + 80, + 225, + 140 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/07bce97cf549f40238f9e27c72a85f305cf645ca7f28cabd5ec1970e5e72a8c4.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 227, + 80, + 354, + 140 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/da6baf104245fee9370493393ed216f6af5595453b8c927d54116af53e3d5dc1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 354, + 80, + 483, + 140 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/f4a86c450df67f4092d6cb05ac0cc78407990c207602e29e51770fd51dd8def2.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 483, + 80, + 614, + 140 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/98d06b248cc8d84624701d18b4e6c3f483490bbadcfdbd61d89da012ad700849.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 614, + 80, + 743, + 140 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/828fcd839fcebaf94ea37a189f757f4c243568167fc5989be992af7da93951c1.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 743, + 80, + 872, + 140 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/93e5858a8d98ab8fb39d18631d673667560c2bf0da2595a51d6bd0f3b0b6f15b.jpg", + "image_caption": [ + "Figure 4. The diversity of scenes. Each point is color-coded by its semantic label. The bottom row displays three seamless areas." + ], + "image_footnote": [], + "bbox": [ + 96, + 140, + 315, + 242 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/c80023903968efa8e8817da1274ba503cb942f9d76577ac1204ebb097a2dd527.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 316, + 140, + 673, + 242 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/2c60dc052dfe80d92c448483f52fd2eb0ccba55522427dd868e211b15c36769a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 674, + 140, + 872, + 242 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/fbdd9f046c084d486ac8787cdb48ba83393fe0ef105fa01178f2edbd1e955c97.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
Semantic segmentationmIoUInstance segmentationmPremRecObject detectionmAP@0.25mAP@0.5
PointNet [35]16.27ASIS [48]37.3225.08VoteNet [37]44.8316.71
PointNet++ [36]28.81
KPConv [45]44.293D-BoNet [51]39.8224.63GroupFree3D [29]46.8018.86
RandLA-Net [17]32.60
", + "bbox": [ + 109, + 272, + 864, + 345 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/0507e70b400e5ca197a3937912cd47c50399b1845a78d8367e0d540d2b0bf93b.jpg", + "table_caption": [ + "Table 2. Statistics of selected emblematic methods on LiDAR-Net. The percent sign (%) is omitted." + ], + "table_footnote": [], + "table_body": "
MethodsHouseplantTreePersonFloorStairCeilingPipeWallPillar
KPConv [45]26.987.9445.2285.4325.7086.5138.4974.925.68
RandLA-Net [17]3.5642.0240.7593.170.4286.1219.4373.810.91
WindowCurtainDoorTableChairSofaBlackboardMonitorBookshelf
KPConv [45]9.4822.2134.4479.8875.4558.0274.7955.2326.76
RandLA-Net [17]18.0041.3351.2261.6942.280.0074.776.067.73
WardrobeBedLightTabletop othersReflection noiseGhostUnknownmIoU
KPConv [45]34.0539.5165.2140.5819.2256.8218.8044.29
RandLA-Net [17]0.000.0054.1314.910.0067.5315.0932.60
", + "bbox": [ + 81, + 369, + 893, + 494 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e61a71b8826317310f3d84739cd2f1f57a64507e562129cdef7c817b2ec86f16.jpg", + "image_caption": [ + "Figure 5. Distribution of room areas. LiDAR-Net encompasses a diverse array of rooms, reflecting a broad spectrum of spatial configurations." + ], + "image_footnote": [], + "bbox": [ + 102, + 521, + 444, + 657 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/a77a538e27816c0113d84edb6f9d9acea74451232d953c97345c7932786e2b13.jpg", + "table_caption": [ + "Table 3. Comparison of IoU for each semantic category. The percent sign $(\\%)$ is omitted." + ], + "table_footnote": [], + "table_body": "
DatasetsSemantic segmentationInstance segmentationObject detection
mIoUmPremRecmAP@0.25mAP@0.5
S3DIS [2]35.5815.727.847.930.28
ScanNet [11]33.1815.8814.4420.911.21
ScanNet++ [53]23.6026.484.6813.311.67
LiDAR-Net39.7532.9220.3932.969.22
", + "bbox": [ + 81, + 707, + 468, + 789 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 4. Quantitative comparisons of deep models trained on different datasets and tested on real-scanned data. The percent sign $(\\%)$ is omitted.", + "bbox": [ + 75, + 799, + 468, + 840 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "points. To evaluate it, we train the benchmark methods on existing popular datasets, including S3DIS [2], ScanNet [11], and ScanNet++ [53]. Then, the deep models", + "bbox": [ + 75, + 854, + 468, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "are tested on 5 real-scanned rooms, captured using a Leica BLK2GO scanner in locations not included in LiDAR-Net. Due to the categories of the four datasets are different, we test the models on the communal categories. Fig. 6 and Table 4 show the qualitative and quantitative comparisons, selecting RandLA-Net [17] for semantic segmentation, ASIS [48] for instance segmentation, and GroupFree3D [29] for object detection. Detailed statistics of other methods and each category are listed in the supplementary materials. Benefited from the realistic distribution of raw points in LiDAR-Net, deep models trained on it demonstrate superior performances across all three tasks.", + "bbox": [ + 496, + 523, + 890, + 705 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Challenges", + "text_level": 1, + "bbox": [ + 500, + 722, + 616, + 739 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "This section focuses on the key challenges presented by our dataset, which inherently stem from the authentic LiDAR collection process. Then, we provide an in-depth analysis of these challenges with a potential to drive advancements in the current field. Concurrently, we delve into tentative discussions of viable solutions. It is crucial to clarify that the aim of this paper is not to introduce a new method for addressing these challenges. Rather, our goal is to identify data biases potentially caused by existing datasets, to shed light on unresolved issues, and to provide analysis and in-", + "bbox": [ + 496, + 750, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "21994", + "bbox": [ + 478, + 945, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/1656dd47ce4f9abea350977ace063d5f5e597f01b551bc2348db28762e5ca38a.jpg", + "image_caption": [ + "Figure 6. Qualitative comparisons of deep models trained on different datasets and tested on real-scanned data. Each row displays one task. Deep models are tested on the communal categories. It's important to note that ScanNet++ does not include instance labels for floors, walls, and ceilings, and therefore, these elements are excluded from the instance segmentation experiment." + ], + "image_footnote": [], + "bbox": [ + 81, + 87, + 893, + 313 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "sights. Ultimately, we seek to catalyze advancements in the understanding of indoor scene point clouds.", + "bbox": [ + 75, + 369, + 470, + 402 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.1. Differences in Data Distribution", + "text_level": 1, + "bbox": [ + 76, + 412, + 359, + 428 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "LiDAR scanning. In previous discussions, we introduced a point cloud dataset derived from authentic LiDAR scanning, which significantly differs from existing indoor point cloud datasets. While LiDAR and RGB-D scanning produce point clouds with some similar attributes, notable differences exist in their characteristics. The non-uniform distribution of real-scanned points, characterized by scanning holes and lines, is a result of the laser scanning process. LiDAR measures distance by emitting laser pulses and measuring the time they take to return. The laser beam moves directionally, creating linear point captures. Gaps in these lines lead to scanning holes. Furthermore, the distance from the scanner affects point distribution. Points closer to the scanner are denser, while those at greater distances tend to be sparser, a phenomenon owing to the dispersion and weakening of laser pulse energy. LiDAR's capability to operate over long distances inherently leads to a noticeable decrease in point density at farther ranges.", + "bbox": [ + 75, + 438, + 473, + 712 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "RGB-D cameras. Conversely, RGB-D cameras, which utilize structured light or Time of Flight (ToF) technology, determine distance using a distinct methodology. Points closer to the sensor tend to be denser due to variations in observational angles, while farther points show relative sparsity owing to resolution limits. RGB-D cameras are capable of providing relatively dense data within a specific range, but this density noticeably decreases or even disappears beyond their operational limit. Therefore, although both authentic LiDAR and RGB-D cameras exhibit the challenge of variable point density, there is a fundamental difference", + "bbox": [ + 75, + 734, + 470, + 902 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/c689e18cad17b9f42c9ffbad7e9d3a14087ce793fc7df817e728f7160cf369ff.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 509, + 373, + 696, + 472 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/3e80d594acaa493c64a2cebbdd6d2811d6936e53126ce28c63c19181b984fdc7.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 375, + 883, + 472 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/d1cc222a2db47a40035750a5a09df22531f503dc2a3f2d87542278f85353db6b.jpg", + "image_caption": [ + "Figure 7. Point and voxel distributions in S3DIS, ScanNet, ScanNet++ and LiDAR-Net." + ], + "image_footnote": [], + "bbox": [ + 509, + 474, + 696, + 573 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/33f4a845b736e5785d85c0d7421e5990079b3ef937dd5cc7244dd8b54282dc74.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 474, + 883, + 573 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "in their respective point cloud distributions. In the indoor conditions, authentic LiDAR typically encompasses a point distribution radius spanning $2 \\sim 7$ meters, in sharp contrast to the $2 \\sim 5$ meters typically covered by RGB-D cameras (as illustrated in Fig. 7).", + "bbox": [ + 496, + 617, + 893, + 694 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Comparison of the datasets. Due to the distinctions in acquisition technologies, LiDAR and RGB-D systems exhibit notable discrepancies in factors such as scanning precision, noise, color information, and performance in different lighting conditions. This type of data variance becomes particularly conspicuous in deep learning methodologies heavily reliant upon data. Fig. 7 illustrates the point and voxel distributions in existing indoor datasets compared to LiDAR-Net. Firstly, the three existing datasets predominantly contain points within a $2 \\sim 5$ meters range from the scanner, while our LiDAR-Net provides a distinct distribution. It is worth to be explored that would the deep", + "bbox": [ + 496, + 719, + 895, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "21995", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "models trained on previous datasets over-fitted to the distribution of $2 \\sim 5$ meters? Our LiDAR-Net, with its broader range of $2 \\sim 7$ meters, provides an expanded scope for future research in this area. Secondly, since the points in the previous three datasets are generated by sampling on annotated 3D reconstructions, they mirror the voxel distribution. In contrast, the primary strength of LiDAR-Net lies in its annotated raw points, which are non-uniform, leading to distinct point and voxel distributions. This divergence introduces new challenges to the field. Our dataset adeptly encapsulates these genuine characteristics of real-world data, thereby establishing a robust foundation for various forthcoming applications in indoor perception technology.", + "bbox": [ + 75, + 90, + 472, + 287 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.2. Impact of Imbalance Class Distribution", + "text_level": 1, + "bbox": [ + 76, + 295, + 416, + 311 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Upon further investigation, we discern a more critical issue within indoor scene datasets: a conspicuous performance discrepancy resulting from imbalanced class distribution. We showcase the cumulative count of 3D points per semantic category in the top of Fig. 8, and the instance distribution is shown in the bottom. It is observable that the primary semantic categories, including ceilings, floors, walls, etc., make up over $80\\%$ of the total points. In contrast, smaller yet crucial categories (e.g., monitors) constitute a mere $0.16\\%$ of the total points, highlighting a stark imbalance in the distribution of semantic classes. This disproportion is inherent to indoor scenes, where walls, ceilings, and floors naturally cover large surface areas, while items like monitors are considerably smaller.", + "bbox": [ + 75, + 318, + 468, + 529 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Data imbalance poses a significant challenge in 3D scene understanding, an issue that is also evident in LiDAR-Net. As shown in Table 3, the skew in segment headers is especially marked in the semantic segmentation task, owing to the disparity in point cloud quantities at the point level. For instance, looking at the results of RandLA-Net in specific categories, the semantic segmentation accuracy for floors is around $93\\%$ , while for stairs, it nearly drops to zero. Essentially, indoor scenes are dominated by a few categories such as ceilings and walls, whereas categories like stairs, though minor but critical, have an extremely sparse data distribution. When considering instance segmentation, the combination of instance-level and point-level imbalances exacerbates the problem, leading to a more severe dual-imbalance situation. Detailed instance segmentation results of each category are listed and discussed in the supplementary materials. This profound imbalance in distribution poses another significant challenge introduced by our dataset.", + "bbox": [ + 75, + 530, + 470, + 803 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 76, + 815, + 194, + 830 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this study, we present a comprehensive indoor point cloud dataset derived from authentic LiDAR scanning. This dataset encompasses three meticulously labeled scenes with a total of 3.6 billion points, covering $30,000m^2$ . Designed", + "bbox": [ + 75, + 839, + 470, + 902 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a8613cf2deecad64a43f81c22fd78748d47eedb2cd006ba326d078914cc3dd25.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 506, + 93, + 890, + 266 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/0bfe43797d27879c3765f7db9da55b35b62864bfe230114790ad4c5e7bb86eed.jpg", + "image_caption": [ + "Figure 8. Top: Point number distribution of semantic categories. Bottom: Instance number distribution. Unknown points do not have instance labels." + ], + "image_footnote": [], + "bbox": [ + 504, + 268, + 890, + 445 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "for a variety of applications including semantic segmentation, instance segmentation, and object detection, our dataset serves as a versatile resource for related research tasks. Our comprehensive benchmark testing not only highlights persistent challenges but also emphasizes the distinct advantages of our dataset, particularly regarding the differences between annotated raw points from genuine LiDAR and points sampled from annotated 3D reconstructions. We have thoroughly examined issues such as the pronounced effects of imbalanced class distribution and the adaptability of models to unseen real-scanned scenes. Looking towards a future where autonomous indoor robots navigate diverse human-centric environments, we underscore the importance of real-time perception using authentic LiDAR-scanned data. The precision and high resolution of real-world LiDAR point cloud data are crucial for emerging cyber-physical systems like smart homes and digital twins. We believe our dataset and benchmarks will spur further progress in related areas of study.", + "bbox": [ + 496, + 505, + 893, + 792 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgments", + "text_level": 1, + "bbox": [ + 500, + 804, + 658, + 821 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work was supported by the National Natural Science Foundation of China (62032011), the Natural Science Foundation of Jiangsu Province (No. BK20211147), and the program B for Outstanding PhD candidate of Nanjing University.", + "bbox": [ + 496, + 824, + 893, + 902 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "21996", + "bbox": [ + 478, + 944, + 519, + 957 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Iro Armeni, Ozan Sener, Amir R Zamir, Helen Jiang, Ioannis Brilakis, Martin Fischer, and Silvio Savarese. 3d semantic parsing of large-scale indoor spaces. 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Dublincity: Annotated lidar point cloud and its applications. arXiv preprint arXiv:1909.03613, 2019. 3" + ], + "bbox": [ + 78, + 90, + 470, + 824 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "21999", + "bbox": [ + 478, + 945, + 519, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/LiDAR-Net_ A Real-scanned 3D Point Cloud Dataset for Indoor Scenes/966078f8-f41c-47ed-993a-88a5e306b677_model.json b/2024/LiDAR-Net_ A Real-scanned 3D Point Cloud Dataset for Indoor Scenes/966078f8-f41c-47ed-993a-88a5e306b677_model.json new file mode 100644 index 0000000000000000000000000000000000000000..9304939f6745d50dba60b9001cf19cceb253b1bb --- /dev/null +++ b/2024/LiDAR-Net_ A Real-scanned 3D Point Cloud Dataset for Indoor Scenes/966078f8-f41c-47ed-993a-88a5e306b677_model.json @@ -0,0 +1,2158 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.0, + 0.812, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.126, + 0.131, + 0.844, + 0.151 + ], + "angle": 0, + "content": "LiDAR-Net: A Real-scanned 3D Point Cloud Dataset for Indoor Scenes" + }, + { + "type": "text", + "bbox": [ + 0.086, + 0.18, + 0.888, + 0.27 + ], + "angle": 0, + "content": "Yanwen Guo\\(^{1*}\\), Yuanqi Li\\(^{1}\\), Dayong Ren\\(^{1}\\), Xiaohong Zhang\\(^{1}\\), Jiawei Li\\(^{1}\\), Liang Pu\\(^{1}\\), Changfeng Ma\\(^{1}\\), Xiaoyu Zhan\\(^{1}\\), Jie Guo\\(^{1}\\), Mingqiang Wei\\(^{2}\\), Yan Zhang\\(^{1}\\), Piaopiao Yu\\(^{2}\\), Shangyu Yang\\(^{1}\\), Donghao Ji\\(^{1}\\), Huisheng Ye\\(^{1}\\), Hao Sun\\(^{1}\\), Yansong Liu\\(^{1}\\), Yinuo Chen\\(^{1}\\), Jiaqi Zhu\\(^{1}\\), Hongyu Liu\\(^{1}\\) \n\\(^{1}\\)Nanjing University, Nanjing, China \n\\(^{2}\\)Nanjing University of Aeronautics and Astronautics, Nanjing, China" + }, + { + "type": "text", + "bbox": [ + 0.12, + 0.273, + 0.856, + 0.341 + ], + "angle": 0, + "content": "{ywguo,guojie,zhangyannju}@nju.edu.cn,rdyedu@gmail.com {yuanqili,xiaohongzhang,lijiawei,puliang,changfengma}@smail.nju.edu.cn {zhanxy,shuangyuyang,donghaoji,huishengye,hao.sun,yansongliu}@smail.nju.edu.cn {mqwei,yupiaopiao}@nuaa.edu.cn,{yinuochen,jiaqizhu,hongyu.liu}@smail.nju.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.375, + 0.314, + 0.391 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.408, + 0.474, + 0.726 + ], + "angle": 0, + "content": "In this paper, we present LiDAR-Net, a new real-scanned indoor point cloud dataset, containing nearly 3.6 billion precisely point-level annotated points, covering an expansive area of \\(30,000m^2\\). It encompasses three prevalent daily environments, including learning scenes, working scenes, and living scenes. LiDAR-Net is characterized by its nonuniform point distribution, e.g., scanning holes and scanning lines. Additionally, it meticulously records and annotates scanning anomalies, including reflection noise and ghost. These anomalies stem from specular reflections on glass or metal, as well as distortions due to moving persons. LiDAR-Net's realistic representation of non-uniform distribution and anomalies significantly enhances the training of deep learning models, leading to improved generalization in practical applications. We thoroughly evaluate the performance of state-of-the-art algorithms on LiDAR-Net and provide a detailed analysis of the results. Crucially, our research identifies several fundamental challenges in understanding indoor point clouds, contributing essential insights to future explorations in this field. Our dataset can be found online: http://lidar-net.njumeta.com." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.757, + 0.21, + 0.772 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.784, + 0.47, + 0.875 + ], + "angle": 0, + "content": "Owing to its reliability and accuracy, Light Detection And Ranging (LiDAR) technology becomes increasingly popular, finding broad applications in autonomous vehicles for perception and localization [23, 26, 54] as well as expanding its applications in consumer electronics [3, 34, 37]. Introduced in 2020, the LiDAR scanner on the iPhone has en" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.375, + 0.889, + 0.511 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.521, + 0.895, + 0.62 + ], + "angle": 0, + "content": "Figure 1. LiDAR-Net comprises 3.6 billion real-scanned points, each annotated with semantic and instance labels. Points of LiDAR-Net have real-scanned characteristics including scanning holes, scanning lines, and anomalies such as ghosts (indicated by red points) caused by moving persons. These characteristics significantly enhance the ability of trained deep models to generalize to real-world applications." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.629, + 0.895, + 0.903 + ], + "angle": 0, + "content": "abled a multitude of innovative applications in virtual reality (VR) and 3D measurements. Deep learning has achieved remarkable success in computer vision, particularly in analyzing and understanding 3D scenes [35, 36, 49, 56]. Datasets undoubtedly have played a critical role in this process, since training a deep models usually requires extensive annotated datasets, especially for supervised learning [2, 8, 11, 19, 42, 53]. In the domain of 3D computer vision for indoor scenes, the most widely recognized datasets in the academic community are S3DIS [2], ScanNet [11], and the recent ScanNet++ [53], etc. S3DIS and ScanNet have been used to train models for various 3D scene understanding tasks, such as 3D object detection, along with semantic and instance segmentation. S3DIS and ScanNet collect RGB-D images, and then reconstruct and annotate textured meshes. ScanNet++ relies on a scanner to capture point clouds, however, the provided annotations are attached to the Poisson reconstruction instead of raw points." + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.887, + 0.222, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "21989" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.141, + 0.088, + 0.832, + 0.171 + ], + "angle": 0, + "content": "
#Name#Year#Spatial size#Classes#Points# Raw points# Anomalies#Sensors
S3DIS [1]20176×103m213273MXXMatterport
ScanNet [11]20173.4×104m220242MXXRGB-D
ScanNet++ [53]20231.5×104m21000+446MXXTLS
LiDAR-Net (Ours)20233.0×104m2243619M✓✓MLS
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.173, + 0.895, + 0.218 + ], + "angle": 0, + "content": "Table 1. In comparison with well-known indoor scene datasets, LiDAR-Net exceeds both S3DIS and ScanNet++ regarding spatial size and resolution. Although ScanNet covers a larger spatial size than ours, we provide points with annotations at a higher resolution. TLS is Terrestrial Laser Scanning system. MLS is Mobile Laser Scanning system." + }, + { + "type": "image", + "bbox": [ + 0.084, + 0.226, + 0.177, + 0.302 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.099, + 0.302, + 0.16, + 0.311 + ], + "angle": 0, + "content": "Original points" + }, + { + "type": "image", + "bbox": [ + 0.178, + 0.226, + 0.269, + 0.301 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.189, + 0.302, + 0.255, + 0.311 + ], + "angle": 0, + "content": "Semantic labels" + }, + { + "type": "image", + "bbox": [ + 0.27, + 0.226, + 0.365, + 0.301 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.287, + 0.302, + 0.347, + 0.311 + ], + "angle": 0, + "content": "Original points" + }, + { + "type": "image", + "bbox": [ + 0.366, + 0.226, + 0.465, + 0.301 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.383, + 0.302, + 0.449, + 0.311 + ], + "angle": 0, + "content": "Semantic labels" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.322, + 0.47, + 0.364 + ], + "angle": 0, + "content": "Figure 2. Illustration of reflection noise. These noise points usually suspend in the air. Purple highlights reflection noise in the semantic label figures" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.381, + 0.469, + 0.502 + ], + "angle": 0, + "content": "The 3D accuracy of these datasets is inferior to that of raw point clouds directly collected using laser scanners. Annotated data in existing datasets also lack characteristic distributions of real-scanned points, including scanning lines and scanning holes, as illustrated in Fig. 1. Consequently, deep models trained on these datasets tend to perform poorly when applied to actual, real-scanned point cloud data, significantly impeding their practical applicability." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.504, + 0.469, + 0.7 + ], + "angle": 0, + "content": "In this paper, we contribute a new dataset, LiDAR-Net, to the academic community. Distinct from existing indoor scene datasets, LiDAR-Net is captured by real laser scanners and contains precise semantic and instance annotations for each raw point. LiDAR-Net encompasses three common daily scenes: learning, working, and living environments. It contains 3.6 billion 3D points, covering \\(30,000m^2\\) of indoor space. Using professional LiDAR scanning systems, the 3D point clouds the dataset ensures the high authenticity of its 3D point clouds. Detailed information about the data collection process is provided in Section 3. Across all scenes, each point is carefully annotated and classified into 24 semantic categories, such as floor, ceiling, and window." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.702, + 0.469, + 0.747 + ], + "angle": 0, + "content": "Compared to previous indoor scene datasets primarily collected using RGB-D cameras or annotated on reconstructed meshes, LiDAR-Net offers several advantages:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.75, + 0.469, + 0.81 + ], + "angle": 0, + "content": "- Firstly, LiDAR-Net distinguishes itself by its authentically captured point cloud data, which leads to non-uniform point distributions, characterized by scanning holes and lines, as depicted in Fig. 1." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.811, + 0.469, + 0.871 + ], + "angle": 0, + "content": "- Secondly, LiDAR-Net includes comprehensive annotations of scanning anomalies including reflection noises (purple points in Fig. 2) and ghosts caused by moving objects, particularly persons (red points in Fig. 1)." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.871, + 0.469, + 0.901 + ], + "angle": 0, + "content": "- Thirdly, LiDAR-Net covers corridors and stairs connecting each room, creating seamless and complete spaces" + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.75, + 0.469, + 0.901 + ], + "angle": 0, + "content": null + }, + { + "type": "text", + "bbox": [ + 0.512, + 0.228, + 0.819, + 0.243 + ], + "angle": 0, + "content": "crucial for integrated tasks across entire areas." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.245, + 0.892, + 0.351 + ], + "angle": 0, + "content": "Table 1 presents a comparative analysis with other popular indoor scene datasets. While many outdoor point cloud datasets [43, 44] contain real-scanned data, the significant disparity in scene characteristics presents challenges for adapting outdoor datasets to indoor tasks. Moreover, outdoor point clouds generally show a higher level of sparsity and incompleteness compared to LiDAR-Net." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.353, + 0.893, + 0.61 + ], + "angle": 0, + "content": "Using LiDAR-Net, we recognize several challenges and conduct studies on them, as outlined in Section 5. We first investigate the process of annotating a large indoor point cloud dataset. Then, we discuss the significance of real-scanned point cloud data for semantic learning, emphasizing the advantages of raw LiDAR-based point clouds over those from depth cameras or from reconstructed meshes. Additionally, we investigate the imbalance of semantic classes in indoor environments. While this paper does not provide exhaustive solutions, it introduces these challenges for further exploration by the research community. Our discussion on the complexities of multi-task learning in indoor 3D point clouds aims to spur developments in fields such as intelligent home systems, digital twins, indoor robotic navigation, asset management in extensive indoor infrastructures, and smart construction sites, etc. To summarize, our work makes the following contributions:" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.611, + 0.892, + 0.671 + ], + "angle": 0, + "content": "- We introduce LiDAR-Net, a comprehensive large-scale 3D point cloud dataset. This dataset is equipped with point-level semantic and instance annotations, making it ideal for multi-task training and testing." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.672, + 0.892, + 0.747 + ], + "angle": 0, + "content": "- LiDAR-Net is characterized by its distinct features such as non-uniform point distributions, scanning anomalies, and seamless spatial coverage. These attributes notably enhance the generalization capabilities of trained deep models for real-world applications." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.748, + 0.891, + 0.792 + ], + "angle": 0, + "content": "- We assess the efficacy of current algorithms within real-scanned point cloud environments and identify key challenges in this field." + }, + { + "type": "list", + "bbox": [ + 0.5, + 0.611, + 0.892, + 0.792 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.805, + 0.642, + 0.821 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Booming deep learning-based 3D scene understanding methods desire various 3D scene datasets. Guo et al. [15] give a comprehensive survey on this topic. We briefly summary 3D scene datasets and 3D point cloud scene understanding methods below." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "21990" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.078, + 0.091, + 0.254, + 0.106 + ], + "angle": 0, + "content": "2.1. 3D Scene Datasets" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.114, + 0.47, + 0.159 + ], + "angle": 0, + "content": "According to the application scenario, existing 3D datasets can be divided into three categories: (i) 3D objects, (ii) indoor scenes, (iii) outdoor scenes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.16, + 0.47, + 0.266 + ], + "angle": 0, + "content": "3D objects. ModelNet [50] and ShapeNet [9] are both 3D synthetic mesh datasets for shape classification. Mo et al. [32] propose PartNet containing hierarchical labels for part segmentation. ABC dataset [22] contains 1M CAD models with structure information. Deitke et al. [12] propose Objaverse-XL, which is a universe of \\(10\\mathrm{M} + 3\\mathrm{D}\\) objects." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.266, + 0.471, + 0.735 + ], + "angle": 0, + "content": "Indoor scenes. Early indoor 3D datasets are acquired by using commodity short-range depth scanners such as NYUv2 [41] and SUN RGB-D [42], comprising short RGB-D sequences with limited resolution. While SceneNN [19] and PiGraphs [39] provide reconstructed and labeled scenes, their scene counts are restricted. Armeni et al. [2] propose S3DIS, which is a widely used benchmark in many tasks, by collecting RGB-D images and reconstructing 3D textured mesh model for each scene. The colored 3D point clouds in S3DIS are densely and uniformly sampled from the textured meshes. ScanNet [11] also provide 3D reconstructions captured by an iPad equipped with a structure sensor, accompanied by annotations. Matterport3D [8] generates low-resolution meshes from panoramic RGB-D images. ARKitScenes [5] offers high-resolution ground truth geometry by using laser scans, but it only provides bounding box annotations. Novel view synthesis methods, such as neural radiance fields (NeRFs) [31], development rapidly in recent years [4, 28]. Yeshwanth et al. [53] propose ScanNet++, containing 460 scenes with DSLR images and iPhone RGB-D frames. They obtain each scene by using the Faro Focus Premium laser scanner and implementing Poisson reconstruction [20, 21] to obtain meshes. Then the meshes are annotated. Comparing to S3DIS [2], ScanNet [11], and ScanNet++ [53], LiDAR-Net provides annotated raw points, which can be directly employed for training deep models specializing in 3D point cloud scene understanding. LiDAR-Net meticulously preserves the characteristics of raw point clouds captured by sensors, encompassing non-uniform distributions like scanning holes and lines, as well as anomalies like reflection noises and ghosts." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Outdoor scenes. These datasets are usually captured by static Terrestrial Laser Scanners (TLS), Mobile Laser Scanners (MLS), and Airborne Laser Scanners (ALS). The representative datasets in this domain comprise roadway-level datasets, such as KITTI [14], Paris-rue-Madame [40], IQmulus [46], Semantic3D [16], Paris-Lille-3D [38], Ar-goverse [10], SemanticKITTI [6], SemanticPOSS [33], Toronto-3D [44], nuScenes [7], and Waymo dataset [43]. Additionally, urban-level aerial 3D point cloud datasets include DublinCity [57], DALES [47], LASDU [52], Campus3D [24], and SensatUrban [18]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.091, + 0.868, + 0.108 + ], + "angle": 0, + "content": "2.2. Deep Learning on 3D Scene Understanding" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.116, + 0.892, + 0.406 + ], + "angle": 0, + "content": "Pioneered by PointNet [35], neural networks are used to process the unordered point cloud data [25, 36, 49, 56], leading to numerous innovative applications [13, 27, 30, 55]. We choose three representative tasks to evaluate LiDAR-Net dataset. 1) Semantic segmentation. Thomas et al. [45] propose Kernel Point Convolution (KPCConv) operators for 3D point clouds using a set of learnable kernel points. Hu et al. [17] propose RandLA-Net utilizing random point sampling to achieve remarkably high efficiency. 2) Instance segmentation. ASIS [48] uses a feature fusion structure to enhance both semantic and instance branches by leveraging information from each other. Yang et al. [51] propose a single-stage and anchor-free network called 3D-BoNet for instance segmentation. 3) Object detection. VoteNet [37] implements a unique voting scheme among points to infer object bounding box centers. GroupFree3D [29] leverages a sophisticated attention mechanism that obviates the need for point candidate grouping, enabling direct inference of object instances." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.425, + 0.825, + 0.442 + ], + "angle": 0, + "content": "3. Dataset Acquisition and Annotation" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.453, + 0.722, + 0.469 + ], + "angle": 0, + "content": "3.1. Point Cloud Acquisition" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.478, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Acknowledging the marked advantages of LiDAR technology in securing authentic three-dimensional data over traditional RGBD data acquisition methods, our research utilizes Leica BLK2GO, a device combining dual-axis LiDAR technology. The BLK2GO is equipped not only with a commercial dual-axis LiDAR and a 12-megapixel detail camera but also with a 4.8-megapixel, 3-shot panoramic camera. This integration enables stable collection of point cloud data with an accuracy of \\(\\pm 3\\text{mm} @10m\\) and a capture speed of 420,000 points/second within a \\(0.5\\sim 25m\\) range, while simultaneously obtaining high-resolution color images. Significantly, the BLK2GO implements GrandSLAM dual-positioning technology, seamlessly blending laser SLAM and visual SLAM. This approach involves using point cloud from LiDAR and inertial navigation from IMU for one aspect of positioning, and determining the current position and orientation by analyzing disparities between consecutive frames captured by the panoramic camera. For the LiDAR-Net, all data acquisition routes are meticulously pre-planned by professional surveyors, ensuring comprehensive and consistent coverage of the targeted area. To mirror the various interferences typical in real-world point cloud acquisition scenarios, all data are manually collected by human surveyors. Due to the device's battery capacity constraints, each data collection session is strategically limited to approximately one hour. To encompass the entire area, data from multiple individual sessions are manually integrated." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "21991" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.102, + 0.082, + 0.87, + 0.602 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.102, + 0.611, + 0.867, + 0.626 + ], + "angle": 0, + "content": "Figure 3. Semantic and instance labels. LiDAR-Net provides point-level annotations directly associated with each raw data point." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.638, + 0.297, + 0.652 + ], + "angle": 0, + "content": "3.2. Point Cloud Annotation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.675, + 0.473, + 0.901 + ], + "angle": 0, + "content": "In the dataset, we address three sub-tasks: semantic segmentation, instance segmentation, and object detection. The categorization criteria are based on two key principles: 1) Each category should possess a distinct and unambiguous semantic meaning, aligning with both academic research and practical business applications. This alignment facilitates advanced visual tasks such as 3D reconstruction, point cloud completion, and applications in virtual reality, building upon baseline tasks. 2) The categories should exhibit significant geometric or appearance differences, ensuring clear distinction across different groups. We provide a Point Cloud AnnoTation system (PCAT system) to annotate all point clouds in the LiDAR-Net with both semantic and instance labels. Subsequently, object detection labels, in the form of bounding boxes, are derived from these instances" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.638, + 0.892, + 0.759 + ], + "angle": 0, + "content": "labels. The PCAT system is set to be released, allowing users to easily modify or subdivide labels according to their specific requirements. Each label in LiDAR-Net is rigorously manually annotated and verified, ensuring the consistency and high quality of the semantic categories. The entire dataset labeling consumes approximately 550 working hours. Illustrative examples of our annotations are displayed in Fig. 3." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.765, + 0.893, + 0.901 + ], + "angle": 0, + "content": "We annotate various indoor components, including floors, stairs, and ceilings, as well as a wide range of furniture and fixtures such as tables, chairs, and sofas. Additionally, we carefully annotate anomalies captured by LiDAR, encompassing reflection noises and ghosts, as they introduce inaccuracies into the data and present challenges in data analysis. Specular reflections from smooth surfaces like glass or metal can disrupt LiDAR systems, resulting in reflection noise points. LiDAR systems would capture" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.957 + ], + "angle": 0, + "content": "21992" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.471, + 0.184 + ], + "angle": 0, + "content": "incomplete and repetitive ghosts when persons or other objects move in front of the scanner. These anomalies, commonly encountered in real-world applications like robotics and consumer electronics, are accurately recorded in our LiDAR-Net dataset to aid in training deep learning models capable of handling these challenges." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.195, + 0.205, + 0.21 + ], + "angle": 0, + "content": "3.3. Benchmark" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.219, + 0.47, + 0.355 + ], + "angle": 0, + "content": "LiDAR-Net contains classrooms, study lounges, seminar rooms, auditoriums for learning scenes, offices, meeting rooms, lounges for working scenes, and living rooms, bedrooms, dining rooms, washrooms for living scenes. Fig. 4 shows the diversity of scenes. Furthermore, We record world coordinates of rooms to form connecting areas, including 2, 7, and 5 seamless areas of learning, working and living scenes, which facilitate navigation and understanding large-scale indoor scenes." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.356, + 0.471, + 0.552 + ], + "angle": 0, + "content": "For the facilitation of GPU-accelerated batch training and testing, we divide the point clouds from various scenes into individual rooms based on their primary structural features, particularly the wall orientations. It is important to note that we provide coordinate correspondences for each room to facilitate tasks working in a whole area. Point clouds from learning scenes are divided into 216 rooms, including 173 rooms for training and 43 for testing. Similarly, we split the working scenes into 206 rooms, including 169 and 37 for training and testing, each room covering approximately \\(100m^2\\). In living scenes, of the 43 rooms analyzed, 33 are used for training and 10 for testing. The distribution of room areas is illustrated in Fig. 5." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.553, + 0.471, + 0.903 + ], + "angle": 0, + "content": "LiDAR-Net contains 24 semantic categories, including houseplant (low potted plants), tree (tall trees typically positioned on the floor), person, floor, stair, ceiling, pipe, wall, pillar, window, curtain, door, table, chair, sofa, blackboard (common in learning or working scenes), monitor, bookshelf, wardrobe, bed, light, tabletop others (miscellaneous small objects on tables), reflection noise, ghost (resulting from moving entities, such as people). Additionally, an 'unknown' class exists outside these 24 categories, encompassing points not classified into any specific category. Each point within the 24 semantic categories is assigned instance labels. 17 categories are used for object detection. Floors, ceilings, pipes, walls, pillars, reflection noises and ghosts, which lack definite boundaries, are excluded from object detection task, following [29, 37]. It is important to note that instance labels are provided for these excluded categories, facilitating use cases like smart construction sites and vectorized indoor modeling. The LiDAR-Net dataset will be publicly released, with the goal of establishing benchmarks in indoor point cloud semantic segmentation, instance segmentation, and object detection, which will be evaluated through an online public platform. Following ScanNet [11] and ScanNet++ [53], labels of the test" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.092, + 0.655, + 0.106 + ], + "angle": 0, + "content": "set will remain hidden." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.121, + 0.633, + 0.138 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.146, + 0.727, + 0.162 + ], + "angle": 0, + "content": "4.1. Representative Baselines" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.169, + 0.892, + 0.321 + ], + "angle": 0, + "content": "In Section 2.2, we explore the three main tasks in learning-based 3D point cloud scene understanding. To comprehensively evaluate our LiDAR-Net dataset, we carefully select eight emblematic methods, applying them as benchmarks across different tasks to conduct an extensive benchmark test on our dataset. Precisely, we utilize PointNet [35], PointNet++ [36], KPCov [45], and RandLA-Net [17], for point cloud semantic segmentation, ASIS [48] and 3D-BoNet [51] for instance segmentation, VoteNet [37] and GroupFree3D [29] for object detection." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.331, + 0.684, + 0.345 + ], + "angle": 0, + "content": "4.2. Evaluation Metrics" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.354, + 0.892, + 0.535 + ], + "angle": 0, + "content": "Consistent with prevailing benchmarks, our evaluation framework is designed for a thorough assessment across various segmentation and detection tasks. For semantic segmentation, we focus primarily on mean Intersection-over-Union (mIoU) as the key evaluation metric, following [17, 45]. In instance segmentation, our analysis emphasizes mean precision (mPre) and mean recall rate (mRec) to measure algorithmic performance, following [48, 51]. Moreover, within the domain of object detection, we concentrate on the mean of per-category object detection average precision with 3D IoU threshold 0.25 and 0.5, denoted as mAP@0.25 and mAP@0.5, following [29, 37]." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.545, + 0.687, + 0.56 + ], + "angle": 0, + "content": "4.3. Benchmark Results" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.568, + 0.892, + 0.87 + ], + "angle": 0, + "content": "To ensure a fair comparison, we rigorously follow the experimental settings outlined in the original publications of each benchmark algorithm. Table 2 presents the quantitative results across three tasks. The overall performances in segmentation and detection has not reached a satisfactory level. For instance, examining RandLA-Net [17] and KPCov [45], which show the best performance in semantic segmentation, Table 3 details the IoU for each semantic category of the two methods. Table 3 reveals that certain key categories, such as window and bookshelf, were poorly segmented. RandLA-Net achieves \\(42.02\\%\\) for the IoU of tree, which is higher than \\(7.94\\%\\) of KPCov, however for the IoU of sofa, performance of KPCov is much better than that of RandLA-Net. There is a significant variation in performance across different algorithms within these challenging categories, and no single algorithm consistently outperforms the other. Comprehensive quantitative results of other semantic segmentation, instance segmentation and object detection methods for each category are given in the supplementary materials." + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "A key advantage of our LiDAR-Net is that its annotated raw points closely mirror the distribution of real-scanned" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "21993" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.099, + 0.082, + 0.226, + 0.141 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.228, + 0.082, + 0.355, + 0.141 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.356, + 0.082, + 0.484, + 0.141 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.485, + 0.082, + 0.615, + 0.141 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.616, + 0.082, + 0.744, + 0.141 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.745, + 0.082, + 0.874, + 0.141 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.098, + 0.141, + 0.316, + 0.243 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.317, + 0.141, + 0.674, + 0.243 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.675, + 0.141, + 0.874, + 0.243 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.104, + 0.253, + 0.863, + 0.268 + ], + "angle": 0, + "content": "Figure 4. The diversity of scenes. Each point is color-coded by its semantic label. The bottom row displays three seamless areas." + }, + { + "type": "table", + "bbox": [ + 0.111, + 0.273, + 0.865, + 0.346 + ], + "angle": 0, + "content": "
Semantic segmentationmIoUInstance segmentationmPremRecObject detectionmAP@0.25mAP@0.5
PointNet [35]16.27ASIS [48]37.3225.08VoteNet [37]44.8316.71
PointNet++ [36]28.81
KPConv [45]44.293D-BoNet [51]39.8224.63GroupFree3D [29]46.8018.86
RandLA-Net [17]32.60
" + }, + { + "type": "table_caption", + "bbox": [ + 0.189, + 0.35, + 0.779, + 0.364 + ], + "angle": 0, + "content": "Table 2. Statistics of selected emblematic methods on LiDAR-Net. The percent sign (%) is omitted." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.37, + 0.894, + 0.495 + ], + "angle": 0, + "content": "
MethodsHouseplantTreePersonFloorStairCeilingPipeWallPillar
KPConv [45]26.987.9445.2285.4325.7086.5138.4974.925.68
RandLA-Net [17]3.5642.0240.7593.170.4286.1219.4373.810.91
WindowCurtainDoorTableChairSofaBlackboardMonitorBookshelf
KPConv [45]9.4822.2134.4479.8875.4558.0274.7955.2326.76
RandLA-Net [17]18.0041.3351.2261.6942.280.0074.776.067.73
WardrobeBedLightTabletop othersReflection noiseGhostUnknownmIoU
KPConv [45]34.0539.5165.2140.5819.2256.8218.8044.29
RandLA-Net [17]0.000.0054.1314.910.0067.5315.0932.60
" + }, + { + "type": "table_caption", + "bbox": [ + 0.22, + 0.498, + 0.747, + 0.512 + ], + "angle": 0, + "content": "Table 3. Comparison of IoU for each semantic category. The percent sign \\((\\%)\\) is omitted." + }, + { + "type": "image", + "bbox": [ + 0.103, + 0.522, + 0.445, + 0.658 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.662, + 0.47, + 0.704 + ], + "angle": 0, + "content": "Figure 5. Distribution of room areas. LiDAR-Net encompasses a diverse array of rooms, reflecting a broad spectrum of spatial configurations." + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.708, + 0.47, + 0.79 + ], + "angle": 0, + "content": "
DatasetsSemantic segmentationInstance segmentationObject detection
mIoUmPremRecmAP@0.25mAP@0.5
S3DIS [2]35.5815.727.847.930.28
ScanNet [11]33.1815.8814.4420.911.21
ScanNet++ [53]23.6026.484.6813.311.67
LiDAR-Net39.7532.9220.3932.969.22
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.8, + 0.469, + 0.842 + ], + "angle": 0, + "content": "Table 4. Quantitative comparisons of deep models trained on different datasets and tested on real-scanned data. The percent sign \\((\\%)\\) is omitted." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.903 + ], + "angle": 0, + "content": "points. To evaluate it, we train the benchmark methods on existing popular datasets, including S3DIS [2], ScanNet [11], and ScanNet++ [53]. Then, the deep models" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.524, + 0.892, + 0.706 + ], + "angle": 0, + "content": "are tested on 5 real-scanned rooms, captured using a Leica BLK2GO scanner in locations not included in LiDAR-Net. Due to the categories of the four datasets are different, we test the models on the communal categories. Fig. 6 and Table 4 show the qualitative and quantitative comparisons, selecting RandLA-Net [17] for semantic segmentation, ASIS [48] for instance segmentation, and GroupFree3D [29] for object detection. Detailed statistics of other methods and each category are listed in the supplementary materials. Benefited from the realistic distribution of raw points in LiDAR-Net, deep models trained on it demonstrate superior performances across all three tasks." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.723, + 0.617, + 0.74 + ], + "angle": 0, + "content": "5. Challenges" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.901 + ], + "angle": 0, + "content": "This section focuses on the key challenges presented by our dataset, which inherently stem from the authentic LiDAR collection process. Then, we provide an in-depth analysis of these challenges with a potential to drive advancements in the current field. Concurrently, we delve into tentative discussions of viable solutions. It is crucial to clarify that the aim of this paper is not to introduce a new method for addressing these challenges. Rather, our goal is to identify data biases potentially caused by existing datasets, to shed light on unresolved issues, and to provide analysis and in-" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.946, + 0.519, + 0.957 + ], + "angle": 0, + "content": "21994" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.083, + 0.088, + 0.895, + 0.314 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.32, + 0.895, + 0.364 + ], + "angle": 0, + "content": "Figure 6. Qualitative comparisons of deep models trained on different datasets and tested on real-scanned data. Each row displays one task. Deep models are tested on the communal categories. It's important to note that ScanNet++ does not include instance labels for floors, walls, and ceilings, and therefore, these elements are excluded from the instance segmentation experiment." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.371, + 0.471, + 0.403 + ], + "angle": 0, + "content": "sights. Ultimately, we seek to catalyze advancements in the understanding of indoor scene point clouds." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.414, + 0.36, + 0.429 + ], + "angle": 0, + "content": "5.1. Differences in Data Distribution" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.439, + 0.474, + 0.713 + ], + "angle": 0, + "content": "LiDAR scanning. In previous discussions, we introduced a point cloud dataset derived from authentic LiDAR scanning, which significantly differs from existing indoor point cloud datasets. While LiDAR and RGB-D scanning produce point clouds with some similar attributes, notable differences exist in their characteristics. The non-uniform distribution of real-scanned points, characterized by scanning holes and lines, is a result of the laser scanning process. LiDAR measures distance by emitting laser pulses and measuring the time they take to return. The laser beam moves directionally, creating linear point captures. Gaps in these lines lead to scanning holes. Furthermore, the distance from the scanner affects point distribution. Points closer to the scanner are denser, while those at greater distances tend to be sparser, a phenomenon owing to the dispersion and weakening of laser pulse energy. LiDAR's capability to operate over long distances inherently leads to a noticeable decrease in point density at farther ranges." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.471, + 0.903 + ], + "angle": 0, + "content": "RGB-D cameras. Conversely, RGB-D cameras, which utilize structured light or Time of Flight (ToF) technology, determine distance using a distinct methodology. Points closer to the sensor tend to be denser due to variations in observational angles, while farther points show relative sparsity owing to resolution limits. RGB-D cameras are capable of providing relatively dense data within a specific range, but this density noticeably decreases or even disappears beyond their operational limit. Therefore, although both authentic LiDAR and RGB-D cameras exhibit the challenge of variable point density, there is a fundamental difference" + }, + { + "type": "image", + "bbox": [ + 0.51, + 0.374, + 0.697, + 0.473 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.698, + 0.375, + 0.884, + 0.473 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.511, + 0.476, + 0.697, + 0.574 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.698, + 0.475, + 0.884, + 0.574 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.585, + 0.892, + 0.613 + ], + "angle": 0, + "content": "Figure 7. Point and voxel distributions in S3DIS, ScanNet, ScanNet++ and LiDAR-Net." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.618, + 0.895, + 0.695 + ], + "angle": 0, + "content": "in their respective point cloud distributions. In the indoor conditions, authentic LiDAR typically encompasses a point distribution radius spanning \\(2 \\sim 7\\) meters, in sharp contrast to the \\(2 \\sim 5\\) meters typically covered by RGB-D cameras (as illustrated in Fig. 7)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Comparison of the datasets. Due to the distinctions in acquisition technologies, LiDAR and RGB-D systems exhibit notable discrepancies in factors such as scanning precision, noise, color information, and performance in different lighting conditions. This type of data variance becomes particularly conspicuous in deep learning methodologies heavily reliant upon data. Fig. 7 illustrates the point and voxel distributions in existing indoor datasets compared to LiDAR-Net. Firstly, the three existing datasets predominantly contain points within a \\(2 \\sim 5\\) meters range from the scanner, while our LiDAR-Net provides a distinct distribution. It is worth to be explored that would the deep" + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "21995" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.289 + ], + "angle": 0, + "content": "models trained on previous datasets over-fitted to the distribution of \\(2 \\sim 5\\) meters? Our LiDAR-Net, with its broader range of \\(2 \\sim 7\\) meters, provides an expanded scope for future research in this area. Secondly, since the points in the previous three datasets are generated by sampling on annotated 3D reconstructions, they mirror the voxel distribution. In contrast, the primary strength of LiDAR-Net lies in its annotated raw points, which are non-uniform, leading to distinct point and voxel distributions. This divergence introduces new challenges to the field. Our dataset adeptly encapsulates these genuine characteristics of real-world data, thereby establishing a robust foundation for various forthcoming applications in indoor perception technology." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.296, + 0.418, + 0.312 + ], + "angle": 0, + "content": "5.2. Impact of Imbalance Class Distribution" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.319, + 0.47, + 0.53 + ], + "angle": 0, + "content": "Upon further investigation, we discern a more critical issue within indoor scene datasets: a conspicuous performance discrepancy resulting from imbalanced class distribution. We showcase the cumulative count of 3D points per semantic category in the top of Fig. 8, and the instance distribution is shown in the bottom. It is observable that the primary semantic categories, including ceilings, floors, walls, etc., make up over \\(80\\%\\) of the total points. In contrast, smaller yet crucial categories (e.g., monitors) constitute a mere \\(0.16\\%\\) of the total points, highlighting a stark imbalance in the distribution of semantic classes. This disproportion is inherent to indoor scenes, where walls, ceilings, and floors naturally cover large surface areas, while items like monitors are considerably smaller." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.531, + 0.471, + 0.804 + ], + "angle": 0, + "content": "Data imbalance poses a significant challenge in 3D scene understanding, an issue that is also evident in LiDAR-Net. As shown in Table 3, the skew in segment headers is especially marked in the semantic segmentation task, owing to the disparity in point cloud quantities at the point level. For instance, looking at the results of RandLA-Net in specific categories, the semantic segmentation accuracy for floors is around \\(93\\%\\), while for stairs, it nearly drops to zero. Essentially, indoor scenes are dominated by a few categories such as ceilings and walls, whereas categories like stairs, though minor but critical, have an extremely sparse data distribution. When considering instance segmentation, the combination of instance-level and point-level imbalances exacerbates the problem, leading to a more severe dual-imbalance situation. Detailed instance segmentation results of each category are listed and discussed in the supplementary materials. This profound imbalance in distribution poses another significant challenge introduced by our dataset." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.816, + 0.196, + 0.831 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.471, + 0.903 + ], + "angle": 0, + "content": "In this study, we present a comprehensive indoor point cloud dataset derived from authentic LiDAR scanning. This dataset encompasses three meticulously labeled scenes with a total of 3.6 billion points, covering \\(30,000m^2\\). Designed" + }, + { + "type": "image", + "bbox": [ + 0.507, + 0.094, + 0.891, + 0.267 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.506, + 0.27, + 0.891, + 0.446 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.454, + 0.893, + 0.495 + ], + "angle": 0, + "content": "Figure 8. Top: Point number distribution of semantic categories. Bottom: Instance number distribution. Unknown points do not have instance labels." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.506, + 0.895, + 0.793 + ], + "angle": 0, + "content": "for a variety of applications including semantic segmentation, instance segmentation, and object detection, our dataset serves as a versatile resource for related research tasks. Our comprehensive benchmark testing not only highlights persistent challenges but also emphasizes the distinct advantages of our dataset, particularly regarding the differences between annotated raw points from genuine LiDAR and points sampled from annotated 3D reconstructions. We have thoroughly examined issues such as the pronounced effects of imbalanced class distribution and the adaptability of models to unseen real-scanned scenes. Looking towards a future where autonomous indoor robots navigate diverse human-centric environments, we underscore the importance of real-time perception using authentic LiDAR-scanned data. The precision and high resolution of real-world LiDAR point cloud data are crucial for emerging cyber-physical systems like smart homes and digital twins. We believe our dataset and benchmarks will spur further progress in related areas of study." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.805, + 0.66, + 0.822 + ], + "angle": 0, + "content": "Acknowledgments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.825, + 0.894, + 0.903 + ], + "angle": 0, + "content": "This work was supported by the National Natural Science Foundation of China (62032011), the Natural Science Foundation of Jiangsu Province (No. BK20211147), and the program B for Outstanding PhD candidate of Nanjing University." + }, + { + "type": "page_number", + "bbox": [ + 0.479, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "21996" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Iro Armeni, Ozan Sener, Amir R Zamir, Helen Jiang, Ioannis Brilakis, Martin Fischer, and Silvio Savarese. 3d semantic parsing of large-scale indoor spaces. 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It encompasses three prevalent daily environments, including learning scenes, working scenes, and living scenes. LiDAR-Net is characterized by its nonuniform point distribution, e.g., scanning holes and scanning lines. Additionally, it meticulously records and annotates scanning anomalies, including reflection noise and ghost. These anomalies stem from specular reflections on glass or metal, as well as distortions due to moving persons. LiDAR-Net's realistic representation of non-uniform distribution and anomalies significantly enhances the training of deep learning models, leading to improved generalization in practical applications. We thoroughly evaluate the performance of state-of-the-art algorithms on LiDAR-Net and provide a detailed analysis of the results. Crucially, our research identifies several fundamental challenges in understanding indoor point clouds, contributing essential insights to future explorations in this field. Our dataset can be found online: http://lidar-net.njumeta.com. + +# 1. Introduction + +Owing to its reliability and accuracy, Light Detection And Ranging (LiDAR) technology becomes increasingly popular, finding broad applications in autonomous vehicles for perception and localization [23, 26, 54] as well as expanding its applications in consumer electronics [3, 34, 37]. Introduced in 2020, the LiDAR scanner on the iPhone has en + +![](images/c56edca1fc4969c1ae2755a12889581f4080f285592a4336ef251ff860e8fa72.jpg) +Figure 1. LiDAR-Net comprises 3.6 billion real-scanned points, each annotated with semantic and instance labels. Points of LiDAR-Net have real-scanned characteristics including scanning holes, scanning lines, and anomalies such as ghosts (indicated by red points) caused by moving persons. These characteristics significantly enhance the ability of trained deep models to generalize to real-world applications. + +abled a multitude of innovative applications in virtual reality (VR) and 3D measurements. Deep learning has achieved remarkable success in computer vision, particularly in analyzing and understanding 3D scenes [35, 36, 49, 56]. Datasets undoubtedly have played a critical role in this process, since training a deep models usually requires extensive annotated datasets, especially for supervised learning [2, 8, 11, 19, 42, 53]. In the domain of 3D computer vision for indoor scenes, the most widely recognized datasets in the academic community are S3DIS [2], ScanNet [11], and the recent ScanNet++ [53], etc. S3DIS and ScanNet have been used to train models for various 3D scene understanding tasks, such as 3D object detection, along with semantic and instance segmentation. S3DIS and ScanNet collect RGB-D images, and then reconstruct and annotate textured meshes. ScanNet++ relies on a scanner to capture point clouds, however, the provided annotations are attached to the Poisson reconstruction instead of raw points. + +
#Name#Year#Spatial size#Classes#Points# Raw points# Anomalies#Sensors
S3DIS [1]20176×103m213273MXXMatterport
ScanNet [11]20173.4×104m220242MXXRGB-D
ScanNet++ [53]20231.5×104m21000+446MXXTLS
LiDAR-Net (Ours)20233.0×104m2243619M✓✓MLS
+ +Table 1. In comparison with well-known indoor scene datasets, LiDAR-Net exceeds both S3DIS and ScanNet++ regarding spatial size and resolution. Although ScanNet covers a larger spatial size than ours, we provide points with annotations at a higher resolution. TLS is Terrestrial Laser Scanning system. MLS is Mobile Laser Scanning system. + +![](images/747abd6b5228f2c1f1fdb116d074b1a6ff0819ad73fe21dcc182eafb9e4dee6f.jpg) +Original points +Figure 2. Illustration of reflection noise. These noise points usually suspend in the air. Purple highlights reflection noise in the semantic label figures + +![](images/7b8d0110e3b8e1799ffb9e54dd547eeee1b79de3aefd76650165e2fc090f1001.jpg) +Semantic labels + +![](images/1f65431e5e3566136ca242a60dfbdb5ad4be585218e60ef2bf50130734467f91.jpg) +Original points + +![](images/010f8f032920a18597c5f2baf6140b4ab6aa031dd1948329e5dabe204cb2681f.jpg) +Semantic labels + +The 3D accuracy of these datasets is inferior to that of raw point clouds directly collected using laser scanners. Annotated data in existing datasets also lack characteristic distributions of real-scanned points, including scanning lines and scanning holes, as illustrated in Fig. 1. Consequently, deep models trained on these datasets tend to perform poorly when applied to actual, real-scanned point cloud data, significantly impeding their practical applicability. + +In this paper, we contribute a new dataset, LiDAR-Net, to the academic community. Distinct from existing indoor scene datasets, LiDAR-Net is captured by real laser scanners and contains precise semantic and instance annotations for each raw point. LiDAR-Net encompasses three common daily scenes: learning, working, and living environments. It contains 3.6 billion 3D points, covering $30,000m^2$ of indoor space. Using professional LiDAR scanning systems, the 3D point clouds the dataset ensures the high authenticity of its 3D point clouds. Detailed information about the data collection process is provided in Section 3. Across all scenes, each point is carefully annotated and classified into 24 semantic categories, such as floor, ceiling, and window. + +Compared to previous indoor scene datasets primarily collected using RGB-D cameras or annotated on reconstructed meshes, LiDAR-Net offers several advantages: + +- Firstly, LiDAR-Net distinguishes itself by its authentically captured point cloud data, which leads to non-uniform point distributions, characterized by scanning holes and lines, as depicted in Fig. 1. +- Secondly, LiDAR-Net includes comprehensive annotations of scanning anomalies including reflection noises (purple points in Fig. 2) and ghosts caused by moving objects, particularly persons (red points in Fig. 1). +- Thirdly, LiDAR-Net covers corridors and stairs connecting each room, creating seamless and complete spaces + +crucial for integrated tasks across entire areas. + +Table 1 presents a comparative analysis with other popular indoor scene datasets. While many outdoor point cloud datasets [43, 44] contain real-scanned data, the significant disparity in scene characteristics presents challenges for adapting outdoor datasets to indoor tasks. Moreover, outdoor point clouds generally show a higher level of sparsity and incompleteness compared to LiDAR-Net. + +Using LiDAR-Net, we recognize several challenges and conduct studies on them, as outlined in Section 5. We first investigate the process of annotating a large indoor point cloud dataset. Then, we discuss the significance of real-scanned point cloud data for semantic learning, emphasizing the advantages of raw LiDAR-based point clouds over those from depth cameras or from reconstructed meshes. Additionally, we investigate the imbalance of semantic classes in indoor environments. While this paper does not provide exhaustive solutions, it introduces these challenges for further exploration by the research community. Our discussion on the complexities of multi-task learning in indoor 3D point clouds aims to spur developments in fields such as intelligent home systems, digital twins, indoor robotic navigation, asset management in extensive indoor infrastructures, and smart construction sites, etc. To summarize, our work makes the following contributions: + +- We introduce LiDAR-Net, a comprehensive large-scale 3D point cloud dataset. This dataset is equipped with point-level semantic and instance annotations, making it ideal for multi-task training and testing. +- LiDAR-Net is characterized by its distinct features such as non-uniform point distributions, scanning anomalies, and seamless spatial coverage. These attributes notably enhance the generalization capabilities of trained deep models for real-world applications. +- We assess the efficacy of current algorithms within real-scanned point cloud environments and identify key challenges in this field. + +# 2. Related Work + +Booming deep learning-based 3D scene understanding methods desire various 3D scene datasets. Guo et al. [15] give a comprehensive survey on this topic. We briefly summary 3D scene datasets and 3D point cloud scene understanding methods below. + +# 2.1. 3D Scene Datasets + +According to the application scenario, existing 3D datasets can be divided into three categories: (i) 3D objects, (ii) indoor scenes, (iii) outdoor scenes. + +3D objects. ModelNet [50] and ShapeNet [9] are both 3D synthetic mesh datasets for shape classification. Mo et al. [32] propose PartNet containing hierarchical labels for part segmentation. ABC dataset [22] contains 1M CAD models with structure information. Deitke et al. [12] propose Objaverse-XL, which is a universe of $10\mathrm{M} + 3\mathrm{D}$ objects. + +Indoor scenes. Early indoor 3D datasets are acquired by using commodity short-range depth scanners such as NYUv2 [41] and SUN RGB-D [42], comprising short RGB-D sequences with limited resolution. While SceneNN [19] and PiGraphs [39] provide reconstructed and labeled scenes, their scene counts are restricted. Armeni et al. [2] propose S3DIS, which is a widely used benchmark in many tasks, by collecting RGB-D images and reconstructing 3D textured mesh model for each scene. The colored 3D point clouds in S3DIS are densely and uniformly sampled from the textured meshes. ScanNet [11] also provide 3D reconstructions captured by an iPad equipped with a structure sensor, accompanied by annotations. Matterport3D [8] generates low-resolution meshes from panoramic RGB-D images. ARKitScenes [5] offers high-resolution ground truth geometry by using laser scans, but it only provides bounding box annotations. Novel view synthesis methods, such as neural radiance fields (NeRFs) [31], development rapidly in recent years [4, 28]. Yeshwanth et al. [53] propose ScanNet++, containing 460 scenes with DSLR images and iPhone RGB-D frames. They obtain each scene by using the Faro Focus Premium laser scanner and implementing Poisson reconstruction [20, 21] to obtain meshes. Then the meshes are annotated. Comparing to S3DIS [2], ScanNet [11], and ScanNet++ [53], LiDAR-Net provides annotated raw points, which can be directly employed for training deep models specializing in 3D point cloud scene understanding. LiDAR-Net meticulously preserves the characteristics of raw point clouds captured by sensors, encompassing non-uniform distributions like scanning holes and lines, as well as anomalies like reflection noises and ghosts. + +Outdoor scenes. These datasets are usually captured by static Terrestrial Laser Scanners (TLS), Mobile Laser Scanners (MLS), and Airborne Laser Scanners (ALS). The representative datasets in this domain comprise roadway-level datasets, such as KITTI [14], Paris-rue-Madame [40], IQmulus [46], Semantic3D [16], Paris-Lille-3D [38], Ar-goverse [10], SemanticKITTI [6], SemanticPOSS [33], Toronto-3D [44], nuScenes [7], and Waymo dataset [43]. Additionally, urban-level aerial 3D point cloud datasets include DublinCity [57], DALES [47], LASDU [52], Campus3D [24], and SensatUrban [18]. + +# 2.2. Deep Learning on 3D Scene Understanding + +Pioneered by PointNet [35], neural networks are used to process the unordered point cloud data [25, 36, 49, 56], leading to numerous innovative applications [13, 27, 30, 55]. We choose three representative tasks to evaluate LiDAR-Net dataset. 1) Semantic segmentation. Thomas et al. [45] propose Kernel Point Convolution (KPCConv) operators for 3D point clouds using a set of learnable kernel points. Hu et al. [17] propose RandLA-Net utilizing random point sampling to achieve remarkably high efficiency. 2) Instance segmentation. ASIS [48] uses a feature fusion structure to enhance both semantic and instance branches by leveraging information from each other. Yang et al. [51] propose a single-stage and anchor-free network called 3D-BoNet for instance segmentation. 3) Object detection. VoteNet [37] implements a unique voting scheme among points to infer object bounding box centers. GroupFree3D [29] leverages a sophisticated attention mechanism that obviates the need for point candidate grouping, enabling direct inference of object instances. + +# 3. Dataset Acquisition and Annotation + +# 3.1. Point Cloud Acquisition + +Acknowledging the marked advantages of LiDAR technology in securing authentic three-dimensional data over traditional RGBD data acquisition methods, our research utilizes Leica BLK2GO, a device combining dual-axis LiDAR technology. The BLK2GO is equipped not only with a commercial dual-axis LiDAR and a 12-megapixel detail camera but also with a 4.8-megapixel, 3-shot panoramic camera. This integration enables stable collection of point cloud data with an accuracy of $\pm 3\text{mm} @10m$ and a capture speed of 420,000 points/second within a $0.5\sim 25m$ range, while simultaneously obtaining high-resolution color images. Significantly, the BLK2GO implements GrandSLAM dual-positioning technology, seamlessly blending laser SLAM and visual SLAM. This approach involves using point cloud from LiDAR and inertial navigation from IMU for one aspect of positioning, and determining the current position and orientation by analyzing disparities between consecutive frames captured by the panoramic camera. For the LiDAR-Net, all data acquisition routes are meticulously pre-planned by professional surveyors, ensuring comprehensive and consistent coverage of the targeted area. To mirror the various interferences typical in real-world point cloud acquisition scenarios, all data are manually collected by human surveyors. Due to the device's battery capacity constraints, each data collection session is strategically limited to approximately one hour. To encompass the entire area, data from multiple individual sessions are manually integrated. + +![](images/6de1bc955587ab42b9fd077a5ea14f4c042a938945441650f434bc02625cd3f7.jpg) +Figure 3. Semantic and instance labels. LiDAR-Net provides point-level annotations directly associated with each raw data point. + +# 3.2. Point Cloud Annotation + +In the dataset, we address three sub-tasks: semantic segmentation, instance segmentation, and object detection. The categorization criteria are based on two key principles: 1) Each category should possess a distinct and unambiguous semantic meaning, aligning with both academic research and practical business applications. This alignment facilitates advanced visual tasks such as 3D reconstruction, point cloud completion, and applications in virtual reality, building upon baseline tasks. 2) The categories should exhibit significant geometric or appearance differences, ensuring clear distinction across different groups. We provide a Point Cloud AnnoTation system (PCAT system) to annotate all point clouds in the LiDAR-Net with both semantic and instance labels. Subsequently, object detection labels, in the form of bounding boxes, are derived from these instances + +labels. The PCAT system is set to be released, allowing users to easily modify or subdivide labels according to their specific requirements. Each label in LiDAR-Net is rigorously manually annotated and verified, ensuring the consistency and high quality of the semantic categories. The entire dataset labeling consumes approximately 550 working hours. Illustrative examples of our annotations are displayed in Fig. 3. + +We annotate various indoor components, including floors, stairs, and ceilings, as well as a wide range of furniture and fixtures such as tables, chairs, and sofas. Additionally, we carefully annotate anomalies captured by LiDAR, encompassing reflection noises and ghosts, as they introduce inaccuracies into the data and present challenges in data analysis. Specular reflections from smooth surfaces like glass or metal can disrupt LiDAR systems, resulting in reflection noise points. LiDAR systems would capture + +incomplete and repetitive ghosts when persons or other objects move in front of the scanner. These anomalies, commonly encountered in real-world applications like robotics and consumer electronics, are accurately recorded in our LiDAR-Net dataset to aid in training deep learning models capable of handling these challenges. + +# 3.3. Benchmark + +LiDAR-Net contains classrooms, study lounges, seminar rooms, auditoriums for learning scenes, offices, meeting rooms, lounges for working scenes, and living rooms, bedrooms, dining rooms, washrooms for living scenes. Fig. 4 shows the diversity of scenes. Furthermore, We record world coordinates of rooms to form connecting areas, including 2, 7, and 5 seamless areas of learning, working and living scenes, which facilitate navigation and understanding large-scale indoor scenes. + +For the facilitation of GPU-accelerated batch training and testing, we divide the point clouds from various scenes into individual rooms based on their primary structural features, particularly the wall orientations. It is important to note that we provide coordinate correspondences for each room to facilitate tasks working in a whole area. Point clouds from learning scenes are divided into 216 rooms, including 173 rooms for training and 43 for testing. Similarly, we split the working scenes into 206 rooms, including 169 and 37 for training and testing, each room covering approximately $100m^2$ . In living scenes, of the 43 rooms analyzed, 33 are used for training and 10 for testing. The distribution of room areas is illustrated in Fig. 5. + +LiDAR-Net contains 24 semantic categories, including houseplant (low potted plants), tree (tall trees typically positioned on the floor), person, floor, stair, ceiling, pipe, wall, pillar, window, curtain, door, table, chair, sofa, blackboard (common in learning or working scenes), monitor, bookshelf, wardrobe, bed, light, tabletop others (miscellaneous small objects on tables), reflection noise, ghost (resulting from moving entities, such as people). Additionally, an 'unknown' class exists outside these 24 categories, encompassing points not classified into any specific category. Each point within the 24 semantic categories is assigned instance labels. 17 categories are used for object detection. Floors, ceilings, pipes, walls, pillars, reflection noises and ghosts, which lack definite boundaries, are excluded from object detection task, following [29, 37]. It is important to note that instance labels are provided for these excluded categories, facilitating use cases like smart construction sites and vectorized indoor modeling. The LiDAR-Net dataset will be publicly released, with the goal of establishing benchmarks in indoor point cloud semantic segmentation, instance segmentation, and object detection, which will be evaluated through an online public platform. Following ScanNet [11] and ScanNet++ [53], labels of the test + +set will remain hidden. + +# 4. Experiments + +# 4.1. Representative Baselines + +In Section 2.2, we explore the three main tasks in learning-based 3D point cloud scene understanding. To comprehensively evaluate our LiDAR-Net dataset, we carefully select eight emblematic methods, applying them as benchmarks across different tasks to conduct an extensive benchmark test on our dataset. Precisely, we utilize PointNet [35], PointNet++ [36], KPCov [45], and RandLA-Net [17], for point cloud semantic segmentation, ASIS [48] and 3D-BoNet [51] for instance segmentation, VoteNet [37] and GroupFree3D [29] for object detection. + +# 4.2. Evaluation Metrics + +Consistent with prevailing benchmarks, our evaluation framework is designed for a thorough assessment across various segmentation and detection tasks. For semantic segmentation, we focus primarily on mean Intersection-over-Union (mIoU) as the key evaluation metric, following [17, 45]. In instance segmentation, our analysis emphasizes mean precision (mPre) and mean recall rate (mRec) to measure algorithmic performance, following [48, 51]. Moreover, within the domain of object detection, we concentrate on the mean of per-category object detection average precision with 3D IoU threshold 0.25 and 0.5, denoted as mAP@0.25 and mAP@0.5, following [29, 37]. + +# 4.3. Benchmark Results + +To ensure a fair comparison, we rigorously follow the experimental settings outlined in the original publications of each benchmark algorithm. Table 2 presents the quantitative results across three tasks. The overall performances in segmentation and detection has not reached a satisfactory level. For instance, examining RandLA-Net [17] and KPCov [45], which show the best performance in semantic segmentation, Table 3 details the IoU for each semantic category of the two methods. Table 3 reveals that certain key categories, such as window and bookshelf, were poorly segmented. RandLA-Net achieves $42.02\%$ for the IoU of tree, which is higher than $7.94\%$ of KPCov, however for the IoU of sofa, performance of KPCov is much better than that of RandLA-Net. There is a significant variation in performance across different algorithms within these challenging categories, and no single algorithm consistently outperforms the other. Comprehensive quantitative results of other semantic segmentation, instance segmentation and object detection methods for each category are given in the supplementary materials. + +A key advantage of our LiDAR-Net is that its annotated raw points closely mirror the distribution of real-scanned + +![](images/c04539faf3784505505d106906593d59c369211c7e48c91c5650677a15df8080.jpg) + +![](images/07bce97cf549f40238f9e27c72a85f305cf645ca7f28cabd5ec1970e5e72a8c4.jpg) + +![](images/da6baf104245fee9370493393ed216f6af5595453b8c927d54116af53e3d5dc1.jpg) + +![](images/f4a86c450df67f4092d6cb05ac0cc78407990c207602e29e51770fd51dd8def2.jpg) + +![](images/98d06b248cc8d84624701d18b4e6c3f483490bbadcfdbd61d89da012ad700849.jpg) + +![](images/828fcd839fcebaf94ea37a189f757f4c243568167fc5989be992af7da93951c1.jpg) + +![](images/93e5858a8d98ab8fb39d18631d673667560c2bf0da2595a51d6bd0f3b0b6f15b.jpg) +Figure 4. The diversity of scenes. Each point is color-coded by its semantic label. The bottom row displays three seamless areas. + +![](images/c80023903968efa8e8817da1274ba503cb942f9d76577ac1204ebb097a2dd527.jpg) + +![](images/2c60dc052dfe80d92c448483f52fd2eb0ccba55522427dd868e211b15c36769a.jpg) + +
Semantic segmentationmIoUInstance segmentationmPremRecObject detectionmAP@0.25mAP@0.5
PointNet [35]16.27ASIS [48]37.3225.08VoteNet [37]44.8316.71
PointNet++ [36]28.81
KPConv [45]44.293D-BoNet [51]39.8224.63GroupFree3D [29]46.8018.86
RandLA-Net [17]32.60
+ +Table 2. Statistics of selected emblematic methods on LiDAR-Net. The percent sign (%) is omitted. + +
MethodsHouseplantTreePersonFloorStairCeilingPipeWallPillar
KPConv [45]26.987.9445.2285.4325.7086.5138.4974.925.68
RandLA-Net [17]3.5642.0240.7593.170.4286.1219.4373.810.91
WindowCurtainDoorTableChairSofaBlackboardMonitorBookshelf
KPConv [45]9.4822.2134.4479.8875.4558.0274.7955.2326.76
RandLA-Net [17]18.0041.3351.2261.6942.280.0074.776.067.73
WardrobeBedLightTabletop othersReflection noiseGhostUnknownmIoU
KPConv [45]34.0539.5165.2140.5819.2256.8218.8044.29
RandLA-Net [17]0.000.0054.1314.910.0067.5315.0932.60
+ +![](images/e61a71b8826317310f3d84739cd2f1f57a64507e562129cdef7c817b2ec86f16.jpg) +Figure 5. Distribution of room areas. LiDAR-Net encompasses a diverse array of rooms, reflecting a broad spectrum of spatial configurations. + +Table 3. Comparison of IoU for each semantic category. The percent sign $(\%)$ is omitted. + +
DatasetsSemantic segmentationInstance segmentationObject detection
mIoUmPremRecmAP@0.25mAP@0.5
S3DIS [2]35.5815.727.847.930.28
ScanNet [11]33.1815.8814.4420.911.21
ScanNet++ [53]23.6026.484.6813.311.67
LiDAR-Net39.7532.9220.3932.969.22
+ +Table 4. Quantitative comparisons of deep models trained on different datasets and tested on real-scanned data. The percent sign $(\%)$ is omitted. + +points. To evaluate it, we train the benchmark methods on existing popular datasets, including S3DIS [2], ScanNet [11], and ScanNet++ [53]. Then, the deep models + +are tested on 5 real-scanned rooms, captured using a Leica BLK2GO scanner in locations not included in LiDAR-Net. Due to the categories of the four datasets are different, we test the models on the communal categories. Fig. 6 and Table 4 show the qualitative and quantitative comparisons, selecting RandLA-Net [17] for semantic segmentation, ASIS [48] for instance segmentation, and GroupFree3D [29] for object detection. Detailed statistics of other methods and each category are listed in the supplementary materials. Benefited from the realistic distribution of raw points in LiDAR-Net, deep models trained on it demonstrate superior performances across all three tasks. + +# 5. Challenges + +This section focuses on the key challenges presented by our dataset, which inherently stem from the authentic LiDAR collection process. Then, we provide an in-depth analysis of these challenges with a potential to drive advancements in the current field. Concurrently, we delve into tentative discussions of viable solutions. It is crucial to clarify that the aim of this paper is not to introduce a new method for addressing these challenges. Rather, our goal is to identify data biases potentially caused by existing datasets, to shed light on unresolved issues, and to provide analysis and in- + +![](images/1656dd47ce4f9abea350977ace063d5f5e597f01b551bc2348db28762e5ca38a.jpg) +Figure 6. Qualitative comparisons of deep models trained on different datasets and tested on real-scanned data. Each row displays one task. Deep models are tested on the communal categories. It's important to note that ScanNet++ does not include instance labels for floors, walls, and ceilings, and therefore, these elements are excluded from the instance segmentation experiment. + +sights. Ultimately, we seek to catalyze advancements in the understanding of indoor scene point clouds. + +# 5.1. Differences in Data Distribution + +LiDAR scanning. In previous discussions, we introduced a point cloud dataset derived from authentic LiDAR scanning, which significantly differs from existing indoor point cloud datasets. While LiDAR and RGB-D scanning produce point clouds with some similar attributes, notable differences exist in their characteristics. The non-uniform distribution of real-scanned points, characterized by scanning holes and lines, is a result of the laser scanning process. LiDAR measures distance by emitting laser pulses and measuring the time they take to return. The laser beam moves directionally, creating linear point captures. Gaps in these lines lead to scanning holes. Furthermore, the distance from the scanner affects point distribution. Points closer to the scanner are denser, while those at greater distances tend to be sparser, a phenomenon owing to the dispersion and weakening of laser pulse energy. LiDAR's capability to operate over long distances inherently leads to a noticeable decrease in point density at farther ranges. + +RGB-D cameras. Conversely, RGB-D cameras, which utilize structured light or Time of Flight (ToF) technology, determine distance using a distinct methodology. Points closer to the sensor tend to be denser due to variations in observational angles, while farther points show relative sparsity owing to resolution limits. RGB-D cameras are capable of providing relatively dense data within a specific range, but this density noticeably decreases or even disappears beyond their operational limit. Therefore, although both authentic LiDAR and RGB-D cameras exhibit the challenge of variable point density, there is a fundamental difference + +![](images/c689e18cad17b9f42c9ffbad7e9d3a14087ce793fc7df817e728f7160cf369ff.jpg) + +![](images/3e80d594acaa493c64a2cebbdd6d2811d6936e53126ce28c63c19181b984fdc7.jpg) + +![](images/d1cc222a2db47a40035750a5a09df22531f503dc2a3f2d87542278f85353db6b.jpg) +Figure 7. Point and voxel distributions in S3DIS, ScanNet, ScanNet++ and LiDAR-Net. + +![](images/33f4a845b736e5785d85c0d7421e5990079b3ef937dd5cc7244dd8b54282dc74.jpg) + +in their respective point cloud distributions. In the indoor conditions, authentic LiDAR typically encompasses a point distribution radius spanning $2 \sim 7$ meters, in sharp contrast to the $2 \sim 5$ meters typically covered by RGB-D cameras (as illustrated in Fig. 7). + +Comparison of the datasets. Due to the distinctions in acquisition technologies, LiDAR and RGB-D systems exhibit notable discrepancies in factors such as scanning precision, noise, color information, and performance in different lighting conditions. This type of data variance becomes particularly conspicuous in deep learning methodologies heavily reliant upon data. Fig. 7 illustrates the point and voxel distributions in existing indoor datasets compared to LiDAR-Net. Firstly, the three existing datasets predominantly contain points within a $2 \sim 5$ meters range from the scanner, while our LiDAR-Net provides a distinct distribution. It is worth to be explored that would the deep + +models trained on previous datasets over-fitted to the distribution of $2 \sim 5$ meters? Our LiDAR-Net, with its broader range of $2 \sim 7$ meters, provides an expanded scope for future research in this area. Secondly, since the points in the previous three datasets are generated by sampling on annotated 3D reconstructions, they mirror the voxel distribution. In contrast, the primary strength of LiDAR-Net lies in its annotated raw points, which are non-uniform, leading to distinct point and voxel distributions. This divergence introduces new challenges to the field. Our dataset adeptly encapsulates these genuine characteristics of real-world data, thereby establishing a robust foundation for various forthcoming applications in indoor perception technology. + +# 5.2. Impact of Imbalance Class Distribution + +Upon further investigation, we discern a more critical issue within indoor scene datasets: a conspicuous performance discrepancy resulting from imbalanced class distribution. We showcase the cumulative count of 3D points per semantic category in the top of Fig. 8, and the instance distribution is shown in the bottom. It is observable that the primary semantic categories, including ceilings, floors, walls, etc., make up over $80\%$ of the total points. In contrast, smaller yet crucial categories (e.g., monitors) constitute a mere $0.16\%$ of the total points, highlighting a stark imbalance in the distribution of semantic classes. This disproportion is inherent to indoor scenes, where walls, ceilings, and floors naturally cover large surface areas, while items like monitors are considerably smaller. + +Data imbalance poses a significant challenge in 3D scene understanding, an issue that is also evident in LiDAR-Net. As shown in Table 3, the skew in segment headers is especially marked in the semantic segmentation task, owing to the disparity in point cloud quantities at the point level. For instance, looking at the results of RandLA-Net in specific categories, the semantic segmentation accuracy for floors is around $93\%$ , while for stairs, it nearly drops to zero. Essentially, indoor scenes are dominated by a few categories such as ceilings and walls, whereas categories like stairs, though minor but critical, have an extremely sparse data distribution. When considering instance segmentation, the combination of instance-level and point-level imbalances exacerbates the problem, leading to a more severe dual-imbalance situation. Detailed instance segmentation results of each category are listed and discussed in the supplementary materials. This profound imbalance in distribution poses another significant challenge introduced by our dataset. + +# 6. Conclusion + +In this study, we present a comprehensive indoor point cloud dataset derived from authentic LiDAR scanning. This dataset encompasses three meticulously labeled scenes with a total of 3.6 billion points, covering $30,000m^2$ . Designed + +![](images/a8613cf2deecad64a43f81c22fd78748d47eedb2cd006ba326d078914cc3dd25.jpg) + +![](images/0bfe43797d27879c3765f7db9da55b35b62864bfe230114790ad4c5e7bb86eed.jpg) +Figure 8. Top: Point number distribution of semantic categories. Bottom: Instance number distribution. Unknown points do not have instance labels. + +for a variety of applications including semantic segmentation, instance segmentation, and object detection, our dataset serves as a versatile resource for related research tasks. Our comprehensive benchmark testing not only highlights persistent challenges but also emphasizes the distinct advantages of our dataset, particularly regarding the differences between annotated raw points from genuine LiDAR and points sampled from annotated 3D reconstructions. We have thoroughly examined issues such as the pronounced effects of imbalanced class distribution and the adaptability of models to unseen real-scanned scenes. Looking towards a future where autonomous indoor robots navigate diverse human-centric environments, we underscore the importance of real-time perception using authentic LiDAR-scanned data. The precision and high resolution of real-world LiDAR point cloud data are crucial for emerging cyber-physical systems like smart homes and digital twins. We believe our dataset and benchmarks will spur further progress in related areas of study. + +# Acknowledgments + +This work was supported by the National Natural Science Foundation of China (62032011), the Natural Science Foundation of Jiangsu Province (No. BK20211147), and the program B for Outstanding PhD candidate of Nanjing University. + +# References + +[1] Iro Armeni, Ozan Sener, Amir R Zamir, Helen Jiang, Ioannis Brilakis, Martin Fischer, and Silvio Savarese. 3d semantic parsing of large-scale indoor spaces. 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It encompasses three prevalent daily environments, including learning scenes, working scenes, and living scenes. LiDAR-Net is characterized by its nonuniform point distribution, e.g., scanning holes and scanning lines. Additionally, it meticulously records and annotates scanning anomalies, including reflection noise and ghost. These anomalies stem from specular reflections on glass or metal, as well as distortions due to moving persons. LiDAR-Net's realistic representation of non-uniform distribution and anomalies significantly enhances the training of deep learning models, leading to improved generalization in practical applications. We thoroughly evaluate the performance of state-of-the-art algorithms on LiDAR-Net and provide a detailed analysis of the results. Crucially, our research identifies several fundamental challenges in understanding indoor point clouds, contributing essential insights to future explorations in this field. Our dataset can be found online: http://lidar-net.njumeta.com." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 599, + 128, + 611 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 599, + 128, + 611 + ], + "spans": [ + { + "bbox": [ + 47, + 599, + 128, + 611 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 620, + 287, + 693 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 620, + 287, + 693 + ], + "spans": [ + { + "bbox": [ + 46, + 620, + 287, + 693 + ], + "type": "text", + "content": "Owing to its reliability and accuracy, Light Detection And Ranging (LiDAR) technology becomes increasingly popular, finding broad applications in autonomous vehicles for perception and localization [23, 26, 54] as well as expanding its applications in consumer electronics [3, 34, 37]. 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#Name#Year#Spatial size#Classes#Points# Raw points# Anomalies#Sensors
S3DIS [1]20176×103m213273MXXMatterport
ScanNet [11]20173.4×104m220242MXXRGB-D
ScanNet++ [53]20231.5×104m21000+446MXXTLS
LiDAR-Net (Ours)20233.0×104m2243619M✓✓MLS
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MLS is Mobile Laser Scanning system." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "type": "image", + "bbox": [ + 51, + 178, + 108, + 239 + ], + "blocks": [ + { + "bbox": [ + 51, + 178, + 108, + 239 + ], + "lines": [ + { + "bbox": [ + 51, + 178, + 108, + 239 + ], + "spans": [ + { + "bbox": [ + 51, + 178, + 108, + 239 + ], + "type": "image", + "image_path": "747abd6b5228f2c1f1fdb116d074b1a6ff0819ad73fe21dcc182eafb9e4dee6f.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 60, + 239, + 97, + 246 + ], + "lines": [ + { + "bbox": [ + 60, + 239, + 97, + 246 + ], + "spans": [ + { + "bbox": [ + 60, + 239, + 97, + 246 + ], + "type": "text", + "content": "Original points" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 255, + 287, + 288 + ], + "lines": [ + { + "bbox": [ + 46, + 255, + 287, + 288 + ], + "spans": [ + { + "bbox": [ + 46, + 255, + 287, + 288 + ], + "type": "text", + "content": "Figure 2. Illustration of reflection noise. These noise points usually suspend in the air. Purple highlights reflection noise in the semantic label figures" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 108, + 178, + 164, + 238 + ], + "blocks": [ + { + "bbox": [ + 108, + 178, + 164, + 238 + ], + "lines": [ + { + "bbox": [ + 108, + 178, + 164, + 238 + ], + "spans": [ + { + "bbox": [ + 108, + 178, + 164, + 238 + ], + "type": "image", + "image_path": "7b8d0110e3b8e1799ffb9e54dd547eeee1b79de3aefd76650165e2fc090f1001.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 115, + 239, + 156, + 246 + ], + "lines": [ + { + "bbox": [ + 115, + 239, + 156, + 246 + ], + "spans": [ + { + "bbox": [ + 115, + 239, + 156, + 246 + ], + "type": "text", + "content": "Semantic labels" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 165, + 178, + 223, + 238 + ], + "blocks": [ + { + "bbox": [ + 165, + 178, + 223, + 238 + ], + "lines": [ + { + "bbox": [ + 165, + 178, + 223, + 238 + ], + "spans": [ + { + "bbox": [ + 165, + 178, + 223, + 238 + ], + "type": "image", + "image_path": "1f65431e5e3566136ca242a60dfbdb5ad4be585218e60ef2bf50130734467f91.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 175, + 239, + 212, + 246 + ], + "lines": [ + { + "bbox": [ + 175, + 239, + 212, + 246 + ], + "spans": [ + { + "bbox": [ + 175, + 239, + 212, + 246 + ], + "type": "text", + "content": "Original points" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 223, + 178, + 284, + 238 + ], + "blocks": [ + { + "bbox": [ + 223, + 178, + 284, + 238 + ], + "lines": [ + { + "bbox": [ + 223, + 178, + 284, + 238 + ], + "spans": [ + { + "bbox": [ + 223, + 178, + 284, + 238 + ], + "type": "image", + "image_path": "010f8f032920a18597c5f2baf6140b4ab6aa031dd1948329e5dabe204cb2681f.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 234, + 239, + 274, + 246 + ], + "lines": [ + { + "bbox": [ + 234, + 239, + 274, + 246 + ], + "spans": [ + { + "bbox": [ + 234, + 239, + 274, + 246 + ], + "type": "text", + "content": "Semantic labels" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 301, + 287, + 397 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 301, + 287, + 397 + ], + "spans": [ + { + "bbox": [ + 46, + 301, + 287, + 397 + ], + "type": "text", + "content": "The 3D accuracy of these datasets is inferior to that of raw point clouds directly collected using laser scanners. Annotated data in existing datasets also lack characteristic distributions of real-scanned points, including scanning lines and scanning holes, as illustrated in Fig. 1. Consequently, deep models trained on these datasets tend to perform poorly when applied to actual, real-scanned point cloud data, significantly impeding their practical applicability." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 399, + 287, + 554 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 399, + 287, + 554 + ], + "spans": [ + { + "bbox": [ + 46, + 399, + 287, + 554 + ], + "type": "text", + "content": "In this paper, we contribute a new dataset, LiDAR-Net, to the academic community. Distinct from existing indoor scene datasets, LiDAR-Net is captured by real laser scanners and contains precise semantic and instance annotations for each raw point. LiDAR-Net encompasses three common daily scenes: learning, working, and living environments. It contains 3.6 billion 3D points, covering " + }, + { + "bbox": [ + 46, + 399, + 287, + 554 + ], + "type": "inline_equation", + "content": "30,000m^2" + }, + { + "bbox": [ + 46, + 399, + 287, + 554 + ], + "type": "text", + "content": " of indoor space. Using professional LiDAR scanning systems, the 3D point clouds the dataset ensures the high authenticity of its 3D point clouds. Detailed information about the data collection process is provided in Section 3. Across all scenes, each point is carefully annotated and classified into 24 semantic categories, such as floor, ceiling, and window." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 555, + 287, + 591 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 555, + 287, + 591 + ], + "spans": [ + { + "bbox": [ + 46, + 555, + 287, + 591 + ], + "type": "text", + "content": "Compared to previous indoor scene datasets primarily collected using RGB-D cameras or annotated on reconstructed meshes, LiDAR-Net offers several advantages:" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 47, + 594, + 287, + 713 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 47, + 594, + 287, + 641 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 594, + 287, + 641 + ], + "spans": [ + { + "bbox": [ + 47, + 594, + 287, + 641 + ], + "type": "text", + "content": "- Firstly, LiDAR-Net distinguishes itself by its authentically captured point cloud data, which leads to non-uniform point distributions, characterized by scanning holes and lines, as depicted in Fig. 1." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 47, + 642, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 642, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 47, + 642, + 287, + 689 + ], + "type": "text", + "content": "- Secondly, LiDAR-Net includes comprehensive annotations of scanning anomalies including reflection noises (purple points in Fig. 2) and ghosts caused by moving objects, particularly persons (red points in Fig. 1)." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 713 + ], + "type": "text", + "content": "- Thirdly, LiDAR-Net covers corridors and stairs connecting each room, creating seamless and complete spaces" + } + ] + } + ], + "index": 16 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 313, + 180, + 501, + 192 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 180, + 501, + 192 + ], + "spans": [ + { + "bbox": [ + 313, + 180, + 501, + 192 + ], + "type": "text", + "content": "crucial for integrated tasks across entire areas." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 194, + 545, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 194, + 545, + 277 + ], + "spans": [ + { + "bbox": [ + 304, + 194, + 545, + 277 + ], + "type": "text", + "content": "Table 1 presents a comparative analysis with other popular indoor scene datasets. While many outdoor point cloud datasets [43, 44] contain real-scanned data, the significant disparity in scene characteristics presents challenges for adapting outdoor datasets to indoor tasks. Moreover, outdoor point clouds generally show a higher level of sparsity and incompleteness compared to LiDAR-Net." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 279, + 546, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 279, + 546, + 483 + ], + "spans": [ + { + "bbox": [ + 304, + 279, + 546, + 483 + ], + "type": "text", + "content": "Using LiDAR-Net, we recognize several challenges and conduct studies on them, as outlined in Section 5. We first investigate the process of annotating a large indoor point cloud dataset. Then, we discuss the significance of real-scanned point cloud data for semantic learning, emphasizing the advantages of raw LiDAR-based point clouds over those from depth cameras or from reconstructed meshes. Additionally, we investigate the imbalance of semantic classes in indoor environments. While this paper does not provide exhaustive solutions, it introduces these challenges for further exploration by the research community. Our discussion on the complexities of multi-task learning in indoor 3D point clouds aims to spur developments in fields such as intelligent home systems, digital twins, indoor robotic navigation, asset management in extensive indoor infrastructures, and smart construction sites, etc. To summarize, our work makes the following contributions:" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 483, + 545, + 627 + ], + "type": "list", + "angle": 0, + "index": 24, + "blocks": [ + { + "bbox": [ + 306, + 483, + 545, + 531 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 483, + 545, + 531 + ], + "spans": [ + { + "bbox": [ + 306, + 483, + 545, + 531 + ], + "type": "text", + "content": "- We introduce LiDAR-Net, a comprehensive large-scale 3D point cloud dataset. This dataset is equipped with point-level semantic and instance annotations, making it ideal for multi-task training and testing." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 306, + 532, + 545, + 591 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 532, + 545, + 591 + ], + "spans": [ + { + "bbox": [ + 306, + 532, + 545, + 591 + ], + "type": "text", + "content": "- LiDAR-Net is characterized by its distinct features such as non-uniform point distributions, scanning anomalies, and seamless spatial coverage. These attributes notably enhance the generalization capabilities of trained deep models for real-world applications." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 592, + 545, + 627 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 592, + 545, + 627 + ], + "spans": [ + { + "bbox": [ + 306, + 592, + 545, + 627 + ], + "type": "text", + "content": "- We assess the efficacy of current algorithms within real-scanned point cloud environments and identify key challenges in this field." + } + ] + } + ], + "index": 23 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 637, + 392, + 650 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 637, + 392, + 650 + ], + "spans": [ + { + "bbox": [ + 306, + 637, + 392, + 650 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 25 + }, + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 713 + ], + "type": "text", + "content": "Booming deep learning-based 3D scene understanding methods desire various 3D scene datasets. Guo et al. [15] give a comprehensive survey on this topic. We briefly summary 3D scene datasets and 3D point cloud scene understanding methods below." + } + ] + } + ], + "index": 26 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "21990" + } + ] + } + ], + "index": 27 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 155, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 155, + 83 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 155, + 83 + ], + "type": "text", + "content": "2.1. 3D Scene Datasets" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 90, + 287, + 125 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 90, + 287, + 125 + ], + "spans": [ + { + "bbox": [ + 47, + 90, + 287, + 125 + ], + "type": "text", + "content": "According to the application scenario, existing 3D datasets can be divided into three categories: (i) 3D objects, (ii) indoor scenes, (iii) outdoor scenes." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 126, + 287, + 210 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 126, + 287, + 210 + ], + "spans": [ + { + "bbox": [ + 46, + 126, + 287, + 210 + ], + "type": "text", + "content": "3D objects. ModelNet [50] and ShapeNet [9] are both 3D synthetic mesh datasets for shape classification. Mo et al. [32] propose PartNet containing hierarchical labels for part segmentation. ABC dataset [22] contains 1M CAD models with structure information. Deitke et al. [12] propose Objaverse-XL, which is a universe of " + }, + { + "bbox": [ + 46, + 126, + 287, + 210 + ], + "type": "inline_equation", + "content": "10\\mathrm{M} + 3\\mathrm{D}" + }, + { + "bbox": [ + 46, + 126, + 287, + 210 + ], + "type": "text", + "content": " objects." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 210, + 288, + 582 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 210, + 288, + 582 + ], + "spans": [ + { + "bbox": [ + 46, + 210, + 288, + 582 + ], + "type": "text", + "content": "Indoor scenes. Early indoor 3D datasets are acquired by using commodity short-range depth scanners such as NYUv2 [41] and SUN RGB-D [42], comprising short RGB-D sequences with limited resolution. While SceneNN [19] and PiGraphs [39] provide reconstructed and labeled scenes, their scene counts are restricted. Armeni et al. [2] propose S3DIS, which is a widely used benchmark in many tasks, by collecting RGB-D images and reconstructing 3D textured mesh model for each scene. The colored 3D point clouds in S3DIS are densely and uniformly sampled from the textured meshes. ScanNet [11] also provide 3D reconstructions captured by an iPad equipped with a structure sensor, accompanied by annotations. Matterport3D [8] generates low-resolution meshes from panoramic RGB-D images. ARKitScenes [5] offers high-resolution ground truth geometry by using laser scans, but it only provides bounding box annotations. Novel view synthesis methods, such as neural radiance fields (NeRFs) [31], development rapidly in recent years [4, 28]. Yeshwanth et al. [53] propose ScanNet++, containing 460 scenes with DSLR images and iPhone RGB-D frames. They obtain each scene by using the Faro Focus Premium laser scanner and implementing Poisson reconstruction [20, 21] to obtain meshes. Then the meshes are annotated. Comparing to S3DIS [2], ScanNet [11], and ScanNet++ [53], LiDAR-Net provides annotated raw points, which can be directly employed for training deep models specializing in 3D point cloud scene understanding. LiDAR-Net meticulously preserves the characteristics of raw point clouds captured by sensors, encompassing non-uniform distributions like scanning holes and lines, as well as anomalies like reflection noises and ghosts." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 287, + 714 + ], + "type": "text", + "content": "Outdoor scenes. These datasets are usually captured by static Terrestrial Laser Scanners (TLS), Mobile Laser Scanners (MLS), and Airborne Laser Scanners (ALS). The representative datasets in this domain comprise roadway-level datasets, such as KITTI [14], Paris-rue-Madame [40], IQmulus [46], Semantic3D [16], Paris-Lille-3D [38], Ar-goverse [10], SemanticKITTI [6], SemanticPOSS [33], Toronto-3D [44], nuScenes [7], and Waymo dataset [43]. Additionally, urban-level aerial 3D point cloud datasets include DublinCity [57], DALES [47], LASDU [52], Campus3D [24], and SensatUrban [18]." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 72, + 531, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 531, + 85 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 531, + 85 + ], + "type": "text", + "content": "2.2. Deep Learning on 3D Scene Understanding" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 91, + 545, + 321 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 545, + 321 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 545, + 321 + ], + "type": "text", + "content": "Pioneered by PointNet [35], neural networks are used to process the unordered point cloud data [25, 36, 49, 56], leading to numerous innovative applications [13, 27, 30, 55]. We choose three representative tasks to evaluate LiDAR-Net dataset. 1) Semantic segmentation. Thomas et al. [45] propose Kernel Point Convolution (KPCConv) operators for 3D point clouds using a set of learnable kernel points. Hu et al. [17] propose RandLA-Net utilizing random point sampling to achieve remarkably high efficiency. 2) Instance segmentation. ASIS [48] uses a feature fusion structure to enhance both semantic and instance branches by leveraging information from each other. Yang et al. [51] propose a single-stage and anchor-free network called 3D-BoNet for instance segmentation. 3) Object detection. VoteNet [37] implements a unique voting scheme among points to infer object bounding box centers. GroupFree3D [29] leverages a sophisticated attention mechanism that obviates the need for point candidate grouping, enabling direct inference of object instances." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 305, + 336, + 504, + 350 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 336, + 504, + 350 + ], + "spans": [ + { + "bbox": [ + 305, + 336, + 504, + 350 + ], + "type": "text", + "content": "3. Dataset Acquisition and Annotation" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 306, + 358, + 441, + 371 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 358, + 441, + 371 + ], + "spans": [ + { + "bbox": [ + 306, + 358, + 441, + 371 + ], + "type": "text", + "content": "3.1. Point Cloud Acquisition" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 378, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 378, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 378, + 545, + 713 + ], + "type": "text", + "content": "Acknowledging the marked advantages of LiDAR technology in securing authentic three-dimensional data over traditional RGBD data acquisition methods, our research utilizes Leica BLK2GO, a device combining dual-axis LiDAR technology. The BLK2GO is equipped not only with a commercial dual-axis LiDAR and a 12-megapixel detail camera but also with a 4.8-megapixel, 3-shot panoramic camera. This integration enables stable collection of point cloud data with an accuracy of " + }, + { + "bbox": [ + 304, + 378, + 545, + 713 + ], + "type": "inline_equation", + "content": "\\pm 3\\text{mm} @10m" + }, + { + "bbox": [ + 304, + 378, + 545, + 713 + ], + "type": "text", + "content": " and a capture speed of 420,000 points/second within a " + }, + { + "bbox": [ + 304, + 378, + 545, + 713 + ], + "type": "inline_equation", + "content": "0.5\\sim 25m" + }, + { + "bbox": [ + 304, + 378, + 545, + 713 + ], + "type": "text", + "content": " range, while simultaneously obtaining high-resolution color images. Significantly, the BLK2GO implements GrandSLAM dual-positioning technology, seamlessly blending laser SLAM and visual SLAM. This approach involves using point cloud from LiDAR and inertial navigation from IMU for one aspect of positioning, and determining the current position and orientation by analyzing disparities between consecutive frames captured by the panoramic camera. For the LiDAR-Net, all data acquisition routes are meticulously pre-planned by professional surveyors, ensuring comprehensive and consistent coverage of the targeted area. To mirror the various interferences typical in real-world point cloud acquisition scenarios, all data are manually collected by human surveyors. Due to the device's battery capacity constraints, each data collection session is strategically limited to approximately one hour. To encompass the entire area, data from multiple individual sessions are manually integrated." + } + ] + } + ], + "index": 9 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "21991" + } + ] + } + ], + "index": 10 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 62, + 64, + 532, + 476 + ], + "blocks": [ + { + "bbox": [ + 62, + 64, + 532, + 476 + ], + "lines": [ + { + "bbox": [ + 62, + 64, + 532, + 476 + ], + "spans": [ + { + "bbox": [ + 62, + 64, + 532, + 476 + ], + "type": "image", + "image_path": "6de1bc955587ab42b9fd077a5ea14f4c042a938945441650f434bc02625cd3f7.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 62, + 483, + 530, + 495 + ], + "lines": [ + { + "bbox": [ + 62, + 483, + 530, + 495 + ], + "spans": [ + { + "bbox": [ + 62, + 483, + 530, + 495 + ], + "type": "text", + "content": "Figure 3. Semantic and instance labels. LiDAR-Net provides point-level annotations directly associated with each raw data point." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 505, + 181, + 516 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 505, + 181, + 516 + ], + "spans": [ + { + "bbox": [ + 47, + 505, + 181, + 516 + ], + "type": "text", + "content": "3.2. Point Cloud Annotation" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 534, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 534, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 534, + 289, + 713 + ], + "type": "text", + "content": "In the dataset, we address three sub-tasks: semantic segmentation, instance segmentation, and object detection. The categorization criteria are based on two key principles: 1) Each category should possess a distinct and unambiguous semantic meaning, aligning with both academic research and practical business applications. This alignment facilitates advanced visual tasks such as 3D reconstruction, point cloud completion, and applications in virtual reality, building upon baseline tasks. 2) The categories should exhibit significant geometric or appearance differences, ensuring clear distinction across different groups. We provide a Point Cloud AnnoTation system (PCAT system) to annotate all point clouds in the LiDAR-Net with both semantic and instance labels. Subsequently, object detection labels, in the form of bounding boxes, are derived from these instances" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 505, + 545, + 601 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 505, + 545, + 601 + ], + "spans": [ + { + "bbox": [ + 304, + 505, + 545, + 601 + ], + "type": "text", + "content": "labels. The PCAT system is set to be released, allowing users to easily modify or subdivide labels according to their specific requirements. Each label in LiDAR-Net is rigorously manually annotated and verified, ensuring the consistency and high quality of the semantic categories. The entire dataset labeling consumes approximately 550 working hours. Illustrative examples of our annotations are displayed in Fig. 3." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 605, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 546, + 713 + ], + "type": "text", + "content": "We annotate various indoor components, including floors, stairs, and ceilings, as well as a wide range of furniture and fixtures such as tables, chairs, and sofas. Additionally, we carefully annotate anomalies captured by LiDAR, encompassing reflection noises and ghosts, as they introduce inaccuracies into the data and present challenges in data analysis. Specular reflections from smooth surfaces like glass or metal can disrupt LiDAR systems, resulting in reflection noise points. LiDAR systems would capture" + } + ] + } + ], + "index": 5 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 757 + ], + "type": "text", + "content": "21992" + } + ] + } + ], + "index": 6 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 145 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 145 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 145 + ], + "type": "text", + "content": "incomplete and repetitive ghosts when persons or other objects move in front of the scanner. These anomalies, commonly encountered in real-world applications like robotics and consumer electronics, are accurately recorded in our LiDAR-Net dataset to aid in training deep learning models capable of handling these challenges." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 154, + 125, + 166 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 154, + 125, + 166 + ], + "spans": [ + { + "bbox": [ + 47, + 154, + 125, + 166 + ], + "type": "text", + "content": "3.3. Benchmark" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 173, + 287, + 281 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 173, + 287, + 281 + ], + "spans": [ + { + "bbox": [ + 46, + 173, + 287, + 281 + ], + "type": "text", + "content": "LiDAR-Net contains classrooms, study lounges, seminar rooms, auditoriums for learning scenes, offices, meeting rooms, lounges for working scenes, and living rooms, bedrooms, dining rooms, washrooms for living scenes. Fig. 4 shows the diversity of scenes. Furthermore, We record world coordinates of rooms to form connecting areas, including 2, 7, and 5 seamless areas of learning, working and living scenes, which facilitate navigation and understanding large-scale indoor scenes." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 281, + 288, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 281, + 288, + 437 + ], + "spans": [ + { + "bbox": [ + 46, + 281, + 288, + 437 + ], + "type": "text", + "content": "For the facilitation of GPU-accelerated batch training and testing, we divide the point clouds from various scenes into individual rooms based on their primary structural features, particularly the wall orientations. It is important to note that we provide coordinate correspondences for each room to facilitate tasks working in a whole area. Point clouds from learning scenes are divided into 216 rooms, including 173 rooms for training and 43 for testing. Similarly, we split the working scenes into 206 rooms, including 169 and 37 for training and testing, each room covering approximately " + }, + { + "bbox": [ + 46, + 281, + 288, + 437 + ], + "type": "inline_equation", + "content": "100m^2" + }, + { + "bbox": [ + 46, + 281, + 288, + 437 + ], + "type": "text", + "content": ". In living scenes, of the 43 rooms analyzed, 33 are used for training and 10 for testing. The distribution of room areas is illustrated in Fig. 5." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 437, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 437, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 437, + 288, + 715 + ], + "type": "text", + "content": "LiDAR-Net contains 24 semantic categories, including houseplant (low potted plants), tree (tall trees typically positioned on the floor), person, floor, stair, ceiling, pipe, wall, pillar, window, curtain, door, table, chair, sofa, blackboard (common in learning or working scenes), monitor, bookshelf, wardrobe, bed, light, tabletop others (miscellaneous small objects on tables), reflection noise, ghost (resulting from moving entities, such as people). Additionally, an 'unknown' class exists outside these 24 categories, encompassing points not classified into any specific category. Each point within the 24 semantic categories is assigned instance labels. 17 categories are used for object detection. Floors, ceilings, pipes, walls, pillars, reflection noises and ghosts, which lack definite boundaries, are excluded from object detection task, following [29, 37]. It is important to note that instance labels are provided for these excluded categories, facilitating use cases like smart construction sites and vectorized indoor modeling. The LiDAR-Net dataset will be publicly released, with the goal of establishing benchmarks in indoor point cloud semantic segmentation, instance segmentation, and object detection, which will be evaluated through an online public platform. Following ScanNet [11] and ScanNet++ [53], labels of the test" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 72, + 400, + 83 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 400, + 83 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 400, + 83 + ], + "type": "text", + "content": "set will remain hidden." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 306, + 95, + 387, + 109 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 95, + 387, + 109 + ], + "spans": [ + { + "bbox": [ + 306, + 95, + 387, + 109 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 306, + 115, + 444, + 128 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 115, + 444, + 128 + ], + "spans": [ + { + "bbox": [ + 306, + 115, + 444, + 128 + ], + "type": "text", + "content": "4.1. Representative Baselines" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 133, + 545, + 254 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 133, + 545, + 254 + ], + "spans": [ + { + "bbox": [ + 304, + 133, + 545, + 254 + ], + "type": "text", + "content": "In Section 2.2, we explore the three main tasks in learning-based 3D point cloud scene understanding. To comprehensively evaluate our LiDAR-Net dataset, we carefully select eight emblematic methods, applying them as benchmarks across different tasks to conduct an extensive benchmark test on our dataset. Precisely, we utilize PointNet [35], PointNet++ [36], KPCov [45], and RandLA-Net [17], for point cloud semantic segmentation, ASIS [48] and 3D-BoNet [51] for instance segmentation, VoteNet [37] and GroupFree3D [29] for object detection." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 262, + 418, + 273 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 262, + 418, + 273 + ], + "spans": [ + { + "bbox": [ + 306, + 262, + 418, + 273 + ], + "type": "text", + "content": "4.2. Evaluation Metrics" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 280, + 545, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 280, + 545, + 423 + ], + "spans": [ + { + "bbox": [ + 304, + 280, + 545, + 423 + ], + "type": "text", + "content": "Consistent with prevailing benchmarks, our evaluation framework is designed for a thorough assessment across various segmentation and detection tasks. For semantic segmentation, we focus primarily on mean Intersection-over-Union (mIoU) as the key evaluation metric, following [17, 45]. In instance segmentation, our analysis emphasizes mean precision (mPre) and mean recall rate (mRec) to measure algorithmic performance, following [48, 51]. Moreover, within the domain of object detection, we concentrate on the mean of per-category object detection average precision with 3D IoU threshold 0.25 and 0.5, denoted as mAP@0.25 and mAP@0.5, following [29, 37]." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 431, + 420, + 443 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 431, + 420, + 443 + ], + "spans": [ + { + "bbox": [ + 306, + 431, + 420, + 443 + ], + "type": "text", + "content": "4.3. Benchmark Results" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 449, + 545, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 449, + 545, + 689 + ], + "spans": [ + { + "bbox": [ + 304, + 449, + 545, + 689 + ], + "type": "text", + "content": "To ensure a fair comparison, we rigorously follow the experimental settings outlined in the original publications of each benchmark algorithm. Table 2 presents the quantitative results across three tasks. The overall performances in segmentation and detection has not reached a satisfactory level. For instance, examining RandLA-Net [17] and KPCov [45], which show the best performance in semantic segmentation, Table 3 details the IoU for each semantic category of the two methods. Table 3 reveals that certain key categories, such as window and bookshelf, were poorly segmented. RandLA-Net achieves " + }, + { + "bbox": [ + 304, + 449, + 545, + 689 + ], + "type": "inline_equation", + "content": "42.02\\%" + }, + { + "bbox": [ + 304, + 449, + 545, + 689 + ], + "type": "text", + "content": " for the IoU of tree, which is higher than " + }, + { + "bbox": [ + 304, + 449, + 545, + 689 + ], + "type": "inline_equation", + "content": "7.94\\%" + }, + { + "bbox": [ + 304, + 449, + 545, + 689 + ], + "type": "text", + "content": " of KPCov, however for the IoU of sofa, performance of KPCov is much better than that of RandLA-Net. There is a significant variation in performance across different algorithms within these challenging categories, and no single algorithm consistently outperforms the other. Comprehensive quantitative results of other semantic segmentation, instance segmentation and object detection methods for each category are given in the supplementary materials." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "A key advantage of our LiDAR-Net is that its annotated raw points closely mirror the distribution of real-scanned" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "21993" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 60, + 64, + 138, + 111 + ], + "blocks": [ + { + "bbox": [ + 60, + 64, + 138, + 111 + ], + "lines": [ + { + "bbox": [ + 60, + 64, + 138, + 111 + ], + "spans": [ + { + "bbox": [ + 60, + 64, + 138, + 111 + ], + "type": "image", + "image_path": "c04539faf3784505505d106906593d59c369211c7e48c91c5650677a15df8080.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 139, + 64, + 217, + 111 + ], + "blocks": [ + { + "bbox": [ + 139, + 64, + 217, + 111 + ], + "lines": [ + { + "bbox": [ + 139, + 64, + 217, + 111 + ], + "spans": [ + { + "bbox": [ + 139, + 64, + 217, + 111 + ], + "type": "image", + "image_path": "07bce97cf549f40238f9e27c72a85f305cf645ca7f28cabd5ec1970e5e72a8c4.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 217, + 64, + 296, + 111 + ], + "blocks": [ + { + "bbox": [ + 217, + 64, + 296, + 111 + ], + "lines": [ + { + "bbox": [ + 217, + 64, + 296, + 111 + ], + "spans": [ + { + "bbox": [ + 217, + 64, + 296, + 111 + ], + "type": "image", + "image_path": "da6baf104245fee9370493393ed216f6af5595453b8c927d54116af53e3d5dc1.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 296, + 64, + 376, + 111 + ], + "blocks": [ + { + "bbox": [ + 296, + 64, + 376, + 111 + ], + "lines": [ + { + "bbox": [ + 296, + 64, + 376, + 111 + ], + "spans": [ + { + "bbox": [ + 296, + 64, + 376, + 111 + ], + "type": "image", + "image_path": "f4a86c450df67f4092d6cb05ac0cc78407990c207602e29e51770fd51dd8def2.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 376, + 64, + 455, + 111 + ], + "blocks": [ + { + "bbox": [ + 376, + 64, + 455, + 111 + ], + "lines": [ + { + "bbox": [ + 376, + 64, + 455, + 111 + ], + "spans": [ + { + "bbox": [ + 376, + 64, + 455, + 111 + ], + "type": "image", + "image_path": "98d06b248cc8d84624701d18b4e6c3f483490bbadcfdbd61d89da012ad700849.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 455, + 64, + 534, + 111 + ], + "blocks": [ + { + "bbox": [ + 455, + 64, + 534, + 111 + ], + "lines": [ + { + "bbox": [ + 455, + 64, + 534, + 111 + ], + "spans": [ + { + "bbox": [ + 455, + 64, + 534, + 111 + ], + "type": "image", + "image_path": "828fcd839fcebaf94ea37a189f757f4c243568167fc5989be992af7da93951c1.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 59, + 111, + 193, + 192 + ], + "blocks": [ + { + "bbox": [ + 59, + 111, + 193, + 192 + ], + "lines": [ + { + "bbox": [ + 59, + 111, + 193, + 192 + ], + "spans": [ + { + "bbox": [ + 59, + 111, + 193, + 192 + ], + "type": "image", + "image_path": "93e5858a8d98ab8fb39d18631d673667560c2bf0da2595a51d6bd0f3b0b6f15b.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 63, + 200, + 528, + 212 + ], + "lines": [ + { + "bbox": [ + 63, + 200, + 528, + 212 + ], + "spans": [ + { + "bbox": [ + 63, + 200, + 528, + 212 + ], + "type": "text", + "content": "Figure 4. 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The bottom row displays three seamless areas." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 194, + 111, + 412, + 192 + ], + "blocks": [ + { + "bbox": [ + 194, + 111, + 412, + 192 + ], + "lines": [ + { + "bbox": [ + 194, + 111, + 412, + 192 + ], + "spans": [ + { + "bbox": [ + 194, + 111, + 412, + 192 + ], + "type": "image", + "image_path": "c80023903968efa8e8817da1274ba503cb942f9d76577ac1204ebb097a2dd527.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 413, + 111, + 534, + 192 + ], + "blocks": [ + { + "bbox": [ + 413, + 111, + 534, + 192 + ], + "lines": [ + { + "bbox": [ + 413, + 111, + 534, + 192 + ], + "spans": [ + { + "bbox": [ + 413, + 111, + 534, + 192 + ], + "type": "image", + "image_path": "2c60dc052dfe80d92c448483f52fd2eb0ccba55522427dd868e211b15c36769a.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + } + ], + "index": 8 + }, + { + "type": "table", + "bbox": [ + 67, + 216, + 529, + 274 + ], + "blocks": [ + { + "bbox": [ + 67, + 216, + 529, + 274 + ], + "lines": [ + { + "bbox": [ + 67, + 216, + 529, + 274 + ], + "spans": [ + { + "bbox": [ + 67, + 216, + 529, + 274 + ], + "type": "table", + "html": "
Semantic segmentationmIoUInstance segmentationmPremRecObject detectionmAP@0.25mAP@0.5
PointNet [35]16.27ASIS [48]37.3225.08VoteNet [37]44.8316.71
PointNet++ [36]28.81
KPConv [45]44.293D-BoNet [51]39.8224.63GroupFree3D [29]46.8018.86
RandLA-Net [17]32.60
", + "image_path": "fbdd9f046c084d486ac8787cdb48ba83393fe0ef105fa01178f2edbd1e955c97.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "type": "table", + "bbox": [ + 50, + 293, + 547, + 392 + ], + "blocks": [ + { + "bbox": [ + 115, + 277, + 476, + 288 + ], + "lines": [ + { + "bbox": [ + 115, + 277, + 476, + 288 + ], + "spans": [ + { + "bbox": [ + 115, + 277, + 476, + 288 + ], + "type": "text", + "content": "Table 2. Statistics of selected emblematic methods on LiDAR-Net. The percent sign (%) is omitted." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 293, + 547, + 392 + ], + "lines": [ + { + "bbox": [ + 50, + 293, + 547, + 392 + ], + "spans": [ + { + "bbox": [ + 50, + 293, + 547, + 392 + ], + "type": "table", + "html": "
MethodsHouseplantTreePersonFloorStairCeilingPipeWallPillar
KPConv [45]26.987.9445.2285.4325.7086.5138.4974.925.68
RandLA-Net [17]3.5642.0240.7593.170.4286.1219.4373.810.91
WindowCurtainDoorTableChairSofaBlackboardMonitorBookshelf
KPConv [45]9.4822.2134.4479.8875.4558.0274.7955.2326.76
RandLA-Net [17]18.0041.3351.2261.6942.280.0074.776.067.73
WardrobeBedLightTabletop othersReflection noiseGhostUnknownmIoU
KPConv [45]34.0539.5165.2140.5819.2256.8218.8044.29
RandLA-Net [17]0.000.0054.1314.910.0067.5315.0932.60
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DatasetsSemantic segmentationInstance segmentationObject detection
mIoUmPremRecmAP@0.25mAP@0.5
S3DIS [2]35.5815.727.847.930.28
ScanNet [11]33.1815.8814.4420.911.21
ScanNet++ [53]23.6026.484.6813.311.67
LiDAR-Net39.7532.9220.3932.969.22
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The percent sign " + }, + { + "bbox": [ + 46, + 633, + 287, + 666 + ], + "type": "inline_equation", + "content": "(\\%)" + }, + { + "bbox": [ + 46, + 633, + 287, + 666 + ], + "type": "text", + "content": " is omitted." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 715 + ], + "type": "text", + "content": "points. To evaluate it, we train the benchmark methods on existing popular datasets, including S3DIS [2], ScanNet [11], and ScanNet++ [53]. Then, the deep models" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 415, + 545, + 559 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 415, + 545, + 559 + ], + "spans": [ + { + "bbox": [ + 304, + 415, + 545, + 559 + ], + "type": "text", + "content": "are tested on 5 real-scanned rooms, captured using a Leica BLK2GO scanner in locations not included in LiDAR-Net. Due to the categories of the four datasets are different, we test the models on the communal categories. Fig. 6 and Table 4 show the qualitative and quantitative comparisons, selecting RandLA-Net [17] for semantic segmentation, ASIS [48] for instance segmentation, and GroupFree3D [29] for object detection. Detailed statistics of other methods and each category are listed in the supplementary materials. Benefited from the realistic distribution of raw points in LiDAR-Net, deep models trained on it demonstrate superior performances across all three tasks." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 572, + 377, + 586 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 572, + 377, + 586 + ], + "spans": [ + { + "bbox": [ + 306, + 572, + 377, + 586 + ], + "type": "text", + "content": "5. Challenges" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 713 + ], + "type": "text", + "content": "This section focuses on the key challenges presented by our dataset, which inherently stem from the authentic LiDAR collection process. Then, we provide an in-depth analysis of these challenges with a potential to drive advancements in the current field. Concurrently, we delve into tentative discussions of viable solutions. It is crucial to clarify that the aim of this paper is not to introduce a new method for addressing these challenges. Rather, our goal is to identify data biases potentially caused by existing datasets, to shed light on unresolved issues, and to provide analysis and in-" + } + ] + } + ], + "index": 21 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 749, + 317, + 757 + ], + "type": "text", + "content": "21994" + } + ] + } + ], + "index": 22 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 69, + 547, + 248 + ], + "blocks": [ + { + "bbox": [ + 50, + 69, + 547, + 248 + ], + "lines": [ + { + "bbox": [ + 50, + 69, + 547, + 248 + ], + "spans": [ + { + "bbox": [ + 50, + 69, + 547, + 248 + ], + "type": "image", + "image_path": "1656dd47ce4f9abea350977ace063d5f5e597f01b551bc2348db28762e5ca38a.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 253, + 547, + 288 + ], + "lines": [ + { + "bbox": [ + 46, + 253, + 547, + 288 + ], + "spans": [ + { + "bbox": [ + 46, + 253, + 547, + 288 + ], + "type": "text", + "content": "Figure 6. Qualitative comparisons of deep models trained on different datasets and tested on real-scanned data. Each row displays one task. Deep models are tested on the communal categories. It's important to note that ScanNet++ does not include instance labels for floors, walls, and ceilings, and therefore, these elements are excluded from the instance segmentation experiment." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 293, + 288, + 319 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 293, + 288, + 319 + ], + "spans": [ + { + "bbox": [ + 46, + 293, + 288, + 319 + ], + "type": "text", + "content": "sights. Ultimately, we seek to catalyze advancements in the understanding of indoor scene point clouds." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 327, + 220, + 339 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 327, + 220, + 339 + ], + "spans": [ + { + "bbox": [ + 47, + 327, + 220, + 339 + ], + "type": "text", + "content": "5.1. Differences in Data Distribution" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 347, + 290, + 564 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 347, + 290, + 564 + ], + "spans": [ + { + "bbox": [ + 46, + 347, + 290, + 564 + ], + "type": "text", + "content": "LiDAR scanning. In previous discussions, we introduced a point cloud dataset derived from authentic LiDAR scanning, which significantly differs from existing indoor point cloud datasets. While LiDAR and RGB-D scanning produce point clouds with some similar attributes, notable differences exist in their characteristics. The non-uniform distribution of real-scanned points, characterized by scanning holes and lines, is a result of the laser scanning process. LiDAR measures distance by emitting laser pulses and measuring the time they take to return. The laser beam moves directionally, creating linear point captures. Gaps in these lines lead to scanning holes. Furthermore, the distance from the scanner affects point distribution. Points closer to the scanner are denser, while those at greater distances tend to be sparser, a phenomenon owing to the dispersion and weakening of laser pulse energy. LiDAR's capability to operate over long distances inherently leads to a noticeable decrease in point density at farther ranges." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 288, + 715 + ], + "type": "text", + "content": "RGB-D cameras. Conversely, RGB-D cameras, which utilize structured light or Time of Flight (ToF) technology, determine distance using a distinct methodology. Points closer to the sensor tend to be denser due to variations in observational angles, while farther points show relative sparsity owing to resolution limits. RGB-D cameras are capable of providing relatively dense data within a specific range, but this density noticeably decreases or even disappears beyond their operational limit. Therefore, although both authentic LiDAR and RGB-D cameras exhibit the challenge of variable point density, there is a fundamental difference" + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 312, + 296, + 426, + 374 + ], + "blocks": [ + { + "bbox": [ + 312, + 296, + 426, + 374 + ], + "lines": [ + { + "bbox": [ + 312, + 296, + 426, + 374 + ], + "spans": [ + { + "bbox": [ + 312, + 296, + 426, + 374 + ], + "type": "image", + "image_path": "c689e18cad17b9f42c9ffbad7e9d3a14087ce793fc7df817e728f7160cf369ff.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 427, + 297, + 541, + 374 + ], + "blocks": [ + { + "bbox": [ + 427, + 297, + 541, + 374 + ], + "lines": [ + { + "bbox": [ + 427, + 297, + 541, + 374 + ], + "spans": [ + { + "bbox": [ + 427, + 297, + 541, + 374 + ], + "type": "image", + "image_path": "3e80d594acaa493c64a2cebbdd6d2811d6936e53126ce28c63c19181b984fdc7.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 312, + 376, + 426, + 454 + ], + "blocks": [ + { + "bbox": [ + 312, + 376, + 426, + 454 + ], + "lines": [ + { + "bbox": [ + 312, + 376, + 426, + 454 + ], + "spans": [ + { + "bbox": [ + 312, + 376, + 426, + 454 + ], + "type": "image", + "image_path": "d1cc222a2db47a40035750a5a09df22531f503dc2a3f2d87542278f85353db6b.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 463, + 545, + 485 + ], + "lines": [ + { + "bbox": [ + 305, + 463, + 545, + 485 + ], + "spans": [ + { + "bbox": [ + 305, + 463, + 545, + 485 + ], + "type": "text", + "content": "Figure 7. Point and voxel distributions in S3DIS, ScanNet, ScanNet++ and LiDAR-Net." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 427, + 376, + 541, + 454 + ], + "blocks": [ + { + "bbox": [ + 427, + 376, + 541, + 454 + ], + "lines": [ + { + "bbox": [ + 427, + 376, + 541, + 454 + ], + "spans": [ + { + "bbox": [ + 427, + 376, + 541, + 454 + ], + "type": "image", + "image_path": "33f4a845b736e5785d85c0d7421e5990079b3ef937dd5cc7244dd8b54282dc74.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 489, + 547, + 550 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 489, + 547, + 550 + ], + "spans": [ + { + "bbox": [ + 304, + 489, + 547, + 550 + ], + "type": "text", + "content": "in their respective point cloud distributions. In the indoor conditions, authentic LiDAR typically encompasses a point distribution radius spanning " + }, + { + "bbox": [ + 304, + 489, + 547, + 550 + ], + "type": "inline_equation", + "content": "2 \\sim 7" + }, + { + "bbox": [ + 304, + 489, + 547, + 550 + ], + "type": "text", + "content": " meters, in sharp contrast to the " + }, + { + "bbox": [ + 304, + 489, + 547, + 550 + ], + "type": "inline_equation", + "content": "2 \\sim 5" + }, + { + "bbox": [ + 304, + 489, + 547, + 550 + ], + "type": "text", + "content": " meters typically covered by RGB-D cameras (as illustrated in Fig. 7)." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 570, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 548, + 715 + ], + "type": "text", + "content": "Comparison of the datasets. Due to the distinctions in acquisition technologies, LiDAR and RGB-D systems exhibit notable discrepancies in factors such as scanning precision, noise, color information, and performance in different lighting conditions. This type of data variance becomes particularly conspicuous in deep learning methodologies heavily reliant upon data. Fig. 7 illustrates the point and voxel distributions in existing indoor datasets compared to LiDAR-Net. Firstly, the three existing datasets predominantly contain points within a " + }, + { + "bbox": [ + 304, + 570, + 548, + 715 + ], + "type": "inline_equation", + "content": "2 \\sim 5" + }, + { + "bbox": [ + 304, + 570, + 548, + 715 + ], + "type": "text", + "content": " meters range from the scanner, while our LiDAR-Net provides a distinct distribution. It is worth to be explored that would the deep" + } + ] + } + ], + "index": 12 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "21995" + } + ] + } + ], + "index": 13 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": "models trained on previous datasets over-fitted to the distribution of " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "2 \\sim 5" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " meters? Our LiDAR-Net, with its broader range of " + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "inline_equation", + "content": "2 \\sim 7" + }, + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": " meters, provides an expanded scope for future research in this area. Secondly, since the points in the previous three datasets are generated by sampling on annotated 3D reconstructions, they mirror the voxel distribution. In contrast, the primary strength of LiDAR-Net lies in its annotated raw points, which are non-uniform, leading to distinct point and voxel distributions. This divergence introduces new challenges to the field. Our dataset adeptly encapsulates these genuine characteristics of real-world data, thereby establishing a robust foundation for various forthcoming applications in indoor perception technology." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 234, + 255, + 247 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 234, + 255, + 247 + ], + "spans": [ + { + "bbox": [ + 47, + 234, + 255, + 247 + ], + "type": "text", + "content": "5.2. Impact of Imbalance Class Distribution" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 252, + 287, + 419 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 252, + 287, + 419 + ], + "spans": [ + { + "bbox": [ + 46, + 252, + 287, + 419 + ], + "type": "text", + "content": "Upon further investigation, we discern a more critical issue within indoor scene datasets: a conspicuous performance discrepancy resulting from imbalanced class distribution. We showcase the cumulative count of 3D points per semantic category in the top of Fig. 8, and the instance distribution is shown in the bottom. It is observable that the primary semantic categories, including ceilings, floors, walls, etc., make up over " + }, + { + "bbox": [ + 46, + 252, + 287, + 419 + ], + "type": "inline_equation", + "content": "80\\%" + }, + { + "bbox": [ + 46, + 252, + 287, + 419 + ], + "type": "text", + "content": " of the total points. In contrast, smaller yet crucial categories (e.g., monitors) constitute a mere " + }, + { + "bbox": [ + 46, + 252, + 287, + 419 + ], + "type": "inline_equation", + "content": "0.16\\%" + }, + { + "bbox": [ + 46, + 252, + 287, + 419 + ], + "type": "text", + "content": " of the total points, highlighting a stark imbalance in the distribution of semantic classes. This disproportion is inherent to indoor scenes, where walls, ceilings, and floors naturally cover large surface areas, while items like monitors are considerably smaller." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 420, + 288, + 636 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 420, + 288, + 636 + ], + "spans": [ + { + "bbox": [ + 46, + 420, + 288, + 636 + ], + "type": "text", + "content": "Data imbalance poses a significant challenge in 3D scene understanding, an issue that is also evident in LiDAR-Net. As shown in Table 3, the skew in segment headers is especially marked in the semantic segmentation task, owing to the disparity in point cloud quantities at the point level. For instance, looking at the results of RandLA-Net in specific categories, the semantic segmentation accuracy for floors is around " + }, + { + "bbox": [ + 46, + 420, + 288, + 636 + ], + "type": "inline_equation", + "content": "93\\%" + }, + { + "bbox": [ + 46, + 420, + 288, + 636 + ], + "type": "text", + "content": ", while for stairs, it nearly drops to zero. Essentially, indoor scenes are dominated by a few categories such as ceilings and walls, whereas categories like stairs, though minor but critical, have an extremely sparse data distribution. When considering instance segmentation, the combination of instance-level and point-level imbalances exacerbates the problem, leading to a more severe dual-imbalance situation. Detailed instance segmentation results of each category are listed and discussed in the supplementary materials. This profound imbalance in distribution poses another significant challenge introduced by our dataset." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 646, + 119, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 646, + 119, + 658 + ], + "spans": [ + { + "bbox": [ + 47, + 646, + 119, + 658 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 665, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 715 + ], + "type": "text", + "content": "In this study, we present a comprehensive indoor point cloud dataset derived from authentic LiDAR scanning. This dataset encompasses three meticulously labeled scenes with a total of 3.6 billion points, covering " + }, + { + "bbox": [ + 46, + 665, + 288, + 715 + ], + "type": "inline_equation", + "content": "30,000m^2" + }, + { + "bbox": [ + 46, + 665, + 288, + 715 + ], + "type": "text", + "content": ". Designed" + } + ] + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 310, + 74, + 545, + 211 + ], + "blocks": [ + { + "bbox": [ + 310, + 74, + 545, + 211 + ], + "lines": [ + { + "bbox": [ + 310, + 74, + 545, + 211 + ], + "spans": [ + { + "bbox": [ + 310, + 74, + 545, + 211 + ], + "type": "image", + "image_path": "a8613cf2deecad64a43f81c22fd78748d47eedb2cd006ba326d078914cc3dd25.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 309, + 213, + 545, + 353 + ], + "blocks": [ + { + "bbox": [ + 309, + 213, + 545, + 353 + ], + "lines": [ + { + "bbox": [ + 309, + 213, + 545, + 353 + ], + "spans": [ + { + "bbox": [ + 309, + 213, + 545, + 353 + ], + "type": "image", + "image_path": "0bfe43797d27879c3765f7db9da55b35b62864bfe230114790ad4c5e7bb86eed.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 359, + 546, + 392 + ], + "lines": [ + { + "bbox": [ + 305, + 359, + 546, + 392 + ], + "spans": [ + { + "bbox": [ + 305, + 359, + 546, + 392 + ], + "type": "text", + "content": "Figure 8. Top: Point number distribution of semantic categories. Bottom: Instance number distribution. Unknown points do not have instance labels." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 400, + 547, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 400, + 547, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 400, + 547, + 628 + ], + "type": "text", + "content": "for a variety of applications including semantic segmentation, instance segmentation, and object detection, our dataset serves as a versatile resource for related research tasks. Our comprehensive benchmark testing not only highlights persistent challenges but also emphasizes the distinct advantages of our dataset, particularly regarding the differences between annotated raw points from genuine LiDAR and points sampled from annotated 3D reconstructions. We have thoroughly examined issues such as the pronounced effects of imbalanced class distribution and the adaptability of models to unseen real-scanned scenes. Looking towards a future where autonomous indoor robots navigate diverse human-centric environments, we underscore the importance of real-time perception using authentic LiDAR-scanned data. The precision and high resolution of real-world LiDAR point cloud data are crucial for emerging cyber-physical systems like smart homes and digital twins. We believe our dataset and benchmarks will spur further progress in related areas of study." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 637, + 403, + 651 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 637, + 403, + 651 + ], + "spans": [ + { + "bbox": [ + 306, + 637, + 403, + 651 + ], + "type": "text", + "content": "Acknowledgments" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 653, + 547, + 715 + ], + "type": "text", + "content": "This work was supported by the National Natural Science Foundation of China (62032011), the Natural Science Foundation of Jiangsu Province (No. BK20211147), and the program B for Outstanding PhD candidate of Nanjing University." + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 318, + 758 + ], + "type": "text", + "content": "21996" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 12, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Iro Armeni, Ozan Sener, Amir R Zamir, Helen Jiang, Ioannis Brilakis, Martin Fischer, and Silvio Savarese. 3d semantic parsing of large-scale indoor spaces. 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However, cameras often lack the perception of 3D morphological information of human and are susceptible to various limitations, such as inadequate illumination, complex background, and personal privacy. In this paper, we propose a LiDAR-based ReID framework, ReID3D, that utilizes pre-training strategy to retrieve features of 3D body shape and introduces Graph-based Complementary Enhancement Encoder for extracting comprehensive features. Due to the lack of LiDAR datasets, we build LReID, the first LiDAR-based person ReID dataset, which is collected in several outdoor scenes with variations in natural conditions. Additionally, we introduce LReID-sync, a simulated pedestrian dataset designed for pre-training encoders with tasks of point cloud completion and shape parameter learning. Extensive experiments on LReID show that ReID3D achieves exceptional performance with a rank-1 accuracy of 94.0, highlighting the significant potential of LiDAR in addressing person ReID tasks. To the best of our knowledge, we are the first to propose a solution for LiDAR-based ReID. The code and dataset are available at https://github.com/GWxuan/ReID3D.", + "bbox": [ + 75, + 335, + 473, + 684 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 713, + 209, + 729 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Person ReID has numerous practical applications, such as video surveillance, intelligent transportation and public security. Most ReID systems use cameras as sensors, aiming to recognize the same individual in images or videos caught by different cameras. With the development of computer vision technology, camera-based ReID has witnessed continuous advancements. However, certain challenges have not yet been effectively addressed. Firstly, cameras introduce limitations in terms of visual ambiguity caused by poor illu", + "bbox": [ + 75, + 739, + 468, + 876 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/1a342af47cc0ca31e827bff81a9aeaad559435e0bbaa565d44b6dfd1f9b9f262.jpg", + "image_caption": [ + "Figure 1. Overview of camera-based and LiDAR-based person ReID. Camera-based methods primarily learn the 2D appearance of human, such as color of clothes, accessories, and shoes. LiDAR-based methods utilize 3D structural information to learn intrinsic features, such as height, body shape, and gait." + ], + "image_footnote": [], + "bbox": [ + 511, + 301, + 880, + 434 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "mination and complex backgrounds [34]. Additionally, current camera-based ReID models primarily learn appearance information [47]. Therefore, variations in human appearance considerably impact the performance of models [19]. Furthermore, camera-based person ReID systems raise personal privacy issues [1, 4] for applications in some areas.", + "bbox": [ + 496, + 532, + 892, + 623 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In recent years, Kinect-based ReID approaches have been proposed [28, 32] to address these challenges by utilizing depth information. However, Kinect is primarily designed for indoor scenes and has a limited measurement range [17], restricting its applicability in large-scale outdoor scenarios. Recently, researchers have explored the use of radar for gait recognition, identity recognition, and person ReID [7, 26]. While radar is cost-effective, it suffers from poor angular and distance resolution, as well as a limited effective measurement range [7], which poses challenges in discriminating individuals with similar body shapes.", + "bbox": [ + 496, + 625, + 893, + 792 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "In the past few years, LiDAR has been widely adopted in autonomous driving, driven by its improved accuracy and reduced costs [38]. The successful applications of LiDAR motivate us to explore its potential in person ReID within complex outdoor scenes. LiDAR can offer a broader measurement range and higher resolution, enabling precise perception about individuals in large-scale outdoor settings.", + "bbox": [ + 496, + 794, + 893, + 902 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Corresponding author", + "bbox": [ + 94, + 887, + 220, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "17437", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "LiDAR provides precise 3D structural information without being affected by lighting conditions or complex backgrounds, which enables the extraction of intrinsic features of individuals, such as height, body shape, and gait, irrespective of clothing color. LiDAR has been utilized in the task of gait recognition [34], which focuses on recognizing cooperative subjects walking along a specified route in small-scale scenes. However, ReID primarily focuses on the identification of unscripted pedestrians in large-scale scenes with a small sample size for each identity, which often requires multiple acquisition devices. In our work, we leverage low-cost LiDARs to tackle person ReID challenges, as shown in Fig. 1.", + "bbox": [ + 75, + 90, + 472, + 287 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To the best of our knowledge, this paper presents the first study on LiDAR-based person ReID. We build LReID, the first LiDAR-based ReID dataset to facilitate research on utilizing LiDAR point clouds for person ReID. We collect the dataset in several outdoor scenes using multiple collection nodes, each including a Livox Mid-100 LiDAR and an industrial camera. LReID offers several distinctive features: (1) Real-world scenes. The dataset is captured in outdoor scenes where pedestrians demonstrate unscripted behavior, leading to occlusions between pedestrians, as well as the presence of dynamic objects like vehicles and bicycles that may impact person ReID. (2) Data diversity. LReID encompasses dynamic data and annotations of 320 pedestrian gathered in varying seasons, times of day, and lighting conditions, amounting to a total of 156,000 frames of point clouds and images, thus enabling comprehensive analysis of the impact of different factors on person ReID. (3) Precision. The Livox Mid-100 LiDAR has a distance accuracy of $2\\mathrm{cm}$ and an angular accuracy of $0.1^{\\circ}$ , which provides high-precision 3D structural information for ReID problems.", + "bbox": [ + 75, + 289, + 472, + 593 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Additionally, we introduce a simulated dataset, named LReID-sync, including 360,000 frames of point clouds for 600 pedestrians captured by multi-view synchronous LiDARs. LReID-sync comprises annotations for point cloud completion from single view to full views, and Skinned Multi-Person Linear Model (SMPL) parameters [24].", + "bbox": [ + 75, + 595, + 472, + 686 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Based on point clouds, the identification of pedestrians relies on their static anthropometric features, including height, body shape, and limb structure, as well as their dynamic gait features. Accurately extracting complete shape features of a pedestrian is beneficial for both aspects. To address this, we propose an efficient LiDAR-based framework, termed ReID3D. ReID3D utilizes a pre-training strategy to guide the encoder in learning 3D body features based on LReID-sync. Moreover, in order to extract discriminative static and dynamic features of pedestrians, the ReID network of ReID3D comprises a Graph-based Complementary Enhancement Encoder (GCEE) and a temporal module. Extensive experiments on LReID demonstrate the following: (1) ReID3D outperforms the state-of-the-art camera", + "bbox": [ + 75, + 688, + 472, + 901 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "based methods, particularly under low light, highlighting the significant potential of LiDAR in addressing person ReID tasks. (2) The use of LReID-sync for pre-training significantly enhances feature encoding capability of the model. (3) Compared to commonly used point cloud encoders, our GCEE exhibits a higher proficiency in extracting comprehensive and discriminative features.", + "bbox": [ + 496, + 90, + 890, + 196 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To summarize, our main contributions are as follows:", + "bbox": [ + 517, + 196, + 872, + 210 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- To the best of our knowledge, this is the first work on LiDAR-based person ReID, demonstrating the practicality of utilizing LiDAR for person ReID in challenging real-world outdoor scenes.", + "- We build LReID, the first LiDAR-based person ReID dataset, which is collected in several outdoor scenes with variations in natural conditions. Moreover, we introduce LReID-sync, a new simulated pedestrian dataset designed for pre-training ReID models with tasks of point cloud completion and shape parameter learning.", + "- We propose a LiDAR-based ReID framework, termed ReID3D, that utilizes pre-training strategy to guide the encoder in learning 3D body features and introduces GCEE for extracting comprehensive and discriminative features. Experimental results on dataset LReID indicate that ReID3D outperforms camera-based methods." + ], + "bbox": [ + 496, + 212, + 893, + 454 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 465, + 640, + 479 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Person ReID. Camera-based ReID has been extensively researched in the past decades. Researchers have employed various convolutional neural networks [48] to extract human features from images or videos. Some video-based ReID models adopt recurrent neural networks (RNNs) [25, 45, 57] or transformer blocks [6, 56] to aggregate temporal features. These models primarily focus on extracting appearance features, which serve as efficient but short-lived identifiers. By contrast, intrinsic and behavioral features exhibit minimal change over time. Given the constraints of using cameras at night, infrared sensors have been introduced for RGB-IR cross-modality person ReID [29, 42]. However, the infrared sensor only captures 2D single-channel intensity information, constraining its perceptive ability.", + "bbox": [ + 496, + 489, + 890, + 700 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In order to extract intrinsic features of individuals, researches on ReID utilizing Kinect [28, 32] and radar [7] have emerged. Kinect and radar provide 3D structural information to help the model extract physiological and behavioral features, reducing reliance on the appearance of individuals [10, 32]. However, they are constrained by significant hardware limitations [7, 17]. In comparison, LiDAR serves as a more advantageous option, offering superior practicality. Despite this, LiDAR-based person ReID has not been researched.", + "bbox": [ + 496, + 702, + 890, + 852 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Point Cloud Completion. Point cloud completion is the task to predict missing parts based on the rest of the point", + "bbox": [ + 496, + 869, + 893, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "17438", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 1 + }, + { + "type": "table", + "img_path": "images/37ad0987fb4ec0be9e39486fdd824a0b31a7e6068c68163ca8be94936903a1bd.jpg", + "table_caption": [ + "Table 1. Comparison of publicly available 3D datasets for person ReID." + ], + "table_footnote": [], + "table_body": "
DatasetYearIdentitySensorSceneUnscriptedNatural diversityOcclusion
RGBD-ID [3]2012801 KinectIndoorXXX
BIWI RGBD-ID [27]2014501 KinectIndoorXXX
Kinect-REID [30]2015711 KinectIndoorXXX
LReLUID20233204 LiDARs + 4 CamerasOutdoor✓✓✓
LReLUID-sync20236004 LiDARsSimulation✓X✓
", + "bbox": [ + 122, + 108, + 844, + 186 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "cloud. To accomplish this, networks need to learn the intrinsic geometric structures and semantic knowledge of the 3D object. Additionally, the learned representations can be transferred to downstream tasks. The entire process does not require human annotations and therefore falls under the category of unsupervised representation learning [44].", + "bbox": [ + 75, + 205, + 467, + 296 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Point cloud completion has received increasing attention in the past decade [13, 16, 23, 40]. In terms of completing the missing parts caused by a single viewpoint, Wang et al. [36] utilize an encoder-decoder model to recover the occluded points. However, there has been limited research focusing on point cloud completion for pedestrians.", + "bbox": [ + 75, + 296, + 467, + 387 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Person ReID Dataset. Depending on the used representations, person ReID datasets can be classified into 2D and 3D datasets. Due to the early emergence and widespread use of cameras, 2D datasets are mainly composed of camera-based datasets [12, 21, 22, 37, 54, 55], which have advanced research in person ReID. In addition, some 2D datasets utilize infrared cameras as sensors [29, 42]. Kinect-based datasets [3, 27, 30] serve as typical examples of 3D datasets. However, the current Kinect datasets have limited scales as they are often collected in small indoor scenes with only one cooperative subject. Additionally, Cheng and Liu [7] collected a radar dataset containing 40 identities, but it is not publicly available and also involves only one cooperative subject in each frame. To address these limitations, we introduce a novel LiDAR-based 3D dataset. The comparison of publicly available 3D datasets is shown in Tab. 1.", + "bbox": [ + 75, + 405, + 467, + 647 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 76, + 660, + 166, + 676 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "ReID3D adopts multi-task pre-training to guide the encoder in learning 3D body features based on LReID-sync, as shown in Fig. 2. The ReID network of ReID3D comprises a Graph-based Complementary Enhancement Encoder (GCEE), which consists of a GCN backbone and a Complementary Feature Extractor (CFE), along with a temporal module, as shown in Fig. 3. The pre-trained GCEE is used to initialize the ReID network.", + "bbox": [ + 75, + 686, + 467, + 806 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Pre-training with Multiple Tasks", + "text_level": 1, + "bbox": [ + 76, + 816, + 364, + 832 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Based on our observations, the crucial factors that are likely to impact the performance of ReID models are (1) the variations in information resulted from different viewpoints under cross-view settings, and (2) the incomplete information", + "bbox": [ + 75, + 839, + 467, + 900 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/c9ed05b69b9fe1183be141a28aa1f188830702ac975aa67bc0eab954c79261f9.jpg", + "image_caption": [ + "Figure 2. The pre-training approach of ReID3D. Simulated single-view point cloud is taken as input, and the encoder is pre-trained for tasks of point cloud completion and SMPL parameter learning." + ], + "image_footnote": [], + "bbox": [ + 517, + 200, + 870, + 335 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "acquired from single view. Besides, the collection and annotation of real-world data involve significant costs, while simulated data is low-cost, and comes with rich and accurate annotations. Hence, we leverage simulated data to pretrain the encoder for tasks of point cloud completion and SMPL parameter learning. The overall idea of our proposed pre-training approach is shown in Fig. 2, which enables the encoder to effectively extract anthropometric characteristics and mitigate the influence of viewpoint disparities.", + "bbox": [ + 496, + 402, + 890, + 537 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Multi-task Network. Throughout we define point cloud $\\mathcal{P}$ as a set of points in 3D Euclidean space, $\\mathcal{P} = \\{p_i | i = 1, 2, \\dots, N\\}$ , where each point $p_i$ can be represented by its coordinates $(x_i, y_i, z_i)$ . The network is fed with the single-view point cloud $\\tilde{\\mathcal{P}}$ , then embed it into a latent vector $z$ using encoder $\\Phi(\\cdot)$ . The first branch of the network focuses on the task of point cloud completion, where the decoder $\\Psi(\\cdot)$ complete the point cloud based on $z$ . The process can be formulated as:", + "bbox": [ + 498, + 555, + 890, + 690 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\mathcal {P}} = \\Psi (\\Phi (\\tilde {\\mathcal {P}})), \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 640, + 698, + 890, + 715 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\hat{\\mathcal{P}}$ is the predicted complete point cloud.", + "bbox": [ + 500, + 722, + 808, + 738 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The second branch aims to learn the characteristics of human body, i.e. SMPL shape parameters $\\beta$ . The latent vector $z$ is expected to encompass shape information. Therefore, a straightforward MLP network is utilized to convert $z$ into predicted SMPL shape parameters $\\hat{\\beta}$ . The process can be formulated as:", + "bbox": [ + 496, + 739, + 890, + 827 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\beta} = \\operatorname {M L P} (\\Phi (\\tilde {\\mathcal {P}})). \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 632, + 835, + 890, + 852 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Training. We adapt the folding-based decoder PCN [49] to complete the single-view point cloud in two steps, out", + "bbox": [ + 498, + 869, + 890, + 900 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "17439", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/c1716af5e8585a4893af676074ce35926b2611f766bf1a43fe04ee862da2fa73.jpg", + "image_caption": [ + "Figure 3. The ReID network of ReID3D. The Graph-based Complementary Enhancement Encoder (GCEE) extracts frame-level features from the pedestrian point clouds, and the transformer module aggregates the sequential features. GCEE consists of a GCN backbone and a Complementary Feature Extractor (CFE)." + ], + "image_footnote": [], + "bbox": [ + 158, + 85, + 816, + 289 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "putting a coarse shape $\\hat{\\mathcal{P}}_{\\mathrm{coarse}}$ and a detailed shape $\\hat{\\mathcal{P}}_{\\mathrm{detail}}$ . The pre-training model is trained with a combined loss corresponding to the two branches. In the branch of point clout completion, we use Chamfer Distance (CD) as the difference measure between prediction $\\hat{\\mathcal{P}}$ and ground-truth $\\mathcal{V}$ :", + "bbox": [ + 75, + 359, + 472, + 439 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\operatorname {C D} (\\hat {\\mathcal {P}}, \\mathcal {Y}) = \\frac {1}{| \\hat {\\mathcal {P}} |} \\sum_ {\\hat {p} \\in \\hat {\\mathcal {P}}} \\min _ {p \\in \\mathcal {Y}} \\| \\hat {p} - p \\| + \\frac {1}{| \\mathcal {Y} |} \\sum_ {p \\in \\mathcal {Y}} \\min _ {\\hat {p} \\in \\hat {\\mathcal {P}}} \\| p - \\hat {p} \\|. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 76, + 446, + 468, + 498 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The loss of the completion branch is a sum of the Chamfer distances on the coarse and detailed shapes weighted by a hyperparameter $\\delta$ :", + "bbox": [ + 75, + 500, + 470, + 545 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\mathrm {c o m}} = \\mathrm {C D} (\\hat {\\mathcal {P}} _ {\\text {c o a r s e}}, \\mathcal {Y}) + \\delta \\mathrm {C D} (\\hat {\\mathcal {P}} _ {\\text {d e t a i l}}, \\mathcal {Y}). \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 133, + 554, + 468, + 571 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The branch of shape parameter learning utilizes mean squared error (MSE) as the loss function:", + "bbox": [ + 76, + 582, + 468, + 613 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {s h a p e}} = \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\left(\\beta_ {i} - \\hat {\\beta} _ {i}\\right) ^ {2}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 183, + 622, + 468, + 661 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $n$ is the dimension of $\\beta$ , i.e. $n = 10$ .", + "bbox": [ + 76, + 671, + 362, + 684 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The pre-training loss is a combination of the two branches with a weighted hyperparameter $\\eta$ :", + "bbox": [ + 75, + 686, + 468, + 715 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {\\text {c o m}} + \\eta \\mathcal {L} _ {\\text {s h a p e}}. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 202, + 728, + 468, + 744 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. ReID Network", + "text_level": 1, + "bbox": [ + 76, + 753, + 227, + 767 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To extract spatio-temporal features from the sequence of point clouds, the ReID Network of ReID3D comprises a GCEE, which consists of a GCN backbone and CFE, along with a temporal module, as illustrated in Fig. 3.", + "bbox": [ + 75, + 776, + 470, + 838 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "GCN Backbone. To extract local and global features from point clouds effectively, we employ graph convolutional structure as the backbone. We construct the directed", + "bbox": [ + 75, + 854, + 470, + 900 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/eed0ff5897a3d3caaf46cd0f4a2e6b1f828fc9bb8e6d1f7b88bc94a5a03e5554.jpg", + "image_caption": [ + "Figure 4. The architecture of the Eraser module in CFE." + ], + "image_footnote": [], + "bbox": [ + 542, + 359, + 852, + 470 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "graph $\\mathcal{G}(\\mathcal{V},\\mathcal{E})$ by using the k-nearest neighbors (KNN) of each point including self-loop, where $\\mathcal{V}$ represents the points and $\\mathcal{E}$ represents the set of edges. For the original point cloud, we construct the graph based on the nearest neighbors in its coordinate space. However, we update the graph at each layer of the network in feature space based on the feature similarity among points, rather than fixed spatial positions.", + "bbox": [ + 496, + 527, + 890, + 648 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Denote that $p_i$ is the central point of once graph convolution operation, and $\\mathcal{N}(i) = \\{j | (i, j) \\in \\mathcal{E}\\}$ is the set of points in its neighborhood with features $\\mathcal{F}(i) = \\{f_j | j \\in \\mathcal{N}(i)\\}$ . To integrate the global shape structure and local neighborhood feature differences [39], we define $f_{ij} = [f_i, f_j - f_i]$ as the input feature, where $[\\cdot, \\cdot]$ is the concatenation operation. The convolution process can be formulated as:", + "bbox": [ + 496, + 652, + 890, + 773 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nf _ {i} ^ {\\prime} = \\max _ {j \\in \\mathcal {N} (i)} \\sigma \\left(f _ {i j} \\times k\\right), \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 614, + 791, + 890, + 818 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $f_{i}^{\\prime}$ is the output feature of the central point $p_i$ , $k$ is the convolution kernel, max is a channel-wise max-pooling function, $\\times$ represents matrix multiplication and $\\sigma(\\cdot)$ is the activation function LeakyReLU.", + "bbox": [ + 496, + 838, + 893, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "17440", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Complementary Feature Extractor. One viable method for extracting frame-level pedestrian features is to apply pooling directly to the features output by the GCN backbone. However, applying the same operation to each frame results in highly redundant extraction, which only emphasizes a part of the most salient features. To this end, inspired by [15], we design CFE to extract complementary features and improving representation learning of the encoder.", + "bbox": [ + 75, + 90, + 468, + 210 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "For each frame in a sequence, we consider it as the primary frame. The CFE further extracts its features based on the output of the GCN backbone. Then, the next frame is taken as the supplementary frame, from which the Eraser module erases the previously discovered salient features. We duplicate the last frame $\\mathcal{P}_n$ as its own supplementary frame. In particular, for a sequence of point clouds $\\{\\mathcal{P}_i\\}_{i=1}^n (\\mathcal{P}_i \\in \\mathbb{R}^{N \\times 3})$ , the feature sequence $\\{\\mathcal{F}_i\\}_{i=1}^n (\\mathcal{F}_i \\in \\mathbb{R}^{N \\times D})$ is obtained by the GCN backbone, where $N$ is the number of points and $D$ is the dimension of features. For the primary frame, CFE utilizes a graph convolution layer and a global max-pooling layer to extract the most salient features $f_{\\mathrm{p}} \\in \\mathbb{R}^{1 \\times D_{\\mathrm{c}}}$ . Then, the Eraser module reconstructs the features of the supplementary frame $\\mathcal{F}_{\\mathrm{s}}$ guided by the discovered features $f_{\\mathrm{p}}$ . The reconstructed features $\\mathcal{F}_{\\mathrm{s}}'$ is fed into similar graph convolution layer and global max-pooling layer to extract auxiliary features $f_{\\mathrm{s}}$ . $f_{\\mathrm{p}}$ and $f_{\\mathrm{s}}$ are concatenated to obtain the complementary features $f_{\\mathrm{cfe}} \\in \\mathbb{R}^{1 \\times 2D_{\\mathrm{c}}}$ of the primary frame.", + "bbox": [ + 75, + 212, + 470, + 498 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The architecture of the Erasure module is shown in Fig. 4. Firstly, the correlation layer is used to obtain the correlation vector $R \\in \\mathbb{R}^{N \\times 1}$ between $\\mathcal{F}_{\\mathrm{s}}$ and $f_{\\mathrm{p}}$ , through computing the semantic relevance between $f_{\\mathrm{p}}$ and all the local descriptors of $\\mathcal{F}_{\\mathrm{s}}$ , formulated as:", + "bbox": [ + 75, + 500, + 468, + 575 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\nR = \\mathcal {F} _ {\\mathrm {s}} \\times \\left(f _ {\\mathrm {p}} \\times \\omega\\right) ^ {T}, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 197, + 583, + 468, + 602 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\omega \\in \\mathbb{R}^{D_{\\mathrm{c}} \\times D}$ is a learnable variable projecting $f_{\\mathrm{p}}$ to the feature space of $\\mathcal{F}_{\\mathrm{s}}$ . Then, the Binarization module generates the binary mask based on $R$ to identify the points to be erased. Specifically, for each point in $\\mathcal{F}_{\\mathrm{s}}$ , calculate the sum of the correlation values of the point and its $K_{\\mathrm{B}}$ nearest neighbors in the feature space. The calculated sum represents the correlation of the region centered on the point. We select the region with the highest correlation value to be erased, through setting the corresponding value in the binary mask $B$ to 0 and others to 1. Finally, $\\mathcal{F}_{\\mathrm{s}}$ is erased according to $B$ to obtain the reconstructed features $\\mathcal{F}_{\\mathrm{s}}'$ .", + "bbox": [ + 75, + 609, + 468, + 777 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Temporal Fusion Module. The sequence of pedestrian point clouds includes distinctive dynamic features, such as gait frequency and amplitude of limb swings. We utilize a transformer module [35] with four encoder layers to extract the dynamic features. The transformer module takes the sequence of features $\\{f_{\\mathrm{cfe}}^i\\}_{i = 1}^n$ as input and outputs the final features $f\\in \\mathbb{R}^{D_{\\mathrm{T}}}$ .", + "bbox": [ + 75, + 794, + 468, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Training and Inference. Following the standard paradigm of camera-based ReID [5, 15, 46, 52], we exploit a combination of cross-entropy and batch-hard triplet terms [14] as the loss function, with the hyperparameter $\\gamma$ :", + "bbox": [ + 496, + 90, + 890, + 151 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {\\mathrm {c e}} + \\gamma \\mathcal {L} _ {\\mathrm {t r i}}. \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 637, + 157, + 890, + 174 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "During inference, the similarity between query and gallery set is measured using the cosine distance.", + "bbox": [ + 496, + 180, + 890, + 210 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4. Person ReID Dataset", + "text_level": 1, + "bbox": [ + 498, + 220, + 699, + 237 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this paper, we build a real-world LiDAR-based ReID dataset LReID and a simulated pedestrian point cloud dataset LReID-sync. LReID is captured by a multimodal imaging system, which consists of 4 Livox Mid-100 LiDAR sensors and 4 industrial cameras [51]. LReID includes 320 identities, 156,000 point cloud frames and synchronized RGB images with corresponding 2D and 3D annotations.", + "bbox": [ + 496, + 246, + 890, + 353 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Data Acquisition. LReID is collected in two extensive outdoor scenes: a crossroad and a square in front of a building, capturing different time periods and weather conditions, as shown in Fig. 6. We synchronize each pair of LiDAR and camera with $\\sim 5$ ms accuracy and provide an accurate extrinsic and intrinsic calibration. All sequences are recorded with a frame rate of $10\\mathrm{Hz}$ . The images are captured of a resolution of $2048\\times 1536$ pixels and the density of LiDAR points is about 30,000 points per frame.", + "bbox": [ + 496, + 369, + 890, + 505 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "The square scene is located in front of a building with frequent pedestrian traffic, and many pedestrians walk together in groups, which makes it more complex for person ReID tasks. We collected data in the square scene during two different times in summer to analyze the impact of lighting conditions on person ReID. Additionally, to explore the impact of different scenes, weather conditions, and pedestrian attire in different seasons, we also collected data at a crossroads scene in winter. Figure 5 shows the samples of two pedestrians collected from different scenes. Furthermore, we analyze the point distribution in LReID and LReID-sync, as shown in Fig. 6.", + "bbox": [ + 496, + 506, + 890, + 686 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Annotations. To ensure efficient and accurate annotation, we utilize a point cloud-based 3D detector [18] to locate pedestrians. Additionally, we employ a 3D multi-object tracking method [41] to establish continuous trajectories, and manually rectify them. Furthermore, we adjust the IDs of the pedestrians that appeared repeatedly in the field of view based on the images. After obtaining precise 3D ReID annotations, we project them onto synchronized RGB images and perform manual corrections.", + "bbox": [ + 496, + 704, + 890, + 839 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To avoid the influence of absolute coordinate information on the network, we normalize the pedestrian point clouds by subtracting the center coordinates of their respective bounding boxes.", + "bbox": [ + 496, + 839, + 890, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "17441", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/75060989987a2bee1f2c54f8be2a1c56689e0d4a482c97ae4c52c3493c1cbb85.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 101, + 88, + 153, + 176 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/7e63e026d097ee9a083f9df8c2731c88b2a5725306b4e7f68502e2b2839aa341.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 160, + 88, + 310, + 176 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/b36503a53d7540e7a7dd7dc8e5d323ec7906a4ac6d63f85ad6695a010c7d4afb.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 313, + 89, + 401, + 176 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/25ce9b30c719c9c786b7c50a77ad4d26a499012e5f96fb3b7fe8e37e86a563d3.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 403, + 90, + 506, + 176 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/898dfff2acdd2bcfd1ee754484445120dafed91e821f2f31bdb13beea1b55d9f.jpg", + "image_caption": [ + "Figure 5. Samples of two pedestrians collected from the square scene in summer (top row), and the crossroads scene in winter (bottom row)." + ], + "image_footnote": [], + "bbox": [ + 99, + 179, + 153, + 258 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/a045f1182ed8237ec375559c640410675a465ee2d20d5e29ddd2d39ea0bb9882.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 158, + 179, + 310, + 258 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/7ee7d0c42d12c6b7db086cfc53f74ebc25fb7b6bd86238d464b2fe6995e9210a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 310, + 179, + 400, + 258 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/ad1dd98ff8648781e48183967fc553f09b0252d67c8b5b43544024a33deadf6f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 401, + 179, + 506, + 258 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/4bff8758f14584ca397b6f22dad81408585551896b9d33781bb571d49d0a5283.jpg", + "image_caption": [ + "Figure 6. Data acquisition scenes and statistics about points in LReID and LReID-sync (lower right)." + ], + "image_footnote": [], + "bbox": [ + 566, + 88, + 859, + 258 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e38b8d7baeb4e03a3667b443a89c0b171877b09047ae0779bd12e14e7cc65b41.jpg", + "image_caption": [ + "Figure 7. Samples of LReid-sync for full views and each single view." + ], + "image_footnote": [], + "bbox": [ + 84, + 335, + 460, + 419 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Evaluation. LReID is divided into two splits: a training set with 220 identities and a test set with the remaining 100 identities. Both sets include different scenes, seasons, and lighting conditions. Within the test set, 30 identities are captured under low light, whereas 70 identities are captured under normal light. Following the standard paradigm of video-based datasets [20, 43, 55], the evaluation focuses on recognition across different LiDARs.", + "bbox": [ + 75, + 486, + 468, + 606 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We select one sample of each identity in the test set to build the query set and use the other samples as the gallery set. In the test set, we ensure that the data collected by different LiDARs does not overlap in time, which is to prevent the model from recognizing individuals based on human pose at a certain time. To maximize the use of training data, we divide the sequences in training set into several fragments that may partially overlap in time. The evaluation metrics for LReID include Cumulative Matching Characteristics (CMC) and mean Average Precision (mAP), which are consistent with camera-based datasets.", + "bbox": [ + 75, + 608, + 468, + 773 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "LReLU-sync. LReLU-sync is a novel pedestrian dataset generated using the software Unity3D, which simulates pedestrians in scenes captured by multiple synchronized LiDARs from various views, as shown in Fig. 7. With this setup, LReLU-sync accurately simulates the information loss and point cloud sparsity that occur when pedestrians are captured using a single-view LiDAR. Additionally,", + "bbox": [ + 75, + 794, + 470, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "LReID-sync includes annotations for point cloud completion from single view to full views, as well as SMPL parameters. Therefore, LReID-sync can be utilized for pretraining. LReID-sync comprises 600 pedestrians with various actions, each exhibiting unique body shapes and gaits, ensuring diversity within the dataset.", + "bbox": [ + 496, + 338, + 890, + 429 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 441, + 633, + 458 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Implementation Details", + "text_level": 1, + "bbox": [ + 500, + 465, + 717, + 482 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "ReID Network. The ReID network is trained for 700 epochs using the AdamW optimizer with a weight decay of 5e-5. The learning rate, initially set to 5e-5, is updated using a Cosine Annealing Learning Rate (CosineAnnealingLR) scheduler with a cycle of 200 epochs. Each frame of pedestrian point clouds in LReID is upsampled or downsampled to 256 points as input to the network. To train our model, we randomly choose 6 identities, and sample 6 sequences for each identity with a sequence length of 30 frames. The loss weight $\\gamma$ is set to 1. The neighborhood size is set to 10 and 8 for each graph convolution layer and Binarization module, respectively. And the feature dimensions $D$ , $D_{\\mathrm{C}}$ and $D_{\\mathrm{T}}$ are set to 512, 512 and 1024, respectively.", + "bbox": [ + 496, + 489, + 892, + 686 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Pre-training. The pre-training model follows a similar training strategy as described above, except that the initial learning rate is set to 1e-4. The loss weight $\\eta$ is set to 1. The coefficient $\\delta$ in Eq. 4 is set to 0.01 for the first 100 epochs, then increased to 0.1, 0.5 and 1.0 after 100, 200 and 400 epochs. The coarse shape $\\hat{\\mathcal{P}}_{\\mathrm{coarse}}$ contains 128 points, while the detailed shape $\\hat{\\mathcal{P}}_{\\mathrm{detail}}$ contains 512 points. The weights of the pre-trained GCEE are used as initialization for the ReID network.", + "bbox": [ + 496, + 703, + 890, + 838 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Comparison with Camera-based Methods", + "text_level": 1, + "bbox": [ + 500, + 847, + 856, + 863 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We compare ReID3D with the state-of-the-art video-based methods [2, 9, 15, 50]. The input images are resized in the", + "bbox": [ + 500, + 869, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "17442", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/67abce3276730368331974a5de833833eed17e3c1bf63b1acd9c454bfe7a6d2c.jpg", + "table_caption": [ + "Table 2. Comparison with state-of-the-art camera-based methods on LReID. Numbers in bold indicate the best performance and underscored ones are the second best. To ensure fairness, ReID3D without pre-training is evaluated." + ], + "table_footnote": [ + "B-ReID3D: ReID3D without pre-training." + ], + "table_body": "
MethodVenueModalityNormal lightLow lightOverall
Rank-1Rank-3mAPRank-1Rank-3mAPRank-1Rank-3mAP
TCLNet [15]ECCV 2020Camera98.698.694.8860.073.346.1887.091.080.27
STMN [9]ICCV 202194.398.693.8130.050.031.1775.084.075.02
SINet [2]CVPR 202297.1100.094.6343.360.043.9781.088.079.43
PiT [50]TII 202294.395.786.2133.360.035.7476.085.071.07
B-ReID3DOursLiDAR90.097.182.0490.093.381.6490.096.081.92
ReID3DOurs94.398.683.6593.396.782.4394.098.083.28
", + "bbox": [ + 114, + 125, + 856, + 224 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/e069a6725154ed89e311be55897527700530da8dd5f419cee2b1963baf8eb351.jpg", + "table_caption": [ + "Table 3. Comparison for different pre-training method." + ], + "table_footnote": [], + "table_body": "
Pre-training MethodRank-1Rank-3mAP
Baseline(w/o pre-training)90.096.081.92
ReID91.096.082.13
Completion93.097.082.73
Completion + SMPL94.098.083.28
", + "bbox": [ + 109, + 282, + 434, + 348 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "resolution of $128 \\times 64$ . To ensure fairness, ReID3D without pre-training (B-ReID3D) is also evaluated. All methods are evaluated with the same dataset settings and metrics.", + "bbox": [ + 75, + 368, + 468, + 412 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The comparative results are shown in Tab. 2, from which the following observations can be obtained: (1) ReID3D and B-ReID3D demonstrate their superiority to the video-based methods, primarily benefiting from the utilization of point clouds, which is unaffected by lighting conditions and complex background. (2) ReID3D achieves state-of-the-art results in overall and low light conditions, but it falls behind video-based methods in normal light conditions. This is because video-based methods make full use of appearance information under normal light. (3) Video-based methods perform poorly under low light, while ReID3D and B-ReID3D demonstrate comparable reliability under both low light and normal light.", + "bbox": [ + 75, + 414, + 470, + 609 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "5.3. Pre-training", + "text_level": 1, + "bbox": [ + 76, + 619, + 209, + 636 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "To demonstrate the effectiveness of pre-training with simulated dataset LReID-sync, we evaluate the performance of different pre-training method. The following four methods are evaluated: (1) ReID3D without pre-training. (2) Pretraining with similar ReID task, in which the pre-training model and loss are consistent with the ReID network. (3) Pre-training with only the branch of point cloud completion. (4) Pre-training with multiple tasks, as described in Section 3.1. The experimental results are shown in Tab. 3. It can be observed that pre-training with multiple tasks makes an improvement to the accuracy of ReID3D, with the rank-1 accuracy increasing from 90.0 to 94.0. This improvement can be attributed to two factors: (1) The simulated data comprises a diverse collection of pedestrian point clouds with various body shapes, which supplements the real-world data. (2) Multi-task pre-training effectively leverages the performance of the encoder. Besides, pre-training with", + "bbox": [ + 75, + 643, + 472, + 902 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/0d33fddb0ba11bf8e1b54ecf6c9ccbdfdd1e8fe08dbce51e8e4faba482cdb6b4.jpg", + "image_caption": [ + "(a)" + ], + "image_footnote": [], + "bbox": [ + 509, + 260, + 689, + 364 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/0d201789505030dc165803eb53620f345022b2d51a36d2e951bf3e2f98ccb650.jpg", + "image_caption": [ + "(b)" + ], + "image_footnote": [], + "bbox": [ + 705, + 260, + 883, + 364 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/61357e73f4d721fbde1fe44129706b1e3c334da4291dc88868df0465b3707cef.jpg", + "image_caption": [ + "(c)" + ], + "image_footnote": [], + "bbox": [ + 511, + 381, + 687, + 484 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a65124066ae6eb87fda8de765b1a486b84e0c481d5cbdb8f98e0f136930d2ff7.jpg", + "image_caption": [ + "(d)", + "Figure 8. Completion results for real-world pedestrian point clouds obtained by the pre-trained model. In each sample, the detailed shape, coarse shape, and image are shown from left to right. The red points represent the input point cloud, and the blue points represent the predicted complete point cloud." + ], + "image_footnote": [], + "bbox": [ + 705, + 381, + 883, + 484 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "task of ReID or point cloud completion also leads to an improvement in performance.", + "bbox": [ + 496, + 597, + 890, + 627 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "To showcase the robust feature encoding capabilities attained by the encoder through pre-training, we visualize the completion results for several real-world pedestrian point clouds with different characteristics, as shown in Fig. 8. We can observe that: (1) Intuitively, the detailed and coarse shape closely resemble the actual human shape, which indicates that the encoder has successfully captured the complete features of the human body. (2) The detailed shape is an extension based on the coarse shape, with higher resolution and more information. (3) The pre-trained encoder has the ability to estimate the features of the missing part in the point cloud. As shown in Fig. 8a, the unobserved parts of the legs are accurately completed. (4) Due to motion blur or object carrying, the point cloud may contain some noise points. For example, in Fig. 8b and Fig. 8c, there are red noise points located between the legs and from the carrying bags, respectively. However, the model can effectively filter out the noise points that do not conform to the body shape.", + "bbox": [ + 496, + 628, + 892, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "17443", + "bbox": [ + 478, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/aa1f631d69e8cf606e883c6fc4b6e749c95e4b45d60c810f6a7c87148059831d.jpg", + "table_caption": [ + "Table 4. Performance of B-ReID3D with different encoders." + ], + "table_footnote": [], + "table_body": "
EncoderRank-1Rank-3mAP
PointNet [31]74.088.060.31
Point Transformer [53]83.093.074.86
3DCNN [8]34.051.028.27
GCEE90.096.081.92
", + "bbox": [ + 119, + 109, + 426, + 175 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/37825f65ab299654cc46846146b73979a8590da7d7e98d9802d2a562cabc8244.jpg", + "table_caption": [ + "Table 5. Ablation study on the CFE module and Eraser module." + ], + "table_footnote": [], + "table_body": "
Encoder TypeRank-1Rank-3mAP
B-ReID3D-w/o CFE83.094.074.15
B-ReID3D-w/o Eraser85.095.080.47
B-ReID3D90.096.081.92
", + "bbox": [ + 120, + 212, + 426, + 266 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Ablation Study", + "text_level": 1, + "bbox": [ + 76, + 292, + 228, + 309 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effect of Encoders. To evaluate the effectiveness of our GCEE, we also implement several commonly used encoders in point cloud tasks to replace GCEE in the ReID network for comparison, including PointNet [31], Point Transformer [53], and 3DCNN [8]. All methods use consistent training strategies and employ a same transformer module as the temporal fusion network. We report the results on LReID in Tab. 4, obtaining the following observations: (1) GCEE outperforms other encoders, which is mainly beneficial by its flexible graph structure in the feature space and the strategy of complementary enhancement. (2) Point-based encoders are superior to voxel-based encoder 3DCNN, which indicates that point-based encoders can provide a more detailed understanding of humans in tasks like ReID.", + "bbox": [ + 75, + 316, + 472, + 544 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effect of CFE. CFE is a crucial component in our proposed encoder, used to extract complementary features. We compared our full model with two ablated versions: one without CFE and another without the Eraser module, as shown in Tab. 5. Removing CFE results in a lower rank-1 accuracy, with a score of 83.0 compared to our 90.0, which highlights the effectiveness of the complementary enhancement in constructing distinctive and comprehensive features. While removing the Eraser module retains the features of the complementary frame, it might lead to the extraction of similar features from the primary frame, thus restricting the improvement in accuracy, with a score of 85.0 compared to 83.0 of the version without CFE.", + "bbox": [ + 75, + 571, + 468, + 768 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effect of the Temporal Module. We evaluate the effectiveness of different temporal modules in combination with GCEE, as shown in Tab. 6. We can observe that the attention-based transformer structure demonstrates significant superiority over the LSTM structure. The rank-1 accuracy of transformer exceeds that of LSTM by 8 points, and that of BiLSTM by 10 points.", + "bbox": [ + 75, + 794, + 468, + 902 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/fa88324629a8eca6f20ff94f0d8d9f1de553715ed3c2e9ee9a64bb20b0ca2c01.jpg", + "table_caption": [ + "Table 6. Results of B-ReID3D with different temporal modules." + ], + "table_footnote": [], + "table_body": "
Temporal ModuleRank-1Rank-3mAP
LSTM [11]82.089.072.34
Bi-LSTM [33]80.090.070.92
Transformer [35]90.096.081.92
", + "bbox": [ + 555, + 107, + 836, + 160 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/8d90b62be49500c13600e8c81ebed5034decf03e903c430537c0fe5d2aa9d329.jpg", + "image_caption": [ + "(a)" + ], + "image_footnote": [], + "bbox": [ + 509, + 172, + 630, + 265 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c5ddb489cb6ff4f8a963c171fefd591475461c8534ff526d91b8594aaf9a63db.jpg", + "image_caption": [ + "(b)" + ], + "image_footnote": [], + "bbox": [ + 640, + 172, + 746, + 265 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/e842e42ca3143b1a28a8ec0961600aa36e65230d0ba6b5d8b9965790fd2a509c.jpg", + "image_caption": [ + "(c)", + "Figure 9. Feature visualization of CFE. The features of the primary frame and the supplementary frame are presented on left and right, respectively. The color bar on the right indicates the feature value." + ], + "image_footnote": [], + "bbox": [ + 759, + 172, + 885, + 265 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.5. Visualization Analysis", + "text_level": 1, + "bbox": [ + 500, + 343, + 705, + 359 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "For qualitative analysis, we visualize the feature values output by the two graph convolutional layers in the CFE, as shown in Fig. 9. Three samples are taken from different actions of a person in the test set of LReID, with each sample comprising two consecutive frames. In each sample, the features of the primary frame and the supplementary frame are presented. We can observe that primary ones pay more attention to the head and arms, potentially linked to the discriminative height parameter, while supplementary ones predominantly emphasize the torso and legs. The combination of them creates a complementary and comprehensive feature representation.", + "bbox": [ + 496, + 367, + 890, + 547 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusions", + "text_level": 1, + "bbox": [ + 500, + 561, + 625, + 577 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This paper presents the first research on person ReID using precise 3D structural information provided by LiDAR. Firstly, We propose a LiDAR-based ReID framework, named ReID3D, that utilizes pre-training to guide Graph-based Complementary Enhancement Encoder (GCEE) for extracting comprehensive 3D intrinsic features. Moreover, we build the first LiDAR-based person ReID dataset, termed LReID, which contains 320 pedestrians in various outdoor scenes and lighting conditions. Additionally, we introduce LReID-sync, a new simulated pedestrian dataset designed for pre-training encoders with tasks of point cloud completion and shape parameter learning. Our proposed ReID3D demonstrates exceptional performance on LReID, highlighting the significant potential of LiDAR in addressing person ReID tasks.", + "bbox": [ + 496, + 587, + 890, + 815 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgement", + "text_level": 1, + "bbox": [ + 500, + 828, + 660, + 844 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This work is supported by the National Key Research and Development Program of China under Grant (2018AAA0102803).", + "bbox": [ + 498, + 852, + 890, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "17444", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Sk Miraj Ahmed, Aske R Lejbolle, Rameswar Panda, and Amit K Roy-Chowdhury. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 4747–4756, 2017. 2" + ], + "bbox": [ + 78, + 90, + 468, + 443 + ], + "page_idx": 10 + }, + { + "type": "page_number", + "text": "17447", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 10 + } +] \ No newline at end of file diff --git a/2024/LiDAR-based Person Re-identification/9f64a85c-6e54-4870-b464-e9b92b89bbaa_model.json b/2024/LiDAR-based Person Re-identification/9f64a85c-6e54-4870-b464-e9b92b89bbaa_model.json new file mode 100644 index 0000000000000000000000000000000000000000..445903535fac6d0d1659587a326363c1c0c2b6ed --- /dev/null +++ b/2024/LiDAR-based Person Re-identification/9f64a85c-6e54-4870-b464-e9b92b89bbaa_model.json @@ -0,0 +1,2521 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.29, + 0.131, + 0.68, + 0.151 + ], + "angle": 0, + "content": "LiDAR-based Person Re-identification" + }, + { + "type": "text", + "bbox": [ + 0.205, + 0.18, + 0.764, + 0.199 + ], + "angle": 0, + "content": "Wenxuan Guo1 Zhiyu Pan1 Yingping Liang2 Ziheng Xi1" + }, + { + "type": "text", + "bbox": [ + 0.291, + 0.199, + 0.716, + 0.217 + ], + "angle": 0, + "content": "Zhicheng Zhong\\(^{1}\\) Jianjiang Feng\\(^{1*}\\) Jie Zhou\\(^{1}\\)" + }, + { + "type": "text", + "bbox": [ + 0.108, + 0.217, + 0.863, + 0.235 + ], + "angle": 0, + "content": "\\(^{1}\\)Department of Automation, BNrist, Tsinghua University \\(^{2}\\)Beijing Institute of Technology" + }, + { + "type": "text", + "bbox": [ + 0.131, + 0.237, + 0.84, + 0.252 + ], + "angle": 0, + "content": "\\(\\{gwx22,pzy20,xizh21,zhongzc18\\} \\text{}@\\) mails.tsinghua.edu.cn liangyingping@bit.edu.cn" + }, + { + "type": "text", + "bbox": [ + 0.357, + 0.255, + 0.612, + 0.269 + ], + "angle": 0, + "content": "{jfeng,jzhou}@tsinghua.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.304, + 0.313, + 0.32 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.337, + 0.474, + 0.685 + ], + "angle": 0, + "content": "Camera-based person re-identification (ReID) systems have been widely applied in the field of public security. However, cameras often lack the perception of 3D morphological information of human and are susceptible to various limitations, such as inadequate illumination, complex background, and personal privacy. In this paper, we propose a LiDAR-based ReID framework, ReID3D, that utilizes pre-training strategy to retrieve features of 3D body shape and introduces Graph-based Complementary Enhancement Encoder for extracting comprehensive features. Due to the lack of LiDAR datasets, we build LReID, the first LiDAR-based person ReID dataset, which is collected in several outdoor scenes with variations in natural conditions. Additionally, we introduce LReID-sync, a simulated pedestrian dataset designed for pre-training encoders with tasks of point cloud completion and shape parameter learning. Extensive experiments on LReID show that ReID3D achieves exceptional performance with a rank-1 accuracy of 94.0, highlighting the significant potential of LiDAR in addressing person ReID tasks. To the best of our knowledge, we are the first to propose a solution for LiDAR-based ReID. The code and dataset are available at https://github.com/GWxuan/ReID3D." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.714, + 0.21, + 0.73 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.74, + 0.47, + 0.877 + ], + "angle": 0, + "content": "Person ReID has numerous practical applications, such as video surveillance, intelligent transportation and public security. Most ReID systems use cameras as sensors, aiming to recognize the same individual in images or videos caught by different cameras. With the development of computer vision technology, camera-based ReID has witnessed continuous advancements. However, certain challenges have not yet been effectively addressed. Firstly, cameras introduce limitations in terms of visual ambiguity caused by poor illu" + }, + { + "type": "image", + "bbox": [ + 0.513, + 0.303, + 0.882, + 0.435 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.445, + 0.893, + 0.515 + ], + "angle": 0, + "content": "Figure 1. Overview of camera-based and LiDAR-based person ReID. Camera-based methods primarily learn the 2D appearance of human, such as color of clothes, accessories, and shoes. LiDAR-based methods utilize 3D structural information to learn intrinsic features, such as height, body shape, and gait." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.533, + 0.893, + 0.624 + ], + "angle": 0, + "content": "mination and complex backgrounds [34]. Additionally, current camera-based ReID models primarily learn appearance information [47]. Therefore, variations in human appearance considerably impact the performance of models [19]. Furthermore, camera-based person ReID systems raise personal privacy issues [1, 4] for applications in some areas." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.626, + 0.895, + 0.793 + ], + "angle": 0, + "content": "In recent years, Kinect-based ReID approaches have been proposed [28, 32] to address these challenges by utilizing depth information. However, Kinect is primarily designed for indoor scenes and has a limited measurement range [17], restricting its applicability in large-scale outdoor scenarios. Recently, researchers have explored the use of radar for gait recognition, identity recognition, and person ReID [7, 26]. While radar is cost-effective, it suffers from poor angular and distance resolution, as well as a limited effective measurement range [7], which poses challenges in discriminating individuals with similar body shapes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.795, + 0.895, + 0.903 + ], + "angle": 0, + "content": "In the past few years, LiDAR has been widely adopted in autonomous driving, driven by its improved accuracy and reduced costs [38]. The successful applications of LiDAR motivate us to explore its potential in person ReID within complex outdoor scenes. LiDAR can offer a broader measurement range and higher resolution, enabling precise perception about individuals in large-scale outdoor settings." + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.888, + 0.221, + 0.9 + ], + "angle": 0, + "content": "*Corresponding author" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17437" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.473, + 0.288 + ], + "angle": 0, + "content": "LiDAR provides precise 3D structural information without being affected by lighting conditions or complex backgrounds, which enables the extraction of intrinsic features of individuals, such as height, body shape, and gait, irrespective of clothing color. LiDAR has been utilized in the task of gait recognition [34], which focuses on recognizing cooperative subjects walking along a specified route in small-scale scenes. However, ReID primarily focuses on the identification of unscripted pedestrians in large-scale scenes with a small sample size for each identity, which often requires multiple acquisition devices. In our work, we leverage low-cost LiDARs to tackle person ReID challenges, as shown in Fig. 1." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.29, + 0.473, + 0.594 + ], + "angle": 0, + "content": "To the best of our knowledge, this paper presents the first study on LiDAR-based person ReID. We build LReID, the first LiDAR-based ReID dataset to facilitate research on utilizing LiDAR point clouds for person ReID. We collect the dataset in several outdoor scenes using multiple collection nodes, each including a Livox Mid-100 LiDAR and an industrial camera. LReID offers several distinctive features: (1) Real-world scenes. The dataset is captured in outdoor scenes where pedestrians demonstrate unscripted behavior, leading to occlusions between pedestrians, as well as the presence of dynamic objects like vehicles and bicycles that may impact person ReID. (2) Data diversity. LReID encompasses dynamic data and annotations of 320 pedestrian gathered in varying seasons, times of day, and lighting conditions, amounting to a total of 156,000 frames of point clouds and images, thus enabling comprehensive analysis of the impact of different factors on person ReID. (3) Precision. The Livox Mid-100 LiDAR has a distance accuracy of \\(2\\mathrm{cm}\\) and an angular accuracy of \\(0.1^{\\circ}\\), which provides high-precision 3D structural information for ReID problems." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.596, + 0.473, + 0.688 + ], + "angle": 0, + "content": "Additionally, we introduce a simulated dataset, named LReID-sync, including 360,000 frames of point clouds for 600 pedestrians captured by multi-view synchronous LiDARs. LReID-sync comprises annotations for point cloud completion from single view to full views, and Skinned Multi-Person Linear Model (SMPL) parameters [24]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.473, + 0.902 + ], + "angle": 0, + "content": "Based on point clouds, the identification of pedestrians relies on their static anthropometric features, including height, body shape, and limb structure, as well as their dynamic gait features. Accurately extracting complete shape features of a pedestrian is beneficial for both aspects. To address this, we propose an efficient LiDAR-based framework, termed ReID3D. ReID3D utilizes a pre-training strategy to guide the encoder in learning 3D body features based on LReID-sync. Moreover, in order to extract discriminative static and dynamic features of pedestrians, the ReID network of ReID3D comprises a Graph-based Complementary Enhancement Encoder (GCEE) and a temporal module. Extensive experiments on LReID demonstrate the following: (1) ReID3D outperforms the state-of-the-art camera" + }, + { + "type": "text", + "bbox": [ + 0.497, + 0.092, + 0.892, + 0.197 + ], + "angle": 0, + "content": "based methods, particularly under low light, highlighting the significant potential of LiDAR in addressing person ReID tasks. (2) The use of LReID-sync for pre-training significantly enhances feature encoding capability of the model. (3) Compared to commonly used point cloud encoders, our GCEE exhibits a higher proficiency in extracting comprehensive and discriminative features." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.198, + 0.874, + 0.212 + ], + "angle": 0, + "content": "To summarize, our main contributions are as follows:" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.213, + 0.894, + 0.272 + ], + "angle": 0, + "content": "- To the best of our knowledge, this is the first work on LiDAR-based person ReID, demonstrating the practicality of utilizing LiDAR for person ReID in challenging real-world outdoor scenes." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.273, + 0.894, + 0.363 + ], + "angle": 0, + "content": "- We build LReID, the first LiDAR-based person ReID dataset, which is collected in several outdoor scenes with variations in natural conditions. Moreover, we introduce LReID-sync, a new simulated pedestrian dataset designed for pre-training ReID models with tasks of point cloud completion and shape parameter learning." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.364, + 0.894, + 0.455 + ], + "angle": 0, + "content": "- We propose a LiDAR-based ReID framework, termed ReID3D, that utilizes pre-training strategy to guide the encoder in learning 3D body features and introduces GCEE for extracting comprehensive and discriminative features. Experimental results on dataset LReID indicate that ReID3D outperforms camera-based methods." + }, + { + "type": "list", + "bbox": [ + 0.498, + 0.213, + 0.894, + 0.455 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.466, + 0.642, + 0.481 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.497, + 0.491, + 0.892, + 0.702 + ], + "angle": 0, + "content": "Person ReID. Camera-based ReID has been extensively researched in the past decades. Researchers have employed various convolutional neural networks [48] to extract human features from images or videos. Some video-based ReID models adopt recurrent neural networks (RNNs) [25, 45, 57] or transformer blocks [6, 56] to aggregate temporal features. These models primarily focus on extracting appearance features, which serve as efficient but short-lived identifiers. By contrast, intrinsic and behavioral features exhibit minimal change over time. Given the constraints of using cameras at night, infrared sensors have been introduced for RGB-IR cross-modality person ReID [29, 42]. However, the infrared sensor only captures 2D single-channel intensity information, constraining its perceptive ability." + }, + { + "type": "text", + "bbox": [ + 0.497, + 0.703, + 0.892, + 0.853 + ], + "angle": 0, + "content": "In order to extract intrinsic features of individuals, researches on ReID utilizing Kinect [28, 32] and radar [7] have emerged. Kinect and radar provide 3D structural information to help the model extract physiological and behavioral features, reducing reliance on the appearance of individuals [10, 32]. However, they are constrained by significant hardware limitations [7, 17]. In comparison, LiDAR serves as a more advantageous option, offering superior practicality. Despite this, LiDAR-based person ReID has not been researched." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.894, + 0.903 + ], + "angle": 0, + "content": "Point Cloud Completion. Point cloud completion is the task to predict missing parts based on the rest of the point" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17438" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.272, + 0.089, + 0.697, + 0.104 + ], + "angle": 0, + "content": "Table 1. Comparison of publicly available 3D datasets for person ReID." + }, + { + "type": "table", + "bbox": [ + 0.123, + 0.109, + 0.846, + 0.187 + ], + "angle": 0, + "content": "
DatasetYearIdentitySensorSceneUnscriptedNatural diversityOcclusion
RGBD-ID [3]2012801 KinectIndoorXXX
BIWI RGBD-ID [27]2014501 KinectIndoorXXX
Kinect-REID [30]2015711 KinectIndoorXXX
LReLUID20233204 LiDARs + 4 CamerasOutdoor✓✓✓
LReLUID-sync20236004 LiDARsSimulation✓X✓
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.206, + 0.468, + 0.297 + ], + "angle": 0, + "content": "cloud. To accomplish this, networks need to learn the intrinsic geometric structures and semantic knowledge of the 3D object. Additionally, the learned representations can be transferred to downstream tasks. The entire process does not require human annotations and therefore falls under the category of unsupervised representation learning [44]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.297, + 0.468, + 0.388 + ], + "angle": 0, + "content": "Point cloud completion has received increasing attention in the past decade [13, 16, 23, 40]. In terms of completing the missing parts caused by a single viewpoint, Wang et al. [36] utilize an encoder-decoder model to recover the occluded points. However, there has been limited research focusing on point cloud completion for pedestrians." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.406, + 0.468, + 0.648 + ], + "angle": 0, + "content": "Person ReID Dataset. Depending on the used representations, person ReID datasets can be classified into 2D and 3D datasets. Due to the early emergence and widespread use of cameras, 2D datasets are mainly composed of camera-based datasets [12, 21, 22, 37, 54, 55], which have advanced research in person ReID. In addition, some 2D datasets utilize infrared cameras as sensors [29, 42]. Kinect-based datasets [3, 27, 30] serve as typical examples of 3D datasets. However, the current Kinect datasets have limited scales as they are often collected in small indoor scenes with only one cooperative subject. Additionally, Cheng and Liu [7] collected a radar dataset containing 40 identities, but it is not publicly available and also involves only one cooperative subject in each frame. To address these limitations, we introduce a novel LiDAR-based 3D dataset. The comparison of publicly available 3D datasets is shown in Tab. 1." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.661, + 0.168, + 0.677 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.687, + 0.468, + 0.807 + ], + "angle": 0, + "content": "ReID3D adopts multi-task pre-training to guide the encoder in learning 3D body features based on LReID-sync, as shown in Fig. 2. The ReID network of ReID3D comprises a Graph-based Complementary Enhancement Encoder (GCEE), which consists of a GCN backbone and a Complementary Feature Extractor (CFE), along with a temporal module, as shown in Fig. 3. The pre-trained GCEE is used to initialize the ReID network." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.817, + 0.365, + 0.833 + ], + "angle": 0, + "content": "3.1. Pre-training with Multiple Tasks" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Based on our observations, the crucial factors that are likely to impact the performance of ReID models are (1) the variations in information resulted from different viewpoints under cross-view settings, and (2) the incomplete information" + }, + { + "type": "image", + "bbox": [ + 0.518, + 0.202, + 0.871, + 0.337 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.344, + 0.892, + 0.387 + ], + "angle": 0, + "content": "Figure 2. The pre-training approach of ReID3D. Simulated single-view point cloud is taken as input, and the encoder is pre-trained for tasks of point cloud completion and SMPL parameter learning." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.403, + 0.892, + 0.538 + ], + "angle": 0, + "content": "acquired from single view. Besides, the collection and annotation of real-world data involve significant costs, while simulated data is low-cost, and comes with rich and accurate annotations. Hence, we leverage simulated data to pretrain the encoder for tasks of point cloud completion and SMPL parameter learning. The overall idea of our proposed pre-training approach is shown in Fig. 2, which enables the encoder to effectively extract anthropometric characteristics and mitigate the influence of viewpoint disparities." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.556, + 0.892, + 0.691 + ], + "angle": 0, + "content": "Multi-task Network. Throughout we define point cloud \\(\\mathcal{P}\\) as a set of points in 3D Euclidean space, \\(\\mathcal{P} = \\{p_i | i = 1, 2, \\dots, N\\}\\), where each point \\(p_i\\) can be represented by its coordinates \\((x_i, y_i, z_i)\\). The network is fed with the single-view point cloud \\(\\tilde{\\mathcal{P}}\\), then embed it into a latent vector \\(z\\) using encoder \\(\\Phi(\\cdot)\\). The first branch of the network focuses on the task of point cloud completion, where the decoder \\(\\Psi(\\cdot)\\) complete the point cloud based on \\(z\\). The process can be formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.642, + 0.699, + 0.891, + 0.716 + ], + "angle": 0, + "content": "\\[\n\\hat {\\mathcal {P}} = \\Psi (\\Phi (\\tilde {\\mathcal {P}})), \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.723, + 0.81, + 0.739 + ], + "angle": 0, + "content": "where \\(\\hat{\\mathcal{P}}\\) is the predicted complete point cloud." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.74, + 0.892, + 0.828 + ], + "angle": 0, + "content": "The second branch aims to learn the characteristics of human body, i.e. SMPL shape parameters \\(\\beta\\). The latent vector \\(z\\) is expected to encompass shape information. Therefore, a straightforward MLP network is utilized to convert \\(z\\) into predicted SMPL shape parameters \\(\\hat{\\beta}\\). The process can be formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.633, + 0.836, + 0.891, + 0.853 + ], + "angle": 0, + "content": "\\[\n\\hat {\\beta} = \\operatorname {M L P} (\\Phi (\\tilde {\\mathcal {P}})). \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.871, + 0.891, + 0.901 + ], + "angle": 0, + "content": "Training. We adapt the folding-based decoder PCN [49] to complete the single-view point cloud in two steps, out" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17439" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.159, + 0.087, + 0.817, + 0.29 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.301, + 0.895, + 0.345 + ], + "angle": 0, + "content": "Figure 3. The ReID network of ReID3D. The Graph-based Complementary Enhancement Encoder (GCEE) extracts frame-level features from the pedestrian point clouds, and the transformer module aggregates the sequential features. GCEE consists of a GCN backbone and a Complementary Feature Extractor (CFE)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.361, + 0.473, + 0.44 + ], + "angle": 0, + "content": "putting a coarse shape \\(\\hat{\\mathcal{P}}_{\\mathrm{coarse}}\\) and a detailed shape \\(\\hat{\\mathcal{P}}_{\\mathrm{detail}}\\). The pre-training model is trained with a combined loss corresponding to the two branches. In the branch of point clout completion, we use Chamfer Distance (CD) as the difference measure between prediction \\(\\hat{\\mathcal{P}}\\) and ground-truth \\(\\mathcal{V}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.077, + 0.447, + 0.47, + 0.499 + ], + "angle": 0, + "content": "\\[\n\\operatorname {C D} (\\hat {\\mathcal {P}}, \\mathcal {Y}) = \\frac {1}{| \\hat {\\mathcal {P}} |} \\sum_ {\\hat {p} \\in \\hat {\\mathcal {P}}} \\min _ {p \\in \\mathcal {Y}} \\| \\hat {p} - p \\| + \\frac {1}{| \\mathcal {Y} |} \\sum_ {p \\in \\mathcal {Y}} \\min _ {\\hat {p} \\in \\hat {\\mathcal {P}}} \\| p - \\hat {p} \\|. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.5, + 0.471, + 0.546 + ], + "angle": 0, + "content": "The loss of the completion branch is a sum of the Chamfer distances on the coarse and detailed shapes weighted by a hyperparameter \\(\\delta\\):" + }, + { + "type": "equation", + "bbox": [ + 0.134, + 0.555, + 0.47, + 0.573 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\mathrm {c o m}} = \\mathrm {C D} (\\hat {\\mathcal {P}} _ {\\text {c o a r s e}}, \\mathcal {Y}) + \\delta \\mathrm {C D} (\\hat {\\mathcal {P}} _ {\\text {d e t a i l}}, \\mathcal {Y}). \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.583, + 0.47, + 0.614 + ], + "angle": 0, + "content": "The branch of shape parameter learning utilizes mean squared error (MSE) as the loss function:" + }, + { + "type": "equation", + "bbox": [ + 0.184, + 0.623, + 0.47, + 0.662 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {s h a p e}} = \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\left(\\beta_ {i} - \\hat {\\beta} _ {i}\\right) ^ {2}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.672, + 0.364, + 0.685 + ], + "angle": 0, + "content": "where \\(n\\) is the dimension of \\(\\beta\\), i.e. \\(n = 10\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.687, + 0.47, + 0.717 + ], + "angle": 0, + "content": "The pre-training loss is a combination of the two branches with a weighted hyperparameter \\(\\eta\\):" + }, + { + "type": "equation", + "bbox": [ + 0.203, + 0.729, + 0.47, + 0.745 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {\\text {c o m}} + \\eta \\mathcal {L} _ {\\text {s h a p e}}. \\tag {6}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.754, + 0.228, + 0.768 + ], + "angle": 0, + "content": "3.2. ReID Network" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.777, + 0.471, + 0.839 + ], + "angle": 0, + "content": "To extract spatio-temporal features from the sequence of point clouds, the ReID Network of ReID3D comprises a GCEE, which consists of a GCN backbone and CFE, along with a temporal module, as illustrated in Fig. 3." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.471, + 0.901 + ], + "angle": 0, + "content": "GCN Backbone. To extract local and global features from point clouds effectively, we employ graph convolutional structure as the backbone. We construct the directed" + }, + { + "type": "image", + "bbox": [ + 0.543, + 0.36, + 0.853, + 0.472 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.529, + 0.48, + 0.863, + 0.494 + ], + "angle": 0, + "content": "Figure 4. The architecture of the Eraser module in CFE." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.528, + 0.892, + 0.65 + ], + "angle": 0, + "content": "graph \\(\\mathcal{G}(\\mathcal{V},\\mathcal{E})\\) by using the k-nearest neighbors (KNN) of each point including self-loop, where \\(\\mathcal{V}\\) represents the points and \\(\\mathcal{E}\\) represents the set of edges. For the original point cloud, we construct the graph based on the nearest neighbors in its coordinate space. However, we update the graph at each layer of the network in feature space based on the feature similarity among points, rather than fixed spatial positions." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.654, + 0.892, + 0.774 + ], + "angle": 0, + "content": "Denote that \\( p_i \\) is the central point of once graph convolution operation, and \\( \\mathcal{N}(i) = \\{j | (i, j) \\in \\mathcal{E}\\} \\) is the set of points in its neighborhood with features \\( \\mathcal{F}(i) = \\{f_j | j \\in \\mathcal{N}(i)\\} \\). To integrate the global shape structure and local neighborhood feature differences [39], we define \\( f_{ij} = [f_i, f_j - f_i] \\) as the input feature, where \\( [\\cdot, \\cdot] \\) is the concatenation operation. The convolution process can be formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.615, + 0.792, + 0.892, + 0.819 + ], + "angle": 0, + "content": "\\[\nf _ {i} ^ {\\prime} = \\max _ {j \\in \\mathcal {N} (i)} \\sigma \\left(f _ {i j} \\times k\\right), \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.839, + 0.895, + 0.903 + ], + "angle": 0, + "content": "where \\( f_{i}^{\\prime} \\) is the output feature of the central point \\( p_i \\), \\( k \\) is the convolution kernel, max is a channel-wise max-pooling function, \\( \\times \\) represents matrix multiplication and \\( \\sigma(\\cdot) \\) is the activation function LeakyReLU." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "17440" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.212 + ], + "angle": 0, + "content": "Complementary Feature Extractor. One viable method for extracting frame-level pedestrian features is to apply pooling directly to the features output by the GCN backbone. However, applying the same operation to each frame results in highly redundant extraction, which only emphasizes a part of the most salient features. To this end, inspired by [15], we design CFE to extract complementary features and improving representation learning of the encoder." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.213, + 0.471, + 0.499 + ], + "angle": 0, + "content": "For each frame in a sequence, we consider it as the primary frame. The CFE further extracts its features based on the output of the GCN backbone. Then, the next frame is taken as the supplementary frame, from which the Eraser module erases the previously discovered salient features. We duplicate the last frame \\(\\mathcal{P}_n\\) as its own supplementary frame. In particular, for a sequence of point clouds \\(\\{\\mathcal{P}_i\\}_{i=1}^n (\\mathcal{P}_i \\in \\mathbb{R}^{N \\times 3})\\), the feature sequence \\(\\{\\mathcal{F}_i\\}_{i=1}^n (\\mathcal{F}_i \\in \\mathbb{R}^{N \\times D})\\) is obtained by the GCN backbone, where \\(N\\) is the number of points and \\(D\\) is the dimension of features. For the primary frame, CFE utilizes a graph convolution layer and a global max-pooling layer to extract the most salient features \\(f_{\\mathrm{p}} \\in \\mathbb{R}^{1 \\times D_{\\mathrm{c}}}\\). Then, the Eraser module reconstructs the features of the supplementary frame \\(\\mathcal{F}_{\\mathrm{s}}\\) guided by the discovered features \\(f_{\\mathrm{p}}\\). The reconstructed features \\(\\mathcal{F}_{\\mathrm{s}}'\\) is fed into similar graph convolution layer and global max-pooling layer to extract auxiliary features \\(f_{\\mathrm{s}}\\). \\(f_{\\mathrm{p}}\\) and \\(f_{\\mathrm{s}}\\) are concatenated to obtain the complementary features \\(f_{\\mathrm{cfe}} \\in \\mathbb{R}^{1 \\times 2D_{\\mathrm{c}}}\\) of the primary frame." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.5, + 0.47, + 0.576 + ], + "angle": 0, + "content": "The architecture of the Erasure module is shown in Fig. 4. Firstly, the correlation layer is used to obtain the correlation vector \\( R \\in \\mathbb{R}^{N \\times 1} \\) between \\( \\mathcal{F}_{\\mathrm{s}} \\) and \\( f_{\\mathrm{p}} \\), through computing the semantic relevance between \\( f_{\\mathrm{p}} \\) and all the local descriptors of \\( \\mathcal{F}_{\\mathrm{s}} \\), formulated as:" + }, + { + "type": "equation", + "bbox": [ + 0.199, + 0.584, + 0.47, + 0.603 + ], + "angle": 0, + "content": "\\[\nR = \\mathcal {F} _ {\\mathrm {s}} \\times \\left(f _ {\\mathrm {p}} \\times \\omega\\right) ^ {T}, \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.611, + 0.47, + 0.779 + ], + "angle": 0, + "content": "where \\(\\omega \\in \\mathbb{R}^{D_{\\mathrm{c}} \\times D}\\) is a learnable variable projecting \\(f_{\\mathrm{p}}\\) to the feature space of \\(\\mathcal{F}_{\\mathrm{s}}\\). Then, the Binarization module generates the binary mask based on \\(R\\) to identify the points to be erased. Specifically, for each point in \\(\\mathcal{F}_{\\mathrm{s}}\\), calculate the sum of the correlation values of the point and its \\(K_{\\mathrm{B}}\\) nearest neighbors in the feature space. The calculated sum represents the correlation of the region centered on the point. We select the region with the highest correlation value to be erased, through setting the corresponding value in the binary mask \\(B\\) to 0 and others to 1. Finally, \\(\\mathcal{F}_{\\mathrm{s}}\\) is erased according to \\(B\\) to obtain the reconstructed features \\(\\mathcal{F}_{\\mathrm{s}}'\\)." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Temporal Fusion Module. The sequence of pedestrian point clouds includes distinctive dynamic features, such as gait frequency and amplitude of limb swings. We utilize a transformer module [35] with four encoder layers to extract the dynamic features. The transformer module takes the sequence of features \\(\\{f_{\\mathrm{cfe}}^i\\}_{i = 1}^n\\) as input and outputs the final features \\(f\\in \\mathbb{R}^{D_{\\mathrm{T}}}\\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.152 + ], + "angle": 0, + "content": "Training and Inference. Following the standard paradigm of camera-based ReID [5, 15, 46, 52], we exploit a combination of cross-entropy and batch-hard triplet terms [14] as the loss function, with the hyperparameter \\(\\gamma\\):" + }, + { + "type": "equation", + "bbox": [ + 0.638, + 0.159, + 0.892, + 0.175 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {\\mathrm {c e}} + \\gamma \\mathcal {L} _ {\\mathrm {t r i}}. \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.181, + 0.892, + 0.212 + ], + "angle": 0, + "content": "During inference, the similarity between query and gallery set is measured using the cosine distance." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.222, + 0.7, + 0.238 + ], + "angle": 0, + "content": "4. Person ReID Dataset" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.247, + 0.892, + 0.354 + ], + "angle": 0, + "content": "In this paper, we build a real-world LiDAR-based ReID dataset LReID and a simulated pedestrian point cloud dataset LReID-sync. LReID is captured by a multimodal imaging system, which consists of 4 Livox Mid-100 LiDAR sensors and 4 industrial cameras [51]. LReID includes 320 identities, 156,000 point cloud frames and synchronized RGB images with corresponding 2D and 3D annotations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.37, + 0.892, + 0.506 + ], + "angle": 0, + "content": "Data Acquisition. LReID is collected in two extensive outdoor scenes: a crossroad and a square in front of a building, capturing different time periods and weather conditions, as shown in Fig. 6. We synchronize each pair of LiDAR and camera with \\(\\sim 5\\) ms accuracy and provide an accurate extrinsic and intrinsic calibration. All sequences are recorded with a frame rate of \\(10\\mathrm{Hz}\\). The images are captured of a resolution of \\(2048\\times 1536\\) pixels and the density of LiDAR points is about 30,000 points per frame." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.507, + 0.892, + 0.688 + ], + "angle": 0, + "content": "The square scene is located in front of a building with frequent pedestrian traffic, and many pedestrians walk together in groups, which makes it more complex for person ReID tasks. We collected data in the square scene during two different times in summer to analyze the impact of lighting conditions on person ReID. Additionally, to explore the impact of different scenes, weather conditions, and pedestrian attire in different seasons, we also collected data at a crossroads scene in winter. Figure 5 shows the samples of two pedestrians collected from different scenes. Furthermore, we analyze the point distribution in LReID and LReID-sync, as shown in Fig. 6." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.705, + 0.892, + 0.84 + ], + "angle": 0, + "content": "Annotations. To ensure efficient and accurate annotation, we utilize a point cloud-based 3D detector [18] to locate pedestrians. Additionally, we employ a 3D multi-object tracking method [41] to establish continuous trajectories, and manually rectify them. Furthermore, we adjust the IDs of the pedestrians that appeared repeatedly in the field of view based on the images. After obtaining precise 3D ReID annotations, we project them onto synchronized RGB images and perform manual corrections." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "To avoid the influence of absolute coordinate information on the network, we normalize the pedestrian point clouds by subtracting the center coordinates of their respective bounding boxes." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "17441" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.102, + 0.089, + 0.155, + 0.177 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.161, + 0.089, + 0.312, + 0.177 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.315, + 0.09, + 0.403, + 0.177 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.405, + 0.091, + 0.508, + 0.177 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.101, + 0.18, + 0.155, + 0.26 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.16, + 0.18, + 0.311, + 0.26 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.312, + 0.18, + 0.401, + 0.26 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.403, + 0.18, + 0.507, + 0.26 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.1, + 0.272, + 0.51, + 0.3 + ], + "angle": 0, + "content": "Figure 5. Samples of two pedestrians collected from the square scene in summer (top row), and the crossroads scene in winter (bottom row)." + }, + { + "type": "image", + "bbox": [ + 0.568, + 0.089, + 0.86, + 0.26 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.556, + 0.272, + 0.871, + 0.3 + ], + "angle": 0, + "content": "Figure 6. Data acquisition scenes and statistics about points in LReID and LReID-sync (lower right)." + }, + { + "type": "image", + "bbox": [ + 0.085, + 0.337, + 0.462, + 0.42 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.431, + 0.47, + 0.459 + ], + "angle": 0, + "content": "Figure 7. Samples of LReid-sync for full views and each single view." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.487, + 0.47, + 0.607 + ], + "angle": 0, + "content": "Evaluation. LReID is divided into two splits: a training set with 220 identities and a test set with the remaining 100 identities. Both sets include different scenes, seasons, and lighting conditions. Within the test set, 30 identities are captured under low light, whereas 70 identities are captured under normal light. Following the standard paradigm of video-based datasets [20, 43, 55], the evaluation focuses on recognition across different LiDARs." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.609, + 0.47, + 0.775 + ], + "angle": 0, + "content": "We select one sample of each identity in the test set to build the query set and use the other samples as the gallery set. In the test set, we ensure that the data collected by different LiDARs does not overlap in time, which is to prevent the model from recognizing individuals based on human pose at a certain time. To maximize the use of training data, we divide the sequences in training set into several fragments that may partially overlap in time. The evaluation metrics for LReID include Cumulative Matching Characteristics (CMC) and mean Average Precision (mAP), which are consistent with camera-based datasets." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.471, + 0.903 + ], + "angle": 0, + "content": "LReLU-sync. LReLU-sync is a novel pedestrian dataset generated using the software Unity3D, which simulates pedestrians in scenes captured by multiple synchronized LiDARs from various views, as shown in Fig. 7. With this setup, LReLU-sync accurately simulates the information loss and point cloud sparsity that occur when pedestrians are captured using a single-view LiDAR. Additionally," + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.339, + 0.892, + 0.43 + ], + "angle": 0, + "content": "LReID-sync includes annotations for point cloud completion from single view to full views, as well as SMPL parameters. Therefore, LReID-sync can be utilized for pretraining. LReID-sync comprises 600 pedestrians with various actions, each exhibiting unique body shapes and gaits, ensuring diversity within the dataset." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.442, + 0.634, + 0.459 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.467, + 0.718, + 0.483 + ], + "angle": 0, + "content": "5.1. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.49, + 0.893, + 0.687 + ], + "angle": 0, + "content": "ReID Network. The ReID network is trained for 700 epochs using the AdamW optimizer with a weight decay of 5e-5. The learning rate, initially set to 5e-5, is updated using a Cosine Annealing Learning Rate (CosineAnnealingLR) scheduler with a cycle of 200 epochs. Each frame of pedestrian point clouds in LReID is upsampled or downsampled to 256 points as input to the network. To train our model, we randomly choose 6 identities, and sample 6 sequences for each identity with a sequence length of 30 frames. The loss weight \\(\\gamma\\) is set to 1. The neighborhood size is set to 10 and 8 for each graph convolution layer and Binarization module, respectively. And the feature dimensions \\(D\\), \\(D_{\\mathrm{C}}\\) and \\(D_{\\mathrm{T}}\\) are set to 512, 512 and 1024, respectively." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.704, + 0.892, + 0.839 + ], + "angle": 0, + "content": "Pre-training. The pre-training model follows a similar training strategy as described above, except that the initial learning rate is set to 1e-4. The loss weight \\(\\eta\\) is set to 1. The coefficient \\(\\delta\\) in Eq. 4 is set to 0.01 for the first 100 epochs, then increased to 0.1, 0.5 and 1.0 after 100, 200 and 400 epochs. The coarse shape \\(\\hat{\\mathcal{P}}_{\\mathrm{coarse}}\\) contains 128 points, while the detailed shape \\(\\hat{\\mathcal{P}}_{\\mathrm{detail}}\\) contains 512 points. The weights of the pre-trained GCEE are used as initialization for the ReID network." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.848, + 0.857, + 0.864 + ], + "angle": 0, + "content": "5.2. Comparison with Camera-based Methods" + }, + { + "type": "text", + "bbox": [ + 0.5, + 0.871, + 0.892, + 0.901 + ], + "angle": 0, + "content": "We compare ReID3D with the state-of-the-art video-based methods [2, 9, 15, 50]. The input images are resized in the" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17442" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.089, + 0.892, + 0.119 + ], + "angle": 0, + "content": "Table 2. Comparison with state-of-the-art camera-based methods on LReID. Numbers in bold indicate the best performance and underscored ones are the second best. To ensure fairness, ReID3D without pre-training is evaluated." + }, + { + "type": "table", + "bbox": [ + 0.116, + 0.125, + 0.857, + 0.226 + ], + "angle": 0, + "content": "
MethodVenueModalityNormal lightLow lightOverall
Rank-1Rank-3mAPRank-1Rank-3mAPRank-1Rank-3mAP
TCLNet [15]ECCV 2020Camera98.698.694.8860.073.346.1887.091.080.27
STMN [9]ICCV 202194.398.693.8130.050.031.1775.084.075.02
SINet [2]CVPR 202297.1100.094.6343.360.043.9781.088.079.43
PiT [50]TII 202294.395.786.2133.360.035.7476.085.071.07
B-ReID3DOursLiDAR90.097.182.0490.093.381.6490.096.081.92
ReID3DOurs94.398.683.6593.396.782.4394.098.083.28
" + }, + { + "type": "table_footnote", + "bbox": [ + 0.136, + 0.227, + 0.361, + 0.241 + ], + "angle": 0, + "content": "B-ReID3D: ReID3D without pre-training." + }, + { + "type": "table_caption", + "bbox": [ + 0.11, + 0.262, + 0.437, + 0.276 + ], + "angle": 0, + "content": "Table 3. Comparison for different pre-training method." + }, + { + "type": "table", + "bbox": [ + 0.11, + 0.283, + 0.436, + 0.349 + ], + "angle": 0, + "content": "
Pre-training MethodRank-1Rank-3mAP
Baseline(w/o pre-training)90.096.081.92
ReID91.096.082.13
Completion93.097.082.73
Completion + SMPL94.098.083.28
" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.369, + 0.47, + 0.414 + ], + "angle": 0, + "content": "resolution of \\(128 \\times 64\\). To ensure fairness, ReID3D without pre-training (B-ReID3D) is also evaluated. All methods are evaluated with the same dataset settings and metrics." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.415, + 0.471, + 0.611 + ], + "angle": 0, + "content": "The comparative results are shown in Tab. 2, from which the following observations can be obtained: (1) ReID3D and B-ReID3D demonstrate their superiority to the video-based methods, primarily benefiting from the utilization of point clouds, which is unaffected by lighting conditions and complex background. (2) ReID3D achieves state-of-the-art results in overall and low light conditions, but it falls behind video-based methods in normal light conditions. This is because video-based methods make full use of appearance information under normal light. (3) Video-based methods perform poorly under low light, while ReID3D and B-ReID3D demonstrate comparable reliability under both low light and normal light." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.621, + 0.21, + 0.637 + ], + "angle": 0, + "content": "5.3. Pre-training" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.644, + 0.473, + 0.903 + ], + "angle": 0, + "content": "To demonstrate the effectiveness of pre-training with simulated dataset LReID-sync, we evaluate the performance of different pre-training method. The following four methods are evaluated: (1) ReID3D without pre-training. (2) Pretraining with similar ReID task, in which the pre-training model and loss are consistent with the ReID network. (3) Pre-training with only the branch of point cloud completion. (4) Pre-training with multiple tasks, as described in Section 3.1. The experimental results are shown in Tab. 3. It can be observed that pre-training with multiple tasks makes an improvement to the accuracy of ReID3D, with the rank-1 accuracy increasing from 90.0 to 94.0. This improvement can be attributed to two factors: (1) The simulated data comprises a diverse collection of pedestrian point clouds with various body shapes, which supplements the real-world data. (2) Multi-task pre-training effectively leverages the performance of the encoder. Besides, pre-training with" + }, + { + "type": "image", + "bbox": [ + 0.511, + 0.261, + 0.691, + 0.365 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.591, + 0.367, + 0.609, + 0.379 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.706, + 0.261, + 0.884, + 0.365 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.786, + 0.367, + 0.803, + 0.379 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image", + "bbox": [ + 0.512, + 0.382, + 0.688, + 0.486 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.591, + 0.489, + 0.609, + 0.5 + ], + "angle": 0, + "content": "(c)" + }, + { + "type": "image", + "bbox": [ + 0.706, + 0.382, + 0.884, + 0.486 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.786, + 0.489, + 0.804, + 0.5 + ], + "angle": 0, + "content": "(d)" + }, + { + "type": "image_caption", + "bbox": [ + 0.498, + 0.507, + 0.892, + 0.577 + ], + "angle": 0, + "content": "Figure 8. Completion results for real-world pedestrian point clouds obtained by the pre-trained model. In each sample, the detailed shape, coarse shape, and image are shown from left to right. The red points represent the input point cloud, and the blue points represent the predicted complete point cloud." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.598, + 0.891, + 0.628 + ], + "angle": 0, + "content": "task of ReID or point cloud completion also leads to an improvement in performance." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.63, + 0.893, + 0.901 + ], + "angle": 0, + "content": "To showcase the robust feature encoding capabilities attained by the encoder through pre-training, we visualize the completion results for several real-world pedestrian point clouds with different characteristics, as shown in Fig. 8. We can observe that: (1) Intuitively, the detailed and coarse shape closely resemble the actual human shape, which indicates that the encoder has successfully captured the complete features of the human body. (2) The detailed shape is an extension based on the coarse shape, with higher resolution and more information. (3) The pre-trained encoder has the ability to estimate the features of the missing part in the point cloud. As shown in Fig. 8a, the unobserved parts of the legs are accurately completed. (4) Due to motion blur or object carrying, the point cloud may contain some noise points. For example, in Fig. 8b and Fig. 8c, there are red noise points located between the legs and from the carrying bags, respectively. However, the model can effectively filter out the noise points that do not conform to the body shape." + }, + { + "type": "page_number", + "bbox": [ + 0.48, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17443" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.095, + 0.09, + 0.452, + 0.103 + ], + "angle": 0, + "content": "Table 4. Performance of B-ReID3D with different encoders." + }, + { + "type": "table", + "bbox": [ + 0.12, + 0.111, + 0.428, + 0.176 + ], + "angle": 0, + "content": "
EncoderRank-1Rank-3mAP
PointNet [31]74.088.060.31
Point Transformer [53]83.093.074.86
3DCNN [8]34.051.028.27
GCEE90.096.081.92
" + }, + { + "type": "table_caption", + "bbox": [ + 0.084, + 0.192, + 0.462, + 0.206 + ], + "angle": 0, + "content": "Table 5. Ablation study on the CFE module and Eraser module." + }, + { + "type": "table", + "bbox": [ + 0.121, + 0.213, + 0.428, + 0.267 + ], + "angle": 0, + "content": "
Encoder TypeRank-1Rank-3mAP
B-ReID3D-w/o CFE83.094.074.15
B-ReID3D-w/o Eraser85.095.080.47
B-ReID3D90.096.081.92
" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.294, + 0.23, + 0.31 + ], + "angle": 0, + "content": "5.4. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.318, + 0.473, + 0.545 + ], + "angle": 0, + "content": "Effect of Encoders. To evaluate the effectiveness of our GCEE, we also implement several commonly used encoders in point cloud tasks to replace GCEE in the ReID network for comparison, including PointNet [31], Point Transformer [53], and 3DCNN [8]. All methods use consistent training strategies and employ a same transformer module as the temporal fusion network. We report the results on LReID in Tab. 4, obtaining the following observations: (1) GCEE outperforms other encoders, which is mainly beneficial by its flexible graph structure in the feature space and the strategy of complementary enhancement. (2) Point-based encoders are superior to voxel-based encoder 3DCNN, which indicates that point-based encoders can provide a more detailed understanding of humans in tasks like ReID." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.572, + 0.47, + 0.769 + ], + "angle": 0, + "content": "Effect of CFE. CFE is a crucial component in our proposed encoder, used to extract complementary features. We compared our full model with two ablated versions: one without CFE and another without the Eraser module, as shown in Tab. 5. Removing CFE results in a lower rank-1 accuracy, with a score of 83.0 compared to our 90.0, which highlights the effectiveness of the complementary enhancement in constructing distinctive and comprehensive features. While removing the Eraser module retains the features of the complementary frame, it might lead to the extraction of similar features from the primary frame, thus restricting the improvement in accuracy, with a score of 85.0 compared to 83.0 of the version without CFE." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.795, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Effect of the Temporal Module. We evaluate the effectiveness of different temporal modules in combination with GCEE, as shown in Tab. 6. We can observe that the attention-based transformer structure demonstrates significant superiority over the LSTM structure. The rank-1 accuracy of transformer exceeds that of LSTM by 8 points, and that of BiLSTM by 10 points." + }, + { + "type": "table_caption", + "bbox": [ + 0.507, + 0.09, + 0.885, + 0.104 + ], + "angle": 0, + "content": "Table 6. Results of B-ReID3D with different temporal modules." + }, + { + "type": "table", + "bbox": [ + 0.557, + 0.108, + 0.838, + 0.161 + ], + "angle": 0, + "content": "
Temporal ModuleRank-1Rank-3mAP
LSTM [11]82.089.072.34
Bi-LSTM [33]80.090.070.92
Transformer [35]90.096.081.92
" + }, + { + "type": "image", + "bbox": [ + 0.511, + 0.173, + 0.631, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.562, + 0.269, + 0.58, + 0.28 + ], + "angle": 0, + "content": "(a)" + }, + { + "type": "image", + "bbox": [ + 0.642, + 0.173, + 0.747, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.686, + 0.269, + 0.704, + 0.28 + ], + "angle": 0, + "content": "(b)" + }, + { + "type": "image", + "bbox": [ + 0.76, + 0.173, + 0.887, + 0.266 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.805, + 0.269, + 0.822, + 0.28 + ], + "angle": 0, + "content": "(c)" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.284, + 0.892, + 0.326 + ], + "angle": 0, + "content": "Figure 9. Feature visualization of CFE. The features of the primary frame and the supplementary frame are presented on left and right, respectively. The color bar on the right indicates the feature value." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.344, + 0.706, + 0.361 + ], + "angle": 0, + "content": "5.5. Visualization Analysis" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.368, + 0.892, + 0.549 + ], + "angle": 0, + "content": "For qualitative analysis, we visualize the feature values output by the two graph convolutional layers in the CFE, as shown in Fig. 9. Three samples are taken from different actions of a person in the test set of LReID, with each sample comprising two consecutive frames. In each sample, the features of the primary frame and the supplementary frame are presented. We can observe that primary ones pay more attention to the head and arms, potentially linked to the discriminative height parameter, while supplementary ones predominantly emphasize the torso and legs. The combination of them creates a complementary and comprehensive feature representation." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.563, + 0.627, + 0.578 + ], + "angle": 0, + "content": "6. Conclusions" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.588, + 0.892, + 0.816 + ], + "angle": 0, + "content": "This paper presents the first research on person ReID using precise 3D structural information provided by LiDAR. Firstly, We propose a LiDAR-based ReID framework, named ReID3D, that utilizes pre-training to guide Graph-based Complementary Enhancement Encoder (GCEE) for extracting comprehensive 3D intrinsic features. Moreover, we build the first LiDAR-based person ReID dataset, termed LReID, which contains 320 pedestrians in various outdoor scenes and lighting conditions. Additionally, we introduce LReID-sync, a new simulated pedestrian dataset designed for pre-training encoders with tasks of point cloud completion and shape parameter learning. Our proposed ReID3D demonstrates exceptional performance on LReID, highlighting the significant potential of LiDAR in addressing person ReID tasks." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.829, + 0.661, + 0.845 + ], + "angle": 0, + "content": "Acknowledgement" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.853, + 0.892, + 0.899 + ], + "angle": 0, + "content": "This work is supported by the National Key Research and Development Program of China under Grant (2018AAA0102803)." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "17444" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.184 + ], + "angle": 0, + "content": "[1] Sk Miraj Ahmed, Aske R Lejbolle, Rameswar Panda, and Amit K Roy-Chowdhury. 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However, cameras often lack the perception of 3D morphological information of human and are susceptible to various limitations, such as inadequate illumination, complex background, and personal privacy. In this paper, we propose a LiDAR-based ReID framework, ReID3D, that utilizes pre-training strategy to retrieve features of 3D body shape and introduces Graph-based Complementary Enhancement Encoder for extracting comprehensive features. Due to the lack of LiDAR datasets, we build LReID, the first LiDAR-based person ReID dataset, which is collected in several outdoor scenes with variations in natural conditions. Additionally, we introduce LReID-sync, a simulated pedestrian dataset designed for pre-training encoders with tasks of point cloud completion and shape parameter learning. Extensive experiments on LReID show that ReID3D achieves exceptional performance with a rank-1 accuracy of 94.0, highlighting the significant potential of LiDAR in addressing person ReID tasks. To the best of our knowledge, we are the first to propose a solution for LiDAR-based ReID. The code and dataset are available at https://github.com/GWxuan/ReID3D. + +# 1. Introduction + +Person ReID has numerous practical applications, such as video surveillance, intelligent transportation and public security. Most ReID systems use cameras as sensors, aiming to recognize the same individual in images or videos caught by different cameras. With the development of computer vision technology, camera-based ReID has witnessed continuous advancements. However, certain challenges have not yet been effectively addressed. Firstly, cameras introduce limitations in terms of visual ambiguity caused by poor illu + +![](images/1a342af47cc0ca31e827bff81a9aeaad559435e0bbaa565d44b6dfd1f9b9f262.jpg) +Figure 1. Overview of camera-based and LiDAR-based person ReID. Camera-based methods primarily learn the 2D appearance of human, such as color of clothes, accessories, and shoes. LiDAR-based methods utilize 3D structural information to learn intrinsic features, such as height, body shape, and gait. + +mination and complex backgrounds [34]. Additionally, current camera-based ReID models primarily learn appearance information [47]. Therefore, variations in human appearance considerably impact the performance of models [19]. Furthermore, camera-based person ReID systems raise personal privacy issues [1, 4] for applications in some areas. + +In recent years, Kinect-based ReID approaches have been proposed [28, 32] to address these challenges by utilizing depth information. However, Kinect is primarily designed for indoor scenes and has a limited measurement range [17], restricting its applicability in large-scale outdoor scenarios. Recently, researchers have explored the use of radar for gait recognition, identity recognition, and person ReID [7, 26]. While radar is cost-effective, it suffers from poor angular and distance resolution, as well as a limited effective measurement range [7], which poses challenges in discriminating individuals with similar body shapes. + +In the past few years, LiDAR has been widely adopted in autonomous driving, driven by its improved accuracy and reduced costs [38]. The successful applications of LiDAR motivate us to explore its potential in person ReID within complex outdoor scenes. LiDAR can offer a broader measurement range and higher resolution, enabling precise perception about individuals in large-scale outdoor settings. + +LiDAR provides precise 3D structural information without being affected by lighting conditions or complex backgrounds, which enables the extraction of intrinsic features of individuals, such as height, body shape, and gait, irrespective of clothing color. LiDAR has been utilized in the task of gait recognition [34], which focuses on recognizing cooperative subjects walking along a specified route in small-scale scenes. However, ReID primarily focuses on the identification of unscripted pedestrians in large-scale scenes with a small sample size for each identity, which often requires multiple acquisition devices. In our work, we leverage low-cost LiDARs to tackle person ReID challenges, as shown in Fig. 1. + +To the best of our knowledge, this paper presents the first study on LiDAR-based person ReID. We build LReID, the first LiDAR-based ReID dataset to facilitate research on utilizing LiDAR point clouds for person ReID. We collect the dataset in several outdoor scenes using multiple collection nodes, each including a Livox Mid-100 LiDAR and an industrial camera. LReID offers several distinctive features: (1) Real-world scenes. The dataset is captured in outdoor scenes where pedestrians demonstrate unscripted behavior, leading to occlusions between pedestrians, as well as the presence of dynamic objects like vehicles and bicycles that may impact person ReID. (2) Data diversity. LReID encompasses dynamic data and annotations of 320 pedestrian gathered in varying seasons, times of day, and lighting conditions, amounting to a total of 156,000 frames of point clouds and images, thus enabling comprehensive analysis of the impact of different factors on person ReID. (3) Precision. The Livox Mid-100 LiDAR has a distance accuracy of $2\mathrm{cm}$ and an angular accuracy of $0.1^{\circ}$ , which provides high-precision 3D structural information for ReID problems. + +Additionally, we introduce a simulated dataset, named LReID-sync, including 360,000 frames of point clouds for 600 pedestrians captured by multi-view synchronous LiDARs. LReID-sync comprises annotations for point cloud completion from single view to full views, and Skinned Multi-Person Linear Model (SMPL) parameters [24]. + +Based on point clouds, the identification of pedestrians relies on their static anthropometric features, including height, body shape, and limb structure, as well as their dynamic gait features. Accurately extracting complete shape features of a pedestrian is beneficial for both aspects. To address this, we propose an efficient LiDAR-based framework, termed ReID3D. ReID3D utilizes a pre-training strategy to guide the encoder in learning 3D body features based on LReID-sync. Moreover, in order to extract discriminative static and dynamic features of pedestrians, the ReID network of ReID3D comprises a Graph-based Complementary Enhancement Encoder (GCEE) and a temporal module. Extensive experiments on LReID demonstrate the following: (1) ReID3D outperforms the state-of-the-art camera + +based methods, particularly under low light, highlighting the significant potential of LiDAR in addressing person ReID tasks. (2) The use of LReID-sync for pre-training significantly enhances feature encoding capability of the model. (3) Compared to commonly used point cloud encoders, our GCEE exhibits a higher proficiency in extracting comprehensive and discriminative features. + +To summarize, our main contributions are as follows: + +- To the best of our knowledge, this is the first work on LiDAR-based person ReID, demonstrating the practicality of utilizing LiDAR for person ReID in challenging real-world outdoor scenes. +- We build LReID, the first LiDAR-based person ReID dataset, which is collected in several outdoor scenes with variations in natural conditions. Moreover, we introduce LReID-sync, a new simulated pedestrian dataset designed for pre-training ReID models with tasks of point cloud completion and shape parameter learning. +- We propose a LiDAR-based ReID framework, termed ReID3D, that utilizes pre-training strategy to guide the encoder in learning 3D body features and introduces GCEE for extracting comprehensive and discriminative features. Experimental results on dataset LReID indicate that ReID3D outperforms camera-based methods. + +# 2. Related Work + +Person ReID. Camera-based ReID has been extensively researched in the past decades. Researchers have employed various convolutional neural networks [48] to extract human features from images or videos. Some video-based ReID models adopt recurrent neural networks (RNNs) [25, 45, 57] or transformer blocks [6, 56] to aggregate temporal features. These models primarily focus on extracting appearance features, which serve as efficient but short-lived identifiers. By contrast, intrinsic and behavioral features exhibit minimal change over time. Given the constraints of using cameras at night, infrared sensors have been introduced for RGB-IR cross-modality person ReID [29, 42]. However, the infrared sensor only captures 2D single-channel intensity information, constraining its perceptive ability. + +In order to extract intrinsic features of individuals, researches on ReID utilizing Kinect [28, 32] and radar [7] have emerged. Kinect and radar provide 3D structural information to help the model extract physiological and behavioral features, reducing reliance on the appearance of individuals [10, 32]. However, they are constrained by significant hardware limitations [7, 17]. In comparison, LiDAR serves as a more advantageous option, offering superior practicality. Despite this, LiDAR-based person ReID has not been researched. + +Point Cloud Completion. Point cloud completion is the task to predict missing parts based on the rest of the point + +Table 1. Comparison of publicly available 3D datasets for person ReID. + +
DatasetYearIdentitySensorSceneUnscriptedNatural diversityOcclusion
RGBD-ID [3]2012801 KinectIndoorXXX
BIWI RGBD-ID [27]2014501 KinectIndoorXXX
Kinect-REID [30]2015711 KinectIndoorXXX
LReLUID20233204 LiDARs + 4 CamerasOutdoor✓✓✓
LReLUID-sync20236004 LiDARsSimulation✓X✓
+ +cloud. To accomplish this, networks need to learn the intrinsic geometric structures and semantic knowledge of the 3D object. Additionally, the learned representations can be transferred to downstream tasks. The entire process does not require human annotations and therefore falls under the category of unsupervised representation learning [44]. + +Point cloud completion has received increasing attention in the past decade [13, 16, 23, 40]. In terms of completing the missing parts caused by a single viewpoint, Wang et al. [36] utilize an encoder-decoder model to recover the occluded points. However, there has been limited research focusing on point cloud completion for pedestrians. + +Person ReID Dataset. Depending on the used representations, person ReID datasets can be classified into 2D and 3D datasets. Due to the early emergence and widespread use of cameras, 2D datasets are mainly composed of camera-based datasets [12, 21, 22, 37, 54, 55], which have advanced research in person ReID. In addition, some 2D datasets utilize infrared cameras as sensors [29, 42]. Kinect-based datasets [3, 27, 30] serve as typical examples of 3D datasets. However, the current Kinect datasets have limited scales as they are often collected in small indoor scenes with only one cooperative subject. Additionally, Cheng and Liu [7] collected a radar dataset containing 40 identities, but it is not publicly available and also involves only one cooperative subject in each frame. To address these limitations, we introduce a novel LiDAR-based 3D dataset. The comparison of publicly available 3D datasets is shown in Tab. 1. + +# 3. Method + +ReID3D adopts multi-task pre-training to guide the encoder in learning 3D body features based on LReID-sync, as shown in Fig. 2. The ReID network of ReID3D comprises a Graph-based Complementary Enhancement Encoder (GCEE), which consists of a GCN backbone and a Complementary Feature Extractor (CFE), along with a temporal module, as shown in Fig. 3. The pre-trained GCEE is used to initialize the ReID network. + +# 3.1. Pre-training with Multiple Tasks + +Based on our observations, the crucial factors that are likely to impact the performance of ReID models are (1) the variations in information resulted from different viewpoints under cross-view settings, and (2) the incomplete information + +![](images/c9ed05b69b9fe1183be141a28aa1f188830702ac975aa67bc0eab954c79261f9.jpg) +Figure 2. The pre-training approach of ReID3D. Simulated single-view point cloud is taken as input, and the encoder is pre-trained for tasks of point cloud completion and SMPL parameter learning. + +acquired from single view. Besides, the collection and annotation of real-world data involve significant costs, while simulated data is low-cost, and comes with rich and accurate annotations. Hence, we leverage simulated data to pretrain the encoder for tasks of point cloud completion and SMPL parameter learning. The overall idea of our proposed pre-training approach is shown in Fig. 2, which enables the encoder to effectively extract anthropometric characteristics and mitigate the influence of viewpoint disparities. + +Multi-task Network. Throughout we define point cloud $\mathcal{P}$ as a set of points in 3D Euclidean space, $\mathcal{P} = \{p_i | i = 1, 2, \dots, N\}$ , where each point $p_i$ can be represented by its coordinates $(x_i, y_i, z_i)$ . The network is fed with the single-view point cloud $\tilde{\mathcal{P}}$ , then embed it into a latent vector $z$ using encoder $\Phi(\cdot)$ . The first branch of the network focuses on the task of point cloud completion, where the decoder $\Psi(\cdot)$ complete the point cloud based on $z$ . The process can be formulated as: + +$$ +\hat {\mathcal {P}} = \Psi (\Phi (\tilde {\mathcal {P}})), \tag {1} +$$ + +where $\hat{\mathcal{P}}$ is the predicted complete point cloud. + +The second branch aims to learn the characteristics of human body, i.e. SMPL shape parameters $\beta$ . The latent vector $z$ is expected to encompass shape information. Therefore, a straightforward MLP network is utilized to convert $z$ into predicted SMPL shape parameters $\hat{\beta}$ . The process can be formulated as: + +$$ +\hat {\beta} = \operatorname {M L P} (\Phi (\tilde {\mathcal {P}})). \tag {2} +$$ + +Training. We adapt the folding-based decoder PCN [49] to complete the single-view point cloud in two steps, out + +![](images/c1716af5e8585a4893af676074ce35926b2611f766bf1a43fe04ee862da2fa73.jpg) +Figure 3. The ReID network of ReID3D. The Graph-based Complementary Enhancement Encoder (GCEE) extracts frame-level features from the pedestrian point clouds, and the transformer module aggregates the sequential features. GCEE consists of a GCN backbone and a Complementary Feature Extractor (CFE). + +putting a coarse shape $\hat{\mathcal{P}}_{\mathrm{coarse}}$ and a detailed shape $\hat{\mathcal{P}}_{\mathrm{detail}}$ . The pre-training model is trained with a combined loss corresponding to the two branches. In the branch of point clout completion, we use Chamfer Distance (CD) as the difference measure between prediction $\hat{\mathcal{P}}$ and ground-truth $\mathcal{V}$ : + +$$ +\operatorname {C D} (\hat {\mathcal {P}}, \mathcal {Y}) = \frac {1}{| \hat {\mathcal {P}} |} \sum_ {\hat {p} \in \hat {\mathcal {P}}} \min _ {p \in \mathcal {Y}} \| \hat {p} - p \| + \frac {1}{| \mathcal {Y} |} \sum_ {p \in \mathcal {Y}} \min _ {\hat {p} \in \hat {\mathcal {P}}} \| p - \hat {p} \|. \tag {3} +$$ + +The loss of the completion branch is a sum of the Chamfer distances on the coarse and detailed shapes weighted by a hyperparameter $\delta$ : + +$$ +\mathcal {L} _ {\mathrm {c o m}} = \mathrm {C D} (\hat {\mathcal {P}} _ {\text {c o a r s e}}, \mathcal {Y}) + \delta \mathrm {C D} (\hat {\mathcal {P}} _ {\text {d e t a i l}}, \mathcal {Y}). \tag {4} +$$ + +The branch of shape parameter learning utilizes mean squared error (MSE) as the loss function: + +$$ +\mathcal {L} _ {\text {s h a p e}} = \frac {1}{n} \sum_ {i = 1} ^ {n} \left(\beta_ {i} - \hat {\beta} _ {i}\right) ^ {2}, \tag {5} +$$ + +where $n$ is the dimension of $\beta$ , i.e. $n = 10$ . + +The pre-training loss is a combination of the two branches with a weighted hyperparameter $\eta$ : + +$$ +\mathcal {L} = \mathcal {L} _ {\text {c o m}} + \eta \mathcal {L} _ {\text {s h a p e}}. \tag {6} +$$ + +# 3.2. ReID Network + +To extract spatio-temporal features from the sequence of point clouds, the ReID Network of ReID3D comprises a GCEE, which consists of a GCN backbone and CFE, along with a temporal module, as illustrated in Fig. 3. + +GCN Backbone. To extract local and global features from point clouds effectively, we employ graph convolutional structure as the backbone. We construct the directed + +![](images/eed0ff5897a3d3caaf46cd0f4a2e6b1f828fc9bb8e6d1f7b88bc94a5a03e5554.jpg) +Figure 4. The architecture of the Eraser module in CFE. + +graph $\mathcal{G}(\mathcal{V},\mathcal{E})$ by using the k-nearest neighbors (KNN) of each point including self-loop, where $\mathcal{V}$ represents the points and $\mathcal{E}$ represents the set of edges. For the original point cloud, we construct the graph based on the nearest neighbors in its coordinate space. However, we update the graph at each layer of the network in feature space based on the feature similarity among points, rather than fixed spatial positions. + +Denote that $p_i$ is the central point of once graph convolution operation, and $\mathcal{N}(i) = \{j | (i, j) \in \mathcal{E}\}$ is the set of points in its neighborhood with features $\mathcal{F}(i) = \{f_j | j \in \mathcal{N}(i)\}$ . To integrate the global shape structure and local neighborhood feature differences [39], we define $f_{ij} = [f_i, f_j - f_i]$ as the input feature, where $[\cdot, \cdot]$ is the concatenation operation. The convolution process can be formulated as: + +$$ +f _ {i} ^ {\prime} = \max _ {j \in \mathcal {N} (i)} \sigma \left(f _ {i j} \times k\right), \tag {7} +$$ + +where $f_{i}^{\prime}$ is the output feature of the central point $p_i$ , $k$ is the convolution kernel, max is a channel-wise max-pooling function, $\times$ represents matrix multiplication and $\sigma(\cdot)$ is the activation function LeakyReLU. + +Complementary Feature Extractor. One viable method for extracting frame-level pedestrian features is to apply pooling directly to the features output by the GCN backbone. However, applying the same operation to each frame results in highly redundant extraction, which only emphasizes a part of the most salient features. To this end, inspired by [15], we design CFE to extract complementary features and improving representation learning of the encoder. + +For each frame in a sequence, we consider it as the primary frame. The CFE further extracts its features based on the output of the GCN backbone. Then, the next frame is taken as the supplementary frame, from which the Eraser module erases the previously discovered salient features. We duplicate the last frame $\mathcal{P}_n$ as its own supplementary frame. In particular, for a sequence of point clouds $\{\mathcal{P}_i\}_{i=1}^n (\mathcal{P}_i \in \mathbb{R}^{N \times 3})$ , the feature sequence $\{\mathcal{F}_i\}_{i=1}^n (\mathcal{F}_i \in \mathbb{R}^{N \times D})$ is obtained by the GCN backbone, where $N$ is the number of points and $D$ is the dimension of features. For the primary frame, CFE utilizes a graph convolution layer and a global max-pooling layer to extract the most salient features $f_{\mathrm{p}} \in \mathbb{R}^{1 \times D_{\mathrm{c}}}$ . Then, the Eraser module reconstructs the features of the supplementary frame $\mathcal{F}_{\mathrm{s}}$ guided by the discovered features $f_{\mathrm{p}}$ . The reconstructed features $\mathcal{F}_{\mathrm{s}}'$ is fed into similar graph convolution layer and global max-pooling layer to extract auxiliary features $f_{\mathrm{s}}$ . $f_{\mathrm{p}}$ and $f_{\mathrm{s}}$ are concatenated to obtain the complementary features $f_{\mathrm{cfe}} \in \mathbb{R}^{1 \times 2D_{\mathrm{c}}}$ of the primary frame. + +The architecture of the Erasure module is shown in Fig. 4. Firstly, the correlation layer is used to obtain the correlation vector $R \in \mathbb{R}^{N \times 1}$ between $\mathcal{F}_{\mathrm{s}}$ and $f_{\mathrm{p}}$ , through computing the semantic relevance between $f_{\mathrm{p}}$ and all the local descriptors of $\mathcal{F}_{\mathrm{s}}$ , formulated as: + +$$ +R = \mathcal {F} _ {\mathrm {s}} \times \left(f _ {\mathrm {p}} \times \omega\right) ^ {T}, \tag {8} +$$ + +where $\omega \in \mathbb{R}^{D_{\mathrm{c}} \times D}$ is a learnable variable projecting $f_{\mathrm{p}}$ to the feature space of $\mathcal{F}_{\mathrm{s}}$ . Then, the Binarization module generates the binary mask based on $R$ to identify the points to be erased. Specifically, for each point in $\mathcal{F}_{\mathrm{s}}$ , calculate the sum of the correlation values of the point and its $K_{\mathrm{B}}$ nearest neighbors in the feature space. The calculated sum represents the correlation of the region centered on the point. We select the region with the highest correlation value to be erased, through setting the corresponding value in the binary mask $B$ to 0 and others to 1. Finally, $\mathcal{F}_{\mathrm{s}}$ is erased according to $B$ to obtain the reconstructed features $\mathcal{F}_{\mathrm{s}}'$ . + +Temporal Fusion Module. The sequence of pedestrian point clouds includes distinctive dynamic features, such as gait frequency and amplitude of limb swings. We utilize a transformer module [35] with four encoder layers to extract the dynamic features. The transformer module takes the sequence of features $\{f_{\mathrm{cfe}}^i\}_{i = 1}^n$ as input and outputs the final features $f\in \mathbb{R}^{D_{\mathrm{T}}}$ . + +Training and Inference. Following the standard paradigm of camera-based ReID [5, 15, 46, 52], we exploit a combination of cross-entropy and batch-hard triplet terms [14] as the loss function, with the hyperparameter $\gamma$ : + +$$ +\mathcal {L} = \mathcal {L} _ {\mathrm {c e}} + \gamma \mathcal {L} _ {\mathrm {t r i}}. \tag {9} +$$ + +During inference, the similarity between query and gallery set is measured using the cosine distance. + +# 4. Person ReID Dataset + +In this paper, we build a real-world LiDAR-based ReID dataset LReID and a simulated pedestrian point cloud dataset LReID-sync. LReID is captured by a multimodal imaging system, which consists of 4 Livox Mid-100 LiDAR sensors and 4 industrial cameras [51]. LReID includes 320 identities, 156,000 point cloud frames and synchronized RGB images with corresponding 2D and 3D annotations. + +Data Acquisition. LReID is collected in two extensive outdoor scenes: a crossroad and a square in front of a building, capturing different time periods and weather conditions, as shown in Fig. 6. We synchronize each pair of LiDAR and camera with $\sim 5$ ms accuracy and provide an accurate extrinsic and intrinsic calibration. All sequences are recorded with a frame rate of $10\mathrm{Hz}$ . The images are captured of a resolution of $2048\times 1536$ pixels and the density of LiDAR points is about 30,000 points per frame. + +The square scene is located in front of a building with frequent pedestrian traffic, and many pedestrians walk together in groups, which makes it more complex for person ReID tasks. We collected data in the square scene during two different times in summer to analyze the impact of lighting conditions on person ReID. Additionally, to explore the impact of different scenes, weather conditions, and pedestrian attire in different seasons, we also collected data at a crossroads scene in winter. Figure 5 shows the samples of two pedestrians collected from different scenes. Furthermore, we analyze the point distribution in LReID and LReID-sync, as shown in Fig. 6. + +Annotations. To ensure efficient and accurate annotation, we utilize a point cloud-based 3D detector [18] to locate pedestrians. Additionally, we employ a 3D multi-object tracking method [41] to establish continuous trajectories, and manually rectify them. Furthermore, we adjust the IDs of the pedestrians that appeared repeatedly in the field of view based on the images. After obtaining precise 3D ReID annotations, we project them onto synchronized RGB images and perform manual corrections. + +To avoid the influence of absolute coordinate information on the network, we normalize the pedestrian point clouds by subtracting the center coordinates of their respective bounding boxes. + +![](images/75060989987a2bee1f2c54f8be2a1c56689e0d4a482c97ae4c52c3493c1cbb85.jpg) + +![](images/7e63e026d097ee9a083f9df8c2731c88b2a5725306b4e7f68502e2b2839aa341.jpg) + +![](images/b36503a53d7540e7a7dd7dc8e5d323ec7906a4ac6d63f85ad6695a010c7d4afb.jpg) + +![](images/25ce9b30c719c9c786b7c50a77ad4d26a499012e5f96fb3b7fe8e37e86a563d3.jpg) + +![](images/898dfff2acdd2bcfd1ee754484445120dafed91e821f2f31bdb13beea1b55d9f.jpg) +Figure 5. Samples of two pedestrians collected from the square scene in summer (top row), and the crossroads scene in winter (bottom row). + +![](images/a045f1182ed8237ec375559c640410675a465ee2d20d5e29ddd2d39ea0bb9882.jpg) + +![](images/7ee7d0c42d12c6b7db086cfc53f74ebc25fb7b6bd86238d464b2fe6995e9210a.jpg) + +![](images/ad1dd98ff8648781e48183967fc553f09b0252d67c8b5b43544024a33deadf6f.jpg) + +![](images/4bff8758f14584ca397b6f22dad81408585551896b9d33781bb571d49d0a5283.jpg) +Figure 6. Data acquisition scenes and statistics about points in LReID and LReID-sync (lower right). + +![](images/e38b8d7baeb4e03a3667b443a89c0b171877b09047ae0779bd12e14e7cc65b41.jpg) +Figure 7. Samples of LReid-sync for full views and each single view. + +Evaluation. LReID is divided into two splits: a training set with 220 identities and a test set with the remaining 100 identities. Both sets include different scenes, seasons, and lighting conditions. Within the test set, 30 identities are captured under low light, whereas 70 identities are captured under normal light. Following the standard paradigm of video-based datasets [20, 43, 55], the evaluation focuses on recognition across different LiDARs. + +We select one sample of each identity in the test set to build the query set and use the other samples as the gallery set. In the test set, we ensure that the data collected by different LiDARs does not overlap in time, which is to prevent the model from recognizing individuals based on human pose at a certain time. To maximize the use of training data, we divide the sequences in training set into several fragments that may partially overlap in time. The evaluation metrics for LReID include Cumulative Matching Characteristics (CMC) and mean Average Precision (mAP), which are consistent with camera-based datasets. + +LReLU-sync. LReLU-sync is a novel pedestrian dataset generated using the software Unity3D, which simulates pedestrians in scenes captured by multiple synchronized LiDARs from various views, as shown in Fig. 7. With this setup, LReLU-sync accurately simulates the information loss and point cloud sparsity that occur when pedestrians are captured using a single-view LiDAR. Additionally, + +LReID-sync includes annotations for point cloud completion from single view to full views, as well as SMPL parameters. Therefore, LReID-sync can be utilized for pretraining. LReID-sync comprises 600 pedestrians with various actions, each exhibiting unique body shapes and gaits, ensuring diversity within the dataset. + +# 5. Experiments + +# 5.1. Implementation Details + +ReID Network. The ReID network is trained for 700 epochs using the AdamW optimizer with a weight decay of 5e-5. The learning rate, initially set to 5e-5, is updated using a Cosine Annealing Learning Rate (CosineAnnealingLR) scheduler with a cycle of 200 epochs. Each frame of pedestrian point clouds in LReID is upsampled or downsampled to 256 points as input to the network. To train our model, we randomly choose 6 identities, and sample 6 sequences for each identity with a sequence length of 30 frames. The loss weight $\gamma$ is set to 1. The neighborhood size is set to 10 and 8 for each graph convolution layer and Binarization module, respectively. And the feature dimensions $D$ , $D_{\mathrm{C}}$ and $D_{\mathrm{T}}$ are set to 512, 512 and 1024, respectively. + +Pre-training. The pre-training model follows a similar training strategy as described above, except that the initial learning rate is set to 1e-4. The loss weight $\eta$ is set to 1. The coefficient $\delta$ in Eq. 4 is set to 0.01 for the first 100 epochs, then increased to 0.1, 0.5 and 1.0 after 100, 200 and 400 epochs. The coarse shape $\hat{\mathcal{P}}_{\mathrm{coarse}}$ contains 128 points, while the detailed shape $\hat{\mathcal{P}}_{\mathrm{detail}}$ contains 512 points. The weights of the pre-trained GCEE are used as initialization for the ReID network. + +# 5.2. Comparison with Camera-based Methods + +We compare ReID3D with the state-of-the-art video-based methods [2, 9, 15, 50]. The input images are resized in the + +Table 2. Comparison with state-of-the-art camera-based methods on LReID. Numbers in bold indicate the best performance and underscored ones are the second best. To ensure fairness, ReID3D without pre-training is evaluated. + +
MethodVenueModalityNormal lightLow lightOverall
Rank-1Rank-3mAPRank-1Rank-3mAPRank-1Rank-3mAP
TCLNet [15]ECCV 2020Camera98.698.694.8860.073.346.1887.091.080.27
STMN [9]ICCV 202194.398.693.8130.050.031.1775.084.075.02
SINet [2]CVPR 202297.1100.094.6343.360.043.9781.088.079.43
PiT [50]TII 202294.395.786.2133.360.035.7476.085.071.07
B-ReID3DOursLiDAR90.097.182.0490.093.381.6490.096.081.92
ReID3DOurs94.398.683.6593.396.782.4394.098.083.28
+ +B-ReID3D: ReID3D without pre-training. + +Table 3. Comparison for different pre-training method. + +
Pre-training MethodRank-1Rank-3mAP
Baseline(w/o pre-training)90.096.081.92
ReID91.096.082.13
Completion93.097.082.73
Completion + SMPL94.098.083.28
+ +resolution of $128 \times 64$ . To ensure fairness, ReID3D without pre-training (B-ReID3D) is also evaluated. All methods are evaluated with the same dataset settings and metrics. + +The comparative results are shown in Tab. 2, from which the following observations can be obtained: (1) ReID3D and B-ReID3D demonstrate their superiority to the video-based methods, primarily benefiting from the utilization of point clouds, which is unaffected by lighting conditions and complex background. (2) ReID3D achieves state-of-the-art results in overall and low light conditions, but it falls behind video-based methods in normal light conditions. This is because video-based methods make full use of appearance information under normal light. (3) Video-based methods perform poorly under low light, while ReID3D and B-ReID3D demonstrate comparable reliability under both low light and normal light. + +# 5.3. Pre-training + +To demonstrate the effectiveness of pre-training with simulated dataset LReID-sync, we evaluate the performance of different pre-training method. The following four methods are evaluated: (1) ReID3D without pre-training. (2) Pretraining with similar ReID task, in which the pre-training model and loss are consistent with the ReID network. (3) Pre-training with only the branch of point cloud completion. (4) Pre-training with multiple tasks, as described in Section 3.1. The experimental results are shown in Tab. 3. It can be observed that pre-training with multiple tasks makes an improvement to the accuracy of ReID3D, with the rank-1 accuracy increasing from 90.0 to 94.0. This improvement can be attributed to two factors: (1) The simulated data comprises a diverse collection of pedestrian point clouds with various body shapes, which supplements the real-world data. (2) Multi-task pre-training effectively leverages the performance of the encoder. Besides, pre-training with + +![](images/0d33fddb0ba11bf8e1b54ecf6c9ccbdfdd1e8fe08dbce51e8e4faba482cdb6b4.jpg) +(a) + +![](images/0d201789505030dc165803eb53620f345022b2d51a36d2e951bf3e2f98ccb650.jpg) +(b) + +![](images/61357e73f4d721fbde1fe44129706b1e3c334da4291dc88868df0465b3707cef.jpg) +(c) + +![](images/a65124066ae6eb87fda8de765b1a486b84e0c481d5cbdb8f98e0f136930d2ff7.jpg) +(d) +Figure 8. Completion results for real-world pedestrian point clouds obtained by the pre-trained model. In each sample, the detailed shape, coarse shape, and image are shown from left to right. The red points represent the input point cloud, and the blue points represent the predicted complete point cloud. + +task of ReID or point cloud completion also leads to an improvement in performance. + +To showcase the robust feature encoding capabilities attained by the encoder through pre-training, we visualize the completion results for several real-world pedestrian point clouds with different characteristics, as shown in Fig. 8. We can observe that: (1) Intuitively, the detailed and coarse shape closely resemble the actual human shape, which indicates that the encoder has successfully captured the complete features of the human body. (2) The detailed shape is an extension based on the coarse shape, with higher resolution and more information. (3) The pre-trained encoder has the ability to estimate the features of the missing part in the point cloud. As shown in Fig. 8a, the unobserved parts of the legs are accurately completed. (4) Due to motion blur or object carrying, the point cloud may contain some noise points. For example, in Fig. 8b and Fig. 8c, there are red noise points located between the legs and from the carrying bags, respectively. However, the model can effectively filter out the noise points that do not conform to the body shape. + +Table 4. Performance of B-ReID3D with different encoders. + +
EncoderRank-1Rank-3mAP
PointNet [31]74.088.060.31
Point Transformer [53]83.093.074.86
3DCNN [8]34.051.028.27
GCEE90.096.081.92
+ +Table 5. Ablation study on the CFE module and Eraser module. + +
Encoder TypeRank-1Rank-3mAP
B-ReID3D-w/o CFE83.094.074.15
B-ReID3D-w/o Eraser85.095.080.47
B-ReID3D90.096.081.92
+ +# 5.4. Ablation Study + +Effect of Encoders. To evaluate the effectiveness of our GCEE, we also implement several commonly used encoders in point cloud tasks to replace GCEE in the ReID network for comparison, including PointNet [31], Point Transformer [53], and 3DCNN [8]. All methods use consistent training strategies and employ a same transformer module as the temporal fusion network. We report the results on LReID in Tab. 4, obtaining the following observations: (1) GCEE outperforms other encoders, which is mainly beneficial by its flexible graph structure in the feature space and the strategy of complementary enhancement. (2) Point-based encoders are superior to voxel-based encoder 3DCNN, which indicates that point-based encoders can provide a more detailed understanding of humans in tasks like ReID. + +Effect of CFE. CFE is a crucial component in our proposed encoder, used to extract complementary features. We compared our full model with two ablated versions: one without CFE and another without the Eraser module, as shown in Tab. 5. Removing CFE results in a lower rank-1 accuracy, with a score of 83.0 compared to our 90.0, which highlights the effectiveness of the complementary enhancement in constructing distinctive and comprehensive features. While removing the Eraser module retains the features of the complementary frame, it might lead to the extraction of similar features from the primary frame, thus restricting the improvement in accuracy, with a score of 85.0 compared to 83.0 of the version without CFE. + +Effect of the Temporal Module. We evaluate the effectiveness of different temporal modules in combination with GCEE, as shown in Tab. 6. We can observe that the attention-based transformer structure demonstrates significant superiority over the LSTM structure. The rank-1 accuracy of transformer exceeds that of LSTM by 8 points, and that of BiLSTM by 10 points. + +Table 6. Results of B-ReID3D with different temporal modules. + +
Temporal ModuleRank-1Rank-3mAP
LSTM [11]82.089.072.34
Bi-LSTM [33]80.090.070.92
Transformer [35]90.096.081.92
+ +![](images/8d90b62be49500c13600e8c81ebed5034decf03e903c430537c0fe5d2aa9d329.jpg) +(a) + +![](images/c5ddb489cb6ff4f8a963c171fefd591475461c8534ff526d91b8594aaf9a63db.jpg) +(b) + +![](images/e842e42ca3143b1a28a8ec0961600aa36e65230d0ba6b5d8b9965790fd2a509c.jpg) +(c) +Figure 9. Feature visualization of CFE. The features of the primary frame and the supplementary frame are presented on left and right, respectively. The color bar on the right indicates the feature value. + +# 5.5. Visualization Analysis + +For qualitative analysis, we visualize the feature values output by the two graph convolutional layers in the CFE, as shown in Fig. 9. Three samples are taken from different actions of a person in the test set of LReID, with each sample comprising two consecutive frames. In each sample, the features of the primary frame and the supplementary frame are presented. We can observe that primary ones pay more attention to the head and arms, potentially linked to the discriminative height parameter, while supplementary ones predominantly emphasize the torso and legs. The combination of them creates a complementary and comprehensive feature representation. + +# 6. Conclusions + +This paper presents the first research on person ReID using precise 3D structural information provided by LiDAR. Firstly, We propose a LiDAR-based ReID framework, named ReID3D, that utilizes pre-training to guide Graph-based Complementary Enhancement Encoder (GCEE) for extracting comprehensive 3D intrinsic features. Moreover, we build the first LiDAR-based person ReID dataset, termed LReID, which contains 320 pedestrians in various outdoor scenes and lighting conditions. Additionally, we introduce LReID-sync, a new simulated pedestrian dataset designed for pre-training encoders with tasks of point cloud completion and shape parameter learning. Our proposed ReID3D demonstrates exceptional performance on LReID, highlighting the significant potential of LiDAR in addressing person ReID tasks. + +# Acknowledgement + +This work is supported by the National Key Research and Development Program of China under Grant (2018AAA0102803). + +# References + +[1] Sk Miraj Ahmed, Aske R Lejbolle, Rameswar Panda, and Amit K Roy-Chowdhury. Camera on-boarding for person re-identification using hypothesis transfer learning. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 12144–12153, 2020. 1 +[2] Shutao Bai, Bingpeng Ma, Hong Chang, Rui Huang, and Xilin Chen. Salient-to-broad transition for video person re-identification. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 7339–7348, 2022. 6, 7 +[3] Igor Barros Barbosa, Marco Cristani, Alessio Del Bue, Loris Bazzani, and Vittorio Murino. Re-identification with rgb-d sensors. 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However, cameras often lack the perception of 3D morphological information of human and are susceptible to various limitations, such as inadequate illumination, complex background, and personal privacy. In this paper, we propose a LiDAR-based ReID framework, ReID3D, that utilizes pre-training strategy to retrieve features of 3D body shape and introduces Graph-based Complementary Enhancement Encoder for extracting comprehensive features. Due to the lack of LiDAR datasets, we build LReID, the first LiDAR-based person ReID dataset, which is collected in several outdoor scenes with variations in natural conditions. Additionally, we introduce LReID-sync, a simulated pedestrian dataset designed for pre-training encoders with tasks of point cloud completion and shape parameter learning. Extensive experiments on LReID show that ReID3D achieves exceptional performance with a rank-1 accuracy of 94.0, highlighting the significant potential of LiDAR in addressing person ReID tasks. To the best of our knowledge, we are the first to propose a solution for LiDAR-based ReID. The code and dataset are available at https://github.com/GWxuan/ReID3D." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 47, + 565, + 128, + 578 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 565, + 128, + 578 + ], + "spans": [ + { + "bbox": [ + 47, + 565, + 128, + 578 + ], + "type": "text", + "content": "1. Introduction" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 586, + 287, + 694 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 586, + 287, + 694 + ], + "spans": [ + { + "bbox": [ + 46, + 586, + 287, + 694 + ], + "type": "text", + "content": "Person ReID has numerous practical applications, such as video surveillance, intelligent transportation and public security. Most ReID systems use cameras as sensors, aiming to recognize the same individual in images or videos caught by different cameras. With the development of computer vision technology, camera-based ReID has witnessed continuous advancements. However, certain challenges have not yet been effectively addressed. Firstly, cameras introduce limitations in terms of visual ambiguity caused by poor illu" + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 313, + 239, + 539, + 344 + ], + "blocks": [ + { + "bbox": [ + 313, + 239, + 539, + 344 + ], + "lines": [ + { + "bbox": [ + 313, + 239, + 539, + 344 + ], + "spans": [ + { + "bbox": [ + 313, + 239, + 539, + 344 + ], + "type": "image", + "image_path": "1a342af47cc0ca31e827bff81a9aeaad559435e0bbaa565d44b6dfd1f9b9f262.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 304, + 352, + 546, + 407 + ], + "lines": [ + { + "bbox": [ + 304, + 352, + 546, + 407 + ], + "spans": [ + { + "bbox": [ + 304, + 352, + 546, + 407 + ], + "type": "text", + "content": "Figure 1. Overview of camera-based and LiDAR-based person ReID. Camera-based methods primarily learn the 2D appearance of human, such as color of clothes, accessories, and shoes. LiDAR-based methods utilize 3D structural information to learn intrinsic features, such as height, body shape, and gait." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 422, + 546, + 494 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 422, + 546, + 494 + ], + "spans": [ + { + "bbox": [ + 304, + 422, + 546, + 494 + ], + "type": "text", + "content": "mination and complex backgrounds [34]. Additionally, current camera-based ReID models primarily learn appearance information [47]. Therefore, variations in human appearance considerably impact the performance of models [19]. Furthermore, camera-based person ReID systems raise personal privacy issues [1, 4] for applications in some areas." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 495, + 547, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 495, + 547, + 628 + ], + "spans": [ + { + "bbox": [ + 304, + 495, + 547, + 628 + ], + "type": "text", + "content": "In recent years, Kinect-based ReID approaches have been proposed [28, 32] to address these challenges by utilizing depth information. However, Kinect is primarily designed for indoor scenes and has a limited measurement range [17], restricting its applicability in large-scale outdoor scenarios. Recently, researchers have explored the use of radar for gait recognition, identity recognition, and person ReID [7, 26]. While radar is cost-effective, it suffers from poor angular and distance resolution, as well as a limited effective measurement range [7], which poses challenges in discriminating individuals with similar body shapes." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 629, + 547, + 715 + ], + "type": "text", + "content": "In the past few years, LiDAR has been widely adopted in autonomous driving, driven by its improved accuracy and reduced costs [38]. The successful applications of LiDAR motivate us to explore its potential in person ReID within complex outdoor scenes. LiDAR can offer a broader measurement range and higher resolution, enabling precise perception about individuals in large-scale outdoor settings." + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "spans": [ + { + "bbox": [ + 58, + 703, + 135, + 712 + ], + "type": "text", + "content": "*Corresponding author" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17437" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 289, + 228 + ], + "type": "text", + "content": "LiDAR provides precise 3D structural information without being affected by lighting conditions or complex backgrounds, which enables the extraction of intrinsic features of individuals, such as height, body shape, and gait, irrespective of clothing color. LiDAR has been utilized in the task of gait recognition [34], which focuses on recognizing cooperative subjects walking along a specified route in small-scale scenes. However, ReID primarily focuses on the identification of unscripted pedestrians in large-scale scenes with a small sample size for each identity, which often requires multiple acquisition devices. In our work, we leverage low-cost LiDARs to tackle person ReID challenges, as shown in Fig. 1." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 229, + 289, + 470 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 229, + 289, + 470 + ], + "spans": [ + { + "bbox": [ + 46, + 229, + 289, + 470 + ], + "type": "text", + "content": "To the best of our knowledge, this paper presents the first study on LiDAR-based person ReID. We build LReID, the first LiDAR-based ReID dataset to facilitate research on utilizing LiDAR point clouds for person ReID. We collect the dataset in several outdoor scenes using multiple collection nodes, each including a Livox Mid-100 LiDAR and an industrial camera. LReID offers several distinctive features: (1) Real-world scenes. The dataset is captured in outdoor scenes where pedestrians demonstrate unscripted behavior, leading to occlusions between pedestrians, as well as the presence of dynamic objects like vehicles and bicycles that may impact person ReID. (2) Data diversity. LReID encompasses dynamic data and annotations of 320 pedestrian gathered in varying seasons, times of day, and lighting conditions, amounting to a total of 156,000 frames of point clouds and images, thus enabling comprehensive analysis of the impact of different factors on person ReID. (3) Precision. The Livox Mid-100 LiDAR has a distance accuracy of " + }, + { + "bbox": [ + 46, + 229, + 289, + 470 + ], + "type": "inline_equation", + "content": "2\\mathrm{cm}" + }, + { + "bbox": [ + 46, + 229, + 289, + 470 + ], + "type": "text", + "content": " and an angular accuracy of " + }, + { + "bbox": [ + 46, + 229, + 289, + 470 + ], + "type": "inline_equation", + "content": "0.1^{\\circ}" + }, + { + "bbox": [ + 46, + 229, + 289, + 470 + ], + "type": "text", + "content": ", which provides high-precision 3D structural information for ReID problems." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 472, + 289, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 472, + 289, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 472, + 289, + 544 + ], + "type": "text", + "content": "Additionally, we introduce a simulated dataset, named LReID-sync, including 360,000 frames of point clouds for 600 pedestrians captured by multi-view synchronous LiDARs. LReID-sync comprises annotations for point cloud completion from single view to full views, and Skinned Multi-Person Linear Model (SMPL) parameters [24]." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 289, + 714 + ], + "type": "text", + "content": "Based on point clouds, the identification of pedestrians relies on their static anthropometric features, including height, body shape, and limb structure, as well as their dynamic gait features. Accurately extracting complete shape features of a pedestrian is beneficial for both aspects. To address this, we propose an efficient LiDAR-based framework, termed ReID3D. ReID3D utilizes a pre-training strategy to guide the encoder in learning 3D body features based on LReID-sync. Moreover, in order to extract discriminative static and dynamic features of pedestrians, the ReID network of ReID3D comprises a Graph-based Complementary Enhancement Encoder (GCEE) and a temporal module. Extensive experiments on LReID demonstrate the following: (1) ReID3D outperforms the state-of-the-art camera" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 156 + ], + "type": "text", + "content": "based methods, particularly under low light, highlighting the significant potential of LiDAR in addressing person ReID tasks. (2) The use of LReID-sync for pre-training significantly enhances feature encoding capability of the model. (3) Compared to commonly used point cloud encoders, our GCEE exhibits a higher proficiency in extracting comprehensive and discriminative features." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 317, + 156, + 534, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 156, + 534, + 167 + ], + "spans": [ + { + "bbox": [ + 317, + 156, + 534, + 167 + ], + "type": "text", + "content": "To summarize, our main contributions are as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 168, + 547, + 360 + ], + "type": "list", + "angle": 0, + "index": 9, + "blocks": [ + { + "bbox": [ + 304, + 168, + 547, + 215 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 168, + 547, + 215 + ], + "spans": [ + { + "bbox": [ + 304, + 168, + 547, + 215 + ], + "type": "text", + "content": "- To the best of our knowledge, this is the first work on LiDAR-based person ReID, demonstrating the practicality of utilizing LiDAR for person ReID in challenging real-world outdoor scenes." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 216, + 547, + 287 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 216, + 547, + 287 + ], + "spans": [ + { + "bbox": [ + 304, + 216, + 547, + 287 + ], + "type": "text", + "content": "- We build LReID, the first LiDAR-based person ReID dataset, which is collected in several outdoor scenes with variations in natural conditions. Moreover, we introduce LReID-sync, a new simulated pedestrian dataset designed for pre-training ReID models with tasks of point cloud completion and shape parameter learning." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 288, + 547, + 360 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 288, + 547, + 360 + ], + "spans": [ + { + "bbox": [ + 304, + 288, + 547, + 360 + ], + "type": "text", + "content": "- We propose a LiDAR-based ReID framework, termed ReID3D, that utilizes pre-training strategy to guide the encoder in learning 3D body features and introduces GCEE for extracting comprehensive and discriminative features. Experimental results on dataset LReID indicate that ReID3D outperforms camera-based methods." + } + ] + } + ], + "index": 8 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 369, + 392, + 380 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 369, + 392, + 380 + ], + "spans": [ + { + "bbox": [ + 306, + 369, + 392, + 380 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 388, + 545, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 388, + 545, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 545, + 555 + ], + "type": "text", + "content": "Person ReID. Camera-based ReID has been extensively researched in the past decades. Researchers have employed various convolutional neural networks [48] to extract human features from images or videos. Some video-based ReID models adopt recurrent neural networks (RNNs) [25, 45, 57] or transformer blocks [6, 56] to aggregate temporal features. These models primarily focus on extracting appearance features, which serve as efficient but short-lived identifiers. By contrast, intrinsic and behavioral features exhibit minimal change over time. Given the constraints of using cameras at night, infrared sensors have been introduced for RGB-IR cross-modality person ReID [29, 42]. However, the infrared sensor only captures 2D single-channel intensity information, constraining its perceptive ability." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 556, + 545, + 675 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 556, + 545, + 675 + ], + "spans": [ + { + "bbox": [ + 304, + 556, + 545, + 675 + ], + "type": "text", + "content": "In order to extract intrinsic features of individuals, researches on ReID utilizing Kinect [28, 32] and radar [7] have emerged. Kinect and radar provide 3D structural information to help the model extract physiological and behavioral features, reducing reliance on the appearance of individuals [10, 32]. However, they are constrained by significant hardware limitations [7, 17]. In comparison, LiDAR serves as a more advantageous option, offering superior practicality. Despite this, LiDAR-based person ReID has not been researched." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 689, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 547, + 715 + ], + "type": "text", + "content": "Point Cloud Completion. Point cloud completion is the task to predict missing parts based on the rest of the point" + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "17438" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 75, + 86, + 517, + 148 + ], + "blocks": [ + { + "bbox": [ + 166, + 70, + 426, + 82 + ], + "lines": [ + { + "bbox": [ + 166, + 70, + 426, + 82 + ], + "spans": [ + { + "bbox": [ + 166, + 70, + 426, + 82 + ], + "type": "text", + "content": "Table 1. Comparison of publicly available 3D datasets for person ReID." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 75, + 86, + 517, + 148 + ], + "lines": [ + { + "bbox": [ + 75, + 86, + 517, + 148 + ], + "spans": [ + { + "bbox": [ + 75, + 86, + 517, + 148 + ], + "type": "table", + "html": "
DatasetYearIdentitySensorSceneUnscriptedNatural diversityOcclusion
RGBD-ID [3]2012801 KinectIndoorXXX
BIWI RGBD-ID [27]2014501 KinectIndoorXXX
Kinect-REID [30]2015711 KinectIndoorXXX
LReLUID20233204 LiDARs + 4 CamerasOutdoor✓✓✓
LReLUID-sync20236004 LiDARsSimulation✓X✓
", + "image_path": "37ad0987fb4ec0be9e39486fdd824a0b31a7e6068c68163ca8be94936903a1bd.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 163, + 286, + 235 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 163, + 286, + 235 + ], + "spans": [ + { + "bbox": [ + 46, + 163, + 286, + 235 + ], + "type": "text", + "content": "cloud. To accomplish this, networks need to learn the intrinsic geometric structures and semantic knowledge of the 3D object. Additionally, the learned representations can be transferred to downstream tasks. The entire process does not require human annotations and therefore falls under the category of unsupervised representation learning [44]." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 235, + 286, + 307 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 235, + 286, + 307 + ], + "spans": [ + { + "bbox": [ + 46, + 235, + 286, + 307 + ], + "type": "text", + "content": "Point cloud completion has received increasing attention in the past decade [13, 16, 23, 40]. In terms of completing the missing parts caused by a single viewpoint, Wang et al. [36] utilize an encoder-decoder model to recover the occluded points. However, there has been limited research focusing on point cloud completion for pedestrians." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 321, + 286, + 513 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 321, + 286, + 513 + ], + "spans": [ + { + "bbox": [ + 46, + 321, + 286, + 513 + ], + "type": "text", + "content": "Person ReID Dataset. Depending on the used representations, person ReID datasets can be classified into 2D and 3D datasets. Due to the early emergence and widespread use of cameras, 2D datasets are mainly composed of camera-based datasets [12, 21, 22, 37, 54, 55], which have advanced research in person ReID. In addition, some 2D datasets utilize infrared cameras as sensors [29, 42]. Kinect-based datasets [3, 27, 30] serve as typical examples of 3D datasets. However, the current Kinect datasets have limited scales as they are often collected in small indoor scenes with only one cooperative subject. Additionally, Cheng and Liu [7] collected a radar dataset containing 40 identities, but it is not publicly available and also involves only one cooperative subject in each frame. To address these limitations, we introduce a novel LiDAR-based 3D dataset. The comparison of publicly available 3D datasets is shown in Tab. 1." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 523, + 102, + 536 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 523, + 102, + 536 + ], + "spans": [ + { + "bbox": [ + 47, + 523, + 102, + 536 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 544, + 286, + 639 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 286, + 639 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 286, + 639 + ], + "type": "text", + "content": "ReID3D adopts multi-task pre-training to guide the encoder in learning 3D body features based on LReID-sync, as shown in Fig. 2. The ReID network of ReID3D comprises a Graph-based Complementary Enhancement Encoder (GCEE), which consists of a GCN backbone and a Complementary Feature Extractor (CFE), along with a temporal module, as shown in Fig. 3. The pre-trained GCEE is used to initialize the ReID network." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 647, + 223, + 659 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 647, + 223, + 659 + ], + "spans": [ + { + "bbox": [ + 47, + 647, + 223, + 659 + ], + "type": "text", + "content": "3.1. Pre-training with Multiple Tasks" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 286, + 713 + ], + "type": "text", + "content": "Based on our observations, the crucial factors that are likely to impact the performance of ReID models are (1) the variations in information resulted from different viewpoints under cross-view settings, and (2) the incomplete information" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 317, + 159, + 533, + 266 + ], + "blocks": [ + { + "bbox": [ + 317, + 159, + 533, + 266 + ], + "lines": [ + { + "bbox": [ + 317, + 159, + 533, + 266 + ], + "spans": [ + { + "bbox": [ + 317, + 159, + 533, + 266 + ], + "type": "image", + "image_path": "c9ed05b69b9fe1183be141a28aa1f188830702ac975aa67bc0eab954c79261f9.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 272, + 545, + 306 + ], + "lines": [ + { + "bbox": [ + 305, + 272, + 545, + 306 + ], + "spans": [ + { + "bbox": [ + 305, + 272, + 545, + 306 + ], + "type": "text", + "content": "Figure 2. The pre-training approach of ReID3D. Simulated single-view point cloud is taken as input, and the encoder is pre-trained for tasks of point cloud completion and SMPL parameter learning." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 319, + 545, + 426 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 319, + 545, + 426 + ], + "spans": [ + { + "bbox": [ + 304, + 319, + 545, + 426 + ], + "type": "text", + "content": "acquired from single view. Besides, the collection and annotation of real-world data involve significant costs, while simulated data is low-cost, and comes with rich and accurate annotations. Hence, we leverage simulated data to pretrain the encoder for tasks of point cloud completion and SMPL parameter learning. The overall idea of our proposed pre-training approach is shown in Fig. 2, which enables the encoder to effectively extract anthropometric characteristics and mitigate the influence of viewpoint disparities." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "spans": [ + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": "Multi-task Network. Throughout we define point cloud " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": " as a set of points in 3D Euclidean space, " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\mathcal{P} = \\{p_i | i = 1, 2, \\dots, N\\}" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": ", where each point " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "p_i" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": " can be represented by its coordinates " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "(x_i, y_i, z_i)" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": ". The network is fed with the single-view point cloud " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\tilde{\\mathcal{P}}" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": ", then embed it into a latent vector " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "z" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": " using encoder " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\Phi(\\cdot)" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": ". The first branch of the network focuses on the task of point cloud completion, where the decoder " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "\\Psi(\\cdot)" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": " complete the point cloud based on " + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "inline_equation", + "content": "z" + }, + { + "bbox": [ + 305, + 440, + 545, + 547 + ], + "type": "text", + "content": ". The process can be formulated as:" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 392, + 553, + 545, + 567 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 392, + 553, + 545, + 567 + ], + "spans": [ + { + "bbox": [ + 392, + 553, + 545, + 567 + ], + "type": "interline_equation", + "content": "\\hat {\\mathcal {P}} = \\Psi (\\Phi (\\tilde {\\mathcal {P}})), \\tag {1}", + "image_path": "c0fe57e2041a5a875d6570b8a98ea0cb48c17a3c1b2cbe739d7567542870fc94.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 306, + 572, + 495, + 585 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 572, + 495, + 585 + ], + "spans": [ + { + "bbox": [ + 306, + 572, + 495, + 585 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 306, + 572, + 495, + 585 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 306, + 572, + 495, + 585 + ], + "type": "text", + "content": " is the predicted complete point cloud." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "spans": [ + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "text", + "content": "The second branch aims to learn the characteristics of human body, i.e. SMPL shape parameters " + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "text", + "content": ". The latent vector " + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "inline_equation", + "content": "z" + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "text", + "content": " is expected to encompass shape information. Therefore, a straightforward MLP network is utilized to convert " + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "inline_equation", + "content": "z" + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "text", + "content": " into predicted SMPL shape parameters " + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "inline_equation", + "content": "\\hat{\\beta}" + }, + { + "bbox": [ + 304, + 586, + 545, + 655 + ], + "type": "text", + "content": ". The process can be formulated as:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 387, + 662, + 545, + 675 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 387, + 662, + 545, + 675 + ], + "spans": [ + { + "bbox": [ + 387, + 662, + 545, + 675 + ], + "type": "interline_equation", + "content": "\\hat {\\beta} = \\operatorname {M L P} (\\Phi (\\tilde {\\mathcal {P}})). \\tag {2}", + "image_path": "7de9f96cadcd8342185287ebe9a890de32669bcf7502c46c876792678c4754a4.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 689, + 545, + 713 + ], + "type": "text", + "content": "Training. We adapt the folding-based decoder PCN [49] to complete the single-view point cloud in two steps, out" + } + ] + } + ], + "index": 17 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17439" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 97, + 68, + 500, + 229 + ], + "blocks": [ + { + "bbox": [ + 97, + 68, + 500, + 229 + ], + "lines": [ + { + "bbox": [ + 97, + 68, + 500, + 229 + ], + "spans": [ + { + "bbox": [ + 97, + 68, + 500, + 229 + ], + "type": "image", + "image_path": "c1716af5e8585a4893af676074ce35926b2611f766bf1a43fe04ee862da2fa73.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 238, + 547, + 273 + ], + "lines": [ + { + "bbox": [ + 46, + 238, + 547, + 273 + ], + "spans": [ + { + "bbox": [ + 46, + 238, + 547, + 273 + ], + "type": "text", + "content": "Figure 3. The ReID network of ReID3D. The Graph-based Complementary Enhancement Encoder (GCEE) extracts frame-level features from the pedestrian point clouds, and the transformer module aggregates the sequential features. GCEE consists of a GCN backbone and a Complementary Feature Extractor (CFE)." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "spans": [ + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "text", + "content": "putting a coarse shape " + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}_{\\mathrm{coarse}}" + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "text", + "content": " and a detailed shape " + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}_{\\mathrm{detail}}" + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "text", + "content": ". The pre-training model is trained with a combined loss corresponding to the two branches. In the branch of point clout completion, we use Chamfer Distance (CD) as the difference measure between prediction " + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}" + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "text", + "content": " and ground-truth " + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 46, + 285, + 289, + 348 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 354, + 287, + 395 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 354, + 287, + 395 + ], + "spans": [ + { + "bbox": [ + 47, + 354, + 287, + 395 + ], + "type": "interline_equation", + "content": "\\operatorname {C D} (\\hat {\\mathcal {P}}, \\mathcal {Y}) = \\frac {1}{| \\hat {\\mathcal {P}} |} \\sum_ {\\hat {p} \\in \\hat {\\mathcal {P}}} \\min _ {p \\in \\mathcal {Y}} \\| \\hat {p} - p \\| + \\frac {1}{| \\mathcal {Y} |} \\sum_ {p \\in \\mathcal {Y}} \\min _ {\\hat {p} \\in \\hat {\\mathcal {P}}} \\| p - \\hat {p} \\|. \\tag {3}", + "image_path": "47e370aafea64f9960282aa0247b21597b0939bc06a1b6c367c6a810d8abe8be.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 396, + 288, + 432 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 396, + 288, + 432 + ], + "spans": [ + { + "bbox": [ + 46, + 396, + 288, + 432 + ], + "type": "text", + "content": "The loss of the completion branch is a sum of the Chamfer distances on the coarse and detailed shapes weighted by a hyperparameter " + }, + { + "bbox": [ + 46, + 396, + 288, + 432 + ], + "type": "inline_equation", + "content": "\\delta" + }, + { + "bbox": [ + 46, + 396, + 288, + 432 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 82, + 439, + 287, + 453 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 82, + 439, + 287, + 453 + ], + "spans": [ + { + "bbox": [ + 82, + 439, + 287, + 453 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\mathrm {c o m}} = \\mathrm {C D} (\\hat {\\mathcal {P}} _ {\\text {c o a r s e}}, \\mathcal {Y}) + \\delta \\mathrm {C D} (\\hat {\\mathcal {P}} _ {\\text {d e t a i l}}, \\mathcal {Y}). \\tag {4}", + "image_path": "dbb27e99eaa3686c8455c7e12ffdcebbb0bf9ff2f210f575a18cd752b372de1f.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 461, + 287, + 486 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 461, + 287, + 486 + ], + "spans": [ + { + "bbox": [ + 47, + 461, + 287, + 486 + ], + "type": "text", + "content": "The branch of shape parameter learning utilizes mean squared error (MSE) as the loss function:" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 112, + 493, + 287, + 524 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 112, + 493, + 287, + 524 + ], + "spans": [ + { + "bbox": [ + 112, + 493, + 287, + 524 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {s h a p e}} = \\frac {1}{n} \\sum_ {i = 1} ^ {n} \\left(\\beta_ {i} - \\hat {\\beta} _ {i}\\right) ^ {2}, \\tag {5}", + "image_path": "1ca76b364d14fc00424b2b6ee866528bdb8b8bdf5aab4cab96388d6807d52d26.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "spans": [ + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "type": "inline_equation", + "content": "n" + }, + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "type": "text", + "content": " is the dimension of " + }, + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "type": "inline_equation", + "content": "\\beta" + }, + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "type": "text", + "content": ", i.e. " + }, + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "type": "inline_equation", + "content": "n = 10" + }, + { + "bbox": [ + 47, + 532, + 222, + 542 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 544, + 287, + 567 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 544, + 287, + 567 + ], + "spans": [ + { + "bbox": [ + 46, + 544, + 287, + 567 + ], + "type": "text", + "content": "The pre-training loss is a combination of the two branches with a weighted hyperparameter " + }, + { + "bbox": [ + 46, + 544, + 287, + 567 + ], + "type": "inline_equation", + "content": "\\eta" + }, + { + "bbox": [ + 46, + 544, + 287, + 567 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 124, + 577, + 287, + 590 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 124, + 577, + 287, + 590 + ], + "spans": [ + { + "bbox": [ + 124, + 577, + 287, + 590 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {\\text {c o m}} + \\eta \\mathcal {L} _ {\\text {s h a p e}}. \\tag {6}", + "image_path": "32789e31a372c5281c84375b5b0c5f3bef1539eefa715a19d033b75159f7ad02.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 47, + 597, + 139, + 608 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 597, + 139, + 608 + ], + "spans": [ + { + "bbox": [ + 47, + 597, + 139, + 608 + ], + "type": "text", + "content": "3.2. ReID Network" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 615, + 288, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 615, + 288, + 664 + ], + "spans": [ + { + "bbox": [ + 46, + 615, + 288, + 664 + ], + "type": "text", + "content": "To extract spatio-temporal features from the sequence of point clouds, the ReID Network of ReID3D comprises a GCEE, which consists of a GCN backbone and CFE, along with a temporal module, as illustrated in Fig. 3." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 288, + 713 + ], + "type": "text", + "content": "GCN Backbone. To extract local and global features from point clouds effectively, we employ graph convolutional structure as the backbone. We construct the directed" + } + ] + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 332, + 285, + 522, + 373 + ], + "blocks": [ + { + "bbox": [ + 332, + 285, + 522, + 373 + ], + "lines": [ + { + "bbox": [ + 332, + 285, + 522, + 373 + ], + "spans": [ + { + "bbox": [ + 332, + 285, + 522, + 373 + ], + "type": "image", + "image_path": "eed0ff5897a3d3caaf46cd0f4a2e6b1f828fc9bb8e6d1f7b88bc94a5a03e5554.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 323, + 380, + 528, + 391 + ], + "lines": [ + { + "bbox": [ + 323, + 380, + 528, + 391 + ], + "spans": [ + { + "bbox": [ + 323, + 380, + 528, + 391 + ], + "type": "text", + "content": "Figure 4. The architecture of the Eraser module in CFE." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "spans": [ + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "type": "text", + "content": "graph " + }, + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "type": "inline_equation", + "content": "\\mathcal{G}(\\mathcal{V},\\mathcal{E})" + }, + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "type": "text", + "content": " by using the k-nearest neighbors (KNN) of each point including self-loop, where " + }, + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "type": "inline_equation", + "content": "\\mathcal{V}" + }, + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "type": "text", + "content": " represents the points and " + }, + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 304, + 418, + 545, + 514 + ], + "type": "text", + "content": " represents the set of edges. For the original point cloud, we construct the graph based on the nearest neighbors in its coordinate space. However, we update the graph at each layer of the network in feature space based on the feature similarity among points, rather than fixed spatial positions." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "spans": [ + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "text", + "content": "Denote that " + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "inline_equation", + "content": "p_i" + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "text", + "content": " is the central point of once graph convolution operation, and " + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "inline_equation", + "content": "\\mathcal{N}(i) = \\{j | (i, j) \\in \\mathcal{E}\\}" + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "text", + "content": " is the set of points in its neighborhood with features " + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "inline_equation", + "content": "\\mathcal{F}(i) = \\{f_j | j \\in \\mathcal{N}(i)\\}" + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "text", + "content": ". To integrate the global shape structure and local neighborhood feature differences [39], we define " + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "inline_equation", + "content": "f_{ij} = [f_i, f_j - f_i]" + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "text", + "content": " as the input feature, where " + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "inline_equation", + "content": "[\\cdot, \\cdot]" + }, + { + "bbox": [ + 304, + 517, + 545, + 613 + ], + "type": "text", + "content": " is the concatenation operation. The convolution process can be formulated as:" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 376, + 627, + 545, + 648 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 376, + 627, + 545, + 648 + ], + "spans": [ + { + "bbox": [ + 376, + 627, + 545, + 648 + ], + "type": "interline_equation", + "content": "f _ {i} ^ {\\prime} = \\max _ {j \\in \\mathcal {N} (i)} \\sigma \\left(f _ {i j} \\times k\\right), \\tag {7}", + "image_path": "90586a0e573af5870bc8cc2e5cdcfed64afd21639faf61f23a838ebee51a490b.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "f_{i}^{\\prime}" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " is the output feature of the central point " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "p_i" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "k" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " is the convolution kernel, max is a channel-wise max-pooling function, " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\times" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " represents matrix multiplication and " + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "inline_equation", + "content": "\\sigma(\\cdot)" + }, + { + "bbox": [ + 304, + 664, + 547, + 715 + ], + "type": "text", + "content": " is the activation function LeakyReLU." + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "17440" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 167 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 167 + ], + "type": "text", + "content": "Complementary Feature Extractor. One viable method for extracting frame-level pedestrian features is to apply pooling directly to the features output by the GCN backbone. However, applying the same operation to each frame results in highly redundant extraction, which only emphasizes a part of the most salient features. To this end, inspired by [15], we design CFE to extract complementary features and improving representation learning of the encoder." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "spans": [ + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": "For each frame in a sequence, we consider it as the primary frame. The CFE further extracts its features based on the output of the GCN backbone. Then, the next frame is taken as the supplementary frame, from which the Eraser module erases the previously discovered salient features. We duplicate the last frame " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "\\mathcal{P}_n" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " as its own supplementary frame. In particular, for a sequence of point clouds " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{P}_i\\}_{i=1}^n (\\mathcal{P}_i \\in \\mathbb{R}^{N \\times 3})" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": ", the feature sequence " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "\\{\\mathcal{F}_i\\}_{i=1}^n (\\mathcal{F}_i \\in \\mathbb{R}^{N \\times D})" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " is obtained by the GCN backbone, where " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " is the number of points and " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " is the dimension of features. For the primary frame, CFE utilizes a graph convolution layer and a global max-pooling layer to extract the most salient features " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{p}} \\in \\mathbb{R}^{1 \\times D_{\\mathrm{c}}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": ". Then, the Eraser module reconstructs the features of the supplementary frame " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\mathrm{s}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " guided by the discovered features " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{p}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": ". The reconstructed features " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\mathrm{s}}'" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " is fed into similar graph convolution layer and global max-pooling layer to extract auxiliary features " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{s}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": ". " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{p}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{s}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " are concatenated to obtain the complementary features " + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{cfe}} \\in \\mathbb{R}^{1 \\times 2D_{\\mathrm{c}}}" + }, + { + "bbox": [ + 46, + 168, + 288, + 395 + ], + "type": "text", + "content": " of the primary frame." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "spans": [ + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "content": "The architecture of the Erasure module is shown in Fig. 4. Firstly, the correlation layer is used to obtain the correlation vector " + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "inline_equation", + "content": "R \\in \\mathbb{R}^{N \\times 1}" + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "content": " between " + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\mathrm{s}}" + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{p}}" + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "content": ", through computing the semantic relevance between " + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{p}}" + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "content": " and all the local descriptors of " + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\mathrm{s}}" + }, + { + "bbox": [ + 46, + 396, + 287, + 456 + ], + "type": "text", + "content": ", formulated as:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 121, + 462, + 287, + 477 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 121, + 462, + 287, + 477 + ], + "spans": [ + { + "bbox": [ + 121, + 462, + 287, + 477 + ], + "type": "interline_equation", + "content": "R = \\mathcal {F} _ {\\mathrm {s}} \\times \\left(f _ {\\mathrm {p}} \\times \\omega\\right) ^ {T}, \\tag {8}", + "image_path": "a3844cdef51b510a81c8b2d4cf5cb697bdf4779f8f4344444795e931ee53c057.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "spans": [ + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\omega \\in \\mathbb{R}^{D_{\\mathrm{c}} \\times D}" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": " is a learnable variable projecting " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "f_{\\mathrm{p}}" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": " to the feature space of " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\mathrm{s}}" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": ". Then, the Binarization module generates the binary mask based on " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "R" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": " to identify the points to be erased. Specifically, for each point in " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\mathrm{s}}" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": ", calculate the sum of the correlation values of the point and its " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "K_{\\mathrm{B}}" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": " nearest neighbors in the feature space. The calculated sum represents the correlation of the region centered on the point. We select the region with the highest correlation value to be erased, through setting the corresponding value in the binary mask " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "B" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": " to 0 and others to 1. Finally, " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\mathrm{s}}" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": " is erased according to " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "B" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": " to obtain the reconstructed features " + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "inline_equation", + "content": "\\mathcal{F}_{\\mathrm{s}}'" + }, + { + "bbox": [ + 46, + 483, + 287, + 616 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": "Temporal Fusion Module. The sequence of pedestrian point clouds includes distinctive dynamic features, such as gait frequency and amplitude of limb swings. We utilize a transformer module [35] with four encoder layers to extract the dynamic features. The transformer module takes the sequence of features " + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "inline_equation", + "content": "\\{f_{\\mathrm{cfe}}^i\\}_{i = 1}^n" + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": " as input and outputs the final features " + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "inline_equation", + "content": "f\\in \\mathbb{R}^{D_{\\mathrm{T}}}" + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "content": "Training and Inference. Following the standard paradigm of camera-based ReID [5, 15, 46, 52], we exploit a combination of cross-entropy and batch-hard triplet terms [14] as the loss function, with the hyperparameter " + }, + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 304, + 72, + 545, + 120 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 390, + 125, + 545, + 138 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 390, + 125, + 545, + 138 + ], + "spans": [ + { + "bbox": [ + 390, + 125, + 545, + 138 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {\\mathrm {c e}} + \\gamma \\mathcal {L} _ {\\mathrm {t r i}}. \\tag {9}", + "image_path": "6d25fed5a36e61e6cd559263b7a2fd08a8c96db38d240193711554e1c3ffbc4d.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 143, + 545, + 167 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 143, + 545, + 167 + ], + "spans": [ + { + "bbox": [ + 304, + 143, + 545, + 167 + ], + "type": "text", + "content": "During inference, the similarity between query and gallery set is measured using the cosine distance." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 175, + 428, + 188 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 175, + 428, + 188 + ], + "spans": [ + { + "bbox": [ + 305, + 175, + 428, + 188 + ], + "type": "text", + "content": "4. Person ReID Dataset" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 195, + 545, + 280 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 195, + 545, + 280 + ], + "spans": [ + { + "bbox": [ + 304, + 195, + 545, + 280 + ], + "type": "text", + "content": "In this paper, we build a real-world LiDAR-based ReID dataset LReID and a simulated pedestrian point cloud dataset LReID-sync. LReID is captured by a multimodal imaging system, which consists of 4 Livox Mid-100 LiDAR sensors and 4 industrial cameras [51]. LReID includes 320 identities, 156,000 point cloud frames and synchronized RGB images with corresponding 2D and 3D annotations." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "spans": [ + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "type": "text", + "content": "Data Acquisition. LReID is collected in two extensive outdoor scenes: a crossroad and a square in front of a building, capturing different time periods and weather conditions, as shown in Fig. 6. We synchronize each pair of LiDAR and camera with " + }, + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "type": "inline_equation", + "content": "\\sim 5" + }, + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "type": "text", + "content": " ms accuracy and provide an accurate extrinsic and intrinsic calibration. All sequences are recorded with a frame rate of " + }, + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "type": "inline_equation", + "content": "10\\mathrm{Hz}" + }, + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "type": "text", + "content": ". The images are captured of a resolution of " + }, + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "type": "inline_equation", + "content": "2048\\times 1536" + }, + { + "bbox": [ + 304, + 293, + 545, + 400 + ], + "type": "text", + "content": " pixels and the density of LiDAR points is about 30,000 points per frame." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 401, + 545, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 401, + 545, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 401, + 545, + 544 + ], + "type": "text", + "content": "The square scene is located in front of a building with frequent pedestrian traffic, and many pedestrians walk together in groups, which makes it more complex for person ReID tasks. We collected data in the square scene during two different times in summer to analyze the impact of lighting conditions on person ReID. Additionally, to explore the impact of different scenes, weather conditions, and pedestrian attire in different seasons, we also collected data at a crossroads scene in winter. Figure 5 shows the samples of two pedestrians collected from different scenes. Furthermore, we analyze the point distribution in LReID and LReID-sync, as shown in Fig. 6." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 558, + 545, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 558, + 545, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 558, + 545, + 665 + ], + "type": "text", + "content": "Annotations. To ensure efficient and accurate annotation, we utilize a point cloud-based 3D detector [18] to locate pedestrians. Additionally, we employ a 3D multi-object tracking method [41] to establish continuous trajectories, and manually rectify them. Furthermore, we adjust the IDs of the pedestrians that appeared repeatedly in the field of view based on the images. After obtaining precise 3D ReID annotations, we project them onto synchronized RGB images and perform manual corrections." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": "To avoid the influence of absolute coordinate information on the network, we normalize the pedestrian point clouds by subtracting the center coordinates of their respective bounding boxes." + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17441" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 62, + 70, + 94, + 140 + ], + "blocks": [ + { + "bbox": [ + 62, + 70, + 94, + 140 + ], + "lines": [ + { + "bbox": [ + 62, + 70, + 94, + 140 + ], + "spans": [ + { + "bbox": [ + 62, + 70, + 94, + 140 + ], + "type": "image", + "image_path": "75060989987a2bee1f2c54f8be2a1c56689e0d4a482c97ae4c52c3493c1cbb85.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 98, + 70, + 190, + 140 + ], + "blocks": [ + { + "bbox": [ + 98, + 70, + 190, + 140 + ], + "lines": [ + { + "bbox": [ + 98, + 70, + 190, + 140 + ], + "spans": [ + { + "bbox": [ + 98, + 70, + 190, + 140 + ], + "type": "image", + "image_path": "7e63e026d097ee9a083f9df8c2731c88b2a5725306b4e7f68502e2b2839aa341.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_body" + } + ], + "index": 1 + }, + { + "type": "image", + "bbox": [ + 192, + 71, + 246, + 140 + ], + "blocks": [ + { + "bbox": [ + 192, + 71, + 246, + 140 + ], + "lines": [ + { + "bbox": [ + 192, + 71, + 246, + 140 + ], + "spans": [ + { + "bbox": [ + 192, + 71, + 246, + 140 + ], + "type": "image", + "image_path": "b36503a53d7540e7a7dd7dc8e5d323ec7906a4ac6d63f85ad6695a010c7d4afb.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + } + ], + "index": 2 + }, + { + "type": "image", + "bbox": [ + 247, + 72, + 310, + 140 + ], + "blocks": [ + { + "bbox": [ + 247, + 72, + 310, + 140 + ], + "lines": [ + { + "bbox": [ + 247, + 72, + 310, + 140 + ], + "spans": [ + { + "bbox": [ + 247, + 72, + 310, + 140 + ], + "type": "image", + "image_path": "25ce9b30c719c9c786b7c50a77ad4d26a499012e5f96fb3b7fe8e37e86a563d3.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_body" + } + ], + "index": 3 + }, + { + "type": "image", + "bbox": [ + 61, + 142, + 94, + 205 + ], + "blocks": [ + { + "bbox": [ + 61, + 142, + 94, + 205 + ], + "lines": [ + { + "bbox": [ + 61, + 142, + 94, + 205 + ], + "spans": [ + { + "bbox": [ + 61, + 142, + 94, + 205 + ], + "type": "image", + "image_path": "898dfff2acdd2bcfd1ee754484445120dafed91e821f2f31bdb13beea1b55d9f.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 61, + 215, + 312, + 237 + ], + "lines": [ + { + "bbox": [ + 61, + 215, + 312, + 237 + ], + "spans": [ + { + "bbox": [ + 61, + 215, + 312, + 237 + ], + "type": "text", + "content": "Figure 5. Samples of two pedestrians collected from the square scene in summer (top row), and the crossroads scene in winter (bottom row)." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "image_caption" + } + ], + "index": 4 + }, + { + "type": "image", + "bbox": [ + 97, + 142, + 190, + 205 + ], + "blocks": [ + { + "bbox": [ + 97, + 142, + 190, + 205 + ], + "lines": [ + { + "bbox": [ + 97, + 142, + 190, + 205 + ], + "spans": [ + { + "bbox": [ + 97, + 142, + 190, + 205 + ], + "type": "image", + "image_path": "a045f1182ed8237ec375559c640410675a465ee2d20d5e29ddd2d39ea0bb9882.jpg" + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "image_body" + } + ], + "index": 5 + }, + { + "type": "image", + "bbox": [ + 190, + 142, + 245, + 205 + ], + "blocks": [ + { + "bbox": [ + 190, + 142, + 245, + 205 + ], + "lines": [ + { + "bbox": [ + 190, + 142, + 245, + 205 + ], + "spans": [ + { + "bbox": [ + 190, + 142, + 245, + 205 + ], + "type": "image", + "image_path": "7ee7d0c42d12c6b7db086cfc53f74ebc25fb7b6bd86238d464b2fe6995e9210a.jpg" + } + ] + } + ], + "index": 6, + "angle": 0, + "type": "image_body" + } + ], + "index": 6 + }, + { + "type": "image", + "bbox": [ + 246, + 142, + 310, + 205 + ], + "blocks": [ + { + "bbox": [ + 246, + 142, + 310, + 205 + ], + "lines": [ + { + "bbox": [ + 246, + 142, + 310, + 205 + ], + "spans": [ + { + "bbox": [ + 246, + 142, + 310, + 205 + ], + "type": "image", + "image_path": "ad1dd98ff8648781e48183967fc553f09b0252d67c8b5b43544024a33deadf6f.jpg" + } + ] + } + ], + "index": 7, + "angle": 0, + "type": "image_body" + } + ], + "index": 7 + }, + { + "type": "image", + "bbox": [ + 347, + 70, + 526, + 205 + ], + "blocks": [ + { + "bbox": [ + 347, + 70, + 526, + 205 + ], + "lines": [ + { + "bbox": [ + 347, + 70, + 526, + 205 + ], + "spans": [ + { + "bbox": [ + 347, + 70, + 526, + 205 + ], + "type": "image", + "image_path": "4bff8758f14584ca397b6f22dad81408585551896b9d33781bb571d49d0a5283.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 340, + 215, + 533, + 237 + ], + "lines": [ + { + "bbox": [ + 340, + 215, + 533, + 237 + ], + "spans": [ + { + "bbox": [ + 340, + 215, + 533, + 237 + ], + "type": "text", + "content": "Figure 6. Data acquisition scenes and statistics about points in LReID and LReID-sync (lower right)." + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 52, + 266, + 282, + 332 + ], + "blocks": [ + { + "bbox": [ + 52, + 266, + 282, + 332 + ], + "lines": [ + { + "bbox": [ + 52, + 266, + 282, + 332 + ], + "spans": [ + { + "bbox": [ + 52, + 266, + 282, + 332 + ], + "type": "image", + "image_path": "e38b8d7baeb4e03a3667b443a89c0b171877b09047ae0779bd12e14e7cc65b41.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 341, + 287, + 363 + ], + "lines": [ + { + "bbox": [ + 47, + 341, + 287, + 363 + ], + "spans": [ + { + "bbox": [ + 47, + 341, + 287, + 363 + ], + "type": "text", + "content": "Figure 7. Samples of LReid-sync for full views and each single view." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "bbox": [ + 46, + 385, + 287, + 480 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 385, + 287, + 480 + ], + "spans": [ + { + "bbox": [ + 46, + 385, + 287, + 480 + ], + "type": "text", + "content": "Evaluation. LReID is divided into two splits: a training set with 220 identities and a test set with the remaining 100 identities. Both sets include different scenes, seasons, and lighting conditions. Within the test set, 30 identities are captured under low light, whereas 70 identities are captured under normal light. Following the standard paradigm of video-based datasets [20, 43, 55], the evaluation focuses on recognition across different LiDARs." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 482, + 287, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 482, + 287, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 482, + 287, + 613 + ], + "type": "text", + "content": "We select one sample of each identity in the test set to build the query set and use the other samples as the gallery set. In the test set, we ensure that the data collected by different LiDARs does not overlap in time, which is to prevent the model from recognizing individuals based on human pose at a certain time. To maximize the use of training data, we divide the sequences in training set into several fragments that may partially overlap in time. The evaluation metrics for LReID include Cumulative Matching Characteristics (CMC) and mean Average Precision (mAP), which are consistent with camera-based datasets." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 288, + 715 + ], + "type": "text", + "content": "LReLU-sync. LReLU-sync is a novel pedestrian dataset generated using the software Unity3D, which simulates pedestrians in scenes captured by multiple synchronized LiDARs from various views, as shown in Fig. 7. With this setup, LReLU-sync accurately simulates the information loss and point cloud sparsity that occur when pedestrians are captured using a single-view LiDAR. Additionally," + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 268, + 545, + 340 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 268, + 545, + 340 + ], + "spans": [ + { + "bbox": [ + 304, + 268, + 545, + 340 + ], + "type": "text", + "content": "LReID-sync includes annotations for point cloud completion from single view to full views, as well as SMPL parameters. Therefore, LReID-sync can be utilized for pretraining. LReID-sync comprises 600 pedestrians with various actions, each exhibiting unique body shapes and gaits, ensuring diversity within the dataset." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 350, + 388, + 363 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 350, + 388, + 363 + ], + "spans": [ + { + "bbox": [ + 306, + 350, + 388, + 363 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 306, + 369, + 439, + 382 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 369, + 439, + 382 + ], + "spans": [ + { + "bbox": [ + 306, + 369, + 439, + 382 + ], + "type": "text", + "content": "5.1. Implementation Details" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "spans": [ + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "text", + "content": "ReID Network. The ReID network is trained for 700 epochs using the AdamW optimizer with a weight decay of 5e-5. The learning rate, initially set to 5e-5, is updated using a Cosine Annealing Learning Rate (CosineAnnealingLR) scheduler with a cycle of 200 epochs. Each frame of pedestrian point clouds in LReID is upsampled or downsampled to 256 points as input to the network. To train our model, we randomly choose 6 identities, and sample 6 sequences for each identity with a sequence length of 30 frames. The loss weight " + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "inline_equation", + "content": "\\gamma" + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "text", + "content": " is set to 1. The neighborhood size is set to 10 and 8 for each graph convolution layer and Binarization module, respectively. And the feature dimensions " + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "inline_equation", + "content": "D" + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{C}}" + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "inline_equation", + "content": "D_{\\mathrm{T}}" + }, + { + "bbox": [ + 304, + 388, + 546, + 544 + ], + "type": "text", + "content": " are set to 512, 512 and 1024, respectively." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "spans": [ + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "text", + "content": "Pre-training. The pre-training model follows a similar training strategy as described above, except that the initial learning rate is set to 1e-4. The loss weight " + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "inline_equation", + "content": "\\eta" + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "text", + "content": " is set to 1. The coefficient " + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "inline_equation", + "content": "\\delta" + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "text", + "content": " in Eq. 4 is set to 0.01 for the first 100 epochs, then increased to 0.1, 0.5 and 1.0 after 100, 200 and 400 epochs. The coarse shape " + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}_{\\mathrm{coarse}}" + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "text", + "content": " contains 128 points, while the detailed shape " + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{P}}_{\\mathrm{detail}}" + }, + { + "bbox": [ + 304, + 557, + 545, + 664 + ], + "type": "text", + "content": " contains 512 points. The weights of the pre-trained GCEE are used as initialization for the ReID network." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 671, + 524, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 671, + 524, + 684 + ], + "spans": [ + { + "bbox": [ + 306, + 671, + 524, + 684 + ], + "type": "text", + "content": "5.2. Comparison with Camera-based Methods" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 306, + 689, + 545, + 713 + ], + "type": "text", + "content": "We compare ReID3D with the state-of-the-art video-based methods [2, 9, 15, 50]. The input images are resized in the" + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17442" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 70, + 99, + 524, + 178 + ], + "blocks": [ + { + "bbox": [ + 46, + 70, + 545, + 94 + ], + "lines": [ + { + "bbox": [ + 46, + 70, + 545, + 94 + ], + "spans": [ + { + "bbox": [ + 46, + 70, + 545, + 94 + ], + "type": "text", + "content": "Table 2. Comparison with state-of-the-art camera-based methods on LReID. Numbers in bold indicate the best performance and underscored ones are the second best. To ensure fairness, ReID3D without pre-training is evaluated." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 70, + 99, + 524, + 178 + ], + "lines": [ + { + "bbox": [ + 70, + 99, + 524, + 178 + ], + "spans": [ + { + "bbox": [ + 70, + 99, + 524, + 178 + ], + "type": "table", + "html": "
MethodVenueModalityNormal lightLow lightOverall
Rank-1Rank-3mAPRank-1Rank-3mAPRank-1Rank-3mAP
TCLNet [15]ECCV 2020Camera98.698.694.8860.073.346.1887.091.080.27
STMN [9]ICCV 202194.398.693.8130.050.031.1775.084.075.02
SINet [2]CVPR 202297.1100.094.6343.360.043.9781.088.079.43
PiT [50]TII 202294.395.786.2133.360.035.7476.085.071.07
B-ReID3DOursLiDAR90.097.182.0490.093.381.6490.096.081.92
ReID3DOurs94.398.683.6593.396.782.4394.098.083.28
", + "image_path": "67abce3276730368331974a5de833833eed17e3c1bf63b1acd9c454bfe7a6d2c.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + }, + { + "bbox": [ + 83, + 179, + 220, + 190 + ], + "lines": [ + { + "bbox": [ + 83, + 179, + 220, + 190 + ], + "spans": [ + { + "bbox": [ + 83, + 179, + 220, + 190 + ], + "type": "text", + "content": "B-ReID3D: ReID3D without pre-training." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_footnote" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 67, + 224, + 266, + 276 + ], + "blocks": [ + { + "bbox": [ + 67, + 207, + 267, + 218 + ], + "lines": [ + { + "bbox": [ + 67, + 207, + 267, + 218 + ], + "spans": [ + { + "bbox": [ + 67, + 207, + 267, + 218 + ], + "type": "text", + "content": "Table 3. Comparison for different pre-training method." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 67, + 224, + 266, + 276 + ], + "lines": [ + { + "bbox": [ + 67, + 224, + 266, + 276 + ], + "spans": [ + { + "bbox": [ + 67, + 224, + 266, + 276 + ], + "type": "table", + "html": "
Pre-training MethodRank-1Rank-3mAP
Baseline(w/o pre-training)90.096.081.92
ReID91.096.082.13
Completion93.097.082.73
Completion + SMPL94.098.083.28
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All methods are evaluated with the same dataset settings and metrics." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 328, + 288, + 483 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 328, + 288, + 483 + ], + "spans": [ + { + "bbox": [ + 46, + 328, + 288, + 483 + ], + "type": "text", + "content": "The comparative results are shown in Tab. 2, from which the following observations can be obtained: (1) ReID3D and B-ReID3D demonstrate their superiority to the video-based methods, primarily benefiting from the utilization of point clouds, which is unaffected by lighting conditions and complex background. (2) ReID3D achieves state-of-the-art results in overall and low light conditions, but it falls behind video-based methods in normal light conditions. This is because video-based methods make full use of appearance information under normal light. (3) Video-based methods perform poorly under low light, while ReID3D and B-ReID3D demonstrate comparable reliability under both low light and normal light." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 491, + 128, + 504 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 491, + 128, + 504 + ], + "spans": [ + { + "bbox": [ + 47, + 491, + 128, + 504 + ], + "type": "text", + "content": "5.3. Pre-training" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 289, + 715 + ], + "type": "text", + "content": "To demonstrate the effectiveness of pre-training with simulated dataset LReID-sync, we evaluate the performance of different pre-training method. The following four methods are evaluated: (1) ReID3D without pre-training. (2) Pretraining with similar ReID task, in which the pre-training model and loss are consistent with the ReID network. (3) Pre-training with only the branch of point cloud completion. (4) Pre-training with multiple tasks, as described in Section 3.1. The experimental results are shown in Tab. 3. It can be observed that pre-training with multiple tasks makes an improvement to the accuracy of ReID3D, with the rank-1 accuracy increasing from 90.0 to 94.0. This improvement can be attributed to two factors: (1) The simulated data comprises a diverse collection of pedestrian point clouds with various body shapes, which supplements the real-world data. (2) Multi-task pre-training effectively leverages the performance of the encoder. Besides, pre-training with" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 312, + 206, + 422, + 289 + ], + "blocks": [ + { + "bbox": [ + 312, + 206, + 422, + 289 + ], + "lines": [ + { + "bbox": [ + 312, + 206, + 422, + 289 + ], + "spans": [ + { + "bbox": [ + 312, + 206, + 422, + 289 + ], + "type": "image", + "image_path": "0d33fddb0ba11bf8e1b54ecf6c9ccbdfdd1e8fe08dbce51e8e4faba482cdb6b4.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 361, + 290, + 372, + 300 + ], + "lines": [ + { + "bbox": [ + 361, + 290, + 372, + 300 + ], + "spans": [ + { + "bbox": [ + 361, + 290, + 372, + 300 + ], + "type": "text", + "content": "(a)" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 432, + 206, + 541, + 289 + ], + "blocks": [ + { + "bbox": [ + 432, + 206, + 541, + 289 + ], + "lines": [ + { + "bbox": [ + 432, + 206, + 541, + 289 + ], + "spans": [ + { + "bbox": [ + 432, + 206, + 541, + 289 + ], + "type": "image", + "image_path": "0d201789505030dc165803eb53620f345022b2d51a36d2e951bf3e2f98ccb650.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 481, + 290, + 491, + 300 + ], + "lines": [ + { + "bbox": [ + 481, + 290, + 491, + 300 + ], + "spans": [ + { + "bbox": [ + 481, + 290, + 491, + 300 + ], + "type": "text", + "content": "(b)" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 313, + 302, + 421, + 384 + ], + "blocks": [ + { + "bbox": [ + 313, + 302, + 421, + 384 + ], + "lines": [ + { + "bbox": [ + 313, + 302, + 421, + 384 + ], + "spans": [ + { + "bbox": [ + 313, + 302, + 421, + 384 + ], + "type": "image", + "image_path": "61357e73f4d721fbde1fe44129706b1e3c334da4291dc88868df0465b3707cef.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 361, + 387, + 372, + 396 + ], + "lines": [ + { + "bbox": [ + 361, + 387, + 372, + 396 + ], + "spans": [ + { + "bbox": [ + 361, + 387, + 372, + 396 + ], + "type": "text", + "content": "(c)" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 432, + 302, + 541, + 384 + ], + "blocks": [ + { + "bbox": [ + 432, + 302, + 541, + 384 + ], + "lines": [ + { + "bbox": [ + 432, + 302, + 541, + 384 + ], + "spans": [ + { + "bbox": [ + 432, + 302, + 541, + 384 + ], + "type": "image", + "image_path": "a65124066ae6eb87fda8de765b1a486b84e0c481d5cbdb8f98e0f136930d2ff7.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 481, + 387, + 492, + 396 + ], + "lines": [ + { + "bbox": [ + 481, + 387, + 492, + 396 + ], + "spans": [ + { + "bbox": [ + 481, + 387, + 492, + 396 + ], + "type": "text", + "content": "(d)" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 304, + 401, + 545, + 456 + ], + "lines": [ + { + "bbox": [ + 304, + 401, + 545, + 456 + ], + "spans": [ + { + "bbox": [ + 304, + 401, + 545, + 456 + ], + "type": "text", + "content": "Figure 8. Completion results for real-world pedestrian point clouds obtained by the pre-trained model. In each sample, the detailed shape, coarse shape, and image are shown from left to right. The red points represent the input point cloud, and the blue points represent the predicted complete point cloud." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 473, + 545, + 497 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 473, + 545, + 497 + ], + "spans": [ + { + "bbox": [ + 304, + 473, + 545, + 497 + ], + "type": "text", + "content": "task of ReID or point cloud completion also leads to an improvement in performance." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 304, + 498, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 498, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 498, + 546, + 713 + ], + "type": "text", + "content": "To showcase the robust feature encoding capabilities attained by the encoder through pre-training, we visualize the completion results for several real-world pedestrian point clouds with different characteristics, as shown in Fig. 8. We can observe that: (1) Intuitively, the detailed and coarse shape closely resemble the actual human shape, which indicates that the encoder has successfully captured the complete features of the human body. (2) The detailed shape is an extension based on the coarse shape, with higher resolution and more information. (3) The pre-trained encoder has the ability to estimate the features of the missing part in the point cloud. As shown in Fig. 8a, the unobserved parts of the legs are accurately completed. (4) Due to motion blur or object carrying, the point cloud may contain some noise points. For example, in Fig. 8b and Fig. 8c, there are red noise points located between the legs and from the carrying bags, respectively. However, the model can effectively filter out the noise points that do not conform to the body shape." + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 293, + 748, + 317, + 757 + ], + "type": "text", + "content": "17443" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 73, + 87, + 261, + 139 + ], + "blocks": [ + { + "bbox": [ + 58, + 71, + 276, + 81 + ], + "lines": [ + { + "bbox": [ + 58, + 71, + 276, + 81 + ], + "spans": [ + { + "bbox": [ + 58, + 71, + 276, + 81 + ], + "type": "text", + "content": "Table 4. Performance of B-ReID3D with different encoders." + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 73, + 87, + 261, + 139 + ], + "lines": [ + { + "bbox": [ + 73, + 87, + 261, + 139 + ], + "spans": [ + { + "bbox": [ + 73, + 87, + 261, + 139 + ], + "type": "table", + "html": "
EncoderRank-1Rank-3mAP
PointNet [31]74.088.060.31
Point Transformer [53]83.093.074.86
3DCNN [8]34.051.028.27
GCEE90.096.081.92
", + "image_path": "aa1f631d69e8cf606e883c6fc4b6e749c95e4b45d60c810f6a7c87148059831d.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 74, + 168, + 261, + 211 + ], + "blocks": [ + { + "bbox": [ + 51, + 152, + 282, + 163 + ], + "lines": [ + { + "bbox": [ + 51, + 152, + 282, + 163 + ], + "spans": [ + { + "bbox": [ + 51, + 152, + 282, + 163 + ], + "type": "text", + "content": "Table 5. Ablation study on the CFE module and Eraser module." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 74, + 168, + 261, + 211 + ], + "lines": [ + { + "bbox": [ + 74, + 168, + 261, + 211 + ], + "spans": [ + { + "bbox": [ + 74, + 168, + 261, + 211 + ], + "type": "table", + "html": "
Encoder TypeRank-1Rank-3mAP
B-ReID3D-w/o CFE83.094.074.15
B-ReID3D-w/o Eraser85.095.080.47
B-ReID3D90.096.081.92
", + "image_path": "37825f65ab299654cc46846146b73979a8590da7d7e98d9802d2a562cabc8244.jpg" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_body" + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 232, + 140, + 245 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 232, + 140, + 245 + ], + "spans": [ + { + "bbox": [ + 47, + 232, + 140, + 245 + ], + "type": "text", + "content": "5.4. Ablation Study" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 251, + 289, + 431 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 251, + 289, + 431 + ], + "spans": [ + { + "bbox": [ + 46, + 251, + 289, + 431 + ], + "type": "text", + "content": "Effect of Encoders. To evaluate the effectiveness of our GCEE, we also implement several commonly used encoders in point cloud tasks to replace GCEE in the ReID network for comparison, including PointNet [31], Point Transformer [53], and 3DCNN [8]. All methods use consistent training strategies and employ a same transformer module as the temporal fusion network. We report the results on LReID in Tab. 4, obtaining the following observations: (1) GCEE outperforms other encoders, which is mainly beneficial by its flexible graph structure in the feature space and the strategy of complementary enhancement. (2) Point-based encoders are superior to voxel-based encoder 3DCNN, which indicates that point-based encoders can provide a more detailed understanding of humans in tasks like ReID." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 453, + 287, + 609 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 453, + 287, + 609 + ], + "spans": [ + { + "bbox": [ + 46, + 453, + 287, + 609 + ], + "type": "text", + "content": "Effect of CFE. CFE is a crucial component in our proposed encoder, used to extract complementary features. We compared our full model with two ablated versions: one without CFE and another without the Eraser module, as shown in Tab. 5. Removing CFE results in a lower rank-1 accuracy, with a score of 83.0 compared to our 90.0, which highlights the effectiveness of the complementary enhancement in constructing distinctive and comprehensive features. While removing the Eraser module retains the features of the complementary frame, it might lead to the extraction of similar features from the primary frame, thus restricting the improvement in accuracy, with a score of 85.0 compared to 83.0 of the version without CFE." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 629, + 287, + 715 + ], + "type": "text", + "content": "Effect of the Temporal Module. We evaluate the effectiveness of different temporal modules in combination with GCEE, as shown in Tab. 6. We can observe that the attention-based transformer structure demonstrates significant superiority over the LSTM structure. The rank-1 accuracy of transformer exceeds that of LSTM by 8 points, and that of BiLSTM by 10 points." + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 340, + 85, + 512, + 127 + ], + "blocks": [ + { + "bbox": [ + 310, + 71, + 541, + 82 + ], + "lines": [ + { + "bbox": [ + 310, + 71, + 541, + 82 + ], + "spans": [ + { + "bbox": [ + 310, + 71, + 541, + 82 + ], + "type": "text", + "content": "Table 6. Results of B-ReID3D with different temporal modules." + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 340, + 85, + 512, + 127 + ], + "lines": [ + { + "bbox": [ + 340, + 85, + 512, + 127 + ], + "spans": [ + { + "bbox": [ + 340, + 85, + 512, + 127 + ], + "type": "table", + "html": "
Temporal ModuleRank-1Rank-3mAP
LSTM [11]82.089.072.34
Bi-LSTM [33]80.090.070.92
Transformer [35]90.096.081.92
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Feature visualization of CFE. The features of the primary frame and the supplementary frame are presented on left and right, respectively. The color bar on the right indicates the feature value." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 306, + 272, + 432, + 285 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 272, + 432, + 285 + ], + "spans": [ + { + "bbox": [ + 306, + 272, + 432, + 285 + ], + "type": "text", + "content": "5.5. Visualization Analysis" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 291, + 545, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 291, + 545, + 434 + ], + "spans": [ + { + "bbox": [ + 304, + 291, + 545, + 434 + ], + "type": "text", + "content": "For qualitative analysis, we visualize the feature values output by the two graph convolutional layers in the CFE, as shown in Fig. 9. Three samples are taken from different actions of a person in the test set of LReID, with each sample comprising two consecutive frames. In each sample, the features of the primary frame and the supplementary frame are presented. We can observe that primary ones pay more attention to the head and arms, potentially linked to the discriminative height parameter, while supplementary ones predominantly emphasize the torso and legs. The combination of them creates a complementary and comprehensive feature representation." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 445, + 383, + 457 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 445, + 383, + 457 + ], + "spans": [ + { + "bbox": [ + 306, + 445, + 383, + 457 + ], + "type": "text", + "content": "6. Conclusions" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 465, + 545, + 646 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 465, + 545, + 646 + ], + "spans": [ + { + "bbox": [ + 304, + 465, + 545, + 646 + ], + "type": "text", + "content": "This paper presents the first research on person ReID using precise 3D structural information provided by LiDAR. Firstly, We propose a LiDAR-based ReID framework, named ReID3D, that utilizes pre-training to guide Graph-based Complementary Enhancement Encoder (GCEE) for extracting comprehensive 3D intrinsic features. Moreover, we build the first LiDAR-based person ReID dataset, termed LReID, which contains 320 pedestrians in various outdoor scenes and lighting conditions. Additionally, we introduce LReID-sync, a new simulated pedestrian dataset designed for pre-training encoders with tasks of point cloud completion and shape parameter learning. Our proposed ReID3D demonstrates exceptional performance on LReID, highlighting the significant potential of LiDAR in addressing person ReID tasks." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 656, + 404, + 669 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 656, + 404, + 669 + ], + "spans": [ + { + "bbox": [ + 306, + 656, + 404, + 669 + ], + "type": "text", + "content": "Acknowledgement" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 305, + 675, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 675, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 305, + 675, + 545, + 712 + ], + "type": "text", + "content": "This work is supported by the National Key Research and Development Program of China under Grant (2018AAA0102803)." + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17444" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 14, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 145 + ], + "type": "text", + "content": "[1] Sk Miraj Ahmed, Aske R Lejbolle, Rameswar Panda, and Amit K Roy-Chowdhury. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 4747–4756, 2017. 2" + } + ] + } + ], + "index": 5 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "17447" + } + ] + } + ], + "index": 7 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 10 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/6a80c1df-3dbd-46be-ba3b-340e6d1a9ff3_content_list.json b/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/6a80c1df-3dbd-46be-ba3b-340e6d1a9ff3_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..6f58ad93840de6ca86ad4220bfaa87259b7ea2ca --- /dev/null +++ b/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/6a80c1df-3dbd-46be-ba3b-340e6d1a9ff3_content_list.json @@ -0,0 +1,1580 @@ +[ + { + "type": "text", + "text": "LiDAR4D: Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis", + "text_level": 1, + "bbox": [ + 84, + 128, + 883, + 152 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Zehan Zheng, Fan Lu, Weiyi Xue, Guang Chen†, Changjun Jiang Tongji University", + "bbox": [ + 215, + 180, + 751, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "{zhengzehan, lufan, xwy, guangchen, cjjiang}@tongji.edu.cn", + "bbox": [ + 225, + 219, + 738, + 233 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 265, + 313, + 282 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Although neural radiance fields (NeRFs) have achieved triumphs in image novel view synthesis (NVS), LiDAR NVS remains largely unexplored. Previous LiDAR NVS methods employ a simple shift from image NVS methods while ignoring the dynamic nature and the large-scale reconstruction problem of LiDAR point clouds. In light of this, we propose LiDAR4D, a differentiable LiDAR-only framework for novel space-time LiDAR view synthesis. In consideration of the sparsity and large-scale characteristics, we design a 4D hybrid representation combined with multi-planar and grid features to achieve effective reconstruction in a coarse-to-fine manner. Furthermore, we introduce geometric constraints derived from point clouds to improve temporal consistency. For the realistic synthesis of LiDAR point clouds, we incorporate the global optimization of ray-drop probability to preserve cross-region patterns. Extensive experiments on KITTI-360 and NuScenes datasets demonstrate the superiority of our method in accomplishing geometry-aware and time-consistent dynamic reconstruction. Codes are available at https://github.com/ispc-lab/LiDAR4D.", + "bbox": [ + 75, + 297, + 473, + 599 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 627, + 209, + 642 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Dynamic scene reconstruction is of crucial importance across various fields such as AR/VR, robotics and autonomous driving. Existing advanced methods in computer vision enable high-fidelity 3D scene reconstruction and novel view synthesis (NVS), which can further serve a wide range of downstream tasks and applications. For instance, we could reconstruct driving scenarios directly from collected sensor logs, allowing for scene replay and novel data generation [43]. It shows great potential for boosting data diversity, forming data closed-loop, and improving the generalizability of the autonomous driving system.", + "bbox": [ + 75, + 652, + 468, + 818 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "However, the majority of current research focuses on novel view synthesis for cameras, while other sensors such as LiDAR remain largely unexplored. Similar to camera images, LiDAR point clouds are also partial observations", + "bbox": [ + 75, + 819, + 468, + 878 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/02712cacf46b6f519b53009aaafb2fb50135c4fa25ad4ffaa52b0a404f717893.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 503, + 267, + 888, + 338 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/ebd986dd1fae82dd259bebeb44b2f4b4033109b5e9637c9b32c0a688045de9a9.jpg", + "image_caption": [ + "Figure 1. Dynamic scenes of LiDAR point clouds in autonomous driving. Large-scale vehicle motion poses a significant challenge for dynamic reconstruction and novel space-time view synthesis. White dots indicate the ego-car trajectory." + ], + "image_footnote": [], + "bbox": [ + 503, + 339, + 888, + 487 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "of the scene that vary across different locations and views. The reconstruction faces considerable challenges due to the sparsity, discontinuity and occlusion of LiDAR point clouds. Furthermore, as illustrated in Figure 1, dynamic scenarios combine novel spatial view and temporal view synthesis simultaneously. Meanwhile, the large motion of dynamic objects makes it difficult to align and reconstruct.", + "bbox": [ + 496, + 577, + 890, + 683 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Traditional LiDAR-based 3D scene reconstruction techniques aggregate multiple sparse point cloud frames directly in the world coordinate system [19] and further convert them into explicit surface representations such as triangular meshes [25]. Subsequently, the intersection of the LiDAR beams with the mesh surface can be calculated by performing ray-casting to render novel-view LiDAR point clouds.", + "bbox": [ + 496, + 684, + 890, + 790 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Nevertheless, high-quality surface reconstruction of complex large-scale scenes is challenging to accomplish, which may lead to significant geometric errors. Furthermore, the aforementioned explicit reconstruction method is limited to static scenes and struggles to accurately model the intensity or ray-drop characteristics of actual LiDAR points.", + "bbox": [ + 496, + 792, + 890, + 883 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Neural radiance fields [26] implicitly reconstruct the", + "bbox": [ + 517, + 885, + 890, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "† Corresponding author.", + "bbox": [ + 101, + 886, + 230, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "5145", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "scene and generate novel-view data through volume rendering in a continuous representation space, which also offers an alternative solution for LiDAR reconstruction. Consequently, the most recent researches [16, 39, 44] are shifting their attention towards the novel view synthesis of LiDAR. NeRF-LiDAR [44] integrates image and point cloud modalities for LiDAR synthesis, whereas LiDAR-only methods like LiDAR-NeRF [39] and NFL [16] explore the possibility of LiDAR reconstruction and generation without RGB images. Most prior methods directly apply the image NVS pipeline to LiDAR point clouds. However, LiDAR point clouds are inherently different from 2D images, which poses challenges for current LiDAR NVS methods to achieve high-quality reconstruction: (1) previous methods are limited to static scenes, ignoring the dynamic nature of autonomous driving scenarios; (2) the vast scale and high sparsity of LiDAR point clouds pose higher demands on the representations; and (3) intensity and ray-drop characteristics modeling are required for synthesis realism.", + "bbox": [ + 76, + 90, + 472, + 378 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "To overcome the aforementioned limitations, we propose LiDAR4D, shedding light on three pivotal insights to elevate the current LiDAR NVS pipeline. To tackle the dynamic objects, we introduce geometric constraints derived from point clouds and aggregate multi-frame dynamic features for temporal consistency. Regarding compact large-scale scene reconstruction, we design a coarse-to-fine hybrid representation combined with multi-planar and grid features to reconstruct the smooth geometry and high-frequency intensity. Additionally, we employ global optimization to preserve patterns across regions for raydrop probability refinement. Therefore, LiDAR4D is capable of achieving geometry-aware and time-consistent reconstruction under large-scale dynamic scenarios.", + "bbox": [ + 76, + 378, + 472, + 589 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "We evaluate our method on diverse dynamic scenarios of KITTI-360 [23] and NuScenes [3] autonomous driving datasets. With comprehensive experiments, LiDAR4D significantly outperforms previous state-of-the-art NeRF-based implicit approaches and explicit reconstruction methods. In comparison to LiDAR-NeRF [39], we achieve $24.3\\%$ and $24.2\\%$ reduction in CD error on KITTI-360 dataset and NuScenes dataset, respectively. Similar leadership exists for other metrics of range depth and intensity. In summary, our main contributions are three-fold:", + "bbox": [ + 76, + 590, + 472, + 742 + ], + "page_idx": 1 + }, + { + "type": "list", + "sub_type": "text", + "list_items": [ + "- We propose LiDAR4D, a differentiable LiDAR-only framework for novel space-time LiDAR view synthesis, which reconstructs dynamic driving scenarios and generates realistic LiDAR point clouds end-to-end.", + "- We introduce 4D hybrid neural representations and motion priors derived from point clouds for geometry-aware and time-consistent large-scale scene reconstruction.", + "- Comprehensive experiments demonstrate the state-of-the-art performance of LiDAR4D in challenging dynamic scene reconstruction and novel view synthesis." + ], + "bbox": [ + 76, + 743, + 468, + 897 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 500, + 89, + 640, + 106 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "LiDAR Simulation. Traditional simulators [7, 18, 36] such as CARLA are based on physics engines, which can generate LiDAR point clouds via ray casting within handcrafted virtual environments. However, it has diversity limitations and a heavy reliance on costly 3D assets. And there is still a large domain gap compared to real-world data. Thus, several recent works [13, 19, 25] further narrowed this gap by reconstructing the scene from real data before simulation. LiDARsim [25] reconstructs the mesh surfel representation and employs a neural network to learn the ray-drop characteristics. Besides, it is noted that there are other surface reconstruction works like NKSR [15] that can convert LiDAR point clouds into mesh representations. Nonetheless, these explicit reconstruction works are troublesome for recovering precise surfaces in large-scale complex scenes, which further leads to a decrease in the accuracy of point cloud synthesis. Instead, PCGen [19] directly reconstructs from the point clouds, followed by rendering in a rasterization-like manner and first peak averaging. Although it preserves the original information better, the rendering point clouds remain relatively noisy. Moreover, all these explicit methods mentioned above are only applicable to static scenes. In contrast, our approach implicitly reconstructs the continuous representation via space-time neural radiance fields, which achieves higher-quality realistic point cloud synthesis and gets rid of static reconstruction limitations.", + "bbox": [ + 496, + 114, + 893, + 507 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Neural Radiance Fields. Considerable recent research [1, 4, 5, 11, 14, 24, 26, 28, 38] based on neural radiance fields has led to breakthroughs as well as remarkable achievements in novel view synthesis (NVS) tasks. A wide variety of neural representations based on MLPs [1, 26], voxel grids [11, 24, 38], tri-planes [4, 14], vector decomposition [5], and multi-level hash grids [28] have been fully exploited for reconstruction and synthesis. Yet, most of the work focuses on object-centered reconstruction of small indoor scenes. Subsequently, several works [2, 33, 42] gradually extended it to large-scale outdoor scenarios. Despite this, neural radiance fields typically suffer from geometric ambiguity with RGB image inputs. Therefore, DS-NeRF [6] and DDP-NeRF [34] introduce the depth prior to enhancing efficiency, and URF [33] also utilizes Li-DAR point clouds to facilitate reconstruction. In this paper, we employ novel hybrid representations and neural LiDAR fields to reconstruct large-scale scenarios for LiDAR NVS.", + "bbox": [ + 496, + 507, + 893, + 779 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "NeRF for LiDAR NVS. Very recently, a few studies [16, 39, 43, 44] have pioneered in novel view synthesis of LiDAR point clouds based on neural radiance fields, significantly surpassing traditional simulation methods. Among them, NeRF-LiDAR [44] and UniSim [43] require both RGB images and LiDAR point clouds as inputs and reconstruct the driving scene with photometric loss and depth supervision. Subsequently, novel-view LiDAR point clouds", + "bbox": [ + 496, + 779, + 893, + 901 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "5146", + "bbox": [ + 482, + 944, + 516, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/c9c921e6c7979116a08482083634ba85aed222024ae9c81bb1bc67e22fbca0af.jpg", + "image_caption": [ + "Figure 2. Overview of our proposed LiDAR4D. For large-scale autonomous driving scenarios, we utilize the 4D hybrid representation, which combines low-resolution multi-planar features and high-resolution hash grid features to achieve effective reconstruction. Then, multi-level spatio-temporal features aggregated by flow MLP are fed into neural LiDAR fields for density, intensity and ray-drop probability prediction. Finally, novel space-time view LiDAR point clouds are synthesized via differentiable rendering. Furthermore, we construct geometric constraints derived from point clouds for temporal consistency and the global optimization of ray-drop for generation realism." + ], + "image_footnote": [], + "bbox": [ + 133, + 89, + 877, + 349 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "can be generated through neural depth rendering. Among LiDAR-only methods, LiDAR-NeRF [39] and NFL [16] firstly proposed the differentiable LiDAR NVS framework, which reconstructed depth, intensity, and ray-drop probability simultaneously. Nevertheless, these approaches [16, 39, 44] are restricted to static scene reconstruction and incapable of handling dynamic objects such as moving vehicles. Although UniSim [43] does support dynamic scenes, it is largely limited by the need for ground-truth labeling of 3D object detection and decoupling the background and dynamic objects before reconstruction. Instead, our research focuses on LiDAR-only inputs for dynamic scene reconstruction and novel space-time view synthesis without the help of RGB images or ground-truth labels. And it's noteworthy that NFL [16] has contributed significantly to the detailed physical modeling of LiDAR, such as beam divergence and secondary returns, which is orthogonal to ours and could be beneficial to all LiDAR NVS works.", + "bbox": [ + 75, + 455, + 472, + 728 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Dynamic Scene Reconstruction. A substantial amount of research [9, 12, 21, 22, 29, 30, 32, 37, 40] has been devoted to expanding neural radiance fields to encompass dynamic scene reconstruction. In general, dynamic NeRFs can be broadly categorized into two groups. One is the deformable neural radiance fields [9, 29, 30, 32] that map coordinates into the canonical space via continuous deformation fields. While the decoupling of deformation and radiance fields simplifies the optimization, establishing accurate long-distance correspondence remains challenging. The other is spatio-temporal neural fields [12, 21, 22, 37],", + "bbox": [ + 75, + 734, + 472, + 902 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "which consider time as an additional dimensional input to construct a 4D spatio-temporal representation. Thus, it is flexible to simultaneously model appearance, geometry, and motion as a continuous time-varying function. Most previous work has concentrated on relatively smaller displacements indoors, whereas large-scale vehicle movements in autonomous driving scenarios are even more challenging. Furthermore, our work is also the first to introduce dynamic neural radiance fields into the LiDAR NVS task.", + "bbox": [ + 496, + 455, + 893, + 594 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Methodology", + "text_level": 1, + "bbox": [ + 500, + 612, + 635, + 630 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "In this section, we start with the problem formulation of novel LiDAR view synthesis and the preliminary for NeRFs. Following this, a detailed description of our proposed LiDAR4D framework is provided.", + "bbox": [ + 496, + 638, + 893, + 700 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Problem Formulation. In the dynamic driving scenario, given the collected LiDAR point cloud sequence $S = \\{S_0, S_1, \\dots, S_{n-1}\\}$ ( $S_i \\in \\mathbb{R}^{K \\times 4}$ ), along with the corresponding sensor poses $P_s = \\{P_0, P_1, \\dots, P_{n-1}\\}$ ( $P_i \\in SE(3)$ ) and timestamps $T_s = \\{t_0, t_1, \\dots, t_{n-1}\\}$ ( $t_i \\in \\mathbb{R}$ ) as inputs. Each single LiDAR frame $S_i$ contains $K$ points of 3D coordinates $x$ and 1D reflection intensity $\\rho$ .", + "bbox": [ + 496, + 702, + 893, + 808 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The goal of LiDAR4D is to reconstruct this dynamic scene as a continuous implicit representation based on neural fields. Furthermore, given a novel sensor pose $P_{novel}$ and any moment $t_{novel}$ , LiDAR4D performs neural rendering to synthesize the LiDAR point cloud $S_{novel}$ with intensities under the novel space-time view.", + "bbox": [ + 496, + 810, + 893, + 902 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "5147", + "bbox": [ + 482, + 944, + 516, + 957 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/00d3f7789b3f4ab48b86df245cf042c11c6bd4288490432059fa75e509291b01.jpg", + "image_caption": [ + "Figure 3. 4D decomposition of hybrid planar-grid representation. Dynamic features can be further aggregated using flow MLP." + ], + "image_footnote": [], + "bbox": [ + 83, + 89, + 460, + 220 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Preliminary for NeRF. Neural radiance fields, NeRFs for short, take 5D inputs of position $\\mathbf{x} \\in \\mathbb{R}^3$ and viewing direction $(\\theta, \\phi)$ as inputs and establish the mapping to the volume density $\\sigma$ and color $\\mathbf{c}$ . Afterward, it performs volume rendering to estimate pixel values and synthesize images in unknown novel views. In detail, it emits a light ray $\\mathbf{r}$ from the sensor center $\\mathbf{o}$ with the direction $\\mathbf{d}$ , i.e., $\\mathbf{r}(t) = \\mathbf{o} + t\\mathbf{d}$ , and then integrates the neural field outputs of $N$ samples along this ray to approximate the pixel color $\\mathcal{C}$ . The volume rendering function can be formed as follows:", + "bbox": [ + 75, + 273, + 472, + 426 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\mathcal {C}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\left(1 - e ^ {- \\sigma_ {i} \\delta_ {i}}\\right) \\mathbf {c} _ {i}, T _ {i} = \\exp \\left(- \\sum_ {j = 1} ^ {i - 1} \\sigma_ {j} \\delta_ {j}\\right) (1)\n$$\n", + "text_format": "latex", + "bbox": [ + 84, + 436, + 468, + 479 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $T$ indicates the accumulated transmittance, $\\sigma$ denotes the density and $\\delta$ refers to the distance between samples.", + "bbox": [ + 76, + 488, + 468, + 518 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.1. LiDAR4D Overview", + "text_level": 1, + "bbox": [ + 76, + 527, + 269, + 542 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Following neural radiance fields, our proposed LiDAR4D reconstructs the point cloud scene into an implicit continuous representation. Differing from original NeRFs with photometric loss for RGB images, we redefine the neural fields based on LiDAR, which are dubbed neural LiDAR fields. As depicted in Figure 2, it focuses on modeling the geometric depth, reflection intensity, and ray-drop probability of LiDAR point clouds. For large-scale dynamic driving scenarios, LiDAR4D combines coarse-resolution multi-planar features with high-resolution hash grid representation to achieve efficient and effective reconstruction. Then, we lift it to 4D and introduce temporal information encoding for novel space-time view synthesis. To ensure geometry-aware and time-consistent results, we additionally incorporate explicit geometric constraints derived from point clouds. Ultimately, we predict the ray-drop probability for each ray and perform global refinement with a runtime-optimized U-Net to improve generation realism.", + "bbox": [ + 75, + 550, + 472, + 824 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "3.2. 4D Hybrid Planar-Grid Representation", + "text_level": 1, + "bbox": [ + 76, + 830, + 416, + 848 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Figure 3 illustrates how our proposed novel hybrid representation breaks down the 4D space into planar and hash grid features, which further subdivide into static and", + "bbox": [ + 75, + 854, + 468, + 900 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/3fa061ea4fc2b9f5f7dc1e922ee2884f6688a4244ca2c406898368c18166ad30.jpg", + "image_caption": [ + "K-Planes (Planes only)" + ], + "image_footnote": [], + "bbox": [ + 521, + 88, + 687, + 138 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/54352bcedbff2724f624b5ffe71c7e2ed9358452b99ae11e07d55fccffe21a72.jpg", + "image_caption": [ + "LiDAR4D (w/ Hybrid Representations)" + ], + "image_footnote": [], + "bbox": [ + 694, + 88, + 861, + 138 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/d6f5dc9c74ae67198a1fc63dadad0f45434c81eb38ee62e343ea714ab276cfe6.jpg", + "image_caption": [ + "LiDAR-NeRF (Hash Grid only)" + ], + "image_footnote": [], + "bbox": [ + 521, + 152, + 687, + 205 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/6524055ecbaac99ea1f389a582e57e26385a90d7374f2b21901d684e7bde7fa1.jpg", + "image_caption": [ + "GT", + "Figure 4. Qualitative comparison for the hybrid representation. Compared to the noisy intensity reconstruction of LiDAR-NeRF and the blurry one of K-Planes, our hybrid representation achieves more precise and smooth results." + ], + "image_footnote": [], + "bbox": [ + 694, + 152, + 861, + 205 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "dynamic ones. Different from the reconstruction of small indoor objects, large-scale autonomous driving scenes place higher demands on the representation ability and resolution of the features. However, the dense grid representation such as TiNeuVox [9] is unscalable for large-scale scenarios due to its cubically growing complexity. Therefore, we follow K-planes [12] and decompose the scene space into a combination of features in multiple orthogonal planes to drastically reduce the parameter quantities. The planar feature can be obtained as follows:", + "bbox": [ + 496, + 301, + 890, + 452 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {f} _ {\\text {p l a n a r}} = \\mathcal {S} (\\mathbf {V}, (x, y, z, t)), \\mathbf {V} \\in \\mathbb {R} ^ {(3 M ^ {2} + 3 M H) C} \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 519, + 462, + 890, + 482 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\mathbf{V}$ stores features with $M$ spatial resolution, $H$ temporal resolution and $C$ channels. $S$ refers to the sampling function that projects 4D coordinates into the corresponding planes $(xy, xz, yz, xt, yt, zt)$ and interpolates features bilinearly. Static $(xy, xz, yz)$ and dynamic $(xt, yt, zt)$ features are multiplied separately by Hadamard product and multiscale features are concatenated in a coarse-to-fine manner.", + "bbox": [ + 496, + 494, + 890, + 599 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Nonetheless, for scenes spanning hundreds of meters, this improvement in resolution remains inadequate, especially for the high-frequency intensity reconstruction. Owing to the hash grids proposed in Instant-NGP [28], an explicit grid structure with ultra-high resolution is possible. Additionally, the sparsity of the LiDAR point cloud scene substantially avoids the adverse effects of hash collisions.", + "bbox": [ + 496, + 599, + 890, + 705 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {f} _ {\\text {h a s h}} = \\mathcal {S} (\\mathbf {G}, (x, y, z, t)), \\mathbf {G} \\in \\mathbb {R} ^ {(M ^ {3} + 3 M ^ {2} H) C} \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 524, + 717, + 890, + 738 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where the dense grid $\\mathbf{G}$ will be further compressed into limited storage via hash mapping for parameter reduction. Similarly, the 4D coordinates are projected into static $(xyz)$ and dynamic $(xyt, xzt, yzt)$ multi-level hash grids before tri-linear interpolation and concatenation, where the dynamic features are multiplied using Hadamard product.", + "bbox": [ + 496, + 750, + 890, + 839 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "However, it's notable that pure hash grid representation still suffers from visual artifacts and noisy reconstruction results (as shown in Figure 4), which impede the construction of accurate object geometry. In light of this, we adopt", + "bbox": [ + 496, + 839, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "5148", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "multi-planar features at lower resolutions for overall smooth representation and employ hash grids at higher resolutions to handle finer details, ultimately achieving high accuracy and efficiency in large-scale scene reconstruction.", + "bbox": [ + 75, + 90, + 468, + 151 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.3. Scene Flow Prior", + "text_level": 1, + "bbox": [ + 76, + 162, + 245, + 176 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "To enhance the temporal consistency of the current 4D spatio-temporal representations, we further incorporate a flow MLP [20, 46] for motion estimation. It takes the encoded spatio-temporal coordinates as input and constructs the mapping from coordinate fields $\\mathbb{R}^4$ to motion fields $\\mathbb{R}^3$ .", + "bbox": [ + 75, + 186, + 468, + 262 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\Delta \\mathbf {x} = \\operatorname {M L P} _ {\\text {f l o w}} (\\gamma (\\mathbf {x}, t)), \\quad \\mathbf {x} ^ {\\prime} = \\mathbf {x} + \\Delta \\mathbf {x} \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 132, + 279, + 468, + 295 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Since the vehicle motion range may span a long distance in autonomous driving scenarios, it is extremely hard to establish long-term correspondences to the canonical space in deformable neural radiance fields. Thus, as with Li et al. [21, 22], we utilize the flow MLP to predict motion only between adjacent frames and aggregate multi-frame dynamic features to achieve time-consistent reconstruction.", + "bbox": [ + 75, + 305, + 468, + 409 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In addition, explicit geometric constraints can be further derived from the input LiDAR point clouds. By feeding point clouds into the flow MLP to produce the scene flow prediction, we can regulate the chamfer distance as a geometric loss $(\\mathcal{L}_{\\mathrm{flow}})$ . It imposes motion prior and additional supervision on LiDAR4D, thus accomplishing the geometry-aware reconstruction. Chamfer Distance between two frames of point cloud $S$ and $\\hat{S}$ is defined as follows:", + "bbox": [ + 75, + 410, + 468, + 523 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathrm {C D} = \\frac {1}{K} \\sum_ {\\hat {p} _ {i} \\in \\hat {S}} \\min _ {p _ {i} \\in S} \\| \\hat {p} _ {i} - p _ {i} \\| _ {2} ^ {2} + \\frac {1}{K} \\sum_ {p _ {i} \\in S} \\min _ {\\hat {p} _ {i} \\in \\hat {S}} \\| p _ {i} - \\hat {p} _ {i} \\| _ {2} ^ {2} \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 84, + 534, + 468, + 570 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {f l o w}} = \\sum_ {j \\in \\pm 1} \\mathrm {C D} \\left(S _ {i} + \\mathrm {M L P} _ {\\text {f l o w}} \\left(S _ {i}\\right), S _ {i + j}\\right), i \\in (0, n - 1) \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 84, + 580, + 468, + 609 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.4. Neural LiDAR Fields", + "text_level": 1, + "bbox": [ + 76, + 621, + 276, + 636 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "LiDAR emits laser pulses and measures the time-of-flight (ToF) to determine object distance, along with the intensity of reflected lights. Spinning LiDAR has a 360-degree horizontal field of view (FOV) and a limited range of vertical field of view, which perceives the environment with certain angular resolution lasers. In the same way for neural LiDAR fields, we transmit lasers at specific angular intervals within the FOV, using the center of the LiDAR sensor as the origin o. The direction d of the laser is determined by the azimuth angle $\\theta$ and elevation angle $\\phi$ under the polar coordinate system, which is shown below.", + "bbox": [ + 75, + 645, + 468, + 810 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {d} = (\\cos \\theta \\cos \\phi , \\sin \\theta \\sin \\phi , \\cos \\phi) ^ {T} \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 145, + 823, + 468, + 840 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Then we query 3D point coordinates sampled along the laser and feed them into neural fields to predict the density at the corresponding location. Following this, the density", + "bbox": [ + 75, + 854, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/58714d57a7bbdb076a18f43ec6e88e2391477953201cd3bbaba370f7b27170ba.jpg", + "image_caption": [ + "Figure 5. Qualitative comparison for the ray-drop refinement. The point-wise prediction of ray-drop probability by MLP cannot preserve global patterns well. Instead, LiDAR4D drastically improves generation realism via runtime-optimized U-Net." + ], + "image_footnote": [], + "bbox": [ + 506, + 85, + 890, + 176 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "along the ray is integrated to obtain the expectation of depth value $\\mathcal{D}$ , which serves as the laser beam's return distance.", + "bbox": [ + 498, + 257, + 890, + 287 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\mathcal {D}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\left(1 - e ^ {- \\sigma_ {i} \\delta_ {i}}\\right) z _ {i}, \\quad \\alpha_ {i} = 1 - e ^ {- \\sigma_ {i} \\delta_ {i}} \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 516, + 297, + 890, + 338 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $z_{i}$ is the depth value of queried points on the ray $\\mathbf{r}$ , and $\\alpha$ is the definition of the opacity.", + "bbox": [ + 498, + 348, + 890, + 378 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In addition, we predict the intensity $\\mathcal{I}$ and ray-drop probability $\\mathcal{P}$ separately for each point and similarly conduct alpha-composition along the ray.", + "bbox": [ + 498, + 378, + 890, + 422 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\hat {\\mathcal {I}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\alpha_ {i} i _ {i}, \\quad \\hat {\\mathcal {P}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\alpha_ {i} p _ {i} \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 555, + 434, + 890, + 474 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $i_{i}$ and $p_{i}$ are the point-wise intensity and ray-drop probability outputs of LiDAR4D. We use separate MLPs to take temporal aggregated planar and hash features, as well as position-encoded viewpoints as inputs for prediction.", + "bbox": [ + 498, + 484, + 890, + 546 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\ni = \\operatorname {M L P} _ {\\text {i n t e n s i t y}} \\left(\\mathbf {f} _ {\\text {p l a n a r}}, \\mathbf {f} _ {\\text {h a s h}}, \\gamma (\\mathbf {d})\\right) \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 566, + 556, + 890, + 573 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\rho = \\mathrm {M L P} _ {\\text {r a y d r o p}} \\left(\\mathbf {f} _ {\\text {p l a n a r}}, \\mathbf {f} _ {\\text {h a s h}}, \\gamma (\\mathbf {d})\\right) \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 583, + 890, + 599 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\gamma (x) = \\left(\\sin \\left(2 ^ {0} x\\right), \\cos \\left(2 ^ {0} x\\right), \\dots , \\sin \\left(2 ^ {L - 1} x\\right), \\cos \\left(2 ^ {L - 1} x\\right)\\right) \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 516, + 609, + 890, + 638 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "3.5. Ray-drop Refinement", + "text_level": 1, + "bbox": [ + 500, + 648, + 700, + 665 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "During laser ranging, a portion of the emitted rays is not reflected back to the sensor, which is termed the ray-drop characteristic. In fact, the ray-drop of LiDAR is significantly impacted by various aspects, including distance, surface properties and sensor noise. As in LiDAR-NeRF [39], ray-drop prediction is directly accomplished with a pointwise MLP head, which is essentially noisy and unreliable. To address this issue, we employ the U-Net [35] with residuals to refine the ray-drop mask globally and better preserve the consistent pattern across regions. It takes the full ray-drop probability, depth and intensity prediction of LiDAR4D as inputs (different from previous work) and refines the final mask via binary cross-entropy loss as follows:", + "bbox": [ + 496, + 672, + 890, + 868 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {r e f i n e}} = \\operatorname {B C E L o s s} \\left(\\hat {\\mathcal {M}} _ {\\text {P r e d}}, \\mathcal {M} _ {\\mathrm {G T}}\\right) \\tag {13}\n$$\n", + "text_format": "latex", + "bbox": [ + 568, + 878, + 890, + 904 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "5149", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/668a2b8f98141803163361cee8ef523bf80deee12dedba33eee5e2d54884d5d1.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.3.22280.71576.91530.12790.29260.634221.46080.16660.05690.32760.350215.5853
NKSR [15]E./S./M.1.89820.68555.84030.09960.27520.640923.03680.17420.05900.33370.351715.2081
PCGen [19]E./S.0.46360.80235.65830.20400.53910.490323.16750.19700.07630.59260.135114.1181
LiDAR-NeRF [39]I./S.0.14380.90914.17530.05660.27970.656825.98780.14040.04430.31350.383117.1549
D-NeRF [32]I./D.0.14420.91284.01940.05080.30610.663426.23440.13690.04400.34090.374817.3554
TiNeuVox-B [9]I./D.0.17480.90594.12840.05020.34270.651426.02670.13630.04530.43650.345717.3535
K-Planes [12]I./D.0.13020.91234.13220.05390.34570.638526.02360.14150.04980.40810.300817.0167
LiDAR4D (Ours)I./D.0.10890.92723.52560.04040.10510.764727.47670.11950.03270.18450.530418.5561
", + "bbox": [ + 84, + 88, + 893, + 229 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/ead8f22724dd429b5d404d69c0fc1f02823f26df098e075edb2ae5b8fc104780.jpg", + "table_caption": [ + "Table 1. Quantitative comparison on KITTI-360 dataset. We compare our method to different types of previous approaches and color the top results as best and second best. $\\mathcal{E}$ : Explicit, $\\mathcal{I}$ : Implicit, $\\mathcal{S}$ : Static, $\\mathcal{D}$ : Dynamic, $\\mathcal{M}$ : Mesh." + ], + "table_footnote": [], + "table_body": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.12.13830.651210.55390.35720.18710.565317.78410.06590.01150.11600.517023.7791
NKSR [15]E./S./M.11.49100.61789.37310.57630.21110.563718.77740.06800.01190.12900.503123.4905
PCGen [19]E./S.2.19980.63418.83640.40110.17920.544019.27990.07680.01470.13080.441022.4428
LiDAR-NeRF [39]I./S.0.32250.85767.15660.03380.07020.718821.21290.04670.00760.04830.726426.9927
D-NeRF [32]I./D.0.32960.85137.10890.03680.07890.713021.25940.04670.00800.04920.718026.9951
TiNeuVox-B [9]I./D.0.39200.86277.20930.02900.15490.687321.09320.04620.00800.12940.710726.8620
K-Planes [12]I./D.0.29820.88876.79600.02090.12180.725821.62030.04380.00760.11270.736427.4227
LiDAR4D (Ours)I./D.0.24430.89156.78310.02580.05690.739621.71890.04260.00710.04590.749827.7977
", + "bbox": [ + 84, + 281, + 890, + 422 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Quantitative comparison on NuScenes dataset. The notations are consistent with the KITTI-360 Table 1 above.", + "bbox": [ + 120, + 430, + 844, + 443 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "where $\\mathcal{M}$ indicates the global mask rendered from range view and $\\mathcal{M}_{GT}$ is calculated from the input point clouds.", + "bbox": [ + 75, + 455, + 468, + 487 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "We emphasize that the lightweight network is randomly initialized and optimized at runtime efficiently for reconstruction. As illustrated in Figure 5, the global optimization greatly improves the prediction results and further enhances the fidelity of the generated LiDAR point cloud.", + "bbox": [ + 75, + 487, + 468, + 561 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "3.6. Optimization", + "text_level": 1, + "bbox": [ + 76, + 569, + 217, + 585 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "For the optimization of LiDAR4D, the total reconstruction loss is the weighted combination of the depth loss, intensity loss, ray-drop loss, flow loss and refinement loss, which can be formalized as follows:", + "bbox": [ + 75, + 592, + 468, + 652 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {d e p t h}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {D} (\\mathbf {r}) - D (\\mathbf {r}) \\right\\| _ {1} \\tag {14}\n$$\n", + "text_format": "latex", + "bbox": [ + 165, + 664, + 468, + 696 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {i n t e n s i t y}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {I} (\\mathbf {r}) - I (\\mathbf {r}) \\right\\| _ {2} ^ {2} \\tag {15}\n$$\n", + "text_format": "latex", + "bbox": [ + 163, + 698, + 468, + 729 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {r a y d r o p}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {P} (\\mathbf {r}) - P (\\mathbf {r}) \\right\\| _ {2} ^ {2} \\tag {16}\n$$\n", + "text_format": "latex", + "bbox": [ + 163, + 732, + 468, + 763 + ], + "page_idx": 5 + }, + { + "type": "equation", + "text": "\n$$\n\\begin{array}{l} \\mathcal {L} = \\lambda_ {\\alpha} \\mathcal {L} _ {\\text {d e p t h}} + \\lambda_ {\\beta} \\mathcal {L} _ {\\text {i n t e n s i t y}} + \\lambda_ {\\gamma} \\mathcal {L} _ {\\text {r a y d r o p}} \\tag {17} \\\\ + \\lambda_ {\\eta} \\mathcal {L} _ {\\text {f l o w}} + \\lambda_ {\\mathrm {r}} \\mathcal {L} _ {\\text {r e f i n e}} \\\\ \\end{array}\n$$\n", + "text_format": "latex", + "bbox": [ + 112, + 770, + 468, + 806 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4. Experiments", + "text_level": 1, + "bbox": [ + 76, + 821, + 209, + 838 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 76, + 847, + 267, + 863 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Datasets. We conducted comprehensive experiments on the public autonomous driving datasets KITTI-360 [23] and", + "bbox": [ + 75, + 869, + 468, + 900 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/c99d767231491fefa5f54bcb2461bf5f31b0504e3f9527469df61e34feaa5f94.jpg", + "image_caption": [ + "Figure 6. Qualitative novel view LiDAR point cloud synthesis results on KITTI-360 dataset. As highlighted in the red bounding box, LiDAR-NeRF fails to reconstruct the dynamic vehicles. In contrast, LiDAR4D generates more accurate geometry for moving cars, even in sparse point clouds far away." + ], + "image_footnote": [], + "bbox": [ + 504, + 454, + 630, + 628 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/85333eccd1b1e4139758598bea2f1c50cdace5e302e950095f8fb7157c80ee18.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 630, + 454, + 756, + 628 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/dbb7753a95a08274b165f6d99413a7ef8ccf5ba452f26d69d23c680178569877.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 759, + 454, + 888, + 628 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "NuScenes [3], from which we collected multiple dynamic point cloud sequences containing largely moving vehicles. KITTI-360 is equipped with a LIDAR of 64-beam, a 26.4-degree vertical FOV, and an acquisition frequency of $10\\mathrm{Hz}$ . We selected 51 consecutive frames as a single scene and held out 4 samples at a 10-frame interval for NVS evaluation. Meanwhile, Nuscenes' LiDAR has 32 beams, a 40-degree vertical FOV, and a $20\\mathrm{-Hz}$ acquisition frequency. To cover a larger range of reconstruction, i.e., spanning $100\\sim 200$ meters, we still selected samples at a frequency of $10\\mathrm{Hz}$ , which is consistent with the KITTI-360.", + "bbox": [ + 496, + 734, + 890, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "5150", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/f8e21f279796e3b9888574ac02aed694403cbb4286ab61ba33494dadf4ce4ba8.jpg", + "image_caption": [ + "Figure 7. Qualitative comparison for LiDAR intensity reconstruction and synthesis." + ], + "image_footnote": [], + "bbox": [ + 127, + 87, + 852, + 369 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/52d028571a52e0c979fe120ed55907e681d6293c1e9070b5afc380e2bb626742.jpg", + "image_caption": [ + "Figure 8. Qualitative comparison for LiDAR depth reconstruction and synthesis." + ], + "image_footnote": [], + "bbox": [ + 127, + 417, + 852, + 700 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Baselines. We present a comprehensive comparison of LiDAR4D with different types of baselines, encompassing explicit and implicit reconstruction approaches as well as dynamic NeRFs. We reproduce the mesh-based reconstruction method LiDARsim [25] and also replace the surface reconstruction model with the state-of-the-art method NKSR [15] for convincing. It's noted that we employ U-Net trained from original point clouds to further predict ray-drop for these two methods. Meanwhile, PCGen [19] reconstructs", + "bbox": [ + 75, + 762, + 472, + 900 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "directly based on the point clouds and predicts ray-drop with the MLP. LiDAR-NeRF [39] is our primary comparison, and we directly adopt the official implements. In addition, we migrate dynamic neural radiance field methods such as D-NeRF [32], K-Planes [12], and TiNeuVox [9] to LiDAR NVS pipeline for a thorough comparison.", + "bbox": [ + 496, + 762, + 890, + 853 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Metrics. We offer multi-faceted metrics for evaluation. Chamfer Distance [8] measures the 3D geometric error between the generated and the ground-truth point clouds by", + "bbox": [ + 496, + 854, + 892, + 902 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "5151", + "bbox": [ + 482, + 944, + 513, + 955 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/fa92a009dd5f74e57279792f35d4a508f1d33f7ac555bfe8dc1714207677156c.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.2.22490.86676.54700.07590.22890.715721.77460.15320.05060.25020.447916.3045
NKSR [15]E./S./M.0.57800.86854.66470.06980.22950.705222.53900.15650.05360.24290.420016.1159
PCGen [19]E./S.0.20900.85974.88380.17850.52100.506224.30500.20050.08180.61000.124813.9606
LiDAR-NeRF [39]I./S.0.09230.92263.68010.06670.35230.604326.76630.15570.05490.42120.276816.1683
LiDAR4D (Ours)I./D.0.08940.92643.23700.05070.13130.721827.88400.13430.04040.21270.469817.4529
", + "bbox": [ + 84, + 88, + 893, + 193 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. Quantitative comparison on KITTI-360 Static Scene Sequence. We bold the best results and underline the second-best.", + "bbox": [ + 96, + 202, + 870, + 217 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "nearest neighbor, and we also report the F-score value with an error threshold of $5\\mathrm{cm}$ . In addition, we introduce Root Mean Square Error (RMSE) and Median Absolute Error (MedAE) to calculate the pixel-by-pixel error of the projected range images, as well as LPIPS [45], SSIM [41] and PSNR to measure the overall variance. We evaluate both the depth and intensity reconstruction results.", + "bbox": [ + 75, + 244, + 470, + 349 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.2. Implementation Details", + "text_level": 1, + "bbox": [ + 76, + 359, + 294, + 376 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Consistent with LiDAR-NeRF [39], the entire point cloud scene is scaled within the unit cube space. And we uniformly sampled 768 points along each laser. The optimization of LiDAR4D is implemented on Pytorch [31] with Adam [17] optimizer. The maximum iteration is set to $30\\mathrm{k}$ for each scene, with a batch size of 1024 rays, followed by the fast ray-drop refinement with 300 epochs. We construct multi-planar representations following K-Planes [12] and hash grids built on tiny-cuda-nn [27]. The multi-level features of planes and hash grids are concatenated before feeding into MLPs. All experiments were conducted on a single NVIDIA GeForce RTX 4090 GPU. For more implementation details, please refer to Supplementary Material.", + "bbox": [ + 75, + 383, + 470, + 580 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "4.3. Evaluation of Novel-View LiDAR Synthesis", + "text_level": 1, + "bbox": [ + 76, + 589, + 444, + 606 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Results on KITTI-360 dataset. The quantitative comparison on KITTI-360 dataset is displayed in Table 1. Our proposed LiDAR4D exhibits remarkable performance across all metrics in comparison to prior SOTA methods, demonstrating its superiority in dynamic reconstruction. In comparison to LiDAR-NeRF, our approach has led to a $24.3\\%$ reduction in the CD error of the novel-view point cloud synthesis. As illustrated in Figure 6, LiDAR4D achieves accurate reconstruction of every dynamic vehicle, whereas LiDAR-NeRF encounters failure. As shown in Figures 7 and 8, the resolution limitation causes blurring and oversmooth results of dynamic NeRFs such as TiNeuVox and K-Planes. This demonstrates again the effectiveness of our designed hybrid representation for large-scale scenes. Additionally, we follow the setting in LiDAR-NeRF to repeat experiments in static scenarios, and Table 3 verifies that there is no performance degradation in LiDAR4D.", + "bbox": [ + 75, + 613, + 468, + 869 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Results on NuScenes dataset. To further validate the generalizability of LiDAR4D, we conducted the same experi", + "bbox": [ + 76, + 869, + 468, + 902 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "ment on NuScenes. As illustrated in Table 2, our method still achieves the best reconstruction quality even with a completely different LiDAR configuration. Ultimately, our method still excels in the reconstruction of depth and intensity, as evidenced by the $24.2\\%$ reduction in CD error to LiDAR-NeRF. Please refer to Supplementary Material for more quantitative and qualitative experimental results on KITTI-360 and NuScenes datasets, as well as the ablation study and further applications.", + "bbox": [ + 496, + 244, + 893, + 380 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Limitations", + "text_level": 1, + "bbox": [ + 500, + 390, + 624, + 406 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Despite the fact that LiDAR4D has exhibited exceptional performance in a substantial number of experiments, the long-distance vehicle motion and occlusion problem of point clouds remain open questions. There is still a significant gap in the reconstruction of dynamic objects compared to static ones. In addition, foreground and background may be difficult to separate well. Furthermore, based on real-world datasets, quantitative evaluation of NVS is limited within the ego-car trajectory and does not allow for the decoupling of novel spatial and temporal view synthesis.", + "bbox": [ + 496, + 416, + 893, + 568 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 582, + 619, + 598 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we revisit the limitations of existing LiDAR NVS methods and propose a novel framework to address three major challenges, namely dynamic reconstruction, large-scale scene characterization, and realistic synthesis. Our proposed method LiDAR4D proves its superiority under extensive experiments, achieving geometry-aware and time-consistent reconstruction of large-scale dynamic point cloud scenes and generating novel space-time view LiDAR point clouds closer to the real distribution. We believe that more future work will focus on combining LiDAR point clouds with neural radiance fields and explore more possibilities for dynamic scene reconstruction and synthesis.", + "bbox": [ + 496, + 607, + 893, + 789 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgment. This work is supported by the National Natural Science Foundation of China (No.62372329), in part by the National Key Research and Development Program of China (No.2021YFB2501104), in part by Shanghai Rising Star Program (No.21QC1400900), in part by Tongji-Qomolo Autonomous Driving Commercial Vehicle Joint Lab Project, and in part by Xiaomi Young Talents Program.", + "bbox": [ + 496, + 795, + 893, + 902 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "5152", + "bbox": [ + 482, + 944, + 516, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Jonathan T Barron, Ben Mildenhall, Matthew Tancik, Peter Hedman, Ricardo Martin-Brualla, and Pratul P Srinivasan. Mip-nerf: A multiscale representation for anti-aliasing neural radiance fields. 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Neuralpci: Spatio-temporal neural field for 3d point cloud multi-frame non-linear interpolation. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 909-918, 2023. 5" + ], + "bbox": [ + 503, + 92, + 890, + 753 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "5154", + "bbox": [ + 482, + 944, + 514, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/6a80c1df-3dbd-46be-ba3b-340e6d1a9ff3_model.json b/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/6a80c1df-3dbd-46be-ba3b-340e6d1a9ff3_model.json new file mode 100644 index 0000000000000000000000000000000000000000..97152cd7e54d56034331e722502f1472da5c8a66 --- /dev/null +++ b/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/6a80c1df-3dbd-46be-ba3b-340e6d1a9ff3_model.json @@ -0,0 +1,2156 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.086, + 0.13, + 0.885, + 0.154 + ], + "angle": 0, + "content": "LiDAR4D: Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis" + }, + { + "type": "text", + "bbox": [ + 0.217, + 0.181, + 0.753, + 0.218 + ], + "angle": 0, + "content": "Zehan Zheng, Fan Lu, Weiyi Xue, Guang Chen†, Changjun Jiang Tongji University" + }, + { + "type": "text", + "bbox": [ + 0.227, + 0.22, + 0.74, + 0.234 + ], + "angle": 0, + "content": "{zhengzehan, lufan, xwy, guangchen, cjjiang}@tongji.edu.cn" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.266, + 0.314, + 0.283 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.298, + 0.474, + 0.601 + ], + "angle": 0, + "content": "Although neural radiance fields (NeRFs) have achieved triumphs in image novel view synthesis (NVS), LiDAR NVS remains largely unexplored. Previous LiDAR NVS methods employ a simple shift from image NVS methods while ignoring the dynamic nature and the large-scale reconstruction problem of LiDAR point clouds. In light of this, we propose LiDAR4D, a differentiable LiDAR-only framework for novel space-time LiDAR view synthesis. In consideration of the sparsity and large-scale characteristics, we design a 4D hybrid representation combined with multi-planar and grid features to achieve effective reconstruction in a coarse-to-fine manner. Furthermore, we introduce geometric constraints derived from point clouds to improve temporal consistency. For the realistic synthesis of LiDAR point clouds, we incorporate the global optimization of ray-drop probability to preserve cross-region patterns. Extensive experiments on KITTI-360 and NuScenes datasets demonstrate the superiority of our method in accomplishing geometry-aware and time-consistent dynamic reconstruction. Codes are available at https://github.com/ispc-lab/LiDAR4D." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.628, + 0.21, + 0.643 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.653, + 0.47, + 0.819 + ], + "angle": 0, + "content": "Dynamic scene reconstruction is of crucial importance across various fields such as AR/VR, robotics and autonomous driving. Existing advanced methods in computer vision enable high-fidelity 3D scene reconstruction and novel view synthesis (NVS), which can further serve a wide range of downstream tasks and applications. For instance, we could reconstruct driving scenarios directly from collected sensor logs, allowing for scene replay and novel data generation [43]. It shows great potential for boosting data diversity, forming data closed-loop, and improving the generalizability of the autonomous driving system." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.82, + 0.47, + 0.88 + ], + "angle": 0, + "content": "However, the majority of current research focuses on novel view synthesis for cameras, while other sensors such as LiDAR remain largely unexplored. Similar to camera images, LiDAR point clouds are also partial observations" + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.268, + 0.89, + 0.339 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.34, + 0.89, + 0.488 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.498, + 0.894, + 0.554 + ], + "angle": 0, + "content": "Figure 1. Dynamic scenes of LiDAR point clouds in autonomous driving. Large-scale vehicle motion poses a significant challenge for dynamic reconstruction and novel space-time view synthesis. White dots indicate the ego-car trajectory." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.578, + 0.892, + 0.684 + ], + "angle": 0, + "content": "of the scene that vary across different locations and views. The reconstruction faces considerable challenges due to the sparsity, discontinuity and occlusion of LiDAR point clouds. Furthermore, as illustrated in Figure 1, dynamic scenarios combine novel spatial view and temporal view synthesis simultaneously. Meanwhile, the large motion of dynamic objects makes it difficult to align and reconstruct." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.685, + 0.892, + 0.791 + ], + "angle": 0, + "content": "Traditional LiDAR-based 3D scene reconstruction techniques aggregate multiple sparse point cloud frames directly in the world coordinate system [19] and further convert them into explicit surface representations such as triangular meshes [25]. Subsequently, the intersection of the LiDAR beams with the mesh surface can be calculated by performing ray-casting to render novel-view LiDAR point clouds." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.793, + 0.892, + 0.884 + ], + "angle": 0, + "content": "Nevertheless, high-quality surface reconstruction of complex large-scale scenes is challenging to accomplish, which may lead to significant geometric errors. Furthermore, the aforementioned explicit reconstruction method is limited to static scenes and struggles to accurately model the intensity or ray-drop characteristics of actual LiDAR points." + }, + { + "type": "text", + "bbox": [ + 0.518, + 0.886, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Neural radiance fields [26] implicitly reconstruct the" + }, + { + "type": "page_footnote", + "bbox": [ + 0.102, + 0.887, + 0.232, + 0.9 + ], + "angle": 0, + "content": "† Corresponding author." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5145" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.379 + ], + "angle": 0, + "content": "scene and generate novel-view data through volume rendering in a continuous representation space, which also offers an alternative solution for LiDAR reconstruction. Consequently, the most recent researches [16, 39, 44] are shifting their attention towards the novel view synthesis of LiDAR. NeRF-LiDAR [44] integrates image and point cloud modalities for LiDAR synthesis, whereas LiDAR-only methods like LiDAR-NeRF [39] and NFL [16] explore the possibility of LiDAR reconstruction and generation without RGB images. Most prior methods directly apply the image NVS pipeline to LiDAR point clouds. However, LiDAR point clouds are inherently different from 2D images, which poses challenges for current LiDAR NVS methods to achieve high-quality reconstruction: (1) previous methods are limited to static scenes, ignoring the dynamic nature of autonomous driving scenarios; (2) the vast scale and high sparsity of LiDAR point clouds pose higher demands on the representations; and (3) intensity and ray-drop characteristics modeling are required for synthesis realism." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.379, + 0.473, + 0.59 + ], + "angle": 0, + "content": "To overcome the aforementioned limitations, we propose LiDAR4D, shedding light on three pivotal insights to elevate the current LiDAR NVS pipeline. To tackle the dynamic objects, we introduce geometric constraints derived from point clouds and aggregate multi-frame dynamic features for temporal consistency. Regarding compact large-scale scene reconstruction, we design a coarse-to-fine hybrid representation combined with multi-planar and grid features to reconstruct the smooth geometry and high-frequency intensity. Additionally, we employ global optimization to preserve patterns across regions for raydrop probability refinement. Therefore, LiDAR4D is capable of achieving geometry-aware and time-consistent reconstruction under large-scale dynamic scenarios." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.591, + 0.473, + 0.743 + ], + "angle": 0, + "content": "We evaluate our method on diverse dynamic scenarios of KITTI-360 [23] and NuScenes [3] autonomous driving datasets. With comprehensive experiments, LiDAR4D significantly outperforms previous state-of-the-art NeRF-based implicit approaches and explicit reconstruction methods. In comparison to LiDAR-NeRF [39], we achieve \\(24.3\\%\\) and \\(24.2\\%\\) reduction in CD error on KITTI-360 dataset and NuScenes dataset, respectively. Similar leadership exists for other metrics of range depth and intensity. In summary, our main contributions are three-fold:" + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.744, + 0.47, + 0.804 + ], + "angle": 0, + "content": "- We propose LiDAR4D, a differentiable LiDAR-only framework for novel space-time LiDAR view synthesis, which reconstructs dynamic driving scenarios and generates realistic LiDAR point clouds end-to-end." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.806, + 0.47, + 0.851 + ], + "angle": 0, + "content": "- We introduce 4D hybrid neural representations and motion priors derived from point clouds for geometry-aware and time-consistent large-scale scene reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.078, + 0.853, + 0.47, + 0.898 + ], + "angle": 0, + "content": "- Comprehensive experiments demonstrate the state-of-the-art performance of LiDAR4D in challenging dynamic scene reconstruction and novel view synthesis." + }, + { + "type": "list", + "bbox": [ + 0.078, + 0.744, + 0.47, + 0.898 + ], + "angle": 0, + "content": null + }, + { + "type": "title", + "bbox": [ + 0.501, + 0.09, + 0.642, + 0.107 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.115, + 0.895, + 0.508 + ], + "angle": 0, + "content": "LiDAR Simulation. Traditional simulators [7, 18, 36] such as CARLA are based on physics engines, which can generate LiDAR point clouds via ray casting within handcrafted virtual environments. However, it has diversity limitations and a heavy reliance on costly 3D assets. And there is still a large domain gap compared to real-world data. Thus, several recent works [13, 19, 25] further narrowed this gap by reconstructing the scene from real data before simulation. LiDARsim [25] reconstructs the mesh surfel representation and employs a neural network to learn the ray-drop characteristics. Besides, it is noted that there are other surface reconstruction works like NKSR [15] that can convert LiDAR point clouds into mesh representations. Nonetheless, these explicit reconstruction works are troublesome for recovering precise surfaces in large-scale complex scenes, which further leads to a decrease in the accuracy of point cloud synthesis. Instead, PCGen [19] directly reconstructs from the point clouds, followed by rendering in a rasterization-like manner and first peak averaging. Although it preserves the original information better, the rendering point clouds remain relatively noisy. Moreover, all these explicit methods mentioned above are only applicable to static scenes. In contrast, our approach implicitly reconstructs the continuous representation via space-time neural radiance fields, which achieves higher-quality realistic point cloud synthesis and gets rid of static reconstruction limitations." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.508, + 0.895, + 0.78 + ], + "angle": 0, + "content": "Neural Radiance Fields. Considerable recent research [1, 4, 5, 11, 14, 24, 26, 28, 38] based on neural radiance fields has led to breakthroughs as well as remarkable achievements in novel view synthesis (NVS) tasks. A wide variety of neural representations based on MLPs [1, 26], voxel grids [11, 24, 38], tri-planes [4, 14], vector decomposition [5], and multi-level hash grids [28] have been fully exploited for reconstruction and synthesis. Yet, most of the work focuses on object-centered reconstruction of small indoor scenes. Subsequently, several works [2, 33, 42] gradually extended it to large-scale outdoor scenarios. Despite this, neural radiance fields typically suffer from geometric ambiguity with RGB image inputs. Therefore, DS-NeRF [6] and DDP-NeRF [34] introduce the depth prior to enhancing efficiency, and URF [33] also utilizes Li-DAR point clouds to facilitate reconstruction. In this paper, we employ novel hybrid representations and neural LiDAR fields to reconstruct large-scale scenarios for LiDAR NVS." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.895, + 0.902 + ], + "angle": 0, + "content": "NeRF for LiDAR NVS. Very recently, a few studies [16, 39, 43, 44] have pioneered in novel view synthesis of LiDAR point clouds based on neural radiance fields, significantly surpassing traditional simulation methods. Among them, NeRF-LiDAR [44] and UniSim [43] require both RGB images and LiDAR point clouds as inputs and reconstruct the driving scene with photometric loss and depth supervision. Subsequently, novel-view LiDAR point clouds" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.517, + 0.957 + ], + "angle": 0, + "content": "5146" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.134, + 0.09, + 0.878, + 0.351 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.364, + 0.895, + 0.437 + ], + "angle": 0, + "content": "Figure 2. Overview of our proposed LiDAR4D. For large-scale autonomous driving scenarios, we utilize the 4D hybrid representation, which combines low-resolution multi-planar features and high-resolution hash grid features to achieve effective reconstruction. Then, multi-level spatio-temporal features aggregated by flow MLP are fed into neural LiDAR fields for density, intensity and ray-drop probability prediction. Finally, novel space-time view LiDAR point clouds are synthesized via differentiable rendering. Furthermore, we construct geometric constraints derived from point clouds for temporal consistency and the global optimization of ray-drop for generation realism." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.457, + 0.473, + 0.729 + ], + "angle": 0, + "content": "can be generated through neural depth rendering. Among LiDAR-only methods, LiDAR-NeRF [39] and NFL [16] firstly proposed the differentiable LiDAR NVS framework, which reconstructed depth, intensity, and ray-drop probability simultaneously. Nevertheless, these approaches [16, 39, 44] are restricted to static scene reconstruction and incapable of handling dynamic objects such as moving vehicles. Although UniSim [43] does support dynamic scenes, it is largely limited by the need for ground-truth labeling of 3D object detection and decoupling the background and dynamic objects before reconstruction. Instead, our research focuses on LiDAR-only inputs for dynamic scene reconstruction and novel space-time view synthesis without the help of RGB images or ground-truth labels. And it's noteworthy that NFL [16] has contributed significantly to the detailed physical modeling of LiDAR, such as beam divergence and secondary returns, which is orthogonal to ours and could be beneficial to all LiDAR NVS works." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.735, + 0.473, + 0.904 + ], + "angle": 0, + "content": "Dynamic Scene Reconstruction. A substantial amount of research [9, 12, 21, 22, 29, 30, 32, 37, 40] has been devoted to expanding neural radiance fields to encompass dynamic scene reconstruction. In general, dynamic NeRFs can be broadly categorized into two groups. One is the deformable neural radiance fields [9, 29, 30, 32] that map coordinates into the canonical space via continuous deformation fields. While the decoupling of deformation and radiance fields simplifies the optimization, establishing accurate long-distance correspondence remains challenging. The other is spatio-temporal neural fields [12, 21, 22, 37]," + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.457, + 0.895, + 0.595 + ], + "angle": 0, + "content": "which consider time as an additional dimensional input to construct a 4D spatio-temporal representation. Thus, it is flexible to simultaneously model appearance, geometry, and motion as a continuous time-varying function. Most previous work has concentrated on relatively smaller displacements indoors, whereas large-scale vehicle movements in autonomous driving scenarios are even more challenging. Furthermore, our work is also the first to introduce dynamic neural radiance fields into the LiDAR NVS task." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.613, + 0.637, + 0.631 + ], + "angle": 0, + "content": "3. Methodology" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.64, + 0.895, + 0.701 + ], + "angle": 0, + "content": "In this section, we start with the problem formulation of novel LiDAR view synthesis and the preliminary for NeRFs. Following this, a detailed description of our proposed LiDAR4D framework is provided." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.703, + 0.895, + 0.809 + ], + "angle": 0, + "content": "Problem Formulation. In the dynamic driving scenario, given the collected LiDAR point cloud sequence \\( S = \\{S_0, S_1, \\dots, S_{n-1}\\} \\) (\\( S_i \\in \\mathbb{R}^{K \\times 4} \\)), along with the corresponding sensor poses \\( P_s = \\{P_0, P_1, \\dots, P_{n-1}\\} \\) (\\( P_i \\in SE(3) \\)) and timestamps \\( T_s = \\{t_0, t_1, \\dots, t_{n-1}\\} \\) (\\( t_i \\in \\mathbb{R} \\)) as inputs. Each single LiDAR frame \\( S_i \\) contains \\( K \\) points of 3D coordinates \\( x \\) and 1D reflection intensity \\( \\rho \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.811, + 0.895, + 0.903 + ], + "angle": 0, + "content": "The goal of LiDAR4D is to reconstruct this dynamic scene as a continuous implicit representation based on neural fields. Furthermore, given a novel sensor pose \\( P_{novel} \\) and any moment \\( t_{novel} \\), LiDAR4D performs neural rendering to synthesize the LiDAR point cloud \\( S_{novel} \\) with intensities under the novel space-time view." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.517, + 0.958 + ], + "angle": 0, + "content": "5147" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.084, + 0.09, + 0.462, + 0.222 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.232, + 0.47, + 0.261 + ], + "angle": 0, + "content": "Figure 3. 4D decomposition of hybrid planar-grid representation. Dynamic features can be further aggregated using flow MLP." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.275, + 0.473, + 0.427 + ], + "angle": 0, + "content": "Preliminary for NeRF. Neural radiance fields, NeRFs for short, take 5D inputs of position \\(\\mathbf{x} \\in \\mathbb{R}^3\\) and viewing direction \\((\\theta, \\phi)\\) as inputs and establish the mapping to the volume density \\(\\sigma\\) and color \\(\\mathbf{c}\\). Afterward, it performs volume rendering to estimate pixel values and synthesize images in unknown novel views. In detail, it emits a light ray \\(\\mathbf{r}\\) from the sensor center \\(\\mathbf{o}\\) with the direction \\(\\mathbf{d}\\), i.e., \\(\\mathbf{r}(t) = \\mathbf{o} + t\\mathbf{d}\\), and then integrates the neural field outputs of \\(N\\) samples along this ray to approximate the pixel color \\(\\mathcal{C}\\). The volume rendering function can be formed as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.086, + 0.437, + 0.47, + 0.48 + ], + "angle": 0, + "content": "\\[\n\\hat {\\mathcal {C}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\left(1 - e ^ {- \\sigma_ {i} \\delta_ {i}}\\right) \\mathbf {c} _ {i}, T _ {i} = \\exp \\left(- \\sum_ {j = 1} ^ {i - 1} \\sigma_ {j} \\delta_ {j}\\right) (1)\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.489, + 0.47, + 0.52 + ], + "angle": 0, + "content": "where \\(T\\) indicates the accumulated transmittance, \\(\\sigma\\) denotes the density and \\(\\delta\\) refers to the distance between samples." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.528, + 0.27, + 0.543 + ], + "angle": 0, + "content": "3.1. LiDAR4D Overview" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.551, + 0.473, + 0.825 + ], + "angle": 0, + "content": "Following neural radiance fields, our proposed LiDAR4D reconstructs the point cloud scene into an implicit continuous representation. Differing from original NeRFs with photometric loss for RGB images, we redefine the neural fields based on LiDAR, which are dubbed neural LiDAR fields. As depicted in Figure 2, it focuses on modeling the geometric depth, reflection intensity, and ray-drop probability of LiDAR point clouds. For large-scale dynamic driving scenarios, LiDAR4D combines coarse-resolution multi-planar features with high-resolution hash grid representation to achieve efficient and effective reconstruction. Then, we lift it to 4D and introduce temporal information encoding for novel space-time view synthesis. To ensure geometry-aware and time-consistent results, we additionally incorporate explicit geometric constraints derived from point clouds. Ultimately, we predict the ray-drop probability for each ray and perform global refinement with a runtime-optimized U-Net to improve generation realism." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.832, + 0.418, + 0.849 + ], + "angle": 0, + "content": "3.2. 4D Hybrid Planar-Grid Representation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.901 + ], + "angle": 0, + "content": "Figure 3 illustrates how our proposed novel hybrid representation breaks down the 4D space into planar and hash grid features, which further subdivide into static and" + }, + { + "type": "image", + "bbox": [ + 0.522, + 0.089, + 0.689, + 0.14 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.558, + 0.142, + 0.652, + 0.151 + ], + "angle": 0, + "content": "K-Planes (Planes only)" + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.089, + 0.862, + 0.14 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.697, + 0.142, + 0.86, + 0.151 + ], + "angle": 0, + "content": "LiDAR4D (w/ Hybrid Representations)" + }, + { + "type": "image", + "bbox": [ + 0.522, + 0.154, + 0.689, + 0.207 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.539, + 0.208, + 0.67, + 0.217 + ], + "angle": 0, + "content": "LiDAR-NeRF (Hash Grid only)" + }, + { + "type": "image", + "bbox": [ + 0.695, + 0.154, + 0.862, + 0.207 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.771, + 0.208, + 0.786, + 0.216 + ], + "angle": 0, + "content": "GT" + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.228, + 0.894, + 0.285 + ], + "angle": 0, + "content": "Figure 4. Qualitative comparison for the hybrid representation. Compared to the noisy intensity reconstruction of LiDAR-NeRF and the blurry one of K-Planes, our hybrid representation achieves more precise and smooth results." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.303, + 0.892, + 0.453 + ], + "angle": 0, + "content": "dynamic ones. Different from the reconstruction of small indoor objects, large-scale autonomous driving scenes place higher demands on the representation ability and resolution of the features. However, the dense grid representation such as TiNeuVox [9] is unscalable for large-scale scenarios due to its cubically growing complexity. Therefore, we follow K-planes [12] and decompose the scene space into a combination of features in multiple orthogonal planes to drastically reduce the parameter quantities. The planar feature can be obtained as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.521, + 0.463, + 0.892, + 0.483 + ], + "angle": 0, + "content": "\\[\n\\mathbf {f} _ {\\text {p l a n a r}} = \\mathcal {S} (\\mathbf {V}, (x, y, z, t)), \\mathbf {V} \\in \\mathbb {R} ^ {(3 M ^ {2} + 3 M H) C} \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.495, + 0.892, + 0.6 + ], + "angle": 0, + "content": "where \\(\\mathbf{V}\\) stores features with \\(M\\) spatial resolution, \\(H\\) temporal resolution and \\(C\\) channels. \\(S\\) refers to the sampling function that projects 4D coordinates into the corresponding planes \\((xy, xz, yz, xt, yt, zt)\\) and interpolates features bilinearly. Static \\((xy, xz, yz)\\) and dynamic \\((xt, yt, zt)\\) features are multiplied separately by Hadamard product and multiscale features are concatenated in a coarse-to-fine manner." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.601, + 0.892, + 0.706 + ], + "angle": 0, + "content": "Nonetheless, for scenes spanning hundreds of meters, this improvement in resolution remains inadequate, especially for the high-frequency intensity reconstruction. Owing to the hash grids proposed in Instant-NGP [28], an explicit grid structure with ultra-high resolution is possible. Additionally, the sparsity of the LiDAR point cloud scene substantially avoids the adverse effects of hash collisions." + }, + { + "type": "equation", + "bbox": [ + 0.525, + 0.718, + 0.892, + 0.739 + ], + "angle": 0, + "content": "\\[\n\\mathbf {f} _ {\\text {h a s h}} = \\mathcal {S} (\\mathbf {G}, (x, y, z, t)), \\mathbf {G} \\in \\mathbb {R} ^ {(M ^ {3} + 3 M ^ {2} H) C} \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.892, + 0.84 + ], + "angle": 0, + "content": "where the dense grid \\(\\mathbf{G}\\) will be further compressed into limited storage via hash mapping for parameter reduction. Similarly, the 4D coordinates are projected into static \\((xyz)\\) and dynamic \\((xyt, xzt, yzt)\\) multi-level hash grids before tri-linear interpolation and concatenation, where the dynamic features are multiplied using Hadamard product." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.892, + 0.901 + ], + "angle": 0, + "content": "However, it's notable that pure hash grid representation still suffers from visual artifacts and noisy reconstruction results (as shown in Figure 4), which impede the construction of accurate object geometry. In light of this, we adopt" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5148" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.152 + ], + "angle": 0, + "content": "multi-planar features at lower resolutions for overall smooth representation and employ hash grids at higher resolutions to handle finer details, ultimately achieving high accuracy and efficiency in large-scale scene reconstruction." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.163, + 0.246, + 0.178 + ], + "angle": 0, + "content": "3.3. Scene Flow Prior" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.187, + 0.47, + 0.263 + ], + "angle": 0, + "content": "To enhance the temporal consistency of the current 4D spatio-temporal representations, we further incorporate a flow MLP [20, 46] for motion estimation. It takes the encoded spatio-temporal coordinates as input and constructs the mapping from coordinate fields \\(\\mathbb{R}^4\\) to motion fields \\(\\mathbb{R}^3\\)." + }, + { + "type": "equation", + "bbox": [ + 0.133, + 0.28, + 0.469, + 0.296 + ], + "angle": 0, + "content": "\\[\n\\Delta \\mathbf {x} = \\operatorname {M L P} _ {\\text {f l o w}} (\\gamma (\\mathbf {x}, t)), \\quad \\mathbf {x} ^ {\\prime} = \\mathbf {x} + \\Delta \\mathbf {x} \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.306, + 0.469, + 0.41 + ], + "angle": 0, + "content": "Since the vehicle motion range may span a long distance in autonomous driving scenarios, it is extremely hard to establish long-term correspondences to the canonical space in deformable neural radiance fields. Thus, as with Li et al. [21, 22], we utilize the flow MLP to predict motion only between adjacent frames and aggregate multi-frame dynamic features to achieve time-consistent reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.411, + 0.469, + 0.525 + ], + "angle": 0, + "content": "In addition, explicit geometric constraints can be further derived from the input LiDAR point clouds. By feeding point clouds into the flow MLP to produce the scene flow prediction, we can regulate the chamfer distance as a geometric loss \\((\\mathcal{L}_{\\mathrm{flow}})\\). It imposes motion prior and additional supervision on LiDAR4D, thus accomplishing the geometry-aware reconstruction. Chamfer Distance between two frames of point cloud \\(S\\) and \\(\\hat{S}\\) is defined as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.085, + 0.535, + 0.469, + 0.571 + ], + "angle": 0, + "content": "\\[\n\\mathrm {C D} = \\frac {1}{K} \\sum_ {\\hat {p} _ {i} \\in \\hat {S}} \\min _ {p _ {i} \\in S} \\| \\hat {p} _ {i} - p _ {i} \\| _ {2} ^ {2} + \\frac {1}{K} \\sum_ {p _ {i} \\in S} \\min _ {\\hat {p} _ {i} \\in \\hat {S}} \\| p _ {i} - \\hat {p} _ {i} \\| _ {2} ^ {2} \\tag {5}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.085, + 0.581, + 0.469, + 0.61 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {f l o w}} = \\sum_ {j \\in \\pm 1} \\mathrm {C D} \\left(S _ {i} + \\mathrm {M L P} _ {\\text {f l o w}} \\left(S _ {i}\\right), S _ {i + j}\\right), i \\in (0, n - 1) \\tag {6}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.622, + 0.277, + 0.637 + ], + "angle": 0, + "content": "3.4. Neural LiDAR Fields" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.646, + 0.469, + 0.811 + ], + "angle": 0, + "content": "LiDAR emits laser pulses and measures the time-of-flight (ToF) to determine object distance, along with the intensity of reflected lights. Spinning LiDAR has a 360-degree horizontal field of view (FOV) and a limited range of vertical field of view, which perceives the environment with certain angular resolution lasers. In the same way for neural LiDAR fields, we transmit lasers at specific angular intervals within the FOV, using the center of the LiDAR sensor as the origin o. The direction d of the laser is determined by the azimuth angle \\(\\theta\\) and elevation angle \\(\\phi\\) under the polar coordinate system, which is shown below." + }, + { + "type": "equation", + "bbox": [ + 0.146, + 0.824, + 0.469, + 0.842 + ], + "angle": 0, + "content": "\\[\n\\mathbf {d} = (\\cos \\theta \\cos \\phi , \\sin \\theta \\sin \\phi , \\cos \\phi) ^ {T} \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.469, + 0.902 + ], + "angle": 0, + "content": "Then we query 3D point coordinates sampled along the laser and feed them into neural fields to predict the density at the corresponding location. Following this, the density" + }, + { + "type": "image", + "bbox": [ + 0.508, + 0.087, + 0.892, + 0.177 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.183, + 0.892, + 0.24 + ], + "angle": 0, + "content": "Figure 5. Qualitative comparison for the ray-drop refinement. The point-wise prediction of ray-drop probability by MLP cannot preserve global patterns well. Instead, LiDAR4D drastically improves generation realism via runtime-optimized U-Net." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.258, + 0.892, + 0.288 + ], + "angle": 0, + "content": "along the ray is integrated to obtain the expectation of depth value \\(\\mathcal{D}\\), which serves as the laser beam's return distance." + }, + { + "type": "equation", + "bbox": [ + 0.517, + 0.298, + 0.891, + 0.339 + ], + "angle": 0, + "content": "\\[\n\\hat {\\mathcal {D}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\left(1 - e ^ {- \\sigma_ {i} \\delta_ {i}}\\right) z _ {i}, \\quad \\alpha_ {i} = 1 - e ^ {- \\sigma_ {i} \\delta_ {i}} \\tag {8}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.349, + 0.891, + 0.379 + ], + "angle": 0, + "content": "where \\(z_{i}\\) is the depth value of queried points on the ray \\(\\mathbf{r}\\), and \\(\\alpha\\) is the definition of the opacity." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.379, + 0.892, + 0.424 + ], + "angle": 0, + "content": "In addition, we predict the intensity \\(\\mathcal{I}\\) and ray-drop probability \\(\\mathcal{P}\\) separately for each point and similarly conduct alpha-composition along the ray." + }, + { + "type": "equation", + "bbox": [ + 0.557, + 0.435, + 0.891, + 0.476 + ], + "angle": 0, + "content": "\\[\n\\hat {\\mathcal {I}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\alpha_ {i} i _ {i}, \\quad \\hat {\\mathcal {P}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\alpha_ {i} p _ {i} \\tag {9}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.486, + 0.892, + 0.547 + ], + "angle": 0, + "content": "where \\( i_{i} \\) and \\( p_{i} \\) are the point-wise intensity and ray-drop probability outputs of LiDAR4D. We use separate MLPs to take temporal aggregated planar and hash features, as well as position-encoded viewpoints as inputs for prediction." + }, + { + "type": "equation", + "bbox": [ + 0.568, + 0.557, + 0.891, + 0.574 + ], + "angle": 0, + "content": "\\[\ni = \\operatorname {M L P} _ {\\text {i n t e n s i t y}} \\left(\\mathbf {f} _ {\\text {p l a n a r}}, \\mathbf {f} _ {\\text {h a s h}}, \\gamma (\\mathbf {d})\\right) \\tag {10}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.57, + 0.584, + 0.891, + 0.601 + ], + "angle": 0, + "content": "\\[\n\\rho = \\mathrm {M L P} _ {\\text {r a y d r o p}} \\left(\\mathbf {f} _ {\\text {p l a n a r}}, \\mathbf {f} _ {\\text {h a s h}}, \\gamma (\\mathbf {d})\\right) \\tag {11}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.517, + 0.61, + 0.891, + 0.64 + ], + "angle": 0, + "content": "\\[\n\\gamma (x) = \\left(\\sin \\left(2 ^ {0} x\\right), \\cos \\left(2 ^ {0} x\\right), \\dots , \\sin \\left(2 ^ {L - 1} x\\right), \\cos \\left(2 ^ {L - 1} x\\right)\\right) \\tag {12}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.65, + 0.702, + 0.666 + ], + "angle": 0, + "content": "3.5. Ray-drop Refinement" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.673, + 0.892, + 0.869 + ], + "angle": 0, + "content": "During laser ranging, a portion of the emitted rays is not reflected back to the sensor, which is termed the ray-drop characteristic. In fact, the ray-drop of LiDAR is significantly impacted by various aspects, including distance, surface properties and sensor noise. As in LiDAR-NeRF [39], ray-drop prediction is directly accomplished with a pointwise MLP head, which is essentially noisy and unreliable. To address this issue, we employ the U-Net [35] with residuals to refine the ray-drop mask globally and better preserve the consistent pattern across regions. It takes the full ray-drop probability, depth and intensity prediction of LiDAR4D as inputs (different from previous work) and refines the final mask via binary cross-entropy loss as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.569, + 0.879, + 0.891, + 0.905 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {r e f i n e}} = \\operatorname {B C E L o s s} \\left(\\hat {\\mathcal {M}} _ {\\text {P r e d}}, \\mathcal {M} _ {\\mathrm {G T}}\\right) \\tag {13}\n\\]" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5149" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.085, + 0.089, + 0.895, + 0.23 + ], + "angle": 0, + "content": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.3.22280.71576.91530.12790.29260.634221.46080.16660.05690.32760.350215.5853
NKSR [15]E./S./M.1.89820.68555.84030.09960.27520.640923.03680.17420.05900.33370.351715.2081
PCGen [19]E./S.0.46360.80235.65830.20400.53910.490323.16750.19700.07630.59260.135114.1181
LiDAR-NeRF [39]I./S.0.14380.90914.17530.05660.27970.656825.98780.14040.04430.31350.383117.1549
D-NeRF [32]I./D.0.14420.91284.01940.05080.30610.663426.23440.13690.04400.34090.374817.3554
TiNeuVox-B [9]I./D.0.17480.90594.12840.05020.34270.651426.02670.13630.04530.43650.345717.3535
K-Planes [12]I./D.0.13020.91234.13220.05390.34570.638526.02360.14150.04980.40810.300817.0167
LiDAR4D (Ours)I./D.0.10890.92723.52560.04040.10510.764727.47670.11950.03270.18450.530418.5561
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.239, + 0.895, + 0.269 + ], + "angle": 0, + "content": "Table 1. Quantitative comparison on KITTI-360 dataset. We compare our method to different types of previous approaches and color the top results as best and second best. \\(\\mathcal{E}\\) : Explicit, \\(\\mathcal{I}\\) : Implicit, \\(\\mathcal{S}\\) : Static, \\(\\mathcal{D}\\) : Dynamic, \\(\\mathcal{M}\\) : Mesh." + }, + { + "type": "table", + "bbox": [ + 0.086, + 0.282, + 0.892, + 0.423 + ], + "angle": 0, + "content": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.12.13830.651210.55390.35720.18710.565317.78410.06590.01150.11600.517023.7791
NKSR [15]E./S./M.11.49100.61789.37310.57630.21110.563718.77740.06800.01190.12900.503123.4905
PCGen [19]E./S.2.19980.63418.83640.40110.17920.544019.27990.07680.01470.13080.441022.4428
LiDAR-NeRF [39]I./S.0.32250.85767.15660.03380.07020.718821.21290.04670.00760.04830.726426.9927
D-NeRF [32]I./D.0.32960.85137.10890.03680.07890.713021.25940.04670.00800.04920.718026.9951
TiNeuVox-B [9]I./D.0.39200.86277.20930.02900.15490.687321.09320.04620.00800.12940.710726.8620
K-Planes [12]I./D.0.29820.88876.79600.02090.12180.725821.62030.04380.00760.11270.736427.4227
LiDAR4D (Ours)I./D.0.24430.89156.78310.02580.05690.739621.71890.04260.00710.04590.749827.7977
" + }, + { + "type": "table_caption", + "bbox": [ + 0.121, + 0.431, + 0.846, + 0.444 + ], + "angle": 0, + "content": "Table 2. Quantitative comparison on NuScenes dataset. The notations are consistent with the KITTI-360 Table 1 above." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.457, + 0.469, + 0.488 + ], + "angle": 0, + "content": "where \\(\\mathcal{M}\\) indicates the global mask rendered from range view and \\(\\mathcal{M}_{GT}\\) is calculated from the input point clouds." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.488, + 0.469, + 0.563 + ], + "angle": 0, + "content": "We emphasize that the lightweight network is randomly initialized and optimized at runtime efficiently for reconstruction. As illustrated in Figure 5, the global optimization greatly improves the prediction results and further enhances the fidelity of the generated LiDAR point cloud." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.57, + 0.218, + 0.586 + ], + "angle": 0, + "content": "3.6. Optimization" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.593, + 0.469, + 0.653 + ], + "angle": 0, + "content": "For the optimization of LiDAR4D, the total reconstruction loss is the weighted combination of the depth loss, intensity loss, ray-drop loss, flow loss and refinement loss, which can be formalized as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.166, + 0.665, + 0.469, + 0.697 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {d e p t h}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {D} (\\mathbf {r}) - D (\\mathbf {r}) \\right\\| _ {1} \\tag {14}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.165, + 0.699, + 0.469, + 0.731 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {i n t e n s i t y}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {I} (\\mathbf {r}) - I (\\mathbf {r}) \\right\\| _ {2} ^ {2} \\tag {15}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.164, + 0.733, + 0.469, + 0.765 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {r a y d r o p}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {P} (\\mathbf {r}) - P (\\mathbf {r}) \\right\\| _ {2} ^ {2} \\tag {16}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.113, + 0.771, + 0.469, + 0.807 + ], + "angle": 0, + "content": "\\[\n\\begin{array}{l} \\mathcal {L} = \\lambda_ {\\alpha} \\mathcal {L} _ {\\text {d e p t h}} + \\lambda_ {\\beta} \\mathcal {L} _ {\\text {i n t e n s i t y}} + \\lambda_ {\\gamma} \\mathcal {L} _ {\\text {r a y d r o p}} \\tag {17} \\\\ + \\lambda_ {\\eta} \\mathcal {L} _ {\\text {f l o w}} + \\lambda_ {\\mathrm {r}} \\mathcal {L} _ {\\text {r e f i n e}} \\\\ \\end{array}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.823, + 0.21, + 0.839 + ], + "angle": 0, + "content": "4. Experiments" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.848, + 0.268, + 0.864 + ], + "angle": 0, + "content": "4.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.469, + 0.901 + ], + "angle": 0, + "content": "Datasets. We conducted comprehensive experiments on the public autonomous driving datasets KITTI-360 [23] and" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.455, + 0.631, + 0.63 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.632, + 0.455, + 0.758, + 0.63 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.76, + 0.455, + 0.89, + 0.63 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.639, + 0.892, + 0.71 + ], + "angle": 0, + "content": "Figure 6. Qualitative novel view LiDAR point cloud synthesis results on KITTI-360 dataset. As highlighted in the red bounding box, LiDAR-NeRF fails to reconstruct the dynamic vehicles. In contrast, LiDAR4D generates more accurate geometry for moving cars, even in sparse point clouds far away." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.892, + 0.901 + ], + "angle": 0, + "content": "NuScenes [3], from which we collected multiple dynamic point cloud sequences containing largely moving vehicles. KITTI-360 is equipped with a LIDAR of 64-beam, a 26.4-degree vertical FOV, and an acquisition frequency of \\(10\\mathrm{Hz}\\). We selected 51 consecutive frames as a single scene and held out 4 samples at a 10-frame interval for NVS evaluation. Meanwhile, Nuscenes' LiDAR has 32 beams, a 40-degree vertical FOV, and a \\(20\\mathrm{-Hz}\\) acquisition frequency. To cover a larger range of reconstruction, i.e., spanning \\(100\\sim 200\\) meters, we still selected samples at a frequency of \\(10\\mathrm{Hz}\\), which is consistent with the KITTI-360." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.516, + 0.957 + ], + "angle": 0, + "content": "5150" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.129, + 0.088, + 0.854, + 0.371 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.223, + 0.384, + 0.747, + 0.399 + ], + "angle": 0, + "content": "Figure 7. Qualitative comparison for LiDAR intensity reconstruction and synthesis." + }, + { + "type": "image", + "bbox": [ + 0.129, + 0.418, + 0.853, + 0.702 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.231, + 0.716, + 0.738, + 0.731 + ], + "angle": 0, + "content": "Figure 8. Qualitative comparison for LiDAR depth reconstruction and synthesis." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.763, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Baselines. We present a comprehensive comparison of LiDAR4D with different types of baselines, encompassing explicit and implicit reconstruction approaches as well as dynamic NeRFs. We reproduce the mesh-based reconstruction method LiDARsim [25] and also replace the surface reconstruction model with the state-of-the-art method NKSR [15] for convincing. It's noted that we employ U-Net trained from original point clouds to further predict ray-drop for these two methods. Meanwhile, PCGen [19] reconstructs" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.763, + 0.892, + 0.854 + ], + "angle": 0, + "content": "directly based on the point clouds and predicts ray-drop with the MLP. LiDAR-NeRF [39] is our primary comparison, and we directly adopt the official implements. In addition, we migrate dynamic neural radiance field methods such as D-NeRF [32], K-Planes [12], and TiNeuVox [9] to LiDAR NVS pipeline for a thorough comparison." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.893, + 0.903 + ], + "angle": 0, + "content": "Metrics. We offer multi-faceted metrics for evaluation. Chamfer Distance [8] measures the 3D geometric error between the generated and the ground-truth point clouds by" + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.514, + 0.957 + ], + "angle": 0, + "content": "5151" + } + ], + [ + { + "type": "table", + "bbox": [ + 0.085, + 0.089, + 0.895, + 0.194 + ], + "angle": 0, + "content": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.2.22490.86676.54700.07590.22890.715721.77460.15320.05060.25020.447916.3045
NKSR [15]E./S./M.0.57800.86854.66470.06980.22950.705222.53900.15650.05360.24290.420016.1159
PCGen [19]E./S.0.20900.85974.88380.17850.52100.506224.30500.20050.08180.61000.124813.9606
LiDAR-NeRF [39]I./S.0.09230.92263.68010.06670.35230.604326.76630.15570.05490.42120.276816.1683
LiDAR4D (Ours)I./D.0.08940.92643.23700.05070.13130.721827.88400.13430.04040.21270.469817.4529
" + }, + { + "type": "table_caption", + "bbox": [ + 0.098, + 0.203, + 0.872, + 0.218 + ], + "angle": 0, + "content": "Table 3. Quantitative comparison on KITTI-360 Static Scene Sequence. We bold the best results and underline the second-best." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.245, + 0.471, + 0.351 + ], + "angle": 0, + "content": "nearest neighbor, and we also report the F-score value with an error threshold of \\(5\\mathrm{cm}\\). In addition, we introduce Root Mean Square Error (RMSE) and Median Absolute Error (MedAE) to calculate the pixel-by-pixel error of the projected range images, as well as LPIPS [45], SSIM [41] and PSNR to measure the overall variance. We evaluate both the depth and intensity reconstruction results." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.36, + 0.295, + 0.377 + ], + "angle": 0, + "content": "4.2. Implementation Details" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.384, + 0.471, + 0.581 + ], + "angle": 0, + "content": "Consistent with LiDAR-NeRF [39], the entire point cloud scene is scaled within the unit cube space. And we uniformly sampled 768 points along each laser. The optimization of LiDAR4D is implemented on Pytorch [31] with Adam [17] optimizer. The maximum iteration is set to \\(30\\mathrm{k}\\) for each scene, with a batch size of 1024 rays, followed by the fast ray-drop refinement with 300 epochs. We construct multi-planar representations following K-Planes [12] and hash grids built on tiny-cuda-nn [27]. The multi-level features of planes and hash grids are concatenated before feeding into MLPs. All experiments were conducted on a single NVIDIA GeForce RTX 4090 GPU. For more implementation details, please refer to Supplementary Material." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.59, + 0.446, + 0.607 + ], + "angle": 0, + "content": "4.3. Evaluation of Novel-View LiDAR Synthesis" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.614, + 0.47, + 0.87 + ], + "angle": 0, + "content": "Results on KITTI-360 dataset. The quantitative comparison on KITTI-360 dataset is displayed in Table 1. Our proposed LiDAR4D exhibits remarkable performance across all metrics in comparison to prior SOTA methods, demonstrating its superiority in dynamic reconstruction. In comparison to LiDAR-NeRF, our approach has led to a \\(24.3\\%\\) reduction in the CD error of the novel-view point cloud synthesis. As illustrated in Figure 6, LiDAR4D achieves accurate reconstruction of every dynamic vehicle, whereas LiDAR-NeRF encounters failure. As shown in Figures 7 and 8, the resolution limitation causes blurring and oversmooth results of dynamic NeRFs such as TiNeuVox and K-Planes. This demonstrates again the effectiveness of our designed hybrid representation for large-scale scenes. Additionally, we follow the setting in LiDAR-NeRF to repeat experiments in static scenarios, and Table 3 verifies that there is no performance degradation in LiDAR4D." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.871, + 0.47, + 0.903 + ], + "angle": 0, + "content": "Results on NuScenes dataset. To further validate the generalizability of LiDAR4D, we conducted the same experi" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.245, + 0.895, + 0.381 + ], + "angle": 0, + "content": "ment on NuScenes. As illustrated in Table 2, our method still achieves the best reconstruction quality even with a completely different LiDAR configuration. Ultimately, our method still excels in the reconstruction of depth and intensity, as evidenced by the \\(24.2\\%\\) reduction in CD error to LiDAR-NeRF. Please refer to Supplementary Material for more quantitative and qualitative experimental results on KITTI-360 and NuScenes datasets, as well as the ablation study and further applications." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.391, + 0.625, + 0.407 + ], + "angle": 0, + "content": "5. Limitations" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.417, + 0.895, + 0.569 + ], + "angle": 0, + "content": "Despite the fact that LiDAR4D has exhibited exceptional performance in a substantial number of experiments, the long-distance vehicle motion and occlusion problem of point clouds remain open questions. There is still a significant gap in the reconstruction of dynamic objects compared to static ones. In addition, foreground and background may be difficult to separate well. Furthermore, based on real-world datasets, quantitative evaluation of NVS is limited within the ego-car trajectory and does not allow for the decoupling of novel spatial and temporal view synthesis." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.583, + 0.62, + 0.599 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.608, + 0.894, + 0.79 + ], + "angle": 0, + "content": "In this paper, we revisit the limitations of existing LiDAR NVS methods and propose a novel framework to address three major challenges, namely dynamic reconstruction, large-scale scene characterization, and realistic synthesis. Our proposed method LiDAR4D proves its superiority under extensive experiments, achieving geometry-aware and time-consistent reconstruction of large-scale dynamic point cloud scenes and generating novel space-time view LiDAR point clouds closer to the real distribution. We believe that more future work will focus on combining LiDAR point clouds with neural radiance fields and explore more possibilities for dynamic scene reconstruction and synthesis." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.796, + 0.894, + 0.903 + ], + "angle": 0, + "content": "Acknowledgment. This work is supported by the National Natural Science Foundation of China (No.62372329), in part by the National Key Research and Development Program of China (No.2021YFB2501104), in part by Shanghai Rising Star Program (No.21QC1400900), in part by Tongji-Qomolo Autonomous Driving Commercial Vehicle Joint Lab Project, and in part by Xiaomi Young Talents Program." + }, + { + "type": "page_number", + "bbox": [ + 0.483, + 0.945, + 0.517, + 0.957 + ], + "angle": 0, + "content": "5152" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.174, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.197 + ], + "angle": 0, + "content": "[1] Jonathan T Barron, Ben Mildenhall, Matthew Tancik, Peter Hedman, Ricardo Martin-Brualla, and Pratul P Srinivasan. Mip-nerf: A multiscale representation for anti-aliasing neural radiance fields. 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Previous LiDAR NVS methods employ a simple shift from image NVS methods while ignoring the dynamic nature and the large-scale reconstruction problem of LiDAR point clouds. In light of this, we propose LiDAR4D, a differentiable LiDAR-only framework for novel space-time LiDAR view synthesis. In consideration of the sparsity and large-scale characteristics, we design a 4D hybrid representation combined with multi-planar and grid features to achieve effective reconstruction in a coarse-to-fine manner. Furthermore, we introduce geometric constraints derived from point clouds to improve temporal consistency. For the realistic synthesis of LiDAR point clouds, we incorporate the global optimization of ray-drop probability to preserve cross-region patterns. Extensive experiments on KITTI-360 and NuScenes datasets demonstrate the superiority of our method in accomplishing geometry-aware and time-consistent dynamic reconstruction. Codes are available at https://github.com/ispc-lab/LiDAR4D. + +# 1. Introduction + +Dynamic scene reconstruction is of crucial importance across various fields such as AR/VR, robotics and autonomous driving. Existing advanced methods in computer vision enable high-fidelity 3D scene reconstruction and novel view synthesis (NVS), which can further serve a wide range of downstream tasks and applications. For instance, we could reconstruct driving scenarios directly from collected sensor logs, allowing for scene replay and novel data generation [43]. It shows great potential for boosting data diversity, forming data closed-loop, and improving the generalizability of the autonomous driving system. + +However, the majority of current research focuses on novel view synthesis for cameras, while other sensors such as LiDAR remain largely unexplored. Similar to camera images, LiDAR point clouds are also partial observations + +![](images/02712cacf46b6f519b53009aaafb2fb50135c4fa25ad4ffaa52b0a404f717893.jpg) + +![](images/ebd986dd1fae82dd259bebeb44b2f4b4033109b5e9637c9b32c0a688045de9a9.jpg) +Figure 1. Dynamic scenes of LiDAR point clouds in autonomous driving. Large-scale vehicle motion poses a significant challenge for dynamic reconstruction and novel space-time view synthesis. White dots indicate the ego-car trajectory. + +of the scene that vary across different locations and views. The reconstruction faces considerable challenges due to the sparsity, discontinuity and occlusion of LiDAR point clouds. Furthermore, as illustrated in Figure 1, dynamic scenarios combine novel spatial view and temporal view synthesis simultaneously. Meanwhile, the large motion of dynamic objects makes it difficult to align and reconstruct. + +Traditional LiDAR-based 3D scene reconstruction techniques aggregate multiple sparse point cloud frames directly in the world coordinate system [19] and further convert them into explicit surface representations such as triangular meshes [25]. Subsequently, the intersection of the LiDAR beams with the mesh surface can be calculated by performing ray-casting to render novel-view LiDAR point clouds. + +Nevertheless, high-quality surface reconstruction of complex large-scale scenes is challenging to accomplish, which may lead to significant geometric errors. Furthermore, the aforementioned explicit reconstruction method is limited to static scenes and struggles to accurately model the intensity or ray-drop characteristics of actual LiDAR points. + +Neural radiance fields [26] implicitly reconstruct the + +scene and generate novel-view data through volume rendering in a continuous representation space, which also offers an alternative solution for LiDAR reconstruction. Consequently, the most recent researches [16, 39, 44] are shifting their attention towards the novel view synthesis of LiDAR. NeRF-LiDAR [44] integrates image and point cloud modalities for LiDAR synthesis, whereas LiDAR-only methods like LiDAR-NeRF [39] and NFL [16] explore the possibility of LiDAR reconstruction and generation without RGB images. Most prior methods directly apply the image NVS pipeline to LiDAR point clouds. However, LiDAR point clouds are inherently different from 2D images, which poses challenges for current LiDAR NVS methods to achieve high-quality reconstruction: (1) previous methods are limited to static scenes, ignoring the dynamic nature of autonomous driving scenarios; (2) the vast scale and high sparsity of LiDAR point clouds pose higher demands on the representations; and (3) intensity and ray-drop characteristics modeling are required for synthesis realism. + +To overcome the aforementioned limitations, we propose LiDAR4D, shedding light on three pivotal insights to elevate the current LiDAR NVS pipeline. To tackle the dynamic objects, we introduce geometric constraints derived from point clouds and aggregate multi-frame dynamic features for temporal consistency. Regarding compact large-scale scene reconstruction, we design a coarse-to-fine hybrid representation combined with multi-planar and grid features to reconstruct the smooth geometry and high-frequency intensity. Additionally, we employ global optimization to preserve patterns across regions for raydrop probability refinement. Therefore, LiDAR4D is capable of achieving geometry-aware and time-consistent reconstruction under large-scale dynamic scenarios. + +We evaluate our method on diverse dynamic scenarios of KITTI-360 [23] and NuScenes [3] autonomous driving datasets. With comprehensive experiments, LiDAR4D significantly outperforms previous state-of-the-art NeRF-based implicit approaches and explicit reconstruction methods. In comparison to LiDAR-NeRF [39], we achieve $24.3\%$ and $24.2\%$ reduction in CD error on KITTI-360 dataset and NuScenes dataset, respectively. Similar leadership exists for other metrics of range depth and intensity. In summary, our main contributions are three-fold: + +- We propose LiDAR4D, a differentiable LiDAR-only framework for novel space-time LiDAR view synthesis, which reconstructs dynamic driving scenarios and generates realistic LiDAR point clouds end-to-end. +- We introduce 4D hybrid neural representations and motion priors derived from point clouds for geometry-aware and time-consistent large-scale scene reconstruction. +- Comprehensive experiments demonstrate the state-of-the-art performance of LiDAR4D in challenging dynamic scene reconstruction and novel view synthesis. + +# 2. Related Work + +LiDAR Simulation. Traditional simulators [7, 18, 36] such as CARLA are based on physics engines, which can generate LiDAR point clouds via ray casting within handcrafted virtual environments. However, it has diversity limitations and a heavy reliance on costly 3D assets. And there is still a large domain gap compared to real-world data. Thus, several recent works [13, 19, 25] further narrowed this gap by reconstructing the scene from real data before simulation. LiDARsim [25] reconstructs the mesh surfel representation and employs a neural network to learn the ray-drop characteristics. Besides, it is noted that there are other surface reconstruction works like NKSR [15] that can convert LiDAR point clouds into mesh representations. Nonetheless, these explicit reconstruction works are troublesome for recovering precise surfaces in large-scale complex scenes, which further leads to a decrease in the accuracy of point cloud synthesis. Instead, PCGen [19] directly reconstructs from the point clouds, followed by rendering in a rasterization-like manner and first peak averaging. Although it preserves the original information better, the rendering point clouds remain relatively noisy. Moreover, all these explicit methods mentioned above are only applicable to static scenes. In contrast, our approach implicitly reconstructs the continuous representation via space-time neural radiance fields, which achieves higher-quality realistic point cloud synthesis and gets rid of static reconstruction limitations. + +Neural Radiance Fields. Considerable recent research [1, 4, 5, 11, 14, 24, 26, 28, 38] based on neural radiance fields has led to breakthroughs as well as remarkable achievements in novel view synthesis (NVS) tasks. A wide variety of neural representations based on MLPs [1, 26], voxel grids [11, 24, 38], tri-planes [4, 14], vector decomposition [5], and multi-level hash grids [28] have been fully exploited for reconstruction and synthesis. Yet, most of the work focuses on object-centered reconstruction of small indoor scenes. Subsequently, several works [2, 33, 42] gradually extended it to large-scale outdoor scenarios. Despite this, neural radiance fields typically suffer from geometric ambiguity with RGB image inputs. Therefore, DS-NeRF [6] and DDP-NeRF [34] introduce the depth prior to enhancing efficiency, and URF [33] also utilizes Li-DAR point clouds to facilitate reconstruction. In this paper, we employ novel hybrid representations and neural LiDAR fields to reconstruct large-scale scenarios for LiDAR NVS. + +NeRF for LiDAR NVS. Very recently, a few studies [16, 39, 43, 44] have pioneered in novel view synthesis of LiDAR point clouds based on neural radiance fields, significantly surpassing traditional simulation methods. Among them, NeRF-LiDAR [44] and UniSim [43] require both RGB images and LiDAR point clouds as inputs and reconstruct the driving scene with photometric loss and depth supervision. Subsequently, novel-view LiDAR point clouds + +![](images/c9c921e6c7979116a08482083634ba85aed222024ae9c81bb1bc67e22fbca0af.jpg) +Figure 2. Overview of our proposed LiDAR4D. For large-scale autonomous driving scenarios, we utilize the 4D hybrid representation, which combines low-resolution multi-planar features and high-resolution hash grid features to achieve effective reconstruction. Then, multi-level spatio-temporal features aggregated by flow MLP are fed into neural LiDAR fields for density, intensity and ray-drop probability prediction. Finally, novel space-time view LiDAR point clouds are synthesized via differentiable rendering. Furthermore, we construct geometric constraints derived from point clouds for temporal consistency and the global optimization of ray-drop for generation realism. + +can be generated through neural depth rendering. Among LiDAR-only methods, LiDAR-NeRF [39] and NFL [16] firstly proposed the differentiable LiDAR NVS framework, which reconstructed depth, intensity, and ray-drop probability simultaneously. Nevertheless, these approaches [16, 39, 44] are restricted to static scene reconstruction and incapable of handling dynamic objects such as moving vehicles. Although UniSim [43] does support dynamic scenes, it is largely limited by the need for ground-truth labeling of 3D object detection and decoupling the background and dynamic objects before reconstruction. Instead, our research focuses on LiDAR-only inputs for dynamic scene reconstruction and novel space-time view synthesis without the help of RGB images or ground-truth labels. And it's noteworthy that NFL [16] has contributed significantly to the detailed physical modeling of LiDAR, such as beam divergence and secondary returns, which is orthogonal to ours and could be beneficial to all LiDAR NVS works. + +Dynamic Scene Reconstruction. A substantial amount of research [9, 12, 21, 22, 29, 30, 32, 37, 40] has been devoted to expanding neural radiance fields to encompass dynamic scene reconstruction. In general, dynamic NeRFs can be broadly categorized into two groups. One is the deformable neural radiance fields [9, 29, 30, 32] that map coordinates into the canonical space via continuous deformation fields. While the decoupling of deformation and radiance fields simplifies the optimization, establishing accurate long-distance correspondence remains challenging. The other is spatio-temporal neural fields [12, 21, 22, 37], + +which consider time as an additional dimensional input to construct a 4D spatio-temporal representation. Thus, it is flexible to simultaneously model appearance, geometry, and motion as a continuous time-varying function. Most previous work has concentrated on relatively smaller displacements indoors, whereas large-scale vehicle movements in autonomous driving scenarios are even more challenging. Furthermore, our work is also the first to introduce dynamic neural radiance fields into the LiDAR NVS task. + +# 3. Methodology + +In this section, we start with the problem formulation of novel LiDAR view synthesis and the preliminary for NeRFs. Following this, a detailed description of our proposed LiDAR4D framework is provided. + +Problem Formulation. In the dynamic driving scenario, given the collected LiDAR point cloud sequence $S = \{S_0, S_1, \dots, S_{n-1}\}$ ( $S_i \in \mathbb{R}^{K \times 4}$ ), along with the corresponding sensor poses $P_s = \{P_0, P_1, \dots, P_{n-1}\}$ ( $P_i \in SE(3)$ ) and timestamps $T_s = \{t_0, t_1, \dots, t_{n-1}\}$ ( $t_i \in \mathbb{R}$ ) as inputs. Each single LiDAR frame $S_i$ contains $K$ points of 3D coordinates $x$ and 1D reflection intensity $\rho$ . + +The goal of LiDAR4D is to reconstruct this dynamic scene as a continuous implicit representation based on neural fields. Furthermore, given a novel sensor pose $P_{novel}$ and any moment $t_{novel}$ , LiDAR4D performs neural rendering to synthesize the LiDAR point cloud $S_{novel}$ with intensities under the novel space-time view. + +![](images/00d3f7789b3f4ab48b86df245cf042c11c6bd4288490432059fa75e509291b01.jpg) +Figure 3. 4D decomposition of hybrid planar-grid representation. Dynamic features can be further aggregated using flow MLP. + +Preliminary for NeRF. Neural radiance fields, NeRFs for short, take 5D inputs of position $\mathbf{x} \in \mathbb{R}^3$ and viewing direction $(\theta, \phi)$ as inputs and establish the mapping to the volume density $\sigma$ and color $\mathbf{c}$ . Afterward, it performs volume rendering to estimate pixel values and synthesize images in unknown novel views. In detail, it emits a light ray $\mathbf{r}$ from the sensor center $\mathbf{o}$ with the direction $\mathbf{d}$ , i.e., $\mathbf{r}(t) = \mathbf{o} + t\mathbf{d}$ , and then integrates the neural field outputs of $N$ samples along this ray to approximate the pixel color $\mathcal{C}$ . The volume rendering function can be formed as follows: + +$$ +\hat {\mathcal {C}} (\mathbf {r}) = \sum_ {i = 1} ^ {N} T _ {i} \left(1 - e ^ {- \sigma_ {i} \delta_ {i}}\right) \mathbf {c} _ {i}, T _ {i} = \exp \left(- \sum_ {j = 1} ^ {i - 1} \sigma_ {j} \delta_ {j}\right) (1) +$$ + +where $T$ indicates the accumulated transmittance, $\sigma$ denotes the density and $\delta$ refers to the distance between samples. + +# 3.1. LiDAR4D Overview + +Following neural radiance fields, our proposed LiDAR4D reconstructs the point cloud scene into an implicit continuous representation. Differing from original NeRFs with photometric loss for RGB images, we redefine the neural fields based on LiDAR, which are dubbed neural LiDAR fields. As depicted in Figure 2, it focuses on modeling the geometric depth, reflection intensity, and ray-drop probability of LiDAR point clouds. For large-scale dynamic driving scenarios, LiDAR4D combines coarse-resolution multi-planar features with high-resolution hash grid representation to achieve efficient and effective reconstruction. Then, we lift it to 4D and introduce temporal information encoding for novel space-time view synthesis. To ensure geometry-aware and time-consistent results, we additionally incorporate explicit geometric constraints derived from point clouds. Ultimately, we predict the ray-drop probability for each ray and perform global refinement with a runtime-optimized U-Net to improve generation realism. + +# 3.2. 4D Hybrid Planar-Grid Representation + +Figure 3 illustrates how our proposed novel hybrid representation breaks down the 4D space into planar and hash grid features, which further subdivide into static and + +![](images/3fa061ea4fc2b9f5f7dc1e922ee2884f6688a4244ca2c406898368c18166ad30.jpg) +K-Planes (Planes only) + +![](images/54352bcedbff2724f624b5ffe71c7e2ed9358452b99ae11e07d55fccffe21a72.jpg) +LiDAR4D (w/ Hybrid Representations) + +![](images/d6f5dc9c74ae67198a1fc63dadad0f45434c81eb38ee62e343ea714ab276cfe6.jpg) +LiDAR-NeRF (Hash Grid only) + +![](images/6524055ecbaac99ea1f389a582e57e26385a90d7374f2b21901d684e7bde7fa1.jpg) +GT +Figure 4. Qualitative comparison for the hybrid representation. Compared to the noisy intensity reconstruction of LiDAR-NeRF and the blurry one of K-Planes, our hybrid representation achieves more precise and smooth results. + +dynamic ones. Different from the reconstruction of small indoor objects, large-scale autonomous driving scenes place higher demands on the representation ability and resolution of the features. However, the dense grid representation such as TiNeuVox [9] is unscalable for large-scale scenarios due to its cubically growing complexity. Therefore, we follow K-planes [12] and decompose the scene space into a combination of features in multiple orthogonal planes to drastically reduce the parameter quantities. The planar feature can be obtained as follows: + +$$ +\mathbf {f} _ {\text {p l a n a r}} = \mathcal {S} (\mathbf {V}, (x, y, z, t)), \mathbf {V} \in \mathbb {R} ^ {(3 M ^ {2} + 3 M H) C} \tag {2} +$$ + +where $\mathbf{V}$ stores features with $M$ spatial resolution, $H$ temporal resolution and $C$ channels. $S$ refers to the sampling function that projects 4D coordinates into the corresponding planes $(xy, xz, yz, xt, yt, zt)$ and interpolates features bilinearly. Static $(xy, xz, yz)$ and dynamic $(xt, yt, zt)$ features are multiplied separately by Hadamard product and multiscale features are concatenated in a coarse-to-fine manner. + +Nonetheless, for scenes spanning hundreds of meters, this improvement in resolution remains inadequate, especially for the high-frequency intensity reconstruction. Owing to the hash grids proposed in Instant-NGP [28], an explicit grid structure with ultra-high resolution is possible. Additionally, the sparsity of the LiDAR point cloud scene substantially avoids the adverse effects of hash collisions. + +$$ +\mathbf {f} _ {\text {h a s h}} = \mathcal {S} (\mathbf {G}, (x, y, z, t)), \mathbf {G} \in \mathbb {R} ^ {(M ^ {3} + 3 M ^ {2} H) C} \tag {3} +$$ + +where the dense grid $\mathbf{G}$ will be further compressed into limited storage via hash mapping for parameter reduction. Similarly, the 4D coordinates are projected into static $(xyz)$ and dynamic $(xyt, xzt, yzt)$ multi-level hash grids before tri-linear interpolation and concatenation, where the dynamic features are multiplied using Hadamard product. + +However, it's notable that pure hash grid representation still suffers from visual artifacts and noisy reconstruction results (as shown in Figure 4), which impede the construction of accurate object geometry. In light of this, we adopt + +multi-planar features at lower resolutions for overall smooth representation and employ hash grids at higher resolutions to handle finer details, ultimately achieving high accuracy and efficiency in large-scale scene reconstruction. + +# 3.3. Scene Flow Prior + +To enhance the temporal consistency of the current 4D spatio-temporal representations, we further incorporate a flow MLP [20, 46] for motion estimation. It takes the encoded spatio-temporal coordinates as input and constructs the mapping from coordinate fields $\mathbb{R}^4$ to motion fields $\mathbb{R}^3$ . + +$$ +\Delta \mathbf {x} = \operatorname {M L P} _ {\text {f l o w}} (\gamma (\mathbf {x}, t)), \quad \mathbf {x} ^ {\prime} = \mathbf {x} + \Delta \mathbf {x} \tag {4} +$$ + +Since the vehicle motion range may span a long distance in autonomous driving scenarios, it is extremely hard to establish long-term correspondences to the canonical space in deformable neural radiance fields. Thus, as with Li et al. [21, 22], we utilize the flow MLP to predict motion only between adjacent frames and aggregate multi-frame dynamic features to achieve time-consistent reconstruction. + +In addition, explicit geometric constraints can be further derived from the input LiDAR point clouds. By feeding point clouds into the flow MLP to produce the scene flow prediction, we can regulate the chamfer distance as a geometric loss $(\mathcal{L}_{\mathrm{flow}})$ . It imposes motion prior and additional supervision on LiDAR4D, thus accomplishing the geometry-aware reconstruction. Chamfer Distance between two frames of point cloud $S$ and $\hat{S}$ is defined as follows: + +$$ +\mathrm {C D} = \frac {1}{K} \sum_ {\hat {p} _ {i} \in \hat {S}} \min _ {p _ {i} \in S} \| \hat {p} _ {i} - p _ {i} \| _ {2} ^ {2} + \frac {1}{K} \sum_ {p _ {i} \in S} \min _ {\hat {p} _ {i} \in \hat {S}} \| p _ {i} - \hat {p} _ {i} \| _ {2} ^ {2} \tag {5} +$$ + +$$ +\mathcal {L} _ {\text {f l o w}} = \sum_ {j \in \pm 1} \mathrm {C D} \left(S _ {i} + \mathrm {M L P} _ {\text {f l o w}} \left(S _ {i}\right), S _ {i + j}\right), i \in (0, n - 1) \tag {6} +$$ + +# 3.4. Neural LiDAR Fields + +LiDAR emits laser pulses and measures the time-of-flight (ToF) to determine object distance, along with the intensity of reflected lights. Spinning LiDAR has a 360-degree horizontal field of view (FOV) and a limited range of vertical field of view, which perceives the environment with certain angular resolution lasers. In the same way for neural LiDAR fields, we transmit lasers at specific angular intervals within the FOV, using the center of the LiDAR sensor as the origin o. The direction d of the laser is determined by the azimuth angle $\theta$ and elevation angle $\phi$ under the polar coordinate system, which is shown below. + +$$ +\mathbf {d} = (\cos \theta \cos \phi , \sin \theta \sin \phi , \cos \phi) ^ {T} \tag {7} +$$ + +Then we query 3D point coordinates sampled along the laser and feed them into neural fields to predict the density at the corresponding location. Following this, the density + +![](images/58714d57a7bbdb076a18f43ec6e88e2391477953201cd3bbaba370f7b27170ba.jpg) +Figure 5. Qualitative comparison for the ray-drop refinement. The point-wise prediction of ray-drop probability by MLP cannot preserve global patterns well. Instead, LiDAR4D drastically improves generation realism via runtime-optimized U-Net. + +along the ray is integrated to obtain the expectation of depth value $\mathcal{D}$ , which serves as the laser beam's return distance. + +$$ +\hat {\mathcal {D}} (\mathbf {r}) = \sum_ {i = 1} ^ {N} T _ {i} \left(1 - e ^ {- \sigma_ {i} \delta_ {i}}\right) z _ {i}, \quad \alpha_ {i} = 1 - e ^ {- \sigma_ {i} \delta_ {i}} \tag {8} +$$ + +where $z_{i}$ is the depth value of queried points on the ray $\mathbf{r}$ , and $\alpha$ is the definition of the opacity. + +In addition, we predict the intensity $\mathcal{I}$ and ray-drop probability $\mathcal{P}$ separately for each point and similarly conduct alpha-composition along the ray. + +$$ +\hat {\mathcal {I}} (\mathbf {r}) = \sum_ {i = 1} ^ {N} T _ {i} \alpha_ {i} i _ {i}, \quad \hat {\mathcal {P}} (\mathbf {r}) = \sum_ {i = 1} ^ {N} T _ {i} \alpha_ {i} p _ {i} \tag {9} +$$ + +where $i_{i}$ and $p_{i}$ are the point-wise intensity and ray-drop probability outputs of LiDAR4D. We use separate MLPs to take temporal aggregated planar and hash features, as well as position-encoded viewpoints as inputs for prediction. + +$$ +i = \operatorname {M L P} _ {\text {i n t e n s i t y}} \left(\mathbf {f} _ {\text {p l a n a r}}, \mathbf {f} _ {\text {h a s h}}, \gamma (\mathbf {d})\right) \tag {10} +$$ + +$$ +\rho = \mathrm {M L P} _ {\text {r a y d r o p}} \left(\mathbf {f} _ {\text {p l a n a r}}, \mathbf {f} _ {\text {h a s h}}, \gamma (\mathbf {d})\right) \tag {11} +$$ + +$$ +\gamma (x) = \left(\sin \left(2 ^ {0} x\right), \cos \left(2 ^ {0} x\right), \dots , \sin \left(2 ^ {L - 1} x\right), \cos \left(2 ^ {L - 1} x\right)\right) \tag {12} +$$ + +# 3.5. Ray-drop Refinement + +During laser ranging, a portion of the emitted rays is not reflected back to the sensor, which is termed the ray-drop characteristic. In fact, the ray-drop of LiDAR is significantly impacted by various aspects, including distance, surface properties and sensor noise. As in LiDAR-NeRF [39], ray-drop prediction is directly accomplished with a pointwise MLP head, which is essentially noisy and unreliable. To address this issue, we employ the U-Net [35] with residuals to refine the ray-drop mask globally and better preserve the consistent pattern across regions. It takes the full ray-drop probability, depth and intensity prediction of LiDAR4D as inputs (different from previous work) and refines the final mask via binary cross-entropy loss as follows: + +$$ +\mathcal {L} _ {\text {r e f i n e}} = \operatorname {B C E L o s s} \left(\hat {\mathcal {M}} _ {\text {P r e d}}, \mathcal {M} _ {\mathrm {G T}}\right) \tag {13} +$$ + +
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.3.22280.71576.91530.12790.29260.634221.46080.16660.05690.32760.350215.5853
NKSR [15]E./S./M.1.89820.68555.84030.09960.27520.640923.03680.17420.05900.33370.351715.2081
PCGen [19]E./S.0.46360.80235.65830.20400.53910.490323.16750.19700.07630.59260.135114.1181
LiDAR-NeRF [39]I./S.0.14380.90914.17530.05660.27970.656825.98780.14040.04430.31350.383117.1549
D-NeRF [32]I./D.0.14420.91284.01940.05080.30610.663426.23440.13690.04400.34090.374817.3554
TiNeuVox-B [9]I./D.0.17480.90594.12840.05020.34270.651426.02670.13630.04530.43650.345717.3535
K-Planes [12]I./D.0.13020.91234.13220.05390.34570.638526.02360.14150.04980.40810.300817.0167
LiDAR4D (Ours)I./D.0.10890.92723.52560.04040.10510.764727.47670.11950.03270.18450.530418.5561
+ +Table 1. Quantitative comparison on KITTI-360 dataset. We compare our method to different types of previous approaches and color the top results as best and second best. $\mathcal{E}$ : Explicit, $\mathcal{I}$ : Implicit, $\mathcal{S}$ : Static, $\mathcal{D}$ : Dynamic, $\mathcal{M}$ : Mesh. + +
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.12.13830.651210.55390.35720.18710.565317.78410.06590.01150.11600.517023.7791
NKSR [15]E./S./M.11.49100.61789.37310.57630.21110.563718.77740.06800.01190.12900.503123.4905
PCGen [19]E./S.2.19980.63418.83640.40110.17920.544019.27990.07680.01470.13080.441022.4428
LiDAR-NeRF [39]I./S.0.32250.85767.15660.03380.07020.718821.21290.04670.00760.04830.726426.9927
D-NeRF [32]I./D.0.32960.85137.10890.03680.07890.713021.25940.04670.00800.04920.718026.9951
TiNeuVox-B [9]I./D.0.39200.86277.20930.02900.15490.687321.09320.04620.00800.12940.710726.8620
K-Planes [12]I./D.0.29820.88876.79600.02090.12180.725821.62030.04380.00760.11270.736427.4227
LiDAR4D (Ours)I./D.0.24430.89156.78310.02580.05690.739621.71890.04260.00710.04590.749827.7977
+ +Table 2. Quantitative comparison on NuScenes dataset. The notations are consistent with the KITTI-360 Table 1 above. + +where $\mathcal{M}$ indicates the global mask rendered from range view and $\mathcal{M}_{GT}$ is calculated from the input point clouds. + +We emphasize that the lightweight network is randomly initialized and optimized at runtime efficiently for reconstruction. As illustrated in Figure 5, the global optimization greatly improves the prediction results and further enhances the fidelity of the generated LiDAR point cloud. + +# 3.6. Optimization + +For the optimization of LiDAR4D, the total reconstruction loss is the weighted combination of the depth loss, intensity loss, ray-drop loss, flow loss and refinement loss, which can be formalized as follows: + +$$ +\mathcal {L} _ {\text {d e p t h}} = \sum_ {\mathbf {r} \in R} \left\| \hat {D} (\mathbf {r}) - D (\mathbf {r}) \right\| _ {1} \tag {14} +$$ + +$$ +\mathcal {L} _ {\text {i n t e n s i t y}} = \sum_ {\mathbf {r} \in R} \left\| \hat {I} (\mathbf {r}) - I (\mathbf {r}) \right\| _ {2} ^ {2} \tag {15} +$$ + +$$ +\mathcal {L} _ {\text {r a y d r o p}} = \sum_ {\mathbf {r} \in R} \left\| \hat {P} (\mathbf {r}) - P (\mathbf {r}) \right\| _ {2} ^ {2} \tag {16} +$$ + +$$ +\begin{array}{l} \mathcal {L} = \lambda_ {\alpha} \mathcal {L} _ {\text {d e p t h}} + \lambda_ {\beta} \mathcal {L} _ {\text {i n t e n s i t y}} + \lambda_ {\gamma} \mathcal {L} _ {\text {r a y d r o p}} \tag {17} \\ + \lambda_ {\eta} \mathcal {L} _ {\text {f l o w}} + \lambda_ {\mathrm {r}} \mathcal {L} _ {\text {r e f i n e}} \\ \end{array} +$$ + +# 4. Experiments + +# 4.1. Experimental Setup + +Datasets. We conducted comprehensive experiments on the public autonomous driving datasets KITTI-360 [23] and + +![](images/c99d767231491fefa5f54bcb2461bf5f31b0504e3f9527469df61e34feaa5f94.jpg) +Figure 6. Qualitative novel view LiDAR point cloud synthesis results on KITTI-360 dataset. As highlighted in the red bounding box, LiDAR-NeRF fails to reconstruct the dynamic vehicles. In contrast, LiDAR4D generates more accurate geometry for moving cars, even in sparse point clouds far away. + +![](images/85333eccd1b1e4139758598bea2f1c50cdace5e302e950095f8fb7157c80ee18.jpg) + +![](images/dbb7753a95a08274b165f6d99413a7ef8ccf5ba452f26d69d23c680178569877.jpg) + +NuScenes [3], from which we collected multiple dynamic point cloud sequences containing largely moving vehicles. KITTI-360 is equipped with a LIDAR of 64-beam, a 26.4-degree vertical FOV, and an acquisition frequency of $10\mathrm{Hz}$ . We selected 51 consecutive frames as a single scene and held out 4 samples at a 10-frame interval for NVS evaluation. Meanwhile, Nuscenes' LiDAR has 32 beams, a 40-degree vertical FOV, and a $20\mathrm{-Hz}$ acquisition frequency. To cover a larger range of reconstruction, i.e., spanning $100\sim 200$ meters, we still selected samples at a frequency of $10\mathrm{Hz}$ , which is consistent with the KITTI-360. + +![](images/f8e21f279796e3b9888574ac02aed694403cbb4286ab61ba33494dadf4ce4ba8.jpg) +Figure 7. Qualitative comparison for LiDAR intensity reconstruction and synthesis. + +![](images/52d028571a52e0c979fe120ed55907e681d6293c1e9070b5afc380e2bb626742.jpg) +Figure 8. Qualitative comparison for LiDAR depth reconstruction and synthesis. + +Baselines. We present a comprehensive comparison of LiDAR4D with different types of baselines, encompassing explicit and implicit reconstruction approaches as well as dynamic NeRFs. We reproduce the mesh-based reconstruction method LiDARsim [25] and also replace the surface reconstruction model with the state-of-the-art method NKSR [15] for convincing. It's noted that we employ U-Net trained from original point clouds to further predict ray-drop for these two methods. Meanwhile, PCGen [19] reconstructs + +directly based on the point clouds and predicts ray-drop with the MLP. LiDAR-NeRF [39] is our primary comparison, and we directly adopt the official implements. In addition, we migrate dynamic neural radiance field methods such as D-NeRF [32], K-Planes [12], and TiNeuVox [9] to LiDAR NVS pipeline for a thorough comparison. + +Metrics. We offer multi-faceted metrics for evaluation. Chamfer Distance [8] measures the 3D geometric error between the generated and the ground-truth point clouds by + +
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.2.22490.86676.54700.07590.22890.715721.77460.15320.05060.25020.447916.3045
NKSR [15]E./S./M.0.57800.86854.66470.06980.22950.705222.53900.15650.05360.24290.420016.1159
PCGen [19]E./S.0.20900.85974.88380.17850.52100.506224.30500.20050.08180.61000.124813.9606
LiDAR-NeRF [39]I./S.0.09230.92263.68010.06670.35230.604326.76630.15570.05490.42120.276816.1683
LiDAR4D (Ours)I./D.0.08940.92643.23700.05070.13130.721827.88400.13430.04040.21270.469817.4529
+ +Table 3. Quantitative comparison on KITTI-360 Static Scene Sequence. We bold the best results and underline the second-best. + +nearest neighbor, and we also report the F-score value with an error threshold of $5\mathrm{cm}$ . In addition, we introduce Root Mean Square Error (RMSE) and Median Absolute Error (MedAE) to calculate the pixel-by-pixel error of the projected range images, as well as LPIPS [45], SSIM [41] and PSNR to measure the overall variance. We evaluate both the depth and intensity reconstruction results. + +# 4.2. Implementation Details + +Consistent with LiDAR-NeRF [39], the entire point cloud scene is scaled within the unit cube space. And we uniformly sampled 768 points along each laser. The optimization of LiDAR4D is implemented on Pytorch [31] with Adam [17] optimizer. The maximum iteration is set to $30\mathrm{k}$ for each scene, with a batch size of 1024 rays, followed by the fast ray-drop refinement with 300 epochs. We construct multi-planar representations following K-Planes [12] and hash grids built on tiny-cuda-nn [27]. The multi-level features of planes and hash grids are concatenated before feeding into MLPs. All experiments were conducted on a single NVIDIA GeForce RTX 4090 GPU. For more implementation details, please refer to Supplementary Material. + +# 4.3. Evaluation of Novel-View LiDAR Synthesis + +Results on KITTI-360 dataset. The quantitative comparison on KITTI-360 dataset is displayed in Table 1. Our proposed LiDAR4D exhibits remarkable performance across all metrics in comparison to prior SOTA methods, demonstrating its superiority in dynamic reconstruction. In comparison to LiDAR-NeRF, our approach has led to a $24.3\%$ reduction in the CD error of the novel-view point cloud synthesis. As illustrated in Figure 6, LiDAR4D achieves accurate reconstruction of every dynamic vehicle, whereas LiDAR-NeRF encounters failure. As shown in Figures 7 and 8, the resolution limitation causes blurring and oversmooth results of dynamic NeRFs such as TiNeuVox and K-Planes. This demonstrates again the effectiveness of our designed hybrid representation for large-scale scenes. Additionally, we follow the setting in LiDAR-NeRF to repeat experiments in static scenarios, and Table 3 verifies that there is no performance degradation in LiDAR4D. + +Results on NuScenes dataset. To further validate the generalizability of LiDAR4D, we conducted the same experi + +ment on NuScenes. As illustrated in Table 2, our method still achieves the best reconstruction quality even with a completely different LiDAR configuration. Ultimately, our method still excels in the reconstruction of depth and intensity, as evidenced by the $24.2\%$ reduction in CD error to LiDAR-NeRF. Please refer to Supplementary Material for more quantitative and qualitative experimental results on KITTI-360 and NuScenes datasets, as well as the ablation study and further applications. + +# 5. Limitations + +Despite the fact that LiDAR4D has exhibited exceptional performance in a substantial number of experiments, the long-distance vehicle motion and occlusion problem of point clouds remain open questions. There is still a significant gap in the reconstruction of dynamic objects compared to static ones. In addition, foreground and background may be difficult to separate well. Furthermore, based on real-world datasets, quantitative evaluation of NVS is limited within the ego-car trajectory and does not allow for the decoupling of novel spatial and temporal view synthesis. + +# 6. Conclusion + +In this paper, we revisit the limitations of existing LiDAR NVS methods and propose a novel framework to address three major challenges, namely dynamic reconstruction, large-scale scene characterization, and realistic synthesis. Our proposed method LiDAR4D proves its superiority under extensive experiments, achieving geometry-aware and time-consistent reconstruction of large-scale dynamic point cloud scenes and generating novel space-time view LiDAR point clouds closer to the real distribution. We believe that more future work will focus on combining LiDAR point clouds with neural radiance fields and explore more possibilities for dynamic scene reconstruction and synthesis. + +Acknowledgment. This work is supported by the National Natural Science Foundation of China (No.62372329), in part by the National Key Research and Development Program of China (No.2021YFB2501104), in part by Shanghai Rising Star Program (No.21QC1400900), in part by Tongji-Qomolo Autonomous Driving Commercial Vehicle Joint Lab Project, and in part by Xiaomi Young Talents Program. + +# References + +[1] Jonathan T Barron, Ben Mildenhall, Matthew Tancik, Peter Hedman, Ricardo Martin-Brualla, and Pratul P Srinivasan. Mip-nerf: A multiscale representation for anti-aliasing neural radiance fields. In Proceedings of the IEEE/CVF International Conference on Computer Vision, pages 5855–5864, 2021. 2 +[2] Jonathan T Barron, Ben Mildenhall, Dor Verbin, Pratul P Srinivasan, and Peter Hedman. Mip-nerf 360: Unbounded anti-aliased neural radiance fields. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 909-918, 2023. 5 \ No newline at end of file diff --git a/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/images.zip b/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..5bc2a6d58f49b921cf833ad7907fde93c7f54b32 --- /dev/null +++ b/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:0f6b844b8444af206b64479bad3740323ef10e8a5af05d057147737d3d510ecd +size 858090 diff --git a/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/layout.json b/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..715e971584ae5525fe4d0c7077d1d64cd5d29c4a --- /dev/null +++ b/2024/LiDAR4D_ Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis/layout.json @@ -0,0 +1,8027 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 52, + 102, + 541, + 121 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 102, + 541, + 121 + ], + "spans": [ + { + "bbox": [ + 52, + 102, + 541, + 121 + ], + "type": "text", + "content": "LiDAR4D: Dynamic Neural Fields for Novel Space-time View LiDAR Synthesis" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 132, + 143, + 460, + 172 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 132, + 143, + 460, + 172 + ], + "spans": [ + { + "bbox": [ + 132, + 143, + 460, + 172 + ], + "type": "text", + "content": "Zehan Zheng, Fan Lu, Weiyi Xue, Guang Chen†, Changjun Jiang Tongji University" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 138, + 174, + 452, + 185 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 138, + 174, + 452, + 185 + ], + "spans": [ + { + "bbox": [ + 138, + 174, + 452, + 185 + ], + "type": "text", + "content": "{zhengzehan, lufan, xwy, guangchen, cjjiang}@tongji.edu.cn" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 210, + 192, + 224 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 210, + 192, + 224 + ], + "spans": [ + { + "bbox": [ + 143, + 210, + 192, + 224 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 236, + 290, + 475 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 236, + 290, + 475 + ], + "spans": [ + { + "bbox": [ + 46, + 236, + 290, + 475 + ], + "type": "text", + "content": "Although neural radiance fields (NeRFs) have achieved triumphs in image novel view synthesis (NVS), LiDAR NVS remains largely unexplored. 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Meanwhile, the large motion of dynamic objects makes it difficult to align and reconstruct." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 542, + 545, + 626 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 542, + 545, + 626 + ], + "spans": [ + { + "bbox": [ + 304, + 542, + 545, + 626 + ], + "type": "text", + "content": "Traditional LiDAR-based 3D scene reconstruction techniques aggregate multiple sparse point cloud frames directly in the world coordinate system [19] and further convert them into explicit surface representations such as triangular meshes [25]. 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Furthermore, the aforementioned explicit reconstruction method is limited to static scenes and struggles to accurately model the intensity or ray-drop characteristics of actual LiDAR points." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 317, + 701, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 701, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 317, + 701, + 545, + 713 + ], + "type": "text", + "content": "Neural radiance fields [26] implicitly reconstruct the" + } + ] + } + ], + "index": 16 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 62, + 702, + 141, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 62, + 702, + 141, + 712 + ], + "spans": [ + { + "bbox": [ + 62, + 702, + 141, + 712 + ], + "type": "text", + "content": "† Corresponding author." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5145" + } + ] + } + ], + "index": 18 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 300 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 300 + ], + "type": "text", + "content": "scene and generate novel-view data through volume rendering in a continuous representation space, which also offers an alternative solution for LiDAR reconstruction. Consequently, the most recent researches [16, 39, 44] are shifting their attention towards the novel view synthesis of LiDAR. NeRF-LiDAR [44] integrates image and point cloud modalities for LiDAR synthesis, whereas LiDAR-only methods like LiDAR-NeRF [39] and NFL [16] explore the possibility of LiDAR reconstruction and generation without RGB images. Most prior methods directly apply the image NVS pipeline to LiDAR point clouds. However, LiDAR point clouds are inherently different from 2D images, which poses challenges for current LiDAR NVS methods to achieve high-quality reconstruction: (1) previous methods are limited to static scenes, ignoring the dynamic nature of autonomous driving scenarios; (2) the vast scale and high sparsity of LiDAR point clouds pose higher demands on the representations; and (3) intensity and ray-drop characteristics modeling are required for synthesis realism." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 300, + 289, + 467 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 300, + 289, + 467 + ], + "spans": [ + { + "bbox": [ + 47, + 300, + 289, + 467 + ], + "type": "text", + "content": "To overcome the aforementioned limitations, we propose LiDAR4D, shedding light on three pivotal insights to elevate the current LiDAR NVS pipeline. To tackle the dynamic objects, we introduce geometric constraints derived from point clouds and aggregate multi-frame dynamic features for temporal consistency. Regarding compact large-scale scene reconstruction, we design a coarse-to-fine hybrid representation combined with multi-planar and grid features to reconstruct the smooth geometry and high-frequency intensity. Additionally, we employ global optimization to preserve patterns across regions for raydrop probability refinement. Therefore, LiDAR4D is capable of achieving geometry-aware and time-consistent reconstruction under large-scale dynamic scenarios." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 468, + 289, + 588 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 468, + 289, + 588 + ], + "spans": [ + { + "bbox": [ + 47, + 468, + 289, + 588 + ], + "type": "text", + "content": "We evaluate our method on diverse dynamic scenarios of KITTI-360 [23] and NuScenes [3] autonomous driving datasets. With comprehensive experiments, LiDAR4D significantly outperforms previous state-of-the-art NeRF-based implicit approaches and explicit reconstruction methods. In comparison to LiDAR-NeRF [39], we achieve " + }, + { + "bbox": [ + 47, + 468, + 289, + 588 + ], + "type": "inline_equation", + "content": "24.3\\%" + }, + { + "bbox": [ + 47, + 468, + 289, + 588 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 47, + 468, + 289, + 588 + ], + "type": "inline_equation", + "content": "24.2\\%" + }, + { + "bbox": [ + 47, + 468, + 289, + 588 + ], + "type": "text", + "content": " reduction in CD error on KITTI-360 dataset and NuScenes dataset, respectively. Similar leadership exists for other metrics of range depth and intensity. In summary, our main contributions are three-fold:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 589, + 287, + 711 + ], + "type": "list", + "angle": 0, + "index": 6, + "blocks": [ + { + "bbox": [ + 47, + 589, + 287, + 636 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 589, + 287, + 636 + ], + "spans": [ + { + "bbox": [ + 47, + 589, + 287, + 636 + ], + "type": "text", + "content": "- We propose LiDAR4D, a differentiable LiDAR-only framework for novel space-time LiDAR view synthesis, which reconstructs dynamic driving scenarios and generates realistic LiDAR point clouds end-to-end." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 638, + 287, + 673 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 638, + 287, + 673 + ], + "spans": [ + { + "bbox": [ + 47, + 638, + 287, + 673 + ], + "type": "text", + "content": "- We introduce 4D hybrid neural representations and motion priors derived from point clouds for geometry-aware and time-consistent large-scale scene reconstruction." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 675, + 287, + 711 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 675, + 287, + 711 + ], + "spans": [ + { + "bbox": [ + 47, + 675, + 287, + 711 + ], + "type": "text", + "content": "- Comprehensive experiments demonstrate the state-of-the-art performance of LiDAR4D in challenging dynamic scene reconstruction and novel view synthesis." + } + ] + } + ], + "index": 5 + } + ], + "sub_type": "text" + }, + { + "bbox": [ + 306, + 71, + 392, + 84 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 71, + 392, + 84 + ], + "spans": [ + { + "bbox": [ + 306, + 71, + 392, + 84 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 91, + 547, + 402 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 91, + 547, + 402 + ], + "spans": [ + { + "bbox": [ + 304, + 91, + 547, + 402 + ], + "type": "text", + "content": "LiDAR Simulation. Traditional simulators [7, 18, 36] such as CARLA are based on physics engines, which can generate LiDAR point clouds via ray casting within handcrafted virtual environments. However, it has diversity limitations and a heavy reliance on costly 3D assets. And there is still a large domain gap compared to real-world data. Thus, several recent works [13, 19, 25] further narrowed this gap by reconstructing the scene from real data before simulation. LiDARsim [25] reconstructs the mesh surfel representation and employs a neural network to learn the ray-drop characteristics. Besides, it is noted that there are other surface reconstruction works like NKSR [15] that can convert LiDAR point clouds into mesh representations. Nonetheless, these explicit reconstruction works are troublesome for recovering precise surfaces in large-scale complex scenes, which further leads to a decrease in the accuracy of point cloud synthesis. Instead, PCGen [19] directly reconstructs from the point clouds, followed by rendering in a rasterization-like manner and first peak averaging. Although it preserves the original information better, the rendering point clouds remain relatively noisy. Moreover, all these explicit methods mentioned above are only applicable to static scenes. In contrast, our approach implicitly reconstructs the continuous representation via space-time neural radiance fields, which achieves higher-quality realistic point cloud synthesis and gets rid of static reconstruction limitations." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 402, + 547, + 617 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 402, + 547, + 617 + ], + "spans": [ + { + "bbox": [ + 304, + 402, + 547, + 617 + ], + "type": "text", + "content": "Neural Radiance Fields. Considerable recent research [1, 4, 5, 11, 14, 24, 26, 28, 38] based on neural radiance fields has led to breakthroughs as well as remarkable achievements in novel view synthesis (NVS) tasks. A wide variety of neural representations based on MLPs [1, 26], voxel grids [11, 24, 38], tri-planes [4, 14], vector decomposition [5], and multi-level hash grids [28] have been fully exploited for reconstruction and synthesis. Yet, most of the work focuses on object-centered reconstruction of small indoor scenes. Subsequently, several works [2, 33, 42] gradually extended it to large-scale outdoor scenarios. Despite this, neural radiance fields typically suffer from geometric ambiguity with RGB image inputs. Therefore, DS-NeRF [6] and DDP-NeRF [34] introduce the depth prior to enhancing efficiency, and URF [33] also utilizes Li-DAR point clouds to facilitate reconstruction. In this paper, we employ novel hybrid representations and neural LiDAR fields to reconstruct large-scale scenarios for LiDAR NVS." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 547, + 714 + ], + "type": "text", + "content": "NeRF for LiDAR NVS. Very recently, a few studies [16, 39, 43, 44] have pioneered in novel view synthesis of LiDAR point clouds based on neural radiance fields, significantly surpassing traditional simulation methods. Among them, NeRF-LiDAR [44] and UniSim [43] require both RGB images and LiDAR point clouds as inputs and reconstruct the driving scene with photometric loss and depth supervision. Subsequently, novel-view LiDAR point clouds" + } + ] + } + ], + "index": 10 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "type": "text", + "content": "5146" + } + ] + } + ], + "index": 11 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 82, + 71, + 537, + 277 + ], + "blocks": [ + { + "bbox": [ + 82, + 71, + 537, + 277 + ], + "lines": [ + { + "bbox": [ + 82, + 71, + 537, + 277 + ], + "spans": [ + { + "bbox": [ + 82, + 71, + 537, + 277 + ], + "type": "image", + "image_path": "c9c921e6c7979116a08482083634ba85aed222024ae9c81bb1bc67e22fbca0af.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 288, + 547, + 346 + ], + "lines": [ + { + "bbox": [ + 46, + 288, + 547, + 346 + ], + "spans": [ + { + "bbox": [ + 46, + 288, + 547, + 346 + ], + "type": "text", + "content": "Figure 2. Overview of our proposed LiDAR4D. For large-scale autonomous driving scenarios, we utilize the 4D hybrid representation, which combines low-resolution multi-planar features and high-resolution hash grid features to achieve effective reconstruction. Then, multi-level spatio-temporal features aggregated by flow MLP are fed into neural LiDAR fields for density, intensity and ray-drop probability prediction. Finally, novel space-time view LiDAR point clouds are synthesized via differentiable rendering. Furthermore, we construct geometric constraints derived from point clouds for temporal consistency and the global optimization of ray-drop for generation realism." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 361, + 289, + 577 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 361, + 289, + 577 + ], + "spans": [ + { + "bbox": [ + 46, + 361, + 289, + 577 + ], + "type": "text", + "content": "can be generated through neural depth rendering. Among LiDAR-only methods, LiDAR-NeRF [39] and NFL [16] firstly proposed the differentiable LiDAR NVS framework, which reconstructed depth, intensity, and ray-drop probability simultaneously. Nevertheless, these approaches [16, 39, 44] are restricted to static scene reconstruction and incapable of handling dynamic objects such as moving vehicles. Although UniSim [43] does support dynamic scenes, it is largely limited by the need for ground-truth labeling of 3D object detection and decoupling the background and dynamic objects before reconstruction. Instead, our research focuses on LiDAR-only inputs for dynamic scene reconstruction and novel space-time view synthesis without the help of RGB images or ground-truth labels. And it's noteworthy that NFL [16] has contributed significantly to the detailed physical modeling of LiDAR, such as beam divergence and secondary returns, which is orthogonal to ours and could be beneficial to all LiDAR NVS works." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 582, + 289, + 715 + ], + "type": "text", + "content": "Dynamic Scene Reconstruction. A substantial amount of research [9, 12, 21, 22, 29, 30, 32, 37, 40] has been devoted to expanding neural radiance fields to encompass dynamic scene reconstruction. In general, dynamic NeRFs can be broadly categorized into two groups. One is the deformable neural radiance fields [9, 29, 30, 32] that map coordinates into the canonical space via continuous deformation fields. While the decoupling of deformation and radiance fields simplifies the optimization, establishing accurate long-distance correspondence remains challenging. The other is spatio-temporal neural fields [12, 21, 22, 37]," + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 304, + 361, + 547, + 471 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 361, + 547, + 471 + ], + "spans": [ + { + "bbox": [ + 304, + 361, + 547, + 471 + ], + "type": "text", + "content": "which consider time as an additional dimensional input to construct a 4D spatio-temporal representation. Thus, it is flexible to simultaneously model appearance, geometry, and motion as a continuous time-varying function. Most previous work has concentrated on relatively smaller displacements indoors, whereas large-scale vehicle movements in autonomous driving scenarios are even more challenging. Furthermore, our work is also the first to introduce dynamic neural radiance fields into the LiDAR NVS task." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 306, + 485, + 389, + 499 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 485, + 389, + 499 + ], + "spans": [ + { + "bbox": [ + 306, + 485, + 389, + 499 + ], + "type": "text", + "content": "3. Methodology" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 506, + 547, + 555 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 506, + 547, + 555 + ], + "spans": [ + { + "bbox": [ + 304, + 506, + 547, + 555 + ], + "type": "text", + "content": "In this section, we start with the problem formulation of novel LiDAR view synthesis and the preliminary for NeRFs. Following this, a detailed description of our proposed LiDAR4D framework is provided." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "spans": [ + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": "Problem Formulation. In the dynamic driving scenario, given the collected LiDAR point cloud sequence " + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "S = \\{S_0, S_1, \\dots, S_{n-1}\\}" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "S_i \\in \\mathbb{R}^{K \\times 4}" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": "), along with the corresponding sensor poses " + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "P_s = \\{P_0, P_1, \\dots, P_{n-1}\\}" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "P_i \\in SE(3)" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": ") and timestamps " + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "T_s = \\{t_0, t_1, \\dots, t_{n-1}\\}" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": " (" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "t_i \\in \\mathbb{R}" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": ") as inputs. Each single LiDAR frame " + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "S_i" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": " contains " + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": " points of 3D coordinates " + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "x" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": " and 1D reflection intensity " + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "inline_equation", + "content": "\\rho" + }, + { + "bbox": [ + 304, + 556, + 547, + 640 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "content": "The goal of LiDAR4D is to reconstruct this dynamic scene as a continuous implicit representation based on neural fields. Furthermore, given a novel sensor pose " + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "inline_equation", + "content": "P_{novel}" + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "content": " and any moment " + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "inline_equation", + "content": "t_{novel}" + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "content": ", LiDAR4D performs neural rendering to synthesize the LiDAR point cloud " + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "inline_equation", + "content": "S_{novel}" + }, + { + "bbox": [ + 304, + 642, + 547, + 715 + ], + "type": "text", + "content": " with intensities under the novel space-time view." + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 316, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 316, + 758 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 316, + 758 + ], + "type": "text", + "content": "5147" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 51, + 71, + 282, + 175 + ], + "blocks": [ + { + "bbox": [ + 51, + 71, + 282, + 175 + ], + "lines": [ + { + "bbox": [ + 51, + 71, + 282, + 175 + ], + "spans": [ + { + "bbox": [ + 51, + 71, + 282, + 175 + ], + "type": "image", + "image_path": "00d3f7789b3f4ab48b86df245cf042c11c6bd4288490432059fa75e509291b01.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 183, + 287, + 206 + ], + "lines": [ + { + "bbox": [ + 46, + 183, + 287, + 206 + ], + "spans": [ + { + "bbox": [ + 46, + 183, + 287, + 206 + ], + "type": "text", + "content": "Figure 3. 4D decomposition of hybrid planar-grid representation. Dynamic features can be further aggregated using flow MLP." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "spans": [ + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": "Preliminary for NeRF. Neural radiance fields, NeRFs for short, take 5D inputs of position " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "\\mathbf{x} \\in \\mathbb{R}^3" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": " and viewing direction " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "(\\theta, \\phi)" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": " as inputs and establish the mapping to the volume density " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": " and color " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "\\mathbf{c}" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": ". Afterward, it performs volume rendering to estimate pixel values and synthesize images in unknown novel views. In detail, it emits a light ray " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "\\mathbf{r}" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": " from the sensor center " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "\\mathbf{o}" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": " with the direction " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "\\mathbf{d}" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": ", i.e., " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "\\mathbf{r}(t) = \\mathbf{o} + t\\mathbf{d}" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": ", and then integrates the neural field outputs of " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "N" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": " samples along this ray to approximate the pixel color " + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "inline_equation", + "content": "\\mathcal{C}" + }, + { + "bbox": [ + 46, + 217, + 289, + 338 + ], + "type": "text", + "content": ". The volume rendering function can be formed as follows:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 52, + 346, + 287, + 380 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 346, + 287, + 380 + ], + "spans": [ + { + "bbox": [ + 52, + 346, + 287, + 380 + ], + "type": "interline_equation", + "content": "\\hat {\\mathcal {C}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\left(1 - e ^ {- \\sigma_ {i} \\delta_ {i}}\\right) \\mathbf {c} _ {i}, T _ {i} = \\exp \\left(- \\sum_ {j = 1} ^ {i - 1} \\sigma_ {j} \\delta_ {j}\\right) (1)", + "image_path": "5fdc04b498d261984fb90140916ddd266bbe1f2cd76e9e95f5f4a0d2de10fdbf.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "spans": [ + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "type": "inline_equation", + "content": "T" + }, + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "type": "text", + "content": " indicates the accumulated transmittance, " + }, + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "type": "text", + "content": " denotes the density and " + }, + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "type": "inline_equation", + "content": "\\delta" + }, + { + "bbox": [ + 47, + 387, + 287, + 411 + ], + "type": "text", + "content": " refers to the distance between samples." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 418, + 165, + 430 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 418, + 165, + 430 + ], + "spans": [ + { + "bbox": [ + 47, + 418, + 165, + 430 + ], + "type": "text", + "content": "3.1. LiDAR4D Overview" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 436, + 289, + 653 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 436, + 289, + 653 + ], + "spans": [ + { + "bbox": [ + 46, + 436, + 289, + 653 + ], + "type": "text", + "content": "Following neural radiance fields, our proposed LiDAR4D reconstructs the point cloud scene into an implicit continuous representation. Differing from original NeRFs with photometric loss for RGB images, we redefine the neural fields based on LiDAR, which are dubbed neural LiDAR fields. As depicted in Figure 2, it focuses on modeling the geometric depth, reflection intensity, and ray-drop probability of LiDAR point clouds. For large-scale dynamic driving scenarios, LiDAR4D combines coarse-resolution multi-planar features with high-resolution hash grid representation to achieve efficient and effective reconstruction. Then, we lift it to 4D and introduce temporal information encoding for novel space-time view synthesis. To ensure geometry-aware and time-consistent results, we additionally incorporate explicit geometric constraints derived from point clouds. Ultimately, we predict the ray-drop probability for each ray and perform global refinement with a runtime-optimized U-Net to improve generation realism." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 658, + 255, + 672 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 658, + 255, + 672 + ], + "spans": [ + { + "bbox": [ + 47, + 658, + 255, + 672 + ], + "type": "text", + "content": "3.2. 4D Hybrid Planar-Grid Representation" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 713 + ], + "type": "text", + "content": "Figure 3 illustrates how our proposed novel hybrid representation breaks down the 4D space into planar and hash grid features, which further subdivide into static and" + } + ] + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 319, + 70, + 421, + 110 + ], + "blocks": [ + { + "bbox": [ + 319, + 70, + 421, + 110 + ], + "lines": [ + { + "bbox": [ + 319, + 70, + 421, + 110 + ], + "spans": [ + { + "bbox": [ + 319, + 70, + 421, + 110 + ], + "type": "image", + "image_path": "3fa061ea4fc2b9f5f7dc1e922ee2884f6688a4244ca2c406898368c18166ad30.jpg" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 341, + 112, + 399, + 119 + ], + "lines": [ + { + "bbox": [ + 341, + 112, + 399, + 119 + ], + "spans": [ + { + "bbox": [ + 341, + 112, + 399, + 119 + ], + "type": "text", + "content": "K-Planes (Planes only)" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_caption" + } + ], + "index": 9 + }, + { + "type": "image", + "bbox": [ + 425, + 70, + 527, + 110 + ], + "blocks": [ + { + "bbox": [ + 425, + 70, + 527, + 110 + ], + "lines": [ + { + "bbox": [ + 425, + 70, + 527, + 110 + ], + "spans": [ + { + "bbox": [ + 425, + 70, + 527, + 110 + ], + "type": "image", + "image_path": "54352bcedbff2724f624b5ffe71c7e2ed9358452b99ae11e07d55fccffe21a72.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 426, + 112, + 526, + 119 + ], + "lines": [ + { + "bbox": [ + 426, + 112, + 526, + 119 + ], + "spans": [ + { + "bbox": [ + 426, + 112, + 526, + 119 + ], + "type": "text", + "content": "LiDAR4D (w/ Hybrid Representations)" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 319, + 121, + 421, + 163 + ], + "blocks": [ + { + "bbox": [ + 319, + 121, + 421, + 163 + ], + "lines": [ + { + "bbox": [ + 319, + 121, + 421, + 163 + ], + "spans": [ + { + "bbox": [ + 319, + 121, + 421, + 163 + ], + "type": "image", + "image_path": "d6f5dc9c74ae67198a1fc63dadad0f45434c81eb38ee62e343ea714ab276cfe6.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 329, + 164, + 410, + 171 + ], + "lines": [ + { + "bbox": [ + 329, + 164, + 410, + 171 + ], + "spans": [ + { + "bbox": [ + 329, + 164, + 410, + 171 + ], + "type": "text", + "content": "LiDAR-NeRF (Hash Grid only)" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "type": "image", + "bbox": [ + 425, + 121, + 527, + 163 + ], + "blocks": [ + { + "bbox": [ + 425, + 121, + 527, + 163 + ], + "lines": [ + { + "bbox": [ + 425, + 121, + 527, + 163 + ], + "spans": [ + { + "bbox": [ + 425, + 121, + 527, + 163 + ], + "type": "image", + "image_path": "6524055ecbaac99ea1f389a582e57e26385a90d7374f2b21901d684e7bde7fa1.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 471, + 164, + 481, + 171 + ], + "lines": [ + { + "bbox": [ + 471, + 164, + 481, + 171 + ], + "spans": [ + { + "bbox": [ + 471, + 164, + 481, + 171 + ], + "type": "text", + "content": "GT" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 305, + 180, + 547, + 225 + ], + "lines": [ + { + "bbox": [ + 305, + 180, + 547, + 225 + ], + "spans": [ + { + "bbox": [ + 305, + 180, + 547, + 225 + ], + "type": "text", + "content": "Figure 4. Qualitative comparison for the hybrid representation. Compared to the noisy intensity reconstruction of LiDAR-NeRF and the blurry one of K-Planes, our hybrid representation achieves more precise and smooth results." + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 239, + 545, + 358 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 239, + 545, + 358 + ], + "spans": [ + { + "bbox": [ + 304, + 239, + 545, + 358 + ], + "type": "text", + "content": "dynamic ones. Different from the reconstruction of small indoor objects, large-scale autonomous driving scenes place higher demands on the representation ability and resolution of the features. However, the dense grid representation such as TiNeuVox [9] is unscalable for large-scale scenarios due to its cubically growing complexity. Therefore, we follow K-planes [12] and decompose the scene space into a combination of features in multiple orthogonal planes to drastically reduce the parameter quantities. The planar feature can be obtained as follows:" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 318, + 366, + 545, + 382 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 366, + 545, + 382 + ], + "spans": [ + { + "bbox": [ + 318, + 366, + 545, + 382 + ], + "type": "interline_equation", + "content": "\\mathbf {f} _ {\\text {p l a n a r}} = \\mathcal {S} (\\mathbf {V}, (x, y, z, t)), \\mathbf {V} \\in \\mathbb {R} ^ {(3 M ^ {2} + 3 M H) C} \\tag {2}", + "image_path": "868327f303b4e73ac949bc94293d7dd7ec01a364f783cdc7a088a3885f89e014.jpg" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "spans": [ + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "inline_equation", + "content": "\\mathbf{V}" + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": " stores features with " + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "inline_equation", + "content": "M" + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": " spatial resolution, " + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "inline_equation", + "content": "H" + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": " temporal resolution and " + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "inline_equation", + "content": "C" + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": " channels. " + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": " refers to the sampling function that projects 4D coordinates into the corresponding planes " + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "inline_equation", + "content": "(xy, xz, yz, xt, yt, zt)" + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": " and interpolates features bilinearly. Static " + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "inline_equation", + "content": "(xy, xz, yz)" + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": " and dynamic " + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "inline_equation", + "content": "(xt, yt, zt)" + }, + { + "bbox": [ + 304, + 392, + 545, + 475 + ], + "type": "text", + "content": " features are multiplied separately by Hadamard product and multiscale features are concatenated in a coarse-to-fine manner." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 475, + 545, + 559 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 475, + 545, + 559 + ], + "spans": [ + { + "bbox": [ + 304, + 475, + 545, + 559 + ], + "type": "text", + "content": "Nonetheless, for scenes spanning hundreds of meters, this improvement in resolution remains inadequate, especially for the high-frequency intensity reconstruction. Owing to the hash grids proposed in Instant-NGP [28], an explicit grid structure with ultra-high resolution is possible. Additionally, the sparsity of the LiDAR point cloud scene substantially avoids the adverse effects of hash collisions." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 321, + 568, + 545, + 585 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 321, + 568, + 545, + 585 + ], + "spans": [ + { + "bbox": [ + 321, + 568, + 545, + 585 + ], + "type": "interline_equation", + "content": "\\mathbf {f} _ {\\text {h a s h}} = \\mathcal {S} (\\mathbf {G}, (x, y, z, t)), \\mathbf {G} \\in \\mathbb {R} ^ {(M ^ {3} + 3 M ^ {2} H) C} \\tag {3}", + "image_path": "f28a2d576e66bdb927b80d9352181bf5f96facd47dd65d0a61475dbc4fc91e23.jpg" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "type": "text", + "content": "where the dense grid " + }, + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "type": "inline_equation", + "content": "\\mathbf{G}" + }, + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "type": "text", + "content": " will be further compressed into limited storage via hash mapping for parameter reduction. Similarly, the 4D coordinates are projected into static " + }, + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "type": "inline_equation", + "content": "(xyz)" + }, + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "type": "text", + "content": " and dynamic " + }, + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "type": "inline_equation", + "content": "(xyt, xzt, yzt)" + }, + { + "bbox": [ + 304, + 594, + 545, + 665 + ], + "type": "text", + "content": " multi-level hash grids before tri-linear interpolation and concatenation, where the dynamic features are multiplied using Hadamard product." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 545, + 713 + ], + "type": "text", + "content": "However, it's notable that pure hash grid representation still suffers from visual artifacts and noisy reconstruction results (as shown in Figure 4), which impede the construction of accurate object geometry. In light of this, we adopt" + } + ] + } + ], + "index": 24 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5148" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 120 + ], + "type": "text", + "content": "multi-planar features at lower resolutions for overall smooth representation and employ hash grids at higher resolutions to handle finer details, ultimately achieving high accuracy and efficiency in large-scale scene reconstruction." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 129, + 150, + 140 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 129, + 150, + 140 + ], + "spans": [ + { + "bbox": [ + 47, + 129, + 150, + 140 + ], + "type": "text", + "content": "3.3. Scene Flow Prior" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 148, + 287, + 208 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 148, + 287, + 208 + ], + "spans": [ + { + "bbox": [ + 46, + 148, + 287, + 208 + ], + "type": "text", + "content": "To enhance the temporal consistency of the current 4D spatio-temporal representations, we further incorporate a flow MLP [20, 46] for motion estimation. It takes the encoded spatio-temporal coordinates as input and constructs the mapping from coordinate fields " + }, + { + "bbox": [ + 46, + 148, + 287, + 208 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^4" + }, + { + "bbox": [ + 46, + 148, + 287, + 208 + ], + "type": "text", + "content": " to motion fields " + }, + { + "bbox": [ + 46, + 148, + 287, + 208 + ], + "type": "inline_equation", + "content": "\\mathbb{R}^3" + }, + { + "bbox": [ + 46, + 148, + 287, + 208 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 81, + 221, + 287, + 234 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 81, + 221, + 287, + 234 + ], + "spans": [ + { + "bbox": [ + 81, + 221, + 287, + 234 + ], + "type": "interline_equation", + "content": "\\Delta \\mathbf {x} = \\operatorname {M L P} _ {\\text {f l o w}} (\\gamma (\\mathbf {x}, t)), \\quad \\mathbf {x} ^ {\\prime} = \\mathbf {x} + \\Delta \\mathbf {x} \\tag {4}", + "image_path": "5cf23dc97c5cc2c99f23a9dbcaaac4279577108580bfaac0defd18fc70fa1386.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 242, + 287, + 324 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 242, + 287, + 324 + ], + "spans": [ + { + "bbox": [ + 46, + 242, + 287, + 324 + ], + "type": "text", + "content": "Since the vehicle motion range may span a long distance in autonomous driving scenarios, it is extremely hard to establish long-term correspondences to the canonical space in deformable neural radiance fields. Thus, as with Li et al. [21, 22], we utilize the flow MLP to predict motion only between adjacent frames and aggregate multi-frame dynamic features to achieve time-consistent reconstruction." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "spans": [ + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "type": "text", + "content": "In addition, explicit geometric constraints can be further derived from the input LiDAR point clouds. By feeding point clouds into the flow MLP to produce the scene flow prediction, we can regulate the chamfer distance as a geometric loss " + }, + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "type": "inline_equation", + "content": "(\\mathcal{L}_{\\mathrm{flow}})" + }, + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "type": "text", + "content": ". It imposes motion prior and additional supervision on LiDAR4D, thus accomplishing the geometry-aware reconstruction. Chamfer Distance between two frames of point cloud " + }, + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "type": "inline_equation", + "content": "S" + }, + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "type": "inline_equation", + "content": "\\hat{S}" + }, + { + "bbox": [ + 46, + 325, + 287, + 415 + ], + "type": "text", + "content": " is defined as follows:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 52, + 423, + 287, + 452 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 423, + 287, + 452 + ], + "spans": [ + { + "bbox": [ + 52, + 423, + 287, + 452 + ], + "type": "interline_equation", + "content": "\\mathrm {C D} = \\frac {1}{K} \\sum_ {\\hat {p} _ {i} \\in \\hat {S}} \\min _ {p _ {i} \\in S} \\| \\hat {p} _ {i} - p _ {i} \\| _ {2} ^ {2} + \\frac {1}{K} \\sum_ {p _ {i} \\in S} \\min _ {\\hat {p} _ {i} \\in \\hat {S}} \\| p _ {i} - \\hat {p} _ {i} \\| _ {2} ^ {2} \\tag {5}", + "image_path": "39156f28f56eeba2e0665c5a0e641feac7e9013084dce561c31960ab6fe5c7d2.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 52, + 460, + 287, + 483 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 52, + 460, + 287, + 483 + ], + "spans": [ + { + "bbox": [ + 52, + 460, + 287, + 483 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {f l o w}} = \\sum_ {j \\in \\pm 1} \\mathrm {C D} \\left(S _ {i} + \\mathrm {M L P} _ {\\text {f l o w}} \\left(S _ {i}\\right), S _ {i + j}\\right), i \\in (0, n - 1) \\tag {6}", + "image_path": "3327ce5e5201e1a9cd4328a6c6f8beeb6ab815381412c40416df93382e6ecee5.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 492, + 169, + 504 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 492, + 169, + 504 + ], + "spans": [ + { + "bbox": [ + 47, + 492, + 169, + 504 + ], + "type": "text", + "content": "3.4. Neural LiDAR Fields" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 511, + 287, + 642 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 511, + 287, + 642 + ], + "spans": [ + { + "bbox": [ + 46, + 511, + 287, + 642 + ], + "type": "text", + "content": "LiDAR emits laser pulses and measures the time-of-flight (ToF) to determine object distance, along with the intensity of reflected lights. Spinning LiDAR has a 360-degree horizontal field of view (FOV) and a limited range of vertical field of view, which perceives the environment with certain angular resolution lasers. In the same way for neural LiDAR fields, we transmit lasers at specific angular intervals within the FOV, using the center of the LiDAR sensor as the origin o. The direction d of the laser is determined by the azimuth angle " + }, + { + "bbox": [ + 46, + 511, + 287, + 642 + ], + "type": "inline_equation", + "content": "\\theta" + }, + { + "bbox": [ + 46, + 511, + 287, + 642 + ], + "type": "text", + "content": " and elevation angle " + }, + { + "bbox": [ + 46, + 511, + 287, + 642 + ], + "type": "inline_equation", + "content": "\\phi" + }, + { + "bbox": [ + 46, + 511, + 287, + 642 + ], + "type": "text", + "content": " under the polar coordinate system, which is shown below." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 89, + 652, + 287, + 666 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 89, + 652, + 287, + 666 + ], + "spans": [ + { + "bbox": [ + 89, + 652, + 287, + 666 + ], + "type": "interline_equation", + "content": "\\mathbf {d} = (\\cos \\theta \\cos \\phi , \\sin \\theta \\sin \\phi , \\cos \\phi) ^ {T} \\tag {7}", + "image_path": "b77343499aff10c8521781da51854ae54688398f0f9a95c35c69c362dfdfd907.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": "Then we query 3D point coordinates sampled along the laser and feed them into neural fields to predict the density at the corresponding location. Following this, the density" + } + ] + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 310, + 68, + 545, + 140 + ], + "blocks": [ + { + "bbox": [ + 310, + 68, + 545, + 140 + ], + "lines": [ + { + "bbox": [ + 310, + 68, + 545, + 140 + ], + "spans": [ + { + "bbox": [ + 310, + 68, + 545, + 140 + ], + "type": "image", + "image_path": "58714d57a7bbdb076a18f43ec6e88e2391477953201cd3bbaba370f7b27170ba.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 144, + 545, + 190 + ], + "lines": [ + { + "bbox": [ + 305, + 144, + 545, + 190 + ], + "spans": [ + { + "bbox": [ + 305, + 144, + 545, + 190 + ], + "type": "text", + "content": "Figure 5. Qualitative comparison for the ray-drop refinement. The point-wise prediction of ray-drop probability by MLP cannot preserve global patterns well. Instead, LiDAR4D drastically improves generation realism via runtime-optimized U-Net." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "bbox": [ + 305, + 204, + 545, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 204, + 545, + 228 + ], + "spans": [ + { + "bbox": [ + 305, + 204, + 545, + 228 + ], + "type": "text", + "content": "along the ray is integrated to obtain the expectation of depth value " + }, + { + "bbox": [ + 305, + 204, + 545, + 228 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 305, + 204, + 545, + 228 + ], + "type": "text", + "content": ", which serves as the laser beam's return distance." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 316, + 236, + 545, + 268 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 316, + 236, + 545, + 268 + ], + "spans": [ + { + "bbox": [ + 316, + 236, + 545, + 268 + ], + "type": "interline_equation", + "content": "\\hat {\\mathcal {D}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\left(1 - e ^ {- \\sigma_ {i} \\delta_ {i}}\\right) z _ {i}, \\quad \\alpha_ {i} = 1 - e ^ {- \\sigma_ {i} \\delta_ {i}} \\tag {8}", + "image_path": "032b829739fbdf0296e5670f0723a6f9de5398470f00bd3b033d066ad6c02c6f.jpg" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "spans": [ + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "type": "inline_equation", + "content": "z_{i}" + }, + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "type": "text", + "content": " is the depth value of queried points on the ray " + }, + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "type": "inline_equation", + "content": "\\mathbf{r}" + }, + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 305, + 276, + 545, + 300 + ], + "type": "text", + "content": " is the definition of the opacity." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 305, + 300, + 545, + 335 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 300, + 545, + 335 + ], + "spans": [ + { + "bbox": [ + 305, + 300, + 545, + 335 + ], + "type": "text", + "content": "In addition, we predict the intensity " + }, + { + "bbox": [ + 305, + 300, + 545, + 335 + ], + "type": "inline_equation", + "content": "\\mathcal{I}" + }, + { + "bbox": [ + 305, + 300, + 545, + 335 + ], + "type": "text", + "content": " and ray-drop probability " + }, + { + "bbox": [ + 305, + 300, + 545, + 335 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 305, + 300, + 545, + 335 + ], + "type": "text", + "content": " separately for each point and similarly conduct alpha-composition along the ray." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 340, + 344, + 545, + 376 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 340, + 344, + 545, + 376 + ], + "spans": [ + { + "bbox": [ + 340, + 344, + 545, + 376 + ], + "type": "interline_equation", + "content": "\\hat {\\mathcal {I}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\alpha_ {i} i _ {i}, \\quad \\hat {\\mathcal {P}} (\\mathbf {r}) = \\sum_ {i = 1} ^ {N} T _ {i} \\alpha_ {i} p _ {i} \\tag {9}", + "image_path": "4064ac580013f30dfc27320d174c7c28261ca12055c545a6fc9d6f7b18caaf1a.jpg" + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 305, + 384, + 545, + 433 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 384, + 545, + 433 + ], + "spans": [ + { + "bbox": [ + 305, + 384, + 545, + 433 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 305, + 384, + 545, + 433 + ], + "type": "inline_equation", + "content": "i_{i}" + }, + { + "bbox": [ + 305, + 384, + 545, + 433 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 305, + 384, + 545, + 433 + ], + "type": "inline_equation", + "content": "p_{i}" + }, + { + "bbox": [ + 305, + 384, + 545, + 433 + ], + "type": "text", + "content": " are the point-wise intensity and ray-drop probability outputs of LiDAR4D. We use separate MLPs to take temporal aggregated planar and hash features, as well as position-encoded viewpoints as inputs for prediction." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 347, + 441, + 545, + 454 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 347, + 441, + 545, + 454 + ], + "spans": [ + { + "bbox": [ + 347, + 441, + 545, + 454 + ], + "type": "interline_equation", + "content": "i = \\operatorname {M L P} _ {\\text {i n t e n s i t y}} \\left(\\mathbf {f} _ {\\text {p l a n a r}}, \\mathbf {f} _ {\\text {h a s h}}, \\gamma (\\mathbf {d})\\right) \\tag {10}", + "image_path": "a42999314115fea767192952e20caf21adaac65cdd1d25b7571792d78f7236cf.jpg" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 348, + 462, + 545, + 475 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 462, + 545, + 475 + ], + "spans": [ + { + "bbox": [ + 348, + 462, + 545, + 475 + ], + "type": "interline_equation", + "content": "\\rho = \\mathrm {M L P} _ {\\text {r a y d r o p}} \\left(\\mathbf {f} _ {\\text {p l a n a r}}, \\mathbf {f} _ {\\text {h a s h}}, \\gamma (\\mathbf {d})\\right) \\tag {11}", + "image_path": "151b9052e8872143fa29288def1806bb7658eae1c309ef6e131685bc7f85b8cb.jpg" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 316, + 483, + 545, + 506 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 316, + 483, + 545, + 506 + ], + "spans": [ + { + "bbox": [ + 316, + 483, + 545, + 506 + ], + "type": "interline_equation", + "content": "\\gamma (x) = \\left(\\sin \\left(2 ^ {0} x\\right), \\cos \\left(2 ^ {0} x\\right), \\dots , \\sin \\left(2 ^ {L - 1} x\\right), \\cos \\left(2 ^ {L - 1} x\\right)\\right) \\tag {12}", + "image_path": "27660939432fba066736175dcbb7694e93e806a53d55187bd700221e2aa91e38.jpg" + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 306, + 514, + 429, + 527 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 514, + 429, + 527 + ], + "spans": [ + { + "bbox": [ + 306, + 514, + 429, + 527 + ], + "type": "text", + "content": "3.5. Ray-drop Refinement" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 304, + 533, + 545, + 688 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 533, + 545, + 688 + ], + "spans": [ + { + "bbox": [ + 304, + 533, + 545, + 688 + ], + "type": "text", + "content": "During laser ranging, a portion of the emitted rays is not reflected back to the sensor, which is termed the ray-drop characteristic. In fact, the ray-drop of LiDAR is significantly impacted by various aspects, including distance, surface properties and sensor noise. As in LiDAR-NeRF [39], ray-drop prediction is directly accomplished with a pointwise MLP head, which is essentially noisy and unreliable. To address this issue, we employ the U-Net [35] with residuals to refine the ray-drop mask globally and better preserve the consistent pattern across regions. It takes the full ray-drop probability, depth and intensity prediction of LiDAR4D as inputs (different from previous work) and refines the final mask via binary cross-entropy loss as follows:" + } + ] + } + ], + "index": 24 + }, + { + "bbox": [ + 348, + 696, + 545, + 716 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 348, + 696, + 545, + 716 + ], + "spans": [ + { + "bbox": [ + 348, + 696, + 545, + 716 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {r e f i n e}} = \\operatorname {B C E L o s s} \\left(\\hat {\\mathcal {M}} _ {\\text {P r e d}}, \\mathcal {M} _ {\\mathrm {G T}}\\right) \\tag {13}", + "image_path": "3d76ca5bd0186a2d5bbf26300305c9e2bdb256dd06928368269a141daafed897.jpg" + } + ] + } + ], + "index": 25 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5149" + } + ] + } + ], + "index": 26 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 52, + 70, + 547, + 182 + ], + "blocks": [ + { + "bbox": [ + 52, + 70, + 547, + 182 + ], + "lines": [ + { + "bbox": [ + 52, + 70, + 547, + 182 + ], + "spans": [ + { + "bbox": [ + 52, + 70, + 547, + 182 + ], + "type": "table", + "html": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.3.22280.71576.91530.12790.29260.634221.46080.16660.05690.32760.350215.5853
NKSR [15]E./S./M.1.89820.68555.84030.09960.27520.640923.03680.17420.05900.33370.351715.2081
PCGen [19]E./S.0.46360.80235.65830.20400.53910.490323.16750.19700.07630.59260.135114.1181
LiDAR-NeRF [39]I./S.0.14380.90914.17530.05660.27970.656825.98780.14040.04430.31350.383117.1549
D-NeRF [32]I./D.0.14420.91284.01940.05080.30610.663426.23440.13690.04400.34090.374817.3554
TiNeuVox-B [9]I./D.0.17480.90594.12840.05020.34270.651426.02670.13630.04530.43650.345717.3535
K-Planes [12]I./D.0.13020.91234.13220.05390.34570.638526.02360.14150.04980.40810.300817.0167
LiDAR4D (Ours)I./D.0.10890.92723.52560.04040.10510.764727.47670.11950.03270.18450.530418.5561
", + "image_path": "668a2b8f98141803163361cee8ef523bf80deee12dedba33eee5e2d54884d5d1.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "type": "table", + "bbox": [ + 52, + 223, + 545, + 335 + ], + "blocks": [ + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "lines": [ + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "spans": [ + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "text", + "content": "Table 1. Quantitative comparison on KITTI-360 dataset. We compare our method to different types of previous approaches and color the top results as best and second best. " + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "inline_equation", + "content": "\\mathcal{E}" + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "text", + "content": " : Explicit, " + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "inline_equation", + "content": "\\mathcal{I}" + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "text", + "content": " : Implicit, " + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "inline_equation", + "content": "\\mathcal{S}" + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "text", + "content": " : Static, " + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "inline_equation", + "content": "\\mathcal{D}" + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "text", + "content": " : Dynamic, " + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "inline_equation", + "content": "\\mathcal{M}" + }, + { + "bbox": [ + 46, + 189, + 547, + 213 + ], + "type": "text", + "content": " : Mesh." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 52, + 223, + 545, + 335 + ], + "lines": [ + { + "bbox": [ + 52, + 223, + 545, + 335 + ], + "spans": [ + { + "bbox": [ + 52, + 223, + 545, + 335 + ], + "type": "table", + "html": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.12.13830.651210.55390.35720.18710.565317.78410.06590.01150.11600.517023.7791
NKSR [15]E./S./M.11.49100.61789.37310.57630.21110.563718.77740.06800.01190.12900.503123.4905
PCGen [19]E./S.2.19980.63418.83640.40110.17920.544019.27990.07680.01470.13080.441022.4428
LiDAR-NeRF [39]I./S.0.32250.85767.15660.03380.07020.718821.21290.04670.00760.04830.726426.9927
D-NeRF [32]I./D.0.32960.85137.10890.03680.07890.713021.25940.04670.00800.04920.718026.9951
TiNeuVox-B [9]I./D.0.39200.86277.20930.02900.15490.687321.09320.04620.00800.12940.710726.8620
K-Planes [12]I./D.0.29820.88876.79600.02090.12180.725821.62030.04380.00760.11270.736427.4227
LiDAR4D (Ours)I./D.0.24430.89156.78310.02580.05690.739621.71890.04260.00710.04590.749827.7977
", + "image_path": "ead8f22724dd429b5d404d69c0fc1f02823f26df098e075edb2ae5b8fc104780.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_body" + } + ], + "index": 2 + }, + { + "bbox": [ + 74, + 341, + 517, + 351 + ], + "lines": [ + { + "bbox": [ + 74, + 341, + 517, + 351 + ], + "spans": [ + { + "bbox": [ + 74, + 341, + 517, + 351 + ], + "type": "text", + "content": "Table 2. Quantitative comparison on NuScenes dataset. The notations are consistent with the KITTI-360 Table 1 above." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 361, + 287, + 386 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 361, + 287, + 386 + ], + "spans": [ + { + "bbox": [ + 46, + 361, + 287, + 386 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 361, + 287, + 386 + ], + "type": "inline_equation", + "content": "\\mathcal{M}" + }, + { + "bbox": [ + 46, + 361, + 287, + 386 + ], + "type": "text", + "content": " indicates the global mask rendered from range view and " + }, + { + "bbox": [ + 46, + 361, + 287, + 386 + ], + "type": "inline_equation", + "content": "\\mathcal{M}_{GT}" + }, + { + "bbox": [ + 46, + 361, + 287, + 386 + ], + "type": "text", + "content": " is calculated from the input point clouds." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 386, + 287, + 445 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 386, + 287, + 445 + ], + "spans": [ + { + "bbox": [ + 46, + 386, + 287, + 445 + ], + "type": "text", + "content": "We emphasize that the lightweight network is randomly initialized and optimized at runtime efficiently for reconstruction. As illustrated in Figure 5, the global optimization greatly improves the prediction results and further enhances the fidelity of the generated LiDAR point cloud." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 47, + 451, + 133, + 464 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 451, + 133, + 464 + ], + "spans": [ + { + "bbox": [ + 47, + 451, + 133, + 464 + ], + "type": "text", + "content": "3.6. Optimization" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 469, + 287, + 517 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 469, + 287, + 517 + ], + "spans": [ + { + "bbox": [ + 46, + 469, + 287, + 517 + ], + "type": "text", + "content": "For the optimization of LiDAR4D, the total reconstruction loss is the weighted combination of the depth loss, intensity loss, ray-drop loss, flow loss and refinement loss, which can be formalized as follows:" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 101, + 526, + 287, + 552 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 101, + 526, + 287, + 552 + ], + "spans": [ + { + "bbox": [ + 101, + 526, + 287, + 552 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {d e p t h}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {D} (\\mathbf {r}) - D (\\mathbf {r}) \\right\\| _ {1} \\tag {14}", + "image_path": "ca26590000d18f5fd248c374cfb45470f4a99ff4b6f12662da814f6d71dd3b12.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 100, + 553, + 287, + 578 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 100, + 553, + 287, + 578 + ], + "spans": [ + { + "bbox": [ + 100, + 553, + 287, + 578 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {i n t e n s i t y}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {I} (\\mathbf {r}) - I (\\mathbf {r}) \\right\\| _ {2} ^ {2} \\tag {15}", + "image_path": "d2e334cb371b00f28edf221572c771315de493d26430a9a1a30306db6f99e420.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 100, + 580, + 287, + 605 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 100, + 580, + 287, + 605 + ], + "spans": [ + { + "bbox": [ + 100, + 580, + 287, + 605 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {r a y d r o p}} = \\sum_ {\\mathbf {r} \\in R} \\left\\| \\hat {P} (\\mathbf {r}) - P (\\mathbf {r}) \\right\\| _ {2} ^ {2} \\tag {16}", + "image_path": "ce1e7a84f5bf112e6085fa36f68f3dace3ad32af8b0743871fdd54671bb855b6.jpg" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 69, + 610, + 287, + 639 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 69, + 610, + 287, + 639 + ], + "spans": [ + { + "bbox": [ + 69, + 610, + 287, + 639 + ], + "type": "interline_equation", + "content": "\\begin{array}{l} \\mathcal {L} = \\lambda_ {\\alpha} \\mathcal {L} _ {\\text {d e p t h}} + \\lambda_ {\\beta} \\mathcal {L} _ {\\text {i n t e n s i t y}} + \\lambda_ {\\gamma} \\mathcal {L} _ {\\text {r a y d r o p}} \\tag {17} \\\\ + \\lambda_ {\\eta} \\mathcal {L} _ {\\text {f l o w}} + \\lambda_ {\\mathrm {r}} \\mathcal {L} _ {\\text {r e f i n e}} \\\\ \\end{array}", + "image_path": "72853e4f566072829d217f5616b5eefaebbb8465f15eda3d8e11c2aabf27111a.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 47, + 651, + 128, + 664 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 651, + 128, + 664 + ], + "spans": [ + { + "bbox": [ + 47, + 651, + 128, + 664 + ], + "type": "text", + "content": "4. Experiments" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 47, + 671, + 164, + 684 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 671, + 164, + 684 + ], + "spans": [ + { + "bbox": [ + 47, + 671, + 164, + 684 + ], + "type": "text", + "content": "4.1. Experimental Setup" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "type": "text", + "content": "Datasets. We conducted comprehensive experiments on the public autonomous driving datasets KITTI-360 [23] and" + } + ] + } + ], + "index": 14 + }, + { + "type": "image", + "bbox": [ + 309, + 360, + 386, + 498 + ], + "blocks": [ + { + "bbox": [ + 309, + 360, + 386, + 498 + ], + "lines": [ + { + "bbox": [ + 309, + 360, + 386, + 498 + ], + "spans": [ + { + "bbox": [ + 309, + 360, + 386, + 498 + ], + "type": "image", + "image_path": "c99d767231491fefa5f54bcb2461bf5f31b0504e3f9527469df61e34feaa5f94.jpg" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 506, + 545, + 562 + ], + "lines": [ + { + "bbox": [ + 305, + 506, + 545, + 562 + ], + "spans": [ + { + "bbox": [ + 305, + 506, + 545, + 562 + ], + "type": "text", + "content": "Figure 6. Qualitative novel view LiDAR point cloud synthesis results on KITTI-360 dataset. As highlighted in the red bounding box, LiDAR-NeRF fails to reconstruct the dynamic vehicles. In contrast, LiDAR4D generates more accurate geometry for moving cars, even in sparse point clouds far away." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_caption" + } + ], + "index": 15 + }, + { + "type": "image", + "bbox": [ + 386, + 360, + 463, + 498 + ], + "blocks": [ + { + "bbox": [ + 386, + 360, + 463, + 498 + ], + "lines": [ + { + "bbox": [ + 386, + 360, + 463, + 498 + ], + "spans": [ + { + "bbox": [ + 386, + 360, + 463, + 498 + ], + "type": "image", + "image_path": "85333eccd1b1e4139758598bea2f1c50cdace5e302e950095f8fb7157c80ee18.jpg" + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_body" + } + ], + "index": 16 + }, + { + "type": "image", + "bbox": [ + 465, + 360, + 544, + 498 + ], + "blocks": [ + { + "bbox": [ + 465, + 360, + 544, + 498 + ], + "lines": [ + { + "bbox": [ + 465, + 360, + 544, + 498 + ], + "spans": [ + { + "bbox": [ + 465, + 360, + 544, + 498 + ], + "type": "image", + "image_path": "dbb7753a95a08274b165f6d99413a7ef8ccf5ba452f26d69d23c680178569877.jpg" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_body" + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": "NuScenes [3], from which we collected multiple dynamic point cloud sequences containing largely moving vehicles. KITTI-360 is equipped with a LIDAR of 64-beam, a 26.4-degree vertical FOV, and an acquisition frequency of " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "10\\mathrm{Hz}" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": ". We selected 51 consecutive frames as a single scene and held out 4 samples at a 10-frame interval for NVS evaluation. Meanwhile, Nuscenes' LiDAR has 32 beams, a 40-degree vertical FOV, and a " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "20\\mathrm{-Hz}" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " acquisition frequency. To cover a larger range of reconstruction, i.e., spanning " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "100\\sim 200" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": " meters, we still selected samples at a frequency of " + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "inline_equation", + "content": "10\\mathrm{Hz}" + }, + { + "bbox": [ + 304, + 582, + 545, + 713 + ], + "type": "text", + "content": ", which is consistent with the KITTI-360." + } + ] + } + ], + "index": 19 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5150" + } + ] + } + ], + "index": 20 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 78, + 69, + 522, + 293 + ], + "blocks": [ + { + "bbox": [ + 78, + 69, + 522, + 293 + ], + "lines": [ + { + "bbox": [ + 78, + 69, + 522, + 293 + ], + "spans": [ + { + "bbox": [ + 78, + 69, + 522, + 293 + ], + "type": "image", + "image_path": "f8e21f279796e3b9888574ac02aed694403cbb4286ab61ba33494dadf4ce4ba8.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 136, + 304, + 457, + 316 + ], + "lines": [ + { + "bbox": [ + 136, + 304, + 457, + 316 + ], + "spans": [ + { + "bbox": [ + 136, + 304, + 457, + 316 + ], + "type": "text", + "content": "Figure 7. Qualitative comparison for LiDAR intensity reconstruction and synthesis." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 78, + 331, + 522, + 555 + ], + "blocks": [ + { + "bbox": [ + 78, + 331, + 522, + 555 + ], + "lines": [ + { + "bbox": [ + 78, + 331, + 522, + 555 + ], + "spans": [ + { + "bbox": [ + 78, + 331, + 522, + 555 + ], + "type": "image", + "image_path": "52d028571a52e0c979fe120ed55907e681d6293c1e9070b5afc380e2bb626742.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 141, + 567, + 451, + 578 + ], + "lines": [ + { + "bbox": [ + 141, + 567, + 451, + 578 + ], + "spans": [ + { + "bbox": [ + 141, + 567, + 451, + 578 + ], + "type": "text", + "content": "Figure 8. Qualitative comparison for LiDAR depth reconstruction and synthesis." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 604, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 604, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 604, + 289, + 713 + ], + "type": "text", + "content": "Baselines. We present a comprehensive comparison of LiDAR4D with different types of baselines, encompassing explicit and implicit reconstruction approaches as well as dynamic NeRFs. We reproduce the mesh-based reconstruction method LiDARsim [25] and also replace the surface reconstruction model with the state-of-the-art method NKSR [15] for convincing. It's noted that we employ U-Net trained from original point clouds to further predict ray-drop for these two methods. Meanwhile, PCGen [19] reconstructs" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 604, + 545, + 676 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 604, + 545, + 676 + ], + "spans": [ + { + "bbox": [ + 304, + 604, + 545, + 676 + ], + "type": "text", + "content": "directly based on the point clouds and predicts ray-drop with the MLP. LiDAR-NeRF [39] is our primary comparison, and we directly adopt the official implements. In addition, we migrate dynamic neural radiance field methods such as D-NeRF [32], K-Planes [12], and TiNeuVox [9] to LiDAR NVS pipeline for a thorough comparison." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 677, + 546, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 546, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 546, + 715 + ], + "type": "text", + "content": "Metrics. We offer multi-faceted metrics for evaluation. Chamfer Distance [8] measures the 3D geometric error between the generated and the ground-truth point clouds by" + } + ] + } + ], + "index": 6 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 314, + 757 + ], + "type": "text", + "content": "5151" + } + ] + } + ], + "index": 7 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 52, + 70, + 547, + 153 + ], + "blocks": [ + { + "bbox": [ + 52, + 70, + 547, + 153 + ], + "lines": [ + { + "bbox": [ + 52, + 70, + 547, + 153 + ], + "spans": [ + { + "bbox": [ + 52, + 70, + 547, + 153 + ], + "type": "table", + "html": "
MethodTypePoint CloudDepthIntensity
CD↓F-score↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑RMSE↓MedAE↓LPIPS↓SSIM↑PSNR↑
LiDARsim [25]E./S./M.2.22490.86676.54700.07590.22890.715721.77460.15320.05060.25020.447916.3045
NKSR [15]E./S./M.0.57800.86854.66470.06980.22950.705222.53900.15650.05360.24290.420016.1159
PCGen [19]E./S.0.20900.85974.88380.17850.52100.506224.30500.20050.08180.61000.124813.9606
LiDAR-NeRF [39]I./S.0.09230.92263.68010.06670.35230.604326.76630.15570.05490.42120.276816.1683
LiDAR4D (Ours)I./D.0.08940.92643.23700.05070.13130.721827.88400.13430.04040.21270.469817.4529
", + "image_path": "fa92a009dd5f74e57279792f35d4a508f1d33f7ac555bfe8dc1714207677156c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_body" + } + ], + "index": 0 + }, + { + "bbox": [ + 59, + 160, + 533, + 172 + ], + "lines": [ + { + "bbox": [ + 59, + 160, + 533, + 172 + ], + "spans": [ + { + "bbox": [ + 59, + 160, + 533, + 172 + ], + "type": "text", + "content": "Table 3. Quantitative comparison on KITTI-360 Static Scene Sequence. We bold the best results and underline the second-best." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 194, + 288, + 277 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 194, + 288, + 277 + ], + "spans": [ + { + "bbox": [ + 46, + 194, + 288, + 277 + ], + "type": "text", + "content": "nearest neighbor, and we also report the F-score value with an error threshold of " + }, + { + "bbox": [ + 46, + 194, + 288, + 277 + ], + "type": "inline_equation", + "content": "5\\mathrm{cm}" + }, + { + "bbox": [ + 46, + 194, + 288, + 277 + ], + "type": "text", + "content": ". In addition, we introduce Root Mean Square Error (RMSE) and Median Absolute Error (MedAE) to calculate the pixel-by-pixel error of the projected range images, as well as LPIPS [45], SSIM [41] and PSNR to measure the overall variance. We evaluate both the depth and intensity reconstruction results." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 285, + 180, + 298 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 285, + 180, + 298 + ], + "spans": [ + { + "bbox": [ + 47, + 285, + 180, + 298 + ], + "type": "text", + "content": "4.2. Implementation Details" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 304, + 288, + 460 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 304, + 288, + 460 + ], + "spans": [ + { + "bbox": [ + 46, + 304, + 288, + 460 + ], + "type": "text", + "content": "Consistent with LiDAR-NeRF [39], the entire point cloud scene is scaled within the unit cube space. And we uniformly sampled 768 points along each laser. The optimization of LiDAR4D is implemented on Pytorch [31] with Adam [17] optimizer. The maximum iteration is set to " + }, + { + "bbox": [ + 46, + 304, + 288, + 460 + ], + "type": "inline_equation", + "content": "30\\mathrm{k}" + }, + { + "bbox": [ + 46, + 304, + 288, + 460 + ], + "type": "text", + "content": " for each scene, with a batch size of 1024 rays, followed by the fast ray-drop refinement with 300 epochs. We construct multi-planar representations following K-Planes [12] and hash grids built on tiny-cuda-nn [27]. The multi-level features of planes and hash grids are concatenated before feeding into MLPs. All experiments were conducted on a single NVIDIA GeForce RTX 4090 GPU. For more implementation details, please refer to Supplementary Material." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 467, + 272, + 480 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 467, + 272, + 480 + ], + "spans": [ + { + "bbox": [ + 47, + 467, + 272, + 480 + ], + "type": "text", + "content": "4.3. Evaluation of Novel-View LiDAR Synthesis" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 486, + 287, + 689 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 486, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 46, + 486, + 287, + 689 + ], + "type": "text", + "content": "Results on KITTI-360 dataset. The quantitative comparison on KITTI-360 dataset is displayed in Table 1. Our proposed LiDAR4D exhibits remarkable performance across all metrics in comparison to prior SOTA methods, demonstrating its superiority in dynamic reconstruction. In comparison to LiDAR-NeRF, our approach has led to a " + }, + { + "bbox": [ + 46, + 486, + 287, + 689 + ], + "type": "inline_equation", + "content": "24.3\\%" + }, + { + "bbox": [ + 46, + 486, + 287, + 689 + ], + "type": "text", + "content": " reduction in the CD error of the novel-view point cloud synthesis. As illustrated in Figure 6, LiDAR4D achieves accurate reconstruction of every dynamic vehicle, whereas LiDAR-NeRF encounters failure. As shown in Figures 7 and 8, the resolution limitation causes blurring and oversmooth results of dynamic NeRFs such as TiNeuVox and K-Planes. This demonstrates again the effectiveness of our designed hybrid representation for large-scale scenes. Additionally, we follow the setting in LiDAR-NeRF to repeat experiments in static scenarios, and Table 3 verifies that there is no performance degradation in LiDAR4D." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 689, + 287, + 715 + ], + "type": "text", + "content": "Results on NuScenes dataset. To further validate the generalizability of LiDAR4D, we conducted the same experi" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 194, + 547, + 301 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 194, + 547, + 301 + ], + "spans": [ + { + "bbox": [ + 304, + 194, + 547, + 301 + ], + "type": "text", + "content": "ment on NuScenes. As illustrated in Table 2, our method still achieves the best reconstruction quality even with a completely different LiDAR configuration. Ultimately, our method still excels in the reconstruction of depth and intensity, as evidenced by the " + }, + { + "bbox": [ + 304, + 194, + 547, + 301 + ], + "type": "inline_equation", + "content": "24.2\\%" + }, + { + "bbox": [ + 304, + 194, + 547, + 301 + ], + "type": "text", + "content": " reduction in CD error to LiDAR-NeRF. Please refer to Supplementary Material for more quantitative and qualitative experimental results on KITTI-360 and NuScenes datasets, as well as the ablation study and further applications." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 309, + 382, + 322 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 309, + 382, + 322 + ], + "spans": [ + { + "bbox": [ + 306, + 309, + 382, + 322 + ], + "type": "text", + "content": "5. Limitations" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 330, + 547, + 450 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 330, + 547, + 450 + ], + "spans": [ + { + "bbox": [ + 304, + 330, + 547, + 450 + ], + "type": "text", + "content": "Despite the fact that LiDAR4D has exhibited exceptional performance in a substantial number of experiments, the long-distance vehicle motion and occlusion problem of point clouds remain open questions. There is still a significant gap in the reconstruction of dynamic objects compared to static ones. In addition, foreground and background may be difficult to separate well. Furthermore, based on real-world datasets, quantitative evaluation of NVS is limited within the ego-car trajectory and does not allow for the decoupling of novel spatial and temporal view synthesis." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 461, + 379, + 474 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 461, + 379, + 474 + ], + "spans": [ + { + "bbox": [ + 306, + 461, + 379, + 474 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 481, + 547, + 625 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 481, + 547, + 625 + ], + "spans": [ + { + "bbox": [ + 304, + 481, + 547, + 625 + ], + "type": "text", + "content": "In this paper, we revisit the limitations of existing LiDAR NVS methods and propose a novel framework to address three major challenges, namely dynamic reconstruction, large-scale scene characterization, and realistic synthesis. Our proposed method LiDAR4D proves its superiority under extensive experiments, achieving geometry-aware and time-consistent reconstruction of large-scale dynamic point cloud scenes and generating novel space-time view LiDAR point clouds closer to the real distribution. We believe that more future work will focus on combining LiDAR point clouds with neural radiance fields and explore more possibilities for dynamic scene reconstruction and synthesis." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 630, + 547, + 715 + ], + "type": "text", + "content": "Acknowledgment. This work is supported by the National Natural Science Foundation of China (No.62372329), in part by the National Key Research and Development Program of China (No.2021YFB2501104), in part by Shanghai Rising Star Program (No.21QC1400900), in part by Tongji-Qomolo Autonomous Driving Commercial Vehicle Joint Lab Project, and in part by Xiaomi Young Talents Program." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 316, + 757 + ], + "type": "text", + "content": "5152" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 106, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 713 + ], + "type": "list", + "angle": 0, + "index": 13, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 156 + ], + "type": "text", + "content": "[1] Jonathan T Barron, Ben Mildenhall, Matthew Tancik, Peter Hedman, Ricardo Martin-Brualla, and Pratul P Srinivasan. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 909-918, 2023. 5" + } + ] + } + ], + "index": 23 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "spans": [ + { + "bbox": [ + 295, + 748, + 315, + 757 + ], + "type": "text", + "content": "5154" + } + ] + } + ], + "index": 25 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/LiSA_ LiDAR Localization with Semantic Awareness/a6e01367-c5ea-4fd3-9c99-a8b4204b195f_content_list.json b/2024/LiSA_ LiDAR Localization with Semantic Awareness/a6e01367-c5ea-4fd3-9c99-a8b4204b195f_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..5cddb61a89c1857227e102278b1ba1406d0e47ec --- /dev/null +++ b/2024/LiSA_ LiDAR Localization with Semantic Awareness/a6e01367-c5ea-4fd3-9c99-a8b4204b195f_content_list.json @@ -0,0 +1,1773 @@ +[ + { + "type": "text", + "text": "LiSA: LiDAR Localization with Semantic Awareness", + "text_level": 1, + "bbox": [ + 217, + 130, + 751, + 150 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Bochun Yang $^{1*}$ Zijun Li $^{1*}$ Wen Li $^{1}$ Zhipeng Cai $^{2\\dagger}$", + "bbox": [ + 267, + 179, + 709, + 198 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Chenglu Wen1 Yu Zang1 Matthias Müller2 Cheng Wang1†", + "bbox": [ + 233, + 198, + 745, + 217 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Fujian Key Laboratory of Sensing and Computing for Smart Cities, Xiamen University 2 Intel Labs", + "bbox": [ + 88, + 215, + 883, + 234 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 268, + 313, + 284 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "LiDAR localization is a fundamental task in robotics and computer vision, which estimates the pose of a LiDAR point cloud within a global map. Scene Coordinate Regression (SCR) has demonstrated state-of-the-art performance in this task. In SCR, a scene is represented as a neural network, which outputs the world coordinates for each point in the input point cloud. However, SCR treats all points equally during localization, ignoring the fact that not all objects are beneficial for localization. For example, dynamic objects and repeating structures often negatively impact SCR. To address this problem, we introduce LiSA, the first method that incorporates semantic awareness into SCR to boost the localization robustness and accuracy. To avoid extra computation or network parameters during inference, we distill the knowledge from a segmentation model to the original SCR network. Experiments show the superior performance of LiSA on standard LiDAR localization benchmarks compared to state-of-the-art methods. Applying knowledge distillation not only preserves high efficiency but also achieves higher localization accuracy than introducing extra semantic segmentation modules. We also analyze the benefit of semantic information for LiDAR localization. Our code is released at https://github.com/Ybchun/LiSA.", + "bbox": [ + 75, + 300, + 473, + 662 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 690, + 209, + 705 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "LiDAR localization estimates the pose of a LiDAR point cloud in a global scene map, which is a fundamental task in computer vision and robotics.", + "bbox": [ + 75, + 715, + 468, + 760 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Learning-based regression methods [3-5, 19, 23, 36, 45] have shown state-of-the-art performance in LiDAR localization, where they memorize the specific scene in a neural network. Based on their regression objectives, these methods can be divided into Absolute Pose Regression (APR) and Scene Coordinates Regression (SCR). APR [5, 19, 36, 45] directly regresses the sensor pose. Despite", + "bbox": [ + 75, + 761, + 468, + 867 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/4549b39663d14eff43a059370cea4aecfdfe39ba139e1544c6241e11e343ca8b.jpg", + "image_caption": [ + "Figure 1. Teaser. This work studies the problem of LiDAR localization. We propose a novel method LiSA, which equips Li-DAR localization methods with semantic awareness. We show the ground-truth and predicted trajectories on Oxford (left) and NCLT (right). Compared to the baseline method (SGLoc), LiSA achieves a much higher average localization accuracy and has much fewer catastrophic failures, without introducing extra computation or network parameters during inference." + ], + "image_footnote": [], + "bbox": [ + 501, + 267, + 697, + 428 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/eb566751a42c2ee64ecc8e71c816664c00aa39cf77aba51625604180f5b55770.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 268, + 890, + 426 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "the compact architectures, direct pose regression without explicitly utilizing the geometric information limits the accuracy of APR. Unlike APR, SCR [3, 4, 23] regresses the coordinate of each point in the global map, which provides correspondences between the input and the global point clouds. Then RANSAC [10] is applied to the correspondences to estimate the final pose. Utilizing the geometric information more explicitly allows SCR to more effectively embed and understand the scene geometry in its model parameters, resulting in higher accuracy and better robustness.", + "bbox": [ + 496, + 566, + 890, + 717 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "SCR treats all points of the input equally. This is non-ideal for the task of localization – objects that are dynamic (e.g., pedestrians and vehicles) or repetitive (e.g., road surface and trees) intuitively should be less important than salient and static objects. Motivated by this observation, we propose LiSA, a novel method that equips SCR with semantic awareness. LiSA can robustly handle distracting objects and significantly improves the localization accuracy. To avoid introducing extra computation or network parameters during inference, we apply diffusion-based knowledge distillation during training so that we can enable semantic understanding of the original SCR network by extracting", + "bbox": [ + 496, + 719, + 892, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 44 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "*Equal contribution.", + "bbox": [ + 94, + 875, + 207, + 887 + ], + "page_idx": 0 + }, + { + "type": "page_footnote", + "text": "† Corresponding author.", + "bbox": [ + 96, + 887, + 220, + 898 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "15271", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "knowledge from a teacher segmentation model, which is dropped after training. To the best of our knowledge, LiSA is the first method that effectively utilizes semantic context for LiDAR localization.", + "bbox": [ + 75, + 90, + 468, + 150 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In our experiments, LiSA shows superior performance on standard LiDAR localization benchmarks compared to state-of-the-art methods. Without introducing extra computation or network parameters during inference, it achieves a relative improvement of more than $38\\%$ and $29\\%$ in position and orientation on the QEOxford dataset and $17\\%$ and $34\\%$ on the NCLT dataset (see Fig. 1 for an example).", + "bbox": [ + 75, + 152, + 468, + 258 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 275, + 218, + 290 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Conventional localization. Conventional re-localization methods can be broadly categorized into 1) retrieval-based [1, 42, 43, 51] and 2) matching-based [32, 33, 38] approaches. The former searches for frames most similar to the query frame in a pre-constructed global descriptor database, while the latter employs SfM tools to build a sparse 3D point cloud of the scene and matches features to find correspondences between the query frame and the point cloud. These methods require pre-stored map information, making them time-consuming and labor-intensive.", + "bbox": [ + 75, + 305, + 467, + 455 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Regression-based localization. Due to the advancement of deep learning, regression-based localization methods have received much attention recently. Regression-based methods can be further separated into two categories: 1) Absolute Pose Regression (APR) and 2) Scene Coordinate Regression (SCR). APR directly regresses the 6-DoF pose of the sensor (e.g., a camera or a LiDAR scanner). PoseNet[19] and several variants [5, 18, 24, 36, 44, 45] adopt a pipeline that includes only a feature extractor and an MLP to directly output the camera pose in an end-to-end manner. However, Sattler et al.[34] pointed out that APR methods are similar to retrieval-based methods, which only learn the mapping relationship between high-dimensional abstract feature vectors and poses rather than the scene information. To alleviate this issue, SCR [3, 4] estimates the sensor pose in a different way: the neural network predicts the 3D coordinates of each pixel/3D point in the world coordinate system, which embeds the scene information more explicitly and effectively. Then, candidate correspondences are constructed using the local coordinate and the predicted world coordinate of each point. These correspondences are finally used in RANSAC [10] to obtain the sensor pose.", + "bbox": [ + 75, + 460, + 467, + 792 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In recent years, the widespread use of LiDAR stimulated several works for regression-based LiDAR localization. LiDAR APR methods, such as PointLoc[47], PosePN++[54], and HypLiLoc[46], and the SCR method SGLoc[22], have shown impressive performance on large-scale outdoor localization. Compared to the images, point clouds exhibit robustness to changes in lighting conditions and inherently", + "bbox": [ + 75, + 795, + 467, + 900 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "carry depth information. In this work, we show that SCR methods have not fully utilized the semantic information of the scene. We introduce a novel method with semantic awareness during localization, which significantly improves the performance without introducing extra computation or network parameters during inference.", + "bbox": [ + 496, + 90, + 890, + 181 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Localization using auxiliary information. Semantic information has been demonstrated to be important in conventional non-regression-based methods. Retrieval-based approaches [27, 35, 37] employ semantic information to enhance the robustness of the descriptors or serve it as the posterior information to refine the predicted pose. Several matching-based methods [9, 41], attach semantic labels to the point features during matching. This modification helps mitigate the risk of erroneous matching and significantly increases their localization accuracy.", + "bbox": [ + 496, + 186, + 890, + 335 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Object detection has been applied to regression-based methods. For instance, AD-PoseNet[17] utilizes Mask R-CNN[12] to minimize the impact of dynamic foreground objects on scene understanding. ORGPoseNet[30] uses graph neural networks to learn the geometric position relationships of objects in the scene and gain more precise localization results. However, object detection tends to concentrate solely on foreground objects rather than the whole observation in the frame. On the contrary, semantic segmentation contains exhaustive scene geometry information and intricate details. This inspires us to explore the incorporation of semantic information to enhance the accuracy of regression-based LiDAR localization.", + "bbox": [ + 496, + 338, + 890, + 534 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "LiDAR-based semantic segmentation. LiDAR-based semantic segmentation [20, 39] aims to assign a semantic label to each point in the input LiDAR scan. Methods can generally be divided into several categories: point-based [15, 28, 29, 40], voxel-based [11, 55], projection-based [21, 25, 50], and their combination [39, 52]. Regardless of the specifics of the network architecture, they consistently expand the perception field by merging the individual point features with the coarse-grain features in the scene. In this way, the semantic segmentation networks can better understand the scene information and the characteristics of each point. In this paper, we apply a point cloud semantic segmentation model as the teacher to distill semantic knowledge to a LiDAR localization method, which effectively improves localization accuracy.", + "bbox": [ + 496, + 539, + 890, + 766 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "3. Method", + "text_level": 1, + "bbox": [ + 500, + 782, + 589, + 797 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "LiSA relies on scene coordinate regression (SCR) for LiDAR localization [22]. The input of SCR is a query point cloud $\\mathcal{P} = \\{\\mathbf{p}_i\\}_{i=1}^N$ where $\\mathbf{p}_i \\in \\mathbb{R}^3$ represents a 3D point in the local coordinate frame with the LiDAR scanner at the origin. The output of SCR is a set of coordinates $\\mathcal{P}' = \\{\\mathbf{p}_{i'}'\\}_{i'=1}^{N'}$ representing the location of the down-", + "bbox": [ + 496, + 809, + 890, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "15272", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 1 + }, + { + "type": "image", + "img_path": "images/b3fc5795239b36bd7858c4bf3a06eaa70e6581b1c9017b5fa9414c51b0d41a2d.jpg", + "image_caption": [ + "Figure 2. The pipeline of LiSA. It consists of three modules: scene coordinate regression, semantic segmentation (frozen), and knowledge distillation. In the scene coordinate regression module, the coordinate regression head in the regressor directly outputs scene coordinates $\\mathcal{P}'$ , and the semantic feature regression head learns semantic segmentation features ( $\\mathbf{F}_{\\mathrm{stu}}$ ) from the knowledge distillation module and the semantic segmentation module. After distilling the semantic knowledge during training, both semantic segmentation and knowledge distillation modules are discarded, which ensures that no extra computation and network parameters are introduced during inference." + ], + "image_footnote": [], + "bbox": [ + 78, + 85, + 898, + 345 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "sampled points in world coordinates. (SCR down-samples the input to $N' = \\frac{N}{8}$ points, i.e., by a factor of 8.) The world coordinate $\\mathbf{p}_{i'}'$ represents the corresponding location of $\\mathbf{p}_{i'}$ in the global point cloud $\\mathcal{P}^*$ , which covers the complete scene of interest and is used during training.", + "bbox": [ + 75, + 441, + 468, + 516 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "SCR trains one model for each scene. The training loss is typically as follows:", + "bbox": [ + 76, + 517, + 468, + 547 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {l o c} = \\frac {\\sum_ {i = 1} ^ {N ^ {\\prime}} \\left| \\mathbf {p} _ {i ^ {\\prime}} ^ {\\prime} - \\mathbf {p} _ {i ^ {\\prime}} ^ {*} \\right|}{N ^ {\\prime}}, \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 184, + 555, + 468, + 589 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathbf{p}_{i'}'$ and $\\mathbf{p}_{i'}^*$ are respectively the predicted and ground-truth world coordinates, $|\\cdot|$ is the L1 loss.", + "bbox": [ + 75, + 597, + 468, + 626 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "To obtain the relative pose of $\\mathcal{P}$ w.r.t. $\\mathcal{P}^*$ for the final localization, RANSAC is performed on the candidate correspondences constructed by $\\mathcal{P}$ and the predicted world coordinates $\\mathcal{P}'$ .", + "bbox": [ + 75, + 627, + 468, + 686 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.1. Motivation", + "text_level": 1, + "bbox": [ + 76, + 696, + 199, + 710 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "The key idea of LiSA is to utilize semantic information to assist with localization. To motivate the importance of semantic information, we conduct a preliminary analysis where we filter out points belonging to specific classes in SCR, i.e., the filtered points do not participate in inference and training. Instead of using the ground-truth semantic labels which are unavailable in practical applications, we use labels predicted by a pre-trained state-of-the-art 3D semantic segmentation model [20].", + "bbox": [ + 75, + 719, + 468, + 854 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Tab. 1 shows the localization accuracy with different semantic categories on the QEOxford dataset [22]. It is clear to see that the localization performance varies significantly", + "bbox": [ + 75, + 854, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "table", + "img_path": "images/73769226a3a6ecebabbc1f67061a0d403c058d217e2ee6493ed11640af82dfbb.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
FilterMean Error (m/°)FilterMean Error (m/°)
all (no filter)1.79m, 1.41°all (no filter)1.79m, 1.41°
no plant1.20m, 1.97°plant only59.08m, 13.25°
no building1.39m, 2.26°building only1.63m, 1.91°
no sidewalk1.77m, 1.45°sidewalk only2.47m, 5.92°
no road2.03m, 3.42°road only1.71m, 2.59°
no transportation2.07m, 3.42°transportation only20.10m, 21.95°
", + "bbox": [ + 503, + 438, + 890, + 531 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Table 1. Impact of semantic information on LiDAR localization. Filtering out objects from different classes can significantly reduce or increase the position error. However, the noise in the semantic labels makes it hard to consistently improve both rotation and translation accuracy with point filtering, which motivates the design of LiSA.", + "bbox": [ + 496, + 541, + 893, + 625 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "with different filtering strategies, e.g., without plants the position error reduces significantly. This result shows the importance of semantic information in SCR. However, due to noise in the predicted labels and the hard threshold, naive filtering does not fully utilize the semantic information – some filters improve the position accuracy while sacrificing the orientation accuracy. Moreover, segmentation models introduce significant overhead in terms of memory and computing during inference, which may be prohibitive for many practical applications. This motivates us to design LiSA, a novel framework that effectively and efficiently incorporates semantic information into SCR.", + "bbox": [ + 496, + 638, + 893, + 821 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3.2.LiSA", + "text_level": 1, + "bbox": [ + 500, + 830, + 576, + 845 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "As shown in Fig. 2, LiSA can be divided into three modules, namely scene coordinate regression (SCR), semantic segmentation, and knowledge distillation. During training, the", + "bbox": [ + 496, + 854, + 893, + 901 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "15273", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "semantic segmentation module and the knowledge distillation module are used to transfer semantic knowledge into the SCR module. After training, only the SCR module is maintained, which can effectively utilize the transferred semantic knowledge for localization, without introducing extra computation or network parameters.", + "bbox": [ + 75, + 90, + 467, + 181 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The SCR module mostly follows the architecture of SGLoc [22], which contains a multi-scale feature extractor and a regressor. To enable semantic awareness without extra computation, we add a new branch to the regressor, which is used to regress a per-point semantic feature $\\mathbf{F}_{\\mathrm{stu}} \\in \\mathbb{R}^{N' \\times d}$ , where $N'$ is the number of output points which is equivalent to the number of output world coordinates $\\mathcal{P}'$ , and $d$ is the feature dimension. The original coordinate regressor branch outputs the world coordinates $\\mathcal{P}'$ and is supervised by the loss in Eq. (1). The semantic regressor branch is supervised by distilling knowledge from the semantic segmentation model.", + "bbox": [ + 75, + 181, + 468, + 361 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The semantic segmentation module consists of a pretrained 3D semantic segmentation model with frozen network parameters during training. We take the per-point last layer feature $\\mathbf{F}_{\\mathrm{seg}} \\in \\mathbb{R}^{N \\times d}$ of the segmentation model, down-sample it into $\\mathbf{F}_{\\mathrm{tea}} \\in \\mathbb{R}^{N' \\times d}$ so that $\\mathbf{F}_{\\mathrm{tea}}$ has the same dimension as $\\mathbf{F}_{\\mathrm{stu}}$ . To verify the robustness of LiSA, we experiment with SphereFormer [20] and SPVNAS [39] pretrained on datasets non-overlapping with any LiDAR localization dataset. We ensure $\\mathbf{F}_{\\mathrm{tea}}$ and $\\mathbf{F}_{\\mathrm{stu}}$ have the same dimension $d$ for each feature point by adjusting the output dimension of the semantic regressor branch.", + "bbox": [ + 75, + 363, + 467, + 530 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Knowledge distillation [13] is the standard approach for reducing network parameters or transferring knowledge across different modalities, resulting in a (lightweight) student network that preserves the capabilities of the teacher network. LiSA applies knowledge distillation to transfer the semantic knowledge from the segmentation module to the SCR module. This is achieved by optimizing the following distillation loss:", + "bbox": [ + 75, + 531, + 467, + 650 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {k d} = \\delta \\left(\\mathbf {F} _ {\\mathrm {s t u}}, \\mathbf {F} _ {\\mathrm {t e a}}\\right), \\tag {2}\n$$\n", + "text_format": "latex", + "bbox": [ + 204, + 660, + 467, + 676 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\delta (\\cdot)$ measures the difference between the features from the teacher $(\\mathbf{F}_{\\mathrm{tea}})$ and the student $(\\mathbf{F}_{\\mathrm{stu}})$ . Intuitively, the distillation process encourages the semantic feature $\\mathbf{F}_{\\mathrm{stu}}$ from SCR to be similar to $\\mathbf{F}_{\\mathrm{tea}}$ , which requires the SCR module to be able to distinguish different semantic classes. The final loss function of the entire network is:", + "bbox": [ + 75, + 685, + 467, + 773 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {l o c} + \\mathcal {L} _ {k d}. \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 214, + 785, + 467, + 800 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Various knowledge distillation methods can be applied to realize $\\mathcal{L}_{kd}$ . LiSA applies the recent diffusion-based distillation [16]. Specifically, we train a diffusion model with the teacher feature $\\mathbf{F}_{\\mathrm{tea}}$ by gradually adding noise to $\\mathbf{F}_{\\mathrm{tea}}$ and let the diffusion model learn to predict the noise. Following the forward noise process of DDPM [14], the noisy", + "bbox": [ + 75, + 809, + 467, + 900 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "teacher feature $\\mathbf{F}_{\\mathrm{tea}}^{(t)}$ at time step $t$ can be obtained by:", + "bbox": [ + 498, + 89, + 852, + 107 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {F} _ {\\mathrm {t e a}} ^ {(t)} = \\sqrt {\\bar {\\alpha} ^ {(t)}} \\mathbf {F} _ {\\mathrm {t e a}} + \\sqrt {1 - \\bar {\\alpha} ^ {(t)}} \\boldsymbol {\\epsilon} ^ {(t)}, \\boldsymbol {\\epsilon} ^ {(t)} \\sim \\mathcal {N} (\\mathbf {0}, \\mathbf {I}). \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 511, + 117, + 890, + 138 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The loss for training the diffusion model is", + "bbox": [ + 517, + 148, + 803, + 162 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {d d p m} = \\left| \\left| \\sigma \\left(\\mathbf {F} _ {\\mathrm {t e a}} ^ {(t)}, t\\right) - \\boldsymbol {\\epsilon} ^ {(t)} \\right| \\right| _ {2}, \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 591, + 175, + 890, + 194 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\sigma (\\mathbf{F}_{\\mathrm{tea}}^{(t)},t)$ represents the predicted noise from the diffusion model given the time step $t$ and the noisy feature input $\\mathbf{F}_{\\mathrm{tea}}^{(t)},\\epsilon^{(t)}$ represents the ground-truth noise.", + "bbox": [ + 496, + 207, + 890, + 255 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "To enable the knowledge transfer between $\\mathbf{F}_{\\mathrm{stu}}$ and $\\mathbf{F}_{\\mathrm{tea}}$ , we consider $\\mathbf{F}_{\\mathrm{stu}}$ as the noisy version of $\\mathbf{F}_{\\mathrm{tea}}$ , and use the diffusion model to obtain a denoised version $\\mathbf{F}_{\\mathrm{stu}}^{\\prime}$ of $\\mathbf{F}_{\\mathrm{stu}}$ . Then we apply the normal knowledge distillation (L1) loss to $\\mathbf{F}_{\\mathrm{stu}}^{\\prime}$ and $\\mathbf{F}_{\\mathrm{tea}}$ :", + "bbox": [ + 496, + 256, + 890, + 332 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {k d} ^ {\\prime} = \\left| \\mathbf {F} _ {\\mathrm {s t u}} ^ {\\prime} - \\mathbf {F} _ {\\mathrm {t e a}} \\right|. \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 624, + 342, + 890, + 359 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "The final distillation loss is:", + "bbox": [ + 519, + 369, + 705, + 383 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {k d} = \\lambda_ {1} \\mathcal {L} _ {d d p m} + \\lambda_ {2} \\mathcal {L} _ {k d} ^ {\\prime}, \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 602, + 396, + 890, + 412 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "where $\\lambda_{1}$ and $\\lambda_{2}$ are hyper-parameters to balance the losses. Simply setting both $\\lambda_{1}$ and $\\lambda_{2}$ to 1 works well in practice. Note that we use the vanilla DDPM architecture instead of latent diffusion [31]. Hence, we do not have losses on autoencoders as in Sec. 3.2 of [16].", + "bbox": [ + 496, + 424, + 890, + 500 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Besides introducing no overhead to SCR (by dropping both segmentation and distillation modules after training), knowledge distillation also allows the network to more effectively utilize the imperfect output of the semantic segmentation models — we only use the semantic features to transfer the knowledge, instead of using hard filtering based on the imperfect semantic labels. Our experiments (Sec. 4.2) show that this design remarkably reduces both the position and orientation error.", + "bbox": [ + 496, + 500, + 890, + 635 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4. Experiment", + "text_level": 1, + "bbox": [ + 500, + 648, + 624, + 665 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.1. Setup", + "text_level": 1, + "bbox": [ + 500, + 672, + 581, + 690 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Baseline. We compare LiSA against different types of state-of-the-art methods: 1) For retrieval-based methods, we choose PNVLAD [43] which employs PointNet [28] and NetVLAD [1] to generate high-quality global descriptors. 2) For 3D matching-based methods, we choose DCP [48] which utilizes PointNet [28] and DGCNN [49] as embedding networks. 3) For $APR$ methods, we choose PointLoc [47], PosePN++ [54], HyLiLoc [46] and STCLoc [53]. For SCR, SGLoc [22] is the first method of this type in LiDAR localization and it is also the most competitive baseline.", + "bbox": [ + 496, + 700, + 890, + 851 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Dataset. Following [22], we perform evaluations on 3 public datasets, namely Oxford Radar RobotCar [2], QEOxford [22] and NCLT [6]. Oxford Radar RobotCar contains", + "bbox": [ + 496, + 854, + 890, + 900 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "15274", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 3 + }, + { + "type": "table", + "img_path": "images/66d1aa768c906c011a85345b7ffcd8db9595eea7e1628f23a41c0407b2aa9f10.jpg", + "table_caption": [ + "QEOxford dataset" + ], + "table_footnote": [], + "table_body": "
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
15-13-06-3710.90m, 2.49°10.61m, 2.56°10.75m, 2.36°4.54m, 1.83°5.14m, 1.27°5.03m, 1.46°1.79m, 1.67°0.94m, 1.10°
17-13-26-3914.60m, 2.46°11.44m, 2.14°11.07m, 2.21°6.44m, 1.78°6.12m, 1.21°4.31m, 1.43°1.81m, 1.76°1.17m, 1.21°
17-14-03-0011.28m, 2.21°10.90m, 2.01°11.53m, 1.92°4.89m, 1.55°5.32m, 1.08°3.61m, 1.11°1.33m, 1.59°0.84m, 1.15°
18-14-14-429.00m, 1.90°9.51m, 2.08°9.82m, 2.07°4.64m, 1.61°4.76m, 1.19°2.61m, 1.09°1.19m, 1.39°0.85m, 1.11°
Average11.45m, 2.27°10.62m, 2.20°10.79m, 2.14°5.13m, 1.69°5.34m, 1.18°3.89m, 1.27°1.53m, 1.60°0.95m, 1.14°
", + "bbox": [ + 81, + 104, + 890, + 199 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/53848adbd532478d036175437aa092bc6b39eaac1f5d1e8a51003696dfead8af.jpg", + "table_caption": [ + "Table 2. Quantitative results on QEOxford. Mean position error (m) and mean orientation error $(^{\\circ})$ for various methods are reported. Best performance is highlighted in bold, lower is better. LiSA outperforms all baseline methods in terms of both position and orientation accuracy.", + "Oxford dataset" + ], + "table_footnote": [], + "table_body": "
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
15-13-06-3718.14m, 3.28°16.04m, 4.54°12.42m, 2.26°9.59m, 1.92°6.93m, 1.48°6.88m, 1.09°3.01m, 1.91°2.36m, 1.29°
17-13-26-3924.57m, 3.08°16.22m, 3.56°13.14m, 2.50°10.66m, 1.92°7.55m, 1.23°6.79m, 1.29°4.07m, 2.07°3.47m, 1.43°
17-14-03-0019.93m, 3.13°14.87m, 3.45°12.91m, 1.92°9.01m, 1.51°7.44m, 1.24°5.82m, 0.97°3.37m, 1.89°3.19m, 1.34°
18-14-14-4215.59m, 2.63°12.97m, 3.99°11.31m, 1.98°8.44m, 1.71°6.13m, 1.15°3.45m, 0.84°2.12m, 1.66°1.95m, 1.23°
Average19.56m, 3.03°15.03m, 3.89°12.45m, 2.17°9.43m, 1.77°7.01m, 1.28°5.74m, 1.05°3.14m, 1.88°2.74m, 1.32°
", + "bbox": [ + 81, + 282, + 888, + 377 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Table 3. Quantitative results on Oxford. Mean position error (m) and mean orientation error $(^{\\circ})$ for various methods are reported; best performance is highlighted in bold, lower is better. LiSA significantly improves both the position and rotation accuracy of the baseline SGLoc. The ground-truth trajectory noise in the original Oxford dataset makes SCR perform slightly worse in terms of rotational accuracy compared to the best APR methods HypLiLoc. However, the positional accuracy is much higher.", + "bbox": [ + 75, + 387, + 892, + 444 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "32 repeated traversals along the central Oxford with diverse weather and complex traffic conditions, roughly $10km$ of the trajectory length, and a $2km^2$ range coverage. QEOxford is a quality-enhanced version of the Oxford dataset, with GPS/INS errors minimized by alignment techniques, which has been demonstrated to be beneficial for localization [22]. NCLT is an extensive collection of LiDAR data captured at the Michigan North Campus. It comprises 27 tracks, each approximately $5.5km$ long, covering an area of $0.45km^2$ . The dataset contains challenging scenarios such as dynamic objects, illumination variation, seasonal and weather changes, and long-term structural alterations due to ongoing construction projects.", + "bbox": [ + 73, + 463, + 470, + 660 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Implementation. LiSA is implemented with Pytorch [26], Spconv [8] and the Minkowski Engine [7]. We conduct our experiments on a server equipped with an Intel(R) Xeon(R) Silver 4314 CPU, 256GB of RAM, and four NVIDIA RTX 3090 GPUs. During training, we employ the Adam optimizer with an initial learning rate of 0.01, weight decay of 0.95, and batch size of 100.", + "bbox": [ + 75, + 665, + 468, + 772 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.2. Main Results", + "text_level": 1, + "bbox": [ + 76, + 785, + 215, + 800 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Results on Oxford. Tab. 2 shows the quantitative results on the quality-enhanced Oxford dataset. LiSA achieves the lowest position and orientation error at $0.95\\mathrm{m}$ and $1.14^{\\circ}$ , respectively. This result improves the previous state-of-the-art (SGLoc [22]) by $38\\%$ and $29\\%$ on position and orientation respectively without sacrificing the efficiency. In ad", + "bbox": [ + 75, + 809, + 470, + 902 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "dition, it is the first time that a sub-meter accuracy can be achieved without additional backend optimization, such as pose graph optimization (PGO) [5, 22]. LiSA achieves better results with much higher efficiency than SGLoc+PGO (38ms vs 288ms); see Appendix 3 for details. Fig. 3 shows the qualitative results on trajectory 15-13-06-37. LiSA closely aligns with the ground-truth trajectory and has significantly fewer outliers, i.e., fewer catastrophic failures. The experimental results demonstrate that semantic awareness helps LiSA to understand the scene information and obtain more accurate localization results.", + "bbox": [ + 496, + 463, + 892, + 628 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Tab. 3 reports the results on the (non-enhanced) Oxford dataset. LiSA also significantly improves over the baseline SGLoc in both position and orientation on this dataset. Although LiSA has some gaps in terms of orientation compared to the best APR method [46], it surpasses all previous methods in terms of position accuracy. We discuss this in detail in Appendix 3.", + "bbox": [ + 496, + 635, + 890, + 742 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Results on NCLT. Tab. 4 shows the quantitative result on the NCLT dataset. Though the segmentation model used to train LiSA performs much worse on NCLT than on Oxford (see Appendix 2 for visualization of segmentation results on Oxford and NCLT), LiSA still outperforms all competitors, achieving sub-meter accuracy on 3 of the 4 trajectories. Compared to the previous state-of-the-art method, SGLoc [22], there is an improvement of $17\\%$ and $34\\%$ in these metrics. This further demonstrates the robustness of our framework. Fig. 4 shows the qualitative results on trajectory", + "bbox": [ + 496, + 750, + 893, + 902 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "15275", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "image", + "img_path": "images/f25af4498912080a3a8a9426a02c164d7023ef46630f80c902bdce5a2d9f5e8c.jpg", + "image_caption": [ + "(a)PNVLAD" + ], + "image_footnote": [], + "bbox": [ + 84, + 90, + 282, + 220 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/a31b665b8861a8c11a18c00e000b3e5aab090c99ba7e90e23f587412352bd3fe.jpg", + "image_caption": [ + "(b) DCP" + ], + "image_footnote": [], + "bbox": [ + 282, + 90, + 483, + 220 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e509aabf4050cae6269df0ba5209aa3a718f440c7ed83fe7d1c03a97e57e02c6.jpg", + "image_caption": [ + "(c) PointLoc" + ], + "image_footnote": [], + "bbox": [ + 486, + 90, + 684, + 220 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/d097b497adf86a66a296d7a663a031e8a677a85b919f1bb711d147c98a5f4c2c.jpg", + "image_caption": [ + "(d) PosePN++" + ], + "image_footnote": [], + "bbox": [ + 687, + 90, + 887, + 220 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/ded909b286bc74f878ec6664b8b4b7e2439a9cc8b6362a9796f840471cafdfb1.jpg", + "image_caption": [ + "(e) STCLoc" + ], + "image_footnote": [], + "bbox": [ + 84, + 250, + 282, + 364 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/0de59e620b75dcea888ed89ec8477a5427dec55fb035b934f249912d8d6a79a0.jpg", + "image_caption": [ + "(f) HypLiLoc" + ], + "image_footnote": [], + "bbox": [ + 282, + 250, + 483, + 364 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/ef932d1abea99288b4885518eb561a5c2bb936540302decdd67cdfb954aa90f7.jpg", + "image_caption": [ + "(g) SGLoc", + "Figure 3. Visualization of different methods on QEOxford. The black and red points represent the ground-truth and estimation poses respectively, and the star indicates the first frame. Compared with retrieval and APR, trajectories of SCR methods (LiSA and its baseline SGLoc) are much more consistent with the ground-truth. LiSA not only is more accurate on average, but also does not suffer from catastrophic prediction errors existing in other baselines." + ], + "image_footnote": [], + "bbox": [ + 486, + 250, + 684, + 364 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/e7b53da0369b13bb1bdb9936aea54c1c08fc6aed69ecfaac66727b02568a8b85.jpg", + "image_caption": [ + "(h) LiSA" + ], + "image_footnote": [], + "bbox": [ + 687, + 250, + 887, + 364 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/5d3c17149070d3900160aca006f62135e8b5f6dc4c5dc3f16d619d31f112af4f.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
NCLT dataset
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
2012-02-127.75m, 6.49°9.84m, 6.84°7.23m, 4.88°4.97m, 3.75°4.91m, 4.43°1.71m, 3.56°1.20m, 3.08°0.97m, 2.23°
2012-02-197.47m, 5.49°8.27m, 5.16°6.31m, 3.89°3.68m, 2.65°3.25m, 3.10°1.68m, 2.69°1.20m, 3.05°0.91m, 2.09°
2012-03-316.98m, 5.67°8.94m, 5.96°6.71m, 4.32°4.35m, 3.38°3.75m, 4.04°1.52m, 2.90°1.12m, 3.28°0.87m, 2.21°
2012-05-2614.34m, 7.93°15.62m, 7.99°10.02m, 5.32°9.59m, 4.49°8.67m, 5.23°2.90m, 3.47°3.81m, 4.74°3.30m, 2.84°
Average9.14m, 6.40°10.67m, 6.49°7.57m, 4.60°5.65m, 3.57°5.15m, 4.18°1.95m, 3.16°1.83m, 3.54°1.51m, 2.34°
", + "bbox": [ + 78, + 465, + 890, + 578 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 4. Quantitative results on NCLT. Mean position error (m) and mean orientation error $(^{\\circ})$ for various methods are reported. Even though the semantic segmentation model [20] performs not perfectly on the NCLT dataset, LiSA still demonstrates outstanding performance, surpassing all competitors by a large margin.", + "bbox": [ + 75, + 588, + 892, + 631 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "'2012-03-31'. Similar to Fig. 3, LiSA demonstrates accurate and robust localization results with much fewer catastrophic failures than other methods. The results on NCLT provide further evidence that LiSA can effectively leverage semantic information for localization tasks to boost performance.", + "bbox": [ + 75, + 643, + 468, + 733 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Speed. Inference time is a crucial metric in the localization task. Given the laser scanning rates of $20\\mathrm{Hz}$ and $10\\mathrm{Hz}$ for the Oxford and NCLT datasets respectively, a real-time algorithm needs to keep the inference time below 50ms and 100ms. Due to the use of distillation-based training, LiSA only uses the baseline SCR module during inference, which does not introduce additional time and memory compared to the baseline [22]. The average run time of LiSA on Oxford and NCLT is 38ms and 75ms respectively (batch size = 1), which satisfies the real-time speed requirement.", + "bbox": [ + 75, + 750, + 472, + 902 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "4.3. Analysis", + "text_level": 1, + "bbox": [ + 500, + 643, + 601, + 659 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Effect of semantic information. To further understand the behavior of LiSA, we compare the network activation with and without semantic awareness. Fig. 6 (a) illustrates the distribution of activation values on a point cloud sampled from QEOxford (shown in Fig. 5). Without semantic awareness, most activation values cluster around the center, indicating that nearly all points are treated equally. In contrast, LiSA (with semantic awareness) learns to adaptively focus on more important points and ignore distracting points, resulting in widely distributed activation values and a much higher localization accuracy (Fig. 6 (b)). In Fig. 5, we show the activation on individual points of the sampled point cloud in Fig. 6. As shown in the zoom-in views on the right, the activation of LiSA is higher on salient objects (trunks, buildings, and parked cars), which are impor", + "bbox": [ + 496, + 674, + 890, + 902 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "15276", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/51512a32bfd50f9b2e23130dd60d133a813d085fabdd430e828e95d1d1dff42d.jpg", + "image_caption": [ + "(a)PNVLAD" + ], + "image_footnote": [], + "bbox": [ + 81, + 90, + 279, + 220 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/a7f55b6aabb9f3a578fe1bf7a25e3237f65e4e6382eac5482187677f36ff7329.jpg", + "image_caption": [ + "(b) DCP" + ], + "image_footnote": [], + "bbox": [ + 282, + 90, + 480, + 220 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/29ce0cde35091b1875ea0d771d632e8494af14f5275fb939c8ee446ab33eef1f.jpg", + "image_caption": [ + "(c) PointLoc" + ], + "image_footnote": [], + "bbox": [ + 483, + 90, + 681, + 220 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ee2ccd5e0a145a3255b33c5cdc09dfaa3d9442d778fb50fe8b69146e14969a8d.jpg", + "image_caption": [ + "(d) PosePN++" + ], + "image_footnote": [], + "bbox": [ + 686, + 90, + 883, + 220 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/9c5dff6cbcdf625a04af1b001eadb1853887c54c5de274662972a02237baac24.jpg", + "image_caption": [ + "(e) STCLoc" + ], + "image_footnote": [], + "bbox": [ + 81, + 252, + 279, + 367 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/96316143149c24ff770a69f48ccfb9c481baa1e9a7a1bb73e1ea32a52684c313.jpg", + "image_caption": [ + "(f) HypLiLoc" + ], + "image_footnote": [], + "bbox": [ + 282, + 252, + 480, + 366 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5e137a71763a5a3820fc60fd70191fb582fcdb79c47f4e81ade93c7286202f51.jpg", + "image_caption": [ + "(g) SGLoc", + "Figure 4. Visualization of different methods on NCLT. The black and red points represent the ground-truth and estimation poses respectively, and the star indicates the first frame. Similar to Fig. 3, LiSA outperforms all competitors with much fewer frequent catastrophic localization errors." + ], + "image_footnote": [], + "bbox": [ + 483, + 252, + 681, + 366 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/5304af79f3d450ccd8cb42bd6d036571317a2bd9dee5be6446a6a8c17e6cae82.jpg", + "image_caption": [ + "(h) LiSA" + ], + "image_footnote": [], + "bbox": [ + 686, + 252, + 883, + 366 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "tant for localization. Dynamic objects such as pedestrians have lower activation values, making LiSA insensitive to them. In contrast, the activation value remains similar for different objects without the help of semantic knowledge. This behavior clearly shows the importance of the semantic knowledge for LiDAR localization.", + "bbox": [ + 75, + 453, + 468, + 542 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "The way to use semantic information. LiSA applies knowledge distillation (KD) to provide the SCR network with semantic awareness. Here, we analyze the importance of this strategy. Specifically, we replace this strategy with 3 alternatives: 1) No semantic, where we do not use any semantic information. 2) Point filter, which, as described in Sec. 3.1, ignores the points from specific classes, with the class labels provided by a segmentation network. We use the best setup from Tab. 1 in this case. 3) Feature concatenate, which concatenates the features from the semantic segmentation and localization networks and then feeds the aggregated features into the regressor. We perform analysis on the quality-enhanced Oxford dataset. As shown in Tab. 5, though more accurate than 'no semantic', 'point filter' and 'feature concatenate' cannot encode the semantic knowledge into the SCR network, resulting in worse performance than knowledge distillation (KD). Meanwhile, these two alternatives rely on the segmentation model during inference, which introduces extra computation and memory.", + "bbox": [ + 75, + 547, + 468, + 835 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Segmentation quality. We also investigate the influence of the semantic segmentation quality on localization. As shown in Fig. 7, SphereFormer [20] has higher segmentation performance than SPVNAS [39]. Tab. 6 shows the", + "bbox": [ + 75, + 839, + 468, + 901 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/4c808da546a7b32c0756dc007637edd58ddaac1ccf4fdcdda5d4037506c99a04.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
No semanticPoint filterFeature concatenateKD
15-13-06-371.83m, 1.43°1.17m, 1.86°1.11m, 1.57°0.94m, 1.10°
17-13-26-392.10m, 1.47°1.64m, 2.14°1.47m, 1.72°1.17m, 1.21°
17-14-03-001.59m, 1.39°1.00m, 2.01°0.99m, 1.60°0.84m, 1.15°
18-14-14-421.62m, 1.33°0.98m, 1.87°0.97m, 1.51°0.85m, 1.11°
Average1.79m, 1.41°1.20m, 1.97°1.14m, 1.60°0.95m, 1.14°
", + "bbox": [ + 503, + 450, + 888, + 523 + ], + "page_idx": 6 + }, + { + "type": "table", + "img_path": "images/e077136bffd71dd56de3f3079bda6bf71f13c694c90ab7e9a1ccde1515cda666.jpg", + "table_caption": [ + "Table 5. Different ways of combining semantic information. Methods 'point filter' and 'feature concatenate' indeed show some improvement in accuracy after incorporating semantic information, but there is a slight decline in orientation. In comparison, LiSA, which integrates semantic information using knowledge distillation, exhibits a significant advantage." + ], + "table_footnote": [], + "table_body": "
loss function of KDquality of semantic featuresMean Error (m/°)
1L1low (SPVNAS)1.28m/1.53°
2L1high (SphereFormer)1.00m/1.15°
3DDPMlow (SPVNAS)1.15m/1.40°
4DDPMhigh (SphereFormer)0.95m/1.14°
", + "bbox": [ + 503, + 628, + 888, + 698 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "Table 6. Impact of the segmentation quality and the KD loss on QEOxford. Positive correlations exist between the segmentation accuracy of the teacher model and the localization accuracy of LiSA. Nonetheless, LiSA outperforms the baseline SGLoc by a large margin even with the low quality segmentation teacher (SPV-NAS). Utilizing DDPM to obtain better student features also contributes to the improvement in accuracy.", + "bbox": [ + 498, + 709, + 890, + 806 + ], + "page_idx": 6 + }, + { + "type": "text", + "text": "performance of LiSA with both models, which reflects the positive correlation between the segmentation performance and the localization accuracy, indicating the potential improvement of LiSA by incorporating better segmentation models in the future. Meanwhile, LiSA still outperforms", + "bbox": [ + 498, + 824, + 892, + 900 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "15277", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/ba070135ce6df7f166d08de1beabcf4883c7466c8c1d2d64bbe8d59ffb94092f.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 81, + 89, + 330, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/43d42ece98982e64cc93f08ac3a83247525124aaac6ec3c8b76ad55096bf6158.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 336, + 93, + 454, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d1ab1ef2e616dc76f9419925b9df80087bbc06023e0d5957535e1767c9a475d8.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 460, + 93, + 576, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/f3e753bf4ee267f536897da181a54a7668fbc0becca896bfff320f73d7d97c7a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 583, + 93, + 700, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/b3dcad38025ccbde5a2f849f351defbf41d29d15b7b0861aa95e731a4bb2bfee.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 705, + 93, + 826, + 186 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/a5e9620b1557673c3cc75daeba912992a6960557c2c8354ab5b26cb04930ac33.jpg", + "image_caption": [ + "complete point cloud" + ], + "image_footnote": [], + "bbox": [ + 81, + 189, + 330, + 286 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/92ba73b9a820356259c85133b1dd5aa11f5cb6ee679365594067aa0fdb4d1795.jpg", + "image_caption": [ + "trunk" + ], + "image_footnote": [], + "bbox": [ + 336, + 191, + 454, + 284 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/7dce7d170e46a6eacc19006f6e44e67c9f1abbb9766ff5dbb01e8c42b38ee503.jpg", + "image_caption": [ + "building" + ], + "image_footnote": [], + "bbox": [ + 460, + 191, + 576, + 284 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/d13ebaa8f85d8cab38ab0478e2e379d5b64750c5639e606355769e8ea7542da9.jpg", + "image_caption": [ + "parked car" + ], + "image_footnote": [], + "bbox": [ + 583, + 191, + 700, + 284 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/b85fd7b7dc9112bea70a898c9c866d068d4a42f27ae00985aa0eb2069cae000d.jpg", + "image_caption": [ + "pedestrian" + ], + "image_footnote": [], + "bbox": [ + 705, + 191, + 826, + 285 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/476e4812e5464d0ec9c71fa66997e0e94ee1b2b84727e88c4b21f22947454d77.jpg", + "image_caption": [ + "(a) Activation value distribution", + "Figure 6. Activation value distributions and localization results of LiSA (w/ semantic) and SGLoc (w/o semantic). (a): Given a point cloud sampled from QEOxford, we first aggregate features in the regressor (before heads) and normalize their activation values into [0, 255]. Without semantic awareness, most activation values of SGLoc are clustered in the center, indicating that almost all points are treated equally. (b): The localization accuracy with semantic awareness (LiSA) is much higher than the baseline (SGLoc) without semantic awareness." + ], + "image_footnote": [], + "bbox": [ + 81, + 391, + 290, + 513 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/6c8a156ddb17459d71c33a50443bfab5648ed26f27b1847f04993bd2ce4855c8.jpg", + "image_caption": [ + "(b) Localization results" + ], + "image_footnote": [], + "bbox": [ + 299, + 391, + 464, + 513 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "the baseline method SGLoc by a large margin, even with the low-quality segmentation model SPVNAS. This demonstrates the robustness of our pipeline w.r.t. the choice of segmentation methods.", + "bbox": [ + 75, + 676, + 468, + 737 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Knowledge distillation loss. We further investigate the impact of different loss functions on the knowledge distillation module. As shown in Tab. 6, diffusion-based distillation performs better than using the L1 loss across different segmentation models, especially on low-quality segmentation models.", + "bbox": [ + 75, + 739, + 467, + 830 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5. Conclusion", + "text_level": 1, + "bbox": [ + 76, + 844, + 194, + 859 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this work, we propose LiSA, a novel scene coordinate regression framework for LiDAR localization. To the best", + "bbox": [ + 75, + 869, + 468, + 900 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/38f7f556ce16bd6d1c229f53db904d1b5cd0afc9d68b461763fb3b4961ee2108.jpg", + "image_caption": [ + "Figure 5. The behavior of SCR with and without semantic awareness. Given a point cloud sampled from QEOxford, we show the pointwise activation value with and without using semantic information. Warmer colors denote higher activation values. Left: The activation map of the complete point cloud. Right: Zoom-in local views. Similar activation values are assigned to all points if no semantic knowledge is utilized, whereas LiSA can discriminate important points for localization and down-weight distracting points such as pedestrians.", + "Figure 7. Qualitative comparison of segmentation methods. SphereFormer on the right performs better as SPVNAS misclassifies more points on the ground and buildings." + ], + "image_footnote": [], + "bbox": [ + 503, + 387, + 697, + 517 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/c6114273f693fc674c35e00b333d431ff3b7ff2a8d2db4598cb52a3fd0c46575.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 697, + 387, + 892, + 517 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "of our knowledge, LiSA is the first work that integrates semantic information into regression-based localization. Instead of naively relying on labels generated by segmentation models, we apply diffusion-based knowledge distillation to transfer relevant semantic knowledge from a segmentation model directly into the SCR network. This enables adaptive extraction of semantic knowledge useful for localization with minimum negative impact from noisy segmentation. At the same time, due to the distillation-based training all extra modules can be discarded after training avoiding additional computation or network parameters w.r.t. the base SCR network during inference. LiSA achieves state-of-the-art performance on challenging LiDAR localization datasets, significantly surpassing previous methods.", + "bbox": [ + 496, + 599, + 890, + 811 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Acknowledgements This work was supported by the National Natural Science Foundation of China (No.62171393), the Fundamental Research Funds for the Central Universities (No.20720220064, No.20720230033), and PDL (2022-PDL-12).", + "bbox": [ + 496, + 825, + 890, + 898 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "15278", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 174, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. Netvlad: Cnn architecture for weakly supervised place recognition. 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CVPR, 2021. 2" + ], + "bbox": [ + 501, + 92, + 890, + 556 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "15280", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/LiSA_ LiDAR Localization with Semantic Awareness/a6e01367-c5ea-4fd3-9c99-a8b4204b195f_model.json b/2024/LiSA_ LiDAR Localization with Semantic Awareness/a6e01367-c5ea-4fd3-9c99-a8b4204b195f_model.json new file mode 100644 index 0000000000000000000000000000000000000000..064f6ce1b2617a597e5af28010a3e2781df19998 --- /dev/null +++ b/2024/LiSA_ LiDAR Localization with Semantic Awareness/a6e01367-c5ea-4fd3-9c99-a8b4204b195f_model.json @@ -0,0 +1,2563 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.045 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.218, + 0.131, + 0.753, + 0.151 + ], + "angle": 0, + "content": "LiSA: LiDAR Localization with Semantic Awareness" + }, + { + "type": "text", + "bbox": [ + 0.269, + 0.18, + 0.71, + 0.199 + ], + "angle": 0, + "content": "Bochun Yang\\(^{1*}\\) Zijun Li\\(^{1*}\\) Wen Li\\(^{1}\\) Zhipeng Cai\\(^{2\\dagger}\\)" + }, + { + "type": "text", + "bbox": [ + 0.235, + 0.199, + 0.746, + 0.218 + ], + "angle": 0, + "content": "Chenglu Wen1 Yu Zang1 Matthias Müller2 Cheng Wang1†" + }, + { + "type": "text", + "bbox": [ + 0.089, + 0.217, + 0.885, + 0.235 + ], + "angle": 0, + "content": "Fujian Key Laboratory of Sensing and Computing for Smart Cities, Xiamen University 2 Intel Labs" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.269, + 0.314, + 0.285 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.301, + 0.474, + 0.664 + ], + "angle": 0, + "content": "LiDAR localization is a fundamental task in robotics and computer vision, which estimates the pose of a LiDAR point cloud within a global map. Scene Coordinate Regression (SCR) has demonstrated state-of-the-art performance in this task. In SCR, a scene is represented as a neural network, which outputs the world coordinates for each point in the input point cloud. However, SCR treats all points equally during localization, ignoring the fact that not all objects are beneficial for localization. For example, dynamic objects and repeating structures often negatively impact SCR. To address this problem, we introduce LiSA, the first method that incorporates semantic awareness into SCR to boost the localization robustness and accuracy. To avoid extra computation or network parameters during inference, we distill the knowledge from a segmentation model to the original SCR network. Experiments show the superior performance of LiSA on standard LiDAR localization benchmarks compared to state-of-the-art methods. Applying knowledge distillation not only preserves high efficiency but also achieves higher localization accuracy than introducing extra semantic segmentation modules. We also analyze the benefit of semantic information for LiDAR localization. Our code is released at https://github.com/Ybchun/LiSA." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.691, + 0.21, + 0.707 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.716, + 0.47, + 0.761 + ], + "angle": 0, + "content": "LiDAR localization estimates the pose of a LiDAR point cloud in a global scene map, which is a fundamental task in computer vision and robotics." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.762, + 0.47, + 0.868 + ], + "angle": 0, + "content": "Learning-based regression methods [3-5, 19, 23, 36, 45] have shown state-of-the-art performance in LiDAR localization, where they memorize the specific scene in a neural network. Based on their regression objectives, these methods can be divided into Absolute Pose Regression (APR) and Scene Coordinates Regression (SCR). APR [5, 19, 36, 45] directly regresses the sensor pose. Despite" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.268, + 0.698, + 0.429 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.698, + 0.269, + 0.892, + 0.428 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.439, + 0.894, + 0.55 + ], + "angle": 0, + "content": "Figure 1. Teaser. This work studies the problem of LiDAR localization. We propose a novel method LiSA, which equips Li-DAR localization methods with semantic awareness. We show the ground-truth and predicted trajectories on Oxford (left) and NCLT (right). Compared to the baseline method (SGLoc), LiSA achieves a much higher average localization accuracy and has much fewer catastrophic failures, without introducing extra computation or network parameters during inference." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.567, + 0.892, + 0.718 + ], + "angle": 0, + "content": "the compact architectures, direct pose regression without explicitly utilizing the geometric information limits the accuracy of APR. Unlike APR, SCR [3, 4, 23] regresses the coordinate of each point in the global map, which provides correspondences between the input and the global point clouds. Then RANSAC [10] is applied to the correspondences to estimate the final pose. Utilizing the geometric information more explicitly allows SCR to more effectively embed and understand the scene geometry in its model parameters, resulting in higher accuracy and better robustness." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.72, + 0.893, + 0.901 + ], + "angle": 0, + "content": "SCR treats all points of the input equally. This is non-ideal for the task of localization – objects that are dynamic (e.g., pedestrians and vehicles) or repetitive (e.g., road surface and trees) intuitively should be less important than salient and static objects. Motivated by this observation, we propose LiSA, a novel method that equips SCR with semantic awareness. LiSA can robustly handle distracting objects and significantly improves the localization accuracy. To avoid introducing extra computation or network parameters during inference, we apply diffusion-based knowledge distillation during training so that we can enable semantic understanding of the original SCR network by extracting" + }, + { + "type": "page_footnote", + "bbox": [ + 0.096, + 0.875, + 0.208, + 0.888 + ], + "angle": 0, + "content": "*Equal contribution." + }, + { + "type": "page_footnote", + "bbox": [ + 0.098, + 0.888, + 0.222, + 0.9 + ], + "angle": 0, + "content": "† Corresponding author." + }, + { + "type": "list", + "bbox": [ + 0.096, + 0.875, + 0.222, + 0.9 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.518, + 0.957 + ], + "angle": 0, + "content": "15271" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.47, + 0.151 + ], + "angle": 0, + "content": "knowledge from a teacher segmentation model, which is dropped after training. To the best of our knowledge, LiSA is the first method that effectively utilizes semantic context for LiDAR localization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.153, + 0.47, + 0.259 + ], + "angle": 0, + "content": "In our experiments, LiSA shows superior performance on standard LiDAR localization benchmarks compared to state-of-the-art methods. Without introducing extra computation or network parameters during inference, it achieves a relative improvement of more than \\(38\\%\\) and \\(29\\%\\) in position and orientation on the QEOxford dataset and \\(17\\%\\) and \\(34\\%\\) on the NCLT dataset (see Fig. 1 for an example)." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.276, + 0.219, + 0.291 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.306, + 0.468, + 0.457 + ], + "angle": 0, + "content": "Conventional localization. Conventional re-localization methods can be broadly categorized into 1) retrieval-based [1, 42, 43, 51] and 2) matching-based [32, 33, 38] approaches. The former searches for frames most similar to the query frame in a pre-constructed global descriptor database, while the latter employs SfM tools to build a sparse 3D point cloud of the scene and matches features to find correspondences between the query frame and the point cloud. These methods require pre-stored map information, making them time-consuming and labor-intensive." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.462, + 0.468, + 0.794 + ], + "angle": 0, + "content": "Regression-based localization. Due to the advancement of deep learning, regression-based localization methods have received much attention recently. Regression-based methods can be further separated into two categories: 1) Absolute Pose Regression (APR) and 2) Scene Coordinate Regression (SCR). APR directly regresses the 6-DoF pose of the sensor (e.g., a camera or a LiDAR scanner). PoseNet[19] and several variants [5, 18, 24, 36, 44, 45] adopt a pipeline that includes only a feature extractor and an MLP to directly output the camera pose in an end-to-end manner. However, Sattler et al.[34] pointed out that APR methods are similar to retrieval-based methods, which only learn the mapping relationship between high-dimensional abstract feature vectors and poses rather than the scene information. To alleviate this issue, SCR [3, 4] estimates the sensor pose in a different way: the neural network predicts the 3D coordinates of each pixel/3D point in the world coordinate system, which embeds the scene information more explicitly and effectively. Then, candidate correspondences are constructed using the local coordinate and the predicted world coordinate of each point. These correspondences are finally used in RANSAC [10] to obtain the sensor pose." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.796, + 0.468, + 0.901 + ], + "angle": 0, + "content": "In recent years, the widespread use of LiDAR stimulated several works for regression-based LiDAR localization. LiDAR APR methods, such as PointLoc[47], PosePN++[54], and HypLiLoc[46], and the SCR method SGLoc[22], have shown impressive performance on large-scale outdoor localization. Compared to the images, point clouds exhibit robustness to changes in lighting conditions and inherently" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.892, + 0.182 + ], + "angle": 0, + "content": "carry depth information. In this work, we show that SCR methods have not fully utilized the semantic information of the scene. We introduce a novel method with semantic awareness during localization, which significantly improves the performance without introducing extra computation or network parameters during inference." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.187, + 0.892, + 0.337 + ], + "angle": 0, + "content": "Localization using auxiliary information. Semantic information has been demonstrated to be important in conventional non-regression-based methods. Retrieval-based approaches [27, 35, 37] employ semantic information to enhance the robustness of the descriptors or serve it as the posterior information to refine the predicted pose. Several matching-based methods [9, 41], attach semantic labels to the point features during matching. This modification helps mitigate the risk of erroneous matching and significantly increases their localization accuracy." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.339, + 0.892, + 0.535 + ], + "angle": 0, + "content": "Object detection has been applied to regression-based methods. For instance, AD-PoseNet[17] utilizes Mask R-CNN[12] to minimize the impact of dynamic foreground objects on scene understanding. ORGPoseNet[30] uses graph neural networks to learn the geometric position relationships of objects in the scene and gain more precise localization results. However, object detection tends to concentrate solely on foreground objects rather than the whole observation in the frame. On the contrary, semantic segmentation contains exhaustive scene geometry information and intricate details. This inspires us to explore the incorporation of semantic information to enhance the accuracy of regression-based LiDAR localization." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.54, + 0.892, + 0.767 + ], + "angle": 0, + "content": "LiDAR-based semantic segmentation. LiDAR-based semantic segmentation [20, 39] aims to assign a semantic label to each point in the input LiDAR scan. Methods can generally be divided into several categories: point-based [15, 28, 29, 40], voxel-based [11, 55], projection-based [21, 25, 50], and their combination [39, 52]. Regardless of the specifics of the network architecture, they consistently expand the perception field by merging the individual point features with the coarse-grain features in the scene. In this way, the semantic segmentation networks can better understand the scene information and the characteristics of each point. In this paper, we apply a point cloud semantic segmentation model as the teacher to distill semantic knowledge to a LiDAR localization method, which effectively improves localization accuracy." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.784, + 0.591, + 0.799 + ], + "angle": 0, + "content": "3. Method" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.81, + 0.892, + 0.903 + ], + "angle": 0, + "content": "LiSA relies on scene coordinate regression (SCR) for LiDAR localization [22]. The input of SCR is a query point cloud \\(\\mathcal{P} = \\{\\mathbf{p}_i\\}_{i=1}^N\\) where \\(\\mathbf{p}_i \\in \\mathbb{R}^3\\) represents a 3D point in the local coordinate frame with the LiDAR scanner at the origin. The output of SCR is a set of coordinates \\(\\mathcal{P}' = \\{\\mathbf{p}_{i'}'\\}_{i'=1}^{N'}\\) representing the location of the down-" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15272" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.08, + 0.086, + 0.899, + 0.346 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.358, + 0.895, + 0.43 + ], + "angle": 0, + "content": "Figure 2. The pipeline of LiSA. It consists of three modules: scene coordinate regression, semantic segmentation (frozen), and knowledge distillation. In the scene coordinate regression module, the coordinate regression head in the regressor directly outputs scene coordinates \\(\\mathcal{P}'\\), and the semantic feature regression head learns semantic segmentation features (\\(\\mathbf{F}_{\\mathrm{stu}}\\)) from the knowledge distillation module and the semantic segmentation module. After distilling the semantic knowledge during training, both semantic segmentation and knowledge distillation modules are discarded, which ensures that no extra computation and network parameters are introduced during inference." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.442, + 0.47, + 0.517 + ], + "angle": 0, + "content": "sampled points in world coordinates. (SCR down-samples the input to \\( N' = \\frac{N}{8} \\) points, i.e., by a factor of 8.) The world coordinate \\( \\mathbf{p}_{i'}' \\) represents the corresponding location of \\( \\mathbf{p}_{i'} \\) in the global point cloud \\( \\mathcal{P}^* \\), which covers the complete scene of interest and is used during training." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.518, + 0.47, + 0.549 + ], + "angle": 0, + "content": "SCR trains one model for each scene. The training loss is typically as follows:" + }, + { + "type": "equation", + "bbox": [ + 0.185, + 0.556, + 0.47, + 0.59 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {l o c} = \\frac {\\sum_ {i = 1} ^ {N ^ {\\prime}} \\left| \\mathbf {p} _ {i ^ {\\prime}} ^ {\\prime} - \\mathbf {p} _ {i ^ {\\prime}} ^ {*} \\right|}{N ^ {\\prime}}, \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.598, + 0.47, + 0.627 + ], + "angle": 0, + "content": "where \\(\\mathbf{p}_{i'}'\\) and \\(\\mathbf{p}_{i'}^*\\) are respectively the predicted and ground-truth world coordinates, \\(|\\cdot|\\) is the L1 loss." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.628, + 0.47, + 0.688 + ], + "angle": 0, + "content": "To obtain the relative pose of \\(\\mathcal{P}\\) w.r.t. \\(\\mathcal{P}^*\\) for the final localization, RANSAC is performed on the candidate correspondences constructed by \\(\\mathcal{P}\\) and the predicted world coordinates \\(\\mathcal{P}'\\)." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.697, + 0.2, + 0.711 + ], + "angle": 0, + "content": "3.1. Motivation" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.72, + 0.47, + 0.856 + ], + "angle": 0, + "content": "The key idea of LiSA is to utilize semantic information to assist with localization. To motivate the importance of semantic information, we conduct a preliminary analysis where we filter out points belonging to specific classes in SCR, i.e., the filtered points do not participate in inference and training. Instead of using the ground-truth semantic labels which are unavailable in practical applications, we use labels predicted by a pre-trained state-of-the-art 3D semantic segmentation model [20]." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.856, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Tab. 1 shows the localization accuracy with different semantic categories on the QEOxford dataset [22]. It is clear to see that the localization performance varies significantly" + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.439, + 0.892, + 0.532 + ], + "angle": 0, + "content": "
FilterMean Error (m/°)FilterMean Error (m/°)
all (no filter)1.79m, 1.41°all (no filter)1.79m, 1.41°
no plant1.20m, 1.97°plant only59.08m, 13.25°
no building1.39m, 2.26°building only1.63m, 1.91°
no sidewalk1.77m, 1.45°sidewalk only2.47m, 5.92°
no road2.03m, 3.42°road only1.71m, 2.59°
no transportation2.07m, 3.42°transportation only20.10m, 21.95°
" + }, + { + "type": "table_caption", + "bbox": [ + 0.498, + 0.542, + 0.894, + 0.626 + ], + "angle": 0, + "content": "Table 1. Impact of semantic information on LiDAR localization. Filtering out objects from different classes can significantly reduce or increase the position error. However, the noise in the semantic labels makes it hard to consistently improve both rotation and translation accuracy with point filtering, which motivates the design of LiSA." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.64, + 0.894, + 0.822 + ], + "angle": 0, + "content": "with different filtering strategies, e.g., without plants the position error reduces significantly. This result shows the importance of semantic information in SCR. However, due to noise in the predicted labels and the hard threshold, naive filtering does not fully utilize the semantic information – some filters improve the position accuracy while sacrificing the orientation accuracy. Moreover, segmentation models introduce significant overhead in terms of memory and computing during inference, which may be prohibitive for many practical applications. This motivates us to design LiSA, a novel framework that effectively and efficiently incorporates semantic information into SCR." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.832, + 0.578, + 0.846 + ], + "angle": 0, + "content": "3.2.LiSA" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.894, + 0.902 + ], + "angle": 0, + "content": "As shown in Fig. 2, LiSA can be divided into three modules, namely scene coordinate regression (SCR), semantic segmentation, and knowledge distillation. During training, the" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15273" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.092, + 0.468, + 0.182 + ], + "angle": 0, + "content": "semantic segmentation module and the knowledge distillation module are used to transfer semantic knowledge into the SCR module. After training, only the SCR module is maintained, which can effectively utilize the transferred semantic knowledge for localization, without introducing extra computation or network parameters." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.183, + 0.47, + 0.362 + ], + "angle": 0, + "content": "The SCR module mostly follows the architecture of SGLoc [22], which contains a multi-scale feature extractor and a regressor. To enable semantic awareness without extra computation, we add a new branch to the regressor, which is used to regress a per-point semantic feature \\(\\mathbf{F}_{\\mathrm{stu}} \\in \\mathbb{R}^{N' \\times d}\\), where \\(N'\\) is the number of output points which is equivalent to the number of output world coordinates \\(\\mathcal{P}'\\), and \\(d\\) is the feature dimension. The original coordinate regressor branch outputs the world coordinates \\(\\mathcal{P}'\\) and is supervised by the loss in Eq. (1). The semantic regressor branch is supervised by distilling knowledge from the semantic segmentation model." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.364, + 0.468, + 0.531 + ], + "angle": 0, + "content": "The semantic segmentation module consists of a pretrained 3D semantic segmentation model with frozen network parameters during training. We take the per-point last layer feature \\(\\mathbf{F}_{\\mathrm{seg}} \\in \\mathbb{R}^{N \\times d}\\) of the segmentation model, down-sample it into \\(\\mathbf{F}_{\\mathrm{tea}} \\in \\mathbb{R}^{N' \\times d}\\) so that \\(\\mathbf{F}_{\\mathrm{tea}}\\) has the same dimension as \\(\\mathbf{F}_{\\mathrm{stu}}\\). To verify the robustness of LiSA, we experiment with SphereFormer [20] and SPVNAS [39] pretrained on datasets non-overlapping with any LiDAR localization dataset. We ensure \\(\\mathbf{F}_{\\mathrm{tea}}\\) and \\(\\mathbf{F}_{\\mathrm{stu}}\\) have the same dimension \\(d\\) for each feature point by adjusting the output dimension of the semantic regressor branch." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.532, + 0.468, + 0.651 + ], + "angle": 0, + "content": "Knowledge distillation [13] is the standard approach for reducing network parameters or transferring knowledge across different modalities, resulting in a (lightweight) student network that preserves the capabilities of the teacher network. LiSA applies knowledge distillation to transfer the semantic knowledge from the segmentation module to the SCR module. This is achieved by optimizing the following distillation loss:" + }, + { + "type": "equation", + "bbox": [ + 0.205, + 0.661, + 0.468, + 0.677 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {k d} = \\delta \\left(\\mathbf {F} _ {\\mathrm {s t u}}, \\mathbf {F} _ {\\mathrm {t e a}}\\right), \\tag {2}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.686, + 0.468, + 0.775 + ], + "angle": 0, + "content": "where \\(\\delta (\\cdot)\\) measures the difference between the features from the teacher \\((\\mathbf{F}_{\\mathrm{tea}})\\) and the student \\((\\mathbf{F}_{\\mathrm{stu}})\\). Intuitively, the distillation process encourages the semantic feature \\(\\mathbf{F}_{\\mathrm{stu}}\\) from SCR to be similar to \\(\\mathbf{F}_{\\mathrm{tea}}\\), which requires the SCR module to be able to distinguish different semantic classes. The final loss function of the entire network is:" + }, + { + "type": "equation", + "bbox": [ + 0.215, + 0.786, + 0.468, + 0.801 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {l o c} + \\mathcal {L} _ {k d}. \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.468, + 0.901 + ], + "angle": 0, + "content": "Various knowledge distillation methods can be applied to realize \\(\\mathcal{L}_{kd}\\). LiSA applies the recent diffusion-based distillation [16]. Specifically, we train a diffusion model with the teacher feature \\(\\mathbf{F}_{\\mathrm{tea}}\\) by gradually adding noise to \\(\\mathbf{F}_{\\mathrm{tea}}\\) and let the diffusion model learn to predict the noise. Following the forward noise process of DDPM [14], the noisy" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.09, + 0.853, + 0.108 + ], + "angle": 0, + "content": "teacher feature \\(\\mathbf{F}_{\\mathrm{tea}}^{(t)}\\) at time step \\(t\\) can be obtained by:" + }, + { + "type": "equation", + "bbox": [ + 0.513, + 0.118, + 0.892, + 0.139 + ], + "angle": 0, + "content": "\\[\n\\mathbf {F} _ {\\mathrm {t e a}} ^ {(t)} = \\sqrt {\\bar {\\alpha} ^ {(t)}} \\mathbf {F} _ {\\mathrm {t e a}} + \\sqrt {1 - \\bar {\\alpha} ^ {(t)}} \\boldsymbol {\\epsilon} ^ {(t)}, \\boldsymbol {\\epsilon} ^ {(t)} \\sim \\mathcal {N} (\\mathbf {0}, \\mathbf {I}). \\tag {4}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.15, + 0.804, + 0.164 + ], + "angle": 0, + "content": "The loss for training the diffusion model is" + }, + { + "type": "equation", + "bbox": [ + 0.592, + 0.176, + 0.892, + 0.195 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {d d p m} = \\left| \\left| \\sigma \\left(\\mathbf {F} _ {\\mathrm {t e a}} ^ {(t)}, t\\right) - \\boldsymbol {\\epsilon} ^ {(t)} \\right| \\right| _ {2}, \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.208, + 0.891, + 0.256 + ], + "angle": 0, + "content": "where \\(\\sigma (\\mathbf{F}_{\\mathrm{tea}}^{(t)},t)\\) represents the predicted noise from the diffusion model given the time step \\(t\\) and the noisy feature input \\(\\mathbf{F}_{\\mathrm{tea}}^{(t)},\\epsilon^{(t)}\\) represents the ground-truth noise." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.257, + 0.892, + 0.333 + ], + "angle": 0, + "content": "To enable the knowledge transfer between \\(\\mathbf{F}_{\\mathrm{stu}}\\) and \\(\\mathbf{F}_{\\mathrm{tea}}\\), we consider \\(\\mathbf{F}_{\\mathrm{stu}}\\) as the noisy version of \\(\\mathbf{F}_{\\mathrm{tea}}\\), and use the diffusion model to obtain a denoised version \\(\\mathbf{F}_{\\mathrm{stu}}^{\\prime}\\) of \\(\\mathbf{F}_{\\mathrm{stu}}\\). Then we apply the normal knowledge distillation (L1) loss to \\(\\mathbf{F}_{\\mathrm{stu}}^{\\prime}\\) and \\(\\mathbf{F}_{\\mathrm{tea}}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.625, + 0.343, + 0.892, + 0.36 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {k d} ^ {\\prime} = \\left| \\mathbf {F} _ {\\mathrm {s t u}} ^ {\\prime} - \\mathbf {F} _ {\\mathrm {t e a}} \\right|. \\tag {6}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.52, + 0.371, + 0.706, + 0.385 + ], + "angle": 0, + "content": "The final distillation loss is:" + }, + { + "type": "equation", + "bbox": [ + 0.603, + 0.397, + 0.891, + 0.414 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {k d} = \\lambda_ {1} \\mathcal {L} _ {d d p m} + \\lambda_ {2} \\mathcal {L} _ {k d} ^ {\\prime}, \\tag {7}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.425, + 0.892, + 0.5 + ], + "angle": 0, + "content": "where \\(\\lambda_{1}\\) and \\(\\lambda_{2}\\) are hyper-parameters to balance the losses. Simply setting both \\(\\lambda_{1}\\) and \\(\\lambda_{2}\\) to 1 works well in practice. Note that we use the vanilla DDPM architecture instead of latent diffusion [31]. Hence, we do not have losses on autoencoders as in Sec. 3.2 of [16]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.501, + 0.892, + 0.636 + ], + "angle": 0, + "content": "Besides introducing no overhead to SCR (by dropping both segmentation and distillation modules after training), knowledge distillation also allows the network to more effectively utilize the imperfect output of the semantic segmentation models — we only use the semantic features to transfer the knowledge, instead of using hard filtering based on the imperfect semantic labels. Our experiments (Sec. 4.2) show that this design remarkably reduces both the position and orientation error." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.65, + 0.625, + 0.666 + ], + "angle": 0, + "content": "4. Experiment" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.674, + 0.582, + 0.691 + ], + "angle": 0, + "content": "4.1. Setup" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.701, + 0.892, + 0.852 + ], + "angle": 0, + "content": "Baseline. We compare LiSA against different types of state-of-the-art methods: 1) For retrieval-based methods, we choose PNVLAD [43] which employs PointNet [28] and NetVLAD [1] to generate high-quality global descriptors. 2) For 3D matching-based methods, we choose DCP [48] which utilizes PointNet [28] and DGCNN [49] as embedding networks. 3) For \\(APR\\) methods, we choose PointLoc [47], PosePN++ [54], HyLiLoc [46] and STCLoc [53]. For SCR, SGLoc [22] is the first method of this type in LiDAR localization and it is also the most competitive baseline." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.856, + 0.892, + 0.901 + ], + "angle": 0, + "content": "Dataset. Following [22], we perform evaluations on 3 public datasets, namely Oxford Radar RobotCar [2], QEOxford [22] and NCLT [6]. Oxford Radar RobotCar contains" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15274" + } + ], + [ + { + "type": "table_caption", + "bbox": [ + 0.435, + 0.094, + 0.536, + 0.106 + ], + "angle": 0, + "content": "QEOxford dataset" + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.106, + 0.891, + 0.2 + ], + "angle": 0, + "content": "
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
15-13-06-3710.90m, 2.49°10.61m, 2.56°10.75m, 2.36°4.54m, 1.83°5.14m, 1.27°5.03m, 1.46°1.79m, 1.67°0.94m, 1.10°
17-13-26-3914.60m, 2.46°11.44m, 2.14°11.07m, 2.21°6.44m, 1.78°6.12m, 1.21°4.31m, 1.43°1.81m, 1.76°1.17m, 1.21°
17-14-03-0011.28m, 2.21°10.90m, 2.01°11.53m, 1.92°4.89m, 1.55°5.32m, 1.08°3.61m, 1.11°1.33m, 1.59°0.84m, 1.15°
18-14-14-429.00m, 1.90°9.51m, 2.08°9.82m, 2.07°4.64m, 1.61°4.76m, 1.19°2.61m, 1.09°1.19m, 1.39°0.85m, 1.11°
Average11.45m, 2.27°10.62m, 2.20°10.79m, 2.14°5.13m, 1.69°5.34m, 1.18°3.89m, 1.27°1.53m, 1.60°0.95m, 1.14°
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.211, + 0.893, + 0.255 + ], + "angle": 0, + "content": "Table 2. Quantitative results on QEOxford. Mean position error (m) and mean orientation error \\((^{\\circ})\\) for various methods are reported. Best performance is highlighted in bold, lower is better. LiSA outperforms all baseline methods in terms of both position and orientation accuracy." + }, + { + "type": "table_caption", + "bbox": [ + 0.444, + 0.272, + 0.527, + 0.283 + ], + "angle": 0, + "content": "Oxford dataset" + }, + { + "type": "table", + "bbox": [ + 0.082, + 0.284, + 0.89, + 0.378 + ], + "angle": 0, + "content": "
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
15-13-06-3718.14m, 3.28°16.04m, 4.54°12.42m, 2.26°9.59m, 1.92°6.93m, 1.48°6.88m, 1.09°3.01m, 1.91°2.36m, 1.29°
17-13-26-3924.57m, 3.08°16.22m, 3.56°13.14m, 2.50°10.66m, 1.92°7.55m, 1.23°6.79m, 1.29°4.07m, 2.07°3.47m, 1.43°
17-14-03-0019.93m, 3.13°14.87m, 3.45°12.91m, 1.92°9.01m, 1.51°7.44m, 1.24°5.82m, 0.97°3.37m, 1.89°3.19m, 1.34°
18-14-14-4215.59m, 2.63°12.97m, 3.99°11.31m, 1.98°8.44m, 1.71°6.13m, 1.15°3.45m, 0.84°2.12m, 1.66°1.95m, 1.23°
Average19.56m, 3.03°15.03m, 3.89°12.45m, 2.17°9.43m, 1.77°7.01m, 1.28°5.74m, 1.05°3.14m, 1.88°2.74m, 1.32°
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.388, + 0.893, + 0.445 + ], + "angle": 0, + "content": "Table 3. Quantitative results on Oxford. Mean position error (m) and mean orientation error \\((^{\\circ})\\) for various methods are reported; best performance is highlighted in bold, lower is better. LiSA significantly improves both the position and rotation accuracy of the baseline SGLoc. The ground-truth trajectory noise in the original Oxford dataset makes SCR perform slightly worse in terms of rotational accuracy compared to the best APR methods HypLiLoc. However, the positional accuracy is much higher." + }, + { + "type": "text", + "bbox": [ + 0.075, + 0.464, + 0.471, + 0.661 + ], + "angle": 0, + "content": "32 repeated traversals along the central Oxford with diverse weather and complex traffic conditions, roughly \\(10km\\) of the trajectory length, and a \\(2km^2\\) range coverage. QEOxford is a quality-enhanced version of the Oxford dataset, with GPS/INS errors minimized by alignment techniques, which has been demonstrated to be beneficial for localization [22]. NCLT is an extensive collection of LiDAR data captured at the Michigan North Campus. It comprises 27 tracks, each approximately \\(5.5km\\) long, covering an area of \\(0.45km^2\\). The dataset contains challenging scenarios such as dynamic objects, illumination variation, seasonal and weather changes, and long-term structural alterations due to ongoing construction projects." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.666, + 0.47, + 0.773 + ], + "angle": 0, + "content": "Implementation. LiSA is implemented with Pytorch [26], Spconv [8] and the Minkowski Engine [7]. We conduct our experiments on a server equipped with an Intel(R) Xeon(R) Silver 4314 CPU, 256GB of RAM, and four NVIDIA RTX 3090 GPUs. During training, we employ the Adam optimizer with an initial learning rate of 0.01, weight decay of 0.95, and batch size of 100." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.786, + 0.216, + 0.801 + ], + "angle": 0, + "content": "4.2. Main Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.81, + 0.471, + 0.903 + ], + "angle": 0, + "content": "Results on Oxford. Tab. 2 shows the quantitative results on the quality-enhanced Oxford dataset. LiSA achieves the lowest position and orientation error at \\(0.95\\mathrm{m}\\) and \\(1.14^{\\circ}\\), respectively. This result improves the previous state-of-the-art (SGLoc [22]) by \\(38\\%\\) and \\(29\\%\\) on position and orientation respectively without sacrificing the efficiency. In ad" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.464, + 0.893, + 0.63 + ], + "angle": 0, + "content": "dition, it is the first time that a sub-meter accuracy can be achieved without additional backend optimization, such as pose graph optimization (PGO) [5, 22]. LiSA achieves better results with much higher efficiency than SGLoc+PGO (38ms vs 288ms); see Appendix 3 for details. Fig. 3 shows the qualitative results on trajectory 15-13-06-37. LiSA closely aligns with the ground-truth trajectory and has significantly fewer outliers, i.e., fewer catastrophic failures. The experimental results demonstrate that semantic awareness helps LiSA to understand the scene information and obtain more accurate localization results." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.636, + 0.892, + 0.743 + ], + "angle": 0, + "content": "Tab. 3 reports the results on the (non-enhanced) Oxford dataset. LiSA also significantly improves over the baseline SGLoc in both position and orientation on this dataset. Although LiSA has some gaps in terms of orientation compared to the best APR method [46], it surpasses all previous methods in terms of position accuracy. We discuss this in detail in Appendix 3." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.75, + 0.895, + 0.903 + ], + "angle": 0, + "content": "Results on NCLT. Tab. 4 shows the quantitative result on the NCLT dataset. Though the segmentation model used to train LiSA performs much worse on NCLT than on Oxford (see Appendix 2 for visualization of segmentation results on Oxford and NCLT), LiSA still outperforms all competitors, achieving sub-meter accuracy on 3 of the 4 trajectories. Compared to the previous state-of-the-art method, SGLoc [22], there is an improvement of \\(17\\%\\) and \\(34\\%\\) in these metrics. This further demonstrates the robustness of our framework. Fig. 4 shows the qualitative results on trajectory" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15275" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.086, + 0.092, + 0.283, + 0.221 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.139, + 0.224, + 0.232, + 0.239 + ], + "angle": 0, + "content": "(a)PNVLAD" + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.091, + 0.485, + 0.221 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.358, + 0.224, + 0.416, + 0.239 + ], + "angle": 0, + "content": "(b) DCP" + }, + { + "type": "image", + "bbox": [ + 0.487, + 0.091, + 0.686, + 0.221 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.545, + 0.224, + 0.631, + 0.239 + ], + "angle": 0, + "content": "(c) PointLoc" + }, + { + "type": "image", + "bbox": [ + 0.688, + 0.091, + 0.888, + 0.221 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.741, + 0.224, + 0.838, + 0.239 + ], + "angle": 0, + "content": "(d) PosePN++" + }, + { + "type": "image", + "bbox": [ + 0.086, + 0.25, + 0.283, + 0.366 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.145, + 0.37, + 0.225, + 0.385 + ], + "angle": 0, + "content": "(e) STCLoc" + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.25, + 0.485, + 0.366 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.341, + 0.37, + 0.432, + 0.385 + ], + "angle": 0, + "content": "(f) HypLiLoc" + }, + { + "type": "image", + "bbox": [ + 0.487, + 0.25, + 0.686, + 0.366 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.552, + 0.37, + 0.624, + 0.385 + ], + "angle": 0, + "content": "(g) SGLoc" + }, + { + "type": "image", + "bbox": [ + 0.688, + 0.25, + 0.888, + 0.366 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.758, + 0.37, + 0.82, + 0.384 + ], + "angle": 0, + "content": "(h) LiSA" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.403, + 0.893, + 0.459 + ], + "angle": 0, + "content": "Figure 3. Visualization of different methods on QEOxford. The black and red points represent the ground-truth and estimation poses respectively, and the star indicates the first frame. Compared with retrieval and APR, trajectories of SCR methods (LiSA and its baseline SGLoc) are much more consistent with the ground-truth. LiSA not only is more accurate on average, but also does not suffer from catastrophic prediction errors existing in other baselines." + }, + { + "type": "table", + "bbox": [ + 0.08, + 0.466, + 0.891, + 0.579 + ], + "angle": 0, + "content": "
NCLT dataset
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
2012-02-127.75m, 6.49°9.84m, 6.84°7.23m, 4.88°4.97m, 3.75°4.91m, 4.43°1.71m, 3.56°1.20m, 3.08°0.97m, 2.23°
2012-02-197.47m, 5.49°8.27m, 5.16°6.31m, 3.89°3.68m, 2.65°3.25m, 3.10°1.68m, 2.69°1.20m, 3.05°0.91m, 2.09°
2012-03-316.98m, 5.67°8.94m, 5.96°6.71m, 4.32°4.35m, 3.38°3.75m, 4.04°1.52m, 2.90°1.12m, 3.28°0.87m, 2.21°
2012-05-2614.34m, 7.93°15.62m, 7.99°10.02m, 5.32°9.59m, 4.49°8.67m, 5.23°2.90m, 3.47°3.81m, 4.74°3.30m, 2.84°
Average9.14m, 6.40°10.67m, 6.49°7.57m, 4.60°5.65m, 3.57°5.15m, 4.18°1.95m, 3.16°1.83m, 3.54°1.51m, 2.34°
" + }, + { + "type": "table_caption", + "bbox": [ + 0.076, + 0.589, + 0.893, + 0.632 + ], + "angle": 0, + "content": "Table 4. Quantitative results on NCLT. Mean position error (m) and mean orientation error \\((^{\\circ})\\) for various methods are reported. Even though the semantic segmentation model [20] performs not perfectly on the NCLT dataset, LiSA still demonstrates outstanding performance, surpassing all competitors by a large margin." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.645, + 0.47, + 0.734 + ], + "angle": 0, + "content": "'2012-03-31'. Similar to Fig. 3, LiSA demonstrates accurate and robust localization results with much fewer catastrophic failures than other methods. The results on NCLT provide further evidence that LiSA can effectively leverage semantic information for localization tasks to boost performance." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.473, + 0.903 + ], + "angle": 0, + "content": "Speed. Inference time is a crucial metric in the localization task. Given the laser scanning rates of \\(20\\mathrm{Hz}\\) and \\(10\\mathrm{Hz}\\) for the Oxford and NCLT datasets respectively, a real-time algorithm needs to keep the inference time below 50ms and 100ms. Due to the use of distillation-based training, LiSA only uses the baseline SCR module during inference, which does not introduce additional time and memory compared to the baseline [22]. The average run time of LiSA on Oxford and NCLT is 38ms and 75ms respectively (batch size = 1), which satisfies the real-time speed requirement." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.644, + 0.602, + 0.66 + ], + "angle": 0, + "content": "4.3. Analysis" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.675, + 0.892, + 0.903 + ], + "angle": 0, + "content": "Effect of semantic information. To further understand the behavior of LiSA, we compare the network activation with and without semantic awareness. Fig. 6 (a) illustrates the distribution of activation values on a point cloud sampled from QEOxford (shown in Fig. 5). Without semantic awareness, most activation values cluster around the center, indicating that nearly all points are treated equally. In contrast, LiSA (with semantic awareness) learns to adaptively focus on more important points and ignore distracting points, resulting in widely distributed activation values and a much higher localization accuracy (Fig. 6 (b)). In Fig. 5, we show the activation on individual points of the sampled point cloud in Fig. 6. As shown in the zoom-in views on the right, the activation of LiSA is higher on salient objects (trunks, buildings, and parked cars), which are impor" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.958 + ], + "angle": 0, + "content": "15276" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.092, + 0.28, + 0.222 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.136, + 0.226, + 0.227, + 0.24 + ], + "angle": 0, + "content": "(a)PNVLAD" + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.092, + 0.481, + 0.222 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.354, + 0.226, + 0.413, + 0.24 + ], + "angle": 0, + "content": "(b) DCP" + }, + { + "type": "image", + "bbox": [ + 0.484, + 0.092, + 0.683, + 0.222 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.542, + 0.226, + 0.628, + 0.24 + ], + "angle": 0, + "content": "(c) PointLoc" + }, + { + "type": "image", + "bbox": [ + 0.687, + 0.092, + 0.885, + 0.222 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.739, + 0.226, + 0.835, + 0.24 + ], + "angle": 0, + "content": "(d) PosePN++" + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.253, + 0.28, + 0.368 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.142, + 0.372, + 0.221, + 0.386 + ], + "angle": 0, + "content": "(e) STCLoc" + }, + { + "type": "image", + "bbox": [ + 0.284, + 0.253, + 0.481, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.338, + 0.372, + 0.429, + 0.387 + ], + "angle": 0, + "content": "(f) HypLiLoc" + }, + { + "type": "image", + "bbox": [ + 0.484, + 0.253, + 0.683, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.549, + 0.372, + 0.621, + 0.387 + ], + "angle": 0, + "content": "(g) SGLoc" + }, + { + "type": "image", + "bbox": [ + 0.687, + 0.253, + 0.885, + 0.367 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.756, + 0.372, + 0.817, + 0.386 + ], + "angle": 0, + "content": "(h) LiSA" + }, + { + "type": "image_caption", + "bbox": [ + 0.075, + 0.404, + 0.893, + 0.446 + ], + "angle": 0, + "content": "Figure 4. Visualization of different methods on NCLT. The black and red points represent the ground-truth and estimation poses respectively, and the star indicates the first frame. Similar to Fig. 3, LiSA outperforms all competitors with much fewer frequent catastrophic localization errors." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.454, + 0.47, + 0.544 + ], + "angle": 0, + "content": "tant for localization. Dynamic objects such as pedestrians have lower activation values, making LiSA insensitive to them. In contrast, the activation value remains similar for different objects without the help of semantic knowledge. This behavior clearly shows the importance of the semantic knowledge for LiDAR localization." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.549, + 0.47, + 0.837 + ], + "angle": 0, + "content": "The way to use semantic information. LiSA applies knowledge distillation (KD) to provide the SCR network with semantic awareness. Here, we analyze the importance of this strategy. Specifically, we replace this strategy with 3 alternatives: 1) No semantic, where we do not use any semantic information. 2) Point filter, which, as described in Sec. 3.1, ignores the points from specific classes, with the class labels provided by a segmentation network. We use the best setup from Tab. 1 in this case. 3) Feature concatenate, which concatenates the features from the semantic segmentation and localization networks and then feeds the aggregated features into the regressor. We perform analysis on the quality-enhanced Oxford dataset. As shown in Tab. 5, though more accurate than 'no semantic', 'point filter' and 'feature concatenate' cannot encode the semantic knowledge into the SCR network, resulting in worse performance than knowledge distillation (KD). Meanwhile, these two alternatives rely on the segmentation model during inference, which introduces extra computation and memory." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.47, + 0.902 + ], + "angle": 0, + "content": "Segmentation quality. We also investigate the influence of the semantic segmentation quality on localization. As shown in Fig. 7, SphereFormer [20] has higher segmentation performance than SPVNAS [39]. Tab. 6 shows the" + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.451, + 0.89, + 0.525 + ], + "angle": 0, + "content": "
No semanticPoint filterFeature concatenateKD
15-13-06-371.83m, 1.43°1.17m, 1.86°1.11m, 1.57°0.94m, 1.10°
17-13-26-392.10m, 1.47°1.64m, 2.14°1.47m, 1.72°1.17m, 1.21°
17-14-03-001.59m, 1.39°1.00m, 2.01°0.99m, 1.60°0.84m, 1.15°
18-14-14-421.62m, 1.33°0.98m, 1.87°0.97m, 1.51°0.85m, 1.11°
Average1.79m, 1.41°1.20m, 1.97°1.14m, 1.60°0.95m, 1.14°
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.535, + 0.892, + 0.62 + ], + "angle": 0, + "content": "Table 5. Different ways of combining semantic information. Methods 'point filter' and 'feature concatenate' indeed show some improvement in accuracy after incorporating semantic information, but there is a slight decline in orientation. In comparison, LiSA, which integrates semantic information using knowledge distillation, exhibits a significant advantage." + }, + { + "type": "table", + "bbox": [ + 0.504, + 0.629, + 0.89, + 0.699 + ], + "angle": 0, + "content": "
loss function of KDquality of semantic featuresMean Error (m/°)
1L1low (SPVNAS)1.28m/1.53°
2L1high (SphereFormer)1.00m/1.15°
3DDPMlow (SPVNAS)1.15m/1.40°
4DDPMhigh (SphereFormer)0.95m/1.14°
" + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.71, + 0.892, + 0.807 + ], + "angle": 0, + "content": "Table 6. Impact of the segmentation quality and the KD loss on QEOxford. Positive correlations exist between the segmentation accuracy of the teacher model and the localization accuracy of LiSA. Nonetheless, LiSA outperforms the baseline SGLoc by a large margin even with the low quality segmentation teacher (SPV-NAS). Utilizing DDPM to obtain better student features also contributes to the improvement in accuracy." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.825, + 0.893, + 0.901 + ], + "angle": 0, + "content": "performance of LiSA with both models, which reflects the positive correlation between the segmentation performance and the localization accuracy, indicating the potential improvement of LiSA by incorporating better segmentation models in the future. Meanwhile, LiSA still outperforms" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15277" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.083, + 0.09, + 0.331, + 0.188 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.337, + 0.094, + 0.455, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.461, + 0.094, + 0.578, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.584, + 0.094, + 0.701, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.706, + 0.094, + 0.828, + 0.187 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.19, + 0.331, + 0.287 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.153, + 0.29, + 0.29, + 0.305 + ], + "angle": 0, + "content": "complete point cloud" + }, + { + "type": "image", + "bbox": [ + 0.338, + 0.192, + 0.455, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.377, + 0.291, + 0.413, + 0.304 + ], + "angle": 0, + "content": "trunk" + }, + { + "type": "image", + "bbox": [ + 0.461, + 0.192, + 0.578, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.492, + 0.29, + 0.548, + 0.305 + ], + "angle": 0, + "content": "building" + }, + { + "type": "image", + "bbox": [ + 0.584, + 0.192, + 0.701, + 0.285 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.61, + 0.29, + 0.678, + 0.305 + ], + "angle": 0, + "content": "parked car" + }, + { + "type": "image", + "bbox": [ + 0.706, + 0.192, + 0.828, + 0.286 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.735, + 0.291, + 0.803, + 0.304 + ], + "angle": 0, + "content": "pedestrian" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.321, + 0.895, + 0.378 + ], + "angle": 0, + "content": "Figure 5. The behavior of SCR with and without semantic awareness. Given a point cloud sampled from QEOxford, we show the pointwise activation value with and without using semantic information. Warmer colors denote higher activation values. Left: The activation map of the complete point cloud. Right: Zoom-in local views. Similar activation values are assigned to all points if no semantic knowledge is utilized, whereas LiSA can discriminate important points for localization and down-weight distracting points such as pedestrians." + }, + { + "type": "image", + "bbox": [ + 0.082, + 0.392, + 0.291, + 0.514 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.114, + 0.517, + 0.264, + 0.528 + ], + "angle": 0, + "content": "(a) Activation value distribution" + }, + { + "type": "image", + "bbox": [ + 0.3, + 0.392, + 0.465, + 0.514 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.334, + 0.517, + 0.444, + 0.528 + ], + "angle": 0, + "content": "(b) Localization results" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.542, + 0.47, + 0.668 + ], + "angle": 0, + "content": "Figure 6. Activation value distributions and localization results of LiSA (w/ semantic) and SGLoc (w/o semantic). (a): Given a point cloud sampled from QEOxford, we first aggregate features in the regressor (before heads) and normalize their activation values into [0, 255]. Without semantic awareness, most activation values of SGLoc are clustered in the center, indicating that almost all points are treated equally. (b): The localization accuracy with semantic awareness (LiSA) is much higher than the baseline (SGLoc) without semantic awareness." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.677, + 0.47, + 0.738 + ], + "angle": 0, + "content": "the baseline method SGLoc by a large margin, even with the low-quality segmentation model SPVNAS. This demonstrates the robustness of our pipeline w.r.t. the choice of segmentation methods." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.741, + 0.468, + 0.831 + ], + "angle": 0, + "content": "Knowledge distillation loss. We further investigate the impact of different loss functions on the knowledge distillation module. As shown in Tab. 6, diffusion-based distillation performs better than using the L1 loss across different segmentation models, especially on low-quality segmentation models." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.845, + 0.196, + 0.861 + ], + "angle": 0, + "content": "5. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.47, + 0.901 + ], + "angle": 0, + "content": "In this work, we propose LiSA, a novel scene coordinate regression framework for LiDAR localization. To the best" + }, + { + "type": "image", + "bbox": [ + 0.504, + 0.388, + 0.699, + 0.518 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.699, + 0.388, + 0.893, + 0.518 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.53, + 0.892, + 0.573 + ], + "angle": 0, + "content": "Figure 7. Qualitative comparison of segmentation methods. SphereFormer on the right performs better as SPVNAS misclassifies more points on the ground and buildings." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.6, + 0.892, + 0.813 + ], + "angle": 0, + "content": "of our knowledge, LiSA is the first work that integrates semantic information into regression-based localization. Instead of naively relying on labels generated by segmentation models, we apply diffusion-based knowledge distillation to transfer relevant semantic knowledge from a segmentation model directly into the SCR network. This enables adaptive extraction of semantic knowledge useful for localization with minimum negative impact from noisy segmentation. At the same time, due to the distillation-based training all extra modules can be discarded after training avoiding additional computation or network parameters w.r.t. the base SCR network during inference. LiSA achieves state-of-the-art performance on challenging LiDAR localization datasets, significantly surpassing previous methods." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.826, + 0.892, + 0.9 + ], + "angle": 0, + "content": "Acknowledgements This work was supported by the National Natural Science Foundation of China (No.62171393), the Fundamental Research Funds for the Central Universities (No.20720220064, No.20720230033), and PDL (2022-PDL-12)." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "15278" + } + ], + [ + { + "type": "title", + "bbox": [ + 0.08, + 0.09, + 0.175, + 0.106 + ], + "angle": 0, + "content": "References" + }, + { + "type": "ref_text", + "bbox": [ + 0.087, + 0.115, + 0.47, + 0.17 + ], + "angle": 0, + "content": "[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. Netvlad: Cnn architecture for weakly supervised place recognition. 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Scene Coordinate Regression (SCR) has demonstrated state-of-the-art performance in this task. In SCR, a scene is represented as a neural network, which outputs the world coordinates for each point in the input point cloud. However, SCR treats all points equally during localization, ignoring the fact that not all objects are beneficial for localization. For example, dynamic objects and repeating structures often negatively impact SCR. To address this problem, we introduce LiSA, the first method that incorporates semantic awareness into SCR to boost the localization robustness and accuracy. To avoid extra computation or network parameters during inference, we distill the knowledge from a segmentation model to the original SCR network. Experiments show the superior performance of LiSA on standard LiDAR localization benchmarks compared to state-of-the-art methods. Applying knowledge distillation not only preserves high efficiency but also achieves higher localization accuracy than introducing extra semantic segmentation modules. We also analyze the benefit of semantic information for LiDAR localization. Our code is released at https://github.com/Ybchun/LiSA. + +# 1. Introduction + +LiDAR localization estimates the pose of a LiDAR point cloud in a global scene map, which is a fundamental task in computer vision and robotics. + +Learning-based regression methods [3-5, 19, 23, 36, 45] have shown state-of-the-art performance in LiDAR localization, where they memorize the specific scene in a neural network. Based on their regression objectives, these methods can be divided into Absolute Pose Regression (APR) and Scene Coordinates Regression (SCR). APR [5, 19, 36, 45] directly regresses the sensor pose. Despite + +![](images/4549b39663d14eff43a059370cea4aecfdfe39ba139e1544c6241e11e343ca8b.jpg) +Figure 1. Teaser. This work studies the problem of LiDAR localization. We propose a novel method LiSA, which equips Li-DAR localization methods with semantic awareness. We show the ground-truth and predicted trajectories on Oxford (left) and NCLT (right). Compared to the baseline method (SGLoc), LiSA achieves a much higher average localization accuracy and has much fewer catastrophic failures, without introducing extra computation or network parameters during inference. + +![](images/eb566751a42c2ee64ecc8e71c816664c00aa39cf77aba51625604180f5b55770.jpg) + +the compact architectures, direct pose regression without explicitly utilizing the geometric information limits the accuracy of APR. Unlike APR, SCR [3, 4, 23] regresses the coordinate of each point in the global map, which provides correspondences between the input and the global point clouds. Then RANSAC [10] is applied to the correspondences to estimate the final pose. Utilizing the geometric information more explicitly allows SCR to more effectively embed and understand the scene geometry in its model parameters, resulting in higher accuracy and better robustness. + +SCR treats all points of the input equally. This is non-ideal for the task of localization – objects that are dynamic (e.g., pedestrians and vehicles) or repetitive (e.g., road surface and trees) intuitively should be less important than salient and static objects. Motivated by this observation, we propose LiSA, a novel method that equips SCR with semantic awareness. LiSA can robustly handle distracting objects and significantly improves the localization accuracy. To avoid introducing extra computation or network parameters during inference, we apply diffusion-based knowledge distillation during training so that we can enable semantic understanding of the original SCR network by extracting + +knowledge from a teacher segmentation model, which is dropped after training. To the best of our knowledge, LiSA is the first method that effectively utilizes semantic context for LiDAR localization. + +In our experiments, LiSA shows superior performance on standard LiDAR localization benchmarks compared to state-of-the-art methods. Without introducing extra computation or network parameters during inference, it achieves a relative improvement of more than $38\%$ and $29\%$ in position and orientation on the QEOxford dataset and $17\%$ and $34\%$ on the NCLT dataset (see Fig. 1 for an example). + +# 2. Related Work + +Conventional localization. Conventional re-localization methods can be broadly categorized into 1) retrieval-based [1, 42, 43, 51] and 2) matching-based [32, 33, 38] approaches. The former searches for frames most similar to the query frame in a pre-constructed global descriptor database, while the latter employs SfM tools to build a sparse 3D point cloud of the scene and matches features to find correspondences between the query frame and the point cloud. These methods require pre-stored map information, making them time-consuming and labor-intensive. + +Regression-based localization. Due to the advancement of deep learning, regression-based localization methods have received much attention recently. Regression-based methods can be further separated into two categories: 1) Absolute Pose Regression (APR) and 2) Scene Coordinate Regression (SCR). APR directly regresses the 6-DoF pose of the sensor (e.g., a camera or a LiDAR scanner). PoseNet[19] and several variants [5, 18, 24, 36, 44, 45] adopt a pipeline that includes only a feature extractor and an MLP to directly output the camera pose in an end-to-end manner. However, Sattler et al.[34] pointed out that APR methods are similar to retrieval-based methods, which only learn the mapping relationship between high-dimensional abstract feature vectors and poses rather than the scene information. To alleviate this issue, SCR [3, 4] estimates the sensor pose in a different way: the neural network predicts the 3D coordinates of each pixel/3D point in the world coordinate system, which embeds the scene information more explicitly and effectively. Then, candidate correspondences are constructed using the local coordinate and the predicted world coordinate of each point. These correspondences are finally used in RANSAC [10] to obtain the sensor pose. + +In recent years, the widespread use of LiDAR stimulated several works for regression-based LiDAR localization. LiDAR APR methods, such as PointLoc[47], PosePN++[54], and HypLiLoc[46], and the SCR method SGLoc[22], have shown impressive performance on large-scale outdoor localization. Compared to the images, point clouds exhibit robustness to changes in lighting conditions and inherently + +carry depth information. In this work, we show that SCR methods have not fully utilized the semantic information of the scene. We introduce a novel method with semantic awareness during localization, which significantly improves the performance without introducing extra computation or network parameters during inference. + +Localization using auxiliary information. Semantic information has been demonstrated to be important in conventional non-regression-based methods. Retrieval-based approaches [27, 35, 37] employ semantic information to enhance the robustness of the descriptors or serve it as the posterior information to refine the predicted pose. Several matching-based methods [9, 41], attach semantic labels to the point features during matching. This modification helps mitigate the risk of erroneous matching and significantly increases their localization accuracy. + +Object detection has been applied to regression-based methods. For instance, AD-PoseNet[17] utilizes Mask R-CNN[12] to minimize the impact of dynamic foreground objects on scene understanding. ORGPoseNet[30] uses graph neural networks to learn the geometric position relationships of objects in the scene and gain more precise localization results. However, object detection tends to concentrate solely on foreground objects rather than the whole observation in the frame. On the contrary, semantic segmentation contains exhaustive scene geometry information and intricate details. This inspires us to explore the incorporation of semantic information to enhance the accuracy of regression-based LiDAR localization. + +LiDAR-based semantic segmentation. LiDAR-based semantic segmentation [20, 39] aims to assign a semantic label to each point in the input LiDAR scan. Methods can generally be divided into several categories: point-based [15, 28, 29, 40], voxel-based [11, 55], projection-based [21, 25, 50], and their combination [39, 52]. Regardless of the specifics of the network architecture, they consistently expand the perception field by merging the individual point features with the coarse-grain features in the scene. In this way, the semantic segmentation networks can better understand the scene information and the characteristics of each point. In this paper, we apply a point cloud semantic segmentation model as the teacher to distill semantic knowledge to a LiDAR localization method, which effectively improves localization accuracy. + +# 3. Method + +LiSA relies on scene coordinate regression (SCR) for LiDAR localization [22]. The input of SCR is a query point cloud $\mathcal{P} = \{\mathbf{p}_i\}_{i=1}^N$ where $\mathbf{p}_i \in \mathbb{R}^3$ represents a 3D point in the local coordinate frame with the LiDAR scanner at the origin. The output of SCR is a set of coordinates $\mathcal{P}' = \{\mathbf{p}_{i'}'\}_{i'=1}^{N'}$ representing the location of the down- + +![](images/b3fc5795239b36bd7858c4bf3a06eaa70e6581b1c9017b5fa9414c51b0d41a2d.jpg) +Figure 2. The pipeline of LiSA. It consists of three modules: scene coordinate regression, semantic segmentation (frozen), and knowledge distillation. In the scene coordinate regression module, the coordinate regression head in the regressor directly outputs scene coordinates $\mathcal{P}'$ , and the semantic feature regression head learns semantic segmentation features ( $\mathbf{F}_{\mathrm{stu}}$ ) from the knowledge distillation module and the semantic segmentation module. After distilling the semantic knowledge during training, both semantic segmentation and knowledge distillation modules are discarded, which ensures that no extra computation and network parameters are introduced during inference. + +sampled points in world coordinates. (SCR down-samples the input to $N' = \frac{N}{8}$ points, i.e., by a factor of 8.) The world coordinate $\mathbf{p}_{i'}'$ represents the corresponding location of $\mathbf{p}_{i'}$ in the global point cloud $\mathcal{P}^*$ , which covers the complete scene of interest and is used during training. + +SCR trains one model for each scene. The training loss is typically as follows: + +$$ +\mathcal {L} _ {l o c} = \frac {\sum_ {i = 1} ^ {N ^ {\prime}} \left| \mathbf {p} _ {i ^ {\prime}} ^ {\prime} - \mathbf {p} _ {i ^ {\prime}} ^ {*} \right|}{N ^ {\prime}}, \tag {1} +$$ + +where $\mathbf{p}_{i'}'$ and $\mathbf{p}_{i'}^*$ are respectively the predicted and ground-truth world coordinates, $|\cdot|$ is the L1 loss. + +To obtain the relative pose of $\mathcal{P}$ w.r.t. $\mathcal{P}^*$ for the final localization, RANSAC is performed on the candidate correspondences constructed by $\mathcal{P}$ and the predicted world coordinates $\mathcal{P}'$ . + +# 3.1. Motivation + +The key idea of LiSA is to utilize semantic information to assist with localization. To motivate the importance of semantic information, we conduct a preliminary analysis where we filter out points belonging to specific classes in SCR, i.e., the filtered points do not participate in inference and training. Instead of using the ground-truth semantic labels which are unavailable in practical applications, we use labels predicted by a pre-trained state-of-the-art 3D semantic segmentation model [20]. + +Tab. 1 shows the localization accuracy with different semantic categories on the QEOxford dataset [22]. It is clear to see that the localization performance varies significantly + +
FilterMean Error (m/°)FilterMean Error (m/°)
all (no filter)1.79m, 1.41°all (no filter)1.79m, 1.41°
no plant1.20m, 1.97°plant only59.08m, 13.25°
no building1.39m, 2.26°building only1.63m, 1.91°
no sidewalk1.77m, 1.45°sidewalk only2.47m, 5.92°
no road2.03m, 3.42°road only1.71m, 2.59°
no transportation2.07m, 3.42°transportation only20.10m, 21.95°
+ +Table 1. Impact of semantic information on LiDAR localization. Filtering out objects from different classes can significantly reduce or increase the position error. However, the noise in the semantic labels makes it hard to consistently improve both rotation and translation accuracy with point filtering, which motivates the design of LiSA. + +with different filtering strategies, e.g., without plants the position error reduces significantly. This result shows the importance of semantic information in SCR. However, due to noise in the predicted labels and the hard threshold, naive filtering does not fully utilize the semantic information – some filters improve the position accuracy while sacrificing the orientation accuracy. Moreover, segmentation models introduce significant overhead in terms of memory and computing during inference, which may be prohibitive for many practical applications. This motivates us to design LiSA, a novel framework that effectively and efficiently incorporates semantic information into SCR. + +# 3.2.LiSA + +As shown in Fig. 2, LiSA can be divided into three modules, namely scene coordinate regression (SCR), semantic segmentation, and knowledge distillation. During training, the + +semantic segmentation module and the knowledge distillation module are used to transfer semantic knowledge into the SCR module. After training, only the SCR module is maintained, which can effectively utilize the transferred semantic knowledge for localization, without introducing extra computation or network parameters. + +The SCR module mostly follows the architecture of SGLoc [22], which contains a multi-scale feature extractor and a regressor. To enable semantic awareness without extra computation, we add a new branch to the regressor, which is used to regress a per-point semantic feature $\mathbf{F}_{\mathrm{stu}} \in \mathbb{R}^{N' \times d}$ , where $N'$ is the number of output points which is equivalent to the number of output world coordinates $\mathcal{P}'$ , and $d$ is the feature dimension. The original coordinate regressor branch outputs the world coordinates $\mathcal{P}'$ and is supervised by the loss in Eq. (1). The semantic regressor branch is supervised by distilling knowledge from the semantic segmentation model. + +The semantic segmentation module consists of a pretrained 3D semantic segmentation model with frozen network parameters during training. We take the per-point last layer feature $\mathbf{F}_{\mathrm{seg}} \in \mathbb{R}^{N \times d}$ of the segmentation model, down-sample it into $\mathbf{F}_{\mathrm{tea}} \in \mathbb{R}^{N' \times d}$ so that $\mathbf{F}_{\mathrm{tea}}$ has the same dimension as $\mathbf{F}_{\mathrm{stu}}$ . To verify the robustness of LiSA, we experiment with SphereFormer [20] and SPVNAS [39] pretrained on datasets non-overlapping with any LiDAR localization dataset. We ensure $\mathbf{F}_{\mathrm{tea}}$ and $\mathbf{F}_{\mathrm{stu}}$ have the same dimension $d$ for each feature point by adjusting the output dimension of the semantic regressor branch. + +Knowledge distillation [13] is the standard approach for reducing network parameters or transferring knowledge across different modalities, resulting in a (lightweight) student network that preserves the capabilities of the teacher network. LiSA applies knowledge distillation to transfer the semantic knowledge from the segmentation module to the SCR module. This is achieved by optimizing the following distillation loss: + +$$ +\mathcal {L} _ {k d} = \delta \left(\mathbf {F} _ {\mathrm {s t u}}, \mathbf {F} _ {\mathrm {t e a}}\right), \tag {2} +$$ + +where $\delta (\cdot)$ measures the difference between the features from the teacher $(\mathbf{F}_{\mathrm{tea}})$ and the student $(\mathbf{F}_{\mathrm{stu}})$ . Intuitively, the distillation process encourages the semantic feature $\mathbf{F}_{\mathrm{stu}}$ from SCR to be similar to $\mathbf{F}_{\mathrm{tea}}$ , which requires the SCR module to be able to distinguish different semantic classes. The final loss function of the entire network is: + +$$ +\mathcal {L} = \mathcal {L} _ {l o c} + \mathcal {L} _ {k d}. \tag {3} +$$ + +Various knowledge distillation methods can be applied to realize $\mathcal{L}_{kd}$ . LiSA applies the recent diffusion-based distillation [16]. Specifically, we train a diffusion model with the teacher feature $\mathbf{F}_{\mathrm{tea}}$ by gradually adding noise to $\mathbf{F}_{\mathrm{tea}}$ and let the diffusion model learn to predict the noise. Following the forward noise process of DDPM [14], the noisy + +teacher feature $\mathbf{F}_{\mathrm{tea}}^{(t)}$ at time step $t$ can be obtained by: + +$$ +\mathbf {F} _ {\mathrm {t e a}} ^ {(t)} = \sqrt {\bar {\alpha} ^ {(t)}} \mathbf {F} _ {\mathrm {t e a}} + \sqrt {1 - \bar {\alpha} ^ {(t)}} \boldsymbol {\epsilon} ^ {(t)}, \boldsymbol {\epsilon} ^ {(t)} \sim \mathcal {N} (\mathbf {0}, \mathbf {I}). \tag {4} +$$ + +The loss for training the diffusion model is + +$$ +\mathcal {L} _ {d d p m} = \left| \left| \sigma \left(\mathbf {F} _ {\mathrm {t e a}} ^ {(t)}, t\right) - \boldsymbol {\epsilon} ^ {(t)} \right| \right| _ {2}, \tag {5} +$$ + +where $\sigma (\mathbf{F}_{\mathrm{tea}}^{(t)},t)$ represents the predicted noise from the diffusion model given the time step $t$ and the noisy feature input $\mathbf{F}_{\mathrm{tea}}^{(t)},\epsilon^{(t)}$ represents the ground-truth noise. + +To enable the knowledge transfer between $\mathbf{F}_{\mathrm{stu}}$ and $\mathbf{F}_{\mathrm{tea}}$ , we consider $\mathbf{F}_{\mathrm{stu}}$ as the noisy version of $\mathbf{F}_{\mathrm{tea}}$ , and use the diffusion model to obtain a denoised version $\mathbf{F}_{\mathrm{stu}}^{\prime}$ of $\mathbf{F}_{\mathrm{stu}}$ . Then we apply the normal knowledge distillation (L1) loss to $\mathbf{F}_{\mathrm{stu}}^{\prime}$ and $\mathbf{F}_{\mathrm{tea}}$ : + +$$ +\mathcal {L} _ {k d} ^ {\prime} = \left| \mathbf {F} _ {\mathrm {s t u}} ^ {\prime} - \mathbf {F} _ {\mathrm {t e a}} \right|. \tag {6} +$$ + +The final distillation loss is: + +$$ +\mathcal {L} _ {k d} = \lambda_ {1} \mathcal {L} _ {d d p m} + \lambda_ {2} \mathcal {L} _ {k d} ^ {\prime}, \tag {7} +$$ + +where $\lambda_{1}$ and $\lambda_{2}$ are hyper-parameters to balance the losses. Simply setting both $\lambda_{1}$ and $\lambda_{2}$ to 1 works well in practice. Note that we use the vanilla DDPM architecture instead of latent diffusion [31]. Hence, we do not have losses on autoencoders as in Sec. 3.2 of [16]. + +Besides introducing no overhead to SCR (by dropping both segmentation and distillation modules after training), knowledge distillation also allows the network to more effectively utilize the imperfect output of the semantic segmentation models — we only use the semantic features to transfer the knowledge, instead of using hard filtering based on the imperfect semantic labels. Our experiments (Sec. 4.2) show that this design remarkably reduces both the position and orientation error. + +# 4. Experiment + +# 4.1. Setup + +Baseline. We compare LiSA against different types of state-of-the-art methods: 1) For retrieval-based methods, we choose PNVLAD [43] which employs PointNet [28] and NetVLAD [1] to generate high-quality global descriptors. 2) For 3D matching-based methods, we choose DCP [48] which utilizes PointNet [28] and DGCNN [49] as embedding networks. 3) For $APR$ methods, we choose PointLoc [47], PosePN++ [54], HyLiLoc [46] and STCLoc [53]. For SCR, SGLoc [22] is the first method of this type in LiDAR localization and it is also the most competitive baseline. + +Dataset. Following [22], we perform evaluations on 3 public datasets, namely Oxford Radar RobotCar [2], QEOxford [22] and NCLT [6]. Oxford Radar RobotCar contains + +QEOxford dataset + +
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
15-13-06-3710.90m, 2.49°10.61m, 2.56°10.75m, 2.36°4.54m, 1.83°5.14m, 1.27°5.03m, 1.46°1.79m, 1.67°0.94m, 1.10°
17-13-26-3914.60m, 2.46°11.44m, 2.14°11.07m, 2.21°6.44m, 1.78°6.12m, 1.21°4.31m, 1.43°1.81m, 1.76°1.17m, 1.21°
17-14-03-0011.28m, 2.21°10.90m, 2.01°11.53m, 1.92°4.89m, 1.55°5.32m, 1.08°3.61m, 1.11°1.33m, 1.59°0.84m, 1.15°
18-14-14-429.00m, 1.90°9.51m, 2.08°9.82m, 2.07°4.64m, 1.61°4.76m, 1.19°2.61m, 1.09°1.19m, 1.39°0.85m, 1.11°
Average11.45m, 2.27°10.62m, 2.20°10.79m, 2.14°5.13m, 1.69°5.34m, 1.18°3.89m, 1.27°1.53m, 1.60°0.95m, 1.14°
+ +Table 2. Quantitative results on QEOxford. Mean position error (m) and mean orientation error $(^{\circ})$ for various methods are reported. Best performance is highlighted in bold, lower is better. LiSA outperforms all baseline methods in terms of both position and orientation accuracy. +Oxford dataset + +
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
15-13-06-3718.14m, 3.28°16.04m, 4.54°12.42m, 2.26°9.59m, 1.92°6.93m, 1.48°6.88m, 1.09°3.01m, 1.91°2.36m, 1.29°
17-13-26-3924.57m, 3.08°16.22m, 3.56°13.14m, 2.50°10.66m, 1.92°7.55m, 1.23°6.79m, 1.29°4.07m, 2.07°3.47m, 1.43°
17-14-03-0019.93m, 3.13°14.87m, 3.45°12.91m, 1.92°9.01m, 1.51°7.44m, 1.24°5.82m, 0.97°3.37m, 1.89°3.19m, 1.34°
18-14-14-4215.59m, 2.63°12.97m, 3.99°11.31m, 1.98°8.44m, 1.71°6.13m, 1.15°3.45m, 0.84°2.12m, 1.66°1.95m, 1.23°
Average19.56m, 3.03°15.03m, 3.89°12.45m, 2.17°9.43m, 1.77°7.01m, 1.28°5.74m, 1.05°3.14m, 1.88°2.74m, 1.32°
+ +Table 3. Quantitative results on Oxford. Mean position error (m) and mean orientation error $(^{\circ})$ for various methods are reported; best performance is highlighted in bold, lower is better. LiSA significantly improves both the position and rotation accuracy of the baseline SGLoc. The ground-truth trajectory noise in the original Oxford dataset makes SCR perform slightly worse in terms of rotational accuracy compared to the best APR methods HypLiLoc. However, the positional accuracy is much higher. + +32 repeated traversals along the central Oxford with diverse weather and complex traffic conditions, roughly $10km$ of the trajectory length, and a $2km^2$ range coverage. QEOxford is a quality-enhanced version of the Oxford dataset, with GPS/INS errors minimized by alignment techniques, which has been demonstrated to be beneficial for localization [22]. NCLT is an extensive collection of LiDAR data captured at the Michigan North Campus. It comprises 27 tracks, each approximately $5.5km$ long, covering an area of $0.45km^2$ . The dataset contains challenging scenarios such as dynamic objects, illumination variation, seasonal and weather changes, and long-term structural alterations due to ongoing construction projects. + +Implementation. LiSA is implemented with Pytorch [26], Spconv [8] and the Minkowski Engine [7]. We conduct our experiments on a server equipped with an Intel(R) Xeon(R) Silver 4314 CPU, 256GB of RAM, and four NVIDIA RTX 3090 GPUs. During training, we employ the Adam optimizer with an initial learning rate of 0.01, weight decay of 0.95, and batch size of 100. + +# 4.2. Main Results + +Results on Oxford. Tab. 2 shows the quantitative results on the quality-enhanced Oxford dataset. LiSA achieves the lowest position and orientation error at $0.95\mathrm{m}$ and $1.14^{\circ}$ , respectively. This result improves the previous state-of-the-art (SGLoc [22]) by $38\%$ and $29\%$ on position and orientation respectively without sacrificing the efficiency. In ad + +dition, it is the first time that a sub-meter accuracy can be achieved without additional backend optimization, such as pose graph optimization (PGO) [5, 22]. LiSA achieves better results with much higher efficiency than SGLoc+PGO (38ms vs 288ms); see Appendix 3 for details. Fig. 3 shows the qualitative results on trajectory 15-13-06-37. LiSA closely aligns with the ground-truth trajectory and has significantly fewer outliers, i.e., fewer catastrophic failures. The experimental results demonstrate that semantic awareness helps LiSA to understand the scene information and obtain more accurate localization results. + +Tab. 3 reports the results on the (non-enhanced) Oxford dataset. LiSA also significantly improves over the baseline SGLoc in both position and orientation on this dataset. Although LiSA has some gaps in terms of orientation compared to the best APR method [46], it surpasses all previous methods in terms of position accuracy. We discuss this in detail in Appendix 3. + +Results on NCLT. Tab. 4 shows the quantitative result on the NCLT dataset. Though the segmentation model used to train LiSA performs much worse on NCLT than on Oxford (see Appendix 2 for visualization of segmentation results on Oxford and NCLT), LiSA still outperforms all competitors, achieving sub-meter accuracy on 3 of the 4 trajectories. Compared to the previous state-of-the-art method, SGLoc [22], there is an improvement of $17\%$ and $34\%$ in these metrics. This further demonstrates the robustness of our framework. Fig. 4 shows the qualitative results on trajectory + +![](images/f25af4498912080a3a8a9426a02c164d7023ef46630f80c902bdce5a2d9f5e8c.jpg) +(a)PNVLAD + +![](images/a31b665b8861a8c11a18c00e000b3e5aab090c99ba7e90e23f587412352bd3fe.jpg) +(b) DCP + +![](images/e509aabf4050cae6269df0ba5209aa3a718f440c7ed83fe7d1c03a97e57e02c6.jpg) +(c) PointLoc + +![](images/d097b497adf86a66a296d7a663a031e8a677a85b919f1bb711d147c98a5f4c2c.jpg) +(d) PosePN++ + +![](images/ded909b286bc74f878ec6664b8b4b7e2439a9cc8b6362a9796f840471cafdfb1.jpg) +(e) STCLoc + +![](images/0de59e620b75dcea888ed89ec8477a5427dec55fb035b934f249912d8d6a79a0.jpg) +(f) HypLiLoc + +![](images/ef932d1abea99288b4885518eb561a5c2bb936540302decdd67cdfb954aa90f7.jpg) +(g) SGLoc +Figure 3. Visualization of different methods on QEOxford. The black and red points represent the ground-truth and estimation poses respectively, and the star indicates the first frame. Compared with retrieval and APR, trajectories of SCR methods (LiSA and its baseline SGLoc) are much more consistent with the ground-truth. LiSA not only is more accurate on average, but also does not suffer from catastrophic prediction errors existing in other baselines. + +![](images/e7b53da0369b13bb1bdb9936aea54c1c08fc6aed69ecfaac66727b02568a8b85.jpg) +(h) LiSA + +
NCLT dataset
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
2012-02-127.75m, 6.49°9.84m, 6.84°7.23m, 4.88°4.97m, 3.75°4.91m, 4.43°1.71m, 3.56°1.20m, 3.08°0.97m, 2.23°
2012-02-197.47m, 5.49°8.27m, 5.16°6.31m, 3.89°3.68m, 2.65°3.25m, 3.10°1.68m, 2.69°1.20m, 3.05°0.91m, 2.09°
2012-03-316.98m, 5.67°8.94m, 5.96°6.71m, 4.32°4.35m, 3.38°3.75m, 4.04°1.52m, 2.90°1.12m, 3.28°0.87m, 2.21°
2012-05-2614.34m, 7.93°15.62m, 7.99°10.02m, 5.32°9.59m, 4.49°8.67m, 5.23°2.90m, 3.47°3.81m, 4.74°3.30m, 2.84°
Average9.14m, 6.40°10.67m, 6.49°7.57m, 4.60°5.65m, 3.57°5.15m, 4.18°1.95m, 3.16°1.83m, 3.54°1.51m, 2.34°
+ +Table 4. Quantitative results on NCLT. Mean position error (m) and mean orientation error $(^{\circ})$ for various methods are reported. Even though the semantic segmentation model [20] performs not perfectly on the NCLT dataset, LiSA still demonstrates outstanding performance, surpassing all competitors by a large margin. + +'2012-03-31'. Similar to Fig. 3, LiSA demonstrates accurate and robust localization results with much fewer catastrophic failures than other methods. The results on NCLT provide further evidence that LiSA can effectively leverage semantic information for localization tasks to boost performance. + +Speed. Inference time is a crucial metric in the localization task. Given the laser scanning rates of $20\mathrm{Hz}$ and $10\mathrm{Hz}$ for the Oxford and NCLT datasets respectively, a real-time algorithm needs to keep the inference time below 50ms and 100ms. Due to the use of distillation-based training, LiSA only uses the baseline SCR module during inference, which does not introduce additional time and memory compared to the baseline [22]. The average run time of LiSA on Oxford and NCLT is 38ms and 75ms respectively (batch size = 1), which satisfies the real-time speed requirement. + +# 4.3. Analysis + +Effect of semantic information. To further understand the behavior of LiSA, we compare the network activation with and without semantic awareness. Fig. 6 (a) illustrates the distribution of activation values on a point cloud sampled from QEOxford (shown in Fig. 5). Without semantic awareness, most activation values cluster around the center, indicating that nearly all points are treated equally. In contrast, LiSA (with semantic awareness) learns to adaptively focus on more important points and ignore distracting points, resulting in widely distributed activation values and a much higher localization accuracy (Fig. 6 (b)). In Fig. 5, we show the activation on individual points of the sampled point cloud in Fig. 6. As shown in the zoom-in views on the right, the activation of LiSA is higher on salient objects (trunks, buildings, and parked cars), which are impor + +![](images/51512a32bfd50f9b2e23130dd60d133a813d085fabdd430e828e95d1d1dff42d.jpg) +(a)PNVLAD + +![](images/a7f55b6aabb9f3a578fe1bf7a25e3237f65e4e6382eac5482187677f36ff7329.jpg) +(b) DCP + +![](images/29ce0cde35091b1875ea0d771d632e8494af14f5275fb939c8ee446ab33eef1f.jpg) +(c) PointLoc + +![](images/ee2ccd5e0a145a3255b33c5cdc09dfaa3d9442d778fb50fe8b69146e14969a8d.jpg) +(d) PosePN++ + +![](images/9c5dff6cbcdf625a04af1b001eadb1853887c54c5de274662972a02237baac24.jpg) +(e) STCLoc + +![](images/96316143149c24ff770a69f48ccfb9c481baa1e9a7a1bb73e1ea32a52684c313.jpg) +(f) HypLiLoc + +![](images/5e137a71763a5a3820fc60fd70191fb582fcdb79c47f4e81ade93c7286202f51.jpg) +(g) SGLoc +Figure 4. Visualization of different methods on NCLT. The black and red points represent the ground-truth and estimation poses respectively, and the star indicates the first frame. Similar to Fig. 3, LiSA outperforms all competitors with much fewer frequent catastrophic localization errors. + +![](images/5304af79f3d450ccd8cb42bd6d036571317a2bd9dee5be6446a6a8c17e6cae82.jpg) +(h) LiSA + +tant for localization. Dynamic objects such as pedestrians have lower activation values, making LiSA insensitive to them. In contrast, the activation value remains similar for different objects without the help of semantic knowledge. This behavior clearly shows the importance of the semantic knowledge for LiDAR localization. + +The way to use semantic information. LiSA applies knowledge distillation (KD) to provide the SCR network with semantic awareness. Here, we analyze the importance of this strategy. Specifically, we replace this strategy with 3 alternatives: 1) No semantic, where we do not use any semantic information. 2) Point filter, which, as described in Sec. 3.1, ignores the points from specific classes, with the class labels provided by a segmentation network. We use the best setup from Tab. 1 in this case. 3) Feature concatenate, which concatenates the features from the semantic segmentation and localization networks and then feeds the aggregated features into the regressor. We perform analysis on the quality-enhanced Oxford dataset. As shown in Tab. 5, though more accurate than 'no semantic', 'point filter' and 'feature concatenate' cannot encode the semantic knowledge into the SCR network, resulting in worse performance than knowledge distillation (KD). Meanwhile, these two alternatives rely on the segmentation model during inference, which introduces extra computation and memory. + +Segmentation quality. We also investigate the influence of the semantic segmentation quality on localization. As shown in Fig. 7, SphereFormer [20] has higher segmentation performance than SPVNAS [39]. Tab. 6 shows the + +
No semanticPoint filterFeature concatenateKD
15-13-06-371.83m, 1.43°1.17m, 1.86°1.11m, 1.57°0.94m, 1.10°
17-13-26-392.10m, 1.47°1.64m, 2.14°1.47m, 1.72°1.17m, 1.21°
17-14-03-001.59m, 1.39°1.00m, 2.01°0.99m, 1.60°0.84m, 1.15°
18-14-14-421.62m, 1.33°0.98m, 1.87°0.97m, 1.51°0.85m, 1.11°
Average1.79m, 1.41°1.20m, 1.97°1.14m, 1.60°0.95m, 1.14°
+ +Table 5. Different ways of combining semantic information. Methods 'point filter' and 'feature concatenate' indeed show some improvement in accuracy after incorporating semantic information, but there is a slight decline in orientation. In comparison, LiSA, which integrates semantic information using knowledge distillation, exhibits a significant advantage. + +
loss function of KDquality of semantic featuresMean Error (m/°)
1L1low (SPVNAS)1.28m/1.53°
2L1high (SphereFormer)1.00m/1.15°
3DDPMlow (SPVNAS)1.15m/1.40°
4DDPMhigh (SphereFormer)0.95m/1.14°
+ +Table 6. Impact of the segmentation quality and the KD loss on QEOxford. Positive correlations exist between the segmentation accuracy of the teacher model and the localization accuracy of LiSA. Nonetheless, LiSA outperforms the baseline SGLoc by a large margin even with the low quality segmentation teacher (SPV-NAS). Utilizing DDPM to obtain better student features also contributes to the improvement in accuracy. + +performance of LiSA with both models, which reflects the positive correlation between the segmentation performance and the localization accuracy, indicating the potential improvement of LiSA by incorporating better segmentation models in the future. Meanwhile, LiSA still outperforms + +![](images/ba070135ce6df7f166d08de1beabcf4883c7466c8c1d2d64bbe8d59ffb94092f.jpg) + +![](images/43d42ece98982e64cc93f08ac3a83247525124aaac6ec3c8b76ad55096bf6158.jpg) + +![](images/d1ab1ef2e616dc76f9419925b9df80087bbc06023e0d5957535e1767c9a475d8.jpg) + +![](images/f3e753bf4ee267f536897da181a54a7668fbc0becca896bfff320f73d7d97c7a.jpg) + +![](images/b3dcad38025ccbde5a2f849f351defbf41d29d15b7b0861aa95e731a4bb2bfee.jpg) + +![](images/a5e9620b1557673c3cc75daeba912992a6960557c2c8354ab5b26cb04930ac33.jpg) +complete point cloud + +![](images/92ba73b9a820356259c85133b1dd5aa11f5cb6ee679365594067aa0fdb4d1795.jpg) +trunk + +![](images/7dce7d170e46a6eacc19006f6e44e67c9f1abbb9766ff5dbb01e8c42b38ee503.jpg) +building + +![](images/d13ebaa8f85d8cab38ab0478e2e379d5b64750c5639e606355769e8ea7542da9.jpg) +parked car + +![](images/b85fd7b7dc9112bea70a898c9c866d068d4a42f27ae00985aa0eb2069cae000d.jpg) +pedestrian + +![](images/476e4812e5464d0ec9c71fa66997e0e94ee1b2b84727e88c4b21f22947454d77.jpg) +(a) Activation value distribution +Figure 6. Activation value distributions and localization results of LiSA (w/ semantic) and SGLoc (w/o semantic). (a): Given a point cloud sampled from QEOxford, we first aggregate features in the regressor (before heads) and normalize their activation values into [0, 255]. Without semantic awareness, most activation values of SGLoc are clustered in the center, indicating that almost all points are treated equally. (b): The localization accuracy with semantic awareness (LiSA) is much higher than the baseline (SGLoc) without semantic awareness. + +![](images/6c8a156ddb17459d71c33a50443bfab5648ed26f27b1847f04993bd2ce4855c8.jpg) +(b) Localization results + +the baseline method SGLoc by a large margin, even with the low-quality segmentation model SPVNAS. This demonstrates the robustness of our pipeline w.r.t. the choice of segmentation methods. + +Knowledge distillation loss. We further investigate the impact of different loss functions on the knowledge distillation module. As shown in Tab. 6, diffusion-based distillation performs better than using the L1 loss across different segmentation models, especially on low-quality segmentation models. + +# 5. Conclusion + +In this work, we propose LiSA, a novel scene coordinate regression framework for LiDAR localization. To the best + +![](images/38f7f556ce16bd6d1c229f53db904d1b5cd0afc9d68b461763fb3b4961ee2108.jpg) +Figure 5. The behavior of SCR with and without semantic awareness. Given a point cloud sampled from QEOxford, we show the pointwise activation value with and without using semantic information. Warmer colors denote higher activation values. Left: The activation map of the complete point cloud. Right: Zoom-in local views. Similar activation values are assigned to all points if no semantic knowledge is utilized, whereas LiSA can discriminate important points for localization and down-weight distracting points such as pedestrians. +Figure 7. Qualitative comparison of segmentation methods. SphereFormer on the right performs better as SPVNAS misclassifies more points on the ground and buildings. + +![](images/c6114273f693fc674c35e00b333d431ff3b7ff2a8d2db4598cb52a3fd0c46575.jpg) + +of our knowledge, LiSA is the first work that integrates semantic information into regression-based localization. Instead of naively relying on labels generated by segmentation models, we apply diffusion-based knowledge distillation to transfer relevant semantic knowledge from a segmentation model directly into the SCR network. This enables adaptive extraction of semantic knowledge useful for localization with minimum negative impact from noisy segmentation. At the same time, due to the distillation-based training all extra modules can be discarded after training avoiding additional computation or network parameters w.r.t. the base SCR network during inference. LiSA achieves state-of-the-art performance on challenging LiDAR localization datasets, significantly surpassing previous methods. + +Acknowledgements This work was supported by the National Natural Science Foundation of China (No.62171393), the Fundamental Research Funds for the Central Universities (No.20720220064, No.20720230033), and PDL (2022-PDL-12). + +# References + +[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. Netvlad: Cnn architecture for weakly supervised place recognition. In CVPR, pages 5297-5307, 2016. 2, 4 +[2] Dan Barnes, Matthew Gadd, Paul Murcutt, Paul Newman, and Ingmar Posner. The oxford radar robotcar dataset: A radar extension to the oxford robotcar dataset. In ICRA, pages 6433-6438. IEEE, 2020. 4, 1 +[3] Eric Brachmann and Carsten Rother. Visual camera relocalization from rgb and rgb-d images using dsac. 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Scene Coordinate Regression (SCR) has demonstrated state-of-the-art performance in this task. In SCR, a scene is represented as a neural network, which outputs the world coordinates for each point in the input point cloud. However, SCR treats all points equally during localization, ignoring the fact that not all objects are beneficial for localization. For example, dynamic objects and repeating structures often negatively impact SCR. To address this problem, we introduce LiSA, the first method that incorporates semantic awareness into SCR to boost the localization robustness and accuracy. To avoid extra computation or network parameters during inference, we distill the knowledge from a segmentation model to the original SCR network. Experiments show the superior performance of LiSA on standard LiDAR localization benchmarks compared to state-of-the-art methods. 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Introduction" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 567, + 287, + 602 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 567, + 287, + 602 + ], + "spans": [ + { + "bbox": [ + 46, + 567, + 287, + 602 + ], + "type": "text", + "content": "LiDAR localization estimates the pose of a LiDAR point cloud in a global scene map, which is a fundamental task in computer vision and robotics." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 603, + 287, + 687 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 603, + 287, + 687 + ], + "spans": [ + { + "bbox": [ + 46, + 603, + 287, + 687 + ], + "type": "text", + "content": "Learning-based regression methods [3-5, 19, 23, 36, 45] have shown state-of-the-art performance in LiDAR localization, where they memorize the specific scene in a neural network. Based on their regression objectives, these methods can be divided into Absolute Pose Regression (APR) and Scene Coordinates Regression (SCR). APR [5, 19, 36, 45] directly regresses the sensor pose. Despite" + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 307, + 212, + 427, + 339 + ], + "blocks": [ + { + "bbox": [ + 307, + 212, + 427, + 339 + ], + "lines": [ + { + "bbox": [ + 307, + 212, + 427, + 339 + ], + "spans": [ + { + "bbox": [ + 307, + 212, + 427, + 339 + ], + "type": "image", + "image_path": "4549b39663d14eff43a059370cea4aecfdfe39ba139e1544c6241e11e343ca8b.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 347, + 547, + 435 + ], + "lines": [ + { + "bbox": [ + 305, + 347, + 547, + 435 + ], + "spans": [ + { + "bbox": [ + 305, + 347, + 547, + 435 + ], + "type": "text", + "content": "Figure 1. Teaser. This work studies the problem of LiDAR localization. We propose a novel method LiSA, which equips Li-DAR localization methods with semantic awareness. We show the ground-truth and predicted trajectories on Oxford (left) and NCLT (right). Compared to the baseline method (SGLoc), LiSA achieves a much higher average localization accuracy and has much fewer catastrophic failures, without introducing extra computation or network parameters during inference." + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 427, + 213, + 545, + 338 + ], + "blocks": [ + { + "bbox": [ + 427, + 213, + 545, + 338 + ], + "lines": [ + { + "bbox": [ + 427, + 213, + 545, + 338 + ], + "spans": [ + { + "bbox": [ + 427, + 213, + 545, + 338 + ], + "type": "image", + "image_path": "eb566751a42c2ee64ecc8e71c816664c00aa39cf77aba51625604180f5b55770.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 449, + 545, + 568 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 449, + 545, + 568 + ], + "spans": [ + { + "bbox": [ + 304, + 449, + 545, + 568 + ], + "type": "text", + "content": "the compact architectures, direct pose regression without explicitly utilizing the geometric information limits the accuracy of APR. Unlike APR, SCR [3, 4, 23] regresses the coordinate of each point in the global map, which provides correspondences between the input and the global point clouds. Then RANSAC [10] is applied to the correspondences to estimate the final pose. Utilizing the geometric information more explicitly allows SCR to more effectively embed and understand the scene geometry in its model parameters, resulting in higher accuracy and better robustness." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 570, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 570, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 570, + 546, + 713 + ], + "type": "text", + "content": "SCR treats all points of the input equally. This is non-ideal for the task of localization – objects that are dynamic (e.g., pedestrians and vehicles) or repetitive (e.g., road surface and trees) intuitively should be less important than salient and static objects. Motivated by this observation, we propose LiSA, a novel method that equips SCR with semantic awareness. LiSA can robustly handle distracting objects and significantly improves the localization accuracy. To avoid introducing extra computation or network parameters during inference, we apply diffusion-based knowledge distillation during training so that we can enable semantic understanding of the original SCR network by extracting" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 35 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 58, + 693, + 127, + 703 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 693, + 127, + 703 + ], + "spans": [ + { + "bbox": [ + 58, + 693, + 127, + 703 + ], + "type": "text", + "content": "*Equal contribution." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 59, + 703, + 135, + 712 + ], + "type": "page_footnote", + "angle": 0, + "lines": [ + { + "bbox": [ + 59, + 703, + 135, + 712 + ], + "spans": [ + { + "bbox": [ + 59, + 703, + 135, + 712 + ], + "type": "text", + "content": "† Corresponding author." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15271" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 287, + 119 + ], + "type": "text", + "content": "knowledge from a teacher segmentation model, which is dropped after training. To the best of our knowledge, LiSA is the first method that effectively utilizes semantic context for LiDAR localization." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "spans": [ + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "text", + "content": "In our experiments, LiSA shows superior performance on standard LiDAR localization benchmarks compared to state-of-the-art methods. Without introducing extra computation or network parameters during inference, it achieves a relative improvement of more than " + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "inline_equation", + "content": "38\\%" + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "inline_equation", + "content": "29\\%" + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "text", + "content": " in position and orientation on the QEOxford dataset and " + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "inline_equation", + "content": "17\\%" + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "inline_equation", + "content": "34\\%" + }, + { + "bbox": [ + 46, + 121, + 287, + 205 + ], + "type": "text", + "content": " on the NCLT dataset (see Fig. 1 for an example)." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 218, + 134, + 230 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 218, + 134, + 230 + ], + "spans": [ + { + "bbox": [ + 47, + 218, + 134, + 230 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 242, + 286, + 361 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 242, + 286, + 361 + ], + "spans": [ + { + "bbox": [ + 46, + 242, + 286, + 361 + ], + "type": "text", + "content": "Conventional localization. Conventional re-localization methods can be broadly categorized into 1) retrieval-based [1, 42, 43, 51] and 2) matching-based [32, 33, 38] approaches. The former searches for frames most similar to the query frame in a pre-constructed global descriptor database, while the latter employs SfM tools to build a sparse 3D point cloud of the scene and matches features to find correspondences between the query frame and the point cloud. These methods require pre-stored map information, making them time-consuming and labor-intensive." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 365, + 286, + 628 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 365, + 286, + 628 + ], + "spans": [ + { + "bbox": [ + 46, + 365, + 286, + 628 + ], + "type": "text", + "content": "Regression-based localization. Due to the advancement of deep learning, regression-based localization methods have received much attention recently. Regression-based methods can be further separated into two categories: 1) Absolute Pose Regression (APR) and 2) Scene Coordinate Regression (SCR). APR directly regresses the 6-DoF pose of the sensor (e.g., a camera or a LiDAR scanner). PoseNet[19] and several variants [5, 18, 24, 36, 44, 45] adopt a pipeline that includes only a feature extractor and an MLP to directly output the camera pose in an end-to-end manner. However, Sattler et al.[34] pointed out that APR methods are similar to retrieval-based methods, which only learn the mapping relationship between high-dimensional abstract feature vectors and poses rather than the scene information. To alleviate this issue, SCR [3, 4] estimates the sensor pose in a different way: the neural network predicts the 3D coordinates of each pixel/3D point in the world coordinate system, which embeds the scene information more explicitly and effectively. Then, candidate correspondences are constructed using the local coordinate and the predicted world coordinate of each point. These correspondences are finally used in RANSAC [10] to obtain the sensor pose." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 630, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 630, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 630, + 286, + 713 + ], + "type": "text", + "content": "In recent years, the widespread use of LiDAR stimulated several works for regression-based LiDAR localization. LiDAR APR methods, such as PointLoc[47], PosePN++[54], and HypLiLoc[46], and the SCR method SGLoc[22], have shown impressive performance on large-scale outdoor localization. Compared to the images, point clouds exhibit robustness to changes in lighting conditions and inherently" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 545, + 144 + ], + "type": "text", + "content": "carry depth information. In this work, we show that SCR methods have not fully utilized the semantic information of the scene. We introduce a novel method with semantic awareness during localization, which significantly improves the performance without introducing extra computation or network parameters during inference." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 148, + 545, + 266 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 148, + 545, + 266 + ], + "spans": [ + { + "bbox": [ + 304, + 148, + 545, + 266 + ], + "type": "text", + "content": "Localization using auxiliary information. Semantic information has been demonstrated to be important in conventional non-regression-based methods. Retrieval-based approaches [27, 35, 37] employ semantic information to enhance the robustness of the descriptors or serve it as the posterior information to refine the predicted pose. Several matching-based methods [9, 41], attach semantic labels to the point features during matching. This modification helps mitigate the risk of erroneous matching and significantly increases their localization accuracy." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 268, + 545, + 423 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 268, + 545, + 423 + ], + "spans": [ + { + "bbox": [ + 304, + 268, + 545, + 423 + ], + "type": "text", + "content": "Object detection has been applied to regression-based methods. For instance, AD-PoseNet[17] utilizes Mask R-CNN[12] to minimize the impact of dynamic foreground objects on scene understanding. ORGPoseNet[30] uses graph neural networks to learn the geometric position relationships of objects in the scene and gain more precise localization results. However, object detection tends to concentrate solely on foreground objects rather than the whole observation in the frame. On the contrary, semantic segmentation contains exhaustive scene geometry information and intricate details. This inspires us to explore the incorporation of semantic information to enhance the accuracy of regression-based LiDAR localization." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 304, + 427, + 545, + 607 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 427, + 545, + 607 + ], + "spans": [ + { + "bbox": [ + 304, + 427, + 545, + 607 + ], + "type": "text", + "content": "LiDAR-based semantic segmentation. LiDAR-based semantic segmentation [20, 39] aims to assign a semantic label to each point in the input LiDAR scan. Methods can generally be divided into several categories: point-based [15, 28, 29, 40], voxel-based [11, 55], projection-based [21, 25, 50], and their combination [39, 52]. Regardless of the specifics of the network architecture, they consistently expand the perception field by merging the individual point features with the coarse-grain features in the scene. In this way, the semantic segmentation networks can better understand the scene information and the characteristics of each point. In this paper, we apply a point cloud semantic segmentation model as the teacher to distill semantic knowledge to a LiDAR localization method, which effectively improves localization accuracy." + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 306, + 620, + 361, + 632 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 620, + 361, + 632 + ], + "spans": [ + { + "bbox": [ + 306, + 620, + 361, + 632 + ], + "type": "text", + "content": "3. Method" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "type": "text", + "content": "LiSA relies on scene coordinate regression (SCR) for LiDAR localization [22]. The input of SCR is a query point cloud " + }, + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{P} = \\{\\mathbf{p}_i\\}_{i=1}^N" + }, + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "type": "text", + "content": " where " + }, + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_i \\in \\mathbb{R}^3" + }, + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "type": "text", + "content": " represents a 3D point in the local coordinate frame with the LiDAR scanner at the origin. The output of SCR is a set of coordinates " + }, + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "type": "inline_equation", + "content": "\\mathcal{P}' = \\{\\mathbf{p}_{i'}'\\}_{i'=1}^{N'}" + }, + { + "bbox": [ + 304, + 641, + 545, + 715 + ], + "type": "text", + "content": " representing the location of the down-" + } + ] + } + ], + "index": 11 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15272" + } + ] + } + ], + "index": 12 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 48, + 68, + 550, + 274 + ], + "blocks": [ + { + "bbox": [ + 48, + 68, + 550, + 274 + ], + "lines": [ + { + "bbox": [ + 48, + 68, + 550, + 274 + ], + "spans": [ + { + "bbox": [ + 48, + 68, + 550, + 274 + ], + "type": "image", + "image_path": "b3fc5795239b36bd7858c4bf3a06eaa70e6581b1c9017b5fa9414c51b0d41a2d.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 283, + 547, + 340 + ], + "lines": [ + { + "bbox": [ + 46, + 283, + 547, + 340 + ], + "spans": [ + { + "bbox": [ + 46, + 283, + 547, + 340 + ], + "type": "text", + "content": "Figure 2. The pipeline of LiSA. It consists of three modules: scene coordinate regression, semantic segmentation (frozen), and knowledge distillation. In the scene coordinate regression module, the coordinate regression head in the regressor directly outputs scene coordinates " + }, + { + "bbox": [ + 46, + 283, + 547, + 340 + ], + "type": "inline_equation", + "content": "\\mathcal{P}'" + }, + { + "bbox": [ + 46, + 283, + 547, + 340 + ], + "type": "text", + "content": ", and the semantic feature regression head learns semantic segmentation features (" + }, + { + "bbox": [ + 46, + 283, + 547, + 340 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}" + }, + { + "bbox": [ + 46, + 283, + 547, + 340 + ], + "type": "text", + "content": ") from the knowledge distillation module and the semantic segmentation module. After distilling the semantic knowledge during training, both semantic segmentation and knowledge distillation modules are discarded, which ensures that no extra computation and network parameters are introduced during inference." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "spans": [ + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "text", + "content": "sampled points in world coordinates. (SCR down-samples the input to " + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "inline_equation", + "content": "N' = \\frac{N}{8}" + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "text", + "content": " points, i.e., by a factor of 8.) The world coordinate " + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i'}'" + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "text", + "content": " represents the corresponding location of " + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i'}" + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "text", + "content": " in the global point cloud " + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "inline_equation", + "content": "\\mathcal{P}^*" + }, + { + "bbox": [ + 46, + 350, + 287, + 409 + ], + "type": "text", + "content": ", which covers the complete scene of interest and is used during training." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 410, + 287, + 434 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 410, + 287, + 434 + ], + "spans": [ + { + "bbox": [ + 47, + 410, + 287, + 434 + ], + "type": "text", + "content": "SCR trains one model for each scene. The training loss is typically as follows:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 113, + 440, + 287, + 467 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 113, + 440, + 287, + 467 + ], + "spans": [ + { + "bbox": [ + 113, + 440, + 287, + 467 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {l o c} = \\frac {\\sum_ {i = 1} ^ {N ^ {\\prime}} \\left| \\mathbf {p} _ {i ^ {\\prime}} ^ {\\prime} - \\mathbf {p} _ {i ^ {\\prime}} ^ {*} \\right|}{N ^ {\\prime}}, \\tag {1}", + "image_path": "1158107bffd71bc17a0de25db2ccf29e4f1d505c78984f29703201b942bc7280.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "spans": [ + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i'}'" + }, + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_{i'}^*" + }, + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "type": "text", + "content": " are respectively the predicted and ground-truth world coordinates, " + }, + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "type": "inline_equation", + "content": "|\\cdot|" + }, + { + "bbox": [ + 46, + 473, + 287, + 496 + ], + "type": "text", + "content": " is the L1 loss." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "spans": [ + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "text", + "content": "To obtain the relative pose of " + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "text", + "content": " w.r.t. " + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\mathcal{P}^*" + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "text", + "content": " for the final localization, RANSAC is performed on the candidate correspondences constructed by " + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\mathcal{P}" + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "text", + "content": " and the predicted world coordinates " + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "inline_equation", + "content": "\\mathcal{P}'" + }, + { + "bbox": [ + 46, + 497, + 287, + 544 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 47, + 552, + 122, + 563 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 552, + 122, + 563 + ], + "spans": [ + { + "bbox": [ + 47, + 552, + 122, + 563 + ], + "type": "text", + "content": "3.1. Motivation" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 570, + 287, + 677 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 570, + 287, + 677 + ], + "spans": [ + { + "bbox": [ + 46, + 570, + 287, + 677 + ], + "type": "text", + "content": "The key idea of LiSA is to utilize semantic information to assist with localization. To motivate the importance of semantic information, we conduct a preliminary analysis where we filter out points belonging to specific classes in SCR, i.e., the filtered points do not participate in inference and training. Instead of using the ground-truth semantic labels which are unavailable in practical applications, we use labels predicted by a pre-trained state-of-the-art 3D semantic segmentation model [20]." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 677, + 287, + 714 + ], + "type": "text", + "content": "Tab. 1 shows the localization accuracy with different semantic categories on the QEOxford dataset [22]. It is clear to see that the localization performance varies significantly" + } + ] + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 308, + 347, + 545, + 421 + ], + "blocks": [ + { + "bbox": [ + 308, + 347, + 545, + 421 + ], + "lines": [ + { + "bbox": [ + 308, + 347, + 545, + 421 + ], + "spans": [ + { + "bbox": [ + 308, + 347, + 545, + 421 + ], + "type": "table", + "html": "
FilterMean Error (m/°)FilterMean Error (m/°)
all (no filter)1.79m, 1.41°all (no filter)1.79m, 1.41°
no plant1.20m, 1.97°plant only59.08m, 13.25°
no building1.39m, 2.26°building only1.63m, 1.91°
no sidewalk1.77m, 1.45°sidewalk only2.47m, 5.92°
no road2.03m, 3.42°road only1.71m, 2.59°
no transportation2.07m, 3.42°transportation only20.10m, 21.95°
", + "image_path": "73769226a3a6ecebabbc1f67061a0d403c058d217e2ee6493ed11640af82dfbb.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 429, + 547, + 495 + ], + "lines": [ + { + "bbox": [ + 304, + 429, + 547, + 495 + ], + "spans": [ + { + "bbox": [ + 304, + 429, + 547, + 495 + ], + "type": "text", + "content": "Table 1. Impact of semantic information on LiDAR localization. Filtering out objects from different classes can significantly reduce or increase the position error. However, the noise in the semantic labels makes it hard to consistently improve both rotation and translation accuracy with point filtering, which motivates the design of LiSA." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 506, + 547, + 651 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 506, + 547, + 651 + ], + "spans": [ + { + "bbox": [ + 304, + 506, + 547, + 651 + ], + "type": "text", + "content": "with different filtering strategies, e.g., without plants the position error reduces significantly. This result shows the importance of semantic information in SCR. However, due to noise in the predicted labels and the hard threshold, naive filtering does not fully utilize the semantic information – some filters improve the position accuracy while sacrificing the orientation accuracy. Moreover, segmentation models introduce significant overhead in terms of memory and computing during inference, which may be prohibitive for many practical applications. This motivates us to design LiSA, a novel framework that effectively and efficiently incorporates semantic information into SCR." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 306, + 658, + 353, + 670 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 658, + 353, + 670 + ], + "spans": [ + { + "bbox": [ + 306, + 658, + 353, + 670 + ], + "type": "text", + "content": "3.2.LiSA" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 677, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 547, + 714 + ], + "type": "text", + "content": "As shown in Fig. 2, LiSA can be divided into three modules, namely scene coordinate regression (SCR), semantic segmentation, and knowledge distillation. During training, the" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15273" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 286, + 144 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 286, + 144 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 286, + 144 + ], + "type": "text", + "content": "semantic segmentation module and the knowledge distillation module are used to transfer semantic knowledge into the SCR module. After training, only the SCR module is maintained, which can effectively utilize the transferred semantic knowledge for localization, without introducing extra computation or network parameters." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "spans": [ + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "text", + "content": "The SCR module mostly follows the architecture of SGLoc [22], which contains a multi-scale feature extractor and a regressor. To enable semantic awareness without extra computation, we add a new branch to the regressor, which is used to regress a per-point semantic feature " + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}} \\in \\mathbb{R}^{N' \\times d}" + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "text", + "content": ", where " + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "inline_equation", + "content": "N'" + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "text", + "content": " is the number of output points which is equivalent to the number of output world coordinates " + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "inline_equation", + "content": "\\mathcal{P}'" + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "text", + "content": ", and " + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "text", + "content": " is the feature dimension. The original coordinate regressor branch outputs the world coordinates " + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "inline_equation", + "content": "\\mathcal{P}'" + }, + { + "bbox": [ + 46, + 144, + 287, + 286 + ], + "type": "text", + "content": " and is supervised by the loss in Eq. (1). The semantic regressor branch is supervised by distilling knowledge from the semantic segmentation model." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "spans": [ + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "content": "The semantic segmentation module consists of a pretrained 3D semantic segmentation model with frozen network parameters during training. We take the per-point last layer feature " + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{seg}} \\in \\mathbb{R}^{N \\times d}" + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "content": " of the segmentation model, down-sample it into " + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}} \\in \\mathbb{R}^{N' \\times d}" + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "content": " so that " + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}" + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "content": " has the same dimension as " + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}" + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "content": ". To verify the robustness of LiSA, we experiment with SphereFormer [20] and SPVNAS [39] pretrained on datasets non-overlapping with any LiDAR localization dataset. We ensure " + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}" + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}" + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "content": " have the same dimension " + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "inline_equation", + "content": "d" + }, + { + "bbox": [ + 46, + 288, + 286, + 420 + ], + "type": "text", + "content": " for each feature point by adjusting the output dimension of the semantic regressor branch." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 421, + 286, + 515 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 421, + 286, + 515 + ], + "spans": [ + { + "bbox": [ + 46, + 421, + 286, + 515 + ], + "type": "text", + "content": "Knowledge distillation [13] is the standard approach for reducing network parameters or transferring knowledge across different modalities, resulting in a (lightweight) student network that preserves the capabilities of the teacher network. LiSA applies knowledge distillation to transfer the semantic knowledge from the segmentation module to the SCR module. This is achieved by optimizing the following distillation loss:" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 125, + 523, + 286, + 536 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 125, + 523, + 286, + 536 + ], + "spans": [ + { + "bbox": [ + 125, + 523, + 286, + 536 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {k d} = \\delta \\left(\\mathbf {F} _ {\\mathrm {s t u}}, \\mathbf {F} _ {\\mathrm {t e a}}\\right), \\tag {2}", + "image_path": "31ee4177aa58916785c97c70e8085ec2050382d71a7033db1c0e973787d071ff.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "spans": [ + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "inline_equation", + "content": "\\delta (\\cdot)" + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "text", + "content": " measures the difference between the features from the teacher " + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "inline_equation", + "content": "(\\mathbf{F}_{\\mathrm{tea}})" + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "text", + "content": " and the student " + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "inline_equation", + "content": "(\\mathbf{F}_{\\mathrm{stu}})" + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "text", + "content": ". Intuitively, the distillation process encourages the semantic feature " + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}" + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "text", + "content": " from SCR to be similar to " + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}" + }, + { + "bbox": [ + 46, + 543, + 286, + 613 + ], + "type": "text", + "content": ", which requires the SCR module to be able to distinguish different semantic classes. The final loss function of the entire network is:" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 131, + 622, + 286, + 634 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 131, + 622, + 286, + 634 + ], + "spans": [ + { + "bbox": [ + 131, + 622, + 286, + 634 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {l o c} + \\mathcal {L} _ {k d}. \\tag {3}", + "image_path": "55fc108c1d8253a816ddbcf8964d627d40f45622c0948edd6f36adf14d1ec8c3.jpg" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "content": "Various knowledge distillation methods can be applied to realize " + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{kd}" + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "content": ". LiSA applies the recent diffusion-based distillation [16]. Specifically, we train a diffusion model with the teacher feature " + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}" + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "content": " by gradually adding noise to " + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}" + }, + { + "bbox": [ + 46, + 641, + 286, + 713 + ], + "type": "text", + "content": " and let the diffusion model learn to predict the noise. Following the forward noise process of DDPM [14], the noisy" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 305, + 71, + 522, + 85 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 71, + 522, + 85 + ], + "spans": [ + { + "bbox": [ + 305, + 71, + 522, + 85 + ], + "type": "text", + "content": "teacher feature " + }, + { + "bbox": [ + 305, + 71, + 522, + 85 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}^{(t)}" + }, + { + "bbox": [ + 305, + 71, + 522, + 85 + ], + "type": "text", + "content": " at time step " + }, + { + "bbox": [ + 305, + 71, + 522, + 85 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 305, + 71, + 522, + 85 + ], + "type": "text", + "content": " can be obtained by:" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 313, + 93, + 545, + 110 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 313, + 93, + 545, + 110 + ], + "spans": [ + { + "bbox": [ + 313, + 93, + 545, + 110 + ], + "type": "interline_equation", + "content": "\\mathbf {F} _ {\\mathrm {t e a}} ^ {(t)} = \\sqrt {\\bar {\\alpha} ^ {(t)}} \\mathbf {F} _ {\\mathrm {t e a}} + \\sqrt {1 - \\bar {\\alpha} ^ {(t)}} \\boldsymbol {\\epsilon} ^ {(t)}, \\boldsymbol {\\epsilon} ^ {(t)} \\sim \\mathcal {N} (\\mathbf {0}, \\mathbf {I}). \\tag {4}", + "image_path": "8d317263d6906a60cac364281b57ef413389512548b78721611d0c84b04e006c.jpg" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 317, + 118, + 492, + 129 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 118, + 492, + 129 + ], + "spans": [ + { + "bbox": [ + 317, + 118, + 492, + 129 + ], + "type": "text", + "content": "The loss for training the diffusion model is" + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 362, + 139, + 545, + 154 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 362, + 139, + 545, + 154 + ], + "spans": [ + { + "bbox": [ + 362, + 139, + 545, + 154 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {d d p m} = \\left| \\left| \\sigma \\left(\\mathbf {F} _ {\\mathrm {t e a}} ^ {(t)}, t\\right) - \\boldsymbol {\\epsilon} ^ {(t)} \\right| \\right| _ {2}, \\tag {5}", + "image_path": "599cd1da10ce81cbbed43fad3105b4b5e5e0c180dc908b33b005de1b61bbcdee.jpg" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "spans": [ + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "type": "inline_equation", + "content": "\\sigma (\\mathbf{F}_{\\mathrm{tea}}^{(t)},t)" + }, + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "type": "text", + "content": " represents the predicted noise from the diffusion model given the time step " + }, + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "type": "text", + "content": " and the noisy feature input " + }, + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}^{(t)},\\epsilon^{(t)}" + }, + { + "bbox": [ + 304, + 164, + 545, + 202 + ], + "type": "text", + "content": " represents the ground-truth noise." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "spans": [ + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": "To enable the knowledge transfer between " + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}" + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}" + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": ", we consider " + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}" + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": " as the noisy version of " + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}" + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": ", and use the diffusion model to obtain a denoised version " + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}^{\\prime}" + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": " of " + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}" + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": ". Then we apply the normal knowledge distillation (L1) loss to " + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{stu}}^{\\prime}" + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "inline_equation", + "content": "\\mathbf{F}_{\\mathrm{tea}}" + }, + { + "bbox": [ + 304, + 203, + 545, + 263 + ], + "type": "text", + "content": ":" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 382, + 271, + 545, + 285 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 382, + 271, + 545, + 285 + ], + "spans": [ + { + "bbox": [ + 382, + 271, + 545, + 285 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {k d} ^ {\\prime} = \\left| \\mathbf {F} _ {\\mathrm {s t u}} ^ {\\prime} - \\mathbf {F} _ {\\mathrm {t e a}} \\right|. \\tag {6}", + "image_path": "436e6a2e2cc47f8f303f57256e4877930a6c984fafb84390587f123c59295cfe.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 318, + 293, + 432, + 304 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 318, + 293, + 432, + 304 + ], + "spans": [ + { + "bbox": [ + 318, + 293, + 432, + 304 + ], + "type": "text", + "content": "The final distillation loss is:" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 369, + 314, + 545, + 327 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 369, + 314, + 545, + 327 + ], + "spans": [ + { + "bbox": [ + 369, + 314, + 545, + 327 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {k d} = \\lambda_ {1} \\mathcal {L} _ {d d p m} + \\lambda_ {2} \\mathcal {L} _ {k d} ^ {\\prime}, \\tag {7}", + "image_path": "d249580180bfe39a127238ac5ac855334e8224f2d7cfde7d50feec186dd080bd.jpg" + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "spans": [ + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "inline_equation", + "content": "\\lambda_{1}" + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "inline_equation", + "content": "\\lambda_{2}" + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "text", + "content": " are hyper-parameters to balance the losses. Simply setting both " + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "inline_equation", + "content": "\\lambda_{1}" + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "inline_equation", + "content": "\\lambda_{2}" + }, + { + "bbox": [ + 304, + 336, + 545, + 396 + ], + "type": "text", + "content": " to 1 works well in practice. Note that we use the vanilla DDPM architecture instead of latent diffusion [31]. Hence, we do not have losses on autoencoders as in Sec. 3.2 of [16]." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 396, + 545, + 503 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 396, + 545, + 503 + ], + "spans": [ + { + "bbox": [ + 304, + 396, + 545, + 503 + ], + "type": "text", + "content": "Besides introducing no overhead to SCR (by dropping both segmentation and distillation modules after training), knowledge distillation also allows the network to more effectively utilize the imperfect output of the semantic segmentation models — we only use the semantic features to transfer the knowledge, instead of using hard filtering based on the imperfect semantic labels. Our experiments (Sec. 4.2) show that this design remarkably reduces both the position and orientation error." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 306, + 514, + 382, + 527 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 514, + 382, + 527 + ], + "spans": [ + { + "bbox": [ + 306, + 514, + 382, + 527 + ], + "type": "text", + "content": "4. Experiment" + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 306, + 533, + 356, + 547 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 533, + 356, + 547 + ], + "spans": [ + { + "bbox": [ + 306, + 533, + 356, + 547 + ], + "type": "text", + "content": "4.1. Setup" + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 304, + 555, + 545, + 674 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 555, + 545, + 674 + ], + "spans": [ + { + "bbox": [ + 304, + 555, + 545, + 674 + ], + "type": "text", + "content": "Baseline. We compare LiSA against different types of state-of-the-art methods: 1) For retrieval-based methods, we choose PNVLAD [43] which employs PointNet [28] and NetVLAD [1] to generate high-quality global descriptors. 2) For 3D matching-based methods, we choose DCP [48] which utilizes PointNet [28] and DGCNN [49] as embedding networks. 3) For " + }, + { + "bbox": [ + 304, + 555, + 545, + 674 + ], + "type": "inline_equation", + "content": "APR" + }, + { + "bbox": [ + 304, + 555, + 545, + 674 + ], + "type": "text", + "content": " methods, we choose PointLoc [47], PosePN++ [54], HyLiLoc [46] and STCLoc [53]. For SCR, SGLoc [22] is the first method of this type in LiDAR localization and it is also the most competitive baseline." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 677, + 545, + 713 + ], + "type": "text", + "content": "Dataset. Following [22], we perform evaluations on 3 public datasets, namely Oxford Radar RobotCar [2], QEOxford [22] and NCLT [6]. Oxford Radar RobotCar contains" + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15274" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "table", + "bbox": [ + 50, + 83, + 545, + 158 + ], + "blocks": [ + { + "bbox": [ + 266, + 74, + 328, + 83 + ], + "lines": [ + { + "bbox": [ + 266, + 74, + 328, + 83 + ], + "spans": [ + { + "bbox": [ + 266, + 74, + 328, + 83 + ], + "type": "text", + "content": "QEOxford dataset" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 83, + 545, + 158 + ], + "lines": [ + { + "bbox": [ + 50, + 83, + 545, + 158 + ], + "spans": [ + { + "bbox": [ + 50, + 83, + 545, + 158 + ], + "type": "table", + "html": "
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
15-13-06-3710.90m, 2.49°10.61m, 2.56°10.75m, 2.36°4.54m, 1.83°5.14m, 1.27°5.03m, 1.46°1.79m, 1.67°0.94m, 1.10°
17-13-26-3914.60m, 2.46°11.44m, 2.14°11.07m, 2.21°6.44m, 1.78°6.12m, 1.21°4.31m, 1.43°1.81m, 1.76°1.17m, 1.21°
17-14-03-0011.28m, 2.21°10.90m, 2.01°11.53m, 1.92°4.89m, 1.55°5.32m, 1.08°3.61m, 1.11°1.33m, 1.59°0.84m, 1.15°
18-14-14-429.00m, 1.90°9.51m, 2.08°9.82m, 2.07°4.64m, 1.61°4.76m, 1.19°2.61m, 1.09°1.19m, 1.39°0.85m, 1.11°
Average11.45m, 2.27°10.62m, 2.20°10.79m, 2.14°5.13m, 1.69°5.34m, 1.18°3.89m, 1.27°1.53m, 1.60°0.95m, 1.14°
", + "image_path": "66d1aa768c906c011a85345b7ffcd8db9595eea7e1628f23a41c0407b2aa9f10.jpg" + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "table_body" + } + ], + "index": 1 + }, + { + "type": "table", + "bbox": [ + 50, + 224, + 544, + 299 + ], + "blocks": [ + { + "bbox": [ + 46, + 167, + 546, + 201 + ], + "lines": [ + { + "bbox": [ + 46, + 167, + 546, + 201 + ], + "spans": [ + { + "bbox": [ + 46, + 167, + 546, + 201 + ], + "type": "text", + "content": "Table 2. Quantitative results on QEOxford. Mean position error (m) and mean orientation error " + }, + { + "bbox": [ + 46, + 167, + 546, + 201 + ], + "type": "inline_equation", + "content": "(^{\\circ})" + }, + { + "bbox": [ + 46, + 167, + 546, + 201 + ], + "type": "text", + "content": " for various methods are reported. Best performance is highlighted in bold, lower is better. LiSA outperforms all baseline methods in terms of both position and orientation accuracy." + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 271, + 215, + 322, + 224 + ], + "lines": [ + { + "bbox": [ + 271, + 215, + 322, + 224 + ], + "spans": [ + { + "bbox": [ + 271, + 215, + 322, + 224 + ], + "type": "text", + "content": "Oxford dataset" + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "table_caption" + }, + { + "bbox": [ + 50, + 224, + 544, + 299 + ], + "lines": [ + { + "bbox": [ + 50, + 224, + 544, + 299 + ], + "spans": [ + { + "bbox": [ + 50, + 224, + 544, + 299 + ], + "type": "table", + "html": "
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
15-13-06-3718.14m, 3.28°16.04m, 4.54°12.42m, 2.26°9.59m, 1.92°6.93m, 1.48°6.88m, 1.09°3.01m, 1.91°2.36m, 1.29°
17-13-26-3924.57m, 3.08°16.22m, 3.56°13.14m, 2.50°10.66m, 1.92°7.55m, 1.23°6.79m, 1.29°4.07m, 2.07°3.47m, 1.43°
17-14-03-0019.93m, 3.13°14.87m, 3.45°12.91m, 1.92°9.01m, 1.51°7.44m, 1.24°5.82m, 0.97°3.37m, 1.89°3.19m, 1.34°
18-14-14-4215.59m, 2.63°12.97m, 3.99°11.31m, 1.98°8.44m, 1.71°6.13m, 1.15°3.45m, 0.84°2.12m, 1.66°1.95m, 1.23°
Average19.56m, 3.03°15.03m, 3.89°12.45m, 2.17°9.43m, 1.77°7.01m, 1.28°5.74m, 1.05°3.14m, 1.88°2.74m, 1.32°
", + "image_path": "53848adbd532478d036175437aa092bc6b39eaac1f5d1e8a51003696dfead8af.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 46, + 307, + 546, + 352 + ], + "lines": [ + { + "bbox": [ + 46, + 307, + 546, + 352 + ], + "spans": [ + { + "bbox": [ + 46, + 307, + 546, + 352 + ], + "type": "text", + "content": "Table 3. Quantitative results on Oxford. Mean position error (m) and mean orientation error " + }, + { + "bbox": [ + 46, + 307, + 546, + 352 + ], + "type": "inline_equation", + "content": "(^{\\circ})" + }, + { + "bbox": [ + 46, + 307, + 546, + 352 + ], + "type": "text", + "content": " for various methods are reported; best performance is highlighted in bold, lower is better. LiSA significantly improves both the position and rotation accuracy of the baseline SGLoc. The ground-truth trajectory noise in the original Oxford dataset makes SCR perform slightly worse in terms of rotational accuracy compared to the best APR methods HypLiLoc. However, the positional accuracy is much higher." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "spans": [ + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "text", + "content": "32 repeated traversals along the central Oxford with diverse weather and complex traffic conditions, roughly " + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "inline_equation", + "content": "10km" + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "text", + "content": " of the trajectory length, and a " + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "inline_equation", + "content": "2km^2" + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "text", + "content": " range coverage. QEOxford is a quality-enhanced version of the Oxford dataset, with GPS/INS errors minimized by alignment techniques, which has been demonstrated to be beneficial for localization [22]. NCLT is an extensive collection of LiDAR data captured at the Michigan North Campus. It comprises 27 tracks, each approximately " + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "inline_equation", + "content": "5.5km" + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "text", + "content": " long, covering an area of " + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "inline_equation", + "content": "0.45km^2" + }, + { + "bbox": [ + 45, + 367, + 288, + 523 + ], + "type": "text", + "content": ". The dataset contains challenging scenarios such as dynamic objects, illumination variation, seasonal and weather changes, and long-term structural alterations due to ongoing construction projects." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 527, + 287, + 612 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 527, + 287, + 612 + ], + "spans": [ + { + "bbox": [ + 46, + 527, + 287, + 612 + ], + "type": "text", + "content": "Implementation. LiSA is implemented with Pytorch [26], Spconv [8] and the Minkowski Engine [7]. We conduct our experiments on a server equipped with an Intel(R) Xeon(R) Silver 4314 CPU, 256GB of RAM, and four NVIDIA RTX 3090 GPUs. During training, we employ the Adam optimizer with an initial learning rate of 0.01, weight decay of 0.95, and batch size of 100." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 47, + 622, + 132, + 634 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 622, + 132, + 634 + ], + "spans": [ + { + "bbox": [ + 47, + 622, + 132, + 634 + ], + "type": "text", + "content": "4.2. Main Results" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "text", + "content": "Results on Oxford. Tab. 2 shows the quantitative results on the quality-enhanced Oxford dataset. LiSA achieves the lowest position and orientation error at " + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "inline_equation", + "content": "0.95\\mathrm{m}" + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "inline_equation", + "content": "1.14^{\\circ}" + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "text", + "content": ", respectively. This result improves the previous state-of-the-art (SGLoc [22]) by " + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "inline_equation", + "content": "38\\%" + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "inline_equation", + "content": "29\\%" + }, + { + "bbox": [ + 46, + 641, + 288, + 715 + ], + "type": "text", + "content": " on position and orientation respectively without sacrificing the efficiency. In ad" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 367, + 546, + 498 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 367, + 546, + 498 + ], + "spans": [ + { + "bbox": [ + 304, + 367, + 546, + 498 + ], + "type": "text", + "content": "dition, it is the first time that a sub-meter accuracy can be achieved without additional backend optimization, such as pose graph optimization (PGO) [5, 22]. LiSA achieves better results with much higher efficiency than SGLoc+PGO (38ms vs 288ms); see Appendix 3 for details. Fig. 3 shows the qualitative results on trajectory 15-13-06-37. LiSA closely aligns with the ground-truth trajectory and has significantly fewer outliers, i.e., fewer catastrophic failures. The experimental results demonstrate that semantic awareness helps LiSA to understand the scene information and obtain more accurate localization results." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 503, + 545, + 588 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 503, + 545, + 588 + ], + "spans": [ + { + "bbox": [ + 304, + 503, + 545, + 588 + ], + "type": "text", + "content": "Tab. 3 reports the results on the (non-enhanced) Oxford dataset. LiSA also significantly improves over the baseline SGLoc in both position and orientation on this dataset. Although LiSA has some gaps in terms of orientation compared to the best APR method [46], it surpasses all previous methods in terms of position accuracy. We discuss this in detail in Appendix 3." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 594, + 547, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 594, + 547, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 594, + 547, + 715 + ], + "type": "text", + "content": "Results on NCLT. Tab. 4 shows the quantitative result on the NCLT dataset. Though the segmentation model used to train LiSA performs much worse on NCLT than on Oxford (see Appendix 2 for visualization of segmentation results on Oxford and NCLT), LiSA still outperforms all competitors, achieving sub-meter accuracy on 3 of the 4 trajectories. Compared to the previous state-of-the-art method, SGLoc [22], there is an improvement of " + }, + { + "bbox": [ + 304, + 594, + 547, + 715 + ], + "type": "inline_equation", + "content": "17\\%" + }, + { + "bbox": [ + 304, + 594, + 547, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 304, + 594, + 547, + 715 + ], + "type": "inline_equation", + "content": "34\\%" + }, + { + "bbox": [ + 304, + 594, + 547, + 715 + ], + "type": "text", + "content": " in these metrics. This further demonstrates the robustness of our framework. 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419, + 289 + ], + "blocks": [ + { + "bbox": [ + 298, + 198, + 419, + 289 + ], + "lines": [ + { + "bbox": [ + 298, + 198, + 419, + 289 + ], + "spans": [ + { + "bbox": [ + 298, + 198, + 419, + 289 + ], + "type": "image", + "image_path": "ef932d1abea99288b4885518eb561a5c2bb936540302decdd67cdfb954aa90f7.jpg" + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 337, + 293, + 381, + 304 + ], + "lines": [ + { + "bbox": [ + 337, + 293, + 381, + 304 + ], + "spans": [ + { + "bbox": [ + 337, + 293, + 381, + 304 + ], + "type": "text", + "content": "(g) SGLoc" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 319, + 546, + 363 + ], + "lines": [ + { + "bbox": [ + 46, + 319, + 546, + 363 + ], + "spans": [ + { + "bbox": [ + 46, + 319, + 546, + 363 + ], + "type": "text", + "content": "Figure 3. Visualization of different methods on QEOxford. The black and red points represent the ground-truth and estimation poses respectively, and the star indicates the first frame. Compared with retrieval and APR, trajectories of SCR methods (LiSA and its baseline SGLoc) are much more consistent with the ground-truth. LiSA not only is more accurate on average, but also does not suffer from catastrophic prediction errors existing in other baselines." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 421, + 198, + 543, + 289 + ], + "blocks": [ + { + "bbox": [ + 421, + 198, + 543, + 289 + ], + "lines": [ + { + "bbox": [ + 421, + 198, + 543, + 289 + ], + "spans": [ + { + "bbox": [ + 421, + 198, + 543, + 289 + ], + "type": "image", + "image_path": "e7b53da0369b13bb1bdb9936aea54c1c08fc6aed69ecfaac66727b02568a8b85.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 463, + 293, + 501, + 304 + ], + "lines": [ + { + "bbox": [ + 463, + 293, + 501, + 304 + ], + "spans": [ + { + "bbox": [ + 463, + 293, + 501, + 304 + ], + "type": "text", + "content": "(h) LiSA" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "type": "table", + "bbox": [ + 48, + 369, + 545, + 458 + ], + "blocks": [ + { + "bbox": [ + 48, + 369, + 545, + 458 + ], + "lines": [ + { + "bbox": [ + 48, + 369, + 545, + 458 + ], + "spans": [ + { + "bbox": [ + 48, + 369, + 545, + 458 + ], + "type": "table", + "html": "
NCLT dataset
MethodsRetrievalMatchingAbsolute Pose RegressionSence Coordinate Regression
PNVLADDCPPointLocPosePN++STCLocHypLiLocSGLocLiSA (ours)
2012-02-127.75m, 6.49°9.84m, 6.84°7.23m, 4.88°4.97m, 3.75°4.91m, 4.43°1.71m, 3.56°1.20m, 3.08°0.97m, 2.23°
2012-02-197.47m, 5.49°8.27m, 5.16°6.31m, 3.89°3.68m, 2.65°3.25m, 3.10°1.68m, 2.69°1.20m, 3.05°0.91m, 2.09°
2012-03-316.98m, 5.67°8.94m, 5.96°6.71m, 4.32°4.35m, 3.38°3.75m, 4.04°1.52m, 2.90°1.12m, 3.28°0.87m, 2.21°
2012-05-2614.34m, 7.93°15.62m, 7.99°10.02m, 5.32°9.59m, 4.49°8.67m, 5.23°2.90m, 3.47°3.81m, 4.74°3.30m, 2.84°
Average9.14m, 6.40°10.67m, 6.49°7.57m, 4.60°5.65m, 3.57°5.15m, 4.18°1.95m, 3.16°1.83m, 3.54°1.51m, 2.34°
", + "image_path": "5d3c17149070d3900160aca006f62135e8b5f6dc4c5dc3f16d619d31f112af4f.jpg" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "table_body" + } + ], + "index": 17 + }, + { + "bbox": [ + 46, + 466, + 546, + 500 + ], + "lines": [ + { + "bbox": [ + 46, + 466, + 546, + 500 + ], + "spans": [ + { + "bbox": [ + 46, + 466, + 546, + 500 + ], + "type": "text", + "content": "Table 4. Quantitative results on NCLT. Mean position error (m) and mean orientation error " + }, + { + "bbox": [ + 46, + 466, + 546, + 500 + ], + "type": "inline_equation", + "content": "(^{\\circ})" + }, + { + "bbox": [ + 46, + 466, + 546, + 500 + ], + "type": "text", + "content": " for various methods are reported. Even though the semantic segmentation model [20] performs not perfectly on the NCLT dataset, LiSA still demonstrates outstanding performance, surpassing all competitors by a large margin." + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 510, + 287, + 581 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 510, + 287, + 581 + ], + "spans": [ + { + "bbox": [ + 46, + 510, + 287, + 581 + ], + "type": "text", + "content": "'2012-03-31'. Similar to Fig. 3, LiSA demonstrates accurate and robust localization results with much fewer catastrophic failures than other methods. The results on NCLT provide further evidence that LiSA can effectively leverage semantic information for localization tasks to boost performance." + } + ] + } + ], + "index": 19 + }, + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "type": "text", + "content": "Speed. Inference time is a crucial metric in the localization task. Given the laser scanning rates of " + }, + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "type": "inline_equation", + "content": "20\\mathrm{Hz}" + }, + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "type": "text", + "content": " and " + }, + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "type": "inline_equation", + "content": "10\\mathrm{Hz}" + }, + { + "bbox": [ + 46, + 594, + 289, + 715 + ], + "type": "text", + "content": " for the Oxford and NCLT datasets respectively, a real-time algorithm needs to keep the inference time below 50ms and 100ms. Due to the use of distillation-based training, LiSA only uses the baseline SCR module during inference, which does not introduce additional time and memory compared to the baseline [22]. The average run time of LiSA on Oxford and NCLT is 38ms and 75ms respectively (batch size = 1), which satisfies the real-time speed requirement." + } + ] + } + ], + "index": 20 + }, + { + "bbox": [ + 306, + 510, + 368, + 522 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 510, + 368, + 522 + ], + "spans": [ + { + "bbox": [ + 306, + 510, + 368, + 522 + ], + "type": "text", + "content": "4.3. Analysis" + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 304, + 534, + 545, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 534, + 545, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 534, + 545, + 715 + ], + "type": "text", + "content": "Effect of semantic information. To further understand the behavior of LiSA, we compare the network activation with and without semantic awareness. Fig. 6 (a) illustrates the distribution of activation values on a point cloud sampled from QEOxford (shown in Fig. 5). Without semantic awareness, most activation values cluster around the center, indicating that nearly all points are treated equally. In contrast, LiSA (with semantic awareness) learns to adaptively focus on more important points and ignore distracting points, resulting in widely distributed activation values and a much higher localization accuracy (Fig. 6 (b)). In Fig. 5, we show the activation on individual points of the sampled point cloud in Fig. 6. As shown in the zoom-in views on the right, the activation of LiSA is higher on salient objects (trunks, buildings, and parked cars), which are impor" + } + ] + } + ], + "index": 22 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "15276" + } + ] + } + ], + "index": 23 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 72, + 171, + 175 + ], + "blocks": [ + { + "bbox": [ + 50, + 72, + 171, + 175 + ], + "lines": [ + { + "bbox": [ + 50, + 72, + 171, + 175 + ], + "spans": [ + { + "bbox": [ + 50, + 72, + 171, + 175 + ], + "type": "image", + "image_path": "51512a32bfd50f9b2e23130dd60d133a813d085fabdd430e828e95d1d1dff42d.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + 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305 + ], + "lines": [ + { + "bbox": [ + 86, + 294, + 135, + 305 + ], + "spans": [ + { + "bbox": [ + 86, + 294, + 135, + 305 + ], + "type": "text", + "content": "(e) STCLoc" + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "image_caption" + } + ], + "index": 8 + }, + { + "type": "image", + "bbox": [ + 173, + 200, + 294, + 290 + ], + "blocks": [ + { + "bbox": [ + 173, + 200, + 294, + 290 + ], + "lines": [ + { + "bbox": [ + 173, + 200, + 294, + 290 + ], + "spans": [ + { + "bbox": [ + 173, + 200, + 294, + 290 + ], + "type": "image", + "image_path": "96316143149c24ff770a69f48ccfb9c481baa1e9a7a1bb73e1ea32a52684c313.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 206, + 294, + 262, + 306 + ], + "lines": [ + { + "bbox": [ + 206, + 294, + 262, + 306 + ], + "spans": [ + { + "bbox": [ + 206, + 294, + 262, + 306 + ], + "type": "text", + "content": "(f) HypLiLoc" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + 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Visualization of different methods on NCLT. The black and red points represent the ground-truth and estimation poses respectively, and the star indicates the first frame. Similar to Fig. 3, LiSA outperforms all competitors with much fewer frequent catastrophic localization errors." + } + ] + } + ], + "index": 16, + "angle": 0, + "type": "image_caption" + } + ], + "index": 12 + }, + { + "type": "image", + "bbox": [ + 420, + 200, + 541, + 290 + ], + "blocks": [ + { + "bbox": [ + 420, + 200, + 541, + 290 + ], + "lines": [ + { + "bbox": [ + 420, + 200, + 541, + 290 + ], + "spans": [ + { + "bbox": [ + 420, + 200, + 541, + 290 + ], + "type": "image", + "image_path": "5304af79f3d450ccd8cb42bd6d036571317a2bd9dee5be6446a6a8c17e6cae82.jpg" + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 462, + 294, + 500, + 305 + ], + "lines": [ + { + "bbox": [ + 462, + 294, + 500, + 305 + ], + "spans": [ + { + "bbox": [ + 462, + 294, + 500, + 305 + ], + "type": "text", + "content": "(h) LiSA" + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + } + ], + "index": 14 + }, + { + "bbox": [ + 46, + 359, + 287, + 430 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 359, + 287, + 430 + ], + "spans": [ + { + "bbox": [ + 46, + 359, + 287, + 430 + ], + "type": "text", + "content": "tant for localization. Dynamic objects such as pedestrians have lower activation values, making LiSA insensitive to them. In contrast, the activation value remains similar for different objects without the help of semantic knowledge. This behavior clearly shows the importance of the semantic knowledge for LiDAR localization." + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 46, + 434, + 287, + 662 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 434, + 287, + 662 + ], + "spans": [ + { + "bbox": [ + 46, + 434, + 287, + 662 + ], + "type": "text", + "content": "The way to use semantic information. LiSA applies knowledge distillation (KD) to provide the SCR network with semantic awareness. Here, we analyze the importance of this strategy. Specifically, we replace this strategy with 3 alternatives: 1) No semantic, where we do not use any semantic information. 2) Point filter, which, as described in Sec. 3.1, ignores the points from specific classes, with the class labels provided by a segmentation network. We use the best setup from Tab. 1 in this case. 3) Feature concatenate, which concatenates the features from the semantic segmentation and localization networks and then feeds the aggregated features into the regressor. We perform analysis on the quality-enhanced Oxford dataset. As shown in Tab. 5, though more accurate than 'no semantic', 'point filter' and 'feature concatenate' cannot encode the semantic knowledge into the SCR network, resulting in worse performance than knowledge distillation (KD). Meanwhile, these two alternatives rely on the segmentation model during inference, which introduces extra computation and memory." + } + ] + } + ], + "index": 18 + }, + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 287, + 714 + ], + "type": "text", + "content": "Segmentation quality. We also investigate the influence of the semantic segmentation quality on localization. As shown in Fig. 7, SphereFormer [20] has higher segmentation performance than SPVNAS [39]. Tab. 6 shows the" + } + ] + } + ], + "index": 19 + }, + { + "type": "table", + "bbox": [ + 308, + 357, + 544, + 415 + ], + "blocks": [ + { + "bbox": [ + 308, + 357, + 544, + 415 + ], + "lines": [ + { + "bbox": [ + 308, + 357, + 544, + 415 + ], + "spans": [ + { + "bbox": [ + 308, + 357, + 544, + 415 + ], + "type": "table", + "html": "
No semanticPoint filterFeature concatenateKD
15-13-06-371.83m, 1.43°1.17m, 1.86°1.11m, 1.57°0.94m, 1.10°
17-13-26-392.10m, 1.47°1.64m, 2.14°1.47m, 1.72°1.17m, 1.21°
17-14-03-001.59m, 1.39°1.00m, 2.01°0.99m, 1.60°0.84m, 1.15°
18-14-14-421.62m, 1.33°0.98m, 1.87°0.97m, 1.51°0.85m, 1.11°
Average1.79m, 1.41°1.20m, 1.97°1.14m, 1.60°0.95m, 1.14°
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loss function of KDquality of semantic featuresMean Error (m/°)
1L1low (SPVNAS)1.28m/1.53°
2L1high (SphereFormer)1.00m/1.15°
3DDPMlow (SPVNAS)1.15m/1.40°
4DDPMhigh (SphereFormer)0.95m/1.14°
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Utilizing DDPM to obtain better student features also contributes to the improvement in accuracy." + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 305, + 653, + 546, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 653, + 546, + 713 + ], + "spans": [ + { + "bbox": [ + 305, + 653, + 546, + 713 + ], + "type": "text", + "content": "performance of LiSA with both models, which reflects the positive correlation between the segmentation performance and the localization accuracy, indicating the potential improvement of LiSA by incorporating better segmentation models in the future. 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"spans": [ + { + "bbox": [ + 69, + 409, + 161, + 418 + ], + "type": "text", + "content": "(a) Activation value distribution" + } + ] + } + ], + "index": 17, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 46, + 429, + 287, + 529 + ], + "lines": [ + { + "bbox": [ + 46, + 429, + 287, + 529 + ], + "spans": [ + { + "bbox": [ + 46, + 429, + 287, + 529 + ], + "type": "text", + "content": "Figure 6. Activation value distributions and localization results of LiSA (w/ semantic) and SGLoc (w/o semantic). (a): Given a point cloud sampled from QEOxford, we first aggregate features in the regressor (before heads) and normalize their activation values into [0, 255]. Without semantic awareness, most activation values of SGLoc are clustered in the center, indicating that almost all points are treated equally. (b): The localization accuracy with semantic awareness (LiSA) is much higher than the baseline (SGLoc) without semantic awareness." + } + ] + } + ], + "index": 20, + "angle": 0, + "type": "image_caption" + } + ], + "index": 16 + }, + { + "type": "image", + "bbox": [ + 183, + 310, + 284, + 407 + ], + "blocks": [ + { + "bbox": [ + 183, + 310, + 284, + 407 + ], + "lines": [ + { + "bbox": [ + 183, + 310, + 284, + 407 + ], + "spans": [ + { + "bbox": [ + 183, + 310, + 284, + 407 + ], + "type": "image", + "image_path": "6c8a156ddb17459d71c33a50443bfab5648ed26f27b1847f04993bd2ce4855c8.jpg" + } + ] + } + ], + "index": 18, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 204, + 409, + 271, + 418 + ], + "lines": [ + { + "bbox": [ + 204, + 409, + 271, + 418 + ], + "spans": [ + { + "bbox": [ + 204, + 409, + 271, + 418 + ], + "type": "text", + "content": "(b) Localization results" + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + } + ], + "index": 18 + }, + { + "bbox": [ + 46, + 536, + 287, + 584 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 536, + 287, + 584 + ], + "spans": [ + { + "bbox": [ + 46, + 536, + 287, + 584 + ], + "type": "text", + "content": "the baseline method SGLoc by a large margin, even with the low-quality segmentation model SPVNAS. This demonstrates the robustness of our pipeline w.r.t. the choice of segmentation methods." + } + ] + } + ], + "index": 21 + }, + { + "bbox": [ + 46, + 586, + 286, + 658 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 586, + 286, + 658 + ], + "spans": [ + { + "bbox": [ + 46, + 586, + 286, + 658 + ], + "type": "text", + "content": "Knowledge distillation loss. We further investigate the impact of different loss functions on the knowledge distillation module. As shown in Tab. 6, diffusion-based distillation performs better than using the L1 loss across different segmentation models, especially on low-quality segmentation models." + } + ] + } + ], + "index": 22 + }, + { + "bbox": [ + 47, + 669, + 119, + 681 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 669, + 119, + 681 + ], + "spans": [ + { + "bbox": [ + 47, + 669, + 119, + 681 + ], + "type": "text", + "content": "5. Conclusion" + } + ] + } + ], + "index": 23 + }, + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 713 + ], + "type": "text", + "content": "In this work, we propose LiSA, a novel scene coordinate regression framework for LiDAR localization. To the best" + } + ] + } + ], + "index": 24 + }, + { + "type": "image", + "bbox": [ + 308, + 307, + 427, + 410 + ], + "blocks": [ + { + "bbox": [ + 46, + 254, + 547, + 299 + ], + "lines": [ + { + "bbox": [ + 46, + 254, + 547, + 299 + ], + "spans": [ + { + "bbox": [ + 46, + 254, + 547, + 299 + ], + "type": "text", + "content": "Figure 5. The behavior of SCR with and without semantic awareness. Given a point cloud sampled from QEOxford, we show the pointwise activation value with and without using semantic information. Warmer colors denote higher activation values. Left: The activation map of the complete point cloud. Right: Zoom-in local views. Similar activation values are assigned to all points if no semantic knowledge is utilized, whereas LiSA can discriminate important points for localization and down-weight distracting points such as pedestrians." + } + ] + } + ], + "index": 15, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 308, + 307, + 427, + 410 + ], + "lines": [ + { + "bbox": [ + 308, + 307, + 427, + 410 + ], + "spans": [ + { + "bbox": [ + 308, + 307, + 427, + 410 + ], + "type": "image", + "image_path": "38f7f556ce16bd6d1c229f53db904d1b5cd0afc9d68b461763fb3b4961ee2108.jpg" + } + ] + } + ], + "index": 25, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 419, + 545, + 453 + ], + "lines": [ + { + "bbox": [ + 305, + 419, + 545, + 453 + ], + "spans": [ + { + "bbox": [ + 305, + 419, + 545, + 453 + ], + "type": "text", + "content": "Figure 7. Qualitative comparison of segmentation methods. SphereFormer on the right performs better as SPVNAS misclassifies more points on the ground and buildings." + } + ] + } + ], + "index": 27, + "angle": 0, + "type": "image_caption" + } + ], + "index": 25 + }, + { + "type": "image", + "bbox": [ + 427, + 307, + 546, + 410 + ], + "blocks": [ + { + "bbox": [ + 427, + 307, + 546, + 410 + ], + "lines": [ + { + "bbox": [ + 427, + 307, + 546, + 410 + ], + "spans": [ + { + "bbox": [ + 427, + 307, + 546, + 410 + ], + "type": "image", + "image_path": "c6114273f693fc674c35e00b333d431ff3b7ff2a8d2db4598cb52a3fd0c46575.jpg" + } + ] + } + ], + "index": 26, + "angle": 0, + "type": "image_body" + } + ], + "index": 26 + }, + { + "bbox": [ + 304, + 475, + 545, + 643 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 475, + 545, + 643 + ], + "spans": [ + { + "bbox": [ + 304, + 475, + 545, + 643 + ], + "type": "text", + "content": "of our knowledge, LiSA is the first work that integrates semantic information into regression-based localization. Instead of naively relying on labels generated by segmentation models, we apply diffusion-based knowledge distillation to transfer relevant semantic knowledge from a segmentation model directly into the SCR network. This enables adaptive extraction of semantic knowledge useful for localization with minimum negative impact from noisy segmentation. At the same time, due to the distillation-based training all extra modules can be discarded after training avoiding additional computation or network parameters w.r.t. the base SCR network during inference. LiSA achieves state-of-the-art performance on challenging LiDAR localization datasets, significantly surpassing previous methods." + } + ] + } + ], + "index": 28 + }, + { + "bbox": [ + 304, + 654, + 545, + 712 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 654, + 545, + 712 + ], + "spans": [ + { + "bbox": [ + 304, + 654, + 545, + 712 + ], + "type": "text", + "content": "Acknowledgements This work was supported by the National Natural Science Foundation of China (No.62171393), the Fundamental Research Funds for the Central Universities (No.20720220064, No.20720230033), and PDL (2022-PDL-12)." + } + ] + } + ], + "index": 29 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "15278" + } + ] + } + ], + "index": 30 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 7 + }, + { + "para_blocks": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "spans": [ + { + "bbox": [ + 48, + 71, + 107, + 83 + ], + "type": "text", + "content": "References" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 48, + 91, + 288, + 712 + ], + "type": "list", + "angle": 0, + "index": 17, + "blocks": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "ref_text", + "angle": 0, + "lines": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "spans": [ + { + "bbox": [ + 53, + 91, + 287, + 134 + ], + "type": "text", + "content": "[1] Relja Arandjelovic, Petr Gronat, Akihiko Torii, Tomas Pa-jdla, and Josef Sivic. 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CVPR, 2021. 2" + } + ] + } + ], + "index": 25 + } + ], + "sub_type": "ref_text" + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "15280" + } + ] + } + ], + "index": 27 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 9 + } + ], + "_backend": "vlm", + "_version_name": "2.6.4" +} \ No newline at end of file diff --git a/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_content_list.json b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_content_list.json new file mode 100644 index 0000000000000000000000000000000000000000..24b031541dd769433d39edb8052f0094fdce8368 --- /dev/null +++ b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_content_list.json @@ -0,0 +1,1533 @@ +[ + { + "type": "text", + "text": "LidaRF: Delving into Lidar for Neural Radiance Field on Street Scenes", + "text_level": 1, + "bbox": [ + 125, + 130, + 843, + 151 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Shanlin Sun $^{1}$ Bingbing Zhuang $^{3}$ Ziyu Jiang $^{3}$ Buyu Liu $^{3}$ Xiaohui Xie $^{1}$ Manmohan Chandraker $^{2,3}$", + "bbox": [ + 233, + 179, + 733, + 215 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1University of California, Irvine 2University of California, San Diego 3NEC Labs America", + "bbox": [ + 117, + 219, + 849, + 238 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Abstract", + "text_level": 1, + "bbox": [ + 233, + 273, + 312, + 287 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Photorealistic simulation plays a crucial role in applications such as autonomous driving, where advances in neural radiance fields (NeRFs) may allow better scalability through the automatic creation of digital 3D assets. However, reconstruction quality suffers on street scenes due to largely collinear camera motions and sparser samplings at higher speeds. On the other hand, the application often demands rendering from camera views that deviate from the inputs to accurately simulate behaviors like lane changes. In this paper, we propose several insights that allow a better utilization of Lidar data to improve NeRF quality on street scenes. First, our framework learns a geometric scene representation from Lidar, which are fused with the implicit grid-based representation for radiance decoding, thereby supplying stronger geometric information offered by explicit point cloud. Second, we put forth a robust occlusion-aware depth supervision scheme, which allows utilizing densified Lidar points by accumulation. Third, we generate augmented training views from Lidar points for further improvement. Our insights translate to largely improved novel view synthesis under real driving scenes.", + "bbox": [ + 75, + 304, + 473, + 622 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "1. Introduction", + "text_level": 1, + "bbox": [ + 76, + 648, + 207, + 662 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Photorealistic simulation is needed in many applications like autonomous driving, where it is hard to ensure the diversity and coverage of real data. More critically, extensive verification has to be carried out in simulated environment before road testing, in order to ensure safety. Traditional simulation pipeline typically requires graphic artists to manually create 3D assets and compose into virtual environment of interest. However, the demand on human efforts and expertise has prevented it from being scalable in practice.", + "bbox": [ + 75, + 672, + 468, + 809 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Neural Radiance Field (NeRF [22]) has recently emerged as a promising way to approach simulation. NeRF has proven an effective implicit representation of scene radiance, with remarkable abilities to capture and interpolate appearances. However, such good performance often requires dense view coverage in training data, in order for", + "bbox": [ + 75, + 810, + 470, + 901 + ], + "page_idx": 0 + }, + { + "type": "image", + "img_path": "images/508fb4bcf46dc7ace57f33491dde943a12bc13fb772416d5a7e8baf5be5af903.jpg", + "image_caption": [ + "Figure 1. Our framework leverages Lidar to a deep extent to unlock its potential for neural rendering on street scenes, leading to state-of-the-art performance in comparison to UniSim [43]." + ], + "image_footnote": [], + "bbox": [ + 504, + 276, + 888, + 532 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "sufficient constraints to learn accurately the underlying geometry, material properties and illumination. While dense view coverage is not much of a problem in controlled environments, it poses challenges on street scenes – the data collection vehicle typically drives forward along lanes at a potentially high speed, leading to sparse and nearly collinear camera paths. Besides sparsity, forward camera trajectories are well-known [31] to be challenging for 3D reconstruction as it provides much weaker multi-view geometric constraints. Furthermore, road surface is typically low-texture, further introducing ambiguity in scene reconstruction.", + "bbox": [ + 496, + 595, + 893, + 762 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "To address these challenges, and in view of the implicit representation of NeRF lacking explicit geometric constraint, our key idea lies in leveraging Lidar as an explicit complementary to NeRF. Despite Lidar being used in existing works [27, 40, 43] for street scenes, high-quality rendering remains challenging. Our work delves into Lidar (dubbed LidaRF) and reaps its benefits to a greater extent, yielding largely improved view synthesis quality as shown in Fig. 1.", + "bbox": [ + 496, + 763, + 893, + 883 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "Our contributions are three-fold. (i) Fusing Lidar en", + "bbox": [ + 517, + 885, + 893, + 900 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "CVF", + "bbox": [ + 106, + 2, + 181, + 42 + ], + "page_idx": 0 + }, + { + "type": "header", + "text": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore.", + "bbox": [ + 236, + 0, + 807, + 46 + ], + "page_idx": 0 + }, + { + "type": "page_number", + "text": "19563", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 0 + }, + { + "type": "text", + "text": "While Lidar has been applied as a natural depth supervision, involving Lidar in the NeRF input offers great potential for geometric inductive bias but remains less straightforward. To this end, we adopt the grid-based representation [24] but fuse features learned from point clouds into the grid, to inherit benefits from the explicit point cloud representation. Inspired by the success of 3D perception frameworks [21, 44], we leverage 3D sparse convolution network as an effective and efficient architecture to extract geometric features from the local and global context of Lidar point clouds. (ii) Robust occlusion-aware depth supervision. Similar to existing works [40, 43], we also apply Lidar as a source of depth supervision, but do so to a greater degree. Due to the sparsity of Lidar points limiting its utility, especially in low-texture regions, we densify Lidar points across nearby frames to generate denser depth maps. However, the depth map so obtained does not account for occlusion, yielding ghost depth supervision. Hence, we put forth a robust depth supervision scheme in a curriculum learning fashion – supervising depth from near to far field while gradually filtering out bogus depth as the NeRF trains, leading to more effective learning of depth from Lidar. (iii) Lidar-based view augmentation. Furthermore, in view of the view sparsity and limited coverage in the driving scene, we leverage Lidar to densify training views. That is, we project accumulated Lidar points to novel training views; note they could be views deviating from the driving trajectories to some extent. These views projected from Lidar are added into the pool of training data, but recall that they do not account for occlusion. However, we apply the fore-mentioned supervision scheme to address the occlusion issue, yielding improved performance.", + "bbox": [ + 76, + 90, + 472, + 574 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "While our insights are also applicable for general scenes, we focus the evaluation on street scenes in this work, which leads to significant improvement compared to prior art, both quantitatively and qualitatively. Our LidaRF also shows advantage in interesting applications such as lane changes that require greater deviation from input views.", + "bbox": [ + 76, + 575, + 470, + 665 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "In summary, our proposed insights on better incorporation of Lidar lead to significantly improved quality of NeRF in challenging street scene applications.", + "bbox": [ + 76, + 665, + 470, + 710 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "2. Related Work", + "text_level": 1, + "bbox": [ + 76, + 724, + 218, + 739 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "NeRF fundamentals. Neural radiance field (NeRF) [22] has become a widely applied scene representation thanks to its remarkable capability for photorealistic novel view synthesis. Since its advent, rapid progress has been made to increase its range of applicability. Notably, given the positional encoding in NeRF does not account for scene scale and causes aliasing when training and testing images are of different resolutions, Mip-NeRF [4] proposes to anti-alias it by casting conical frustums instead of rays, with integrated positional encoding with scale awareness. Mip-NeRF 360 [5] further extends it", + "bbox": [ + 76, + 750, + 472, + 902 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "to handle unbounded scenes by a nonlinear mapping of space for scene contraction. In view of querying large MLPs being the bottleneck for efficiency, Instant-NPG [24] proposes the grid-based scene representation stored using a hash map, with the learned features decoded into radiance by a tiny and fast MLP [23]. We build our framework on top of the successful recipes of Mip-NeRF 360 and Instant-NPG, but makes important advancement to seamlessly integrate the valuable information offered by additional Lidar sensors.", + "bbox": [ + 496, + 90, + 893, + 227 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Point-based NeRFs. In contrast to the implicit scene representation, point could is an explicit representation holding the advantage of capturing accurate scene geometry. Point cloud is also widely available, either from structure-from-motion and multi-view stereo, or directly from time-of-flight depth sensors like Kinect or Lidar. This leads to the line of research [3, 26, 42, 47] in rendering images from point clouds or surfaces. Point-NeRF [41] represents one of the pioneering works that assign image features to the point clouds, from which the radiance filed along the rendering ray is decoded by querying features from nearby points. Point2Pix [16] utilizes point encoding to render point clouds in indoor scenes to images. TriVol [15] adopts triple slim volume to encode point cloud efficiently. Pointersect [8] proposes to render point clouds by directly inferring the intersection of the ray with the underlying surface. However, these works only demonstrate results on objects or small-scale indoor scenes. Chang et al. [9] has recently extended Point-NeRF to street scenes, but the rendering remains low-resolution and incomplete due to the sparse nature of Lidar point clouds. In contrast, our LidaRF fuses Lidar encoding with high-resolution grid-based representation for feature learning, yielding results far superior to [9].", + "bbox": [ + 496, + 229, + 895, + 577 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Street scene NeRFs. The need for photorealistic simulation in autonomous driving inspires researches [12, 19, 20, 25, 28, 35, 38, 40, 43, 46] to explore NeRFs on unconstrained street scenes. Notably, UniSim [43] demonstrates the promising applicability of NeRF for closed-loop simulation of the autonomy, taking only a real driving log as input. Some works focus on handling sparse view observations [7, 49] or improving geometry of NeRF [12, 33]. Despite these efforts, high-quality rendering of street scenes remains challenging for NeRF. Our work improves NeRF by leveraging Lidar data to a greater extent, with insights on hybrid feature encoding and robust depth supervision with densified Lidar. It is worth noting that while S-NeRF [40] also densifies Lidar with a depth completion network, our strategy distinguishes itself by relying only on actual Lidar frames without additional training data, and is not affected by potential errors in the depth prediction.", + "bbox": [ + 496, + 580, + 895, + 837 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "Depth-supervised NeRFs. The vanilla NeRF does not enforce any explicit constraint on geometry, often leading to inaccurate depth or surface recovery. This inspires many works to impose depth supervision in various", + "bbox": [ + 496, + 839, + 895, + 902 + ], + "page_idx": 1 + }, + { + "type": "page_number", + "text": "19564", + "bbox": [ + 480, + 944, + 519, + 957 + ], + "page_idx": 1 + }, + { + "type": "text", + "text": "forms [11, 32, 34, 36, 42, 45]. Notably, NeRFs on street scenes [27, 40, 43] typically involve derived depth supervision from Lidar. Our work distinguishes itself by reap benefits from Lidar to a deeper extent, by Lidar aggregation while accounting for occlusions.", + "bbox": [ + 75, + 90, + 470, + 167 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "3. Preliminaries", + "text_level": 1, + "bbox": [ + 76, + 181, + 217, + 196 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Neural Radiance Field (NeRF) [22] represents a radiance field with a continuous neural network $f:(\\mathbf{x},\\mathbf{d})\\to (c,\\sigma)$ , mapping spatial location $\\mathbf{x} = (x,y,z)$ and viewing direction $\\mathbf{d} = (\\theta ,\\phi)$ to the RGB color $c$ and volumetric density $\\sigma$ at that point. The network is queried at each point along the rendering ray to estimate color and density, which are then composed into the final pixel color using the volume rendering equation [17]. NeRF is optimized through the loss function $\\mathcal{L}_{\\mathrm{rgb}}$ defined as the mean squared error between the predicted and true colors of the training RGB images.", + "bbox": [ + 75, + 207, + 468, + 358 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Nerfacto is the recommended approach within the open-source project Nerfstudio [29], integrating a variety of recipes that have proven effective for a wide range of real-world data. First, Nerfactor is capable of handling unbound scenes as required by street scenes, by applying the scene contraction strategy as in MipNeRF-360 [5]. For efficiency, it follows [5] to use proposal networks with small MLPs to consolidate the sampled locations along each ray to the regions near the first surface intersection. In terms of NeRF network architecture, it follows Instant-NGP [24] to leverage the grid-based feature representation parameterized by a hash map, which allows to decode color and density with the so-called fused MLPs, i.e. small MLPs that admits fast implementation [23].", + "bbox": [ + 75, + 359, + 472, + 570 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4. Method", + "text_level": 1, + "bbox": [ + 76, + 585, + 169, + 599 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.1. Overview", + "text_level": 1, + "bbox": [ + 76, + 609, + 187, + 625 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "We build LidaRF on top of Nerfacto, but develop several insights to integrate the use of Lidar for high-quality view synthesis on street scenes, as illustrated in Fig. 2. Our pipeline takes Lidar point clouds as input (Sec. 4.2), extracts geometric features from the point clouds, and fuses it with the hash-based feature grid to combine their complementary benefits. The hybrid features are fed to MLPs for decoding color and density, followed by standard volume rendering. In the output, we leverage denser Lidar points accumulated across frames as depth supervision while accounting for occlusion. This leads to two extra losses $\\mathcal{L}_{\\mathrm{ds}}$ (Sec. 4.3) and $\\mathcal{L}_{\\mathrm{aug}}$ (Sec. 4.4), besides the original losses from Nerfactor $\\mathcal{L}_{\\mathrm{nerfacto}}$ . All together, our loss $\\mathcal{L}$ is written as", + "bbox": [ + 75, + 633, + 472, + 832 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} = \\mathcal {L} _ {\\text {n e r f a c t o}} + \\lambda_ {1} \\cdot \\underbrace {\\mathcal {L} _ {\\mathrm {d s}}} _ {\\text {S e c . 4 . 3}} + \\lambda_ {2} \\cdot \\underbrace {\\mathcal {L} _ {\\text {a u g}}} _ {\\text {S e c . 4 . 4}}, \\tag {1}\n$$\n", + "text_format": "latex", + "bbox": [ + 163, + 847, + 468, + 882 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $\\mathcal{L}_{\\mathrm{nerfacto}} = \\mathcal{L}_{\\mathrm{rgb}} + \\lambda_3 \\cdot \\mathcal{L}_{\\mathrm{dist}} + \\lambda_4 \\cdot \\mathcal{L}_{\\mathrm{interval}}$ . (2)", + "bbox": [ + 99, + 885, + 468, + 901 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "4.2. Hybrid Representation with Lidar Encoding", + "text_level": 1, + "bbox": [ + 500, + 90, + 877, + 107 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Motivation. Lidar point clouds holds strong potential for geometric guidance that is highly valuable for NeRF. However, relying on Lidar features alone for scene representation, as done in [9], results in low-resolution rendering, due to the sparse nature of Lidar points despite temporal accumulation. In addition, Lidar does not cover the entire scene due to its limited field of view, e.g. it does not capture building surface above a certain height, yielding blank rendering in those regions as in [9]. Our framework, in contrast, fuses the Lidar features with the high-resolution spatial grid of features to leverage the strength of both, which are jointly learned for high-quality and complete scene rendering.", + "bbox": [ + 496, + 113, + 893, + 296 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Lidar feature extraction. We detail here the extraction of geometric features for each Lidar point. Referring to Fig. 2, we first aggregate Lidar point clouds from all frames of the entire sequence to construct a denser set of point clouds. We then voxelize the point clouds into a voxel grid, where the spatial position of points falling into each voxel cell are averaged, yielding a 3-dim feature for each voxel cell. Inspired by its wide success on 3D perception frameworks [21, 44], we encode the scene geometry feature with a 3D sparse UNet [10, 30] on the voxel grid, which permits learning from a more global context of the scene geometry. The 3D sparse UNet takes the voxel grid along with its 3-dim features as input and outputs neural volumetric features, consisting of n-dim feature for each occupied voxel. This yields our Lidar embeddings $P = \\{(\\mathbf{p}_i,f_i)|i = 1,\\dots,N\\}$ , where each point $i$ is located at $\\mathbf{p}_i$ and associated with a vector $f_{i}$ , which is the neural feature of the voxel cell it resides in, encoding the local and global geometry around $\\mathbf{p}_i$ .", + "bbox": [ + 496, + 297, + 895, + 570 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Query of Lidar features. For each sample point $\\mathbf{x}$ along the ray to be rendered, we query its Lidar feature if there are at least $K$ nearby Lidar points within a search radius $R$ ; otherwise, its Lidar feature is set as empty (i.e. all-zero). Specifically, we employ a Fixed Radius Nearest Neighbors (FRNN) approach [14] to search a $K$ -nearest Lidar point index set with respect to $\\mathbf{x}$ , denoted as $S_{\\mathbf{x}}^{K}$ . Different from [9] where ray sampling is predetermined prior to initiating the training process, our method conducts FRNN searching online as the distribution of the sampled points from our proposal networks shift dynamically towards concentrating on the surface as the NeRF training converges.", + "bbox": [ + 496, + 574, + 893, + 755 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "Following Point-NeRF [41], our method harnesses an MLP, $\\mathcal{F}$ , to map Lidar feature from each point to a neural scene description. For the $i$ -th point neighbor of $\\mathbf{x}$ , $\\mathcal{F}$ takes as input the Lidar feature $f_{i}$ and relative position $\\mathbf{x} - \\mathbf{p}_{i}$ , and outputs the neural scene description as", + "bbox": [ + 496, + 755, + 893, + 830 + ], + "page_idx": 2 + }, + { + "type": "equation", + "text": "\n$$\nf _ {i, \\mathbf {x}} = \\mathcal {F} \\left(\\left[ f _ {i}, \\mathbf {x} - \\mathbf {p} _ {i} \\right]\\right), \\tag {3}\n$$\n", + "text_format": "latex", + "bbox": [ + 612, + 842, + 890, + 859 + ], + "page_idx": 2 + }, + { + "type": "text", + "text": "where $[,]$ indicates concatenation. To obtain the final Lidar encoding $\\phi_L(\\mathbf{x})$ at the sampled location $\\mathbf{x}$ , we use standard", + "bbox": [ + 496, + 869, + 893, + 901 + ], + "page_idx": 2 + }, + { + "type": "page_number", + "text": "19565", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 2 + }, + { + "type": "image", + "img_path": "images/c265ed64e12b2f07c0791957c538c9991b6f97963df3ebadb45b42315ad656e6.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 120, + 89, + 849, + 202 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/5aee7ac903503bc01370fba9c4e3218c31044ed563f667b83da08515e4af7a1b.jpg", + "image_caption": [ + "LiDAR " + ], + "image_footnote": [], + "bbox": [ + 122, + 203, + 540, + 311 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/3ce6913e2f7b8adb01bd130d5255a27dcc78448698e1d73b21629649bc8d8ef6.jpg", + "image_caption": [ + "Encoding" + ], + "image_footnote": [], + "bbox": [ + 153, + 316, + 183, + 339 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/23e2889009970a258a5315167a39a4845c55e5ff69973a132e11218995ceb62c.jpg", + "image_caption": [ + "Hash", + "Encoding" + ], + "image_footnote": [], + "bbox": [ + 250, + 316, + 279, + 339 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/55978d834c151dea79c06fcd97ce5cd8509b47730bef99a6e26cb63f54f2f411.jpg", + "image_caption": [ + "Spherical", + "Harmonics" + ], + "image_footnote": [], + "bbox": [ + 346, + 316, + 379, + 339 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/6ce091aabacbc4faf8d2e2f7d9b103f2b0c0826cf56838053f120f9ec7cd8c74.jpg", + "image_caption": [ + "MID" + ], + "image_footnote": [], + "bbox": [ + 452, + 318, + 478, + 339 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/e68125d03df58224edf044326209d4c9ee54add31ce879d215bba115c0ce81d5.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 545, + 204, + 692, + 271 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/2b84d8b3689b8bd5af3c53678440a700056182df55d2b55c505719569e2219b3.jpg", + "image_caption": [ + "Original View" + ], + "image_footnote": [], + "bbox": [ + 545, + 271, + 694, + 330 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/ef2c875ed5fd1d5dc8dc85c0df84734bf85551fb9d1eb1941437857745d9ea1a.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 694, + 205, + 843, + 271 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/c9c69fbed34af21d098890ce2a0e72899f0e58cf17fd4e4c1bbe26fea5321ebf.jpg", + "image_caption": [ + "Augmented View" + ], + "image_footnote": [], + "bbox": [ + 694, + 271, + 843, + 330 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "inverse-distance weighting to aggregate the neural scene description $f_{i,\\mathbf{x}}$ from its $K$ neighboring points,", + "bbox": [ + 75, + 417, + 468, + 448 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\phi_ {L} (\\mathbf {x}) = \\left\\{ \\begin{array}{l l} \\frac {\\sum_ {i \\in S _ {\\mathbf {x}} ^ {K}} w _ {i} f _ {i , \\mathbf {x}}}{\\sum_ {i \\in S _ {\\mathbf {x}} ^ {K}} w _ {i}}, & \\text {i f} S _ {\\mathbf {x}} ^ {K} \\text {i s n o t} \\varnothing , \\\\ \\mathbf {0}, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {4}\n$$\n", + "text_format": "latex", + "bbox": [ + 130, + 455, + 468, + 505 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\nw _ {i} = \\frac {1}{\\left\\| \\mathbf {p} _ {i} - \\mathbf {x} \\right\\|}. \\tag {5}\n$$\n", + "text_format": "latex", + "bbox": [ + 122, + 507, + 468, + 540 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Feature fusion for radiance decoding. Different from [9, 41] that solely relies on point features, we concatenate the Lidar encoding $\\phi_L$ with hash encoding $\\phi_h$ [24], and apply an MLP $\\mathcal{F}_{\\alpha}$ to predict the per-sample density $\\alpha$ and density embedding $\\mathbf{h}$ . Finally, the corresponding color $\\mathbf{c}$ is predicted from the spherical harmonics encoding $SH$ of the viewing direction $\\mathbf{d}$ and density embedding $\\mathbf{h}$ , via another MLP $\\mathcal{F}_{\\mathbf{c}}$ :", + "bbox": [ + 75, + 547, + 472, + 654 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\alpha , \\mathbf {h} = \\mathcal {F} _ {\\alpha} \\left(\\left[ \\phi_ {L} (\\mathbf {x}), \\phi_ {h} (\\mathbf {x}) \\right]\\right), \\tag {6}\n$$\n", + "text_format": "latex", + "bbox": [ + 176, + 667, + 468, + 685 + ], + "page_idx": 3 + }, + { + "type": "equation", + "text": "\n$$\n\\mathbf {c} = \\mathcal {F} _ {\\mathbf {c}} ([ \\mathbf {h}, S H (\\mathbf {d}) ]). \\tag {7}\n$$\n", + "text_format": "latex", + "bbox": [ + 197, + 686, + 468, + 703 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "4.3. Robust Depth Supervision", + "text_level": 1, + "bbox": [ + 76, + 726, + 313, + 742 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Motivation. In addition to the feature encoding, we also derive depth supervision from the Lidar points by projecting them onto the image plane. However, the sparse nature of Lidar points yields limited benefits, that are not sufficient for reconstructing low-texture regions such as road surface. Here, we put forth to accumulate adjacent Lidar frames to increase density. Despite the 3D points accurately capturing the scene structure, one needs to account for inter-points occlusion when projecting them onto the image plane for depth supervision. The occlusion arises due to the increased", + "bbox": [ + 75, + 750, + 472, + 900 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/d42417409edc8e0f3941161d1021f46a5b8b788a4666435c7b92d42626bbb870.jpg", + "image_caption": [ + "Figure 2. Overview of LidaRF - it takes as input the sampled 3D positions $\\mathbf{x}$ and ray directions $\\mathbf{d}$ , and outputs corresponding density $\\alpha$ and color $\\mathbf{c}$ . It incorporates both hash encoding and LiDAR encoding using a sparse UNet. Additionally, augmented training data is generated through LiDAR projections, and the geometry prediction is trained with our proposed robust depth supervision scheme.", + "Figure 3. Illustration of the occlusion issue on the depth map projected from accumulated Lidar points. Observe that multiple layers of surface points may project to the same region on the image, yielding ghost depth points." + ], + "image_footnote": [], + "bbox": [ + 501, + 417, + 883, + 580 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "displacement between the camera and the Lidar from its adjacent frames, yielding bogus depth supervision, as illustrated in Fig. 3. This is non-trivial to handle due to the sparsity of Lidar even after accumulation, making principled graphic techniques such as z-buffering not applicable. In this work, we propose a robust supervision scheme to automatically filter out bogus depth supervision in while training NeRF.", + "bbox": [ + 496, + 667, + 893, + 775 + ], + "page_idx": 3 + }, + { + "type": "text", + "text": "Occlusion-aware robust supervision scheme. We design a curriculum training strategy such that the model initially trains with closer, more reliable depth data, which are less prone to occlusion. As training progresses, the model gradually begins to incorporate more distant depth data. Concurrently, the model develops the capacity to discard depth supervisions that are anomalously distant compared to its predictions. Formally, with the pool of all depth points de", + "bbox": [ + 496, + 779, + 895, + 902 + ], + "page_idx": 3 + }, + { + "type": "page_number", + "text": "19566", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 3 + }, + { + "type": "image", + "img_path": "images/5688e5207e26c48382066f5059221a898f0e9e4f5141d2a6c7ea397abacc2a94.jpg", + "image_caption": [ + "Figure 4. Illustration of the true probability mass and its mid-point approximation." + ], + "image_footnote": [], + "bbox": [ + 81, + 90, + 467, + 218 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "noted as $\\mathcal{D} = \\{\\mathcal{D}_1,\\mathcal{D}_2,\\dots,\\mathcal{D}_N\\}$ , and further denoting the NeRF-rendered depth corresponding to $\\mathcal{D}_i$ as $\\hat{\\mathcal{D}}_i$ , we identify the reliable subset of depth points $\\mathcal{D}_{\\mathrm{reliable}}^m$ in the $m$ -th training iteration as:", + "bbox": [ + 75, + 266, + 470, + 325 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m} = \\left\\{\\mathcal {D} _ {i} \\mid \\mathcal {D} _ {i} \\leq \\epsilon_ {t} ^ {m}, \\mathcal {D} _ {i} \\leq \\hat {\\mathcal {D}} _ {i} + \\epsilon_ {o} ^ {m}, \\mathcal {D} _ {i} \\in \\mathcal {D} \\right\\}, \\tag {8}\n$$\n", + "text_format": "latex", + "bbox": [ + 94, + 335, + 468, + 353 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\epsilon_ {t} ^ {m} = \\min \\left\\{\\alpha_ {t} \\epsilon_ {t} ^ {m - 1}, \\epsilon_ {t} \\right\\}, \\quad \\alpha_ {t} > 1, \\tag {9}\n$$\n", + "text_format": "latex", + "bbox": [ + 125, + 356, + 468, + 375 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\epsilon_ {o} ^ {m} = \\max \\left\\{\\alpha_ {o} \\epsilon_ {o} ^ {m - 1}, \\epsilon_ {o} \\right\\}, \\quad \\alpha_ {o} < 1. \\tag {10}\n$$\n", + "text_format": "latex", + "bbox": [ + 125, + 377, + 468, + 393 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "One notices that $\\mathcal{D}_{\\mathrm{reliable}}^m$ is governed by two scheduled parameters: valid depth threshold $\\epsilon_t^m$ and valid depth offset $\\epsilon_o^m$ . The $\\epsilon_t^m$ serves to filter out depth samples exceeding this threshold, thereby prioritizing nearer depth samples which are less likely to be occluded. As training progresses, $\\epsilon_t^m$ is exponentially increased at a rate of $\\alpha_t$ to involve more depth supervision from further field. Meanwhile, samples exhibiting a depth value far larger than the predicted depth $\\hat{\\mathcal{D}}_i$ are omitted, as they are likely occluded points. This is thresholded by $\\hat{\\mathcal{D}}_i + \\epsilon_o^m$ , with $\\epsilon_o^m$ decaying exponentially at a rate of $\\alpha_o$ , in tandem with the improvement of depth predictions over the course of training.", + "bbox": [ + 75, + 402, + 470, + 585 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Lidar Depth Loss For samples in $\\mathcal{D}_{\\mathrm{reliable}}^m$ , we adopt the pixel-level depth loss proposed in URF [27], written as $\\mathcal{L}_{\\mathrm{ds}} = \\mathcal{L}_{\\mathrm{depth}} + \\mathcal{L}_{\\mathrm{sight}}$ . In addition to a $L_{2}$ loss $\\mathcal{L}_{\\mathrm{depth}}$ between the rendered depth and the ground truth, a line-of-sight prior $\\mathcal{L}_{\\mathrm{sight}}$ is applied to further constrain each sampling point individually. But in contrast an approximate computation of $\\mathcal{L}_{\\mathrm{sight}}$ in NeRFstudio, we implement an exact one. Specifically, we first note that the volume rendering boils down to a weighted sum of the predicted color on sampled points along the ray (see supplementary for equations). Given the weight should ideally concentrate around surfaces, $\\mathcal{L}_{\\mathrm{sight}}$ enforces the weight distribution to resemble a Gaussian distribution $\\mathcal{N}(\\hat{\\mathcal{D}}_i,\\epsilon_n)$ centered at the ground truth depth $\\hat{\\mathcal{D}}_i$ along the rendering ray, written as", + "bbox": [ + 75, + 602, + 468, + 815 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {s i g h t}} = \\mathbb {E} _ {\\mathcal {D} _ {i} \\in \\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m}} \\left[ \\int_ {t _ {\\text {n e a r}}} ^ {t _ {\\text {f a r}}} (w (t) - \\mathcal {N} (\\hat {\\mathcal {D}} _ {i}, \\epsilon_ {n})) ^ {2} d t \\right], \\tag {11}\n$$\n", + "text_format": "latex", + "bbox": [ + 93, + 821, + 468, + 869 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $w$ indicates the weight to be integrated along the distance $t$ on the rendering ray from $t_{near}$ to $t_{far}$ . Since the", + "bbox": [ + 75, + 869, + 468, + 901 + ], + "page_idx": 4 + }, + { + "type": "table", + "img_path": "images/0bba22e80c19692de3b3f65d05ca3472a8b7046365ce7039e844fefe178db042.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodsInterpolationLane Shift
PSNR↑SSIM↑LPIPS↓FID↓@2mFID↓@3.7m
Instant-NGP24.2820.7330.408140.3173.2
Mip-NeRF 36023.6930.6910.496189.4231.1
Nerfacto27.1220.8040.268116.7151.0
UniSim26.0140.7680.342118.5141.3
LidaRF (Ours)27.2550.8120.224106.5126.0
", + "bbox": [ + 504, + 88, + 893, + 180 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Table 1. Quantitative comparisons on view synthesis with state-of-the-art NeRF variants.", + "bbox": [ + 498, + 190, + 893, + 217 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "weight $w$ is computed on discrete intervals given by point sampling in NeRF, this loss is discretized to", + "bbox": [ + 498, + 233, + 890, + 263 + ], + "page_idx": 4 + }, + { + "type": "equation", + "text": "\n$$\n\\mathcal {L} _ {\\text {s i g h t}} = \\mathbb {E} _ {\\mathcal {D} _ {i} \\in \\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m}} \\left[ \\sum_ {i} \\left(w _ {i} - \\mathcal {N} _ {i}\\right) ^ {2} \\right], \\tag {12}\n$$\n", + "text_format": "latex", + "bbox": [ + 563, + 276, + 890, + 318 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "where $\\mathcal{N}_i$ indicates the probability mass within the $i$ -th interval. Here, a possible implementation (e.g. in Nerfstudio [29]) to obtain $\\mathcal{N}_i$ is by mid-point approximation as illustrated in Fig. 4. However, we note that this approximation is unnecessary and implement differently based on cumulative distribution function (CDF) - the probability mass of a Gaussian distribution can be obtained through its tabulated CDF. We show in supplementary that our exact implementation leads to improved PSNRs.", + "bbox": [ + 496, + 325, + 893, + 460 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "4.4. Augmented View Supervision", + "text_level": 1, + "bbox": [ + 498, + 472, + 761, + 488 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "Recall that a vehicle-mounted camera generates sparse training images with limited view coverage due to its forward motion, posing challenges for NeRF reconstruction, especially when the novel views deviate from vehicle trajectory. Here, we propose to augment training data leveraging Lidar. First, we colorize the point clouds in each Lidar frame by projecting onto its synchronized camera and interpolate the image for RGB values. The colorized point clouds are accumulated as described in Sec. 4.3 and projected onto a set of synthetically augmented views, yielding synthesized images and depth maps as illustrated in Fig. 2. These augmented training views are derived from existing ones, by introducing stochastic perturbations to their camera centers, with the shifting magnitude $\\epsilon_{a} \\in \\mathcal{N}(0, \\epsilon_{a})$ . Nonetheless, such augmented data fails to account for potential occlusions as depicted in Sec. 4.3. Our model, fortified by robust depth supervision, is adept at discerning and excluding occluded Lidar points online. The augmented views are used to train NeRF similarly as the real training views, and we denote the extra loss separately as $\\mathcal{L}_{\\text{aug}}$ .", + "bbox": [ + 496, + 496, + 893, + 800 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "5. Experiments", + "text_level": 1, + "bbox": [ + 500, + 814, + 632, + 830 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "In this section, we detail our experimental setup and benchmark our method against state-of-the-art NeRF techniques, demonstrating superior photorealism. We further ablate our design choices, underscoring the effectiveness of ro", + "bbox": [ + 496, + 839, + 893, + 900 + ], + "page_idx": 4 + }, + { + "type": "page_number", + "text": "19567", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 4 + }, + { + "type": "text", + "text": "bust depth supervision, LiDAR encoding, and augmented view supervision in enhancing realism.", + "bbox": [ + 76, + 90, + 468, + 121 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.1. Experimental Setup", + "text_level": 1, + "bbox": [ + 76, + 128, + 266, + 145 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Datasets. Following [43], we rely on Pandaset [39] as the primary dataset for evaluation, using its front camera and synchronized spinning Lidar. Each scene is consisting of 80 frames captured at $10\\mathrm{Hz}$ . We leverage its sensor localization for Lidar accumulation. Since our focus is on static scenes, the dynamic vehicles are masked out during evaluation, similarly as in [9]. We also evaluate on NuScenes [6] and Argoverse2 [37] to compare with S-NeRF [40] and NeRF-LiDAR-cGAN [9], respectively.", + "bbox": [ + 75, + 152, + 470, + 287 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Baselines. On Pandaset, we compare our model against several modern implicit-based neural radiance fields methods: Instant-NGP, Mip-NeRF 360, Nerfacto and UniSim. Instant-NGP [24] adopts multi-resolution hashing encoding for compact scene representation and efficient rendering. Mip-NeRF 360 [5] adopts integrated position encoding with scene contraction for handling unbounded scenes. Nerfacto [29] combines the compact representation from Instant-NGP and proposal network from Mip-NeRF 360. UniSim [43] is the state-of-the-art simulator for street scenes, reconstructing both the static background and dynamic actors with neural feature grids. In our experiments, we mainly focus on modeling the static background.", + "bbox": [ + 75, + 292, + 470, + 488 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Implementation Details. We mask dynamic objects in RGB images using dataset bounding box annotations and an instance segmentation model [13]. Static Lidar points are isolated by omitting points within dynamic objects' 3D bounding boxes. For nearest neighbor searches, we use a CUDA-based FRNN search algorithm [1] to query $K = 6$ nearest Lidar points within a $0.3m$ radius. Our loss weights and scheduling parameters in depth training scheme are given in supplementary. Instant-NGP, Nerfacto, UniSim and our proposed LidaRF use identical size of hash grid and hidden layers in MLPs. Additional details are in the supplementary.", + "bbox": [ + 75, + 491, + 468, + 657 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.2. Novel View Synthesis Results", + "text_level": 1, + "bbox": [ + 76, + 665, + 336, + 681 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In our experiments, we assess novel view synthesis under interpolation and extrapolation settings. For interpolation setting, we randomly subsample RGB and Lidar frames, testing on every fourth frame and training on the rest. We follow common practice to report PSNR, SSIM, and LPIPS interpolation views. For extrapolation setting, following [43], we simulate new trajectories by laterally shifting them left or right by 2 or 3.7 meters (lane width of Interstate Highway standards [2]). We report FID at the perceptual level since ground-truth is unavailable,", + "bbox": [ + 75, + 688, + 468, + 838 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "As shown in Tab. 1, our method outperforms all others in every metric. While methods such as Nerfacto and UniSim show robust performance in the interpolation setting, MipNeRF 360 lags behind. The qualitative gap becomes even", + "bbox": [ + 75, + 839, + 470, + 901 + ], + "page_idx": 5 + }, + { + "type": "table", + "img_path": "images/fc72e2104a1a86c46058f9190ece9d00333a17aa794d591d15f1a237c2e87b3d.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
LdsLdsHPRdsLrobustdsφLLaugPSNR↑SSIM↑LPIPS↓FID↓ @3.7m
□□□□□□27.1220.8040.268151.0
✓□□□□□27.0160.8000.264138.2
□✓□□□□26.9460.7970.264137.7
□□✓□□□27.0000.7990.261139.1
□□□✓□□27.0900.8040.247131.7
□□□✓✓□27.2190.8100.228128.7
□□□✓✓✓27.2540.8120.223126.0
", + "bbox": [ + 504, + 90, + 890, + 207 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Table 2. Ablation study of our robust depth supervision, Lidar encoding, and training view augmentation on Pandaset.", + "bbox": [ + 498, + 218, + 890, + 246 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "more significant in extrapolation scenarios. Fig. 5 displays these qualitative differences, where our method exhibits enhanced visual realism compared to the baselines, particularly in rendering fine structures, thanks to our LiDAR encoding. This is especially notable as, even though UniSim also utilizes LiDAR depth supervision, our method more effectively renders low-texture areas like road surfaces, demonstrating the advantage of our deeper utilization of Lidar.", + "bbox": [ + 496, + 260, + 893, + 381 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "5.3. Ablation Study", + "text_level": 1, + "bbox": [ + 500, + 390, + 651, + 406 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "In our ablation study presented in Tab. 2, we evaluate the impact of three key components - robust depth supervision, Lidar encoding, and augmented view supervision. The baseline for comparison, shown in the first row of Table 2, is the Nerfacto method. We denote different depth supervision strategies as follows: $\\mathcal{L}_{ds}^{1}$ for single-frame Lidar depth supervision, $\\mathcal{L}_{ds}^{10}$ for depth map supervision using 10 adjacent Lidar frames, and $\\mathcal{L}_{ds}$ for the same but within our robust supervision scheme. As another baseline for occlusion handling, we apply hidden point removal (HPR) algorithm [18] implemented in Open3D [48] to remove occluded points as data preprocessing; the supervision after HPR is denoted as $\\mathcal{L}_{ds}^{\\mathrm{HPR}}$ . Lidar encoding is represented by $\\phi_L$ . Lastly, $\\mathcal{L}_{\\mathrm{aug}}$ signifies supervision with augmented RGB and depth data derived from Lidar projections.", + "bbox": [ + 496, + 412, + 893, + 641 + ], + "page_idx": 5 + }, + { + "type": "text", + "text": "Effects of Robust Depth Supervision. In Tab. 2, we illustrate that Lidar depth markedly improves LPIPS and FID in lane shift settings with marginal PSNR drop compared to Nerfacto. Notably, our robust supervision scheme with accumulated Lidar points further enhances all metrics. Also note the offline HPR significantly lags behind our more adaptive, NeRF-informed scheme for occlusion handling. Fig. 6 compares different Lidar depth supervision settings. Under the supervision of $\\mathcal{L}_{\\mathrm{ds}}^{1}$ , which utilizes single-frame Lidar depth maps known for their sparsity and reduced occlusions, the rendered depths exhibit high accuracy in texture-rich areas (as indicated by the yellow boxes). However, this accuracy significantly diminishes in regions with thin structures, due to a lack of abundant geometric guidance, as observed in the red boxes. Conversely, the supervision with $\\mathcal{L}_{\\mathrm{ds}}^{10}$ , involving with noisy Lidar depth maps accumulated from 10 adjacent frames, leads to rendered depths that display noticeable noise.", + "bbox": [ + 496, + 643, + 893, + 900 + ], + "page_idx": 5 + }, + { + "type": "page_number", + "text": "19568", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 5 + }, + { + "type": "image", + "img_path": "images/b84b6860bbcd5c7b5e34f7e8560089ae279738c6db738046af7b5c2b35f4099c.jpg", + "image_caption": [], + "image_footnote": [], + "bbox": [ + 99, + 78, + 861, + 579 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/f1ff4e8eb982cb263387651b75f1470b93f2c2212fc08c29065250bb28d081ab.jpg", + "image_caption": [ + "Figure 5. Qualitative Comparison on novel view synthesis from different methods. We evaluate on both the interpolation and extrapolation views, the latter of which corresponds to a lane shift. We highlight the performance gap with boxes.", + "Figure 6. Qualitative comparison between different LiDAR Depth Supervisions – With sparse depths, Nerfacto w/ $\\mathcal{L}_{\\mathrm{ds}}^i$ fails to model thin structures. With denser but noisy depths, Nerfacto w/ $\\mathcal{L}_{\\mathrm{ds}}^i$ generate ambiguous depth predictions. Our proposed schemes is robust to occlusions and able to learn delicate structures. Our proposed depth supervision scheme can learn delicate structures with noisy depth map, while the other settings both fail." + ], + "image_footnote": [], + "bbox": [ + 78, + 611, + 890, + 847 + ], + "page_idx": 6 + }, + { + "type": "page_number", + "text": "19569", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 6 + }, + { + "type": "image", + "img_path": "images/50e810f82b7a4428aaa80fc0bbd8f6bb6f2dfc04c670c4fa5a7b9613213d4d0e.jpg", + "image_caption": [ + "Figure 7. Qualitative comparison w.r.t Lidar encoding - Lidar encoding is beneficial in modelling sharp textures, e.g. power lines." + ], + "image_footnote": [], + "bbox": [ + 81, + 90, + 467, + 196 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/88224021f52d8cb4282018aa550f0b6bacf2399f701ac3f7d43ec95d95616872.jpg", + "image_caption": [ + "Figure 8. Qualitative comparison w.r.t augmented view supervision - it largely improves rendering quality on the regions which are scarcely captured in the raw training data." + ], + "image_footnote": [], + "bbox": [ + 78, + 231, + 467, + 301 + ], + "page_idx": 7 + }, + { + "type": "table", + "img_path": "images/ec118df39f8b922f03567b338d9755318d9613daba5e3ebf5182bd79c4eae831.jpg", + "table_caption": [], + "table_footnote": [], + "table_body": "
MethodsS-NeRFLidaRF (Ours)
w/o Ldsw/o φLw/o LaugFull
PSNR↑29.37730.62931.00131.13331.162
SSIM↑0.8590.8710.8730.8830.884
LPIPS↓0.3490.2780.2370.2220.211
", + "bbox": [ + 89, + 354, + 457, + 438 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Table 3. Evaluation on NuScenes with comparison to S-NeRF.", + "bbox": [ + 86, + 443, + 457, + 455 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "This is attributed to the prevalent depth ambiguities within the data. Employing our proposed $\\mathcal{L}_{ds}^{\\mathrm{robust}}$ , our methodology effectively leverages denser depth maps for the precise reconstruction of intricate structures (highlighted in red boxes), as well as excludes some occluded depths (noted in yellow boxes). See more examples in the supplementary materials.", + "bbox": [ + 75, + 483, + 468, + 575 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effects of Lidar Encoding. From Tab. 2, it is evident that Lidar encoding contributes to enhancements across all metrics. As shown in Fig. 7, Lidar encoding enables our method to produce sharper textures. This enhancement stems from our sparse convolution-based architecture, which is resilient to Lidar point noise and density variations.", + "bbox": [ + 75, + 577, + 468, + 667 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Effects of Augmented View Supervision. While the quantitative benefits of augmented view supervision, as per Tab. 2, appear modest, it consistently enhances performance in extrapolation scenarios across all test scenes. This is particularly notable in scenes where other methodologies fall short. Fig. 8 showcases an instance of this: in scenes with parking cars that are scarcely captured in the raw training data due to the rapid movement of the camera vehicle, our augmented view supervision significantly elevates the quality.", + "bbox": [ + 75, + 671, + 470, + 808 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "5.4. Results on NuScenes and Argoverse", + "text_level": 1, + "bbox": [ + 76, + 816, + 387, + 832 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "we evaluate LidaRF on the NuScenes dataset with comparison to S-NeRF, by adapting their method to using the single front camera. We present quantitative results in Tab. 3 and qualitative example in Fig. 9, both showing superior per", + "bbox": [ + 75, + 839, + 470, + 901 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/dcc382e0b0e231f28b853a3f90d02154ac1c898543e9beabae1e75370d99b9f4.jpg", + "image_caption": [ + "Figure 9. Visual Comparison with S-NeRF on NuScenes." + ], + "image_footnote": [], + "bbox": [ + 504, + 92, + 888, + 200 + ], + "page_idx": 7 + }, + { + "type": "image", + "img_path": "images/aa0d999fb4b83214be07bf0c18f8788249e7e7fc008026852cb0e993a656d2a5.jpg", + "image_caption": [ + "Figure 10. Qualitative results on Argoverse with comparison to NeRF-LiDAR-cGAN [9] that solely relies on Lidar encoding, unlike our hybrid scene representation." + ], + "image_footnote": [], + "bbox": [ + 501, + 224, + 888, + 436 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "formance from our method over S-NeRF. Ablation study results are also shown in Tab. 3, which further consolidate the efficacy of our proposed components.", + "bbox": [ + 498, + 505, + 890, + 551 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "Next, we evaluate on Argoverse dataset following the protocol in [9]. We present example qualitative comparisons in Fig. 10 while leaving more evaluations to the supplementary. As can be seen, our LidaRF achieves far superior rendering quality with high resolution. We note the [9]'s blank rendering on regions not covered by Lidar, as they solely rely on Lidar for radiance decoding. This illustrates the advantage of our framework in combining the complementary benefits from Lidar encoding and high-resolution hash grid.", + "bbox": [ + 496, + 551, + 893, + 689 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "6. Conclusion", + "text_level": 1, + "bbox": [ + 500, + 707, + 617, + 722 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "In this paper, we focus on unlocking the potential of Lidar to improve NeRF on road scenes, which remain a challenging scenario for novel view synthesis due to highly constrained camera motions. We develop insights on fusing Lidar encoding with high-resolution grid based representation to reap their complementary benefits, and further, extract more robust and extensive depth supervision from Lidar. A limitation of our work is that we currently handle static background only. We envision that the key insights developed in this paper can benefit dynamic objects as well, which remains an interesting future direction to explore.", + "bbox": [ + 496, + 734, + 893, + 900 + ], + "page_idx": 7 + }, + { + "type": "page_number", + "text": "19570", + "bbox": [ + 480, + 944, + 517, + 955 + ], + "page_idx": 7 + }, + { + "type": "text", + "text": "References", + "text_level": 1, + "bbox": [ + 78, + 89, + 173, + 104 + ], + "page_idx": 8 + }, + { + "type": "list", + "sub_type": "ref_text", + "list_items": [ + "[1] GitHub - lxxue/FRNN: Fixed Radius Nearest Neighbor Search on GPU — github.com. https://github.com/lxxue/FRNN. [Accessed 18-11-2023]. 6", + "[2] Interstate Highway standards - Wikipedia -en.wikipedia.org. https://en.wikipedia.org/wiki/Interstate_Highway_standards. [Accessed 18-11-2023]. 6", + "[3] Kara-Ali Aliev, Artem Sevastopolsky, Maria Kolos, Dmitry Ulyanov, and Victor Lempitsky. Neural point-based graphics. 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In ICCV, 2023. 2" + ], + "bbox": [ + 501, + 92, + 893, + 739 + ], + "page_idx": 9 + }, + { + "type": "page_number", + "text": "19572", + "bbox": [ + 480, + 944, + 519, + 955 + ], + "page_idx": 9 + } +] \ No newline at end of file diff --git a/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_model.json b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_model.json new file mode 100644 index 0000000000000000000000000000000000000000..3936762d6d25b691429dfa176ad732638e7a53d9 --- /dev/null +++ b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_model.json @@ -0,0 +1,2145 @@ +[ + [ + { + "type": "header", + "bbox": [ + 0.107, + 0.003, + 0.182, + 0.043 + ], + "angle": 0, + "content": "CVF" + }, + { + "type": "header", + "bbox": [ + 0.237, + 0.001, + 0.808, + 0.047 + ], + "angle": 0, + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + }, + { + "type": "title", + "bbox": [ + 0.127, + 0.131, + 0.844, + 0.152 + ], + "angle": 0, + "content": "LidaRF: Delving into Lidar for Neural Radiance Field on Street Scenes" + }, + { + "type": "text", + "bbox": [ + 0.235, + 0.18, + 0.734, + 0.216 + ], + "angle": 0, + "content": "Shanlin Sun\\(^{1}\\) Bingbing Zhuang\\(^{3}\\) Ziyu Jiang\\(^{3}\\) Buyu Liu\\(^{3}\\) Xiaohui Xie\\(^{1}\\) Manmohan Chandraker\\(^{2,3}\\)" + }, + { + "type": "text", + "bbox": [ + 0.119, + 0.22, + 0.851, + 0.239 + ], + "angle": 0, + "content": "1University of California, Irvine 2University of California, San Diego 3NEC Labs America" + }, + { + "type": "title", + "bbox": [ + 0.235, + 0.274, + 0.313, + 0.289 + ], + "angle": 0, + "content": "Abstract" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.305, + 0.474, + 0.623 + ], + "angle": 0, + "content": "Photorealistic simulation plays a crucial role in applications such as autonomous driving, where advances in neural radiance fields (NeRFs) may allow better scalability through the automatic creation of digital 3D assets. However, reconstruction quality suffers on street scenes due to largely collinear camera motions and sparser samplings at higher speeds. On the other hand, the application often demands rendering from camera views that deviate from the inputs to accurately simulate behaviors like lane changes. In this paper, we propose several insights that allow a better utilization of Lidar data to improve NeRF quality on street scenes. First, our framework learns a geometric scene representation from Lidar, which are fused with the implicit grid-based representation for radiance decoding, thereby supplying stronger geometric information offered by explicit point cloud. Second, we put forth a robust occlusion-aware depth supervision scheme, which allows utilizing densified Lidar points by accumulation. Third, we generate augmented training views from Lidar points for further improvement. Our insights translate to largely improved novel view synthesis under real driving scenes." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.649, + 0.208, + 0.664 + ], + "angle": 0, + "content": "1. Introduction" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.674, + 0.47, + 0.81 + ], + "angle": 0, + "content": "Photorealistic simulation is needed in many applications like autonomous driving, where it is hard to ensure the diversity and coverage of real data. More critically, extensive verification has to be carried out in simulated environment before road testing, in order to ensure safety. Traditional simulation pipeline typically requires graphic artists to manually create 3D assets and compose into virtual environment of interest. However, the demand on human efforts and expertise has prevented it from being scalable in practice." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.811, + 0.471, + 0.902 + ], + "angle": 0, + "content": "Neural Radiance Field (NeRF [22]) has recently emerged as a promising way to approach simulation. NeRF has proven an effective implicit representation of scene radiance, with remarkable abilities to capture and interpolate appearances. However, such good performance often requires dense view coverage in training data, in order for" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.277, + 0.889, + 0.533 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.539, + 0.895, + 0.582 + ], + "angle": 0, + "content": "Figure 1. Our framework leverages Lidar to a deep extent to unlock its potential for neural rendering on street scenes, leading to state-of-the-art performance in comparison to UniSim [43]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.597, + 0.895, + 0.763 + ], + "angle": 0, + "content": "sufficient constraints to learn accurately the underlying geometry, material properties and illumination. While dense view coverage is not much of a problem in controlled environments, it poses challenges on street scenes – the data collection vehicle typically drives forward along lanes at a potentially high speed, leading to sparse and nearly collinear camera paths. Besides sparsity, forward camera trajectories are well-known [31] to be challenging for 3D reconstruction as it provides much weaker multi-view geometric constraints. Furthermore, road surface is typically low-texture, further introducing ambiguity in scene reconstruction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.764, + 0.895, + 0.885 + ], + "angle": 0, + "content": "To address these challenges, and in view of the implicit representation of NeRF lacking explicit geometric constraint, our key idea lies in leveraging Lidar as an explicit complementary to NeRF. Despite Lidar being used in existing works [27, 40, 43] for street scenes, high-quality rendering remains challenging. Our work delves into Lidar (dubbed LidaRF) and reaps its benefits to a greater extent, yielding largely improved view synthesis quality as shown in Fig. 1." + }, + { + "type": "text", + "bbox": [ + 0.519, + 0.886, + 0.894, + 0.901 + ], + "angle": 0, + "content": "Our contributions are three-fold. (i) Fusing Lidar en" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19563" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.473, + 0.575 + ], + "angle": 0, + "content": "While Lidar has been applied as a natural depth supervision, involving Lidar in the NeRF input offers great potential for geometric inductive bias but remains less straightforward. To this end, we adopt the grid-based representation [24] but fuse features learned from point clouds into the grid, to inherit benefits from the explicit point cloud representation. Inspired by the success of 3D perception frameworks [21, 44], we leverage 3D sparse convolution network as an effective and efficient architecture to extract geometric features from the local and global context of Lidar point clouds. (ii) Robust occlusion-aware depth supervision. Similar to existing works [40, 43], we also apply Lidar as a source of depth supervision, but do so to a greater degree. Due to the sparsity of Lidar points limiting its utility, especially in low-texture regions, we densify Lidar points across nearby frames to generate denser depth maps. However, the depth map so obtained does not account for occlusion, yielding ghost depth supervision. Hence, we put forth a robust depth supervision scheme in a curriculum learning fashion – supervising depth from near to far field while gradually filtering out bogus depth as the NeRF trains, leading to more effective learning of depth from Lidar. (iii) Lidar-based view augmentation. Furthermore, in view of the view sparsity and limited coverage in the driving scene, we leverage Lidar to densify training views. That is, we project accumulated Lidar points to novel training views; note they could be views deviating from the driving trajectories to some extent. These views projected from Lidar are added into the pool of training data, but recall that they do not account for occlusion. However, we apply the fore-mentioned supervision scheme to address the occlusion issue, yielding improved performance." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.576, + 0.472, + 0.666 + ], + "angle": 0, + "content": "While our insights are also applicable for general scenes, we focus the evaluation on street scenes in this work, which leads to significant improvement compared to prior art, both quantitatively and qualitatively. Our LidaRF also shows advantage in interesting applications such as lane changes that require greater deviation from input views." + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.666, + 0.472, + 0.711 + ], + "angle": 0, + "content": "In summary, our proposed insights on better incorporation of Lidar lead to significantly improved quality of NeRF in challenging street scene applications." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.725, + 0.22, + 0.74 + ], + "angle": 0, + "content": "2. Related Work" + }, + { + "type": "text", + "bbox": [ + 0.077, + 0.75, + 0.473, + 0.903 + ], + "angle": 0, + "content": "NeRF fundamentals. Neural radiance field (NeRF) [22] has become a widely applied scene representation thanks to its remarkable capability for photorealistic novel view synthesis. Since its advent, rapid progress has been made to increase its range of applicability. Notably, given the positional encoding in NeRF does not account for scene scale and causes aliasing when training and testing images are of different resolutions, Mip-NeRF [4] proposes to anti-alias it by casting conical frustums instead of rays, with integrated positional encoding with scale awareness. Mip-NeRF 360 [5] further extends it" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.092, + 0.895, + 0.228 + ], + "angle": 0, + "content": "to handle unbounded scenes by a nonlinear mapping of space for scene contraction. In view of querying large MLPs being the bottleneck for efficiency, Instant-NPG [24] proposes the grid-based scene representation stored using a hash map, with the learned features decoded into radiance by a tiny and fast MLP [23]. We build our framework on top of the successful recipes of Mip-NeRF 360 and Instant-NPG, but makes important advancement to seamlessly integrate the valuable information offered by additional Lidar sensors." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.23, + 0.897, + 0.578 + ], + "angle": 0, + "content": "Point-based NeRFs. In contrast to the implicit scene representation, point could is an explicit representation holding the advantage of capturing accurate scene geometry. Point cloud is also widely available, either from structure-from-motion and multi-view stereo, or directly from time-of-flight depth sensors like Kinect or Lidar. This leads to the line of research [3, 26, 42, 47] in rendering images from point clouds or surfaces. Point-NeRF [41] represents one of the pioneering works that assign image features to the point clouds, from which the radiance filed along the rendering ray is decoded by querying features from nearby points. Point2Pix [16] utilizes point encoding to render point clouds in indoor scenes to images. TriVol [15] adopts triple slim volume to encode point cloud efficiently. Pointersect [8] proposes to render point clouds by directly inferring the intersection of the ray with the underlying surface. However, these works only demonstrate results on objects or small-scale indoor scenes. Chang et al. [9] has recently extended Point-NeRF to street scenes, but the rendering remains low-resolution and incomplete due to the sparse nature of Lidar point clouds. In contrast, our LidaRF fuses Lidar encoding with high-resolution grid-based representation for feature learning, yielding results far superior to [9]." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.581, + 0.897, + 0.838 + ], + "angle": 0, + "content": "Street scene NeRFs. The need for photorealistic simulation in autonomous driving inspires researches [12, 19, 20, 25, 28, 35, 38, 40, 43, 46] to explore NeRFs on unconstrained street scenes. Notably, UniSim [43] demonstrates the promising applicability of NeRF for closed-loop simulation of the autonomy, taking only a real driving log as input. Some works focus on handling sparse view observations [7, 49] or improving geometry of NeRF [12, 33]. Despite these efforts, high-quality rendering of street scenes remains challenging for NeRF. Our work improves NeRF by leveraging Lidar data to a greater extent, with insights on hybrid feature encoding and robust depth supervision with densified Lidar. It is worth noting that while S-NeRF [40] also densifies Lidar with a depth completion network, our strategy distinguishes itself by relying only on actual Lidar frames without additional training data, and is not affected by potential errors in the depth prediction." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Depth-supervised NeRFs. The vanilla NeRF does not enforce any explicit constraint on geometry, often leading to inaccurate depth or surface recovery. This inspires many works to impose depth supervision in various" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.521, + 0.958 + ], + "angle": 0, + "content": "19564" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.076, + 0.091, + 0.472, + 0.168 + ], + "angle": 0, + "content": "forms [11, 32, 34, 36, 42, 45]. Notably, NeRFs on street scenes [27, 40, 43] typically involve derived depth supervision from Lidar. Our work distinguishes itself by reap benefits from Lidar to a deeper extent, by Lidar aggregation while accounting for occlusions." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.182, + 0.218, + 0.198 + ], + "angle": 0, + "content": "3. Preliminaries" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.208, + 0.47, + 0.359 + ], + "angle": 0, + "content": "Neural Radiance Field (NeRF) [22] represents a radiance field with a continuous neural network \\( f:(\\mathbf{x},\\mathbf{d})\\to (c,\\sigma) \\), mapping spatial location \\( \\mathbf{x} = (x,y,z) \\) and viewing direction \\( \\mathbf{d} = (\\theta ,\\phi) \\) to the RGB color \\( c \\) and volumetric density \\( \\sigma \\) at that point. The network is queried at each point along the rendering ray to estimate color and density, which are then composed into the final pixel color using the volume rendering equation [17]. NeRF is optimized through the loss function \\( \\mathcal{L}_{\\mathrm{rgb}} \\) defined as the mean squared error between the predicted and true colors of the training RGB images." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.36, + 0.473, + 0.571 + ], + "angle": 0, + "content": "Nerfacto is the recommended approach within the open-source project Nerfstudio [29], integrating a variety of recipes that have proven effective for a wide range of real-world data. First, Nerfactor is capable of handling unbound scenes as required by street scenes, by applying the scene contraction strategy as in MipNeRF-360 [5]. For efficiency, it follows [5] to use proposal networks with small MLPs to consolidate the sampled locations along each ray to the regions near the first surface intersection. In terms of NeRF network architecture, it follows Instant-NGP [24] to leverage the grid-based feature representation parameterized by a hash map, which allows to decode color and density with the so-called fused MLPs, i.e. small MLPs that admits fast implementation [23]." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.587, + 0.17, + 0.601 + ], + "angle": 0, + "content": "4. Method" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.611, + 0.188, + 0.626 + ], + "angle": 0, + "content": "4.1. Overview" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.635, + 0.473, + 0.833 + ], + "angle": 0, + "content": "We build LidaRF on top of Nerfacto, but develop several insights to integrate the use of Lidar for high-quality view synthesis on street scenes, as illustrated in Fig. 2. Our pipeline takes Lidar point clouds as input (Sec. 4.2), extracts geometric features from the point clouds, and fuses it with the hash-based feature grid to combine their complementary benefits. The hybrid features are fed to MLPs for decoding color and density, followed by standard volume rendering. In the output, we leverage denser Lidar points accumulated across frames as depth supervision while accounting for occlusion. This leads to two extra losses \\(\\mathcal{L}_{\\mathrm{ds}}\\) (Sec. 4.3) and \\(\\mathcal{L}_{\\mathrm{aug}}\\) (Sec. 4.4), besides the original losses from Nerfactor \\(\\mathcal{L}_{\\mathrm{nerfacto}}\\). All together, our loss \\(\\mathcal{L}\\) is written as" + }, + { + "type": "equation", + "bbox": [ + 0.164, + 0.848, + 0.47, + 0.883 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} = \\mathcal {L} _ {\\text {n e r f a c t o}} + \\lambda_ {1} \\cdot \\underbrace {\\mathcal {L} _ {\\mathrm {d s}}} _ {\\text {S e c . 4 . 3}} + \\lambda_ {2} \\cdot \\underbrace {\\mathcal {L} _ {\\text {a u g}}} _ {\\text {S e c . 4 . 4}}, \\tag {1}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.1, + 0.886, + 0.47, + 0.902 + ], + "angle": 0, + "content": "where \\(\\mathcal{L}_{\\mathrm{nerfacto}} = \\mathcal{L}_{\\mathrm{rgb}} + \\lambda_3 \\cdot \\mathcal{L}_{\\mathrm{dist}} + \\lambda_4 \\cdot \\mathcal{L}_{\\mathrm{interval}}\\). (2)" + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.091, + 0.879, + 0.108 + ], + "angle": 0, + "content": "4.2. Hybrid Representation with Lidar Encoding" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.114, + 0.895, + 0.297 + ], + "angle": 0, + "content": "Motivation. Lidar point clouds holds strong potential for geometric guidance that is highly valuable for NeRF. However, relying on Lidar features alone for scene representation, as done in [9], results in low-resolution rendering, due to the sparse nature of Lidar points despite temporal accumulation. In addition, Lidar does not cover the entire scene due to its limited field of view, e.g. it does not capture building surface above a certain height, yielding blank rendering in those regions as in [9]. Our framework, in contrast, fuses the Lidar features with the high-resolution spatial grid of features to leverage the strength of both, which are jointly learned for high-quality and complete scene rendering." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.299, + 0.897, + 0.571 + ], + "angle": 0, + "content": "Lidar feature extraction. We detail here the extraction of geometric features for each Lidar point. Referring to Fig. 2, we first aggregate Lidar point clouds from all frames of the entire sequence to construct a denser set of point clouds. We then voxelize the point clouds into a voxel grid, where the spatial position of points falling into each voxel cell are averaged, yielding a 3-dim feature for each voxel cell. Inspired by its wide success on 3D perception frameworks [21, 44], we encode the scene geometry feature with a 3D sparse UNet [10, 30] on the voxel grid, which permits learning from a more global context of the scene geometry. The 3D sparse UNet takes the voxel grid along with its 3-dim features as input and outputs neural volumetric features, consisting of n-dim feature for each occupied voxel. This yields our Lidar embeddings \\( P = \\{(\\mathbf{p}_i,f_i)|i = 1,\\dots,N\\} \\), where each point \\( i \\) is located at \\( \\mathbf{p}_i \\) and associated with a vector \\( f_{i} \\), which is the neural feature of the voxel cell it resides in, encoding the local and global geometry around \\( \\mathbf{p}_i \\)." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.575, + 0.895, + 0.756 + ], + "angle": 0, + "content": "Query of Lidar features. For each sample point \\(\\mathbf{x}\\) along the ray to be rendered, we query its Lidar feature if there are at least \\(K\\) nearby Lidar points within a search radius \\(R\\); otherwise, its Lidar feature is set as empty (i.e. all-zero). Specifically, we employ a Fixed Radius Nearest Neighbors (FRNN) approach [14] to search a \\(K\\)-nearest Lidar point index set with respect to \\(\\mathbf{x}\\), denoted as \\(S_{\\mathbf{x}}^{K}\\). Different from [9] where ray sampling is predetermined prior to initiating the training process, our method conducts FRNN searching online as the distribution of the sampled points from our proposal networks shift dynamically towards concentrating on the surface as the NeRF training converges." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.756, + 0.895, + 0.832 + ], + "angle": 0, + "content": "Following Point-NeRF [41], our method harnesses an MLP, \\(\\mathcal{F}\\), to map Lidar feature from each point to a neural scene description. For the \\(i\\)-th point neighbor of \\(\\mathbf{x}\\), \\(\\mathcal{F}\\) takes as input the Lidar feature \\(f_{i}\\) and relative position \\(\\mathbf{x} - \\mathbf{p}_{i}\\), and outputs the neural scene description as" + }, + { + "type": "equation", + "bbox": [ + 0.614, + 0.843, + 0.892, + 0.861 + ], + "angle": 0, + "content": "\\[\nf _ {i, \\mathbf {x}} = \\mathcal {F} \\left(\\left[ f _ {i}, \\mathbf {x} - \\mathbf {p} _ {i} \\right]\\right), \\tag {3}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.871, + 0.895, + 0.902 + ], + "angle": 0, + "content": "where \\([,]\\) indicates concatenation. To obtain the final Lidar encoding \\(\\phi_L(\\mathbf{x})\\) at the sampled location \\(\\mathbf{x}\\), we use standard" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19565" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.122, + 0.09, + 0.85, + 0.203 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.123, + 0.204, + 0.542, + 0.313 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.154, + 0.318, + 0.184, + 0.34 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.188, + 0.32, + 0.216, + 0.328 + ], + "angle": 0, + "content": "LiDAR " + }, + { + "type": "image_caption", + "bbox": [ + 0.188, + 0.33, + 0.231, + 0.34 + ], + "angle": 0, + "content": "Encoding" + }, + { + "type": "image", + "bbox": [ + 0.25, + 0.318, + 0.28, + 0.34 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.284, + 0.321, + 0.308, + 0.328 + ], + "angle": 0, + "content": "Hash" + }, + { + "type": "image_caption", + "bbox": [ + 0.284, + 0.33, + 0.326, + 0.34 + ], + "angle": 0, + "content": "Encoding" + }, + { + "type": "image", + "bbox": [ + 0.347, + 0.318, + 0.38, + 0.34 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.387, + 0.321, + 0.434, + 0.329 + ], + "angle": 0, + "content": "Spherical" + }, + { + "type": "image_caption", + "bbox": [ + 0.387, + 0.33, + 0.436, + 0.34 + ], + "angle": 0, + "content": "Harmonics" + }, + { + "type": "image", + "bbox": [ + 0.453, + 0.319, + 0.479, + 0.34 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.484, + 0.321, + 0.507, + 0.33 + ], + "angle": 0, + "content": "MID" + }, + { + "type": "image", + "bbox": [ + 0.546, + 0.205, + 0.693, + 0.272 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.546, + 0.272, + 0.695, + 0.332 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.587, + 0.333, + 0.659, + 0.343 + ], + "angle": 0, + "content": "Original View" + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.206, + 0.844, + 0.272 + ], + "angle": 0, + "content": null + }, + { + "type": "image", + "bbox": [ + 0.696, + 0.272, + 0.844, + 0.332 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.724, + 0.333, + 0.816, + 0.343 + ], + "angle": 0, + "content": "Augmented View" + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.361, + 0.895, + 0.404 + ], + "angle": 0, + "content": "Figure 2. Overview of LidaRF - it takes as input the sampled 3D positions \\(\\mathbf{x}\\) and ray directions \\(\\mathbf{d}\\), and outputs corresponding density \\(\\alpha\\) and color \\(\\mathbf{c}\\). It incorporates both hash encoding and LiDAR encoding using a sparse UNet. Additionally, augmented training data is generated through LiDAR projections, and the geometry prediction is trained with our proposed robust depth supervision scheme." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.418, + 0.47, + 0.449 + ], + "angle": 0, + "content": "inverse-distance weighting to aggregate the neural scene description \\(f_{i,\\mathbf{x}}\\) from its \\(K\\) neighboring points," + }, + { + "type": "equation", + "bbox": [ + 0.132, + 0.457, + 0.47, + 0.506 + ], + "angle": 0, + "content": "\\[\n\\phi_ {L} (\\mathbf {x}) = \\left\\{ \\begin{array}{l l} \\frac {\\sum_ {i \\in S _ {\\mathbf {x}} ^ {K}} w _ {i} f _ {i , \\mathbf {x}}}{\\sum_ {i \\in S _ {\\mathbf {x}} ^ {K}} w _ {i}}, & \\text {i f} S _ {\\mathbf {x}} ^ {K} \\text {i s n o t} \\varnothing , \\\\ \\mathbf {0}, & \\text {o t h e r w i s e .} \\end{array} \\right. \\tag {4}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.124, + 0.508, + 0.47, + 0.541 + ], + "angle": 0, + "content": "\\[\nw _ {i} = \\frac {1}{\\left\\| \\mathbf {p} _ {i} - \\mathbf {x} \\right\\|}. \\tag {5}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.549, + 0.473, + 0.655 + ], + "angle": 0, + "content": "Feature fusion for radiance decoding. Different from [9, 41] that solely relies on point features, we concatenate the Lidar encoding \\(\\phi_L\\) with hash encoding \\(\\phi_h\\) [24], and apply an MLP \\(\\mathcal{F}_{\\alpha}\\) to predict the per-sample density \\(\\alpha\\) and density embedding \\(\\mathbf{h}\\). Finally, the corresponding color \\(\\mathbf{c}\\) is predicted from the spherical harmonics encoding \\(SH\\) of the viewing direction \\(\\mathbf{d}\\) and density embedding \\(\\mathbf{h}\\), via another MLP \\(\\mathcal{F}_{\\mathbf{c}}\\):" + }, + { + "type": "equation", + "bbox": [ + 0.177, + 0.668, + 0.47, + 0.686 + ], + "angle": 0, + "content": "\\[\n\\alpha , \\mathbf {h} = \\mathcal {F} _ {\\alpha} \\left(\\left[ \\phi_ {L} (\\mathbf {x}), \\phi_ {h} (\\mathbf {x}) \\right]\\right), \\tag {6}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.198, + 0.688, + 0.47, + 0.704 + ], + "angle": 0, + "content": "\\[\n\\mathbf {c} = \\mathcal {F} _ {\\mathbf {c}} ([ \\mathbf {h}, S H (\\mathbf {d}) ]). \\tag {7}\n\\]" + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.727, + 0.315, + 0.743 + ], + "angle": 0, + "content": "4.3. Robust Depth Supervision" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.75, + 0.473, + 0.901 + ], + "angle": 0, + "content": "Motivation. In addition to the feature encoding, we also derive depth supervision from the Lidar points by projecting them onto the image plane. However, the sparse nature of Lidar points yields limited benefits, that are not sufficient for reconstructing low-texture regions such as road surface. Here, we put forth to accumulate adjacent Lidar frames to increase density. Despite the 3D points accurately capturing the scene structure, one needs to account for inter-points occlusion when projecting them onto the image plane for depth supervision. The occlusion arises due to the increased" + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.419, + 0.885, + 0.582 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.596, + 0.892, + 0.652 + ], + "angle": 0, + "content": "Figure 3. Illustration of the occlusion issue on the depth map projected from accumulated Lidar points. Observe that multiple layers of surface points may project to the same region on the image, yielding ghost depth points." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.669, + 0.895, + 0.776 + ], + "angle": 0, + "content": "displacement between the camera and the Lidar from its adjacent frames, yielding bogus depth supervision, as illustrated in Fig. 3. This is non-trivial to handle due to the sparsity of Lidar even after accumulation, making principled graphic techniques such as z-buffering not applicable. In this work, we propose a robust supervision scheme to automatically filter out bogus depth supervision in while training NeRF." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.78, + 0.897, + 0.903 + ], + "angle": 0, + "content": "Occlusion-aware robust supervision scheme. We design a curriculum training strategy such that the model initially trains with closer, more reliable depth data, which are less prone to occlusion. As training progresses, the model gradually begins to incorporate more distant depth data. Concurrently, the model develops the capacity to discard depth supervisions that are anomalously distant compared to its predictions. Formally, with the pool of all depth points de" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "19566" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.092, + 0.468, + 0.219 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.226, + 0.47, + 0.254 + ], + "angle": 0, + "content": "Figure 4. Illustration of the true probability mass and its mid-point approximation." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.267, + 0.471, + 0.327 + ], + "angle": 0, + "content": "noted as \\(\\mathcal{D} = \\{\\mathcal{D}_1,\\mathcal{D}_2,\\dots,\\mathcal{D}_N\\}\\), and further denoting the NeRF-rendered depth corresponding to \\(\\mathcal{D}_i\\) as \\(\\hat{\\mathcal{D}}_i\\), we identify the reliable subset of depth points \\(\\mathcal{D}_{\\mathrm{reliable}}^m\\) in the \\(m\\)-th training iteration as:" + }, + { + "type": "equation", + "bbox": [ + 0.095, + 0.336, + 0.47, + 0.354 + ], + "angle": 0, + "content": "\\[\n\\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m} = \\left\\{\\mathcal {D} _ {i} \\mid \\mathcal {D} _ {i} \\leq \\epsilon_ {t} ^ {m}, \\mathcal {D} _ {i} \\leq \\hat {\\mathcal {D}} _ {i} + \\epsilon_ {o} ^ {m}, \\mathcal {D} _ {i} \\in \\mathcal {D} \\right\\}, \\tag {8}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.126, + 0.357, + 0.47, + 0.375 + ], + "angle": 0, + "content": "\\[\n\\epsilon_ {t} ^ {m} = \\min \\left\\{\\alpha_ {t} \\epsilon_ {t} ^ {m - 1}, \\epsilon_ {t} \\right\\}, \\quad \\alpha_ {t} > 1, \\tag {9}\n\\]" + }, + { + "type": "equation", + "bbox": [ + 0.126, + 0.378, + 0.47, + 0.395 + ], + "angle": 0, + "content": "\\[\n\\epsilon_ {o} ^ {m} = \\max \\left\\{\\alpha_ {o} \\epsilon_ {o} ^ {m - 1}, \\epsilon_ {o} \\right\\}, \\quad \\alpha_ {o} < 1. \\tag {10}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.404, + 0.471, + 0.587 + ], + "angle": 0, + "content": "One notices that \\(\\mathcal{D}_{\\mathrm{reliable}}^m\\) is governed by two scheduled parameters: valid depth threshold \\(\\epsilon_t^m\\) and valid depth offset \\(\\epsilon_o^m\\). The \\(\\epsilon_t^m\\) serves to filter out depth samples exceeding this threshold, thereby prioritizing nearer depth samples which are less likely to be occluded. As training progresses, \\(\\epsilon_t^m\\) is exponentially increased at a rate of \\(\\alpha_t\\) to involve more depth supervision from further field. Meanwhile, samples exhibiting a depth value far larger than the predicted depth \\(\\hat{\\mathcal{D}}_i\\) are omitted, as they are likely occluded points. This is thresholded by \\(\\hat{\\mathcal{D}}_i + \\epsilon_o^m\\), with \\(\\epsilon_o^m\\) decaying exponentially at a rate of \\(\\alpha_o\\), in tandem with the improvement of depth predictions over the course of training." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.603, + 0.47, + 0.816 + ], + "angle": 0, + "content": "Lidar Depth Loss For samples in \\(\\mathcal{D}_{\\mathrm{reliable}}^m\\), we adopt the pixel-level depth loss proposed in URF [27], written as \\(\\mathcal{L}_{\\mathrm{ds}} = \\mathcal{L}_{\\mathrm{depth}} + \\mathcal{L}_{\\mathrm{sight}}\\). In addition to a \\(L_{2}\\) loss \\(\\mathcal{L}_{\\mathrm{depth}}\\) between the rendered depth and the ground truth, a line-of-sight prior \\(\\mathcal{L}_{\\mathrm{sight}}\\) is applied to further constrain each sampling point individually. But in contrast an approximate computation of \\(\\mathcal{L}_{\\mathrm{sight}}\\) in NeRFstudio, we implement an exact one. Specifically, we first note that the volume rendering boils down to a weighted sum of the predicted color on sampled points along the ray (see supplementary for equations). Given the weight should ideally concentrate around surfaces, \\(\\mathcal{L}_{\\mathrm{sight}}\\) enforces the weight distribution to resemble a Gaussian distribution \\(\\mathcal{N}(\\hat{\\mathcal{D}}_i,\\epsilon_n)\\) centered at the ground truth depth \\(\\hat{\\mathcal{D}}_i\\) along the rendering ray, written as" + }, + { + "type": "equation", + "bbox": [ + 0.094, + 0.823, + 0.47, + 0.87 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {s i g h t}} = \\mathbb {E} _ {\\mathcal {D} _ {i} \\in \\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m}} \\left[ \\int_ {t _ {\\text {n e a r}}} ^ {t _ {\\text {f a r}}} (w (t) - \\mathcal {N} (\\hat {\\mathcal {D}} _ {i}, \\epsilon_ {n})) ^ {2} d t \\right], \\tag {11}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.871, + 0.47, + 0.902 + ], + "angle": 0, + "content": "where \\( w \\) indicates the weight to be integrated along the distance \\( t \\) on the rendering ray from \\( t_{near} \\) to \\( t_{far} \\). Since the" + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.089, + 0.894, + 0.181 + ], + "angle": 0, + "content": "
MethodsInterpolationLane Shift
PSNR↑SSIM↑LPIPS↓FID↓@2mFID↓@3.7m
Instant-NGP24.2820.7330.408140.3173.2
Mip-NeRF 36023.6930.6910.496189.4231.1
Nerfacto27.1220.8040.268116.7151.0
UniSim26.0140.7680.342118.5141.3
LidaRF (Ours)27.2550.8120.224106.5126.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.191, + 0.894, + 0.218 + ], + "angle": 0, + "content": "Table 1. Quantitative comparisons on view synthesis with state-of-the-art NeRF variants." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.234, + 0.892, + 0.265 + ], + "angle": 0, + "content": "weight \\( w \\) is computed on discrete intervals given by point sampling in NeRF, this loss is discretized to" + }, + { + "type": "equation", + "bbox": [ + 0.565, + 0.277, + 0.892, + 0.319 + ], + "angle": 0, + "content": "\\[\n\\mathcal {L} _ {\\text {s i g h t}} = \\mathbb {E} _ {\\mathcal {D} _ {i} \\in \\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m}} \\left[ \\sum_ {i} \\left(w _ {i} - \\mathcal {N} _ {i}\\right) ^ {2} \\right], \\tag {12}\n\\]" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.326, + 0.895, + 0.462 + ], + "angle": 0, + "content": "where \\(\\mathcal{N}_i\\) indicates the probability mass within the \\(i\\)-th interval. Here, a possible implementation (e.g. in Nerfstudio [29]) to obtain \\(\\mathcal{N}_i\\) is by mid-point approximation as illustrated in Fig. 4. However, we note that this approximation is unnecessary and implement differently based on cumulative distribution function (CDF) - the probability mass of a Gaussian distribution can be obtained through its tabulated CDF. We show in supplementary that our exact implementation leads to improved PSNRs." + }, + { + "type": "title", + "bbox": [ + 0.499, + 0.473, + 0.763, + 0.489 + ], + "angle": 0, + "content": "4.4. Augmented View Supervision" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.497, + 0.895, + 0.801 + ], + "angle": 0, + "content": "Recall that a vehicle-mounted camera generates sparse training images with limited view coverage due to its forward motion, posing challenges for NeRF reconstruction, especially when the novel views deviate from vehicle trajectory. Here, we propose to augment training data leveraging Lidar. First, we colorize the point clouds in each Lidar frame by projecting onto its synchronized camera and interpolate the image for RGB values. The colorized point clouds are accumulated as described in Sec. 4.3 and projected onto a set of synthetically augmented views, yielding synthesized images and depth maps as illustrated in Fig. 2. These augmented training views are derived from existing ones, by introducing stochastic perturbations to their camera centers, with the shifting magnitude \\(\\epsilon_{a} \\in \\mathcal{N}(0, \\epsilon_{a})\\). Nonetheless, such augmented data fails to account for potential occlusions as depicted in Sec. 4.3. Our model, fortified by robust depth supervision, is adept at discerning and excluding occluded Lidar points online. The augmented views are used to train NeRF similarly as the real training views, and we denote the extra loss separately as \\(\\mathcal{L}_{\\text{aug}}\\)." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.815, + 0.633, + 0.831 + ], + "angle": 0, + "content": "5. Experiments" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.84, + 0.895, + 0.901 + ], + "angle": 0, + "content": "In this section, we detail our experimental setup and benchmark our method against state-of-the-art NeRF techniques, demonstrating superior photorealism. We further ablate our design choices, underscoring the effectiveness of ro" + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19567" + } + ], + [ + { + "type": "text", + "bbox": [ + 0.077, + 0.092, + 0.47, + 0.122 + ], + "angle": 0, + "content": "bust depth supervision, LiDAR encoding, and augmented view supervision in enhancing realism." + }, + { + "type": "title", + "bbox": [ + 0.078, + 0.13, + 0.267, + 0.146 + ], + "angle": 0, + "content": "5.1. Experimental Setup" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.153, + 0.471, + 0.289 + ], + "angle": 0, + "content": "Datasets. Following [43], we rely on Pandaset [39] as the primary dataset for evaluation, using its front camera and synchronized spinning Lidar. Each scene is consisting of 80 frames captured at \\(10\\mathrm{Hz}\\). We leverage its sensor localization for Lidar accumulation. Since our focus is on static scenes, the dynamic vehicles are masked out during evaluation, similarly as in [9]. We also evaluate on NuScenes [6] and Argoverse2 [37] to compare with S-NeRF [40] and NeRF-LiDAR-cGAN [9], respectively." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.293, + 0.471, + 0.489 + ], + "angle": 0, + "content": "Baselines. On Pandaset, we compare our model against several modern implicit-based neural radiance fields methods: Instant-NGP, Mip-NeRF 360, Nerfacto and UniSim. Instant-NGP [24] adopts multi-resolution hashing encoding for compact scene representation and efficient rendering. Mip-NeRF 360 [5] adopts integrated position encoding with scene contraction for handling unbounded scenes. Nerfacto [29] combines the compact representation from Instant-NGP and proposal network from Mip-NeRF 360. UniSim [43] is the state-of-the-art simulator for street scenes, reconstructing both the static background and dynamic actors with neural feature grids. In our experiments, we mainly focus on modeling the static background." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.492, + 0.47, + 0.659 + ], + "angle": 0, + "content": "Implementation Details. We mask dynamic objects in RGB images using dataset bounding box annotations and an instance segmentation model [13]. Static Lidar points are isolated by omitting points within dynamic objects' 3D bounding boxes. For nearest neighbor searches, we use a CUDA-based FRNN search algorithm [1] to query \\( K = 6 \\) nearest Lidar points within a \\( 0.3m \\) radius. Our loss weights and scheduling parameters in depth training scheme are given in supplementary. Instant-NGP, Nerfacto, UniSim and our proposed LidaRF use identical size of hash grid and hidden layers in MLPs. Additional details are in the supplementary." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.666, + 0.337, + 0.683 + ], + "angle": 0, + "content": "5.2. Novel View Synthesis Results" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.689, + 0.47, + 0.839 + ], + "angle": 0, + "content": "In our experiments, we assess novel view synthesis under interpolation and extrapolation settings. For interpolation setting, we randomly subsample RGB and Lidar frames, testing on every fourth frame and training on the rest. We follow common practice to report PSNR, SSIM, and LPIPS interpolation views. For extrapolation setting, following [43], we simulate new trajectories by laterally shifting them left or right by 2 or 3.7 meters (lane width of Interstate Highway standards [2]). We report FID at the perceptual level since ground-truth is unavailable," + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.471, + 0.902 + ], + "angle": 0, + "content": "As shown in Tab. 1, our method outperforms all others in every metric. While methods such as Nerfacto and UniSim show robust performance in the interpolation setting, MipNeRF 360 lags behind. The qualitative gap becomes even" + }, + { + "type": "table", + "bbox": [ + 0.505, + 0.091, + 0.892, + 0.208 + ], + "angle": 0, + "content": "
LdsLdsHPRdsLrobustdsφLLaugPSNR↑SSIM↑LPIPS↓FID↓ @3.7m
□□□□□□27.1220.8040.268151.0
✓□□□□□27.0160.8000.264138.2
□✓□□□□26.9460.7970.264137.7
□□✓□□□27.0000.7990.261139.1
□□□✓□□27.0900.8040.247131.7
□□□✓✓□27.2190.8100.228128.7
□□□✓✓✓27.2540.8120.223126.0
" + }, + { + "type": "table_caption", + "bbox": [ + 0.499, + 0.219, + 0.892, + 0.247 + ], + "angle": 0, + "content": "Table 2. Ablation study of our robust depth supervision, Lidar encoding, and training view augmentation on Pandaset." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.261, + 0.895, + 0.382 + ], + "angle": 0, + "content": "more significant in extrapolation scenarios. Fig. 5 displays these qualitative differences, where our method exhibits enhanced visual realism compared to the baselines, particularly in rendering fine structures, thanks to our LiDAR encoding. This is especially notable as, even though UniSim also utilizes LiDAR depth supervision, our method more effectively renders low-texture areas like road surfaces, demonstrating the advantage of our deeper utilization of Lidar." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.391, + 0.653, + 0.407 + ], + "angle": 0, + "content": "5.3. Ablation Study" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.414, + 0.895, + 0.642 + ], + "angle": 0, + "content": "In our ablation study presented in Tab. 2, we evaluate the impact of three key components - robust depth supervision, Lidar encoding, and augmented view supervision. The baseline for comparison, shown in the first row of Table 2, is the Nerfacto method. We denote different depth supervision strategies as follows: \\(\\mathcal{L}_{ds}^{1}\\) for single-frame Lidar depth supervision, \\(\\mathcal{L}_{ds}^{10}\\) for depth map supervision using 10 adjacent Lidar frames, and \\(\\mathcal{L}_{ds}\\) for the same but within our robust supervision scheme. As another baseline for occlusion handling, we apply hidden point removal (HPR) algorithm [18] implemented in Open3D [48] to remove occluded points as data preprocessing; the supervision after HPR is denoted as \\(\\mathcal{L}_{ds}^{\\mathrm{HPR}}\\). Lidar encoding is represented by \\(\\phi_L\\). Lastly, \\(\\mathcal{L}_{\\mathrm{aug}}\\) signifies supervision with augmented RGB and depth data derived from Lidar projections." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.644, + 0.895, + 0.901 + ], + "angle": 0, + "content": "Effects of Robust Depth Supervision. In Tab. 2, we illustrate that Lidar depth markedly improves LPIPS and FID in lane shift settings with marginal PSNR drop compared to Nerfacto. Notably, our robust supervision scheme with accumulated Lidar points further enhances all metrics. Also note the offline HPR significantly lags behind our more adaptive, NeRF-informed scheme for occlusion handling. Fig. 6 compares different Lidar depth supervision settings. Under the supervision of \\(\\mathcal{L}_{\\mathrm{ds}}^{1}\\), which utilizes single-frame Lidar depth maps known for their sparsity and reduced occlusions, the rendered depths exhibit high accuracy in texture-rich areas (as indicated by the yellow boxes). However, this accuracy significantly diminishes in regions with thin structures, due to a lack of abundant geometric guidance, as observed in the red boxes. Conversely, the supervision with \\(\\mathcal{L}_{\\mathrm{ds}}^{10}\\), involving with noisy Lidar depth maps accumulated from 10 adjacent frames, leads to rendered depths that display noticeable noise." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.957 + ], + "angle": 0, + "content": "19568" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.101, + 0.079, + 0.862, + 0.58 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.584, + 0.891, + 0.611 + ], + "angle": 0, + "content": "Figure 5. Qualitative Comparison on novel view synthesis from different methods. We evaluate on both the interpolation and extrapolation views, the latter of which corresponds to a lane shift. We highlight the performance gap with boxes." + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.612, + 0.892, + 0.848 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.076, + 0.854, + 0.893, + 0.909 + ], + "angle": 0, + "content": "Figure 6. Qualitative comparison between different LiDAR Depth Supervisions – With sparse depths, Nerfacto w/ \\(\\mathcal{L}_{\\mathrm{ds}}^i\\) fails to model thin structures. With denser but noisy depths, Nerfacto w/ \\(\\mathcal{L}_{\\mathrm{ds}}^i\\) generate ambiguous depth predictions. Our proposed schemes is robust to occlusions and able to learn delicate structures. Our proposed depth supervision scheme can learn delicate structures with noisy depth map, while the other settings both fail." + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.519, + 0.956 + ], + "angle": 0, + "content": "19569" + } + ], + [ + { + "type": "image", + "bbox": [ + 0.082, + 0.092, + 0.468, + 0.197 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.078, + 0.2, + 0.468, + 0.227 + ], + "angle": 0, + "content": "Figure 7. Qualitative comparison w.r.t Lidar encoding - Lidar encoding is beneficial in modelling sharp textures, e.g. power lines." + }, + { + "type": "image", + "bbox": [ + 0.08, + 0.232, + 0.468, + 0.302 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.077, + 0.306, + 0.47, + 0.348 + ], + "angle": 0, + "content": "Figure 8. Qualitative comparison w.r.t augmented view supervision - it largely improves rendering quality on the regions which are scarcely captured in the raw training data." + }, + { + "type": "table", + "bbox": [ + 0.09, + 0.355, + 0.458, + 0.439 + ], + "angle": 0, + "content": "
MethodsS-NeRFLidaRF (Ours)
w/o Ldsw/o φLw/o LaugFull
PSNR↑29.37730.62931.00131.13331.162
SSIM↑0.8590.8710.8730.8830.884
LPIPS↓0.3490.2780.2370.2220.211
" + }, + { + "type": "table_caption", + "bbox": [ + 0.088, + 0.444, + 0.458, + 0.457 + ], + "angle": 0, + "content": "Table 3. Evaluation on NuScenes with comparison to S-NeRF." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.484, + 0.47, + 0.576 + ], + "angle": 0, + "content": "This is attributed to the prevalent depth ambiguities within the data. Employing our proposed \\(\\mathcal{L}_{ds}^{\\mathrm{robust}}\\), our methodology effectively leverages denser depth maps for the precise reconstruction of intricate structures (highlighted in red boxes), as well as excludes some occluded depths (noted in yellow boxes). See more examples in the supplementary materials." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.578, + 0.47, + 0.669 + ], + "angle": 0, + "content": "Effects of Lidar Encoding. From Tab. 2, it is evident that Lidar encoding contributes to enhancements across all metrics. As shown in Fig. 7, Lidar encoding enables our method to produce sharper textures. This enhancement stems from our sparse convolution-based architecture, which is resilient to Lidar point noise and density variations." + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.672, + 0.471, + 0.809 + ], + "angle": 0, + "content": "Effects of Augmented View Supervision. While the quantitative benefits of augmented view supervision, as per Tab. 2, appear modest, it consistently enhances performance in extrapolation scenarios across all test scenes. This is particularly notable in scenes where other methodologies fall short. Fig. 8 showcases an instance of this: in scenes with parking cars that are scarcely captured in the raw training data due to the rapid movement of the camera vehicle, our augmented view supervision significantly elevates the quality." + }, + { + "type": "title", + "bbox": [ + 0.077, + 0.818, + 0.388, + 0.833 + ], + "angle": 0, + "content": "5.4. Results on NuScenes and Argoverse" + }, + { + "type": "text", + "bbox": [ + 0.076, + 0.84, + 0.471, + 0.902 + ], + "angle": 0, + "content": "we evaluate LidaRF on the NuScenes dataset with comparison to S-NeRF, by adapting their method to using the single front camera. We present quantitative results in Tab. 3 and qualitative example in Fig. 9, both showing superior per" + }, + { + "type": "image", + "bbox": [ + 0.505, + 0.093, + 0.89, + 0.201 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.525, + 0.203, + 0.866, + 0.217 + ], + "angle": 0, + "content": "Figure 9. Visual Comparison with S-NeRF on NuScenes." + }, + { + "type": "image", + "bbox": [ + 0.503, + 0.226, + 0.89, + 0.438 + ], + "angle": 0, + "content": null + }, + { + "type": "image_caption", + "bbox": [ + 0.499, + 0.446, + 0.893, + 0.489 + ], + "angle": 0, + "content": "Figure 10. Qualitative results on Argoverse with comparison to NeRF-LiDAR-cGAN [9] that solely relies on Lidar encoding, unlike our hybrid scene representation." + }, + { + "type": "text", + "bbox": [ + 0.499, + 0.506, + 0.892, + 0.552 + ], + "angle": 0, + "content": "formance from our method over S-NeRF. Ablation study results are also shown in Tab. 3, which further consolidate the efficacy of our proposed components." + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.553, + 0.894, + 0.69 + ], + "angle": 0, + "content": "Next, we evaluate on Argoverse dataset following the protocol in [9]. We present example qualitative comparisons in Fig. 10 while leaving more evaluations to the supplementary. As can be seen, our LidaRF achieves far superior rendering quality with high resolution. We note the [9]'s blank rendering on regions not covered by Lidar, as they solely rely on Lidar for radiance decoding. This illustrates the advantage of our framework in combining the complementary benefits from Lidar encoding and high-resolution hash grid." + }, + { + "type": "title", + "bbox": [ + 0.5, + 0.708, + 0.619, + 0.723 + ], + "angle": 0, + "content": "6. Conclusion" + }, + { + "type": "text", + "bbox": [ + 0.498, + 0.735, + 0.895, + 0.901 + ], + "angle": 0, + "content": "In this paper, we focus on unlocking the potential of Lidar to improve NeRF on road scenes, which remain a challenging scenario for novel view synthesis due to highly constrained camera motions. We develop insights on fusing Lidar encoding with high-resolution grid based representation to reap their complementary benefits, and further, extract more robust and extensive depth supervision from Lidar. A limitation of our work is that we currently handle static background only. 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In ICCV, 2023. 2" + }, + { + "type": "list", + "bbox": [ + 0.503, + 0.093, + 0.894, + 0.74 + ], + "angle": 0, + "content": null + }, + { + "type": "page_number", + "bbox": [ + 0.481, + 0.945, + 0.52, + 0.957 + ], + "angle": 0, + "content": "19572" + } + ] +] \ No newline at end of file diff --git a/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_origin.pdf b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_origin.pdf new file mode 100644 index 0000000000000000000000000000000000000000..65fde8376dd9c3ad5f48df1f98eb669e8d7540e3 --- /dev/null +++ b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/19449483-1443-4082-8fc3-3172cf73192a_origin.pdf @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:e6562e22c5d9ea89a17ba16a6cf073b72cedebb5fcf1838c015428acb597210e +size 9356372 diff --git a/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/full.md b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/full.md new file mode 100644 index 0000000000000000000000000000000000000000..5722eff60f1479db88a569414871fb7a68834d38 --- /dev/null +++ b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/full.md @@ -0,0 +1,310 @@ +# LidaRF: Delving into Lidar for Neural Radiance Field on Street Scenes + +Shanlin Sun $^{1}$ Bingbing Zhuang $^{3}$ Ziyu Jiang $^{3}$ Buyu Liu $^{3}$ Xiaohui Xie $^{1}$ Manmohan Chandraker $^{2,3}$ + +1University of California, Irvine 2University of California, San Diego 3NEC Labs America + +# Abstract + +Photorealistic simulation plays a crucial role in applications such as autonomous driving, where advances in neural radiance fields (NeRFs) may allow better scalability through the automatic creation of digital 3D assets. However, reconstruction quality suffers on street scenes due to largely collinear camera motions and sparser samplings at higher speeds. On the other hand, the application often demands rendering from camera views that deviate from the inputs to accurately simulate behaviors like lane changes. In this paper, we propose several insights that allow a better utilization of Lidar data to improve NeRF quality on street scenes. First, our framework learns a geometric scene representation from Lidar, which are fused with the implicit grid-based representation for radiance decoding, thereby supplying stronger geometric information offered by explicit point cloud. Second, we put forth a robust occlusion-aware depth supervision scheme, which allows utilizing densified Lidar points by accumulation. Third, we generate augmented training views from Lidar points for further improvement. Our insights translate to largely improved novel view synthesis under real driving scenes. + +# 1. Introduction + +Photorealistic simulation is needed in many applications like autonomous driving, where it is hard to ensure the diversity and coverage of real data. More critically, extensive verification has to be carried out in simulated environment before road testing, in order to ensure safety. Traditional simulation pipeline typically requires graphic artists to manually create 3D assets and compose into virtual environment of interest. However, the demand on human efforts and expertise has prevented it from being scalable in practice. + +Neural Radiance Field (NeRF [22]) has recently emerged as a promising way to approach simulation. NeRF has proven an effective implicit representation of scene radiance, with remarkable abilities to capture and interpolate appearances. However, such good performance often requires dense view coverage in training data, in order for + +![](images/508fb4bcf46dc7ace57f33491dde943a12bc13fb772416d5a7e8baf5be5af903.jpg) +Figure 1. Our framework leverages Lidar to a deep extent to unlock its potential for neural rendering on street scenes, leading to state-of-the-art performance in comparison to UniSim [43]. + +sufficient constraints to learn accurately the underlying geometry, material properties and illumination. While dense view coverage is not much of a problem in controlled environments, it poses challenges on street scenes – the data collection vehicle typically drives forward along lanes at a potentially high speed, leading to sparse and nearly collinear camera paths. Besides sparsity, forward camera trajectories are well-known [31] to be challenging for 3D reconstruction as it provides much weaker multi-view geometric constraints. Furthermore, road surface is typically low-texture, further introducing ambiguity in scene reconstruction. + +To address these challenges, and in view of the implicit representation of NeRF lacking explicit geometric constraint, our key idea lies in leveraging Lidar as an explicit complementary to NeRF. Despite Lidar being used in existing works [27, 40, 43] for street scenes, high-quality rendering remains challenging. Our work delves into Lidar (dubbed LidaRF) and reaps its benefits to a greater extent, yielding largely improved view synthesis quality as shown in Fig. 1. + +Our contributions are three-fold. (i) Fusing Lidar en + +While Lidar has been applied as a natural depth supervision, involving Lidar in the NeRF input offers great potential for geometric inductive bias but remains less straightforward. To this end, we adopt the grid-based representation [24] but fuse features learned from point clouds into the grid, to inherit benefits from the explicit point cloud representation. Inspired by the success of 3D perception frameworks [21, 44], we leverage 3D sparse convolution network as an effective and efficient architecture to extract geometric features from the local and global context of Lidar point clouds. (ii) Robust occlusion-aware depth supervision. Similar to existing works [40, 43], we also apply Lidar as a source of depth supervision, but do so to a greater degree. Due to the sparsity of Lidar points limiting its utility, especially in low-texture regions, we densify Lidar points across nearby frames to generate denser depth maps. However, the depth map so obtained does not account for occlusion, yielding ghost depth supervision. Hence, we put forth a robust depth supervision scheme in a curriculum learning fashion – supervising depth from near to far field while gradually filtering out bogus depth as the NeRF trains, leading to more effective learning of depth from Lidar. (iii) Lidar-based view augmentation. Furthermore, in view of the view sparsity and limited coverage in the driving scene, we leverage Lidar to densify training views. That is, we project accumulated Lidar points to novel training views; note they could be views deviating from the driving trajectories to some extent. These views projected from Lidar are added into the pool of training data, but recall that they do not account for occlusion. However, we apply the fore-mentioned supervision scheme to address the occlusion issue, yielding improved performance. + +While our insights are also applicable for general scenes, we focus the evaluation on street scenes in this work, which leads to significant improvement compared to prior art, both quantitatively and qualitatively. Our LidaRF also shows advantage in interesting applications such as lane changes that require greater deviation from input views. + +In summary, our proposed insights on better incorporation of Lidar lead to significantly improved quality of NeRF in challenging street scene applications. + +# 2. Related Work + +NeRF fundamentals. Neural radiance field (NeRF) [22] has become a widely applied scene representation thanks to its remarkable capability for photorealistic novel view synthesis. Since its advent, rapid progress has been made to increase its range of applicability. Notably, given the positional encoding in NeRF does not account for scene scale and causes aliasing when training and testing images are of different resolutions, Mip-NeRF [4] proposes to anti-alias it by casting conical frustums instead of rays, with integrated positional encoding with scale awareness. Mip-NeRF 360 [5] further extends it + +to handle unbounded scenes by a nonlinear mapping of space for scene contraction. In view of querying large MLPs being the bottleneck for efficiency, Instant-NPG [24] proposes the grid-based scene representation stored using a hash map, with the learned features decoded into radiance by a tiny and fast MLP [23]. We build our framework on top of the successful recipes of Mip-NeRF 360 and Instant-NPG, but makes important advancement to seamlessly integrate the valuable information offered by additional Lidar sensors. + +Point-based NeRFs. In contrast to the implicit scene representation, point could is an explicit representation holding the advantage of capturing accurate scene geometry. Point cloud is also widely available, either from structure-from-motion and multi-view stereo, or directly from time-of-flight depth sensors like Kinect or Lidar. This leads to the line of research [3, 26, 42, 47] in rendering images from point clouds or surfaces. Point-NeRF [41] represents one of the pioneering works that assign image features to the point clouds, from which the radiance filed along the rendering ray is decoded by querying features from nearby points. Point2Pix [16] utilizes point encoding to render point clouds in indoor scenes to images. TriVol [15] adopts triple slim volume to encode point cloud efficiently. Pointersect [8] proposes to render point clouds by directly inferring the intersection of the ray with the underlying surface. However, these works only demonstrate results on objects or small-scale indoor scenes. Chang et al. [9] has recently extended Point-NeRF to street scenes, but the rendering remains low-resolution and incomplete due to the sparse nature of Lidar point clouds. In contrast, our LidaRF fuses Lidar encoding with high-resolution grid-based representation for feature learning, yielding results far superior to [9]. + +Street scene NeRFs. The need for photorealistic simulation in autonomous driving inspires researches [12, 19, 20, 25, 28, 35, 38, 40, 43, 46] to explore NeRFs on unconstrained street scenes. Notably, UniSim [43] demonstrates the promising applicability of NeRF for closed-loop simulation of the autonomy, taking only a real driving log as input. Some works focus on handling sparse view observations [7, 49] or improving geometry of NeRF [12, 33]. Despite these efforts, high-quality rendering of street scenes remains challenging for NeRF. Our work improves NeRF by leveraging Lidar data to a greater extent, with insights on hybrid feature encoding and robust depth supervision with densified Lidar. It is worth noting that while S-NeRF [40] also densifies Lidar with a depth completion network, our strategy distinguishes itself by relying only on actual Lidar frames without additional training data, and is not affected by potential errors in the depth prediction. + +Depth-supervised NeRFs. The vanilla NeRF does not enforce any explicit constraint on geometry, often leading to inaccurate depth or surface recovery. This inspires many works to impose depth supervision in various + +forms [11, 32, 34, 36, 42, 45]. Notably, NeRFs on street scenes [27, 40, 43] typically involve derived depth supervision from Lidar. Our work distinguishes itself by reap benefits from Lidar to a deeper extent, by Lidar aggregation while accounting for occlusions. + +# 3. Preliminaries + +Neural Radiance Field (NeRF) [22] represents a radiance field with a continuous neural network $f:(\mathbf{x},\mathbf{d})\to (c,\sigma)$ , mapping spatial location $\mathbf{x} = (x,y,z)$ and viewing direction $\mathbf{d} = (\theta ,\phi)$ to the RGB color $c$ and volumetric density $\sigma$ at that point. The network is queried at each point along the rendering ray to estimate color and density, which are then composed into the final pixel color using the volume rendering equation [17]. NeRF is optimized through the loss function $\mathcal{L}_{\mathrm{rgb}}$ defined as the mean squared error between the predicted and true colors of the training RGB images. + +Nerfacto is the recommended approach within the open-source project Nerfstudio [29], integrating a variety of recipes that have proven effective for a wide range of real-world data. First, Nerfactor is capable of handling unbound scenes as required by street scenes, by applying the scene contraction strategy as in MipNeRF-360 [5]. For efficiency, it follows [5] to use proposal networks with small MLPs to consolidate the sampled locations along each ray to the regions near the first surface intersection. In terms of NeRF network architecture, it follows Instant-NGP [24] to leverage the grid-based feature representation parameterized by a hash map, which allows to decode color and density with the so-called fused MLPs, i.e. small MLPs that admits fast implementation [23]. + +# 4. Method + +# 4.1. Overview + +We build LidaRF on top of Nerfacto, but develop several insights to integrate the use of Lidar for high-quality view synthesis on street scenes, as illustrated in Fig. 2. Our pipeline takes Lidar point clouds as input (Sec. 4.2), extracts geometric features from the point clouds, and fuses it with the hash-based feature grid to combine their complementary benefits. The hybrid features are fed to MLPs for decoding color and density, followed by standard volume rendering. In the output, we leverage denser Lidar points accumulated across frames as depth supervision while accounting for occlusion. This leads to two extra losses $\mathcal{L}_{\mathrm{ds}}$ (Sec. 4.3) and $\mathcal{L}_{\mathrm{aug}}$ (Sec. 4.4), besides the original losses from Nerfactor $\mathcal{L}_{\mathrm{nerfacto}}$ . All together, our loss $\mathcal{L}$ is written as + +$$ +\mathcal {L} = \mathcal {L} _ {\text {n e r f a c t o}} + \lambda_ {1} \cdot \underbrace {\mathcal {L} _ {\mathrm {d s}}} _ {\text {S e c . 4 . 3}} + \lambda_ {2} \cdot \underbrace {\mathcal {L} _ {\text {a u g}}} _ {\text {S e c . 4 . 4}}, \tag {1} +$$ + +where $\mathcal{L}_{\mathrm{nerfacto}} = \mathcal{L}_{\mathrm{rgb}} + \lambda_3 \cdot \mathcal{L}_{\mathrm{dist}} + \lambda_4 \cdot \mathcal{L}_{\mathrm{interval}}$ . (2) + +# 4.2. Hybrid Representation with Lidar Encoding + +Motivation. Lidar point clouds holds strong potential for geometric guidance that is highly valuable for NeRF. However, relying on Lidar features alone for scene representation, as done in [9], results in low-resolution rendering, due to the sparse nature of Lidar points despite temporal accumulation. In addition, Lidar does not cover the entire scene due to its limited field of view, e.g. it does not capture building surface above a certain height, yielding blank rendering in those regions as in [9]. Our framework, in contrast, fuses the Lidar features with the high-resolution spatial grid of features to leverage the strength of both, which are jointly learned for high-quality and complete scene rendering. + +Lidar feature extraction. We detail here the extraction of geometric features for each Lidar point. Referring to Fig. 2, we first aggregate Lidar point clouds from all frames of the entire sequence to construct a denser set of point clouds. We then voxelize the point clouds into a voxel grid, where the spatial position of points falling into each voxel cell are averaged, yielding a 3-dim feature for each voxel cell. Inspired by its wide success on 3D perception frameworks [21, 44], we encode the scene geometry feature with a 3D sparse UNet [10, 30] on the voxel grid, which permits learning from a more global context of the scene geometry. The 3D sparse UNet takes the voxel grid along with its 3-dim features as input and outputs neural volumetric features, consisting of n-dim feature for each occupied voxel. This yields our Lidar embeddings $P = \{(\mathbf{p}_i,f_i)|i = 1,\dots,N\}$ , where each point $i$ is located at $\mathbf{p}_i$ and associated with a vector $f_{i}$ , which is the neural feature of the voxel cell it resides in, encoding the local and global geometry around $\mathbf{p}_i$ . + +Query of Lidar features. For each sample point $\mathbf{x}$ along the ray to be rendered, we query its Lidar feature if there are at least $K$ nearby Lidar points within a search radius $R$ ; otherwise, its Lidar feature is set as empty (i.e. all-zero). Specifically, we employ a Fixed Radius Nearest Neighbors (FRNN) approach [14] to search a $K$ -nearest Lidar point index set with respect to $\mathbf{x}$ , denoted as $S_{\mathbf{x}}^{K}$ . Different from [9] where ray sampling is predetermined prior to initiating the training process, our method conducts FRNN searching online as the distribution of the sampled points from our proposal networks shift dynamically towards concentrating on the surface as the NeRF training converges. + +Following Point-NeRF [41], our method harnesses an MLP, $\mathcal{F}$ , to map Lidar feature from each point to a neural scene description. For the $i$ -th point neighbor of $\mathbf{x}$ , $\mathcal{F}$ takes as input the Lidar feature $f_{i}$ and relative position $\mathbf{x} - \mathbf{p}_{i}$ , and outputs the neural scene description as + +$$ +f _ {i, \mathbf {x}} = \mathcal {F} \left(\left[ f _ {i}, \mathbf {x} - \mathbf {p} _ {i} \right]\right), \tag {3} +$$ + +where $[,]$ indicates concatenation. To obtain the final Lidar encoding $\phi_L(\mathbf{x})$ at the sampled location $\mathbf{x}$ , we use standard + +![](images/c265ed64e12b2f07c0791957c538c9991b6f97963df3ebadb45b42315ad656e6.jpg) + +![](images/5aee7ac903503bc01370fba9c4e3218c31044ed563f667b83da08515e4af7a1b.jpg) +LiDAR + +![](images/3ce6913e2f7b8adb01bd130d5255a27dcc78448698e1d73b21629649bc8d8ef6.jpg) +Encoding + +![](images/23e2889009970a258a5315167a39a4845c55e5ff69973a132e11218995ceb62c.jpg) +Hash +Encoding + +![](images/55978d834c151dea79c06fcd97ce5cd8509b47730bef99a6e26cb63f54f2f411.jpg) +Spherical +Harmonics + +![](images/6ce091aabacbc4faf8d2e2f7d9b103f2b0c0826cf56838053f120f9ec7cd8c74.jpg) +MID + +![](images/e68125d03df58224edf044326209d4c9ee54add31ce879d215bba115c0ce81d5.jpg) + +![](images/2b84d8b3689b8bd5af3c53678440a700056182df55d2b55c505719569e2219b3.jpg) +Original View + +![](images/ef2c875ed5fd1d5dc8dc85c0df84734bf85551fb9d1eb1941437857745d9ea1a.jpg) + +![](images/c9c69fbed34af21d098890ce2a0e72899f0e58cf17fd4e4c1bbe26fea5321ebf.jpg) +Augmented View + +inverse-distance weighting to aggregate the neural scene description $f_{i,\mathbf{x}}$ from its $K$ neighboring points, + +$$ +\phi_ {L} (\mathbf {x}) = \left\{ \begin{array}{l l} \frac {\sum_ {i \in S _ {\mathbf {x}} ^ {K}} w _ {i} f _ {i , \mathbf {x}}}{\sum_ {i \in S _ {\mathbf {x}} ^ {K}} w _ {i}}, & \text {i f} S _ {\mathbf {x}} ^ {K} \text {i s n o t} \varnothing , \\ \mathbf {0}, & \text {o t h e r w i s e .} \end{array} \right. \tag {4} +$$ + +$$ +w _ {i} = \frac {1}{\left\| \mathbf {p} _ {i} - \mathbf {x} \right\|}. \tag {5} +$$ + +Feature fusion for radiance decoding. Different from [9, 41] that solely relies on point features, we concatenate the Lidar encoding $\phi_L$ with hash encoding $\phi_h$ [24], and apply an MLP $\mathcal{F}_{\alpha}$ to predict the per-sample density $\alpha$ and density embedding $\mathbf{h}$ . Finally, the corresponding color $\mathbf{c}$ is predicted from the spherical harmonics encoding $SH$ of the viewing direction $\mathbf{d}$ and density embedding $\mathbf{h}$ , via another MLP $\mathcal{F}_{\mathbf{c}}$ : + +$$ +\alpha , \mathbf {h} = \mathcal {F} _ {\alpha} \left(\left[ \phi_ {L} (\mathbf {x}), \phi_ {h} (\mathbf {x}) \right]\right), \tag {6} +$$ + +$$ +\mathbf {c} = \mathcal {F} _ {\mathbf {c}} ([ \mathbf {h}, S H (\mathbf {d}) ]). \tag {7} +$$ + +# 4.3. Robust Depth Supervision + +Motivation. In addition to the feature encoding, we also derive depth supervision from the Lidar points by projecting them onto the image plane. However, the sparse nature of Lidar points yields limited benefits, that are not sufficient for reconstructing low-texture regions such as road surface. Here, we put forth to accumulate adjacent Lidar frames to increase density. Despite the 3D points accurately capturing the scene structure, one needs to account for inter-points occlusion when projecting them onto the image plane for depth supervision. The occlusion arises due to the increased + +![](images/d42417409edc8e0f3941161d1021f46a5b8b788a4666435c7b92d42626bbb870.jpg) +Figure 2. Overview of LidaRF - it takes as input the sampled 3D positions $\mathbf{x}$ and ray directions $\mathbf{d}$ , and outputs corresponding density $\alpha$ and color $\mathbf{c}$ . It incorporates both hash encoding and LiDAR encoding using a sparse UNet. Additionally, augmented training data is generated through LiDAR projections, and the geometry prediction is trained with our proposed robust depth supervision scheme. +Figure 3. Illustration of the occlusion issue on the depth map projected from accumulated Lidar points. Observe that multiple layers of surface points may project to the same region on the image, yielding ghost depth points. + +displacement between the camera and the Lidar from its adjacent frames, yielding bogus depth supervision, as illustrated in Fig. 3. This is non-trivial to handle due to the sparsity of Lidar even after accumulation, making principled graphic techniques such as z-buffering not applicable. In this work, we propose a robust supervision scheme to automatically filter out bogus depth supervision in while training NeRF. + +Occlusion-aware robust supervision scheme. We design a curriculum training strategy such that the model initially trains with closer, more reliable depth data, which are less prone to occlusion. As training progresses, the model gradually begins to incorporate more distant depth data. Concurrently, the model develops the capacity to discard depth supervisions that are anomalously distant compared to its predictions. Formally, with the pool of all depth points de + +![](images/5688e5207e26c48382066f5059221a898f0e9e4f5141d2a6c7ea397abacc2a94.jpg) +Figure 4. Illustration of the true probability mass and its mid-point approximation. + +noted as $\mathcal{D} = \{\mathcal{D}_1,\mathcal{D}_2,\dots,\mathcal{D}_N\}$ , and further denoting the NeRF-rendered depth corresponding to $\mathcal{D}_i$ as $\hat{\mathcal{D}}_i$ , we identify the reliable subset of depth points $\mathcal{D}_{\mathrm{reliable}}^m$ in the $m$ -th training iteration as: + +$$ +\mathcal {D} _ {\text {r e l i a b l e}} ^ {m} = \left\{\mathcal {D} _ {i} \mid \mathcal {D} _ {i} \leq \epsilon_ {t} ^ {m}, \mathcal {D} _ {i} \leq \hat {\mathcal {D}} _ {i} + \epsilon_ {o} ^ {m}, \mathcal {D} _ {i} \in \mathcal {D} \right\}, \tag {8} +$$ + +$$ +\epsilon_ {t} ^ {m} = \min \left\{\alpha_ {t} \epsilon_ {t} ^ {m - 1}, \epsilon_ {t} \right\}, \quad \alpha_ {t} > 1, \tag {9} +$$ + +$$ +\epsilon_ {o} ^ {m} = \max \left\{\alpha_ {o} \epsilon_ {o} ^ {m - 1}, \epsilon_ {o} \right\}, \quad \alpha_ {o} < 1. \tag {10} +$$ + +One notices that $\mathcal{D}_{\mathrm{reliable}}^m$ is governed by two scheduled parameters: valid depth threshold $\epsilon_t^m$ and valid depth offset $\epsilon_o^m$ . The $\epsilon_t^m$ serves to filter out depth samples exceeding this threshold, thereby prioritizing nearer depth samples which are less likely to be occluded. As training progresses, $\epsilon_t^m$ is exponentially increased at a rate of $\alpha_t$ to involve more depth supervision from further field. Meanwhile, samples exhibiting a depth value far larger than the predicted depth $\hat{\mathcal{D}}_i$ are omitted, as they are likely occluded points. This is thresholded by $\hat{\mathcal{D}}_i + \epsilon_o^m$ , with $\epsilon_o^m$ decaying exponentially at a rate of $\alpha_o$ , in tandem with the improvement of depth predictions over the course of training. + +Lidar Depth Loss For samples in $\mathcal{D}_{\mathrm{reliable}}^m$ , we adopt the pixel-level depth loss proposed in URF [27], written as $\mathcal{L}_{\mathrm{ds}} = \mathcal{L}_{\mathrm{depth}} + \mathcal{L}_{\mathrm{sight}}$ . In addition to a $L_{2}$ loss $\mathcal{L}_{\mathrm{depth}}$ between the rendered depth and the ground truth, a line-of-sight prior $\mathcal{L}_{\mathrm{sight}}$ is applied to further constrain each sampling point individually. But in contrast an approximate computation of $\mathcal{L}_{\mathrm{sight}}$ in NeRFstudio, we implement an exact one. Specifically, we first note that the volume rendering boils down to a weighted sum of the predicted color on sampled points along the ray (see supplementary for equations). Given the weight should ideally concentrate around surfaces, $\mathcal{L}_{\mathrm{sight}}$ enforces the weight distribution to resemble a Gaussian distribution $\mathcal{N}(\hat{\mathcal{D}}_i,\epsilon_n)$ centered at the ground truth depth $\hat{\mathcal{D}}_i$ along the rendering ray, written as + +$$ +\mathcal {L} _ {\text {s i g h t}} = \mathbb {E} _ {\mathcal {D} _ {i} \in \mathcal {D} _ {\text {r e l i a b l e}} ^ {m}} \left[ \int_ {t _ {\text {n e a r}}} ^ {t _ {\text {f a r}}} (w (t) - \mathcal {N} (\hat {\mathcal {D}} _ {i}, \epsilon_ {n})) ^ {2} d t \right], \tag {11} +$$ + +where $w$ indicates the weight to be integrated along the distance $t$ on the rendering ray from $t_{near}$ to $t_{far}$ . Since the + +
MethodsInterpolationLane Shift
PSNR↑SSIM↑LPIPS↓FID↓@2mFID↓@3.7m
Instant-NGP24.2820.7330.408140.3173.2
Mip-NeRF 36023.6930.6910.496189.4231.1
Nerfacto27.1220.8040.268116.7151.0
UniSim26.0140.7680.342118.5141.3
LidaRF (Ours)27.2550.8120.224106.5126.0
+ +Table 1. Quantitative comparisons on view synthesis with state-of-the-art NeRF variants. + +weight $w$ is computed on discrete intervals given by point sampling in NeRF, this loss is discretized to + +$$ +\mathcal {L} _ {\text {s i g h t}} = \mathbb {E} _ {\mathcal {D} _ {i} \in \mathcal {D} _ {\text {r e l i a b l e}} ^ {m}} \left[ \sum_ {i} \left(w _ {i} - \mathcal {N} _ {i}\right) ^ {2} \right], \tag {12} +$$ + +where $\mathcal{N}_i$ indicates the probability mass within the $i$ -th interval. Here, a possible implementation (e.g. in Nerfstudio [29]) to obtain $\mathcal{N}_i$ is by mid-point approximation as illustrated in Fig. 4. However, we note that this approximation is unnecessary and implement differently based on cumulative distribution function (CDF) - the probability mass of a Gaussian distribution can be obtained through its tabulated CDF. We show in supplementary that our exact implementation leads to improved PSNRs. + +# 4.4. Augmented View Supervision + +Recall that a vehicle-mounted camera generates sparse training images with limited view coverage due to its forward motion, posing challenges for NeRF reconstruction, especially when the novel views deviate from vehicle trajectory. Here, we propose to augment training data leveraging Lidar. First, we colorize the point clouds in each Lidar frame by projecting onto its synchronized camera and interpolate the image for RGB values. The colorized point clouds are accumulated as described in Sec. 4.3 and projected onto a set of synthetically augmented views, yielding synthesized images and depth maps as illustrated in Fig. 2. These augmented training views are derived from existing ones, by introducing stochastic perturbations to their camera centers, with the shifting magnitude $\epsilon_{a} \in \mathcal{N}(0, \epsilon_{a})$ . Nonetheless, such augmented data fails to account for potential occlusions as depicted in Sec. 4.3. Our model, fortified by robust depth supervision, is adept at discerning and excluding occluded Lidar points online. The augmented views are used to train NeRF similarly as the real training views, and we denote the extra loss separately as $\mathcal{L}_{\text{aug}}$ . + +# 5. Experiments + +In this section, we detail our experimental setup and benchmark our method against state-of-the-art NeRF techniques, demonstrating superior photorealism. We further ablate our design choices, underscoring the effectiveness of ro + +bust depth supervision, LiDAR encoding, and augmented view supervision in enhancing realism. + +# 5.1. Experimental Setup + +Datasets. Following [43], we rely on Pandaset [39] as the primary dataset for evaluation, using its front camera and synchronized spinning Lidar. Each scene is consisting of 80 frames captured at $10\mathrm{Hz}$ . We leverage its sensor localization for Lidar accumulation. Since our focus is on static scenes, the dynamic vehicles are masked out during evaluation, similarly as in [9]. We also evaluate on NuScenes [6] and Argoverse2 [37] to compare with S-NeRF [40] and NeRF-LiDAR-cGAN [9], respectively. + +Baselines. On Pandaset, we compare our model against several modern implicit-based neural radiance fields methods: Instant-NGP, Mip-NeRF 360, Nerfacto and UniSim. Instant-NGP [24] adopts multi-resolution hashing encoding for compact scene representation and efficient rendering. Mip-NeRF 360 [5] adopts integrated position encoding with scene contraction for handling unbounded scenes. Nerfacto [29] combines the compact representation from Instant-NGP and proposal network from Mip-NeRF 360. UniSim [43] is the state-of-the-art simulator for street scenes, reconstructing both the static background and dynamic actors with neural feature grids. In our experiments, we mainly focus on modeling the static background. + +Implementation Details. We mask dynamic objects in RGB images using dataset bounding box annotations and an instance segmentation model [13]. Static Lidar points are isolated by omitting points within dynamic objects' 3D bounding boxes. For nearest neighbor searches, we use a CUDA-based FRNN search algorithm [1] to query $K = 6$ nearest Lidar points within a $0.3m$ radius. Our loss weights and scheduling parameters in depth training scheme are given in supplementary. Instant-NGP, Nerfacto, UniSim and our proposed LidaRF use identical size of hash grid and hidden layers in MLPs. Additional details are in the supplementary. + +# 5.2. Novel View Synthesis Results + +In our experiments, we assess novel view synthesis under interpolation and extrapolation settings. For interpolation setting, we randomly subsample RGB and Lidar frames, testing on every fourth frame and training on the rest. We follow common practice to report PSNR, SSIM, and LPIPS interpolation views. For extrapolation setting, following [43], we simulate new trajectories by laterally shifting them left or right by 2 or 3.7 meters (lane width of Interstate Highway standards [2]). We report FID at the perceptual level since ground-truth is unavailable, + +As shown in Tab. 1, our method outperforms all others in every metric. While methods such as Nerfacto and UniSim show robust performance in the interpolation setting, MipNeRF 360 lags behind. The qualitative gap becomes even + +
LdsLdsHPRdsLrobustdsφLLaugPSNR↑SSIM↑LPIPS↓FID↓ @3.7m
□□□□□□27.1220.8040.268151.0
✓□□□□□27.0160.8000.264138.2
□✓□□□□26.9460.7970.264137.7
□□✓□□□27.0000.7990.261139.1
□□□✓□□27.0900.8040.247131.7
□□□✓✓□27.2190.8100.228128.7
□□□✓✓✓27.2540.8120.223126.0
+ +Table 2. Ablation study of our robust depth supervision, Lidar encoding, and training view augmentation on Pandaset. + +more significant in extrapolation scenarios. Fig. 5 displays these qualitative differences, where our method exhibits enhanced visual realism compared to the baselines, particularly in rendering fine structures, thanks to our LiDAR encoding. This is especially notable as, even though UniSim also utilizes LiDAR depth supervision, our method more effectively renders low-texture areas like road surfaces, demonstrating the advantage of our deeper utilization of Lidar. + +# 5.3. Ablation Study + +In our ablation study presented in Tab. 2, we evaluate the impact of three key components - robust depth supervision, Lidar encoding, and augmented view supervision. The baseline for comparison, shown in the first row of Table 2, is the Nerfacto method. We denote different depth supervision strategies as follows: $\mathcal{L}_{ds}^{1}$ for single-frame Lidar depth supervision, $\mathcal{L}_{ds}^{10}$ for depth map supervision using 10 adjacent Lidar frames, and $\mathcal{L}_{ds}$ for the same but within our robust supervision scheme. As another baseline for occlusion handling, we apply hidden point removal (HPR) algorithm [18] implemented in Open3D [48] to remove occluded points as data preprocessing; the supervision after HPR is denoted as $\mathcal{L}_{ds}^{\mathrm{HPR}}$ . Lidar encoding is represented by $\phi_L$ . Lastly, $\mathcal{L}_{\mathrm{aug}}$ signifies supervision with augmented RGB and depth data derived from Lidar projections. + +Effects of Robust Depth Supervision. In Tab. 2, we illustrate that Lidar depth markedly improves LPIPS and FID in lane shift settings with marginal PSNR drop compared to Nerfacto. Notably, our robust supervision scheme with accumulated Lidar points further enhances all metrics. Also note the offline HPR significantly lags behind our more adaptive, NeRF-informed scheme for occlusion handling. Fig. 6 compares different Lidar depth supervision settings. Under the supervision of $\mathcal{L}_{\mathrm{ds}}^{1}$ , which utilizes single-frame Lidar depth maps known for their sparsity and reduced occlusions, the rendered depths exhibit high accuracy in texture-rich areas (as indicated by the yellow boxes). However, this accuracy significantly diminishes in regions with thin structures, due to a lack of abundant geometric guidance, as observed in the red boxes. Conversely, the supervision with $\mathcal{L}_{\mathrm{ds}}^{10}$ , involving with noisy Lidar depth maps accumulated from 10 adjacent frames, leads to rendered depths that display noticeable noise. + +![](images/b84b6860bbcd5c7b5e34f7e8560089ae279738c6db738046af7b5c2b35f4099c.jpg) + +![](images/f1ff4e8eb982cb263387651b75f1470b93f2c2212fc08c29065250bb28d081ab.jpg) +Figure 5. Qualitative Comparison on novel view synthesis from different methods. We evaluate on both the interpolation and extrapolation views, the latter of which corresponds to a lane shift. We highlight the performance gap with boxes. +Figure 6. Qualitative comparison between different LiDAR Depth Supervisions – With sparse depths, Nerfacto w/ $\mathcal{L}_{\mathrm{ds}}^i$ fails to model thin structures. With denser but noisy depths, Nerfacto w/ $\mathcal{L}_{\mathrm{ds}}^i$ generate ambiguous depth predictions. Our proposed schemes is robust to occlusions and able to learn delicate structures. Our proposed depth supervision scheme can learn delicate structures with noisy depth map, while the other settings both fail. + +![](images/50e810f82b7a4428aaa80fc0bbd8f6bb6f2dfc04c670c4fa5a7b9613213d4d0e.jpg) +Figure 7. Qualitative comparison w.r.t Lidar encoding - Lidar encoding is beneficial in modelling sharp textures, e.g. power lines. + +![](images/88224021f52d8cb4282018aa550f0b6bacf2399f701ac3f7d43ec95d95616872.jpg) +Figure 8. Qualitative comparison w.r.t augmented view supervision - it largely improves rendering quality on the regions which are scarcely captured in the raw training data. + +
MethodsS-NeRFLidaRF (Ours)
w/o Ldsw/o φLw/o LaugFull
PSNR↑29.37730.62931.00131.13331.162
SSIM↑0.8590.8710.8730.8830.884
LPIPS↓0.3490.2780.2370.2220.211
+ +Table 3. Evaluation on NuScenes with comparison to S-NeRF. + +This is attributed to the prevalent depth ambiguities within the data. Employing our proposed $\mathcal{L}_{ds}^{\mathrm{robust}}$ , our methodology effectively leverages denser depth maps for the precise reconstruction of intricate structures (highlighted in red boxes), as well as excludes some occluded depths (noted in yellow boxes). See more examples in the supplementary materials. + +Effects of Lidar Encoding. From Tab. 2, it is evident that Lidar encoding contributes to enhancements across all metrics. As shown in Fig. 7, Lidar encoding enables our method to produce sharper textures. This enhancement stems from our sparse convolution-based architecture, which is resilient to Lidar point noise and density variations. + +Effects of Augmented View Supervision. While the quantitative benefits of augmented view supervision, as per Tab. 2, appear modest, it consistently enhances performance in extrapolation scenarios across all test scenes. This is particularly notable in scenes where other methodologies fall short. Fig. 8 showcases an instance of this: in scenes with parking cars that are scarcely captured in the raw training data due to the rapid movement of the camera vehicle, our augmented view supervision significantly elevates the quality. + +# 5.4. Results on NuScenes and Argoverse + +we evaluate LidaRF on the NuScenes dataset with comparison to S-NeRF, by adapting their method to using the single front camera. We present quantitative results in Tab. 3 and qualitative example in Fig. 9, both showing superior per + +![](images/dcc382e0b0e231f28b853a3f90d02154ac1c898543e9beabae1e75370d99b9f4.jpg) +Figure 9. Visual Comparison with S-NeRF on NuScenes. + +![](images/aa0d999fb4b83214be07bf0c18f8788249e7e7fc008026852cb0e993a656d2a5.jpg) +Figure 10. Qualitative results on Argoverse with comparison to NeRF-LiDAR-cGAN [9] that solely relies on Lidar encoding, unlike our hybrid scene representation. + +formance from our method over S-NeRF. Ablation study results are also shown in Tab. 3, which further consolidate the efficacy of our proposed components. + +Next, we evaluate on Argoverse dataset following the protocol in [9]. We present example qualitative comparisons in Fig. 10 while leaving more evaluations to the supplementary. As can be seen, our LidaRF achieves far superior rendering quality with high resolution. We note the [9]'s blank rendering on regions not covered by Lidar, as they solely rely on Lidar for radiance decoding. This illustrates the advantage of our framework in combining the complementary benefits from Lidar encoding and high-resolution hash grid. + +# 6. Conclusion + +In this paper, we focus on unlocking the potential of Lidar to improve NeRF on road scenes, which remain a challenging scenario for novel view synthesis due to highly constrained camera motions. We develop insights on fusing Lidar encoding with high-resolution grid based representation to reap their complementary benefits, and further, extract more robust and extensive depth supervision from Lidar. A limitation of our work is that we currently handle static background only. We envision that the key insights developed in this paper can benefit dynamic objects as well, which remains an interesting future direction to explore. + +# References + +[1] GitHub - lxxue/FRNN: Fixed Radius Nearest Neighbor Search on GPU — github.com. https://github.com/lxxue/FRNN. [Accessed 18-11-2023]. 6 +[2] Interstate Highway standards - Wikipedia -en.wikipedia.org. https://en.wikipedia.org/wiki/Interstate_Highway_standards. 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In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 5438–5448, 2022. 2, 3, 4 +[42] Chen Yang, Peihao Li, Zanwei Zhou, Shanxin Yuan, Bingbing Liu, Xiaokang Yang, Weichao Qiu, and Wei Shen. Nerfvs: Neural radiance fields for free view synthesis via geometry scaffolds. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 16549-16558, 2023. 2, 3 +[43] Ze Yang, Yun Chen, Jingkang Wang, Sivabalan Manivasagam, Wei-Chiu Ma, Anqi Joyce Yang, and Raquel Urtasun. Unisim: A neural closed-loop sensor simulator. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, 2023. 1, 2, 3, 6 +[44] Tianwei Yin, Xingyi Zhou, and Philipp Krahenbuhl. Center-based 3d object detection and tracking. In Proceedings of the IEEE/CVF conference on computer vision and pattern recognition, 2021. 2, 3 +[45] Zehao Yu, Songyou Peng, Michael Niemeyer, Torsten Sattler, and Andreas Geiger. Monosdf: Exploring monocular geometric cues for neural implicit surface reconstruction. NeurIPS, 2022. 3 +[46] Xiaoshuai Zhang, Abhijit Kundu, Thomas Funkhouser, Leonidas Guibas, Hao Su, and Kyle Genova. Nerflets: Local radiance fields for efficient structure-aware 3d scene representation from 2d supervision. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 8274-8284, 2023. 2 +[47] Yi Zhang, Xiaoyang Huang, Bingbing Ni, Teng Li, and Wenjun Zhang. Frequency-modulated point cloud rendering with easy editing. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, pages 119-129, 2023. 2 +[48] Qian-Yi Zhou, Jaesik Park, and Vladlen Koltun. Open3D: A modern library for 3D data processing. arXiv:1801.09847, 2018.6 +[49] Xiaoyu Zhou, Zhiwei Lin, Xiaojun Shan, Yongtao Wang, Deqing Sun, and Ming-Hsuan Yang. Sampling: Scene-adaptive hierarchical multiplane images representation for novel view synthesis from a single image. In ICCV, 2023. 2 \ No newline at end of file diff --git a/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/images.zip b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/images.zip new file mode 100644 index 0000000000000000000000000000000000000000..9c1df70c55b172de108c6b7b6e9d0efe9dc79f58 --- /dev/null +++ b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/images.zip @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:bb900265f3de0113e71d2cfb422bdf8cbbb101bb55c5de9d8927ceaf89782418 +size 841110 diff --git a/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/layout.json b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/layout.json new file mode 100644 index 0000000000000000000000000000000000000000..7c4d7b24773f021061adabba210179d7c252cdfc --- /dev/null +++ b/2024/LidaRF_ Delving into Lidar for Neural Radiance Field on Street Scenes/layout.json @@ -0,0 +1,8697 @@ +{ + "pdf_info": [ + { + "para_blocks": [ + { + "bbox": [ + 77, + 103, + 516, + 120 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 77, + 103, + 516, + 120 + ], + "spans": [ + { + "bbox": [ + 77, + 103, + 516, + 120 + ], + "type": "text", + "content": "LidaRF: Delving into Lidar for Neural Radiance Field on Street Scenes" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "spans": [ + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "text", + "content": "Shanlin Sun" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "text", + "content": " Bingbing Zhuang" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "text", + "content": " Ziyu Jiang" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "text", + "content": " Buyu Liu" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "inline_equation", + "content": "^{3}" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "text", + "content": " Xiaohui Xie" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "inline_equation", + "content": "^{1}" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "text", + "content": " Manmohan Chandraker" + }, + { + "bbox": [ + 143, + 142, + 449, + 171 + ], + "type": "inline_equation", + "content": "^{2,3}" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 72, + 174, + 520, + 189 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 72, + 174, + 520, + 189 + ], + "spans": [ + { + "bbox": [ + 72, + 174, + 520, + 189 + ], + "type": "text", + "content": "1University of California, Irvine 2University of California, San Diego 3NEC Labs America" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 143, + 217, + 191, + 228 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 143, + 217, + 191, + 228 + ], + "spans": [ + { + "bbox": [ + 143, + 217, + 191, + 228 + ], + "type": "text", + "content": "Abstract" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 241, + 290, + 493 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 241, + 290, + 493 + ], + "spans": [ + { + "bbox": [ + 46, + 241, + 290, + 493 + ], + "type": "text", + "content": "Photorealistic simulation plays a crucial role in applications such as autonomous driving, where advances in neural radiance fields (NeRFs) may allow better scalability through the automatic creation of digital 3D assets. However, reconstruction quality suffers on street scenes due to largely collinear camera motions and sparser samplings at higher speeds. On the other hand, the application often demands rendering from camera views that deviate from the inputs to accurately simulate behaviors like lane changes. In this paper, we propose several insights that allow a better utilization of Lidar data to improve NeRF quality on street scenes. First, our framework learns a geometric scene representation from Lidar, which are fused with the implicit grid-based representation for radiance decoding, thereby supplying stronger geometric information offered by explicit point cloud. Second, we put forth a robust occlusion-aware depth supervision scheme, which allows utilizing densified Lidar points by accumulation. Third, we generate augmented training views from Lidar points for further improvement. 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Traditional simulation pipeline typically requires graphic artists to manually create 3D assets and compose into virtual environment of interest. However, the demand on human efforts and expertise has prevented it from being scalable in practice." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 642, + 288, + 714 + ], + "type": "text", + "content": "Neural Radiance Field (NeRF [22]) has recently emerged as a promising way to approach simulation. NeRF has proven an effective implicit representation of scene radiance, with remarkable abilities to capture and interpolate appearances. 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Our framework leverages Lidar to a deep extent to unlock its potential for neural rendering on street scenes, leading to state-of-the-art performance in comparison to UniSim [43]." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_caption" + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 472, + 547, + 604 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 472, + 547, + 604 + ], + "spans": [ + { + "bbox": [ + 304, + 472, + 547, + 604 + ], + "type": "text", + "content": "sufficient constraints to learn accurately the underlying geometry, material properties and illumination. While dense view coverage is not much of a problem in controlled environments, it poses challenges on street scenes – the data collection vehicle typically drives forward along lanes at a potentially high speed, leading to sparse and nearly collinear camera paths. Besides sparsity, forward camera trajectories are well-known [31] to be challenging for 3D reconstruction as it provides much weaker multi-view geometric constraints. Furthermore, road surface is typically low-texture, further introducing ambiguity in scene reconstruction." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 605, + 547, + 700 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 605, + 547, + 700 + ], + "spans": [ + { + "bbox": [ + 304, + 605, + 547, + 700 + ], + "type": "text", + "content": "To address these challenges, and in view of the implicit representation of NeRF lacking explicit geometric constraint, our key idea lies in leveraging Lidar as an explicit complementary to NeRF. Despite Lidar being used in existing works [27, 40, 43] for street scenes, high-quality rendering remains challenging. Our work delves into Lidar (dubbed LidaRF) and reaps its benefits to a greater extent, yielding largely improved view synthesis quality as shown in Fig. 1." + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 317, + 701, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 317, + 701, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 317, + 701, + 547, + 713 + ], + "type": "text", + "content": "Our contributions are three-fold. (i) Fusing Lidar en" + } + ] + } + ], + "index": 14 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "spans": [ + { + "bbox": [ + 65, + 2, + 111, + 34 + ], + "type": "text", + "content": "CVF" + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "header", + "angle": 0, + "lines": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "spans": [ + { + "bbox": [ + 145, + 0, + 494, + 37 + ], + "type": "text", + "content": "This CVPR paper is the Open Access version, provided by the Computer Vision Foundation. Except for this watermark, it is identical to the accepted version; the final published version of the proceedings is available on IEEE Xplore." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19563" + } + ] + } + ], + "index": 15 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 0 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 289, + 455 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 289, + 455 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 289, + 455 + ], + "type": "text", + "content": "While Lidar has been applied as a natural depth supervision, involving Lidar in the NeRF input offers great potential for geometric inductive bias but remains less straightforward. To this end, we adopt the grid-based representation [24] but fuse features learned from point clouds into the grid, to inherit benefits from the explicit point cloud representation. Inspired by the success of 3D perception frameworks [21, 44], we leverage 3D sparse convolution network as an effective and efficient architecture to extract geometric features from the local and global context of Lidar point clouds. (ii) Robust occlusion-aware depth supervision. Similar to existing works [40, 43], we also apply Lidar as a source of depth supervision, but do so to a greater degree. Due to the sparsity of Lidar points limiting its utility, especially in low-texture regions, we densify Lidar points across nearby frames to generate denser depth maps. However, the depth map so obtained does not account for occlusion, yielding ghost depth supervision. Hence, we put forth a robust depth supervision scheme in a curriculum learning fashion – supervising depth from near to far field while gradually filtering out bogus depth as the NeRF trains, leading to more effective learning of depth from Lidar. (iii) Lidar-based view augmentation. Furthermore, in view of the view sparsity and limited coverage in the driving scene, we leverage Lidar to densify training views. That is, we project accumulated Lidar points to novel training views; note they could be views deviating from the driving trajectories to some extent. These views projected from Lidar are added into the pool of training data, but recall that they do not account for occlusion. However, we apply the fore-mentioned supervision scheme to address the occlusion issue, yielding improved performance." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 456, + 288, + 527 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 456, + 288, + 527 + ], + "spans": [ + { + "bbox": [ + 47, + 456, + 288, + 527 + ], + "type": "text", + "content": "While our insights are also applicable for general scenes, we focus the evaluation on street scenes in this work, which leads to significant improvement compared to prior art, both quantitatively and qualitatively. Our LidaRF also shows advantage in interesting applications such as lane changes that require greater deviation from input views." + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 47, + 527, + 288, + 563 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 527, + 288, + 563 + ], + "spans": [ + { + "bbox": [ + 47, + 527, + 288, + 563 + ], + "type": "text", + "content": "In summary, our proposed insights on better incorporation of Lidar lead to significantly improved quality of NeRF in challenging street scene applications." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 47, + 574, + 134, + 586 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 574, + 134, + 586 + ], + "spans": [ + { + "bbox": [ + 47, + 574, + 134, + 586 + ], + "type": "text", + "content": "2. Related Work" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 594, + 289, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 594, + 289, + 715 + ], + "spans": [ + { + "bbox": [ + 47, + 594, + 289, + 715 + ], + "type": "text", + "content": "NeRF fundamentals. Neural radiance field (NeRF) [22] has become a widely applied scene representation thanks to its remarkable capability for photorealistic novel view synthesis. Since its advent, rapid progress has been made to increase its range of applicability. Notably, given the positional encoding in NeRF does not account for scene scale and causes aliasing when training and testing images are of different resolutions, Mip-NeRF [4] proposes to anti-alias it by casting conical frustums instead of rays, with integrated positional encoding with scale awareness. Mip-NeRF 360 [5] further extends it" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "spans": [ + { + "bbox": [ + 304, + 72, + 547, + 180 + ], + "type": "text", + "content": "to handle unbounded scenes by a nonlinear mapping of space for scene contraction. In view of querying large MLPs being the bottleneck for efficiency, Instant-NPG [24] proposes the grid-based scene representation stored using a hash map, with the learned features decoded into radiance by a tiny and fast MLP [23]. We build our framework on top of the successful recipes of Mip-NeRF 360 and Instant-NPG, but makes important advancement to seamlessly integrate the valuable information offered by additional Lidar sensors." + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 304, + 182, + 548, + 457 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 182, + 548, + 457 + ], + "spans": [ + { + "bbox": [ + 304, + 182, + 548, + 457 + ], + "type": "text", + "content": "Point-based NeRFs. In contrast to the implicit scene representation, point could is an explicit representation holding the advantage of capturing accurate scene geometry. Point cloud is also widely available, either from structure-from-motion and multi-view stereo, or directly from time-of-flight depth sensors like Kinect or Lidar. This leads to the line of research [3, 26, 42, 47] in rendering images from point clouds or surfaces. Point-NeRF [41] represents one of the pioneering works that assign image features to the point clouds, from which the radiance filed along the rendering ray is decoded by querying features from nearby points. Point2Pix [16] utilizes point encoding to render point clouds in indoor scenes to images. TriVol [15] adopts triple slim volume to encode point cloud efficiently. Pointersect [8] proposes to render point clouds by directly inferring the intersection of the ray with the underlying surface. However, these works only demonstrate results on objects or small-scale indoor scenes. Chang et al. [9] has recently extended Point-NeRF to street scenes, but the rendering remains low-resolution and incomplete due to the sparse nature of Lidar point clouds. In contrast, our LidaRF fuses Lidar encoding with high-resolution grid-based representation for feature learning, yielding results far superior to [9]." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 304, + 460, + 548, + 663 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 460, + 548, + 663 + ], + "spans": [ + { + "bbox": [ + 304, + 460, + 548, + 663 + ], + "type": "text", + "content": "Street scene NeRFs. The need for photorealistic simulation in autonomous driving inspires researches [12, 19, 20, 25, 28, 35, 38, 40, 43, 46] to explore NeRFs on unconstrained street scenes. Notably, UniSim [43] demonstrates the promising applicability of NeRF for closed-loop simulation of the autonomy, taking only a real driving log as input. Some works focus on handling sparse view observations [7, 49] or improving geometry of NeRF [12, 33]. Despite these efforts, high-quality rendering of street scenes remains challenging for NeRF. Our work improves NeRF by leveraging Lidar data to a greater extent, with insights on hybrid feature encoding and robust depth supervision with densified Lidar. It is worth noting that while S-NeRF [40] also densifies Lidar with a depth completion network, our strategy distinguishes itself by relying only on actual Lidar frames without additional training data, and is not affected by potential errors in the depth prediction." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 304, + 665, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 548, + 715 + ], + "type": "text", + "content": "Depth-supervised NeRFs. The vanilla NeRF does not enforce any explicit constraint on geometry, often leading to inaccurate depth or surface recovery. This inspires many works to impose depth supervision in various" + } + ] + } + ], + "index": 8 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 758 + ], + "type": "text", + "content": "19564" + } + ] + } + ], + "index": 9 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 1 + }, + { + "para_blocks": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "spans": [ + { + "bbox": [ + 46, + 72, + 288, + 133 + ], + "type": "text", + "content": "forms [11, 32, 34, 36, 42, 45]. Notably, NeRFs on street scenes [27, 40, 43] typically involve derived depth supervision from Lidar. Our work distinguishes itself by reap benefits from Lidar to a deeper extent, by Lidar aggregation while accounting for occlusions." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 144, + 133, + 156 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 144, + 133, + 156 + ], + "spans": [ + { + "bbox": [ + 47, + 144, + 133, + 156 + ], + "type": "text", + "content": "3. Preliminaries" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "spans": [ + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "text", + "content": "Neural Radiance Field (NeRF) [22] represents a radiance field with a continuous neural network " + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "inline_equation", + "content": "f:(\\mathbf{x},\\mathbf{d})\\to (c,\\sigma)" + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "text", + "content": ", mapping spatial location " + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "inline_equation", + "content": "\\mathbf{x} = (x,y,z)" + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "text", + "content": " and viewing direction " + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "inline_equation", + "content": "\\mathbf{d} = (\\theta ,\\phi)" + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "text", + "content": " to the RGB color " + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "inline_equation", + "content": "c" + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "text", + "content": " and volumetric density " + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "inline_equation", + "content": "\\sigma" + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "text", + "content": " at that point. The network is queried at each point along the rendering ray to estimate color and density, which are then composed into the final pixel color using the volume rendering equation [17]. NeRF is optimized through the loss function " + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{rgb}}" + }, + { + "bbox": [ + 46, + 164, + 287, + 284 + ], + "type": "text", + "content": " defined as the mean squared error between the predicted and true colors of the training RGB images." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 285, + 289, + 452 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 285, + 289, + 452 + ], + "spans": [ + { + "bbox": [ + 46, + 285, + 289, + 452 + ], + "type": "text", + "content": "Nerfacto is the recommended approach within the open-source project Nerfstudio [29], integrating a variety of recipes that have proven effective for a wide range of real-world data. First, Nerfactor is capable of handling unbound scenes as required by street scenes, by applying the scene contraction strategy as in MipNeRF-360 [5]. For efficiency, it follows [5] to use proposal networks with small MLPs to consolidate the sampled locations along each ray to the regions near the first surface intersection. In terms of NeRF network architecture, it follows Instant-NGP [24] to leverage the grid-based feature representation parameterized by a hash map, which allows to decode color and density with the so-called fused MLPs, i.e. small MLPs that admits fast implementation [23]." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 47, + 464, + 104, + 475 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 464, + 104, + 475 + ], + "spans": [ + { + "bbox": [ + 47, + 464, + 104, + 475 + ], + "type": "text", + "content": "4. Method" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 483, + 115, + 495 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 483, + 115, + 495 + ], + "spans": [ + { + "bbox": [ + 47, + 483, + 115, + 495 + ], + "type": "text", + "content": "4.1. Overview" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "spans": [ + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "text", + "content": "We build LidaRF on top of Nerfacto, but develop several insights to integrate the use of Lidar for high-quality view synthesis on street scenes, as illustrated in Fig. 2. Our pipeline takes Lidar point clouds as input (Sec. 4.2), extracts geometric features from the point clouds, and fuses it with the hash-based feature grid to combine their complementary benefits. The hybrid features are fed to MLPs for decoding color and density, followed by standard volume rendering. In the output, we leverage denser Lidar points accumulated across frames as depth supervision while accounting for occlusion. This leads to two extra losses " + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{ds}}" + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "text", + "content": " (Sec. 4.3) and " + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{aug}}" + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "text", + "content": " (Sec. 4.4), besides the original losses from Nerfactor " + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{nerfacto}}" + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "text", + "content": ". All together, our loss " + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "inline_equation", + "content": "\\mathcal{L}" + }, + { + "bbox": [ + 46, + 502, + 289, + 659 + ], + "type": "text", + "content": " is written as" + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 100, + 671, + 287, + 699 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 100, + 671, + 287, + 699 + ], + "spans": [ + { + "bbox": [ + 100, + 671, + 287, + 699 + ], + "type": "interline_equation", + "content": "\\mathcal {L} = \\mathcal {L} _ {\\text {n e r f a c t o}} + \\lambda_ {1} \\cdot \\underbrace {\\mathcal {L} _ {\\mathrm {d s}}} _ {\\text {S e c . 4 . 3}} + \\lambda_ {2} \\cdot \\underbrace {\\mathcal {L} _ {\\text {a u g}}} _ {\\text {S e c . 4 . 4}}, \\tag {1}", + "image_path": "8ab127d24fddbe36f1acf876a2100e11d22d6d5e159752fef2c3cbe97db9f1ff.jpg" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 61, + 701, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 61, + 701, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 61, + 701, + 287, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 61, + 701, + 287, + 714 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{nerfacto}} = \\mathcal{L}_{\\mathrm{rgb}} + \\lambda_3 \\cdot \\mathcal{L}_{\\mathrm{dist}} + \\lambda_4 \\cdot \\mathcal{L}_{\\mathrm{interval}}" + }, + { + "bbox": [ + 61, + 701, + 287, + 714 + ], + "type": "text", + "content": ". (2)" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 306, + 72, + 537, + 85 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 72, + 537, + 85 + ], + "spans": [ + { + "bbox": [ + 306, + 72, + 537, + 85 + ], + "type": "text", + "content": "4.2. Hybrid Representation with Lidar Encoding" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 304, + 90, + 547, + 235 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 90, + 547, + 235 + ], + "spans": [ + { + "bbox": [ + 304, + 90, + 547, + 235 + ], + "type": "text", + "content": "Motivation. Lidar point clouds holds strong potential for geometric guidance that is highly valuable for NeRF. However, relying on Lidar features alone for scene representation, as done in [9], results in low-resolution rendering, due to the sparse nature of Lidar points despite temporal accumulation. In addition, Lidar does not cover the entire scene due to its limited field of view, e.g. it does not capture building surface above a certain height, yielding blank rendering in those regions as in [9]. Our framework, in contrast, fuses the Lidar features with the high-resolution spatial grid of features to leverage the strength of both, which are jointly learned for high-quality and complete scene rendering." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "spans": [ + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "text", + "content": "Lidar feature extraction. We detail here the extraction of geometric features for each Lidar point. Referring to Fig. 2, we first aggregate Lidar point clouds from all frames of the entire sequence to construct a denser set of point clouds. We then voxelize the point clouds into a voxel grid, where the spatial position of points falling into each voxel cell are averaged, yielding a 3-dim feature for each voxel cell. Inspired by its wide success on 3D perception frameworks [21, 44], we encode the scene geometry feature with a 3D sparse UNet [10, 30] on the voxel grid, which permits learning from a more global context of the scene geometry. The 3D sparse UNet takes the voxel grid along with its 3-dim features as input and outputs neural volumetric features, consisting of n-dim feature for each occupied voxel. This yields our Lidar embeddings " + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "inline_equation", + "content": "P = \\{(\\mathbf{p}_i,f_i)|i = 1,\\dots,N\\}" + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "text", + "content": ", where each point " + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "text", + "content": " is located at " + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_i" + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "text", + "content": " and associated with a vector " + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "inline_equation", + "content": "f_{i}" + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "text", + "content": ", which is the neural feature of the voxel cell it resides in, encoding the local and global geometry around " + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "inline_equation", + "content": "\\mathbf{p}_i" + }, + { + "bbox": [ + 304, + 236, + 548, + 452 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "spans": [ + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "text", + "content": "Query of Lidar features. For each sample point " + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "text", + "content": " along the ray to be rendered, we query its Lidar feature if there are at least " + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "text", + "content": " nearby Lidar points within a search radius " + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "inline_equation", + "content": "R" + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "text", + "content": "; otherwise, its Lidar feature is set as empty (i.e. all-zero). Specifically, we employ a Fixed Radius Nearest Neighbors (FRNN) approach [14] to search a " + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "inline_equation", + "content": "K" + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "text", + "content": "-nearest Lidar point index set with respect to " + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "text", + "content": ", denoted as " + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "inline_equation", + "content": "S_{\\mathbf{x}}^{K}" + }, + { + "bbox": [ + 304, + 455, + 547, + 598 + ], + "type": "text", + "content": ". Different from [9] where ray sampling is predetermined prior to initiating the training process, our method conducts FRNN searching online as the distribution of the sampled points from our proposal networks shift dynamically towards concentrating on the surface as the NeRF training converges." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "spans": [ + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "text", + "content": "Following Point-NeRF [41], our method harnesses an MLP, " + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "inline_equation", + "content": "\\mathcal{F}" + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "text", + "content": ", to map Lidar feature from each point to a neural scene description. For the " + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "text", + "content": "-th point neighbor of " + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "text", + "content": ", " + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "inline_equation", + "content": "\\mathcal{F}" + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "text", + "content": " takes as input the Lidar feature " + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "inline_equation", + "content": "f_{i}" + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "text", + "content": " and relative position " + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "inline_equation", + "content": "\\mathbf{x} - \\mathbf{p}_{i}" + }, + { + "bbox": [ + 304, + 598, + 547, + 658 + ], + "type": "text", + "content": ", and outputs the neural scene description as" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 375, + 667, + 545, + 681 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 375, + 667, + 545, + 681 + ], + "spans": [ + { + "bbox": [ + 375, + 667, + 545, + 681 + ], + "type": "interline_equation", + "content": "f _ {i, \\mathbf {x}} = \\mathcal {F} \\left(\\left[ f _ {i}, \\mathbf {x} - \\mathbf {p} _ {i} \\right]\\right), \\tag {3}", + "image_path": "eb426ca3c0c2e41005d19deb14e68d596f80443a5188f2bbb4e5e55c803be3a6.jpg" + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "spans": [ + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "type": "inline_equation", + "content": "[,]" + }, + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "type": "text", + "content": " indicates concatenation. To obtain the final Lidar encoding " + }, + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "type": "inline_equation", + "content": "\\phi_L(\\mathbf{x})" + }, + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "type": "text", + "content": " at the sampled location " + }, + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 304, + 689, + 547, + 714 + ], + "type": "text", + "content": ", we use standard" + } + ] + } + ], + "index": 15 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19565" + } + ] + } + ], + "index": 16 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 2 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 74, + 71, + 520, + 160 + ], + "blocks": [ + { + 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Robust Depth Supervision" + } + ] + } + ], + "index": 26 + }, + { + "bbox": [ + 46, + 594, + 289, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 594, + 289, + 713 + ], + "spans": [ + { + "bbox": [ + 46, + 594, + 289, + 713 + ], + "type": "text", + "content": "Motivation. In addition to the feature encoding, we also derive depth supervision from the Lidar points by projecting them onto the image plane. However, the sparse nature of Lidar points yields limited benefits, that are not sufficient for reconstructing low-texture regions such as road surface. Here, we put forth to accumulate adjacent Lidar frames to increase density. Despite the 3D points accurately capturing the scene structure, one needs to account for inter-points occlusion when projecting them onto the image plane for depth supervision. The occlusion arises due to the increased" + } + ] + } + ], + "index": 27 + }, + { + "type": "image", + "bbox": [ + 307, + 331, + 541, + 460 + ], + "blocks": [ + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "lines": [ + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "spans": [ + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "text", + "content": "Figure 2. Overview of LidaRF - it takes as input the sampled 3D positions " + }, + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "inline_equation", + "content": "\\mathbf{x}" + }, + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "text", + "content": " and ray directions " + }, + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "inline_equation", + "content": "\\mathbf{d}" + }, + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "text", + "content": ", and outputs corresponding density " + }, + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "inline_equation", + "content": "\\alpha" + }, + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "text", + "content": " and color " + }, + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "inline_equation", + "content": "\\mathbf{c}" + }, + { + "bbox": [ + 46, + 285, + 547, + 319 + ], + "type": "text", + "content": ". It incorporates both hash encoding and LiDAR encoding using a sparse UNet. Additionally, augmented training data is generated through LiDAR projections, and the geometry prediction is trained with our proposed robust depth supervision scheme." + } + ] + } + ], + "index": 19, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 307, + 331, + 541, + 460 + ], + "lines": [ + { + "bbox": [ + 307, + 331, + 541, + 460 + ], + "spans": [ + { + "bbox": [ + 307, + 331, + 541, + 460 + ], + "type": "image", + "image_path": "d42417409edc8e0f3941161d1021f46a5b8b788a4666435c7b92d42626bbb870.jpg" + } + ] + } + ], + "index": 28, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 472, + 545, + 516 + ], + "lines": [ + { + "bbox": [ + 305, + 472, + 545, + 516 + ], + "spans": [ + { + "bbox": [ + 305, + 472, + 545, + 516 + ], + "type": "text", + "content": "Figure 3. Illustration of the occlusion issue on the depth map projected from accumulated Lidar points. Observe that multiple layers of surface points may project to the same region on the image, yielding ghost depth points." + } + ] + } + ], + "index": 29, + "angle": 0, + "type": "image_caption" + } + ], + "index": 28 + }, + { + "bbox": [ + 304, + 529, + 547, + 614 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 529, + 547, + 614 + ], + "spans": [ + { + "bbox": [ + 304, + 529, + 547, + 614 + ], + "type": "text", + "content": "displacement between the camera and the Lidar from its adjacent frames, yielding bogus depth supervision, as illustrated in Fig. 3. This is non-trivial to handle due to the sparsity of Lidar even after accumulation, making principled graphic techniques such as z-buffering not applicable. In this work, we propose a robust supervision scheme to automatically filter out bogus depth supervision in while training NeRF." + } + ] + } + ], + "index": 30 + }, + { + "bbox": [ + 304, + 617, + 548, + 715 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 617, + 548, + 715 + ], + "spans": [ + { + "bbox": [ + 304, + 617, + 548, + 715 + ], + "type": "text", + "content": "Occlusion-aware robust supervision scheme. We design a curriculum training strategy such that the model initially trains with closer, more reliable depth data, which are less prone to occlusion. As training progresses, the model gradually begins to incorporate more distant depth data. Concurrently, the model develops the capacity to discard depth supervisions that are anomalously distant compared to its predictions. Formally, with the pool of all depth points de" + } + ] + } + ], + "index": 31 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 318, + 757 + ], + "type": "text", + "content": "19566" + } + ] + } + ], + "index": 32 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 3 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 72, + 286, + 173 + ], + "blocks": [ + { + "bbox": [ + 50, + 72, + 286, + 173 + ], + "lines": [ + { + "bbox": [ + 50, + 72, + 286, + 173 + ], + "spans": [ + { + "bbox": [ + 50, + 72, + 286, + 173 + ], + "type": "image", + "image_path": "5688e5207e26c48382066f5059221a898f0e9e4f5141d2a6c7ea397abacc2a94.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 178, + 287, + 201 + ], + "lines": [ + { + "bbox": [ + 46, + 178, + 287, + 201 + ], + "spans": [ + { + "bbox": [ + 46, + 178, + 287, + 201 + ], + "type": "text", + "content": "Figure 4. Illustration of the true probability mass and its mid-point approximation." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "spans": [ + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "text", + "content": "noted as " + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "inline_equation", + "content": "\\mathcal{D} = \\{\\mathcal{D}_1,\\mathcal{D}_2,\\dots,\\mathcal{D}_N\\}" + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "text", + "content": ", and further denoting the NeRF-rendered depth corresponding to " + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_i" + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "text", + "content": " as " + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{D}}_i" + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "text", + "content": ", we identify the reliable subset of depth points " + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathrm{reliable}}^m" + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "text", + "content": " in the " + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "inline_equation", + "content": "m" + }, + { + "bbox": [ + 46, + 211, + 288, + 258 + ], + "type": "text", + "content": "-th training iteration as:" + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 58, + 266, + 287, + 280 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 58, + 266, + 287, + 280 + ], + "spans": [ + { + "bbox": [ + 58, + 266, + 287, + 280 + ], + "type": "interline_equation", + "content": "\\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m} = \\left\\{\\mathcal {D} _ {i} \\mid \\mathcal {D} _ {i} \\leq \\epsilon_ {t} ^ {m}, \\mathcal {D} _ {i} \\leq \\hat {\\mathcal {D}} _ {i} + \\epsilon_ {o} ^ {m}, \\mathcal {D} _ {i} \\in \\mathcal {D} \\right\\}, \\tag {8}", + "image_path": "07ae5bf8a606ce6d678e47d2cb78223a9babeec2230c15fbe98974f670d02bca.jpg" + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 77, + 282, + 287, + 297 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 77, + 282, + 287, + 297 + ], + "spans": [ + { + "bbox": [ + 77, + 282, + 287, + 297 + ], + "type": "interline_equation", + "content": "\\epsilon_ {t} ^ {m} = \\min \\left\\{\\alpha_ {t} \\epsilon_ {t} ^ {m - 1}, \\epsilon_ {t} \\right\\}, \\quad \\alpha_ {t} > 1, \\tag {9}", + "image_path": "1cdf119aca48e0ac4065526e3d710a2ecac2213c31c4d2e950c5adf55ec78150.jpg" + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 77, + 299, + 287, + 312 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 77, + 299, + 287, + 312 + ], + "spans": [ + { + "bbox": [ + 77, + 299, + 287, + 312 + ], + "type": "interline_equation", + "content": "\\epsilon_ {o} ^ {m} = \\max \\left\\{\\alpha_ {o} \\epsilon_ {o} ^ {m - 1}, \\epsilon_ {o} \\right\\}, \\quad \\alpha_ {o} < 1. \\tag {10}", + "image_path": "d3d6c9ac8205a284072ce079de13e5d81f6cf8bda0433a219e059d4e1b80638b.jpg" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "spans": [ + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": "One notices that " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathrm{reliable}}^m" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": " is governed by two scheduled parameters: valid depth threshold " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\epsilon_t^m" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": " and valid depth offset " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\epsilon_o^m" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": ". The " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\epsilon_t^m" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": " serves to filter out depth samples exceeding this threshold, thereby prioritizing nearer depth samples which are less likely to be occluded. As training progresses, " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\epsilon_t^m" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": " is exponentially increased at a rate of " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\alpha_t" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": " to involve more depth supervision from further field. Meanwhile, samples exhibiting a depth value far larger than the predicted depth " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{D}}_i" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": " are omitted, as they are likely occluded points. This is thresholded by " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{D}}_i + \\epsilon_o^m" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": ", with " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\epsilon_o^m" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": " decaying exponentially at a rate of " + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "inline_equation", + "content": "\\alpha_o" + }, + { + "bbox": [ + 46, + 319, + 288, + 464 + ], + "type": "text", + "content": ", in tandem with the improvement of depth predictions over the course of training." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "spans": [ + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": "Lidar Depth Loss For samples in " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "\\mathcal{D}_{\\mathrm{reliable}}^m" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": ", we adopt the pixel-level depth loss proposed in URF [27], written as " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{ds}} = \\mathcal{L}_{\\mathrm{depth}} + \\mathcal{L}_{\\mathrm{sight}}" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": ". In addition to a " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "L_{2}" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": " loss " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{depth}}" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": " between the rendered depth and the ground truth, a line-of-sight prior " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{sight}}" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": " is applied to further constrain each sampling point individually. But in contrast an approximate computation of " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{sight}}" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": " in NeRFstudio, we implement an exact one. Specifically, we first note that the volume rendering boils down to a weighted sum of the predicted color on sampled points along the ray (see supplementary for equations). Given the weight should ideally concentrate around surfaces, " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{sight}}" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": " enforces the weight distribution to resemble a Gaussian distribution " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "\\mathcal{N}(\\hat{\\mathcal{D}}_i,\\epsilon_n)" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": " centered at the ground truth depth " + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "inline_equation", + "content": "\\hat{\\mathcal{D}}_i" + }, + { + "bbox": [ + 46, + 477, + 287, + 646 + ], + "type": "text", + "content": " along the rendering ray, written as" + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 57, + 651, + 287, + 689 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 57, + 651, + 287, + 689 + ], + "spans": [ + { + "bbox": [ + 57, + 651, + 287, + 689 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {s i g h t}} = \\mathbb {E} _ {\\mathcal {D} _ {i} \\in \\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m}} \\left[ \\int_ {t _ {\\text {n e a r}}} ^ {t _ {\\text {f a r}}} (w (t) - \\mathcal {N} (\\hat {\\mathcal {D}} _ {i}, \\epsilon_ {n})) ^ {2} d t \\right], \\tag {11}", + "image_path": "b1410c73e1164e32513baf2688fa5fdd09683d395579f563c6b8ebb8542b64b8.jpg" + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": " indicates the weight to be integrated along the distance " + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "t" + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": " on the rendering ray from " + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "t_{near}" + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": " to " + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "inline_equation", + "content": "t_{far}" + }, + { + "bbox": [ + 46, + 689, + 287, + 714 + ], + "type": "text", + "content": ". Since the" + } + ] + } + ], + "index": 9 + }, + { + "type": "table", + "bbox": [ + 309, + 70, + 547, + 143 + ], + "blocks": [ + { + "bbox": [ + 309, + 70, + 547, + 143 + ], + "lines": [ + { + "bbox": [ + 309, + 70, + 547, + 143 + ], + "spans": [ + { + "bbox": [ + 309, + 70, + 547, + 143 + ], + "type": "table", + "html": "
MethodsInterpolationLane Shift
PSNR↑SSIM↑LPIPS↓FID↓@2mFID↓@3.7m
Instant-NGP24.2820.7330.408140.3173.2
Mip-NeRF 36023.6930.6910.496189.4231.1
Nerfacto27.1220.8040.268116.7151.0
UniSim26.0140.7680.342118.5141.3
LidaRF (Ours)27.2550.8120.224106.5126.0
", + "image_path": "0bba22e80c19692de3b3f65d05ca3472a8b7046365ce7039e844fefe178db042.jpg" + } + ] + } + ], + "index": 10, + "angle": 0, + "type": "table_body" + } + ], + "index": 10 + }, + { + "bbox": [ + 305, + 151, + 547, + 172 + ], + "lines": [ + { + "bbox": [ + 305, + 151, + 547, + 172 + ], + "spans": [ + { + "bbox": [ + 305, + 151, + 547, + 172 + ], + "type": "text", + "content": "Table 1. Quantitative comparisons on view synthesis with state-of-the-art NeRF variants." + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 305, + 185, + 545, + 209 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 185, + 545, + 209 + ], + "spans": [ + { + "bbox": [ + 305, + 185, + 545, + 209 + ], + "type": "text", + "content": "weight " + }, + { + "bbox": [ + 305, + 185, + 545, + 209 + ], + "type": "inline_equation", + "content": "w" + }, + { + "bbox": [ + 305, + 185, + 545, + 209 + ], + "type": "text", + "content": " is computed on discrete intervals given by point sampling in NeRF, this loss is discretized to" + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 345, + 219, + 545, + 252 + ], + "type": "interline_equation", + "angle": 0, + "lines": [ + { + "bbox": [ + 345, + 219, + 545, + 252 + ], + "spans": [ + { + "bbox": [ + 345, + 219, + 545, + 252 + ], + "type": "interline_equation", + "content": "\\mathcal {L} _ {\\text {s i g h t}} = \\mathbb {E} _ {\\mathcal {D} _ {i} \\in \\mathcal {D} _ {\\text {r e l i a b l e}} ^ {m}} \\left[ \\sum_ {i} \\left(w _ {i} - \\mathcal {N} _ {i}\\right) ^ {2} \\right], \\tag {12}", + "image_path": "bcb6ce0c651bb83e4e052a065e9fa8a313e58f763768994d8af0ab56c5341611.jpg" + } + ] + } + ], + "index": 13 + }, + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "spans": [ + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "type": "text", + "content": "where " + }, + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_i" + }, + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "type": "text", + "content": " indicates the probability mass within the " + }, + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "type": "inline_equation", + "content": "i" + }, + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "type": "text", + "content": "-th interval. Here, a possible implementation (e.g. in Nerfstudio [29]) to obtain " + }, + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "type": "inline_equation", + "content": "\\mathcal{N}_i" + }, + { + "bbox": [ + 304, + 258, + 547, + 365 + ], + "type": "text", + "content": " is by mid-point approximation as illustrated in Fig. 4. However, we note that this approximation is unnecessary and implement differently based on cumulative distribution function (CDF) - the probability mass of a Gaussian distribution can be obtained through its tabulated CDF. We show in supplementary that our exact implementation leads to improved PSNRs." + } + ] + } + ], + "index": 14 + }, + { + "bbox": [ + 305, + 374, + 466, + 387 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 374, + 466, + 387 + ], + "spans": [ + { + "bbox": [ + 305, + 374, + 466, + 387 + ], + "type": "text", + "content": "4.4. Augmented View Supervision" + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 393, + 547, + 634 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 393, + 547, + 634 + ], + "spans": [ + { + "bbox": [ + 304, + 393, + 547, + 634 + ], + "type": "text", + "content": "Recall that a vehicle-mounted camera generates sparse training images with limited view coverage due to its forward motion, posing challenges for NeRF reconstruction, especially when the novel views deviate from vehicle trajectory. Here, we propose to augment training data leveraging Lidar. First, we colorize the point clouds in each Lidar frame by projecting onto its synchronized camera and interpolate the image for RGB values. The colorized point clouds are accumulated as described in Sec. 4.3 and projected onto a set of synthetically augmented views, yielding synthesized images and depth maps as illustrated in Fig. 2. These augmented training views are derived from existing ones, by introducing stochastic perturbations to their camera centers, with the shifting magnitude " + }, + { + "bbox": [ + 304, + 393, + 547, + 634 + ], + "type": "inline_equation", + "content": "\\epsilon_{a} \\in \\mathcal{N}(0, \\epsilon_{a})" + }, + { + "bbox": [ + 304, + 393, + 547, + 634 + ], + "type": "text", + "content": ". Nonetheless, such augmented data fails to account for potential occlusions as depicted in Sec. 4.3. Our model, fortified by robust depth supervision, is adept at discerning and excluding occluded Lidar points online. The augmented views are used to train NeRF similarly as the real training views, and we denote the extra loss separately as " + }, + { + "bbox": [ + 304, + 393, + 547, + 634 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\text{aug}}" + }, + { + "bbox": [ + 304, + 393, + 547, + 634 + ], + "type": "text", + "content": "." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 645, + 387, + 658 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 645, + 387, + 658 + ], + "spans": [ + { + "bbox": [ + 306, + 645, + 387, + 658 + ], + "type": "text", + "content": "5. Experiments" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 665, + 547, + 713 + ], + "type": "text", + "content": "In this section, we detail our experimental setup and benchmark our method against state-of-the-art NeRF techniques, demonstrating superior photorealism. We further ablate our design choices, underscoring the effectiveness of ro" + } + ] + } + ], + "index": 18 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19567" + } + ] + } + ], + "index": 19 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 4 + }, + { + "para_blocks": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "spans": [ + { + "bbox": [ + 47, + 72, + 287, + 96 + ], + "type": "text", + "content": "bust depth supervision, LiDAR encoding, and augmented view supervision in enhancing realism." + } + ] + } + ], + "index": 0 + }, + { + "bbox": [ + 47, + 102, + 163, + 115 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 102, + 163, + 115 + ], + "spans": [ + { + "bbox": [ + 47, + 102, + 163, + 115 + ], + "type": "text", + "content": "5.1. Experimental Setup" + } + ] + } + ], + "index": 1 + }, + { + "bbox": [ + 46, + 121, + 288, + 228 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 121, + 288, + 228 + ], + "spans": [ + { + "bbox": [ + 46, + 121, + 288, + 228 + ], + "type": "text", + "content": "Datasets. Following [43], we rely on Pandaset [39] as the primary dataset for evaluation, using its front camera and synchronized spinning Lidar. Each scene is consisting of 80 frames captured at " + }, + { + "bbox": [ + 46, + 121, + 288, + 228 + ], + "type": "inline_equation", + "content": "10\\mathrm{Hz}" + }, + { + "bbox": [ + 46, + 121, + 288, + 228 + ], + "type": "text", + "content": ". We leverage its sensor localization for Lidar accumulation. Since our focus is on static scenes, the dynamic vehicles are masked out during evaluation, similarly as in [9]. We also evaluate on NuScenes [6] and Argoverse2 [37] to compare with S-NeRF [40] and NeRF-LiDAR-cGAN [9], respectively." + } + ] + } + ], + "index": 2 + }, + { + "bbox": [ + 46, + 232, + 288, + 387 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 232, + 288, + 387 + ], + "spans": [ + { + "bbox": [ + 46, + 232, + 288, + 387 + ], + "type": "text", + "content": "Baselines. On Pandaset, we compare our model against several modern implicit-based neural radiance fields methods: Instant-NGP, Mip-NeRF 360, Nerfacto and UniSim. Instant-NGP [24] adopts multi-resolution hashing encoding for compact scene representation and efficient rendering. Mip-NeRF 360 [5] adopts integrated position encoding with scene contraction for handling unbounded scenes. Nerfacto [29] combines the compact representation from Instant-NGP and proposal network from Mip-NeRF 360. UniSim [43] is the state-of-the-art simulator for street scenes, reconstructing both the static background and dynamic actors with neural feature grids. In our experiments, we mainly focus on modeling the static background." + } + ] + } + ], + "index": 3 + }, + { + "bbox": [ + 46, + 389, + 287, + 521 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 389, + 287, + 521 + ], + "spans": [ + { + "bbox": [ + 46, + 389, + 287, + 521 + ], + "type": "text", + "content": "Implementation Details. We mask dynamic objects in RGB images using dataset bounding box annotations and an instance segmentation model [13]. Static Lidar points are isolated by omitting points within dynamic objects' 3D bounding boxes. For nearest neighbor searches, we use a CUDA-based FRNN search algorithm [1] to query " + }, + { + "bbox": [ + 46, + 389, + 287, + 521 + ], + "type": "inline_equation", + "content": "K = 6" + }, + { + "bbox": [ + 46, + 389, + 287, + 521 + ], + "type": "text", + "content": " nearest Lidar points within a " + }, + { + "bbox": [ + 46, + 389, + 287, + 521 + ], + "type": "inline_equation", + "content": "0.3m" + }, + { + "bbox": [ + 46, + 389, + 287, + 521 + ], + "type": "text", + "content": " radius. Our loss weights and scheduling parameters in depth training scheme are given in supplementary. Instant-NGP, Nerfacto, UniSim and our proposed LidaRF use identical size of hash grid and hidden layers in MLPs. Additional details are in the supplementary." + } + ] + } + ], + "index": 4 + }, + { + "bbox": [ + 47, + 527, + 206, + 540 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 527, + 206, + 540 + ], + "spans": [ + { + "bbox": [ + 47, + 527, + 206, + 540 + ], + "type": "text", + "content": "5.2. Novel View Synthesis Results" + } + ] + } + ], + "index": 5 + }, + { + "bbox": [ + 46, + 545, + 287, + 664 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 545, + 287, + 664 + ], + "spans": [ + { + "bbox": [ + 46, + 545, + 287, + 664 + ], + "type": "text", + "content": "In our experiments, we assess novel view synthesis under interpolation and extrapolation settings. For interpolation setting, we randomly subsample RGB and Lidar frames, testing on every fourth frame and training on the rest. We follow common practice to report PSNR, SSIM, and LPIPS interpolation views. For extrapolation setting, following [43], we simulate new trajectories by laterally shifting them left or right by 2 or 3.7 meters (lane width of Interstate Highway standards [2]). We report FID at the perceptual level since ground-truth is unavailable," + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "content": "As shown in Tab. 1, our method outperforms all others in every metric. While methods such as Nerfacto and UniSim show robust performance in the interpolation setting, MipNeRF 360 lags behind. The qualitative gap becomes even" + } + ] + } + ], + "index": 7 + }, + { + "type": "table", + "bbox": [ + 309, + 72, + 545, + 164 + ], + "blocks": [ + { + "bbox": [ + 309, + 72, + 545, + 164 + ], + "lines": [ + { + "bbox": [ + 309, + 72, + 545, + 164 + ], + "spans": [ + { + "bbox": [ + 309, + 72, + 545, + 164 + ], + "type": "table", + "html": "
LdsLdsHPRdsLrobustdsφLLaugPSNR↑SSIM↑LPIPS↓FID↓ @3.7m
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", + "image_path": "fc72e2104a1a86c46058f9190ece9d00333a17aa794d591d15f1a237c2e87b3d.jpg" + } + ] + } + ], + "index": 8, + "angle": 0, + "type": "table_body" + } + ], + "index": 8 + }, + { + "bbox": [ + 305, + 173, + 545, + 195 + ], + "lines": [ + { + "bbox": [ + 305, + 173, + 545, + 195 + ], + "spans": [ + { + "bbox": [ + 305, + 173, + 545, + 195 + ], + "type": "text", + "content": "Table 2. Ablation study of our robust depth supervision, Lidar encoding, and training view augmentation on Pandaset." + } + ] + } + ], + "index": 9, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 304, + 206, + 547, + 302 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 206, + 547, + 302 + ], + "spans": [ + { + "bbox": [ + 304, + 206, + 547, + 302 + ], + "type": "text", + "content": "more significant in extrapolation scenarios. Fig. 5 displays these qualitative differences, where our method exhibits enhanced visual realism compared to the baselines, particularly in rendering fine structures, thanks to our LiDAR encoding. This is especially notable as, even though UniSim also utilizes LiDAR depth supervision, our method more effectively renders low-texture areas like road surfaces, demonstrating the advantage of our deeper utilization of Lidar." + } + ] + } + ], + "index": 10 + }, + { + "bbox": [ + 306, + 309, + 399, + 322 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 309, + 399, + 322 + ], + "spans": [ + { + "bbox": [ + 306, + 309, + 399, + 322 + ], + "type": "text", + "content": "5.3. Ablation Study" + } + ] + } + ], + "index": 11 + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "spans": [ + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "text", + "content": "In our ablation study presented in Tab. 2, we evaluate the impact of three key components - robust depth supervision, Lidar encoding, and augmented view supervision. The baseline for comparison, shown in the first row of Table 2, is the Nerfacto method. We denote different depth supervision strategies as follows: " + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ds}^{1}" + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "text", + "content": " for single-frame Lidar depth supervision, " + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ds}^{10}" + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "text", + "content": " for depth map supervision using 10 adjacent Lidar frames, and " + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ds}" + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "text", + "content": " for the same but within our robust supervision scheme. As another baseline for occlusion handling, we apply hidden point removal (HPR) algorithm [18] implemented in Open3D [48] to remove occluded points as data preprocessing; the supervision after HPR is denoted as " + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ds}^{\\mathrm{HPR}}" + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "text", + "content": ". Lidar encoding is represented by " + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "inline_equation", + "content": "\\phi_L" + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "text", + "content": ". Lastly, " + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{aug}}" + }, + { + "bbox": [ + 304, + 327, + 547, + 508 + ], + "type": "text", + "content": " signifies supervision with augmented RGB and depth data derived from Lidar projections." + } + ] + } + ], + "index": 12 + }, + { + "bbox": [ + 304, + 510, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 510, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 510, + 547, + 713 + ], + "type": "text", + "content": "Effects of Robust Depth Supervision. In Tab. 2, we illustrate that Lidar depth markedly improves LPIPS and FID in lane shift settings with marginal PSNR drop compared to Nerfacto. Notably, our robust supervision scheme with accumulated Lidar points further enhances all metrics. Also note the offline HPR significantly lags behind our more adaptive, NeRF-informed scheme for occlusion handling. Fig. 6 compares different Lidar depth supervision settings. Under the supervision of " + }, + { + "bbox": [ + 304, + 510, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{ds}}^{1}" + }, + { + "bbox": [ + 304, + 510, + 547, + 713 + ], + "type": "text", + "content": ", which utilizes single-frame Lidar depth maps known for their sparsity and reduced occlusions, the rendered depths exhibit high accuracy in texture-rich areas (as indicated by the yellow boxes). However, this accuracy significantly diminishes in regions with thin structures, due to a lack of abundant geometric guidance, as observed in the red boxes. Conversely, the supervision with " + }, + { + "bbox": [ + 304, + 510, + 547, + 713 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{ds}}^{10}" + }, + { + "bbox": [ + 304, + 510, + 547, + 713 + ], + "type": "text", + "content": ", involving with noisy Lidar depth maps accumulated from 10 adjacent frames, leads to rendered depths that display noticeable noise." + } + ] + } + ], + "index": 13 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19568" + } + ] + } + ], + "index": 14 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 5 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 61, + 62, + 527, + 459 + ], + "blocks": [ + { + "bbox": [ + 61, + 62, + 527, + 459 + ], + "lines": [ + { + "bbox": [ + 61, + 62, + 527, + 459 + ], + "spans": [ + { + "bbox": [ + 61, + 62, + 527, + 459 + ], + "type": "image", + "image_path": "b84b6860bbcd5c7b5e34f7e8560089ae279738c6db738046af7b5c2b35f4099c.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 48, + 484, + 545, + 671 + ], + "blocks": [ + { + "bbox": [ + 46, + 462, + 545, + 483 + ], + "lines": [ + { + "bbox": [ + 46, + 462, + 545, + 483 + ], + "spans": [ + { + "bbox": [ + 46, + 462, + 545, + 483 + ], + "type": "text", + "content": "Figure 5. Qualitative Comparison on novel view synthesis from different methods. We evaluate on both the interpolation and extrapolation views, the latter of which corresponds to a lane shift. We highlight the performance gap with boxes." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + }, + { + "bbox": [ + 48, + 484, + 545, + 671 + ], + "lines": [ + { + "bbox": [ + 48, + 484, + 545, + 671 + ], + "spans": [ + { + "bbox": [ + 48, + 484, + 545, + 671 + ], + "type": "image", + "image_path": "f1ff4e8eb982cb263387651b75f1470b93f2c2212fc08c29065250bb28d081ab.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 46, + 676, + 546, + 719 + ], + "lines": [ + { + "bbox": [ + 46, + 676, + 546, + 719 + ], + "spans": [ + { + "bbox": [ + 46, + 676, + 546, + 719 + ], + "type": "text", + "content": "Figure 6. Qualitative comparison between different LiDAR Depth Supervisions – With sparse depths, Nerfacto w/ " + }, + { + "bbox": [ + 46, + 676, + 546, + 719 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{ds}}^i" + }, + { + "bbox": [ + 46, + 676, + 546, + 719 + ], + "type": "text", + "content": " fails to model thin structures. With denser but noisy depths, Nerfacto w/ " + }, + { + "bbox": [ + 46, + 676, + 546, + 719 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{\\mathrm{ds}}^i" + }, + { + "bbox": [ + 46, + 676, + 546, + 719 + ], + "type": "text", + "content": " generate ambiguous depth predictions. Our proposed schemes is robust to occlusions and able to learn delicate structures. Our proposed depth supervision scheme can learn delicate structures with noisy depth map, while the other settings both fail." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + } + ], + "discarded_blocks": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "page_number", + "angle": 0, + "lines": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "spans": [ + { + "bbox": [ + 294, + 748, + 317, + 757 + ], + "type": "text", + "content": "19569" + } + ] + } + ], + "index": 4 + } + ], + "page_size": [ + 612, + 792 + ], + "page_idx": 6 + }, + { + "para_blocks": [ + { + "type": "image", + "bbox": [ + 50, + 72, + 286, + 156 + ], + "blocks": [ + { + "bbox": [ + 50, + 72, + 286, + 156 + ], + "lines": [ + { + "bbox": [ + 50, + 72, + 286, + 156 + ], + "spans": [ + { + "bbox": [ + 50, + 72, + 286, + 156 + ], + "type": "image", + "image_path": "50e810f82b7a4428aaa80fc0bbd8f6bb6f2dfc04c670c4fa5a7b9613213d4d0e.jpg" + } + ] + } + ], + "index": 0, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 158, + 286, + 179 + ], + "lines": [ + { + "bbox": [ + 47, + 158, + 286, + 179 + ], + "spans": [ + { + "bbox": [ + 47, + 158, + 286, + 179 + ], + "type": "text", + "content": "Figure 7. Qualitative comparison w.r.t Lidar encoding - Lidar encoding is beneficial in modelling sharp textures, e.g. power lines." + } + ] + } + ], + "index": 1, + "angle": 0, + "type": "image_caption" + } + ], + "index": 0 + }, + { + "type": "image", + "bbox": [ + 48, + 183, + 286, + 239 + ], + "blocks": [ + { + "bbox": [ + 48, + 183, + 286, + 239 + ], + "lines": [ + { + "bbox": [ + 48, + 183, + 286, + 239 + ], + "spans": [ + { + "bbox": [ + 48, + 183, + 286, + 239 + ], + "type": "image", + "image_path": "88224021f52d8cb4282018aa550f0b6bacf2399f701ac3f7d43ec95d95616872.jpg" + } + ] + } + ], + "index": 2, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 47, + 242, + 287, + 275 + ], + "lines": [ + { + "bbox": [ + 47, + 242, + 287, + 275 + ], + "spans": [ + { + "bbox": [ + 47, + 242, + 287, + 275 + ], + "type": "text", + "content": "Figure 8. Qualitative comparison w.r.t augmented view supervision - it largely improves rendering quality on the regions which are scarcely captured in the raw training data." + } + ] + } + ], + "index": 3, + "angle": 0, + "type": "image_caption" + } + ], + "index": 2 + }, + { + "type": "table", + "bbox": [ + 55, + 281, + 280, + 347 + ], + "blocks": [ + { + "bbox": [ + 55, + 281, + 280, + 347 + ], + "lines": [ + { + "bbox": [ + 55, + 281, + 280, + 347 + ], + "spans": [ + { + "bbox": [ + 55, + 281, + 280, + 347 + ], + "type": "table", + "html": "
MethodsS-NeRFLidaRF (Ours)
w/o Ldsw/o φLw/o LaugFull
PSNR↑29.37730.62931.00131.13331.162
SSIM↑0.8590.8710.8730.8830.884
LPIPS↓0.3490.2780.2370.2220.211
", + "image_path": "ec118df39f8b922f03567b338d9755318d9613daba5e3ebf5182bd79c4eae831.jpg" + } + ] + } + ], + "index": 4, + "angle": 0, + "type": "table_body" + } + ], + "index": 4 + }, + { + "bbox": [ + 53, + 351, + 280, + 361 + ], + "lines": [ + { + "bbox": [ + 53, + 351, + 280, + 361 + ], + "spans": [ + { + "bbox": [ + 53, + 351, + 280, + 361 + ], + "type": "text", + "content": "Table 3. Evaluation on NuScenes with comparison to S-NeRF." + } + ] + } + ], + "index": 5, + "angle": 0, + "type": "text" + }, + { + "bbox": [ + 46, + 383, + 287, + 456 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 383, + 287, + 456 + ], + "spans": [ + { + "bbox": [ + 46, + 383, + 287, + 456 + ], + "type": "text", + "content": "This is attributed to the prevalent depth ambiguities within the data. Employing our proposed " + }, + { + "bbox": [ + 46, + 383, + 287, + 456 + ], + "type": "inline_equation", + "content": "\\mathcal{L}_{ds}^{\\mathrm{robust}}" + }, + { + "bbox": [ + 46, + 383, + 287, + 456 + ], + "type": "text", + "content": ", our methodology effectively leverages denser depth maps for the precise reconstruction of intricate structures (highlighted in red boxes), as well as excludes some occluded depths (noted in yellow boxes). See more examples in the supplementary materials." + } + ] + } + ], + "index": 6 + }, + { + "bbox": [ + 46, + 457, + 287, + 529 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 457, + 287, + 529 + ], + "spans": [ + { + "bbox": [ + 46, + 457, + 287, + 529 + ], + "type": "text", + "content": "Effects of Lidar Encoding. From Tab. 2, it is evident that Lidar encoding contributes to enhancements across all metrics. As shown in Fig. 7, Lidar encoding enables our method to produce sharper textures. This enhancement stems from our sparse convolution-based architecture, which is resilient to Lidar point noise and density variations." + } + ] + } + ], + "index": 7 + }, + { + "bbox": [ + 46, + 532, + 288, + 640 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 532, + 288, + 640 + ], + "spans": [ + { + "bbox": [ + 46, + 532, + 288, + 640 + ], + "type": "text", + "content": "Effects of Augmented View Supervision. While the quantitative benefits of augmented view supervision, as per Tab. 2, appear modest, it consistently enhances performance in extrapolation scenarios across all test scenes. This is particularly notable in scenes where other methodologies fall short. Fig. 8 showcases an instance of this: in scenes with parking cars that are scarcely captured in the raw training data due to the rapid movement of the camera vehicle, our augmented view supervision significantly elevates the quality." + } + ] + } + ], + "index": 8 + }, + { + "bbox": [ + 47, + 647, + 237, + 659 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 47, + 647, + 237, + 659 + ], + "spans": [ + { + "bbox": [ + 47, + 647, + 237, + 659 + ], + "type": "text", + "content": "5.4. Results on NuScenes and Argoverse" + } + ] + } + ], + "index": 9 + }, + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "spans": [ + { + "bbox": [ + 46, + 665, + 288, + 714 + ], + "type": "text", + "content": "we evaluate LidaRF on the NuScenes dataset with comparison to S-NeRF, by adapting their method to using the single front camera. We present quantitative results in Tab. 3 and qualitative example in Fig. 9, both showing superior per" + } + ] + } + ], + "index": 10 + }, + { + "type": "image", + "bbox": [ + 309, + 73, + 544, + 159 + ], + "blocks": [ + { + "bbox": [ + 309, + 73, + 544, + 159 + ], + "lines": [ + { + "bbox": [ + 309, + 73, + 544, + 159 + ], + "spans": [ + { + "bbox": [ + 309, + 73, + 544, + 159 + ], + "type": "image", + "image_path": "dcc382e0b0e231f28b853a3f90d02154ac1c898543e9beabae1e75370d99b9f4.jpg" + } + ] + } + ], + "index": 11, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 321, + 160, + 529, + 171 + ], + "lines": [ + { + "bbox": [ + 321, + 160, + 529, + 171 + ], + "spans": [ + { + "bbox": [ + 321, + 160, + 529, + 171 + ], + "type": "text", + "content": "Figure 9. Visual Comparison with S-NeRF on NuScenes." + } + ] + } + ], + "index": 12, + "angle": 0, + "type": "image_caption" + } + ], + "index": 11 + }, + { + "type": "image", + "bbox": [ + 307, + 178, + 544, + 346 + ], + "blocks": [ + { + "bbox": [ + 307, + 178, + 544, + 346 + ], + "lines": [ + { + "bbox": [ + 307, + 178, + 544, + 346 + ], + "spans": [ + { + "bbox": [ + 307, + 178, + 544, + 346 + ], + "type": "image", + "image_path": "aa0d999fb4b83214be07bf0c18f8788249e7e7fc008026852cb0e993a656d2a5.jpg" + } + ] + } + ], + "index": 13, + "angle": 0, + "type": "image_body" + }, + { + "bbox": [ + 305, + 353, + 546, + 387 + ], + "lines": [ + { + "bbox": [ + 305, + 353, + 546, + 387 + ], + "spans": [ + { + "bbox": [ + 305, + 353, + 546, + 387 + ], + "type": "text", + "content": "Figure 10. Qualitative results on Argoverse with comparison to NeRF-LiDAR-cGAN [9] that solely relies on Lidar encoding, unlike our hybrid scene representation." + } + ] + } + ], + "index": 14, + "angle": 0, + "type": "image_caption" + } + ], + "index": 13 + }, + { + "bbox": [ + 305, + 400, + 545, + 437 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 305, + 400, + 545, + 437 + ], + "spans": [ + { + "bbox": [ + 305, + 400, + 545, + 437 + ], + "type": "text", + "content": "formance from our method over S-NeRF. Ablation study results are also shown in Tab. 3, which further consolidate the efficacy of our proposed components." + } + ] + } + ], + "index": 15 + }, + { + "bbox": [ + 304, + 437, + 547, + 546 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 437, + 547, + 546 + ], + "spans": [ + { + "bbox": [ + 304, + 437, + 547, + 546 + ], + "type": "text", + "content": "Next, we evaluate on Argoverse dataset following the protocol in [9]. We present example qualitative comparisons in Fig. 10 while leaving more evaluations to the supplementary. As can be seen, our LidaRF achieves far superior rendering quality with high resolution. We note the [9]'s blank rendering on regions not covered by Lidar, as they solely rely on Lidar for radiance decoding. This illustrates the advantage of our framework in combining the complementary benefits from Lidar encoding and high-resolution hash grid." + } + ] + } + ], + "index": 16 + }, + { + "bbox": [ + 306, + 560, + 378, + 572 + ], + "type": "title", + "angle": 0, + "lines": [ + { + "bbox": [ + 306, + 560, + 378, + 572 + ], + "spans": [ + { + "bbox": [ + 306, + 560, + 378, + 572 + ], + "type": "text", + "content": "6. Conclusion" + } + ] + } + ], + "index": 17 + }, + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "type": "text", + "angle": 0, + "lines": [ + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "spans": [ + { + "bbox": [ + 304, + 582, + 547, + 713 + ], + "type": "text", + "content": "In this paper, we focus on unlocking the potential of Lidar to improve NeRF on road scenes, which remain a challenging scenario for novel view synthesis due to highly constrained camera motions. We develop insights on fusing Lidar encoding with high-resolution grid based representation to reap their complementary benefits, and further, extract more robust and extensive depth supervision from Lidar. A limitation of our work is that we currently handle static background only. 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